Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Rational material design can accelerate the discovery of materials with improved functionalities. This approach can be implemented in Heusler compounds with tunable magnetic sublattices to demonstrate unprecedented magnetic properties. Here, we have designed a family of Heusler alloys with a compensated ferrimagnetic state. In the vicinity of the compensation composition in Mn–Pt–Ga, a giant exchange bias (EB) of more than 3 T and a large coercivity are established.
The large exchange anisotropy originates from the Exchange interaction between the compensated host and ferrimagnetic clusters that arise from intrinsic anti-site disorder. Our design approach is also demonstrated on a second material with a magnetic transition above room temperature, Mn–Fe–Ga, exemplifying the universality of the concept and the feasibility of room-temperature applications. These findings may lead to the development of magneto-electronic devices and rareearth-free exchange-biased hard magnets, where the second quadrant magnetization can be stabilized by the exchange bias.

Preferential adsorption of Cu contained in wastewaters is desirable as the Cu can then be reprocessed and reused more easily. In this study, biogenic elemental selenium nanoparticles (BioSeNPs) were assessed for their ability to preferentially adsorb Cu from an equimolar mixture containing Cu, Cd and Zn. Both metal to BioSeNPs ratio and initial metal solution pH have been shown to affect the preferential adsorption capacity of BioSeNPs towards Cu. BioSeNPs adsorbed 2.3 times more Cu from an equimolar mixture of Cu, Zn and Cd at an initial metal solution pH of 5.2 and metal to BioSeNPs ratio of 0.21 mg mg−1, while adsorbing more than 78% of added Cu. Infrared spectroscopy revealed that the Cu, Cd and Zn were interacting with hydroxyl and carboxyl surface functional groups of the BioSeNPs. The modeling of BioSeNPs' acid-base titration revealed the presence of high concentrations of carboxylic groups (C = 60.26 mol Kg−1) with a pKa of 3.9 providing, further evidence of their interaction with Cu. The adsorption of Cu resulted in a lower colloidal stability of the BioSeNPs as indicated by less negative ζ-potential values. BioSeNPs showed good preferential adsorption capacity towards Cu when compared to oxidized carbon nanotubes. This study provides proof-of-concept for preferential adsorption of Cu onto BioSeNPs which are present in the effluent of a bioreactor treating selenium oxyanions containing wastewater.

Sphalerite (ZnS) is an important source of a number of high-tech metals. However, while a large amount of analytical data on trace and minor element concentrations in sphalerite has been collected over the last decades, our understanding of the geological controls on their enrichment or depletion remains limited. No comprehensive meta-analysis of this data has ever been conducted. This talk presents the results of such a meta-analysis, based on an extensive collection of data from the scientific literature. Nine elements (Ag, Cd, Co, Cu, Fe, Ga, Ge, In and Mn) were considered. For five of these elements (Fe, Ga, Ge, In, Mn) significant differences were found between different geological types of deposits. The regularity of these differences suggests the operation of a single underlying control parameter – possibly formation temperature – with obvious implications for the identification of future sources of these elements.

The availability of minerals and metals required for high technology applications has in recent years been widely recognized as being of strategic importance for future development - especially for highly industrialized economies. Because the absolute tonnage of such high technology minerals and metals in industrial products is typically small, inventories in the technosphere will remain limited and widely disseminated. This will significantly hamper recycling efforts. As a direct consequence, primary resources will need to be utilized to secure supply into the foreseeable future. Tapping primary resources appears as a reasonable approach, as these are readily available for most high technology metals. Geoscientists will have to make an important contribution – not only towards exploration and discovery, but also to the implementation of technological concepts for comprehensive resource utilization, i.e., mining operations that are not only economic, but also resource-efficient and environmentally benign.

The demand for some of the rarer elements in the Earth's crust for high-tech applications is increasing rapidly. Many of these elements are produced exclusively as by-products resulting in potentially significant supply limitations. However, despite their increasing importance, reliable assessments of these limitations are not readily available. Gallium, germanium, indium, tellurium and rhenium are good examples of such elements.
In this work, a general methodology is presented for the estimation of the supply potential of by-product elements as a function of their distribution in the relevant raw materials, the state of technology and market prices. Geochemical data from the scientific literature is used to generate numerical models of the distribution of the elements over separable production volumes, while data on the partitioning behaviour of the elements during the production of the main products is used to assess the fraction which is profitably extractable as a function of cut-off grade in a waste or intermediate process stream. The exact value of this cut-off grade may be taken to reflect both the current state of extraction technology as well as market prices for the element in question. A combination of the distribution and process behaviour models in Monte Carlo-type numerical simulations yields a median estimate and confidence interval for the supply potential as a function of the cut-off grade.
The results can be presented in the form of availability curves. This allows not only for the assessment of the current situation but also enables simple adaptation to changed technological and market conditions. Furthermore it makes it possible to assess the chief supply limitations, i.e. whether they are geological or technological, as well as the magnitude of inefficiencies in the markets of these metals. A simple example is used to illustrate the application of the method.

Neves-Corvo is a world-class volcanic-hosted massive sulphide (VHMS) deposit located in the Iberian Pyrite Belt (IPB). It is both one of the largest and richest deposits in the IPB. Besides its size, other notable features include its high tin content and the unusual ore types within which most of this tin was originally hosted. High indium concentrations (30 - 50 ppm in whole ore) also make it an attractive source of this rare metal. However, the mine does not currently profit from this potential.

It was the aim of this study to generate the data required for a detailed quantitative evaluation of different valorisation options for indium at Neves-Corvo. In addition to data on the spatial distribution of the element, this also requires a detailed understanding of its mineralogical deportment. While previous studies had reported elevated indium concentrations in a number of different minerals (e.g. stannite, sphalerite, cassiterite, tetrahedrite-tennantite, chalcopyrite) as well as the occurrence of two discrete indium minerals (roquesite, CuInS2, and sakuraiite, (Cu, Zn, Fe)3(In,Sn)S4), modal mineralogy and consequently the deportment of indium in the studied samples were never quantified.

In the present work, a combination of whole ore geochemistry, automated scanning electron microscope (SEM)-based image analysis and electron probe microanalysis (EPMA) was used to study the mineralogical deportment of indium in a representative set of more than 70 ore and process samples. It was found that, depending on ore type, sphalerite and/or chalcopyrite are the most important host minerals while stannite, roquesite and sakuraiite are not important due to their generally low abundance. Indium concentrations in sphalerite are highly variable, but are usually 2 - 3 times higher than in coexisting chalcopyrite. The exact concentrations depend on the total concentration of indium in the ore in relation to the abundance of these two minerals. This apparent equilibrium partitioning behaviour is thought to be mostly a consequence of the extensive syntectonic recrystallisation of the ore minerals.

The clear dominance of sphalerite and chalcopyrite as indium carriers has obvious consequences for valorisation options at the mine. First, the indium contained in the ores should be recoverable from the ores with the zinc and copper concentrates. Second, the production of separate concentrates enriched to the minimum concentrations required by smelters will only be possible by the separate processing of indium-rich ores.

To the best knowledge of the authors, this is the first detailed deportment study for indium ever conducted. The results have obvious implications not only for indium valorisation at Neves-Corvo, but also in other massive sulphide deposits affected by extensive tectonically induced recrystallisation. They should therefore be of interest to the wider geometallurgical and economic geology communities.

This is a contribution to the ZHINC project (PTDC/CTE-GIX/114208/2009). Thanks are due to the authors' host institutions for the provision of the funding and infrastructure necessary to conduct this work.

The statistical analysis of a comprehensive collection of analytical data compiled from the scientific literature shows that significant differences exist in the mean concentrations of Ga, Ge, In and Fe in sphalerite samples from different types of Pb-Zn deposits. A systematic trend is present in these mean concentrations: going from Mississippi Valley-type via vein-type to high-temperature hydrothermal replacement deposits, mean Ga and Ge concentrations decrease, while Fe and In concentrations increase. The same trend is observed going from Mississippi Valley-type via sediment-hosted massive sulphide to volcanic-hosted massive sulphide deposits. The two trends are virtually indistinguishable and seem to reflect a general increase in the magmatic contribution to the ore-forming process. While the exact geological controls remain unclear, this trend constitutes an important observation with immediate implications for the exploration for new resources of Ga, Ge and In.

By-product availability curves were constructed for the production of gallium (Ga) from bauxite, sulphidic zinc ores and coal. They were used to assess both the current nature of its supply regime, as well as its potential future development. Not only was the current situation found to be firmly in the elastic supply regime for all three raw materials, indicating that significant future increases in primary Ga production are possible without increases in the production of the corresponding main products, but it was also found that estimated current supply potential from bauxite and sulphidic zinc ores alone is at least five times larger than actual primary production. Coal offers a significant additional supply potential (currently at least ~ 1.5 times primary Ga production). An extrapolation of growth trends in the primary production of Al, Zn and Ga into the future indicates that the minimum supply potential of Ga will not be exhausted before 2050. Once this point is reached, additional increases in Ga production relative to the production of Al and Zn will be possible via decreases in the relevant cut-off grades for its extraction. No significant shortages are therefore expected in the foreseeable future. Our results clearly refute the widely-held notion that the supply of certain by-product metals is currently limited by the production of the corresponding main products. Rather, the chief limitation appears to be installed production capacity.

While a significant amount of analytical data on trace and minor element concentrations in sphalerite has been collected over the last six decades, no meta-analysis of this data has ever been conducted. In this study, the results of such an analysis are presented. While the study focusses on Ga, Ge and In, data for six other elements (Ag, Cd, Co, Cu, Fe and Mn) was also included.
The results show that there are systematic, statistically significant differences in the mean concentrations of Fe, Ga, Ge, In and Mn in sphalerite from different deposit types, while Cd and Cu concentrations show no such differences, and Ag and Co concentrations are only significantly different for vein-type deposits. A principal component analysis demonstrates that the differences between deposit types are approximately one-dimensional, being expressible in terms of a single number. This number correlates strongly with the homogenisation temperature of fluid inclusions (R2 = 0.82, p < 2∙10-16). It may be expressed as follows:

PC 1*=ln((C_Ga^0.22⋅C_Ge^0.22)/(C_Fe^0.37⋅C_Mn^0.20⋅C_In^0.11 ))

with Ga, Ge, In and Mn concentrations in ppm, and Fe concentration in wt.%. The relationship is sufficiently strong to be used as a geothermometer (GGIMFis). The empirical relationship between PC 1* and the homogenisation temperature, T, is:

T(°C)=(54.4±7.3)⋅PC 1*+(208±10)

Our results indicate a strong control of sphalerite chemistry by fluid temperature, particularly for the concentrations of Ga (R2 ~ 0.40), Ge (R2 ~ 0.65), Fe (R2 ~ 0.30) and Mn (R2 ~ 0.60), and to a lesser degree In (R2 ~ 0.10). The concentrations of Ag, Cd, Co and Cu appear to be independent of temperature.
As a consequence of the strong temperature control on PC 1*, metamorphic overprinting of Pb-Zn deposits, even by lower greenschist facies events, may lead to significant changes in sphalerite composition, namely a relative decrease in Ga and Ge concentrations, and increase in Fe, Mn and, to a lesser degree, In concentrations. The closure temperature of sphalerite in regional metamorphic events appears to be around 310 ± 50°C, such that higher-grade events will not be reflected in its composition.
Factors other than temperature, such as differences in fluid salinity or source-rock composition, do not appear to be responsible for differences between deposit types, but rather appear to cause differences between individual deposits. Particularly, the Cu activity in ore-forming systems appears to have a strong influence on In concentrations in sphalerite.
The observed trends in sphalerite compositions provide a useful tool for future studies of different types of Pb-Zn deposits, as well as for mineral exploration. They should be particularly relevant for the identification of new resources of Ga, Ge and In.

The demand for some of the rarer elements in the Earth's crust, mostly from high-tech applications, is increasing rapidly. Many of these elements are produced exclusively as by-products resulting in potentially significant supply limitations. In this article, a general method for the assessment of the supply potential of such elements is developed from a conceptual model of the supply-chain. Namely, statistical and deterministic models are introduced to quantify both the variability in by-product concentrations in the relevant raw materials, as well as the effects of this variability on achievable recoveries. The assessment of uncertainties is implemented via Monte-Carlo-type simulations. Presentation of the results in availability curves ensures adaptability to future changes in market conditions, while extensive documentation of the assessment method, available as electronic supplementary material with this article, ensures reproducibility.
A simple example is used to illustrate the complete estimation process. It shows that in addition to ensuring future adaptability of the results, availability curves are also useful for the assessment of the current supply regime of a given by-product. An elastic and inelastic regime might be distinguished – in the elastic regime, significant demand-driven increases in by-product supply are possible without increases in the production of the main product, while in the inelastic regime this is not the case. The method presented in this article is the first to enable such an assessment to be made in a reliable and transparent manner.

Impurities play an important role in determining the electrical, optical and structural properties of semiconductors. It has been proposed that deep level impurities, such as Titanium (Ti) or chalcogens in Si, can induce an impurity band inside the bandgap at high enough doping concentration. The insertion of an impurity band can enhance the absorption at a broader wavelength range and leads to applications in the so-called intermediate band solar cell. However, deep level impurities have relatively low solid solubility limit in Si. We prepared deep level impurities doped silicon to above the Mott insulator concentration by ion implantation followed by sub-second annealing. The degree of crystalline lattice recovery in implanted layers and the lattice location of impurities in Si were analyzed by Rutherford backscattering spectrometry/Channeling. Our results show that S and Se atoms are occupying substitutional lattice sites in Si [1], while Ti impurities have no ordered lattice occupation [2].

[1] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, W. Skorupa and M. Helm, Scientific Report 5, 8329 (2015).
[2] F. Liu, et al., in preparation (2015).

Impurities play an important role in determining the electrical, optical and structural properties of semiconductors. It has been proposed that deep level impurities, such as Titanium (Ti) or chalcogens in Si, can induce an impurity band inside the bandgap at high enough doping concentration. The insertion of an impurity band can enhance the absorption at a broader wavelength range and leads to applications in the so-called intermediate band solar cell. However, deep level impurities have relatively low solid solubility limit in Si. We prepared deep level impurities doped silicon to above the Mott insulator concentration by ion implantation followed by sub-second annealing. The degree of crystalline lattice recovery in implanted layers and the lattice location of impurities in Si were analyzed by Rutherford backscattering spectrometry/Channeling. Our results show that S and Se atoms are occupying substitutional lattice sites in Si [1], while Ti impurities have no ordered lattice occupation [2].

[1] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, W. Skorupa and M. Helm, Scientific Report 5, 8329 (2015).
[2] F. Liu, et al., in preparation (2015).

Nanosafety research requires versatile tools for detection of nanoparticles in living and non-living media within a wide range of concentration. This is a great challenge due to the very low environmentally relevant concentration of (engineered) nanoparticles expected and the presence of background concentrations of the respective elements. Radiolabelling of nanoparticles offers an excellent alternative to enable nanoparticle detection in these complex media down to trace amounts. Even online in situ tracing and visualisation techniques are accessible.

In this work we present different techniques for the radiolabelling of nanoparticles (Ag⁰, TiO₂, CeO₂, MWCNT) including activation of NP, radiosynthesis of NP, radiolabelling of NP, self-diffusion of radioisotopes into NP and recoil labelling. A cyclotron Cyclone 18/9 was used for the radiolabelling of the nanoparticles via proton activation (Ti-48(p,n)V-48, Ce-140(p,2n)Pr-139  Ce-139), Be-7 - recoil labelling (Li 7(p,n)Be-7) and the radioisotope production. Different targets were developed and different labelling strategies were tested. As a result, labelling yields and labelling stabilities were determined and the influence of the labelling procedure on the particle properties was evaluated.

These radiolabelled nanoparticles are successfully used in comprehensive environmental studies. Our recent studies with application of the radiolabelled nanoparticles focus on nanoparticle uptake in plants, distribution and mobility of nanoparticles in sewage sludge, and fate of nanoparticles in wastewater treatment processes.

In solar thermal energy conversion systems, receivers containing the heat transfer fluid are coated by a solar selective coating which must exhibit high absorption in the solar region and low thermal emittance. Additionally, the coating materials have to be structurally, optically, and mechanically stable at high temperatures. Nowadays, temperatures of up to 450 °C and up to 550°C are reached using parabolic trough arrays and solar tower absorbers, respectively, whereas temperatures up to 800 °C could be reached if the receiver materials were stable enough. Solar selective coatings can be formed by a transparent conductive oxide (TCOs) film deposited on a black body absorber to have both, high absorption in the ultraviolet, visible and near infrared spectral range (300 nm – 2500 nm) as well as high reflectivity in the infrared (> 2500 nm). The former is to absorb as much sunlight as possible, the latter for preventing thermal radiation losses from the system to the environment. In this work Ta:TiO2 and Ta:SnO2 TCOs thin films are reactively magnetron sputtered from tantalum doped metallic targets. The oxygen flow during deposition is precisely controlled by a plasma emission unit which is crucial to obtain optimal electrical and therefore also optical properties by maintaining high sputtering rates. While the as-deposited films are amorphous and non-conductive, they are crystallized and therefore electrically activated upon a subsequent thermal treatment at 425 °C for 1 hour. The correlation between structural, optical, and electrical properties is shown by Rutherford Backscattering Spectroscopy (RBS), X-ray Diffraction (XRD), Raman Spectroscopy, Spectroscopic Ellipsometry (SE) (both at room- and high- temperatures), UV-VIS spectrometry, and Hall Effect measurements. Preliminary tests show that optical constants of Ta:TiO2 films are maintained after annealing at 700ºC.

Transparent conductive oxides (TCOs) are already widely used in the optoelectronic industry e.g. as electrodes for liquid crystal displays (LCDs), organic light emitting diodes (OLEDs), or thin film solar cells. Less attention has been devoted to their optical properties and thermal stability until now.
In this work, Tantalum doped TiO2 and SnO2 TCO films are investigated with respect to their structural, optical, and electrical properties at temperatures from RT to 700°C. The films are prepared at room temperature by direct current reactive magnetron sputtering from metallic as well as ceramic targets and subsequently isothermally annealed at temperatures of 425°C. For compositional and structural analysis x-ray diffraction (XRD), Raman spectroscopy, and Rutherford backscattering spectroscopy (RBS) are used. The optical properties are determined by spectroscopic ellipsometry, spectral photometry, and subsequent modelling. Hall effect measurements are used to determine the electrical properties of the TCO films.
The as-deposited layers are amorphous and isolating. By thermal annealing they are activated and become conductive.

A steady axial magnetic field is applied to a liquid metal zone heated by induction currents. The resulting alternating Lorentz force causes pressure oscillations that being strong enough lead to cavitation in the molten metal. Amplitude of the pressure oscillations is proportional to the product of the induced currents and the steady axial magnetic field induction. We follow an approach where the acoustic pressure is maximized by the induction currents. The onset of cavitation is identified by the occurrence of sub-harmonics of the drive frequency in sound recorded at the surface of the experimental cell. It is demonstrated that cavitation in a liquid metal may be excited by a superimposed axial magnetic field of a moderate 0.5 T induction.

Understanding the macro segregation formed by applying electric currents is of high commercial importance. This paper investigates how electric currents control the solute distribution in the directionally solidified Al-20.5wt%Si hypereutectic alloy. Experimental results show that a severe macro segregation of the primary silicon phase occurs at the initial solidification stage of the samples. This is accompanied by two interface transitions in the mushy zone: quasi planar → upwards V-shaped → quasi planar. The corresponding numerical simulations present a vortex ring flow pattern as a consequence of the electric current distortion in the mushy zone. The peculiar macro segregation phenomenon can be fully explained by considering the effect of the forced flow on the solute distribution. At the initial growth of the samples, the forced flow generates a rigorous solute exchange between the mushy zone and the bulk melt and encourages the primary silicon to continuously precipitate and segregate. As the solute content in the bulk melt gradually approaches the eutectic point, the precipitation of primary silicon is profoundly reduced. Eventually, a significant segregation of the primary silicon phase is observed in the initial directional growth. The present study not only presents a new approach to control the solute distribution by applying an electric current through a generated forced flow, it also facilitates the understanding of the underlying grain refinement mechanism and the growth of crystals in the solute that are controlled by the electric currents.

Wire'mesh sensors have so far been widely applied in gas'liquid flows where resistance or capacitance distributions are measured and converted into gas or liquid holdup distributions. In this work we report on the qualification of the wire'mesh imaging technique for the measurement of cross'sectional solid concentrations in solid–liquid mixtures. As the dielectric constants of solid particles are different from those of gas, water or oil in the flow, measuring this property can be used as an indication of solids distribution. Experiments were performed in a stirred tank of 100 mm diameter equipped with a capacitance wire'mesh sensor. The wire'mesh sensor was operated 4000 frames per second acquisition speed and has a spatial resolution of 6.25 mm. As solids we used silica sand particles (diameter ~ 105 μm) which were stirred with water in a volume concentration range of 1% to 35% to form slurries. By varying the stirring speed, different solid concentration distributions were produced and investigated. In order to convert the measured relative permittivity distribution into a solid concentration distribution, an empirical approach was employed.

We report to our knowledge the first short pulse generation experiment
in bulk volume Yb-doped fused silica utilizing a Q-switched cavity.

In 1974, Nelson, Kase, and Svenson published an experimental investigation on muon shielding using the SLAC high energy LINAC. They measured muon fluence and absorbed dose induced by a 18 GeV electron beam hitting a copper/water beam dump and attenuated in a thick steel shielding. In their paper, they compared the results with the theoretical mode ls available at the time. In order to compare their experimental results with present model calculations, we use the modern transport Monte Carlo codes MARS15, FLUKA2011 and GEANT4 to model the experimental setup and run simulations. The results will then be compared between the codes, and with the SLAC data.

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SrCu₂(BO₃)₂ is a prominent realization of the Shastry-Sutherland lattice model [1]. In this quasi-two-dimensional compound, Cu²⁺ ions form orthogonal spin-singlet dimers with strong geometrical frustration of the next-nearest and nearest neighbor exchange interactions. SrCu₂(BO₃)₂ has been studied extensively using a variety of techniques, such as nuclear magnetic resonance (NMR) spectroscopy, or recent magnetization measurements up to 118 T. These experiments reveal a complex sequence of magnetization plateaus with differing commensurate magnetic superstructure, stemming from a stripe type order of triplet states [2-4]. Due to its highly sensitive local probe character, NMR can provide deep insight into the spin-coupling mechanisms and excitations at highest magnetic fields. We present ¹¹B NMR spectra measured in pulsed magnetic fields up to 56 T, and compare those with prior results obtained in highest static magnetic fields. Herewith, we prove the feasibility and efficacy of this new technique, yielding the capability for extended studies at highest magnetic fields up to the 100 T regime that determine the spin structure in the 1/3 magnetization plateau and beyond.

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Ferromagnetic semiconductors (FSs) have been under intensive investigation during the last decade. Until now, the prototype ferromagnetic semiconductor GaMnAs has revealed a variety of unique features induced by the combination of its magnetic and semiconducting properties. As a non-equilibrium process, ion implantation can overcome the difficulty that the Mn concentration in ferromagnetic III-V (FS) is far beyond the solid solubility of Mn in III-V compounds. However, the activation of dopants remains challenging due to the clustering of implanted ions during post-annealing. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. On the other hand, one notes that the solubility limit in the liquid phase is generally much larger than that in the solid phase. Short-time annealing within nanoseconds regime allows the epitaxial growth from a liquid phase. The approach combining ion implantation and pulsed laser melting allows us to prepare ferromagnetic semiconductors covering the full spectrum of III-V compound semiconductors.
We have successfully synthesized ferromagnetic Mn doped III-V from InAs and GaAs to InP and GaP with different bandgaps. The results of magnetization, magnetic anisotropy, resistivity, anomalous Hall effect, magnetoresistance and x-ray magnetic circular dichroism obtained from the synthesized samples confirm the intrinsic origin and the carrier-mediated nature of the ferromagnetism. Moreover, in different III-V hosts we observe distinct differences regarding the magnetic anisotropy and conduction mechanism which are related with the intrinsic parameters such as the lattice mismatch, energy gap and the acceptor level of Mn. These results could allow a panorama-like understanding of III-V:Mn based ferromagnetic semiconductors.

The objective of this study is to examine the influence of different vertical tube bundle designs on the bubble dynamics and on the mass transfer rates in a bubble column. The studies in the open literature examining the performance of bubble columns with vertically inserted tube bundles have focused primarily on the coverage of the cross-sectional area of the bubble column by the tube bundle (CSA). The most frequently used coverages are the 5% and the 25% (± 3%) which mimic the heat exchangers utilized in the processes of methanol and Fischer-Tropsch syntheses. Other than that, the designs of tube bundles seem to be arbitrarily chosen and feature a number of different configurations of layouts, tube diameters and tube lengths. From the current state of research, it is thus rather difficult to draw conclusions on the optimal design of a heat exchanger suitable for use in bubble columns (Youssef et al., 2013). Intuitively, it can be concluded that the most important design features of tube bundles affecting the flow are the distance between the tubes and the unit cell area enclosed by the tubes in their respective arrangements. Accordingly, the study aims on a systematic analysis on the effect of these geometric parameters.

The uranium(VI) sorption onto orthoclase and muscovite, representing feldspars and micas as important components of the earth crust, was investigated in the presence and absence of Ca2+ under aerobic conditions. Batch experiments were accompanied by time-resolved laser-induced fluorescence spectroscopy (TRLFS) as well as in situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy. The results indicate that the U(VI) sorption is reduced by Ca2+ at pH ≥ 8 up to 30% due to the formation of the neutral aqueous Ca2UO2(CO3)3 complex. TRLFS measurements on the supernatant confirmed the predominance of this Ca2UO2(CO3)3 complex in accordance with thermodynamic calculations. Furthermore, TRLFS measurements on the mineral suspension as a function of pH (4 – 9) and Ca2+ revealed the existence of several species. Parallel factor analysis (PARAFAC) indicated the formation of three surface species totally. In the absence of Ca2+, the ≡XO UO2+ and ≡XO UO2CO3– surface complexes were formed, whereas the presence of Ca2+ leads to the formation of ≡XO UO2+ and ≡XO UO2OH as the formation of the aqueous Ca2UO2(CO3)3 complex reduces the free UO22+ concentration in the solution. Additional, ATR FT-IR confirmed an outer-sphere surface species in the absence of Ca2+. These experimental results were used for the assessment of surface complexation parameters to improve the basis for a mechanistic modeling of the sorption processes of U(VI) onto orthoclase and muscovite including the influence of Ca2+. Namely, log K≡XO-UO2+ = 1.69 and log K≡XO-UO2CO3− = 8.96 were determined for sorption onto orthoclase, whereas log K≡XO-UO2+ = 0.41 and log K≡XO-UO2CO3− = 8.71 best describe sorption onto muscovite.

The removal of nitrogen and organic components by micro-organisms is an essential step in the biodegradable wastewater treatment plants. These biological reactions take place in large aerated cross flow reactors. In fact, up to 80 % of the total energy budget of wastewater treatment plants is consumed by the aeration process. Engineering and design of the plants are mostly based on empirical knowledge and limited instrumentation for single points of measurement. Thus, the complex hydrodynamic and biochemical processes in the large-scale vessels are not well understood, and there is a high potential for optimization of these processes. Recently, numerical tools, such as CFD, have been used for the design and prediction of improved operation of the reactors. However, the models used in the software show a significant deviation from experimental data and need improvement due to the complexity of the multiphase flows of aerated sludges (bubbles, microbial flakes, water). A detailed study has been carried out in a vertical column of 3.5 m in height at HZDR to obtain an improved understanding of the hydrodynamics of aerated sludges. To capture the temporal evolution of the rising bubbles in the opaque liquors the ultra-fast electron beam X-ray tomography system of HZDR was used. The target parameters are bubble size distribution, equivalent sauter diameter of the bubbles, bubble rise velocity and local gas hold-up under the variation of sparger type (rubber, monolithic material), gas flow rate, rheology of the fluid (deionized water, salty water, sludge) and height in the liquid column. Therefore enhanced image analysis algorithms, developed at HZDR, were applied to the reconstructed tomographic images, which are also presented in the paper. In the future, the experimental data set will be used as reference data for the improvement of numerical models of CFD software.

Investigation of the fluid circulation and the macro-mixing process in a stirred model fermenter of non-NEWTONIAN liquid was conducted by the comparative use of flow following sensor particles and ERT. Average fluid circulation times were estimated from (i) the measured vertical position of the sensor particle, (ii) the fluctuating ERT signals of single ERT planes and (iii) the measured mixing times of ERT-NaCl tracer experiments. The estimated average circulation times of all the three methods are comparable for the two investigated impeller positions. Furthermore, axial residence profiles of the sensor particles were extracted, which reveal the impact of the impeller configuration to the axial mixing homogeneity. Moreover, the results confirm the conclusions about the effect of the lifted impeller position derived by Reinecke et al. (2012) in a 1000 L pilot fermenter. The excellent detectability of the particles and the consistent results confirm the feasibility of the combined method for further investigation of the complex flows in biogas fermenters.

Zur Untersuchung der ablaufenden Prozesse in großen Behältern, wie z. B. Biogasfermentern, Bioreaktoren und Belebtschlammbecken, wurde am HZDR das Konzept instrumentierter, strömungsfolgender Sensorpartikel entwickelt [1]. Die Sensorpartikel werden als auftriebsneutrale Strömungsfolger eingesetzt und erfassen dabei kontinuierlich Prozessparameter. Diese Daten werden nach der Rückgewinnung der Sensorpartikel aus dem Prozess einem computergestützten Analysesystem zur Verfügung gestellt. Die erweiterten Sensorpartikel bestehen aus robusten Kapseln, welche mit einer integrierten Messelektronik und einer mechanischen Auftriebseinheit ausgestattet sind (siehe Abb. 1). Das Systemkonzept berücksichtigt derzeit miniaturisierte Sensoren für die Umgebungstemperatur, die Eintauchtiefe als Funktion des hydrostatischen Drucks, die Beschleunigung, die Drehrate und das Magnetfeld. Das Konzept ist zudem offen für die Einbindung ergänzender miniaturisierter Messfühler, wie z. B. für pH-Wert und Gelöst-Sauerstoff. Die Auftriebseinheit erlaubt eine automatisierte Tarierung der Sensorpartikel im ruhenden Prozessmedium, wodurch ein aufwändiges manuelles Justieren der Partikelmasse entfällt. Zudem ist mit der Auftriebseinheit eine erleichterte Rückgewinnung der Sensorpartikel von der Flüssigkeitsoberfläche nach Beendigung der Messung möglich.
Im Beitrag werden das erweiterte Konzept zur Positionsdetektion der Strömungsfolger und erste Testergebnisse vorgestellt. Es werden zum einen die Signale der Beschleunigung, der Drehrate und der magnetischen Flussdichte zur Rekonstruktion von Positionsveränderungen genutzt. Weiterhin ist die Detektion von externen Positionsmarkern, wie z. B. dem Signal einer Tauschspule, möglich. Beide Varianten wurden in praxisrelevanten Szenarien getestet. Zudem wird sowohl die Dimensionierung und der Aufbau der integrierten Auftriebseinheit als auch der Test unter realen Strömungsbedingungen vorgestellt.

Die Erzeugung von Energie aus Biogas ist ein wichtiger Baustein unseres zukünftigen Energiekonzepts. Das Biogas dafür wird in Biogasfermentern gewonnen. In den letzten Jahren ist die Anzahl solcher Anlagen allein in Deutschland auf etwa 8.000 gestiegen. Allerdings zeigt sich, dass die bisherige Ausnutzung des Potenzials, das das Biogas bietet, bisher sehr gering ist. Biogasanlagen verwenden nahezu keine Instrumentierung, um die Anlagentechnik geeignet steuern und damit effizient betreiben zu können. Dadurch ist auch das Wissen über die Mischvorgänge in Biogasfermentern und die entscheidenden Einflüsse auf die Prozessführung völlig unzureichend. Es wurde untersucht, wie man durch strömungsfolgende Sensoren, die in Biogasfermentern eingebracht werden und dann die relevanten Prozessparameter räumlich verteilt messen, Kenntnis über die ablaufenden Mischprozesse erlangt. Damit lassen sich einerseits direkte Schlussfolgerungen für den Betrieb von Biogasfermentern ableiten, andererseits aber auch theoretische Prozessmodelle entwickeln, validieren und anpassen, um Biogasanlagen zukünftig viel effizienter betreiben zu können.

We have prepared the dilute magnetic semiconductor (DMS) InMnAs with different Mn concentrations by ion implantation and pulsed laser melting. The Curie temperature of the In1−xMnxAs epilayer depends on the Mn concentration x, reaching 82K for x = 0.105. The substitution of Mn ions at the indium sites induces a compressive strain perpendicular to the InMnAs layer and a tensile strain along the in-plane direction. This gives rise to a large perpendicular magnetic anisotropy, which is often needed for the demonstration of the electrical control of magnetization and for spin-transfer-torque induced magnetization reversal

CsCl-type HoZn undergoes two successive magnetic phase transitions: (i) paramagnetic to ferromagnetic (FM) at T-C similar to 72 K and (ii) a spin reorientation (SR) at T-SR similar to 26 K. Magnetization and modified Arrott plots indicate that HoZn undergoes a second-order magnetic phase transition around T-C. The obtained critical exponents have some small deviations from the mean-field theory, indicating a short range or a local magnetic interaction which is properly related to the coexistence of FM and SR transitions at low temperature. Two successive magnetic transitions in HoZn induce one broad pronounced peak together with a shoulder in the temperature dependence of the magnetic entropy change -Delta S-M(T) curves, resulting in a wide temperature range with a large relative cooling power (RCP). For a field change of 0-7 T, the maximum value of -Delta S-M is 15.2 J/kg K around T-C with a large RCP value of 1124 J/kg. The large reversible magnetocaloric effect (MCE) and RC indicate that HoZn is a good candidate for active magnetic refrigeration.

Geomorphic footprints of past large Himalayan earthquakes are elusive, though urgently needed for gauging and predicting recovery times of seismically perturbed mountain landscapes. We present evidence of catastrophic valley infill following at least three medieval earthquakes in the Nepal Himalayas. Radiocarbon ages from peat beds, plant macrofossils, and humic silts in fine-grained tributary sediments near Pokhara, Nepal’s second largest city, match the timing of nearby M~8 earthquakes in ~1100, 1255, and 1344 AD. The upstream dip of these valley fills and X-ray fluorescence spectrometry of their provenance rule out any local source. Instead, geomorphic and sedimentary evidence is consistent with catastrophic debris flows that had invaded and plugged several tributaries with tens of meters of calcareous sediment from a Higher Himalayan source >60 km away.

Die Erfindung betrifft Verfahren und Einrichtungen zur Kontrolle einer therapeutischen Bestrahlung durch eine Bestrahlungseinrichtung mit einem mikrogepulsten Teilchenstrahl mittels eines Positronen-Emissions-Tomografen. Diese zeichnen sich insbesondere dadurch aus, dass eine therapeutische Bestrahlung durch eine Bestrahlungseinrichtung mit einem mikrogepulsten Teilchenstrahl mittels eines Positronen-Emissions-Tomografen während der Bestrahlung kontrollierbar ist. Dazu werden wahre Koinzidenzen mittels – des durch die erlaubte Zeitdifferenz des Auftreffens zweier Photonen in verschiedenen Detektoren des Tomografen bestimmten Koinzidenzzeitfensters und – der Differenz zwischen prompten Fenster und verzögerten Fenster ohne wahre Koinzidenzen ermittelt. Dabei sind sowohl das Koinzidenzzeitfenster als auch die Zeitdifferenz zwischen prompten und verzögerten Fenster ein ganzzahliges Vielfaches der durch die Frequenz der beschleunigenden Wechselspannung des Hochfrequenzbeschleunigers gegebenen Zeitdauer einer Mikropulsperiode des Teilchenstrahls. Die Mikropulsperiode ist durch den Mikropuls und die Pause zwischen Mikropulsen definiert. Diese Zeitdauer ist durch die Frequenz der die Teilchen des Teilchenstrahls beschleunigenden Wechselspannung gegeben und damit zu wählen.

The influence of the grid size on the rise velocity of a single bubble simulated with an Eulerian two-fluid method is investigated. This study is part of the development of an elaborated Eulerian two-fluid framework, which is able to predict complex flow phenomena as arising in nuclear reactor safety research issues. Such flow phenomena cover a wide range of interfacial length scales. An important aspect of the simulation method is the distinction into small flow structures, which are modeled, and large structures, which are resolved. To investigate the requirements on the numerical grid for the simulation of such resolved structures the velocity of rising gas bubbles is a good example since theoretical values are available. It is well known that the rise velocity of resolved bubbles is clearly underestimated in a one-fluid approach if they span over only few numerical cells. In the present paper it is shown that in the case of the two-fluid model the bubble rise velocity depends only slightly on the grid size. This is explained with the use of models for the gas–liquid interfacial forces. Good approximations of the rise velocity and the bubble shape are obtained with only few grid points per bubble diameter. This result justifies the resolved treatment of flow structures, which cover only few grid cells. Thus, a limit for the distinction into resolved and modeled structures in the two-fluid context may be established.

Magnetic silk fibroin protein (SFP) scaffolds integrating magnetic materials and featuring magnetic gradients were prepared for potential utility in magnetic-field assisted tissue engineering. Magnetic nanoparticles (MNPs) were introduced into SFP scaffolds via dip-coating methods, resulting in magnetic SFP scaffolds with different strengths of magnetization. Magnetic SFP scaffolds showed excellent hyperthermia properties achieving temperature increases up to 8 °C in about 100 s. The scaffolds were not toxic to osteogenic cells and improved cell adhesion and proliferation. These findings suggest that tailored magnetized silk-based biomaterials can be engineered with interesting features for biomaterials and tissue-engineering applications.

The Fifteenth International Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS15) was organized by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the Technische Universität (TU) Dresden and held at TU Dresden from August 25 to August 29, 2014.
CGS15 was the fifteenth symposium in a series that started in 1969.
This conference continued the general themes of earlier meetings with special emphasis on gamma-ray spectroscopy used in neutron capture and also in a wider context in nuclear structure, nuclear reactions, nuclear astrophysics, statistical properties of nuclei, nuclear probes for fundamental physics, nuclear data, novel techniques and applications.
These proceedings include a collection of articles from all these topics.

Objectives: Purine nucleotides such as ATP and ADP are important extracellular signaling molecules in almost all tissues. Via P2Y₁R activation they mediate brain functions by trophic effects like differentiation and proliferation but also via fast synaptic transmission. The understanding of its role in brain disorders is limited because of lack of suitable brain-penetrating P2Y₁R-selective drugs. Chao and co workers recently reported the first non-nucleotidic, diarylurea ligands with high affinity and selectivity for the P2Y₁R^[1]. We selected this scaffold for the development a ¹⁸F labeled P2Y₁R ligand for brain imaging.

Methods: Based on the lead compounds 1-3 (K_i = 6-8 nM),^[1] we designed derivative 5, suitable for aliphatic radiofluorination using the corresponding tosyl precursor 4. The radiolabeling was systematically optimized (eg. phase transfer catalyst, solvent, temperature, amount of precursor and heating method) and [¹⁸F]5 successfully provided for subsequent evaluation. The lead structure was further modified by fluorinating pyridine at the 2-position, replacing the urea subunit C with 2 aminothiazole, and substituting ring D with various fluoroaromatic and non-aromatic rings.

Results: Reference compound 5 has been synthesized from the tosylate 4 in 62% yield. Under optimized conditions, [¹⁸F]5 has been obtained in high radiochemical yield (30%) and purity (≥99%) at a specific activity of ~182 GBq/µmol. A series of 30 new fluorinated derivatives has been synthesized.

Conclusions: The first ¹⁸F-labeled P2Y₁R ligand, [¹⁸F]5 has been successfully synthesized. To evaluate the newly designed compounds, an in vitro binding assay using stably transfected P2Y₁R-1321N1 cells and [¹⁸F]5 is currently developed.

Literature: [1] Chao et al. J. Med. Chem. 2013, 56, 1704−1714

Glutathione (GSH), a ubiquitous intracellular reducing tripeptide, is able to reduce hexavalent uranium, U(VI), to its tetravalent form, U(IV), in aqueous media in vitro, inducing the formation of nanocrystalline mixed-valence uranium oxide particles. After initial reduction to U(V) and subsequent dismutation, yielded U(IV) rapidly hydrolyses at near-neutral conditions forming 2–5 nm sized nanoparticles. The latter further aggregate to 20–40 nm chain-like building blocks that finally arrange as network-like structures.

Investigations on two- and multiphase flow phenomena inside technical apparatuses or feedings are of highest interest for designers and operators since the knowledge helps to understand the fundamental physics behind processes, e.g. in chemical and process engineering. It expedites the development of safer and more efficiently operated industrial facilities. Furthermore, measured data are used to validate new models developed for multiphase flow simulation, e.g. CFD. For non-intrusive two-phase flow investigations, two radiation-based computed tomography (CT) scanners are operated at the Helmholtz-Zentrum Dresden - Rossendorf (HZDR) at the department of Fluid Dynamics: a high-resolution gamma-ray computed tomography scanner (HireCT) and an ultrafast electron beam X-ray CT scanner (ROFEX). They are able to recover non-superimposed cross-sectional material distributions of the scanned plane or volume section within the flow as time averaged images or time resolved image sequences. The capabilities of both CT systems are demonstrated exemplarily at experiments on an industrial scale bubble column, a fluidized bed and a static mixer.

As in 2007 the first 3.5 cell superconducting radio frequency (SRF) gun was taken into operation at Helmholtz-Zentrum Dresden-Rossendorf, it turned out that the specified performance to realize an electron energy of 9.4 MeV has not been achieved. Instead, the resonator of the gun was limited by field emission to about one third of this value and the measured beam parameters remained significantly below its expectations.

However, to demonstrate the full potential of this electron source for the ELBE linear accelerator, a second and slightly modified SRF gun was developed and built in collaboration with Thomas Jefferson National Accelerator Facility.

We will report on commissioning and first RF results of this new SRF gun. This includes in particular the characterization of the most important RF properties as well as their comparison with previous vertical test results. Additionally, investigations are presented that try to explain a particle contamination that happened recently during the first cathode transfer.

The radiation effects and relaxation processes in solid N₂ and N₂-doped Ne matrices, preirradiated by an electron beam, have been studied in the temperature range of 5–40 and 5–15 K, respectively. The study was performed using luminescence methods: cathodoluminescence CL and developed by our group nonstationary luminescence NsL, as well as optical and current activation spectroscopy methods: spectrally resolved thermally stimulated luminescence TSL and exoelectron emission TSEE. An appreciable accumulation of N radicals, N⁺, N₂ ⁺ ions, and trapped electrons is found in nitrogen-containing Ne matrices. Neutralization reactions were shown to dominate relaxation scenario in the low-temperature range, while at higher temperatures diffusion-controlled reactions of neutral species contribute. It was conceived that in α-phase of solid N₂, the dimerization reaction (N₂ ⁺ + N₂ → N₄ ⁺) proceeds: “hole self-trapping”. Tetranitrogen cation N₄ ⁺ manifests itself by the dissociative recombination reaction with electron: N₄ ⁺ + e^– → N₂*(a^’1Σ_u ^–) + N₂ → N2 + N₂ + hν. In line with this assumption, we observed a growth of the a^’1Σ_u ^– → X¹Σ_g ⁺ transition intensity with an exposure time in CL spectra and the emergence of this emission in the course of electron detrapping on sample heating in the TSL and NsL experiments.

We study the dependence of the magnetocaloric effect on the magnetic field-change-rate the first order magnetostructural transition in Mn₃GaC by measuring the adiabatic temperature change ΔT at three different time scales: 11 mTs^-1, 700 mTs^-1, and ~1000 Ts^-1. We find that the Maximum adiabatic temperature-change of about 5 K is reached in the 11 mTs^-1 and 700 mTs^-1 rates, whereas for the ~1000 Ts^-1 the transition lags the change in the magnetic field so that the maximum adiabatic temperature-change is not attained.

We measured the optical conductivity of superconducting LiFeAs. In the superconducting state, the formation of the condensate leads to a spectral-weight loss and yields a penetration depth of 225 nm. No sharp signature of the superconducting gap is observed. This suggests that the system is likely in the clean limit. A Drude-Lorentz parametrization of the data in the normal state reveals a quasiparticle scattering rate supportive of spin fluctuations and proximity to a quantum critical point.

We investigated the doping effects of Sb on the magnetic, transport and structural properties in FeTe_1-xSb_x single crystals. Resistivity, magnetic susceptibility and heat capacity experiments consistently reveal that the magnetic/structural transition temperature T_N ~ 70 K in undoped Fe_1.05Te is gradually suppressed by Sb doping, but no superconductivity is observed for x up to 10%. It is found that the electronic heat capacity coefficient gamma increases with Sb content, implying the increase of the density of states at Fermi level. Referring to previous calculation reports, this means that the Sb substituent plays a role of hole carrier doping, which is consistent with our measurements on Hall coefficient. Structural Analysis shows that Sb doping induces an expansion of the lattice along the a axis and a shrinkage along the c axis. Our work suggests that the antiferromagnetism in Fe_1+yTe may be different in nature with other parent compounds of FeAs-based systems.

Reliability and safety are perpetual topics in the development of nuclear installations. Generation III reactor concepts contain additional passive safety systems for improved accident control and mitigation. Main aspect of these passive systems is to operate with a minimum of external energy and signals. One example is the emergency condenser of the KERENA reactor concept, which removes heat from the core passively, e.g. after a station blackout. The governing natural circulation flow with condensation is only coarsely understood and current simulation methods need to be improved. During the condensation process a complex interaction between flow structure and heat transfer takes places and this determines the total efficiency of the passive safety system and hence the reliability in managing an incident.
The experimental facility COSMEA (condensation test rig for flow morphology and heat transfer studies) at HZDR is designated to provide experimental results to support the further development of CFD calculation methods. The test rig consists of a 3 m long emergency condenser pipe (ID 43 mm) which is 0.76° inclined and cooled by forced water flow. The experiments are conducted in a pressure range between 5 bar and 65 bar with steam mass flow rates up to 1 kg/s. Measurements of pressure, temperature, flow rate and condensation rate deliver integral understanding of the process. To investigate the details of the resulting stratified flow structures, x-ray tomography is applied. Parallel temperature measurements inside the heat transferring wall provide information about the azimuthal distribution of the heat flux.
A phase injection system was developed to operate the experiment in a stepwise condensation mode, which allows the measuring of condensation rates, flow morphologies and heat transfer distribution for different steam fraction values. The combination between cross sectional images from x-ray tomography and the azimuthally resolved heat transfer clarify the coupling between flow structure and heat transfer during condensation.
The experimental results are supported by a system code calculation. The COSMEA facility was modeled with the RELAP5 code. The original condensation model of the code was modified such that the heat transfer coefficient depends on the local mass fraction of the flow field. The experimental and calculation results agreed well for the steady state condensation process in the condensation rate, secondary side temperature and the heat flux data.

The γ-strength functions and level densities of 73,74 Ge have been extracted from particle-γ coincidence data using the Oslo method. In addition the γ-strength function of 74 Ge above the neutron separation threshold, Sn = 10.196 MeV has been extracted from photoneutron measurements. When combined, these two experiments give a γ-strength function covering the energy range of ~ 1-13 MeV for 74 Ge. This thorough investigation of 74Ge is a part of an international campaign to study the previously reported low energy enhancement in this mass region in the γ-strength function from ~ 3 MeV towards lower γ energies. The obtained data show that both 73,74 Ge display an increase in strength at low γ energies.

Baryon resonance production in proton-proton collisions at a kinetic beam energy of 1.25 GeV is investigated. The multi-differential data were measured by the HADES collaboration. Exclusive channels with one pion in the final state (nπ⁺ and pπ⁰) were put to extended studies based on various observables in the framework of a one-pion exchange model and with solutions obtained within the framework of a partial wave analysis (PWA) of the Bonn-Gatchina group. The results of the PWA confirm the dominant contribution of the Δ(1232), yet with a sizable impact of the N(1440) and non-resonant partial waves. The obtained resonance production cross sections provide a useful normalization for the further analysis of the Δ⁺ -> pe⁺e^- Dalitz decay.

A pronounced spike at low energy in the strength function for magnetic radiation (LEMAR) is found by means of Shell Model calculations, which explains the experimentally observed enhancement of the dipole strength. LEMAR originates from statistical low-energy M1-transitions between many excited complex states.
Re-coupling of the proton and neutron high-j orbitals generates the strong magnetic radiation. LEMAR is predicted for nuclides with A ~ 132 participating in the r-process of element synthesis. It increases the reaction rates by a factor of 2.5. The spectral function of LEMAR follows Planck's Law. A power law for the size distribution of the B(M1) values is found.

The condensation of saturated steam bubbles in sub-cooled water inside a vertical pipe is studied by poly-disperse CFD simulations. Six test cases with varied pressure, liquid sub-cooling and diameter of the gas injection orifices are investigated. Baseline closures presented for non-drag forces in previous work are found to be reliable also in non-isothermal cases. The effect of bubble coalescence and breakup is negligible in cases with small orifice diameter. The Ranz-Marshall correlation leads to a global under-estimation of the condensation rate, especially at high pressure levels.

The main objective of this Diploma thesis was to determine the regime transition between trickling and pulsing flow for solid ceramic foams made of silicium carbid with extra silicium coating (SiSiC). Two pressure transducers were used in order to determine this transition. Additional to the experimental determination, a predictive model was developed after the idea of Grosser et al. (1988) as well as Attou and Ferschneider (2000). Therefore, bed specific parameters (specific surface area, pressure drop parameters, static liquid holdup, porosity of the bed) and fluid specific parameters (gas and liquid density and viscosity, surface tension) had to be known. Since these models were only validated for conventional FBRs with a packing of spheres, modifications have been carried out in order to fit the model to foam related parameters.
In order to describe the regime transition through the models, further experiments had been carried out. The static liquid holdup as well as the singe phase (gas phase) pressure drop were investigated and afterwards modeled though different approaches.
To obtain the influences of changing the surface tension as well as the viscosity on the regime transition, additional experiments with tergitol and glycerin were carried out.
Three different pore sizes (20 PPI, 30 PPI and 45PPI) as well as two different foam diameters (0.05m and 0.1 m) were investigated with two different spray systems. For the change of viscosity and surface tension, only foams with a diameter of 0.1m had been used.

The neutron capture reaction at 77 Se has been studied with cold neutrons in the course of the EXILL campaign at the high-flux reactor of the Institut Laue-Langevin Grenoble. A simulation of the detector array with Geant4 has been accomplished and evaluated. The detector response has been deduced and measured spectra were unfolded, which have been compared with simulations using γDex to determine strength functions.

The bremsstrahlung facility at the ELBE accelerator offers the possibility to investigate dipole strength distributions up to the neutron-separation energies with photon up to 16 MeV in energy. The facility and various results for nuclides measured during recent years are presented. One example is the study of the N = 80 nuclide 136 Ba. The other presented example is the study of the chain of xenon isotopes from N = 70 to N = 80 which aimed to investigate the influence of nuclear deformation an neutron excess on the dipole strength in the pygmy region. An overview of the analysis is given. GEANT4 simulations were performed to determine the non-nuclear background that has to be removed from the measured spectra. This opens up the possibility to take into account also the strength of unresolved transitions. Simulations of gamma-ray cascades were carried out that consider the transitions from states in the quasi-continuum and allow us to estimate their branching ratios. As a result, the photoabsorption cross sections obtained from corrected intensities of ground-state transitions are compared with theoretical predictions and results within the chain of isotopes. With the help of the measured dipole distribution it is possible to describe gamma-ray spectra following neutron capture more precisely.

Collaboration on strength function measurements and level density determinations is ongoing between the Budapest Prompt Gamma Neutron Activation Analysis and the ELBE Nuclear Physics groups within the framework of EU FP6 EFNUDAT project. The idea is to prove that good theoretical fits to the measured gamma-ray spectra collected in the (n,γ) and (γ,γ’) reactions can be carried out using common photon strength and level density functions over a wide spectral energy range from 1 to 10 MeV for the same residual nucleus. Here, preliminary results on the isotope pair of 113,114Cd are presented for which the neutron capture state in 114Cd has 1+ or 0+ spin and parity.

We report the synthesis and magnetic properties of the molecular cluster Cu₃(μ₃−OH)(μ-OH)(μ-O₂Ar^4F-Ph)₂(py)₃(OTf)₂, abbreviated as (Cu₃(OH)). Using magnetization, electron paramagnetic resonance and spin dimer analysis, we derive a microscopic magnetic model of (Cu₃(OH)) and measure the electron T₁ and T₂ relaxation times. The Cu²⁺ ions are arranged to form a distorted triangular structure with the three different exchange coupling constants J₁ = −43.5 K, J₂ = −53.0 K, and J₃ = −37.7 K. At T = 1.5 K T₁ is of the order of 10⁻⁴ s and T₂ is evaluated to be 0.26 μs. We find that the temperature dependence of 1/T₁ and 1/T₂ is governed by Orbach process and spin bath fluctuations, respectively. We discuss the role of spin–phonon mechanism in determining a spin decoherence time in a class of spin triangular clusters.

We have performed magnetic measurements in two melt-textured NdBa₂Cu₃O_7-δ samples with Nd422 inclusions under magnetic fields from 0.05 up to 14 T, applied parallel to the ab planes. The measurements were made with a superconducting quantum interference device (SQUID) and a vibrating sample magnetometer (VSM). Paramagnetic moments could be observed during FCC (field-cooled cooling) and FCW (field-cooled warming) experiments. This effect, known as Paramagnetic Meissner Effect (PME), persisted up to 14 T and strong irreversibilities were observed among FCC and FCW experiments, revealing the presence of time effects. These time effects were confirmed by specific magnetic relaxation experiments in different cooling rates and temperatures, showing an anomalous and curious paramagnetic behavior. We explain our results based on the flux-compressed state generated within nonsuperconducting regions of the sample, such as the Nd422 inclusions dispersed into the superconducting matrix. These inclusions may produce a strong vortex pinning that stabilize the paramagnetic state, allowing the admission of extra vortices into the sample responsible for the positive moments during the relaxation experiments.

We experimentally study intrinsic tunneling and high magnetic field (up to 65 T) transport characteristics of the single-layer cuprate Bi_2+xSr_2−yCuO_6+δ, with a very low superconducting critical temperature T_c ≲ 4 K. It is observed that the superconducting gap, the collective bosonic mode energy, the upper critical field, and the fluctuation temperature range are scaling down with T_c, while the corresponding pseudogap characteristics remain the same as in high-T_c cuprates with 20 to 30 times higher T_c. The observed disparity of the superconducting and pseudogap scales clearly reveals their different origins.

⁷⁹Se und ⁹⁹Tc sind als Spaltprodukte im nuklearen Brennstoffkreislauf für die Sicherheitsanalyse eines zukünftigen Endlagers von besonderem Interesse. Eine Abschätzung der Migration dieser Elemente im Nah- und Fernfeld eines geologischen Tiefenlagers ist nur möglich auf der Basis der umfassenden Kenntnis der Wechselwirkungen der Spezies mit mineralischen Oberflächen. Insbesondere die Oxoanionen Se(VI)O₄ ^2– und Tc(VII)O₄ ^– gelten auf Grund ihrer hohen Löslichkeit und negativen Ladung als besonders mobile Spezies in Aquiferen.
Die Oberflächenreaktionen von in Wasser gelösten Oxoanionen an Mineraloberflächen können mittels in situ Schwingungsspektroskopie dezidiert untersucht werden. Dabei können sowohl die Sorptions- als auch die Desorptionsreaktionen der gelösten Ionen an einer stationären mineralischen Phase in Echtzeit erfasst werden. [1–2]
Für das Selenation wurden an zwei verschiedenen Mineralphasen unterschiedliche Arten von außersphärischen Oberflächenkomplexen gefunden. Obwohl die makroskopischen Eigenschaften dieser Oberflächenkomplexe an beiden Mineralen auf eine außersphärische Anbindung (Physisorption) schließen lassen, zeigen die Infrarotspektren eine signifikant abweichende spektrale Signatur, die nur mit unterschiedlichen Molekülsymmetrien erklärt werden kann. So zeigen die Spektren je nach Mineraloberfläche, dass das Selenat mit einer leicht verzerrten – der aquatischen Spezies sehr ähnlichen – tetraedrischen bzw. mit einer bidendaten C_2v Symmetrie an die Oberfläche sorbiert wird. Diese Spezies können demnach als „erweiterte“ bzw. als „klassische“ außersphärische Komplexe bezeichnet werden. [3–4]
Entsprechende Experimente mit dem isostrukturellen Tc(VII)O₄ ^–-Anion zeigen, dass auch dieses Ion vorwiegend außersphärische Oberflächenkomplexe an verschiedenen Mineraloberflächen bildet. Dabei weisen die ersten Ergebnisse auf eine geringere Spezifizität des TcO₄ ^– bei der Anbindung an die verschiedenen Oberflächen hin.

[1] Foerstendorf, H. et al. (2012) J. Colloid Interface Sci. 377, 299–306. [2] Müller, K. et al. (2015) Environ. Sci. Technol. 49, 2560–2567. [3] Jordan, N. et al. (2011) Geochim. Cosmochim. Acta 75, 1519–1530. [4] Jordan, N. et al. (2013) Geochim. Cosmochim. Acta 103, 63–75.

The color X-ray camera SLcam® is a full-field, single photon detector providing scanning-free, energy and spatially resolved X-ray imaging. Spatial resolution is achieved with the use of polycapillary optics guiding Xray photons from small regions on a sample to distinct energy dispersive pixels on a charged-coupled device detector. Applying sub-pixel resolution, signals from individual capillary channels can be distinguished. Therefore, the SLcam® spatial resolution, which is normally limited to the pixel size of the charge-coupled device, can be improved to the size of individual polycapillary channels. In this work a new approach to a sub-pixel resolution algorithm comprising photon events also from the pixel centers is proposed. The details of the employed numerical method and several sub-pixel resolution examples are presented and discussed.

Speciation analysis of fast equilibrium processes is often challenging. Metal hydrolysis is one example of such a system. It is the basis for more complex aquatic systems and thus a deep understanding of those systems is indispensable. In the case of uranyl(VI) hydrolysis spectroscopic studies are hindered by low solubility over an wide pH range. Additionally occurrence of polynuclear complexes further complicates the system when working close to the solubility limit (e.g. 10-5 M uranyl(VI)). In a previous study we demonstrated that a combination of luminescence spectroscopic methods together with state of the art data analysis (parallel factor analysis; PARAFAC) and quantum chemical calculations is a powerful setup to gain information on that system [1]. Since uranyl(VI) has high affinities to several minerals and biopolymers systems containing trace metal concentrations have to be considered. In the present study we focus on this low concentration range (10-8 M uranyl(VI)).
We were able to extract thermodynamic constants for this system [(UO2(OH)(H2O)4+), (UO2(OH)2(H2O)3), (UO2(OH)3(H2O)2-)] using optimized data processing. Furthermore, advanced deconvolution of individual luminescence spectra demonstrates the correlation of luminescence spectroscopy and vibrational spectroscopy. Raman frequencies result from symmetrical stretching of the uranyl(VI) unit. We could show that features of individual emission spectra are separated by the same energy. Thus a further luminescence signal to chemical structure correlation is demonstrated which was missing for that system.

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Inhibition of cyclooxygenase-2 (COX-2) is a promising anti-inflammatory therapeutic strategy, but longterm medication with COX-2-inhibitors (coxibs) may be associated with adverse cardiovascular effects. Functionalization of existing lead structures with nitric oxide (NO)-releasing moieties is an auspicious approach to minimize these effects. In this regard, an organic nitrate (–O–NO₂) substituent was introduced at a (pyrazolyl)benzenesulfonamide lead structure. The novel NO-coxibs selectively inhibited COX-2 in a low micromolar range (IC₅₀(COX-2): 0.22–1.27 lM) and are supposed to be promising antiinflammatory compounds with, in parallel, positive effects on vascular homeostasis.

Ghrelin and Y2 receptors play a central role in appetite regulation inducing opposite effects. The Y2 receptor induces satiety, while the ghrelin receptor promotes hunger and weight gain. However, the food regulating system is tightly controlled by interconnected pathways where redundancies can lead to poor efficacy and drug tolerance when addressing a single molecule. We developed a multitarget strategy to synthesize dual peptides simultaneously inhibiting the ghrelin receptor and stimulating the Y2 receptor. Dual peptides showed dual activity in vitro, and one compound induced a slight diminution of food intake in a rodent model of obesity. In addition, stability studies in rats revealed different behaviors between the dual peptide and its corresponding monomers. The Y2 receptor agonist was unstable in blood, while the dual peptide showed an intermediate stability compared to that of the highly stable ghrelin receptor inverse agonist.

We investigate the question of how the blob approach is related to tube of response based modelling of the system matrix. In our model, the tube of response (TOR) is approximated as a cylinder with constant density (TOR-CD) and the cubic voxels are replaced by spheres. Here we investigate a modification of the TOR model that makes it effectively equivalent to the blob model, which models the intersection of lines of response (LORs) with radially variant basis functions ('blobs') replacing the cubic voxels. Implications of the achieved equivalence regarding the necessity of final resampling in blob-based reconstructions are considered. We extended TOR-CD to a variable density tube model (TOR-VD) that yields a weighting function (defining all system matrix elements) which is essentially identical to that of the blob model. The variable density of TOR-VD was modelled by a Gaussian and a Kaiser-Bessel function, respectively. The free parameters of both model functions were determined by fitting the corresponding weighting function to the weighting function of the blob model. TOR-CD and the best-fitting TOR-VD were compared to the blob model with a final resampling step (BLOB-RS) and without resampling (BLOB-NRS) in phantom studies. For three different contrast ratios and two different voxel sizes, resolution noise curves were generated. TOR-VD and BLOB-NRS lead to nearly identical images for all investigated contrast ratios and voxel sizes. Both models showed strong Gibbs artefacts at 4 mm voxel size, while at 2 mm voxel size there were no Gibbs artefacts visible.
The spatial resolution was similar to the resolution with TOR-CD in all cases. The resampling step removed most of the Gibbs artefacts and reduced the noise level but also degraded the spatial resolution substantially. We conclude that the blob model can be considered just as a special case of a TOR-based reconstruction. The latter approach provides a more natural description of the detection process and allows for modifications that are not readily representable within the blob framework.

A new type of an intense source of positrons for materials research has been set up at the superconducting electron linear. The source employs hard X-rays from electron-bremsstrahlung production generating energetic electron-positron pairs inside the sample under investigation. CW-operation allows performing experiments with significantly reduced pile-up artefacts in the detectors compared to pulsed mode operation in conventional accelerators. The high-resolution timing of the accelerator with bunch lengths below 10 ps full width at half maximum (FWHM) allows positron annihilation lifetime spectroscopy (PALS) measurements with high time resolution. A single-component annihilation lifetime of Kapton has been measured as (381.3 ± 0.3) ps. Employing segmented detectors for the detection of both annihilation photons allows for the first time to perform a 4D tomographic reconstruction of the annihilation sites including the annihilation lifetime.

A prototype of Multi-strip Multi-gap Resistive Plate chamber (MMRPC) with active area 40 cm x 20 cm has been developed at SINP, Kolkata. Detailed response of the developed detector was studied with the pulsed electron beam from ELBE at Helmholtz-Zentrum Dresden-Rossendorf. In this report the response of SINP developed MMRPC with different controlling parameters is described in details. The obtained time resolution of the detector after slew correction was 91.5 +- 3 ps. Position resolution measured along x and across y the strip was 2.8+-0.6 cm and 0.58 cm, respectively. The measured absolute efficiency of the detector for minimum ionizing particle like electron was 95.8+-1.3 %. Better timing resolution of the detector can be achieved by restricting the events to a single strip. The response of the detector was mainly in avalanche mode but a few percentage of streamer mode response was also observed. A comparison of the response of these two modes with trigger rate was studied.

The spout fluidized bed is a very successful combination of spouted and fluidized bed, which is most interesting for processing particles with larger or varying diameter. However, the more complex hydrodynamics of the combined configuration is yet not fully understood. Here, we propose the application of ultrafast X-ray computed tomography (CT), which has proven to be a valuable measurement technique for the analysis of highly dynamic processes, for example multiphase flows. It is able to resolve material distributions with up to 8,000 frames per second and a spatial resolution down to 1 mm. Especially for opaque systems, such as fluidized beds, ultrafast X-ray CT can reveal details, which are not recoverable by e.g. optical measurement techniques. Besides the recovering of the dynamic phase distribution, determining local particle velocities is essential to understand the complex flow in fluidized beds. As we will demonstrate here for the first time, this is possible via a dual-plane ultrafast X-ray CT by using suitable marker particles. In this article, the methodology for determining particle velocities under highly dynamic conditions within a cylindrical spout fluidized bed is presented. Complementary analysis techniques for different flow conditions have been combined to increase confidence in the velocity data.

The 26Si(p;gamma)27P reaction, which might play an important role in the rp process, was studied by the Coulomb Dissociation method. The experiment was performed at GSI, Darmstadt. A secondary 27P ion beam of 500 MeV/nucleon was directed onto a Pb target. From this experiment, the Coulomb Dissociation cross section will be deduced and then converted to the photoabsorption cross section, and the radiative-capture cross section. Also information on the structure of 27P will be obtained. The analysis is in progress.

Layered materials and sp2 hybridized structures like graphite and hexagonal-boron nitride (h-BN) have been subjected to electron cyclotron resonance (ECR) ion beam implantation of proton and argon ions at different fluences and studied primarily employing slow positron beam technique using positron annihilation Doppler broadening spectroscopy (DBS). The results show remarkable structural perturbation effects in the implantation areas around the depth of 200–300 nm from the top surface, in both the systems but with glaring differences in the trends of the line shape analysis in terms of S and W parameters. Due to proton and argon ion implantation, structurally damaged lattice with open volume defects exists in graphite. But, for both the ion implantations at the high fluence, profound clustering effect of the respective atoms within the interstitial space are evident in h-BN. The structural effects of both graphite and h-BN lattice after the said implantation have been studied and corroborated through grazing incidence X-ray diffraction (GI-Xray) method and Raman scattering spectroscopy as complementary analytical techniques.

The presentation introduces the Institute of Resource Ecology and the Helmholtz Institute Freiberg for Resource Technology and provides an insight into the work of the Biotechnology Group.

In this paper we report on the investigation of baryonic resonance production in proton-proton collisions at the kinetic energies of 1.25 GeV and 3.5 GeV, based on data measured with HADES. Exclusive channels npπ+ and ppπ0 as well as ppe+e− were studied simultaneously in the framework of a one-boson exchange model. The resonance cross sections were determined from the one-pion channels for Δ(1232) and N(1440) (1.25 GeV) as well as further Δ and N* resonances up to 2 GeV/c2 for the 3.5 GeV data. The data at 1.25 GeV energy were also analysed within the framework of the partial wave analysis together with the set of several other measurements at lower energies. The obtained solutions provided the evolution of resonance production with the beam energy, showing a sizeable non-resonant contribution but with still dominating contribution of Δ(1232)P33. In the case of 3.5 GeV data, the study of the ppe+e− channel gave the insight on the Dalitz decays of the baryon resonances and, in particular, on the electromagnetic transition form-factors in the time-like region. We show that the assumption of a constant electromagnetic transition form-factors leads to underestimation of the yield in the dielectron invariant mass spectrum below the vector mesons pole. On the other hand, a comparison with various transport models shows the important role of intermediate ρ production, though with a large model dependency. The exclusive channels analysis done by the HADES collaboration provides new stringent restrictions on the parameterizations used in the models.

During evolution nature has evolved different kinds of specific binding macro-molecules being crucial for cell metabolism and their interaction with the environment. Most important examples therefore are proteins and nucleic acids. But beside biogenic molecules, specific proteins and nucleic acids can also be selected by doing an in vitro evolution using large molecule libraries. In this way specific ligands for various targets can be obtained allowing the development of new materials for different industrial applications.

The visible matter in the universe is turbulent and magnetized. Turbulence in galaxy clusters is produced by mergers and by jets of the central galaxies and believed responsible for the amplification of magnetic fields. We report on experiments looking at the collision of two laser-produced plasma clouds, mimicking, in the laboratory, a cluster merger event. By measuring the spectrum of the density fluctuations, we infer developed, Kolmogorov-like turbulence. From spectral line broadening, we estimate a level of turbulence consistent with turbulent heating balancing radiative cooling, as it likely does in galaxy clusters. We show that the magnetic field is amplified by turbulent motions, reaching a nonlinear regime that is a precursor to turbulent dynamo. Thus, our experiment provides a promising platform for understanding the structure of turbulence and the amplification of magnetic fields in the universe.

The incorporation of radionuclides into a host mineral’s crystal structure is a particularly efficient means of retention, due to the fact that the incorporated radionuclide is removed from the water path. The process is relevant, both, naturally occurring under repository conditions[1], and as a technical means for the sequestration of actinide waste streams. Consequently, it is of utmost importance to understand the processes leading up to the incorporation, as well as the structural properties of the formed solid solution at the molecular level[2].
We will give an overview on the incorporation of trivalent actinides and lanthanides into Ca- and Ln-bearing mineral phases of technical and geochemical relevance. The minor actinides dominate the radiotoxicity in a nuclear waste storage site over hundreds of thousands of years. For Am and Cm the trivalent oxidation states is the only relevant oxidation in aqueous solutions, and even Pu may be present as Pu(III) under reducing repository conditions. The trivalent actinides have ionic radii closely matched to their lanthanides homologues as well as calcium, making mineral phases with these host cations ideal matrices for the incorporation of the trivalent minor actinides.
To identify and characterize actinides in solid solutions at the trace concentration level, we make use of time-resolved laser fluorescence spectroscopy (TRLFS). TRLFS allows for speciation of Cm(III) at concentrations below 10-9 mol/L, or 1 ppm in the solid state. Cm TRLFS can be complemented by experiments with Eu(III), which, while less sensitive, are more sensitive to changes in the local coordination geometry of the fluorescent probe.
An overview will be given on the characterization of solid solutions of secondary phases relevant under repository conditions. We will compare a phase formed close to equilibrium (calcite) with a metastable phase undergoing a phase transition (vaterite[3]), as well as a phase from high-temperature synthesis (powellite[4]). The effect of various reaction parameters on the reactions, and their implications for the stability of the formed solid solutions, and hence the retention of the radionuclides will be discussed.
[1] T. Stumpf and Th. Fanghänel, J. Colloid Interf. Sci. 249, 119 (2002).
[2] H. Geckeis, et al., Chem. Rev. 113, 1016 (2013).
[3] M. Schmidt, et al., J. Colloid Interf. Sci. 351, 50 (2010).
[4] M. Schmidt, et al., Dalton Trans. 42, 8387 (2013).

Magnesium chips were processed by means of re-melting. An important requirement of re-melting the chips is the removal of oil and moisture. The results show that using acetone in a soxhlet as an organic solvent is a more efficient method to obtain good results compared to vacuum distillation with a rotational evaporator. The subsequent re-melting has been successfully performed without the addition of flux between temperatures of 580 °C and 600°C. At this temperature range, the exothermic reaction of magnesium with the oxygen present in the surrounding atmosphere was avoided. Results show that more than 95 % of the magnesium chips were able to be recovered as metal. Experiments were performed at different scales to obtain production parameters for the recycling process. Larger particle size of magnesium chips were able to be faster remelted than the smaller ones. In the case of added lime for oil removal, the yield of recovered magnesium was lower due to the reaction towards magnesium foam. The ability of re-melting at low temperatures without the need for flux demonstrates the possibility of recovering virtually all of the metal from the chips.

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The integration of III-V compound semiconductors in Si is a crucial step towards faster and smaller devices in future technologies. In this work, we investigate the formation process of III-V compound semiconductor nanocrystals, namely, GaAs, GaSb, and InP, by ion implantation and sub-second flash lamp annealing in a SiO2/Si/SiO2 layer stack on Si grown by plasma-enhanced chemical vapor deposition. Raman spectroscopy, Rutherford Backscattering spectrometry, and transmission electron microscopy were performed to identify the structural and optical properties of these structures. Raman spectra of the nanocomposites show typical phonon modes of the compound semiconductors. The formation process of the III-V compounds is found to be based on liquid phase epitaxy, and the model is extended to the case of an amorphous matrix without an epitaxial template from a Si substrate. It is shown that the particular segregation and diffusion coefficients of the implanted group-III and group-V ions in molten Si significantly determine the final appearance of the nanostructure and thus their suitability for potential applications.

Within this work, flash lamp annealing (FLA) is utilized to thermally enhance the film growth in atomic layer deposition (ALD). First, the basic principles of this flash-enhanced ALD (FEALD) are presented in detail, the technology is reviewed and classified. Thereafter, results of our studies on the FEALD of aluminum-based and ruthenium thin films are presented. These depositions were realized by periodically flashing on a substrate during the precursor exposure. In both cases, the film growth is induced by the flash heating and the processes exhibit typical ALD characteristics such as layer-by-layer growth and growth rates smaller than one angstrom/cycle. The obtained relations between process parameters and film growth parameters are discussed with the main focus on the impact of the FLA-caused temperature profile on the film growth.

Similar, substrate-dependent growth rates are attributed to the different optical characteristics of the applied substrates. Regarding the ruthenium deposition, a single-source process was realized. It was also successfully applied to significantly enhance the nucleation behavior in order to overcome substrate-inhibited film growth. Besides, this work addresses technical challenges for the practical realization of this film deposition method and demonstrates the potential of this technology to extend the capabilities of thermal ALD.

Speciation constitutes the basis for actinide complexation studies. These systems can be very complex and challenging especially because of the polynuclear species. An advanced combination of theoretical and experimental methods is proposed here. Continuous wave (CW) and time-resolved laser-induced fluorescence spectroscopy (TRLFS) data of uranyl(VI) hydrolysis were analyzed using parallel factor analysis (PARAFAC). Distribution patterns of five major species were thereby derived under a fixed uranyl concentration (10-5) over a wide pH range from 2 to 11. UV (180 nm to 370 nm) excitation spectra were extracted for individual species. Time-dependent density functional theory (TD-DFT) calculations revealed ligand excitation (water, hydroxo, oxo) in this region and ligand-to-metal charge transfer (LMCT) responsible for luminescence. Thus excitation in the UV is extreme ligand sensitive and highly specific. Combining findings from PARAFAC and DFT the [UO2(H2O)5]2+ cation (aquo complex, 1:0) and four hydroxo complexes (1:1, 3:5, 3:7 and 1:3) were identified. Refined structural and thermodynamical data of uranyl(VI) hydrolysis is thus acquired.

The trickle-to-pulse flow regime transition in silicon-infiltrated silicon carbide (SiSiC) foam packed fixed bed reactors has been investigated. Based on the film stability concepts of Grosser et al.¹ (DOI: 10.1002/aic.690341111) as well as Attou and Ferschneider² (DOI: 10.1016/S0009-2509(99)00344-9), two predictive models have been adapted to foams’ specific geometric parameters. To account for the different nature of solid foams and their interactions with various fluids, the fixed bed characteristics (specific surface area and bed porosity) and fluid specific parameters (gas and liquid density, liquid viscosity, surface tension) have been incorporated in the model. Ergun parameters and static liquid holdup which are required for the modelling of the prevailing tractive forces were determined experimentally.
The modelling results were compared to regime transition measurements performed for SiSiC solid foams with different linear pore densities (20, 30 and 45 PPI), for different reactor diameters (50 and 100 mm) and initial liquid distributors (spray cone nozzle and multipoint distributor) as well as liquids with various physicochemical properties (water, Tergitol®, 50% glycerin) under ambient operating conditions. Compared to conventional random fixed bed reactors, the onset of pulsing in solid foam packed fixed beds is significantly shifted towards larger liquid and gas fluxes allowing high throughputs in the trickle regime. Moreover, the homogeneity of initial liquid distribution strongly affects the trickle-to-pulse flow transition.

In the present study a first found of agates in Chile is reported from the Cordón de Lila region in northern Chile. The agates occur as veins and lenses in altered Permian volcanic rocks. The rock composition is rhyodacitic/dacitic consisting of a fine-grained K-feldspar-quartz groundmass with phenocrysts of plagioclase (An50-60) and pyroxene (augite). The volcanic host rocks show strong features of alteration and brecciation.
Results of XRD, polarizing microscopy and cathodoluminescence (CL) microscopy and spectroscopy point to a late- to postvolcanic formation of the agates by hydrothermal fluids and SiO2 which was released during the alteration of unstable minerals and volcanic glass. Strongly varying agate micro-textures and the appearance of euhedral quartz crystals with μm-sized growth lamellae (so called Bambauer quartz) indicate fluctuations in the physico-chemical conditions (SiO2 concentration, pH) during alteration and agate formation. Another indication for the alteration processes is the occurrence of secondary calcite in the agate-bearing rocks.

Magnetic and magneto-optical properties of Pt/Co/Au and Pt/Co/Pt trilayers subjected to 30 keV Ga+ ion irradiation are compared. In two-dimensional maps of these properties as a function of cobalt thickness and ion fluence, two branches with perpendicular magnetic anisotropy (PMA) for Pt/Co/Pt trilayers are well distinguished. The replacement of the Pt capping layer with Au results in the two branches still being visible but the in-plane anisotropy for the low-fluence branch is suppressed whereas the high-fluence branch displays PMA. The X-ray absorption spectra and X-ray magnetic circular dichroism (XMCD) spectra are discussed and compared with non-irradiated reference samples. The changes of their shapes and peak amplitude, particularly for the high-fluence branch, are related to the modifications of the local environment of Co(Pt) atoms and the etching effects induced by ion irradiation. Additionally, in irradiated trilayers the XMCD measurements at the Pt L-2,L-3-edge reveal an increase of the magnetic moment induced in Pt atoms.

Die vorliegende Erfindung betrifft eine Vorrichtung und ein Verfahren zur Gewinnung von Metallen aus primären und sekundären Rohstoffen, basierend auf der Nutzung von organischen Säuren und anderen mikrobiellen Metaboliten.
Die Gewinnung von 2- und/oder 3-wertigen Metallionen erfolgt aus primären und/oder sekundären Rohstoffen, erfolgt mittels einer Vorrichtung mit zwei Kompartimenten. Das erste Kompartiment enthält ein heterogenes Gemisch aus einem oder mehreren primären und/oder sekundären Rohstoffen mit einer wässrigen Lösung. Das zweite Kompartiment ist vom ersten Kompartiment durch eine Membran abgetrennt und enthält Mikroorganismen oder einen Kulturüberstand oder einen oder mehrere Komplexbildner.

We perform numerical simulations of the dynamo effect driven by various flow fields of a conducting liquid interacting with "magnetic material" characterized by a large relative permeability. The examinations are motivated by the key role of soft iron impellers for the Von-Kármán-Sodium (VKS) dynamo [1] and by the repeatedly expressed idea to make use of Oxide Dispersion Strengthened (ODS) ferritic/martensitic alloys in the core of a fast reactor which may exhibit a permeability much larger than one [2].

The results of our simulations that consider a localized distribution with finite permeability clearly differ from computations using simplyfying pseudo-vacuum boundary conditions (vanishing tangential field conditions) in order to mimic the impact of infinite permeability. Our kinematic simulations of an axisymmetric model of the VKS dynamo show a close connection between the exclusive occurrence of dynamo action in the presence of soft iron impellers and the observed axisymmetry of the magnetic field [3]. We qualitatively explain this effect by paramagnetic pumping at the fluid-disk interface and propose a simplified analytical model that quantitatively reproduces numerical results. In order to fully explain the observation of growing magnetic fields in the VKS dynamo we resort to mean-field dynamo theory [4] in terms of an α-effect caused by helical outflows between adjacent blades attached to the impeller disks.

In order to examine the properties of the α- and β-effect (which is closely related to the turbulent diffusivity) under influence of magnetic material [5] we use an idealized helical flow field (a modified Roberts flow). We compute the mean-field coefficients using the test-field method [6] and proof that the corresponding mean-field models are indeed capable to reproduce growth-rates and principle field structure of the fully resolved model by requiring much less computational efforts.

Further remarkable results are the observed reduction of the critical magnetic Reynolds number by roughly 30 percent independently of configuration or flow geometry when the permeability is sufficiently large. However, this universality is not reflected in the behavior of the mean-field coefficients. In particular, the β-effect strongly depends on the geometry and the permeability. A striking feature is the occurrence of negative β which has previously been observed in simulations [7] and, more recently, in experiments [8].

Our results for the mean-field coefficients allow the development of dynamo models for nearly arbitrary systems of various sizes consisting of a large number of helical small scale flow cells embedded into some large flow structure.

[1]Monchaux, R. et al., Phys. Rev. Lett. 98 (2007), 044502
[2]Dubuisson, P., de Carlan, Y., Garat, V. and Blat, M., J. Nucl. Mater. 428 (2012), 6–12
[3]Giesecke, A. et al., New J. Phys. 14 (2012), 053005
[4]Krause, F. and Rädler, K.-H. Mean-field Magnetohydrodynamics and dynamo theory, Pergamon Press 1980
[5]Giesecke, A. et al., New J. Phys. 16 (2014), 073034
[6]Schrinner, M. et al., Astron. Nachr. 326 (2005), 245-249
[7]Rädler, K.-H. and Brandenburg, A., Phys. Rev. E 67 (2003), 026401
[8]Frick, P., Noskov, V., Denisov, S. and Stepanov ,R., Phys. Rev. Lett. 105 (2010), 184502

Many minerals have a strong tendency to sorb ions from the surrounding environment. An understanding of this process allows a realistic prediction of distribution and transport of the elements in nature. In case of uranium this is of high importance with respect to former mining sites or envisaged deposits. In this work, sorption of uranium(VI) onto orthoclase and muscovite, representing important components (feldspars and micas) of the earth crust, was investigated in absence and presence of calcium under aerobic conditions.
Batch experiments with both minerals were performed as triplicates in 0.01 M NaClO4 in the pH range of 5 to 8, with solid-to-liquid ratios of 1/20 and 1/80 g/mL, uranium concentrations of 10-5 and 10-6 M, with and without 1.5×10-3 M Ca. Furthermore time-resolved laser-induced fluorescence spectroscopy (TRLFS) was performed at batch samples with orthoclase (pH 4 to 9, with 10-5 M U and 1.5×10-3 M Ca). There, the aquatic solutions as well as the mineral suspensions were investigated as described in [1].
Uranium sorption shows its maximum at circumneutral pH values. At pH ≥ 8 in presence of calcium a reduced uranium(VI) sorption was observed which is due to the formation of the non-sorbing neutral Ca2UO2(CO3)3 complex. The evaluation of the spectroscopic results by Parallel factor analysis (PARAFAC) indicates the formation of three surface species. In detail the sorption of U(VI) onto orthoclase indicate two surface species. Based on the peak positions given in [2] they can be attributed to the formation of ≡SiO2UO20 and ≡SiO2UO2OHCO33– surface complexes. In presence of Ca2+ the ≡SiO2UO2OHCO33– surface complex disappears and instead the ≡SiO2UO2OH– surface complex also given in [2] can be observed. It occurs at lower pH values than the carbonate complex and shows different peak positions of the fluorescence bands.
The results improve the basis for a mechanistic modeling of the U(VI) sorption onto orthoclase and muscovite, which is important for long-term safety analysis of nuclear waste repositories.
With regard to the U(VI) sorption onto mica and feldspars not only the binary systems have to be understood because in natural systems many more components are present. For calcium this work already showed a significant influence on the speciation and thus on the potential transport of U(VI). But many other elements leached from surrounding minerals or contained in the groundwater may affect the overall sorption, too. Thus future work has to focus on more complex systems representing natural conditions as well as on the generation of surface complexation parameters for predictions of the U(VI) speciation.

Fluid catalytic cracking (FCC) reactors are applied to convert gas oils and residues to lighter, higher-value products. Circulating fluidized bed technologies are used in modern FCC units, where cracking reactions take place in the riser with co-current upflow of the vaporized gasoil feed and the catalyst. After the disengagement from the product gas, the catalyst needs to be regenerated to compensate the deactivation due to coke deposition. The deactivation of the FCC catalyst can occur already in a few seconds and regeneration of the deactivated catalyst plays an important role for the yield of the FCC unit. For an effective regeneration, burning of deposited coke in the fluidized bed solves the early decay time of the catalysts. During the process the heavy hydrocarbons deposit on the catalyst, which subsequently block the active sites. To restore the activity, deposited hydrocarbons are oxidized with air in the regenerator reactor. The performance of the regenerator as well as its coupling with the cracking reactor are important to reach a high overall yield in the FCC unit. Usually, Geldart-A particles are used as catalyst in the FCC reactors. As the aeration rate of the FCC catalyst is low and the particles are cohesive, big bubbles are formed, channeling occurs and fluidization is often nonhomogeneous, which makes the hydrodynamic modeling a challenge. The clustering behavior of the fluidizing gas also increases the complexity of the reactor design. The complicated hydrodynamic behavior of gas phase and solid particles is a critical point to model coupled heat and mass transfer phenomena inside the fluidized reactors. The aim of the work is to develop an Eulerian-Eulerian numerical model for the FCC regenerator reactor operated as a fluidized bed based on the kinetic theory of granular flows to consider the clustering effect of the FCC catalysts in the regeneration process. In addition, the model shall consider the impact of the shrinkage of the deposited coke on FCC catalyst regeneration time, product yield, and temperature history of the regenerator reactor.

The ability to accurately predict the bubble size distribution in bubble column reactors is a requirement for any process design as well as for scale-up. The bubble size distribution depends mainly on the magnitude of bubble breakup and coalescence. Several breakup and coalescence models have been developed assuming different driving mechanisms, such as turbulence dissipation and shear rate of the liquid phase. The proposed breakup and coalescence models contain turbulence contributions in breakup and coalescence of the bubbles and also the relative velocity of the bubbles. The realistic expressionfor the mentioned terms is missing for the implementation of the breakup and coalescence models due to poor knowledge on the turbulence behavior of the bubbly flows. Here, bubble-liquid turbulence interactions of the bubbly flows are considered to predictparticipating turbulence energy in breakup and also relative velocity of the bubbles at coalescence of the bubbles.

Conversion of biomass into fuel and chemicals is currently receiving a great deal of attention because of the reduction of greenhouse gas emissions and national energy security and sustainability. The design of the pyrolysis process is important to reach higher bio-oil products and a key factor to produce higher bio-oil than char, is supplying high heat transfer rate to the biomass particles (fast pyrolysis) and fast removal of the volatiles. Although fluidized bed reactors provide higher heat transfer than conventional pyrolysis reactors, the heat transfer is limited by the convection at particle surface and conduction inside particle. The added inert particles to the fluidized bed improve heat transfer rate and fluidization properties of the biomass to reach desired fluidization velocity and good mixing of the particles. In this work, instead of using heated wall, performance of a circulating fluidized bed reactor with the heating loop of inert particles at the circulation path is investigated for pyrolysis of biomass.

The majority of pharmaceuticals and other organic compounds including radiotracers that are considered foreign to the body undergo metabolic changes in vivo. Most of these compounds are metabolic degraded by a system of enzymes of low substrate specificity requirement which is present mainly in the liver but drug metabolism may also take place in the kidneys or other organs. Thus, radiotracers and all other pharmaceuticals are faced with enormous challenges to maintain their stability in vivo implicating a high requirement on their structure. Often in practice, such biologically active molecules with manifested properties are found in vitro but these results could not be confirmed in vivo due to an increased metabolism within minutes. Many pharmacologically and biologically interesting compounds fail for further application due to their lack of stability.
One of the most important issues of radiotracers development based on fluorine-18 is the stability in vitro and in vivo. Sometimes, the metabolism of ¹⁸F-radiotracers goes along with the cleavage of the F-C bond and with the rejection of [¹⁸F]fluoride mostly combined with high background and accumulation in the skeleton. This review deals with the impact of radiodefluorination and with approaches to stabilize the F-C bond to avoid the cleavage between fluorine and carbon.

A novel, promising strategy for cancer diagnosis and therapy is the use of a pretargeting approach. For this purpose, the non-natural DNA/RNA analogues Peptide Nucleic Acids (PNAs) are ideal candidates as in vivo recognition units due to their high metabolic stability and lack of unspecific accumulation. In the pretargeting approach, an unlabeled, highly specific antibody-PNA conjugate has sufficient time to target a tumor before administration of a small fast-clearing radiolabeled complementary PNA that hybridizes with the antibody-PNA conjugate at the tumor site. Herein, we report the first successful application of this multistep process using a PNA-modified epidermal growth factor receptor (EGFR) specific antibody (Cetuximab) and a complementary ^99mTc-labeled PNA. In vivo studies on tumor bearing mice demonstrated a rapid and efficient in vivo hybridization of the radiolabeled PNA with the antibody-PNA conjugate. Decisively, a high specific tumor accumulation was observed with a tumor-to-muscle ratio of >8, resulting in a clear visualization of the tumor by single photon emission computed tomography (SPECT).

This paper presents a framework of optimization of design and operation of a chain of identical cells or operator units that splits a raw input stream into two streams, increasing their total monetary value. This can be seen as a simplified conceptualization of several mineral processing or metallurgical techniques, where a cell itself badly separates the stream, hence its repeated operation seems appropriate. The solution is based on standard theory of linear differential equations. Uncertainty in the composition of the feed can be accounted for by Monte Carlo techniques.

A geostatistical version of the classical Fisher rule (linear discriminant analysis) is presented. This method is applicable when a large dataset of multivariate observations is available within a domain split in several known subdomains, and it assumes that the variograms (or covariance functions) are comparable between subdomains, which only differ in the mean values of the available variables. The method consists on finding the eigen-decomposition of the matrix inv(W) B, where W is the matrix of sills of all direct- and cross-variograms, and B is the covariance matrix of the vectors of weighted means within each subdomain, obtained by generalized least squares. The method is used to map peat blanket occurrence in Northern Ireland, with data from the Tellus survey, which requires a minimal change to the general recipe: to use compositionally-compliant variogram tools and models, and work with log-ratio transformed data.

Unintended impurities, such as oxygen, can significantly influence the growth morphology, structure, and mechanical properties of many materials. Therefore, we study the origin and impact of oxygen impurities (between ~ 0.3 and 1.3 at.%) on sputtered Ti_1‐xAl_xN thin films by using targets with three different oxygen impurity levels and modifying the deposition conditions such as the base pressure. The oxygen impurity content of our coatings was always (by around ≥ 0.1 at.%) above that of the target used. Detailed atom probe tomography as well as secondary ion mass spectroscopy indicate a homogeneous distribution of the oxygen impurities across our face centred cubic structured Ti_0.50Al_0.50N coatings. Except for higher oxygen levels at the interface to the substrate, which is more pronounced when the target is not sputter‐cleaned prior to the deposition, and at the coating surface, there are no detectable oxygen variations at the grain or column boundaries. Based on our results we can conclude that the growth orientation of our coatings changes from random (for the cleanest coatings with ~ 0.3 at.% O) to pronounced 111 (for the coatings with the highest oxygen content of ~ 1.3 at.% O) with increasing oxygen impurity content. Thereby, also the coherently diffracting crystallite sizes increase from around 35 to 100 nm, the growth morphology changes from dense columnar grains to more open, porous columnar grains, and thus the hardness decreases from around 35 to 20 GPa.
Our study highlights the importance of well‐defined deposition conditions and high quality targets for developing high quality thin films.

High-resolution gamma-ray computed tomography (HireCT) was applied to clarify the two phase flow distribution inside the impeller wheel of a running pump. Thus, the accumulated gas holdup inside the impeller of an industrial centrifugal pump was investigated and analysed, depending on the suction side gas volume fraction and type of two phase flow regime. Using time-averaging rotation-synchronized tomographic imaging technique, effects on the conveying performance of the centrifugal pump could be clarified. The obtained results contributes to a better understanding of the flow behavior and its effects inside the impeller of a centrifugal pump, which is running under two phase flow conditions due to gas entrainment. Moreover, the results can help to develop improved pump designs to avoid loss of conveying performance due to gas entrainment.

Zentrifugalpumpen sind sehr weitverbreitet und werden in vielfältiger Weise unter anderem in der Prozessindustrie oder im Kraftwerksbereich eingesetzt. Beispielweise nutzt man Kreiselpumpen in Raffinerien als Speisepumpen oder in Kraftwerken als Umwälzpumpen in Kühlkreisläufen. Erfolgt der Einsatz auch in sicherheitsrelevanten Bereichen, wie z. B. in der Reaktornotkühlung von Kernkraftwerken, muss unbedingt ein störungsfreier und zuverlässiger Betrieb gewährleistet werden. Obwohl diese Pumpen einfach aufgebaut sind, bieten sie eine Reihe von Vorteilen, wie zum Beispiel hohe Effizienz bei geringem Energieverbrauch, ruhiger und kontinuierlicher Förderstrom und hohe Haltbarkeit und Beständigkeit. Es ist bekannt, dass sowohl Gaseintrag als auch Dampfbildung durch Kavitation schädlich und kritisch für den Betrieb von Kreiselpumpen sind, welche eigentlich für den einphasigen Betrieb ausgelegt sind. Gaseintrag kann beispielsweise in Situationen entstehen, wo Flüssigkeiten aus Reservoirs mit einem zu niedrigen Füllstand gefördert werden. Hier können sich als Konsequenz aus der unzureichenden Überdeckung des Pumpenansaugstutzens und der Anwesenheit von Initialwirbeln an der Flüssigkeitsoberfläche Hohlwirbel ausprägen. Derartige Situationen sind insbesondere in Kernkraftwerken, wo beispielsweise Notkühlmittel aus einem Reservoir wie der Kondensationskammer gefördert wird, unbedingt zu vermeiden. Der Gaseintrag führt zu einer verminderten Förderleistung der Pumpe, bis hin zum vollständigen Zusammenbruch der Förderrate. Außerdem kann vorhandenes Gas in Pumpen unter anderem zum Verlust der Kühlung der Lager und der Gleitringdichtung führen, was zu einer früheren Abnutzung bis hin zum Versagen der Pumpe führt. Auch starke Vibrationen welche ebenfalls zur Schädigung der Lager beitragen, sowie Abnutzungserscheinungen an den Laufradschaufeln können eintreten. Die vorgestellte Arbeit leistet mit quantitativen Messungen, Visualisierungen und Analysen der Gas-Flüssigkeits-Phasenverteilungen innerhalb des Laufrades und des umgebenden Pumpengehäuses einer fördernden Kreiselpumpe einen Beitrag zum fundamentalen Verständnis der Auswirkungen von Gaseintrag in Zentrifugalpumpen.

Ultrasound Doppler velocimetry is an important tool for the characterization of liquid metal flows, including those caused by magnetohydrodynamic instabilities. Here we consider the Tayler Instability (TI), which is driven by a high current flowing through the system. This can entail a great deal of electromagnetic noise, which must be decoupled from the signal produced by ultrasound scatterers within the liquid metal. In the experiment described herein, two ultrasound transducers encased within a copper electrode are in contact with a cylindrical liquid GaInSn column. Currents in the order of several kA produced by a switching-mode power supply flow through the electrode and the liquid GaInSn, resulting in the TI, which causes vortices with vertical velocity components in the range of several mm/s to appear. Noise produced by the power supply was significantly reduced by adding film capacitors and toroidal cores, including a common-mode choke to the circuit. Electromagnetic interference was further reduced by adding toroidal and split cores to the coaxial cables connecting the ultrasound transducers to the velocimeter, with the latter drawing power through an isolating transformer. These precautions permitted the retrieval of reliable velocity data, which generally agree with previously conducted B_z-measurements.

Derivatives of quinoxalinedione (QX) were chosen as chemical lead for the development of new radioligands of the AMPA receptor, since there are several examples of QX-derivatives with high affinity. The radiosyntheses of the new compounds 6-[18F]fluoro-7-nitro-QX ([18F]FNQX) and 7-[18F]fluoro-6-cyano-QX ([18F]FCQX) with radiochemical yields of 8 ± 2 and 3 ± 2 %, respectively, as well as the evaluation of their binding properties to the AMPA-receptor were performed. A comparison of the Ki-values of the new QX-derivatives FCQX and FNQX with mono-substituted cyanoand nitro-QX shows negligibly small differences of affinity (within the range of 1.4 to 5 µM), but exhibits a tenfold lower affinity than derivatives with two electron withdrawing groups like the 7-cyano-6-nitro-compound CNQX and the 6,7- dinitro compound DNQX. Thus, with respect to the low affinity and a high non-specific binding with in vitro and ex vivo autoradiographic studies, the new compounds do not lend themselves for in vivo imaging.

The understanding of magnetohydrodynamic phenomena in liquid metals relies heavily on measurement techniques such as ultrasound Doppler velocimetry that can be used to characterize flow patterns within them. The Tayler instability (TI), as well as electro-vortex flow (EVF) in a liquid GaInSn column whose top and bottom are bounded by copper current collectors connected to a switching mode power supply are considered here. The TI is driven by currents above a critical value of 2.7 kA and results in a number of vortices with vertical velocity components of the order of several mm s^−1 , whereas EVF is caused by inhomogeneities in the current density from the current collectors. Ultrasound transducers embedded within the top current collector are in direct contact with the liquid metal. At the high currents required to investigate the TI such a configuration is problematic, because the electromagnetic noise the transducers are exposed to greatly overshadows the signal from ultrasound echoes, if left unchecked. The noise generated by the power supply was significantly damped with the addition of toroidal cores and film capacitors to the current circuit. Moreover, coiling the coaxial cables connecting the transducers to the velocimeter around ring and split cores reduced the noise further. The velocimeter itself drew power through an isolation transformer and was thus prevented from being disturbed by ground loops. Reliable velocity data could be obtained from the experiment after these measures were taken and will be discussed here.

Der Vortrag stell das laufende BMBF-Vorhaben "Nichtinvasive Zustandsüberwachung von Kernreaktoren zur Detektion von Füllstandsänderungen und Deformationen des Kerns" vor. Berichtet wird über den Hintergrund des Vorhabens, Zielstellungen im Rahmen der Reaktorsicherheitsforschung und Nachwuchsförderung in der Kerntechnik sowie über aktuelle Projektergebnisse.