Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

A new synthetic pathway for the preparation of benzoate-functionalized phosphanes for microwave-mediated traceless Staudinger ligations is described. Novel phosphane derivatives based on 4-substituted iodophenyl benzoates were prepared via palladium(II)-catalyzed P–C cross-coupling reaction strategy in high yields. The application of microwave conditions for the ligation reactions reduced the reaction time considerably. An approach to fast and facile labeling strategies using this ligation was established.

Summary
Background/Methods: Coating a silica surface with the isolated lipoprotein receptor heparan sulfate proteoglycan (HS-PG) from arterial endothelium and vascular matrices, we could observe the very earliest stages of arteriosclerotic plaque development by ellipsometric techniques in vitro (patent EP 0 946 876). This so-called nanoplaque formation is represented by the ternary aggregational complex of the HS-PG receptor, lipoprotein particles and calcium ions. The model was validated in several clinical studies on statins in cardiovascular high-risk patients applying their native blood lipoprotein fractions.
Results: In 7 patients who had undergone a valvular defect operation, the reduction of arteriosclerotic nanoplaque formation in normal Krebs solution amounted to 6.1 ± 2.3% (p < 0.0156) and of nanoplaque size to 37.5 ± 13.2% (p < 0.0312), respectively, after a 3-month therapy with n-3 fatty acids (3 × 3 g daily, Ameu® 500 mg). Additionally, the quotient oxLDL/LDL was lowered by 6.8 ± 2.1% (p < 0.0166), the MDA concentration remained unchanged and the lipoprotein(a) concentration decreased by 15.8 ± 5.6% (p < 0.0469) in the patients’ blood. The concentration of the nanoplaque promoting particles VLDL and total triglycerides was diminished by 34.1 ± 11.6% (p < 0.0469) and 26.7 ± 10.8% (p < 0.0156), respectively. Furthermore, the ratio of the strongly atherogenic small dense to the total LDL cholesterol (LDL5+LDL6)/LDL_tot decreased by 9.9 ± 3.0% (p < 0.0174).
Conclusions: A combinatorial regression analysis revealed a basis for a mechanistic explanation of nanoplaque reduction under n-3 fatty acid treatment. This effect was possibly due to the beneficial changes in lipid concentrations and an attenuation of the risk factors oxLDL/LDL and (LDL5+LDL6)/LDL_tot.

Zusammenfassung
Hintergrund/Methode: Durch Beschichtung einer Silikatoberfläche mit dem Lipoproteinrezeptor Heparansulfat-Proteoglykan (HS-PG), der aus arteriellem Endothel und der Gefäßmatrix isoliert wurde, konnten wir mithilfe ellipsometrischer Techniken die ersten Anfangsstadien arteriosklerotischer Plaques in vitro beobachten (Patent EP 0 946 876). Die sogenannten Nanoplaques werden durch den ternären Aggregatkomplex aus HS-PGRezeptor, Lipoproteinpartikeln und Kalziumionen gebildet. Das Modell wurde in mehreren klinischen Studien zur Wirkung von Statinen bei kardiovaskulären Hochrisikopatienten bestätigt, wobei deren natürliche Blut-Lipoprotein-Fraktionen eingesetzt wurden.

Ergebnisse: Bei 7 Patienten nach Herzklappenoperation betrug die Reduktion der arteriosklerotischen Nanoplaquebildung und -größe nach 3-monatiger Therapie mit ω-3-Fettsäuren (3 × 3 g/d Ameu® 500 mg) in normaler Krebslösung 6,1 ± 2,3% (p < 0,0156) bzw. 37,5 ± 13,2% (p < 0,0312). Zusätzlich wurde im Patientenblut der oxLDL/LDL-Quotient um 6,8 ± 2,1% (p < 0,0166) gesenkt, die MDA-Konzentration blieb unverändert und die Lipoprotein(a)-Konzentration nahm um 15,8 ± 5,6% (p < 0,0469) ab. Die Konzentration der Nanoplaque fördernden VLDLs und Gesamttriglyzeride wurde um 34,1 ± 11,6% (p < 0,0469) sowie 26,7 ± 10,8% (p < 0,0156) reduziert. Ferner verringerte sich das Verhältnis der stark atherogenen, kleinen dichten LDL-Fraktionen zum Gesamt-LDL (LDL5+LDL6)/LDL_tot um 9,9 ± 3,0% (p < 0,0174).

Schlussfolgerungen: Eine mehrfache Regressionsanalyse ergab eine Grundlage für eine mechanistische Erklärung der Nanoplaquereduktion unter ω-3-Fettsäure-Behandlung. Dieser Effekt beruht möglicherweise auf günstigen Veränderungen der Lipidkonzentrationen und einer Verminderung der Risikofaktoren oxLDL/LDL und (LDL5+LDL6)/LDL_tot.

The study describes the use of [F-18]FDG as F-18 building block for the direct labelling of various aminooxy-functionalised peptides via chemoselective oxime formation.

Transparent conductive oxides (TCOs) are attracting an increasing attention as materials for transparent electrodes in thin film solar cells. The characteristic features of TCOs are low formation energy of defects, which enables n-type doping, and low probability of compensating defects formation. These materials are mainly based on In2O3, SnO2 and ZnO, wide band gap (>3 eV) semiconductors, which may be easily converted by doping to degenerate semiconductors with electrical resistivity as low as ~10^-4 Ohm cm and high transmittance (>80%) in the visible spectral range. In addition to these properties, photovoltaic applications require TCO materials with increased near-IR transmittance, adjustable work function and defined surface morphology, which improves light trapping in PV absorber layer (e.g. a-Si:H-based cells). The need to decrease TCO production costs has stimulated research activity on reactive pulsed magnetron sputtering (RPMS) as a versatile deposition method.
In order to explore potential advantages of RPMS, the relationship between the deposition parameters and structure, phase composition, and physical properties of TCOs should be established. Understanding the mechanisms of donor impurity incorporation and its electrical activation is of special importance. For this purpose, indium oxide (IO), ITO, ZnO, and AZO films (with Al concentrations 0.7-8.7 at. %) were grown by RPMS with a precise control of the oxygen partial pressure at substrate temperatures ranging from ~40 °C to 580 °C. The magnetron plasma parameters were determined by a Langmuir probe. The resulting films were characterized by spectroscopic ellipsometry, Hall effect measurements, X-ray diffraction (XRD) and, in case of ZnO and AZO films, by X-ray absorption near edge spectroscopy (XANES). The Sn concentration in ITO was determined by Auger analysis, while the Al concentration in ZnO matrix was estimated by elastic recoil detection analysis.
The comparison of the real-time behavior of the IO and ITO film structure and electrical properties during annealing provides a direct evidence of Sn donor activation (with an estimated efficiency of 40%) in ITO due to amorphous-to-crystalline transition. The ITO film crystallinity always improves with increasing substrate temperature or during isothermal annealing, with the electrical resistivity decreasing. In contrast, the electrical resistivity of ZnO:Al films shows a clear minimum at a certain substrate temperature (250-400 °C), which depends on Zn/O2 flux ratio and correlates with a maximum in crystallinity (grain size). In this case, the highest mobility value of 46 cm2 V-1 s-1 is comparable to the best values achieved in AZO films grown by less cost-efficient techniques. This value is achieved at the free electron density of 6x10²⁰ cm-3 which corresponds to maximum ~30% electrical activation of Al impurity. At higher temperatures, the AZO electrical properties and crystalline quality deteriorate abruptly. This is likely due to formation of a new metastable phase, which is identified by XANES as homologous (ZnO)3(Al2O3). Its formation is triggered by an increase of the Al/Zn ratio in the film, and leads to electrical deactivation of the Al impurity in AZO. In order to improve electrical activation of the donor impurity and to extend the functionality of TCOs, the formation of epitaxial AZO and TiO2:Nb films by RPMS is proposed.

Introduction and Aim:

The radiopharmacological evaluation of the new compound 3-[4’-[18F]fluorobenzylidenyl]-indolin-2-one is described. The compound is a radiolabeled derivative of an inhibitor of the VEGF-mediated signaling through the Flk-1/KDR (VEGFR-2) tyrosine kinase receptor pathway (SU5416 (NSC 696819) [3-(3,5-dimethyl-1H-pyrrol-2-ylmethylene)-1,3-dihydro-indol-2-one]).

Materials and Methods:

The radiosynthesis was accomplished by Knoevenagel condensation of 4-[18F]fluorobenzaldehyde with oxindole in a remotely controlled synthesis module. The radiotracer was obtained after a two-step labeling procedure in 4% decay-corrected radiochemical yield at a specific activity of 48-61 GBq/µmol within 90 min. The radiochemical purity after semi-preparative HPLC purification exceeded 98%. The biodistribution, metabolism and excretion were studied in Wistar rats. Small animal PET studies in rats and FaDu tumor bearing nude mice were carried out. Results: After distribution the radiotracer was rapidly accumulated in the adrenals, liver and kidneys, however, it was cleared from these and the most other organs. Only the adipose tissue retained the activity over 60 min. Unexpected high transient uptake was observed in the brain, pancreas, heart and lung. The fast blood clearance of 3-[4’-[18F]fluorobenzylidenyl]-indolin-2-one was caused by excretion, approximately one half each was renal and biliary excreted and other metabolic processes. Only the original compound was entering the brain. In arterial blood plasma were two more polar radiometabolites detected. The blood clearance was fast and could be described by a two phase elimination with half-lifes of 8 and 267 s. Consequently, in small animal PET studies with FaDu tumor bearing mice - no specific uptake in the tumors could be detected.

Conclusion:

The investigation of the 3-[4’-[18F]fluorobenzylidenyl]-indolin-2-one revealed that the uptake in high perfused organs was transiently, and only in the adipose tissue the compound was accumulated. However, it seems to be it is not applicable for angiogenesis imaging.

Introduction and Aim:

Phosphopeptides are very useful reagents to study signal transduction pathways related with cellular protein phosphorylation/dephosphorylation processes. Phosphopeptides also have been identified as important drug candidates to modulate intracellular signal transduction pathways. The present study describes the use of cell-penetrating peptides (CPPs) sC18 and hCT(18-32)-k7 coupled to Polo-like kinase-1 (Plk-1)-binding hexaphosphopeptide H-Met-Gln-Ser-pThr-Pro-Leu-OH to investigate cell uptake of the corresponding phosphopeptide-CPP hybrids.

Materials and Methods:

Peptide syntheses were accomplished using a combination of automated and manual solid-phase peptide syntheses following standard Fmoc chemistry. Fluorescence labeling was carried out via coupling 5(6)-carboxyfluoresceine (CF) to the N-terminal end of the phosphopeptide using HATU as the activation agent, DIPEA as the base, and DMF as the solvent. Cell uptake studies of CF-Met-Gln-Ser-pThr-Pro-Leu-sC18 (CF-I) and CF-Met-Gln-Ser-pThr-Pro-Leu-hCT(18-32)-k7 (CF-II) were performed using the human breast cancer cell line MCF-7 and human cervical carcinoma epithelial (HeLa) cells on a Zeiss Axio fluorescence confocal microscope. Results: Peptide hybrids CF-I and CF-II showed cellular uptake in both cell lines after incubation at 37°C for 60 min. Cell uptake was more pronounced in HeLa cells compared to MCF-7 cells. Phosphopeptide conjugated to sC18 showed higher cell uptake compared to phosphopeptide-hCT(18-32)-k7 conjugate. As expected, CF-labeled phosphopeptide without being conjugated to CPPs as molecular shuttles was not internalized into both cell lines. Quantification of cellular uptake using flow cytometry analysis and fluorine-18 labeled phosphopeptide-CPP hybrids are currently in progress.

Conclusion:

Cell-penetrating peptides sC18 and hCT(18-32)-k7 are useful drug delivery systems enabling sufficient membrane transport of phosphopeptides to further promote studies on intracellular metabolic pathways involving phosphopeptides.

We report first results on a deep subthreshold production of the doubly strange hyperon Xi- in a heavy-ion reaction. At a beam energy of 1.76A GeV the reaction Ar+KCl was studied with the High Acceptance Di-Electron Spectrometer at SIS18/GSI. A high-statistics and high-purity Lambda sample was collected, allowing for the investigation of the decay channel Xi--->Lambdapi-. The deduced Xi-/(Lambda+Sigma0) production ratio of (5.6±1.2_-1.7 ^+1.8)×10-3 is significantly larger than available model predictions.

We present de Haas-van Alphen (dHvA) investigations in the nonmagnetic borocarbide superconductor LuNi₂B₂C both in the normal and in the superconducting state. The measurements have been carried out by use of the torque method as well as by the field-modulation method. The quantum oscillations in the normal state give information on the elaborated Fermi surfaces which consists of several open and closed parts [1]. In the superconducting state we observe dHvA oscillations that belong to a spheroidal Fermi surface deep into the superconducting state down to B = 2.5 T far below the upper critical field, B_c2. We find only a minor additional damping of the dHvA oscillation amplitude in the superconducting state compared to the normal state. Only close to B_c2 the oscillations appear to be more strongly damped. There, the background signal shows a strong peak effect which complicates the analysis of the dHvA signal in this region. However, the apparent increase of the additional damping in the peak-effect range hints at the influence of increased flux-line pinning in this region

We report on combined experimental and theoretical efforts to elucidate the magnetic properties of the organic magnets [Cu(HF₂)(pyz)₂]X with X = BF₄ and PF₆. By use of high-resolution specific-heat measurements on high-quality single crystals we were able to resolve small lambda-type anomalies indicative for a phase transition into a long-range ordered state. First-principles density-functional calculations allow to estimate the exchange couplings and confirm a three-dimensional antiferromagnetic order between ad-jacent Cu centers with a stronger coupling within the layers of pyz-bridged Cu and a much weaker cou-pling across the HF₂ linker units. Specific-heat data in magnetic field, B,reveal a slightly anisotropic nonmonotonic dependence of the Néel temperature T_N with B. The increase of T_N at low fields can be un-derstood by the reduction of phase fluctuations that are prominent in these highly anisotropic quasi-two-dimensional magnets. Towards higher fields, B suppresses the amplitude of the antiferromag-netic order parameter, and correspondingly T_N, by aligning the spins parallel to B. This nonmonotonic be-havior of T_N, as well as the magnetic part of the specific heat, cannot be described by a mean field theory that neglects the crucial role played by phase fluctuations. In contrast, we show that both properties are very well reproduced by Quantum Monte Carlo simulations. Pulsed-field magnetization data corroborate the strong anisotropy of the exchange interactions. The ratio of the inter- to intralayer exchange interac-tion is estimated as 0.0025 (for X = BF₄) and 0.009 (X = PF₆). High-field electron spin resonance meas-urements reveal a magnetic easy-plane anisotropy.

We report systematic de Haas–van Alphen (dHvA) investigations in the normal and superconducting state of RNi₂B₂C (R = Y and Lu). The observed rich frequency spectrum of the dHvA signals results from a rather complex electronic band structure with different open and closed Fermi-surface sheets. From our data in combination with full-potential local-orbital calculations we are able to extract the angular-resolved mass-enhancement factors, lambda, for different bands. We find a strong anisotropy and band dependence of lambda, clearly reflecting the multiband character of the superconductivity in RNi₂B₂C. We further were able to resolve dHvA oscillations deep into the superconducting state. The observed additional damping of the dHvA amplitudes is much less than expected from most theories. This hints at a reduced or even zero superconducting gap for the detected Fermi surface

In view of the increasing age of the European NPPs and envisaged life time extensions up to an EOL of 80 years, there is a need for an improved understanding and prediction of RPV irradiation embrittlement effects connected with long term operation (LTO). Effects caused by high neutron fluences such as the possible formation of Late Blooming Phases and as yet unknown defects must be considered adequately in safety assessments. However, the surveillance database for long irradiation times (>20 years) and low neutron flux is sparse, which leads to uncertainties in the treatment of LTO irradiation effects. In this context microstructural data are essential for the understanding of the involved mechanisms. The proposed project aims at: 1) improved knowledge on LTO phenomena relevant for European reactors; 2) assessment and proposed improvements of prediction tools, codes and standards; 3) elaboration of best practice guidelines for irradiation embrittlement surveillance.
The suggested scope of work is:
i) Summary of boundary conditions for LTO and systematic (re)evaluation of the international prediction procedures of irradiation embrittlement
ii) Generation of microstructural data of irradiated representative or original RPV materials; demonstration that damage models are (or not) consistent with the mechanisms of irradiation damage in the LTO (use of PERFORM60 prediction tools)
iii) Investigation of specific LTO relevant phenomena like late blooming phases and flux effect from available results; role of Cu, Ni, Mn, P, Si under the aspect of LTO;
iv) Correlation of microstructural data with mechanical properties and identification of the most important influencing factors (link with PERFORM60)
v) Influence of high neutron fluences on fracture toughness curves shape
vi) Comparison of embrittlement results from decommissioned plants with surveillance data
vii) Elaboration of recommendations for RPV embrittlement surveillance under LTO conditions

Kein Abstract, da vertraulicher Bericht.

Kein Abstract, da Bericht vertraulich.

The long-term in-vessel corium retention (IVR) in the lower head bears a risk of the vessel wall deterioration caused by steel corrosion. The ISTC METCOR Project has studied physicochemical impact of prototypic coria having different compositions in air and steam and has generated valuable experimental data on vessel steel corrosion. It is found that the corrosion rate is sensitive to corium composition, but the composition of oxidizing above-melt atmosphere (air, steam) has practically no influence on it. A model of the corrosion process that integrates the experimental data, is proposed and used for development of correlations.

At the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, uniquely intensive beams of radioactive ions will become available. One of the experiments at FAIR, called Reactions with Relativistic Radioactive Beams (R3B), will study reactions of such projectiles at energies up to 1 GeV/A. The planned NeuLAND time-of-flight detector will detect the emitted neutrons with a time resolution of sigma = 50 ps and efficiency of better than 90 %. The poster will discuss recent progress in the development of multigap resistive plate chamber based prototypes for NeuLAND. Using the ELBE electron beam facility in Dresden, the time resolution of the prototypes has been shown to fulfill the design criteria.

The migration behaviour of actinide ions in the geosphere is generally influenced by sorption processes in aqueous media. These processes occurring at solid/liquid interfaces can be monitored by in situ Attenuated Total Reflection Fourier-transform Infrared (ATR FT-IR) spectroscopy providing structural information on a molecular level.[1]
In this work, the sorption of neptunium(V) onto metal oxides was investigated for the first time. From the Np(V) sorption studies on the metal oxides, stable surface species of NpO2+ are derived. The type of the sorbed species can be elucidated by a spectral shift (~ 30 cm−1) to lower wavenumbers of the antisymmetric stretching vibration υ3(NpO2+) compared to the aqueous species suggesting an inner-sphere complexation. Outer-sphere complexation is found to play a minor role due to the pH independence of the sorption species throughout the pH range 4 – 7.6. The comparative spectroscopic experiments of Np(V) sorption onto TiO2, SiO2 and ZnO indicate structurally similar bidentate surface complexes.[2]
A detailed insight into the molecular mechanisms occurring during the formation of ternary actinide complexes at the solid/liquid interface is provided upon formation of uranyl carbonato complexes on ferrihydrite (Fh). The influence of the presence of atmospheric carbon dioxide during the sorption processes of the actinide ions was studied by sorption experiments which were carried out under inert gas conditions and in an ambient atmosphere. From the results, the formation of bidentate [Fh•••UO2•••O2CO] complexes can be derived under mildly acid conditions which is in agreement from recent EXAFS results obtained from batch samples.[3]
Furthermore, experiments with 13C labelled carbonate provide an unequivocal assignment of the spectral features reflecting the structural alterations of the carbonate ions upon sorption of uranyl cations onto Fh. From these assignments, the formation of the ternary uranyl complexes can be described at a molecular level.

References
[1] Lefèvre, G. (2004) Adv. Colloid Interface Sci. 107, 109-123.
[2] Müller, K. et al. (2009) Environ. Sci. Technol., in press.
[3] Rossberg, A. et al. (2009) Environ. Sci. Technol. 43, 1400-1406.

Processes leading to homogenization of chemical and phase composition of near-surface layers materials made from titanium and iron-carbon alloys under irradiation of a low energy intense pulsed electron beam have been investigated. It has been shown that preliminary heating leads to appearance of a more homogeneous chemical composition of surface alloy. It has been determined that an electron-beam polishing took place during irradiation. Irradiation results in dissolution of secondary phase inclusions, decreasing of roughness, and as a result in the enhancement of electrical and chemical surface properties of titanium and iron-carbon alloys.

We report on a method, which allows accurate measurements of complex reflection coefficient of a solid at frequencies 1 to 50 cm-1 (30 GHz - 1.5 THz). Backward-wave oscillators (BWOs) are used as sources of monochromatic coherent radiation, tunable in frequency. The amplitude of the complex reflection (the reflectivity) is measured in a standard way, while the phase shift, introduced by the reflection from the sample surface, is measured using a polarizing Michelson interferometer. This method is particular useful for not-transparent samples (such as metals, superconductors, etc.), where phase-sensitive transmission measurements are not possible.
The method requires no Kramers-Kronig transformation in order to extract the sample's electrodynamic properties (such as complex dielectric function or complex conductivity). Another area of application of this method is the study of magnetic materials with complex dynamic permeability different from unity at the measurement frequencies (for example, metamaterials). Measuring both, the phase-sensitive transmission and the phase-sensitive reflection, would allow a straight-forward model-independent determination of the dielectric permittivity and magnetic permeability of such materials.

Crystalline Mn₅Ge₃ nanomagnets are formed inside a Mn-diluted Ge matrix using Mn ion implantation. A temperature-dependent memory effect and slow magnetic relaxation are observed below the superparamagnetic blocking temperature of Mn₅Ge₃. Our findings corroborate that the observed spin-glass-like features are caused by the size distribution of Mn₅Ge₃ nanomagnets, rather than by the inter-particle interaction through the Mn-diluted Ge matrix.

Die Schweizer Richtlinie HSK-AN-425 dient der bruchmechanische Werkstoffcharakterisierung zur Überwachung der Neutronenversprödung von Reaktordruckbehältern für den Langzeitbetrieb von Kernkraftwerken. Eine Besonderheit ist, dass nicht quasistatische, sondern dynamische Bruchzähigkeitskennwerte ermittelt werden. Die Richtlinie deckt den gesamten Bereich der Zähigkeit ferritischer Stähle ab, also vom instabilen Spaltbruch in der Tieflage (tiefe Temperaturen) bis zum duktilen Reissen in der Hochlage (hohe Temperaturen) und dem dazwischen liegenden Bereich des Steilabfalls der Zähigkeit.
Ziel des Forschungsprojektes HSK-AN-6305 war, die zentralen Elemente der neuen Richtlinie HSK-AN-425 Rev. 5 durch experimentelle Überprüfung an vergleichbaren Werkstoffen aus dem RDB Biblis C zu validieren (Einfluss der Risslänge, Fortsetzung der MC im oberen ZSÜ-Bereich). Allfällige Schwachstellen der Richtlinie HSK-AN-425 sind zu korrigieren, bevor sie in der Überwachung der Kernanlagen freigegeben werden kann. Der Einfluss der Probendicke und der Probenart auf die quasistatische MC-Referenztemperatur T0 nach ASTM E 1921 sowie auf die dynamische MC-Referenztemperatur T0d nach HSK-AN-425 ist zu bestimmen (Übertragbarkeit der Ergebnisse auf Bauteile und Komponenten), und ob bei den Bruchmechanikproben der herkömmliche Ermüdungsanriss durch EDM-Kerben ersetzbar ist.
In dieser Publikation werden die Ergebnisse des Forschungsprojektes HSK-AN-6305 ausführlich vorgestellt.

Die Schweizer Richtlinie HSK-AN-425 dient der bruchmechanische Werkstoffcharakterisierung zur Überwachung der Neutronenversprödung von Reaktordruckbehältern für den Langzeitbetrieb von Kernkraftwerken. Eine Besonderheit ist, dass nicht quasistatische, sondern dynamische Bruchzähigkeitskennwerte ermittelt werden. Die Richtlinie deckt den gesamten Bereich der Zähigkeit ferritischer Stähle ab, also vom instabilen Spaltbruch in der Tieflage (tiefe Temperaturen) bis zum duktilen Reissen in der Hochlage (hohe Temperaturen) und dem dazwischen liegenden Bereich des Steilabfalls der Zähigkeit.
Ziel des Forschungsprojektes HSK-AN-6305 war, die zentralen Elemente der neuen Richtlinie HSK-AN-425 Rev. 5 durch experimentelle Überprüfung an vergleichbaren Werkstoffen aus dem RDB Biblis C zu validieren (Einfluss der Risslänge, Fortsetzung der MC im oberen ZSÜ-Bereich). Allfällige Schwachstellen der Richtlinie HSK-AN-425 sind zu korrigieren, bevor sie in der Überwachung der Kernanlagen freigegeben werden kann. Der Einfluss der Probendicke und der Probenart auf die MC-Referenztemperatur T0 ist zu bestimmen (Übertragbarkeit der Ergebnisse auf Bauteile und Komponenten), und ob bei den Bruchmechanikproben der herkömmliche Ermüdungsanriss durch EDM-Kerben ersetzbar ist.
In dieser Publikation werden die Hauptergebnisse des Forschungsprojektes HSK-AN-6305 vorgestellt.

The long-term safety assessment of nuclear waste disposals requires detailed knowledge of the transport and interaction behavior of actinides within the technical, geotechnical and geological barriers. In the case of accidental release of radionuclides into the surrounding environment, their migration behavior can be effectively influenced by the ambient conditions like pH, temperature, ionic strength and especially the presence of inorganic and organic complexing ligands, e.g. bioligands like humic acids, amino acids or phospholipids. Due to their high complexing capacity towards metal ions these ligands may influence the mobility of actinides.

We studied the U(VI) complexation with nitrogen and phosphorous containing model ligands in order to simulate the functionalities of bioligands. The aim of this work is to determine the influence of various nitrogen and phosphorous containing functional groups on the U(VI) complexation and to evaluate their contribution in comparison to oxygen containing functional groups. As nitrogen containing ligands we used the biologically important substances anthranilic acid (AA) and nicotinic acid (NA). Furthermore, phenylphosphonic acid (PPA) was used as aromatic phosphorous containing ligand.

The complexation studies in aqueous solution were performed as a function of pH using time-resolved laser-induced fluorescence spectroscopy (TRLFS). All ligands show a complex formation with U(VI) under the given experimental conditions ([U(VI)] = 0.05 mM, [ligand] = 0 – 0.5 mM, pH 2-4, I = 0.1 M, T = 25°C). The binding of U(VI) by AA and NA takes place via the carboxylic group of the ligands. It can be concluded, that oxygen containing functional groups dominate the U(VI) complexation in the investigated pH range. The nitrogen functionalities of the ligands play only a subordinate role. AA forms a 1:1 complex, with a corresponding stability constant of log ß11 = 3.14 +/- 0.17 [1]. The formation of 1:1 and 1:2 complexes was detected for the U(VI)-nicotinate system (log ß11 = 3.73 +/- 0.30, log ß12 = 7.46 +/- 0.17 [1]) as well as for the U(VI)-phenylphosphonate system (log ß11 = 3.58 +/- 0.17, log ß12 = 6.81 +/- 0.10). At high U(VI) concentrations (1 mM), a precipitation of the formed complexes was observed for the U(VI) complexation by AA and PPA. The precipitates were analyzed with FT-IR spectroscopy and X-ray diffraction. To study the influence of different functional groups on the complexation of actinides in different oxidation states, comparable complexation studies are performed with Am(III).

References:

[1] B. Raditzky, K. Schmeide, S. Sachs, G. Geipel, G. Bernhard, Polyhedron (2009), doi:10.1016/j.poly.2009.08.010.

In various countries clay is discussed as possible host rock for a nuclear waste repository. The interaction of the clay with actinides, especially U(VI), is the focus of our work. Sorption experiments were performed to estimate the actinide migration in clay formations. Also the influence of humic acid (HA) is investigated. HA are ubiquitously found in natural environments and can interact with e.g. actinides of the nuclear waste. Natural clay contains HA and fulvic acid like organic matter, which can be released from the clay [1]. HA also forms stable colloids. Due to this behavior HA can influence the mobility of actinides, e.g. U(VI), in a nuclear waste repository.

Opalinus clay (OPA) from Mont Terri, Switzerland was studied. Batch sorption experiments were performed in order to determine the sorption ability of U(VI) ([U] = 1x10-6 M) onto OPA in the absence and presence of HA ([HA] = 10 mg/L, 50 mg/L) and of HA in the absence and presence of U(VI) using synthetic OPA pore water (OPAWA, [2], pH 7.6, I = 0.39 M) and NaClO4 (pH 3-10, I = 0.1 M) as background electrolyte. During these studies a large influence of calcite on the sorption behavior of U(VI) and HA was determined. Calcite presents a fraction of 13% in OPA and its ions occur also in the OPAWA ([Ca2+] = 0.03 M, [CO32-] = 5x10-4 M). In OPAWA, U(VI) forms with the ions in solution the neutral aquatic complex Ca2UO2(CO3)3 [3]. This complex dominates the speciation with a fraction of 99%. In sorption experiments it was shown, that this complex adsorbs weakly onto OPA. Normalized to the specific surface area of OPA (BET = 41.6 m2/g) the U(VI) sorption was determined with 0.05 ± 0.002 µg U/m2 clay. In further sorption studies it was shown that HA has no influence on the U(VI) sorption onto OPA. This was also proved by speciation calculations, which showed that also in the presence of HA the Ca2UO2(CO3)3(aq) complex is the dominating species in solution. In order to interpret the sorption data onto OPA, additional zeta potential measurements were performed, where between pH 0 and 7.5 a negative zeta potential for OPA was determined.

The HA sorption onto OPA in OPAWA was determined with 3.57±0.01 µg HA/m2 (10 mg/L) and 17.28±0.15 µg HA/m2 (50 mg/L). In the presence of U(VI), a slight increase of HA sorption (D = 0.3 µg HA/m2) was observed for [HA] = 50 mg/L. Species calculations showed that Ca2+ ions influence also the HA speciation, because Ca2+ is complexed by HA. Ca2+ is present in such a high concentration, that it saturates the binding sites of HA. Thus, only few binding sites, about 0.1% according to speciation calculations, are available for the complexation of U(VI). Consequently, U(VI) and HA have no effect on each other during the sorption studies. These experiments show the large influence of the calcite fraction of the OPA and thus the resulting composition of the OPAWA on the U(VI) and HA sorption. Thus, calcite should be taken into account for the safety case analysis of a nuclear waste repository.

[1] F. Claret et al., Sci. Total Environ. 317, 2003, 189.
[2] F.J. Pearson, PSI Internal Report TM-44-98-07, Switzerland, 1998.
[3] G. Bernhard et al., Radiochim. Acta 89, 2001, 511.

Plasma irradiation of high-quality SrTiO3 single crystals leads to room-temperature ferromagnetism. The saturation magnetization is about two orders of magnitude larger than in the pristine material. Structural analysis revealed a polycrystalline layer at the sample surface induced by the plasma irradiation. The results are discussed in the frame of grain-boundary-induced defect ferromagnetism.

Specic heat and magnetic susceptibility measurements, spanning low temperatures (T ≥ 40 mK) and high magnetic elds (B ≤ 14 T), have been performed on Cu(tn)Cl₂ (tn = C₃H₁₀N₂), a two-dimensional (2D) S = 1/2 spatially anisotropic triangular antiferromagnet realized by a square lattice with nearest- neighbor (J=k_B = 3 K), frustrating next-nearest-neighbor (0 < J'/J < 0.6), and interlayer (|J''/k_B| <3 mK) interactions [1]. The absence of long-range magnetic order down to T = 60 mK in B = 0 and the T² behavior of the specific heat for T ≤ 0.4 K and B ≥ 0 are considered evidence of 2D magnetic correlations. In fields lower than the saturation field, B_sat = 6.6 T, a specific heat anomaly, appearing near 0.8 K, is interpreted as a Berezinski-Kosterlitz-Thouless (BKT) phase transition. The magnetic phase diagram is remarkably consistent with the theoretical predictions [2], except for the point that B_sat(T -> 0) is shifted to values significantly lower than expected. Potential explanations for this observation will be discussed.

Anwendungsmöglichkeiten laserbeschleunigter Teilchenstrahlen in der Medizin

In structured or self-organized materials spatial confinement effects lead to structure- and interface-controlled modifications of the bulk transport properties. In part, such modifications can be accounted for by a classical master equation approach for the transport of the different charge carrier species. The rather large quantity of parameters, which enter such an approach, can more or less easily be adjusted to the dimensional characteristics, local potential changes at interfaces, and the electronic settings of the system as well as to temperature effects. On the other hand, a microscopically more detailed and mostly parameter-free picture is obtained from a quantum-mechanical treatment on the basis of the density-functional theory. An extension by a Green's function formalism allows the determination and analysis of electronic transport through contacted nanostructures. Examples will be given to demonstrate the applicability of the different approaches for dissipative and hopping transport through a regular array of nanostructures, for a mechanically triggered metal-insulator transition in nanowires, and for the enhanced conductivity at multiferroic domain walls.

Thermodynamic equilibration of complex systems like spin glasses or (degenerate) anisotropic spin crystals by numerical methods can be challenging due to the presence of multiple minima on the potential energy surface. This problem becomes pronounced especially at low temperature, where the system remains mainly in few states. We employ the anisotropic Heisenberg model in two dimensions to simulate and analyze the domain formation and the domain structure of multiferroic oxides. In particular, we discuss various techniques to improve the low-temperature equilibration behavior by means of a trigonal antiferromagnet with single-ion anisotropy. Furthermore, we present a localized sampling method for the Metropolis algorithm, which increases the acceptance ratio significantly.

Density-functional band-structure calculations have been carried out for two types of material combinations at heterophase boundaries in order to characterise the main influence factors on adhesion.
Strong binding at heterophase interfaces is often related to a favourable and directed electron redistribution in the vicinity of the boundary plane.
The propensity for such redistributions is reflected in materials parameters such as electronegativities, polarisabilities and the differences between the values of the two sides of the interface. Strong adhesion is indirectly also related to the lattice matching or mismatch, because that influences the density of suitable in-teraction sites in the boundary plane.
Finally, fixed local charges, which are characteristic for ionic compounds, introduce additional Coulomb and image charge interactions. The present comparison aims at assessing those latter interactions by comparing material combinations with one ionic partner to completely non-ionic combinations.

In nanostructured materials spatial confinement effects lead to structure-dependent modifications of the bulk transport properties. In part, such modifications can be accounted for by a classical master equation approach for the transport of the different charge carrier species. The rather large quantity of parameters, which enter such an approach, can more or less easily be adjusted to the dimensional characteristics and the electronic settings of the system as well as to temperature effects. On the other hand, a microscopically more detailed and mostly parameter-free picture is obtained from a quantum-mechanical treatment on the basis of the density-functional theory. An extension by a Green's function formalism allows the determination and analysis of electronic transport through contacted nanostructures. Examples will be given to demonstrate the applicability of the different approaches for dissipative and hopping transport through a regular array of nanostructures, for a mechanically triggered metal-insulator transition in nanowires, and for the enhanced conductivity at multiferroic domain walls.

In nanostructured materials spatial confinement effects lead to structure-dependent modifications of the bulk transport properties. In part, such modifications can be accounted for by a classical master equation approach for the transport of the different charge carrier species. The rather large quantity of parameters, which enter such an approach, can more or less easily be adjusted to the dimensional characteristics and the electronic settings of the system as well as to temperature effects. On the other hand, a microscopically more detailed and mostly parameter-free picture is obtained from a quantum-mechanical treatment on the basis of the density-functional theory. An extension by a Green's function formalism allows the determination and analysis of electronic transport through contacted nanostructures. Examples will be given to demonstrate the applicability of the different approaches for dissipative and hopping transport through a regular array of nanostructures, for a mechanically triggered metal-insulator transition in nanowires, and for the enhanced conductivity at multiferroic domain walls.

In structured or self-organized materials spatial confinement effects lead to structure- and interface-controlled modifications of the bulk transport properties. In part, such modifications can be accounted for by a classical master equation approach for the transport of the different charge carrier species. The rather large quantity of parameters, which enter such an approach, can more or less easily be adjusted to the dimensional characteristics, local potential changes at interfaces, and the electronic settings of the system as well as to temperature effects. On the other hand, a microscopically more detailed and mostly parameter-free picture is obtained from a quantum-mechanical treatment on the basis of the density-functional theory. An extension by a Green's function formalism allows the determination and analysis of electronic transport through contacted nanostructures. Examples will be given to demonstrate the applicability of the different approaches for dissipative and hopping transport through a regular array of nanostructures, for a mechanically triggered metal-insulator transition in nanowires, and for the enhanced conductivity at multiferroic domain walls.

We present a first-principles density-functional study of the structural, electronic, and magnetic properties of the ferroelectric domain walls in multiferroic BiFeO3. We find that domain walls in which the rotations of the oxygen octahedra do not change their phase when the polarization reorients are the most favorable and of these, the 109° domain wall centered around the BiO plane has the lowest energy. The 109° and 180° 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. Finally, we show that changes in the Fe-O-Fe bond angles at the domain walls cause changes in the canting of the Fe magnetic moments which can enhance the local magnetization at the domain walls.

We report cyclotron resonance (CR), transverse magnetoresistance (MR), and Hall effect studies of a series of n-type InAs1−xNx epilayers grown on GaAs with x up to 1%. The well-resolved CR absorption lines, the classical linear MR, Shubnikov–de Haas magneto-oscillations, and negative MR revealed in our experiments provide a means of probing the effect of the N atoms on the electronic properties of this alloy system and reveal qualitative differences compared to the case of the wider gap III-N-V compounds, such as GaAs1−xNx. In GaAs1−xNx electron localization by N levels that are resonant with the extended band states of the host crystal act to degrade the electrical conductivity at small x (~0.1%). These phenomena are significantly weaker in InAs1−xNx due to the smaller energy gap and higher energy of the N levels relative to the conduction band minimum. In InAs1−xNx the electrical conductivity retains the characteristic features of transport through extended states, with electron coherence lengths (l~100 nm at 2 K) and electron mobilities (µ=6×103 cm2 V−1 s−1 at 300 K) that remain relatively large even at x=1%.

Microorganisms, along with the abiotic physicochemical factors, strongly influence migration of uranium in nature. In contrast to the well investigated interactions of bacteria with uranium, the influence of archaea on the natural behaviour of this radionuclide is still not well studied. In this work the interactions of the acidothermophilic archaeon Sulfolobus acidocaldarius DSM 639 with U(VI) at acidic conditions (pH 1.5, 3, 4.5 and 6) were investigated. These pH values are relevant for some heavy metal and uranium polluted environments where S. acidocaldarius is also distributed. After the contact with the archaeal cells, U(VI) was rapidly complexed, whereby the binding capacity was strongly influenced by the pH value and the biomass concentration. A combination of X-ray absorption spectroscopy, Fourier-transform infrared spectroscopy, and time-resolved laser-induced fluorescence spectroscopy revealed that at highly acidic conditions (pH 1.5 and 3) U(VI) is predominantly bound to organic phosphate groups. At pH 4.5 carboxylic groups are involved in the U(VI) complexation as well. However, at this pH part of the added U(VI) was precipitated in inorganic uranyl phosphate mineral phases. The latter were the most predominant uranium complexes found after the treatment of the cells with U(VI) for 48 hours at pH 6. Transmission electron microscopic analysis of the cells treated at pH 4.5 showed extracellular and intracellular U(VI) accumulates. The extracellular complexes represented mainly inorganic uranyl phosphate complexes, which were formed due to the liberation of orthophosphate by the cells. The formation of the intracellular uranyl phosphate deposits is attributed to uncontrolled uptake of U(VI) as a result of the increased cell permeability due to the stress of the non-optimal pH and uranium toxicity. Our results demonstrate that at moderate acidic conditions S. acidocaldarius immobilizes U(VI) via biosorption and biomineralization.

Using combined electroluminescence (EL) and photoluminescence (PL) studies we establish that the energy transfer process from the Er³⁺ to the Ge-related oxygen-deficiency centers (GeODCs) plays the key role in enhancing the 404 nm EL intensity in Ge-rich SiO₂. Er doping induced structural modification does not appear to be relevant, which is deduced from the 404 nm PL quenching with increasing Er concentration, implying a gradual loss of GeODCs. In contrast to PL, the 404 nm EL intensity increases by 0.3% Er doping followed by a gradual decrease in intensity for higher Er concentrations, which is described in terms of a competition between the energy transfer process and the gradual segregation of Er due to the destruction of GeODCs with Er doping. This fact is further discussed in the light of ab initio molecular orbital calculations.

This paper reports on structural, optical, vibrational, and morphological properties of cobalt-doped CdS thin films, prepared by 90 keV Co+ implantation at room temperature. In this work, we have used cobalt concentration in the range of 0.34–10.8 at. %. Cobalt doping does not lead to the formation of any secondary phase, either in the form of metallic clusters or impurity complexes. However, with increasing cobalt concentration a decrease in the optical band gap, from 2.39 to 2.26 eV, is observed. This reduction is addressed on the basis of band tailing due to the creation of localized energy states in association with Urbach energy calculations. In addition, implantation gives rise to grain growth and increase in the surface roughness. Size and shape fluctuations of individual CdS grains, at higher fluences, give rise to inhomogeneity in strain. The results are discussed in the light of ion-matter interaction in the keV regime.

The controlled motion of magnetic domain walls (DWs) in nanowires is one of the fundamental issues for the realization of new concepts of high-density and ultrafast non-volatile data-storage devices. Locally welldefined confining potentials, e.g., created by notches, act as pinning sites for individual DWs . A spin polarized current, driven through the nanowire, yields the possibility to manipulate the magnetic configuration due to a transfer of spin-angular momentum. For a reliable spin-torque induced domain-wall depinning, low threshold currents are required in order to reduce stochastic temperature effects, caused by Joule heating as well as to avoid damage to the nanowire.

Here we present a concept to create pinning sites for DWs in magnetic nanowires without geometric constrictions:

The local modification of magnetic properties by means of ion irradiation (magnetic soft spots). Implantation of chromium ions into Ni80Fe20 causes a reduction of the saturation magnetization (Ms) and changes the crystalline magnetic anisotropy. The application of electron beam lithography (EBL) or focused ion beam (FIB) on the other hand enables a spatial resolution below 50 nm for this kind of magnetic patterning process. Pinning of DWs in magnetic soft spots is expected to be preferred compared to the environment, as the locally reduced Ms causes a decrease of the exchange energy associated with the DW. In order to verify the suitability of our concept, we fabricate magnetic soft spots into Ni80Fe20 nanowires by means of 15 kV Cr ion irradiation through an EBL shadow mask and examine the pinning characteristics for DWs.

In conclusion, magnetic soft spots realized via implantation of chromium are suitable as pinning sites for domain walls, avoiding a local increase of the current density in the nanowire due to supplementary spatial constriction.

In recent years, the technology of laser-based particle acceleration has developed at such a rate that compact and potentially more cost-effective accelerators are promised for medical application, e.g. for high precision hadron radiotherapy. Necessary requirements are the supply of stable and reliable particle beams with reproducible properties, sufficient particle intensities and monoenergetic spectra. Additionally, a precise dose delivery in an appropriate time and the exposure of a desired irradiation field are needed. Beside these physical demands, the consequences on detection and dosimetry as well as the radiobiological effect on living cells have to be investigated for the ultra-short pulsed laser-based particle beams. As a first step, the laser accelerator facility at the Jena Titanium:Sapphire system was customized for in vitro cell irradiation experiments and the delivered electron beam was im-proved with regard to its spectrum, diameter, dose rate and dose homogeneity. Furthermore, a custom-designed beam and dose monitoring system was established that enables real-time monitoring of the irradiation experiments and a precise determination of the dose delivered to the cells. Moreover, stable and reproducible beam properties were achieved during the whole three month experiment campaign. Dose-effect-curves were obtained for four cell lines and two endpoints, generally displaying a lower biological effectiveness for short-pulsed laser-accelerated electrons relative to the continuous 200 kV X-ray reference irradiation. Possible reasons will be discussed.

The novel technology of particle acceleration based on high intensity laser systems promises radiotherapy accelerators of compact size and reasonable costs. Laser acceleration results in ultra-short pulsed particle beams (in the region of 100 fs) with very high pulse dose rate (more than 1012 Gy/min) and is used in single shot physics experiments so far. Before a conceivable clinical application such particle beams have to be characterized in terms of their radiobiological properties and dosimetric detection and must allow a stable and reliable dose delivery. First in vitro cell irradiations with laser accelerated electron beams were performed and dose-effect-curves were obtained for four cell lines and two endpoints. Experiments have been performed at the Jena Titanium:Sapphire 10 terawatt laser system JETI, accelerating electrons to energies of up to 20 MeV. Before cell irradiation, the JETI system was optimized, adjusting the electron energy and beam spot size and improving the dose rate and homogeneity. Cell irradiations with doses in the range of 0.3 to 10 Gy have been performed for two squamous cell carcinoma cell lines with different radiosensitivity (FaDu, SKX) and two normal tissue cell lines (mammary gland epithelial cells 184A1, human skin fibroblasts HSF2). Each sample was equipped with radiochromic films used for retrospective precise dose determination. A Roos ionization chamber and a Faraday Cup monitored the beam providing online dose information necessary for irradiation control. Following to the irradiation the cell survival fraction was determined using clonogenic survival assay. Furthermore DNA double strand breaks were analyzed by immunochemical detection of the colocalized γH2AX and 53BP1 proteins 24 h after irradiation. Reference irradiation with a conventional X-ray tube (200 kV) was performed in parallel with experiments at JETI.
Samples were irradiated over a period of 3 months with described doses in which a reasonably stable and reproducible beam could be achieved monitored by the reliable accurate dosimetry system. The dose-effect-curves obtained indicate a lower biological effectiveness for the ultra-short pulsed laser accelerated electron beams in comparison with continuous X-rays. Possible reasons could be the different energy spectra impacting on cells as well as the low mean and ultra-high pulse dose rate of the electron beam. The effects will be discussed based on further experimental results.
This work has been supported by the German Federal Ministry of Education and Research (BMBF), grant no. 03ZIK445.

In recent years, the technology of laser-based particle acceleration was rapidly developed promising compact and potentially more cost-effective accelerators for medical applications, especially for hadron therapy. Beside specific physical requirements, e.g. stability and reliability of the particle beam as well as sufficient particle intensities, these ultra-short pulsed particle beams have to be investigated with regard to their radiobiological characteristics.
As a first step, in vitro cell irradiation experiments were performed using laser accelerated electron beams generated at the Jena Titanium:Sapphire laser system (JETI). Two biological endpoints, the clonogenic survival and remaining DNA double-strand breaks, were analyzed revealing in general a lower biological effectiveness for laser accelerated electrons relative to the continuous 200 kV X-ray reference source. Possible reasons might be the low mean and ultra-high pulse dose rate as well as the different electron spectra delivered to the cells.
The influence of the ultra-high pulse dose rate was assessed using pulsed electrons produced by the electron accelerator ELBE (Electron Linac for beams with high Brilliance and low Emittance) at the Forschungszentrum Dresden-Rossendorf. Based on a superconducting linear accelerator ELBE provides monoenergetic electrons of 20 MeV with a micropulse repetition rate of 13 MHz, a variable time structure that allows for single pulse or continuous irradiations and pulse doses tuneable over more than six orders of magnitude. Consequently, the ELBE beam can be used to mimic laser accelerated ultra-short pulses or for a continuous electron beam generated in a conventional radiotherapy linac.
Both pulse regimes were applied in the present study in order to investigate the influence of the pulse dose rate on the biological effectiveness independent on electron spectra, irradiation setup and dosimetry approach. The biological endpoints assessed at the JETI experiments were also analysed in two normal human cell lines (fibroblast, epithelial). In parallel, the clonogenic survival and DNA double-strand breaks remaining 24 hours post irradiation were also determined at the 200 kV X-ray reference source. To sum up the preliminary results, no significant differences were found for the biological effectiveness of continuous and ultra-short pulsed ELBE electrons relative to 200 kV X-rays. Further results and possible explanations will be discussed.
This work has been supported by the German Federal Ministry of Education and Research (BMBF) under contract 03ZIK445.

Objective
The novel technology of particle acceleration based on high intensity laser systems promises accelerators of compact size and reasonable costs and may significantly contribute to a widespread use of high precision hadron radiotherapy. Although some basic properties of laser acceleration are reasonably well known from theory, simulations and fundamental physical experiments, several further requests have to be fulfilled for its medical application such as supply of a stable and reliable particle beam with reproducible properties and precise delivery of dose in an appropriate irradiation time with required exposure of a desired irradiation field. Moreover, the ultra-short pulsed (in the region of 100 fs) particle beams with resulting high pulse dose-rate (more than 1012 Gy/min) have to be characterized with regard to there radiobiological properties. First in-vitro cell irradiations with laser accelerated electron beams were performed and dose-effect-curves were obtained for four cell lines and two endpoints.

Material and Methods
Experiments have been performed at the Jena Titanium:Sapphire 10 terawatt laser system JeTi. Laser pulses (80 fs duration, 2.5 Hz repetition rate) were focused into a helium gas jet, accelerating electrons to energies of up to few ten MeV. Before irradiation, the JeTi system was optimized for cell experiments: the electron spectrum was limited to a minimum energy of 3 MeV, the beam spot size was adjusted and the dose rate and homogeneity were improved. Cell irradiations with doses in the range of 0.3 to 10 Gy have been performed for two squamous cell carcinoma (FaDu, SKX) and two normal tissue (mammary gland epithelial cells 184A1, human skin fibroblasts HSF2) cell lines. Each sample was equipped with two Gafchromic EBT radiochromic films, one in front and one behind the cell monolayer, used for retrospective precise dose determination. A Roos ionization chamber and a Faraday Cup monitored the beam providing on-line dose information necessary for irradiation control.
Following to the irradiation the cell survival fraction was determined using clonogenic survival assay. In addition, DNA double strand breaks present in cell 24 h after irradiation were analyzed by immunochemical detection of co-localized gamma-H2AX and 53BP1 molecules. Reference irradiation with a conventional X-ray tube (200 kV) was performed in parallel with experiments at JeTi.

Results
Normally used for physical single-shot experiments, the JeTi was customized for a long-time cell irradiation. Samples were irradiated at 13 experiment days over a period of 10 weeks. A reasonably stable and reproducible beam was achieved. Reviewed as average out of all cell irradiations a mean dose per pulse of 2.4 mGy was obtained. Comparing all samples, a variation in beam intensity of up to 40 % within one day and up to 130 % within all days was observed, but was compensated during cell irradiations by means of the on-line dose monitoring system. Dose homogeneity was examined for all samples within the target area and the inhomogeneity obtained was less than 10 % for all days and all applied doses. Although still preliminary, the dose-effect-curves obtained show in general a lower biological effectiveness for the laser accelerated electron beams in comparison with conventional X-rays. Possible reasons will be discussed.

Conclusions
Further experiments are prepared at a 100 terawatt laser system, which will lead to enhanced energy and intensity of the electron beam but also provide laser accelerated proton beams for cell irradiation studies.

The work was supported by the BMBF, grant no. 03ZIK445

Purpose: The novel technology of particle acceleration based on high intensity laser systems promises ion radiotherapy accelerators of compact size and reasonable costs. Laser acceleration results in ultra-short pulsed particle beams with very high pulse dose-rate and is used in single shot physics experiments so far. Such particle beams have to be characterized in terms of their radiobiological properties and dosimetric detection and must allow a stable and reliable dose delivery before a conceivable clinical application. In a first step, systematic in vitro cell irradiations with laser accelerated electron beams were performed and dose-effect-curves were obtained.

Material: Experiments have been performed at the Jena Titanium:Sapphire (JeTi) 10 terawatt laser system. Laser pulses (80 fs duration) were focused into a helium gas jet, accelerating electrons to energies of up to 20 MeV. Before cell irradiation, the JeTi system was optimized, adjusting the electron energy and beam spot size and improving the dose rate and homogeneity. Cell irradiations were realized for two squamous cell carcinoma (FaDu, SKX) and two normal tissue (184A1, HSF2) cell lines in a dose range from 0.3 Gy to 10 Gy. For irradiation control a Roos ionization chamber and a Faraday Cup monitored the beam providing on-line dose information. Additional Gafchromic EBT radiochromic films were used for retrospective exact dose determination at the cell site. Referring to irradiation the survival fraction was determined and furthermore DNA double strand breaks were analyzed by immunochemical detection of the co-localized γH2AX and 53BP1 molecules 24 h after irradiation. A conventional X-ray tube (200 kV) was used for reference irradiation.

Results: The JeTi laser accelerator was successfully customized for long-time irradiation of cell samples with prescribed doses. Samples were irradiated at 13 experiment days over a period of 3 months. A reasonably stable and reproducible beam was achieved. Dose homogeneity was examined for all samples inside the target area and the inhomogeneity obtained was less than 10 % for all days and all applied doses. The determined dose-effect-curves show in general a reduced biological effectiveness for the laser accelerated electron beams in comparison with conventional X-rays. The effect of the high pulse dose-rate among the possible reasons will be discussed.

Conclusion: Further experiments are prepared at a 100 terawatt laser system, which will provide laser accelerated proton beams for cell irradiation studies.

This work was supported by the BMBF, grant no. 03ZIK445

Mit der neuartigen Technologie der Laser-Beschleunigung von Ionen werden kürzere Teilchenpakete (einige 10 Femtosekunden) mit wesentlich geringerer Pulsfrequenz und damit einhergehend einer viel höheren Puls-Dosisleistung erzeugt. Ziel ist es, durch Einsatz dieser Technologie die bisherige Strahlentherapie zu verbessern.
In einem ersten Schritt bei der Ermittlung einer möglicherweise veränderten biologischen Wirksamkeit dieser neuen Strahlenqualität wurden in vitro Bestrahlungsexperimente von Tumor- und Normalgewebszellen mit laserbeschleunigten Elektronen durchgeführt. Für die Experimente wurde das 10-Terawatt-Lasersystem JETI in Jena genutzt. Voraussetzung für die Zellbestrahlung war die Anpassung des Lasersystems und der Aufbau eines geeigneten Bestrahlungsplatzes einschließlich eines Dosimetriesystems. Im Anschluss an die Bestrahlung wurde das klonogene Zellüberleben mittels Koloniebildungstests bestimmt. Ergänzend hierzu wurde als weiterer biologischer Endpunkt der Nachweis der mit der DNA-Reparatur assoziierten Proteine g-H2AX und p53BP1 gewählt. g-H2AX reguliert als Histon die Zugänglichkeit der DNA für Reparaturmechanismen und ist mitverantwortlich für die Arretierung der Zelle in einer Phase des Zellzyklus als zelluläre Antwort auf niedrige Strahlendosen. Zusammen mit p53BP1 bildet es unmittelbar nach der Bestrahlung diskrete Foci an DNA-Doppelstrangbrüchen. Das verglichen mit unbestrahlten Proben erhöhte Auftreten von g-H2AX/p53BP1 Foci 24 h nach Bestrahlung ist ein Maß für residuelle, Dosis vermittelte DNA-Doppelstrangbrüche. Der Nachweis erfolgte mit dem g-H2AX/p53BP1 Foci Assay. Die Dosis-Effekt Kurven für beide Endpunkte werden präsentiert und diskutiert.
Die Genauigkeit beider Assays soll künftig durch Teilautomatisierung (z. B. FACS) verbessert werden. Des Weiteren wurde mit der Vorbereitung von Zellbestrahlungsexperimenten mit laserbeschleunigten Protonenstrahlen begonnen.

Safety assessment of radioactive waste repositories in salt rock formations considers the overlying sedimentary rock above the salt domes as important barrier. Sorption on mineral surfaces of the sediment can retard the transport of many contaminants, namely radionuclides, considerably. Previously, the retention of radionuclides has been described in respective computer programs by temporally constant distribution coefficients.
In the present study, an existing transport program r3t [1] is extended towards a more realistic description of the radionuclide migration under changing geochemical conditions. The methodology developed here is based on a description of the sorption of radionuclides as a function of important influence factors such as pH, pCO2, ionic strength, and the mineral phases being present. Applying surface complexation models, multidimensional matrices of “smart Kd”-values can be computed a-priori. The reactive transport model r3t then can call for each time-space point Kd values adapted for the correct geochemical conditions. The biggest challenge here was finding a fast and robust algorithm for search and averaging in multidimensional matrices with non-equidistant population (see e.g. [2]). First results are presented for a test case where respective site-specific geochemical conditions in the overlying rock have been evaluated, mainly consisting of tertiary and quaternary sands and clays [3].
References:
[1] Fein, E., Software Package r3t. Model for Transport and Retention in Porous Media. Final Report. Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) mbH, Report GRS-192, Braunschweig 2004.
[2] McNames, J.: A fast nearest neighbor algorithm based on a principal axis search tree. IEEE Trans. Pattern Analysis Machine Intell. 23 (2001), 964-976.
[3] Klinge, H., Köthe, A., Ludwig, R.-R., Zwirner, R., Geologie und Hydrogeologie des Deckgebirges über dem Salzstock Gorleben. Z. Angew. Geol. 2 (2002), 7-15.

Die vorliegende Erfindung betrifft eine hochgeordnete Nanostruktur und Sensor, in der bzw. dem organische Molekülgruppen, die spezifische Bindungseigenschaften für ein Zielmolekül haben, geordnet gebunden sind, und deren Verwendung. Anwendungsgebiet dafür finden sich in der Biotechnologie, Verfahrenstechnik, Umwelttechnik und Pharmazie, insbesondere bei der Herstellung von Biosensoren, in der biomedizinischen Analytik, bei der Beseitigung von Schadstoffen und Pathogenen, in der DNA-Analytik, für die Herstellung von Filtermaterialien, für Separationsverfahren, für Katalysatoren und in der medizinischen Therapie. Die Aufgabe der Erfin-dung ist es, eine Struktur zur Verfügung zu stellen, in der organische Molekülgruppen, insbesondere Molekülgruppen, die spezifische Bindungseigenschaften haben, geordnet gebunden sind, und dadurch die von den organischen Molekülgruppen gebundenen Substanzen in die Nähe funktioneller Bestandteile zu bringen. Dies wird gelöst durch eine Nanostruktur, die selbstorganisierende Prote-ine, an die Aptamere oder andere organische Molekülgruppen, die spezifische Bindungseigenschaften für ein Zielmolekül aufweisen, gebunden sind, und an die selbst-organisierenden Proteine gebundene anorganische Nanopartikel enthält.

hat nicht vorgelegen

Background: The novel technology of particle acceleration based on high intensity laser systems promises proton therapy accelerators of compact size and reasonable costs. Laser acceleration results in ultra-short pulsed (≈100 fs) particle beams with very high pulse dose-rate (in the order of 1012 Gy/min). These beams have to be characterized with regard to their radiobiological and dosimetric properties and must allow a stable and reliable dose delivery before a conceivable clinical application is possible. The results of the worldwide first systematic in vitro cell irradiation experiments with laser accelerated electrons will be presented. Moreover, the developed dosimetric requirements for cell irradiation experiments with laser accelerated protons of low energy will be presented.

Material and Methods: The experiments with laser accelerated electrons have been performed at the Jena Titanium:Sapphire (JeTi) 10 TW laser system. Laser pulses were focused into a helium gas jet, accelerating electrons to energies of up to 20 MeV. Cell irradiations were realized for two squamous cell carcinoma and two normal tissue cell lines in a dose range from 0.3 Gy to 10 Gy. For irradiation control an ionization chamber and a Faraday Cup provided online dose information. Additional Gafchromic EBT radiochromic films were used for retrospective exact dose determination at the cell site. Referring to irradiation the survival fraction was determined and furthermore DNA double strand breaks 24 h after irradiation were analyzed.
Moreover, an integrated dosimetry and cell irradiation device (IDCID) has been designed and optimized for laser accelerated proton beams of low energy. It integrates an online- and absolute dosimeter system in combination with an in vitro cell irradiation device. Furthermore, the different detectors and dosimeters of the IDCID have been tested and cross calibrated at the tandem accelerator of the Forschungszentrum Dresden-Rossendorf. For the application of radiochromic films within the IDCID, EBT films have been calibrated for different proton spectra at the eye irradiation facility of the Helmholtz Zentrum Berlin.

Results:

The determined dose-effect-curves for laser accelerated electrons show in general a reduced biological effectiveness in comparison with conventional X-rays. The effect of the high pulse dose-rate among the possible reasons will be discussed. Furthermore, calibration curves for EBT films have been determined for 6 energies between 5 and 62 MeV. For energies between 10 and 62 MeV no significant energy dependence was found. Moreover, results of the optimization and cross calibration of the detectors included in the IDCID will be shown.

Conclusion: A laser particle accelerator was successfully used to perform long-time systematic in vitro cell irradiations. Further cell irradiation experiments with laser accelerated protons from a 100 TW laser system are prepared.

This work was supported by the BMBF, grant no. 03ZIK445

Purpose: The aim of this paper is to investigate the energy dependence of the radiochromic film type, Gafchromic EBT-1, when scanned with a flatbed scanner for film readout.

Methods: Dose response curves were determined for 12 different beam qualities ranging from a 10 kVp x-ray beam to a 15 MVp x-ray beam and include also two high energy electron beam qualities (6 and 18 MeV). The dose responses measured as net optical density (netOD) for the different beam qualities were normalized to the response of a reference beam quality (6 MVp).

Results: A strong systematic energy dependence of the film response was found. The lower the effective beam energy the less sensitive the EBT-1 films get. The maximum decrease in dose for the same film response between the 25 kVp and 6 MVp beam qualities was 44 %. Additionally, a difference in energy dependence for different doses was discovered, meaning that higher doses show a smaller dependency on energy than lower doses. The maximum decrease in normalized netOD was found to be 25 % for a dose of 0.5 Gy relative to the normalized netOD for 10 Gy. Moreover, a scaling procedure is introduced, allowing the correction of the energy dependence for the investigated beam qualities and also for comparable x-ray beam qualities within the energy range studied.

Conclusions: A strong energy dependence for EBT-1 radiochromic films was found. The films were readout with a flatbed scanner. If the effective beam energy is known, the energy dependence can be corrected with the introduced scaling procedure. Further investigation of the influence of the spectral band of the readout device on energy dependence is needed to understand the reason for the different energy dependence found in this and previous works.

Background: The novel technology of particle acceleration based on high intensity laser systems promises accelerators of compact size and reasonable costs and may significantly contribute to a widespread use of hadron radiotherapy. Although some basic properties of laser acceleration are reasonably well known from theory, simulations and fundamental physical experiments, several requests have to be fulfilled for its medical application. Moreover, the ultra-short pulsed (≈100 fs) particle beams with resulting high pulse dose-rate (in the order of 1012 Gy/min) have to be characterized with regard to their radiobiological properties. Therefore a precise dosimetry is necessary that takes into account the special characteristics of the laser accelerated protons. Special attention has to be drawn on the low energy (<10 MeV) of the available laser accelerated proton beams.

Material and Methods: An integrated dosimetry and cell irradiation device has been designed and optimized for the use with a laser accelerated proton beam of low energy. The device consists of a kapton vacuum window, an ultra-thin (25 µm) ionisation chamber for online dose information, a faraday cup inset for absolute dosimetry that can be replaced with a cell holder inset for cell irradiations. Moreover radiochromic films, i.e. Gafchromic EBT, can be placed in the cell holder inset matching the plane of the cell mono layer. Radiochromic films can be used to determine the two dimensional dose distribution and also for absolute dosimetry. For these purposes Gafchromic EBT films have been calibrated for different proton spectra at the eye irradiation facility of the Helmholtz Zentrum Berlin. Moreover first tests of the Faraday cup and the ionisation chamber have been carried out at the tandem accelerator of the Forschungszentrum Dresden-Rossendorf to characterize these detectors.
Fig 1: Integrated dosimetry and cell irradiation device

Results: Calibration curves for EBT films have been determined for 6 energies between 5 and 62 MeV and doses between 0.5 and 15 Gy. For energies between 10 and 62 MeV no significant energy dependence was found, whereas for 5 MeV protons the film response is reduced by up to 25 % compared to the 62 MeV proton beam quality. Moreover, this reduction in film sensitivity is dose depend. At the tandem accelerator the dependency of the Faraday cup signal from air pressure and guard ring voltage was determined. A more detailed cross calibration of Faraday Cup, ionization chamber and radiochromic films is ongoing and will be presented.

Conclusion: An integrated dosimetry and cell irradiation device for in vivo cell irradiation experiments with laser accelerated protons of low energy was designed, built and started to characterize. This includes the calibration of radiochromic films (Gafchromic EBT) and first characterizations of the different detectors.

Purpose: Clinically safe and effective treatment of intra-fractionally moving targets with scanned ion beams requires dedicated delivery techniques such as beam tracking. Apart from treatment delivery, also appropriate methods for validation of the actual tumor irradiation are highly desirable. In this contribution the feasibility of four-dimensionally (space and time) resolved, motion-compensated in-beam positron-emission-tomography (4DibPET) was addressed in experimental studies with scanned carbon ion beams.
Methods: A polymethyl methracrylate (PMMA) block sinusoidally moving left-right in beam's eye view was used as target, radiological depth changes were introduced by placing a stationary ramp-shaped absorber proximal of the moving target. Treatment delivery was compensated for motion by beam tracking. Time-resolved, motion-correlated in-beam PET data acquisition was performed during beam delivery with tracking the moving target, and prolonged after beam delivery first with the activated target still in motion and, finally, with the target at rest. Motion-compensated 4DibPET imaging was implemented and the results were compared to a stationary reference irradiation of the same treatment field. Data were used to determine feasibility of 4DibPET but also to evaluate offline in comparison to in-beam PET acquisition.
Results: 4D in-beam as well as offline PET imaging was found to be feasible and offers the possibility to verify the correct functioning of beam tracking. Motion-compensation of the imaged b+-activity distribution allows recovery of the volumetric extension of the delivered field for direct comparison with the reference stationary condition. Observed differences in terms of lateral field extension and penumbra in the direction of motion were typically less than 1 mm for both imaging strategies in comparison to the corresponding reference distributions. However, in-beam imaging retained a better spatial correlation of the measured activity with the delivered dose.
Conclusions: 4DibPET is a feasible and promising method to validate treatment delivery of scanned ion beams to moving targets. Further investigations will focus on more complex geometries and treatment planning studies with clinical data.

Many bacteria are covered with a protein envelope. These surface layer (s-layer) proteins are closely attached and anchored to the secondary cell wall polymer. The proteins used in our group derive from strains of Lysinibacillus species isolated from a uranium mining waste pile near Johanngeorgenstadt, Saxony, Germany. Once purified the disassembled S-layer keep the ability of self-organizing and self-assembling on interfaces. In vitro they form a paracrystalline protein lattice with defined pores and cavities as it can be naturally found on the bacterial surface. These protein sheets either coil up to tube-like structures or attach to surfaces. In addition to the self- assembling and organizing properties these proteins can bind high amounts of heavy metals. The ability to form monomolecular layers at interfaces qualifies them as tool for nano-patterning of surfaces. We are able to cover various surfaces with these proteins with nearly full coverage. This is possible due to recrystallization of monomers on polyelectrolyte coated surfaces. The recrystallization process can be monitored by AFM. AFM-images show the periodic nature of the protein lattice. The monomolecular character of the attached protein lattice was proven during the growth and afterwards by nanolithographic removal of the proteins. Different functional groups of the proteins are provided as binding sites for modifications such as crosslinking of molecules or binding or nucleation of inorganic particles. Therefore the lattice is a perfect immobilization matrix for different compounds as well as the assembly of sensory surfaces. A recently started project aims the development of a sensor for the optical readout of a chemical signal.
The efficient metal binding combined with the periodic alignment is used in other applications to create nanoparticles with a narrow size distribution. Currently we are optimizing the composition of the particles for photocatalysis. The high metal binding capacity itself turns the proteins into a promising material for filtering solutions as it is naturally used by the bacteria.

In the context of nuclear waste management, long-term safety assessments have shown that selenium-79, released from the solid waste matrix, could be one of the major isotopes contributing to the global radioactivity potentially reaching the biosphere. Selenium has a quite complex speciation, with four main oxidation states, depending on both the pH and the redox potential of the surrounding environment. Sorption onto minerals can strongly affect the availability and the mobility of selenium. It is thus of great importance to be able to characterize both at a macroscopic and a microscopic level the different processes (retention, reduction, surface precipitation, …) that can potentially take place.
Regarding the multi-barrier concept considered for deep underground storage of high level and long-lived radionuclides, clays are candidates as host rock as well as backfill materials. The main phases constituting clay rocks are minerals such as montmorillonite, bentonite, or illite, but also other compounds like iron oxides, titanium oxide, pyrite, calcite and organic matter. It has already been shown that clays and iron oxides can sorb and reduce selenium(VI) and selenium(IV) (Nguyen et al. (2005), Scheinost and Charlet (2008), Charlet et al. (2007)).
Thus, sorption experiments of selenium(VI) and selenium(IV) onto kaolinite and illite have been performed. Kaolinite and illite have been investigated since they are abundant and well crystallized clay mineral in soils. To get a better understanding of involved sorption mechanisms, a combination of both macroscopic and microscopic measurements have been used.
Kaolinite KGa1-b from the Clay Mineral Society repository has been used without further pretreatment. Illite du Puy (France) has been purified in order to remove auxiliary and minor phases to get a homo-ionic “Na-illite” clay. Then, batch experiments aiming at studying the sorption behaviour of selenium(IV) onto kaolinite and illite have been performed in NaCl and NaClO4. Preliminary results show that clays have higher affinity towards selenium(IV) compared to selenium(VI), which is an agreement with former studies on iron and aluminium oxides (Rovira et al. (2008). The influence of the suspensions´pH, as well as the ionic strength effect has been investigated. All the experiments have been performed under anoxic conditions in a glove box under N2 atmosphere (O2 < 1 ppm). Selenium speciation in solution has been checked using Hydride Generation-Atomic Absorption Spectroscopy measurements. The oxidation state of the selenium species once sorbed onto the kaolinite and illite surface has been evidenced using X-Ray Photoelectron Spectroscopy.
Electrophoresis measurements have also been performed during this work. Comparison between the zeta potential of the kaolinite and illite surfaces before and after selenium oxyanions retention has been done, to check whether the sorption takes place by chemical bonding formation or rather by electrostatic attraction.
Finally, ATR-FTIR measurements have been performed using an ATR ZnSe crystal. By comparison with former IR measurements concerning selenato and selenito-ligands containing complexes as well as phases with sorbed selenium species, the fashion binding of selenium(VI) and selenium(IV) onto illite has been evidenced.

Stratified two-phase flow regimes can occur in the main cooling lines of Pressurized Water Reactors, Chemical plants and Oil pipelines. A relevant problem occurring is the development of wavy stratified flows which can lead to slug generation. Because slug flow cannot be predicted with the required accuracy and spatial resolution by the one-dimensional system codes, the stratified flows are increasingly modelled with computational fluid dynamics (CFD) codes. In CFD, closure models are required that must be validated. The recent improvements of the multiphase flow modelling in the ANSYS CFX code make it now possible to simulate these mechanisms in detail. In order to validate existing and further developed multiphase flow models, high-resolution measurement data is needed in time and also in space. For the experimental investigation of co-current air/water flows, the HAWAC (Horizontal Air/Water Channel) was built. The channel allows in particular the study of air/water slug flow under atmospheric pressure. Parallel to the experiments, CFD calculations were carried out. The two-fluid model was applied with a special turbulence damping procedure at the free surface. An Algebraic Interfacial Area Density (AIAD) model on the basis of the implemented mixture model was introduced, which allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface using the local liquid phase volume fraction value. The behaviour of slug generation and propagation at the experimental setup was qualitatively reproduced by the simulation, while local deviations require a continuation of the work. The creation of small instabilities due to pressure surge or an increase of interfacial momentum should be analysed in the future. Furthermore, experiments with pressure and velocity measurements are planned and will allow quantitative comparisons, also at other superficial velocities.

Strong increase of usage of three-dimensional Computational Fluid Dynamics (CFD) in industrial applications because for instance
slugging,
pressurized thermal shocks,
coolant mixing,
thermal striping
cannot be predicted by traditional one-dimensional system codes with the required accuracy and spatial resolution.

To investigate the irradiation-induced degradation of the mechanical properties of Cu-containing reactor pressure vessel steels, a set of model alloys was fabricated and neutron-irradiated up to four different doses, 0.026, 0.052, 0.10, and 0.19 dpa, using the same neutron flux (140 x10^-9 dpa/s). A series of complementary experimental techniques have been applied to these samples, including PAS and SANS. We report here the analyses the of small-angle neutron scattering (SANS) experiments for the two binary Fe-Cu model alloys: Fe-0.3%Cu and Fe-0.1%Cu. Size-resolved cluster distributions functions were extracted from the scattering data and characterized by the peak radius of the distribution and the total volume fraction of the detectable precipitate clusters. A significant difference in the results for the Cu-rich and the Cu-poor model alloys could be observed. The aim of the present study is to understand the observed trends on the base of rate theoretical (RT) cluster dynamic simulations.
To this end, the time evolution of the precipitate clusters under the given irradiation conditions were simulated using standard rate theory models for pure Cu clusters. While reasonable model parameters could be found to describe the experimental data of the Fe-0.3%Cu alloy, it was impossible to reproduce the data for the Cu-poor model alloy this way. By linking the rate theory models to classical nucleation theory it could be demonstrated that no RT model could do so – no matter how involved the point defect dynamics – as long as the Cu precipitation process itself is not changed. Different mechanisms can be thought off to result in such modifications, among them heterogeneous nucleation with nanovoids as nucleus for further Cu growth, or the formation of mixed vacancy-copper aggregates throughout.
We therefore augmented our rate theory model to allow for the additional absorption of vacancies by the Cu-rich precipitates and an accompanied change in the interface energy between iron matrix and mixed clusters. Adjusting the model parameters properly the entire set of data point for all four doses and both compositions could be reproduced giving confidence that the basic idea of our RT model are reasonable. In addition, it was possible to provide some estimates on the time evolution of the average composition of the precipitate clusters. They exhibit – without any re-fitting – the same trends as the experimental cluster compositions deduced from the A-ratio of the SANS signals.

Ferritic-martensitic chromium steels are candidate materials for future applications in both Gen-IV fission and fusion technology. Experimental investigation of Fe-Cr alloys is important for the understanding of the effect of chromium on the irradiation behaviour of more complex alloys.
The materials investigated in this work are four binary Fe-Cr alloys of commercial purity with chromium contents between 2.5 and 12.5at%. Neutron irradiation was performed in the reactor BR2 at Mol (Belgium) at a temperature of 300°C and neutron flux of 9x10¹³ cm^-2s^-1 (E > 1 MeV). The neutron exposures expressed in units of displacements per atom correspond to 0.6 and 1.5 dpa.
In the SANS experiments carried out at the SANS-2 facility of GKSS, a wavelength of 0.58 nm and three detector-sample distances of 1, 4 and 16 m were used. The samples were placed in a saturation magnetic field. Special details related to the analysis of the SANS results (e.g. interference for concentrated solutions, bimodal distribution of scatterers) will be discussed in the full paper. The scattering curves obtained for the unirradiated conditions of the four Fe-Cr alloys were taken as reference in order to calculate difference scattering curves for the irradiated conditions.
We have found that (1) the volume fraction of scatterers slightly increases with neutron exposure (Fe-9at%Cr) or exhibits a saturation (Fe-2.5, 5 and 12.5at%Cr), (2) the volume fraction at 1.5 dpa is an increasing function of the chromium level with a slight increase up to Fe-9at%Cr and an abrupt increase between 9 and 12.5at%Cr, (3) the radii of irradiation-induced scatterers are essentially less than 8 nm and the size distributions can be reasonably described by a monomodal (Fe-2.5, 5 and 12.5at%Cr) or a bimodal (Fe-9at%Cr) distribution, (4) the A-ratio of 2.05 obtained for Fe-12.5at%Cr corresponds with the expectation for the alpha’-phase, (5) for the lower chromium levels the A-ratio can be explained neither as alpha’ nor as vacancy clusters alone, clusters composed of chromium and impurity carbon are possible candidates.
Conclusions will be drawn on the effect of the chromium content and the neutron exposure on the concentration and nature of the irradiation-induced scatterers. For the special case of Fe-12.5at%Cr the volume fraction of alpha’ and the solubility limit for chromium in iron at the irradiation temperature can be estimated.

Invited talk at 440th WE Heraeus Seminar, Frauenwörth 2009, Laser driven particle and x-ray sources for medical applications

Recent success in laser-driven particle acceleration has increased interest in laser-generated “accelerator-quality” beams, for example, protons and ions have been produced with up to several tens of MeV per nucleon, and with extremely low emittance (<0.01 mm mrad, normalized). Compact, high-gradient laser-accelerators are therefore now being discussed as a potentially viable technology for a host of particle-beam applications, including future compact medical accelerators for medical diagnostics and therapy. After commissioning of a 150 TW laser system at the FZD, a joint research center for radiation therapy with laser-accelerator ions is being established together with the OncoRay Center for Radiation Research in Oncology, and the University Clinic of the Technical University of Dresden. The present status and future plans of the center, and the results from first proton acceleration experiments at FZD will be presented.

In the context of nuclear waste management, long-term safety assessments have shown that selenium-79, released from the solid waste matrix, could be one of the major isotopes contributing to the global radioactivity potentially reaching the biosphere. Selenium has a quite complex speciation, with four main oxidation states, depending on both the pH and the redox potential of the surrounding environment. Sorption onto minerals can strongly affect the availability and the mobility of selenium. It is thus of great importance to be able to characterize both at a macroscopic and a microscopic level the different processes (retention, reduction, surface precipitation, …) that can potentially take place.
Regarding the multi-barrier concept considered for deep underground storage of high level and long-lived radionuclides, clays are candidates as host rock as well as backfill materials. Clays like illite, kaolinite, montmorillonite and bentonite constitute the main phases of clay rocks, together with other compounds like iron oxides, titanium oxide, pyrite, calcite and organic matter. We decided to focus our work on Illite since it is an abundant and well crystallized clay mineral in soils.
Thus, retention properties of illite towards selenium(IV) have been investigated during this study, using a combination of both macroscopic and microscopic measurements.
Illite du Puy (France) has been used as the sorbing phase. It has been purified in order to remove auxiliary and minor phases to get a homo-ionic “Na-illite” clay. Then, batch experiments aiming at studying the sorption behaviour of selenium(IV) onto illite have been performed in NaClO4. The influence of the suspensions´pH, as well as the ionic strength effect has been investigated. All the experiments have been performed under anoxic conditions in a glove box under N2 atmosphere (O2 < 1 ppm). Selenium speciation in solution has been checked using Hydride Generation-Atomic Absorption Spectroscopy measurements. The oxidation state of the selenium species once sorbed onto the illite surface has been evidenced using X-Ray Photoelectron Spectroscopy.
Electrophoresis measurements have also been performed during this work. Comparison between the zeta potential of the illite surfaces before and after selenium(IV) sorption has been done, to check whether the sorption takes place by chemical bonding formation or rather by electrostatic attraction.
Finally, ATR-FTIR measurements have been performed using an ATR ZnSe crystal. By comparison with former IR measurements concerning selenito-ligands containing complexes as well as phases with sorbed selenium species, the fashion binding of selenium(IV) onto illite has been evidenced.

As possible host rock and backfill material for a nuclear waste repository clay is discussed. The interaction of the clay with actinides, especially uranium (U), is the focus of our work. Batch sorption and diffusion experiments are performed in order to estimate the actinide migration in clay formations. Furthermore, the influence of humic acid (HA) on these processes is investigated. HA are ubiquitously found in natural environments. In a worst case scenario these polyelectrolytic macromolecules can be transported by aquifers through the clay formation, where they can interact with e.g. actinides of the nuclear waste. Natural clay contains also HA and fulvic acid like organic matter, which can be released from the clay. The extraction of small organic ligands from natural clay was shown in literature (Courdouan et al. 2007). HA has a multitude of functional groups, which are able to complex metal ions, like U(VI), very well. HA also forms stable colloids. Due to this behavior HA can influence the mobility of U(VI) in a nuclear waste repository.
Currently, we are studying the diffusion of U(VI) in opalinus clay (Mont Terri, Switzerland) in the absence and presence of HA by diffusion experiments using synthetic opalinus clay pore water (Pearson 1998; pH 7.6, I = 0.39 M) as mobile phase. In our studies the assembly of Van Loon et al. (2004) is used, where an intact opalinus clay bore core (diameter: 2.57 cm, thickness: 1 cm) is put into a diffusion cell, which is connected with a high and a low concentration reservoir containing the mobile phase with the tracer. All experiments are performed under anaerobic conditions. The direction of diffusion is perpendicular to bedding. The pressure exerted on the bore core samples is 5 MPa. The density of the bore core pieces is 1.85 g/cm3. For the experiments two diffusion cells are used for investigation of i) U(VI) diffusion in the absence and ii) presence of HA. At first the diffusion properties of the opalinus clay samples in the diffusion cells were determined by through- and out-diffusion experiments using HTO as tracer. As diffusion parameters for HTO in opalinus clay De = (5.31 ± 1.01) x 10-11 m2/s and De = (7.23 ± 1.36) x 10-11 m2/s were determined. The diffusion accessible porosities of HTO were ε = 0.44 ± 0.08 and ε = 0.55 ± 0.10. These two different results for two bore core parts show the heterogeneity of the clay. However, the data are in agreement with literature data (e.g. Tevissen et al. 2004). For the U(VI) diffusion experiments 233U and 14C-labeled synthetic HA (Sachs et al. 2004) are used as tracer. The concentrations are set to [U] = 1 x 10-6 M and [HA] = 10 mg/L in synthetic opalinus clay pore water as mobile phase. So far, the experiments are carried out for three months. During this time no activity of 233U was measured in the low concentration reservoirs. That points out the good retention behavior of opalinus clay towards U(VI). However, this result is in contrast to results of batch sorption experiments with opalinus clay powder. There, a low sorption affinity of U(VI) towards opalinus clay was determined in pore water, although a higher surface area was accessible for U(VI) (specific surface area (BET) = 41.6 m2/g). Opalinus clay contains a calcite fraction of 13 % (Nagra 2002). The leached out calcium ions determine the speciation of U(VI) in the pore water, because the neutral aquatic complex Ca2UO2(CO3)3 (Bernhard et al. 2001) is formed, which dominates the U(VI) speciation (99 %). This complex sorbs only weakly onto opalinus clay (0.05 ± 0.002 µg U/m2 clay). The good retention ability of opalinus clay during the diffusion experiments can be attributed to the lack of free length of paths for the present Ca2UO2(CO3)3(aq) in the intact bore core piece. In contrast to the U(VI) diffusion, diffused HA molecules were measured in the low concentration reservoir 13 days after start of the experiment...

We studied selenite (SeO32-) retention by magnetite (FeIIFeIII2O4) using both surface complexation modeling and X-ray absorption spectroscopy (XAS) to characterize the processes of adsorption, reduction, and dissolution/co-precipitation.
The experimental sorption results for magnetite were compared to those of goethite (FeIIIOOH) under similar conditions. Selenite sorption was investigated under both oxic and anoxic conditions and as a function of pH, ionic strength, solid-to-liquid ratio and Se concentration. Sorption onto both oxides was independent of ionic strength and decreased as pH increased, as expected for anion sorption; however, the shape of the sorption edges was different. The goethite sorption data could be modeled assuming the formation of an inner-sphere complex with iron oxide surface sites (SOH). In contrast, the magnetite sorption data at low pH could be modeled only when the dissolution of magnetite, the formation of aqueous iron–selenite species, and the subsequent surface complexation of these species were implemented. The precipitation of ferric selenite was the predominant retention process at higher selenite concentrations (>1 104 M) and pH < 5, which was in agreement with the XAS results. Sorption behavior onto magnetite was similar under oxic and anoxic conditions. Under anoxic conditions, we did not observe the reduction of selenite. Possible reasons for the absence of reduction are discussed. In conclusion, we show that under acidic reaction conditions, selenite retention by magnetite is largely influenced by dissolution and co-precipitation processes.

In our work, we directly observe the interplay between ponderomotive contribution and true intersubband transition (IST). To this end, we probe the conduction IST of an undoped GaAs/Al0.34Ga0.66As multiple quantum well by transmitting broadband THz pulses after resonant photoexcitation with either a broad-band or narrowband laser at the 1s heavy-hole exciton. The field oscillations of the transmitted THz pulses are directly detected by phase-matched electro-optic sampling. We observe that the differential THz transmission transient as the pump-induced change in the transmitted THz field shows a strong beating. In the frequency domain this results in an intersubband resonance with a broad additional peak at lower energy. The line shape of this intersubband resonance strongly resembles a Fano-resonance with an undershoot at the low-frequency side and an asymmetric peak to higher frequencies. However, since we are able to measure differential transmission and total THz absorption separately, we find that the absorption does not show such a Fano-asymmetry, but reveals the expected Lorentzian-like line shape of the intersubband resonance. Especially, it is a single peak and therefore the beating in the time domain cannot originate from an adjacent second absorptive resonance next to the true IST resonance.
In our microscopic theory these features can be explained unambiguously by a phase-sensitive superposition of the true THz intersubband current and the ponderomotive current.

Bubble condensation plays an important role e.g. in sub-cooled boiling or steam injection into pools. Since the condensation rate is proportional to the interfacial area density, bubble size distributions have to be considered in an adequate modelling of the condensation process. To develop and validate closure models for CFD codes new experimental data are required. The effect of bubble sizes is clearly shown in experimental investigations done at the TOPFLOW facility of FZD. Steam bubbles are injected into a sub-cooled upward pipe flow via orifices in the pipe wall located at different distances from measuring plane. 1 mm and 4 mm injection orifices are used to vary the initial bubble size distribution. The variation of the distance between the location of the gas injection and the measuring plane allows investigating the evolution of the flow along the pipe. Measurements are done using wire-mesh sensors and thermocouples. Condensation is clearly faster in case of the injection via the smaller orifices, i.e. in case of smaller bubble sizes. Data on averaged void fraction, radial gas volume fraction profiles, profiles of the gas velocity and bubble size distributions in dependency of the L/D ratio are presented in the paper.

Heavy metals like the actinides possess a high risk potential to the environment not only because of their radiotoxicity but also due to their chemical toxicology. Uranium as one of the major actinide elements has to be considered in particular. Under reducing conditions, tetravalent uranium occurs primarily in the environment. To date, a lack of appropriate analytical techniques that featured sufficient sensitivity made it difficult to study the aqueous phosphate chemistry of uranium(IV) as such complexes show only low solubility. A novel time-resolved laser fluorescence spectroscopy system was set up recently and optimized to do research on uranium(IV). By application of this laser system we could successfully study uranium(IV) phosphate in concentration ranges where no precipitation or formation of colloids occurred. At pH = 1.0, U4+ and one uranium(IV) phosphate complex existed in parallel in aqueous solution. The complex could be identified as [U(H2PO4)]3+. Determination of its corresponding complex formation constant via two different evaluation methods resulted in the finding of (1) logß = 26.37 ± 0.76 and (2) logß = 26.43 ± 0.23. Both values are in very good agreement with each other and prove that [U(H2PO4)]3+ is a very stable complex in solution under experimental conditions.

The AER Working Group D on VVER reactor safety analysis held its 18th meeting in Řež, Czech Republic, during the period 18-19 May, 2009. The meeting was hosted by the Nuclear Research Institute Řež. Altogether 17 participants attended the meeting of the working group D, 16 from AER member organizations and 1 guest from a non-member organization. The co-ordinator of the working group, Mr. S. Kliem, served as chairman of the meeting.

The meeting started with a general information exchange about the recent activities in the participating organizations.

The given presentations and the discussions can be attributed to the following topics:

• Code validation and benchmarking
• Safety analysis and code developments
• Reactor pressure vessel thermal hydraulics
• Future activities including discussion on the participation in the OECD/NEA Benchmark for Kalinin-3 VVER-1000 NPP

A list of the participants and a list of the handouts distributed at the meeting are attached to the report. The corresponding PDF-files can be obtained from the chairman.

Starting point of our research were radio-ecological investigations on the interaction of actinides with bacteria, recovered from uranium mining waste piles. Thereby several isolates were subsequently analyzed regarding their growth in presence of different heavy metals and their heavy metal binding properties, particularly using uranium. Some isolates show a high and selective binding for uranium, cadmium, lead, and a few other heavy metals. Interestingly, the heavy metals were immobilized on the cell surface, preventing any sustainable damage of the cell. Responsible for the binding of heavy metals outside the cell is a proteinaceous cell envelope, a so-called surface layer (S-layer). The highly ordered S-layers are often composed of identical protein monomers, that possess the ability to self-assemble into two-dimensional paracrystalline lattices. The highly regular structure of the S-layers with many pores of identical size and many regularly arranged functional groups offers good binding sites for different kinds of ions and molecules. Furthermore, the pores serve as nucleation sites for the formation of metal nanoclusters or minerals.
In consequence of the mentioned properties, detailed studies on the metal binding of bacterial S-layers were accomplished. As turned out, specific S-layers are able to bind uranium, arsenic, platinum and palladium. By immobilization of the S-layers, metal selective filter materials were developed. Furthermore, the regular structure of the S-layers can be utilized for the production of clustered metal and metal oxide nanoparticles for many different (photo)catalytic approaches, e.g. CNT synthesis, degradation of pharmaceuticals and detoxification of heavy metals. Pd, ZnO, and TiO2 nanoparticles immobilized on S-layer and/or S-layer coated industrial carriers were thusly produced and show a high catalytic activity in comparison to equally chemically produced nanoparticles. Moreover S-layers are very prospective for the development of compound specific biosensors by combining organic or inorganic fluorescence dyes with specific binding molecules.

Das von der EU finanzierte SPIRIT-Projekt (Support of Public and Industrial Research using Ion beam Technology) [1] erlaubt Nutzern aus Forschung und Industrie den kostenfreien transnationalen Zugang zu Ionenstrahl-Infrastrukturen. Daneben fördert es die Weiterentwicklung der ionenstrahlbasierten Methoden und Instrumente zur Materialanalyse und –modifikation sowie die weitere Verbreitung der Verfahren in Gebieten aktueller Forschung und Technik. Die SPRIT-Partner sind die elf führenden Ionenstrahleinrichtungen in Europa.
Schnelle Ionen im Energie-bereich von ca. 10 keV bis 100 MeV werden von den SPIRIT-Partnern eingesetzt und externen Nutzern zur Verfügung gestellt. Diese Ionen dienen insbesondere der Modifikation und Analyse von Oberflächen, Grenzflächen, dünner Schichten und nanostrukturierten Systemen. Anwender aus der Grundlagenforschung und der angewandten Forschung nutzen diese schnellen Ionen in der Materialforschung, Lebens-, Geo- und Umweltwissenschaften, bis hin zur Analyse von Kunst- und Kulturgütern. So können z. B. Elementkonzentrationen zerstörungs- und standardfrei mittels Ionenstrahlanalysemethoden wie
• Rutherford-Rückstreu-Spektrometrie (Rutherford Backscattering Spectrometry - RBS)
• Kernreaktionsanalyse (Nuclear Reaction Analysis - NRA)
• Elastische Rückstreuanalyse (Elastic Recoil Detection - ERD)
• Teilchen-induzierte Röntgen- und Gamma-Emission (Particle-Induced X-Ray – PIXE und Gamma-Emission - PIGE).
bestimmt werden. Alle Elemente sind dabei zugänglich; die meisten Elemente in lateraler, manche sogar in 3-D-Auflösung mit einem analysierbaren Tiefenbereich von nm/µm und einer Tiefenauflösung von 0.5-30 nm. Typische Nachweisgrenzen sind 10 µg/g (H), 500 µg/g - 1% (He-O), 1 µg/g (F) bzw. 10-100 µg/g (Na-U).
Sieben SPIRIT-Partner stehen für den transnationalen Zugang allen Nutzern der europäischen Union kostenfrei zur Verfügung. Anträge [2] für selbst durchgeführte Experimente oder Auftragsarbeiten werden von einem internationalen Expertengremium begutachtet. Bei positiver Entscheidung werden alle Kosten inkl. der Reise- und Aufenthaltskosten von SPIRIT übernommen.

Referenzen
[1] www.spirit-ion.eu, 7.RP #227012. [2] http://www.spirit-ion.eu/application.html.

Das Forschungszentrum Dresden-Rossendorf (FZD) erweitert sein Portfolio um eine weitere hochsensitive analytische Methode: die Beschleunigermassenspektrometrie (accelerator mass spectrometry = AMS). Diese Analysetechnik ist prädestiniert zur Bestimmung langlebiger Radionuklide, die entgegen der allgemein üblichen Zerfallszählung, nicht durch den eigentlichen Zerfall detektiert werden. Vielmehr werden die noch nicht zerfallenen Nuklide wesentlich effizienter massenspektrometrisch bestimmt. Dabei besitzt die AMS gegenüber der konventionellen Massenspektrometrie den Vorteil, dass sie Störsignale von Molekülionen oder Ionen ähnlicher Masse (Isobaren) effektiver unterdrücken kann. Die AMS liefert somit weitaus niedrigere Nachweisgrenzen (20000 Atome/g bzw. 10^-9Bq) als die konventionellen Methoden.
Im Gegensatz zu den in Europa gängigen niederenergetischen AMS-Anlagen, die sich weitgehend auf die Bestimmung von ¹⁴C spezialisiert haben, wird die AMS-Anlage des FZD - DREAMS (DREsden AMS) - als erste moderne Anlage in der EU mit einer Terminalspannung von 6 MV betrieben werden. Anstelle eines üblichen van-de-Graaff-Prinzips zur Hochspannungserzeugung, garantiert ein Hochfrequenz-Kaskadengenerator höchste Stabilität. So wird DREAMS nicht nur hochempfindliche, sondern auch hochpräzise Messungen liefern.
Aufgrund der instrumentellen Weiterentwicklungen der AMS, die die Bestimmung von Isotopenverhältnissen im Bereich von 10^-16 ermöglichen [1], haben sich die interdisziplinären Applikationsgebiete stark ausgeweitet. Anfänglich bevorzugt untersuchte Proben aus Kosmochemie, Astrophysik und nukleare Daten, werden zunehmend von Proben aus Strahlenschutz, Nuklearsicherheit, Nuklearentsorgung, Radioökologie, Phytologie, Ernährungswissenschaften, Toxikologie und Pharmakologie verdrängt. Die Inbetriebnahme von DREAMS in 2009, wird die interne Vernetzung der FZD-Forschungsaktivitäten in der Materialforschung, Strahlenphysik, Radiochemie und Radiopharmazie vorantreiben. Zudem wird DREAMS auch externen Nutzern zur Verfügung stehen. Die Bestimmung langlebiger Radionuklide wie ¹⁰Be, ²⁶Al und ³⁶Cl hat insbesondere in den Geo- und Umweltwissenschaften an Bedeutung gewonnen [2]. Durch deren Quantifizierung können prähistorische Ereignisse wie Vulkanausbrüche, Bergstürze, Tsunamis, Meteoriteneinschläge, Erdbeben und Gletscherbewegungen datiert werden. Untersuchungen an Eisbohrkernen erlauben zudem die Rekonstruktion und Vorrausage von Klimaveränderungen.

Referenzen [1] S. Merchel et al, Nucl. Instr. and Meth. B 266 (2008) 4921. [2] J.C. Gosse und F.M. Phillips, Quat. Sci. Rev. 20(2001) 1475.

Bacteria and fungi in soil, sediment and water may have a significant influence on the transport of radionuclides and other heavy metals in nature. In addition to chemical and physical factors, that affect the migration behaviour of uranium, metabolic processes play an important role in its mobilisation or immobilisation. The aim of this project is to look for possible uranium uptake systems in selected bacteria and fungi, showing high uranium accumulation capacities. In our institute we are using different microscopic, spectroscopic and chromatographic methods for the localization of accumulated uranium and for the identification of binding relevant compounds on the cell surface and inside the cell.
The Arthrobacter strain JG37-Iso2, isolated from a soil sample of a uranium mining waste pile near the town of Johanngeorgenstadt (JG) in Germany, is able to accumulate large amounts of uranium inside the cell. Therefore systematic investigations of the growth behaviour, uranium binding and uranium accumulation of Arthrobacter JG37-Iso2 were performed. As indicated by the TEM analysis, uranium diffuses in the cells during the stationary growth phase, possibly due to a higher permeability caused by damages of the cell membranes. For comparison we also investigate the interaction of uranium(VI) with the reference strains Arthrobacter oxygen and Arthrobacter nicotinae. Both strains show a different binding behaviour for uranium. First spectroscopic results indicate the coordination of uranium via carboxylic groups of the cell compartments, whereas a additional co-ordination to organic phosphate groups can currently not be excluded.

Long-lived radioactive actinides are produced in light water reactors (LWR) using conventional fuel. “Innovative” fuel matrices may reduce the breeding of these nuclides. However, inherent LWR safety features have to be preserved, which restricts the possibilities for new fuel-carrying matrices. Respective fuel-assembly and LWR-core safety studies indicate practicable new fuel options for the near future.

Escherichia coli is one of the best studied microorganisms and is the mostly used host for genetic engineering. The gram-negative single cells are rod-shaped and filaments are usually not found. Here we describe the reproducible formation of elongated E. coli cells. During heterologous expression of the silent S-layer protein gene sllB from Lysinibacillus sphaericus JG-A12 in E. coli Bl21 (DE3) the cells are arranged as long cell chains and surrounded by a highly stable sheath with a length of >100 µm (defined as filaments) while growing at room temperature. In stationary growth phase, microscopic analyses show the formation of unusual long transparent tube-like structures enclosing separated single cells. The tube-like structures were isolated and analyzed by SDS-PAGE, IR-spectroscopy and different microscopic methods in order to identify their special composition and structure. We show that the tube-like structures are outer membrane-like, enriched in protein content and associated with the recombinant S-layer protein, indicating a disordered cell division. However, bacterial cells show a high viability and stability. To our knowledge, this is the first report of such drastic morphological changes of E. coli, induced by the expression of a foreign protein.

A consequence of a total loss of AC power supply (station blackout) leading to unavailability of major active safety systems which could not perform their safety functions is that the safety criteria ensuring a secure operation of the nuclear power plant would be violated and a consequent core heat-up with possible core degradation would occur.

Currently a study which examines the thermal-hydraulic behaviour of the system is being performed. This paper focuses on the possibilities for delay or mitigation of the accident sequence to progress into a severe one by applying accident management measures. The strategy “Primary circuit depressurization” as a basic strategy, which is realized in the management of severe accidents is being investigated. By reducing the load over the vessel in severe accident conditions, prerequisites for keeping the state of the primary circuit are being created. The time-margins for operators’ intervention as key issues are being also assessed.

The analyses are performed applying the GRS (Gesellschaft für Anlagen- und Reaktorsicherheit mbH) thermal-hydraulic system code ATHLET. Comparative analysis of the accident progression for a station blackout event for a reference German PWR and a reference VVER-1000, taking into account the plant specifics is being investigated.

The real toughness response of RPV material can only be determined after the final shut down of the NPP. Such a chance is given now by investigating material from the former Greifswald NPP (VVER-440/230).
In the first part the paper deals with fast neutron fluence calculations and retrospective dosimetry based on Niobium. Unfortunately, a second neutron reaction besides Nb-93(n,n') leading to Nb-93m-activity is the reaction Mo-92(n,gamma)Mo-93. Based on the found Nb and Mo contents in the RPV material, it turned out that the Nb-93m generation on the Mo path mostly dominates over the fast neutron induced generation from Nb.
The comparison between the calculated and the measured Nb-93m activities typically resulted in deviations of 50%. Possible reasons for the observed differences are discussed.
In the second part first results of fracture mechanic investigations are reported. SE(B) specimens from three thickness positions were tested and evaluated according to the test standard ASTM E1921-05. Cleavage fracture toughness values, K-Jc. were determined and Master Curve based reference temperatures (T-0) were evaluated. The T-0 measured at the inner surface of the RPV did not represent the conservative condition. The T-0 of disc 1-1.3 located between the surface and 1/4 thickness is about 40K higher compared with those of the surface.
The measured K-Jc values are not enveloped by the 5% fractile indexed with T-0 according to the Master Curve concept. However, the 5% fractile indexed with the VERLIFE reference temperature RTTo that includes an additional margin envelops the measured K-Jc values. Therefore the VERLIFE lower bound curve conservatively describes the fracture toughness of the investigated weld metal.

To increase the corrosion resistance of Al7075-T7351 and Ti-6Al-4V alloys were performed treatments by PIII. Experiments were made by using a mixture of N2 and H2 at ratio of 1:1. The time of treatment varied between one and three hours to verify its influence on the electrochemical behavior of these materials. After implantation process the samples of the aluminum and titanium alloys showed improved corrosion resistance. The better result was obtained to Al7075 alloy, due its smaller corrosion current density presented at polarization tests.

Radionuclides represent a serious health risk to humans in case of incorporation. To get a first insight into the transport and metabolism in the human organism, we compared the speciation of Eu(III) and Cm(III) in human biological fluids calculated by thermodynamic modelling with spectroscopic results obtained by time-resolved laser-induced fluorescence spectroscopy (TRLFS) with regard to the analogy of lanthanides and actinides.
For spectroscopic studies, fresh saliva and urine samples were collected from healthy volunteers and analyzed within few days. For TRLFS measurements, all samples have been spiked in vitro with europium or curium. To identify the dominant species the measured spectroscopic data were compared to reference spectra with single organic and inorganic constituents of the biological fluids.
The TRLFS spectra with urine showed that all samples with a pH below and all samples with a pH above 5.8 each exhibit strikingly similar spectra. The TRLFS spectra with saliva were all similar in the pH range between 5 and 8. Comparing the measured spectra with the reference data, we found that in urine at lower pH citrate complex species dominate the speciation of both metals while at higher pH and in saliva the spectra were identical to those in inorganic electrolyte solution.
The speciation calculation, carried out with the computer program MEDUSA and the accompanying hydrothermal database HYDRA, showed for urine in accordance to the experimental results at pH values around 5 a dominating citrate speciation for both metals. In contrast to the experiments resulted the calculation at higher pH values for urine and in the whole observed pH for saliva in a simple phosphate complexation. However, spectroscopic investigations signed of a more complex speciation behaviour which cannot be described with single inorganic complexes.
In conclusion, the comparison of experimental speciation investigation and computer modelling shows that because of their simplifications models cannot always image the complex natural processes correctly.

We present revised ⁷Be(p,gamma)⁸B S-factors based on our previously published measurements, using a more detailed target analysis and improved stopping powers.
Extrapolating our data below the 1⁺ resonance to solar energies using the latest cluster model calculations of Descouvemont, we find that S{17}(0) = 21.5 pm 0.6(expt) pm 0.6(theor) eV b. Fitting all modern, low-energy (p,$\gamma$) data with the same theory, we find a ``best" value S{17}(0) = 20.9 pm 0.6(expt) pm 0.6(theor) eV b.

A completely contactless flow measurement technique based on the principle of EM induction measurements—contactless inductive flow tomography (CIFT)—has been previously reported by a team based at Forschungszentrum Dresden-Rossendorf (FZD). This technique is suited to the measurement of velocity fields in high conductivity liquids, and the possible applications range from monitoring metal casting and silicon crystal growth in industry to gaining insights into the working of the geodynamo. The forward problem, i.e. calculating the induced magnetic field from a known velocity profile, can be described as a linear relationship when the magnetic Reynolds number is small. Previously, an integral equation method was used to formulate the forward problem; however, although the sensitivity matrices were calculated, they were not explicitly expressed and computation involved the solution of an ill-conditioned system of equations using a so-called deflation method. In this paper, we present the derivation of the sensitivity matrix directly from electromagnetic field theory and the results are expressed very concisely as the cross product of two field vectors. A numerical method based on a finite difference method has also been developed to verify the formulation. It is believed that this approach provides a simple yet fast route to the forward solution of CIFT. Furthermore, a method for sensor design selection based on eigenvalue analysis is presented.

Due to their radiation and heavy metal properties, radionuclides represent a serious health risk to humans in case of incorporation. To understand their toxicity, transport, deposition and elimination in the human organism, it is therefore crucial to elucidate their chemical behavior and properties on a molecular level. For trivalent actinides originating from nuclear power plants knowledge about their metabolism is very limited. In case of incorporation, they tend to accumulate in liver and skeleton and are excreted to maximum 10 – 20 % within the first week. Nevertheless this excretion occurs mainly through the kidneys, which are known to be particularly radiation sensitive.
To address the lack of knowledge, we studied the speciation of curium (as a representative of trivalent actinides) and europium (as the lanthanide analogue) in human urine and their complexation with single constituents. Since both of these heavy metals exhibit unique fluorescence properties, time-resolved laser-induced fluorescence spectroscopy (TRLFS) is an adequate tool for this purpose.
Fresh 24-hours-urine samples were collected from healthy volunteers and analyzed within few days. The inorganic composition of all samples was determined using mass spectrometry with inductive coupled plasma (ICP-MS) and ion chromatography (IC). Then all samples were spiked in vitro with curium or europium and single as well as time-resolved laser-induced fluorescence spectra were measured. We analyzed at least 10 different urine samples and were able to divide all samples into two different groups according to their fluorescence spectra.
We found that all samples with a pH below 5.6 and all samples with a pH above 6.0 each exhibit strikingly similar spectra. Compared to each other the spectra of both groups are very different and therefore easy to distinguish. Furthermore the lifetime of the metals in samples with higher pH is substantially longer than in samples with lower pH. ICP-MS and IC analysis revealed that the inorganic composition of samples which exhibit the same fluorescence spectra can vary broadly within magnitudes. Therefore the most important factor influencing the speciation of metals in human urine does not seem to be the composition but was determined to be the pH.
To identify the dominating species we also recorded the fluorescence spectra of both metals in electrolyte solution containing all inorganic but no organic components of urine. Furthermore we studied the complexation of both metals with urea and citric acid as main organic urine constituents. Comparing the measured spectra and lifetimes with this reference data, we found that at lower pH a complex citric acid species dominates the speciation of both metals while at higher pH the spectra where identical to those in electrolyte solution ruling out any involvement of organic ligands. The exact nature of this inorganic metal species has yet to be clarified.

With the objective to develop new filter materials for cleaning of arsenic contaminated waters based on sol-gel immobilized microorganisms various bacterial strains and their isolated surface layers were investigated. Interestingly, the binding capacity of four S-layers, namely that of Lysinibacillus sphaericus NCTC 9602, Bacillus soil isolates JG-B 53 and JG-B 62 as well as Geobacillus stearothermophilus ATCC 12980 was 1.5 to 5fold enhanced in comparison to the commercial sorbent Ferrosorp with As(V) model solutions. Thereby, a different binding behaviour between whole cells and their corresponding S-Layers could be observed even in dependence on the used arsenic concentration. AFM investigations revealed more elevated and expanded S-Layer agglomerates in the case of G. stearothermophilus ATCC 12980 after loading with As.

The purpose of this study was to investigate the antiproliferative potential of two novel bio-organometallic drug candidates, based on hydroxyl-phenyl-but-1-ene skeleton and containing the ferrocenyl (Fc) moiety, namely ferrociphenol (Fc-diOH) and ferrocifen (Fc-OH-TAM), on two cell lines, named BR95 (epithelial-like) and MM98 (sarcomatous-like), obtained from pleural effusions of previously untreated malignant pleural mesothelioma (MPM) patients. In vitro chemosensitivity of MPM cells towards the title compounds was evaluated by cell viability assay, alkaline Single Cell Gel Electrophoresis (Comet test) and western blotting evaluation of p53 induction. The two bio-organometallic derivatives were found to be more potent in inhibiting cell proliferation than the reference metallo-drug cisplatin (CDDP). This antiproliferative effect cannot be attributed to estrogenic/antiestrogenic activity, since both cell lines resulted to be estrogen insensitive (ER−). Fc-diOH and CDDP were able to upregulate wild type p53 present in MM98 cell line, while Fc-OH-TAM was not. Similarly, Fc-diOH and CDDP induced early DNA damage, while Fc-OH-TAM did not. This indicates that, albeit the similar structures, the two ferrocifens exhert different mechanisms of cytotoxicity on MPM cells.

After the installation and acceptance test of the French 5 MV AMS facility ASTER, the focus has been on improving ¹⁰Be and ²⁶Al routine measurements. Quality assurance was established by introducing traceable AMS standards for each nuclide, self-monitoring by taking part in round-robin exercises and proficiency testing, and surveillance of long- and short-time variability of blank and reference materials. A background level of 3x10^-14 makes ASTER well-suited for measuring ⁴¹Ca/⁴⁰Ca in the 10^-12 region, which is sufficient for a wide range of applications. Routine AMS measurements of volatile elements like ³⁶Cl and ¹²⁹I are most likely feasible in the very near future after sophisticated ion source improvements took place.

Biofilms are ubiquitous and so they can also be found in regions with high concentrations of heavy metals. Due to their ability to change geochemical parameters e.g. O2-concentrations, Eh, pH, and by generating metabolites they are very important for the investigation of transport processes of heavy metals in nature. However, the influence of biofilms on the migration of uranium in contaminated environments, e.g. the former uranium mining areas in eastern Germany, was disregarded so far. In the former underground uranium mine in Königstein thick biofilms in form of streamers were observed in the mine adit drainages and in form of dripstone-like biofilms with slimy endings.
The biofilm structure was visualized by confocal laser scanning microscopy (CLSM). Fluorescent dyes were used for staining the microorganisms and the extracellular polymeric substances (EPS). Unfortunately, the biofilms from acid mine drainages (AMD) have pH-values not higher than 3 and the most common fluorescent dyes are not stable below pH-values of 4. Hence, the first step in this study was to find new acid-stable fluorescent dyes to stain the acidophilic microorganisms without any increase of the pH. For this purpose a variety of new fluorescent dyes were tested and the most suitable ones were compared with the common fluorescent dyes DAPI and SYTO 59. It was found that the selected new fluorescent dyes did very well stain acidophilic biofilm microorganisms whereas DAPI and SYTO 59 fail.

Laser fluorescence techniques possess some superior features, above all a very high sensitivity for fluorescent heavy metal ions. The predominance of TRLFS compared to other spectroscopic techniques, e.g. XRD and IR was showed in Baumann N. et al. (2008) in analyzing the speciation of U(VI) in a thin layer of an alteration product formed on depleted uranium. With their high sensitivity TRLFS is also suited to identify the U(VI) speciation in plant constituents. Long delay steps in time-resolved measurements avoid annoying fluorescence emission caused by organic substances.
Uranium speciation in seepage water of the Gessenbach grassland was determined by TRLFS. This was done to compare it in a later stage with the uranium speciation in plants, which grow on that grassland and ingest the same uranium contaminated water during their growth. The uranium content in those samples GB 3 and GB 6 was 75.1 and 291 ppb, respectively, and both samples delivered an evaluable fluorescence signal for TRLFS. The positions of the six peak maxima from these signals are in both water samples in concordance with data for uranium sulfate species published in the literature, e. g. in Bernhard G. et al. (1996) at 477, 493, 513, 537, 562 and 591 nm. Moreover, the time-resolved fluorescence signals of both water samples possess a mono-exponential decay, indicating the presence of one species only. These two characteristics, i.e. positions of peak maxima and lifetimes revealed without doubt that the uranium speciation in the seepage water is dominated by uranium (VI) sulfate species.
TRLFS measurements with plant compartments (e.g. roots, leaves, shoots) which grow in association with the seepage water will be carried out in future investigations. U(VI) components could be extracted from the plant compartments by centrifugation as cell sap, or as solid milled plant compartment sample and subsequently studied by TRLFS. Information in preparation of the plant compartments for TRLFS analyses has been reported in Günther A. et al. (2003) and were further refined. As suggested by Carrière M. et al. (2005) reactivity and toxicity of uranium depend on the speciation of heavy metals and accordingly have to be considered as important possible risk factor as uranium may enter economic plants and eventually arrives in the food chain.

Baumann N. et al. Environ. Sci. Technol. 42 8266-8269 (2008)
Bernhard G. et al. Radiochim. Acta 74 87-91(1996)
Günther A. et al. Radiochim. Acta 91 319-328 (2003)
Carrière M. et al. Nucl. Instrum. Methods Phys. Res. Sect. B-Beam Interact. Mater. Atoms 231, 268-273 (2005)

In this work, a cross-sectional averaged two-fluid model combined with a population balance model is applied to simulate the flow field and the bubble size distributions in a two-phase bubble column. The Martinez-Bazan breakage kernel and a modified Prince and Blanch coalescence kernel have been chosen to describe bubble breakage and bubble coalescence, respectively. In the present study, we discuss the use of a higherorder spectral element methodsthe least-squares methodsto compute the system of equations in a coupled manner. The least-squares method is highly accurate and has a number of advantages over the conventional numerical methods like the finite difference and finite volume methods. In contrast to the finite volume method, when desinging an overall solution algorithm, this least-squares method ensures that all the continuity equations are satisfied individually and it deals with both the convective and diffusive terms stably and accurately. The novel iterative algorithm solves the flow and the population balance equation in a coupled manner. The model has been validated against experimental data obtained for two-phase flow in a bubble column. The predicted bubble size distribution and other flow quantities are in good agreement with the experimental data.

Biofilms may immobilize toxic heavy metals in the environment and thereby influence their migration behavior. The mechanisms of these processes are currently not understood. This is due to the complexity occurring in such biofilms creating many discrete geochemical microenvironments which may differ from the surrounding bulk solution in their bacterial diversity, their prevailing geochemical parameters, e.g. pH and dissolved oxygen concentration, their presence of organic molecules, e.g. metabolites, and many more. All of them may affect the metal speciation. To obtain such information, which are necessary for performance assessments studies or the development of new cost effective strategies for cleaning waste waters, it is however very important to develop new non-invasive methods applicable to study the interactions of metals within biofilm systems. Laser fluorescence techniques possess some superior features above all a very high sensitivity for fluorescent heavy metals. An approach of combining confocal laser scanning microscopy and laser induced fluorescence spectroscopy to study the interactions of biofilms with uranium is presented and it was found that the coupling of these techniques is a promising tool to study in situ in non-invasive fashion fluorescent heavy metals within biofilm systems. Information on uranium speciation and uranium redox states can be generated.

The formation of regular nanopatterns during low energy ion sputtering of solid surfaces has become a topic of intense research. This research is mainly motivated by promising applications of nanopatterned surfaces e.g. in thin film growth. On the other hand, these surfaces represent an interesting example of spontaneous pattern formation in non-equilibrium systems exhibiting different features like wavelength coarsening or a transition to spatiotemporal chaos. Different pattern types are observed for different experimental conditions, i.e. wavelike ripple patterns and hexagonally ordered dot arrays under oblique and normal ion incidence, respectively [1].
According to the model of Bradley and Harper (BH) [2], the regular patterns result from the competition between curvature dependent roughening and diffusional smoothing of the surface. Since the local erosion rate is higher in troughs than on crests, the eroded surface is unstable against any periodic perturbances. In the presence of a smoothing mechanism, however, wave vector selection occurs and a periodic pattern with a characteristic spatial frequency is observed. During recent years, several nonlinear extensions of the linear BH model have been proposed with the stochastic Kuramoto-Sivashinsky (KS) equation having played a prominent role [3]. However, although most experimental investigations on ion-induced pattern formation were performed under oblique ion incidence, only few theoretical studies focused on the corresponding anisotropic KS (aKS) equation.
In this work, we have investigated the influence of anisotropy on the morphology evolution in numerical integrations of the aKS equation. For a strong nonlinear anisotropy, a rotation by 90° of the initially formed ripple pattern was observed for intermediate and long integration times. Comparison with analytical predictions indicates that the observed rotated ripple pattern arises from anisotropic renormalization properties of the aKS equation. This result may also offer an explanation for the recent observation of transient structures in high-temperature experiments on Si(111) [4].

[1] W. L. Chan and E. Chason, J. Appl. Phys. 101, 121301 (2007)
[2] R. Bradley and J. Harper, J. Vac. Sci. Technol. A 6, 2390 (1988)
[3] R. Cuerno and A.-L. Barabási, Phys. Rev. Lett. 74, 4746 (1995)
[4] A.-D. Brown, J. Erlebacher, W.-L. Chan, and E. Chason, Phys. Rev. Lett. 95, 056101 (2005)

Nowadays nuclear power is the only greenhouse-free source that can contribute appreciably to the solution of the increasing world-wide energy demand problem. The use of Thorium in the nuclear energy production may offer some unique advantages to accomplish this task. Extensive research and development on the thorium fuel cycle has been conducted in many countries around the world. Starting from the current nuclear waste policy as well as from the (V)HTR good capabilities of Pu burning, the EU PUMA project focus on core physics investigations, in order to further demonstrate the potential benefits of using the HTR core as a Pu/MA transmuter. In this paper the following aspects have been analyzed:

– The state of art about the studies focusing on the use of Th in different core concepts
– The use of Th in HTRs, with a particular emphasis on Th-Pu fuel cycles
– An original assessment of Th-Pu fuel cycles in HTR, on the basis, the energy produced totally, per initial Pu and the ratio between discharged and loaded Pu mass
Some aspects related to Thorium exploitation were outlined, with a particular emphasis on its suitability for working in pebble-bed HTR as a fertile element in a Th-Pu fuel cycle, that is a promising kind of fuel considered in the framework of the EU PUMA project. Particularly, the influence of the Th/Pu weight fraction at BOC in a typical HTR pebble was analyzed as far as the reactivity trend vs. burn-up, the energy produced per Pu unit mass, and the Pu isotopic composition at EOC are concerned. The obtained results suggest us that there is not a best composition for the PBMR Pu/Th fuel. However deeper investigations need to be performed in order to draw final conclusions. Thus, at the moment it is possible to state that some optimized Th percentage in the initial Pu/Th fuel could be suggested on the basis of the aim we are trying to reach.

In order to guarantee a sustainable supply of future energy demand without compromising the environment integrity, some actions for a substantial reduction of CO2 emissions are nowadays deeply analyzed. One of them is the improvement of the nuclear energy use. In this framework, innovative gas-cooled reactors, both the thermal and the fast solutions, seem to be very attractive for the electricity production point of view and for the potential industrial use along the high temperature processes (e.g. H2 production by steam reforming or I-S process). This work focuses on a preliminary (and conservative) evaluation of possible advantages that a symbiotic cycle (EPR-PBMR-GCFR) could entail, with special regard to the reduction of the HLW inventory and the optimization of the exploitation of the fuel resources. The comparison between the symbiotic cycle chosen and the reference one (once-through scenario – EPR-SNF directly disposed) shows a reduction of the time needed to reach a fixed reference level from ~170000 years to ~1550 years, time comparable with typical human times and for this reason more acceptable by the public opinion. In addition, this cycle enable to have a more efficient use of resources involved, obtaining that the total electric energy produced becomes equal to 630.54 TWh/year (instead of only 529.62 TWh/year, case of only EPR) without consuming additional raw materials.

Interactions of the acidothermophilic archaeon Sulfolobus acidocaldarius DSM 639 with U(VI) were studied by using a combination of wet chemistry, X-ray absorption spectroscopy (XAS), and time-resolved laser-induced fluorescence spectroscopy (TRLFS). We demonstrated that at pH 2 this archaeal strain possesses a low tolerance to U(VI) and that its growth is limited to a uranium concentration below 1.1 mM. At similarly high acidic conditions (pH 1.5 and 3.0), covering the physiological pH growth optimum of S. acidocaldarius, at which U(VI) is soluble and highly toxic, rapid accumulation of the radionuclide by the cells of the strain occurred. About half of the uranium bind-ing capacity was reached by the strain after an incubation of five minutes and nearly total saturation of the binding sites was achieved after 30 minutes. Both, EXAFS- and TRLF-spectroscopic analyses showed that the accumulated U(VI) was complexed mainly through organic phosphate groups. The EXAFS measurements revealed that U(VI) is coordinated to the organic phosphate ligands of the archaeal cells in a monodentate binding mode with an average U-P bond distance of 3.60 ± 0.02 Å.

In-beam Positron Emission Tomography (PET) is a system for monitoring high precision radiation therapy which is in the most cases applied to the tumors near organs at risk. High quality and fast availability of in-beam PET images are, therefore, extremely important for successful verification of the dose delivery. Two main problems make an in-beam PET monitoring a challenging task. Firstly, in-beam PET measurements result in a very low counting statistics. Secondly, an integration of the PET scanner into the treatment facility requires significant reduction of the sensitive surface of the scanner and leads to a dual-head form resulting in imaging artifacts. The aim of this work is to bring the imaging process by means of in-beam PET to optimum quality and time scale. The following topics are under consideration:

• analysis of image quality for in-beam PET;
• image reconstruction;
• solutions for building, testing, and integration of a PET monitoring system into the dedicated treatment facility.

The beamline BM20 operated by the Forschungszentrum Dresden-Rossendorf is located at ESRF storage ring and divided into two stations for spectroscopy and diffraction in the range of 6 to 30 keV. The core competences of material research station are different in-situ X-ray scattering and diffraction investigations also combined with X-ray spectroscopy using a dual magnetron sputtering deposition chamber. Hereby the syntheses of SiO2/GeOx multilayers to create Ge nanocrystalls with well defined sizes by thermal decomposition afterward or directly by sputtering at elevated temperature were investigated. These are promising materials is in the field of solar cells. On the other side by the use a hemispherical Beryllium dome (optional with electrical resitivity four-point setup) the catalyst formation for the carbon nano tubes synthesis was characterized by in-situ diffraction experiment under controlled reactive atmosphere. By in-situ investigations process were characterized on-line and structural und functional properties are correlated directly with each other, which increase the comprehension of synthesis and processing of functional materials.

Tumor therapy using particle beams is highly precise and requires methods for monitoring of dose delivery. Solutions based on positron emission tomography (PET) are successfully implemented for the radiation therapy with carbon ions and protons at the Gesellschaft für Schwerionenforschung, Darmstadt, Germany, at the Heavy Ion Medical Accelerator at Chiba, Japan, at the Massachusetts General Hospital, Boston, USA, at the Hyogo Ion Beam Medical Center, Japan as well as at the National Cancer Center Kashiwa, Japan. Furthermore, the PET monitoring technique has been tested experimentally for 3He, 7Li, and 16O. The main requirements for the PET monitoring are (1) to produce images containing relevant information for the evaluation of dose delivery and (2) to reduce the additional time required for imaging as much as possible. There are three technical realizations: (1) In-beam PET (measurement during the irradiation), (2) In-room PET (measurement immediately after the irradiation of each portal using a PET scanner placed in the therapy room), (3) Off-line PET (measurement after the complete irradiation by means of a PET scanner located in a different room). These three concepts have been evaluated concerning workflow, counting statistics, and imaging. The treatment workflow is mostly affected by off-line PET. In the case of in-room and off-line PET, the counting statistics is approximately one half of that for in-beam PET if reasonable measuring times (<= 15 min) are assumed. Furthermore, there is an information loss using off-line PET. Thus, in-beam and in-room PET are the most feasible concepts to integrate PET into the particle therapy for dose monitoring.

Der vorliegende Bericht befasst sich mit der Modellierung des Vergiftungssystems TW und der Simulation von auslegungsüberschreitenden Störfalltransienten, in denen eine Boreinspeisung erfolgt. Die Modellierung des Vergiftungssystems beinhaltet die Simulation des Transports und der Reaktivitätswirksamkeit des Bors während einer beliebigen Transiente. Das Modell berücksichtigt den Verlust des Boranteils, der in die Dampfphase übergeht (Dampfflüchtigkeit des Bors) und damit im Hinblick auf den Neutronenhaushalt verloren geht. Um die Dampfflüchtigkeit des Bors quantitativ zu berücksichtigen, wurden die aktuellen Messdaten der TU Dresden herangezogen. Diese Arbeit wurde im Rahmen eines gemeinsamen Förderprogramms zwischen dem Forschungszentrum Dresden-Rossendorf (FZD) und der Vattenfall Europe Nuclear Energy (VENE) durchgeführt.

We have investigated the third-order nonlinear mixing process between a near-infrared laser and a free-electron laser in an undoped symmetric GaAs/AlGaAs multi quantum well. AC THz electric fields which couple strongly with intraband excitations in semiconductors can lead to spectral sidebands of simultaneous interband excitation. In this nonlinear mixing process a near-infrared (NIR) laser beam is mixed with the THz beam to generate sidebands around the NIR frequency with a frequency spacing equal to the THz frequency or multiples of it: ω = ω_NIR ± n × ω_THz (with integer n). We have investigated the third-order nonlinear mixing process between a near-infrared laser and a free-electron laser (FEL) in an undoped symmetric GaAs/AlGaAs multi quantum well. The sample is studied in transmission under illumination by FELBE, the free-electron laser (FEL) of the Forschungszentrum Dresden-Rossendorf. We use the tunability of the FEL to study the dependence of the mixing efficiency on THz wavelength. We find resonances related to heavy- to light-hole transitions, but also to the heavy-hole intra-exciton 1s-2p transition. It turns out that the conversion efficiency of the n=+2 sideband is largest (up to 0.1 %) for the 1s-2p intra-exciton transition, which is comparable to values previously reported for n=+1.

The existence of magnetohydrodynamic mean-field α²-dynamos with spherically symmetric, isotropic helical turbulence function α is related to a non-self-adjoint spectral problem for a coupled system of two singular second oder ordinary differential equations. We establish global estimates for the eigenvalues of this system in terms of the profile α and its derivative α'. They allow us to formulate an anti-dynamo theorem and a non-oscillation theorem. The conditions of these theorems, which again involve α and α', must be violated in order to reach overcritical and oscillatory regimes, respectively.

In our work we probe the conduction intersubband transition of an undoped GaAs/Al_0.34Ga_0.66As multiple quantum well via broadband terahertz pulses after resonant photoexcitation at the 1s heavy-hole exciton. The pump-induced change in the transmitted terahertz field shows a strong beating. In the frequency domain this results in an asymmetric Fano-like line shape for the intersubband resonance and an additional broad low-frequency peak. However, the total THz absorption shows only the single symmetric peak of the intersubband transition. In our microscopic theory these signatures unambiguously originate from the phase sensitive superposition of ponderomotive and terahertz intersubband currents.

Ziel dieser Arbeit ist es, die Wechselwirkung von Chlorophyll a mit Uranylionen zu untersuchen. Es wurde eine methanolische Chlorophylllösung mittels Absorptionsspektroskopie charakterisiert. Das Absorptionsmaxima befindet sich bei 665,1 nm. Anschließend wurde das Zentralatom aus dem Komplex entfernt. Das Absorptionsmaximum der erhaltenen Pheophytinlösung liegt bei 653,1 nm. Nach Zugabe von Uranylnitrat war eine bathochrome Verschiebung des Peakmaxima nach 691,3 nm zu beobachten. Die aufgenommenen Emissionsspektren deuten ebenfalls darauf hin, dass der Uranylchlorophyll-Komplex synthetisiert werden konnte. Bei ausreichendem Überschuss an Uranylionen wird das Magnesium im Chla-Molekül durch UO22+ ersetzt.
Anhand der Absorptionspektren wurde versucht, die Assoziationskonstante K für die Bildung des U-Chla-Komplexes aus Pheophytin a zu ermitteln. Man erhält log K = 4,70 ± 0,35.