Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31828 Publications
Evaluating Performance of Two-Group Interfacial Area Transport Equation for Vertical Small and Large Diameter Pipes
Dave, A.; Manera, A.; Beyer, M.; Lucas, D.;
In the two-fluid transport model, the coupling of mass, momentum and energy transfer between phases is highly dependent on interfacial area transfer terms. Several research efforts in the past have been focused on the evelopment of an interfacial area transport equation model (IATE), in order to eliminate the drawbacks of static flow regime maps currently used in best-estimate thermal-hydraulic system codes. The IATE attempts to model the dynamics that are involved in two phase flows by accounting for the different interaction mechanisms affecting bubble transport in the flow.
The further development and validation of IATE models has been hindered by the lack of adequate experimental data in regions beyond the bubbly flow regime. At the Helmholtz-Zentrum Dresden Rossendorf (HZDR) experiments utilizing wire mesh sensors have been performed over all flow regimes, establishing a database of high-resolution (in space and time) data. Two sets of data from small and large diameter pipes fitted with wire mesh sensors are utilized in this work. Analysis of flow conditions in the bubbly, churn turbulent and annular flow regimes is presented.
The performance of the Fu-Ishii two-group model is evaluated against small diameter database. Results indicate good performance (< 10% error) for small group 1 bubbles, and poor performance for large group 2 bubbles. The Smith two-group large diameter IATE model is evaluated for the large diameter database. In low void-fraction regimes, the Smith model performs well. In high void-fraction regimes, there is poor group-wise interfacial area prediction – however the total interfacial area is erroneously predicted well as group-wise errors compensate each other. Overall, the study suggests that further efforts and re-evaluation of closure terms are needed in order to extend the range of validity of the IATE models.
Keywords: Interfacial area transport, Validation, Wire mesh sensor, Air-water
  • Lecture (Conference)
    American Nuclear Society Annual Meeting 2016, 12.-16.06.2016, New Orleans LA, USA
  • Contribution to proceedings
    American Nuclear Society Annual Meeting 2016, 12.-16.06.2016, New Orleans LA, USA
    International Topical Meeting on Advances in Thermal Hydraulics 2016

Publ.-Id: 23426 - Permalink


Modellierung von Tayler-Instabilität und Elektrowirbelströmungen in Flüssigmetallbatterien
Weber, N.;
Diese Arbeit behandelt numerisch die Fluiddynamik in Flüssigmetallbatterien. Insbesonders die Tayler-Instabilität und Elektrowirbelströmungen werden ausführlich betrachtet. Die Motivation der Untersuchungen besteht zum einen in einer Steigerung von Leistung und Sicherheit und zum anderen in der Senkung von Produktions- und Betriebskosten von Flüssigmetallbatterien.
Es wird ein Lösungsverfahren für zeitabhängige magnetohydrodynamische Strömungen entwickelt und in OpenFOAM implementiert. Die Basisversion des Lösers erlaubt die Analyse einer flüssige Elektrode. Eine Erweiterung dient der Untersuchung des Einflusses von Stromsammler und Zuleitung der Batterie. Simulationen werden vorwiegend für zylindrische, aber auch für quaderförmige Elektrodengeometrien durchgeführt.
Der Hauptteil der Arbeit widmet sich der stromgetriebenen Tayler-Instabilität, die in großen Batterien bei Strömen von einigen Kiloampere auftritt und dort zu einer Strömung in Form von Konvektionszellen führt. Das Auftreten, Wachstum und die Geschwindigkeiten dieser Instabilität werden analysiert und deren Bedeutung für die Batterie diskutiert. Zur Dämpfung bzw. Unterdrückung der Strömung werden eine Reihe von Gegenmaßnahmen vorgestellt und deren praktischer Nutzen bewertet. Der zweite, kürzere Teil der Arbeit befasst sich mit Elektrowirbelströmungen, deren Charakterisierung und ihren Wechselwirkungen mit der Tayler-Instabilität. Die besondere Bedeutung von Elektrowirbelströmungen für die Integrität der Elektrolytschicht sowie ihre Anwendbarkeit für die Verbesserung des Stofftransports in Flüssigmetallbatterien werden hervorgehoben.
Keywords: Tayler Instabilität, Elektrowirbelströmung; Flüssigmetallbatterie
  • Doctoral thesis
    TU Dresden, 2016

Publ.-Id: 23425 - Permalink


Superlattice growth and rearrangement during evaporation induced nanoparticle self-assembly
Josten, E.; Wetterskog, E.; Glavic, A.; Boesecke, P.; Feoktystov, A.; Brauweiler-Reuters, E.; Rücker, U.; Salazar-Alvarez, G.; Brückel, T.; Bergström, L.;
Understanding the assembly of nanoparticles into superlattices with well-defined morphology and structure is technologically important but challenging as it requires novel combinations of in-situ methods with suitable spatial and temporal resolution. In this study, we have followed evaporationinduced assembly during drop casting of superparamagnetic, oleate-capped γ-Fe2O3 nanospheres dispersed in toluene in real time with Grazing Incidence Small Angle X-ray Scattering (GISAXS) in combination with droplet height measurements and direct observation of the dispersion. The scattering data was evaluated with a novel method that yielded time-dependent information of the relative ratio of ordered (coherent) and disordered particles (incoherent scattering intensities), superlattice tilt angles, lattice constants, and lattice constant distributions. We find that the onset of superlattice growth in the drying drop is associated with the movement of a drying front across the surface of the droplet. We couple the rapid formation of large, highly ordered superlattices to the capillary-induced fluid flow. Further evaporation of interstitital solvent results in a slow contraction of the superlattice.
The distribution of lattice parameters and tilt angles was significantly larger for superlattices prepared by fast evaporation compared to slow evaporation of the solvent.
Keywords: magnetic nanoparticles, in-situ GISAXS, self-assembly, X-ray scattering, 3D nanoparticle superlattice

Publ.-Id: 23424 - Permalink


Vibrational spectroscopy of Ga+ ion implanted ta-C films
Berova, M.; Sandulov, M.; Tsvetkova, T.; Bischoff, L.; Boettger, R.; Abrashev, M.;
In the present work, low energy Ga+ ion beam implantation was used for the structural and optical properties modification of tetrahedral amorphous carbon (ta-C) thin films, using gallium (Ga+) as the ion species. Thin film samples (d~40nm) of ta-C, deposited by filtered cathodic vacuum arc (FCVA), have been implanted with Ga+ at ion energy E = 20 keV and ion doses D=3.1014÷3.1015 cm-2. The Ga+ ion beam induced structural modification of the implanted material results in a considerable change of its optical properties, displayed in a significant shift of the optical absorption edge to lower photon energies as obtained from optical transmission measurements. This shift is accompanied by a considerable increase of the absorption coefficient (photo-darkening effect) in the measured photon energy range (0.5÷3.0 eV). These effects could be attributed both to additional defect introduction and increased graphitisation, as well as to accompanying formation of bonds between the implanted ions and the host atoms of the target, as confirmed by infra-red (IR) and Raman measurements. The optical contrast thus obtained (between implanted and unimplanted film material) could be made use of for information archiving, in the area of high-density optical data storage, while using focused Ga+ ion beams.
Keywords: ta-C, ion implantation, Raman, FTIR, spectroscopy

Publ.-Id: 23423 - Permalink


Silicon nanoparticles: a platform towards multimodal imaging
Faramus, A.; Licciardello, N.; Ddungu, J. L. Z.; Singh, G.; Stephan, H.; de Cola, L.;
Multimodal imaging combines information from several imaging techniques in order to accurately image and diagnose various medical conditions. A well designed probe can offer imaging prospects using optical imaging, positron emission tomography using a radioactive label and magnetic resonance imaging.[1]
Silicon nanoparticles are an interesting material for biological and medical applications. These nanoparticles combine the low toxicity of silicon and the ultrasmall size (< 5 nm) achievable through wet chemistry techniques.[2] The surface termination of silicon nanocrystals can be functionalized from simple amino acid groups to photoemissive dyes, radiotracers and targeting agents, such as peptides, thus making silicon nanoparticles an interesting platform for targeted multimodal imaging.
After synthesis and purification, the crucial step towards the utilization of silicon nanoparticles as multimodal probes is the modification of the surface. An accurate quantification of the number of available functional groups is both important and a great challenge to determine.
Our research is focused on the surface modification and characterization of silicon nanocrystals and their use as imaging agent in biomedicine.

[1]. Louie A. Multimodality Imaging Probes: Design and Challenges. Chem.Rev. 2010, 110, 3146-3195. Doi:10.1021/cr9003538
[2]. Shiohara A., Lai P.-S., Northcote P, Tilley R.D. Sized controlled synthesis, purification, and cell studies with silicon quantum dots. Nanoscale. 2011, 8, 2040-3364. Doi: 10.1039/C1NR10458F
Keywords: silicon nanoparticle, surface modification, multimodal imaging, biomedical application
  • Lecture (Conference)
    E-MRS spring meeting 2016, 02.-06.05.2016, Lille, France

Publ.-Id: 23422 - Permalink


Improvement of Depth Resolution of VEPAS by Sputtering Techniques
Krause-Rehberg, R.; John, M.; Akhmadaliev, S.; Böttger, R.; Anwand, W.; Wagner, A.;
Variable energy positron annihilation spectroscopy (VEPAS) allows to measure depthdependent defect profiles. While the depth resolution is still in the nm range for low positron energies, it broadens strongly at higher penetration energies. The reason is the broad positron implantation profile often described as Makhov profile [1].
To avoid this problem and to determine real defect profiles in a depth of several µm, one can remove the surface step-by-step or continuously by sputtering the surface away, e.g. by low energy Ar ions. Of course, the advantage of VEPAS to have a non-destructing testing tool is lost. However, one gains from relatively sharp depth profile down to several µm and improved defect sensitivity in larger depth.
In the talk details of the sputtering process will be discussed and several examples of photovoltaic CIGS layers and defects after ion implantation in Si will demonstrate the power of this type of defect profiling.
Keywords: VEPAS, Positron annihilation spectroscopy, CIGS, Si, defects, ion implantation
  • Invited lecture (Conferences)
    14th International Workshop on Slow Positron Beam Techniques & Applications, 22.-27.05.2016, Matsue, Japan

Publ.-Id: 23420 - Permalink


Fe doped InAs: what is the exchange interaction?
Yuan, Y.; Hübner, R.; Potzger, K.; Liu, F.; Sawicki, M.; Dietl, T.; Helm, M.; Zhou, S.;
Fe doped InAs layers have been prepared by ion implantation and pulsed laser annealing. Fe ions exist in the +3 valence state when located in Indium sites, which indicates that Fe atoms do not introduce free carriers in the InAs layer and only act as the local spins. However, (In, Fe)As or (In, Fe)As codoped with Se (provide free electrons) exhibits typically superparamagnetic behavior, which is proven by both static and dynamic magnetic measurements. This is most probably due to the formation of Fe-rich nanoregions in the InAs matrix, similarly to the case of Cr-doped ZnTe [1]. However, the co-doping by Zn (which introduces free holes) increases both the saturation magnetization and the Curie temperature. A systematic comparison between (In, Fe)As, (In, Fe)As:Zn and (In, Fe)As:Se leads to the re-affirmation of the pd-exchange as the key gradient in dilute ferromagnetic semiconductors [2].

[1]. K. Kanazawa et al., Nanoscale, 6, 14667-14673 (2014)
[2]. T. Dietl et al., Science, 287, 1019-1022 (2000)
  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie 2016, 06.-11.03.2016, Regensburg, Germany

Publ.-Id: 23419 - Permalink


Thallium dispersal and contamination in surface sediments from South China and its source identification
Liu, J.; Wang, J.; Chen, Y.; Shen, C.-C.; Jiang, X.; Xi, X.; Chen, D.; Lippold, H.; Wang, C.;
Thallium (Tl) is a non-essential element in humans, and it is considered to be highly toxic. In this study, the contents, sources, and dispersal of Tl were investigated in surface sediments from a riverine system (the western Pearl River Basin, China), whose catchment has been contaminated by mining and roasting of Tl-bearing pyrite ores. The isotopic composition of Pb and total contents of Tl and other relevant metals (Pb, Zn, Cd, Co, and Ni) were measured in the pyrite ores, mining and roasting wastes, and the river sediments. Widespread contamination of Tl was observed in the sediments across the river, with the highest concentration of Tl (17.3 mg/kg) measured 4 km downstream from the pyrite industrial site. Application of a modified Institute for Reference Materials and Measurement (IRMM) sequential extraction scheme in representative sediments unveiled that 60 - 90% of Tl and Pb were present in the residual fraction of the sediments. The sediments contained generally lower 206Pb/207Pb and higher 208Pb/206Pb ratios compared with the natural Pb isotope signature (1.2008 and 2.0766 for 206Pb/207Pb and 208Pb/206Pb, respectively). These results suggested that a significant fraction of non-indigenous Pb could be attributed to the mining and roasting activities of pyrite ores, with low 206Pb/207Pb (1.1539) and high 208Pb/206Pb (2.1263). Results also showed that approximately 6 - 88% of Tl contamination in the sediments originated from the pyrite mining and roasting activities. This study highlights that Pb isotopic compositions could be used for quantitatively fingerprinting the sources of Tl contamination in sediments.
Keywords: Tl contamination; Pb isotope; pyrite; binary model

Publ.-Id: 23418 - Permalink


CFD modelling of downward two phase pipe flow
Krepper, E.; Lucas, D.; Rzehak, R.;
A widely used approach to model two-phase bubbly flows for industrial applications is the Eulerian two-fluid framework of interpenetrating continua. The loss of small-scale physics caused by the averaging procedure has to be compensated by introduction of closure relations. These concern the momentum exchange between the phases, the effect of the bubbles on the liquid turbulence and bubble breakup and coalescence. The quest for models with a broad range of applicability allowing predictive simulations is an ongoing venture. A set of best available submodels was assembled and validated against different bubbly flow situations (Rzehak and Krepper 2013, 2015). The present contribution deals with two phase downward pipe flow. Experiments were performed at HZDR using an ultrafast X-ray tomographic measurement technique. Gas fraction distribution, gas velocities, and bubble size distributions were measured at different distances from the gas injection. Deduced from the experimental data, in some tests the complexity of the closure problem could be reduced imposing a fixed bubble size distribution. Considering the effect of bubble sizes on the closure relations the agreement of the simulations with the measurements could be improved remarkably.
Keywords: Multiphase flow, CFD, Euler-Eulerian approach, downward flow
  • Lecture (Conference)
    9th International Conference on Multiphase Flow, 22.-27.05.2016, Florenz, Italien
  • Contribution to proceedings
    9th International Conference on Multiphase Flow, 22.-27.05.2016, Florenz, Italien

Publ.-Id: 23417 - Permalink


Mobility and transport of copper(II) influenced by the microbial siderophore DFOB: Column experiment and modelling
Karimzadeh, L.; Lippmann-Pipke, J.; Franke, K.; Lippold, H.;
Acid Cu leaching from the European Kupferschiefer ore deposits is a challenge e.g. due to its high carbonate content. In this study, we investigated the transport behaviour of Cu under conditions related to a biohydrometallurgical leaching approach using neutrophil microorganisms in neutral to slightly alkaline solutions. We studied the effect of the microbial siderophore desferrioxamineB (DFOB) as a model leaching organic ligand on Cu mobility in column experiments with kaolinite. The results revealed that DFOB strongly enhances Cu mobility. The breakthrough of Cu occurs considerably earlier in the presence of DFOB than in the absence of the organic ligand. Furthermore, complete elution of Cu was observed at 5 pore volume exchanges faster compared to elution with deionized water. The established geochemical transport model shows good agreement with the experimental data and suggests a maximum efficiency at a Cu to DFOB molar ratio of 1:1. In addition, results of modelling revealed that in the absence of the ligand, a pH increase from 6.5 to 8.5 significantly retarded Cu breakthrough, whereas in the presence of DFOB, Cu breakthrough curves were nearly insensitive to pH changes and close to the breakthrough curve of a non-reactive tracer.
Keywords: Mobility of metals, Microbial siderophore DFOB, Kaolinite, Column experiment, Geochemical modelling

Publ.-Id: 23416 - Permalink


Review of Subcooled Boiling Flow Models
Krepper, E.; Ding, W.;
In this chapter the present capabilities of CFD-modelling for wall boiling in industrial applications are described. The basis is the Eulerian two-fluid framework of interpenetrating continua. From the first attempts heat flux partitioning algorithms were used to describe boiling at a heated wall. Based on a mechanistic model representation of the microscopic processes the framework is described by empirical correlations. The developments of the main correlations for the bubble size at detachment and for the nucleation site density are described. Different approaches for the bubble size in the bulk are presented. Further the extension of the conventional heat partitioning model towards the high heat flux will be also stated. Finally an outlook on further model improvement is given.
Keywords: CFD, two phase flow, wall boiling
  • Book chapter
    Guan Heng Yeoh: Handbook of Multiphase Flow Science and Technology, Singapore: Springer, 2017, 978-981-4585-86-6
    DOI: 10.1007/978-981-4585-86-6_20-1

Publ.-Id: 23415 - Permalink


Tuning the structure and crystal habit of mesocrystals using magnetic fields
Wetterskog, E.; Klapper, A.; Disch, S.; Josten, E.; Hermann, R.; Rücker, U.; Brückel, T.; Bergström, L.; Alvarez, G.-S.;
A precise control over the meso- and microstructure of ordered and aligned nanoparticle assemblies, i.e., mesocrystals, is essential in the quest of exploiting collective material properties for potential applications. In this work, we produce evaporation-induced self-assembled mesocrystals with different mesostructures and crystal habits based on iron oxide nanocubes by varying the nanocube size and shape, and by applying magnetic fields. A full 3D characterization of the mesocrystals was performed using image analysis, high-resolution scanning electron microscopy and Grazing Incidence Small Angle X-ray Scattering (GISAXS). This enables structural determination of e.g. multi-domain mesocrystals with complex crystal habits, and the quantification of interparticle distances with sub-nm precision. We find a lower size limit for crystallization in the absence of a magnetic field. Mesocrystals of small nanocubes (l = 8.6 – 12.6 nm) are isostructural with a body centered tetragonal (bct) lattice whereas mesocrystals assembly of the largest nanocubes in this study (l = 13.6 nm) additionally form a simple cubic (sc) lattice. The mesocrystal habit can be tuned from a square, hexagonal to star-like and pillar shapes depending on the particle size, shape, and the applied magnetic field strength. Finally, we outline a qualitative phase diagram of the evaporation-induced self-assembled superparamagnetic iron oxide nanocube mesocrystals based on nanocube edge length and magnetic field strength.
Keywords: iron oxide, nanoparticles, magnetic field, assembly, cubes, GISAXS, mesocrystal, superstructure, normal field instability

Publ.-Id: 23414 - Permalink


Micrometer-sized highly ordered 3D nanoparticle superlattices investigated by microresonator ferromagnetic resonance
Josten, E.; Narkowicz, R.; Kakay, A.; Meertens, D.; Banholzer, A.; Bergström, L.; Suter, D.; Brückel, T.; Lenz, K.; Fassbender, J.ORC; Lindner, J.
Magnetic nanoparticles and their assembly into highly correlated structures are of great interest for future applications as e.g. spin-based data storage. These systems are not only distinguished by the obvious miniaturization but by the novel physical properties emerging due to their limited size and ordered arrangement. These superstructures are formed from nanometer-sized building blocks - ordered like atoms in a crystal - which renders them a new class of materials.

Fundamental investigation of magnetic nanostructures represents an important step towards the control and understanding of these systems. Recently, single micrometer-sized 3-dimensional nanoparticle assemblies (so called mesocrystal) became available, exhibiting a high degree of structural order close to that of an atomic crystal. This system provides a good basis for the magnetic investigation of static and dynamic processes inside and of the nanoparticle superstructure.

Microresonators, provide a straightforward method for the investigation of static and dynamic magnetic properties of nm and micrometer sized objects using ferromagnetic resonance (FMR) [1,2]. Due to the much higher filling factor as compared to conventional microwave cavities, they offer several orders of magnitude increased sensitivity. A focused ion beam (FIB) approach is used to isolate an individual 3D mesocrystal from an ensemble [3] and to transfer it into a microresonator loop. The FMR study reveals the dynamic magnetic properties and magnetic anisotropy of the single mesocrystal - an object composed of highly ordered nanoparticles.
Keywords: magnetic nanoparticles, self-assembly, mesocrystals, microresonator, FMR
  • Poster
    603. Wilhelm und Else Heraeus-Seminar, Magnonics, Spin Waves Connecting Charges, Spins and Photons, 06.-08.01.2016, Physikzentrum Bad Honnef, Deutschland
  • Lecture (Conference)
    MMM Intermag, 11.-15.01.2016, San Diego, USA

Publ.-Id: 23413 - Permalink


How to catch the generation Y: Identifying consumers of ecological innovations among youngsters
Gurtner, S.; Soyez, K.;
The economic damage of environmental pollution is remarkable, thus protecting the environment has become a pressing issue during the last decades. Consequently, for companies there is an obvious need to consider environmental issues in product development and to understand why consumers adopt ecological innovations. The success of eco-innovations, however, depends on the individual adoption decision of the consumer. Hence, the question arises, why do consumers adopt ecological innovations? By integrating two areas of consumer characteristics, namely environmental consciousness and consumer innovativeness with a special focus of young consumers as the next generation of eco-innovators, the present study provides an answer to this question. Furthermore, we focus on the promising market segment of young consumers as potential agents of change. In total 446 young consumers were surveyed. The results provide insights on what drives eco-innovativeness and thus, how to market new eco-logical products. Structural equation modeling led to the result that joyful consumption is an important antecedent of domain-specific eco-innovativeness. Additionally, a biospheric value orientation leads to higher eco-innovativeness, whereas altruistic values reduce ecoinnovativeness.
The results show that practitioners and product designers have to take into account not only the benefit for nature but also the hedonic component of a new product.
Keywords: consumer innovativeness, new product adoption, eco-innovations, structural equation modeling, generation Y, young consumers

Publ.-Id: 23412 - Permalink


Numerical simulations for the DRESDYN precession dynamo
Giesecke, A.; Gundrum, T.; Stefani, F.; Gerbeth, G.;
In a next generation dynamo experiment currently under development at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) a fluid flow of liquid sodium, solely driven by precession, will be considered as a possible source for magnetic field generation. We will present results from non-linear hydrodynamic simulations with moderate precessional forcing dedicated to the planned experiment.
Our results have been used for flow models in kinematic dynamo simulations in order to determine whether a precession driven flow will be capable to drive a dynamo at experimental conditions and to limit the parameter space within which the occurrence of dynamo action is most promising.
Keywords: dynamo precession DRESDYN
  • Lecture (Conference)
    PAMIR 2016 International Conference Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italia
  • Contribution to proceedings
    PAMIR 2016 International Conference Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italia

Downloads:

Publ.-Id: 23411 - Permalink


Numerical simulations of precession driven flows and their ability to drive a dynamo.
Giesecke, A.; Stefani, F.;
In a next generation dynamo experiment currently under development at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) a fluid flow of liquid sodium, solely driven by precession, will be considered as a possible source for magnetic field generation.

In my talk I will present results from hydrodynamic simulations of a precession driven flow in cylindrical geometry. In a second step, the velocity fields obtained from the hydrodynamic simulations have been applied to a kinematic solver for the magnetic induction equation in order to determine whether a precession driven flow will be capable to drive a dynamo at experimental conditions.

It turns out that excitation of dynamo action in a precessing cylinder at moderate precession rates is difficult and future dynamo simulations are required in more extreme parameter regimes where a more complex fluid flow is observed in water experiments which is supposed to be beneficial for dynamo action.
Keywords: dynamo precession DRESDYN
  • Invited lecture (Conferences)
    PASC16 - Platform for Scientifik Computing, 08.-10.06.2016, Lausanne, Switzerland

Downloads:

Publ.-Id: 23410 - Permalink


Measurement of isomeric ratios for 89g,mZr, 91g,mMo, and 97g,mNb in the bremsstrahlung end-point energies of 16 and 45-70 MeV
Naik, H.; Kim, G. N.; Schwengner, R.; Kim, K.; Zaman, M.; Yang, S. C.; Shin, S. G.; Kye, Y.-U.; Massarczyk, R.; John, R.; Junghans, A.; Wagner, A.; Goswami, A.; Cho, M.-H.;
The independent isomeric yield ratios of 89g,mZr from the nat Zr(gamma,xn) reactions and those of 91g,mMo and 97g,m Nb from the nat Mo(g,x) reactions with the bremsstrahlung end-point energy of 45 - 70 MeV were determined by an off-line gamma-ray spectrometric technique using the 100 MeV electron linac at the Pohang Accelerator Laboratory, Korea. The isomeric yield ratios of 89g,mZr and 97g,mNb from the nat Zr(g,xn) and nat Mo(gamm,x) reactions at the bremsstrahlung end-point energy of 16 MeV were also determined by the same technique using the 20 MeV electron linac at Helmholtz-Zentrum Dresden-Rossendorf, Germany. The measured isomeric yield ratios of 89g,mZr, 91g,mMo, and 97g,mNb were compared with literature data to examine the role of the Giant Dipole Resonance (GDR). The isomeric yield ratios of the 89g,mZr, 91g,mMo, and 97g,mNb from the above reactions were also calculated by using the computer code TALYS 1.6 and compared with the experimental data to examine the validity of the theoretical model for independent isomeric yield ratio calculations.
Keywords: Photodissociation, Photoactivation, isomeric yield ratios.

Publ.-Id: 23409 - Permalink


Multidimensional “smart Kd-matrices” for realistic description of sorption processes
Stockmann, M.; Brendler, V.; Flügge, J.; Noseck, U.;
Sorption on mineral surfaces is an important retardation process to be considered in safety assessments of both chemotoxic and radioactive waste repositories. Most often conventional conservative concepts with temporally and spatially constant distribution coefficients (Kd values) are applied in reactive transport simulations.
In this work, the reactive transport program r³t is extended towards a more realistic description of the contaminant migration by implementing pre-computed multidimensional smart Kd matrices that are able to reflect changing geochemical conditions, e.g. caused by climatic changes.
Three computer codes were coupled to form one tool: PHREEQC, UCODE and SIMLAB. This strategy has various benefits: (1) One can calculate smart Kd values for a reasonable numbers of environmental parameter combinations; (2) It is possible to perform uncertainty and sensitivity analysis based on such smart Kd matrices; (3) The approach is highly flexible with respect to chemical reactions and environmental conditions; (4) The overall methodology is much more efficient in computing time than a direct coupling of the geochemical speciation code with the transport code r3t.
The capability of this new methodology is demonstrated for the sorption of repository-relevant radionuclides on a natural sandy aquifer. This proof-of-concept is able to describe the sorption behavior in dependence of changing geochemical conditions quite well.
Keywords: Waste Disposal, Safety Assessment; Smart Kd; Sorption; Radionuclides; Sensitivity and Uncertainty Analysis
  • Lecture (Conference)
    Water-Rock Interaction, 16.-21.10.2016, Évora, Portugal

Publ.-Id: 23408 - Permalink


Metal leaching from Kupferschiefer using bulk and biotechnologically produced organic acids
Kostudis, S.; Bachmann, K.; Kutschke, S.; Pollmann, K.; Gutzmer, J.;
The European Kupferschiefer deposits constitute a challenging local resource of base metals such as copper. In order to exploit them both efficiently and environmentally benignly, biotechnological leaching approaches are investigated. Commonly used acidophilic bioleaching is limited by high carbonate content of up to 18 % resulting in an increased pH value of more than 2. Hence, alternative processes such as neutral leaching are tested. We could show that using organic acids in neutral pH range has a higher leaching impact than in acidic milieu.
The paper summarises research results on bioleaching of copper from Kupferschiefer ore in neutral to alkaline environment: Glutamic and citric acid were investigated regarding their leaching performance depending on pH, particle size and temperature. Furthermore the leaching performance of biotechnologically produced citric acid was investigated. For that purpose the yeast Yarrowia lipolytica was grown on raw glycerol, and leaching effect of the cultivation supernatant was ascertained.
  • Lecture (Conference)
    Biohydromet'16, 20.-22.06.2016, Falmouth, United Kingdom

Publ.-Id: 23407 - Permalink


Further insights into the chemistry of the Bi-U-O system
Popa, K.; Prieur, D.; Manara, D.; Naji, M.; Vigier, J.-F.; Martin, P.; Blanco, O. D.; Scheinost, A. C.; Prüssmann, T.; Vitova, T.; Raison, P. E.; Somers, J.; Konings, R. J. M.;
Cubic fluorite-type phases have been reported in the UIVO2-Bi2O3 system for the entire compositional range, but an unusual non-linear variation of the lattice parameter with uranium substitution has been observed. In the current extensive investigation of the uranium(IV) oxide - bismuth (III) oxide system, this behaviour of the lattice parameter evolution with composition has been confirmed and its origin identified. Even under inert atmosphere at 800 oC, UIV oxidises to UV/UVI as a function of the substitution degree. Thus, using a combination of three methods (XRD, XANES and Raman) we have identified the formation of the BiUVO4 and Bi2UVIO6 compounds, within this series. Moreover, we present here the Rietveld refinement of BiUVO4 at room temperature and we report the thermal expansion of both BiUVO4 and Bi2UVIO6 compounds.
Keywords: XRD XANES XAFS Raman lead bismuth eutectic fast reactor

Publ.-Id: 23406 - Permalink


Simulating spectral detectors - synthetic radiation diagnostics with PIConGPU and ClaRa
Pausch, R.; Debus, A.; Huebl, A.; Irman, A.; Krämer, J.; Steiniger, K.; Widera, R.; Schramm, U.; Bussmann, M.;
We present both the in-situ far field radiation diagnostics in the particle-in-cell code PIConGPU and the offline radiation diagnostic code ClaRa. The first was developed to close the gap between simulated plasma dynamics and radiation observed in laser plasma experiments. The second is used to quantitatively simulate radiation observed in e.g. Thomson scattering experiment. Both methods are based on the far field approximation of the Liénard-Wiechert potential. Their predictive capabilities, both qualitative and quantitative, have been tested against analytical models.

We will discuss the advantages of the in-situ approach of PIConGPU over ClaRa that allows predicting both coherent and incoherent radiation spectrally from infrared to x-rays and provides the capability to resolve the radiation polarization and determine the temporal and spatial origin of the radiation. Furthermore, we explain why the direct integration into the highly-scalable GPU framework of PIConGPU allows computing radiation spectra for thousands of frequencies, hundreds of detector positions and billions of particles efficiently.

In this talk we will demonstrate these capabilities on resent simulations of laser wakefield acceleration (LWFA), high harmonics generation during target normal sheath acceleration (TNSA) and Thomson scattering during laser electron interactions.
Keywords: radiation, synthetic diagnostics, spectra, ClaRa, PIConGPU, LWFA, HHG, TNSA, Thomson scattering, GPU, PHOENIX
  • Poster
    2. Annual MT Meeting, 08.-10.03.2016, Karlsruhe, Deutschland

Publ.-Id: 23405 - Permalink


Radiation as synthetic diagnostic in the particle-in-cell code PIConGPU
Pausch, R.; Debus, A.; Huebl, A.; Steiniger, K.; Widera, R.; Bussmann, M.; Schramm, U.;
A brief talk starting on how to simulate laser plasma interactions for laser driven accelerators and light sources and conclude on how simulating radiation on top of the laser plasma simulation can give insights for diagnostics in experiments.
Keywords: PIConGPU, laser, plasma, LWFA, radiation, spectra
  • Lecture (Conference)
    Second MT Student Retreat, 07.-08.03.2016, Karlsruhe, Deutschland

Publ.-Id: 23404 - Permalink


The inverse-trans-influence as a general principle of f-block chemistry
Gregson, M.; Lu, E.; Mills, D. P.; Tuna, F.; Mcinnes, E. J. L.; Hennig, C.; Scheinost, A. C.; Mcmaster, J.; Lewis, W.; Blake, A. J.; Kerridge, A.; Liddle, S. T.;
Across the periodic table the trans-influence operates, where tightly-bonded ligands selectively lengthen mutually-trans metal-ligand bonds. Conversely, in high oxidation state actinide complexes the inverse-trans-influence (ITI) operates, where normally cis strongly-donating ligands instead reside trans and actually strengthen each other. However, restricted to high valent actinyls and a few uranium(V/VI) complexes, over decades the ITI has had limited scope in an area with few unifying rules. Here, we report cerium, uranium, and thorium bis(carbene) complexes with trans C=M=C cores where characterization data consistently suggest the presence of an ITI. By applying appropriate metal-ligand-matching, this work now demonstrates the occurrence of the ITI beyond high oxidation state 5f metals extended to encompass mid-range oxidation state actinides and lanthanides. Thus, the ITI emerges as an overarching f-block principle.
Keywords: actinides lanthanides coordination chemistry cerium uranium thorium XAFS

Publ.-Id: 23403 - Permalink


99mTc-Cyclopentadienyl Tricarbonyl Chelate-Labeled Compounds as Selective Sigma‑2 Receptor Ligands for Tumor Imaging
Li, D.; Chen, Y.; Wang, X.; Deuther-Conrad, W.; Chen, X.; Jia, B.; Dong, C.; Steinbach, J.; Brust, P.; Liu, B.; Jia, H.;
We have designed and synthesized a series of cyclopentadienyl tricarbonyl rhenium complexes containing a 5,6-dimethoxyisoindoline or a 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline pharmacophore as σ2 receptor ligands. Rhenium compound 20a possessed low nanomolar σ2 receptor affinity (Ki = 2.97 nM) and moderate subtype selectivity (10-fold). Moreover, it showed high selectivity toward vesicular acetylcholine transporter (2374-fold), dopamine D2L receptor, NMDA receptor, opiate receptor, dopamine transporter, norepinephrine transporter, and serotonin transporter. Its corresponding radiotracer [99mTc]20b showed high uptake in a time- and dose-dependent manner in DU145 prostate cells and C6 glioma cells. In addition, this tracer exhibited high tumor uptake (5.92% ID/g at 240 min) and high tumor/blood and tumor/muscle ratios (21 and 16 at 240 min, respectively) as well as specific binding to σ receptors in nude mice bearing C6 glioma xenografts. Small animal SPECT/CT imaging of [99mTc]20b in the C6 glioma xenograft model demonstrated a clear visualization of the tumor at 180 min after injection.

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Publ.-Id: 23402 - Permalink


PET imaging and biodistribution studies with ultrasmall nanoparticles
Licciardello, N.; Hunoldt, S.; Faramus, A.; Prasetyanto, E. A.; Bergmann, R.; Silvestrini, S.; Maggini, M.; Stephan, H.; de Cola, L.;
For the past decade, renally clearable ultrasmall nanoparticles (sub-10 nm size) have attracted enormous attention for biomedical applications[1]. In this direction, ultrasmall silicon nanoparticles (Si NPs) and carbon “quantum” dots (CQDs) are gaining in importance[2, 3]. These quantum-sized particles display tunable photoluminescence, they are highly resistant against photo-bleaching, chemically stable after functionalization and biocompatible. Covalent functionalization of the surface with appropriate bifunctional chelator agents (BFCAs) for radiometals such as 99mTc, 111In, 64Cu, 68Ga enabling SPECT or PET, and simultaneously targeting vector molecules opens the avenue for the development of promising targeted dual-labelled imaging agents.
Here we report on the synthesis and characterization of Si NPs and CQDs (size < 5 nm), containing 64CuII-NOTA for PET imaging. The biodistribution data demonstrate that the 64Cu-labelled particles are rapidly excreted from the body using the renal pathway. In particular, the surface charge of Si NPs and CQDs seems to influence the biodistribution pattern.

Work financially supported by Helmholtz Virtual Institute “Nano-Tracking”, Agreement No. VH-VI-421


[1] B. H. Kim, M. J. Hackett, J. Park, T. Hyeon, Chemistry of Materials 2014, 26, 59-71

[2] Tu, C., X. Ma, A. House, S. M. Kauzlarich, A. Y. Louie, ACS Medicinal Chemistry Letters 2011, 2, 285

[3] Hong, G., S. Diao, A. L. Antaris, H. Dai, Chemical Reviews 2015, 115, 10816–10906
  • Lecture (Conference)
    E-MRS spring meeting 2016, 02.-06.05.2016, Lille, France

Publ.-Id: 23401 - Permalink


Synthesis and characterization of ultrasmall nanoparticles for biomedical applications
Singh, G.; Hunoldt, S.; Faramus, A.; Licciardello, N.; Stephan, H.; de Cola, L.;
The synthesis of multimodal imaging agents is indeed a growing field and a lot of research is currently being done in this area because of its wide biomedical applications. The idea behind this research is to prepare a single molecule/nanoparticle which is suitable for two or more imaging techniques and thus can act as a multimodal imaging agent, for example, the combination of optical and nuclear imaging modalities may provide complementary information for improving diagnosis as well as the treatment of diseases. These imaging agents combat the limitations of sensitivity, spatial and temporal resolution and also tissue penetrability. The high hydrophilicity of the nanoparticles and fast renal clearance of the complex from the body are the major highlights.
Amine terminated ultrasmall Silicon nanoparticles of size <4 nm were synthesized by hydrothermal method and purified by dialysis. Sulfo-Cy5 and NOTA-Bn-SCN was attached selectively to the amine terminated Si USNPs. Next step would be the radiolabeling of the particles by 64Cu and could be used for the in vitro and in vivo studies. Bispidines can also be tried as a copper chelator in the complex. Further, we could also attach single domain antibodies via PEG linkers bearing maleimide group.
The substituents after coupling with the USNPs are assumed to act as excellent multimodal imaging agent which can be used for the cancer diagnosis and therapy.
Keywords: multimodal imaging agent, ultrasmall silicon nanoparticles, bispidines
  • Poster
    2nd International Symposium on Nanoparticles/Nanomaterials and Applications, 18.-21.01.2016, Caparica, Portugal

Publ.-Id: 23400 - Permalink


Closure of the Mott gap and formation of a superthermal metal in the Fröhlich-type nonequilibrium polaron Bose-Einstein condensate in UO2+x
Conradson, S.; Durakiewicz, T.; Tayal, A.; Andersson, D.; Bagus, P.; Baldinozzi, G.; Bishop, A.; Boland, K.; Bradley, J.; Byler, D.; Clark, D.; Conradson, D.; Espinosa-Faller, F.; Gilbertson, S. M.; Kas, J.; Kozimor, S.; Kvashnina, K.; Lezama-Pacheco, J.; Martucci, M.; Nordlund, D.; Rehr, J.; Rodriguez, G.; Seidler, G.; Valdez, J.;
Mixed valence O-doped UO2+x and photoexcited UO2 containing transitory U3+ and U5+ host a coherent polaronic quantum phase (CPQP) that exhibits the characteristics of a Fröhlich-type, nonequilibrium, phononcoupled Bose-Einstein condensatewhose stability and coherence are amplified by collective, anharmonic motions of atoms and charges. Complementary to the available, detailed, real space information from scattering and EXAFS, an outstanding question is the electronic structure. Mapping the Mott gap in UO2, U4O9, and U3O7 with O XAS and NIXS and UM5 RIXS shows that O doping raises the peak of the U5f states of the valence band by ∼0.4 eV relative to a calculated value of 0.25 eV. However, it lowers the edge of the conduction band by 1.5 eV vs the calculated 0.6 eV, a difference much larger than the experimental error. This 1.9 eV reduction in the gap width constitutes most of the 2–2.2 eV gap measured by optical absorption. In addition, the XAS spectra show a tail that will intersect the occupied U5f states and give a continuous density-of-states that increases rapidly above its constricted intersection. Femtosecond-resolved photoemission measurements of UO2, coincident with the excitation pulse with 4.7 eV excitation, show the unoccupied 5f states of UO2 and no hot electrons. 3.1 eV excitation, however, complements the O-doping results by giving a continuous population of electrons for several eV above the Fermi level. The CPQP in photoexcited UO2 therefore fulfills the criteria prescribed for a nonequilibrium condensate. The electron distributions resulting from both excitations persist for 5–10 ps, indicating that they are the final state that therefore forms without passing through the initial continuous distribution of nonthermal electrons observed for other materials. Three exceptional findings are:
(1) the direct formation of both of these long lived (>3–10 ps) excited states without the short lived nonthermal intermediate;
(2) the superthermal metallic state is as or more stable than typical photoinduced metallic phases; and
(3) the absence of hot electrons accompanying the insulating UO2 excited state. This heterogeneous, nonequilibrium, Fröhlich BEC stabilized by a Fano-Feshbach resonance therefore continues to exhibit unique properties.

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Publ.-Id: 23399 - Permalink


Benchmarking PET for geoscientific applications: 3D quantitative diffusion coefficient estimation in clay rock
Lippmann-Pipke, J.; Gerasch, R.; Schikora, J.; Kulenkampff, J.;
For the first time ever the diagonal anisotropic effective diffusion coefficient, Deff = (Dxx, Dyy, Dzz), was quantified in a geologic core material in one single object of investigation. That is possible due to the combination of the non-invasive observation of Na+ diffusion in Opalinus clay by means of GeoPET (PET: positron emission tomography) followed by quantitative 3D+t data evaluation by means of finite element numerical modelling (FEM). The extracted anisotropic effective diffusion coefficient parallel (||) and normal (|) to the bedding of the clay rock, Deff =(D||, D|, D||) are comparable to those of earlier experimental studies reported by (Van Loon, et al. 2004. ES&T 38, 5721-5728). They were obtained on the same type of geomaterial (Opalinus clay, Switzerland), but by invasive methods which requires sample aliquots. We consider this study as benchmark for the long-standing development of our GeoPET method. We suggest GeoPET based fluid flow transport visualization combined with computer based process simulation henceforth as gold standard for the effective transport parameter quantification in the geosciences.
Keywords: Benchmarking GeoPET, Ddiffusion, Opalinus clay, FEM simulation

Publ.-Id: 23398 - Permalink


Magnetic storage technology and spintronic applications
Fassbender, J.ORC
Review of magnetic storage technology and spintronic applications
Keywords: magnetic storage, spintronics
  • Lecture (others)
    Invited talk at ICT / Applied Materials, 09.03.2016, München, Deutschland

Publ.-Id: 23397 - Permalink


Ion beam modification of magnetic materials - revisited
Fassbender, J.ORC
In 2009 the Gaede prize was awarded for the ion induced modification and patterning of thin magnetic films. At that time most of the investigations were dealing with the local modification of magnetic anisotropies and exchange bias phenomena. In recent years we could show that also other magnetic properties, e.g. magnetic relaxation processes [1], can be tailored, but also the ferromagnetic state itself can be created [2] or destroyed depending on the material system under investigation. In particular the latter modifications open a route to the creation of nanomagnets [3] and magnonic crystals [4] by local ion irradiation. A current review will be given.
[1] M. Körner et al., Phys. Rev. B 88, 054405 (2013).
[2] R. Bali et al., Nano Lett. 14, 435 (2014).
[3] F. Röder et al., Sci. Rep. 5, 16786 (2015).
[4] B. Obry et al., Appl. Phys. Lett. 102, 202403 (2013).
Keywords: ion beam modification, magnetism
  • Invited lecture (Conferences)
    DPG Spring Meeting, 06.-11.03.2016, Regensburg, Deutschland

Publ.-Id: 23396 - Permalink


Petawatt Lasers for Particle Acceleration at the HZDR Dresden
Schramm, U.;
Vortrag zum Status der Petawattlaserentwicklung beim Symposium Advanced Concepts for High Peak Power Ultrafast Lasers 2016
der DPG Frühjahrstagung
Keywords: Petawatt Laser
  • Invited lecture (Conferences)
    DPG Frühjahrstagung, 29.02.-04.03.2016, Hannover, Deutschland

Publ.-Id: 23395 - Permalink


Identifying the linear phase of the relativistic Kelvin-Helmholtz instability and measuring its growth rate via radiation
Pausch, R.; Bussmann, M.; Huebl, A.; Steiniger, K.; Widera, R.; Debus, A.;
For the relativistic Kelvin-Helmholtz instability (KHI) which occurs at shear interfaces between two plasma streams, we report results on the polarized radiation over all observation directions and frequencies emitted by the plasma electrons from ab-initio kinetic simulations. We find the polarization of the radiation to provide a clear signature for distinguishing the linear phase of the KHI from its other phases. During the linear phase, we predict the growth rate of the KHI radiation power to match the growth rate of the KHI to a high degree. Our predictions are based on a model of the vortex dynamics which describes the electron motion in the vicinity of the shear interface between the two streams. Albeit the complex and turbulent dynamics happening in the shear region, we find excellent agreement between our model and large-scale particle-in-cell simulations. Our findings pave the way for identifying the KHI linear regime and for measuring its growth rate in astrophysical jets observable on earth.
Keywords: Kelvin-Helmholtz instability, KHI, PIConGPU, Astrophysics, radiation, polarization, jets, AGN, SNR

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Publ.-Id: 23394 - Permalink


Upconverting Nanophosphors: Preparation Strategies for highly colloidal Stable Particles; International Caparica Congress on Nanoparticles, Nanomaterials and Applications 2016
Nsubuga, A.; Stephan, H.; Hesse, J.;
Neodymium containing upconverting nanophosphors (UCNPs)[1] Photon-upconverting nanoparticles (UCNPs) can be excited by near-infrared light and emit visible light(anti-Stokes emission) which prevents autofluorescence and over-heating effect of biological tissues. Due to their unique properties lanthanide-doped inorganic nanoparticles are very appealing particularly in bioimaging. Despite the fast progress in lanthanide-doped upconversion nanoparticles (UCNPs), the preparation of ultrasmall, monodisperse and hydrophilic UCNPs that display intense luminescence is still a challenging issue. Only a few examples of ultrasmall and hydrophilic UCNPs have been reported. [2-4] Information about biodistribution, pharmacokinetics and formation of protein corona is still missing for ultrasmall UCNPs. Therefore the aim of this project is to elaborate and to comprehensively characterize sub-10nm hydrophilic UCNPs. The luminescence properties will be tuned by varying the dopants and relative proportions as well as the fabrication of core-shell particles.
The size and shape of the particles will be influenced by controlling the reaction time and temperature course. To render them watersoluble, a ligand-exchange strategy will be used to replace the oleylamine surface groups by stabilization agents such as PEG-phosphates, O-phospho-L-serine, alendronic, zolendronic and risedronic acid.
Keywords: Upconversion, lanthanide, Sub 10nm particles, surface functionalization, Bio imaging
  • Poster
    2nd International Symposium on Nanoparticles/Nanomaterials and Applications, 18.-21.01.2016, Costa de Caparica, Portugal

Publ.-Id: 23393 - Permalink


Analysis of hydrodynamic effects using ultrafast X-ray tomography with GPU accelerated data acquisition
Bieberle, A.;
For effective reconstruction of the ultrafast electron beam X-ray tomography data a new data processing and data management tool is presented. By using multi core CPUs and many core GPUs very fast data processing can be performed.
Keywords: Ultrafast electron beam X-ray tomograph, massive parallel data processing, GPU
  • Lecture (others)
    Workshop on „Parallel Computing for Data Acquisition and Online Monitoring, 07.-08.03.2016, Karlsruhe, Deutschland

Publ.-Id: 23392 - Permalink


Engineering for NEMS with ion beams & flash annealing
Skorupa, W.;
Engineering for NEMS with ion beams & flash annealing will be presented based on recent results of the Rossendorf group working for Semiconductor Materials Modification by Ion Beams.
Keywords: NEMS, ion implantation, flash annealing
  • Invited lecture (Conferences)
    Workshop on Ion Implantation - improving the MEMS processes?, 03.03.2016, Erfurt, Germany

Publ.-Id: 23390 - Permalink


Magnetic hydroxyapatite coatings as a new tool in medicine: A scanning probe investigation
Gambardella, A.; Bianchi, M.; Kaciulis, S.; Mezzi, A.; Brucale, M.; Cavallini, M.; Herrmannsdörfer, T.; Chanda, G.; Uhlarz, M.; Cellini, A.;
Hydroxyapatite films enriched with magnetite have been fabricated via a Pulsed Plasma Deposition (PPD) system with the final aim of representing a new platform able to disincentivate bacterial adhesion and biofilm formation. The chemical composition and magnetic properties of films were respectively examined by X-ray photoelectron spectroscopy (XPS) and Superconducting Quantum Interference Device (SQUID) measurements. The morphology and conductive properties of the magnetic films were investigated via a combination of scanning probe technologies including atomic force microscopy (AFM), electrostatic force microscopy (EFM), and scanning tunneling microscopy (STM). Interestingly, the range of adopted techniques allowed determining the preservation of the chemical composition and magnetic properties of the deposition target material while STM analysis provided new insights on the presence of surface inhomogeneities, revealing the presence of magnetite-rich islands over length scales compatible with the applications. Finally, preliminary results of bacterial adhesion tests, indicated a higher ability of magnetic hydroxyapatite films to reduce Escherichia coli adhesion at 4 h from seeding compared to control hydroxyapatite films.

Publ.-Id: 23389 - Permalink


Magnetic irreversibility: An important amendment in the zero-field-cooling and field-cooling method
Dias, F. T.; Vieira, V. D.; Nunes, S. E.; Pureur, P.; Schaf, J.; Da Silva, G. F. F.; Gouvea, C. D.; Wolff-Fabris, F.; Kampert, E.; Obrados, X.; Puig, T.; Rovira, J. J. R.;
The present work reports about experimental procedures to correct significant deviations of magnetization data, caused by magnetic relaxation, due to small field cycling by sample transport in the inhomogeneous applied magnetic field of commercial magnetometers. The extensively used method for measuring the magnetic irreversibility by first cooling the sample in zero field, switching on a constant applied magnetic field and measuring the magnetization M(T) while slowly warming the sample, and subsequently measuring M(T) while slowly cooling it back in the same field, is very sensitive even to small displacement of the magnetization curve. In our melt-processed YBaCuO superconducting sample we observed displacements of the irreversibility limit up to 7K in high fields. Such displacements are detected only on confronting the magnetic irreversibility limit with other measurements, like for instance zero resistance, in which the sample remains fixed and so is not affected by such relaxation. We measured the magnetic irreversibility, Tirr(H), using a vibrating sample magnetometer (VSM) from Quantum Design. The zero resistance data, Tc0(H), were obtained using a PPMS from Quantum Design. On confronting our irreversibility lines with those of zero resistance, we observed that the Tc0(H) data fell several degrees K above the Tirr(H) data, which obviously contradicts the well known properties of superconductivity. In order to get consistent Tirr(H) data in the H–T plane, it was necessary to do a lot of additional measurements as a function of the amplitude of the sample transport and extrapolate the Tirr(H) data for each applied field to zero amplitude.

Publ.-Id: 23388 - Permalink


Modeling and speciation study of uranium (VI) and technetium (VII) co-extraction with DEHiBA
Moeyaert, P.; Dumas, T.; Guillaumont, D.; Kvashnina, K.; Sorel, C.; Miguirditchian, M.; Dufrêche, P. M. J.-F.;
The monoamide DEHiBA (N,N-di-2-ethylhexyl-isobutyramide) is a promising alternative extractant to TBP in order to extract uranium (VI) selectively towards plutonium (IV) and fission products from spent nuclear fuels. Extraction of technetium, present as pertechnetic acid (HTcO4) in the spent fuel solution, by DEHiBA was studied for different nitric acid and uranium concentrations. Uranium (VI) and technetium (VII) co-extraction mechanism with DEHiBA was particularly investigated by different techniques in the present paper to better understand the behavior of technetium in the solvent extraction process. Uranium and technetium distribution ratio were first determined from batch experiments. Based on these data, a thermodynamic model which takes into account deviations from ideality in aqueous phase using the simple solutions concept was developed. The model allowed a good representation of uranium and technetium distribution data, considering the formation of (〖(DEHiBA)_i (HNO_3 )_j (HTcO_4 )〗_k ) ̅ complexes as well as mixed (〖(DEHiBA)〗_2 (UO_2 )(NO_3 )(TcO_4 ) ) ̅ and (〖(DEHiBA)〗_3 (UO_2 )(NO_3 )(TcO_4 )(HNO_3 ) ) ̅ complexes where one pertechnetate anion substitutes one nitrate in the uranium coordination sphere. Combination of complementary spectroscopic techniques (FT-IR and X-ray absorption) supported by theoretical calculations (Density Functional Theory) enabled to fully characterize for the first time the formation of the mixed uranium-technetium specie (〖(DEHiBA)〗_2 (UO_2 )(NO_3 )(TcO_4 ) ) ̅ in organic phase. The structural parameters of this complex are reported in the paper and lead to the conclusion that the pertechnetate group coordinates the uranyl cation in a monodentate fashion in inner coordination sphere. This study also showed how combining a macroscopic study (distribution data acquisition and modeling) with supramolecular investigations (FT-IR and X-ray absorption analysis supported by theoretical calculations) could provide a new insight in the description of solvent extraction mechanism.
Keywords: Monoamides, technetium, uranium, solvent extraction, modeling, speciation

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Publ.-Id: 23387 - Permalink


Magnetic Field Induced Relaxation Attenuation of Ultrasound by Jahn–Teller Centers: Application to ZnSe:Cr2+
Zhevstovskik, I. V.; Gudkov, V. V.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Bersuker, I. B.; Averkiev, N. S.; Baryshnikov, K. A.; Monakhov, A. M.; Korostelin, Y. V.;
The influence of magnetic fields on ultrasonic attenuation caused by relaxation in Jahn–Teller centers is studied using chromium ions as Zn Substitute impurities in the ZnSe crystal as an example. The changes of the position and shape of the relaxation peak with the applied magnetic field induction B were observed in the temperature dependence of the ultrasonic attenuation of the shear waves at the frequency of 29.5 MHz propagating along the [110] axis with the polarization vector parallel to the [110] axis. To rationalize the results, a simulation procedure was employed assuming that there are two thermal activation mechanism of relaxation with different relaxation times. One of them emerged with activation energy V0 = 75 K that remains unchanged in the magnetic fields, the other occurs with increasing V0 up to V0 = 106 K at B =14 T.

Publ.-Id: 23386 - Permalink


Anomalous Magnetothermopower in a Metallic Frustrated Antiferromagnet
Arsenijevic, S.; Ok, J. M.; Robinson, P.; Ghannadzadeh, S.; Katsnelson, M. I.; Kim, J. S.; Hussey, N. E.;
We report the temperature T and magnetic field H dependence of the thermopower S of an itinerant triangular antiferromagnet PdCrO2 in high magnetic fields up to 32 T. In the paramagnetic phase, the zerofield thermopower is positive with a value typical of good metals with a high carrier density. In marked contrast to typical metals, however, S decreases rapidly with increasing magnetic field, approaching zero at the maximum field scale for T > 70 K. We argue here that this profound change in the thermoelectric response derives from the strong interaction of the 4d correlated electrons of the Pd ions with the shortrange spin correlations of the Cr3+ spins that persist beyond the Néel ordering temperature due to the combined effects of geometrical frustration and low dimensionality.

Publ.-Id: 23385 - Permalink


Dynamical Effects of the Martensitic Transition in Magnetocaloric Heusler Alloys from Direct ΔTad Measurements under Different Magnetic-Field-Sweep Rates
Gottschall, T.; Skokov, K. P.; Scheibel, F.; Acet, M.; Ghorbani Zavareh, M.; Skourski, Y.; Wosnitza, J.; Farle, M.; Gutfleisch, O.;
Large magnetocaloric effects can be obtained in Ni-Mn-based Heusler alloys due to the magnetostructural transition between martensite and austenite. This phase transformation proceeds via nucleation and growth. By direct measurements of the adiabatic temperature change ΔTad using different magneticfield-sweeping rates from 0.01 up to 1500 Ts−1, we study the dynamic behavior of the two Heusler compounds Ni50Mn35In15 and Ni45Mn37In13Co5 transforming near room temperature. From these experiments, we conclude that the nucleation process is rather slow in contrast to the relatively fast movement of the phase boundary between martensite and austenite. This is a limiting factor for cooling concepts operating at frequencies beyond 100 Hz. However, the dynamic effects of the transition are negligible in field rates typically used in magnetic refrigeration. These findings are essential considering the suitability of Heusler compounds for energy-efficient solid-state cooling.

Publ.-Id: 23384 - Permalink


High Magnetic Field Study of Elastic Constants of the Cage-structure Compound SmBe13
Mombetsu, S.; Murazumi, T.; Hiura, K.; Yamazaki, S.; Shimizu, Y.; Hidaka, H.; Yanagisawa, T.; Amitsuka, H.; Yasin, S.; Zherlitsyn, S.; Wosnitza, J.;
Ultrasonic measurements were performed on the cage-structure compound SmBe13. We have investigated the magnetic field-temperature phase diagram of this material by using pulsed magnetic fields. We found that the low-temperature magnetic order is suppressed by a magnetic field of 43 T for H ‖, which is smaller than the estimated value from mean-field approximation assuming the Г8 quartet crystal-electric-field ground state and simple antiferromagnetic order. We found that the elastic constant C44 shows softening below the ordering temperature and has a local minimum below 7 T. These facts suggest that the lowtemperature state is not a simple antiferromagnetically ordered state. In addition, no elastic anomaly due to rattling modes was found in the present measurements.

Publ.-Id: 23383 - Permalink


Narrow-band near-field nanoscopy in the spectral range from 1.3 to 8.5 THz
Kuschewski, F.; von Ribbeck, H.-G.; Döring, J.; Winnerl, S.; Eng, L. M.; Kehr, S. C.;
Nano-spectroscopy in the terahertz frequency range remains challenging despite recent technological progress in developing both THz emitter sources and near-field optical microscopy (SNOM). Here we combine scattering-type SNOM with a free-electron laser (FEL) light source, to tune into the 1.3 - 8.5 THz range. A significant portion of this range, namely the frequencies above ~3 THz, is not covered by previously reported near-field microscopy systems. However, it constitutes an indispensable regime where many elementary processes in solids including collective lattice excitations, charge and spin transport occur. Our approach of nano-spectroscopy and nano-imaging provides a versatile analysis of nanostructures as small as 50 nm, hence beating the optical diffraction limit by λ/4600.
Keywords: near-field microscopy, nanoscopy, terahertz

Publ.-Id: 23382 - Permalink


LC-MS supported Studies on the in vitro Metabolism of both Enantiomers of Flubatine and the in vivo Metabolism of (+)-[18F]Flubatine – a Positron Emission Tomography Radioligand for Imaging α4β2-Nicotinic Acetylcholine Receptors
Ludwig, F.-A.; Smits, R.; Fischer, S.; Donat, C. K.; Hoepping, A.; Brust, P.; Steinbach, J.;
Both enantiomers of [18F]flubatine are promising radioligands for neuroimaging of α4β2 nicotinic acetylcholine receptors (nAChRs) by positron emission tomography (PET). To support clinical studies in patients with early Alzheimer’s disease, a detailed examination of the metabolism in vitro and in vivo is required. (+)- and (–)-flubatine, respectively, were incubated with liver microsomes from mouse and human in the presence of NADPH. Phase I in vitro metabolites were detected and their structures elucidated by LC-MS/MS. Selected metabolite candidates were synthesized and investigated for structural confirmation. Besides a high level of in vitro stability, the microsomal incubations revealed some species differences as well as enantiomer discrimination with regard to the formation of monohydroxylated products, that was identified as the main metabolic pathway in this assay. Further, after injection of 280 MBq (+)-[18F]flubatine (specific acitivity > 350 GBq/µmol) into a CD-1 mouse, samples were prepared from liver, plasma, and urine after 30 min and investigated by HPLC with radioactivity detection. For structure elucidation of the radiometabolites of (+)-[18F]flubatine formed in vivo, identical chromatographic conditions were applied to LC-MS and radio-HPLC to compare samples obtained in vitro and in vivo. By this correlation we assigned 3 of 4 main in vivo radiometabolites to products exclusively C- or N-hydroxylated at the azabicyclic ring system of the parent molecule.
Keywords: Nicotinic acetylcholine receptors (nAChRs), Flubatine (NCFHEB), Positron emission tomography (PET), Radiometabolites, Liquid chromatography-mass spectrometry (LC-MS), Liver microsomes

Publ.-Id: 23381 - Permalink


Origin of the Zero-Field Splitting in Mononuclear Octahedral MnIV Complexes: A Combined Experimental and Theoretical Investigation
Zlatar, M.; Gruden, M.; Vassilyeva, O. Y.; Buvaylo, E. A.; Ponomarev, A. N.; Zvyagin, S.; Wosnitza, J.; Krzystek, J.; Garcia-Fernandez, P.; Duboc, C.;
The aim of this work was to determine and understand the origin of the electronic properties of MnIV complexes, especially the zero-field splitting (ZFS), through a combined experimental and theoretical investigation on five well-characterized mononuclear octahedral MnIV compounds, with various coordination spheres (N6, N3O3, N2O4 in both trans (trans-NO) and cis configurations (cis-N2O4) and O4S2). High-frequency and -field EPR (HFEPR) spectroscopy has been applied to determine the ZFS parameters of two of these compounds, MnLtrans‑N2O4 and MnLO4S2. While at X-band EPR, the axial-component of the ZFS tensor, D, was estimated to be +0.47 cm−1 for MnLO4S2, and a D-value of +2.289(5)cm−1 was determined by HFEPR, which is the largest D-magnitude ever measured for a Mn complex. A moderate D value of −0.997(6) cm−1 has been found for MnLtrans‑N2O4. Quantum chemical calculations based on two theoretical frameworks (the Density Functional Theory based on a coupled perturbed approach (CP-DFT) and the hybrid Ligand-Field DFT (LF-DFT)) have been performed to define appropriate methodologies to calculate the ZFS tensor for MnIV centers, to predict the orientation of the magnetic axes with respect to the molecular ones, and to define and quantify the physical origin of the different contributions to the ZFS. Except in the case of MnLtrans‑N2O4, the experimental and calculated D values are in good agreement, and the sign of D is well predicted, LF-DFT being more satisfactory than CP-DFT. The calculations performed on MnLcis‑N2O4 are consistent with the orientation of the principal anisotropic axis determined by single-crystal EPR, validating the calculated ZFS tensor orientation. The different contributions to D were analyzed demonstrating that the d-d transitions mainly govern D in Mn ion. However, a deep analysis evidences that many factors enter into the game, explaining why no obvious magnetostructural correlations can be drawn in this series of MnIV complexes.

Publ.-Id: 23380 - Permalink


Large pinning forces and matching effects in YBa2Cu3O7-δ thin films with Ba2Y(Nb/Ta)O6 nanoprecipitates
Opherden, L.; Sieger, M.; Pahlke, P.; Hühne, R.; Schultz, L.; Meledin, A.; van Tendeloo, G.; Nast, R.; Holzapfel, B.; Bianchetti, M.; Macmanus-Driscoll, J. L.; Hänisch, J.;
The addition of mixed double perovskite Ba2Y(Nb/Ta)O6 (BYNTO) to YBa2Cu3O7−δ (YBCO) thin films leads to a large improvement of the in-field current carrying capability. For low deposition rates, BYNTO grows as well-oriented, densely distributed nanocolumns. We achieved a pinning force density of 25 GN/m3 at 77 K at a matching field of 2.3 T, which is among the highest values reported for YBCO. The anisotropy of the critical current density shows a complex behavior whereby additional maxima are developed at field dependent angles. This is caused by a matching effect of the magnetic fields c-axis component. The exponent N of the current-voltage characteristics (inversely proportional to the creep rate S) allows the depinning mechanism to be determined. It changes from a double-kink excitation below the matching field to pinning-potential-determined creep above it.

Publ.-Id: 23379 - Permalink


Big Lasers, Small Particles & GPUs: Our Weapons of Choice to Fight Cancer
Huebl, A.; Widera, R.; Zenker, E.; Burau, H.; Pausch, R.; Matthes, A.; Grund, A.; Eckert, C.; Debus, A.; Hilz, P.; Schreiber, J.; Kluge, T.; Cowan, T.; Schramm, U.; Bussmann, M.;
We'll present results on our INCITE project "Targeting Cancer with High Power Lasers," which aims to deliver beams of ions for cancer therapy accelerated by high power lasers. With a novel target design in which the target is levitated in a trap to isolate it from its environment, we study the properties of the generated ion beams and their potential for radiation therapy of cancer. In the discussion, we'll also present performance results of our own plasma simulation code PIConGPU on the Titan system, which has been used to study the laser plasma interaction in 3D.
Keywords: Computational Physics; Computational Chemistry; Supercomputing & HPC; CUDA; PIConGPU
  • Lecture (Conference)
    GPU Technology Conference, 04.-07.04.2016, San Jose, CA, USA

Publ.-Id: 23378 - Permalink


Live, Interactive, In-Situ Visualization of Large-Scale Plasma Simulations
Huebl, A.; Matthes, A.; Widera, R.; Zenker, E.; Bussmann, M.;
In large-scale scientific simulations, I/O has become a bottleneck that can slow down the exploration of unknown physical scenarios. We show that it is vital to view a HPC system not only in its ability to simulate the system but also to visualize the simulated data. By keeping the data of the simulation in the GPU memory, remote analysis via a Wi-Fi connection can work at frame rates well above 10 fps while latencies are not of importance, even when spanning continents. This presentation includes a live demo.
Keywords: In-Situ and Scientific Visualization; Supercomputing & HPC; Computational Physics; CUDA; Alpaka
  • Lecture (Conference)
    GPU Technology Conference, 04.-07.04.2016, San Jose, CA, USA

Publ.-Id: 23377 - Permalink


Interaction of a highly radiative shock with a solid obstacle
Koenig, M.; Yurchak, R.; Michaut, C.; Laffite, S.; Falize, E.; Sakawa, Y.; Barroso, P.; Pelka, A.; Morita, T.; Kuramitsu, Y.; Gregori, G.; Albertazzi, B.; Kodama, R.; Ozaki, N.;
In this paper, we present recent results obtained on highly radiative shocks (RS) generated in a low-density gas filled cell obtained on the GEKKO XII laser facility. The RS was generated by using an ablator-pusher two-layer target (CH/Ti) and propagation media (Xe). High velocity RS have been generated (100-140 km/s) while limiting the preheating produced by the corona emission. Both self-emission and visible probe diagnostics highlighted a strong and anisotropic emission well ahead of the shock front. Its characteristics that depend on the initial conditions are described here as well as its interaction with an aluminium foil used as an obstacle. The obtained results are discussed showing a strong extension of the radiative precursor (1 mm) leading to an expansion of the obstacle at a velocity ≈ 6 km/s compatible to a 1-2 eV temperature.
Keywords: Laboratory astrophysics; Radiative shocks; High-power laser; Hydrodynamics; Radiative transfer, Plasma

Publ.-Id: 23376 - Permalink


Liquid metal batteries: Numerical simulations
Weber, N.; Herreman, W.; Landgraf, S.; Nore, C.; Stefani, F.; Weier, T.;
Liquid metal batteries (LMB) are built as a stable density stratification of two liquid metals, separated by a likewise liquid salt. If the materials are correctly chosen, all three phases self-assemble. During discharge, the anode metal will lose electrons, diffuse through the electrolyte layer and alloy then with the cathode metal. The main advantage of LMBs is the very low price: low-cost raw materials together with a simple set-up and scalability make such cells an ideal stationary storage, which is highly needed for buffering fluctuating renewable energies. The liquid-liquid interfaces allow for optimal kinetics, i.e. for a fast response time and current densities up to 10 A/cm 2 . Furthermore, they avoid micro-degradation - as known from solid cells - and allow for potentially very high life-times. Safety will play a major role in the construction of such cells – especially due to the high amount of liquid and reactive metals. In that context, a short circuit of the thin electrolyte layer should be avoided. In large liquid metal batteries with diameters in the order of several decimetres, even the discharging current itself may lead to a fluid flow, able to short-circuit the battery. After showing some experimental examples of Na||Bi and Li||Bi cells, we will present numerical simulations of the fluid flow in LMBs and estimate their relevance for real cells. Reviewed phenomena include electro-vortex flow, the Tayler-instability as well as metal pad rolling, which is well known from aluminium reduction cells.
Keywords: liquid metal battery; OpenFOAM; numerical simulation; Tayler instability; electro-vortex flow; metal pad roll
  • Poster
    67th Annual Meeting of the International Society of Electrochemistry, 21.08.2016, Den Haag, Niederlande

Publ.-Id: 23375 - Permalink


Direct numerical simulations and experiments of a pseudo-2D gas-fluidized bed
Tang, Y.; Lau, Y. M.; Deen, N. G.; Peters, E. A. J. F.; Kuipers, J. A. M.;
This paper reports our study on fluidization of 5000 spherical particles in a pseudo-2D gas-fluidized bed by direct numerical simulations (DNS) and experiments as well. Simulations are performed using an immersed boundary method, together with the methodology developed in our earlier work for accurate prediction of gas–solid interactions at relatively low grid resolutions. This modelling approach provides detailed information on the gas flow and the motion of individual particles, which allows for a priori calculation of the bed hydrodynamics. Experimental measurements of solids mean motion are conducted using a combined technique of Particle Image Velocimetry (PIV) and Digital Image Analysis (DIA). Fur- ther, the PIV technique is extended and applied for instantaneous measurements of the particle granular temperature, which is the key characteristics of particle velocity fluctuations. For the first time, this paper reports a direct comparison in great detail between DNS results and experimental data for realistic gas fluidization. The detailed comparison reveals a reasonably good agreement with respect to the time-averaged solids motion and the pressure fluctuations. In addition, the granular temperatures calculated from the simulations agree well with the experimental data, but provide more details with respect to the variations corresponding to bubble formation and eruption. From our investigation, it also becomes clear that attention should be paid on the measurement and interpretation of the granular temperature.
Keywords: DIA; DNS; Gas-fluidized bed; Granular temperature; PIV

Publ.-Id: 23374 - Permalink


The Λp interaction studied via femtoscopy in p + Nb reactions at sqrt( sNN) = 3.18 GeV
Adamczewski-Musch, J.; Agakishiev, G.; 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.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, 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.; Krasa, 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.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; 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.; Wüstenfeld, J.; Zanevsky, Y.; Zumbruch, P.;
We report on the first measurement of pΛ and pp correlations via the femtoscopy method in p+Nb reactions at √sNN=3.18 GeV, studied with the High Acceptance Di-Electron Spectrometer (HADES). By comparing the experimental correlation function to model calculations, a source size for pp pairs of r0,pp=2.02±0.01(stat)+0.11−0.12(sys) fm and a slightly smaller value for pΛ of r0,Λp=1.62±0.02(stat)+0.19−0.08(sys) fm is extracted. Using the geometrical extent of the particle emitting region, determined experimentally with pp correlations as reference together with a source function from a transport model, it is possible to study different sets of scattering parameters. The pΛ correlation is proven sensitive to predicted scattering length values from chiral effective field theory. We demonstrate that the femtoscopy technique can be used as valid alternative to the analysis of scattering data to study the hyperon-nucleon interaction.

Downloads:

Publ.-Id: 23373 - Permalink


State-of-the-art quantitative mineral phase determination of resource materials by XRD
Möckel, R.; Kleeberg, R.; Luhmer, R.;
Quantitative powder X-ray diffraction (PXRD) analysis is a traditional and powerful tool widely used in numerous fields like industrial product control, material sciences, and par-ticularly in geosciences. Resource materials and their comprehensive characterization play an important role in the recent developments focused on efficient and sustainable usage of valuable materials from both primary and secondary sources. PXRD offers the opportunity to quantify crystalline materials from a large part of the value chain, from raw materials (ores) to the characterization of concentrates and residues during processing and – closing the loop – of recycling products. Although several approaches are available, nowadays Rietveld analysis is widely used to quantify mineral phases. This method is based on crystal structure and peak profile models, whose parameters are refined by least-squares algorithms to match the measured raw diffraction pattern. The software packages BGMN and Profex [1] are especially suitable for Rietveld phase analysis, as their convolution-based peak shape models together with a structure interpreter language enable the formulation of structure models even for complex disordered structures like clay minerals. In this way, standardless mineral quantification is possible even critical matrices like iron ores or clays, what is hard to perform with any (electron) optically or chemically based method. The successful participation in several round robins (e.g. the Reynolds Cup) as well as extensive in-house testing by synthetic reference mixtures, adjusted to match real-life samples, proved the accuracy and potential of this approach. Although the limits of detection of PXRD are generally considered to be high compared to spatially resolved methods like microscopy, new instrumental developments like multistrip detectors in combination with improved peak profile modeling enable a significant improvement of this critical parameter. Thus, in a case study on processing residues of a cassiterite (SnO2) bearing Greisen deposit limits of determination in the magnitude of 0.2 mass% were reached and verified by geochemical methods.
Literature:
[1] Doebelin, N., Kleeberg, R., Journal of Applied Crystallography 2015, 48, 1573-1580.
Keywords: keine
  • Invited lecture (Conferences)
    analytica conference 2016, 10.-13.05.2016, München, Deutschland

Publ.-Id: 23372 - Permalink


Activities of the Institute of Resource Ecology in the field of radioecology
Arnold, T.; Sachs, S.;
Our presentation will give a short overview of the Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology (HZDR/IRE), its main objectives, its structure, and its analytical and spectroscopic capabilities.
The main part of the talk will focus on our current activities in the field of radioecology on the European level. Here, our engagement in the European Radioecological Alliance (ALLIANCE), including our role as leader of the roadmap working group NORM (Naturally Occurring Radioactive Materials) is described. In addition, our EU project activities will be discussed.
Some examples of current research activities of the IRE in the field of radioecology, including water analyses of uranium contaminated surface and underground environments, as well as uranium plant, fungi and uranium cell interactions related to former uranium mining activities in Eastern Germany are presented.
Keywords: Radioecology, European Radioecology ALLIANCE, Working group NORM, Research activities
  • Lecture (others)
    SUBATECH Seminar, 10.03.2016, Nantes, France

Publ.-Id: 23371 - Permalink


The single component geochemical map: Fact or fiction?
Mckinley, J. M.; Hron, K.; Grunsky, E. C.; Reimann, C.; de Caritat, P.; Filzmoser, P.; van den Boogaart, K. G.; Tolosana-Delgado, R.;
Single component geochemical maps are the most basic representation of spatial elemental distributions and commonly used in environmental and exploration geochemistry. However, the compositional nature of geochemical data imposes several limitations on how the data should be presented. The problems relate to the constant sum problem (closure), and the inherently multivariate relative information conveyed by compositional data. Well known is, for instance, the tendency of all heavy metals to show lower values in soils with significant contributions of diluting elements (e.g., the quartz dilution effect); or the contrary effect, apparent enrichment in many elements due to removal of potassium during weathering. The validity of classical single component maps is thus investigated, and reasonable alternatives that honour the compositional character of geochemical concentrations are presented. The first recommended such method relies on knowledge-driven log-ratios, chosen to highlight certain geochemical relations or to filter known artefacts (e.g. dilution with SiO2 or volatiles). This is similar to the classical normalisation approach to a single element. The second approach uses the (so called) log-contrasts, that employ suitable statistical methods (such as classification techniques, regression analysis, principal component analysis, clustering of variables, etc.) to extract potentially interesting geochemical summaries. The caution from this work is that if a compositional approach is not used, it becomes difficult to guarantee that any identified pattern, trend or anomaly is not an artefact of the constant sum constraint. In summary the authors recommend a chain of enquiry that involves searching for the appropriate statistical method that can answer the required geological or geochemical question whilst maintaining the integrity of the compositional nature of the data. The required log-ratio transformations should be applied followed by the chosen statistical method. Interpreting the results may require a closer working relationship between statisticians, data analysts and geochemists.
Keywords: Soil geochemistry; Compositional data analysis; Log-ratios; Mapping

Publ.-Id: 23370 - Permalink


U and Np uptake on biogenic and abiotic ferrihydrite – a comparison by EXAFS spectroscopy
Krawczyk-Bärsch, E.; Schmeide, K.; Rossberg, A.; Scheinost, A. C.;
The ferrous iron-oxidizing and stalk-forming bacterium Gallionella ferruginea was cultivated in laboratory experiments. Since this bacterium is gaining energy for its growth from the oxidation of ferrous iron, ferric iron is precipitating quickly and forming biogenic ferrihydrite. UO2(NO3)2 and NpO2(ClO4) was added to these samples under anaerobic conditions in the neutral pH range, adjusting a final U and Np concentration of 0.08 mM, respectively. The results showed an uptake of 91 mg U and 38 mg Np/g dry mass by the abundant surface area of the samples.
At the ROBL Beamline of the European Synchrotron Radiation Facility in Grenoble Extended X-ray absorption fine structure (EXAFS) spectroscopy at the uranium LIII–edge and the neptunium LIII–edge were carried out. The k3-weighted chi-spectrum and its Fourier transform magnitude of the studied biogenic ferrihydrite sample bears close resemblance to the bidentate edge-sharing innersphere sorption complex (1E), which is the most prominent surface species in the absence of carbonate and the main sorption species on abiotic ferrihydrite [1]. As a second species a smaller portion of the aqueous type-B ternary uranyl-carbonato complex was determined as a result of the addition of a carbon source during the cultivation of the Gallionella ferruginea strain. By iterative target test factor analysis (ITFA), using the spectra of the two endmember species, we determined that the 1E complex is in fact predominant with 95%, while the ternary uranyl-carbonato complex is present only to 5%. Based on the shell fit analysis, the distances of the coordination shells U–Oeq ~ 2.34 Å, U–Oax ~ 1.79 Å, and U–Fe ~ 3.44 Å are similar to those determined of abiotic ferrihydrite samples [2]. The data of the biogenic Np ferrihydrite sample were compared to Np interaction with a hematite surface and showed similar distances of the coordination shells, also indicating a bidentate edge-sharing coordination [3].
Keywords: uranium, neptunium, gallionella ferruginea, ferrihydrite, sorption
  • Lecture (Conference)
    Goldschmidt Conference 2016, 26.06.-01.07.2016, Yokohama, Japan

Publ.-Id: 23369 - Permalink


New spectroscopic insights into the uranyl-acetate system by TRLFS and UV-vis
Brinkmann, H.; Moll, H.; Arnold, T.; Stumpf, T.;
The interaction of acetic acid as the smallest carboxylic acid with a side chain with uranium (VI) is of importance in two respects: firstly, it occurs often as a degradation product of organic components of radioactive waste (e.g. cellulose, bitumen, PVC), and secondly it can serve as model for more complex organic compounds like humic acids. Three complexes can be formed in aqueous solutions: UO2(AcO)n2-n, where n is 1,2, or 3. These complexes are well characterized under various experimental conditions in terms of stability and structure, reported in a number of publications. Recently published articles focused also on spectroscopic properties of uranium (VI) acetate complexes using on the one hand time-resolved laser-induced fluorescence spectroscopy (TRLFS) and on the other hand UV-vis spectroscopy. The uranium concentrations used (between 0.1 and 0.2 M) are comparatively high. However, both works revealed only data for the 1:1 complex UO2(AcO)+. Therefore, the aim of this study was to provide spectroscopic data for all three UO2(AcO)n2-n complexes to fill in the gaps in the uranium-acetate system.
Both the TRLFS and UV-vis experiments were performed with solutions containing only 50 µM uranium (VI). The parameters of the test series were varied in a way that the speciation changes from the free uranyl-ion, over the 1:1 and 1:2, to the 1:3 complex UO2(AcO)3-. Thereby the pH was fixed and the acetate concentration was varied or vice versa. In contrast to conventional UV-vis set ups, we used a Liquid Waveguide Capillary Cell with a path length of 250 cm to obtain spectra of high quality at this very low uranium concentration. The absorption spectra were evaluated on the basis of factor analysis and it was possible to calculate reproducible single component spectra for all the uranyl-acetate species (see Fig. 1). The TRLFS experiments at 25°C revealed the known quenching of the 1:1 complex (see Fig. 2 left) but also at pH > 3 a strong increase in intensity, band shifts, and a rise of a new band at 461 nm (see Fig. 2). These findings allow the assumption that the 1:2 and 1:3 complexes are luminescent. To examine whether the 1:1 complex is non luminescent TRLFS measurements at 152 K to avoid dynamic quenching of the acetate ion will be carried out.
Our approach of using a combination of UV-vis, TRLFS, and cryo-TRLFS allows the spectroscopic characterization of all three uranyl-acetate complexes including the determination of the corresponding stability constants.
Keywords: Uranium, Acetate, TRLFS, UV-vis
  • Lecture (Conference)
    10th International Biometals Symposium, 10.-15.07.2016, Dresden, Deutschland

Publ.-Id: 23368 - Permalink


Analysis of granular material flow characteristics during silo discharging process using ultrafast X-ray CT
Waktola, S.; Babout, L.; Grudzień, K.; Bieberle, M.; Barthel, F.; Hampel, U.;
In various industrial products, granular materials are required to flow under gravity in different kinds of silo shapes and through openings in horizontal bottoms. There are a number of interrelated parameters, which affect the flow, such as internal friction, bulk and packing density, hopper geometry, material type and so on. Silo gravitational flow has been investigated for many years; however, most published research findings are concerned on the numerical modeling of flow or usually the results are obtained by using equipment with some technical limitations. Due to the lack of possibility to visualize center of silo (as in case of CCD camera systems) or conditions of scanning speed and slightly low resolution of conventional X-ray CT and ECT systems respectively, so far, it was not able to conduct effective analysis of flow characteristics (MICHALOWSKI et al., 1984, CHOI et al., 2005, WILDE et al., 2010 and BABOUT et al., 2013). More in-depth investigation and analysis of silo flow behaviors than being conducting till now, will allow better understand the flow process and additionally to conduct comparison between real measurements and simulation results.
Using the ultra-fast electron beam X-ray CT scanner (ROFEX) from Helmholtz-Zentrum Dresden-Rossendorf, which is a very high temporal resolution system, it is possible to investigate structural changes within a granular material during the flow process. Since the images, which were scanned using this technology have high spatial and temporal resolution, specified particle movements can be tracked and local velocities can be determined. Thus, the dynamic flow behavior of the material during the discharging process can be investigated.
This study gives a new insight into the gravitational flow during silo discharging process inside a cylindrical silo model. The granular material is a mixture of sand and tracer particles. The properties of tracer particles are characterized by higher absorption of X-ray radiation and different shape than sand particles, which allows observing motion of tracking particles (GRUDZIEN et al., 2013). Such type of experiments (using ultra-fast X-ray system and particle tracking methods) were conducted for different construction of silo models, which allows evaluating the radial and axial local velocity of granular materials.
Keywords: granular material, silo discharging, ultrafast X-ray CT
  • Contribution to proceedings
    WCIPT8 - 8th World Congress on Industrial Process Tomography, 26.-29.09.2016, Iguassu Falls, Brazil
    Proceedings of WCIPT8
  • Poster
    WCIPT8 - 8th World Congress on Industrial Process Tomography, 26.-29.09.2016, Iguassu Falls, Brazil

Publ.-Id: 23367 - Permalink


Geometallurgy of iron ores - a mineralogists' perspective
Gutzmer, J.;
To the superficial observer iron ore deposits appear as huge and uniform bodies comprising of iron oxide - or carbonate - and little else. They should, therefore, be simple to exploit and beneficiate. This may have indeed applied to the giant high-grade BIF-hosted deposits that have dominated global iron supply for the last half a century. However, it does certainly not apply to iron ore deposits that will govern future supply. The latter deposits will still be very large, but of lower grade and marked by increasing concentrations of deleterious elements such as phosphorous, titanium or alkali elements. Careful ore characterization and geometallurgical modelling will be key drivers to convert iron ore resources into reserves – and deposits into new mines.
Keywords: iron ore, geometallurgy
  • Invited lecture (Conferences)
    Mineralteknik 2016, 02.-03.02.2016, Lulea, Sweden
  • Contribution to proceedings
    Mineralteknik 2016, 02.-03.02.2016, Lulea, Sweden
    Mineralteknik 2016 - Proceedings, Lulea: Lulea Technical University, 18-19

Publ.-Id: 23366 - Permalink


The Paleoproterozoic Manganese Bonanza in Africa
Gutzmer, J.; Beukes, N. J.;
Africa hosts just over 80 percent of the currently known land-based resources of manganese (Mn). The bulk of the African Mn resource is of sedimentary origin and hosted by strata of Paleoproterozoic age, although epigenetic processes, including hydrothermal enrichment and/or deep chemical weathering, have significantly enriched some of the deposits. Host strata and geological context have been used to categorize the deposits into four types, namely BIF-associated, black shale-associated, sandstone-associated (oolitic) and karst-associated. Mn deposits occur geographically clustered and related to a number of prominent sedimentary successions of Late Archean to Late Paleoprozerozoic age. The greatest concentration and genetic diversity occurs undoubtedly on the Kaapvaal Craton of Southern Africa. The Transvaal Supergroup (TVL SG) hosts the ~ 2,2 Ga BIF-associated deposits of the Kalahari Manganese Field – with an estimated 4,2 Gt of contained Mn by far the largest of all land-based Mn deposits globally. However, the TVL SG also hosts the ~ 2,4 Ga BIF-associated Rooinekke deposit and the 2,0-2.2 Ga Postmasburg Manganese Field, the latter comprising the worlds oldest karst-associated Mn deposits. The record of sedimentary Mn deposits of Paleoproterozoic age on the Kaapvaal Craton is complemented by the Tolwe deposit of the ~1,9 Ga Soutpansberg Group, the oldest known example of sandstone-associated oolitic Mn ores.
Other important Paleoproterozoic manganese deposits in Africa are all limited to sedimentary strata of ~ 2,1-2,2 Ga age. These successions may comprise cratonic cover sequences, such as the Francevillian Supergroup on the northwestern part of the Congo Craton, or are associated with the formation of Paleoproterozoic juvenile crust, such as the Birimian Supergroup of West Africa or the Lukoshi Complex in the DRC. Manganiferous carbonate beds closely associated with greywackes and pyritic black shales are geographically and stratigraphically widespread in these successions. In most cases, Late Mesozoic and Cenozoic lateritic weathering markedly enrich the manganiferous strata to form high-grade manganese oxide ores.
All major African Mn deposits occur in strata that immediately postdate the great oxidation event (GOE). Furthermore, they are associated with – or immediately postdate the deposition of banded iron formations. Together with an abundance of geochemical evidence this close temporal affiliation may be used to invoke that the unique concentration of Mn in the sedimentary environment is a consequence of the establishment of oxic conditions in the shallow marine as well as the terrestrial environment.
Keywords: Manganese, Africa, ore deposits
  • Invited lecture (Conferences)
    5th International Geologica Bellica Meeting, 26.-29.01.2016, Mons, Belgium
  • Contribution to proceedings
    5th International Geologica Belgica 2016 Congress, 26.-29.01.2016, Mons, Belgium
    5th International Geologica Belgica 2016 Congress Abstract Book, Mons: Geological Society of Belgium, 197-197

Publ.-Id: 23365 - Permalink


Thyroid hormone status defines brown adipose tissue activity and browning of white adipose tissues in mice
Weiner, J.; Kranz, M.; Klöting, N.; Kunath, A.; Steinhoff, K.; Rijntjes, E.; Köhrle, J.; Zeisig, V.; Hankir, M.; Gebhardt, C.; Deuther-Conrad, W.; Heiker, J.; Kralisch, S.; Stumvoll, M.; Bluher, M.; Sabri, O.; Hesse, S.; Brust, P.; Tönjes, A.; Krause, K.;
The present study aimed to determine the effect of thyroid hormones dysfunction on brown adipose tissue activity and white adipose tissue browning in mice.
Twenty randomized female C57BL/6NTac mice per treatment group housed at room temperature were rendered hypothyroid or hyperthyroid. In-vivo small animal 18F-FDG PET/MRI was performed to determine the effects of hypo- and hyperthyroidism on BAT mass and BAT activity. Ex-vivo 14C-acetate loading assay and the assessment of expression of thermogenic genes and proteins allowed for the quantification of the oxidative and thermogenic capacities of WAT and BAT of eu-, hyper and hypothyroid mice.
18F-FDG PET/MRI revealed lack of brown adipose tissue activity in hypothyroid mice, whereas hyperthyroid mice displayed increased BAT mass alongside enhanced 18F-FDG uptake. In white adipose tissue of both, hyper- and hypothyroid mice, we found a significant induction of thermogenic genes together with a multilocular adipocytes expressing Ucp1.
Taken together, these results suggest that both the hyperthyroid and hypothyroid state affect WAT thermogenesis most likely as a consequence of enhanced adrenergic signaling or compensation for impaired adaptive thermogenesis, respectively.

Publ.-Id: 23364 - Permalink


Multistage uranium bioassociation kinetics of two Halobacterium noricense strains under highly saline conditions
Bader, M.; Müller, K.; Foerstendorf, H.; Swanson, J. S.; Cherkouk, A.;
Salt rock is one potential host rock formation being considered by Germany for the final disposal of radioactive waste. In addition to the characterization of geochemical and geophysical parameters, it is of great importance to take microbial activity of indigenous microorganisms into account for the safety assessment. Few studies have been conducted to investigate the microbial influence on the migration of radionuclides at high ionic strength. In this work, the extremely halophilic archaeon Halobacterium (Hbt.) noricense and its interactions with uranium were studied. Two different strains of the in salt rock common Hbt. noricense [1-4] were investigated. One was originally isolated from an Austrian salt mine (Hbt. noricense DSM-15987) [1] and the other from the US nuclear waste disposal site Waste Isolation Pilot Plant (WIPP, Carlsbad, NM) [2].
Biosorption kinetics were monitored in 3 M NaCl containing 40 or 50 µM uranium at pH 5.5 in the presence of Hbt. noricense cells. The fraction of bioassociated uranium was calculated from the uranium remaining in solu-tion analyzed by ICP-MS. Surprisingly, both strains of Hbt. noricense do not reflect typical sorption behavior; i.e. fast sorption within the first hours until reaching a stable equilibrium state. In this study, a fraction of uranium was sorbed within the first two hours of exposure time followed by a release of the radionuclide for a certain time. Subsequently, the amount of bioassociated uranium was found to increase very slowly until a maximum sorption of 80% was reached after 48 h. For a better understanding of this unique behavior, spectroscopic as well as microscopic methods were applied. Results from in situ Attenuated Total Reflection Fourier-transform Infrared (ATR FT-IR) spectroscopy evidenced that within the first two hours the actinide binds to carboxylic as well as to phosphate groups to cells of Hbt. noricense DSM-15987 simultaneously. The viability of Hbt. noricense cells was checked after contact with uranium by using the LIVE/DEAD® Bac LightTM Bacterial Viability Kit and analyzed with fluorescence microscopy. Almost all cells were alive even after one week of exposure to uranium. However, cell agglomeration was observed with increasing incubation time in both Hbt. noricense strains. For Hbt. noricense DSM-15987, a faster agglomeration process with agglomerates up to 200 µm in size was observed compared to the WIPP strain, which formed only microscopically visible agglomerates. The unusual, but reproducible bioassociation kinetics suggests that the WIPP strain and the Austrian strain react in the same way to uranium presence.

REFERENCES
[1] Gruber, C. et al. (2004) Extremophiles, Vol. 8, 431-439.
[2] Swanson, J. et al. (2012) LANL Report, LA-UR-12-22824.
[3] Gramain, A. et al. (2011) Environ. Microbiol., Vol. 13, 2105-2121.
[4] Yildiz, E. et al. (2012) Pol. J. Microbiol., Vol. 61, 111-117.
Keywords: Uranium biosorption, Halobacterium noricense
  • Lecture (Conference)
    Biometals (10th International Biometals Symposium), 10.-15.07.2016, Dresden, Deutschland

Publ.-Id: 23363 - Permalink


Euler-Euler Multiphase CFD (with focus on bubbly flows)
Rzehak, R.;
Vorstellung der Arbeiten in der Abteilung CFD des Instituts für Fluiddynamik am HZDR
  • Invited lecture (Conferences)
    Arbeitstreffen bei der Firma Bosch, 14.-15.01.2016, Renningen, Deutschland

Publ.-Id: 23362 - Permalink


Euler-Euler Modeling of Mass-Transfer in Bubbly Flows
Rzehak, R.; Krepper, E.;
CFD simulations of dispersed bubbly flow on the scale of technical equipment are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, accurate numerical predictions rely on suitable closure models. Concerning the fluid dynamics of bubbly flows a certain degree of predictive capability has been reached recently. However, concerning mass transfer only few studies have been performed to date.
The present contribution gives an overview over the available results on closure relations for physical absorption/desorption, i.e. mass transfer without chemical reactions. Unsolved issues are highlighted, in particular on which parameters a suitable correlation for the mass transfer coefficient should be based.
In addition, a preliminary study on model validation is presented which makes use of experimentally determined mass transfer coefficients. The need for and requirements on suitable data for this purpose are emphasized.
Keywords: mass-transfer, dispersed gas-liquid multiphase flow, Euler-Euler two-fluid-model, closure relations, CFD simulation, model validation
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Agglomerations- und Schüttguttechnik, Computational Fluid Dynamics und Mehrphasenströmungen, 29.02.-02.03.2016, Bingen, Deutschland

Publ.-Id: 23361 - Permalink


Euler-Euler Modeling of Hydrodynamics and Mass-Transfer in Bubbly Flows
Rzehak, R.; Kriebitzsch, S.; Krepper, E.;
CFD simulations of dispersed bubbly flow on the scale of technical equipment are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, accurate numerical predictions rely on suitable closure models. To achieve predictive capability all details of the closure models have to be fixed in advance without reference to any measured data. Concerning the fluid dynamics of bubbly flows a baseline model has recently been proposed to this end and is shown to work for a range of different applications in a unified manner. This provides a reliable background which is well suited to add more complex physics. The content of the present contribution is such an extension to include also mass-transfer from / to the bubbles to the surrounding liquid. Shrinking / growth of the bubbles is taken into account within the inhomogeneous MUSIG model. A preliminary validation is provided using constant values for the mass transfer coefficient and the bubble size, but comparison is made with a set of experimental data providing axially resolved measurements. This contrasts previous works where comparison has been made only with integral data. A verification of the implementation is provided for the case with shrinking bubbles. The need for and requirements on suitable data for validation of a more refined model is emphasized.
Keywords: : mass-transfer, dispersed gas-liquid multiphase flow, Euler-Euler two-fluid-model, closure relations, CFD simulation, model validation
  • Contribution to proceedings
    9th International Conference on Multiphase Flow, ICMF-2016, 22.-27.05.2016, Firenze, Italia

Publ.-Id: 23360 - Permalink


In-situ X-ray observations showing the impact of natural and forced convection on dendritic solidification
Eckert, S.; Shevchenko, N.; Roshchupkina, O.; Sokolova, O.;
The directional solidification of Ga–25wt%In alloys was investigated using X-ray radioscopy, which offers a visual access to opaque melts and enables a basic, intuitional understanding of the complex interplay between melt flow and dendritic growth. Natural convection occurs owing to an unstable density stratification at the solid-liquid interface. Forced convection was produced by a rotating wheel. Our observations show a facilitation of the growth of primary trunks or lateral branches, suppression of side branching, dendrite remelting and fragmentation. The manifestation of all phenomena depends on the dendrite orientation, local direction and intensity of the flow. The forced flow eliminates the solutal plumes and damps the local fluctuations of solute concentration. It provokes a preferential growth of the secondary arms at the upstream side of the primary dendrite arms, whereas the high solute concentration at the downstream side of the dendrites can inhibit the formation of secondary arms.
Keywords: solidification, dendritic growth, macrosegregation, fragmentation, X-ray radioscopy
  • Invited lecture (Conferences)
    Michel Rappaz Honory Symposium: Frontiers in Solidification; TMS2016, 145th Annual Meeting and Exhibition, 14.-18.02.2016, Nashville, USA

Publ.-Id: 23359 - Permalink


Microbial biomineralization of uranium and its application
Raff, J.; Vogel, M.; Günther, A.; Wollenberg, A.; Stumpf, T.;
Microbes are per definition small organisms and are specialists in adapting to changing environmental conditions. Thus they successfully conquer almost all kinds of environments even the harshest and most forbidden ones. One reason for that is, nature is very creative in the development of effective survival strategies. The various interaction mechanisms of microbes with radionuclides are therefor a good example. In general, microbes can not only inactivate reactive oxygen species formed by radiolysis of water or the Fenton reaction, but also detoxify the radio-metals themselves. First of all microbes are able to immobilize radio-metals by sorption, accumulation, mineralization or reduction. Furthermore, they can also mobilize metals by complexation or oxidation.
With regard to a molecular understanding of the microbe-uranium interaction and its possible application for the precautionary radiation protection and/or bio-remediation, sorption, accumulation and mineralization of uranium by living bacteria, fungi and algae were investigated. Interestingly, the different groups of organisms show significant differences in the interaction with uranium proved by different spectroscopic methods combined with electron microscopy. While the gram-positive bacterium Lysinibacillus sphaericus binds uranium via carboxyl and phosphate groups and subsequently forms meta-autunite like minerals outside the cell [1], the alga Chlorella vulgaris first binds uranium via same functional groups but afterwards desorbs the uranium by the secretion of complexing bio-ligands [2]. In contrast, the fungus Schizophyllum commune binds uranium at low concentrations (1 mg/L) outside the cell via organic phosphates but accumulates it inside the cell at higher uranium concentrations (100 mg/L) by forming inorganic phosphates [3]. Due to their high uranium resistance and high accumulation rates a fungal-based concept for the immobilization of released radionuclides was developed and is currently investigated.

[1] Merroun et al. (2005), Appl. Environ. Microbiol. 71(9), 5532-5543. [2] Vogel et. al (2010), Sci. Total Environ. 409, 384-395. [3] Günther et al. (2014), Biometals 27,775-785
Keywords: biomineralization, bacteria, algae, fungi, uranium
  • Invited lecture (Conferences)
    26th Goldschmidt Conference, 26.06.-01.07.2016, Yokohama, Japan

Publ.-Id: 23358 - Permalink


Mechanistic sorption models: Species, Thermodynamic, Application
Bok, F.; Richter, C.; Stockmann, M.; Brendler, V.;
During the last two decades mechanistic sorption models not only continued their development and parameterization, but also gained ground for application in real-world scenarios such as in the long-term safety analysis of potential nuclear waste repositories. This was only possible because fundamentals such as a proper identification of surface species (their numbers, stoichiometries, structures & denticity) could be based on combinations of spectroscopic experiments, thermodynamic modelling and quantum chemical calculations. Similar progress can be reported for the mineral characterization (specific surface area, binding sites, protolysis reactions). Based on realistic species set and mineral properties, respective formation constants can be derived from batch sorption experiments, also providing information about temperature dependence and kinetics (namely reversibility). Nowadays, mechanistic sorption models are not only a synonym for surface complexation models (SCM), but ideally also account for additional phenomena such as ion exchange or surface precipitation, as well as the formation of secondary phases (smart Kd-values).
The above sketched developments are illustrated for a recent case study about Np(V) and U(VI) sorption onto components of Gorleben overburden sediments. The talk presents the analysis of the on-site data situation. Then own measurements to complete the thermodynamic data base including species identification by means of time-resolved laser-induced fluorescence and attenuated total reflection Fourier-transform infrared spectroscopies are addressed, together with the fit procedure to obtain SCM parameter sets. Next, the scheme utilized for smart Kd computation (including its implementation into reactive transport codes) is explained, and results from an uncertainty and sensitivity analysis are discussed.
Conclusions will incorporate a strategy to join international expertise (and man power) aiming at a comprehensive sorption raw data re-evaluation. This would allow to derive an internally consistent (with respect to EDL definition, mineral characteristics and species set) data set for the computation of smart Kd-values. This strategy covers data assembly, evaluation, processing and storage into an appropriate data structure.
Keywords: smart Kd, Sorption, Surface species, reactive transport modelling
  • Invited lecture (Conferences)
    American Chemical Society Spring meeting, 13.-17.03.2016, San Diego, USA

Publ.-Id: 23357 - Permalink


Directional Spin Wave Emission From Topological Spin Textures
Sluka, V.; Weigand, M.; Kakay, A.; Schultheiss, K.; Warnatz, T.; Erbe, A.; Tyberkevych, V.; Slavin, A.; Deac, A.; Lindner, J.; Fassbender, J.ORC; Raabe, J.; Wintz, S.
The investigation of propagating spin waves is a key topic of magnetism at present. For the excitation of spin waves with short wavelengths, it was typically necessary to either use patterned transducers with sizes on the order of the desired wavelengths (striplines or point-contacts) or to generate those spin waves parametrically by a spatially uniform double-frequency microwave signal. Only recently, a new mechanism for the local excitation of spin waves has been discovered, which overcomes the lower wavelength limit given by the minimum patterning size. This method utilizes the translation of natural topological defects, namely the gyration of magnetic vortex cores to generate isotropically propagating spin waves.
Keywords: spin wave, vortex
  • Lecture (Conference)
    The 9th International Symposium on Metallic Multilayers, 19.-23.06.2016, Uppsala, Schweden
  • Lecture (Conference)
    8th Joint European Symposia, 21.-26.08.2016, Glasgow, United Kingdom
  • Poster
    39th International Conference on Vacuum Ultraviolet and X-Ray Physics, 03.-08.07.2016, Zürich, Schweiz
  • Invited lecture (Conferences)
    1st Baltic Spin, 09.-13.08.2016, Jurmala, Lettland

Publ.-Id: 23356 - Permalink


Changes in Binding of [123I]CLINDE, a High-Affinity Translocator Protein 18 kDa (TSPO) Selective Radioligand in a Rat Model of Traumatic Brain Injury
Donat, C. K.; Gaber, K.; Meixensberger, J.; Brust, P.; Pinborg, L. H.; Hansen, H. H.; Mikkelsen, J. D.;
The neuropathology following traumatic brain injury (TBI) is poorly understood. From the primary biomechanical injury, secondary injuries develop, including neuro-inflammatory processes. These secondary injuries are regarded as a potential targets for treatment and diagnostics. The translocator protein 18 kDa (TSPO) is robustly upregulated in response to brain injury, making it a suitable biomarker for glia activation and the neuro-inflammatory response. Second-generation radioligands of TSPO, such as [123I]CLINDE, offer higher affinity and signal-to-noise ratio compared to PK11195, the prototypical ligand. Applicability of [123I]CLINDE was demonstrated in both neurodegenerative disease models and patient studies and therefore demonstrate the translational value of this tracer. We therefore investigated TSPO expression in a rat model of TBI with [123I]CLINDE , a selective and clinically relevant TSPO-radioligand.
Adult Sprague-Dawley rats were subjected to moderate Controlled-Cortical-Impact injury (CCI, n=5 per group). Sham (n=5), craniotomy (n=3), and naïve animals (n=3) served as different control groups. Animals were sacrificed at 6h, 24h, 72h, and 28 days post-surgery, and TSPO expression was assessed in brain section employing [123I]CLINDE in vitro autoradiography.
From 24 h to 28 d post-surgery, injured animals exhibited a marked and time-dependent increase of binding in the ipsilateral motor, somatosensory and parietal cortex, as well as in the hippocampus and thalamus. Furthermore, binding was significantly elevated in the contralateral motor cortex following TBI. Craniotomy also caused a significant increase in [123I]CLINDE binding per se. Radioligand binding was consistent with an increase in TSPO mRNA expression and OX-42 immunoreactivity at the contusion site.
In conclusion, this study demonstrates the applicability of [123I]CLINDE for brain regional and quantitative assessment of neuro-inflammatory activity in experimental models of TBI.

Publ.-Id: 23355 - Permalink


A Local Superlens
Kehr, S. C.; Mcquaid, R. G. P.; Ortmann, L.; Kämpfe, T.; Kuschewski, F.; Lang, D.; Döring, J.; Gregg, J. M.; Eng, L. M.;
Superlenses enable near-field imaging beyond the optical diffraction limit. However, their widespread implementation in optical imaging technology so far has been limited by large-scale fabrication, fixed lens position, and specific object materials. Here we demonstrate that a dielectric lamella of subwavelength size in all three spatial dimensions behaves as a compact superlens that operates at infrared wavelengths and can be positioned to image any local microscopic area of interest on the sample. In particular, the lamella superlens may be placed in contact with any type of object and therefore enables examination of hard-to-scan samples, for example, with high topography or in liquids, without altering the specimen design. This lamella-based local superlens design is directly applicable to subwavelength light-based technology, such as integrated optics.
Keywords: superlens; subwavelength imaging; near-field microscopy; barium titanate; mid-infrared; free-electron laser

Publ.-Id: 23354 - Permalink


Concepts for the development of new biosorbents on the base of microbial constituents
Matys, S.; Schönberger, N.; Raff, J.; Günther, T.; Lederer, F.; Lehmann, F.; Flemming, K.; Pollmann, K.;
The world's growing demand for high-tech metals together with a simultaneously deteriorating availability is one of the central challenges of our modern society. Thusly, the development of new and innovative processes for a more efficient extraction of raw materials as well as economic methods for recycling is needed. Established methods for reclaiming production residues often include the chemical treatment with concentrated acids or alkalis, and are also polluting and energy-intensive. To overcome existing deficiencies and disadvantages of such methods emphasis is increasingly placed on biological alternatives. Thereby, biosorptive materials are prevalent for the recovery of dissolved chemical species. They are inexpensive and manufacturable in large quantities and often have excellent binding properties as compared to synthetic materials. Microorganisms are particularly in focus for biosorption processes because of their ubiquity and their enormous variability. A number of microbial cell structures and metabolites have been developed evolutionarily in direct interaction with toxic or essential elements, including heavy metals. Mediated by a variety of functional groups combined with the perfect structural fit these molecules are able to bind such elements partially highly selective and specific. In our group we are investigating the potential suitability of biomolecules such as siderophores, short peptides, and S-layer proteins as biosorptive compound. Our presentation discusses the usability of these compounds for the development of novel, selective binding filter materials for removing toxic elements and the recovery of valuable metals from aqueous solutions.
Keywords: biosorption, bioremediation, metal recovery, siderophores, peptides, S-layer proteins
  • Poster
    VAAM 2016, 13.-16.03.2016, Jena, Deutschland

Publ.-Id: 23353 - Permalink


Electron-phonon coupling and energy flow in a simple metal beyond the two-temperature approximation
Waldecker, L.; Bertoni, R.; Ernstorfer, R.; Vorberger, J.;
The electron-phonon coupling and the corresponding energy exchange was investigated experimentally and by ab initio theory in non-equilibrium states of the free-electron metal aluminium. The temporal evolution of the atomic mean squared displacement in laser-excited thin free-standing films was monitored by femtosecond electron diffraction. The electron-phonon coupling strength was obtained for a range of electronic and lattice temperatures from density functional theory molecular dynamics (DFT-MD) simulations. The electron-phonon coupling parameter extracted from the experimental data in the framework of a two-temperature model (TTM) deviates significantly from the ab initio values. We introduce a non-thermal lattice model (NLM) for describing non-thermal phonon distributions as a sum of thermal distributions of the three phonon branches. The contributions of individual phonon branches to the electron-phonon coupling are considered independently and found to be dominated by longitudinal acoustic phonons. Using all material parameters from first-principle calculations besides the phonon-phonon coupling strength, the prediction of the energy transfer from electrons to phonons by the NLM is in excellent agreement with time-resolved diffraction data. Our results suggest that the TTM is insufficient for describing the microscopic energy flow even for simple metals like aluminium and that the determination of the electron-phonon coupling constant from time-resolved experiments by means of the TTM leads to incorrect values. In contrast, the NLM describing transient phonon populations by three parameters appears to be a sufficient model for quantitatively describing electron-lattice equilibration in aluminium. We discuss the general applicability of the NLM and provide a criterion for the suitability of the two-temperature approximation for other metals.
Keywords: two temperature model, electron-phonon coupling, laser interaction with solids, warm dense matter, non-equilibrium

Publ.-Id: 23350 - Permalink


Numerical simulations on copper droplet collisions in an electromagnetic slag cleaning process
Yang, H.; Wolters, J.; Pischke, P.; Soltner, H.; Fröhlich, J.; Eckert, S.;
The copper slag cleaning process contains complex physico-chemical phenomena, among which the collisions between liquid metal droplets possess an enormous influence on the cleaning efficiency. An Euler-Lagrange approach is employed to numerically study the slag-copper droplet system with the CFD code FLUENT. For the dispersed phase a new hybrid collision algorithm was implemented to overcome the mesh-dependency problem of the pure stochastic algorithm. It provides better prediction of the collision probability among the in-homogeneously distributed droplets and liberates the Discrete Phase Model calculation from using the mesh of the continuous phase. Due to the high viscosity and density of both phases, the slag-droplet collision system is distinctly different from conventional collision systems, such as liquid droplets in air or gas bubbles in liquids. Therefore a new regime map for droplets in a viscous shear flow with low velocities is proposed on the basis of literature data. The results obtained with the simulations of the entire process highlight the importance of the collision model for the overall efficiency of the process.
Keywords: MHD, copper slag cleaning, stochastic collision, liquid metal droplet, coalescence
  • Lecture (Conference)
    ICMF-2016 – 9th International Conference on Multiphase Flow, 22.-27.05.2016, Firenze, Italy
  • Contribution to proceedings
    ICMF-2016 – 9th International Conference on Multiphase Flow, 22.-27.05.2016, Firenze, Italy

Publ.-Id: 23349 - Permalink


Mechanism of attenuation of uranyl toxicity by glutathione in Lactococcus lactis
Obeid, M. H.; Oertel, J.; Solioz, M.; Fahmy, K.;
Both prokaryotic and eukaryotic organisms possess mechanisms for the detoxification of heavy metals, which are found among distantly related species. We have investigated the role of intracellular glutathione (GSH), which in a large number of taxa plays a role in the protection against the toxicity of common heavy metals. Anaerobically grown Lactococcus lactis containing an inducible GSH synthesis pathway was used as a model organism This physiological trait allows study of putative GSH-dependent uranyl detoxification mechanisms without interference from additional reactive oxygen species. By microcalorimetric measurements of the metabolic heat during cultivation, it was shown that intracellular GSH attenuates the toxicity of uranium at a concentration in the range of 10-150 µM; in this concentration range, no effect was observed with copper which was used as a reference for redox-metal toxicity. At higher copper concentrations, GSH aggrevates metal toxicity. Isothermal titration calorimetry reveals the endothermic binding of U(VI) to the carboxyl group(s) of GSH, rather than to the reducing thiol group involved in copper interactions. The data indicate that the primary detoxifying mechanism is the intracellular sequestration of carboxyl-coordinated U(VI) into an insoluble complex with GSH. The opposite effects of GSH on uranyl and copper toxicity can be related to the difference in coordination chemistry of the respective metal-GSH complexes, which cause distinct growth phase-specific effects on enzyme metal interactions.
Keywords: Microcalorimetry Isothermal Calorimetry
  • Poster
    Biometals 2016, 10.-15.06.2016, Dresden, Germany

Publ.-Id: 23348 - Permalink


Quantitative experimental monitoring of molecular diffusion in clay with positron emission tomography
Kulenkampff, J.; Gründig, M.; Lippman-Pipke, J.; Zakhnini, A.;
Clay plays a prominent role as barrier material in the geosphere. Their small particle sizes cause extremely small pore sizes and induce low permeability and high sorption capacity. Transport of dissolved species by molecular diffusion is less sensitive to the pore size. Heterogeneous structures on centimetre scale could cause heterogeneous effects, like preferential transport zones, which are difficult to assess. Laboratory measurements with diffusion cells yield limited information on heterogeneity, and pore space imaging methods have to consider scale effects. We established positron emission tomography (PET), applying a high-resolution PET-scanner, as spatially resolved quantitative method for direct laboratory observation of the diffusion process of a PET-tracer on the prominent scale of 1 to 100 mm. Although PET is rather insensitive to bulk effects, quantification required significant improvements of the image reconstruction procedure with respect to Compton scatter and attenuation. The experiments were conducted with 22Na and 124I over periods of 100 resp. 25 days. From the images we derived trustable anisotropic diffusion coefficients and, in addition, we identified indications for preferential transport zones. We thus demonstrated the unique potential of the PET imaging modality for geoscientific process monitoring under conditions where other methods fail, taking advantage of the extremely high detection sensitivity that is specific to radiotracer applications.

Downloads:

Publ.-Id: 23346 - Permalink


Development of a High-Affinity PET Radioligand for Imaging Cannabinoid Subtype 2 Receptor
Moldovan, R.-P.; Teodoro, R.; Deuther-Conrad, W.; Kranz, M.; Wang, Y.; Nakano, M.; Valentine, H.; Fischer, S.; Pomper, M.; Wong, D. F.; Dannals, R. F.; Brust, P.; Horti, A. G.;
Cannabinoid receptors type 2 (CB2) represent a target with increasing importance for neuroimaging due to its upregulation under various pathological conditions. Encouraged by preliminary results obtained with [11C](Z)-N-(3-(2-methoxyethyl)-4,5-dimethylthiazol-2(3H)-ylidene)-2,2,3,3-tetramethyl-cyclopropanecarboxamide ([11C]A-836339, [11C]1) in a mouse model of acute neuroinflammation (induced by lipopolysaccharide, LPS), we designed a library of fluorinated analogues aiming for an [18F]-labeled radiotracer with improved CB2 binding affinity and selectivity. Compound (Z)-N-(3-(4-fluorobutyl)-4,5-dimethylthiazol-2(3H)-ylidene)-2,2,3,3-tetramethyl-cyclopropanecarboxamide (29) was selected as the ligand with the highest CB2 affinity (Ki = 0.39 nM) and selectivity over those of CB1 (factor of 1000). [18F]29 was prepared starting from the bromo precursor (53). Specific binding was shown in vitro, whereas fast metabolism was observed in vivo in CD-1 mice. Animal PET revealed a brain uptake comparable to that of [11C]1. In the LPS-treated mice, a 20−30% higher uptake in brain was found in comparison to that in nontreated mice (n = 3, P < 0.05).
Keywords: Cannabinoid receptor type 2, Neuroinflammation, A-836339, Radiofluorination, Positron emission tomography

Publ.-Id: 23345 - Permalink


Geoscientific process monitoring with positron emission tomography (GeoPET)
Kulenkampff, J.; Gründig, M.; Zakhnini, A.; Lippmann-Pipke, J.;
Transport processes in geomaterials can be observed with input-output experiments, which yield no direct information on the impact of heterogeneities, or they can be assessed by model simulations based on structural imaging with µCT. Positron emission tomography (PET) provides an alternative experimental observation method which directly and quantitatively yields the spatiotemporal distribution of tracer concentration. Process observation with PET benefits from its extremely high sensitivity together with a resolution that is acceptable in relation to standard drill core sizes. We strongly recommend applying high-resolution PET scanners in order to achieve a resolution in the order of 1 mm.
We discuss the particularities of PET applications in geoscientific experiments (GeoPET), which essentially are due to the high material density. Although PET is rather insensitive to matrix effects, mass attenuation and Compton scattering have to be corrected thoroughly in order to derive quantitative values.
Examples of process monitoring with GeoPET of advection and diffusion processes are illustrating the procedure and the experimental conditions, as well as the benefits and limits of the method.

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Publ.-Id: 23344 - Permalink


Tailoring nonlinear optical properties of Bi2Se3 through ion irradiation
Tan, Y.; Guo, Z.; Shang, Z.; Liu, F.; Böttger, R.; Zhou, S.; Shao, J.; Yu, X.; Zhang, H.; Chen, F.;
The nonlinear optical property of topological insulator bismuth selenide (Bi2Se3) is found to be welltailored through ion irradiation by intentionally introducing defects. The increase of the optical modulation depth sensitively depends on the careful selection of the Irradiation condition. By implementing the ion irradiated Bi2Se3 film as an optical saturable absorber device for the Q-switched wave-guide laser, an enhanced laser performance has been obtained including narrower pulse duration and higher peak power. Our work provides a new approach of tailoring the nonlinear optical properties of materials through ion irradiation, a well-developed chip-technology, which could find wider applicability to other layered two-dimensional materials beyond topological insulators, such as graphene, MoS2, black phosphours etc.
Keywords: ion Irradiation, Bi2Se3 film, chip-technology

Publ.-Id: 23343 - Permalink


Development of quality-assured Thermodynamic Database for Rare Earth Elements
Jordan, N.; Barkleit, A.; Steudtner, R.; Bok, F.; Heller, A.; Brendler, V.;
New materials showing specific magnetic and/or electrooptic properties often incorporate Rare Earth Elements (REE). Due to their very specific technological application, it is necessary to separate and enrich the REE from each other. The optimization of physico-chemical conditions for the design of effective extraction and recycling processes of REE has to rely on accurate and reliable thermodynamic data. However, no fundamental, consolidated and internationally recognized Thermodynamic Databases (TDB) is currently available for REE.
This study aims at providing a reliable, quality assured and internally consistent TDB for Europium. The thorough evaluation of all available primary literature sources for Eu(III) complexation constants (log β) with inorganic ligands (OH−, Cl−, NO3−, SO42− and CO32−) enabled identifying several critical issues: i) inconsistencies between different sources ii) lack of accurate activity coefficient treatment in case of formation of weak complexes iii) absence of independent spectroscopic validation of the stoichiometry of the proposed complexes.
Thus, several actions have been undertaken for the Eu-chloro, -nitrato and -sulfato complexes:
a) recalculation of the log β of weak complexes by using an hypothetical reference state (at trace ligand concentration) [1]
b) use of advanced spectroscopic techniques (e.g. Time-resolved Laser-induced Fluorescence Spectroscopy), allowing to monitor on line the speciation evolution at micromolar range concentrations. This also enabled identifying the prevailing species as well as their stoichiometries. Finally, complexation constants were determined from the spectroscopic data sets.
c) The conditional log β were extrapolated to standard conditions (I = 0 M, T = 298.15 K) using the Specific Ion Interaction Theory.

[1] Spahiu, K. et al. (1998) Radiochim. Acta 82, 413-419.
  • Contribution to proceedings
    Goldschmidt 2016, 26.06.-01.07.2016, Yokohama, Japan
    Proceedings of Goldschmidt 2016
  • Lecture (Conference)
    Goldschmidt 2016, 26.06.-01.07.2016, Yokohama, Japan

Publ.-Id: 23342 - Permalink


Use of multiple age tracers to estimate groundwater residence times and long-term recharge rates in arid southern Oman
Müller, T.; Osenbrueck, K.; Strauch, G.; Pavetich, S.; Al-Mashikhi, K.-S.; Herb, C.; Merchel, S.; Rugel, G.; Aeschbach, W.; Sanford, W.;
Multiple age tracers were measured to estimate groundwater residence times in the regional aquifer system underlying southwestern Oman. The three isotopic age tracers 14C, 4He, and 36Cl were measured in waters collected from 20 wells along a line that extended roughly from the Dhofar Mountains near the Arabian Sea northward 400 km into the Empty Quarter of the Arabian Peninsula. The wells sampled were mostly open to the Umm Er Radhuma confined aquifer, although some were completed in the mostly unconfined Rus aquifer. The combined results from the three tracers indicate the age of the confined groundwater is <40k years in the recharge area in the Dhofar Mountains, >100 k years in the central section north of the mountains, and up to and >1 M years in the Empty Quarter. The 14C data were used to help calibrate the 4He and 36Cl data. Additional measurements of noble gases made were consistent with the age interpretations. Mixing models suggest that long open boreholes north of the mountains compromise 14C-only interpretations there, in contrast to 4He and 36Cl calculations that are less sensitive to borehole mixing. Thus only the latter two tracers from these more distal wells were considered reliable. In addition to the age tracers, 2H and 18O data suggest that seasonal monsoon and infrequent tropical cyclones are both substantial contributors to the recharge. The study highlights the advantages of using multiple chemical and isotopic data when estimating groundwater travel times and recharge rates, and differentiating recharge mechanisms.
Keywords: stable isotopes, groundwater residence times, carbon-14, helium-4, chlorine-36, arid region, groundwater flow, groundwater recharge , accelerator mass spectrometry

Publ.-Id: 23341 - Permalink


Comeback of Mercury as 197(m)Hg for Theranostics
Walther, M.; Wang, C.; Bergmann, R.; Pietzsch, H.-J.; Steinbach, J.;
The no-carrier-added (NCA) radionuclide 197(m)Hg is accessible in adequate quantity and quality for radiopharmaceutical research through the proton irradiation of gold using a cyclotron.1 The interest in this mercury isotope was prompted primarily by the decay characteristics of both nuclear isomers, like convenient half-life (197mHg = 23.8 h, 197Hg = 64.14 h), low energy gamma radiations useful for diagnosis (197mHg = 133.98 keV, 33.5% , 197Hg = 77.4 keV, 18.7%) and numerous Auger- and conversion electrons with high potential for cancer therapy. Additionally, the unique chemical properties of mercury allow for the development of promising radiolabeling tools and new radiopharmaceuticals. In addition to the typical metal properties to form coordination compounds with sulfur, nitrogen and oxygen containing ligands, mercury has the special ability to build water stable carbon-metal bonds. The reactivity of the mercury(II) ions towards sulfur containing ligands, solvomercuration of alkenes and electrophilic aromatic substitutions were investigated to prepare a stable labeling unit at NCA level with 197(m)Hg. While both the mercury thiolate complexes and the products of solvomercuration exhibited low stability in the presence of competing thiol ligands and are therefore unsuitable for radiopharmaceutical applications, symmetric diarylmercury compounds showed high stability against competing ligands. The development and application of a prelabeling tool based on a bis-benzoyl-mercury derivative as succinimidyl ester will be reported.
Keywords: theranostic, cancer therapy
  • Poster
    42nd edition of the International Conference on Coordination Chemistry, 03.-08.07.2016, Brest, France

Publ.-Id: 23340 - Permalink


Insights into binding of S100 proteins to scavenger receptors: class B scavenger receptor CD36 binds S100A12 with high affinity
Tondera, C.; Laube, M.; Pietzsch, J.;
The EF-hand type calcium-binding protein S100A12 exerts numerous intra- and extracellular functions of (patho)physiological relevance. Therefore, receptors of S100A12 are of high interest for research and clinical applications. Beside the extensively studied receptor for advanced glycation endproducts (RAGE), G-protein coupled receptors and, more recently, scavenger receptors are suggested to be putative S100A12 receptors. Own findings and further information from the literature predestined CD36, a class B scavenger receptor, as promising candidate. In order to substantiate or prove against this hypothesis the present study aimed at investigation of interaction of S100A12 and CD36 on molecular and cellular level by the use of surface plasmon resonance (SPR), radio- and fluorescence-tracer-based cell binding, and cell activation experiments. S100A12 revealed binding affinity to CD36 in the low nanomolar range, essentially, at the CD36 thrombospondin-1 binding site. Additionally, S100A12-mediated translocation of CD36 to the membrane and elevation of both CD36 and peroxisome proliferator-activated receptor γ (PPARγ) expression was observed, which suggest a potential regulatory function of S100A12-CD36 interaction.
Keywords: EF-hand calcium-binding proteins, surface plasmon resonance, pattern recognition receptors, damage-associated molecular patterns, receptor for advanced glycation endproducts (RAGE)

Publ.-Id: 23339 - Permalink


Ultrasmall inorganic nanoparticles: state-of-the-art and perspectives for biomedical applications
Zarschler, K.; Rocks, L.; Licciardello, N.; Boselli, L.; Polo, E.; Pombo Garcia, K.; de Cola, L.; Stephan, H.; Dawson, K. A.;
Ultrasmall nanoparticulate materials with core sizes in the 1-3 nm range bridge the gap between single molecules and classical, larger-sized nanomaterials, not only in terms of spatial dimension, but also as regards physicochemical and pharmacokinetic properties. Due to these unique properties, ultrasmall nanoparticles appear to be promising materials for nanomedicinal applications.
This review overviews the different synthetic methods of inorganic ultrasmall nanoparticles as well as their properties, characterization, surface modification and toxicity. We moreover summarize the current state of knowledge regarding pharmacokinetics, biodistribution and targeting of nanoscale materials. Aside from addressing the issue of biomolecular corona formation and elaborating on the interactions of ultrasmall nanoparticles with individual cells, we discuss the potential diagnostic, therapeutic and theranostic applications of ultrasmall nanoparticles in the emerging field of nanomedicine in the final part of this review.
Keywords: ultrasmall nanoparticles; nanomedicine; pharmacokinetics; protein corona; active targeting; cancer; renal excretion

Publ.-Id: 23338 - Permalink


Atomistic study on mixed-mode fracture mechanisms of ferrite iron interacting with coherent copper and nickel nanoclusters
Al-Motasem, A. T.; Mai, N. T.; Choi, S. T.; Posselt, M.;
The effect of copper and/or nickel nanoclusters, generally formed by neutron irradiation, on fracture mechanisms of ferrite iron was investigated by using molecular statics simulation. The equilibrium configuration of nanoclusters was obtained by using a combination of an on-lattice annealing based on Metropolis Monte Carlo method and an off-lattice relaxation by molecular dynamics simulation. Residual stress distributions near the nanoclusters were also calculated, since compressive or tensile residual stresses may retard or accelerate, respectively, the propagation of a crack running into a nanocluster. One of the nanoclusters was located in front of a straight crack in ferrite iron with a body-centered cubic crystal structure. Two crystallographic directions, of which the crack plane and crack front direction are (010)[001] and (111)[-110], were considered, representing cleavage and non-cleavage orientations in ferrite iron, respectively. Displacements corresponding to pure opening-mode and mixed-mode loadings were imposed on the boundary region and the energy minimizationwas performed. It was observed that the fracture mechanisms of ferrite iron under the pure opening-mode loading are strongly influenced by the presence of nanoclusters, while under the mixed-mode loading the nanoclusters have no significant effect on the crack propagation behavior of ferrite iron.
Keywords: fracture, Molecular Dynamics, Monte Carlo, nanoclusters, deformation twinning, dislocation.

Publ.-Id: 23336 - Permalink


High-Rate Timing Resistive Plate Chambers with Ceramic Electrodes
Laso Garcia, A.; Kotte, R.; Naumann, L.; Stach, D.; Wendisch, C.; Wüstenfeld, J.; Kämpfer, B.;
We describe recent advances in developing radiation-hard ceramic resistive plate chambers (CRPCs) with Si3N4/SiC composites. Bulk resistivity measurements for this material for different manufacturing processes are reported. The results show that the bulk resistivity can vary between 10^7 - 10^13 Ohm cm. The varistor type behaviour of the material is analyzed. A comparison with other materials used in timing RPCs is given.
We describe the assembly and tests of CRPC prototypes in electron and proton beams. For a prototype with bulk resistivity 5 x 10^9 Ohm cm, the effciency of the detectors is 95% at a fux of 2 x 10^5 cm^-2 s^-1. The time resolution at the same fux is about 120 ps. A prototype with bulk resistivity 2 x 10^10 Ohm cm shows an effciency of about 85% up to fuxes of 5 x 10^4 cm^-2 s^-1 with a time resolution better than 80 ps. The results are compared with RPC models.
Keywords: RPC; Timing; Ceramic; High-rate capabilities; High flux

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Publ.-Id: 23335 - Permalink


Uptake mechanisms of selenium oxyanions during the ferrihydrite-hematite recrystallization
Börsig, N.; Scheinost, A. C.; Shaw, S.; Schild, D.; Neumann, T.;
Se is an essential nutrient at trace levels, but also a toxic environmental contaminant at higher concentrations. The mobility of the trace element Se in natural environments is mainly controlled by the occurrence of the highly soluble Se oxyanions – selenite [Se(IV)] and selenate [Se(VI)] - and their interaction with geological materials. Since iron oxides are ubiquitous in nature, many previous studies investigated Se retention by adsorption onto iron oxides. However, little is known about the retention of Se oxyanions during the formation process of iron oxides. In this paper, we therefore studied the immobilization of Se oxyanions during the crystallization of hematite from ferrihydrite. In coprecipitation studies, hematite was synthesized by the precipitation and aging of ferrihydrite in an oxidized Se(IV)- or Se(VI)-containing system (pH 7.5). Hydrochemical data revealed the complete uptake of all available Se(IV) up to initial concentrations of 10-3 mol/L (m/V ratio = 9.0 g/L), while the retention of Se(VI) was extremely low (max. 15 %). In case of high initial Se(IV) concentrations, the results also demonstrated that the interaction of Se with ferrihydrite can affect the type of the final transformation product. Comparative adsorption studies, performed at identical conditions, allowed a distinction between pure adsorption and coprecipitation and showed a significantly higher Se retention by coprecipitation than by adsorption. Desorption studies indicated that Se coprecipitation leads to the occurrence of a resistant, non-desorbable Se fraction. According to time-resolved studies of Se(IV) or Se(VI) retention during the hematite formation and detailed spectroscopic analyses (XPS, XAS), this fraction is the result of an incorporation process, which is not attributable to Fe-for-Se substitution or the Se occupation of vacancies. Se initially adsorbs to the ferrihydrite surface, but after the transformation of ferrihydrite into hematite, it is mostly incorporated by hematite. In systems without mineral transformation, however, Se remains as a sorption complex. In case of Se(VI), an outersphere complex forms, while Se(IV) forms a mixture of bidentate mononuclear edge-sharing and bidentate binuclear corner-sharing inner-sphere complexes. The results of this study demonstrate that occlusion of Se oxyanions by hematite is an important retention mechanism, in addition to pure adsorption, for immobilizing Se in natural systems, which may control Se migration processes in polluted environments.
Keywords: selenium structural incorporation EXAFS ferrihydrite hematite

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Publ.-Id: 23334 - Permalink


Inter-sublevel dynamics in single InAs/GaAs quantum dots induced by strong terahertz excitation
Stephan, D.; Bhattacharyya, J.; Huo, Y. H.; Schmidt, O. G.; Rastelli, A.; Helm, M.; Schneider, H.;
We combine micro-photoluminescence with terahertz excitation to investigate the response of single self-assembled InAs/GaAs quantum dots to intense terahertz pulses tuned to the s-to-p transition. Spectra and transients of single photoluminescence lines reveal the dynamics of electrons upon excitation and subsequent relaxation back into the initial state. Under certain circumstances, the terahertz pulse can release trapped charge carriers which relax into the quantum dot. Furthermore, we demonstrate near-total depletion of the positive trion PL by an intense terahertz pulse.
Keywords: Quantum dots, Photoluminescence, Terahertz, Carrier relaxation

Publ.-Id: 23333 - Permalink


Redox dependent interfacial reactivity of hexavalent radionuclides
Hellebrandt, S.; Knope, K. E.; Lee, S. S.; Stubbs, J. E.; Eng, P. J.; Soderholm, L.; Fenter, P.; Schmidt, M.;
Understanding the behavior of radionuclides at mineral-water interfaces is important to make reliable statements for the safety assessments of nuclear waste disposals. Here, the interaction of UVIO22+ and PuVIO22+ with muscovite mica were investigated using a combination of surface X-ray diffraction (crystal truncation rods, CTR, and resonant anomalous X ray reflectivity, RAXR), alpha spectrometry and Grazing-incidence X-ray adsorption near-edge spectroscopy (GI-XANES). The interfacial behavior highlights the effect of the actinides’ different redox properties on their environmental mobility.
The interfacial structures obtained by CTR measurements, on the muscovite (001) basal plane after reaction with PuO22+ exhibit a large, broadly distributed electron density, which must be related to Pu uptake. This observation could be confirmed by RAXR and alpha spectrometry. In contrast, no significant uptake of UO22+ür is evident by CTR or RAXR.
GI-XANES identifies Pu on the surface as Pu(IV). The oxidation state of Pu in the reaction solution had been adjusted electrochemically, and was controlled by UV/vis spectroscopy, hence a reduction must have occurred during the experiment. In consequence of this reduction, obviously formation of Pu(IV)-oxo-nanoparticles occurred. We attribute the difference in the observed reactivity to the greater stability of low oxidation states for Pu relative to U, in combination with the increased “hardness” of the Pu4+ cation, relative to U4+. Once a threshold of [Pu4+] interface is reached, oligomerization may occur, and Pu4+ is removed from the redox equilibrium [1]. The reaction then becomes “auto-catalytic”. The results demonstrate how redox behavior strongly influences the sorption behavior of hexavalent actinides.

[1] Hellebrandt, S. et al. (2016), J. Phys. Chem. C. in preparation.
Keywords: Redox, Plutonium, Uranium, Muscovite, Mica, Surface
  • Lecture (Conference)
    Goldschmidt 2016, 26.06.-01.07.2016, Yokohama, Japan

Publ.-Id: 23332 - Permalink


1-(4-[18F]Fluorobenzyl)-4-((tetrahydrofuran-2-yl)methyl)piperazine: A novel radiotracer for mapping sigma-1 receptors in the living brain
He, Y.; Xie, F.; Deuther-Conrad, W.; Huang, Y.; Lu, J.; Yu, Q.; Ye, J.; Wang, L.; Steinbach, J.; Brust, P.; Jia, H.;
Objectives: The sigma-1 receptors (Sig-1R) represent a distinct class of intracellular “ligand-operated receptor chaperones”.1 Increasing evidence suggests that the sigma-1 receptors are involved in various human diseases including depression, schizophrenia, drug addiction, Alzheimer’s disease, and neuroinflammation.2 Herein we report the design, synthesis and biological evaluation of 1-(4-[18F]fluorobenzyl)-4-((tetrahydrofuran-2-yl)methyl)piperazine ([18F]1) as a potent PET imaging probe for mapping sigma-1 receptors in the living brain.

Methods: Among a new series of disubstituted piperazine derivatives with binding selectivity for Sig-1R, compound 1 was identified as a candidate for radiolabeling. [18F]1 was synthesized using a one-pot, two-step labeling procedure (Scheme 1). The biological properties of the radioligand were determined in biodistribution and inhibition studies in ICR mice. Effect of P-glycoprotein (P-gp) on brain uptake, and the in vivo metabolic stability of the ligand were also investigated.

Results: In vitro competition binding assays showed that compound 1 exhibited nanomolar affinity for σ1 receptors (Ki (σ1) = 3.70 ± 0.02 nM) and good subtype selectivity (Ki (σ2) = 213.4 ± 13.4 nM; Ki (σ2)/Ki (σ1) = 58). [18F]1 was prepared in 20-30% isolated radiochemical yields with radiochemical purity of >95% and specific activity of 54-86 GBq/μmol (n = 3). The log D value of [18F]1 was determined to be 0.76 ± 0.01. Biodistribution studies in mice revealed high initial brain uptake of [18F]1 with 12.75 ± 0.79 %ID/g at 2 min after injection. The brain-to-blood ratios of [18F]1 were high (22, 21, 20 and 14, respectively, at 15, 30, 60 and 120 min after injection). Administration of the selective Sig-1R ligand SA4503 (5 mol/kg, 0.1 mL, iv) at 5 min prior to injection of [18F]1 significantly reduced the radiotracer uptake in brain (by 79%, 88% and 86%, respectively, at 15, 30 and 60 min after injection) and other organs known to express sigma-1 receptors, suggesting binding specificity of [18F]1 to sigma-1 receptors in vivo. Administration of the P-gp inhibitor cyclosporine A (50 mg/kg, 0.1 mL, iv) before tracer injection slightly increased the uptake of radiotracer both in the brain and the blood at 2 min after injection (saline,0.83 ± 0.07% ID/g in the blood, 10.11 ± 1.0 % ID/g in the brain; cyclosporine A, 0.89 ± 0.03% ID/g in the blood, 10.86 ± 0.69 % ID/g in the brain). But the difference between the control and blocking groups was small and not significant, suggesting that [18F]1 is not a substrate for P-gp. At 30 min after injection, the intact parent tracer [18F]1 accounted for 98% of the radioactivity (n = 2) in the mouse brain, indicating no entry of radioactive metabolites into the brain.

Conclusions: These results suggest that [18F]1 displayed high uptake levels and specific binding in brain. Further investigation is warranted to determine the imaging characteristics of this novel radiotracer, and to assess its potential to image Sig-1R in the living brain.

Acknowledgements: Supported by NSFC (21471019).

References: [1] Hayashi, T.; Su, T.-P. Cell 2007, 131, 596. [2] Maurice, T.; Su, T.-P. Pharmacol. Ther. 2009, 124, 195.
  • Lecture (Conference)
    11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain, 13.-16.07.2016, Boston, USA
  • Contribution to proceedings
    11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain, 13.-16.07.2016, Boston, USA
    Proceedings of the 11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain

Publ.-Id: 23331 - Permalink


Kinetic Modeling of (+)-[18F]Flubatine Binding to Nicotinic α4β2* Acetylcholine Receptors in Human Brains
Becker, G. A.; Tiepolt, S.; Patt, M.; Luthardt, J.; Rullmann, M.; Hesse, S.; Wilke, S.; Meyer, P. M.; Barthel, H.; Wagenknecht, G.; Höpping, A.; Gertz, H.; Steinbach, J.; Brust, P.; Sabri, O.;
Objectives: Nicotinic α4β2* acetylcholine receptors (nAChR) are an important target for diagnostic neuroimaging because of their involvement e.g. in Alzheimer's and Parkinson's diseases, and nicotine addiction. The development of new PET-tracers for these receptors is an active field of research. Here we present the PET quantification of the new nAChR-ligand (+)-[18F]Flubatine, an enantiomer of (-)-[18F]Flubatine, also known as (-)-[18F]NCFHEB, which is already used for clinical PET imaging of nAChRs.

Methods: After intravenous administration of 284.1±13.2 MBq (+)-[18F]Flubatine PET brain recordings were performed in 11 healthy non-smoking subjects (age 66.6±4.4 years) using an ECAT EXACT HR+ system in 3D-acquisition mode. 41 frames were acquired from 0-270 min post injection and motion corrected with SPM2. Kinetic modeling using 1- and 2-tissue compartment models (1TCM, 2TCM) with arterial input-function was applied to the volume of interest (VOI) based tissue time-activity curves (TACs) generated for 36 brain regions (anatomically defined via MRI co-registration). Time ranges from 0 to 90 and 0 to 270 min were investigated. Model-based receptor parameter was the total distribution volume VT (ml/cm-3). Metabolites in plasma were measured by radioactivity HPLC and the free fraction of (+)-[18F]Flubatine in plasma was determined by ultracentrifugation.

Results: The tracer showed high stability in vivo with more than 97% remaining as untransformed parent compound at 90 and 270 min. The free fraction in plasma was high and showed only small interindividual variations (0.86±0.02, n=11). Given the negligible amounts of metabolites present in plasma the arterial input function was not corrected for metabolites.
TACs of all 36 regions could be described with the 1- or 2TCM. VT in all cortical regions could be reliably estimated from 90 min PET data. VT increased with receptor density as expected. Using the 2TCM and 270 min PET-data: CC (VT: 7.9±1.5, n=11), frontal cortex (10.8±1.2), pons (16.3±3.1), thalamus (41.3±8.7). For 90 min PET data the distribution volumes were very similar: CC (VT: 7.9±1.3), frontal cortex (10.3±1.4), pons (15.4±3.0), thalamus (41.0±9.0). The distribution volumes computed with the 1TCM were comparable to the results of the 2TCM: Frontal cortex (10.9±1.3, 270 min) and (10.2±1.4, 90 min).
The previously investigated enantiomer (-)-[18F]Flubatine showed very similar VT in cortical structures e.g., frontal (10.4±1.3, n=12) but lower VT in pons (12.4±1.9) and especially thalamus (27.6±4.2) (2TCM, 90 min; Sabri et al., 2015).

Conclusions: (+)-[18F]Flubatine has an optimal metabolic profile. The amount of metabolites is very low and no metabolite correction has to be applied to the arterial input function. The high VT values in subcortical structures are favorable. Receptor parameters can be estimated with a 1- or 2TCM from 90 min PET-data. If a model derived receptor parameter is used in a classification problem, e.g., distinguishing patients with Alzheimer’s disease from healthy controls the bias-variance tradeoff problem associated with the simpler 1TCM (higher bias) and the more complex 2TCM (higher variance) has to be solved. The final decision which model should be used will be made on the basis of the PET-data of both groups.

Reference: Sabri O et al. (2015) Neuroimage 118:199-208


Figure Legend: 2TCM fits (270 min) in 8 brain regions. Abscissa: Time in min, ordinate: Activity (kBq/cm3). Computed total tracer amount in tissue is presented but also the tracer amount in the non-displaceable and specific tissue compartment, the total distribution volume V and influx rate constant K1.
  • Poster
    NRM 2016 - 11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain, 13.-16.07.2016, Boston, USA

Publ.-Id: 23330 - Permalink


Two Novel Sigma-1 Receptor PET Radiotracers with Favorable Imaging Properties: Evaluation in Nonhuman Primates
Cai, Z.; Baum, E.; Bois, F.; Holden, D.; Lin, S.; Lara-Jaime, T.; Kapinos, M.; Chen, Y.; Deuther-Conrad, W.; Fischer, S.; Wünsch, B.; Brust, P.; Jia, H.; Huang, Y.;
Objectives: Sigma-1 receptors (Sig-1Rs) are intramolecular chaperone proteins, the abnormal expression of which has been indicated in a variety of CNS disorders [1]. As a result, Sig-1R is proposed as a therapeutic target for schizophrenia, depression, and Alzheimer’s disease. PET imaging of S1Rs would provide an in vivo tool to investigate the involvement of Sig-1Rs in these diseases, and to assist in drug development. Hence, great efforts have been devoted to the development of effective PET radiotracers for Sig-1Rs, though most have failed to reach the human evaluation stage due to unfavorable pharmacokinetic and imaging properties. Through our Sig-1R PET ligand discovery programs, we have identified a number of spirocyclic piperidine analogs with attractive characteristics for development as in vivo imaging agents [2-4]. The objective of this study was to evaluate the two most promising ligands in rhesus monkeys in preparation for clinical translation.
Methods: The two 18F-labeled radiotracers (1 and 2) were prepared by nucleophilic displacement of the tosylate on the precursors and evaluated in the same rhesus monkeys (n = 2). Baseline scans of 4-h duration were obtained on a FOCUS 220 scanner after injection of ~5 mCi radioactivity. Blocking scans were performed with pre-administration of the selective Sig-1R agonist SA4503. Arterial blood was collected at pre-selected time points for measurement of plasma activity and HPLC analysis of radiometabolites to generate the plasma input functions for the parent tracer. Analysis of regional brain time-activity curves (TACs) was performed with one-tissue (1T), two-tissue (2T), and the multilinear analysis-1 (MA1) models to estimate kinetic parameters and regional volumes of distribution (VT). Tracer free fraction (fP) in plasma was measured via ultrafiltration method. Log D of each radiotracer was determined by the shake-flask method.
Results: Radiotracer 1 and 2 were prepared in high radiochemical purity and specific activity. In rhesus monkeys both tracers displayed moderate rates of metabolism, with 35% and 19% of parent fraction for 1 and 2 at 60 min post-injection. Plasma fP values were 2% and 17% for 1 and 2, in line with their respective measured Log D values of 2.8 and 2.5. Both radiotracers exhibited excellent brain uptake (peak SUV > 4) and fast tissue kinetics (activity peaked in all regions at <30 min post-injection) (Fig. 1). Both the 1T and MA1 models provided good fits of regional TACs and reliable VT estimates. Overall, ligand 2 displayed higher uptake levels, greater differential uptake among brain regions and higher regional VT values than 1. SA4503 (0.5 mg/kg. iv) blocked ~85% (1) and ~95% (2) of radiotracer uptake, indicating the binding specificity of both radiotracers in the monkey brain.
Conclusions: The novel Sig-1R radiotracers 1 and 2 display excellent brain uptake, fast tissue kinetics, and high levels of specific binding in vivo. Both have proved to be suitable for the imaging and quantification of Sig-1R in the monkey brain, therefore, further evaluation in humans is warranted. In comparison, tracer 2 has a ten-fold higher fP, higher brain uptake, and greater VT values in rhesus monkey.
Figure 1. TACs of ligands 1 and 2 in selected monkey brain regions with and without blocking.
References.
1. Maurice T and Su T-P, Pharmacol Ther, 2009. 124:195.
2. Brust P et al., J Nucl Med, 2014. 55:1730.
3. Li Y et al., J Med Chem, 2013. 56:3478.
4. Chen Y-Y et al., Bioorg Med Chem, 2014. 22:5270.
  • Lecture (Conference)
    11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain, 13.-16.07.2016, Boston, USA

Publ.-Id: 23329 - Permalink


Direct evidence of defect coordination and magnetic interaction in local structure of wurtzite type Zn1-xCoxO thin films
Satyarthi, P.; Ghosh, S.; Wang, Y.; Zhou, S.; Bürger, D.; Skorupa, I.; Schmidt, H.; Olivi, L.; Srivastava, P.;
The local structure of as deposited and post treated Zn0.95Co0.05O films is investigated to understand the origin of their paramagnetic and tunable ferromagnetic properties for scientific advancements in spintronics. The crystallographic perfect short range ordering in the vicinity of tetrahedrally substituted Zn and Co atoms is responsible for mediating purely paramagnetic behavior in Zn0.95Co0.05O film grown by pulsed laser deposition. Irradiating the as deposited Zn0.95Co0.05O films with 500 keV inert xenon ions of different fluences, leads to creation of O, Zn and Co related defects in coordination shells of tetrahedrally substituted Zn and Co atoms. Apart from defect creation, spinel type ZnCo2O4 phase is evident for the film irradiated at highest fluence, in which Zn and Co atoms exist in tetrahedral and octahedral symmetry around the oxygen atoms. The tunable ferromagnetism in post irradiated Zn0.95Co0.05O films is understood from a model that includes strong ferromagnetic and weak antiferromagnetic interactions operating within their local structure. The ferromagnetic interaction is explained from (i) dopant defect hybridization of O vacancies and high spin (S = 3/2) Co atoms and (ii) spin interaction at O 2p orbital's in Zn vacancy rich regions in tetrahedral symmetry. The weak antiferromagnetic interaction is discussed from the presence of octahedral coordinated low spin (S = 0) Co atoms in ZnCo2O4 structure.
Keywords: Diluted Magnetic Semiconductors; Spintronics; EXAFS

Publ.-Id: 23328 - Permalink


U(VI) reduction by anaerobic microorganisms isolated from the flooding water of the former uranium mine Königstein (Saxony/Germany)
Gerber, U.; Krawczyk-Bärsch, E.; Scheinost, A. C.; Arnold, T.;
The former uranium mine Königstein (Saxony, Germany) is currently in the process of remediation. The underground is flooded in a controlled way, and the flooding water is cleaned up in a dedicated waste water treatment plant. Despite high U concentrations up to 13 mg/L and a low pH of 2.9, these waters contain a high microbial diversity as detected by culture-independent methods. Microorganisms are known to interact with metals and radionuclides in different ways. Anaerobic bacteria which are able to gain energy from the reduction of several metals, are known to change the redox state of metals and radionuclides. For instance, anaerobic sulfate-reducing bacteria (SRB) reduce U(VI) to U(IV) and thus change the migration behavior from the more soluble U(VI) into the less soluble U(IV). Genomic sequence analysis of the flooding water revealed the presence of such anaerobic SRB. By culture-dependent methods it was possible to isolate anaerobic microorganisms from the flooding water. They were incubated with 10 mM glycerol using the flooding water as background medium. During an incubation time of six weeks the redox potential decreased from 660 mV to 300 mV. After four and six weeks of incubation, the cells were separated from the incubation medium by centrifugation and than analyzed by U-LIII edge EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure) measurements. By Iterative Target-Factor Analysis (ITFA) we determined that 100 % of U(VI) was reduced to U(IV). Simultaneously, investigations of the supernatant with UV-vis resulted in the same findings. The results show that naturally occurring anaerobic microorganisms within the flooding water of the former uranium mine Königstein are able to reduce U(VI) to U(IV).
Keywords: Uranium reduction, Sulfate-reducing bacteria, Bioremediation
  • Contribution to proceedings
    Goldschmidt 2016, 26.06.-01.07.2016, Yokohama, Japan

Publ.-Id: 23326 - Permalink


Assessment of a hybrid CFD model for simulation of complex vertical upward gas-liquid churn flow
Parsi, M.; Agrawal, M.; Srinivasan, V.; Vieira, R. E.; Torres, C. F.; Mclaury, B. S.; Shirazi, S. A.; Schleicher, E.; Hampel, U.;
Gas-liquid multiphase flow can be observed within different industrial processes, and Computational Fluid Dynamics (CFD) can be utilized as a tool for scrutiny of this kind of flows. Although the CFD simulations of multiphase are computationally-demanding, they can deliver a great deal of information. But, the larger point is whether the available CFD multiphase flow models are able to deliver a realistic solution for a complex flow pattern like churn flow? And if yes, to what extent are the results accurate?To shed light on these issues, the Eulerian-Eulerian MultiFluid VOF model offered by ANSYS FLUENT 15 (2015 15.0 User's Guide, ANSYS Inc.) was used to simulate high flow rate air-water multiphase flow in a 76.2 mm-diameter pipe upstream of an elbow in the vertical-horizontal configuration. In the simulations, superficial gas velocity ranged from 10.3 m/s to 33.9 m/s, and two superficial liquid velocities of 0.3, and 0.79 m/s were employed. From the CFD simulations, data such as phase distributions, mean void fractions, and average void fraction time series were extracted. They were then compared to experimental Wire Mesh Sensor (WMS) data formerly obtained. Interestingly, evaluation of the model revealed that it was successful in terms of capturing different liquid structures present within the flow and delivering void fraction data which were in agreement with those of experiments.
Keywords: CFD; Churn flow; Huge wave; MultiFluid VOF; Multiphase flow; Wire mesh sensor

Publ.-Id: 23324 - Permalink


Ferromagnetic Mn-Implanted GaP: Microstructures vs Magnetic Properties
Yuan, Y.; Hübner, R.; Liu, F.; Sawicki, M.; Gordan, O.; Salvan, G.; Zahn, D. R. T.; Banerjee, D.; Baehtz, C.; Helm, M.; Zhou, S.;
Ferromagnetic GaMnP layers were prepared by ion implantation and pulsed laser annealing (PLA). We present a systematic investigation on the evolution of microstructure and magnetic properties depending on the pulsed laser annealing energy. The sample microstructure was analyzed by high-resolution X-ray diffraction (HR-XRD), transmission electron microscopy (TEM), Rutherford backscattering spectrometry (RBS), ultraviolet Raman spectroscopy (UV-RS), and extended X-ray absorption fine structure (EXAFS) spectroscopy. The presence of X-ray Pendellösung fringes around GaP (004) and RBS channeling prove the epitaxial structure of the GaMnP layer annealed at the optimized laser energy density (0.40 J/cm2). However, a forbidden TO vibrational mode of GaP appears and increases with annealing energy, suggesting the formation of defective domains inside the layer. These domains mainly appear in the sample surface region and extend to almost the whole layer with increasing annealing energy. The reduction of the Curie temperature (TC) and of the uniaxial magnetic anisotropy gradually happens when more defects and the domains appear as increasing the annealing energy density. This fact univocally points to the decisive role of the PLA parameters on the resulting magnetic characteristics in the processed layers, which eventually determine the magnetic (or spintronics) figure of merit.
Keywords: GaMnP, ion implantation, pulsed laser annealing, dilute ferromagnetic semiconductors, microstructures, magnetic properties

Publ.-Id: 23323 - Permalink


Functional PET/MR Discloses Gender Differences in Color Processing in Mice
Njemanze, P.; Kranz, M.; Brust, P.;
OBJECTIVES: Color processing is a central component of human vision. There has been much debate about the existence of color vision in animals. Mice have two types of cone pigments, one with a peak sensitivity at about 510 nm, and the other with a peak at 370 nm in the ultraviolet range. Most studies of color vision have used behavioral experiments, and hence uncertainties remain whether the two cone types yield color vision. Since PET has been used to measure changes of rCBF of rhesus monkeys performing color discrimination we have hypothesized that FDG-PET combined with anatomical MR can be used to study color processing in mice. Here we demonstrate gender differences in color processing in mice.
METHODS: Ten anaesthetized CD-1 mice were repeatedly injected on different days with 12 MBq 18F-FDG and subjected in random order to separate monocular stimulation of the left and right eye with white, blue and yellow lights, respectively, for 20 min using gelatin-(Wratten)-filters affixed within a viewing device (Chromatoscope) specially designed for small animals. The SUV of 18F-FDG was determined at 27.5, 32.5, 37.5 and 42.5 min p.i. in the whole cortex and in the left and right visual cortex. Data were analyzed with MANOVA and t-test.
RESULTS: In both genders no hemispheric differences are revealed in dark baseline condition and during stimulation with white light of either eye. Male mice have 13-16% higher SUV (p< 0.001) than female mice in the cortical area, right and left visual cortex in dark baseline condition and during stimulation with white, blue and yellow lights through the right eye but not the left. In male mice, the SUV was higher in the left visual cortex (1.53 ± 0.08) during Blue stimulation through the right eye compared to the right visual cortex (1.47 ± 0.10, p<0.05) (Fig. left) while the SUV did not differ during Blue stimulation through the left eye. Conversely, in female mice, the SUV was higher in the right visual cortex (1.34 ± 0.08) during Blue stimulation through the left eye compared to the left visual cortex (1.30 ± 0.11, p<0.01) (Fig. right) while there was no change during stimulation with Blue through the right eye. Yellow stimulation through the right eye revealed hemispheric differences only in female mice, while Yellow stimulation through the left eye revealed hemispheric differences only in male mice.
CONCLUSION: The experimental setup using FDG-PET combined with anatomical MR is suitable to study color processing in mice. As previously has been shown for human in a functional transcranial Doppler study (Njemanze 2011) gender differences in the perception of blue and yellow colors appear to exist also in rodents. In both species Blue provided the highest stimulation. In opposite to human the visual cortex in male mice revealed higher metabolism than in female.
REFERENCE
Njemanze PC. Gender-related differences in physiologic color space: a functional transcranial Doppler (fTCD) study. Exp. Transl Stroke Med. 2011; 3: 1.
  • Poster
    NMR 2016 - 11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain, 13.-16.07.2016, Boston, USA

Publ.-Id: 23322 - Permalink


Animal PET/MR with the new radioligand [18F]AQ28A demonstrates the involvement of phosphodiesterase 10A in the regulation of energy homeostasis
Kranz, M.; Hankir, M. K.; Deuther-Conrad, W.; Wagner, S.; Teodoro, R.; Fischer, S.; Wenzel, B.; Fenske, W. K.; Brust, P.;
OBJECTIVES: Cyclic nucleotide phosphodiesterases (PDEs) are enzymes that cleave the phosphodiester bond in the second messenger molecules cAMP and cGMP. PDE10A is dual-specific and mainly expressed in the striatum, a brain region which coordinates a great variety of cognitive functions, including motor and action planning, decision-making, motivation, reinforcement, and reward perception. Knock-out mice provided evidence for involvement of PDE10A in the regulation of energy balance as shown by their resistance to diet induced obesity (DIO). Therefore, we have used the novel selective radioligand [18F]AQ28A [1] to investigate the expression of PDE10A in the striatum and brown adipose tissue (BAT) of lean, diet-induced (DIO) and leptin-deficient genetically obese mice. As BAT activation could previously be visualized by using [18F]FDG [2], we also assessed whether inhibition of PDE10A modulates BAT activity.
METHODS: Isoflurane-anaesthetized female mice were injected with either [18F]AQ28A (11±3 MBq) or [18F]FDG (14±2 MBq) and subjected to 1 h PET/MR (Mediso nanoScan®). After co-registration of the dual modality image data volumes of interest (striatum, hypothalamus, interscapular BAT and muscle) were drawn manually with reference to the structural MRI data using ROVER software (ABX, Radeberg).The selectivity of [18F]AQ28A towards PDE10A was investigated by baseline (n=3) and blocking (n=3) experiments with the PDE10A inhibitor MP-10 (5 mg/kg). Another set of animals was provided over 16 weeks either with standard food (lean, n=5) or high-fat high-sugar diet (DIO, n=5) and received [18F]AQ28A PET/MR thereafter. A further group of lean mice (n=10), which was overnight fasted and housed under thermoneutral conditions, received either i.p. injection of MP-10 (n=5) or vehicle (n=5) followed 30 min later by 1 h [18F]FDG PET/MR. Thereafter the mice were sacrificed and striatum, hypothalamus and BAT were collected. Relative mRNA expressions of PDE10A, thermoregulatory genes and the indirect neuronal activity marker Fos were analyzed by real-time qPCR.
RESULTS: PDE10A selectivity of [18F]AQ28A was proven by blocking with MP-10 (SUV15min striatum baseline/blocking: 1.02±0.19/0.54±0.08; p<0.01). A 7-fold higher mRNA expression of PDE10A in striatum compared to hypothalamus was found (p<0.001). Acute pharmacological inhibition of PDE10A altered cAMP levels (p<0.01) and thermoregulatory gene and Fos expression in striatum (p<0.05), but not in hypothalamus. DIO resulted in ~60% and 80% higher PDE10A expression (p<0.05) in striatum and BAT, respectively, accompanied by an increased SUV of [18F]AQ28A in both targets (p<0.05). Acute administration of MP-10 to lean mice resulted in significantly higher FDG uptake by BAT (SUV55min: 0.40±0.01) compared to vehicle administration (SUV55min: 0.25±0.02; p<0.01).
CONCLUSION: Distinct alterations of gene expression together with significant changes of PDE10A availability and glucose metabolism in BAT after PDE10A inhibition reveal a novel thermoregulatory role for PDE10A. The data suggest that PDE10A inhibitors offer the potential to treat obesity by increasing thermogenesis and reducing hedonic feeding through recruiting striatal and BAT circuits.
[1]Wagner, S., et al. Eur J Med Chem 2016 107;97.
[2]Gnad, T.;…;Kranz, M.;…Pfeifer, A. Nature. 2014 18;516
  • Poster
    NMR 2016 - 11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain, 13.-16.09.2016, Boston, USA

Publ.-Id: 23321 - Permalink


First-order magnetization process as a tool of magnetic-anisotropy determination: Application to the uranium-based intermetallic U3Cu4Ge4
Gorbunov, D. I.; Henriques, M. S.; Andreev, A. V.; Skourski, Y.; Richter, M.; Havela, L.; Wosnitza, J.;
Uranium-based intermetallic compounds often display very strong magnetic anisotropies, the energy of which is usually not directly accessible by common experimental methods. Here, we report on static- and pulsed-field studies of U3Cu4Ge4. This material orders ferromagnetically at TC = 73 K with the easy magnetization direction along the a axis and a strong bc-plane anisotropy. The magnetization measured for fields along the hard b direction displays a first-order magnetization process that can be described well by use of a phenomenological theory yielding anisotropy constants up to the sixth order. This phenomenological description,working excellently for U3Cu4Ge4, may also be applied for other uranium-based compounds.

Publ.-Id: 23320 - Permalink


LiF – a spectroscopic method for rare earth elements identification
Fuchs, M.; Gloaguen, R.; Beyer, J.; Jakob, S.; Heitmann, J.;
Laser-induced fluorescence (LiF) has a great potential for the exploration and identification of rare earth elements (REE) in natural environments. This spectroscopic technique can provide an efficient way to secure resource availability, while the economic and ecological costs are reduced. No time-consuming sample preparation and analysis is needed prior to decisions along the raw material processing chain. Such non-destructive approaches allow for a fast access to analytical results and hence, are the basis for an immediate adjustment of processing steps.
The method uses the material-specific luminescence emissions that are induced by laser-stimulation of a certain wavelength. The distinct emission lines of REE make them well suited for the development of a LiF-based exploration technique. However, typical REE emission peaks known from the free elements may shift or be masked in natural materials due to their position in the crystal lattice, varying compositions of minerals or other natural conditions such as water content. The natural variability therefore, demands for comprehensive investigations of REE and their spectral characteristics in minerals.
To identify those spectral information that are robust and unequivocal, we analyse spectra of REE standards measured in different matrix minerals including phosphates and fluorides. We use variable laser wavelengths from UV (325 nm) to green (532 nm) and a detection range from 340 nm to 1080 nm. Results show spectral characteristics that sort REE in three groups due to: no distinct emission lines, absorption features, distinct luminescence emission lines. Measured in different matrix minerals, we determine shifts for some of the spectral features and some disappear or decline in intensity. Changing the wavelength of the laser allows for a more selective stimulation of REE emissions, especially wavelengths longer than UV can reduce the unspecific emission of all luminescent components of a sample and thus enhance individual spectral information. To test the applicability of LiF, we additionally investigated natural rocks with a well-characterized REE content. First results show that LiF is able to reproduce spectral characteristics of REE in natural rocks.
Keywords: Luminescence, REE, emission spectroscopy
  • Lecture (Conference)
    European Geoscience Union, 17.-22.04.2016, Vienna, Austria

Publ.-Id: 23319 - Permalink


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