Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32228 Publications
Dissipative Taylor-Couette flows under the influence of helical magnetic fields
Rüdiger, G.; Gellert, M.; Schultz, M.; Hollerbach, R.;
The linear stability of magnetohydrodynamic Taylor-Couette flows in axially unbounded cylinders is considered for magnetic Prandtl number unity. Magnetic background fields varying from purely axial to purely azimuthal are imposed, with a general helical field parametrized by beta=B-phi/B-z. We map out the transition from the standard magnetorotational instability (MRI) for beta=0 to the nonaxisymmetric azimuthal magnetorotational instability for beta ->infinity. For finite beta, positive and negative wave numbers m, corresponding to right and left spirals, are no longer degenerate. For the nonaxisymmetric modes, the most unstable mode spirals in the opposite direction to the background field. The standard (beta=0) MRI is axisymmetric for weak fields (including the instability with the lowest Reynolds number) but is nonaxisymmetric for stronger fields. If the azimuthal field is due in part to an axial current flowing through the fluid itself (and not just along the central ax! is), then it is also unstable to the nonaxisymmetric Tayler instability which is most effective without rotation. For purely toroidal fields the solutions for m=+/- 1 are identical so that in this case no preferred helicity results. For large beta the wave number m=-1 is preferred, whereas for beta less than or similar to 1 the mode with m=-2 is most unstable. The most unstable modes always spiral in the same direction as the background field. For background fields with positive and not too large beta the kinetic helicity of the fluctuations proves to be negative for all the magnetic instabilities considered.
  • Physical Review E 82(2010), 016319

Publ.-Id: 14342 - Permalink


Laser-Based Particle Acceleration for Future Ion Therapy: Current Status of the Joint Project onCOOPtics with Special Focus On Beam Delivery and Dosimetry
Richter, C.; Beyreuther, E.; Dammene, Y.; Enghardt, W.; Kaluza, M.; Karsch, L.; Laschinsky, L.; Lessmann, E.; Naumburger, D.; Nicolai, M.; Sauerbrey, R.; Schlenvoigt, H. P.; Schürer, M.; Sobiella, M.; Weber, A.; Pawelke, J.; Baumann, M.;
Purpose: Before the novel technology of laser-based particle acceleration can be used for clinical applications, several requirements have to be fulfilled. These are the supply of stable and reliable particle beams with reproducible properties, sufficient particle intensity and useable energy spectra. Additionally, a precise dose delivery in an appropriate time and the exposure of a desired irradiation field are needed. Beside these demands, consequences on dosimetry as well as on the radiobiological effect have to be investigated for ultra-short pulsed laser-accelerated particle beams. Method andMaterials: The joint project onCOOPtics, an interdisciplinary and multicenter institution focusing on the development of a laser particle accelerator for radiation oncology, is introduced. The worldwide first systematic in vitro irradiations with laser-accelerated electrons performed with the JeTi laser system will be presented focusing on the experimental setup, practical experiences and on dosimetric and radiobiological results. In a next step, cell irradiation experiments with laser-accelerated protons have been prepared. Therefore, a dedicated dosimetric system was developed. It is integrated into a device that can be installed at different laser and conventional accelerators and serves also as cell or animal irradiation device. Results: A laser accelerator was successfully optimized for systematic radiobiological experiments performed over 3 months. No significant differences between laser-accelerated and conventional 6 MeV electron beams were found. An integrated dosimetry and cell irradiation device for systematic in vitro and in vivo experiments with laser-accelerated protons was developed, characterized, calibrated and successfully tested with both continuous and pulsed proton beams. Cell irradiations with protons have been started. Conclusion: Laser accelerators can be used for radiobiological experiments, meeting all necessary requirements like homogeneity, stability and precise dose delivery. Nevertheless, before fulfilling the much higher requirements for clinical application, several improvements concerning i.e. proton energy, spectral shaping and patient safety are necessary. Supported by BMBF (03ZIK445).
  • Abstract in refereed journal
    Medical Physics 37(2010)6, 3292-3292
    DOI: 10.1118/1.3468857
  • Poster
    AAPM 2010, 18.-22.07.2010, Philadelphia, USA

Publ.-Id: 14340 - Permalink


Tilting of self-organized layered arrays of encapsulated metal nanoparticles in C:Ni nanocomposite films by means of hyperthermal ion deposition
Abrasonis, G.; Oates, T. W. H.; Kovacs, G. J.; Grenzer, J.; Persson, P. O. A.; Heinig, K. H.; Martinavicius, A.; Jeutter, N.; Baehtz, C.; Grötzschel, R.; Tucker, M.; Rosen, J.; Bilek, M. M. M.; Möller, W.;
Self-organization at the nanoscale is a key issue in modern material science as it promises a potential route to commercially scalable production of functional nanomaterials. Here we present the growth-structure study of self-organized layered arrays of carbon encapsulated Ni nanoparticles grown by means of pulsed filtered cathodic vacuum arc deposition. Influence of the oblique ion incidence and Ni content on the film morphology is investigated. The film morphology has been determined by transmission electron microscopy (TEM) and grazing incidence small angle x-ray scattering (GISAXS) while C/Ni ratio was determined by means of nuclear reaction analysis. The C:Ni films with the Ni content in the range of ~6-50 at.% are considered. The results show that for the perpendicular incoming depositing ion incidence the C:Ni film structure consists of alternating self-organized nickel carbide and carbon layer oriented parallel to the film surface. However, for the oblique ion incidence the layered structure tilts in relation to the surface. The tilting angle and periodicity strongly depends on the deposition angle as well as on the Ni content. Combined TEM and GISAXS analysis shows that the film cross-sections can be described by two density modulation waves advancing with the growing film surface – one towards the incoming ions, another one with the weaker amplitude moving in roughly perpendicular direction. The results are discussed on the basis of the interplay between thermodynamically driven phase separation and energetic ion induced ballistic effects. Such structures show significant anisotropy which can be considered for tribological, optical, magnetic or magnetotransport applications.
  • Lecture (Conference)
    ICMCTF 2010 38th International Conference on Metallurgical Coatings & Thin Films, 02.-06.05.2010, San Diego, California, United States of America

Publ.-Id: 14339 - Permalink


(i)PVD growth of carbon-transition metal nanocomposites: from energetic condensation to periodic precipitation patterns
Abrasonis, G.;
(i)PVD growth of carbon-transition metal nanocomposites: from energetic condensation to periodic precipitation patterns
  • Invited lecture (Conferences)
    Nanofair 2010, 06.-07.07.2010, Dresden, Germany

Publ.-Id: 14338 - Permalink


High-energy break-up of 6Li as a tool to study the Big-Bang nucleosynthesis reaction D(alpha,gamma)6Li
Hammache, F.; Heil, M.; Typel, S.; Galaviz, D.; Sümmerer, K.; Coc, A.; Uhlig, F.; Attallah, F.; Caamano, M.; Cortina, D.; Geissel, H.; Hellström, M.; Iwasa, N.; Kiener, J.; Koczon, P.; Kohlmeyer, B.; Mohr, P.; Schwab, E.; Schwarz, K.; Schümann, F.; Senger, P.; Sorlin, O.; Tatischeff, V.; Thibaud, J. P.; Vangioni, E.; Wagner, A.; Walus, W.;
The recently claimed observations of non-negligible amounts of 6Li in old halo stars have renewed interest in the Big-Bang Nucleosynthesis (BBN) of 6Li. One important ingredient in the predicted BBN abundance of 6Li is the low-energy D(alpha,gamma)6Li cross section. Up to now, the only available experimental result for this cross section showed an almost constant astrophysical S-factor below 400 keV, contrary to theoretical expectations. We report on a new measurement of the D(alpha,gamma)6Li reaction using the break-up of 6Li at 150 A MeV. Even though we cannot separate experimentally the Coulomb contribution from the nuclear one, we nd clear evidence for Coulomb-nuclear interference by analyzing the scattering-angular distributions. This is in-line with our theoretical description which indicates a drop of the S24-factor at low energies as predicted also by most other models. Consequently, we find even lower upper limits for the calculated primordial 6Li abundance than before.
Keywords: 6Li halo stars Big-Bang Nucleosynthesis BBNcross section astrophysical S-factor break-up

Publ.-Id: 14337 - Permalink


Modification of the Reactivity Equivalent Physical Transformation Method for HTGR Fuel Element Analysis
Fridman, E.; Merk, B.;
The so called “double-heterogeneity”, characterizing High Temperature Gas cooled Reactors (HTGR) block type fuel elements, presents a challenge for existing deterministic lattice codes that were originally developed for LWR applications. A large number of TRISO particles randomly dispersed in the fuel compact introduces an additional complexity into the modeling. The Monte Carlo (MC) based codes, which are capable of simulating complex geometries of HTGR fuel elements, are mainly used for the reference calculations. The use of MC codes as production tools for a few-group cross section generation for 3D nodal codes is still very limited due to the high computational costs.
Recently a new few-group cross section generation methodology for a full core analysis of HTGRs was proposed. This methodology is based on homogenization approach called Reactivity equivalent Physical Transformation (RPT). The RPT methodology combines high spatial resolution of MC codes with superior computational speed of deterministic lattice codes. At the first stage, a MC code is used to simulate an HTGR fuel element with explicitly described TRISO particles at the beginning of life (BOL) and at the nominal operational conditions. At the second stage the TRISO particles are homogenized with the fuel compact graphite to get rid of double-heterogeneity problem. It is well known that a simple volume-weighted homogenization of TRISO particles in the graphite matrix results in the underestimation of the self-shielding effect. However, according to the RPT approach, TRISO particles are homogenized in a smaller central volume rather than in entire fuel compact. The volume of the smeared region is adjusted in such way that k-inf of homogenized geometry matches that of the reference heterogeneous one obtained from MC reference calculations. Since the radius of the smeared zone was determined at the beginning of life (BOL) it is kept constant and is used for depletion and branch-off calculations by lattice codes.
The main disadvantage of the RPT approach is the fact that TRISO particles are smeared together with the compact graphite and constitute one homogeneous material. Keeping in mind that the fuel and graphite temperatures may significantly vary during the reactor operation, these temperatures should be decoupled during a few-group cross section generation. However in the majority of lattice codes temperatures are assigned to the regions (e.c. HELIOS code) or to the homogeneous materials (e.c. CASMO code) rather than to particular nuclides like in the MC codes. In order to overcome this disadvantage the RPT methodology has been modified in a way that only TRISO particles are smeared in the central compact region while all compact graphite is concentrated in the remained outer compact region. This modification allows assigning different temperatures to the fuel and as well as to the compact matrix graphite.
The main objective of this study is to verify the modified RPT methodology. A set of depletion calculations of a prismatic block-type HTGR fuel lattice of fuel and coolant channels was performed. Two models of prismatic fuel assembly are considered: 1) 3D model with explicitly described TRISO particles; 2) 2D model, in which TRISO particles are homogenized using the modified RPT approach. 3D calculations are performed with MCNP based depletion code BGCore. 2D calculations are carried out with BGCore code and deterministic lattice code HELIOS 1.9. The comparison between 3D and 2D results is reported. Conclusions regarding validity of modified RPT approach are drawn.
Keywords: HTGR, double-heterogeneity treatment, BGCore, HELIOS
  • Contribution to proceedings
    5th International Topical Meeting on High Temperature Reactor Technology, 18.-20.10.2010, Prague, Czech Republic
    Modification of the Reactivity Equivalent Physical Transformation Method for HTGR Fuel Element Analysis
  • Lecture (Conference)
    5th International Topical Meeting on High Temperature Reactor Technology, 18.-20.10.2010, Prague, Czech Republic

Publ.-Id: 14336 - Permalink


Preliminary analysis of HTGR core with DYN3D nodal diffusion code
Fridman, E.; Kliem, S.; Rohde, U.;
DYN3D is an advanced nodal code for the three-dimensional steady-state and transient analysis of LWR cores with quadratic and hexagonal fuel assemblies. Although a new version of DYN3D for the simulation of block type High Temperature Gas cooled Reactors (HTGR) is currently under development, the main objective of this work is to demonstrate the applicability of the standard DYN3D version for the steady-state analysis of HTGR core. A preliminary reactor physic analysis procedure in which few group cross section sets are generated using HELIOS 1.9 transport lattice code and full core calculations are performed by DYN3D will be established. The Reactivity equivalent Physical Transformation (RPT) approach will be applied in order to eliminate the double-heterogeneity of HTGR fuel elements in HELIOS calculations. The full core analysis of the reference simplified HTGR core will be performed with DYN3D using macroscopic nodal cross sections provided by HELIOS. At this stage thermo-hydraulic feedback is not considered. The results of DYN3D calculations such as neutron multiplication factor, radial and axial power distribution, will be compared with those obtained from reference full core MCNP simulation.
Keywords: HTGR full core analysis, DYN3D, MCNP, HELIOS
  • Contribution to proceedings
    5th International Topical Meeting on High Temperature Reactor Technology, 18.-20.10.2010, Prague, Czech Republic
    Preliminary analysis of HTGR core with DYN3D nodal diffusion code
  • Lecture (Conference)
    5th International Topical Meeting on High Temperature Reactor Technology, 18.-20.10.2010, Czech Republic, Prague

Publ.-Id: 14335 - Permalink


Die Verwendung von Thorium in Druckwasserreaktoren
Fridman, E.;
Die Verwendung von Th-basierten Brennstoffkreisläufen als Alternative zum U-Brennstoffkreislauf wurde ausgiebig in den Anfangsjahren der Kernenergienutzung zwischen Mitte der 1950er und Mitte der 1970er Jahre erforscht. Obwohl der Nachweis zur Nutzung von Th in einer Reihe von thermischen und schnellen Systemen erbracht wurde, ist es nicht zur kommerziellen Anwendung von Th-Brennstoffen gekommen, bis das Interesse an Th-Brennstoffkreisläufen in den 1980er Jahren schließlich einschlief, vor allem wegen der großen Uranreserven und der Furcht vor nuklearer Proliferation. Die neuerliche Wiederbelebung des Interesses an Th-Kreisläufen, insbesondere in kommerziell betriebenen Druckwasserreaktoren (DWR), ist in erster Linie auf ihr Potential zur Lösung von Proliferationsrisiken, bei der Schonung natürlicher Uranvorkommen und bei der Entsorgungsproblematik im konventionellen Urankreislauf zurückzuführen. Der vorliegende Artikel gibt eine Übersicht über einige der neuesten Studien, die sich mit Implementierungsszenarien und den zu erwartenden Vor- und Nachteilen von Th-basierten Brennstoffen in der aktuellen DWR-Generation auseinandersetzen.
  • Contribution to proceedings
    Kraftwerkstechnischen Kolloquium, 12.-13.10.2010, Dresden, Germany
    Die Verwendung von Thorium in Druckwasserreaktoren
  • Lecture (Conference)
    Kraftwerkstechnischen Kolloquium, 12.-13.10.2010, Dresden, Germany

Publ.-Id: 14334 - Permalink


Electrical transport in Al doped ZnO grown by reactive pulsed magnetron sputtering
Cornelius, S.; Vinnichenko, M.; Kolitsch, A.; Möller, W.;
The synthesis of transparent conductive oxides (TCO) with high transmittance in the near infrared (IR) spectral range is a key requirement for increasing the power conversion efficiency in thin film solar cells. As the absorption at energies close to the Si band gap (1.1 eV) is caused by the free electron plasma it is necessary to maximize their mobility at moderate densities (~5x1020 cm-3) in order to simultaneously reach low resistivities of ~2x10-4 Ohm*cm and improve the IR transmittance.
Therefore a reactive magnetron sputtering method using metallic Zn/Al alloy targets was developed to achieve high carrier mobilities (~45 cm2/Vs) in ZnO:Al thin films. The influence of growth temperature, oxygen partial pressure and target Al concentration on the electrical film properties has been investigated systematically by Hall effect measurements.
Additionally XRD, X-TEM, AFM, ERDA, RBS and spectroscopic ellipsometry were employed to reveal film structure, composition and optical properties. The experimentally observed limit of mobility in polycrystalline ZnO:Al is discussed in terms of ionized impurity scattering and clustering as well as grain boundary limited transport.
Keywords: transparent conductive oxides, TCO, reactive magnetron sputtering, ZnO:Al, AZO, electrical properties, mobility, ionized impurity scattering, grain boundary limited transport
  • Lecture (Conference)
    5th Forum on New Materials (in the framework of 12th International Conference on Modern Materials and Technologies - CIMTEC 2010), 13.-18.06.2010, Montecatini Terme, Italien

Publ.-Id: 14333 - Permalink


Optical conductivity of LuNi2B2C in the terahertz range
Fischer, T.; Pronin, A. V.; Wosnitza, J.; Lobo, R. P. S. M.; Niemeier, T.; Holzapfel, B.;
es hat kein Abstract vorgelegen.
  • Poster
    Terahertz spectroscopy and its high-field applications & EuroMagNET II user meeting, 14.-16.06.2010, Dresden, Deutschland

Publ.-Id: 14332 - Permalink


Spin-orbit interaction in chiral carbon nanotubes probed in pulsed magnetic fields
Jhang, S. H.; Marganska, M.; Skourski, Y.; Preusche, D.; Witkamp, B.; Grifoni, M.; van der Zant, H.; Wosnitza, J.; Strunk, C.;
The magnetoconductance of an open carbon nanotube (CNT)-quantum wire was measured in pulsed magnetic fields. At low temperatures, we find a peculiar split magnetoconductance peak close to the chargeneutrality point. Our analysis of the data reveals that this splitting is intimately connected to the spin-orbit interaction and the tube chirality. Band-structure calculations suggest that the current in the peak regions is highly spin polarized, which calls for application in future CNT-based spintronic devices.
  • Physical Review B 82(2010), 041404(R)

Publ.-Id: 14331 - Permalink


Spin dynamics in S= 1/2 chains with next-nearest-neighbor exchange interactions
Ozerov, M.; Zvyagin, A. A.; Cizmár, E.; Wosnitza, J.; Feyerherm, R.; Xiao, F.; Landee, C. P.; Zvyagin, S. A.;
Low-energy magnetic excitations in the S= 1/2 chain compound [(C6H9N2)CuCl3]CuCl3 [known as (6MAP)CuCl3] are probed by means of tunable-frequency electron spin resonance. Two modes with asymmetric (with respect to the hnu =gµBB line) frequency-field dependences are resolved, illuminating the striking incompatibility with a simple uniform S= 1/2 Heisenberg chain model. The unusual ESR spectrum is explained in terms of the recently developed theory for S= 1/2 chains, suggesting the important role of next-nearest-neighbor interactions in this compound. Our conclusion is supported by model calculations for the magnetic susceptibility of (6MAP)CuCl3, revealing a good qualitative agreement with experiment
  • Physical Review B 82(2010), 014416

Publ.-Id: 14330 - Permalink


Einfluss der Al-Konzentration auf Struktur und elektrische Eigenschaften von mittels reaktivem gepulstem Magnetronsputtern gewachsenen ZnO:Al Schichten
Cornelius, S.; Vinnichenko, M.; Shevchenko, N.; Kolitsch, A.; Möller, W.;
Reactive pulsed magnetron sputtering (RPMS) is employed to grow Al-doped ZnO (AZO) films on fused silica and epitaxially on Al2O3(001). The RPMS process window for obtaining highly transparent and conductive AZO with high mobility and the influence of process parameters such as oxygen partial pressure and substrate temperature are discussed. It is shown that the optimum electrical properties depend stronly on the Al concentration of the sputtering target and that mobility on fused silica is limited to about 45 cm²/Vs. The relations between depostion conditions and film microstructure, stochiometry and electrical properties are investigated, pointing to an enrichment of Al with increasing substrate temperature leading to a deterioration of crystalline structure and carrier mobility.
Finally the observed limitations of electrical properties are categorized and discussed in terms of ionized impurity scattering and grain boundary limited transport.
Keywords: reactive pulsed magnetron sputtering, Al-doped ZnO, AZO, mobility, ionized impurity scattering, grain boundary limited transport
  • Lecture (Conference)
    Workshop „Transparente leitfähige Oxide – Festkörperphysikalische Grundlagen und Technologie“, 01.-02.06.2010, Dresden, Deutschland

Publ.-Id: 14329 - Permalink


Design and Performance of Non-Destructive Pulsed Magnets at the Dresden High Magnetic Field Laboratory
Zherlitsyn, S.; Herrmannsdörfer, T.; Wustmann, B.; Wosnitza, J.;
In this paper we consider various issues of design, fabrication, and performance of non-destructive pulsed magnets at the Dresden High Magnetic Field Laboratory. Currently, a variety of pulsed magnets are in operation in the laboratory. A 70 T/8.5 MJ magnet, having a 24 mm bore and generating field pulses of about 150 ms duration serves as a workhorse for external users and for in-house research. Smaller 60–65 T/1.5 MJ magnets with a bore of 20 mm and pulse duration of 25 ms have been proven to be very reliable in operation. In addition, a new 90 T/9MJdual-coil magnet has recently achieved 87.2 T in a 20 mm bore. A 60 T/43 MJ longpulse magnet is currently tested. Questions of magnet longevity, coil monitoring, as well as magnetic-field measurements are addressed. Further magnet-technology developments and the route to 100 T are discussed.
  • IEEE Transactions on Applied Superconductivity 20(2010), 672

Publ.-Id: 14328 - Permalink


Spin relaxation and resonant phonon trapping in [Gd2(fum)3(H2O)4]·3H2O
Orendáč, M.; Sedláková, L.; Cizmár, E.; Orendácová, A.; Feher, A.; Zvyagin, S. A.; Wosnitza, J.; Zhu, W. H.; Wang, Z. M.; Gao, S.;
Results of ac-susceptibility, specific-heat, magnetization, and electron-spin-resonance studies of a [Gd2(fum)3(H2O)4]·3H2O (fum=fumarate, C4H2O4) powder samples are reported. The results of these measurements enabled us to identify the studied compound as a three-dimensional S = 7/2 Heisenberg magnet with TN = 0.19 K and dominant crystal-field anisotropy. The susceptibility studies conducted at audio frequencies and temperatures from 2 to 30 K revealed that the application of static magnetic fields induces a slow spin relaxation. The relaxation is not associated with an anisotropy energy barrier and is explicable assuming resonant phonon trapping. The magnetic field dependence of the relaxation time is consistent with the proposed scenario and suggests that a strong spin-lattice interaction may be the mechanism governing the relaxation properties in the studied system
  • Physical Review B 81(2010), 214410

Publ.-Id: 14327 - Permalink


Eigenschaften und Mikrostruktur von mittels gepulstem reaktivem Magentronsputtern abgeschiedenen Metalloxid-Schichten
Cornelius, S.; Vinnichenko, M.; Rogozin, A.; Shevchenko, N.; Kolitsch, A.; Möller, W.;
An overview of the activity on metal oxides grown by reactive pulsed magnetron sputtering (RPMS) is presented, including high refractive index materials (Nb2O5) and transparent conductive oxides (Sn-doped In2O3 and Al-doped ZnO). For Nb2O5 the influence of process parameters such as plasma density and substrate temperature on optical properties, their thermal stability and film microstructure are discussed. In case of Sn-doped In2O3 (ITO) it is shown that by isothermal or electric current annealing amorphous films crystallize at different activation energies and that the resistivity decreases in two steps ascribed to relaxation and Sn donor activation. Finally it is shown that by RPMS films of Al-doped ZnO (AZO) with high mobility (45 cm²/Vs) can be obtained. The existence and dependence of an optimum substrate temperature for maximum mobility is discussed. Furthermore it is shown that in polycrystalline AZO the carrier mobility is limited by a combination of ionized impurity scattering and grain boundary limited transport depending on the carrier concentration. These effects are also influenced by the Al concentration in the sputtering target.
Keywords: reactive pulsed magnetron sputtering, refractive index, Nb2O5, ITO, AZO, zinc oxide, mobility, ionized impurity scattering, grain boundary limited transport, annealing
  • Lecture (Conference)
    PLASMA Germany - Frühjahrssitzung 2010, 05.-06.05.2010, Dresden, Deutschland

Publ.-Id: 14326 - Permalink


Acoustic Faraday effect in Tb3Ga5O12
Sytcheva, A.; Löw, U.; Yasin, S.; Wosnitza, J.; Zherlitsyn, S.; Thalmeier, P.; Goto, T.; Wyder, P.; Lüthi, B.;
The transverse acoustic wave propagating along the [100] axis of the cubic Tb3Ga5O12 (acoustic c44 mode) is doubly degenerate. A magnetic field applied in the direction of propagation lifts this degeneracy and leads to the rotation of the polarization vector - the magnetoacoustic Faraday rotation. Here, we report on the observation and analysis of the magnetoacoustic Faraday effect in Tb3Ga5O12 in static and pulsed magnetic fields. We present also a theoretical model based on magnetoelastic coupling of 4f electrons to both, acoustic and optical phonons and an effective coupling between them. This model explains the observed linear frequency dependence of the Faraday rotation angle.
  • Physical Review B 81(2010), 214415

Publ.-Id: 14325 - Permalink


High mobility Al-doped ZnO grown by reactive pulsed magnetron sputtering
Cornelius, S.; Vinnichenko, M.; Kolitsch, A.; Möller, W.;
Increasing the power conversion efficiency of modern thin film solar cells based on absorbers like silicon (Eg=1.11 eV), CuIn_xGa_(1-x)Se_2 (Eg=1.0-1.5 eV) and CdTe (Eg=1.44 eV) is one of the major goals of research devoted to photovoltaics. These cells rely on transparent electrodes made of transparent conductive oxides (TCO) whose high transmittance and low resistivity result in a high short circuit current and fill factor enabling high cell efficiency.

In TCOs absorption in the near infrared (NIR) and visible spectral region is caused by the free electrons and is influenced by their density and mobility inside the host lattice. Due to this inter-relation of optical and electrical properties TCOs with highest carrier mobility at moderate electron densities (~5x1020 cm-3) are required to simultaneously reach low resistivities and high NIR transmittance. Furthermore the deposition process used should be cost effective and scalable to large area substrates.

Therefore a reactive magnetron sputtering method using metallic Zn/Al alloy targets was developed to achieve high carrier mobilities (µ~45 cm²/Vs) in ZnO:Al (AZO) thin films [1], which is comparable to values achieved with other methods like RF magnetron sputtering or pulsed laser deposition.
Mass spectrometry and high accuracy capacitive pressure sensing together with a variation of the magnetron discharge parameters allowed for a fine control of oxygen partial pressure (p_O2). The dependence of the films electrical properties on the substrate temperature (T_S), the Al content in the sputter targets and p_O2 have been investigated systematically by Hall-effect measurements. Spectroscopic ellipsometry was used to determine film thickness and optical properties. The film structure, morphology and elemental composition was analysed by various methods including AFM, XRD, X-TEM, ERDA and RBS. Analysis of the film composition together with Hall-effect data was used to estimate Al donor activation.

Results show that there are optimum values of T_S and p_O2 at which films with resistivities down to ~2.3x10-4 Ohm*cm and free electron densities of ~6.0x1020 cm-3 were achieved. A shift of these optimum growth parameters and the resulting film properties with the target Al content has been detected. The observed limit of mobility in polycrystalline AZO is discussed in terms of ionized impurity scattering and clustering as well as grain boundary limited transport.
Recent investigations of Al concentration in the films and local bonding structure, revealed by XANES seem to explain the well known deterioration of resistivity in AZO at elevated substrate temperatures or after annealing.
Keywords: reactive magnetron sputtering, zinc oxide, ZnO, mobility, transparent conductive oxide, TCO, AZO
  • Lecture (Conference)
    NANOCOATINGS 2010 - International Conference on Functional Nanocoatings, 28.-30.03.2010, Dresden, Deutschland

Publ.-Id: 14324 - Permalink


Chemical speciation of trivalent actinides and lanthanides in biological fluids: The dominant in vitro binding form of curium(III) and europium(III) in human urine
Heller, A.; Barkleit, A.; Bernhard, G.;
Radionuclides represent a serious health risk to humans in case of incorporation. To get a first insight into the transport and metabolism of trivalent actinides in the human organism, we investigated the in vitro speciation of curium(III) in human urine samples using fluorescence spectroscopy. Since in speciation studies trivalent lanthanides are often used as analogs for trivalent actinides, we probed the suitability of this theory by investigating the speciation of europium(III) in human urine, too. Comparison with reference spectra of both heavy metals in model urine and of their complexes with single organic urine constituents then allowed for the determination of the dominant species. Furthermore the chemical composition of all urine samples was analyzed and the parameters affecting the metals’ speciation were determined. Surprisingly the chemical composition of the natural urine samples does not seem to have a great influence on the dominant species. Instead the pH was found to be the most important parameter. For both, the actinide and the lanthanide, two analog species were identified in dependence on the pH: In samples with slight acidic pH a curium(III) and europium(III) citrate complex dominates, respectively, while in samples with near neutral pH a ternary complex with phosphate and citrate as ligands is formed in each case. Comparison with thermodynamic modeling yields some discrepancies especially at higher pH which is due to a lack of data for the ternary species of both heavy metals.
Keywords: biofluid, Eu(III), Cm(III), heavy metal speciation, TRLFS, complexation, body fluid

Publ.-Id: 14323 - Permalink


Bioconjugation of the estrogen receptor hER(alpha) to a quantum dot dye for a controlled immobilization on the SiO2 surface
Cherkouk, C.; Rebohle, L.; Skorupa, W.;
We investigated the immobilization of the estrogen receptors hERα on the silanized SiO2 surfaces for biosensor applications. The conjugation of the estrogen receptor hERα to the quantum dot dye QD655 was achieved. In order to obtain an optimal immobilization of the estrogen receptor hERα on the functionalized SiO2 surface, the bioconjugate hERα-QD655 (Rcpt-qd655) solution was prepared with higher a molarity ratio of 10 to 20 between the QDs and the receptors. A blue laser with an excitation wavelength of 405 nm was used for photoluminescence spectroscopy (PL) investigations to monitor the bioconjugate Rcpt-qd655 immobilization on the silanized SiO2 surfaces with three different functional groups namely -NH2, -COO- and -SH. Several wash processes were applied to remove the excess receptors from the surface after the immobilization. A Fourier transform infrared spectroscopy (FTIR) was used to control the biofilm background after each wash of the receptor coated surface which allows the optimization of the immobilization protocol. In order to test its stability the Quartz crystal microbalance (QCM) was employed and the receptor density was calculated.
Finally the optimal biolayer (silane film+ hERα receptor) was tested for measurements of 17 ß-estradiol (E2) concentration of 1µM in waterish solution. The measurement concept outlined in [L. Rebohle et al., Vacuum 83 (2009) 24-28] was applied. The whole system was investigated by PL, which exhibits two color signals, namely from the receptor and the detected E2 molecules.
Keywords: estrogen receptor hERα, immobilization, Si-based light emitter, photoluminescence spectroscopy, 17 ß-estradiol, QDs dye

Publ.-Id: 14322 - Permalink


Study of beltline weld and base metal of WWER-440 first generation reactor pressure vessel
Schuhknecht, J.; Rindelhardt, U.; Viehrig, H.-W.;
The investigation of reactor pressure vessel (RPV) materials from decommissioned NPPs offers the unique opportunity to scrutinize the irradiation behaviour under real conditions. Material samples taken from the RPV wall enable a comprehensive material characterisation. The paper describes the investigation of trepans taken from the decommissioned WWER-440 first generation RPVs of the Greifswald NPP. Those RPVs represent different material conditions such as irradiated (I), irradiated and recovery annealed (IA) and irradiated, recovery annealed and re-irradiated (IAI). The working program is focussed on the characterisation of the RPV steels (base and weld metal) through the RPV wall. The key part of the testing is aimed at the determination of the reference temperature T0 following the ASTM Test Standard E1921-05 to determine the fracture toughness of the RPV steel in different thickness locations.
In a first step the trepans taken from the RPV Greifswald Unit 1 containing the X-butt multilayer submerged welding seam and from base metal ring 0.3.1 both located in the beltline region were investigated. Unit 1 represents the IAI condition. It is shown that the Master Curve approach as adopted in ASTM E1921 is applicable to the investigated original WWER-440 weld metal. The evaluated T0 varies through the thickness of the welding seam. The lowest T0 value was measured in the root region of the welding seam representing a uniform fine grain ferritic structure. Beyond the welding root T0 shows a wavelike behaviour. The highest T0 of the weld seam was not measured at the inner wall surface. This is important for the assessment of ductile-to-brittle temperatures measured on sub size Charpy specimens made of weld metal compact samples removed from the inner RPV wall. Our findings imply that these samples do not represent the most conservative condition. Nevertheless, the Charpy transition temperature TT41J estimated with results of sub size specimens after the recovery annealing was confirmed by the testing of standard Charpy V-notch specimens. The evaluated Charpy-V TT41J shows a better accordance with the irradiation fluence along the wall thickness than the Master Curve reference temperature T0.
The evaluated T0 from the trepan of base metal ring 0.3.1 varies through the thickness of the RPV wall. T0 increases from -120°C at the inner surface to -104°C at a distance of 33 mm from it and again to -115°C at the outer RPV wall. The KJc values generally follow the course of the MC, although the scatter is large. The re-embrittlement during 2 campaigns operation can be assumed to be low for the weld and base metal.
Keywords: reactor pressure vessel steel, fracture toughness, Master Curve, integrity assessment, thermal annealing
  • Strength of materials 403(2010)1, 95-104

Publ.-Id: 14321 - Permalink


Evaluation of a new bond-ordered potential for Si
Posselt, M.;
The reliability and predictability of classical molecular dynamics simulations is based on the precision of the interatomic potential used. Because Si has such a great technological importance there is a clear need for more accurate potentials. Recently, a new bond-order potential has been developed [1] by modifying the well-known analytical form given by Tersoff. It has been shown that this potential can reproduce many structural and thermodynamic properties of diamond-structure Si, such as the elastic constants and the melting characteristics, and it is able to determine the cohesive energy and the lattice constants of other solid phases reasonably well [1,2]. Furthermore, the potential yields rather correct data on structure and thermodynamics of liquid and amorphous Si. [2].
In the present work the new bond-order potential is applied to investigate point defect energetics and kinetics as well as solid phase epitaxial recrystallization of amorphous Si. The structure and the formation energy of the most stable configurations of vacancies and self-interstitials are determined. The migration of point defects is simulated and the characteristic migration pathways are identified. A more comprehensive study on preparation and properties of amorphous Si than in [2] is performed, and the results are compared with available experimental data. Solid phase epitaxial recrystallization is simulated at different temperatures and the recrystallization rate is determined. The results on point defect properties and solid phase epitaxial recrystallization are compared with those obtained by the Stillinger-Weber and the Tersoff potential as well as with experimental data and results of first principle calculations. Finally, a comparison is made with available results determined by two other bond-order potentials which have been recently developed [3-6].

[1] T. Kumagai, S. Izumi, S. Hara, S. Sakai, Comput. Mater. Sci. 39 (2007) 457.
[2] P. K. Schelling, Comput. Mater. Sci. 44 (2008) 274.
[3] B. A. Gillespie, X. W. Zhou, D. A. Murdick, H. N. G. Wadley, R. Drautz, D. G. Pettifor, Phys. Rev. B 75
(2007) 155207.
[4] B. A. Gillespie, H. N. G. Wadley, J. Crystal Growth 311 (2009) 3195.
[5] J. D.Schall, G. Gao, J. A. Harrison, Phys. Rev. B 77 (2008) 115209.
[6] B.-J. Lee, CALPHAD 31 (2007) 95.
Keywords: atomistic computer simulations, interatomic potential, silicon
  • Lecture (Conference)
    10th Int. Conf. on Computer Simulations of Radiation Effects in Solids (COSIRES 2010), 19.-23.07.2010, Krakow, Poland

Publ.-Id: 14319 - Permalink


The basic physics of intersubband transitions – from the simple to the subtle
Helm, M.;
I will describe the basic properties of intersubband transitions in quantum wells, partly along the lines of the now ten-years-old review paper [1]. I will proceed from the very basic to the discussion of some more specific systems, like superlattices or transitions within the valence band, and to some recently discovered, rather subtle effects.
An interesting interplay is found with transitions between shallow impurity states, which becomes particularly striking in superlattices and coupled quantum wells [2]. Based on a calculation that treats the heterostructure potential and the random-impurity potential on the same footing [3], we can successfully explain or re-interpret some old, hitherto poorly understood data (see Fig. 1).
Another subtle effect emerges, if intersubband spectra are recorded using time-domain terahertz spectroscopy, i.e. fully resolving the phase of the electric field. We show that transmission and absorption spectra are not equivalent, and whereas the absorption line has a standard Lorentzian shape, the transmission spectrum exhibits a Fano-type lineshape (see Fig. 2). This has been explained with the influence of the so-called ponderomotive current [4].
Most of the more recent experimental work discussed here was performed mainly by Dominik Stehr and Martin Wagner (both FZD), most of the samples used were provided by Gottfried Strasser (TU Vienna) and his group, and for part of this work the collaboration with the theory group of Univ. Marburg (D. Golde, M. Kira, S. W. Koch) was indispensable.
[1] M. Helm, “The basic physics of intersubband transitions”, in “Semiconductors and Semimetals”, Vol. 62, p. 1-99 (2000).
[2] D. Stehr, C. Metzner, M. Helm, T. Roch, and G. Strasser, “Resonant impurity bands in semiconductor superlattices”, Phys. Rev. Lett. 95, 257401 (2005).
[3] D. Stehr, M. Helm, C. Metzner, and M. C. Wanke, “Microscopic theory of impurity states in coupled quantum wells and superlattices”, Phys. Rev. B 74, 085311 (2006).
[4] D. Golde, M. Wagner, D. Stehr, H. Schneider, M. Helm, A.M. Andrews, T. Roch, G. Strasser, M. Kira, and S.W. Koch: “Fano signatures in the intersubband terahertz response of optically excited semiconductor quantum wells”, Phys. Rev. Lett. 102, 127403 (2009).
Keywords: intersubband, quantum wells
  • Invited lecture (Conferences)
    International Quantum Cascade Lasers School & Workshop, 30.08.-03.09.2010, Florenz, Italien

Publ.-Id: 14318 - Permalink


Terahertz nonlinear optics of excitons in semiconductor quantum wells
Wagner, M.; Stehr, D.; Schneider, H.; Winnerl, S.; Helm, M.;
We report the investigation of two nonlinear optical phenomena which are related to intra-excitonic transitions in semiconductor quantum wells and thus occur in the THz range. This is, on one hand, the generation of THz sidebands of near-band gap radiation, a perturbative process, and on the other hand, the AC Stark effect manifested by the Autler-Townes splitting as a non-perturbative effect. Both phenomena are induced by the strong THz field of the Dresden THz free-electron laser.
Keywords: AC Stark effect, Autler Townes effect, excitons, terahertz, sideband generation, nonlinear optics
  • Invited lecture (Conferences)
    20th International Conference on Applied Electromagnetics and Communications, 20.-23.09.2010, Dubrovnik, Kroatien
  • Contribution to proceedings
    20th International Conference on Applied Electromagnetics and Communications, 20.-23.09.2010, Dubrovnik, Kroatien
    ICECom, 2010 Conference Proceedings: IEEE, 978-1-61284-998-0

Downloads:

Publ.-Id: 14317 - Permalink


Superconductivity in Ga-doped Germanium above 1 K
Heera, V.; Herrmannsdörfer, T.; Skrotzki, R.; Ignatchik, O.; Uhlarz, M.; Fiedler, J.; Mücklich, A.; Voelskow, M.; Posselt, M.; Wündisch, C.; Heinig, K.-H.; Skorupa, W.; Wosnitza, J.; Helm, M.;
The discovery of superconductivity in heavily boron-doped diamond [1] has demonstrated that group-IV semiconductors can become superconducting upon carrier doping even at ambient conditions. Meanwhile superconductivity has been found in further heavily doped group-IV semiconductors such as Si and SiC [2]. Compared to these semiconductors, Ge seems to be less promising for realizing superconductivity as was based upon estimates of the electron-phonon coupling strength [3]. The challenge is to achieve extremely high hole concentrations which are commonly limited by the equilibrium solid solubility of the acceptor. Nevertheless, we succeeded in making Ge superconducting as recently reported [4]. A nonequilibrium doping process consisting of 100 keV Ga+-ion implantation with a fluence of 21016cm-2 and subsequent 3 ms flash-lamp annealing (FLA) enabled hole concentrations as high as 1.41021 cm-2. The superconducting state was observed in a thin (~60 nm) Ge layer with a maximum Ga content of about 8 at.% at critical temperatures below 0.5 K. From the measured critical parameters it follows that Ga-doped Ge is a type-II superconductor with a large Ginzburg-Landau parameter (>103).
The structure as well as the superconducting properties of the Ga-doped Ge layers depend sensitively on the preparation conditions as shown in Fig. 1. In search for higher transition temperatures, implantation and annealing conditions were varied in a more comprehensive study. Critical temperatures above 1 K were obtained for samples either implanted with 41016 cm-2 and flash-lamp annealed at 52 Jcm-2 or implanted with 21016 cm-2 and subjected to rapid thermal annealing (RTA) at 910°C for 60 s (Fig. 2). Critical magnetic fields perpendicular and parallel to the Ge:Ga plane up to about 0.3 and 1 T, respectively, were observed. Thus superconductivity in thin Ge:Ge layers is a robust effect and could be utilized in superconducting quantum devices.

[1] E. A. Ekimov, V. A. Sidorov, E. D. Bauer, et al., Nature 428, 542 (2004)
[2] K. Iakoubovskii, Physica C 469, 675 (2009)
[3] L. Boeri, J. Kortus, O. K. Anderson, J. Phys. Chem. Solids 67, 552 (2006)
[4] T. Herrmannsdörfer, V. Heera, O. Ignatchik, et al., Phys. Rev. Lett. 102, 217003 (2009)
Keywords: superconductivity, germanium
  • Lecture (Conference)
    30th International Conference on the Physics of Semiconductors (ICPS), 25.-30.07.2010, Seoul, Korea

Publ.-Id: 14316 - Permalink


Fourier Transform Infrared Spectroscopy for Biophysical Applications: Technical Aspects
Fahmy, K.;
FTIR spectroscopy has become an important non-destructive tool in gathering structural information of biological macromolecules at atomic resolution and under functional conditions. Modern instrumentation allows recording high resolution IR spectra of biomolecules in liquids, thin films, and adsorbed monolayers without chemical modification. The time-course of structural changes of biomolecules can be followed easily down to ~20 ms time resolution with rapidly scanning interferometers. If such reactions are highly reproducible, molecular mechanisms can be studied at a time resolution down to ns by step scan interferometers. Despite the advanced user-friendliness in operating modern FTIR spectrometers, the use of the adequate detector type, the correct adjustment of the signal to noise ratio, the setting of optical and electronic filters to physically restrict the band width and the corresponding choice of the interferometer scanning speed are crucial parameters in the hand of the user. Their prudential use is essential for gaining high quality spectra by proper signal averaging procedures in static as well as time-resolved experiments and for avoiding spectral artefacts inherent to improper sampling of both the optical path and the intensity of the IR interferogram.
Keywords: FTIR difference spectroscopy time-resolved step scan rapid scan bacteriorhodopsin
  • Book chapter
    Gordon C. K. Roberts: Encyclopedia of Biophysics, Berlin: Springer, 2013, 978-3-642-16711-9, 844-852
    DOI: 10.1007/978-3-642-16712-6_113

Publ.-Id: 14313 - Permalink


64Cu-Labeled Peptides for Tumor Visualization
Stephan, H.; Bergmann, R.; Steinbach, J.;
Over the past decade, molecular imaging has revolutionized medical diagnostics especially the detection of cancer. Among this new frontier, positron emission tomography (PET) allows early diagnoses, efficient monitoring of therapeutic treatment, and quantitative imaging of cancer. One of the most attractive positron-emitting radionuclide is 64Cu, which is meanwhile readily available in high specific activity from small cyclotrons. 64Cu-labeled peptides represent very interesting vector molecules for certain entities of cancer.

Figure 1: Bifunctional chelating agents (BFCAs) for stable binding of copper radionuclides (arrows show the position of BFCAs for the linkage to peptides)

Pyridine-containing macrocyclic amine ligands I, bispidine II and cyclam tetrapropionic acid III derivatives (Fig. 1), which simultaneously allow the coupling to peptides, have been developed for the stable fixation of copper radionuclides.[1-3] Corresponding bioconjugates with bombesin as well as neurotensin form rapidly very stable radiocopper complexes which permit clear visualization of tumor tissue in small animal PET studies.

Literature:

[1] G. Gasser, L. Tjioe, B. Graham, M.J. Belousoff, S. Juran, M. Walther, J.-U. Künstler, R. Bergmann, H. Stephan, L. Spiccia, Bioconjugate Chem. 2008, 19, 719-730. [2] S. Juran, M. Walther, H. Stephan, R. Bergmann, L. Steinbach, W. Kraus, F. Emmerling, P.Comba, Bioconjugate Chem. 2009, 20, 347-59. [3] A. Röhrich, R. Bergmann, A. Kretzschmann, S. Noll, J. Steinbach, J. Pietzsch, H. Stephan, 2010, submitted.
  • Poster
    3rd EuCheMS Chemistry Congress, 29.08.-02.09.2010, Nürnberg, D

Publ.-Id: 14311 - Permalink


Dendrimer-encapsulated rhenium cluster complexes
Kuhlmann, M.; Stephan, H.; Geipel, G.; Appelhans, D.;
The extreme versatility of dendrimers makes them attractive for drug delivery applications. In this perspective, binding of potential drug molecules non-covalently at the interior of dendritic hosts seems to be the most appropriated strategy. We have established glycodendrimers with dense maltose shell which may be utilized to encapsulate nanometer sized guest molecules. [1] This is of particular interest since it has been shown that polynuclear cluster compounds have antitumoral as well as antiviral properties. [2]

The encapsulation and release of an anionic rhenium cluster complex [Re6S8(OH)6]4- [3] in biocompatible maltose-decorated dendrimers (generation 4 and 5) have been studied in detail applying different physico-chemical methods, e.g. UV/vis, time-resolved laser-induced fluorescence spectroscopy, laser induced liquid bead ion desorption mass spectrometry and dynamic light scattering measurements. On average, 4 – 5 cluster anions can be captured in the interior of sugar-coated dendrimers, and a slow release of cluster complexes was observed under physiological conditions.

The encapsulation and release properties of maltose-decorated nanocarriers imply the possibility for the development of the next generation dendritic hosts with targeting moieties.

Literature:
[1] B. Klajnert et al., Chem. Eur. J. 2008, 14, 7030. [2] J. T. Rhule et al., Chem. Rev. 1998, 98, 327. [3] K. A. Brylev et al., Inorg. Chem. 2007, 46, 7414.
  • Poster
    3rd EuCheMS Chemistry Congress, 29.08.-02.09.2010, Nürnberg, D

Publ.-Id: 14310 - Permalink


Facile Synthesis of a PNA Oligomer containing 2,2´-Dipicolylamine as Chelator for 99mTc and 188Re
Jäger, K.; Gasser, G.; Bergmann, R.; Steinbach, J.; Stephan, H.; Metzler-Nolte, N.;
Since their discovery in 1991, Peptide Nucleic Acids (PNAs) have been used in molecular biology, mainly for detecting single base mismatches in oligonucleotide sequences. [1] Due to their non natural pseudo-peptide backbone, which replaces the phosphate-ribose backbone of natural DNA, PNAs are stable against enzymatic degradation. Furthermore, as they form very stable hybrids with both DNA and RNA, PNAs have also been thought to be useful for antisense and antigene therapies. Nuclear medicine is another field of research where PNAs have been used, as, for example, possible agents in the so-called “pretargeting approach”.[2] In this context, we are interested in the radiolabeling of PNA strands with therapeutically relevant nuclides, e.g. 188Re. En route to explore the wide potential of this “pretargeting using PNA” principle, we prepared a new azido derivative of 2,2´-dipicolylamine, namely 2-azido-N,N-bis((pyridin-2-yl)methyl)ethanamine (Dpa-N3). It was demonstrated that Dpa-N3 could be efficiently labeled with both [Re(CO)3(H2O)3]Br and [99mTc(H2O)3(CO)3]+ to give [Re(CO)3(Dpa-N3)]Br and [99mTc(CO)3(Dpa-N3)]+, respectively. Furthermore, Dpa-N3 was successfully coupled to a PNA oligomer. Subsequent labeling of Dpa-PNA with [99mTc(H2O)3(CO)3]+ afforded [99mTc(CO)3Dpa-PNA] in radiochemical yields > 90% (Figure 1). Biodistribution studies of [99mTc(CO)3Dpa-PNA] in Wistar rats showed a very fast blood clearance and modest accumulation in the kidneys. There was no significant activity in the thyroid and the stomach, demonstrating a high in vivo stability of the 99mTc-labeled Dpa-PNA conjugate.

[1] P. E. Nielsen, M. Egholm, R. H. Berg, O. Buchhardt, Science, 1991, 254, 1497
[2] G. Mardirossian, K. Lei, M. Rusckowski, F. Chang, T. Qu, M. Egholm, D.J. Hnatowich, J Nucl Med, 1997, 38, 907
[3] G. Gasser, K. Jäger, M. Zenker, R.Bergmann, J. Steinbach, H. Stephan, N. Metzler-Nolte, 2010, submitted.
  • Poster
    3rd EuCheMS Chemistry Congress, 29.08.-02.09.2010, Nürnberg, D

Publ.-Id: 14309 - Permalink


Radiolabeled Compounds in Analytics and Medicine
Stephan, H.;
kein Abstract verfügbar
  • Invited lecture (Conferences)
    Kolloquium University of Zurich, 01.07.2010, Zürich, Schweiz

Publ.-Id: 14308 - Permalink


Starch Coated Magnetic Nanoparticles With Pendant Chelating Agents
Stephan, H.;
kein Abstract verfügbar
  • Invited lecture (Conferences)
    Nanosight User Workshop “Nanoparticle Measurement”, 22.-23.06.2010, Langen, D

Publ.-Id: 14307 - Permalink


Emerging Opportunities for Application of Nanomaterials in Nuclear Medicine
Stephan, H.;
kein Abstract verfügbar
  • Lecture (Conference)
    7th SUPRAPHONE Meeting, 28.04.-01.05.2010, Maria Laach, D

Publ.-Id: 14306 - Permalink


Novel 64Cu-labeled bombesins capable of GRP receptor-targeted tumor imaging
Ruffani, A.; Stephan, H.; Bergmann, R.; Pietzsch, J.; Steinbach, J.; Graham, B.; Spiccia, L.;
A new macrocyclic ligand, 2-[4,7-bis(2-pyridylmethyl)-1,4,7-triazacyclononan-1-yl]acetic acid (1), binds copper strongly and the resulting radiocopper(II)-ligand complex exhibits high in vivo stability. The pendant carboxylic group enables this derivative to be conjugated to the N-terminal amino acid residues of peptides. Exploiting this, two stabilized bombesin derivatives have been coupled to 1 and radiolabeled with the positron emitter copper-64.
In vitro binding characteristics of the [64Cu]CuII-labeled bombesin conjugates in gastrinreleasing peptide receptor (GRPR) overexpressing prostate cancer (PC-3) cells have been evaluated. Biodistribution studies performed in Wistar rats indicate a specific uptake in the GRPR-rich pancreas and rapid renal elimination. Small animal PET imaging studies confirmed a high extent of tumor accumulation in NMRI nu/nu mice bearing the human prostate tumor PC-3. Incorporation of one additional glutamic acid residue within the spacer between bombesin and the radiolabeled complex leads to a higher tumor-to-muscle uptake ratio.
Keywords: TACN, bombesin, copper-64, prostate cancer, small animal positron emission tomography
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 692-693
    DOI: 10.1016/j.nucmedbio.2010.04.093
  • Contribution to external collection
    U. Mazzi, W. C. Eckelman, W. A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali Padova, 2010, 217-220

Publ.-Id: 14305 - Permalink


Versatile new bifunctional chelators for copper radionuclides
Stephan, H.; Bergmann, R.; Steinbach, J.; Spiccia, L.; Comba, P.;
Three new bifunctional chelating agents (BFCAs) I – III have been prepared. These ligands can be efficiently radiolabeled with 64CuII under mild conditions. The carboxylate and alcohol substituents allow to introduce appropriate biomolecules, e.g. peptides such as bombesin and neurotensin by amide coupling. The new BFCAs were found to be hydrophilic and therefore are attractive candidates for developing new copper(II)-based radiopharmaceuticals.
Keywords: TACN, bispidine, cyclam, bifunctional chelating agents, copper-64
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 695
    DOI: 10.1016/j.nucmedbio.2010.04.086
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 241-242

Publ.-Id: 14304 - Permalink


Multimeric cyclam derivatives with tunable surface modification for radiopharmaceutical applications
Kuhlmann, M.; Stephan, H.; Steinbach, J.; Röhrich, A.;
1,4,8,11-Tetraazacyclotetradecane (cyclam) derivatives with one to four appending dipeptide residues (Arg-Tyr) have been synthesized. Kinetics of complex formation with copper(II) was investigated by UV/vis spectroscopy to show a deceleration with increasing substitution degree of the cyclam core. Radiolabeling experiments with 64CuII on the peptide tetramer 5 revealed a smooth and efficient complexation. Challenge studies of 64Cu5 in the presence of cyclam as competing ligand prove the high kinetic inertness of the radiocopper(II) complex formed with 5.
Keywords: cyclam, peptide, multimers, copper-64
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 681
    DOI: 10.1016/j.nucmedbio.2010.04.066
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 77-80

Publ.-Id: 14303 - Permalink


Very stable copper(II) complexes of bispidines and their radiopharmaceutical behavior
Fähnemann, S.; Stephan, H.; Walther, M.; Steinbach, J.; Haaf, C.; Comba, P.;
The three bispidine-derived ligands L1 - L3 (bispidine = 3,7-diazabicyclo[3.3.1]-nonane) have been labeled with 64Cu, and the radioactive copper(II) complexes have been investigated for potential radiopharmaceutical applications. The thermodynamic stability of copper(II) complexes with the 2nd generation bispidines L2 and L3 is significantly higher than with L1 as a 1st generation bispidine. Despite this, labeling kinetics and challenge experiments indicate that L1 has advantages as a ligand for radiocopper(II) applications over the new ligands L2 and L3. The copper(II) complexes of all three bispidine ligands were found to be rather hydrophilic (log Do/w at pH = 7.4: 64Cu-L1 = -2.88, 64Cu-L2 = -1.45, 64Cu-L3 = -1.94). In vitro experiments with rat plasma give evidence that the 64Cu complexes of L1 – L3 are very stable.
Keywords: bispidine, coordination geometry, stability, copper-64
  • Lecture (Conference)
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 678-679
    DOI: 10.1016/j.nucmedbio.2010.04.085
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 51-56

Publ.-Id: 14302 - Permalink


Eph Receptors and Ephrin Ligands: Important Players in Angiogenesis and Tumor Angiogenesis
Mosch, B.; Reissenweber, B.; Neuber, C.; Pietzsch, J.;
Eph receptors and their ephrin ligands were identified in the late 1980's. Subsequently, they were linked to different physiological and pathophysiological processes like embryonic development, angiogenesis, and tumorigenesis. In this regard, recent work focused on the distribution and effects of Eph receptors and ephrins on tumor cells and tumor microenvironment. The purpose of this review is to outline the role of these molecules in physiological angiogenesis and pathophysiological tumor angiogenesis. Furthermore, novel therapeutical approaches are discussed as Eph receptors and ephrins represent attractive targets for antiangiogenic therapy.

Publ.-Id: 14301 - Permalink


Oxidation of Phenol by Microbubble-assisted Microelectrolysis
Ren, Y.; Wu, Z.; Ondruschka, B.; Braeutigam, P.; Franke, M.; Nehring, H.; Hampel, U.;
Removal of phenol under iron-carbon (Fe-C) microelectrolysis was enhanced by O2-microbubble. The removal rate (R0) of phenol reached 65% in 2 h. O2 bubbling plays a critical role, as compared to the air and N2 bubbling, in which only 9.5% and 4% of phenol is removed in 2 h, respectively. It shows that more dissolved oxygen in water is favorable for the oxidation process. Phenol removal is effective at lower temperature or/and higher dissolution pressure also confirms the role of dissolved oxygen. In the microbubble-assisted microelectrolysis system, O2, Fe-C pellets, and H2SO4 are the necessary conditions for the oxidation of phenol. The conversion of phenol follows the kinetics of the pseudo-first order, polynomially increases with the increasing amount of Fe-C pellets or/and sulfuric acid. Catechol, hydroquinone, and low molecular carboxylic acids are the major products.
Keywords: microelectrolysis, microbubble, oxidation, phenol

Publ.-Id: 14300 - Permalink


Implementation of 89Zr production and in vivo imaging of B-cells in mice with 89Zr-labeled anti B-cell antibodies by small animal PET/CT
Walther, M.; Gebhardt, P.; Grosse-Gehling, P.; Würbach, L.; Irmler, I.; Preusche, S.; Khalid, M.; Opfermann, T.; Kamradt, T.; Steinbach, J.; Saluz, H.-P.;
Aim.
Labeling of specific monoclonal antibodies or their fragments with suitable radionuclides can be utilized for diagnosis of autoimmune disorders or in preclinical research for elucidation of the role of specific cell types in underlying disease pathophysiology. In contrast to other radionuclides, 89Zr as a marker for positron emission tomography (PET) and protocols for 89Zr production so far have found relatively little interest despite the many advantages of this radionuclide.
Methods.
We examined the production, separation, and characterization of 89Zr, including supplementation of a commercial Cyclone® 18/9 with a self-made Solid Target System (STS) and the construction of a re-usable target holder. Optimized conditions to reduce undesired long-lived side products were specified. Obtained [89Zr]Zr-oxalate was used for labeling of anti-B cell antibodies with desferrioxamine-p-SCN as a bifunctional chelator. 89Zr-labeled antibodies were injected in DBA/1 mice to examine usability for detection of B cells in vivo by PET.
Results.
The improved conditions yielded 89Zr of high purity with smaller amounts of long living 88Zr isotope compared to other methods. The antibody labeling procedure yielded crude mixtures containing non-chelated metal, which were separated using desalting columns. Analytical radio-HPLC and TLC revealed 89Zr-labeled antibodies of sufficient purity. PET measurements showed binding of 89Zr-labeled anti-B cell antibodies in tissues with high frequencies of B cells, i.e. in spleen and lymph nodes.
Conclusion.
Labeling of antibodies directed to specific cell types with 89Zr according to our protocol turned out to be an effective tool for in vivo visualization and tracking of cells in mice by immuno-PET.

Publ.-Id: 14299 - Permalink


Cyclin-Dependent Kinase 4/6 (Cdk4/6) Inhibitors: Perspectives in Cancer Therapy and Imaging
Graf, F.; Mosch, B.; Koehler, L.; Bergmann, R.; Wuest, F.; Pietzsch, J.;
Cyclin-dependent kinases 4 and 6 (Cdk4/6) are important components of cell cycle activation and control in early G1 phase. Both enzymes and their regulators, e.g., cyclins, play critical roles in embryogenesis, homeostasis, and cancerogenesis. Cdk4/6 are attractive targets for cancer treatment. Recently, numerous selective small molecule inhibitors of Cdk4/6 have been developed. The potential of Cdk4/6 inhibitors, particularly, pyrido[2,3-d]pyrimidine derivatives, as both anti-cancer drugs and 124I- and 18F-radiolabeled tracers for cancer imaging using positron emission tomography is discussed.
  • Mini-Reviews in Medicinal Chemistry 10(2010), 527-539

Publ.-Id: 14298 - Permalink


Positron annihilation study of vacancies in Fe–Al based alloys
Melikhova, O.; Cizek, J.; Kuriplach, J.; Prochazka, I.; Cieslar, M.; Anwand, W.; Brauer, G.;
In the present contribution, high-resolution positron lifetime and coincidence Doppler broadening spectroscopies are used to characterize defects in Fe76Al24 and Fe72Al28 alloys. In order to facilitate defect identification, we also perform a theoretical study of basic vacancy-like defects in three phases of the Fe–Al system: ordered, short-range ordered, and disordered. Positron characteristics, like positron lifetime, positron binding energy to defects, high-momentum parts of Doppler broadening curves and specific trapping rates, are calculated for various defect configurations. The results are discussed in the context of experimental data obtained here and available in literature.
Keywords: Iron aluminides, based on Fe3Al; Point defects; Ab-initio calculations; Non-destructive evaluation; Positron characteristics
  • Intermetallics 18(2010)-598

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Publ.-Id: 14297 - Permalink


Optimization of [89Zr]ZrCl4 production and purification for high resolution PET imaging
Walther, M.; Gebhardt, P.; Würbach, L.; Irmler, I.; Grosse-Gehling, P.; Preusche, S.; Opfermann, T.; Kamradt, T.; Saluz, H.-P.; Steinbach, J.;
The exchange of solvent and anions from [89Zr]Zr-oxalate in oxalic acid to [89Zr]ZrCl4 in HCl is a crucial step in the production of 89Zr. A fast and reproducible method using cation instead of anion exchange resin giving a recovery of 98.5 ± 1.1% is described here. Obtained 89Zr was used for labeling a monoclonal antibody directed against CD4+ T helper cells.
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 697
    DOI: 10.1016/j.nulmedbio.2010.04.032
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 259-260

Publ.-Id: 14296 - Permalink


Sektionsberichte Jahrestagung Kerntechnik 2010 - Sektion Reaktorphysik und Berechnungsmethoden
Rohde, U.;
Es wird ein Überblick über die Vorträge zu Berechnungsmethoden für Hochtemperaturreaktoren (HTR) und andere Reaktorsysteme innerhalb der Technischen Sitzungen der Sektion Reaktorphysik und Berechnungsmethoden auf der Jahrestagung kerntechnik 2010 gegeben. Zu HTR wurden 4 Vorträge präsentiert, die sich vor allem mit dem Problem der so genannten doppelten Heterogenität und mit Methoden zur genauen Abbrandberechnung beschäftigen. In der Sitzung wurde in 2 weiteren Vorträgen über Fortschritte in Berechnungsmethoden für andere Reaktorsysteme als Hochtemperaturreaktoren berichtet.

The article gives an overview on the papers presented at the Technical Sessions of the Annual meeting of the German Nuclear Society 2010 in the section "Reactor physics and Methods of calculation". There are referred four papers on calculation methods for High Temperature Reactors and two papers on advances in calculational metods for other reactor systems. The papers on HTR are dealing mainly with the treatment of the double heterogeneity and with precise methods for burn-up calculations.
Keywords: Annual meeting; German Nuclear Society; reactor physics; methods of calculations; High Temperature Reactors
  • atw - International Journal for Nuclear Power (2010)10, 648-655

Publ.-Id: 14295 - Permalink


The impact of hypoxia on gene expression and protein synthesis of Eph receptors and ephrin ligands in human melanoma cells
Reißenweber, B.; Mosch, B.; Pietzsch, J.;
Background
The transmembrane Eph receptors (Eph) and their ephrin ligands represent the largest subfamily of receptor tyrosine kinases. Eph/ephrins are key players in cell-cell communication due to their capability of bidirectional signaling. There is evidence that Eph/ephrins also play an important role in tumor progression and metastasis. Since hypoxia is an important elicitor for metastatic behaviour of tumor cells, the aim of our study was to investigate the influence of hypoxia on Eph and ephrin expression in primary and metastatic melanoma cell lines.

Materials and methods
The influence of experimental hypoxia (6 to 72 h) on viability and metabolism of three melanoma cell lines (Mel-Juso, A375, and A2058) was characterized using MTT tests and cellular uptake of both 18F-fluoromisonidazole (FMISO) and 18F-fluorodeoxyglucose (FDG). The mRNA expression of EphA2, EphB4, ephrinA1 and ephrinB2 was analyzed with quantitative RT-PCR. Protein synthesis was determined by flow cytometry.

Results
The uptake of FMISO increased in all three melanoma cell lines after incubation under hypoxic conditions. The FDG uptake under hypoxic conditions decreased in all three cell lines. The MTT test demonstrated that viability of A375 cells decreased to 29±3% after 72 h of hypoxia. A2058 cells showed only a weak decrease of viability by approximately 30%, whereas viability of Mel-Juso cells under hypoxia was not influenced. In all cells Eph/ephrin gene expression under hypoxic and normoxic conditions showed only minor differences, except for EphA2 expression in A375 cells, which increased by >40% after 12 h hypoxia. Flow cytometry showed no alteration in ephrin ligands under hypoxic conditions. In contrast, after 72 h hypoxia we detected a slight increase in EphB4 protein in all melanoma cell lines, and enhanced EphA2 protein only in metastatic cell lines A375 and A2058.

Conclusion
The metastatic melanoma cell lines A375 and A2058 react more sensitive to hypoxic conditions than the primary melanoma cell line Mel-Juso. Experimental hypoxia increases Eph receptor gene expression and protein synthesis, particularly, in metastatic melanoma cell lines, which could be indicative for a further mechanism by which hypoxia affects tumor metastasis.
  • Poster
    21st Meeting of the European Association for Cancer Research (EACR-21), 26.-29.06.2010, Oslo, Norway
  • Abstract in refereed journal
    European Journal of Cancer 8(2010), 119

Publ.-Id: 14294 - Permalink


Efficient laser-ion acceleration from closely stacked ultrathin foils
Kluge, T.; Enghardt, W.; Kraft, S. D.; Schramm, U.; Sentoku, Y.; Zeil, K.; Cowan, T. E.; Sauerbrey, R.; Bussmann, M.;
A new scheme to efficiently accelerate protons by a single linear polarized high-intensity ultrashort laser pulse using multiple ultrathin foils is proposed. The foils are stacked at a spacing comparable to their thickness and subsequently irradiated by the same laser pulse. The foil thicknesses are chosen such that the laser light pressure can displace all electrons out of the foil. The authors present a simple, yet precise dynamical model of the acceleration process from which both optimum foil thickness and spacing can be derived. Extensive two-dimensional (2D) particle-in-cell simulations verify the model predictions and suggest an enhancement of the maximum proton kinetic energy by 30% for the two-foil case compared to a single foil.

Publ.-Id: 14293 - Permalink


Anwendung von computertomographischen Methoden (Synchrotron-CT, Röntgen-CT, Neutronen-CT) sowie Radiotracer-Experimente (Positronen-Emission-Tomographie) zur mehrskaligen Beschreibung von Strukturen und Rissen in Gesteinen
Kulenkampff, J.; Enzmann, F.;
Es ist kein Abstract vorhanden.
  • Lecture (others)
    Kolloquium, 24.02.2010, Hannover, Deutschland

Publ.-Id: 14292 - Permalink


Synthesis and SERT Binding Properties of 5-Fluoroindol-3-yl cyclobutylamines
Scheunemann, M.; Steinbach, J.;
Several mental diseases are associated with disorders of the serotonergic neurotransmission.[1] The serotonin transporter (SERT) regulates the synaptic concentration of this neurotransmitter and represents a primary target in the development of antidepressant drugs. Indol-3-yl-cyclo-alkanyl/-alkenyl amines (CnH2n-2(4), n=6,5,3), considered as conformationally constrained analogues of 5-hydroxytryptamine (5-HT, serotonin), have been introduced as a class of candidates holding highly potent SERT inhibitors[.2] In the search for new SERT ligands for PET with improved binding profiles we turned our interest towards rigid structures containing a 1,3-disubstituted cyclobutane (CnH2n-2, n=4), as spacer between the indole moiety and the amino group.
The present work describes our work on the synthesis and biological evaluation of the mono-fluorinated (2a,3a,4a) and double-fluorinated target molecules (1 b,2b).
The carbonyl group of both 3-(2-benzyloxy-ethyl)- and 3-(3-benzyloxy-propyl)cyclobutanone was converted by appropriate steps to yield the N-methyl, N-Boc protected cis- or trans-cyclobutyl amines. After removing the O-benzyl group, the alcohol was oxidized to the aldehyde applying the known TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) procedure. The secondary amines (1a-4a) were then directly obtained from the cyclobutyl aldehyde precursor via Fischer indole synthesis; for the tertiary amines 1 b and 2b an N-alkylation of 1 a and 2a with 3-fluoropropyliodide was performed.
Displacement experiments on hSERT-HEK293 cells labeled with [3H]citalopram have shown that cis-derivatives (Ki values: 1 b, 6.74±0.79 nM; 2a, 5.43±0.54 nM; 2b, 6.31 ±1 .37 nM) have nanomolar affinity for human SERT. The trans compound shows somewhat lower affinity (3a, 10.7±1.88 nM). By contrast, parallel studies applying [3H]paroxetine as radioligand indicated significantly lower SERT affinities [90 nM < Ki (1 b,2a,2b,3a,4a) <155 nM]. Thus, potential radiotracers based on the new derivatives may be able to selectively label the citalopram binding site of the SERT.
We have developed a general access to 5-fluoroindol-3-yl cyclobutylamines both in cis(1a, 1b, 2a, 2b) and trans-configuration (3a, 4a) obtained from readily accessible starting materials. Five synthesized compounds (1b, 2a, 2b, 3a, 4a) displayed promising affinities for SERT.
Keywords: SERT; cyclobutylindole
  • Poster
    Frontiers in Medicinal Chemistry, 14.-17.03.2010, Münster, Germany

Publ.-Id: 14291 - Permalink


High regiocontrol in the nucleophilic ring opening of 3-aralkyl-7-oxa-3-aza-bicyclo[4.1.0]heptanes with aliphatic and aromatic amines – A new short-step synthesis of FBT (4-fluorobenzyltrozamicol)
Scheunemann, M.; Steinbach, J.;
The 3,4-disubstituted piperidine framework plays an important role in many fields of pharmaceutical research[1] The ring opening of a conformationally rigid oxirane, annelleted to an N-protected six membered piperidine by an amine nucleophile, is a powerful method for establishing a trans-beta-aminoalcohol at the 3,4-position. Compounds derived from azavesamicol (trozamicol), which have been reported as usefulligands for the vesicular acetylcholine transporter (VAChT),[2] are displaying a 3-amino-piperidin-4-ol as a consistent structural feature. As part of our efforts in the search for new VAChT ligands for F18-PET (positron emission tomography) we have found a regioselective ring opening approach applying 3-(4-fluorobenzyl)-7-oxa-3-azabicyclo[4.1.0]heptane, which was utilized for a new 4-step synthesis of 4-fluorobenzyltrozamicol.
In contrast to former methodology, processing a common acyl[3] or carbamoyl[4] protective group at the piperidine nitrogen, we choose an N-benzyl protection. Starting from pyridine, which was converted to an N-4-fluorobenzylpyridinium salt, we obtained the corresponding N-protected 1,2,3,6-tetrahydropyridine via a standard hydrogenation using NaBH4 in EtOH. It was possible to epoxidize the olefine in high yield without interfering the basic tertiary amine, if applying trifluoroacetic acid in combination with its anhydride and H2O2-urea. As expected, the LiCIO4 assisted reaction of 1-aralkyl-3,4-epoxypiperidines with a series of aliphatic and aromatic amines in acetonitril led to a regioselective attack at position 4 of the piperidine to obtain 1-aralkyl-4-amino-piperidin-3-ol.[5] However, if applying EtOH as a protic solvent, without a coordinating Li-cation as additive, the inverse reg ioselectivity was observed. In this case, 1-aralkyl-3-aminopiperidin-4-oIs were derived as main products from the cleavage of the epoxy C-O bond at position 3. Following these protocols the aminoalcohol products were obtained as pure compounds by simple work-up without the need of chromatographic
separation.
In summary, we present an efficient method for the preparation of 3-amino-4-hydroxypiperidines and its regioisomers in 4-steps. The highly VAChT affine 4-fluorobenzyltrozamicol was obtained in an overall yield of 35%.
Keywords: VAChT; epoxide ring opening; 4-fluorobenzyltrozamicol; FBT
  • Poster
    Frontiers in Medicinal Chemistry, 14.-17.03.2010, Münster, Germany

Publ.-Id: 14290 - Permalink


Fibre agglomerate transport in a horizontal flow
Cartland Glover, G. M.; Krepper, E.; Kryk, H.; Weiss, F. P.; Renger, S.; Seeliger, A.; Zacharias, F.; Kratzsch, A.; Alt, S.; Kästner, W.;
An experimental and theoretical study of the transport of mineral wool fibre agglomerates in nuclear power plant containment sumps is being performed. A racetrack channel was devised to provide data for the validation of numerical models, which are intended to model the transport of fibre agglomerates. The racetrack channel provides near uniform and steady conditions that lead to either the sedimentation or suspension of the agglomerates. Various experimental techniques were used to determine the velocity conditions and the distribution of the fibre agglomerates in the channel. The fibre agglomerates are modelled as fluid particles in the Eulerian reference frame. Simulations of pure sedimentation of a known mass and volume of agglomerations show that the transport of the fibre agglomerates can be replicated. The suspension of the fibres is also replicated in the simulations; however, the definition of the fibre agglomerate phase is strongly dependent on the selected density and diameter. Detailed information on the morphology of the fibre agglomerates is lacking for the suspension conditions, as the fibre agglomerates may undergo breakage and erosion. Therefore, ongoing work, which is described here, is being pursued to improve the experimental characterisation of the suspended transport of the fibre agglomerates.
  • Lecture (Conference)
    Benchmarking of CFD Codes for Application to Nuclear Reactor Safety (CFD4NRS-3), 14.-16.09.2010, Bethesda, Maryland, United States of America
  • Contribution to proceedings
    Benchmarking of CFD Codes for Application to Nuclear Reactor Safety (CFD4NRS-3), 14.-16.09.2010, Bethesda, Maryland, United States of America
    Proceedings of CFD4NRS-3

Publ.-Id: 14289 - Permalink


Extention of the AIAD model - The free surface drag model
Höhne, T.;
Problem: Different models necessary for dispersed particles and separated continuous phases (interfacial drag etc.)
Keywords: AIAD, CFX, CFD, horizontal flow, surface drag
  • Lecture (Conference)
    CFD-network meeting, 21.-22.07.2010, Jülich, Deutschland

Publ.-Id: 14288 - Permalink


Swift Heavy Ion Beam Shaping of Au and Ge Nanoparticles in SiO2
Schmidt, B.; Heinig, K.-H.; Mücklich, A.; Akhmadaliev, C.; Ridgway, M.; Kluth, P.;
Lasers can process materials at spatiotemporal µm and ps scales. Here it will be shown that swift heavy ions can be used for materials processing at even shorter length and time scales. Swift-heavy-ion-induced deformation of spherical Au and Ge nanoclusters (NCs) embedded in SiO2 was studied experimentally and theoretically. Ge NC shaping is size dependent under irradiation with 38 MeV iodine ions and with 89 and 185 MeV gold ions. Large NCs don’t deform, smaller ones become discus-shaped, and very small ones show Ge loss at their equator. Small Au NCs deform into rods and wires, and, rather exotic, at critical NC size Au wires are squeezed out of the poles of the Au spheres.
Modeling and atomistic computer simulations identified the main driving forces: (i) The materials dependent electronic stopping power, (ii) the volume change upon melting, (iii) the asymmetric hydrodynamic flow due to stress field hysteresis, as well as (iv) far-from-equilibrium steady-state solubilities and strongly anisotropic diffusion. The latter one leads to “Ostwald ripening” of deformed NCs. The NC size distributions, shapes and anisotropies can be tailored by appropriate tuning of the driving forces. Our model describes the ion-induced shape evolution of different elements for different ion species, energies and fluences even quantitatively, where only one fit parameter describes all experiments. It is based on classical thermodynamics and hydrodynamics only. An even stronger proof is the shape change of nanospheres of critical size under swift heavy ion irradiation. For such particles, exclusively central ion impacts induce shaping, where Au is squeezed out of the poles. Using an unimodal size distributions and changing the ion impact angle during irradiation, tailoring of very exotic nanoparticle shapes become feasible.
Keywords: swift heavy ion irradiation, nanoparticles, silicon dioxide
  • Invited lecture (Conferences)
    21st International Conference on the Application of Accelerators in Research and Industry (CAARI 2010), 08.-13.08.2010, Dallas/Fortworth, Texas, USA

Publ.-Id: 14287 - Permalink


Ion Beam synthesis of Nano-crystals for Electronics and Photonics
Schmidt, B.; Heinig, K.-H.;
One of the main goals of materials research using ion beams is to synthesize nanostructures, for example semiconducting or metallic nanocrystals (NCs) in insulating films. A great effort is currently devoted to NC fabrication for micro- and optoelectronics by ion beam synthesis (IBS), because this method is compatible with modern CMOS technology. The present contribution addresses the Si NC formation by conventional ion implantation into the gate oxide and by a non-conventional IBS approach of ion beam mixing of SiO2/Si interfaces in thin gate oxides, with special emphasis on well-controlled size and position tailoring. The two approaches will be compared and related technological challenges discussed. Compared to conventional Si NC synthesis by Si+ ion implantation into the gate oxide, we take advantage of the self-alignment ion beam mixing process, i.e., the Si NCs are formed in SiO2 at a well-controlled small distance of ca. 2 nm from the Si/SiO2 interfaces. The technical applications in non-volatile nanocrystal memories and in light emitting field-effect transistors (LEFET) are demonstrated.
The Si NC MOSFETs were fabricated as nMOSFET devices in a standard 0.6 µm CMOS process line. Their electrical characteristics have been evaluated in terms of write/erase voltage, duration of the programming time, endurance and retention for different ion irradiation and annealing conditions. For the investigation of the light-emitting characteristics of the same nMOSFETs, an AC voltage was applied to the gate in order to inject charges of both polarities into the NCs. AC voltage and frequency dependent electroluminescence spectra in the wavelength region of 400-1000 nm were recorded for different annealing conditions. The performance of the Si NC memories and LEFETs with further possibilities of optimization of efficient charge storage and light emission properties will be discussed.
Keywords: Si nanocrystal, ion beam synthesis. nanocrystal memory, electroluminescence
  • Invited lecture (Conferences)
    21st International Conference on the APPLICATION OF ACCELERATORS IN RESEARCH AND INDUSTRY (CAARI 2010), 08.-13.08.2010, Dallas/Fortworth, Texas, USA
  • Contribution to proceedings
    21st International Conference APPLICATION OF ACCELERATORS IN RESEARCH AND INDUSTRY (CAARI 2010), 08.-13.08.2010, Fort Worth, Texas, USA
    AIP Conference Proceedings Volume 1336 APPLICATION OF ACCELERATORS IN RESEARCH AND INDUSTRY: Twenty-First International Conference Fort Worth, Texas, (USA), 8–13 August 2010 Editor(s): Floyd D. McDaniel, Barney L. Doyle: American Institute of Physics, 978-0-7354-0891-3, 233-238

Publ.-Id: 14286 - Permalink


Memory and electroluminescence properties of silicon nanocrystal MOS-FETs
Schmidt, B.; Heinig, K.-H.; Beyer, V.;
One of the main goals of materials research using ion beams is to synthesize nanostructures, for example semiconducting or metallic nanocrystals (NCs) in insulating films. A great effort is currently devoted to NC fabrication for micro- and optoelectronics by ion beam synthesis (IBS), because this method is compatible with modern CMOS technology. The present contribution addresses the Si NC formation by a non-conventional IBS approach of ion beam mixing of SiO2/Si interfaces in thin gate oxides [1], with special emphasis on well-controlled size and position tailoring as well as their application in non-volatile nanocrystal memories and in light emitting field-effect transistors (LEFET). Compared to conventional Si NC synthesis by Si+ ion implantation into the gate oxide [2], we take advantage of this self-alignment process, i.e., the Si NCs are formed in SiO2 at a well-controlled small distance of ca. 2 nm from the Si/SiO2 interfaces.
In order to implement our novel technique in CMOS technology, ion irradiation through a MOS-FET stack of 50nm poly-Si/15nm SiO2/Si substrate was performed with 50 keV Si+ ions. The ion beam mixing of the upper poly-Si/SiO2 interface and the lower SiO2/(001)Si interface leads to Si excess in the gate oxide. Subsequent rapid thermal annealing reforms sharp interfaces and separates the excess Si from SiO2. Adjacent to the recovered interfaces, 3-4 nm thick SiO2 zones denuded completely of excess Si have been found, whereas the more distant tails of excess Si form well-aligned narrow layers of NCs with 2-3 nm diameter. The self-alignment of the NC layers with the SiO2/Si interfaces allows to control shorter (direct) tunneling distances between the NCs and the Si electrodes with the potential of faster devices operating at reduced voltages.
The Si NC MOSFETs with an active gate area of 20x20 µm2 were fabricated as nMOSFET devices in a standard 0.6 µm CMOS process line. Their electrical characteristics have been evaluated in terms of write/erase voltage, duration of the programming time, endurance and retention for different ion irradiation and annealing conditions. For the investigation of the light-emitting characteristics of the same nMOSFETs, an AC voltage was applied to the gate in order to inject charges of both polarities into the NCs. AC voltage and frequency dependent electroluminescence spectra in the wavelength region of 400-1000 nm were recorded for different annealing conditions. The performance of the Si NC memories and LEFETs with further possibilities of optimization of efficient charge storage and light emission properties will be discussed.
Keywords: Silicon nanocrystals, ion beam mixing, charge storage, electroluminesence
  • Poster
    18th International Conference on Ion implantation Technology (IIT 2010), 06.-11.06.2010, Kyoto, Japan

Publ.-Id: 14285 - Permalink


First Synthesis of Uranyl Aluminate Nanoparticles
Chave, T.; Nikitenko, S. I.; Scheinost, A. C.; Berthon, C.; Arab-Chapelet, B.; Moisy, P.;
This paper describes, for the first time, a simple method for the synthesis of uranyl aluminate (URAL) nanoparticles. URAL was prepared by U(VI) hydrolytic precipitation with ammonia at pH = 11 in the presence of mesoporous alumina MSU-X under 20 kHz of sonication followed by annealing of the obtained solids at 800 C. TEM, XAFS, powder XRD, and 27Al MAS NMR studies revealed that the speciation of uranium in this system strongly depends on uranium concentration. The sample with 5 wt % of uranium yields air-stable nanoparticles (∼5 nm) of URAL. Presumably, UO2 2þ cations in this compound are coordinated with bidentate AlO2 - groups. The increase of uranium concentration to 30 wt % causes mostly formation of U3O8 fine particles (∼50 nm) and small amounts of URAL.
Keywords: uranyl nanoparticles XAFS NMR

Publ.-Id: 14284 - Permalink


SWOP—Charge Carrier Depth Profiling of Boron Doped Single Crystalline Silicon
Philipp, P.; Schmidt, B.; Zier, M.;
According to the subsequently continued shrinking of semiconductor device dimensions the fabrication of ultra shallow pn-junctions is the essential requirement for modern CMOS technology. Therefore the importance of measurement techniques for dopant depth profiles is rising and the demands in resolution and accuracy are increasing. The established methods like SIMS and spreading resistance profiling become less suitable for these applications because of their disadvantages at measurements near the silicon surface.
Stepwise Oxidation Profiling was applied to boron doped p+ layers as a new measurement technique for ultra shallow doped layers. Single crystalline n-type silicon (1…10 Ohmcm) with <100>- orientation was used as base material. One sample type was implanted with boron at an ion energy of 1 keV and an implantation fluence of 3x1014 cm-2. After implantation the samples were annealed by rapid thermal annealing (RTA) at 1000 °C and 10 s annealing time. On the other sample type boron was deposited by e-beam evaporation. Following, a 400 keV Si pre-implant was done to avoid transient enhanced diffusion and then a flash lamp diffusion (FLD) was carried out with 600 °C preheating and a 1300 °C Xe flash of about 3 ms duration. The two sample types were fabricated as planar van der Pauw (VDP) test structures.
Compared to the Continuous Anodic Oxidation Technique (CAOT) developed by S. Prussin the measurement procedure of SWOP is similar and the dopant depth profiles are measured by altering between an electrical VDP measurement of the sheet resistance and the electrochemical growth of thin anodic SiO2 layers (in steps of 1 nm and below). The SWOP measurement can be done in one apparatus without removing the sample for anodic oxidation or electrical VDP measurement. The values of the active boron concentration are calculated using the hole mobility values based on the Thurber expression.
Keywords: anodic oxidation, boron implantation, ultra shallow junction, depth profiling, van-der-Pauw
  • Poster
    The 18th International Conference on Ion Implantation Technology (IIT 2010), 06.-11.06.2010, Kyoto, Japan
  • AIP Conference Proceedings 1321(2010), 216-219
    DOI: 10.1063/1.3548353

Publ.-Id: 14283 - Permalink


Numerical study of bubbly flows using direct quadrature method of moments
Cheung, S. C. P.; Yeoh, G. H.; Tu, J. Y.; Krepper, E.; Lucas, D.;
To model the macroscopic bubble interactions (e.g. coalescence and breakage), the two-fluid model in conjunction with the population balance equation (PBE) approach has been considered as a practical and accurate formulation of handling bubbly flow systems. Recently, the MUltiple SIze Group (MUSIG) model appears to be one of the most direct solution methods which solves the PBE with discrete class approach and fuses seamlessly with the computational fluid dynamics (CFD) framework. Nonetheless, for complex bubbly flow structures with wide range of bubble size, large number of classes must be used to attain sufficient resolution for the bubble size distribution (BSD). This poses severe limitations on both computational time and resources. This paper focuses on introducing an alternative direct quadrature method of moments (DQMOM) (Marchisio and Fox, 2005) where the BSD is tracked through its moments by integrating out the internal coordinate. The main advantage of DQMOM is that the number of scalars to be solved is very small (i.e. usually 4-6). To assess the performance of DQMOM in measure-up with the MUSIG model, predictions of both models are validated against two experimental data by Hibiki et al. (2001) and Lucas et al. (2005). In general, the model predictions compared very well against the measured data. Associated
numerical issues and drawbacks for the DQMOM model are also discussed.
Keywords: Population Balance, Method of Moment, Bubbly Flow
  • Contribution to proceedings
    7th International Conference on Multiphase Flow, ICMF, 30.05.-04.06.2010, Tampa, USA

Publ.-Id: 14281 - Permalink


Steam bubble condensation in polydispersed flow - Experiments and CFD simulations
Krepper, E.; Schmidtke, M.; Lucas, D.; Beyer, M.; Lifante, C.;
Many activities were done in the last years to improve the modeling of adiabatic bubbly flows in the frame of CFD. In this case models for momentum transfer between the phases are most important. Usually they are expressed as so-called bubble forces. Experimental investigation as well as Direct Numerical Simulations (DNS) showed, that these bubble forces strongly depend on the bubble size. In addition to the well known drag force also virtual mass, lift, turbulent dispersion and wall forces have to be considered. The lift force even changes its sign in dependence of the bubble size (Tomiyama, 1989). In consequence large bubbles are pushed to the opposite direction than small bubbles if a gradient of the liquid velocity perpendicular to the relative bubble velocity exists (Lucas et al. 2001, Prasser et al. 2007). To simulate the separation of small and large bubbles more than one momentum equation is required (Krepper et al. 2005). For this reason recently so-called Inhomogeneous-MUSIG (MUlti SIze Group) model was implemented into the ANSYS-CFX code (Frank et al. 2008, Krepper et al. 2008). It allows the consideration of a number of bubble classes independently for the mass balance (for a proper modeling of bubble coalescence and breakup a large number of bubble groups is required) and for the momentum balance (only very few classes can be considered due to the high computational effort, criteria for the classification can be derived from the dependency of the bubble forces on the bubble size, e.g. the change of the sign of the lift force). In the presently implemented version of the Inhomogeneous MUSIG model only transfers between the bubble classes due to bubble coalescence and breakup can be modeled. In case of flows with phase transfer additional transfers between the single classes and the liquid and transfers between bubble classes caused by growth or shrinking of bubbles have to be considered. The equations for the extension of the MUSIG models are derived in Section 2. of this paper (see also Lucas et al. 2009). They were recently implemented into the CFX code and are presently verified (see Section 4).
Keywords: CFD-simulations, population balance models, heat and mass transfer, experiments
  • Poster
    7th International Conference on Multiphase Flow, ICMF 2010, 30.05.-04.06.2010, Tampa, USA

Publ.-Id: 14280 - Permalink


A new CFD-grade database on condensation in poly-dispersed bubbly flows
Lucas, D.; Beyer, M.; Szalinski, L.;
Experiments were done at the TOPFLOW facility of the Forschungszentrum Dresden-Rossendorf to establish a CFD-grade database on the condensation of steam bubbles injected into sub-cooled upwards vertical pipe flow. Bubble size distributions are important, since the condensation rate is proportional to the interfacial area density. To develop and validate closure models for CFD codes experimental data with high resolution in space and time are required. The steam was injected via orifices in the pipe wall located at different distances from measuring plane. 1 mm and 4 mm injection orifices are used to vary the initial bubble size distribution. The variation of the distance between the location of the gas injection and the measuring plane allows investigating the evolution of the flow along the pipe. Pressure, steam and water flow rates and the sub-cooling were also varied. Measurements are done using wire-mesh sensors and thermocouples. Data on averaged void fraction, radial gas volume fraction profiles, profiles of the gas velocity and bubble size distributions in dependency of the L/D ratio are presented.
Keywords: bubbly flow, condensation, experiment, phase transfer
  • Lecture (Conference)
    Workshop on Multiphase Flows - Simulation, Experiment and Application, 22.-24.06.2010, Dresden, Deutschland

Publ.-Id: 14279 - Permalink


Landau levels and magnetopolaron effect in dilute GaAs:N
Krstajic, P. M.; Peeters, F. M.; Helm, M.;
The magnetic-field dependence of the energy spectrum of GaAs doped with nitrogen impurities is investigated. Our theoretical model is based on the phenomenological band anticrossing model (BAC) which we extended in order to include the magnetic field and electron-phonon interaction. Due to the highly localized nature of the nitrogen state, we find that the energy levels are very different from those of pure GaAs. The polaron correction results in a lower cyclotron resonance energy as compared to pure GaAs. The magneto-absorption spectrum exhibits series of asymmetric peaks close to the cyclotron energy.
Keywords: semiconductors, impurities, nitrides, cyclotron resonance

Publ.-Id: 14278 - Permalink


Aqueous coordination chemistry and photochemistry of uranyl(VI) oxalate revisited: a density functional theory study
Tsushima, S.; Brendler, V.; Fahmy, K.;
Using density functional theory (DFT) calculations, we revisited a classical problem of uranyl(VI) oxalate photochemical decomposition. Photoreactivities of uranyl(VI) oxalate complexes are found to correlate largely with ligand-structural arrangements. Importantly, the intramolecular photochemical reaction is inhibited when oxalate is bound to uranium exclusively in chelate binding mode. Previously proposed mechanisms involving a UO2(C2O4)22- (1:2) complex as the main photoreactive species are thus unlikely to apply, because the two oxalic acids are bound to uranium in a chelating binding mode. Our DFT results suggest that the relevant photoreactive species are UO2(C2O4)34- (1:3) and (UO2)2(C2O4)56- (2:5) complexes binding uranium in an unidentate fashion. These species go through decarboxylation upon excitation to the triplet state, which ensues the release of CO2 and reduction of U(VI) to U(V). The calculations also suggest an alternative intermolecular pathway at low pH via an electron transfer between the excited state *UO22+ and hydrogen oxalate (HC2O4-) which eventually leads to the production of CO and OH- with no net reduction of U(VI). The calculated results are consistent with previous experimental findings that CO is only detected at low pH while U(IV) is detected only at high pH.

Publ.-Id: 14277 - Permalink


Synthesis and biological evaluation of a radioiodinated spiropiperidine ligand as a potential σ1 receptor imaging agent
Chen, R.-Q.; Li, Y.; Zhang, Q.-Y.; Jia, H.-M.; Deuther-Conrad, W.; Schepmann, D.; Steinbach, J.; Brust, P.; Wuensch, B.; Liu, B.-L.;
We report the synthesis and evaluation of 1'-(4-[125I]iodobenzyl)-3H-spiro[isobenzofuran-1,4'-piperidine] ([125I]Spiro-I) as a potential SPECT tracer for imaging of σ1 receptors. [125I]Spiro-I was prepared in 55–65% isolated radiochemical yield, with radiochemical purity of >99%, via iododestannylation of the corresponding tributyltin precursor. In receptor binding studies, Spiro-I displayed low nanomolar affinity for σ1 receptors (σ1: Ki = 2.75 ± 0.12 nM; σ2: Ki = 340 nM) and high subtype selectivity (σ2/σ1 = 124). Biodistribution in mice demonstrated relatively high concentration of radioactivity in organs known to contain σ1 receptors, including the lung, kidney, heart, spleen, and brain. Administration of haloperidol 5 min prior to injection of [125I]Spiro-I significantly reduced the concentration of radioactivity in the above-mentioned organs. These findings suggest that the binding of [125I]Spiro-I to σ1 receptors in vivo is specific.
Keywords: σ1 receptor; spiropiperidine; Iodine-125
  • Journal of Labelled Compounds and Radiopharmaceuticals 53(2010), 569-574
    DOI: 10.1002/jlcr.1777

Publ.-Id: 14276 - Permalink


Design von Radiotracern für das Neuroimaging neuropsychiatrischer und neurodegenativer Erkrankungen
Brust, P.;
Es ist kein Abstract vorhanden
  • Lecture (others)
    Kolloquium an der Universität Bonn, 19.07.2010, Bonn, Germany

Publ.-Id: 14275 - Permalink


Positron Emission Tomography (PET): Basic Principles of Radiotracer Design and Evaluation
Brust, P.;
Es ist kein Abstract vorhanden.
  • Lecture (others)
    Kolloquium MPI Leipzig, 19.04.2010, Leipzig, Germany

Publ.-Id: 14274 - Permalink


Phenyl-HPLC-Säulen als hochselektive RP-Phasen zur Trennung aromatischer Verbindungen
Wenzel, B.;
Es ist kein Abstract vorhanden.
  • Lecture (others)
    3. HPLC-Workshop "Möglichkeiten und Grenzen der HPLC in den Lebenswissenschaften", 29.01.2010, Rossendorf, Germany

Publ.-Id: 14273 - Permalink


Design, Synthesis and in Vitro Biological Evaluation of Reference Compounds of 123I and 99Tcm Labeled Indole Radiotracers for σ2 Receptor Imaging
in Chinese
Li, Y.; Jia, H.-M.; Deuther-Conrad, W.; Brust, P.; Steinbach, J.; Liu, B.-L.;
Novel indole radiotracers for 123I and 99Tcm labeling were designed. The corresponding reference compounds (Indole-I and Indole-MAMA-Re) and the precursor for 99Tcm labelling were synthesized. The compounds were characterized by IR, NMR, and MS analyses. Competition binding assays in vitro show that the Ki values of Indole-I for σ1 and σ2 receptors are (0.574 ± 0.355) μmol/L and (0.162 ± 0.030 2) μmol/L, respectively. The Ki values of Indole-MAMA-Re for σ1 and σ2 receptors are (3.75 ± 2.22) μmol/L and (7.83 ± 4.87) μmol/L, respectively. Furthermore, 99Tcm-Indole-MAMA was successfully prepared. The radio-chemical purity (RCP) of 99Tcm-Indole-MAMA after purification was higher than 90% by HPLC analysis. The compounds reported in this paper may be used as lead compounds for further structural modification to develop indole SPECT tumor imaging agents.
Keywords: Indole; σ receptors; 99Tcm; 123I
  • Open Access LogoJournal of Nuclear and Radiochemistry 32(2010)2, 132-138

Publ.-Id: 14272 - Permalink


Sorption of selenium(VI) onto anatase: macroscopic and microscopic characterization
Jordan, N.; Foerstendorf, H.; Weiß, S.; Heim, K.; Schild, D.; Brendler, V.;
The sorption of selenium(VI) onto pure anatase, a polymorph of titanium dioxide, was investigated. At the macroscopic level, batch experiments and electrophoretic mobility measurements have been performed. Selenium(VI) retention was found to be pH-dependent, i.e. sorption of selenium(VI) decreases with increasing pH (pH range 3.5-11). Selenium(VI) sorption dependence on the ionic strength was also evidenced, i.e. sorption increases while the ionic strength decreases. Electrophoretic mobility measurements showed that selenium(VI) sorption had no effect on the isoelectric point of anatase. At the microscopic level, XPS (X-ray Photoelectron Spectroscopy) measurements evidenced the absence of reduction of selenium(VI) during the sorption process. Furthermore, the nature of the sorbed surface species at the anatase/liquid interface has been elucidated using Attenuated Total Reflection Fourier-Transform Infrared (ATR FT-IR) spectroscopy. The spectroscopic results strongly suggest the formation of outer-sphere complexes on the whole pH range, which is in agreement with batch sorption experiments and electrophoretic mobility findings.
Keywords: selenium(VI); anatase; sorption; electrophoresis measurement; XPS; ATR FT-IR

Publ.-Id: 14271 - Permalink


In Vivo Binding of [18F]NS10743 on α7 Nicotinic Acetylcholine Receptors (α7-nAChR) in Pig Brain
Brust, P.; Deuther-Conrad, W.; Becker, G.; Fischer, S.; Hiller, A.; Østergaard Nielsen, E.; Brunicardi Timmermann, D.; Patt, M.; Sabri, O.; Peters, D.; Steinbach, J.;
Aim: Alterations of α7-nAChR have been observed in schizophrenia, brain trauma and neurodegenerative diseases. For PET imaging of α7 nAChR [18F]NS10743 has been successfully developed and evaluated in mice by tissue distribution and specificity studies. Here we report on baseline and blocking PET studies with [18F]NS10743 in pig brain.

Materials and Methods: Dynamic PET scanning (2h) was performed in anesthetized female piglets (13-15 kg), intravenously injected with ~ 330 MBq [18F]NS10743 (specific activity >150 GBq/µmol). Three animals additionally received 5 mg/kg of the α7 nAChR antagonist NS6740. Plasma samples were taken and metabolite-corrected input functions were estimated. Individual regions of interest were defined using an MRI-based template of pig brain. SUV, distribution volume (VT= K1/k2) and binding potential (BPND = (VT region - VT reference)/VT reference) were estimated.

Results: [18F]NS10743 readily passed the blood-brain barrier and the uptake of radioactivity peaked with SUV = 2.23±0.71 at 8-10 min in the baseline scan while in NS6740-blocking studies the radioactivity levels peaked significantly earlier (SUV = 3.02 ± 1.28 at 6 min) and decreased faster. At the end of study (between 90 and 120 min pi) SUV was significantly decreased by NS6740 in all investigated brain regions except olfactory bulb, which was chosen as reference region for calculation of BPND. At baseline, a mean VT value of 6.07±1.54 was estimated with the highest radiotracer accumulation in temporal, parietal, and occipital lobe, thalamus, striatum, and middle cortex (VT = 7.27±1.95 – 7.10±1.58). Intermediate binding was observed in hippocampus, colliculi, midbrain, frontal lobe, and ventral cortex (VT = 6.76±1.71 – 6.09±1.05), and lowest values were assessed in the cerebellum, pons, and olfactory bulb (VT = 5.71±1.18 – 4.11±0.96). Baseline BPND values for high (temporal lobe), median (hippocampus) and low specific binding (cerebellum) were 0.76±0.07, 0.54±0.08, and 0.39±0.08, respectively. NS6740 significantly reduced the binding potential BPND in regions with high [18F]NS10743 binding (temporal lobe: -29 %, p = 0.01; midbrain: -35 %, p = 0.02) while the decrease in regions with low binding was not significant (cerebellum: -16 %, p = 0.2).

Conclusion: The data provide clear evidence of in vivo binding of [18F]NS10743 at α7 nAChR. However, with regard to the low density of α7 nAChR expression in the brain further modifications of the NS10743 core structure are needed to increase the target affinity of the tracer compound.
Keywords: α7-nAChR; neurodegenerative diseases; [18F]NS10743; PET; blood-brain barrier
  • Lecture (Conference)
    23rd Annual Congress of the European Association of Nuclear Medicine (EANM), 09.-13.10.2010, Wien, Österreich
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 37(2010)2, 198-311

Publ.-Id: 14270 - Permalink


Interaction of ephrinB2 with its receptors EphB4 and EphB6 – potential impact on tumor-associated inflammation in human melanoma
Neuber, C.; Mosch, B.; Mamat, C.; Pietzsch, J.;
Background
Tumor-associated inflammatory cells (TAIC) are a major component of the tumor microenvironment and can contribute to both tumor progression and metastasis for instance by direct cell-cell interaction via membrane-bound proteins. Tumor cells show varying expression of Eph receptors and their ephrin ligands, which both are receptor tyrosine kinases. Eph/ephrins are hypothesized to be possible mediators of tumor-associated inflammation. The aim of our study was to analyze the distribution of ephrinB2 and its receptors EphB4 and EphB6 in inflammatory and melanoma cells and to clarify proinflammatory effects due to Eph/ephrin-mediated cell-cell contact.

Material and Methods
HL-60 promyelocytes and THP-1 monocytes, differentiated into granulocytes and macrophages, were used as a model for TAIC. Undifferentiated and differentiated cells were co-cultivated with Mel-Juso and A2058 melanoma cells. EphrinB2, EphB4 and EphB6 mRNA expression and protein synthesis was investigated using qRT-PCR and flow cytometry. Secretion of the proinflammatory cytokines IL-6 and TNF-α was analyzed using ELISA.

Results
No alteration in gene expression of ephrinB2, EphB4 and EphB6 could be observed during differentiation of HL-60 and THP-1 cells. In contrast, protein synthesis of ephrinB2, EphB4 and EphB6 was two- to threefold higher in HL-60 granulocytes compared to HL-60 promyelocytes and HL-60 macrophages. THP-1 macrophages showed a slightly increased protein synthesis of EphB4 and EphB6 compared to THP-1 monocytes whereas ephrinB2 protein content remained constant. Co-culture of both THP-1 monocytes and macrophages with Mel-Juso cells caused a substantial increment in secretion of proinflammatory cytokines. Co-culture of both HL-60 granulocytes and THP-1 monocytes with A2058 cells did not affect cytokine secretion. By contrast, co-culture of HL-60 macrophages with A2058 cells resulted in increased IL-6 secretion whereas co-culture of THP-1 macrophages with A2058 cells resulted in increased IL-6 secretion but decreased TNF-α release.

Conclusions
To our knowledge, mRNA expression and protein synthesis of ephrinB2, EphB4 and EphB6 was investigated for the first time in undifferentiated and differentiated HL-60 and THP-1 cells and, moreover, in Mel-Juso and A2058 melanoma cells. Co-culture of TAIC with melanoma cells resulted in proinflammatory effects. To differentiate the role of various Eph receptors and ephrin ligands in mediation of these effects after direct cell-cell contact of TAIC and melanoma cells selective inhibitors for Eph are applied in ongoing studies.
Keywords: Cell and Tumour Biology
  • Poster
    21st Meeting of the European Association for Cancer Research (EACR-21), 26.-29.06.2010, Oslo, Norway
  • Abstract in refereed journal
    European Journal of Cancer 8(2010), 120-121

Publ.-Id: 14269 - Permalink


Setting-up chemistry labs for accelerator mass spectrometry
Merchel, S.; Andermann, C.; Arnold, M.; Aumaître, G.; Bourlès, D.; Braucher, R.; Fuchs, M.; Gloaguen, R.; Klemm, K.; Martschini, M.; Schildgen, T. F.; Steier, P.; Wallner, A.; Yildirim, C.;
Introduction: The AMS business is booming: Many low-energy (< 1 MV) facilities, which are fully dedicated for 14C-analysis, are under construction or in funding status. Additionally, medium-energy accelerators such as the British 5 MV-NEC machine at “SUERC” Glas-gow, the French 5 MV-HVEE-machine “ASTER” at Aix-en-Provence [1] and the two German 6 MV-HVEE-machines “DREAMS” at Dresden [2] and “Cologne AMS” have been recently installed or are still in testing mode in Central Europe. Of course, these bigger machines need not only experienced physicists and technicians to get them running. It also seems to be advisable to have some experienced scientists around, who knows how to prepare AMS targets for 10Be, 26Al, 36Cl, 41Ca, and 129I measurements.
Quality assurance: In contrast to the 14C-community, where e.g. round-robin exercises are routine business, the idea of quality assurance and traceable standards has only been brought up lately for the other cosmogenic radionuclides. Thus, world-wide accepted standards issued by metrology institutes are rare: NIST is selling two kinds of 129I/127I-standards, and the Institute for Reference Materials and Measurements (IRMM) provides one set of 41Ca/40Ca solutions having eight different ratios [3]. Unfortunately, the most commonly used 10Be/9Be standard provided by NIST has been recently sold-out and will not be reissued. Other primary standard-type materials (26Al,36Cl), which are not commercially available, have been prepared by diluting certified activities and subsequent analysis within round-robin exercises [4,5]. After production of big quantities of in-house secondary standards for all nuclides, cross-calibration vs. primary standard-type materials has to be performed in-house and elsewhere [1].
Finally, as commercial 9Be contains intrinsic 10Be up to a level of 4x10-14 [6] sophisticated production of in-house carriers, used as machine blanks and for processing samples, such as Be2SiO4 originating from a deep mine in Brazil (Fig. 1), is needed.

Fig. 1: Origins of terrestrial samples yet processed at FZD chemistry labs: Antarctica, Brazil (carrier), Italy, Macedonia, Nepal, Slovenia, Tajikistan and Turkey.

Only after production and measurement of all these materials, the AMS facility is ready for real sample measurements.
Real samples: As it is always not advisable to change two important “things” at the same time, here machine and chemistry, first and foremost, a close cooperation with the AMS teams of “ASTER” and “VERA” (Vienna Environmental Research Accelerator) needed to check the quality of the new chemical sample preparation at FZD.
A “good” AMS sample is defined by two main features: high stable isotope current and low isobar concentration. A high chemical yield and low concentrations of other elements – originating either from the matrix or chemical products used – are less important. A corresponding low processing blank, i.e. with a very low radionuclide/stable nuclide ratio, is, however, essential for projects working near the detection limit. For high sample throughput and reasonable costs a fast, easy and cheap chemical separation is also favorable. Though, as it is the case for most destructive analytical methods, AMS sample preparation takes much longer, i.e. 24 h (ice, water) to 2-4 weeks (sediments, rocks), and is more expensive than the actual AMS measurement [7], which takes about 10-60 min.
For 10Be-AMS-targets isolated from quartz-rich river sediments (Himalaya, erosion rate study) and a calcite-rich boulder from a Slovenian rockfall area, 9Be-currents had been in the range of “ASTER” standards and machine blanks. The processing blanks produced at FZD were in the same order as the machine blank (1x10-15), thus, more than one order of magnitude lower than the lowest sample ratio.
Ten 36Cl-AMS-targets prepared from river terraces (Anatolian Plateau, Turkey, uplift rate study) will be investigated in June at “VERA”, hopefully validating the high quality of 36Cl-AMS targets.
Conclusion: We successfully started AMS chemistry in 2009 at FZD and are now open to more collaborations with research institutes and universities.
Acknowledgments: Thanks to E. Strub (26Al-activity), M. Bichler (neutron-irradiation of 9Be), C. Varajão (Be2SiO4 crystals), AWI & U Heidelberg (Antarctic & Italian ice/snow samples), DAAD & DFG (cash) & L. Benedetti, R.C. Finkel, I. Mrak, W. Möller, HVEE, FZD-AMS-team (great cooperation).
References: [1] Arnold M. et al. NIMB 268 (2010) 1954. [2] Akhmadaliev Sh. et al. this meeting. [3] Hennessy C. et al. NIMB 229 (2005) 281. [4] Merchel S., Bremser W. NIMB 223–224 (2004) 393. [5] Merchel S. et al. GCA 73 (2009) A871. [6] Merchel S. et al. NIMB 266 (2008) 4921. [7] Merchel S., Herpers U. RCA 84 (1999) 215.
Keywords: AMS, cosmogenic radionuclides, TCN
  • Poster
    6. Workshop RCA (Radiochemische Analytik bei Betrieb und Rückbau kerntechnischer Anlagen, der Deklaration von Abfällen und im Strahlenschutz) & 23. SAAGAS (Seminar Aktivierungsanalyse und Gammaspektroskopie), 06.-08.09.2010, Dresden-Rossendorf, Deutschland

Publ.-Id: 14268 - Permalink


Pyramidal pits created by single highly charged ions in BaF2 single crystals
El-Said, A. S.; Heller, R.; Aumayr, F.; Facsko, S.;
In various insulators, the impact of individual slow highly charged ions (eV-keV) creates surface nanostructures, whose size depends on the deposited potential energy. Here we report on the damage created on a cleaved BaF2 (111) surface by irradiation with 4.5×q keV highly charged xenon ions from a room-temperature electron-beam ion trap. Up to charge states q=36, no surface topographic changes on the BaF2 surface are observed by scanning force microscopy. The hidden stored damage, however, can be made visible using the technique of selective chemical etching. Each individual ion impact develops into a pyramidal etch pits, as can be concluded from a comparison of the areal density of observed etch pits with the applied ion fluence (typically 108 ions/cm2). The dimensional analysis of the measured pits reveals the significance of the deposited potential energy in the creation of lattice distortions/defects in BaF2.
Keywords: Slow Highly Charged Ions, BaF2
  • Physical Review B 82(2010), 033403

Publ.-Id: 14267 - Permalink


Amorphous solid foam structures on germanium by heavy ion irradiation
Bischoff, L.; Pilz, W.; Schmidt, B.;
Ge (100) surfaces were irradiated by heavy Bi+ and Bi++ ions extracted from a Bi-liquid metal ion source in a mass separated focused ion beam system with energy of 30 and 60 keV, respectively. Networks of different nanoporous (or sponge like) structures were found depending on ion energy, fluence, angle of incidence and irradiation temperature. The porous and amorphous surface structures are explained in terms of high concentration vacancies close to the surface. The surface modification was investigated using SEM and AFM imaging and FIB for cross section preparation.
Keywords: Germanium; porous network: Bi-LMIS; FIB; fluence; angle of incidence

Publ.-Id: 14266 - Permalink


Some recent developments in the field of measuring techniques and instrumentation for liquid metal flows
Eckert, S.; Buchenau, D.; Gerbeth, G.; Stefani, F.; Weiss, F.-P.;
The paper reports on new developments in the field of measuring techniques for liquid metal flows. We present three variants of a fully contactless electromagnetic flow meter for determining the integral flow rate in a channel flow. Respective test measurements have been performed at a liquid sodium and lead loop, respectively. One of the sensors is of particular interest since its operation does not depend on the electrical conductivity of the liquid metal, hence it is independent on the melt temperature. The Ultrasound Doppler Velocimetry (UDV) determines the velocity profile along the ultrasonic beam, and has the capability to work even through the channel wall. We present measurements obtained in a liquid sodium channel flow. Further, we report on the development of a contactless magnetic tomography of the global flow pattern in liquid metals. This method provides the full three-dimensional mean velocity distribution in a given liquid metal volume.
Keywords: liquid metal, flow measurements, electromagnetic flow meter, Ultrasound Doppler Velocimetry (UDV), Contactless Inductive Flow Tomography (CIFT)
  • Journal of Nuclear Science and Technology 48(2011), 490-498

Publ.-Id: 14265 - Permalink


Micro-pixe studies for archaeological gold identification – the case of transylvanian gold and of dacian gold staters (kosons)
Constantinescu, B.; Bugoi, R.; Munnik, F.; Pichon, L.;
Trace elements are more significant for provenance of archaeological metallic artifacts than the main components. For gold, the most promising elements are Platinum Group Elements (PGE), Sb, Hg, Pb, and, especially for alluvial (panned) gold, Sn and Pt. Several small fragments of ancient gold objects from some Bronze Age objects and Greek and Dacian (KOSON – type) coins were analyzed. To check if the Transylvanian gold was used, some fragments of nuggets from Transylvanian mines and alluvial gold were also studied. The measurements were performed by using the AGLAE accelerator of the Centre de Recherche et de Restauration des Musees de France. The samples were bombarded with a 3 MeV proton micro-beam (roughly 50 µm diameter). The employed beam current was around 10 nA. We also used the micro-PIXE technique at the nuclear microprobe facility of the Forschungszentrum Dresden-Rossendorf. A 3 MeV proton beam was employed; the beam diameter was roughly 150 μm. The total accumulated charge was around 3 μC.
As conclusions of the performed experiments, one can quote the following findings:
- Sn was detected as a trace-element in all the KOSON without monogram coins; in one of them we could acquire spectra in several spots; in one of them a very high concentration of Sn was found but not in the surrounding areas, most probably a cassiterite grain;
- No trace-elements were detected in the KOSON with monogram coins and the pseudo-Lysimach staters issued by the Greek colonies at the Black Sea coast; it was concluded that highly refined gold was used to manufacture these coins; the above findings led us to the idea that the two kind of KOSON coins were manufactured by using different gold sources
- Sn was also found as trace element in a fragment taken from a Early Bronze Age bracelet from Tauteu, hoard (Transylvania) and in a fragment from the Vulchitrun-like disk (Late Bronze Age) found in Calarasi, Oltenia; we could conclude that alluvial gold was most likely used to manufacture these Bronze Age objects;
- Te was found in several geological samples (e.g. in the ones from Rosia Montana), a fact that is of particular importance, since this element appears to be a characteristic of the Transylvanian gold minerals, but it is easily evaporated during the native gold melting, so, its presence in gold objects is very improbable;
- A very interesting finding was the presence of Pd traces in one of the alluvial gold samples, the one coming from Mures river.
  • Poster
    ICNMTA 2010 - 12th International Conference on Nuclear Microprobe Technology and Applications, 26.-30.07.2010, Leipzig, Germany

Publ.-Id: 14264 - Permalink


Spatially-resolved detection of iodine in natural platinum–palladium nuggets: a comparison of PIXE and XRF
Munnik, F.; Cabral, A. R.; Lehmann, B.; Radtke, M.; Reinholz, U.; Riesemeier, H.;
Recently, the role of microbial activity in mineral formation has become of great interest. In this case, the question arose for platinum–palladium nuggets recovered from an alluvial deposit (unconsolidated sediments deposited by streams) in the state of Minas Gerais in Brazil [1]. The morphological features of these aggregates of noble metals intuitively suggest that biological processes play a role in the formation of these particles. However, a geochemical fingerprint of microbial activity in precious-metal fixation is lacking. Iodine can provide such a fingerprint because it is a strongly biophile element. However, the detection of iodine at the µg/g level in a heavy matrix is quite challenging.
There are various techniques for the quantitative chemical analysis based on the detection of X-rays. Two of these techniques are PIXE (Particle Induced X-ray Emission) and XRF (X-Ray Fluorescence). In the past, only PIXE could be combined with a focussed ion beam to obtain elemental distribution maps with micrometer lateral resolution. PIXE was performed using a 3 MeV and 2 MeV H+ beam focussed to about 5x5 µm² coming from a 3 MV Tandetron accelerator at FZD, Dresden [2]. Another possibility is a mobile micro-XRF spectrometer, called MICROTAX or ArtTAX [2], in which X-rays from an X-ray tube are focussed by a polycapillary lens to a spot size of less than 100 µm. Both techniques, PIXE and µ-XRF, failed in detecting any iodine. The best detection limit obtained by PIXE was 70 µg/g for I in this matrix.
Nowadays, Synchrotron Radiation-induced XRF (SR-XRF) can also achieve spot sizes in the micrometer range. The SR-XRF analysis was carried out at the high energy beam line of the BAM, BAMline, at BESSY II. The excitation energy was 40 keV. An ~1 µm² spot size was achieved by focusing with an compound refractive lens CRL [3]. Only SR-XRF succeeded and indicated a significant positive correlation between iodine and palladium concentrations.
The measurements confirm that SR-XRF is very suitable for the detection of trace elements in heavy-metal matrices, which is mainly due to the tunability of the X-ray energy. The results of the SR-XRF measurements suggest that iodine may be used as a tracer for biologically mediated mineral formation.
[1] A.R. Cabral et al., Econ. Geol. 104, 1265-1276 (2009)
[2] F. Herrmann and D. Grambole, Nucl. Instr. Meth. B 104, 26-30 (1995)
[3] H. Bronk et al., Fresenius J Anal Chem 371, 307–316 (2001)
[4] E. Strub et al., Nucl. Instr. Meth. B 266, 2165-2168 (2008)
  • Lecture (Conference)
    ICNMTA 2010 - 12th International Conference on Nuclear Microprobe Technology and Applications, 26.-30.07.2010, Leipzig, Germany

Publ.-Id: 14263 - Permalink


µ-ERD and µ-PIXE characterization of H as-implanted and post-implanted annealed Oxide Dispersion Strengthened steel for fusion applications
Munnik, F.; González-Arrabal, R.; Romero, P.; Fernández, P.; Hernández, T.; Gonzalez, M.;
Ferritic/martensitic ODS-steel has been proposed as one of the best candidates as structural materials to be located in future fusion reactors, i.e. ITER and DEMO. One of the points of concern in further material development for fusion applications is the study of the diffusion and/or retention of light atoms, like H, which can be produced by transmutation. In this work, we investigated the chemical composition as well as the H distribution for H as-implanted and post-implanted annealed ODS-steel samples by means of simultaneous µ-PIXE and µ-ERD measurements. In general, µ-PIXE data evidence a quite inhomogeneous distribution of yttrium in some of the samples. It has been found that those regions with a larger Y content correspond with iron- and chromium- depleted regions. The possible correlation between Y and H content is discussed, on the basis of a large H diffusion even at room temperature.
  • Poster
    ICNMTA 2010 - 12th International Conference on Nuclear Microprobe Technology and Applications, 26.-30.07.2010, Leipzig, Deutschland

Publ.-Id: 14262 - Permalink


Dipole strength in Sm-144 studied via (gamma,n), (gamma,p), and (gamma,alpha) reactions
Nair, C.; Junghans, A. R.; Erhard, M.; Bemmerer, D.; Beyer, R.; Grosse, E.; Kosev, K.; Marta, M.; Rusev, G.; Schilling, K. D.; Schwengner, R.; Wagner, A.;
Photoactivation measurements on Sm-144 have been performed with bremsstrahlung endpoint energies from 10.0 to 15.5 MeV at the bremsstrahlung facility of the superconducting electron accelerator ELBE of Forschungszentrum Dresden-Rossendorf. The measured activation yield for the Sm-144(gamma,n) reaction is compared with the calculated yield using cross sections from previous photoneutron experiments. The activation yields measured for all disintegration channels Sm-144(gamma,n), (gamma,p), and (gamma,alpha) are compared to the yield calculated by using Hauser-Feshbach statistical models. A new parametrization of the photon strength function is presented and the yield simulated by using the modified photon strength parameters is compared to the experimental data.

Publ.-Id: 14261 - Permalink


Imaging of neurotensin receptors in tumors by a novel stabilized 64Cu-DOTA-neurotensin analog
Bergmann, R.; Brans, L.; Tourwe, D.; Schlottig, K.; Pietzsch, J.;
Background:
Neurotensin (NT) and its receptors (NTR) are overexpressed in various tumors (breast, prostate, lung, ductal pancreas, pituitary) and play a crucial role in tumor progression and malignancy. For tumor diagnosis and optimized targeted, individualized therapy it is important to image and quantify functional expression of these receptors. The development and radiopharmacological characterization of a novel stable neurotensin analog radiolabeled with 64Cu is described.

Material and methods:
The peptide (ArgΨ(CH2NH)ArgProdmTyrtLeuLeu-OH) was synthesized by manual solid phase synthesis on a Merrifield-resin and conjugated with DOTA (1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid). Radiolabeling of the peptide (3 nmol) with 64CuCl2 was carried out in 0.1 M ammonium acetate at pH 5.5, 37°C and 15 min. The IC50 was determined on HT-29 cell membranes. Cell uptake and internalization was studied in HT-29 and PC3 cells. The biodistribution of the radiotracer was investigated in HT-29 tumor bearing NMRI nu/nu mice (5 min, 60 min p.i.; 4 animals per time point) and imaged by small animal PET (8 animals). The metabolic stability was analyzed in Wistar rats.

Results:
The binding affinity of the radiotracer towards NTR1 was 7 nM (4-12 nM, 95% confidence interval). The radiochemical purity after one step radiolabeling was greater than 92%. After single intravenous administration the activity concentration increased fast in the tumor (0.8±0.1 SUV, 5 min p.i.) and decreased to 0.3±0.1 SUV (60 min). At 60 min p.i. the tumor to organ ratios were 2.8±0.7 (blood), 5.2±0.9 (muscle), 4.2±0.6 (pancreas), 0.6±0.5 (liver), and 0.4±0.4 (kidneys). The radiotracer was fast accumulated in the kidneys (3.7±0.6 SUV, 5 min p.i.; 0.8±0.1 SUV, 60 min p.i.) and eliminated in the urine (60±6% injected dose, 60 min p.i.). The tumors were clearly delineated in the PET images. The tumor uptake of the radiotracer was competitively inhibited by 73% by simultaneous injection of the neurotensin derivative 8-13. In rat plasma 33% of the radioactivity accounted for the original compound at 60 min p.i.

Conclusions:
The novel 64Cu-neurotensin analog with good stability and high receptor affinity allows for the in vivo imaging and functional characterization of NTR1 receptor overexpressing tumors. These findings are a prerequisite for other imaging applications, e.g., using SPECT radionuclides (111In), and potentially also for targeted radionuclide therapy (67Cu, 90Y or 177Lu).
Acknowledgement: This project was supported in part by the EC (Grant agreement no. 223057, GIPIO).
  • Poster
    21st Meeting of the European Association for Cancer Research (EACR-21), 26.-29.06.2010, Oslo, Norway
  • Abstract in refereed journal
    European Journal of Cancer 61(2010), 68-69

Publ.-Id: 14258 - Permalink


Fluorine-18 and iodine-124 labeled cyclin-dependent kinase 4 and 6 inhibitors as radiotracers for tumor imaging by positron emission tomography (PET)
Graf, F.; Bergmann, R.; Koehler, L.; Mosch, B.; Steinbach, J.; Wuest, F.; Pietzsch, J.;
Background
Cyclin-dependent kinases 4 and 6 (Cdk4/6) function as critical activators of cell cycle progression in human tumors. Pyrido[2,3 d]pyrimidine derivatives CKIA and CKIE are selective Cdk4/6 inhibitors with high potency for the inhibition of G1 phase progression and tumor cell proliferation. The aim of this study was the evaluation of radiolabeled compounds [124I]CKIA and [18F]CKIE as radiotracers for PET imaging of Cdk4/6 in tumors in vivo.

Materials and methods
Cellular uptake of radiotracers [124I]CKIA and [18F]CKIE was studied in human colorectal (HT-29) and squamous cell (FaDu) carcinoma cells. Small animal PET studies of both radiotracers were performed in FaDu xenograft-bearing nude mice.

Results
Radiotracer uptake studies showed fast and high uptake (up to 800%ID/mg protein) of [124I]CKIA in both cell lines after 1 h at 37°C. Cellular uptake of [18F]CKIE was lower (HT 29, 46.3±11.2%ID/mg protein; FaDu, 46.2±13.8%ID/mg protein). Radiotracer uptake was significantly lower at 4°C for [124I]CKIA (150%ID/mg protein) and [18F]CKIE (15%ID/mg protein) after 1 h in both cell lines. Cellular uptake of [18F]CKIE was reduced to 18.0±4.9%ID/mg protein in the presence of 10 µM of nonradioactive CKIE at 37°C. Dynamic small animal PET studies showed rapid clearance of [124I]CKIA and [18F]CKIE from the blood and fast hepatobiliary excretion. The half-life of radiotracer elimination from the blood was calculated to be 7.2 min for [124I]CKIA and 7.9 min for [18F]CKIE, respectively. Radiotracers were rapidly metabolized in blood in vivo, yielding >90% (1 min p.i.), 20% (30 min), and <5% (1 h) of the original compounds. Small animal PET studies with [124I]CKIA only showed marginal uptake of the radiotracer in the FaDu tumor. In the case of [18F]CKIE a higher uptake was detected in the peripheral proliferative region of the tumor after 1 h p.i. However, the constant tumor-to-muscle ratio of 1.5 suggests a non-Cdk4/6-mediated uptake of [18F]CKIE in human tumor xenografts in mice.

Conclusions
Synthesis of pyrido[2,3-d]pyrimidine-based radiotracers [124I]CKIA and [18F]CKIE allowed for the first time the quantification of cellular uptake in vitro and imaging of tissue-specific distribution of Cdk4/6 inhibitors in vivo. However, the short biological half-life in the blood and low tumor uptake of [124I]CKIA and [18F]CKIE limit the use of both radiotracers for the characterization of Cdk4/6 expression in tumors by means of PET. Further development of suitable radiolabeled Cdk4/6 inhibitors for functional characterization of Cdk4/6 in tumors continues to be of great interest in current translational cancer research.
  • Poster
    21st Meeting of the European Association for Cancer Research (EACR-21), 26.-29.06.2010, Oslo, Norway
  • Open Access LogoAbstract in refereed journal
    European Journal of Cancer 8(2010)5, 61

Publ.-Id: 14257 - Permalink


Effects of irradiation on viability, growth, metastatic properties and expression of Eph receptors and their ephrin ligands in human melanoma cells
Mosch, B.; Pietzsch, J.;
Background:
It is accepted that X-ray irradiation influences growth, viability and metastatic potential of tumor cells. Furthermore, it is supposed that tumor cell invasion and metastasis is regulated by Eph receptors and their ephrin ligands. The aim of our study was to investigate the influence of irradiation on cell viability, growth, and metastasis in human melanoma cells and whether this is mediated by dysregulated Eph receptor or ephrin ligand expression.

Material and Methods:
Primary (Mel-Juso) and metastatic (A375, A2058) human melanoma cell lines were irradiated with 5 or 10 Gy. Up to 7 days after irradiation we examined cell viability (MTT test). At 1 day and 7 days post irradiation we further analyzed cellular growth, motility (scratch assay), adhesion to fibronectin, and migration through a porous membrane. Furthermore, the mRNA expression of 8 different Eph receptors and 6 ephrin ligands was analyzed using RT-PCR.

Results:
In all cell lines a dose dependent decrease in viability and cell growth for up to 1 week after irradiation was demonstrated. Analysis of metastatic properties 1 day after X-ray showed decelerated scratch closure, slight increase in migration, and increased adhesion to fibronectin in all investigated cell lines. In contrast, 1 week after irradiation we detected faster scratch closure in irradiated primary Mel-Juso cells but unaltered motility in metastatic cell lines and, moreover, decreased migration in primary Mel-Juso cells and, by trend also in metastatic A375 cells. In addition, in Mel-Juso and A375 cells capability to adhere to fibronectin remained elevated. RT-PCR analysis revealed that Eph receptors and ephrins investigated have similar mRNA expression levels in primary and metastatic cell lines, with exception of both EphA2 and ephrinA5 showing enhanced expression in metastatic A375 cells. After irradiation changes in mRNA expression were not
detected with exception of an increase in EphA2 and EphA3 in A375 cells and ephrins A1 and A5 in A375 and Mel-Juso cells 7 days after treatment.

Conclusion:
Irradiation considerably influences viability and metastatic properties of melanoma cells. The different effects depending on time after irradiation observed suggest an involvement of cell-cell interaction via A-type Eph receptors and ephrins in irradiation-induced metastatic potency of melanoma cells.
  • Poster
    21st Meeting of the European Association for Cancer Research (EACR-21), 26.-29.06.2010, Oslo, Norway
  • Abstract in refereed journal
    European Journal of Cancer 8(2010), 211

Publ.-Id: 14256 - Permalink


Concomitant targeting of cyclooxygenase-2 and oxidant stress pathways for radioprotection of normal vascular tissue
Pietzsch, J.; Pietzsch, F.-J.; Laube, M.; Bergmann, R.; Kniess, T.; Wuest, F.;
Background:
Radiotherapy of various cancers is closely associated with increased cardiovascular morbidity and mortality. Arachidonic acid metabolites are supposed to play a key role in radiation-induced vascular dysfunction, inflammation, and injury. This study was designed to evaluate the effects of novel selective cyclooxygenase-2 (COX-2) inhibitors on radiation-induced formation of arachidonic acid metabolites via cyclooxygenase-2 and oxidant stress pathways in endothelial cells.

Materials and methods:
Acute effects (1 d, 3 d) of X-ray radiation at moderate doses (2 to 10 Gy) without or with presence of selective COX-2 inhibitors (cyclopentene/indole/indomethacin derivatives (2 each); 1 µM, 10 µM) in human arterial (HAEC) and microvascular (HDMEC) endothelial cells compared to sham-irradiated controls were assessed. Therefore, the following parameters were measured: COX-2 induction; secretion of cytokines tumor necrosis factor-α, interleukin-6, and monocyte chemoattractant protein-1; release of prostaglandins PGE2 and PGI2; release of isoprostanes 8-iso-PGE2 and 8-iso-PGF2α; and oxidative stress (lipid peroxides).

Results:
Irradiation of endothelial cells without presence of COX-2 inhibitors resulted in a dose-dependent augmentation of all parameters studied. When endothelial cells were exposed to COX-2 inhibitors during and for 24 h post irradiation, indole derivatives showed highest potency to inhibit release of both prostaglandins and isoprostanes. Furthermore, when irradiated cells were treated with indole derivatives a significant decrease of lipid peroxide formation and cytokine secretion could be observed, which indicates a direct interaction with oxidant stress-pathways. By contrast, both cyclopentene and indomethacin derivatives majorily inhibited prostaglandin release, but showed only slight effects on formation of isoprostanes, lipid peroxides and cytokines. Model experiments using human low density lipoproteins oxidized by radiolytically generated oxygen radicals showed that indole derivatives differently interact with peroxidation of polyunsaturated fatty acids, than the cyclopentene/indomethacin derivatives, suggesting a physico-chemical rationale for observed anti-oxidant activity.

Conclusion:
Indole-based selective COX-2 inhibitors substantially decreased radiation-induced formation of vasoactive isoprostanes
8-iso-PGE2 and 8-iso-PGF2α by endothelial cells. These findings may have particular importance in radiation-induced processes in which COX-2 is induced and oxidant stress occurs. The reduction of radiation-induced vascular dysfunction by antioxidative COX-2 inhibitors may widen the therapeutic window of cyclooxygenase-2 targeted treatment.
  • Poster
    21st Meeting of the European Association for Cancer Research (EACR-21), 26.-29.06.2010, Oslo, Norway
  • Abstract in refereed journal
    European Journal of Cancer 8(2010), 211

Publ.-Id: 14255 - Permalink


Autocrine regulation of receptor for advanced glycation endproducts (RAGE) by S100A4 promotes migration and invasion in A375 melanoma cells
Wolf, S.; Haase-Kohn, C.; Lenk, J.; Pietzsch, J.;
Background
The calcium-binding protein S100A4 is associated with metastasis of different cancer entities, including melanoma. The multiligand receptor for advanced glycation endproducts (RAGE) has been suggested to interact with extracellular S100A4 protein. We hypothesized that the interaction between RAGE and S100A4 plays an important role in activation of growth, adhesion, motility and migration in a human melanoma cell line with high metastatic potential.

Materials and methods
In order to investigate the cellular role of the RAGE-S100A4 interaction in vitro, we produced recombinant S100A4 and soluble RAGE (sRAGE). Furthermore, we established A375 melanoma cells stably transfected with S100A4 using vector pIRES2-AcGFP1 (A375-S100A4). The overexpression of S100A4 has been verified by western blot and flow cytometry. Assays for determination of migratory, invasive and adhesive behaviour of A375-S100A4 cells were performed. Furthermore, specific interaction of S100A4 with RAGE was characterized by surface plasmon resonance spectroscopy using immobilized sRAGE.

Results
The overexpression of S100A4 did not influence growth properties and adhesive behaviour of the A375-S100A4 cells; however, it affects their motility and migratory activity in comparison to mock-transfected cells. A375-S100A4 cells show an increased secretion of S100A4 into the extracellular space and, in consequence, an enhanced RAGE protein expression. Molecular interaction studies revealed high affinity (lower micromolar range) of S100A4 towards immobilized sRAGE, suggesting a biochemical rationale for the observed effects.

Conclusion
This investigation shows that overexpression of S100A4 influences the metastatic behavior of A375 melanoma cells. The enhanced secretion of S100A4 leads to an autocrine upregulation of RAGE expression and synthesis in A375-S100A4 cells. The findings support the supposed functional role of RAGE-S100A4 interaction in promoting a metastatic phenotype of human melanoma.
  • Poster
    21st Meeting of the European Association for Cancer Research (EACR-21), 26.-29.06.2010, Oslo, Norway
  • Abstract in refereed journal
    European Journal of Cancer 8(2010), 118-119

Publ.-Id: 14254 - Permalink


In-Medium Effects on K0 Mesons in Relativistic Heavy-Ion Collisions
Agakishiev, G.; Balanda, A.; Bannier, B.; Bassini, R.; Belver, D.; Belyaev, A. V.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Díaz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Epple, E.; Fabbietti, L.; Fateev, O. V.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; González-Díaz, D.; Guber, F.; Heilmann, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krizek, F.; Krücken, R.; Kühn, W.; Kugler, A.; Kurepin, A.; Lang, S.; Lange, J. S.; Lapidus, K.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Mishra, D.; Morinière, E.; Mousa, J.; Müntz, C.; Naumann, L.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Perez-Cavalcanti, T.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Schwab, E.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Weber, M.; Wisniowski, M.; Wojcik, T.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y. V.; Zhou, P.; Zumbruch, P.;
We present the transverse momentum spectra and rapidity distributions of \pi^{-} and K^0_S in Ar+KCl reactions at a beam kinetic energy of 1.756 A GeV measured with the spectrometer HADES. The reconstructed K^0_S sample is characterized by good event statistics for a wide range in momentum and rapidity. We compare the experimental \pi^{-} and K^0_S distributions to predictions by the IQMD model. The model calculations show that K^0_S at low tranverse momenta constitute a particularly well suited tool to investigate the kaon in-medium potential. Our K^0_S data suggest a strong repulsive in-medium K^0 potential of about 40 MeV strength.

Publ.-Id: 14253 - Permalink


Direct Measurement of Electrical Transport Through G-Quadruplex DNA with Mechanically Controllable Break Junction Electrodes
Liu, S.-P.; Weisbrod, S.; Tang, Z.; Marx, A.; Scheer, E.; Erbe, A.;
Here we report on direct transport measurements on a G-quadruplex covalently wired between two gold electrodes realized by the mechanically controllable break junction technique. We found that the G-quadruplex shows a rather high conductance. Interestingly, when the distance of both electrodes was reversibly varied over a several nm-span this conductance behavior persists reproducibly. These hitherto unprecedented properties make G-quadruplexes interesting candidates for nanoelectronic applications where varied distances between electrodes need bridging without loss of conductance.
Keywords: molecular electronics, DNA, mechanically controlled break junctions, nanoelectronics

Publ.-Id: 14252 - Permalink


Influence of irradiation on para- and autocrine regulation of extracellular S100A4 (metastasin) and its receptor RAGE in B16 mouse melanoma cells
Haase-Kohn, C.; Wolf, S.; Pietzsch, J.;
Background:
Malignant melanoma is one of the most invasive and metastatic tumors. A common therapeutic approach towards metastases will combine radiation with chemotherapy and/or surgery. The interaction between tumor and inflammatory cells, e.g., via S100A4 (metastasin) and the receptor for advanced glycation endproducts (RAGE), is hypothesized to play a key role in metastasis of melanoma. In this study the contribution of para- and autocrine S100A4-RAGE activation to growth, motility and migration of metastatic melanoma and inflammatory cells before and post irradiation was investigated.

Materials and methods:
Mouse melanoma cells (B16), macrophages (RAW; a model for tumor associated macrophages (TAM)) and B16/RAW cocultures (ratio 1 to 5) were exposed to single dose irradiation (5, 10, and 20 Gy, compared to sham-irradiated controls) for 0, 3 and 6 days. S100A4 and RAGE expression in these cells was quantified via real-time RT-PCR, Western-blot analysis and immunochemistry. Cell growth and cellular viability was detected by MTT assay. Migration assays of non- and irradiated cells were performed with and without chemoattractants (supernatants of irradiated cocultures after 6 days). Additionally, the actin cross-linker L-plastin was investigated as a migratory marker.

Results:
Post irradiation, S100A4 and RAGE mRNA expression was significantly increased in B16 and RAW cells but not in cocultivated cells. S100A4 protein expression was only detected in irradiated B16 cells whereas RAW cells always showed high levels in non- and irradiated cells. Interestingly, cocultures showed only minor S100A4 expression levels with a further reduction of S100A4 after irradiation. In contrast, RAGE protein showed only slight differences. A significant reduction of cell viability was observed after irradiation via MTT assay. On the other hand, migratory activity was significantly increased in B16 and cocultures after irradiation whereas RAW cells showed a significant decrease. Furthermore, chemoattractants significantly induced the migration in non-irradiated B16 cells.

Conclusion:
Irradiation of both melanoma cells and macrophages alters their migratory and invasive activity. Under conditions of cocultivation these effects were more pronounced. We suppose an involvement of para- and autocrine regulation of extracellular S100A4 and its receptor RAGE in melanoma cells and TAM, thereby changing functional properties of melanoma cells towards a promigratory phenotype.
  • Poster
    21st meeting of the European Association for Cancer Research (EACR-21), 26.-29.06.2010, Oslo, Norway
  • Abstract in refereed journal
    European Journal of Cancer 8(2010), 211-212

Publ.-Id: 14251 - Permalink


The impact of hypoxia on differential expression of neurotensin receptors (NTR) in colorectal and prostate carcinoma cells
Schlottig, K.; Bergmann, R.; Steinbach, J.; Haase-Kohn, C.; Pietzsch, J.;
Background:
Recent studies showed increased expression of neurotensin receptors (NTR), particularly, NTR1 and NTR3, in various tumors, thus NTR is assumed a potential target for tumor imaging and therapy. However, the knowledge about the quantitative expression of NTR on mRNA and protein level, e.g., under hypoxic conditions is limited. The aim of this study was to develop a quantitative method for determination of absolute NTR mRNA amount in tumor and non-tumor cells and tissues. For method evaluation the NTR mRNA amounts in human colorectal (HT-29) and prostate (PC3) carcinoma cell lines under normoxic and hypoxic conditions in vitro were compared.

Material and methods:
A novel real-time RT-PCR method using an external standard was established. The elongation factor 1 alpha (EF1α) gene served as housekeeping gene and glucose transporter protein type 1 gene (GLUT1) was used as indicator for cellular hypoxic regulation effects. The derived standard curves allow for calculation of the number of specific mRNA molecules normalized to 1000 molecules of EF1α. Acute and chronic experimental hypoxia was induced by cultivation of cells at an oxygen concentration of 0.6% for 4 to 72 hours.

Results:
Both HT-29 cells and PC3 cells show high mRNA expression of NTR1 in normoxia. In acute hypoxia (
Conclusion:
A novel standardizable and reproducible quantitative method for measurement of NTR mRNA in cancer cells was established. The use of NTR1 as a target for imaging or therapy strongly depends on tumor cell type and tumor hypoxia. Ongoing investigations will compare quantitative mRNA expression with data on functional expression of NTR, e.g., protein synthesis and radioligand interaction, in human samples and rodent tumor (xenograft) models.
  • Poster
    21st meeting of the European Association for Cancer Research (EACR-21), 26.-29.06.2010, Oslo, Norway
  • Abstract in refereed journal
    European Journal of Cancer 8(2010), 61

Publ.-Id: 14250 - Permalink


Structural characterization of H plasma-doped ZnO single crystals by Hall measurements and photoluminescence studies
Anwand, W.; Brauer, G.; Cowan, T. E.; Heera, V.; Schmidt, H.; Skorupa, W.; von Wenckstern, H.; Brandt, M.; Benndorf, G.; Grundmann, M.;
Nominally undoped, hydrothermally grown ZnO single crystals have been investigated prior to and after doping in remote H plasma. Characterizations have been made by temperature-dependent Hall effect (TDH) and low temperature photoluminescence (PL) measurements. The H content before and after the doping has been de-termined using nuclear reaction analysis and is compared to the density of shallow donors derived from the TDH measurements.
The electrical properties of the as-grown ZnO sin-gle crystals are found to differ significantly. This is as-cribed to the density ratio of shallow donors and compen-sating acceptors. PL measurements showed that AlZn, GaZn, and interstitial zinc (Zni) are prominent shallow donors in the as-grown samples.
Remote H plasma treatment produced a metallic conducting near-surface layer thus masking the electrical properties of the bulk. The electrical properties of the in-vestigated samples are very similar after the treatment, independent of the as-grown state, because the density of shallow donors far exceeds that of compensating accep-tors in the affected near-surface region. The maximum of the broad near-band-edge emission is found to be located at 3.3595 eV due to the high doping density.
Keywords: ZnO single crystals, H plasma doping, temperature-dependent Hall effect, low temperature photoluminescence

Publ.-Id: 14249 - Permalink


Hochauflösende Rutherford-Streuspektrometrie zur Untersuchung von ZrO2-Schichtwachstum im Anfangsstadium
Vieluf, M.;
Die vorliegende Arbeit entstand im Rahmen einer Kooperation des Forschungszentrums Dresden-Rossendorf mit Qimonda Dresden GmbH & Co. OHG. Mithilfe der hochauflösenden Rutherford-Streuspektrometrie (HR-RBS) wurden das Diffusionsverhalten und Schichtwachstum von ZrO2 auf SiO2 und TiN im Anfangsstadium untersucht. Auf Grund der exzellenten Tiefenauflösung von 0,3 nm an der Oberfläche stand die Analyse von Konzentrationsprofilen in ultradünnen Schichten, respektive an deren Grenzflächen im Vordergrund.
Zur qualitativen Verbesserung der Messergebnisse wurde erstmals ein zweidimensionaler positionsempfindlicher Halbleiterdetektor in den Aufbau der HR-RBS implementiert und charakterisiert. Außerdem wurde ein Messverfahren in Betrieb genommen, das mögliche Schädigungen durch den Ioneneintrag in die Messprobe minimiert. Durch die Optimierung der experimentellen Bedingungen und die Entwicklung eines Programmpaketes zur Unterstützung des Analysten konnte ein effizienter Routine-Messablauf erstellt werden.
Im Moment einer binären Kollision zwischen einfallendem Ion und Targetelement kommt es bei kleinem Stoßparameter zu Veränderungen des Ladungszustands der gestreuten Ionen, insbesondere durch die abrupte Geschwindigkeitsänderung des Projektils und der Überlappung der Elektronenwolken. Bei der HR-RBS mit Energie separierendem Dipolmagneten muss zur Interpretation von Streuspektren die Ladungszustandsverteilung der gestreuten Projektile bekannt sein. Erstmalig konnte eine signifikante Abhängigkeit der Ladungszustandsverteilung gestreuter C-Ionen sowohl von der Schichtdicke als auch der Ordnungszahl des detektierten Targetelements, hier der vierten Nebengruppe, nachgewiesen werden.
Diese gewonnen Erkenntnisse ermöglichten systematische Untersuchungen zum ZrO2-Schichtwachstum im Anfangsstadium. Zur Herstellung der ZrO2-Schichten wurde die Atomlagenabscheidung (ALD) verwendet. Anhand der nachgewiesenen Agglomeration von ZrO2 auf nativen SiO2 wurde mithilfe der Rasterkraftmikroskopie (AFM) zur Bestimmung von Oberflächenrauigkeiten eine Methode konzipiert, welche die Auswirkung lokaler Schichtdickeninhomogenitäten auf die niederenergetische Flanke eines Streuspektrums berücksichtigt. Auf dieser Grundlage durchgeführte Simulationsrechnungen ergeben, dass keine Diffusion von Zr in die darunter liegende Schicht stattfand, jedoch eine ZrSiO4-Grenzflächenschicht existiert. Für das Wachstum von ZrO2 auf TiN wird aus den hoch aufgelösten Streuspektren ein völlig anderes Verhalten abgeleitet. Messungen zu Oberflächentopografien der TiN-Schicht liefern nicht zu vernachlässigende Werte für die Rauigkeit. Um den Einfluss der Oberflächenrauigkeit auf die Form des hoch aufgelösten Spektrums erfassen zu können, wurde eine Software entwickelt. Auf Basis von AFM-Messungen ermöglicht dieses Programm das Extrahieren einer Energieverteilung aus den Weglängen von ausschließlich an der Oberfläche gestreuten Ionen. Unter Berücksichtigung des Effekts der Oberflächenrauigkeit auf die HR-RBS Spektrenform konnte die Diffusion von Zr in das polykristalline TiN erstmals verifiziert werden. Die Beobachtungen weisen daraufhin, dass bereits nach dem ersten ALD-Zyklus ein geringer Anteil der deponierten Zr-Atome bis in eine Tiefe von etwa 3 nm in das TiN diffundiert. Die vorläufigen Ergebnisse legen Korngrenzendiffusion nahe.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-537 2010
    ISSN: 1437-322X

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Publ.-Id: 14247 - Permalink


Chiral symmetry and medium modifications of mesons
Hilger, T.;
Using QCD sum rules we investigate the in-medium behavior of pseudo-scalar and vector mesons. The rho meson is considered within a scenario of pure chiral restoration by dropping the chirally odd condensates. The interplay of mass shift and broadening of the spectral function is highlighted. We apply finite density QCD sum rules to mesons consisting of a heavy and a light quark (D, Ds and B) and investigate their sensitivity to the chiral condensate and consider the splitting of particle and antiparticle spectral functions with increasing density of the ambient nuclear matter. In order to gain a more direct dependence on the chiral condensate and other potential order parameters of chiral symmetry we present a series of Weinberg-Shuryak type sum rules for heavy-light systems at finite densities. Furthermore, the special role of the gluon condensates for systems consisting of two heavy quarks (e.g. J/Psi) and the QCD trace anomalie allows an extension of the method to large temperatures at non-zero baryon densities using the Rossendorf quasi-particle model.
Keywords: QCD sum rules, chiral symmetry, rho meson, D meson, open charm, chiral partner, J/Psi, Dyson-Schwinger equation, Bethe-Salpeter equation
  • Lecture (Conference)
    EMMI workshop "Quarkonium and the deconfined matter in the LHC era", 15.-20.06.2010, Martina Franca, Italien
  • Lecture (Conference)
    QCD 10 - 15th high-energy physics international conference in quantum, 28.06.-3.7.2010, Montpellier, Frankreich
  • Lecture (Conference)
    QCHS 9 - IX Quark Confinement and the Hadron Spectrum, 30.08.-03.09.2010, Madrid, Spanien

Publ.-Id: 14245 - Permalink


Chiral condensate and medium modifications of open charm mesons
Hilger, T.;
Mit Hilfe von QCD-Summenregeln untersuchen wir die Sensitivität von pseudoskalaren Mesonen bestehend aus einem leichten und einem schweren Quark (D, D_s und B) auf das chirale Kondensat und betrachten mögliche Verschiebungen oder Aufspaltungen der Massen (d.h. Änderungen der Spektralfunktionen) von Teilchen und Antiteilchen unter Annahme einer linearen Dichteabhängigkeit der Kondensate.
Um Systeme mit direkterer Abhängigkeit vom chiralen Kondensat zu untersuchen, betrachten wir Weinberg-Kapusta-Shuryak Summenregeln bei endlichen Dichten im schwer-leicht Sektor.
Die besondere Rolle der Gluonenkondensate in Systemen aus zwei schweren Quarks (z.B. J/psi) und deren Beziehung zur QCD Spur Anomalie ermöglicht eine Erweiterung der Methode der QCD Summenregeln auf Temperaturen nahe T_c. Unter Verwendung des Rossendorfer Quasi-Teilchen-Modells bestimmen wir die Temperaturabhängigkeit des Digluonen-Kondensats bei endlichen Baryondichten nahe T_c und diskutieren deren Auswirkung auf das J/psi.
Keywords: QCD sum rules, D mesons, open charm, J/Psi, chiral partner
  • Lecture (Conference)
    74. Jahrestagung der DPG und DPG Frühjahrstagung der Fachverbände, 15.-19.03.2010, Bonn, Deutschland

Publ.-Id: 14244 - Permalink


CFD modelling to predict the counter-current flow limitations of the air/water counter-current two-phase flow in 1/3rd flat channel model of a hot-leg pressurized water reactor
Deen, D.; Höhne, T.; Lucas, D.; Vallée, C.;
The analytical simulation of the counter-current flow limitation phenomenon in a PWR is an essential element to understand safety-related issues in nuclear power plants. It is expected that the introduction of computational fluid dynamics (CFD) tools will enhance the accuracy of the simulation predictions compared to the established one-dimensional thermal hydraulic analyses. Nevertheless, the use of CFD for this complicated task is still a challenge today. Due to the need to understand the CCFL phenomenon in a PWR for reasons of safety and characterisation of normal operation, it is necessary to validate computer codes and to verify computational results using experimental data. Therefore it is also interest to prove the understanding of the general fluid dynamic mechanism leading CCFL and to identify the critical parameters affecting this phenomenon.

In order to improve the transient analysis of counter-current two-phase flows, experimental and numerical studies were conducted at Forschungszentrum Dresden-Rossendorf (FZD). A 1/3rd scale model of the hot leg PWR of a German Konvoy Pressurized Water Reactor with rectangular cross section was used. The experimental results on this topic were reported in previous reports [Deendarlianto et al. (2008) & Vallée et al. (2009)]. Selected an air-water CCFL experiment at 0.15 MPa and room temperature at FZD (experimental running number 30-09) was numerically modelled with three-dimensional two-fluid models of computer code CFX 12.0 (ANSYS CFX). The aim of this CFD simulation is to validate the prediction model of the CCFL with the existing multiphase flow models built in the commercial code ANSYS CFX. CFD simulation was performed using the multi-fluid Euler-Euler modeling approach or free surface model available in CFX. The calculation was carried out in fully transient manner using a gas/liquid inhomogeneous multiphase flow model coupled with a shear stress transport (SST) turbulence model. In the present numerical study, the drag coefficient was approach by using the Algebraic Interfacial Area Density (AIAD) model. The results indicated that quantitative agreement between calculation and experimental data was obtained for the occurrence of flooding point. Next, it was found also that a comparison with the high-speed video observations shows a good qualitative agreement.
Keywords: Computational fluid dynamic, Counter-current flow limitation, Algebraic Interfacial Area Density (AIAD) Model
  • Contribution to proceedings
    7th Multiphase Flows Workshop: Simulation, Experiment and Application, 22.-24.06.2010, Forschungszentrum Dresden, Germany
    CFD modelling to predict the counter-Current flow limitations of the air/water counter-current two-phase flow in 1/3rd flat channel model of a hot-leg pressurized water reactor
  • Lecture (Conference)
    7th Multiphase Flows Workshop: Simulation, Experiment and Application, 22.-24.06.2010, Forschungszentrum Dresden, Germany

Publ.-Id: 14243 - Permalink


CFD: Mixing process is it an art of science?
Höhne, T.;
Basic Phenomenon
Boron 10 = strong thermal neutron absorber
Used as boric acid solved in the coolant of PWRs to compensate excess reactivity inadvertant or unavoidable decrease of boron concentration (boron dilution) might result in a reactivity transient
Power peak depends on coolant mixing in Cold leg, Downcomer Lower plenum Density differences can strongly influence the mixing
Keywords: CFD, mixing, boron dilution
  • Invited lecture (Conferences)
    CFD Validation Training, Malaysia, KLCC, KL, 10.-12.07.2010, Kualar Lumpur, Malaysia
  • Contribution to proceedings
    CFD Validation Training, Malaysia, KLCC, KL, 10.-12.07.2010, Kualar Lumpur, Malaysia
    Hand-out

Publ.-Id: 14242 - Permalink


CFD: Validation of Multiphase flow
Höhne, T.;
CFD codes for application in horizontal multiphase flows:
the investigation of the feasibility of numerical prediction of stratified two phase flow with existing multiphase flow models in ANSYS CFX to prove the understanding of the general fluid dynamic mechanism
to identify the critical parameters (like e.g. slug length, frequency and propagation velocity, pressure drop, CCFL) to improve the multiphase flow modeling (interfacial momentum transfer, turbulence at the free surface et.) experimental data required for the validation
Keywords: CFD , stratified two phase flow, turbulence, interfacial momentum transfer
  • Invited lecture (Conferences)
    CFD Validation Training, Malaysia, KLCC, KL, 10.-12.07.2010, Kualar Lumpur, Malaysia
  • Contribution to proceedings
    CFD Validation Training, Malaysia, KLCC, KL, 10.-12.07.2010, Kualar Lumpur, Malaysia
    Hand-out

Publ.-Id: 14241 - Permalink


CFD: European experience of 15 years
Höhne, T.;
CFD (Computational Fluid Dynamics) is the simulation of fluids engineering systems using modeling (mathematical physical problem formulation) and numerical methods (discretization methods, solvers, numerical parameters, and grid generations, etc.)
CFD made possible by the advent of digital computer and advancing with improvements of computer resources (500 Floating Point Operations per Second (flops), 1947 1 Petaflops, 2009)
Keywords: CFD
  • Invited lecture (Conferences)
    CFD Validation Training, Malaysia, KLCC, KL, 10.-12.07.2010, Kualar Lumpur, Malaysia
  • Contribution to proceedings
    CFD Validation Training, Malaysia, KLCC, KL, 10.-12.07.2010, Kualar Lumpur, Malaysia
    Hand-out

Publ.-Id: 14240 - Permalink


CFD: In Nuclear Reactor Safety
Höhne, T.;
Strong increase of usage of three-dimensional Computational Fluid Dynamics (CFD) in industrial applications because for instance
slugging,
pressurized thermal shocks,
coolant mixing,
thermal striping
cannot be predicted by traditional one-dimensional system codes with the required accuracy and spatial resolution.
Keywords: CFD, Nuclear Safety
  • Invited lecture (Conferences)
    CFD Validation Training, Malaysia, KLCC, KL, 10.-12.07.2010, Kualar Lumpur, Malaysia
  • Contribution to proceedings
    CFD Validation Training, Malaysia, KLCC, KL, 10.-12.07.2010, Kualar Lumpur, Malaysia
    Hand-out

Publ.-Id: 14239 - Permalink


Hot Electrons Transverse Refluxing in Ultraintense Laser-Solid Interactions
Buffechoux, S.; Psikal, J.; Nakatsutsumi, M.; Romagnani, L.; Andreev, A.; Zeil, K.; Amin, M.; Antici, P.; Burris-Mog, T.; Compant-La-Fontaine, A.; D’Humières, E.; Fourmaux, S.; Gaillard, S.; Gobet, F.; Hannachi, F.; Kraft, S.; Mancic, A.; Plaisir, C.; Sarri, G.; Tarisien, M.; Toncian, T.; Schramm, U.; Tampo, M.; Audebert, P.; Willi, O.; Cowan, T. E.; Pépin, H.; Tikhonchuk, V.; Borghesi, M.; Fuchs, J.;
We have analyzed the coupling of ultraintense lasers (at ∼2×1019   W/cm2) with solid foils of limited transverse extent (∼10  s of μm) by monitoring the electrons and ions emitted from the target. We observe that reducing the target surface area allows electrons at the target surface to be reflected from the target edges during or shortly after the laser pulse. This transverse refluxing can maintain a hotter, denser and more homogeneous electron sheath around the target for a longer time. Consequently, when transverse refluxing takes places within the acceleration time of associated ions, we observe increased maximum proton energies (up to threefold), increased laser-to-ion conversion efficiency (up to a factor 30), and reduced divergence which bodes well for a number of applications.

Publ.-Id: 14238 - Permalink


Modeling poly-dispersed flows with the Inhomogeneous MUSIG model
Lucas, D.; Krepper, E.;
The qualification of Computational Fluid Dynamics (CFD) codes for two-phase flows is an important topic in the frame of German CFD initiative initiated by the Gesellschaft für Anlagen- und Reaktorsicherheit (GRS). This concerted action especially aims on phenomena in the primary system of light water reactors. Forschungszentrum Dresden-Rossendorf e.V. (FZD) is involved in both – the generation of CFD-grade databases and CFD model development and validation. The data obtained in our TOPFLOW experiments clearly show a separation of small and large bubbles over the pipe radius due to the action of the lateral lift force. This has a considerable influence on the local interfacial area density. Also the other bubble forces as drag and turbulent dispersion force clearly depend on the bubble size. For this reason it is important to introduce bubble size dependent velocities fields in a proper modeling of poly-dispersed flows.
Keywords: bubbly flow, interfacial area transport, dispersed flow, MUSIG, CFD
  • Contribution to proceedings
    ANS 2010 Winter Meeting, 07.-11.11.2010, Las Vegas, U.S.A.
    Transactions of the ANS 2010 Winter Meeting
  • Invited lecture (Conferences)
    ANS 2010 Winter Meeting, 07.-11.11.2010, Las Vegas, U.S.A.

Publ.-Id: 14237 - Permalink


CFD-grade databases on two-phase upwards vertical pipe flows
Lucas, D.; Beyer, M.; Szalinski, L.;
The qualification of Computational Fluid Dynamics (CFD) codes for two-phase flows is an important topic in the frame of German CFD initiative initiated by the Gesellschaft für Anlagen- und Reaktorsicherheit (GRS). This concerted action especially aims on phenomena in the primary system of light water reactors. The Transient twO Phase FLOW (TOPFLOW) test facility is one of the reference experimental facilities within this CFD network. One type of experiments aims on generation of CFD-grade data (i.e. data with high resolution in space and time) for poly-dispersed bubbly flows. Such data were obtained at the TOPFLOW facility for upwards vertical pipe flow using the wire-mesh sensor technique. Different experimental series were done for adiabatic air-water and steam-water flows as well as for condensing and evaporating flows. Beside bubbly flows the database also comprises measurements for slug, churn-turbulent and wispy-annular flows. The aim of this presentation is to give an overview on the available database.
Keywords: bubbly flow, interfacial area transport, pipe flow, bubble size distributions, CFD-grade data
  • Contribution to proceedings
    ANS 2010 Winter Meeting, 07.-11.11.2010, Las Vegas, U.S.A.
    Transactions of the ANS 2010 Winter Meeting
  • Invited lecture (Conferences)
    ANS 2010 Winter Meeting, 07.-11.11.2010, Las vegas, U.S.A.

Publ.-Id: 14236 - Permalink


Experimental observations related to the lateral lift force in poly-dispersed bubbly flows
Lucas, D.;
The influence of the lateral lift force on trajectories of single bubbles under idealized conditions was investigated in the past by means of Direct Numerical Simulations (DNS) and by well defined experiments. However, contradictory discussions can be found in literature on the meaning of this force for poly-dispersed flows, i.e. flow with medium or high gas volume fraction. Usually such flows are turbulent and bubble-bubble interaction, i.e. bubble coalescence and breakup play an important role. For this reason it is not self-evident, that the correlation for the lift force coefficient obtained by Tomiyama can be applied for such flows.
The separation of small and large bubbles in poly-dispersed flows was clearly shown in experiments on vertical pipe flow basing on wire-mesh sensor measurements which allow the measurement of bubble size distributions. The critical diameter at which the lift force changes its sign predicted by the Tomiyama correlations (5.8 mm for air-water flow at ambient conditions) seems to fit in general well with the transition between wall and core peaks in the radial gas volume fraction profiles decomposed according to the bubble size. This was also confirmed for steam-water flows at a pressure of 6.5 MPa for which the critical diameter is at about 3.5 mm according to the correlation.
However in case of void fraction larger than about 5 % the effect of the lift force is superposed by dynamic effects as bubble coalescence and breakup and radial migration of the bubbles. For this reason it is not possible to conclude on the critical diameter directly from the shape of the radial gas volume fraction profiles. Also, it was argued, that the wall peak of small bubbles can be caused by large bubbles moving fast upwards in the pipe centre and pushing the small bubbles towards the wall. For this reason in the presented work the distribution of bubbles in dependence on radial position and on bubble sizes is investigated in detail for developing flows. New, high-quality data on air-water as well as on steam-water flows in a DN200 pipe are used for these investigations. The validity of the Tomiyama correlation can be confirmed for a wide range of flow rates. Finally the consequences of the lateral lift force on the flow bubble columns, on the stability of homogeneous bubbly flows and on bubble plumes produced by bubble entrainment from impinging jets are discussed.
Keywords: bubbly flow, lift force, dispersed flow
  • Lecture (Conference)
    48th European Two Phase Flow Group Meeting, 27.-30.06.2010, London, United Kingdom

Publ.-Id: 14235 - Permalink


Nitrogen interstitial induced texture depth gradient in stainless steel
Templier, C.; Stinville, J. C.; Renault, P. O.; Abrasonis, G.; Villechaise, P.; Riviere, J. P.; Drouet, M.;
The microstructural changes induced by the incorporation of large quantities of nitrogen in austenitic stainless steel are analyzed. Phase and texture modification as well as grain rotation are investigated by X-ray and electron backscatter diffraction. A quantitative dependence of the rotation on the grain orientation is determined by means of depth profiling and diffraction techniques. Correlation between local nitrogen interstitial content, associated crystallographic rotation and degree of texturing is established.
Keywords: Texture; Lattice rotation; Nitriding; Stainless steel

Publ.-Id: 14234 - Permalink


Out-of-plane magnetic patterning on austenitic stainless steels using plasma nitriding
Menendez, E.; Stinville, J. C.; Tromas, C.; Templier, C.; Villechaise, P.; Rivière, J. P.; Drouet, M.; Martinavicius, A.; Abrasonis, G.; Fassbender, J.ORC; Baro, M. D.; Sort, J.; Nogues, J.
A correlation between the grain orientation and the out-of-plane magnetic properties of nitrogen-enriched polycrystalline austenitic stainless steel surface is performed. Due to the competition between the magnetocrystalline anisotropy, the exchange and dipolar interactions, and the residual stresses induced by nitriding, the resulting effective magnetic easy-axis can lay along unusual directions. It is also demonstrated that, by choosing an appropriate stainless steel texturing, arrays of ferromagnetic structures with out-of-plane magnetization, embedded in a paramagnetic matrix, can be produced by local plasma nitriding through shadow masks.

Publ.-Id: 14233 - Permalink


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