Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The clear understanding of exchange interactions between magnetic ions in substituted BiFeO3 is the prerequisite for the comprehensive studies on magnetic properties. BiFe0.5Mn0.5O3 films and BiFeO3/BiMnO3 superlattices have been fabricated by pulsed laser deposition on (001) SrTiO3 substrates. Using piezoresponse force microscopy (PFM), the ferroelectricity at room temperature has been inferred from the observation of PFM hysteresis loops and electrical writing of ferroelectric domains for both samples. Spin glass behavior has been observed in both samples by temperature dependent magnetization curves and decay of thermo-remnant magnetization with time. The magnetic ordering has been studied by X-ray magnetic circular dichroism measurements, and Fe-O-Mn interaction has been confirmed to be antiferromagnetic (AF). The observed spin glass in BiFe0.5Mn0.5O3 films has been attributed to cluster spin glass due to Mn-rich ferromagnetic (FM) clusters in AF matrix, while spin glass in BiFeO3/BiMnO3 superlattices is due to competition between AF Fe-O-Fe, AF Fe-O-Mn and FM Mn-O-Mn interactions in the well ordered square lattice with two Fe ions in BiFeO3 layer and two Mn ions in BiMnO3 layer at interfaces.

Particle therapy is a highly conformal radiotherapy technique which reduces the dose deposited to the surrounding normal tissues. In order to fully exploit its advantages, treatment monitoring is necessary to minimize uncertainties related to the dose delivery. Up to now, the only clinically feasible technique for the monitoring of therapeutic irradiation with particle beams is Positron Emission Tomography (PET).
In this work we have compared a Resistive Plate Chamber (RPC)-based PET scanner with a scintillation-crystal-based PET scanner for this application. In general, the main advantages of the RPC-PET system are its excellent timing resolution, low cost, and the possibility of building large area systems. We simulated a partial-ring scanner based on an RPC prototype under construction within the Fondazione per Adroterapia Oncologica (TERA). For comparison with the crystal-based PET scanner we have chosen the geometry of a commercially available PET scanner, the Philips Gemini TF.
The coincidence time resolution used in the simulations takes into account the current achievable values as well as expected improvements of both technologies. Several scenarios (including patient data) have been simulated to evaluate the performance of different scanners. Initial results have shown that the low sensitivity of the RPC hampers its application to hadron-beam monitoring, which has an intrinsically low positron yield compared to diagnostic PET. In addition, for in-beam PET there is a further data loss due to the partial ring configuration. In order to improve the performance of the RPC-based scanner, an improved version of the RPC detector (modifying the thickness of the gas and glass layers), providing a larger sensitivity, has been simulated and compared with an axially extended version of the crystalbased device. The improved version of the RPC shows better performance than the prototype, but the extended version of the crystal-based PET outperforms all other options.

The talk summarises PhD research activities and results with respect to (bio)leaching of copper from copper shale.

Safety analysis of a cement-based repository for low- and intermediate level nuclear waste (L/ILW) has shown that 79Se is an important redox-sensitive, dose-determining radio-nuclide due to its long half-life and weak retardation by common near- and far field minerals. In the sorption data bases currently used for safety analysis it is considered that 79Se is predominantly present as SeO32- in the cementitious near field because oxidizing conditions prevail during waste conditioning. With time, however, reducing conditions will establish in the near field caused by oxygen consumption in the course of metal corrosion. In these conditions Se(-II) is expected to be the dominant redox state of Se. Hence, investigations into the interaction of Se(IV) and Se(-II) with cementitious materials and the reduction of Se(IV) to Se(-II) enable us to assess the long-term fate of Se in conditions relevant to a cement-based repository.
Sorption studies with Se on cementitious materials indicate that Se(IV) and Se(-II) uptake by hydrated calcium aluminates (AFm) and calcium silicate hydrates (C-S-H) phases, the principal host phases for radionuclides in cement paste, is significant and comparable to the uptake by cement paste. The uptake mechanisms of the Se species, however, are only poorly understood. EXAFS studies on Se(IV)-loaded cement phase and wet chemistry experiments suggest that Se(IV) could be taken up into the structure of the cement phases. In the case of AFm phases, for example, anions bound in the interlayer can be replaced, at least partially, by Se(IV) and Se(-II). This explains why AFm phases are more effective in removing Se(IV) and Se(-II) from solution than C-S-H phases.
Investigations into redox transformation are ongoing and the first results already suggest that the uptake mechanism of the Se species plays an important role in the reduction of Se(IV) to Se(-II) in cementitious materials.

Polymetallic Cu–Ag ores of the Central European Kupferschiefer deposits are one of the most important sources of copper in Europe. Because the ores are typically complex and often exceptionally fine-grained the development of efficient alternatives to conventional beneficiation strategies are an important target of current research. Biomining – the use of biological components for metal extraction – may offer solutions that are both efficient and environmentally benign. As conventional bioleaching with acidophilic microorganisms is impeded by the high carbonate content of the Kupferschiefer ores, heterotrophic microorganisms and glutamic acid are investigated as a possible alternative in the present study. The focus of this investigation is solely on the recovery of copper from the Kupferschiefer sensu strictu. Bioleaching experiments were carried out using such material from the Polkowice Mine in Poland. This material is marked by high grade (3.8 wt.% Cu), complex ore mineralogy (chalcocite, bornite, chalcopyrite and covellite in significant quantity) and a gangue mineralogy that is rich in carbonate, organic carbon and clay minerals that together form a very fine-grained matrix. (Bio)leaching experiments yield best results when glutamic acid alone is used – reaching copper recoveries up to 44%. Recoveries are consistently lower in experiments in which glutamic acid and microbiological metabolites are both present. The leaching of chalcocite renders the greatest contribution to the copper recovered to the leach solution in all experiments. It can be concluded that glutamic acid solubilises copper efficiently from Kupferschiefer, mainly from chalcocite.

Der Vortrag stellt das Helmholtz-Zentrum Dresden-Rossendorf sowie das Helmholtz-Institut Freiberg für Ressourcentechnologie vor und liefert allgemeine Informationen zu biotechnologischen Prozessen in der Kupfergewinnung sowie Einlick in Arbeiten der Arbeitsgruppe Biotechnologie.

Vancomycin is an important glycopeptide antibiotic which is used to treat serious infections caused by Gram positive bacteria. However, during the last years a tremendous rise in vancomycin resistances, especially among enterococci, was reported, making fast diagnostic methods inevitable.
In this contribution, we apply Raman spectroscopy to systematically characterize vancomycin-enterococci interactions over a time span of 90 minutes using a sensitive E. faecalis strain and two different vancomycin concentrations above the minimal inhibitory concentration (MIC). Successful action of the drug on the pathogen could be observed already after 30 minutes of interaction time. Characteristic spectral changes are visualized with the help of multivariate statistical analysis (linear discriminant analysis and partial least squares regressions). Those changes were employed to train a statistical model to predict vancomycin treatment based on the Raman spectra. The robustness of the model was tested using data recorded by an independent operator. Classification accuracies of >90% were obtained for vancomycin concentrations in the lower range of a typical trough serum concentration recommended for most patients during appropriate vancomycin therapy.
Characterization of drug-pathogen interactions by means of label-free spectroscopic methods, such as Raman spectroscopy, can provide the knowledge base for innovative and fast susceptibility assays which could speed up microbiological analysis as well as could find applications in novel antibiotic screenings assays.

Epoxy blocks for automated mineralogy typically contain unsorted material from feeds, concentrates or tailings of the processing chain. In these cases, accuracy and precision of SEM-based analytics not only depend on stable measurement parameters and conditions but also on sample preparation. The major aim of sample preparation is the production of representative specimen mounts to generate valid information about the given samples. However, experiences in preparation indicate an influence on the analytic results of many factors such as resin type, resin viscosity, mineral grain density, grain shape and sample material/resin ratio.
This study aims at evaluating the influence of different material/resin ratios on the representativity of a mineral sample. In order to investigate possible gravitational and shape related settling effects during sample preparation, the use of homogenized Zinnwaldite ore is suitable as it provides sample material with a heterogeneous mineral composition, mineral density (Quartz – Topaz), grain shape (Mica – Quartz) and grain size. Eight specimens were prepared with equal weight aliquots of the same ore material, with increasing resin amount. These polished epoxy mounts were analyzed three times with the Mineral Liberation Analyzer (MLA) at Helmholtz Institute Freiberg for Resource Technology (HIF) to evaluate their difference in modal mineralogy, grain sizes and grain shapes. Each sample was analysed as usual on the XY plane, then polished a bit and measured again on a deeper XY plane; and finally the samples were cut along the YZ plane, remounted and measured again, thus capturing a plane orthogonal to the classical measurement plane.
First visual inspection indicates a connection between the amount of resin and the appearance of gravitational and shape related settling effects. The effects such as fractionating of grains by size and density or specific orientation of elongated grains became stronger the more resin was used. These aspects are statistically tested by comparing the frequency distributions of intersection segments between grains and families of lines (random in the XY planes, 9 equally spaced lines in the case of YZ plane observations), a way to circumvent Stereological degeneration effects. Results suggest a range of material/resin ratio that is suited for sample preparation of this particular ore type, by showing no statistical deviations between the distributions on the XY and YZ planes, hence no or very small gravitational or shape related settling effects.

In U1 xAmxO2±δ compounds with low americium content (x ≤ 20 at.%) and O/M (oxygen to metal) ratios close to 2.0, trivalent Am is charge-balanced by an equivalent amount of pentavalent U while maintaining the fluorite structure of pure U+IVO2. Up to now, it is unknown, whether this observation holds also for higher americium contents. In this study, we combined therefore X-ray diffraction with Raman and X-ray absorption spectroscopies to investigate U0.5Am0.5O2±δ. Our results indicate that americium is again only present as Am+III, while U+V remains below the amount required for charge balance. Contrary to lower americium contents, this leads to an overall oxygen hypo-stoichiometry with an average O/M ratio of 1.92(2). The cationic sublattice is only slightly affected by the coexistence of large amounts of reduced (Am+III) and oxidized (U+V) cations. Significant deviations from the fluorite structure are, however, evidenced by both EXAFS and Raman spectroscopy in the oxygen sublattice, with the coexistence of vacancies and interstitials consistent with the insertion of U6O12 cuboctahedral-type clusters (as observed in the U4O9 or U3O7 phases). These results thus highlight the specificities of uranium-americium mixed oxides, their behavior being closer to that of trivalent-lanthanide-doped UO2 than to that of U1 xPuxO2±δ MOX fuels.

Annular two-phase flow has been vastly investigated because of its large and deep involvement in industrial processes, particularly in nuclear engineering and petroleum production facilities. Much effort has been devoted to investigating upward flows involving the flow patterns, void fraction, as well as local interfacial characteristics. However, research for vertical downward two-phase flow, especially of the interfacial characteristics, are comparatively scarce. In order to gain insight on void fraction, interfacial structures and characteristics frequencies, experimental work was performed in downward annular two-phase flow with water and air as process fluids at low pressure conditions. A flow loop, including a 76 mm ID, 16.5 m long vertical pipe, has been instrumented. A state2 of-the-art instrument for two-phase flow measurements based on the fluid conductivity, namely dual Wire-Mesh Sensor (WMS) has been utilized to acquire the experimental data. A total of 43 data points have been acquired at superficial liquid velocities that ranged from 0.005 m/s to 0.10 m/s and superficial gas velocities that varied from 10 m/s to 31 m/s. The effects of liquid viscosity on the measured parameters are also investigated using two different viscosities of 1 and 10 cP. Analysis of time series void fraction data from the dual Wire-Mesh sensors allows the determination of cross-sectional averaged void fraction, local time averaged void fraction distribution, liquid phase distribution around the tube periphery, interfacial structure frequencies, pseudo 3D reconstruction as well as Probability Density Function (PDF) and Power Spectral Density (PSD). The experimental results indicate that the interfacial shape and frequencies are significantly altered by the superficial gas velocity. Comparisons between mechanistic model predictions and the acquired experimental data show a maximum absolute average relative error of approximately 7% for the cross-section void fraction.

In the churn flow regime, periodical interfacial structures such as liquid slugs and huge waves can coexist and undoubtedly, a phase property such as liquid viscosity can dominate the behavior of these structures. Regrettably, neither are the characteristics of churn flow widely understood nor have the effects of liquid viscosity on gas-liquid flow received enough attention. A Wire Mesh Sensor (WMS) with a 16×16 spatial resolution was employed to discover the effects of liquid viscosity on the behavior of churn flow in a vertical 76.2 mm pipe. Three liquid viscosities of 1, 10, and 40 cP, and superficial liquid velocities of 0.46, 0.61, and 0.76 m/s were employed; whereas, superficial gas velocity ranged from 10 to 27 m/s. Different techniques such as Probability Density Function (PDF), and 2-D and 3-D image reconstruction methods were applied to study the flow. It was noticed that increasing liquid viscosity not only affected the flow pattern but also the appearance frequencies of interfacial structures.

Since 2003, ELBE operates as a user facility for fundamental research and life sciences, providing highly brilliant electromagnetic radiation in a broad spectral range, as well as particle beams. The driving source is a 40 MeV, 1 mA electron LINAC in cw mode, utilizing a 13 MHz pulsed thermionic gun and Tesla acceleration technology. Infrared light from two FELs between 3 and 280μm [1] is the foremost secondary radiation used at ELBE. For its applications, different demands in beam stability are put for successful experiments. Therefore, a feedback system for the electron beam position and energy in combination with IR beam intensity feedback using FPGA technology is under development. It is aimed at suppressing beam instabilities caused by thermal behaviour, microphonics and the 50 Hz mains frequency with upper harmonics. This article depicts hardware and software details of the measurement and feedback system and provides first performance results.

The systematic uncertainty in the holdup measurements of a capacitance based WMS has been experimentally evaluated, and a methodology for its quantification is proposed. Tests are conducted in laboratory and in-situ conditions for different mesh grid and pipe inclination angles, and different flow conditions in a high pressure (1.37 MPa) facility with a range of gas and liquid velocity ranges of 2.8 m/s ≤ νSg ≤ 6.9 m/s and 1 cm/s ≤ vSL ≤ 5 cm/s, respectively.
The angle between the phase interface and the sensor wires is ineffective while the pipe inclination angle plays a major role in the deviations of the holdup measurements. Using the proposed methodology, the systematic uncertainty is shown to follow a logarithmic increase as a function of the measured holdup for smaller holdup values (HL ≤ 15%) and to be lower than 1.5% for HL > 15%. This behavior is representative of the systematic uncertainty in the actual flow loop installation.
Under actual flow conditions, the holdup measurements of the trapped liquid by WMS show an Offset compared to the Canty measurements which can be corrected by using the quantified uncertainty in the laboratory tests. Furthermore, the dynamic measurements with WMS show a good agreement with the holdup of the trapped liquid volume within the quantified uncertainty bounds.

This book chapter gives an overview of fundamentals of bacterial S-layers and their use for the production of nano-materials subdivided in the following sections

• What are S-layer?,
• Molecular biology of S-layer proteins,
• General application potential of bacterial S-layers,
• S-layer based coatings and their production,
• New S-layer based nano-materials.

Metalle interagieren auf vielfältige Art und Weise mit lebenden Organismen. Dies wirkt sich zunächst auf die Metalle selbst aus. Eine veränderte Speziation kann beispielsweise zu einer veränderten Mobilität wie auch zu einer veränderten Bioverfügbarkeit der Metalle in der Umwelt führen. Umgekehrt haben Metalle einen direkten Einfluss auf die Vitalität von Zellen. Neben essentiellen Metallen, die grundlegende Funktionen für den Stoffwechsel erfüllen und damit lebenswichtig sind, gibt es auch toxische Metalle, die den Organismus in höherer Konzentration nachhaltig schädigen können. Radioaktive Metalle, die im Einzelfall nicht nur eine chemische sondern zusätzlich ein radiologische Toxizität aufweisen, können auf Grund der ionisierenden Strahlung Zellbestandteile schädigen oder gar zerstören. Radiometalle können hierbei natürlichen Ursprungs sein oder durch anthropogene Aktivitäten in die Umwelt gelangen. Letzteres umfasst zum Beispiel den Bergbau, die Zementproduktion, die Ausbringung von Phosphatdünger wie auch die störfallbedingte Freisetzung von Radionukliden, Atomwaffentests und die Aufbereitung und Lagerung von radioaktiven Abfällen. Eine Zusammenstellung der wichtigsten Wechselwirkungsmechanismen von Mikroorganismen mit Radiometallen in der Umwelt zeigt nebenstehende Abbildung.
Im Rahmen des Vortrags sollen unterschiedliche Mechanismen auf molekularer Ebene und an Hand von Beispielen ausführlich diskutiert werden. Des Weiteren sollen neben den verschiedenen Varianten einer chemischen Wechselwirkung auch biochemische Effekte in der Zelle berücksichtigt werden. Ziel ist es, auf Basis der unterschiedlichen Wirkungsmechanismen von Radiometallen mit biologischen Systemen, den wechselseitigen Einfluss zum einen auf das Verhalten von Radiometallen in der Umwelt und zum anderen auf den Stoffwechsel von Zellen aufzuzeigen. Die genannten Aspekte sind nicht nur für die Abschätzung der Langzeitsicherheit eines Endlagers für radioaktive Abfälle von Bedeutung, sondern auch für die generelle Abschätzung des Gefährdungspotenzials von Radiometallen für Mensch und Umwelt.

Three-phase gas-liquid-liquid flows are very common in petroleum extraction, production and transport. In this work a dual-modality measuring technique is introduced which may be well applied for gas-liquid-liquid flow visualization. Measuring principle is based on simultaneous excitation with two distinct frequencies to interrogate each crossing point of a mesh sensor which in turn are linked to conductive and capacitive parts of impedance. The developed system can operate 8 transmitter and 8 receiver electrodes at a frame repetition frequency up to 781 Hz. The system has been evaluated by measuring reference components. Deviations to references values are below 10% which considering the fast repetition frequency of measurements is suitable for flow investigation. Furthermore, the developed system was applied to visualize three-phase air-oil-water mixtures in static and dynamic (flowing) conditions, showing that the sensor is a valuable tool to investigate such flows.

no abstract available

Superconducting RF injectors are promising candidates for the particle sources of future accelerators. While machines like high power free electron lasers or energy recovery linacs are planned to be operated with large duty factors, or even continuous wave mode, to increase the beam intensity, they also demand high beam quality. As this is already determined at the very start of the generation of each particle bunch, the concept of an SRF gun becomes appealing. Transverse Emittance marks the beam quality which is of tremendous relevance for all beam optics and further more sets the level of angular resolution of any scattering experiment performed with the beam. Several concepts to enhance this quality with the lately comissioned Rossendorf SRF Gun II have been presented in recent year’s conferences. The talk will summarize the expended efforts, discuss some of the reflections on installation and operation of the used tools and present preliminary results of the recent achievements.

Bubble columns are widely used in industrial application and are an actual object of research. The performance of a bubble column strongly depends on the characteristic of the flow, which can be modeled with the methods of computational fluid dynamics (CFD). A widely used CFD approach for modeling such dispersed multiphase flows is the Eulerian two-fluid approach.
With the Eulerian two-fluid approach large apparatuses can be simulated in a short time; however, the interaction between the dispersed and the continuous phases has to be modelled with closure models. The closure models refer to different forces and effects, such as drag, lift, virtual mass, turbulent dispersion, coalescence & break up and bubble induced turbulence. The usage of a proper set of closure models is an actual discussion in the scientific community (Rzehak & Krepper 2013) and proper experiments are needed for model validation.
To validate the above mentioned effects that the closure models have to cover, a wide range of experiments are needed. In addition, such experiments should allow measuring the relevant data for a model validation. The must have relevant data are the bubble size distribution, the local void fraction and the liquid velocity at different positions.
In the present study an airlift air-water bubble column, a partially aerated air-water bubble column and an air-NaCl solution bubble column is investigated. The bubble size distribution, the local void fraction and the liquid velocity will be shown at different positions in the bubble column. In addition, a comparison of the experimental results with simulations using an Euler-Euler unsteady Reynolds averaged Navier Stokes equation approach as described in Ziegenhein et al. 2015 is given.

No abstract available

No abstract available.

Work in progress report about the measurement of the neutron field during proton therapy at OncoRay.

In gas well production, liquid is produced in two forms, droplets entrained in the gas core and liquid film flowing on the tubing wall. For most of the gas well life cycle, the predominant flow pattern is annular flow. As gas wells mature, the produced gas flow rate reduces decreasing the liquid carrying capability initiating the condition where the liquid film is unstable and flow pattern changes from fully cocurrent annular flow to partially cocurrent annular flow. The measurement and visualization of annular flow and liquid loading characteristics is of great importance from a technical point of view for process control or from a theoretical point of view for the improvement and validation of current modeling approaches. In this experimental investigation, a Wire-Mesh technique based on conductance measurements was applied to enhance the understanding of the air-water flow in vertical pipes. The flow test section consisting of a 76 mm ID pipe, 18 m long was employed to generate annular flow and liquid loading at low pressure conditions. A 16×16 wire configuration sensor is used to determine the void fraction within the cross-section of the pipe. Data sets were collected with a sampling frequency of 10,000 Hz. Physical flow parameters were extracted based on processed raw measured data obtained by the sensors using signal processing. In this work, the principle of Wire-Mesh Sensors and the methodology of flow parameter extraction are described. From the obtained raw data, time series of void fraction, mean local void fraction distribution, characteristic frequencies and structure velocities are determined for different superficial liquid and gas velocities that ranged from 0.005 to 0.1 m/s and from 10 to 40 m/s, respectively. In order to investigate dependence of liquid loading phenomenon on viscosity, three different liquid viscosities were used. Results from the Wire-Mesh Sensors are compared with results obtained from previous experimental work using Quick Closing Valves and existing modeling approaches available in the literature.

Photoexcited uranyl(VI) is a mild oxidant and can decompose various biological substances including large molecule like DNA. This reaction constitutes another environmental risk of uranium in addition to its radiotoxicity and chemotoxicity. There are several different mechanisms which may lead to decomposition of organic substances by photoexcited uranyl(VI). This includes hydrogen abstraction by “yl”-oxygen, decarboxylation of uranyl-bound carboxylic group, and ligand-to-metal charge transfer. These mechanisms may also compete with each other and makes mechanistic understanding far from being straightforward. In my talk, I will focus on our recent experimental and theoretical development on DNA photocleavage study. Although hydrogen abstraction is widely believed to be the key reaction in uranyl(VI)–mediated photocleavage of DNA, density functional theory calculations show that direct charge transfer from DNA to photoexcited uranyl(VI) can be an alternative pathway that leads to DNA strand break. In the oxidized state of DNA, electron deficiency is centered mainly on guanine as well as on uranyl–free phosphate, and lesser extent is distributed on adenine and thymine. Presumably there is no unique “hot spot” in DNA and upon irradiation local oxidation occurs in nucleobase or in uranyl–free phosphate in the vicinity of uranium. Oxidation of phosphate eventually leads to DNA strand break. Experiments using circular dichroism (CD) and X-ray absorption spectroscopy (XAS) are in progress.

Because of their high charge density, the aqueous chemistry of f-elements with lower valences (i.e. tri- and tetravalent) is predominantly controlled by strong hydrolysis producing a variety of hydroxide species. Interestingly enough, this strong hydrolysis often induces the intrinsic formation of polymer and nano-sized cluster complexes which are stable even in aqueous solutions. This seminar will provide a recent overview of the hydrolysis-induced polymer/cluster formation of tetravalent f-elements particularly from the viewpoint of structural chemistry, as well as the associated characterisation techniques (e.g. X-ray absorption spectroscopy or X-ray scattering).

The effect of magnetic annealing on crystallographic texture ,microstructure, defects density and magnetic properties of a Fe-2.6%Si steel has been analyzed. After two stage cold rolling (75% and 60% cold rolled) with intermediate annealing process at (600 °C/1 h) the sample annealed at 600 °C for one hour during which different magnetic field of 0,7 and 14 T were applied has been investigated. The effect of defects density after cold rolling process on the recrystallization texture and magnetic properties was characterized. Heat treatments under a high external field of14 T show a drastic improvement of the magnetic properties such as significantly increased permeability. Neutron diffraction measurements were preferred for measurement of the bulk sample texture so that sufficient grain statistics were obtained. Because of its small wavelength (0.05–0.2 Å) synchrotron diffraction with high photon energy was used to evaluate the defects density by a modified Williamson–Hall plot.

In the last 20 years the development of new analytical methods and devices provided the possibility of high-resolution data in almost every field of science. Information is much easier to retrieve and in a depth never known before. But often these methods are expensive and a lot of time is needed for proper data acquisition and analysis. For example, in geosciences the Mineral Liberation Analyser (MLA) provides quantitative mineralogical microstructural information. This is a scanning electron microscope with automated software for high resolution images of rock specimen and sample compounds from mineral processing. The information can be used for evaluating the effect of mineral processing on a given ore sample in order to find the optimal processing parameters of each step and predict the overall recovery and grade the requested value minerals.

For example, the magnetic susceptibility of a mineral phase determines its behaviour during magnetic separation. It can be modelled as a linear combination of the susceptibilities of each occurring mineral phase with respect to its mass fraction:
\begin{equation} \label{equ} \overline{\chi_s} = \sum_{i=1}^{n} \frac{m_i}{m_s}\chi_i. \end{equation} (chi_s: susceptibility of the whole sample, chi_i: susceptibility of the i-th mineral phase, m_s: mass of the whole sample, m_i mass of the i-th mineral phase)

Unfortunately, quite often only the susceptibility of the composition can be measured in an experiment due to several reasons, e.g. if the composition consists of too many distinct components and the contained mineral particles consist of several mineral phases. During the separation the sample is split into several classes. The susceptibility can only be measured for such a class.
But we would like to infer the susceptibility for every single mineral phase. The common approach is a linear model, which fails if we have more mineral phases than susceptibility classes found in the experiment.

Our approach uses bootstrapping for constructing new subsamples out of the measured ones. Since every particle has the given mean property, taking such subsamples is like repeating the experiment. This provides a broader base with subsamples having a much higher variability of phase compositions. We repeat this procedure for every susceptibility class.

Furthermore we often do not only have one single value for each class found in the experiment, but a set of them within a certain bounded range. Instead of using the average we arbitrarily assign one of them to each new sample. This additionally prevents us from too many linear dependent equations using (\ref{equ}). We end up in an over-determined system of linear equations. For the solution we use the Moore-Penrose inverse, giving us the possibility to compute an estimation error for every mineral phase relying on the corresponding eigenvalue.

We will discuss simulation results and apply the method to actual experimental data.

A prompt gamma (PG) slit camera prototype recently demonstrated a 1-2 mm accuracy to detect proton range shifts at clinical beam currents by comparing an expected PG detection profile to a measured one. An analytical model has been recently developed to compute the expected profile at practical speed (< 1 s). We present here its benchmark against measurements in heterogeneous phantoms.

Monazite ceramics are being considered as potential waste forms for immobilization of minor actinides since they exhibit advantageous properties such as high chemical durability and radiation tolerance.
The overall objective of our study is to reveal the mechanisms of solid solution formation as well as the incorporation of the actinides into the crystal structure of the waste matrix. A fundamental understanding of these mechanisms is of great importance with regard to the long-term stability of monazites for safe nuclear waste disposal.
(La,Eu)PO4 and due to quenching effects of high Eu-contents in TRLFS measurements Eu doped (La,Gd)PO4 monazite solid solutions were synthesized by wet chemical methods. Eu serves as surrogate for trivalent actinides. Samples were characterized by XRD, Raman, IR, EXAFS and TRLFS spectroscopies. Structural refinement of XRD data as well as a linear shift of Raman and IR bands towards higher wave numbers shows a linear dependency of lattice parameters on the Eu content according to Vegard’s law. In contrast, EXAFS analysis reveals a decrease only for the La-O distances in the first coordination shell and the first metal-metal distance, while the Eu-O local coordination remains unchanged. TRLFS investigations show that the host cation size in the monazites has very little influence on the Eu3+ incorporation into these materials, but a broadening of the excitation spectra indicate a local disordering of the crystal structure around the dopant

Nano-structured materials are important for many applications, including energy technologies. The desired structures can be created using bottom-up processes, which utilize self-assembling. By way of spinodal decomposition of a metastable phase, like SiO_x into Si and SiO₂, sponge-like networks of nanowires can be obtained. Understanding the coarsening kinetics of spinodal structures is crucial not only for bottom-up production, but also helps to increase the life-time of components like porous matrices in fuel cells, where suppression of coarsening has a huge economic impact.

Two theories on coarsening of spinodal structures exist: one assuming diffusion through the bulk [1], the other along interfaces [2]. Since orders of magnitude in both space and time have to be covered by simulations, numerical studies are quite demanding. Nevertheless, simulations are essential in studying systems containing size-inhomogeneities in initial nano-structures, where strongly accelerated coarsening is observed.

Here, a multi-GPU Kinetic Metropolis Lattice Monte-Carlo implementation, capable of atomistic simulations of phase-separation and coarsening at spatio-temporal experimental scales (billions of particles over millions of time-steps) is presented while laying focus on the above-mentioned applications.

[1] A. Chakrabarti, R. Toral, J.D. Gunton, Phys. Rev. B 39(7) 4386 (1989) suggesting a modified Lifschitz-Slyozov law: I.M. Lifshitz, V.V. Slyozov, J. Phys. Chem. Solids 19(1-2), 35-50 (1961)
[2] W.W. Mullins, J. Appl. Phys. 28(3), 333-339 (1957)

Restricted solid on solid surface growth models can be mapped onto binary lattice gases. We show that efficient simulation algorithms can be realized on GPUs either by CUDA or by OpenCL programming. We consider a deposition/evaporation model following Kardar–Parisi–Zhang growth in d+1 dimensions, related to the Asymmetric Simple Exclusion Process. Up to 100 - 400 x speedup can be achieved with respect to the serial code running on a I5 core. This permits studying disorder and aging behavior in these system.

We present current large scale, full 3D particle-in-cell simulations and studies of laser-ion acceleration utilizing highly over-dense, mass and volume limited micro targets with PIConGPU. Powered by thousands of GPGPUs on Oak Ridge's supercomputer Titan, we show early results such as the influence of the target to laser spot size and the arising acceleration regimes thereof.

The simulations show the capability of PIConGPU, a highly scalable particle-in-cell code for many-core compute architectures that allows for in-situ, real time visualization and ultra-fast computation of large systems.

Magnetic dipole strength functions have been deduced from averages of a large number of M 1 transition strengths calculated within the shell model for the nuclides 90 Zr, 94Mo, 95 Mo, and 96 Mo. An enhancement of M1 strength toward low transition energy has been found for all nuclides considered. Large M1 strengths appear for transitions between close-lying states with configurations including proton as well as neutron high-j orbits that re-couple their spins and add up their magnetic moments coherently. The M 1 strength function deduced from the calculated M 1 transition strengths is compatible with the low-energy enhancement found in (3He,3He') and (d,p) experiments. The present work presents an explanation of the experimental findings.

The Institute of Resource Ecology (IRE) is one of the eight institutes of the Helmholtz-Zentrum Dresden – Rossendorf (HZDR).
The research activities are mainly integrated into the program “Nuclear Waste Management, Safety and Radiation Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”.
Additionally, various activities have been started investigating chemical and environmental aspects of processing and recycling of strategic metals, namely rare earth elements. These activities are located in the HGF program “Energy Efficiency, Materials and Resources (EMR)”. Both programs, and therefore all work which is done at IRE, belong to the research sector “Energy” of the HGF.
The research objectives are the protection of humans and the environment from hazards caused by pollutants resulting from technical processes that produce energy and raw materials. Treating technology and ecology as a unity is the major scientific challenge in assuring the safety of technical processes and gaining their public acceptance. We investigate the ecological risks exerted by radioactive and nonradioactive metals in the context of nuclear waste disposal, the production of energy in nuclear power plants, and in processes along the value chain of metalliferous raw materials. A common goal is to generate better understanding about the dominating processes essential for metal mobilization and immobilization on the molecular level by using advanced spectroscopic methods. This in turn enables us to assess the macroscopic phenomena, including models, codes, and data for predictive calculations, which determine the transport and distribution of contaminants in the environment.

Die Mechanismen von Immobilisierungsprozessen radioaktiver Schwermetall-Ionen innerhalb von Biofilmen sind noch weitgehend unerforscht. Das liegt an der Komplexität der Biofilme, welche häufig diskrete geochemische Mikromilieus bilden, die sich vom umgebenden Milieu („Bulk Solution“) in Bezug auf dessen Biozönose (der mikrobiellen Diversität), den darin herrschenden geochemischen Bedingung (z. B. Red/Ox-Potential u./o. gelöster Sauerstoffmenge), aber auch in der Konzentration möglicher Komplexbildner (z. B. Metaboliten u./o. EPS-Komponenten) deutlich unterscheiden. Alle diese Faktoren können die Speziation der Radionuklide verändern und damit auch deren Transportverhalten. Für ein besseres Prozessverständnis zu den Wechselwirkungen von Radionukliden mit natürlichen, in Uran-kontaminierten Milieus lebende Mikroorganismen und den damit verbunden Stoffen wurde die Biozönose in Biofilmen und im Grubenwasser des ehem. WISMUT-Uranbergwerkes Königstein nach klassischen mikrobiologischen- und molekularbiologischen Methoden bestimmt. Aus einem Vergleich der Chemie im Biofilm mit der Chemie der umgebenden Lösung wird der Einfluss der Biofilme auf das Migrationsverhalten von Radionukliden in der Natur beurteilt. Die Identifizierung und Quantifizierung von Prokaryoten erfolgte u. a. mit der CARD FISH Methode. Die selektive Visualisierung der EPS-Komponenten in der Matrix der Biofilme wurde mit Hilfe der Konfokalen Laser Scanning Mikroskopie (CLSM) bewerkstelligt.
Zur Untersuchung der Speziation von fluoreszierenden Schwermetall-Ionen wie U(VI) kam die zeitaufgelöste, laser-induzierte Fluoreszenzspektroskopie (TRLFS) zum Einsatz. Um diese Methode auch im mikroskopischen Bereich anwenden zu können, wurde sie weiter zum CLSM hin entwickelt: Da ein 80-MHz-MaiTai-Laser zur Verfügung stand, wurde durch im kHz-Bereich alternierendes Beugen des Anregungslaserstrahls von der Probe weg (und wieder zu ihr hin) mittels akusto-optischem Modulator (AOM) eine quasi-gepulste Laseranregung im kHz-Bereich erreicht. Durch Einbindung von Frequenzvervielfachern („Harmonixx“ von APE Berlin und „Inspire“ von Spectra-Physics) konnte so eine gepulste Anregung innerhalb eines breiten Wellenlängenbereiches (ca. 230-1090 nm) ermöglicht werden. Für die Auswertung des als äußerst schwach zu erwartenden Fluoreszenzsignales (entsprechend des mikroskopisch kleinen Anregungsraumes) wurde die Time-Correlated Single-Photon Counting Methode (TCSPC) – auch „zeitbezügliche Einzelphotonenzählungs-Methode“ – an das Laser-Anregungssystem angepasst. Die Fluoreszenzlebenszeitkurve des Fluoreszenzsignals von U(VI) Species, die sich an der Oberfläche von den Protozoen Euglena Mutabilis befanden, konnte z. B. auf diese Art mit Hilfe der TCSPC ermittelt werden.

Graphene, the two-dimensional lattice of sp2-hybridized carbon atoms, has a great potential for future electronics, in particular for opto-electronic devices. The carrier relaxation dynamics, which is of key importance for such applications, is in the main focus of this thesis. Besides a short introduction into the most prominent material properties of graphene and the experimental techniques, this thesis is divided into three main parts.
The investigation of the carrier relaxation dynamics in the absence of a magnetic field is presented in Chapter 3. In the first experiment, the anisotropy of the carrier excitation and relaxation in momentum space was investigated by pump-probe measurements in the near-infrared range. While this anisotropy was not considered in all previous experiments, our measurements with a temporal resolution of less than 50 fs revealed the polarization dependence of the carrier excitation and the subsequent relaxation. About 150 fs after the electrons are excited, the carrier distribution in momentum space gets isotropic, caused by electron-phonon scattering. In a second set of two-color pump-probe experiments, the temperature of the hot carrier distribution, which was obtained within the duration of the pump pulse (about 200 fs), could be estimated. Furthermore, a change in sign of the pump-probe signal can be used as an indicator for the Fermi energy of different graphene layers. Pump-probe experiments in the far-infrared range in reflection and transmission geometry were performed at high pump power. A strong saturation of the pump-induced transmission was found in previous experiments, which was attributed to the pump-induced change in absorption. Our investigation shows the strong influence of pump-induced reflection at long wavelengths, as well as a lot smaller influence of the saturation of the pump-induced change in absorption. At a high pump power, the increase of the reflection exceeds the change in absorption strongly, which leads to negative pump-probe signals in transmission geometry.
In Chapter 4, investigations of the carrier dynamics of graphene in magnetic fields of up to 7T are presented. Even though the optical properties of Landau-quantized graphene are very interesting, the carrier dynamics were nearly unexplored. A low photon energy of 14meV allows the investigation of the intraband Landau-level (LL) transitions. These experiments revealed two main findings: Firstly, the Landau quantization strongly suppresses the carrier relaxation via optical-phonon scattering, resulting in an increased relaxation time. Secondly, a change in sign of the pumpprobe signal can be observed when the magnetic field is varied. This change in sign indicates a hot carrier distribution shortly after the pump pulse, which means that carrier-carrier scattering remains very strong in magnetic fields. In a second set of pump-probe measurements, carried out at a photon energy of 75meV, the relaxation dynamics of interband LL transitions was investigated. In particular, experiments on the two energetically degenerate LL transitions LL−1 ) LL0 and LL0 ) LL1 showed the influence of extremely strong Auger processes.
An ultrafast and extremely broadband terahertz detector, based on a graphene flake, is presented in the last chapter of this thesis. To couple the radiation efficiently to the small flake, the inner part of a logarithmic periodic antenna is connected to it. With a rise time of about 50 ps in a wavelength range of 9 μm to 500 μm, this detector is very interesting to obtain the temporal overlap in two-color pump-probe experiments with the free-electron laser FELBE. Furthermore, the importance of the substrate material, in particular for the high-speed performance, is discussed.

The Tb₃Ru₄Al₁₂ compound (hexagonal crystal structure) having a distorted kagome net of the Tb atoms is studied on a single crystal by measurements of magnetization, specific heat and electrical resistivity. The system is an antiferromagnet with the Néel temperature T_N = 22 K. A substantial magnetic anisotropy is observed that persists at least up to 60 T. Tb₃Ru₄Al₁₂ displays field-induced magnetic phase transitions: one along [100] and [120] and two along the [001] axis. The transitions are accompanied by sharp peaks in magnetoresistance and subsequently lead to a large negative effect in it, −20% in the longitudinal and −40% in the transverse geometry. The peaks are explained by changes in conduction electron spectra at the transitions due to the interaction between the conduction electrons and localized magnetic moments. The large negative effect suggests field-induced magnetic phases with a reduced period as compared to zero field.

The compact neutron-time-of-flight facility nELBE at the superconducting electron accelerator ELBE of Helmholtz-Zentrum Dresden-Rossendorf is being rebuilt and extended with a low-background experimental hall. The neutron radiator consists of a liquid lead circuit without additional neutron moderators. The useful neutron spectrum extends from some tens of keV to about 10 MeV. nELBE is intended to deliver cross section data of fast-neutron nuclear interactions e.g. for the transmutation of nuclear waste and improvement of neutron physical simulations of innovative nuclear systems. Before the extension of the facility, the photon production cross section of 56 Fe was measured with an HPGe detector and the inelastic neutron scattering cross section to the first few excited states in Fe-56 was determined. The neutron total cross sections of Au and Ta were determined in the energy from 200 keV to 7 MeV in a transmission experiment.

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In microbeam measurements on inhomogeneous samples large variations in count-rate can occur. These variations result in variations in deadtime that have to be used to correct elemental distribution maps. However, the deadtime is usually not available on a pixel by pixel basis. In this work, a simple model is proposed to calculate the deadtime for each pixel. Measurements to determine the deadtime per event, needed in the model, are presented and the deadtime corrections are presented for real samples.

Superconducting Pr₂CuO_x, x similar or equal to 4 films with T' structure and a T_c of 27 K have been investigated by millimeter-wave transmission and broadband (infrared-to-ultraviolet) reflectivity measurements in the normal and superconducting state. The results obtained by both experimental methods show a consistent picture of the superconducting condensate formation below T_c. An Eliashberg analysis of the data proves d-wave superconductivity and unitary-limit impurity scattering of the charge carriers below T_c. The derived electron-exchange boson interaction spectral function I²chi(omega) shows only marginal changes at the superconducting transition with the mass enhancement factor lambda, the first inverse moment of I²chi(omega), being equal to 4.16 at 30 K and to 4.25 at 4 K.

A comparative study of nitrogen depth profiles in low energy ion implantation nitrided austenitic stainless steel 1.4301 by glow discharge optical emission spectroscopy (GDOES), secondary ion mass spectrometry (SIMS) and nuclear reaction analysis (NRA) is presented. All methods require calibration either from reference samples or known scattering or reaction cross sections for the nitrogen concentration, while the methods producing a sputter crater – SIMS and GDOES – need additional conversion from sputter time to depth. NRA requires an assumption of material density for a correct conversion from the ‘natural’ units inherent to all ion beam analysis methods into ‘conventional’ depth units. It is shown that a reasonable agreement of the absolute concentrations and very good agreement of the layer thickness is obtained. The observed differences in broadening between the nitrogen distribution near the surface and the deeper region of the nitrided layer–steel interface are discussed on the basis of surface contaminations, surface roughening and energy straggling effects.

Particle-in-Cell (PIC) codes are a ubiquitous tool to study laser-plasma physics in a fully relativistic environment. Theoretical models for plasma based accelerators and corresponding experiments, as planned by the HIBEF collaboration (XFEL), depend dramatically on the ability to precisely predict the complex processes inside of targets.

Unfortunately, basic atomic processes like the ionization dynamics of solid foil target in ultra-high fields of modern short-pulse laser systems in the PW class are not covered by the basic PIC algorithm. This talk shows ways to introduce the microscopic ionization dynamics inside the targets in a self-consistent and rigorous way. Combined with modern compute hardware such as GPUs and manycore systems in general, this paves the road to a new quality of multi-physics simulations with ab-initio modeling of atomic processes in strong laser fields.

The dynamics of heating and ionization, which determines the crucial plasma parameters such as temperature, free electron density and so on, is one of the fundamental issues in the realm of ultra-short relativistic laser-solid target interactions. We present our work on investigation of heating and ionization dynamics in solid copper target irradiated by ultra-short intense laser using two dimensional particle-in-cell simulations. The simulation results show that the bulk electron temperature is very sensitive to the initial preplasma scale length. By varying the preplasma scale length from 0 to 0.1 λ_0, the bulk electron temperatures in the interest of region increase from ~26 eV to ~109 eV, which agrees very well with the theory based on Ohmic heating mechanism by treating the return current correctly. The bulk electron heating is finally translated into bulk ionization, which leads to the average Cu ion charge state increasing from ~4.3 to ~10.7.

Neptunium (Np) is one of the most important components of nuclear waste to consider for the long-term safety assessment of nuclear waste repositories, due to the increasing enrichment through decay of Am-241, the long half-life and the high toxicity of Np-237. Hence, great attention is attracted to its geochemistry [1]. The molecular processes occurring at the solid-water interfaces present in the biogeosphere, strongly affect its migration [2]. Components of geological materials, such as metal oxides and hydroxides with a widespread environmental presence, high sorption capacity and tendency to form coatings on mineral surfaces, play an important role in regulating the Np mobility [3].
For a better understanding of the molecular events occurring at the mineral surfaces, x-ray absorption and vibrational spectroscopies are useful tools for the in-situ identification of actinyl surface species. In addition, time-resolved measurements provide kinetic information on the surface reactions [4].
In this work, Np(V) sorption on the oxyhydroxides of Fe, Mn, and Al is investigated by a combination of in-situ ATR FT-IR and EXAFS spectroscopies under a variety of environmentally relevant sorption conditions. By comparing Np(V) surface complexation reactions on hematite, magnetite, birnessite, and corrundum a very similar sorption behavior, namely the formation of one single inner-sphere complex can be elucidated. The spectroscopic results improve the geochemical transport modeling of Np(V) macroscopic data [4].

[1] Kaszuba, J.P. et al. (1999) Environ. Sci. Technol. 33, 4427-4433.
[2] O'Day, P.A. (1999) Rev. Geophys. 37, 249-274.
[3] Tochiyama, O. et al. (1996) Radiochim. Acta 73, 191-198.
[4] Müller, K. et al. (2015) Environ. Sci. Technol. 49, 2560-2567.

U(VI) biosorption experiments were performed using isolated Acidovorax facilis cell. From TRLFS measurements it can be concluded that phosphoryl groups are the main binding sites for uranyl, located in the lipopolysaccharide (LPS) unit in the outer membrane by Gram-negative Acidovorax facilis cells. In addition, EF-TEM/EELS studies provide microscopically and spectroscopically evidence of U sorbed at the outer membrane of Acidovorax facilis cells by showing high electron density and U ionization intensity peaks. The results support the TRLFS measurements and contribute to a better understanding of the binding mechanisms of U(VI) on Acidovorax facilis cells.

Hohe Magnetfelder und Supraleitung vertragen sich üblicherweise nicht: Das Magnetfeld favorisiert parallel ausgerichtete Elektronenspins, während die Supraleitung Cooper-Paare mit antiparallelen Spins voraussetzt. Daher sollte bei ausreichend großen Feldern die Supraleitung zusammenbrechen. Wie Fulde und Ferrell sowie Larkin und Ovchinnikov bereits 1964 vorhergesagt haben, können räumlich getrennte supraleitende sowie magnetisch geordnete Bereiche aber auch bei noch höheren Magnetfeldern koexistieren.

A new magnetic phase transition, which we assign to the separation of two different spiral phases, has been observed by ultrasound studies below the Néel temperature (T_N = 7.8 K) in the frustrated antiferromagnet CdCr₂O₄. This transition renormalizes the velocity and amplitude of the transverse acoustic mode c_T whereas the longitudinal mode c_L is not affected. The specific heat does not show any significant change in the entropy at this transition. Furthermore, in an applied magnetic field, the mode c_T exhibits extended metastable magnetostructural states neighboring the one-half magnetization plateau in CdCr₂O₄. By applying an exchange-striction model we can quantitatively describe the field dependence of the sound velocity below and above the one-half magnetization plateau.

We have studied the magnetocaloric effect (MCE) in the shape-memory Heusler alloy Ni₅₀Mn₃₅In₁₅ by direct measurements in pulsed magnetic fields up to 6 and 20 T. The results in 6 T are compared with data obtained from heat-capacity experiments. We find a saturation of the inverse MCE, related to the first-order martensitic transition, with a maximum adiabatic temperature change of ΔT_ad= - 7 at 250 K and a conventional field-dependent MCE near the second-order ferromagnetic transition in the austenitic phase. The pulsed magnetic field data allow for an analysis of the temperature response of the sample to the magnetic field on a time scale of 10 to 100 ms, which is on the order of typical operation frequencies (10–100 Hz) of magnetocaloric cooling devices. Our results disclose that in shape-memory alloys, the different contributions to the MCE and Hysteresis effects around the martensitic transition have to be carefully considered for future cooling applications.

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The successful prediction of gas holdups in (slurry) bubble columns is very important for both the design and scale-up of these reactors. In the literature hitherto there are only few reliable empirical gas holdup correlations (mainly for gas-liquid bubble columns). In this work, a new approach has been developed for predicting the gas holdups at ambient conditions in gas-liquid bubble columns (0.095 and 0.102 m in ID) operated with 21 pure organic liquids, 17 liquid mixtures and tap water. The same approach was also applied for prediction of gas holdups in a slurry bubble column (0.095 m in ID) operated with 7 three-phase systems under ambient conditions.
The new model for gas holdup prediction in (slurry) bubble columns is based on the theoretical calculation of the gas-liquid interfacial area: a=6ɛg/ds. This correlation is explicitly valid for rigid spherical bubbles. In the case of slurry bubble columns, an empirical correlation developed by Schumpe et al. (1987) for the interfacial area prediction is frequently used. When both correlations are set equal, then the theoretical gas holdup can be calculated provided that one knows how to estimate the Sauter-mean bubble diameter ds and the effective viscosity μeff. The same approach was also applied to gas-liquid bubble columns. However, the interfacial areas were estimated by the empirical correlation of Akita and Yoshida (1974).
In the above-mentioned approaches the estimation of the Sauter-mean bubble diameters ds was based on empirical correlations (Wilkinson et al. (1994) for bubble columns and Lemoine et al. (2008) for slurry bubble columns).
For given gas-liquid-solid system, gas distributor layout and column diameter, the ds value is a function of both the superficial gas velocity and gas holdup (1-ɛg)^1.56 (Lemoine et al., 2008). Following the above-described approach, the ɛg value was calculated (based on a trial and error method) from the ratio ɛg/(1-ɛg)^1.56. The obtained ɛg value in this way was multiplied by a correction factor (a function of Eӧtvӧs number Eo) since the formed bubbles under the tested experimental conditions were oblate ellipsoidal (i.e. non-spherical). In the case of slurry bubble columns, the Eo number was based on the slurry density ρSL.
Following the above-described approach in two-phase bubble columns, it was found that for given gas-liquid system, column diameter and Ug value the theoretical gas holdup could be estimated from the simplified correlation: ɛg^0.13=const. Then the obtained ɛg value was also multiplied by a correction factor (a function of Eo). So, the objective of this part of the research work was to find the best expressions for the correction factors in two-phase and three-phase bubble columns, which fit successfully the experimental gas holdups ɛg.
The determination of the scale of liquid mixing in the main hydrodynamic regimes of bubble column operation is also of essential importance for their design and scale-up. In this context, a new method (and correlation) has been proposed by Kawase and Tokunaga (1991) for the determination of the mixing length (L). The parameter L characterizes the degree and scale of mixing. It can be also associated with the distance over which a turbulent eddy retains its identity.
In this work, a new definition of entropy (E) has been developed on the basis of gas holdup time series data measured by a conductivity wire-mesh sensor in an air-water bubble column (0.15 m in ID). The new entropy has been estimated by means of multiple reconstructions of the signal. It was found that in the Ug range from 0.034 to 0.101 m/s (see Fig. 2), the entropy (E) decreased monotonously and it was correlated to the mixing length L (a function of both column diameter Dc and Ug^−0.38). Secondly, a newly defined information entropy (IE) has been also extracted from the gas holdup fluctuations and correlated to the mixing length in almost the same Ug range (0.022−0.101 m/s).
In a previous publication (Nedeltchev et al., 2014), it was shown that the Kolmogorov entropy (KE) and a new statistical parameter (called “maximum number of signal’s visits in a region” Nvmax) were capable of identifying the range of applicability (0.034≤ Ug≤0.112 m/s) of the mixing length concept. Another statistical parameter F (average/(3×average absolute deviation)) was also introduced by Nedeltchev and Schubert (2015) for validating the range of applicability of the mixing length concept. It was also found that the F index is a function of the mixing length L in the Ug range from 0.034 to 0.112 m/s.
In this work, a comparison of the results obtained by the five different parameters (E, IE, KE, Nvmax and F) is performed. Most of them (except for KE) are new and such a comparison has not been reported in the literature hitherto. It revealed that the determination of the boundaries of the transition flow regime and the range of applicability of the mixing length concept depends to some extent on the parameter used. Based on the above-mentioned parameters it was found that the mixing length concept was applicable only in the transition flow regime. Such a result has not been reported in the previous papers (for instance, in Kawase and Tokunaga, 1991).

Colloids and nanoparticulate matter play an important role in the environment since they can act as carriers for (toxic) compounds and thereby enhance migration of substances that might normally be immobile under the given environmental conditions. The carrier properties of colloidal clay particles, humic substances and silica actinide colloids may play an important role in nuclear waste repositories. However, monitoring of these colloids in complex systems such as geological formations or groundwater is nearly impossible using conventional methods, especially at environmentally relevant concentrations and the high background load of other colloids or dissolved species of the same element. This obstacle can be overcome by the use of radiolabelling, which may be of crucial value in enabling such research.
We have developed various methods of introducing radiotracers into natural organic colloids such as humic or fulvic acids [1] and some of the most common technical nanoparticles, such as Ag⁰ [2], carbon and TiO₂ nanoparticles [3]. Current studies are dealing with radiolabelling of CeO₂ and quantum dots.
Five different approaches can be pursued in the radiolabelling of colloids or nanoparticles:
(1) Radiosynthesis – the synthesis of a compound using radioactive material
(2) Radiochemistry – the binding of a radioactive tracer to an existing compound
(3) In-diffusion – the in-diffusion of radioisotopes into existing particles
(4) Direct Activation – the activation of existing particles by proton irradiation
(5) Recoil labelling – the implantation of radionuclides into an existing particles using the recoil of a nuclear reaction

Radiosynthesis can be used to produce custom-made radiolabelled nanoparticles provided a suitable radiotracer is available. If the labelling is isotopic no difference in properties compared to non-radioactive particles are expected. We used this method to produce radiolabelled [^105/110mAg]Ag nanoparticles.
Binding a radiotracer to a compound is a way of radiolabelling existing commercial or natural materials by a suitable radiochemical protocol. Carbon nanotubes and humic acids were successfully labelled with radioactive Iodine following the one-pot Iodogen method to yield [^124/125/131I]CNTs and [¹²⁵I]humic acid. No significant change in properties was detected compared to the original compounds.
Commercial TiO₂ and Ag⁰ nanoparticles were labelled by the in-diffusion of isotopic radionuclides into surface defects and lattice structure at elevated temperatures. The resulting [^110mAg]Ag⁰ and [^44/45Ti]TiO₂ nanoparticles showed no change in properties and the radiolabel proved to be stable under various conditions.
If a cyclotron is available, nanoparticles can be radiolabelled by activation via proton irradiation. The proton irradiation causes a nuclear reaction in the nanopowder producing the radiolabel inside the particles. Commercial TiO₂ particles were labelled with ⁴⁸V via a ⁴⁸Ti(p,n)⁴⁸V reaction.
If no suitable radiotracers/nuclear reactions are available for the above described methods, nanoparticles can be labelled utilising the recoil of a nuclear reaction to implant a radiotracer. Typically a mixture of a lithium compound and the to-be-labelled particles is irradiated with protons. The nuclear reaction ⁷Li(p,n)⁷Be produces ⁷Be which is implanted in the nanoparticles due to the recoil of the nuclear reaction. [⁷Be]MWCNT were produced successfully.
Table 1 shows the results for radiolabelling of particles. The described methods are adaptable for a wide range of other nanoparticles or colloids. The so-labelled nanoparticles can be detected at minimal concentrations well in the ng/L range even with a background of the same element and without complicated sample preparations necessary. In the research area of radioactive waste repositories the radiolabelling of humic substances, clay colloids and actinide silica colloids may be of particular interest.

Table 1: Comparison of the radiolabelling procedures and the resulting radiolabelled NP analysis.
Radiolabeling procedure Resulting NP Half-life of the radionuclide Activity concentration [MBq/mg] Detection limit [ng/L]
Radiosynthesis [^110mAg]Ag⁰ 250 d 1.5 33
[¹⁰⁵Ag]Ag⁰ 41.3 d 0.65 77

Radiochemistry [¹²⁴I]CNT 4.2 d 8.0 6
[¹²⁵I]CNT 59.4 d 19.9 2
[¹³¹I]CNT 8.0 d 3.7 14

In-Diffusion [^110mAg]Ag 250 d 1 50
[⁴⁴Ti]TiO₂ 60.4 a 0.01 5000
[⁴⁵Ti]TiO₂ 3.08 h 135 0.5

Direct Activation [⁴⁸V]TiO₂ 15.97 d 3.7 14
[⁷Be]MWCNT 53.29 d 0.041 1000

Recoil Labelling [⁷Be]TiO₂ 0.3 170
[⁷Be]SiO₂ [4] 53.29 d 1.4 36
[⁷Be]MWCNT 0.055 1000
References:
[1] Franke, K., Patt, J.T., Kupsch, H., Warwick, P.: Radioiodination of Humic Substances via Azocoupling with 3-[¹²⁵I]Iodoaniline. Environ Sci Technol 42(11) (2008) 4083 - 4087.
[2] Hildebrand, H., Franke, K.: A new radiolabeling method for commercial Ag⁰ nanopowder with ^110mAg for sensitive nanoparticle detection in complex media. J Nanopart Res 14 (2012) 1142.
[3] Hildebrand, H., Schymura, S., Holzwarth, U., Gibson, N., Dalmiglio, M., Franke, K.: Strategies for radiolabeling of commercial TiO₂ nanopowder as a tool for sensitive nanoparticle detection. J Nanopart Res, submitted.
[4] Holzwarth, U., Bellido, E., Dalmiglio, M., Kozempel, J., Cotogno, G., Gibson, N.: ⁷Be-recoil radiolabelling of industrially manufactured silica nanoparticles. J Nanopart Res 16 (2014) 2574.

The flow induced by a single-phase alternating magnetic field (AMF) is studied mainly numerically, and by two preliminary experiments of quite different size. For validation, the well known dependence of the characteristic velocity on magnetic induction is reproduced experimentally and in the simulations. It is shown that the flow structure depends drastically on the frequency of the AMF. An investigation of the change of the characteristic velocity with frequency results in a quantitative difference of flows in an AMF compared to rotating and travelling magnetic fields.

In a bubble column (0.15 m in ID) operated with an air-water system, a new entropy was extracted from gas holdup fluctuations measured by conductivity wire-mesh sensor. It was capable of identifying three transition velocities Utrans at 0.045, 0.089 and 0.112 m/s. In a different bubble column (0.162 m in ID) operated with an air-therminol LT system at ambient conditions, the new entropy was extracted from photon count time series measured by computed tomography. Three Utrans values were also identified at 0.03, 0.08 and 0.1 m/s. The information entropies yielded similar results.
Based on the new entropy results it can be concluded that the type of fluid and gas sparger used do not affect significantly the second and third Utrans values. There is an effect on the first Utrans value which can be explained with the strong gas maldistribution in the case of the bubble column operated with an air-water system.

A prototype composed of four resistive plate chamber layers has been exposed to quasi-monoenergetic neutrons produced from a deuteron beam of varying energy (300 to 1500 AMeV) in experiment S406 at GSI, Darmstad, Germany. Each layer, with an active area of about 2000 × 500 mm2, is made of modules containing the active gaps, all in multigap construction. Each gap is defined by 0.3 mm nylon mono-filaments positioned between 2.85 mm thick float glass electrodes. The modules are operated in avalanche mode with a non-flammable gas mixture composed of 90% C2H2F4 and 10% SF6. The signals are readout by a pick-up electrode formed by 15 copper strips (per layer), spaced at a pitch of 30 mm, connected at both sides to timing front end electronics. Measurements of the time of flight jitter of neutrons, in the mentioned energy range, point to a contribution of the resistive plate chamber in the order of 150 ps, independent of the neutron energy.

Tunnel magnetoresistance was measured in CoFeB-MgO-based double-barrier magnetic tunnel junctions. Variation of the sputtering power density is used to control the relative B content of the middle electrode. Magnetoresistance ratios in both upper and lower junctions are suppressed with respect to the single-barrier case. While the lower junction shows a saturation of the magnetoresistance as a function of high temperature annealing for all sputtering power densities, the upper junction exhibits an increase in magnetoresistance as a function of annealing temperature with higher values for higher sputtering power density. The suppression of high magnetoresistance is attributed to a lack of strong crystallisation in the middle electrode, which is confirmed by cross-section transmission electron microscopy. Slight crystallisation of the middle electrode is achieved at the highest sputtering power density despite that fact that boron diffusion is suppressed due to the adjacent MgO tunnel barriers. Optimal deposition and post annealing conditions resulted in magnetoresistance values of 140 % and 80 % for the upper and lower junctions, respectively.

A prototype composed of four resistive plate chamber layers has been exposed to quasi-monoenergetic protons produced from a deuteron beam of varying energy (200 to 800 AMeV) in experiment S406 at GSI, Darmstadt, Germany. The aim of the experiment is to characterize the response of the prototype to protons in this energy range, which deposit from 1.75 to 6 times more energy than minimum ionizing particles. Each layer, with an active area of about 2000 × 500 mm2, is made of modules containing the active gaps, all in multigap construction. Each gap is defined by 0.3 mm nylon mono-filaments positioned between 2.85 mm thick float glass electrodes. The modules are operated in avalanche mode with a non-flammable gas mixture composed of 90% C2H2F4 and 10% SF6. The signals are readout by a pick-up electrode formed by 15 copper strips (per layer), spaced at a pitch of 30 mm, connected at both sides to timing front end electronics. Results show an uniform efficiency close to 100% along with a timing resolution of around 60 ps on the entire 2000 × 500 mm2 area.

In order to elucidate the separation mechanism of metals in chemical processes, understanding of the chemical species formed in the processes is fundamental particularly on a molecular level. Structural characterisation is of particular importance to understand the interaction between the metal of interest and separating reagents (i.e. ligands), which would be also beneficial to further improve the efficiency of separation processes and/or to develop new separation ligands. This talk will focus on the development of selective ligands for the separation of f-elements, as well as the coordination chemistry of f-elements with the developed ligands based on several X-ray spectroscopic techniques.

Amorphous, polycrystalline anatase and epitaxial anatase TiO2 films have been implanted with 5 at. % Co+. The magnetic and structural properties of different microstructures of TiO2:Co, along with the local coordination of the implanted Co atoms within the host lattice are investigated. In amorphous TiO2:Co film, Co atoms are in the (II) oxidation state with a complex coordination and exhibit a paramagnetic response. However, for the TiO2:Co epitaxial and polycrystalline anatase films, Co atoms have a distorted octahedral (II) oxygen coordination assigned to a substitutional environment with traces of metallic Co clusters, which gives a rise to a superparamagnetic behavior. Despite the incorporation of the implanted atoms into the host lattice, high temperature ferromagnetism is absent in the films. On the other hand, it is found that the concentration and size of the implantation-induced nanoclusters and the magnetic properties of TiO2:Co films have a strong dependency on the initial microstructure of TiO2. Consequently, metallic nanocluster formation within ion implantation prepared transition metal doped TiO2 can be suppressed by tuning the film microstructure.

Ion irradiation induced modifications of the thermomagnetic properties of equiatomic FeRh thin films have been investigated. The application of 20 keV Ne+ ions at different fluencies leads to broadening of the antiferromagnetic to ferromagnetic phase transition as well as a shift towards lower temperatures with increasing ion fluence. Moreover, the ferromagnetic background at low temperatures generated by the ion irradiation leads to pronounced saturation magnetization at 5 K. Complete erasure of the transition, i.e. ferromagnetic ordering through the whole temperature regime was achieved at a Ne+ fluence of 3E14 cm-2. It does not coincide with the complete randomization of the chemical ordering of the crystal lattice.

Helium Ion Microscopy is known for its surface sensitivity and high lateral resolution. Here, we present results of a Helium Ion Microscopy based investigation of a surface confined alloy of Ag on Pt(111). Based on a change of the work function of 25 meV across the atomically flat terraces we can distinguish Pt rich from Pt poor areas and visualize the single atomic layer high steps between the terraces. Furthermore, dechanneling contrast has been utilized to measure the periodicity of the hcp/fcc pattern formed in the 2 ML thick Ag alloy layer. A periodicity of 6.65 nm along the $\langle\overline{11}2\rangle$ surface direction has been measured. In terms of crystallography a hcp domain is obtained through a lateral displacement of a part of the outermost layer by $1/\sqrt{3}$ of a nearest neighbour spacing along $\langle\overline{11}2\rangle$. The findings are perfectly in line with results obtained with Low Energy Electron Microscopy and Phase Contrast Atomic Force Microscopy.

In this paper, a clear and structured economic model is introduced to illustrate complex past and future developments of the market for rare earth elements (REE). The model consists of a sequence of four supply and demand models that give explanations how the mining and separation step of the REE value chain could concentrate in China. Furthermore, the sequence allows giving a coherent scenario for the future developments of the REE market. According to this scenario, the market could transform into an at least oligopoly due to a growing market demand. The validity of this scenario is discussed and evaluated from the perspective of western countries, investors and China. Additionally, a scenario, based on the models, of a propagating monopoly along the value chain will be discussed. Finally, suggestions are made for western governments to promote the transformation and lead it to a positive outcome.

Besides conventional low efficiency lithographic techniques broad ion beam irradiation is a simple and potentially mass productive technique to fabricate nanoscale patterns on various semiconductor surfaces. The main drawback of this method is that the irradiated semiconductor surfaces are amorphized, which strongly limits the potential application of these nanostructures in electronic and optoelectronic devices. In this work we report that high-quality crystalline nanostructure patterns are formed on Ge surfaces via Ar+ irradiation at elevated temperatures.
This pattern formation process resembles the pattern formation in homoepitaxy. Therefore, the process is discussed based on a "reverse epitaxy" mechanism.

In Germany salt rock and clay are considered as potential host rock for the final repository of radioactive waste in deep geological formations. Both possibilities have in common that high saline conditions can occur. In clay deposits of Northern Germany pore water salt concentrations of 4.3 M were measured [1] and in salt rock the salt concentration is up to saturation. Despite these extreme environments some microbes are able to survive. To date little is known about the interactions of halophilic microorganisms with actinides and hence to the migration behavior. But for the safety assessment of the final repository it is important to know the impact of indigenous microorganisms. Microbes can interact with actinides in different ways [2]. Within this study, the sorption of uranium on the cell surface (so called biosorption) of Halobacterium noricense DSM 15987 cells was studied. This halophilic archaeum was chosen due to its worldwide occurrence in salt rock [3]. The reference strain was isolated in an Austrian salt mine [4] and similar species occurred also in the Waste Isolation Pilot Plant (WIPP, Carlsbad, New Mexico, USA) [3].
Biosorption studies were undertaken at pH 6.0 and a NaCl concentration of 3.0 M in dependence of uranium concentration, time and temperature. The uranium content in the supernatant after sorption was measured with ICP-MS (Inductively Coupled Plasma Mass Spectrometry). Both, supernatant and cell pellet, were analyzed with TRLFS (Time-resolved Laser-induced Fluorescence Spectroscopy) to get information about the formed complexes. Furthermore the cells were analyzed with Infrared Spectroscopy.
The results demonstrated that independent of the uranium concentration (10 – 120 µM) around 90 % of the added uranium was sorbed by the cells at room temperature. A time-dependent sorption study showed that this maximal sorption was reached after an incubation time of 42 h. A slightly faster sorption of added uranium could be seen at higher temperatures. Particularly at 50 °C, the maximal sorption was already reached after 24 h. In general, the obtained sorption curve indicated a two-step binding process of added uranium with a fast step within the first hours and a second slower one. For a uranium concentration of 100 µM the metal sorption rate of 37.5 ± 0.7 mg U(VI) per 1 g dry biomass of Halobacterium noricense DSM 15987 was determined .
Interestingly, with increasing time, uranium concentration and temperature the cells began to form agglomerates. Live/Dead staining (LIVE/DEAD® Bac LightTM Bacterial Viability Kit L7012, Molecular Probes) of cells after the biosorption with uranium showed that nearly all single cells were dead whereas agglomerated cells were alive. One conclusion is that this process is a kind of stress response to protect the cells themselves from environmental challenges.
The characterization of the formed cell-uranium-complexes with TRLFS indicated that uranium was bound to cellular carboxylic groups. This can be seen by comparing with literature spectra [5]. The obtained lifetimes of the uranyl complexes differed from those due to the quenching effect of the high chloride concentration to uranium luminescence. The binding of uranium to the carboxylic groups of the cell could be also verified with Infrared Spectroscopy.

[1] J. Larue, VerSi Endlagerung im Tonstein, Abschlussbericht 3607R02538 (2010).
[2] K. Morris, et al., Interactions of microorganisms with radionuclides 2, 101 (2002).
[3] J. S. Swanson, et al., Status report Los Alamos National Laboratory (2012).
[4] C. Gruber, et al., Extremophiles 8, 431 (2004).
[5] M. Vogel, et al., Sci. Total Environ. 409, 384 (2010).

We investigate the coherent precessional motion of the magnetic moment in the canted antiferromagnetic YFeO3 single crystal after excitation by the transient magnetic field of an ultra-short THz pulse. Time-resolved measurements of the magneto-optical response in the presence of external magnetic fields confirm the exclusive magnetic origin of the interaction between THz pulse and the spin system.. By tuning the spectral component of the input THz pulse around the quasi-ferromagnetic mode located near 0.3 THz, we have experimentally verified that the THz control of the spin state requires resonant excitation. We could confirm these results from the simulation based on the Landau-Lifshitz-Gilbert equation with two sub-lattice model for the canted antiferromagnet. Furthermore, we demonstrate that the spin state can be switched all-optically on a picosecond timescale using THz pulses of square and oscillating shapes. Whereas the oscillating THz pulse with a spectral component resonant with the magnetic excitations is necessary for an efficient magnetization switching, we study the possibility for a further reduction of the necessary THz field strength by examining influences of variations in the anisotropy energy and Dzyaloshinskii-Moriya interaction upon the switching behaviors.

Two-phase flows are regularly involved in the heat and mass transfer of industrial processes. To ensure the safety and efficiency of such processes, accurate predictions of the flow field and phase distribution by means of Computational Fluid Dynamics (CFD) are required. Direct Numerical Simulations (DNS) of large-scale two-phase flow problems are not feasible due to the computational costs involved. Therefore the Euler-Euler framework is often employed for large-scale simulations which involves macro-scale modelling of the turbulent shear stress and the interphase momentum transfer.
As a long term objective, the research activities at Helmholtz-Zentrum Dresden - Rossendorf (HZDR) pursue the development of general models for two-phase flows which are based on first principles and include less empiricism. Part of this effort is focused on the development of an algebraic interfacial area density model (AIAD) [1,2] which enables the simulation of two-phase flows with general morphologies including bubble, droplet and stratified flow regimes with the two-fluid approach.
In this work a short overview of the AIAD model is given and recent developments are presented.
The modelling of the interfacial drag in free surface flows is of particular interest and subject to ongoing research. Apart from empirical correlations which are limited to certain flow regimes, different models have been developed for the local computation of the interfacial drag coefficient [3,4]. In the AIAD model the drag model given by Höhne et al. [3] is used. It has recently been subject to modifications which are presented and validated as a part of this study.
Furthermore, special attention is paid to the turbulence treatment at the phase boundary of free surface flows. A model for the damping effect on the turbulent fluctuations in the near interface region as proposed in [1] is validated in this work.
Model validation is performed by means of simulations of horizontal stratified two-phase flow with the Euler-Euler two-fluid approach and the results are compared to experimental data given by Stäbler [5].

The ionosphere is the upper part of the atmosphere where sufficient free electrons exist to affect the propagation of radio waves. Typically, the ionosphere extends from about 50 -1000 km and its morphology is mainly driven by solar radiation, particle precipitation and charge exchange. In the last decade Global Navigation Satellite Systems (GNSS, e.g. GPS and GLONASS) measurements have become one of the major tools for ionospheric sounding enabling the derivation of the total electron content (TEC) along a satellite to receiver ray path.

Our interest is the reconstruction of the ionosphere's electron density in order to mitigate the ionospheric delay in applications such as GNSS positioning and satellite-based radar imaging. Following the ionosphere's behaviour we establish a non-stationary spatial covariance model of the electron density, where its parameters are estimated in a maximum likelihood approach. Henceforth the integral GNSS TEC measurements and a non-stationary trend model are incorporated. Based on the derived spatial covariance the electron density is estimated by kriging with linear functionals.

Geometallurgy is concerned with optimal mining and processing decisions based on a quantitative modeling of the ore micro fabric and the processes. The optimal choice is then inferred from a geostatistical model and a processing model (), typically by applying an optimization algorithm to select the best processing within a model formulation. The aim of our contribution is to discuss and show the effect of the problem formulation and on the performance of the optimal solution.

This analysis contains the effect limit input (e.g. grade vs. microfabric, joint distributions vs. correlation, ...), the scope of the decision (e.g. processing path, processing parameters, block decisions vs. shape decisions, decisions on sampling, blending, invest into capacity, sequencing) and of model accuracy (e.g. concerning unmodelled details).

The effects will be demonstrated with simulation examples in perfectly controlled stochastic settings. It can be shown, that problem formulation can have a major impact on the economic result, and that the effect of problem formulation depends on the actual setting.

European Kupferschiefer deposits are one of the most important regional copper sources. Its complex structure and fine granularity demand smelting processes which require much energy and release environmentally unfriendly gases like sulphur dioxide. Thus alternative beneficiation strategies like biomining are worthwhile. Furthermore the Kupferschiefer challenges common acidophilic bioleaching approaches due to its high carbonate load consuming acid during decomposition. Therefore leaching in neutral pH ranges seems attractive. However, as decomposition of carbonates may also expose further copper minerals we investigated the influence of carbonate solubilisation on the leaching performance of organic acids. Leaching of copper from Kupferschiefer using biologically produced organic acids was proven to be feasible. Different parameters like pH, particle size and leaching temperature were evaluated. Copper solubilisation was monitored using mass spectrometry and scanning electron microscopy. The paper presents results and provides leaching strategies.

The long-term disposal of radioactive wastes in a deep geological repository (DGR) is the accepted international solution for the treatment and management of these special residues, mainly produced by the nuclear energy industry. The present work describes the structure and composition of microbial communities in Spanish bentonites, considered as natural analogue of the bentonite-engineered barrier, by two different culture- independent approaches based on the 16S ribosomal RNA gene analysis: clone libraries and Illumina sequencing platform. These two techniques showed a high microbial diversity of the bentonite samples studied. The microbial community was dominated by Proteobacteria and Bacteroidetes, and contained bacteria potentially involved in the possible microbial deterioration processes of DGR safety case including transformations of clay minerals, mobilization/immobilization of radionuclides, etc. When analysing all of the datasets from the samples en masse we observed high similarity between the clone libraries and Illumina datasets in terms of dominant groups and the community profiles at the phylum level, while significant differences in the proportion of some phyla and class between the samples were observed. Illumina-sequencing was more sensitive to Bacteroidetes, while in the case of Gammaproteobacteria class, the traditional clone library was much more efficient. The structure and composition of the microbial communities present in the bentonites samples will be discussed in term of geochemistry and mineralogy of the clays, and also on their impact in the safety case of DGR. The results obtained indicate that the combination of both molecular techniques provide an accurate and boarder view of the microbial communities present in complex environmental samples.

Hematite plays a decisive role in regulating the mobility of contaminants in rocks and soils. The Np(V) reactions at the hematite−water interface were comprehensively investigated by a combined approach of in situ vibrational spectroscopy, X-ray absorption spectroscopy and surface complexation modeling. A variety of sorption parameters such as Np(V) concentration, pH, ionic strength, and the presence of bicarbonate was considered. Time-resolved IR spectroscopic sorption experiments at the iron oxide−water interface evidenced the formation of a single monomer Np(V) inner-sphere sorption complex. EXAFS provided complementary information on bidentate edge-sharing coordination. In the presence of atmospherically derived bicarbonate the formation of the bis-carbonato inner-sphere complex was confirmed supporting previous EXAFS findings.1 The obtained molecular structure allows more reliable surface complexation modeling of recent and future macroscopic data. Such confident modeling is mandatory for evaluating water contamination and for predicting the fate and migration of radioactive contaminants in the subsurface environment as it might occur in the vicinity of a radioactive waste repository or a reprocessing plant.

Precession has long been discussed as a complementary energy source for driving the geodynamo. A fluid flow of liquid sodium in a cylindrical container, solely driven by precession, is considered as a source for magnetic field generation in the next generation dynamo experiment currently under development in the framework of DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies).
We present results from three-dimensional non-linear hydrodynamic simulations of a precession driven flow in cylindrical geometry. The main focus will be on non-axisymmetric time-dependent flow structures that could be responsible for dynamo action. Promising candidates may be triadic resonances that are caused by non-linear interaction of three distinct inertial modes. These modes have a comparable structure as the columnar convection cells that are responsible for dynamo action in geodynamo simulations, and it seems reasonable to expect similar properties in case of precessional forcing.
Our simulations reveal clear triads at aspect ratios close to predictions from the linear theory. However, the emergence of these structures requires a remarkable long time-span of the order of a few hundred rotation periods till a (quasi-)steady state is reached. Furthermore, the amplitude of the waves with higher azimuthal wavenumbers remains well below the forced m=1 mode. Their ability for dynamo action will have to be verified in future simulations of the magnetic induction equation.

Studies of the mineralogical deportment of indium generally focus on the measurement of trace concentrations in major ore minerals. The importance of actual In-minerals such as indite, roquesite and sakuraiite is not usually assessed. This is due to their low abundance and optical similarity to other, more common, sulphide minerals (e.g. sphalerite) rendering the reliable assessment of their concentration by traditional methods (point-counting) difficult at best. Their low abundance also means that reference materials for many of the relevant minerals are not readily available.
This contribution presents a general method developed to overcome these problems with SEM-based automated mineralogy. Using five carefully selected ore samples from the Neves-Corvo deposit it is shown that this approach not only allows for the reliable identification of trace indium minerals (roquesite) present within the ores, but it also enables the quantification of their respective concentrations and thus their contribution to the overall indium budget. Furthermore, additional information on other geologically and/or technologically relevant parameters like mineral association, grain shape and grain size are readily available.

In this work, high-resolution gamma-ray computed tomography (HireCT) was applied for the first time on a viscous coupling to visualize the internal operating fluid distribution. The HireCT measurement system comprises a 137Cs isotopic source and a gamma-ray detector arc operated in single photon counting mode and is able to produce cross-sectional images of dense objects with a spatial resolution of about 2 mm. To scan fast rotating parts rotation-synchronized CT scanning mode was employed in these experiments. The analyzed viscous coupling (Visco® clutch of MAHLE Behr) mainly consists of a driven primary disc and a secondary housing with an engine cooling fan mounted on it and is assembled within an experimental rig. The viscous coupling’s primary and secondary parts are axially assembled and a coupling liquid is pumped into engaged radial ring profiles to provide a defined torque transfer. The internal ring channel width, where the coupling liquid is to be observed, is considerably lower than one millimeter. Although the HireCT measurement system is not able to resolve these micro-channels, the coupling liquid can be successfully visualized via its contrast. Investigations have been performed at different filling levels corresponding to different transmission slips of the test coupling. Moreover, both radial and tangential liquid distributions for different operational steady states could be determined. The obtained experimental data were compared to results from computational fluid dynamics (CFD) simulations in some operating points and are in good agreement.

Sorption on mineral surfaces is one important retardation process to be considered in long-term safety assessments for radioactive waste repositories. So far a conservative concept with temporally and spatially constant distribution coefficients (Kd values) for each model unit is applied in the respective transport simulations.
In this work we describe a new methodology for integrating temporally and spatially variable distribution coefficients, so-called smart Kd values, into the transport code r³t [1]. These smart Kd values are pre-calculated with a bottom-up approach from mechanistic sorption models (namely surface complexation and ion exchange) and stored in a multidimensional matrix by coupling of three computer codes: PHREEQC [2], UCODE [3] and SimLab [4]. This strategy has numerous advantages over reactive transport codes: (1) One can calculate smart Kd values for a reasonable number of environmental parameter combinations; (2) It is possible to perform uncertainty analysis based on such smart Kd matrices; (3) In contrast to UCODE, SimLab also provides methods for global sensitivity analysis; (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 exemplarily for the sorption of uranium UVI on a natural sandy aquifer [5] and is able to describe the sorption behavior in dependence of changing geochemical conditions quite well. Complex proof-of-concept scenarios were simulated for the sedimentary overburden of the Gorleben salt formation. Here, results for the upper aquifer are presented and discussed. As a prerequisite, the data processing of the field data [6, 7] is explained, including approximate correlations of environmental input parameters. Eventually, five environmental factors span the multidimensional parameter space for the Kd matrices.
Smart Kd distributions based on Latin-Hypercube samplings are given for different radionuclides covering the elements Am, Cs, Ni, NpV, Ra, SeVI, Th and UVI; with Am and Th also used as chemical analogues for Cm and Pu, respectively. They are then compared to constant values, determined in laboratory experiments [8], which have been used so far in transport calculations for long-term safety assessment. In a last step, ranked sensitivity indices are provided for all the investigated radionuclides to identify the most relevant environmental factors, which should be investigated in more detail in the future to improve both the data base and process understanding.

The impact of low-energy multipole excitations and pygmy resonances on radiative neutron and proton capture cross sections in nuclei close to the -stability line is investigated. For this purpose, a microscopic theoretical approach based on self-consistent density functional theory and QRPA formalism extended with multi-phonon degrees of freedom, is implemented in a statistical reaction model. The advantage of the method is the fully microscopic nuclear structure input for unified description of low-energy multi-phonon excitations, pygmy and giant resonances. This is found important for the understanding of the fine structure and dynamics of nuclear response functions at low energies which strongly influence nuclear reaction rates of astrophysical significance. Calculations of the radiative capture cross sections of the reactions 85Kr(n,)86Kr, 87Sr(n,)88Sr and 89Y(p,)90Zr are discussed in comparison with the experiment. For the reactions 89Zr(n,)90Zr and 91Mo(n,)92Mo theoretical predictions of the reaction cross sections are made.

In recent years, bispecific antibodies (bsAb) have emerged as promising tools for a target-specific redirection of T cells in order to eliminate malignant cells. However, CD3-engaging constructs might also activate T regulatory cells (Tregs) present in the tumor microenvironment. Whether this has detrimental or beneficial effects for tumor therapy is still controversially discussed.

Background
Clay deposits such as the Opalinus Clay formation are studied as host rocks for geological disposal of high- and intermediate-level long-lived radioactive waste in several European countries. Bituminized intermediate-level long-lived radioactive waste contains, besides bitumen and radionuclides, also large amounts of organics, nitrates and sulphates. Over time, these salts will dissolve, leach and diffuse into the surrounding clay host rock, together with water soluble organic substances. To mimic the potential effect of such inorganic– and organic leachates, pulses of nitrate and/or acetate have been injected in intervals of an in situ experiment, called Bitumen-Nitrate-Clay interaction (BN) experiment, running at the Mont Terri geological laboratory (St. Ursanne, Switzerland).
Objectives
To elucidate whether the microbial communities, present in the BN experiment, are affected or involved in the observed biogeochemical changes.
Methods
Beside classical microbial analyses, at pivotal moments (i.e. before, during and after these pulse injection tests), priority was given to DNA-based molecular biology analysis methods, as these methods provide very accurate information on the composition, the metabolic capacity and possible evolution of bacterial communities in response to the nitrate and/or acetate injections.
Conclusions
The changes observed in the bacterial populations appeared to correlate well with the imposed physico-chemical changes. As soon as nitrate was added an overwhelming community shift appeared to nitrate reducing bacteria. If in parallel acetate was offered, the community composition did not alter that much, but the speed of nitrate reduction was increased twentyfold. This high nitrate removal speed was maintained as long as the easily consumable carbon source was abundant.

Clay deposits such as the Opalinus Clay formation are studied as host rocks for geological disposal of high- and intermediate-level long-lived radioactive waste in several European countries. Bituminized intermediate-level long-lived radioactive waste contains, besides bitumen and radionuclides, also large amounts of nitrates and sulphates. Over time, these salts will dissolve, leach and diffuse into the surrounding clay host rock, together with water soluble organic substances. The presence of these compounds will induce several processes (e.g. ionic strength changes, ion exchange reactions with Na+, redox reactions with NO3-) that may affect the barrier properties of the clay host rock.
To study the fate of such inorganic– and organic leachates, an in situ experiment, called Bitumen-Nitrate-Clay interaction (BN) experiment, was installed in the Opalinus Clay at the Mont Terri underground research laboratory (St. Ursanne, Switzerland). The BN experiment aims to investigate the impact of a nitrate plume, with or without acetate, on the biogeochemistry of the near-field host rock. Acetate is used as representative of the organic water soluble fraction of bitumen degradation products. At a later stage, the BN experiment also aims to investigate the impact of nitrate and acetate on radionuclide reactivity and transport, especially for the redox sensitive radionuclides (e.g. 79Se, 99Tc, 23xU, …). The microbial analyses of the BN experiment intend to elucidate if and how currently present microbial communities are affected, and if and how microbes are involved in the observed biogeochemical processes. In this respect it is noteworthy to mention that the current BN set-up does not take into account any cement matrix or backfill, and offers the microbes only a pure aquatic environment, at almost neutral pH, in the form of a water-filled borehole. Such set-up allows free movement of nutrients, energy sources and dissolved electron donors and – acceptors, and does not impose any physical and/or chemical restriction on the microorganisms. In a real radioactive waste repository, the conditions will mostly deviate from the ones present in the BN experiment. Therefore, the in situ BN experiment can only be considered as a well engineered disposal 'test case'...

Over the last decades, XAS has evolved as a very useful tool to investigate nuclear materials with applications for fuel manufacturing of for the behavior for fission products. Nowadays, the possibility of applying HERFD measurements to radioactive compounds offers even more possibilities. Two recent studies dealing with the behavior of fission gases in UO2 nuclear fuel and investigating both the electronic and structural properties of uranium based mixed oxide fuels will be presented to illustrate the use of HERFD. Furthermore, recent experimental developments allowing to perform in-situ XAS measurements on actinide-based materials at high temperature and under controlled atmosphere, will be illustrated by the first results obtained on UO2±x and (U,La)O2±x samples.

The incorporation of aliovalent cations into the UO2 structure leads to a change of the U oxidation state and can ultimately affects the physical propertiesy of these U1-yMyO2±x compounds. U1-yLayO2±x, U1-yPuyO2±x and U1-yAmyO2±xhave been investigated in the present work, as these materials are particularly relevant for the nuclear fuel cycle. LIII XANES, LIII HERFD-XANES and MIV HERFD-XANES measurements have been performed to study both electronic and structural environments of these fluorite-type solid solutions.

In the present contribution we will show that in a stacked vortex pair system with uniaxial magnetic anisotropy, spin waves of different symmetries and dimensionalities can be excited.

The electromagnetic dipole strength in several even nuclei in the chain of Xenon isotopes has been investigated at the bremsstrahlung facility of the ELBE accelerator in Dresden, Germany and at the HIγS facility in Durham, USA. The goal of these measurements is to extend the knowledge about the general behavior of the dipole strength in the energy region below the neutron separation energy under the aspect of neutron excess and nuclear deformation.

Brown staining on both pristine and painted sandstone surfaces is a regular problem reported from new building construction and restoration actions. During the recent restoration of the Großer Wendelstein, an impressive airy stone staircase in the castle Hartenfels in Torgau, Germany, extensive brown staining appeared in distinctive places. Due to the fact that such an incidence occurred while desalination with poultice compresses the usually extreme rare chance of sampling was possible and executed. Several chemical tests combined with Nuclear Magnetic Resonance (NMR) and Infrared (IR) spectroscopy proved humic substances as causation of the intensive staining. In the consequence restorative recommendations are drawn.

The temperature impact on sorption processes of selenium oxyanions onto alumina was investigated.

The last decades have seen a number of liquid metal experiments on the interaction of magnetic fields with the flow of electrically conducting fluids. The opaqueness of liquid metals requires non-optical methods for inferring the velocity structure of the flow. Quite often, such experiments are carried out in the presence of high electrical currents to generate the necessary magnetic fields. Depending on the specific purpose, these currents can reach several kiloamperes. The utilized switching mode power supply can then influence seriously the measurement system by electromagnetic interference. A recent experiment on the azimuthal magnetorotational instability (AMRI) has shown that a hydrodynamically stable Taylor-Couette flow becomes unstable under the influence of a high azimuthal magnetic field. Therefor an electrical current along the axis of the experiment with up to 20 kA generates the necessary field to destabilize the flow. We present experimental results on this AMRI experiment carried out at the PROMISE facility with an enhanced power supply. For this setup, we discuss the elaborate measures that were needed to obtain a reasonable signal-to-noise ratio of the ultrasonic Doppler velocimetrie (UDV) system. In dependence on various parameter variations, some typical features of the observed instability, such as the energy content, the wavelength, and the frequency are analyzed and compared with theoretical predictions.

One of the most intensively developing areas in the LWR multi-physics is a coupling of different best estimate 3-D neutron kinetic (BIPR, DYN3D, KIKO3D, NEM, PARCS, etc.) and thermal hydraulic (ATHLET, CATHARE, RELAP5, etc.) codes. Resulting coupled code systems have advanced capabilities of modeling both steady-state spatial distributions of the core power and their evolutions during different kinds of reactor transients. They are also highly useful in the analyses of possible reactor instabilities. Initial steady-state core power distributions can be disturbed by changes in the reactor loop mass flow rates and/or temperatures, by relocations of the low-temperature/diluted-boron water slugs within the primary system or by movements of control rods.
The coupled code used for LWR simulations in HZDR is DYN3D/ATHLET, which includes the 3-D core neutron kinetic and thermal hydraulic model of own development – DYN3D. The paper reports major capabilities of DYN3D as well as different ways of its coupling with the thermal hydraulic code ATHLET (external, internal and parallel), but mainly focuses on the validation and verification of the coupled code DYN3D/ATHLET. In the course of DYN3D/ATHLET validation/verification nearly 20 real plant transients and dynamic benchmarks have been simulated and analysed. The LWR types covered by these tasks are: VVER-440 (Bohunice-3, Greifswald-5 and Loviisa-1 units), VVER-1000 (Balakovo-1, Balakovo-4, Kalinin-3, Kozloduy-6, Saporozhye-6 and Temelin-2 units), B&W PWR (TMI-1) and BWR/4 MK-1 (Peach Bottom-2). For each reactor unit a computational model was developed according with the benchmark specifications. The simulated tasks describe different scenarios of increasing complexity, including the transients initiated by the main steam header or main steam line breaks, switching off/on of main circulation pumps, turbine trip and generator load drop. Some of the transients are characterized by a strongly asymmetric behavior of the primary system (e.g. caused by a steam line break), and the processes of coolant mixing in the lower and upper reactor plenums as well as in the downcomer are important for these cases. The coupled code DYN3D/ATHLET models the primary coolant mixing in two ways – whether by an appropriate nodalization of the mixing area or by using two specific models for mixing in the lower plenum. The first of the lower plenum mixing models is a part of the coupling interface at the core inlet plane, while the second one is the analytical coolant mixing model developed for the downcomer and the lower plenum regions of VVER-440.
The results of DYN3D/ATHLET simulations were assessed both against available measured data and calculations performed with similar multi-physics codes. The paper includes an overview of the simulated problems and the most representative results of DYN3D/ATHLET validation/verification for all coupling modes. The obtained experience of code validation provides a better understanding of reactor transients with a strong interaction between neutron kinetics and thermal hydraulics, helping to improve computation models. This experience is also useful for the present and further activities in coupling of DYN3D with other best estimate codes, like CFX, TRANSURANUS, etc.

Particle therapy positron emission tomography (PT-PET) is an in vivo and non-invasive imaging technique to monitor treatment delivery in particle therapy. The inevitable patient respiratory motion during irradiation causes artefacts and inaccurate activity distribution in PET images. 4D maximum likelihood expectation maximization (4D MLEM) allows for a compensation of these effects, but has up to now been restricted to regular motion for PT-PET investigations. However, intra-fractional motion during treatment might differ from that during acquisition of the 4D-planning CT (e.g. amplitude variation, baseline drift) and, therefore, might induce inaccurate 4D PET reconstruction results. This study investigates the impact of different irregular analytical motion patterns on PT-PET imaging by means of experiments with radioactive source and irradiated moving phantoms. Three sorting methods, namely phase sorting, equal amplitude sorting and event-based amplitude sorting, were applied to manage PET list-mode data. The inuence of these sorting methods on the motion compensating algorithm has analysed. The event-based amplitude sorting presented superior performance, although the 4D PT-PET reconstructions still suffered partly from the inexact deformation specifications due to the irregular motion.

Magnetic phase transition in the Fe60Al40 transition metal aluminide from the ferromagnetic disordered A2-phase to the paramagnetic ordered B2-phase as a function of annealing up to 1000°C has been investigated by means of magneto-optical and spectroscopy techniques, i.e., Kerr effect, positron annihilation and Mössbauer spectroscopy. The positron annihilation spectroscopy (PAS) has been performed in-situ sequentially after each annealing step at the Apparatus for In-situ Defect Analysis (AIDA) that is a unique tool combining positron annihilation spectroscopy with temperature treatment, material evaporation, ion irradiation, and sheet resistance measurement techniques. The overall goal was to investigate importance of the open volume defects onto the magnetic phase transition. No evidence of variation in the vacancy concentration in matching the magnetic phase transition temperature range (400-600°C) has been found, whereas higher temperatures showed an increase in the vacancy concentration.

Radiation effects in solid nitrogen irradiated with an electron beam were studied with emphasis on the role of charged centers in radiation-induced phenomena. The experiments were performed employing luminescence method and activation spectroscopy techniques - spectrally resolved thermally stimulated luminescence TSL and thermally stimulated exoelectron emission. Samples were probed in depth by varying electron energy, thus discriminating radiation-induced processes in the bulk and at the surface. Spectroscopic evidence of the excited N₂ * (C³Π_u) molecule desorption was obtained for the first time and mechanism of the phenomenon based on recombination of electron with intrinsic charged center N₄ ⁺ was proposed. The key role of N₃ ⁺ center dissociative recombination in generation of N radicals is suggested.

Eine besondere Herausforderung der Protonentherapie besteht in der Unsicherheit der Protonenreichweite im Patienten und den resultierenden Unsicherheiten der Dosisverteilung. Hier bietet die Methode der Reichweiten-Verifikation anhand der protoneninduzierten Prompt-Gamma-Emission einen vielversprechenden Ansatz zur Verringerung der Unsicherheiten. Hierfür wurde ein Prototyp einer Prompt-Gamma-Kamera von der Firma IBA entwickelt und für die zukünftige klinische Anwendung an der Dresdner Protonentherapieanlage installiert. In Zusammenarbeit mit IBA erfolgte die umfangreiche Charakterisierung und Vorbereitung der Kamera für die klinische Anwendung. Dies beinhaltete die Hardware- und Softwareentwicklung, Kalibrierung und Qualitätssicherung sowie die Erprobung am Phantom für unterschiedliche Bestrahlungsmodalitäten.

Spin waves constitute an important part of research in the field of magnetization dynamics. Spin waves are the elementary excitations of the spin system in a magnetically ordered material state and magnons are their quasi particles. In the following article, we will discuss the optical method of Brillouin light scattering (BLS) spectroscopy which is a now a well established tool for the characterization of spin waves. BLS is the inelastic scattering of light from spin waves and confers several benefits: the ability to map the spin wave intensity distribution with spatial resolution and high sensitivity as well as the potential to simultaneously measure the frequency and the wave vector and, therefore, the dispersion properties.

For several decades, the field of spin waves gained huge interest by the scientific community due to its relevance regarding fundamental issues of spindynamics in the field of solid states physics. The ongoing research in recent years has put emphasis on the high potential of spin waves regarding information technology. In the emerging field of \textit{magnonics}, several concepts for a spin-wave based logic have been proposed and realized. Opposed to charge-based schemes in conventional electronics and spintronics, magnons are charge-free currents of angular momentum, and, therefore, less subject to scattering processes that lead to heating and dissipation. This fact is highlighted by the possibility to utilize spin waves as information carriers in electrically insulating materials. These developments have propelled the quest for ways and mechanisms to guide and manipulate spin-wave transport. In particular, a lot of effort is put into the miniaturization of spin-wave waveguides and the excitation of spin waves in structures with sub-micrometer dimensions.

For the further development of potential spin-wave-based devices, the ability to directly observe spin-wave propagation with spatial resolution is crucial. As an optical technique BLS does not only allow to map the spin-wave intensity in general, but it, in particular, enables the realization of sub-micron space resolution. Focusing of the laser beam to a sub-micrometer spot size can be realized by implementing a microscope objective into the optical setup. Over the last decade, this micro-focus BLS technique has become an established method for the investigation of spin waves in microstructured magnetic elements and proved its value in particular regarding magnonics.

In this article, we will discuss the basic principles of the BLS process and illustrate the experimental optical setup. Particular emphasis will be put on the implementation of the high spatial resolution of the BLS microscope and the consequences this has for the experimental realization. In addition, the outline of a computer based operation principle and automated sample positioning will be given. Owing to these improvements in ease of use as well as experimental applicability, the BLS technique has maintained its relevance for investigations of today's research on spin waves in miniaturized magnetic structures. A selection of experiments in this field will be described.

The Tayler instability (TI), a kink-type current-driven instability, is discussed as a crucial ingredient of an alternative α-Ω stellar dynamo model. In the framework of the Tayler-Spruit dynamo, a finite current helicity generated by the TI may produce an α-effect, transforming an azimuthal into a poloidal magnetic field. Going from astrophysics to engineering, the TI may be relevant for Liquid Metal Batteries, too. In the context of renewable energies, such batteries have recently received considerable interest for large scale energy storage. Their main advantages (cheap raw materials, long life-time, low cost) result from their simple construction. Built as a stable density stratification of two liquid metals separated by a molten salt layer, such batteries can be easily scaled up. In that case, currents in the order of a few kA will appear and possibly trigger the TI. If the resulting fluid flow becomes too strong, it may disrupt the electrolyte layer, leading to a battery failure.
A quasi-static numerical model, using an integro-differential approach for the coupling of velocity and magnetic field, is presented and used to simulate the TI in the medium to low magnetic Prandtl number range (1e−3 to 1e−6 ). The properties of the instability (growth rate, velocities in saturation), the influence of the geometric aspect ratio and scaling laws are explored. The relevance of the TI for Liquid Metal Batteries as well as several possible ountermeasures are discussed. Further, the influence of different axial boundary conditions and the interaction of TI and electro-vortex flow is analysed.
The saturation mechanism of the TI at high magnetic Prandtl numbers is commonly explained by the β-effect. We propose a second, hydrodynamic saturation mechanism for the TI at low magnetic Prandtl numbers. This allows us to explain the moderate fluid velocities, observed by Seilmayer et al. in a liquid metal TI experiment. Finally, we analyse the occurence of kinetic and current helicity at magnetic Prandtl numbers between 1e−3 and 1e−6 and show the limit of the quasi-static approximation. We finish with a description of helicity waves of the saturated TI. It’s occurence, frequency and amplitude are characterised in the astrophysical context.

Violet crystals of {[Cu(pn)₂]₂[Pt(CN)₄]}[Pt(CN)₄]·2H₂O (1, pn=1,2-diaminopropane) and blue crystals of [Cu(pn)Pt(CN)₄]_n·nH₂O (2) were prepared under hydrothermal conditions and characterized using elemental analysis, IR and UV–vis spectroscopy and by X-ray crystal structure analysis. Different number of ν(C≡N) absorption bands of these two compounds reflects their different structures. An X-ray crystal structure analysis has shown that complex 1 is of ionic character and is formed from trinuclear [Cu(pn)₂–Pt(CN)₄–Cu(pn)₂]²⁺ complex cation and discrete [Pt(CN)₄]^2– anion together with two molecules of crystal water. On the other hand, complex 2 is of polymeric character and is formed by 2D networks of [Cu(pn)Pt(CN)₄]_n composition and completed by n molecules of crystal water. Magnetic measurements show the presence of a weak antiferromagnetic exchange interaction in complex 1 (Θ = –0.2 K), while the magnetic susceptibility of complex 2 is well described by the model of uniform S = 1/2 spin chain with exchange interaction J/k_B = –1.64 K.

(EN) FIELD: chemistry. SUBSTANCE: fluoride nanoceramic is obtained by thermomechanical treatment of the starting crystalline material made from CaF2-YbF3, at plastic deformation temperature to obtain a workpiece in form of a polycrystalline microstructured substance, which is characterised by crystal grain size of 3-100 mcm and a nanostructure inside the grains, by annealing on air at temperature of not less than 0.5 of the melting point with compaction of the obtained workpiece in a vacuum at pressure of 1-3 tf/cm2 until the end of the deformation process, followed by annealing in an active medium of carbon tetrafluoride at pressure of 800-1200 mmHg. The starting crystalline material used can be a fine powder which has been subjected to heat treatment in carbon tetrafluoride, or a moulded workpiece of crystalline material made from the powder and heat treated in carbon tetrafluoride. EFFECT: invention enables to obtain a fluoride nanoceramic with high degree of purity and high uniformity of the structure of said optical material. 4 cl, 3 ex

(RU) Изобретение относится к технологии получения оптических поликристаллических материалов, а именно фторидной керамики, имеющей наноразмерную структуру и усовершенствованные оптические, лазерные и генерационные характеристики. Фторидную нанокерамику получают термомеханической обработкой исходного кристаллического материала, выполненного из CaF2-YbF3, при температуре пластической деформации до получения заготовки в виде поликристаллического микроструктурированного вещества, характеризующегося размером зерен кристаллов 3-100 мкм и наноструктурой внутри зерен, путем отжига на воздухе при температуре не менее 0,5 от температуры плавления с уплотнением полученной заготовки в вакууме при давлении 1-3 тс/см2 до окончания процесса деформации, после чего отжигают в активной среде тетрафторида углерода при давлении 800-1200 мм рт.ст. В качестве исходного кристаллического материала могут быть использованы мелкодисперсный порошок, прошедший термообработку в тетрафториде углерода, или отформованная заготовку кристаллического материала, полученная из порошка и термообработанная в тетрафториде углерода. Изобретение позволяет получать фторидную нанокерамику высокой степени чистоты с повышенной однородностью структуры данного оптического материала. 2 н. и 2 з.п. ф-лы, 3 пр., 1 табл.

Uranium-plutonium mixed oxide containing 30% of PuO2 is a candidate fuel for several fast neutron and accelerator driven reactor systems. In this work, a detailed structural investigation on sol-gel synthesized stoichiometric U0.7Pu0.3O2.00 and substoichiometric U0.7Pu0.3O2-x, using X-ray diffraction (XRD), oxygen 17 magic angle spinning nuclear magnetic resonance (17O MAS-NMR) and X-ray absorption spectroscopy is described. As observed by XRD, the stoichiometric U0.7Pu0.3O2.00 is monophasic with a lattice parameter in good agreement with Vegard’s law, while the substoichiometric U0.7Pu0.3O2-x material is biphasic. 17O MAS-NMR confirmed a random distribution of metal atoms and hence an ideal solid solution behaviour for U0.7Pu0.3O2.00. X-ray absorption near-edge structure (XANES) spectroscopy showed the prevalence of plutonium (III) in U0.7Pu0.3O2-x. Extended X-ray absorption fine-structure (EXAFS) spectroscopy indicated a similar local structure around U and Pu, in agreement with the long-range order determined by XRD.

Die Strahlentherapie ist einer der drei Partner im interdisziplinären Feld der Onkologie. In Europa, Asien und den USA besteht zunehmend die Möglichkeit einer Therapie mit Strahlen aus geladenen Ionen anstelle von Photonen. Eine Anlage in Dresden befindet sich in der Kommissionierungsphase.
Die Ionenstrahltherapie bietet den Vorteil einer sehr konformalen Behandlung des Tumorvolumens durch die endliche Reichweite der Strahlen und ein ausgeprägtes Dosismaximum kurz vor dem Ende des Strahlpfades. Da eine Therapie in der Regel über bis zu 30 Sitzungen an verschiedenen Tagen durchgeführt wird und der Strahlweg stark von dem durchdrungenen Gewebe beeinflusst wird, sind Verfahren für eine in vivo Verifikation der Strahlapplikation wünschenswert. Eine dieser Methoden ist die Partikeltherapie–Positronen-Emissions-Tomografie (PT-PET). Sie beruht auf der Messung der vom Therapiestrahl erzeugten β⁺-Aktivitätsverteilung. Da eine direkte Berechnung der Dosis aus der Aktivität in lebendem Gewebe nicht möglich ist, wird die gemessene Aktivitätsverteilung mit einer berechneten Vorhersage verglichen und anschließend entschieden, ob die nächste Therapiesitzung wie geplant erfolgen kann oder Anpassungen notwendig sind. Die vorliegende Arbeit beschäftigt sich mit drei Themen aus dem Bereich der Datenverarbeitung für die PT-PET.
Im ersten Teil wird ein Algorithmus zur Bestimmung von Reichweitendifferenzen aus zwei β⁺- Aktivitätsverteilungen adaptiert und evaluiert. Dies geschieht zunächst anhand einer Simulationsstudie mit realen Patientendaten. Ein Ansatz für eine automatisierte Analyse der Daten lieferte keine zufriedenstellenden Ergebnisse. Daher wird ein Software-Prototyp für eine semiautomatische, assistierte Datenanalyse entwickelt. Die Evaluierung erfolgt durch Experimente mit Phantomen am ¹²C-Strahl.
Die erzeugte Aktivitätsverteilung wird von physiologischen Prozessen im Organismus beeinflusst.
Dies führt zu einer Entfernung von Emittern vom Ort ihrer Erzeugung und damit zu einer Verringerung der diagnostischen Wertigkeit der erfassten Verteilung. Zur Quantifizierung dieses als Washout bezeichneten Effektes existiert ein am Tierexperiment gewonnenes Modell. Dieses Modell wird im zweiten Teil der Arbeit auf reale Patientendaten angewendet. Es konnte gezeigt werden, dass das Modell grundsätzlich anwendbar ist und für die betrachtete Tumorlokalisation Schädelbasis ein Washout mit einer Halbwertszeit von (155,7±4,6) s existiert.
Die Berechnung der Vorhersage der β⁺-Aktivitätsverteilung kann durch übliche Monte-Carlo-Verfahren erfolgen. Dabei werden die Wechselwirkungsquerschnitte zahlreicher Reaktionskanäle benötigt. Als alternatives Verfahren wurde die Verwendung gemessener Ausbeuten (Yields) radioaktiver Nuklide in verschiedenen Referenzmaterialien vorgeschlagen. Auf Basis einer vorhandenen Datenbank dieser Yields und einer existierenden Condensed-History-Monte-Carlo-Simulation wird ein Programm zur Berechnung von Aktivitätsverteilungen auf Yieldbasis entwickelt. Mit der Methode kann die β⁺-Aktivitätsverteilung in Phantomen und Patienten zufriedenstellend vorhergesagt werden.
Die entwickelten Verfahren sollen einen Einsatz der PT-PET im klinischen Umfeld erleichtern und damit einen breiten Einsatz ermöglichen, um das volle Potential der Ionenstrahltherapie nutzbar zu machen.