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Linking elastic, mechanical and transport properties in anisotropically cracked rocks
NASA Astrophysics Data System (ADS)
Damage and crack porosity can result in a decrease of the mechanical strength of the rock, the development of elastic and mechanical anisotropy and the enhancement of transport properties. Using Non-Interactive Crack Effective Medium (NIC) theory as a fundamental tool, it is possible to calculate dry and wet elastic properties of cracked rocks in terms of a crack density tensor, average crack aspect ratio and mean crack fabric orientation using the solid grains and fluid elastic properties. Using the same tool, we show that the anisotropy, the shear wave splitting and the dispersion of elastic waves can be derived for anisotropic crack fabrics. Mechanically, the existence of embedded microcrack fabrics in rocks also significantly influences the fracture toughness (KIC) of rocks. We show that KIC can show large amounts of anisotropy as well, the degree and orientation of which being largely constrained once again by the microcrack fabric. NIC can predict relatively well KIC at high crack density, by simply using dimensionless crack densities inverted from velocities. A decrease of 50% for crack densities larger than 1, 80% for crack densities larger than 5 is predicted, in close agreement with our observed experimental variation of KIC. At the microscale, this can be interpreted by the fact that the main fracture is strongly interacting with the pre-existing microcrack fabric. Finally, and above the percolation threshold, macroscopic fluid flow also depends on the porosity, crack density and aspect ratio. Using the permeability model of Guķguen and Dienes (1989) and the crack density and aspect ratio recovered from the elastic wave velocity inversion, we successfully predict the evolution of permeability with pressure for direct comparison with the laboratory measurements. These combined experimental and modelling results illustrate the importance of understanding the details of how rock microstructures change in response to an external stimulus in predicting the simultaneous evolution of rock physical properties.
Schubnel, A.; Benson, P.; Nasseri, F.; Gueguen, Y.; Meredith, P.; Young, R.
Transport properties and the large anisotropic magnetoresistance of Cu(x)NbS(2) single crystals.
The transport properties of Cu(x)NbS(2) (x = 0.09, 0.44 and 0.55) single crystals were systematically studied. The in-plane and out-of-plane resistivities decrease with increasing Cu content, and a transition with hysteresis shows up for the crystals with x = 0.44 and 0.55. The thermopower and Hall coefficient of Cu(x)NbS(2) show opposite signs, indicating that there are two kinds of carriers in this system. The angular dependences of the in-plane magnetoresistance (MR(ab) = (?(ab)(H)-?(ab)(0))/?(ab)(0) ū 100%) at different temperatures were also studied. The single crystals with x = 0.44 and 0.55 show a strong anisotropic MR(ab). For the x = 0.55 sample, MR(ab) reaches 80% with a magnetic field of 14ĀT applied along the c-axis, while MR(ab) is less than 5% for the magnetic field applied within the ab-plane. These results can be well understood in the light of the anisotropic Fermi surface in the multiband system. PMID:21828495
Wu, G; Wu, T; Li, Z; Zhao, L; Liu, R H; Chen, H; Fang, D F; Luo, J L; Chen, X H
Electron transport properties in m-plane and c-plane AlN/GaN heterostructures with interface roughness and anisotropic in-plane strain scatterings
NASA Astrophysics Data System (ADS)
Anisotropic transport properties of a two-dimensional electron gas in nonpolar m-plane AlN/GaN heterostructures with the interface roughness coupled anisotropic in-plane strain scattering were investigated theoretically using a path-integral framework. The scattering potential was composed of the interface roughness and the effective field from the electron charge and the net piezoelectric polarization. We showed that the anisotropic biaxial strains generate only the net piezoelectric polarization along the [0?0?0?1]-direction and cause anisotropy in electron mobility with a magnitude lower than the ?ft[11\\bar{2}0\\right] -direction. We also showed that the anisotropy in electron mobility reduced with increasing electron density. Moreover, the anisotropic electron mobility disappeared when the anisotropic in-plane strain scattering was removed, and the relation for pure interface roughness scattering was reestablished. This formulation with existing roughness parameters gave a good description for the experimental results of polar c-plane AlN/GaN heterostructures.
Thongnum, Anusit; Pinsook, Udomsilp
Elastic Anisotropy and Anisotropic Transport Properties of Cu3SbSe4 and Cu3SbS4
NASA Astrophysics Data System (ADS)
Copper-based ternary chalcogenide semiconductors with zincblende-related crystal structures have recently emerged as some of the best performing p-type thermoelectric materials. Here, first-principles calculations are used to investigate the structural, elastic, and thermoelectric properties of Cu3SbSe4 and Cu3SbS4. The calculated lattice constants and atomic coordinates are in good agreement with those obtained in the previous experiments, which shows that our method is reliable. We found that the hybridization among atoms forms [SbSe4] and [CuSe4] tetrahedral structures. The spin¢orbit (SO) interaction is included in the calculations for electronic structures and thermoelectric properties. It is predicted that Cu3SbSe4 and Cu3SbS4 are mechanically stable, relatively soft materials with high compressibility, and are low small-hardness ionic materials, and with more anisotropy in shear than in compressibility. The results also show that the mechanical stability of these materials is limited by the shear modulus G. Furthermore, Cu3SbSe4 can be classified as a brittle material, whereas Cu3SbS4 can be classified as a ductile material. The semiclassical Boltzmann transport theory was used to calculate the Seebeck coefficients, electrical conductivities, electronic thermal conductivities, power factors, and thermoelectric figures of merit ZeT of Cu3SbSe4 and Cu3SbS4 along two crystallographic directions, and the optimal doping concentrations were estimated on the basis of the predicted thermoelectric properties. The temperature dependences of the thermoelectric transport properties of Cu3SbSe4 and Cu3SbS4 were also estimated and compared with experimental data, with good agreement observed.
Xu, Bin; Zhang, Xiangdan; Sun, Yunzhou; Zhang, Jing; Wang, Yusheng; Yi, Lin
On the anisotropic elastic properties of hydroxyapatite.
NASA Technical Reports Server (NTRS)
Experimental measurements of the isotropic elastic moduli on polycrystalline specimens of hydroxyapatite and fluorapatite are compared with elastic constants measured directly from single crystals of fluorapatite in order to derive a set of pseudo single crystal elastic constants for hydroxyapatite. The stiffness coefficients thus derived are given. The anisotropic and isotropic elastic properties are then computed and compared with similar properties derived from experimental observations of the anisotropic behavior of bone.
Katz, J. L.; Ukraincik, K.
Synthesis of cubic SrCoO3 single crystal and its anisotropic magnetic and transport properties.
A large-size single crystal of nearly stoichiometric SrCoO(3) was prepared with a two-step method combining the floating-zone technique and subsequent high oxygen pressure treatment. SrCoO(3) crystallizes in a cubic perovskite structure with space group Pm3m, and displays an itinerant ferromagnetic behavior with the Curie temperature of 305 K. The easy magnetization axis is found to be along the [111] direction, and the saturation moment is 2.5 Ą(B)/f.u., in accord with the picture of the intermediate spin state. The resistivity at low temperatures (T) is proportional to T(2), indicative of the possible effect of orbital fluctuation in the intermediate spin ferromagnetic metallic state. Unusual anisotropic magnetoresistance is also observed and its possible origin is discussed. PMID:21628787
Long, Youwen; Kaneko, Yoshio; Ishiwata, Shintaro; Taguchi, Yasujiro; Tokura, Yoshinori
Anisotropic properties of tracheal smooth muscle tissue.
The anisotropic (directional-dependent) properties of contracting tracheal smooth muscle tissue are estimated from a computational model based on the experimental data of length-dependent stiffness. The area changes are obtained at different muscle lengths from experiments in which stimulated muscle undergoes unrestricted shortening. Then, through an interative process, the anisotropic properties are estimated by matching the area changes obtained from the finite element analysis to those derived from the experiments. The results obtained indicate that the anisotropy ratio (longitudinal stiffness to transverse stiffness) is about 4 when the smooth muscle undergoes 70% strain shortening, indicating that the transverse stiffness reduces as the longitudinal stiffness increases. It was found through a sensitivity analysis from the simulation model that the longitudinal stiffness and the in-plane shear modulus are not very sensitive as compared to major Poisson's ratio to the area changes of the muscle tissue. PMID:12635147
Sarma, P A; Pidaparti, R M; Meiss, R A
Anisotropic transport in modulation doped quantum well structures
NASA Technical Reports Server (NTRS)
The degree of anisotropy in the anisotropic electron transport that has been observed in GaAs modulation-doped quantum wells grown by MBE on Al(0.3)Ga(0.7)As is related to the thickness and growth parameters of this substrate, which is grown just prior to the inverted interface. It is presently observed that the inverted interface has an anisotropic roughness which affects the 77 K low field electron transport parallel to the interface, and gives rise to anisotropic electron scattering in the GaAs modulation-doped quantum well.
Radulescu, D. C.; Wicks, G. W.; Schaff, W. J.; Calawa, A. R.; Eastman, L. F.
Transport equations for multicomponent anisotropic space plasmas - A review
NASA Technical Reports Server (NTRS)
An attempt is made to present a unified approach to the study of transport phenomena in multicomponent anisotropic space plasmas. In particular, a system of generalized transport equations is presented that can be applied to widely different plasma flow conditions. The generalized transport equations can describe subsonic and supersonic flows, collision-dominated and collisionless flows, plasma flows in rapidly changing magnetic field configurations, multicomponent plasma flows with large temperature differences between the interacting species, and plasma flows that contain anisotropic temperature distributions. In addition, if Maxwell's equations of electricity and magnetism are added to the system of transport equations, they can be used to model electrostatic shocks, double layers, and magnetic merging processes. These transport equations also contain terms which act to regulate both the heat flow and temperature anisotropy, processes which appear to be operating in the solar wind.
Barakat, A. R.; Schunk, R. W.
Intricate Short-Range Ordering and Strongly Anisotropic Transport Properties of Li1-xSn2+xAs2.
A new ternary compound, Li1-xSn2+xAs2, 0.2 < x < 0.4, was synthesized via solid-state reaction of elements. The compound crystallizes in a layered structure in the R3?m space group (No. 166) with Sn-As layers separated by layers of jointly occupied Li/Sn atoms. The Sn-As layers are comprised of Sn3As3 puckered hexagons in a chair conformation that share all edges. Li/Sn atoms in the interlayer space are surrounded by a regular As6 octahedron. Thorough investigation by synchrotron X-ray and neutron powder diffraction indicate no long-range Li/Sn ordering. In contrast, the local Li/Sn ordering was revealed by synergistic investigations via solid-state (6,7)Li NMR spectroscopy, HRTEM, STEM, and neutron and X-ray pair distribution function analyses. Due to their different chemical natures, Li and Sn atoms tend to segregate into Li-rich and Sn-rich regions, creating substantial inhomogeneity on the nanoscale. The inhomogeneous local structure has a high impact on the physical properties of the synthesized compounds: the local Li/Sn ordering and multiple nanoscale interfaces result in unexpectedly low thermal conductivity and highly anisotropic resistivity in Li1-xSn2+xAs2. PMID:25702752
Lee, Kathleen; Kaseman, Derrick; Sen, Sabyasachi; Hung, Ivan; Gan, Zhehong; Gerke, Birgit; P÷ttgen, Rainer; Feygenson, Mikhail; Neuefeind, J÷rg; Lebedev, Oleg I; Kovnir, Kirill
Anisotropic transport processes in the chromosphere and overlying atmosphere
NASA Astrophysics Data System (ADS)
Energy flow and transformation in the solar atmosphere is a complex process. Fluxes of particle kinetic and electromagnetic energy flow in both directions through the photosphere, and are transformed into one another in the overlying atmosphere. Diffusive transport processes such as electrical and thermal conduction, and viscous and thermoelectric effects play a major role in determining energy fluxes and transformation rates. Almost the entire atmosphere is strongly magnetized, meaning that charged particle cyclotron frequencies significantly exceed their collision frequencies. This causes transport processes to be anisotropic, so they must be described by tensors in MHD models. Only models that include the relevant transport tensors can reveal the processes that create and maintain the chromosphere, transition region, and corona because only such models can accurately describe energy flow and transformation. This paper outlines the importance of anisotropic transport processes in the atmosphere, especially of anisotropic electrical conduction in the weakly ionized, strongly magnetized chromosphere, and presents MHD model evidence that anisotropic electrical conduction plays a major role in shock wave and Alfvķn wave heating in the chromosphere. It is proposed that magnetization induced resistivity increases with height from the photosphere, exceeds the Spitzer resistivity eta S near the height of the local temperature minimum, increases with height to orders of magnitude > eta S, and causes proton Pedersen current dissipation to be a major source of chromospheric heating.
Goodman, M. L.; Kazeminezhad, F.
Anisotropic flow in transport+hydrodynamics hybrid approaches
This contribution to the focus issue covers anisotropic flow in hybrid approaches. The historical development of hybrid approaches and their impact on the interpretation of flow measurements is reviewed. The major ingredients of a hybrid approach and the transition criteria between transport and hydrodynamics are discussed. The results for anisotropic flow in (event-by-event) hybrid approaches are presented. Some hybrid approaches rely on hadronic transport for the late stages for the reaction (so called afterburner) and others employ transport approaches for the early non equilibrium evolution. In addition, there are 'full' hybrid calculations where a fluid evolution is dynamically embedded in a transport simulation. After demonstrating the success of hybrid approaches at high RHIC and LHC energies, existing hybrid caluclations for collective flow observables at lower beam energies are discussed and remaining challenges outlined.
Hannah Petersen
Anisotropic transport rates in heterogeneous porous media
We applied a recently developed method of aquifer characterization, which combines geophysics and geostatistics to create several heterogeneous realizations of a shallow fluvial aquifer that contain representations of sedimentary bounding surfaces. The influence of such small-scale (several centimeters) features on subsurface transport was investigated using high-resolution groundwater models of each of the subsurface realizations. Flow and transport through the models
Nicholas B. Engdahl; Gary S. Weissmann
Anisotropic magnetization and transport properties of RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm)
This study of the RAgSb{sub 2} series of compounds arose as part of an investigation of rare earth intermetallic compounds containing antimony with the rare earth in a position with tetragonal point symmetry. Materials with the rare earth in a position with tetragonal point symmetry frequently manifest strong anisotropies and rich complexity in the magnetic properties, and yet are simple enough to analyze. Antimony containing intermetallic compounds commonly possess low carrier densities and have only recently been the subject of study. Large single grain crystals were grown of the RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm) series of compounds out of a high temperature solution. This method of crystal growth, commonly known as flux growth is a versatile method which takes advantage of the decreasing solubility of the target compound with decreasing temperature. Overall, the results of the crystal growth were impressive with the synthesis of single crystals of LaAgSb{sub 2} approaching one gram. However, the sample yield diminishes as the rare earth elements become smaller and heavier. Consequently, no crystals could be grown with R=Yb or Lu. Furthermore, EuAgSb{sub 2} could not be synthesized, likely due to the divalency of the Eu ion. For most of the RAgSb{sub 2} compounds, strong magnetic anisotropies are created by the crystal electric field splitting of the Hund's rule ground state. This splitting confines the local moments to lie in the basal plane (easy plane) for the majority of the members of the series. Exceptions to this include ErAgSb{sub 2} and TmAgSb{sub 2}, which have moments along the c-axis (easy axis) and CeAgSb{sub 2}, which at intermediate temperatures has an easy plane, but exchange coupling at low temperatures is anisotropic with an easy axis. Additional anisotropy is also observed within the basal plane of DyAgSb{sub 2}, where the moments are restricted to align along one of the {l_angle}110{r_angle} axes. Most of the RAgSb{sub 2} compounds containing magnetic rare earths, antiferromagnetically ordered at low temperatures. The ordering temperatures of these compounds are approximately proportional to the de Gennes factor, which suggests that the RKKY interaction is the dominant exchange interaction between local moments. Although metamagnetic transitions were observed in many members of the series, the series of sharp step-like transitions in DyAgSb{sub 2} are impressive. In this compound, up to 11 different magnetic states are stable depending on the magnitude and direction of the applied field. The saturated magnetization of these states and the critical fields needed to induce a phase transition vary with the direction of the applied field. Through detailed study of the angular dependence of the magnetization and critical fields, the net distribution of magnetic moments was determined for most, of the metamagnetic states. In DyAgSb{sub 2}, the crystal electric field (CEF) splitting of the Hund's rule ground state creates a strong anisotropy where the local Dy{sup 3+} magnetic moments are constrained to one of the equivalent {l_angle}110{r_angle} directions within the basal plane. The four position clock model was introduced to account for this rich metamagnetic system. Within this model, the magnetic moments are constrained to one of four equivalent orientations within the basal plane and interactions are calculated for up third nearest neighbors. The theoretical phase diagram, generated from the coupling constants is in excellent agreement with the experimental phase diagram. Further investigation of this compound using magnetic X-ray or neutron diffraction would be extremely useful to verify the net distributions of moments and determine the wave vectors of each of the ordered states.
Myers, Kenneth D.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Effective Anisotropic Dielectric Properties of Crystal Composites
Transformation field method (TFM) is developed to estimate the anisotropic dielectric properties of crystal composites having arbitrary shapes and dielectric properties of crystal inclusions, whose principal dielectric axis are different from those of anisotropic crystal matrix. The complicated boundary-value problem caused by inclusion shapes is circumvented by introducing a transformation electric field into the crystal composites regions, and the effective
En-Bo Wei; Guo-Qing Gu; Ying-Ming Poon; G. Shin Franklin
Anisotropic Tribological Properties of Silicon Carbide
NASA Technical Reports Server (NTRS)
The anisotropic friction, deformation and fracture behavior of single crystal silicon carbide surfaces were investigated in two categories. The categories were called adhesive and abrasive wear processes, respectively. In the adhesive wear process, the adhesion, friction and wear of silicon carbide were markedly dependent on crystallographic orientation. The force to reestablish the shearing fracture of adhesive bond at the interface between silicon carbide and metal was the lowest in the preferred orientation of silicon carbide slip system. The fracturing of silicon carbide occurred near the adhesive bond to metal and it was due to primary cleavages of both prismatic (10(-1)0) and basal (0001) planes.
Miyoshi, K.; Buckley, D. H.
Anisotropic parton escape is the dominant source of azimuthal anisotropy from A Multi-Phase Transport
We trace the development of azimuthal anisotropy ($v_n$) in A Multi-Phase Transport (AMPT) model using parton-parton collision history. The parton $v_n$ is studied as a function of the number of collisions of each parton in Au+Au and d+Au collisions at $\\sqrt{S_{NN}}$=200~GeV. It is found that the majority of $v_n$ comes from the anisotropic escape probability of partons, with no fundamental difference at low and high transverse momenta. The contribution to $v_n$ from the parton collective flow appears small; however, it is this small anisotropy from the collective flow, not that from the anisotropic escape probability, that is most relevant for medium properties in heavy ion collisions.
Liang He; Terrence Edmonds; Zi-Wei Lin; Feng Liu; Denes Molnar; Fuqiang Wang
Anisotropic nanomaterials: Synthesis, optical and magnetic properties, and applications
As nanoscience and nanotechnology mature, anisotropic metal nanostructures are emerging in a variety of contexts as valuable class of nanostructures due to their distinctive attributes. With unique properties ranging from optical to magnetic and beyond, these structures are useful in many new applications. Chapter two discusses the nanodisk code: a linear array of metal disk pairs that serve as surface-enhanced
Matthew John Banholzer
Transport properties of Dirac ferromagnet
NASA Astrophysics Data System (ADS)
We propose a model ferromagnet based on the Dirac Hamiltonian in three spatial dimensions, and study its transport properties which include anisotropic magnetoresistance (AMR) and anomalous Hall (AH) effect. This relativistic extension allows two kinds of ferromagnetic order parameters, denoted by M and S , which are distinguished by the relative sign between the positive- and negative-energy states (at zero momentum) and become degenerate in the nonrelativistic limit. Because of the relativistic coupling between the spin and the orbital motion, both M and S induce anisotropic deformations of the energy dispersion (and the Fermi surfaces) but in mutually opposite ways. The AMR is determined primarily by the anisotropy of the Fermi surface (group velocity), and secondarily by the anisotropy of the damping; the latter becomes important for M =▒S , where the Fermi surfaces are isotropic. Even when the chemical potential lies in the gap, the AH conductivity is found to take a finite nonquantized value ?i j=-(? /3 ?2? ) ?i j kSk , where ? is the (effective) fine structure constant. This offers an example of Hall insulator in three spatial dimensions.
Fujimoto, Junji; Kohno, Hiroshi
Origin of anisotropic nonmetallic transport in the Al80Cr15Fe5 decagonal approximant
NASA Astrophysics Data System (ADS)
We present a study of the anisotropic transport properties (electrical resistivity, thermoelectric power, Hall coefficient, and thermal conductivity) of a single-crystalline Al80Cr15Fe5 complex metallic alloy that is an excellent approximant to the decagonal quasicrystal with six atomic layers in one periodic unit. Temperature-dependent electrical resistivity along the b and c crystalline directions shows a nonmetallic behavior with a broad maximum, whereas it shows a metallic positive temperature coefficient along the a direction perpendicular to the (b,c) atomic planes. Ab initio calculations of the electronic density of states reveal that the nonmetallic transport occurs in the presence of a high density of charge carriers. The very different temperature-dependent electrical resistivities along the three crystalline directions can all be treated within the same physical model of slow charge carriers due to weak dispersion of the electronic bands, where the increased electron-phonon scattering upon raising the temperature induces transition from dominant Boltzmann (metallic) to dominant non-Boltzmann (insulatinglike) regime. The temperature dependence of the resistivity is governed predominantly by the temperature dependence of the electronic diffusion constant D and the transition has no resemblance to the Anderson-type metal-to-insulator transition based on the gradual electron localization. Structural considerations of the Al80Cr15Fe5 phase show that the anisotropy of the transport properties is a consequence of anisotropic atomic order on the scale of nearest-neighbor atoms, suggesting that the role of quasiperiodicity in the anisotropic transport of decagonal quasicrystals is marginal. We also present a relaxed version of the Al4(Cr,Fe) structural model by Deng [J. Phys.: Condens. Matter 16, 2283 (2004)].
DolinÜek, J.; Jegli?, P.; Komelj, M.; Vrtnik, S.; Smontara, Ana; Smiljani?, I.; BiluÜi?, A.; Ivkov, J.; Stani?, D.; Zijlstra, E. S.; Bauer, Birgitta; Gille, P.
Transport Properties of Nanocomposites
Transport Properties of Nanocomposites were studied in this work. A Monte Carlo technique was used to model the percolation behavior of fibers in a nanocomposite. Once the percolation threshold was found, the effect of fiber dimensions...
Narayanunni, Vinay
Anisotropic behavior of quantum transport in graphene superlattices: Coexistence of ballistic conduction with Anderson insulating regime
NASA Astrophysics Data System (ADS)
We report on the possibility to generate highly anisotropic quantum conductivity in disordered graphene-based superlattices. Our quantum simulations, based on an efficient real-space implementation of the Kubo-Greenwood formula, show that in disordered graphene superlattices the strength of multiple scattering phenomena can strongly depend on the transport measurement geometry. This eventually yields the coexistence of a ballistic waveguide and a highly resistive channel (Anderson insulator) in the same two-dimensional platform, evidenced by a ?yy/?xx ratio varying over several orders of magnitude, and suggesting the possibility of building graphene electronic circuits based on the unique properties of chiral massless Dirac fermions in graphene.
Pedersen, Jesper Goor; Cummings, Aron W.; Roche, Stephan
Oxygen-driven anisotropic transport in ultra-thin manganite films
Transition metal oxides have a range of unique properties due to coupling of charge, spin, orbital and lattice degrees of freedom and nearly degenerate multiple ground states. These properties make them interesting for applications and for fundamental investigations. Here we report a new phase with abnormal transport anisotropy in La0.7Sr0.3MnO3 ultra-thin films under large tensile strain. This anisotropy is absent in films under smaller tensile strain or compressive strain. Furthermore, thickness and magnetic-field-dependent experiments suggest that the tensile-strain-induced two-dimensional character is crucial for the observed phenomena. X-ray absorption spectroscopy results indicate that this anisotropy is likely driven by O 2p orbital, which hybridizes with Mn 3d. Ab initio calculations confirm this result. Our results may help to understand the anisotropic transport behaviour observed in other systems. PMID:24219875
Wang, Baomin; You, Lu; Ren, Peng; Yin, Xinmao; Peng, Yuan; Xia, Bin; Wang, Lan; Yu, Xiaojiang; Mui Poh, Sock; Yang, Ping; Yuan, Guoliang; Chen, Lang; Rusydi, Andrivo; Wang, Junling
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Effective Anisotropic Dielectric Properties of Crystal Composites
NASA Astrophysics Data System (ADS)
Transformation field method (TFM) is developed to estimate the anisotropic dielectric properties of crystal composites having arbitrary shapes and dielectric properties of crystal inclusions, whose principal dielectric axis are different from those of anisotropic crystal matrix. The complicated boundary-value problem caused by inclusion shapes is circumvented by introducing a transformation electric field into the crystal composites regions, and the effective anisotropic dielectric responses are formulated in terms of the transformation field. Furthermore, the numerical results show that the effective anisotropic dielectric responses of crystal composites periodically vary as a function of the rotating angle between the principal dielectric axes of inclusion and matrix crystal materials. It is found that at larger inclusion volume fraction the inclusion shapes induce profound effect on the effective anisotropic dielectric responses.
Wei, En-Bo; Gu, Guo-Qing; Poon, Ying-Ming; Franklin, G. Shin
Anisotropic electron transport properties in sumanene crystal.
The high electron mobility with large anisotropy was attained in the needle-like single crystal of sumanene, which was indicated by time-resolved microwave conductivity (TRMC) measurement. PMID:19105693
Amaya, Toru; Seki, Shu; Moriuchi, Toshiyuki; Nakamoto, Kana; Nakata, Takuto; Sakane, Hiroyuki; Saeki, Akinori; Tagawa, Seiichi; Hirao, Toshikazu
Conformational properties of polymers in anisotropic environments
We analyze the conformational properties of polymer macromolecules in solutions in presence of extended structural obstacles of (fractal) dimension $\\varepsilon_d$ causing the anisotropy of environment. Applying the pruned-enriched Rosenbluth method (PERM), we obtain numerical estimates for scaling exponents and universal shape parameters of polymers in such environments for a wide range $0polymer renormalization scheme. Both numerical and analytical studies qualitatively confirm the existence of two characteristic length scales of polymer chain in directions parallel and perpendicular to the extended defects.
K. Haydukivska; V. Blavatska
Identifying Heterogeneous Anisotropic Properties in Cerebral Aneurysms: A Pointwise Approach
The traditional approaches of estimating heterogeneous properties in a soft tissue structure using optimization based inverse methods often face difficulties because of the large number of unknowns to be simultaneously determined. This article proposes a new method for identifying the heterogeneous anisotropic nonlinear elastic properties in cerebral aneurysms. In this method, the local properties are determined directly from the pointwise stress-strain data, thus avoiding the need for simultaneously optimizing for the property values at all points/regions in the aneurysm. The stress distributions needed for a pointwise identification are computed using an inverse elastostatic method without invoking the material properties in question. This paradigm is tested numerically through simulated inflation tests on an image-based cerebral aneurysm sac. The wall tissue is modeled as an eight-ply laminate whose constitutive behavior is described by an anisotropic hyperelastic strain-energy function containing four parameters. The parameters are assumed to vary continuously in the sac. Deformed configurations generated from forward finite element analysis are taken as input to inversely establish the parameter distributions. The delineated and the assigned distributions are in excellent agreement. A forward verification is conducted by comparing the displacement solutions obtained from the delineated and the assigned material parameters at a different pressure. The deviations in nodal displacements are found to be within 0.2% in most part of the sac. The study highlights some distinct features of the proposed method, and demonstrates the feasibility of organ level identification of the distributive anisotropic nonlinear properties in cerebral aneurysms. PMID:20490886
Zhao, Xuefeng; Raghavan, Madhavan L.; Lu, Jia
Anisotropic transport in modulation-doped quantum-well structures
NASA Technical Reports Server (NTRS)
Anisotropic electron transport has been observed in GaAs modulation-doped quantum wells grown by molecular-beam epitaxy on a thick (001) Al(0.3)Ga(0.7)As buffer grown at 620 C. Thicker quantum wells (150, 200, and 300 A) show progressively less anisotropy, which vanishes for a 300-A quantum well. The degree of anisotropy is also reduced or eliminated by suspending growth of the Al(0.3)Ga(0.7)As for a period of 300 s prior to growing the GaAs quantum well. Growing the Al(0.3)Ga(0.7)As buffer at higher temperatures (680 C) also reduces the degree of anisotropy. Higher two-dimensional electron gas sheet densities result in less anisotropy.The anisotropy is eliminated by replacing the thick Al(0.3)Ga(0.7)As buffer with a periodic multilayer structure comprising 15 A of GaAs and 200 A of Al(0.3)Ga(0.7)As. The degree of anisotropy is related to the thickness and growth parameters of the Al(0.3)Ga(0.7)As layer grown just prior to the growth of the GaAs.
Radulescu, D. C.; Wicks, G. W.; Schaff, W. J.; Calawa, A.R.; Eastman, L. F.
Synthetic acceleration methods for linear transport problems with highly anisotropic scattering
This paper reports on the diffusion synthetic acceleration (DSA) algorithm that effectively accelerates the iterative solution of transport problems with isotropic or mildly anisotropic scattering. However, DSA loses its effectiveness for transport problems that have strongly anisotropic scattering. Two generalizations of DSA are proposed, which, for highly anisotropic scattering problems, converge at least an order of magnitude (clock time) faster than the DSA method. These two methods are developed, the results of Fourier analyses that theoretically predict their efficiency are described, and numerical results that verify the theoretical predictions are presented.
Khattab, K.M.; Larsen, E.W. (Michigan Univ., Ann Arbor, MI (United States). Dept. of Nuclear Engineering)
Thermal transport properties of graphene nanomeshes
NASA Astrophysics Data System (ADS)
Using molecular-dynamics simulations, we study the thermal transport properties of graphene nanomeshes (GNMs) as a function of material density, pore morphology, pore edge passivation, and the lattice arrangement of the nanomesh pores. Relations for the density dependence of the GNMs' thermal conductivity are established. For GNMs with circular pores, we find that the thermal conductivity is an exponential function of the GNM's neck width with a very weak dependence on the pore lattice structure and pore edge passivation. For GNMs with elliptical pores, the thermal conductivity becomes anisotropic and this anisotropy becomes stronger with decreasing GNM density.
Hu, Lin; Maroudas, Dimitrios
Anisotropic heat transport in reversed shear configurations: shearless Cantori barriers and nonlocal transport
NASA Astrophysics Data System (ADS)
Heat transport in magnetized plasmas is a problem of fundamental interest in controlled fusion. In Ref.footnotetext D. del-Castillo-Negrete, and L. Chac'on, Phys. Rev. Lett., 106, 195004 (2011); Phys. Plasmas 19, 056112 (2012). we proposed a Lagrangian-Green's function (LG) method to study this problem in the strongly anisotropic (?=0) regime. The LG method bypasses the need to discretize the transport operators on a grid and it is applicable to general parallel flux closures and 3-D magnetic fields. Here we apply the LG method to parallel transport (with local and nonlocal parallel flux closures) in reversed shear magnetic field configurations known to exhibit robust transport barriers in the vicinity of the extrema of the q-profile. By shearless Cantori (SC) we mean the invariant Cantor sets remaining after the destruction of toroidal flux surfaces with zero magnetic shear, q^'=0. We provide numerical evidence of the role of SC in the anomalously slow relaxation of radial temperature gradients in chaotic magnetic fields with no transport barriers. The spatio-temporal evolution of temperature pulses localized in the reversed shear region exhibits non-diffusive self-similar evolution and nonlocal effective radial transport.
Blasevski, D.; Del-Castillo-Negrete, D.
Anisotropic MRI contrast reveals enhanced ionic transport in plastic crystals.
Organic ionic plastic crystals (OIPCs) are attractive as solid-state electrolytes for electrochemical devices such as lithium-ion batteries and solar and fuel cells. OIPCs offer high ionic conductivity, nonflammability, and versatility of molecular design. Nevertheless, intrinsic ion transport behavior of OIPCs is not fully understood, and their measured properties depend heavily on thermal history. Solid-state magnetic resonance imaging experiments reveal a striking image contrast anisotropy sensitive to the orientation of grain boundaries in polycrystalline OIPCs. Probing triethyl(methyl)phosphonium bis(fluorosulfonyl)imide (P1222FSI) samples with different thermal history demonstrates vast variations in microcrystallite alignment. Upon slow cooling from the melt, microcrystallites exhibit a preferred orientation throughout the entire sample, leading to an order of magnitude increase in conductivity as probed using impedance spectroscopy. This investigation describes both a new conceptual window and a new characterization method for understanding polycrystalline domain structure and transport in plastic crystals and other solid-state conductors. PMID:25312993
Romanenko, Konstantin; Jin, Liyu; Madsen, Louis A; Pringle, Jennifer M; O'Dell, Luke A; Forsyth, Maria
Anisotropic magnetic properties of EuAl2Si2
NASA Astrophysics Data System (ADS)
EuAl2Si2 is known to crystallize in the CaAl2Si2-type trigonal structure. We have grown single crystals of EuAl2Si2 by flux method, using Al-Si eutectic (87.8% Al) as self-flux, and investigated their anisotropic magnetic properties by means of magnetization, electrical resistivity and heat capacity in zero and applied magnetic fields, and 151Eu M÷ssbauer spectroscopy. Magnetic susceptibility data show an antiferromagnetic transition at TN = 33.3 K in agreement with the previously reported value on polycrystalline sample. The isothermal magnetization at 2 K measured along and perpendicular to the c-axis shows anisotropic behaviour, which is rather unexpected as Eu2+ is an S-state ion. The spin flip fields along the two directions are 2.8 and 4.8 T, respectively, while two closely spaced spin-flop transitions in the ab-plane are observed near 1.4 and 1.6 T. The electrical resistivity shows an upturn between TN and 60 K as the temperature is lowered below ~ 60 K, suggesting the presence of antiferromagnetic correlations in the paramagnetic state. Magnetoresistivity at 2 K in 14 T is nearly 1070 % for H // [0001]. The results of heat capacity and 151Eu M÷ssbauer spectroscopy are in conformity with a bulk transition at 33.3 K.
Maurya, Arvind; Kulkarni, Ruta; Thamizhavel, A.; Bonville, P.; Dhar, S. K.
Local and nonlocal anisotropic transport in reversed shear magnetic fields: shearless Cantori and nondiffusive transport.
A study of anisotropic heat transport in reversed shear (nonmonotonic q-profile) magnetic fields is presented. The approach is based on a recently proposed Lagrangian-Green's function method that allows an efficient and accurate integration of the parallel (i.e., along the magnetic field) heat transport equation. The magnetic field lines are described by a nontwist Hamiltonian system, known to exhibit separatrix reconnection and robust shearless (dq/dr=0) transport barriers. The changes in the magnetic field topology due to separatrix reconnection lead to bifurcations in the equilibrium temperature distribution. For perturbations of moderate amplitudes, magnetic chaos is restricted to bands flanking the shearless region. As a result, the temperature flattens in the chaotic bands and develops a very sharp radial gradient at the shearless region. For perturbations with larger amplitude, shearless Cantori (i.e., critical magnetic surfaces located at the minimum of the q profile) give rise to anomalous temperature relaxation involving widely different time scales. The first stage consists of the relatively fast flattening of the radial temperature profile in the chaotic bands with negligible flux across the shearless region that, for practical purposes, on a short time scale acts as an effective transport barrier despite the lack of magnetic flux surfaces. In the long-time scale, heat starts to flow across the shearless region, albeit at a comparatively low rate. The transport of a narrow temperature pulse centered at the reversed shear region exhibits weak self-similar scaling with non-Gaussian scaling functions indicating that transport at this scale cannot be modeled as a diffusive process with a constant diffusivity. Evidence of nonlocal effective radial transport is provided by the existence of regionsĀwith nonzero heat flux and zero temperature gradient. Parametric flux-gradient plots exhibit multivalued loops that question the applicability of the Fourier-Fick's prescription even in the presence of a finite pinch velocity. PMID:23848788
Blazevski, Daniel; del-Castillo-Negrete, Diego
Local and nonlocal anisotropic transport in reversed shear magnetic fields: Shearless Cantori and nondiffusive transport
NASA Astrophysics Data System (ADS)
A study of anisotropic heat transport in reversed shear (nonmonotonic q-profile) magnetic fields is presented. The approach is based on a recently proposed Lagrangian-Green's function method that allows an efficient and accurate integration of the parallel (i.e., along the magnetic field) heat transport equation. The magnetic field lines are described by a nontwist Hamiltonian system, known to exhibit separatrix reconnection and robust shearless (dq/dr=0) transport barriers. The changes in the magnetic field topology due to separatrix reconnection lead to bifurcations in the equilibrium temperature distribution. For perturbations of moderate amplitudes, magnetic chaos is restricted to bands flanking the shearless region. As a result, the temperature flattens in the chaotic bands and develops a very sharp radial gradient at the shearless region. For perturbations with larger amplitude, shearless Cantori (i.e., critical magnetic surfaces located at the minimum of the q profile) give rise to anomalous temperature relaxation involving widely different time scales. The first stage consists of the relatively fast flattening of the radial temperature profile in the chaotic bands with negligible flux across the shearless region that, for practical purposes, on a short time scale acts as an effective transport barrier despite the lack of magnetic flux surfaces. In the long-time scale, heat starts to flow across the shearless region, albeit at a comparatively low rate. The transport of a narrow temperature pulse centered at the reversed shear region exhibits weak self-similar scaling with non-Gaussian scaling functions indicating that transport at this scale cannot be modeled as a diffusive process with a constant diffusivity. Evidence of nonlocal effective radial transport is provided by the existence of regions with nonzero heat flux and zero temperature gradient. Parametric flux-gradient plots exhibit multivalued loops that question the applicability of the Fourier-Fick's prescription even in the presence of a finite pinch velocity.
Blazevski, Daniel; del-Castillo-Negrete, Diego
Structural properties of anisotropically confined binary Coulomb balls.
We investigate the structural properties of a small binary system of dusty plasma subjected to an anisotropic external confinement. We have found that the ground state can form various symmetrical configurations, which generally correspond to variations of a multiple-ring structure. The presence of such structures is given through a detailed phase diagram constructed for the systems with N=18 and 24 particles. Furthermore, we show that the configurations of multiple rings can present a persistent behavior for the case in which the number of less-charged particles is equal to a multiple of the number of particles per ring. Finally, we discuss the main characteristics of the transitions of first and second orders since these are related to the main configurational changes of the ground states. PMID:25019787
Silva, F C O; Apolinario, S W S
Structural properties of anisotropically confined binary Coulomb balls
NASA Astrophysics Data System (ADS)
We investigate the structural properties of a small binary system of dusty plasma subjected to an anisotropic external confinement. We have found that the ground state can form various symmetrical configurations, which generally correspond to variations of a multiple-ring structure. The presence of such structures is given through a detailed phase diagram constructed for the systems with N =18 and 24 particles. Furthermore, we show that the configurations of multiple rings can present a persistent behavior for the case in which the number of less-charged particles is equal to a multiple of the number of particles per ring. Finally, we discuss the main characteristics of the transitions of first and second orders since these are related to the main configurational changes of the ground states.
Silva, F. C. O.; Apolinario, S. W. S.
Quantum transport in Dirac materials: Signatures of tilted and anisotropic Dirac and Weyl cones
NASA Astrophysics Data System (ADS)
We calculate conductance and noise for quantum transport at the nodal point for arbitrarily tilted and anisotropic Dirac or Weyl cones. Tilted and anisotropic dispersions are generic in the absence of certain discrete symmetries, such as particle-hole and lattice point group symmetries. Whereas anisotropy affects the conductance g , but leaves the Fano factor F (the ratio of shot noise power and current) unchanged, a tilt affects both g and F . Since F is a universal number in many other situations, this finding is remarkable. We apply our general considerations to specific lattice models of strained graphene and a pyrochlore Weyl semimetal.
Trescher, Maximilian; Sbierski, Bj÷rn; Brouwer, Piet W.; Bergholtz, Emil J.
Anisotropic vanadium dioxide sculptured thin films with superior thermochromic properties
VO2 (M) STF through reduction of V2O5 STF was prepared. The results illustrate that V2O5 STF can be successfully obtained by oblique angle thermal evaporation technique. After annealing at 550░C/3?min, the V2O5 STF deposited at 85░ can be easily transformed into VO2 STF with slanted columnar structure and superior thermochromic properties. After deposition SiO2 antireflective layer, Tlum of VO2 STF is enhanced 26% and ?Tsol increases 60% compared with that of normal VO2 thin films. Due to the anisotropic microstructure of VO2 STF, angular selectivity transmission of VO2 STF is observed and the solar modulation ability is further improved from 7.2% to 8.7% when light is along columnar direction. Moreover, the phase transition temperature of VO2 STF can be depressed into 54.5░C without doping. Considering the oblique incidence of sunlight on windows, VO2 STF is more beneficial for practical application as smart windows compared with normal homogenous VO2 thin films. PMID:24067743
Sun, Yaoming; Xiao, Xiudi; Xu, Gang; Dong, Guoping; Chai, Guanqi; Zhang, Hua; Liu, Pengyi; Zhu, Hanmin; Zhan, Yongjun
Anisotropic vanadium dioxide sculptured thin films with superior thermochromic properties.
VO2 (M) STF through reduction of V2O5 STF was prepared. The results illustrate that V2O5 STF can be successfully obtained by oblique angle thermal evaporation technique. After annealing at 550 ░C/3 min, the V2O5 STF deposited at 85░ can be easily transformed into VO2 STF with slanted columnar structure and superior thermochromic properties. After deposition SiO2 antireflective layer, Tlum of VO2 STF is enhanced 26% and ?Tsol increases 60% compared with that of normal VO2 thin films. Due to the anisotropic microstructure of VO2 STF, angular selectivity transmission of VO2 STF is observed and the solar modulation ability is further improved from 7.2% to 8.7% when light is along columnar direction. Moreover, the phase transition temperature of VO2 STF can be depressed into 54.5 ░C without doping. Considering the oblique incidence of sunlight on windows, VO2 STF is more beneficial for practical application as smart windows compared with normal homogenous VO2 thin films. PMID:24067743
Sun, Yaoming; Xiao, Xiudi; Xu, Gang; Dong, Guoping; Chai, Guanqi; Zhang, Hua; Liu, Pengyi; Zhu, Hanmin; Zhan, Yongjun
Viscous corrections to anisotropic flow and transverse momentum spectra from transport theory
Viscous hydrodynamics is commonly used to model the evolution of the matter created in an ultra-relativistic heavy-ion collision. It provides a good description of transverse momentum spectra and anisotropic flow. These observables, however, cannot be consistently derived using viscous hydrodynamics alone, because they depend on the microscopic interactions at freeze-out. We derive the ideal hydrodynamic limit and the first-order viscous correction to anisotropic flow ($v_2$, $v_3$ and $v_4$) and momentum spectrum using a transport calculation. The linear response coefficient to the initial anisotropy, $v_n(p_T)/\\varepsilon_n$, depends little on $n$ in the ideal hydrodynamic limit. The viscous correction to the spectrum depends not only on the differential cross section, but also on the initial momentum distribution. This dependence is not captured by standard second-order viscous hydrodynamics. The viscous correction to anisotropic flow increases with $p_T$, but this increase is slower than usually assumed i...
Plumari, Salvatore; Greco, Vincenzo; Ollitrault, Jean-Yves
Dynamical stability of a thermally stratified intracluster medium with anisotropic momentum and heat transport
In weakly-collisional plasmas such as the intracluster medium (ICM), heat and momentum transport become anisotropic with respect to the local magnetic field direction. Anisotropic heat conduction causes the slow magnetosonic wave to become buoyantly unstable to the magnetothermal instability (MTI) when the temperature increases in the direction of gravity and to the heat-flux--driven buoyancy instability (HBI) when the temperature decreases in the direction of gravity. The local changes in magnetic field strength that attend these instabilities cause pressure anisotropies that viscously damp motions parallel to the magnetic field. In this paper we employ a linear stability analysis to elucidate the effects of anisotropic viscosity (i.e. Braginskii pressure anisotropy) on the MTI and HBI. By stifling the convergence/divergence of magnetic field lines, pressure anisotropy significantly affects how the ICM interacts with the temperature gradient. Instabilities which depend upon the convergence/divergence of magn...
Kunz, Matthew W
Cartilaginous tissues, such as articular cartilage and intervertebral disc, are avascular tissues which rely on transport for cellular nutrition. Comprehensive knowledge of transport properties in such tissues is therefore necessary in the understanding of nutritional supply to cells. Furthermore, poor cellular nutrition in cartilaginous tissues is believed to be a primary source of tissue degeneration, which may result in osteoarthritis (OA) or disc degeneration. In this mini-review, we present an overview of the current status of the study of transport properties and behavior in cartilaginous tissues. The mechanisms of transport in these tissues, as well as experimental approaches to measuring transport properties and results obtained are discussed. The current status of bioreactors used in cartilage tissue engineering is also presented. PMID:20126303
Jackson, AR; Gu, WY
Anisotropic nanomaterials: Synthesis, optical and magnetic properties, and applications
NASA Astrophysics Data System (ADS)
As nanoscience and nanotechnology mature, anisotropic metal nanostructures are emerging in a variety of contexts as valuable class of nanostructures due to their distinctive attributes. With unique properties ranging from optical to magnetic and beyond, these structures are useful in many new applications. Chapter two discusses the nanodisk code: a linear array of metal disk pairs that serve as surface-enhanced Raman scattering substrates. These multiplexing structures employ a binary encoding scheme, perform better than previous nanowires designs (in the context of SERS) and are useful for both convert encoding and tagging of substrates (based both on spatial disk position and spectroscopic response) as well as biomolecule detection (e.g. DNA). Chapter three describes the development of improved, silver-based nanodisk code structures. Work was undertaken to generate structures with high yield and reproducibility and to reoptimize the geometry of each disk pair for maximum Raman enhancement. The improved silver structures exhibit greater enhancement than Au structures (leading to lower DNA detection limits), convey additional flexibility, and enable trinary encoding schemes where far more unique structures can be created. Chapter four considers the effect of roughness on the plasmonic properties of nanorod structures and introduces a novel method to smooth the end-surfaces of nanorods structures. The smoothing technique is based upon a two-step process relying upon diffusion control during nanowires growth and selective oxidation after each step of synthesis is complete. Empirical and theoretical work show that smoothed nanostructures have superior and controllable optical properties. Chapter five concerns silica-encapsulated gold nanoprisms. This encapsulation allows these highly sensitive prisms to remain stable and protected in solution, enabling their use as class-leading sensors. Theoretical study complements the empirical work, exploring the effect of encapsulation on the SPR of these structures. Chapter six focuses on the magnetic properties of Au-Ni heterostructures. In addition to demonstration of nanoconfinement effects based upon the anisotropy of the nanorods/nanodisk structure, the magnetic coupling of rod-disk heterostructures is examined. Subsequent investigations suggest that the magnetic behavior of disks can be influenced by nearby rod segments, leading to the creation of a three-state spin system that may prove useful in device applications.
Banholzer, Matthew John
Anisotropic quantum transport in a network of vertically aligned graphene sheets.
Novel anisotropic quantum transport was observed in a network of vertically aligned graphene sheets (VAGSs), which can be regarded as composed of plenty of quasi-parallel, nearly intrinsic, freestanding monolayers of graphene. When a magnetic field was perpendicular to most graphene sheets, magnetoresistance (MR) curves showed a weak localization (WL) effect at low field and a maximum value at a critical field ascribed to diffusive boundary scattering. While the magnetic field was parallel to the graphene sheets, the MR maximum disappeared and exhibited a transition from WL to weak antilocalization (WAL) with increasing temperature and magnetic field. Edges as atomically sharp defects are the main elastic and inelastic intervalley scattering sources, and inelastic scattering is ascribed to electron-electron intervalley scattering in the ballistic regime. This is the first time simultaneously observing WL, WAL and diffusive boundary scattering in such a macroscopic three-dimensional graphene system. These indicate the VAGS network is a robust platform for the study of the intrinsic physical properties of graphene. PMID:25090659
Huang, J; Guo, L-W; Li, Z-L; Chen, L-L; Lin, J-J; Jia, Y-P; Lu, W; Guo, Y; Chen, X-L
Anisotropic Water Transport in the Human Eye Lens Studied by Diffusion Tensor NMR Micro-imaging
We report in vitro measurements of effective diffusion tensors characterising the anisotropic transport of water in human eye lenses ranging in age from 13 to 86 years. The measurements were obtained by means of a pulsed field gradient spin echo (PFGSE) magnetic resonance imaging (MRI) technique at a spatial resolution of 218ū218ū1000?m3. The results show that water diffusion is both
B. A. Moffat; J. M. Pope
Transport properties of uranium dioxide
In order to provide reliable and consistent data on the thermophysical properties of reactor materials for reactor safety studies, this revision is prepared for the transport properties of the uranium dioxide portion of the fuel property section of the report Properties for LMFBR Safety Analysis. Since the original report was issued in 1976, measurements of thermal diffusivity and emissivity have been made. In addition to incorporating this new data, new equations have been derived to fit the thermal diffusivity and thermal conductivity data. This analysis is consistent with the analysis of enthalpy and heat capacity. A new form of equation for the emissivity is also given. The present report comprises the transport part of the UO/sub 2/ portion of section A of the planned complete revision of Properties for LMFBR Safety Analysis.
Fink, J.K.; Chasanov, M.G.; Leibowitz, L.
An Algorithm for the Transport of Anisotropic Neutrons
NASA Technical Reports Server (NTRS)
One major obstacle to human space exploration is the possible limitations imposed by the adverse effect of long-term exposure to the space environment. Even before human spaceflight began, the potentially brief exposure of astronauts to the very intense random solar particle events (SPE) were of great concern. A new challenge appears in deep space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays (GCR) since the missions are of long duration and the accumulated GCR exposures can be high. Because cancer induction rates increase behind low to rather large thicknesses of aluminum shielding, according to available biological data on mammalian exposures to GCR like ions, the shield requirements for a Mars mission are prohibitively expensive in terms of mission launch costs. Therefore, a critical issue in the Human Exploration and Development of Space enterprise is cost effective mitigation of risk associated with ionizing radiation exposure. In order to estimate astronaut risk to GCR exposure and associated cancer risks and health hazards, it is necessary to do shield material studies. To determine an optimum radiation shield material it is necessary to understand nuclear interaction processes such as fragmentation and secondary particle production which is a function of energy dependent cross sections. This requires knowledge of material transmission characteristics either through laboratory testing or improved theoretical modeling. Here ion beam transport theory is of importance in that testing of materials in the laboratory environment generated by particle accelerators is a necessary step in materials development and evaluation for space use. The approximations used in solving the Boltzmann transport equation for the space setting are often not sufficient for laboratory work and those issues are a major emphasis of the present work.
Tweed, J.
Mechanical transport and porous media equivalence in anisotropic fracture networks
The objective of this work is to investigate the directional characteristics of hydraulic effective porosity in an effort to understand porous medium equivalence for continuous and discontinuous fracture systems. Continuous systems contain infinitely long fractures. Discontinuous systems consist of fractures with finite lengths. The distribution of apertures (heterogeneity) has a major influence on the degree of porous medium equivalence for distributed continuous and discontinuous systems. When the aperture distribution is narrow, the hydraulic effective porosity is slightly less than the total porosity for continuous systems, and greater than the rock effective porosity for discontinuous systems. However, when heterogeneity is significant, the hydraulic effective porosity is directionally dependent and greater than total porosity for both systems. Non-porous medium behavior ws found to differ for distributed continuous systems and for continuous systems with parallel sets. For the latter systems, hydraulic effective porosity abruptly decreases below total porosity in those particular directions where the hydraulic gradient and the orientation of a fracture set are orthogonal. The results for the continuous systems with parallel sets also demonstrate that a system that behaves like a continuum for fluid flux may not behave like a continuum for mechanical transport. 3 references, 13 figures.
Endo, H.K.; Witherspoon, P.A.
Synthesis and Optical Properties of Anisotropic Metal Nanoparticles
In this paper we overview our recent studies of anisotropic noble metal (e.g. gold and silver) nanoparticles, in which a combination of theory and experiment has been used to elucidate the extinction spectra of the particles, as well as information related to their surface enhanced Raman spectroscopy. We used wet-chemical methods to generate several structurally well-defined nanostructures other than solid
Encai Hao; George C. Schatz; Joseph T. Hupp
Anisotropic elastic properties of thermal spray coatings determined via resonant ultrasound spectroscopy
It is difficult to determine the elastic properties of thermal-sprayed ceramic and metallic coatings owing to the microstructural complexity, sample size and geometry, heterogeneity and availability of suitable techniques. Furthermore, the splat-based build-up of the coating results in transverse anisotropy in the elastic properties. This work reports on such anisotropic elastic properties of these coatings determined by resonant ultrasound spectroscopy.
Yang Tan; Amit Shyam; Wanhuk Brian Choi; Edgar Lara-Curzio; Sanjay Sampath
Anisotropic gold nanoparticles: synthesis, properties, applications, and toxicity.
Anisotropic gold nanoparticles (AuNPs) have attracted the interest of scientists for over a century, but research in this field has considerably accelerated since 2000 with the synthesis of numerous 1D, 2D, and 3D shapes as well as hollow AuNP structures. The anisotropy of these nonspherical, hollow, and nanoshell AuNP structures is the source of the plasmon absorption in the visible region as well as in the near-infrared (NIR) region. This NIR absorption is especially sensitive to the AuNP shape and medium and can be shifted towards the part of the NIR region in which living tissue shows minimum absorption. This has led to crucial applications in medical diagnostics and therapy ("theranostics"), especially with Au nanoshells, nanorods, hollow nanospheres, and nanocubes. In addition, Au nanowires (AuNWs) can be synthesized with longitudinal dimensions of several tens of micrometers and can serve as plasmon waveguides for sophisticated optical devices. The application of anisotropic AuNPs has rapidly spread to optical, biomedical, and catalytic areas. In this Review, a brief historical survey is given, followed by a summary of the synthetic modes, variety of shapes, applications, and toxicity issues of this fast-growing class of nanomaterials. PMID:24421264
Li, Na; Zhao, Pengxiang; Astruc, Didier
Influence of spherically anisotropic core on the optical properties of gold nanoshell
The optical properties of gold nanoshell with a core of spherically anisotropic material have been investigated by means of quasi-static theory. It is found with increasing the extent of anisotropy of the core that the surface plasmon resonance for the particle shows a red-shift and that the full width at half maximum (FWHM) of the plasmon resonance peak increases. The
D. J. Wu; X. J. Liu
Influence of spherically anisotropic core on the optical properties of gold nanoshell
NASA Astrophysics Data System (ADS)
The optical properties of gold nanoshell with a core of spherically anisotropic material have been investigated by means of quasi-static theory. It is found with increasing the extent of anisotropy of the core that the surface plasmon resonance for the particle shows a red-shift and that the full width at half maximum (FWHM) of the plasmon resonance peak increases. The local electric field of the particle with anisotropic core is found to be enhanced compared to that with isotropic core. The larger enhancement of the local electric field for the particle is observed in the particle with smaller extent of anisotropy.
Wu, D. J.; Liu, X. J.
Time-resolved measurements of the optical properties of fibrous media using the anisotropic diffusion equation
NASA Astrophysics Data System (ADS)
Transmittance and reflectance from spruce wood and bovine ligamentum nuchae as two different fibrous media are examined by time-of-flight spectroscopy for varying source detector separations and several orientations of the fibers in the sample. The anisotropic diffusion theory is used to obtain the absorption coefficient and the diffusion coefficients parallel and perpendicular to the fibers. The results are compared to those obtained with the isotropic diffusion theory. It is shown that for increasing source detector separations, the retrieved optical properties change as expected from Monte Carlo simulations performed in a previous study. This confirms that the anisotropic diffusion theory yields useful results for certain experimental conditions.
Simon, Emanuel; Krauter, Philipp; Kienle, Alwin
Properties of solid and gaseous hydrogen, based upon anisotropic pair interactions
NASA Technical Reports Server (NTRS)
Properties of H2 are studied on the basis of an analytic anisotropic potential deduced from atomic orbital and perturbation calculations. The low-pressure solid results are based on a spherical average of the anisotropic potential. The ground state energy and the pressure-volume relation are calculated. The metal-insulator phase transition pressure is predicted. Second virial coefficients are calculated for H2 and D2, as is the difference in second virial coefficients between ortho and para H2 and D2.
Etters, R. D.; Danilowicz, R.; England, W.
The generalized P{sub N} synthetic acceleration method for linear transport problems with highly anisotropic scattering
The diffusion synthetic acceleration (DSA) method has been known to be an effective tool for accelerating the iterative solution of transport equations with isotropic or mildly anisotropic scattering. However, the DSA method is not effective for transport equations that have strongly anisotropic scattering. A generalization of the modified DSA (MDSA) method is proposed that converges (clock time) faster than the MDSA method. This method is developed, the results of a Fourier analysis that theoretically predicts its efficiency are described, and numerical results that verify the theoretical prediction are presented.
Khattab, K.M. [Atomic Energy Commission, Damascus (Syrian Arab Republic)
Anisotropic properties of RFe_2Ge2 single crystals
NASA Astrophysics Data System (ADS)
We have grown RFe_2Ge2 single crystals for R = Y and ten members of the lanthanide series (Pr, Nd, Sm, Gd-Tm, Lu) using Sn flux as the solvent. The method yields clean, high quality crystal plates as evidenced by residual resistivities and RRR values in the range of 3-12 ?? cm and 20-70 respectively. The crystals are also virtually free of magnetic impurities or secondary phases, allowing the study of the intrinsic anisotropic magnetic behavior of each compound. Characterization was made with X-Ray diffraction, temperature and field dependent magnetization, specific heat and resistivity. Strong anisotropies arising mostly from CEF effects were observed for all magnetic rare earths except Gd. Anti-ferromagnetic ordering occurred at temperatures between 16.5 K (Nd) and 1.25 K (Ho) and for some members there are further well-defined metamagnetic transitions. The calculated effective moments per rare earth atom tend to be larger than the expected values at high temperatures while smaller at low temperatures, probably indicating temperature-dependent contributions of d-band electrons to the magnetic behavior. We acknowledge the help of R. A. Ribeiro and C. Petrovic in the X-Ray diffraction measurements, and K. Myers in the early development and characterization of the crystals. Ames Laboratory is operated for the US Department of Energy by Iowa State University under Contract No. W-7405-Eng-82. This work was supported by the Director for Energy Research, Office of Basic Energy Sciences.
Avila, M. A.; Bud'Ko, S. L.; Canfield, P. C.
Magnetic properties of electrons confined in an anisotropic cylindrical potential
NASA Astrophysics Data System (ADS)
In the present paper a theoretical model, describing the effects of external electric and magnetic fields on an electron confined in an anisotropic parabolic potential, is considered. The exact wave functions are used to calculate electron current and orbital magnetic dipole momentum for the single electron. Exact expressions, giving the force and energy of the dipole-dipole interaction, are also determined. Further, the system is coupled to a heat bath, and mean values and fluctuations of the magnetic dipole momentum, utilizing the canonical ensemble are calculated. Influences of the temperature, as well as the external magnetic field, expressed via the Larmor frequency are analyzed. We also include the dependencies of the magnetic dipole momentum and its fluctuations on the effective mass of the electron, considering some experimental values for low-dimensional systems, that are extensively studied for various applications in electronics. Our results suggest that the average momentum or its fluctuations are strongly related to the effective mass of the electron. Having on mind that parabolically shaped potentials have very wide area of application in the low-dimensional systems, such as quantum dots and rings, carbon nanotubes, we believe that the proposed model and the consequent analysis is of general importance, since it offers exact analytical approach.
Nedelkoski, Zlatko; Petreska, Irina
Phonon heat conduction in layered anisotropic crystals
NASA Astrophysics Data System (ADS)
The thermal properties of anisotropic crystals are of both fundamental and practical interest, but transport phenomena in anisotropic materials such as graphite remain poorly understood because solutions of the Boltzmann equation often assume isotropy. Here, we extend an analytic solution of the transient, frequency-dependent Boltzmann equation to highly anisotropic solids and examine its predictions for graphite. We show that this simple model predicts key results, such as long c -axis phonon mean free paths and a negative correlation of cross-plane thermal conductivity with in-plane group velocity, that were previously observed with computationally expensive molecular-dynamics simulations. Further, using our analytic solution, we demonstrate a method to reconstruct the anisotropic mean free path spectrum of crystals with arbitrary dispersion relations without any prior knowledge of their harmonic or anharmonic properties using observations of quasiballistic heat conduction. These results provide a useful analytic framework to understand thermal transport in anisotropic crystals.
Minnich, A. J.
Rotational positioning system adapted to atomic force microscope for measuring anisotropic surface properties
The diverse atomic configurations induce the anisotropic surface properties. For investigating anisotropic phenomena, we developed a rotational positioning system adapted to atomic force microscope (AFM). This rotational positioning system is applied to revolve the measured sample to defined angular direction, and it composed of an inertial rotational stepper and a visual angular measurement. The inertial rotational stepper with diameter 30 mm and height 7.6 mm can be easily attached to the AFM-system built in any general optical microscope. Based on a clearance less bearing and the inertial driving method, its bidirectional angular resolution reaches 0.005 deg. per step. For realizing a close-loop controlled angular positioning function, the visual measurement method is utilized. Through the feedback control, the angular positioning error is less than 0.01 deg. For verifying the system performance, we used it to investigate the anisotropic surface properties of graphite. Through a modified cantilever tip, the atomic-scale stick-slip, and the anisotropic friction phenomena can be distinctly detected.
Liao, H.-S.; Juang, B.-J. [Department of Mechanical Engineering, National Taiwan University, 10617, Taipei, Taiwan (China); Institute of Physics, Academia Sinica, 11529, Taipei, Taiwan (China); Chang, W.-C.; Lai, W.-C.; Chang, C.-S. [Institute of Physics, Academia Sinica, 11529, Taipei, Taiwan (China); Huang, K.-Y. [Department of Mechanical Engineering, National Taiwan University, 10617, Taipei, Taiwan (China)
Evolution, Interaction, and Intrinsic Properties of Dislocations in Intermetallics: Anisotropic 3D Dislocation Dynamics Approach
The generation, motion, and interaction of dislocations play key roles during the plastic deformation process of crystalline solids. 3D Dislocation Dynamics has been employed as a mesoscale simulation algorithm to investigate the collective and cooperative behavior of dislocations. Most current research on 3D Dislocation Dynamics is based on the solutions available in the framework of classical isotropic elasticity. However, due to some degree of elastic anisotropy in almost all crystalline solids, it is very necessary to extend 3D Dislocation Dynamics into anisotropic elasticity. In this study, first, the details of efficient and accurate incorporation of the fully anisotropic elasticity into 3D discrete Dislocation Dynamics by numerically evaluating the derivatives of Green's functions are described. Then the intrinsic properties of perfect dislocations, including their stability, their core properties and disassociation characteristics, in newly discovered rare earth-based intermetallics and in conventional intermetallics are investigated, within the framework of fully anisotropic elasticity supplemented with the atomistic information obtained from the ab initio calculations. Moreover, the evolution and interaction of dislocations in these intermetallics as well as the role of solute segregation are presented by utilizing fully anisotropic 3D dislocation dynamics. The results from this work clearly indicate the role and the importance of elastic anisotropy on the evolution of dislocation microstructures, the overall ductility and the hardening behavior in these systems.
Qian Chen
Synthetic acceleration methods for linear transport problems with highly anisotropic scattering
One of the iterative methods which is used to solve the discretized transport equation is called the Source Iteration Method (SI). The SI method converges very slowly for problems with optically thick regions and scattering ratios ({sigma}{sub s}/{sigma}{sub t}) near unity. The Diffusion-Synthetic Acceleration method (DSA) is one of the methods which has been devised to improve the convergence rate of the SI method. The DSA method is a good tool to accelerate the SI method, if the particle which is being dealt with is a neutron. This is because the scattering process for neutrons is not severely anisotropic. However, if the particle is a charged particle (electron), DSA becomes ineffective as an acceleration device because here the scattering process is severely anisotropic. To improve the DSA algorithm for electron transport, the author approaches the problem in two different ways in this thesis. He develops the first approach by accelerating more angular moments ({phi}{sub 0}, {phi}{sub 1}, {phi}{sub 2}, {phi}{sub 3},...) than is done in DSA; he calls this approach the Modified P{sub N} Synthetic Acceleration (MPSA) method. In the second approach he modifies the definition of the transport sweep, using the physics of the scattering; he calls this approach the Modified Diffusion Synthetic Acceleration (MDSA) method. In general, he has developed, analyzed, and implemented the MPSA and MDSA methods in this thesis and has shown that for a high order quadrature set and mesh widths about 1.0 cm, they are each about 34 times faster (clock time) than the DSA method. Also, he has found that the MDSA spectral radius decreases as the mesh size increases. This makes the MDSA method a better choice for large spatial meshes.
Khattab, K.M.
On-top ?-stacking of quasiplanar molecules in hole-transporting materials: inducing anisotropic carrier mobility in amorphous films.
Dimers of partially oxygen-bridged triarylamines were designed and synthesized as hole-transporting materials. X-ray structural analyses revealed that these compounds form on-top ?-stacking aggregates in the crystalline state. TRMC measurements showed that high levels of anisotropic charge transport were induced in the direction of the ?-stacking. Surprisingly, even in vacuum-deposited amorphous films, these compounds retained some of the face-on ?-stacking, thus facilitating an out-of-plane carrier mobility. PMID:24764307
Wakamiya, Atsushi; Nishimura, Hidetaka; Fukushima, Tatsuya; Suzuki, Furitsu; Saeki, Akinori; Seki, Shu; Osaka, Itaru; Sasamori, Takahiro; Murata, Michihisa; Murata, Yasujiro; Kaji, Hironori
Repeat-proteins films exhibit hierarchical anisotropic mechanical properties.
Complex hierarchical structures provide beneficial structure-property relationships that can be exploited for a variety of applications in engineering and biomedical fields. Here we report on molecular organization and resulting mechanical properties of self-assembled designed repeat-protein films. Wide-angle X-ray diffraction indicates the designed 18-repeat concensus tetratricopeptide repeat protein (CTPR18) orients normal to the casting surface, while small-angle measurements and electron microscopy show a through-plane transversely aligned laminar sheet-like morphology. Self-assembly is driven by the combination of CTPRs head-to-tail stacking and weak dipole-dipole interactions. We highlight the effect that this hierarchical structure has on the material's mechanical properties. We use nanoindentation and dynamic mechanical analysis to test the mechanical properties over multiple length scales, from the molecular level to the bulk. We find that morphology predictably affects the film's mechanics from the nano- to the macroscale, with the axial modulus values ranging from 2 to 5 GPa. The predictable nature of the structure-property relationship of CTPR proteins and their assemblies proves them a promising platform for material engineering. PMID:25642726
Carter, Nathan A; Grove, Tijana Zarkovic
Magnetic properties of anisotropic Sr-La-system ferrite magnets
This paper presents an experiment carried out to investigate the effect of La{sub 2}O{sub 3} addition to the magnetic and physical properties of strontium ferrite magnets. It was found that the La{sub 2}O{sub 3} addition to SrO {center dot} 6Fe{sub 2}O{sub 3} (stoichiometric composition) was very useful in stabilizing the magnetoplumbite structure and that these Sr-La-system ferrites had excellent properties as a permanenent magnet. Compositions were chosen according to the formula ((SrO){sub 1/n+1}(Fe{sub 2}O{sub 3}){sub n/n+1}){sub 100{minus}x}(La{sub 2}O{sub 3}){sub x}, where n was varied between 5.0 and 6.5, and x between 0 and 5.0. The optimum conditions for making magnets and some properties of typical specimens are discussed.
Yamamoto, H.; Nagakura, M. (School of Science and Technology, Meiji Univ., 1-1-1 Higashi-mita, Tama-ku, Kawasaki 214 (JP)); Terada, H. (College of Engineering, Chubu Univ., 1200 Matsumoto-cho, Kasugai 487 (JP))
Influence of spherically anisotropic core on the optical properties of gold nanoshell
The optical properties of gold nanoshell with a core of spherically anisotropic material have been investigated by means of\\u000a quasi-static theory. It is found with increasing the extent of anisotropy of the core that the surface plasmon resonance for\\u000a the particle shows a red-shift and that the full width at half maximum (FWHM) of the plasmon resonance peak increases. The
D. J. Wu; X. J. Liu
Anisotropic material properties of fused deposition modeling ABS
Rapid Prototyping (RP) technologies provide the ability to fabricate initial prototypes from various model materials. Stratasys Fused Deposition Modeling (FDM) is a typical RP process that can fabricate prototypes out of ABS plastic. To predict the mechanical behavior of FDM parts, it is critical to understand the material properties of the raw FDM process material, and the effect that FDM
Sung-Hoon Ahn; Michael Montero; Dan Odell; Shad Roundy; Paul K. Wright
Determination of aggregate physical properties and its effects on cross-anisotropic behavior of unbound aggregate materials
in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY August 2004 Major Subject: Civil Engineering DETERMINATION OF AGGREGATE PHYSICAL PROPERTIES AND ITS EFFECT ON CROSS-ANISOTROPIC BEHAVIOR OF UNBOUND AGGREGATE... of Department) August 2004 Major Subject: Civil Engineering iii ABSTRACT Determination of Aggregate Physical Properties and Its Effect on Cross-Anisotropic Behavior of Unbound Aggregate Materials. (August 2004) Sung-Hee Kim, B.S., Inha University...
Kim, Sung-Hee
Anisotropic magnetic properties of dysprosium iron garnet (DyIG)
The magnetic properties of dysprosium iron garnet (DyIG) have been studied by performing high resolution powder neutron diffraction experiments and high dc fields magnetizations on single crystals. Among all the reflections (hkl) indexed in the nuclear cubic space group (CSG) Ia bar 3 d with h+k+l=2n and k=[000], the superstructure lines (hkl)* forbidden by the symmetry (222)* and (622)* are
M. Lahoubi; W. Younsi; M.-L. Soltani; B. Ouladdiaf
Analytical Approach to Predict Anisotropic Material Properties from Cup Drawings
Typical beverage can alloys have limited elongation (about 3¢5%) under uniaxial tension. However, in order to obtain correct\\u000a material properties, it is recommended to have elongations over 10 percent. Thus, it is very difficult to predict stable r-value\\u000a and stress directionalities experimentally, which are essential for FE simulation of rigid-packing sheet forming operation.\\u000a An innovative simplified analytical approach that relates
J. W. Yoon; R. E. Dick; F. Barlat
Anisotropic transport properties of ferromagnetic-superconducting bilayers
vortex velocit frequency, and higher harmonics of the vortex oscillator DOI: 10.1103/PhysRevB.69.132501 PAC The interest in heterogeneous ferromagnetic-super- conducting systems has grown rapidly in recent years. This interest stems not only from...-superconducting bilayers alery L. Pokrovsky1,2 y, College Station, Texas 77843-4242, USA l Physics, Moscow, Russia ; published 5 April 2004! in a superconducting thin film separated by a thin n alternating stripe structure for both FM and super- . Rev. Lett. 88...
Kayali, MA; Pokrovsky, Valery L.
Characterising the Anisotropic Mechanical Properties of Excised Human Skin
The mechanical properties of skin are important for a number of applications including surgery, dermatology, impact biomechanics and forensic science. In this study we have investigated the influence of location and orientation on the deformation characteristics of 56 samples of excised human skin. Uniaxial tensile tests were carried out at a strain rate of 0.012s$^{-1}$ on skin from the back. Digital Image Correlation was used for 2D strain measurement and a histological examination of the dermis was also performed. The mean ultimate tensile strength (UTS) was 21.6$\\pm$8.4MPa, the mean failure strain 54$\\pm$17%, the mean initial slope 1.18$\\pm$0.88MPa, the mean elastic modulus 83.3$\\pm$34.9MPa and the mean strain energy was 3.6$\\pm$1.6MJ/m$^3$. A multivariate analysis of variance has shown that these mechanical properties of skin are dependent upon the orientation of Langer lines (P$skin using a structural constitutive model.
Aisling Ni Annaidh; Karine Bruyere; Michel Destrade; Michael D. Gilchrist; Melanie Ottenio
Analysis of anisotropic viscoelastoplastic properties of cortical bone tissues.
Bone fractures affect the health of many people and have a significant social and economic effect. Often, bones fracture due to impacts, sudden falls or trauma. In order to numerically model the fracture of a cortical bone tissue caused by an impact it is important to know parameters characterising its viscoelastoplastic behaviour. These parameters should be measured for various orientations in a bone tissue to assess bone's anisotropy linked to its microstructure. So, the first part of this study was focused on quantification of elastic-plastic behaviour of cortical bone using specimens cut along different directions with regard to the bone axis-longitudinal (axial) and transverse. Due to pronounced non-linearity of the elastic-plastic behaviour of the tissue, cyclic loading-unloading uniaxial tension tests were performed to obtain the magnitudes of elastic moduli not only from the initial loading part of the cycle but also from its unloading part. Additional tests were performed with different deformation rates to study the bone's strain-rate sensitivity. The second part of this study covered creep and relaxation properties of cortical bone for two directions and four different anatomical positions-anterior, posterior, medial and lateral-to study the variability of bone's properties. Since viscoelastoplasticity of cortical bone affects its damping properties due to energy dissipation, the Dynamic Mechanical Analysis (DMA) technique was used in the last part of our study to obtain magnitudes of storage and loss moduli for various frequencies. Based on analysis of elastic-plastic behaviour of the bovine cortical bone tissue, it was found that magnitudes of the longitudinal Young's modulus for four cortical positions were in the range of 15-24 GPa, while the transversal modulus was lower--between 10 and 15 GPa. Axial strength for various anatomical positions was also higher than transversal strength with significant differences in magnitudes for those positions. Quantitative data obtained in creep and relaxation tests exhibited no significant position-specific differences. DMA results demonstrated relatively low energy-loss capability due to viscosity of bovine cortical bone that has a loss factor in the range of 0.035-0.1. PMID:21565728
Abdel-Wahab, Adel A; Alam, Khurshid; Silberschmidt, Vadim V
Synthesis and colloidal properties of anisotropic hydrothermal barium titanate
NASA Astrophysics Data System (ADS)
Nanoparticles of high dielectric constant materials, especially BaTiO3, are required to achieve decreased layer thickness in multilayer ceramic capacitors (MLCCs). Tabular metal nanoparticles can produce thin metal layers with low surface roughness via electrophoretic deposition (EPD). To achieve similar results with dielectric layers requires the synthesis and dispersion of tabular BaTiO3 nanoparticles. The goal of this study was to investigate the deposition of thin BaTiO3 layers using a colloidal process. The synthesis, interfacial chemistry and colloidal properties of hydrothermal BaTiO3 a model particle system, was investigated. After characterization of the material system particulates were deposited to form thin layers using EPD. In the current study, the synthesis of BaTiO3 has been investigated using a hydrothermal route. TEM and AFM analyses show that the synthesized particles are single crystal with a majority of the particle having a <111> zone axis and {111} large face. The particles have a median thickness of 5.8 +/- 3.1 nm and face diameter of 27.1 +/- 12.3 nm. Particle growth was likely controlled by the formation of {111} twins and the synthesis pH which stabilizes the {111} face during growth. With limited growth in the <111> direction, the particles developed a plate-like morphology. Physical property characterization shows the powder was suitable for further processing with high purity, low hydrothermal defect concentration, and controlled stoichiometry. TEM observations of thermally treated powders indicate that the particles begin to loose the plate-like morphology by 900 ░C. The aqueous passivation, dispersion, and doping of nanoscale BaTiO 3 powders was investigated. Passivation BaTiO3 was achieved through the addition of oxalic acid. The oxalic acid selectively adsorbs onto the particle surface and forms a chemically stable 2-3 nm layer of barium oxalate. The negative surface charge of the oxalate effectively passivated the BaTiO3 providing a surface suitable for the use of a cationic dispersant, polyethylenimine (PEI). Rheological properties indicate the presence of an oxalate-PEI interaction which can be detrimental to dispersion. With a better understanding of the aqueous surface chemistry of BaTiO3 the surface chemistry was manipulated to control the adsorption of aqueous soluble complexes of Co, Nb, and Bi, three common dopants in the processing of BaTiO3 Surface charge, TEM, and EDS analysis showed that while in suspension the dopants selectively absorbed onto the particle surface forming an engineered coating. (Abstract shortened by UMI.)
Yosenick, Timothy James
Ground-state correlation properties of charged bosons trapped in strongly anisotropic harmonic potentials
We study systems of a few charged bosons contained within a strongly anisotropic harmonic trap. A detailed examination of the ground-state correlation properties of two-, three-, and four-particle systems is carried out within the framework of the single-mode approximation of the transverse components. The linear correlation entropy of the quasi-1D systems is discussed in dependence on the confinement anisotropy and compared with a strictly 1D limit. Only at weak interaction the correlation properties depend strongly on the anisotropy parameter.
Przemyslaw Koscik; Anna Okopinska
A Numerical Model of Anisotropic Mass Transport Through Grain Boundary Networks
NASA Astrophysics Data System (ADS)
Tin (Sn) thin films are commonly used in electronic circuit applications as coatings on contacts and solders for joining components. It is widely observed, for some such system, that whiskers---long, thin crystalline structures---emerge and grow from the film. The Sn whisker phenomenon has become a highly active research area since Sn whiskers have caused a large amount of damage and loss in manufacturing, military, medical and power industries. Though lead (Pb) addition to Sn has been used to solve this problem for over five decades, the adverse environmental and health effects of Pb have motivated legislation to severely constrain Pb use in society. People are researching and seeking the reasons which cause whiskers and corresponding methods to solve the problem. The contributing factors to cause a Sn whisker are potentially many and much still remains unknown. Better understanding of fundamental driving forces should point toward strategies to improve (a) the accuracy with which we can predict whisker formation, and (b) our ability to mitigate the phenomenon. This thesis summarizes recent important research achievements in understanding Sn whisker formation and growth, both experimentally and theoretically. Focus is then placed on examining the role that anisotropy in grain boundary diffusivity plays in determining whisker characteristics (specifically, whether they form and, if so, where on a surface). To study this aspect of the problem and to enable future studies on stress driven grain boundary diffusion, this thesis presents a numerical anisotropic mass transport model. In addition to presenting details of the model and implementation, model predictions for a set of increasingly complex grain boundary networks are discussed. Preliminary results from the model provide evidence that anisotropic grain boundary diffusion may be a primary driving mechanism in whisker formation.
Wang, Yibo
Anisotropic magnetic properties and domain structure in Fe-3%Si (110) steel sheet
NASA Astrophysics Data System (ADS)
The understanding of the anisotropic magnetization mechanism in 3%Si steel is relevant to both the design of the electrotechnical applications of 3%Si steel and the fundamental materials science of soft magnetic materials. In the present study, the relation between the anisotropic magnetic properties and the magnetization curves of 3%Si-Fe (110) steel sheet for various directions of axial magnetization was studied taking into account the domain structure. The magnetic loss of the (110) steel sheet were measured in an applied field at an angle ? to the [001] axis. The angle ? was varied from 0░ to 90░, in steps of 15░. In off-[001] directions, the magnetization resulted in a highly structured domain pattern and domain wall displacements, which could be related to the shape of the magnetization curves. The magnetization curves could be divided in four segments, with each segment related to a specific domain structure.
Shin, Sunmi; Schaefer, Rudolf; DeCooman, B. C.
The report gives results of an evaluation of transport properties of 1, 1, 1, 2, 3, 3-hexafluoropropane (HFC-236ea), with liquid viscosity and thermal conductivity being the two main transport properties of interest. In addition, the specific heat and density of refrigerant/lubri...
The report gives results of an evaluation of transport properties of 1,1,1,2,3,3,-hexafluoropropane (HFC-236ea), with liquid viscosity and thermal conductivity being the two main transport properties of interest. In addition, the specific heat and density of refrigerant/lubrican...
Optical Properties of Anisotropic Polycrystalline Ce+3 activated LSO
Polycrystalline cerium activated lutetium oxyorthosilicate (LSO:Ce) is highly desirable technique to make cost effective and highly reproducible radiation detectors for medical imaging. In this article methods to improve transparency in polycrystalline LSO:Ce were explored. Two commercially available powders of different particulate sizes (average particle size 30 and 1500 nm) were evaluated for producing dense LSO:Ce by pressure assisted densification routes, such as hot pressing and hot isostatic pressing. Consolidation of the powders at optimum conditions produced three polycrystalline ceramics with average grain sizes of 500 nm, 700 and 2000 nm. Microstructural evolution studies showed that for grain sizes larger than 1 Ąm, anisotropy in thermal expansion coefficient and elastic constants of LSO, resulted in residual stress at grain boundaries and triple points that led to intragranular microcracking. However, reducing the grain size below 1 Ąm effectively avoids microcracking, leading to more favorable optical properties. The optical scattering profiles generated by a Stover scatterometer, measured by a He-Ne laser of wavelength 633 nm, showed that by reducing the grain size from 2 Ąm to 500 nm, the in-line transmission increased by a factor of 103. Although these values were encouraging and showed that small changes in grain size could increase transmission by almost 3 orders of magnitude, even smaller grain sizes need to be achieved in order to get truly transparent material with high in-line transmission. PMID:23505329
Roy, Sudesna; Lingertat, Helmut; Brecher, Charles; Sarin, Vinod
Monte Carlo inversion of ultrasonic array data to map anisotropic weld properties.
The quality of an ultrasonic array image depends on accurate information about its acoustic properties. Inaccurate acoustic properties can cause image degradation such as blurring, mislocation of reflectors, and the introduction of artifacts. In this paper, for the specific case of an inhomogeneous and anisotropic austenitic steel weld, Monte Carlo Markov Chain (MCMC) inversion is used to estimate unknown acoustic properties from array data. The approach uses active beacons that transmit ultrasound through the anisotropic weld; the ultrasound is then captured by a receiving array. A forward model of the ultrasonic array data is then optimized with respect to the experimental data using an MCMC inversion. The result of this process is the extraction of a material property map that describes the anisotropy distribution within the weld region. These extracted material properties are then used within an imaging algorithm-the total focusing method in this paper-to produce autofocused images. This MCMC inversion approach is first applied to simulated data to test the convergence, robustness, and accuracy of the method and its implementation. The extracted weld map is used to show improved imaging of defects within the weld, relative to an image formed assuming a constant velocity. Finally, the MCMC inversion approach is used on experimental data from a 110-mm-thick steel plate containing an austenitic weld. Here the extracted weld map is used to show that defect location errors of greater than 5 mm are reduced to around 2 mm when the extracted weld map is used. PMID:23192812
Zhang, Jie; Hunter, Alan; Drinkwater, Bruce W; Wilcox, Paul D
Effect of rare-earth oxides on the magnetic properties of anisotropic barium ferrites
The effect of rare-earth oxides on the properties of anisotropic barium ferrites has been studied by x-ray structural and M÷ssbauer methods. Additions of SrCO3, as well as SrCO3 and La2O3, SrCO3 and Pr6O11, SrCO3 and Nd2O3, SrCO3 and Sm2O3 in amounts of 7.5 mole % Sr and 10 mole % rare-earth element to grade-A barium powder results in the substitution
P. P. Kirpichok; N. B. Voronina; A. F. Sitnikov; V. Ya. Garmash
Caustic aluminate: physical, thermodynamic, and transport properties
Experimental data in the literature on the physical, thermodynamic, and transport properties of caustic aluminate and its precipitate, hydrargillite, are summarized. An analytical expression for the vapor pressure of water over such solutions is derived.
Homsy, R.V.
Predicted transport properties of liquid plutonium
The fluid-phase transport properties, diffusivity and viscosity, are calculated by equilibrium and nonequilibrium techniques for plutonium, whose interatomic interactions are described by the modified embedded-atom method. The transport coefficients are evaluated at zero pressure, for temperatures between 950 K and 1300 K. We find the calculated viscosity to be noticeably higher than experiment, while the structure of liquid Pu appears
F. J. Cherne; M. I. Baskes; B. L. Holian
Imaging Anisotropic Elastic Properties of an Orthotropic Paper Sheet Using Photorefractive Dynamic Holography
An important material property in the paper industry is the anisotropic stiffness distribution due to the fibrous microstructure of paper and to processing procedures. Ultrasonic methods offer a means of determining the stiffness of sheets of paper from the anisotropic propagation characteristics of elastic Lamb waves along the machine direction and the cross direction. That is, along and perpendicular to the direction of paper production. Currently, piezoelectric ultrasonic methods are employed in the industry to measure the elastic polar diagram of paper through multiple contacting measurements made in all directions. This paper describes a new approach utilizing the INEEL Laser Ultrasonic Camera to provide a complete image of the elastic waves traveling in all directions in the plane of the paper sheet. This approach is based on optical dynamic holographic methods that record the out of plane ultrasonic motion over the entire paper surface simultaneously without scanning. The full-field imaging technique offers great potential for increasing the speed of the measurement and it ultimately provides a substantial amount of information concerning local property variations and flaws in the paper. This report shows the success of the method and the manner in which it yields the elastic polar diagram for the paper from the dispersive flexural or antisymmetric Lamb wave.
Telschow, Kenneth Louis; Deason, Vance Albert
Anisotropic elastic properties of thermal spray coatings determined via resonant ultrasound spectroscopy
The determination of elastic properties of plasma-sprayed ceramic and metallic coatings is difficult due to their complex microstructure, which involves a myriad array of pores, interfaces and other defects. Furthermore, the splat-based build-up of the coating results in transverse anisotropy in the elastic properties. In this paper, we report on the anisotropic elastic properties of these coatings determined by resonant ultrasound spectroscopy (RUS). This approach along with the analysis presented enables, for the first time, the determination of elastic properties as a function of direction and temperature for these complex systems with concomitant implications for design. The coating systems investigated included plasma-sprayed yttria-stabilized zirconia (YSZ) and nickel. An additional nickel coating deposited by high-velocity oxygen-fuel process was investigated and its elastic properties were compared to those of plasma-sprayed nickel. Average Young s moduli of the coatings were independently measured by using the instrumented indentation method. The elastic properties determined from the RUS and indentation methodologies allowed description of the microstructure elastic property relationships in the coatings.
Tan, Yang [Stony Brook University (SUNY); Shyam, Amit [ORNL; Choi, Wanhuk Brian [Stony Brook University (SUNY); Lara-Curzio, Edgar [ORNL; Sampath, Sanjay [Stony Brook University (SUNY)
The properties of MHD waves and instabilities in solar plasmas with anisotropic temperature and thermal fluxes
NASA Astrophysics Data System (ADS)
As confirmed by observations, the temperature anisotropy relative to the magnetic field and the thermal fluxes are typical characteristics of the collisionless and magnetized plasma of the solar corona and solar wind. The properties of such plasma are described in terms of the anisotropic magnetohydrodynamics based on the kinetic equation under the 16-moment approximation. MHD waves and instabilities in the collisionless solar plasma have been analyzed under the aforementioned approximation taking into account the anisotropy of the plasma pressure along and across the magnetic field and the thermal flux along the field. It is established that the thermal flux results in the asymmetry of phase velocities of the compressible wave modes with respect to the outer magnetic field, in a strong interaction between the modes (particularly, between the retrograde modes propagating against the magnetic field), and in oscillatory in-stability of these modes. The thresholds of the mirror and fire-hose instabilities coincide with their kinetic expressions; the increments coincide qualitatively. At a certain propagation angle, the resonance interaction of three retrograde modes (fast sound, slow magnetosound, and slow sound ones) under the occurrence conditions of the classical aperiodic fire-hose instability gives rise to the oscillatory "fire-hose" instability of compressible modes, whose maximum increment may exceed the maximum increment of the classical fire-hose instability. A good agreement of the results obtained in terms of anisotropic MHD with the low-frequency limit of the kinetic description allows us to consider the applied approximation adequate for the description of large-scale dynamics of collisionless anisotropic solar plasma and to use it in the study of waves and instabilities in magnetic tubes and other magnetic features in the solar corona, magnetic reconnection, etc.
Kuznetsov, Vladimir; Dzhalilov, Namig
Transport properties of manganates with giant magnetoresistance
A short review of transport properties related to the giant magnetoresistance in perovskite-type double-exchange ferromagnets is presented. The paper deals with the essential experimental results for the understanding of the large MR effect, which is based on the correlation of electric and magnetic properties. These experiments are mainly the dependence of the resistivity on temperature and magnetic field, and also
R. von Helmolt; J. Wecker; K. Samwer; K. Bõrner
Transport properties of fluorite oxides
Theoretical aspects of ionic transport have been revised from the phenomenological and atomistic points of view. Experimental results on ionic conductivity and diffusion coefficient for the important oxide electrolytes are discussed. Compositional dependence of ionic conductivity of the electrolytes have been explained on the basis of both short and long range interactions between the oxygen vacancies and the impurity cations.
E. C. Subbarao; H. S. Maiti
Application of differential effective medium, magnetic pore fabric analysis, and X-ray microtomography to calculate elastic properties of porous and anisotropic rock aggregates
A differential effective medium (DEM) model is used to predict elastic properties for a set of porous and anisotropic aggregates, comprised of mixtures of calcite and muscovite. The DEM takes into consideration an anisotropic background medium with triclinic or higher symmetry, in which inclusions of idealized ellipsoidal shape are added incrementally. In general, the calculated elastic properties of a solid
Bjarne S. G. Almqvist; David Mainprice; Claudio Madonna; Luigi Burlini; Ann M. Hirt
Structure, thermodynamics, mechanical properties and glassy dynamics in anisotropic polymeric materials
Anisotropic polymeric materials are ubiquitous. They can form via self assembly, external mechanical deformation or by geometric confinement. Important examples of anisotropic polymeric materials include liquid crystalline polymers and elastomers, amorphous rubber networks, confined films and grafted polymer brushes. A common feature of these materials is the anisotropic conformation of the constituent polymer chains which leads to significant modification of
Folusho Taiwo Oyerokun
Single-crystal growth and anisotropic magnetic properties of nonstoichiometric three-layer sodium cobalt oxides
Large single crystals of {alpha}-Na{sub x}CoO{sub 2} (x=0.91, 0.92, and 0.93) have been successfully fabricated by using the traveling solvent floating zone method. Details on the crystal growth are discussed. The crystal structures were characterized using powder x-ray diffraction and Rietveld refinement. The magnetic susceptibility measurements show that the magnetic properties depend strongly on x. The compound was found to be antiferromagnetic at T{sub N}{approx_equal}20 K for x=0.91 and x=0.92, and paramagnetic for x=0.93. The in-plane and out-of-plane anisotropies were observed for the x=0.91 crystals. In addition, the derived anisotropic g-factor ratios (g{sub ab}/g{sub c}) from the anisotropic susceptibility along H parallel ab and H parallel c decreased significantly as the sodium composition increased from x=0.91 to x=0.93.
Chen, D. P. [Institute for Superconducting and Electronic Materials, University of Wollongong, New South Wales 2500 (Australia); Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart (Germany); Wang, Xiaolin; Dou, S. X. [Institute for Superconducting and Electronic Materials, University of Wollongong, New South Wales 2500 (Australia); Lin, C. T. [Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart (Germany)
Study of the Anisotropic Properties of Argillite Under Moisture and Mechanical Loads
NASA Astrophysics Data System (ADS)
Due to various factors, such as sedimentation, layered morphology of clay minerals, in situ stress, etc., argillite rocks often exhibit anisotropic behavior. In order to study the anisotropic properties of the Callovo-Oxfordian (COx) argillite of the Meuse-Haute-Marne site in France considered as a possible host rock for high-level radioactive nuclear waste repository, a series of tests including uniaxial compression and dehydration and hydration at different constant applied stress levels are carried out. In this study, a specific setup combining moisture and mechanical loading with optical observation is used and it allows to continuously capture surface images from which the full-field strains are determined by using Digital Image Correlation techniques. The results show evidence of the mechanical and hydric anisotropy of the material. The anisotropy parameters are identified, assuming the studied argillite as transversely isotropic. The shrinkage and swelling depend on the applied stress and the angle with respect to the vertical direction of the mechanical load and the stratification plane, and this dependence is quantified. The non-linearity and the hysteresis observed during dehydration and hydration cycles are discussed.
Yang, Diansen; Chanchole, Serge; Valli, Pierre; Chen, Liufeng
Oriented Morphology and Anisotropic Transport in Uniaxially Stretched Perfluorosulfonate Ionomer Membranes
Relations between morphology and transport sensitively govern proton conductivity in perfluorsulfonate ionomers (PFSIs) and thus determine useful properties of these technologically important materials. In order to understand such relations, we have conducted a broad systematic study of H{sup +}-form PFSI membranes over a range of uniaxial extensions and water uptakes. On the basis of small-angle X-ray scattering (SAXS) and {sup 2}H NMR spectroscopy, uniaxial deformation induces a strong alignment of ionic domains along the stretching direction. We correlate ionic domain orientation to transport using pulsed-field-gradient {sup 1}H NMR measurements of water diffusion coefficients along the three orthogonal membrane directions. Intriguingly, we observe that uniaxial deformation enhances water transport in one direction (parallel-to-draw direction) while reducing it in the other two directions (two orthogonal directions relative to the stretching direction). We evaluate another important transport parameter, proton conductivity, along two orthogonal in-plane directions. In agreement with water diffusion experiments, orientation of ionic channels increases proton conduction along the stretching direction while decreasing it in the perpendicular direction. These findings provide valuable fodder for optimal application of PFSI membranes as well as for the design of next generation polymer electrolyte membranes.
J Park; J Li; G Divoux; L Madsen; R Moore
Probing anisotropic surface properties and interaction forces of chrysotile rods by atomic force microscopy and rheology.
Understanding the surface properties and interactions of nonspherical particles is of both fundamental and practical importance in the rheology of complex fluids in various engineering applications. In this work, natural chrysotile, a phyllosilicate composed of 1:1 stacked silica and brucite layers which coil into cylindrical structure, was chosen as a model rod-shaped particle. The interactions of chrysotile brucite-like basal or bilayered edge planes and a silicon nitride tip were measured using an atomic force microscope (AFM). The force-distance profiles were fitted using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which demonstrates anisotropic and pH-dependent surface charge properties of brucite-like basal plane and bilayered edge surface. The points of zero charge (PZC) of the basal and edge planes were estimated to be around pH 10-11 and 6-7, respectively. Rheology measurements of 7 vol % chrysotile (with an aspect ratio of 14.5) in 10 mM NaCl solution showed pH-dependent yield stress with a local maximum around pH 7-9, which falls between the two PZC values of the edge and basal planes of the rod particles. On the basis of the surface potentials of the edge and basal planes obtained from AFM measurements, theoretical analysis of the surface interactions of edge-edge, basal-edge, and basal-basal planes of the chrysotile rods suggests the yield stress maximum observed could be mainly attributed to the basal-edge attractions. Our results indicate that the anisotropic surface properties (e.g., charges) of chrysotile rods play an important role in the particle-particle interaction and rheological behavior, which also provides insight into the basic understanding of the colloidal interactions and rheology of nonspherical particles. PMID:25115179
Yang, Dingzheng; Xie, Lei; Bobicki, Erin; Xu, Zhenghe; Liu, Qingxia; Zeng, Hongbo
Anisotropic Hc 2, thermodynamic and transport measurements, and pressure dependence of Tc in K2Cr3As3 single crystals
NASA Astrophysics Data System (ADS)
We present a detailed study of single crystalline K2Cr3As3 and analyze its thermodynamic and transport properties, anisotropic Hc 2(T ) , and initial pressure dependence of Tc. In zero field, the temperature-dependent resistivity is metallic. Deviation from a linear temperature dependence is evident below 100 K and a T3 dependence is roughly followed from just above Tc (ś10 K ) to ś40 K . Anisotropic Hc 2(T ) data were measured up to 140 kOe with field applied along and perpendicular to the rodlike crystals. For the applied field perpendicular to the rod, Hc 2(T ) is linear with a slope ś-70 kOe/K. For field applied along the rod, the slope is about -120 kOe/K below 70 kOe. Above 70 kOe, the magnitude of the slope decreases to ś-70 kOe/K. The electronic specific heat coefficient ? , just above Tc, is 73 mJ/mol K2; the Debye temperature ?D is 220 K. The specific heat jump at the superconducting transition ? C ś2.2 ? Tc . Finally, for hydrostatic pressures up to ś7 kbar, Tc decreases under pressure linearly at a rate of -0.034 K /kbar .
Kong, Tai; Bud'ko, Sergey L.; Canfield, Paul C.
A note on conservative transport in anisotropic, heterogeneous porous media in the presence of small-amplitude transients
The late-time macrodispersion coefficients are obtained for the case of flow in the presence of a small-scale deterministic transient in a three-dimensional anisotropic, heterogeneous medium. The transient is assumed to affect only the velocity component transverse to the mean flow direction and to take the form of a periodic function. For the case of a highly stratified medium, these late-time macrodispersion coefficients behave largely as the standard coefficients used in the transport equation. Only in the event that the medium is isotropic is it probable that significant deviations from the standard coefficients would occur.
Naff, R.L.
An asymptotic-preserving semi-Lagrangian algorithm for the time-dependent anisotropic heat transport equation
NASA Astrophysics Data System (ADS)
We propose a semi-Lagrangian numerical algorithm for a time-dependent, anisotropic temperature transport equation in magnetized plasmas in regimes with negligible variation of the magnitude of the magnetic field B along field lines. The approach is based on a formal integral solution of the parallel (i.e., along the magnetic field) transport equation with sources. While this study focuses on a Braginskii (local) heat flux closure, the approach is able to accommodate nonlocal parallel heat flux closures as well. The numerical implementation is based on an operator-split formulation, with two straightforward steps: a perpendicular transport step (including sources), and a Lagrangian (field-line integral) parallel transport step. Algorithmically, the first step is amenable to the use of modern iterative methods, while the second step has a fixed cost per degree of freedom (and is therefore algorithmically scalable). Accuracy-wise, the approach is free from the numerical pollution introduced by the discrete parallel transport term when the perpendicular to parallel transport coefficient ratio ??/?? becomes arbitrarily small, and is shown to capture the correct limiting solution when ?=??L?2/??L?2 ?0 (with L?, L? the parallel and perpendicular diffusion length scales, respectively). Therefore, the approach is asymptotic-preserving. We demonstrate the performance of the scheme with several numerical experiments with varying magnetic field complexity in two dimensions, including the case of heat transport across a magnetic island in cylindrical geometry in the presence of a large guide field.
Chac¾n, L.; del-Castillo-Negrete, D.; Hauck, C. D.
Critical evaluation of known bone material properties to realize anisotropic FE-simulation of the proximal femur
Purpose: In a meta-analysis of the literature we evaluated the present knowledge of the material properties of cortical and cancellous bone to answer the question whether the available data are sufficient to realize anisotropic finite element (FE)-models of the proximal femur. Material and method: All studies that met the following criteria were analyzed: Young's modulus, tensile, compressive and torsional strengths,
Dieter Christian Wirtz; Norbert Schiffers; Thomas Pandorf; Klaus Radermacher; Dieter Weichert; Raimund Forst
Material properties of anisotropic conductive films (ACFs) and their flip chip assembly reliability in NAND flash memory applications
In this paper, the material properties of anisotropic conductive films (ACFs) and ACF flip chip assembly reliability for a NAND flash memory application were investigated. Measurements were taken on the cur- ing behaviors, the coefficient of thermal expansion (CTE), the modulus, the glass transition temperature (Tg), and the die adhesion strength of six types of ACF. Furthermore, the bonding processes
Kyung-Woon Jang; Chang-Kyu Chung; Woong-Sun Lee; Kyung-Wook Paik
Effect of rare-earth oxides on the magnetic properties of anisotropic barium ferrites
NASA Astrophysics Data System (ADS)
The effect of rare-earth oxides on the properties of anisotropic barium ferrites has been studied by x-ray structural and M÷ssbauer methods. Additions of SrCO3, as well as SrCO3 and La2O3, SrCO3 and Pr6O11, SrCO3 and Nd2O3, SrCO3 and Sm2O3 in amounts of 7.5 mole % Sr and 10 mole % rare-earth element to grade-A barium powder results in the substitution of barium ions by Sr and rare-earth ions; consequently, the energy of magnetic anisotropy changes and the technically important parameters Br and (BH)max increase.
Kirpichok, P. P.; Voronina, N. B.; Sitnikov, A. F.; Garmash, V. Ya.
Graphene aerogel/epoxy composites with exceptional anisotropic structure and properties.
3D interconnected graphene aerogels (GAs) are prepared through one-step chemical reduction and rational assembly of graphene oxide (GO) sheets, so that the difficulties to uniformly disperse the individual graphene sheets in the polymer matrixes are avoided. Apart from ultralow density, high porosity, high electrical conductivity, and excellent compressibility, the resulting GAs possess a cellular architecture with a high degree of alignment when the graphene content is above a threshold, ?0.5 wt %. The composites prepared by infiltrating GA with epoxy resin present excellent electrical conductivities, together with high mechanical properties and fracture toughness. The unusual anisotropic structure gives rise to ?67% and ?113% higher electrical conductivity and fracture toughness of the composites, respectively, in the alignment direction than that transverse to it. PMID:25691257
Wang, Zhenyu; Shen, Xi; Akbari Garakani, Mohammad; Lin, Xiuyi; Wu, Ying; Liu, Xu; Sun, Xinying; Kim, Jang-Kyo
Geomechanical and anisotropic acoustic properties of Lower Jurassic Posidonia shales from Whitby (UK)
NASA Astrophysics Data System (ADS)
The Posidonia Shale Formation (PSF) is one of the possible resource shales for unconventional gas in Northern Europe and currently is of great interest to hydrocarbon exploration and production. Due to low permeability of shales, economically viable production requires hydraulic fracturing of the reservoir. The design of hydrofractures requires an estimate of stress state within the reservoir and geomechanical properties such as Young's modulus and Poisson's ratio. Shales are often highly anisotropic and the models which neglect shale anisotropy may fail to predict the behaviour of hydrofractures. Seismic attenuation anisotropy, on the other hand, can play a key role in quantitative rock characterization. Where the attenuation anisotropy can potentially be linked to anisotropic permeability of shales, its fluid/gas saturation and preferred development of anisotropic fracture orientations. In this research, by utilizing the so-called Thomsen's notations, the elastic anisotropy of our (fractured and unfractured) shales has been investigated using a pulse transmission technique in the ultrasonic frequency range (0.3-1 MHz). Assuming transverse isotropy of the shales, and taking the axis x3 as the axis of rotational symmetry, directional Young's moduli and Poisson's ratios were obtained. The Young's modulus measured parallel to bedding (E1) is found to be larger than the Young's modulus measured orthogonal to bedding (E3). In case of the Poisson's ratios, we found that ?31 is larger than ?12, where ?ijrelates elastic strain in xj direction to stress applied in xi direction. Finally, attenuation anisotropy in dry and layer-parallel fractured Posidonia shale samples has been studied in the same frequency range. The attenuation of compressional (QP-1) and shear (QS-1) waves increases substantially with a macro (or wavelength) fracture introduction, especially for P and S waves propagating orthogonal to the bedding. In non-fractured and fractured dry shales, QP-1 is always larger than QS-1. This inequality was also found for the fractured shale using different fluids (water, oil) on the fracture surface. A high-viscosity fluid decreases QP-1 and QS-1 in both (orthogonal and parallel to the bedding) directions, and the QP-1 to QS-1 ratio decreases with the increase of fluid viscosity.
Zhubayev, Alimzhan; Houben, Maartje; Smeulders, David; Barnhoorn, Auke
Spin transport properties of a Dresselhaus-polygonal quantum ring
NASA Astrophysics Data System (ADS)
We propose a theoretical method to investigate the effect of the Dresselhaus spin¢orbit coupling (DSOC) on the spin transport properties of a regular polygonal quantum ring with an arbitrary number of segments. We find that the DSOC can break the time reversal symmetry of the spin conductance in a polygonal ring and that this property can be used to reverse the spin direction of electrons in the polygon with the result that a pure spin up or pure spin down conductance can be obtained by exchanging the source and the drain. When the DSOC is considered in a polygonal ring with Rashba spin¢orbit coupling (RSOC) with symmetric attachment of the leads, the total conductance is independent of the number of segments when both of the two types of spin¢orbit coupling (SOC) have the same value. However, the interaction of the two types of SOC results in an anisotropic and shape-dependent conductance in a polygonal ring with asymmetric attachment of the leads. The method we proposed to solve for the spin conductance of a polygon can be generalized to the circular model. Project supported by the National Natural Science Foundation of China (Grant No. 61176089), the Natural Science Foundation of Hebei Province, China (Grant No. A2011205092), and the Foundation of Shijiazhuang University, China (Grant No. XJPT002).
Tang, Han-Zhao; Zhai, Li-Xue; Shen, Man; Liu, Jian-Jun
Investigation of low field dielectric properties of anisotropic porous Pb(Zr,Ti)O3 ceramics: Experiment and modeling
NASA Astrophysics Data System (ADS)
Anisotropic porous Pb(Zr,Ti)O3 ceramics with various porosity degrees have been studied in order to determine the role of the pore shape and orientation on the low-field dielectric properties. Ceramic samples with formula Pb(Zr0.52Ti0.48)0.976Nb0.024O3 with different porosity degrees (dense, 10%, 20%, 40% vol.) have been prepared by solid state reaction. Taking into consideration the shape and orientation of the pore inclusions, the dielectric properties of porous ceramics have been described by using adapted mixing rules models. Rigorous bounds, derived on the basis on Variational Principle, were used to frame dielectric properties of porous composites. The finite element method (FEM) was additionally used to simulate the dielectric response of the porous composites under various applied fields. Among the few effective medium approximation models adapted for anisotropic oriented inclusions, the best results were obtained in case of needle-like shape inclusions (which do not correspond to the real shape of microstructure inclusions). The general case of Wiener bounds limited well the dielectric properties of anisotropic porous composites in case of parallel orientation. Among the theoretical approaches, FEM technique allowed to simulate the distribution of potential and electric field inside composites and provided a very good agreement between the computed permittivity values and experimental ones.
Olariu, C. S.; Padurariu, L.; Stanculescu, R.; Baldisserri, C.; Galassi, C.; Mitoseriu, L.
Reflection Symmetric Ballistic Microstructures: Quantum Transport Properties
We show that reflection symmetry has a strong influence on quantum transport properties. Using a random S-matrix theory approach, we derive the weak-localization correction, the magnitude of the conductance fluctuations, and the distribution of the conductance for three classes of reflection symmetry relevant for experimental ballistic microstructures. The S-matrix ensembles used fall within the general classification scheme introduced by Dyson, but because the conductance couples blocks of the S-matrix of different parity, the resulting conductance properties are highly non-trivial.
Harold U. Baranger; Pier A. Mello
Anisotropic superconducting and normal state magnetic properties of single crystals of RNi*2*B*2*C compounds (R = Y, Gd, Dy, Ho, Er, and Tm)
The interaction of superconductivity with magnetism has been one of the most interesting and important phenomena in solid state physics since the 1950`s when small amounts of magnetic impurities were incorporated in superconductors. The discovery of the magnetic superconductors RNi{sub 2}B{sub 2}C (R = rare earth, Y) offers a new system to study this interaction. The wide ranges of superconducting transition (T{sub c}) and antiferromagnetic (AF) ordering temperatures (T{sub N}) (0 K {le} T{sub c} {le} 16 K, 0 K {le} T{sub N} {le} 20 K) give a good opportunity to observe a variety of interesting phenomena. Single crystals of high quality with appropriate size and mass are crucial in examining the anisotropic intrinsic properties. Single crystals have been grown successfully by an unusual high temperature flux method and characterized thoroughly by X-ray, electrical transport, magnetization, neutron scattering, scanning electron microscopy, and other measurements.
Cho, B.
Nonlinear Dielectric Properties of Paraelectric (Ba,Sr)TiO3 Thin Films with Isotropic and Anisotropic Epitaxy
The effects of isotropic and anisotropic epitaxy on the nonlinear dielectric response in (Ba0.6,Sr0.4TiO3) thin films were investigated experimentally. Under isotropic epitaxy, it is shown that the misfit is detrimental to the non-linear response of the films with decreasing film thickness. Nonlinear dielectric properties of films with in-plane compression exhibit more pronounced strain dependence, while the same does not set-in
W. K. Simon; J. A. Bellotti; E. K. Akdogan; A. Safari
The Anisotropic Elastic Properties of the Sarcolemma of the Frog Semitendinosus Muscle Fiber
Tension and curvature of the sarcolemmal tube of the frog muscle fiber were measured at different extensions and were used to calculate the anisotropic elastic properties of the sarcolemma. A model was derived to obtain the four parameters of the elasticity matrix of the sarcolemma. Sarcolemmal thickness was taken as 0.1 ?m. Over the range of reversible sarcolemmal tube extension, the longitudinal elastic modulus EL = 6.3 ū 107 dyn/cm2, the circumferential modulus Ec = 0.88 ū 107 dyn/cm2, the longitudinal Poisson's ratio ?L = 1.2, and the circumferential Poisson's ratio ?c = 0.18. At tubular rest length EL = 1.2 ū 107 dyn/cm2. The sarcolemma is less extensible in the longitudinal direction along the fiber axis than in the circumferential direction. It can be extended reversibly to 48% of its rest length, equivalent to extending the intact fiber from a sarcomere length of 3 ?m to about 4.5 ?m. The sarcolemma does not contribute to intact fiber tension at fiber sarcomere lengths <3 ?m, and between 3 and 4 ?m its contribution is about 20%. It also exerts a pressure on the myoplasm, which can be calculated by means of the model. The longitudinal elastic modulus of the whole fiber is 1 ū 105 dyn/cm2 at a sarcomere length of 2.33 ?m. ImagesFIGURE 6FIGURE 7 PMID:4541138
Rapoport, Stanley I.
Structure and anisotropic properties of single crystals nickel doped barium iron arsenide
The crystal structure, anisotropic electrical resistivity and magnetic susceptibility, as well as specific heat results of the pure single crystals of BaFe{sub 2}As{sub 2}, BaFeNiAs{sub 2}, and BaNi{sub 2}As{sub 2} are surveyed. BaFe{sub 2}As{sub 2} properties demonstrate the equivalence of C(T), Fisher's d({chi}T)/dT and d{rho}/dT results in determining the antiferromagnetic transition at T{sub N} = 132(1) K. BaNi{sub 2}As{sub 2} shows a structural phase transition from a high-temperature tetragonal phase to a low-temperature triclinic pol symmetry at T{sub 0} 131 K, with superconducting critical temperature well below at {Tc} 0.69 K. BaFeNiAs{sub 2} does not show any sign of superconductivity and gives behavioral similarity to BaCo{sub 2}As{sub 2}, a renomalized paramagnetic metal.
Ronning, Filip [Los Alamos National Laboratory; Bauer, Eric D [Los Alamos National Laboratory; Sefat, A S [ORNL; Jin, R [ORNL; Mcguire, M A [ORNL; Sales, B C [ORNL; Mandrus, D [ORNL
Thermodynamic and transport properties of gaseous tetrafluoromethane in chemical equilibrium
NASA Technical Reports Server (NTRS)
Equations and in computer code are presented for the thermodynamic and transport properties of gaseous, undissociated tetrafluoromethane (CF4) in chemical equilibrium. The computer code calculates the thermodynamic and transport properties of CF4 when given any two of five thermodynamic variables (entropy, temperature, volume, pressure, and enthalpy). Equilibrium thermodynamic and transport property data are tabulated and pressure-enthalpy diagrams are presented.
Hunt, J. L.; Boney, L. R.
Anisotropic strain in SmSe and SmTe: Implications for electronic transport
NASA Astrophysics Data System (ADS)
Mixed valence rare-earth samarium compounds Sm X (X =Se,Te ) have been recently proposed as candidate materials for use in high-speed, low-power digital switches driven by stress induced changes of resistivity. At room temperature these materials exhibit a pressure driven insulator-to-metal transition with resistivity decreasing by up to seven orders of magnitude over a small pressure range. Thus, the application of only a few GPa's to the piezoresistor (Sm X ) allows the switching device to perform complex logic. Here we study from first principles the electronic properties of these compounds under uniaxial strain and discuss the implications for carrier transport. Based on changes in the band structure and a model we show that the piezoresistive response is mostly governed by the reduction of band gap with strain. Furthermore, the piezoresistive reponse becomes optimal when the Fermi level is pinned near the localized valence band. The piezoresistive effect under uniaxial strain, which must be taken into account in thin films and other systems with reduced dimensionality, is also studied. Under uniaxial strain we find that the piezoresistive response can be substantially larger than in the isotropic case. Analysis of the complex band structure of SmSe yields a tunneling length of the order of 1 nm. This suggest that the conduction mechanism governing the piezoresistive effect in bulk, i.e., thermal promotion of electrons, should still be dominant in few-nanometer-thick films.
Kuroda, Marcelo A.; Jiang, Zhengping; Povolotskyi, Michael; Klimeck, Gerhard; Newns, Dennis M.; Martyna, Glenn J.
Size dependent anisotropic strain and optical properties of strained Si nanocrystals.
We report on the growth of strained Si nanocrystals (NCs) of sizes in the range 5-43 nm and analyze the detailed nature of strain and its influence on the optical properties of the NCs as a function of size. Freestanding Si NPs were prepared in a controlled way using a contamination free mechanical ball milling for duration 2-40 hrs. Structural analysis based on X-ray diffraction (XRD) pattern and high resolution transmission electron microscopy (HRTEM) confirms the good crystalline nature of these Si NCs. A detailed analysis of XRD line profile reveals that nature of the strain is anisotropic and the screw type dislocations are the main contributors to the lattice strain. The dislocation density and corresponding strain changes non-monotonically, while the crystallite size changes monotonically with milling time. Direct evidence of dislocations is shown from HRTEM images. The UV-vis-NIR absorption spectra of the Si NCs show an enhanced absorption band in the visible region that shows a systematic blue shift with reduced NC sizes. Si NCs with size approximately 5-10 nm exhibits a distinct photoluminescence (PL) band in the visible region at 580-585 nm at room temperature, while higher size NCs does not exhibit any visible emission. PL excitation measurement shows a very small Stokes shift for the visible emission band indicating no involvement of defects/interface in the emission. We argue that the observed absorption and emission can be explained based on the enhanced confinement effect on the strained Si NCs due to the combined effect of strain and size quantization. PMID:22400326
Dhara, Soumen; Giri, P K
Parametric fit to electron transport properties
NASA Technical Reports Server (NTRS)
Experimental data acquired over the past few years were gathered, and parametric fits made to these data. The following properties of electron transport were represented by simple functions of atomic number and energy: transmitted electron number, transmitted electron spectra, range, backscatter coefficient, angular distribution, energy deposition, bremsstrahlung intensity and energy spectra, and bremsstrahlung angular distribution and photon attenuation. The formulas cover the energy ranges of interest in space shielding problems (0.1 to 10.0 MeV). Procedures for using these formulas in practical situations are suggested.
Lonergan, J. A.; Shreve, D. C.
Upscaling of Thermal Transport Properties in Enhanced Geothermal Systems
NASA Astrophysics Data System (ADS)
: Engineered Geothermal Systems (EGS) have garnered significant attention as a possible source of geographically disperse, carbon-free energy without the environmental impact of many other renewable energy sources. However, a significant barrier to the adoption of EGS is the uncertainty in whether a specific site is amenable to engineering and how fluid injection rates can affect, either through stimulation of the fracture network or through deleterious channeling of the thermal fluid, the heat extraction rate possible in a specific reservoir. Because of the uncertainties involved in determining the exact fracture network topology extant in any particular reservoir, it is desirable to have a stochastic description (distribution) of the possible heat extraction rates that could be achieved. This work provides both an approach and application of the approach for simulating several synthetic fracture networks. The approach uses a coupled geomechanics and discrete fracture network (DFN) solver coupled uni-directionally with a reservoir scale, hydro-thermal transport code, the Non-isothermal Unsaturated-Saturated Flow and Transport simulation code (NUFT), to capture the coupled hydro-thermo-mechanical behavior of these synthetic networks. Particular attention is paid to the upscaling approach used to determine effective permeability and thermal transfer coefficients that are used in the dual porosity/permeability (DKM) model employed in NUFT. This upscaling is based on a multi-scale treatment of the domain, starting with the upscaling of permeability from explicitly represented fractures in the DFN model, which considers the fracture-scale effects of fluid injection, to a finely resolved, unstructured mesh representation of the subdomain. Effective properties of this subdomain are then determined for a variety of sub-sampled discrete fracture network topologies. The result catalog of spatially correlated thermal and fluid properties are then used to populate the properties of an anisotropic regular grid representation of the reservoir. The resultant reservoir-scale system considering the fully-coupled hydro-thermo-mechanical problem is then simulated to determine the resultant heat transfer rate for each synthetic fracture network realization. To complete the parametric study, several fractally spatially distributed systems are realized for each fractal dimension value. The resultant distributions of heat transfer rate and the trends emergent from this study will be presented. Auspices: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Johnson, S.; Hao, Y.; Chiaramonte, L.
Magnetic and transport properties of oxide thin films
NASA Astrophysics Data System (ADS)
My dissertation research focuses on the investigation of the transport and magnetic properties of transition metal and rare earth doped oxides, particularly SnO2 and HfO2 thin films. Cr- and Fe-doped SnO 2 films were deposited on Al2O3 substrates by pulsed-laser deposition. X-ray-diffraction patterns (XRD) show that the films have rutile structure and grow epitaxially along the (101) plane. The diffraction peaks of Cr-doped samples exhibit a systematic shift toward higher angles with increasing Cr concentration. This indicates that Cr dissolves in SnO 2. On the other hand, there is no obvious shift of the diffraction peaks of the Fe-doped samples. The magnetization curves indicate that the Cr-doped SnO2 films are paramagnetic at 300 and 5 K. The Fe-doped SnO 2 samples exhibit ferromagnetic behaviour at 300 and 5 K. Zero-field-cooled and field-cooled curves indicate super paramagnetic behavior above the blocking temperature of 100 K, suggesting that it is possible that there are ferromagnetic particles in the Fe-doped films. The anisotropic magnetoresistance (AMR) was not observed in any of the samples. It was found that a Sn0.98Cr0.02O2 film became ferromagnetic at room temperature after annealing in H2. We have calculated the activation energy and found it decreasing with the annealing, which is explained by the increased oxygen vacancies/defects due to the H2 treatment of the films. The ferromagnetism may be associated with the presence of oxygen vacancies although AMR was not observed in the samples. Pure HfO2 and Gd-doped HfO2 thin films have been grown on different single crystal substrates by pulsed laser deposition. XRD patterns show that the pure HfO2 thin films are of single monoclinic phase. Gd-doped HfO2 films have the same XRD patterns except that their diffraction peaks have a shift toward lower angles, which indicates that Gd dissolves in HfO2. Transmission electron microscopy images show a columnar growth of the films. Very weak ferromagnetism is observed in pure and Gd-doped HfO2 films on different substrates at 300 and 5 K, which is attributed to either impure target materials or signals from the substrates. The magnetic properties do not change significantly with post deposition annealing of the HfO2 films. Keywords. SnO2, HfO2, pulsed laser deposition, thin film, epitaxial growth, magnetic thin films, ferromagnetic materials, transport properties.
Hong, Yuanjia
Anisotropic heat transport in nanoconfined polyamide-6,6 oligomers: atomistic reverse nonequilibrium molecular dynamics simulation.
While polymers are known as thermal insulators, recent studies show that stretched single chains of polymers have a very high thermal conductivity. In this work, our new simulation scheme for simulation of heat flow in nanoconfined fluids [H. Eslami, L. Mohammadzadeh, and N. Mehdipour, J. Chem. Phys. 135, 064703 (2011)] is employed to study the effect of chain ordering (stretching) on the rate of heat transfer in polyamide-6,6 nanoconfined between graphene surfaces. Our results for the heat flow in the parallel direction (the plane of surfaces) show that the coefficient of thermal conductivity depends on the intersurface distance and is much higher than that of the bulk polymer. A comparison of results in this work with our former findings on the heat flow in the perpendicular direction, with the coefficient of heat conductivity less than the bulk sample, reveal that well-organized polymer layers between the confining surfaces show an anisotropic heat conduction; the heat conduction in the direction parallel to the surfaces is much higher than that in the perpendicular direction. The origin of such anisotropy in nanometric heat flow is shown to be the dramatic anisotropy in chain conformations (chain stretching) beside the confining surfaces. The results indicate that the coefficients of heat conductivity in both directions, normal and parallel to the surfaces, depend on the degree of polymer layering between the surfaces and the pore width. PMID:22423855
Eslami, Hossein; Mohammadzadeh, Laila; Mehdipour, Nargess
Solvothermal synthesis, growth mechanism, and photoluminescence property of sub-micrometer PbS anisotropic structures
The sub-micrometer PbS with anisotropic microstructures including fishbone-like dendrites, multipods, cubes, corallines, and hopper cubes were successfully prepared by the solvothermal process. Different morphologies can be obtained by adjusting the reaction temperatures or using the nontoxic controlled reagents which can tune the relative growth rate in the <100> direction and the <111> direction of PbS nuclei. Based on the viewpoint of crystallography about face-centered cubic crystal structure, the possible formation mechanism for sub-micrometer anisotropic structures has been discussed. The difference between the enhanced growth rates on the {100} and {111} planes induced the change of ratio between the growth rates in the <100> and <111> directions, which resulted in the formation of the different PbS anisotropic microstructures. The PbS anisotropic structures exhibited the different visible emission with a peak in the red regions mainly attributed to the variation of shape, size, and the trap state of as-obtained PbS. PMID:23216819
Colloquium: The transport properties of graphene: An introduction
An introduction to the transport properties of graphene combining experimental results and theoretical analysis is presented. In the theoretical description simple intuitive models are used to illustrate important points on the transport properties of graphene. The concept of chirality, stemming from the massless Dirac nature of the low energy physics of the material, is shown to be instrumental in understanding its transport properties: the conductivity minimum, the electronic mobility, the effect of strain, the weak (anti-)localization, and the optical conductivity.
N. M. R. Peres
Transport properties of epitaxial lift off films
NASA Technical Reports Server (NTRS)
Transport properties of epitaxially lifted-off (ELO) films were characterized using conductivity, Hall, and Shubnikov-de Haas measurements. A 10-15 percent increase in the 2D electron gas concentration was observed in these films as compared with adjacent conventional samples. We believe this result to be caused by a backgating effect produced by a charge build up at the interface of the ELO film and the quartz substrate. This increase results in a substantial decrease in the quantum lifetime in the ELO samples, by 17-30 percent, but without a degradation in carrier mobility. Under persistent photoconductivity, only one subband was populated in the conventional structure, while in the ELO films the population of the second subband was clearly visible. However, the increase of the second subband concentration with increasing excitation is substantially smaller than anticipated due to screening of the backgating effect.
Mena, R. A.; Schacham, S. E.; Young, P. G.; Haugland, E. J.; Alterovitz, S. A.
Charge transport properties of spin crossover systems.
The study of spin crossover compounds by means of theoretical or experimental approaches has provided interesting results in recent decades. The main feature of such compounds is the change in the spin state induced by many different external stimuli, i.e. temperature, light, pressure, solvent coordination and the electric field. Spin crossover systems are potentially more useful than other magnetic molecules because their switching behaviour can occur closer to room temperature, and they are thus candidates for use in spintronic devices. Here, I review the state of the art in quantum chemical approaches to the study of such systems and discuss experiments that have focused on transport properties in single-molecule, nano-objects or thin-film spin crossover systems. PMID:24217339
Ruiz, Eliseo
A review of some charge transport properties of silicon
Basic bulk transport properties of charge carriers in silicon are reviewed, with particular reference to their use in designing solid-state components. The current theoretical model for transport in silicon is outlined, along with experimental techniques for determining most important transport parameters such as the drift velocity and diffusion coefficient. Phenomenological expressions are presented, which are in good agreement with experimental
C. Jacoboni; C. Canali; G. Ottaviani; A. Alberigi Quaranta
Correlations among magnetic, electrical and magneto-transport properties of NiFe nanohole arrays.
In this work, we use anodic aluminum oxide (AAO) templates to build NiFe magnetic nanohole arrays. We perform a thorough study of their magnetic, electrical and magneto-transport properties (including the resistance R(T), and magnetoresistance MR(T)), enabling us to infer the nanohole film morphology, and the evolution from granular to continuous film with increasing thickness. In fact, different physical behaviors were observed to occur in the thickness range of the study (2 nm < t < 100 nm). For t < 10 nm, an insulator-to-metallic crossover was visible in R(T), pointing to a granular film morphology, and thus being consistent with the presence of electron tunneling mechanisms in the magnetoresistance. Then, for 10 nm < t < 50 nm a metallic R(T) allied with a larger anisotropic magnetoresistance suggests the onset of morphological percolation of the granular film. Finally, for t > 50 nm, a metallic R(T) and only anisotropic magnetoresistance behavior were obtained, characteristic of a continuous thin film. Therefore, by combining simple low-cost bottom-up (templates) and top-down (sputtering deposition) techniques, we are able to obtain customized magnetic nanostructures with well-controlled physical properties, showing nanohole diameters smaller than 35 nm. PMID:23315433
Leitao, D C; Ventura, J; Teixeira, J M; Sousa, C T; Pinto, S; Sousa, J B; Michalik, J M; De Teresa, J M; Vazquez, M; Araujo, J P
Electrical Transport and Chemical Sensing Properties of Individual
sensing properties of individual multisegmented Au-poly(3,4-ethylenedioxythiophene)(PEDOT)-Au nanowires transport mechanisms influence these properties in two types of PEDOT nanowires. Charge transport in PEDOT-insulator transition and dominated by hopping, while PEDOT/perchlorate (ClO4) nanowires are slightly on the metallic
Predicting the transport properties of sedimentary rocks from microstructure
Understanding transport properties of sedimentary rocks, including permeability, relative permeability, and electrical conductivity, is of great importance for petroleum engineering, waste isolation, environmental restoration, and other applications. These transport properties axe controlled to a great extent by the pore structure. How pore geometry, topology, and the physics and chemistry of mineral-fluid and fluid-fluid interactions affect the flow of fluids through
Erika M. Schlueter
Manipulation of the Transport Properties of Single-Walled Nanotubes
Manipulation of the Transport Properties of Single-Walled Nanotubes by Alkali Intercalation on the transport properties of individual single-walled nanotubes. This was done in two ways. In the first, we expose devices made of individual nanotubes to alkali metal vapor. This causes no change
Zettl, Alex
Transport properties of transition metal impurities on gold nanowires
Performing first principles density functional theory (DFT) we calculated the electronic and transport properties of a Au thin nanowire with transition metal atoms (Mn, Fe, Ni or Co) bridging the two sides of the Au nanowire. We will show that these systems have strong spin dependent transport properties and that the local symmetry can dramatically change them, leading to a
Renato B. Pontes; Edison Z. da Silva; Adalberto Fazzio; Ant¶nio J. R. da Silva
Analysis of an anisotropic coastal aquifer system using variable-density flow and solute transport simulation
The groundwater system in southern Oahu, Hawaii consists of a thick, areally extensive freshwater lens overlying a zone of transition to a thick saltwater body. This system is analyzed in cross section with a variable-density groundwater flow and solute transport model on a regional scale. The simulation is difficult, because the coastal aquifer system has a saltwater transition zone that is broadly dispersed near the discharge area, but is very sharply defined inland. Steady-state simulation analysis of the transition zone in the layered basalt aquifer of southern Oahu indicates that a small transverse dispersivity is characteristic of horizontal regional flow. Further, in this system flow is generally parallel to isochlors and steady-state behavior is insensitive to the longitudinal dispersivity. Parameter analysis identifies that only six parameters control the complex hydraulics of the system: horizontal and vertical hydraulic conductivity of the basalt aquifer; hydraulic conductivity of the confining "caprock" layer; leakance below the caprock; specific yield; and aquifer matrix compressibility. The best-fitting models indicate the horizontal hydraulic conductivity is significantly greater than the vertical hydraulic conductivity. These models give values for specific yield and aquifer compressibility which imply a considerable degree of compressive storage in the water table aquifer. ?? 1987.
Souza, W.R.; Voss, C.I.
Anisotropic p-ā mixing mechanism explaining anomalous magnetic properties in Ce monopnictides
NASA Astrophysics Data System (ADS)
Anomalously small crystalline field splitting in the paramagnetic region and extremely strong magnetic anisotropy in the ordered phases in CeSb and CeBi are explained based on the anisotropic mixing mechanism between the 4ā states and the valence bands. In the paramagnetic region, the mixing gives the effective crystalline field splitting which is estimated to cancel the splitting of the point charge model in good agreement with experiment. The anisotropy energy of CeSb calculated by using the realistic valence bands is consistent with the strong anisotropy observed experimentally.
Takegahara, K.; Takahashi, H.; Yanasa, A.; Kasuya, T.
A Harris sheet magnetic field with maximum magnitude B{sub 0} and length scale L is combined with the anisotropic electrical conductivity, viscosity, and thermoelectric tensors for an electron-proton plasma to define a magnetohydrodynamic model that determines the steady state of the plasma. The transport tensors are functions of temperature, density, and magnetic field strength, and are computed self-consistently as functions of position x normal to the current sheet. The flow velocity, magnetic field, and gravitational force lie along the z-axis. The plasma is supported against gravity by the viscous force. Analytic solutions are obtained for temperature, density, and velocity. They are valid over a broad range of temperature, density, and magnetic field strength, and so may be generally useful in astrophysical applications. Numerical examples of solutions in the parameter range of the solar atmosphere are presented. The objective is to compare Joule and viscous heating rates, determine the velocity shear that generates viscous forces that support the plasma and are self-consistent with a mean outward mass flux comparable to the solar wind mass flux, and compare the thermoelectric and conduction current contributions to the Joule heating rate. The ratio of the viscous to Joule heating rates per unit mass can exceed unity by orders of magnitude, and increases rapidly with L. The viscous heating rate can be concentrated outside the region where the current density is localized, corresponding to a resistively heated layer of plasma bounded by viscously heated plasma. The temperature gradient drives a thermoelectric current density that can have a magnitude greater than that of the electric-field-driven conduction current density, so thermoelectric effects are important in determining the Joule heating rate.
Goodman, Michael L., E-mail: firstname.lastname@example.com [Advanced Technologies Group, West Virginia High Technology Consortium Foundation, 1000 Galliher Drive, Fairmont, WV 26554 (United States)
Analytic Solutions for Current Sheet Structure Determined by Self-consistent, Anisotropic Transport Processes in a Gravitational Field
NASA Astrophysics Data System (ADS)
A Harris sheet magnetic field with maximum magnitude B 0 and length scale L is combined with the anisotropic electrical conductivity, viscosity, and thermoelectric tensors for an electron-proton plasma to define a magnetohydrodynamic model that determines the steady state of the plasma. The transport tensors are functions of temperature, density, and magnetic field strength, and are computed self-consistently as functions of position x normal to the current sheet. The flow velocity, magnetic field, and gravitational force lie along the z-axis. The plasma is supported against gravity by the viscous force. Analytic solutions are obtained for temperature, density, and velocity. They are valid over a broad range of temperature, density, and magnetic field strength, and so may be generally useful in astrophysical applications. Numerical examples of solutions in the parameter range of the solar atmosphere are presented. The objective is to compare Joule and viscous heating rates, determine the velocity shear that generates viscous forces that support the plasma and are self-consistent with a mean outward mass flux comparable to the solar wind mass flux, and compare the thermoelectric and conduction current contributions to the Joule heating rate. The ratio of the viscous to Joule heating rates per unit mass can exceed unity by orders of magnitude, and increases rapidly with L. The viscous heating rate can be concentrated outside the region where the current density is localized, corresponding to a resistively heated layer of plasma bounded by viscously heated plasma. The temperature gradient drives a thermoelectric current density that can have a magnitude greater than that of the electric-field-driven conduction current density, so thermoelectric effects are important in determining the Joule heating rate.
Goodman, Michael L.
Multiglass properties and magnetoelectric coupling in the uniaxial anisotropic spin-cluster-glass Fe2Ti O5
NASA Astrophysics Data System (ADS)
The compound Fe2Ti O5 (FTO) is a well-known uniaxial anisotropic spin-glass insulator with two successive glassy freezing temperatures, i.e., transverse (TT F= 9 K ) and longitudinal (TL F= 55 K ) . In this article, we present the results of measurements of complex dielectric behavior, electric polarization as a function of temperature (T ), in addition to characterization by magnetic susceptibility and heat capacity, primarily to explore magnetoelectric (ME) coupling and multiglass properties in uniaxial anisotropic spin-cluster-glass FTO. The existence of two magnetic transitions is reflected in the isothermal magnetodielectric (MD) behavior in the sense that the sign of MD is different in the T regime T TT F . The data in addition provide evidence for the glassy dynamics of electric dipoles; interestingly, this occurs at much higher temperature (ś100-150 K) than TL F, with high remnant polarization at 10 K (ś4000 ? C /m2) attributable to short-range magnetic correlations, thereby offering a route to attain ME coupling above 77 K.
Sharma, Shivani; Basu, Tathamay; Shahee, Aga; Singh, K.; Lalla, N. P.; Sampathkumaran, E. V.
Angular momentum transport in a multicomponent solar wind with differentially flowing, thermally anisotropic ions
The Helios measurements of the angular momentum flux $L$ for the fast solar wind show that the individual ion contributions, $L_p$ and $L_\\alpha$, tend to be negative (i.e., in the sense of counter-rotation with the Sun). However, the opposite holds for the slow wind, and the overall particle contribution $L_P = L_p + L_\\alpha$ tends to exceed the magnetic one $L_M$. These aspects are at variance with previous models. We examine whether introducing realistic ion temperature anisotropies can resolve this discrepancy. From the general multifluid transport equations with gyrotropic species pressure tensors, we derive the equations governing both the meridional and azimuthal dynamics of general axisymmetrical, rotating stellar winds that include two major ion species. The azimuthal dynamics are examined in detail, using the empirically constructed meridional flow profiles for the solar wind. We find that $L$ is determined by requiring that the solution to the total angular momentum conservation law is unique and smooth close to the Alfven point, where the combined Alfvenic Mach number $M_T=1$. Introducing realistic ion temperature anisotropies may introduce a change of up to 10% in $L$ and up to 1.8 km/s in azimuthal speeds of individual ions between 0.3 and 1 AU, compared with the isotropic case. The latter has strong consequences on the relative importance of $L_P$ and $L_M$. However, introducing ion temperature anisotropies cannot resolve the discrepancy between measurements and models. For the fast-wind solutions, while in extreme cases $L_P$ becomes negative, $L_p$ never does. On the other hand, for the slow-wind solutions, $L_P$ never exceeds $L_M$, even though $L_M$ may be less than the individual ion contribution, since $L_p$ and $L_\\alpha$ always have opposite signs for the slow and fast wind alike.
Bo Li; Xing Li
Anisotropic charge transport in large single crystals of ?-conjugated organic molecules
NASA Astrophysics Data System (ADS)
The electronic properties of organic semiconductors depend strongly on the nature of the molecules, their conjugation and conformation, their mutual distance and the orientation between adjacent molecules. Variations of intramolecular distances and conformation disturb the conjugation and perturb the delocalization of charges. As a result, the mobility considerably decreases compared to that of a covalently well-organized crystal. Here, we present electrical characterization of large single crystals made of the regioregular octamer of 3-hexyl-thiophene (3HT)8 using a conductive-atomic force microscope (C-AFM) in air. We find a large anisotropy in the conduction with charge mobility values depending on the crystallographic orientation of the single crystal. The smaller conduction is in the direction of ?-? stacking (along the long axis of the single crystal) with a mobility value in the order of 10-3 cm2 V-1 s-1, and the larger one is along the molecular axis (in the direction normal to the single crystal surface) with a mobility value in the order of 0.5 cm2 V-1 s-1. The measured current-voltage (I-V) curves showed that along the molecular axis, the current followed an exponential dependence corresponding to an injection mode. In the ?-? stacking direction, the current exhibits a space charge limited current (SCLC) behavior, which allows us to estimate the charge carrier mobility.
Hourani, Wael; Rahimi, Khosrow; Botiz, Ioan; Vinzenz Koch, Felix Peter; Reiter, G³nter; Lienerth, Peter; Heiser, Thomas; Bubendorff, Jean-Luc; Simon, Laurent
Anisotropic charge transport in large single crystals of ?-conjugated organic molecules.
The electronic properties of organic semiconductors depend strongly on the nature of the molecules, their conjugation and conformation, their mutual distance and the orientation between adjacent molecules. Variations of intramolecular distances and conformation disturb the conjugation and perturb the delocalization of charges. As a result, the mobility considerably decreases compared to that of a covalently well-organized crystal. Here, we present electrical characterization of large single crystals made of the regioregular octamer of 3-hexyl-thiophene (3HT)8 using a conductive-atomic force microscope (C-AFM) in air. We find a large anisotropy in the conduction with charge mobility values depending on the crystallographic orientation of the single crystal. The smaller conduction is in the direction of ?-? stacking (along the long axis of the single crystal) with a mobility value in the order of 10(-3) cm(2) V(-1) s(-1), and the larger one is along the molecular axis (in the direction normal to the single crystal surface) with a mobility value in the order of 0.5 cm(2) V(-1) s(-1). The measured current-voltage (I-V) curves showed that along the molecular axis, the current followed an exponential dependence corresponding to an injection mode. In the ?-? stacking direction, the current exhibits a space charge limited current (SCLC) behavior, which allows us to estimate the charge carrier mobility. PMID:24658783
Hourani, Wael; Rahimi, Khosrow; Botiz, Ioan; Koch, Felix Peter Vinzenz; Reiter, G³nter; Lienerth, Peter; Heiser, Thomas; Bubendorff, Jean-Luc; Simon, Laurent
Transport properties of graphene and its application
NASA Astrophysics Data System (ADS)
This thesis focuses on the transport properties of graphene, a new emerging atomically thin, two-dimensional material, with and without the application of a magnetic field. Because of its high mobility, graphene is a promising candidate for Extraordinary Magnetoresistance (EMR) devices. The magnetoresistance of an EMR device arises mainly from its geometry rather than the intrinsic response of the material itself to an applied magnetic field. As a result, the geometric parameters play an important role in its performance. Experiments employing various combinations of geometric parameters and graphene of different quality levels were conducted to determine the optimal results. We found that the optimized parameters vary for different applied magnetic fields. In a magnetic field of 9 Tesla, magnetoresistance up to 55,000% was observed. In addition, Finite Element Analysis (FEA) simulations are used to complement the experiments and explain the measured magnetoresistance. The excellent agreement between the simulations and experimental results indicates that theoretical simulation can be used as a convenient method to explore EMR devices with alternative geometries or materials. The anomalous quantum Hall effect is one of the most exciting properties of graphene. The observation of the v=0 state above a critical magnetic field is closely related to the quality of the graphene, where a higher quality reduces the critical field needed. With our high quality graphene sample, the critical field is reduced to 6.75 Tesla. Moreover, from 6.75 T to 9T, the resistance at the cross point of the metal-insulator transition (MIT) is very close to h/2e2, which resembles the case of a disordered two-dimensional electron gas (2DEG) and may indicate a similar physical mechanism. In addition to the magnetotransport measurements, the current saturation of graphene in a high electric field is studied both theoretically and experimentally. This thesis focuses primarily on bilayer graphene because of the scarcity of research in this area. For the theoretical part, two models are studied in detail and compared with each other. The phonon spontaneous model is analytical and easy to use while the Boltzmann transport method (BET) with shifted Fermi distribution is more complicated. However, this latter method can provide more information before current saturation. The two models are extended to the case of bilayer graphene. For samples with relatively high carrier density, they agree with each other qualitatively. However, in the low carrier density region, the BET method gave a much lower drift velocity, which was explained by the much larger effective charge carrier density, including additional electrons tunneling from the valence band and holes in the valence band. In experiments of bilayer graphene in a high electric field, the carrier drift velocity has been observed to be comparable or even larger than that in monolayer graphene. This was beyond our expectation because monolayer graphene usually displays a much higher low field mobility. Finally, a simple drying method that takes advantage of capillary force is used to create strain in the graphene films, which can be treated as a pseudo-magnetic field. Uniform and non-uniform distribution of strain up to 0.47 percent has been obtained in different geometric devices. With cleaner surfaces between the graphene and underlying substrate, the van der Waals force increases remarkably, and thus, the strain in graphene may be further enhanced.
Lu, Jianming
Diameter dependence of the transport properties of antimony telluride nanowires.
We report measurements of electronic, thermoelectric, and galvanomagnetic properties of individual single crystal antimony telluride (Sb(2)Te(3)) nanowires with diameters in the range of 20-100 nm. Temperature-dependent resistivity and thermoelectric power (TEP) measurements indicate hole dominant diffusive thermoelectric generation with an enhancement of the TEP for smaller diameter wires up to 110 microV/K at T = 300 K. We measure the magnetoresistance in magnetic fields both parallel and perpendicular to the nanowire [110] axis, where strong anisotropic positive magnetoresistance behavior was observed. PMID:20698617
Zuev, Yuri M; Lee, Jin Seok; Galloy, Clķment; Park, Hongkun; Kim, Philip
Magneto-transport properties of gapped graphene.
Based on the Kubo formula, we have studied the electron transport properties of a gapped graphene in the presence of a strong magnetic field. By solving the Dirac equation, we find that the Landau level spectra in two valleys differ from each other in that the n = 0 level in the K valley is located at top of the valence band, whereas it is at the bottom of the conduction band in the K' valley. Thus, in an individual valley, the symmetry between conduction and valence bands is broken by the presence of a magnetic field. By using the self-consistent Born approximation to treat the long range potential scattering, we formulate the diagonal and the Hall conductivities in terms of the Green function. To perform the numerical calculation, we find that a large bandgap can suppress the quantum Hall effect, owing to the enhancement of the bandgap squeezing the spacing between the low-lying Landau levels. On the other hand, if the bandgap is not very large, the odd integer quantum Hall effect experimentally, observed in the gapless graphene, remains in the gapped one. However, such a result does not indicate the half integer quantum Hall effect in an individual valley of the gapped graphene. This is because the heights of the Hall plateaux in either valley can be continuously tuned by the variation of the bandgap. More interestingly, we find that the height of the diagonal conductivity peak corresponding to the n = 0 Landau level is independent of the bandgap if the scattering is not very strong. In the weak scattering limit, we demonstrate analytically that such a peak takes a universal value e(2)/(hpi), regardless of the bandgap. PMID:20220217
Jiang, Liwei; Zheng, Yisong; Li, Haidong; Shen, Honghai
Brmaud, I., P. Cabrolier, J. Gril, B. Clair, J. Grard, K. Minato & B. Thibaut. Identification of anisotropic vibrational properties of Padauk wood with interlocked grain.
of anisotropic vibrational properties of Padauk wood with interlocked grain. Publiķ dans: Wood Science with interlocked grain Iris Brķmaud Ł Pierre Cabrolier Ł Joseph Gril Ł Bruno Clair Ł Jean Gķrard ŁKazuya Minato.), a species selected for its interlocked grain, high extractives content, and uses in xylophones. Specimens
Boyer, Edmond
Ellipsometric characterization and density-functional theory analysis of anisotropic optical properties of single-crystal ?-SnS
We report on the anisotropic optical properties of single-crystal tin monosulfide (SnS). The components ?{sub a}, ?{sub b}, and ?{sub c} of the pseudodielectric-function tensor ????=???{sub 1}??+?i??{sub 2}? spectra are taken from 0.73 to 6.45?eV by spectroscopic ellipsometry. The measured ??? spectra are in a good agreement with the results of the calculated dielectric response from hybrid density functional theory. The ??? spectra show the direct band-gap onset and a total of eight above-band-gap optical structures that are associated with the interband-transition critical points (CPs). We obtain accurate CP energies by fitting analytic CP expressions to second-energy-derivatives of the ??? data. Their probable electronic origins and implications for photovoltaic applications are discussed.
Banai, R. E.; Brownson, J. R. S. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Burton, L. A.; Walsh, A. [Centre for Sustainable Chemical Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Choi, S. G., E-mail: firstname.lastname@example.com; To, B. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Hofherr, F.; Sorgenfrei, T.; Cr÷ll, A. [CrystallographyŚInstitute of Earth and Environmental Sciences, University of Freiburg, 79104 Freiburg (Germany)
Functional Properties and Genomics of Glucose Transporters
Glucose is the major energy source for mammalian cells as well as an important substrate for protein and lipid synthesis. Mammalian cells take up glucose from extracellular fluid into the cell through two families of structurallyrelated glucose transporters. The facilitative glucose transporter family (solute carriers SLC2A, protein symbol GLUT) mediates a bidirectional and energy-independent process of glucose transport in most tissues and cells, while the NaM+/glucose cotransporter family (solute carriers SLC5A, protein symbol SGLT) mediates an active, Na+-linked transport process against an electrochemical gradient. The GLUT family consists of thirteen members (GLUT1-12 and HMIT). Phylogenetically, the members of the GLUT family are split into three classes based on protein similarities. Up to now, at least six members of the SGLT family have been cloned (SGLT1-6). In this review, we report both the genomic structure and function of each transporter as well as intra-species comparative genomic analysis of some of these transporters. The affinity for glucose and transport kinetics of each transporter differs and ranges from 0.2 to 17mM. The ability of each protein to transport alternative substrates also differs and includes substrates such as fructose and galactose. In addition, the tissue distribution pattern varies between species. There are different regulation mechanisms of these transporters. Characterization of transcriptional control of some of the gene promoters has been investigated and alternative promoter usage to generate different protein isoforms has been demonstrated. We also introduce some pathophysiological roles of these transporters in human. PMID:18660845
Zhao, Feng-Qi; Keating, Aileen F
26 CFR 49.4271-1 - Tax on transportation of property by air.
Code of Federal Regulations, 2010 CFR
...2010-04-01 2010-04-01 true Tax on transportation of property by air. 49.4271-1...FACILITIES AND SERVICES EXCISE TAXES Transportation of Property ¦ 49.4271-1 Tax on transportation of property by air. (a)...
Effect of mechanical boundary conditions on the dynamic and static properties of a strongly anisotropic ferromagnet
The spectra of coupled magnetoelastic waves in a semi-infinite strongly anisotropic easy-plane ferromagnet with a rigidly fixed face are analyzed for two variants of fixation (in the basal plane and perpendicularly to it). The phase states of the system are determined. Differences in the phase diagrams and elementary excitation spectra depending on the choice of the sample fixation plane are considered. When rotational invariance is taken into account, the nonreciprocity effect for the velocities of sound in a crystal appears. It is shown that the velocity of sound in the sample considerably depends on the symmetry of the imposed mechanical boundary conditions. The phase diagrams of the system under investigation are presented.
Gorelikov, G. A.; Fridman, Yu. A., E-mail: firstname.lastname@example.com [Vernadskii Tavria National University (Ukraine)
The microgeometry and transport properties of sedimentary rock
This monograph describes recent progress in modelling the transport properties of sedimentary rock. Statistical descriptions are applied to the pore-space geometry and to the transport processes involving pore fluids. Fractals are used to quantify the pore geometry at length scales shorter than grain size. Percolation theory is applied to fluid flow. The permeability can be expressed in terms of a
A. H. Thompson; A. J. Katz; C. E. Krohn
Electronic and Transport Properties of Ferrocene: Theoretical Study
The transport properties of a single ferrocene molecule have been investigated using the nonequilibrium Green's function formalism for quantum transport and the density functional theory (DFT) of electronic structures using local orbital basis sets. The conductance of a single ferrocenedithiolate molecule depends on the position of the sulfur atoms. The current-voltage characteristics show that the iron atom enhances the conductivity
Tomoki Uehara; Rodion V. Belosludov; Amir A. Farajian; Hiroshi Mizuseki; Yoshiyuki Kawazoe
Computer program for calculating thermodynamic and transport properties of fluids
NASA Technical Reports Server (NTRS)
Computer code has been developed to provide thermodynamic and transport properties of liquid argon, carbon dioxide, carbon monoxide, fluorine, helium, methane, neon, nitrogen, oxygen, and parahydrogen. Equation of state and transport coefficients are updated and other fluids added as new material becomes available.
Hendricks, R. C.; Braon, A. K.; Peller, I. C.
Fluid structure and transport properties of water inside carbon nanotubes
The fluid structure and transport properties of water confined in single-walled carbon nanotubes (CNTs) with different diameters have been investigated by molecular-dynamics simulation. The effects of CNT diameter, density of water, and temperature on the molecular distributions and transport behaviors of water were analyzed. It is interesting that the water molecules ordered in helix inside the (10, 10) CNT, and
Yingchun Liu; Qi Wang; Tao Wu; Li Zhang
Documentation and verification of VST2D; a model for simulating transient, Variably Saturated, coupled water-heat-solute Transport in heterogeneous, anisotropic 2-Dimensional, ground-water systems with variable fluid density
This report describes a model for simulating transient, Variably Saturated, coupled water-heatsolute Transport in heterogeneous, anisotropic, 2-Dimensional, ground-water systems with variable fluid density (VST2D). VST2D was developed to help understand the effects of natural and anthropogenic factors on quantity and quality of variably saturated ground-water systems. The model solves simultaneously for one or more dependent variables (pressure, temperature, and concentration) at nodes in a horizontal or vertical mesh using a quasi-linearized general minimum residual method. This approach enhances computational speed beyond the speed of a sequential approach. Heterogeneous and anisotropic conditions are implemented locally using individual element property descriptions. This implementation allows local principal directions to differ among elements and from the global solution domain coordinates. Boundary conditions can include time-varying pressure head (or moisture content), heat, and/or concentration; fluxes distributed along domain boundaries and/or at internal node points; and/or convective moisture, heat, and solute fluxes along the domain boundaries; and/or unit hydraulic gradient along domain boundaries. Other model features include temperature and concentration dependent density (liquid and vapor) and viscosity, sorption and/or decay of a solute, and capability to determine moisture content beyond residual to zero. These features are described in the documentation together with development of the governing equations, application of the finite-element formulation (using the Galerkin approach), solution procedure, mass and energy balance considerations, input requirements, and output options. The VST2D model was verified, and results included solutions for problems of water transport under isohaline and isothermal conditions, heat transport under isobaric and isohaline conditions, solute transport under isobaric and isothermal conditions, and coupled water-heat-solute transport. The first three problems considered in model verification were compared to either analytical or numerical solutions, whereas the coupled problem was compared to measured laboratory results for which no known analytic solutions or numerical models are available. The test results indicate the model is accurate and applicable for a wide range of conditions, including when water (liquid and vapor), heat (sensible and latent), and solute are coupled in ground-water systems. The cumulative residual errors for the coupled problem tested was less than 10-8 cubic centimeter per cubic centimeter, 10-5 moles per kilogram, and 102 calories per cubic meter for liquid water content, solute concentration and heat content, respectively. This model should be useful to hydrologists, engineers, and researchers interested in studying coupled processes associated with variably saturated transport in ground-water systems.
Friedel, Michael J.
Transport properties of pancreatic cancer describe gemcitabine delivery and response
Background. The therapeutic resistance of pancreatic ductal adenocarcinoma (PDAC) is partly ascribed to ineffective delivery of chemotherapy to cancer cells. We hypothesized that physical properties at vascular, extracellular, and cellular scales influence delivery of and response to gemcitabine-based therapy. Methods. We developed a method to measure mass transport properties during routine contrast-enhanced CT scans of individual human PDAC tumors. Additionally, we evaluated gemcitabine infusion during PDAC resection in 12 patients, measuring gemcitabine incorporation into tumor DNA and correlating its uptake with human equilibrative nucleoside transporter (hENT1) levels, stromal reaction, and CT-derived mass transport properties. We also studied associations between CT-derived transport properties and clinical outcomes in patients who received preoperative gemcitabine-based chemoradiotherapy for resectable PDAC. Results. Transport modeling of 176 CT scans illustrated striking differences in transport properties between normal pancreas and tumor, with a wide array of enhancement profiles. Reflecting the interpatient differences in contrast enhancement, resected tumors exhibited dramatic differences in gemcitabine DNA incorporation, despite similar intravascular pharmacokinetics. Gemcitabine incorporation into tumor DNA was inversely related to CT-derived transport parameters and PDAC stromal score, after accounting for hENT1 levels. Moreover, stromal score directly correlated with CT-derived parameters. Among 110 patients who received preoperative gemcitabine-based chemoradiotherapy, CT-derived parameters correlated with pathological response and survival. Conclusion. Gemcitabine incorporation into tumor DNA is highly variable and correlates with multiscale transport properties that can be derived from routine CT scans. Furthermore, pretherapy CT-derived properties correlate with clinically relevant endpoints. Trial registration. Clinicaltrials.gov NCT01276613. Funding. Lustgarten Foundation (989161), Department of Defense (W81XWH-09-1-0212), NIH (U54CA151668, KCA088084). PMID:24614108
Koay, Eugene J.; Truty, Mark J.; Cristini, Vittorio; Thomas, Ryan M.; Chen, Rong; Chatterjee, Deyali; Kang, YaÆan; Bhosale, Priya R.; Tamm, Eric P.; Crane, Christopher H.; Javle, Milind; Katz, Matthew H.; Gottumukkala, Vijaya N.; Rozner, Marc A.; Shen, Haifa; Lee, Jeffery E.; Wang, Huamin; Chen, Yuling; Plunkett, William; Abbruzzese, James L.; Wolff, Robert A.; Varadhachary, Gauri R.; Ferrari, Mauro; Fleming, Jason B.
Technology Transfer Automated Retrieval System (TEKTRAN)
Hydraulic and chemical transport properties are the major inputs in predictive models that simulate the movement of water and chemicals through the vadose zone. However, there is a lack of field measurements of such properties to verify models describing water and chemical movement through the soil...
Diameter Dependence of the Transport Properties of Antimony Telluride Nanowires
Diameter Dependence of the Transport Properties of Antimony Telluride Nanowires Yuri M. Zuev, Jin properties of individual single crystal antimony telluride (Sb2Te3) nanowires with diameters in the range figure of merit in single crystal chalcogenide Sb2Te3 NWs. Antimony telluride (Sb2Te3) is a small bandgap
Heller, Eric
Magnetic and Transport Properties of Mn-ion implanted Si
NASA Astrophysics Data System (ADS)
We investigate the magnetic and transport properties of Mn-ion implanted Si. Both temperature dependent and field dependent measurements of the samples using a SQUID magnometer reveal ferromagnetic properties at room temperature. Magnetotransport measurements show a large positive magnetoresistance up to 4.5 T with no signs of saturation.
Preisler, V.; Ogawa, M.; Han, X.; Wang, K. L.
Transport Properties from Molecular Simulation with the SPEADMD Model
Molecular dynamics simulation holds the prospect of predicting both thermodynamic and transport properties through a single characterization of molecular interactions and liberal application of Newton's Laws of motion. The SPEADMD model (Step Potential Equilibria And Discontinuous Molecular Dynamics) has been developed based primarily on thermodynamic properties until now. This presentation illustrates how an analogous approach can form the basis for
J. Richard; Elliott C; Neil Gray
Anisotropic electrical and magnetic properties of epitaxial Ga2-xFexO3 thin films with different crystalline orientations
NASA Astrophysics Data System (ADS)
Anisotropy of electrical and magnetic properties in magnetoelectric and multiferroic materials is an important issue for applications of the materials to electronic devices. Ga2-xFexO3 (GFO) has been known as a pyroelectric ferrimagnet at room temperature when x > 1.4. GFO exhibits a permanent polarization along b-axis while a spontaneous net magnetization along c-axis. Exploration of its anisotropic properties requires preferentially oriented epitaxial thin films of GFO with different crystalline orientations. We have grown successfully b-axis oriented GFO thin films on indium-tin oxide(001)/yttria-stabilized zirconia(001). Two additional bottom electrodes such as SrRuO3 on SrTiO3(111), (110) and (100) and Pt(111)/Ti/SiO2/Si substrates were used for epitaxial growth of GFO. X-ray diffraction and transmission electron microscopy have been performed. Dielectric permittivity of the GFO films was measured with external magnetic field as a function of temperature. Local polarization switching behavior was characterized by scanning probe microscopy, which can give a clue to answer a debating question that GFO thin films are pyroelectric with no bistable switching states.
Hye Lee, Ji; Jo, William
and resonant tunneling Ł quantum dot Energy (t) Length and smoothness #12;GAP GAP Finite-mass Fabry-Perot-ballistic transport Optical Fabry-Perot, zero mass like a photon, open system #12;Open system, quasi-ballistic, strong #12;Larger No. of oscillations Fabry-Perot quasiballistic Smothness leads to enhanced confinement
Yannouleas, Constantine
NASA Technical Reports Server (NTRS)
Scientists and engineers need chemical equilibrium composition data to calculate the theoretical thermodynamic properties of a chemical system. This information is essential in the design and analysis of equipment such as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical processing equipment. The substantial amount of numerical computation required to obtain equilibrium compositions and transport properties for complex chemical systems led scientists at NASA's Lewis Research Center to develop CET89, a program designed to calculate the thermodynamic and transport properties of these systems. CET89 is a general program which will calculate chemical equilibrium compositions and mixture properties for any chemical system with available thermodynamic data. Generally, mixtures may include condensed and gaseous products. CET89 performs the following operations: it 1) obtains chemical equilibrium compositions for assigned thermodynamic states, 2) calculates dilute-gas transport properties of complex chemical mixtures, 3) obtains Chapman-Jouguet detonation properties for gaseous species, 4) calculates incident and reflected shock properties in terms of assigned velocities, and 5) calculates theoretical rocket performance for both equilibrium and frozen compositions during expansion. The rocket performance function allows the option of assuming either a finite area or an infinite area combustor. CET89 accommodates problems involving up to 24 reactants, 20 elements, and 600 products (400 of which may be condensed). The program includes a library of thermodynamic and transport properties in the form of least squares coefficients for possible reaction products. It includes thermodynamic data for over 1300 gaseous and condensed species and transport data for 151 gases. The subroutines UTHERM and UTRAN convert thermodynamic and transport data to unformatted form for faster processing. The program conforms to the FORTRAN 77 standard, except for some input in NAMELIST format. It requires about 423 KB memory, and is designed to be used on mainframe, workstation, and mini computers. Due to its memory requirements, this program does not readily lend itself to implementation on MS-DOS based machines.
Mcbride, B.
Transport properties of a meson gas
We present recent results on a systematic method to calculate transport coefficients for a meson gas (in particular, we analyze a pion gas) at low temperatures in the context of Chiral Perturbation Theory. Our method is based on the study of Feynman diagrams with a power counting which takes into account collisions in the plasma by means of a non-zero particle width. In this way, we obtain results compatible with analysis of Kinetic Theory with just the leading order diagram. We show the behavior with temperature of electrical and thermal conductivities and shear and bulk viscosities, and we discuss the fundamental role played by unitarity. We obtain that bulk viscosity is negligible against shear viscosity near the chiral phase transition. Relations between the different transport coefficients and bounds on them based on different theoretical approximations are also discussed. We also comment on some applications to heavy-ion collisions.
D. Fernandez-Fraile; A. Gomez Nicola
Lagrangian transport properties of pulmonary interfacial flows
Disease states characterized by airway fluid occlusion and pulmonary surfactant insufficiency, such as respiratory distress syndrome, have a high mortality rate. Understanding the mechanics of airway reopening, particularly involving surfactant transport, may provide an avenue to increase patient survival via optimized mechanical ventilation waveforms. We model the occluded airway as a liquid-filled rigid tube with the fluid phase displaced by a finger of air that propagates with both mean and sinusoidal velocity components. Finite-time Lyapunov exponent (FTLE) fields are employed to analyse the convective transport characteristics, taking note of Lagrangian coherent structures (LCSs) and their effects on transport. The Lagrangian perspective of these techniques reveals flow characteristics that are not readily apparent by observing Eulerian measures. These analysis techniques are applied to surfactant-free velocity fields determined computationally, with the boundary element method, and measured experimentally with micro particle image velocimetry (?-PIV). We find that the LCS divides the fluid into two regimes, one advected upstream (into the thin residual film) and the other downstream ahead of the advancing bubble. At higher oscillatory frequencies particles originating immediately inside the LCS experience long residence times at the air¢liquid interface, which may be conducive to surfactant transport. At high frequencies a well-mixed attractor region is identified; this volume of fluid cyclically travels along the interface and into the bulk fluid. The Lagrangian analysis is applied to velocity data measured with 0.01 mg ml?1 of the clinical pulmonary surfactant Infasurf in the bulk fluid, demonstrating flow field modifications with respect to the surfactant-free system that were not visible in the Eulerian frame. PMID:23049141
Smith, Bradford J.; Lukens, Sarah; Yamaguchi, Eiichiro; Gaver, Donald P.
Unsaturated Zone and Saturated Zone Transport Properties (U0100)
This Analysis/Model Report (AMR) summarizes transport properties for the lower unsaturated zone hydrogeologic units and the saturated zone at Yucca Mountain and provides a summary of data from the Busted Butte Unsaturated Zone Transport Test (UZTT). The purpose of this report is to summarize the sorption and transport knowledge relevant to flow and transport in the units below Yucca Mountain and to provide backup documentation for the sorption parameters decided upon for each rock type. Because of the complexity of processes such as sorption, and because of the lack of direct data for many conditions that may be relevant for Yucca Mountain, data from systems outside of Yucca Mountain are also included. The data reported in this AMR will be used in Total System Performance Assessment (TSPA) calculations and as general scientific support for various Process Model Reports (PMRs) requiring knowledge of the transport properties of different materials. This report provides, but is not limited to, sorption coefficients and other relevant thermodynamic and transport properties for the radioisotopes of concern, especially neptunium (Np), plutonium (Pu), Uranium (U), technetium (Tc), iodine (I), and selenium (Se). The unsaturated-zone (UZ) transport properties in the vitric Calico Hills (CHv) are discussed, as are colloidal transport data based on the Busted Butte UZTT, the saturated tuff, and alluvium. These values were determined through expert elicitation, direct measurements, and data analysis. The transport parameters include information on interactions of the fractures and matrix. In addition, core matrix permeability data from the Busted Butte UZTT are summarized by both percent alteration and dispersion.
J. Conca
Determination of the anisotropic elastic properties of Ge1Sb2Te4
NASA Astrophysics Data System (ADS)
The elastic properties of Ge-Sb-Te (GST) alloys are important for phase-change devices (such as CD-RW, DVD-RW, Blu-ray, or phase-change random access memory) because the transition between the crystalline and amorphous phases involves a volume change accommodated by a strain estimated to be between 150 MPa and 10 GPa. However, the elastic properties of GST alloys are poorly characterized and the experimental and theoretical values show large discrepancies. We carry out a careful analysis of the elastic properties of a model system, crystalline Ge1Sb2Te4, using density functional theory and elastic anisotropy considerations. We show that Ge1Sb2Te4 exhibits significant anisotropy in its elastic properties.
Marmier, Arnaud; Kohary, Krisztian; Wright, C. David
Properties of intracellular transport: the role of cytoskeleton topology
NASA Astrophysics Data System (ADS)
The eukaryotic cytoskeleton is composed of polarized filaments forming a complex, intertwined network. Various motor proteins such as kinesins or myosins convert ATP into mechanical work and are able to walk processively or even diffuse along the cytoskeleton. Large organelles such as vesicles or mitochondria can randomly bind and unbind to one or several motors and their transport in the cell can be described as alternating phases of diffusion in the cytoplasm and phases of directed or diffusive transport along the cytoskeletal network. Intracellular transport has been the focus of extensive studies both experimentally and theoretically. However, the impact of the cytoskeleton network structure on transport properties, which is expected to be significant, is not fully understood. We develop a computational model of intracellular transport, and explore the impact of the cytoskeletal structure on transport properties. We show that transport can be enhanced even by diffusional motion along the cytoskeleton after memory effects due to cytoskeletal structure are taken into account. We also explore the influence of the network structure on the first passage time distributions for a cargo to reach the cell membrane after being exported from the nucleus and for transport from the membrane to the nucleus.
Korabel, Nickolay; Huang, Kerwyn C.; Gopinathan, Ajay
Enhancement of wall jet transport properties
By enhancing the natural instabilities in the boundary layer and in the free shear layer of a wall jet, the boundary is minimized thereby increasing the transport of heat and mass. Enhancing the natural instabilities is accomplished by pulsing the flow of air that creates the wall jet. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct.
Claunch, Scott D. (Broomfield, CO); Farrington, Robert B. (Golden, CO)
Enhancement of wall jet transport properties
By enhancing the natural instabilities in the boundary layer and in the free shear layer of a wall jet, the boundary is minimized thereby increasing the transport of heat and mass. Enhancing the natural instabilities is accomplished by pulsing the flow of air that creates the wall jet. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct. 17 figs.
Claunch, S.D.; Farrington, R.B.
Transport properties of high-temperature Jupiter atmosphere components
Transport properties of high-temperature helium and hydrogen plasmas as well as Jupiter atmosphere have been calculated for equilibrium and nonequilibrium conditions using higher approximations of the Chapman-Enskog method. A complete database of transport cross sections for relevant interactions has been derived, including minority species, by using both ab initio and phenomenological potentials. Inelastic collision integrals terms, due to resonant charge-exchange channels, have been also considered.
Bruno, D.; Colonna, G.; De Pascale, O.; Laricchiuta, A. [Department of Chemistry, University of Bari, via Orabona 4 Bari 70125 (Italy); Catalfamo, C.; Diomede, P. [CNR-IMIP Bari, via Orabona 4 Bari 70125 (Italy); Capitelli, M.; Gorse, C.; Longo, S. [Department of Chemistry, University of Bari, via Orabona 4 Bari 70125 (Italy); CNR-IMIP Bari, via Orabona 4 Bari 70125 (Italy); Giordano, D. [Aerothermodynamics Section, ESA-ESTEC, Keplerlaan 1 2200 AG Noordwijk (Netherlands); Pirani, F. [Department of Chemistry, University of Perugia, via Elce di Sotto 8 Perugia 06123 (Italy)
High temperature transport properties of air
NASA Technical Reports Server (NTRS)
A general computer code was developed to allow calculation of atom-atom and ion-atom transport collision integrals from accurate potential energy curves described by a set of discrete data points for a broad range of scattering conditions. This code is based upon semiclassical approximations that properly account for quantum mechanical behavior such as tunneling effects near a barrier maximum, resonance charge exchange, and nuclear symmetry effects. Transport collision integrals were determined for N-N, O-O, N(+)-N, and O(+)-O interactions from complete sets of accurate potential functions derived from combined experimental and ab initio structure calculations. For the O-O case, this includes results for excited states. The calculated values of the N(+)-N and O(+)-O resonance charge exchange cross section Q(ex) agree well with measurements from beam experiment that are available at high energies where the diffusion cross section Q(d) satisfies Q(d) approximately equal to 2Q(ex).
Levin, E.; Partridge, Harry; Stallcop, J. R.
Anisotropic Flow from RHIC to the LHC
Anisotropic flow is recognized as one of the main observables providing information on the early stage of a heavy-ion collision. At RHIC the large observed anisotropic flow and its successful description by ideal hydrodynamics is considered evidence for an early onset of thermalization and almost ideal fluid properties of the produced strongly coupled Quark Gluon Plasma. This write-up discusses some key RHIC anisotropic flow measurements and for anisotropic flow at the LHC some predictions.
Raimond Snellings
Transport properties in nontwist area-preserving maps
Nontwist systems, common in the dynamical descriptions of fluids and plasmas, possess a shearless curve with a concomitant transport barrier that eliminates or reduces chaotic transport, even after its breakdown. In order to investigate the transport properties of nontwist systems, we analyze the barrier escape time and barrier transmissivity for the standard nontwist map, a paradigm of such systems. We interpret the sensitive dependence of these quantities upon map parameters by investigating chaotic orbit stickiness and the associated role played by the dominant crossing of stable and unstable manifolds.
Szezech Jr., J. D. [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo (Brazil); Caldas, I. L. [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo (Brazil); Lopes, S. R. [Departamento de Fisica, Universidade Federal do Parana, Curitiba (Brazil); Viana, R. L. [Departamento de Fisica, Universidade Federal do Parana, Curitiba (Brazil); Morrison, P. J. [Univ. of Texas at Austin (United States)
Transport properties associated with carbon-phenolic ablators
NASA Technical Reports Server (NTRS)
Entry vehicle heat shields designed for entry into the atmosphere of the outer planets are usually made of carbonaceous material such as carbon-phenolic ablator. Ablative injection of this material is an important mechanism for reducing the heat at the surface of the entry vehicle. Conductive transport properties in the shock layer are important for some entry conditions. The kinetic theory of gases has been used to calculate the transport properties for 17 gaseous species obtained from the ablation of carbon-phenolic heat shields. Results are presented for the pure species and for the gas mixture.
Biolsi, L.
Thermal transport properties of rolled graphene nanoribbons
NASA Astrophysics Data System (ADS)
Using nonequilibrium Green's function method, we investigate the influence of the curvature and edge effects on the thermal transport during the process of rolling graphene nanoribbons (GNRs) into carbon nanotubes (CNTs) in the transverse direction. The curvature effect results in a slight decrease in the thermal conductance of GNRs, which is remarkably different from that in the longitudinal direction. The curvature and edge effects show a strong size and chirality dependence, while the curvature effect is more sensitive to the size. When the size equals to 12.8 nm (49.2 nm) with the zigzag (armchair) edge, the edge effect results in the reduction of thermal conductance of 2.4% (13.0%) as compared to the corresponding CNT, but the curvature effect vanishes.
Li, Dengfeng; Li, Bolin; Luo, Min; Feng, Chunbao; Ouyang, Tao; Gao, Fei
Field-dependent anisotropic microrheological and microstructural properties of dilute ferrofluids.
We have measured microrheological and microstructural properties of a superparamagnetic ferrofluid made of Mn0.75Zn0.25Fe2O4 (MZF) nanoparticles, using passive microrheology in a home-built inverted microscope. Thermal motion of a probe microsphere was measured for different values of an applied external magnetic field and analysed. The analysis shows anisotropy in magneto-viscous effect. Additional microrheological properties, such as storage modulus and loss modulus and their transition are also seen. We have also obtained microstructural properties such as elongational flow coefficient [Formula: see text] , relaxation time constant [Formula: see text] , coefficient of dissipative magnetization [Formula: see text] , etc., using the analysis given in Oliver Muller et al., J. Phys.: Condens. Matter 18, S2623, (2006) and Stefan Mahle et al., Phys. Rev. E 77, 016305 (2008) over our measured viscosity data. Our values for the above parameters are in agreement with earlier theoretical calculations and macro-rheological experimental measurements. These theoretical calculations consider an ideal situation of zero-shear limit, which is best approximated only in the passive microrheology technique described here and a first time measurement of all these parameters with passive microrheology. PMID:25117500
Yendeti, Balaji; Thirupathi, G; Vudaygiri, Ashok; Singh, R
Abnormal percolative transport and colossal electroresistance induced by anisotropic strain in (011)-Pr0.7(Ca0.6Sr0.4)0.3MnO3/PMN-PT heterostructure
Abnormal percolative transport in inhomogeneous systems has drawn increasing interests due to its deviation from the conventional percolation picture. However, its nature is still ambiguous partly due to the difficulty in obtaining controllable abnormal percolative transport behaviors. Here, we report the first observation of electric-field-controlled abnormal percolative transport in (011)-Pr0.7(Ca0.6Sr0.4)0.3MnO3/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 heterostructure. By introducing an electric-field-induced in-plane anisotropic strain-field in a phase separated PCSMO film, we stimulate a significant inverse thermal hysteresis (~ -17.5?K) and positive colossal electroresistance (~11460%), which is found to be crucially orientation-dependent and completely inconsistent with the well accepted conventional percolation picture. Further investigations reveal that such abnormal inverse hysteresis is strongly related to the preferential formation of ferromagnetic metallic domains caused by in-plane anisotropic strain-field. Meanwhile, it is found that the positive colossal electroresistance should be ascribed to the coactions between the anisotropic strain and the polarization effect from the poling of the substrate which leads to orientation and bias-polarity dependencies for the colossal electroresistance. This work unambiguously evidences the indispensable role of the anisotropic strain-field in driving the abnormal percolative transport and provides a new perspective for well understanding the percolation mechanism in inhomogeneous systems. PMID:25399635
Zhao, Ying-Ying; Wang, Jing; Kuang, Hao; Hu, Feng-Xia; Zhang, Hong-Rui; Liu, Yao; Zhang, Ying; Wang, Shuan-Hu; Wu, Rong-Rong; Zhang, Ming; Bao, Li-Fu; Sun, Ji-Rong; Shen, Bao-Gen
Abnormal percolative transport and colossal electroresistance induced by anisotropic strain in (011)-Pr0.7(Ca0.6Sr0.4)0.3MnO3/PMN-PT heterostructure
NASA Astrophysics Data System (ADS)
Abnormal percolative transport in inhomogeneous systems has drawn increasing interests due to its deviation from the conventional percolation picture. However, its nature is still ambiguous partly due to the difficulty in obtaining controllable abnormal percolative transport behaviors. Here, we report the first observation of electric-field-controlled abnormal percolative transport in (011)-Pr0.7(Ca0.6Sr0.4)0.3MnO3/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 heterostructure. By introducing an electric-field-induced in-plane anisotropic strain-field in a phase separated PCSMO film, we stimulate a significant inverse thermal hysteresis (~ -17.5 K) and positive colossal electroresistance (~11460%), which is found to be crucially orientation-dependent and completely inconsistent with the well accepted conventional percolation picture. Further investigations reveal that such abnormal inverse hysteresis is strongly related to the preferential formation of ferromagnetic metallic domains caused by in-plane anisotropic strain-field. Meanwhile, it is found that the positive colossal electroresistance should be ascribed to the coactions between the anisotropic strain and the polarization effect from the poling of the substrate which leads to orientation and bias-polarity dependencies for the colossal electroresistance. This work unambiguously evidences the indispensable role of the anisotropic strain-field in driving the abnormal percolative transport and provides a new perspective for well understanding the percolation mechanism in inhomogeneous systems.
Zhao, Ying-Ying; Wang, Jing; Kuang, Hao; Hu, Feng-Xia; Zhang, Hong-Rui; Liu, Yao; Zhang, Ying; Wang, Shuan-Hu; Wu, Rong-Rong; Zhang, Ming; Bao, Li-Fu; Sun, Ji-Rong; Shen, Bao-Gen
ElAM: A computer program for the analysis and representation of anisotropic elastic properties
NASA Astrophysics Data System (ADS)
The continuum theory of elasticity has been used for more than a century and has applications in many fields of science and engineering. It is very robust, well understood and mathematically elegant. In the isotropic case elastic properties are easily represented, but for non-isotropic materials, even in the simple cubic symmetry, it can be difficult to visualise how properties such as Young's modulus or Poisson's ratio vary with stress/strain orientation. The ElAM ( Elastic Anisotropy Measures) code carries out the required tensorial operations (inversion, rotation, diagonalisation) and creates 3D models of an elastic property's anisotropy. It can also produce 2D cuts in any given plane, compute averages following diverse schemes and query a database of elastic constants to support meta-analyses. Program summaryProgram title: ElAM1.0 Catalogue identifier: AEHB_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHB_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 43 848 No. of bytes in distributed program, including test data, etc.: 2 498 882 Distribution format: tar.gz Programming language: Fortran90 Computer: Any Operating system: Linux, Windows (XP, Vista) RAM: Depends chiefly on the size of the arrays representing elastic properties in 3D Classification: 7.7 Nature of problem: Representation of elastic moduli and ratios, and of wave velocities, in 3D; automatic discovery of unusual elastic properties. Solution method: Stiffness matrix (6ū6) inversion and conversion to compliance tensor (3ū3ū3ū3), tensor rotation, dynamic matrix diagonalisation, simple optimisation, postscript and VRML output preparation. Running time: Dependent on angular accuracy and size of elastic constant database (from a few seconds to a few hours). The tests provided take from a few seconds for test0 to approximately 1 hour for test4.
Marmier, Arnaud; Lethbridge, Zoe A. D.; Walton, Richard I.; Smith, Christopher W.; Parker, Stephen C.; Evans, Kenneth E.
Transport properties of nonhomogeneous segregated composites
NASA Astrophysics Data System (ADS)
In conductor-insulator composites in which the conducting particles are dispersed in an insulating continuous matrix the electrical connectedness is established by interparticle quantum tunneling. A recent formulation of the transport problem in these kinds of composites treats each conducting particle as electrically connected to all others via tunneling conductances to form a global tunneling network. Here, we extend this approach to nonhomogeneous composites with a segregated distribution of the conducting phase. We consider a model of segregation in which large random insulating spherical inclusions forbid small conducting particles to occupy homogeneously the volume of the composite, and allow tunneling between all pairs of the conducting objects. By solving numerically the corresponding tunneling resistor network, we show that the composite conductivity ? is enhanced by segregation and that it may remain relatively large also for very small values of the conducting filler concentration. We interpret this behavior by a segregation-induced reduction of the interparticle distances, which is confirmed by a critical path approximation applied to the segregated network. Furthermore, we identify an approximate but accurate scaling relation permitting us to express the conductivity of a segregated systems in terms of the interparticle distances of a corresponding homogeneous system, and which provides an explicit formula for ? which we apply to experimental data on segregated RuO2-cermet composites.
Nigro, B.; Ambrosetti, G.; Grimaldi, C.; Maeder, T.; Ryser, P.
Unusual transport and highly anisotropic thermopower in PtCoO2 and PdCoO2
We show, using Boltzmann transport calculations and analysis of experimental data, that hexagonal PdCoO2 and PtCoO2 have a highly unusual metallic transport. The in-plane transport is typical of a very good metal, with high conductivity and low positive thermopower. The c-axis transport is completely different, with 2 orders of magnitude lower, but still coherent, conductivity and remarkably a very large negative thermopower. This large anisotropy of the thermopower provides an opportunity for investigating transport in a highly unusual regime using bulk materials.
Ong, Khuong P [IHPC, Singapore; Singh, David J [ORNL; Wu, Ping [IHPC, Singapore
Unusual Transport and Strongly Anisotropic Thermopower in PtCoO2 and PdCoO2
We show, using Boltzmann transport calculations and analysis of experimental data, that hexagonal PdCoO2 and PtCoO2 have a highly unusual metallic transport. The in-plane transport is typical of a very good metal, with high conductivity and low positive thermopower. The c-axis transport is completely different, with 2 orders of magnitude lower, but still coherent, conductivity and remarkably a very large negative thermopower. This large anisotropy of the thermopower provides an opportunity for investigating transport in a highly unusual regime using bulk materials.
Singh, David J.; Wu, Ping; Ong, Khuong P.
Micropatterned cell sheets with defined cell and extracellular matrix orientation exhibit anisotropic mechanical properties.
For an arterial replacement graft to be effective, it must possess the appropriate strength in order to withstand long-term hemodynamic stress without failure, yet be compliant enough that the mismatch between the stiffness of the graft and the native vessel wall is minimized. The native vessel wall is a structurally complex tissue characterized by circumferentially oriented collagen fibers/cells and lamellar elastin. Besides the biochemical composition, the functional properties of the wall, including stiffness, depend critically on the structural organization. Therefore, it will be crucial to develop methods of producing tissues with defined structures in order to more closely mimic the properties of a native vessel. To this end, we sought to generate cell sheets that have specific ECM/cell organization using micropatterned polydimethylsiloxane (PDMS) substrates to guide cell organization and tissue growth. The patterns consisted of large arrays of alternating grooves and ridges. Adult bovine aortic smooth muscle cells cultured on these substrates in the presence of ascorbic acid produced ECM-rich sheets several cell layers thick in which both the cells and ECM exhibited strong alignment in the direction of the micropattern. Moreover, mechanical testing revealed that the sheets exhibited mechanical anisotropy similar to that of native vessels with both the stiffness and strength being significantly larger in the direction of alignment, demonstrating that the microscale control of ECM organization results in functional changes in macroscale material behavior. PMID:22177672
Isenberg, Brett C; Backman, Daniel E; Kinahan, Michelle E; Jesudason, Rajiv; Suki, Bela; Stone, Phillip J; Davis, Elaine C; Wong, Joyce Y
Structure and transport properties of nanostructured materials.
In the present manuscript, we have presented the simulation of nanoporous aluminum oxide using a molecular-dynamics approach with recently developed dynamic charge transfer potential using serial/parallel programming techniques (Streitz and Mintmire Phys. Rev. B 1994, 50, 11996). The structures resembling recently invented ordered nanoporous crystalline material, MCM-41/SBA-15 (Kresge et al. Nature 1992, 359, 710), and inverted porous solids (hollow nanospheres) with up to 10 000 atoms were fabricated and studied in the present work. These materials have been used for separation of gases and catalysis. On several occasions including the design of the reactor, the knowledge of surface diffusion is necessary. In the present work, a new method for estimating surface transport of gases based on a hybrid Monte Carlo method with unbiased random walk of tracer atom on the pore surface has been introduced. The nonoverlapping packings used in the present work were fabricated using an algorithm of very slowly settling rigid spheres from a dilute suspension into a randomly packed bed. The algorithm was modified to obtain unimodal, homogeneous Gaussian and segregated bimodal porous solids. The porosity of these solids was varied by densification using an arbitrary function or by coarsening from a highly densified pellet. The surface tortuosity for the densified solids indicated an inverted bell shape curve consistent with the fact that at very high porosities there is a reduction in the connectivity while at low porosities the pores become inaccessible or dead-end. The first passage time distribution approach was found to be more efficient in terms of computation time (fewer tracer atoms needed for the linearity of Einstein's plot). Results by hybrid discrete-continuum simulations were close to the discrete simulations for a boundary layer thickness of 5lambda. PMID:16851615
Sonwane, C G; Li, Q
Anisotropic adhesion of micropillars with spatula pads.
Natural gecko adhesive structures consisting of angled setae, branched into thin spatulas, have remarkable properties including easily attachable and releasable anisotropic adhesion. The geometrically asymmetric structures lead to anisotropic adhesive properties. Inspired by the gecko, we fabricated an array of micropillars with asymmetric spatula pads from elastomeric materials. This paper describes the anisotropic properties of the micropillars with spatula pads as established by experimental measurements and observation together with finite element analysis. The results indicate that the structural difference of the spatula pad at one edge of the micropillar provides the anisotropic adhesive properties. PMID:24446878
Seo, Seungwan; Lee, Jehong; Kim, Kwang-Seop; Ko, Kwang Hee; Lee, Jong Hyun; Lee, Jongho
-1- THERMODYNAMIC AND TRANSPORT PROPERTIES OF SILICATE MELTS AND MAGMA Charles E. Lesher Pliny the Elder (c. AD 23-79) ________________________________________ TABLE OF CONTENTS I. GLOSSARY1 II. NOMENCLATURE2 III. INTRODUCTION3 IV. MAGMATIC SYSTEMS: TIME AND LENGTH SCALES4 V. MAGMA THERMODYNAMIC
Spera, Frank J.
Reference Fluid Thermodynamic and Transport Properties Database (REFPROP)
National Institute of Standards and Technology Data Gateway
SRD 23 NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP) (PC database for purchase)ĀĀ NIST 23 contains revised data in a Windows version of the database, including 105 pure fluids and allowing mixtures of up to 20 components. The fluids include the environmentally acceptable HFCs, traditional HFCs and CFCs and 'natural' refrigerants like ammonia
Transport properties of a Bentheim sandstone under deformation.
The mechanical and transport properties of a Bentheim sandstone are studied both experimentally and numerically. Three classical classes of loads are applied to a sample whose permeability is measured. The elasticity and the Stokes equations are discretized on unstructured tetrahedral meshes which precisely follow the deformations of the sample. Numerical results are presented, discussed, and compared to the available experimental data. PMID:25679736
Jasinski, L; Sangarķ, D; Adler, P M; Mourzenko, V V; Thovert, J-F; Gland, N; Bķkri, S
Transport properties of self-affine rough fractures
We present analytical and numerical results of permeability and tracer dispersion in fractures with self-affine rough surfaces. We analize the variation of these macroscopic transport properties with the size of the fracture gap and present scaling relations, in terms of the roughness (Hurst) exponent characterizing the self-affine surfaces, which are confirmed by numerical results. We also analyze the effect of
German Drazer; Joel Koplik
Oxygen transport properties estimation by DSMC-CT simulations
NASA Astrophysics Data System (ADS)
Coupling DSMC simulations with classical trajectories calculations is emerging as a powerful tool to improve predictive capabilities of computational rarefied gas dynamics. The considerable increase of computational effort outlined in the early application of the method (Koura,1997) can be compensated by running simulations on massively parallel computers. In particular, GPU acceleration has been found quite effective in reducing computing time (Ferrigni,2012; Norman et al.,2013) of DSMC-CT simulations. The aim of the present work is to study rarefied Oxygen flows by modeling binary collisions through an accurate potential energy surface, obtained by molecular beams scattering (Aquilanti, et al.,1999). The accuracy of the method is assessed by calculating molecular Oxygen shear viscosity and heat conductivity following three different DSMC-CT simulation methods. In the first one, transport properties are obtained from DSMC-CT simulations of spontaneous fluctuation of an equilibrium state (Bruno et al, Phys. Fluids, 23, 093104, 2011). In the second method, the collision trajectory calculation is incorporated in a Monte Carlo integration procedure to evaluate the Taxman's expressions for the transport properties of polyatomic gases (Taxman,1959). In the third, non-equilibrium zero and one-dimensional rarefied gas dynamic simulations are adopted and the transport properties are computed from the non-equilibrium fluxes of momentum and energy. The three methods provide close values of the transport properties, their estimated statistical error not exceeding 3%. The experimental values are slightly underestimated, the percentage deviation being, again, few percent.
Bruno, Domenico; Frezzotti, Aldo; Ghiroldi, Gian Pietro
Nonlinear transport properties of non-ideal systems
NASA Astrophysics Data System (ADS)
The theory of nonlinear transport is elaborated to determine the Burnett transport properties of non-ideal multi-element plasma and neutral systems. The procedure for the comparison of the phenomenological conservation equations of a continuous dense medium and the microscopic equations for dynamical variable operators is used for the definition of these properties. The Mori algorithm is developed to derive the equations of motion of dynamical value operators of a non-ideal system in the form of the generalized nonlinear Langevin equations. In consequence, the microscopic expressions of transport coefficients corresponding to second-order thermal disturbances (temperature, mass velocity, etc) have been found in the long wavelength and low frequency limits.
Pavlov, G. A.
Exceptional charge transport properties of graphene on germanium.
The excellent charge transport properties of graphene suggest a wide range of application in analog electronics. While most practical devices will require that graphene be bonded to a substrate, such bonding generally degrades these transport properties. In contrast, when graphene is transferred to Ge(001) its conductivity is extremely high and the charge carrier mobility derived from the relevant transport measurements is, under some circumstances, higher than that of freestanding, edge-supported graphene. We measure a mobility of ? 5 ū 10(5) cm(2) V(-1) s(-1) at 20 K, and ? 10(3) cm(2) V(-1) s(-1) at 300 K. These values are close to the theoretical limit for doped graphene. Carrier densities in the graphene are as high as 10(14) cm(-2) at 300 K. PMID:25203974
Cavallo, Francesca; Rojas Delgado, Richard; Kelly, Michelle M; Sßnchez Pķrez, Josķ R; Schroeder, Daniel P; Xing, Huili Grace; Eriksson, Mark A; Lagally, Max G
Effects of nanosized constriction on thermal transport properties of graphene
Thermal transport properties of graphene with nanosized constrictions are investigated using nonequilibrium molecular dynamics simulations. The results show that the nanosized constrictions have a significant influence on the thermal transport properties of graphene. The thermal resistance of the nanosized constrictions is on the order of 107 to 109ĀK/W at 150ĀK, which reduces the thermal conductivity by 7.7% to 90.4%. It is also found that the constriction resistance is inversely proportional to the width of the constriction and independent of the heat current. Moreover, we developed an analytical model for the ballistic thermal resistance of the nanosized constrictions in two-dimensional nanosystems. The theoretical prediction agrees well with the simulation results in this paper, which suggests that the thermal transport across the nanosized constrictions in two-dimensional nanosystems is ballistic in nature. PACS 65.80.CK; 61.48.Gh; 63.20.kp; 31.15.xv PMID:25232292
Electronic transport properties of an armchair boron-nitride nanotube
NASA Astrophysics Data System (ADS)
We present a theoretical study of electron transport properties through boron-nitride nanotube (BNNT) and contrast them to those of carbon nanotube (CNT). The work is based on a tight-binding Hamiltonian model within the framework of a generalized Green's function technique and relies on the Landauer-B³tikker formalism as the basis for studying the current-voltage characteristic of this system. We use an armchair single-walled BNNT in the CNT/BNNT/CNT structure. We numerically compute the transport properties in terms of transmission and current-voltage characteristic. Our calculations show that the electron transport can open a conduction gap in the CNT/BNNT/CNT structure.
Vahedi Fakhrabad, D.; Ashhadi, M.
Universal Multifractal Properties of the Small Scale Intermittency in Anisotropic and Inhomogeneous Turbulence
The notion of self-similar energy cascades and multifractality has long since been connected with fully developed, homogeneous and isotropic turbulence. We introduce a number of amendments to the standard methods for analysing the multifractal properties of the energy dissipation field of a turbulent flow. We conjecture that the scaling assumption for the moments of the energy dissipation rate is valid within the transition range to dissipation introduced by Castaing et al.(Physica D (46), 177 (1990)). The multifractal spectral functions appear to be universal well within the error margins and exhibit some as yet undiscussed features. Furthermore, this universality is also present in the neither homogeneous nor isotropic flows in the wake very close to a cylinder or the off-centre region of a free jet.
M. Alber; S. Lueck; C. Renner; J. Peinke
Transport properties in semiconducting NbS{sub 2} nanoflakes
The electronic transport properties in individual niobium disulphide (NbS{sub 2}) nanoflakes mechanically exfoliated from the bulk crystal with three rhombohedral (3R) structure grown by chemical vapor transport were investigated. It is found that the conductivity values of the single-crystalline nanoflakes are approximately two orders of magnitude lower than that of their bulk counterparts. Temperature-dependent conductivity measurements show that the 3R-NbS{sub 2} nanoflakes exhibit semiconducting transport behavior, which is also different from the metallic character in the bulk crystals. In addition, the noncontinuous conductivity variations were observed at the temperature below 180?K for both the nanoflakes and the bulks, which is attributed to the probable charge density wave transition. The photoconductivities in the semiconducting nanoflakes were also observed under the excitation at 532?nm wavelength. The probable mechanisms resulting in the different transport behaviors between the NbS{sub 2} nanostructure and bulk were discussed.
Huang, Y. H.; Chen, R. S., E-mail: firstname.lastname@example.com; Ho, C. H. [Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Peng, C. C.; Huang, Y. S. [Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China)
Review on measurement techniques of transport properties of nanowires.
Physical properties at the nanoscale are novel and different from those in bulk materials. Over the last few decades, there has been an ever growing interest in the fabrication of nanowire structures for a wide variety of applications including energy generation purposes. Nevertheless, the study of their transport properties, such as thermal conductivity, electrical conductivity or Seebeck coefficient, remains an experimental challenge. For instance, in the particular case of nanostructured thermoelectrics, theoretical calculations have shown that nanowires offer a promising way of enhancing the hitherto low efficiency of these materials in the conversion of temperature differences into electricity. Therefore, within the thermoelectrical community there has been a great experimental effort in the measurement of these quantities in actual nanowires. The measurements of these properties at the nanoscale are also of interest in fields other than energy, such as electrical components for microchips, field effect transistors, sensors, and other low scale devices. For all these applications, knowing the transport properties is mandatory. This review deals with the latest techniques developed to perform the measurement of these transport properties in nanowires. A thorough overview of the most important and modern techniques used for the characterization of different kinds of nanowires will be shown. PMID:24113712
Rojo, Miguel Mu±oz; Calero, Olga Caballero; Lopeandia, A F; Rodriguez-Viejo, J; MartĒn-Gonzalez, Marisol
Transport properties of Fe/GaAs/Ag(001) system.
We present results of ab initio transport calculations for epitaxial magnetic tunnel junctions Fe/GaAs/Ag(001). The electronic structure is calculated by means of the tight-binding linear muffin-tin orbital method and the ballistic conductances are evaluated within the Kubo-Landauer formalism which includes the effect of the spin-orbit interaction. Particular attention is paid to the dependence of the conductances on the orientation of magnetization direction of the Fe electrode with respect to the crystal lattice and on the thickness of the tunneling barrier. We have found that the in-plane tunneling anisotropic magnetoresistance (TAMR) exhibits a non-monotonic thickness dependence with a maximum around 7.5 nm of GaAs. This behavior is ascribed to a hybridization of interface resonances formed on both sides of the junction and manifested as hot spots in k[]-resolved conductances. For thicker GaAs barriers, the relative intensity of the hot spots is reduced on account of the contribution from a narrow central region of the two-dimensional Brillouin zone which leads to the final decrease of the TAMR effect. PMID:23035515
S²kora, Rudolf; Turek, Ilja
Rotationally anisotropic second-harmonic generation studies of the structure and electronic properties of bimetallic interfaces, Ag on Cu(110)
Rotationally anisotropic surface second-harmonic generation (SHG) has been measured from a clean, well-ordered Cu(110) single-crystal surface as a function of both surface temperature and Ag coverage. For the clean Cu(110) surface, the temperature dependence of the SH response at a fixed azimuthal angle can be correlated with a surface phase transformation. A large decrease in the rotationally anisotropic SH response as a function of surface temperature can be related to changes in the surface disorder. The results are compared with other studies of Cu(110) surface structure using both x-ray and He-atom scattering. The rotationally anisotropic SH response has also been measured as a function of Ag coverage with the Cu(110) surface temperature fixed at 300 K. The results closely follow the formation of an ordered Ag(111)-like overlayer, the nucleation of three-dimensional Ag nanoclusters (<20 {angstrom} thick) that enhance the anisotropic SH response, and the subsequent growth of a {approximately}10 monolayer thick Ag film. Variations in the rotationally anisotropic SH response as a function of Ag coverage are used to separate the resonant surface electronic contributions to the nonlinear susceptibility of the interface. 22 refs., 4 figs.
Hoffbauer, M.A.; McVeigh, V.J.
Charge carrier transport properties in layer structured hexagonal boron nitride
NASA Astrophysics Data System (ADS)
Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (ś 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 ░K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of ? ? (T/T0)-? with ? = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ?? = 192 meV (or 1546 cm-1), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.
Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X.
Charge carrier transport properties in layer structured hexagonal boron nitride
Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (~ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700?░K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of ? ? (T/T{sub 0}){sup ??} with ? = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ?? = 192 meV (or 1546 cm{sup -1}), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.
Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X., E-mail: firstname.lastname@example.com [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)
A Novel Multigrid Method for Sn Discretizations of the Mono-Energetic Boltzmann Transport Equation in the Optically Thick and Thin Regimes with Anisotropic Scattering, Part I
This paper presents a new multigrid method applied to the most common Sn discretizations (Petrov-Galerkin, diamond-differenced, corner-balanced, and discontinuous Galerkin) of the mono-energetic Boltzmann transport equation in the optically thick and thin regimes, and with strong anisotropic scattering. Unlike methods that use scalar DSA diffusion preconditioners for the source iteration, this multigrid method is applied directly to an integral equation for the scalar flux. Thus, unlike the former methods that apply a multigrid strategy to the scalar DSA diffusion operator, this method applies a multigrid strategy to the integral source iteration operator, which is an operator for 5 independent variables in spatial 3-d (3 in space and 2 in angle) and 4 independent variables in spatial 2-d (2 in space and 2 in angle). The core smoother of this multigrid method involves applications of the integral operator. Since the kernel of this integral operator involves the transport sweeps, applying this integral operator requires a transport sweep (an inversion of an upper triagular matrix) for each of the angles used. As the equation is in 5-space or 4-space, the multigrid approach in this paper coarsens in both angle and space, effecting efficient applications of the coarse integral operators. Although each V-cycle of this method is more expensive than a V-cycle for the DSA preconditioner, since the DSA equation does not have angular dependence, the overall computational efficiency is about the same for problems where DSA preconditioning {\\it is} effective. This new method also appears to be more robust over all parameter regimes than DSA approaches. Moreover, this new method is applicable to a variety of Sn spatial discretizations, to problems involving a combination of optically thick and thin regimes, and more importantly, to problems with anisotropic scattering cross-sections, all of which DSA approaches perform poorly or not applicable at all. This multigrid approach is most effective in neutron scattering applications, where the total cross-section coefficient $\\sigma_t$ and spatial meshsize $h$ satisfies $\\sigma_t h\\approx 1.$ For this case, coarsening can be done aggressively. For problems with $\\sigma_t h\\approx 10,$ this multigrid scheme requires a moderately coarsened multiple-coarsening scheme. An even slow coarsening, an angle semi-coarsening, is required for problems with $\\sigma_t h$ ranges between 100 and 1000, which occur in high-energy photon applications.
Lee, Barry
Transport and seismoelectric properties of porous permeable rock : numerical modeling and laboratory measurements
The objective of this thesis is to better understand the transport and seismoelectric (SE) properties of porous permeable rock. Accurate information of rock transport properties, together with pore geometry, can aid us to ...
Zhan, Xin, Ph. D. Massachusetts Institute of Technology
Transport properties of anyons in random topological environments
NASA Astrophysics Data System (ADS)
The quasi-one-dimensional transport of Abelian and non-Abelian anyons is studied in the presence of a random topological background. In particular, we consider the quantum walk of an anyon that braids around islands of randomly filled static anyons of the same type. Two distinct behaviors are identified. We analytically demonstrate that all types of Abelian anyons localize purely due to the statistical phases induced by their random anyonic environment. In contrast, we numerically show that non-Abelian Ising anyons do not localize. This is due to their entanglement with the anyonic environment, which effectively induces dephasing. Our study demonstrates that localization properties strongly depend on nonlocal topological interactions, and it provides a clear distinction in the transport properties of Abelian and non-Abelian anyons.
Zatloukal, V.; Lehman, L.; Singh, S.; Pachos, J. K.; Brennen, G. K.
Transport properties of anyons in random topological environments
The quasi one-dimensional transport of Abelian and non-Abelian anyons is studied in the presence of a random topological background. In particular, we consider the quantum walk of an anyon that braids around islands of randomly filled static anyons of the same type. Two distinct behaviours are identified. We analytically demonstrate that all types of Abelian anyons localise purely due to the statistical phases induced by their random anyonic environment. In contrast, we numerically show that non-Abelian Ising anyons do not localise. This is due to their entanglement with the anyonic environment that effectively induces dephasing. Our study demonstrates that localisation properties strongly depend on non-local topological interactions and it provides a clear distinction in the transport properties of Abelian and non-Abelian statistics.
V. Zatloukal; L. Lehman; S. Singh; J. K. Pachos; G. K. Brennen
Transport Properties of Carbon-Nanotube/Cement Composites
NASA Astrophysics Data System (ADS)
This paper preliminarily investigates the general transport properties (i.e., water sorptivity, water permeability, and gas permeability) of carbon-nanotube/cement composites. Carboxyl multi-walled carbon nanotubes (MWNTs) are dispersed into cement mortar to fabricate the carbon nanotubes (CNTs) reinforced cement-based composites by applying ultrasonic energy in combination with the use of surfactants (sodium dodecylbenzene sulfonate and sodium dodecyl sulfate). Experimental results indicate that even at a very small dosage the addition of MWNTs can help decrease water sorptivity coefficient, water permeability coefficient, and gas permeability coefficient of cement mortar, which suggests that CNTs can effectively improve the durability properties of cement-based composites.
Han, Baoguo; Yang, Zhengxian; Shi, Xianming; Yu, Xun
Engineered microstructures and transport properties in YBCO coated conductors.
Each process used to deposit or make the bi-axially textured template, buffer layer(s), and the superconductor in a coated conductor creates interfaces along which defects or interfacial reactions may result. These defects can be additive and propagate through the entire film structure to affect the growth and properties of the superconducting film. Defects within the films and their corresponding transport properties have been correlated with the differences in the thickness of the underlying buffer layer material. This knowledge can be used to control and engineer the structure of the coated conductor to maximize critical current densities.
Holesinger, T. G. (Terry G.); Gibbons, B. J. (Brady J.); Coulter, J. Y. (James Y.); Foltyn, S. R. (Stephen R.); Arendt, P. N. (Paul N.)
Electrical and thermal transport properties of CdO ceramics
NASA Astrophysics Data System (ADS)
High temperature electrical and thermal transport properties, that is, electrical conductivity, Seebeck coefficient and thermal conductivity, of CdO ceramics have been investigated. Because of the good electrical properties and low thermal conductivity, the dimensionless figure-of-merit ZT of the CdO ceramics reaches 0.34 at 1023 K. This value is comparable to the best reported ZT for the n-type oxide ceramic thermoelectric materials and remains as potential to be further improved by porosity controlling or nanostructuring.
L³, Qing; Wang, ShuFang; Li, LongJiang; Wang, JiangLong; Dai, ShouYu; Yu, Wei; Fu, GuangSheng
Transport properties of a two impurity system: a theoretical approach.
NASA Astrophysics Data System (ADS)
Double magnetic-impurity systems have attracted great attention due to their rich physics and possible technological applications. A system of two interacting Co atoms has been studied in a recent STM experiments (Nature Physics 7, 901 (2011)). The precise control of the inter-impurity distance made it possible to explore in detail the transport properties of the system as a function of the impurities' interaction with each other. We explain, for all the parameter range studied, the physics observed in the experiments using a microscopic model, based on the two impurity Anderson model, including a two-path geometry for charge transport. The many-body system is treated in the finite-U Slave Boson Mean Field Approximation. Other results obtained using the Logarithmic Discretization Embedded Cluster Approximation are also discussed. We physically characterize the system and show that, as in the experiments, the features observed in the transport properties depend on the presence of two impurities but also on the existence of two conducting channels for electron transport. In particular, we obtain a splitting in the differential conductance, compatible with the one observed in the experiments, as a result of the superposition of the many-body Kondo states of each impurity.
Hamad, Ignacio J.; Costa Ribeiro, Laercio; Martins, George; Anda, Enrique V.
Seismic wave propagation in anisotropic ice - Part 1: Elasticity tensor and derived quantities from ice-core properties
NASA Astrophysics Data System (ADS)
A preferred orientation of the anisotropic ice crystals influences the viscosity of the ice bulk and the dynamic behaviour of glaciers and ice sheets. Knowledge about the distribution of crystal anisotropy is mainly provided by crystal orientation fabric (COF) data from ice cores. However, the developed anisotropic fabric influences not only the flow behaviour of ice but also the propagation of seismic waves. Two effects are important: (i) sudden changes in COF lead to englacial reflections, and (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded travel times. A framework is presented here to connect COF data from ice cores with the elasticity tensor to determine seismic velocities and reflection coefficients for cone and girdle fabrics. We connect the microscopic anisotropy of the crystals with the macroscopic anisotropy of the ice mass, observable with seismic methods. Elasticity tensors for different fabrics are calculated and used to investigate the influence of the anisotropic ice fabric on seismic velocities and reflection coefficients, englacially as well as for the ice-bed contact. Hence, it is possible to remotely determine the bulk ice anisotropy.
Diez, A.; Eisen, O.
Atomistic Study of Transport Properties at the Nanoscale
thermal conductivity, l, to increase the dimensionless thermoelectric gure of merit, ZT - essentially a measure of the e ciency of the thermoelectric process. To expand upon the potential of these materials for thermal management de- vices... forms from MSDs is given in Eq. A.4, as provided in 12 Appendix A. Though previously only discussed for the case of the di usion coe cient, Einstein relations and Green-Kubo relations exist for the other transport properties relevant to this work...
Haskins, Justin
Studies on magneto-transport properties of dilute magnetic semiconductors
Diluted magnetic semiconductors (DMS) are rare group of promising semiconductors in which a fraction of the constituent ions is replaced by magnetic ions. This study is aimed to understand the magneto-transport properties of magnetic ion doped In2O3 thin films. The films were grown under different temperature and partial oxygen pressures by pulsed laser deposition. The films were characterized using various
R. Gupta; A. Ghosh; Y. Kolekar; K. Ghosh; P. Kahol
The magnetic and transport properties of template-synthesized carbon-based and related nanomaterials
NASA Astrophysics Data System (ADS)
The porous alumina template-assisted method of nanoscale materials preparation provides a simple, relatively inexpensive, yet highly controllable and repeatable process for nanomaterial synthesis. Various nanostructures can then be made utilizing the porous structure as a scaffold. In this dissertation we study the porous alumina anodization process, the synthesis of porous alumina-assisted materials, and the basic physical properties of these materials, primarily concentrating on the magnetic and transport properties. First, we study the porous alumina formation process as a function of anodization voltage, acid type, and acid concentration. We find that while acid type strongly affects the growth characteristics of porous alumina, pH does not. We also study the stability of pore formation. We characterize the two- and three-dimensional stability of the growth process. We find that in three dimensions, an unstable formation region as a function of pH and voltage will cause the formation of dendrite structures. Next, we study the synthesis of materials in the porous alumina templates. Through chemical self-assembly, electrodeposition is able to make a wide variety of nanowires and nanotubes and we seek to optimize this process. Third, we study the optical properties Au and Ag nanowire arrays embedded in porous alumina. We find that such materials have use as negative index metamaterials owing to the existence of both transverse and longitudinal surface plasmon resonances. Next, we study the basic magnetic properties of new PAni-ferromagnet composite nanostructures and compare these properties to the magnetic properties of the nanotubes and the nanowires alone. We find the high dielectric properties of the PAni to strongly shield the ferromagnetic nanowires from magnetostatic interactions. Fifth, we make devices out of carbon nanotubes synthesized by CVD in the alumina templates. We investigate the transport properties of these carbon nanotubes. Further, we find that the contact resistances, which are normally on the order of mega-ohms for these tubes, can be lowered to the order of kilo-ohms by annealing in H 2/Ar atmosphere. We find that the disorder in these carbon nanotubes allows for the uptake of H during the annealing process. These H-complex hydrogen impurities, along with C and H adatoms, induce ferromagnetism in the carbon nanotubes. We carry out a magnetic study on the annealed carbon nanotubes. Moreover, the ferromagnetism of the carbon nanotubes results in hysteric magnetoresistance. We study this effect, attributing it to strong magneto-viscosity effects and anisotropic magnetoresistance. We also study the transport and magnetotransport properties of the annealed carbon nanotubes as a function of temperature and inner diameter. We find that there is an order-disorder transition that occurs at lower temperatures that resembles behavior predicted in disordered carbon fibers by the Bright model. We also find that the nanotubes behave as one-dimensional Luttinger liquids. Finally, as a means of comparison, we fabricate and study the properties of monolayer graphene devices.
Friedman, Adam Louis
Semiconducting black phosphorus: synthesis, transport properties and electronic applications.
Phosphorus is one of the most abundant elements preserved in earth, and it comprises a fraction of ?0.1% of the earth crust. In general, phosphorus has several allotropes, and the two most commonly seen allotropes, i.e. white and red phosphorus, are widely used in explosives and safety matches. In addition, black phosphorus, though rarely mentioned, is a layered semiconductor and has great potential in optical and electronic applications. Remarkably, this layered material can be reduced to one single atomic layer in the vertical direction owing to the van der Waals structure, and is known as phosphorene, in which the physical properties can be tremendously different from its bulk counterpart. In this review article, we trace back to the research history on black phosphorus of over 100 years from the synthesis to material properties, and extend the topic from black phosphorus to phosphorene. The physical and transport properties are highlighted for further applications in electronic and optoelectronics devices. PMID:25307017
Liu, Han; Du, Yuchen; Deng, Yexin; Ye, Peide D
Radiation Transport Properties of Polyethylene-Fiber Composites
NASA Technical Reports Server (NTRS)
Composite materials that can both serve as effective shielding materials against cosmic-ray and energetic solar particles in deep space as well as structural materials for habitat and spacecraft remain a critical and mission enabling piece in mission planning and exploration. Polyethylene is known to have excellent shielding properties due to its low density coupled with high hydrogen content. Polyethylene fiber reinforced composites promise to combine this shielding effectiveness with the required mechanical properties of structural materials. Samples of Polyethylene-fiber reinforced epoxy matrix composite 1-5 cm thick were prepared at NASA's Marshall Space Flight Center and tested against 500 MeV/nucleon Fe beam at the HIMAC facility of NIRS in Chiba, Japan. This paper presents measured and calculated results for the radiation transport properties of these samples.
Kaul, Raj K.; Barghouty, A. F.; Dahche, H. M.
Space radiation transport properties of polyethylene-based composites
NASA Technical Reports Server (NTRS)
Composite materials that can serve as both effective shielding materials against cosmic-ray and energetic solar particles in deep space, as well as structural materials for habitat and spacecraft, remain a critical and mission enabling component in mission planning and exploration. Polyethylene is known to have excellent shielding properties due to its low density, coupled with high hydrogen content. Polyethylene-fiber reinforced composites promise to combine this shielding effectiveness with the required mechanical properties of structural materials. Samples of polyethylene-fiber reinforced epoxy matrix composite 1-5 cm thick were prepared at the NASA Marshall Space Flight Center and tested against a 500 MeV/nucleon Fe beam at the HIMAC facility of NIRS in Chiba, Japan. This paper presents measured and calculated results for the radiation transport properties of these samples.
Kaul, R. K.; Barghouty, A. F.; Dahche, H. M.
A colloid-facilitated transport model with variable colloid transport properties
NASA Astrophysics Data System (ADS)
Anomalous contaminant transport velocities in groundwater for species generally considered to be immobile are often attributed to the mechanism of colloid-facilitated transport. In some of the field observations attributed to colloid facilitation, an extremely small fraction of the total contaminant mass introduced to the groundwater is detected downstream. In this study, a new model of colloid-facilitated contaminant transport is proposed that explains this phenomenon as the variability of mobility of individual colloids in the population. The process of retardation via attachment and detachment of colloids on immobile surfaces is often modeled with time and space invariant parameters; here it is modeled assuming a diverse population of transport properties that account for the inherent variability of colloid size, surface charge and chemical properties, mineralogy, and the concomitant impact on colloid mobility. When the contaminant is assumed to irreversibly attach to or form colloids, the migration of the contaminant plume exhibits extremely non-Fickian behavior. The plume's center of mass travels with a velocity governed by the groundwater velocity divided by the mean colloid retardation factor. However, small quantities of contaminant attached to a few highly mobile colloids travel at velocities up to the groundwater velocity, far exceeding the velocity of the centroid of the plume. This paper introduces the colloid diversity model, presents some sensitivity calculations for an idealized case, and discusses the implications of such a model on data needs, simulation of field observations, and model scaling.
Robinson, Bruce A.; Wolfsberg, Andrew V.; Viswanathan, Hari S.; Reimus, Paul W.
Reservoir transport and poroelastic properties from oscillating pore pressure experiments
NASA Astrophysics Data System (ADS)
Hydraulic transport properties of reservoir rocks, permeability and storage capacity are traditionally defined as rock properties, responsible for the passage of fluids through the porous rock sample, as well as their storage. The evaluation of both is an important part of any reservoir characterization workflow. Moreover, permeability and storage capacity are main inputs into any reservoir simulation study, routinely performed by reservoir engineers on almost any major oil and gas field in the world. An accurate reservoir simulation is essential for production forecast and economic analysis, hence the transport properties directly control the profitability of the petroleum reservoir and their estimation is vital for oil and gas industry. This thesis is devoted to an integrated study of reservoir rocks' hydraulic, streaming potential and poroelastic properties as measured with the oscillating pore pressure experiment. The oscillating pore pressure method is traditionally used to measure hydraulic transport properties. We modified the method and built an experimental setup, capable of measuring all aforementioned rock properties simultaneously. The measurements were carried out for four conventional reservoir-rock quality samples at a range of oscillation frequencies and effective stresses. An apparent frequency dependence of permeability and streaming potential coupling coefficient was observed. Measured frequency dispersion of drained poroelastic properties indicates an intrinsically inelastic nature of the porous mineral rock frame. Standard Linear Model demonstrated the best fit to the experimental dispersion data. Pore collapse and grain crushing effects took place during hydrostatic loading of the dolomitic sample and were observed in permeability, coupling coefficient and poroelastic measurements simultaneously. I established that hydraulically-measured storage capacities are overestimated by almost one order of magnitude when compared to elastically-derived ones. The fact that the values of storage capacities as estimated from the hydraulic component of the oscillating pore pressure experiment are unreliable was also demonstrated by comparing poroelastic Biot and Skempton coefficients. These coefficients were estimated both from hydraulic and strain measurements and the comparison of two datasets points out ambiguity of hydraulic measurements. I also introduce a novel method, which allowed us to estimate the permeability from the full range of acquired frequency data by utilizing a nonlinear least-squares regression. I additionally performed numerical simulation of oscillatory fluid flow. The simulated frequency-dependent results displayed an excellent agreement with both analytical solution and experimental data. This agreement proves that numerical simulation is a powerful tool in predicting frequency response of a porous rock sample to harmonic pore pressure excitations.
Hasanov, Azar K.
Rhamnolipid surface thermodynamic properties and transport in agricultural soil.
Rhamnolipid is a biosurfactant produced by several Pseudomonas species, which can wet hydrophobic soils by lowering the cohesive and/or adhesive surface tension. Because of its biodegradability, rhamnolipid applications bring minimal adverse impact on the soil and groundwater as compared with that of chemical wetting agents. Subsequently, rhamnolipid applications have more advantages when used to improve irrigation in the agricultural soil, especially under draught conditions. In the presence of rhamnolipid, water surface tension dropped linearly with the increase of rhamnolipid concentration until the rhamnolipid critical micelle concentration (CMC) of 30 mg/L was reached. Below the CMC, rhamnolipid had linear adsorption isotherms on the soil with a partition coefficient of 0.126 L/kg. Rhamnolipid transport breakthrough curves had a broad and diffuse infiltration front, indicating retention of rhamnolipid on the soil increased with time. Rhamnolipid transport was found to be well represented by the advection-dispersion equation based on a local equilibrium assumption. When applied at concentrations above the CMC, the formed rhamnolipid micelles prevented rhamnolipid adsorption (both equilibrium adsorption and kinetic adsorption) in the soil. It was discovered in this research that rhamnolipid surface thermodynamic properties played the key role in controlling rhamnolipid transport. The attractive forces between rhamnolipid molecules contributed to micelle formation and facilitated rhamnolipid transport. PMID:24394947
Renfro, Tyler Dillard; Xie, Weijie; Yang, Guang; Chen, Gang
Transport properties of zigzag graphene nanoribbon decorated with copper clusters
Using non-equilibrium green function with density functional theory, the present study investigates the transport properties of decorated zigzag graphene nanoribbon with a copper cluster. We have represented the decoration of zigzag graphene nanoribbon with single copper atom and cluster containing two and three copper atoms. In all the cases, copper atoms tend to occupy the edge state. In addition, we have shown that copper can alter the current-voltage characteristic of zigzag graphene nanoribbon and create new fluctuations and negative differential resistance. These alternations are made due to discontinuity in the combination of orbitals along the graphene nanoribbon. Decoration alters these discontinuities and creates more visible fluctuations. However, in low bias voltages, the changes are similar in all the cases. The study demonstrates that in the decorated zigzag graphene nanoribbon, the edge states are the main states for transporting electron from one electrode to another.
Berahman, M.; Sheikhi, M. H., E-mail: email@example.com [School of Electrical and Computer Eng, Shiraz University, Shiraz (Iran, Islamic Republic of); Nanotechnology Research Institute, Shiraz University, Shiraz (Iran, Islamic Republic of)
Low temperature carrier transport properties in isotopically controlled germanium
Investigations of electronic and optical properties of semiconductors often require specimens with extremely homogeneous dopant distributions and precisely controlled net-carrier concentrations and compensation ratios. The previous difficulties in fabricating such samples are overcome as reported in this thesis by growing high-purity Ge single crystals of controlled {sup 75}Ge and {sup 70}Ge isotopic compositions, and doping these crystals by the neutron transmutation doping (NTD) technique. The resulting net-impurity concentrations and the compensation ratios are precisely determined by the thermal neutron fluence and the [{sup 74}Ge]/[{sup 70}Ge] ratios of the starting Ge materials, respectively. This method also guarantees unprecedented doping uniformity. Using such samples the authors have conducted four types of electron (hole) transport studies probing the nature of (1) free carrier scattering by neutral impurities, (2) free carrier scattering by ionized impurities, (3) low temperature hopping conduction, and (4) free carrier transport in samples close to the metal-insulator transition.
Itoh, K.
Transport properties of ultrathin black phosphorus on hexagonal boron nitride
NASA Astrophysics Data System (ADS)
Ultrathin black phosphorus, or phosphorene, is a two-dimensional material that allows both high carrier mobility and large on/off ratios. Similar to other atomic crystals, like graphene or layered transition metal dichalcogenides, the transport behavior of few-layer black phosphorus is expected to be affected by the underlying substrate. The properties of black phosphorus have so far been studied on the widely utilized SiO2 substrate. Here, we characterize few-layer black phosphorus field effect transistors on hexagonal boron nitrideŚan atomically smooth and charge trap-free substrate. We measure the temperature dependence of the field effect mobility for both holes and electrons and explain the observed behavior in terms of charged impurity limited transport. We find that in-situ vacuum annealing at 400 K removes the p-doping of few-layer black phosphorus on both boron nitride and SiO2 substrates and reduces the hysteresis at room temperature.
Doganov, Rostislav A.; Koenig, Steven P.; Yeo, Yuting; Watanabe, Kenji; Taniguchi, Takashi; ├-zyilmaz, Barbaros
Transport properties of individual C{sub 60}-molecules
Electrical and thermal transport properties of C{sub 60} molecules are investigated with density-functional-theory based calculations. These calculations suggest that the optimum contact geometry for an electrode terminated with a single-Au atom is through binding to one or two C-atoms of C{sub 60} with a tendency to promote the ?sp{sup 2}-hybridization into an ?sp{sup 3}-type one. Transport in these junctions is primarily through an unoccupied molecular orbital that is partly hybridized with the Au, which results in splitting the degeneracy of the lowest unoccupied molecular orbital triplet. The transmission through these junctions, however, cannot be modeled by a single Lorentzian resonance, as our results show evidence of quantum interference between an occupied and an unoccupied orbital. The interference results in a suppression of conductance around the Fermi energy. Our numerical findings are readily analyzed analytically within a simple two-level model.
Gķranton, G. [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany)] [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany); Seiler, C.; Evers, F. [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany) [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany); Center for Functional Nanostructures, Karlsruhe Institute of Technology, Campus South, D-76131 Karlsruhe (Germany); Institut f³r Theorie der Kondensierten Materie, Karlsruhe Institute of Technology, Campus South, D-76128 Karlsruhe (Germany); Bagrets, A. [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany) [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany); Steinbuch Center for Supercomputing, Karlsruhe Institute of Technology, D-76128 Karlsruhe (Germany); Venkataraman, L. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)] [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)
Coefficients for calculating thermodynamic and transport properties of individual species
NASA Technical Reports Server (NTRS)
Libraries of thermodynamic data and transport properties are given for individual species in the form of least-squares coefficients. Values of C(sup 0)(sub p)(T), H(sup 0)(T), and S(sup 0)(T) are available for 1130 solid, liquid, and gaseous species. Viscosity and thermal conductivity data are given for 155 gases. The original C(sup 0)(sub p)(T) values were fit to a fourth-order polynomial with integration constants for H(sup 0)(T) and S(sup 0)(T). For each species the integration constant for H(sup 0)(T) includes the heat of formation. Transport properties have a different functional form. The temperature range for most of the data is 300 to 5000 K, although some of the newer thermodynamic data have a range of 200 to 6000 K. Because the species are mainly possible products of reaction, the data are useful for chemical equilibrium and kinetics computer codes. Much of the data has been distributed for several years with the NASA Lewis equilibrium program CET89. The thermodynamic properties of the reference elements were updated along with about 175 species that involve the elements carbon, hydrogen, oxygen, and nitrogen. These sets of data will be distributed with the NASA Lewis personal computer program for calculating chemical equilibria, CETPC.
Mcbride, Bonnie J.; Gordon, Sanford; Reno, Martin A.
Applying distributions of hydraulic conductivity for anisotropic systems and applications to Tc Transport at the U.S. Department of Energy Hanford Site
43Tc99 is spreading mostly laterally through the U.S. Department of Energy Hanford site sediments. At higher tensions in the unsaturated zone, the hydraulic conductivity may be strongly anisotropic as a consequence of finer soils to retain more water than coarser ones, and for these soils to have been deposited primarily in horizontal structures. We have tried to develop a consistent modeling procedure that could predict the behavior of Tc plumes. Our procedure consists of: (1) Adapting existing numerical recipes based on critical path analysis to calculate the hydraulic conductivity, K, as a function of tension, h, (2) Statistically correlating the predicted K at various values of the tension with fine content, (3) Seeking a tension value, for which the anisotropy and the horizontal K values are both sufficiently large to accommodate multi-kilometer spreading, (4) Predicting the distribution of K values for vertical flow as a function of system support volume, (5) Comparing the largest likely K value in the vertical direction with the expected K in the horizontal direction, (6) Finding the length scale at which the two K values are roughly equal, (7) Comparing that length scale with the horizontal spreading of the plume. We find that our predictions of the value of the tension at which the principle spreading is likely occurring compares very well with experiment. However, we seem to underestimate the physical length scale at which the predominantly horizontal spreading begins to take on significant vertical characteristics. Our data and predictions would seem to indicate that this should happen after horizontal transport of somewhat over a km, but the chiefly horizontal transport appears to continue out to scales of 10km or so.
Allen G Hunt
Electrical tuning of transport properties of topological insulator ultrathin films
NASA Astrophysics Data System (ADS)
Considering that topological insulator (TI) ultrathin films (UTFs) provide an ideal platform for the transport measurement of topologically protected surface states, we have investigated the transport properties of the three-dimensional (3D) TI UTFs through an array of potential barriers. The 3D TI UTF was considered to be thin enough (5 nm) that the top and bottom surface states of the UTF can hybridize to create an energy gap at the Dirac point, which results in a hyperbola-like energy dispersion. It was found that the Klein tunneling effect disappears due to the interaction between the top and bottom surface states. By tuning the barrier strength or the incident energy, three kinds of transport processes can be realized, and the conditions of the transport processes were determined. The oscillatory characters of the transmission (conductance) spectra without a decaying envelope are due to the novel surface states of TIs, which are quite different from that observed for a conventional two-dimensional electron gas. For the structure consisting of two anti-parallel potential barriers, the conductance spectra exhibit a perfect on/off switching effect by tuning the barrier strength, which is favorable for electrically controllable device applications. In the case of a superlattice (SL) structure, due to the mini-gaps induced by the SL geometry, some additional resonant peaks and valleys can be observed in the transmission spectra, and similar characters are also reflected in the conductance spectra. Owing to the Dirac characters of the charge carriers therein, the transmission (conductance) spectra never decay with increasing barrier strength, which is distinguished from that observed for semiconductor SLs. These findings were not only meaningful for understanding the basic physical processes in the transport of TIs, but also useful for developing nanoscaled TI-based devices.
Li, H.; Shao, J. M.; Zhang, H. B.; Yang, G. W.
Novel Properties of a Mouse ?-Aminobutyric Acid Transporter (GAT4)
We expressed the mouse ?-aminobutyric acid (GABA) transporter GAT4 (homologous to rat/human GAT-3) in Xenopus laevis oocytes and examined its functional and pharmacological properties by using electrophysiological and tracer uptake methods. In the coupled mode of transport (Na+/Cl?/GABA cotransport), there was tight coupling between charge flux and GABA flux across the plasma membrane (2 charges/GABA). Transport was highly temperature-dependent with a temperature coeffcient (Q10) of 4.3. The GAT4 turnover rate (1.5 s?1; ?50 mV, 21░C) and temperature dependence suggest physiological turnover rates of 15¢20 s?1. No uncoupled current was observed in the presence of Na+. In the absence of external Na+, GAT4 exhibited two distinct uncoupled currents. (i) A Cl? leak current (IleakCl) was observed when Na+ was replaced with choline or tetraethylammonium. The reversal potential of (IleakCl) followed the Cl? Nernst potential. (ii) A Li+ leak current (IleakLi) was observed when Na+ was replaced with Li+. Both leak currents were inhibited by Na+, and both were temperature-independent (Q10 ? 1). The two leak modes appeared not to coexist, as Li+ inhibited (IleakCl). The results suggest the existence of cation- and anion-selective channel-like pathways in GAT4. Flufenamic acid inhibited GAT4 Na+/C1?/GABA cotransport, IleakLi, and IleakCl, (Ki ? 30 ?M), and the voltage-induced presteady-state charge movements (Ki ? 440 ?M). Flufenamic acid exhibited little or no selectivity for GAT1, GAT2, or GAT3. Sodium and GABA concentration jumps revealed that slow Na+ binding to the transporter is followed by rapid GABA-induced translocation of the ligands across the plasma membrane. Thus, Na+ binding and associated conformational changes constitute the rate-limiting steps in the transport cycle. PMID:15981712
Karakossian, M.H.; Spencer, S.R.; Gomez, A.Q.; Padilla, O.R.; Sacher, A.; Loo, D.D.F.; Nelson, N.; Eskandari, S.
Thermodynamic and transport properties of cryogenic propellants and related fluids
NASA Technical Reports Server (NTRS)
Significant advances have been made in recent years in the quality and range of thermophysical data for the cryogenic propellants, pressurants, and inertants. A review of recently completed and current data compilation projects for helium, hydrogen, argon, nitrogen, oxygen, fluorine, and methane is given together with recommended references for thermodynamic and transport property data tables for these fluids. Modern techniques in the plotting of thermodynamic charts from tabular data (or from functions such as the equation of state) have greatly improved their precision and value. A list of such charts is included.
Johnson, V. J.
Transport properties of graphene nanoroads in boron nitride sheets.
We demonstrate that the one-dimensional (1D) transport channels that appear in the gap when graphene nanoroads are embedded in boron nitride (BN) sheets are more robust when they are inserted at AB/BA grain boundaries. Our conclusions are based on ab initio electronic structure calculations for a variety of different crystal orientations and bonding arrangements at the BN/C interfaces. This property is related to the valley Hall conductivity present in the BN band structure and to the topologically protected kink states that appear in continuum Dirac models with position-dependent masses. PMID:22524401
Jung, Jeil; Qiao, Zhenhua; Niu, Qian; Macdonald, Allan H
Effective Potential Energies and Transport Properties for Nitrogen and Oxygen
NASA Technical Reports Server (NTRS)
The results of recent theoretical studies for N--N2, O--O2, N2--N2 interactions are applied to the transport properties of nitrogen and oxygen gases. The theoretical results are used to select suitable oxygen interaction energies from previous work for determining the diffusion and viscosity coefficients at high temperatures. A universal formulation is applied to determine the collision integrals for O2--O2 interactions at high temperatures and to calculate certain ratios for determining higher-order collision integrals.
Stallcop, James R.; Partridge, Harry; Levin, Eugene; Kwak, Dochan (Technical Monitor)
Stacking-order dependent transport properties of trilayer graphene
NASA Astrophysics Data System (ADS)
We report markedly different transport properties of ABA- and ABC-stacked trilayer graphenes. Our experiments in double-gated trilayer devices provide evidence that a perpendicular electric field opens an energy gap in the ABC trilayer, while it causes the increase of a band overlap in the ABA trilayer. In a perpendicular magnetic field, the ABA trilayer develops quantum Hall plateaus at filling factors of ?=2,4,6,... with a step of ??=2, whereas the inversion-symmetric ABC trilayer exhibits plateaus at ?=6 and 10 with fourfold spin and valley degeneracy.
Jhang, S. H.; Craciun, M. F.; Schmidmeier, S.; Tokumitsu, S.; Russo, S.; Yamamoto, M.; Skourski, Y.; Wosnitza, J.; Tarucha, S.; Eroms, J.; Strunk, C.
Study of electronic transport properties of doped 8AGNR
The electronic and transport properties of 8-armchair graphene nanoribbon (8AGNR) with defect at different sites are investigated by performing first-principles calculations based on density functional theory (DFT). The calculated results show that the 8AGNR are semiconductor. The introduction of 3d transition metals, creates the nondegenerate states in the conduction band, makes 8AGNR metallic. The computed transmission spectrum confirms that AGNR are semiconducting in nature and their band gap remain unchanged and localized states appear when there is vacancy in their structures, and the conductance decreases due to defects compared with the pristine nanoribbon.
Sharma, Uma Shankar, E-mail: email@example.com [Rustamji Institute of Technology, BSF Academy Tekanpur, Gwalior-475005 (India); Srivastava, Anurag [Advanced Materials Research Group, Computational Nanoscience and Technology Lab, ABV-Indian Institute of Information Technology and Management Gwalior-474015 (India); Verma, U. P. [School of Studies in Physics, Jiwaji University, Gwalior-474011 (India)
Geometrical and Transport Properties of Sequential Adsorption Clusters
NASA Astrophysics Data System (ADS)
We investigate transport properties of percolating clusters generated by irreversible cooperative sequential adsorption (CSA) on square lattices with Arrhenius rates given by ki ? qni, where ni is the number of occupied neighbors of the site i, and q a controlling parameter. Our results show a dependence of the prefactors non q and a strong finite size effect for small values of this parameter, both impacting the size of the backbone and the global conductance of the system. These results might be pertinent to practical applications in processes involving adsorption of particles.
Ara·jo, E. B.; Moreira, A. A.; Herrmann, H. J.; da Silva, L. R.; Andrade, J. S.
Graphene on graphene antidot lattices: Electronic and transport properties
NASA Astrophysics Data System (ADS)
Graphene bilayer systems are known to exhibit a band gap when the layer symmetry is broken by applying a perpendicular electric field. The resulting band structure resembles that of a conventional semiconductor with a parabolic dispersion. Here, we introduce a bilayer graphene heterostructure, where single-layer graphene is placed on top of another layer of graphene with a regular lattice of antidots. We dub this class of graphene systems GOAL: graphene on graphene antidot lattice. By varying the structure geometry, band-structure engineering can be performed to obtain linearly dispersing bands (with a high concomitant mobility), which nevertheless can be made gapped with a perpendicular field. We analyze the electronic structure and transport properties of various types of GOALs, and draw general conclusions about their properties to aid their design in experiments.
Gregersen, S°ren Schou; Pedersen, Jesper Goor; Power, Stephen R.; Jauho, Antti-Pekka
Electronic and transport properties of LiCoO2.
Using first principles density functional theory (DFT), the electronic and magnetic properties as well as the Li-ion migration in LiCoO2 have been studied with a gradient corrected functional. The magnetic properties were also investigated in addition using a gradient corrected functional in combination with an on-site repulsion U and a hybrid functional. We find LiCoO2 to be non-magnetic under ambient conditions. A magnetic ground state can be obtained by a volume expansion corresponding to a negative pressure of -8 GPa due to a competition between Hund's rules favoring magnetism on the Co(3+) ions and the crystal field splitting, which suppresses magnetism at zero pressure. The barrier for lithium transport is determined to be 0.44 eV from nudged elastic band (NEB) calculations on the Li0.917CoO2 system. PMID:25264622
Andriyevsky, Bohdan; Doll, Klaus; Jacob, Timo
Simplified curve fits for the transport properties of equilibrium air
NASA Technical Reports Server (NTRS)
New, improved curve fits for the transport properties of equilibruim air have been developed. The curve fits are for viscosity and Prandtl number as functions of temperature and density, and viscosity and thermal conductivity as functions of internal energy and density. The curve fits were constructed using grabau-type transition functions to model the tranport properties of Peng and Pindroh. The resulting curve fits are sufficiently accurate and self-contained so that they can be readily incorporated into new or existing computational fluid dynamics codes. The range of validity of the new curve fits are temperatures up to 15,000 K densities from 10 to the -5 to 10 amagats (rho/rho sub o).
Srinivasan, S.; Tannehill, J. C.
Electron transport properties of carbon nanotube-graphene contacts
NASA Astrophysics Data System (ADS)
The properties of carbon nanotube-graphene junctions are investigated with first-principles electronic structure and electron transport calculations. Contact properties are found to be key factors in determining the performance of nanotube based electronic devices. In a typical single-walled carbon nanotube-metal junction, there is a p-type Schottky barrier of up to ś0.4 eV which depends on the nanotube diameter. Calculations of the Schottky barrier height in carbon nanotube-graphene contacts indicate that low barriers of 0.09 eV and 0.04 eV are present in nanotube-graphene contacts ((8,0) and (10,0) nanotubes, respectively). Junctions with a finite contact region are investigated with simulations of the current-voltage characteristics. The results suggest the suitability of the junctions for applications and provide insight to explain recent experimental findings.
Cook, Brandon G.; French, William R.; Varga, Kßlmßn
Magnetic and Transport Properties of Lanthanum Based CMR Systems
NASA Astrophysics Data System (ADS)
The magnetic and transport properties of bulk polycrystalline samples of Ca doped manganite perovskites have been studied. The material properties were characterized using SEM, EDX and XRD. Magnetization measurements were performed using a SQUID magnetometer in order to determine Curie temperature and moment per Mn ion. The temperature and field (H) dependence of the electrical resistance, R(T,H) and Hall effect were measured by standard ac four and six probe techniques in magnetic fields up to 17 T*. Typical zero field I-M transition peaks near 275 K in R(T) and negative dR/dH at high fields were observed. However, for H < 0.2 T, positive MR is seen. The results of these measurements, including low field positive magnetoresistance, will be reported. *Performed at the National High Magnetic Field Lab (NHMFL) FSU, Tallahassee, FL
Estrada, Javier; Bleiweiss, Michael; Saygi, Salih; Datta, Timir; Yin, Ming; Palm, Eric; Brandt, Bruce; Iqbal, Zafar
NASA Technical Reports Server (NTRS)
The accurate computation of the thermodynamic and transport properties of fluids is a necessity for many engineering calculations. The FLUID program was developed to calculate the thermodynamic and transport properties of pure fluids in both the liquid and gas phases. Fluid properties are calculated using a simple gas model, empirical corrections, and an efficient numerical interpolation scheme. FLUID produces results that are in very good agreement with measured values, while being much faster than older more complex programs developed for the same purpose. A Van der Waals equation of state model is used to obtain approximate state values. These values are corrected for real-gas effects by model correction factors obtained from tables based on experimental data. These tables also accurately compensate for the special circumstances which arise whenever phase conditions occur. Viscosity and thermal conductivity values are computed directly from tables. Interpolation within tables is based on Lagrange's three point formula. A set of tables must be generated for each fluid implemented. FLUID currently contains tables for nine fluids including dry air and steam. The user can add tables for any fluid for which adequate thermal property data is available. The FLUID routine is structured so that it may easily be incorporated into engineering programs. The IBM 360 version of FLUID was developed in 1977. It is written in FORTRAN IV and has been implemented on an IBM 360 with a central memory requirement of approximately 222K of 8 bit bytes. The IBM PC version of FLUID is written in Microsoft FORTRAN 77 and has been implemented on an IBM PC with a memory requirement of 128K of 8 bit bytes. The IBM PC version of FLUID was developed in 1986.
Fessler, T. E.
NASA Technical Reports Server (NTRS)
The accurate computation of the thermodynamic and transport properties of fluids is a necessity for many engineering calculations. The FLUID program was developed to calculate the thermodynamic and transport properties of pure fluids in both the liquid and gas phases. Fluid properties are calculated using a simple gas model, empirical corrections, and an efficient numerical interpolation scheme. FLUID produces results that are in very good agreement with measured values, while being much faster than older more complex programs developed for the same purpose. A Van der Waals equation of state model is used to obtain approximate state values. These values are corrected for real-gas effects by model correction factors obtained from tables based on experimental data. These tables also accurately compensate for the special circumstances which arise whenever phase conditions occur. Viscosity and thermal conductivity values are computed directly from tables. Interpolation within tables is based on Lagrange's three point formula. A set of tables must be generated for each fluid implemented. FLUID currently contains tables for nine fluids including dry air and steam. The user can add tables for any fluid for which adequate thermal property data is available. The FLUID routine is structured so that it may easily be incorporated into engineering programs. The IBM 360 version of FLUID was developed in 1977. It is written in FORTRAN IV and has been implemented on an IBM 360 with a central memory requirement of approximately 222K of 8 bit bytes. The IBM PC version of FLUID is written in Microsoft FORTRAN 77 and has been implemented on an IBM PC with a memory requirement of 128K of 8 bit bytes. The IBM PC version of FLUID was developed in 1986.
Fessler, T. E.
Electronic structure and microscopic charge-transport properties of a new-type diketopyrrolopyrrole-based material.
Recently, diketopyrrolopyrrole (DPP)-based materials have attracted much interest due to their promising performance as a subunit in organic field effect transistors. Using density functional theory and charge-transport models, we investigated the electronic structure and microscopic charge transport properties of the cyanated bithiophene-functionalized DPP molecule (compound 1). First, we analyzed in detail the partition of the total relaxation (polaron) energy into the contributions from each vibrational mode and the influence of bond-parameter variations on the local electron-vibration coupling of compound 1, which well explains the effects of different functional groups on internal reorganization energy (?). Then, we investigated the structural and electronic properties of compound 1 in its isolated molecular state and in the solid state form, and further simulated the angular resolution anisotropic mobility for both electron- and hole-transport using two different simulation methods: (i) the mobility orientation function proposed in our previous studies (method 1); and (ii) the master equation approach (method 2). The calculated electron-transfer mobility (0.00003-0.784 cm(2) V(-1) s(-1) from method 1 and 0.02-2.26 cm(2) V(-1) s(-1) from method 2) matched reasonably with the experimentally reported value (0.07-0.55 cm(2) V(-1) s(-1) ). To the best of our knowledge, this is the first time that the transport parameters of compound 1 were calculated in the context of band model and hopping models, and both calculation results suggest that the intrinsic hole mobility is higher than the corresponding intrinsic electron mobility. Our calculation results here will be instructive to further explore the potential of other higher DPP-containing quinoidal small molecules. ® 2015 Wiley Periodicals, Inc. PMID:25706355
Huang, Jin-Dou; Li, Wen-Liang; Wen, Shu-Hao; Dong, Bin
Soil properties and preferential solute transport at the field scale
NASA Astrophysics Data System (ADS)
An important fraction of water flow and solute transport through soil takes place through preferential flow paths. Although this had been already observed in the nineteenth century, it had been forgotten by the scientific community until it was rediscovered during the 1970s. The awareness of the relevance of preferential flow was broadly re-established in the community by the early 1990s. However, since then, the notion remains widespread among soil scientists that the occurrence and strength of preferential flow cannot be predicted from measurable proxy variables such as soil properties or land management practices (e.g. Beven, K., 1991, Modeling preferential flow - an uncertain future, Preferential Flow, 1-11). In our study, we present evidence that disproves this notion. We evaluated breakthrough curve experiments under a constant irrigation rate of 1 cm/h conducted on 65 soil columns (20 cm diameter and 20 height) which had been sampled from an approximately 1 ha large loamy field-site in Silstrup, Denmark. We show that the holdback factor, which is an indicator for the strength of preferential transport, is strongly correlated to the bulk density, which in turn is correlated to the organic matter content. By applying multiple linear regression in a bootstrapping framework, we could estimate the holdback factor from the bulk density and the very fine sand fraction with a coefficient of determination of 0.65. Our results raise hopes that it is indeed possible to establish pedotransfer functions for soil susceptibility to preferential flow and transport.
Koestel, J. K.; Luong, N. M.; N°rgaard, T.; Vendelboe, A. L.; Moldrup, P.; Jarvis, N. J.; Lamandķ, M.; Iversen, B. V.; Wollesen de Jonge, L.
Anisotropic magnetic properties of Dy{sub 6}Cr{sub 4}Al{sub 43} single crystal
We have studied the anisotropic magnetic behavior of the rare earth intermetallic compound Dy{sub 6}Cr{sub 4}Al{sub 43}. This compound crystallizes in the hexagonal symmetry and orders ferromagnetically at 8.3 K as confirmed by the magnetic susceptibility and heat capacity measurements. A significant anisotropy in the magnetization is observed between the c axis and the ab-plane. The easy axis liesin theab-plane at low temperatures; however it orients itselfalong the c-axis above 170 K as inferred from the susceptibility data.
Maurya, Arvind, E-mail: firstname.lastname@example.com; Thamizhavel, A., E-mail: firstname.lastname@example.com; Dhar, S. K., E-mail: email@example.com [Department of Condensed Matter Physics and Material Science, Tata Institute of Fundamental Research, Mumbai-400005 (India)
Magnetic and Transport Properties of Lanthanum Based CMR Systems
NASA Astrophysics Data System (ADS)
The magnetic and transport properties of bulk polycrystalline samples of Ca doped manganite perovskites have been studied. The material properties were characterized using SEM, EDX and XRD. Curie temperature (277 +/- 3 K) and moment per Mn ion (approximately 4.3 ?_B) were determined via magnetization measurements. The temperature and field (H) dependence of the electrical resistivity, ?(T,H) and Hall effect were measured by standard ac four and six probe techniques in magnetic fields up to 17 T*. Typical zero field I-M transition peaks near 275 K in ?(T) and negative d?/dH at high fields were observed. However, for H < 0.2 T, positive MR is seen. There is evidence of small polaron transport at both above and below T_C, as well as ordinary and anomalous Hall effects. *Performed at the National High Magnetic Field Lab (NHMFL) FSU, Tallahassee, FL. This work was partially supported by grants from NASA_EPSCOR and the USC nanocenter.
Estrada, Javier; Brower, Jerry; Bleiweiss, Michael; Datta, Timir; Palm, Eric; Brandt, Bruce; Tsu, Ray
A general methodology for inverse estimation of the elastic and anelastic properties of anisotropic open-cell porous materialsŚwith application to a melamine foam
NASA Astrophysics Data System (ADS)
This paper proposes an inverse estimation method for the characterisation of the elastic and anelastic properties of the frame of anisotropic open-cell foams used for sound absorption. A model of viscoelasticity based on a fractional differential constitutive equation is used, leading to an augmented Hooke's law in the frequency domain, where the elastic and anelastic phenomena appear as distinctive terms in the stiffness matrix. The parameters of the model are nine orthotropic elastic moduli, three angles of orientation of the material principal directions and three parameters governing the anelastic frequency dependence. The inverse estimation consists in numerically fitting the model on a set of transfer functions extracted from a sample of material. The setup uses a seismic-mass measurement repeated in the three directions of space and is placed in a vacuum chamber in order to remove the air from the pores of the sample. The method allows to reconstruct the full frequency-dependent complex stiffness matrix of the frame of an anisotropic open-cell foam and in particular it provides the frequency of maximum energy dissipation by viscoelastic effects. The characterisation of a melamine foam sample is performed and the relation between the fractional-derivative model and other types of parameterisations of the augmented Hooke's law is discussed.
Cuenca, Jacques; Van der Kelen, Christophe; G÷ransson, Peter
A general methodology for inverse estimation of the elastic and anelastic properties of anisotropic open-cell porous materialsŚwith application to a melamine foam
This paper proposes an inverse estimation method for the characterisation of the elastic and anelastic properties of the frame of anisotropic open-cell foams used for sound absorption. A model of viscoelasticity based on a fractional differential constitutive equation is used, leading to an augmented Hooke's law in the frequency domain, where the elastic and anelastic phenomena appear as distinctive terms in the stiffness matrix. The parameters of the model are nine orthotropic elastic moduli, three angles of orientation of the material principal directions and three parameters governing the anelastic frequency dependence. The inverse estimation consists in numerically fitting the model on a set of transfer functions extracted from a sample of material. The setup uses a seismic-mass measurement repeated in the three directions of space and is placed in a vacuum chamber in order to remove the air from the pores of the sample. The method allows to reconstruct the full frequency-dependent complex stiffness matrix of the frame of an anisotropic open-cell foam and in particular it provides the frequency of maximum energy dissipation by viscoelastic effects. The characterisation of a melamine foam sample is performed and the relation between the fractional-derivative model and other types of parameterisations of the augmented Hooke's law is discussed.
Cuenca, Jacques, E-mail: email@example.com; Van der Kelen, Christophe; G÷ransson, Peter [Marcus Wallenberg Laboratory for Sound and Vibration Research, Royal Institute of Technology (KTH), Teknikringen 8, SE-10044 Stockholm (Sweden)
The goal of the Cementitious Barriers Partnership (CBP) is to develop a reasonable and realible set of tools to reduce the uncertainty in predicting the structural, hydraulic and chemical performance of cement barriers used in nuclear applications that are exposed to dynamic environmental conditions over extended time frames. One of these tools, the responsibility of NIST, is THAMES (Thermodynamic Hydration and Microstructure Evolution Simulator), which is being developed to describe cementitious binder microstructures and calculate important engineering properties during hydration and degradation. THAMES is designed to be a 'micro-probe', used to evaluate changes in microstructure and properties occurring over time because of hydration or degradation reactions in a volume of about 0.001 mm{sup 3}. It will be used to map out microstructural and property changes across reaction fronts, for example, with spatial resolution adequate to be input into other models (e.g., STADIUM{reg_sign}, LeachSX{trademark}) in the integrated CBP package. THAMES leverages thermodynamic predictions of equilibrium phase assemblages in aqueous geochemical systems to estimate 3-D virtual microstructures of a cementitious binder at different times during the hydration process or potentially during degradation phenomena. These virtual microstructures can then be used to calculate important engineering properties of a concrete made from that binder at prescribed times. In this way, the THAMES model provides a way to calculate the time evolution of important material properties such as elastic stiffness, compressive strength, diffusivity, and permeability. Without this model, there would be no way to update microstructure and properties for the barrier materials considered as they are exposed to the environment, thus greatly increasing the uncertainty of long-term transport predictions. This Task 7 report demonstrates the current capabilities of THAMES. At the start of the CBP project, THAMES did not exist, so that it is in the early stages of development. However, extensive experience with 3-D microstructure models at NIST is making possible a timely development process.
Langton, C.; Bullard, J.; Stutzman, P.; Snyder, K.; Garboczi, E.
Quasiparticle band structures and thermoelectric transport properties of p-type SnSe
NASA Astrophysics Data System (ADS)
We used density functional and many-body perturbation theory to calculate the quasiparticle band structures and electronic transport parameters of p-type SnSe both for the low-temperature Pnma and high-temperature Cmcm phases. The Pnma phase has an indirect band gap of 0.829 eV, while the Cmcm has a direct band gap of 0.464 eV. Both phases exhibit multiple local band extrema within an energy range comparable to the thermal energy of carriers from the global extrema. We calculated the electronic transport coefficients as a function of doping concentration and temperature for single-crystal and polycrystalline materials to understand the previous experimental measurements. The electronic transport coefficients are highly anisotropic and are strongly affected by bipolar transport effects at high temperature. Our results indicate that SnSe exhibits optimal thermoelectric performance at high temperature when doped in the 1019-1020 cm-3 range.
Shi, Guangsha; Kioupakis, Emmanouil
A two-step hybrid technique for accurately localizing acoustic source in anisotropic structures without knowing their material properties.
Acoustic source localization techniques generally assume straight line propagation of waves from the acoustic source to the sensor. However, it is well-known that in anisotropic plates the acoustic energy does not always propagate in straight lines. Even for isotropic plates containing a cavity or an inclusion between the acoustic source and the sensor the straight line propagation assumption is violated. In such cases only options available in localizing acoustic source is to use relatively expensive distributed sensor systems, or to follow time reversal techniques based on the impulse response functions which is labor intensive and computationally demanding. A two-step hybrid technique is proposed in this paper for predicting acoustic source in anisotropic plates. During the first step it was assumed that the waves propagated along straight lines from the acoustic source to the sensor. The source was localized with this simplifying assumption. Then this first prediction was improved in the second step by solving an optimization problem. Experimental results showed that the second step always moved the estimates towards the actual source location. Thus it always reduced the prediction error irrespective of whether the final prediction coincided with the actual source location or not. PMID:25245206
Kundu, T; Yang, X; Nakatani, H; Takeda, N
Anisotropic friction for deformable surfaces and solids
This paper presents a method for simulating anisotropic friction for deforming surfaces and solids. Frictional contact is a complex phenomenon that fuels research in mechanical engineering, computational contact mechan- ics, composite material design and rigid body dynamics, to name just a few. Many real-world materials have anisotropic surface properties. As an example, most textiles exhibit direction-dependent frictional behavior, but despite
Simon Pabst; Bernhard Thomaszewski; Wolfgang Stra▀er
Metal Vapors in Gas Tungsten Arcs: Part II. Theoretical Calculations of Transport Properties
( ( Metal Vapors in Gas Tungsten Arcs: Part II. Theoretical Calculations of Transport Properties G. J. DUNN and T. W. EAGAR Theoretical calculations of gas tungsten arc transport properties have, the effects of vapors emitted by the tungsten electrode may have a great effect on arc properties
Eagar, Thomas W.
SIMULATIONS OF TRANSPORT AND FIELD-EMISSION PROPERTIES OF MULTI-WALL CARBON NANOTUBES Alexandre- emission properties of multi-wall carbon nanotubes. The structure considered for the transport properties-saturation of the dangling bonds still improves the emission. I. INTRODUCTION Carbon nanotubes show interesting field-emission
Mayer, Alexandre
Quantifying Effective Flow and Transport Properties in Heterogeneous Porous Media
NASA Astrophysics Data System (ADS)
Spatial heterogeneity, the spatial variation in physical and chemical properties, exists at almost all scales and is an intrinsic property of natural porous media. It is important to understand and quantify how small-scale spatial variations determine large-scale "effective" properties in order to predict fluid flow and transport behavior in the natural subsurface. In this work, we aim to systematically understand and quantify the role of the spatial distribution of sand grains of different sizes in determining effective dispersivity and effective permeability using quasi-2D flow-cell experiments and numerical simulations. Two dimensional flow cells (20 cm by 20 cm) were packed with the same total amount of fine and coarse sands however with different spatial patterns. The homogeneous case has the completely mixed fine and coarse sands. The four zone case distributes the fine sand in four identical square zones within the coarse sand matrix. The one square case has all the fine sands in one square block. With the one square case pattern, two more experiments were designed in order to examine the effect of grain size contrast on effective permeability and dispersivity. Effective permeability was calculated based on both experimental and modeling results. Tracer tests were run for all cases. Advection dispersion equations were solved to match breakthrough data and to obtain average dispersivity. We also used Continuous Time Random Walk (CTRW) to quantify the non-Fickian transport behavior for each case. For the three cases with the same grain size contrast, the results show that the effective permeability does not differ significantly. The effective dispersion coefficient is the smallest for the homogeneous case (0.05 cm) and largest for the four zone case (0.27 cm). With the same pattern, the dispersivity value is the largest with the highest size contrast (0.28 cm), which is higher than the one with the lowest case by a factor of 2. The non-Fickian behavior was quantified by the ? value within the CTRW framework. Fickian transport will result in ? values larger than 2 while its deviation from 2 indicates the extent of non-Fickian behavior. Among the three cases with the same grain size contrast, the ? value is closest to 2 in the homogeneous case (1.95), while smallest in the four zone case (1.89). In the one square case, with the highest size contrast, the ? value was 1.57, indicating increasing extent of non-Fickian behavior with higher size contrast. This study is one step toward understanding how small-scale spatial variation in physical properties affect large-scale flow and transport behavior. This step is important in predicting subsurface transport processes that are relevant to earth sciences, environmental engineering, and petroleum engineering.
Heidari, P.; Li, L.
Configurational temperature and local properties of the anisotropic Gay-Berne liquid crystal model: Applications to the isotropic liquid/vapor interface and isotropic/nematic transition
NASA Astrophysics Data System (ADS)
Molecular simulations in the isothermal statistical ensembles require that the macroscopic thermal and mechanical equilibriums are respected and that the local values of these properties are constant at every point in the system. The thermal equilibrium in Monte Carlo simulations can be checked through the calculation of the configurational temperature, {k_BT_{conf}={< |nabla _r U({r}^N)|2>}/{< nabla _r{^2} U({r}^N) >}}, where nabla _r is the nabla operator of position vector r. As far as we know, T_{conf} was never calculated with the anisotropic Gay-Berne potential, whereas the calculation of T_{conf} is much more widespread with more common potentials (Lennard Jones, electrostatic, ģ). We establish here an operational expression of the macroscopic and local configurational temperatures, and we investigate locally the isotropic liquid phase, the liquid / vapor interface, and the isotropic-nematic transition by Monte Carlo simulations.
Ghoufi, Aziz; Morineau, Denis; Lefort, Ronan; Malfreyt, Patrice
Slow dynamics and the glass transition in anisotropic polymer liquids
A microscopic theory has been developed at the coarse-grained segment level for the onset or crossover temperature (Tc) to highly activated dynamics in deeply supercooled anisotropic polymer liquids. A generalization of a simplified mode coupling theory is employed which utilizes structural and thermodynamic information from anisotropic PRISM theory. Conformational alignment or \\/and deformation modifies equilibrium properties thereby inducing anisotropic segmental
Folusho Oyerokun
Critical transport properties of random metals in large magnetic fields.
The threshold behavior of the transport properties of a random metal in the critical region near a metal-insulator transition is strongly affected by the measuring electromagnetic fields. In spite of the randomness, the electrical conductivity exhibits striking phase-coherent effects due to broken symmetry, which greatly sharpen the transition compared with the predictions of effective medium theories, as previously explained for electrical conductivities. Here broken symmetry explains the sign reversal of the T --> 0 magnetoconductance of the metal-insulator transition in Si(B,P), also previously not understood by effective medium theories. Finally, the symmetry-breaking features of quantum percolation theory explain the unexpectedly very small electrical conductivity temperature exponent alpha = 0.22(2) recently observed in Ni(S,Se)2 alloys at the antiferromagnetic metal-insulator transition below T = 0.8 K. PMID:11038580
Phillips, J C
The electrical transport properties of liquid Rb using pseudopotential theory
Certain electric transport properties of liquid Rb are reported. The electrical resistivity is calculated by using the self-consistent approximation as suggested by Ferraz and March. The pseudopotential due to Hasegawa et al for full electron-ion interaction, which is valid for all electrons and contains the repulsive delta function due to achieve the necessary s-pseudisation was used for the calculation. Temperature dependence of structure factor is considered through temperature dependent potential parameter in the pair potential. Finally, thermo-electric power and thermal conductivity are obtained. The outcome of the present study is discussed in light of other such results, and confirms the applicability of pseudopotential at very high temperature via temperature dependent pair potential.
Patel, A. B., E-mail: firstname.lastname@example.com; Bhatt, N. K., E-mail: email@example.com; Thakore, B. Y., E-mail: email@example.com; Jani, A. R. [Department of Physics, Sardar Patel University, Vallabh Vidyanagar-388120, Gujarat (India); Vyas, P. R. [Department of Physics, School of Sciences, Gujarat University, Ahmedabad-380009, Gujarat (India)
Electron-neutron scattering and transport properties of neutron stars
NASA Astrophysics Data System (ADS)
We show that electrons can couple to the neutron excitations in neutron stars, and find that this can limit their contribution to the transport properties of dense matter, especially the shear viscosity. The coupling between electrons and neutrons is induced by protons in the core, and by ions in the crust. We calculate the effective electron-neutron interaction for the kinematics of relevance to the scattering of degenerate electrons at high density. We use this interaction to calculate the electron thermal conductivity, electrical conductivity, and shear viscosity in the neutron star inner crust, and in the core where we consider both normal and superfluid phases of neutron-rich matter. In some cases, particularly when protons are superconducting and neutrons are in their normal phase, we find that electron-neutron scattering can be more important than the other scattering mechanisms considered previously.
Bertoni, Bridget; Reddy, Sanjay; Rrapaj, Ermal
Electron-neutron scattering and transport properties of neutron stars
We show that electrons can couple to the neutron excitations in neutron stars and find that this can limit their contribution to the transport properties of dense matter, especially the shear viscosity. The coupling between electrons and neutrons is induced by protons in the core, and by ions in the crust. We calculate the effective electron-neutron interaction for the kinematics of relevance to the scattering of degenerate electrons at high density. We use this interaction to calculate the electron thermal conductivity, electrical conductivity, and shear viscosity in the neutron star inner crust, and in the core where we consider both normal and superfluid phases of neutron-rich matter. In some cases, particularly when protons are superconducting and neutrons are in their normal phase, we find that electron-neutron scattering can be more important than the other scattering mechanisms considered previously.
Bridget Bertoni; Sanjay Reddy; Ermal Rrapaj
Universal transport properties of three-dimensional topological insulator nanowires
NASA Astrophysics Data System (ADS)
We report theoretical calculations of electronic and transport properties mediated by topological helical states on the walls of three-dimensional topological insulator (TI) nanowires. A universal regime of quantized conductance and fluctuations is found that is induced by disorder. The average conductance of the disordered nanowire scales as a function of the number of transmission channels N in a universal form
Zhang, Lei; Zhuang, Jianing; Xing, Yanxia; Li, Jian; Wang, Jian; Guo, Hong
Dark matter transport properties and rapidly rotating neutron stars
Neutron stars are attractive places to look for dark matter because their high densities allow repeated interactions. Weakly interacting massive particles (WIMPs) may scatter efficiently in the core or in the crust of a neutron star. In this paper we focus on WIMP contributions to transport properties, such as shear viscosity or thermal conductivity, because these can be greatly enhanced by long mean free paths. We speculate that WIMPs increase the shear viscosity of neutron star matter and help stabilize r-mode oscillations. These are collective oscillations where the restoring force is the Coriolis force. At present r-modes are thought to be unstable in many observed rapidly rotating stars. If WIMPs stabilize the r-modes, this would allow neutron stars to spin rapidly. This likely requires WIMP-nucleon cross sections near present experimental limits and an appropriate density of WIMPs in neutron stars.
C. J. Horowitz
Transport timescales and tracer properties in the extratropical UTLS
NASA Astrophysics Data System (ADS)
A comprehensive evaluation of seasonal backward trajectories initialized in the northern hemisphere lowermost stratosphere (LMS) has been performed to investigate the factors that determine the temporal and spatial structure of troposphere-to-stratosphere-transport (TST) and it's impact on the LMS. In particular we explain the fundamental role of the transit time since last TST (tTST) for the chemical composition of the LMS. According to our results the structure of the LMS can be characterized by a layer with tTST<40 days forming a narrow band around the local tropopause. This layer extends about 30 K above the local dynamical tropopause, corresponding to the extratropical tropopause transition layer (ExTL) as identified by CO. The LMS beyond this layer shows a relatively well defined separation as marked by an aprupt transition to longer tTST indicating less frequent mixing and a smaller fraction of tropospheric air. Thus the LMS constitutes a region of two well defined regimes of tropospheric influence. These can be characterized mainly by different transport times from the troposphere and different fractions of tropospheric air. Carbon monoxide (CO) mirrors this structure of tTST due to it's finite lifetime on the order of three months. Water vapour isopleths, on the other hand, do not uniquely indicate TST and are independent of tTST, but are determined by the Lagrangian Cold Point (LCP) of air parcels. Most of the backward trajectories from the LMS experienced their LCP in the tropics and sub-tropics, and TST often occurs 20 days after trajectories have encountered their LCP. Therefore, ExTL properties deduced from CO and H2O provide totally different informations on transport and particular TST for the LMS.
Hoor, P.; Wernli, H.; Hegglin, M. I.; B÷nisch, H.
Simulating liquid water for determining its structural and transport properties.
Molecular dynamics simulations are carried out for calculating structural and transport properties of pure liquid water, such as radial distribution functions and self-diffusion and viscosity coefficients, respectively. We employed reparameterized versions of the ab initio water potential by Niesar, Clementi and Corongiu (NCC). In order to investigate the role of the electrostatic contribution, the partial charges of the NCC model are adjusted so that to reproduce the dipole moment values of the SPC/E, SPC/Fw and TIP4P/2005 water models. The single and collective transport coefficients are obtained by employing the Green-Kubo relations at various temperatures. Additionally, in order to overcome convergence difficulties arising from the long correlation times of the stress-tensor autocorrelation functions, a previously reported fitting scheme was employed. The present results indicate that there is a significant relationship between the dipole moment value of the model, and the calculated transport coefficients. We found that by adjusting the molecular dipole moment of the NCC to the value of the TIP4P/2005, the obtained values for the self-diffusion and viscosity coefficients are in better agreement with experiment, compared to the values obtained with the original NCC model. Even though the predictions of the present model exhibits an overall correct behavior, we conclude that further improvements are still required. In order to achieve that, a careful reparameterization of the repulsion-dispersion terms of the potential model is proposed. Also, the effect of the inclusion of many-body effects such as polarizability, should also be investigated. PMID:23415103
Arismendi-Arrieta, Daniel; Medina, Juan S; Fanourgakis, George S; Prosmiti, Rita; Delgado-Barrio, Gerardo
Transport Properties through Nanomaterials by First-principles Calculations
NASA Astrophysics Data System (ADS)
Nanoscale molecular devices are potential candidates for this next step, and they would make it possible to realize the most advantageous devices. Our group has covered a wide range of nanoscale materials[1] such as self-assembled nanowires on Si(001) [2, 3], quantum length dependence of conductance in oligomers [4] and single-molecule rotation switch [5] and so on. In this presentation, we will present our recent study on the transport properties of these nanoscale materials using the nonequilibrium Green's function formalism for quantum transport and the density functional theory (DFT) of electronic structures using local orbital basis sets. References 1. http://www-lab.imr.edu/śmizuseki/nanowire.html 2. J.-T. Wang, C. Chen, E. G. Wang, D.-S. Wang, H. Mizuseki, and Y. Kawazoe, Phys. Rev. Lett., 97 (2006) 046103. 3. R. V. Belosludov, A. A. Farajian, H. Mizuseki, K. Miki, and Y. Kawazoe, Phys. Rev. B, 75 (2007) 113411. 4. Y. X. Zhou, F. Jiang, H. Chen, R. Note, H. Mizuseki, and Y. Kawazoe, Phys. Rev. B, 75 (2007) 245407. 5. Y. Y. Liang, F. Jiang, Y. X. Zhou, H. Chen, R. Note, H. Mizuseki, and Y. Kawazoe, J. Chem. Phys. 127 (2007) 084107.
Mizuseki, Hiroshi; Belosludov, Rodion; Uck Lee, Sang; Kawazoe, Yoshiyuki
Transport properties of tetrahedral, network-forming ionic melts.
Molecular dynamics simulations of liquid silica and beryllium fluoride are performed using the van Beest-Kramer-van Santen and transferable rigid ion model potentials, respectively, in order to compare transport properties. The ionic conductivity (sigma), shear viscosity (eta) and ionic self-diffusivities (D(+/-)) are computed over a fairly wide range of temperatures and densities and deviations from Arrhenius behavior along different isochores is studied. The Stokes-Einstein relation is shown to hold over the entire range of state points, though the effective hydrodynamic radius shows small variations due to thermal fluctuations, compression, and local tetrahedral order. Several alternative tests of the Nernst-Einstein relation are implemented which show that significant network-formation in the anomalous regime leads to a breakdown of this relationship. The relaxation times, tau(sigma) and tau(M), associated with the decay of the charge-flux and pressure ACFs respectively, are computed. In the anomalous regime, as the tetrahedral network formation progresses, tau(M) increases rapidly while tau(sigma) shows very little variation, indicating a decoupling of charge and momentum transport processes. PMID:19860439
Agarwal, Manish; Ganguly, Abir; Chakravarty, Charusita
Predicting the transport properties of sedimentary rocks from microstructure
Understanding transport properties of sedimentary rocks, including permeability, relative permeability, and electrical conductivity, is of great importance for petroleum engineering, waste isolation, environmental restoration, and other applications. These transport properties axe controlled to a great extent by the pore structure. How pore geometry, topology, and the physics and chemistry of mineral-fluid and fluid-fluid interactions affect the flow of fluids through consolidated/partially consolidated porous media are investigated analytically and experimentally. Hydraulic and electrical conductivity of sedimentary rocks are predicted from the microscopic geometry of the pore space. Cross-sectional areas and perimeters of individual pores are estimated from two-dimensional scanning electron microscope (SEM) photomicrographs of rock sections. Results, using Berea, Boise, Massilon, and Saint-Gilles sandstones show close agreement between the predicted and measured permeabilities. Good to fair agreement is found in the case of electrical conductivity. In particular, good agreement is found for a poorly cemented rock such as Saint-Gilles sandstone, whereas the agreement is not very good for well-cemented rocks. The possible reasons for this are investigated. The surface conductance contribution of clay minerals to the overall electrical conductivity is assessed. The effect of partial hydrocarbon saturation on overall rock conductivity, and on the Archie saturation exponent, is discussed. The region of validity of the well-known Kozeny-Carman permeability formulae for consolidated porous media and their relationship to the microscopic spatial variations of channel dimensions are established. It is found that the permeabilities predicted by the Kozeny-Carman equations are valid within a factor of three of the observed values methods.
Schlueter, E.M.
Dependence of dynamic magnetization and magneto-transport properties of FeAlSi films with oblique sputtering studied via spin rectification effect
NASA Astrophysics Data System (ADS)
FeAlSi (Sendust) is known to possess excellent soft magnetic properties comparable to traditional soft magnetic alloys such as NiFe (Permalloy), while having a relatively higher resistance for lower eddy current losses. However, their dynamic magnetic and magneto-transport properties are not well-studied. Via the spin rectification effect, we electrically characterize a series of obliquely sputtered FeAlSi films at ferromagnetic resonance. The variations of the anisotropy fields and damping with oblique angle are extracted and discussed. In particular, two-magnon scattering is found to dominate the damping behavior at high oblique angles. An analysis of the results shows large anomalous Hall effect and anisotropic magneto-resistance across all samples, which decreases sharply with increasing oblique incidence.
Soh, Wee Tee; Zhong, Xiaoxi; Ong, C. K.
Dependence of dynamic magnetization and magneto-transport properties of FeAlSi films with oblique sputtering studied via spin rectification effect
FeAlSi (Sendust) is known to possess excellent soft magnetic properties comparable to traditional soft magnetic alloys such as NiFe (Permalloy), while having a relatively higher resistance for lower eddy current losses. However, their dynamic magnetic and magneto-transport properties are not well-studied. Via the spin rectification effect, we electrically characterize a series of obliquely sputtered FeAlSi films at ferromagnetic resonance. The variations of the anisotropy fields and damping with oblique angle are extracted and discussed. In particular, two-magnon scattering is found to dominate the damping behavior at high oblique angles. An analysis of the results shows large anomalous Hall effect and anisotropic magneto-resistance across all samples, which decreases sharply with increasing oblique incidence.
Soh, Wee Tee; Ong, C. K. [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, 2 Science Drive 3, Singapore 117551 (Singapore); Zhong, Xiaoxi, E-mail: firstname.lastname@example.com [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, 2 Science Drive 3, Singapore 117551 (Singapore); School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China)
Elastic and transport properties in polycrystals of crackedgrains: Cross-property relations and microstructure
Some arguments of Bristow (1960) concerning the effects of cracks on elastic and transport (i.e., electrical or thermal conduction) properties of cold-worked metals are reexamined. The discussion is posed in terms of a modern understanding of bounds and estimates for physical properties of polycrystals--in contrast to Bristow's approach using simple mixture theory. One type of specialized result emphasized here is the cross-property estimates and bounds that can be obtained using the methods presented. Our results ultimately agree with those of Bristow, i.e., confirming that microcracking is not likely to be the main cause of the observed elastic behavior of cold-worked metals. However, it also becomes clear that the mixture theory approach to the analysis is too simple and that crack-crack interactions are necessary for proper quantitative study of Bristow's problem.
Berryman, J.G.
Generalized thermodynamic and transport properties. II. Molecular liquids
NASA Astrophysics Data System (ADS)
In the present paper, we extend the method described in paper I [D. Bertolini and A. Tani, preceding paper, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.83.031201 83, 031201 (2011)] to molecular liquids, which allows us to solve the exact kinetic equation proposed by de Schepper [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.38.271 38, 271 (1988)] without approximations. In particular, generalized thermodynamic properties (enthalpy, specific heat, and thermal expansion coefficient) and transport properties (longitudinal viscosity, thermal conductivity) have been calculated for three liquids of increasing complexity, namely dimethyl sulfoxide, hydrogen fluoride, and SPC/E water. All results have been obtained by the molecular formalism as well as the atomic one, corrected for intramolecular correlations that are due to the models adopted. As done for simple liquids, the coupling between the viscous stress tensor and the energy flux vector has been calculated exactly. We also show that the Markov assumption for the dynamics related to thermal conductivity can only be adopted with caution.
Bertolini, D.; Tani, A.
Transport Properties and Diamagnetism of Dirac Electrons in Bismuth
NASA Astrophysics Data System (ADS)
Bismuth crystal is known for its noteworthy properties resulting from particular electronic states, e.g., the Shubnikov¢de Haas effect and the de Haas¢van Alphen effect. Above all, the large diamagnetism of bismuth had been a long-standing puzzle since soon after the establishment of quantum mechanics, which was resolved eventually in 1970, on the basis of the effective Hamiltonian derived by Wolff, as being due to the interband effects of a magnetic field in the presence of a large spin¢orbit interaction. This Hamiltonian is essentially the same as the Dirac Hamiltonian but with spatial anisotropy and an effective velocity much smaller than the light velocity. This paper reviews recent progress in the theoretical understanding of transport and optical properties, such as the weak-field Hall effect together with the spin Hall effect, and the magneto-optic effect, of a system described by the Wolff Hamiltonian and its isotropic version with a special focus on exploring the possible relationship with orbital magnetism. It is shown that there is a fundamental relationship between the spin Hall conductivity and orbital susceptibility in the insulating state, and the possibility of a fully spin-polarized electric current in magneto-optics. Experimental tests of these interesting features have been proposed.
Fuseya, Yuki; Ogata, Masao; Fukuyama, Hidetoshi
Transport properties and nanosensors of oxide nanowires and nanobelts
NASA Astrophysics Data System (ADS)
ZnO is one of the most important materials for electronics, optoelectronics, piezoelectricity and optics. With a wide band gap of 3.37eV and an exiton binding energy of 60meV, ZnO ID nanostructures exhibit promising properties in a lot of optical device applications. It is also an important piezoelectric material and has applications in a new category of nanodevices, nano-piezotronics. Demonstrated prototype of devices includes nanogenerators, piezoelectric-FET, and a series of evolutive devices based on the concept of nanogenerator. This is based on working principle of a semiconductor and piezoelectric coupled property. This thesis is about the growth, characterization and device fabrication of ZnO nanowires and nanobelts for sensors and UV detectors. First, the fundamental synthesis of ZnO nanostructurs is investigated, particularly polar surface dominated nanostructues, to illustrate the unique growth configurations of ZnO nanobelts, nanorings and nanosprings. Detail study in this part includes nanobelts, nanorings, nanocombs, nanonetworks, and nanodiskettes synthesis. Important factors in driving the nanostructure synthesis mechanism are analyzed, such as the chemical activities of different surface of ZnO, the abundant of available Zn ions in the vapor, and the polar surface dominated effects. These factors contribute to the large abundant available ZnO nanostructures. Then, the devices fabricated methods using individual nanowires/nanobelts and their electrical transport properties were carefully characterized. In this part, dominant factors which are critical for nanobelt device performance are investigated, such as the contact properties, interface effects, and durability testing. Also, a metal doping method is studied to explore the controlling and modification of nanowire electric and optical properties. Research results obtained here provide a basic and thoroughly understanding the control process and fabrication criteria in building a functional nanobelt based device. Further more, I will present the surface functionalization of nanobelt for largely improving its electrical, optoelectronic and chemical performance. Surface functionalization of nanobelts is proven to be an effective method in enhancing the semiconductor and metal contact. Piezoelectric field-effect transistors will be demonstrated as a powerful approach as chemical sensors. Finally, a technique is illustrated for functionalizing the surfaces of ZnO nanobelts for enhancing its UV sensitivity by over five orders of magnitude. This demonstrates an effective approach for fabricatiing ultrasensitive UV detectors. The research results presented in this thesis have made great contribution to the growth, device fabrication and novel applications of ZnO nanostructures for photonics, optoelectronics and sensors.
Lao, Changshi
Anisotropic effective medium theories
NASA Astrophysics Data System (ADS)
The optical properties of anisotropic inhomogeneous media are studied within the framework of the classical 3D effective medium theories of Maxwell Garnett and Bruggeman, and the 2D theory of Yamaguchi et al. The origin of the anisotropy is either the nonspherical shape of the metallic inclusions in the 3D systems, or the distribution of the inclusions (even if spherical) on a substrate in the 2D configuration. In both cases, it leads to an anisotropic effective medium. In this paper, it is shown that this surrounding anisotropic medium induces a fictitious deformation of the inclusions which reduces the anisotropy and shifts the resonance wavelengths toward the sphere plasmon resonance. In the case of the mean field theory of Bruggeman, it also affects the percolation threshold value. Although some of these theories are now quite old, they are still extensively used, especially for the predictions of the absorption of the composite media. Therefore the effect presented here for the first time should be taken into account. Les propriķtķs optiques des milieux inhomogĶnes anisotropes sont ķtudiķes dans le cadre des thķories du milieu effectif, tant Ó trois dimensions (3D) (thķories de Maxwell Garnett et de Bruggeman) qu'Ó deux dimensions (2D) (thķorie de Yamaguchi et al.). L'anisotropie du milieu effectif peut provenir soit de l'alignement d'inclusions non sphķriques dans un systĶme Ó deux ou trois dimensions, soit de la distribution plane du systĶme 2D, mĻme pour des particules sphķriques. Nous montrons ici que ce milieu effectif anisotrope induit une dķformation fictive des inclusions qui va dans le sens d'une rķduction de l'anisotropie et rapproche les frķquences de rķsonance de plasmon de surface vers celle de la sphĶre. Par ailleurs, dans le cas de la thķorie de Bruggeman, cela modifie la valeur du seuil de percolation optique. Ces thķories, bien qu'anciennes, sont toujours trĶs utilisķes, en particulier pour prķdire l'absorption optique des composites. L'effet prķsentķ ici doit donc impķrativement Ļtre pris en compte.
Berthier, Serge
Mechanical identification of layer-specific properties of mouse carotid arteries using 3D-DIC and a hyperelastic anisotropic
1 Mechanical identification of layer-specific properties of mouse carotid arteries using 3D;2 Mechanical identification of layer-specific properties of mouse carotid arteries using 3D arterial diseases; however determining mechanical properties of arteries remains a challenge. This paper
Paris-Sud XI, Universitķ de
Effect of Mn substitution on the transport properties of co-sputtered Fe3-xMnxSi epilayers
NASA Astrophysics Data System (ADS)
Motivated by the theoretical calculations that Fe3-xMnxSi can simultaneously exhibit a high spin polarization with a high Curie temperature to be applied in spintronic devices, and in order to further study the effect of Mn contents on the physical properties of Fe3-xMnxSi, we have investigated the effect of Mn substitution on the transport properties of epitaxial Fe3-xMnxSi ( 0 ?x ?1 ) films systematically. The Fe3-xMnxSi films were epitaxially grown on MgO(001) plane with 45░ rotation. The magnetization for various x shows enhanced irreversibility, implying the antiferromagnetic ordering induced by the substitution of Mn. A metal-semiconductor crossover was observed due to the enhanced disorders of interactions and the local lowering of symmetry induced by the substitution of Mn. The single-domain state in the Fe3-xMnxSi films leads to twofold symmetric curves of the anisotropic magnetoresistance and planar Hall resistivity.
Tang, M.; Jin, C.; Bai, H. L.
Universal properties of chaotic transport in the presence of diffusion V. Rom-Kedar
of the transport of passive scalars by a given flow field appears in technological, geophysical, and enviUniversal properties of chaotic transport in the presence of diffusion V. Rom-Kedar Courant transport mechanism which results in the establishment of a ``Lagrangian steady state,'' where only
155 VAPOUR PHASE CHEMICAL TRANSPORT PROPERTIES OF THE CADMIUM TELLURIDE-IODINE SYSTEM C. PAORICI, it was shown that no iodine chemical transport is possible in closed tubes in the hot-cold direction, but only was explained in terms of a reverse (cold-hot) iodine transport associated with a reduced sublimation tendency
Boyer, Edmond
Investigating transport properties of nanofiltration membranes by means of a steric, electric and dielectric exclusion model
The transport properties of nanofiltration (NF) membranes are investigated by means of an improved transport model including dielectric exclusion in terms of both Born dielectric effect and image force contribution. The SEDE model (Steric, Electric and Dielectric Exclusion model) can be used to describe transport through pores of cylindrical or slit geometry. The coupling between the various mechanisms involved in
Anthony Szymczyk; Patrick Fievet
Exact quantum scattering calculations of transport properties: CH2(tilde{X}^3B1, tilde{a}^1A1)-helium
NASA Astrophysics Data System (ADS)
Transport properties for collisions of methylene, in both its ground tilde{X}^3B_1 and low-lying tilde{a}^1A_1 electronic states, with helium have been computed using recently computed high-quality ab initio potential energy surfaces (PESs). Because of the difference in the orbital occupancy of the two electronic states, the anisotropies of the PESs are quite different. The CH2(tilde{a})-He PES is very anisotropic because of the strong interaction of the electrons on the helium atom with the unoccupied CH2 orbital perpendicular to the molecular plane, while the anisotropy of the CH2(tilde{X})-He PES is significantly less since this orbital is singly occupied in this case. To investigate the importance of the anisotropy on the transport properties, calculations were performed with the full potential and with the spherical average of the potential for both electronic states. Significant differences (over 20% for the tilde{a} state at the highest temperatures considered) in the computed transport properties were found.
Dagdigian, Paul J.; Alexander, Millard H.
Regional differences in ciliary epithelial cell transport properties.
Experiments were performed to determine whether the transport properties of the ciliary epithelium vary over different regions. Rabbit iris-ciliary bodies were incubated under experimental or control conditions for 30 min before quick freezing, cryosectioning, dehydration and electron probe X-ray microanalysis. Cryosections were cut from three regions along the major axis of the iris-ciliary body, i.e., the anterior, middle and posterior (pars plicata) regions. In bicarbonate/CO2 solution, the epithelial cells of the anterior and middle regions contained more Cl and K than did those of the posterior region. These higher levels of Cl and K were reduced by the carbonic anhydrase inhibitor acetazolamide. Application of bumetanide, an inhibitor of the Na+-K+-2Cl- cotransporter, resulted in significant increases in Cl and K in the anterior and middle regions but not in the posterior region. In bicarbonate-free solution, the ratio for K/Na contents was higher in the posterior than in the two more anterior regions; Na, K and Cl contents of epithelial cells in the three regions were otherwise similar. Cell composition did not differ significantly between the crests and valleys of the posterior region. The divergent responses to perturbation of epithelial transport in the different regions provide the first demonstration of functional heterogeneity along the major axis of the iris-ciliary body. The response to inhibition of carbonic anhydrase raises the possibility that the anterior aspect of the ciliary epithelium may be the major site of aqueous humor secretion. PMID:11547344
McLaughlin, C W; Zellhuber-McMillan, S; Peart, D; Purves, R D; Macknight, A D; Civan, M M
Avalanche properties in a transport model based on critical-gradient fluctuation dynamics
A simple one-dimensional transport model based on critical-gradient fluctuation dynamics is applied to describe some of the properties of plasma-turbulence-induced transport. This model combines avalanche-like transport with diffusion. The particle flux is self-regulated by the stability properties of the fluctuations. A high-gradient edge region emerges where transport dynamics is close to marginal stability. In steady state, the core remains at the subcritical gradient. The avalanches change from quasiperiodic events triggered mostly near the edge region to intermittent transport events depending on the noise level of the particle source.
Garcia, L.; Carreras, B.A. [Universidad Carlos III, 28911 Leganes, Madrid (Spain); Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States)
Internalization pathways of anisotropic disc-shaped zeolite L nanocrystals with different surface properties in HeLa cancer cells.
Information about the mechanisms underlying the interactions of nanoparticles with living cells is crucial for their medical application and also provides indications of the putative toxicity of such materials. Here the uptake and intracellular delivery of disc-shaped zeolite L nanocrystals as porous aminosilicates with well-defined crystal structure, uncoated as well as with COOH-, NH2 -, polyethyleneglycol (PEG)- and polyallylamine hydrochloride (PAH) surface coatings are reported. HeLa cells are used as a model system to demonstrate the relation between these particles and cancer cells. Interactions are studied in terms of their fates under diverse in vitro cell culture conditions. Differently charged coatings demonstrated dissimilar behavior in terms of agglomeration in media, serum protein adsorption, nanoparticle cytotoxicity and cell internalization. It is also found that functionalized disc-shaped zeolite L particles enter the cancer cells via different, partly not yet characterized, pathways. These in vitro results provide additional insight about low-aspect ratio anisotropic nanoparticle interactions with cancer cells and demonstrate the possibility to manipulate the interactions of nanoparticles and cells by surface coating for the use of nanoparticles in medical applications. PMID:23335435
Li, Zhen; H³ve, Jana; Krampe, Christina; Luppi, Gianluigi; Tsotsalas, Manuel; Klingauf, J³rgen; De Cola, Luisa; Riehemann, Kristina
Anisotropically structured magnetic aerogel monoliths.
Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture. PMID:25255203
Heiligtag, Florian J; Airaghi Leccardi, Marta J I; Erdem, Derya; S³ess, Martin J; Niederberger, Markus
Influence of Si Co-doping on electrical transport properties of magnesium-doped boron nanoswords
Influence of Si Co-doping on electrical transport properties of magnesium- doped boron nanoswords://apl.aip.org/about/rights_and_permissions #12;Influence of Si Co-doping on electrical transport properties of magnesium-doped boron nanoswords; published online 9 March 2012) Magnesium-doped boron nanoswords were synthesized via a thermoreduction
Gao, Hongjun
Computer program for calculation of complex chemical equilibrium compositions and applications. Supplement 1: Transport properties
NASA Technical Reports Server (NTRS)
An addition to the computer program of NASA SP-273 is given that permits transport property calculations for the gaseous phase. Approximate mixture formulas are used to obtain viscosity and frozen thermal conductivity. Reaction thermal conductivity is obtained by the same method as in NASA TN D-7056. Transport properties for 154 gaseous species were selected for use with the program.
Gordon, S.; Mcbride, B.; Zeleznik, F. J.
Avalanche properties in a transport model based on critical-gradient fluctuation dynamics
Avalanche properties in a transport model based on critical-gradient fluctuation dynamics L avalanche-like transport with diffusion. The particle flux is self-regulated by the stability properties. In steady state, the core remains at the subcritical gradient. The avalanches change from quasiperiodic
Mart├Łn-Sol├Łs, Jos├® Ram├│n
Geometrical and transport properties of single fractures: influence of the roughness of the fracture
Geometrical and transport properties of single fractures: influence of the roughness of the fracture walls H. Auradou Univ Pierre et Marie Curie-Paris6, Univ Paris-Sud, CNRS, F-91405. Lab FAST, Bat reviews the main features of the transport properties of single fractures. A particular attention paid
Paris-Sud XI, Universit├® de
Thermodynamic and transport combustion properties of hydrocarbons with air. Part 1: Properties in SI units
Thermodynamic and transport combustion properties were calculated for a wide range of conditions for the reaction of hydrocarbons with air. Three hydrogen-carbon atom ratios (H/C 1.7, 2.0, 2.1) were selected to represent the range of aircraft fuels. For each of these H/C ratios, combustion properties were calculated for the following conditions: Equivalence ratio: 0, 0.25, 0.5, 0.75, 1.0, 1.25 Water - dry air mass ratio: 0, 0.03 Pressure, kPa: 1.01325, 10.1325, 101.325, 1013.25, 5066.25 (or in atm: 0.01, 0.1, 1, 10, 50) Temperature, K: every 10 degrees from 200 to 900 K every 50 degrees from 900 to 3000 K Temperature, R: every 20 degrees from 360 to 1600 R very 100 degrees from 1600 to 5400 R. The properties presented are composition, density, molecular weight, enthalphy, entropy, specific heat at constant pressure, volume derivatives, isentropic exponent, velocity of sound, viscosity, thermal conductivity, and Prandtl number. Property tables are based on composites that were calculated by assuming both: (1) chemical equilibrium (for both homogeneous and heterogeneous phases) and (2) constant compositions for all temperatures. Properties in SI units are presented in this report for the Kelvin temperature schedules.
Gordon, S.
Thermodynamic and transport combustion properties of hydrocarbons with air. Part 1: Properties in SI units
NASA Technical Reports Server (NTRS)
Thermodynamic and transport combustion properties were calculated for a wide range of conditions for the reaction of hydrocarbons with air. Three hydrogen-carbon atom ratios (H/C = 1.7, 2.0, 2.1) were selected to represent the range of aircraft fuels. For each of these H/C ratios, combustion properties were calculated for the following conditions: Equivalence ratio: 0, 0.25, 0.5, 0.75, 1.0, 1.25 Water - dry air mass ratio: 0, 0.03 Pressure, kPa: 1.01325, 10.1325, 101.325, 1013.25, 5066.25 (or in atm: 0.01, 0.1, 1, 10, 50) Temperature, K: every 10 degrees from 200 to 900 K; every 50 degrees from 900 to 3000 K Temperature, R: every 20 degrees from 360 to 1600 R; very 100 degrees from 1600 to 5400 R. The properties presented are composition, density, molecular weight, enthalphy, entropy, specific heat at constant pressure, volume derivatives, isentropic exponent, velocity of sound, viscosity, thermal conductivity, and Prandtl number. Property tables are based on composites that were calculated by assuming both: (1) chemical equilibrium (for both homogeneous and heterogeneous phases) and (2) constant compositions for all temperatures. Properties in SI units are presented in this report for the Kelvin temperature schedules.
Gordon, S.
Microstructure and water vapor transport properties of temperature sensitive polyurethanes
NASA Astrophysics Data System (ADS)
Temperature sensitive polyurethane (TS-PU) is one novel type of smart polymers. The water vapor permeability (WVP) of its membrane could undergo a significant increase as temperature increases within a predetermined temperature range. Such smart property enables this material to have a broad range of potential applications to textile industry, medicine, environmental fields and so on. However, based on the literature review, contradicting results were found on some TS-PUs. The aims of this project are to synthesize TS-PU with Tm in the broader temperature range including ambient temperature range, and then investigate systematically the relationships between microstructure and water vapor transport properties of TS-PU. For this purpose, in this project, a series of polyurethanes (PU) were synthesized using five different crystalline polyols with approximately similar molecule weight and three different hydrophilic contents, and dense membranes were prepared accordingly. The microstructure and properties of these PUs were investigated using DSC, WAXD, DMA, FTIR, GPC, POM, TEM, SEM and PALS. Their equilibrium water sorption and water vapor permeability were measured accordingly. Results show that crystal melting of these resulting PUs take place in the temperature range from -10--60░C as desired. Storage modulus (E') drops down quickly in the temperature range of crystal melting, suggesting a great transition in the predetermined temperature range. The decreased HSC as well as regular chemical structure of polyols results in the larger spherulites and higher melting end temperature, and the higher crystallinity induces the more obvious incompatibility of soft segment and hard segment in the PUs. These PUs are proved to have good enough tensile properties for textile application. The mean free volume size and fractional free volume increase more significantly in the temperature range of crystal melting than in other temperature intervals. Finally, as expected, the WVP of semi-crystalline PU membranes increases significantly in the temperature range of crystal melting. Equilibrium water sorption keeps approximately constant. The significant increase in WVP of semi-crystalline PU is obviously correlated with the sharp increase in the free volume in the predetermined temperature range.
Ding, Xuemei
Transport properties of multicomponent thermal plasmas: Grad method versus Chapman-Enskog method
Transport properties (thermal conductivity, viscosity, and electrical conductivity) for multicomponent Ar-Fe thermal plasmas at atmospheric pressure have been determined by means of two different methods. The transport coefficients set based on Grad's method is compared with the data obtained when using the Chapman-Enskog's method. Results from both applied methods are in good agreement. It is shown that the Grad method is suitable for the determination of transport properties of the thermal plasmas.
Porytsky, P. [Institute for Nuclear Research, 03680 Kyiv (Ukraine); Krivtsun, I.; Demchenko, V. [Paton Welding Institute, 03680 Kyiv (Ukraine); Reisgen, U.; Mokrov, O.; Zabirov, A. [RWTH Aachen University, ISF-Welding and Joining Institute, 52062 Aachen (Germany); Gorchakov, S.; Timofeev, A.; Uhrlandt, D. [Leibniz Institute for Plasma Science and Technology (INP Greifswald), 17489 Greifswald (Germany)
Anisotropically structured magnetic aerogel monoliths
NASA Astrophysics Data System (ADS)
Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture.Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture. Electronic supplementary information (ESI) available: Digital photographs of dispersions and gels with different water-to-ethanol ratios; magnetic measurements of an anatase aerogel containing 0.25 mol% Fe3O4 nanoparticles; XRD patterns of the iron oxide and titania nanoparticles. See DOI: 10.1039/c4nr04694c
Heiligtag, Florian J.; Airaghi Leccardi, Marta J. I.; Erdem, Derya; S³ess, Martin J.; Niederberger, Markus
REVIEWS OF TOPICAL PROBLEMS: Transport properties of carbon nanotubes
NASA Astrophysics Data System (ADS)
The current status of experimental research on the transport characteristics of carbon nanotubes (CNTs) has been reviewed. Methods for measuring transport coefficients of CNTs have been considered. The available experimental data on the temperature dependence of thermal conductivity and electroconductivity of single-walled and multi-walled CNTs have been analyzed in terms of the ballistic mechanism of charge and heat transport.
Eletskii, Aleksandr V.
NASA Technical Reports Server (NTRS)
Accurate numerical prediction of high-temperature, chemically reacting flowfields requires a knowledge of the physical properties and reaction kinetics for the species involved in the reacting gas mixture. Assuming an 11-species air model at temperatures below 30,000 degrees Kelvin, SPECIES (Computer Codes for the Evaluation of Thermodynamic Properties, Transport Properties, and Equilibrium Constants of an 11-Species Air Model) computes values for the species thermodynamic and transport properties, diffusion coefficients and collision cross sections for any combination of the eleven species, and reaction rates for the twenty reactions normally occurring. The species represented in the model are diatomic nitrogen, diatomic oxygen, atomic nitrogen, atomic oxygen, nitric oxide, ionized nitric oxide, the free electron, ionized atomic nitrogen, ionized atomic oxygen, ionized diatomic nitrogen, and ionized diatomic oxygen. Sixteen subroutines compute the following properties for both a single species, interaction pair, or reaction, and an array of all species, pairs, or reactions: species specific heat and static enthalpy, species viscosity, species frozen thermal conductivity, diffusion coefficient, collision cross section (OMEGA 1,1), collision cross section (OMEGA 2,2), collision cross section ratio, and equilibrium constant. The program uses least squares polynomial curve-fits of the most accurate data believed available to provide the requested values more quickly than is possible with table look-up methods. The subroutines for computing transport coefficients and collision cross sections use additional code to correct for any electron pressure when working with ionic species. SPECIES was developed on a SUN 3/280 computer running the SunOS 3.5 operating system. It is written in standard FORTRAN 77 for use on any machine, and requires roughly 92K memory. The standard distribution medium for SPECIES is a 5.25 inch 360K MS-DOS format diskette. The contents of the diskettes are compressed using the PKWARE archiving tools. The utility to unarchive the files, PKUNZIP.EXE, is included. This program was last updated in 1991. SUN and SunOS are registered trademarks of Sun Microsystems, Inc.
Thompson, R. A.
Fabrication and transport properties of silicon nanoelectronic devices
NASA Astrophysics Data System (ADS)
It is estimated that the scaling of conventional silicon MOSFETs will end around the year 2020. While this certainly does not preclude the use of silicon in future devices, it does require new thoughts on the types of practical devices that can be used in integrated circuits. Namely, those that reduce power and work at least partly on the principles of quantum mechanics (such as spintronic or tunneling devices) will tend to be favored. The research presented herein is based on the fabrication and transport properties of nanometer-scale devices in silicon. The most promising of these structures are nanowires fabricated with a scanning tunneling microscope (STM). These high-density nanowires display the low-temperature phenomena of weak localization and one-dimensional conduction. Long-term applications of such nanowires and derivative devices include alternatives to conventional CMOS transistors and very sensitive charge and/or spin-detection devices. In addition, focused ion beams (FIBs) have been used to directly and precisely implant ions in the hope that they may be used to contact nanodevices, but surface damage may preclude that possibility.
Robinson, Stephen John
Transport Properties of Nanoscale Materials by First-principles Calculations
NASA Astrophysics Data System (ADS)
Molecular devices are potential candidates for the next step towards nanoelectronic technology. Our group has covered a wide range of nanoscale wires, which have potential application in molecular electronics using first-principles calculations and nonequilibrium Green's function formalism [1]. Our target materials are supramolecular enamel wires (covered wires) [2], connection between organic molecules and metal electrodes, self-assembled nanowires on silicon surface [3], porphyrin [4], phthalocyanine, metallocene [5], fused-ring thiophene molecules, length dependence of conductance in alkanedithiols and so on. Namely, we have investigated a relationship of the energy levels of delocalized frontier orbitals (HOMO and LUMO) and Fermi level of metal electrodes and estimate the electronic transport properties through atomic and molecular wires using Green's function approach. References [1] http://www-lab.imr.edu/śmizuseki/nanowire.html [2] R. V. Belosludov, A. A. Farajian, H. Baba, H. Mizuseki, and Y. Kawazoe, Jpn. J. Appl. Phys., 44, 2823 (2005). [3] R. V. Belosludov, A. A. Farajian, H. Mizuseki, K. Miki, and Y. Kawazoe, Phys. Rev. B, 75, 113411 (2007). [4] S.-U. Lee, R. V. Belosludov, H. Mizuseki, and Y. Kawazoe, Small 4 (2008) 962. [5] S.-U Lee, R. V. Belosludov, H. Mizuseki, and Y. Kawazoe, J. Phys. Chem. C. 111 (2007) 15397.
Mizuseki, Hiroshi; Belosludov, Rodion V.; Lee, S.-U.; Kawazoe, Yoshiyuki
Phase diagrams, dielectric response, and piezoelectric properties of epitaxial ultrathin (001) lead zirconate titanate films under anisotropic misfit strains
NASA Astrophysics Data System (ADS)
We develop a nonlinear thermodynamic model to predict the phase stability of ultrathin epitaxial (001)-oriented ferroelectric PbZr1-xTixO3 (PZT) films with x =1.0, 0.9, 0.8, and 0.7 on substrates which induce anisotropic in-plane strains. The theoretical formalism incorporates the relaxation by misfit dislocations at the film deposition temperature, the possibility of formation of ferroelectric polydomain structures, and the effect of the internal electric field that is generated due to incomplete charge screening at the film-electrode interfaces and the termination of the ferroelectric layer. This analysis allows the development of misfit strain phase diagrams that provide the regions of stability of monodomain and polydomain structures at a given temperature, film thickness, and composition. It is shown that the range of stability for rotational monodomain phase is markedly increased in comparison to the same ferroelectric films on isotropic substrates. Furthermore, the model finds a strong similarity between ultrathin PbTiO3 and relatively thicker PZT films in terms of phase stability. The combinations of the in-plane misfit strains that yield a phase transition sequence that results in a polarization rotation from the c-phase (polarization parallel to the [001] direction in the film) to the r-phase, and eventually to an in-plane polarization parallel to the [110] direction (the aa-phase) is determined to be the path with the most attractive dielectric and piezoelectric coefficients resulting in enhancements of 10 to 100 times in the dielectric permittivity and piezoresponse compared to bulk tetragonal ferroelectrics of the same PZT composition.
Qiu, Q. Y.; Alpay, S. P.; Nagarajan, V.
A Review of the Thermodynamic, Transport, and Chemical Reaction Rate Properties of High-temperature Air
NASA Technical Reports Server (NTRS)
Thermodynamic and transport properties of high temperature air, and the reaction rates for the important chemical processes which occur in air, are reviewed. Semiempirical, analytic expressions are presented for thermodynamic and transport properties of air. Examples are given illustrating the use of these properties to evaluate (1) equilibrium conditions following shock waves, (2) stagnation region heat flux to a blunt high-speed body, and (3) some chemical relaxation lengths in stagnation region flow.
Hansen, C Frederick; Heims, Steve P
Anisotropic Transport of Electrons in a Novel FET Channel with Chains of InGaAs Nano-Islands Embedded along Quasi-Periodic Multi-Atomic Steps on Vicinal (111)B GaAs
We have studied electron transport in n-AlGaAs/GaAs heterojunction FET channels, in which chains of InGaAs nano-islands are embedded along quasi-periodic steps. By using two samples, conductance G{sub para}(V{sub g}) parallel to the steps and G{sub perp}(V{sub g}) perpendicular to them were measured at 80 K as functions of gate voltage V{sub g}. At sufficiently high V{sub g}, G{sub para} at 80 K is several times as high as G{sub perp}, which manifests the anisotropic two-dimensional transport of electrons. When V{sub g} is reduced to -0.7 V, G{sub perp} almost vanishes, while {sub Gpara} stays sizable unless V{sub g} is set below -0.8 V. These results indicate that 'inter-chain' barriers play stronger roles than 'intra-chain' barriers.
Akiyama, Y.; Kawazu, T. [National Institute for Materials Science, Tsukuba-shi, Ibaraki 305-0047 (Japan); IIS, University of Tokyo, Meguro-ku, Tokyo 153-8505 (Japan); Noda, T. [National Institute for Materials Science, Tsukuba-shi, Ibaraki 305-0047 (Japan); Sakaki, H. [National Institute for Materials Science, Tsukuba-shi, Ibaraki 305-0047 (Japan); IIS, University of Tokyo, Meguro-ku, Tokyo 153-8505 (Japan); Toyota Technological Institute, Tempaku-ku, Nagoya 468-8511 (Japan)
Anisotropic etching of silicon
Anisotropic etching of silicon has become an important technology in silicon semiconductor processing during the past ten years. It will continue to gain stature and acceptance as standard processing technology in the next few years. Anisotropic etching of
K. E. Bean
Evaluation of Baltic Sea transport properties using particle tracking
NASA Astrophysics Data System (ADS)
Particle tracking model (PTM) is an effective tool for quantifying transport properties of large water bodies such as the Baltic Sea. We have applied PTM to our fully calibrated and validated Baltic Sea 3D hydrodynamic model for a 10-years period (2000-9). One hundred particles were released at a constant rate during an initial 10-days period from all the Baltic Sea sub-basins, the major rivers, and the open boundary in the Arkona Basin. In each basin, the particles were released at two different depths corresponding to the deep water and middle water layers. The objectives of the PTM simulations were to analyse the intra-exchange processes between the Baltic Sea basins and to estimate the arrival times and the paths of particles released from the rivers. The novel contribution of this study is determining the paths and arrival times of deeper water masses rather than the surface masses. Advective and diffusive transport processes in the Bornholm and Arkona basins are both driven by the interacting flows of the northern basins of the Baltic Sea and the North Sea. Particles released from Arkona basin flows northwards along the Stople Channel. The Gotland basins are the major contributors to the exchange process in the Baltic Sea. We find high values of the advection ratio, indicative of a forced advective transport process. The Bay of Gdansk is probably the most vulnerable region in the Baltic Sea. This is despite the fact that the main exchanging basins are the Bornholm Sea and the Easter Gotland Basin. The main reason is the intensive supply of the particles from the northern basins that normally take about 3000 days to reach the Bay of Gdansk. The process maintains a high level of particle concentration (90%) along its coastlines even after the 10-years period. Comparing the particle paths in the Western and Eastern Gotland basins two interesting features were found. Particles travelled in all four directions in the former basin and the middle layer particles reached the surface flow in the eastern most part of the Gulf of Finland. This implies mixing of deeper waters of the Western Gotland Basin with the sub-surface waters of the Gulf of Finland. We believe strong density current and upwelling processes drive the process. Surprisingly, the two rivers Narva and Venta have the highest spreading in comparison to other rivers. This is despite the relatively low flow discharge values that rules out a correlation between high moment flows and the extent of spreading. We found the flow discharge to be correlated with the advection lengths. The lack of any correlation for the other rivers, signifies different hydrodynamic characteristics among the basins. The results of our PTM study may be used for a general environmental assessment in terms of sensitivity of the various coastlines and rick to the release of contaminants in the Baltic Sea.
Dargahi, Bijan; Cvetkovic, Vladimir
Decoupling Mechanical and Ion Transport Properties in Polymer Electrolyte Membranes
NASA Astrophysics Data System (ADS)
Polymer electrolytes are mixtures of a polar polymer and salt, in which the polymer replaces small molecule solvents and provides a dielectric medium so that ions can dissociate and migrate under the influence of an external electric field. Beginning in the 1970s, research in polymer electrolytes has been primarily motivated by their promise to advance electrochemical energy storage and conversion devices, such as lithium ion batteries, flexible organic solar cells, and anhydrous fuel cells. In particular, polymer electrolyte membranes (PEMs) can improve both safety and energy density by eliminating small molecule, volatile solvents and enabling an all-solid-state design of electrochemical cells. The outstanding challenge in the field of polymer electrolytes is to maximize ionic conductivity while simultaneously addressing orthogonal mechanical properties, such as modulus, fracture toughness, or high temperature creep resistance. The crux of the challenge is that flexible, polar polymers best-suited for polymer electrolytes (e.g., poly(ethylene oxide)) offer little in the way of mechanical robustness. Similarly, polymers typically associated with superior mechanical performance (e.g., poly(methyl methacrylate)) slow ion transport due to their glassy polymer matrix. The design strategy is therefore to employ structured electrolytes that exhibit distinct conducting and mechanically robust phases on length scales of tens of nanometers. This thesis reports a remarkably simple, yet versatile synthetic strategy---termed polymerization-induced phase separation, or PIPS---to prepare PEMs exhibiting an unprecedented combination of both high conductivity and high modulus. This performance is enabled by co-continuous, isotropic networks of poly(ethylene oxide)/ionic liquid and highly crosslinked polystyrene. A suite of in situ, time-resolved experiments were performed to investigate the mechanism by which this network morphology forms, and it appears to be tied to the disordered structure observed in diblock polymer melts near the order-disorder transition. In the resulting solid PEMs, the conductivity and modulus are both high, exceeding the 1 mS/cm and approaching the 1 GPa metrics, respectively, often cited for lithium-metal batteries. In the final chapter, an alternative synthetic route to generate nanostructured PEMs is presented. This strategy relies on the formation of a thermodynamically stable network morphology exhibited by a triblock terpolymer prepared with crosslinking moieties along the backbone. Although the mechanical properties of the resulting PEM are excellent, the conductivity is found to be somewhat limited by network defects that result from the solvent-casting procedure.
McIntosh, Lucas D.
EquilTheTA: Thermodynamic and transport properties of complex equilibrium plasmas
EquilTheTA (EQUILibrium for plasma THErmodynamics and Transport Applications) is a web-based software which calculates chemical equilibrium product concentrations from any set of reactants and determines thermodynamic and transport properties for the product mixture in wide temperature and pressure ranges. The program calculates chemical equilibrium by using a hierarchical approach, thermodynamic properties and transport coefficients starting from recent and accurate databases of atomic and molecular energy levels and collision integrals. In the calculations, Debye length and cut-off are consistently updated and virial corrections (up to third order) can be considered. Transport coefficients are calculated by using high order approximations of the Chapman-Enskog method.
Colonna, G.; D'Angola, A. [CNR-IMIP Bari, via Amendola 122/D - 70126 Bari (Italy); DIFA, Universita della Basilicata, via dell'Ateneo Lucano, 1085100 Potenza (Italy)
Effects of interlayer coupling on the magnetic and transport properties of superconducting multilayers and high-temperature superconductors
The effect of interlayer coupling on the transport properties and dissipation in a magnetic field is reviewed for superconducting multilayers including highly-anisotropic high-temperature superconductors (HTS). For the applied field parallel to the superconducting layers the absence of any Lorentz-force dependence of the dissipation leads to an explanation other than flux motion. This is consistent with a Josephson junction dissipation which dominates flux motion of the insulating regions between layers. However, in is seen to cross over from phase slips at Josephson junctions to depinning of vortices from the external field at high fields and temperatures. For fields perpendicular to the superconducting layers the much greater resistive broadening in HTS is due to dissipation by thermally-activated flux motion, consistent with a lack of intrinsic pinning. We show experimental evidence that the associated flux motion occurs as a result of a crossover from three dimensional (3D) vortex lines to 2D independent pancake-like vortices, residing in the Cu-O layers. This 3D to 2D crossover occurs after k{sub B}T exceeds the Josephson coupling energy.
Gray, K.E.; Hettinger, J.D.; Kim, D.H.
Procedures for construction of anisotropic elastic plastic property closures for face-centered cubic polycrystals using first-order bounding relations
NASA Astrophysics Data System (ADS)
Microstructure-sensitive design (MSD) is a novel mathematical framework that facilitates a rigorous consideration of the material microstructure as a continuous design variable in the engineering design enterprise [Adams, B.L., Henrie, A., Henrie, B., Lyon, M., Kalidindi, S.R., Garmestani, H., 2001. Microstructure-sensitive design of a compliant beam. J. Mech. Phys. Solids 49(8), 1639-1663; Adams, B.L., Lyon, M., Henrie, B., 2004. Microstructures by design: linear problems in elastic-plastic design. Int. J. Plasticity 20(8-9), 1577-1602; Kalidindi, S.R., Houskamp, J.R., Lyons, M., Adams, B.L., 2004. Microstructure sensitive design of an orthotropic plate subjected to tensile load. Int. J. Plasticity 20(8-9), 1561-1575]. MSD employs spectral representations of the local state distribution functions in describing the microstructure quantitatively, and these in turn enable development of invertible linkages between microstructure and effective properties using established homogenization (composite) theories. As a natural extension of the recent publications in MSD, we provide in this paper a detailed account of the methods that can be readily used by mechanical designers to construct first-order elastic-plastic property closures. The main focus in this paper is on the crystallographic texture (also called Orientation Distribution Function or ODF) as the main microstructural parameter controlling the elastic and yield properties of cubic (fcc and bcc) polycrystalline metals. The following specific advances are described in this paper: (i) derivation of rigorous first-order bounds for the off-diagonal terms of the effective elastic stiffness tensor and their incorporation in the MSD framework, (ii) delineation of the union of the property closures corresponding to both the upper and lower bound theories resulting in comprehensive first-order closures, (iii) development of generalized and readily usable expressions for effective anisotropic elastic-plastic properties that could be applied to all cubic polycrystals, and (iv) identification of the locations of readily available or easily processable ODFs (e.g. textures that are produced by rolling, drawing, etc.) on the property closures. It is anticipated that the advances communicated in this paper will make the mathematical framework of MSD highly accessible to the mechanical designers.
Proust, Gwķnaļlle; Kalidindi, Surya R.
Equations of state and transport properties of mixtures in the warm dense regime
NASA Astrophysics Data System (ADS)
We have performed average-atom molecular dynamics to simulate the CH and LiH mixtures in the warm dense regime, and obtained equations of state and the ionic transport properties. The electronic structures are calculated by using the modified average-atom model, which have included the broadening of energy levels, and the ion-ion pair potentials of mixtures are constructed based on the temperature-dependent density functional theory. The ionic transport properties, such as ionic diffusion and shear viscosity, are obtained through the ionic velocity correlation functions. The equations of state and transport properties for carbon, hydrogen and lithium, hydrogen mixtures in a wide region of density and temperature are calculated. Through our computing the average ionization degree, average ion-sphere diameter and transition properties in the mixture, it is shown that transport properties depend not only on the ionic mass but also on the average ionization degree.
Hou, Yong; Dai, Jiayu; Kang, Dongdong; Ma, Wen; Yuan, Jianmin
Effect of Patch Mechanical Properties on Right Ventricle Function Using MRI-Based Two-Layer Anisotropic Models of Human Right and Left Ventricles
Right and left ventricle (RV/LV) combination models with three different patch materials (Dacron scaffold, treated pericardium, and contracting myocardium), two-layer construction, fiber orientation, and active anisotropic material properties were introduced to evaluate the effects of patch materials on RV function. A material-stiffening approach was used to model active heart contraction. Cardiac magnetic resonance (CMR) imaging was performed to acquire patient-specific ventricular geometries and cardiac motion from a patient with severe RV dilatation due to pulmonary regurgitation needing RV remodeling and pulmonary valve replacement operation. Computational models were constructed and solved to obtain RV stroke volume, ejection fraction, patch area variations, and stress/strain data for patch comparisons. Our results indicate that the patch model with contracting myocardium leads to decreased stress level in the patch area, improved RV function and patch area contractility. Maximum Stress-P1 (maximum principal stress) value at the center of the patch from the Dacron scaffold patch model was 350% higher than that from the other two models. Patch area reduction ratio was 0.3%, 3.1% and 27.4% for Dacron scaffold, pericardium, and contracting myocardium patches, respectively. These findings suggest that the contracting myocardium patch model may lead to improved recovery of RV function in patients with severe chronic pulmonary regurgitation. PMID:21209792
Yang, Chun; Geva, Tal; Gaudette, Glenn; del Nido, Pedro J.
Nanosize storage properties in spinel Li4Ti5O12 explained by anisotropic surface lithium insertion.
Nanosizing is a frequently applied strategy in recent years to improve storage properties of Li-ion electrodes and facilitate novel storage mechanisms. Due to particle size reduction, surface effects increasingly dominate, which can drastically change the storage properties. Using density functional theory calculations we investigate the impact of the surface environment on the Li-ion insertion properties in defective spinel Li(4+x)Ti(5)O(12), a highly promising negative electrode material. The calculations reveal that the storage properties strongly depend on the surface orientation. The lowest energy (1 1 0) surface is predicted to be energetically favorable for Li-ion insertion into the vacant 16c sites. The (1 1 1) surface allows capacities that significantly exceed the bulk capacity Li(7)Ti(5)O(12) at voltages greater than 0 V by occupation of 8a sites in addition to the fully occupied 16c sites. One of the key findings is that the surface environment extends nanometers into the storage material, leading to a distribution of voltages responsible for the curved voltage profile commonly observed in nanosized insertion electrode materials. Both the calculated surface-specific voltage profiles and the calculated particle size dependent voltage profiles are in good agreement with the experimental voltage profiles reported in literature. These results give a unique insight into the impact of nanostructuring and further possibilities of tailoring the Li-ion voltage profiles and capacities in lithium insertion materials. PMID:22953788
Ganapathy, Swapna; Wagemaker, Marnix
An Immersed Boundary Method for Computing Anisotropic Permeability of
Media source: http://gubbins.ncsu.edu/research.html Amorphous nano-porous material (e.g. porous glassAn Immersed Boundary Method for Computing Anisotropic Permeability of Structured Porous Media David for Computing Anisotropic Permeability of Structured Porous Media #12;Outline 1 Averaged transport in porous
Al Hanbali, Ahmad
Theoretical study of conductance, capacitance and transport properties of nanostructures
NASA Astrophysics Data System (ADS)
In the past two decades, significant progress in constructing physical systems of reduced dimensionality has been made. In these systems, quantum effects are observed in the electric current response to an applied bias voltage. Considerable theoretical effort has been made to understand conductance and capacitance which characterize this response. In addition to a fundamental science interest, there has been a significant technological need to build and understand small scale devices in order to maintain the current rate of progress in increasing computer performance. In this thesis, we theoretically investigated the conductance and capacitance of mesoscopic and molecular scale systems. Our approach incorporated Landauer-Buttiker transport theory. We developed a highly efficient method, based on the solution of the time-dependent Schrodinger equation incorporating a magnetic field, to solve the quantum scattering problem in mesoscopic nanostructures. We studied linear response capacitance in a two plate mesoscopic capacitor with one plate a quantum conductor in the ballistic scattering regime. By determining the scattering wavefunctions in the quantum plate, we were able to obtain relevant densities of states and use them to self-consistently calculate capacitance matrix coefficients for the system. We find the capacitance to be highly dependent on the external magnetic field and the number of probes attached to the quantum conductor. To study molecular scale systems, our approach was based on Density Functional Theory within Local Density Approximation and non-equilibrium Green's functions, implemented in the simulation package McDcal. For the work in this thesis, we modified McDcal to run on parallel computer architectures. We studied the current-voltage characteristics of silicon cage nanowires sandwiched between aluminum electrodes. We successfully analyzed our results using the complex band structure of the nanowire. Finally, we studied the capacitance properties of carbon nanotube junctions. In junctions with tubes so far apart that their wavefunctions do not overlap, we studied the variation in capacitance for different relative tube positions and radii. We also studied junctions where the nanotubes are in contact but in which there is no current due to a conductance gap. In this system we find an enhancement in the value of capacitance.
Pomorski, Pawel
Transport properties of high-temperature air in a magnetic field
Transport properties of equilibrium air plasmas in a magnetic field are calculated with the Chapman-Enskog method. The range considered for the temperature is [50-50 000] K and for the magnetic induction is [0-300] T.
Bruno, D. [Institute of Inorganic Methodologies and Plasmas, CNR, 70126 Bari (Italy); Capitelli, M.; Catalfamo, C. [Department of Chemistry, University of Bari, 70126 Bari (Italy); Giordano, D. [Aerothermodynamics Section, ESA-ESTEC, 2200 AG Noordwijk (Netherlands)
Effective transport properties of random composites: Continuum calculations versus mapping to a network
The effective transport properties and percolation of continuum composites have commonly been studied using discrete models, i.e., by mapping the continuum to a lattice or network. In this study we instead directly solve ...
Chen, Ying
Electron Irradiation Induced Changes of the Electrical Transport Properties of Graphene
This research investigates the effect of electron irradiation on transport properties in graphene Field Effect Transistor (FET) devices. Upon irradiation, graphene is doped with electrons and adsorbs molecules by transfer of accumulated electrons...
Woo, Sung Oh
Tables of thermodynamic and transport properties of UO/sub 2/
The thermodynamic and transport properties of solid and liquid UO/sub 2/ are tabulated as a function of temperature. Properties are given for the temperature range 298.15 K to 3120 K for solid UO/sub 2/ and from 3120 to 6000 K for liquid UO/sub 2/. Thermodynamic properties tabulated include enthalpy, heat capacity, pressure, density, instantaneous thermal expansion coefficient, compressibility, thermal pressure coefficient, and speed of sound. Tabulated transport properties include thermal conductivity, thermal diffusivity, emissivity, electrical conductivity, and viscosity. Tables are given in SI units and cgs units.
Fink, J.K.
Optical characterization of complex mechanical and thermal transport properties
Time-resolved impulsive stimulated light scattering (ISS), also known as transient grating spectroscopy, was used to investigate phonon mediated thermal transport in semiconductors and mechanical degrees of freedom linked ...
Johnson, Jeremy A. (Jeremy Andrew)
Transport properties of antimony nanowires J. Heremans and C. M. Thrush
Transport properties of antimony nanowires J. Heremans and C. M. Thrush Delphi Research Labs of the resistivity and the longitudinal and transverse mag- netoresistance of antimony quantum wires with diameters to nanowire arrays of another group-V semimetal: antimony Sb . As in Bi, electronic transport phenomena in Sb
Cronin, Steve
PHYSICAL REVIEW B 86, 075433 (2012) Effect of gadolinium adatoms on the transport properties of graphene
PHYSICAL REVIEW B 86, 075433 (2012) Effect of gadolinium adatoms on the transport properties of graphene doped with gadolinium (Gd) adatoms have been measured. The gate voltage dependence on graphene electrical transport of dilute quantities of gadolinium (Gd). Gd (4f 7 5d1 6s2 ) is a rare
Hellman, Frances
Using a Flume to Demonstrate Fluid Properties and Sediment Transport
NSDL National Science Digital Library
A 20-foot long recirculating flume is used for a series of demonstrations designed to help students explore the principles of fluid dynamics and sediment transport. The design and construction of the flume and four demonstrations are described in the attached activity. The demonstrations build upon each other so that students have a chance to develop an understanding of sedimentary transport processes and the deposits they produce.
Jill Singer
Superconducting transport properties of grain boundaries in YBa2Cu3O7 bicrystals
Previous work on the superconducting transport properties of individual grain boundaries in thin-film bicrystals of YBa2Cu3O7 has been extended to provide a more comprehensive picture of their weak-link characteristics. Grain boundaries with three different geometries have been studied; the transport properties of all three types of boundaries are essentially identical, which implies that the poor superconducting coupling between grains is
D. Dimos; P. Chaudhari; J. Mannhart
Structural, electrical and anisotropic properties of Tl{sub 4}Se{sub 3}S chain crystals
The structure, the anisotropy effect on the current transport mechanism and the space charge limited current in Tl{sub 4}Se{sub 3}S chain crystals have been studied by means of X-ray diffraction, electrical conductivity measurements along and perpendicular to the crystal's c-axis and the current voltage characteristics. The temperature-dependent electrical conductivity analysis in the region of 150-400 K, revealed the domination of the thermionic emission of charge carriers over the chain boundaries above 210 and 270 K along and perpendicular to the c-axis, respectively. Below these temperatures, the variable range hopping is dominant. At a consistent temperature range, the thermionic emission analysis results in conductivity activation energies of 280 and 182 meV, along and perpendicular to the c-axis, respectively. Likewise, the hopping parameters are altered significantly by the conductivity anisotropy. The current-voltage characteristics revealed the existence of hole trapping state being located at 350 meV above the valence band of the crystal.
Qasrawi, A.F., E-mail: firstname.lastname@example.com [Group of Physics, Faculty of Engineering, Atilim University, 06836 Ankara (Turkey); Department of Physics, Arab-American University, Jenin, West Bank, Palestine (Country Unknown); Gasanly, N.M. [Department of Physics, Middle East Technical University, 06531 Ankara (Turkey)
Anisotropic colloidal crystal particles from microfluidics.
Anisotropic colloidal crystal particles (CCPs) have showed their great potential in biotechnology and structural materials due to their anisotropic shapes and tunable optical property. However, their controllable generation is still a challenge. Here, a novel microfluidic approach is developed to generate anisotropic CCPs. The microfluidic device is composed of an injection capillary and a collection capillary with available size and shape. Based on the device, the anisotropic particles with non-close-packed colloidal crystal structures are achieved by photo-polymerizing droplet templates in a confined collection capillary with different shapes and sizes. Moreover, anisotropic close-packed CCPs can be made from non-close-packed CCPs through a thermal process. It is demonstrated that the anisotropic CCPs in different sizes, structural colors and shapes (rods, cuboids and disks) can be generated. These distinguishable features of resultant particles make them ideal barcodes for high-throughput bioassays. In order to prove it, DNA multiplex detection is carried out. The experimental results indicate that achieved particles have a great encoding capacity and are highly practical for multiplex coding bioassays. Therefore, we believe that the anisotropic CCPs would be highly promising barcodes in biomedical applications, including high-throughput bioassays and cell culture research where multiplexing is needed. PMID:24594033
Cheng, Yao; Zhu, Cun; Xie, Zhuoying; Gu, Hongcheng; Tian, Tian; Zhao, Yuanjin; Gu, Zhongze
Anisotropic magnetization and transport properties of RAgSb2 (R = Y, La-Nd, Sm, Gd-Tm)
. Resistivity measurements as a function of temperature are typical of other rare earth intermetallic compounds magnetoresistance is abnormally large compared to other intermetallic compounds and possesses significant deviation the foundation of the physics studied in rare earth intermetallic compounds, including magnetization and magnetic
Canfield, Paul C.
Transport, magnetic, thermodynamic, and optical properties in Ti-doped Sr2RuO4
NASA Astrophysics Data System (ADS)
We report on electrical resistivity, magnetic susceptibility, and magnetization on heat-capacity and optical experiments in single crystals of Sr2Ru1-xTixO4. Samples with x=0.1 and 0.2 reveal purely semiconducting resistivity behavior along c and the charge transport is close to localization within the ab plane. A strong anisotropy in the magnetic susceptibility appears at temperatures below 100 K. Moreover magnetic ordering in the c direction with a moment of order 0.01 ?B/f.u. occurs at low temperatures. On doping the low-temperature linear term of the heat capacity becomes significantly reduced and probably is dominated by spin fluctuations. Finally, the optical conductivity reveals the anisotropic character of the dc resistance, with the in-plane conductance roughly following a Drude-type behavior and an insulating response along c.
Pucher, K.; Hemberger, J.; Mayr, F.; Fritsch, V.; Loidl, A.; Scheidt, E.-W.; Klimm, S.; Horny, R.; Horn, S.; Ebbinghaus, S. G.; Reller, A.; Cava, R. J.
The effect of electron induced hydrogenation of graphene on its electrical transport properties
We report a deterioration of the electrical transport properties of a graphene field effect transistor due to energetic electron irradiation on a stack of Poly Methyl Methacrylate (PMMA) on graphene (PMMA/graphene bilayer). Prior to electron irradiation, we observed that the PMMA layer on graphene does not deteriorate the carrier transport of graphene but improves its electrical properties instead. As a result of the electron irradiation on the PMMA/graphene bilayer, the Raman ōDö band appears after removal of PMMA. We argue that the degradation of the transport behavior originates from the binding of hydrogen generated during the PMMA backbone secession process.
Woo, Sung Oh [Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States)] [Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States); Teizer, Winfried [Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States) [Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States); WPI-Advanced Institute for Materials Research, Tohoku University, Sendai (Japan)
Characterizing the electron transport properties of a single <110> InAs nanowire
NASA Astrophysics Data System (ADS)
InAs nanowire with <110> orientation is proposed for use as an electron spin transport channel for application to spintronics devices, particularly the Datta-Das spin transistor. Stable zinc blende crystal NWs were grown using a molecular beam epitaxy system. Subsequently, global back-gate NW field effect transistors were fabricated, and the superiority of the electrical transport properties within our resultant <110> NWs was demonstrated by comparing the field-effect mobility with a <111> NW control sample. Additionally, single NW Hall-bar devices were fabricated, which allowed us to obtain the transport properties accurately, and Hall effect measurements were successfully taken at different temperatures.
Cui, Zhixin; Perumal, Rajagembu; Ishikura, Tomotsugu; Konishi, Keita; Yoh, Kanji; Motohisa, Junichi
Functional properties of ion channels and transporters in tumour vascularization
Vascularization is crucial for solid tumour growth and invasion, providing metabolic support and sustaining metastatic dissemination. It is now accepted that ion channels and transporters play a significant role in driving the cancer growth at all stages. They may represent novel therapeutic, diagnostic and prognostic targets for anti-cancer therapies. On the other hand, although the expression and role of ion channels and transporters in the vascular endothelium is well recognized and subject of recent reviews, only recently has their involvement in tumour vascularization been recognized. Here, we review the current literature on ion channels and transporters directly involved in the angiogenic process. Particular interest will be focused on tumour angiogenesis in vivo as well as in the different steps that drive this process in vitro, such as endothelial cell proliferation, migration, adhesion and tubulogenesis. Moreover, we compare the ætransportomeÆ system of tumour vascular network with the physiological one. PMID:24493751
Fiorio Pla, Alessandra; Munaron, Luca
Temperature dependence of electronic transport property in ferroelectric polymer films
NASA Astrophysics Data System (ADS)
The leakage current mechanism of ferroelectric copolymer of polyvinylidene fluoride with trifluoroethylene prepared by Langmuir-Blodgett was investigated in the temperature range from 100 K to 350 K. The electron as the dominant injected carrier was observed in the ferroelectric copolymer films. The transport mechanisms in copolymer strongly depend on the temperature and applied voltage. From 100 K to 200 K, Schottky emission dominates the conduction. With temperature increasing, the Frenkel-Poole emission instead of the Schottky emission to conduct the carrier transport. When the temperature gets to 260 K, the leakage current becomes independent of temperature, and the space charge limited current conduction was observed.
Zhao, X. L.; Wang, J. L.; Tian, B. B.; Liu, B. L.; Zou, Y. H.; Wang, X. D.; Sun, S.; Sun, J. L.; Meng, X. J.; Chu, J. H.
[Study of transport properties of the polymeric membranous dressing with silver ions].
The transport properties of polymeric membraneous dresing silver ion containing Textus Bioactive were studied. This dressing is made of three types of theromoplastic polymeric fibers, formed into two-layers membrane. In first layer occure the polymeric fiber, which the core is hydrophobic and hydrophilic surfaces contain a silver zeolite. These fibers neighborours with hydrophilic super absorbing polymers. Third type of polymeric fibers occur in the second layer of membrane and is arranged parallel to surface's skin, creating a net preventing stick of membraneous dressing to treated wound. Using of the Kedem-Katchalsky equations the transport model of this membrane and the temporal and concentration characteristics of transport parameters (hydraulic permeability, refection and solute permeability) were determined. Experimental results show that the polymeric membranous dressing contain the silver ions posses non-linear transport properties, which are consequence of structure and physicochemical properties of polymeric membranes. PMID:16619792
Slezak, Andrzej; Kucharzewski, Marek; Grzegorczyn, S?awomir; Slezak, Izabella H
Controlling anisotropic nanoparticle growth through plasmon excitation
Inorganic nanoparticles exhibit size-dependent properties that are of interest for applications ranging from biosensing and catalysis to optics and data storage. They are readily available in a wide variety of discrete compositions and sizes. Shape-selective synthesis strategies now also yield shapes other than nanospheres, such as anisotropic metal nanostructures with interesting optical properties. Here we demonstrate that the previously described
Rongchao Jin; Y. Charles Cao; Encai Hao; Gabriella S. Mķtraux; George C. Schatz; Chad A. Mirkin
Prediction of transport properties of dense molecular fluids using the effective diameter hard sphere theory
The present paper explores the ability of the effective diameter hard sphere theory to estimate the transport properties of a fluid made up of particles interacting through the Gaussian overlap model. This method relies on the assumption that at high densities the behaviour of a fluid is dominated by harsh repulsive forces. Hence, the properties of the fluid can be
R. Castillo; J. Orozco
Thermoelectric Transport Properties of Single Bismuth Nanowires S. B. Cronin1
Thermoelectric Transport Properties of Single Bismuth Nanowires S. B. Cronin1 , Y.-M. Lin3 , M be made n and p type, thus eliminating this cancellation. Bismuth, as a one- carrier type material, has is based on the unique properties of bulk bismuth. Bi has the smallest effective mass of all known
Cronin, Steve
Flow and transport in unsaturated fractured rock: effects of multiscale heterogeneity of hydrogeologic properties
The heterogeneity of hydrogeologic properties at different scales may have different effects on flow and transport processes in a subsurface system. A model for the unsaturated zone of Yucca Mountain, Nevada, is developed to represent complex heterogeneity at two different scales: (1) layer scale corresponding to geologic layering and (2) local scale. The layer-scale hydrogeologic properties are obtained using inverse
Quanlin Zhou; Hui-Hai Liu; Gudmundur S Bodvarsson; Curtis M Oldenburg
ELECTRONIC AND TRANSPORT PROPERTIES OF THERMOELECTRIC Ru2Si3
NASA Astrophysics Data System (ADS)
We report calculations of the doping and temperature dependent thermopower of Ru2Si3 based on Boltzmann transport theory and the first principles electronic structure. We find that the performance reported to date can be significantly improved by optimization of the doping level and that ultimately n-type should have higher ZT than p-type.
Singh, David J.; Parker, David
Fluid transport properties by equilibrium molecular dynamics. II. Multicomponent systems
^timent 490, Universite┤ Paris-Sud, 91405 Orsay Cedex, France M. Durandeau Total Exploration Production, CSTF modeling, planning of transport and in design of industrial plants. For mixtures of constituents have followed diverse trends: a The development of new computational techniques like the synthetic3
Dysthe, Dag Kristian
Estimation of Effective Transport Properties in Packed Bed Reactors
Packed bed reactors are commonly used for carrying out heterogeneous chemical reactions, and the attendant complexities arising out of the interactions of the momentum, heat, and mass transport processes make the design of such units a very involved and cumbersome task. The strategy for rational design depends strongly on the nature of the reaction scheme and its sensitivity to perturbations
B. D. Kulkarni; L. K. Doraiswamy
The mitochondrial transporter family SLC25: identification, properties and physiopathology.
SLC25 is a large family of nuclear-encoded transporters embedded in the inner mitochondrial membrane and in a few cases other organelle membranes. The members of this superfamily are widespread in eukaryotes and involved in numerous metabolic pathways and cell functions. They can be easily recognized by their striking sequence features, i.e., a tripartite structure, six transmembrane ?-helices and a 3-fold repeated signature motifs. SLC25 members vary greatly in the nature and size of their transported substrates, modes of transport (i.e., uniport, symport or antiport) and driving forces, although the molecular mechanism of substrate translocation may be basically the same. Based on substrate specificity, 24 subfamilies, well conserved throughout evolution, have been functionally characterized mainly by transport assays upon heterologous gene expression, purification and reconstitution into liposomes. Several other SLC25 family members remain to be characterized. In recent years mutations in the SLC25 genes have been shown to be responsible for 11 diseases, highlighting the important role of SLC25 in metabolism. PMID:23266187
Palmieri, Ferdinando
Transport Properties of the Tomato Fruit Tonoplast 1
Calcium transport into tomato (Lycopersicon esculentum Mill, cv Castlemart) fruit tonoplast vesicles was studied. Calcium uptake was stimulated approximately 10-fold by MgATP. Two ATP-dependent Ca2+ transport activities could be resolved on the basis of sensitivity to nitrate and affinity for Ca2+. A low affinity Ca2+ uptake system (Km > 200 micromolar) was inhibited by nitrate and ionophores and is thought to represent a tonoplast localized H+/Ca2+ antiport. A high affinity Ca2+ uptake system (Km = 6 micromolar) was not inhibited by nitrate, had reduced sensitivity to ionophores, and appeared to be associated with a population of low density endoplasmic reticulum vesicles that contaminated the tonoplast-enriched membrane fraction. Arrhenius plots of the temperature dependence of Ca2+ transport in tomato membrane vesicles showed a sharp increase in activation energy at temperatures below 10 to 12░C that was not observed in red beet membrane vesicles. This low temperature effect on tonoplast Ca2+/H+ antiport activity could only by partially ascribed to an effect of low temperature on H+-ATPase activity, ATP-dependent H+ transport, passive H+ fluxes, or passive Ca2+ fluxes. These results suggest that low temperature directly affects Ca2+/H+ exchange across the tomato fruit tonoplast, resulting in an apparent change in activation energy for the transport reaction. This could result from a direct effect of temperature on the Ca2+/H+ exchange protein or by an indirect effect of temperature on lipid interactions with the Ca2+/H+ exchange protein. PMID:16666428
Joyce, Daryl C.; Cramer, Grant R.; Reid, Michael S.; Bennett, Alan B.
In-plane anisotropic effect of magnetoelectric coupled PMN-PT/FePt multiferroic heterostructure: Static and microwave properties
NASA Astrophysics Data System (ADS)
The effects of the electric and magnetic field variation on multiferroic heterostructure were studied in this work. Thin films of polycrystalline Fe50Pt50 (FePt) were grown by dc-sputtering on top of the commercial slabs of lead magnesium niobate-lead titanate (PMN-PT). The sample was a (011)-cut single crystal and had one side polished. In this condition, the PMN-PT/FePt operates in the L-T (longitudinal magnetized-transverse polarized) mode. A FePt thin film of 20 nm was used in this study to avoid the characteristic broad microwave absorption line associated with these films above thicknesses of 40 nm. For the in-plane easy magnetization axis (01-1), a microwave magnetoelectric (ME) coupling of 28 Oe cm kV -1 was estimated, whereas a value of 42 Oe cm kV -1 was obtained through the hard magnetization axis (100). Insight into the effects of the in-plane strain anisotropy on the ME coupling is obtained from the dc-magnetization loops. It was observed that the trend was opposite along the easy and hard magnetic directions. In particular, along the easy-magnetic axis (01-1), a square and narrow loop with a factor of Mr/MS of 0.96 was measured at 10 kV/cm. Along the hard-magnetic axis, a factor of 0.16 at 10 kV/cm was obtained. Using electric tuning via microwave absorption at X-band (9.78 GHz), we observe completely different trends along the easy and hard magnetic directions; Multiple absorption lines along the latter axis compared to a single and narrower absorption line along the former. In spite of its intrinsic complexity, we propose a model which gives good agreement both for static and microwave properties. These observations are of fundamental interest for future ME microwave components, such as filters, phase-shifters, and resonators.
Vargas, Jose M.; G¾mez, Javier
Anisotropic nanomaterials: structure, growth, assembly, and functions
Comprehensive knowledge over the shape of nanomaterials is a critical factor in designing devices with desired functions. Due to this reason, systematic efforts have been made to synthesize materials of diverse shape in the nanoscale regime. Anisotropic nanomaterials are a class of materials in which their properties are direction-dependent and more than one structural parameter is needed to describe them. Their unique and fine-tuned physical and chemical properties make them ideal candidates for devising new applications. In addition, the assembly of ordered one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) arrays of anisotropic nanoparticles brings novel properties into the resulting system, which would be entirely different from the properties of individual nanoparticles. This review presents an overview of current research in the area of anisotropic nanomaterials in general and noble metal nanoparticles in particular. We begin with an introduction to the advancements in this area followed by general aspects of the growth of anisotropic nanoparticles. Then we describe several important synthetic protocols for making anisotropic nanomaterials, followed by a summary of their assemblies, and conclude with major applications. PMID:22110867
Sajanlal, Panikkanvalappil R.; Sreeprasad, Theruvakkattil S.; Samal, Akshaya K.; Pradeep, Thalappil
FORTRAN 4 computer program for calculation of thermodynamic and transport properties of complex chemical systems
NASA Technical Reports Server (NTRS)
A FORTRAN IV computer program for the calculation of the thermodynamic and transport properties of complex mixtures is described. The program has the capability of performing calculations such as:(1) chemical equilibrium for assigned thermodynamic states, (2) theoretical rocket performance for both equilibrium and frozen compositions during expansion, (3) incident and reflected shock properties, and (4) Chapman-Jouguet detonation properties. Condensed species, as well as gaseous species, are considered in the thermodynamic calculation; but only the gaseous species are considered in the transport calculations.
Svehla, R. A.; Mcbride, B. J.
Transverse photothermal beam deflection technique for determining the transport properties of semiconductor thin films
NASA Astrophysics Data System (ADS)
Nonradiative transitions occurring in semiconductors result in thermal emissions carrying information on the material's thermal and electronic properties. A simple one-dimensional theoretical model is devised which accounts for the photothermal signal variations due to nonradiative transitions occurring in semiconductor thinfilms. The theory was verified by determining the transport properties of p-type silicon wafer. We could get the thermal diffusivity, minority carrier lifetime, surface recombination velocity, and minority carrier mobility of CuInS2 thin films, thereby proving the efficiency and simplicity of photothermal beam deflection technique for real time characterization of semiconductor thin films. The film fabrication history, composition, and post deposition treatments play crucial role in determining the transport properties and the effect of these conditions on transport properties of the film as well as on the solar cell parameters is discussed.
Warrier, Anita R.; Sebastian, Tina; Sudha Kartha, C.; Vijayakumar, K. P.
Designing chromonic mesogens for the fabrication of anisotropic optical materials
NASA Astrophysics Data System (ADS)
Perylene monoimides and diimides have applications as luminescent materials and in organic photovoltaic devices as chromophores and conducting materials. Materials in which these compounds are oriented in a preferred direction will possess useful anisotropic properties that are not attainable from materials in which the compounds are randomly oriented. Anisotropic materials of these compounds can be prepared by taking advantage of the unique properties of chromonic liquid crystals. In this paper we describe the principles for designing perylene monoimides and diimides with desired optical properties and chromonic liquid-crystalline properties. In addition, we demonstrate the fabrication of anisotropic optical materials via organization of these compounds into a lyotropic chromonic liquidcrystalline phase.
Tam-Chang, Suk-Wah; Huang, Liming; Gyan, Aryal; Seo, Wonewoo; Mahinay, Delfin; Iverson, Isaac K.
Anomalous solute transport in saturated porous media: Relating transport model parameters to electrical and nuclear magnetic resonance properties
NASA Astrophysics Data System (ADS)
The advection-dispersion equation (ADE) fails to describe commonly observed non-Fickian solute transport in saturated porous media, necessitating the use of other models such as the dual-domain mass-transfer (DDMT) model. DDMT model parameters are commonly calibrated via curve fitting, providing little insight into the relation between effective parameters and physical properties of the medium. There is a clear need for material characterization techniques that can provide insight into the geometry and connectedness of pore spaces related to transport model parameters. Here, we consider proton nuclear magnetic resonance (NMR), direct-current (DC) resistivity, and complex conductivity (CC) measurements for this purpose, and assess these methods using glass beads as a control and two different samples of the zeolite clinoptilolite, a material that demonstrates non-Fickian transport due to intragranular porosity. We estimate DDMT parameters via calibration of a transport model to column-scale solute tracer tests, and compare NMR, DC resistivity, CC results, which reveal that grain size alone does not control transport properties and measured geophysical parameters; rather, volume and arrangement of the pore space play important roles. NMR cannot provide estimates of more-mobile and less-mobile pore volumes in the absence of tracer tests because these estimates depend critically on the selection of a material-dependent and flow-dependent cutoff time. Increased electrical connectedness from DC resistivity measurements are associated with greater mobile pore space determined from transport model calibration. CC was hypothesized to be related to length scales of mass transfer, but the CC response is unrelated to DDMT.
Swanson, Ryan D.; Binley, Andrew; Keating, Kristina; France, Samantha; Osterman, Gordon; Day-Lewis, Frederick D.; Singha, Kamini
Thermodynamic and transport property modeling in super critical water
Supercritical water oxidation (SCWO) is a thermally-based, remediation and waste-treatment process that relies on unique property changes of water when water is heated and pressurized above its critical point. Above its ...
Kutney, Michael C. (Michael Charles)
Colloquium: Structural, electronic, and transport properties of silicon nanowires
. Surface segregation, surface traps, and dopant aggregation 439 2. Quantum confinement 439 3. Dielectric are an extremely attractive alternative to CNTs because it is much easier to control their electrical properties
Wu, Zhigang
Charge transport properties of CdMnTe radiation detectors
Growth, fabrication and characterization of indium-doped cadmium manganese telluride (CdMnTe)radiation detectors have been described. Alpha-particle spectroscopy measurements and time resolved current transient measurements have yielded an average charge collection efficiency approaching 100 %. Spatially resolved charge collection efficiency maps have been produced for a range of detector bias voltages. Inhomogeneities in the charge transport of the CdMnTe crystals have been
Kim K; R. Rafiel; M. Boardman; I. Reinhard; A. Sarbutt; G. Watt; C. Watt; S. Uxa; D. A. Prokopovich; E. Belas; A. E. Bolotnikov; R. B. James
The Transporting Property of Hybrid SCM/Ethernet PON
NASA Astrophysics Data System (ADS)
SCM/Ethernet PON is the hybrid PON, which two wavelengths transport downstream services simultaneously. With the high rate of Ethernet PON and the high subcarrier frequency of SCM PON, the two down-stream wavelengths of hybrid PON are interactional seriously. This paper mainly analysis the impacts of Cross-power Modulation and Dispersion in SCM/Ethernet PON, rewards the relationship of BER and the modulation frequency, modulation index, and the average optical power.
Ji, Wei; Ren, Yongpeng
Transport properties of transition-metal-encapsulated Si cages
We performed density functional pseudopotential calculations of the spin dependent transport through transition-metal-atom-encapsulated Si cages Si12X(X=Mn, Fe and Co). The effect of the metal atom on conductance is studied. Mn and Fe doped systems show highly spin polarized transmission whereas the magnetization in Co doped system is quenched. It is found that electrons are transferred from Si atoms into the
Lingzhu Kong; James R. Chelikowsky
Electrical properties and transport in boron-nitride nanotubes
Boron-nitride nanotubes (BNNT) are nanoscale materials structurally identical to carbon nan-otubes. However, the presence of inequivalent atomic species on the two graphene sublattices in BNNTs leads to a dramatically different electronic structure than in the case of carbon nanotubes. Here we present the first electrical transport measurements on BNNTs which confirm that they are semiconductors. Using prototype BNNT field-effect transistors
Marko Radosavljevic; Joerg Appenzeller; Vincent Derycke; Richard Martel; Phaedon Avouris; Annick Loiseau; Jean-Loup Couchon; Daniel Pigache
Impact of carbonation on the durability of cementitious materials: water transport properties characterization
NASA Astrophysics Data System (ADS)
Within the context of long-lived intermediate level radioactive waste geological disposal, reinforced concrete would be used. In service life conditions, the concrete structures would be subjected to drying and carbonation. Carbonation relates to the reaction between carbon dioxide (CO2) and the main hydrates of the cement paste (portlandite and C-S-H). Beyond the fall of the pore solution pH, indicative of steel depassivation, carbonation induces mineralogical and microstructural changes (due to portlandite and C-S-H dissolution and calcium carbonate precipitation). This results in the modification of the transport properties, which can impact the structure durability. Because concrete durability depends on water transport, this study focuses on the influence of carbonation on water transport properties. In fact, the transport properties of sound materials are known but they still remain to be assessed for carbonated ones. An experimental program has been designed to investigate the transport properties in carbonated materials. Four hardened cement pastes, differing in mineralogy, are carbonated in an accelerated carbonation device (in controlled environmental conditions) at CO2 partial pressure of about 3%. Once fully carbonated, all the data needed to describe water transport, using a simplified approach, will be evaluated.
Auroy, M.; Poyet, S.; Le Bescop, P.; Torrenti, J.-M.
Theoretical studies of the transport properties in compound semiconductors
NASA Technical Reports Server (NTRS)
This final report is an overview of the work done on Cooperative Agreement NCC 3-55 with the Solid State Technology Branch of the NASA-Lewis Research Center (LeRC). Over the period of time that the agreement was in effect, the principal investigator and, in the last three years, the co-principal investigator worked on a significant number of projects and interacted with members of the Solid State Technology (SST) branch in a number of different ways. For the purpose of this report, these efforts will be divided into five categories: 1) work directly with experimental electrical transport studies conducted by members of the SST branch; 2) theoretical work on electrical transport in compound semiconductors; 3) electronic structure calculations which are relevant to the electrical transport in polytypes of SiC and SiC-AlN alloys; 4) the electronic structure calculations of polar interfaces; and 5) consultative and supportive activities related to experiments and other studies carried out by SST branch members. Work in these categories is briefly discussed.
Segall, Benjamin
Effects of nonframework metal cations and phonon scattering mechanisms on the thermal transport properties of polycrystalline zeolite LTA films
properties of polycrystalline zeolite LTA films Abraham Greenstein,1 Yeny Hudiono,2 Samuel Graham,1 of phonon scattering mechanisms on the thermal transport properties of zeolite LTA, via experiment measurements and mechanistic understanding of the thermal transport properties of zeolite materials
Nair, Sankar
Thermoelectric properties, electronic structure and optoelectronic properties of anisotropic Ba2Tl2CuO6 single crystal from DFT approach
NASA Astrophysics Data System (ADS)
First principle calculation was performed for the electronic structure, electronic charge density, Fermi surface, optical and thermoelectric properties of Ba2Tl2CuO6 compound. From the electronic band structure the two overlapping bands and the density of state at Fermi level (29.2 states/Ryd-cell) confirms the superconducting behavior. Colors of the Fermi surface elucidate speed of electrons and strength of the superconductivity as well. The bonding nature was investigated using the calculated charge density contour plot, it shows mixed ionic-covalent nature of Cu3O and Tl3O while Ba3O shows dominant ionic nature with small covalency. The optical properties were calculated and discussed in details. The calculated uniaxial anisotropy value (0.7913) clarifies a considerable anisotropy between two dominant tensor components of dielectric function. Moreover the evaluation of Seebeck coefficient and thermal conductivity conform that the compound is much suitable for thermoelectric applications.
Reshak, A. H.; Khan, Saleem Ayaz
Cytochrome p450 inhibitory properties of common efflux transporter inhibitors.
Drug transporter inhibitors are important tools to elucidate the contribution of transporters to drug disposition both in vitro and in vivo. These inhibitors are often unselective and affect several transporters as well as drug metabolizing enzymes, which can make experimental results difficult to interpret with confidence. We therefore tested 14 commonly used P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and multidrug-resistance associated protein (MRP) inhibitors as inhibitors of cytochrome P450 (P450) enzyme activities using recombinant enzymes. A subset of P-gp and/or CYP3A inhibitors were selected (cyclosporin A, elacridar, ketoconazole, quinidine, reserpine, and tacrolimus) for a comparison of P450 inhibition in human microsomes and hepatocytes. Most P-gp inhibitors showed CYP3A4 inhibition, with potencies often in a similar range as their P-gp inhibition, as well as less potent CYP2C19 inhibition. Other P450 enzymes were not strongly inhibited except a few cases of CYP2D6 inhibition. MRP and BCRP inhibitors showed limited P450 inhibition. Some inhibitors showed less P450 inhibition in human hepatocytes than human liver microsomes, for example, elacridar, probably due to differences in binding, permeability limitations, or active, P-gp mediated efflux of the inhibitor from the hepatocytes. Quinidine was a potent P450 inhibitor in hepatocytes but only showed weak inhibition in microsomes. Quinidine shows an extensive cellular uptake, which may potentiate intracellular P450 inhibition. Elacridar, described as a potent and selective P-gp inhibitor, displayed modest P450 inhibition in this study and is thus a useful model inhibitor to define the role of P-gp in drug disposition without interference with other processes. PMID:24396142
Englund, Gunilla; Lundquist, Patrik; Skogastierna, Cristine; Johansson, Jenny; Hoogstraate, Janet; Afzelius, Lovisa; Andersson, Tommy B; Projean, Denis
Microsphere-chain waveguides: Focusing and transport properties
It is shown that the focusing properties of polystyrene microsphere-chain waveguides (MCWs) formed by sufficiently large spheres (D???20?, where D is the sphere diameter and ? is the wavelength of light) scale with the sphere diameter as predicted by geometrical optics. However, this scaling behavior does not hold for mesoscale MCWs with D???10? resulting in a periodical focusing with gradually reducing beam waists and in extremely small propagation losses. The observed effects are related to properties of nanojet-induced and periodically focused modes in such structures. The results can be used for developing focusing microprobes, laser scalpels, and polarization filters.
Allen, Kenneth W., E-mail: email@example.com; Astratov, Vasily N., E-mail: email@example.com [Department of Physics and Optical Science, Center for Optoelectronics and Optical Communications, University of North Carolina at Charlotte, Charlotte, North Carolina 28223-0001 (United States); Air Force Research Laboratory, Sensors Directorate, Wright Patterson AFB, Ohio 45433 (United States); Darafsheh, Arash; Abolmaali, Farzaneh [Department of Physics and Optical Science, Center for Optoelectronics and Optical Communications, University of North Carolina at Charlotte, Charlotte, North Carolina 28223-0001 (United States); Mojaverian, Neda; Limberopoulos, Nicholaos I. [Air Force Research Laboratory, Sensors Directorate, Wright Patterson AFB, Ohio 45433 (United States); Lupu, Anatole [Institut d'Electronique Fondamentale, UMR 8622 CNRS, Universite Paris-Sud XI, 91405 Orsay (France)
Microsphere-chain waveguides: Focusing and transport properties
NASA Astrophysics Data System (ADS)
It is shown that the focusing properties of polystyrene microsphere-chain waveguides (MCWs) formed by sufficiently large spheres (D ? 20?, where D is the sphere diameter and ? is the wavelength of light) scale with the sphere diameter as predicted by geometrical optics. However, this scaling behavior does not hold for mesoscale MCWs with D ? 10? resulting in a periodical focusing with gradually reducing beam waists and in extremely small propagation losses. The observed effects are related to properties of nanojet-induced and periodically focused modes in such structures. The results can be used for developing focusing microprobes, laser scalpels, and polarization filters.
Allen, Kenneth W.; Darafsheh, Arash; Abolmaali, Farzaneh; Mojaverian, Neda; Limberopoulos, Nicholaos I.; Lupu, Anatole; Astratov, Vasily N.
Magnetic, transport, and thermodynamic properties of CaMn2O4 single crystals
NASA Astrophysics Data System (ADS)
Physical properties including magnetic susceptibility, room-temperature electrical resistivity, thermal conductivity, heat capacity, and thermal expansion are reported for high quality single-crystal samples of marokite CaMn2O4 . We determined that CaMn2O4 is highly electrically insulating and exhibits long-range antiferromagnetic order below TN=217.5▒0.6K with easy axis along a . Anisotropic thermal expansion, similar to that of crystallographically layered materials, is observed, suggesting that the crystal structure of CaMn2O4 is also assembled from previously undescribed layers. An extensive thermodynamic study of the antiferromagnetic transition was undertaken resulting in a heat-capacity critical exponent ?=0.082▒0.007 and calculated pressure derivative dTN/dP=5.154▒0.174K/GPa .
White, B. D.; Souza, J. A.; Chiorescu, C.; Neumeier, J. J.; Cohn, J. L.
Anisotropic pressure and hyperons in neutron stars
We study the effects of anisotropic pressure on properties of the neutron stars with hyperons inside its core within the framework of extended relativistic mean field. It is found that the main effects of anisotropic pressure on neutron star matter is to increase the stiffness of the equation of state, which compensates for the softening of the EOS due to the hyperons. The maximum mass and redshift predictions of anisotropic neutron star with hyperonic core are quite compatible with the result of recent observational constraints if we use the parameter of anisotropic pressure model $h \\le 0.8$[1] and $\\Lambda \\le -1.15$ [2]. The radius of the corresponding neutron star at $M$=1.4 $M_\\odot$ is more than 13 km, while the effect of anisotropic pressure on the minimum mass of neutron star is insignificant. Furthermore, due to the anisotropic pressure in the neutron star, the maximum mass limit of higher than 2.1 $M_\\odot$ cannot rule out the presence of hyperons in the neutron star core.
A. Sulaksono
Pesticide Transport with Runoff from Creeping Bentgrass Turf: Relationship of Pesticide Properties to Mass Transport
Technology Transfer Automated Retrieval System (TEKTRAN)
The off-site transport of pesticides with runoff is both an agronomic and environmental concern resulting from reduced control of target pests in the area of application and contamination of surrounding ecosystems. Experiments were designed to measure the quantity of pesticides in runoff from creepi...
Pesticide transport with runoff from creeping bentgrass turf: Relationship of pesticide properties to mass transport.
The off-site transport of pesticides with runoff is both an agronomic and environmental concern, resulting from reduced control of target pests in the area of application and contamination of surrounding ecosystems. Experiments were designed to measure the quantity of pesticides in runoff from creeping bentgrass (Agrostis palustris) turf managed as golf course fairway to gain a better understanding of factors that influence chemical availability and mass transport. Less than 1 to 23% of applied chloropyrifos, flutolanil, mecoprop-p (MCPP), dimethylamine salt of 2,4-dichlorophenoxyacetic acid (2,4-D), or dicamba was measured in edge-of-plot runoff when commercially available pesticide formulations were applied at label rates 23 +/- 9 h prior to simulated precipitation (62 +/- 13 mm). Time differential between hollow tine core cultivation and runoff did not significantly influence runoff volumes or the percentage of applied chemicals transported in the runoff. With the exception of chlorpyrifos, all chemicals of interest were detected in the initial runoff samples and throughout the runoff events. Chemographs of the five pesticides followed trends in agreement with mobility classifications associated with their soil organic carbon partition coefficient (K(OC).) Data collected from the present study provides information on the transport of chemicals with runoff from turf, which can be used in model simulations to predict nonpoint source pollution potentials and estimate ecological risks. PMID:20821562
Rice, Pamela J; Horgan, Brian P; Rittenhouse, Jennifer L
3D dye patterns and physical soil properties under two contrasting land uses: Anisotropic variance structures and its influence on solute leaching
NASA Astrophysics Data System (ADS)
Leaching of solutes below the root zone has been identified as a main source of potential groundwater pollution. In structured soils, preferential flow paths can have a significant influence on rapid leaching of solutes. Dye tracer experiments have been frequently used to map the spatial distribution of macropore structures. However, the relative influence of the macropore network on solute leaching under field conditions and its correlation with physical properties of the matric soil (texture, density, mechanical strength) and land use effects have not been analyzed yet and require innovative sampling techniques. The objectives of the present study were to map the macropore network and analyze the leaching behaviour of a conservative tracer under two contrasting land uses. Ponded infiltration experiments with Potassiumbromide (KBr) and Brilliant Blue (BB) were conducted on a silt loam soil in Lexington, KY. Two land use systems, grassland and cropland (wheat), were tested. At soil water content close to field capacity, a total of 30 mm multi-tracer solution was infiltrated on an area of 1.2 ū 0.7 m with a ponding head of 20 mm. The concentrations of KBr and BB were 10 and 5 g/L, respectively. After 24 hours, 10 profile sections (width: 100 cm, depth: 70 cm) were excavated in steps of 5 cm and sampled. Dye stained areas were mapped based on digital image analysis. The relative dye coverage was calculated as a function of depth. Vane shear resistance was measured as a proxy for soil mechanical strength. At every other profile section, the soil was sampled for soil water content at regular intervals along a 10 ū 10 cm raster. X-ray fluorescence analysis was used to derive concentrations of Br, SiO2 and Al2O3, the latter two being used as proxy for soil particle size distribution. Anisotropic variance and covariance analysis was applied to derive direction-dependent correlations between physical, mechanical, and hydrological observations and to identify the relative influence of the macropore network and land use regime on solute leaching.
Schwen, Andreas; Backus, Jason; Walton, Riley J.; Wendroth, Ole
Transport and magnetic properties of epitaxial and polycrystalline magnetite thin films
The transport and magnetic properties of magnetite (Fe3O4) thin films grown epitaxially on single crystal MgO(100) and SrTiO3(100) substrates, and with multiple grain orientations on polycrystalline SrTiO3 substrates, have been investigated. The films are grown using pulsed laser deposition and their epitaxial quality determined using ion channeling measurements. Transport and magnetic studies of Fe3O4 films as a function of thickness
X. W. Li; A. Gupta; Gang Xiao; G. Q. Gong
Electrophysiological study of transport systems in isolated perfused pancreatic ducts: properties of the basolateral membrane
In order to study the mechanism of pancreatic HCO3- transport, a perfused preparation of isolated intra-and interlobular ducts (i.d. 20¢40 Ąm) of rat pancreas was developed. Responses of the epithelium to changes in the bath ionic concentration and to addition of transport inhibitors was monitored by electrophysiological techniques. In this report some properties of the basolateral membrane of pancreatic duct
I. Novak; R. Greger
Direct measurements of transport and water properties through the Bering Strait
Four years of temperature, salinity, and velocity data enable a direct computation of volume transport and a temporal description of water properties exchanged through the Bering Strait. The mean volume transport over the 4-year period (September 1990 through September 1994) is 0.83 Sv northward with a weekly standard deviation of 0.66 Sv. The maximum error in this mean estimate is
A. T. Roach; K. Aagaard; C. H. Pease; S. A. Salo; T. Weingartner; V. Pavlov; M. Kulakov
Electrical transport, magnetic, and structural properties of the vortex lattice in superconducting V3Si
Electrical, magnetic, and structural properties of the vortex lattice (VL) in single crystal V3Si were studied by transport, bulk magnetometry and small-angle neutron scattering. Studies focused on the `peak effect' in critical current density just below the upper critical field of this weak-pinning system. The overall picture is a slightly disordered VL easily re-ordered by transport-current `shaking' and ultimately softening
A. A. Gapud; D. K. Christen; J. R. Thompson; M. Yethiraj
Electrical transport, magnetic, and structural properties of the vortex lattice in superconducting V 3Si
Electrical, magnetic, and structural properties of the vortex lattice (VL) in single crystal V3Si were studied by transport, bulk magnetometry and small-angle neutron scattering. Studies focused on the æpeak effectÆ in critical current density just below the upper critical field of this weak-pinning system. The overall picture is a slightly disordered VL easily re-ordered by transport-current æshakingÆ and ultimately softening
A. A. Gapud; D. K. Christen; J. R. Thompson; M. Yethiraj
Transport properties of droplet clusters in gravity-free fields
NASA Technical Reports Server (NTRS)
Clusters of liquid droplets are suspended in an atmosphere of saturated vapor and are subjected to an external force field. This system can be modeled as a continuum whose macroscopic properties may be determined by applying the generalized theory of Taylor dispersion.
Brenner, Howard
Studies of Transport Properties of Fractures: Final Report
We proposed to study several key factors controlling the character and evolution of fracture system permeability and transport processes. We suggest that due to surface roughness and the consequent channeling in single fractures and in fracture intersections, the tendency of a fracture system to plug up, remain permeable, or for permeability to increase due to chemical dissolution/precipitation conditions will depend strongly on the instantaneous flow channel geometry. This geometry will change as chemical interaction occurs, thus changing the permeability through time. To test this hypothesis and advance further understanding toward a predictive capability, we endeavored to physically model and analyze several configurations of flow and transport of inert and chemically active fluids through channels in single fractures and through fracture intersections. This was an integrated program utilizing quantitative observations of fractures and veins in drill core, quantitative and visual observations of flow and chemical dissolution and precipitation within replicas of real rough-walled fractures and fracture intersections, and numerical modeling via lattice Boltzmann methods.
Stephen R. Brown
Magnetic and transport properties of epitaxial stepped Fe3O4(100) thin films
NASA Astrophysics Data System (ADS)
We investigate the magnetic and transport properties of epitaxial stepped Fe3O4 thin films grown with different thicknesses. Magnetization measurements suggest that the steps induce additional anisotropy, which has an easy axis perpendicular to steps and the hard axis along the steps. Separate local transport measurements, with nano-gap contacts along a single step and perpendicular to a single step, suggest the formation of a high density of anti-phase boundaries (APBs) at the step edges are responsible for the step induced anisotropy. Our local transport measurements also indicate that APBs distort the long range charge-ordering of magnetite.
Wu, Han-Chun; Syrlybekov, Askar; Mauit, Ozhet; Mouti, Anas; Coileßin, Cormac ė.; Abid, Mourad; Abid, Mohamed; Shvets, Igor V.
Infinite guided modes in a planar waveguide with a biaxially anisotropic metamaterial
We investigate in detail the guided modes in a two-layered planar waveguide where one layer is filled with an ordinary right-handed material (RHM) and the other is filled with a biaxially anisotropic metamaterial. We show that the mode properties are closely dependent on the spatial dispersion relation of the anisotropic medium. When the dispersion equation for the anisotropic medium becomes
Qiang Cheng; Tie Jun Cui
Mouse organic cation transporter 1 determines properties and regulation of basolateral organic cation transport in renal proximal tubules.
The proximal tubule of mouse kidney expresses mouse organic cation transporter 1 (mOCT1), mOCT2, and much less mOCT3. Therefore, mOCT-mediated transport across the basolateral membrane of proximal tubules reflects properties of at least mOCT1 and mOCT2. Here, we unraveled substrate affinities and modulation of transport activity by acute regulation by protein kinases on mOCT1 and mOCT2 separately and compared these findings with those from isolated proximal tubules of male and female mOCT2?/? mice. These data are also compared to our recent reports on isolated tubules from wild-type and mOCT1/2 double knockout (mOCT1/2?/?) mice. OCT-mediated transport in proximal tubules of mOCT2?/? mice was only 20 % lower compared to those isolated from wild-type mice. While mOCT1 was regulated by all five pathways examined [protein kinase A (PKA), protein kinase C (PKC), p56lck, phosphoinositide 3-kinase (PI3K), and calmodulin (CaM)], mOCT2 activity was modulated by PKA, p56lck, and CaM only, however, in the same direction. As mOCT-mediated transport across the basolateral membrane of mOCT2?/? mice expressing only mOCT1 and to a small amount mOCT3 was identical to that observed for tubules isolated from wild-type mice and to that observed for human embryonic kidney 293 (HEK293) cells stably expressing mOCT1, mOCT1 represents the relevant paralog for OCT-dependent organic cation transport in the mouse kidney. Gender does not play a major role in expression and activity of renal OCT-mediated transport in the mouse. Properties of mouse OCT considerably differ from those of rat or human origin, and thus, observations made in these rodents cannot directly be transferred to the human situation PMID:24233562
Schlatter, Eberhard; Klassen, Philipp; Massmann, Vivian; Holle, Svenja K; Guckel, Denise; Edemir, Bayram; Pavenstõdt, Hermann; Ciarimboli, Giuliano
Al-based systems with unusual mechanical and transport properties
NASA Astrophysics Data System (ADS)
Addition of selected transition-metal elements into aluminum matrix is known to yield systems that exhibit unique structural arrangements and mechanical properties, especially high yield strength obtained after suitable heat treatment. These lightweight systems are known to be compactable from ribbon shape prepared by rapid quenching of the melt into bulk form, yielding physically and technically attractive materials. The combination of knowledge about formation of aluminum-based foams with the physics of rapid quenching and compaction is shown as a possible route for approaching the preparation of lightweight materials with potentially auxetic behavior. Enhancement of this property is discussed briefly in terms of tailoring the network or cell-pore structure of different dimensions, ranging from millimeters down to nanoscale and sub-nanoscale atomic ordering.
M³llerovß, K.; Kovßcik, J.; SimancĒk, F.; Vec, P.
Transport properties of graphene under periodic and quasiperiodic magnetic superlattices
NASA Astrophysics Data System (ADS)
We study the transmission of Dirac electrons through the one-dimensional periodic, Fibonacci, and Thue-Morse magnetic superlattices (MS), which can be realized by two different magnetic blocks arranged in certain sequences in graphene. The numerical results show that the transmission as a function of incident energy presents regular resonance splitting effect in periodic MS due to the split energy spectrum. For the quasiperiodic MS with more layers, they exhibit rich transmission patterns. In particular, the transmission in Fibonacci MS presents scaling property and fragmented behavior with self-similarity, while the transmission in Thue-Morse MS presents more perfect resonant peaks which are related to the completely transparent states. Furthermore, these interesting properties are robust against the profile of MS, but dependent on the magnetic structure parameters and the transverse wave vector.
Lu, Wei-Tao; Wang, Shun-Jin; Wang, Yong-Long; Jiang, Hua; Li, Wen
Anisotropic magnetoresistance in an antiferromagnetic semiconductor
NASA Astrophysics Data System (ADS)
Recent studies in devices comprising metal antiferromagnets have demonstrated the feasibility of a novel spintronic concept in which spin-dependent phenomena are governed by an antiferromagnet instead of a ferromagnet. Here we report experimental observation of the anisotropic magnetoresistance in an antiferromagnetic semiconductor Sr2IrO4. Based on ab initio calculations, we associate the origin of the phenomenon with large anisotropies in the relativistic electronic structure. The antiferromagnet film is exchange coupled to a ferromagnet, which allows us to reorient the antiferromagnet spin-axis in applied magnetic fields via the exchange spring effect. We demonstrate that the semiconducting nature of our AFM electrode allows us to perform anisotropic magnetoresistance measurements in the current-perpendicular-to-plane geometry without introducing a tunnel barrier into the stack. Temperature-dependent measurements of the resistance and anisotropic magnetoresistance highlight the large, entangled tunabilities of the ordinary charge and spin-dependent transport in a spintronic device utilizing the antiferromagnet semiconductor.
Fina, I.; Marti, X.; Yi, D.; Liu, J.; Chu, J. H.; Rayan-Serrao, C.; Suresha, S.; Shick, A. B.; Äelezn², J.; Jungwirth, T.; Fontcuberta, J.; Ramesh, R.
Anisotropic spin transport affected by competition between spin orbit interaction and Zeeman effect in an InGaAs based wire
NASA Astrophysics Data System (ADS)
Spin transport affected by competition between Zeeman effect and spin-orbit interaction (SOI) is investigated in order to check a proposed method to deduce the Rashba SOI ? and Dresselhaus SOI ? ratio. The experimentally obtained ratio ?/? of the present sample is about 4 from angle dependence of magnetoconductance under in-plane magnetic field. The proposed method to detect the ratio by transport measurement is promising although further improvement of sample fabrication and measurement is required.
Nitta, Junsaku; Moulis, Sylvain; Kohda, Makoto
Magneto-transport properties of a random distribution of few-layer graphene patches
NASA Astrophysics Data System (ADS)
In this study, we address the electronic properties of conducting films constituted of an array of randomly distributed few layer graphene patches and investigate on their most salient galvanometric features in the moderate and extreme disordered limit. We demonstrate that, in annealed devices, the ambipolar behaviour and the onset of Landau level quantization in high magnetic field constitute robust hallmarks of few-layer graphene films. In the strong disorder limit, however, the magneto-transport properties are best described by a variable-range hopping behaviour. A large negative magneto-conductance is observed at the charge neutrality point, in consistency with localized transport regime.
Iacovella, Fabrice; Trinsoutrot, Pierre; Mitioglu, Anatolie; Conķdķra, Vķronique; Pierre, Mathieu; Raquet, Bertrand; Goiran, Michel; Vergnes, Hugues; Caussat, Brigitte; Plochocka, Paulina; Escoffier, Walter
Pore-scale heterogeneity, energy dissipation and the transport properties of rocks
The authors construct model systems to study pore scale conductivity, by making the models from an array of spheres, tubes, and cracks with different dimensions. They vary the conductivity of this system by changing the sizes and distributions of the different pore elements. To determine the transport properties of this model system, they equated the sum of the energy lost at each pore junction, to the total energy lost in the array, for either fluid or electrical conduction through the array. The authors argue that this model conduction system should be applicable to study conductivity through rock, and allow one to learn more about transport properties of rock.
Bernabe, Y.; Revil, A. [Universite Louis Pasteur, Strasbourg (France)] [Universite Louis Pasteur, Strasbourg (France)
Scaling properties of charge transport in polycrystalline graphene.
Polycrystalline graphene is a patchwork of coalescing graphene grains of varying lattice orientations and size, resulting from the chemical vapor deposition (CVD) growth at random nucleation sites on metallic substrates. The morphology of grain boundaries has become an important topic given its fundamental role in limiting the mobility of charge carriers in polycrystalline graphene, as compared to mechanically exfoliated samples. Here we report new insights to the current understanding of charge transport in polycrystalline geometries. We created realistic models of large CVD-grown graphene samples and then computed the corresponding charge carrier mobilities as a function of the average grain size and the coalescence quality between the grains. Our results reveal a remarkably simple scaling law for the mean free path and conductivity, correlated to atomic-scale charge density fluctuations along grain boundaries. PMID:23448361
Van Tuan, Dinh; Kotakoski, Jani; Louvet, Thibaud; Ortmann, Frank; Meyer, Jannik C; Roche, Stephan
Charge transport properties of CdMnTe radiation detectors
NASA Astrophysics Data System (ADS)
Growth, fabrication and characterization of indium-doped cadmium manganese telluride (CdMnTe) radiation detectors have been described. Alpha-particle spectroscopy measurements and time resolved current transient measurements have yielded an average charge collection efficiency approaching 100 %. Spatially resolved charge collection efficiency maps have been produced for a range of detector bias voltages. Inhomogeneities in the charge transport of the CdMnTe crystals have been associated with chains of tellurium inclusions within the detector bulk. Further, it has been shown that the role of tellurium inclusions in degrading charge collection is reduced with increasing values of bias voltage. The electron drift velocity was calculated from the rise time distribution of the preamplifier output pulses at each measured bias. From the dependence of drift velocity on applied electric field the electron mobility was found to be ?n = (718 ▒ 55) cm2/Vs at room temperature.
Rafiei, R.; Boardman, D.; Reinhard, M. I.; Sarbutt, A.; Kim, K.; Watt, G. C.; Uxa, S.; Prokopovich, D. A.; Belas, E.; Bolotnikov, A. E.; James, R. B.
Scaling Properties of Charge Transport in Polycrystalline Graphene
Polycrystalline graphene is a patchwork of coalescing graphene grains of varying lattice orientations and size, resulting from the chemical vapor deposition (CVD) growth at random nucleation sites on metallic substrates. The morphology of grain boundaries has become an important topic given its fundamental role in limiting the mobility of charge carriers in polycrystalline graphene, as compared to mechanically exfoliated samples. Here we report new insights to the current understanding of charge transport in polycrystalline geometries. We created realistic models of large CVD-grown graphene samples and then computed the corresponding charge carrier mobilities as a function of the average grain size and the coalescence quality between the grains. Our results reveal a remarkably simple scaling law for the mean free path and conductivity, correlated to atomic-scale charge density fluctuations along grain boundaries. PMID:23448361
Electrical transport properties of CaB6
NASA Astrophysics Data System (ADS)
We report results from a systematic electron-transport study in a broad temperature range on 12 CaB6 single crystals. None of the crystals were intentionally doped. The different carrier densities observed presumably arise from slight variations in the Ca:B stoichiometry. In these crystals, the variation of the electrical resistivity and of the Hall effect with temperature can be consistently accounted for by the model we propose, in which B-antisite defects (B atom replacing Ca atom) are "amphoteric." The magnetotransport measurements reveal that most of the samples we have studied are close to a metal-insulator transition at low temperatures. The magnetoresistance changes smoothly from negativeŚfor weakly metallic samplesŚto positive valuesŚfor samples in a localized regime.
Stankiewicz, Jolanta; Sesķ, Javier; Balakrishnan, Geetha; Fisk, Zachary
Direct measurements of transport properties are essential for site characterization
Direct measurements of transport parameters on subsurface sediments using, the UFA method provided detailed hydrostratigraphic mapping, and subsurface flux distributions at a mixed-waste disposal site at Hanford. Seven hundred unsaturated conductivity measurements on fifty samples were obtained in only six months total of UFA run time. These data are used to provide realistic information to conceptual models, predictive models and restoration strategies. The UFA instrument consists of an ultracentrifuge with a constant, ultralow flow pump that provides fluid to the sample surface through a rotating seal assembly and microdispersal system. Effluent from the sample is collected in a transparent, volumetrically-calibrated chamber at the bottom of the sample assembly. Using a strobe light, an observer can check the chamber while the sample is being centrifuged. Materials can be run in the UFA as recomposited samples or in situ samples can be subcored directly into the sample UFA chamber.
Wright, J. [Pacific Northwest Lab., Richland, WA (United States); Conca, J.L. [Washington State Univ. Tri-Cities, Richland, WA (United States). Environmental Sciences
Charge transport properties of CdMnTe radiation detectors
Growth, fabrication and characterization of indium-doped cadmium manganese telluride (CdMnTe)radiation detectors have been described. Alpha-particle spectroscopy measurements and time resolved current transient measurements have yielded an average charge collection efficiency approaching 100 %. Spatially resolved charge collection efficiency maps have been produced for a range of detector bias voltages. Inhomogeneities in the charge transport of the CdMnTe crystals have been associated with chains of tellurium inclusions within the detector bulk. Further, it has been shown that the role of tellurium inclusions in degrading chargecollection is reduced with increasing values of bias voltage. The electron transit time was determined from time of flight measurements. From the dependence of drift velocity on applied electric field the electron mobility was found to be n = (718 55) cm2/Vs at room temperature.
Kim K.; Rafiel, R.; Boardman, M.; Reinhard, I.; Sarbutt, A.; Watt, G.; Watt, C.; Uxa, S.; Prokopovich, D.A.; Belas, E.; Bolotnikov, A.E.; James, R.B.
Magnetic and transport properties of magnetite thin films
Magnetite (Fe3O4) films were prepared by DC reactive magnetron sputtering at various oxygen partial pressures with the ratio ? of oxygen to argon changing from 0.50:50 to 0.70:50 at room temperature, and then the Fe3O4 films were annealed at 480░C for 80min. The properties of the films were studied by X-ray diffraction, scanning electron microscopy, magnetic hysteresis loops, magnetoresistance (MR),
Guomin Zhang; Chongfei Fan; Liqing Pan; Fengping Wang; Ping Wu; Hong Qiu; Yousong Gu; Yue Zhang
Transport properties of hectorite based nanocomposite single ion conductors
The ionic conductivity and rheological properties of clay filled nanocomposite electrolytes are reported. These electrolytes, which have potential use in lithium-ion batteries, consist of lithium-exchanged hectorite, a 2:1 layered smectite clay, dispersed in ethylene carbonate (EC) or a mixture of EC+polyethylene glycol di-methyl ether (PEG-dm, 250MW). All samples exhibit elastic, gel-like characteristics and room temperature conductivities of order 0.1mS\\/cm. A
Ruchi Gupta Singhal; Michael D. Capracotta; James D. Martin; Saad A. Khan; Peter S. Fedkiw
WETAIR: A computer code for calculating thermodynamic and transport properties of air-water mixtures
NASA Technical Reports Server (NTRS)
A computer program subroutine, WETAIR, was developed to calculate the thermodynamic and transport properties of air water mixtures. It determines the thermodynamic state from assigned values of temperature and density, pressure and density, temperature and pressure, pressure and entropy, or pressure and enthalpy. The WETAIR calculates the properties of dry air and water (steam) by interpolating to obtain values from property tables. Then it uses simple mixing laws to calculate the properties of air water mixtures. Properties of mixtures with water contents below 40 percent (by mass) can be calculated at temperatures from 273.2 to 1497 K and pressures to 450 MN/sq m. Dry air properties can be calculated at temperatures as low as 150 K. Water properties can be calculated at temperatures to 1747 K and pressures to 100 MN/sq m. The WETAIR is available in both SFTRAN and FORTRAN.
Fessler, T. E.
The Effects of Atmospheric pH on the Transport Properties of Gallium Nitride
NASA Astrophysics Data System (ADS)
It has been theorized that there exists a thin layer of water molecules on the surface of many materials when in air. This layer is predicted to have an effect on the electrochemical properties of the material. GaN is one of these materials. It has been demonstrated that the optical properties of GaN are affected by the pH of the atmosphere around the sample. In this study the effects of pH on transport properties are tested. A system was developed to test the Hall coefficient and resistivity of samples under different ambients to discover the effects of pH on carrier concentration and Hall mobility of GaN. Thus far, the results show that the pH of the ambient water vapor does not have an effect on the transport properties. This project was funded through the National Science Foundation (DMR-1006132) and the Huntington and Codrington Foundations.
McElroy, Andrew; Dyck, Jeffrey S.; Kash, Kathleen
Seismic signatures of reservoir transport properties and pore fluid distribution
The authors investigate the effects of permeability, frequency, and fluid distribution on the viscoelastic behavior of rock. The viscoelastic response of rock to seismic waves depends on the relative motion of pore fluid with respect to the solid phase. They consider wave-induced squirt fluid flow at two scales: (1) local microscopic flow at the smallest scale of saturation heterogeneity (e.g., within a single pore) and (2) macroscopic flow at a larger scale of fluid-saturated and dry patches. They explore the circumstances under which each of these mechanisms prevails. They examine such flows under the conditions of uniform confining (bulk) compression and obtain the effective dynamic bulk modulus of rock. The solutions are formulated in terms of generalized frequencies that depend on frequency, saturation, fluid and gas properties, and on the macroscopic properties of rock such as permeability, porosity, and dry bulk modulus. The study includes the whole range of saturation and frequency; therefore, the authors provide the missing link between the low-frequency limit and the high-frequency limit given by Mavko and Jizba. Further, they compare their model with Biot's theory and introduce a geometrical factor whose numeric value gives an indication as to whether local fluid squirt or global mechanisms dominate the viscoelastic properties of porous materials. The important results of their theoretical modeling are: (1) a hysteresis of acoustic velocity versus saturation resulting from variations in fluid distributions, and (2) two peaks of acoustic wave attenuation--one at low frequency and another at higher frequency (caused by local flow). Both theoretical results are compared with experimental data.
Akbar, N. (Saudi Aramco, Dhahran (Saudi Arabia)); Mavko, G.; Nur, A.; Dvorkin, J. (Stanford Univ., CA (United States). Dept. of Geophysics)
Structure evolution and electrical transport property of Si nanowire
NASA Astrophysics Data System (ADS)
Various optimized Si and its alloy nanowires, from a monoatomic chain to helical and multishell coaxial cylinder, have been obtained. Results reveal that the structure of the Si nanowires transforms as the radii of the carbon nanotubes increase, despite of the chirality of the CNTs. We also calculate the physical properties, such as density of states, transmission functions, current-voltage (I-V) characteristics, and conductance spectra (G-V) of optimized nanowires and alloy nanowires sandwiched between two gold contacts. Interestingly, compared with the pure Si nanowires, the conductance of the alloy nanowires is even lower.
Wang, Y.; Li, Q. Q.; Dong, J. C.; He, Y. Z.; Li, H.
Diversity in Expression Patterns and Functional Properties in the Rice HKT Transporter Family1[W
Plant growth under low K+ availability or salt stress requires tight control of K+ and Na+ uptake, long-distance transport, and accumulation. The family of membrane transporters named HKT (for High-Affinity K+ Transporters), permeable either to K+ and Na+ or to Na+ only, is thought to play major roles in these functions. Whereas Arabidopsis (Arabidopsis thaliana) possesses a single HKT transporter, involved in Na+ transport in vascular tissues, a larger number of HKT transporters are present in rice (Oryza sativa) as well as in other monocots. Here, we report on the expression patterns and functional properties of three rice HKT transporters, OsHKT1;1, OsHKT1;3, and OsHKT2;1. In situ hybridization experiments revealed overlapping but distinctive and complex expression patterns, wider than expected for such a transporter type, including vascular tissues and root periphery but also new locations, such as osmocontractile leaf bulliform cells (involved in leaf folding). Functional analyses in Xenopus laevis oocytes revealed striking diversity. OsHKT1;1 and OsHKT1;3, shown to be permeable to Na+ only, are strongly different in terms of affinity for this cation and direction of transport (inward only or reversible). OsHKT2;1 displays diverse permeation modes, Na+-K+ symport, Na+ uniport, or inhibited states, depending on external Na+ and K+ concentrations within the physiological concentration range. The whole set of data indicates that HKT transporters fulfill distinctive roles at the whole plant level in rice, each system playing diverse roles in different cell types. Such a large diversity within the HKT transporter family might be central to the regulation of K+ and Na+ accumulation in monocots. PMID:19482918
Jabnoune, Mehdi; Espeout, Sandra; Mieulet, Delphine; Fizames, Cķcile; Verdeil, Jean-Luc; Conķjķro, GeneviĶve; RodrĒguez-Navarro, Alonso; Sentenac, Hervķ; Guiderdoni, Emmanuel; Abdelly, Chedly; Vķry, Anne-Aliķnor
Gas transport properties of poly(ethylene oxide-co-epichlorohydrin) membranes
Gas permeation properties of crosslinked membranes prepared from a series of poly(ethylene oxide-co-epichlorohydrin) (P(EO\\/EP)) copolymers with different contents of ethylene oxide are determined by using the constant-volume and pressure-increase method. In addition to the chemical composition, the transport properties are related to the main characteristics of copolymers like the glass transition temperature, crystallinity and crosslinking ratio. Permeation measurements of He,
C. Charmette; J. Sanchez; Ph. Gramain; A. Rudatsikira
Comparison of the Water Transporting Properties of MIP and AQP1
.ĀĀ In this paper we compare the water-transport properties of Aquaporin (AQP1), a known water channel, and those of the 28 kD\\u000a Major Intrinsic Protein of Lens (MIP), a protein with an undefined physiological role. To make the comparison as direct as\\u000a possible we measured functional properties in Xenopus laevis oocytes injected with cRNAs coding for the appropriate protein. We
G. Chandy; G. A. Zampighi; M. Kreman; J. E. Hall
Heterogeneous Structure and Ionic Transport Properties of Silver Chalcogenide Glasses
NASA Astrophysics Data System (ADS)
Silver chalcogenide glasses is a new example of the importance of concentration fluctuation in supercooled liquid state to ionic conductivity, which remains as a nano to micro phase separation in glassy state. The frozen heterogeneous structures of Ag-GeSe3 glasses have been investigated precisely by using FE-SEM and EPMA analysis. The variation of the local structure is studied by NMR and Raman scattering. From these structure analyses, the Ag-Ge-Se and Ag-Ge-S system have a bistable structure in supercooled liquid state, which is edge sharing GeSe4 based network with Se-Se chains and corner sharing GeSe4 network combined with Ag without Se-Se bonding. During the glass forming process, the homogeneous liquid separates into these two different structures to form micro heterogeneous structure in the glassy state. The silver ionic transport is only possible in the latter composition region, which is separated with each other below the composition x = 0.3 and is connected with each other to form percolation path above x = 0.3. The previously reported conductivity jump at x = 0.3 is the consequence of the percolation transition and is expressed by generalized effective medium approximation (GEMA).
Kawamura, Junichi; Kuwata, Naoaki; Tanji, Takanari
Transport properties of overheated electrons trapped on a helium surface
NASA Astrophysics Data System (ADS)
An ultra-strong photovoltaic effect has recently been reported for electrons trapped on a liquid helium surface under a microwave excitation tuned at intersubband resonance [D. Konstantinov, A.D. Chepelianskii, K. Kono, J. Phys. Soc. Jpn 81, 093601 (2012)]. In this article, we analyze theoretically the redistribution of the electron density induced by an overheating of the surface electrons under irradiation, and obtain quantitative predictions for the photocurrent dependence on the effective electron temperature and confinement voltages. We show that the photo-current can change sign as a function of the parameters of the electrostatic confinement potential on the surface, while the photocurrent measurements reported so far have been performed only at a fixed confinement potential. The experimental observation of this sign reversal could provide a reliable estimation of the electron effective temperature in this new out of equilibrium state. Finally, we have also considered the effect of the temperature on the outcome of capacitive transport measurement techniques. These investigations led us to develop, numerical and analytical methods for solving the Poisson-Boltzmann equation in the limit of very low temperatures which could be useful for other systems.
Closa, Fabien; Raphõel, Elie; Chepelianskii, Alexei D.
Transport and Magnetic Properties of MgFeVO4
NASA Astrophysics Data System (ADS)
A new spinel compound, MgFeVO4, was prepared by solid-state reactions. On the basis of the M÷ssbauer spectrum, it can be deduced that both Fe and V in MgFeVO4 are trivalent. Structure refinements based on X-ray and neutron diffraction data indicated that V3+ ions are likely to occupy the octahedral site, whereas Fe3+ and Mg2+ ions take both octahedral and tetrahedral sites. The formula of the compound can be represented as (Mg1-xFex)[MgxFe1-xV]O4 (x=0.638). The transport measurements indicate that MgFeVO4 is an n-type semiconductor with the hopping mechanism below 170 K and thermally activated mechanism at high temperatures. The DC and AC magnetic data show the antiferromagnetic interactions and spin glass behavior in MgFeVO4. The time-dependent magnetic relaxation and the exchange bias effect related to the spin glass phase are also analyzed. The curve fittings give long flipping times and large n values, indicating that strongly interacting clusters rather than individual spins are the predominant spin glass features.
Zhang, Xue; Kuang, Xiao-Jun; Wang, Yong-Gang; Wang, Xiao-Ming; Wang, Chun-Hai; Zhang, Yan; Chen, Chinping; Jing, Xi-Ping
Transport properties of stripe-ordered high Tc cuprates
Transport measurements provide important characterizations of the nature of stripe order in the cuprates. Initial studies of systems such as La{sub 1.6?x}Nd{sub 0.4}Sr{sub x}CuO{sub 4} demonstrated the strong anisotropy between in-plane and c-axis resistivities, but also suggested that stripe order results in a tendency towards insulating behavior within the planes at low temperature. More recent work on La{sub 2?x}Ba{sub x}CuO{sub 4} with x = 1/8 has revealed the occurrence of quasi-two-dimensional superconductivity that onsets with spin-stripe order. The suppression of three-dimensional superconductivity indicates a frustration of the interlayer Josephson coupling, motivating a proposal that superconductivity and stripe order are intertwined in a pair-density-wave state. Complementary characterizations of the low-energy states near the Fermi level are provided by measurements of the Hall and Nernst effects, each revealing intriguing signatures of stripe correlations and ordering. We review and discuss this work.
Jie, Q.; Han, S.J.; Dimitrov, I.; Tranquada, J.M.; Li, Q.
Transport Properties of Nanoscale High Temperature Superconducting Wires
NASA Astrophysics Data System (ADS)
The importance of studying nanoscale high temperature superconductors stems from the realization that the characteristic lengths in cuprate materials are in the nanometer scale: the coherence length and lattice spacing are of the order of few angstroms , the penetration depth are of the order of few nanometers . In addition a number of important length scales in various proposed mechanism such as the stripes and their seperation length lie in the nanometer range. Experimental investigation of nanowires of cuprates will therefore enable a better understanding of fundamental mechanisms of high temperature superconductivity. We present a successful nanofabrication technique of epitaxial nanoscale cuprates. Combining advanced electron-beam lithography and nanomachining techniques, we have fabricated a number of first-generation two-probe and four-probe nanowires. We discuss our initial transport measurements of I-V characteristics and magnetoresistance. The research at Boston University is supported by NSF and Sloan Foundation. The work at University of Toronto is supported by NSERC, CFI, OIT, ORDCF, MMO, CIAR and the Connaught Fund.
Ananth, V.
Effect of Alignment on Transport Properties of Carbon Nanotube/Metallic Junctions
NASA Technical Reports Server (NTRS)
Ballistic and spin coherent transport in single walled carbon nanotubes (SWCNT) are predicted to enable high sensitivity single-nanotube devices for strain and magnetic field sensing. Based upon these phenomena, electron beam lithography procedures have been developed to study the transport properties of purified HiPCO single walled carbon nanotubes for development into sensory materials for nondestructive evaluation. Purified nanotubes are dispersed in solvent suspension and then deposited on the device substrate before metallic contacts are defined and deposited through electron beam lithography. This procedure produces randomly dispersed ropes, typically 2 - 20 nm in diameter, of single walled carbon nanotubes. Transport and scanning probe microscopy studies have shown a good correlation between the junction resistance and tube density, alignment, and contact quality. In order to improve transport properties of the junctions a technique has been developed to align and concentrate nanotubes at specific locations on the substrate surface. Lithographic techniques are used to define local areas where high frequency electric fields are to be concentrated. Application of the fields while the substrate is exposed to nanotube-containing solution results in nanotube arrays aligned with the electric field lines. A second electron beam lithography layer is then used to deposit metallic contacts across the aligned tubes. Experimental measurements are presented showing the increased tube alignment and improvement in the transport properties of the junctions.
Wincheski, Buzz; Namkung, Min; Smits, Jan; Williams, Phillip; Harvey, Robert
Computer codes for the evaluation of thermodynamic properties, transport properties, and equilibrium constants of an 11-species air model
NASA Technical Reports Server (NTRS)
The computer codes developed provide data to 30000 K for the thermodynamic and transport properties of individual species and reaction rates for the prominent reactions occurring in an 11-species nonequilibrium air model. These properties and the reaction-rate data are computed through the use of curve-fit relations which are functions of temperature (and number density for the equilibrium constant). The curve fits were made using the most accurate data believed available. A detailed review and discussion of the sources and accuracy of the curve-fitted data used herein are given in NASA RP 1232.
Thompson, Richard A.; Lee, Kam-Pui; Gupta, Roop N.
Central Density Dependent Anisotropic Compact Stars
Stars can be treated as self-gravitating fluid. In this connection, we propose a model for an anisotropic star under the relativistic framework of Krori-Barua (1975) spacetime. It is shown that the solutions are regular and singularity free. The uniqueness of the model is that interior physical properties of the star solely depend on the central density of the matter distribution.
Mehedi Kalam; Farook Rahaman; Sk. Monowar Hossein; Saibal Ray
Carbon dioxide transport properties of composite membranes of a polyetherimide and a liquid crystal polymer
The effect of the addition of a liquid crystal polymer (Rodrun) on the gas sorption and transport properties of a polyetherimide (PEI, Ultem 1000) was investigated. CO2 permeation and sorption measurements were made with films of PEI, Rodrun and heterogeneous PEI\\/Rodrun blends at different pressures and temperatures. In all cases, permeability, diffusion and sorption coefficients decreased when the amount of
C. Uriarte; J. Alfageme; J. J. Iruin
NIST Standard Reference Database 23 NIST Reference Fluid Thermodynamic and Transport Properties--
#12;NIST Standard Reference Database 23 NIST Reference Fluid Thermodynamic and Transport Properties (NIST) uses its best efforts to deliver a high quality copy of the Database and to verify that the data contained therein have been selected on the basis of sound scientific judgment. However, NIST makes
Magee, Joseph W.
Transport and Phase Equilibria Properties for Steam Flooding of Heavy Oils
The objectives of this research included experimental determination and rigorous modeling and computation of phase equilibrium diagrams, volumetric, and transport properties of hydrocarbon/CO2/water mixtures at pressures and temperatures typical of steam injection processes for thermal recovery of heavy oils.
Gabitto, Jorge; Barufet, Maria
Bengal Fan sediment transport activity and response to climate forcing inferred from sediment physical properties
We obtained sediment physical properties and geochemical data from 47 piston and gravity cores located in the Bay of Bengal, to study the complex history of the Late Pleistocene run-off from the Ganges and Brahmaputra rivers and its imprint on the Bengal Fan. Grain-size parameters were predicted from core logs of density and velocity to infer sediment transport energy and
M. E. Weber; M. Wiedicke-Hombach; H. R. Kudrass; H. Erlenkeuser
INVITED FEATURE PAPERS Growth and transport properties of p-type GaNBi alloys
INVITED FEATURE PAPERS Growth and transport properties of p-type GaNBi alloys Alejandro X. Levander 2011) Thin films of GaNBi alloys with up to 12.5 at.% Bi were grown on sapphire using low to the midgap position of GaN, whereas the conduction band edge shifted more gradually. I. INTRODUCTION Alloying
Wu, Junqiao
Electrical Transport Properties of Au-Doped DNA Molecules J. S. Hwang1
as interconnection application for the nanometer-scale circuit. Chemical modification at both ends of DNA moleculesElectrical Transport Properties of Au-Doped DNA Molecules J. S. Hwang1 , S. H. Hong1,2 , H. K. Kim1, Seoul 136-701, Korea 1. Introduction In molecular-scale systems, deoxyribo nucleic acid (DNA) is one
Hwang, Sung Woo
Frequency distribution of water and solute transport properties derived from pan sampler data
Frequency distribution of water and solute transport properties derived from pan sampler data Jan Boll,1 John S. Selker,2 Gil Shalit,3 and Tammo S. Steenhuis4 Abstract. Modeling of water and solute samplers. Spatial distributions of solute velocity, dispersion coefficient, water flux, and solute
Walter, M.Todd
Deformationally dependent fluid transport properties of porcine coronary arteries based on location in the coronary vasculature
Objective Understanding coronary artery mass transport allows researchers to better comprehend how drugs or proteins move through, and deposit into, the arterial wall. Characterizing how the convective component of transport changes based on arterial location could be useful to better understand how molecules distribute in different locations in the coronary vasculature. Methods and results We measured the mechanical properties and wall fluid flux transport properties of de-endothelialized (similar to post-stenting or angioplasty) left anterior descending (LADC) and right (RC) porcine coronary arteries along their arterial lengths. Multiphoton microscopy was used to determine microstructural differences. Proximal LADC regions had a higher circumferential stiffness than all other regions. Permeability decreased by 198% in the LADC distal region compared to other LADC regions. The RC artery showed a decrease of 46.9% from the proximal to middle region, and 51.7% from the middle to distal regions. The porosity increased in the intima between pressure states, without differences through the remainder of the arterial thickness. Conclusions We showed that the permeabilities and mechanical properties do vary in the coronary vasculature. With variations in mechanical properties, overexpansion of stents can occur more easily while variations in permeability may lead to altered transport based on location. PMID:23127633
Keyes, Joseph T.; Lockwood, Danielle R.; Simon, Bruce R.; Vande Geest, Jonathan P.
A law of mixtures for transport properties in binary particulate composites
A connected-grain model was developed earlier to explain mechanical and thermal properties of porous ceramics and sedimentary rocks. We have now generalized this model for binary particulate composites, based on simulation of a connected-grain structure of individual components of the composites by randomly selecting individual grains and shrinking them. Repetition of this procedure results in a structure of a binary particulate composite that contains channels of individual components, through which transport occurs. We developed a generalized law of mixtures in which transport properties are expressed as scaling relationships that depend on the shrinking parameter expressed as an exponent. This parameter provides the skewness of the distribution of the grains. The model is compared with various transport properties of binary composites reported in the literature. In addition, the model is tested on YBa{sub 2}Cu{sub 3}O{sub x} superconductors and Ag composites that were fabricated in our laboratory and tested for electrical conductivity and elastic modulus. This test demonstrates how the model predicts two entirely different transport properties through their common microstructure and grain-size distribution. {copyright} {ital 1998 American Institute of Physics.}
Duncan, K.L.; Lodenquai, J.F. [Physics Department, University of the West Indies, Mona, Kingston 7 (Jamaica)] [Physics Department, University of the West Indies, Mona, Kingston 7 (Jamaica); Wagh, A.S.; Goretta, K.C. [Energy Technology Division, Argonne National Laboratory, Argonne, Illinois 60439-4838 (United States)] [Energy Technology Division, Argonne National Laboratory, Argonne, Illinois 60439-4838 (United States)
Assessment of geometrical and transport properties of a fibrous C/C composite preform as
of carbon or ceramic fibres (SiC, Al2O3...) linked together by a carbon or ceramic matrix. The association1 Assessment of geometrical and transport properties of a fibrous C/C composite preform. Vignoles░*, Olivia Coindreau░, Azita Ahmadi$ , Dominique Bernard# ░ Laboratoire des Composites Thermo
Boyer, Edmond
Electronic structure and quantum transport properties of trilayers formed from graphene and boron nitride
. Positioning gra- phene in proximity to hexagonal boron nitride (h-BN), which has a lattice constant similarElectronic structure and quantum transport properties of trilayers formed from graphene and boron nitride Xiaoliang Zhong,a Rodrigo G. Amorim,a Ralph H. Scheicher,b Ravindra Pandey*a and Shashi P. Karnac
Pandey, Ravi
Transport Properties and Performance of Polymer Electrolyte Membranes for the Hybrid Sulfur Electrolyzer
Transport Properties and Performance of Polymer Electrolyte Membranes for the Hybrid Sulfur and SO2 crossover in the hybrid sulfur cycle electrolyzer were quantified for a poly phenylene -based SO2 to the hydrogen stream, and result in a loss of sulfur from the system. Recent research has
Weidner, John W.
Measurements of water uptake and transport properties in anion-exchange membranes
uptake at each measured temperature is correlated in terms of the relative humidity. Like in Nafion as that of the Nafionę membrane. The measured mass-transfer coefficient of water at the cathode catalyst layer. In developing acid proton electrolyte membrane fuel cells (PEMFCs), the water uptake and transport properties
Zhao, Tianshou
Modulation of Drug Transport Properties by Multicomponent Diffusion in Surfactant Aqueous Solutions
Modulation of Drug Transport Properties by Multicomponent Diffusion in Surfactant Aqueous Solutions diffusion. A multicomponent diffusion study on drug-surfactant-water ternary mixtures is reported here of tyloxapol concentration, and drug-surfactant thermodynamic interactions using the two-phase partitioning
Annunziata, Onofrio
Magnetic and Electrical Transport Properties of Cobalt and Iron Granular Solids
The present work was undertaken in an attempt to comprehensively investigate the magnetic and electrical transport properties of granular solids with emphasis on the origin of the high coercivity and giant magnetoresistance. Co and Fe granules were grown in a number of ceramic and metallic, non-magnetic media, such as BN, SiO _2, Cu, and Ag, via the magnetron sputtering deposition
Antonia Tsoukatos
Carrier transport properties in single-walled carbon nanotubes studied by photoluminescence spectroscopy
Carrier transport properties in single-walled carbon nanotubes studied by photoluminescence. We have investigated the photoluminescence (PL) of in individual single-walled carbon nanotubes-field dependence of PL intensity. Time-resolved photoluminescence of SWNTs dispersed in surfactant solution has
Maruyama, Shigeo
Unique Structural and Transport Properties of Molybdenum Chalcohalide Nanowires Igor Popov,1
Unique Structural and Transport Properties of Molybdenum Chalcohalide Nanowires Igor Popov,1 Teng numbers: 81.05.Zx, 61.46.├┐w, 68.65.├┐k, 73.22.├┐f Chalcohalides of molybdenum and other transition met- als
Electronic transport properties of zigzag carbon- and boron-nitride-nanotube heterostructures
NASA Astrophysics Data System (ADS)
Using first-principles density functional theory and non-equilibrium Green's function formalism for quantum transport calculation, we have investigated the electronic transport properties of heteronanotubes by joining a zigzag (6,0) carbon nanotube and a zigzag (6,0) boron nitride nanotube with different atomic compositions and joint configurations. Our results show that the atomic composition and joint configuration affect strongly the electronic transport properties. Obvious negative differential resistance behavior and large rectifying behavior are obtained in the heterostructure with certain composition and joint configuration. Moreover, tube length and tube radius can affect strongly the observed NDR and rectifying behaviors. The observed negative differential resistance and rectifying behaviors are explained in terms of the evolution of the transmission spectrum with applied bias combined with molecular projected self-consistent Hamiltonian states analysis.
Zhao, P.; Liu, D. S.; Zhang, Y.; Su, Y.; Liu, H. Y.; Li, S. J.; Chen, G.
Carrier Transport Properties of p-Type Silicon-Metal Silicide Nanocrystal Composite Films
NASA Astrophysics Data System (ADS)
In this study, we synthesized p-type nanocomposite films consisting of Si-nickel silicide and Si-molybdenum silicide nanocrystals and measured the temperature dependence of their electrical properties. To evaluate grain boundary potential barrier height, we developed a theoretical model taking into account the effect of ionized impurities, acoustic phonons, and grain boundaries. The potential barrier height was sufficiently low not to substantially affect carrier transport in the Si-nickel silicide composite film. Carrier transport in the Si-molybdenum silicide composite film was found to be affected by a scattering mechanism not included in this model. Thus, the transition metal significantly affects carrier transport and the thermoelectric properties of Si-metal silicide nanocomposite films.
Ohishi, Yuji; Miyazaki, Yoshinobu; Muta, Hiroaki; Kurosaki, Ken; Yamanaka, Shinsuke; Uchida, Noriyuki; Tada, Tetsuya
Effect of stabilizer on dynamic thermal transport property of ZnO nanofluid.
In this paper, we investigate the effect of adding a stabilizer on the dynamic thermal properties of ZnO nanofluid (containing 5 to 10 nm diameter of ZnO nanocrystals) measured using a 3? method. Addition of the stabilizer leads to the stabilization of the nanofluid and also substantial reduction of the enhancement of thermal transport compared to that seen in the bare ZnO nanofluid. This also alters the frequency dependence of the thermal transport and the characteristic time scale associated with it. It is suggested that the addition of the stabilizer inhibits the thermodiffusion-assisted local aggregation thus leading to substantial reduction of the enhancement of thermal transport properties of the bare nanofluid as proposed in some recent models, and this also alters the characteristic time scales by altering the scale of aggregation. PMID:23497347
Neogy, Rajesh Kumar; Raychaudhuri, Arup Kumar
Flow and transport in unsaturated fractured rock: effects of multiscale heterogeneity of hydrogeologic properties.
The heterogeneity of hydrogeologic properties at different scales may have different effects on flow and transport processes in a subsurface system. A model for the unsaturated zone of Yucca Mountain, Nevada, is developed to represent complex heterogeneity at two different scales: (1) layer scale corresponding to geologic layering and (2) local scale. The layer-scale hydrogeologic properties are obtained using inverse modeling, based on the available measurements collected from the Yucca Mountain site. Calibration results show a significant lateral and vertical variability in matrix and fracture properties. Hydrogeologic property distributions in a two-dimensional, vertical cross-section of the site are generated by combining the average layer-scale matrix and fracture properties with local-scale perturbations generated using a stochastic simulation method. The unsaturated water flow and conservative (nonsorbing) tracer transport through the cross-section are simulated for different sets of matrix and fracture property fields. Comparison of simulation results indicates that the local-scale heterogeneity of matrix and fracture properties has a considerable effect on unsaturated flow processes, leading to fast flow paths in fractures and the matrix. These paths shorten the travel time of a conservative tracer from the source (repository) horizon in the unsaturated zone to the water table for small fractions of total released tracer mass. As a result, the local-scale heterogeneity also has a noticeable effect on global tracer transport processes, characterized by an average breakthrough curve at the water table, especially at the early arrival time of tracer mass. However, the effect is not significant at the later time after 20% tracer mass reaches the water table. The simulation results also verify that matrix diffusion plays an important role in overall solute transport processes in the unsaturated zone at Yucca Mountain. PMID:12498572
Zhou, Quanlin; Liu, Hui-Hai; Bodvarsson, Gudmundur S; Oldenburg, Curtis M
Transpacific transport and evolution of the optical properties of Asian dust
NASA Astrophysics Data System (ADS)
Five years of CALIPSO lidar layer products are used to study transpacific transport of Asian dust. We focus on possible changes to dust intrinsic optical properties during the course of transport, with specific emphasis on changes to particulate depolarization ratio (PDR). PDR distributions for Asian dust transported across the Pacific are compared to previously reported PDR distributions for African dust transported across the Atlantic. African dust shows a slight decreasing trend in PDR during westward transport across the Atlantic during its most active long-range transport season in summer. Asian dust, on the other hand, shows some spatial variability in PDR over the Pacific during its most active long-range transport season in spring. The dust PDR is generally smaller over the ocean than over the Tarim basin and nearby downwind regions. PDR also shows a decreasing trend with latitude moving northward toward the Arctic, together with an increasing trend in the dust aerosol optical depth (AOD) when passing over polluted Asian regions. Possible explanations include (i) the mixing of dust externally or internally with other types of aerosol over the heavily developed industrial regions in East Asia, and (ii) the downstream mixing of dust plumes from different source regions (i.e., Tarim and Gobi). Dust from different source regions exhibits relatively large differences in PDR, with mean values of 0.34▒0.07, 0.28▒0.06, and 0.30▒0.08, respectively, over the Tarim basin, Gobi Desert and Northwest African source regions. Different transport mechanisms are seen for African dust and Asian dust. Asian dust transport is originated by cold fronts and driven by westerly jets. In contrast, summer African transatlantic dust transport is driven by trade winds and is generally well confined in altitude in the free troposphere throughout the tropics and subtropics.
Liu, Zhaoyan; Fairlie, T. Duncan; Uno, Itsushi; Huang, Jingfeng; Wu, Dong; Omar, Ali; Kar, Jayanta; Vaughan, Mark; Rogers, Raymond; Winker, David; Trepte, Charles; Hu, Yongxiang; Sun, Wenbo; Lin, Bing; Cheng, Anning
Transport properties of silver-calcium doped lanthanum manganite
NASA Astrophysics Data System (ADS)
Electrical properties of silver-calcium doped lanthanum manganite (La0.5Ca0.5-xAgxMnO3 with 0.0 Cherif, B.; Rahmouni, H.; Smari, M.; Dhahri, E.; Moutia, N.; Khirouni, K. 2015-01-01
Cherif, B.; Rahmouni, H.; Smari, M.; Dhahri, E.; Moutia, N.; Khirouni, K.
Transport properties of hectorite based nanocomposite single ion conductors
NASA Astrophysics Data System (ADS)
The ionic conductivity and rheological properties of clay filled nanocomposite electrolytes are reported. These electrolytes, which have potential use in lithium-ion batteries, consist of lithium-exchanged hectorite, a 2:1 layered smectite clay, dispersed in ethylene carbonate (EC) or a mixture of EC+polyethylene glycol di-methyl ether (PEG-dm, 250 MW). All samples exhibit elastic, gel-like characteristics and room temperature conductivities of order 0.1 mS/cm. A maximum in conductivity is observed at about 25 wt.% clay concentration. A maximum in hectorite basal layer spacing is also observed in the same concentration range, suggesting a direct correlation between conductivity and layer spacing. The elastic modulus and yield stress increase by two orders of magnitude and the conductivity increases by one order of magnitude with increase in hectorite concentration from 5 to 25%, which indicates the significant influence of hectorite content in determining the characteristics of these single-ion conductors. The solvent composition plays a secondary role in this regard, with addition of PEG-dm to the base EC+hectorite electrolyte producing moderate improvement in conductivity. Similarly, the addition of PEG-dm to EC+hectorite affects an increase by only a factor of three in the elastic modulus and yield stress of the electrolyte.
Singhal, Ruchi Gupta; Capracotta, Michael D.; Martin, James D.; Khan, Saad A.; Fedkiw, Peter S.
Structural, magnetic, and transport properties of Permalloy for spintronic experiments
Permalloy (Ni{sub 80}Fe{sub 20}) is broadly used to prepare magnetic nanostructures for high-frequency experiments where the magnetization is either excited by electrical currents or magnetic fields. Detailed knowledge of the material properties is mandatory for thorough understanding its magnetization dynamics. In this work, thin Permalloy films are grown by dc-magnetron sputtering on heated substrates and by thermal evaporation with subsequent annealing. The specific resistance is determined by van der Pauw methods. Point-contact Andreev reflection is employed to determine the spin polarization of the films. The topography is imaged by atomic-force microscopy, and the magnetic microstructure by magnetic-force microscopy. Transmission-electron microscopy and transmission-electron diffraction are performed to determine atomic composition, crystal structure, and morphology. From ferromagnetic resonance absorption spectra the saturation magnetization, the anisotropy, and the Gilbert damping parameter are determined. Coercive fields and anisotropy are measured by magneto-optical Kerr magnetometry. The sum of the findings enables optimization of Permalloy for spintronic experiments.
Nahrwold, Gesche; Scholtyssek, Jan M.; Motl-Ziegler, Sandra; Albrecht, Ole; Merkt, Ulrich; Meier, Guido [Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Universitaet Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany)
Finslerian grounds for four--directional anisotropic kinematics
Upon straightforward four--directional extension of the special--relativistic two--dimensional transformations to the four--dimensional case we lead to convenient totally anisotropic kinematic transformations, which prove to reveal many remarkable group and invariance properties. Such a promise is shown to ground the basic manifold with the Finslerian fourth-root metric function to measure length of relativistic four--vectors. Conversion to the framework of relativistic four--momentum is also elucidated. The relativity principle is strictly retained. An interesting particular algebra for subtraction and composition of three-dimensional relative velocities is arisen. The correspondence principle is operative in the sense that at small relative velocities the transformations introduced tend approximately to ordinary Lorentzian precursors. The transport synchronization remains valid. Abbreviation RF will be used for (inertial) reference frames. {\\bf Keywords:} special relativity, invariance, Finsler geometry.
G. S. Asanov
Transport properties of room temperature ionic liquids from classical molecular dynamics
Room Temperature Ionic Liquids (RTILs) have attracted much of the attention of the scientific community in the past decade due the their novel and highly customizable properties. Nonetheless their high viscosities pose serious limitations to the use of RTILs in practical applications. To elucidate some of the physical aspects behind transport properties of RTILs, extensive classical molecular dynamics (MD) calculations are reported. Bulk viscosities and ionic conductivities of butyl-methyl-imidazole based RTILs are presented over a wide range of temperatures. The dependence of the properties of the liquids on simulation parameters, e.g. system size effects and choice of the interaction potential, is analyzed.
Oliviero Andreussi; Nicola Marzari
Transport properties of room temperature ionic liquids from classical molecular dynamics
Room Temperature Ionic Liquids (RTILs) have attracted much of the attention of the scientific community in the past decade due the their novel and highly customizable properties. Nonetheless their high viscosities pose serious limitations to the use of RTILs in practical applications. To elucidate some of the physical aspects behind transport properties of RTILs, extensive classical molecular dynamics (MD) calculations are reported. Bulk viscosities and ionic conductivities of butyl-methyl-imidazole based RTILs are presented over a wide range of temperatures. The dependence of the properties of the liquids on simulation parameters, e.g. system size effects and choice of the interaction potential, is analyzed.
Andreussi, Oliviero
Electronic Transport Properties of Transition Metal (Cu, Fe) Phthalocyanines Connecting to V-Shaped Zigzag Graphene Nanoribbons
NASA Astrophysics Data System (ADS)
Using nonequlilibrium Green's functions in combination with the density-functional theory, we investigate the spin transport properties of molecular junction based on metal (Cu, Fe) phthalocyanines between V-shaped zigzag-edged graphene nanorribons. The results show that the electronic transport properties mainly depend on the center transition metal. The negative differential resistance behaviors and spin splitting phenomenon can be observed.
Cui, Liling; Yang, Bingchu; Li, Xinmei; He, Jun; Long, Mengqiu
Transport Properties of La- doped SrTiO3 Ceramics Prepared Using Spark Plasma Sintering
NASA Astrophysics Data System (ADS)
In this work, thermoelectric transport properties of La-doped SrTiO3 ceramics prepared using conventional solid state reaction and spark plasma sintering have been investigated. Room temperature power factor of single crystal strontium titanate (SrTiO3), comparable to that of Bi2Te3, has brought new attention to this perovskite-type transition metal-oxide as a potential n-type thermoelectric for high temperature applications. Electronic properties of this model complex oxide, SrTiO3 (ABO3), can be tuned in a wide range through different doping mechanisms. In addition to A site (La-doped) or B site (Nb-doped) substitutional doping, introducing oxygen vacancies plays an important role in electrical and thermal properties of these structures. Having multiple doping mechanisms makes the transport properties of these perovskites more dependent on preparation parameters. The effect of these synthesis parameters and consolidation conditions on the transport properties of these materials has been studied.
Mehdizadeh Dehkordi, Arash; Bhattacharya, Sriparna; Tritt, Terry M.; Alshareef, Husam N.
The magnetic, electrical transport and thermal transport properties of Fe-based antipervoskite compounds ZnCxFe3
NASA Astrophysics Data System (ADS)
The effects of carbon concentration on the crystal structure, magnetic, and electrical/thermal transport properties of ZnCxFe3 (1.0 ? x ? 1.5) have been investigated systematically. Both the Curie temperature and the saturated magnetization decrease firstly and then reach saturation with increasing x. The investigations of heat capacity and resistivity indicate that ZnC1.2Fe3 displays a strongly correlated Fermi liquid behavior considering its Kadowaki-Woods ratio (ś0.64 a0). Around the ferromagnetic-paramagnetic phase transition (ś358 K), a reversible room-temperature magnetocaloric effect is observed. The relative cooling power (RCP) is ś164 J/kg (ś385 J/kg) with the magnetic field change ?H = 20 kOe (45 kOe). Considering the considerable large RCP, inexpensive and innoxious raw materials, ZnC1.2Fe3 is suggested to be a promising candidate for room-temperature magnetic refrigeration. Furthermore, the studies of thermal transport properties indicate that ZnC1.2Fe3 can also be a potential thermoelectric material with the dimensionless figure of merit (ZT = ?2T/?k) reaching its maximum of 0.0112 around 170 K.
Lin, S.; Wang, B. S.; Lin, J. C.; Huang, Y. N.; Hu, X. B.; Lu, W. J.; Zhao, B. C.; Tong, P.; Song, W. H.; Sun, Y. P.
Optical, physical and chemical properties of transported African mineral dust aerosols in the Mediterranean region
NASA Astrophysics Data System (ADS)
The transport of mineral dust aerosols is a global phenomenon with strong climate implications. Depending on the travel distance over source regions, the atmospheric conditions and the residence time in the atmosphere, various transformation processes (size-selective sedimentation, mixing, condensation of gaseous species, and weathering) can modify the physical and chemical properties of mineral dust, which, in turn, can change the dust's optical properties. The model predictions of the radiative effect by mineral dust still suffer of the lack of certainty of these properties, and their temporal evolution with transport time. Within the frame of the ChArMex project (Chemistry-Aerosol Mediterranean experiment, http://charmex.lsce.ipsl.fr/), two intensive airborne campaigns (TRAQA, TRansport and Air QuAlity, 18 June - 11 July 2012, and ADRIMED, Aerosol Direct Radiative Impact in the regional climate in the MEDiterranean region, 06 June - 08 July 2013) have been performed over the Central and Western Mediterranean, one of the two major transport pathways of African mineral dust. In this study we have set up a systematic strategy to determine the optical, physical and optical properties of mineral dust to be compared to an equivalent dataset for dust close to source regions in Africa. This study is based on airborne observations onboard the SAFIRE ATR-42 aircraft, equipped with state of the art in situ instrumentation to measure the particle scattering and backscattering coefficients (nephelometer at 450, 550, and 700 nm), the absorption coefficient (PSAP at 467, 530, and 660 nm), the extinction coefficient (CAPS at 530 nm), the aerosol optical depth (PLASMA at 340 to 1640 nm), the size distribution in the extended range 40 nm - 30 Ąm by the combination of different particle counters (SMPS, USHAS, FSSP, GRIMM) and the chemical composition obtained by filter sampling. The chemistry and transport model CHIMERE-Dust have been used to classify the air masses according to the dust origin and transport. Case studies of dust transport from known but differing origins (source regions in Tunisia, Algeria, and Mauritania) and at different times after transport, will be presented. Results will be compared to equivalent measurements over source regions interpreted in terms of the evolution of the particle size distribution, chemical composition and optical properties.
Denjean, Cyrielle; Di Biagio, Claudia; Chevaillier, Servanne; Gaimoz, Cķcile; Grand, Noel; Loisil, Rodrigue; Triquet, Sylvain; Zapf, Pascal; Roberts, Greg; Bourrianne, Thierry; Torres, Benjamin; Blarel, Luc; Sellegri, Karine; Freney, Evelyn; Schwarzenbock, Alfons; Ravetta, Franńois; Laurent, Benoit; Mallet, Marc; Formenti, Paola
Modulation of the electron transport properties in graphene nanoribbons doped with BN chains
Using density-functional theory and the non-equilibrium Green's function method, the electron transport properties of zigzag graphene nanoribbons (ZGNRs) doped with BN chains are studied by systematically calculating the energy band structure, density of states and the transmission spectra for the systems. The BN chains destroyed the electronic transport properties of the ZGNRs, and an energy gap appeared for the ZGNRs, and displayed variations from a metal to a wide-gap semiconductor. With an increase in the number of BN chains, the band gap increased gradually in the band structure and the transmission coefficient decreased near the Fermi surface. Additionally, the doping position had a significant effect on the electronic properties of the ZGNRs.
Liu, Wu; Zhang, Kaiwang, E-mail: email@example.com; Zhong, JianXin [Department of Physics, Xiangtan University, Xiangtan 411105 (China); Wang, Ru-Zhi, E-mail: email@example.com [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Liu, Li-Min, E-mail: email@example.com [Beijing Computational Science Research Centre, Beijing, 100084 (China)
Apparatus for measurements of transport properties of thin films under sulfur atmosphere at moderate temperatures
NASA Astrophysics Data System (ADS)
An experimental system able to simultaneously measure the electrical resistance and the thermopower of metallic and semiconducting thin films (with thicknesses from ~nm to ~Ąm) under sulfur atmosphere from room temperature up to 400?░C and total pressures >0.5¢1?mbar is designed and implemented. Calibration tests of the system were performed with palladium foils and films as well as p-type and n-type sulfide semiconducting films: iron disulfide and palladium monosulfide. Uncertainties of measured thermopower and resistance values are less than 10% and 5%, respectively. To check the capability of the system under sulfur atmosphere, in situ measurements of transport properties during sulfuration of palladium films were carried out. During the process, sulfur partial pressure and film temperature are accurately controlled. Apparatus may be used to determine the evolution of transport properties of different metal sulfides during their formation/decomposition processes, opening new pathways to investigate the thermoelectric properties of more complex thin film sulfides.
Clamagirand, J. M.; Ares, J. R.; Diaz-Chao, P.; Pascual, A.; Ferrer, I. J.; Sßnchez, C.
Gravitational stresses in anisotropic rock masses
This paper presents closed-form solutions for the stress field induced by gravity in anisotropic rock masses. These rocks are assumed to be laterally restrained and are modelled as a homogeneous, orthotropic or transversely isotropic, linearly elastic material. The analysis, constrained by the thermodynamic requirement that strain energy be positive definite, gives the following important result: inclusion of anisotropy broadens the range of permissible values of gravity-induced horizontal stresses. In fact, for some ranges of anisotropic rock properties, it is thermodynamically admissible for gravity-induced horizontal stresses to exceed the vertical stress component; this is not possible for the classical isotropic solution. Specific examples are presented to explore the nature of the gravity-induced stress field in anisotropic rocks and its dependence on the type, degree and orientation of anisotropy with respect to the horizontal ground surface. ?? 1987.
Amadei, B.; Savage, W.Z.; Swolfs, H.S.
Pollen dispersal over complex terrain: How does anisotropic airborne pollen transport affect interpretation of fossil pollen records? A case study in Northern Patagonia.
NASA Astrophysics Data System (ADS)
Accumulated pollen in stratified fossil reservoirs is used to infer temporal changes in vegetation composition. Transport and dispersal by winds are known to introduce large biases in the interpretation of polynic records. In order to calibrate the models used to infer information about past species distributions, human activities and climate, contemporary time series of polynic records are assessed and modelled. In this study we analyse measurements collected hourly in Bariloche, Argentina (41░ 10' S, 71░ 15' W, 850 masl) of the species Weinmannia trichosperma, a characteristic forest tree which grows only the western (Chilean) slopes of the Andes, but not on the eastern (Argentinian) slopes where the measurements were collected. Instead of the simplistic Gaussian plume mixing model that is usually employed by the palynological community, we apply a full 3D Lagrangian dispersion model to interpret the observations and assess the impact of long-range transport over the Andean mountain range. The Lagrangian calculation of the origins of the air masses (the "backward footprint") is consistent not only with the Chilean Weinmania pollen measurements but also with a set of species only found on the dryer steppe located to the east of the measurement site in Argentina. The agreement of the modelling results indicates that significant interpretation mistakes may arise from inconsistent transport treatment. We also discuss the further application of inverse trajectory modelling to the estimation of source intensity.
Pķrez, Claudio; Bianchi, MarĒa Martha; Gassmann, Marisa; Pisso, Ignacio
Magnetically anisotropic self similarity in plasma turbulence
NASA Astrophysics Data System (ADS)
We present measurements of the anisotropic scaling properties of inertial range magnetohydrodynamic plasma turbulence in the solar wind and show that high order moments of the fluctuations scale more steeply parallel to the magnetic field than perpendicular to it, in common with the power spectrum. We calculate structure function moments up to 4th order and find intermittency present in all directions. We demonstrate, however, that the scaling can be decomposed into independent dependencies on the moment and angle to the magnetic field. This suggests that the intermittent properties of the fluctuations are independent of the field-aligned anisotropy and supports the interpretation of a critically balanced cascade. Conveniently, this self similarity property makes it possible to consider separately the intermittent and anisotropic properties of magnetohydrodynamic turbulence.
Horbury, T. S.; Schekochihin, A.; Chen, C. H.; Wicks, R. T.