Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33828 Publications

Meyer-Neldel rule in ZnO

Schmidt, H.; Wiebe, M.; Dittes, B.; Grundmann, M.

Seventy years ago Meyer and Neldel investigated four polycrystalline n-type conducting ZnO rods [W. Meyer and H. Neldel, Z. Tech. Phys. (Leipzig) 12, 588 (1937)]. The specific conductivity increased exponentially with temperature. A linear relationship between the thermal activation energy for the specific conductivity and the logarithm of the prefactor was observed. Since then thermally activated processes revealing this behavior are said to follow the Meyer-Neldel (MN) rule. We show that the emission of charge carriers from deep electron traps in ZnO follows the MN rule with the isokinetic temperature amounting to 226±4 K.

Publ.-Id: 10859

Short time thermal processing of materials - beyond electronics and photonics to pipe organ materials

Skorupa, W.

There is a clear and increasing interest in short time thermal processing far below one second, i.e. the lower limit of RTP (Rapid Thermal Processing) called spike annealing. It is the world of preocessing in the millisecond or nanosecond range. This was recently driven by the need of suppressing the so-called Transient Enhanced Diffusion in advanced boron-implanted shallow pn-junctions in the front-end silicon chip technology. Meanwhile the interest in flash lamp annealing (FLA) in the millisecond range spread out into other fields related to silicon technology and beyond. This talk reports shortly about the restart in flash lamp annealing of the Rossendorf group in collaboration with other groups and further on recent experiments regarding shallow junction engineering in germanium, annealing of ITO layers on glass and plastic foil to form an conductive layer as well as investigations which we did during the last years in the field of wide band gap semiconductor materials (SiC, ZnO). Moreover recent achievements in the field of silicon-based light emission basing on Metal-Oxide-Semiconductor Light Emitting Devices will be reported. Finally it will be demonstrated that short time thermal processing features also advantages regarding the casting of lead sheets to produce organ pipes in the spirit of the 17th century - as a completely different world of materials processing!

Keywords: short time annealing; flash lamp annealing; transient enhanced diffusion; silicon-based light emission; shallow junction engineering; germanium; silicon; silicon carbide; zinc oxide; indium tin oxide; lead casting; pipe organ materials

  • Invited lecture (Conferences)
    Seminarvortrag am Max Planck Institut für Mikrostrukturphysik, 05.12.2007, Halle/Saale, Germany

Publ.-Id: 10858

Investigations of biochemical interactions of actinides with microorganisms and plants.

Reitz, T.; Geissler, A.; Merroun, M. L.; Selenska-Pobell, S.; et all

This presentation show an overview about the research at the IRC, in particular about the investigations of the biochemical interactions of actinides with microorganisms and plants.

  • Lecture (others)
    2nd phD Seminar, 26.-28.09.2007, Rabenberg, Germany

Publ.-Id: 10857

Changes in archaeal community of a uranium mining waste pile induced by treatments with uranyl or sodium nitrate.

Reitz, T.; Geissler, A.; Merroun, M. L.; Selenska-Pobell, S.

Changes in the archaeal community of a uranium mining waste pile, called Haberland caused by the addition of uranyl or sodium nitrate were investigated by using the 16S rRNA gene retrieval. The natural archaeal diversity in studied environment was limited to only a few lineages of mesophilic Crenarchaeota, predominantly of subgroup 1.1a. Addition of and subsequent incubation with uranyl nitrate for 4 weeks resulted in a significant shifting of the archaeal populations to the soil/sediment cluster 1.1b of Crenarchaeota. The proliferation of the latter populations occurred independently of the amount of the added uranium and the aeration conditions during the incubation. The same shifting of the archaeal populations was also observed in the parallel control samples which were supplemented with sodium nitrate.
Efforts to culture members of the 1.1b Crenarchaeota resulted in their enrichment together with representatives of Firmicutes, mainly of Clostridium spp. Clostridia can effectively interact with uranium and they can also fermentatively reduce nitrate to ammonium. Because an ammonia oxidizing activity was deduced on the basis of meta-genomic analyses of the closest relative to the stimulated in our case 1.1b populations, we speculate that the clostridia possibly supply the crenarchaeal members of the recovered synergetic consortium with ammonia.

  • Poster
    BAGECO 9 - 9th Symposium on Bacterial Genetics and Ecology, 23.-27.07.2007, Wernigerode, Germany

Publ.-Id: 10856

Crenarchaeota 1.1b and Firmicutes consortium recovered from a uranyl nitrate treated uranium waste sample and its possible role against the toxicity of uranium.

Reitz, T.; Geissler, A.; Merroun, M. L.; Selenska-Pobell, S.

Supplementations of a sample collected from a depleted uranium mining waste pile with uranyl nitrate induced significant changes in microbial community structure during the first four weeks of incubation. At the latter stages of the treatment, however, the initial composition of the community, indigenous for the untreated samples and consisting mostly of uranium sensitive populations, started to set up. This indicates that the added uranium was no longer bio-available, possibly due to the interactions of the induced at the first stages of the treatment uranium resistant populations with the added radionuclide. Studies on archaeal diversity demonstrated a strong shifting from the subgroup 1.1a to the subgroup 1.1b of the mesophilic soil Crenarchaeota within the first four weeks of the incubations.
Our efforts to cultivate representatives of this crenarchaeal group on specific enrichment media from the sample treated with uranyl nitrate under anaerobic (corresponding to the natural) conditions, resulted in the recovery of a consortium consisting of the mentioned 1.1b Crenarchaeota mixed with populations of Firmicutes, mainly of Clostridium spp. Clostridia can effectively interact with uranium and they can also fermentatively reduce nitrate to ammonium. Because an ammonia oxidizing activity was deduced on the basis of meta-genomic analyses for the closest relative to the stimulated in our case 1.1b populations, we speculate that the clostridia possibly supply the crenarchaeal members of the recovered synergetic consortium with ammonia. In addition, a Paenibacillus sp. isolate was cultivated from this consortium and its interactions with uranium were studied by using TEM and EDX analyses.

  • Poster
    Jahrestagung der Vereinigung für Allgemeine und Angewandte Mikrobiologie (VAAM), 01.-04.04.2007, Osnabrück, Germany

Publ.-Id: 10855

Interactions of U(VI) with members of a microbial consortium recovered from a uranium mining waste pile.

Reitz, T.; Geissler, A.; Merroun, M. L.; Selenska-Pobell, S.

Treatments of a soil sample from a uranium mining waste pile with uranyl nitrate led to a shifting in the crenarchaeal populations from subgroup 1.1a to 1.1b. Efforts to culture members of these Crenarchaeota resulted in an enrichment of a mixed microbial consortium consisting of representatives of 1.1b Crenarchaeota and Firmicutes.
In this study interactions of U(VI) with a pure culture of Paenibacillus sp. JG35+U4-B1 isolated from the mentioned consortium were studied by using a combination of wet chemistry and microscopic methods. Preliminary analyses on U sorption showed that the Paenibacillus strain studied accumulated up to 85 mg U/g dry biomass from a solution with an initial uranium concentration of 120 mg U/l. Live/Dead cell staining indicated that less than 10% of the U-treated cells were viable. Transmission electron microscope (TEM) analyses showed that the cells of the isolated strain accumulated uranium intracellularly as needle-like fibrils, and also at the cell surface. Energy dispersive X-ray (EDX) analysis of these U accumulates demonstrated the presence of U and P indicating that in both cases the phosphate groups are, probably, the main functional binding sites for U(VI).
Efforts to culture other strains from the mentioned consortium and especially of the yet to be cultured 1.1b-Crenarchaeota are in progress in our laboratory. Because our results indicated that these archaeal populations are strongly induced by the addition of U(VI) the study of these organisms is of importance for understanding the natural behavior of U in soils and also for remediation of contaminated sites.

  • Lecture (Conference)
    37ièmes Journées des Actinides, 27.03.2007, Sesimbra, Portugal

Publ.-Id: 10854

Experimental studies and CFD calculations for buoyancy driven mixing phenomena

Da Silva, M. J.; Thiele, S.; Höhne, T.; Vaibar, R.; Hampel, U.

Buoyancy driven flow is found in many engineering application such as the mixing of fluids with different densities. In nuclear reactor safety the mixing of borated and deborated water is a critical issue that needs investigation, assessment and prediction. Recent progress in computer hardware and numerical techniques has made it viable to predict these mixing patterns using CFD codes. However, as CFD codes contain more or less empirical models it is necessary to validate the predicted results using experimental data. Therefore, a combined numerical and experimental study of buoyant mixing processes has been performed. A newly developed planar sensor was applied to experimentally investigate the mixing process. Validation experiments were performed in the VeMix test facility, which show typical vertical and horizontal flow pattern under different flow regimes. The data from the planar sensor of mixing behavior and velocity fields were used for the validation of the simulation results. Comparisons of the experimental results with the corresponding simulations show similar flow patterns and typical periodic behavior.

Keywords: CFD; validation; buoyancy-driven flow; planar array sensor; image processing

  • Contribution to proceedings
    XCFD4NRS, Experiments and CFD Code Applications to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, France, MIX-02
  • Lecture (Conference)
    XCFD4NRS, Experiments and CFD Code Applications to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, France

Publ.-Id: 10853

An 86Y-Labeled Mirror-Image Oligonucleotide: Influence of Y-DOTA Isomers on the Biodistribution in Rats

Schlesinger, J.; Közle, I.; Bergmann, R.; Tamburini, S.; Bolzati, C.; Tisato, F.; Noll, B.; Klussmann, S.; Vonhoff, S.; Wüst, F.; Pietzsch, H.-J.; Steinbach, J.

A mirror-image oligonucleotide (L-RNA) was radiolabeled with the positron emitting radionuclide 86Y (t1/2 = 14.7 h) via the bifunctional chelator approach. DOTA-modification of the L-RNA (sequence: 5’-Aminohexyl UGA CUG ACU GAC-3’; MW 3975) was performed using (S)-p-SCN-bz-DOTA.

86Y radiolabeling of the DOTA-bz-L-RNA produced more than one species as evidenced by HPLC radiometric detection. For the identification of the 86Y-labeled L-RNA the structural analogue ‘cold’ precursor [Y((S)-p-NH2-bz-DOTA)]- was synthesized. Two coordination isomers were separated via HPLC adopting the square antiprismatic (SAP) and the twisted square antiprismatic (TSAP) geometry, respectively. Their stereochemical configuration in the solution state was assessed by NMR and circular
dichroism spectroscopy. Both [Y((S)-p-NH2-bz-DOTA)]- isomers were converted into isothiocyanate derivatives [Y((S)-p-SCN-bz-DOTA)]- and conjugated to the L-RNA. The identity of the [86Y-DOTA-bz]-L-RNA species was finally established by comparison of the radiometric (86Y) and UV-visible (‘cold’ Y) chromatographic profiles.

Biodistribution studies in Wistar rats showed minor changes in the biodistribution profile of the [86Y((S)-p-NH2-bz-DOTA)]- complex isomers, while no significant differences where observed for the [86Y-DOTA-bz]-L-RNA isomers. High renal excretions were found for the [86Y((S)-p-NH2-bz-DOTA)]- complex isomers as well as for the L-RNA isomers.

  • Bioconjugate Chemistry 19(2008), 928-939
    DOI: 10.1021/bc700453h
  • Lecture (Conference)
    Turku PET Symposium New Targets in Molecular Imaging, 24.-27.05.2008, Turku, Finland
  • Contribution to proceedings
    Turku PET Symposium New Targets in Molecular Imaging, 24.-27.05.2008, Turku, Finland
    Abstracts of the XI Turku PET Symposium, Kaarina, Finland: Painola, 978-951-29-3563-5, 11

Publ.-Id: 10851

Double-electron excitations in L3-edge X-ray absorption spectra of Actinides

Hennig, C.

Multielectron excitations are well known in absorption spectra of noble gases. There, the absorption signal is not affected from neighbored atoms that cause the extended X-ray absorption fine structure (EXAFS). Although EXAFS oscillations often cover these features, they have been revealed also in the spectra of liquids and solids. For the first time, this effect has been observed for actinides.

Keywords: Actinides; EXAFS; 2p4f double electron excitation

  • Poster
    17th ESRF Users Meeting, 07.02.2007, Grenoble, France

Publ.-Id: 10850

Spectroscopic investigation of uranium solution species

Hennig, C.

The concept of in situ measurements in a spectro-electrochemical cell for XAFS measurements is presented.

Keywords: EXAFS; UV-vis; U(IV); U(V); U(VI)

  • Invited lecture (Conferences)
    CEA, Laboratoire de Reconnaissance Ionique et Chimie de Coordination, 08.06.2007, Grenoble, France

Publ.-Id: 10849

Die Koordination von Uran-Spezies in Loesungen - Eine Analyse mit EXAFS Spektroskopie

Hennig, C.

Der Vortrag gibt eine kurze Einfuehrung in die experimentellen Moeglichkeiten und Besonderheiten der EXAFS Spektroskopie. Im Weiteren werden umweltelevante Probleme der Urankontamination im ehemaligen Bergbaugebiet der Wismut anhand spektroskopischer Analysen von umweltrelevanten Modellsystemen diskutiert.

Keywords: EXAFS; ehemaliger Uranbergbau

  • Invited lecture (Conferences)
    Bundesanstalt fuer Materialforschung und -pruefung, 05.06.2007, Berlin, Germany

Publ.-Id: 10848

The structure of actinides in solution - An investigation with XAFS spectroscopy

Hennig, C.

Outline of this poesentation
1. Motivation.
2. Theory.
3. Experimental conditions
4. Comparison between EXAFS and XRD.
5. Electronic transitions in EXAFS and UV-vis.
6. U(VI) and U(IV) in aq. and nonaq. cloride media.
7. Sulfate coordination of aq. Th(IV), U(IV), U(VI), Pa(V),Np(IV), Np(V), and Np(VI) media.
8. Conclusion

Keywords: EXAFS; XRD; UV-vis; Actinides; Coordination; Speciation

  • Invited lecture (Conferences)
    Workshop on Structural Chemistry of Actinide and Lanthanide Inorganic Compounds, 29.09.-01.10.2007, Tsarskoe Selo, St. Petersburg, Russia

Publ.-Id: 10847

Investigation of actinides in solution under controlled redox conditions

Hennig, C.; Ikeda, A.; Rossberg, A.; Funke, H.; Scheinost, H.

The results from the research activities of the last 5 years have been presented. This concerns the development and application of a spectro-electrochemical cell for in situ investigations of speciation and coordination of actinides in solution.

Keywords: actinides; EXAFS; electrochemistry

  • Lecture (others)
    ESRF Beamline Review Panel Meeting, 06.-07.11.2007, Grenoble, France

Publ.-Id: 10846

Complex structure and species distribution of U(VI) cloride in aqueous and nonaqueous solutions

Hennig, C.

New spectroscopic techniques by combining UVvis and EXAFS will be discussed applied to the samples mentioned in the title.

Keywords: UVvis EXAFS uranium

  • Lecture (others)
    Institute de Physique Nucleaire, Groupe de Radiochemie, 13.12.2007, Paris-Orsay, France

Publ.-Id: 10845

Dynamoeffekt und Magnetorotationsinstabilität: Kosmische Magnetfelder im Laborexperiment

Stefani, F.

Im Vortrag wird herausgearbeitet, dass kosmische Magnetfelder einerseits durch den hydromagnetischen Dynamoeffekt erzeugt werden und andererseits vermittels der Magnetorotationsinstabilität eine fundamentale Rolle in der kosmischen Strukturbildung spielen. Die Laborexperimente zum Dynamoeffekt in Riga, Karlsruhe und Cadarache sowie das PROMISE-Experiment zur Magnetorotationsinstabilität werden detailliert behandelt.

  • Invited lecture (Conferences)
    Lehrstuhlseminar Magnetofluiddynamik, TU Dresden, 05.12.2007, Dresden, Germany

Publ.-Id: 10844

Crystallographically oriented Fe nanocrystals formed in Fe-implanted TiO2

Zhou, S.; Potzger, K.; Talut, G.; Shalimov, A.; Grenzer, J.; Skorupa, W.; Helm, M.; Fassbender, J.; Cizmar, E.; Zvyagin, S. A.; Wosnitza, J.

A comprehensive characterization of the structural and magnetic properties of Fe-implanted rutile TiO2(110) is presented. Fe and FeTiO3 (Ilmenite) nanocrystals (NCs) are identified by synchrotron-radiation X-ray diffraction. The majority of Fe NCs are crystallographically oriented with respect to the matrix following the relation Fe(001)[010]kTiO2(110)[110]. Post-annealing induced the out-diffusion of Fe and the growth of FeTiO3 at the cost of Fe NCs. Mössbauer spectroscopy and SQUID magnetometry reveal the corresponding evolution of magnetic properties, i.e. magnetization, and superparamagnetic blocking temperature. We unambiguously identify Fe NCs as the origin of the ferromagnetism. These Fe NCs possess a uniaxial in-plane magnetic anisotropy, such that the two Fe[100] axes are inequivalent.

Keywords: TiO2; Ferromagnetism; Nanocrystals

Publ.-Id: 10843

Structural and magnetic properties of Tb implanted ZnO single crystals

Zhou, S.; Potzger, K.; Mücklich, A.; Eichhorn, F.; Helm, M.; Skorupa, W.; Fassbender, J.

ZnO single crystals have been implanted with Tb ions. For an atomic concentration of 1.5 %, annealing at 823 K leads to an increase of the saturation magnetization per implanted Tb ion up to 1.8 mu_B at room temperature. Structural investigations revealed no secondary phase formation, but the out-diffusion of Tb. No significant evidence is found for Tb substituting Zn sites neither in the as-implanted nor annealed samples. However, indications for the existence of a small amount of Tb nanoclusters however have been found using magnetization vs. temperature measurements. The ferromagnetic properties disappear completely upon annealing at 1023 K. This behavior is related to the formation of oxide complexes or nanoparticles.

Keywords: ZnO; rare earth; diluted magnetic semiconductors

Publ.-Id: 10842

Complexation of Curium(III) with Hydroxamic Acids Investigated by Time-Resolved Laser-Induced Fluorescence Spectroscopy

Glorius, M.; Moll, H.; Bernhard, G.

The unknown complex formation of Cm(III) with two hydroxamic acids, salicylhydroxamic (SHA) and benzohydroxamic acid (BHA) was studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Hydroxamate containing chelating substances have the potential to enhance the solubility and mobility of metals and radionuclides by forming complexes. We explored the fluorescence properties, lifetimes and individual fluorescence emission spectra of the formed Cm(III) hydroxamate species. In both Cm(III)-hydroxamic acid systems a 1: 1 and a 1:2 complex of the type MpLqHr could be identified from the fluorescence emission spectra having peak maxima at 600 and 609 nm, respectively. An indirect excitation mechanism of the Cm(III) fluorescence was observed in the presence of the hydroxamic acids. Consistent stability constants were determined by using either indirect or direct excitation mode of the Cm(III) fluorescence. In the Cm(III)-SHA system, the stability constants are log β111 = 16.52 0.14 and log β121 = 24.09 0.62. The complex formation constants of the Cm(III)-BHA species results to log β110 = 6.52 0.19 and log β120 = 11.60 0.50. The stability constants were compared to those of natural pyoverdins.

Keywords: Cm(III); Complexation; TRLFS; Hydroxamic acids

Publ.-Id: 10841

Initial stages in the metal-dusting process on alloy 800

Röhnert, D.; Phillipp, F.; Reuther, H.; Weber, T.; Wessel, E.; Schütze, M.

The initial stages of the metal-dusting process on Alloy 800 at 620 degrees C were investigated by light optical microscopy, RAMAN spectroscopy, atomic-force microscopy, Auger electron spectroscopy, transmission-electron microscopy and electron back-scatter diffraction. As it turned out the incubation period for metal-dusting is characterized by simultaneous formation of a heterogeneously growing oxide scale and deposition of carbon. The material surface shows different tarnish colors depending on the substrate-grain orientation with different susceptibility to the beginning of metal-dusting attack. "Low-index" grains were not attacked within the times investigated while the other grain orientations showed pitting. Carbon is evidently incorporated into the oxide scale from the very beginning of exposure with different intensities depending on the underlying substrate-grain orientation leading to differences in the tarnish colors. As a consequence carbides are formed even underneath "dense" oxide layers. Evidently metal-dusting attack starts at positions of the oxide scale where "higher carbon concentrations" are present.

  • Oxidation of Metals 68(2007), 271-293

Publ.-Id: 10840

Recent achievement on actinide chemistry at FZD: Short introduction about electrochemical and structural study of uranium and neptunium in solution.

Ikeda, A.

Understanding the electrochemical and complexation behavior of actinides in solution is very fundamental for the assessment of environmental impact on the geological disposal of radioactive wastes, such as predicting the migration behavior of these nuclides in the geosphere. Especially, uranium(U) and neptunium(Np) are some of the important nuclides for this kind of research.Therefore, in order to investigate the electrochemical and complexation properties of U and Np, cyclic voltammetry (CV), electrolysis, and X-ray absorption measurements were carried out in various types of aqueous- and nonaqueous solutions. In this presentation, some remarkable results are introduced and discussed to draw a general conclusion about the electro- and complexation chemistry of U and Np in solution.

Keywords: uranium; neptunium; electrochemistry; complex; solution; cyclic voltammetry; electrolysis; XAFS

  • Invited lecture (Conferences)
    Internal seminar at the Synchrotron Radiation Research Center, Japan Atomic Energy Agency, 29.11.2007, SPring-8, Hyogo, Japan

Publ.-Id: 10839

Time-resolved semiconductor spectroscopy in the mid-infrared and Terahertz regimes

Schneider, H.

This talk will focus on several research topics exploiting our free-electron (FEL) and modelocked Ti:Sapphire lasers to investigate semiconductor nanostructures. Pump-probe spectroscopy and two-photon detection is used for time-resolved investigations of intersubband transitions in quantum wells and for FEL pulse diagnostics. Terahertz emitters based on interdigitated metal stripe arrays will also be discussed.

  • Lecture (others)
    Seminarvortrag, 30.11.2007, Palaiseau, France

Publ.-Id: 10838

Positronen-Emissions-Tomographie (PET) - von der Chemie radioaktiv markierter Verbindungen bis zu deren Herstellung für die klinische Praxis

Knieß, T.

kein Abstract verfügbar

  • Invited lecture (Conferences)
    Reihe der hochschuloffenen Kolloquien des FB MachinenBau/Verfahrenstechnik, Studiengang Chemieingenieurwesen der HTW Dresden, 06.12.2007, Dresden, Germany

Publ.-Id: 10837

Projective Hilbert space structures at exceptional points and Krein space related boost deformations of Bloch spheres

Günther, U.; Rotter, I.; Samsonov, B.

Simple non-Hermitian quantum mechanical matrix toy models are considered in the parameter space vicinity of Jordan-block structures of their Hamiltonians and corresponding exceptional points of their spectra. In the first part of the talk, the operator (matrix) perturbation schemes related to root-vector expansions and expansions in terms of eigenvectors for diagonal spectral decompositions are projectively unified and shown to live on different affine charts of a dimensionally extended projective Hilbert space. The monodromy properties (geometric or Berry phases) of the eigenvectors in the parameter space vicinities of spectral branch points (exceptional points) are briefly discussed.

In the second part of the talk, it is demonstrated that the recently proposed PT-symmetric quantum brachistochrone solution [C. Bender et al, Phys. Rev. Lett. {\bf 98}, (2007), 040403, quant-ph/0609032] has its origin in a mapping artifact of the PT-symmetric 2×2 matrix Hamiltonian in the vicinity of an exceptional point. Over the brachistochrone solution the mapping between the PT-symmetric Hamiltonian as self-adjoint operator in a Krein space and its associated Hermitian Hamiltonian as self-adjoint operator in a Hilbert space becomes singular and yields the physical artifact of a vanishing passage time between orthogonal states. The geometrical aspects of this mapping are clarified with the help of a related hyperbolic Möbius transformation (contraction/dilation boost) of the Bloch (Riemann) sphere of the qubit eigenstates of the 2×2 matrix model.
The controversial discussion on the physics of the brachistochrone solution is briefly commented and a possible resolution of the apparent inconsistencies is sketched.

partially based on:
J. Phys. A 40 (2007) 8815-8833; arXiv:0704.1291 [math-ph].
arXiv:0709.0483 [quant-ph].

Keywords: non-Hermitian Hamiltonian; PT-symmetric Quantum Mechanics; Jordan block; exceptional point; projective Hilbert space; geometric phase; quantum brachistochrone; Bloch sphere; Möbius transformation; hyperbolic dilation-contraction mapping

  • Invited lecture (Conferences)
    7th Workshop Operator Theory in Krein Spaces and Spectral Analysis, 13.-16.12.2007, Berlin, Germany

Publ.-Id: 10836

Flüssigmetallströmung unter dem Einfluß eines elektromagnetischen Wanderfeldes bei der Kristallzüchtung nach der VGF-Methode - Numerische Simulation und Modell-Experimente -

Galindo, V.; Grants, I.; Lantzsch, R.; Pätzold, O.; Gerbeth, G.; Zhang, C.

Die Strömung einer Flüssigmetall-Legierung unter dem Einfluß eines externen elektromagnetischen Wanderfeldes wurde untersucht mit besonderen Augemerk auf die Abhängigkeit von der Feld-Frequenz.

Keywords: crystal growth; traveling magnetic fields

  • Lecture (Conference)
    Workshop Strömungssimulation, 30.11.2007, Dresden, Germany

Publ.-Id: 10834

Use of a traveling magnetic field in VGF growth: flow reversal and resulting dopant distribution

Grants, I.; Gerbeth, G.

The melt flow in a model of a vertical gradient freeze facility under the action of a traveling magnetic field (TMF) is studied numerically. The radial temperature gradient over a concave solidification interface drives a radially converging flow which may cause an undesirable dopant concentration peak on the axis. We study the characteristics of such a flow for parameters beyond the previously reported linear regime. An upward directed TMF induces a body force which counteracts buoyancy. We report conditions under which the TMF reverses the flow direction for a wide parameter range. These conditions depend primarily on the product of the thermal gradient and the interface deflection. The simulation of the dopant transport demonstrates that the concentration peak disappears as soon as the flow direction changes.

  • Journal of Crystal Growth 310(2008), 3699-3705

Publ.-Id: 10831

Magnetohydrodynamic experiments on cosmic magnetic fields

Stefani, F.

It is well known that cosmic magnetic fields, including the fields of planets, stars, and galaxies, are produced by the hydromagnetic dynamo effect in moving electrically conducting fluids. It is less well known that cosmic magnetic fields play also an active role in cosmic structure formation by enabling outward transport of angular momentum in accretion disks via the magnetorotational instability (MRI). Considerable theoretical and computational progress has been made in understanding both processes. In addition to this, the last ten years have seen tremendous efforts in studying these effects in the laboratory. In 1999, magnetic field self-excitation was observed in the large scale liquid sodium facilities in Riga and Karlsruhe. Recently, self-excitation was also observed in the French "von Karman sodium" (VKS) experiment, although with the help of iron propellers which complicates the interpretation of the results. The magnetorotational instability was recently observed in the ''Potsdam Rossendorf Magnetic Instability Experiment'' (PROMISE). In the talk, the history of dynamo and MRI experiments is delineated, and some interesting directions of future work are discussed.

  • Invited lecture (Conferences)
    79th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2008), 31.03.-04.04.2008, Bremen, Germany

Publ.-Id: 10830

Homotopic deformations of the Arnold tongue patterns in the MHD α2-dynamo spectrum

Günther, U.; Kirillov, O.

The spectrum of an MHD α2-dynamo has been studied under perturbations of the α-profile as well as under smooth changes of the boundary conditions (BCs). Basic ingredient was a set of analytically (exactly) calculable bi-orthogonal eigenfunctions for constant α-profiles α0=const. These eigenfunctions have been used as input for both perturbative and numerical Galerkin (weighted residual) analyses with BCs imposed on them as one-parameter homotopic family which smoothly interpolates between idealized (Dirichlet) BCs and physically realistic (Robin) BCs.

For constant α-profiles the spectrum is purely real and depending on the BCs it changes from a spectral mesh (living as line structure on the doubly ruled surface of a hyperbolic paraboloid) into a countably infinite set of parabolic branches. Under inhomogeneous perturbations of the α-profile the spectrum deforms in such a way that complex spectral sectors form from a subset of intersection points of the spectral mesh. With increasing perturbation strength these complex sectors widen and have the well known form of partially merging Arnold tongues. Explicit analytical approximations are derived for the Arnold tongues. Technically the approximations are based on the perturbation theory of multiple eigenvalues applied to the double eigenvalues (diabolical points) at the nodes of the spectral mesh. A detailed analysis is presented of the interplay of inhomogeneous α-perturbations and homotopic BC deformations with the formation of a wealth of Arnold tongues and partially invariant spectral branch patterns. A good correspondence between the numerical and the perturbative approaches is observed.

Keywords: MHD dynamo; non-selfadjoint operator; bi-orthogonal eigenfunctions; spectral analysis; perturbation theory; homotopic deformation family; Arnold tongue; spectral mesh; diabolical point; ruled surface

  • Lecture (Conference)
    79th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM-2008), 31.03.-04.04.2008, Bremen, Germany

Publ.-Id: 10829

Binding form of ingested uranium in human urine

Bernhard, G.; Geipel, G.; Steudtner, R.

The dominant reasons for the increase in uranium emitted to the environment arise from the use of uranium as a fuel for the generation of nuclear energy and as a basic material for nuclear weapons production, which also includes the use of depleted uranium metal in armor piercing ammunition.

Keywords: urine; ingested uranium

  • Contribution to proceedings
    2nd International Nuclear Chemistry Congress, 13.-18.04.2008, Cancun, Mexico
  • Lecture (Conference)
    2nd International Nuclear Chemistry Congress, 13.-18.04.2008, Cancun, Mexico

Publ.-Id: 10828

Implementation of a pressure drop model for the CFD simulation of clogged containment sump strainers

Grahn, A.; Krepper, E.; Alt, S.; Kästner, W.; Weiß, F.-P.; Hampel, R.

In the present article a combination of a semi-empirical flow equation and a material equation is proposed that allows to calculate the pressure drop in beds composed of compressible, fibrous media. The model has been successfully implemented as an extension to the general-purpose CFD code ANSYS-CFX. Its capability to simulate the transient pressure drop build-up at non-uniformly loaded strainers in arbitrary three-dimensional geometries is demonstrated using a step-like flow geometry with a horizontally embedded strainer plate. It will be shown that the increasing pressure drop at the strainer has a rectifying effect on the flow field. The model could as well be implemented into system codes for nuclear reactor and containment simulation. Thus, existing system codes might be enabled for use in the risk assessment of loss-of-coolant accidents.

Keywords: safetety analysis; containment sump; strainer clogging; loss-of-coolant accident; pressure drop; cfd

  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
    Implementation of a pressure drop model for the CFD simulation of clogged containment sump strainers
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany

Publ.-Id: 10827

THEREDA – Ein Beitrag zur Langzeitsicherheit von Endlagern nuklearer und nichtnuklearer Abfälle

Altmaier, M.; Brendler, V.; Hagemann, S.; Herbert, H.-J.; Kienzler, B.; Marquardt, C. M.; Moog, H. C.; Neck, V.; Richter, A.; Voigt, W.; Wilhelm, S.

Im Rahmen von Langzeitsicherheitsanalysen für deutsche Endlager radioaktiver bzw. Untertagedeponien chemotoxischer Abfälle sowie weiterer Einsatzfelder (Altlastensanierung) wird eine einheitliche und umfassende thermodynamische Referenzdatenbasis dringend benötigt. Der ehemalige „Arbeitskreis Thermodynamische Standarddatenbasis“ (ATS) hatte sich die Aufgabe gestellt eine solche Datenbasis zu realisieren. Die Aktivitäten des ATS werden seit Juli 2006 in dem Projektverbund "THEREDA" (Thermodynamische Referenzdatenbasis) von BMBF, BMWi und BfS zunächst für 3 Jahre gefördert. THEREDA setzt sich aktuell aus fünf Partnerinstitutionen zusammen, die im Wesentlichen die deutschen Forschungsinstitutionen auf dem Gebiet der Endlagersicherheitsforschung repräsentieren. THEREDA soll die Transparenz und Belastbarkeit der Sicherheitsanalysen in Deutschland entscheidend verbessern und stellt erstmalig eine konsistente thermodynamische Datensätze für alle in Deutschland diskutierten Endlageroptionen und Wirtsgesteine bereit. Für jede thermodynamische Größe werden anhand eindeutig definierter Evaluierungskriterien Qualitätsstufen angegeben, mit Hilfe derer Anwender Daten, entsprechend der jeweiligen spezifischen Problemstellungen, gezielt einbeziehen oder ausschließen können. Für fehlende thermodynamische Daten werden im Rahmen von THEREDA begründete Schätzwerte ermittelt, sodass Modellrechnungen zur Sicherheitsanalyse in Zukunft auf einer deutlich breiteren Datenbasis durchgeführt werden können. Die Datenbasis wird in einer Datenbank zentral verwaltet und Anwendern über das Internet frei und unentgeltlich verfügbar sein. Importformate, um THEREDA in die gängigsten Modellierungscodes (EQ3/6, PHREEQC, Geochemist’s Workbench, CHEMAPP, usw.) überführen zu können, werden ebenfalls unentgeltlich zur Verfügung gestellt.

  • atw - International Journal for Nuclear Power 53(2008)4, 249-253

Publ.-Id: 10825

Influence of the Time of Flight Information on the Reconstruction of In-Beam PET Data

Shakirin, G.; Crespo, P.; Braess, H.; Enghardt, W.

At the heavy ion therapy facility at the Gesellschaft für Schwerionenforschung Darmstadt, Germany, an in-beam PET scanner is operated for quality assurance monitoring simultaneously to the therapeutic irradiation. The PET scanner, which is completely integrated into the treatment facility, registers the annihilation γ - rays following the decay of minor amounts of β+ radioactive nuclei produced via nuclear reactions between the ions of the therapeutic beam and the atomic nuclei of the irradiated tissue. From a comparison of the reconstructed activity distributions with those predicted from the treatment plan, deviations between the prescribed and the applied dose distributions can be detected. We investigate how reconstruction of in-beam PET data can profit from the time of flight (TOF) information taking into account specific issues of in-beam PET system, namely, a very low counting statistics and the dual head geometry of the PET scanner which results in missing ray sums in certain directions. We simulated β+-activity distributions based on real treatment plans and generated events measured with a timing resolution 1.2 ns FWHM. We further reconstructed the data via list mode MLEM algorithm and via randomly filled subsets expectation maximization (RFS-EM) algorithm (a modification of OSEM adapted for in-beam PET). Two irradiation situations were evaluated: a relatively small field in the head and neck region (clivus chondrosarcoma) and a large field in the pelvic region (prostate carcinoma). Root mean square error is reduced by 20 % for head and neck field and by 36 % for pelvic field for TOF included reconstructions. Also a significant reduction of specific reconstruction artifacts (in particular, elongation of the images caused by the dual head geometry of the scanner) is observed in TOF included reconstructions versus non-TOF ones for both irradiation cases.

Keywords: in-beam PET; reconstruction; time-of-flight; TOF; MLEM; OSEM

  • Poster
    2007 Nuclear Science Symposium & Medical Imaging Conference, 27.10.-03.11.2007, Honolulu, Hawaii, USA
  • Contribution to proceedings
    2007 Nuclear Science Symposium & Medical Imaging Conference, 27.10.-03.11.2007, Honolulu, Hawaii, USA
    Conference Record. 2007 IEEE Nuclear Science Symposium & Medical Imaging Conference: IEEE, 1-4244-0923-3

Publ.-Id: 10824

Two mononuclear Tc complexes: [2,2′-(3-phenylpropylimino)- and [2,2′-(propylimino)-bis(ethanethiolato)](4-methoxybenzenethiolato)-oxidotechnetate(V)

Emmerling, F.; Kraus, W.; Noll, B.; Noll, S.; Pietzsch, H.-J.

The molecular structures of the two mononuclear title complexes, namely (4-methoxybenzene-thiolato-κS)oxido-[2.2′-(3-phenylpropylimino)bis(ethanethiolato)-κ3S,N,S′]technetium(V), [Tc(C14H21NS2)(C7H7OS)O], (I), and (4-methoxybenzenethiolato- κS)oxido[2, 2′-(propylimino)-bis(ethanethiolato) -κ3S,N,S′]technetium(V) [Tc(C7H15NS2)(C7H7OS)O], (II), exhibit the same coordination environment for the central Tc atoms. The atoms are five-coordinated (TcNOS3) with a square-pyramidal geometry comprising a tridentate 2.2′-(3-phenylpropylimino)bis(ethanethiolate) or 2, 2′-(propylimino)-bis(ethanethiolate) ligand, a 4-methoxybenzenethiolate ligand and an additional oxide O atom. Intermolecular C–H …O and C–H...S hydrogen bonds between the monomeric units result in two-dimensional layers with a parallel arrangement.

Publ.-Id: 10823

Determination of charge state in Co- and Mn-doped ZnO films

Markó, D.; Potzger, K.; Küpper, K.; Xu, Q.; Zhou, S.; Schmidt, H.; Fassbender, J.; Lorenz, M.; Arenholz, E.; Denlinger, J. D.

We have investigated Co- and Mn-alloyed ZnO films grown by pulsed laser deposition (PLD) on a-plane sapphire substrates. X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) measurements have been performed at beamline 8.0.1 and beamline 6.3.1 at the Advanced Light Source in Berkeley, USA. From XAS spectra, recorded in both total electron yield and total fluorescence yield mode, the valence states of Mn and Co have been determined. No ferromagnetic properties have been observed by means of XMCD at 20 K at the L2,3-absorption edges of Mn and Co, respectively. This observation agrees with the purely paramagnetic response of those Co- and Mn-alloyed ZnO films from SQUID magnetometry and Hall effect measurements.

Keywords: ZnO; magnetic semiconductor; XAS; XMCD

  • Poster
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10822

Study of dielectron production in C+C collisions at 1 AGeV

Agakichiev, G.; Agodi, C.; Alvarez-Pol, H.; Balanda, A.; Bassini, R.; Bellia, G.; Belver, D.; Belyaev, A.; Blanco, A.; Böhmer, M.; Bortolotti, A.; Boyard, J. L.; Braun-Munziger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Diaz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Grosse, E.; Guber, F.; Heilmann, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kajetanowicz, M.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Krasa, A.; Krizek, F.; Krücken, R.; Kühn, W.; Kugler, A.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, J. S.; Lapidus, K.; Lopes, L.; Maier, L.; Mangiarotti, A.; Marin, J.; Markert, J.; Metag, V.; Michalska, B.; Mishra, D.; Moriniere, E.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Novotny, J.; Otwinowski, J.; Pachmayer, Y.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Perez Cavalcanti, T.; Pietraszko, J.; Pleskac, R.; Pospisil, V.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Schroeder, C.; Schwab, E.; Simon, R. S.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Taranenko, A.; Teilab, K.; Tlusty, P.; Toia, A.; Traxler, M.; Trebacz, R.; Tsertos, H.; Veretenkin, I.; Wagner, V.; Weber, M.; Wen, H.; Wisniovski, M.; Wojcik, T.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zhou, P.; Zumbruch, P.

The emission of e+e- pairs from C+C collisions at an incident energy of 1 GeV per nucleon has been investigated. The measured production probabilities, spanning from the pi0-Dalitz to the rho/omega invariant-mass region, display a strong excess above the cocktail of standard hadronic sources. The bombarding-energy dependence of this excess is found to scale like pion production, rather than like eta production. The data are in good agreement with results obtained in the former DLS experiment.

Publ.-Id: 10821

Elementary Collisions with HADES

Froehlich, I.; Pietraszko, J.; Agakishiev, G.; Agodi, C.; Balanda, A.; Bellia, G.; Belver, D.; Belyaev, A.; Blanco, A.; Boehmer, M.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Diaz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Grosse, E.; Guber, F.; Heilmann, M.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kaempfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Krizek, F.; Kruecken, R.; Kuehn, W.; Kugler, A.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, J. S.; Lopes, L.; Maier, L.; Mangiarotti, A.; Marin, J.; Markert, J.; Metag, V.; Michalska, B.; Mishra, D.; Moriniere, E.; Mousa, J.; Muentz, C.; Naumann, L.; Novotny, R.; Otwinowski, J.; Pachmayer, Y. C.; Palk! A, M.; Pechenov, V.; Pechenova, O.; Cavalcanti, T. P.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Simon, R.; Spataro, S.; Spruck, B.; Stroebele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Veretenkin, I.; Wagner, V.; Wen, H.; Wisniowski, M.; Wojcik, T.; Wuestenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zumbruch, P.

The "High Acceptance DiElectron Spectrometer" (HADES) at GSI, Darmstadt, is investigating the production of e+e- pairs in A+A, p+A and N+N collisions. The latter programm allows for the reconstruction of individual sources. This strategy will be roughly outlined in this contribution and preliminary pp/pn data is shown.

  • Open Access Logo Contribution to proceedings
    MENU2007 11th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon, 10.-14.09.2007, Jülich, Germany Proceedings of MENU 2007 - 11th International conference on Meson-Nucleon Physics and the Structure of the Nucleon, 105-110
  • European Physical Journal A (2007)
  • Contribution to WWW
    arXiv: 0712.1505 [nucl-ex]:

Publ.-Id: 10820

Polyhedral Surface Approximation of Non-Convex Voxel Sets through the Modification of Convex Hulls

Schulz, H.

In this paper we want to introduce an algorithm for the creation of polyhedral approximations for objects represented as strongly connected sets of voxels in three-dimensional binary images. The algorithm generates the convex hull of a given object and modifies the hull afterwards by recursive repetitions of generating convex hulls of subsets of the given voxel set or subsets of the background voxels. The result of this method is a polyhedron which separates object voxels from background voxels. The objects processed by this algorithm and also the background voxel components inside the convex hull of the objects are restricted to have genus 0.

Keywords: Digital Geometry; Convex Hull; Surface Approximation; Abstract Polyhedron

  • Contribution to proceedings
    12th International Workshop on Combinatorial Image Analysis, 07.-09.04.2008, Buffalo, NY, USA
    Combinatorial Image Analysis

Publ.-Id: 10819

Autonomous planar conductivity array sensor for fast liquid distribution imaging in a fluid coupling

Da Silva, M. J.; Lu, Y.; Sühnel, T.; Schleicher, E.; Thiele, S.; Kernchen, R.; Diele, K.-H.; Hampel, U.

In this paper, we introduce a new autonomous planar array sensor based on the measurements of electrical conductivity which has been applied to the visualization of fluid distributions inside a fluid coupling during normal operation. The sensor is composed of approximately 1000 interdigital sensing structures which are used to measure the two-dimensional electrical conductivity distribution at the sensors’s surface with a fast multiplexed probing-sensing scheme at up to 10 kHz frame rate. Two such sensors where used to measure dynamic two-phase flow patterns in a fluid coupling at full operation at 790 rpm rotational speed. Therefore, the sensors were mounted on the pressure-side and the suction-side walls of a blade channel inside a test coupling. The whole measurement system is supplied by a battery and controlled via wireless link, thus being fully autonomous, which enable sensor and electronics to rotate together with the coupling.

Keywords: planar sensor; interdigital electrodes; conductivity measurement; flow measurement; fluid coupling; turbo machinery

Publ.-Id: 10817

A fast way to measure phase fractions in multiphase flow

Ondrey, G. S.

A new measuring technique for the fast measurement of phase fractions in multiphase flow is presented.

Keywords: wire-mesh sensor; capacitance; multiphase flow

  • Chemical Engineering 114(2007)12, 16

Publ.-Id: 10816

Betriebserfahrungen mit PV-Megawattanlagen in Mitteldeutschland

Rindelhardt, U.

Im Vortrag werden Auslegung und Betriebsergebnisse von 7 PV-Megawatt-Anlagen in Mitteldeutschland beschrieben.Die Module der meisten Anlagen haben eine feste, nach Süden ausgerichtete Orientierung, während eine Anlage mit zwei-achsig nachgeführten Trackern ausgerüstet ist. In allen Anlagen wurden poly- oder monokristalline Solarzellen verwendet. Es kamen sowohl Zentralwechselrichter als auch String-Wechselrichter zum Einsatz. Bei vergleichbaren Einstrahlungsbedingungen wurden Erträge zwischen 950 und 1080 kWh/kW erreicht, die Anlage mit nachgeführten Modulen übertraf diese Erträge erheblich. Durch Detailanalysen der Anlagenerträge wurden vermeidbare Quellen von Mindererträgen identifiziert.

Keywords: Solar radiation; grid connected PV systems; performance

  • Invited lecture (Conferences)
    Institutsseminar, 26.02.2008, Hameln-Emmerthal, Germany

Publ.-Id: 10815

Perspektiven der Kernenergie - Herausforderungen und Möglichkeiten

Rindelhardt, U.

Ausgehend von der bisherigen Entwicklung wird der derzeitige Stand der Kernenergienutzung auf der Basis der Kernspaltung vorgestellt. Vertieft wird auf die Brennstoffausnutzung in modernen Kernkraftwerken eingegangen. Die Hauptmerkmale der KKW der 3. Generation und der in Entwicklung befindlichen 4. Generation werden dargestellt.Ein besonderes Gewicht liegt auf der Darstellung der Rolle von schnellen Brutreaktoren. Abschließend wird das Problem der Endlagerung und aktueller Alternativen (Transmutation) erörtert.

Keywords: nuclear power; safety; nuclear fuel cycle

  • Lecture (others)
    Mitgliederversammlung VDE-Bezirksverein Chemnitz, 17.01.2008, Zwickau, Germany

Publ.-Id: 10814

Numerical prediction of horizontal stratified flows

Höhne, T.; Vallee, C.

Usually, the slug flow regime is characterized by an acceleration of the gaseous phase and by the transition of fast liquid slugs, which carry a significant amount of liquid with high kinetic energy. It is potentially hazardous to the structure of a system due to the strong oscillating pressure levels formed behind the liquid slugs as well as the mechanical momentum of the slugs. Because slug flow cannot be predicted with the required accuracy and spatial resolution by the one-dimensional system codes, the stratified flows are increasingly modelled with computational fluid dynamics (CFD) codes. In CFD, closure models are required that must be validated. The recent improvements of the multiphase flow modelling in the ANSYS CFX code make it now possible to simulate these mechanisms in detail. In order to validate existing and further developed multiphase flow models, high-resolution measurement data is needed in time and also in space.

Thanks to the optical access of the test channels built at Forschungszentrum Dresden-Rossendorf, it is possible to study detailed local stratified air/water flow phenomena. These experimental results give an important input for two-phase flow CFD model validation (i.e. interfacial momentum transfer, turbulent profiles of each phase). For the experimental investigation of co-current air/water flows, the HAWAC (Horizontal Air/Water Channel) was built (Fig. 1). Its inlet device provides defined inlet boundary conditions for code comparison. The channel allows in particular the study of air/water slug flow under atmospheric pressure. A flow pattern map (Fig. 2) was arranged constructed on the basis of a visual observation of the flow structure at different combinations of the gas and liquid superficial velocities. Parallel to the experiments, CFD calculations were carried out. A picture sequence recorded during slug flow was compared with the equivalent CFD simulation made (Figs. 3 and 4). The two-fluid model was applied with a special turbulence damping procedure at the free surface. An Algebraic Interfacial Area Density (AIAD) model on the basis of the implemented mixture model was introduced, which allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface using the local liquid phase volume fraction value.

The behaviour of slug generation and propagation at the experimental setup was qualitatively reproduced by the simulation, while local deviations require a continuation of the work. The creation of small instabilities due to pressure surge or an increase of interfacial momentum should be analysed in the future. Furthermore, experiments like pressure and velocity measurements are planned and will allow quantitative comparisons, also at other superficial velocities.

Keywords: horizontal flow; CFD; slug flow; flow pattern; HAWAC

  • Contribution to proceedings
    6th International Conference on COMPUTATIONAL FLUID DYNAMICS in the Oil & Gas, Metallurgical and Process Industries, 10.-12.06.2008, Trondheim, Norway
    CD_ROM, paper 08-12
  • Lecture (Conference)
    6th International Conference on COMPUTATIONAL FLUID DYNAMICS in the Oil & Gas, Metallurgical and Process Industries, 10.-12.06.2008, Trondheim, Norway

Publ.-Id: 10813

Simulation von Vermischungsvorgängen

Höhne, T.; Kliem, S.

Buoyancy driven mixing was investigated under simulated natural circulation conditions at the test facility ROCOM.
Experiments with density differences between the ECC water (higher density) resp. the de-borated slugs (lower density) and the ambient coolant was used to validate the CFD software CFX.
A Reynolds stress turbulence model was employed to model the effects of turbulence on the mean flow.
Hybrid meshes consisting at least of 2 million nodes and 4 million elements were used.
The experiment and CFD calculations show in both cases significant mixing effects due to the density differences.
The ANSYS CFX calculations show a good qualitative agreement with the data. At some local positions differences in the predicted and measured concentration fields occur.

Keywords: Boron Dilution; Coolant Mixing; ROCOM; CFD

  • Invited lecture (Conferences)
    Workshop Strömungssimulation, 30.11.2007, Dresden, Germany

Publ.-Id: 10812

Nachrechnung von experimentell bestimmten Leistungsparametern eines Vollhub-Feder-Sicherheitsventils mit ANSYS CFX

Höhne, T.; Moncalvo, D.

Sicherheitsventile schützen druckbeaufschlagte Räume oder Druckbehälter (z. B. Dampfkessel, Druckbehälter, Rohrleitungen, Transportbehälter) vor einem unzuläs-sigen Druckanstieg, der zu einer Schädigung des angeschlossenen Druckgerätes führen kann. Sicherheitsventile leiten bei Überschreiten des Ansprechdruckes Gase, Dämpfe oder Flüssigkeiten in die Atmosphäre ab. Das Sicherheitsventil wird verwen-det, wenn der Druck in einem Druckbehälter den zulässigen Betriebsdruck bei vor-hersehbaren Störungen um mehr als 10 % übersteigen kann. Bei richtiger Dimensio-nierung des Sicherheitsventils bleibt der Druckaufbau beherrschbar. Nach dem Ansprechen des Sicherheitsventils und Abbau des zu hohen Druckes durch Abblasen in die Umgebung oder über eine Rohrleitung schließt das Ventil wieder und die Anlage kann weiter betrieben werden.
Numerische Strömungs-berechnungsprogramme (CFD-Codes) können helfen, die Leistung von Sicherheitsventilen zu verbessern. Um Leistungsparameter zu studie-ren, wurden Experimente am Institut für Strömungsmechanik der Technischen Universität Hamburg-Haburg (TUHH) für die CFD-Codevalidierung genutzt. Durch die konstante Weiterentwicklung der Numerik bzw. der physikalischen Modelle ist es nun möglich, die relativ komplexen Strömungsvorgänge eines Sicherheitsventils (Jets, Umströmung von Hindernissen, Strömungsseparation, Stagnationsgebiete, Zonen mit hohen Ma-Zahlen) zu simulieren.
Mit dem ANSYS CFX-Code wurden Nachrechnungen von Durchsatzparametern ei-nes Leser Sicherheitsventils mit einem Gitter von 1 Million Hexaeder Zellen vorge-stellt (Abb. 1). Druckrandbedingungen wurden am Ein- und Austritt des Strömungs-gebietes definiert. Die Turbulenz wurde mit dem k-ε und k-ω basierten SST-Modell berechnet. Sehr gute Übereinstimmung wurde bei den Durchsatzkennlinien der Cha-rakteristiken für Luft und Wasser bis 5 bar Stagnationsdruck erzielt, es existierte je-doch eine systematische Abweichung bei Luft im Falle hoher Ansprechdrücke (über 20 bar) durch Realgasverhalten und das Auftreten hohe Ma-Zahlen. CFD-Rechnungen mit Luft/Wasser-Zweiphasengemischen bei 5-9 bar Überdruck und 70-95% Gasanteil ergaben realistische Durchsatzraten. Hierbei wurde das monodisper-se Partikelmodell des homogenen Euler-Euler-Ansatzes für Zweiphasengemische genutzt. Weitere Untersuchungen, insbesondere das Verhalten bei Stoffgemischen (Glukoselösung) bzw. der Einfluss des Hubs des Sicherheitsventils (Stellung des Ventiltellers zwischen Sitz und maximaler Öffnung) auf den Durchsatz im Vergleich mit Experimenten werden vorgestellt.

Keywords: Safety Valve; CFD

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachausschüsse Computational Fluid Dynamics, Gasreinigung, Mechanische Flüssigkeitsabtrennung und Grenzflächenbestimmte Systeme und Prozesse, 18.-20.02.2008, Wiesbaden, Germany
  • Contribution to proceedings
    Jahrestreffen der ProcessNet-Fachausschüsse Computational Fluid Dynamics, Gasreinigung, Mechanische Flüssigkeitsabtrennung und Grenzflächenbestimmte Systeme und Prozesse, 18.-20.02.2008, Wiesbaden, Germany

Publ.-Id: 10811

Experimental and numerical prediction of horizontal stratified flows using the HAWAC facility

Höhne, T.; Vallee, C.

Slug flow is potentially hazardous to the structure of the system due to the strong oscillating pressure levels formed behind the liquid slugs. It is usually characterized by an acceleration of the gaseous phase and by the transition of fast liquid slugs, which carry out a significant amount of liquid with high kinetic energy. For the experimental investigation of air/water flows, a horizontal channel with rectangular cross-section was build at Forschungszentrum Dresden-Rossendorf (FZD). Experimental data were used to check the feasibility to predict the slugging phenomenon with the existing multiphase flow models build in ANSYS CFX. Further it is of interest to prove the understanding of the general fluid dynamic mechanism leading to slug flow and to identify the critical parameters affecting the main slug flow parameters (like e.g. slug length, frequency and propagation velocity; pressure drop).
A selected co-current test run that was carried out at a superficial water velocity of 0.69 m /s and a superficial air velocity of 2.2 m /s at ambient pressure and temperature conditions was analyzed using the software package ANSYS CFX. At these conditions, a slug flow is generated. For free surface simulations, the inhomogeneous multiphase model was used, where the gaseous and liquid phases can be partially mixed in certain areas of the flow domain. In this case the local phase demixing after a gas entrainment is controlled by buoyancy and interphase drag and is not hindered by the phase interface separating the two fluids. A further decision has to be made regarding the applied fluid morphology and interphase drag law for the multiphase flow. The fluid-dependent shear stress transport (SST) turbulence models were selected for each phase. Damping of turbulent diffusion at the interface has been considered. The k-ω based SST model accounts for the transport of the turbulent shear stress and gives highly accurate predictions of the onset and the amount of flow separation under adverse pressure gradients. The tail of the calculated slug and the flow behind it is in good agreement with the experiment. The entrainment of small bubbles in front of the slug could not be observed in the calculation. However, the front wave rolls over and breaks. It is created due to the high air velocity. In contrast to the measurement, the slug period is increasing with the time in the calculation. This could be a result of different amount of water in the channel at the beginning of experiment and CFD simulation. While in the simulation, the liquid phase covers 78% of the channel, it represents about 70% at the beginning of the experiment. Furthermore, in the experiment, this value is also reduced by a first slug which carries a significant amount of water out of the channel. This first slug could not be simulated. The behavior of slug propagation at the experimental setup was qualitatively reproduced, while quantitative deviations require a continuation of the work.
As some uncertainties were noticed at the inlet of this channel, the HAWAC (Horizontal Air/Water Channel) with well defined inlet boundary conditions dedicated to co-current flows was built. A picture sequence recorded during slug flow was compared with the equivalent CFD simulation made with the code ANSYS CFX. The two-fluid model was applied with a special free surface treatment. Due to an interfacial momentum transfer, it was possible to generate slugs based on instabilities. The behaviour of slug generation and propagation at the experimental setup was qualitatively reproduced, while deviations require a continuation of the work. The creation of small instabilities due to pressure surge or an increase of interfacial momentum should be analysed in the future. Furthermore, experiments like pressure and velocity measurements are planned and will allow quantitative comparisons, also at other superficial velocities.

Keywords: CFD; flow pattern; stratified flow; slug flow

  • Invited lecture (Conferences)
    ANSYS Conference & 25th CADFEM Users’ Meeting, 21.-23.11.2007, Dresden, Germany
  • Contribution to proceedings
    ANSYS Conference & 25th CADFEM Users’ Meeting, 21.-23.11.2007, Dresden, Germany
    CD-ROM, paper 679

Publ.-Id: 10810

Rare-earth implanted Y2O3 thin films

Peeva, A.; Dikovska, A. O.; Atanasov, P. A.; Jime´Nez De Castro, M.; Skorupa, W.

Thin Er, Yb co–doped Y2O3 films were grown by pulsed laser deposition from ceramic target. Subsequent ion implantation with 1.1 MeV Er+
ions to a fluence of 6 x 10E14 at/cm2 at room temperature was performed in order to modify the structure of the as-deposited films. The as-depositedfilms have a polycrystalline column-like structure. Ion implantation induces defects into the as-deposited films. After annealing at 900 8C for 1 h inoxygen atmosphere, the films recrystallize in roundly shaped grain-like structure with grain size of about 100 nm. The Er3+ photoluminescence response was obtained for all the films by excitation through cross-relaxation of Yb3+ ions. The IR emission spectrum, consisting of two narrow peaks at 1415 and 1514 nm, differs from the typical spectra of Er-doped materials. The VIS emission spectrum observed in as-deposited films does not appear after implantation and subsequent 900 8C annealing.

Keywords: Rare-earth, erbium, ion implantation, thin films; Y2O3; Pulsed Laser Deposition

Publ.-Id: 10809

Investigation of flow development of co-current gas-liquid vertical slug flow

Kaji, R.; Azzopardi, B. J.; Lucas, D.

Void fraction, Taylor bubble/liquid slug length, and slug frequency are parameters essential to understand the structure of slug flow. In the present study, these parameters were extracted from the time series of cross-sectionally averaged void fraction obtained from two vertical facilities having similar internal pipe diameter but significantly different axial lengths; 51.2mm/3.5m and 52.3mm/9m. To investigate the effect of flow development on slug characteristics measurements were carried out at several axial locations from the mixing section for both facilities. For slug frequency, a new correlation including the effect of the axial length has been proposed and assessed using previously published data.

Keywords: slug flow; vertical pipe; flow structure; flow development; frequency

Publ.-Id: 10807

Search of the origin of ferromagnetism in DMS

Talut, G.; Reuther, H.; Stromberg, F.; Zhou, S.; Potzger, K.; Grenzer, J.; Mücklich, A.; Eichhorn, F.

Transition metal doped wide band gap semiconductors like GaN, ZnO and TiO2 are promising candidates to be diluted magnetic semiconductors (DMS) with Curie temperatures (Tc) above room temperature (RT). In most of the studies reported in literature the presence of metallic precipitates could not be excluded and may play an important role in the discussion of the origin of the ferromagnetism.
Hence, one of the main obstacles while creating a DMS is the formation of secondary phases. The detection of those is very problematic too.
Since solubility limits for the doping atoms, especially in GaN, are rather low, non-equilibrium doping techniques like low temperature film growth or ion implantation are commonly used.
Ion implantation gives the possibility of doping at different temperatures and with high dopand concentrations but is always connected with lattice damage of the target material. Subsequent annealing in a time scale of some minutes mostly results in phase separation. Combining ion implantation with faster techniques, i.e. rapid thermal annealing or flash lamp annealing, leads to a diluted state while the crystallinity of the target material can be partially restored.
Sample sets were implanted with 57Fe ions and concentrations up to 18 at. % and subsequently annealed at different temperatures and time scales.
Conversion electron Mössbauer spectroscopy (CEMS), superconducting quantum interference device (SQUID), x-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and Rutherford backscattering spectroscopy (RBS) were used to characterize the (micro)-structure, magnetic response and radiation damage of specimens as well as the charge state and site location of Fe. The origin of ferromagnetism is discussed on base of these results.

Keywords: DMS; Ferromagnetism; GaN; TiO2

  • Invited lecture (Conferences)
    Condensed Matter Seminar, University of Central Florida, 12.11.2007, Orlando, Florida, USA

Publ.-Id: 10806

Entwicklung und Validierung des Druckstoßprogramms DYVPRO Mod. 3

Neuhaus, T.; Schaffrath, A.; Ronneberger, R.; Altstadt, E.

Druckstöße entstehen in Rohrleitungssystemen immer dann, wenn ein Fluid (z.B. eine Flüssigkeit oder ein Gas) durch das plötzliche Öffnen oder Schließen einer Armatur, die Änderung der Drehzahl einer Pumpe, in Folge von Rohrleitungsbrüchen usw. beschleunigt oder abgebremst wird. Hierbei entstehen Druckwellen, die erhöhte Innendrücke verbunden mit mechanischen Spannungen in den Rohrleitungswänden sowie zeitabhängige axiale Kräfte auf Rohrleitungen und deren Halterungen hervorrufen können. Durch Reflexionen der Druckwellen können Unterdrücke entstehen, die bei Unterschreiten des lokalen Sättigungsdrucks zur Bildung von Dampfblasen (Kavitation) führen können. Bei dem Zusammenfall der Dampfblasen können weitere, sekundäre Druckstöße auftreten, die die primären Druckwellen überlagern. Die Ausbreitungsgeschwindigkeit von Druckwellen hängt zum einen von den Eigenschaften des Fluids (speziell dessen Kompressibilität und Dichte) und zum anderen von den mechanischen Eigenschaften des Rohrleitungssystems (Elastizitätsmodul und Querkontraktionszahl) sowie dessen Geometrie (Durchmesser des Rohrs und Wanddicke) ab. Druckstöße sind oftmals die Ursache für Beschädigungen an Rohrleitungen und Rohrleitungshalterungen und stellen daher für viele verfahrenstechnische Anlagen ein Problem dar.

Die TÜV NORD SysTec GmbH & Co. KG beschäftigt sich seit vielen Jahren mit der Berechnung von Druckstößen in Kraftwerken und speziell in Kernkraftwerken. Hierzu hat sie das Druckstoßprogramm DYVRO entwickelt und qualifiziert. Der vorliegende Beitrag be¬schreibt die nun hinsichtlich des verwendeten partiellen Differentialgleichungssystems und der eingesetzten Numerik überarbeitete Programmversion DYVRO Mod. 3 und deren Validierung anhand repräsentativer Experimente (u.a. anhand des Simpson-Experiments sowie anhand eines Versuches an der Cold Water Hammer Test Facility). Die Ergebnisse der Validierungsrechnungen werden anschließend mit eigenen oder fremden Rechnungen mit Systemcodes (hier ATHLET und RELAP) sowie dem Druckstoßprogramm WAHA verglichen. Bei diesen Vergleichen werden u.a. die Ergebnisse des im 5. EU-Rahmenprogramm geförderten Forschungsvorhabens WAHALOADS mit einbezogen. Die Vergleiche zeigen eine sehr gute Übereinstimmung der Rechenergebnisse von DYVRO mit den Experimenten sowie den Ergebnissen des WAHA-Codes. Die Ergebnisse der Druckstoßcodes WAHA und DYVRO sind – sowohl im einphasigen als auch im zweiphasigen Bereich - deutlich besser als die der Systemcodes. Unsere Analysen belegen, dass DYVRO Mod. 3 dem aktuellen Stand von Wissenschaft und Technik entspricht.

Keywords: water hammer; pipe line; fluid dynamics; pressure wave

  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany

Publ.-Id: 10805

(4-Methoxybenzenethiolato-κS)oxido-[2,2’-propylimino)-bis(ethanethiolato)- κ3S,N,S’]rhenium(V)

Kraus, W.; Emmerling, F.; Noll, B.; Noll, S.; Pietzsch, H.-J.

The central Re atom of the mononuclear title complex, [Re(C8H18NS2)(C6H4OS)O], is five-coordinate (ReNOS3) with a square-pyramidal geometry comprising a tridentate 2,2 0-(propylimino)diethanethiolate ligand, a 4-methoxybenzenethiolate ligand and a doubly-bonded O atom.

Publ.-Id: 10804

Nachweis solarer Neutrinooszillationen an SNO

Wagner, A.

Das Sudbury Neutrino Observatory wird vorgestellt, die Daten zur Flavour-Zusammensetzung des solaren Neutrinoflusses interpretiert und Schlüsse auf Neutrinooszillationen gezogen.

  • Invited lecture (Conferences)
    Vortrag an Fachbereich Physik der Technischen Universität Darmstadt, 31.10.2007, Darmstadt, Germany

Publ.-Id: 10803

The spectrum of a non-Hermitian two-mode Bose-Hubbard system

Graefe, E.-M.; Günther, U.; Niederle, A.; Korsch, H. J.

We study an N-particle, two-mode Bose-Hubbard system, modelling a Bose-Einstein condensate in a double-well potential. By introducing effective complex energies to the modes we describe a coupling to a continuum. The eigenvalues of the resulting non-Hermitian matrix model are in general complex where the imaginary parts (resonance widths) describe the decay rate into the continuum. In dependence on the system parameters, the eigenvalues show intricate patterns of avoided and real crossings, as well as characteristic bifurcations. In the present talk the effect of the interplay between the particle interaction and the non-Hermiticity on characteristic features of the spectrum is analysed and its peculiarities are clarified by perturbational methods.

Keywords: Bose-Einstein condensate; Bose-Hubbard system; non-Hermitian matrix model; perturbation theory; exceptional point; spectral bifurcation

  • Lecture (Conference)
    DPG Frühjahrstagung, 10.-14.03.2008, Darmstadt, Germany

Publ.-Id: 10802

Reduzierung des Out-of-Field-of-View Einflusses auf die Event-basierte Bewegungskorrektur von Hirnuntersuchungen in der PET

Langner, J.

Event-basierte Bewegungskorrekturverfahren erlauben durch räumliche Transformation jedes Koinzidenzereignisses auf einer line-of-response (LOR) eine exakte Korrektur von Patientenbewegungen in der PET. Die Integration dieser komplexen Verfahren in die klinische Routine setzt jedoch ein Bewegungsverfolgungssystem (Motion-Tracking) sowie einen vollautomatischen Verarbeitungsablauf voraus. Ein Schritt hierbei ist die Korrektur des Out-of-Field-of-View (OutFOV) Effektes. Bei diesem Effekt kommt es dazu, dass LORs zeitweise ausserhalb des FOV transformiert und somit nicht in den Emissions-Sinogrammen erfasst werden. Durch entsprechende Normierung der unterbewerteten Bins wird versucht, dies auszugleichen. Werden die Korrekturfaktoren jedoch zu groß, kommt es zu Bildartefakten, welche u.a. die quantitative Auswertung beeinträchtigen. Ziel dieser Arbeit war die Minimierung des OutFOV Einflusses und die Integration der Methode in einen automatisierten Untersuchungsablauf, welcher den Einsatz im klinischen Umfeld ermöglicht.

Meist wird bei event-basierter Korrektur ein einzelner Referenzzeitpunkt für alle Teilabschnitte (Frames) einer dynamischen Aufnahme benutzt – üblicherweise der Startzeitpunkt der Untersuchung. Ein solches Vorgehen führt jedoch i.a. zu den angesprochenen hohen statistischen Unsicherheiten bei der Normierung der OutFOV-Counts. Durch Analyse der Bewegungsdaten, wird für jeden Frame eine
Häufigkeitsverteilung der relativen Patientenbewegung erstellt. Anhand dieser werden optimale Zeitpunkte ermittelt, an denen die Normierungsfaktoren minimal sind. Diese Referenzpositionen erlauben es, jeden Frame einzeln mit ebenfalls räumlich angepassten Transmissionsdaten zu rekonstruieren. Die daraus resultierenden Bildvolumina werden abschließend auf eine gemeinsame
Orientierung transformiert. Hierbei wird die aus den Bewegungsdaten bekannte Orientierung der Bildvolumina zu den Referenzzeitpunkten genutzt.

Die Nutzung für jeden Frame angepasster Referenzzeitpunkte reduziert die OutFOV- Korrekturfaktoren erheblich und gewährleistet eine hinreichende Messstatistik für alle LORs im Gesichtsfeld des Tomographen. Die bewegungskorrigierten Bilddaten sind infolgedessen frei von den erwähnten Artefakten.

Es konnte gezeigt werden, dass durch die Einführung optimierter Referenzpositionen ein wichtiger limitierender Faktor der event-basierten Bewegungskorrektur eliminiert werden kann. Dies zeigt sich auch bei der Auswertung von klinischen Daten, wo das Verfahren in der Lage ist, bewegungsfreie sowie nunmehr quantitativ auswertbare Datensätze zu erzeugen. Nach Kombination dieser Methode mit bereits etablierten Methoden zeigt dies die Machtbarkeit einer klinischen Nutzung einer event-basierten Bewegungskorrektur und deren Potenzial.

  • Abstract in refereed journal
    Nuklearmedizin 47(2008)2, A59
  • Lecture (Conference)
    46. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 23.-26.04.2008, Leipzig, Germany

Publ.-Id: 10801

Helical MRI in MHD Taylor-Couette flow

Szklarski, J.

Magnetorotational Instability (MRI) is believed to be one of the most important instabilities on astrophysical scales. However, it is very difficult to observe it in a laboratory experiment. One possibility is to use a Taylor-Couette setup (a flow between two concentric rotating cylinders) where a liquid metal alloy is used. Problems arise since such metals are characterized by very small magnetic Prandtl number and consequently vast rotation rates are necessary. In the PROMISE experiment a special helical configuration of the applied magnetic field was used in order to dramatically reduce rotation rates. We present numerical simulations and relate it to experimental results confirming the existence of MRI of this type.

  • Lecture (Conference)
    10th MHD Days, 26.-29.11.2007, Garching, Germany

Publ.-Id: 10800

Untersuchungen zur Kontrastabhängigkeit des untergrundbereinigten Schwellwertes bei der Volumenbestimmung in der PET

Dittrich, S.

Bei der quantitativen Bewertung dreidimensionaler Strukturen (VOIs) innerhalb von PET-Bildvolumen wurde in (1) auch nach Untergrundsubtraktion eine Abhängigkeit des relativen Schwellwertes vom Bildkontrast nachgewiesen, welche aus theoretischer Sicht unerwartet ist. Für ein Verständnis dieser Abhängigkeit soll in der vorliegenden Arbeit der Einfluss verschiedener Faktoren wie Auflösung und Streukorrektur genauer untersucht werden. Es soll zudem ein effizientes Kalibrierungsverfahren entwickelt werden, welches für eine korrekte Volumenbestimmung bei einem automatischen Schwellwertverfahren notwendig wird.

Es wurden PET-Volumendatensätze mit unterschiedlichen Bildkontrasten ausgewertet, welche sowohl aus Phantommessungen als auch aus Monte Carlo Simulationen mit dem Programmpaket GATE (2) gewonnen wurden. Für die im rekonstruierten Bildvolumen dargestellten Kugeln wurde der Schwellwert, der zur bekannten wahren Objektgröße führt, bestimmt. Aus Least Squares Fits unter Nutzung des analytischen Ausdrucks für die Faltung der Objektfunktion (Aktivitätsverteilung) mit der Point Spread Function (PSF) wurden ferner die rekonstruierte Auflösung und die Kugelradien ermittelt.

Die aus den gemessenen Daten erhaltene Abhängigkeit des untergrundbereinigten, relativen Schwellwertes vom Bildkontrast konnte mit den simulierten Bilddaten bestätigt werden. Mit abnehmender Auflösung wird der relative Schwellwert zunehmend unabhängig vom Kontrast. Die aus den Least Squares Fits ermittelten Radien waren stets kleiner als die wahren Kugelradien. Diese scheinbare Reduktion der Objektgröße wies ebenfalls eine Abhängigkeit vom Bildkontrast auf, aus der sich wiederum der Zusammenhang zwischen relativen Schwellwert und Kontrast ableiten lässt. Dadurch konnte eine Kalibrierungsvorschrift für automatische Schwellwertverfahren entwickelt werden.

Für eine präzise Volumenbestimmung mittels automatischer Schwellwertanalyse in der PET muss auch nach erfolgter Untergrundsubtraktion die Kontrastabhängigkeit des relativen Schwellwertes beachtet werden. Die beobachtete Abhängigkeit konnte über eine Radiusreduktion erklärt werden, woraus eine allgemeine Kalibrierungsvorschrift für die Volumenbestimmung mit automatischen
Schwellwertverfahren entwickelt wurde.

(1) C. Pötzsch; F. Hofheinz; J. van den Hoff; Minimierung der Inter-Observer-Variabilität bei volumetrischen Auswertungen von onkologischen Ganzkörperstudien in der PET; Nuklearmedizin (2005) 44 p. A16
(2) S. Jan; G. Santin; D. Strul et al.; GATE: a simulation toolkit for PET and SPECT; Phys. Med. Biol. 49 (2004) 4543

  • Abstract in refereed journal
    Nuklearmedizin 47(2008)2, A58
  • Lecture (Conference)
    46. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 23.-26.04.2008, Leipzig, Germany

Publ.-Id: 10799

Multimere Neurotensin-Liganden: Synthese, Komplexbildung gegenüber Kupfer(II) und Affinität zum Neurotensin-Rezeptor 1

Stephan, H.; Röhrich, A.; Noll, S.; Bergmann, R.; Pietzsch, J.; Steinbach, J.

Neben den eingeführten Radionukliden Tc-99m, Re-188 und Y-90 rücken Radionuklide wie Cu-64 und Cu-67 zunehmend in das Interesse für Diagnostik und Therapie von Tumor- und Stoffwechselerkrankungen. In Verbindung mit multifunktionale Liganden eröffnet dies einen neuen Zugang zu spezifischen Radiopharmaka und zwar vor allem dann, wenn die Verkapslung radioaktiver Metallnuklide im Kern topologisch so gelingt, dass diese unter physiologischen Bedingungen kinetisch und thermodynamisch stabil fixiert sind. Eine Modifizierung der Ligandstruktur mit Biomolekülen - wie Zucker oder Peptide - erlaubt dann die Einstellung definierter Löslichkeits- und selektiver Bindungseigenschaften. Ziel ist die Entwicklung metabolisch stabiler, radioaktiv markierter Neurotensin-Konjugate für die Tumordiagnostik und –therapie

  • Lecture (Conference)
    46. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 23.-26.04.2008, Leipzig, Germany
  • Abstract in refereed journal
    Nuklearmedizin 47(2008)2, A82

Publ.-Id: 10798

Nanoscaled silicon-based heterostructures formed by interface mediated endotaxy

Popov, V. P.; Tyschenko, I. E.; Cherkov, A. G.; Pokhil, G. P.; Fridman, V. M.; Voelskow, M.

New types of substrates are needed for further scaling in CMOS microelectronics after 22 nm node. We speculate that this new type of materials can be semiconductor heterostructures on insulator (HOI) compatible with current silicon planar CMOS technology. In this work the effect of interface mediated endotaxial (IME) growth of thin Ge or InSb film at the Si/SiO2 bonded interface was experimentally observed and investigated. A joint semiconductor material stack obtained by hydrogen transfer of one layer material (silicon) and an endotaxially grown second one (germanium or indium antimonide) placed initially into an amorphous silicon dioxide film is presented. Thermodynamic, kinetic and lattice mismatch parameter influences on the IME process are considered.

Keywords: Nanoscaled; heterostructures

  • ECS Transactions 6(2007)1, 87-93

Publ.-Id: 10796

Advanced heterostructure Si-InSb on insulator formed by bonding of hydrogen transferred Si layer and implanted SiO2 film

Popov, V. P.; Tyschenko, I. E.; Cherkov, A. G.; Pokhil, G. P.; Fridman, V. M.; Voelskow, M.

Using bulk silicon may be limited for 22 nm technological node due to silicon mobility limitation. New type of substrates needs for further scaling in CMOS microelectronics. We speculate that this new type of materials can be semiconductor heterostructure on insulator (HOI) compatible with current silicon planar CMOS technology. In this work an effect of interface mediated endotaxial (IME) growth of thin InSb film at Si/SiO2 bonded interface was experimentally observed and investigated for the first time. Joint semiconductor material stack obtained by hydrogen transfer of one layer material (silicon) and endotaxially grown second one (indium antimonide) placed initially into amorphous silicon dioxide film is presented. Thermodynamic, kinetic and lattice mismatch parameter influences on IME process are considered.

Keywords: silicon; heterostructure; InSb

  • ECS Transactions 6(2007)4, 345-350

Publ.-Id: 10794

Detection of intrinsic stress in cubic boron nitride films by x-ray absorption near-edge structure: Stress relaxation mechanisms by simultaneous ion implantation during growth

Gago, R.; Abendroth, B.; Cerda, J. I.; Jimenez, I.; Möller, W.

The bonding structure of cubic boron nitride (cBN) films with different levels of intrinsic stress (1–10 GPa) has been studied from the K-shell x-ray absorption near-edge structure (XANES). The stress level was tuned by the damage induced from simultaneous medium-energy ion implantation (1–10 keV) during growth. The films show a dominant sp3 arrangement for damage values below a certain threshold, with an appreciable sp3 to sp2 transformation taking place above this limit. Interestingly, the degree of stress in sp3 structures is reflected in the B 1s spectral line shape, which progressively converges to that of stress-free cBN powder for increasing ion damage. These results indicate that stress buildup and release occur at a microscopic level. The changes in the spectral line shape are correlated with modifications in the electronic structure due to the presence of intrinsic stress and bond distortion within the cubic network, as predicted by density functional theory calculations. Our findings reveal the potential of XANES spectroscopy to detect stress in disordered BN systems.

Keywords: cubic boron nitride; intrinsic stress; ion implantation; XANES

  • Physical Review B 76(2007), 174111

Publ.-Id: 10793

Statistical properites and clustering of dynamo reversals observed from paleomagnetic records, experimental dynamo, numerical simulations and simplified models

Sorriso-Valvo, L.; Carbone, V.; Stefani, F.; Bourgoin, M.

The statistical properites of the time sequence of the geodynamo reversals show interesting features, such as non-poisson statistics indicating presence of correlations, and clustering in time. Such properties can be used to compare the observed reversals sequence with different dynamos, both experimental and numerical. In this work an experimental Bullard-Von Karman dynamo, which reproduces the field reversal, is studied in comparison with the paleomagnetic data. Moreover, some numerical models (namely an alpha-alpha dynamo, a turbulent dynamo, a dissipative Rikitake dynamo, and a shell model MHD dynamo) are characaterized, and their capacity of reproducing the observed clustering properties are discussed, also allowing the fine tuning of the models parameters.

  • Lecture (Conference)
    AGU Fall Meeting, 10.-14.12.2007, San Francisco, USA
  • Abstract in refereed journal
    Eos, Transactions, American Geophysical Union 88(2007)52, GP33A-0921

Publ.-Id: 10792

On the Influence of Spatial Discretization on Cross Section Preparation with HELIOS 1.9

Merk, B.; Koch, R.

An analysis of the influence of the spatial discretization strategy for cell- and lattice calculations on the neutron flux distribution and the kinf value in a single cell is performed. The analysis shows a significantly different neutron flux distribution and kinf value for different discretizations. In addtion the preparation of few group cross sections for 3D nodal full core simulators is analyzed. Especially these cross sections are very sensitive on an appropriate spatial discretization.

Keywords: Cell- and Lattice calculation; cross section preparation; HELIOS; Discretization

  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany

Publ.-Id: 10791

Vergleich von Abbrandrechnungen mit HELIOS 1.9 und KAPROS/KARBUS mit zeitlich veränderlicher Leistung

Merk, B.

Ein Vergleich des Zell- und Abbrandcodes HELIOS mit der im Programmsystem KAPROS entwickelten Prozedur KARBUS ist für Abbrandrechnungen mit zeitlich veränderlicher Leistung in einer Einheitszelle mit Uranoxid- (UOX) und Mischoxidbrennstoff (MOX) wird durchgeführt und die Ergebnisse für kinf und die Teilchendichten der Transurane analysiert.
A comparison of the cell and burnup code HELIOS with the program procedure KAPROS/KARBUS for burnup calcaultions with time dependent power in a unit cell for UOX and MOX fuel is performed. The results for kinf and the particle densities of transuranium elements are analyzed


  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany

Publ.-Id: 10790

Laser accelerated particle beams

Kraft, S.; Zeil, K.; Kluge, T.; Debus, A.; Bock, S.; Sauerbrey, R.; Schramm, U.

Laser driven particle acceleration has become a rapidly developing field in recent years. Laser pulses with a pulse duration of 10 - 100 fs and up to several Petawatt of power in each pulse are focussed onto either gas targets or thin foils where they create enormous electromagnetic fields. These fields operate as a mm scale accelerator producing quasimonoenergetic electron or ion beams with energies of 1 GeV and several MeV, respectively.

Although the lasers operate at very low repetition rates of around 1 Hz, such a system could become interesting for medical applications since a single bunch accelerated by the laser carries between 108 and 1010 particles.

In this talk, we want to present the current state of laser particle acceleration. Challenges and future developments for clinical applications in cancer therapy will be discussed.

  • Invited lecture (Conferences)
    Ion Beams in Biology and Medicine, 26.-29.09.2007, Heidelberg, Germany

Publ.-Id: 10789

A high-resolution time-of-flight mass spectrometer for the detection of ultracold molecules

Kraft, S. D.; Mikosch, J.; Staanum, P.; Deiglmayr, J.; Lange, J.; Fioretti, A.; Wester, R.; Weidemüller, M.

We have realized a high-resolution time-of-flight mass spectrometer combined with a magneto-optical trap. The spectrometer enables excellent optical access to the trapped atomic cloud using specifically devised acceleration and deflection electrodes. The ions are extracted along a laser beam axis and deflected onto an off-axis detector. The setup is applied to detect atoms and molecules photoassociated from ultracold atoms. The detection is based on resonance-enhanced multiphoton ionization. Mass resolution up to m/Delta m = 1000 at the mass of 133^Cs is achieved. The performance of this spectrometer is demonstrated in the detection of photoassociated ultracold 7^Li133^Cs molecules near a large signal of 133^Cs ions.

  • Applied Physics B 89(2007), 453

Publ.-Id: 10788

Numerical Simulations of the onset of dynamo action with a hybrid finite volume/ boundary element method (FV-BEM)

Giesecke, A.; Stefani, F.

The experimental realization of dynamo excitation as well as theoretical and numerical examinations of the induction equation have shown the relevance of boundary conditions and material properties for a self-sustaining dynamo. Generally, in non-spherical geometry typical insulating boundary conditions are described by elaborated schemes (e.g. solving of the Laplace equation in an extended domain) or by simplifying approximations (pseudo vacuum). A different approach is provided by a modified integral equation procedure, commonly known as the boundary element method (BEM). Integrating the Laplace equation on the boundaries allows to overcome the difficulties of the non-local character of insulating boundary conditions and the direct computation of the magnetic field next to an insulator becomes possible. However, within the interior of a field producing domain geometric constraints or varying material properties (e.g. electrical conductivity of the container walls or localized high-permeability material) might also play a role. For this problem, a more flexible approach utilizing a local discretization like the constraint transport (CT) method as a well known realization of a finite volume scheme is recommendable. The CT-scheme ensures a fast, robust and accurate solution of the kinematic dynamo problem and intrinsically maintains the solenoidal character of the magnetic field. Combining both methods in a hybrid FV-BEM scheme offers the flexibility of a local discretization with a stringent treatment of insulating magnetic boundary conditions in arbitrary geometries. Preliminary simulations of an alpha^2-Dynamo in a cartesian box and/or the decay of an initial magnetic field demonstrate the applicability of the approach.
Further examinations are intended to understand the behavior of the VKS-dynamo experiment where the field producing flow is driven by ferrous propellers and the dynamo mechanism probably is dominated by this high permeability material.
Other applications of the hybrid scheme may also be important for the evaluation of forthcoming dynamo experiments
for which a precise knowledge of the critical magnetic Reynolds number is essential.

  • Lecture (Conference)
    10th MHD Days, 26.-29.11.2007, Garching, Germany

Publ.-Id: 10787

Role of Four-Quark Condensates in QCD Sum Rules

Thomas, R.; Hilger, T.; Kämpfer, B.

The QCD sum rule approach to the in-medium behavior of hadrons is discussed for omega meson, nucleon and D meson.
Emphasis is devoted to the impact of four-quark condensates and to order parameters of spontaneous symmetry breaking.

Publ.-Id: 10786

Characterization of hybrid amorphous-partially crystalline thin films

Martin, N.; Hamann, C.; McCord, J.; Fassbender, J.; Quandt, E.; Gerber, A.; Bigall, N.; Eychmüller, A.; Schultz, L.

Amorphous FeCoBSi thin films with uniaxial anisotropy have been laterally structured by Co ion implantation into stripe arrays. The resulting multiphase samples were investigated regarding the magnetic properties. Hysteresis measurements revealed a large increase in coercivity of the implanted areas. By means of TEM investigations this could be attributed to formed crystallites in the amorphous matrix. Magneto-optical imaging was used to correlate the domain structure to the magnetic hysteresis. It is demonstrated that stripe orientation with respect to the magnetic easy axis governs the coupling between implanted and non implanted areas.

Keywords: magnetism; ion implantation; hybrid materials; crystalization; magnetic microscopy

  • Poster
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10785

The influence of non centric holes on the magnetization dynamics of Landau structures

Wintz, S.; Kuepper, K.; Buess, M.; Raabe, J.; Quitman, C.; Fassbender, J.

Magnetic vortex cores are attracted and can be trapped by artificial defects. If more than one of such defects are created a switching between different vortex core trapped states, which might serve as discrete levels in a multivalent memory device, can be achieved. Up to now a number of studies of circular vortex structures comprising holes has been reported, e. g. [1,2,3]. We report the imaging of the magnetic excitation spectrum in presence of holes, fabricated by focussed ion beam milling, in the magnetic domains and domain walls of Landau structures by means of x-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM). Due to the very high lateral and temporal resolution the magnetization dynamics and the corresponding Eigen modes, which are characteristic for the vortexhole interaction, are investigated in detail. The experimental results are compared to micromagnetic simulations.

[1] M. Rahm et al., Appl. Phys. Lett. 85, 1553 (2004).
[2] T. Uhlig et al., Phys. Rev. Lett. 95, 237205 (2005).
[3] F. Hoffmann et al., Phys. Rev. B 76, 014416 (2007).

Keywords: magnetism; magnetization dynamics; vortex; Landau structure; holes; defects

  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10784

Inclusive di-electron production in C+C collisions with HADES

Dohrmann, F.; Agakishiev, G.; Agodi, C.; Balanda, A.; Bellia, G.; Belver, D.; Belyaev, A.; Blanco, A.; Boehmer, M.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Diaz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Grosse, E.; Guber, F.; Heilmann, M.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kaempfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Krizek, F.; Kruecken, R.; Kuehn, W.; Kugler, A.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, J. S.; Lopes, L.; Maier, L.; Mangiarotti, A.; Marin, J.; Markert, J.; Metag, V.; Michalska, B.; Mishra, D.; Moriniere, E.; Mousa, J.; Muentz, C.; Naumann, L.; Novotny, R.; Otwinowski, J.; Pachmayer, Y. C.; Palk! A, M.; Pechenov, V.; Pechenova, O.; Cavalcanti, T. P.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Simon, R.; Spataro, S.; Spruck, B.; Stroebele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Veretenkin, I.; Wagner, V.; Wen, H.; Wisniowski, M.; Wojcik, T.; Wuestenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zumbruch, P.

Inclusive di-electron production in C+C collisions at 1 and 2 AGeV has recently been measured by the HADES collaboration at GSI. Results are compared to a di-electron cocktail calculated from free hadron pi0, eta, omega decays after freeze-out. For the low invariant masses, M(e+e-) < 0.15 GeV/c2, the measured distributions are largely explained by the pi0 --> e+e- gamma Dalitz decay but for higher masses experimental yields significantly exceed expectations.

Keywords: In-medium properties of hadrons; heavy-ion collisions

  • Contribution to proceedings
    MENU2007 11th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon, 10.-14.09.2007, Jülich, Germany
    Proceedings of the 11th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon, SLAC, 67


Publ.-Id: 10783

Modification of magnetic order in Mn5Si3 and Mn5Ge3 by C ion implantation

Sürgers, C.; Joshi, N.; Montbrun, R.; von Löhneysen, H.; Potzger, K.; Möller, W.

Antiferromagnetically ordered Mn5Si3 can be driven ferromagnetic by incorporation of carbon into the voids of Mn octahedra of the hexagonal structure. While for Mn5Si3Cx polycrystals the Curie temperature saturates for x > 0.22 at TC = 152 K [1], sputtered Mn5Si3C0.8 films exhibit a TC above room temperature [2]. An enhancement of TC is also found after C doping of the isostructural compound Mn5Ge3 which is currently in the focus of possible spintronic applications. In an alternative approach, Mn5Si3Cx and Mn5Ge3Cx films were prepared by implantation of 45 - 195 keV C+ ions into Mn5Si3 or Mn5Ge3 films at elevated temperatures. The carbon-implanted samples exhibit magnetic properties very similar to their respective magnetron-sputtered counterparts as inferred from magnetization and resistivity measurements.

Keywords: Magnetic semiconductors; Implantation; Mn5Ge3

  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.2.2008, Berlin, Germany

Publ.-Id: 10782

Magnetic anisotropies in ferromagnetic and exchange-coupled systems on rippled surfaces

Liedke, M. O.; Liedke, B.; Marko, D.; Keller, A.; Muecklich, A.; Facsko, S.; Fassbender, J.; Cizmar, E.; Zvyagin, S.; Wosnitza, J.

The influence of a surface and interface modulation on the magnetic properties of ferromagnetic materials (Py, Fe and Co) and an exchange bias system (Py/FeMn) is studied. A periodic surface modulation (the so-called ripples) is achieved by low energy ion erosion. Subsequently the magnetic stack is deposited. Due to the film morphology a strong uniaxial anisotropy is induced in the ferromagnetic layers, which is fixed in its orientation along ripples elongation. In the case of the exchange bias system the direction of the induced unidirectional anisotropy can be varied by means of different field annealing cycles. For all mutual orientations both anisotropy contributions are superimposed independently. The angular dependence of the magnetization reversal behavior can be described perfectly by a coherent rotation model [1]. In addition, the magnitude of the uniaxial and the unidirectional anisotropy scales with the step density or wave length of the rippled substrate, which is in full agreement with theoretical predictions.

[1] M. O. Liedke et al., Phys. Rev. B 75, 220407(R) (2007)

Keywords: exchange bias; ripples; ion erosion; exchange coupling; Py; FeMn; Co; Fe; magnetic anisotropy

  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.02.2008, Berlin, Germany

Publ.-Id: 10781

Magnetic microstructures produced by local ion irradiation induced interfacial mixing

Strache, T.; Grenzer, J.; Fassbender, J.; Möller, W.; Kaltofen, R.; Mönch, I.

Ion irradiation of Ni80Fe20/Ta multilayers induces an interfacial mixing of these two materials, which subsequently leads to a suppression of the ferromagnetic properties. In order to quantify the structural change grazing incidence x-ray reflectometry has been used. The ion irradiation induced intermixing has been studied by means of TRIDYN simulations. The broadening of the interfaces due to intermixing causes an enrichment of Ta in Ni80Fe20 and finally an amorphization of Ni80Fe20 above a Ta concentration of 10 to 20 percent [1]. Consequently the ferromagnetic properties are altered or even suppressed completely for high enough ion fluences. It is observed that the critical ion fluence for a complete suppression of the ferromagnetism depends sensitively on the number of interfaces. It is demonstrated that pure magnetic microstructures can be easily fabricated by local ion irradiation without changing the substrate topography.

[1] J. Fassbender et al., Nucl. Instr. and Meth. in Phys. Res. B 248, 343 (2006).

Keywords: magnetism; ion irradiation; amorphization; irradiation induced mixing; magnetic microstructures

  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10780

Facile synthesis of various nitro-substituted derivatives of semaxinib (SU 5416)

Knieß, T.; Kuchar, M.; Wüst, F.

The synthesis of novel nitro-substituted derivatives of the tyrosine kinase inhibitor SEMAXINIB (SU 5416) is described. The reaction of various substituted oxindoles with 3,5-dimethylpyrrol-2-carbaldehyde derivatives under Knoevenagel conditions gave an array of nitro-substituted derivatives of Semaxinib (SU 5416) in high yields of 72-87%.

Keywords: Nitration; semaxinib; tyrosine kinase

Publ.-Id: 10779

Surface improvement and biocompatibility of TiAl24Nb10 intermetallic alloy using rf plasma nitriding

Abd El-Rahman, A. M.; Maitz, M. F.; Kassem, M. A.; El-Hossary, F.; Prokert, F.; Reuther, H.; Pham, M. T.; Richter, E.

The present work describes the surface improvement and biocompatibility of TiAl24Nb10 intermetallic alloy using rf plasma nitriding. The nitriding process was carried out at different plasma power from 400 W to 650 W where the other plasma conditions were fixed. Grazing incidence X-ray diffractometry (GIXRD), Auger electron spectroscopy (AES), tribometer and a nanohardness tester were employed to characterize the nitrided layer. Further potentiodynamic polarization method was used to describe the corrosion behavior of the un-nitrided and nitrided alloy. It has been found that the Vickers hardness (HV) and corrosion resistance values of the nitrided layers increase with increasing plasma power while the wear rates of the nitrided layers reduce by two orders of magnitude as compared to those of the un-nitrided layer. This improvement in surface properties of the intermetallic alloy is due to formation of a thin modified layer which is composed of titanium nitride in the alloy surface. Moreover, all modified layers were tested for their sustainability as a biocompatible material. Concerning the application area of biocompatibility, the present treated alloy show good surface properties especially for the nitrided alloy at low plasma power of 400 W.

  • Applied Surface Science 253(2007), 9067-9072

Publ.-Id: 10778

Radiolabeled glucocorticoids as molecular probes for imaging brain glucocorticoid receptors by means of positron-emission-tomography (PET)

Steiniger, B.; Knieß, T.; Bergmann, R.; Pietzsch, J.; Wüst, F.

Over the last two decades, numerous attempts have been made to develop
11C- and 18F-labeled radiotracers in order to study glucocorticoid receptor (GR)-mediated abnormalities of the hypothalamus-pituitary-adrenocortical (HPA) axis function and regulation in vivo by means of positron emission tomography (PET). The present review wants to address the research efforts dealing with the design, radio-synthesis and radiopharmacological evaluation of PET radiotracers for brain GR im-aging. The underlying problems such as metabolic instability, insufficient blood-brain-barrier penetration and/or high non-specific binding will be discussed.

  • Mini-Reviews in Medicinal Chemistry 8(2008)7, 728-739

Publ.-Id: 10777

Ion irradiation induced local creation of ferromagnetism in Fe60Al40 alloys

Strache, T.; Liedke, M. O.; Fassbender, J.; Möller, W.; Menendez, E.; Sort, J.; Gemming, T.; Weber, A.; Heyderman, L. J.; Rao, K. V.; Deevi, S. C.; Nogues, J.

Ion irradiation of Fe60Al40 alloys results in the phase transformation from the paramagnetic, chemically
ordered B2-phase to the ferromagnetic, chemically disordered A2-phase. The magnetic phase transformation is related to the number of displacements per atom (dpa) during the irradiation. For heavy ions (Ar+, Kr+, Xe+) a universal curve is observed with a steep increase in the fraction of ferromagnetic phase reaching saturation, i. e., a complete phase transformation, at about 0.5 dpa. This proves the purely ballistic nature of the disordering process. If light ions are used (He+, Ne+) a pronounced deviation from the universal curve is observed. This is attributed to bulk vacancy diffusion from dilute collision cascades, which leads to a partial recovery of the thermodynamically favored B2-phase. Comparing different noble gas ion irradiation experiments allows to asses the corresponding counteracting contributions. In addition, the potential to create local ferromagnetic areas embedded in a paramagnetic matrix is demonstrated.

Keywords: magnetism; ion irradiation; binary alloys; intermetallic; FIB; patterning

  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10776

Self-organized surface ripples as a source of magnetic anisotropies

Fassbender, J.; Liedke, M. O.; Keller, A.; Facsko, S.; Marko, D.; Hanisch, A.; Grenzer, J.; Cizmar, E.; Zvyagin, S.

In thin film magnetism surface and interfacemorphologies are important sources of magnetic anisotropy. This can be either due to the reduced coordination of step edge atoms (intrinsic contribution) or due to magnetic stray fields emanating from the film corrugation (extrinsic contribution). Low energy ion erosion is perfectly suited to create a periodic surface modulation (so-called ripples) on the nanoscale. By changing the primary energy of the ions the ripple periodicities can be varied from 20 to 150 nm. Subsequently, thin magnetic films are deposited on these template systems in order to investigate the influence of the surface morphology on the induced magnetic anisotropies. For small ripple periodicities a strong uniaxial magnetic anisotropy is found which rapidly decrease for larger ripple periodicities. In the case of Permalloy (Ni81Fe19) the induced anisotropy can be more than a factor of 20 larger compared to the intrinsic anisotropy of flat Permalloy. The microscopic origin of this effect will be discussed.

Keywords: magnetism; ion erosion; self-organization; magnetic anisotropies; ferromagnetic resonance

  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10775

Magnetic thin film materials tailored by ion irradiation

Fassbender, J.

In recent years the tailoring of magnetic properties by means of ion irradiation techniques has become fashionable.
Since the magnetic properties of multilayers depend sensitively on the mutual interfaces a modification of these interfaces by ion irradiation leads to a local modification of the magnetic anisotropy, the exchange bias or the interlayer exchange coupling [1,2]. Also structural phase transitions can be induced by ion irradiation. If these are accompanied by magnetic phase transformations ferromagnetic regions can immediately be written with a focused ion beam. In addition to pure radiation effects also doping effects can be exploited to achieve a pure magnetic patterning. Finally ion erosion of semiconductor substrates can be used as periodically modulated substrates which modify the magnetic anisotropies of subsequently deposited magnetic films.
Examples of all different approaches will be presented in order to demonstrate the large viability of ion beam technology to tailor magnetic materials.
Refs.: [1] J. Fassbender, D. Ravelosona,Y. Samson, J. Phys. D 37, R179 (2004). [2] J. Fassbender, J. McCord, J. Magn. Magn. Mater. 320, 579 (2008).

Keywords: magnetism; ion irradiation; FIB; self-organization; ripples

  • Invited lecture (Conferences)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10774

Absence of superconductivity in boron-implanted diamond

Heera, V.; Höhne, R.; Ignatchik, O.; Reuther, H.; Esquinazi, P.

Recently, superconductivity has been found in heavily boron doped diamond prepared by high temperature/ high pressure synthesis or chemical vapour deposition. An alternative doping method of technological relevance is ion implantation. It is an open question whether superconductivity can also be obtained in boron implanted diamond. Here we report on the transport and magnetic properties of high-dose (2.3x1016-1.7x1017 cm-2) boron-implanted natural IIa diamond samples doped at elevated temperature of 900°C and subsequently annealed at 1500°C and 1700°C. For comparison implantation at room temperature was also carried out. The samples were further characterized by Raman and infrared spectroscopy. No superconductivity could be detected in the samples at temperatures down to 40 mK. We discuss the possible origin for the absence of superconductivity.

Keywords: diamond; boron implantation; implantation damage; graphitization; resistance; superconductivity; magnetic and electrical properties

Publ.-Id: 10773

Combining theoretical chemistry and XANES multi-edge experiments to probe actinide valence states

Fillaux, C.; Berthet, J.-C.; Conradson, S. D.; Guilbaud, P.; Guillaumont, D.; Hennig, C.; Moisy, P.; Roques, J.; Simoni, E.; Shuh, D. K.; Tyliszczak, T.; Castro-Rodriguez, I.; Den Auwer, C.

Both structural and electronic properties of the actinide cations are of fundamental interest in order to describe the intramolecular interactions. The 5f and 6d orbitals are the first partially or totally vacant states of these elements and their properties reflect the nature of the actinideeligand bond. Because of its chemical and orbital selectivities, XANES spectroscopy is useful to probe the actinides’ frontier orbitals and then understand the cation reactivity toward chelating ligands. The actinide L3 edge contains structural information on the coordination polyhedron because of important scattering features. But very little electronic information can be extracted, due to the short core-hole lifetime, broadening the edge signal. On the other hand, the actinide M4,5 edges provide a better resolution and allow one to achieve electronic and structural information. Furthermore, coupling simulations of the experimental spectra and quantum chemical calculations lead to quantitative information such as the determination of the actinide coordination sphere and its effective charge. To cite this article: C. Fillaux et al., C. R. Chimie 10 (2007). 2007 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Publ.-Id: 10772

RPV Material Investigation of the Former VVER-440 Greifswald NPP

Rindelhardt, U.; Viehrig, H.-W.; Konheiser, J.; Noack, K.; Schuhknecht, J.; Gleisberg, B.

The real toughness response of RPV material can only be determined after the final shut down of the NPP. Such a chance is given now by investigating material from the former Greifswald NPP (VVER-440/230).
In the first part the paper deals with fast neutron fluence calculations and retrospective dosimetry based on Niobium. Unfortunately, a second neutron reaction besides 93Nb(n,n’) leading to 93mNb-activity is the reaction 92Mo(n,γ)93Mo. Based on the found Nb and Mo contents in the RPV material, it turns out that the 93mNb generation on the Mo path mostly dominates over the fast neutron induced generation from Nb.
The comparison between the calculated and the measured 93mNb activities typically resulted in deviations of 50%. Possible reasons for the observed differences are discussed.
In the second part first results of fracture mechanic investigations are reported. SE(B) specimens from three thickness positions were tested and evaluated according to the test standard ASTM E1921-05. Cleavage fracture toughness values, KJc, were determined and Master Curve based reference temperatures (T0) were evaluated. The T0 measured on the surface of this RPV does not show the highest value and, thus, reflect the conservative condition. The T0 of disc 1-1.3 located between the surface and ¼ thickness is about 40K higher compared with the surface.
The KJc values adjusted to a specimen thickness of 1T are enveloped by the WWER specific lower bound fracture toughness curve suggested in the VERLIFE procedure.
The measured KJc values are not enveloped by the 5% fractile indexed with T0 according to the Master Curve concept. However, the 5% fractile indexed with the VERLIFE reference temperature RTTo that includes an additional margin envelops the measured KJc values. Therefore the VERLIFE lower bound curve conservatively describes the fracture toughness of the investigated weld metal.

Keywords: VVER reactor; neutron fluence; Monte-Carlo calculation; retrospective dosimetry; neutron embrittlement; RPV material; Master Curve application

Publ.-Id: 10771

P-Implantation in voramorphisiertes Ge und anschließende Temperung: Festphasen-Epitaxie, P-Diffusion und -Aktivierung

Posselt, M.; Schmidt, B.; Anwand, W.; Grötzschel, R.; Heera, V.; Wündisch, C.; Skorupa, W.; Hortenbach, H.; Gennaro, S.; Bersani, M.; Giubertoni, D.; Möller, A.; Bracht, H.

For details please contact the first author

Keywords: germanium; ion implantation; annealing; phosphorus; diffusion; activation

  • Lecture (Conference)
    38. Treffen der Nutzergruppe Ionenimplantation, 09.11.2007, Dresden, Germany

Publ.-Id: 10770

The truth about ferromagnetic ZnO

Potzger, K.; Zhou, S.; Talut, G.; Kuepper, K.; Reuther, H.; Mücklich, A.; Grenzer, J.; Helm, M.; Fassbender, J.; Schmidt, H.; Xu, Q.; Lorenz, M.

The combination of magnetic and semiconducting properties in oxides is currently one of most popular fields in materials research. Besides the expected gain of knowledge about basic physics, such materials have a large application potential in spin electronics. We present a summary of our results on transition metal doping of ZnO single crystals and thin films by means of ion implantation. We found that none of the samples investigated represents a diluted magnetic semiconductor as predicted by theory [1]. Nevertheless, transition metal ions can be dispersed within the ZnO matrix residing on different sites within the lattice depending on initial preparation conditions. The observed ferromagnetism mainly originates from secondary phase formation (metals or inverted spinels). We discuss the potential of those granular structures in spin-electronics. Moreover, we highlight the suppression of secondary phase formation by means of deliberately lowering the crystalline quality prior to the doping. In that case, purely defect induced ferromagnetic properties are observed. The effect of spin doping of such a defect induced ferromagnet is discussed.
[1] K. Sato and H. Katayama-Yoshida, Physica E 10, 251 (2001).

Keywords: Diluted magnetic semiconductors; ZnO; functional oxides

  • Invited lecture (Conferences)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.2.2008, Berlin, Germany

Publ.-Id: 10769

Fifty Years of radiopharmacy at Rossendorf

Spies, H.; Steinbach, J.

The Central Institute of Nuclear Research was founded in Rossendorf near Dresden in 1956 and the production of radioactive materials and radiopharmaceuticals was started in 1958. The basis for the production was the irradiation of targets in the Rossendorf research reactor and, to a lower extent, at the Rossendorf cyclotron U-120.

This paper gives an account of the accomplishments of Rossendorf in the field of radiopharmacy from the early fifties, in the former department of 'Radioactive Isotopes', till to date. The production of radiopharmaceuticals is reviewed in brief. Investigations in technetium chemistry and pharmacology are discussed in more details, and efforts to set up positron emission tomography (PET) in Rossendorf, as the first PET centre in the former Eastern Block, are described. Nowadays, the research in radiopharmacy is carried out within the well-equipped Institute of Radiopharmacy, established in 1992.

  • Journal of Labelled Compounds and Radiopharmaceuticals 50(2007), 895-902
    DOI: 10.1002/jlcr.1431

Publ.-Id: 10768

Simultaneous determination of beta nuclides by liquid scintillation spectrometry

Nebelung, C.; Jähnigen, P.; Bernhard, G.

The determination of radionuclides in environmental samples is of importance, because a large amount of hazardous radionuclides have been released into the biosphere and spread over large areas by weapon tests, releases from nuclear power plants or nuclear fuel reprocessing facilities. Many nuclides are radiotoxic even in small concentrations. Therefore, it is necessary to determine these nuclides at low levels. The usual way to analyze samples of several nuclides involves time-consuming chemical separations followed by activity measurement of the isolated nuclides. An alternative method is the simultaneous measurement of the nuclides by recording and analyzing the liquid scintillation spectra.
The nuclides 3H, 14C, 55Fe, 60Co, 90Sr, 99Tc, 137Cs were measured in various combinations of mixtures as well as with the TRICARB 3000 and Wallac1414a/b (both devices from PerkinElmer).
The TRICARB 3000 was used to measure up to three nuclides in one sample with the assay type dpm (triple) with a good accuracy even for large activity differences and beta energies close together. It is necessary to generate quench curves for each nuclide.
The multi nuclide spectra measured in the cpm mode in the Wallac1414 were deconvoluted with the knowledge of the shape of the single nuclide spectra [1]. In this case has to be considered the difference between the measured and fitted counts (cpm) and the real activity (dpm) subsequentlyThe spectra deconvolution allows to determine more than three nuclides in one sample but with a lower accuracy.
[1] C. Nebelung et al. 2007 Appl. Radiat. Isot. 65, 209-217

Keywords: liquid scintillation; beta-nuclide; beta-spectrum; deconvolution

  • Lecture (Conference)
    LSC 2008, Advances in Liquid Scintillation Spectrometry, 25.-30.05.2008, Davos, Switzerland
  • Contribution to proceedings
    LSC 2008, International Conference on Advances in Liquid Scintillation Spectrometry, 25.-30.05.2008, Davos, Switzerland
    Book of Abstracts, Villigen Schweiz: PSI Paul Scherrer Institut
  • Contribution to proceedings
    LSC 2008, International Conference on Advances in Liquid Scintillation Spectrometry, 25.-30.05.2008, Davos, Switzerland
    Radiocarbon 2009, Tucson, USA: University of Arizona, 978-0-9638314-6-0, 193-201

Publ.-Id: 10767

Das Hochfeld-Magnetlabor in Dresden – 100 Tesla für die Forschung

Herrmannsdörfer, T.; Wosnitza, J.

  • Physik in unserer Zeit 38(2007), 242-248

Publ.-Id: 10766

Quasiparticle Model of Quark-Gluon Plasma at Imaginary Chemical Potential

Bluhm, M.; Kämpfer, B.

A quasiparticle model of the quark-gluon plasma is compared with lattice QCD data for purely imaginary chemical potential. Net quark number density, susceptibility as well as the deconfinement border line in the phase diagram of strongly interacting matter are investigated. In addition, the impact of baryo-chemical potential dependent quasiparticle masses is discussed. This accomplishes a direct test of the model for non-zero baryon density. The found results are compared with lattice QCD data for real chemical potential by means of analytic continuation and with a different (independent) set of lattice QCD data at zero chemical potential.

Keywords: quasiparticle model; imaginary chemical potential

  • Physical Review D 77(2008), 034004

Publ.-Id: 10765

Photoactivation of 92Mo and investigation of the short-lived isomer in 91Mo with the new pneumatic delivery system at ELBE

Erhard, M.; Bemmerer, D.; Beyer, R.; Crespo, P.; Fauth, M.; Grosse, E.; Junghans, A. R.; Klug, J.; Kosev, K.; Rusev, G.; Schilling, K. D.; Schwengner, R.; Wagner, A.

The photodisintegration cross section of the nucleus 92Mo is important for p-process nucleosynthesis. The superconducting electron accelerator ELBE at Forschungszentrum Dresden-Rossendorf provides the possibility to investigate photodisintegration with bremsstrahlung using the photoactivation technique. The reaction 92Mo(gamma,p)91Nb was studied using the decay of 91mNb with a 60.9 d half-life at ELBE [1]. Now the reaction 92Mo(gamma,n)91Mo has been probed using the new pneumatic delivery system to determine the activity of 91mMo (half-life: 65 s). Since the isomer 91mMo decays also into 91mNb it was necessary to measure this process to separate the (gamma,n) from (gamma,p) contributions.
[1] M. Erhard, C. Nair et al., PoS (NIC-IX) 056 (2006)

Keywords: photodisintegration; p-process; nucleosynthesis; bremsstrahlung; photoactivation; pneumatic delivery

  • Lecture (Conference)
    Frühjahrstagung der DPG, 2007, 13.03.2007, Gießen, Germany

Publ.-Id: 10764

Experimente mit reellen Photonen für die nukleare Astrophysik

Wagner, A.

Experimente am ELBE Bescheuniger zur Photonenstreuung, Photoaktivierung wurden vorgestellt

  • Invited lecture (Conferences)
    Vortrag vor dem Fachbereich Physik der Technischen Universität Darmstadt, 31.10.2007, Darmstadt, Germany

Publ.-Id: 10763

Kerne und Sterne

Wagner, A.

Vortrag vor der Astronomischen Arbeitsgemeinschaft Nürnberg e.V.

  • Lecture (others)
    Besuch der Nürnberger Astronomischen Arbeitsgemeinschaft, 02.11.2007, Dresden, Germany

Publ.-Id: 10762

Jahrestagung Kerntechnik - Sektionsbericht Sektion: Thermo- und Fluiddynamik

Stieglitz, R.; Kliem, S.

Der Beitrag gibt einen Überblick über die in den Sitzungen der Sektion Thermo- und Fluiddynamik gehaltenen Vorträge.

  • atw - International Journal for Nuclear Power 52(2007)10, 652-654

Publ.-Id: 10761

Investigation of antimagnetic rotation in light Cadmium nuclei: Cd-106,Cd-108

Simons, A.; Wadsworth, R.; Jenkins, D.; Clark, R.; Cromaz, M.; Deleplanque, M.; Diamond, R.; Fallon, P.; Lane, G.; Lee, I.; Macchiavelli, A.; Stephens, F.; Svensson, C.; Vetter, K.; Ward, D.; Frauendorf, S.; Gu, Y.

The lifetimes of excited states belonging to the lowest lying positive-parity bands in Cd-106,Cd-108 have been measured using the Doppler-shift attenuation method. The resulting B(E2) transition rates show a significant decrease with increasing spin in Cd-106, whereas in Cd-108 there is tentative evidence for a similar effect. The results are compared with cranking and semiclassical model calculations, which indicate that the structures have the properties expected from an "antimagnetic" rotational band resulting from the coupling of g(9/2) proton holes to aligned pairs of h(11/2) and g(7/2) neutron particles.


  • Physical Review C 72(2005), 024318

Publ.-Id: 10760

Evidence for Zn vacancy – hydrogen complexes in ZnO single crystals

Brauer, G.; Anwand, W.; Grambole, D.; Grenzer, J.; Skorupa, W.; Cizek, J.; Kuriplach, J.; Prochazka, I.; Ling, C. C.; So, C. K.; Schulz, D.; Klimm, D.

A systematic study of various, nominally undoped ZnO single crystals, either hydrothermally grown (HTG) or melt grown (MG), has been performed. The crystal quality has been assessed by x-ray diffraction, and a comprehensive estimation of the detailed impurity and hydrogen contents by inductively coupled plasma mass spectrometry and nuclear reaction analysis, respectively, has been made also. High precision positron lifetime experiments show that a single positron lifetime is observed in all crystals investigated, which clusters at 180–182 ps and 165–167 ps for HTG and MG crystals, respectively. Furthermore, hydrogen is detected in all crystals in a bound state with a high concentration (at least 0.3 at. %), whereas the concentrations of other impurities are very small. From ab initio calculations it is suggested that the existence of Zn-vacancy–hydrogen complexes is the most natural explanation for the given experimental facts at present. Furthermore, the distribution of H at a metal/ZnO interface of a MG crystal, and the H content of a HTG crystal upon annealing and time afterward has been monitored, as this is most probably related to the properties of electrical contacts made at ZnO and the instability in p-type conductivity observed at ZnO nanorods in literature. All experimental findings and presented theoretical considerations support the conclusion that various types of Zn-vacancy–hydrogen complexes exist in ZnO and need to be taken into account in future studies, especially for HTG materials.

Keywords: zinc oxide; single crystal; positron lifetime; nuclear reaction analysis; X-ray diffraction; Inductively Coupled Plasma Mass Spectrometry; hydrogen; open volume defects; zinc vacancy-hydrogen complexes; ab initio calculations

  • Physical Review B 79(2009), 115212

Publ.-Id: 10759

Quantification of DNA double strand breaks

Beyreuther, E.

Introduction and explanation of the quantification of DNA double strand breaks. First results measured for the time, dose and energy dependence for the induction of double strand breaks in cell line 184A1 are shown. Future plans are given.

  • Lecture (others)
    Seminar AG Mikrobiologie, 01.11.2007, Freiberg, Germany

Publ.-Id: 10758

Radiosynthesis of n.c.a. sodium [18F]fluoroacetate and radiopharmacological characterization in rats and tumour-xenografted mice

Richter, S.; Bergmann, R.; Pietzsch, J.; Beuthien-Baumann, B.; Wüst, F.

A convenient remotely-controlled synthesis of no-carrier-added sodium [18F]fluoroacetate is described. Three ethyl esters 1a-1c and three tert.-butyl esters 3a-3c containing either a methanesulfonyloxy- (OMs), p-toluenesulfonyloxy- (OTs) or p-nitrobenzenesulfonyloxy (ONs) leaving group were investigated as labelling precursors. The optimized radiosynthesis of n.c.a. sodium [18F]fluoroacetate was performed in two steps: (1) Incorporation of fluorine into (methanesulfonyloxy)-acetic acid tert.-butyl ester 3a as the superior labelling precursor in acetonitrile at 100°C for 5 min followed by (2) acidic hydrolysis of the resulting [18F]fluoroacetic acid tert.-butyl ester at 100°C for 10 min to afford [18F]fluoroacetic acid. Several consecutive purification steps using anion exchange cartridges (Alltech Maxi-Clean SAX) and Sep-Pak neutral alumina cartridges gave sodium [18F]fluoroacetate in reproducible radiochemical yields of 20-25% (decay-corrected, n=20) in high radiochemical purity (>99%) within 50 min. Radiopharmacological characterization of sodium [18F]fluoroacetate was studied in Wistar rats and HT-29 tumour-bearing mice in comparison with [11C]acetate.

  • Current Radiopharmaceuticals 1(2008)2, 103-109

Publ.-Id: 10757

Characterization of sputtered Shape Memory Alloy Ni-Ti films by cross-sectional TEM and SEM

Martins, R. M. S.; Mücklich, A.; Schell, N.; Silva, R. J. C.; Mahesh, K. K.; Braz Fernandes, F. M.

Characterization of sputtered Shape Memory Alloy Ni-Ti films by cross-sectional TEM and SEM

Keywords: shape memory alloy; Ni-Ti films TEM; SEM

  • Poster
    INCOMAM’07 - International Conference on Microscopy and Microanalysis - XLII Congress of the Portuguese Microscopy Society, 06.-07.12.2007, Coimbra, Portugal
  • Microscopy and Microanalysis 14(2008)supp 3, 85-86
    DOI: 10.1017/S1431927608089460

Publ.-Id: 10756

Spektroskopische Untersuchung der Uran(IV)- und Uran(VI)-Komplexierung mit organischen Modellliganden

Schmeide, K.; Joseph, C.; Raditzky, B.

Spektroskopische Bestimmung von Stabilitätskonstanten für die U(VI)/U(IV)-Komplexierung durch Modellliganden

Keywords: Uran; hexavalent; tetravalent; Citronensäure; Benzolsulfonsäure; 4-Phenolsulfonsäure

  • Lecture (others)
    Workshop zum Forschungsvorhaben "Wechselwirkung und Transport von Actiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika", 11.-12.10.2007, Saarbrücken, Germany

Publ.-Id: 10755

Untersuchungen zur Isomerie des Komplexes [86Y((S) p NH2 bz DOTA)]-

Schlesinger, J.; Tamburini, S.; Bolzati, C.; Tisato, F.; Noll, B.; Bergmann, R.; Pietzsch, H.-J.

Radioisotope des Yttriums und der Lanthaniden werden zu einer immer wichtigeren Komponente in medizinischen Applikationen, z. B. für die nicht-invasive in vivo-Bildgebung oder die Endoradionuklidtherapie von Tumorerkrankungen. Die Konjugation dieser dreiwertigen Metallionen an biologisch aktive Moleküle erfolgt in der Regel über bifunktionelle Chelatoren, z.B. 1,4,7,10-Tetraazacyclododecan-N,N’,N’’,N’’’-tetraessigsäure (DOTA). Die entsprechenden Metall-DOTA-Komplexe zeichnen sich durch eine hohe thermodynamische und kinetische in vivo Stabilität aus. Lanthaniden- und Yttrium-Komplexe optisch aktiver DOTA-Chelatoren treten jedoch als Konformationsisomere auf, über deren in vivo Verhalten, insbesondere über ihren Einfluss auf die markierten Moleküle nur wenig bekannt ist.

Zur Untersuchung der Isomerie des radioaktiven Komplexes [86Y((S) p NH2 bz DOTA)]- wurde der nicht-radioaktive, strukturell analoge Komplex [Y((S) p NH2 bz DOTA)]- synthetisiert und charakterisiert. Zwei Isomere des [Y((S) p NH2 bz DOTA)]- Komplexes wurden über die HPLC getrennt und mittels NMR- und CD-Messungen als Konformationsisomere identifiziert. Die Isomere liegen in einer quadratisch antiprismatischen (SAP) und einer verdrillt quadratisch antiprismatischen (TSAP) Geometrie vor.

Untersuchungen zur Bioverteilung der [86Y((S) p NH2 bz DOTA)]- Isomere in Wistar Ratten zeigten bereits nach 5 min unterschiedliche SUV-Werte (standardized uptake value) für beide Isomere in der Leber ((TSAP) 1,65 ± 0,45; (SAP) 0,50 ± 0,04). Der Vergleich der experimentell bestimmten logD7,0 Werte beider Isomere weist auf eine höhere Lipophilie des TSAP-Isomeren hin (logD7,0: (TSAP) -2,0 ± 0,029; (SAP) -2,3 ± 0,032). Bei der thermischen Behandlung der Isomere bei 90°C konnte auch nach 168 h keine gegenseitige Umwandlung beobachtet werden.

Die unterschiedlichen physikalischen Eigenschaften der [86Y((S) p NH2 bz DOTA)]- Konformationsisomere und deren unterschiedliche Bioverteilung zeigen, dass es unbedingt notwendig ist, den Einfluss der Chelateinheit auf das biologische Verhalten von Metallopharmaka zu berücksichtigen.

  • Poster
    Wissenschaftsforum Chemie 2007, GDCh-Jahrestagung, 16.-19.09.2007, Ulm, Germany

Publ.-Id: 10754

Growth and optical characterization of dielectric/metal nanocomposites

Baumgart, C.; Abendroth, B.; Abrasonis, G.; Kolitsch, A.; Möller, W.

Thin films of Ag nanoclusters embedded in dielectric aC and SiO2 media have been prepared by pulsed cathodic arc and dual magnetron sputtering. The optical properties of the composite layers have been investigated by spectroscopic ellipsometry. The results show the dependence of the plasmon resonance band of the Ag particles from temperature and Ag concentration.

  • Lecture (Conference)
    VEIT 2007 - Fifttienth International Summer School on Vacuum, Electron and Ion Technologies, 17.-21.09.2007, Sozopol, Bulgaria

Publ.-Id: 10753

Quasifree Lambda, Sigma0, and Sigma- electroproduction from 1,2H, 3,4 He, and Carbon

Dohrmann, F.; Ahmidouch, A.; Armstrong, C. S.; Arrington, J.; Asaturyan, R.; Avery, S.; Bailey, K.; Baker, O. K.; Bitao, H.; Breuer, H.; Brown, D. S.; Carlini, R.; Cha, J.; Chant, N.; Christy, E.; Cochran, A.; Cole, L.; Crowder, J.; Danagoulian, S.; Elaasar, M.; Ent, R.; Fenker, H.; Fujii, Y.; Gan, L.; Garrow, K.; Geesaman, D. F.; Gueye, P.; Hafidi, K.; Hinton, W.; Juengst, H.; Keppel, C.; Liang, Y.; Liu, J. H.; Lung, A.; Mack, D.; Markowitz, P.; Mitchell, J.; Miyoshi, T.; Mkrtchyan, H.; Mtingwa, S. K.; Mueller, B.; Niculescu, G.; Niculescu, I.; Potterveld, D. H.; Raue, B. A.; Reimer, P. E.; Reinhold, J.; Roche, J.; Sarsour, M.; Sato, Y.; Segel, R. E.; Semenov, A. Y.; Stepanyan, S.; Tadevosian, V.; Tajima, S.; Tang, L.; Uzzle, A.; Wood, S.; Yamaguchi, H.; Yan, C.; Yuan, L.; Zeier, M.; Zeidman, B.; Zihlmann, B.

Kaon electroproduction from light nuclei and hydrogen, using 1H, 2H, 3He, 4He, and carbon targets has been measured at Jefferson Laboratory. The quasifree angular distributions of Lambda and Sigma hyperons were determined at Q^2= 0.35 (GeV/c)^2 and W= 1.91 GeV. Electroproduction on hydrogen was measured at the same kinematics for reference.

Keywords: Electroproduction of Strangeness; Hyperons; Hypernuclear Physics

Publ.-Id: 10751

MOS light emitting devices based on rare-earth ion implantation

Rebohle, L.; Skorupa, W.

In this article we will give an overview of our work to Si-based light emission which was done in the last years. Si-based light emitters were fabricated by ion implantation of rare earth elements into the oxide layer of a conventional MOS structure. Efficient electroluminescence was obtained for the wavelength range from UV to the visible by using a transparent top electrode made of indium-tin oxide. In the case of Tb-implantation the best devices reach an external quantum efficiency of 16 % which corresponds to a power efficiency in the order of 0.3 %. The properties of the microstructure, the IV characteristics and the electroluminescence spectra were evaluated. The electroluminescence was found to be caused by hot electron impact excitation of rare earth ions, and the electric phenomena of charge transport, luminescence centre excitation, quenching and degradation are explained in detail.

Keywords: Electroluminescence; Silicon-based light emission; Rare earth ion implantation

  • Contribution to external collection
    in: Advances in Light Emitting Materials, Stafa-Zurich: Trans Tech Publications Ltd, 2008, 117-138

Publ.-Id: 10749

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