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Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf
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Krause, M.; Wenisch, R.; Heras, I.; Lungwitz, F.; Janke, D.; Guillén, E.; Erbe, A.; Gemming, S.; Escobar Galindo, R.
Abstract: The development of solar-selective CSP receiver coatings with high-temperature and environmental stability requires new concepts of design and in operando monitoring. Solar receiver tubes are a key component of solar thermal power plants. The increase of their operation temperature from today's maximum of 550°C to about 800°C could increase the CSP efficiency by approximately 15 to 20% and improve the competiveness of this technology compared to other ones of carbon-free electricity generation. Potential alternatives to fast degrading state-of-the-art pigment paint receiver tube coatings are based on refractive metal carbides, nitrides, and oxides because of their high thermal stability and oxidation resistance. New types of solar-selective coatings were studied in situ at temperatures of up to 830°C by Rutherford backscattering spectrometry, Raman spectroscopy, and spectroscopic ellipsometry within a cluster tool. They include carbon- and oxynitride-absorber based multilayers as well as a solarselective transmitter based on a transparent conductive oxide.
Financial support by the EU, grant No. 645725, project FRIENDS2, and the HGF via the W3 program (S.G.) is gratefully acknowledged.
Keywords: Concentrated solar power, in situ analysis, cluster tool, solar-selective coatings
Invited lecture (Conferences)
12th Pacific Rim Conference on Ceramic and Glass Technology including Glass & Optical Materials Division Meeting 2017, 21.-26.05.2017, Waikoloa, USA
Registration No. 25592 - Permalink
Heras, I.; Krause, M.; Lungwitz, F.; Rincon, G.; Alcon-Camas, M.; Azkona, I.; Guillén, E.; Escobar-Galindo, R.
Abstract: Aluminium titanium oxynitrides were studied as candidate materials for high temperature solar-selective coatings due to their excellent stability and their tuneable optical behaviour. A set of individual AlyTi1-y(OxN1-x) layers with different oxygen content was prepared by cathodic vacuum arc (CVA) deposition. The composition, morphology, phase structure and microstructure of the films were characterized by elastic recoil detection (ERD), scanning and transmission electron microscopy and X-ray diffraction.
Keywords: Concentrated solar power, solar-selective coatings, optical simulation
Lecture (Conference)
2017 MRS Spring Meeting & Exhibit, 17.-21.04.2017, Phoenix, USA
Registration No. 25591 - Permalink
Kelling, J.; Ódor, G.; Weigel, M.; Gemming, S.
Abstract: We'll present a method for highly efficient lattice Monte Carlo simulations with correlation-free updates. Achieving freedom from erroneous correlations requires random selection of lattice sites for updates, which must be restricted by suitable domain decomposition to create parallelism. While approaches based on caching limit the number of allowed states, the multisurface-type approach presented here allows arbitrarily complex states. The effectiveness of the method is illustrated in the fact that it allowed us to solve a long-standing dispute around surface growth under random kinetic deposition in the KPZ-universality class. The method has also been applied to Potts models and is suitable for spin-glass simulations, such as those required to test quantum annealers, like D-Wave.
Keywords: Lattice Monte Carlo, GPU, Surface Growth, Kardar-Parisi-Zhang
Lecture (Conference)
GPU Technology Conference, 08.-11.05.2017, San Jose, CA, USA
Contribution to WWW
Registration No. 25585 - Permalink
Beyreuther, E.ORC
Abstract: no abstract available
Invited lecture (Conferences)
Preparation of scientific collaborations on medical applications with laser plasma accelerators, 09.05.2017, Berlin, Deutschland
Registration No. 25581 - Permalink
Liu, Y.; Yuan, Y.; Liu, F.; Böttger, R.; Anwand, W.; Wang, Y.; Semisalova, A.; Ponomaryov, A.; Lu, X.; N'Diaye, A. T.; Arenholz, E.; Heera, V.; Skorupa, W.; Helm, M.; Zhou, S.ORC
Abstract: Elucidating the interaction between magnetic moments and itinerant carriers is an important step to spintronic applications. Here, we investigate magnetic and transport properties in d0 ferromagnetic SiC single crystals prepared by postimplantation pulsed laser annealing. Magnetic moments are contributed by the p states of carbon atoms, but their magnetic circular dichroism is different from that in semi-insulating SiC samples. The anomalous Hall effect and negative magnetoresistance indicate the influence of d0 spin order on free carriers. The ferromagnetism is relatively weak in N-implanted SiC compared with that in Al-implanted SiC after annealing. The results suggest that d0 magnetic moments and itinerant carriers can interact with each other, which will facilitate the development of SiC spintronic devices with d0 ferromagnetism.
Physical Review B 95(2017), 195309
DOI-Link: http://dx.doi.org/10.1103/PhysRevB.95.195309
- Original PDF 2,2 MB Secondary publication
Registration No. 25579 - Permalink
Starace, M.; Weber, N.; Weier, T.; Ashour, R.; Kelley, D.; Salas, A.
Abstract: Introduction
Fluid flow can be both a boon and a curse for liquid metal batteries. One one hand, it may promote mixing of the anode metal into the cathode, preventing it from lingering on the electrolyte-cathode interface. On the other hand, it could momentarily displace part of the electrolyte layer and thus cause a short circuit. The experiment presented here consists of a cylindrical container filled with GaInSn bounded by copper current collectors on the top and bottom, which are attached a power supply unit. The current collector is electrically insulated except for a circular surface whose area is 100 times smaller than that of the bottom current collector. This geometry emulates that of a battery whose cathode consists of a liquid metal drop attached to the top current collector dipped into the electrolyte layer while the anode extends throughout the bottom part of the container. An ultrasound Doppler array was used to perform velocimetry measurements of the electro-vortex flow perpendicularly to the cylindrical axis. In addition, the fluid flow of this setup was also simulated numerically.
While currents ranging from 10 A to 100 A are supplied to the system, the flow pattern appears to consists of multiple stationary swirls, which is in general agreement with numerical results. Additional UDV measurements that are parallel to the cylindrical axis will be performed to obtain a better understanding of the flow structure.
Fig. 1: Velocity profile of the electro-vortex experiment while 100 A are flowing through it. The ultrasound transducers in the array are arranged along the height of the cylinder on the left hand side and measure the radial component of the velocity within one plane.
Keywords: liquid metal battery, electro-vortex flow, ultrasound Doppler velocimetry.
Lecture (Conference)
International workshop on liquid metal battery fluid dynamics (LMBFD 2017), 16.-17.05.2017, Dresden, Deutschland
Registration No. 25578 - Permalink
Osten, J.; Hula, T.; Wagner, K.; Xu, X.; Hlawacek, G.; Bali, R.; Potzger, K.; Lindner, J.; Fassbender, J.; Schultheiss, H.
Abstract: The wave like excitation quanta of ferromagnets, called magnons, waves, the are promising candidates for spin transport in lateral devices. Fe60Al40films in the B2 phase are paramagnetic. Starting from a Fe60Al40film in the paramagnetic phase we use ion irradiation to randomize the site occupancies and, thereby, transform it into the chemically disordered, ferromagnetic A2 phase. To detect spin waves we employed micro-focus Brillouin light scattering spectroscopy (μBLS). Using a highly focused Ne+-ion beam He/Ne-Ion Microscope we create spatially well defined ferromagnetic A2-Fe60Al 40 spin-wave conduits of widths 2 and length 10 μm. One of the ferromagnetic conduit is surrounded by the paramagnetic B2- Fe60Al40. In addition, a freestanding 2 μm wide stripe has been prepared for comparison.
For the excitation of spin waves we processed a microwave antenna on top of these stripes. To investigate the spinwave propagation in the so called Damon-Eshbach geometry, an external magnetic field is applied perpendicular to the long edge of the ferromagnetic stripe. Measurements shows that spin wave spectra are influenced by the surrounding paramagnetic material due to a different internal field distribution.
Furthermore, we have also studied the fundamental transversal mode. Our findings where that the mode width for the embedded stripe was alway larger compared to the freestanding stripe. Surrounding a ferromagnetic conduit with a paramagnetic material, in materials exhibiting disorder-induced ferromagnetism, can be a way to tune spin-wave propagation.
IEEE international magnetics conference Intermag Europe 2017, 24.-28.04.2017, Dublin, Irland
Registration No. 25576 - Permalink
Herreman, W.; Nore, C.; Guermond, J.-L.; Cappanera, L.; Weber, N.
Abstract: Liquid metal batteries (LMBs) structurally have much in common with electrolysis cells that are used in the Al-industry and therefore it can be expected that they are prone to similar magneto-hydrodynamical instabilities. Metal pad rolling is one of many instabilities that is currently in the spotlight.
The physical origin of this metal pad roll instability in reduction cells is well described in a furnished literature that goes back to the 70's. Most theoretical insights have however been found within the restrictive context of quite a number of supplementary assumptions (shallow layers, inviscid, magneto-static, negligible terms in Lorentz force). In lab-scale devices, fluid layers are however not necessarily shallow and the set-up is also small enough for viscous dissipation to become important. Finally, also the magnetic dissipation cannot be ignored given that stronger magnetic fields are necessary to trigger the instability. A critical
comparison between theory and experiments or direct numerical simulation (DNS) dedicated to lab-scale devices requires a more detailed stability model.
In this talk, I present a theoretical stability analysis dedicated to cylindrical reduction cells (2 layers). Using a perturbative approach we find explicit formula for the growth rate of the metal pad roll instability and without making the most common assumptions. We deal with fluid layers of arbitrary heights and incorporate both magnetic and viscous damping effects. We confront our theory to direct numerical simulations (DNS) that are done with two different multiphase MHD solvers (SFEMaNS and OpenFOAM). This comparison also allows us to measure what precision really is required to obtain converged three-dimensional numerical simulations.
Lecture (Conference)
International workshop on liquid metal battery fluid dynamics, 16.-17.05.2017, Dresden, Deutschland
Registration No. 25575 - Permalink
Osten, J.; Hula, T.; Wagner, K.; Xu, X.; Hlawacek, G.; Bali, R.; Potzger, K.; Lindner, J.; Fassbender, J.; Schultheiss, H.
Abstract: Spin waves, the eigen-excitations of ferromagnets, are promising candidates for spin transport in lateral devices. Fe60Al40 films in the B2 phase are paramagnetic. Starting from a FeAl film in the paramagnetic phase the incident ions randomize the site occupancies and, thereby, transform it into the chemically disordered, ferromagnetic A2 phase.
The aim is to investigate spin wave propagation in this ferromagnetic material in free standing structures as well as in ferromagnetic structures embedded within a paramagnetic matrix. Using Helium-Ion microscopy we create spatially well defined ferromagnetic FeAl conduits for spin waves with resolution down to nm range. Two different ferromagnetic stripes were implanted in a microstructured paramagnetic FeAl. A freestanding 2 𝜇m width stripe. And a stripe of the same width which was embedded in a wider paramagnetic FeAl stripe. For the excitation of spin waves we processed a microwave antenna on top of these stripes. To detect spin waves we employed Brillouin light scattering microscopy. We show that the spin wave spectra are influenced by the surrounding paramagnetic material due to a different internal field distribution. The authors acknowledge financial support from the Deutsche Forschungsgemeinschaft within programme SCHU 2922/1-1.
Lecture (Conference)
DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 19.-24.03.2017, Dresden, Deutschland
Registration No. 25574 - Permalink
Prochazka, I.; Cizek, J. A.; Melikhova, O.; Hruska, P.; Anwand, W.; Konstantinova, T. E.; Danilenko, I. A.
Abstract: Porosity in several zirconia-based pressure compacted nanopowders was studied using the positron lifetime technique combined with the mass-density measurements. Two kinds of pores were identified: (i) the larger pores of. 10 to 19 nm diameter arising likely from a formation of secondary particle aggregates, and (ii) the smaller ones (. 1 nm) which are obviously of a more complex origin
Keywords: Nanopowders; Porosity; Positron lifetime; Zirconia
Defect and Diffusion Forum 373(2017), 295-298
DOI-Link: http://dx.doi.org/10.4028/www.scientific.net/DDF.373.295
Registration No. 25566 - Permalink
Günther, F.; Möbius, A.; Schreiber, M.
Abstract: The function of a protein depends strongly on its spatial structure.
Therefore the transition from an unfolded stage to the functional fold is one of the most important problems in computational molecular biology. Since the corresponding free energy landscapes exhibit huge numbers of local minima, the search for the lowest-energy configurations is very demanding. Because of that, efficient heuristic algorithms are of high value. In the present work, we investigate whether and how the thermal cycling (TC) approach can be applied to the hydrophobic-polar (HP) lattice model of protein folding. Evaluating the efficiency of TC for a set of two-and three-dimensional examples, we compare the performance of this strategy with that of multi-start local search (MSLS) procedures and that of simulated annealing (SA). For this aim, we incorporated several simple but rather efficient modifications into the standard procedures: in particular, a strong improvement was achieved by also allowing energy conserving state modifications. Furthermore, the consideration of ensembles instead of single samples was found to greatly improve the efficiency of TC. In the framework of different benchmarks, for all considered HP sequences, we found TC to be far superior to SA, and to be faster than Wang-Landau sampling.
European Physical Journal - Special Topics 226(2017)4, 639-649
DOI-Link: http://dx.doi.org/10.1140/epjst/e2016-60333-2
Registration No. 25561 - Permalink
Opherden, L.; Hornung, J.; Herrmannsdörfer, T.; Xu, J.; Islam, A. T. M. N.; Lake, B.; Wosnitza, J.
Abstract: We report the observation of magnetic domains in the exotic, antiferromagnetically ordered all-in-all-out state of Nd2Zr2O7, induced by spin canting. The all-in-all-out state can be realized by Ising-like spins on a pyrochlore lattice and is established in Nd2Zr2O7 below 0.31 K for external magnetic fields up to 0.14 T. Two different spin arrangements can fulfill this configuration which leads to the possibility of magnetic domains. The all-in-all-out domain structure can be controlled by an external magnetic field applied parallel to the [111] direction. This is a result of different spin canting mechanisms for the two all-in-all-out configurations for such a direction of the magnetic field. The change of the domain structure is observed through a hysteresis in the magnetic susceptibility. No hysteresis occurs, however, in the case the external magnetic field is applied along [100].
Physical Review B 95(2017), 184418
DOI-Link: http://dx.doi.org/10.1103/PhysRevB.95.184418
- Original PDF 1,4 MB Secondary publication
- Fulltext from journals.aps.org
Registration No. 25558 - Permalink
Skorupa, W.; Pelic, B.; Werner, H.; Eule, D.
Abstract: Der Vortrag beschäftigt sich mit materialwissenschaftlichen Arbeiten, die in den letzten 10 Jahren stattfanden, um Probleme zu lösen, die sich aus verschiedenen Aspekten der Verwendung metallischer Werkstoffe im Orgelbau ergaben:
1. Die Zusammenarbeit begann mit der Erkundung alter Gießtechniken, wie sie im Zusammenhang mit einem Restaurierungsprojekt der Fa. Eule in Borgentreich/Ostwestfalen notwendig wurden, um Orgelpfeifen aus der Erbauungszeit der Orgel im 17.Jh und davor zu reparieren bzw. in vergleichbarer Weise nachzubauen. Dabei kam es darauf an, die Temperaturableitung am Gießtisch zu erhöhen, um dem Orgelmetall (Blei mit ca. 2% Zinn) eine feinkristalline Struktur und damit eine höhere Steifheit zu verleihen.
2. Eine weitere Arbeit bezog sich auf die Untersuchung von Korrosionsflecken auf den Prospektpfeifen von Silbermann-Orgeln im sächsischen Raum. Der Prospekt einer Orgel ist der Teil, der direkt dem Betrachter zugewandt ist, also die Pfeifen, die man vom Kirchenraum aus direkt sieht. Man sollte wissen, dass der größte Teil des Pfeifenmaterials hinter dem Prospekt verborgen ist. Dabei wurde eine weltweit relative selten verfügbare Technik eingesetzt, bei der ein hochenergetischer Ionenstrahl (Protonen mit 4 MeV) aus dem Vakuum herausgeführt und an der Oberfläche der Orgelpfeifen die Untersuchung mittel Rutherford-Rückstreuspektrometrie sowie protonen-induzierter Röntgen-und Gammastrahlungs-Spektroskopie ermöglicht.
3. Stark bleihaltiges Orgelmetall und Messing sind innerhalb von historischen, aber auch neuerbauten Orgeln korrosiver Belastung durch Essig-und Ameisensäure-Ausdünstungen aus den in den Orgeln notwendig vorhandenen Holzkonstruktionen ausgesetzt. Es wurde auf der Basis der Ionenimplantation und der Dünnschicht-Abscheidung eine Behandlungsmethode entwickelt, mit denen an der Metalloberfläche antikorrosive Schichten mit Dicken im Bereich kleiner 50 nm erzeugt werden können.
Keywords: Gießtechniken, Korrosion, Plasmaimmersions-Ionenimplantation, Orgelpfeife, Nanotechnologie, Blei-Zinn-Legierungen, Kupfer-Zink-Legierungen (Messing),
Lecture (others)
Eingeladener Seminarvortrag, 26.04.2017, Steinfurt bei Münster, Deutschland
Registration No. 25557 - Permalink
Ling, F. C.-C.; Wang, Z.; Luo, C.; Anwand, W.; Wagner, A.
Abstract: Undoped and Cu-doped ZnO grown on sapphire using pulsed laser deposition (PLD) were studied by positron annihilation spectroscopy (PAS), photoluminescence (PL), high-resolution transmission electron microscopy (HRTEM) and secondary ion mass spectroscopy (SIMS). In the undoped samples, two kinds of VZn-related defects, namely VZn1 and VZn2 are identified. VZn1 was identified in as-grown samples grown at relatively low substrate (~300°C). After annealing at 900°C, VZn-2, the green luminescence (GL) peaking at 2.47 eV and the near band edge (NBE) emission at
3.23 eV in the low temperature photoluminescence (LT-PL) were simultaneously introduced. Another kind of VZn-related defect is identified in the Cu-doped ZnO sample, and is tentatively assigned to the VZn decorated with the Cu.
Keywords: pulsed laser deposition PLD positron annihilation spectroscopy PAS photoluminescence PL transmission electron microscopy TEM secondary ion mass spectroscopy SIMS ZnO
Defect and Diffusion Forum 373(2017), 227-230
DOI-Link: http://dx.doi.org/10.4028/www.scientific.net/DDF.373.227
Registration No. 25556 - Permalink
Anwand, W.; Leguey, T.; Scepanovic, M.; Jose Sanchez, F.; García-Cortés, I.; Wagner, A.
Abstract: Open volume defects created by 1 MeV Fe+ implantation up to a damage of 15 displacements per atom into Fe14wt%Cr and into oxide dispersion strengthened (ODS) Fe14wt%Cr were investigated by positron annihilation spectroscopy, especially single Doppler broadening (DBS) and coincidence Doppler broadening spectroscopies (cDBS). The influence of W and Ti alloying elements on the evolution of defects during ion implantation were probed in addition. Whereas no effect of the W and Ti alloying constituents on the line-shape parameters S and W could be detected both before and after ion implantation, fine dispersed Y2O3 particles showed important changes in the structural properties compared to pure FeCr steel, which could be detected by DBS and cDBS. The distribution of the electron momenta in implanted ODS Fe14Cr, obtained with cDBS, shows that oxide particles form obstacles for expanded vacancy mobility and that the vacancies are localized around the oxide particles.
Keywords: defects implantation oxide dispersion strengthened (ODS) positron annihilation spectroscopy
Defect and Diffusion Forum 373(2017)113-116
DOI-Link: http://dx.doi.org/10.4028/www.scientific.net/DDF.373.113
Registration No. 25555 - Permalink
Schwengner, R.
Abstract: Dipole excitations in the N = 28 nuclide 54Fe were studied in photon-scattering experiments using bremsstrahlung at the gELBE facility of Helmholtz-Zentrum Dresden-Rossendorf and using quasi-monoenergetic, polarized gamma beams at the HIgS facility of the Triangle Universities Nuclear Laboratory in Durham. We identified intense E1 as well as M1 transitions to spin-1 states up to about 10.6 MeV. In the second part, we present low-energy M1 strength functions of 60,64,68Fe determined on the basis of large-scale shell-model calculations with the goal to study their development from the bottom to the middle of the neutron shell. We find that the zero-energy spike develops toward the middle of the shell into a bimodal structure composed of a weaker zero-energy spike and a scissorslike resonance around 3 MeV, where the summed strengths of the two structures changes only slightly. The summed strength of the scissors region exceeds the total gammaabsorption strength from the ground state by a factor of about three, which explains the discrepancy between total strengths of the scissors resonance derived from (gamma,gamma') experiments and from experiments using light-ion induced reactions.
Keywords: Bremsstrahlung, polarized gamma beam, shell model, M1 gamma-strength function, scissors mode.
Invited lecture (Conferences)
6th Workshop on Nuclear Level Density and Gamma Strength, 08.-12.05.2017, Oslo, Norwegen
Registration No. 25554 - Permalink
Braun, R.ORC
Abstract: Usage of Phage Display for identification of peptide binding motifs has long been restricted to medical use. However, in the last years more and more publications focused on the interaction between peptides and inorganic material. Especially in Geobiotechnology the characterization of new metal-binding proteins as well as peptide motifs receives increasing attention, as they may be used in metal recovery, biosorption and bioremediation, as well. Here, we describe the application of artificial peptides for the recovery of metal ions form solutions, e.g. leachates. Limitations arise from complicated identification of metal-binding peptides, from high productions costs of chemical synthesized peptides and difficult heterologous expression of small peptides, as they are relatively fast proteolyzed. Therefore applications of such peptides require efficient and economic production systems. In the present study we aimed for the development of an efficient expression system, expressing previously via Phage Display and Deep sequencing identified peptides as fusions proteins with integrated purification and cleavage tags. Characterization of the purified peptides was performed using quartz crystal microbalance with dissipation monitoring using special coatings for metal immobilization. Knowledge about peptide motifs and metal affinity is crucial for the intended usage of peptides in biosorption processes, e.g. immobilized on membranes. Furthermore, detailed information about peptide-metal interaction may lead to discovery of novel metal-incorporating and –binding enzymes.
Keywords: phage display, peptide, biosorption
Lecture (others)
Microbiology Meeting HZDR - TU Bergakademie Freiberg, 09.01.2017, Freiberg, Deutschland
Registration No. 25551 - Permalink
Braun, R.ORC; Matys, S.ORC; Pollmann, K.
Abstract: Interactions between proteins and metals long been scientifically described but still remain hardly understood. They may be used for industrial purposes. In Geobiotechnology metal binding motifs of proteins and peptides are a promising tool in bioremediation as well as in biosorption processes for the recovery of metals. In this work peptide motifs, which have previously been identified using Phage Display, are characterized for their ability to specifically bind cobalt and nickel ions and for their applicability in industrial biosorption processes. Biosorption may be a future alternative to conventional metal sorption processes, as it is less energy-consuming, environmental-friendly and highly selective.
Keywords: biosorption, peptide, metal recovery, phage display
HZDR PhD seminar, 17.-19.10.2016, Oberwiesenthal, Deutschland
Registration No. 25550 - Permalink
Li, C.; Krauß, N.; Schäfer, G.; Ebner, L.; Kliebisch, O.; Schmidt, J.; Winnerl, S.; Hettich, M.; Dekorsy, T.
Abstract: A low-cost scheme of high-speed asynchronous optical sampling based on Yb:KYW oscillators is reported. Two GHz diode-pumped oscillators with a slight pulse repetition rate offset serve as pump and probe source, respectively. The temporal resolution of this system is limited to 500 fs mainly by the pulse duration of the oscillators and also by relative timing jitter between the oscillators. A near-shot-noise noise floor around 10−6 (ΔR/R) is obtained within a data acquisition time of a few seconds. The performance of the system is demonstrated by measurements of coherent acoustic phonons in a semiconductor sample that resembles a semiconductor saturable absorber mirror or an optically pumped semiconductor chip.
Optics Express 25(2017), 9204-9212
DOI-Link: http://dx.doi.org/10.1364/OE.25.009204
Registration No. 25533 - Permalink
Janke, D.; Hulman, M.; Wenisch, R.; Lungwitz, F.; Gemming, S.; Rafaja, D.; Krause, M.
Abstract: Metal-induced crystallization with and without layer exchange (MIC w/o LE) is a method to decrease the crystallization temperature of amorphous group 14 elements (G14E) by up to several hundred degrees. In situ experiments are expected to provide new insights into thin film evolution and elementary process steps of MIC w/o LE and to improve existing models of this type of phase transformation. While MIC w/o LE has been widely studied for Si and Ge in contact with catalytic metals, there exist only a few studies for the crystallization of amorphous carbon. Therefore, in this contribution in situ Rutherford backscattering spectrometry (RBS), Raman spectroscopy and spectroscopic ellipsometry studies were performed during annealing of amorphous carbon/nickel (a-C/Ni) layer stacks at temperatures up to 750°C.
Due to its small lattice mismatch with the basal plane of graphite and high diffusivity of C atoms, Ni is a suitable catalyst for the growth of graphene and crystalline graphitic nanostructures. During the annealing of an a-C/Ni layer stack covalent bonds between the carbon atoms at the catalyst interface are weakened. Liberated carbon atoms can move along the interface and diffuse along the grain boundaries into the Ni layer towards the catalyst surface, where nucleation and grain growth of graphitic crystallites occur. Our in situ studies showed a change in the stacking sequence between C and Ni layers under defined experimental conditions. According to in situ Raman measurements, this mechanism occurs independent of the stacking sequence, while the velocity of the LE differs significantly. As observed in time and temperature resolved Raman spectra, the position of the G peak and the I(D)/I(G) ratio changed according to the Three-Stage-Model by Ferrari and Robertson, confirming the transformation of amorphous carbon to nc-graphite. With the in situ RBS measurements more insight into LE was given. Here peak positions of C and Ni were shifted, indicating a change of the energy of the scattered ions for both layers respectively and proving the combination of the observed graphitization process with LE during annealing. The thickness of the synthesized crystalline graphitic layer is controlled by the finite carbon source – the deposited a-C film, which is a decisive advantage of this process compared to CVD. It is demonstrated that the structure and the crystallite size of the metallic catalyst layer has a strong influence on the crystallite size and the quality of the graphitic film.
LE is potentially interesting for industrial applications, as it allows the formation of polycrystalline thin films of G14E at much lower temperatures - than during thermal annealing without the metallic catalyst. Depending on the initial stacking sequence, the crystalline graphitic film can be deposited on a suitable device-ready substrate or transferred to another substrate after the dissolution of the transition metal catalyst.
Keywords: In situ RBS, In situ Raman, Amorphous carbon, Metal-induced crystallization
2017 Materials Research Society Spring Meeting, 17.-21.04.2017, Phoenix, United States of America
Registration No. 25530 - Permalink
Hofheinz, F.; Apostolova, I.; Oehme, L.; Kotzerke, J.; van den Hoff, J.
Abstract: Quantitative assessment of radiation- and chemotherapy response with 18F-FDG (fluorodeoxyglucose) whole body PET has attracted increasing interest in recent years. In most published work the standardized uptake value (SUV) is utilized for this purpose. In the context of therapy response assessment the reliability of lesion SUVs, notably their test-retest stability, thus becomes of crucial importance. However, in a recent study substantial test-retest variability (TRV) of SUVs was demonstrated. The purpose of the present study was to investigate if the tumor-to-blood standard uptake ratio (SUR) can improve test-retest variability of tracer uptake. Methods: 73 patients with advanced non small cell ling cancer (NSCLC) from the prospective multicenter trials ACRIN 6678 (N = 34) and Merck MK-0646-008 (N = 39) were included in this study. All patients underwent two 18F-FDG PET/CT investigations at two different days (time difference: (3.6 +/- 2.1) days (range: 1-7)) prior to therapy. For each patient up to seven tumor lesions were evaluated. For each lesion maximum and peak SUV was determined. Blood SUV was determined as mean value of a three-dimensional aorta ROI that was delineated in the attenuation CT and transferred to the PET image. SUR values were computed as ratio of tumor SUV and blood SUV and were uptake time corrected to 75 min p.i.. TRV was quantified as TRV = 1.96 x RMS, where RMS is the root mean square deviation of the fractional paired differences of SUV and SUR, respectively. The combined effect of blood normalization and uptake time correction was inspected by considering the ratio RTRV = TRVSUR /TRVSUV reflecting the reduction in test-retest variability of SUR relative to SUV. RTRV was correlated with the group averaged value dCFmean of the quantity dCF = |CF - 1|, where CF is the numerical factor that converts individual ratios of paired SUV values into corresponding SUR ratios. This correlation analysis was performed by successively increasing a threshold value dCFmin and computing dCFmean and RTRV for the remaining sub-group of patients/lesions with CF >= CFmin. Results: The group-averaged test-retest variability of SUV and SUR was TRVSUV=32.1 and TRVSUR=29.0, respectively, which corresponds to a reduction of variability of SUR by a factor RTRV = 0.9 in comparison to SUV. This rather marginal improvement can be understood as of consequence of the untypically low intra-subject variability of blood SUV and uptake time and accordingly small dCF values in the investigated prospective study groups. In fact, sub-group analysis with increasing thresholds dCFmin revealed a very pronounced negative correlation (Spearman's rho = -0.99, P<0.001) between RTRV and dCFmean where RTRV ~ 0.4 in the dCFmin = 20% sub-group, corresponding to a more than twofold reduction of TRVSUR compared to TRVSUV. Conclusion: Variability of blood SUV and uptake time have been identified as causal factors contributing to the test-retest variability of lesion SUV. Therefore, test-retest variability of lesion uptake measurements can be reduced when replacing SUV by SUR as the uptake measure. The improvement becomes substantial for the level of variability of blood SUV and uptake time typically observed in the clinical context.
Keywords: Oncology: Lung PET FDG PET SUR SUV test-retest
Journal of Nuclear Medicine (2017)
Online First (2017) DOI-Link: http://dx.doi.org/10.2967/jnumed.117.190736
Registration No. 25529 - Permalink
Wenisch, R.; Janke, D.; Heras, I.; Lungwitz, F.; Guillén, E.; Heller, R.; Gemming, S.; Escobar Galindo, R.; Krause, M.
Abstract: The detailed knowledge of composition and microstructure is essential for the understanding of processes and properties of new materials for applications at high temperatures. To ensure materials functionality under in operando conditions, new concepts for analysis and process monitoring are necessary. In this contribution, selected PVD deposited thin film material systems were studied in situ at temperatures up to 830°C by Rutherford backscattering spectrometry (RBS), Raman spectroscopy, and spectroscopic ellipsometry (SE) within a cluster tool.
Metal-induced crystallization with and without layer exchange (MIC w/o LE) is an emerging technique for processing of amorphous group IV elements below their isothermal crystallization temperatures. In this study, a bilayer system of 60 nm amorphous Si covered by 30 nm Ag (a-Si/Ag) was annealed at temperatures of 380 to 700°C by the combination of the above mentioned in situ techniques. The process comprised a relatively long-term incubation period followed by a fast MIC w/o LE step. More than 90% of the initial a-Si could be crystallized on top of the Ag-layer for optimized process conditions with temperatures of about 550°C. The as-formed Si consisted of up to 95% crystalline Si.
As an example for high-temperature solar selective coatings for thermo-solar applications, AlTiN and AlTiN1-xOx (x = 0 - 0.2) thin films were investigated in order to understand the influence of the oxygen/nitrogen ratio on the optical properties and failure mechanisms at high temperatures. The elemental depth profiles and the phase structure of both coatings do not change during annealing in high vacuum at temperatures up to of 750°C, as revealed by unchanged RBS and Raman spectra, respectively. SE and RBS results showed the influence of the initial oxygen content on high temperature stability of AlTiN and AlTiN1-xOx thin films. The low emittance of AlTiN1-xOx, allowed performing in situ RBS analysis at temperatures up to 830°C for the first time.
Keywords: cluster tool in situ analysis RBS Raman ellipsometry
Lecture (Conference)
2017 Materials Research Society Spring Meeting, 17.-21.04.2017, Phoenix, United States of America
Registration No. 25528 - Permalink
Platzek, I.; Beuthien-Baumann, B.; Schramm, G.; Maus, J.; Laniado, M.; Kotzerke, J.; van den Hoff, J.; Schuler, M.
Abstract: Objective: To assess the feasibility of positron emission tomography/magnetic resonance imaging (PET/MR) with 18F-fluordeoxyglucose (FDG) for initial staging of sarcoma.
Materials and methods: Twenty-nine patients with sarcoma were included in this study. Weighted kappa (κ) was used to assess the agreement between PET/MR and conventional imaging (CT and MR). The accuracy of PET/MR and conventional imaging for distant metastases was compared using receiver operating characteristic (ROC) analysis.
Results: T and M stage were identical for PET/MR and conventional modalities in all patients (κ = 1). N stage was identical for 28/29 patients (κ = 0.65).
Conclusions: FDG PET/MR shows excellent agreement with the currently preferred imaging methods (CT and MR) in initial staging of sarcoma.
Keywords: Sarcoma; PET/MR; Staging
Clinical Imaging 42(2017), 126-132
DOI-Link: http://dx.doi.org/10.1016/j.clinimag.2016.11.016
- Secondary publication expected from 29.11.2017
Registration No. 25527 - Permalink
Kotzerke, J.; Oehme, L.; Grosse, J.; Hellwig, D.; Bartenstein, P.; Baum, R. P.; Buck, A. K.; Burchert, W.; Dietlein, M.; Drzezga, A.; Haberkorn, U.; Herrmann, K.; Kluge, R.; Krause, B. J.; Müller, H.-W.; Kuwert, T.; Nitzsche, E.; Reuland, P.; Scheidhauer, K.; Schwaiger, M.; Stabell, U.; van den Hoff, J.; Weber, W.
Abstract: Aim: Five years after the first survey the positron emission tomography (PET) council of the German Society of Nuclear Medicine (DGN) repeated a survey to re-evaluate the status of PET diagnostics in Germany based on the data of the year 2013. Methods: A web-based questionnaire was used for gathering information retrospectively. Details regarding the physicians involved in PET operations, PET systems, and radiopharmaceuticals were also part of the survey as well as indications and number of studies. Furthermore, the role of PET and PET/CT within the diagnostic process was evaluated. In addition, official statistical hospital reports were analysed. Results: Responses from 52 sites were analysed. They reported a total of 38,350 PET studies in 2013. In the majority of cases PET was used in oncologic indications (87%). Further main applications were: neurology 6%, cardiology 1%, and inflammation 5%. University or other hospitals performed 85% of the studies. The portion of in-patients was 26%. Hybrid systems (56 PET/CT, 5 PET/MRT, and 2 stand-alone PET) were most frequently used for imaging. The radiotracers were labelled with F-18 in 90% of the studies, whereas Ga-68 was used in 9% and C-11 in 1%. Lung tumours were the most investigated tumour entity (40%), followed by malignant lymphoma (8%), tumours of the gastrointestinal tract (5%), and NET (5%). 20% of the 333 physicians hold a PET certificate awarded by the DGN. More than 50% of the facilities were certified according ISO9001, KTQ or QEP standard. The findings of nearly 60% of the oncological studies were discussed interdisciplinary in a tumour board. In federal statistical reports a 56% increase of in-patient PET operations during 5 years was found. Conclusion: In Germany, a moderate increase (9% per year) of PET studies is observed, but compared with other industrialised countries PET is still less established.
Keywords: Numerical data; Positron emission tomography; Utilization review; Utilization statistics
Nuklearmedizin 54(2015)2, 53-59
DOI-Link: http://dx.doi.org/10.3413/Nukmed-2015020001
- Secondary publication expected
Registration No. 25526 - Permalink
Gupta, P.; Williams, G. V. M.; Hübner, R.; Vajandar, S.; Osipowicz, T.; Heinig, K.-H.; Becker, H.-W.; Markwitz, A.
Abstract: Mono-energetic cobalt implantation into hydrogenated diamond-like carbon at room temperature results in a bimodal distribution of implanted atoms without any thermal treatment. The ~100 nm thin films were synthesised by mass selective ion beam deposition. The films were implanted with cobalt at an energy of 30 keV and an ion current density of ~5 µA cm-2. Simulations suggest the implantation profile to be single Gaussian with a projected range of ~37 nm. High resolution Rutherford backscattering measurements reveal that a bimodal distribution evolves from a single near-Gaussian distribution as the fluence increases from 1.2 to 7x1016cm-2. Cross-sectional transmission electron microscopy further reveals that the implanted atoms cluster into nanoparticles. At high implantation doses, the nanoparticles assemble primarily in two bands: one near the surface with nanoparticle diameters of up to 5 nm and the other beyond the projected range with ~2 nm nanoparticles. The bimodal distribution along with the nanoparticle formation is explained with diffusion enhanced by energy deposited during collision cascades, relaxation of thermal spikes, and defects formed during ion implantation. This unique distribution of magnetic nanoparticles with the bimodal size and range is of significant interest to magnetic semiconductor and sensor applications.
Applied Physics Letters 110(2017), 141901
DOI-Link: http://dx.doi.org/10.1063/1.4979523
Registration No. 25525 - Permalink
Kotzerke, J.; Oehme, L.; Lindner, O.; Hellwig, D.; Bartenstein, P.; Baum, R. P.; Burchert, W.; Dietlein, M.; Haberkorn, U.; Kluge, R.; Knapp, W. H.; Kuwert, T.; Nitzsche, E.; Reske, S. N.; Reuland, P.; Schicha, H.; Schober, O.; Schwaiger, M.; van den Hoff, J.
Abstract: Aim: The working group on positron emission tomography (PET) of the DGN (German Society of Nuclear Medicine) initiated this first survey to collect and analyse information on the practise of PET in Germany in the year 2008. Methods: A questionnaire was sent to PET performing facilities (medical practices, hospitals, university hospitals and others) for retrospective data acquisition. Details regarding the equipment and examination procedures were examined as well as indications and number of studies. In add ition, the role of PET within the diagnostic process was evaluated. Results: Responses from 65 sites were analysed, Their technical equipment consisted of 77 PET scanners (40 of them were combined PET/CT devices). About 63500 PET studies had been performed with 86% in the field of oncology, 8% in neurology and 3% in cardiology. The radiotracers were labelled with 18F in 91 % of the studies, whereas 68Ga was used in 4% and 11C in 3%. The analyses revealed lung tumours as the most investigated tumour entity, followed by malignant lymphoma, tumours of the g astro-intestinal tract and prostate cancer (about 14000, 6000, 5000 and 2000). Corresponding to the new scanners and software procedures, the number of studies with attenuation correction by CT was high (68%) and nearly all studies were reconstructed iteratively (99%). The PET images were analysed quantitatively in the majority of cases (91%). The clinical reports, which included image documentation for the greater part, were posted regularly within 3 days. However, in 70% of the sites electronic transfer possibilities were used additionally to speed up the diagnostic process. The high standard of quality was demonstrated by the fact, that 40 facilities were engaged in a tumour board. Further on, one third of the physicians had gained a PET certification awarded by the DGN. Conclusion: Relative to the high general standard of diagnostic instrumentation in Germany, PET is less established, in particular when compared with other industrialised countries such as USA and Switzerland.
Keywords: Numerical data; Positron emission tomography; Utilization review; Utilization statistics
Nuklearmedizin 49(2010)2, 58-64
DOI-Link: http://dx.doi.org/10.3413/nukmed-0203
- Secondary publication expected
Registration No. 25524 - Permalink
Krause, B. J.; Beyer, T.; Bockisch, A.; Delbeke, D.; Kotzerke, J.; Minkov, V.; Reiser, M.; Willich, N.; Bartenstein, P.; Baum, R. P.; Burchert, W.; Haberkorn, U.; Kluge, R.; Knapp, W. H.; Kotzerke, J.; Kuwert, T.; Nitzsche, E.; Reske, S. N.; Reuland, P.; Schicha, H.; Schober, O.; Schwaiger, M.; Stabell, U.; van den Hoff, J.
Abstract: FDG-PET/CT examinations combine metabolic and morphologic imaging within an integrated procedure. Over the past decade PET/CT imaging has gained wide clinical acceptance in the field of oncology. This FDG-PET/CT guideline focuses on indications, data acquisition and processing as well as documentation of FDG-PET/CT examinations in oncologic patients within a clinical and social context specific to Germany. Background information and definitions are followed by examples of clinical and research applications of FDG-PET/CT. Furthermore, protocols for CT scanning (low dose and contrast-enhanced CT) and PET emission imaging are discussed. Documentation and reporting of examinations are specified. Image interpretation criteria and sources of errors are discussed. Quality control for FDG and PET/CT-systems, qualification requirements of personnel as well as legal aspects are presented.
Keywords: Guideline, FDG, PET/CT, oncology
Nuklearmedizin 46(2007)6, 291-301
DOI-Link: http://dx.doi.org/10.3413/nukmed-282
- Secondary publication expected
Registration No. 25523 - Permalink
Personnettaz, P.; Köllner, T.; Nimtz, M.; Weber, N.; Weier, T.
Abstract: Liquid metal batteries (LMBs), built as stable density stratification of two liquid metals separated by a molten salt, are a promising electrical energy storage technology. While their operation has been proved for small prototypes, large industrial cells are not yet available. Up-scaling requires the full knowledge of the different phenomena occurring in LMBs. In this work we focus our attention on thermal phenomena, these are one of the main cause of flow inside the cell.
The system is first studied with a 0D electrochemical approach, focusing the attention on reversible and irreversible phenomena. A simple voltage model for the Li||Bi cell and the formulation of heat generation terms are proposed. From multi-physics considerations the geometrical and operating parameters are fully estimated.
Then thermal phenomena proper of LMBs are analyzed in the framework of continuum mechanics. 1D pure heat conduction models are built in order to assess the effect of different heat generation terms. Radiative heat transfer in the molten salt layer is also estimated.
Finally the VOF multiphase solver multiphaseInterFOAM is improved in order to study thermal convection in multi-layer systems. The comparison of results of our solver to the ones of a pseudo-spectral code and the first results of thermal convection in LMBs are also presented.
Lecture (Conference)
International workshop on liquid metal battery fluid dynamics, 16.-17.05.2017, Dresden, Deutschland
Registration No. 25522 - Permalink
Wang, A.; Kampert, E.; Saadaoui, H.; Luetkens, H.; Hu, R.; Morenzoni, E.; Wosnitza, J.; Petrovic, C.
Abstract: We have investigated the magnetotransport above the upper critical field (Hc2) in Fe1.14Te0.7Se0.3, Fe1.02Te0.61Se0.39, Fe1.05Te0.89Se0.11, and Fe1.06Te0.86S0.14. The μSR measurements confirm electronic phase separation in Fe1.06Te0.86S0.14, similar to Fe1+yTe1−xSex. Superconductivity is suppressed in high magnetic fields above 60 T, allowing us to gain insight into the normal-state properties below the zero-field superconducting transition temperature (Tc). We show that the resistivity of Fe1.14Te0.7Se0.3 and Fe1.02Te0.61Se0.39 above Hc2 is metallic as T → 0, just like the normal-state resistivity above Tc. On the other hand, the normal-state resistivity in Fe1.05Te0.89Se0.11 and Fe1.06Te0.86S0.14 is nonmetallic down to lowest temperatures, reflecting the superconductor-insulator transition due to electronic phase separation.
Physical Review B 95(2017), 184504
DOI-Link: http://dx.doi.org/10.1103/PhysRevB.95.184504
Registration No. 25516 - Permalink
Michor, H.; Sereni, J. G.; Giovannini, M.; Kampert, E.; Salamakha, L.; Hilscher, G.; Bauer, E.
Abstract: Magnetic, transport, and thermal properties of CeCu2Mg are investigated to elucidate the lack of magnetic order in this heavy-fermion compound with a specific heat value, Cmag/T |T→0 ≈ 1.2 J/mol K2 and robust effective magnetic moments (μeff ≈ 2.46μB). The lack of magnetic order is attributed to magnetic frustration favored by the hexagonal configuration of the Ce sublattice. In fact, the effect of magnetic field on Cmag/T and residual resistivity ρ0 does not correspond to that of a Fermi liquid (FL) because a broad anomaly appears at Tmax ≈ 1.2 K in Cmag(T )/T , without changing its position up to μ0H = 7.5 T. However, the flattening of Cmag/T |T→0 and its magnetic susceptibility χT→0, together with the T2 dependence of ρ(T ), reveal a FL behavior for T _ 2 K which is also supported by Wilson and Kadowaki-Woods ratios. The unusual coexistence of FL and frustration phenomena can be understood by placing paramagnetic CeCu2Mg in an intermediate section of a frustration-Kondo model. The entropy, Smag, reaches 0.87 R ln 6 at T _ 100 K, with a tendency to approach the expected value Smag = R ln 6 of the J = 5/2 ground state of Ce3+.
Physical Review B 95(2017), 115146
DOI-Link: http://dx.doi.org/10.1103/PhysRevB.95.115146
Registration No. 25514 - Permalink
Helm, M.
Abstract: Dresden has been a center of microelectronics already since the 1960s, and this has continued and even been intensified after the German reunification. Fabs by Siemens, later Infineon and Qimonda, and also by AMD, later Globalfoundries were established. While those were mostly production sites, a concerted effort in fundamental research was started in the framework of the German Excellence Initiative. TU Dresden has established the "Exzellenzcluster" called "Center for Advancing Electronics Dresden (cfaed)". In the first part of my talk I will introduce the concept of this cluster and give an overview about its activities. In the second part I will present some research going on in my institute at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), in particular related to the integration of III-V semiconductor nanostructures into silicon. If time permits, I may also say a few words about our research in terahertz spectroscopy utilizing the unique free-electron laser at HZDR.
Keywords: nanoelectronics, ion beam synthesis
Lecture (others)
Kolloquium der Fakultät für Elektrotechnik und Informationstechnik, 05.05.2017, Wien, Austria
Registration No. 25511 - Permalink
Rasti, B.; Ghamis, I. P.; Gloaguen, R.
Abstract: The classification accuracy of remote sensing data can be increased by integrating ancillary data provided by multisource acquisition of the same scene. We propose to merge the spectral and spatial content of hyperspectral images (HSIs) with elevation information from light detection and ranging (LiDAR) measurements. In this paper, we propose to fuse the data sets using orthogonal total variation component analysis (OTVCA). Extinction profiles are used to automatically extract spatial and elevation information from HSI and rasterized LiDAR features. The extracted spatial and elevation information is then fused with spectral information using the OTVCA-based feature fusion method to produce the final classification map. The extracted features have high dimension, and therefore OTVCA estimates the fused features in a lower dimensional space. OTVCA also promotes piece-wise smoothness while maintaining the spatial structures. Both attributes are important to provide homogeneous regions in the final classification maps. We benchmark the proposed approach (OTVCA-fusion) with an urban data set captured over an urban area in Houston/USA and a rural region acquired in Trento/Italy. In the experiments, OTVCA-fusion is evaluated using random forest and support vector machine classifiers. Our experiments demonstrate the ability of OTVCA-fusion to produce accurate classification maps while using fewer features compared with other approaches investigated in this paper.
Keywords: Extinction profiles (EPs), feature fusion, orthogonal total variation component analysis (OTVCA), random forest (RF), support vector machines (SVMs).
IEEE Transactions on Geoscience and Remote Sensing 99(2017)
DOI-Link: http://dx.doi.org/10.1109/TGRS.2017.2686450
- Secondary publication expected from 17.04.2018
Registration No. 25509 - Permalink
Othman, A. A.; Gloaguen, R.
Abstract: Lithological mapping in mountainous regions is often impeded by limited accessibility due to relief. This study aims to evaluate (1) the performance of different supervised classification approaches using remote sensing data and (2) the use of additional information such as geomorphology. We exemplify the methodology in the Bardi-Zard area in NE Iraq, a part of the Zagros Fold – Thrust Belt, known for its chromite deposits. We highlighted the improvement of remote sensing geological classification by integrating geomorphic features and spatial information in the classification scheme. We performed a Maximum Likelihood (ML) classification method besides two Machine Learning Algorithms (MLA): Support Vector Machine (SVM) and Random Forest (RF) to allow the joint use of geomorphic features, Band Ratio (BR), Principal Component Analysis (PCA), spatial information (spatial coordinates) and multispectral data of the Advanced Space-borne Thermal Emission and Reflection radiometer (ASTER) satellite. The RF algorithm showed reliable results and discriminated serpentinite, talus and terrace deposits, red argillites with conglomerates and limestone, limy conglomerates and limestone conglomerates, tuffites interbedded with basic lavas, limestone and Metamorphosed limestone and reddish green shales. The best overall accuracy (∼80%) was achieved by Random Forest (RF) algorithms in the majority of the sixteen tested combination datasets.
Keywords: Zagros; Classification; Random forest; SVM; remote sensing; Iraq
Journal of Asian Earth Sciences (2017)
DOI-Link: http://dx.doi.org/10.1016/j.jseaes.2017.05.005
- Secondary publication expected from 07.05.2018
Registration No. 25508 - Permalink
Khomenkova, L.; Lehninger, D.; Kondatenko, O.; Ponomaryov, S.; Gudymenko, O.; Tsybrii, Z.; Yukhymchuk, V.; Kladko, V.; von Borany, J.; Heitmann, J.
Abstract: Ge-rich ZrO2 films, fabricated by confocal RF magnetron sputtering of pure Ge and ZrO2 targets in Ar plasma, were studied by multi-angle laser ellipsometry, Raman scattering, Auger electron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction for varied deposition conditions and annealing treatments. It was found that as-deposited films are homogeneous for all Ge contents, thermal treatment stimulated a phase separation and a formation of crystalline Ge and ZrO2. The "start point" of this process is in the range of 640–700 °C depending on the Ge content. The higher the Ge content, the lower is the temperature necessary for phase separation, nucleation of Ge nanoclusters, and crystallization. Along with this, the crystallization temperature of the tetragonal ZrO2 exceeds that of the Ge phase, which results in the formation of Ge crystallites in an amorphous ZrO2 matrix. The mechanism of phase separation is discussed in detail.
Keywords: Germanium, Zirconium oxide, Nanoclusters, Phase separation, Magnetron sputtering, Thin films, X-ray diffraction, Ellipsometry, Raman scattering, Fourier Transform infrared spectroscopy, Auger electron spectroscopy
Nanoscale Research Letters 12(2017), 196
Online First (2017) DOI-Link: http://dx.doi.org/10.1186/s11671-017-1960-9
Registration No. 25503 - Permalink
Oksenhendler, T.; Bizouard, P.; Albert, O.; Bock, S.; Schramm, U.
Abstract: A novel apparatus for the single-shot measurement of the temporal pulse contrast of modern ultra-short pulse lasers is presented, based on a simple yet conceptual refinement of the self-referenced spectral interferometry (SRSI) approach. The introduction of the spatial equivalent of a temporal delay by tilted beams analyzed with a high quality imaging spectrometer, enables unprecedented performance in dynamic, temporal range and resolution simultaneously. Demonstrated consistently in simulation and experiment at the front-end of the PW laser Draco, the full range of the ps temporal contrast defining the quality of relativistic laser-solid interaction could be measured with almost 80 dB dynamic range, 18ps temporal window, and 18fs temporal resolution. Additionally, spatio-temporal coupling as in the case of a pulse front tilt can be quantitatively explored.
Optics Express 25(2017)11, 12588-12600
DOI-Link: http://dx.doi.org/10.1364/OE.25.012588
Registration No. 25502 - Permalink
Schramm, U.ORC
Abstract: Laser proton acceleration history at HZDR in light of medical applications
Keywords: PW laser, Whelmi
Invited lecture (Conferences)
Inauguration of the Weizmann Helmholtz Institute for Laser Matter Interaction WHELMI, 25.-27.04.2017, Rehovot / Tel Aviv, Israel
Registration No. 25501 - Permalink
Schramm, U.ORC; Bussmann, M.; Irman, A.; Siebold, M.; Zeil, K.; Albach, D.; Bernert, C.; Bock, S.; Brack, F.; Branco, J.; Couperus, J. P.; Cowan, T.; Debus, A.; Eisenmann, C.; Garten, M.; Gebhardt, R.; Grams, S.; Helbig, U.; Huebl, A.; Kluge, T.; Köhler, A.; Krämer, J.; Kraft, S.; Kroll, F.; Kuntzsch, M.; Lehnert, U.; Loeser, M.; Metzkes, J.; Michel, P.; Obst, L.; Pausch, R.; Rehwald, M.; Sauerbrey, R.; Schlenvoigt, H.-P.; Steiniger, K.; Zarini, O.
Abstract: We report on first commissioning results of the DRACO Petawatt ultra-short pulse laser system implemented at the ELBE center for high power radiation sources of Helmholtz-Zentrum Dresden-Rossendorf. Key parameters of the laser system essential for efficient and reproducible performance of plasma accelerators are presented and discussed with the demonstration of 40MeV proton acceleration under TNSA conditions as well as peaked electron spectra with unprecedented bunch charge in the 0.5 nC range.
Keywords: PW laser, laser plasma acceleration, beam loading
Invited lecture (Conferences)
17th International Particle Accelerator Conference IPAC17 (see Jacow), 15.-19.05.2017, Copenhagen, Denmark
Registration No. 25498 - Permalink
Smolyansky, S. A.; Churochkin, D. V.; Dmitriev, V. V.; Panferov, A. D.; Kämpfer, B.
Abstract: Abstract. In the framework of strong field QED, the generation of a residual alternating polarization current is demonstrated, which remains after switching off an external field pulse. This effect is stipulated by inertial properties of the physical vacuum. In the standard vacuum D = 2+1 QED, this current is rapidly damped fast but can be available, apparently, for observation in the graphene, where the Fermi velocity vF << c plays an analogous role as the light velocity.
European Physical Journal Web of Conferences 138(2017), 06004
DOI-Link: http://dx.doi.org/10.1051/epjconf/201713806004
- Secondary publication expected
Registration No. 25496 - Permalink
Kern, M.; Möckel, R.; Krause, J.; Teichmann, J.; Gutzmer, J.
Abstract: A method was developed to determine the modal mineralogy and Sn deportment of a fine-grained skarn ore. Mineral Liberation Analysis and electron probe microanalysis was applied to crushed and uncrushed samples for mineralogical characterization. A comprehensive list of mineral references consisting of energy dispersive X-ray spectra and information about elemental concentration and density was created. This conventional approach did not achieve reliable results in the characterization of some of the analyzed ore types. Small grain sizes and the variety of Sn-bearing minerals required adding mineral references with manually mixed EDX-spectra, calculated elemental concentrations and densities. The consequences of classifying a data set with a conventional vs a modified mineral reference list are explained in Figure 1. Comparison of MLA data using this modified approach with bulk chemistry and X-ray powder diffraction illustrates very good agreement for all ore-types characterized. The illustrated approach may well be considered for other mineralogically complex ores containing a multitude of ore minerals and complex deportment of rare metals.
Contribution to proceedings
GOOD Meeting 2017, 20.-22.03.2017, Hannover, Deutschland
Lecture (Conference)
GOOD Meeting 2017, 20.-22.03.2017, Hannover, Deutschland
Registration No. 25487 - Permalink
Kern, M.; Möckel, R.; Krause, J.; Teichmann, J.; Gutzmer, J.
Abstract: A method was developed to determine the modal mineralogy and Sn deportment of a fine-grained skarn ore. Mineral Liberation Analysis and electron probe microanalysis was applied to crushed and uncrushed samples for mineralogical characterization. A comprehensive list of mineral references consisting of energy dispersive X-ray spectra and information about elemental concentration and density was created. This conventional approach did not achieve reliable results in the characterization of some of the analyzed ore types. Small grain sizes and the variety of Sn-bearing minerals required adding mineral references with manually mixed EDX-spectra, calculated elemental concentrations and densities. Comparison of MLA data using this modified approach with bulk chemistry and X-ray powder diffraction illustrates very good agreement for all ore-types characterized. The illustrated approach may well be considered for other mineralogically complex ores containing a multitude of ore minerals and complex deportment of metals.
Keywords: Deportment, tin skarn, Hämmerlein deposit, automated mineralogy, method development
Lecture (Conference)
Process Mineralogy 2017, 20.-23.03.2017, Kapstadt, Südafrika
Contribution to proceedings
Process Mineralogy 2017, 20.-22.03.2017, Kapstadt, Südafrika
Registration No. 25486 - Permalink
Kern, M.; Gutzmer, J.
Abstract: A method was developed to determine the modal mineralogy and Sn deportment of a fine-grained skarn ore. Mineral Liberation Analysis and electron probe microanalysis was applied to crushed and uncrushed samples for mineralogical characterization. A comprehensive list of mineral references consisting of energy dispersive X-ray spectra and information about elemental concentration and density was created. This conventional approach did not achieve reliable results in the characterization of some of the analyzed ore types. Small grain sizes and the variety of Sn-bearing minerals required adding mineral references with manually mixed EDX-spectra, calculated elemental concentrations and densities. The consequences of classifying a data set with a conventional vs a modified mineral reference list are explained in Figure 1. Comparison of MLA data using this modified approach with bulk chemistry and X-ray powder diffraction illustrates very good agreement for all ore-types characterized. The illustrated approach may well be considered for other mineralogically complex ores containing a multitude of ore minerals and complex deportment of rare metals.
Invited lecture (Conferences)
ResErVar Netzwerktreffen Freiberg, 17.-20.10.2016, Freiberg, Deutschland
Registration No. 25485 - Permalink
Kern, M.; Kästner, J.; Gutzmer, J.
Abstract: The Hämmerlein orebody is part of the world class Tellerhäuser deposit in the Erzgebirge, Germany, and represents a compositionally complex polymetallic Sn-In-Zn skarn. Current resources amount to 100000t Sn at a cut-off grade of 0.2 wt.%. In addition, 2100 t of In and 270000t of Zn have been estimated. In the late 1970s, 50000t of ore from the Hämmerlein orebody were mined and processed experimentally in a pilot plant, but grade and recovery remained below expectations. Cited reasons for poor recovery include the complex mineralogy and variability in grain sizes of ore minerals [1].
A consortium of German research institutions currently conducts new beneficiation experiments on the Hämmerlein orebody. Determination of the Sn deportment and the characterization of the different lithological (skarn) units are the first steps in this process. For this purpose, three transects in the central part of the Hämmerlein orebody were mapped and a suite of hand specimen collected to represent all relevant lithotypes within the studied part of the orebody. Thin sections were prepared and analyzed using the Mineral Liberation Analyzer (MLA) to obtain quantitative data about mineralogy, mineral grain sizes, intergrowths, and associations. The remaining material of the hand specimen was crushed to 99% <250µm. This granular material was split to produce grain mounts for further mineralogical studies and in order to prepare sample powders for geochemical analysis.
The Hämmerlein skarn orebody can be subdivided into the following three macroscopically distinct lithotypes: 1. magnetite-dominated (40 – 80 wt.% magnetite), 2. sulphide-dominated (> 20 wt.% sphalerite) and 3. silicate-dominated (> 60 wt.% silicates). In the silicate-dominated unit a gradual transition of different silicate minerals enables further discrimination of a chlorite-rich, an amphibole-chlorite-rich, an epidote-pyroxene-rich and a garnet-rich subunit. The hanging and footwall are best described as mica schist and gneiss, respectively.
The primary host mineral for Sn is cassiterite (SnO2) with grain sizes between 1µm and 1mm. Some of the cassiterite has fibrous crystal habit. Significant amounts (ca. 1.4 wt.%) of coarse-grained (50µm to 1mm) cassiterite is present in the chlorite subunit. The amphibole-chlorite subunit contains an average of 0.3 wt.% cassiterite. Samples from other parts of the Hämmerlein orebody indicate significant amounts of cassiterite in the magnetite- and the sulphide-dominated lithotypes as well.
Malayaite (CaSnSiO5) is the second most abundant Sn mineral. It appears in fine-grained aggregates in the amphibole-chlorite subunit and in the magnetite-dominated ore type reaching concentrations of ca. 0.1 wt.%. Notable Sn concentrations were detected by EDX in some examples of titanite, epidote and iron oxides. However, the total amount of Sn in these minerals accounts for less than 10% of the total Sn content of the deposit.
Our preliminary results illustrate that the Sn mineralisation of the Hämmerlein skarn is indeed very complex. Cassiterite dominates, but other minerals (most notably malayaite) do contribute significantly to the deportment. Further studies will aim to quantify the variability of deportment and other resource characteristics, in order to guide mineral processing test work.
Invited lecture (Conferences)
ResErVar Netzwerktreffen Clausthal, 24.-29.05.2016, Clausthal, Deutschland
Registration No. 25484 - Permalink
Herbig, C.; Knispel, T.; Simon, S.; SchröDer, U. A.; MartíNez-Galera, A. J.; Arman, M. A.; Teichert, C.; Knudsen, J.; Krasheninnikov, A. V.; Michely, T.
Abstract: Our scanning tunneling microscopy and X-ray photoelectron spectroscopy experiments along with first-principles calculations uncover the rich phenomenology and enable a coherent understanding of carbon vapor interaction with graphene on Ir(111). At high temperatures, carbon vapor not only permeates to the metal surface but also densifies the graphene cover. Thereby, in addition to underlayer graphene growth, upon cool down also severe wrinkling of the densified graphene cover is observed. In contrast, at low temperatures the adsorbed carbon largely remains on top and self-organizes into a regular array of fullerene-like, thermally highly stable clusters that are covalently bonded to the underlying graphene sheet. Thus, a new type of predominantly sp2-hybridized nanostructured and ultrathin carbon material emerges, which may be useful to encage or stably bind metal in finely dispersed form.
Keywords: graphene, CVD growth, first-principles calcualtions
Nano Letters (2017)
Online First (2017) DOI-Link: http://dx.doi.org/10.1021/acs.nanolett.7b00550
Registration No. 25480 - Permalink
Kelling, J.; Ódor, G.; Gemming, S.
Abstract: For lattice Monte Carlo simulations parallelization is crucial to make studies of large systems and long Simulation time feasible, while sequential simulations remain the gold-standard for correlation-free dynamics. Here, various domain decomposition schemes are compared, concluding with one which delivers virtually correlation-free simulations on GPUs.
Extensive simulations of the octahedron model for 2 + 1 dimensional Kardar–Parisi–Zhang surface growth, which is very sensitive to correlation in the site-selection dynamics, were performed to show self-consistency of the parallel runs and agreement with the sequential algorithm. We present a GPU implementation providing a speedup of about 30× over a parallel CPU implementation on a single socket and at least 180× with respect to the sequential reference.
Keywords: Lattice Monte Carlo, Kardar-Parisi-Zhang, GPU, autocorrelation
Contribution to WWW
Registration No. 25479 - Permalink
Kelling, J.; Juckeland, G.
Abstract: It was observed, that the RT-PICLS code ran by FWKT on the hypnos cluster was producing an unusual amount of system load, according to Ganglia metrics. Since this may point to an IO-problem in the code, this code was analyzed more closely.
Keywords: particle-in-cell, profiling
Other report
Dresden: Qucosa, 2017
Registration No. 25474 - Permalink
Lutz, B.; Römer, K.; Weinberger, D.; Bemmerer, D.; Fiedler, F.
Abstract: Silicon Photo-Multiplier (SiPM) have attractive features that enable new approaches in detector design. Especially the compact size, the insensitivity to magnetic fields, and the very competitive price, make them a prime candidate for use in detectors for particle therapy. To validate their usability in the secondary radiation field of particle therapy facilities, it is necessary to study their sensitivity to neutron fields of the characteristic spectrum. The talk gives an overview of the plans for such irradiation tests at the OncoRay facility.
Keywords: SiPM, neutron irradiation, MUSE
Lecture (Conference)
MUSE General Meeting, 10.-12.05.2017, Frascati, Italia
Registration No. 25473 - Permalink
Ghannadzadeh, S.; Licciardello, S.; Arsenijevic, S.; Robinson, P.; Takatsu, H.; Katsnelson, M. I.; Hussey, N. E.
Abstract: In many layered metals, coherent propagation of electronic excitations is often confined to the highly conducting planes. While strong electron correlations and/or proximity to an ordered phase are believed to be the drivers of this electron confinement, it is still not known what triggers the loss of interlayer coherence in a number of layered systems with strong magnetic fluctuations, such as cuprates. Here, we show that a definitive signature of interlayer coherence in the metallic-layered triangular antiferromagnet PdCrO2 vanishes at the Néel transition temperature. Comparison with the relevant energy scales and with the isostructural non-magnetic PdCoO2 reveals that the interlayer incoherence is driven by the growth of short-range magnetic fluctuations. This establishes a connection between long-range order and interlayer coherence in PdCrO2 and suggests that in many other low-dimensional conductors, incoherent interlayer transport also arises from the strong interaction between the (tunnelling) electrons and fluctuations of some underlying order.
Nature Communications 8(2017), 15001
DOI-Link: http://dx.doi.org/10.1038/ncomms15001
Registration No. 25468 - Permalink
Götze, K.; Aoki, D.; Lévy-Bertrand, F.; Harima, H.; Sheikin, I.
Abstract: We report high field de Haas–van Alphen (dHvA) effect measurements in CeRh2Si2 both below and above the first-order 26 T metamagnetic transition from an antiferromagnetic to a polarized paramagnetic state. The dHvA frequencies observed above the transition are much higher than those observed below, implying a drastic change of the Fermi-surface size. The dHvA frequencies above the transition and their angular dependence are in good agreement with band-structure calculations for LaRh2Si2, which correspond to CeRh2Si2 with localized f electrons. Given that the f electrons are also localized at low fields in CeRh2Si2, the Fermi-surface reconstruction is due to the suppression of antiferromagnetism and the restoration of the crystallographic Brillouin zone rather than the delocalization of the f electrons. This example suggests that the intuitive notation of "small" and "large" Fermi surfaces commonly used for localized and itinerant f electrons, respectively, requires careful consideration, taking into account the modification of the Brillouin zone in the antiferromagnetic state, when interpreting experimental results.
Physical Review B 95(2017), 161107(R)
DOI-Link: http://dx.doi.org/10.1103/PhysRevB.95.161107
Registration No. 25467 - Permalink
Melkhanova, S.; Haluska, M.; Hübner, R.; Gemming, S.; Krause, M.
Abstract: Predefined catalysts have been recently successfully employed for diameter- and chirality-selective CVD growth of single-walled carbon nanotubes (SWCNTs).[1-3] They simplify the exhausting optimization of parameters for in situ catalyst formation and ensure a very good control of catalyst properties. Using C:Ni nanocomposite templates (NCTs) as catalyst precursors, SWCNTs with a selective, monomodal diameter distribution were obtained. More than the half of the SWCNTs had a diameter of (1.36±0.10) nm.[3]
While the preparation of NCTs is well defined and controlled, the activation of the NPs for nanotube synthesis by CVD is a critical step that is still not fully understood. Element-resolved scanning and high-resolution transmission electron microscopy and Raman spectroscopy were used to clarify the microstructure of C:Ni NCTs in the different stages of the SWCNT growth. These studies reveal a distinct change of the NCT microstructure by conserving the initial nanocomposite morphology to a very large extend.
[1] F. Yang et al., Nature 510, 522 (2014);
[2] H. An et al., Nanoscale 8, 14523 (2016);
[3] S. Melkhanova et al., Nanoscale 8, 14888 (2016)
Keywords: Single-walled carbon nanotubes, nanocomposites, catalysis, Raman spectroscopy, transmission electron microscopy
XXXIstInternational Winterschool on Electronic Properties of Novel Materials, 04.-11.03.2017, Kirchberg, Österreich
Registration No. 25461 - Permalink
Li, R.; Dong, N.; Cheng, C.; Ren, F.; Hübner, R.; Wang, J.; Zhou, S.; Chen, F.
Abstract: We report on the enhancement and modulation of nonlinear optical response in an Nd:Y3Al5O12 (Nd:YAG) laser crystal through embedded silver nanoparticles (NPs) fabricated by Ag+ ion implantation. The linear absorption spectrum of the sample clearly reveals a localized surface plasmon resonance (SPR) band from 350 to 700 nm correlated to the Ag NPs. By using the Z-scan technique with femtosecond pulses at a wavelength of 515 nm, which is considered as an optical excitation within the SPR band, the nonlinear refraction index reaches values as high as ∼10–12 cm2/W, enhanced by ∼4 orders of magnitude in comparison to that of unimplanted Nd:YAG (without Ag NPs). In addition, it has been shown that embedded Ag NPs in the Nd:YAG host reveal saturable absorption signifying the nonlinear responses. We have also observed that the nonlinear absorption coefficients depend significantly on the excitation energy and can be modulated by varying the fluence of Ag+ ions.
ACS Omega 2(2017)4, 1279-1286
DOI-Link: http://dx.doi.org/10.1021/acsomega.7b00003
Registration No. 25456 - Permalink
Das, A.; Viehrig, H. W.; Bergner, F.; Heintze, C.; Altstadt, E.; Hoffmann, J.
Abstract: ODS steels have been known to exhibit anisotropic fracture behaviour and form secondary cracks. In this work, the factors responsible for the anisotropic fracture behaviour have been investigated using scanning electron microscopy and electron backscatter microscopy. Fracture toughness of hot rolled 13Cr ODS steel was determined using unloading compliance method for L-T and T-L orientations at various temperatures. L-T orientation had higher fracture toughness than T-L orientation and also contained more pronounced secondary cracking. Secondary cracks appeared at lower loads than primary cracks in both orientations. Primary crack propagation was found to be preferentially through fine grains in a bimodal microstructure. Grains were aligned and elongated the most towards rolling direction followed by T and S directions resulting in fracture anisotropy. Crystallographic texture and preferential alignment of Ti enriched particles parallel to rolling direction also contributed towards fracture anisotropy.
Keywords: ODS-steel, fracture behaviour, anisotropy, secondary cracking, bimodal microstructure, delamination, fractography
Journal of Nuclear Materials 491(2017), 83-93
DOI-Link: http://dx.doi.org/10.1016/j.jnucmat.2017.04.059
Registration No. 25455 - Permalink
Arnold, T.; Sachs, S.
Abstract: This poster presents the main objectives tasks and milestones of a roadmap, which was developed by the COMET/ALLIANCE working group NORM with focus on important priorities within NORM related research.
Keywords: NORM, roadmap, COMET, ALLIANCE
COMET Final Event, 25.-27.04.2017, Bruges, Belgium
Registration No. 25452 - Permalink
Karlušić, M.; Jakšić, M.; Lebius, H.; Ban-D'Etat, B.; Wilhelm, R. A.ORC; Heller, R.; Schleberger, M.
Abstract: Conditions for ion track formation in single crystal SrTiO3 and TiO2 (rutile) after irradiations using swift heavy ion beams with specific energies below 1 MeV/amu were investigated in this work. Rutherford backscattering spectroscopy in channeling was used to measure ion tracks in the bulk, while atomic force microscopy was used for observation of ion tracks on the surfaces. Variations in the ion track sizes and respective thresholds were observed after irradiations under random, channeling and near-channeling conditions close to normal incidence. These variations are attributed to the specifics of the electronic stopping power of swift heavy ions under the investigated conditions. In the case of ion channeling, electronic stopping power is reduced and observed ion tracks are smaller. The opposite was found under the near-channeling conditions when lowering of the ion track formation threshold was observed. We attribute this finding to the oscillating electronic stopping power with large peak values. For both materials, thresholds for bulk and surface ion track formation were found to be surprisingly close, around 10 keV nm−1. Obtained results are compared with predictions of the analytical thermal spike model.
Keywords: SrTiO3, TiO2, swift heavy ion, ion track, thermal spike, RBS/c, AFM
Journal of Physics D: Applied Physics 50(2017), 205302
DOI-Link: http://dx.doi.org/10.1088/1361-6463/aa678c
Registration No. 25451 - Permalink
Ikeda-Ohno, A.ORC
Abstract: Nuclear weapons tests conducted worldwide have dispersed long-lived and radioactive nuclear debris including plutonium (Pu). A reliable assessment of the environmental impact of these radioactive contaminants and their potential implications for human health requires an understanding of their physical/chemical characteristics at the molecular scale. This lecture focuses particularly on the physical/chemical characterisation of the Pu contaminant, one of the most problematic radioactive contaminants released from nuclear tests, by synchrotron-based X-ray microscopy / spectroscopy. The study reveals direct experimental evidence that the Pu legacy remaining at one of the former testing sites in Australia (Taranaki, Maralinga) exists as particulates of Pu(IV) oxyhydroxide compounds, a very concentrated and low-soluble form of Pu, which will serve as ongoing radioactive sources far into the future. Based on the obtained results, a possible scenario of the physical/chemical transformation of the original Pu materials dispersed in the semi-arid environment at Maralinga can be also deduced. The lecture also highlights the importance of the comprehensive characterization of radioactive contaminants for reliable environmental- and radiotoxicological assessment.
Keywords: Actinides, plutonium, environmental science, chemical transformation, synchrotron, X-ray microscopy, X-ray spectroscopy
Invited lecture (Conferences)
Guest lecture at the lecture series "Radioecology", 18.05.2017, TU Dresden, Germany
Registration No. 25444 - Permalink
Vishwakarma, V.; Schubert, M.; Hampel, U.
Abstract: Cross-flow trays are highly reputed among vapour-liquid contacting devices in distillation columns. Their ability to perform in various operating conditions, low fouling sensitivity, low cost and access for inspections make them potential nominee for column internals. Tray separation efficiency as well as overall performance of the column is strongly dictated by evolving flow patterns on the tray. Liquid plug flow is considered 'ideal' at which the maximum tray efficiency can be expected. On the other hand, liquid channelling, bypassing, retrograde flow and stagnant zones are known to be detrimental to tray efficiency. Schubert et. al. (2016) established the wire-mesh sensor as a novel technique to extract liquid flow patterns on trays and presented the effect of variable liquid load and weir design on the flow patterns.
As a follow up, the most common mathematical models, which were recently revisited by Vishwakarma et al. (2016), are applied to associate flow and mixing patterns with tray efficiency. They indicate serious loss in efficiency for the tray with largest stagnant regions. The location of dead zones is also important as most of the mass transfer on large trays happens in their first half. Any stagnant liquid in these areas is highly disadvantageous for the tray to fractionate as per expectations. This contribution will stimulate to develop a new practicable model that can account for the effect of location and type of non-ideality on the tray efficiency.
(1) M. Schubert, M. Piechotta, M. Beyer, E. Schleicher, U. Hampel and J. Paschold, 'An imaging technique for characterization of fluid flow pattern on industrial-scale column sieve trays', Chemical Engineering Research and Design, vol. 111, pp.138–146, 2016.
(2) V. Vishwakarma, M. Schubert and U. Hampel, 'Distillation tray efficiency modelling: a forgotten chapter', Jahrestreffen der ProcessNet-Fachgruppe Fluidverfahrenstechnik, 16-17 March 2016, Garmisch-Partenkirchen.
Lecture (Conference)
Jahrestreffen der ProcessNet-Fachgruppe Fluidverfahrenstechnik, 08.-10.03.2017, Cologne, Germany
Registration No. 25435 - Permalink
Kipping, R.; Kryk, H.; Hampel, U.
Abstract: Blasensäulenreaktoren zählen aufgrund ihrer einfachen Bauweise und ihres ausgezeichneten Wärme-und Stofftransportverhaltens zu einem der häufig genutzten Reaktortypen in der chemischen Industrie. Gegenstand aktueller Forschungsarbeiten innerhalb des DFG Schwerpunktprogramms 1740 "Reaktive Blasenströmungen" ist die Untersuchung lokaler Transportprozesse, um das Verständnis über die Kopplung von Hydrodynamik und Stofftransport bei reaktiven 2-Phasenströmungen in Blasensäulen zu verbessern. Aufgrund limitierter Messtechnik stellt die Ermittlung von lokalen Konzentrationsfeldern und Stofftransportraten in dichten Blasenströmungen eine besondere Herausforderung dar. In diesem Beitrag werden experimentelle Untersuchungen zum Stofftransport am Beispiel der chemischen Absorption von CO2 vorgestellt, bei der die am HZDR entwickelte Gittersensormesstechnik zur Ermittlung der Konzentration und der Umwandlung ionischer Spezies eingesetzt wird. Für diesen Zweck konnte der Gittersensor anhand eines theoretischen Modells und Validierungsexperimente erfolgreich qualifiziert werden. Die experimentellen Ergebnisse der Stofftransportuntersuchungen in einem Blasensäulenreaktor zeigen die Stofftransportraten für verschiedene Eingangsparameter (z.B. Eingangskonzentration der Natronlauge und Gasdurchsatz des CO2) sowohl in Abhängigkeit des Radius als auch in verschiedenen Höhen des Reaktors.
Jahrestreffen der ProcessNet-Fachgruppen Mehrphasenströmungen, Partikelmesstechnik, Zerkleinern und Klassieren, Computational Fluid Dynamics, Mischvorgänge und dem TAK Aerosoltechnologie, 14.-15.03.2017, Dresden, Deutschland
Registration No. 25431 - Permalink
Lecrivain, G.; Yamamoto, R.; Hampel, U.; Taniguchi, T.
Abstract: We propose an extended smooth profile method which can deal with particle-dynamics dispersed in a binary fluid. The smooth profile method, originally developed for the simulation of particle transport in a homogeneous fluid, has been successfully combined with a binary fluid model based on Ginzburg-Landau free energy functional. In this approach, the three types of interfaces among particles and two fluids are treated as diffuse interfaces. By using the method, we simulated the attachment and detachment dynamics of a colloidal particle to the surface of a position fixed bubble in a Newtonian fluid under various capillary numbers. It is found that the method can reproduce the three micro-processes associated with the particle attachment ((i) particle approach, (ii) collision, (iii) sliding down on the bubble surface) (Gregory et al, 2016). The present method will make it possible to simulate a froth flotation process, where the capture of hydrophobic particles by rising bubbles is of primary importance.
Keywords: Flotation; Direct Numerical Simulation; Smoothed Profile Method; Immersed Boundary Method
Contribution to proceedings
3rd International Symposium on Multiscale Multiphase Process Engineering (MMPE), 08.-11.05.2017, Toyama, Japan
Registration No. 25428 - Permalink
Dhal, S.; Chatterjee, S.; Facsko, S.; Möller, W.; Böttger, R.; Satpati, B.; Ratha, S.; Hübner, R.
Abstract: Nanostructured materials are gaining increasing importance due to their unique properties resulting from the high surface to volume ratio and the altered characteristics of the nanoscaled building blocks. The properties of these materials depend strongly on their microstructure and thus can be controlled by inducing transformation on the nanoscale. In this work, a simple low energy ion beam irradiation technique is presented that can be used to effectively weld the hydrogen titanate nanotubes into a large-scale network of nanowires. By varying the ion fluence, we are able to fragment the entire nanowire network into uniformly distributed nanocrystalline particles with an average size of 5 ± 2 nm. Three-dimensional computer simulations of the ion irradiation effects on the nanotubes reproduce most of the experimental findings and thus confirm that the early development of the system is governed by atomic collision processes. Our study demonstrates that the selective use of ion irradiation can transform metal-oxide nanotubes into large-scale welded networks of nanowires and further into nanocrystalline particles through nucleation and growth.
Keywords: ion irradiation, titanium oxide, nanowelding, nanoparticle
Crystal Growth & Design (2017)
Online First (2017) DOI-Link: http://dx.doi.org/10.1021/acs.cgd.7b00173
Registration No. 25425 - Permalink
Švecová, B.; Vařák, P.; Vytykáčová, S.; Nekvindová, P.; Macková, A.; Malinský, P.; Böttger, R.
Abstract: Glasses containing copper are promising photonic materials for lasing devices and all-optical components. It has already been shown that the oxidation state of the implants depends on many factors. This paper is going to report on one of them, i.e. the influence of the composition of a silicate glass matrix on the behaviour of the implanted Cu ions before and after a subsequent implantation of oxygen ions.
Three types of silicate glasses having a different extent of cross-linking were implanted with copper ions with an energy of 330 keV and a fluence 1 × 1016 ions cm−2. Then the glasses were implanted with oxygen ions with an energy of 110 keV into the same depth as the already implanted Cu ions. The concentration depth profiles of Cu in the glasses were studied by Rutherford Backscattering Spectrometry. After the implantation, the samples were characterised by optical absorption and photoluminescence spectroscopy. The samples were annealed in ambient atmosphere for 1 h at 600 °C, which is near the transformation temperature of those glasses. The effect of annealing on the distribution of the implants and on the absorption and emission spectra of the as-implanted glasses will be discussed as well
Keywords: Silicate glasses; Ion implantation; Copper; Oxygen
Nuclear Instruments and Methods in Physics Research B (2017)
Online First (2017) DOI-Link: http://dx.doi.org/10.1016/j.nimb.2017.03.042
Registration No. 25424 - Permalink
Metzkes, J.
Lecture (Conference)
High Intensity Laser Matter Science at the HED instrument at the European XFEL, 05.-06.04.2017, Schenefeld, Deutschland
High Intensity Laser Matter Science at the HED instrument at the European XFEL, 05.-06.04.2017, Schenefeld, Deutschland
Registration No. 25422 - Permalink
Metzkes, J.
Invited lecture (Conferences)
Arbeitstreffen Kernphysik 2017, 02.-09.03.2017, Schleching, Deutschland
Registration No. 25421 - Permalink
Hoang, D. H.; Leißner, T.; Sterbik, N.; Haser, S.; Rudolph, M.ORC; Peuker, U. A.
Abstract: The Mineral Liberation Analyzer combines an Scanning Electron Microscope (SEM) and multiple Energy Dispersive X-ray detectors with automated quantitative mineralogy software. SEM-based automated mineralogy tools are essential in measuring parameters, such as modal mineralogy, mineral locking, mineral association, theoretical grade - recovery and mineral liberation. Such quantitative information are fundamental to investigate the mineralogical characteristics of an ore and evaluate its mineral processing.
A carbonaceous apatite ore sample from Lao Cai deposit, Vietnam was used in this study. The petrographic, mineralogical and mineral liberation observations showed that the ore sample is quite complex, containing carbonate impurities (dolomite and calcite) and having very fine intergrowth texture. The fine intergrowth in complex apatite ores requires very fine grinding for liberation in flotation.
Keywords: MLA, Flotation, Apatite, sedimentary ore, Calcite, Dolomite
Contribution to proceedings
International Forum - Contest of Young Researches, Topical Issue of Rational Use of Natural Resources, 19.-21.04.2017, St. Petersburg, Russia
International Forum - Contest of Young Researches, Topical Issue of Rational Use of Natural Resources, St. Petersburg, Russia: Gorny Institute, 978-5-94211-780-1, 170-173
Registration No. 25417 - Permalink
Giesecke, A.; Stefani, F.; Herault, J.
Abstract: We examine kinematic dynamo action driven by an axisymmetric large scale flow that is superimposed with an azimuthally propagating non-axisymmetric perturbation with a frequency ω. Although we apply a rather simple large scale velocity field, our simulations exhibit a complex behavior with oscillating and azimuthally drifting eigenmodes as well as stationary regimes. Within these non-oscillating regimes we find parametric resonances characterized by a considerable enhancement of dynamo action and by a locking of the phase of the magnetic field to the pattern of the perturbation. We find an approximate fulfillment of the relationship between the resonant frequency ωres of the disturbed system and the eigenfrequency ω0 of the undisturbed system given by ωres = 2 ω0 which is known from paradigmatic rotating mechanical systems and our prior study [Giesecke et al., Phys. Rev. E, 86, 066303 (2012)]. We find further -- broader -- regimes with weaker enhancement of the growth rates but without phase locking. However, this amplification regime arises only in case of a basic (i.e. unperturbed) state consisting of several different eigenmodes with rather close growth rates. Qualitatively, these observations can be explained in terms of a simple low dimensional model for the magnetic field amplitude that is derived using Floquet theory.
Keywords: Dynamo Instability Parametric Resonance
Physical Review Fluids 2(2017)5, 053701
DOI-Link: http://dx.doi.org/10.1103/PhysRevFluids.2.053701
- Secondary publication expected from 19.05.2018
Registration No. 25414 - Permalink
Karpov, Y.; Erdmann, T.; Stamm, M.; Lappan, U.; Guskova, O.; Malanin, M.; Raguzin, I.; Beryozkina, T.; Bakulev, V.; Günther, F.; Gemming, S.; Seifert, G.; Hambsch, M.; Mannsfeld, S.; Voit, B.; Kiriy, A.
Abstract: Herein we present a molecular doping of a high mobility diketopyrrolopyrrole–dithienylthieno[3,2-b]thiophene donor–acceptor copolymer poly[3,6-(dithiophene-2-yl)-2,5-di(6-dodecyloctadecyl)pyrrolo[3,4-c]pyrrole-1,4-dione-alt-thieno[3,2-b]thiophene], PDPP(6-DO)2TT, with the electron-deficient compound hexafluorotetracyanonaphthoquinodimethane (F6TCNNQ). Despite a slightly negative HOMO(donor)–LUMO(acceptor) offset of −0.12 eV which may suggest a reduced driving force for the charge transfer (CT), a partial charge CT was experimentally observed in PDPP(6-DO)2TT:F6TCNNQ by absorption, vibrational, and electron paramagnetic resonance spectroscopies and predicted by density functional theory calculations. Despite the modest CT, PDPP(6-DO)2TT:F6TCNNQ films possess unexpectedly high conductivities up to 2 S/cm (comparable with the conductivities of the benchmark doped polymer system P3HT:F4TCNQ having a large positive offset). The observation of the high conductivity in doped PDPP(6-DO)2TT films can be explained by a high hole mobility in PDPP(6-DO)2TT blends which compensates a lowered (relatively to P3HT:F4TCNQ) concentration of free charge carriers. We also show that F6TCNNQ-doped P3HT, the system which has not been reported so far to the best of our knowledge, exhibits a conductivity up to 7 S/cm, which exceeds the conductivity of the benchmark P3HT:F4TCNQ system.
Keywords: organic electronics, molecular doping, p-dopant, conjugated polymer, electrical conductivity, charge transfer complex
Macromolecules 50(2017), 914-926
DOI-Link: http://dx.doi.org/10.1021/acs.macromol.6b02452
Registration No. 25413 - Permalink
Henning, S.; Kühn, L.; Herranz, J.; Nachtegaal, M.; Hübner, R.; Werheid, M.; Eychmüller, A.; Schmidt, T. J.
Abstract: Developing highly active and durable oxygen reduction reaction (ORR) catalysts is crucial to reduce the cost of polymer electrolyte fuel cells (PEFCs). To meet those requirements, unsupported Pt-Cu alloy nanochains (aerogels) were synthesized by a simple co-reduction route in aqueous solution and their structure was characterized by X-ray absorption spectroscopy and scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy. These catalysts exceeded the ORR activity of commercial Pt/C catalysts by more than 100% in rotating disk electrode (RDE) experiments and met the corresponding US DOE target for automotive PEFC implementation, thereby qualifying as very promising materials. The behavior of Pt-Cu aerogels under PEFC operation conditions was mimicked by acid washing experiments which showed that the Cu content in the alloy phase and ORR activity decrease through this step. Comparing composition, structure and ORR activity for various specimens, the Cu content in the alloy phase was identified as the main descriptor of ORR activity. An almost linear correlation was found between those two parameters and complemented by supporting data from the literature.
Keywords: Aerogels; Dealloying; ORR; PEFC; X-ray absorption
Electrochimica Acta 233(2017), 210-217
DOI-Link: http://dx.doi.org/10.1016/j.electacta.2017.03.019
Registration No. 25412 - Permalink
Čížek, J.; Vlček, M.; Hruška, P.; Lukáč, F.; Melikhova, O.; Anwand, W.; Selim, F.; Hugenschmidt, C.; Egger, W.
Abstract: In the present work point defects in ZnO crystals were characterized by positron lifetime spectroscopy combined with back-diffusion measurement of slow positrons. Defects in ZnO crystals grown by various techniques were compared. Hydrothermally grown ZnO crystals contain defects characterized by lifetime of ≈181 ps. These defects were attributed to Zn vacancies associated with hydrogen. ZnO crystals prepared by other techniques (Bridgman, pressurized melt growth, and seeded chemical vapour transport) exhibit shorter lifetime of ≈165 ps. Positron back-diffusion studies revealed that hydrothermally grown ZnO crystals contain higher density of defects than the crystals grown by other techniques. The lowest concentration of defects was detected in the crystal grown by seeded chemical vapor transport.
Journal of Physics: Conference Series 791(2017)1, 012017
DOI-Link: http://dx.doi.org/10.1088/1742-6596/791/1/012017
Registration No. 25411 - Permalink
Pilz, K.; Leger, S.; Zwanenburg, A.; Richter, C.; Krause, M.; Baumann, M.; Löck, S.; Troost, E.
Abstract: Purpose/Objective: Radiochemotherapy (RCT) for patients with head and neck squamous cell carcinoma (HNSCC) frequently causes xerostomia and dysphagia, which may be alleviated by treatment adaption, e.g., modulation of dose distribution to the salivary glands. Current clinical models, which are based on dosimetric parameters, mostly achieve moderate prediction accuracy. Therefore, we aimed to improve the prediction of xerostomia and dysphagia by using additional imaging biomarkers based on computed tomography (CT) scans.
Material/Methods: In this study 46 patients with UICC stage III/IV advanced head and neck squamous cell carcinoma (HNSCC) were considered (NCT00180180, [1]). All patients received primary RCT and underwent a pre-treatment CT scan without intravenous contrast agent. Patient-reported xerostomia and dysphagia were evaluated at baseline, every week during RCT, four weeks after treatment and three monthly thereafter. 5040 imaging features were extracted from the parotid and submandibular glands. Feature reproducibility tests based on the RIDER re-test data set [2] were performed leading to 1513 imaging features in total. The most informative features were selected by a univariate logistic regression analysis. The developed radiomic signature was used to train and validate multivariate logistic regression and random forest models using repeated 5-fold cross validation. The predication accuracy was assessed by the area under the curve (AUC).
Results: The logistic regression and the random forest model achieved similar performance in predicting xerostomia (AUC=0.71). The developed signature consisted of one dosimetric parameter and one imaging feature. For the prediction of dysphagia both models achieved only a moderate prediction accuracy (AUC=0.55).
Conclusions: For prediction of xerostomia, a signature was developed and showed a good performance. For dysphagia only moderately performing models could be obtained in this cohort. Based on our results, subgroups of patients at a high risk of xerostomia may be identified and offered treatment adaption. However, further investigations are currently ongoing, i.e., externally validating the developed signature, which is an important step in developing clinically relevant prediction models.
ESTRO 36, 05.-09.05.2017, Wien, Österreich
Registration No. 25410 - Permalink
Andreev, A. V.; Gorbunov, D. I.; Skourski, Y.; Kuz'Min, M. D.; Tereshina, E. A.; Henriques, M. S.
Abstract: Magnetization of a Ho2Fe14Si3 single crystal was measured in a steady magnetic field of up to 9 T and in pulsed fields of up to 60 T applied along the principal axes. Ho2Fe14Si3 is a ferrimagnet below TC = 480 K, has a spontaneous magnetic moment of about 8 µB/f.u. (at T = 4.2 K) and exhibits a large easy-plane magnetic anisotropy. There is also a certain anisotropy within the basal plane, the b axis [120] being the easy-magnetization direction. In fields applied along the a and b axes field-induced first-order phase transitions are observed at 29 T and at 22 T, respectively. Along the easy axis b we observe also an S-shaped anomaly at about 47 T, which does not correspond to a phase transition. A simple model predicts that the two observed first-order transitions are the only ones taking place in Ho2Fe14Si3; the magnetization should subsequently grow continuously and arrive at saturation at ~100 T. This is in stark contrast to the behavior of the parent compound Ho2Fe17, where as many as three sequential first-order transitions are expected for H‖b. The reason for the disparity is that the basal-plane anisotropy constant KHo is at least one order of magnitude smaller in Ho2Fe14Si3 than it is in Ho2Fe17.
Journal of Alloys and Compounds 694(2017), 761-766
DOI-Link: http://dx.doi.org/10.1016/j.jallcom.2016.10.069
Registration No. 25409 - Permalink
Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcy, G.; Kornakov, G.; Kotte, R.; Kühn, W.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Nowakowski, K. N.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Reshetin, A.; Rodriguez-Ramos, P.; Rosier, P.; Rost, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.
Abstract: We present first data on charged kaons and {\phi} mesons in Au+Au collisions at a kinetic beam energy of 1.23A GeV. As observed already at slightly higher beam energies, we find significantly different slopes for the K+ and K- transverse-mass spectra, and no significant increase of the the K-/K+ multiplicity ratio with increasing centrality of the collision. The {\phi}/K- multiplicity ratio is found to be surprisingly high with a value of 0.52 ± 0.16 and shows no dependence on the centrality, either. The different slopes of the K+ and K- spectra can be explained by feed-down from {\phi} mesons, which substantially softens the spectra of K- mesons.
Contribution to WWW
Registration No. 25408 - Permalink
Müller, S. E.ORC; Konheiser, J.; Naumann, B.; Ferrari, A.; Magin, A.
Abstract: A new cyclotron is currently being commissioned at the Center of Radiopharmaceutical Cancer Research of the HZDR. The energy range of up to 28 MeV protons for the 18O(p,n)18F reaction required a recalculation of the neutron source terms needed in the shielding calculations, since the manufacturer supplied data was based on a 24 MeV proton beam. The radiation transport programs MCNP6 and FLUKA were used to calculate the neutron fluence emerging from the 18O-enriched water target during operation. Both Monte Carlo programs agree within 20 % on the neutron yield per incident proton for 24 and 28 MeV proton beams, while at 24 MeV, the manufacturer supplied data is considerably lower than the simulation results. To validate the radiation fields obtained in the simulations, an experimental program has been started using activation samples which are placed close to the water target of the cyclotron which is currently used to produce 18F. After irradiation, the samples are analyzed, and the resulting activation is compared to Monte Carlo calculations of the expected sample activation.
Lecture (Conference)
DPG Spring Meeting 2017, 27.-31.03.2017, Münster, Germany
Registration No. 25401 - Permalink
Wolter, J.-M.; Philipp, T.; Lippold, H.; Schmeide, K.; Stumpf, T.
Abstract: Leaching experiments of uranium(VI) doped calcium-silicate-hydrate (CSH) phases with various calcium to silicon ratios were carried out in NaCl, NaCl/Na2SO4, NaCl/NaHCO3 and NaHCO3 containing solutions to study the time-dependent release of Ca, Si and U. Potential changes of the U(VI)-CSH binding induced by leaching were monitored with time-resolved laser-induced fluorescence spectroscopy (TRLFS), infrared spectroscopy (IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD).
Lecture (others)
4. Workshop des BMWi-Verbundvorhabens "Geochemische Radionuklidrückhaltung an Zementalterationsphasen (GRaZ)", 05.-06.04.2017, Mainz, Deutschland
Registration No. 25399 - Permalink
Brinkmann, H.; Moll, H.
Abstract: Low and intermediate level waste contain cellulosic material in considerable amounts. In a repository nuclear waste is often surrounded by cementitious backfill material. If water ingresses a hyperalkaline environment will be established. Since cellulose will be relatively fast degraded under alkaline conditions, there is a high risk that small organic, water soluble molecules will be formed. These molecules can act as complexing agents for radionuclides and thereby affecting their sorption behavior and solubility adversely. Therefore the focus of current investigations is on the interaction of uranium (VI) with Isosaccharinic acid (ISA) as main degradation product of cellulose first in the acidic pH range. The progress and results of these studies within the MIND project (work package 1) will be presented.
Keywords: Cellulose, Isosaccharinic acid, Uranium, Speciation
Lecture (others)
MIND Project Annual Meeting 2017, 03.-05.05.2017, Prague, Czech Republic
Registration No. 25397 - Permalink
Kaczmarz, S.; Göttler, J.; Griese, V.; Petr, J.ORC; Zimmer, C.; Sorg, C.; Preibisch, C.
Abstract: Objectives:
Internal carotid-artery stenosis (ICAS) is a major public health issue, as it accounts for approximately 20% of all strokes1. However, related complex hemodynamic impairments are not well understood2. We therefore propose a multimodal MRI-protocol. The major aims were to evaluate its reliability and investigate physiological changes.
In the ongoing clinical study, 52 subjects (29 healthy controls: 70.3±4.7y, 13 males; 23 patients with asymptomatic unilateral ICAS, NASCET>70%: 70.5±6.8y, 15 males) underwent MRI on a Philips 3T-Ingenia. We propose a combination of three different MR-based methods, accounting for cerebrovascular reactivity (CVR) by breathhold-fMRI (voxelsize 3x3x3mm3, 38 slices, TE/TR=30ms/1200ms, acq.time=5:48min), CBF by pCASL (3D-readout, voxelsize 2.7x2.8x6mm3, 16 slices, TE/TR=7.4ms/4403ms, label duration=1800ms, PLD=2000ms, acq.time 5:43min) and relative oxygen extraction fraction (rOEF) by a multi-parametric quantitative-BOLD approach3 (voxelsize 2x2x3mm3, 30 slices). For each participant, individual masks of watershed areas were defined for both hemispheres in grey-matter and mean values of all three modalities were compared.
In healthy participants, our results show no significant lateralization of all three modalities on a group level. For ICAS-patients, regionally reduced CVR (p=0.003) as well as hypoperfusion (p< 0.001) were found ipsilateral to the stenosis (figure). In accordance with the literature, we did not find ICAS-induced changes in oxygen extraction on a group level (p=0.310).4 Even though focal rOEF increases could be suspected in single patients.
The presented preliminary results thus imply successful application of our multimodal-MRI approach and are highly promising with respect to gaining a deeper insight into ICAS-related physiological changes. Further investigations of the relations between the parameters are currently in progress.
Contribution to proceedings
28rd International Symposium on Cerebral Blood Flow, Metabolism and Function, 01.04.2017, Berlin, Germany
Proceedings of the 28rd International Symposium on Cerebral Blood Flow, Metabolism and Function
Registration No. 25394 - Permalink
Kaever, P.; Balzer, M.; Kopmann, A.; Zimmer, M.; Rongen, H.
Abstract: Various centres of the German Helmholtz Association (HGF) started in 2012 to develop a modular data acquisition (DAQ) platform, covering the entire range from detector readout to data transfer into parallel computing environments. This platform integrates generic hardware components like the multi-purpose HGF-Advanced Mezzanine Card or a smart scientific camera framework, adding user value with Linux drivers and board support packages. Technically the scope comprises the DAQ-chain from FPGA-modules to computing servers, notably frontend-electronics-interfaces, microcontrollers and GPUs with their software plus high-performance data transmission links. The core idea is a generic and component-based approach, enabling the implementation of specific experiment requirements with low effort. This so called DTS-platform will support standards like MTCA.4 in hard- and software to ensure compatibility with commercial components. Its capability to deploy on other crate standards or FPGA-boards with PCI express or Ethernet interfaces remains an essential feature. Competences of the participating centres are coordinated in order to provide a solid technological basis for both research topics in the Helmholtz Programme "Matter and Technology", "Detector Technology and Systems" and "Accelerator Research and Development". The DTS-platform aims at reducing costs and development time and will ensure access to latest technologies for the collaboration. Due to its flexible approach, it has the potential to be applied in other scientific programs.
Keywords: Data acquisition concepts; Software architectures (event data models, frameworks and databases); Detector control systems (detector and experiment monitoring and slow-control systems, architecture, hardware, algorithms, databases); Image reconstruction in medical imaging
Contribution to proceedings
Topical Workshop on Electronics for Particle Physics (TWEPP2016), 26.-30.09.2016, Karlsruhe, Deutschland
Journal of Instrumentation 12(2017),C04004: IOPscience
DOI-Link: http://dx.doi.org/10.1088/1748-0221/12/04/C04004
Registration No. 25393 - Permalink
Joseph, T.; Fuchs, F.; Schuster, J.; Schulz, S. E.
Abstract: Fully Depleted Silicon on Insulator transistors (FDSOI) are a promising approach for further scaling. The device features a fully depleted body which is isolated by an insulator box. This introduces better electrostatics, lower leakage current and thus better channel control. The device performance is heavily influenced by the orientation, confinement and strain in the ultra-thin body. In this work the electronic structure of ultra-thin silicon layers is investigated using Density Functional Theory (DFT). The simulation parameters for the model system were calibrated to reproduce the experimental band gap of bulk silicon. This ensures that the model describes the electronic structure of ultra-thin silicon layers accurately. Our study demonstrates the impact of confinement, orientation and strain on material dependent transport properties and their influence on the device performance. For this purpose our results will be used as an input for device simulations using Synopsys Sentaurus TCAD.
We find that the band gap of the silicon layer increases with decreasing slab thickness which is a clear indication of quantum confinement. From the simulation, the band gap for the {100} confinement is found to be higher than {110} and {111} scenarios. Band gap is one of the factors which influence the intrinsic carrier in the semiconductor and thereby the transport. Another important factor for the transport is lattice strain. Strain is a useful method for modulating band structures. One good example is the transformation of direct band gap in {100} confined silicon slab to indirect band gap with 2 % biaxial compression. In our presentation we will discuss the influence of the effective mass as well. Furthermore, the strain dependence of the electronic structure and its impact on device properties is analyzed systematically.
Keywords: silicon, confinement, density functional theory, FDSOI, strain engineering
Material for Advanced Metallization (MAM), 26.-29.03.2017, Dresden, Deutschland
Registration No. 25392 - Permalink
Fuchs, F.; Schuster, J.; Gemming, S.
Abstract: Reconfigurable transistors (RFETs) can be switched between electron and hole current by changing the polarity of the gate potential. This allows a much higher functionality and hence, logic operations can be realized with fewer transistors. The device performance of such a transistor is strongly dominated by the contact physics.
In this work, the electron transport across the NiSi 2 -Si interface is studied using the NEGF formalism and density functional theory, which allows us to consider the atomic structure of the interface. A new model is then presented which relates the electron transport through the interface to the transfer characteristic of an RFET. The model is compared to experimental data, which shows very good agreement, especially with respect to the ratio between electron and hole current (left figure).
Based on the model, different structure variations at the interface and their consequences on the device performance are discussed. It is demonstrated that best symmetry between electron and hole current is achieved for the <110> crystal orientation, which is much worse for <100> orientation (right figure). This makes the <110> orientation advantageous for RFETs. Also the influence of strain generated parallel to the interface plane is investigated (right figure). It is shown that strain can be used to tune the symmetry in case of <110> crystal orientation even further. This is entirely different for the <100> crystal orientation, where the highest electron currents are observed for all strain states. In this state, the electron currents are about three orders of magnitude higher than the hole currents. A detailed discussion of these differences based on work function and band structure analysis will be given in our contribution.
Keywords: reconfigurable transistor, RFET, density functional theory, metal-semiconductor interface
Lecture (Conference)
Material for Advanced Metallization (MAM), 26.-29.03.2017, Dresden, Deutschland
Registration No. 25391 - Permalink
Fuchs, F.; Schuster, J.; Gemming, S.
Abstract: The electron transport across metal-semiconductor interfaces is crucial for the functionality of reconfigurable field-effect transistors, which can be switched between electron and hole current. Devices were already fabricated experimentally, however, a profound understanding of the underlaying mechanism is not yet available.
This study focuses on the NiSi2-Si interface, which is studied using the NEGF formalism. Based on the calculated transmission spectra, the transfer characteristic of a reconfigurable transistor is obtained using a simplified approach. Even though this model strongly simplifies the electrostatic environment in a transistor, very good agreement with experimental devices is demonstrated. The impact of strain on the device characteristic is studied as well. It is shown that the magnitude of electron and hole current can be altered successfully. They can also be tuned to be symmetric, which fits to experimental observations. Finally, new insight into the device functionality is gained based on our calculations of the work functions and effective masses of the isolated NiSi 2 and Si.
Keywords: reconfigurable transistor, RFET, density functional theory, metal-semiconductor interface
Lecture (Conference)
DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Deutschland
Registration No. 25390 - Permalink
Komsa, H.-P.; Krasheninnikov, A. V.ORC
Abstract: Grain boundaries in 2D materials can have marked influence on the material properties. The effects can be not only detrimental, but also beneficial in transition metal dichalcogenides (TMDs), so that controlling the density and type of the boundaries in these systems should be important for engineering their properties. However, this is often possibly only during the growth stage. Molybdenum and tungsten dichalcogenides feature a particular set of 60° mirror twin boundaries, which are reported to occur upon merging of the growing flakes, to appear during growth to accommodate for the nonstoichiometry of the sample, or to be produced a posteriori by electron irradiation or thermal annealing. Furthermore, different preparation conditions lead to different atomic structure of the boundary, which consequently exhibit different electronic properties. This has obviously garnered interest for the ability to control grain boundary types and densities. In this progress report, the recent experimental and theoretical work related to the characterization of mirror twin boundaries is reviewed. A consistent set of formation energies for the mirror twin boundaries is provided, which then allows a coherent picture on the formation mechanisms under different conditions to be drawn. Finally, the electronic structure of these boundaries is analyzed and their potential applications are discussed.
Keywords: 2D materials, first principles calculations
Advanced Electronic Materials (2017), 1600468
DOI-Link: http://dx.doi.org/10.1002/aelm.201600468
- Secondary publication expected from 01.03.2018
Registration No. 25387 - Permalink
Nguyen, L.; Komsa, H.-P.; Khestanova, E.; Kashtiban, R.; Peters, J. P.; Lawlor1, S.; Sanchez, A. M.; Sloan, J.; Gorbachev, R.; Grigorieva, I.; Krasheninnikov, A. V.ORC; Haigh, S. J.
Abstract: We have investigated the structure of atomic defects within monolayer NbSe2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reveal that adventitious impurities of C, N, and O can substitute into the NbSe2 lattice stabilizing Se divacancies. We further observe evidence of Pt substitution into both Se and Nb vacancy sites. This knowledge of the character and relative frequency of different atomic defects provides the potential to better understand and control the unusual electronic and magnetic properties of this exciting two-dimensional material.
Keywords: graphene, 2D materials, TEM, first-principles calculations
ACS Nano 11(2017), 2894-2904
DOI-Link: http://dx.doi.org/10.1021/acsnano.6b08036
- Secondary publication expected from 14.02.2018
Registration No. 25386 - Permalink
Langford-Paden, M. H.; Andrews, M. B.; Swinburn, A. N.; Alker, A.; Beal, K.; Anuar, N. S. B. K.; Knight, M. E.; Jones, J. E.; Beele, B.; Adam, C.; Panak, P.; Geist, A.; Kaden, P.; Natrajan, L. S.
Abstract: Multi-dentate ligands are instrumental to extraction and separations chemistry associated with nuclear fuel reprocessing. Specifically, the TALSPEAK (Trivalent Actinide Lanthanide Separation by Phosphorus reagent Extraction from Aqueous Komplexations) process utilises DTPA to facilitate the separation of minor actinides, MA3+ (Am3+ and Cm3+), from Ln3+ and Y3+, allowing the MA3+ to be reprocessed further by transmutation. The TALSPEAK process involves the preferential extraction of the major component (Ln3+) into the organic phase using HDEHP, while the DTPA-derived ligands remain in the aqueous phase coordinating MA3+ which favour soft donor interactions. The process requires the use of lactic acid as a buffer to maintain pH 3.6 in order to prevent the precipitation of DTPA complexes at low pH, commonly experienced during the processing cycle. Amino acid conjugates derived from EDTA and DTPA present ideal candidates as self-buffering DTPA/EDTA ligands, therefore removing the need for lactic acid in the TALSPEAK process. The ligands (right) produce an internal buffer pH 1.5-2.5 at μM to mM concentrations. The synthesis, coordination chemistry, photophysical properties and separation behaviour of these new ligands and stability towards ionising radiation is presented.
Keywords: Lanthanide(III), Actinide(III), amino acids, DTPA
ThUL School in Actinide chemistry 2016, 19.-23.09.2016, Dresden, Deutschland
Registration No. 25385 - Permalink
Ghorbani-Asl, M.; Kretschmer, S.; Spearot, D. E.; Krasheninnikov, A. V.ORC
Corresponding author: Krasheninnikov, A. V.
Abstract: Two-dimensional (2D) transition metal dichalcogenides (TMDs), like MoS2, have unique electronic and optical properties, which can further be tuned using ion bombardment and post-synthesis ion-beam mediated methods combined with exposure of the irradiated sample to precursor gases. The optimization of these techniques requires a complete understanding of the response of 2D TMDs to ion irradiation, which is affected by the reduced dimensionality of the system. By combining analytical potential molecular dynamics with first-principles calculations, we study the production of defects in free-standing MoS2 sheets under noble gas ion irradiation for a wide range of ion energies when nuclear stopping dominates, and assess the probabilities for different defects to appear. We show that depending on the incident angle, ion type and energy, sulfur atoms can be sputtered away predominantly from the top or bottom layers, creating unique opportunities for engineering mixed MoSX compounds where X are chemical elements from group V or VII. We study the electronic structure of such systems, demonstrate that they can be metals, and finally discuss how metal/semiconductor/metal junctions, which exhibit negative differential resistance, can be designed using focused ion beams combined with the exposure of the system to fluorine.
Keywords: Two-dimensional materials, ion irradiation, atomistic simulations, defects
2D Materials 4(2017), 025078
DOI-Link: http://dx.doi.org/10.1088/2053-1583/aa6b17
Registration No. 25384 - Permalink
Saramsamkan, J.; Fischer, S.; Deuther-Conrad, W.; Ludwig, F.-A.; Scheunemann, M.; Arunrungvichian, K.; Vajragupta, O.; Brust, P.
Abstract: Recent pharmacologic data revealed the implication of α3β4 nicotinic acetylcholine receptors (nAChRs) in nicotine and drug addiction. To image α3β4 nAChRs in vivo, we aimed to establish the synthesis of a [18F]-labelled analog of the highly affine and selective α3β4 ligand (S)-3-(4-(4-fluorophenyl)-1H-1,2,3-triazol-1-yl)quinuclidine ((S)-T1). (S)-[18F]T1 was synthesized from ethynyl-4-[18F]fluorobenzene ([18F]5) and (S)-azidoquinuclidine by click reaction.
After a synthesis time of 130 min (S)-[18F]T1 was obtained with a radiochemical yield (non-decay corrected) of 4.3 ± 1.3%, a radiochemical purity of > 99% and a molar activity of > 158 GBq/µmol. The brain uptake and the brain-to-blood ratio of (S)-[18F]T1 in mice at 30 min post injection were 2.02 (SUV) and 6.1, respectively.
According to an ex-vivo analysis, the tracer remained intact (> 99%) in brain. Only one major radiometabolite was detected in plasma and urine samples. In-vitro autoradiography on pig brain slices revealed binding of (S)-[18F]T1 to brain regions associated with the expression of α3β4 nAChRs, which could be reduced by the α3β4 nAChR selective drug AT-1001. These findings make (S)-[18F]T1 a potential tool for the non-invasive imaging of α3β4 nAChRs in the brain by PET.
Keywords: α3β4 Nicotinic acetylcholine receptor Click reaction Drug addiction Positron emission tomography [18F]-Radioligand (S)-[18F]T1 Radiofluorination
Applied Radiation and Isotopes 124(2017), 106-113
DOI-Link: http://dx.doi.org/10.1016/j.apradiso.2017.03.015
Registration No. 25383 - Permalink
Cansever, H.; Fowley, C.; Narkowicz, R.; Kowalska, E.; Aleksandrov, Y.; Yildirim, O.; Titova, A.; Lenz, K.; Lindner, J.; Fassbender, J.; Deac, A. M.
Abstract: Magnetic tunnel junctions have been commonly used in spintronics applications, such as magnetic random access memory (M-RAM), spin transfer torque RAM (STT-RAM) and hard disc drive (HDD) because of high storage capacity. A spin polarized current flowing through a ferromagnetic layer can exert spin-transfer-torque (STT) on the local magnetization. When we apply thermal gradient across the junction we can induce what is called thermal spin transfer torque (T-STT). In this study, the microresonator FMR technique is used in order to analyze how the ferromagnetic resonance signal corresponding to the free layer of an in-plane MgO-based tunnel junction device is modified in the presence of a temperature gradients across the barrier. Details of resonator fabrication and preliminary measurements are presented. This work is supported by DFG-SPP1538.
Keywords: spin transfer torque, microresonator, thermal gradient
Lecture (Conference)
DPG-Frühjahrstagung 2017, 19.-24.03.2017, Dresden, Germany
Registration No. 25376 - Permalink
Sabdenov, C. K.; Davydova, M. D.; Zvezdin, K. A.; Zvezdin, A. K.; Andreev, A. V.; Gorbunov, D. I.; Tereshina, E. A.; Skourski, Y.; Sebek, J.; Tereshina, I. S.
Abstract: Ferrimagnet HoFe6Al6 (tetragonal ThMn12-type crystal structure) has a compensation point for the Ho and Fe magnetic sublattices at a temperature close to absolute zero. The experimental study was carried out in fields up to 60 T. H-T phase diagrams and a full magnetization process along the principal crystallographic directions of a single-crystalline sample are obtained theoretically by using a model of a f-d ferrimagnet with two anisotropic sublattices, coupled by weak exchange interaction. The two first-order phase transitions, found experimentally along the [110] and [100] axes, were explained theoretically. The transition along the [110] direction occurs between noncollinear and collinear phases, it starts at the compensation point and ends at a tricritical point around 60 T. The transition along the [100] direction goes also from the point of compensation to the point of the liquid-vapor type at 40 T. This transition was shown to occur between two distinct noncollinear phases. The crucial role of the strong rare-earth anisotropy for the positions of the obtained critical points was revealed.
Journal of Alloys and Compounds 708(2017), 1161-1167
DOI-Link: http://dx.doi.org/10.1016/j.jallcom.2017.02.213
Registration No. 25374 - Permalink
Salazar Mejia, C.; Küchler, R.; Nayak, A. K.; Felser, C.; Nicklas, M.
Abstract: Combined strain and magnetization measurements on the Heusler shape-memory alloys Ni45Co5Mn38Sb12 and Ni44Co6Mn38Sb12 give evidence for strong magneto-structural coupling. The sample length changes up to 1% at the martensitic transformation, between a ferromagnetic, austenitic phase at high temperatures and a weakly magnetic, low-symmetry martensitic phase at lower temperatures. Under moderate uniaxial stress, the change in the sample length increases to and saturates at about 3%, pointing to stabilization of a single martensitic variant. A reverse martensitic transformation can also be induced by applying magnetic field: we find that within the temperature range of thermal hysteresis of the martensitic transformation, applying a field can induce a metastable expansion of the sample, while at slightly lower temperatures, the field response is reversible. These findings provide key information for future use of Ni(Co)-Mn-Sb-based Heusler compounds in, e.g., actuators and mechanical switches.
Applied Physics Letters 110(2017), 071901
DOI-Link: http://dx.doi.org/10.1063/1.4976212
Registration No. 25373 - Permalink
Adamczewski-Musch, J.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Kuc, H.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Maurus, S.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.
Abstract: We report on the investigation of dielectron production in tagged quasi-free neutron-proton collisions by using a deuteron beam of kinetic energy 1.25 GeV/u inpinging on a liquid hydrogen target. Our measurements with HADES confirm a significant excess of e+e− pairs above the π0 mass in the exclusive channel dp→npe+e−(pspect) as compared to the exclusive channel ppe+e− measured in proton-proton collisions at the same energy. That excess points to different bremsstrahlung production mechanisms. Two models were evaluated for the role of the charged pion exchange between nucleons and double-Δ excitation combined with intermediate ρ-meson production. Differential cross sections as a function of the e+e− invariant mass and of the angles of the virtual photon, proton and electrons provide valuable constraints and encourage further investigations on both experimental and theoretical side.
Contribution to WWW
Registration No. 25372 - Permalink
Legrand, M.; Preunkert, S.; Weller, R.; Zipf, L.; Elsässer, C.; Merchel, S.; Rugel, G.; Wagenbach, D.
Abstract: Multiple year-round (2006-2015) records of the bulk and size-segregated composition of aerosol were obtained at the inland site of Concordia located in East Antarctica. The well-marked maximum of non-sea-salt sulfate (nssSO4) in January (84 ± 25 ng m-3 against 4.4 ± 2.3 ng m-3 in July) is consistent with observations made at the coast (280 ± 78 ng m-3 in January against 16 ± 9 ng m-3 in July at Dumont d'Urville, for instance). In contrast, the well-marked maximum of MSA at the coast in January (60 ± 23 ng m-3 at Dumont d'Urville) is not observed at Concordia (4.6 ± 2.4 ng m-3 in January). Instead, the MSA level at Concordia peaks in October (5.6 ± 1.9 ng m-3) and March (13.2 ± 6.1 ng m-3).
As a result, a surprisingly low MSA to nssSO4 ratio (RMSA) is observed at Concordia in midsummer (0.05 ± 0.02 in January against 0.25 ± 0.09 in March). We find that the low value of RMSA in mid-summer at Concordia is mainly driven by a drop of MSA levels that takes place in submicron aerosol (0.3 μm diameter). The drop of MSA coincides with periods of high photochemical activity as indicated by high ozone levels, strongly suggesting the occurrence of an efficient chemical destruction of MSA over the Antarctic plateau in mid-summer. The relationship between MSA and nssSO4 levels is examined separately for each season and indicates that concentration of non-biogenic sulfate over the Antarctic plateau does not exceed 1 ng m-3 in fall and winter and remains below 5 ng m-3 in spring. This weak non-biogenic sulfate level is discussed in the light of radionuclides (210Pb, 10Be, and 7Be) also measured on bulk aerosol samples collected at Concordia. The findings highlight the complexity in using MSA in deep ice cores extracted from inland Antarctica as a proxy of past DMS emissions from the southern ocean.
Keywords: Methanesulfonate, MSA to non-sea-salt sulfate ratio, DMS emissions, sea-salt aerosol, 210Pb, 10Be and 7Be, Chemistry(chemical composition and reactions)
Atmospheric Chemistry and Physics (2017)
Online First (2017) DOI-Link: http://dx.doi.org/10.5194/acp-2017-305
Registration No. 25367 - Permalink
Marques Fernandes, M.; Scheinost, A. C.; Baeyens, B.
Abstract: For the safety case for high-level radioactive waste repositories, redox phenomena play an important role for radionuclide retention. In the near field, the corrosion of steel canisters will release large amounts of ferrous iron and in addition produce H2 with a strong influence on the "in situ" redox potential (Eh). This combination of high {FeII} and low (Eh) in the interstitial waters of the engineered barrier system (bentonite, consisting predominantly of the phyllosilicate montmorillonite) is expected to have a strong impact on the retention of redox sensitive radionuclides like Tc, Se and the early actinides U, Np, and Pu, all of high relevance for safety of radioactive waste repositories.
In the present work we investigated by X-ray absorption spectroscopy (XAS) the influence of FeII on the retention of the redox sensitive NpV by montmorillonite. Since natural montmorillonite always contains structural Fe, we made use of a synthetic iron-free montmorillonite (IFM) [1] to discriminate the influence of sorbed FeII from that of structural iron. For FeII loadings below 40 mmol·kg-1, sorbed Fe had no effect, with Np showing the typical sorption behaviour of the pentavalent aquo-ion by forming comparatively weak inner-sphere sorption complexes at the edge sites of montmorillonite. For FeIIsorb above 40 mmol·kg-1, however, we observed an increasing reduction of NpV to NpIV, with a complete reduction for FeIIsorb 80 mmol·kg-1. In spite of the low solubility of NpO2, we did not observe precipitation of this phase, but formation of mononuclear innersphere sorption complexes (Fig. 1-A). The influence of structural FeII was investigated using citrate-dithionite–bicarbonate (CDB) reduced SWy montmorillonite (i.e. structural FeIII fully reduced to FeII). XAS showed that Np is present only as NpIV on the clay surface (Fig. 1-B).
Our study demonstrates that both structural and adsorbed FeII on montmorillonite lead to a surface mediated reduction of NpV, thereby increasing the retention by more than two orders of magnitude.
Keywords: montmorillonite iron neptunium EXAFS XANES sorption modeling
Lecture (Conference)
AnXAS 2017: 8th Workshop on Speciation, Techniques, and Facilities for Radioactive Materials at Synchrotron Light Sources, 11.-13.04.2017, Oxford, United Kingdom
Registration No. 25366 - Permalink
Mohseni, E.; Herrmann-Heber, R.; Reinecke, S.; Hampel, U.
Abstract: Current endeavor experimentally studies the initial bubble size distribution from the stainless steel diffusers and needle spargers with very fine orifice diameters range from 30 to 200 µm. To evaluate the performance of these spargers, the results where compared with four industrial rubber membranes in terms of Sauter mean diameter, pressure drop and frequency of bubble formation. Outcomes of current study showed that, the stainless steel perforated plates impose their superiority over the flexible membranes, by generating 50% smaller bubbles, and 70% higher bubble generation frequency at 60% less pressure drop. Moreover, the perforated stainless steel plates are able to produce bubble sizes in the same class as needles at 40% of the pressure drop caused by needle spargers and average of 60% higher bubble generation frequency.
Keywords: Bubble Generation, Activated Sludge, Aeration, Biological Wastewater Treatment, Multiphase Flow
Lecture (Conference)
The 9th Eastern European Young Water Professionals Conference, 24.-27.05.2017, Budapest, Hungary
Registration No. 25361 - Permalink
Schneider, H.
Abstract: In this talk I will present our recent experimental investigations on carrier dynamics in graphene studied via nonlinear laser spectroscopy, on time-resolved photoluminescence dynamics of single InAs/GaAs quantum dots under pulsed inter-sublevel excitation, and on sub-diffraction limited terahertz imaging by a GaAs-based superlens studied by scattering near-field optical microscopy. The experiments have been carried out using the mid-infrared/terahertz free-electron laser facility FELBE in Dresden, Germany.
Keywords: terahertz, free-electron laser, graphene, quantum dots, superlens
Lecture (others)
Seminarvortrag, University of Wollongong, 02.03.2017, Wollongong, Australia
Registration No. 25360 - Permalink
Reuter, M. A.
Invited lecture (Conferences)
Tag der Metallurgie, 02.-04.03.2016, Goslar, Deutschland
Invited lecture (Conferences)
Berliner Recycling- und Rohstoffkonferenz, 06.-07.03.2016, Berlin, Deutschland
Registration No. 25359 - Permalink
Helm, M.
Abstract: THz spectroscopy of solids with a free electron laser
Keywords: terahertz, free electron laser, spectroscopy
Invited lecture (Conferences)
2nd German THz Conference, 29.-31.03.2017, Bochum, Germany
Registration No. 25356 - Permalink
Jones, J. E.; Langford, M. H.; Geist, A.; Panak, P. J.; Kaden, P.; Adam, C.; Adam, N.; Sharrad, C. A.; Martin, L.; Natrajan, L. S.
Abstract: The necessity to reprocess spent nuclear fuel has arisen from increasing volumes of highly active and long-lived radionuclides associated with nuclear fission alongside increasing environmental impact concerns. In particular, one major challenge is the separation of the long-lived trivalent minor actinides (here, AmIII and CmIII) from the trivalent lanthanides in order to allow the future transmutation of the actinides into shorter lived radionuclides for the purpose of reducing the long-term radiotoxicity of the waste and the volume build up in storage. There are currently a number of different processes under development world-wide, all of which rely on the coordination chemistry and selective extraction of the minor actinides from the trivalent lanthanides using solvent partitioning. Of these, The TALSPEAK process (Trivalent Actinide Lanthanide Separation by Phosphorus reagent Extraction from Aqueous Komplexations) has showed great promise in separating the trivalent lanthanides from the minor actinides. The process uses DTPA (diethylenetriamine pentaacetic acid) as the chelating holdback reagent, HDEHP (bis-2-ethylhexyl phosphoric acid) as the extracting ligand and lactic acid as the buffer to prevent precipitation of DTPA that occurs at below pH 3.6. However, despite the considerable separation factors obtainable, and the fact the process exhibits promising radiolysis resistance, the process operates at sub optimal pH values. To overcome these limitations, we have developed a family of DTPA-amino acid conjugates that operate under TALSPEAK-like conditions over a much lower pH range of 1.5-2.5. Additionally, these ligands show comparable selectivity to the TALSPEAK process and are also relatively resistant to radiolysis. We will discuss the coordination chemistry of these ligands with the lanthanides and minor actinides using a combination of luminescence and NMR spectroscopies.
Keywords: DTPA, amino acids, actinides(III), lanthanides(III)
Lecture (Conference)
253rd ACS National Meeting & Exposition, 02.-06.04.2017, San Francisco, CA, United States
Registration No. 25350 - Permalink
Personnettaz, P.
Abstract: Liquid Metal Batteries (LMBs) are a promising electrical energy storage technology, built as a stable density stratification of two liquid metals separated by a molten salt. Their operation has been proved only for small prototypes, in order to transfer it to the industrial scale full knowledge of the different phenomena occurring in LMBs is required. In this work, done at Helmholtz-Zentrum Dresden-Rossendorf, we focus our attention on the thermal phenomena that appear inside Li||Bi LMBs . The system is first analyzed in the framework of the electrochemistry, a simple voltage model is developed and the heat generation terms are estimated. The geometrical and operating parameters are fully defined from multi-physics considerations. Then LMBs are studied with the continuum mechanics approach and all possible thermal phenomena are discussed. In the hypothesis of pure heat conduction, the first assessment of the effects of the reversible heat generation was done. Moreover the multiphase solver multiphaseInterFOAM is extended in order to take into account the thermal convection inside the cell. The results of our solver are compared to the one of a pseudo-spectral code. Finally some simulation results of thermal convection in LMBs are proposed.
Master thesis
Politecnico di Torino, 2017
Registration No. 25349 - Permalink
Elfick, A.; Rischitor, G.; Mouras, R.; Azfer, A.; Lungaro, L.; Uhlarz, M.; Herrmannsdörfer, T.; Lucocq, J.; Gamal, W.; Bagnaninchi, P.; Semple, S.; Salter, D. M.
Abstract: The use of stem cells to support tissue repair is facilitated by loading of the therapeutic cells with magnetic nanoparticles (MNPs) enabling magnetic tracking and targeting. Current methods for magnetizing cells use artificial MNPs and have disadvantages of variable uptake, cellular cytotoxicity and loss of nanoparticles on cell division. Here we demonstrate a transgenic approach to magnetize human mesenchymal stem cells (MSCs). MSCs are genetically modified by transfection with the mms6 gene derived from Magnetospirillum magneticum AMB-1, a magnetotactic bacterium that synthesises single-magnetic domain crystals which are incorporated into magnetosomes. Following transfection of MSCs with the mms6 gene there is bio-assimilated synthesis of intracytoplasmic magnetic nanoparticles which can be imaged by MR and which have no deleterious effects on cell proliferation, migration or differentiation. The assimilation of magnetic nanoparticle synthesis into mammalian cells creates a real and compelling, cytocompatible, alternative to exogenous administration of MNPs.
Scientific Reports 7(2017), 39755
DOI-Link: http://dx.doi.org/10.1038/srep39755
Registration No. 25341 - Permalink
Hilliard, D.; Yildirim, O.; Fowley, C.; Kanth Arekapudi, S. S. P. K.; Cansever, H.; Böttger, R.; Hlawacek, G.; Hellwig, O.; Lindner, J.; Fassbender, J.; Deac, A. M.; Perzanowski, M.
Abstract: Spintronic devices are often patterned from continuous films into micro- or nanostructures. Fabrication of those nano-devices is self-limited and depends on the lateral resolution of the chosen fabrication method. Ion irradiation offers an alternative route to introduce smaller magnetic patterns limited by the size of the ion beam. Irradiation of oxide materials can cause chemical reduction and lead to the local formation of metallic species. By using the oxide family of ferromagnets (e.g., Fe, Ni and Co), reduction leads to the formation of ferromagnetic and conducting volumes limited by the size of the ion irradiated area that are embedded into a non-magnetic and insulating matrix. On the other hand, the physical mechanism behind ion irradiation-induced oxide reduction could not be explained. Therefore, our studies focus on ion (H, He, Ne, O) irradiated cobalt-oxide (CoO or Co3O4) systems in order to explain the physics behind the process. Also, the knowledge is being exploited to tune exchange-bias direction, prepare nano contacts for synchronized spin torque oscillators, and to form topographically stabilized magnetic skyrmions.
Keywords: Cobalt oxide, Ion irradiation, Oxygen reduction, Ferromagnetic
DPG-Frühjahrstagung (DPG Spring Meeting), 19.-24.03.2017, Dresden, Deutschland
Registration No. 25338 - Permalink
Raja, N.; Murali, D.; Posselt, M.; Satyanarayana, S. V. M.
Abstract: BaZrO3 (BZO) is a potential candidate material for electrode in solid oxide fuel cells (SOFL) because of its excellent reported proton conductivity [1, 2]. It is suggested that presence of intrinsic point defects such as O vacancies act as sinks for O atoms produced upon hydrogenation of water molecule and promote proton conductivity. For this, the formation energy of O atom should be lower and its migration should be suppressed [3]. Since these materials are used at high temperature, it is very important to consider effects of phonons on the defect chemistry [4, 5, 6]. In this work, first, we identify thermodynamically favorable conditions for the formation of BZO by free energy calculations of bulk phases using Density Functional Theory. Next, we study the free energy of formation of both neutral and charged O vacancies of stable BZO phase and discuss significance of these results for experimental growth conditions. Initial results show that phonon contributions to free formation energy of charged vacancy is significantly high compared to neutral vacancy due to large lattice distortion and negative formation entropy for charged vacancy. Studies also show that acceptor doping both at A and B site lowers the formation energy of O vacancy in the vicinity of dopant atoms resulting in increase of proton conductivity [7, 8]. In order to understand the mechanism of this enhancement, we study the free energy of formation of O clusters in reducing conductions for acceptor doping at A and B sites.
[1] K. D. Kreuer, Annu. Rev. Mater. Res. 2003, 33:333–59.
[2] K. D. Kreuer, ed. T. Ishihara, Springer, 2009, pp. 261–271.
[3] Emile B´ evillon, Guilhem Dezanneau, and Gr´ egory Geneste, Physical Review B 2011, 83,
[4] Jessica Hermet, Francois Bottin, Guilhem Dezanneau, and Gregory Geneste Physical Review
[5] Denis Gryaznov, Evgeny Blokhin, Alexandre Sorokine, Eugene A. Kotomin, Robert A.
Evarestov, Annette Bussmann-Holder, and Joachim Maier J. Phys. Chem. C 2013, 117,
[6] Tor S. Bjørheim, Marco Arrigoni, Denis Gryaznov, Eugene Kotomin and Joachim Maier
Phys. Chem. Chem. Phys. 2015, 17, 20765.
[7] Marten E. Bjorketun, Per G. Sundell, and Goran Wahnstrom Physical Review B, 2007,
76, 054307.
[8] Andreas Løken, Sarmad W. Saeed, Marit N. Getz, Xin Liu and Tor S. Bjørheim, J. Mater.
Chem. A, 2016, 4, 9229.
Keywords: DFT, proton conductivity, solid oxide fuel cells
Lecture (Conference)
International Conference on Advances in Functional Materials, 06.-08.01.2017, Chennai, Madras, India
Registration No. 25336 - Permalink
Vorberger, J.
Abstract: Warm dense matter states in the transition region from high pressure solids to high temperature plasmas are found in terrestrial planets, giant planets, and exoplanets. Such states are created in the laboratory during interaction of lasers or shock waves with matter. The intention is usually to obtain direct experimental access to equilibrium or nonequilibrium warm dense matter states or it might be an intermediate state on the way to fusion plasmas states or laser-plasma acceleration experiments.
Studying warm dense matter, one faces several challenges. The first is the determination of a full set of basic parameter like density, charge state, temperature, or the momentum distribution function that fixes the state of matter in the phase space. Only then is it meaningful to investigate important quantities like the equation of state, phase transitions, structure, collective excitations, relaxation processes, or the stopping power.
Here, we present recent developments and results in warm dense matter physics. The close interplay between theory and experiment via x-ray scattering and first principle simulations is highlighted. The dynamic structure factor containing a wealth of information serves as the connection between measurements and calculations. Results are given for a number of elements like aluminium, carbon, or iron, and materials like plastic.
Keywords: warm dense matter, dynamic structure, x-ray scattering, non-equilibrium, equilibrium, ionisation, strong coupling, giant planets, ICF
Invited lecture (Conferences)
DPG Frühjahrstagung Bremen, 13.-17.03.2017, Bremen, Deutschland
Registration No. 25334 - Permalink
Vorberger, J.
Abstract: Powerful femtosecond pump lasers and femtosecond x-ray probe beams created by free electron lasers make it possible to create and diagnose strongly correlated states of matter in which the electron and ion Wigner distribution functions are of a strongly non-equilibrium type.
We therefore present a quantum theory for the dynamic structure factors in just such non-equilibrium, correlated, two-component systems.
To make our theory applicable for x-ray scattering as in equilibrium, a generalized Chihara decomposition for the total electron structure factor in non-equilibrium is derived. Examples are given and the influence of correlations and exchange on the structure and the x-ray scattering spectrum are discussed for a model non-equilibrium distribution, as often encountered during laser heating of materials, as well as for two-temperature systems.
Keywords: warm dense matter, structure, x-ray scattering, dynamic structure, non-equilibrium
Lecture (Conference)
37th International Workshop on High Energy Density Physics with Intense Ion and Laser Beams, 29.01.-03.02.2017, Hirschegg, Österreich
Registration No. 25333 - Permalink
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