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Photoionization of atoms and molecules. [of hydrogen, helium, and xenon
NASA Technical Reports Server (NTRS)
Samson, J. A. R.
A literature review on the present state of knowledge in photoionization is presented. Various experimental techniques that have been developed to study photoionization, such as fluorescence and photoelectron spectroscopy, mass spectroscopy, are examined. Various atoms and molecules were chosen to illustrate these techniques, specifically helium and xenon atoms and hydrogen molecules. Specialized photoionization such as in positive and negative ions, excited states, and free radicals is also treated. Absorption cross sections and ionization potentials are also discussed.
High kinetic stability of HXeBr upon interaction with carbon dioxide: HXeBrĘĘĘCO2 complex in a xenon matrix and HXeBr in a carbon dioxide matrix.
Tsuge, Masashi; Berski, Slawomir; Stachowski, Radoslaw; Rõsõnen, Markku; Latajka, Zdzislaw; Khriachtchev, Leonid
We investigate the conditions when noble-gas hydrides can be found in real environments and report on the preparation and identification of the HXeBrĘĘĘCO(2) complex in a xenon matrix and HXeBr in a carbon dioxide matrix. The H-Xe stretching mode of the HXeBrĘĘĘCO(2) complex in a xenon matrix is observed at 1557 cm(-1), showing a spectral shift of +53 cm(-1) from the HXeBr monomer. The calculations at the CCSD(T)/aug-cc-pVTZ-PP(Xe,Br) level of theory give two stable structures for the HXeBrĘĘĘCO(2) complex with frequency shifts of +55 and +103 cm(-1), respectively. On the basis of the calculations, the experimentally observed band is assigned to the more stable structure with a "parallel" geometry. The HXeBr molecule was prepared in a carbon dioxide matrix and has the H-Xe stretching frequency of 1646 cm(-1), meaning a strong matrix shift and stabilization of the H-Xe bond. The deuterated species DXeBr in a carbon dioxide matrix absorbs at 1200 cm(-1). This is the first case where a noble-gas hydride is prepared in a molecular solid. The thermal stabilities of HXeBr and HXeBrĘĘĘCO(2) complex in a xenon matrix and HXeBr in a carbon dioxide matrix were examined. We have found a high thermal stability of HXeBr in carbon dioxide ice (at least up to 100 K), i.e., under conditions that may occur in nature. PMID:22494007
Migration of defect clusters and xenon-vacancy clusters in uranium dioxide
Chen, Dong; Gao, Fei; Deng, Huiqiu; Hu, Wangyu; Sun, Xin
The possible transition states, minimum energy paths and migration mechanisms of defect clusters and xenon-vacancy defect clusters in uranium dioxide have been investigated using the dimer and the nudged elastic-band methods. The nearby O atom can easily hop into the oxygen vacancy position by overcoming a small energy barrier, which is much lower than that for the migration of a uranium vacancy. A simulation for a vacancy cluster consisting of two oxygen vacancies reveals that the energy barrier of the divacancy migration tends to decrease with increasing the separation distance of divacancy. For an oxygen interstitial, the migration barrier for the hopping mechanism is almost three times larger than that for the exchange mechanism. Xe moving between two interstitial sites is unlikely a dominant migration mechanism considering the higher energy barrier. A net migration process of a Xe-vacancy pair containing an oxygen vacancy and a xenon interstitial is identified by the NEB method. We expect the oxygen vacancy-assisted migration mechanism to possibly lead to a long distance migration of the Xe interstitials in UO2. The migration of defect clusters involving Xe substitution indicates that Xe atom migrating away from the uranium vacancy site is difficult.
From carbon dioxide to C{sub 2} organic molecules
Gong, J.K.; Wright, C.A.; Thorn, M. [Southeast Missouri State Univ., Cape Girardeau, MO (United States)] [and others
Research on the conversion of carbon dioxide into C{sub 2} or higher organic molecules has received much attention in recent years. The key to the success of this research is carbon-carbon coupling. This paper reports the modified synthesis of a nickel carbon dioxide complex, (Cy{sub 3}P){sub 2}NiCO{sub 2}, (Cy = cyclohexane) and the {open_quotes}Wittig Reaction{close_quotes} of this coordinated nickel carbon dioxide complex. The formed nickel ketene complex, (Cy{sub 3}P){sub 2}Ni[{eta}{sup 2}- (C,O)-CH{sub 2}=C=O], has an unusual {eta}{sub 2}-C,O bonding mode instead of the normal {eta}{sup 2}-C,C for the later transition metals. The pathway of this {open_quotes}Witting Reaction{close_quotes} is an unprecedented example for a transition metal carbon dioxide complex.
Ab initio potential energy surface for the carbon dioxide molecule pair and thermophysical properties of dilute carbon dioxide gas
NASA Astrophysics Data System (ADS)
Hellmann, Robert
A four-dimensional intermolecular potential energy surface (PES) for two rigid carbon dioxide molecules was determined from quantum-chemical ab initio calculations. Interaction energies for 1229 CO2-CO2 configurations were computed at the CCSD(T) level of theory using basis sets up to aug-cc-pVQZ supplemented with bond functions. An analytical site-site potential function with seven sites per CO2 molecule was fitted to the interaction energies. The PES was validated by calculating the second virial coefficient as well as viscosity and thermal conductivity in the dilute-gas limit.
Enantioselective Small Molecule Synthesis by Carbon Dioxide Fixation using a Dual Br°nsted Acid/Base Organocatalyst.
Vara, Brandon A; Struble, Thomas J; Wang, Weiwei; Dobish, Mark C; Johnston, Jeffrey N
Carbon dioxide exhibits many of the qualities of an ideal reagent: it is nontoxic, plentiful, and inexpensive. Unlike other gaseous reagents, however, it has found limited use in enantioselective synthesis. Moreover, unprecedented is a tool that merges one of the simplest biological approaches to catalysis-Br°nsted acid/base activation-with this abundant reagent. We describe a metal-free small molecule catalyst that achieves the three component reaction between a homoallylic alcohol, carbon dioxide, and an electrophilic source of iodine. Cyclic carbonates are formed enantioselectively. PMID:26039818
Xenon-Photosensitized Formation of Metastable Nitrogen
William M. Jackson; Milton D. Scheer
Metastable nitrogen molecules are produced by collision with xenon atoms excited with 1470- angstrom radiation. The photolytically excited species were detected by measuring the rate at which electrons were ejected from a gold surface. Hydrogen was shown to be more efficient than helium in quenching the photo-excited xenon atoms.
Xenon-Photosensitized Formation of Metastable Nitrogen.
Jackson, W M; Scheer, M D
Metastable nitrogen molecules are produced by collision with xenon atoms excited with 1470-A radiation. The photolytically excited species were detected by measuring the rate at which electrons were ejected from a gold surface. Hydrogen was shown to be more efficient than helium in quenching the photo-excited xenon atoms. PMID:17819421
Properties of excited xenon atoms in a plasma display panel
Han S. Uhm; Byoung H. Hong; Phil Y. Oh; Eun H. Choi
The luminance efficiency of a plasma display panel is directly related to the vacuum ultraviolet (VUV) light that is emitted from excited xenon (Xe) atoms and molecules. It is therefore necessary to investigate the properties of excited xenon atoms. This study presents experimental data associated with the behavior of excited xenon atoms in a PDP discharge cell and compares the
Noble-gas-induced disproportionation reactions: facile superoxo-to-peroxo conversion on chromium dioxide.
Zhao, Yanying; Su, Jing; Gong, Yu; Li, Jun; Zhou, Mingfei
Laser-evaporated chromium atoms are shown to insert into dioxygen to form CrO 2 in solid argon. Annealing allows diffusion and reactions to form (eta (2)-O 2) 2CrO 2, which is characterized as [(O 2 (-)) 2(CrO 2) (2+)], a side-on bonded disuperoxo-chromium dioxide complex. The (eta (2)-O 2) 2CrO 2 complex further reacts with xenon atom doped in solid argon to give (eta (1)-OO)(eta (2)-O 2)CrO 2(Xe), which can be regarded as an O 2 molecule weakly interacting with [(O 2) (2-)(CrO 2) (2+)Xe], a side-on bonded peroxo-chromium dioxide-xenon complex. The results indicate surprisingly that xenon atom induces a disproportionation reaction from superoxo to peroxo and dioxygen complex. PMID:18729425
Dynamic (hyper)polarizabilities of the sulphur dioxide molecule: coupled cluster calculations including vibrational corrections.
Naves, EmĒlio S; Castro, Marcos A; Fonseca, Tertius L
In this work we report results for dynamical (hyper)polarizabilities of the sulphur dioxide molecule with inclusion of vibrational corrections. The electronic contributions were computed analytically at the single and double coupled cluster level through response theories for the frequencies 0, 0.0239, 0.0428, 0.0656, 0.0720, and 0.0886 hartree. Contributions of the connected triple excitations to the dynamic electronic properties were also estimated through the multiplicative correction scheme. Vibrational corrections were calculated by means of the perturbation theoretical method. The results obtained show that the zero point vibrational correction is very small for all properties studied while the pure vibrational correction is relevant for the dc-Pockels effect, intensity dependent refractive index, and dc-Kerr effect. For these nonlinear optical processes, the pure vibrational corrections represent approximately 75%, 13%, and 6% of the corresponding electronic contributions for the higher frequencies quoted. The results presented for the polarizability are in good agreement with experimental values available in the literature. For the hyperpolarizabilities we have not obtained experimental results with precision sufficient for comparison. PMID:22239777
Exciton mechanism for radical formation in a xenon matrix during bombardment of the surface with metastable xenon and argon atoms
Grigor'ev, E.I.; Pshezhetskii, S.Y.; Trakhtenberg, L.I.
This article describes how the bombardment at 77 degrees K of the surface of a xenon matrix containing 1-10 mole % methane or propane with metastable argon or xenon atoms leads to the formation of methyl or propyl radicals. The results are explained on the basis of an exciton mechanism of radical formation. It was calculated that the radius for the capture of a triplet xenon exciton by a methane molecule is 0.25 nm.
Studies of Rydberg Atomic Xenon and Molecular Hydrogen
Liang-Guo Wang
This work has studied the Rydberg states of atomic xenon and molecular hydrogen by laser spectroscopy of a thermal metastable atomic or molecular beam. Both xenon atoms and H(,2) molecules have structured cores, resulting in similarities of their spectra. The existence of metastable states in both systems allows us to use the same experimental techniques and almost the same experimental
Molecular dynamics simulation of vibrational energy relaxation of highly excited molecules in fluids. III. Equilibrium simulations of vibrational energy relaxation of azulene in carbon dioxide
C. Heidelbach; V. S. Vikhrenko; D. Schwarzer; I. I. Fedchenia; J. Schroeder
The expressions for vibrational energy relaxation (VER) rates of polyatomic molecules in terms of equilibrium capacity time correlation functions (TCFs) derived in the first paper of this series [J. Chem. Phys. 110, 5273 (1999)] are used for the investigation of VER of azulene in carbon dioxide at low (3.2 MPa) and high (270 MPa) pressure. It is shown that for
The incorporation and migration of a single xenon atom in ceria
NASA Astrophysics Data System (ADS)
Miao, Yinbin; Chen, Wei-Ying; Oaks, Aaron; Mo, Kun; Stubbins, James F.
The behavior of xenon gas is crucial for the performance of nuclear fuel materials. We report molecular statics calculation results for the characteristics of a single xenon atom in cerium oxide, a non-radioactive surrogate of uranium dioxide. A variety of possible xenon incorporation sites, including the octahedral interstitial position, single-Ce-vacancy clusters, and double-Ce-vacancy clusters were considered. The binding energies and corresponding xenon incorporation energies were computed to reveal the preferred xenon positions in ceria. Different migration mechanisms of single xenon atoms were found to be involved with various incorporation sites. The energy barriers of all possible migration pathways were calculated. Only the mobility of single xenon atoms in the double-Ce-vacancy sites, which is due to the vacancy-assisted xenon migration, can account for the xenon diffusivity implied by bubble formation observed in experiments. The results also validated the role of ceria as a reliable surrogate of uranium dioxide in studies involving xenon gas.
Ionization of water and carbon dioxide molecules by electron impact near threshold
A. N. Zavilopulo; F. F. Chipev; O. B. Shpenik
A measurement technique is described and relative cross-sections for direct and dissociative ionization of H2O and CO2 molecules by electron impact near the threshold are obtained. The experiment is performed by a setup with mass separation of the ions by a monopole mass spectrometer and their detection by a secondary electron multiplicator. The energy dependencies of the cross-sections for the
Ionization of nitrogen, oxygen, water, and carbon dioxide molecules by near-threshold electron impact
A. N. Zavilopulo; F. F. Chipev; O. B. Shpenik
An experimental technique for measuring the cross sections of direct and dissociative ionization of N2, O2, H2O, and CO2 molecules by electron impact in the near-threshold energy range is described. The setup used in the experiments allows mass\\u000a separation of ions with a monopole mass spectrometer. It is shown that such a setup can be used to advantage in separation
Quenching rate constants for metastable argon, krypton, and xenon atoms by fluorine containing molecules and branching ratios for metastable XeF and KrF formation
J. E. Velazco; J. H. Kolts; D. W. Setser
Total quenching rate constants and branching ratios for reactions of fluorine-containing molecules with metastable Xe and Kr are reported along with rate constants for metastable Ar reactions with fluorine- and other halogen-containing molecules. The rate constants were determined by the flowing-afterglow technique, and the branching ratios were measured by comparing total integrated excimer emission intensities from a given reaction with
Aggregation of amphiphilic molecules in supercritical carbon dioxide: A small angle X-ray scattering study
Fulton, J.L.; Pfund, D.M. [Pacific Northwest Lab., Richland, WA (United States); McClain, J.B.; Romack, T.J.; Maury, E.E.; Combes, J.R.; Samulski, E.T.; DeSimone, J.M. [Univ. of Noth Carolina, Chapel Hill, NC (United States); Capel, M. [Brookhaven National Lab., Upton, NY (United States)
Highly soluble amphiphilic materials are shown to form aggregates in supercritical CO{sub 2}. The strategy for synthesis of these amphiphilic molecules involves incorporating CO{sub 2}-philic segments that, for this study, are perfluorinated alkyl chains. These CO{sub 2} -philic regions function like the hydrocarbon tails of conventional surfactant molecules used in liquid organic solvents. Synthesis and characterization of three different CO{sub 2} amphiphiles are reported. Subsequent small angle X-ray scattering (SAXS) measurements were used to characterize the aggregation of these materials in supercritical CO{sub 2}. Each of the three amphiphiles studied showed a different type of aggregation behavior. A graft copolymer consisting of a CO{sub 2}-philic backbone and CO{sub 2}-phobic grafts associated into a micellar structure in the presence of water to promote hydrogen bonding. These aggregates contain approximately 600 grafts in the core. The commercially available surfactant perfluoroalkylpoly( ethylene oxide), or F(CF{sub 2}){sub 6-10}CH{sub 2} CH{sub 2}O(CH{sub 2}CH{sub 2}O){sub 3-8}H, forms classic reverse micelle structures having radii of about 84 A under the conditions of high pressure required to solubilize the material. A third amphiphile, the semifluorinated alkane diblock molecule F(CF{sub 2}){sub 10}(CH{sub 2}){sub 10}H, may form small aggregates of at most 4 unimers per aggregate. 41 refs., 10 figs., 1 tab.
The radiation-induced chemistry in solid xenon matrices
NASA Astrophysics Data System (ADS)
Feldman, V. I.; Kobzarenko, A. V.; Orlov, A. Y.; Sukhov, F. F.
The paper presents an overview of recent studies of the radiation-chemical transformations of guest molecules in solid xenon induced by fast electrons and x-ray irradiation. Specific features of the experimental approach based on the combination of matrix isolation IR and EPR spectroscopy are briefly outlined (with a particular emphasis on monoisotopic and isotopically enriched xenon matrices). The results reveal rich and diverse radiation-induced chemistry in solid xenon, which is considered in the following major aspects: (1) matrix-induced and matrix-assisted transformations of the primary guest radical cations; (2) production and dynamics of hydrogen atoms; (3) formation of xenon hydrides. Finally, preliminary results on the radiation-induced generation of oxygen atoms and ions in solid xenon are presented.
NASA Technical Reports Server (NTRS)
The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The sample cell at the heart of CVX-2 will sit inside a thermostat providing three layers of insulation. The cell itself comprises a copper body that conducts heat efficiently and smoothes out thermal variations that that would destroy the xenon's uniformity. Inside the cell, the oscillating screen viscometer element is supported between two pairs of electrodes that deflect the screen and then measure screen motion.
NASA Technical Reports Server (NTRS)
The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Because xenon near the critical point will collapse under its own weight, experiments on Earth (green line) are limited as they get closer (toward the left) to the critical point. CVX in the microgravity of space (red line) moved into unmeasured territory that scientists had not been able to reach.
Solid xenon radiation detectors
NASA Astrophysics Data System (ADS)
Dolinski, Michelle J.
Cryogenic liquid xenon detectors have become a popular technology in the search for rare events, such as dark matter interactions and neutrinoless double beta decay. The power of the liquid xenon detector technology is in the combination of the ionization and scintillation signals, resulting in particle discrimination and improved energy resolution over the ionization-only signal. The improved energy resolution results from a unique anti-correlation phenomenon that has not been described from first principles. Solid xenon bolometers, under development at Drexel University, are expected to have excellent counting statistics in the phonon channel, with energy resolution of 0.1% or better. This additional energy channel may offer the final piece of the puzzle in understanding liquid xenon detector energy response. Supported by a grant from the Charles E. Kaufman Foundation.
NASA Technical Reports Server (NTRS)
The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of liquid xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Resembling a tiny bit of window screen, the oscillator at the heart of CVX-2 will vibrate between two pairs of paddle-like electrodes. The slight bend in the shape of the mesh has no effect on the data. What counts are the mesh's displacement in the xenon fluid and the rate at which the displacement dampens. The unit shown here is encased in a small test cell and capped with a sapphire windown to contain the xenon at high pressure.
NASA Technical Reports Server (NTRS)
The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Shear thirning will cause a normally viscous fluid -- such as pie filling or whipped cream -- to deform and flow more readily under high shear conditions. In shear thinning, a pocket of fluid will deform and move one edge forward, as depicted here.
NASA Technical Reports Server (NTRS)
The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2001 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The thermostat for CVX sits inside the white cylinder on a support structure that is placed inside a pressure canister. A similar canister holds the electronics and control systems. The CVX-2 arrangement is identical. The principal investigator is Dr. Robert F. Berg (not shown) of the National Institutes of Standards and Technology, Gaithersburg, MD. This is a detail view of MSFC 0100143.
NASA Astrophysics Data System (ADS)
Marti, K.; Kim, J. S.; Lavielle, B.; Pellas, P.; Perron, C.
The authors report xenon isotopic abundances observed in the stepwise release of noble gases in a high-purity metal separate of the Forest Vale (H4) chondrite. They identify a 244Pu-derived fission component, due to recoils into the metal, a cosmic-ray-produced spallation component and a new trapped component which is isotopically distinct from known solar system reservoirs. The authors discuss several processes which might account for observed isotopic shifts and conclude that the signature of FVM xenon may provide clues regarding the origin of chondritic metal.
Monitoring Xenon in the Breathing Circuit with a Thermal Conductivity Sensor
Martin Luginb³hl; Rolf Lauber; Peter Feigenwinter; Alex M. Zbinden
Objective. To test the accuracy of a thermal conductivityxenon sensor inĀvitroand inĀvivoand totest the effect of xenon on other anesthetic gas analyzers as determinedby aĀmass spectrometry gold standard. Methods.The xenonconcentration was measured with a prototype of a thermal conductivitysensor and a mass spectrometer inĀvitroand in6Āpatients. Further inĀvitroexperiments determinedthe impact of xenon on the measurements of oxygen, carbon dioxide anddesflurane with
Measurements and correlation of effect of cosolvents on the solubilities of complex molecules in supercritical carbon dioxide
Min Jeong Noh; Tae Gyun Kim; In Kwon Hong; Ki-Pung Yoo
A new transparent microscale circulation-type high pressure equilibrium cell with on-line sampling was devised. With this\\u000a apparatus, experimental solubility of molecularly complex species such as steroids (cholesterol, stigmasterol and ergosterol)\\u000a and fatty acids (palmitic acid and stearic acid) in supercritical carbon dioxide(sc-C02) were measured. Also, to find an appropriate substance for enhancing both the polarity and the solubility power of
NASA Technical Reports Server (NTRS)
Bergm Robert F.; Moldover, Michael R.; Yao, Minwu; Zimmerli, Gregory A.
We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids such as molten plastics or ketchup, near the critical point of xenon. The data span a wide range of dimensionless shear rate: the product of the shear rate and the relaxation time of critical fluctuations was greater than 0.001 and was less than 700. As predicted by theory, shear thinning occurred when this product was greater than 1. The measurements were conducted aboard the Space Shuttle Columbia to avoid the density stratification caused by Earth's gravity.
Raftery, M.D.
Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping {sup 129}Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the {sup 131}Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.
Raftery, M.D.
Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping [sup 129]Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the [sup 131]Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.
Infrared-Microwave Double Resonance Probing of the Population-Depopulation of Rotational States in the Nitrogen Dioxide and the Sulfur Dioxide Molecules.
NASA Astrophysics Data System (ADS)
Khoobehi, Bahram
A 10.6 (mu)m CO(,2) laser operating a power range S P 200 watts was used to pump some select vibrational transitions in the NO(,2) molecule while monitoring the rotational transitions (9(,1,9) (--->) 10(,0,10)), (23(,2,22) (--->) 24(,2,23)), (40(,2,38) (--->) 39(,3,37)) in the (0, 0, 0) vibrational level and the (8(,0,8) (--->) 7(,1,7)) rotational transition in the (0, 1, 0) vibrational level. These rotational transitions were monitored by microwave probing to determine how the population of states in the rotational manifolds were being altered by the laser. Coincidences between some components of the (nu)(,3)-(nu)(,2) band of NO(,2) and the CO(,2) infrared laser lines in the 10 (mu)m region appeared to be responsible for the strong interaction between the continuous laser beams and the molecular states. The same CO(,2) laser was used to establish the nature of the coupling with the SO(,2). There is a weak coupling of the R-branch of the CO(,2) laser at 986 cm(' -1) to the SO(,2) molecule. The laser is made incident upon the SO(,2) while the rotational transitions (4(,0,4) (--->) 3(,1,3)), (8(,1,7) (--->) 7(,2,6)), (8(,2,6) (- -->) 9(,1,9)), (15(,4,12) (--->) 16(,3,13)), (16(,2,14) (--->) 17(,1,7)), (17(,2,16) (--->) 16(,3,13)), (21(,3,19) (--->) 20(,4,16)), (21(,5,17) (--->) 22(,4,18)), (30(,5,25) (--->) 29(,6,24)), (31(,5,25) (--->) 30(,6,24)), (35(,6,30) (--->) 34(,7,27)) and (51(,9,43) (--->) 50(,10,40)) in the (0, 0, 0) vibrational level, the (19(,2,18) (--->) 18(,3,15)), (23(,2,22) (--->) 22(,3,19)) rotational transitions in the (0, 1, 0) vibrational level and the (26(,6,20) ( --->) 27(,5,23)) rotational transition in the (0, 0, 1) vibrational level are monitored. There appear to be three basic behaviour patterns we denote as being regular, phase changing, and irregular intensity changing in character. Characteristic rate curves for population-depopulation changes in the chosen rotational levels listed above were found for various power levels from the laser pump and are presented in this work. Rate coefficients for intensity decay for various laser powers were calculated from experimental data and are presented.
Studies of Rydberg atomic xenon and molecular hydrogen
Wang, L.G.
The Rydberg states of atomic xenon and molecular hydrogen were studied by laser spectroscopy of a thermal metastable atomic or molecular beam. Both xenon atoms and H/sub 2/ molecules have structured cores, resulting in similarities of their spectra. The existence of metastable states in both systems allows use of the same experimental techniques and almost the same experimental arrangement to carry out studies in both xenon and in H/sub 2/. Using the metastable-beam laser-excitation technique, even-parity bound np(1/2)/sub 1/ and nf(3/2)/sub 1/ Rydberg series in xenon to n = 51 and n = 82, respectively, were observed. Both even- and odd-parity autoionizing Rydberg states were also studied extensively. Unlike most of the previous work done on H/sub 2/, the author observed and measured the bound and autoionizing triplet nd Rydberg states of para-and ortho-H/sub 2/- (previous experimental data on H/sub 2/ were mostly that of p states of singlet H/sub 2/). In studies of Rydberg states in H/sub 2/, he carried out calculations based on a long-range ab initio Hund's case-d model to predict the transition frequencies and to identify observed transition peaks. Ten Rydberg series of more than 400 levels in atomic xenon and seven triplet Rydberg series of 150 levels in molecular hydrogen were observed and measured in this work.
NASA Astrophysics Data System (ADS)
Zahnle, K. J.
Xenon has been regarded as an important goal of many proposed missions to Venus. This talk is intended to explain why. Despite its being the heaviest gas found in natural planetary atmospheres, there is more evidence that Xe escaped from Earth than for any element apart from helium: (i) Atmospheric Xe is very strongly mass fractionated (at about 4% per amu) from any known solar system source. This suggests fractionating escape that preferentially left the heavy Xe isotopes behind. (ii) Xe is underabundant compared to Kr, a lighter noble gas that is not strongly mass fractionated in air. (iii) Radiogenic Xe is strongly depleted by factors of several to ~100 compared to the quantities expected from radioactive decay of primordial solar system materials. In these respects Xe on Mars is similar to Xe on Earth, but with one key difference: Xe on Mars is readily explained by a simple process like hydrodynamic escape that acts on an initially solar or meteoritic Xe. This is not so for Earth. Earth's Xe cannot be derived by an uncontrived mass fractionating process acting on any known type of Solar System Xe. Earth is a stranger, made from different stuff than any known meteorite or Mars or even the Sun. Who else is in Earth's family? Comets? We know nothing. Father Zeus? Data from Jupiter are good enough to show that jovian Xe is not strongly mass-fractionated but not good enough to determine whether Jupiter resembles the Earth or the Sun. Sister Venus? Noble gas data from Venus are incomplete, with Kr uncertain and Xe unmeasured. Krypton was measured by several instruments on several spacecraft. The reported Kr abundances are discrepant and were once highly controversial. These discrepancies appear to have been not so much resolved as forgotten. Xenon was not detected on Venus. Upper limits were reported for the two most abundant xenon isotopes 129Xe and 132Xe. From the limited data it is not possible to tell whether Venus's affinities lie with the solar wind, or with the chondrites, with Earth, or with none of the above. Modern spacecraft mass spectrometers are at least 100-fold more sensitive to noble gases. Sending such an instrument to Venus may be the last best hope for decrypting what Earth's noble gases have been trying to tell us.
Critical Viscosity of Xenon investigators
NASA Technical Reports Server (NTRS)
Dr. Dr. Robert F. Berg (right), principal investigator and Dr. Micheal R. Moldover (left), co-investigator, for the Critical Viscosity of Xenon (CVX/CVX-2) experiment. They are with the National Institutes of Standards and Technology, Gaithersburg, MD. The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Although it does not easily combine with other chemicals, its viscosity at the critical point can be used as a model for a range of chemicals.
Electron excitation coefficients in xenon
A. Strinic; G. Malovic; J. Bozin; Z. Lj. Petrovic
We have performed measurements of excitation coefficients for electron swarms in xenon for the range of E\\/N from 90 Td to 10 kTd. The measurements were performed for 2p_1, 2p_2, 2p_3, 2p_4, 2p_5, 2p_6, 3p_5, 3p_6, 3p_7, 3p_8, and 3p_10 levels of neutral xenon and for 6p^4D^0 and 6p^4P^0 of xenon ion. The results were obtained in self-sustained low current
Stable Xenon Nitride at High Pressures
NASA Astrophysics Data System (ADS)
Zhang, Yunwei; Peng, Feng; Ma, Yanming
Nitrogen is the most abundant element on Earth and exists as inert N2 molecules in the atmosphere. Noble gas nitrides are missing in nature because N2 molecules do not interact with noble gases at ambient conditions, greatly impeding the understanding of physics and chemistry of such nitrides. We report here a pressure-induced chemical reaction of N2 with xenon predicted using a swarm-structure searching calculation as implemented in the CALYPSO code. This reaction leads to the formation of a hitherto unexpected Xe nitride at megabar pressure accessible to high-pressure experiments. The high-pressure phase with a hypervalent state of Xe by accepting unprecedented Xe-N covalent bonds appears to be the most stable stoichiometry. The Xe bonding situation in this new phase is substantially different from earlier high-pressure examples of ionic Xe bonding or van der Waals interactions.
Evaluation of acrylic polymeric resin and small siloxane molecule for protecting cultural heritage monuments against sulfur dioxide corrosion
John Kapolos; Nicholas Bakaoukas; Athanasia Koliadima; George Karaiskakis
The experimental technique of reversed-flow version of inverse gas chromatography was applied in order to evaluate the ability of an acrylic copolymer, Paraloid B-72 and a small siloxane molecule, Silo 111 to protect cultural heritage monuments against corrosion caused by the SO2 dry deposition. Because these materials act as surface modifiers the calculation of the time distribution of various physicochemical
Solubilized xenon 133 lung scintigraphy
Oates, E.; Sarno, R.C.
Lung scanning using solubilized xenon 133 can provide important information concerning both pulmonary perfusion and ventilation. This technique proved valuable in establishing the diagnosis of congenital lobar emphysema in a 7-month-old baby.
Investigation of the xenon excimer continuum in gas-discharge plasma
Baranov, I.Y.; Devdariani, A.Z.; Kryukov, N.A. [Univ. of Pervogo Maya, Peterhof (Russian Federation)] [and others
The shape of the spectral band profile of xenon excimer molecule radiation in the near VUV region is studied as a function of the rare gas pressure. Excited states were formed in a pulsed gas discharge plasma is pure xenon. Spectral transitions BO{sub u}{sup +}{r_arrow}XO{sub g}{sup +} and A1{sub u}{r_arrow}XO{sub g}{sup +} were recorded. The spectrum transformation in discharge afterglow is studied. A model describing peculiarities of xenon excimer continuum formation is proposed. 13 refs., 5 figs.
The growth of fission gas bubbles in irradiated uranium dioxide
R. M. Cornell
The growth of fission gas bubbles from supersaturated solution in irradiated uranium dioxide has been studied by electron microscopy under isothermal annealing conditions between 1300░ and 1500░C. Measurements of the kinetics of bubble growth have enabled the diffusion coefficients of atomic xenon and krypton in irradiated uranium dioxide to be determined. The diffusion coefficients obtained may be expressed by the
Direct WIMP searches with XENON100 and XENON1T
NASA Astrophysics Data System (ADS)
Alfredo Davide, Ferella
The XENON100 experiment is the second phase of the XENON direct Dark Matter search program. It consists of an ultra-low background double phase (liquid-gas) xenon filled time projection chamber with a total mass of 161 kg (62 in the target region and 99 in the active shield), installed at the Laboratori Nazionali del Gran Sasso (LNGS). Here the results from the 224.6 live days of data taken between March 2011 and April 2012 are reported. The experiment set one of the most stringent limits on the WIMP-nucleon spin-independent cross section to date (2 ū 10-45 cm2 for a 55 Gev/c2 WIMP mass at 90 % confidence level) and the most stringent on the spin-dependent WIMP-neutron interaction (3.5 ū 10-40 for a 45 GeV/c2 WIMP mass). With the same dataset, XENON100 excludes also solar axion coupling to electrons at gAe > 7.7 ū 10-12 for a mass of mAxion <1 keV/c2 and galactic axion couplings by gAe > 1 ū 10-12 at a mass range of mAxion = 5-10 keV/c2 (both 90 % C.L.). Moreover an absolute spectral comparison between simulated and measured nuclear recoil distributions of light and charge signals from a 241AmBe source demonstrates a high level of detector and systematics understanding. Finally, the third generation of the XENON experiments, XENON1T, is the first tonne scale direct WIMP search experiment currently under construction. The commissioning phase of XENON1T is expected to start in early 2015 followed, a few months after, by the first science run. The experiment will reach sensitivities on the WIMP-nucleon spin-independent cross section down to 2 ū10-47 cm2 after two years of data taking.
Xenon Filled Silicon Germanium Thermoelectric Generators
NASA Technical Reports Server (NTRS)
Dewinter, F.
An analysis is presented that shows the desirability and feasibility of using a xenon fill in the initial stages of operation of a silicon-germanium radioisotope thermoelectric generator to be used in outer-planetary exploration. The xenon cover gas offers protection against oxidation and against material sublimation, and allows the generator to deliver required power throughout the prelaunch and launch phases. The protective mechanisms afforded by the xenon cover gas and the mechanization of a xenon supply system are also discussed.
Single molecule magnets with protective ligand shells on gold and titanium dioxide surfaces: in situ electrospray deposition and x-ray absorption spectroscopy.
Handrup, Karsten; Richards, Victoria J; Weston, Matthew; Champness, Neil R; O'Shea, James N
Two single molecule magnets based on the dodecamanganese (III, IV) cluster with either benzoate or terphenyl-4-carboxylate ligands, have been studied on the Au(111) and rutile TiO2(110) surfaces. We have used in situ electrospray deposition to produce a series of surface coverages from a fraction of a monolayer to multilayer films in both cases. X-ray absorption spectroscopy measured at the Mn L-edge (Mn 2p) has been used to study the effect of adsorption on the oxidation states of the manganese atoms in the core. In the case of the benzoate-functionalised complex reduction of the manganese metal centres is observed due to the interaction of the manganese core with the underlying surface. In the case of terphenyl-4-carboxylate, the presence of this much larger ligand prevents the magnetic core from interacting with either the gold or the titanium dioxide surfaces and the characteristic Mn(3+) and Mn(4+) oxidation states necessary for magnetic behaviour are preserved. PMID:24160534
Cryptophane-xenon complexes in organic solvents observed through NMR spectroscopy.
Huber, Gaspard; Beguin, Laetitia; Desvaux, Hervķ; Brotin, Thierry; Fogarty, Heather A; Dutasta, Jean-Pierre; Berthault, Patrick
The interaction of xenon with cryptophane derivatives is analyzed by NMR by using either thermal or hyperpolarized noble gas. Twelve hosts differing by their stereochemistry, cavity size, and the nature and the number of the substituents on the aromatic rings have been included in the study, in the aim of extracting some clues for the optimization of (129)Xe-NMR based biosensors derived from these cage molecules. Four important properties have been examined: xenon-host binding constant, in-out exchange rate of the noble gas, chemical shift, and relaxation of caged xenon. This work aims at understanding the main characteristics of the host-guest interaction in order to choose the best candidate for the biosensing approach. Moreover, rationalizing xenon chemical shift as a function of structural parameters would also help for setting up multiplexing applications. Xenon exhibits the highest affinity for the smallest cryptophane, namely cryptophane-111, and a long relaxation time inside it, convenient for conservation of its hyperpolarization. However, very slow in-out xenon exchange could represent a limitation for its future applicability for the biosensing approach, because the replenishment of the cage in laser-polarized xenon, enabling a further gain in sensitivity, cannot be fully exploited. PMID:18925727
Critical Viscosity of Xenon team
NASA Technical Reports Server (NTRS)
The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The thermostat for CVX sits inside the white cylinder on a support structure (at left) that is placed inside a pressure canister. A similar canister (right) holds the electronics and control systems. The CVX-2 arrangement is identical. The principal investigator is Dr. Robert F. Berg (left) of the National Institutes of Standards and Technology, Gaithersburg, MD.
Critical Viscosity of Xenon team
NASA Technical Reports Server (NTRS)
The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The thermostat for CVX sits inside the white cylinder on a support structure (at left) that is placed inside a pressure canister. A similar canister (right) holds the electronics and control systems. The CVX-2 arrangement is identical. The principal investigator is Dr. Robert F. Berg (not shown) of the National Institutes of Standards and Technology, Gaithersburg, MD.
Exciton mechanism of radical formation in irradiated xenon matrixes containing methane
Grigor'ev, E.I.; Pshezhetskii, S.Ya.; Slavinskaya, N.A.; Trakhtenberg, L.I.
A study of the laws governing the formation of methyl radicals from methane present in xenon matrixes at 77 K has been carried out for the cases of /gamma/-irradiation and bombardment of the matrix surface with metastable xenon atoms.The radicals are shown to be formed by the interaction of triplet xenon excitons with methane molecules. The exciton capture radius of the methane moleucle is 0.08 nm. The exciton lifetime in the surface layer is 2.3/centered dot/10/sup /minus/13/ sec, while within the matrix it is 5/centered dot/10/sup /minus/12/ sec. The radiation yield of xenon excitons is 0.8.
Viscosity of Xenon Examined in Microgravity
NASA Technical Reports Server (NTRS)
Zimmerli, Gregory A.; Berg, Robert F.; Moldover, Michael R.
Why does water flow faster than honey? The short answer, that honey has a greater viscosity, merely rephrases the question. The fundamental answer is that viscosity originates in the interactions between a fluid s molecules. These interactions are so complicated that, except for low-density gases, the viscosity of a fluid cannot be accurately predicted. Progress in understanding viscosity has been made by studying moderately dense gases and, more recently, fluids near the critical point. Modern theories predict a universal behavior for all pure fluids near the liquid-vapor critical point, and they relate the increase in viscosity to spontaneous fluctuations in density near this point. The Critical Viscosity of Xenon (CVX) experiment tested these theories with unprecedented precision when it flew aboard the Space Shuttle Discovery (STS-85) in August 1997. Near the critical point, xenon is a billion times more compressible than water, yet it has about the same density. Because the fluid is so "soft," it collapses under its own weight when exposed to the force of Earth s gravity - much like a very soft spring. Because the CVX experiment is conducted in microgravity, it achieves a very uniform fluid density even very close to the critical point. At the heart of the CVX experiment is a novel viscometer built around a small nickel screen. An oscillating electric field forces the screen to oscillate between pairs of electrodes. Viscosity, which dampens the oscillations, can be calculated by measuring the screen motion and the force applied to the screen. So that the fluid s delicate state near the critical point will not be disrupted, the screen oscillations are set to be both slow and small.
Xenon preconditioning: molecular mechanisms and biological effects
Xenon is one of noble gases and has been recognized as an anesthetic for more than 50?years. Xenon possesses many of the characteristics of an ideal anesthetic, but it is not widely applied in clinical practice mainly because of its high cost. In recent years, numerous studies have demonstrated that xenon as an anesthetic can exert neuroprotective and cardioprotective effects in different models. Moreover, xenon has been applied in the preconditioning, and the neuroprotective and cardioprotective effects of xenon preconditioning have been investigated in a lot of studies in which some mechanisms related to these protections are proposed. In this review, we summarized these mechanisms and the biological effects of xenon preconditioning. PMID:23305274
Preparation of neutron-activated xenon for liquid xenon detector calibration
K. Ni; R. Hasty; T. M. Wongjirad; L. Kastens; A. Manzur; D. N. McKinsey
We report the preparation of neutron-activated xenon for the calibration of liquid xenon (LXe) detectors. Gamma rays from the decay of xenon metastable states, produced by fast neutron activation, were detected and their activities measured in a LXe scintillation detector. Following a 5-day activation of natural xenon gas with a 252Cf (4ū105n\\/s) source, the activities of two gamma ray lines
Investigation of xenon metastable atoms
Tian Xia; Yuan-Yu Jau; William Happer
The electron configuration of a xenon atom in its metastable state consists of tightly bound core electrons with a single missing electron in the 5P shell, and a loosely bound ``valence electron'' in the 6S shell. For our current work, we have been using pyrex cells with internal tungsten electrodes, filled with isotopically enriched Xe129 gas. Ti-sapphire laser is used
Xenon Fractionation and Archean Hydrogen Escape
NASA Technical Reports Server (NTRS)
Zahnle, K. J.
Xenon is the heaviest gas found in significant quantities in natural planetary atmospheres. It would seem the least likely to escape. Yet there is more evidence for xenon escape from Earth than for any element other than helium and perhaps neon. The most straightforward evidence is that most of the radiogenic Xe from the decay of (129)I (half-life 15.7 Myr) and (244)Pu (half-life 81 Myr) that is Earth's birthright is missing. The missing xenon is often attributed to the impact erosion of early atmospheres of Earth and its ancestors. It is obvious that if most of the radiogenic xenon were driven off by impacts, most of the rest of the atmophiles fared the same fate. The other line of evidence is in the nonradiogenic isotopes of xenon and its silent partner, krypton. Atmospheric xenon is strongly mass fractionated (at about 4% per amu) compared to any known solar system source (Figure 1). This is in stark contrast to krypton, which may not be fractionated at all: atmospheric Kr is slightly heavier than solar Kr (at about 0.5% per amu), but it is the same as in carbonaceous chondrites. Nonradiogenic xenon is also under abundant relative to krypton (the so-called "missing xenon" problem). Together these observations imply that xenon has been subject to fractionating escape and krypton not.
Surface diffusion of xenon on Pt(111)
NASA Astrophysics Data System (ADS)
Meixner, D. Laurence; George, Steven M.
The surface diffusion of xenon on the Pt(111) surface was investigated using laser induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. The surface diffusion coefficient at 80 K decreased dramatically from D=8ū10-7 cm2/s at ?=0.05?s to approximately D=2ū10-8 cm2/s at ?=?s, where ?s denotes the saturation coverage at 85 K, corresponding to a commensurate monolayer coverage of 5.0ū1014 xenon atoms/cm2. This coverage dependence was consistent with attractive interactions between the adsorbed xenon atoms and the existence of two-dimensional condensed phases of xenon on Pt(111). The kinetic parameters for surface diffusion at ?=?s were Edif=1.3▒0.1 kcal/mol and D0=1.1ū10-4▒0.2 cm2/s. The magnitude of Edif at ?=?s represented the combined effect of the intrinsic corrugation of the adsorbate-surface potential and attractive interactions between the adsorbed xenon atoms. LITD experiments at ?=0.25 ?s revealed diffusion kinetic parameters of Edif=1.2▒0.2 kcal/mol and D0=3.4ū10-4▒0.5 cm2/s. The constant Edif at low and high coverage was attributed to the ``breakaway'' of xenon atoms from the edges of condensed phase xenon islands. The coverage dependence of the surface diffusion coefficient for Xe/Pt(111) was explained by a multiple site diffusion mechanism, where collisions with xenon islands limit diffusional motion. Thermal desorption kinetics for xenon on Pt(111) were determined using TPD experiments. Using the variation of heating rates method, the desorption parameters were Edes=6.6▒0.2 kcal/mol and ?des=1.3ū1013▒0.4 s-1, in good agreement with previous studies. The xenon TPD peak shifted to higher temperature versus initial coverage at a fixed heating rate, providing further evidence for attractive interactions between the adsorbed xenon atoms.
Weird muonium diffusion in solid xenon
V. G. Storchak; B. F. Kirillov; A. V. Pirogov; V. A. Duginov; V. G. Grebinnik; T. N. Mamedov; V. G. Ol'Shevsky; V. A. Xhukov; J. H. Brewer; G. D. Morris
Muon and muonium spin rotation and relaxation parameters were studied in liquid and solid xenon. The small diamagnetic fraction (~10%) observed in condensed xenon is believed to be Xemu+. The muonium hyperfine frequency was measured for the first time in liquid Xe and was found to be in agreement with the vacuum value. A nonmonotonic temperature dependence of the muonium
Xenon poisoning calculations based on tube power
A method of calculating the steady state xenon poisoning was developed using parameters derived from the power production of individual tubes in the pile. The power of individual tubes was recorded automatically at some of the production piles. The necessary parameter is derived from these data by the use of IBM computers. This method of calculating xenon poisoning eliminates the
Hyperpolarized Xenon for NMR and MRI Applications
Witte, Christopher; Kunth, Martin; D÷pfert, J÷rg; Rossella, Federica; Schr÷der, Leif
Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) suffer from intrinsic low sensitivity because even strong external magnetic fields of ~10 T generate only a small detectable net-magnetization of the sample at room temperature 1. Hence, most NMR and MRI applications rely on the detection of molecules at relative high concentration (e.g., water for imaging of biological tissue) or require excessive acquisition times. This limits our ability to exploit the very useful molecular specificity of NMR signals for many biochemical and medical applications. However, novel approaches have emerged in the past few years: Manipulation of the detected spin species prior to detection inside the NMR/MRI magnet can dramatically increase the magnetization and therefore allows detection of molecules at much lower concentration 2. Here, we present a method for polarization of a xenon gas mixture (2-5% Xe, 10% N2, He balance) in a compact setup with a ca. 16000-fold signal enhancement. Modern line-narrowed diode lasers allow efficient polarization 7 and immediate use of gas mixture even if the noble gas is not separated from the other components. The SEOP apparatus is explained and determination of the achieved spin polarization is demonstrated for performance control of the method. The hyperpolarized gas can be used for void space imaging, including gas flow imaging or diffusion studies at the interfaces with other materials 8,9. Moreover, the Xe NMR signal is extremely sensitive to its molecular environment 6. This enables the option to use it as an NMR/MRI contrast agent when dissolved in aqueous solution with functionalized molecular hosts that temporarily trap the gas 10,11. Direct detection and high-sensitivity indirect detection of such constructs is demonstrated in both spectroscopic and imaging mode. PMID:22986346
Hyperpolarized xenon for NMR and MRI applications.
Witte, Christopher; Kunth, Martin; D÷pfert, J÷rg; Rossella, Federica; Schr÷der, Leif
Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) suffer from intrinsic low sensitivity because even strong external magnetic fields of ~10 T generate only a small detectable net-magnetization of the sample at room temperature (1). Hence, most NMR and MRI applications rely on the detection of molecules at relative high concentration (e.g., water for imaging of biological tissue) or require excessive acquisition times. This limits our ability to exploit the very useful molecular specificity of NMR signals for many biochemical and medical applications. However, novel approaches have emerged in the past few years: Manipulation of the detected spin species prior to detection inside the NMR/MRI magnet can dramatically increase the magnetization and therefore allows detection of molecules at much lower concentration (2). Here, we present a method for polarization of a xenon gas mixture (2-5% Xe, 10% N2, He balance) in a compact setup with a ca. 16000-fold signal enhancement. Modern line-narrowed diode lasers allow efficient polarization (7) and immediate use of gas mixture even if the noble gas is not separated from the other components. The SEOP apparatus is explained and determination of the achieved spin polarization is demonstrated for performance control of the method. The hyperpolarized gas can be used for void space imaging, including gas flow imaging or diffusion studies at the interfaces with other materials (8,9). Moreover, the Xe NMR signal is extremely sensitive to its molecular environment (6). This enables the option to use it as an NMR/MRI contrast agent when dissolved in aqueous solution with functionalized molecular hosts that temporarily trap the gas (10,11). Direct detection and high-sensitivity indirect detection of such constructs is demonstrated in both spectroscopic and imaging mode. PMID:22986346
Pure xenon hexafluoride prepared for thermal properties studies
NASA Technical Reports Server (NTRS)
Malm, J. G.; Osborne, D. W.; Schreiner, F.
Preparation of a xenon hexafluoride and sodium fluoride salt yields a sample of the highest possible purity for use in thermal measurements. The desired hexafluoride can easily be freed from the common contaminants, xenon tetra-fluoride, xenon difluoride, and xenon oxide tetrafluoride, because none of these compounds reacts with sodium fluoride.
Moloy, Kenneth G. (Charleston, WV)
A process for the production of organic bisphosphine dioxides from organic bisphosphonates. The organic bisphosphonate is reacted with a Grignard reagent to give relatively high yields of the organic bisphosphine dioxide.
Moloy, K.G.
A process is described for the production of organic bisphosphine dioxides from organic bisphosphonates. The organic bisphosphonate is reacted with a Grignard reagent to give relatively high yields of the organic bisphosphine dioxide.
Hydrogen atoms in solid xenon: Trapping site structure, distribution, and stability as revealed by EPR studies in monoisotopic and isotopically enriched xenon matrices
Vladimir I. Feldman; Fedor F. Sukhov; Aleksei Yu. Orlov
Trapping and decay of hydrogen atoms generated by fast electron irradiation of solid xenon doped with small hydrogen-containing molecules (acetylene, water) were studied by EPR using monoisotopic 136Xe matrix (I=0) and highly isotopically enriched 129Xe matrix (I=12). It was found that more than 99% of H atoms observed by EPR are initially trapped in the octahedral interstitial trapping sites, whereas
Cryogenic xenon droplets for advanced lithography
Gouge, M.J.; Fisher, P.W.
A cryogenic xenon droplet production system for use in anadvanced laser plasma source for x-ray lithography has been designed, fabricated, and tested at ORNL. The droplet generator is based on proven (ink jet printer) drop-on-demand.
Transportable Xenon Laboratory (TXL-1) Operations Manual
Thompson, Robert C.; Stewart, Timothy L.; Willett, Jesse A.; Woods, Vincent T.
The Transportable Xenon Laboratory Operations Manual is a guide to set up and shut down TXL, a fully contained laboratory made up of instruments to identify and measure concentrations of the radioactive isotopes of xenon by taking air samples and analyzing them. The TXL is housed in a standard-sized shipping container. TXL can be shipped to and function in any country in the world.
Ventilator-driven xenon ventilation studies
Chilcoat, R.T.; Thomas, F.D.; Gerson, J.I.
A modification of a common commercial Xe-133 ventilation device is described for mechanically assisted ventilation imaging. The patient's standard ventilator serves as the power source controlling the ventilatory rate and volume during the xenon study, but the gases in the two systems are not intermixed. This avoids contamination of the ventilator with radioactive xenon. Supplemental oxygen and positive end-expiratory pressure (PEEP) are provided if needed. The system can be converted quickly for conventional studies with spontaneous respiration.
Ventilator-driven xenon ventilation studies
Chilcoat, R.T.; Thomas, F.D.; Gerson, J.I.
A modification of a common commerical Xe-133 ventilation device is described for mechanically assisted ventilation imaging. The patient's standard ventilator serves as the power source controlling the ventilator rate and volume during the xenon study, but the gases in the two systems are not intermixed. This avoids contamination of the ventilator with radioactive xenon. Supplemental oxygen and positive end-expiratory pressure (PEEP) are provided if needed. The system can be converted quickly for conventional studies with spontaneous respiration.
XENON dark matter searches: Results and the future
NASA Astrophysics Data System (ADS)
Brown, Andrew; Xenon Collaboration
XENON100 is a dark matter search experiment looking for elastic WIMP scattering using a 62 kg liquid target. WIMP search data from XENON100 published in 2012 has set the world's strongest limits on WIMP-nucleus spinindependent, elastic scattering. It has also set the strongest limits on WIMP-nucleus spin-dependent scattering considering neutron scattering only, and competitive limits considering proton scattering only. The successor experiment to XENON100, XENON1T, is currently under construction, with commissioning scheduled to begin in 2014. XENON1T's design goal is a 100 fold increase in sensitivity for elastic WIMP searches over XENON100.
Stirring Up an Elastic Fluid: Critical Viscosity of Xenon-2 (CVX-2)
NASA Technical Reports Server (NTRS)
Berg, Robert F.; Moldover, Michael R.; Zimmerli, Gregory A.; Motil, Susan M. (Technical Monitor)
Whipped cream stays in place even when turned upside down. Yet it readily flows through the nozzle of a spray can to reach the dessert plate. This demonstrates the phenomenon of shear thinning that is important to many industrial and physical processes. Paints, film emulsions, and other complex solutions that are highly viscous under normal conditions but become thin and flow easily under shear forces. A simple fluid, such as water, does not exhibit shear thinning under normal conditions. Very close to the liquid-vapor critical point, where the distinction between liquid and vapor disappears, the fluid becomes more complex and is predicted to display shear thinning. At the critical point, xenon atoms interact over long distances in a classical model of cooperative phenomena. Physicists rely on this system to learn how long-range order arises. The Critical Viscosity of Xenon Experiment (CVX-2) will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Although it does not easily combine with other chemicals, its viscosity at the critical point can be used as a model for a range of fluids. Viscosity originates from the interactions of individual molecules. It is so complicated that, except for the simplest gas, it cannot be calculated accurately from theory. Tests with critical fluids can provide key data, but are limited on Earth because critical fluids are highly compressed by gravity. CVX-2 employs a tiny metal screen vibrating between two electrodes in a bath of critical xenon. The vibrations and how they dampen are used to measure viscosity. CVX flew on STS-85 (1997), where it revealed that, close to the critical point, the xenon is partly elastic: it can 'stretch' as well as flow. For STS-107, the hardware has been enhanced to determine if critical xenon is a shear-thinning fluid.
Synthesis of Cryptophanes with Two Different Reaction Sites: Chemical Platforms for Xenon Biosensing.
Chapellet, Laure-Lise; Cochrane, James R; Mari, Emilie; Boutin, Cķline; Berthault, Patrick; Brotin, Thierry
We report the synthesis of new water-soluble cryptophane host molecules that can be used for the preparation of (129)Xe NMR-based biosensors. We show that the cryptophane-223 skeleton can be modified to introduce a unique secondary alcohol to the propylenedioxy linker. This chemical functionality can then be exploited to introduce a functional group that is different from the six chemical groups attached to the aromatic rings. In this approach, the generation of a statistical mixture when trying to selectively functionalize a symmetrical host molecule is eliminated, which enables the efficient large-scale production of new cryptophanes that can be used as chemical platforms ready to use for the preparation of xenon biosensors. To illustrate this approach, two molecular platforms have been prepared, and the ability of these new derivatives to bind xenon has been investigated. PMID:26020365
NWA 8114: Analysis of Xenon in this Unique Martian Meteorite
NASA Astrophysics Data System (ADS)
Crowther, S. A.; Jastrzebski, N. D.; Nottingham, M.; Theis, K. J.; Gilmour, J. D.
The Xe composition of NWA 8114 is dominated by martian atmospheric xenon, with contributions from terrestrial atmospheric contamination at low temperature and fissiogenic xenon at high temperature. The overall systematics are similar to Nakhla.
Adsorption of xenon on vicinal copper and platinum surfaces
Layton Baker
The adsorption of xenon was studied on Cu(111), Cu(221), Cu(643) and on Pt(111), Pt(221), and Pt(531) using low energy electron diffraction (LEED), temperature programmed desorption (TPD) of xenon, and ultraviolet photoemission of adsorbed xenon (PAX). These experiments were performed to study the atomic and electronic structure of stepped and step-kinked, chiral metal surfaces. Xenon TPD and PAX were performed on
Vibrationally resolved photoelectron angular distributions and branching ratios for the carbon dioxide molecule in the wavelength region 685-795 Å
NASA Astrophysics Data System (ADS)
West, J. B.; Hayes, M. A.; Siggel, M. R. F.; Dehmer, J. L.; Dehmer, P. M.; Parr, A. C.; Hardis, J. E.
Measurements of vibrational branching ratios and photoelectron angular distributions have been made in the regions of the Tanaka-Ogawa, Lindholm, and Henning series for the CO2 molecule. The behavior of these parameters was found to be sensitive to which particular resonance is excited, with considerable intensity going into vibrational modes other than the symmetric stretch. An initial analysis of some of the data taken is presented.
Dendrite engineering on xenon crystals.
Fell, Marco; Bilgram, J÷rg
The experimental work presented focuses on transient growth, morphological transitions, and control of xenon dendrites. Dendritic free growth is perturbed by two different mechanisms: Shaking and heating up to the melting temperature. Spontaneous and metastable multitip configurations are stabilized, coarsening is reduced, leading to a denser sidebranch growth, and a periodic tip splitting is found during perturbation by shaking. On the other hand, heating leads to controlled sidebranching and characteristic transitions of the tip shape. A deterministic behavior is found besides the random-noise-driven growth. The existence of a limit cycle is supported by the findings. Together the two perturbation mechanisms allow a "dendrite engineering"--i.e., a reproducible controlling of the crystal shape during its growth. The tip splitting for dendritic free growth is found not to be a splitting of the tip in two; rather, the respective growth velocities of the main tip and the fins change. The latter then surpass the main tip and develop into new tips. The occurrence of three- and four-tip configurations is explained with this mechanism. Finite-element calculations of the heat flow and the convective flow in the growth vessel show that the idea of a single axisymmetric toroidal convection roll across the whole growth vessel has to be dropped. The main effect of convection under Earth's gravity is the compression of the diffusive temperature field around the downward-growing tip. A model to explain the symmetry of dendritic crystals--e.g., snow crystals--is developed, based on the interaction of crystal shape and heat flow in the crystal. PMID:17677269
Reflectance of polytetrafluoroethylene for xenon scintillation light
NASA Astrophysics Data System (ADS)
Silva, C.; Pinto da Cunha, J.; Pereira, A.; Chepel, V.; Lopes, M. I.; Solovov, V.; Neves, F.
Gaseous and liquid xenon particle detectors are being used in a number of applications including dark matter search and neutrino-less double beta decay experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors both as electrical insulator and as a light reflector to improve the efficiency of detection of scintillation photons. However, xenon emits in the vacuum ultraviolet (VUV) wavelength region (? ?175 nm) where the reflecting properties of PTFE are not sufficiently known. In this work, we report on measurements of PTFE reflectance, including its angular distribution, for the xenon scintillation light. Various samples of PTFE, manufactured by different processes (extruded, expanded, skived, and pressed) have been studied. The data were interpreted with a physical model comprising both specular and diffuse reflections. The reflectance obtained for these samples ranges from about 47% to 66% for VUV light. Other fluoropolymers, namely, ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), and perfluoro-alkoxyalkane (PFA) were also measured.
Reflectance of polytetrafluoroethylene for xenon scintillation light
Silva, C.; Pinto da Cunha, J.; Pereira, A.; Chepel, V.; Lopes, M. I.; Solovov, V.; Neves, F. [Department of Physics, LIP-Coimbra, University of Coimbra, P-3004 516 Coimbra (Portugal)
Gaseous and liquid xenon particle detectors are being used in a number of applications including dark matter search and neutrino-less double beta decay experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors both as electrical insulator and as a light reflector to improve the efficiency of detection of scintillation photons. However, xenon emits in the vacuum ultraviolet (VUV) wavelength region ({lambda}{approx_equal}175 nm) where the reflecting properties of PTFE are not sufficiently known. In this work, we report on measurements of PTFE reflectance, including its angular distribution, for the xenon scintillation light. Various samples of PTFE, manufactured by different processes (extruded, expanded, skived, and pressed) have been studied. The data were interpreted with a physical model comprising both specular and diffuse reflections. The reflectance obtained for these samples ranges from about 47% to 66% for VUV light. Other fluoropolymers, namely, ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), and perfluoro-alkoxyalkane (PFA) were also measured.
M. Damy de Souza Santos; P. Saraiva de Toledo
A method of power calibration using the reactivity variation due to ; xenon poisoning is developed. Two cases are considered: reactivity variation ; after reacting the xenon equillbrium poisoning; time variation of reactiviyy due ; to the non-equilibrium xenon poisoning. Both methods are applicable in the high ; flux region. In the second method some care must be taken in
Results from the XENON100 Experiment
NASA Astrophysics Data System (ADS)
Melgarejo, Antonio; Xenon Collaboration
The XENON100 detector, located at the LNGS Laboratory in Italy, has been taking dark matter data between 2008 and 2014, producing some of the best limits in the field thanks to its low background and large sensitive volume. In this talk we present the results from the last science run of the detector and the preliminary results from the combined exposure of all the science data, as well as the status of the ongoing analyses with these data. We gratefully acknowledge continued support for the XENON Dark Matter program from the National Science Foundation.
Preparation of Neutron-activated Xenon for Liquid Xenon Detector Calibration
Ni, K; Wongjirad, T M; Kastens, L; Manzur, A; McKinsey, D N
We report the preparation of neutron-activated xenon for the calibration of liquid xenon (LXe) detectors. Gamma rays from the decay of xenon metastable states, produced by fast neutron activation, were detected and their activities measured in a LXe scintillation detector. Following a five-day activation of natural xenon gas with a Cf-252 (4 x 10^5 n/s) source, the activities of two gamma ray lines at 164 keV and 236 keV, from Xe-131m and Xe-129m metastable states, were measured at about 95 and 130 Bq/kg, respectively. We also observed three additional lines at 35 keV, 100 keV and 275 keV, which decay away within a few days. No long-lifetime activity was observed after the neutron activation.
Decay of metastable xenon atoms Xe*(3P2) in a xenon afterglow
A. Barbet; N. Sadeghi; J. C. Pebay-Peyroula
Using the light absorption technique, the decay constant for the density of metastable xenon atoms Xe*(3P2) has been measured in a pure xenon afterglow at pressures between 4*10-2 and 8 Torr. At a gas temperature at 300K the diffusion coefficients D0 for the Xe*(3P2) metastable atoms in the parent gas has been found to be 19+or-2 cm2 Torr s-1, the
Thermal Infrared Radiation and Carbon Dioxide in the Atmosphere
Olver, Peter
Thermal Infrared Radiation and Carbon Dioxide in the Atmosphere Bill Satzer 3M Company #12;Outline,840 Ę Oxygen (O2) 209,460 Ę Argon (Ar) 9340 Ę Carbon dioxide (CO2) 394 Ę Methane (CH4) 1.79 Ę Ozone (O3) 0 wavelength of interest is about 400 times the size of a carbon dioxide molecule. Interaction is via
Material screening and selection for XENON100
E. Aprile; K. Arisaka; F. Arneodo; A. Askin; L. Baudis; A. Behrens; K. Bokeloh; E. Brown; J. M. R. Cardoso; B. Choi; D. Cline; S. Fattori; A. D. Ferella; K. L. Giboni; A. Kish; C. W. Lam; J. Lamblin; R. F. Lang; K. E. Lim; J. A. M. Lopes; T. Marrodßn Undagoitia; Y. Mei; A. J. Melgarejo Fernandez; K. Ni; U. Oberlack; S. E. A. Orrigo; E. Pantic; G. Plante; A. C. C. Ribeiro; R. Santorelli; J. M. F. dos Santos; M. Schumann; P. Shagin; A. Teymourian; D. Thers; E. Tziaferi; H. Wang; C. Weinheimer; M. Laubenstein; S. Nisi
Results of the extensive radioactivity screening campaign to identify materials for the construction of XENON100 are reported. This dark matter search experiment is operated underground at Laboratori Nazionali del Gran Sasso (LNGS), Italy. Several ultra sensitive High Purity Germanium detectors (HPGe) have been used for gamma ray spectrometry. Mass spectrometry has been applied for a few low mass plastic samples.
Spectroscopy of Ba and Ba$^+$ deposits in solid xenon for barium tagging in nEXO
Mong, B; Walton, T; Chambers, C; Craycraft, A; Benitez-Medina, C; Hall, K; Fairbank, W; Albert, J B; Auty, D J; Barbeau, P S; Basque, V; Beck, D; Breidenbach, M; Brunner, T; Cao, G F; Cleveland, B; Coon, M; Daniels, T; Daugherty, S J; DeVoe, R; Didberidze, T; Dilling, J; Dolinski, M J; Dunford, M; Fabris, L; Farine, J; Feldmeier, W; Fierlinger, P; Fudenberg, D; Giroux, G; Gornea, R; Graham, K; Gratta, G; Heffner, M; Hughes, M; Jiang, X S; Johnson, T N; Johnston, S; Karelin, A; Kaufman, L J; Killick, R; Koffas, T; Kravitz, S; Krucken, R; Kuchenkov, A; Kumar, K S; Leonard, D S; Licciardi, C; Lin, Y H; Ling, J; MacLellan, R; Marino, M G; Moore, D; Odian, A; Ostrovskiy, I; Piepke, A; Pocar, A; Retiere, F; Rowson, P C; Rozo, M P; Schubert, A; Sinclair, D; Smith, E; Stekhanov, V; Tarka, M; Tolba, T; Twelker, K; Vuilleumier, J -L; Walton, J; Weber, M; Wen, L J; Wichoski, U; Yang, L; Yen, Y -R; Zhao, Y B
Progress on a method of barium tagging for the nEXO double beta decay experiment is reported. Absorption and emission spectra for deposits of barium atoms and ions in solid xenon matrices are presented. Excitation spectra for prominent emission lines, temperature dependence and bleaching of the fluorescence reveal the existence of different matrix sites. A regular series of sharp lines observed in Ba$^+$ deposits is identified with some type of barium hydride molecule. Lower limits for the fluorescence quantum efficiency of the principal Ba emission transition are reported. Under current conditions, an image of $\\le10^4$ Ba atoms can be obtained. Prospects for imaging single Ba atoms in solid xenon are discussed.
The Genesis solar xenon composition and its relationship to planetary xenon signatures
NASA Astrophysics Data System (ADS)
Crowther, S. A.; Gilmour, J. D.
The fluence and isotopic composition of solar wind xenon have been determined from silicon collector targets flown on the NASA Genesis mission. A protocol was developed to extract gas quantitatively from samples of ?9-25 mm2, and xenon measured using the RELAX mass spectrometer. The fluence of implanted solar wind xenon is 1.202(87) ū 106 atoms 132Xe cm-2, which equates to a flux of 5.14(21) ū 106 atoms 132Xe cm-2 year-1 at the L1 point. This value is in good agreement with those reported in other studies. The isotopic composition of the solar wind is consistent with that extracted from the young lunar regolith and other Genesis collector targets. The more precise xenon isotopic data derived from the Genesis mission confirm models of relationships among planetary xenon signatures. The underlying composition of Xe-Q is mass fractionated solar wind; small, varying contributions of Xe-HL and 129Xe from 129I decay are present in reported meteorite analyses. In contrast, an s-process deficit is apparent in Xe-P3, which appears to have been mass fractionated to the same extent as Xe-Q from a precursor composition, suggesting similar trapping mechanisms. Solar wind xenon later evolved by the addition of ?1% (at 132Xe) of s-process xenon to this precursor. As an alternative model to a single source reservoir for Xe-P3, we propose that trapping of xenon onto carbonaceous carriers has been an ongoing process across galactic history, and that preparation of the residues in which Xe-P3 has been identified preferentially preserves longer lived host phases; a higher proportion of these sample xenon isotopic compositions from earlier in galactic chemical evolution, allowing the s-process deficit to become apparent. The relationships among SW-Xe, Xe-Q and Xe-P3 predict that the 124Xe/132Xe ratio for the solar wind is 0.00481(6).
The Large Underground Xenon (LUX) Experiment
Akerib, D S; Bedikian, S; Bernard, E; Bernstein, A; Bolozdynya, A; Bradley, A; Byram, D; Cahn, S B; Camp, C; Carmona-Benitez, M C; Carr, D; Chapman, J J; Chiller, A; Chiller, C; Clark, K; Classen, T; Coffey, T; Curioni, A; Dahl, E; Dazeley, S; de Viveiros, L; Dobi, A; Dragowsky, E; Druszkiewicz, E; Edwards, B; Faham, C H; Fiorucci, S; Gaitskell, R J; Gibson, K R; Gilchriese, M; Hall, C; Hanhardt, M; Holbrook, B; Ihm, M; Jacobsen, R G; Kastens, L; Kazkaz, K; Knoche, R; Kyre, S; Kwong, J; Lander, R; Larsen, N A; Lee, C; Leonard, D S; Lesko, K T; Lindote, A; Lopes, M I; Lyashenko, A; Malling, D C; Mannino, R; Marquez, Z; McKinsey, D N; Mei, D -M; Mock, J; Moongweluwan, M; Morii, M; Nelson, H; Neves, F; Nikkel, J A; Pangilinan, M; Parker, P D; Pease, E K; Pech, K; Phelps, P; Rodionov, A; Roberts, P; Shei, A; Shutt, T; Silva, C; Skulski, W; Solovov, V N; Sofka, C J; Sorensen, P; Spaans, J; Stiegler, T; Stolp, D; Svoboda, R; Sweany, M; Szydagis, M; Taylor, D; Thomson, J; Tripathi, M; Uvarov, S; Verbus, J R; Walsh, N; Webb, R; White, D; White, J T; Whitis, T J; Wlasenko, M; Wolfs, F L H; Woods, M; Zhang, C
The Large Underground Xenon (LUX) collaboration has designed and constructed a dual-phase xenon detector, in order to conduct a search for Weakly Interacting Massive Particles(WIMPs), a leading dark matter candidate. The goal of the LUX detector is to clearly detect (or exclude) WIMPS with a spin independent cross section per nucleon of $2\\times 10^{-46}$ cm$^{2}$, equivalent to $\\sim$1 event/100 kg/month in the inner 100-kg fiducial volume (FV) of the 370-kg detector. The overall background goals are set to have $<$1 background events characterized as possible WIMPs in the FV in 300 days of running. This paper describes the design and construction of the LUX detector.
Xenon ion propulsion for orbit transfer
NASA Technical Reports Server (NTRS)
Rawlin, V. K.; Patterson, M. J.; Gruber, R. P.
The status of critical ion propulsion system elements is reviewed. Electron bombardment ion thrusters for primary propulsion have evolved to operate on xenon in the 5-10 kW power range. Thruster efficiencies of 0.7 and specific impulse values of 4000 s have been documented. The baseline thruster currently under development by NASA LeRC includes ring-cusp magnetic field plasma containment and dished two-grid ion optics. Based on past experience and demonstrated simplifications, power processors for these thrusters should have approximately 500 parts, a mass of 40 kg, and an efficiency near 0.94. Thrust vector control, via individual thruster gimbals, is a mature technology. High pressure, gaseous xenon propellant storage and control schemes, using flight qualified hardware, result in propellant tankage fractions between 0.1 and 0.2. In-space and ground integration testing has demonstrated that ion propulsion systems can be successfully integrated with their host spacecraft.
Secondary scintillation yield in pure xenon
NASA Astrophysics Data System (ADS)
Monteiro, C. M. B.; Fernandes, L. M. P.; Lopes, J. A. M.; Coelho, L. C. C.; Veloso, J. F. C. A.; dos Santos, J. M. F.; Giboni, K.; Aprile, E.
The xenon secondary scintillation yield was studied as a function of the electric field in the scintillation region, in a gas proportional scintillation counter operated at room temperature. A large area avalanche photodiode was used for the readout of the VUV secondary scintillation produced in the gas, together with the 5.9 keV x-rays directly absorbed in the photodiode. The latter was used as a reference for the determination of the number of charge carriers produced by the scintillation pulse and, thus, the number of VUV photons impinging the photodiode. A value of 140 photons/kV was obtained for the scintillation amplification parameter. The attained results are in good agreement with those predicted, for room temperature, by Monte Carlo simulation and Boltzmann calculations, as well as with those obtained for saturated xenon vapour, at cryogenic temperatures, and are about a factor of two higher than former results measured at room temperature.
Port and harbor patrol car loaded Xenon search light
NASA Astrophysics Data System (ADS)
Amoh, Hiroshi; Takenami, Takashi
The container ship yard is brighten by the lighting, but after Sunset of the sea side is dark during a crescent. On the sea side lighting, we propose to use to patrol car loaded Xenon search light. Generally, the Pacific Ocean of a surface of the sea swimming fishes such as Samma (Mackerel pike) likes strong visible light as a Xenon search light beam. In the feeling of the human eyes and brains with a strong visible light beam such as Xenon search light, the reaction is divided two kind of types, to avoid reaction's humans have a feeling that bad conscience, and no reaction's humans tend to have a feeling of good mind. For the black painted unmanned objects of visible watching is needed as possible as strong visible light beam of the Xenon search light. The optical system of the Xenon search light consists of a Xenon lamp, a parabolic mirror and the filters.
Ultracold ionizing collisions in metastable xenon
Chad Ryan Orzel
This work presents the results of a series of experiments investigating Penning and associative ionization collisions in laser-cooled samples of metastable xenon. An absolute measurement of the collisional rate coefficient for the ionizing collision process is made for an unpolarized sample of 132 Xe, and the rate coefficients for unpolarized samples of three bosonic (132Xe, 134Xe, and 136Xe) and two
NASA Astrophysics Data System (ADS)
Witteman, Wilhelmus J.; Peters, Peter J. M.; Botma, Hako; Tskhai, S. N.; Udalov, Yuri B.; Mei, Qi-Chu; Ochkin, V. N.
The high pressure atomic xenon laser is becoming the most promising light source in the wavelength region of a few microns. The merits are high efficiency (so far up to 8 percent), high output energies (15 J/liter at 9 bar), high continuous output power (more than 200 W/liter), no gas dissociation and thermal heating of the lower laser level. Compared with the well-known low pressure xenon laser the power performance is now roughly a factor thousand higher. The operation of the system, based on three-body-collisions, uses the metastable state of the xenon atom as the ground state so that in the recirculation of energy a high quantum efficiency is obtained. Furthermore the homogeneous line broadening caused by the high collision frequency has also a strong beneficial effect on the efficiency. However, the required intense homogeneous excitation of the gas medium at high density is from a technical point of view a great challenge. From our experimental and theoretical work we found that at optimum performance the input power must be 1 to 2.5 [KW cm-3 atm-2]. We describe our results obtained with e-beam sustained and x-ray preionized systems delivering pulsed energies in the range of joules per liter. Furthermore we describe our recent results on continuous RF excited wave guide systems of about 37 cm length with output powers in the range of watts.
High-Rydberg Xenon Submillimeter-Wave Detector
NASA Technical Reports Server (NTRS)
Chutjian, Ara
Proposed detector for infrared and submillimeter-wavelength radiation uses excited xenon atoms as Rydberg sensors instead of customary beams of sodium, potassium, or cesium. Chemically inert xenon easily stored in pressurized containers, whereas beams of dangerously reactive alkali metals must be generated in cumbersome, unreliable ovens. Xenon-based detector potential for infrared astronomy and for Earth-orbiter detection of terrestrial radiation sources. Xenon atoms excited to high energy states in two stages. Doubly excited atoms sensitive to photons in submillimeter wavelength range, further excited by these photons, then ionized and counted.
NSDL National Science Digital Library
Arie Melamed-Katz (None; )
Bubbles are an indicator of a chemical reaction. An indicator is an object, material, or organism that tells you if a specific substance is present. In the sugar test, carbon dioxide gas release is an indicator that yeast is using sugar to grow. The more gas produced, the more sugar a specific substance contains.
A photochemical answer to the 'xenon paradox'
NASA Astrophysics Data System (ADS)
Hķbrard; Marty, B.
Xenon is depleted by one order of magnitude relative to other volatile elements when normalized to the chondritic composition. Furthermore, atmospheric xenon is far more enriched in the heavy isotopes relatively to chondritic and solar compositions (3-4%.amu-1) than atmospheric krypton (< 1%.amu-1). This discrepancy, known as the 'xenon paradox', has led to sophisticated models of atmospheric evolution coupled with mantle geodynamics (Pepin, 1991; Tolstikhin and Marty, 1998) and cometary contributions (Dauphas, 2003; Owen et al., 1992) that could explain terrestrial noble gas patterns under ad hoc conditions during the building stages of the Earth, no more than ~200 Ma following the beginning of solar system formation. Yet, xenon having an isotopic composition intermediate between the atmospheric and the chondritic ones has been recently documented in Archean (?3 Ga-old) sedimentary rocks (Pujol et al., 2011), suggesting that isotopic fractionation of Xe occurred over a much longer period of time than previously thought, during the Hadean and the Archean eons. In that case, assuming a Rayleigh type isotope evolution for atmospheric Xe requires an enrichment fractionation factor of 1.3% in heavy isotopes for Xe remaining in the atmosphere. This is clearly within the range of values observed in laboratory experiments aimed at trapping and fractionating Xe isotopes in solids, which is only effective upon ionization (Marrocchi et al., 2011; Kuga et al., 2012). We report here a possibility for explaining the 'xenon paradox' through interaction of the Hadean/Archean atmosphere with EUV light from the young Sun. By using a new photochemical model, we have found out that atmospheric Xe depletion and enrichment in heavy Xe isotopes could be achieved by EUV photoionization deep enough in the atmosphere to allow the preferential implantation of the heavier Xe isotopes in organic aerosols, the formation of which is itself triggered by UV photochemistry. Most of the ionized Xe would have escaped from the atmosphere into space by hydrodynamic escape (Zahnle, 2011). We have established that this mechanism specifically affected Xe and was particularly effective during the Hadean/Archean times, since the irradiation flux was expected to be orders of magnitude higher than today (Ribas et al., 2010). Dauphas (2003), Icarus 165, 326-339. Kuga et al. (2012), #2347 Goldschmidt 2012 Marrocchi et al. (2011), GCA 75, 6255-6266. Owen et al. (1992), Nature 358, 43-46. Pepin (1991), Icarus 92, 1-79. Pujol et al. (2011), Earth Planet. Sci. Lett. 308, 298-306. Ribas et al. (2010), Astrophys. J. 714, 384-395. Srinivasan, (1976), Earth Planet. Sci. Lett. 31, 129-141. Tolstikhin and Marty (1998), Chem. Geol. 147, 27-52. Zahnle (2011), #2241 Goldschmidt 2011
Thermal Conductivity Measurement of Xe-Implanted Uranium Dioxide Thick Films using Multilayer Laser Flash Analysis
Nelson, Andrew T. [Los Alamos National Laboratory
The Fuel Cycle Research and Development program's Advanced Fuels campaign is currently pursuing use of ion beam assisted deposition to produce uranium dioxide thick films containing xenon in various morphologies. To date, this technique has provided materials of interest for validation of predictive fuel performance codes and to provide insight into the behavior of xenon and other fission gasses under extreme conditions. In addition to the structural data provided by such thick films, it may be possible to couple these materials with multilayer laser flash analysis in order to measure the impact of xenon on thermal transport in uranium dioxide. A number of substrate materials (single crystal silicon carbide, molybdenum, and quartz) containing uranium dioxide films ranging from one to eight microns in thickness were evaluated using multilayer laser flash analysis in order to provide recommendations on the most promising substrates and geometries for further investigation. In general, the uranium dioxide films grown to date using ion beam assisted deposition were all found too thin for accurate measurement. Of the substrates tested, molybdenum performed the best and looks to be the best candidate for further development. Results obtained within this study suggest that the technique does possess the necessary resolution for measurement of uranium dioxide thick films, provided the films are grown in excess of fifty microns. This requirement is congruent with the material needs when viewed from a fundamental standpoint, as this length scale of material is required to adequately sample grain boundaries and possible second phases present in ceramic nuclear fuel.
Xenon NMR measurements of permeability and tortuosity in reservoir rocks
Walsworth, Ronald L.
Xenon NMR measurements of permeability and tortuosity in reservoir rocks Ruopeng Wanga,b , Tina of permeability, effective porosity and tortuosity on a variety of rock samples using NMR/MRI of thermal and laser of laser-polarized xenon into the rock core. Tortuosity is determined from measurements of the time
Transmission electron microscope study of xenon implanted into metals
C. Templier; H. Garem; J. P. Riviere
Recent investigations of rare gases in metals have shown that argon, xenon and krypton implanted into aluminium tend to cluster and form small overpressurized precipitates exhibiting a f.c.c. crystallographic structure. In the present work electron microscopy diffraction patterns were used to perform a systematic study of the crystallographic structure of xenon precipitates in several metals. It was found that Xe
Dielectronic recombination cross sections of neonlike xenon
NASA Astrophysics Data System (ADS)
Dewitt, D. R.; Schneider, D.; Chen, M. H.; Clark, M. W.; McDonald, J. W.; Schneider, M. B.
High-resolution measurements of dielectronic recombination cross sections for neonlike xenon (Xe44+) are presented. The experimental method consists of the formation and interaction of ions with electrons in an ion trap followed by an analysis of the extracted ions to determine relative yields. Low beam currents are used to obtain an energy resolution of 16 eV FWHM. Reductions in the number of initial ions of more than 3 orders of magnitude are observed as the strongest resonances are scanned. The relative contributions of the LMM, LMN, LMO, LMP, and LMQ groups of resonances are compared to theoretical calculations. The agreement with theory is excellent.
Exciton mechanism for radical formation in a xenon matrix during bombardment of the surface with metastable xenon and argon atoms
E. I. Grigorev; S. Y. Pshezhetskii; L. I. Trakhtenberg
This article describes how the bombardment at 77 degrees K of the surface of a xenon matrix containing 1-10 mole % methane or propane with metastable argon or xenon atoms leads to the formation of methyl or propyl radicals. The results are explained on the basis of an exciton mechanism of radical formation. It was calculated that the radius for
NSDL National Science Digital Library
In this activity, learners use gumdrops and toothpicks to model the composition and molecular structure of three greenhouse gases: carbon dioxide (CO2), water vapor (H2O) and methane (CH4). Learners explore how greenhouse gases are released into the atmosphere as well as how these gases contribute to global climate change. This activity guide includes an extension activity in which learners move their bodies to model the arrangement of atoms in a methane molecule.
Xenon ion propulsion for orbit transfer
NASA Technical Reports Server (NTRS)
Rawlin, V. K.; Patterson, M. J.; Gruber, R. P.
For more than 30 years, NASA has conducted an ion propulsion program which has resulted in several experimental space flight demonstrations and the development of many supporting technologies. Technologies appropriate for geosynchronous stationkeeping, earth-orbit transfer missions, and interplanetary missions are defined and evaluated. The status of critical ion propulsion system elements is reviewed. Electron bombardment ion thrusters for primary propulsion have evolved to operate on xenon in the 5 to 10 kW power range. Thruster efficiencies of 0.7 and specific impulse values of 4000 s were documented. The baseline thruster currently under development by NASA LeRC includes ring-cusp magnetic field plasma containment and dished two-grid ion optics. Based on past experience and demonstrated simplifications, power processors for these thrusters should have approximately 500 parts, a mass of 40 kg, and an efficiency near 0.94. Thrust vector control, via individual thruster gimbals, is a mature technology. High pressure, gaseous xenon propellant storage and control schemes, using flight qualified hardware, result in propellant tankage fractions between 0.1 and 0.2. In-space and ground integration testing has demonstrated that ion propulsion systems can be successfully integrated with their host spacecraft. Ion propulsion system technologies are mature and can significantly enhance and/or enable a variety of missions in the nation's space propulsion program.
Incorporation of Xenon in magmas at depth
NASA Astrophysics Data System (ADS)
Leroy, C.; Sanloup, C.; Bureau, H.; Schmidt, B.; Konopkova, Z.; Raepsaet, C.
Incorporation of volatile elements in magmas is enhanced at high pressure. The dissolved volatiles affect in turn the physical and chemical properties of silicate melts. Understanding volatiles incorporation in magmas and their effect on the melt's structure can be approached by in situ characterizations such as X-ray diffraction or Raman spectroscopy.Here, we focus on Xenon (Xe) in order to constrain its past and modern geochemical cycles. Indeed the 129I/129Xe extinct isotopic system is used to constrain planetary and atmosphere formation models. Moreover, some studies propose that Xe is currently recycled from the atmosphere to the mantle.To study the solubility of Xe in silicate melts, we have performed in situ X-ray diffraction experiments on the synchrotron beam line P02 in PetraIII (DESY, Hamburg). Experiments were carried out using resistive heating diamond-anvil cells up to 7 GPa and 1300░C. Two compositions have been studied: a hydrous haplogranite (HPG) reference and a hydrous HPG doped with Xe. This composition is a magma analogue that is extremely well documented by petrological studies. Xenon can be identified on the radial distribution functions obtained by processing the x-ray diffraction data. Solubility mechanisms of Xe in silicate melts at depth will be discussed.
Status of xenon ion propulsion technology
NASA Technical Reports Server (NTRS)
Beattie, J. R.; Matossian, J. N.; Robson, R. R.
This paper describes a working-model xenon ion propulsion subsystem (XIPS) designed for north-south stationkeeping (NSSK) of 2500-kg-class geosynchronous communication satellites. The XIPS consists of a 25-cm-diameter laboratory-model thruster, a breadboard-model power supply, and a flight-prototype pressure regulator (the critical component of the pressure-regulated xenon feed system). With a thrust of 63.5 mN, specific impulse of 2800 sec, and thruster efficiency of 65 percent, the XIPS performance is believed to be the highest ever reported for an ion thruster operated at 1.3-kW input power. The XIPS power supply accepts an input power of about 1.4 kW from a 28- to 35-V bus and converts it into the seven outputs required for startup and operation of the thruster. The simplified power supply contains only about 500 parts and has demonstrated an unprecedented efficiency of 90 percent and a specific mass of about 8 kg/kW. The results of a highly successful wear-mechanism test in which the working-model XIPS was operated for 4350 hours and 3850 ON/OFF cycles are presented. These hours and cycles are equivalent to over ten years of NSSK on large communication satellites.
High fidelity equation of state for xenon : integrating experiments and first principles simulations in developing a wide-range equation of state model for a fifth-row element.
Flicker, Dawn G.; Root, Seth; Mattsson, Thomas Kjell Rene; Magyar, Rudolph J.; Carpenter, John H.
The noble gas xenon is a particularly interesting element. At standard pressure xenon is an fcc solid which melts at 161 K and then boils at 165 K, thus displaying a rather narrow liquid range on the phase diagram. On the other hand, under pressure the melting point is significantly higher: 3000 K at 30 GPa. Under shock compression, electronic excitations become important at 40 GPa. Finally, xenon forms stable molecules with fluorine (XeF{sub 2}) suggesting that the electronic structure is significantly more complex than expected for a noble gas. With these reasons in mind, we studied the xenon Hugoniot using DFT/QMD and validated the simulations with multi-Mbar shock compression experiments. The results show that existing equation of state models lack fidelity and so we developed a wide-range free-energy based equation of state using experimental data and results from first-principles simulations.
Improvement of optical diagnostic methods for a xenon operating thruster plasma
Georgy Karabadzhak
Improvement of contemporary plasma optical diagnostic technique for xenon Hall effect based thrusters is considered. This improvement has become possible after critical revision of collisional radiative model for the thruster plasma. In particular, three important processes have been included into the collisional radiative model: excitation of the xenon emissions in collisions between xenon ions and atoms; step-wise excitation of xenon
Model of a low pressure argon-xenon positive column
Sommerer, T.J. [General Electric Co., Schenectady, NY (United States). Corporate Research and Development
The authors are investigating various discharge-phosphor systems with the goal of developing a mercury-free replacement for existing fluorescent lamps. The initial work centers on a low pressure argon-xenon positive column discharge combined with a quantum splitting phosphor. This talk will outline the modeling issues and report results from modeling of the argon-xenon positive column. The model predictions will be compared with experimental measurements described in detail elsewhere at this conference. Xenon is the active radiating gas in a low pressure argon-xenon positive column, emitting resonance radiation near 147 nm. Argon serves as a relatively inactive buffer gas to retard diffusion of the charged species to the wall and thereby control the electron temperature. For use in a fluorescent lamp, they want to find conditions which maximize the efficiency for conversion of input electrical power to emitted 147 nm radiation. Acceptably high efficiency must be obtained simultaneously with power densities comparable to existing argon-mercury fluorescent lamps, around 0.4 W per cm of tube length. Seven to none electronically excited levels of the xenon atom are included in the present model. For the conditions modeled to date, they find that xenon ions are produced predominantly by electron impact on the lowest-lying excited xenon levels.
Liquid Xenon Scintillation:. Light Propagation and Detection with Avalanche Photodiodes
NASA Astrophysics Data System (ADS)
Chepel, V.; Solovov, V. N.; Neves, F.; Lopes, M. I.; Lindote, A.; da Cunha, J. Pinto; Marques, R. Ferreira; Policarpo, A. J. P. L.
In this paper we describe our recent results on the study of avalanche photodiodes for detection of scintillation of liquid xenon, namely measurements of very low intensity light pulses and the photodiode excess noise as a function of temperature. Some other aspects relevant to the use of liquid xenon scintillation for particle detection are also addressed. In particular, we refer our measurements of the refraction index and attenuation length of the liquid for the VUV light emitted by xenon, which were found to be 1.69▒0.02 and 36.4▒1.8 cm, respectively.
Modeling Pulse Characteristics in Xenon with NEST
Mock, Jeremy; Kazkaz, Kareem; Szydagis, Matthew; Tripathi, Mani; Uvarov, Sergey; Woods, Michael; Walsh, Nicholas
A comprehensive model for describing the characteristics of pulsed signals, generated by particle interactions in xenon detectors, is presented. An emphasis is laid on two-phase time projection chambers, but the models presented are also applicable to single phase detectors. In order to simulate the pulse shape due to primary scintillation light, effects such as the ratio of singlet and triplet dimer state populations, as well as their corresponding decay times, and the recombination time are incorporated into the model. In a two phase time projection chamber, when simulating the pulse caused by electroluminescence light, parameters such as ionization electron mean free path in gas, the drift velocity, singlet and triplet decay times, diffusion constants, and the electron trapping time, have been implemented. This modeling has been incorporated into a complete software package, which realistically simulates the expected pulse shapes for these types of detectors.
Modeling pulse characteristics in Xenon with NEST
NASA Astrophysics Data System (ADS)
Mock, J.; Barry, N.; Kazkaz, K.; Stolp, D.; Szydagis, M.; Tripathi, M.; Uvarov, S.; Woods, M.; Walsh, N.
A comprehensive model for describing the characteristics of pulsed signals, generated by particle interactions in xenon detectors, is presented. An emphasis is laid on two-phase time projection chambers, but the models presented are also applicable to single phase detectors. In order to simulate the pulse shape due to primary scintillation light, the effects of the ratio of singlet and triplet dimer state populations, as well as their corresponding decay times, and the recombination time are incorporated into the model. In a two phase time projection chamber, when simulating the pulse caused by electroluminescence light, the ionization electron mean free path in gas, the drift velocity, singlet and triplet decay times, diffusion constants, and the electron trapping time, have been implemented. This modeling has been incorporated into a complete software package, which realistically simulates the expected pulse shapes for these types of detectors.
High-power xenon ion thrusters
NASA Technical Reports Server (NTRS)
Beattie, J. R.; Matossian, J. N.
Steady state performance characteristics for a 25-cm diameter laboratory-model xenon ion thruster operating over the power range from 1.8 to 6.8 kW are described. Performance data are also presented for a similar 30-cm diameter thruster operated over the 1.4 to 11.1 kW power range. For each of the two thrusters, thermal characteristics, discharge-chamber performance data, overall thruster performance data, and beam-current density profiles are presented. A high level of performance and stability over a wide range of input power is demonstrated for the two thrusters. It is concluded that there appears to be no technological obstacles in the way of developing flight-design thrusters that operate in the 5- to 10-kW power range for near-term applications to orbit raising.
Pulse Shape in 2-Phase Xenon Detectors
NASA Astrophysics Data System (ADS)
Mock, Jeremy
Understanding the shape and size of the primary (S1) and secondary (S2) scintillation pulses in noble elements is crucial for discriminating between different particle interactions. Monte Carlo results from NEST (the Noble Element Simulation Technique) will be presented which match the available data from liquid xenon on the dependence of the recombination time, which is a critical piece of the S1 pulse timing structure, on dE/dx, interaction type, and electric field magnitude. In addition, a model for the S2 pulse shape and the dependence of its width on the depth of an interaction in a detector will be presented which takes into account drift speed, the single/triplet time constants, diffusion, thermal electron trapping at a liquid-gas interface, and other effects.
Dielectronic recombination cross sections of neonlike xenon
DeWitt, D.R.; Schneider, D.; Chen, M.H.; Clark, M.W.; McDonald, J.W.; Schneider, M.B. (Lawrence Livermore National Laboratory, University of California, Livermore, California 94550 (United States))
High-resolution measurements of dielectronic recombination cross sections for neonlike xenon (Xe{sup 44+}) are presented. The experimental method consists of the formation and interaction of ions with electrons in an ion trap followed by an analysis of the extracted ions to determine relative yields. Low beam currents are used to obtain an energy resolution of 16 eV FWHM. Reductions in the number of initial ions of more than 3 orders of magnitude are observed as the strongest resonances are scanned. The relative contributions of the {ital LMM}, {ital LMN}, {ital LMO}, {ital LMP}, and {ital LMQ} groups of resonances are compared to theoretical calculations. The agreement with theory is excellent.
Penile blood flow by xenon-133 washout
Haden, H.T.; Katz, P.G.; Mulligan, T.; Zasler, N.D.
Penile erectile failure is often attributed to abnormalities of vascular supply or drainage, but few direct measurements of penile blood flow have been made. We describe the xenon washout method for measurement of penile blood flow, and present the results obtained in a group of normal and impotent subjects. The procedure was performed with standard nuclear imaging equipment. Flaccid-state penile blood flow in the impotent patients studied was not significantly different from the normal group, suggesting that flaccid-state measurements may not be helpful in evaluation of erectile failure. However, this method can be used to measure penile venous outflow with stimulated or induced erection, and may provide a method for detecting abnormal venous leakage.
Ethane-xenon mixtures under shock conditions
NASA Astrophysics Data System (ADS)
Magyar, Rudolph J.; Root, Seth; Cochrane, Kyle; Mattsson, Thomas R.; Flicker, Dawn G.
Mixtures of light elements with heavy elements are important in inertial confinement fusion. We explore the physics of molecular scale mixing through a validation study of equation of state (EOS) properties. Density functional theory molecular dynamics (DFT-MD) at elevated temperature and pressure is used to obtain the thermodynamic state properties of pure xenon, ethane, and various compressed mixture compositions along their principal Hugoniots. To validate these simulations, we have performed shock compression experiments using the Sandia Z-Machine. A bond tracking analysis correlates the sharp rise in the Hugoniot curve with the completion of dissociation in ethane. The DFT-based simulation results compare well with the experimental data along the principal Hugoniots and are used to provide insight into the dissociation and temperature along the Hugoniots as a function of mixture composition. Interestingly, we find that the compression ratio for complete dissociation is similar for several compositions suggesting a limiting compression for C-C bonded systems.
Effect of relativity on the ionization spectra of the xenon fluorides XeFn (n=2, 4, 6).
Pernpointner, Markus; Cederbaum, Lorenz S
Noble gas compounds exhibit special chemical bonding situations and have been investigated by various spectroscopic and theoretical techniques. In this work we calculate the ionization spectra of the xenon fluorides (XeF2,XeF4, and XeF6) in the valence and subvalence (down to Xe 4d) areas by application of the recently developed Dirac-Hartree-Fock one-particle propagator technique. In this technique, the relativistic (four-component) and electron correlation effects are computed simultaneously. The xenon compounds show considerable spin-orbit splitting strongly influencing the photoelectron spectrum not reproducible in prior calculations. Comparison to one-component methods is made and the occurring satellite structures are interpreted. The satellite structures can be attributed either to the breakdown of the one-particle picture or to a reflection of intra-atomic and interatomic Auger decay processes within the molecule. PMID:15974733
Utilizing a Water-Soluble Cryptophane with Fast Xenon Exchange Rates for Picomolar Sensitivity NMR Measurements
Bai, Yubin; Hill, P. Aru; Dmochowski, Ivan J.
Hyperpolarized 129Xe chemical exchange saturation transfer (129Xe Hyper-CEST) NMR is a powerful technique for the ultrasensitive, indirect detection of Xe host molecules (e.g., cryptophane-A). Irradiation at the appropriate Xe-cryptophane resonant radio frequency results in relaxation of the bound hyperpolarized 129Xe and rapid accumulation of depolarized 129Xe in bulk solution. The cryptophane effectively æcatalyzesÆ this process by providing a unique molecular environment for spin depolarization to occur, while allowing xenon exchange with the bulk solution during the hyperpolarized lifetime (T1 ? 1 min). Following this scheme, a triacetic acid cryptophane-A derivative (TAAC) was indirectly detected at 1.4 picomolar concentration at 320 K in aqueous solution, which is the record for a single-unit xenon host. To investigate this sensitivity enhancement, the xenon binding kinetics of TAAC in water was studied by NMR exchange lifetime measurement. At 297 K, kon ? 1.5 ū 106 M?1s?1 and koff = 45 s?1, which represent the fastest Xe association and dissociation rates measured for a high-affinity, water-soluble xenon host molecule near rt. NMR linewidth measurements provided similar exchange rates at rt, which we assign to solvent-Xe exchange in TAAC. At 320 K, koff was estimated to be 1.1 ū 103 s?1. In Hyper-CEST NMR experiments, the rate of 129Xe depolarization achieved by 14 pM TAAC in the presence of RF pulses was calculated to be 0.17 ĄMĘs?1. On a per cryptophane basis, this equates to 1.2 ū 104 129Xe atoms s?1 (or 4.6 ū 104 Xe atoms s?1, all Xe isotopes), which is more than an order of magnitude faster than koff, the directly measurable Xe-TAAC exchange rate. This compels us to consider multiple Xe exchange processes for cryptophane-mediated bulk 129Xe depolarization, which provide at least 107-fold sensitivity enhancements over directly detected hyperpolarized 129Xe NMR signals. PMID:23106513
Radon removal from gaseous xenon with activated charcoal
NASA Astrophysics Data System (ADS)
Abe, K.; Hieda, K.; Hiraide, K.; Hirano, S.; Kishimoto, Y.; Kobayashi, K.; Koshio, Y.; Liu, J.; Martens, K.; Moriyama, S.; Nakahata, M.; Nishiie, H.; Ogawa, H.; Sekiya, H.; Shinozaki, A.; Suzuki, Y.; Takachio, O.; Takeda, A.; Ueshima, K.; Umemoto, D.; Yamashita, M.; Hosokawa, K.; Murata, A.; Otsuka, K.; Takeuchi, Y.; Kusaba, F.; Motoki, D.; Nishijima, K.; Tasaka, S.; Fujii, K.; Murayama, I.; Nakamura, S.; Fukuda, Y.; Itow, Y.; Masuda, K.; Nishitani, Y.; Takiya, H.; Uchida, H.; Kim, Y. D.; Kim, Y. H.; Lee, K. B.; Lee, M. K.; Lee, J. S.; Xmass Collaboration
Many low background experiments using xenon need to remove radioactive radon to improve their sensitivities. However, no method of continually removing radon from xenon has been described in the literature. We studied a method to remove radon from xenon gas through an activated charcoal trap. From our measurements we infer a linear relationship between the mean propagation velocity vRn of radon and vXe of xenon in the trap with vRn/vXe=(0.96▒0.10)ū10-3 at -85 ░C. As the mechanism for radon removal in this charcoal trap is its decay, knowledge of this parameter allows us to design an efficient radon removal system for the XMASS experiment. The verification of this system found that it reduces radon by a factor of 0.07, which is in line with its expected average retention time of 14.8 days for radon.
Liquid Xenon Purity Studies for nEXO
NASA Astrophysics Data System (ADS)
Jewell, Michael
The EXO collaboration is currently searching for neutrinoless double-beta decay using the scintillation and ionization response of a liquid xenon time projection chamber (TPC). To optimize the signal of such a detector, the xenon needs to be kept free of electronegative impurities which could interact with drifting electrons and limit energy resolution. The current 200 kg prototype detector, EXO-200, achieves electron lifetimes above 1ms to limit charge attenuation. With the next generation ton scale detector nEXO, more stringent limits will be needed to achieve expected energy resolution. In addition there is a need for real-time monitoring to allow for timely response in the event that xenon purity begins to show signs of degradation. This talk will discuss research and development of new purity monitoring techniques that will directly measure electron lifetime in liquid xenon. The results of this research will have direct applications for nEXO as well as other large noble liquid detectors.
Modeling of the pressurized xenon gamma ray scintillation detector
NASA Astrophysics Data System (ADS)
Meek, Romney; Barzilov, Alexander; Novikov, Ivan
We are developing a high pressure xenon detector for photon measurements. Xenon produces electroluminescence (EL) scintillation emission that we use as the primary signal in our strategy to acquire information. The detector consists of a high pressure chamber, a thin radiation input window with the supporting grid of collimator ribs and electrode grids to create the electric field, and a photo sensor -- the large area silicon avalanche photodiode. The electrode grids are made of thin wire. The modeling of the electric field is a crucial step in developing a working prototype. It has been previously shown that the uniform electric field divided by the number density of xenon gas needs to be above approximately 3 Td to give enough energy to ionize the xenon atoms, but less than 16 Td to prevent electron avalanches from occurring. The electric field was modeled using Comsol Multiphysics. This presentation discusses the results of electric field modeling for the detector (absorption, drift, and EL regions).
Modeling the selectivity of activated carbons for efficient separation of hydrogen and carbon dioxide
Wu, Jianzhong
the separation of hydrogen and carbon dioxide via adsorption in activated carbons. In the simulations, both hydrogen and carbon dioxide molecules are modeled as Lennard-Jones spheres, and the activated carbons essentially no preference over the two gases and the selectivity of carbon dioxide relative to hydrogen falls
Xenon diffusion studies with prompt gamma activation analysis
Carlos A. Rios Perez; Justin D. Lowrey; Steven Biegalski; Mark R. Deinert
Developing a better understanding of xenon transport through porous systems is critical to predicting how this gas will enter\\u000a the atmosphere after a below ground nuclear weapons test. Radioxenon monitoring is a vital part of the Comprehensive Nuclear-Test-Ban\\u000a Treaty (CTBT) International Monitoring System. This work details the development of prompt gamma activation analysis for measuring\\u000a the diffusion rates of xenon
Factors affecting the adsorption of xenon on activated carbon
Underhill, D.W.; DiCello, D.C.; Scaglia, L.A.; Watson, J.A.
The presence of water vapor was found to interfere strongly with the dynamic adsorption of /sup 133/Xe on coconut-base activated charcoal. The percent loss in the xenon adsorption coefficient was similar to values reported earlier for the adsorption of krypton on humidified charcoal. Attempts to increase the adsorption of xenon by (a) using a petroleum-based adsorbent with an extremely high surface area and (b) by impregnation of the adsorbent with iodine were not successful.
NMR study of the dissolution of laser-polarized xenon
P. Berthault; H. Desvaux
: ĀĀNMR of laser-polarized xenon is used to probe the dissolution behaviour of the noble gas in different liquids. The dissolution\\u000a and self-relaxation rates are extracted via a macroscopic model, and comparison of the decay rate of the xenon magnetization in deuterated and non-deuterated solvent\\u000a pairs allows the determination of the pure dipole-dipole contribution to relaxation. A transient convective effect,
Hyperpolarized xenon NMR and MRI signal amplification by gas extraction
Zhou, Xin; Graziani, Dominic; Pines, Alexander
A method is reported for enhancing the sensitivity of NMR of dissolved xenon by detecting the signal after extraction to the gas phase. We demonstrate hyperpolarized xenon signal amplification by gas extraction (Hyper-SAGE) in both NMR spectra and magnetic resonance images with time-of-flight information. Hyper-SAGE takes advantage of a change in physical phase to increase the density of polarized gas in the detection coil. At equilibrium, the concentration of gas-phase xenon is ?10 times higher than that of the dissolved-phase gas. After extraction the xenon density can be further increased by several orders of magnitude by compression and/or liquefaction. Additionally, being a remote detection technique, the Hyper-SAGE effect is further enhanced in situations where the sample of interest would occupy only a small proportion of the traditional NMR receiver. Coupled with targeted xenon biosensors, Hyper-SAGE offers another path to highly sensitive molecular imaging of specific cell markers by detection of exhaled xenon gas. PMID:19805177
Cold Ion-Molecule Chemistry with a Stark Decelerator Beamline
NASA Astrophysics Data System (ADS)
Oldham, James M.; Bell, Martin T.; Harper, Lee D.; Softley, Timothy P.
We describe an experimental method for studying ion-molecule reactive collisions at very low energies. Building on our previous work using an electrostatic quadrupole guide as a source of cold neutral molecules, we discuss a proof of principle study of the charge-exchange reaction between cold xenon ions and Stark decelerated ammonia molecules. Ammonia molecules from a pulsed supersonic expansion are produced at low velocities using the Stark deceleration technique of Meijer and co-workers. The decelerated molecules are focussed using pulsed electrostatic hexapoles into the centre of a radiofrequency ion trap where they collide with cold xenon ions. A fast-opening vacuum-compatible mechanical shutter installed in the beamline is used to prevent transmission of the undecelerated molecules and carrier gas into the ion trap chamber. To prepare the target ions, the ion trap is loaded with calcium ions, which are Doppler laser cooled to form a low-temperature ordered ``Coulomb crystal'' phase. Xenon ions formed by resonant multiphoton ionisation are subsequently loaded and sympathetically cooled through their Coulomb interaction with the laser-cooled ions. The spatial distribution of fluorescence emitted by the laser-cooled ions in the multicomponent crystal is imaged; reactive collisions of Xe^+ with ND_3 are observed and quantified through changes in this distribution. By varying the high voltage switching sequence applied to the decelerator, the velocity of the ammonia molecules can be tuned from around 250 m/s to 35 m/s. For collisions with trapped xenon ions, this corresponds to collision energies (expressed in temperature units) from 65 K down to close to 1 K.
Precision Magnetometry with Spin-Polarized Xenon
NASA Astrophysics Data System (ADS)
Degenkolb, Skyler; Leanhardt, Aaron; Chupp, Tim
Atomic magnetometer sensitivity is a limiting factor in precision measurements, medical imaging, and industrial applications. In particular, searches for permanent electric dipole moments (EDMs) require sensitive magnetometers which interact minimally with the primary samples. Techniques based on spin-polarized gases have been very successful in this capacity, but it remains difficult to perform correct spatial and temporal averages. Previous magnetometers (e.g. alkalis or ^199Hg) also suffer from material problems at the high voltages and low temperatures common in EDM experiments. We propose as a remedy real-time optical magnetometry based on spectroscopy of two-photon transitions in spin-polarized ^129Xe. Thermal, diffusive, and dielectric properties of xenon allow sensitive measurements in a wide range of electromagnetic field strengths and sample volumes, while long spin coherence times and a low neutron capture cross-section are favorable in neutron EDM experiments. We report on preliminary work validating the technique in ^171Yb and a parallel effort measuring the ^129Xe EDM, and discuss applications to contemporary neutron EDM measurements.
Prospects for Barium Tagging in Gaseous Xenon
Sinclair, D.; /Carleton U. /TRIUMF; Rollin, E.; /Carleton U.; Smith, J.; /Carleton U.; Mommers, A.; /Ottawa U.; Ackerman, N.; /SLAC; Aharmim, B.; /Laurentian U.; Auger, M.; /Bern U., LHEP; Barbeau, P.S.; /Stanford U., Phys. Dept.; Benitez-Medina, C.; /Colorado State U.; Breidenbach, M.; /SLAC; Burenkov, A.; /Moscow, ITEP; Cook, S.; /SLAC; Coppens, A.; /Carleton U.; Daniels, T.; /Massachusetts U., Amherst; DeVoe, R.; /Stanford U., Phys. Dept.; Dobi, A.; /Maryland U.; Dolinski, M.J.; Donato, K.; /Stanford U., Phys. Dept.; Fairbank, W., Jr.; /Colorado State U.; Farine, J.; /Laurentian U.; Giroux, G.; /Bern U., LHEP /Carleton U. /Stanford U., Phys. Dept. /Carleton U. /Laurentian U. /Carleton U. /SLAC /Indiana U. /Indiana U., CEEM /Korea U. /Stanford U., Phys. Dept. /SLAC /Alabama U. /Colorado State U. /Stanford U., Phys. Dept. /Alabama U. /SLAC /Stanford U., Phys. Dept. /Alabama U. /Massachusetts U., Amherst /SLAC /Alabama U. /SLAC /Maryland U. /Moscow, ITEP /Stanford U., Phys. Dept. /Maryland U. /Bern U., LHEP /Laurentian U. /SLAC /Maryland U.
Tagging events with the coincident detection of a barium ion would greatly reduce the background for a neutrino-less double beta decay search in xenon. This paper describes progress towards realizing this goal. It outlines a source that can produce large quantities of Ba++ in gas, shows that this can be extracted to vacuum, and demonstrates a mechanism by which the Ba++ can be efficiently converted to Ba+ as required for laser identification. It is clear from this study that electrospray is a convenient mechanism for producing Ba++ is gas at atmospheric pressure. It is likely that the source will perform just as effectively at higher pressures. Even though the source region has water vapour and methanol vapour at the 0.3% level, there is no evidence for molecular formation. The use of TEA offers an effective method to achieve the charge state conversion. The overall design of the ion extraction from high pressure to vacuum is very similar to the scheme proposed for the final detector and this appears to work well although the efficiency is not yet determined.
Optimization of Xenon Difluoride Vapor Delivery
Sweeney, Joseph; Marganski, Paul; Kaim, Robert; Wodjenski, Mike; Gregg, John; Yedave, Sharad; Sergi, Steve; Bishop, Steve; Eldridge, David; Zou Peng [ATMI, Inc., Danbury, Connecticut 06810 (United States)
Xenon difluoride (XeF{sub 2}) has been shown to provide many process benefits when used as a daily maintenance recipe for ion implant. Regularly flowing XeF{sub 2} into the ion source cleans the deposits generated by ion source operation. As a result, significant increases in productivity have been demonstrated. However, XeF{sub 2} is a toxic oxidizer that must be handled appropriately. Furthermore, it is a low vapor pressure solid under standard conditions ({approx}4.5 torr at 25 deg. C). These aspects present unique challenges for designing a package for delivering the chemistry to an ion implanter. To address these challenges, ATMI designed a high-performance, re-usable cylinder for dispensing XeF{sub 2} in an efficient and reliable manner. Data are presented showing specific attributes of the cylinder, such as the importance of internal heat transfer media and the cylinder valve size. The impact of mass flow controller (MFC) selection and ion source tube design on the flow rate of XeF{sub 2} are also discussed. Finally, cylinder release rate data are provided.
NSDL National Science Digital Library
Carlyn Little
In this activity, learners use marshmallows and gum drops to construct seven models of molecules. Learners classify (solid, liquid or gas) and draw diagrams of the molecules. Learners can also create a table showing the chemical formula for each molecule and identify a common use for each chemical. Use this activity to introduce learners to molecules, compounds, and bonds.
Hugoniot measurements of double-shocked precompressed dense xenon plasmas.
Zheng, J; Chen, Q F; Gu, Y J; Chen, Z Y
The current partially ionized plasmas models for xenon show substantial differences since the description of pressure and thermal ionization region becomes a formidable task, prompting the need for an improved understanding of dense xenon plasmas behavior at above 100 GPa. We performed double-shock compression experiments on dense xenon to determine accurately the Hugoniot up to 172 GPa using a time-resolved optical radiation method. The planar strong shock wave was produced using a flyer plate impactor accelerated up to ?6 km/s with a two-stage light-gas gun. The time-resolved optical radiation histories were acquired by using a multiwavelength channel optical transience radiance pyrometer. Shock velocity was measured and mass velocity was determined by the impedance-matching methods. The experimental equation of state of dense xenon plasmas are compared with the self-consistent fluid variational calculations of dense xenon in the region of partial ionization over a wide range of pressures and temperatures. PMID:23368058
Output power characteristics of the neutral xenon long laser
Linford, G.J. [TRW Space and Electronics Group, Redondo Beach, CA (United States). Space and Technology Div.
Lasers which oscillate within inhomogeneously broadened gain media exhibit spectral hole burning and concomitant reduction in output power compared with equivalent homogeneously-broadened laser gain media. By increasing the cavity length, it may be possible to demonstrate at least a partial transition from an inhomogeneous laser cavity mode spectrum to a homogeneous spectrum. There are a number of high gain laser lines which are inhomogeneously-broadened transitions in electric discharges of neutral xenon. In neutral xenon lasers, as in the cases of many other gas lasers, the inhomogeneous spectral broadening mechanism arises from Doppler shifts, {Delta}{nu}{sub D}, of individual atoms in thermal motion within the electric discharge comprising the laser gain medium. Optical transitions corresponding to these noble gas atoms have natural linewidths, {Delta}{nu}{sub n}{lt}{Delta}{nu}{sub D}. Simulations of the output power characteristics of the xenon laser were carried out as a function of laser cavity parameters, including the cavity length, L. These calculations showed that when the intracavity mode spacing frequency, c/2L{lt}{Delta}{nu}{sub n}, the inhomogeneously broadened xenon mode spectrum converted to a homogeneously broadened oscillation spectrum with an increase in output power. These simulations are compared with experimental results obtained for the long laser oscillation characteristics of the (5d[5/2]{degree}{sub 2}{r_arrow}6p[3/2]{sub 1}) transition corresponding to the strong, high-gain 3.508 {mu} line in xenon.
Collisional excitation and radiation of atoms and molecules. Final technical report, 1 July 1978-30 June 1983
Lin, C.C.
The general objectives of this research project are to study collisional excitation of atoms and molecules and the radiation emitted by these excited atoms and molecules. Our major efforts include electron excitation of the sodium and xenon atoms, excitation of electronic states of nitrogen molecules, formation of excited nitrogen atoms by electron-impact dissociation of nitrogen molecules, Measurement of electron excitation cross sections of metastable levels of neon atoms, excitation of atoms by H+, H0, H- impact.
Sinha, Dipen N. (Los Alamos, NM); Agnew, Stephen F. (Los Alamos, NM); Christensen, William H. (Buena Park, CA)
Method and apparatus for detecting the presence of gaseous nitrogen dioxide and determining the amount of gas which is present. Though polystyrene is normally an insulator, it becomes electrically conductive in the presence of nitrogen dioxide. Conductance or resistance of a polystyrene sensing element is related to the concentration of nitrogen dioxide at the sensing element.
Dynamics of xenon binding inside the hydrophobic cavity of pseudo-wild-type bacteriophage T4 lysozyme explored through xenon-based NMR spectroscopy.
Desvaux, Hervķ; Dubois, Lionel; Huber, Gaspard; Quillin, Michael L; Berthault, Patrick; Matthews, Brian W
Wild-type bacteriophage T4 lysozyme contains a hydrophobic cavity with binding properties that have been extensively studied by X-ray crystallography and NMR. In the present study, the monitoring of 1H chemical shift variations under xenon pressure enables the determination of the noble gas binding constant (K = 60.2 M(-1)). Although the interaction site is highly localized, dipolar cross-relaxation effects between laser-polarized xenon and nearby protons (SPINOE) are rather poor. This is explained by the high value of the xenon-proton dipolar correlation time (0.8 ns), much longer than the previously reported values for xenon in medium-size proteins. This indicates that xenon is highly localized within the protein cavity, as confirmed by the large chemical shift difference between free and bound xenon. The exploitation of the xenon line width variation vs xenon pressure and protein concentration allows the extraction of the exchange correlation time between free and bound xenon. Comparison to the exchange experienced by protein protons indicates that the exchange between the open and closed conformations of T4 lysozyme is not required for xenon binding. PMID:16104744
Measuring Double-Electron Capture with Liquid Xenon Experiments
D. -M. Mei; I. Marshall; W. -Z. Wei; C. Zhang
We investigate the possibilities of observing the decay mode for $^{124}$Xe in which two electrons are captured, two neutrinos are emitted, and the final daughter nucleus is in its ground state, using dark matter experiments with liquid xenon. The first upper limit of the decay half-life is calculated to be 1.66$\\times10^{21}$ years at a 90% confidence level (C.L.) obtained with the published background data from the XENON100 experiment. Employing a known background model from the Large Underground Xenon (LUX) experiment, we predict that the detection of double-electron capture of $^{124}$Xe to the ground state of $^{124}$Te with LUX will have approximately 115 events, assuming a half-life of 2.9 $\\times$ 10$^{21}$ years. We conclude that measuring $^{124}$Xe 2$\
Development of a xenon detector for treaty verification. Final report
The project objective was to determine the feasibility of the gas proportional scintillator detector (GPSD) technology to sensitively and selectively detect the decay products of the metastable xenon isotopes as a means of treaty verification for the CTBT. During the course of the project, the investigation involved both computer simulations and laboratory measurements with a GPSD. During the fourth quarter the authors have further investigated the dedicated GPSD response to x-rays and conversion electrons from {sup 109}Cd and {sup 57}Co radioactive sources, comparing simulated and experimental results. The response of a customized high pressure GPSC was also simulated to the higher energy conversion electrons from xenon radioisotopes. An alternative hybrid detector system is proposed showing excellent prospects for xenon radioisotope detection.
Modeling the Energy Resolution of Xenon with NEST
NASA Astrophysics Data System (ADS)
Uvarov, Sergey
In addition to explaining the mean yields, NEST (the Noble Element Simulation Technique) can also address the energy resolution degrading effects in noble elements, for both electron and nuclear recoils (ER and NR). Liquid and gaseous xenon will be presented as examples. A non-binomial recombination fluctuation model will be discussed which well describes the intrinsic, supra-Poissonian resolution observed in xenon. It is combined with electric field effects, the Fano factor, and detector efforts, such as finite light collection efficiency and PMT quantum efficiency. In matters of conflicting dark matter search results observed by experiments such as XENON100 and CoGeNT, a stochastic, non-analytic, partially non-Gaussian understanding of the energy resolution for low-energy, WIMP-like nuclear recoils may be part of the solution. ER-NR discrimination can be predicted well with such an understanding.
Liquid Hole Multipliers: bubble-assisted electroluminescence in liquid xenon
L. Arazi; E. Erdal; A. E. C. Coimbra; M. L. Rappaport; D. Vartsky; V. Chepel; A. Breskin
In this work we discuss the mechanism behind the large electroluminescence signals observed at relatively low electric fields in the holes of a Thick Gas Electron Multiplier (THGEM) electrode immersed in liquid xenon. We present strong evidence that the scintillation light is generated in xenon bubbles trapped below the THGEM holes. The process is shown to be remarkably stable over months of operation, providing - under specific thermodynamic conditions - energy resolution similar to that of present dual-phase liquid xenon experiments. The observed mechanism may serve as the basis for the development of Liquid Hole Multipliers (LHMs), capable of producing local charge-induced electroluminescence signals in large-volume single-phase noble-liquid detectors for dark matter and neutrino physics experiments.
Liquid Hole Multipliers: bubble-assisted electroluminescence in liquid xenon
Arazi, L; Coimbra, A E C; Rappaport, M L; Vartsky, D; Chepel, V; Breskin, A
In this work we discuss the mechanism behind the large electroluminescence signals observed at relatively low electric fields in the holes of a Thick Gas Electron Multiplier (THGEM) electrode immersed in liquid xenon. We present strong evidence that the scintillation light is generated in xenon bubbles trapped below the THGEM holes. The process is shown to be remarkably stable over months of operation, providing - under specific thermodynamic conditions - energy resolution similar to that of present dual-phase liquid xenon experiments. The observed mechanism may serve as the basis for the development of Liquid Hole Multipliers (LHMs), capable of producing local charge-induced electroluminescence signals in large-volume single-phase noble-liquid detectors for dark matter and neutrino physics experiments.
Single Ion Trapping for the Enriched Xenon Observatory
Waldman, Samuel J.; /Stanford U., Phys. Dept. /SLAC; ,
In the last decade, a variety of neutrino oscillation experiments have established that there is a mass difference between neutrino flavors, without determining the absolute neutrino mass scale. The Enriched Xenon Observatory for neutrinoless double beta decay (EXO) will search for the rare decays of xenon to determine the absolute value of the neutrino mass. The experiment uses a novel technique to minimize backgrounds, identifying the decay daughter product in real time using single ion spectroscopy. Here, we describe single ion trapping and spectroscopy compatible with the EXO detector. We extend the technique of single ion trapping in ultrahigh vacuum to trapping in xenon gas. With this technique, EXO will achieve a neutrino mass sensitivity of
Calibration of a Liquid Xenon Detector with Kr-83m
Kastens, L W; Manzur, A; McKinsey, D N
We report the preparation of a Kr-83m source and its subsequent use in calibrating a liquid xenon detector. Kr-83m atoms were produced through the decay of Rb-83 atoms trapped in zeolite molecular sieve and were then introduced into liquid xenon. Decaying Kr-83m nuclei were detected through liquid xenon scintillation. Conversion electrons with energies of 9.4 keV and 32.1 keV from the decay of Kr-83m were both observed. This calibration source will allow the characterization of the scintillation and ionization response of noble liquid detectors at low energies, highly valuable for the search for WIMP dark matter. Kr-83m may also be useful for measuring fluid flow dynamics, both to understand purification in noble liquid-based particle detectors, as well as for studies of classical and quantum turbulence in superfluid helium.
Reflectance of Polytetrafluoroethylene (PTFE) for Xenon Scintillation Light
Silva, C; Pereira, A; Chepel, V; Lopes, M I; Solovov, V
Gaseous and liquid xenon particle detectors are being used in a number of applications including dark matter search and neutrino-less double beta decay experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors both as electrical insulator and as a light reflector to improve the efficiency of detection of scintillation photons. However, xenon emits in the vacuum ultraviolet wavelength region (175 nm) where the reflecting properties of PTFE are not sufficiently known. In this work we report on measurements of PTFE reflectance, including its angular distribution, for the xenon scintillation light. Various samples of PTFE, manufactured by different processes (extruded, expanded, skived and pressed) have been studied. The data were interpreted with a physical model comprising both specular and diffuse reflections. The reflectance obtained for these samples ranges from about 47% to 66% for VUV light. Fluoropolymers, namely ETFE, FEP and PFA were also measured.
Bronchial imaging in humans using xenon K-edge dichromography
NASA Astrophysics Data System (ADS)
Giacomini, J. C.; Gordon, H.; O'Neil, R.; Van Kessel, A.; Cason, B.; Chapman, D.; Lavendar, W.; Gmur, N.; Menk, R.; Thomlinson, W.; Zhong, Z.; Rubenstein, E.
This report describes the initial use of K-edge xenon dichromography for imaging the bronchial tree in humans. The subjects inhale an anatomic dead-space volume of a mixture of 80% xenon and 20% oxygen, following which a dichromographic line-scan image is recorded using two monochromatic synchrotron radiation beams closely bracketing the k-edge of xenon (34.56 keV). Images of airways, from main-stem bronchi to fourth-order branches, are recorded with a pixel resolution of 0.5ū0.5 mm. The scanning rate is 12 cm/s, the line exposure time is 4 ms, the skin dose to the exposed area (125 mm ū 150 mm) is <0.35 rad.
Estimation of Anomalous Single Scatter Events in XENON100 Data
NASA Astrophysics Data System (ADS)
Lim, Kyungeun; Xenon100 Collaboration
Anomalous single scatter events in XENON100 are events that have only one scintillation pulse (S1) and one ionization pulse (S2), but are multiple scatters in nature. Only one scatter takes place inside the detector's charge and light sensitive volume, resulting in a S2/S1 ratio that is lower than that of true single scatter events and typical of that expected from a WIMP interaction. The identification and suppression of these anomalous events is therefore essential for a sensitive dark matter search. I present results from a Monte Carlo (MC) study that was carried out to estimate the expected number of anomalous single scatter events in the XENON100 WIMP search data. The MC was validated with a comparison with Co-60 gamma-calibration data. We gratefully acknowledge support from NSF, DOE, SNF, the Volkswagen Foundation, FCT, and STCSM. We are grateful to the LNGS for hosting and supporting the XENON program.
Observation of Single-File Diffusion in Dipeptide Nanotubes by Xenon-129 High Field NMR Diffusometry
Weston, Ken
Observation of Single-File Diffusion in Dipeptide Nanotubes by Xenon-129 High Field NMR evidence for molecular single file diffusion of xenon gas confined inside model nanotube systems, i.e. L of xenon measured by Xe-129 PFG NMR in dipeptide nanotubes at 298 K. The experimental data in the figure
Mass transfer of helium, neon, argon, and xenon through a steady-state upper mantle
D. Porcelli; G. J. Wasserburg
We have examined the steady-state upper mantle model for helium, neon, argon, and xenon following the mass transfer approach presented by Kellogg and Wasserburg (1990) for helium and Porcelli and Wasserburg (1995a) for xenon. The model explains the available observational data of mantle helium, neon, argon, and xenon isotope compositions and provides specific predictions regarding the rare gas isotopic compositions
Applications of controlled-flow laser-polarized xenon gas to porous and granular media study
Walsworth, Ronald L.
Applications of controlled-flow laser-polarized xenon gas to porous and granular media study R. W of continuous flow laser-polarized xenon gas, both in unrestricted tubing, and in a model porous media of continuous flow laser-polarized xenon gas in unrestricted tubing indicate clear diffraction minima resulting
Monitoring radioactive xenon gas in room air using activated charcoal
Langford, J.; Thompson, G. (Princess Margaret Hospital for Children, Perth (Australia) Sir Charles Gairdner Hospital, Perth (Australia))
A method for monitoring room air for radioactive xenon gas is described. It uses activated charcoal vials, a vacuum source and a well-type scintillation counter. The method may be adapted for detection and identification of any radioactive gas excluding those with ultra-short half-lives. Sampling room air during xenon-133 ({sup 133}Xe) ventilation lung studies was performed using this technique. The results show that low concentrations of {sup 133}Xe in room air can be reliably detected and that staff exposure to {sup 133}Xe at this institution was within ICRP recommendations.
Total elastic cross sections for metastable argon on xenon
Barrios, A.; Faxas, M.; Li, J. [and others
Total scattering cross sections have been measured using single beam attenuation of a metastable argon atom mixed {sup 3}P{sub 2,0} beam scattered from xenon. After relative velocity and angular corrections are made, preliminary data give a total scattering cross section of 700 {plus_minus} 65 {Angstrom}{sup 2} (at a relative velocity of 1000 m/s) is found. Earlier experiments give a total cross section for metastable argon atoms scattered from xenon of approximately 754 {Angstrom}{sup 2} and 580 {Angstrom}{sup 2} (at 1000 m/s).
Deactivation of the xenon atom in the 6s metastable state in collisions with xenon and helium atoms
D A Zayarnyi; Ludmila V Semenova; N N Ustinovskii; I V Kholin; A Yu Chugunov
The absorption probing method was used to investigate collisional deactivation of the metastable 6s[3\\/2]░(│P) state of the xenon atom in high-pressure He - Xe mixtures with a low xenon concentration. Measurements were made of the rate constants of the plasma-chemical reactions Xe*+Xe+He Xe*+He [(1.7 {+-}0.2) x10│▓ cm s╣], Xe*+2He HeXe*+He (less than 3 x 10│ cm s╣), and Xe*+He products+He
ACTIVE MEDIA: Deactivation of the xenon atom in the 6s metastable state in collisions with xenon and helium atoms
D. A. Zayarnyi; Ludmila V. Semenova; N. N. Ustinovskii; I. V. Kholin; A. Yu Chugunov
The absorption probing method was used to investigate collisional deactivation of the metastable 6s[3\\/2]20(3P2) state of the xenon atom in high-pressure He --- Xe mixtures with a low xenon concentration. Measurements were made of the rate constants of the plasma-chemical reactions Xe*+Xe+He --> Xe2*+He [(1.7 ▒0.2) ū10-32 cm6 s-1], Xe*+2He--> HeXe*+He (less than 3 ū 10-35 cm6 s-1), and Xe*+He-->
Virial equation of state of helium, xenon, and helium-xenon mixtures from speed-of-sound and burnett P ? T measurements
J. J. Hurly; J. W. Schmidt; S. J. Boyes; M. R. Moldover
The virial equation of state was determined for helium, xenon, and helium-xenon mixtures for the pressure and temperature\\u000a ranges 0.5 to 5 MPa and 210 to 400 K. Two independent experimental techniques were employed: BurnettP?T measurements and speed-of-sound measurements. The temperature-dependent second and third density virial coefficients for\\u000a pure xenon and the second and third interaction density virial coefficients for
Uranium dioxide films with xenon filled bubbles for fission gas behavior studies
NASA Astrophysics Data System (ADS)
Usov, I. O.; Dickerson, R. M.; Dickerson, P. O.; Byler, D. D.; McClellan, K. J.
Electron beam evaporation and ion beam assisted deposition (IBAD) methods were utilized to fabricate depleted UO2 films and UO2 films with embedded Xe atoms, respectively. The films were fabricated at elevated temperature of 700 ░C and also subsequently annealed at 1000 ░C to induce grain growth and Xe atom redistribution. The goal of this work was to synthesize reference UO2 samples with controlled microstructures and Xe-filled bubble morphologies, without the effects attendant to rector irradiation-induced fission. Transmission electron microscopy (TEM) microstructural characterization revealed that fine Xe-filled bubbles nucleated in the as grown films and subsequent annealing resulted in noticeable bubble size increase. Reported results demonstrate the great potential IBAD techniques and UO2 films have for various areas of nuclear materials studies.
XENON in medical area: emphasis on neuroprotection in hypoxia and anesthesia
Xenon is a medical gas capable of establishing neuroprotection, inducing anesthesia as well as serving in modern laser technology and nuclear medicine as a contrast agent. In spite of its high cost, its lack of side effects, safe cardiovascular and organoprotective profile and effective neuroprotective role after hypoxic-ischemic injury (HI) favor its applications in clinics. Xenon performs its anesthetic and neuroprotective functions through binding to glycine site of glutamatergic N-methyl-D-aspartate (NMDA) receptor competitively and blocking it. This blockage inhibits the overstimulation of NMDA receptors, thus preventing their following downstream calcium accumulating cascades. Xenon is also used in combination therapies together with hypothermia or sevoflurane. The neuroprotective effects of xenon and hypothermia cooperate synergistically whether they are applied synchronously or asynchronously. Distinguishing properties of Xenon promise for innovations in medical gas field once further studies are fulfilled and XenonÆs high cost is overcome. PMID:23369273
Measurement of the reflectivity to 178 nm light of the PTFE used in the Xenon100
NASA Astrophysics Data System (ADS)
Choi, Bin; Xenon Collaboration
The XENON100 time projection chamber (TPC) uses polytetrafluoroethylene (PTFE) both as insulator and as VUV-light reflector. The reflectivity of PTFE, however, is not well established, especially considering that it significantly depends on the surface finish. Furthermore, the PTFE in XENON100 is in contact with the liquid xenon at about - 100░C, which can also affect the reflecting property. A set-up consisting of a monochromator and a vacuum chamber was developed within the XENON100 collaboration and operated at the Columbia University Nevis Laboratory to measure the reflectivity of PTFE and other material samples, relevant for future XENON detectors. The chamber is equipped with an Iwatani PDC08 pulse tube refrigerator (PTR) to be able to cool down the samples to liquid xenon temperature. The same set-up has also been used to measure, for the first time, the quantum efficiency (QE) of the Hamamatsu R8520-06-AL XENON100 photomultipliers at low temperature.
NEST: A Comprehensive Model for Scintillation Yield in Liquid Xenon
M. Szydagis; N. Barry; K. Kazkaz; J. Mock; D. Stolp; M. Sweany; M. Tripathi; S. Uvarov; N. Walsh; M. Woods
A comprehensive model for explaining scintillation yield in liquid xenon is introduced. We unify various definitions of work function which abound in the literature and incorporate all available data on electron recoil scintillation yield. This results in a better understanding of electron recoil, and facilitates an improved description of nuclear recoil. An incident gamma energy range of O(1 keV) to
Diffusion NMR Methods Applied to Xenon Gas for Materials Study
R. W. Mair; M. S. Rosen; R. Wang; D. G. Cory; R. L. Walsworth
We report initial NMR studies of i) xenon gas diffusion in model heterogeneous porous media, and ii) continuous flow laser-polarized xenon gas. Both areas utilize the Pulsed Gradient Spin Echo techniques in the gas-phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients - a brief overview of this area is provided in the introduction. The heterogeneous or multiple-length scale model porous media consisted of random packs of mixed glass beads of two different sizes. We focus on observing the approach of the time-dependent gas diffusion coefficient, D(t), (an indicator of mean squared displacement) to the long-time asymptote, with the aim of understanding the long-length scale structural information that may be derived from a heterogeneous porous system. The Pade approximation is used to interpolate D(t) data between the short and long time limits. Initial studies of continuous flow laser-polarized xenon gas demonstrate velocity-sensitive imaging of much higher flows than can generally be obtained with liquids (20 - 200 mm/s). Gas velocity imaging is, however, found to be limited to a resolution of about 1 mm/s due to the high diffusivity of gases compared to liquids. We also present the first gas-phase NMR scattering, or diffusive-diffraction, data: namely, flow-enhanced structural features in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack.
Xe-129 NMR of xenon dissolved in biological media.
NASA Astrophysics Data System (ADS)
Mazitov, R. K.; Kuzma, N. N.; Happer, W.; Driehuys, B.; Merrill, G. F.
The high solubility and large chemical shift of ^129Xe in various tissues makes it an ideal, non-invasive probe for pathological conditions such as cancer or atherosclerosis. To this end, we report NMR measurements of lineshapes, chemical shifts, and relaxation times of ^129Xe dissolved in the following biological tissues in vitro: heart, muscle, sinew, stomach(R.K. Mazitov, K. M. Enikeev, et al., Dokl. Akad. Nauk) 365, 396 (1999)., and the white and yolk of egg. NMR measurements of xenon dissolved in olive and sunflower oils are also reported. Tissues weighing 160--250 mg, not exposed to freezing, were studied in a 11.75 T field at the ^129Xe resonance frequency of 138.4 MHz; the pressure of xenon in the sealed-sample ampoules was ~20 bar. The influence of drugs and water content on tissues was studied. No xenon-water clathrates(J.A. Ripmeester and D.W. Davidson, J. Mol. Struct. ) 75, 67 (1981). were observed in the tissues, even at the high pressures used. The aim of this study is to establish possible correlations between the NMR parameters of dissolved xenon and the state of the tissue.
Pulsed xenon flashlamp device for the treatment of psoriasis
NASA Astrophysics Data System (ADS)
Baumgardner, Jonathan M.; Hennings, David R.; Johnston, Thomas F., Jr.; Taylor, Eric
We present our research into a pulsed xenon lamp source for the treatment of psoriasis and other skin disorders. Various filtering techniques, lamp configurations, power supply configurations and delivery systems are discussed. Comparisons are made to existing treatment modalities. Cryogen cooling of the treatment site is discussed.
On the spin-dependent sensitivity of XENON100
Mathias Garny; Alejandro Ibarra; Miguel Pato; Stefan Vogl
The latest XENON100 data severely constrains dark matter elastic scattering off nuclei, leading to impressive upper limits on the spin-independent cross-section. The main goal of this paper is to stress that the same data set has also an excellent \\emph{spin-dependent} sensitivity, which is of utmost importance in probing dark matter models. We show in particular that the constraints set by XENON100 on the spin-dependent neutron cross-section are by far the best at present, whereas the corresponding spin-dependent proton limits lag behind other direct detection results. The effect of nuclear uncertainties on the structure functions of xenon isotopes is analysed in detail and found to lessen the robustness of the constraints, especially for spin-dependent proton couplings. Notwithstanding, the spin-dependent neutron prospects for XENON1T and DARWIN are very encouraging. We apply our constraints to well-motivated dark matter models and demonstrate that in both mass-degenerate scenarios and the minimal supersymmetric standard model the spin-dependent neutron limits can actually override the spin-independent limits. This opens the possibility of probing additional unexplored regions of the dark matter parameter space with the next generation of ton-scale direct detection experiments.
Discovery of palladium, antimony, tellurium, iodine, and xenon isotopes
Kathawa, J; Thoennessen, M
Currently, thirty-eight palladium, thirty-eight antimony, thirty-nine tellurium, thirty-eight iodine, and forty xenon isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.
Spectroscopic investigations of the plasma of xenon arc lamps
G. S. Antonov; Yu. A. Kalinin; L. I. Kiselevskii; D. A. Solov'yanchik; Z. P. Feshchenko; V. D. Shimanovich
A diagram of the lamp is shown in Fig. 1. The inside diameter is 4 ram. The electrodes are made of tungsten, soldered in, and separated by a distance of 120 ram. The lamp is cooled by flowing water; the thickness of the water sleeve 3 is about 6 mm. The initial pressure of xenon in the tube is less
Dynamics of Xenon Plasma Streams Generated by Magnetoplasma Compressor
Garkusha, I. E.; Chebotarev, V. V.; Ladygina, M. S.; Marchenko, A. K.; Petrov, Yu. V.; Solyakov, D. G.; Tereshin, V. I.; Trubchaninov, S. A.; Byrka, O. V. [Institute of Plasma Physics, NSC KIPT, 61108, Kharkov (Ukraine); Hassanein, A. [Argonne National Laboratory (United States)
The paper presents the investigations of parameters of xenon plasma streams generated by magnetoplasma compressor (MPC) of compact geometry with conical-shaped electrodes and pulsed gas supply. Discharge characteristics and dynamics of the plasma streams, generated by MPC in different operation modes are analyzed. First results of Xe plasma radiation measurements in EUV wave range, obtained with AXUV diodes are presented.
The effect of nitrogen on xenon ion engine erosion
NASA Technical Reports Server (NTRS)
Garner, Charles E.; Brophy, John R.; Pless, L. C.; Barnett, John W.
Erosion studies were performed on a 30-cm diameter J-series ion engine modified for operation on xenon propellant. The erosion rates of molybdenum and tantalum badges placed at different locations within the discharge chamber were measured as a function of the percentage of nitrogen (by mass) added to the xenon propellant. Reductions in the erosion rates of these badges of a factor of 8 to 50 were observed at nitrogen addition fractions between 0.5 to 2.0 percent. Reductions in cathode-side baffle erosion were achieved by adding nitrogen to the xenon propellant or by increasing the cathode orifice diameter. Analyses show that no significant degradation in ion engine performance should be expected at these nitrogen mass fractions. XRD, XPS and Auger analyses indicate the existence of nitrogen and nitrides in the surface of some but not all of the badges used in the tests where nitrogen was added to the xenon. Difficulty in identifying surface nitrides in the samples may be due to the existence of surface oxides and contaminants, or to the small thicknesses of the nitride layers.
Output power characteristics of the neutral xenon long laser
Gary J. Linford
Lasers which oscillate within inhomogeneously broadened gain media exhibit spectral hole burning and concomitant reduction in output power compared with equivalent homogeneously broadened laser gain media. By increasing the cavity length, it may be possible to demonstrate at least a partial transition from an inhomogeneous laser cavity mode spectrum to a homogeneous spectrum. In neutral xenon lasers the inhomogeneous spectral
Near-threshold photoionization of xenon metastable atoms
R. D. Rundel; F. B. Dunning; H. C. Goldwire Jr.; R. F. Stebbings
Photoionization from metastable levels of atomic xenon has been studied in the wavelength range from the threshold at 4622 A to 2700 A. Structure in the photoionization signal, due to autoionization, is analyzed to provide term values, lifetimes, and line-shape parameters of the autoionizing states. These parameters, together with the estimated absolute cross sections, are used to derive discrete and
Total elastic scattering cross sections for metastable argon on xenon
J. Li; M. Faxas; J. W. Sheldon; K. A. Hardy
The interaction potential between metastable argon (Ar*) and xenon has been determined by a measurement of the velocity dependence of the total elastic-scattering cross section for the reaction Ar*+Xe. The cross sections have been corrected for the inelastic contribution to the reaction. The potential parameters have been determined by comparing the data with potential parameters calculated with both semiclassical and
Optical Control of Ultracold Collisions in Metastable Xenon
M. Walhout; U. Sterr; C. Orzel; M. Hoogerland; S. L. Rolston
Near-resonant light is used to modify the collision dynamics of magneto-optically trapped metastable xenon atoms. Enhanced collisional ionization occurs for a ``control laser'' tuned below resonance, greatly exceeding the predictions of existing models of trap loss very close to resonance. With the trapping laser off, control light tuned above resonance suppresses ionization by a factor of 8. With the trap
Ultracold collisions and optical shielding in metastable xenon
K.-A. Suominen; K. Burnett; P. S. Julienne; M. Walhout; U. Sterr; C. Orzel; M. Hoogerland; S. L. Rolston
Collisions between laser-cooled metastable xenon atoms in the presence of laser fields provide a good experimental test for ultracold collision theories as the observed ionization can be directly linked to the atomic binary collisions. Hyperfine structure is not present for the even isotopes Xe132 and Xe136, which simplifies the theoretical work. We present our results and show how these and
NASA's Evolutionary Xenon Thruster (NEXT) Ion Propulsion System Information Summary
NASA Technical Reports Server (NTRS)
Pencil, Eirc S.; Benson, Scott W.
This document is a guide to New Frontiers mission proposal teams. The document describes the development and status of the NASA's Evolutionary Xenon Thruster (NEXT) ion propulsion system (IPS) technology, its application to planetary missions, and the process anticipated to transition NEXT to the first flight mission.
Applications of highly spin-polarized xenon in NMR
Long, H.W. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; [Lawrence Berkeley Lab., CA (United States)
The main goal of the work presented in this thesis is produce highly spin-polarized xenon to create much greater signal intensities (up to 54,000 times greater) so as to allow studies to be made on systems with low surface area and long spin-lattice relaxation times. The spin-exchange optical pumping technique used to create high nuclear spin polarization is described in detail in chapter two. This technique is initially applied to some multiple-pulse optically detected NMR experiments in low magnetic field (50G) that allow the study of quadrupoler interactions with a surface of only a few square centimeters. In chapter three the apparatus used to allow high field {sup 129}Xe NMR studies to be performed with extremely high sensitivity is described and applied to experiments on diamagnetic susceptibility effects in thin ({approximately}2000 layers) films of frozen xenon. Preliminary surface investigations of laser polarized {sup 129}Xe adsorbed an a variety of materials (salts, molecular crystals, amorphous carbon, graphite) are then discussed. A full detailed study of the surface of a particular polymer, poly(acrylic acid), is presented in chapter four which shows the kind of detailed information that can be obtained from this technique. Along with preliminary results for several similar polymers, a summary is given of xenon studies of a novel ultra-high surface area polymer, poly(triarylcarbinol). Finally in chapter five the exciting possibility of transferring the high spin order of the laser polarized xenon has been used to transfer nuclear spin order to {sup 13}CO{sub 2} in a xenon matrix and to protons on poly(triarylcarbinol).
NSDL National Science Digital Library
In this activity, students examine the relationship between carbon dioxide levels and global temperature change by studying a graph of these two variables. They will discover that by using data from ice cores, scientists can determine temperature and carbon dioxide levels in the air as far back as a hundred thousand years in the past. The students try to predict which variable is the independent one and then make a graph of temperature change and carbon dioxide levels. After making their graph, students describe the relationship between temperature and carbon dioxide levels in the atmosphere to determine if their predictions were correct.
NASA Technical Reports Server (NTRS)
Townes, C. H.
Progress in the discovery and study of interstellar molecules is summarized. The 36 molecular species thus far identified in interstellar space are listed in several groups which include simple hydrides, oxides, and sulfides, various derivatives of ammonia, molecules involving linear carbon chains, cyanides, and molecules related in structure to formaldehyde, alcohols, or ethers. Several free radicals are described, the discovery of molecules in external galaxies is discussed, and possible mechanisms for molecular formation are noted. Methods for examining relative isotopic abundances by measuring molecules in interstellar clouds are outlined, mechanisms for the excitation of interstellar molecules are reviewed, and values are presented for the C-12/C-13 abundance ratio in a number of interstellar clouds. The detection of interstellar masers is discussed along with pumping mechanisms and masing transitions in H2CO, CH, OH, and SiO. The nature of dense interstellar clouds is examined in terms of several simple and complex cloud models, with emphasis on multiple condensation models.
The Electron Impact Excitation of Neon and Xenon
NASA Astrophysics Data System (ADS)
Gastineau, John Edward
Absolute electron impact excitation optical cross sections of ninety-seven transitions in xenon have been measured using the optical method, over an energy range of 10 to 100 eV. The cross sections are generally pressure dependent over the range of 3 to below 0.10 mT, and are increasingly pressure dependent at electron energies above 50 eV. This is a much lower range for pressure effects than is seen in other gases. The apparent cross sections of the lowest lying p levels, configuration 5p('5)6p, labeled 2p in Paschen's notation, have been calculated from the appropriate optical cross sections. The low pressure limiting cross sections for the 2p(,1), 2p(,3), 2p(,6), 2p(,9), and 2p(,10) levels were reached. The apparent cross sections of xenon at energies well above threshold are generally an order of magnitude larger than those of helium and neon, with xenon cross sections being near 10('-18) cm('2). The xenon excitation functions are more sharply peaked than the functions of neon or helium. The cascade contributions at 3 mT to six (2p(,5-10)) levels were partially measured, and at 50 eV the apparent cross sections are 10-50% cascade. The form of the pressure dependence of the xenon 2p levels and of several cascade levels to the 2p levels were studied. All cross sections that were pressure dependent tended toward asymptotic limits at pressure of 2 to 3 mT. Radiation trapping of resonant levels was determined to be the dominate source of the pressure dependence, as the pressure dependence was made less severe by reducing the size of the collision chamber. The 2p levels, which are not resonant, are pressure dependent from receiving cascade from resonant levels. The neon 2p levels are similarly pressure dependent, chiefly from pressure dependent cascade from resonant levels. Absolute apparent cross sections for the 2p states were determined at pressures below 0.25 mT. The pressure dependence in neon is milder and occurs at higher pressure than in xenon. The decay components of several neon 2p and 2p cascade levels were studied with time resolved spectroscopy. Levels that showed pressure dependence in the above experiments also show significant decay components of lifetime more than 0.5 (mu)s.
NSDL National Science Digital Library
A new molecular science journal, Single Molecules, from Wiley Interscience, "will provide researchers with a broad overview of current methods and techniques, recent applications and shortcomings of present techniques in the field of single molecules." With temporary free access, the journal's latest issue contains a few full-text articles, with more articles being regularly added. This journal is currently calling for papers.
ERIC Educational Resources Information Center
Kang, Seong-Joo; Ryu, Eun-Hee
This article presents the development of a carbon dioxide fountain. The advantages of the carbon dioxide fountain are that it is odorless and uses consumer chemicals. This experiment also is a nice visual experiment that allows students to see evidence of a gaseous reagent being consumed when a pressure sensor is available. (Contains 3 figures.)ģ
Chlorine dioxide and hemodialysis
Because it has little or no tendency to generate carcinogenic trihalomethanes such as chloroform, chlorine dioxide is an attractive alternative to chlorine for drinking water disinfection. There are, however, concerns about its acute toxicity, and the toxic effects of its by-products, chlorite and chlorate. The human experience with chlorine dioxide in both controlled, prospective studies and in actual use situations
NSDL National Science Digital Library
The Science House
In this chemistry activity, learners use common chemicals to produce carbon dioxide and observe its properties. This resource includes brief questions for learners to answer after the experiment. Use this activity to introduce learners to carbon dioxide and its use as a fire extinguisher. Note: this activity involves an open flame.
Carbon Dioxide Emission Estimates
NSDL National Science Digital Library
The Carbon Dioxide Information Analysis Center of the Oak Ridge National Laboratory provides this new data on carbon dioxide emissions from fossil fuel burning, hydraulic cement production, and gas flaring in 1995. Data for one degree grid cells can be downloaded from the site in addition to code for analysis of the data.
Hydrogen atoms in solid xenon: trapping site structure, distribution, and stability as revealed by EPR studies in monoisotopic and isotopically enriched xenon matrices.
Feldman, Vladimir I; Sukhov, Fedor F; Orlov, Aleksei Yu
Trapping and decay of hydrogen atoms generated by fast electron irradiation of solid xenon doped with small hydrogen-containing molecules (acetylene, water) were studied by EPR using monoisotopic (136)Xe matrix (I = 0) and highly isotopically enriched (129)Xe matrix (I = 12). It was found that more than 99% of H atoms observed by EPR are initially trapped in the octahedral interstitial trapping sites, whereas initial population of the substitutional trapping sites is very small (less than 1%). The (129)Xe hyperfine coupling tensor parameters for major trapping site were determined from direct measurements in a (136)Xe matrix doped with small amount of (129)Xe: A(0) ((129)Xe) = -92.1 MHz and B((129)Xe) = -22 MHz. Final proof for the trapping site structure was obtained from comparison between experiment and simulation for the highly enriched (129)Xe matrix. The mean interspin distance of approximately 4 nm was estimated from the EPR signal linewidth in a (136)Xe matrix, the hydrogen atom loss upon irradiation being negligible at low doses. Decay of trapped H atoms occurring at 38-45 K leads to population (or creation) of metastable traps of lower symmetry. PMID:18537437
Xenon NMR studies of dynamics and exchange in zeolites
Moudrakovski, I.L.; Ratcliffe, C.I.; Ripmeester, J.A. [Steacie Institute for Molecular Sciences, Ottawa, Ontario (Canada)
We have found, despite earlier reports to the contrary, that for many microporous solids with one-dimensional channels (ZSM-12, ALPO-5, VPI-5, SSZ-24) the chemical shift has an anisotropic component. For ALPO-11, a detailed model has been developed which accounts for the loading-dependent chemical shift in terms of intraparticle exchange of statistical distributions of xenon atoms with 0, 1 or 2 nearest neighbors. A similar model can be applied to ZSM-12 up to moderate loadings. At higher loading levels 2D exchange methods show that interparticle exchange occurs as well. The same approach was used to study interparticle exchange in X and Y zeolite mixtures, exchange amongst zeolite clusters of up to 8 xenon atoms in the supercages of AgA zeolite, and main channel - side pocket exchange in mordenite. The parameters derived are directly relevant to the understanding of sorption and diffusion processes in zeolites.
A Study of Radon Background in the XENON100 Experiment
Weber, Marc [Max-Planck-Institut fuer Kernphysik, Postfach 103980, D-69029 Heidelberg (Germany)
The XENON100 Dark Matter experiment has recently published first results from an analysis of 11.2 live days of data, setting an upper limit on the spin-independent WIMP-nucleon elastic scattering cross section of 3.4x10{sup -44} cm{sup 2} at 55 GeV/c{sup 2} and 90% confidence level. This article focuses on one specific background component of the XENON100 detector by presenting two independent methods of measuring the {sup 222}Rn concentration during operation phase. A first estimate of radon activity is derived for the 11.2 days analysis, proving the feasibility of on-line radon monitoring. Remaining systematic uncertainties are discussed.
Molecular Dynamics Calculation of the Viscosity of Xenon Gas
NASA Astrophysics Data System (ADS)
Mountain, Raymond D.
The density variation of the viscosity of xenon gas is determined using molecular dynamics simulation with a semi-empirical pair potential fit to low-density gas properties. The gas states ranged in density from 0.37 to 7.62 mol Ę dm-3, and varied in temperature from 240 -591 K. The simulation results match the kinetic-theory predictions for the model potential at the lowest density, and systematically lie below the experimental values for higher densities. This indicates the need for many-body interactions to accurately predict the viscosity of xenon gas at even moderate densities. An operational criterion for identifying the density region where kinetic theory is appropriate is proposed.
Constraints on inelastic dark matter from XENON10
Angle, J; Aprile, E; Arneodo, F; Baudis, L; Bernstein, A; Bolozdynya, A; Coelho, L C; Dahl, C E; DeViveiros, L; Ferella, A D; Fernandes, L P; Fiorucci, S; Gaitskell, R J; Giboni, K L; Gomez, R; Hasty, R; Kastens, L; Kwong, J; Lopes, J M; Madden, N; Manalaysay, A; Manzur, A; McKinsey, D N; Monzani, M E; Ni, K; Oberlack, U; Orboeck, J; Plante, G; Santorelli, R; dos Santos, J; Shagin, P; Shutt, T; Sorensen, P; Schulte, S; Winant, C; Yamashita, M
It has been suggested that dark matter particles which scatter inelastically from detector target nuclei could explain the apparent incompatibility of the DAMA modulation signal (interpreted as evidence for particle dark matter) with the null results from CDMS-II and XENON10. Among the predictions of inelastically interacting dark matter are a suppression of low-energy events, and a population of nuclear recoil events at higher nuclear recoil equivalent energies. This is in stark contrast to the well-known expectation of a falling exponential spectrum for the case of elastic interactions. We present a new analysis of XENON10 dark matter search data extending to E{sub nr} = 75 keV nuclear recoil equivalent energy. Our results exclude a significant region of previously allowed parameter space in the model of inelastically interacting dark matter. In particular, it is found that dark matter particle masses m{sub x} {approx}> 150 GeV are disfavored.
Searching for Double Beta Decay with the Enriched Xenon Observatory
Hall, C.; /SLAC
The Enriched Xenon Observatory (EXO) Collaboration is building a series of experiments to search for the neutrinoless double beta decay of {sup 136}Xe. The first experiment, known as EXO-200, will utilize 200 kg of xenon enriched to 80% in the isotope of interest, making it the largest double beta decay experiment to date by one order of magnitude. This experiment is rapidly being constructed, and will begin data taking in 2007. The EXO collaboration is also developing a technique to identify on an event-by-event basis the daughter barium ion of the double beta decay. If successful, this method would eliminate all conventional radioactive backgrounds to the decay, resulting in an ideal experiment. We summarize here the current status of EXO-200 construction and the barium tag R&D program.
Gamma background discrimination in the XENON100 experiment
NASA Astrophysics Data System (ADS)
Melgarejo, Antonio; Xenon100 Collaboration
Direct dark matter detection experiments rely on the ability to have an expected background close to 0 in order to be able to identify possible WIMP signals. Among the multiple strategies to achieve this goal, most of the experiments use background reduction techniques which exploit the difference between electron-like signal (most radioactive backgrounds) and neutron-like signals (neutrons and WIMPs). In this talk we will show the studies and measurements within the XENON100 experiment to distinguish signals from electrons and neutrons by comparing their light to signal ratio. A straightforward prediction of this work is the amount of events expected in the dark matter region in this experiment. We gratefully acknowledge support from NSF, DOE, SNF, the Volkswagen Foundation, FCT and STCSM. We are grateful to the LNGS for hosting and supporting the XENON program.
XENON1T - Direct Dark Matter Search on the Verge of a New Detector Generation
NASA Astrophysics Data System (ADS)
Aprile, Elena
The XENON dark matter project aims at finding direct evidence for the scattering of weakly interacting massive dark matter particles (WIMPs) with target nuclei in an ultra-low background liquid xenon detector. After the successful operation of the XENON100 instrument - for many years the world's most sensitive deep underground WIMP detector - the next generation detector XENON1T is presently being built at the Italian Gran Sasso underground facility. The commissioning and first data taking of the experiment are expected to start in 2015. The talk will focus on the special challenges related to a ton-scale liquid xenon detector, provide a comprehensive overview of the ongoing construction phase, and discuss the prospects and projected physics reach of the experiment. We gratefully acknowledge the continuing support of the XENON dark matter project by the National Science Foundation.
The mobilities of xenon ions in xenon and the derived charge transfer cross section for Xe+(2P3\\/2) ions in xenon
P. H. Larsen; M. T. Elford
A drift tube of the four-gauze Tyndall-Powell type has been used to obtain accurate mobility data for ground-state Xe+(2P3\\/2) ions, metastable Xe+(2P1\\/2) ions and molecular Xe2+\\/Xe3+ ions in xenon at room temperature (294.1+or-0.2K) over a wide E\\/N range (E is the electric field strength and N is the gas number density). The measurements were made at E\\/N values from 50
A 20 atmosphere imaging xenon gas scintillation drift chamber
T. K. Edberg; A. Parsons; B. Sadoulet; S. Weiss; J. Wilkerson; G. Smith
We describe the high pressure xenon imaging gas scintillation drift chamber with waveshifting fiber readout, a novel detector for hard X-ray (30 keV to at least 300 keV) observations. This technique promises good energy resolution (24%\\/&surd;E (keV) FWHM), excellent imaging ( ~ 200 mum FWHM), and very high sensitivity due to large effective area and low backgrounds. We describe a
Neutrino physics with multi-ton scale liquid xenon detectors
L. Baudis; A. Ferella; A. Kish; A. Manalaysay; T. Marrodan Undagoitia; M. Schumann
We study the sensitivity of large-scale xenon detectors to low-energy solar neutrinos, to coherent neutrino-nucleus scattering and to neutrinoless double beta decay. As a concrete example, we consider the xenon part of the proposed DARWIN (Dark Matter WIMP Search with Noble Liquids) experiment. We perform detailed Monte Carlo simulations of the expected backgrounds, considering realistic energy resolutions and thresholds in the detector. In a low-energy window of 2-30 keV, where the sensitivity to solar pp and $^7$Be-neutrinos is highest, an integrated pp-neutrino rate of 5900 events can be reached in a fiducial mass of 14 tons of natural xenon, after 5 years of data. The pp-neutrino flux could thus be measured with a statistical uncertainty around 1%, reaching the precision of solar model predictions. These low-energy solar neutrinos will be the limiting background to the dark matter search channel for WIMP-nucleon cross sections below $\\sim$2$\\times$10$^{-48}$ cm$^2$ and WIMP masses around 50 GeV$\\cdot$c$^{-2}$, for an assumed 99.5% rejection of electronic recoils due to elastic neutrino-electron scatters. Nuclear recoils from coherent scattering of solar neutrinos will limit the sensitivity to WIMP masses below $\\sim$6 GeV$\\cdot$c$^{-2}$ to cross sections above $\\sim$4$\\times$10$^{-45}$cm$^2$. DARWIN could reach a competitive half-life sensitivity of 5.6$\\times$10$^{26}$ y to the neutrinoless double beta decay of $^{136}$Xe after 5 years of data, using 6 tons of natural xenon in the central detector region.
A metastable xenon isotope detector for treaty verification
J. A. M. Lopes; R. E. Morgado; C. A. N. Conde
A system to selectively detect and quantify the xenon metastable isotopes 131mXe, 133mXe, 133Xe, and 135Xe has been designed, fabricated, and tested. The system combines high-resolution electron and gamma-ray spectrometry with coincidence\\/anticoincidence timing for signal selectivity and background rejection. By utilizing X-ray-fluorescence gating, backgrounds from other sources are expected to be reduced to the sub-becquerel level. Coincidence and anti-coincidence triggers
A metastable xenon isotope detector for treaty verification
J. A. M. Lopes; R. E. Morgado; C. A. N. Conde
A system to selectively detect and quantify the xenon metastable isotopes 131mXe, 133mXe, 133Xe, and 135Xe has been designed, fabricated, and tested. The system combines high-resolution electron and gamma-ray spectrometry with coincidence\\/anti-coincidence timing for signal selectivity and background rejection. By utilizing X-ray-fluorescence gating, backgrounds from other sources are expected to be reduced to the sub-becquerel level. Coincidence and anti-coincidence triggers
Metastability-exchange and depolarising collisions in xenon and krypton
V. Lefevre-Seguin; M. Leduc
Collisions between rare-gas atoms in the 3P2 metastable state and in the ground state were studied. The metastable atoms were created by a discharge and oriented by optical pumping, and pressure broadening of their magnetic-resonance curves was measured. For xenon, mixtures of even and odd isotopes were used, leading to a determination of the cross section for metastability-exchange collisions. For
Total elastic cross sections for metastable argon on xenon
A. Barrios; M. Faxas; J. Li
Total scattering cross sections have been measured using single beam attenuation of a metastable argon atom mixed ┬│P{sub 2,0} beam scattered from xenon. After relative velocity and angular corrections are made, preliminary data give a total scattering cross section of 700 ┬▒ 65 Ō½┬▓ (at a relative velocity of 1000 m\\/s) is found. Earlier experiments give a total cross section
A Comprehensive Study of the Large Underground Xenon Detector
NASA Astrophysics Data System (ADS)
Woods, Michael Austin
The Large Underground Xenon (LUX) dark matter search experiment operates a time projection chamber constructed of 370 kg of xenon, currently installed in the Homestake gold mine. The goal of the experiment is to detect Weakly Interacting Massive Particles (WIMPs). Novel calibration methods for this uniquely large detector are discussed. Background events due to standard model physics processes including cosmogenically activated xenon, alpha emission, and neutron production are shown to be negligible in recent 85 day WIMP search data. The LUX Monte Carlo simulation includes a new physical model, the Nobel Element Simulation Technique (NEST), for scintillation and ionization. NEST describes energy-, particle-, field- and medium-dependent behavior of a charge recombination model. A simulated data acquisition chain that bridges the gap between simulation and data has been developed to permit full testing of the analysis tools employed by LUX. Signal generation by cumulative photon responses are described algorithmically. Computational optimization has been performed to decrease processing time by a factor of fifty. A new technique for event depth estimation using machine learning and image analysis is introduced. Variable length waveforms are converted to fixed dimension field maps for use in machine learning. A support vector machine trained against pulse shapes with known depth successfully regressed depth without direct measurement of highly variable pulse widths. The world's most stringent limits on spin-independent WIMP-nucleon scattering cross section are presented.
Electron-impact excitation of neon and xenon
Gastineau, J.E.
Absolute electron impact excitation optical cross sections of 97 transitions in xenon were measured, using the optical method, over an energy range of 10 to 100 eV. The cross sections are generally pressured-dependent over the range of 3 to below 0.10 mT, and are increasingly pressured-dependent at electron energies about 50 eV. This is a much lower range for pressure effects than is seen in other gases. The apparent cross sections of the lowest-lying p levels, configuration 5p/sup 5/6p, labeled 2p in Paschen's notation, were calculated from the appropriate optical cross sections. The form of the pressure dependence on the xenon 2p levels and of several cascade levels to the 2p levels were studied. All cross sections that were pressure dependent tended toward asymptotic limits at pressure of 2 to 3 mT. The neon 2p levels are similarly pressure-dependent, chiefly from pressure-dependent cascade from resonant levels. Absolute apparent cross sections for the 2p states were determined at pressures below 0.25 mT. The pressure dependence in neon is milder and occurs at higher pressure than in xenon.
Allende meteorite: Isotopically anomalous xenon is accompanied by normal osmium.
Takahashi, H; Higuchi, H; Gros, J; Morgan, J W; Anders, E
The (184)Os/(190)Os ratio of six Allende meteorite samples was determined by neutron activation analysis. Four chromite concentrates gave a ratio differing from the terrestrial ratio by only -0.1 +/- 0.4%, although they contained highly anomalous xenon enriched by up to 67% in (124)Xe and 93% in (136)Xe. In view of this result and the normal isotopic composition of carbon and oxygen in these fractions, it seems very unlikely that the xenon anomalies were produced in a supernova by the p and r processes. More probably, the xenon anomalies were established in the early solar system, by mass fractionation during trapping of noble gases in solids and by spontaneous fission of a superheavy element.Two other samples, containing osmium from the calcium,aluminum-rich inclusions, also gave an (184)Os/(190)Os ratio within -0.1 +/- 0.5% of the terrestrial value, although these inclusions show well-established anomalies in the light elements oxygen and magnesium, which appear to be due to pre-solar dust grains of distinctive nuclear history. Apparently the stellar source of the anomalous oxygen and magnesium did not synthesize heavier elements. PMID:16592365
Intermittent Exposure to Xenon Protects against Gentamicin-Induced Nephrotoxicity
Jia, Ping; Teng, Jie; Zou, Jianzhou; Fang, Yi; Jiang, Suhua; Yu, Xiaofang; Kriegel, Alison J.; Liang, Mingyu; Ding, Xiaoqiang
Aminoglycoside antibiotics, especially gentamicin, are widely used to treat Gram-negative infections due to their efficacy and low cost. Nevertheless the use of gentamicin is limited by its major side effect, nephrotoxicity. Xenon (Xe) provided substantial organoprotective effects in acute injury of the brain and the heart and protected against renal ischemic-reperfusion injury. In this study, we investigated whether xenon could protect against gentamicin-induced nephrotoxicity. Male Wistar rats were intermittently exposed to either 70% xenon or 70% nitrogen (N2) balanced with 30% oxygen before and during gentamicin administration at a dose of 100 mg/kg for 7 days to model gentamicin-induced kidney injury. We observed that intermittent exposure to Xe provided morphological and functional renoprotection, which was characterized by attenuation of renal tubular damage, apoptosis, and oxidative stress, but not a reduction in inflammation. We also found that Xe pretreatment upregulated hypoxia-inducible factor 2? (HIF-2?) and its downstream effector vascular endothelial growth factor, but not HIF-1?. With regard to the three HIF prolyl hydroxylases, Xe pretreatment upregulated prolyl hydroxylase domain-containing protein-2 (PHD2), suppressed PHD1, and had no influence on PHD3 in the rat kidneys. Pretreatment with Xe also increased the expression of miR-21, a microRNA known to have anti-apoptotic effects. These results support Xe renoprotection against gentamicin-induced nephrotoxicity. PMID:23737979
Very-low-field MRI of laser polarized xenon-129
NASA Astrophysics Data System (ADS)
Zheng, Yuan; Cates, Gordon D.; Tobias, William A.; Mugler, John P.; Miller, G. Wilson
We describe a homebuilt MRI system for imaging laser-polarized xenon-129 at a very low holding field of 2.2 mT. A unique feature of this system was the use of Maxwell coils oriented at so-called 'magic angles' to generate the transverse magnetic field gradients, which provided a simple alternative to Golay coils. We used this system to image a laser-polarized xenon-129 phantom with both a conventional gradient-echo and a fully phase-encoded pulse sequence. In other contexts, a fully phase-encoded acquisition, also known as single-point or constant-time imaging, has been used to enable distortion-free imaging of short-T2?species. Here we used this technique to overcome imperfections associated with our homebuilt MRI system while also taking full advantage of the long T2?available at very low field. Our results demonstrate that xenon-129 image quality can be dramatically improved at low field by combining a fully phase-encoded k-space acquisition with auxiliary measurements of system imperfections including B0 field drift and gradient infidelity.
Allende meteorite: Isotopically anomalous xenon is accompanied by normal osmium
Takahashi, H.; Higuchi, H.; Gros, Jacques; Morgan, John W.; Anders, Edward
The 184Os/190Os ratio of six Allende meteorite samples was determined by neutron activation analysis. Four chromite concentrates gave a ratio differing from the terrestrial ratio by only -0.1 ▒ 0.4%, although they contained highly anomalous xenon enriched by up to 67% in 124Xe and 93% in 136Xe. In view of this result and the normal isotopic composition of carbon and oxygen in these fractions, it seems very unlikely that the xenon anomalies were produced in a supernova by the p and r processes. More probably, the xenon anomalies were established in the early solar system, by mass fractionation during trapping of noble gases in solids and by spontaneous fission of a superheavy element. Two other samples, containing osmium from the calcium,aluminum-rich inclusions, also gave an 184Os/190Os ratio within -0.1 ▒ 0.5% of the terrestrial value, although these inclusions show well-established anomalies in the light elements oxygen and magnesium, which appear to be due to pre-solar dust grains of distinctive nuclear history. Apparently the stellar source of the anomalous oxygen and magnesium did not synthesize heavier elements. PMID:16592365
First Results from the XENON10 Dark Matter Experiment at the Gran Sasso National Laboratory
J. Angle; E. Aprile; F. Arneodo; L. Baudis; A. Bernstein; A. Bolozdynya; P. Brusov; L. C. C. Coelho; C. E. Dahl; L. Deviveiros; A. D. Ferella; L. M. P. Fernandes; S. Fiorucci; R. J. Gaitskell; K. L. Giboni; R. Gomez; R. Hasty; L. Kastens; J. Kwong; J. A. M. Lopes; N. Madden; A. Manalaysay; A. Manzur; D. N. McKinsey; M. E. Monzani; K. Ni; U. Oberlack; J. Orboeck; G. Plante; R. Santorelli; J. M. F. Dos Santos; P. Shagin; T. Shutt; P. Sorensen; S. Schulte; C. Winant; M. Yamashita
The XENON10 experiment at the Gran Sasso National Laboratory uses a 15 kg xenon dual phase time projection chamber to search for dark matter weakly interacting massive particles (WIMPs). The detector measures simultaneously the scintillation and the ionization produced by radiation in pure liquid xenon to discriminate signal from background down to 4.5 keV nuclear-recoil energy. A blind analysis of
The Analgesic Effect of Xenon on the Formalin Test in Rats: A Comparison with Nitrous Oxide
Taeko Fukuda; Chikako Nishimoto; Setsuji Hisano; Masayuki Miyabe; Hidenori Toyooka
To investigate the analgesic effects of xenon, we performed formalin tests in rats under 0.5 minimum alveolar anes- thetic concentration xenon or nitrous oxide and stained the lumbar spinal cord for c-fos (n 18) and the phosphory- lated N-methyl-d-aspartate (NMDA) receptor (n 24) by using the avidin-biotin-peroxidase method. After 20 min of 79% xenon, 68% nitrous oxide, or 100% inhaled
Temperature dependent gain of the atomic xenon laser Gregory A. Hebne?)
Kushner, Mark
the gain and efficiency of the atomic xenon laser at gas tem- peratures less than 325 K,1-3,6the functionalTemperature dependent gain of the atomic xenon laser Gregory A. Hebne?) Sandia National(3/2),-6p(5/2),] and 2.03 pm [5d(3/2)t- 6p( 3/2) t] atomic xenon transitions for gas temperatures
NMR investigations of surfaces and interfaces using spin-polarized xenon
Gaede, H C [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry
{sup 129}Xe NMR is potentially useful for the investigation of material surfaces, but has been limited to high surface area samples in which sufficient xenon can be loaded to achieve acceptable signal to noise ratios. In Chapter 2 conventional {sup 129}Xe NMR is used to study a high surface area polymer, a catalyst, and a confined liquid crystal to determine the topology of these systems. Further information about the spatial proximity of different sites of the catalyst and liquid crystal systems is determined through two dimensional exchange NMR in Chapter 3. Lower surface area systems may be investigated with spin-polarized xenon, which may be achieved through optical pumping and spin exchange. Optically polarized xenon can be up to 10{sup 5} times more sensitive than thermally polarized xenon. In Chapter 4 highly polarized xenon is used to examine the surface of poly(acrylonitrile) and the formation of xenon clathrate hydrates. An attractive use of polarized xenon is as a magnetization source in cross polarization experiments. Cross polarization from adsorbed polarized xenon may allow detection of surface nuclei with drastic enhancements. A non-selective low field thermal mixing technique is used to enhance the {sup 13}C signal of CO{sub 2} of xenon occluded in solid CO{sub 2} by a factor of 200. High-field cross polarization from xenon to proton on the surface of high surface area polymers has enabled signal enhancements of {approximately}1,000. These studies, together with investigations of the efficiency of the cross polarization process from polarized xenon, are discussed in Chapter 5. Another use of polarized xenon is as an imaging contrast agent in systems that are not compatible with traditional contrast agents. The resolution attainable with this method is determined through images of structured phantoms in Chapter 6.
Self-Assembled Monolayers deposition in Supercritical Carbon Dioxide Paper ID: 114 (Page 1 / 4)
Paris-Sud XI, Universitķ de
Self-Assembled Monolayers deposition in Supercritical Carbon Dioxide Paper ID: 114 (Page 1 / 4 -------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------- Self-Assembled Monolayers deposition in Supercritical Carbon Dioxide L. Rabbia1 , V. Perrut1 , P. Pons2 ----------------------------------------------------------------------------------------------------------------- Abstract Self-Assembled Monolayers of organic molecules have been successfully deposited onto wafer surface
Threshold Value of Carbon Dioxide Concentration in Photosynthesis of Foliage Leaves
E. K. Gabrielsen
How much can the carbon dioxide concentration of the atmosphere be diminished by photosynthesis of green leaves? Blackman1, in his researches in vegetable assimilation and respiration, observed that leaves exposed to sunlight took up completely all the carbon dioxide molecules from an enclosed volume of air in a very short time. Reinau2 did not accept this result which, he thought,
Deactivation of the xenon atom in the 6s metastable state in collisions with xenon and helium atoms
Zayarnyi, D A; Semenova, Ludmila V; Ustinovskii, N N; Kholin, I V; Chugunov, A Yu [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)
The absorption probing method was used to investigate collisional deactivation of the metastable 6s[3/2]{sub 2}{sup 0}({sup 3}P{sub 2}) state of the xenon atom in high-pressure He - Xe mixtures with a low xenon concentration. Measurements were made of the rate constants of the plasma-chemical reactions Xe*+Xe+He {yields} Xe{sub 2}*+He [(1.7 {+-}0.2) x10{sup -32} cm{sup 6} s{sup -1}], Xe*+2He{yields} HeXe*+He (less than 3 x 10{sup -35} cm{sup 6} s{sup -1}), and Xe*+He{yields} products+He (less than 10{sup -15} cm{sup 3} s{sup -1}). (active media)
Early outgassing of Mars supported by differential water solubility of iodine and xenon
NASA Technical Reports Server (NTRS)
Musselwhite, Donald S.; Drake, Michael J.; Swindle, Timothy D.
The Martian atmosphere has a high X-129/Xe-132 ratio compared to the Martian mantle. As Xe-129 is the daughter product of the extinct nuclide I-129, a means of fractionating iodine from xenon early in Martian history appears necessary to account for the X-129/Xe-132 ratios of its known reservoirs. A model is presented here to account for the Marian xenon data which relies on the very different solubilities of xenon and iodine in water to fractionate them after outgassing. Atmospheric xenon is lost by impact erosion during heavy bombardment, followed by release of Xe-129 produced from I-129 decay in the crust.
Shock compression of a fifth period element: liquid xenon to 840 GPa.
Root, Seth; Magyar, Rudolph J; Carpenter, John H; Hanson, David L; Mattsson, Thomas R
Current equation of state (EOS) models for xenon show substantial differences in the Hugoniot above 100 GPa, prompting the need for an improved understanding of xenon's behavior at extreme conditions. We performed shock compression experiments on liquid xenon to determine the Hugoniot up to 840 GPa, using these results to validate density functional theory (DFT) simulations. Despite the nearly fivefold compression, we find that the limiting Thomas-Fermi theory, exact in the high density limit, does not accurately describe the system. Combining the experimental data and DFT calculations, we developed a free-energy-based, multiphase EOS capable of describing xenon over a wide range of pressures and temperatures. PMID:20868109
NSDL National Science Digital Library
The PhET project at the University of Colorado creates "fun, interactive, research-based simulations of physical phenomena." This particular one deals with molecular polarity. When is a molecule polar? Change the electronegativity of atoms in a molecule to see how it affects polarity. This simulation will allow visitors to see how molecules behave in an electric field, and change the bond angle to see how shape affects polarity for real molecules in 3D. The simulation is also paired with teaching tips and user-contirubed Teaching Ideas, lessons using the simulation in context, that can be found near the bottom of the page. The simulation is also available in multiple languages.
NASA Technical Reports Server (NTRS)
The molecule modeling method known as Multibody Order (N) Dynamics, or MBO(N)D, was developed by Moldyn, Inc. at Goddard Space Flight Center through funding provided by the SBIR program. The software can model the dynamics of molecules through technology which stimulates low-frequency molecular motions and properties, such as movements among a molecule's constituent parts. With MBO(N)D, a molecule is substructured into a set of interconnected rigid and flexible bodies. These bodies replace the computation burden of mapping individual atoms. Moldyn's technology cuts computation time while increasing accuracy. The MBO(N)D technology is available as Insight II 97.0 from Molecular Simulations, Inc. Currently the technology is used to account for forces on spacecraft parts and to perform molecular analyses for pharmaceutical purposes. It permits the solution of molecular dynamics problems on a moderate workstation, as opposed to on a supercomputer.
Diffusion NMR methods applied to xenon gas for materials study.
Mair, R W; Rosen, M S; Wang, R; Cory, D G; Walsworth, R L
We report initial NMR studies of (i) xenon gas diffusion in model heterogeneous porous media and (ii) continuous flow laser-polarized xenon gas. Both areas utilize the pulsed gradient spin-echo (PGSE) techniques in the gas phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients--a brief overview of this area is provided in the Introduction. The heterogeneous or multiple-length scale model porous media consisted of random packs of mixed glass beads of two different sizes. We focus on observing the approach of the time-dependent gas diffusion coefficient, D(t) (an indicator of mean squared displacement), to the long-time asymptote, with the aim of understanding the long-length scale structural information that may be derived from a heterogeneous porous system. We find that D(t) of imbibed xenon gas at short diffusion times is similar for the mixed bead pack and a pack of the smaller sized beads alone, hence reflecting the pore surface area to volume ratio of the smaller bead sample. The approach of D(t) to the long-time limit follows that of a pack of the larger sized beads alone, although the limiting D(t) for the mixed bead pack is lower, reflecting the lower porosity of the sample compared to that of a pack of mono-sized glass beads. The Pade approximation is used to interpolate D(t) data between the short- and long-time limits. Initial studies of continuous flow laser-polarized xenon gas demonstrate velocity-sensitive imaging of much higher flows than can generally be obtained with liquids (20-200 mm s-1). Gas velocity imaging is, however, found to be limited to a resolution of about 1 mm s-1 owing to the high diffusivity of gases compared with liquids. We also present the first gas-phase NMR scattering, or diffusive-diffraction, data, namely flow-enhanced structural features in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack. PMID:12807139
Reactive quenching of two-photon excited xenon atoms by Cl/sub 2/. [Xenon chloride laser
Bruce, M.R.; Layne, W.B.; Meyer, E.; Keto, J.W.
Total binary and tertiary quench rates have been measured for the reaction Xe (5p/sup 5/6p) + Cl/sub 2/ at thermal temperatures. Xenon atoms are excited by state-selective, two-photon absorption with a uv laser. The time dependent fluorescence from the excited atom in the IR and from XeCl* (B) product near 308 nm have been measured with subnanosecond time resolution. The decay rates are measured as a function of Cl/sub 2/ pressure to 20 Torr and Xe pressure to 400 Torr. The measured reaction rates (k/sub 2/ approx. 10/sup -9/ cm/sup 3/sec/sup -1/) are consistent with a harpoon model described in a separate paper. We also measure large termolecular reaction rates for collisions with xenon atoms (k/sub 3/ approx. 10/sup -28/ cm/sup 6/sec/sup -1/). Total product fluorescence has been examined using a gated optical multichannel analyzer. We measure unit branching fractions for high vibrational levels of XeCl* (B) with very little C state fluorescence observed. The measured termolecular rates suggest similar processes will dominate at the high buffer-gas pressures used in XeCl lasers. The effect of these large reactive cross sections for neutral xenon atoms on models of the XeCl laser will be discussed.
51A Simple Model for Atmospheric Carbon Dioxide The graph to the left shows the 'Keeling Curve' which plots the increase in
51A Simple Model for Atmospheric Carbon Dioxide The graph to the left shows the 'Keeling Curve' which plots the increase in atmospheric carbon dioxide between 1958-2005. The average net annual rate of the element carbon on Earth. Note that, for every 44 gigatons of the carbon dioxide molecule, there are 12
Neutral compounds with xenon-germanium bonds: a theoretical investigation on FXeGeF and FXeGeF?.
Borocci, Stefano; Giordani, Maria; Grandinetti, Felice
The structure and stability of FXeGeF and FXeGeF3 were investigated by MP2, CCSD(T), and B3LYP calculations, and their bonding situation was examined by NBO and AIM analysis. These molecules are thermochemically stable with respect to dissociation into F + Xe + GeF(n) (n = 1, 3), and kinetically stable with respect to dissociation into Xe + GeF(n+1), thus suggesting their conceivable existence as metastable species. FXeGeF and FXeGeF3 are best described by the resonance structures F(-)(Xe-GeF(+)) and F(-)(Xe-GeF3(+)), and feature essentially ionic xenon-fluorine interactions. The xenon-germanium bonds have instead a significant contribution of covalency. The comparison with XeGeF(+) and XeGeF3(+) suggests that the stability of FXeGeF and FXeGeF3 arises from the F(-)-induced stabilization of these ionic moieties. This structural motif resembles that encountered in other noble-gas neutral and ionic species. PMID:24720441
NASA Technical Reports Server (NTRS)
Williams, C. F.; Huebscher, R. G.
Passed exhaled air through electrochemical cell containing alkali metal carbonate aqueous solution, and utilizes platinized electrodes causing reaction of oxygen at cathode with water in electrolyte, producing hydroxyl ions which react with carbon dioxide to form carbonate ions.
NSDL National Science Digital Library
American Museum of Natural History
In this experiment, students will observe a natural process that removes carbon dioxide (CO2) from Earth's atmosphere. This process is a part of the carbon cycle and results in temperature suitable for life. Students will learn that the carbon cycle is a fundamental Earth process. Throughout Earth's history, the balance of carbon has kept the atmosphere's carbon dioxide (CO2) and Earth's temperature within relatively narrow ranges.
Carbon dioxide removal process
Baker, Richard W.; Da Costa, Andre R.; Lokhandwala, Kaaeid A.
A process and apparatus for separating carbon dioxide from gas, especially natural gas, that also contains C.sub.3+ hydrocarbons. The invention uses two or three membrane separation steps, optionally in conjunction with cooling/condensation under pressure, to yield a lighter, sweeter product natural gas stream, and/or a carbon dioxide stream of reinjection quality and/or a natural gas liquids (NGL) stream.
Xenon in And at the End of the Tunnel of Bifunctional Carbon Monoxide Dehydrogenase/Acetyl-CoA Synthase
Doukov, T.I.; Blasiak, L.C.; Seravalli, J.; Ragsdale, S.W.; Drennan, C.L.; /MIT /SLAC, SSRL /Nebraska U.
A fascinating feature of some bifunctional enzymes is the presence of an internal channel or tunnel to connect the multiple active sites. A channel can allow for a reaction intermediate generated at one active site to be used as a substrate at a second active site, without the need for the intermediate to leave the safety of the protein matrix. One such bifunctional enzyme is carbon monoxide dehydrogenase/acetyl-CoA synthase from Moorella thermoacetica (mtCODH/ACS). A key player in the global carbon cycle, CODH/ACS uses a Ni-Fe-S center called the C-cluster to reduce carbon dioxide to carbon monoxide and uses a second Ni-Fe-S center, called the A-cluster, to assemble acetyl-CoA from a methyl group, coenzyme A, and C-cluster-generated CO. mtCODH/ACS has been proposed to contain one of the longest enzyme channels (138 A long) to allow for intermolecular CO transport. Here, we report a 2.5 A resolution structure of xenon-pressurized mtCODH/ACS and examine the nature of gaseous cavities within this enzyme. We find that the cavity calculation program CAVENV accurately predicts the channels connecting the C- and A-clusters, with 17 of 19 xenon binding sites within the predicted regions. Using this X-ray data, we analyze the amino acid composition surrounding the 19 Xe sites and consider how the protein fold is utilized to carve out such an impressive interior passageway. Finally, structural comparisons of Xe-pressurized mtCODH/ACS with related enzyme structures allow us to study channel design principles, as well as consider the conformational flexibility of an enzyme that contains a cavity through its center.
Xenon in and at the end of the tunnel of bifunctional carbon monoxide dehydrogenase/acetyl-CoA synthase.
Doukov, Tzanko I; Blasiak, Leah C; Seravalli, Javier; Ragsdale, Stephen W; Drennan, Catherine L
A fascinating feature of some bifunctional enzymes is the presence of an internal channel or tunnel to connect the multiple active sites. A channel can allow for a reaction intermediate generated at one active site to be used as a substrate at a second active site, without the need for the intermediate to leave the safety of the protein matrix. One such bifunctional enzyme is carbon monoxide dehydrogenase/acetyl-CoA synthase from Moorella thermoacetica (mtCODH/ACS). A key player in the global carbon cycle, CODH/ACS uses a Ni-Fe-S center called the C-cluster to reduce carbon dioxide to carbon monoxide and uses a second Ni-Fe-S center, called the A-cluster, to assemble acetyl-CoA from a methyl group, coenzyme A, and C-cluster-generated CO. mtCODH/ACS has been proposed to contain one of the longest enzyme channels (138 A long) to allow for intermolecular CO transport. Here, we report a 2.5 A resolution structure of xenon-pressurized mtCODH/ACS and examine the nature of gaseous cavities within this enzyme. We find that the cavity calculation program CAVENV accurately predicts the channels connecting the C- and A-clusters, with 17 of 19 xenon binding sites within the predicted regions. Using this X-ray data, we analyze the amino acid composition surrounding the 19 Xe sites and consider how the protein fold is utilized to carve out such an impressive interior passageway. Finally, structural comparisons of Xe-pressurized mtCODH/ACS with related enzyme structures allow us to study channel design principles, as well as consider the conformational flexibility of an enzyme that contains a cavity through its center. PMID:18293927
Theoretical studies of vibrational relaxation of iodine in low density liquid xenon
Paris-Sud XI, Universitķ de
1787 Theoretical studies of vibrational relaxation of iodine in low density liquid xenon J. K for vibrational relaxation of iodine in low density liquid xenon are presented. Simple generalized Langevin relaxation data. This is explained, at least in part, by noting that the iodine vibrational motion perturbs
Electronic spectroscopy of oxygen atoms trapped in solid xenon W. G. Lawrence and V. A. Apkarian
Apkarian, V. Ara
Electronic spectroscopy of oxygen atoms trapped in solid xenon W. G. Lawrence and V. A. Apkarian28 August 1992) The electronic spectroscopyof oxygen atoms trapped in solid xenon are reported and -covalent many-body surfacesare discussed. I. INTRODUCTION The electronic spectroscopyof atomic impurities
Deep mantle neon and xenon preserve a record of early planetary differentiation and heterogeneous volatile accretion
Mukhopadhyay, Sujoy
1 Deep mantle neon and xenon preserve a record of early planetary differentiation mantle outgassing and volatile loss from Earth1,2 . The low ratios of radiogenic to non-radiogenic xenon used as evidence for the existence of a relatively undegassed primitive deep mantle reservoir1
Separation of krypton and xenon from reactor atmospheres by selective permeation. Final report. [LMFBR
S. A. Stern; S. M. Leone; F. J. Onorato; S. C. Wang
The removal of krypton and xenon from nuclear reactor atmospheres by permeation through silicone rubber capillaries has been studied theoretically and experimentally. Permeator modules resembling shell-and-tube heat exchangers have been constructed and tested. Permeation cascades were designed for the removal of krypton and xenon from the following nuclear atmospheres: (a) the atmosphere of a reactor containment building after a nuclear
Properties of excited xenon atoms in an alternating current plasma display panel
Han S. Uhm; Phil Y. Oh; Eun H. Choi
The properties of excited xenon atoms in the discharge cells of a plasma display panel are investigated by measuring the excited atom density via laser absorption spectroscopy. The density of the excited xenon atoms in the metastable state increases from zero, reaches its peak, and decreases with time in the discharge cells, as expected from a theoretical model. The profile
Excitation mechanism of IR transitions in the xenon atom in a nuclear-pumped laser
A numerical simulation is used to show that new experimental data on the rate constants of xenon atoms in metastable and resonant states lead to a revision of the existing views on the mechanism of excitation of the upper active levels of a laser operating on IR transitions in xenon. (lasers, active media)
Excitation mechanism of IR transitions in the xenon atom in a nuclear-pumped laser
Karelin, A V [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)
A numerical simulation is used to show that new experimental data on the rate constants of xenon atoms in metastable and resonant states lead to a revision of the existing views on the mechanism of excitation of the upper active levels of a laser operating on IR transitions in xenon. (lasers, active media)
IPredictions for gain in the fission-fragment-excited atomic xenon laser Jong W. Shon and Mark J. Kushnera)
Kushner, Mark
IPredictions for gain in the fission-fragment-excited atomic xenon laser Jong W. Shon and Mark J xenon laser (5d-6p) is an attractive candidate for fission fragment excitation, which provides low gain at 1.73 and 2.03 pm has recently been measured in a reactor-excited xenon laser yielding values
Fast oscillatory behavior of the excited xenon density in the discharge cells of a plasma display panel
Han S. Uhm; Eun H. Choi
Fast oscillation of the excited xenon density occurs universally after an electrical discharge in the cells of a plasma display panel. A theoretical model based on ion plasma oscillation simulates this oscillatory behavior of the excited xenon density reasonably well. The magnitude and lifetime of the excited xenon density in a metastable state depend highly on the electrode configuration. Particularly,
Temporal VUV Emission Characteristics Related to Generations and Losses of Metastable Atoms in Xenon Pulsed Barrier Discharge
Hideki Motomura; Ka Hong Loo; Yoshihisa Ikeda; Masafumi Jinno; Masaharu Aono
Although xenon pulsed dielectric barrier discharge is one of the most promising substitutes for mercury low-pressure discharge for fluorescent lamps, the efficacy of xenon fluorescent lamp is not enough for practical use for general lighting. To improve the efficacy it is indispensable to clarify mechanisms of vacuum ultraviolet (VUV) emissions, which excite phosphor, from xenon discharge related to plasma characteristics.
NSDL National Science Digital Library
Paul Anderson
Paul Anderson describes the four major biological molecules found in living things. He begins with a brief discussion of polymerization. Dehydration synthesis is used to connect monomers into polymers and hydrolysis breaks them down again. The major characteristics of nucleic acids are described as well as there directionality from 3' to 5' end.
Frequency-Dependent Viscosity of Xenon Near the Critical Point
NASA Technical Reports Server (NTRS)
Berg, Robert F.; Moldover, Michael R.; Zimmerli, Gregory A.
We used a novel, overdamped oscillator aboard the Space Shuttle to measure the viscosity eta of xenon near its critical density rho(sub c), and temperature T(sub c). In microgravity, useful data were obtained within 0.1 mK of T(sub c), corresponding to a reduced temperature t = (T -T(sub c))/T(sub c) = 3 x 10(exp -7). The data extend two decades closer to T(sub c) than the best ground measurements, and they directly reveal the expected power-law behavior eta proportional to t(sup -(nu)z(sub eta)). Here nu is the correlation length exponent, and our result for the small viscosity exponent is z(sub eta) = 0.0690 +/- 0.0006. (All uncertainties are one standard uncertainty.) Our value for z(sub eta) depends only weakly on the form of the viscosity crossover function, and it agrees with the value 0.067 +/- 0.002 obtained from a recent two-loop perturbation expansion. The measurements spanned the frequency range 2 Hz less than or equal to f less than or equal to 12 Hz and revealed viscoelasticity when t less than or equal to 10(exp -1), further from T(sub c) than predicted. The viscoelasticity scales as Af(tau), where tau is the fluctuation-decay time. The fitted value of the viscoelastic time-scale parameter A is 2.0 +/- 0.3 times the result of a one-loop perturbation calculation. Near T(sub c), the xenon's calculated time constant for thermal diffusion exceeded days. Nevertheless, the viscosity results were independent of the xenon's temperature history, indicating that the density was kept near rho(sub c), by judicious choices of the temperature vs. time program. Deliberately bad choices led to large density inhomogeneities. At t greater than 10(exp -5), the xenon approached equilibrium much faster than expected, suggesting that convection driven by microgravity and by electric fields slowly stirred the sample.
A 5-kW xenon ion thruster lifetest
NASA Technical Reports Server (NTRS)
Patterson, Michael J.; Verhey, Timothy R.
The results of the first life test of a high power ring-cusp ion thruster are presented. A 30-cm laboratory model thruster was operated steady-state at a nominal beam power of 5 kW on xenon propellant for approximately 900 hours. This test was conducted to identify life-timing erosion modifications, and to demonstrate operation using simplified power processing. The results from this test are described including the conclusions derived from extensive post-test analyses of the thruster. Modifications to the thruster and ground support equipment, which were incorporated to solve problems identified by the lifetest, are also described.
Simplified Ion Thruster Xenon Feed System for NASA Science Missions
NASA Technical Reports Server (NTRS)
Snyder, John Steven; Randolph, Thomas M.; Hofer, Richard R.; Goebel, Dan M.
The successful implementation of ion thruster technology on the Deep Space 1 technology demonstration mission paved the way for its first use on the Dawn science mission, which launched in September 2007. Both Deep Space 1 and Dawn used a "bang-bang" xenon feed system which has proven to be highly successful. This type of feed system, however, is complex with many parts and requires a significant amount of engineering work for architecture changes. A simplified feed system, with fewer parts and less engineering work for architecture changes, is desirable to reduce the feed system cost to future missions. An attractive new path for ion thruster feed systems is based on new components developed by industry in support of commercial applications of electric propulsion systems. For example, since the launch of Deep Space 1 tens of mechanical xenon pressure regulators have successfully flown on commercial spacecraft using electric propulsion. In addition, active proportional flow controllers have flown on the Hall-thruster-equipped Tacsat-2, are flying on the ion thruster GOCE mission, and will fly next year on the Advanced EHF spacecraft. This present paper briefly reviews the Dawn xenon feed system and those implemented on other xenon electric propulsion flight missions. A simplified feed system architecture is presented that is based on assembling flight-qualified components in a manner that will reduce non-recurring engineering associated with propulsion system architecture changes, and is compared to the NASA Dawn standard. The simplified feed system includes, compared to Dawn, passive high-pressure regulation, a reduced part count, reduced complexity due to cross-strapping, and reduced non-recurring engineering work required for feed system changes. A demonstration feed system was assembled using flight-like components and used to operate a laboratory NSTAR-class ion engine. Feed system components integrated into a single-string architecture successfully operated the engine over the entire NSTAR throttle range over a series of tests. Flow rates were very stable with variations of at most 0.2%, and transition times between throttle levels were typically 90 seconds or less with a maximum of 200 seconds, both significant improvements over the Dawn bang-bang feed system.
Evaluation of carrier agents for hyperpolarized xenon MRI
NASA Technical Reports Server (NTRS)
Venkatesh, A. K.; Zhao, L.; Balamore, D.; Jolesz, F. A.; Albert, M. S.
Several biocompatible carrier agents, in which xenon is highly soluble and has a long T(1), were tested, and injected in living rats. These included saline, Intralipid suspension, perfluorocarbon emulsion and (129)Xe gas-filled liposomes. The T(1) of (129)Xe in these compounds ranged from 47 to 116 s. Vascular injection of these carrier agents was tolerated well, encouraging their use for further experiments in live animals. In vivo spectra, obtained from gas-filled liposomes and perfluorocarbon solutions, suggest that these carrier agents have potential for use in angiography and perfusion imaging. Copyright 2000 John Wiley & Sons, Ltd.
The adsorption of argon, krypton and xenon on activated charcoal
Underhill, D.W. [Univ. of South Carolina, Columbia, SC (United States)
Charcoal adsorption beds are commonly used to remove radioactive noble gases from contaminated gas streams. The design of such beds requires the adsorption coefficient for the noble gas. Here an extension of the Dubinin-Radushkevich theory of adsorption is developed to correlate the effects of temperature, pressure, concentration, and carrier gas on the adsorption coefficients of krypton, xenon, and argon on activated carbon. This model is validated with previously published adsorption measurements. It accurately predicts the equilibrium adsorption coefficient at any temperature and pressure if the potential energies of adsorption, the micropore volume, and the van der Waals constants of the gases are known. 18 refs., 4 figs.
Xenon Fractionation, Hydrogen Escape, and the Oxidation of the Earth
NASA Astrophysics Data System (ADS)
Zahnle, K. J.; Catling, D. C.
Xenon in Earth's atmosphere is severely mass fractionated and depleted compared to any plausible solar system source material, yet Kr is unfractionated. These observations seem to imply that Xe has escaped from Earth. Vigorous hydrodynamic hydrogen escape can produce mass fractionation in heavy gases. The required hydrogen flux is very high but within the range permitted by solar EUV heating when Earth was 100 Myrs old or younger. However this model cannot explain why Xe escapes but Kr does not. Recently, what appears to be ancient atmospheric xenon has been recovered from several very ancient (3-3.5 Ga) terrestrial hydrothermal barites and cherts (Pujol 2011, 2013). What is eye-catching about this ancient Xe is that it is less fractionated that Xe in modern air. In other words, it appears that a process was active on Earth some 3 to 3.5 billion years ago that caused xenon to fractionate. By this time the Sun was no longer the EUV source that it used to be. If xenon was being fractionated by escape Ś currently the only viable hypothesis Ś it had to be in Earth's Archean atmosphere and under rather modest levels of EUV forcing. It should be possible for Xe, but not Kr, to escape from Earth as an ion. In a hydrodynamically escaping hydrogen wind the hydrogen is partially ionized. The key concepts are that ions are much more strongly coupled to the escaping flow than are neutrals (so that a relatively modest flow of H and H+ to space could carry Xe+ along with it, the flux can be small enough to be consistent with diffusion-limited flux), and that Xe alone among the noble gases is more easily ionized than hydrogen. This sort of escape is possible along the polar field lines, although a weak or absent magnetic field would likely work as well. The extended history of hydrogen escape implicit in Xe escape in the Archean is consistent with other suggestions that hydrogen escape in the Archean was considerable. Hydrogen escape plausibly played the key role in creating oxidizing conditions at the surface of the Earth and setting the stage for the creation of an O2 atmosphere (Urey 1951, Catling et al 2001, Zahnle et al 2013). Catling, McKay, Zahnle (2001) Science 293, 839. Pujol, Marty, Burnard, Phillipot (2009) GCA 73, 6834. Pujol, Marty, Burgess (2011) EPSL 308, 298. Urey, H.C. (1952) PNAS 38, 351. Zahnle, Catling, Claire (2013) Ch. Geol. 362, 26.
Clathrate phase equilibria of binary and ternary mixtures containing carbon dioxide, phenol and p-cresol
Yi-Ho Yoon; Seong-Pil Kang; Huen Lee [KAIST, Taejon (Korea, Republic of)
Clathrate compounds are crystalline molecules formed by a physical reaction between host molecules and low molecular-weight gases. The gas molecules occupy cavities in a network of host molecules composed of unit crystal structures. Experimental apparatus equipped with sapphire windows for visual observation was uniquely designed and built to measure clathrate phase equilibria. Phenolic compounds such as phenol and p-cresol were used as host molecules and carbon dioxide and methane as guest molecules. The dissociation pressures and temperatures were measured for several binary systems in order to investigate clathrate three-phase (vapor-clathrate-organic liquid equilibria). 10 refs., 4 figs., 2 tabs.
Cryogenic Large Liquid Xenon Detector for Dark Matter Searches
NASA Astrophysics Data System (ADS)
Mei, D.-M.; Akerib, D. S.; Bai, X.-H.; Bedikian, S.; Bernard, E.; Bolozdynya, A.; Bradley, A.; Cahn, S. B.; Camp, C.; Carmona-Benitez, M. C.; Carr, D.; Chapman, J. J.; Clark, K.; Classen, T.; Coffey, T.; Curioni, A.; Dahl, E.; Dazeley, S.; de Viveiros, L.; Dragowsky, M.; Druszkiewicz, E.; Faham, C. H.; Fiorucci, S.; Gaitskell, R. J.; Gibson, K. R.; Hall, C.; Hanhardt, M.; Holbrook, B.; Ihm, M.; Jacobsen, R. G.; Kastens, L.; Kazkaz, K.; Lander, R.; Lee, C.; Leonard, D.; Lesko, K.; Lyashenko, A.; Malling, Dc; Mannino, R.; Marquez, Z.; McKinsey, D.; Mock, J.; Morii, M.; Nelson, H.; Nokkel, Ja; Pangilinan, M.; Phelps, P.; Rodionov, A.; Roberts, P.; Shutt, T.; Skulski, W.; Sofka, Cj; Sorensen, P.; Spaans, J.; Stiegler, T.; Svoboda, R.; Sweany, M.; Thomson, J.; Tripathi, M.; Verbus, J. R.; Walsh, N.; Webb, R.; White, Jt; Wlasenko, M.; Wolfs, Flh; Woods, M.; Zhang, C.
Observation of rotational curve of spiral galaxies shows that a large fraction (~23%) of the mass density of the universe is unaccounted for. Such a significant percentage of missing dark matter suggests that the universe may consist of new types of elementary particles. A compelling explanation for the new particles is the existence of Weakly Interacting Massive Particles (WIMPs), which are non-baryonic particles characterized by particle physics theories beyond the Standard Model. WIMPs are believed to only interact through the weak force and gravity; hence the interaction cross section with ordinary matter is extremely small. Therefore, experimental techniques that combine low radioactivity, low energy thresholds, efficient discrimination against electronic recoil backgrounds, and scalability to large detector masses can only be performed at a deep underground environment where the interference of cosmic rays is obviated. In this paper, we report a cryogenic large liquid xenon detector for dark matter searches at Sanford Lab (Davis Cavern) in the Homestake Mine, USA. The goal of the large underground xenon (LUX) dual-phase detector is to clearly detect (or exclude) WIMPs with a spin independent cross-section per nucleon of 7 ū 10-46 cm2, equivalent to ~0.5 events/100 kg/month in an inner 100 kg fiducial volume (FV) of a 300 kg LXe detector.
First Axion Results from the XENON100 Experiment
The XENON100 Collaboration; E. Aprile; F. Agostini; M. Alfonsi; K. Arisaka; F. Arneodo; M. Auger; C. Balan; P. Barrow; L. Baudis; B. Bauermeister; A. Behrens; P. Beltrame; K. Bokeloh; A. Brown; E. Brown; S. Bruenner; G. Bruno; R. Budnik; J. M. R. Cardoso; A. P. Colijn; H. Contreras; J. P. Cussonneau; M. P. Decowski; E. Duchovni; S. Fattori; A. D. Ferella; W. Fulgione; F. Gao; M. Garbini; C. Geis; L. W. Goetzke; C. Grignon; E. Gross; W. Hampel; R. Itay; F. Kaether; G. Kessler; A. Kish; H. Landsman; R. F. Lang; M. Le Calloch; D. Lellouch; C. Levy; S. Lindemann; M. Lindner; J. A. M. Lopes; K. Lung; A. Lyashenko; S. Macmullin; T. Marrodan Undagoitia; J. Masbou; F. V. Massoli; D. Mayani Paras; A. J. Melgarejo Fernandez; Y. Meng; M. Messina; B. Miguez; A. Molinario; M. Murra; J. Naganoma; U. Oberlack; S. E. A. Orrigo; E. Pantic; R. Persiani; F. Piastra; J. Pienaar; G. Plante; N. Priel; S. Reichard; C. Reuter; A. Rizzo; S. Rosendahl; J. M. F. dos Santos; G. Sartorelli; S. Schindler; J. Schreiner; M. Schumann; L. Scotto Lavina; M. Selvi; P. Shagin; H. Simgen; A. Teymourian; D. Thers; A. Tiseni; G. Trinchero; O. Vitells; H. Wang; M. Weber; C. Weinheimer
We present the first results of searches for axions and axion-like-particles with the XENON100 experiment. The axion-electron coupling constant, $g_{Ae}$, has been tested by exploiting the axio-electric effect in liquid xenon. A profile likelihood analysis of 224.6 live days $\\times$ 34 kg exposure has shown no evidence for a signal. By rejecting $g_{Ae}$, larger than $7.7 \\times 10^{-12}$ (90% CL) in the solar axion search, we set the best limit to date on this coupling. In the frame of the DFSZ and KSVZ models, we exclude QCD axions heavier than 0.3 eV/c$^2$ and 80 eV/c$^2$, respectively. For axion-like-particles, under the assumption that they constitute the whole abundance of dark matter in our galaxy, we constrain $g_{Ae}$, to be lower than $1 \\times 10^{-12}$ (90% CL) for masses between 5 and 10 keV/c$^2$.
Study of a zirconium getter for purification of xenon gas
Dobi, A; Hall, C; Kaufman, L; Langford, T; Slutsky, S; Yen, Y R
Oxygen, nitrogen and methane purification efficiencies for a common zirconium getter are measured in 1050 Torr of xenon gas. Starting with impurity concentrations near 10^{-6} g/g, the outlet impurity level is found to be less than 120*10^{-12} g/g for O2 and less than 950*10^{-12} g/g for N2. For methane we find residual contamination of the purified gas at concentrations varying over three orders of magnitude, depending on the purifier temperature and the gas flow rate. A slight reduction in the purifier's methane efficiency is observed after 13 mg of this impurity has been absorbed, which we attribute to partial exhaustion of the purifier's capacity for this species. We also find that the purifier's ability to absorb N2 and methane can be extinguished long before any decrease in O2 performance is observed, and slower flow rates should be employed for xenon purification due to the cooling effect that the heavy gas has on the getter.
Current Developments towards a Xenon Advanced Compton Telescope
NASA Astrophysics Data System (ADS)
Oberlack, Uwe; Aprile, Elena; Kocevski, Daniel
Gamma-ray astronomy in the energy range of nuclear transitions holds great promise for a great number of astrophysical questions. Gamma-ray lines, in particular, probe deeply into the explosion mechanisms of supernovae and provide unique insight into formation, evolution, and death of stars and their associated nucleosynthesis. Yet, the most exciting science topics have barely been probed by gamma-ray telescopes to-date. Sensitivity is therefore the most important characteristic of a next-generation instrument. An ``Advanced Compton Telescope,'' a visionary NASA mission currently under study, aims at improving sensitivity 100-fold over current instruments. We have recently been approved to continue the development of a detector technology based on multiple liquid xenon time projection chambers (LXeTPC). Recent advances in UV photosensors have opened new opportunities for the successful development of a Xenon ACT. These are: (a) Improvement of Energy Resolution by combination of charge and scintillation. (b) Application of Time-of-Flight in a compact telescope configuration. We report on the status of the LXeTPC technology to-date, and on our current and planned efforts to develop a telescope module that will meet the ACT challenge.
Vacuum ultraviolet radiometry of xenon positive column discharges
NASA Astrophysics Data System (ADS)
Doughty, D. A.; Fobare, D. F.
In order to judge the potential fluorescent lamp applications of various low-pressure positive column discharges it is necessary to measure the absolute power emitted in the ultraviolet region of the spectrum. For rare-gas discharges the principle emission occurs in the vacuum ultraviolet so that it is difficult to measure the radiant emittance (power per unit area) of the resonance radiation by standard methods. Two independent techniques are discussed for measuring the radiant emittance of positive column discharges in the vacuum ultraviolet. These techniques are used to study xenon positive column discharges at the resonance wavelength of 147 nm. The first method relies on the measurement of the resonance level density by absorption techniques. The effective decay rate of the resonance level is then determined by the simulation of resonance radiation transport. These two quantities are combined to yield the radiant emittance at 147 nm without implementing vacuum ultraviolet techniques. The second method uses a measurement of the resonance radiation normal to the positive column axis made with a calibrated vacuum ultraviolet detector. The angular distribution of the resonance radiation leaving the tube is determined by the simulation of resonance radiation transport. The detector measurement places the angular distribution of the radiance on an absolute scale, which can then be integrated to yield the radiant emittance. These two techniques are compared for pure xenon discharges at various pressures and currents.
Lifetime Modeling of Xenon Hollow Cathodes Used in Electric Propulsion
NASA Astrophysics Data System (ADS)
Kovaleski, Scott
Xenon hollow cathodes with barium calcium aluminate impregnated tungsten inserts are widely used in electric propulsion. These high current, low power cathodes are employed in ion thrusters, Hall thrusters, and on the International Space Station in plasma contactors. The entitlement lifetime of a thermionic emission cathode impregnated with barium-containing compounds is determined by the evolution and transport of barium away from the emitter surface. A model is being developed to study the process of barium transport and loss from the emitter insert in hollow cathodes. A thermodynamic model of the chemical process of barium evolution has been adapted from that of Lipeles and Kan^1. The model accounts for the diffusion of barium and barium oxide gas through the xenon expellant and loss of barium-containing gases through the cathode orifice as well as loss by condensation. Axial barium density profiles are presented and cathode lifetimes are estimated. Results of the model are compared with experimental results from the extensive hollow cathode life test database at the NASA Glenn Research Center. 1. Lipeles, R.A., Kan, H.K.A., Appl. Surf. Sci. 16, 189(1983).
NSDL National Science Digital Library
In this activity about molecular diffusion (located on page 2 of the PDF), learners will make predictions and move molecules of iodine through a seemingly solid plastic sandwich bag. The process of diffusion will be visually indicated by a color change when the iodine reacts with starch inside the bag. Information in the resource explains how this activity relates to nanoparticles and research. Related to linked video, DragonflyTV Nano: Nanosilver.
NSDL National Science Digital Library
Randy Richardson
In this activity, students work in groups, plotting carbon dioxide concentrations over time on overheads and estimating the rate of change over five years. Stacked together, the overheads for the whole class show an increase on carbon dioxide over five years and annual variation driven by photosynthesis. This exercise enables students to practice basic quantitative skills and understand how important sampling intervals can be when studying changes over time. A goal is to see how small sample size may give incomplete picture of data.
8, 73157337, 2008 Carbon dioxide
Paris-Sud XI, Universitķ de
ACPD 8, 7315Ł7337, 2008 Carbon dioxide distributions over Europe C. Gurk et al. Title Page Abstract distributions of carbon dioxide over Europe C. Gurk1 , H. Fischer1 , P. Hoor1 , M.G. Lawrence1 , J. Lelieveld1 Publications on behalf of the European Geosciences Union. 7315 #12;ACPD 8, 7315Ł7337, 2008 Carbon dioxide
Arnold Schwarzenegger THE CARBON DIOXIDE
i Arnold Schwarzenegger Governor THE CARBON DIOXIDE ABATEMENT POTENTIAL OF CALIFORNIA'S MID, Afzal Siddiqui, and Judy Lai. 2011. The Carbon Dioxide Abatement Potential of California's Mid/Agricultural/Water EndUse Energy Efficiency Ę Renewable Energy Technologies Ę Transportation The Carbon Dioxide
Ionization and scintillation response of high-pressure xenon gas to alpha particles
NASA Astrophysics Data System (ADS)
┴lvarez, V.; Borges, F. I. G.; Cßrcel, S.; Cebrißn, S.; Cervera, A.; Conde, C. A. N.; Dafni, T.; DĒaz, J.; Egorov, M.; Esteve, R.; Evtoukhovitch, P.; Fernandes, L. M. P.; Ferrario, P.; Ferreira, A. L.; Freitas, E. D. C.; Gehman, V. M.; Gil, A.; Goldschmidt, A.; G¾mez, H.; G¾mez-Cadenas, J. J.; Gonzßlez-DĒaz, D.; Gutiķrrez, R. M.; Hauptman, J.; Hernando Morata, J. A.; Herrera, D. C.; Irastorza, I. G.; Jinete, M. A.; Labarga, L.; Laing, A.; Liubarsky, I.; Lopes, J. A. M.; Lorca, D.; Losada, M.; Luz¾n, G.; MarĒ, A.; MartĒn-Albo, J.; Miller, T.; Moiseenko, A.; Monrabal, F.; Monteiro, C. M. B.; Mora, F. J.; Moutinho, L. M.; Mu±oz Vidal, J.; Natal da Luz, H.; Navarro, G.; Nebot-Guinot, M.; Nygren, D.; Oliveira, C. A. B.; Palma, R.; Pķrez, J.; Pķrez Aparicio, J. L.; Renner, J.; Ripoll, L.; RodrĒguez, A.; RodrĒguez, J.; Santos, F. P.; dos Santos, J. M. F.; SeguĒ, L.; Serra, L.; Shuman, D.; Sim¾n, A.; Sofka, C.; Sorel, M.; Toledo, J. F.; Tomßs, A.; Torrent, J.; Tsamalaidze, Z.; Vßzquez, D.; Veloso, J. F. C. A.; Webb, R.; White, J. T.; Yahlali, N.
High-pressure xenon gas is an attractive detection medium for a variety of applications in fundamental and applied physics. In this paper we study the ionization and scintillation detection properties of xenon gas at 10 bar pressure. For this purpose, we use a source of alpha particles in the NEXT-DEMO time projection chamber, the large scale prototype of the NEXT-100 neutrinoless double beta decay experiment, in three different drift electric field configurations. We measure the ionization electron drift velocity and longitudinal diffusion, and compare our results to expectations based on available electron scattering cross sections on pure xenon. In addition, two types of measurements addressing the connection between the ionization and scintillation yields are performed. On the one hand we observe, for the first time in xenon gas, large event-by-event correlated fluctuations between the ionization and scintillation signals, similar to that already observed in liquid xenon. On the other hand, we study the field dependence of the average scintillation and ionization yields. Both types of measurements may shed light on the mechanism of electron-ion recombination in xenon gas for highly-ionizing particles. Finally, by comparing the response of alpha particles and electrons in NEXT-DEMO, we find no evidence for quenching of the primary scintillation light produced by alpha particles in the xenon gas.
Numerical study on xenon positive column discharges of mercury-free lamp
Ouyang, Jiting; He, Feng; Miao, Jinsong; Wang, Jianqi; Hu, Wenbo [School of Science, Beijing Institute of Technology, P.O. Box 327, Beijing 100081 (China); Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an 710049 (China)
In this paper, the numerical study has been performed on the xenon positive column discharges of mercury-free fluorescent lamp. The plasma discharge characteristics are analyzed by numerical simulation based on two-dimensional fluid model. The effects of cell geometry, such as the dielectric layer, the electrode width, the electrode gap, and the cell height, and the filling gas including the pressure and the xenon percentage are investigated in terms of discharge current and discharge efficiency. The results show that a long transient positive column will form in the xenon lamp when applying ac sinusoidal power and the lamp can operate in a large range of voltage and frequency. The front dielectric layer of the cell plays an important role in the xenon lamp while the back layer has little effect. The ratio of electrode gap to cell height should be large to achieve a long positive column xenon lamp and higher efficiency. Increase of pressure or xenon concentration results in an increase of discharge efficiency and voltage. The discussions will be helpful for the design of commercial xenon lamp cells.
Xenon treatment attenuates early renal allograft injury associated with prolonged hypothermic storage in rats.
Zhao, Hailin; Yoshida, Akira; Xiao, Wei; Ologunde, Rele; O'Dea, Kieran P; Takata, Masao; Tralau-Stewart, Catherine; George, Andrew J T; Ma, Daqing
Prolonged hypothermic storage elicits severe ischemia-reperfusion injury (IRI) to renal grafts, contributing to delayed graft function (DGF) and episodes of acute immune rejection and shortened graft survival. Organoprotective strategies are therefore needed for improving long-term transplant outcome. The aim of this study is to investigate the renoprotective effect of xenon on early allograft injury associated with prolonged hypothermic storage. Xenon exposure enhanced the expression of heat-shock protein 70 (HSP-70) and heme oxygenase 1 (HO-1) and promoted cell survival after hypothermia-hypoxia insult in human proximal tubular (HK-2) cells, which was abolished by HSP-70 or HO-1 siRNA. In the brown Norway to Lewis rat renal transplantation, xenon administered to donor or recipient decreased the renal tubular cell death, inflammation, and MHC II expression, while delayed graft function (DGF) was therefore reduced. Pathological changes associated with acute rejection, including T-cell, macrophage, and fibroblast infiltration, were also decreased with xenon treatment. Donors or recipients treated with xenon in combination with cyclosporin A had prolonged renal allograft survival. Xenon protects allografts against delayed graft function, attenuates acute immune rejection, and enhances graft survival after prolonged hypothermic storage. Furthermore, xenon works additively with cyclosporin A to preserve post-transplant renal function. PMID:23759444
GraXe, graphene and xenon for neutrinoless double beta decay searches
NASA Astrophysics Data System (ADS)
G¾mez-Cadenas, J. J.; Guinea, F.; Fogler, M. M.; Katsnelson, M. I.; MartĒn-Albo, J.; Monrabal, F.; Mu±oz Vidal, J.
We propose a new detector concept, GraXe (to be pronounced as grace), to search for neutrinoless double beta decay in 136XE. GraXe combines a popular detection medium in rare-event searches, liquid xenon, with a new, background-free material, graphene. In our baseline design of GraXe, a sphere made of graphene-coated titanium mesh and filled with liquid xenon (LXe) enriched in the 136XE isotope is immersed in a large volume of natural LXe instrumented with photodetectors. Liquid xenon is an excellent scintillator, reasonably transparent to its own light. Graphene is transparent over a large frequency range, and impermeable to the xenon. Event position could be deduced from the light pattern detected in the photosensors. External backgrounds would be shielded by the buffer of natural LXe, leaving the ultra-radiopure internal volume virtually free of background. Industrial graphene can be manufactured at a competitive cost to produce the sphere. Enriching xenon in the isotope 136XE is easy and relatively cheap, and there is already near one ton of enriched xenon available in the world (currently being used by the EXO, KamLAND-Zen and NEXT experiments). All the cryogenic know-how is readily available from the numerous experiments using liquid xenon. An experiment using the GraXe concept appears realistic and affordable in a short time scale, and its physics potential is enormous.
GraXe, graphene and xenon for neutrinoless double beta decay searches
Gomez-Cadenas, J J; Fogler, M M; Katsnelson, M I; Martin-Albo, J; Monrabal, F; Mu±oz-Vidal, J
We propose a new detector concept, GraXe (to be pronounced as grace), to search for neutrinoless double beta decay in Xe-136. GraXe combines a popular detection medium in rare-event searches, liquid xenon, with a new, background-free material, graphene. Our baseline design of GraXe is a balloon made of graphene (possibly held together with a very thin structure made of radiopure fiber) and filled with xenon enriched in the Xe-136 isotope. The balloon is immersed in a large tank containing 20 tons of natural liquid xenon and instrumented with large photomultipliers. Liquid xenon is an excellent scintillator, reasonably transparent to its own light. Graphene is transparent over a large frequency range, an impermeable to the xenon. External backgrounds would be shielded by the buffer liquid xenon, and the inner volume has virtually zero background. Industrial graphene can be manufactured at a competitive cost to produce the inner balloon, and there is already near one ton of enriched Xenon available in the world...
Pretreatment for cellulose hydrolysis by carbon dioxide explosion
Zheng, Y.; Lin, H.M.; Tsao, G.T. [Purdue Univ., West Lafayette, IN (United States). Lab of Renewable Resources Engineering] [Purdue Univ., West Lafayette, IN (United States). Lab of Renewable Resources Engineering
Cellulosic materials were treated with supercritical carbon dioxide to increase the reactivity of cellulose, thereby to enhance the rate and the extent of cellulose hydrolysis. In this pretreatment process, the cellulosic materials such as Avicel, recycled paper mix, sugarcane bagasse and the repulping waste of recycled paper are placed in a reactor under pressurized carbon dioxide at 35 C for a controlled time period. Upon an explosive release of the carbon dioxide pressure, the disruption of the cellulosic structure increases the accessible surface area of the cellulosic substrate to enzymatic hydrolysis. Results indicate that supercritical carbon dioxide is effective for pretreatment of cellulose. An increase in pressure facilitates the faster penetration of carbon dioxide molecules into the crystalline structures, thus more glucose is produced from cellulosic materials after the explosion as compared to those without the pretreatment. This explosion pretreatment enhances the rate of cellulosic material hydrolysis as well as increases glucose yield by as much as 50%. Results from the simultaneous saccharification and fermentation tests also show the increase in the available carbon source from the cellulosic materials for fermentation to produce ethanol. As an alternative method, this supercritical carbon dioxide explosion has a possibility to reduce expense compared with ammonia explosion, and since it is operated at the low temperature, it will not cause degradation of sugars such as those treated with steam explosion due to the high-temperature involved.
Investigating Nitrogen Dioxide
NSDL National Science Digital Library
Students will investigate Nitrogen Dioxide levels in the atmosphere during a one year time span using data sets from MyNASAData website. They will draw conclusions about what factors around the world effect NO2 levels (season, population, industry, etc.)
NSDL National Science Digital Library
Austen Saltz
In this activity, learners investigate carbon sequestration by creating a carbonated beverage out of apple juice and dry ice. This experiment illustrates how carbon dioxide can be stored in a substance. Learners compare and contrast the results to determine if liquid carbonation is an effective method for carbon sequestration. Safety note: this activity involves dry ice; please follow recommended guidelines.
NSDL National Science Digital Library
In this problem set, learners will analyze the Keeling Curve showing carbon dioxide concentration in the atmosphere since 1985 to answer a series of questions. Answer key is provided. This is part of Earth Math: A Brief Mathematical Guide to Earth Science and Climate Change.
D. W. Brite; R. J. Anicetti
The techniques developed for fabricating (UOŌ fuel element cores ; and swageable powders at HAPO are described. A simplified flow chart of some of ; the processes is presented. Types of fuel cores fabricated since the program ; began in 1956 are indicated. The experiences and observations are related both ; in fabricating the uranium dioxide fuel element cores for
Bench Remarks: Carbon Dioxide.
ERIC Educational Resources Information Center
Bent, Henry A.
Discusses the properties of carbon dioxide in its solid "dry ice" stage. Suggests several demonstrations and experiments that use dry ice to illustrate Avogadro's Law, Boyle's Law, Kinetic-Molecular Theory, and the effects of dry ice in basic solution, in limewater, and in acetone. (TW)
Dutta, Prabir K. (Worthington, OH); Lee, Inhee (Columbus, OH); Akbar, Sheikh A. (Hilliard, OH)
The present invention generally relates to carbon dioxide (CO.sub.2) sensors. In one embodiment, the present invention relates to a carbon dioxide (CO.sub.2) sensor that incorporates lithium phosphate (Li.sub.3PO.sub.4) as an electrolyte and sensing electrode comprising a combination of lithium carbonate (Li.sub.2CO.sub.3) and barium carbonate (BaCO.sub.3). In another embodiment, the present invention relates to a carbon dioxide (CO.sub.2) sensor has a reduced sensitivity to humidity due to a sensing electrode with a layered structure of lithium carbonate and barium carbonate. In still another embodiment, the present invention relates to a method of producing carbon dioxide (CO.sub.2) sensors having lithium phosphate (Li.sub.3PO.sub.4) as an electrolyte and sensing electrode comprising a combination of lithium carbonate (Li.sub.2CO.sub.3) and barium carbonate (BaCO.sub.3).
Technology Transfer Automated Retrieval System (TEKTRAN)
Chlorine dioxide (ClO2) gas is registered by the U.S. Environmental Protection Agency (EPA) as a sterilant for use in manufacturing, laboratory equipment, medical devices, environmental surfaces, tools and clean rooms. Aqueous ClO2 is registered by the EPA as a surface disinfectant and sanitizer fo...
The recycling of carbon dioxide to methanol and dimethyl ether is seen to offer a substantial route to renewable and environmentally carbon neutral fuels. One of the authors has championed the ?Methanol Economy" in articles and a book. By recycling ambient CO2, the authors argue ...
Using carbon dioxide as a building block in organic synthesis.
Liu, Qiang; Wu, Lipeng; Jackstell, Ralf; Beller, Matthias
Carbon dioxide exits in the atmosphere and is produced by the combustion of fossil fuels, the fermentation of sugars and the respiration of all living organisms. An active goal in organic synthesis is to take this carbon--trapped in a waste product--and re-use it to build useful chemicals. Recent advances in organometallic chemistry and catalysis provide effective means for the chemical transformation of CO? and its incorporation into synthetic organic molecules under mild conditions. Such a use of carbon dioxide as a renewable one-carbon (C1) building block in organic synthesis could contribute to a more sustainable use of resources. PMID:25600683
NSDL National Science Digital Library
Rensselaer Polytechnic Institute
This online interactive has three activities in the NanoLab (press the upper right button): Build, Zoom, and Transform. In Build, learners build increasingly complex molecules out of carbon, oxygen, and hydrogen, and is useful for connecting subscripts and the number of atoms, and for introducing 3D molecular structures which are automatically built. Zoom is a "powers of 10" zoom-in ranging from 10,000 kilometers to 1 nanometer. Transform is a simulation of water changing phase from solid to liquid to gas. Through exploration of the site learners form a better understanding of the composition of matter.
Carbon dioxide dangers demonstration model
Venezky, Dina; Wessells, Stephen
Carbon dioxide is a dangerous volcanic gas. When carbon dioxide seeps from the ground, it normally mixes with the air and dissipates rapidly. However, because carbon dioxide gas is heavier than air, it can collect in snowbanks, depressions, and poorly ventilated enclosures posing a potential danger to people and other living things. In this experiment we show how carbon dioxide gas displaces oxygen as it collects in low-lying areas. When carbon dioxide, created by mixing vinegar and baking soda, is added to a bowl with candles of different heights, the flames are extinguished as if by magic.
Heterogeneous Nuclear Reactor Models for Optimal Xenon Control.
NASA Astrophysics Data System (ADS)
Gondal, Ishtiaq Ahmad
Nuclear reactors are generally modeled as homogeneous mixtures of fuel, control, and other materials while in reality they are heterogeneous-homogeneous configurations comprised of fuel and control rods along with other materials. Similarly, for space-time studies of a nuclear reactor, homogeneous, usually one-group diffusion theory, models are used, and the system equations are solved by either nodal or modal expansion approximations. Study of xenon-induced problems has also been carried out using similar models and with the help of dynamic programming or classical calculus of variations or the minimum principle. In this study a thermal nuclear reactor is modeled as a two-dimensional lattice of fuel and control rods placed in an infinite-moderator in plane geometry. The two-group diffusion theory approximation is used for neutron transport. Space -time neutron balance equations are written for two groups and reduced to one space-time algebraic equation by using the two-dimensional Fourier transform. This equation is written at all fuel and control rod locations. Iodine -xenon and promethium-samarium dynamic equations are also written at fuel rod locations only. These equations are then linearized about an equilibrium point which is determined from the steady-state form of the original nonlinear system equations. After studying poisonless criticality, with and without control, and the stability of the open-loop system and after checking its controllability, a performance criterion is defined for the xenon-induced spatial flux oscillation problem in the form of a functional to be minimized. Linear -quadratic optimal control theory is then applied to solve the problem. To perform a variety of different additional useful studies, this formulation has potential for various extensions and variations; for example, different geometry of the problem, with possible extension to three dimensions, heterogeneous -homogeneous formulation to include, for example, homogeneously -distributed burnable poisons, inclusion of additional terms, for example, fast fission and resonance absorption, different fuel and control rod diameters, different distances between rods, different fuel enrichment in different fuel rods, different control concentration in different control rods, and different forms of the performance index, to name a few.
Performance of 10-kW class xenon ion thrusters
NASA Technical Reports Server (NTRS)
Patterson, Michael J.; Rawlin, Vincent K.
Presented are performance data for laboratory and engineering model 30 cm-diameter ion thrusters operated with xenon propellant over a range of input power levels from approximately 2 to 20 kW. Also presented are preliminary performance results obtained from laboratory model 50 cm-diameter cusp- and divergent-field ion thrusters operating with both 30 cm- amd 50 cm-diameter ion optics up to a 20 kW input power. These data include values of discharge chamber propellant and power efficiencies, as well as values of specific impulse, thruster efficiency, thrust and power. The operation of the 30 cm- and 50 cm-diameter ion optics are also discussed.
A New Approach to the Origin of Xenon-HL
NASA Astrophysics Data System (ADS)
Ott, U.
Xenon-HL carried by interstellar diamonds in primitive meteorites [1] resembles xenon produced in the p- and r-processes of nucleosynthesis (thought to occur in supernovae) in that it is enriched in the light (hence 'L'), p-only, isotopes 124,126Xe and the heavy (hence 'H'), r-only, isotopes 134,136Xe. Detailed comparison reveals different levels of enhancement in Xe-H, however, of 134Xe and 136Xe. As a result, ad-hoc scenarios have been suggested, like a mini-r-process, intermediate between s-and r-process, for producing Xe-H [2]. However, inventing a special process in order to account for a significant fraction of one element (several percent of the Xe in primitive meteorites is Xenon-HL) without evidence for such a process to have contributed significantly to anything else, is not a very attractive solution. Here we propose to consider instead that Xe-H is basically 'normal' r-process Xe that a chemical fractionation effect has turned into Xe-H. In doing so we compare r-process Xe with 'pure 'Xe-HL (i.e. Xe-HL extrapolated to 130Xe degrees 0, where 'real' HL-Xe is the product of mixing with ~ normal Xe). The r-process acts on a rapid (~1 sec) timescale (e.g. [3]), producing neutron-rich nuclides far from stability, that subsequently decay via a series of beta-decays into stable endproducts. As the precursors of the different Xe isotopes have different lifetimes, the isotopic composition of the Xe in supernova ejecta will be time-dependent on that time-scale. From the figure, where the development of the ratio 134Xe/136Xe is shown, it is obvious that after approx. 2 hours this ratio is equal to that of 'pure' Xe-H. If, at that time, a chemical separation can be achieved between the Te and I precursors on one hand and Xe on the other, we are left with Xe for which this ratio is identical to that in Xe-H. At this time little 129,131,132Xe will have been produced, because their precursors have much longer half-lives. In order to account for the small, but non-zero abundances in pure Xe-H of these isotopes, on the order of 5% of fully developed r-process Xe may have to be admixed, an observation supported by the fact that in 'pure' Xe-H these isotopes occur in ratios relative to each other that are consistent with r-process Xe proper. Also, because in the p-process 126Xe is in part originally produced as 126Ba with a half-life of 97 min., a separation of Ba from Xe on a similar time-scale may account for the fact that (126Xe/124Xe)L < (126Xe/124Xe)p. Condensation comes to mind as an obvious means to achieve a separation between xenon and the other elements, but timescales usually associated with the formation of supernova condensates are years rather than hours. We note, however, that for certain assumptions about the cooling process of supernovae, the first condensates may form in the ejecta after about 10^3-10^4sec. already [4]. Taken at face value, the existence of Xe-HL may serve to support such a fast cooling scenario. References: [1] Lewis R. S. et al. (1987) Nature, 326, 160-162. [2] Clayton D. D. (1989) Astrophys. J., 340, 613-619. [3] Kratz K.-L. et al. (1993) Astrophys. J., 403, 216-238. [4] Lattimer J. M. et al. (1978) Astrophys. J., 219, 230-249.
Investigation of many-body forces in krypton and xenon
Salacuse, J.J.; Egelstaff, P.A.
The simplicity of the state dependence at relatively high temperatures ofthe many-body potential contribution to the pressure and energy has been pointed out previously (J. Ram and P. A. Egelstaff, J. Phys. Chem. Liq. 14, 29 (1984); A. Teitsima and P. A. Egelstaff, Phys. Rev. A 21, 367 (1980)). In this paper, we investigate how far these many-body potential terms may be represented by simple models in the case of krypton on the 423-, 273-, 190-, and 150-K isotherms, and xenon on the 170-, 210-, and 270-K isotherms. At the higher temperatures the best agreement is found for the mean-field type of theory, and some consequences are pointed out. On the lower isotherms a state point is found where the many-body energy vanishes, and large departures from mean-field behavior are observed. This is attributed to the influence of short-ranged many-body forces.
Investigation of a pulsed xenon discharge at medium pressure
NASA Astrophysics Data System (ADS)
Gnybida, M.; Uhrlandt, D.; Loffhagen, D.
The pulsed discharge in xenon at pressures between 10 and 50 Torr and a peak current of 130 mA has been analysed by means of a time-dependent, spatially one-dimensional fluid model. Main features of the model of the radially inhomogeneous discharge plasma in a discharge tube with an inner diameter of 6.5 mm are given. The comparison of results of model calculations with experimental data shows good agreement for the axial electric field, and the qualitative behaviour of measured axis densities of low-lying excited states is reproduced well by the model. The analysis of the spatiotemporal variation of the pulsed discharge shows the formation of a constricted column plasma at increasing pressure. In particular, a pronouncedly nonlocal behaviour of the electron component is found, and the densities of the metastable and resonance atoms are predicted to have a radial profile with a maximum out of the axis during the discharge phase.
Multiple-ionization of xenon atoms by positron impact
NASA Technical Reports Server (NTRS)
Kruse, Georg; Quermann, Andreas; Raith, Wilhelm; Sinapius, Guenther
Previously the cross sections were measured for positronium formation and single ionization by positron impact for He and H2. With the same apparatus, slightly modified, the single and multiple ionization of xenon is now investigated. The principle of the method is the detection of ion and positron in time correlation which allows the discrimination of positronium formation (whereby the positron vanishes) and the destinction of single, double and triple impact ionization (which lead to different ion flight times from the gas target to the ion detector). By using secondary electrons from the positron moderator, similar measurements were performed on electron impact ionization. By comparing with literature values for electron multiple ionization cross sections, the detection-probability ratios were determined for the differently charged ions.
Position Reconstruction in a Dual Phase Xenon Scintillation Detector
NASA Astrophysics Data System (ADS)
Solovov, V. N.; Belov, V. A.; Akimov, D. Yu.; Araujo, H. M.; Barnes, E. J.; Burenkov, A. A.; Chepel, V.; Currie, A.; DeViveiros, L.; Edwards, B.; Ghag, C.; Hollingsworth, A.; Horn, M.; Kalmus, G. E.; Kobyakin, A. S.; Kovalenko, A. G.; Lebedenko, V. N.; Lindote, A.; Lopes, M. I.; Luscher, R.; Majewski, P.; Murphy, A. S. J.; Neves, F.; Paling, S. M.; Pinto da Cunha, J.; Preece, R.; Quenby, J. J.; Reichhart, L.; Scovell, P. R.; Silva, C.; Smith, N. J. T.; Smith, P. F.; Stekhanov, V. N.; Sumner, T. J.; Thorne, C.; Walker, R. J.
We studied the application of statistical reconstruction algorithms, namely maximum likelihood and least squares methods, to the problem of event reconstruction in a dual phase liquid xenon detector. An iterative method was developed for in-situ reconstruction of the PMT light response functions from calibration data taken with an uncollimated gamma-ray source. Using the techniques described, the performance of the ZEPLIN-III dark matter detector was studied for 122 keV gamma-rays. For the inner part of the detector (R<100 mm), spatial resolutions of 13 mm and 1.6 mm FWHM were measured in the horizontal plane for primary and secondary scintillation, respectively. An energy resolution of 8.1% FWHM was achieved at that energy. The possibility of using this technique for improving performance and reducing cost of scintillation cameras for medical applications is currently under study.
Scintillation Response of Liquid Xenon to Low Energy Nuclear Recoils
E. Aprile; K. L. Giboni; P. Majewski; K. Ni; M. Yamashita; R. Hasty; A. Manzur; D. N. McKinsey
Liquid Xenon (LXe) is expected to be an excellent target and detector medium to search for dark matter in the form of Weakly Interacting Massive Particles (WIMPs). Knowledge of LXe ionization and scintillation response to low energy nuclear recoils expected from the scattering of WIMPs by Xe nuclei is important for determining the sensitivity of LXe direct detection experiments. Here we report on new measurements of the scintillation yield of Xe recoils with kinetic energy as low as 10 keV. The dependence of the scintillation yield on applied electric field was also measured in the range of 0 to 4 kV/cm. Results are in good agreement with recent theoretical predictions that take into account the effect of biexcitonic collisions in addition to the nuclear quenching effect.
Multiphoton ionization and third-harmonic generation in atoms and molecules
Miller, J.C.; Compton, R.N.
We will discuss recent experiments on multiphoton ionization and third-harmonic generation in rare gases and small molecules using focused laser power densities of 10/sup 9/ to 10/sup 11/ W/cm/sup 2/. Also, some elementary experiments using vacuum ultraviolet light generated by frequency tripling in xenon and krypton will be described. These experiments include absorption and ionization studies using vacuum ultraviolet radiation as well as two-photon ionization using one vacuum ultraviolet photon and one laser photon.
An Ultra-Low Background PMT for Liquid Xenon Detectors
D. S. Akerib; X. Bai; E. Bernard; A. Bernstein; A. Bradley; D. Byram; S. B. Cahn; M. C. Carmona-Benitez; D. Carr; J. J. Chapman; Y-D. Chan; K. Clark; T. Coffey; L. deViveiros; M. Dragowsky; E. Druszkiewicz; B. Edwards; C. H. Faham; S. Fiorucci; R. J. Gaitskell; K. R. Gibson; C. Hall; M. Hanhardt; B. Holbrook; M. Ihm; R. G. Jacobsen; L. Kastens; K. Kazkaz; N. Larsen; C. Lee; K. Lesko; A. Lindote; M. I. Lopes; A. Lyashenko; D. C. Malling; R. Mannino; D. McKinsey; D. Mei; J. Mock; M. Morii; H. Nelson; F. Neves; J. A. Nikkel; M. Pangilinan; K. Pech; P. Phelps; T. Shutt; C. Silva; W. Skulski; V. N. Solovov; P. Sorensen; J. Spaans; T. Stiegler; M. Sweany; M. Szydagis; D. Taylor; J. Thomson; M. Tripathi; S. Uvarov; J. R. Verbus; N. Walsh; R. Webb; J. T. White; M. Wlasenko; F. L. H. Wolfs; M. Woods; C. Zhang
Results are presented from radioactivity screening of two models of photomultiplier tubes designed for use in current and future liquid xenon experiments. The Hamamatsu 5.6 cm diameter R8778 PMT, used in the LUX dark matter experiment, has yielded a positive detection of four common radioactive isotopes: 238U, 232Th, 40K, and 60Co. Screening of LUX materials has rendered backgrounds from other detector materials subdominant to the R8778 contribution. A prototype Hamamatsu 7.6 cm diameter R11410 MOD PMT has also been screened, with benchmark isotope counts measured at <0.4 238U / <0.3 232Th / <8.3 40K / 2.0+-0.2 60Co mBq/PMT. This represents a large reduction, equal to a change of \\times 1/24 238U / \\times 1/9 232Th / \\times 1/8 40K per PMT, between R8778 and R11410 MOD, concurrent with a doubling of the photocathode surface area (4.5 cm to 6.4 cm diameter). 60Co measurements are comparable between the PMTs, but can be significantly reduced in future R11410 MOD units through further material selection. Assuming PMT activity equal to the measured 90% upper limits, Monte Carlo estimates indicate that replacement of R8778 PMTs with R11410 MOD PMTs will change LUX PMT electron recoil background contributions by a factor of \\times1/25 after further material selection for 60Co reduction, and nuclear recoil backgrounds by a factor of \\times 1/36. The strong reduction in backgrounds below the measured R8778 levels makes the R11410 MOD a very competitive technology for use in large-scale liquid xenon detectors.
Rest and exercise right ventricular function from gated xenon scans
Tweddel, A.C.; Martin, W.; McGhie, A.I.; McKillop, J.H.; Hutton, I.
Right ventricular function is of considerable clinical interest in acute myocardial infarction involving the right ventricular wall and in the patient with obstructive airways disease. The aim of this study was to assess the use of Xe-133 to evaluate right ventricular ejection fraction (RVEF), as both standard first pass and gated blood pool techniques present methodological problems. 400 MBq of Xe-133 were injected intravenously over 20-25 seconds and listmode data acquired using a mobile gamma camera with an ultra high sensitivity parallel collimator. A 15/sup 0/ left anterior oblique projection was used, acquisition being initiated when right ventricular activity becomes apparent and terminated as this leaves the ventricle. With the rapid excretion of Xenon, scans can be repeated after 5 minutes. In 10 healthy volunteers, RVEF ranged from 40-55%, compared to a range 8-38% in 10 patients with acute myocardial infarction involving right ventricular wall. In 5 patients with scans repeated at 10 minutes a mean difference of 2% in RVEF was obtained. The analysis of RVEF was only subject to small inter-observer (3%), and inter-observer (2.5%) variation. In comparison with gated blood pool scintigrams good correlation of resting RVEF was obtained (r=.91, n=15). In volunteers resting RVEF increased from a mean of 43% -+ 4 to 49% -+ 7 during peak maximal supine exercise. In 10 patients with chronic obstructive airways disease, where resting RVEF was above 30%, exercise RVEF tended to increase, whereas, below 30% on peak exercise RVEF was further impaired. Gated Xenon scans offer a simple, reliable assessment of RVEF in various clinical situations with interventions.
How Many Water Molecules Are Actively Involved in the Neutral Hydration of Carbon Minh Tho Nguyen,* Greet Raspoet, and Luc G. Vanquickenborne
Nguyen, Minh Tho
How Many Water Molecules Are Actively Involved in the Neutral Hydration of Carbon Dioxide? Minh Tho, 1997; In Final Form: May 23, 1997X The detailed reaction pathways for the hydration of carbon dioxide constitutes a case of active solvent catalysis where solvent molecules actively participate as a catalyst
Detection of brown adipose tissue and thermogenic activity in mice by hyperpolarized xenon MRI
Branca, Rosa Tamara; He, Ting; Zhang, Le; Floyd, Carlos S.; Freeman, Matthew; White, Christian; Burant, Alex
The study of brown adipose tissue (BAT) in human weight regulation has been constrained by the lack of a noninvasive tool for measuring this tissue and its function in vivo. Existing imaging modalities are nonspecific and intrinsically insensitive to the less active, lipid-rich BAT of obese subjects, the target population for BAT studies. We demonstrate noninvasive imaging of BAT in mice by hyperpolarized xenon gas MRI. We detect a greater than 15-fold increase in xenon uptake by BAT during stimulation of BAT thermogenesis, which enables us to acquire background-free maps of the tissue in both lean and obese mouse phenotypes. We also demonstrate in vivo MR thermometry of BAT by hyperpolarized xenon gas. Finally, we use the linear temperature dependence of the chemical shift of xenon dissolved in adipose tissue to directly measure BAT temperature and to track thermogenic activity in vivo. PMID:25453088
Detection of brown adipose tissue and thermogenic activity in mice by hyperpolarized xenon MRI.
Branca, Rosa Tamara; He, Ting; Zhang, Le; Floyd, Carlos S; Freeman, Matthew; White, Christian; Burant, Alex
The study of brown adipose tissue (BAT) in human weight regulation has been constrained by the lack of a noninvasive tool for measuring this tissue and its function in vivo. Existing imaging modalities are nonspecific and intrinsically insensitive to the less active, lipid-rich BAT of obese subjects, the target population for BAT studies. We demonstrate noninvasive imaging of BAT in mice by hyperpolarized xenon gas MRI. We detect a greater than 15-fold increase in xenon uptake by BAT during stimulation of BAT thermogenesis, which enables us to acquire background-free maps of the tissue in both lean and obese mouse phenotypes. We also demonstrate in vivo MR thermometry of BAT by hyperpolarized xenon gas. Finally, we use the linear temperature dependence of the chemical shift of xenon dissolved in adipose tissue to directly measure BAT temperature and to track thermogenic activity in vivo. PMID:25453088
Progress on Acoustic Measurements of the Bulk Viscosity of Near-Critical Xenon (BVX)
NASA Technical Reports Server (NTRS)
Gillis, Keith A.; Shinder, Iosif I.; Moldover, Michael R.; Zimmerli, Gregory A.
We plan to determine the bulk viscosity of xenon 10 times closer [in reduced temperature tau = (T-Tc)/Tc] to its liquid-vapor critical point than ever before. (Tc is the critical temperature.) To do so, we must measure the dispersion and attenuation of sound at frequencies 1/100 of those used previously. In general, sound attenuation has contributions from the bulk viscosity acting throughout the volume of the xenon as well as contributions from the thermal conductivity and the shear viscosity acting within thin thermoacoustic boundary layers at the interface between the xenon and the solid walls of the resonator. Thus, we can determine the bulk viscosity only when the boundary layer attenuation is small and well understood. We present a comparison of calculations and measurements of sound attenuation in the acoustic boundary layer of xenon near its liquid-vapor critical point.
The equation of state of metastable liquid xenon near the critical point
V. G. Baidakov; A. M. Rubshtein; V. R. Pomortsev; I. J. Sulla
This paper presents the results of measurements of xenon density near the critical liquid-vapour point in stable and metastable states. The spinodal has been approximated. The equation of state of metastable liquid is discussed.
Experimental studies of a zeeman-tuned xenon laser differential absorption apparatus.
Linford, G J
A Zeeman-tuned cw xenon laser differential absorption device is described. The xenon laser was tuned by axial magnetic fields up to 5500 G generated by an unusually large water-cooled dc solenoid. Xenon laser lines at 3.37 micro, 3.51 micro, and 3.99 micro were tuned over ranges of 6 A, 6 A, and 11 A, respectively. To date, this apparatus has been used principally to study the details of formaldehyde absorption lines lying near the 3 .508-micro xenon laser transition. These experiments revealed that the observed absorption spectrum of formaldehyde exhibits a sufficiently unique spectral structure that the present technique may readily be used to measure relative concentrations of formaldehyde in samples of polluted air. PMID:20125492
Measurement of the Cotton-Mouton effect in nitrogen, oxygen, carbon dioxide, argon, and krypton with the Q & A apparatus
Mei, Hsien-Hao; Chen, Sheng-Jui; Pan, Sheau-shi
Experiments for vacuum birefringence and vacuum dichroism have set up high-finesse high magnetic experimental apparatuses which are ideal for gaseous Cotton-Mouton effect measurements. PVLAS Collaboration has recently measured Cotton-Mouton effects in krypton, xenon and neon at the wavelength of 1064 nm. In this Letter, we report on our measurement of Cotton-Mouton effects in nitrogen, oxygen, carbon dioxide, argon, and krypton at pressure P = 0.5-300 Torr, temperature T = 295-298 K, and laser wavelength of 1064 nm in a magnetic field B = 2.3 T, using our Q & A experimental setup, which are in agreement with the PVLAS results.
Measurement of the Cotton-Mouton effect in nitrogen, oxygen, carbon dioxide, argon, and krypton with the Q & A apparatus
Hsien-Hao Mei; Wei-Tou Ni; Sheng-Jui Chen; Sheau-shi Pan
Experiments for vacuum birefringence and vacuum dichroism have been set up with high-finesse high magnetic experimental apparatuses, which seem to be ideal for small gaseous Cotton-Mouton effect (CME) measurements. PVLAS Collaboration has measured CMEs in krypton, xenon and neon at the wavelength of 1064 nm. In this Letter, we report on our measurement of CMEs in nitrogen, oxygen, carbon dioxide, argon, and krypton at the same wavelength in a magnetic field B = 2.3 T at pressure P = 0.5-300 Torr and temperature T = 295-298 K. Our results agree with the PVLAS results in the common cases.
Anomalous nanostructured titanium dioxide.
Nad, Suddhasattwa; Sharma, Parvesh; Roy, Indrajit; Maitra, Amarnath
Titanium dioxide nanoparticles prepared in water-in-oil microemulsion droplets by controlled hydrolysis of TiCl(4)-generated crystalline nanoparticles of sizes from 115 nm down to 6 nm diameter depending on the size of the aqueous core of the micellar droplets. Powder X-ray diffraction of the vacuum-dried product (without sintering) indicated the presence of an unusual type of orthorhombic crystal structure nearly similar to titanium dioxide crystals prepared at high pressure. On gradual heating up to 900 degrees C these metastable crystals are converted into relatively more stable nanorods perhaps through making and breaking of the Ti-O-Ti bonds. It has been concluded that chemical pressure generated within the constrained volume of aqueous core of the reverse micellar droplets is responsible for the unusual crystal structure of TiO(2) nanoparticles. PMID:12885523
NASA Technical Reports Server (NTRS)
2005-01-0123 July 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a view of some of the widely-varied terrain of the martian south polar residual cap. The landforms here are composed mainly of frozen carbon dioxide. Each year since MGS arrived in 1997, the scarps that bound each butte and mesa, or line the edges of each pit, in the south polar region, have changed a little bit as carbon dioxide is sublimed away. The scarps retreat at a rate of about 3 meters (3 yards) per martian year. Most of the change occurs during each southern summer. Location near: 86.7oS, 9.8oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring
Determination of the average ionization and thermodynamic regimes of xenon plasmas with an application to the characterization of blast waves launched in xenon clusters
NASA Astrophysics Data System (ADS)
Rodriguez, R.; Gil, J. M.; Florido, R.; Rubiano, J. G.; Mendoza, M. A.; Martel, P.; Minguez, E.; Symes, D. R.; Hohenberger, M.; Smith, R. A.
Radiative shock waves play a pivotal role in the transport energy into the stellar medium. This fact has led to many efforts to scale the astrophysical phenomena to accessible laboratory conditions and their study has been highlighted as an area requiring further experimental investigations. Low density material with high atomic mass is suitable to achieve radiative regime, and, therefore, low density xenon gas is commonly used for the medium in which the radiative shock propagates. In this work the average ionization and the thermodynamic regimes of xenon plasmas are determined as functions of the matter density and temperature in a wide range of plasma conditions. The results obtained will be applied to characterize blast waves launched in xenon clusters.
Titanium dioxide photocatalysis
Akira Fujishima; Tata N. Rao; Donald A. Tryk
Scientific studies on photocatalysis started about two and a half decades ago. Titanium dioxide (TiO2), which is one of the most basic materials in our daily life, has emerged as an excellent photocatalyst material for environmental purification. In this review, current progress in the area of TiO2 photocatalysis, mainly photocatalytic air purification, sterilization and cancer therapy are discussed together with
Solar carbon dioxide fixation offers the possibility of a renewable source of chemicals and fuels in the future. Its realization rests on future advances in the efficiency of solar energy collection and development of suitable catalysts for CO{sub 2} conversion. Recent achievements in the efficiency of solar energy conversion and in catalysis suggest that this approach holds a great deal of promise for contributing to future needs for fuels and chemicals.
J. E. Hart; D. L. Shuck; W. L. Lyon
A continuous, four stage fluidized bed process for converting uranium hexafluoride (UFŌ) to ceramic-grade uranium dioxide (UOŌ) powder suitable for use in the manufacture of fuel pellets for nuclear reactors is disclosed. The process comprises the steps of first reacting UFŌ with steam in a first fluidized bed, preferably at about 550┬░C, to form solid intermediate reaction products UOŌFŌ, UŌOŌ
Ultrafast measurements of chlorine dioxide photochemistry
Ludowise, P.D.
Time-resolved mass spectrometry and time-resolved photoelectron spectroscopy are used to study the ultrafast photodissociation dynamics of chlorine dioxide, an important constituent in stratospheric ozone depletion. Chapter 1 introduces these pump/probe techniques, in which a femtosecond pump pulse excites a molecule to a dissociative state. At a later time, a second femtosecond probe pulse ionizes the molecule. The resulting mass and photoelectron spectra are acquired as a function of the delay between the pump and probe pulses, which follows the evolution of the molecule on the excited state. A comparison to other techniques used to study reaction dynamics is discussed. Chapter 2 includes a detailed description of the design and construction of the experimental apparatus, which consists of a femtosecond laser system, a molecular beam time-of-flight spectrometer, and a data acquisition system. The time-of-flight spectrometer is specifically designed to have a short flight distance to maximize the photoelectron collection efficiency without degrading the resolution, which is limited by the bandwidth of the femtosecond laser system. Typical performance of the apparatus is demonstrated in a study of the time-resolved photoelectron spectroscopy of nitric oxide. The results of the time-resolved mass spectrometry experiments of chlorine dioxide are presented in Chapter 3. Upon excitation to the A {sup 2}A{sub 2} state near 3.2 eV, the molecule dissociates through an indirect two-step mechanism. The direct dissociation channel has been predicted to be open, but is not observed. A quantum beat is observed in the OClO{sup +} species, which is described as a vibrational coherence of the optically prepared A {sup 2}A{sub 2} state. Chapter 4 presents the results of the time-resolved photoelectron experiments of chlorine dioxide. At short delay time, the quantum beat of the OClO{sup +} species is observed in the X {sup 1}A{sub 1} state of the ion. At infinite delay, the signal is dominated by the ClO{sup +} ion, observed in a variety of electronic states. The photoelectron data is shown to support the indirect two-step dissociation mechanism derived from the mass results. Conclusions of the mass and photoelectron results are discussed in context of the stratospheric ozone depletion problem.
Xenon and krypton isotopes in extraterrestrial regolith soils and in the solar wind
R. O. Pepin; R. H. Becker; P. E. Rider
Isotopic distributions of pure solar-wind xenon and krypton are derived from an extensive data base of xenon and krypton compositions evolved from lunar and meteoritic regolith samples by acid-etching or combustion-pyrolysis experiments in several different laboratories. Regolith Xe and Kr are nonuniform mixtures of primary solar-wind components with others arising in situ from cosmic-ray spallation, neutron-capture in iodine and bromine,
14. 6MeV neutron activation cross sections for the xenon isotopes. [(n,2n)
R. A. Sigg; P. K. Kuroda
Activation cross sections for 14 (n,2n) and 5 (n,p) reactions on xenon isotopes have been determined with 14.6-MeV neutrons using sodium perxenate and Ge(Li) gamma-ray spectroscopy. The values obtained are compared to the one earlier set of measurements on the xenon isotopes and to theoretical empirical values. The ┬╣┬▓ŌüĖXe(n,p)┬╣┬▓ŌüĖI cross section is reported for the first time.
Xenon pretreatment may prevent early memory decline after isoflurane anesthesia and surgery in mice.
Vizcaychipi, Marcela P; Lloyd, Dafydd G; Wan, Yanjie; Palazzo, Mark G; Maze, Mervyn; Ma, Daqing
Postoperative cognitive decline (POCD) is a common complication following surgery, but its aetiology remains unclear. We hypothesized that xenon pretreatment prevents POCD by suppressing the systemic inflammatory response or through an associated protective signaling pathway involving heat shock protein 72 (Hsp72) and PI3-kinase. Twenty-four hours after establishing long-term memory using fear conditioning training, C57BL/6 adult male mice (n = 12/group) received one of the following treatments: 1) no treatment group (control); 2) 1.8% isoflurane anesthesia; 3) 70% xenon anesthesia; 4) 1.8% isoflurane anesthesia with surgery of the right hind leg tibia that was pinned and fractured; or 5) pretreatment with 70% xenon for 20 minutes followed immediately by 1.8% isoflurane anesthesia with the surgery described above. Assessments of hippocampal-dependent memory were performed on days 1 and 7 after treatment. Hsp72 and PI3-kinase in hippocampus, and plasma IL-1?, were measured using western blotting and ELISA respectively, from different cohorts on day 1 after surgery. Isoflurane induced memory deficit after surgery was attenuated by xenon pretreatment. Xenon pretreatment prevented the memory deficit typically seen on day 1 (P = 0.04) but not on day 7 (P = 0.69) after surgery under isoflurane anesthesia, when compared with animals that underwent surgery without pretreatment. Xenon pretreatment modulated the expression of Hsp72 (P = 0.054) but had no significant effect on PI3-kinase (P = 0.54), when compared to control. Xenon pretreatment also reduced the plasma level increase of IL-1? induced by surgery (P = 0.028). Our data indicated that surgery and/or Isoflurane induced memory deficit was attenuated by xenon pretreatment. This was associated with a reduction in the plasma level of IL-1? and an upregulation of Hsp72 in the hippocampus. PMID:22073162
Performance of a Liquid Xenon Calorimeter Cryogenic System for the MEG Experiment
T. Haruyama; K. Kasami; Y. Hisamitsu; T. Iwamoto; S. Mihara; T. Mori; H. Nishiguchi; W. Otani; R. Sawada; Y. Uchiyama; T. Nishitani
The mu-particle rare decay physics experiment, the MU-E-GAMMA (MEG) experiment, will soon be operational at the Paul Scherrer Institute in Zurich. To achieve the extremely high sensitivity required to detect gamma rays, 800 L of liquid xenon is used as the medium in the calorimeter, viewed by 830 photomultiplier tubes (PMT) immersed in it. The required liquid xenon purity is
Applications of controlled-flow laser-polarized xenon gas to porous and granular media study
R. W. Maira; R. Wang; M. S. Rosen; D. Candela; D. G. Cory; R. L. Walsworth
We report initial NMR studies of continuous flow laser-polarized xenon gas, both in unrestricted tubing, and in a model porous media. The study uses Pulsed Gradient Spin Echo-based techniques in the gas-phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients. Pulsed Gradient Echo studies of continuous flow laser-polarized xenon gas in unrestricted tubing indicate clear
Magneto-optical trapping of metastable xenon: Isotope-shift measurements
M. Walhout; H. J. L. Megens; A. Witte; S. L. Rolston
We have magneto-optically trapped the nine stable isotopes of xenon. Using the Zeeman slowing method to decelerate a beam of xenon atoms in the metastable 6s 3\\/2 [3\\/2]2 state (notation representing nl Jcore [K=Jcore+l]J), we load our trap to a collisionally limited density of more than 1010 atoms\\/cm3. The two odd isotopes are trapped without a repumping frequency, even though
Spot mode operation of a helium-xenon discharge for lighting
J. Winter; H. Lange; I. A. Porokhova; F. Sigeneger; D. Uhrlandt
A dc low-pressure discharge in a helium-xenon mixture with the cathode spot on a flat oxide cathode has been investigated. The temperature of the cathode surface in the vicinity of the spot was determined experimentally. Furthermore, the gas temperature and the spatial density profile of the xenon 1s5 metastable atoms were measured in front of the spot. A fluid model
Determination of the Relative Two-photon Absorption Cross-section Between Xenon and Hydrogen
NASA Astrophysics Data System (ADS)
Elliott, Drew; Scime, Earl; McCarren, Dustin; Vandervort, Robert; Soderholm, Mark
Two-photon Absorption Laser Induced Fluorescence (TALIF) is a non-perturbative method for measuring the density and temperature of neutral hydrogen in a fusion plasma. Calibration of a TALIF system, for absolute density measurements, requires a measurement of a known density of particles under controlled conditions. Since hydrogen is diatomic, hydrogen TALIF system calibration requires measurements of target cold monatomic gas with a two-photon transition from the ground state and fluorescence decay at accessible energies. Here we present single-sided TALIF (angular momentum change of 2) measurements of a new transition in xenon with absorption and emission wavelengths nearly identical to those of the hydrogen TALIF sequence (the n = 3 to n = 2 emission in hydrogen is at 656.27 nm whereas it is at 655.99 nm in xenon). The xenon calibration approach provides the first opportunity for absolute calibration of Doppler-free (angular momentum change of 0) hydrogen TALIF. We first measure the relative TALIF absorption cross section between xenon and krypton and then use the known cross section ratio between the krypton and hydrogen transitions to calculate the relative xenon-hydrogen cross section. Single isotope xenon samples are used to remove the confounding factors of isotopic and hyperfine splitting.
Control of spatial xenon oscillations in pressurized water reactors via the Kalman filter
Lin, C.; Lin, Y.J. (National Tsing Hua Univ., Hsinchu (Taiwan, Province of China). Dept. of Nuclear Engineering)
A direct control method is developed to control the spatial xenon oscillations in pressurized water reactors. The xenon and iodine concentration difference between the top and bottom halves of the core is estimated by using the extended Kalman filter (EKF), which is a closed-loop estimation method. The measurement equation used in the observer is the axial offset measurement equation, which reflects the xenon unbalanced effect on the axial offset. Meanwhile, some of the coefficients of the observer are estimated on-line to reduce estimation error resulting from model error, i.e., simplified xenon and iodine dynamics. Therefore, the estimation can be guaranteed to be accurate, and the success of the estimation does not greatly depend on the accuracy of the observer model. The predicted one-step ahead xenon concentration, by using the EKF, was used to calculate the possible axial offset variation, and then the control rod motion was calculated to compensate for it. The simulation results show that the proposed method successfully controls the xenon oscillations.
Study of the hydrophobic cavity of beta-cryptogein through laser-polarized xenon NMR spectroscopy.
Berthault, Patrick; Huber, Gaspard; Ha, Phuong Thu; Dubois, Lionel; Desvaux, Hervķ; Guittet, Eric
The interaction of xenon with beta-cryptogein, a basic 10 kDa protein belonging to the elicitin family, has been studied by using dissolved thermal and laser-polarized gas in liquid-state NMR. 13C and 1H chemical-shift-mapping experiments were unfruitful, the proton lines only experienced a slight narrowing but no significant frequency variation when the xenon concentration was increased. Nevertheless magnetization transfer from hyperpolarized xenon to protons of the protein demonstrates an undoubted interaction and enables localization of the noble-gas-binding site. Due to the proton-proton cross-relaxation efficiency, however, this experiment is subjected to important spin-diffusion. An automatic procedure that takes spin-diffusion into account when assigning the protons that interact with xenon is then used. The binding site, as defined by 30 Xe--H interactions, is situated in the inner core of the protein. The protons that interact with xenon border the channel by which sterols are known to enter into the cavity. These results support the idea that xenon is a good probe for hydrophobic protein regions. PMID:16292784
MiX: A Position Sensitive Dual-Phase Liquid Xenon Detector
Stephenson, S; Lin, Q; Ni, K; Pushkin, K; Raymond, R; Schubnell, M; Shutty, N; Tarlķ, G; Weaverdyck, C; Lorenzon, W
The need for precise characterization of dual-phase xenon detectors has grown as the technology has matured into a state of high efficacy for rare event searches. The Michigan Xenon detector was constructed to study the microphysics of particle interactions in liquid xenon across a large energy range in an effort to probe aspects of radiation detection in liquid xenon. We report the design and performance of a small 3D position sensitive dual-phase liquid xenon time projection chamber with high light yield ($L_y^{122}=15.2 $pe/keV at zero field), long electron lifetime ($\\tau > 200 \\mu$s), and excellent energy resolution ($\\sigma/E = 1\\%$ for 1,333 keV gamma rays in a drift field of 200 V/cm). Liquid xenon time projection chambers with such high energy resolution may find applications not only in dark matter direct detection searches, but also in neutrinoless double beta decay experiments and other applications.
Design and construction of a cryogenic distillation device for removal of krypton for liquid xenon dark matter detectors.
Wang, Zhou; Bao, Lei; Hao, Xihuan; Ju, Yonglin
Liquid xenon (Xe) is one of the commendable detecting media for the dark matter detections. However, the small content of radioactive krypton-85 ((85)Kr) always exists in the commercial xenon products. An efficient cryogenic distillation system to remove this krypton (Kr) from commercial xenon products has been specifically designed, developed, and constructed in order to meet the requirements of the dark matter experiments with high- sensitivity and low-background. The content of krypton in regular commercial xenon products can be reduced from 10(-9) to 10(-12), with 99% xenon collection efficiency at maximum flow rate of 5 kg/h (15SLPM). The purified xenon gases produced by this distillation system can be used as the detecting media in the project of Panda X, which is the first dark matter detector developed in China. PMID:24517821
Carbon Dioxide in Exoplanetary Atmospheres: Rarely Dominant Compared to Carbon Monoxide and Water
Heng, Kevin
We present a comprehensive study of the abundance of carbon dioxide in exoplanetary atmospheres. We construct analytical models of systems in chemical equilibrium that include carbon monoxide, carbon dioxide, water, methane and acetylene and relate the equilibrium constants of the chemical reactions to temperature and pressure via the tabulated Gibbs free energies. We prove that such chemical systems may be described by a quintic equation for the mixing ratio of methane. By examining the abundances of these molecules across a broad range of temperatures (spanning equilibrium temperatures from 600 to 2500 K), pressures (via temperature-pressure profiles that explore albedo and opacity variations) and carbon-to-oxygen ratios (from 0.1 to 100), we conclude that carbon dioxide is subdominant compared to carbon monoxide and water. Atmospheric mixing does not alter this conclusion if carbon dioxide is subdominant everywhere in the atmosphere. Carbon dioxide and carbon monoxide may attain comparable abundances if th...
Collisional transfer between the 6s'[12]0,1 and 6p[12]1 xenon levels
N. Sadeghi; J. Sabbagh
The destruction rates of the xenon 6s'[12]0 metastable and 6s'[12]1 resonance atoms by collisions with ground-state xenon atoms have been measured by studying the temporal dependence of the number densities of the 6s' and 6p atoms. The studies have been made both during the earlier afterglow of a xenon pulsed discharge and after the selective production of the 6s'[12]0,1 atoms
Photodissociation of condensed carbon dioxide below the gas phase thresholds
J. M. Coquel; L. Siller; J. Wilkes; R. Carrapa; C. L. A. Lamont; T. Almeida Gasche; R. E. Palmer; A. M. C. Moutinho
We have investigated photodesorption from condensed carbon dioxide for photon energies ranging from 13 to 35 eV using synchrotron radiation. We report the desorption of O2+ ions at energies as low as 13 eV, and discuss this behaviour in terms of ion¢molecule reactions. The desorbed CO+ ion yield shows resonances at ?15.4 and ?17 eV, below the gas-phase thermodynamic threshold
21 CFR 73.1575 - Titanium dioxide.
Code of Federal Regulations, 2013 CFR
...2013-04-01 2013-04-01 false Titanium dioxide. 73.1575 Section...CERTIFICATION Drugs ¦ 73.1575 Titanium dioxide. (a) Identity and specifications. (1) The color additive titanium dioxide shall conform in...
21 CFR 73.3126 - Titanium dioxide.
Code of Federal Regulations, 2013 CFR
...2013-04-01 2013-04-01 false Titanium dioxide. 73.3126 Section 73... Medical Devices ¦ 73.3126 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide (CAS Reg. No....
21 CFR 73.3126 - Titanium dioxide.
Code of Federal Regulations, 2012 CFR
...2012-04-01 2012-04-01 false Titanium dioxide. 73.3126 Section 73... Medical Devices ¦ 73.3126 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide (CAS Reg. No....
21 CFR 73.1575 - Titanium dioxide.
Code of Federal Regulations, 2014 CFR
...2014-04-01 2014-04-01 false Titanium dioxide. 73.1575 Section...CERTIFICATION Drugs ¦ 73.1575 Titanium dioxide. (a) Identity and specifications. (1) The color additive titanium dioxide shall conform in...
21 CFR 73.3126 - Titanium dioxide.
Code of Federal Regulations, 2014 CFR
...2014-04-01 2014-04-01 false Titanium dioxide. 73.3126 Section 73... Medical Devices ¦ 73.3126 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide (CAS Reg. No....
21 CFR 73.1575 - Titanium dioxide.
Code of Federal Regulations, 2011 CFR
...2011-04-01 2011-04-01 false Titanium dioxide. 73.1575 Section...CERTIFICATION Drugs ¦ 73.1575 Titanium dioxide. (a) Identity and specifications. (1) The color additive titanium dioxide shall conform in...
21 CFR 73.1575 - Titanium dioxide.
Code of Federal Regulations, 2012 CFR
...2012-04-01 2012-04-01 false Titanium dioxide. 73.1575 Section...CERTIFICATION Drugs ¦ 73.1575 Titanium dioxide. (a) Identity and specifications. (1) The color additive titanium dioxide shall conform in...
21 CFR 573.940 - Silicon dioxide.
Code of Federal Regulations, 2011 CFR
... 2011-04-01 2011-04-01 false Silicon dioxide. 573.940 Section 573.940 ...ANIMALS Food Additive Listing ¦ 573.940 Silicon dioxide. The food additive silicon dioxide may be safely used in animal feed...
21 CFR 573.940 - Silicon dioxide.
Code of Federal Regulations, 2010 CFR
... 2010-04-01 2010-04-01 false Silicon dioxide. 573.940 Section 573.940 ...ANIMALS Food Additive Listing ¦ 573.940 Silicon dioxide. The food additive silicon dioxide may be safely used in animal feed...
Carbon Dioxide Reduction Through Urban Forestry
Standiford, Richard B.
Carbon Dioxide Reduction Through Urban Forestry: Guidelines for Professional and Volunteer Tree; Simpson, James R. 1999. Carbon dioxide reduction through urban forestry of Agriculture; 237 p. Carbon dioxide reduction through urban forestry--Guidelines for professional and volunteer
40 CFR 180.1195 - Titanium dioxide.
Code of Federal Regulations, 2010 CFR
... 2010-07-01 2010-07-01 false Titanium dioxide. 180.1195 Section 180.1195 Protection... Exemptions From Tolerances ¦ 180.1195 Titanium dioxide. Titanium dioxide is exempted from the requirement of a...
21 CFR 73.1575 - Titanium dioxide.
Code of Federal Regulations, 2010 CFR
...2010-04-01 2010-04-01 false Titanium dioxide. 73.1575 Section 73...CERTIFICATION Drugs ¦ 73.1575 Titanium dioxide. (a) Identity and specifications... (1) The color additive titanium dioxide shall conform in identity...
Xenon is an inhibitor of tissue-plasminogen activator: adverse and beneficial effects in a rat model of thromboembolic stroke
David, HķlĶne N; Haelewyn, BenoŅt; Risso, Jean-Jacques; Colloc'h, Nathalie; Abraini, Jacques H
Preclinical evidence in rodents has proven that xenon may be a very promising neuroprotective agent for treating acute ischemic stroke. This has led to the general thinking that clinical trials with xenon could be initiated in acute stroke patients in a next future. However, an unappreciated physicochemical property of xenon has been that this gas also binds to the active site of a series of serine proteases. Because the active site of serine proteases is structurally conserved, we have hypothesized and investigated whether xenon may alter the catalytic efficiency of tissue-type plasminogen activator (tPA), a serine protease that is the only approved therapy for acute ischemic stroke today. Here, using molecular modeling and in vitro and in vivo studies, we show (1) xenon is a tPA inhibitor; (2) intraischemic xenon dose dependently inhibits tPA-induced thrombolysis and subsequent reduction of ischemic brain damage; (3) postischemic xenon virtually suppresses ischemic brain damage and tPA-induced brain hemorrhages and disruption of the blood¢brain barrier. Taken together, these data indicate (1) xenon should not be administered before or together with tPA therapy; (2) xenon could be a golden standard for treating acute ischemic stroke if given after tPA-induced reperfusion, with both unique neuroprotective and antiproteolytic (anti-hemorrhaging) properties. PMID:20087367
Ion-Molecule Reactions in Gas Phase Radiation Chemistry.
ERIC Educational Resources Information Center
Willis, Clive
Discusses some aspects of the radiation chemistry of gases, focusing on the ion-molecule and charge neutralization reactions which set study of the gas phase apart. Uses three examples that illustrate radiolysis, describing the radiolysis of (1) oxygen, (2) carbon dioxide, and (3) acetylene. (CS)
21 CFR 582.3862 - Sulfur dioxide.
Code of Federal Regulations, 2012 CFR
...SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Chemical Preservatives ¦ 582.3862 Sulfur dioxide. (a) Product. Sulfur dioxide. (b) [Reserved] (c) Limitations,...
21 CFR 582.3862 - Sulfur dioxide.
Code of Federal Regulations, 2011 CFR
...SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Chemical Preservatives ¦ 582.3862 Sulfur dioxide. (a) Product. Sulfur dioxide. (b) [Reserved] (c) Limitations,...
21 CFR 582.3862 - Sulfur dioxide.
Code of Federal Regulations, 2013 CFR
...SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Chemical Preservatives ¦ 582.3862 Sulfur dioxide. (a) Product. Sulfur dioxide. (b) [Reserved] (c) Limitations,...
21 CFR 582.3862 - Sulfur dioxide.
Code of Federal Regulations, 2014 CFR
...SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Chemical Preservatives ¦ 582.3862 Sulfur dioxide. (a) Product. Sulfur dioxide. (b) [Reserved] (c) Limitations,...
An Ultra-Low Background PMT for Liquid Xenon Detectors
Akerib, D S; Bernard, E; Bernstein, A; Bradley, A; Byram, D; Cahn, S B; Carmona-Benitez, M C; Carr, D; Chapman, J J; Chan, Y-D; Clark, K; Coffey, T; deViveiros, L; Dragowsky, M; Druszkiewicz, E; Edwards, B; Faham, C H; Fiorucci, S; Gaitskell, R J; Gibson, K R; Hall, C; Hanhardt, M; Holbrook, B; Ihm, M; Jacobsen, R G; Kastens, L; Kazkaz, K; Larsen, N; Lee, C; Lesko, K; Lindote, A; Lopes, M I; Lyashenko, A; Malling, D C; Mannino, R; McKinsey, D; Mei, D; Mock, J; Morii, M; Nelson, H; Neves, F; Nikkel, J A; Pangilinan, M; Pech, K; Phelps, P; Shutt, T; Silva, C; Skulski, W; Solovov, V N; Sorensen, P; Spaans, J; Stiegler, T; Sweany, M; Szydagis, M; Taylor, D; Thomson, J; Tripathi, M; Uvarov, S; Verbus, J R; Walsh, N; Webb, R; White, J T; Wlasenko, M; Wolfs, F L H; Woods, M; Zhang, C
Results are presented from radioactivity screening of two models of photomultiplier tubes designed for use in current and future liquid xenon experiments. The Hamamatsu 5.6 cm diameter R8778 PMT, used in the LUX dark matter experiment, has yielded a positive detection of four common radioactive isotopes: 238U, 232Th, 40K, and 60Co. Screening of LUX materials has rendered backgrounds from other detector materials subdominant to the R8778 contribution. A prototype Hamamatsu 7.6 cm diameter R11410 MOD PMT has also been screened, with benchmark isotope counts measured at <0.4 238 U / <0.3 232 Th / <8.3 40 K / 2.0+-0.2 60 Co mBq/PMT. This represents a large reduction, equal to a change of \\times 1/24 238U / \\times 1/9 232Th / \\times 1/8 40K per PMT, between R8778 and R11410 MOD, concurrent with a doubling of the photocathode surface area (4.5 cm to 6.4 cm diameter). 60Co measurements are comparable between the PMTs, but can be significantly reduced in future R11410 MOD units through further material selec...
NEST: A Comprehensive Model for Scintillation Yield in Liquid Xenon
Szydagis, M; Kazkaz, K; Mock, J; Stolp, D; Sweany, M; Tripathi, M; Uvarov, S; Walsh, N; Woods, M
A comprehensive model for explaining scintillation yield in liquid xenon is introduced. We unify various definitions of work function which abound in the literature and incorporate all available data on electron recoil scintillation yield. This results in a better understanding of electron recoil, and facilitates an improved description of nuclear recoil. An incident gamma energy range of O(1 keV) to O(1 MeV) and electric fields between 0 and O(10 kV/cm) are incorporated into this heuristic model. We show results from a Geant4 implementation, but because the model has a few free parameters, implementation in any simulation package should be simple. We use a quasi-empirical approach, with an objective of improving detector calibrations and performance verification. The model will aid in the design and optimization of future detectors. This model is also easy to extend to other noble elements. In this paper we lay the foundation for an exhaustive simulation code which we call NEST (Noble Element Simulation Tech...
First Detection of Krypton and Xenon in a White Dwarf
NASA Technical Reports Server (NTRS)
Werner, Klaus; Rauch, Thomas; Ringat, Ellen; Kruk, Jeffrey W.
We report on the first detection of the noble gases krypton (Z = 36) and xenon (54) in a white dwarf. About 20 KrVI-VII and Xe VI-VII lines were discovered in the ultraviolet spectrum of the hot DO-type white dwarf RE 0503-289. The observations, performed with the Far Ultraviolet Spectroscopic Explorer, also reveal highly ionized photospheric lines from other trans-iron group elements, namely Ga (31), Ge (32), As (33), Se (34), Mo (42), Sn (50), Te (52), and I (53), from which gallium and molybdenum are new discoveries in white dwarfs, too. For Kr and Xe, we performed an NLTE analysis and derived mass fractions of log Kr = -4.3 plus or minus 0.5 and log Xe = -4.2 plus or minus 0.6, corresponding to an enrichment by factors of 450 and 3800, respectively, relative to the Sun. The origin of the large overabundances is unclear. We discuss the roles of neutron-capture nucleosynthesis in the-precursor star and radiation-driven diffusion. It is possible that diffusion is insignificant and thaI the observed metal abundances constrain the evolutionary history of the star. Its hydrogen deficiency may be the consequence of a late helium-shell nash or a binary white dwarf merger.
Werner, Klaus; Rauch, Thomas; Ringat, Ellen [Institute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, Eberhard Karls University Tuebingen, Sand 1, 72076 Tuebingen (Germany); Kruk, Jeffrey W. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
We report on the first detection of the noble gases krypton (Z = 36) and xenon (54) in a white dwarf. About 20 Kr VI- VII and Xe VI- VII lines were discovered in the ultraviolet spectrum of the hot DO-type white dwarf RE 0503-289. The observations, performed with the Far Ultraviolet Spectroscopic Explorer, also reveal highly ionized photospheric lines from other trans-iron group elements, namely Ga (31), Ge (32), As (33), Se (34), Mo (42), Sn (50), Te (52), and I (53), from which gallium and molybdenum are new discoveries in white dwarfs, too. For Kr and Xe, we performed an NLTE analysis and derived mass fractions of log Kr = -4.3 {+-} 0.5 and log Xe = -4.2 {+-} 0.6, corresponding to an enrichment by factors of 450 and 3800, respectively, relative to the Sun. The origin of the large overabundances is unclear. We discuss the roles of neutron-capture nucleosynthesis in the precursor star and radiation-driven diffusion. It is possible that diffusion is insignificant and that the observed metal abundances constrain the evolutionary history of the star. Its hydrogen deficiency may be the consequence of a late helium-shell flash or a binary white dwarf merger.
The Enriched Xenon Observatory: EXO-200 and Ba+ tagging
NASA Astrophysics Data System (ADS)
Dolinski, M. J.; EXO Collaboration
The Enriched Xenon Observatory (EXO) is a proposed ton-scale double beta decay experiment with a tentative design sensitivity to the Majorana mass of ś10 meV. The first phase of EXO is EXO-200, which uses 200 kg of Xe enriched to 80% in 136Xe to search for neutrinoless double beta decay. EXO-200 is a liquid Xe time projection chamber with the ability to detect both scintillation and ionization signals. The detector is constructed from ultra-low background materials and is currently installed at the Waste Isolation Pilot Plant, a salt mine with a 1600 meter water equivalent overburden. The projected 2 year sensitivity for EXO-200 is T1/20?>6.4ū1025 y at 90% confidence level. Looking toward a ton-scale EXO, one unique feature of the experiment is the proposal to identify the barium daughter produced by 136Xe double beta decay on an event-by-event basis. This technique will allow for the elimination of all backgrounds other than the background from the two-neutrino double beta decay spectrum. The EXO Collaboration is exploring a number of options to implement Ba-daughter tagging in the next generation EXO experiment.
Defect controlled ferromagnetism in xenon ion irradiated zinc oxide
NASA Astrophysics Data System (ADS)
Satyarthi, P.; Ghosh, S.; Mishra, P.; Sekhar, B. R.; Singh, F.; Kumar, P.; Kanjilal, D.; Dhaka, R. S.; Srivastava, P.
We report evolution of magnetic properties in zinc oxide (ZnO) single crystals and polycrystalline films induced by 500 KeV xenon ion (Xe3+) irradiation. Room temperature ferromagnetism (RT-FM) behavior is observed in as deposited polycrystalline ZnO film and strength of FM enhances with ion fluence up to 2ū1017 ions/cm2 and then decreases. However, RT-FM is not observed in ZnO single crystals even after irradiation with fluence up to 3.5ū1017 ions/cm2. The X-ray diffraction (XRD) and Raman measurements of ZnO single crystal reveal slightly disordered hexagonal wurtzite structure after irradiation. However, as deposited and irradiated polycrystalline ZnO films indicate excessive lattice defects in the wurtzite structure. X-ray photoelectron spectroscopy (XPS) reveals that Zn vacancy/interstitial defects are absent in all samples, although oxygen vacancy lattice defects are present. Density of oxygen vacancies is much higher in as deposited and irradiated polycrystalline ZnO films as compared to single crystals. This seems to be the determining factor for the presence and absence of RT-FM in ZnO films and single crystals respectively. The observed FM behavior in as deposited and irradiated polycrystalline ZnO films is explained on the basis of spin split impurity band formation from singly and doubly occupied oxygen vacancies which initiates d0 ferromagnetism.
Extended-testing of xenon ion thruster hollow cathodes
NASA Technical Reports Server (NTRS)
Sarver-Verhey, Timothy R.
A hollow cathode wear-test of 508 hours was successfully completed at an emission current of 23.0 A and a xenon flow rate of 10 Pa-L/s. This test was the continuation of a hollow cathode contamination investigation. Discharge voltage was stable at 16.7 V. The cathode temperature averaged 1050 C with a 7 percent drop during the wear-test. Discharge ignition voltage was found to be approximately 20 V and was repeatable over four starts. Post-test analyses of the hollow cathode found a much improved internal cathode condition with respect to earlier wear-test cathodes. Negligible tungsten movement occurred and no formation of mono-barium tungsten was observed. These results correlated with an order-of-magnitude reduction in propellant feed-system leakage rate. Ba2CaWO6 and extensive calcium crystal formation occurred on the upstream end of the insert. Ba-Ca compound depositions were found on the Mo insert collar, on the Re electrical leads, and in the gap between the insert and cathode wall. This wear-test cathode was found to be in the best internal condition and had the most stable operating performance of any hollow cathode tested during this contamination investigation.
s-process studies - Xenon and krypton isotopic abundances
NASA Technical Reports Server (NTRS)
Clayton, D. D.; Ward, R. A.
We propose an analysis of the s-process contributions to the isotopes of xenon and krypton. The object is to aid studies of the possibility that meteorites may contain gas that was carried in presolar grains that were grown in stellar ejecta and that were not degassed prior to incorporation into parent bodies. That model suggests routine interstellar fractionation of s-isotopes from r-isotopes owing to differential incorporation into dust. We show that a deficiency of s-process nuclei cannot yield details of Xe-X, but the gross similarities are strong enough to lead one to think that such a deficiency may play a role in a more complicated explanation. We predict the existence of an s-rich complement somewhere if fractional separation of this type has played a role in Xe-X. We show that the analogous decomposition of krypton is more uncertain, and we call for measurements of neutron-capture cross sections to alleviate these uncertainties.
Thrust Stand Characterization of the NASA Evolutionary Xenon Thruster (NEXT)
NASA Technical Reports Server (NTRS)
Diamant, Kevin D.; Pollard, James E.; Crofton, Mark W.; Patterson, Michael J.; Soulas, George C.
Direct thrust measurements have been made on the NASA Evolutionary Xenon Thruster (NEXT) ion engine using a standard pendulum style thrust stand constructed specifically for this application. Values have been obtained for the full 40-level throttle table, as well as for a few off-nominal operating conditions. Measurements differ from the nominal NASA throttle table 10 (TT10) values by 3.1 percent at most, while at 30 throttle levels (TLs) the difference is less than 2.0 percent. When measurements are compared to TT10 values that have been corrected using ion beam current density and charge state data obtained at The Aerospace Corporation, they differ by 1.2 percent at most, and by 1.0 percent or less at 37 TLs. Thrust correction factors calculated from direct thrust measurements and from The Aerospace Corporation s plume data agree to within measurement error for all but one TL. Thrust due to cold flow and "discharge only" operation has been measured, and analytical expressions are presented which accurately predict thrust based on thermal thrust generation mechanisms.
Axial Magnetic Field Effects on Xenon Short-Arc Lamps
NASA Astrophysics Data System (ADS)
Wang, Cheng; Chen, Tang; Li, Wanwan; Zha, Jun; Xia, Weidong
The effect of an axial magnetic field (AMF) on an old xenon short-arc lamp is experimentally investigated in this work. As the AMF increases up to 18 mT, the visible radiation power and electric power ascend more than 80% and 70% respectively, and the radiation efficiency is improved by 23% for the best increment at 12 mT AMF. The measurement of radiation intensity shows that the increment of radiation intensity comes mostly from the plasma area close to the cathode tip, and partially from the other area of the arc column. Successive images of the arc indicate that the arc column not only rotates about its axis, but revolves around the axis of electrodes with the AMF. The arc column structure is constricted, distorted and elongated as the AMF increases. It is suggested that the improvements of the radiation intensity and radiation efficiency are attributed to the constriction of the arc column, which is mainly induced by the enhanced cathode jet.
Why Do Some Molecules Absorb Infrared Energy?
NSDL National Science Digital Library
In this demonstration activity, students make structural models of gas molecules using pipe cleaners and polystyrene balls and test their molecules for their resonant frequency. Students shake the models, count vibrations, and compare the resonance frequencies of different gases. Students learn that photons of infrared energy vibrate at the right frequency to transfer their energy to carbon dioxide and methane, which in turn causes those molecules to vibrate, which is experienced in the real world as heat. The teacher's guide includes illustrative videos for this resource. This activity is supported by a textbook chapter, What's So Special about CO▓?, part of the unit, Climate Change, in Global Systems Science (GSS), an interdisciplinary course for high school students that emphasizes how scientists from a wide variety of fields work together to understand significant problems of global impact.
Carbon dioxide and terrestrial ecosystems
G. W. Koch; H. A. Mooney
This book is a summary of the current research which addresses the effects of elevated carbon dioxide on terrestrial ecosystems and an identification of significant unresolved issues. Chapters address the carbon dioxide effects on trees and forests, unmanaged herbaceous ecosystems, and crops. Included are experimental studies, conceptual models, general mathematical models, dynamic simulation models.
Carbon Dioxide: Friend or Foe?
C. Muller
Carbon Dioxide: Friend or Foe is a short rnonograph on the so-called carbon dioxide greenhouse effect. The author challenges the established view that the present CO2 increase would, in the long term, lead to a global ground temperature increase. S. B. Idso, from four sets of observations, has deduced that the temperature response to an increased received energy at the
Carbon Dioxide Capture and Disposal
K. S. Lackner
Unless carbon dioxide from fossil fuel combustion is captured and disposed of safely and permanently, the concerns over climate change will eventually lead to the demise of fossil fuels. Because of their importance in today's energy market the phasing out of fossil fuels would likely precipitate a major energy crisis. Mineral sequestration and extraction of carbon dioxide from the air
Coral reefs and carbon dioxide
Buddemeier, R.W. [Kansas Geological Survey, Lawrence, KS (United States)
This commentary argues the conclusion from a previous article, which investigates diurnal changes in carbon dioxide partial pressure and community metabolism on coral reefs, that coral `reefs might serve as a sink, not a source, for atmospheric carbon dioxide.` Commentaries from two groups are given along with the response by the original authors, Kayanne et al. 27 refs.
Single Molecule Conductance of Oligothiophene Derivatives
NASA Astrophysics Data System (ADS)
Dell, Emma J.
This thesis studies the electronic properties of small organic molecules based on the thiophene motif. If we are to build next-generation devices, advanced materials must be designed which possess requisite electronic functionality. Molecules present attractive candidates for these ad- vanced materials since nanoscale devices are particularly sought after. However, selecting a molecule that is suited to a certain electronic function remains a challenge, and characterization of electronic behavior is therefore critical. Single molecule conductance measurements are a powerful tool to determine properties on the nanoscale and, as such, can be used to investigate novel building blocks that may fulfill the design requirements of next-generation devices. Combining these conductance results with strategic chemical synthesis allows for the development of new families of molecules that show attractive properties for future electronic devices. Since thiophene rings are the fruitflies of organic semiconductors on the bulk scale, they present an intriguing starting point for building functional materials on the nanoscale, and therefore form the structural basis of all molecules studied herein. First, the single-molecule conductance of a family of bithiophene derivatives was measured. A broad distribution in the single-molecule conductance of bithiophene was found compared with that of a biphenyl. This increased breadth in the conductance distribution was shown to be explained by the difference in 5-fold symmetry of thiophene rings as compared to the 6-fold symmetry of benzene rings. The reduced symmetry of thiophene rings results in a restriction on the torsion angle space available to these molecules when bound between two metal electrodes in a junction, causing each molecular junction to sample a different set of conformers in the conductance measurements. By contrast, the rotations of biphenyl are essentially unimpeded by junction binding, allowing each molecular junction to sample similar conformers. This work demonstrates that the conductance of bithiophene displays a strong dependence on the conformational fluctuations accessible within a given junction configuration, and that the symmetry of such small molecules can significantly influence their conductance behavior. Next, the single-molecule conductance of a family of oligothiophenes comprising one to six thiophene units was measured. An anomalous behavior was found: the peak of the conductance histogram distribution did not follow a clear exponential decay with increasing number of thiophene units in the chain. The electronic properties of the materials were characterized by optical spectroscopy and electrochemistry to gain an understanding of the factors affecting the conductance of these molecules. Different conformers in the junction were postulated to be a contributing factor to the anomalous trend in the observed conductance as a function of molecule length. Then, the electronic properties of the thiophene-1,1-dioxide unit were investigated. These motifs have become synthetically accessible in the last decade, due to Rozen's unprecedentedly potent oxidizing reagent - HOF?CH 3CN - which has been shown to be powerful yet selective enough to oxidize thiophenes in various environments. The resulting thiophene-1,1-dioxides show great promise for electronic devices. The oxidation chemistry of thiophenes was expanded and tuning of the frontier energy levels was demonstrated through combining electron poor and electron rich units. Finally, charge carriers in single-molecule junctions were shown to be tunable within a family of molecules containing these thiophene-1,1-dioxide (TDO) building blocks. Oligomers of TDO were designed in order to increase electron affinity, maintain delocalized frontier orbitals, while significantly decreasing the transport gap. Through thermopower measurements, the dominant charge carriers were shown to change from holes to electrons as the number of TDO units was increased. This resulted in a unique system in which the charge carrier depends on ba
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Scientific and public interest in greenhouse gases, climate warming, and global change virtually exploded in 1988. The Department's focused research on atmospheric CO{sub 2} contributed sound and timely scientific information to the many questions produced by the groundswell of interest and concern. Research projects summarized in this document provided the data base that made timely responses possible, and the contributions from participating scientists are genuinely appreciated. In the past year, the core CO{sub 2} research has continued to improve the scientific knowledge needed to project future atmospheric CO{sub 2} concentrations, to estimate climate sensitivity, and to assess the responses of vegetation to rising concentrations of CO{sub 2} and to climate change. The Carbon Dioxide Research Program's goal is to develop sound scientific information for policy formulation and governmental action in response to changes of atmospheric CO{sub 2}. The Program Summary describes projects funded by the Carbon Dioxide Research Program during FY 1990 and gives a brief overview of objectives, organization, and accomplishments.
Photokilling of T-24 human bladder cancer cells with titanium dioxide.
Kubota, Y.; Shuin, T.; Kawasaki, C.; Hosaka, M.; Kitamura, H.; Cai, R.; Sakai, H.; Hashimoto, K.; Fujishima, A.
A photoexcited titanium dioxide surface has a strong ability to decompose water into hydrogen and oxygen. We have studied this effect in order to use it to kill cancer cells in vitro and in vivo. A distinct cell killing effect was observed on cultured T-24 human bladder cancer cells treated with titanium dioxide particles and 300-400 nm UV light irradiation. Titanium dioxide plus UV light also dramatically suppressed the tumour growth of T-24 cells that were implanted in nude mice. Cells cultured on the titanium dioxide electrode were also killed under UV irradiation when the electrode was anodically polarised, suggesting that photogenerated holes are involved in the cell killing. The cell killing effect caused by titanium dioxide particles plus UV light irradiation was significantly hampered in the presence of L-cysteine and catalase, scavengers of hydroxyl radicals and hydrogen peroxide respectively. Transmission electron microscopic observations showed the titanium dioxide particles to be distributed on the cell surface and inside the cells. These results suggest that titanium dioxide particles under UV light irradiation produced photogenerated holes on the surface yielding hydroxyl radicals and hydrogen peroxide inside or outside the cells and the cells were then killed by the action of these highly oxidising molecules. The possible application of photoexcited titanium dioxide particles to cancer treatment as a new anti-cancer modality is discussed. Images Figure 6 PMID:7981061
Evaluation of pulmonary perfusion in lung regions showing isolated xenon-133 ventilation washout defects
Bushnell, D.L.; Sood, K.B.; Shirazi, P.; Pal, I. (VA Hines Hospital, IL (USA))
Xenon-133 washout phase imaging is often used to help determine whether the etiology of a perfusion defect is embolic or due to pulmonary parenchymal pathology, such as chronic obstructive pulmonary disease. This study was designed to evaluate the pulmonary blood flow patterns associated with isolated defects on xenon washout images. Scintigraphic lung studies were reviewed until 100 cases with abnormal ventilation results were obtained. Ventilation abnormalities were compared with the corresponding perfusion scan results at the same anatomic site. Of the 208 individual lung regions with xenon abnormalities, 111 showed isolated washout defects (that is, with normal washin). Ninety-four of these 111 sites showed either normal perfusion or a small, nonsegmental corresponding perfusion defect. Three segmental perfusion defects were noted in association with isolated xenon retention. In each of these cases, however, the patient was felt actually to have pulmonary embolism. Thus, it is recommended that, for interpretation of scintigraphic images in the assessment of pulmonary embolism, lung pathology associated with isolated xenon retention not be considered a potential cause for large or segmental perfusion defects.
Measurement of xenon plasma properties in an ion thruster using laser Thomson scattering technique.
Yamamoto, N; Tomita, K; Sugita, K; Kurita, T; Nakashima, H; Uchino, K
This paper reports on the development of a method for measuring xenon plasma properties using the laser Thomson scattering technique, for application to ion engine system design. The thresholds of photo-ionization of xenon plasma were investigated and the number density of metastable atoms, which are photo-ionized by a probe laser, was measured using laser absorption spectroscopy, for several conditions. The measured threshold energy of the probe laser using a plano-convex lens with a focal length of 200 mm was 150 mJ for a xenon mass flow rate of 20 ?g/s and incident microwave power of 6 W; the probe laser energy was therefore set as 80 mJ. Electron number density was found to be (6.2 ▒ 0.4) ū 10(17) m(-3) and electron temperature was found to be 2.2 ▒ 0.4 eV at a xenon mass flow rate of 20 ?g/s and incident microwave power of 6 W. The threshold of the probe laser intensity against photo-ionization in a miniature xenon ion thruster is almost constant for various mass flow rates, since the ratio of population of the metastable atoms to the electron number density is little changed. PMID:22852670
Electronic relaxai:ion of Xe,CI in gaseous and supercritical fluid xenon F. Okada"'and V. A. Apkarianb)
Apkarian, V. Ara
Electronic relaxai:ion of Xe,CI in gaseous and supercritical fluid xenon F. Okada"'and V. A in gaseous and supercritical fluid xenon up to 150 atm are reported. Clustering of the exciplex with Xe atoms
Method for the simultaneous preparation of radon-211, xenon-125, xenon-123, astatine-211, iodine-125 and iodine-123
Mirzadeh, S.; Lambrecht, R.M.
The invention relates to a practical method for commercially producing radiopharmaceutical activities and, more particularly, relates to a method for the preparation of about equal amount of Radon-211 (/sup 211/Rn) and Xenon-125 (/sup 125/Xe) including a one-step chemical procedure following an irradiation procedure in which a selected target of Thorium (/sup 232/Th) or Uranium (/sup 238/U) is irradiated. The disclosed method is also effective for the preparation in a one-step chemical procedure of substantially equal amounts of high purity /sup 123/I and /sup 211/At. In one preferred arrangement of the invention almost equal quantities of /sup 211/Rn and /sup 125/Xe are prepared using a onestep chemical procedure in which a suitably irradiated fertile target material, such as thorium-232 or uranium-238, is treated to extract those radionuclides from it. In the same one-step chemical procedure about equal quantities of /sup 211/At and /sup 123/I are prepared and stored for subsequent use. In a modified arrangement of the method of the invention, it is practiced to separate and store about equal amounts of only /sup 211/Rn and /sup 125/Xe, while preventing the extraction or storage of the radionuclides /sup 211/At and /sup 123/I.
Pulsed-discharge carbon dioxide lasers
NASA Technical Reports Server (NTRS)
Willetts, David V.
The purpose is to attempt a general introduction to pulsed carbon dioxide lasers of the kind used or proposed for laser radar applications. Laser physics is an excellent example of a cross-disciplinary topic, and the molecular spectroscopy, energy transfer, and plasma kinetics of the devices are explored. The concept of stimulated emission and population inversions is introduced, leading on to the molecular spectroscopy of the CO2 molecule. This is followed by a consideration of electron-impact pumping, and the pertinent energy transfer and relaxation processes which go on. Since the devices are plasma pumped, it is necessary to introduce a complex subject, but this is restricted to appropriate physics of glow discharges. Examples of representative devices are shown. The implications of the foregoing to plasma chemistry and gas life are discussed.
NASA Technical Reports Server (NTRS)
2004-01-017 July 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a mid-summer view of the south polar residual cap at full MOC resolution, 1.5 m (5 ft) per pixel. During each of the three summers since the start of the MGS mapping mission in March 1999, the scarps that form mesas and pits in the 'Swiss cheese'-like south polar terrain have retreated an average of about 3 meters (1 yard). The material is frozen carbon dioxide; another 3 meters or so of each scarp is expected to be removed during the next summer, in late 2005. This image is located near 86.0oS, 350.8oW, and covers an area about 1.5 km (0.9 mi) wide. Sunlight illuminates the scene from the top/upper left.
PHYSICAL REVIEW A 89, 023408 (2014) High-spectral-resolution attosecond absorption spectroscopy of autoionization in xenon
Neumark, Daniel M.
of autoionization in xenon Birgitta Bernhardt,1,2,* Annelise R. Beck,1,2 Xuan Li,1 Erika R. Warrick,1,2 M. Justine; published 10 February 2014) The decay of highly excited states of xenon after absorption of extreme
Radioactive Plume from the Three Mile Island Accident: Xenon133 in Air at a Distance of 375 Kilometers
Martin Wahlen; Charles O. Kunz; John M. Matuszek; William E. Mahoney; Roger C. Thompson
The transit of an air mass containing radioactive gas released from the Three Mile Island reactor was recorded in Albany, New York, by measuring xenon-133. These measurements provide an evaluation of Three Mile Island effluents to distances greater than 100 kilometers. Two independent techniques identified xenon-133 in ambient air at concentrations as high as 3900 picocuries per cubic meter. The
Temporal pulse compression in a xenon-filled Kagome-type hollow-core photonic crystal fiber
Keller, Ursula
Temporal pulse compression in a xenon-filled Kagome-type hollow-core photonic crystal fiber at high: In this study we demonstrate the suitability of Hollow-Core Photonic Crystal Fibers (HC-PCF) for multiwatt disk laser in a xenon gas filled Kagome-type HC-PCF and compressed these pulses to below 250 fs
Reflectance measurement of the VUV spectrum of solid xenon and its temperature dependence up to the triple point
Boyer, Edmond
L-339 Reflectance measurement of the VUV spectrum of solid xenon and its temperature dependence up disparition vers 135 K. Abstract. 2014 Accurate solid xenon reflectance measurements in the energy range 6. Introduction. - Since Baldini's paper [ 1 ], exten- sive studies on solid rare gas excitonic spectra near
LASERS, ACTIVE MEDIA: Excitation mechanism of IR transitions in the xenon atom in a nuclear-pumped laser
A. V. Karelin
A numerical simulation is used to show that new experimental data on the rate constants of xenon atoms in metastable and resonant states lead to a revision of the existing views on the mechanism of excitation of the upper active levels of a laser operating on IR transitions in xenon. Bibtex entry for this abstract Preferred format for this abstract
An experiment to search for an electric dipole moment in the 3P2 metastable state of xenon
M. A. Player; P. G. H. Sandars
The authors describe an atomic beam resonance experiment to search for an electric dipole movement in the 3P2 metastable state in xenon. The experiment avoids the ' nu *E' difficulty of earlier work by using an atomic state which has a high differential polarizability. Small residual effects are cancelled by comparison between xenon and krypton. The result is interpreted to
Facile xenon capture and release at room temperature using a metal-organic framework: a comparison with activated charcoal
Thallapally, Praveen K.; Grate, Jay W.; Motkuri, Radha K.
Two well known Metal organic frameworks (MOF-5, NiDOBDC) were synthesized and studied for facile xenon capture and separation. Our results indicate the NiDOBDC adsorbs significantly more xenon than MOF-5, releases it more readily than activated carbon, and is more selective for Xe over Kr than activated carbon.
Performance improvement of 150-mN xenon ion thrusters
NASA Astrophysics Data System (ADS)
Kitamura, Shoji; Miyazaki, Katsuhiro; Hayakawa, Yukio; Yoshida, Hideki; Akai, Kouseki
Research was conducted to establish basic xenon ion thruster technology for future applications. In an iterative design and test process to improve thruster performance, four thrusters of three designs were fabricated: the first laboratory model mark 1 (LM-1-MK-1), the first laboratory model mark 2 (LM-1-MK-2), the second laboratory model (LM-2), and the first breadboard model (BBM-1). Performance targets were a thrust of 150 mN, a specific impulse of 3500 s, and an ion production cost less than 150 W/ A at 90% propellant utilization. Magnet temperature was limited to 200░C. The LM-1-MK-1 thruster used a 30 cm diameter two-grid system, with azimuthal springs in the grid supports to absorb thermal expansion, a discharge chamber with double sidewalls, an inner effective chamber and an outer magnet yoke. Test results showed an ion production cost of 178 W/ A. The LM-1-MK-2 thruster was designed to give more stable operation and lower magnet temperatures, with a resulting maximum magnet temperature of 254░C. The LM-2 thruster used axial springs in the grid supports and a discharge chamber with a single soft-iron wall. It gave an ion production cost of 168 W/ A and a magnet temperature of 240░C. The BBM-1 thruster used a 35 cm diameter three-grid system for longer life. The grid fabrication method was improved to achieve greater grid aperture dimensional accuracy. This thruster achieved the performance targets with an ion production cost of 134 W/ A and a magnet temperature of 172░C.
Low-energy recoils and energy scale in liquid xenon detector for direct dark matter searches
NASA Astrophysics Data System (ADS)
Wang, Lu; Mei, Dongming; Cubed Collaboration
Liquid xenon has been proven to be a great detector medium for the direct search of dark matter. However, in the energy region of below 10 keV, the light yield and charge production are not fully understood due to the convolution of excitation, recombination and quenching. We have already studied a recombination model to explain the physics processes involved in liquid xenon. Work is continued on the average energy expended per electron-ion pair as a function of energy based on the cross sections for different type of scattering processes. In this paper, the results will be discussed in comparison with available experimental data using Birk's Law to understand how scintillation quenching contributes to the non-linear light yield for electron recoils with energy below 10 keV in liquid xenon. This work is supported by DOE Grant DE-FG02-10ER46709 and the state of South Dakota.
Thermodynamics, compressibility, and phase diagram: shock compression of supercritical fluid xenon.
Zheng, J; Chen, Q F; Gu, Y J; Chen, Z Y; Li, C J
Supercritical fluids have intriguing behaviors at extreme pressure and temperature conditions, prompting the need for thermodynamic properties of supercritical fluid xenon (SCF) under shock compression. Double-shock experimental data on SCF xenon in the 140 GPa pressure range were directly measured by means of a multi-channel pyrometer and a Doppler-pins-system. It entered the so-called warm dense region. We found that the shock compressed SCF Xe had higher dynamic compression and higher number density than that of liquid Xe at same shock pressure. The larger compressibility of SCF Xe in our experiments could be explained that the increase of electronic excitations and ionizations leaded to a large drop of thermal pressure and a softening of Hugoniot. The high pressure phase diagram of xenon was depicted with the aid of the degeneracy, coupling parameter, and current available experiments on the pressure-temperature plane. PMID:25273430
A Search for Nonstandard Neutron Spin Interactions using Dual Species Xenon Nuclear Magnetic Resonance
NASA Astrophysics Data System (ADS)
Bulatowicz, Michael; Larsen, Michael; Mirijanian, James; Fu, Changbo; Yan, Haiyang; Smith, Erick; Snow, Mike; Walker, Thad
NMR measurements using polarized noble gases can constrain possible exotic spin-dependent interactions involving nucleons. A differential measurement insensitive to magnetic field fluctuations can be performed using a mixture of two polarized species with different ratios of nucleon spin to magnetic moment. We used the NMR cell test station at Northrop Grumman Corporation (NGC) (developed to evaluate dual species xenon vapor cells for the Nuclear Magnetic Resonance Gyroscope) to search for NMR frequency shifts of xenon-129 and xenon-131 when a non-magnetic zirconia rod is modulated near the NMR cell. We simultaneously excited both Xe isotopes and detected free-induction-decay transients. In combination with theoretical calculations of the neutron spin contribution to the nuclear angular momentum, the measurements put a new upper bound on possible monopole-dipole interactions of the neutron for ranges around 1mm. This work is supported by the NGC Internal Research and Development (IRAD) funding, the Department of Energy, and the NSF.
J. Phys. Chem. 1990, 94, 6671-6678 6671 Photodynamics in CI,-Doped Xenon under High Pressures: A Diamond Anvil Cell Study
Apkarian, V. Ara
J. Phys. Chem. 1990, 94, 6671-6678 6671 Photodynamics in CI,-Doped Xenon under High Pressures xenon contained in a diamond anvil cell. The photogeneration of atoms is monitored by following emission studies. Xenon-doped with molecular chlorine was the system chosen for these studies. Our main intention
arXiv:1106.1812v1[physics.ins-det]9Jun2011 A Xenon Gas Purity Monitor for EXO
Gratta, Giorgio
arXiv:1106.1812v1[physics.ins-det]9Jun2011 A Xenon Gas Purity Monitor for EXO A. Dobia , C. Halla discuss the design, operation, and calibration of two versions of a xenon gas purity monitor (GPM. The EXO-200 detector is a liquid xenon TPC, while the successor experiments may be based on liquid or gas
Carbon Dioxide Sequestration Industrial-scale processes are available for separating carbon dioxide from the post-
Carbon Dioxide Sequestration Industrial-scale processes are available for separating carbon dioxide dioxide separation and sequestration because the lower cost of carbon dioxide separation from for injection of carbon dioxide into oil or gas-bearing formations. An advantage of sequestration involving
Xenon behavior in TiN: A coupled XAS/TEM study
NASA Astrophysics Data System (ADS)
BĶs, R.; Gaillard, C.; Millard-Pinard, N.; Gavarini, S.; Martin, P.; Cardinal, S.; Esnouf, C.; MalchĶre, A.; Perrat-Mabilon, A.
Titanium nitride is a refractory material that is being considered as an inert matrix in future Generation IV nuclear reactors, in particular in relation to the Gas-cooled Fast Reactor. The main role of this matrix would be to act as a barrier against the release of fission products, in particular gaseous ones like xenon. This release phenomenon will be enhanced by high temperatures expected in the fuel vicinity: 1200 ░C under normal conditions, and up to 1800 ░C under accidental conditions. It is therefore necessary to investigate the behavior of volatile fission products in TiN under high temperature and irradiation. Indeed, these basic data are very useful to predict the volatile fission products released under these extreme conditions. Our previous work has shown that Xe introduced by ion implantation in sintered TiN tends to be released as a result of annealing, due to a transport mechanism towards the sample surface. The aim of the present work is to determine under which physical state Xe is in TiN. Xenon was first introduced using ion implantation at 800 keV in TiN samples obtained by hot pressing at several concentrations ranging from 0.4 to 8 at.%. Secondly, samples were annealed at high temperature, from 1000 ░C to 1500 ░C. Xe was then characterized by X-ray Absorption Spectroscopy and Transmission Electron Microscopy. The formation of intragranular xenon bubbles was demonstrated, and the xenon concentration which is sufficient to form bubbles is found to be lower than 0.4 at.% under our experimental conditions. These bubbles were found unpressurised at 15 K. Their size increases with the temperature and the local xenon concentration. For the highest xenon concentrations, a mechanism involving the formation of a Xe interconnected bubble network is proposed to explain Xe massive release observed by Rutherford Backscattering Spectrometry experiments.
Analysis of Substrate Access to Active Sites in Bacterial Multicomponent Monooxygenase Hydroxylases: X-ray Crystal Structure of Xenon-Pressurized Phenol Hydroxylase from Pseudomonas sp. OX1å,ć
McCormick, Michael S.; Lippard, Stephen J.
In all structurally characterized bacterial multicomponent monooxygenase (BMM) hydroxylase proteins, a series of hydrophobic cavities in the ?-subunit trace a conserved path from the protein exterior to the carboxylate-bridged diiron active site. The present study examines these cavities as a potential route for dioxygen transport to the active site by crystallographic characterization of a xenon-pressurized sample of the hydroxylase component of phenol hydroxylase from Pseudomonas sp. OX1. Computational analyses of the hydrophobic cavities in the hydroxylase ?-subunits of phenol hydroxylase (PHH), toluene/o-xylene monooxygenase (ToMOH), and soluble methane monooxygenase (sMMOH) are also presented. The results, together with previous findings from crystallographic studies of xenon-pressurized sMMO hydroxylase, clearly identify the propensity for these cavities to bind hydrophobic gas molecules in the protein interior. This proposed functional role is supported by recent stopped flow kinetic studies of ToMOH variants (Song, et al., 2011). In addition to information about the Xe sites, the structure determination revealed significantly reduced regulatory protein binding to the hydroxylase in comparison to the previously reported structure of PHH, as well as the presence of a newly identified metal binding site in the ?-subunit that adopts a linear coordination environment consistent with Cu(I), and a glycerol molecule bound to Fe1 in a fashion that is unique among hydrocarbon-diiron site adducts reported to date in BMM hydroxylase structures. Finally, a comparative analysis of the ?-subunit structures of MMOH, ToMOH, and PHH details proposed routes for the other three BMM substrates, the hydrocarbon, electrons, and protons, comprising cavities, channels, hydrogen-bonding networks, and pores in the structures of their ?-subunits. PMID:22136180
Search for Periodic Rate Variations in XENON100 and Comparison with DAMA/LIBRA Annual Modulation
NASA Astrophysics Data System (ADS)
Goetzke, Luke; Xenon Collaboration
The stability of the XENON100 detector and electronic recoil event rate in the (2-6) keV energy range was studied for the 224.5 live-days of dark matter search data taken between February, 2011 and March, 2012. An un-binned profile likelihood analysis is used to identify potential periodic signatures in the electronic recoil data, with any period between 7 and 500 days. The results of these studies and a comparison with the DAMA/LIBRA annual modulation will be presented. We gratefully acknowledge the continued support of the XENON program by the National Science Foundation.
Measurement of Xenon Viscosity as a Function of Low Temperature and Pressure
NASA Technical Reports Server (NTRS)
Grisnik, Stanley P.
The measurement of xenon gas viscosity at low temperatures (175-298 K) and low pressures (350 torr-760 torr) has been performed in support of Hall Thruster testing at NASA Lewis Research Center. The measurements were taken using the capillary flow technique. Viscosity measurements were repeatable to within 3%. The results in this paper are in agreement with data from Hanley and Childs and suggest that the data from Clarke and Smith is approximately 2% low. There are no noticeable pressure effects on xenon absolute viscosity for the pressure range from 350 torr to 760 torr.
Xenon Protects Against Septic Acute Kidney Injury via miR-21 Target Signaling Pathway*
Jia, Ping; Teng, Jie; Zou, Jianzhou; Fang, Yi; Wu, Xie; Liang, Mingyu
Objectives: Septic acute kidney injury is one of the most common and life-threatening complications in critically ill patients, and there is no approved effective treatment. We have shown xenon provides renoprotection against ischemia-reperfusion injury and nephrotoxicity in rodents via inhibiting apoptosis. Here, we studied the effects of xenon preconditioning on septic acute kidney injury and its mechanism. Design: Experimental animal investigation. Setting: University research laboratory. Subjects: Experiments were performed with male C57BL/6 mice, 10 weeks of age, weighing 20¢25?g. Interventions: We induced septic acute kidney injury by a single intraperitoneal injection of Escherichia coli lipopolysaccharide at a dose of 20?mg/kg. Mice were exposed for 2 hours to either 70% xenon or 70% nitrogen, 24 hours before the onset of septic acute kidney injury. In vivo knockdown of miR-21 was performed using locked nucleic acid-modified anti-miR, the role of miR-21 in renal protection conferred by the xenon preconditioning was examined, and miR-21 signaling pathways were analyzed. Measurements and Main Results: Xenon preconditioning provided morphologic and functional renoprotection, characterized by attenuation of renal tubular damage, apoptosis, and a reduction in inflammation. Furthermore, xenon treatment significantly upregulated the expression of miR-21 in kidney, suppressed proinflammatory factor programmed cell death protein 4 expression and nuclear factor-?B activity, and increased interleukin-10 production. Meanwhile, xenon preconditioning also suppressed the expression of proapoptotic protein phosphatase and tensin homolog deleted on chromosome 10, activating protein kinase B signaling pathway, subsequently increasing the expression of antiapoptotic B-cell lymphoma-2, and inhibiting caspase-3 activity. Knockdown of miR-21 upregulated its target effectors programmed cell death protein 4 and phosphatase and tensin homolog deleted on chromosome 10 expression, resulted in an increase in apoptosis, and exacerbated lipopolysaccharide-induced acute kidney injury. Conclusion: Our findings demonstrated that xenon preconditioning protected against lipopolysaccharide-induced acute kidney injury via activation of miR-21 target signaling pathways. PMID:25844699
Thermodynamic properties and transport coefficients of arc lamp plasmas: argon, krypton and xenon
NASA Astrophysics Data System (ADS)
Murphy, Anthony B.; Tam, Eugene
Calculated values of the density, specific heat, enthalpy, viscosity, thermal conductivity and electrical conductivity of thermal plasmas formed from three gases used in arc lamps, krypton, argon and xenon, are presented. The calculations, which assume local thermodynamic equilibrium, were performed for pressures from 1 to 100 atm and for the temperature range 300-30?000 K. The results were compared with those of previously published studies. Some discrepancies were found for krypton and xenon; these are attributed to the improved values of the collision integrals used here in calculating the transport coefficients.
Results from the XENON10 and the Race to Detect Dark Matter with Noble Liquids
Shutt, Tom (Case Western Reserve) [Case Western Reserve
Detectors based on liquid noble gases have the potential to revolutionize the direct search for WIMP dark matter. The XENON10 experiment, of which I am a member, has recently announced the results from it's first data run and is now the leading WIMP search experiment. This and other experiments using xenon, argon and neon have the potential to rapidly move from the current kg-scale target mass to the ton scale and well beyond. This should allow a (nearly) definitive test or discovery of dark matter if it is in the form of weakly interacting massive particles.
Saturated absorption at nanowatt power levels using metastable xenon in a high-finesse optical cavity.
Hickman, G T; Pittman, T B; Franson, J D
Strong saturated absorption at nanowatt power levels has been demonstrated using metastable xenon in a high finesse optical cavity. The use of metastable xenon allows a high quality factor of Q = 2 ū 10(8) to be achieved at relatively high atomic densities without any contamination or damage to the optical surfaces, which is often a problem when using high-density rubidium or other alkali atoms. This technique provides a relatively straightforward way to produce nonlinearities at the single-photon level with possible applications in quantum communications and computing. PMID:25321758
Lifetime of the metastable 6s' [(1/2)](0) clock state in xenon.
Walhout, M; Sterr, U; Witte, A; Rolston, S L
To investigate the potential of a proposed optical frequency standard, we have measured the lifetime of the metastable 6s' [(1/2)](0) state in xenon. Magneto-optically trapped xenon atoms were prepared in the 6s' [(1/2)](0) state, and the time dependence of the vacuum-ultraviolet decay signature was analyzed. The total decay rate of 75(3) s(-1) is the sum of a 7.8(38)-s(-1) spontaneous emission rate (1-sigma uncertainties) and a much larger deexcitation rate that is due to a transition driven by room-temperature blackbody radiation. PMID:19859469
Performance of a Chamber for Studying the Liquid Xenon Response to Nuclear Recoils
V. Chepel; F. Neves; V. Solovov; A. Pereira; M. I. Lopes; J. Pinto da Cunha; P. Mendes; A. Lindote; C. P. Silva; R. Ferreira Marques; A. J. P. L. Policarpo
The design and performance of a 1.2 liter liquid xenon chamber equipped with\\u000a7 two-inch photomultiplier tubes, with the purpose of studying the\\u000ascintillation response of xenon to gamma-rays and neutrons, is described.\\u000aMeasurements with gamma-rays indicate a high VUV light collection efficiency\\u000aresulting in ~5.5 photoelectrons per 1 keV of deposited energy. The energy\\u000aresolution (FWHM) is 18% and
Incipient triple point for adsorbed xenon monolayers: Pt(111) versus graphite substrates
NASA Astrophysics Data System (ADS)
Novaco, Anthony D.; Bruch, L. W.; Bavaresco, Jessica
Simulation evidence of an incipient triple point is reported for xenon submonolayers adsorbed on the (111) surface of platinum. This is in stark contrast to the "normal" triple point found in simulations and experiments for xenon on the basal plane surface of graphite. The motions of the atoms in the surface plane are treated with standard 2D "NVE" molecular dynamics simulations using modern interactions. The simulation evidence strongly suggests an incipient triple point in the 120 -150 K range for adsorption on the Pt (111) surface while the adsorption on graphite shows a normal triple point at about 100 K.
The photodetachment cross-section and threshold energy of negative ions in carbon dioxide
NASA Technical Reports Server (NTRS)
Helmy, E. M.; Woo, S. B.
Threshold energy and sunlight photodetachment measurements on negative carbon dioxide ions, using a 2.5 kw light pressure xenon lamp, show that: (1) Electron affinity of CO3(+) is larger than 2.7 e.V. and that an isomeric form of CO3(+) is likely an error; (2) The photodetachment cross section of CO3(-) will roughly be like a step function across the range of 4250 to 2500A, having its threshold energy at 4250A; (3) Sunlight photodetachment rate for CO3(-) is probably much smaller than elsewhere reported; and (4) The probability of having photodetached electrons re-attach to form negative ions is less than 1%. Mass identifying drift tube tests confirm that the slower ion is CO3(-), formed through the O(-) + 2CO2 yields CO3(-) + CO2 reaction.
NASA Satellite Sees Carbon Dioxide
NSDL National Science Digital Library
In this problem set, learners will analyze a map of atmospheric carbon dioxide derived from satellite data. Answer key is provided. This is part of Earth Math: A Brief Mathematical Guide to Earth Science and Climate Change.
Chemistry of titanium dioxide nanoparticles
NASA Astrophysics Data System (ADS)
McCormick, John
With increasing energy costs, government regulations, and an expanding population, alternative low-cost methods for the treatment of waste air and water have shown renewed interest. The utilization of solar energy to promote catalytic reactions, including photodegradation of pollutants, is an attractive and well-established field of research. Titanium dioxide nanoparticles are the most widely employed catalyst material in photocatalytic studies. Owing to its high surface area and electronic structure, the anatase phase of TiO 2 is an excellent photocatalyst. However, a detailed understanding of the physical, chemical, and electronic properties of TiO2 that influence the photocatalytic reaction rate does not exist. One goal of this work is the determination of how the degradation rate over TiO2 nanoparticle is influenced by the particle size. To meet this goal, detailed analysis of the particles was carried out using standard catalytic techniques combined with infrared spectroscopy to probe the decomposition of an organic probe molecule, formic acid. It was shown using infrared spectroscopy that the size of the particle does influence the rate of photodegradation. However for particles as small as five nanometers, the increased rate could be described by accounting for the increased surface area of the particles. Novel synthesis conditions for the synthesis of high purity particles is required to develop a better understanding of how the size can influence the particle's catalytic properties. Combustion synthesis serves as an attractive method for the synthesis of high purity TiO2 nanoparticles. The high temperatures present in a combustion flame promotes the decomposition of organometallic precursors and subsequent synthesis of metal oxide nanoparticles. Numerous synthesis conditions can influence the product powder. This research investigated some of these conditions for the synthesis of TiO2 nanoparticles. Additionally the thermal properties of TiO2 nanoparticles was investigated. It is known that the more active phase for photocatalysis, anatase, is metastable at extremely small particle sizes (< 15 nm). A premixed ethylene combustion flame was employed in conjunction with a novel rapid-insertion sampler. This allowed for the extraction of high purity anatase particles before sintering and phase transformation to the less photoactive rutile phase could occur. The thermal properties of these particles were then investigated as part of an effort to investigate the catalytic properties of the flame synthesized particles. Results show that high-purity phase-pure anatase particles in the nanometer size range could be synthesized in a combustion flame. These particles were shown to be thermally stable to 773 K before sintering and phase transformation to rutile occurred.
Anisotropic contribution to the van der Waals and the Casimir-Polder energies for CO$_2$ and CH$_4$ molecules near surfaces and thin films
Thiyam, Priyadarshini; Shajesh, K V; Persson, Clas; Schaden, Martin; Brevik, Iver; Parsons, Drew F; Milton, Kimball A; Malyi, Oleksandr I; Bostr÷m, Mathias
In order to understand why carbon dioxide (CO$_2$) and methane (CH$_4$) molecules interact differently with surfaces, we investigate the Casimir-Polder energy of a linearly polarizable CO$_2$ molecule and an isotropically polarizable CH$_4$ molecule in front of an atomically thin gold film and an amorphous silica slab. We quantitatively analyze how the anisotropy in the polarizability of the molecule influences the van der Waals contribution to the binding energy of the molecule.
Hyperpolarized Xenon-129 Magnetic Resonance Imaging of Functional Lung Microstructure
NASA Astrophysics Data System (ADS)
Dregely, Isabel
Hyperpolarized 129Xe (HXe) is a non-invasive contrast agent for lung magnetic resonance imaging (MRI), which upon inhalation follows the functional pathway of oxygen in the lung by dissolving into lung tissue structures and entering the blood stream. HXe MRI therefore provides unique opportunities for functional lung imaging of gas exchange which occurs from alveolar air spaces across the air-blood boundary into parenchymal tissue. However challenges in acquisition speed and signal-to-noise ratio have limited the development of a HXe imaging biomarker to diagnose lung disease. This thesis addresses these challenges by introducing parallel imaging to HXe MRI. Parallel imaging requires dedicated hardware. This work describes design, implementation, and characterization of a 32-channel phased-array chest receive coil with an integrated asymmetric birdcage transmit coil tuned to the HXe resonance on a 3 Tesla MRI system. Using the newly developed human chest coil, a functional HXe imaging method, multiple exchange time xenon magnetization transfer contrast (MXTC) is implemented. MXTC dynamically encodes HXe gas exchange into the image contrast. This permits two parameters to be derived regionally which are related to gas-exchange functionality by characterizing tissue-to-alveolar-volume ratio and alveolar wall thickness in the lung parenchyma. Initial results in healthy subjects demonstrate the sensitivity of MXTC by quantifying the subtle changes in lung microstructure in response to orientation and lung inflation. Our results in subjects with lung disease show that the MXTC-derived functional tissue density parameter exhibits excellent agreement with established imaging techniques. The newly developed dynamic parameter, which characterizes the alveolar wall, was elevated in subjects with lung disease, most likely indicating parenchymal inflammation. In light of these observations we believe that MXTC has potential as a biomarker for the regional quantification of 1) emphysematous tissue destruction in chronic obstructive pulmonary disease (using the tissue density parameter) and 2) parenchymal inflammation or thickening (using the wall thickness parameter). By simultaneously quantifying two lung function parameters, MXTC provides a more comprehensive picture of lung microstructure than existing lung imaging techniques and could become an important non-invasive and quantitative tool to characterize pulmonary disease.
Vibrational Relaxation of Carbon-Dioxide at Lithium FLUORIDE(100) and Aluminum-Oxide Surfaces
Jeanne Carol Sawicki
The vibrational relaxation of CO_2 (101) at LiF(100) and aluminum oxide surfaces has been investigated by laser induced fluorescence. For these experiments, carbon dioxide is introduced to a cell, where the cell walls form the surface being studied. Laser radiation passing through the cell prepares the (101) state of the molecule, which subsequently collides with the surface and may lose
I-Type Doubling in Energy Levels of Carbon Dioxide Coupled by Fermi Resonance
J. de Heer; Harald H. Nielsen
In this paper we discuss the l-type doubling in levels of linear molecules which are coupled by Fermi resonance; in particular we consider here a triad of such levels in carbon dioxide. In principle, it becomes necessary to consider simultaneously the perturbations related to both anharmonic resonance interaction and l-type doubling. A further analysis reveals, however, that we are justified
Assessment of the UV camera sulfur dioxide retrieval for point source plumes
Marika P. Dalton; I. Matthew Watson; Patricia A. Nadeau; Cynthia Werner; Jeremy M. Shannon
Digital cameras, sensitive to specific regions of the ultra-violet (UV) spectrum, have been employed for quantifying sulfur dioxide (SO2) emissions in recent years. The instruments make use of the selective absorption of UV light by SO2 molecules to determine pathlength concentration. Many monitoring advantages are gained by using this technique, but the accuracy and limitations have not been thoroughly investigated.
Cholesterol aggregation and interaction with cholesterol oxidase in supercritical carbon dioxide.
Randolph, T W; Clark, D S; Blanch, H W; Prausnitz, J M
High-pressure EPR spectroscopy indicates that cholesterol forms aggregates in supercritical carbon dioxide. In pure carbon dioxide, changes in cholesterol aggregate size or packing structure are observed with changing pressure. Near the critical point of carbon dioxide, cholesterol solubility is too low to permit significant aggregation, and monomeric cholesterol is observed. Addition of small amounts of dopants to supercritical carbon dioxide strongly affects cholesterol aggregation. Branched butanols (2-methyl-1-propanol and 2-methyl-2-propanol) and ethanol (to a lesser degree) promote cholesterol aggregation, while methanol, acetone, and 1-butanol do not. Cosolvents that promote aggregation also increase the rate at which cholesterol oxidase from Gloeocysticum chrysocreas catalyzes the oxidation of cholesterol. In supercritical carbon dioxide solutions, the EPR spectroscopy reveals little or no conformational change in cholesterol oxidase as 2-methyl-2-propanol or methanol is added. Damp cholesterol oxidase binds multiple cholesterol molecules; dry enzyme loses the ability to bind cholesterol. When molecular oxygen is the oxidizing agent, the rate of enzymatic cholesterol oxidation is greatly reduced in bone-dry carbon dioxide compared to that in water-saturated carbon dioxide. PMID:2834725
Actinide Dioxides in Water: Interactions at the Interface
Alexandrov, Vitaly [Univ. of California, Davis, CA (United States). Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU),; Shvareva, Tatiana Y. [Univ. of California, Davis, CA (United States). Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU),; Hayun, Shmuel [Univ. of California, Davis, CA (United States). Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU),; Asta, Mark [Univ. of California, Davis, CA (United States). Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU),; Navrotsky, Alexandra [Univ. of California, Davis, CA (United States). Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU),
A comprehensive understanding of chemical interactions between water and actinide dioxide surfaces is critical for safe operation and storage of nuclear fuels. Despite substantial previous research, understanding the nature of these interactions remains incomplete. In this work, we combine accurate calorimetric measurements with first-principles computational studies to characterize surface energies and adsorption enthalpies of water on two fluorite-structured compounds, ThO? and CeO?, that are relevant for understanding the behavior of water on actinide oxide surfaces more generally. We determine coverage-dependent adsorption enthalpies and demonstrate a mixed molecular and dissociative structure for the first hydration layer. The results show a correlation between the magnitude of the anhydrous surface energy and the water adsorption enthalpy. Further, they suggest a structural model featuring one adsorbed water molecule per one surface cation on the most stable facet that is expected to be a common structural signature of water adsorbed on actinide dioxide compounds.
Some necessary conditions for a critical velocity interaction between the ionospheric plasma and a xenon cloud
I. Axnas
The condition for an experiment to study the critical ionization velocity effect in the interaction between a xenon cloud, released from a satellite, and the ionospheric plasma are investigated. The model used is based on the assumption that there exists an effective process that transfers the energy that is available in the relative motion to the electrons. Some necessary conditions
Some necessary parameters for a critical velocity interaction between the ionospheric plasma and a Xenon cloud
I. Axnaes
The conditions for an experiment to study the critical ionization velocity effect in the interaction between a Xenon cloud, released from a satellite, and the ionospheric plasma, are investigated. The model used is based on the assumption that there exists an effective process that transfers the energy, that is available in the relative motion, to the electrons. Some necessary conditions
Chemiluminescence in the oxidation of uranium (IV) by xenon trioxide and its analytical possibilities
Khamidullina, L.A.; Lotnik, S.V.; Gusev, Yu.K.; Kazakov, V.P.
This work is devoted to an investigation of the previously detected chemiluminescence in the oxidation of uranium (IV) by xenone trioxide and to evaluating the possibility of using it in determining nanogram quantities of U/sup (IV)/ in solution, including solutions containing a large excess of U/sup (VI)/.
Clinical comparison of Technegas and xenon-133 in 50 patients with suspected pulmonary embolus
Sullivan, P.J.; Burke, W.M.; Burch, W.M.; Lomas, F.E.
A comparison of Technegas and xenon-133 was performed in 50 patients presenting with a clinical diagnosis of pulmonary embolus. All patients underwent studies with xenon inhalation, Technegas inhalation, and macroaggregated albumin perfusion. Technegas is a new ultrafine ventilatory agent with a particle size of 50 to 200A produced from technetium pertechnetate and graphite in an argon environment. Although particulate in nature, Technegas is transported and diffuses like a gaseous agent. Its production results in a high specific activity yield with high efficiency. There is no significant deposition in the central airways, and good peripheral visualization of the lung is obtained. The study was designed to assess whether Technegas could be used as a ventilatory agent to obtain high-quality diagnostic images. All studies were reported as in normal clinical practice, and no statistical analysis was performed. The aim of the study was simply to see what role Technegas had in a busy clinical department and how well it reflected ventilation by comparison with xenon. Patient compliance with Technegas was 100 percent and for xenon was 94 percent. Technegas enables one to obtain high-quality ventilatory images and has an important role to play in the assessment of pulmonary ventilation.
Purification of krypton-xenon mixture from fluorine-containing gases
NASA Astrophysics Data System (ADS)
Adamov, V. S.; Yatkin, V. A.
Active alumina was used to purify krypton-xenon mixtures from fluorine-containing gases (tetrafluoromethane and sulfur hexafluoride). At 580░C, the admixtures are converted into aluminum trifluoride, with their content in the test gas mixture reducing from hundreds of ppm to 0.1 ppm or even below.
Pulse Rise Time Characterization of a High Pressure Xenon Gamma Detector for use in Resolution Enhancement
High pressure xenon ionization chamber detectors are possible alternatives to traditional thallium doped sodium iodide (NaI(Tl)) and hyperpure germanium as gamma spectrometers in certain applications. Xenon detectors incorporating a Frisch grid exhibit energy resolutions comparable to cadmium/zinc/telluride (CZT) (e.g. 2% {at} 662keV) but with far greater sensitive volumes. The Frisch grid reduces the position dependence of the anode pulse risetimes, but it also increases the detector vibration sensitivity, anode capacitance, voltage requirements and mechanical complexity. We have been investigating the possibility of eliminating the grid electrode in high-pressure xenon detectors and preserving the high energy resolution using electronic risetime compensation methods. A two-electrode cylindrical high pressure xenon gamma detector coupled to time-to-amplitude conversion electronics was used to characterize the pulse rise time of deposited gamma photons. Time discrimination was used to characterize the pulse rise time versus photo peak position and resolution. These data were collected to investigate the effect of pulse rise time compensation on resolution and efficiency.
Combined Liquid Xenon and crystal CsI calorimeter of the CMD-3 detector
NASA Astrophysics Data System (ADS)
Shebalin, V. E.; Anisenkov, A. V.; Bashtovoy, N. S.; Epifanov, D. A.; Erofeev, A. L.; Grebenuk, A. A.; Karpov, S. V.; Khazin, B. I.; Kovalenko, O. A.; Kozyrev, A. N.; Kuzmin, A. S.; Mikhailov, K. Yu; Razuvaev, G. P.; Ruban, A. A.; Shwartz, B. A.; Titov, V. M.; Talyshev, A. A.; Yudin, Yu V.
The barrel electromagnetic calorimeter of the CMD-3 detector consists of two subsystems: the Liquid Xenon calorimeter and the calorimeter based on CsI scintillation crystals. Its structure and main characteristics are presented. The energy calibration procedures of the combined calorimeter are described.
Isotopically anomalous xenon in meteorites - A new clue to its origin
NASA Technical Reports Server (NTRS)
Lewis, R. S.; Anders, E.
The CCF xenon component in primitive meteorites, which has been attributed either to fission of a superheavy element or to nucleosynthesis in a supernova, does not show the large enrichment in Xe-129 (from decay of 16 Myr I-129) expected for supernova ejecta. Although this problem can be circumvented by ad hoc assumptions, a fission origin of CCFXe seems more likely.
Design of Solid Form Xenon124 Target for Producing I-123 Radioisotope Using Computer Simulation Techniques
K. Kamali Moghaddam; M. Sadeghi; T. Kakavand; S. Shokri Bonab
Recently in Cyclotron and Nuclear Medicine Department of NRCAM, at Atomic Energy organization of Iran (AEOI), a system for producing 1-123 via Xe-124 gas target technology, has been constructed and installed. One of the major problems in this system is the highly expensive cost of the enriched Xenon-124 gas. Therefore, saving this gas inside the system is very important. Unfortunately,
Effects of xenon irradiation of the stellate ganglion region on fibromyalgia.
Nakajima, Fukami; Komoda, Akihiro; Aratani, Satoko; Fujita, Hidetoshi; Kawate, Mariko; Nakatani, Kou; Akiyama, Masako; Makita, Koshi; Nakajima, Toshihiro
[Purpose] The aim of the study was to determine the effect of xenon irradiation of the stellate ganglion region on fibromyalgia. [Subjects] The study included 5 men and 22 women (age, 56.4 ▒ 16.3?years [range, 25-84?years]) who were diagnosed with fibromyalgia according to the modified 2010 criteria of the American College of Rheumatology between July and August 2013. [Methods] Bilateral xenon light irradiation (0.38-1.1 ?m) around the stellate ganglion was performed in the supine position by physical therapists using a xenon phototherapy device. We evaluated pain before and after irradiation using the visual analogue scale. [Results] We did not observe a relationship between the change in the visual analogue scale score and duration of fibromyalgia. However, we observed a relationship between the change in the visual analogue scale score and the score for the Japanese version of the Fibromyalgia Impact Questionnaire using the Cochran-Armitage test for trend. [Conclusion] Xenon light irradiation of the stellate ganglion significantly decreased the visual analogue scale score in patients with fibromyalgia having a higher score in the Fibromyalgia Impact Questionnaire, suggesting that a stronger effect could be obtained in patients with more severe fibromyalgia. PMID:25642075
XENON100 exclusion limit without considering Leff as a nuisance parameter
NASA Astrophysics Data System (ADS)
Davis, Jonathan H.; B£hm, Cķline; Oppermann, Niels; Ensslin, Torsten; Lacroix, Thomas
In 2011, the XENON100 experiment has set unprecedented constraints on dark matter-nucleon interactions, excluding dark matter candidates with masses down to 6 GeV if the corresponding cross section is larger than 10-39cm2. The dependence of the exclusion limit in terms of the scintillation efficiency (Leff) has been debated at length. To overcome possible criticisms XENON100 performed an analysis in which Leff was considered as a nuisance parameter and its uncertainties were profiled out by using a Gaussian likelihood in which the mean value corresponds to the best fit Leff value (smoothly extrapolated to 0 below 3 keVnr). Although such a method seems fairly robust, it does not account for more extreme types of extrapolation nor does it enable us to anticipate how much the exclusion limit would vary if new data were to support a flat behavior for Leff below 3 keVnr, for example. Yet, such a question is crucial for light dark matter models which are close to the published XENON100 limit. To answer this issue, we use a maximum likelihood ratio analysis, as done by the XENON100 Collaboration, but do not consider Leff as a nuisance parameter. Instead, Leff is obtained directly from the fits to the data. This enables us to define frequentist confidence intervals by marginalizing over Leff.
Cryptophane Xenon-129 Nuclear Magnetic Resonance Biosensors Targeting Human Carbonic Anhydrase
Chambers, Jennifer M.; Hill, P. Aru; Aaron, Julie A.; Han, Zhaohui; Christianson, David W.; Kuzma, Nicholas N.; Dmochowski, Ivan J.
129Xe NMR biosensors are promising agents for the early detection of diseases, given that biomolecular interactions can perturb 129Xe chemical shifts well beyond the typical field inhomogeneity of clinical MRI. We introduce human carbonic anhydrase (CA) as a single-binding-site enzyme for studying xenon biosensor-protein interactions. A xenon-binding cryptophane was substituted with linkers of varying lengths to p-benzenesulfonamide to yield non-diastereomeric biosensors with a single 129Xe NMR resonance. X-ray crystallography confirmed binding of the 8-bond-linked biosensor containing a single xenon atom in the CAII active site. Biosensor dissociation constants (Kd = 20¢110 nM) were determined by isothermal titration calorimetry (ITC) for isozymes CA I and II. The biosensor-CA complexes yielded ōboundö hyperpolarized 129Xe NMR resonances of narrow linewidth that were shifted by 3.0 to 7.5 ppm downfield, signifying much larger shifts than seen previously. Moreover, isozyme-specific chemical shifts clearly differentiated CA I and II, despite their similar active-site architectures. Thus, xenon biosensors may provide a powerful strategy for diagnosing human diseases characterized by the upregulation of specific CA isozymes and other protein biomarkers. PMID:19140795
Free-Free Transitions Following Six-Photon Ionization of Xenon Atoms
P. Agostini; F. Fabre; G. Mainfray; G. Petite; N. K. Rahman
The energy spectrum of electrons produced by multiphoton ionization of xenon atoms has been analyzed with a retarding potential technique. We have shown that the discrete absorption of photons above the six-photon ionization threshold was observable under specified conditions. A simple model based upon inverse bremsstrahlung gives a resonable agreement with the experiments.
Observations of the artificially injected Porcupine xenon ion beam in the ionosphere
B. Haeusler; R. A. Treumann; O. H. Bauer; G. Haerendel; R. Bush; C. W. Carlson; B. Theile; M. C. Kelley; V. S. Dokukin; Yu. Ya. Ruzhin
Results are given of ion beam injection experiments performed in the auroral ionosphere in connection with the German Sounding Rocket Project Porcupine. A heavy (xenon) ion beam was injected into the collisionless ionospheric plasma approximately perpendicular to the ambient magnetic field at altitudes from 190 km to about 450 km. The beam propagates nearly undistorted across the plasma because it
Improvement of gate oxide reliability for tantalum-gate MOS devices using xenon plasma sputtering technology
Takeo Ushiki; Kunihiro Kawai; Mo-Chiun Yu; Toshikuni Shinohara; Kazuhide Ino; Mizuho Morita; Tadahiro Ohmi
The effects of ion species in the sputtering deposition process on gate oxide reliability have been experimentally investigated. The use of xenon (Xe) plasma instead of argon (Ar) plasma in tantalum (Ta) film sputtering deposition for gate electrode formation makes it possible to improve the gate oxide reliability. The Xe plasma process exhibits 1.5 times higher breakdown field and five
Penile xenon (/sup 133/Xe) washout: a rapid method of screening for vasculogenic impotence
Nseyo, U.O.; Wilbur, H.J.; Kang, S.A.; Flesh, L.; Bennett, A.H.
The radioactive inert gas xenon (/sup 133/Xe) is a well-established isotopic indicator used to assess vascular status in many organ systems. Xenon-133 was used to evaluate male impotence. Xenon-133 was injected subcutaneously at the level of the coronal sulcus in the detumescent state. Using the gamma camera, sequential images were obtained and computer-generated curves calculated. The clearance time for 50 per cent washout of the injected /sup 133/Xe (T1/2) was then calculated for each patient, as well as a control group. Preliminary findings indicate a correlation with such established techniques of evaluating erectile impotence as history, physical examination, penile pulse Doppler tracings, and brachial-penile blood pressure index. The xenon-133 washout study was a rapid, minimally invasive, reproducible, and cost-effective method of screening those impotent patients for vasculogenic etiology of their erectile impotence. We recommend the addition of this method to the surgeon engaged in the care of impotent males.
Reduced xenon diffusion for quantitative lung studythe role of SF6
Walsworth, Ronald L.
measurements in human alveoli using time-dependent gas diffusion NMR. KEYWORDS: xenon; diffusion; sulfur the development of lung ventilation MRI using laser-polarized noble gases (129 Xe and 3 He),1,2 attention has been given to NMR measures of noble gas diffusion as a new tool for studying lung structure and function.3
Pressure-induced bonding and compound formation in xenon-hydrogen solids.
Somayazulu, Maddury; Dera, Przemyslaw; Goncharov, Alexander F; Gramsch, Stephen A; Liermann, Peter; Yang, Wenge; Liu, Zhenxian; Mao, Ho-Kwang; Hemley, Russell J
Closed electron shell systems, such as hydrogen, nitrogen or group 18 elements, can form weakly bound stoichiometric compounds at high pressures. An understanding of the stability of these van der Waals compounds is lacking, as is information on the nature of their interatomic interactions. We describe the formation of a stable compound in the Xe-H(2) binary system, revealed by a suite of X-ray diffraction and optical spectroscopy measurements. At 4.8 GPa, a unique hydrogen-rich structure forms that can be viewed as a tripled solid hydrogen lattice modulated by layers of xenon, consisting of xenon dimers. Varying the applied pressure tunes the Xe-Xe distances in the solid over a broad range from that of an expanded xenon lattice to the distances observed in metallic xenon at megabar pressures. Infrared and Raman spectra indicate a weakening of the intramolecular covalent bond as well as persistence of semiconducting behaviour in the compound to at least 255 GPa. PMID:21124380
High-resolution spectroscopy on a fast beam of metastable xenon ions
Th. Meier; H. H³hnermann; H. Wagner
For the case of xenon we show that metastable ions are very suitable for optical experiments on fast ion beams (FIB experiments). It is possible to study the hyperfine structure of spectral lines in absorption from a mass separated ion beam which is exposed to a monomode laser beam. The absorption is detected by observing the fluorescence radiation. As expected,
1D fluid simulations of a helium-xenon filled AC plasma display panel
R. Veerasingam; R. B. Campbell; R. T. McGrath
A one dimensional multi-species fluid model has been developed to analyze the operation of an ac plasma display panel (AC PDP) that is filled with a helium-xenon Penning mixture. The AC PDP is a promising candidate in the flat panel display industry especially for information displays having large screen areas. A PDP consists of a matrix of gas cells operating
Isochoric heat capacity of metastable liquid xenon near the critical point
V. G. Baidakov; A. M. Rubshtein
This paper presents the results of measurements of the isochoric heat capacity of liquid xenon in stable and metastable states. The behaviour of thermodynamic quantities near the boundary of the essential instability is discussed. It is shown that at the spinodal points (with the exception of the critical point) the isochoric heat capacity and the adiabatic compressibility have finite nonzero
Lyubomir N. SOTIROV; Stefan T. BARUDOV; Stela L. SOTIROVA
The paper presents a new approach of discrete adaptive observation and modeling of discharge processes in Xenon pulse tubes considered so far as nonlinear and non-stationary continuous processes. The tools of the Theory of Optimal Singular Adaptive Computer Observation and Discrete Modeling, which have been developed in the recent 25 years in the Technical University Varna are applied.
Nuclear spin-spin coupling in a van der Waals-bonded system: xenon dimer.
Vaara, Juha; Hanni, Matti; Jokisaari, Jukka
Nuclear spin-spin coupling over van der Waals bond has recently been observed via the frequency shift of solute protons in a solution containing optically hyperpolarized (129)Xe nuclei. We carry out a first-principles computational study of the prototypic van der Waals-bonded xenon dimer, where the spin-spin coupling between two magnetically non-equivalent isotopes, J((129)Xe - (131)Xe), is observable. We use relativistic theory at the four-component Dirac-Hartree-Fock and Dirac-density-functional theory levels using novel completeness-optimized Gaussian basis sets and choosing the functional based on a comparison with correlated ab initio methods at the nonrelativistic level. J-coupling curves are provided at different levels of theory as functions of the internuclear distance in the xenon dimer, demonstrating cross-coupling effects between relativity and electron correlation for this property. Calculations on small Xe clusters are used to estimate the importance of many-atom effects on J((129)Xe - (131)Xe). Possibilities of observing J((129)Xe - (131)Xe) in liquid xenon are critically examined, based on molecular dynamics simulation. A simplistic spherical model is set up for the xenon dimer confined in a cavity, such as in microporous materials. It is shown that the on the average shorter internuclear distance enforced by the confinement increases the magnitude of the coupling as compared to the bulk liquid case, rendering J((129)Xe - (131)Xe) in a cavity a feasible target for experimental investigation. PMID:23514495
[Biophysics of single molecules].
Serdiuk, I N; Deriusheva, E I
The modern methods of research of biological molecules whose application led to the development of a new field of science, biophysics of single molecules, are reviewed. The measurement of the characteristics of single molecules enables one to reveal their individual features, and it is just for this reason that much more information can be obtained from one molecule than from the entire ensample of molecules. The high sensitivity of the methods considered in detail makes it possible to come close to the solution of the basic problem of practical importance, namely, the determination of the nucleotide sequence of a single DNA molecule. PMID:22117447
Probing the hydrophobic cavity of lipid transfer protein from Nicotiana tabacum through xenon-based NMR spectroscopy.
Dubois, Lionel; Da Silva, Pedro; Landon, Cķline; Huber, J Gaspard; Ponchet, Michel; Vovelle, Franńoise; Berthault, Patrick; Desvaux, Hervķ
The hydrophobic cavity of Lipid Transfer Protein 1 from Nicotiana tabacum is investigated in detail by NMR using xenon as a spy. The analysis of the (129)Xe chemical shifts and self-relaxation times gives evidence of protein-xenon interaction. Thermodynamics of the binding is characterized through the study of aliphatic (1)H and (13)C chemical shift variation as a function of xenon pressure. The binding constant is evaluated to 75.5 +/- 1.0 M(-1) at 293 K. The location of xenon inside the cavity is deduced from SPINOE experiments. The noble gas appears to occupy four sites, and xenon self-relaxation experiments indicate that it quickly jumps between different sites. The chemical shifts of amide protons and nitrogens also depend on the xenon concentration, either specifically or nonspecifically for atoms at the external surface of the protein. Yet, contrary to aliphatic atoms, they do not correspond to short-range interactions as confirmed by magnetization transfer experiments between laser-polarized xenon and protons in H(2)O. These (15)N chemical shift variations, used in combination with (15)N transverse self-relaxation rates to determine the lower limit of the binding rate, consequently reveal subtle changes in the structure of the protein upon binding. PMID:15571396
Design of Solid Form Xenon-124 Target for Producing I-123 Radioisotope Using Computer Simulation Techniques
Kamali Moghaddam, K.; Sadeghi, M. [Nuclear Research Center for Agriculture and Medicine - NRCAM, AEOI, P.O. Box 31585-4395, Karaj (Iran, Islamic Republic of); Kakavand, T.; Shokri Bonab, S. [Zanjan University, Zanjan (Iran, Islamic Republic of)
Recently in Cyclotron and Nuclear Medicine Department of NRCAM, at Atomic Energy organization of Iran (AEOI), a system for producing 1-123 via Xe-124 gas target technology, has been constructed and installed. One of the major problems in this system is the highly expensive cost of the enriched Xenon-124 gas. Therefore, saving this gas inside the system is very important. Unfortunately, by accidental rupture of the window foil or bad function of O-rings, the whole Xenon gas will escape from the system immediately. In this paper, by using computer codes; ALICE91, SRIM and doing some calculations we are going to demonstrate our latest effort for feasibility study of producing I-123 with the above mentioned reactions, but using Xe-124 solid target instead. According to our suggested design, a conical shaped irradiation vessel made of copper with 1 mm thickness, 1 cm outlet diameter, 5 cm length and 12 deg. angle at summit can be fixed inside a liquid nitrogen housing chamber. The Xenon-124 gas will be sent to the inside of this very cold conical trap and eventually deposited on its surface in solid form. Our calculation shows that during bombardment with 17-28 MeV proton energy, the thickness of solidified Xenon layer will remain around .28 mm. Likewise; thermo-dynamical calculation shows that in order to prevent the evaporation of solidified Xenon, the maximum permissible proton beam current for this system should be less than 1.4 {mu}A. According to these working conditions, the production yield of I-123 can be predicted to be around 150 mCi/{mu}Ah. (authors)
Phase behavior of mixed submonolayer films of krypton and xenon on graphite.
Patrykiejew, A; Soko?owski, S
Using the results of extensive Monte Carlo simulations in the canonical and grand canonical ensembles, we discuss the phase behavior of mixed submonolayer films of krypton and xenon adsorbed on the graphite basal plane. The calculations have been performed using two- and three-dimensional models of the systems studied. It has been demonstrated that out-of-plane motion does not affect the properties of the films as long as the total density is well below the monolayer completion and at moderate temperatures. For the total densities close to the monolayer completion, the promotion of particles to the second layer considerably affects the film properties. Our results are in a reasonable agreement with the available experimental data. The melting point of submonolayer films has been shown to exhibit non-monotonous changes with the film composition, and reaches minimum for the xenon concentration of about 50%. At the temperatures below the melting point, the structure of solid phases depends upon the film composition and the temperature; one can also distinguish commensurate and incommensurate phases. Two-dimensional calculations have demonstrated that for the xenon concentration between about 15% and 65% the adsorbed film exhibits the formation of a superstructure, in which each Xe atom is surrounded by six Kr atoms. This superstructure is stable only at very low temperatures and transforms into the mixed commensurate (?3ū?3)R30░ phase upon the increase of temperature. Such a superstructure does not appear when a three-dimensional model is used. Grand canonical ensemble calculations allowed us to show that for the xenon concentration of about 3% the phase diagram topology of monolayer films changes from the krypton-like (with incipient triple point) to the xenon-like (with ordinary triple point). PMID:22502538
A. Fioretti; M. Fazzi; M. Mazzoni; T. Ban; C. Gabbanini
In this paper we overview recent results on the formation of translationally cold molecules. While there are some methods relying on direct cooling of molecules, we shall concentrate on the photoassociation technique that starts from laser-cooled atoms. The detection methods for the ultra-cold molecules will be presented together with a report on the trapping techniques. The treatment is mainly focused
Molecular Structure of Carbon Dioxide
NSDL National Science Digital Library
Carbon dioxide was first described in the 17th century by Jan Baptist van Helmont, a Belgium chemist. The chemical CO2 is released into the atmosphere when carbon-containing fossil fuels like oil, natural gas, and coal are burned in air. It is also produced by various microorganisms in fermentation and is breathed out by animals. Plants absorb carbon dioxide during photosynthesis, using both the carbon and the oxygen to construct carbohydrates. Every year the amount of CO2 in the atmosphere is increasing. CO2 build-up in the atmosphere is caused by deforestation, therefore reducing the number of trees available to absorb CO2. Excess CO2 in the environment causes Global Warming and the Greenhouse Effect. It is also toxic to humans since inhalation of large amounts of CO2 can cause suffocation. Some beverages, such as beer and sparkling wine contain carbon dioxide as a result of fermentation.
Effect of endogenous sulfur dioxide in regulating cardiovascular oxidative stress.
Zhu, Mingzhu; Du, Junbao; Liu, Angie Dong; Holmberg, Lukas; Tang, Chaoshu; Jin, Hongfang
In the middle of the 1980s, nitric oxide received extensive attention because of its significant effects in life science. Then, carbon monoxide and hydrogen sulfide were discovered to be gasotransmitters playing important roles in regulating cellular homeostasis. As a common air pollutant, sulfur dioxide (SO?) can cause great harm to the human body by producing free radicals, which causes oxidative damage to various organs. Recently, endogenous SO2 was found to be produced in the cardiovascular system and might be a bioactive molecule regulating the physiological activities including cardiovascular oxidative stress. PMID:24718903
Gamma radiation characteristics of plutonium dioxide fuel
NASA Technical Reports Server (NTRS)
Gingo, P. J.
Investigation of plutonium dioxide as an isotopic fuel for Radioisotope Thermoelectric Generators yielded the isotopic composition of production-grade plutonium dioxide fuel, sources of gamma radiation produced by plutonium isotopes, and the gamma flux at the surface.
VAPOR + LIQUID EQUILIBRIUM OF WATER, CARBON DIOXIDE, AND THE BINARY SYSTEM WATER + CARBON DIOXIDE the vapor-liquid equilibrium of water (between 323 and 573 K), carbon dioxide (between 230 and 290 K) and their binary mixtures (between 348 and 393 K). The properties of supercritical carbon dioxide were determined
Nitrogen dioxide, sulfur dioxide, and ammonia detector for remote sensing of vehicle emissions
Denver, University of
Nitrogen dioxide, sulfur dioxide, and ammonia detector for remote sensing of vehicle emissions the capability to measure nitrogen dioxide in the UV with one spectrometer and to measure SO2 and NH3 along with sulfuric and nitric acids formed from at- mospheric oxidations of sulfur dioxide SO2 and nitrogen oxides
Seventh International Carbon Dioxide Conference
NSDL National Science Digital Library
Organized by NOAA's Climate Monitoring and Diagnostic Laboratory (CMDL), the Seventh International Carbon Dioxide Conference is planned September 25-30 in Broomfield, Colo. At this website, scientists involved in various aspects of the global carbon cycle, especially the current increases of carbon dioxide in the atmosphere, are encouraged to attend. Users can read the preliminary announcement and can learn about the themes of the conference. Researchers can learn about abstract submissions and accommodations. The Brief Conference History link offers a nice synopsis of the accomplishments of past conferences.
Carbon Dioxide Absorption Heat Pump
NASA Technical Reports Server (NTRS)
Jones, Jack A. (Inventor)
A carbon dioxide absorption heat pump cycle is disclosed using a high pressure stage and a super-critical cooling stage to provide a non-toxic system. Using carbon dioxide gas as the working fluid in the system, the present invention desorbs the CO2 from an absorbent and cools the gas in the super-critical state to deliver heat thereby. The cooled CO2 gas is then expanded thereby providing cooling and is returned to an absorber for further cycling. Strategic use of heat exchangers can increase the efficiency and performance of the system.
Structural study of supercritical carbon dioxide confined in nanoporous silica by in situ neutron diffraction
NASA Astrophysics Data System (ADS)
Stefanopoulos, K. L.; Steriotis, Th A.; Katsaros, F. K.; Kanellopoulos, N. K.; Hannon, A. C.; Ramsay, J. D. F.
In situ neutron diffraction measurements of adsorbed carbon dioxide in an ordered mesoporous silica (MCM-41) have been carried out along an isotherm slightly above the critical point (308 K) and at a range of pressures below and above the critical one (30-125 bar). The experiment has been performed with the aid of a novel high-pressure adsorption apparatus and the GEM diffractometer (ISIS, Rutherford Appleton Laboratory, UK). Diffraction measurements of both bulk supercritical and bulk liquid carbon dioxide have also been carried out. The structure factors and the total differential correlation functions of the adsorbed carbon dioxide suggest that the confined carbon dioxide has liquid-like properties. However, some differences are observed when the confined phase is compared to those of bulk liquid and bulk supercritical fluid respectively, mainly arising from orientational correlations between adsorbed molecules. These differences could be attributed either to strong interactions between the silica walls and CO2 molecules or to the confinement of the fluid combined with the relatively large quadrupole moment of carbon dioxide.
Conversion of Uranium Oxide into Nitrate with Nitrogen Dioxide
Kayo Sawada; Daisuke Hirabayashi; Youichi Enokida; Ichiro Yamamoto
In order to decrease the amount of aqueous liquid waste discharged from nuclear fuel reprocessing, the conversion of uranium dioxide into its nitrate using liquefied nitrogen dioxide was studied. Uranium dioxide powder was immersed in liquefied nitrogen dioxide at 313 K after a pretreatment by the oxidation of the uranium dioxide with nitrogen dioxide and air at 523 K. Seventy-nine
Enhancements of rescattered electron yields in above-threshold ionization of molecules
Cornaggia, C. [CEA IRAMIS, Service Photons Atomes et Molecules, Saclay, Batiment 522, F-91191 Gif-sur-Yvette (France)
In above-threshold ionization of rare-gas atoms, photoelectron spectra recorded in the 10{sup 13}-10{sup 14} W cm{sup -2} range exhibit enhancements in the rescattering plateaus that do not have a unified theoretical interpretation yet. Here an experimental search for such enhancements is reported in simple molecules with ionization potentials near those of rare-gas atoms such as H{sub 2} and N{sub 2} for argon and O{sub 2} for xenon, and in other molecules such as CO{sub 2} and N{sub 2}O. Only H{sub 2} exhibits the enhancements previously observed in atoms. The H{sub 2} particularity is interpreted in terms of its simpler ion structure and associated ionization paths compared with other molecules.
Carbon dioxide recovery by vacuum swing adsorption
Cheng-Tung Chou; Chao-Yuh Chen
According to an investigation by the Intergovernmental Panel on Climate Change (IPCC), carbon dioxide is the most significant greenhouse gas produced as a result of human activities. The amount of carbon dioxide emissions has to be reduced to meet global treaty. The concentration and recovery of carbon dioxide from flue gases is the first important step in solving the carbon
2, 18491865, 2005 Carbon dioxide in
Paris-Sud XI, Universitķ de
BGD 2, 1849Ł1865, 2005 Carbon dioxide in southern Poland L. Chmura et al. Title Page Abstract is licensed under a Creative Commons License. 1849 #12;BGD 2, 1849Ł1865, 2005 Carbon dioxide in southern urban environment with numerous local sources of carbon dioxide. Despite of relative proximity of those
7Carbon Dioxide Increases The Keeling Curve,
7Carbon Dioxide Increases The Keeling Curve, shown to the left, shows the variation in concentration of atmospheric carbon dioxide since 1958-1974. It is based on continuous measurements taken of rapidly increasing carbon dioxide levels in the atmosphere. Additional measurements by scientists working
21 CFR 184.1240 - Carbon dioxide.
Code of Federal Regulations, 2014 CFR
...3 2014-04-01 2014-04-01 false Carbon dioxide. 184.1240 Section 184.1240 Food and...Specific Substances Affirmed as GRAS ¦ 184.1240 Carbon dioxide. (a) Carbon dioxide (empirical formula CO2 , CAS Reg....
Santos, Juan
SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW J. E. Santos1 1 Department of Mathematics, Purdue University, USA Purdue University, March 1rst, 2013 SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW Ł p. #12 (North Sea). SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW Ł p. #12;Introduction. II CO2 is separated
Santos, Juan
SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW J. E. Santos1, G. B. Savioli2, J. M. Carcione3, D┤e, Argentina SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW Ł p. #12;Introduction. I Storage of CO2). SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW Ł p. #12;Introduction. II CO2 is separated from natural
The microporous structure of coals and a microporous carbon studied using xenon-129 NMR spectroscopy
NASA Astrophysics Data System (ADS)
Anderson, Stasia A.
sp{129}Xe nuclear magnetic resonance spectroscopy of xenon gas adsorbed in coal is used to describe coal microporous structure. Emphasis is on establishing micropore diameter, whether pores are open, the type of connectivity, and changes associated with coal rank. Pressure dependent sp{129}Xe NMR spectra were acquired for a rank-varied set of coals. Micropore diameters calculated from the spectra range from 5.6 to 7.5 A and are related to coal rank. Signal linewidths decrease with increasing coal rank. The packing density of powdered coal affected the spectral appearance. Micropore diameters were also calculated for a microporous carbon before and after pore-size alteration. Selective low power presaturation of the adsorbed xenon signal for four coals produces a hole-burning effect in the spectra indicating that the signal is composed of a series of overlapped chemical shifts. Saturation transfer to the external gas signal, (which most likely originates from xenon in large pores) is observed as presaturation time is increased. Saturation transfer occurs significantly faster in two low-rank than in two higher-rank coals. The process of xenon adsorption was monitored by acquisition of sp{129}Xe NMR during adsorption. Equilibrium is achieved faster in smaller particle size anthracite than in larger, and for either, the time is slower than for the microporous carbon. The external xenon is observed only in the larger particle size and loses intensity as the internally-adsorbed xenon increases. No intermediate signal location is indicated prior to equilibrium. These experiments indicate coal porosity is open and that it constitutes a constricted network. The degree of constriction is higher in coals over ś89% carbon. Microporosity in low-rank coals is consistent with a dendritic pore structure. For higher rank coals over 89% carbon, the microporosity is more isolated and is open via constricted micropores but lacks a route through larger pores. Smaller particle size anthracite has less constriction in its porosity than larger particle size, and may also have less larger porosity or fracture.
Xenon-induced inhibition of Ca 2+ -regulated transitions in the cell cycle of human endothelial cells
Christian Petzelt; Grit Taschenberger; Wolfgang Schmehl; Wolfgang J. Kox
Xenon is an anesthetic with very few side-effects, yet its targets at the cellular level are still unclear. It interferes\\u000a with many aspects of intracellular Ca2+ homeostasis, but so far no specific event or defined regulatory complex of the Ca2+-signaling system has been identified. Specific effects of xenon were found by investigating its effects on the cell cycle\\u000a in human
Radioactive plume from the Three Mile Island accident: xenon-133 in air at a distance of 375 kilometers
M. Wahlen; C. O. Kunz; J. M. Matuszek; W. E. Mahoney; R. C. Thompson
As a result of the Three Mile Island nuclear reactor accident in March 1979, the passage of radioactive xenon-133 through Albany, N.Y., was monitored from March 29-April 2, 1979. Monitoring techniques are described. Ambient air Xenon-133 concentrations as high as 3900 pico Ci\\/cu m were recorded. The local gamma ray whole body dose from the passing radioactivity amounted to 0.004
Latest Results from Zeplin i, a Liquid Xenon Detector for Dark Matter Searches at the Boulby Mine
NASA Astrophysics Data System (ADS)
Barton, J. C.; Alner, G. J.; Arnison, G. J.; Carter, R. C.; Hart, S. P.; Homer, G.; Lewin, J. D.; L³scher, R.; Preece, R. M.; Roberts, J. W.; Smith, N. J. T.; Smith, P. F.; Ahmed, B.; Bewick, A.; Davidge, D.; Dawson, J. V.; Howard, A. S.; Jones, W. G.; Joshi, M. K.; Lebedenko, V.; Liubarsky, I.; Quenby, J. J.; Sumner, T. J.; Carson, M. J.; Gamble, T.; Hollingworth, R.; Kudryavtsev, V. A.; Lawson, T. B.; Lightfoot, P. K.; McMillan, J. E.; Morgan, B.; Nicklin, G.; Paling, S. M.; Robinson, M.; Spooner, N. J. C.; Tovey, D. R.
Results from 75 days of data collected by the ZEPLIN I detector are presented. The detector, a 3.1kg liquid xenon target operated by the UKDMC at the Boulby mine, is described. Calibration techniques, efficiency calculations and the techniques used to remove background events are described, including the use of active turrets of liquid xenon to reject low energy events from the photomultipliers.
Xenon isotopic signature study of the primary coolant of CANDU nuclear power plant to enhance CTBT verification
W. Zhang; K. Ungar; I. Hoffman; R. Lawrie
To support interpretation of observed atmospheric 135Xe, 133Xe, 133mXe and 131mXe, a database of xenon radioisotope in the primary coolant of CANDU reactors has been established. This database is comprised\\u000a of 40000 records of high-quality xenon radioisotope analyses. Records from the database were retrieved by a specifically designed\\u000a data-mining module and subjected to further analysis. Results from the analysis were
Luminance and efficacy improvement of low-pressure xenon pulsed fluorescent lamps by using an auxiliary external electrode
Masafumi Jinno; Masahiro Okamoto; Masashi Takeda; Hideki Motomura
As the environmental awareness of people becomes stronger, the demand for mercury-free light sources also becomes stronger. The authors have been keeping their interest in developing mercury-free discharge lamps, especially in low-pressure xenon as the most promising UV sources to substitute mercury. In this paper the authors report the effect of auxiliary external electrode (AEE) on the pulsed xenon fluorescent
Performance of a chamber for studying the liquid xenon response to \\/spl gamma\\/-rays and nuclear recoils
F. Neves; V. Chepel; V. Solovov; A. Pereira; M. I. Lopes; J. Pinto da Cunha; P. Mendes; A. Lindote; C. P. Silva; R. Ferreira Marques; A. J. P. L. Policarpo
The design and performance of a 1.2 liter liquid xenon chamber equipped with 7 two-inch photomultiplier tubes, with the purpose of studying the scintillation response of xenon to gamma-rays and neutrons, is described. Measurements with gamma-rays indicate a high VUV light collection efficiency resulting in ~5.5 photoelectrons per 1 keV of deposited energy. The energy resolution (FWHM) is 18% and
Gaffron, Hans
1. Unicellular algae possessing a hydrogenase system (Scenedesmus and other species), and having been adapted by anaerobic incubation to the hydrogen metabolism, reduce oxygen to water according to the equation O2 + 2H2 ? 2H2O. 2. The oxyhydrogen reaction proceeds undisturbed only in the presence of carbon dioxide, which simultaneously is reduced according to the equation CO2 + 2H2 ? H2O + (CH2O) = (carbohydrate). 3. The maximum yield of the induced reduction is one-half molecule of carbon dioxide reduced for each molecule of oxygen absorbed. 4. Partial reactions are recognizable in the course of the formation of water and it is with the absorption of the second equivalent of hydrogen that the carbon dioxide reduction appears to be coupled. 5. The velocity of the reaction increases in proportion to the partial pressure of oxygen, but only up to a certain point where any excess of oxygen causes the inactivation of the hydrogenase system. The reaction then ends prematurely. 6. During the oxyhydrogen reaction little or no oxygen is consumed for normal respiratory processes. 7. Small concentrations of cyanide, affecting neither photosynthesis nor photoreduction in the same cells, first inhibit the induced reduction of carbon dioxide and then lead to a complete inactivation of the hydrogenase system. 8. Hydroxylamine, added after adaptation, has either no inhibitory effect at all, or prevents solely the induced reduction of carbon dioxide without inactivating the hydrogenase system. 9. Dinitrophenol prevents the dark reduction of carbon dioxide while the reduction of oxygen continues to the formation of water. 10. Glucose diminishes the absorption of hydrogen, probably in its capacity as a competing hydrogen donor. 11. The induced reduction of carbon dioxide can be described as an oxido-reduction similar to that produced photochemically in the same cells. PMID:19873340
Emission characteristics and electron kinetic coefficients of the plasma of a transverse volume discharge initiated in a mixture of heavy inert gases with chlorine molecules
A. K. Shuaibov; V. I. Chygin; L. L. Shimon; I. V. Shevera; P. P. Gorun; R. O. Obukhovskii
The results of studying the radiation due to argon, krypton, and xenon monochloride bands, as well as to the bands of chlorine\\u000a molecules, from the plasma of a transverse Ar-Kr-Xe-Cl2 volume discharge are reported. The working mixture of a pulse radiation source is optimized with regard to its pressure and\\u000a elemental composition and parameters of an excitation system. By numerically
Xenon migration in UO2 under irradiation studied by SIMS profilometry
NASA Astrophysics Data System (ADS)
Marchand, B.; Moncoffre, N.; Pipon, Y.; Bķrerd, N.; Garnier, C.; Raimbault, L.; Sainsot, P.; Epicier, T.; Delafoy, C.; Fraczkiewicz, M.; Gaillard, C.; Toulhoat, N.; Perrat-Mabilon, A.; Peaucelle, C.
During Pressurized Water Reactor operation, around 25% of the created Fission Products (FP) are Xenon and Krypton. They have a low solubility in the nuclear fuel and can either (i) agglomerate into bubbles which induce mechanical stress in the fuel pellets or (ii) be released from the pellets, increasing the pressure within the cladding and decreasing the thermal conductivity of the gap between pellets and cladding. After fifty years of studies on the nuclear fuel, all mechanisms of Fission Gas Release (FGR) are still not fully understood. This paper aims at studying the FGR mechanisms by decoupling thermal and irradiation effects and by assessing the Xenon behavior for the first time by profilometry. Samples are first implanted with 136Xe at 800 keV corresponding to a projected range of 140 nm. They are then either annealed in the temperature range 1400-1600 ░C, or irradiated with heavy energy ions (182 MeV Iodine) at Room Temperature (RT), 600 ░C or 1000 ░C. Depth profiles of implanted Xenon in UO2 are determined by Secondary Ion Mass Spectrometry (SIMS). It is shown that Xenon is mobile during irradiation at 1000 ░C. In contrast, thermal treatments do not induce any Xenon migration process: these results are correlated to the formation of Xenon bubbles observed by Transmission Electron Microscopy. At depths lower than about 40 nm (zone 1), no bubbles are observed, At depths in between 40 nm and 110 nm (zone 2), a large number of small bubbles (around 2 nm in diameter) can be observed. By comparing with the SRIM profile, it appears that this area corresponds to the maximum of the defect profile, The third zone displays two bubble populations. The first population has the same size than the bubbles present in zone 2. The bubble size of the second population is significantly larger (up to around 10 nm). A STEM micrograph is presented in Fig. 4. It highlights the Xenon bubbles more clearly. It appears that the largest bubbles are located mainly near dislocations which are predominantly in zone 3. TEM micrographs obtained on the samples annealed at 1400 ░C (not shown here) show only small sized bubbles (around 2 nm). The presence of these bubbles could explain that no Xenon migration occurs even after annealing at 1600 ░C during 16 h. Moreover, concerning Xe thermal resolution, this can only occur if the bubble is overpressurized [21]. It was shown by Martin et al. [22] that at high temperature (over 1400 ░C) non pressurized aggregates are observed. So in our experiments, Xe thermal resolution is unlikely.The bubble sizes measured after 1400 ░C and 1600 ░C annealing are in agreement with literature data, in particular, with those of Michel et al. [23] obtained in Xenon implanted UO2 samples. Indeed they observed 1 nm sized bubbles at 600 ░C, which could reach 3 nm at 1400 ░C. Either conditions of the Neumann type for which the surface is impermeable which means that the Xenon flux is equal to zero and can be expressed by Eq. (2). {dC}/{dx}|surface=0 Or conditions of the Dirichlet type with a constant Xenon concentration at the surface expressed by Eq. (3). C(0,t)=constant We chose Neumann conditions since we observed a slight increase of Xenon concentration at the surface for the profiles of the samples irradiated at 600 ░C and at 1000 ░C. In order to simulate the evolution of the Xenon concentration profiles, as-implanted profiles were first fitted with Gaussian shaped curves. The evolution of these curves was then simulated by using the one dimensional finite difference method. Therefore, the total depth profile was discretized into 1.5 nm slices. D, v, k parameters were thus deduced from successive iterations until the final profile is correctly fitted. It is important to keep in mind that each migration mechanism induces a particular modification of the profile shape: a broadening is characteristic of a diffusion process, a profile shift is significant of a transport process and an area decrease means a release mechanism. Consequently, only one set of parameters can allow a correct fit of the final profile
Modelling Sublimation of Carbon Dioxide
ERIC Educational Resources Information Center
Winkel, Brian
In this article, the author reports results in their efforts to model sublimation of carbon dioxide and the associated kinetics order and parameter estimation issues in their model. They have offered the reader two sets of data and several approaches to determine the rate of sublimation of a piece of solid dry ice. They presented several modelsģ
Homogeneous hydrogenation of carbon dioxide
Philip G. Jessop; Takao. Ikariya; Ryoji. Noyori
Carbon dioxide (COŌ) is of the greatest interest as a CŌü feedstock because of the vast amounts of carbon which exist in this form and because of the low cost of bulk COŌ. Currently, toxic carbon monoxide, the main competitor for many processes, is used in industry instead because COŌ is perceived to be less reactive and its efficient catalytic
This map shows industrial plants which emit 100 tons/year or more of sulfur dioxide (SO2) in Alaska. The SO2 sources are plotted on a background map of cities and county boundaries. Data Sources: SO2 Sites: U.S. EPA AIRS System, County Outlines: 1990 Census Tiger Line Files 1:1...
Redox Reactions of Metalloporphyrins and their Role in Catalyzed Reduction of Carbon Dioxide
Neta, P.
Pulse radiolysis and laser photolysis are used to study redox processes of metalloporphyrins and related complexes in order to evaluate these light absorbing molecules as sensitizers and intermediates in solar energy conversion schemes. The main thrust of the current studies is to investigate the role of reduced metalloporphyrins as intermediates in the catalyzed reduction of carbon dioxide. Studies involve cobalt and iron porphyrins, phthalocyanines, corroles, and corrins as homogeneous catalysts for reduction of carbon dioxide in solution. The main aim is to understand the mechanisms of these photochemical schemes in order to facilitate their potential utilization.
Atlas of high resolution infrared spectra of carbon dioxide
NASA Technical Reports Server (NTRS)
Rinsland, C. P.; Benner, D. C.; Devi, V. M.; Ferry, P. S.; Sutton, C. H.; Richardson, D. J.
An atlas of long-path room-temperature absorption spectra of carbon dioxide is presented for the spectral intervals 1830-2100 cm, 2395-2680 cm, and 3140-3235 cm. The spectral data were recorded at high signal to noise with the 0.01 cm resolution Fourier transform interferometer. The spectra were obtained with pressures between 1 and 10 Torr of CO2 and with total paths between 24 and 384 meters. A compilation of the measured line positions and the assignments derived from the analysis are presented. Of the 3336 lines in the atlas, 94 percent were identified as CO2 lines or as residual lines H2O and CO. Calculated positions are presented for the carbon dioxide lines; a total of 52 bands of C-12O2-16, C-13O2-16, C-12O-16O-18, C-12O-16O-17, and C-13O-16O18 were identified. The weakest carbon dioxide lines marked in the atlas have intensities of approximately 0.5 x 10 to the negative 26th power cm/molecule at room temperature.
A liquid xenon imaging telescope for 1-30 MeV gamma-ray astrophysics
NASA Technical Reports Server (NTRS)
Aprile, Elena; Mukherjee, Reshmi; Suzuki, Masayo
A study of the primary scintillation light in liquid xenon excited by 241 Am alpha particles and 207 Bi internal conversion electrons are discussed. The time dependence and the intensity of the light at different field strengths have been measured with a specifically designed chamber, equipped with a CaF sub 2 light transmitting window coupled to a UV sensitive PMT. The time correlation between the fast light signal and the charge signal shows that the scintillation signals produced in liquid xenon by ionizing particles provides an ideal trigger in a Time Projection type LXe detector aiming at full imaging of complex gamma-ray events. Researchers also started Monte Carlo calculations to establish the performance of a LXe imaging telescope for high energy gamma-rays.
SAUNAŚa system for automatic sampling, processing, and analysis of radioactive xenon
NASA Astrophysics Data System (ADS)
Ringbom, A.; Larson, T.; Axelsson, A.; Elmgren, K.; Johansson, C.
A system for automatic sampling, processing, and analysis of atmospheric radioxenon has been developed. From an air sample of about 7 m3 collected during 12 h, 0.5 cm3 of xenon is extracted, and the atmospheric activities from the four xenon isotopes 133Xe, 135Xe, 131mXe, and 133mXe are determined with a beta-gamma coincidence technique. The collection is performed using activated charcoal and molecular sieves at ambient temperature. The sample preparation and quantification are performed using preparative gas chromatography. The system was tested under routine conditions for a 5-month period, with average minimum detectable concentrations below 1 mBq/ m3 for all four isotopes.
Development and Characterization of a Multi-APD Xenon Electroluminescence TPC
Lux, T; Ballester, O; Bordoni, S; Gil-Botella, I; Hamer, N; Illa, J; Ma±as, G Jover; Martin-Mari, C; Palomares, C; Rico, J; Sanchez, F; Santorelli, R; Verdugo, A
The performance of an electroluminescence (EL) time projection chamber (TPC) with a multi avalanche photodiode (APD) readout was studied in pure xenon at 3.8 bar. Intercalibration and reconstruction methods were developed and applied to the data yielding energy resolutions as good as 5.3$+-$0.1 % FWHM for 59.5 keV gammas from 241-Am. The result was verified with a Monte Carlo (MC) based on Geant4 and Penelope predicting 5.2 % FWHM for the used setup. Point resolutions of about 0.5 mm were obtained by a pitch of 15 mm between the APDs. The results show that a multi-APD readout is a competitive technology for EL detectors filled with pure xenon with possible applications as Compton Cameras.
Search for solar axions in XMASS, a large liquid-xenon detector
K. Abe; K. Hieda; K. Hiraide; S. Hirano; Y. Kishimoto; K. Kobayashi; S. Moriyama; K. Nakagawa; M. Nakahata; H. Ogawa; N. Oka; H. Sekiya; A. Shinozaki Y. Suzuki; A. Takeda; O. Takachio; K. Ueshima; D. Umemoto; M. Yamashita; B. S. Yang; S. Tasaka; J. Liu; K. Martens; K. Hosokawa; K. Miuchi; A. Murata; Y. Onishi; Y. Otsuka; Y. Takeuchi; Y. H. Kim; K. B. Lee; M. K. Lee; J. S. Lee; Y. Fukuda; Y. Itow; K. Masuda; Y. Nishitani; H. Takiya; H. Uchida; N. Y. Kim; Y. D. Kim; F. Kusaba; D. Motoki; K. Nishijima; K. Fujii; I. Murayama; S. Nakamura
XMASS, a low-background, large liquid-xenon detector, was used to search for solar axions that would be produced by bremsstrahlung and Compton effects in the Sun. With an exposure of 5.6ton days of liquid xenon, the model-independent limit on the coupling for mass $\\ll$ 1keV is $|g_{aee}|< 5.4\\times 10^{-11}$ (90% C.L.), which is a factor of two stronger than the existing experimental limit. The bounds on the axion masses for the DFSZ and KSVZ axion models are 1.9 and 250eV, respectively. In the mass range of 10-40keV, this study produced the most stringent limit, which is better than that previously derived from astrophysical arguments regarding the Sun to date.
Haruyama, T.; Kasami, K. [KEK, High Energy Accelerator Research Organization 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Hisamitsu, Y.; Iwamoto, T.; Mihara, S.; Mori, T.; Nishiguchi, H.; Otani, W.; Sawada, R.; Uchiyama, Y. [ICEPP, University of Tokyo 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Nishitani, T. [Iwatani Industrial Gases Corp. Moriyama, Shiga (Japan)
The {mu}-particle rare decay physics experiment, the MU-E-GAMMA (MEG) experiment, will soon be operational at the Paul Scherrer Institute in Zurich. To achieve the extremely high sensitivity required to detect gamma rays, 800 L of liquid xenon is used as the medium in the calorimeter, viewed by 830 photomultiplier tubes (PMT) immersed in it. The required liquid xenon purity is of the order of ppb of water, and is obtained by using a cryogenic centrifugal pump and cold molecular sieves. The heat load of the calorimeter at 165 K is to be approximately 120 W, which is removed by a pulse-tube cryocooler developed at KEK and built by Iwatani Industrial Gas Corp., with a cooling power of about 200 W at 165 K. The cryogenic system is also equipped with a 1000-L dewar. This paper describes the results of an initial performance test of each cryogenic component.
Absolute number of photons produced by alpha-particles in liquid and gaseous xenon
NASA Astrophysics Data System (ADS)
Miyajima, Mitsuhiro; Sasaki, Shinichi; Shibamura, Eido
The Ws which is defined as an average energy expended per scintillation photon, was found to be 16.3 ▒ 0.3 eV for alpha-particles in liquid xenon, and 49.6 ▒ 1.1 eV in gaseous xenon, respectively. These results followed from the number of photoelectrons measured with a VUV sensitive photomultiplier tube, which was used as a photodiode. The number of photoelectrons from the photomultiplier photocathode was measured absolutely with a well calibrated charge sensitive amplifier system as a function of distance between the alpha-source and the photomultiplier photocathode. The detection geometries included both reflective and nonreflective walls. The data were well fitted to corresponding curves obtained with a Monte Carlo simulation, and yielded the total number of scintillation photons.
Performance of a Liquid Xenon Calorimeter Cryogenic System for the MEG Experiment
NASA Astrophysics Data System (ADS)
Haruyama, T.; Kasami, K.; Hisamitsu, Y.; Iwamoto, T.; Mihara, S.; Mori, T.; Nishiguchi, H.; Otani, W.; Sawada, R.; Uchiyama, Y.; Nishitani, T.
The ?-particle rare decay physics experiment, the MU-E-GAMMA (MEG) experiment, will soon be operational at the Paul Scherrer Institute in Zurich. To achieve the extremely high sensitivity required to detect gamma rays, 800 L of liquid xenon is used as the medium in the calorimeter, viewed by 830 photomultiplier tubes (PMT) immersed in it. The required liquid xenon purity is of the order of ppb of water, and is obtained by using a cryogenic centrifugal pump and cold molecular sieves. The heat load of the calorimeter at 165 K is to be approximately 120 W, which is removed by a pulse-tube cryocooler developed at KEK and built by Iwatani Industrial Gas Corp., with a cooling power of about 200 W at 165 K. The cryogenic system is also equipped with a 1000-L dewar. This paper describes the results of an initial performance test of each cryogenic component.
Numerical simulation of the Zeeman effect in neutral xenon from NIR diode-laser spectroscopy
Ngom, Baielo B.; Smith, Timothy B.; Huang Wensheng; Gallimore, Alec D. [Department of Aerospace Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States)
We present a numerical method for simulating neutral xenon absorption spectra from diode-laser spectroscopy of the Zeeman-split 6S{sup '}[1/2]{yields}6P{sup '}[1/2] line at 834.682 nm-air in a galvatron's plasma. To simulate the spectrum, we apply a Voigt profile to a spectrum of {sigma}-transition lines of even- and odd-numbered isotopes computed from anomalous Zeeman and nonlinear Zeeman hyperfine structure theories, respectively. Simulated spectra agree well with Zeeman-split spectra measured from 30 to 300 G. A commercial nonlinear least-squares solver (LSQNONLIN) returns field strengths and translational plasma kinetic temperatures that minimize the error between simulated and experimental spectra. This work is a preamble to computing magnetic field topology and the speed distribution of neutral xenon particles in the plume of a Hall thruster from diode laser-induced fluorescence.
Electron-impact excitation cross sections from the xenon J=2 metastable level
Jung, R.O.; Boffard, John B.; Anderson, L.W.; Lin, Chun C. [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States)
Cross sections for electron-impact excitation from the 5p{sup 5}6s J=2 metastable level of xenon to the lowest six levels of the 5p{sup 5}6p configuration have been measured. The cross sections generally have very large magnitudes (10{sup -15} cm{sup 2}) and scale with the corresponding optical oscillator strengths. The substantial variations observed in the energy dependence of the cross sections for the six levels can also be related to the optical oscillator strengths. Cross sections for excitation out of the J=2 metastable level into the upper four levels of the 5p{sup 5}6p configuration are much smaller. The large disparity in cross sections between the upper and lower groups is explained in terms of the electronic structure of the excited states of xenon.
Near-infrared scintillation of xenon by {sup 63}Ni beta decay
Yoshimizu, Norimasa; Lal, Amit; Pollock, Clifford R. [SonicMEMS Laboratory, Department of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853 (United States)
The near-infrared scintillation of xenon gas by the {beta} decay of 37 MBq of {sup 63}Ni was studied, in the interest of its use in integrated devices for applications such as optical beacons and wavelength calibration. The emission was imaged and analyzed using Spencer's theory of electron penetration using xenon scattering cross sections derived from Thomas-Fermi theory. The total emission was approximately 2x10{sup 5} photons/s at 20 kPa and 1x10{sup 5} photons/s at 100 kPa. Spectral data show three dominant peaks at 823, 828, and 882 nm as well as the formation of metastable states.
Study of high-pressure xenon discharges with metal-halide additives
NASA Astrophysics Data System (ADS)
Wendt, Martin; Schneidenbach, Hartmut; Kettlitz, Manfred; Sieg, Michael; Marco, Redwitz
The plasma column of atmospheric pressure wall-stabilized discharges in xenon with metal-halide additives has been studied theoretically considering an axially homogeneous arc column. The energy balance with radiation transport has been solved numerically with the assumption of local thermodynamic equilibrium. The convection has been neglected and a pressure constant in time and space has been assumed. The transport properties have been calculated in higher-order Chapman-Cowling approximation with recently published electron-atom collision cross-sections for xenon. The resulting electrical characteristics, temperature profiles, radiation intensities and fluxes for Xe-discharges with and without admixtures of NaI, TlI and rare-earth iodides are discussed. The analysis is done for dc, ac and pulsed discharges in a current range between 1 and 20 amperes. Temperature profiles and radiation intensities are compared with measurements.
Development and characterization of a multi-APD xenon electroluminescence TPC
NASA Astrophysics Data System (ADS)
Lux, T.; Garcia Soto, A.; Ballester, O.; Bordoni, S.; Gil-Botella, I.; Hamer, N.; Illa, J.; Jover Ma±as, G.; MartĒn-MarĒ, C.; Palomares, C.; Rico, J.; Sanchez, F.; Santorelli, R.; Verdugo, A.
The performance of an electroluminescence (EL) Time Projection Chamber (TPC) with a multi avalanche photodiode (APD) readout was studied in pure xenon at 3.8 bar. Intercalibration and reconstruction methods were developed and applied to the data yielding energy resolutions as good as 5.3▒ 0.1% FWHM for 59.5 keV gammas from 241Am. This result was reproduced with a Monte Carlo (MC) based on Geant4 and Penelope which predicted 5.2% FWHM for the used setup. Point resolutions of ? 0.5 mm were obtained with a pitch of 15 mm between the APDs. These results show that multi-APD readout is a competitive technology for EL detectors filled with pure xenon.
NASA Astrophysics Data System (ADS)
Patterson, David
Recent years have seen an enormous growth of rich physics performed with cold samples of diatomic molecules, as well as impressive demonstrations of techniques to cool polyatomic molecules containing several (~7) atoms. Here we present progress in our methods to produce cold, dense, slow moving samples of molecules of many (>20) atoms from cryogenic buffer gas cells. The ability to produce cold, slow samples of such molecules opens up a host of potential research paths, including ultra-high precision spectroscopy, searches for changes in fundamental constants, and a rich set of experiments in the complex, low-decoherence Hilbert space spanned by the rotational and hyperfine states of such molecules. As an early demonstration of the rich physics offered in such systems, recent results demonstrating chirality-sensitive microwave spectroscopy of cold molecules will be presented.
Amidothionophosphates: Novel Antioxidant Molecules
Oren Tirosh; Yehoshua Katzhendler; Yechezkel Barenholz; Isaac Ginsburg; Ron Kohen
This work describes the synthesis and characterization of a new family of antioxidants. The molecules have the same active group, but different oil-to-water and octanol-to-water partition coefficients due to different substituents. Three new molecules were synthesized based on the chemical structure of the primary amide attached to a thiophosphate group forming an amidothionophosphate. The amidothionophosphate molecules were exposed to the
High resoluton spectrum of xenon ions at 13.4 nm
Sergei Churilov; Sergey Churilov; Joseph Reader
We have obtained high-resolution spectra of Xe ions in the region of prime importance for the development of extreme ultraviolet (EUV) projection lithography. The spectra were produced by injecting xenon gas into the gap of a low-inductance vacuum spark through an axial hole in a carbon cathode. The spectra were photographed on a 10.7-m grazing-incidence vacuum spectrograph having a 1200
Performance of the light trigger system in the liquid xenon ?-ray imaging telescope LXeGRIT
Uwe Oberlack; Elena Aprile; Alessandro Curioni; Karl-Ludwig Giboni
LXeGRIT is a balloon-borne Compton telescope for MeV ?-ray astrophysics, based on a liquid xenon time projection chamber with charge and light readout. The energy and direction of an incident ?-ray are reconstructed from the three-dimensional locations and energy deposits of individual interactions taking place in the homogeneous detector volume. While the charge signals provide energy information and X-Y-positions, the
Satellite structure of the xenon valence shell by electron-momentum spectroscopy
S. Braidwood; M. Brunger; Erich Weigold
Momentum distributions and spectroscopic factors are obtained in a high-resolution electron-momentum spectroscopy study of xenon at 1000 eV. The shapes and relative magnitudes of the momentum profiles are in excellent agreement with distorted-wave (DW) impulse approximations using the target Dirac-Fock (DF) approximation. The DWDF approximation accurately describes the relative magnitudes of the 5p and 5s manifold cross sections as well
Low-Temperature Specific Heats of Solid Neon and Solid Xenon
H. Fenichel; B. Serin
The specific heats of solid neon and xenon have been measured in the temperature range 1.5 to 24░K, using a calorimeter with a mechanical heat switch. Carbon resistance thermometers were calibrated against a gas thermometer and the helium vapor-pressure scale. The results were analyzed to obtain the temperature dependence of the Debye temperature, Thetac(T). In the range 0.020<~TTheta0c<~0.505, the data
Neutron capture cross-sections of stable xenon isotopes and their application in stellar nucleosynthesis
H. Beer; F. Kaeppeler; G. Reffo; G. Venturini
The neutron capture cross-sections of124, 132, 134Xe have been measured by the activation technique at 25 keV neutron energy. These data were supplemented by calculated capture cross-sections for128, 129, 130, 131Xe via the statistical model. The complete set of capture cross-sections obtained in this way served to determine the solar xenon abundance throughs-process systematics and to study a variety of
Bubble dynamics and sonoluminescence from helium or xenon in mercury and water.
Yasui, Kyuichi; Kato, Kazumi
Numerical simulations of bubble pulsation and sonoluminescence (SL) have been performed for helium or xenon bubbles in mercury and water under the experimental conditions of Futakawa et al. [M. Futakawa, T. Naoe, and M. Kawai, in Nonlinear Acoustics-Fundamentals and Applications: 18th International Symposium on Nonlinear Acoustics (ISNA 18), AIP Conf. Proc. No. 1022, edited by B. O. Enflo, C. M. Hedberg, and L. Kari (AIP, New York, 2008), p. 197]. The results of the numerical simulations have revealed that the bubble expansion is much larger in water than in mercury mainly because the density of water is one order of magnitude smaller than that of mercury. The SL intensity is higher in water than that in mercury although the maximum bubble temperature is lower. This is caused by the much larger amount of vapor inside a bubble as the saturated vapor pressure of water is four orders of magnitude larger than that of mercury at room temperature. The SL intensity from xenon is much larger than that from helium due both to lower ionization potential and higher bubble temperature due to lower thermal conductivity. The instantaneous SL power may be as large as 200 W from xenon in water. The maximum temperature inside a xenon bubble in mercury may be as high as about 80?000ĀK. It is suggested that the maximum pressure in mercury due to shock waves emitted from bubbles increases as the SL intensity increases, although they are not simply correlated in water because the amount of water vapor trapped inside a bubble influences the SL intensity in a complex way. PMID:23031026
Precision measurement of the metastable 6s [3\\/2]2 lifetime in xenon
M. Walhout; A. Witte; S. L. Rolston
Using a magneto-optical trap to isolate an isotopically pure sample of xenon, we determine the metastable 6s [3\\/2]2 state lifetime by measuring the rate of VUV emisson due to magnetic quadrupole decay. We find lifetimes of 42.9(9) s and 42.4(13) s for 132Xe and 136Xe, respectively (1sigma uncertainties). These values are less than half the theoretical predictions. We also find
Electron impact excitation of xenon from the metastable state to the excited states
Jun Jiang; Chen-Zhong Dong; Lu-You Xie; Xiao-Xin Zhou; Jian-Guo Wang
The electron impact excitation cross sections from the lowest metastable state 5p56sJ = 2 to the six lowest excited states of the 5p56p configuration of xenon are calculated systematically by using the fully relativistic distorted wave method. In order to discuss the effects of target state descriptions on the electron impact excitation cross sections, two correlation models are used to
Effects of Lasering upon the Electron Gas and Excited-State Populations in Xenon Discharges
R. J. Freiberg; L. A. Weaver
Spatially resolved electron density measurements are reported for dc-excited xenon laser discharges over a pressure range of 12.5 to 25.5 mTorr. Due to electrophoretic effects within the closed capillary tube, anode-directed gradients in electron density are established which affect local population inversions. The influence of lasering upon these discharges is investigated experimentally by using a 3.51-? (5d33?6p22) laser whose optical
Ultralow-power nonlinear optics using tapered optical fibers in metastable xenon
T. B. Pittman; D. E. Jones; J. D. Franson
We demonstrate nanowatt-level saturated absorption using a sub-wavelength diameter tapered optical fiber (TOF) suspended in a gas of metastable xenon atoms. This ultralow-power nonlinearity is enabled by a small optical mode area propagating over a relatively long distance through the Xe gas. The use of inert noble gasses in these kinds of TOF experiments may offer practical advantages over the use of reactive alkali vapors such as rubidium.
Ultralow-power nonlinear optics using tapered optical fibers in metastable xenon
Pittman, T B; Franson, J D
We demonstrate nanowatt-level saturated absorption using a sub-wavelength diameter tapered optical fiber (TOF) suspended in a gas of metastable xenon atoms. This ultralow-power nonlinearity is enabled by a small optical mode area propagating over a relatively long distance through the Xe gas. The use of inert noble gasses in these kinds of TOF experiments may offer practical advantages over the use of reactive alkali vapors such as rubidium.
Electron-impact excitation cross sections from the xenon J=2 metastable level
R. O. Jung; John B. Boffard; L. W. Anderson; Chun C. Lin
Cross sections for electron-impact excitation from the 5pŌüĄ6s J=2 metastable level of xenon to the lowest six levels of the 5pŌüĄ6p configuration have been measured. The cross sections generally have very large magnitudes (10Ōü╗┬╣ŌüĄ cm┬▓) and scale with the corresponding optical oscillator strengths. The substantial variations observed in the energy dependence of the cross sections for the six levels can
High-resolution electron impact excitation functions of metastable states of neon, argon, krypton and xenon
S J Buckman; P Hammond; G C King; F H Read
Electron impact excitation of the lowest-lying metastable states of neon, argon, krypton and xenon have been studied as a function of incident electron energy over the range from threshold to the 2P1\\/2 ionisation potential and at an energy resolution of 20 meV or better. A wealth of structure is observed. Several of the features are very narrow and are coincident
Chemical Applications of Metastable Argon Atoms. III. Production of Krypton and Xenon Metastable Atoms
D. H. Stedman; D. W. SETSERt
An inexpensive experimental technique has been developed for the production of argon, krypton, and xenon metastable atoms using a discharge-flow system. The reactions of these metastable atoms with N2, CO, and N2O were investigated in the pressure range 0.3¢10 torr, and the emission spectra resulting from the reactions were identified. These spectra gave information about the collision event and also
Electron-impact excitation cross sections from the xenon J=2 metastable level
R. O. Jung; John B. Boffard; L. W. Anderson; Chun C. Lin
Cross sections for electron-impact excitation from the 5p65s J=2 metastable level of xenon to the lowest six levels of the 5p65p configuration have been measured. The cross sections generally have very large magnitudes (10-15cm2) and scale with the corresponding optical oscillator strengths. The substantial variations observed in the energy dependence of the cross sections for the six levels can also
Spontaneous Fission-Neutron Fission Xenon: A New Technique for Dating Geological Events
Albert Teitsma; W. B. Clarke; C. J. Allegre
A method for dating geological samples which uses fission product xenon in a manner similar to the use of radiogenic argon in the 40Ar-39 Ar technique has been developed. The results of stepwise heating experiments for a zircon from the Ahaggar region in the Sahara are compared to the geochronology determined by the rubidiumstrontium, uranium-thorium-lead, and potassium-argon dating methods.
Spontaneous fission--neutron fission xenon: a new technique for dating geological events
A. Teitsma; W. B. Clarke; C. J. Allegre
A method for dating geological samples which uses fission product xenon ; in a manner similar to the use of radiogenic argon in the Ōü┤┬░Ar--┬│Ōü╣Ar ; technique has been developed. The results of stepwise heating experiments for a ; zircon from the Ahaggar region in the Sahara are compared to the geochronology ; determined by the rubidium--strontium, uranium--thorium--lead, and potassium--;
A new coplanar-grid high-pressure xenon gamma-ray spectrometer
Scott D. Kiff; Zhong He; Gary C. Tepper
High-pressure xenon (HPXe) gas is a desirable radiation detection medium for many reasons, including its large atomic number, high density, low mean energy to produce an electron-ion pair, and the ability to produce devices with large detection volumes. While past work in HPXe has produced relatively successful detectors with energy resolution at 662 keV as good as approximately 2% FWHM,
Photochemistry of interstellar molecules
NASA Technical Reports Server (NTRS)
Stief, L. J.
The role of photochemistry in determining the lifetime of interstellar molecules is considered. The probability of photodecomposition depends on three factors, including the absorption cross section, the quantum yield or probability of dissociation following photon absorption, and the interstellar radiation field. A more detailed discussion of the photochemistry of five molecules is presented, giving attention to carbonyl sulfide, methyl acetylene, nitric oxide, acetylene, and benzene. Lifetimes of interstellar molecules in unobscured regions are in the range from 5 to 100 years. It is concluded that polyatomic molecules can exist only in dense clouds which protect them from the full interstellar radiation field.
Applications of controlled-flow laser-polarized xenon gas to porous and granular media study
R. W. Mair; R. Wang; M. S. Rosen; D. Candela; D. G. Cory; R. L. Walsworth
We report initial NMR studies of continuous flow laser-polarized xenon gas, both in unrestricted tubing, and in a model porous media. The study uses Pulsed Gradient Spin Echo-based techniques in the gas-phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients. Pulsed Gradient Echo studies of continuous flow laser-polarized xenon gas in unrestricted tubing indicate clear diffraction minima resulting from a wide distribution of velocities in the flow field. The maximum velocity experienced in the flow can be calculated from this minimum, and is seen to agree with the information from the complete velocity spectrum, or motion propagator, as well as previously published images. The susceptibility of gas flows to parameters such as gas mixture content, and hence viscosity, are observed in experiments aimed at identifying clear structural features from echo attenuation plots of gas flow in porous media. Gas-phase NMR scattering, or position correlation flow-diffraction, previously clearly seen in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack is not so clear in experiments using a different gas mixture. A propagator analysis shows most gas in the sample remains close to static, while a small portion moves through a presumably near-unimpeded path at high velocities.
Isotopic Enrichment of Boron in the Sputtering of Boron Nitride with Xenon Ions
NASA Technical Reports Server (NTRS)
Ray, P. K.; Shutthanandan, V.
An experimental study is described to measure the isotopic enrichment of boron. Xenon ions from 100 eV to 1.5 keV were used to sputter a boron nitride target. An ion gun was used to generate the ion beam. The ion current density at the target surface was approximately 30 microA/sq cm. Xenon ions impinged on the target surface at 50 deg angle to the surface normal. Since boron nitride is an insulator, a flood electron gun was used in our experiments to neutralize the positive charge buildup on the target surface. The sputtered secondary ions of boron were detected by a quadrupole mass spectrometer. The spectrometer entrance aperture was located perpendicular to the ion beam direction and 10 mm away from the target surface. The secondary ion flux was observed to be enriched in the heavy isotopes at lower ion energies. The proportion of heavy isotopes in the sputtered secondary ion flux was found to decrease with increasing primary ion energy from 100 to 350 eV. Beyond 350 eV, light isotopes were sputtered preferentially. The light isotope enrichment factor was observed to reach an asymptotic value of 1.27 at 1.5 keV. This trend is similar to that of the isotopic enrichment observed earlier when copper was sputtered with xenon ions in the same energy range.
Energy Resolution Optimization of the Yale ``PIXeY'' Two-Phase Xenon Detector
NASA Astrophysics Data System (ADS)
Destefano, Nicholas; Gai, Moshe; McKinsey, Daniel; Bernard, Ethan; Wahl, Christopher; Edwards, Blair; Horn, Markus; Larsen, Nicole; Tennyson, Brian
PIXeY (Particle Identification in Xenon at Yale) is a two-phase (liquid/gas) xenon prototype detector with 3-kg active mass. The two-phase xenon technology has many applications that include gamma-ray imaging, neutrinoless double beta decay searches, dark matter searches, and 4 ? gamma-ray detectors for studies in Nuclear Astrophysics. PIXeY was built to optimize energy resolution, position resolution, and gamma/neutron discrimination. A number of fiducial cuts and correction factors were used to optimize energy resolution. The light and charge signals were corrected by the spatial location of the event within the detector, taking into account effects such as the electron lifetime, geometric light collection, and any other position and field-dependent variations. The energy spectrum of various sources was studied by varying the cathode, anode, and PMT voltages. Optimal configurations for the drift and scintillation fields were found for energies ranging from 41.5 keV (83m Kr) to 2.61 MeV (228 Th), resolving the light signal and keeping the charge signal unsaturated. In addition, after optimizing for the energy resolution of Cs-137 (662 keV) the value obtained was 1.4% ?/E. Once the energy resolution studies have concluded, PIXeY will serve as a platform for future improvements, including multiple optical volumes and single-wire readout for R&D on gamma-ray imaging.
Barium Tagging n Solid Xenon for nEXO Neutrinoless Double Beta Decay
NASA Astrophysics Data System (ADS)
Walton, Tim; Chambers, Chris; Craycraft, Adam; Fairbank, William; nEXO Collaboration
nEXO is a next-generation experiment designed to search for neutrinoless double beta decay of the isotope Xe136 in a liquid xenon time projection chamber. Positive observation of this decay would determine the nature of the neutrino to be a Majorana particle. Since the daughter of this decay is barium (Ba136), detecting the presence of Ba136 at a decay site (called ``barium tagging'') would provide strong rejection of backgrounds in the search for this decay. This would involve detecting a single barium ion from within a macroscopic volume of liquid xenon. This technique may be available for a second phase of the nEXO detector and sensitivity beyond the inverted hierarchy to neutrino oscillations. Several methods of barium tagging are being explored by the nEXO collaboration, but here we present a method of trapping the barium ion/atom (it may neutralize) in solid xenon (SXe) at the end of a cold probe, and then detecting the ion/atom by its fluorescence in the SXe. Our group at CSU has been studying the fluorescence of Ba in SXe by laser excitation, in order to ultimately detect a single Ba +/Ba in a SXe sample. We present studies of fluorescence signals, as well as recent results on imaging small numbers of Ba atoms in SXe, in a focused laser region. This work is supported by grants from the National Science Foundation and the Department of Energy.
The Spectra of Solid Xenon Luminescence Excited by the Bulk Electric Discharge.
NASA Astrophysics Data System (ADS)
Gordon, E. B.; Sizov, V. D.; Matyushenko, V. I.
The spectra of solid xenon bulk luminescence initiated by electric discharge were observed for the first time. Along with powerful excitonic resonance emission in VUV the spectrum contained numerous strong lines in UV and visible originated from the transitions between excited states of the matrix. The main peculiarity in these UV and visible spectra was the complete absence of lines belonged to neutral excited species - atom-like Xe^{*} and molecular-like Xe_{2}^{*} excitons, although these lines are usually very strong in xenon gas discharges. The lines of molecular ions Xe_{2}^{+} were absent as well. The most lines were identified as atomic ion Xe^{+} transitions which are unobservable in relatively dense gas due to their fast conversion into Xe_{2}^{+}. The Xe^{+} lines positions were slightly (0.1 - 0.3 nm) shifted in relation to their positions in the gas phase and their shapes in many cases were rather distorted. The mechanism of solid xenon excitation and ionization by the fast electrons drifted in electric field has been proposed on the basis of experimental data analysis. E.B.Gordon, V.I. Matyushenko, V.D.Sizov, and V.B.Fokin, Optics and Spectroscopy 34, 786 (2009).
Measurements of the equations of state and spectrum of nonideal xenon plasma under shock compression.
Zheng, J; Gu, Y J; Chen, Z Y; Chen, Q F
Experimental equations of state on generation of nonideal xenon plasma by intense shock wave compression was presented in the ranges of pressure of 2-16 GPa and temperature of 31-50 kK, and the xenon plasma with the nonideal coupling parameter ? range from 0.6-2.1 was generated. The shock wave was produced using the flyer plate impact and accelerated up to ?6?km/s with a two-stage light gas gun. Gaseous specimens were shocked from two initial pressures of 0.80 and 4.72 MPa at room temperature. Time-resolved spectral radiation histories were recorded by using a multiwavelength channel pyrometer. The transient spectra with the wavelength range of 460-700 nm were recorded by using a spectrometer to evaluate the shock temperature. Shock velocity was measured and particle velocity was determined by the impedance matching methods. The equations of state of xenon plasma and ionization degree have been discussed in terms of the self-consistent fluid variational theory. PMID:20866920
Radiation properties of low-pressure discharges in rare-gas mixtures containing xenon
NASA Astrophysics Data System (ADS)
Gortchakov, S.; Uhrlandt, D.
Glow discharges in mixtures of xenon with other rare gases can be used as alternatives to mercury-containing UV/VUV radiation sources and fluorescent lamps. The advantages of such sources are environmental compatibility, instant light output after switching on, and less pronounced temperature dependence. However, the optimum choice of the gas composition with respect to the maximum efficiency and power of the xenon resonance radiation as well as to a stable discharge operation still remains an open question. The dc cylindrical positive column of low-pressure discharges in rare-gas mixtures is studied by a detailed self-consistent kinetic description. The influence of the buffer gases helium, neon and argon as well as the appropriate choice of the xenon admixture are revealed by analysing different triple-gas mixtures. Changes in the global power budget and the radial structure of the plasma are discussed. A mixture of He and about 1-2% Xe arises as an optimum composition.
Distribution of Hyperpolarized Xenon in the Brain Following Sensory Stimulation: Preliminary MRI Findings
Mazzanti, Mary L.; Walvick, Ronn P.; Zhou, Xin; Sun, Yanping; Shah, Niral; Mansour, Joey; Gereige, Jessica; Albert, Mitchell S.
In hyperpolarized xenon magnetic resonance imaging (HP 129Xe MRI), the inhaled spin-1/2 isotope of xenon gas is used to generate the MR signal. Because hyperpolarized xenon is an MR signal source with properties very different from those generated from water-protons, HP 129Xe MRI may yield structural and functional information not detectable by conventional proton-based MRI methods. Here we demonstrate the differential distribution of HP 129Xe in the cerebral cortex of the rat following a pain stimulus evoked in the animal's forepaw. Areas of higher HP 129Xe signal corresponded to those areas previously demonstrated by conventional functional MRI (fMRI) methods as being activated by a forepaw pain stimulus. The percent increase in HP 129Xe signal over baseline was 13¢28%, and was detectable with a single set of pre and post stimulus images. Recent innovations in the production of highly polarized 129Xe should make feasible the emergence of HP 129Xe MRI as a viable adjunct method to conventional MRI for the study of brain function and disease. PMID:21789173
1-D fluid simulations of a helium-xenon filled AC plasma display panel
Veerasingam, R.; Campbell, R.B.; McGrath, R.T. [Sandia National Labs., Albuquerque, NM (United States)
A one dimensional multi-species fluid model has been developed to analyze the operation of an ac plasma display panel (AC PDP) that is filled with a helium-xenon Penning mixture. The AC PDP is a promising candidate in the flat panel display industry especially for information displays having large screen areas. A PDP consists of a matrix of gas cells operating at pressures of several hundred Torr. In each cell a micro discharge is initiated using special driving circuitry that typically have address, sustain and erase pulse wave forms. The AC PDP has a memory characteristic which eliminates the need for a refresh pulse once a cell has been addressed. To ensure that a single sustain pulse can maintain a cell in the ON or OFF state, a large memory margin is essential. The model can be used for parametric studies to observe the effects of variations in pressure, gap width, and percentage of xenon on the first on and first off voltages, bi-stable margin and on xenon metastable and dimer populations. The authors present results of such parametric variations and comparisons with experiments.
Measuring Neutron Response using Data and Monte Carlo Simulation in Xenon100
NASA Astrophysics Data System (ADS)
Scovell, Paul
A relative scintillation yield (Leff) above 5.5 keVr (nuclear recoil energy) is determined using data from an exposure of XENON100 to neutrons from an Americium-Beryilium (AmBe) source. The technique requires a signal in the XENON100 Time Projection Chamber (TPC) to be in coincidence with a signal in the active liquid xenon (LXe) veto such that efficiency to low energy nuclear recoils is not compromised by the requirement of a signal in 2 or more photomultiplier tubes (PMTs). The Leff is then deduced (independently of any Monte Carlo simulation) through the comparison of the scintillation and ionization signals recorded. The calculated Leff is in excellent agreement with recent direct and indirect measurements. Comparison of the detector response to AmBe neutrons with an equivalent Monte Carlo generated spectrum is also performed. With the measured detector efficiency and a global fit to all measured values of Leff, agreement between data and Monte Carlo down to a low photoelectron level is obtained.
Kinetics of the processes, plasma parameters, and output characteristics of a UV emitter operating on XeI molecules and iodine molecules and atoms
Shuaibov, A. K.; Grabovaya, I. A.; Minya, A. I.; Homoki, Z. T. [Uzhgorod National University (Ukraine); Kalyuzhnaya, A. G.; Shchedrin, A. I. [National Academy of Sciences of Ukraine, Institute of Physics (Ukraine)
A kinetic model of the processes occurring in the plasma of a high-power low-pressure gas-discharge lamp is presented, and the output characteristics of the lamp are described. The lamp is excited by a longitudinal glow discharge and emits the I{sub 2}(D Prime -A Prime ) 342-nm and XeI(B-X) 253-nm bands and the 206.2-nm spectral line of atomic iodine. When the emitter operates in a sealed-off mode on the p(He): p(Xe): p(I{sub 2}) = 400: 120: (100-200) Pa mixture, the fractions of the UV radiation power of iodine atoms, exciplex molecules of xenon iodide, and iodine molecules comprise 55, 10, and 35%, respectively. At the optimal partial pressure, the maximum total radiation power of the lamp reaches 37 W, the energy efficiency being about 15%.
Amplification of Xenon NMR and MRI by remote detection
Moule, Adam J.; Spence, Megan M.; Han, Song-I.; Seeley, JulietteA.; Pierce, Kimberly L.; Saxena, Sunil; Pines, Alexander
A novel technique is proposed in which a nuclear magneticresonance (NMR) spectrum or magnetic resonance image (MRI) is encoded andstored as spin polarization and is then moved to a different physicallocation to be detected. Remote detection allows the separateoptimization of the encoding and detection steps, permitting theindependent choice of experimental conditions, and excitation anddetection methodologies. In the first experimental demonstration of thistechnique, we show that NMR signal can be amplified by taking diluted129Xe from a porous sample placed inside a large encoding coil, andconcentrating it into a smaller detection coil. In general, the study ofNMR active molecules at low concentration that have low physical fillingfactor is facilitated by remote detection. In the second experiment, MRIinformation encoded in a very low field magnet (4-7mT) is transferred toa high field magnet (4.2 T) in order to be detected under optimizedconditions. Furthermore, remote detection allows the utilization ofultra-sensitive optical or superconducting detection techniques, whichbroadens the horizon of NMR experimentation.
NASA Technical Reports Server (NTRS)
Joyce, Gerald F. (Inventor); Breaker, Ronald R. (Inventor)
The present invention discloses deoxyribonucleic acid enzymes--catalytic or enzymatic DNA molecules--capable of cleaving nucleic acid sequences or molecules, particularly RNA, in a site-specific manner, as well as compositions including same. Methods of making and using the disclosed enzymes and compositions are also disclosed.
NSDL National Science Digital Library
This lesson explains the difference between molecules in living systems and inanimate objects. In living systems, atoms and molecules are organized to a much greater degree and provide the structure of the organism. Lipids, carbohydrates, proteins, and nucleic acids are also discussed.
Carbon Dioxide Removal via Passive Thermal Approaches
NASA Technical Reports Server (NTRS)
Lawson, Michael; Hanford, Anthony; Conger, Bruce; Anderson, Molly
A paper describes a regenerable approach to separate carbon dioxide from other cabin gases by means of cooling until the carbon dioxide forms carbon dioxide ice on the walls of the physical device. Currently, NASA space vehicles remove carbon dioxide by reaction with lithium hydroxide (LiOH) or by adsorption to an amine, a zeolite, or other sorbent. Use of lithium hydroxide, though reliable and well-understood, requires significant mass for all but the shortest missions in the form of lithium hydroxide pellets, because the reaction of carbon dioxide with lithium hydroxide is essentially irreversible. This approach is regenerable, uses less power than other historical approaches, and it is almost entirely passive, so it is more economical to operate and potentially maintenance- free for long-duration missions. In carbon dioxide removal mode, this approach passes a bone-dry stream of crew cabin atmospheric gas through a metal channel in thermal contact with a radiator. The radiator is pointed to reject thermal loads only to space. Within the channel, the working stream is cooled to the sublimation temperature of carbon dioxide at the prevailing cabin pressure, leading to formation of carbon dioxide ice on the channel walls. After a prescribed time or accumulation of carbon dioxide ice, for regeneration of the device, the channel is closed off from the crew cabin and the carbon dioxide ice is sublimed and either vented to the environment or accumulated for recovery of oxygen in a fully regenerative life support system.
Carbon Dioxide: Friend or Foe?
NASA Astrophysics Data System (ADS)
Muller, C.
Carbon Dioxide: Friend or Foe is a short rnonograph on the so-called carbon dioxide greenhouse effect. The author challenges the established view that the present CO2 increase would, in the long term, lead to a global ground temperature increase. S. B. Idso, from four sets of observations, has deduced that the temperature response to an increased received energy at the ground should be less than or equal to 0.113 K (W/m2). If this result is combined with the 2.28 W/m2 of increased radiation expected from CO2 doubling, he finds a temperature increase of 0.26 K, which cannot be distinguished form the natural temperature fluctuation. This conclusion is in disagreement with virtually all the current mathematical models that predict a ground temperature response of an order of magnitude or more higher.
Vanadium dioxide based plasmonic modulators.
Sweatlock, Luke A; Diest, Kenneth
Actively tunable metal-insulator-metal waveguides that employ vanadium dioxide films as the active medium are analyzed numerically. Vanadium dioxide exhibits strong contrast between the optical properties of its insulating and metallic phases. In particular, the large optical absorption in the metallic phase makes it straightforward to implement broadband attenuation modulators and switches, but this strong loss can also complicate the design of other types of devices. We present a plasmonic waveguide that functions as an index modulator with ?n > 20% at ?0 = 1,550 nm (0.80 eV), by using a thin active layer to strike a balance between maximizing index contrast while mitigating attenuation. A second device is configured as a band-stop absorption modulator, taking advantage of symmetry to selectively suppress the TM1 and TM3 modes, with relatively minimal attenuation of the TM0 and TM2 modes. PMID:22513580
Exposure to Titanium Dioxide Nanomaterials Provokes Inflammation of an in Vitro Human Immune Construct
Schanen, Brian C.; Karakoti, Ajay S.; Seal, Sudipta; Drake, Donald R.; Warren, William L.; Self, William T.
Nanoparticle technology is undergoing significant expansion largely because of the potential of nanoparticles as biomaterials, drug delivery vehicles, cancer therapeutics, and immunopotentiators. Incorporation of nanoparticle technologies for in vivo applications increases the urgency to characterize nanomaterial immunogenicity. This study explores titanium dioxide, one of the most widely manufactured nanomaterials, synthesized into its three most common nanoarchitectures: anatase (7¢10 nm), rutile (15¢20 nm), and nanotube (10¢15 nm diameters, 70¢150 nm length). The fully human autologous MIMIC immunological construct has been utilized as a predictive, nonanimal alternative to diagnose nanoparticle immunogenicity. Cumulatively, treatment with titanium dioxide nanoparticles in the MIMIC system led to elevated levels of proinflammatory cytokines and increased maturation and expression of costimulatory molecules on dendritic cells. Additionally, these treatments effectively primed activation and proliferation of na've CD4+ T cells in comparison to dendritic cells treated with micrometer-sized (>1 ?m) titanium dioxide, characteristic of an in vivo inflammatory response. PMID:19769402
Photoinduced reactivity of titanium dioxide
O. Carp; C. L. Huisman; A. Reller
The utilization of solar irradiation to supply energy or to initiate chemical reactions is already an established idea. If a wide-band gap semiconductor like titanium dioxide (TiO2) is irradiated with light, excited electron¢hole pairs result that can be applied in solar cells to generate electricity or in chemical processes to create or degrade specific compounds. Recently, a new process used
Saunders, Brian; Lyon, Stephen; Day, Matthew; Riley, Brenda; Chenette, Emily; Subramaniam, Shankar; Vadivelu, Ilango
The UCSD-Nature Signaling Gateway Molecule Pages (http://www.signaling-gateway.org/molecule) provides essential information on more than 3800 mammalian proteins involved in cellular signaling. The Molecule Pages contain expert-authored and peer-reviewed information based on the published literature, complemented by regularly updated information derived from public data source references and sequence analysis. The expert-authored data includes both a full-text review about the molecule, with citations, and highly structured data for bioinformatics interrogation, including information on protein interactions and states, transitions between states and protein function. The expert-authored pages are anonymously peer reviewed by the Nature Publishing Group. The Molecule Pages data is present in an object-relational database format and is freely accessible to the authors, the reviewers and the public from a web browser that serves as a presentation layer. The Molecule Pages are supported by several applications that along with the database and the interfaces form a multi-tier architecture. The Molecule Pages and the Signaling Gateway are routinely accessed by a very large research community. PMID:17965093
The Change in Carbon Dioxide Levels
NSDL National Science Digital Library
In this lesson students discover that ice cores can help us learn not only the temperature of the Earth in times past, but also the amount of Carbon Dioxide trapped in the air bubbles in the ice. This activity uses as source data a plot of each versus time, and asks the students to plot the Temperature variable versus the other variable which is the Carbon Dioxide content. Students can fit the data to a line y = mx + b to see how changes in Temperature and related to changes in Carbon Dioxide. After they make a graph of Carbon Dioxide concentration as a function of time, they will learn about linear trends in the data, as well as the annual variation of Carbon Dioxide and will then predict the level of Carbon Dioxide in a future year from the data.
An analysis of the impact of having uranium dioxide mixed in with plutonium dioxide
An assessment was performed to show the impact on airborne release fraction, respirable fraction, dose conversion factor and dose consequences of postulated accidents at the Plutonium Finishing Plant involving uranium dioxide rather than plutonium dioxide.
Hodgkin's disease following thorium dioxide angiography.
Gotlieb, A. I.; Kirk, M. E.; Hutchison, J. L.
Hodgkin's disease occurred in a 53-year-old man who, 25 years previously, had undergone cerebral angiography, for which thorium dioxide suspension (Thorotrast) was used. Deposits of throium dioxide were noted in reticuloendothelial cells in various locations. An association between thorium dioxide administration and the subsequent development of malignant tumours and neoplastic hematologic disorders has previously been reported. Images FIG. 1 FIG. 2 PMID:953918
Climate models should include carbon dioxide increases
NSDL National Science Digital Library
Narisma et al.
The specific impacts of elevated atmospheric carbon dioxide concentrations during the Australian summer were examined. It was found that plant response to increased carbon dioxide influences atmospheric temperatures and the climate in ways that are not currently captured by climate models. The authors suggest that local and global climate models should include a measure of vegetation response to natural and man-made carbon dioxide increases to accurately account for biospheric feedback.
ERIC Educational Resources Information Center
Brinner, Bonnie
Presents an activity in which models help students visualize both the DNA process and transcription. After constructing DNA, RNA messenger, and RNA transfer molecules; students model cells, protein synthesis, codons, and RNA movement. (MDH)
Activation and splitting of carbon dioxide on the surface of an inorganic electride material
Toda, Yoshitake; Hirayama, Hiroyuki; Kuganathan, Navaratnarajah; Torrisi, Antonio; Sushko, Peter V.; Hosono, Hideo
Activation of carbon dioxide is the most important step in its conversion into valuable chemicals. Surfaces of stable oxide with a low work function may be promising for this purpose. Here we report that the surfaces of the inorganic electride [Ca24Al28O64]4+(e?)4 activate and split carbon dioxide at room temperature. This behaviour is attributed to a high concentration of localized electrons in the near-surface region and a corrugation of the surface that can trap oxygen atoms and strained carbon monoxide and carbon dioxide molecules. The [Ca24Al28O64]4+(e?)4 surface exposed to carbon dioxide is studied using temperature-programmed desorption, and spectroscopic methods. The results of these measurements, corroborated with ab initio simulations, show that both carbon monoxide and carbon dioxide adsorb on the [Ca24Al28O64]4+(e?)4 surface at RT and above and adopt unusual configurations that result in desorption of molecular carbon monoxide and atomic oxygen upon heating. PMID:23986101