Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Es handelt sich um einen Überblicksvortrag über die am NVision untersuchten und/oder hergestellten Nanostrukturen und ihre Verwendung am HZDR.

We applied swift heavy ions (SHI) for shaping of already existing submicron- and nano-scale structures by irradiation at small angles and simultaneous azimuthal rotation. The investigated samples consisted of 100nm thick films of NiO or ZnO deposited on an oxidized Si-wafer by reactive magnetron sputtering. Prestructuring into 3-dimensional sub-μm and nm-sized objects with quadratic or rectangular cross-sections was done by means of focused ion beam technique. The process produced a grid of perpendicular lines cut into the film, reaching from the surface down to the interface and having line distances varying between 5 μm and 250 nm. These samples were then irradiated with SHI in the chamber of our new in-situ scanning electron microscope (SEM) installed at the M1-beamline of the UNILAC.

We have recently investigated restructuring effects in thin oxide films (NiO, Fe2O3 and ZnO on pure Si- or oxidized Si-substrates) during swift heavy ion (SHI) irradiation. On the one hand we have observed that the films rupture upon SHI bomdardment under normal ion incidence and exhibit dewetting patterns similar to those observed for liquid polymer films on Si. On the other hand, grazing incidence irradiation of NiO-films leads to an instability against cracking perpendicular to the beam direction projected onto the surface and subsequent growth of an almost periodic lamellae pattern with lamellae thicknesses of the order of 100 nm and heights of the order of 2 µm. Subsequent irradiation under perpendicular directions at sufficiently low ion fluences results in a more or less rectangular crack pattern, i.e. the generation of spacially separated rectangular NiO-plates on top of the substrate. By further irradiation under grazing incidence and continuous azimuthal rotation of the sample, the oxide plates shrink in their lateral dimensions and grow in height. At the same time the egdes become round and finally a ”forest” of cylindrical NiO-pillars with radii of the order of 100 nm forms. However, because of the irregular cracking, the pillar are not arranged in a regular manner and exhibit a wide distribution of heigth and radius. These limitations can be overcome by replacing the initial cracking due to the ”Grinfeld instability” by artificial production of regularely ordered rectangular ”oxide plates” utilizing the focused ion beam (FIB) technique. SHI irradiation under grazing angle incidence and continuous azimuthal rotation than indeed results in the formation of regularely ordered objects of various (not only pillar-like) shapes, depending on the size of the initial plate. These phenomena can be understood in terms of the ”ion hammering effect” and ion-induced visco-elastic flow due to yield stresses and surface tensions as well as interface energies (capillary forces). However, until now it is not clear whether or not the above described phenomena are influenced also by phase formation and separation in the film and at its interfaces. Related studies require the utilization of phase- or at least element-sensitive analysis techniques with good lateral spacial or/and depth resolution. In the present report we’ll present our first EDX- (Energy Dispersive X-Ray Spectroscopy) and XPS- (Foto-Electron Spectroscopy) results on SHI irradiated coherent as well as pre-structured NiO-layers on Si and SiO2, respectively.

Materials modification by swift heavy ion (SHI) irradiation has become a field of investigation in the early 80’s, when Klaumünzer and Schumacher observed that irradiation of metallic glasses with swift heavy ions of some MeV/amu results in anistropic plastic deformation (shrinking along and expansion perpendicular to the beam direction). Since such a behaviour is reminiscent of treating a metal sheet with a hammer, it is often called hammering effect”. Trinkaus has theoretically explained this phenomenon by the local rapid solid-liquid-solid phase transition, which is caused by the passage of a SHI through the material with sufficient ionisation cross-section (electronic stopping power). This transient melting and rapid resolidification (within some tens of ps) of a cylinder (ion track) of typically 10 nm in diameter along the ion trajectory creates tensile stresses along and compressive stresses perpendicular to the ion track axis. As we have shown before, these induced stresses may result in surface instabilities of thin oxide films, causing self-organised restructuring into lamellae- and pillar-like patterns on a nm-scale.
Here we will report about the continuation of our recently started exploration of the potential use of the hammering effect for shaping and modifying micron and sub-micron structures by swift heavy ion irradiation. In addition to the results on pre-structured NiO-films presented in the preceeding annual report we will now discuss the results of our recent experiment on pre-structured ZnO-films on oxidized Si-wafers and compare them with the previous study.

Investigation of the magnetization reversal in arrays of magnetic nanostructures is relevant for both fundamental understanding as well as application for magnetic data storage.We present a study of the magnetization reversal in granular CoCrPt:SiO2 recording media with weakly interacting magnetic grains grown onto pre-structured templates fabricated by ion irradiation of GaSb. By tuning the irradiation conditions, assemblies of nanocones of dierent size and periodicity were prepared. Columnar CoCrPt grains with their c-axis normal to the surface of the cones were formed as evidenced by HR-TEM. The spread of the caxis of these grains results in a tilted easy magnetization axis with respect to the substrate normal. Investigation of the integral magnetic properties by vector-VSM reveals a decrease of the remanence with increasing cone size. The magnetic domain patterns observed by MFM suggest that the CoCrPt behaves as a single-domain cap structure on the cones. This work is supported by DFG FA 314-7.1 and AL 618-6.

Already in 1983 it was discovered, that swift heavy ion (SHI) irradiation of metallic glasses results in anisotropic deformation (shrinking along the beam direction expansion in perpendicular directions) [1]. We have employed this ”hammering effect” to reshape sub-micrometer structures by SHI bombardment under proper variation of the beam incidence angle. Utilizing the focused ion beam (FIB) technique, a rectangular grid with varying lateral distances of 100 to 5000 nm was cut into a 100 nm thick NiO- resp. ZnO-film from their surfaces down to the oxidized Si-substrate, in order to produce small oxide ”ashlars”. The samples were then irradiated under grazing incidence and continuous azimuthal target rotation with 1.4 GeV U- (NiO) and 0.95 GeV Au-ions (ZnO), respectively, in our new in-situ SEM at the UNILAC accelerator of GSI [2]. After certain fluence steps, the irradiation was stopped and one and the same spot was analyzed by means of SEM in order to investigate the evolution of the irradiated objects. Depending on their initial size complex structures (egg-, cone-, pillar-, forceps-, tooth-like) were formed, which can only be understood if besides the hammering effect deformation due to surface tension and yield stress are taken into account.
[1] S. Klaumünzer, G. Schumacher, Phys. Rev. Lett. 51 (1983),
[2] S. Amirthapandian, et al., Rev.Sci.Instr. 81, (2010)

The morphology of surfaces strongly influences optical, electrical, and magnetic properties of thin films. Using low energy ion beam sputtering different self-organized periodic patterns can be obtained. These are ripple patterns with periodicities in the nanometre range for oblique ion incidence and hexagonal dot patterns on compound materials for normal incidence. Low energy ion beam sputtering of Ge at normal incidence using a 5 keV Ga+ focused ion beam (FIB) produces periodic nanohole patterns [1]. In this work we studied the flux dependence of nanohole formation using FIB technique and compared the results with patterns produced by broad Ga+ beam sputtering with a six orders of magnitude smaller ion flux. In both cases Ga+ ions with an energy of 5 keV at normal incidence were used. Obtaining the same results shows that nanohole formation is independent of flux over a few orders of magnitude and that rastering of the FIB does not add extra contributions.
[1] Q. Wei, X. Zhou, B. Joshi, Y. Chen, K. Li, Q. Wei, K. Sun, and L. Wang, Adv. Mater. 21, 2865 (2009).

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The irradiation-enhanced formation and evolution of Cu-rich precipitates in reactor pressure vessel steels are multiscale phenomena. These processes can be effectively investigated by rate theory using thermodynamic parameters which must be obtained from atomistic simulations. The present work reports on the structure, energetics, thermodynamics and kinetics of nanoclusters consisting of vacancies and/or Cu. The most recent Fe-Cu interatomic potential by Pasianot and Malerba is used. A combination of Metropolis Monte Carlo and Molecular Dynamics simulation is applied to determine the most stable configurations the Cu-rich nanoclusters. The phonon contributions to the free formation energies of the clusters are evaluated from vibrational density of states obtained using dynamical matrix method. The absolute value of the total free binding energy decreases for vacancy clusters with increasing temperature while the increase is observed for pure Cu clusters. Mixed vacancy-Cu defect clusters show non-uniform behaviour in the absolute value of total free binding energy.

The irradiation-enhanced formation and evolution of Cu-rich precipitates in reactor pressure vessel steels are multiscale phenomena. These processes can be effectively investigated by rate theory using thermodynamic parameters which must be obtained from atomistic simulations. The present work reports on the vibrational effects on the thermodynamics of nanoclusters consisting of vacancies and/or Cu. The most recent Fe-Cu interatomic potential by Pasianot and Malerba is used. The vibrational density of states obtained from dynamical matrix method is used to evaluate the phonon contributions to the free energy of formation and free binding energy of defect clusters. Pure bcc-Fe and pure fcc-Cu are used as references. The vibrational effects on total free energy of pure bcc-Fe and pure fcc-Cu are compared with available CALPHAD data and literature data obtained by first-principle calculations or other interatomic potentials. The absolute value of the total free binding energy decreases for pure vacancy clusters with increasing temperature, while the increase is observed for pure Cu clusters. Mixed vacancy-Cu defect clusters show the non-uniform behaviour in the absolute value of the total free binding energy .

Biosensing devices based on fluorescence emission and detection become more and more increasing common in the fields of agricultural science, health science and food industry. Endocrine-disrupting compounds (EDC´s), such as estrogen, constitute a wide group of environmental pollutants, especially in drinking water. For this reason, there is an increasing demand for fast and convenient detection methods for estrogenic activity in water, but current detection methods base on laboratory facilities. Further miniaturization can be achieved by using light sources integrated on chip. In our case a metal-oxide-semiconductor based light emitting device (MOSLED) was developed, which is placed directly beneath the bioactive layer consisting of a silane coupling agent, a receptor and a dye-labeled analyte. However, the sensitivity of the biosensor crucially depends on the specific binding of estrogen to the receptor. Furthermore, the binding pocket inside the receptor has to be oriented toward the top of the chip surface.
In this work we investigate immobilization strategies for the estrogen receptor. A ligand binding domain tagged with histidine (hERa-LBD-10xHis) was synthesized and used. The surface plasmon resonance (SPR) method was applied in order to control and quantify the immobilization of the receptor. The SPR chip is based on a nickel nitrilotriacetic acid (Ni-NTA) matrix on gold substrate with high affinity to histidine, which allows a free linking of the receptor to the surface and thus the estrogen docking into the binding pocket of the receptor. Finally, concentration measurements of β-estradiol as an analyte have been done.

Reactor pressure vessel (RPV) steels consist of polycrystalline bcc-Fe containing Cu, Ni and other foreign atoms. The continuous irradiation by fast neutrons leads to supersaturation of vacancies and self-interstitials and enhances the diffusion of Cu and Ni which occurs via the vacancy mechanism. These processes favor the formation of nanoclusters consisting of vacancies, Cu and Ni. The interaction of dislocations with these precipitates is considered to be the main cause of hardening and embrittlement of the RPV steels. In order to model the evolution of the precipitates under irradiation by rate theory or object kinetic Monte Carlo simulations, the energetics and thermodynamics of the clusters must be known. These data are hardly obtainable by experiments, however, they can be provided by atomic-level computer simulations. In the present work a combination of on-lattice simulated annealing based on Metropolis Monte Carlo simulations and off-lattice relaxation by Molecular Dynamics calculations is employed to determine structure and energetics of the nanoclusters. In particular the influence of Ni on the formation of clusters containing Cu and/or vacancies is investigated. The atomistic simulations show that ternary clusters exhibit a shell structure with a core consisting of vacancies followed by a shell of Cu and an outer shell of Ni. Binary vacancy-Cu and Ni-Cu clusters show a similar shell structure, whereas the atomic configuration of vacancy-Ni agglomerates is completely different. For further application in rate theory and object kinetic Monte Carlo simulations compact and physically-based fit formulae are derived from the atomistic data for the total and the monomer binding energy.

Germanium (Ge) as material for microelectronic applications has received renewed attention over the past decade. This is due to the advantageous electron and hole mobilities that are higher than those of silicon (Si). However, several obstacles still exist that limit the fabrication of Ge-based nanoelectronic devices. One aspect concerns the limited activation of donor atoms. The deactivation is mainly attributed to the formation of dopant-vacancy clusters whose existence is supported by density functional theory calculations. In this work we discuss experiments on the diffusion of implanted phosphorous (P) and arsenic (As) in Ge under proton irradiation. Continuum theoretical simulations of dopant profiles measured by means of secondary ion mass spectrometry reveal that diffusion under irradiation is much less affected by inactive donor-vacancy clusters than diffusion under annealing only. The suppression of donor-vacancy clusters is caused by interstitials in supersaturation and vacancy concentrations close to thermal equilibrium. Applying the approach of concurrent annealing and irradiation high active doping levels in Ge can be realized even at low processing temperatures.

In the continuous casting process the flow structure in the mold plays an important role for the quality of the produced steel. Open issues of this technoloqy concern the influence of a two phase flow in the submerged entry nozzle and the influence of electromagnetic stirrers.

One possible method to determine the flow structure in the mold is the contactless inductive flow tomography (CIFT) which is able to reconstruct the three-dimensional velocity field in electrically conducting melts from externally measured induced magnetic fields. Since for thin slab casting the velocity can be assumed to be mainly two-dimensional it is sufficient to apply only one external magnetic field and to measure the induced fields at the narrow faces of the mold. The actual time resolution is about 1 Hz.

We will present the results [1,2] of an experiment with a two phase flow regime and the effects of an electromagnetic stirrer around the submerged entry nozzle on the flow field in the mold.

[1] Th. Wondrak et al. (2010), Meas. Sci. Techn. 21, 045402
[2] N. Terzija et al. (2011), Meas. Sci. Techn. 22, 015501

The contactless inductive flow tomography (CIFT) allows the reconstruction of the full three- dimensional mean velocity field in electrically conducting melts from externally measured induced magnetic fields. One of its possible applications is the velocity reconstruction in the continuous casting process. We present CIFT measurements performed at the small-scale liquid metal facility Mini-LIMMCAST which uses the room-temperature liquid alloy GaInSn for modelling of the thin-slab casting process. It will be shown that the flow structure, in general, and the jet position and intensity, in particular, can be reliably determined from magnetic field data using only a modest number (in the order of 5) of sensors. Even the very asymmetric flow in case of artificially closing one of the two nozzle outlets is reproduced by CIFT. The CIFT measurements are partly validated by comparison with ultrasonic velocity measurements.

Continuous casting is a widely used technique in the steel producing industry today. The flow structure in the mold has a great impact on the quality of the produced steel. Open issues of this technology concern the influence of a two phase flow in the submerged entry nozzle and the influence of electromagnetic stirrers.

One possible technique to visualize the flow structure in electrically conducting melts is the contactless inductive flow tomography (CIFT) which is able to reconstruct the three-dimensional velocity field by measuring induced magnetic fields outside the melt. Since for thin slab casting the velocity in the mold can be assumed to be mainly two-dimensional it is sufficient to apply only one external magnetic field and to measure the induced fields at the narrow faces of the mold. The actual time resolution is about 1 Hz.

We will present the results [1,2] of an experiment with a two phase flow regime combining CIFT and the mutual inductance tomography to measure the flow structure in the mold and the gas/liquid distribution in the submerged entry nozzle. Additionally we show the effects of an electromagnetic stirrer around the submerged entry nozzle on the flow field in the mold.

[1] Th. Wondrak et al. (2010), Meas. Sci. Techn. 21, 045402
[2] N. Terzija et al. (2011), Meas. Sci. Techn. 22, 015501

The unknown complex formation of Cm(III) with two naphthalene ligands, 2,3­dihydroxynaphthalene (23NAP) and 2­naphthalene (2NAP) as well as 6­hydroxyquinoline (6HQ) was studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Aromatic molecules with hydroxyl groups have the potential to enhance the solubility and mobility of metals by forming complexes. We explored both the luminescence (lifetimes and individual emission spectra) and the excitation properties (excitation spectra) of the formed Cm(III) species. The experiments were performed at a fixed total Cm(III) concentration of 0.3 µM by varying the ligand concentrations (0.03-3.0 mM) and the pH (1.9-12.4) at an ionic strength of 0.1 M (NaClO4). The spectroscopic speciation indicates the formation of CmpLqHr species. In more detail, Cm(III) forms 1:1 and 1:2 complexes with 23NAP, a 1:2 complex with 2NAP and a 1:1 complex with 6HQ. Independent from the ligand and at pH values above 9.5 strong indications were found for ternary complexes with OH- with a 1:2:-1 stoichiometry. The Cm(III)-23NAP complexes exhibited the largest red shift of the Cm3+ emission maximum at 593.7 nm to: 598.3 nm for Cm(23NAP)H2+, 604.4 nm for Cm(23NAP)+, 608.4 nm for Cm(23NAP)2-, and 616 nm for Cm(23NAP)2OH2-. Based on the factor analysis of the emission data the stability constants were calculated to be: (a) for 23NAP log ß111 = 20.2 ± 0.8, log ß110 = 12.7 ± 0.4, log ß120 = 20.5 ± 0.4, and log ß12-1 = 9.7 ± 0.4; (b) for 2NAP log ß120 = 19.4 ± 0.2, and log ß12-1 = 10.3 ± 0.1; and (c) for 6HQ log ß110 = 8.8 ± 0.3, and log ß12-1 = 5.1 ± 0.9 at an ionic strength of 0.1 M (NaClO4). The stability constants were compared to those of natural pyoverdins.

The use of Computational Fluid Dynamics (CFD) Codes for two-phase flow problems in Nuclear Safety Research is discussed. Examples for recent developments are the qualification of MUSIG model for dispersed flows and the modelling of free surfaces. Up to now the predictive capabilities of CFD codes for two-phase flows are limited to special cases. Nevertheless a valuable contribution to understand such complex flows is obtained. The aim of the future research is to develop CFD codes towards a quantitative method to obtain reliable predictions for broad range of applications.

This paper presents a combined experimental and numerical study of the flow characteristics of round vertical liquid jets plunging into a cylindrical liquid bath. The main objective of the experimental work consists in determining the plunging jet flow patterns, entrained air bubble sizes and the influence of the jet velocity and variations of jet falling lengths on the jet penetration depth. The instability of the jet influenced by the jet velocity and falling length is also probed. On the numerical side, two different approaches were used, namely the mixture model approach and interface-tracking approach using the level-set technique with the standard two-equation turbulence model. The numerical results are contrasted with the experimental data. Good agreements were found between experiments and the two modelling approaches on the jet penetration depth and entraining flow characteristics, with interface tracking rendering better predictions. However, visible differences are observed as to the jet instability, free surface deformation and subsequent air bubble entrainment, where interface tracking is seen to be more accurate. The CFD results support the notion that the jet with the higher flow rate thus more susceptible to surface instabilities, entrains more bubbles, reflecting in turn a smaller penetration depth as a result of momentum diffusion due to bubble concentration and generated fluctuations. The liquid average velocity field and air concentration under tank water surface were compared to existing semianalytical correlations. Noticeable differences were revealed as to the maximum velocity at the jet centreline and associated bubble concentration. The mixture model predicts a higher velocity than the level-set and the theory at the early stage of jet penetration, due to a higher concentration of air that cannot rise to the surface and remain trapped around the jet head. The location of the maximum air content and the peak value of air holdup are also predicted differently.

Experiments and computational fluid dynamics (CFD) simulations have been carried out to predict a turbulent water jet plunging into a tank filled with the same liquid. A zero distance of the free falling water jet to the free surface of the tank is considered in order to avoid air bubble entrainment which may be caused by surface instabilities.
For both impinging region and recirculation zone, measurements are made using Particle Image Velocimetry (PIV). Instantaneous and time-averaged velocity fields are obtained over the cross-section of the tank. Numerical data is obtained on the basis of both k-ε and SSG (Speziale, Sarkar and Gatski) of Reynolds Stresses Turbulent Model (RSM) in three dimensional frame and compared to experimental results via the axial velocity and turbulent kinetic energy.
It was found that, for axial distances lower than 5 cm from the jet impact point, the axial velocity matches well the measurements, using both models. A progressive difference is noticed near the jet for higher axial distances from the jet impact point. These discrepancies are more important in the case of RSM than in the case of k-ε model. Nevertheless, it was observed that the turbulent kinetic energy agrees very well with the measurements when applying the SSG-RSM model for the lower part of the tank, whereas it is underestimated in the upper region, especially in the region near the jet exit. Inversely, the k-ε model shows better results in the upper part of the water tank and underestimates results for the lower part of the water tank. From the overall results, it can be concluded that the k-ε model describes well the average axial velocity, whereas the turbulent kinetic energy is better represented by the SSG-RSM model. The flow pattern obtained using both turbulent models and the corresponding comments of the results are detailed in the paper.

Vorstellung aktueller Arbeiten zur Entwcklung S-Layer-basierter Materialien

no abstract available

A detector for high-resolution momentum measurements of neutrons in the energy range 0.2-1.0 GeV is being developed for the R3 B experiment at FAIR. Two solutions are currently being studied: A pure scintillator concept and an approach based on a sequence of converter material (iron) to produce secondary charged particles, and Multigap Resistive Plate Chambers (MRPC’s) to detect these particles. Here, work on the latter solution is reported.

The acronym NeuLAND (new Large Area Neutron De-tector) stands for the high-efficiency time-of-flight spectrometer for high-energy neutrons (200 to 1000 MeV) within the R3B experiment being designed for FAIR. A spatial resolution of approximately sigma~1 cm and a time resolution of approximately sigma~100 ps are envisaged together with an efficiency of more than 90 % for one-neutron events, as well as a high multi-neutron recognition capability.

An experiment has been performed by the R3B collaboration aiming at the investigation of light neutron-rich nuclei utilizing kinematically complete measurements of reactions at relativistic energies with the R3 B-LAND reaction setup at Cave C. The physics topics to be studied comprise the measurement of astrophysical reaction rates relevant for r-process nucleosynthesis using heavy-ion induced electromagnetic excitation and quasi-free knockout reactions to study the evolution of shell and cluster structures close to and beyond the dripline.

The magnetic phase diagram of multiferroic MnWO₄ is studied in magnetic fields up to 60 T using sound velocity and sound attenuation measurements. Anomalies are observed at temperatures T_N1 = 7.6 K, T_N2 = 12.6 K and T_N3 = 13.6 K that separate commensurate antiferromagnetic (AF1) to helical AF2 and commensurate AF3 to paramagnetic phases, respectively. The anomalies are significantly different and shed light on the spin–phonon coupling and evolution of the various order parameters in this multiferroic material. For temperatures below T_N2 pronounced field hysteresis effects are also observed in the sound velocity, indicating field-induced transformations. In the temperature dependence of the attenuation we observe anomalies distinctively different from the usual maxima related to relaxation effects. They are attributed to the combination of dispersion effects due to domain walls and the discontinuously changing sound velocity. In total, six different magnetic phases, at various temperatures and fields including a novel high-field phase, are revealed and analyzed.

The islet amyloid polypeptide (IAPP) Is a hormonal factor secreted by the beta-cells in the pancreas. Aggregation of misfolded IAPP molecules and subsequent assembly of amyloid nanofibrils are critical for the development Of type 2 diabetes mellitus. In the physiological environment, amyloid aggregation is affected by the presence of interfaces such as cell membranes. The physicochemical properties of the interface dictates the interaction of the peptide with the surface, i.e., electrostatic and hydrophobic Interactions on hydrophilic and hydrophobic surfaces, respectively. We have studied the Influence of hydrophobicity on the surface-catalyzed assembly of IAPP on ultrasmooth hydrocarbon films grown on ion-beam-modified mica surfaces by atomic force microscopy. The contact angle theta of these surfaces can be tuned continuously in the range from <= 20 degrees to similar to 90 degrees by aging the samples without Significant changes of the chemical composition or the topography of the surface. On hydrophilic surfaces with a theta of similar to 20 degrees, electrostatic interactions Induce the assembly of IAPP nanofibrils, whereas aggregation of large (similar to 2.6 nm) oligomers Is observed at hydrophobic surfaces with a theta of similar to 90 degrees. At intermediate contact angles, the interplay between electrostatic and hydrophobic substrate interactions dictates the pathway of aggregation with fibrillation getting continuously delayed when the contact angle is increased. In addition, the morphology of the formed protofibrils and mature fibrils at intermediate contact angles differs from those observed at more hydrophilic surfaces. These results might contribute to the understanding of the surface-catalyzed assembly of different amyloid aggregates and may also have implications for the technologically relevant controlled synthesis of amyloid nanofibrils of desired morphology.

The main disadvantages of;peptide pharmaceuticals are their rapid degradation and excretion, their low hydrophilicity, and low shelf lifes. These bottlenecks can be circumvented by acylation with fatty acids (lipidation) or polyethylene glycol (PEGylation). Here, we describe the Modification of a human pancreatic polypeptide analogue specific for the human (h)Y₂ and hY₄ receptor with PEGs of different size and palmitic acid. Receptor specificity was demonstrated by competitive binding studies. Modifications had only small influence on binding affinities and no influence on secondary structure. Both modifications improved pharmacokinetic properties of the hPP analogue in vivo and in vitro,,however, lipidation showed a greater resistance to degradation and excretion than PEGylation, Furthermore, the lipidated peptide is taken up and degraded solely by the liver but not the kidneys. Lipidation resulted in prolonged action of the hPP analogue in respect of reducing food intake in mice after subcutaneous administration. Therefore, the lipidated hPP analogue could constitute a potential new therapeutic agent against obesity.

Doping stainless steels or iron chromium alloys with oxygen reactive elements like Y and rare earth elements (REE) like Ce, La, Er and others improves their oxidation resistance at high temperature.
There are numerous methods of incorporating REE into steel by surface treatment, e.g.: ion implantation, metalo-organic, chemical vapour deposition, sol-gel coating, pack cementation, screen-printing, molten-salt electrodeposition.
Recently we undertook an attempt to incorporate REE into steels using a new approach based on the use of high intensity pulsed plasma beams (HIPPB). The characteristic feature of this method rely upon the fact that the REE elements are alloyed into the near-surface region of the substrate in its transient liquid state. The preliminary results obtained on AISI 316L steel samples doped with Ce-La in this way and then oxidized in air for 80 hours at 1000°C were encouraging as regards the scales which were thinner, more compact and well adhered.
In the present work we report on the use of yttrium as an active element incorporated into 316 stainless steel using HIPPB. The surface modification of treated samples was performed using 3 pulses with their energy density of 2 Jcm-2 each. Nitrogen was used as a working gas. The yttrium doses accumulated in stainless steel range from 2.34e16 to 1.28e17 cm-2.
The samples are examined by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), X-ray diffraction (XRD) and crucially important Rutherford Back Scattering (RBS) measurements and subjected to oxidation in air at a temperature of 1000°C for a period of 100 h.

Mixing of fluids in T-junction geometries is of significant interest for nuclear safety research. The most prominent example is the thermal striping phenomena in piping T-junctions, where hot and cold streams join and turbulently mix, however not completely or not immediately at the T-junction. This results in significant temperature fluctuations near the piping wall, either at the side of the secondary pipe branch or at the opposite side of the main branch pipe. The wall temperature fluctuation can cause cyclical thermal stresses and subsequently fatigue cracking of the wall.

Thermal mixing in a T-junction has been studied for validation of CFD-calculations. A T-junction thermal mixing test was carried out at the Älvkarleby Laboratory of Vattenfall Research and Development (VRD) in Sweden. Data from this test have been reserved specifically for a OECD CFD benchmark exercise. The computational results show that RANS fail to predict a realistic mixing between the fluids. The results were significantly better with scale-resolving methods such as LES, showing fairly good predictions of the velocity field and mean temperatures. The calculation predicts also similar fluctuations and frequencies observed in the model test.

Positron emission tomography (PET) is applied in geosciences for the visualization of flow and transport processes in various rock formations (GeoPET [1]). Denser rock material requires more demanding and stronger corrections of scatter and attenuation of the gamma rays than in human body tissue. Once the quantification of scatter and attenuation is acquired, correction strategies can be established and the physical limit of the spatial resolution of ~1 mm for the GeoPET method be accomplished. We suggest Monte Carlo (MC) simulations of a ClearPET camera (Raytest) as means for achieving this aim.

We report simulation results of the GeoPET using software GATE (Geant4 Application for Tomographic Emission [2]). The purpose of this investigation is to determine the scatter fraction of gamma rays in various rock formations with different gantry diameter configurations, various Isotopes and different energy windows.
The simulations show that the energy window and increasing gantry diameter are important physical parameters affecting the scatter fraction values in denser material. Reconstructed images from measurements and simulations show good qualitative agreement.
[1] Kulenkampff, J. et al. (2008) Phys. Chem. Earth 33, 937-942.
[2] Jan, S. et al. (2011) Phys. Med. Biol. (56) 881-901.

Die Belastung des Reaktordruckbehälters von Druckwasserreaktoren wird in Thermoschock-Szenarien insbesondere durch Vermischungsvorgänge und von Direktkondensation bestimmt. Die zunehmend auch für Fragestellungen der Reaktorsicherheitsforschung verwendeten CFD-Modelle können diese Phänomene bislang nur mit einigen Einschränkungen abbilden. Die zur Weiterentwicklung der Modelle benötigten Experimente werden gegenwärtig im Helmholtz-Zentrum Dresden-Rossendorf vorbereitet. In einem Bassin werden verschiedene Experimente mit unterkühltem Wasser in Dampfatmosphäre durchgeführt und mit zeitlich und örtlich hoch aufgelösten Messverfahren beobachtet.

Ceramics materials, such as: oxides, nitrides, borides, carbides and carbon are widely used in modern constructions and devices. Their advantages are: low density, high mechanical strength and corrosion resistance at high temperature and favourable performance/weight relationship. However, an application of these materials in joints or in composites with metals is very difficult, because usually the ceramics are non-wettable by liquid metals.
In the present work, we used high intensity plasma pulses technique for the preparation of carbon and silicon carbide surface before the wetting process by liquid copper. The Ti, Zr and Cu plasma was applied to induce the wettability.
The experiments were preceded by thermodynamical considerations. The prepared samples were investigated by sessile-drop tests, SEM observations, EPMA, GXRD analysis and RBS measurements.
The results of Ti and Zr plasma modifications were beneficial and similar to each other. The measured contact angles were below 90°. The results of Cu plasma were unfavorable with contact angles close to 180°.

The addition of some amount of oxygen reactive elements like Y and rare earth elements (REE) Ce, La, Er and others into stainless steels or iron chromium alloys improves their oxidation resistance at high temperature.
There are numerous methods of incorporation of REE into steel by surface treatment, e.g.: ion implantation, metal organic, chemical vapour deposition, sol-gel coating, pack cementation, screen-printing, molten-salt electrodeposition.
In the present work we intend to use yttrium as an active element which will be incorporated into 304, 316 and 430 stainless using conventional implantation with MEVVA type of Y ion source.
The samples will be examined by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), X-ray diffraction (XRD) and crucially important Rutherford Back Scattering (RBS) measurements and subjected to oxidation in air at a temperature of 1000°C for a period 100 h.
Results obtained with the use of HIPPB method and ion implantation will be compared and discussed.

Die simultane Kombination verschiedener Ionenenergien mittels Plasma Immersions Ionenimplantation und reaktivem Magnetronsputtern zur Herstellung extrem glatter, superharter und haftfester tribologischer Schichten für Hochtechnologieanwendungen wird beschrieben

We analysed shallow (to ~1 km) and deep fracture waters (to > 3 km) from the Witwatersrand Basin, South Africa for their noble gas isotopic composition. Their neon signature clearly differentiates a group of typical crustal fluids from another one with a significantly enriched nucleogenic neon signal with the highest 21Ne/22Ne ratios (0.160 +/- 0.003) ever reported in groundwater [1]. Fluid inclusions in adjacent rocks yield even higher 21Ne/22Ne ratios between 0.219 and 0.515, consistent with an extrapolated 21Ne/22Ne value of 3.3 +/- 0.2 at 20Ne/22Ne = 0. We show that this enriched nucleogenic neon end-member represents a fluid component that was produced in the fluorine-depleted Archaean formations and trapped in fluid inclusions > 2 Ga ago [1]. The observation of enriched nucleogenic neon signatures in deep fracture water implies the release of this billion year old neon component from the fluid inclusions and its accumulation in exceptionally isolated fracture water systems. The observed association of this Archaean neon signature with H2-hydrocarbon-rich geogases of proposed abiogenic origin [2] dissolved in the same deep groundwater suggests that the fracture systems have also allowed for the accumulation of various products of water-rock reactions throughout geologic times. One of these fracture systems contained a chemolithotrophic, single species ecosystem surviving on radiolytically produced H2 and sulfate completely independent of the surface photosphere [3,4].

[1] Lippmann-Pipke et al. 2011 Chem. Geol. 283, 287-296
[2] Sherwood Lollar et al. 2002 Nature 416(6880) 522-524
[3] Lin L.-H. et al. 2006 Science 314(5798), 479-482
[4] Chivian, D. et al. 2008 Science 322(5899), 275-278

Ein internationales Forscherteam untersucht Wasserproben aus den tiefsten Bergwerken der Welt. Eine Wasserkomponente entpuppt sich als ein "urzeitliches" Signal und belegt die außerordentliche Isolation dieser tiefen, mikrobiell besiedelten Wasserreservoire.

no abstract available

The natural volcanic glass obsidian was one of the most appreciated materials of ancient man for cutting tools and has been found in many locations far away from any natural source. Reliable provenancing by means of its highly specific chemical composition, the “chemical fingerprint”, can provide information about economy, policy and the social system of ancient societies.
The application of three complementary analytical techniques enables both a maximum element spectrum and a comparison of the chemical compositions to provide the actual degree of the re-liability of the analytical results.
This approach reveals the most characteristic “chemical fingerprint“ and allow us to decide which least invasive analytical method should be chosen for the analysis of an archaeological artefact most likely stem from Melos by three different methods:

• Neutron Activation Analysis (NAA)
• Ion Beam Analysis (IBA) comprising of Proton Induced X-ray Emission (PIXE), Proton Induced Gamma-ray Emission (PIGE) and Rutherford Backscattering Spectrometry (RBS)
• Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS)

Produced by fiery volcanic eruptions obsidian solidified as natural glass and was again under fire at the three different research facilities. Obsidian, also called the “Stone Age black gold” was an important raw material for cutting tools during prehistoric time and has been found by research-ers at great distances from potential natural sources. Reliable provenancing by means of its highly specific chemical composition, the “chemical fingerprint”, can provide information about economy, policy and the social system of ancient societies.
The application of three complementary analytical techniques enables both a maximum element spectrum and a comparison of the chemical compositions to provide the actual degree of the re-liability of the analytical results. This approach allows us to assess accuracy and precision of ar-chaeometric elemental analyses by three different methods:

• Neutron Activation Analysis (NAA)
• Ion Beam Analysis (IBA) comprising of Proton Induced X-ray Emission (PIXE), Proton Induced Gamma-ray Emission (PIGE) and Rutherford Backscattering Spectrometry (RBS)
• Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS)

Bei einem Kühlmittelverluststörfall eines Druckwasserreaktors (DWR) können sich in der Anfangsphase an den Sumpfansaugsieben Mineralwolleablagerungen aus dem Isolationsmaterial bilden und dadurch die Notkühlung beeinträchtigen. Das borsäurehaltige Primärkühlmittel verursacht eine Korrosion an Einbauten im Containment, die überwiegend aus feuerverzinktem Stahl bestehen. Feste Korrosionsprodukte bewirken durch Anlagerung an den Mineralwolleablagerungen einen Anstieg des Differenzdrucks über den Sumpfansaugsieben, der bis zur Blockade und dem Ausfall der Notkühlung führen kann. Ausgehend vom Schichtaufbau der Feuerverzinkung konnte der Ablauf der Korrosion aufgeklärt werden, wobei zunächst lösliche Korrosionsprodukte des Zinks entstehen und erst nach Freilegung von Stahl Rost gebildet wird, der sich am Faserbett anlagern kann. Die Ergebnisse, die auf den Analysen der Lösungen, der Ablagerungen auf den Faserbetten und den Metallproben nach Ende der Versuche beruhen, stehen in Übereinstimmung mit dem Differenzdruckanstieg als technisch wichtigen Parameter. Die anfangs starke Korrosion unter Bildung von Zinkionen verursacht eine Zunahme des pH-Werts, die aber zu einer Verringerung der Korrosionsrate führt. Entscheidend für den Korrosionsverlauf sind neben einem ausreichenden Angebot an Zinkoberfläche besonders die Strömungsverhältnisse und die Zusammensetzung des Primärkühlmittels bei lokaler Freilegung des Basismaterials.

The high affinity of uranyl(VI) ions to distinct functional groups of biomolecules is considered to contribute decisively to the migration behaviour of these metal ions in the biogeosphere [1]. In particular, organic phosphate groups are predestined to form actinide complexes at a physiologically relevant pH level [2]. Because the phosphorylated sites of biomolecules often represent a key role in their proper physiological function, the study on the complexation is of great significance.
In this work, U(VI) complexes of phosphorylated amino acids, namely p-serine and p-tyrosine, were investigated by vibrational spectroscopy serving as model compounds for more complex systems. The spectra obtained demonstrate the high affinity of the actinyl ion to phosphate groups. Contributions from the carboxyl and amino groups to the U(VI) complexes can be neglected.
These results are compared with spectra obtained from our recent investigation with a naturally occurring highly phosphorylated protein, phosvitin [3]. The spectral homologies confirm the suggestion that U(VI) is preferentially bound by organic phosphate groups under physiologically relevant conditions.
The derivation of molecular structures from vibrational spectra can be supported by theoretical approaches, such as density functional theory (DFT) calculations. A series of calculations was performed to reproduce the vibrational spectral data focusing on the frequency range of the vibrational modes of the phosphate groups. A comparison with the experimental data provides additional structural information on a molecular level.

[1] Van Horn, J. D. et al. (2006) Coord. Chem. Rev. 250, 765-775. [2] Barkleit, A. et al. (2008) Dalton Trans., 2879-2886. [3] Li, B. et al. (2010) J. Inorg. Biochem. 104, 718-725.

no abstract available

Partitioning and Transmutation (P&T) of minor actinides (MA) is currently studied to reduce the nuclear waste inventory. In this context, the fabrication of MA bearing materials is of great interest to achieve an effective recycling of these highly radioactive elements. In order to ensure the inpile behavior, these fuels have to respect several criteria including preservation of the fluorite structure and defined oxygen to metal ratio (O/M). In the case of Am bearing materials, such as U1-yAmyO2±x (y=0.10, 0.15, 0.20), the O/M determination is quite challenging using conventional methods (TGA, XRD) due to the particular Am thermodynamic properties. Despite the lack of experimental data in the U-Am-O system, thermodynamical modeling are currently developed to effectively assess the O/M ratio. In this work, the O/M ratios were calculated for various oxygen potentials using the cation molar fraction determined by XAS measurements. These results are an important addition to the experimental data available for the U-Am-O system. Moreover, XRD and XAS indicated that the fabrication of fluorite U1-yAmyO2±x solid solution can be achieved for all Am content and oxygen potentials investigated. Based on the molar fraction, a description of the solid solution was proposed depending on the considered sintering conditions. Finally, the occurrence of an expected charge compensation mechanism between Am(+III) and U(+V) was pointed out.

We report cyclotron resonance (CR) experiments on the midinfrared alloy InAs1-xNx grown on GaAs with x from 0% to 1.9%. Using magnetic fields up to 60 T and terahertz photon sources from 3 to 30 THz, we determine the dependence on x of the electron density and CR mass. The increase in the carrier density with increasing x is accompanied by a redshift in the interband photoluminescence emission and is explained in terms of the pinning of the Fermi level to its value at x = 0. The high carrier densities (similar to 10(18) cm(-3)) at x similar to 1% give rise to a CR mass that is only weakly dependent on the excitation energy, significantly weaker than that in InAs. (C) 2011 American Institute of Physics.

In electron beam tomography a rotating X-ray source is generated by electromagnetic scanning of a high-power electron beam across a spatially fixed circular metal target. The X-rays passing the object of investigation are registered by a circular fast X-ray detector array. A basic problem associated with this scanning principle is the angular overlap of the X-ray focal spot path and the detector, which is required for image reconstruction. Therefore, the X-ray production target and the detector array are commonly arranged with some axial displacement. This displacement may produce image artifacts because X-rays are not longer confined to a transversal plane. We propose a novel transparent X-ray target, which fully solves this problem. The new target concept has been practically tested with respect to thermal behavior and electron beam resistance. Its successful application in an experimental tomography setup is demonstrated.

In the kink-type Tayler instability (TI) a toroidal magnetic field becomes unstable against non-axisymmetric perturbations for a sufficiently large field amplitude. The TI has been discussed as a possible ingredient of the solar dynamo and a source of the helical structures in cosmic jets. It has also to be considered as a limiting criterion for the size of large scale liquid metal batteries. We report on first TI experiments with a cylindrical column of GaInSn to which electrical currents of up to 8 kA are applied. We present results of external magnetic field measurements that indicate the occurrence of the TI.

Starting from the present version of the Riga dynamo experiment with its rotating magnetic eigenfield dominated by a single frequency we ask for those flow modifications that would allow for a non-trivial magnetic field behaviour in the saturation regime. Increasing the ratio of azimuthal to axial flow velocity, numerically we obtain energy oscillations with a frequency below the eigenfrequency of the magnetic field. These new oscillations are identified as magneto-inertial waves that result from a slight imbalance of Lorentz and inertial forces. Increasing the azimuthal velocity further, or increasing the total magnetic Reynolds number, we find transitions to a chaotic behaviour of the dynamo.

The DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN) is intended to become a platform both for large scale experiments related to geo- and astrophysics as well as for safety and thermohydraulic studies related to liquid metal batteries and sodium fast reactors. The most ambitious parts of DRESDYN are a homogeneous dynamo driven solely by precession and a large Tayler-Couette like experiment for the combined investigation of the magnetorotational instability and the Tayler instability. In the talk we give a short summary of the previous achievements, and we delineate the next steps for the realization of DRESDYN.

We report on Alfvén wave experiments with liquid Rubidium at the Dresden High Magnetic Field Laboratory (HLD). With pulsed magnetic fields reaching up 62 T we enter the interesting region where the Alfvén speed crosses the sound speed.

This paper is concerned with a liquid metal flow driven by a rotating magnetic field inside a stationary cylinder. We consider especially the secondary meridional flow during the time the fluid spins up from rest. The developing flow is investigated experimentally and by direct numerical simulations. The vertical profiles of the axial velocity are measured by means of the ultrasound Doppler velocimetry. Evolving instabilities in form of Taylor-Görtler vortices have been observed just above the instability threshold. The transition to a three-dimensional flow in the side layers results from the advection or a precession and splitting of the Taylor-Görtler vortex rings. The numerical simulations agree very well with the flow measurements.

The kink-type instability of a toroidal magnetic field, also known as Tayler instability (TI) is a current-driven instability of a strong enough field due to non-axisymmetric perturbations. In astrophysical context the TI has been discussed as a principal ingredient of a dynamo mechanism (Taylor-Spruit dynamo). It is also a possible source of helicity, in particular of helical structures in galactic jets and outflows. TI is also widely used as a mechanism to enhance angular momentum transport in star evolution models even if there is not yet observational evidence for its existence. Nonetheless an ongoing laboratory experiment in cylindrical geometry indeed shows that TI exists in liquid metal flows influenced by a strong axial current.

Die Untersuchung des Strömungsverhaltens von flüssigen Metallen besitzt sowohl in der Grundlagenforschung als auch in der industriellen Anwendung eine besondere Bedeutung. Dieses liegt zum einen an den Eigenschaften des Fluids selbst, zum anderen an der interessanten Möglichkeit, daß sich diese Strömungen aufgrund ihrer hohen elektrischen Leitfähigkeit aktiv durch elektromagnetische Kräfte beeinflussen lassen. Für die Kristallzucht wird beispielsweise der Einsatz rotierender oder wandernder Magnetfelder verfolgt, um eine gute Durchmischung und damit eine hohe Homogenität der Schmelze zu erreichen. Die dort auftretenden Strömungsstrukturen können relativ komplex werden, was wiederum eine örtlich hochauflösende, bildgebende Meßtechnik erfordert, um z. B. numerische Simulationen zu validieren. Es wird ein bildgebendes Ultraschall-Meßsystem vorgestellt, daß durch Einsatz segmentierter Wandler und deren weitgehendem Parallelbetrieb sowohl eine hohe Zeit- als auch eine hohe Ortsauflösung ermöglicht. Kernelemente des Systems sind zwei orthogonal angeordnete Ultraschallwandler-Arrays, deren einzelne Wandlerelemente durch eine mikroprozessorgesteuerte Schaltmatrix nach einem speziellen Muster angesteuert und ausgelesen werden.

This paper considers the situation where the liquid metal flow with a free surface covered by an oxide layer is driven by a rotating magnetic field. The cylindrical configuration was investigated in an experiment accompanied by numerical simulations. The oxide layer feels the effect of the viscous force arising from the moving liquid beneath and the friction force from the side walls. A complex interaction occurs if both forces are in the same order of magnitude. Our measurements demonstrate that the occurrence of the oxide layer may lead to an unexpected oscillating behaviour of the bulk flow. Our numerical model was shown to be able to reproduce essential features of the phenomenon in a qualitative way.

We present the new experimental facility LIMMCAST for modelling the continuous casting process of steel using the alloy SnBi at temperatures of 200-400°C. In addition, a smaller set-up Mini-LIMMCAST operates with the room-temperature liquid alloy GaInSn. First results will be presented covering the following phenomena: fully contactless electromagnetic tomography of the flow in the mould, mould flow monitoring by an array of ultrasonic sensors, analysis of the flow in the mould under the influence of an electromagnetic brake and the injection of argon bubbles through the stopper rod. Numerical simulations using ANSYS-CFX were performed which basically confirm the measuring results.

We describe an experimental set-up for the investigation of the Tayler instability (TI), we show first results, and we discuss the possible relevance of the TI for large-scale liquid metal batteries as they are presently under consideration as cheap means for the storage of renewable energies.

At the end of 1999, the dynamo experiments in Riga and Karlsruhe initiated a period of strong activity to simulate the origin and the action of cosmic magnetic fields in the liquid metal laboratory. With main focus on our own efforts, we summarize the recent liquid metal experiments on homogeneous dynamo action and related magnetic instabilities. We delineate our plans for a new liquid sodium facility that will comprise a large scale dynamo experiment based on precession, and a Taylor-Couette experiment for the combined investigation of the magnetorotational instability and of the kink-type Tayler instability. We further discuss the capabilities of alkali metal experiments to study Alfvén waves in a parameter region where the Alfvén speed crosses the sound speed.

The dynamics of patterns in large two-dimensional domains remains a challenge in non-equilibrium phenomena. Often it is addressed through mild extensions of one-dimensional equations. We show that full 2D generalizations of the latter can lead to unexpected dynamical behavior. As an example we consider the anisotropic Kuramoto-Sivashinsy equation, that is a generic model of anisotropic pattern forming systems and has been derived in different instances of thin film dynamics. A rotation of a ripple pattern by 90◦ occurs in the system evolution when nonlinearities are strongly suppressed along one direction. This effect originates in non-linear parameter renormalization at different rates in the two system dimensions, showing a dynamical interplay between scale invariance and wavelength selection. Potential experimental realizations of this phenomenon are identified.

The hydrophobicity of surfaces has a strong influence on their interactions with biomolecules such as proteins. Therefore, for in vitro studies of bio-surface interactions model surfaces with tailored hydrophobicity are of utmost importance. Here, we present a method for tuning the hydrophobicity of atomically flat mica surfaces by hyperthermal Ar ion irradiation. Due to the sub-100 eV energies, only negligible roughening of the surface is observed at low ion fluences and also the chemical composition of the mica crystal remains almost undisturbed. However, the ion irradiation induces the preferential removal of the outermost layer of K+ ions from the surface, leading to the exposure of the underlying aluminosilicate sheets which feature a large number of centers for C adsorption. The irradiated surface thus exhibits an enhanced chemical reactivity toward hydrocarbons, resulting in the adsorption of a thin hydrocarbon film from the environment. Aging these surfaces under ambient conditions leads to a continuous increase of their contact angle until a fully hydrophobic surface with a contact angle > 80 degrees is obtained after a period of about 3 months. This method thus enables the fabrication of ultrasmooth biological model surfaces with precisely tailored hydrophobicity.

We report on an efficient procedure for the preparation of [¹⁸⁸Re(N)(PNP)]-based complexes (where PNP is diphosphinoamine) useful in the development of target-specific radiopharmaceuticals. The radiochemical yield of the compounds was optimized considering such reaction parameters as nature of the nitrido nitrogen donor, reaction times and pH level. The chemical identity of the ¹⁸⁸Re agents was determined by high-performance liquid chromatography comparison with the corresponding well-characterized cold Re compounds. ¹⁸⁸Re(N) mixed compounds have been evaluated with regard to stability toward transchelation with GSH and degradation by serum enzymes. The clearance of selected radiocompounds from normal tissues and their in vivo stability were evaluated in rats by biodistribution and imaging studies. [¹⁸⁸Re(N)(cys∼)(PNP)]^+/0 mixed-ligand compounds were efficiently prepared in aqueous solution from perrhenate using a multistep procedure based on the preliminary formation of the labile ¹⁸⁸Re^III–EDTA species, which easily undergo oxidation/ligand exchange reaction to afford the [¹⁸⁸Re^V≡N]²⁺ core in the presence of dithiocarbazate. The final mixed-ligand compounds were obtained, at 100°C, by adding the two bidentate ligands to the buffered [¹⁸⁸Re^V≡N]²⁺ solution (pH 3.2–3.6). However, a relatively high amount of cys∼ ligand was required to obtain a quantitative radiochemical yield. The complexes were stable toward reoxidation to perrhenate and ligand exchange reactions. In vivo studies showed rapid distribution and elimination of the complexes from the body. No specific uptakes in sensitive tissues/organs were detected. A positive correlation of the distribution of the complexes estimated with biodistribution studies (%ID) and with micro-SPECT semiquantification imaging analysis (standard uptake values) was observed. These results support the possibility of applying [¹⁸⁸Re(N)(PNP)] technology to the preparation of target-specific agents.

Our aim was to assess feasibility and performance of novel semi-automated image analysis software called ROVER to quantify metabolically active volume (MAV), maximum standardized uptake value-maximum (SUV_max), 3D partial volume corrected mean SUV (cSUV_mean), and 3D partial volume corrected mean MVP (cMVP_mean) of spinal bone marrow metastases on fluorine-18 fluorodeoxyglucose-positron emission tomography/computerized tomography (¹⁸F-FDG-PET/CT). We retrospectively studied 16 subjects with 31 spinal metastases on FDG-PET/CT and MRI. Manual and ROVER determinations of lesional MAV and SUV_max, and repeated ROVER measurements of MAV, SUV_max, cSUV_mean and cMVP_mean were made. Bland-Altman and correlation analyses were performed to assess reproducibility and agreement. Our results showed that analyses of repeated ROVER measurements revealed MAV mean difference (D)=-0.03±0.53cc (95% CI(-0.22, 0.16)), lower limit of agreement (LLOA)=-1.07cc, and upper limit of agreement (ULOA)=1.01cc; SUV_max D=0.00±0.00 with LOAs=0.00; cSUV_mean D=-0.01±0.39 (95% CI(-0.15, 0.13)), LLOA=-0.76, and ULOA=0.75; cMVP_mean D=-0.52±4.78cc (95% CI(-2.23, 1.23)), LLOA=-9.89cc, and ULOA=8.86cc. Comparisons between ROVER and manual measurements revealed volume D= -0.39±1.37cc (95% CI (-0.89, 0.11)), LLOA=-3.08cc, and ULOA=2.30cc; SUV_max D=0.00±0.00 with LOAs=0.00. Mean percent increase in lesional SUV_mean and MVP_mean following partial volume correction using ROVER was 84.25±36.00% and 84.45±35.94% , respectively. In conclusion, it is feasible to estimate MAV, SUV_max, cSUV_mean, and cMVP_mean of spinal bone marrow metastases from ¹⁸F-FDG-PET/CT quickly and easily with good reproducibility via ROVER software. Partial volume correction is imperative, as uncorrected SUV_mean and MVP_mean are significantly underestimated, even for large lesions. This novel approach has great potential for practical, accurate, and precise combined structural-functional PET quantification of disease before and after therapeutic intervention.

Die Aktivierung flacher Dotanden stellt einen wichtigen Prozess in der Siliziumtechnologie dar. Typische Dotiermaterialien, wie z. B. Bor, Phosphor, Arsen oder Antimon, besitzen eine sehr hohe Löslichkeit in Silizium. Deswegen können in Silizium hohe Dotierkonzentrationen mit konventionellen Ausheilmethoden in der festen Phase auf der Millisekunden-Zeitskale erreicht werden.
Neuartige, mit Übergangsmetallen dotierte Halbleiter, benötigen für die gewünschte ferromagnetische Kopplung Dotierkonzentrationen weit oberhalb der geringen Löslichkeit magnetischer Dotanden. Ausreichend hohe Dotierkonzentrationen magnetischer Dotanden werden mittels Lasertempern in der flüssigen Phase erreicht. Lasertempern ist ein Prozess, welcher unter thermodynamischen Nichtgleichgewichtsbedingungen auf der ns-Zeitskale stattfindet und eine Diffusion der Dotanden extrem unterdrückt.
In dem Vortrag werden typische Anwendungsgebiete der Lasertemperung vorgestellt und ein Blick auf den aktuellen Stand der Forschung auf dem Gebiet der Lasertemperung zur Herstellung ferromagnetischer Halbleiter geworfen.

We investigate the time-resolved photoluminescence (PL) dynamics of an undoped GaAs/AlGaAs multiple quantum well under mid-infrared (MIR) irradiation. A time-delayed MIR laser pulse from a free electron laser, tuned to the intersubband transition energy of the quantum well, induces temporal quenching of the PL intensity with subsequent recovery. The experimental data can be accurately described by a simple rate-equation model, which accounts for the cooling of the non-radiative states to radiative states. By performing polarization sensitive measurements, we are able to discriminate the contributions of free-carrier absorption from that of intersubband absorption, where the latter is about 50 times more efficient.

Hydrogen release from various elastomers upon irradiation with H+, He+ and Ar+ ions has been studied using nuclear reaction analysis (NRA) method. A massive loss of hydrogen atoms upon irradiation has been noted, the results point to the saturation of hydrogen content at about 10 at.%. The analysis of the experimental data indicates that the hydrogen release is controlled by inelastic collisions between ions and target electrons.

In surgery for focal congenital hyperinsulinism (CHI), the identification and complete resection of the focus without collateral damage is of utmost importance. In a pilot study we applied intra-abdominal high-frequency sonography during surgery for focal CHI in 2 infants. The focus could be identified, its relation to the pancreatic and common bile duct could be shown, and the typical octopus-like tentacles could be demonstrated. In one case the resection was successful; in the other it was not. These preliminary results suggest that intraoperative sonography could be a valuable tool in the surgical therapy of focal CHI and warrants further evaluation in a clinical study.

In 1918 Brouwer considered stability of a heavy particle in a rotating vessel. This was the first demonstration of a rotating saddle trap which is a mechanical analogue for quadrupole particle traps of Penning and Paul. We revisit this pioneering work in order to uncover its intriguing connections with classical rotor dynamics and fluid dynamics, stability theory of Hamiltonian and non-conservative systems as well as with the modern works on crystal optics and atomic physics. In particular, we find that the boundary of the stability domain of the undamped Brouwers problem possesses the Swallowtail singularity corresponding to the quadruple zero eigenvalue. In the presence of dissipative and non-conservative positional forces there is a couple of Whitney umbrellas on the boundary of the asymptotic stability domain. The handles of the umbrellas form a set where all eigenvalues of the system are pure imaginary despite the presence of dissipative and non-conservative positional forces.

The dynamic magnetic properties of soft-ferromagnetic thin film element arrays are strongly influenced by long range interelement magnetostatic interaction. In order to estimate the effective array dipolar field a quantitative model is presented, which is based on the superposition of stray fields that arise from the neighborhood of a reference element. Kittel's equation, that describes the magnetodynamics, is generalized for magnetically saturated arrays by additional array dipolar field terms. Measurements of the magnetodynamic response of quasi-saturated arrays with a rectangular base agree with theoretical predictions. Thus, our model allows the estimation of the frequency of the uniform precessional mode in mesoscopic thin film arrays with non-negligible magnetostatic interaction.

We report on the experimental study of an exceptional point (EP) in a dissipative microwave billiard with induced time-reversal invariance (T) violation. The associated two-state Hamiltonian is non-Hermitian and nonsymmetric. It is determined experimentally on a narrow grid in a parameter plane around the EP. At the EP the size of T violation is given by the relative phase of the eigenvector components. The eigenvectors are adiabatically transported around the EP, whereupon they gather geometric phases and in addition geometric amplitudes different from unity.

In situ leaching of uranium ores with sulfuric acid during active uranium mining activity on the Gessenheap has caused longstanding environmental problems of acid mine drainage and elevated concentrations of uranium. To study there remediation measures the test site Gessenwiese, a recultivated former uranium mining heap near Ronnenburg/East Thuringia/Germany, was installed as a part of a research program of the Friedrich Schiller University Jena to study, amongs other techniques, the phytoremediation capacity of native and selected plants towards uranium. In a first step the uranium speciation in surface seepage and soil pore waters from the Gessenwiese, ranging in pH from 3.2 to 4.0, were studied by Time-resolved Laser-induced Fluorescence Spectroscopy (TRLFS). Both types of water samples showed a mono-exponential fluorescene decay, indicating the presence of only one major species. The detected emission bands were found at 477, 491, 513, 537, 562, and 591 nm (478 – 492 – 513 – 538 – 562 – 590). These characteristic peak maxima together with the observed mono-exponential decay revealed indicated that the uranium speciation in the seepage and soil pore waters is dominated by the uranium (VI) sulfate species UO2SO4(aq). Due to the presence of fluorescence quenchers in the natural water samples the measured fluorescence lifetimes of the UO2SO4(aq) species of 1.0 to 2.6 µs were reduced in comparison to pure uranium sulphate solutions, which show a fluorescence lifetime of 4.7µs.
This results convincingly show that in the pH range of 3.2 to 4.0 TRLFS is a suitable and very useful technique to study the uranium speciation in naturally occurring water samples.

Thomson sources, driven by laser-wakefield accelerated (LWFA) electrons or small linacs are compact in size and can provide ultrashort, hard X-ray pulses of high brilliance [1]. However, in head-on (180°) Thomson setups, the finite Rayleigh length at small interaction diameters ultimately prevents further advances in peak brilliance, since it becomes increasingly difficult to avoid the nonlinear Thomson regime.
Effectively, not the laser or electron properties, but the interaction geometry limits the performance of all future Thomson sources that aim for high single-shot photon yields.
In order to circumvent this bottleneck, we present a novel concept, which allows obtaining centimeter to meter long optical undulators, where interaction length and diameter are independent of each other.
With an ultrashort, high-power laser pulse in an oblique angle scattering geometry using tilted pulse fronts, electrons and laser remain overlapped while both beams travel over distances much longer than the Rayleigh length.
Such a Traveling-wave Thomson scattering (TWTS) design [2] is particularly interesting for future LWFA-driven Thomson sources with photon yields per pulse that can be orders of magnitudes beyond current designs. In addition, TWTS offeres unique advantages with respect to the minimum scattered bandwidth, which here is independent of the ultrashort laser pulse duration. Instead, it is controlled by the width of a cylindrically focused laser beam.
The possibility to freely choose a side-scattering angle -- from 0 to over 120° -- enables tuning of the photon energy without having to change the electron energy. For optimized LWFA electron sources operating within a narrow energy range, this opens up access to large parts of the X-ray spectrum and hence many applications.
Towards experimental realization, we show how a Traveling-wave setup has to be implemented. An emphasis is put on the use of varied-line spacing (VLS) gratings for dispersion precompensation of the laser beam at large interaction angles to achieve the required overlap between laser and electrons within the interaction region.

[1] A. D. Debus et al., Linear and non-linear Thomson-scattering x-ray sources driven by conventionally and laser plasma accelerated electrons, Proc. SPIE, Vol. 7359, 735908, 2009
[2] A. D. Debus et al., Traveling-wave Thomson scattering and optical undulators for high-yield EUV and X-ray sources, Applied Physics B: Lasers and Optics 100(1), 61-76, 2010

BGCore reactor analysis system was recently developed at Ben-Gurion University for calculating in-core fuel composition and spent fuel emissions following discharge. It couples the Monte Carlo transport code MCNP with an independently developed burnup and decay module SARAF. Most of the existing MCNP based depletion codes (e.g. MOCUP, Monteburns, MCODE) tally directly the one-group fluxes and reaction rates in order to prepare one-group cross sections necessary for the fuel depletion analysis. BGCore, on the other hand, uses a multi-group (MG) approach for generation of one group cross-sections. This coupling approach significantly reduces the code execution time without compromising the accuracy of the results.
Substantial reduction in the BGCore code execution time allows consideration of problems with much higher degree of complexity, such as introduction of thermal hydraulic (TH) feedback into the calculation scheme. Recently, a simplified TH feedback module, THERMO, was developed and integrated into the BGCore system. To demonstrate the capabilities of the upgraded BGCore system, a coupled neutronic TH analysis of a full PWR core was performed. The BGCore results were compared with those of the state of the art 3D deterministic nodal diffusion code DYN3D. Very good agreement in major core operational parameters including k-eff eigenvalue, axial and radial power profiles, and temperature distributions between the BGCore and DYN3D results was observed. This agreement confirms the consistency of the implementation of the TH feedback module.
Although the upgraded BGCore system is capable of performing both, depletion and TH analyses, the calculations were performed for the beginning of cycle state with pre-generated fuel compositions.

Closed capped WS₂ nanotubes with diameters from 30 to 110 nm are studied by high resolution transmission electron microscopy. The tubes exhibit preferentially a hexagonal stacking order. Atomic resolution images of a 30 nm diameter tube reveal a zigzag chirality. A lattice expansion in c-axis direction of ≤ 11% is found within the outermost triple layers. The tube caps often display regular polygon angles. Structural defects like grain boundaries, non-planar triple layers, dislocations, platelet-like fragments, terraces, and amorphous precipitates are identified.

Carrier dynamics and relaxation processes in self assembled quantum dots (QDs) are of fundamental interest due to their influences on the efficiency and performances of optoelectronic devices [1]. The intersublevel relaxation mechanisms influence the temporal response of the photoluminescence (PL) [2]. It is therefore interesting to study the carrier relaxation in a series of QD samples where the intersublevel separation varies, resulting in different relaxation times. In this paper we present our work on time-resolved PL quenching measurements on QD ensembles using terahertz pulses, to study the effect of carrier redistribution on PL. Interband quasi-resonant excitation was done by a Ti-Sapphire laser and the PL emission was measured using a spectrometer coupled to a streak camera. Terahertz pulses were obtained from a Free Electron Laser (FEL) synchronized to the Ti:Sapphire laser. The FEL wavelengths were tuned to excite intersublevel transitions in the QDs (ranging from 23 meV to 15 meV) which caused partial depletion of the electronic ground state resulting in quenching of the interband PL. The samples studied consisted of a series of self-assembled InAs/GaAs QDs for which the intersublevel relaxation times varied from few ps to ns, as a result of thermal annealing [3]. Simultaneous time and wavelength resolved measurements enabled us to study the carrier redistribution by the terahertz pulse and their dynamics. PL measurements were done with and without FEL pulses. Figure 1 shows the calculated difference of two such streak camera images measured for a typical QD sample. The blue regions show the PL quenching dip caused by the FEL excitation for two interband transition energies corresponding to the QD ensemble. The data was fitted using exponential functions convoluted with a Gaussian system response. From the fitting parameters the PL quenching depth and recovery times were extracted. The recovery times were found to be significantly shorter than the intersublevel relaxation times suggesting that other mechanisms like interdot transfer and multiphoton excitations were also involved. We performed measurements for different FEL excitation powers, which showed an eventual saturation of the PL quenching. We observed an increase in the PL signal for the lower energy transition after the recovery of the PL, as shown by the orange region in Figure 1. However the carrier redistribution was found to depend on the intersublevel properties of the samples. In this work we will present a comparative analysis for different QD samples, with emphasis on the effect of intersublevel relaxation times on the carrier dynamics.

Metal dichalcogenide (MX₂) nanotubes and particles, commonly classified as inorganic fullerene-like (IF) materials, represent the inorganic counterparts of carbon nanotubes and fullerenes. They are usually constituted of several MS₂ triple layers, whose curvature is provided by specific defect sites. WS₂ and MoS₂ IF's have recently attracted much interest as dry lubricants and grease additives due to friction coefficients lower than those of platelet based standard mineral oil additives.

In this study WS₂ nanotubes with diameters in the range of 28 nm to 290 nm are studied by electron microscopy and resonant 1st and 2nd order Raman spectroscopy. The Raman response is compared to that of 2H-WS₂ single crystals and microcrystalline 2H-WS₂ powder. With decreasing tube diameter a disorder induced line in the A_1g range, termed D-A_1g line, is increasingly enhanced. For the thinnest tubes it is even stronger than the fundamental A_1g crystal mode. The intensity ratio I (D-A_1g)/ I (A_1g) follows a simple functional relationship. It resembles that of the well known I_D/ I_G ratio in disordered carbon. The enhancement mechanism of the D-A_1g line is discussed in terms of the increasing number of local defects, which is the consequence of the increasing curvature.

[1] M. Krause, M. Viršek, M. Remškar, N. Salacan, N. Fleischer, L. Chen, P. Hatto, A. Kolitsch, W. Möller, "Diameter and Morphology Dependent Raman Signatures of WS₂ Nanostructures", ChemPhysChem, 10, 2221-2225 (2009)

Eingeladener Vortrag ohne Abstract

Introduction: The Kamil crater in southern Egypt was first identified during a Google Earth survey. A closer inspection during a geophysical expedition in February 2010 not only revealed details of its structure but also identified several thousand iron meteorite specimens with a total weight of ~1.7 tons [1, 2]. The meteorite is classified as an ungrouped Ni-rich ataxite [3]. He, Ne and Ar measurements have been performed on samples from the only regmaglypted 83 kg individual as well as from a piece of the shrapnel produced during the impact [1, 2].
Experimental:We measured two samples each from the individual and the shrapnel, separated by a distance of ~1 cm in each case. Material from in between is being used for accelerator mass spectrometry of long-lived cosmogenic radionuclides. Because of instabilities in the gain of the electron multiplier, the noble gas abundances were not determined by the (standard) peak height method, but rather by isotope dilution. For that, about 1/3 of the sample gas was “spiked” with a gas mixture (³He/⁴He/²²Ne/³⁶Ar ~ 1.2x10^-8/1.1x10^-6/1.0x10^-10/3.8x10^-9 cc, Ne and Ar isotopic compositions atmospheric).
Results: As normal for iron meteorites, noble gases are purely spallogenic. Relevant results are listed in Table 1 (concentrations in 10^-8 cc/g units; uncertainties in the last digits in parentheses; I = individual, S = shrapnel).
Sample ³He ⁴He ²¹Ne ³⁸Ar
I-C 147 (10) 622 (18) 1.59 (4) 9.47 (29)
I-g 138 (9) 604 (20) 1.58 (4) 8.20 (34)
S-C 44 (5) 214 (16) 0.42 (1) 2.39 (10)
S-f 41 (5) 193 (18) 0.35 (1) 2.31 (11)
Discussion: Using the model calculations of [4], we can derive bounds on the pre-atmospheric size of the object and can define a possible range of cosmic ray exposure ages. Most useful is the ⁴He/³⁸Ar ratio (cf. Fig. 13 in [4]). Based on the maximum ratio of ~90 (S-C), a minimum radius for the meteoroid is ~85 cm. This implies a preatmospheric mass of >20,000 kg, in excellent agreement with the estimate of [1]. Furthermore, the shrapnel samples must originate from further inside the meteoroid than the individual (35-45 cm vs. 15-25 cm). To reach agreement between ⁴He/³⁸Ar and ⁴He/²¹Ne, a sulfur / phosphorus content in the range 0.4-0.8 wt % contributing to ²¹Ne production is required ([4, 5; cf. Fig. 11 in [4]). Conflicting cosmic ray exposure ages, however, follow from the relation between ⁴He/³⁸Ar ratio and ³⁸Ar production rate according to [4]. While for the individual an age on the order of 400 to 500 Ma is indicated, estimates for the shrapnel samples are lower in the 200 to 300 Ma range. The discrepancy may be solved by the radionuclide measurements, which are in progress.
References: [1] Folco L. et al. 2010. Science 329:804. [2] Folco L. et al. 2011. Geology 39:179-182. [3] Weisberg M. K. et al. 2010. Meteoritics & Planetary Science 45:1530-1551. [4] Ammon K. et al. 2009. Meteoritics & Planetary Science 44:485-503; in detail at: http://noblegas.unibe.ch/index.php?content=noblegas/data. [5] Ammon K. et al. 2008. Meteoritics & Planetary Science 43:685-699.

Single-phase perovskite 5 at.% Mn-doped and undoped polycrystalline BaTiO₃ thin films have been grown under different oxygen partial pressures by pulsed laser deposition on platinum-coated sapphire substrates. Ferroelectricity is only observed for the Mn-doped and undoped BaTiO₃ thin films grown under relatively high oxygen partial pressure. Compared to undoped BaTiO₃, Mn-doped BaTiO₃ reveals a low leakage current, increased dielectric loss, and a decreased dielectric constant. Ferromagnetism is seen on Mn-doped BaTiO₃ thin films prepared under low oxygen partial pressure and is attributed to the formation of bound magnetic polarons (BMPs). This BMP formation is enhanced by oxygen vacancies. The present work confirms a theoretical work from C. Ederer and N. Spaldin on ferroelectric perovskites [Nature Mat. 3, 849 (2004)] which shows that the existence of ferroelectricity is incompatible with the existence of a spontaneous magnetization in Mn-doped BaTiO₃ thin films.

Heavy metals are naturally occurring in the earth‘s crust but anthropogenic and industrial activities have led to drastic environmental pollutions in distinct areas. Plants are able to colonize such sites due to several mechanisms of heavy metal tolerance. Understanding of these pathways enables different fruitful approaches like phytoremediation and biofortification.
Therefore, this review addresses mechanisms of heavy metal tolerance and toxicity in plants possessing a sophisticated network for maintenance of metal homeostasis. Key elements of this are chelation and sequestration which result either in removal of toxic metal from sensitive sites or conduct essential metal to their specific cellular destination. This implies shared pathways which can result in toxic symptoms especially in an excess of metal. These overlaps go on with signal transduction pathways induced by heavy metals which include common elements of other signal cascades. Nevertheless, there are specific reactions some of them will be discussed with special focus on the cellular level.

Electromagnetic stirring during solidification has been proved to be a striking method for achieving a purposeful alteration of the microstructure of casting ingots, such as grain refinement or the promotion of a transition from a columnar to an equiaxed dendritic groth (CET). However, the imposition of a rotating (RMF) or a travelling magnetic field (TMF) also causes problems like the occurrence of typical segregation pattern or a deflection of the upper free surface. A permanent radial inward (RMF and downward TMF) or outward (upward TMF) flow along the solidification front is responsible for the transport of solute to the axis or the wall of the ingot resulting in typical freckle segregation pattern filled with alloy of eutectic composition. Recent studies have shown, that modulated AC magnetic fields are appropriate to overcome these problems.
We present an experimental study concerning measurements of the flow inside a liquid metal column exposed to a pulsed rotating magnetic field. A novel ultrasound Doppler system was used two measure two-dimensional velocity fields of the secondary flow in the radial-meridional plane. It employs an array of 25 transducer elements allowing a fast electronic traversing with concurrently high spatial and temporal resolution. The measurements revealed transient flow regimes showing distinct inertial oscillations and coherent vortex structures. The results demonstrate that the arising flow structure depends sensitively on the frequency of the RMF pulses.

A detailed analysis of the differences between the diffusion and the SP3 method is given. The analysis is based on one dimensional analytical solutions for the one and two group diffusion and SP3 method. Different cases from a benchmark core configuration are analyzed with the help of the one dimensional analytical solutions. It is shown that only a limited part of the gain achievable due to the use of the SP3 approximation will be seen in nodal calculations.

The article focuses on forming of holding groups and unified economic control in the frame of them. The globalization of markets leads to a need for bigger and stronger companies. Therefore, we can talk about dramatic increases in the frequency and volume of corporate groups. The most important reason for these combinations is to acquire advantages, which can have economic and noneconomic character. Another important is the limitation or elimination of competitive influences. [1] A holding group as a form of corporate group is a reality, which can go behind the borders of the European Union nowadays. Although, holding groups have been in advanced industrial countries for more than several decades, this type of structure has a relatively brief history in Slovakia. Also the theoretical background of this issue is, in Slovak literature, relatively poor.

Observations of very metal-poor stars have yielded evidence for the less abundant lithium isotope ⁶Li in several cases. These findings prompt the question whether there is a non-negligible primordial contribution to the observed ⁶Li abundances. Network calculations show that the ²H(α,γ)⁶Li reaction dominates ⁶Li production in the Big Bang. A recent Coulomb dissociation work on this reaction produced only an upper limit for the astrophysical S-factor. At the 400 kV underground accelerator LUNA in Gran Sasso/Italy, an experiment is underway to gain direct cross section data, but the background is formidable. Preliminary data of the first phase of the LUNA experiment will be shown, and an outlook will be given.

The talk summarizes the first phase of the direct d(alpha,gamma)⁶Li cross section measurement at energies of astrophysical interest by the LUNA collaboration at Laboratori Nazionali del Gran Sasso. The role of ⁶Li during primordial nucleosynthesis, the current problems of explaining its abundance in very old stars, the measurement approach, details about the beam induced background and ideas to control it are the main topics.

Superconducting nanolayers in Ge and Si can be fabricated by high fluence Ga ion implantation and subsequent rapid thermal annealing.

The underground uranium mine Königstein (Saxony, Germany), currently in the process of remediation, represents a underground acid mine drainage environment (AMD), i.e. low pH conditions and high concentrations of heavy metals including uranium, in which eye-catching biofilm formations were observed. During active uranium mining from 1967-1990 technical leaching with sulphuric acid was applied underground on-site resulting in a change of the underground mine environment and initiated the formation of AMD and also the growth of AMD-related copious biofilms.
Biofilms grow underground in the mine galleries in a depth of 250 m (50 m above sea level) either as stalactite-like slime communities or as acid streamers in the drainage channels. The eukaryotic diversity of these biofilms was analyzed by microscopic investigations and by molecular methods, i.e. 18S rDNA PCR, cloning and sequencing. The biofilm communities of the Königstein environment showed a low eukaryotic biodiversity and consisted of a variety of groups belonging to nine major taxa: ciliates, flagellates, amoebae, heterolobosea, fungi, apicomplexa, stramenopiles, rotifers and arthropoda and a large number of uncultured eukaryotes, denoted as acidotolerant eukaryotic cluster (AEC). In Königstein the flagellates Bodo saltans, the stramenopiles Diplophrys archeri and the phylum of rotifers, class Bdelloidea were detected for the first time in an AMD environment characterized by high concentrations of uranium. This study shows that not only bacteria and archaea may live in radioactive contaminated environments, but also species of eukaryotes, clearly indicating their potential influence on carbon cycling and metal immobilization within AMD affected environment.

This article evaluates a patent application of the company Medivir (SE/UK) describing the synthesis of dipeptide-derived alpha alpha-ketoamides containing a propylene glycine moiety in P1 as selective inhibitors of cathepsin S for the potential treatment of various systemic human diseases such as several autoimmune diseases, MS, rheumatoid arthritis, endometriasis and chronic pain. The claims of the patent are discussed in light of recent results in the field of cathepsin S research.

This paper presents different CFD-simulations on flows which are relevant for nuclear reactor safety using a new modelling approach for the interfacial drag at free surfaces. The developed drag coefficient model was implemented together with the Algebraic Interfacial Area Density (AIAD) model (Höhne, 2009) into the three-dimensional (3-D) computational fluid dynamics (CFD) code ANSYS-CFX. The applications considered include the prediction of counter-current flow limitations (CCFL) in a PWR hot leg, the development of hydraulic jump during the air-water co-current flow in a horizontal channel, and pressurized thermal shock (PTS) phenomena in a PWR cold leg and downcomer. For the modelling of these tasks, an Euler–Euler approach was used. This approach allows the use of different models depending on the local morphology. In the frame of an Euler-Euler simulation, the local morphology of the phases has to be considered in the drag model.

To demonstrate the feasibility of the present approach, the computed main parameters of each case were compared with experimental data. It is shown that the CFD calculations agree well with the experimental data. This indicates that the AIAD model combined with new drag force modeling is a promising way to simulate the phenomena in frame of the Euler-Euler approach. Moreover the further validation of the model by including mass transfer effects should be carried out.

Near-field optical microscopy has attracted remarkable attention, as it is the only technique that allows the investigation of local optical properties with a resolution far below the diffraction limit. Especially, the scattering-type near-field optical microscopy allows the nondestructive examination of surfaces without restrictions to the applicable wavelengths. However, its usability is limited by the availability of appropriate light sources. In the context of this work, this limit was overcome by the development of a scattering-type near-field microscope that uses a widely tunable free-electron laser as primary light source.
In the theoretical part, it is shown that an optical near-field contrast can be expected when materials with different dielectric functions are combined. It is derived that these differences yield different scattering cross-sections for the coupled system of the probe and the sample. Those cross-sections define the strength of the near-field signal that can be measured for different materials. Hence, an optical contrast can be expected, when different scattering cross-sections are probed. This principle also applies to vertically stacked or even buried materials, as shown in this thesis experimentally for two sample systems.
In the first example, the different dielectric functions were obtained by locally changing the carrier concentration in silicon by the implantation of boron. It is shown that the concentration of free charge-carriers can be deduced from the near-field contrast between implanted and pure silicon. For this purpose, two different experimental approaches were used, a non-interferometric one by using variable wavelengths and an interferometric one with a fixed wavelength. As those techniques yield complementary information, they can be used to quantitatively determine the effective carrier concentration. Both approaches yield consistent results for the carrier concentration, which excellently agrees with predictions from literature. While the structures of the first system were in the micrometer regime, the capability to probe buried nanostructures is demonstrated at a sample of indium arsenide quantum dots. Those dots are covered by a thick layer of gallium arsenide. For the first time ever, it is shown experimentally that transitions between electron states in single quantum dots can be investigated by near-field microscopy. By monitoring the near-field response of these quantum dots while scanning the wavelength of the incident light beam, it was possible to obtain characteristic near-field signatures of single dots. Near-field contrasts up to 30 % could be measured for resonant excitation of electrons in the conduction band of the indium arsenide dots.

Dosimetrie in Organismen oder in Zellkulturen erfordert Detektoren mit einer angepassten Größe, die zugleich chemisch und biologisch völlig inert sind. In Rahmen der an der Technischen Universität Dresden angefertigten Diplomarbeit wurden miniaturisierte Detektoren aus gesintertem Berylliumoxid mit positivem Ergebnis auf ihre Anwendbarkeit in der OSL-Dosimetrie und der Biotechnologie untersucht. Die Dosischarakteristik, die typische Messabweichung und die untere Erkennungsgrenze wurden bestimmt. Die Ergebnisse werden in Zusammenhang zur Theorie der Dosimetrie und der Wechselwirkungen der Strahlungsfelder gebracht. In Zusammenarbeit mit der Karlsruhe Beryllium Handling Facility wurde eine weitere Miniaturisierung der Detektoren erreicht, die aber mit einer erhöhten Erkennungsgrenze und einer zunehmend schwierigen Handhabung verbunden ist.

Numerical simulations of kinematic dynamo action have been carried out in a setup that resembles the configuration of the Von-Karman-Sodium (VKS) dynamo experiment. The results show that the high permeability domains introduced by soft iron impellers essentially determine the field generation process and are also responsible for the selection of the dominating azimuthal dynamo mode.

The material heterogeneity within the fluid give rise to three distinct effects that may influence the dynamo process. In addition to the local decrease of the magnetic diffusivity eta=(mu_0\mu_r\sigma)^(-1) so called paramagnetic pumping occurs which is proportional to the gradient of the permeability and describes the suction of magnetic field into domains with high permeability. Beside the modifications of the induction equation itself, jump conditions of the magnetic field (respectively the electric field) are enforced on the material interfaces between fluid and impellers. These jump conditions and the pumping term are responsible for the distinct behavior of high conducting(i.g. copper) and soft iron impellers.

At reasonable values for the magnetic Reynolds number (i.e around Rm=30) and rather moderate permeability (around values of 60 as suggested from recent measurements) the simulated magnetic field is dominated by an axisymmetric component. However, to obtain a growing axisymmetric eigenmode still an alpha-effect is necessary that parametrizes the induction effects of helical small scale motions. In contrast to preliminary mean field models for the VKS dynamo that have been based solely on an alpha-omega mechanism, the necessary magnitude for the alpha effect remains reasonable small if soft iron impellers are utilized.

The LUNA experiment is dedicated to measure low energy cross sections of reactions of astrophysical interest. Motivating these measurements with the question about the origin and the different abundances of isotopes in our universe, the reason to perform them in a deep underground laboratory is also mentioned. Using the example of the ²H(alpha, gamma)⁶Li reaction, the measurement approach and the apparatus are introduced.

Das Nuklid 44Ti (Halbwertszeit 59 Jahre) wird in Supernovae erzeugt. Die Gamma-Strahlung aus seinem Zerfall lässt sich in weltraumgestützten Gamma-Teleskopen nachweisen und kann als Werkzeug zum Test von Supernova-Modellen genutzt werden. Hierfür ist eine genaue Kenntnis der Kernreaktionsraten für die Erzeugung und Zerstörung von 44Ti erforderlich. Die 40Ca(alpha,gamma)44Ti-Reaktion dominiert die Erzeugung von 44Ti. Ihre Rate wird von einer Vielzahl von Resonanzen bestimmt. Um präzise Daten zu gewinnen, wurde die Stärke des Resonanztripletts bei 4.5MeV Gamma-Energie am Dresdner 3MV Tandetron sowohl mittels in-beam Gamma-Spektrometrie als auch durch eine Aktivierungsmessung im Felsenkeller-Niederniveaumesslabor gemessen. Eine Untersuchung der bestrahlten Proben mittels Beschleunigermassenspektrometrie ist geplant. – Gefördert von der EU (FP7-SPIRIT 227012) und der DFG (BE 4100/2-1).

Eine der größten Herausforderungen der Gegenwart ist der verantwortungsvolle Umgang mit den Ressourcen unseres Planeten. In diesem Zusammenhang ist die Entwicklung neuartiger Verfahren zur Gewinnung und vor allem Rückgewinnung von seltenen Metallen aus Industrieprodukten als wichtige Rohstoffe zahlreicher Zukunftstechnologien von besonderer Relevanz.

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In this study, extracellular concentrations of adenosine and ATP from the rat striatum were estimated by the microdialysis technique under physiological conditions and during focal cerebral ischemia induced by middle cerebral artery occlusion (MCAo). Under these conditions, adenosine and ATP concentrations were in the range of 130 nM and 30 nM, respectively. Blocking the ecto-ATPases with the novel inhibitor polyanion [TiW₁₁CoO₄₀]^8- (PV4: 100 μM), recently synthesized and characterized by Stephan and Müller, we could demonstrate that the extracellular concentration of ATP increased 12-fold and that adenosine concentration was not modified. This result indicates that, under physiological conditions, adenosine is released per se from cells. In the presence of PV4 and of the adenosine equilibrative transporter inhibitor dipyridamole (100 μM), adenosine extracellular concentration was increased 3-fold. This result excludes the possibility that adenosine is carried out of cells by a carrier mediated efflux. By using immunolabeling and electron microscopy, we showed the presence of the CNT2 on plasma membrane of synaptic terminals and on vesicle membranes. Results suggest that under in vivo physiological conditions adenosine is transported in vesicles and is released in an excitation-secretion manner.
In the first 4 hours after in vivo ischemia induced by MCAo, adenosine increased to ~690 nM and ATP to ~50 nM. In the presence of PV4 the extracellular concentration of ATP increased to ~440 nM and extracellular adenosine decreased to ~270 nM. An upregualtion of ecto-nucleotidases after ischemia might represent an important mechanism in hydrolysis of ATP and formation of extracellular adenosine in the first hours after ischemia.

Wetting properties of ceramic materials may be enhanced by treating them with high-intensity plasma pulses carrying a substantial fraction of metallic ions. Rod Plasma Injectors (RPI), developed originally for fusion studies, may generate such plasma pulses containing the working gas used for discharge initiation and the metal ions eroded from the discharge electrodes. We examined the plasma pulse technology and concluded that it is possible to extend the range of system parameters appropriate for wetting enhancement. We also studied the physical properties of plasma treated carbon and silicon carbide samples in an attempt to disclose the origin of wettability differences between them. We finally conclude that these differences are due to the morphology of the treated surfaces.

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The most stable atomic configuration of coherent nanoclusters in bcc-Fe formed by vacancies, Cu and Ni as well as the corresponding energetics are determined by on-lattice simulated annealing and subsequent off-lattice relaxation. Ternary v_l Cu_m Ni_n clusters show a core-shell structure with vacancies in the core coated by a shell of Cu atoms, followed by a shell of Ni atoms. In binary Cu_m Ni_n clusters the Cu core is covered by a shell of Ni atoms. On the contrary, binary v_l Ni_n clusters consist of a pure vacancy cluster surrounded by an agglomeration of Ni atoms. The latter is similar to a pure Ni cluster (Ni_n) and consists of Ni atoms at the second nearest neighbor distance. In all clusters investigated Ni atoms may be nearest neighbors of Cu atoms but never nearest neighbors of vacancies or other Ni atoms. The structure obtained for Cu_m Ni_n clusters is in agreement with previous theoretical results and with indications from measurements while for the other clusters reference data are not available. It is shown that the presence of Ni atoms promotes the nucleation of clusters containing vacancies and Cu. This is in agreement with experimental observations and recent theoretical results Compact and rather accurate analytical formulae for the total binding energy have been derived from the results of the atomistic simulations. These relations can be used in rate theory or object kinetic Monte Carlo simulations of nanocluster evolution.

A series of high quality Zn_1-xCo_xO films prepared by reactive magnetron sputtering displays altered magnetic properties ranging from paramagnetic (PM) to ferromagnetic (FM)- like at room temperature. With tuning the properties of the Zn_1-xCo_xO films from PM- to FMlike, the temperature dependent resistivity of the films changes from a Mott variable-range hopping to an Efros variable-range hopping process. This indicates the emergence of a Coulomb gap, which can be explained by the presence of nanoclusters. Moreover, the anhysteretic M (H)-curves above the blocking temperature for superparamagnetic (SPM) films can be described by a Langevin function, which confirms the existence of FM nanoclusters. The investigation on the magneto-transport of these films shows no spin-dependent transport behaviour associated with the observed FM-like/SPM properties.