Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41421 Publications

Interaction of actinides with Desulfovibrio äspöensis. What have we achieved after 3 years of research on this topic?

Merroun, M.; Geipel, G.; Stumpf, T.; Rossberg, A.; Selenska-Pobell, S.; Bernhard, G.

Die Wechselwirkungsprozesse zwischen U, Np und Cm mit Bakterien des Typs Desulfovibrio äspöensis werden dargestellt.

Keywords: Actinides; Bacteria; Desulfovibrio äspöensis; Biosorption; Bioreduction; Bioaccumulation

  • Lecture (others)
    The Äspö - FZR Workshop, 17.-18.05.2004, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-7635
Publ.-Id: 7635


Diagnostic Tools for Operation and Optimization of the ELBE-FEL

Michel, P.; Evtushenko, P.; Lehnert, U.; Schneider, C.; Schurig, R.; Teichert, J.; Seidel, W.; Wohlfarth, D.

A FEL in the mid infrared range is one of the applications of the ELBE cw-electron accelerator. The successful operation of the lasing process for the different wavelength is mainly determined by the alignment of the optical cavities, the bunch length and the energy spread of the electron beam so as the transversal adjustment of the beam through the FEL. The energy spread and the bunch length of the electron beam have their minima at different phase conditions of the accelerator. For various energy settings of the accelerator a special adjustment of both parameters has to be found for the lasing process. The presentation describes the diagnostic tools used at ELBE for the correct alignment of the optical cavity, the steering of the electron beam through the FEL and the adjustment of the electron beam parameters with respect to energy spread and bunch length.

  • Poster
    27th International Free Electron Laser Conference 2005, 21.-26.08.2005, Stanford, California, USA
  • Contribution to proceedings
    27th International Free Electron Laser Conference 2005, 21.-26.08.2005, Stanford, CA, USA
    Proceedings of the 27th International Free Electron Laser Conference,: JACoW / eConf C0508213, 102-104

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Permalink: https://www.hzdr.de/publications/Publ-7633
Publ.-Id: 7633


Optical Beam Properties and Performance of the MID-IR FEL at ELBE

Lehnert, U.; Michel, P.; Teichert, J.; Seidel, W.; Stehr, D.; Wohlfarth, D.; Wünsch, R.

First lasing of the mid-infrared free-electron laser at ELBE was achieved on May 7, 2004. Since then stable lasing has been achieved in the IR range from 4 to 22~μm using electron beam energies from 15 to 35~MeV. At all wavelengths below 20~μm a cw optical power higher than 1~W can be produced with an electron beam of 50~pC bunch charge or less. The optical pulse width at its minimum (2.2~ps measured at 17~μm) resembles the typical electron bunch length of 2~ps without bunch compression but can be increased by detuning the optical cavity. The optical bandwidth was in all cases close to the fourier limit.

  • Poster
    27th International Free Electron Laser Conference 2005, 21.-26.08.2005, Stanford, California, USA
  • Contribution to proceedings
    27th International Free Electron Laser Conference, 21.-26.08.2005, Stanford, CA, USA
    Proceedings of the 27th International Free Electron Laser Conference: JACoW / eConf C0508213, 286-287

Permalink: https://www.hzdr.de/publications/Publ-7632
Publ.-Id: 7632


Progress of the Rossendorf SRF Gun Project

Teichert, J.; Arnhold, A.; Buettig, H.; Janssen, D.; Lehnert, P.; Michel, P.; Moeller, K.; Schneider, C.; Staufenbiel, F.; Xiang, R.; Kamps, T.; Lipka, D.; Marhauser, F.; Volkov, V.; Stephan, J.; Lehman, W.-D.; Will, I.

A superconducting rf photo electron injector (SRF gun) is under development at the Forschungszentrum Rossendorf. The project aims at several issues: improvement of the beam quality for the ELBE superconducting electron linac, demonstration of feasibility of this gun type, investigation of critical components, and parameter studies for future application (BESSY-FEL, 4GLS). In 2005, a substantial progress has been made. The two 3.5-cell niobium cavities for the gun have been delivered from the company ACCEL. The main parts for gun cryostat like vacuum vessel, cryogenic and magnetic shields are ready. Test benches for the cathode cooling system and the cavity tuner are being assembled. The photo cathode preparation lab has been arranged, and the diagnostic beam line has been designed (see T. Kamps et al., this conference). After delivering the gun cavities, their rf properties are being measured at room temperature and the warm tuning is being carried out. The set-up for this treatment and measurement as well as the results will be presented.

  • Poster
    27th International Free Electron Laser Conference 2005, 21.-26.08.2005, Stanford, California, USA
  • Contribution to proceedings
    27th International Free Electron Laser Conference 2005, 21.-26.08.2005, Stanford, CA, USA
    Proceedings of the 27th International Free Electron Laser Conference: JACoW / eConf C0508213, 534-537
  • Poster
    1 st Annual EUROFEL Workshop 2005, 07.-09.11.2005, Orsay, France

Permalink: https://www.hzdr.de/publications/Publ-7631
Publ.-Id: 7631


Transport Theories for Heavy-Ion Collisions in the 1 AGeV Regime

Kolomeitsev, E. E.; Hartnack, C.; Barz, H. W.; Bleicher, M.; Bratkovskaya, E.; Cassing, W.; Chen, L. W.; Danielewicz, P.; Fuchs, C.; Gaitanos, T.; Ko, C. M.; Larionov, A.; Reiter, M.; Wolf, G.; Aichelin, J.

We compare multiplicities as well as rapidity and transverse momentum distributions of protons, pions and kaons calculated within presently available transport approaches for heavy ion collisions around 1 AGeV. For this purpose, three reactions have been selected: Au+Au at 1 and 1.48 AGeV and Ni+Ni at 1.93 AGeV.

  • Journal of Physics G - Nuclear and Particle Physics 31(2005), S741-S757

Permalink: https://www.hzdr.de/publications/Publ-7629
Publ.-Id: 7629


Small-angle neutron scattering and rate theory applied to neutron-irradiation-induced clustering of defects and copper atoms in iron

Bergner, F.; Gokhman, A. R.; Ulbricht, A.

Results of small-angle neutron scattering (SANS) experiments are presented for a low-Cu (0.015 wt%) and a high-Cu (0.42 wt%) iron-based model alloy as well as selected reactor pressure vessel (RPV) steels. In order to exclude a strong participation of nickel atoms in the cluster formation, the selection of RPV steels is restricted to either low Ni content or low Cu in connection with medium Ni content according to the present status of knowledge. These materials were irradiated at about the RPV service temperature up to two or more levels of neutron fluence each. A low-temperature irradiation (60°C) is also included. The results are analysed in terms of both measured cluster size distribution and ratio of magnetic and nuclear contributions to SANS intensities. The assumptions underlying the analysis (e. g. spherical vs. plane scatterers) are addressed.

Calculations are based on the direct solution of the master equation of rate theory for three special cases: (1) Long-term evolution of vacancy clusters (VCs) in the absence of copper atoms, (2) long-term evolution of copper clusters in the absence of vacancies but assuming irradiation-enhanced copper diffusion to occur, and (3) co-clustering of copper and vacancies. Assumptions and limitations are discussed and the results are compared with SANS results.

It turned out that pure VCs or pure copper clusters were never observed. The observations for the low-Cu model alloy and the high-Cu model alloy can be interpreted as being due to spherical vacancy-rich clusters and Cu-rich clusters, respectively. The mean radius is about 1 nm in both cases. The parameters of the rate theory models can be adjusted so as to correctly reflect some major observations. The remaining discrepancies are also discussed.

  • Lecture (Conference)
    Micromechanics and Microstructure Evolution: Modeling Simulation and Experiments, 12.-16.09.2005, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-7628
Publ.-Id: 7628


Skaleninvarianz und deren Bedeutung für die Modellierung der Ermüdungsrißausbreitung in Aluminiumlegierungen

Bergner, F.

Die Arbeit ruht auf zwei Säulen: Die eine besteht in der Aufbereitung, Erprobung und konsequenten Anwendung von Methoden der Skaleninvarianzanalyse, die andere in einem breiten Fundus an experimentellen Daten für aushärtbare Aluminiumknetlegierungen in der Form dünner Bleche, die unter gleichartigen, streng kontrollierten Bedingungen gewonnen worden sind. Als methodische Weiterentwicklungen sind die Fundierung des Umgangs mit der algebraischen Korrelation zwischen Vorfaktor und Exponent einer beliebigen Potenzgleichung, die Übertragung des Ansatzes der finiten Skaleninvarianz auf die Ermüdungsrißausbreitung sowie die Kombination der Idee eines geschwindigkeitsbestimmenden Schrittes mit der Dimensionsanalyse der umgebungsabhängigen Ermüdungsrißausbreitung bis hin zur Kartierung der geschwindigkeitsbestimmenden Schritte zu nennen. Auf experimenteller Seite wurde eine Datensammlung mit gemessenen Streubändern für die Ermüdungsrißausbreitung und das Verfestigungsverhalten von 39 Orientierungen bzw. Auslagerungszuständen von Aluminiumlegierungen aufgebaut. Diese Sammlung wird durch ausgewählte Messungen der Ermüdungsrißausbreitung im schwellenwertnahen Bereich, Restfestigkeitsversuche, Rißschließmessungen, Rauheitsmessungen an Bruchflächen, frequenzabhängige Messungen zum Umgebungseinfluß sowie Untersuchungen an drei Stählen und einer Magnesiumlegierung sinnvoll ergänzt. Auf der Basis der Meßdaten und der Analysemethoden wurde der Werkstoffeinfluß auf die Ermüdungsrißausbreitung in dünnen Blechen aus Aluminiumknetlegierungen bei Belastung mit konstanter Amplitude im Gültigkeitsbereich der linear-elastischen Bruchmechanik untersucht. Dabei wurden folgende Größen als wesentliche Einflußfaktoren identifiziert: - für die Gruppenzugehörigkeit: der Kohärenz- und Ordnungsgrad der festigkeitsbestimmenden Ausscheidungen und die resultierende Gleitverteilung, - für den gemeinsamen Vorfaktor der Legierungen der Gruppe 1: die elastischen Eigenschaften und das Spannungsverhältnis (Translation der Paris-Geraden), - für die Exponenten der Legierungen der Gruppe 1: 0,2%-Dehngrenze, athermischer Verfestigungsparameter, Probendicke und Kc-Wert als dimensionsloses Potenzprodukt (Rotation der Paris-Geraden), - für die Legierungen der Gruppe 2: das Ausmaß der Rißablenkung und eine bleibende Mode-II-Komponente der Rißöffnungsverschiebung, - für den Umgebungseinfluß der Legierung 6013 T6: Frequenz und Schwingbreite des Spannungsintensitätsfaktors. Die Diskussion umfaßt den wertenden Vergleich der experimentellen Ergebnisse mit Befunden und Modellen aus der Literatur, Erklärungsansätze für die Ursachen der Einflußnahme der wesentlichen Parameter sowie einen Modellansatz für die Legierungen der Gruppe 1 auf der Basis einer Mischungsregel. Dabei hatte sich erwiesen, daß keines der aus der Literatur bekannten Modelle alle Befunde richtig wiedergibt. Einige der ausgearbeiteten Erklärungsansätze bedürfen der zukünftigen Vertiefung.

Keywords: aluminium alloys; damage tolerance; dimensional analysis; environmental effects; fatigue crack growth; scale invariance

Permalink: https://www.hzdr.de/publications/Publ-7627
Publ.-Id: 7627


Vector Meson Production in Collisions of Nucleons.

Brinkmann, K.; Abdel-Bary, M.; Abdel-Samad, S.; Clement, H.; Doroshkevich, E.; Dshemuchadse, S.; Dutz, H.; Ehrhardt, K.; Erhardt, A.; Eyrich, W.; Filippi, A.; Freiesleben, H.; Fritsch, M.; Georgi, J.; Gillitzer, A.; Gonser, P.; Jakel, R.; Karsch, L.; Kilian, K.; Koch, H.; Kress, J.; Kuhlmann, E.; Marcello, S.; Meyer, W.; Michel, P.; Morsch, H. P.; Moller, K.; Mortel, H.; Naumann, L.; Pinna, L.; Pizzolotto, C.; Roderburg, E.; Schamlott, A.; Schonmeier, P.; Schroeder, W.; Schulte-Wissermann, M.; Sefzick, T.; Steinke, M.; Stinzing, F.; Sun, G. Y.; Ucar, A.; Ullrich, W.; Wagner, G. J.; Wagner, M.; Wilms, A.; Wintz, P.; Wirth, S.; Wustner, P.; Zupranski, P.

The production of vector mesons in collisions between nucleons is studied in order to address a variety of issues concerning nucleon-nucleon interaction, reaction mechanism and properties of baryons. These studies are summarized with emphasis on the most recent experiments at the Time-of-Flight spectrometer TOF and results obtained at the COoler SYnchrotron COSY in Jülich. While currently the open questions regarding the so-called OZI violation, its relation to the meson exchange picture and the relative importance of contributions to the production mechanism from various channels within this formalism are still unresolved, the present-day experiments hold the potential to clarify the situation greatly. Possible extensions of the experimental program on vector mesons using 4π detection techniques for charged as well as neutral particles, in particular π0, are discussed.

Keywords: Nucleon-nucleon interaction; vector meson production; reaction mechanism and resonances

  • International Journal of Modern Physics A 20(2005)2-3, 427-435

Permalink: https://www.hzdr.de/publications/Publ-7626
Publ.-Id: 7626


Microstructure and non-basal plane growth of epitaxial MAX phase Ti2AlN thin films

Beckers, M.; Schell, N.; Martins, R. M. S.; Mücklich, A.; Möller, W.; Hultman, L.; (Editors)

Thin films of the MAX phase Ti2AlN were epitaxially grown onto single crystal MgO(111) and MgO(100) substrates by DC reactive magnetron co sputtering from Ti and Al targets in an Ar/N2 gas mixture at a temperature of 690 °C. To promote the nucleation of the MAX phase, an fcc (Ti0.63Al0.37)N seed layer was deposited before changing to Ti2AlN growth parameters. The nucleation processes have been studied by real time in situ specular x ray reflectivity. Independent of substrate orientation, the seed layer shows no roughening until its final thickness of approximately 100 Å indicating pseudomorphic layer by layer growth within the descriptive step-flow growth model of Kodambaka et al. [1]. The MAX phase shows heteroepitaxial layer by layer growth on MgO(111), with increased surface roughening up to approximately 200 Å, whereas on MgO(100) the growth mode changes to Volmer Weber type already after three monolayers. X ray scattering in Bragg Brentano geometry of the final, approximately 1000 Å thick, Ti2AlN film reveals lattice parameters of c = 13.463 Å and a = 2.976 Å on the MgO(111) substrate and c = 13.740 Å and a = 2.224 Å on the MgO(100) substrate. From ex situ pole figure measurements the epitaxial relationship between film and substrate lattice was determined to be MgO{111}<110> // Ti2AlN{101‾2}<1‾21‾0>, regardless of the substrate orientation. This tilted, non basal plane growth leads to a threefold grain orientation of Ti2AlN along the MgO<110> directions and a polycrystalline morphology, which is also confirmed by cross sectional transmission electron microscopy. The growth can be assumed to take place in a step-flow mode, i.e. emerging steps on the high surface free energy (0001) plane where adatoms come to rest after diffusion along A-facets, irrespective of epitaxial relationship.

Keywords: Nucleation and growth; Ti-Al-N MAX phase; sputter deposition; in situ x-ray diffraction

  • Journal of Applied Physics 99(2006), 34902

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Permalink: https://www.hzdr.de/publications/Publ-7625
Publ.-Id: 7625


In-beam PET at high-energy photon beams: a feasibility study

H., M.; W., E.

For radiation therapy with carbon ion beams, either of the stable isotope {}^{12}C or of the radioactive one {}^{11}C, it has been demonstrated that the beta+-activity distribution created or deposited, respectively, within the irradiated volume can be visualised by means of positron emission tomography (PET). Those PET images provide valuable information for quality assurance and precision improvement of ion therapy. For this, dedicated PET scanners have been integrated into treatment sites at HIMAC (Japan) and GSI (Germany) to make feasible PET imaging during therapeutic irradiation (in-beam PET). A similar technique may be worthwhile for radiotherapy with hard bremsstrahlung. In addition to the dose delivery monitoring, in-beam PET has been primarily developed for, it may be expected that radiation response of tissue can be detected by means of in-beam PET. We investigate the applicability of PET for treatment control in case of using bremsstrahlung spectra produced by 15 - 50~MeV electrons. Target activation due to (gamma,n)~reactions at energies above 20~MeV yields moderate beta+-activity levels, which can be employed for imaging. The radiation from positrons produced by pair production turns out to be not usable at present because the detectors are overloaded due to the low duty cycle of medical electron linear accelerators, although the degradation of images caused by travelling of positrons between creation and annihilation seems to be tolerable.

  • Physics in Medicine and Biology 51(2006)7, 1779-1789

Permalink: https://www.hzdr.de/publications/Publ-7623
Publ.-Id: 7623


Steam bubble condensation in sub-cooled water in case of co-current vertical pipe flow

Lucas, D.; Prasser, H.-M.

The structure of a steam-water flow in a vertical pipe of 195.3 mm inner diameter was studied using novel wire-mesh sensors for high-pressure / high-temperature operation (max. 7 MPa / 286 °C). Tests were carried out at pressures of 1 and 2 MPa under nearly adiabatic conditions as well as with slightly sub-cooled water. Steam was injected into sub-cooled water and condensed during the upwards flow. The evolution of radial gas fraction profiles and bubble-size distributions along the pipe in a high-pressure steam-water flow was measured for the first time. The experimental data allow correlating the intensity of steam condensation in contact with sub-cooled water with the structure of the interfacial area and the bubble size distribution, which is very important for the model development. The data were used to test the complex interaction of local bubble distributions, bubble size distributions and local heat and mass transfer. The model considers a large number of bubble classes (50). This allows the investigation of the influence of the bubble size distribution. The results of the simulations show a good agreement with the experimental data. The condensation process is clearly slower, if the injection nozzle diameter is increased (from 1 to 4 mm orifices). Also bubble break-up has a strong influence on the condensation process because of the change of the interfacial area. Some modelling errors arises from the uncertainty of the interfacial area for large bubbles and the heat transfer coefficient.

Keywords: bubbly flow; phase transfer; condensation; bubble size distribution; population balance; vertical pipe

Permalink: https://www.hzdr.de/publications/Publ-7622
Publ.-Id: 7622


Influence of melt convection on microstructure evolution of Nd-Fe-B alloys using a forced crucible rotation technique

Biswas, K.; Hermann, R.; Filip, O.; Acker, J.; Gerbeth, G.; Priede, J.

The forced crucible rotation technique has been applied to the solidification of Nd-Fe-B alloys. Specially sealed samples were subjected to well-defined forced rotation during induction heating and solidification. The resulting microstructure of the Nd-Fe-B alloys in consideration of melt convection has been investigated using scanning electron probe microscopy. The determination of the a-Fe volume fraction by measuring the magnetic moment in a vibrating sample magnetometer (VSM) resulted in a distinct reduction of the a-Fe volume fraction in samples with high crucible rotation frequencies. Furthermore, a new category of experiment has been started where a tailored magnetic field was applied in order to study the microstructure evolution due to an enhancement or suppression of the melt convection by additional alternating magnetic fields.

  • Lecture (Conference)
    Magnetic and Superconducting Materials, 05.-09.09.2005, Agadir, Marocco
  • Physica Status Solidi (C) 3(2006), 3277-3280

Permalink: https://www.hzdr.de/publications/Publ-7621
Publ.-Id: 7621


Activities on applied MHD at Forschungszentrum Rossendorf

Gerbeth, G.

Magnetic fields provide an attractive contact-less influence on the motion of metallic or semiconductor melts and the related heat and mass transfer. An optimal design of the magnetic field is often difficult due to the lack of experimental access to the velocity field in such opaque melts. Several recently developed measuring techniques will be presented which allow an almost complete velocity resolution in metallic melts up to temperatures of about 400C. On this basis a combination of cold liquid metal model experiments with numerical simulations represents a powerful approach. Various examples will be presented ranging from crystal growth, aluminum investment casting to liquid metal two-phase flows. For the electromagnetic levitation process results will be given on sample instabilities and active means for stabilization as well as the flow field inside a molten sample.

  • Invited lecture (Conferences)
    Materials Science & Technology, Symposium “Electromagnetics in materials Processing”, 25.-28.09.2005, Pittsburgh, United States

Permalink: https://www.hzdr.de/publications/Publ-7620
Publ.-Id: 7620


HeT-SiC-05International Topical Workshop on Heteroepitaxy of 3C-SiC on Silicon and its Application to Sensor DevicesApril 26 to May 1, 2005,Hotel Erbgericht Krippen / Germany- Selected Contributions -

Brauer, G.; Skorupa, W.; (Editors)

This report collects selected outstanding scientific and technological results obtained within the frame of the European project “FLASiC” (Flash LAmp Supported Deposition of 3C-SiC) but also other work performed in adjacent fields. Goal of the project was the production of large-area epitaxial 3C-SiC layers grown on Si, where in an early stage of SiC deposition the SiC/Si interface is rigorously improved by energetic electromagnetic radiation from purpose-built flash lamp equipment developed at Forschungszentrum Rossendorf. Background of this work is the challenging task for areas like microelectronics, biotechnology, or biomedicine to meet the growing demands for high-quality electronic sensors to work at high temperatures and under extreme environmental conditions. First results in continuation of the project work – for example, the deposition of the topical semiconductor material zinc oxide (ZnO) on epitaxial 3C-SiC/Si layers – are reported too.

Keywords: beta-silicon carbide; biocompatibility; biosensor; doped metal oxide; epitaxy; flash lamp annealing; heterostructure; high-temperature device; hotplate; ion implantation; luminescence; magnetic ion; misfit defect; pulsed laser deposition; resonator; sensor; silicon carbide; simulation; stress; surface melting; zinc oxide

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZR-433 2005
    ISSN: 1437-322X

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Permalink: https://www.hzdr.de/publications/Publ-7616
Publ.-Id: 7616


A possible mechanism for enhanced magnetic quantum oscillations in the mixed state of layered superconductors with incoherent electronic transport

Gvozdikov, V. M.; Wosnitza, J.

We present a new mechanism for the scattering rate in the mixed state of layered superconductors. This mechanism acts through the modification of the layer-stacking factor which suppresses magnetic quantum oscillations if the interlayer electron hopping is incoherent. In the superconducting state, the interlayer incoherence restores and gives a negative contribution to the interlayer quasiparticle scattering rate. The mechanism may explain recent findings of enhanced magnetic quantum-oscillation amplitudes in the superconducting state of a layered organic conductor which displays an incoherent electronic transport across the layers.

Keywords: Quantum magnetic oscillations; Superconductivity; Incoherence

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Permalink: https://www.hzdr.de/publications/Publ-7615
Publ.-Id: 7615


Iron matrix effects on cluster evolution in neutron irradiated reactor steels

Gokhman, A. R.; Bergner, F.; Ulbricht, A.

The present model of vacancy cluster evolution in bcc iron under neutron irradiation, which is based on rate theory according to Odette, can be adjusted with respect to volume fraction and mean radius of vacancy clusters obtained by means of SANS measurements on a low-copper iron alloy. The values of the specific surface energy of clusters and the dislocation density taken to adjust the model are both reasonable. The expectation that the surface energies for the two dose rates considered should agree is best fulfilled, if the real solution model for vacancies in iron is taken into account.

Keywords: Reactor pressure vessel steels; Neutron irradiation; Rate theory; Small angle scattering

  • Contribution to external collection
    Schmelzer, J. W. P., Roepke, G., Priezzhev, V.B.: Nucleation Theory and Applications, Dubna, Russia: Joint Institute for Nuclear Research Publ., 2006, 408-419
  • Invited lecture (Conferences)
    9th Research Workshop Nucleation Theory and Applications, 25.06.-03.07.2005, Dubna, Russia

Permalink: https://www.hzdr.de/publications/Publ-7614
Publ.-Id: 7614


Magnetic quantum oscillations in the normal state of YNi2B2C

Ignatchik, O.; Coffey, T.; Hagel, J.; Jäckel, M.; Jobiliong, E.; Souptel, D.; Behr, G.; Wosnitza, J.

We present de Haas–van Alphen (dHvA) measurements of different YNi2B2C single crystals in magnetic fields up to 32 T. At high magnetic fields three different dHvA frequencies could be detected. The lowest frequency, Fα; could be well resolved down to lower fields just above the upper critical field. An unexpectedly sudden vanishing of the dHvA signal in the mixed state has been observed

Keywords: Rare earth–transition metal alloys; de Haas–van Alphen effect; Electronic structure; Superconductivity

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Permalink: https://www.hzdr.de/publications/Publ-7611
Publ.-Id: 7611


Resistivity studies under hydrostatic pressure on a low-resistance variant of the quasi-2D organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br: quest for instrinsic scattering contributions

Strack, C.; Akinci, C.; Pashchenko, V.; Wolf, B.; Uhrig, E.; Assmus, W.; Lang, M.; Schreuer, J.; Wiehl, L.; Schlueter, J. A.; Wosnitza, J.; Schweitzer, D.; Müller, J.; Wykhoff, J.

Resistivity measurements have been performed on a low (LR)- and high (HR)-resistance variant of the κ-(BEDT-TTF)2Cu[N(CN)2]Br superconductor. While the HR sample was synthesized following the standard procedure, the LR crystal is a result of a somewhat modified synthesis route. Judging by their residual resistivities and residual resistivity ratios, the LR crystal is of distinctly superior quality. He-gas pressure was used to study the effect of hydrostatic pressure on the different transport regimes for both variants. The main results of these comparative investigations are (i) a significant part of the inelastic-scattering contribution, which causes the anomalous ρ(T) maximum in standard HR crystals around 90 K, is sample dependent, i.e., extrinsic in nature; (ii) the abrupt change in ρ(T) at T* ≈ 40 K from a strongly temperature-dependent behavior at T>T* to an only weakly T-dependent ρ(T) at T2 dependence at low temperatures, i.e., for Tc≤T≤T0, although with strongly sample-dependent coefficients A and upper bounds for the T2 behavior measured by T0. Provided that there are no differences in the Fermi surface between both variants—the present experiments give no indications for such differences—the latter result is inconsistent with the T2 dependence originating from coherent Fermi-liquid excitations.

Permalink: https://www.hzdr.de/publications/Publ-7610
Publ.-Id: 7610


Incoherence and enhanced magnetic quantum oscillations in the mixed state of a layered organic superconductor

Gvozdikov, V. M.; Wosnitza, J.

We present a theory which is able to explain enhanced magnetic quantum-oscillation amplitudes in the superconducting state of a layered metal with incoherent electronic transport across the layers. The incoherence acts through the deformation of the layer-stacking factor which becomes complex and decreases the total scattering rate in the mixed state. This novel mechanism can compensate the usual decrease of the Dingle factor below the upper critical magnetic field caused by the intralayer scattering.

  • Open Access Logo HAIT Journal of Science and Engineering 1(2004)4, 771-781

Permalink: https://www.hzdr.de/publications/Publ-7609
Publ.-Id: 7609


First Structural Characterization of a Protactinium(V) Single Oxo Bond in Aqueous Media

Le Naour, C.; Trubert, D.; Di Giandomenico, V. M.; Fillaux, C.; Den Auwer, C.; Moisy, P.; Hennig, C.

We report here the first structural characterization of Pa(V) adducts in concentrated sulfuric and hydrofluoric solutions. In sulfuric medium, X ray Absorption Spectroscopic data show that unlike the other early actinide elements as uranium or neptunium, protactinium doesn’t form a transdioxo cation but a monooxo adduct. In contrast, concentrated hydrofluoric medium precludes the formation of any oxo bond.

Permalink: https://www.hzdr.de/publications/Publ-7608
Publ.-Id: 7608


A spectro-electrochemical cell for Actinide speciation

Hennig, C.

A new spectro-electrochemical cell for EXAFS spectroscopy was presented. The cell was specifically designed for the safe use of radioactive solutions. EXAFS spectra of the U(VI)/U(IV) couple in different ligand systems were discussed.

Keywords: spectro-electrochemical cell; EXAFS

  • Lecture (others)
    ACTINET Meeting, 25.08.2005, Manchester, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-7607
Publ.-Id: 7607


Coolant mixing studies of natural circulation flows at the ROCOM test facility using CFX-10

Höhne, T.; Kliem, S.

Coolant mixing in the cold leg, downcomer and the lower plenum of pressurized water reactors is an important phenomenon mitigating the reactivity insertion into the core. Therefore, mixing of the de-borated slugs with the ambient coolant in the reactor pressure vessel was investigated at the four loop 1:5 scaled ROCOM mixing test facility. Thermal hydraulics analyses showed, that weakly borated condensate can accumulate in particular in the pump loop seal of those loops, which do not receive safety injection. After refilling of th primary circuit, natural circulation in the stagnant loops can re-establish simultaneously and the deborated slugs are shifted towards the reactor pressure vessel (RPV). In the ROCOM experiments, the length of the flow ramp and the initial density difference between the slugs and the ambient coolant was varied.

From the test matrix an experiment with 2% density difference between the de-borated slugs and the ambient coolant was used to validate the CFD software CFX-10. To model the effects of turbulence on the mean flow a Reynolds stress turbulence model was employed and a hybrid mesh consisting of 3.6 million nodes and 6.4 million elements was used.

The experiment and CFD calculation show a stratification in the downcomer. The less dense slugs flow around the core barrel at the top of the downcomer. At the opposite side the lower borated coolant is entrained by the colder safety injection water and transported to the core.The validation proves that CFX-10 is able to simulate appropriately the flow field and mixing effects of coolant with different densities.

Keywords: CFD; ROCOM; boron dilution; PWR

  • Lecture (Conference)
    23rd CADFEM Users’ Meeting 2005, 11.11.2005, Bonn, Germany
  • Contribution to proceedings
    23rd CADFEM Users’ Meeting 2005, 09.-11.11.2005, Bonn, Germany
    CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-7606
Publ.-Id: 7606


Analyses of the V1000CT-1 benchmark with the DYN3D/ATHLET and DYN3D/RELAP coupled code systems including a coolant mixing model validated against CFD calculations

Kliem, S.; Kozmenkov, Y.; Höhne, T.; Rohde, U.

Plant-measured data provided within the specification of the OECD/NEA VVER-1000 coolant transient benchmark (V1000CT) were used to validate the DYN3D/RELAP5 and DYN3D/ATHLET coupled code systems. Phase 1 of the benchmark (V1000CT-1) refers to the MCP (main coolant pump) switching on experiment conducted in the frame of the plant-commissioning activities at the Kozloduy NPP Unit 6 in Bulgaria. The experiment was started at the beginning of cycle (BOC) with average core expose of 30.7 effective full power days (EFPD), when the reactor power was at 27.5% of the nominal level and 3 out of 4 MCPs were operating. The transient is characterized by a rapid increase in the primary coolant flow through the core and, as a consequence, a decrease of the space-dependent core inlet temperature. Both DYN3D/RELAP5 and DYN3D/ATHLET analyses were based on the same reactor model, including identical MCP characteristics, boundary conditions, benchmark-specified nuclear data library and nearly identical nodalization schemes. For an adequate modelling of the redistribution of the coolant flow in the reactor pressure vessel during the transient a simplified mixing model for the DYN3D/ATHLET code was developed and validated against a computational fluid dynamics calculation.

The results of both coupled code calculations are in good agreement with the available experimental data. The discrepancies between experimental data and the results of both coupled code calculations do not exceed the accuracy of the measurement data. This concerns the initial steady state data as well as the time histories during the transient. In addition to the validation of the coupled code systems against measured data, a code-to-code comparison between simulation results has been performed to evaluate relevant thermal hydraulic models of the system codes RELAP5 and ATHLET and to explain differences between the calculation results.

Keywords: Coupled code systems; 3D neutron kinetics; code validation; VVER-1000; coolant transient benchmark

Permalink: https://www.hzdr.de/publications/Publ-7605
Publ.-Id: 7605


Nanofabrication with a mass-separated FIB

Bischoff, L.

In the last two decades focused ion beams (FIB) have become a very useful tool for many tasks in micro- as well as in nano-technology. Probe sizes of less than 10 nm and current densities of more than 10 Acm-2 are now available and allow to use these beams for many applications. Integrated circuit repair and modification, failure analysis, TEM specimen preparation, lithographic mask repair or FIB lithography as well as the writing maskless implantation are the main application in microelectronic research and industry. Especially, in R&D the FIB is very advantageous because of its high spatial resolution and its flexibility varying dose, energy and pattern design on one chip, or even in one structure detail. Therefore also in the field of basic and applied research the FIB became more important, including plasmonics, photonics and nano-optics.
Most of the FIB systems employ a Ga liquid metal ion source (LMIS). Due of the broad spectrum of applications with Ga beams many cases suffer from the impurity incorporation. For special purposes like writing ion implantation or ion mixing in the µm- or nm range different ion species are needed. Therefore alloy liquid metal ion sources (LMIS) are used and the FIB column must be equipped with a mass separation, namely an ExB mass filter system.
The assembly of a modern FIB system is presented and the development and investigation of different alloy LMIS`s working with other materials than Ga as well as their corresponding application in FIB nano-fabrication will be dicussed.
The energy distribution of the ions from an alloy LMIS is one of the determining factors for the performance of an FIB column. Different source materials like Au73Ge27, Au82Si18, Au77Ge14Si9, Co36Nd64, Er69Ni31, and Er70Fe22Ni5Cr3 were investigated with respect to the energy spread of the different ion species as a function of emission current, ion mass and emitter temperature. The alloy LMIS`s discussed above have been used in the Rossendorf FIB system IMSA-100 and later in the improved IMSA-OrsayPhysics machine especially for writing implantation to fabricate nm pattern without any lithographic steps. A Co-FIB was applied for the ion beam synthesis of CoSi2 nano-structures. Also the Co-FIB was applied to modify thin magnetic multi-layers in the nm-scale. Additionally, the possibility of varying the current density of the FIB by changing the pixel dwell-time was used to investigate the radiation damage and the dynamic annealing in Si and SiC at elevated implantation temperatures. Furthermore, a broad spectrum of ions was employed to study the sputtering process depending on temperature, angle of incidence and ion mass on a couple of target materials using the volume loss method. Especially this technique was used for the fabrication of various kinds of micro-tools and other 3D devices. A nano-hole was made into an AFM tip acting as an aperture in a single ion implantation project.
The presented examples underline useful application possibilities to different tasks of nanotechnology (or nanofabrication) applying FIB tools equipped with a mass separation system to chose from a broad spectrum of ion species the desired one.

Keywords: focused ion beam; mass separation; liquid metal ion source; nanofabrication

  • Invited lecture (Conferences)
    FAHL Academica, 26.-27.09.2005, Wörlitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-7604
Publ.-Id: 7604


Novel triazinium-imidothioate zwitterions: intermediates in the reaction of [1,3,4]thiadiazolo[2,3-d][1,2,4]triazolo[1,5-a][1,3,5]-triazinium cations with amines

Wermann, K.; Walther, M.; Günther, W.; Görls, H.; Anders, E.

Starting with bis([1,3,4]thiadiazolo)[1,3,5]triazinium halides 1, a novel class of heterocyclic compounds, the [1,3,4]thiadiazolo[2,3-d][1,2,4]triazolo[1,5-a][1,3,5]triazinium halides 5 were prepared. The reaction between 5 and primary or secondary amines 6 yielded highly substituted guanidines 8 and fused tricyclic bis([1,2,4]triazolo)[1,5-a:10,50-d][1,3,5]triazinium halides 9. The formation of the reactive triazinium-imidothioate zwitterions 7, which is controlled by the influence of negative hyperconjugation, was proven by NMR data and the X-ray structure of 7c. The subsequent ring-closure/ring-opening steps can be understood in terms of an SN(ANRORC) process accompanied by intramolecular proton-transfer reactions. The zwitterions 7 were reacted with EtI forming cationic derivatives 10 or hydrolyzed at pH 6–7 to give novel heterocyclic ethanethioamide 11.

  • Tetrahedron 61(2005)3, 673-685

Permalink: https://www.hzdr.de/publications/Publ-7603
Publ.-Id: 7603


Kortikobasale Degeneration. Asymmetrisch mit Dystonie, Myoklonus und Apraxie

Herting, B.; Beuthien-Baumann, B.; Reichmann, H.

Die kortikobasale Degeneration (CBD) ist eine in der 6. und 7. Lebensdekade sporadisch auftretende neurodegenerative Erkrankung, die klinisch durch ein asymmetrisches akinetisch-rigides Parkinson-Syndrom mit Dystonie, Myoklonus und kortikalen Funktionsstörungen (v.a. eine idiomotorische Apraxie) charakterisiert ist. In fortgeschrittenen Krankheitsstadien können Depression, Demenz und frontale Verhaltensveränderungen hinzutreten. Aktuellle molekulargenetische Befunde sprechen für eine einheitliche Ursache der CBD und der progressiven supranukleären Blickparese (PSP) im Sinne von Tauopathien. Diese Arbeit fasst klinisches Bild, aktuelle Diagnosekriterien, Differenzialdiagnosen, apparative Zusatzdiagnostik und Therapieoperationen zusammen.

  • Der Neurologe und Psychiater 1-2(2005), 41-44

Permalink: https://www.hzdr.de/publications/Publ-7602
Publ.-Id: 7602


Gene Expression Analysis of CD34+ Hematopoietic Stem Cultivated On Bioartifical Materials

Oswald, J.; Steudel, C.; Joergensen, B.; Salchert, K.; Ehninger, G.; Thiede, M.; Bornhäuser, M.; Werner, C.

Abstract wird nachgereicht.

  • Poster
    2nd Max Bergmann Symposium, 17.-18.02.2005, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-7601
Publ.-Id: 7601


β decay of 95Ag

Harissopulos, S.; Döring, J.; La Commara, M.; Schmidt, K.; Mazzocchi, C.; Borcea, R.; Galanopoulos, S.; Górska, M.; Grawe, H.; Hellström, M.; Janas, Z.; Kirchner, R.; Roeckl, E.; Johnstone, I. P.; Schwengner, R.; Skouras, L. D.

We studied the β-decay properties of the N=Z+1 nucleus 95Ag by measuring β-delayed γ-rays and β-γ-γ coincidences with a plastic scintillator as β-detector and a Ge-detector array. The 95Ag nuclei were produced by means of the 58Ni(40Ca,p2n) reaction and separated with the GSI online mass separator. The previously reported level scheme of the 95Pd daughter nucleus was extended considerably. The deduced level scheme is compared with different shell-model calculations with or without breaking the 100Sn core.

  • Physical Review C 72(2005)2, 4303

Permalink: https://www.hzdr.de/publications/Publ-7600
Publ.-Id: 7600


Module-assisted synthesis of the bifunctional labelling agent N-succinimidy 4-[18F]fluorobenzoate ([18F]SFB)

Mäding, P.; Füchtner, F.; Wüst, F.

The three-step radiosynthesis of N-succinimidyl 4-[18F]fluorobenzoate ([18F]SFB) was adapted to a remotely controlled synthesis module. After optimization of the reaction conditions, the final [18F]SFB was obtained in decay-corrected radiochemical yields of 34 - 38 % (related to [18]fluoride; n = 12) within a synthesis time of 68 min. The radiochemical purity was in the range of 93 -96 %.

Keywords: 18F-labelling; Positron emission tomography (PET); [18F]SFB; Automated module synthesis

  • Applied Radiation and Isotopes 63(2005), 329-332

Permalink: https://www.hzdr.de/publications/Publ-7598
Publ.-Id: 7598


Synthesis and copper(II) complexation of glycodendrimers having a cyclam-core

Röhrich, A.; Bernhard, G.; Geipel, G.; Stephan, H.

Derivatives of cyclam and its metal complexes are of considerable interest in bioinorganic chemistry, biology and medicine. In the latter nexus, cyclam compounds show anti-HIV activities, and metallated cyclams may be used in radiotherapy applying 64/67Cu or 186/188Re.1 Recently, we could show that the grafting of polyethylene glycol arms on the cyclam core leads to both a higher complex stability and an increasing shielding effect for copper(II).2 In this contribution the synthesis of two novel cyclams 1 and 2 (cf. Fig. 2) carrying sugar molecules as terminal groups will be presented. The complex formation of these glycodendrimers with copper(II) has been studied by UV-vis and time-resolved laser-induced fluorescence (TRLFS) measurements showing rapid formation of 1:1 complexes.

  • Poster
    XXX International Symposium on Macrocyclic Chemistry (ISMC), 17.-21.07.2005, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-7596
Publ.-Id: 7596


Material data measurements of molten Nd2Fe14B

Plevachuk, Y.; Sklyarchuk, V.; Hermann, R.; Gerbeth, G.

High performance Nd-Fe-B magnets are of enormous economic interest and play a key role in the development of electronics and motors. The excellent ferromagnetic properties of the Rare - Earth magnets are due to the hart magnetic Nd2Fe14B-phase (f-Phase) with high saturation polarization and magnetocrystalline anisotropy. Stoichiometric Nd-Fe-B alloys perform a peritectic reaction under near-equilibrium conditions, and the phase and microstructure selection plays a crucial role on the hard magnetic properties of this material. Besides additions and substitutes, the melt convection strongly influences the microstructure formation of Nd-Fe-B alloys, in particular the volume fraction and grain size of the properitectic g-Fe phase which deteriorates the hard magnetic properties of the material. Numerical simulations are essential in order to understand and design the various flow structures. Therefore, the investigation of electrophysical and structure sensitive properties of the system in the liquid state prior to solidification is very important.
We present new results for the electrical and thermal conductivity, thermoelectric power and viscosity carried out in a temperature range from the liquidus (1553 K) to 1620 K. The electrical conductivity and thermoelectric power were measured using a contact 4-probe method. The thermal conductivity was investigated by a steady-state concentric cylinder method. The shear viscosity measurements were performed using an oscillating-cup viscometer. Special attention was paid to the region close to the liquidus where heating and cooling rates were reduced and the measurement steps shortened to 1 K.

  • Poster
    European Congress on Advanced Materials and Processes (EUROMAT 2005), 05.-08.09.2005, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-7595
Publ.-Id: 7595


Anomalous ion accelerated bulk diffusion of interstitial nitrogen

Abrasonis, G.; Möller, W.; Ma, X. X.

Interstitial N diffusion under low energy (~700 eV) Ar+ bombardment at 673 K in ion beam nitrided austenitic stainless steel is investigated. Ar+ ion bombardment increases the N mobility in depths far beyond the ion penetration depth, resulting in an increased broadening of the N depth profile as a function of Ar+ flux. This effect cannot be explained by any established mechanism of radiation-enhanced diffusion. An explanation based on quasiparticle-enhanced mobility is proposed.

Keywords: Diffusion of impurities; Ion radiation effects; Anharmonic lattice modes

  • Physical Review Letters 96(2006), 065901

Permalink: https://www.hzdr.de/publications/Publ-7594
Publ.-Id: 7594


Experimental study on bubble motion in a rectangular bubble column using high-speed video observations

Zaruba, A.; Krepper, E.; Prasser, H.-M.; Reddy Vanga, B. N.

A two-phase flow in a rectangular bubble column of 100×20 mm cross-section and 1.5 mm height was studied using a high-speed video system. Series of images were taken at different elevations at a frequency of 500 Hz. The images were processed using a bubble recognition algorithm. In such a way, an individual bubble in the gas swarm could be tracked. The time-averaged velocity profiles and the turbulent diffusion coefficients were derived as a function of the superficial gas velocity. The lateral displacement of bubbles travelling over a certain vertical distance was transformed into a probability density distribution in order to measure the turbulent diffusion coefficient of the gaseous phase. The shape of the distributions obtained was found to fit well to the Gaussian standard distribution. The dispersion coefficients were observed to grow proportionally to the square root of the vertical distance. The diffusion coefficients were calculated from the proportionality factor and were compared with some correlations published in the literature. The experiments were performed for superficial gas velocities ranging from 1 to 6 mm/s. The bubbles were generated either by a porous sparger or a set of capillaries placed at the bottom of the column. The measurements were taken at different heights between 1 and 1.2 m where the bubble cloud was occupying the entire cross-section.

Keywords: Bubble flow; Rectangular channel; Image processing; Bubble dispersion; Turbulent diffusion

  • Flow Measurement and Instrumentation 16(2005)5, 277-287

Permalink: https://www.hzdr.de/publications/Publ-7593
Publ.-Id: 7593


TEM-Investigation of Si(001) Modified by Pr Implantation

Mücklich, A.; Kögler, R.; Eichhorn, F.

TEM-Investigation of Si(001) Modified by Pr Implantation

Keywords: high-K dielectrics; Pr oxide; Pr silicide; Pr silicate

  • Poster
    Microscopy Conference, 28.08.-02.09.2005, Davos, Schweiz
  • Contribution to proceedings
    Microscopy Conference 2005, 28.08.-02.09.2005, Davos, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-7592
Publ.-Id: 7592


Complex formation of small organic ligands with uranium(VI) - comparison of stability constants with proton dissociation

Geipel, G.; Vulpius, D.; Brendler, V.; Bernhard, G.

During the past we have studied the complex formation behavior of uranium(VI) towards several aromatic carboxylic acids. These studies were continued, so that the formation constants of the monohydroxo- and dihydroxo- as well as some trihydroxobenzoic acids are available. A short review of these formation constants will be given.
Besides this we have compared the complex formation constants to the protonation constants of the carboxyl group. A linear relationship between these two properties was found. An decreasing protonation constant is connected to an increasing complex formation constant.
Nevertheless some exceptions of this rule were observed. These deviations can be explained by the different type of complex formation between uranium(VI) and the organic ligand. This concerns especially the number and position of the hydroxo groups in phenolic carboxylic acids. In the case of 2,3-dihydroxybenzoic the two OH-groups are involved in the complex formation already at relative low pH values. During the complex formation two protons are released from the organic ligand. The formed complex does not include the carboxylic group. The two phenolic hydroxo groups form a stable five atom ring with the uranylion. This result could be confirmed by EXAFS measurements.

  • Contribution to proceedings
    Migration 2005, 10th International Conference on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 18.-23.09.2005, Avignon, France
  • Poster
    Migration 2005, 10th International Conference on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 18.-23.09.2005, Avignon, France

Permalink: https://www.hzdr.de/publications/Publ-7591
Publ.-Id: 7591


Interaction mechanisms of bacterial strains isolated from extreme habitats with uranium

Merroun, M.; Nedelkova, M.; Rossberg, A.; Hennig, C.; Selenska-Pobell, S.

This paper summarizes the effect of pH on the speciation and cellular localization of uranium bound by bacterial strains isolated from the S15 deep-well montoring site, located at the Siberian radioactive subsurface depository Tomsk-7, Russia. Microbiological methods in combination with extended X-ray absorption fine structure (EXAFS) spectroscopy, transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX) were applied. EXAFS analysis showed that the cells of the two isolates, Microbacterium oxydans S15-M2 and Sphingomonas sp. S15-S1, precipitate U(VI) as m-autunite-like phase at pH 4.5, probably due to the release of inorganic phosphate from the cells as result of the microbial metabolism. However, at pH 2 uranium formed complexes with organically bound phosphates of the cell surface. The results of the EXAFS studies corroborate those found using TEM and EDX analysis. Different hypothesis explaining the different coordination chemistry of uranium to bacteria as a function of pH of uranium solution in terms of solubility of m-autunite and/or microbial activity will be discussed.

  • Radiochimica Acta 94(2006), 723-729
  • Contribution to proceedings
    Migration 2005, 10th International Conference on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 18.-23.09.2005, Avignon, France
  • Lecture (others)
    FZR - FSU Jena Workshop, 27.-28.07.2005, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-7590
Publ.-Id: 7590


Entwicklung neuer Chelatsysteme für nuklearmedizinische Anwendungen

Juran, S.; Schubert, R.; Stephan, H.; Kraus, W.

Ziel ist es radioaktive Kupfer(II)-Komplexe hoher Stabilität mit einstellbarer Bioverteilung auf der Basis von 3,7-Diazabicyclo[3.3.1]nonan (Bispidin) zu entwickeln. Voruntersuchungen haben gezeigt, dass insbesondere sechszähnige Liganden ein hohes inhärentes Anwendungspotential für die Radionuklidtherapie aufweisen. [1]
Es wird die Darstellung neuer sechszähniger Bispidinderivate mit Pyridin- und Imidazolgruppen präsentiert. Die Komplexbildungseigenschaften gegenüber Kupfer(II) sowie Möglichkeiten zur Kopplung von Biomolekülen werden diskutiert.
Die Synthese der Bispidinliganden (1) erfolgt durch zwei aufeinanderfolgende Mannich-Kondensationen, wobei Pyridin- und Imidazol-Edukte variieren.

Von ausgewählten Vertretern wurden kristalline Kupfer(II)-Komplexe isoliert und die Struktur mittels Röntgendiffraktometrie gelöst. Weiterhin erfolgten Untersuchungen zur Langzeitstabilität dieser Kupfer(II)-Komplexe in Anwesenheit der Konkurrenzliganden Glutathion und Histidin mittels UV/Vis-Spektroskopie.

  • Lecture (others)
    Wissenschaftstage Fachhochschule Lausitz, 23.-25.11.2005, Senftenberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-7589
Publ.-Id: 7589


Synthese und Charakterisierung neuer sechszähniger 3,7-Diazabicyclo-[3.3.1]nonan-Derivate und ihrer Kupfer(II)-Komplexe

Juran, S.; Schubert, R.; Steinbach, J.; Stephan, H.; Kraus, W.

Ziel/Aim:

Es sollen radioaktive Kupfer(II)-Komplexe hoher Stabilität mit einstellbarer Bioverteilung auf der Basis von 3,7-Diazabicyclo[3.3.1]nonan (Bispidin) entwickelt werden. Voruntersuchungen haben gezeigt, dass hier sechszähnige Liganden am aussichtsreichsten sind [1]. Durch Modifizierung des Bispidingerüstes ergeben sich günstige Möglichkeiten zur Einführung von Biomolekülen und damit zur gezielten Beeinflussung der Bioverteilung.
Es wird die Darstellung sechszähniger Bispidinderivate mit Pyridin- und Imidazolgruppen vorgestellt. Die Komplexbildungseigenschaften gegenüber Kupfer(II) sowie Möglichkeiten zur Kopplung von Biomolekülen werden diskutiert.
Methodik/Methods:
Die Synthese der Bispidinliganden erfolgt durch zwei aufeinanderfolgende Mannich-Kondensationen, wobei Pyridin- und Imidazol-Edukte eingesetzt werden. Von ausgewählten Vertretern wurden kristalline Kupfer(II)-Komplexe isoliert und die Struktur mittels Röntgendiffraktometrie gelöst. Untersuchungen zur Stabilität dieser Kupfer(II)-Komplexe in Anwesenheit der Konkurrenzliganden Glutathion und Histidin sind mittels UV/Vis-Spektroskopie durchgeführt worden.
Ergebnisse/Results:
Die dargestellten sechszähnigen Bispidinliganden weisen eine schnelle Kinetik für die Komplexbildung mit Kupfer(II) in wässriger Lösung auf. Die kristallinen Kupfer(II)-Komplexe zeigen eine verzerrte oktaedrische Koordinationsgeometrie, wobei das Zentralatom nahezu vollständig von der Umgebung abgeschirmt ist. Die entsprechenden Kupfer(II)-Komplexe mit Bispidinliganden sind auch bei einem Überschuss von Konkurrenzliganden wie Glutathion und Histidin stabil.
Schlussfolgerung/Consequences:
Die dargestellten Kupfer(II)-Komplexe mit sechszähnigen Bispidinliganden weisen eine sehr hohe Stabilität auf und verfügen damit über ein hohes inhärentes Anwendungspotential für radiopharmazeutische Anwendungen in Diagnostik und Therapie. Dazu ist es notwendig, Biomoleküle an das Grundgerüst anzukoppeln, um eine selektive Anreicherung der radioaktiven Kupferkomplexe im Zielgewebe zu erzielen. Radiopharmakologische Untersuchungen zur Optimierung der radioaktiven Markierung der Bispidinderivate mit 64/67Cu sowie zur Biodistribution ausgewählter Radiotracer mittels micro-PET sollen sich anschließen.

  • Lecture (others)
    13. Arbeitstreffen AG Radiochemie/Radiopharmazie, 06.-08.10.2005, Seefeld, Austria

Permalink: https://www.hzdr.de/publications/Publ-7588
Publ.-Id: 7588


Synthese und Komplexbildungseigenschaften neuer sechszähniger Bispidinderivate mit Pyridin- und Imidazolgruppen

Juran, S.; Stephan, H.; Schubert, R.; Geipel, G.; Kraus, W.; Jakob, M.; Kerscher, M.; Comba, P.

Sechszähnige Derivate des Bispidins (3,7-Diazabicyclo[3.3.1]nonan) bilden mit einer Reihe von Übergangsmetallen Komplexe hoher Stabilität [1]. Insbesondere die Kupfer(II)-Komplexe weisen ein hohes inhärentes Anwendungspotential für die Radionuklidtherapie auf.
Zum Verbindungstyp 1 gelangt man durch zwei aufeinanderfolgende Mannich-Kondensationen, wobei durch Variation der Pyridin- und Imidazol-Edukte das Löslichkeits- und Komplexbildungsverhalten gezielt eingestellt werden kann.

Die zeitaufgelöste Laser-Fluoreszenz-Spektroskopie wurde eingesetzt, um Aussagen zur Stabilität von Kupfer(II)-Komplexen mit den Bispidinderivaten 1 zu erhalten. Die Struktur ausgewählter Komplexe konnte mittels Röntgendiffraktometrie aufgeklärt werden. Weiterhin wurden spektroskopische Untersuchungen (UV-Vis) zur Langzeitstabilität der Kupferkomplexe in Anwesenheit der Konkurrenzliganden Glutathion und Histidin durchgeführt.

  • Poster
    GDCh-Jahrestagung 2005, 11.-14.09.2005, Düsseldorf, Deutschland
  • Contribution to proceedings
    GDCh-Jahrestagung 2005: Chemie schafft neue Strukturen, 11.-14.09.2005, Düsseldorf, Deutschland
    Kurzreferate, 535

Permalink: https://www.hzdr.de/publications/Publ-7587
Publ.-Id: 7587


DYN3D version 3.2 - code for calculation of transients in light water reactors (LWR) with hexagonal or quadratic fuel elements - description of models and methods -

Grundmann, U.; Rohde, U.; Mittag, S.; Kliem, S.

DYN3D is an best estimate advanced code for the three-dimensional simulation of steady-states and transients in light water reactor cores with quadratic and hexagonal fuel assemblies. Burnup and poison-dynamic calculations can be performed. For the investigation of wide range transients, DYN3D is coupled with system codes as ATHLET and RELAP5.

The neutron kinetic model is based on the solution of the three-dimensional two-group neutron diffusion equation by nodal expansion methods. The thermal-hydraulics comprises a one- or two-phase coolant flow model on the basis of four differential balance equations for mass, energy and momentum of the two-phase mixture and the mass balance for the vapour phase. Various cross section libraries are linked with DYN3D.

Systematic code validation is performed by FZR and independent organizations.

Keywords: light water reactors; transients; computer code; core model; three-dimensional; two group neutron diffusion; nodal methods; two-phase flow; thermal hydraulics; fuel rod model; reactor safety; cross section libraries; burnup calculation; Xenon and Samarium dynamics; coupling; system codes

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZR-434 2005
    ISSN: 1437-322X

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Permalink: https://www.hzdr.de/publications/Publ-7586
Publ.-Id: 7586


Nachrechnung des ROCOM Experiments T6655_Y1 mit dem CFD-Programm CFX-5

Burwell, M. J.; Höhne, T.; Scheuerer, M.

Im Rahmen des Vorhabens SR 2444 wurde eine Nachrechnung des ROCOM Experiments T6655_Y1 mit dem CFD-Programm CFX-5 durchgeführt. Die Anlage ROCOM dient zur Untersuchung der Vermischung hypotethischer Kühlmittelpfropfen mit verringerter Borkonzentration bei unterschiedlichen Schleifendurchsetzen des Primärkreislaufs. Für die Nachrechnung mit CFX wurde der Versuch T6655_Y1 ausgewählt. In diesem Versuch beträgt die Dichtedifferenz zwischen dem, in benachbarten Schleifen 1 und 2, vorgelegten Pfropfen und Umgebung 0,25 %. Das Ergebnis des Experiments besteht hauptsächlich in den mittleren und maximalen relativen Absenkungen der Borkonzentrationen (entspricht mittlerer und maximaler Tracerkonzentration in den Versuchen) am Kerneintritt. Die Ergebnisse der Rechnungen zeigen, dass das Rechenprogramm die Phenomena der Vermischung generell gut erfasst hat.

Keywords: Coolant Mixing; CFD; ROCOM

  • Other report
    München: GRS - A - 2871, 2005
    14 Seiten

Permalink: https://www.hzdr.de/publications/Publ-7585
Publ.-Id: 7585


A Far-Infrared FEL for the Radiation Source ELBE

Grosse, E.; Lehnert, U.; Michel, P.; Schlenk, R.; Seidel, W.; Wolf, A.; Willkommen, U.; Wohlfarth, D.; Wünsch, R.

After successfully commissioning the mid‐infrared FEL (U27) and adjoining a second accelerator unit (up to 35 MeV) at ELBE we have modified our plan how to produce radiation in the far infrared.To ensure the continuous variation of the wavelength up to 150 microns we want to complement the U27 undulator by a permanent magnet undulator with a period of 100 mm (U100). The minimum gap of 24 mm and the hybrid construction consisting of Sm/Co magnets and soft iron poles ensures sufficient radiation resistance and allows rms undulator parameters up to 2.7. The large field variation allows us to cover the whole wavelength range by only two different electron energies (e.g. 20 and 35 MeV). To reduce the transverse beam size we use a partial waveguide which is 10 mm high and wide enough to allow free propagation inhorizontal direction. It spans from the last quadrupole in front of the undulator up to the downstream mirror and is somewhat longer than 8 m. To minimize the coupling losses between free propagation and the waveguide mode appropriate bifocal resonator mirrors will be sed. Detailed calculations and computer simulations predict an outcoupled laser power of roughly 35 W around 40 microns and 20 W at150 microns.

Keywords: undulator; free-electron laser; waveguide; radiation source ELBE

  • Poster
    27th Int. Free Electron Laser Conference, 21.-26.08.2005, Palo Alto, USA
  • Contribution to proceedings
    27th Free Electron Laser Conference, 21.-26.08.2005, Palo Alto, USA
    Proceedings of the 27th International Free Electron Laser Conference, 290-292

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Permalink: https://www.hzdr.de/publications/Publ-7584
Publ.-Id: 7584


Spin correlations in the reaction pi(+/-)(D)over-right-arrow ->(Sigma)over-right-arrow(+/-)Theta(+) and the parity of Theta(+)

Kampfer, B.; Titov, A. I.

We analyze two types of spin observables in the reaction pi D->->Sigma(->)Theta(+) near the threshold. One concerns the spin-transfer coefficients K-x(x) and K-z(z). The second is the deuteron spin anisotropy. These observables are sensitive to the Theta(+) parity and can be used as a tool for the Theta(+) parity determination.

  • Physical Review C 71(2005), 062201(R)

Permalink: https://www.hzdr.de/publications/Publ-7583
Publ.-Id: 7583


Di-electron bremsstrahlung in intermediate-energy pn and Dp

Kämpfer, B.; Kaptari, K. L.

Invariant mass spectra of di-electrons stemming from bremsstrahlung processes are calculated in a covariant diagrammatical approach for the exclusive reaction Dp to pspnpe+e- with detection of a forward spectator proton, psp. We employ an effective nucleon-meson theory for parameterizing the sub-reaction np to pspnpe+e- and, within the Bethe-Salpeter formalism, derive a factorization of the cross section in the form dsigmaDp to pspnpe+e- /dM = dsigmanp to pspnpe+e- /dM x kinematical factor related solely to the deuteron (M is the e+e- invariant mass). The effective nucleon-meson interactions, including the exchange mesons pi, sigma, omega and rho as well as excitation and radiative decay of Delta(1232), have been adjusted to the process pp to pp e+e- at energies below the vector meson production threshold. At higher energies, contributions from omega and rho meson excitations are analyzed in both, NN and Dp collisions. A relation to two-step models is discussed. Subthreshold di-electron production in Dp collisions at low spectator momenta is investigated as well. Calculations have been performed for kinematical conditions envisaged for forthcoming experiments at HADES.

  • Nuclear Physics A 764(2006), 338-370

Permalink: https://www.hzdr.de/publications/Publ-7582
Publ.-Id: 7582


Algebraic approach to bare nucleon matrix elements of quark operators

Zschocke, S.; Kämpfer, B.; Plunien, G.

An algebraic method for evaluating bare nucleon matrix elements of quark operators is proposed. Thereby, bare nucleon matrix elements are traced back to vacuum matrix elements. The method is similar to the soft pion theorem. Matrix elements of two-quark, four-quark and six-quark operators inside the bare nucleon are considered.

  • Physical Review D 72(2005), 014005

Permalink: https://www.hzdr.de/publications/Publ-7581
Publ.-Id: 7581


In-depth distribution of silica nanoparticles in free-standing silica/vinyl polymer nanocomposite films

Gago, R.; Vazquez, L.; Grambole, D.; Herrmann, F.; Groetzschel, R.; Vela, M.; Amalvy, J. I.; Munoz-Martin, A.; Climent-Font, A.

Film-forming silica-based materials are potentially useful as tough, abrasion-resistant coatings and fire-retardants. However, these formulations are often solvent-based, and there is an actual tendency to replace them by more environmentally friendly, water-borne coatings. Herein we study surfactant-free and water-borne nanocomposite films consisting of silica nanoparticles (20 nm size) embedded in a vinyl polymer matrix. Highly transparent free-standing films were prepared by copolymerizing of 4-vinlypyridine (4VP) with low glass transition temperature comonomers such as n-butyl acrylate (n-BuA) or n-butyl methacrylate (n-BuMA) in the presence of an ultrafine aqueous silica sol. Films with different silica contents (ranging from 14% to 61%) were prepared with thickness around 100 um. The in-depth distribution of the nanoparticles has been studied by extracting the Si profile from Rutherford backscattering spectrometry (RBS) measurements. Standard RBS with 2 MeV He+ was performed to established the Si profile in the near surface region while a focused 3MeV Li+ ion beam (3-4 um) provided by a nuclear microprobe was used in cross-section specimens to determine the in-depth profile at larger depths.

  • Poster
    17th International Conference on Ion Beam Analysis, 26.06.-01.07.2005, Seville, Spain

Permalink: https://www.hzdr.de/publications/Publ-7577
Publ.-Id: 7577


Possible consideration of METCOR experimental results in FE models for IVR

Altstadt, E.; Willschuetz, H.-G.

At the Institute of Safety Research of the FZR a finite element model has been developed simulating the thermal processes and the viscoplastic behaviour of the vessel wall. An advanced model for creep and material damage has been established and has been validated using experimental data. The thermal hydraulic and the mechanical calculations are sequentially and recursively coupled. The model is capable of evaluating fracture time and fracture position of a vessel with an internally heated melt pool.
At the Alexandrov Research Institute of Technology in Sosnovy Bor (Russia), the thermo-chemical interaction between molten corium and RPV steel is experimentally investigated. The work is done in the frame of the ISTC project METCOR. The experiments show that the ablation of the steel occurs at interface temperatures below the steel melting temperature. The ablation rate significantly depends on the chemical compostion of the corium melt.
The presentation shows a concept for using the METCOR data within the finite element model of the FZR.

Keywords: In-vessel retention; finite element analysis; corium-steel interaction; METCOR; Nuclear rectors; Severe accident management

  • Lecture (others)
    6th METCOR Project Meeting, 12.07.2005, Sankt Petersburg, Russia

Permalink: https://www.hzdr.de/publications/Publ-7572
Publ.-Id: 7572


Potential of proton microbeam in the study of dental composites. 2. Compositional heterogeneity by micro-PIXE and complementary analysis by micro-PIGE and micro-PBS

Harangus, L.; Iordan, A.; Preoteasa, E. A.; Preoteasa, E.; Grambole, D.; Herrmann, F.; Groetzschel, R.

To investigate the structural and chemical heterogeneity of dental composites, we analyzed their composition both in whole maps and in selected points by μPIXE, μPIGE and μPBS (Proton Backscattering). Two qualitatively similar biomaterials labeled IV.a and V were studied. Thick disk-shaped, flat-surface samples were prepared by photopolymerization on a glass plate, and investigated at the Rossendorf nuclear microprobe with a 3.1 MeV proton beam focused to a ~3 μm spot. Areas of 250 x 250 μm² were mapped, and selected inclusions were analyzed in point mode using three detectors simultaneously. Five areas located ~0.5-2 mm apart of each other and five inclusions from a map for IV.a, as well as one area for V were analysed. Hydroxylapatite and pyrite were used as reference materials. Concentrations from μPIXE spectra were determined by GUPIX calculations. Up to 19 elements were detected, i.e. Ca, Zr, Ba, Yb (major), Fe, Sr, Hf (minor), Mn, Se, Ho (traces) by μPIXE; F, Na, Al, Si by μPIGE; and C, O, F, Al, Si, Ca (and possibly N, Na, Cl) by μPBS. As compared to IV.a, in composite V higher Ca, lower Zr and Ba, and similar Yb levels were found. The mixture in composite IV.a appeared as a heterogeneous map both on a ~1.0 and on a ~0.1 mm scale of the sample. Thus in all μPIXE maps the absolute concentrations of Ca, Zr, Ba and Yb showed rather high dispersion (relative standard deviations ~31-44 %), but the ratios Zr/Ca, Ba/Ca and Yb/Ca were largely constant. The inclusions analyzed in point mode were Zr-rich and although their relative concentrations were roughly constant the absolute ones showed very high dispersion (rel. SD ~120 %). Hence proton microprobe analysis methods are well suited to study the dental composites and to characterize in detail their heterogeneous structure.

  • Poster
    17th International Conference on Ion Beam Analysis, 26.06.-01.07.2005, Seville, Spain

Permalink: https://www.hzdr.de/publications/Publ-7571
Publ.-Id: 7571


Proton microprobe for analysis of normal and osteoporosis-affected compact bone. 2. Low-Z elements

Iordan, A.; Harangus, L.; Preoteasa, E. A.; Grambole, D.; Neelmeijer, C.; Herrmann, F.; Groetzschel, R.; Mihul, A.; Noveanu, D.; Batrina, D.

While μPIXE of normal and osteoporosis-affected bones was suitable for metals from Ca on (abstract 1 from our group, this volume), it fails to detect low-Z elements. Some of them may be involved in osteoporosis, e.g. F prevents demineralization and N occurs in bone proteins. Here we examined the potential of μPIGE, μPBS and μPIXE to study low-Z elements in the outer surface layer of rat and human bones with osteoporosis. The bone sections were as described (abstract 1), and the μPIGE, μPBS and μPIXE measurements were performed at the Rossendorf nuclear microprobe with 3.1 MeV protons focused to ~3 μm, using concomitantly three detectors.
μPIGE was useful to detect light elements like F, P, Na, S- the concentrations of these elements can be calculated by comparing the characteristic X- ray lines of suitable standards. CaF2, NaCl, pyrite and hydroxylapatite (HA) were used as reference materials. PBS provided information about C, N, O, F, Mg, P and Ca, mainly qualitative at this stage.
Further development would allow N and S analysis, which may help evaluate the bone collagen, supposedly altered in osteoporosis. Only P, S, Cl and Ca were monitored here by PIXE and the concentrations of these elements were calculated by GUPIX. In all bones, a P/Ca ratio of 0.32-0.39 was found, below the 0.46 value of HA, suggesting a fraction of Ca as carbonate in addition to HA. Both P and S concentrations showed variability from bone to bone. The μPIXE maps of P were positively corelated to the Ca maps, evidencing well- ressolved patterns.
Thus the information yielded by μPIGE and μPBS on the light elements from osteoporosis-affected bones was potentially quantitative, complementary to μPIXE, and pathologically relevant, and the three methods complement each other in understanding this bone disease.

  • Poster
    17th International Conference on Ion Beam Analysis, 26.06.-01.07.2005, Seville, Spain

Permalink: https://www.hzdr.de/publications/Publ-7570
Publ.-Id: 7570


Potential of proton microbeam in the study of dental composites. 1. Micro-PIXE mapping of Ca, Zr, Ba and Yb

Preoteasa, E. A.; Preoteasa, E.; Harangus, L.; Iordan, A.; Grambole, D.; Herrmann, F.; Neelmeijer, C.

In recent studies, PIXE and ERDA showed a high potential for dental composites [1, 2]. However, wide-beam IBA techniques can not explore the biomaterials' granular structure, which requires microbeam methods to be accounted for.
In this report we applied proton μPIXE for mapping the major elements in dental composites, with the aim of evaluating the method's potential. A flat sample with a smooth surface (~ 1 mm thick) of the composite previously labeled IV.a [1,2] was prepared by photopolymerization on a glass plate. Measurements were carried out at the Rossendorf nuclear microprobe with a 3.1 MeV proton beam focused to a spot of ~3 μm. Five areas ~250 x 250 μrn located ~0.5-2 mm apart of each other were mapped on the flat specimen at ~4 μm resolution. The μPIXE maps of Ca, Zr, Ba and Yb clearly evidenced the granular structure of the composite. The mineral particles revealed a polydisperse size distribution and different compositions. Thus while most mineral particles were Ca-rich and not larger than ~8 μm, a small number of much larger inclusions were seen, with size in the ~16-60 μm range and with high levels of Zr, Ba and Yb. Generally the maps of the elements were complementary, but some apparent deviations from this rule were seen in the different areas. This suggests that the mixture of mineral particles may show some degree of heterogeneity visible in the sample on a ~1 mm scale, which is comparable to the diameter of a dental filling. Therefore μPIXE mapping gives structural insight on the dental composites, potentially relevant for the study of their properties and behavior in the oral environment.
[1] E.A. Preoteasa et al., Nucl. Instr. and Meth. in Phys. Res. B 189 (2002) 426-430.
[2] E.A. Preoteasa et al., Anal. Bioanal. Chem. 379 (2004) 825-841.

  • Poster
    17th International Conference on Ion Beam Analysis, 26.06.-01.07.2005, Seville, Spain

Permalink: https://www.hzdr.de/publications/Publ-7569
Publ.-Id: 7569


Proton microprobe analysis of normal and osteoporosis-affected compact bone. 1. Calcium and other divalent metals

Harangus, L.; Iordan, A.; Preoteasa, E. A.; Grambole, D.; Herrmann, F.; Gomez, S.; Mihul, A.; Lonescu-Tirgoviste, C.; Gutu, D.

Normal and disease-affected bones have been studied by wide- and microbeam PIXE and other IBA methods, but the biologically-active outer surface layer of bone was not examined in detail. In osteoporosis, the altered metabolism of Ca and trace elements leading to low bone density is not fully understood. μPIXE, μPIGE and μPBS were applied to analyze Ca and other divalent cation-forming metals in the outer layer of femur and tibia from normal and experimental diabetes-affected rats, tibia from humans with osteoporosis-complicated diabetes, clinically sound human femoral neck and normal bovine metacarp. Measurements were carried out at the Rossendorf nuclear microprobe with a 3.1 MeV proton beam focused to a spot of ~3 μm, using concomitantly three detectors. Thick (~1 mm) transversal bone sections were scanned near the surface at ~4 μm effective resolution. Hydroxylapatite was used as a reference. Concentrations were determined from PIXE spectra by GUPIX calculations.
Most elements of the second main group were detected: Mg (at minor levels) by μPIGE and μPBS, and Ca (major) as well as Sr and Ba (traces) by μPIXE.
Other divalent ion-forming trace metals found by μPIXE included Cr, Mn, Fe, Ni, Cu and Zn from the transition groups, and Pb. Only normal bones contained Cr, Mn and Cu. Levels of Ca, Fe, Ni and Zn varied strongly even in the same bone, while Sr showed little change. Ca maps evidenced spatially well-defined patterns of bands, and diabetic rat bones presented Ca-poor regions at the surface. The spatial resolution was weaker in the Fe, Zn and Sr maps and improved in mean profiles normal to the surface.
Near the outer surface of bones the maps, profiles and area concentrations of most divalent metals determined by μPIXE evidenced complex features of element distributions and composition, which may be potentially relevant to the osteoporosis.

  • Poster
    17th International Conference on Ion Beam Analysis, 26.06.-01.07.2005, Seville, Spain

Permalink: https://www.hzdr.de/publications/Publ-7568
Publ.-Id: 7568


Micro-PIXE and histochemical studies of Zn and Ca distribution in normal bone

Gomez, S.; Preoteasa, E. A.; Harangus, L.; Iordan, A.; Grambole, D.; Herrmann, F.

To better understand the role of zinc in bone mineralization we studied the distribution of Ca and Zn by microbeam particle-induced X-ray emission (µ-PIXE) profiling and mapping, and of Zn by histochemical mapping and profiling in cortical bovine bone. For µ-PIXE, measurements were carried out at the Rossendorf nuclear microprobe with a 3.1 MeV proton beam focused to a spot of ca. 3 µm, at ca. 4-8 µm effective resolution. Maps, unique scans and side-to-side scan sequences were done for Ca and Zn. The noise in Zn profiles was filtered by Fast Fourier Transform (FFT). For histochemistry, Zn was stained in thick sections by the sulphide-silver reaction. Both µ-PIXE and histochemistry showed that Zn was localized mainly at the surfaces of various structures in bone tissue.

Keywords: Micro-PIXE; Bone; Calcium; Zinc; Histochemistry

  • Poster
    17th International Conference on Ion Beam Analysis, 26.06.-01.07.2005, Seville, Spain
  • Nuclear Instruments and Methods in Physics Research B 249(2006), 673-676
    ISSN: 0168-583X

Permalink: https://www.hzdr.de/publications/Publ-7567
Publ.-Id: 7567


The effects of ion bombardment of ultra-high molecular weight polyethylene

Turos, A.; Abdul-Kader, A. M.; Grambole, D.; Jagielski, J.; Piątkowska, A.; Madi, N. K.; Al-Maadeed, M.

Ion bombardment is a suitable tool to improve tribological properties of polymers. In this study UHMWPE samples were bombarded with 130 keV He ions to the fluences ranging from 1 x 10(14) to 2 x 10(16) cm(-2). RBS and NRA techniques were applied to study compositional transformations induced by ion beam bombardment. Important hydrogen release was observed with increasing ion dose and was correlated with the linear energy transfer (LET). Another important effect observed was the rapid oxidation of samples, which apparently occurs after exposure of implanted samples to the air. Oxygen uptake continues during the prolonged storage of the samples in the air at RT. Up to 10 at.% of oxygen can be incorporated in the implanted layer. Changes of surface layer composition produced important increase in the layer hardness. Scratch tests revealed that the hardening of surface layers does not lead to their higher brittleness.

Keywords: Ultra-high molecular weight polyethylene; Surface modification; Ion bombardment; Hydrogen release; Oxidation

  • Lecture (Conference)
    17th International Conference on Ion Beam Analysis, 26.06.-01.07.2005, Seville, Spain
  • Nuclear Instruments and Methods in Physics Research B 249(2006), 660-664
    ISSN: 0168-583X

Permalink: https://www.hzdr.de/publications/Publ-7566
Publ.-Id: 7566


Traditional Hot-Electron MOS Devices for Novel Optoelectronic Applications

Dekorsy, T.; Sun, J. M.; Skorupa, W.; Helm, M.; Rebohle, L.; Gebel, T.

We report the realization of highly-efficient light emitting MOS devices which are based on hot-electron excitation of rare-earth ions implanted into SiO2. The implantation of Gd+ and Tb+ ions yields emission wavelengths of 316 nm and 541 nm with external quantum efficiencies up to 1% and 16%, respectively. The observed threshold electric fields for observing electroluminescence is in accordance with the injection of hot electrons via Fowler-Nordheim tunneling into SiO2 at field strengths in the range of 8-9 MV/cm. The presence of different electroluminescence bands of the Tb-implanted devices allows us to study details of the hot-electron excitation process.

Keywords: MOS devices; light emmtitting diode; rare earth

  • Poster
    14th Int. Conf. on Nonequilibrium Carriers in Semiconductors (HCIS-14), 24.-29.07.2005, Chiacgo, USA
  • Springer Proceedings in Physics 110(2006), 265

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Permalink: https://www.hzdr.de/publications/Publ-7565
Publ.-Id: 7565


AdS and stabilized extra dimensions in multi-dimensional gravitational models with nonlinear scalar curvature terms R-1 and R4

Günther, U.; Zhuk, A.; Bezerra, V.; Romero, C.

We study multi-dimensional gravitational models with scalar curvature nonlinearities of types R-1 and R4. It is assumed that the corresponding higher dimensional spacetime manifolds undergo a spontaneous compactification to manifolds with a warped product structure. Special attention has been paid to the stability of the extra-dimensional factor spaces. It is shown that for certain parameter regions the systems allow for a freezing stabilization of these spaces. In particular, we find for the R-1 model that configurations with stabilized extra dimensions do not provide a late-time acceleration (they are AdS), whereas the solution branch which allows for accelerated expansion (the dS branch) is incompatible with stabilized factor spaces. In the case of the R4 model, we obtain that the stability region in parameter space depends on the total dimension D = dim(M) of the higher dimensional spacetime M. For D > 8 the stability region consists of a single (absolutely stable) sector which is shielded from a conformal singularity (and an antigravity sector beyond it) by a potential barrier of infinite height and width. This sector is smoothly connected with the stability region of a curvature-linear model. For D < 8 an additional (metastable) sector exists which is separated from the conformal singularity by a potential barrier of finite height and width so that systems in this sector are prone to collapse into the conformal singularity. This second sector is not smoothly connected with the first (absolutely stable) one. Several limiting cases and the possibility of inflation are discussed for the R4 model.

  • Classical and Quantum Gravity 22(2005), 3135-3167

Permalink: https://www.hzdr.de/publications/Publ-7564
Publ.-Id: 7564


Massive scalar fields in the early universe

Zhuk, A.; Günther, U.

We discuss the role of gravitational excitons/radions in different cosmological scenarios. Gravitational excitons are massive moduli fields which describe conformal excitations of the internal spaces and which, due to their Planck-scale suppressed coupling to matter fields, are WIMPs. It is demonstrated that, depending on the concrete scenario, observational cosmological data set strong restrictions on the allowed masses and initial oscillation amplitudes of these particles.

  • International Journal of Modern Physics D 13(2004)7, 1167-1175

Permalink: https://www.hzdr.de/publications/Publ-7563
Publ.-Id: 7563


Status of the 31/2 cell SRF gun project in Rossendorf

Xiang, R.; Büttig, H.; Evtushenko, P.; Janssen, D.; Lehnert, U.; Michel, P.; Schneider, C.; Schurig, R.; Teichert, J.; Möller, K.; Lehmann, W.-D.; Stephan, J.; Kamps, T.; Lipka, D.; Will, I.; Volkov, V.

In the paper, we report on the status and progress of the superconducting RF gun project in Rossendorf. The gun is designed for cw operation mode with 1 mA current and 9.5 MeV electron energy, and it will be installed at the ELBE superconducting electron linear accelerator. The gun will have a 3½ cell niobium cavity operating at 1.3 GHz. The cavity consists of three cells with TESLA geometry and a specially designed half-cell in which the photocathode will be placed. The production of two Nb cavities, with RRR 300 and 40 respectively, has be finished at the beginning of 2005. After delivery, the RF tests will be performed and the preparation of the cavities will be started. At the same time, the design of the cryostat and the fabrication of its components are already finished. Further activities are the design of the diagnostic beam line, the testing of the new photocathode preparation system, and the upgrade of the 262 nm driver laser system.

  • Poster
    Particle Accelerator Conference 2005, 16.-20.05.2005, Knoxville, TN, USA
  • Contribution to proceedings
    Particle Accelerator Conference 2005, 16.-20.05.2005, Knoxville, Tennessee, USA
    Proceedings of 2005 Particle Accelerator Conference, 1081-1083

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Permalink: https://www.hzdr.de/publications/Publ-7560
Publ.-Id: 7560


Pygmy dipole strength close to particle-separation energies - the case of the Mo isotopes

Rusev, G.; Grosse, E.; Erhard, M.; Junghans, A. R.; Kosev, K.; Schilling, K. D.; Schwengner, R.; Wagner, A.

The distribution of electromagnetic dipole strength in {92, 98, 100}Mo has been investigated by photon scattering using bremsstrahlung from the new ELBE facility. The experimental data for well separated nuclear resonances indicate a transition from a regular to a chaotic behaviour above 4 MeV of excitation energy. As the strength distributions follow a Porter-Thomas distribution much of the dipole strength is found in weak and in unresolved resonances appearing as fluctuating cross section. An analysis of this quasi-continuum - here applied to nuclear resonance fluorescence in a novel way - delivers dipole strength functions, which are combining smoothly to those obtained from (gamma, n)-data. Enhancements at 6.5 MeV and at ca. 9 MeV are linked to the pygmy dipole resonances postulated to occur in heavy nuclei.

Permalink: https://www.hzdr.de/publications/Publ-7559
Publ.-Id: 7559


Coherent Theta+ and Lambda(1520) photoproduction off the deuteron

Titov, A. I.; Kämpfer, B.; Date, S.; Ohashi, Y.

We analyze an effect of the coherent Theta+Lambda(1520) photoproduction in gamma D interaction near the threshold. We demonstrate that the coherence effect becomes manifest in a comparison of the nK+ invariant mass distribution when the pK- invariant equals the Lambda(1520) mass. Our model calculations indicate a sizeable contribution of resonant and non-resonant background processes in the gamma D to np K+K- reaction which generally exceed the contribution of the coherent resonant channel. However, we find that the coherent Theta+Lambda(1520) photoproduction is enhanced relative to the background processes in the forward hemisphere of the pK- pair photoproduction. Moreover, the coherence effect does not depend on the Theta+ photoproduction amplitude and is defined by the probabilities of the Lambda(1520) photoproduction and the Theta+ to NK transition. Therefore, this coherence effect may be used as an independent method for studying the mechanism of Theta+ production and Theta+ properties.

  • Physical Review C 72(2005), 035206

Permalink: https://www.hzdr.de/publications/Publ-7558
Publ.-Id: 7558


A Novel High-Resolution Time-of-Flight Spectrometer with Tracking Capabilities for Photo-FissionFragments and Beams of Exotic Nuclei

Nankov, N.; Grosse, E.; Hartmann, A.; Junghans, A. R.; Kosev, K.; Schilling, K. D.; Sobiella, M.; Wagner, A.

Bremsstrahlung photons, produced at superconducting electron accelerator ELBE at the
FZ Rossendorf will be used for the production of neutron-rich nuclei by photo-induced fission. The properties of such exotic nuclei will be studied by decay spectroscopy. The mass and charge identification plays a key role in such experiments and is based on a double time-of-flight (TOF) method for both fission fragments. The reaction products are registered using secondary electrons emitted by thin foils and detected by position-sensitive MCP detectors. Currently a position resolution of 1.8(0.3) mm (FWHM) in both x and y directions and a time resolution of about 330 ps (FWHM) have been deduced using a source of alpha-particles.

Keywords: nuclear structure; nuclear astrophysics; bremsstahlung; photo-induced fission; time-of-flight spectrometry

  • Contribution to proceedings
    3rd International Workshop on Nuclear Fission and Fission-Product Spectroscopy, 11.-14.05.2005, Château de Cadarache, Saint Paul lez Durance, France
    AIP 798, 357

Permalink: https://www.hzdr.de/publications/Publ-7557
Publ.-Id: 7557


Photodissociation of p-process nuclei studied by bremsstrahlung induced activation

Erhard, M.; Junghans, A. R.; Beyer, R.; Grosse, E.; Klug, J.; Kosev, K.; Nair, C.; Nankov, N.; Rusev, G.; Schilling, K. D.; Schwengner, R.; Wagner, A.

A research program has been started to study experimentally the near-threshold photodissociation of nuclides in the chain of cosmic heavy element production with bremsstrahlung from the ELBE accelerator. An important prerequisite for such studies is good knowledge of the bremsstrahlung distribution which was determined by measuring the photodissociation of the deuteron and by comparison with model calculations. First data were obtained for the astrophysically important target nucleus 92-Mo by observing the radioactive decay of the nuclides produced by bremsstrahlung irradiation at end-point energies between 11.8 and 14.0 MeV. The results are compared to recent statistical model calculations.

Keywords: Photonuclear reactions; Photon absorption and scattering; Nucleosynthesis in novae; supernovae and other explosive environments

Permalink: https://www.hzdr.de/publications/Publ-7556
Publ.-Id: 7556


The new bremsstrahlung facility at the superconducting electron accelerator ELBE

Wagner, A.; Beyer, R.; Erhard, M.; Dönau, F.; Grosse, E.; Hartmann, A.; Junghans, A.; Käubler, L.; Kosev, K.; Mallion, S.; Nair, C.; Nankov, N.; Rusev, G.; Schilling, K. D.; Schulze, W.; Schwengner, R.

A new facility for the production of polarised bremsstrahlung has been built at the superconducting electron accelerator ELBE of the Forschungszentrum Rossendorf. The bremsstrahlung facility and the detector setup are designed such that the background radiation due to scattering of photons and production of neutrons is minimised allowing for experiments close to and above particle separation energies in nuclei.
First results of photon-scattering and photo-dissociation experiments on {92,98,100}Mo are presented.
The results are compared to recent cross-section calculations for astrophysical networks.

Keywords: polarised; bremsstrahlung; superconducting; electron accelerator; ELBE; nuclear astrophysics; Mo100; Mo98; Mo92; photo-dissociation; photon-scattering

  • Journal of Physics G - Nuclear and Particle Physics 31(2005), S1969

Permalink: https://www.hzdr.de/publications/Publ-7555
Publ.-Id: 7555


Experimente zur CFD-Validierung der Zweiphasen-Strömung im Heißstrang eines Druckwasser-Reaktors

Vallee, C.; Höhne, T.; Sühnel, T.

Zur Validierung von CFD-Codes bei reaktornahen Versuchsbedingungen wird derzeit das Heißstrang-Modell in der Druckkammer der TOPFLOW-Anlage in Betrieb genommen.
Vorversuche fanden bereits an einem horizontalen Luft/Wasser-Strömungskanal bei Atmosphärendruck statt. Es wurden optische Messungen mit einer Hochgeschwindigkeits-Kamera durchgeführt, die durch synchronisierte dynamische Druckmessungen ergänzt wurden. Außerdem wurden Geschwindigkeitsfelder in einem Schwall mit PIV (Particle Image Velocimetry) gemessen.
Zur Validierung des Codes CFX-5 wurden Nachrechnungen durchgeführt. Diese stimmten mit dem Experiment qualitativ gut überein. Zudem wurde eine Vorrausrechnung zum Heißstrang-Modell gezeigt.

Keywords: Horizontal two-phase flow; Slug flow; High-speed video observations; Image processing; PIV; CFD

  • Lecture (Conference)
    Annual Meeting on Nuclear Technology 2005, 10.-12.05.2005, Nürnberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-7554
Publ.-Id: 7554


Experimental investigation and CFD simulation of an air/water flow in a horizontal channel (Part 1: Measurements)

Vallee, C.; Sühnel, T.

For the investigation of air/water stratified flow, a horizontal channel with rectangular cross-section was build at Forschungszentrum Rossendorf. The channel allows the investigation of air/water co- and counter-current flows under atmospheric pressure, especially the slug behaviour.
Optical measurements were performed with a high-speed video camera, and were complemented by simultaneous dynamic pressure measurements. An interface capture technique was developed, which allows to plot the time dependent water level in each cross-section. Further, Particle Image Velocimetry (PIV) measurements where presented, which shows the flow pattern inside of a slug.

Keywords: Horizontal two-phase flow; Slug flow; High-speed video observations; Image processing; PIV

  • Lecture (Conference)
    FZR & Ansys Multiphase flow workshop, 31.05.-03.06.2005, Dresden, Germany
  • Contribution to proceedings
    FZR & Ansys Multiphase flow workshop, 31.05.-03.06.2005, Dresden, Germany
    Workshop proceedings

Permalink: https://www.hzdr.de/publications/Publ-7553
Publ.-Id: 7553


High-Intensity THz Radiation from a Large-Aperture Photoconductive Emitter

Winnerl, S.; Dreyhaupt, A.; Peter, F.; Stehr, D.; Helm, M.; Dekorsy, T.

We report on the performance of photoconductive THz emitters based on an interdigitated metal-semiconductor-metal finger structure. In every second period of this structure optical excitation is inhibited. Thus carrier acceleration is unidirectional over the whole device area. Excitation with amplified laser pulses leads to THz amplitudes of 6 kV/cm. Saturation of the emission due to screening of the bias field was observed for excitation densities in the 1018 cm-3 range.

  • Lecture (Conference)
    14th International Conference on Nonequilibrium Carrier Dynamics in Semiconductors (HCIS-14), 24.-29.07.2005, Chicago, USA
  • Springer Proceedings in Physics 110(2006), 73-76

Downloads

Permalink: https://www.hzdr.de/publications/Publ-7552
Publ.-Id: 7552


Evolution of sp2 networks with substrate temperature in amorphous carbon films: Experiment and theory

Gago, R.; Vinnichenko, M.; Jäger, H. U.; Belov, A. Y.; Jiménez, I.; Huang, N.; Sun, H.; Maitz, M. F.

The evolution of sp2 hybrids in amorphous carbon (a-C) films deposited at different substrate temperatures was studied experimentally and theoretically. The bonding structure of a-C films prepared by filtered cathodic vacuum arc was assessed by the combination of visible Raman spectroscopy, x-ray absorption, and spectroscopic ellipsometry, while a-C structures were generated by molecular-dynamics deposition simulations with the Brenner interatomic potential to determine theoretical sp2 site distributions. The experimental results show a transition from tetrahedral a-C (ta-C) to sp2 -rich structures at ~500 K. The sp2 hybrids are mainly arranged in chains or pairs whereas graphitic structures are only promoted for sp2 fractions above 80%. The theoretical analysis confirms the preferred pairing of isolated sp2 sites in ta-C, the coalescence of sp2 clusters for medium sp2 fractions, and the pronounced formation of rings for sp2 fractions >80%. However, the dominance of sixfold rings is not reproduced theoretically, probably related to the functional form of the interatomic potential used.

Keywords: amorphous carbon; bonding structure; sp2 clustering; molecular dynamics

  • Physical Review B 72(2005)1, 014120-1-014120-9

Permalink: https://www.hzdr.de/publications/Publ-7551
Publ.-Id: 7551


Real time evidence of two-magnon scattering in exchange coupled bilayers

Weber, M. C.; Nembach, H.; Carey, M. J.; Hillebrands, B.; Fassbender, J.

Coherent spin waves in exchange biased bilayers have been excited by ultrafast photomodulation of the exchange bias anisotropy. Vector and time resolved Kerr effect was employed to trace the trajectory of the magnetization vector of the ferromagnetic layer in real time on the picosecond timescale. Photoinduced easy axis precession in CoFe/IrMn samples with different IrMn thicknesses, thus, different exchange bias fields, has been studied. The antiferromagnetic thickness dependence of the decay rate of the induced precession was investigated as a measure of the effective magnetic damping in the system.
The observed increase of the extracted effective damping parameter is proportional to the square of the exchange bias field. Two-magnon scattering of the coherent spin precession of the ferromagnetic layer at local interfacial fluctuations of the exchange bias field can account for an additional dissipation mechanism. The two-magnon damping field in exchange bias systems is proportional to the square of the exchange bias field. Hence, there is time-domain evidence of two-magnon damping involved in magnetic relaxation processes of photoexcited exchange coupled bilayers.

Keywords: magnetism; spin waves; exchange-bias; time-resolved measurements; pump-probe

Permalink: https://www.hzdr.de/publications/Publ-7550
Publ.-Id: 7550


Influence of He-ion-irradiation on thin NiMn/NiFe exchange bias films

Cantelli, V.; von Borany, J.; Grenzer, J.; Kaltofen, R.; Schumann, J.; Fassbender, J.

He ion irradiation has been demonstrated to be a versatile tool not only for interfacial mixing in the case of Co/Pt mulilayers [1] but also for low temperature L10-ordering of FePt alloys [2]. L10 ordered NiMn films are due to the high blocking temperature and if exchange coupled to a ferromagnetic material due to the large shift filed a promising candidate for magnetic sensor applications. However, for the creation of the L10 phase an annealing is required. The corresponding thermal budget should be as low as possible to impede the detrimental effect of fast Mn diffusion. In order to reduce the thermal budget for A1 - L10 phase transformation the potential of ion induced vacancy formation has been exploited.
Magnetron sputtered film stacks of 5nm Ta/50(15)nm NiMn/20nm Fe20Ni80 /5nm Ta deposited at Si/SiO2 substrates were subsequently irradiated with He+ ions (30 keV, 10^15-3*10^16cm-2, RT or 250°C). The transition from the paramagnetic NiMn phase (fcc) to the chemically ordered, antiferromagnetic tetragonal L10 phase during annealing (100-500°C, Vacuum) was studied by in-situ X-ray diffraction using synchrotron radiation. A small L10 fraction (< 15%) is already available after deposition. The transformation to a dominating L10 (LRO-parameter S > 0.5) ordered NiMn film takes place between 250-300°C irrespective of the irradiation. Annealing at elevated temperatures (T > 400°C) leads to a loss of L10 ordering due to a complete intermixing of the NiMn and the Permalloy films. A benefit of ion iradiation is the improvement of the crystallinity and the degree of <111> texture in the NiMn films already after low fluence (10^15 cm-2) implantation.

[1] C. Chappert, H. Bernas, J. Ferre, V. Kottler, J.-P. Jamet, Y. Chen, E. Cambril, T. Devolder, F. Rousseaux, V. Mathet, H. Launois, Science 280, 1919 (1998).
[2] H. Bernas, J.-P. Attane, K.-H. Heinig, D. Halley, D. Ravelosona, A. Marty, P. Auric, C. Chappert, Y. Samson, Phys. Rev. Lett. 91, 077203 (2003).

Keywords: magnetism; exchange-bias; NiMn; ion irradiation; interfacial mixing; phase transformation

Permalink: https://www.hzdr.de/publications/Publ-7549
Publ.-Id: 7549


L10 ordering of magnetron sputtered FePt films at temperatures below 400°C

Cantelli, V.; von Borany, J.; Beckers, M.; Fassbender, J.

Due to the high uniaxial anisotropy L10-ordered FePt is currently the most favoured candidate for future high density storage applications. However, in order to achieve the L10-phase either the deposition or post deposition annealing at temperatures above typically 500°C is required. Many attempts ranging from alternating monolayer deposition [1], different seed or cap layers [2] or doping with third elements [3] have been tried to reduce the ordering temperature with various degree of success.
Here we report on the L10-ordering of stoichiometric 30-125 nm thick FePt films which have been magnetron co-sputtered from elemental targets on SiO2/Si substrates with a deposition rate of (0.30-0.2) Å/s at various temperatures. Surprisingly, already for a deposition at 350°C the films are well chemically ordered in the tetragonal L10 structure with a long- range order parameter S=0.8-0.9 which has been determined by grazing incidence X-ray diffraction. The films exhibit a polycrystalline fiber texture with mean grain sizes of 12-18 nm and a random orientation distribution confirmed by pole figures measurements. In contrast, FePt films deposited at room temperature exhibit the fcc A1-phase with a mean grain size of (5.0 - 0.5) nm. In a sequence of annealing steps with successively increased temperatures, the A1 - L10 transition has been obtained between 300-400°C. After annealing at 400°C the films show nearly complete L10 ordering with S values equivalent to the films deposited at 350°C. During annealing the mean grain size grows to 10-12 nm. Using textured seed layers L10 ordered FePt films with preferred orientation can be realized. One of the key issues in observing the L10-ordering already at rather low temperatures is a combination of low deposition rate and low-energy ion irradiation during deposition.

[1] T. Shima, T. Moriguchi, S. Mitani, K. Takanashi, Appl. Phys. Lett. 80, 288 (2002).
[2] Z. L. Zhao, J. Ding, K. Inaba, J. S. Chen, J. P. Wang, Appl. Phys. Lett. 83, 2196 (2003).
[3] T. Maeda, T. Kai, A. Kiktsu, T. Nagase, J.-I. Akiyama, Appl. Phys. Lett. 80, 2147 (2002).

Keywords: magnetism; FePt; L10; ordering; phase transformation

  • Lecture (Conference)
    Magnetism and Magnetic Materials Conference, 30.10.-03.11.2005, San Jose, USA

Permalink: https://www.hzdr.de/publications/Publ-7548
Publ.-Id: 7548


Doping ZnO with Fe far from thermal equilibrium

Potzger, K.; Zhou, S.; Reuther, H.; Mücklich, F.; Talut, G.; Fassbender, J.; Herrmannsdörfer, T.; Bianchi, A.

The fabrication of diluted magnetic semiconductors (DMS) by transition-metal (TM) doping of ZnO has attracted tremendous interest within the last 3 years. However, there are still vivid discussions if the ferromagnetic state stems from Zener-interaction between diluted TM ions or from magnetic secondary phases. In order to prove or exclude the possible formation of TM-secondary phases in ZnO we have investigated iron doping, since Fe-ZnO (n-type) DMS are theoretically predicted to exhibit ferromagnetism [1].
For these investigations Fe-ions have been implanted with an ion energy of 180 keV (projected range Rp=80 nm) at 420 K into ZnO single crystals. Two fluences of either 0.4 or 4x1016 ions per cm2 were chosen which correspond to 0.5 and 5 at%, respectively. The samples were characterized by CEMS (conversion electron Mössbauer spectroscopy), XRD (X-ray diffraction) using synchrotron radiation, RBS (Rutherford back scattering), TEM (transmission electron microscopy) and SQUID (superconducting quantum interference device) magnetometry.
For the as implanted sample a high solubility of Fe was found, e.g. 100% for the low fluence and ~90% for the high fluence sample. The ionic states are 2+ and 3+ but none of the ionic fractions could be clearly determined to occupy substitutional lattice sites. The high fluence implanted sample exhibits ferromagnetic behavior at room temperature as was observed by CEMS and SQUID. However, CEMS and XRD measurements confirm that the origin of the ferromagnetic behavior is due to Fe-nanocluster formation. These nanoclusters show the magnetic moment and hyperfine field of metallic bcc-Fe. After annealing the samples at 800°C secondary phases (mainly zinc ferrite clusters) form and no ferromagnetic behavior could be detected. For the low fluence implanted sample neither as-implanted nor after annealing a ferromagnetic behavior could be detected although after annealing the Fe-ions develop a 2+ state suggesting an occupation of substitutional lattice sites.

[1] K. Sato, H. Katayama-Yoshida, Jpn. J. Appl. Phys. 40, L334 (2001)

Keywords: magnetism; doping; ZnO; magnetic semiconductors; nanoparticles

  • Lecture (Conference)
    Magnetism and Magnetic Materials Conference, 30.10.-03.11.2005, San Jose, USA

Permalink: https://www.hzdr.de/publications/Publ-7547
Publ.-Id: 7547


Ion beam synthesis of Fe nanoparticles in MgO and Y:ZrO2

Potzger, K.; Reuther, H.; Zhou, S.; Mücklich, A.; Grötzschel, R.; Eichhorn, F.; Liedke, M. O.; Fassbender, J.

In order to prepare epitaxially oriented Fe nanoparticles near the surface of a single crystalline host material the method of ion beam synthesis has been explored. Two different host matrices, i. e., MgO(001) and Y:ZrO2(001), were employed to study the influence of the lattice misfit, the solubility and the host oxidizing/reducing properties on the formation of the Fe nanoparticles. The Fe ions were implanted at a primary energy of 100 – 110 keV (mean projected range: 50 nm) with a constant fluence of 6x1016 cm-2 at implantation temperatures varying between 25 °C and 1000°C. Structural and magnetic characterization was performed by means of CEMS (conversion electron Mössbauer spectroscopy), XRD (X-ray diffraction), RBS (Rutherford back scattering), TEM (transmission electron microscopy) and MOKE (magneto-optical Kerr effect).
For MgO substrates the fraction of metallic Fe increases from 28% (25°C) to 60% (800°C) as a function of implantation temperature, whilst the Fe depth profile remains the same. For an implantation temperature of 800°C fcc Fe nanoparticles with a mean diameter of 5 nm and an exclusive orientation relationship of -Fe(111)//MgO(111) and -Fe[220]//MgO[220] have been found. However, for an implantation temperature of 1000°C, the amount of Fe incorporated in the calculated depth profile is strongly reduced due to an enhanced mobility and diffusion of the Fe ions in the matrix material. The remaining Fe is found to be in the 3+ oxidation state.
Also in Y:ZrO2 the fraction of metallic Fe increases with increasing implantation temperature reaching 96% at 1000 °C. However, the nanoparticles formed are mainly bcc with a mean diameter of 13 nm. The dominant epitaxial relation is Fe(110)//Y:ZrO2(001) and Fe[001]//Y:ZrO2[100]. The ferromagnetic behavior is reflected by a magnetic hyperfine field of 330 kOe and a hysteretic magnetization reversal. No in-plane anisotropy could be detected.

Keywords: magnetism; ion beam synthesis; nanoparticles

Permalink: https://www.hzdr.de/publications/Publ-7546
Publ.-Id: 7546


Domain structure during magnetization reversal of PtMn/CoFe exchange bias micro-patterned lines

Liedke, M. O.; Potzger, K.; Bischoff, L.; Bothmer, A. H.; Hillebrands, B.; Rickart, M.; Freitas, P. P.; Fassbender, J.

In order to investigate the relation between shape anisotropy and unidirectional anisotropy in exchange biased lines, the magnetic domain configuration during magnetization reversal was studied as a function of the ratio between both anisotropy contributions. For that purpose a number of glass / Ta 7nm / PtMn 20nm / CoFe 4nm / Ta 4nm samples were sputter deposited. By means of either optical lithography and physical etching or focus ion beam (FIB) milling several line pattern in the range between 0.5 and 2.5 µm width and 20 µm length have been prepared. In order to modify the ratio between both anisotropy contributions the exchange bias field strength was reduced by means of 5 keV He+ ion irradiation. The domain structure during magnetization reversal was then investigated by means of magnetic force microscopy. For the as-prepared samples a mono-domain magnetization state with the magnetization direction aligned along the exchange bias field direction was found regardless of its shape. After irradiation, i. e., reduction of the unidirectional anisotropy, the situation has changed completely. The homogeneous magnetization state broke up into small domains with 360° domain walls in between. The appearance of these domain walls was only observed for the descending branch of the magnetization reversal. In addition it was found that the number of domain walls created depends strongly on the stripe width and orientation.

Keywords: magnetism; ion irradiation; FIB; exchange-bias; magnetic domains; MFM

  • Poster
    Magnetism and Magnetic Materials Conference, 30.10.-03.11.2005, San Jose, USA

Permalink: https://www.hzdr.de/publications/Publ-7545
Publ.-Id: 7545


Magnetic domains and magnetization reversal of ion-induced magnetically patterned RKKY-coupled Ni81Fe19/Ru/Co90Fe10 films

Fassbender, J.; Bischoff, L.; Mattheis, R.; Fischer, P.

Pure magnetic patterning by means of ion beam irradiation of magnetic thin films and multilayers result from a post deposition local modification of the interface structure with only minor effects on the film topography. In the study presented here a 50 keV fine focused Co ion beam was used to change the coupling in a Ni81Fe19/Ru/Co90Fe10 structure from antiferromagnetic to ferromagnetic on a micron scale. Thereby an artificial structure with locally varying interlayer coupling and therefore magnetization alignment is produced. High-resolution full-field x-ray microscopy is used to determine the magnetic domain configuration during the magnetization reversal process locally and layer resolved due to the element specific contrast in circular x-ray dichroism. In the magnetically patterned structure there is in addition to the locally varying interlayer exchange coupling across the Ru layer also the direct exchange coupling within each ferromagnetic layer present. Therefore the magnetization reversal behaviour of the irradiated stripes is largely influenced by the surrounding magnetic film. We found that at the boundaries between irradiated and non-irradiated areas magnetic domain walls form during magnetization reversal with a magnetization component perpendicular to the film plane. This can be explained by the stray field generated by this domain wall which is partially compensated by a corresponding domain wall in the second ferromagnetic layer with opposite direction. It is expected that a pure magnetic patterning, as demonstrated here, can provide an additional degree of freedom in tailoring the overall magnetic properties of thin multilayer structures.

Keywords: ion irradiation; magnetic patterning; magnetism; RKKY coupling; magnetic domains; x-ray microscopy; XMCD

Permalink: https://www.hzdr.de/publications/Publ-7544
Publ.-Id: 7544


Neue Konzepte für die kombinierte Leitfähigkeits- und Impedanzmessung in hochtransienten Mehrphasenströmungen

Da Silva, M. J.; Hampel, U.; Schleicher, E.

Messungen mit leitfähigkeitsbasierter Nadelsondensysteme sind gängige Messverfahren für hochtransiente Zweiphasenströmungen. Leitfähigkeits-Nadelsonden eignen sich jedoch nicht zur Untersuchung nichtleitender Fluide bzw. Mehrphasenströmungen. Um dieses Problem zu behandeln, kann die kombinierte Leitfähigkeits- und Permittivitäts- bzw. Kompleximpedanzmessung eingesetzt werden. Dafür wird in diesem Beitrag eine Impedanznadelsonde und eine dazugehörige Messelektronik vorgestellt. Erste vielversprechende Ergebnisse von Messungen an ausgewählten organischen Fluiden werden dargestellt und diskutiert.

Keywords: needle probe; impedance measurement; complex permittivity; multiphase flow

  • Contribution to proceedings
    7. Dresdner Sensor-Symposium - Neue Herausforderungen und Anwendung in der Sensortechnik, 12.-14.12.2005, Dresden, Deutschland
    Proceedings: TUDpress, 139-142

Permalink: https://www.hzdr.de/publications/Publ-7543
Publ.-Id: 7543


Electron-phonon interaction in quantum cascade structures probed by Landau level spectroscopy

Drachenko, O.; Leotin, J.; Galibert, J.; Sirtori, C.; Page, H.; Semtsiv, M. P.; Ziegler, M.; Dreßler, S.; Müller, U.; Masselink, T.

In this work we present a method to study the energy of the phonon modes responsible for nonradiative energy relaxation of electrons in the active zone of quantum cascade lasers (QCLs). The method is based on the analysis of the oscillations pattern of QCLs emission intensity as a function of magnetic field applied along the growth direction. We studied first GaAs/AlGaAs QCLs with different Al concentration in the barriers (33% and 45%). We demonstrated that in the case of high Al concentration the relaxation via AlAs- like LO phonon can be significant. We have also shown that in case of In0.73Ga0.27As/AlAs short-wavelength QCL in spite of the high Al concentration in the barriers and the low GaAs contents in the wells, the nonradiative energy relaxation happens principally via GaAs-like or InAs-like (or mixed modes) phonon emission, while a clear signature of AlAs-like phonons was not observed.

Keywords: Quantum Cascade Lasers; Phonon spectroscopy; High magnetic fields; magneto-phonon resonance

  • Contribution to proceedings
    12th International Conference on Narrow Gap Semiconductors, 03.-7.07.2005, Toulouse, France
    Proceedings of the 12th International Conference on Narrow Gap Semiconductors, Part VII, 530-535

Permalink: https://www.hzdr.de/publications/Publ-7542
Publ.-Id: 7542


Modeling of a buoyancy-driven flow experiment at the ROCOM test facility using the CFD-codes CFX-5 and TRIO_U

Höhne, T.; Kliem, S.; Bieder, U.

The influence of density differences on the mixing of the primary loop inventory and the Emergency Core Cooling (ECC) water in the downcomer of a Pressurized Water Reactor (PWR) was analysed at the ROssendorf COolant Mixing (ROCOM) test facility. ROCOM is a 1:5 scaled model of a German PWR, and has been designed for coolant mixing studies. It is equipped with advanced instrumentation, which delivers high-resolution information for temperature or Boron concentration fields.

An experiment with 5 % of the design flow rate in one loop and 10 % density difference between the ECC and loop water was selected for validation of the CFD software packages CFX-5 and Trio_U. Two similar meshes with approximately two million control volumes were used for the calculations. The effects of turbulence on the mean flow were modelled with a Reynolds stress turbulence model in CFX-5 and LES approach in Trio_U. CFX-5 is a commercial code package offered from ANSYS Inc. and Trio_U is a single-phase CFD tool which is developed by the CEA-Grenoble, France.

The results of the experiment and of the numerical calculations show that mixing is dominated by buoyancy effects: At higher mass flow rates (close to nominal conditions) the injected slug propagates in the circumferential direction around the core barrel. Buoyancy effects reduce this propagation. The ECC water falls in an almost vertical path and reaches the lower down¬comer sen¬sor directly below the inlet nozzle. Therefore, density effects play an important role during natural convection with ECC injection in PWRs. Both CFD codes were able to predict the observed flow patterns and mixing phenomena quite well.

Keywords: PWR; CFD; Mixing; Boron Dilution; ROCOM; CFX; TRIO_U

Permalink: https://www.hzdr.de/publications/Publ-7541
Publ.-Id: 7541


CFD modeling of the mixing of deborated with borated water in a reactor pressure vessel

Lycklama À. Nijeholt, J.-A.; Höhne, T.

In a Pressurized Water Reactor, negative reactivity is present in the core by means of Boric acid as a soluble neutron absorber in the coolant water. The main functions of the boric acid are to compensate for the fuel burn up and Xenon poisoning during normal operation and to provide the required sub-criticality of reactor shutdown during refueling and maintenance. During a so called Boron Dilution Transient (BDT), the borated coolant water is diluted by mixing with unborated water. The resulting decrease in the boron concentration leads to an insertion of positive reactivity in the core, which may lead to a reactivity excursion. The associated power peak may damage the fuel rods.

The most severe BDT involves scenarios in which a slug of unborated water has been formed in a cold leg in a stationary (Main Coolant Pumps are down) primary circuit. An inadvertent start-up of the MCP of the affected loop causes the transport of the unborated slug into the Reactor Pressure Vessel (RPV). The resulting positive reactivity insertion in the core is governed by the degree of mixing of the unborated slug and the borated water in the cold leg, the downcomer and the lower plenum. This mixing of borated and unborated water is an important process, because it mitigates and determines the degree of reactivity insertion.

The objective of the present study is to develop a validated Computational Fluid Dynamics (CFD) model for the prediction of the boron concentration distribution in the RPV as function of time during a BDT. This CFD model has been validated using the measurement data from the Rossendorf coolant mixing model (ROCOM) experiment. The ROCOM test facility represents the primary cooling system of a KONVOI type of PWR (1300 MWel). The linear scale of the ROCOM experimental facility is 1:5. The RPV is connected with four circulation loops.

A detailed CFD model of the RPV including the inlet nozzles, the downcomer, and the lower plenum has been developed to predict the mixing of unborated and borated water in this RPV. The validation of the model has been achieved by comparison of the calculated and measured relative boron concentration at the core inlet plane as function of time. In spite of the complicated spatial, temporal, and geometrical aspects of the flow in the RPV, the agreement between the calculated and the experimental data is good. In the ROCOM03 experiment, the minimal relative boron concentration measured at the core inlet is 64% and the calculated minimum value is 60%.

  • Contribution to proceedings
    ENC 2005 European Nuclear Conference, 11.-14.12.2005, Versailles, France
    CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-7540
Publ.-Id: 7540


Kaon and pion emission in asymmetric C+Au and Au+C collisions at 1.0A GeV and 1.8A GeV

Schmah, A.; Lang, S.; Böttcher, I.; Dohrmann, F.; Förster, A.; Grosse, E.; Koczoñ, P.; Kohlmeyer, B.; Laue, F.; Menzel, M.; Naumann, L.; Oeschler, H.; Scheinast, W.; Schuck, T.; Schwab, E.; Senger, P.; Shin, Y.; Ströbele, H.; Sturm, C.; Surówska, G.; Uhlig, F.; Wagner, A.; Walu, W.

The emission of K+ and ± mesons has been studied in the asymmetric collision system Au+C and in the inverse reaction C+Au at 1.0A GeV (and at 1.8A GeV for C+Au only) in order to extract the effective source rapidities based on their distribution in the pt-y plane. The extracted source rapidity of K+ mesons is about ys/ybeam=0.25 at both incident energies [y(Au)=0,y(C)=ybeam]. This corresponds to a reaction volume consisting of the C nucleus and a tube cut out of the Au nucleus. In clear contrast, the source rapidities of ± mesons vary from ys/ybeam=0.5 in peripheral collisions (corresponding to NN interactions) to about ys/ybeam<0.33 in central reactions. The multiplicities of K+ and are compared to symmetric collision systems and, together with detailed transport model calculations, are used to study the sensitivity to the nuclear equation of state.

  • Physical Review C 71(2005), 064907

Permalink: https://www.hzdr.de/publications/Publ-7539
Publ.-Id: 7539


Design of a photoneutron source for time-of-flight experiments at the radiation source ELBE

Altstadt, E.; Beckert, C.; Freiesleben, H.; Galindo, V.; Grosse, E.; Naumann, B.; Weiß, F.-P.

The Forschungszentrum Rossendorf and the Technische Universität Dresden are working together in a networking project for the construction and the use of a compact time-of-flight facility. The aim is to investigate the energy dispersive interaction of fast neutrons with materials. The planned time-of-flight experiments with pulsed neutrons will be carried out at the radiation source ELBE. First results for the design of a neutron radiator are presented. The distribution of the energy disposal of the used electron beam from the radiation source ELBE, the temperature in the neutron radiator and the expected particle spectra and fluxes at the measuring position were calculated by means of radiation-transport and finite-elements programs. Considerations for the design of the beam dump are discussed.

Keywords: neutron; source; photoneutron; flux; pulsed; radiator; time-of-flight; cross section

  • Lecture (Conference)
    International Workshop FAST NEUTRON PHYSICS, 05.-07.09.2002, Dresden, Deutschland
  • Contribution to proceedings
    International Workshop FAST NEUTRON PHYSICS, 05.-07.09.2002, Dresden, Deutschland
    International Workshop FAST NEUTRON PHYSICS on CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-7537
Publ.-Id: 7537


The photon-scattering facility at the superconducting electron accelerator ELBE

Schwengner, R.; Beyer, R.; Dönau, F.; Grosse, E.; Hartmann, A.; Junghans, A. R.; Mallion, S.; Rusev, G.; Schilling, K. D.; Schulze, W.; Wagner, A.

A new facility for the production of polarised bremsstrahlung has been built
at the superconducting electron accelerator ELBE of the Forschungszentrum
Rossendorf. The bremsstrahlung facility and the setup for photon-scattering
experiments are designed such that the background radiation due to scattering
of photons and production of neutrons is minimised. The sensitive setup in
connection with electron energies up to 20 MeV and average currents up to 1 mA
delivered by the ELBE accelerator enables novel experiments using
photon-induced reactions. First results of photon-scattering experiments are
presented.

Keywords: superconducting electron accelerator; polarised bremsstrahlung; photon scattering

  • Nuclear Instruments and Methods in Physics Research A 555(2005), 211-219

Permalink: https://www.hzdr.de/publications/Publ-7536
Publ.-Id: 7536


Fullerene-like arrangements in carbon nitride thin films grown by direct ion beam sputtering

Gago, R.; Abrasonis, G.; Mücklich, A.; Möller, W.; Czigany, Z.; Radnoczi, G.

Carbon nitride (CNx) thin films were grown by direct N-2/Ar ion beam sputtering of a graphite target at moderate substrate temperatures (300-750 K). The resulting microstructure of the films was studied by high-resolution transmission electron microscopy. The images showed the presence of curved basal planes in fullerenelike arrangements. The achievement and evolution of these microstructural features are discussed in terms of nitrogen incorporation, film-forming flux, and ion bombardment effects, thus adding to the understanding of the formation mechanisms of curved graphitic structures in CNx materials. (C) 2005 American Institute of Physics.

  • Applied Physics Letters 87(2005)7, 71901

Permalink: https://www.hzdr.de/publications/Publ-7535
Publ.-Id: 7535


Extreme habitats as reservoir for unusual bacterial strains: Perspectives for bioremediation and nanotechnology

Merroun, M.

Microorganisms can mobilise radionuclides/metals through autotrophic and heterotrophic leaching, chelation by microbial metabolites and siderophores, and methylation, which can result in volatilisation. Conversely, immobilisation can result from sorption to cell components or exopolymers, intracellular sequestration or precipitation as insoluble organic and inorganic compounds. In this talk, we will present the last results about the spectroscopic and microscopic characterization of interaction mechanisms between radionuclides and bacterial strains isolated from extreme habitats, including uranium mining waste piles. Some of the isolated strains could be used as templates for the formation of metallic nanoparticles (Pd, Au).

  • Invited lecture (Conferences)
    Civil Engineering Department, 01.07.2005, Sheffield, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-7534
Publ.-Id: 7534


Urankontamination durch Erzbergbau und Aufarbeitung

Bernhard, G.

Ausgehend von der Hintergrundkonzentration in den Eintrag von Uran in geochemische und biologische Systeme, wird über die Bestimmung der Speziation des Urans in kontaminierten Wässern, die aus dem ehemaligen Uranerzbergbau resultieren, berichtet.

  • Invited lecture (Conferences)
    Uran-Statusseminar, 21.07.2005, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-7533
Publ.-Id: 7533


188Re(III) Mixed-ligand Complexes: Stability Studies and Labeling of Biomolecules

Schiller, E.; Seifert, S.; Tisato, F.; Refosco, F.; Kraus, W.; Spies, H.; Pietzsch, H.-J.

Trigonal-bipyramidal Re(III) complexes with tetra-dentate/monodetate NS3/P ‘4+1’-coordination are inter-esting agents for the development of rhenium-188 com-plexes for potential therapeutic application. In order to understand relationships between the structure of rhenium-188 ‘4+1’ complexes and their in vitro stability we synthesized a series of rhenium model complexes 1, 2 and determined their stability in human plasma.
The complexes were prepared as described in [1] using various combinations of NS3 derivatives and mono-dentate phosphorus(III) ligands.
Since instability in aqueous solution always leads to the formation of perrhenate, we determined the amount of perrhenate formed after 1h, 24 h and 48 by TLC.
By means of physico-chemical parameters of the corres-ponding non-radioactive rhenium complexes we tried to find factors which may govern the formation of complexes showing high in vitro stability.
Finally, the most stable representative 3 was studied in 188Re labeling experiments with a phosphine-arginine-tyrosine model conjugate using the water-soluble N-hydroxysulfosuccinimidyl ester of the monodentate phosphine.

  • Poster
    „Radiotracers for In vivo Assessment of Biological Function New Directions“, 22.-23.04.2005, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-7532
Publ.-Id: 7532


Analysen zur Kühlmittelvermischung und zum Kernverhalten bei unterstellter Borverdünnung in Druckwasserreaktoren

Weiß, F.-P.; Kliem, S.

Bor ist ein starker Absorber für thermische Neutronen und wird dem Kühlmittel von DWR zugesetzt, um die Überschussreaktivität des Reaktorkerns zu kompensieren. Die unbeabsichtigte Verringerung der Borkonzentration, die sog. Borverdünnung, im Kern hat deshalb eine Reaktivitätserhöhung zur Folge und könnte im Extremfall die Rekritikalität des abgeschalteten Reaktors nach sich ziehen.

  • Invited lecture (Conferences)
    Kolloquium des Institutes für Kern- und Energietechnik des FZ Karlsruhe, 28.06.2005, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-7531
Publ.-Id: 7531


The Synthesis of Novel „4+1” Tc(III)/Re(III) Mixed-ligand Complexes with a Dendritic Modified Monodentate Ligand

Gniazdowska, E.; Stephan, H.; Pietzsch, H.-J.

Inert, so-called “4+1” trigonal-bipyramidal coordinated mixed–ligand complexes of the trivalent technetium and rhenium with tetradentate and monodentate ligands proved to be more stable than the pentavalent “3+1” mixed–ligand complexes with the (M=O)3+ core. They have appeared not to undergo a substitution in vivo with SH groups of such species as cysteine or glutathione [1].
In the presented paper we describe the synthesis of novel 99mTc(III) and 188Re(III) complexes containing the tripodal chelator 2,2’,2’’-nitrilotris(ethanethiol), NS3, and a dendritic modified monodentate isocyanide, CN-R(den). The reaction course was monitored with TLC and the radiochemical purity was monitored by HPLC. As a reference compound we have synthesized also the non-radioactive rhenium(III) complex which has been characterized by elemental analysis, IR, MS, 1H and 13C NMR.

  • Poster
    4th National Conference on Radiochemistry and Nucler Chemistry, 09.-11.05.2005, Kraków-Przegorzały, Poland

Permalink: https://www.hzdr.de/publications/Publ-7530
Publ.-Id: 7530


{2-Carboxy-2-{bis[(2-thiolato-_S)ethyl]amino-_N}ethanthiolato-_S} (triphenylphosphin-_P)rhenium(III)

Schiller, E.; Kraus, W.; Reck, G.; Spies, H.; Pietzsch, H.-J.

The title compound, [Re(C7H12NO2S3)(C18H15P)]center dot C3H6O, crystallizes from a solution in chloroform - acetone - cyclohexane with enantiomers disordered equally over each molecular site. Hydrogen bonds between the carboxyl groups form dimers in the crystal structure.

Keywords: COMPLEXES; THERAPY; RE-188

  • Open Access Logo Acta Crystallographica Section E 61(2005), M1373-M1375
    ISSN: 1600-5368

Permalink: https://www.hzdr.de/publications/Publ-7529
Publ.-Id: 7529


A new molecular mechanics force field for the design of oxotechnetium(V) and oxorhenium(V) radiopharmaceuticals

Comba, P.; Daubinet, A.; Martin, B.; Pietzsch, H.-J.; Stephan, H.

Force field parameters for the modeling of oxotechnetium(V) and oxorhenium(V) complexes with amine, amide, imine, carboxylate and thiolate donors have been derived and optimized with 131 published solid state structures. An automated procedure, based on a simplex algorithm, was used to optimize the 35 sets of metal-dependent structural parameters for each metal ion. These were introduced into the established MOMEC97 force field. The application of the new force field in the prediction of a novel radio-pharmaceutical’s structure was successful; the predicted structures of the two isomers compared well with the corresponding crystal structures obtained (RMS around the metal core: 0.153 and 0.035 Å, respectively).

  • Journal of Organometallic Chemistry 691(2006)11, 2495-2502

Permalink: https://www.hzdr.de/publications/Publ-7528
Publ.-Id: 7528


A model of low-frequency rotating magnetic field with a weak axial gradient

Priede, J.; Gerbeth, G.

We introduce a model of rotating magnetic field with a weak axial gradient which approximates the field generated by a slightly conical and sufficiently long inductor. The axial variation of the free-space field is assumed to be weak and its amplitude is approximated by the first linear term of expansion in a power series of the axial coordinate. This allows us to obtain an analytic solution for the azimuthal harmonics of the induced scalar electric potential and the azimuthal driving force in a cylinder of finite length. The results are verified by comparison with a numerical solution obtained by a Chebyshev-tau method.

  • Magnetohydrodynamics 41(2005)2, 189-198

Permalink: https://www.hzdr.de/publications/Publ-7526
Publ.-Id: 7526


A novel rhenium chelate system derived from dimercaptosuccinic acid for the selective labeling of biomolecules

Heinrich, T.; Kraus, W.; Pietzsch, H.-J.; Smuda, C.; Spies, H.

This work is part of efforts to develop chelating agents for stable binding and easy conjugation of rhenium-188 to biologically interesting structures. Starting from the well-known high in vivo stability of [188ReO(DMSA)2]- we want to exploit this coordination system for the design of 188ReO(V) chelates which are stable towards re-oxidation to perrhenate and towards ligand exchange under all conditions of radiopharmaceutical procedures and applications. Therefor a new type of tetradentate ligand has been synthesized by bridging two molecules of N,N’-diisobutyl-2,3-dimercaptosuccinamide with N-(3-aminopropyl)propane-1,3-diamine. The resulting stereoisomeric tetrathiolato S4 ligand of the composition (iBu)2N(O)C-C(SH)-C(SH)-C(O)NH-(CH2)3–NH-(CH2)3–NHC(O)-C(SH)-C(SH)-C(O)N(iBu)2 forms anionic five-coordinated oxorhenium(V) complexes by ligand exchange reaction of NBu4[ReOCl4] in methanol. Without addition of base the compounds will be isolated as “betain”, [ReO(S4)], with the protonated nitrogen of the bridge as internal “counter ion”. Two representatives have been fully characterized both in solid and solution states and found to adopt the expected square-pyramidal coordination geometry. The equatorial plane is formed by four thiolate sulfur atoms, whereas the oxygen occupies the apical position. The orientation of the metal oxo group is exo in relation to the carbamido groups in both isomers. Both complexes are stereoisomeric regarding the junction of the triamine chain.

  • Inorganic Chemistry 44(2005)26, 9930-9937

Permalink: https://www.hzdr.de/publications/Publ-7525
Publ.-Id: 7525


Einfluss von Wasserstoff auf die Zähigkeit von bestrahlten Reaktordruckbehälterstählen

Uhlemann, M.; Müller, G.; Ulbricht, A.; Böhmert, J.

Das Projekt liefert einen Beitrag zum Kenntnisstand der Wirkung von Bestrah-lung und Umgebungseinflüssen auf den Reaktordruckbehälter und dient zur Aufrechterhaltung eines hohen Sicherheitsstandards. Bis heute ist der Me-chanismus der Versprödung von RDB-Stählen nicht vollständig verstanden. Gesichert ist die Wirkung des Neutronenfeldes auf die Zähigkeitsabnahme von RDB Stählen. Zunehmend wird aber ein synergistischer Effekt zwischen Wasserstoff und den durch Bestrahlung erzeugten nanodispersen Strukturde-fekten diskutiert.
Ziel des Projektes war es eine experimentellen Nachweis über die Wechsel-wirkung von Wasserstoff und den bestrahlungsbedingten Strukturdefekten zu erbringen, den möglichen Einfluss auf die Zähigkeitsabnahme von RDB Stäh-len zu untersuchen und Unterschiede im Verhalten gegenüber dem unbe-strahlten Zustand auszuweisen.
Zur Untersuchung des Einflusses von Wasserstoff auf das Zähigkeitsverhal-ten von Reaktordruckbehälterstählen wurden einachsige Zugversuche bei verschiedenen Dehnraten an unbestrahlten und bestrahlten, wasserstoffvor- und in-situ beladenen Proben bei Raumtemperatur und 250°C durchgeführt. Die Bestimmung der mechanischen Eigenschaften wurde durch fraktografi-sche Untersuchungen der Bruchflächen ergänzt.
Mit SANS-Untersuchungen, der Analyse von Wasserstoffgehalten und Ther-modesorptions-untersuchungen wurde geprüft, ob Strahlendefekte als Haft-stellen für Wasserstoff wirksam werden.
Es konnte gezeigt werden, dass die Empfindlichkeit gegenüber Wasserstoff-versprödung von der chemischen Zusammensetzung des RDB-Stahles, der Fluenz bis zu der bestrahlt wurde, der Bestrahlungstemperatur und der Art der gebildeten Strahlendefekte bestimmt wird. Eine verstärkte Anfälligkeit ge-genüber Wasserstoffversprödung wird bei RT, in-situ Wasserstoffbeladung und langsamen Dehnraten sowie geringen Bestrahlungstemperaturen beo-bachtet. Bei 250°C ist eine Versprödung durch Wasserstoff nicht mehr nach-weisbar. Aus den Ergebnissen ist abzuleiten, dass bestrahlungsinduzierte De-fekte keine bevorzugten Plätze für eine höhere Aufenthaltswahrscheinlichkeit für Wasserstoff unter Betriebstemperaturen von RDB darstellen. Sie sind so-mit keine internen Quellen für Wasserstoff. Bei Betriebstemperaturen ist des-halb nicht mit einer erhöhten Versprödungsanfälligkeit zur zu rechnen. Durch die höheren Festigkeiten der bestrahlten Stähle steigt aber allgemein die Empfindlichkeit gegenüber Wasserstoffversprödung.
Der Integritätsnachweis von RDB’s außerhalb des Leistungsbetriebes unter Wasserstoffwirkung ist deshalb noch zu erbringen.

Keywords: diffusivity; hydrogen embrittlement; mechanical properties; reaktor pressure vessel steels; solubility; SANS

  • Invited lecture (Conferences)
    55. Sitzung des RSK-Ausschusses „Druckführende Komponenten und Werkstoffe“, 05.-06.07.2005, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-7524
Publ.-Id: 7524


Spectroscopic ellipsometry study of the role of the annealing time on nickel induced crystallization of a-Si

Pereira, L.; Águas, H.; Beckers, M.; Martins, R. M. S.; Fortunato, E.; Martins, R.

wird nachgereicht

  • Lecture (Conference)
    21st International Conference on Amorphous and Nanocrystalline Semiconductors (ICANS 21), 04.-09.09.2005, -, Portugal

Permalink: https://www.hzdr.de/publications/Publ-7523
Publ.-Id: 7523


Octahedral rhenium cluster complexes with inner organic ligands: synthesis, structure and properties of [Re6Q8(3,5-Me2PzH)6]Br2·2(3,5-Me2PzH) (Q = S, Se)

Mironov, Y.; Bryleva, K.; Shestopalova, M.; Yarovoia, S.; Fedorova, V.; Spies, H.; Pietzsch, H.-J.; Stephan, H.; Geipel, G.; Bernhard, G.; Kraus, W.

Two new octahedral cluster complexes – [Re6S8(3,5-Me2PzH)6]Br2·2(3,5-Me2PzH) (1) and [Re6Se8(3,5-Me2PzH)6]Br2·2(3,5-Me2PzH) (2), where 3,5-Me2PzH is 3,5-dimethyl-pyrazole, have been synthesized using reaction of rhenium chalcobromide complexes Cs4[Re6S8Br6]·2H2O and Cs3[Re6Se8Br6]·H2O respectively with molten 3,5-dimethylpyrazole. Both compounds synthesized were characterised by X-ray single-crystal diffraction and chemical analysis, IR and luminescent spectra.

  • Inorganica Chimica Acta (2006)359, 1129-1134

Permalink: https://www.hzdr.de/publications/Publ-7522
Publ.-Id: 7522


Synthesis and biodistribution of an 18F-labelled resveratrol derivative for small animal positron emission tomography (PET)

Gester, S.; Wüst, F.; Pawelke, B.; Bergmann, R.; Pietzsch, J.

Resveratrol (3,4',5-trihydroxy-trans-stilbene) is a naturally occurring phytoalexin and polyphenol existing in grapes and various other plants, and one of the best known 'nutriceuticals' . It shows a multiplicity of beneficial biological effects, particularly, by attenuating atherogenic, inflammatory, and carcinogenic processes. However, despite convincing evidence from experimental and clinical studies, data concerning the role of resveratrol and other members of the large polyphenols family for human health is still a matter of debate. One reason for this is the lack of suitable sensitive and specific methods, which would allow direct assessment of biodistribution, biokinetics, and the metabolic fate of these compounds in vivo. The unique features of positron emission tomography (PET) as a non-invasive in vivo imaging methodology in combination with suitable PET radiotracers have great promise to assess quantitative information on physiological effects of polyphenols in vivo. Herein we describe the radiosynthesis of an 18F-labelled resveratrol derivative, 3,5-dihydroxy-4'-[18F]fluoro-trans-stilbene ([ 18 F]-1), using the Horner-Wadsworth-Emmons reaction as a novel radiolabelling technique in PET radiochemistry for subsequent functional imaging of polyphenol metabolism in vivo. In a typical "three-step/one-pot reaction, 18F-labelled resveratrol derivative [ 18 F]-1 could be synthesized within 120-130 min including HPLC separation at a specific radioactivity of about 90 GBq/mumol. The radiochemical yield was about 9% (decay-corrected) related to [18F]fluoride and the radiochemical purity exceeded 97%. First radiopharmacological evaluation included measurement of biodistribution ex vivo and positron emission tomography (PET) studies in vivo after intravenous application of [ 18 F]-1 in male Wistar rats using a dedicated small animal PET camera with very high spatial resolution. Concordantly with data on bioavailability and metabolism of native resveratrol from the literature, these investigations revealed an extensive uptake and metabolism in the liver and kidney, respectively, of [ 18 F]-1. This study represents the first investigation of polyphenols in vivo by means of PET.

Keywords: Polyphenols; Resveratrol; [18F]Fluorobenzaldehyde; Horner-Wadsworth-Emmons reaction; Positron emission tomography (PET)

Permalink: https://www.hzdr.de/publications/Publ-7521
Publ.-Id: 7521


Aspects of positron emission tomography (PET) radiochemistry as relevant for food chemistry

Wüst, F.

Positron emission tomography (PET) is a medical imaging technique using compounds labelled with short-lived positron emitting radioisotopes to obtain functional information of physiological, biochemical and pharmacological processes in vivo. The need to understand the potential link between the ingestion of individual dietary agents and the effect of health promotion or health risk requires the exact metabolic characterization of food ingredients in vivo. This exciting but rather new research field of PET would provide new insights and perspectives on food chemistry by assessing quantitative information on pharmocokinetics and pharmacodynamics of food ingredients and dietary agents. To fully exploit PET technology in food chemistry appropriately radiolabelled compounds as relevant for food sciences are needed. The most widely used short-lived positron emitters are 11C (t1/2 = 20.4 min) and 18F (t1/2 = 109.8 min). Longer-lived radioisotopes are available by using 76Br (t1/2 = 16.2 h) and 124I (t1/2 = 4.12 d). The present review article tries to discuss some aspects for the radiolabelling of food ingredients and dietary agents either by means of isotopic labelling with 11C or via prosthetic group labelling approaches using the positron emitting halogens 18F, 76Br and 124I.

Keywords: Positron emission tomography; Radiolabelling; Prosthetic group

Permalink: https://www.hzdr.de/publications/Publ-7520
Publ.-Id: 7520


Dramatic effect of the tridentate ligand on the stability of Tc-99m "3+1" oxo complexes bearing arylpiperazine derivatives

Fernandes, C.; Correia, D. G.; Gano, L.; Santos, I.; Seifert, S.; Syhre, R.; Bergmann, R.; Spies, H.

Mixed - ligand model complexes of general formula [Tc-99m(O)(kappa(3) -SPh)(kappa(1)-SPh))] [X = O (1a), S (2a)] were prepared in a one-step procedure from [(TcO4-)-Tc-99m] using stannous chloride as reducing agent. Stability studies and challenge experiments with glutathione showed that complex 2a presented promising features for pursuing animal studies. The activity in the brain (% dose injected/organ) at 5 min (0.14% +/- 0.03) and 120 min (0.11% +/- 0.02) pi encouraged the synthesis of several mixed-ligand "3 + 1" oxo complexes of general formula [M(O)(kappa(3)-PNS)(kappa(1)-SL))] (M = Tc-99m, 3a-6a, Re, 3-6), in which the tridentate ligand is the heterofunctionalized phosphine 2-(diphenylphosphanyl)-N-(2-thioethyl)benzamide (PNS) and the co-ligands are different arylpiperazine derivatives (HSL1-HSL4). The Tc-99m complexes have been characterized by comparison of their retention times in the HPLC chromatogram (gamma-detection) with the retention times of the analogous Re complexes (UV detection at 254 nm). The 99mTc complexes, obtained with radiochemical purity higher than 95%, after HPLC purification, are stable in saline, 0.01 M PBS (pH 7.4), rat plasma (4 h, 37 degrees C), and glutathione (10 mM solutions, 2h, 37 degrees C). Binding affinity and selectivity for 5-HT1A receptors (relative to the 5-HT2A receptor) were determined, complex 5 demonstrating the best values (IC50 for the 5-HT1A 2.35 +/- 0.02 nM; competitor 5-HT2A 372 +/- 11 nM). Biodistribution and stability studies in mice indicated a preferred hepatobiliary excretion, a high in vivo stability, but a poor brain uptake.

Keywords: SMALL-MOLECULE RADIOPHARMACEUTICALS; DONOR ATOM SET; OXORHENIUM(V) COMPLEXES; 5-HT1A RECEPTORS; IMAGING AGENTS; IN-VIVO; RADIOLIGANDS; REACTIVITY

  • Bioconjugate Chemistry 16(2005)3, 660-668
    ISSN: 1043-1802

Permalink: https://www.hzdr.de/publications/Publ-7519
Publ.-Id: 7519


Flow structure during steam condensation in sub-cooled water in a large vertical pipe using wire-mesh sensors

Prasser, H.-M.; Beyer, M.; Carl, H.; Gregor, S.; Schütz, P.; Weiss, F.-P.

The structure of a steam-water flow in a vertical pipe of 195.3 mm inner diameter was studied using novel wire-mesh sensors for high-pressure / high-temperature operation (max. 7 MPa / 286 °C). Tests were carried out at pressures of 1 and 2 MPa under nearly adiabatic conditions as well as with slightly sub-cooled water. The evolution of radial gas fraction profiles and bubble-size distributions along the pipe in a high-pressure steam-water flow was measured for the first time. The experimental data allow to correlate the intensity of steam condensation in contact with sub-cooled water with the structure of the interfacial area and the bubble size distribution, which is very important for the model development.

Keywords: bubbly flow; phase transfer; bubble size distribution; vertical pipe

  • Contribution to proceedings
    4th International Conference on transport phenomena in multiphase systems, 26.-30.06.2005, Gdansk, Poland
    Proceedings of HEAT-2005, 433-438

Permalink: https://www.hzdr.de/publications/Publ-7518
Publ.-Id: 7518


Novel surface layer protein genes in Bacillus sphaericus associated with unusual insertion elements

Pollmann, K.; Raff, J.; Schnorpfeil, M.; Radeva, G.; Selenska-Pobell, S.

The surface layer (S-layer) protein genes of the uranium mining waste pile isolate Bacillus sphaericus JG-A12 and of its relative B. sphaericus NCTC 9602 were analyzed. The almost identical N-termini of both S-layer proteins possess a unique structure, comprising three Nterminal S-layer homologous domains (SLH). The central parts of the proteins share a high homology and are related to the S-layer proteins of B. sphaericus CCM 2177 and P-1. In contrast, the C-terminal parts of the studied S-layer proteins differ significantly between each other. Surprisingly, the C-terminal part of the S-layer protein of JG-A12 shares a high identity with that of the S-layer protein of B. sphaericus CCM 2177. In both strains the chromosomal S-layer protein genes were followed by a newly identified putative insertion element comprising three ORFs, which encode a putative transposase, a putative integrase/recombinase, a putative protein containing a DNA binding helix turn helix motif, and the S-layer protein-like gene copies sllA (9602) or sllB (JG-A12). Interestingly, both studied B. sphaericus strains were found to contain an additional, plasmid located and silent S-layer protein gene possessing the same sequence as sllA and sllB. The primary structures of the corresponding putative proteins are almost identical in both strains. The N-terminal and central parts of these S-layer proteins share a high identity with those of the chromosomally encoded functional S-layer proteins. Their C-terminal parts, however, differ significantly. These results strongly suggest that the S-layer protein genes have evolved via horizontal transfer of genetic information followed by DNA rearrangements mediated by mobile elements.

Permalink: https://www.hzdr.de/publications/Publ-7517
Publ.-Id: 7517


Metal binding by bacteria from uranium mining waste piles and its technological applications

Pollmann, K.; Raff, J.; Merroun, M.; Fahmy, K.; Selenska-Pobell, S.

Uranium mining waste piles, heavily polluted with radionuclides and other toxic metals, are a reservoir for bacteria that have evolved special strategies to survive in these extreme environments. Understanding the mechanisms of bacterial adaptation may enable the development of novel bioremediation strategies and other technological applications. Cell isolates of Bacillus sphaericus JG-A12 from a uranium mining waste pile in Germany are able to accumulate high amounts of toxic metals such as U, Cu, Pb, Al, and Cd as well as precious metals. Some of these metals, i.e. U, Cu, Pd(II), Pt(II) and Au(III), are also bound by the highly orderd paracrystalline proteinaceous surface layer (S-layer) that envelopes the cells of this strain. These special capabilities of the cells and the S-layer proteins of B. sphaericus JG-A12 are highly interesting for the clean-up of uranium contaminated waste waters, for the recovery of precious metals from electronic wastes, and for the production of metal nanoclusters. The fabricated nanoparticles are promising for the development of novel catalysts. This work reviews the molecular biology of the S-layer of the strain JG-A12 and the S-layer dependent interactions of the bacterial cells with metals. It presents future perspectives for their application in bioremediation and nanotechnology.

Keywords: Uranium mining waste piles; Bacillus sphaericus; S-layer; bioremediation; biocers; metal nanoclusters

Permalink: https://www.hzdr.de/publications/Publ-7516
Publ.-Id: 7516


Characterization of L Amino Acid Transporter 1 (LAT1) for 3-O-Methyl-6-18F-Fluoro-L-DOPA (OMFD) in Tumor Cells and Tumor Tissues

Haase, C.; Oswald, J.; Pietzsch, J.; Bergmann, R.

18F-labeled amino acids represent a promising class of imaging agents in tumors visualized by means of positron emission tomography (PET). Because of the high uptake it is still problematic to clear differentiate between tumors and inflammation.
The high enrichment in tumor tissues assumed the uptake of the tracer via a tumor-specific amino acid transporter, which is not or different expressed in inflammatory cells suggesting a different endowment of neutral amino acids. As previously shown, L-type amino acid transporter 1 (LAT1) is playing a key role because of its high up-regulation in malignant tumors. For the functional expression of LAT1 a single membrane-spanning protein, the heavy chain of 4F2 antigen (4F2hc), essentially forms a heterodimeric complex via disulfide bonds.
The present study investigated the amino acid transport mechanism of LAT1 for 3-O-methyl-6-18F-Fluoro-L-DOPA (OMFD), a novel 18F-labeled phenylalanine derivative, into tumor cells.
For molecular characterisation of L-type amino acid transporters focusing on the LAT1-4F2hc subtype we used two different tumor cells like FaDu (squamous cell carcinoma)/HT29 (colorectal adenocarcinoma) and tumor bearing mice performing quantitative RT-PCR, Western-Blot, and immunhistochemistry. In vitro uptake assays with HT29 and FaDu were performed with OMFD under physiological amino acid concentrations.
OMFD demonstrated a saturable and sodium- and energy-independent accumulation in vitro in different tumor cell lines, suggesting its uptake to be mediated exclusively by sodium-independent LAT1.
Our data emphasize the relevance of OMFD as a PET tracer for imaging of specific amino acid transport via LAT1 in tumors. Furthermore, the identification and characterization of tumor specific amino acid transporters like LAT1 will be a helpful tool for therapeutic implications. The inhibition of LAT1 activity in tumor cells could be effective in the inhibition of tumor cell growth by depriving tumor cells of essential amino acids, too.

Keywords: LAT1; OMFD; PET; tumor

  • Poster
    Fourth Annual Meeting of the Society for Molecular Imaging, 07.-10.09.2005, Köln, Deutschland
  • Abstract in refereed journal
    Molecular Imaging 4(2005)3, 285

Permalink: https://www.hzdr.de/publications/Publ-7515
Publ.-Id: 7515


Pages: [1.] [2.] [3.] [4.] [5.] [6.] [7.] [8.] [9.] [10.] [11.] [12.] [13.] [14.] [15.] [16.] [17.] [18.] [19.] [20.] [21.] [22.] [23.] [24.] [25.] [26.] [27.] [28.] [29.] [30.] [31.] [32.] [33.] [34.] [35.] [36.] [37.] [38.] [39.] [40.] [41.] [42.] [43.] [44.] [45.] [46.] [47.] [48.] [49.] [50.] [51.] [52.] [53.] [54.] [55.] [56.] [57.] [58.] [59.] [60.] [61.] [62.] [63.] [64.] [65.] [66.] [67.] [68.] [69.] [70.] [71.] [72.] [73.] [74.] [75.] [76.] [77.] [78.] [79.] [80.] [81.] [82.] [83.] [84.] [85.] [86.] [87.] [88.] [89.] [90.] [91.] [92.] [93.] [94.] [95.] [96.] [97.] [98.] [99.] [100.] [101.] [102.] [103.] [104.] [105.] [106.] [107.] [108.] [109.] [110.] [111.] [112.] [113.] [114.] [115.] [116.] [117.] [118.] [119.] [120.] [121.] [122.] [123.] [124.] [125.] [126.] [127.] [128.] [129.] [130.] [131.] [132.] [133.] [134.] [135.] [136.] [137.] [138.] [139.] [140.] [141.] [142.] [143.] [144.] [145.] [146.] [147.] [148.] [149.] [150.] [151.] [152.] [153.] [154.] [155.] [156.] [157.] [158.] [159.] [160.] [161.] [162.] [163.] [164.] [165.] [166.] [167.] [168.] [169.] [170.] [171.] [172.] [173.] [174.] [175.] [176.] [177.] [178.] [179.] [180.] [181.] [182.] [183.] [184.] [185.] [186.] [187.] [188.] [189.] [190.] [191.] [192.] [193.] [194.] [195.] [196.] [197.] [198.] [199.] [200.] [201.] [202.] [203.] [204.] [205.] [206.] [207.] [208.] [209.] [210.] [211.] [212.] [213.] [214.] [215.] [216.] [217.] [218.] [219.] [220.] [221.] [222.] [223.] [224.] [225.] [226.] [227.] [228.] [229.] [230.] [231.] [232.] [233.] [234.] [235.] [236.] [237.] [238.] [239.] [240.] [241.] [242.] [243.] [244.] [245.] [246.] [247.] [248.] [249.] [250.] [251.] [252.] [253.] [254.] [255.] [256.] [257.] [258.] [259.] [260.] [261.] [262.] [263.] [264.] [265.] [266.] [267.] [268.] [269.] [270.] [271.] [272.] [273.] [274.] [275.] [276.] [277.] [278.] [279.] [280.] [281.] [282.] [283.] [284.] [285.] [286.] [287.] [288.] [289.] [290.] [291.] [292.] [293.] [294.] [295.] [296.] [297.] [298.] [299.] [300.] [301.] [302.] [303.] [304.] [305.] [306.] [307.] [308.] [309.] [310.] [311.] [312.] [313.] [314.] [315.] [316.] [317.] [318.] [319.] [320.] [321.] [322.] [323.] [324.] [325.] [326.] [327.] [328.] [329.] [330.] [331.] [332.] [333.] [334.] [335.] [336.] [337.] [338.] [339.] [340.] [341.] [342.] [343.] [344.] [345.] [346.] [347.] [348.] [349.]