Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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We have studied thermal fluctuations of the electrical conductivity in melt-textured YBa₂Cu₃O₇ (YBCO) samples under low magnetic fields. Measurements were performed either for current applied parallel or perpendicular to the c-axis and fluctuation conductivity was studied in the proximity of the superconducting transition. Two melt processed samples were prepared with different concentrations of Y₂Ba₁Cu₁O₅ (Y211) phase. For the sample with lower concentration, 3D-Gaussian and genuine critical 3D-XY-E fluctuation regimes were identified in the conductivity parallel to the ab plane and a regime beyond 3D-XY was also observed. The 3D-XY-E scaling was also identified in the fluctuation conductivity along the c-axis. In the sample with higher concentration of the Y211 phase, disorder effects are relevant. The results indicate that the superconducting state in YBCO has a three-dimensional character, and suggest the presence of a sub-dominant order-parameter component that has an appreciable projection along the c-axis.

In this paper we present a magnetic study of Co_1-xBi_xFe₂O₄ nanoparticles obtained by applying magnetic fields up to 14 T and for temperatures in the range of 5 to 340 K. Hysteresis loops yield a saturation magnetization (M_s), coercive field (H_c), and remanent magnetization (M_r) that vary significantly with temperature and bismuth content. The T-dependence of M_s obtained for H = 5 T presents a maximum at 150 K and a minimum at 25 K that are also dependent on the value of x. However, for H = 14 T, this anomalous behavior disappears and the magnetization smoothly approaches saturation down to 5 K. The magnetic cubic anisotropy constant for different Bi contents, determined by a “law of approach” to saturation, was found to be smaller than those values for pure cobalt ferrite nanoparticles and strongly dependent on temperature. A discussion on the implications of the anomalous behavior in the determination of the anisotropy constant in these sample materials is also presented.

Visualizations of the solidification process were obtained by means of X-ray radioscopy within a Hele-Shaw cell filled with Ga-25wt%In alloy. The complete temperature field was measured in additional experiments by an infrared camera (Trotec IC 080 LV). The evolution of segregation channels (so-called ‘chimneys’) and microstructure of mushy zone was investigated and convection effects were highlighted. In the case of thermo-solutal convection the probability of chimney formation depends sensitively on variations of the horizontal temperature distribution. The temperature difference between the central part and the periphery of the solidification cell may cause a modification of the natural circulation inside the melt.
The second part of this study concerns the case when the natural convection is superimposed by an electromagnetically driven flow perpendicular to the dendrites growth direction. The main effects of forced melt flow are a modification of the dendritic structure and flow-induced redistribution of the solute concentration.
A quantitative assessment of the melt convection directly at the solid-liquid interface was obtained by applying the optical flow approach, which provided information about the velocity field. This quantitative analysis and experimental data of flow field and temperature distribution gives a better understanding of the interplay be-tween melt flow and solidification process.

High magnetic fields are one of the most powerful tools available to scientists for the study, modification, and control of the state of matter. The application of magnetic fields, therefore, has become a commonly used instrument in condensed-matter physics. For the observation of many phenomena very high magnetic fields are es-sential. Consequently, the demand for the highest possible magnetic-field strengths is increasing. At the Dresden High Magnetic Field Laboratory (Hochfeld-Magnetlabor Dresden, HLD), that in 2007 has opened its doors for external users, pulsed magnetic fields up to about 72 T are readily available and a European record field of 87.2 T has been reached. The laboratory has set the ambitious goal of reaching 100 T on a 10 ms timescale. As a unique feature, a free-electron-laser facility next door allows high-brilliance radiation to be fed into the pulsed field cells of the HLD, thus making possible high-field magneto-optical experiments in the range 3-250 µm. Cryotech-niques and different sample probes for a broad range of experimental techniques custom designed for the pulsed magnets are available for users. In-house research of the HLD focuses on electronic properties of strongly correlated materials at high magnetic fields. Besides introducing some highlights of the HLD experimental infra-structure, some recent scientific research results will be presented. This includes the determination of the doping-dependent evolution of the Fermi surface of elec-tron-doped high-temperature superconductors by means of Shubnikov de Haas measurements. The observed reconstruction of the Fermi surface gives evidence for the existence of a superlattice potential, the origin of which is still under debate. Fur-ther, the recently found evidence for the Fulde Ferrell Larkin Ovchinnikov state in an organic superconductor will be presented. Emphasis will be laid on such examples where neutron research at high fields might be able to contribute in unravelling topical open questions.

AC magnetic fields unlock an enormous potential to realize a variety of flow structures in molten metals, which makes the electromagnetic stirring attractive for control-ling the melt flow during solidification. Many studies have shown that beneficial effects like a distinct grain refinement or the promotion of a transition from a columnar to an equiaxed dendritic growth (CET) can be obtained. However, electromagnetically-driven melt convection may also produce segregation freckles on the macro-scale especially in solute-rich alloys showing different equilibrium concentrations of solute in the mixed crystal and the surrounding melt. The achievement of superior casting structures needs a well-aimed control of melt convection during solidification, which in turn requires a detailed knowledge of the flow structures and a profound understanding of the complex interaction between melt flow, temperature and concentration field.
Previous investigations considered the use of time-modulated AC magnetic field to control the heat and mass transfer at the solidification front. It has been shown recently under laboratory conditions, that an accurate tuning of the magnetic field parameters can avoid segregation effects, however, a mismatch of the relevant modulation parameter may lead to worse results. Further investigations in form of numerical simulations accompanied by model experiments are necessary to achieve a quantitative understanding of the effect of fluid flow on the microstructure evolution.
This paper presents an experimental study which at first is focused on obtaining quantitative information about the isothermal flow field exposed to various magnetic field configurations. In a second step solidification experiments are carried out to verify the effect of a certain flow field on the solidification process. Furthermore, a new experimental set-up has been constructed to investigate electromagnetically-driven flows under realistic conditions of directional solidification, in particular the behaviour of the flow pattern in case of a propagating interface.

At the Dresden High Magnetic Field Laboratory (Hochfeld-Magnetlabor Dresden, HLD), that in 2007 has opened its doors for external users, pulsed magnetic fields up to 70 T on a timescale of 150 ms as well as 60 T with 1.5 s pulse duration are available and a European record field of 87.2 T has been reached [1,2]. The laboratory has set the ambitious goal of reaching 100 T on a 10 ms timescale. As a unique feature, a free-electron-laser facility next door allows high-brilliance radiation to be fed into the pulsed-field cells of the HLD, thus making possible high-field magneto-optical experiments in the range 3-250 µm. Cryotechniques and different sample probes for a broad range of experimental techniques custom designed for the pulsed magnets are readily available for users. These techniques include magnetization, ultrasound, electron spin resonance, cyclotron resonance, as well as nuclear magnetic resonance and specific-heat measurements. Recent improvements in signal-to-noise ratios allow to resolve relative resistance changes in electrical-transport measurements of about 10^-4 [3] and relative length changes in magnetostriction experiments of about 10^-7 [4]. In reply to the very strong user demand an extension of the HLD with additional pulse-field cells, capacitor bank, and improved infrastructure will be built starting from 2011. In-house research of the HLD focuses on electronic properties of strongly correlated electron systems at high magnetic fields. Besides introducing some highlights of the HLD experimental infrastructure, some recent scientific research results will be presented.

Oscillatory flow instabilities in a liquid metal cylinder with a free upper surface, exposed to a rotating magnetic field (RMF), are analysed by numerical simulations of the axisymmetric Navier-Stokes equations. The critical Taylor number designating the onset of the oscillatory flow regime decreases with increasing aspect ratio A= H/R while the Taylor-number interval, where the flow oscillations occur, becomes narrower. The instability is initiated near the free surface, where an oscillatory variation of the size and position of the upper vortex in the secondary flow can be observed accompanied by a horizontal oscillation of the azimuthal velocity maximum at the free surface. The predicted flow regimes have been observed in corresponding model experiments with GaInSn using the Ultrasound Doppler Velocimetry (UDV) for flow field measurements. The occurrence of the oscillatory flow regime depends sensitively on the cleanliness of the liquid metal surface.

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The Dresden High Magnetic Field Laboratory (HLD) is a pulsed-field user facility which offers to researches a variety of experimental techniques combined with nondestructive pulsed magnetic fields. Recently a new, 9.5 MJ dualcoil magnet has been commissioned. This magnet has achieved magnetic field of 91.4 T in a 16 mm bore and it is available for users now. In this paper, we report on some key upgrades in the magnet design which have led to breaking the 90 T limit at the HLD. Further possible design improvements are discussed. In addition, we share our operational experience obtained with the pulsed magnets.

The effect of multivalency manganese doping on the defect structure and enhanced electrical resistivity is studied for the high-temperature piezoelectric (1 - x)BiScO₃-xPbTiO₃ (BSPT) solid-solution system by means of multifrequency electron paramagnetic resonance spectroscopy combined with conductivity measurements. The results show that manganese is rather incorporated on a scandium than a titanium site as an isovalent substitute (Mn_Sc ^x) instead of acceptor-type centers, such as Mn(Ti)', Mn(Ti)'', or Mn(Sc)'. The enhanced electric resistivity is found being on the one hand due to the trapping of conduction electrons at the manganese functional center sites (Mn(Sc)(x) + e' -> Mn(Sc)'). On the other hand, through the formation of (Mn(Sc)' - V(O)(center dot center dot))(center dot) defect complexes the ionic conductivity is reduced. Concerning the overall mechanism of charge compensation in that material, both kinds of defects mutually compensate.

The bimetallic subsulfide Bi₈Ni₈S was synthesized by reduction of Bi₈Ni₈SI₂ with n-BuLi. Bi₈Ni₈S is metastable and decomposes exothermically at about 180°C. In a pseudomorphosis, the shiny black crystals of the precursor were preserved, while the iodide ions were extracted and the pre-formed ¹ _\infinity[Bi₈Ni₈S] fragments rearranged into a pseudo-hexagonal rod packing [space group Pbam, a = 1750.14(7) pm, b = 1007.7(2) pm, c = 419.6(3) pm]. The rods have an effective diameter of about 1 nm and consist of an outer octagonal tube of bismuth atoms and an inner octagonal tube of nickel atoms. This arrangement markedly resembles the columnar Ta₄Te₄Si structure type. The difference comes with the disulfide groups that reside on the cen-tral axis. Interatomic distances inside the rods are almost not affected by the reduction, and thus the electronic band structure is not much altered. Yet, the additional electrons raise the Fermi level into a local maximum of the density of states and occupy predominantly antibonding Ni–Ni and S–S states. The dominant Bi–Ni multicenter bonding is accompanied by localized two-center bonds between nickel atoms. The charges of the nickel atoms as well as ELI-D basin populations of Ni– Ni and Ni–Bi bonds change considerably, indicating that the tube is (un)charging quite flexibly and acts as an electron reservoir. In contrast to the iodide precursor, the weak Pauli paramagnetism of Bi₈Ni₈S is slightly enhanced and spin correlations are observed below 20 K.

Rare-earth intermetallic compounds R₂Co₁₇ and R₂Fe₁₇ form an interesting group of magnetic materials and their properties have been extensively studied in the last decades. In these compounds, as generally in R-T transition-metal compounds, the strongest interaction is the 3d-3d interaction which primarily determines T_C. The 4f-3d interaction, although much weaker than the 3d-3d interaction, is of special importance since it couples the strongly anisotropic R-sublattice moment to that one of much less anisotropic T-sublattice. R₂Co₁₇ and R₂Fe₁₇ compounds (crystallizing in the hexagonal Th₂Ni₁₇-type structure), where R is a heavy rare-earth element, are ferrimagnetic and high magnetic fields are needed to induce changes in the magnetic configuration.

The low-temperature excitation spectrum in copper pyrimidine dinitrate, a spin-1/2 antiferromagnetic chain with alternating g-tensor and Dzyaloshinskii-Moriya interactions that exhibits a eld-induced spin gap, is probed by means of ESR spectroscopy in magnetic elds up to 63 T. In particular, we report on a minimum of the gap in the vicinity of the saturation field Hsat = 48:5 T associated with a transition from the sine-Gordon region (with soliton-breather elementary excitations) to a spin-polarized state (with magnon excitations). This interpretation is fully conrmed by the quantitative agreement over the entire eld range of the experimental data with the DMRG calculations for spin-1/2 Heisenberg chain with a staggered transverse field.
This work was partly supported by the DFG and EuroMagNET II under the EU contract 228043.

We report the observation of highly anisotropic Dirac fermions in a Bi square net of SrMnBi₂, based on a first-principles calculation, angle-resolved photoemission spectroscopy, and quantum oscillations for high-quality single crystals. We found that the Dirac dispersion is generally induced in the (SrBi)⁺ layer containing a double-sized Bi square net. In contrast to the commonly observed isotropic Dirac cone, the Dirac cone in SrMnBi₂ is highly anisotropic with a large momentum-dependent disparity of Fermi velocities of ~8. These findings demonstrate that a Bi square net, a common building block of various layered pnictides, provides a new platform that hosts highly anisotropic Dirac fermions.

CeAu₂Ge₂ single crystals (with tetragonal ThCr₂Si₂ structure) have been grown in Au-Ge flux (AGF) as well as in Sn flux (SF). X-ray powder diffraction and EDX measurements indicate that in the latter case, Sn atoms from the flux are incorporated in the samples, leading to a decrease of the lattice constants by ≈0.3% compared to AGF samples. For both types of samples, a strong anisotropy of the magnetization M for the magnetic field B parallel and perpendicular to the c direction is observed with M||/M⊥ ≈ 6–7 in low fields just above 10 K. This anisotropy is preserved to high fields and temperatures and can be quantitatively explained by crystal electric field effects. Antiferromagnetic ordering sets in around 10 K as previously found for polycrystalline samples. From the magnetization data of our single crystals we obtain the phase diagrams for the AGF and SF samples. The magnetic properties depend strongly on the flux employed. While the AGF samples exhibit a complex behavior indicative of several magnetic transitions, the SF samples adopt a simpler antiferromagnetic structure with a single spin-flop transition. This effect of a more ordered state induced by disorder in form of Sn impurities is qualitatively explained within the anisotropic next-nearest neighbor Ising (ANNNI) model, which assumes ferromagnetic and antiferromagnetic interactions in agreement with the magnetic structure previously inferred from neutron-scattering experiments on polycrystalline CeAu₂Ge₂ by Loidl et al.

We reportmarkedly different transport properties ofABA- andABC-stacked trilayer graphenes. Our experiments in double-gated trilayer devices provide evidence that a perpendicular electric field opens an energy gap in the ABC trilayer, while it causes the increase of a band overlap in the ABA trilayer. In a perpendicular magnetic field, the ABA trilayer develops quantum Hall plateaus at filling factors of nu = 2,4,6, . . . with a step of Δnu = 2, whereas the inversion-symmetric ABC trilayer exhibits plateaus at nu = 6 and 10 with fourfold spin and valley degeneracy.

A thermodynamic method to extract the interchain coupling (IC) of spatially anisotropic 2D or 3D spin-1/2 systems from their empirical saturation field H_s(T = 0) is proposed. Using modern theoretical methods we study how H_s is affected by an antiferromagnetic (AFM) IC between frustrated chains described in the J₁-J₂-spin model with ferromagnetic 1st and AFM 2nd neighbor in-chain exchange. A complex 3D-phase diagram has been found. For Li₂CuO₂ and Ca₂Y₂Cu₅O₁₀, we show that H_s is solely determined by the IC and predict H_s \apprx 61 T for the latter. With H_s \approx 55 T from magnetization data one reads out a weak IC for Li₂CuO₂ close to that obtained from inelastic neutron scattering.

We report new experimental results on how superconductivity in gallium-doped germanium (Ge:Ga) is influenced by hole concentration and microstructure. Ion implantation and subsequent flash-lamp annealing at various temperatures have been utilized to prepare highly p-doped thin films consisting of nanocrystalline and epitaxially grown sublayers with Ga-peak concentrations of up to 8 at.%. Successive structural investigations were carried out by means of Rutherford-backscattering spectrometry in combination with ion channelling, secondaryion-mass spectrometry, and high-resolution cross-sectional transmission electron microscopy. Hole densities of 1.8·10²⁰ to 5.3·10²⁰ cm^-3 (0.4 to 1.2 at.%) were estimated via Hall-effect measurements revealing that only a fraction of the incorporated gallium has been activated electrically to generate free charge carriers. The coincidence of a sufficiently high hole and Ga concentration is required for the formation of a superconducting condensate. Our data reflect a critical hole concentration of around 0.4 at.%. Higher concentrations lead to an increase of T_c from 0.24 to 0.43 K as characterized by electrical-transport measurements. A short mean-free path indicates superconductivity in the dirty limit. In addition, small critical-current densities of max. 20 kA/m² point to a large impact of the microstructure

Improvement of CBERS-3/4 Imaging Camera Pin-pull Components by Plasma Immersion Ion Implantation

RAGE, the receptor for advanced glycation endproducts, is a pattern recognition receptor that belongs to the immunoglobulin superfamily. In homeostasis, RAGE is expressed ubiquitously high only in the lung, and moderate to low in a wide range of cells such as endothelial cells, mononuclear phagocytes, smooth muscle cells, mesangial cells, and certain neurons. It is found either as a membrane-bound or soluble protein that is markedly and quickly upregulated by stress in both epithelial and inflammatory cells. RAGE binds multiple ligands, including advanced glycation end products (AGEs), amyloid fibrils, amphoterin, and various members of the S100 family of EF-hand calcium-binding proteins such as S100A4, S100A8/A9, S100A11, S100A12, and S100B. Activation and upregulation through a positive feedback loop of RAGE and, subsequently, perpetual RAGE S100 engagement effects the activation of diverse signaling cascades that initiate and stimulate chronic stress and survival pathways, depending on the distinct interacting S100 protein, environment, and developmental stage. This can result in chronic inflammation and is supposed a setting in which predominantly epithelial malignancies can arise. Therefore, exploring the function of RAGE and its panoply of S100 ligands in the setting of inflammation is critically important in understanding the role of this receptor in carcinogenesis and metastasis, but also in other pathological conditions such as radiation therapy-related vascular dysfunction. In this review, we summarize novel findings on RAGE S100 protein interaction and subsequently triggered signaling cascades from published reports and own ongoing studies. In particular, a comprehensive evaluation of S100 protein metabolism in rodent models using fluorine-18 radiolabeled recombinant S100 proteins and small animal positron emission tomography, further underlining the role of RAGE S100 protein interaction in normal and disease states in vivo, is demonstrated. These recent experiments also support the potential of RAGE and its S100 ligands as attractive theragnostic markers and targets, respectively.

Human polo-like kinase 1 (Plk1) is involved in cell proliferation and overexpressed in a broad variety of different cancer types. Due to its crucial role in cancerogenesis Plk1 is a potential target for diagnostic and therapeutic applications. Peptidic ligands can specifically interact with the polo-box domain (PBD) of Plk1, a C-terminal located phosphoepitope binding motif. Recently, phosphopeptide MQSpTPL has been identified as ligand with high binding affinity. However, a radiolabeled version of this peptide showed only insufficient cellular uptake. The present study investigated peptide dimers consisting of PBD-targeting phosphopeptide MQSpTPL and a cell-penetrating peptide (CPP) moiety. The new constructs demonstrate superior uptake in different cancer cell-lines compared to the phosphopeptide alone. Furthermore, we could demonstrate binding of phosphopeptide-CPP dimers to PBD of Plk1 making the compounds interesting leads for the development of molecular probes for imaging Plk1 in cancer.

Thomson sources, either driven by small linacs or laser-wakefield accelerated (LWFA) electrons are compact in size and can provide ultrashort, hard X-ray pulses of high brilliance. However, the finite Rayleigh length at small interaction diameters makes it increasingly difficult in head-on (180°) Thomson scenarios to avoid higher laser intensities and thus the onset of the nonlinear regime. Effectively, such a geometry limits the peak brilliance of all future Thomson sources.

We present a novel concept, Traveling-wave Thomson scattering (TWTS), 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.
This allows realizing side-scattering in laser-electron beam interactions, without compromises with regard to luminosity or overlap. Furthermore, the smallest achievable scattered bandwidth is controlled by the width of a cylindrically focused laser beam and thus is independent of the ultrashort laser bandwidth. Due to the flexibility in side-scattering angle, photon energies become tunable over a large spectral range without requiring a change in electron energy.

TWTS is particularly interesting for “pink beam” experiments at hard X-rays in which high photon yields in single, ultrashort pulses are needed. Above 100keV photon energy, this approach potentially leads to peak brilliances that are beyond the capabilities of existing synchrotron radiation sources and 2-3 orders of magnitudes higher than in current head-on Thomson scattering designs.

Towards experimental realization, we show how such 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.

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Chemical processes are often controlled by monitoring pressure and temperature in the process chamber. However, usually these parameters are only available at selected positions, e.g. the inlet and outlet. And they are often not sufficient to operate the processes at the limit, i.e., to ensure high production rates and safety requirements, respectively. The knowledge of temperature fields is even more required if multiphase processes with a high tendency of segregation are considered due to occurrence of dead zones or by-passes.
A sensor concept for two-dimensional measurement of temperature fields for the monitoring of mixing processes was developed and tested. The sensor consists of a 32x32 matrix of small NTC temperature sensors. The measurement electronics is based on a multiplexing driving scheme. This set up enables the measurement of liquid temperatures at the surface of the sensor in each crossing point of the matrix. Applying the new electronic scheme, scanning frequencies up to 100 Hz allow fast temperature measurement to derive conclusions about heat transfer, flow regimes and mixing conditions.
The sensor performance was tested in two experimental setups. Heated phantoms of known geometric shape were applied to study the spatial resolution of the sensor. Furthermore, the 32x32 temperature sensor was installed at the wall of a flat mixing chamber. The flow chamber was fed by two liquid streams of different temperature connected at the inlet ports. Temporal evolution of the mixing temperature and steady-state mixing temperature patterns were observed.

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X-ray irradiation has an influence on survival and metastatic properties of tumor cells. In turn, metastasis and cellular motility can be modified by EphA2 and EphA3, two members of the Eph receptor/ephrin family of receptor tyrosine kinases. However, links between irradiation, Eph receptor expression and modification of metastasis-relevant cellular properties have not yet been shown. In this study, we irradiated one pre-metastatic and three metastatic human melanoma cells lines, including one self-generated metastatic cell line with X-rays. At day 1 and day 7 post irradiation we analyzed cellular viability, proliferation, motility, adhesion, migration, and clonal growth. Additionally, selected Eph receptors and ephrin ligands were analyzed regarding radiationdependent changes in mRNA and protein content.

In all cell lines a dose-dependent decrease in viability and cell growth for up to 1 week after irradiation was demonstrated. Motility was decreased 1 day after treatment but showed recurrence at 7 days after X-ray. In adhesion to fibronectin, we detected an irradiation-induced increase with similar decrease in migration and clonal growth. Thus, we assume that X-ray acts merely antimetastatic on the investigated melanoma cells. For EphA2 we detected an increase in mRNA in 2 of 3 metastatic cell lines, with simultaneously decreased protein level. EphA3 was found to be upregulated in mRNA and protein in 3 of 4 cell lines. Expression of ephrinA1 and A5 was generally low and seemed unaffected by irradiation.
In conclusion, our data indicate irradiation-induced downregulation of EphA2 and up-regulation of EphA3 in human melanoma cells, leading to anti-metastatic effects such as decreased motility and migration and increased adhesion to fibronectin. Ongoing studies will further clarify underlying mechanisms and the importance of EphA2 and EphA3 in melanoma metastasis.

Hintergrund:

Der epidermale Wachstumsfaktor-Rezeptor (EGFR) wird in einer Vielzahl maligner Tumore überexprimiert. Die Hemmung des Rezeptors durch den monoklonalen Antikörper Cetuximab (C225) in Kombination mit fraktionierter Bestrahlung führte bei dieser Tumorentität (prä)klinisch zu einer verbesserten lokalen Tumorkontrolle (1).
Ziel:
Radiochemische Entwicklung, Charakterisierung und Herstellung von [⁹⁰Y]Y-CHX-A´´-DTPACetuximab ([⁹⁰Y]C225). Präklinische Evaluierung von [⁹⁰Y]C225 in Kombination mit externer Bestrahlung. Kann [⁹⁰Y]C225 die lokale Tumorkontrolle in Mäusen nach externer Bestrahlung weiter verbessern?
Methoden:
CHX-A´´-DTPA wurde über Thioharnstoffkupplung in HEPES-Puffer bei pH 7,2 mit C225 konjugiert. Die Reinigung des Konjugates erfolgte durch Ultrafiltration. Das Chelator-C225-Verhältnis wurde durch MALDI-TOF-MS bestimmt. Die Affinität gegenüber EGFR wurde durchflusszytometrisch ermittelt. Die Radiomarkierung erfolgte in MES-Puffer durch 30-minütige Inkubation mit [⁹⁰Y/⁸⁶Y]YCl₃ bei pH 6,1 und 30°C. Die radiopharmakologische Charakterisierung erfolgte mittels Ex-vivo-Autoradiographie ([⁹⁰Y]C225) und Kleintier-Positronen-Emissions-Tomographie ([⁸⁶Y]C225) nach intravenöser Applikation in NMRI-Nacktmäusen (nu/nu) mit subkutan xenotransplantiertem humanen Plattenepithelkarzinom (FaDu) als Modell. Im Rahmen der Therapieexperimente wurden FaDu-NMRI(nu/nu)-Mäuse mit [⁹⁰Y]C225 (je 2,8 MBq/13 μg C225 i.v.) und/oder externer Bestrahlung (26, 32 und 38 Gy, 200 kV Röntgen, 0,5 mm Cu-Filter, 1,1 Gy/min, Einzeldosis) behandelt. Endpunkte der Therapieexperimente waren Wachstumsverzögerung und lokale Tumorkontrolle 180 Tage nach externer Bestrahlung.
Ergebnisse:
Es wurden 4 CHX-A´´-DTPA-Moleküle an C225 gekuppelt. Das Konjugat weist mit einem KD-Wert von 0,33 nM im Vergleich zu nativem C225 keinen Affinitätsverlust gegenüber EGFR auf. Bei der Radiomarkierung mit [⁹⁰Y]YCl₃ wurden reproduzierbar spezifische Aktivitäten bis zu 9 GBq/mg C225 und radiochemische Ausbeuten von >95% erzielt. Autoradiographie und PET zeigten 48 h p.i. eine hohe Anreicherung im Tumor. Diese Ergebnisse zeigen, dass das Konjugat für Therapieversuche geeignet ist. Die Kombinationstherapie wurde gut toleriert und es konnten im Vergleich zu den Kontrolltieren histologisch keine Organveränderungen festgestellt werden. Die Tumorkontrolle nach alleiniger externer Bestrahlung zeigt einen klaren Dosiseffekt. Nach 26 Gy externer Bestrahlung war eine signifikant höhere Tumorkontrolle nach Applikation von 13 μg [⁹⁰Y]C225 im Vergleich zu alleiniger externer Bestrahlung oder zu externer Bestrahlung und unmarkiertem Cetuximab zu verzeichnen.
Referenzen:
(1) Krause et al. Radiother Oncol. 2005 Feb;74(2):109-15
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High molecular (above 10 kDa) melanoidins isolated from coffee beans of varying roasting degree were found to be efficient inhibitors for the zinc-containing matrix metalloproteases MMP-1, MMP-2, and MMP-9 with IC50 values ranging between 0.2 and 1.1 mg/mL in vitro. The inhibitory potential increased with roasting degree. No or only slight inhibition of other zinc-containing peptidases closely related to MMPs, namely, Clostridium histolyticum collagenase and angiotensin converting enzyme, was found, indicating specific structural features of melanoidins to be responsible for the interaction with MMPs. A continuous increase on the apparent molecular weight of melanoidins as well as incorporation of phenolic substances into the melanoidin structure with progress of roasting was observed, concomitant with a significant increase in the carbon/nitrogen of the melanoidins. This suggests that the melanoidins are mainly formed by incorporation of carbohydrates and phenolic compounds onto a proteinaceous backbone. As MMP-1, MMP-2, and MMP-9 play a pivotal role in pathogenesis of colorectal cancer, studies on possible physiological effects of melanoidins are mandatory.

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The neutronics model of the nodal reactor dynamics code DYN3D developed for 3D analyses of steady states and transients in Light-Water Reactors has been extended by a simplified P3 (SP3) neutron transport option – to overcome the limitations of the diffusion approach at regions with significant anisotropy effects.
To provide a method being applicable to reactors with hexagonal fuel assemblies and to furthermore allow flexible mesh refinement, the nodal SP3 method has been developed on the basis of a flux expansion in trigonal-z geometry.
In this paper, the derivation of the trigonal SP3 method is presented in a condensed form and a verification of the methodology on quasi-pin level is performed by means of single-assembly test examples. The corresponding pin-wise few-group cross sections were obtained by the deterministic lattice code HELIOS. The power distributions were calculated using both the trigonal DYN3D diffusion and SP3 solver and compared to the HELIOS reference solutions. Close to regions with non-negligible flux anisotropies, e.g., caused by the presence of a strong absorbing material, the power distribution calculated by DYN3D-SP3 shows a significant improvement in comparison to the diffusion method.

The electron accelerator facility ELBE is the central experimental site of the Helmholtz-Zentrum Dresden-Rossendorf, Germany. Experiments with Bremsstrahlung started in 2001 and since that, through a series of expansions and modifications, ELBE has evolved to a 24/7 user facility running a total of seven secondary sources including two IR FELs. As its control system, ELBE uses WinCC on top of a networked PLC architecture. For data acquisition with high temporal resolution, PXI and PC based systems are in use, applying National Instruments hardware and LabVIEW application software. Machine protection systems are based on in-house built digital and analogue hardware. An overview of the system is given, along with an experience report on maintenance, reliability and efforts to keep track with ongoing IT, OS and security developments. Limits of application and new demands imposed by the forthcoming facility upgrade as a centre for high intensity beams (in conjunction with TW/PW femtosecond lasers) are discussed.

Fe-Cr alloys play an important role both in science and technology. The former stems from their interesting and unique properties which make them to be regarded as model alloys. The latter follows from the fact that they are a basic component of stainless steels (SS) that, thanks to their properties, have been used as construction materials in various branches of industry like power plants or fusion and fission reactors. In these applications they often undergo radiation damage that causes degradation of materials properties. A new generation of SS should provide better characteristics, and, in particular, better resistance to the radiation damage. To achieve this goal, one has to better understand effects caused by the radiation like short-range ordering (SRO).

QCD sum rules for chiral partners in the open-charm meson sector are presented at nonzero baryon net density or temperature. We focus on the differences between pseudo-scalar and scalar as well as vector and axial-vector D mesons and derive the corresponding Weinberg-type sum rules. This allows for the identification of such QCD condensates which drive the nondegeneracy of chiral partners in the lowest order of the strong coupling αs and which, therefore, may serve as “order parameters” for chiral restoration (or elements thereof).

Introduction: Our GeoEPT-method allows the 4D monitoring of transport processes in geological material on laboratory scale (Gründig et al., 2007; Kulenkampff et al., 2008; Richter et al., 2005). We apply COMSOL Multiphysics for reproducing our experiments and extracting parameter sets for our 4D problems. We learn that importing realistic structures from computer tomography (CT) as well as matching our experimental and simulated 4D data sets are complex tasks.

Use of COMSOL Multiphysics: A granite drill core (length = 198 mm, diameter = 50 mm) with a prominent fracture is scanned by means of a medical CT with a spatial resolution of about 1 mm³ (3∙106 voxels, Figure 1, bottom). The data segmentation is conducted with Avizo® Fire under consideration of beam hardening effects. A voxel based fracture geometry is transferred to COMSOL Multiphysics in stl-file format (11 MB, Figure 1, top). After scaling the geometry object and converting it to solid, we allocate the material water to its volume of about 20 ml. First Laminar flow is assigned to the domain and solved stationary. By attributing No slip walls, initial (u = 0, p0 = 0), inflow (u0 = 2∙10-5 m/s) and outflow conditions (p = 0) the experimental conditions are well represented by the model. A user-controlled mesh (free tetrahedral, normal element size) calibrated for Fluid dynamics consists of ~370,000 elements (Figure 2). The stationary flow and pressure field is solved by the GMRES solver in less than four minutes. We add Transport of a diluted species with a Gaussian concentration-input function (standard deviation ~14 min at t = 30 min) for simulating our time dependent experiment (Figure 3). This computing time amounts to additional 23 minutes.

Results: We obtain 4D simulation results covering 10 hours with 10 min resolution. The 4D data sets (Figure 3) as well as breakthrough curves (BTC) are matched with our 4D experimental results obtained in GeoPET experiments (Figure 4). Although effects caused by filter plates at the flange facings were not yet considered in the COMSOL, model the BTC matches fairly well.

Conclusion: The development of algorithms for flow pattern identification, parameterisation of pattern evolution and pattern tracking might allow for quantitative similarity studies of 4D flow and transport processes. In parallel, refining the geometry on the basis of higher resolution CT measurements will help approaching better matches between simulated and measured 4D data sets of flow and transport in heterogeneous geological media.

Outlook: Intermediate and long-term aim of such matching attempts of 4D simulation results with corresponding measurement results is (A) to quantify the effect a simplified geometry from high resolution CT measurements has on the quality of reproducing our real GeoPET flow and transport monitoring results, (B) to quantify the effect a simplified geometry has on the quality of reactive transport in geological material, when additional interactions have to be considered and (C) to evaluate appropriate algorithms for reducing high resolution, high dimension, complex physics models to continuum scale models capable of capturing the relevant processes ruling on the field scale.

References:

Gründig, M., Richter, M., Seese, A. and Sabri, O., 2007. Tomographic radiotracer studies of the spatial distribution of heterogeneous geochemical transport processes. Appl. Geochem., 22: 2334-2343.
Kulenkampff, J., Gründig, M., Richter, M. and Enzmann, F., 2008. Evaluation of positron emission tomography for visualisation of migration processes in geomaterials. Physics and Chemistry of the Earth, 33: 937-942.
Richter, M., Gründig, M., Zieger, K., Seese, A. and Sabri, O., 2005. Positron Emission Tomography for modelling of geochmical transport processes in clay. Radiochim. Acta, 93: 643-651.

Neutron radiation is a highly penetrating probe, routinely used for non-destructive testing of engineering components and for analysis of the structure and dynamics of novel advanced materials. The same analytical techniques can be employed for characterizing objects of art, museum pieces and archaeological findings. In particular, neutron radiography, neutron diffraction and neutron activation analysis provide valuable and complementary information to address questions of provenance, authenticity, fabrication techniques and conservation. This paper surveys some basic concepts and recent applications of neutrons in cultural heritage research at the ISIS neutron spallation source.

Depleted uranium used a ammunition corrodes in the environment forming mineral phases and then dissolved uranium species like uranium carbonates (Schimmack et al. 2007) and hydroxides. These hydroxide species were contacted with plant cells (canula). After 24 h contact time the cells were fractionated and the uranium speciation in the fraction was determined by TRLFS (time resolved laser-induced fluorescence spectroscopy) at room temperature as well at 120K. It could be shown that the uranium speciation in the fractions is different to that in the nutrient solution. Comparison of the emission bands with literature data allows assignment of the uranium binding forms.

Application of laser-induced and time-resolved methods allow the direct determination of uranium speciation at extremely low concentrations. This behaviour can be directly observed due to the extraordinary luminescence properties of uranium-(VI).
Some examples for luminescence properties of uranium species relevant to the environment are shown. As for example carbonate species do not show any luminescence behaviour at room temperature cryogenic techniques were applied to decrease the quench processes of the excited species and to determine the uranium speciation. Change of this speciation can be observed due to a change in luminescence properties (emission wavelength and luminescence lifetime). Due to different dependence of the lifetime on temperature for the several uranium species additional luminescence measurements of the prepared solutions at room temperature and in the frozen state give more detailed information about the uranium speciation.
Contact of dissolved uranium with living cells at ambient conditions changes dramatically the uranium speciation. Besides of several organic phosphate binding forms although other uranium species were found as uranium bond to phenolic and thiol groups. Some of them do not emit any luminescence at room temperature. Nevertheless the low temperature measurements allow the assignment of species not fluorescing at room temperature, due to strong dynamic quench effects of H2O molecules and COO- groups. By use of the combined temperature dependent methods for several plant cell compartments we can now assign the uranium speciation in more detail.
Besides this plant cells provide a reducing environment in order to prevent oxidative stress. Due to the redox properties of uranium, it might be possible that uranium-(VI) in a cell matrix is reduced. By laser-induced photo-acoustic spectroscopy we were able to detect also uranium-(IV).

First results on luminescence of upconverting Nanoparticles are given

Heavy metals are explained from a radiochemist’s view. The Interaction of uranium with widespread flavanoids like quercetin have been discussed. Additionally glutathione can be seen as a multifunctional ligand. Information about the binding of uranium is provided. Last not least some onformation about binding forms of uranium in cell compartments of plant cells were given

Presently, argillaceous rock formations are under investigation as potential host rocks for nuclear waste repositories. In addition to the diffusion the sorption of radionuclides on mineral phases is an important physicochemical process in a nuclear waste repository in the case of a water inleakage. Concerning the required long-term safety and risk assessment of the storage of high-level radioactive waste the understanding of these processes is essential.
Opalinus Clay (OPA) is a complex composed argillaceous rock. This natural occurring clay rock is discussed as host rock formation for nuclear waste repositories.
In a repository based on argillaceous rock an initial temperature of around 100°C is expected due to the radioactive decay and the release of geothermal energy. But although elevated temperatures are able to influence the sorption behaviour of radionuclides on mineral phases the temperature effect is still investigated insufficiently.
The investigations concentrated on the sorption of Eu(III) on OPA under realistic OPA pore water conditions (pH 7.6, I = 0.4 mol•L-1) up to 50°C. In addition to the temperature dependent investigations the influence of organic matter (tartrate, citrate) on the Eu(III) sorption on OPA was studied up to 50°C.
The Eu(III) sorption is characterized by a very strong sorption to the clay surface. A significant temperature dependency of the Eu(III) sorption was observed. In the presence of tartrate or citrate the Eu(III) sorption decreases with rising ligand concentration. A surface species, most likely a EuCO3 surface species, was detected using TRLFS. The formation of a surface species containing tartrate or citrate was not observed with TRLFS.

Im Vortrag werden die experimentellen Schwierigkeiten bei der spektroskopischen Charakterisierung von U(VI) in salinaren Lösungen aufgezeigt. Desweiteren wird der Einflusses von der Ionenstärke auf die U(VI)-Komplexierung durch Citronensäure vorgestellt.

for Nuclear Reactors called NURESIM is being developed. This development follows a roadmap which is consistent with the SRA (Strategic Research Agenda) of the European SNETP (Sustainable Nuclear Energy Technology Platform). After delivery of two successive versions during the course of the NURESIM project, the numerical simulation platform is presently being developed in the frame of the NURISP European Collaborative Project (FP7), which includes 22 organizations from 14 European countries.
NURESIM intends to be a reference platform providing high quality software tools, physical models, generic functions and assessment results.
The NURESIM platform provides an accurate representation of the physical phenomena by promoting and incorporating the latest advances in core physics, two-phase thermal-hydraulics and fuel modelling. It includes multi-scale and multi-physics features, especially for coupling core physics and thermalhydraulics models for reactor safety. Easy coupling of the different codes and solvers is provided through the use of a common data structure and generic functions (e.g., for interpolation between nonconforming meshes).
More generally, the platform includes generic pre-processing, post-processing and supervision functions through the open-source SALOME software, in order to make the codes more user-friendly.
The platform also provides the informatics environment for testing and comparing different codes. For this purpose, it is essential to permit connection of the codes in a standardized way. The standards are being progressively built, concurrently with the process of developing the platform.
The NURESIM platform and the individual models, solvers and codes are being validated through challenging applications corresponding to nuclear reactor situations, and including reference calculations, experiments and plant data. Quantitative deterministic and statistical sensitivity and uncertainty analyses tools are also developed and provided through the platform.
A Users’ Group of European and non-European countries, including vendors, utilities, TSOs, and additional research organizations (beyond the current partners) has also been established in order to enhance the role of the simulation platform in meeting the needs of the nuclear industry, as applied to current and future nuclear reactors.
This presentation summarizes the achievements and ongoing developments of the simulation platform in core physics, thermal-hydraulics, multi-physics, uncertainties and code integration.

not available, please ask the authors

We present strangeness data taken with the High Acceptance Di-Electron Spectrometer (HADES) at the SchwerIonenSynchrotron SIS18 at the GSI Helmholtzzentrum Darmstadt. HADES, primarily designed to measure dielectrons, offers excellent hadron identification capabilities, too. Yields and phase-space distributions have been determined for the collision system Ar+KCl at 1.76A GeV and for strange particle species, with a substantial number of them being produced well below the production threshold in elementary nucleon-nucleon collisions. Here, sub-threshold production of φ mesons appeared to contribute substantially to the K⁻ yield. Confronting the K⁰ _s spectra, measured over a wide range in momentum and rapidity, to predictions of the IQMD transport model points to a repulsive in-medium K⁰ potential of about 40 MeV. Furthermore, we present our results on Λ-p intensity interferometry in Ar+KCl and compare them to other data.

ZnO:Al films with a thickness of about 880nm were deposited by magnetron sputtering. The glass substrate was not heated neither before during nor after the deposition. Subsequently the deposited layers were treated by flash lamp annealing (FLA) at 1.3 ms. Using this method, the resistivity of the ZnO:Al films was decreased by a factor of two, down to 1.0 x 10-3 Ωcm. These results are in good agreement with results reported from rapid thermal processing or furnace annealing treatments. Despite the very short annealing time of only 1.3 ms not only the resistivity but also the transmittance in the UV and the blue range were considerably improved.

Using the methods of cold neutron capture and photon scattering the electric dipole strength function of the nuclei 78Se and 196Pt are investigated. Considering that the deexcitation process could be described by the same strength functions one could describe both experiments in a statistical model code. The report shows the data analysis as well as a new very fast statistical code, which was used to get the complete strength information up to the neutron seperation energy.

An experimental study on drag-reduction phenomenon in dispersed oil-water flow has been performed in a 26-mm-i.d. 12 m long horizontal glass pipe. The flow was characterized using a novel wire-mesh sensor based on capacitance measurements and high-speed video recording. New two-phase pressure gradient, volume fraction and phase distribution data have been used in the analysis. Drag reduction and slip ratio were detected at oil volume fractions between 10% and 45% and high mixture Reynolds numbers, and with water as the dominant phase. Phase-fraction distribution diagrams and cross-sectional imaging of the flow suggested the presence of a higher amount of water near to the pipe wall. Based on that, a phenomenology for explaining drag reduction in dispersed flow in a flow situation where slip ratio is significant is proposed. A simple phenomenological model is developed and the agreement between model predictions and data, including data from the literature, is encouraging.

The provenance of at least five out of seven variously colored glass beakers in the collection of the Naturalienkabinett Waldenburg (Saxony) indicates their relation to the famous glass chemist Johann Kunckel. The technological characteristics of four corner-cut glasses, which show a ruby-rose, transparent blue-green, transparent dark purple, respectively an opaque striated brownish-red color, are described. Crizzling phenomena, cracking due to frozen strains and inhomogeneous coloring were closer examined with a light microscope and under a short-wave UV-lamp.
Combined simultaneous PIXE and PIGE analysis conducted at the Helmholtz-Zentrum Dresden-Rossendorf allowed the detection of all glass constituents from lead up to boron in elemental concentrations above c. 0.01 w%. Different types of potassium-rich crystal glasses with varying amounts of calcium, arsenic and lead were found. There is evidence for the use of highly refined raw materials and the addition of various ionic and colloidal glass colorants.
The Waldenburg beakers seem to be early examples of Kunckel’s experimental efforts to establish elevated standards for the production of luxury glass in northern Europe, as additionally supported by accounts in his publications from the years between 1678 and 1716.

Radiation therapy is an important treatment modality in cancer therapy. New radiation species, like protons and light ions have the potential to increase tumor conformality of irradiation. Because of the way these particles deposit energy on their path through tissue they allow for an increased dose deposition in the tumor volume and reduce the damage of the surrounding normal tissue.
Such high precision radiotherapy treatment requires efficient quality assurance techniques. Small changes in the irradiated volume will lead to a mismatch of the deposited dose maximum and the tumor. This causes missing dose in the tumor volume and potential damage to healthy tissue. Therefore, a dose monitoring system is highly desirable. Between 1997 and 2008, the in-beam Positron Emission Tomography (PET) method was used at the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany, for monitoring the dose delivered by 12C beams (cf. figure 1). The spatial distribution of positron emitters generated via nuclear interactions between projectile ions and atomic nuclei of the tissue is measured during and shortly after the irradiation. Due to different physical processes for dose deposition and activity production a simulation of the expected activity is required. By means of a comparison between measured and simulated activity distribution conclusions on the accuracy of the dose localization can be drawn. Since ion therapy is normally applied during a fractionated treatment over more than 15 days, detected deviations can be corrected for in the following fractions. Different modalities of PET, i.e. measuring during the irradiation versus taking data after the treatment have been compared. Since the positive clinical impact of the method has been shown, an in-room PET/CT will be installed for the same purpose at the Dresden Proton Therapy facility. Recent investigation and limits of the PET method used for in vivo dose monitoring at ion beams will be presented and discussed.

Due to inherent physical restrictions of this method, a direct quantification of the delivered dose is not feasible. Therefore, another approach based on dose monitoring by detection of prompt gamma rays is currently under investigation. In contrast to PET this method relies on the detection of prompt gamma rays emitted almost instantaneously during the therapeutic irradiation. These gammas are expected to possess a wide energy range between 0 and 10 MeV. To measure these photons a Compton camera design was evaluated with respect to the special requirements and conditions that arise from this application (cf. figure 1). Different concepts were compared by means of simulation. The complete chain from simulation based on the treatment plan to the iterative reconstruction of the data was developed and is now under optimization. First measurements have been successfully performed with radioactive sources and ion beams. Results of the first test of this prototype at a proton beam will be shown.

This paper describes a new methodology for volumetric assay of defects in large engineering materials nondestructively. It utilizes high energy photons produced by nuclear reaction to create positrons in situ whose fate is followed using conventional positron spectroscopic techniques. The photon induced positron annihilation (PIPA) spectroscopy system has been set-up using a Folded Tandem Ion Accelerator (FOTIA). Possibility of using prompt gamma-rays produced in nuclear reactions 27Al (1H,γ)28Si and 19F(1H,γ)16O have been examined. The reaction 19F(1H,γ)16O is seen to provide higher photon flux and measurements have been carried out in large samples of metals and polymers. We could establish good sensitivity of the technique as well as reproducibility in a number of samples. This technique has been used to carry out defect studies in cold worked Zircaloy-2 plates. The measured S-parameter, indicative of defect concentration, was seen to correlate well with the measured residual stress using X-ray technique. The results were validated by gamma-induced positron annihilation lifetime measurements at ELBE LINAC based GiPS facility.

The R2PdSi3 intermetallic compounds have been reported to crystallize in a hexagonal AlB2-derived structure, with the rare earth atoms on the Al sites and Pd and Si atoms randomly distributed on the B sites. However, the intricate magnetic properties observed in the series of compounds have always suggested complications to the assumed structure. To clarify the situation, x-ray and neutron diffraction measurements were performed on the heavy rare earth compounds with R=Gd, Tb, Dy, Ho, Er, Tm, which revealed the existence of a crystallographic superstructure. The superstructure features a doubled unit cell in the hexagonal basal plane and an octuplication along the perpendicular c direction with respect to the primitive cell. No structural transition was observed between 300 and 1.5 K. Extended x-ray absorption fine structure (EXAFS) analysis as well as density functional theory (DFT) calculations were utilized to investigate the local environments of the respective atoms. In this paper the various experimental results will be presented and it will be shown that the superstructure is mainly due to the Pd-Si order on the B sites. A structure model will be proposed to fully describe the superstructure of Pd-Si order in R2PdSi3. The connection between the crystallographic superstructure and the magnetic properties will be discussed in the framework of the presented model.

Transition metal oxides exhibit a wealth of physical phenomena, among them ferroic properties such as ferroelasticity, ferroelectricity and ferromagnetism, or their combination in multiferroics. In addition, transition metal oxides are sensitive to the chemical environment via the external partial pressure of oxygen; changes induce stoichiometry deviations, which cause conductivity changes and modify the ferroic characteristics. Ternary and quaternary compounds from the perovskite family will be discussed as examples, which correlate local changes due to point and planar defects with changes of the elastic, polarization and magnetic properties. The microscopic interactions are determined by density functional calculations, which yield the basis for more large-scale simulations with effective Hamiltonian approaches. Under oxygen-poor conditions, oxygen vacancies in SrTiO3 accumulate in an external electric field and reduce the hardness. In an Sr/O-rich environment the phases SrO(SrTiO3)n are formed, which yield a distinct change of the X-Ray reflectivity due to the regular arrangement of extrinsic SrO(001) stacking faults. YMn2O5 has a series of complex antiferromagnetic phases in coexistence with ferroelectricity. In YFeMnO5, only one commensurable ferrimagnetic phase was found and ferroelectricity is absent. Based on spin-polarized DFT calculations a Heisenberg model yields the coupling constants of the Fe-substituted and the mangenese-only compounds and relates them to
crystal-field interactions. BiFeO3 is a rhombohedral multiferroic with several domain wall configurations. Among them, the 109° and 180º degrees walls have a significant change in the component of their polarization perpendicular to the wall; the corresponding step in the electrostatic potential is consistent with a recent report of electrical conductivity at the domain walls. Changes in the Fe-O-Fe bond angles at the walls change the canting of the Fe magnetic moments which can enhance the local magnetization.

The basic concept of two-group average bubble number density equations along with three-fluid model has been demonstrated for vertical gas-liquid flow. Specifically, the current study focused on:

(i) classification of bubble interaction between spherical bubbles (Group-1) and cap bubbles (Group-2),
(ii) preliminary consideration of source and sink terms in the averaged bubble number density equations via the model of Hibiki and Ishii [1] and (iii) assessment by means of experimental data sets at bubbly-to-cap flow transition. Reasonable agreement was achieved between measured and predicted distributions of void fraction, interfacial area concentration (IAC) and volume equivalent bubble diameter.

This work describes the mechanisms of uranium biomineralization at acidic conditions by Bacillus sphaericus JG-7B and Sphingomonas sp. S15-S1 both recovered from extreme environments. The U bacterial interaction experiments were performed at low pH values (2.0-4.5) and using 0.1 M NaClO₄ as electrolyte background where the uranium aqueous speciation is dominated by the free uranyl ion. As demonstrated by X-ray absorption (XAS) studies, the cells of the studied strains precipitated uranium at pH 3.0 and 4.5 as a uranium phosphate mineral phase belonging to the meta-autunite group. The observed U(VI) biomineralization was associated with the activity of indigenous acid phosphatase detected at these pH values without the supply of an organic phosphate substrate. At pH 2.0, however, no uranium biomineralization occurred, and U(VI) formed complexes with organically bound phosphates of the cells. Transmission electron microscopic (TEM) analyses showed strain-specific localization of the uranium precipitates. In the case of B. sphaericus JG-7B U(VI) was bound to the cell wall while in the case of Sphingomonas sp. S15-S1, U(VI) precipitates were found not only on the cell surface but also intracellularly. This study contributes to the expansion of the number of bacterial strains that have been demonstrated to precipitate uranium phosphates at acidic conditions via the activity of acid phosphatase.

Bei einem Kühlmittelverluststörfall (Loss of coolant Accident LOCA) eines Druckwasserreaktors (DWR) können sich in der Anfangsphase an den Sumpfansaugsieben des Notkühlsystems Mineralwolleablagerungen aus dem Isolationsmaterial der Anlagenkomponenten bilden und dadurch die Notkühlung beeinträchtigen. Im weiteren Verlauf des Störfalles verursacht das borsäurehaltige Primärkühlmittel eine Korrosion an Einbauten im Containment, die überwiegend aus feuerverzinktem Stahl bestehen. Feste Korrosionsprodukte bewirken in diesem Falle durch Anlagerung an die Mineralwolleablagerungen einen Anstieg des Differenzdrucks über den Sumpfansaugsieben, der bis zur Blockade und dem Ausfall der Notkühlung führen kann.
Zur Untersuchung der chemischen Aspekte dieses Vorgangs wurde im HZDR eine Laborversuchsanlage (KorrVA) errichtet, in welcher die Korrosion verzinkter Materialproben unterschiedlicher Größe und Geometrie bei verschiedenen Anströmbedingungen des borsäurehaltigen Kühlmittels und bei Temperaturen bis 70°C untersucht werden kann. Volumen, Durchfluss, Größe von Proben und Sumpfansaugsieb sowie dessen Belegung wurden skaliert an den Verhältnissen eines typischen DWR-Sumpfes nach einem LOCA.
Dabei sind verschiedene Einflüsse auf die Korrosion zu beobachten, die von der Zusammensetzung des Mediums (Borsäurekonzentration, pH-Anhebung durch LiOH-Zusatz), Temperatur des Mediums, Größe und Geometrie der Probe sowie auch von der Anströmung durch das Medium abhängen und einen unterschiedlichen Differenzdruckverlauf bewirken.
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 von Lösungen und Ablagerungen auf den Faserbetten und den Untersuchungen der Metallproben nach Ende der Versuche beruhen, stehen in Übereinstimmung mit dem Differenzdruckanstieg als technisch wichtigem Parameter, der im Wesentlichen durch Rost verursacht wird. Die anfangs starke Korrosion unter Bildung von Zinkionen bedingt eine Zunahme des pH-Werts, die aber zu einer wesentlichen Verringerung der Korrosionsrate führt. Bei ausreichender Zinkmenge kommt die Korrosion nahezu zum Erliegen. Im weiteren Verlauf bilden sich aber auch an der Oberfläche des Zinks weiße Korrosionsprodukte.
Entscheidend für den Ablauf der Korrosion sind neben dem Angebot an Zinkoberfläche besonders die Strömungsverhältnisse und die Zusammensetzung des Primärkühlmittels nach lokaler Freilegung des Basismaterials. Verursacht wird eine Verblockung des Faserbetts nicht nur durch eine Bildung von Rost sondern erst durch dessen Transport und Ablagerung am Fasermaterial.

Intersubband transitions and quantum cascade lssers

Corrosion products of hot-dip galvanized steel containment internals may cause serious problems during a loss-of-coolant accident (LOCA) at a nuclear power plant by clogging insulation debris laden sump strainers of the emergency core cooling system. The chemical and physical conditions influence the formation and deposition of the sparingly soluble corrosion products. In nearly neutral boric acid media, the corrosion starts by a dissolution process of zinc. A fast local coolant flow accelerates the dissolution of Zn (flow accelerated corrosion) and leads to rust formation on steel rapidly. Additionally, the local flow conditions prevent the known cathodic protection mechanism of zinc on steel. Furthermore, a sufficient flow impact is presumed to transport the rust particles into the insulation fibres mats on the strainers where they may blocked in the worst case. As a result of fibre bed analyses, corrosion products of iron and not of zinc are regarded as the main source of clogging. The mechanism of zinc dissolution in the absence of other anions can be explained by formation of borate ions originate from boric acid as a coolant ingredient in pressurized water reactors (PWR).

Investigations of bacterial composition of biofilm samples from uranium contaminated underground mine Königstein by molecular methods and FISH.

Talk on prospects of laser proton acceleration for applications in oncology.

The idea is use S-layer proteins as binding matrix to couple aptamers and fluorescence dyes in a sequential way. This sensory layer will be able to detect very small amounts of analyte in aqueous environment. The fluorophores which are able to perform a FRET serve as optical system whereas aptameres work as specific receptor for one analyte.

Biotechnologische Methoden zur Metallgewinnung; Vortrag zum 1. Workshop des Innovationsforums Geobiotechnologie

The aim of the study was to estimate normal ranges and test-retest measures for various parameters characterising dopamine metabolism from a prolonged F-18-dopa positron emission tomography (PET) measurement using a reference tissue model and compare their value for the detection of early Parkinson's disease (PD).
Healthy volunteers (n = 9) and patients (n = 36) in an early stage of PD underwent an F-18-dopa PET measurement lasting 4 h. The influx rate constant k(occ) and the effective distribution volume ratio (EDVR, its inverse is an indicator for dopamine turnover) were estimated by a graphical approach using dynamic data in the striatum and, as a reference region, the occipital cortex. Furthermore, ratios of activity concentrations between striatum and occipital brain taken for three time intervals completed the data analysis. All parameters were determined both in eight small volumes of interest placed in the striatum as well as averaged for caudate nucleus and putamen. For the control group, reproducibility was checked in a second study 3 months later and ranges for normal values were derived from mean +/- 2 standard deviations. Receiver-operating characteristic (ROC) analyses were performed to assess the value of the parameters for diagnostic purposes.
Patients with early-stage PD and healthy volunteers could be separated by the values of the putamen, not the caudate nucleus. The normal ranges of the putamen were 0.0151-0.0216/min for the influx rate constant k(occ) and 2.02-3.00 for EDVR. For the various time intervals used the striato-occipital ratios yielded 2.24-3.06, 2.43-3.42 and 2.35-3.21, respectively. Patients were characterised by significantly lower values (p < 0.001) and significant differences between ipsi- and contralateral sides (p < 0.001) with regard to their clinical symptoms and a rostrocaudal gradient. EDVR as well as k(occ) for the putamen were able to effectively differentiate between groups (sensitivity > 97%, specificity 100%). In contrast, striato-occipital ratios showed a sensitivity of about only 85%.
For clinical applications, our data do not demonstrate any superiority of the EDVR determination compared to influx rate constant, while requiring long and tedious acquisition protocols. The normal range estimates do not represent absolute quantitative measures for dopamine metabolism but are specific for the chosen acquisition and processing procedures.

Reaction of equimolar amounts of AgCIO and bis4-(2-pyridylmethyleneamino)phenyl] methane (L1) or bis[4-(2-pyridylmethyleneamino)phenyl] ether (L2) in a 1:1 solvent mixture of CH3CN and CH2CL2 leads to the formation of two infinite coordination polymers of the composition {[Ag(L1)]ClO4•CH3CN}n (1) and {[Ag(L2)]ClO4•CH2Cl2}n (2). Whereas 1 represents a homochiral single-stranded helicate the related complex 2 shows a typical zigzag chain arrangement. Both structures are characterized by a distorted tetrahedral coordination environment of the Ag(I) centres each based on a N4 coordination pattern of two ligand molecules. The resulting strands are connected by a hydrogen bonding network including ClO4¯ anions and solvent molecules forming 2-D layers. Additional π-π and CH- π interactions between the aromatic parts of the ligand molecules give a 3-D arrangement of the packing. In contrast, a discrete dinuclear metallocycle, [Ag2(L2)2 has a distorted tetrahedral geometry and is coordinated to two pyridylimine units of two ligand molecules. Additional weak hydrogen bonds involving perchlorate and solvent molecules as well as edge-to-face and face-to-face π-π interactions allow a 3-D packing arrangement.

The first part of the paper reviews the different temporal coupling methodologies that are currently employed for the transient simulation of LWR cores. The second part shows preliminary results from the implementation of some suggested coupling improvements, including high-order corrections to the exchanged coupling fields and a dynamic time step control technique.

The working group “Analytical Methods using Radionuclides and High-performance Sources” (in German: Analytik mit Radionukliden und Hochleistungsstrahlenquellen, ARH) of the German Chemical Society (in German: Gesellschaft Deutscher Chemiker, GDCh) is supported by the GDCh Groups Nuclear Chemistry, Analytical Chemistry, Macromolecular Chemistry, Solid State Chemistry and Materials Research and the Wöhler Association of Inorganic Chemistry.

The ARH working group aims at promoting and supporting the use of radionuclides especially for quality assurance of other analytical methods and analytical methods using large research facilities including synchrotron, neutron and ion sources. The main specific objectives and tasks of ARH are:

• Dissemination of scientific methodology and experience, knowledge transfer
• Coordination and promotion of analytical work with radioactive substances
• Utilization of radio-analytical methods by improving access to radiation facilities, associated instrumentation and isotope laboratories
• Facilitate access to high-performance radiation sources
• Contribution to quality assurance and validation in analytical methods
• Establishment and reinforcing contacts with other scientific associations
• Organization of scientific conferences and meetings

The ARH is continually growing, with the largest relative growth of student members over the past six years. You can become a member of the ARH working group if you belong to one of the supporting GDCh Groups listed above, are an interested company, which is a corporate GDCh member, or are an associated GDCh member in Germany or abroad (note, this is with limited member rights). Members of the German Physical Society (DPG) are also welcome to join the ARH working group with guest status.

More information can be found at our website www.gdch.de/arh.

Using I-124 for PET imaging applications implies some difficulties concerning the image quality: The resolution is degraded by the large maximum positron energy of 2.1 MeV and the resultant long positron range. In addition I-124 is a non-pure PET isotope exhibiting additional gamma ray emissions with high contributions to the total decay scheme: 602.72 keV with 63% and 722.78 keV with 10.35%. These fractions cannot be quantified exactly in PET measurements. Therefore in our work we utilized GATE 6.1 [1] to investigate the effects of these supplementary “false” coincidences on a spectral, sinogram- and image-based basis. Three PET systems were modeled with GATE and confirming measurements were accomplished on them: Two small animal PET scanners (ClearPET and MicroPET) and one human scanner (Gemini TF). Derived from the simulated energy spectra, we propose narrower energy window configurations for the ClearPET and the Gemini TF in order to minimize the amount of false coincidences. Separating the simulated sinograms for true and false coincidences revealed that a two-component correction for I-124 has to be implemented. A homogenous background subtraction has to be amended by a part which considers an additional portion within the phantom borders.
[1] S. Jan et al.: GATE V6: a major enhancement of the GATE simulation platform enabling modelling of CT and radiotherapy. Phys. Med. Biol. (56) (2011) 881-901

Die lange Halbwertszeit des Radionuklids I-124 (4,18d) ermöglicht es langsame biochemische Prozesse über einen längeren Zeitraum zu quantifizieren, als dies mit herkömmlichen reinen Positronenstrahler, wie beispielsweise F-18, der Fall ist. Nachteilig beim komplexen Zerfallsschema von I-124 sind neben der geringen Positronenausbeute von 22,8% zusätzlich koinzident emittierte Gammalinien. Mit Energien von z. B. 602.72keV und 722.78keV liegen sie in den Energiefenstern der verwendeten Kleintier-PET-Scannern. Ziel dieser Arbeit war es, einerseits die Datenakquisition bzgl. der Wahl des Energiefensters zu optimieren und andererseits Korrekturen zur Bildverbesserung direkt in die Datenrekonstruktion einzuarbeiten.

Ferritic/martensitic high-chromium steels are leading candidates for fission and fusion reactor components. Oxide dispersion strengthening is an effective way to improve properties related to thermal and irradiation-induced creep and to extend their elevated temperature applications. An extensive experimental study focusing on the microstructural characterization of oxide-dispersion strengthened Fe-9wt%Cr model alloys is reported. Several material variants were produced by means of high-energy milling of elemental powders of Fe, Cr and commercial yttria powders. Consolidation was based on spark plasma sintering. Special emphasis is placed on the characterization of the nano-particles using transmission electron microscopy, small-angle neutron scattering and atom probe tomography. The microstructure of the investigated alloys and the role of the process parameters are discussed. Implications for the reliability of the applied characterization techniques are also highlighted.

Ferritic/martensitic high-chromium steels are candidate structural materials for future nuclear applications for reasons such as resistance to swelling, irradiation creep and oxidation but suffer hardening and embrittlement due to neutron irradiation. Ion irradiation has been proven to be a useful tool to simulate neutron irradiation effects without the drawbacks of producing radioactive material and being restricted to time consuming and expensive in-reactor irradiations. In the present work ion-irradiation in combination with nanoindentation has been applied to study the irradiation-induced hardening of binary Fe-Cr alloys and 9% Cr steels. The details of the approach are specified and the effects of Cr content and irradiation conditions including both single-beam and dual-beam irradiations are considered. Transmission electron microscopy is used to characterize irradiation-induced defects. Ion-irradiation-induced hardening is compared to hardening observed after neutron irradiation at similar conditions and dominant hardening mechanisms are identified in terms of obstacle strength.

Ferritic/martensitic high-chromium steels are candidate structural materials for future nuclear applications such as fusion and generation IV fission reactors. Nevertheless these steels suffer hardening and embrittlement due to neutron irradiation. Ion irradiation is an efficient tool to simulate neutron irradiation effects without the drawbacks of producing radioactive material. In the present work ion-irradiation in combination with nanoindentation has been applied to study the irradiation-induced hardening of binary Fe-Cr alloys and 9% Cr steels. The details of the approach are specified and the effects of Cr content and irradiation conditions including both single-beam and dual-beam irradiations are considered. Transmission electron microscopy is used to characterize irradiation-induced defects. Ion-irradiation-induced hardening is compared to hardening observed after neutron irradiation at similar conditions and dominant hardening mechanisms are identified.

Damage to fibrous insulation materials located near to a LWR primary circuit coolant leak may compromise the operation of the emergency core cooling system, if insulation fibers are transported to the containment sump strainers, where they may block or penetrate the strainers. Beside insulation material, other forms of debris may influence the sump strainer clogging behavior as well as the cooling water chemistry. Especially, the long-term contact of the water jet from the leak with hot-dip galvanized steel grating treads installed in the containment may cause corrosion of the corresponding materials. Subsequently, the formation of particulate corrosion products may occur by spalling of solid corrosion products from the metallic surfaces or precipitation of solids from the liquid phase. In the event of a LOCA, such processes may lead to an accelerated clogging of the fiber-laden sump strainers. This is especially important in PWRs, where post-LOCA corrosion is accelerated due to the specific primary coolant water chemistry.
Detailed experimental investigations regarding the influence of corrosion processes on the chemical composition of the coolant as well as on the strainer clogging behavior were established within a research project funded by the BMWi, where the priority of the presented investigations is given to the mechanisms that cause sump strainer clogging. As a result of corrosion experiments in the lab-scale KorrVA test facility using hot-dip galvanized steel as well as pure steel samples, it was found that the increase of the head loss is mainly caused by the flow-accelerated corrosion of the base material (steel) whereas the corrosion of the zinc coating leads to soluble corrosion products influencing the cooling water chemistry. Depending on the hydrodynamic conditions, the particulate corrosion products may be removed from the surface and suspended in the coolant, which may lead to further increase of the head loss. In addition, the water chemistry as well as the ratio of coolant volume to corrosion material surface affects the corrosion and clogging behavior significantly.

The multi-group version of DYN3D code was used for calculations of a new concept of boiling water reactor with a tight lattice of fuel rods and reduced neutron moderation. For that purpose a 5-group cross section library was prepared and connected to the DYN3D code. Comparison calculations with the steady-state finite-difference code ACADEM showed a very good agreement.

The capability of the DYN3D multi-group code in modeling transients in boiling water reactors with tight fuel element lattices was demonstrated by the analysis of two reactivity accidents initiated by the ejection of one control rod and unauthorized withdrawal of a control rod bank from the reactor core. The corresponding analyses were performed for begin of cycle conditions, when the considered control rods are at their maximum insertion depth.

9-18% Cr steels and oxide dispersion strengthened (ODS) steels being candidate structural materials for future nuclear applications for reasons such as resistance to swelling, irradiation creep and oxidation suffer hardening and embrittlement due to neutron irradiation. Ion irradiation has proven useful to simulate neutron irradiation effects without the drawbacks of producing radioactive material and being restricted to time consuming and expensive in-reactor irradiations. We have applied ion irradiation in combination with nanoindentation to study the irradiation-induced hardening of binary Fe-Cr alloys, 9% Cr steels and experimental ODS alloys. The details of the approach are specified and the effects of Cr content and irradiation conditions including dual-beam irradiations are considered. Transmission electron microscopy is used to characterize nanoscale oxide particles and irradiation-induced dislocation loops. The dimensionless obstacle strength is estimated. On a scale assigning unity to non-shearable obstacles, we have found a ranking from about 0.012 for Cr-rich α’-phase particles, 0.1 to 0.2 for ODS nanoparticles up to about 0.5 for dislocation loops.

The complexation of perrhenate (ReO4-) anions by the uranyl (UO22+) cation is investigated by joined molecular dynamics simulations and spectroscopic (UV-Vis, TRLFS and EXAFS) studies in aqueous solution, acetonitrile and three ionic liquids (ILs), namely [Bmi][Tf2N], [Me3BuN][Tf2N] and [Bu3MeN][Tf2N] that are based on the same Tf2N- anion (bis(trifluoromethylsulfonyl)imide) and either Bmi+ (1-butyl,3-methylimidazolium), Me3BuN+ or Bu3MeN+ cations. They show that ReO4- behaves as a weak ligand in aqueous solution and as a strong ligand in acetonitrile and in the ILs. In aqueous solution, the simulated UO2(ReO4)2 complex quickly dissociates to form the UO2(H2O)52+ species, while in acetonitrile the simulated UO2(ReO4)53- complex forms from dissociated ions and remains stable along 100 ns of dynamics. When the UO2(ReO4)n2-n complexes (n = 1 to 5) are simulated in the ILs, the uranyl cation remains coordinated to the ReO4- ligands, and to additional OTf2N oxygens when n < 5. To assess the relative stabilities of these complexes, we computed the free energy profiles for stepwise ReO4- complexation by uranyl (PMF calculations). In the two studied ILs, perrhenate complexation is favoured, leading to the UO2(ReO4)53- species in [Bmi][Tf2N] and to UO2(ReO4)42- in [Bu3MeN][Tf2N]. Furthermore, in both acetonitrile and [Bmi][Tf2N] solutions, MD and PMF simulations support the formation of dimeric uranyl complexes [UO2(ReO4)4]24- with two bridging ReO4- ligands. The simulation results are qualitatively consistent with spectroscopic observations in the different solvents, without firmly concluding, however, on the precise composition and structure of the complexes in the solutions.

Based on strong-field QED in the Furry picture we use the Dirac-Volkov propagator to derive a compact expression for the differential emission probability of the two-photon Compton process in a pulsed intense laser field. The relation of real and virtual intermediate states is discussed, and the natural regularization of the on-shell contributions due to the finite laser pulse is highlighted. The inclusive two-photon spectrum is two orders of magnitude stronger than expected from a perturbative estimate.

Lithium silicate thin films, which are interesting materials for example in lithium ion batteries, were grown by the atomic layer deposition technique from lithium hexamethyldisilazide [LiHMDS, Li(N(SiMe₃)₂)] and ozone precursors. Films were obtained at a wide deposition temperature range between 150 and 400 °C. All the films were amorphous except at 400 °C, where partial decomposition of LiHMDS was also observed. The growth behavior was examined in detail at 250 °C, and saturation of growth rates and refractive indices with precursor doses was confirmed, thereby verifying self-limiting surface reactions. Likewise, the linear thickness dependence of the films with the number of deposition cycles was verified. Strong dependence of growth rate and film composition on deposition temperature was also seen. Overall, the amorphous films grown at 250 °C had a stoichiometry close to lithium metasilicate (Li_2.0SiO_2.9) with 0.7 at. % carbon and 4.6 at. % hydrogen impurities. The corresponding growth rate and refractive index (n₅₈₀) were 0.8 A/cycle and about 1.55.

Auger decay, i.e. the spontaneous emission of an electron upon relaxation of the atomic shell, carries valuable information about the electronic structure and dynamics of atoms and their compounds. While the energetic properties are well investigated, little is known about the detailed temporal profile of Auger electron wave packets. Here we furnish evidence, that under certain conditions Auger electrons are subject to an energetic chirp imprinting a non-linear change of energy over time on the escaping wave packet. The origin of this unexpected finding is shown to be the exchange of energy between the Auger electron and a slightly earlier emitted photoelectron in the presence of a laser field. The interpretation in terms of this long-range electron correlation is substantiated by fs-time-resolved experiments on the xenon NOO and Kr MNN Auger decay together with extensive theoretical modelling using semi-classical as well as quantum-mechanical simulations.

Tetravalent cerium (Ce(IV)) is known to be one of the most commonly-used oxidizing agents in various chemical studies, such as organic synthesis. Furthermore, it recently draws considerable attention to its catalytic applications to water oxidation or biotechnology. As a versatile catalytic oxidant, Ce(IV) is often employed in the form of aqueous solution. Therefore, fundamental knowledge of Ce(IV) species in aqueous solution is essential not only for discussing its functionality in the applied systems, but also for further developing its applications; nevertheless, the nature of Ce(IV) species in aqueous solution is far less well understood. In this context, the present study aims to elucidate the chemical speciation and complex structure of soluble Ce(IV) species formed on hydrolysis, which is the most fundamental reaction of metal cations in the aqueous solution system, by employing X-ray absorption spectroscopy (XAS), high energy solution X-ray scattering (HEXS), and dynamic light scattering (DLS).
The obtained XAS data have clearly showed the systematic growing of Ce–Ce bonding in the soluble Ce(IV) hydrolytic species, as an increase in pH. This indicates that some soluble polymeric or cluster complexes are formed on the hydrolysis of Ce(IV). The diffraction patterns of Ce(IV) hydrolytic species have further revealed that the observed polymeric or cluster complex has a crystalline structure, not the amorphous one. The results of the detailed analysis on XAS and HEXS data will be presented on site, along with the DLS data for discussing the size of Ce(IV) hydrolytic polymers/clusters and its aging effect.

Es ist kein Abstract vorhanden.

Granite is the aspired potential host rock material for future nuclear waste storage in Sweden. The Äspö Hard Rock Laboratory (Äspö HRL) today is an interdisciplinary research facility for geological disposal in granite rock. The research within the Äspö HRL programme involves international cooperation with various countries including Germany.
This presentation drafts the operations done at Äspö and the contribution by the IRC. Here the objectives and results of the study on the interaction of uranium(VI) with Pseudomonas fluorescens, a strain that has been isolated at the Äspö site, are presented. Explicitly results about the accumulation capability of the strain, TRLFS investigations and potentiometric titration results are shown.

The radiation emitted by axially channeled electrons has been investigated by computer simulations. Using the Doyle-Turner approximation for the atomic scattering factor and taking thermal vibrations of the crystal atoms into account, two-dimensional continuous potentials for the <100> and <110> crystallographic axes of a thin Ge single crystal have been calculated. The trajectories, velocities and accelerations of channeled electrons are obtained by solving numerically the classical equations of motion in three dimensions. In the framework of classical electrodynamics, these data allow realistic simulations of spectral-angular distributions and energy spectra of axial channeling radiation as well.

The NeuLAND detector at the R3B experiment at the future FAIR facility in Darmstadt aims to detect fast neutrons (0.2–1.0 GeV) with high time and spatial resolutions . This task can be performed either with a scintillator or based on the multigap resistive plate chamber (MRPC) technology. Here, prototyping and test for an MRPC-based solution are discussed. In order to reach 90% detection efficiency, the final detector must consist of 50 consecutive MRPC stacks. Each stack contains a 4 mm thick anode made of iron converter material, with an additional 4 mm of converter material between two stacks. The secondary charged particles stemming from hadronic interactions of the high energetic neutrons in the converter will be detected in the MRPCs. As part of the ongoing development effort, a number of prototypes for this detector have been developed and built. They have been tested in experiments with a single-electron beam with picosecond resolution at the superconducting linac ELBE (Dresden, Germany). The results of the tests are presented here, and an outlook is given.

The NO cycle takes place in the deepest layer of a H-burning core or shell, when the temperature exceeds T {\simeq} 30 {\cdot} 106 K. The O depletion observed in some globular cluster giant stars, always associated with a Na enhancement, may be due to either a deep mixing during the RGB (red giant branch) phase of the star or to the pollution of the primordial gas by an early population of massive AGB (asymptotic giant branch) stars, whose chemical composition was modified by the hot bottom burning. In both cases, the NO cycle is responsible for the O depletion. The activation of this cycle depends on the rate of the 15N(p,{\gamma})16O reaction. A precise evaluation of this reaction rate at temperatures as low as experienced in H-burning zones in stellar interiors is mandatory to understand the observed O abundances. We present a new measurement of the 15N(p,{\gamma})16O reaction performed at LUNA covering for the first time the center of mass energy range 70-370 keV, which corresponds to stellar temperatures between 65 {\cdot} 106 K and 780 {\cdot}106 K. This range includes the 15N(p,{\gamma})16O Gamow-peak energy of explosive H-burning taking place in the external layer of a nova and the one of the hot bottom burning (HBB) nucleosynthesis occurring in massive AGB stars. With the present data, we are also able to confirm the result of the previous R-matrix extrapolation. In particular, in the temperature range of astrophysical interest, the new rate is about a factor of 2 smaller than reported in the widely adopted compilation of reaction rates (NACRE or CF88) and the uncertainty is now reduced down to the 10% level.

The 44Ti(alpha,p)47V reaction is of crucial importance for the destruction of Ti-44 in the alpha-rich freezeout of a supernova. Here I report on a feasibility study. Using radioactive Ti-44 and alpha-emitting sources and sputtering simulations, I study the feasibility and safety of a possible experiment using an alpha-beam from an accelerator and a radioactive Ti-44 target.

Presentation of the complexation of Uranium(VI) with selected Schiff bases in methanol investigated by UV/Vis spectroscopy and time-resolved laser-induced fluorescence spectroscopy (TRLFS)

Positron emission tomography (PET) is a dedicated tool for quality assurance in ion beam therapy. By measuring the spatial distribution of positron emitters generated via nuclear interactions between projectiles and atomic nuclei of the tissue during the therapeutic irradiation, conclusions on the accuracy of the dose localization can be drawn. In the following, the physical background as well as the technical realization of PET is depicted. Furthermore, current PET installations for quality assurance of proton and ion beam therapy are presented.

I will review the state of the art of stable-ion beam experiments for nuclear astrophysics. Special mention will be made of the so-called solar abundance problem and the contributions that experimental nuclear astrophysics may make to solve it. Topics where ERAWAST nuclides have played a special role will be mentioned.

I will review the status of the standard solar model, with special mention given to the so-called solar abundance problem that ha recently developed. Then, I will discuss the experimental status of the nuclear reactions of the carbon-nitrogen-oxygen (CNO) cycle of hydrogen burning.

Numerical and experimental modelling of a VGF-type (VGF - Vertical Gradient Freeze) buoyant flow under the influence of both travelling and rotating magnetic fields (TMF and RMF, respectively) is presented. Low-temperature flow experiments were carried out using a GaInSn alloy as model fluid. Radial heating and cooling of the melt leading to a meridional double vortex flow like in typical VGF growth, was introduced using a double-walled melt container. The flow was found to be significantly influenced by the mutual interaction of buoyant and electromagnetically driven forces. With increasing axial temperature difference, the buoyant flow becomes more concentrated in the upper and lower part of the melt leaving an extended melt zone with low flow velocity around the mid-height. Furthermore, VGF-type buoyancy is found to stabilize TMF- and RMF-induced melt flows. Besides, the time evolution of the flow just above the stability threshold is studied. In the case of combined VGF-type/RMF flow complex fluctuation patterns are observed, which depends sensitively on the applied thermal field.

The international LUNA collaboration studies nuclear reactions at very low energy, directly relevant to the Sun. To this end, it uses a 0.4 MV accelerator deep underground in the Gran Sasso laboratory in Italy. I will review the motivations, techniques and achievements of LUNA.

Bacterial isolates from the uranium mining waste pile Haberland (Johanngeorgenstadt, Saxony) possess high affinities to heavy metals and uranium. This binding effect is caused by the components of the bacterial cell wall, mainly effected by surface layer proteins.
Aim of this work is the construction of a stable multi-layer system for the simulation of cell walls of Gram-positive bacteria and the investigation of metal interactions with single compounds and whole complex systems.
The quartz crystal microbalance (QCM-D) and atomic force microscopy (AFM) is used to track and control this multi-layer formation.
First result of these tasks is the proof of recrystallization of S-layer proteins as part of the cell wall of Bacillus spec. JG-B53 via QCM-D and AFM.

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Vortrag ohne Abstrakt!

Heterologous expression is a common method of molecular biology, which finds applications for example in up scaling of protein production and structural analyses of naturally unexpressed proteins. An experimental setup is started by the amplification of the template gene. Afterwards this gene is cloned into coiled DNA, called vectors and transformed into the host organism. The desired protein, which is encoded by the cloned gene, is produced inside the host organism. Host strains are for example Escherichia coli, Lactococcus lactis or Pichia pastoris.

Presentation of motivation and objectives of the PhD theses “Spectroscopic characterization of trivalent actinides Am and Cm on bacterial cell walls” and “Evidence and characterization of silica-containing colloids of tetravalent Th, U, Np”.

We report on carrier relaxation dynamics close to the Dirac point in epitaxially grown graphene under pulsed excitation with 10 – 250 meV photons. With decreasing photon energy, we identify different regimes – induced transmission with bi- and single-exponential decay as well as induced absorption - and discuss their physical origin.