Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34122 Publications

Investigation of Si nanocluster formation in sputter deposited silicon sub-oxides for nanocluster-memory structures

Schmidt, J.-U.; Schmidt, B.

In silicon-nanocluster (Si-NC) memories, Si-NC embedded in the gate oxide of a MOSFET are used to store and release electrons thereby modifying the threshold of a transistor. This article describes the formation of its core functional structure, the Si-NC MOS memory capacitor, by annealing a SiO2/SiOX (x < 2) stack, deposited onto a thin direct tunneling oxide on silicon by a sputtering method. To achieve a high density of isolated Si-NC, both, the initial silicon excess in the SiOX layer and the thermal annealing treatment must be optimized. Optimum conditions are expected just at the end of the nucleation stage of the NC ensemble. Therefore the effect of various rapid thermal anneals (RTA) on SiOX/Si structures with different silicon excess x was investigated
focusing on two optical methods: infrared absorption and photoluminescence (PL). The rate of nucleation and phase separation was found to depend strongly on both, silicon excess and annealing temperature. The characteristic size dependence of Si-NC PL was used to differentiate annealing regimes yielding NC ensembles being 'frozen' in the process of nucleation or in their growth/ripening phase respectively. Additionally, Si-NC MOS memory capacitors were prepared and characterized using both, optical and electrical tests. The devices prepared under optimized conditions yield a high flat-band shift and good charge retention characteristics.

Keywords: phase-separation; non-volatile memory; silicon nanocrystal; sputter deposition

  • Materials Science and Engineering B101 (2003) 28

Permalink: https://www.hzdr.de/publications/Publ-4524
Publ.-Id: 4524


FEM-Calculation of Different Creep-Tests with French and German RPV-Steels

Willschütz, H.-G.; Altstadt, E.; Sehgal, B. R.; Weiß, F.-P.

For calculations of Lower Head Failure experiments like FOREVER it is necessary to model creep and plasticity processes. Therefore a Finite Element Model is developed using a numerical approach which avoids the use of a single creep law employing constants derived from the data for a limited stress and temperature range. Instead of this a numerical creep data base (CDB) is developed where the creep strain rate is evaluated in dependence on the current total strain, temperature and equivalent stress. A main task for this approach is the generation and validation of the CDB. For an evaluation of the failure times a damage model according to an approach of Lemaitre is applied.
The validation of the numerical model is performed by the simulation of and compari-son with experiments. This is done in 3 levels: starting with the simulation of single uniaxial creep tests, which is considered as a 1D-problem. In the next level so called “tube-failure-experiments” are modeled: the RUPTHER-14 and the “MPA-Meppen”-experiment. These experiments are considered as 2D-problems. Finally the numerical model is applied to scaled 3D-experiments, where the lower head of a PWR is represented in its hemispherical shape, like in the FOREVER-experiments.
An interesting question to be solved in this frame is the comparability of the French 16MND5 and the German 20MnMoNi55 RPV-steels, which are chemically nearly identical. If these 2 steels show a similar behavior, it should be allowed to transfer experimental and numerical data from one to the other.

Keywords: FEM-Calculation; Creep-Tests; French and German RPV-steel

  • Lecture (Conference)
    17th International Conference on Structural Mechanics in Reactor Technology, SMiRT 17, Prague, Czech Republic, August 17-22, 2003
  • Contribution to proceedings
    17th International Conference on Structural Mechanics in Reactor Technology, SMiRT 17, Prague, Czech Republic, August 17-22, 2003

Permalink: https://www.hzdr.de/publications/Publ-4523
Publ.-Id: 4523


MoSys - ein Online-Zustandserkennungssystem für exotherme chemische Reaktionen

Hessel, G.; Hilpert, R.; Kryk, H.; Roth, M.; Schmitt, W.; Seiler, T.; Deerberg, G.

Es wird das entwickelte Online-Zustandserkennungssystem MoSys beschrieben, das dem Anlagenfahrer zusätzliche Informationen über den Prozessfortschritt, das voraussichtliche Reaktionsende, die Akkummulation von Edukten oder Zwischenprodukten oder über die Gefahr einer thermischen Explosion bei unzureichender Kühlung zur Verfügung stellt. Das Zustandserkennungssytem, das auf adaptiven Stoff-und Wärmebilanzen basiert, kann sowohl in direkter Kopplung mit dem Prozessleitsystem als auch als Komponente eines komplexen Batch-Informations-Management-Systems betrieben werden. Die Leistungsfähigkeit von MoSys konnte für homogen katalysierte Veresterungsreaktionen in einer Technikumsanlage und für heterogen katalysierte Hydrierprozesse in einer industriellen Chemieanlage nachgewiesen werden. Neben einer Erhöhung der Anlagen- und Umweltsicherheit wird durch den Einsatz von MoSys weiterführendes Prozesswissen generiert, das als Grundlage für eine Prozessoptimierung genutzt werden kann.

  • Lecture (Conference)
    Tagungsband der 6. GVC·VDI-Fachtagung "Anlagen-, Arbeits- und Umweltsicherheit", Köthen, 7./8. November 2002, Herausgeber: GVC·VDI-Gesellschaft Verfahrenstechnik und Chemieingenieurwesen, Düsseldorf, 2002, Vortrag E-05
  • Contribution to proceedings
    Tagungsband der 6. GVC·VDI-Fachtagung "Anlagen-, Arbeits- und Umweltsicherheit", Köthen, 7./8. November 2002, Herausgeber: GVC·VDI-Gesellschaft Verfahrenstechnik und Chemieingenieurwesen, Düsseldorf, 2002, Vortrag E-05

Permalink: https://www.hzdr.de/publications/Publ-4522
Publ.-Id: 4522


Design of CNS receptor imaging agents based on organometallic Tc(III) and Tc(I) complexes

Pietzsch, H.-J.; Alberto, R.

There is a considerable interest in the development of 99mTc radiopharmaceuticals for imaging serotonergic CNS receptors using single-photon emission tomography (SPET). To date most Tc compounds assigned as CNS receptor targeted agents are square-pyramidal complexes of the oxo ion [Tc=O]3+. However, the in vivo behaviour of such complexes are strongly influenced by the quite polar Tc=O unit offering a free position trans to the oxo ligand for further reaction in vivo. To reduce this in vivo reactivity, oxo-free Tc complexes containing the metal in lower oxidation states are considered to be appropriate alternatives.
Tc(III) mixed-ligand complexes (1) with tetradentate/monodentate NS3/isonitrile coordination appear suitable to wrap the metal well in a molecule with receptor-targeting functionality. The here introduced compounds contain a methoxyphenyl-piperazine moiety derived from the selective 5-HT1A receptor antagonist WAY 100,635 linked to the Tc chelate unit via an alkyl chain [1].

The low-pressure synthesis of a Tc-carbonyl precursor as inaugurated by Alberto et al. allows a convenient exploitation of the potential of the "Tc(CO)3" moiety in the design of receptor-binding agents [2]. A bidentate N-donor anchor group has been considered well suitable for combining the Tc(I) tricarbonyl center with the antagonist moiety (2). Alternatively, a bidentate thioether group to link the Tc(I) tricarbonyl center with 4,7-dithiaoctanoic acid (3beta-(4-fluorophenyl)tropane-2beta)-methyl ester (3) as receptor-targeting moiety has been chosen [3].
We report the synthesis, in vitro receptor affinity and biodistribution of three candidates in order to demonstrate the suitability of the concept and to elucidate the influence of the building blocks on the biobehaviour of the complexes.

Keywords: Technetium; radiopharmaceuticals; Tc(I) carbonyl complexes; Tc(III) isocyanide complexes; CNS receptor imaging; serotonin-5-HT1A receptor

  • Lecture (Conference)
    1. International Symposium on Bioorganometallic Chemistry, Paris, 18.-20.07.2002
  • Poster
    1. International Symposium on Bioorganometallic Chemistry, Paris, 18.-20.07.2002

Permalink: https://www.hzdr.de/publications/Publ-4521
Publ.-Id: 4521


A New Approach for a 11C-C Bond Formation: Synthesis of 17alpha-(3'-[11C]Prop-1-yn-1-yl)-3-Methoxy-3,17beta-Estradiol

Wüst, F.; Zessin, J.; Johannsen, B.

A new approach for a 11C-C bond formation via a Sonogashira-like cross-coupling reaction of terminal alkynes with [11C]methyl iodide was exemplified by the synthesis of 17alpha-(3'-[11C]prop-1-yn-1-yl)-3-methoxy-3,17beta-estradiol. The title compound was obtained in decay-corrected radiochemical yields of 27-47% (n=8) based on [11C]methyl iodide within 21-27 minutes after EOB. In a typical synthesis, 1-2 GBq of 17alpha-(3'-[11C]prop-1-yn-1-yl)-3-methoxy-3,17beta-estradiol was synthesized in radiochemical purity >99%. The specific activity ranged between 10-19 GBq/µmol, and the labeling position was verified by the synthesis of the corresponding 13C-labeled compound.

  • Journal of Labelled Compounds and Radiopharmaceuticals 46 (2003) 333-342

Permalink: https://www.hzdr.de/publications/Publ-4520
Publ.-Id: 4520


MHD investigations for material technologies at Forschungszentrum Rossendorf

Gerbeth, G.; Galindo, V.

A review will be given on the R&D activities in this field at FZR. Emphasis
will be given to the inverse approach to MHD problems comprising the tools
of model experiments and measuring techniques for metallic melts.
Applications of this approach to crystal growth problems will be presented.

  • Lecture (others)
    Vortrag bei Workshop "Use of magnetic fields in crystal growth", Riga (Latvia), June 13-14, 2002

Permalink: https://www.hzdr.de/publications/Publ-4519
Publ.-Id: 4519


Application of a rotating magnetic field to the VGF growth of GaAs: basics of melt control and growth results

Grants, I.; Gerbeth, G.; Wunderwald, U.; Pätzold, O.; Cröll, A.

The idea of an inverse design of the heat transfer during the VGF-growth of
GaAs will be presented. Optimization of the solid-liquid phase boundary is,
however, only possible by an additional melt flow control which is provided
here by a rotating magnetic field. Theoretical calculations and experimental
growth results will be compared.

  • Lecture (others)
    Vortrag bei Workshop "Use of magnetic fields in crystal growth", Riga (Latvia), June 13-14, 2002

Permalink: https://www.hzdr.de/publications/Publ-4518
Publ.-Id: 4518


On the dynamics of liquid metal ion sources

Mair, G.; Aidinis, C. J.; Bischoff, L.; Ganetsos, T.

The mechanisms govering the formation of the liquid metal cone that constitutes the basis of a liquid metal ion source (LMIS) are investigated. Cone formation times ranging from < 20 ns up to several hundreds of ms have been reported in the literature. The paper attempts to explain these differences by devising a theoretical model that encompasses inertial and flow effects.

Keywords: liquid metal ion source; cone formation time; model

  • Journal of Physics D: Applied Physics 35 (2002) 1392 - 1396

Permalink: https://www.hzdr.de/publications/Publ-4517
Publ.-Id: 4517


Simulation des Ausbreitungsverhaltens und der Kühlung einer Kernschmelze im Sicherheitsbehälter von LWR-Anlagen

Spengler, C.; Allelein, H.-J.; Breest, A.; Chakraborty, A. K.; Erdmann, W.; Heitsch, M.; Kelmes, I.; Scheuerer, M.; Rastogi, A. K.; Willschütz, H.-G.; Latché, J.-C.

Erkenntnisse zum Verhalten geschmolzener Kernmaterialien im Sicherheitsbehälter und zu deren langzeitiger Kühlung sind für die Begrenzung der Auswirkungen eines schweren Unfalles von erheblicher Bedeutung. Mit dem Bestreben, die Auswirkungen eines Kernschmelzunfalles auf die Anlage zu beschränken, kommt der zuverlässigen Simulation des Verhaltens einer Kernschmelze im Sicherheitsbehälter eine zentrale Bedeutung zu. Nach der Aufbereitung der verfügbaren einschlägigen Versuchsergebnisse und Modellansätze sind auf der Grundlage der dabei gewonnenen Erkenntnisse die zu modilierenden Einzelphänomene identifiziert, verfügbare Modellansätze bewertet und Prioritäten hinsichtlich Neu- bzw. Weiterenrwicklung von Modellen für Einzelphänomene gesetzt worden.

Für die Simulation der Schmelzeausbreitung ist ein auf vulkanologischen Ansätzen basierender Rechencode ausgewählt und unter dem Namen "LAVA" weiterentwickelt worden. In LAVA wird der Immobilisierungsprozess am Ende der Ausbreitung über eine nicht-Newtonsche Materialcharakteristik in Form einer vom Feststoffgehalt des erstarrenden Materials abhängigen Binghamschen Fließgrenze beschrieben. Zur Berechnung der rheologischen Stoffwerte Viskosität und Fließgrenze für erstarrende Schmelzen sind Korrelationen aus der Literatur ausgewählt und Modellparameter abgeschätzt worden. LAVA ist umfassend an den Experimenten der COMAS und KATS Versuchsreihe validiert worden.

Ein Konzept für das Gesamtmodell zum Schmelzeverhalten im Sicherheitsbehälter ist hinsichtlich der physikalischen und programmtechnischen Verknüpfung konzipiert worden, wobei die Randbedingungen für die Implementierung des Gesamtmodells COCOSYS berücksichtigt sind. Dieses Konzept sieht eine Kopplung eigenständiger Module für Schmelzeausbreitung (LAVA) und -kühlung (CCI) vor. Für die Neuformulierung des CCI-Moduls sind in detaillierten Untersuchungen grundlegende Erkenntnisse gewonnen worden: Die Leistungsfähigkeit von CFD-Codes für die Simulation von 3D-Wärmetransportphänomenen in Schmelzepools wurde in einem umfassenden Codevergleich analysiert. Ferner wurde ein Modell zur Beschreibung der bewegten Phasengrenzflächen bei Aufschmelz- bzw. Erstarrungsvorgängen in dem CFD-Code CFX implementiert und angewendet. Aus den hieraus gewonnenen Erkenntnissen ist ein Konzept für die Neuentwicklung des CCI-Moduls in COCOSYS erstellt worden.

Keywords: Kernschmelze in KKW; Verhalten im Sicherheitsbehälter; Schmelzeausbreitung und Kühlung; Anwendung verschiedener CFD-Codes

  • Other report
    Abschlussbericht, Gesellschaft für Anlagen- und Reaktorsicherheit (GRS (mbH), Reaktorsicherheitsforschung RS 1042, GRS-A-2959, Mai 2002

Permalink: https://www.hzdr.de/publications/Publ-4516
Publ.-Id: 4516


Intersubband transitions in strain compensated InxGa1-xAs/AlAs quantum well structures grown on InP substrates

Georgiev, N.; Semtsiv, M.; Dekorsy, T.; Eichhorn, F.; Bauer, A.; Helm, M.; Masselink, T.

There is considerable interest in developing shorter (< 3 mm) wavelength optical devices based on the intersubband transitions (ISBT) such as ultrafast switchers, modulators and quantum cascade lasers. The choice of the suitable system for short-wavelength ISBT is restricted to the combination of materials that provide an appropriate large conduction band offset. In this letter, we report the optical and structural characterization of the InxGa1-x As/AlAs, x>0.6, quantum well (QW) structures grown on InP substrates. In these structures, an increased In content helps to compensate the larger AlAs tensile strain. Secondly, it provides a smaller InGaAs band gap that results in a shift of the 1st G well subband to lower energies relative to the X minimum in the barrier layers even in very narrow wells.
We have grown InxGa1-xAs/AlAs MQW with InAlAs layers between QW's and superlattice (SL) structures with different well thickness by gas source MBE on semi-insulating InP(001) substrates. Since, the compressively strained InxGa1-xAs layers do not fully compensate the tensile strained AlAs barriers, an In0.55Al0.45As slightly compressive strained buffer layer was inserted. The buffer layer was grown at 490 C and the QW structure at 440 C. The InxGa1-x As wells were Si doped to 2.0x1018cm-3.
The X-ray diffraction pattern and a theoretical fit using a dynamical diffraction theory of the MQW sample with 7ML thick In0.7Ga0.3As and AlAs layers, and 20.0 nm In0.55Al0.45As barriers between the QW's is presented in Fig.1. The data show a very good fit to the model using interfaces with little or no compositional grading.
The transmission spectrum of this sample is shown in Fig.2. The band offsets were determined using the model-solid theory, and the energy-level diagram as calculated within the effective mass approximation of the designed structure is shown in the right inset of Fig.2. There is a relatively large deviation between the calculated and measured ISBT wavelength. Due to the large conduction band offset in this system, ~1.4 eV, the monolayer fluctuations of the well thickness can explain the shift to lower energies of the ISBT for the narrow QW structure compared to the calculated on the assumption of abrupt interfaces as well as its broader ISBT spectrum. In addition, the large In composition and the ability of In atoms to segregate at the surface of the growing InGaAs layer probably leads to excess In at the upper interfaces, although the growth temperature of the QW is decreased to 440 C. This causes a nominal decrease of the In composition in the well at the expense of the formation of an In rich composition in the interface and an eventual intermixing with AlAs, i.e. the formation of an additional InyAl1-yAs interface layer at the bottom side of the barrier. When we incorporate a modified band diagram assuming 1-2 ML In intermixing in the upper interfaces we can calculated an ISBT of 1.91 mm (left insert in Fig.2), which is close to the experimental value. Our interpretation of the intermixing at the interfaces is confirmed by photoluminescence spectra.

Keywords: intersubband transitions; quantum well structures; strain compensated structures; photoluminescence

  • Poster
    International symposium on compound semiconductors 2002, 07-10.10.2002, Lausanne, Switzerland, Institute of Physics Conference Series Number 174 (2002) 109-112
  • Contribution to proceedings
    International symposium on compound semiconductors 2002, 07-10.10.2002, Lausanne, Switzerland, Institute of Physics Conference Series Number 174 (2002) 109-112

Permalink: https://www.hzdr.de/publications/Publ-4515
Publ.-Id: 4515


Electroluminescence from thin SiO2 layers after Si- and C-Coimplantation

Gebel, T.; Rebohle, L.; Sun, J.; Skorupa, W.

The strong need for optoelectronic devices which can be integrated into the current silicon technology has initiated an extensive research for silicon-based light emitters. One of the promising approaches is the formation of luminescence centers in dielectric layers by means of ion beam synthesis. In this paper we explore the EL properties of thermally grown SiO2 layers co-implanted with silicon and carbon ions. The main motivation for this work was the expectation of a higher device stability using Si/C compounds within the SiO2 network compared to our former work with Ge and Sn implants. 360 nm thick SiO2 layers were implanted with Si, followed by an intermediate annealing step and a second implantation of C. Finally the structures were annealed at 1100°C. The doses were chosen in order to achieve peak concentrations of excess Si and C of 5-10 %. The devices show a broad PL between 400 and 600 nm with a main peak around 450 nm. The broad EL spectra show additional peaks around 370 nm and between 500-550 nm which are increased with decreasing Si/C concentration. The shape of the EL spectrum does not change with increasing injection currents, which implies that various types of defects occur for the different concentrations. The device stability is improved in comparison to Ge / Sn implanted oxide layers.

Keywords: nanocluster; ion implantation; electroluminescence

  • Physica E 16/3-4 (2003) 366-369
  • Poster
    E-MRS Spring Meeting, Symp. H, Strasbourg (France), 18.-21.06.2002

Permalink: https://www.hzdr.de/publications/Publ-4514
Publ.-Id: 4514


Correlation of charge trapping and electroluminescence in highly efficient Si-based light emitters

Gebel, T.; Rebohle, L.; Sun, J.; Skorupa, W.; Nazarov, A.; Osiyuk, I.

Silicon based light emitters are of great interest for future integrated optical systems. One possible approach for the formation of such devices is ion beam synthesis. Thermally grown SiO2 layers (80 nm) were implanted with germanium ions at energies of 30…50 keV to peak concentrations of 1…6 at%. Rapid thermal annealing was performed at 1000°C for 1…150 s under a nitrogen atmosphere in order to form luminescence centers. In previous investigations we observed strong photo- and electro-luminescence (EL) in the blue/violet wavelength range from such layers. In this paper we correlate these optical properties to effects of charge trapping which were observed by using a combination of capacitance-voltage (CV) and current-voltage (IV) methods. Electron trapping occurs at low electric fields. However, at high electric fields (>8MV/cm), which are typically required for the excitation of the defect related EL, positive charge trapping occurs. This might be attributed to hole trapping at oxygen deficiency centers - probably the same defects which cause the EL.

Keywords: nanocluster; ion implantation; charge trapping; electroluminescence

  • Physica E 16/3-4 (2003) 499-504
  • Poster
    E-MRS Spring Meeting, Symp. H, Strasbourg (France), 18.-21.06.2002

Permalink: https://www.hzdr.de/publications/Publ-4513
Publ.-Id: 4513


Atomistic study of ion beam deposition conditions for hard amorphous carbon

Belov, A.; Jäger, H.-U.

The effect of deposition temperature on the formation of hard amorphous carbon (a-C) films from low and medium energy ions was studied by atomic scale simulation. Applying classical molecular dynamics with a modified hydrocarbon potential of Brenner, ion-beam deposition of carbon films with a thickness of ~3-10 nm was simulated for ion energies E = 10-80 eV, and for substrate temperatures ranging from 100 to 900 K. The dependence of the sp3 content and intrinsic stress in the simulated films on substrate temperature was found to agree qualitatively with experiment. At low ion energies and low substrate temperatures, the sp3 fraction increases with ion energy, giving at E > 30 eV a highly sp3-bonded tetrahedral amorphous carbon (ta-C) with a high compressive stress. This trend also remains at room temperature, however with lower values of the sp3 content and stress, whereas above 200 °C simulations with the Brenner potential predict a sharp transition from ta-C to graphitic carbon with dominating sp2 bonding.

Keywords: Molecular dynamics; Ion-beam deposition; Tetrahedral amorphous carbon; Intrinsic stress

  • Computational Materials Science 27 (2003) 16-22

Permalink: https://www.hzdr.de/publications/Publ-4502
Publ.-Id: 4502


Nanocluster Synthesis by High-Fluence Ion Implantation in Thin Films Studied by MC Simulations

Müller, T.; Heinig, K.-H.; Möller, W.

The nanocluster (NC) formation by phase separation of implanted impurity atoms from the host matrix has been studied. The deposition of impurity atoms by high fluence Si+ implantation into SiO2 was simulated using the computer code TRIDYN including dynamic target changes due to by sputtering, ion mixing and swelling. The depth profiles differ considerably from that predicted by the TRIM code. The TRIDYN profiles were used as input for kinetic lattice Monte-Carlo simulations of phase separation. The interaction of the Si atoms in the SiO2 layer is approximated by the nearest-neighbor Ising Hamiltonian, while the time evolution of the system is governed by the importance sampling of configurations according the Metropolis algorithm. The simulations show that NC formation proceeds via (i) nucleation and growth at low impurity concentrations, and via (ii) spinodal decomposition and interface minimization at high concentrations. Due to the small distance between the NCs and the SiO2/Si interface, Si atoms condense steadily onto the substrate and a zone denuded by NCs is formed at the interface. As the mass conservation is violated for impurity atoms within the SiO2, the description of the NC coarsening by the Lifshitz-Slyozov-Wagner theory is not applicable. Rather, the evolution of the NCs is determined by the competition of coarsening and dissolution.

  • Lecture (Conference)
    6th International Conference on Computer Simulation of Radiation Effects in Solids, COSIRES, June 23 - 27, 2002, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-4501
Publ.-Id: 4501


Regular Chains Of Nanocrystals Fabricated from Nanowires – Predictions Based On Kinetic MC Simulations

Müller, T.; Heinig, K.-H.

The fabrication of regularly arranged nanostructures remains a challenge of today's materials research. In this contribution, Kinetic 3D Lattice Monte Carlo (MC) simulations of the shape evolution of single crystalline nanowires by thermally activated interface diffusion will be presented. Interface minimizations leads to the Rayleigh (or pearling) instability; during annealing nanowires develop peristaltic thickness undulations, which finally results in the decay of the wire into a regular chain of nanocrystals (NC’s). For temperatures above the roughening transition it could be shown that size and spacing of the NC’s are in good agreement with results of the classical stability analysis performed by Rayleigh and Mullins. The competition between peristaltic undulations having different wavelength (modes) results in the decay of the wire into equal-spaced NC’s due to self-selection of the fastest growing mode. This mode selection is demonstrated by the Fourier analysis of the MC results. Other than in the analytical stability analysis it has been found that short-wavelength modes develop first, whereas long-wavelength modes are missing initially. Below the roughening transition, the results differ quantitatively. The spacing between NC’s becomes larger and depend on the crystal orientation of the nanowire, which is due to the anisotropy of the interface energy.

  • Poster
    European Materials Research Society 2002 Spring Meeting, 18.6 - 21.6.2002, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-4500
Publ.-Id: 4500


Nanocluster Formation by Phase Separation in Ultra-Thin Ion Implanted Gate Oxides

Müller, T.; Heinig, K.-H.; Möller, W.; Schmidt, B.

Non-volatile memories concepts based on semiconductor nanocrystals (NC) embedded in the gate oxide of MOS transistors with have attracted much in-terest. In order to synthesize the NC’s, ion implantation followed by annealing is the most compatible method with the current CMOS technology. In this contribution, fundamental studies of NC formation by phase separation in very-low energy ion implanted ultra-thin gate oxides will be presented. Ki-netic 3D lattice Monte-Carlo (MC) simulations show that for low ion fluences (low concentrations) the NC formation proceeds via nucleation, growth and Ostwald ripening. However, for high fluences spinodal decomposition results in a laterally connected network of nanostructures resembling a conventional floating gate memory. In general, the Si/SiO2 interface being in close neighbourhood to the NC’s has substantial influence on the NC evolution. Specifically, it leads to a NC-free tunnel oxide at the interface. Although the analysis of Si NC’s in SiO2 is a challenge for current methods, TEM investiga-tions of Si+ implanted gate oxides on (001) Si are in qualitative agreement with our predictions based on MC simulations. However, quantitatively, the fluence necessary for Si NC formation exceeds the predicted one by up to an order of magnitude. Recent studies have shown that this discrepancy origi-nates from oxidation of a large fraction of implanted Si by moisture absorbed in the damaged SiO2 surface layer.

  • Lecture (Conference)
    European Materials Research Society 2002 Spring Meeting, 18.6 - 21.6.2002, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-4499
Publ.-Id: 4499


Synthesis of novel arylpyrazolo corticosteroids as potential ligands for imaging brain glucocorticoid receptors

Wüst, F.; Carlson, K. E.; Katzenellenbogen, J. A.

Corticosteroids regulate a variety of essential physiological functions, such as mineral balance and stress. The great interest in these steroids, especially the glucocorticoids, stems from roles they are thought to play in neuropsychiatric disorders, such as severe depression and anxiety.
The development of glucocorticoid receptor (GR) ligands which are appropriately labeled with short-lived positron-emitting radioisotopes would allow the non-invasive in-vivo imaging and mapping of brain GRs by means of positron emission tomography (PET). In this context we have synthesized a series of novel arylpyrazolo steroids exhibiting different substitution patterns at the D-ring of the steroid skeleton, as ligands for brain GRs. Special attention was given to 4-fluorophenyl pyrazolo steroids, which are known to display high binding affinity toward the GR. The compounds were evaluated in a competitive radiometric receptor binding assay to determine their relative binding affinities (RBA) to the GR. Some compounds show good binding affinities of up to 56% in comparison to dexamethasone (100%). In initial experiments, selected candidates were labeled with the positron emitter fluorine-18 and in one case with the gamma-emitter iodine-131.

Keywords: arylpyrazolo corticosteroids; glucocorticoid receptor binding; radiolabeling; positron emission tomography (PET)

  • Steroids, 68 (2) (2003) 177-191

Permalink: https://www.hzdr.de/publications/Publ-4498
Publ.-Id: 4498


Ion beam sythesized Au nanocrystals in ultra-thin SiO2

Beyer, V.; Müller, T.; von Borany, J.; Heinig, K.-H.

Studies of semiconductor nanocrystals (NC's) in the MOS gate oxide received much interest due to their potential application in non-volatile memory devices. However, the detailed charge storage mechanism is still under discussion. Defect-based charge trapping at NC surfaces is hard to distinguish from storage in the conduction band of NC's. For metal NC's in SiO2 the situation is different. Charge traps at the Au/SiO2 interface are assumed to be negligible at first sight. In this contribution, Au NC's serve as a model system for the charge storage phenomena in NC containing gate oxides with dox<40 nm. For the present study, Au NC's were synthesized by low-energy ion implantation followed by annealing. The Au depth distribution was measured by RBS with high depth-resolution. The process of phase separation during annealing is traced by a series of X-TEM images. A fraction of Au diffuses to the Si/SiO2 interface, forms silicon supersaturated by Au and nucleates liquid Au:Si lenses at the interface. The Au NC's in the SiO2 layer above these lenses are stabilized due to the modified detailed balance of Au-atoms detachment/attachment. Additionally, a zone denuded by NC's forms at the interface. Preliminary electrical results will be presented.

Keywords: nanocrystals based memory; Au; ripening; ion beam synthesis

  • Poster
    Konferenzbeitrag E-MRS Strasbourg 2002 Konferenz: E-MRS 2002 Spring Meeting / Strasbourg (Frankreich), 18.-21. Juni 2002

Permalink: https://www.hzdr.de/publications/Publ-4497
Publ.-Id: 4497


Investigation of Si nanocluster formation in sputter deposited silicon suboxides and application to nanocluster memory structures

Schmidt, J. U.; Schmidt, B.

Silicon rich silicon oxide films (SRO) were prepared by co-sputtering from silica and silicon targets in an argon atmosphere. The formation of silicon nanoclusters (Si NCs) by a thermally stimulated phase separation was
investigated. The influence of sample composition and annealing temperature has been studied by optical methods (infrared absorbtion and photoluminescence). Both methods reveal that phase separation proceeds
more quickly in SRO films with a higher Si excess. Additionally MOS capacitors with embedded Si NCs were prepared and investigated by capacitance-voltage measurements.
The embedded Si NCs could be charged by direct tunneling. For optimized samples held at flat-band potential, the charge loss after 2 days at room temperature was below 10%.

Keywords: Sputtering; Silicon; Nanocrystal Memory; Silicon Rich Oxide

  • Lecture (Conference)
    EMRS 2002 Spring Conference Strassburg, France, 18.-21.07. 2002

Permalink: https://www.hzdr.de/publications/Publ-4496
Publ.-Id: 4496


Observation of the growth mode of TiN during magnetron sputtering using synchrotron radiation

Bottiger, J.; Chevallier, J.; Petersen, J. H.; Schell, N.; Matz, W.; Mücklich, A.

The heteroepitaxial growth of TiN on MgO(001), deposited by reactive magnetron sputtering, has been studied in situ. Using real-time specular X-ray reflectivity, layer-by-layer growth was observed, with the surface-roughening decreasing with increasing deposition temperature. Higher temperatures also resulted in lower growth rates. The film thickness was measured with specular X-ray reflectivity. Using off-plane Bragg-Brentano as well as grazing incidence in-plane wide angle scattering, the pseudomorphic growth of TiN to the underlying MgO(001) was established. Transmission electron microscopy reveals atomic planes passing through the MgO–TiN boundary, thus confirming the heteroepitaxial growth.

Keywords: sputter deposition; TiN; thin film growth; X-ray diffraction; synchrotron radiation

  • Journal of Applied Physics Vol. 91 No.8 (2002) 5429-5433

Permalink: https://www.hzdr.de/publications/Publ-4495
Publ.-Id: 4495


Thickness dependent phase transformations in implanted iron layers

Jagielski, J.; Kopcewicz, M.; Gawlik, G.; Matz, W.; Thomé, L.

This article shows that phase transformations in implanted iron may strongly depend on the sample thickness. The effect essentially relies on lower impurity concentration required for given phase formation in thin films as compared with thick layers or bulk samples. The phase transformation in thin films is also more complete. In this work the total transformation of pure iron into iron nitrides was observedn upon nitrogen implantation of thin iron layers, whereas about 20 % of Fe atoms remains in crystalline a-Fe phase in nitrogen-implantedin bulk samples.

Keywords: iron layers; ion implantation, Phase formation; Moessbauer spectroscopy

  • J. Appl. Phys. 91 (2002) 6565-6470

Permalink: https://www.hzdr.de/publications/Publ-4494
Publ.-Id: 4494


Interaction of Organic Ligands with Metal Ions studied by Time-resolved Laser-Induced Fluorescence Spectroscopy

Geipel, G.

Migration of heavy metals in the aquatic environment is often combined with the complex formation of these metals with organic ligands, like humic substances and wood degradation products. To simulate the functionality of these polyelectrolytes simple hydroxybenzoic acids are studied.
The fluorescence properties of organic molecules were used for the determination of metal complexation. Due to short fluorescence lifetimes of the ligand molecules a dedicated spectrofluorimeter using ultra short laser pulses as excitation source was developed. The laser system consists mainly of the oscillator system for generation of femtosecond laser pulses, the amplifier system to increase the pulse energy of the generated pulses to about 2 mJ and an optical parametrical amplifier system to provide tunable laser pulses over a wide wavelength range (280 nm to about 10 µm). The emitted fluorescence was detected using a fast gating intensified CCD-camera based spectrometer. The system allows to determine time-resolved fluorescence spectra in solid and aqueous (solution) systems with fluorescence lifetimes between about 150 ps and about 10 ns and concentrations of the organic ligand down to 1 x10-6 M.
To verify the system the well known protonation constant log K3 = 3.10 ± 0.20 (I = 0.1 M, T = 298 K) [1,2] of the 2,3-dihydroxybenzoic acid was determined.
The fluorescence lifetime of C6H3(OH)2-COO- is determined to be 375 ± 32 ps and the fluorescence emission maximum was found at a wavelength of 438 nm. We obtain from fluorescence data a protonation constant of log K3 = 3.17 ± 0.05 for the first dissociation step at ionic strength of 0.1 M and 294 K exploiting the Stern-Volmer mechanism. The agreement of data and the derived error of the protonation constant demonstrate the accuracy of the developed system.
The complex formation of the 2,3-dihydroxybenzoic acid with neptunium(V) was studied in the range from pH 3.0 to 7.0. At lower pH - values a 1:1 complex was identified, showing only an interaction of the neptunium(V) with the carboxylic group of the ligand. A second 2:1 complex is formed at the higher pH-values. This indicates that the phenolic OH-group also forms complexes with the metal ion. The formation constants are found to be log K11= 0.11 ± 0.04 and log K12 = 6.97 ± 0.10. Also a third intermediate complex was detected by its fluorescence properties.

Literature:
[1] L. Lajunen, R. Portanova, J. Piispanen et al; Pure & Appl.Chem., 1997, 69, 329, [2] H. Harada; Bull.Chem.Soc.Jpn., 1971, 44, 3459

  • Poster
    Euroanalysis, Dortmund 9.-13.Sept. 2002

Permalink: https://www.hzdr.de/publications/Publ-4493
Publ.-Id: 4493


Bacterial communities in uranium mining waste piles and their interaction with heavy metals

Selenska-Pobell, S.; Flemming, K.; Tzvetkova, T.; Raff, J.; Geißler, A.; Schnorpfeil, M.

High diversity and significant differences were found in the structures of bacterial communities present in several U mill tailings and U mining waste piles. Many bacterial strains were successfully cultured from those uranium wastes, most of which are unusually effective in different biotransformations of U. The molecular basis for the selective and reversible binding of U and some other toxic metals by one of the natural bacterial isolates was found to be a novel kind of S-layer protein. Our analysis indicates that uranium wastes are a valuable reservoir for unusual microorganisms prospective for bacteria-based bioremediation.

  • Contribution to external collection
    UMH-III, Freiberg 15.-21.9.2002

Permalink: https://www.hzdr.de/publications/Publ-4492
Publ.-Id: 4492


Characterization of uranium (VI) complexes formed by different bacteria relevant to uranium mining waste piles

Merroun, M.; Hennig, C.; Rossberg, A.; Reich, T.; Nicolai, R.; Heise, K.-H.; Selenska-Pobell, S.

A combination of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy and Infrared (IR) spectroscopy was used to characterize the uranium complexes formed by different bacterial strains of Acidithiobacillus ferrooxidans isolated from uranium mining wastes, and by some reference strains relevant to the predominantly distributed in the wastes Pseudomonas stutzeri, and Pseudomonas migulae. The results demonstrated that all these bacteria accumulate uranium as phosphate compounds with different structural parameters.

  • Poster
    International Conference Uranium Mining and Hydrogeology III and the International Mine Water Association Symposium, 15.-21.09.2002, Freiberg, Germany
  • Contribution to proceedings
    Internat. Conf. UMH III and the IMWA Symposium,, 19.-21.09.2002, Freiberg, Germany
    Uranium in the Aquatic Environment;, Berlin: Springer Verlag, 505-511

Permalink: https://www.hzdr.de/publications/Publ-4491
Publ.-Id: 4491


Bacteria-based bioremediation of uranium mining waste waters by using sol-gel ceramics

Raff, J.; Soltmann, U.; Matys, S.; Schnorpfeil, M.; Böttcher, H.; Pompe, W.; Selenska-Pobell, S.

Abstract. Cells, spores and the surface layer protein (S-layer) of the Bacillus sphaericus strain JG-A12, recovered from a uranium mining waste pile, were embedded in SiO2 matrices by using sol-gel techniques. Sorption and desorption of uranium and copper by the free biocomponents and the obtained biological ceramics (biocers) were investigated. The biocer with cells possesses the highest binding capacity, followed by the S-layer biocer and the spore biocer. For renewed use of the biocers, the bound uranium and copper can be completely removed by washing with aqueous citric acid.

  • Contribution to HZDR-Annual report
    Tagungsband UMH Feiberg, 15.-19.9.2002 Springer Verlag Berlin pp. 615-622

Permalink: https://www.hzdr.de/publications/Publ-4490
Publ.-Id: 4490


Biosorption of Uranium and Copper by Biocers

Raff, J.; Soltmann, U.; Matys, S.; Selenska-Pobell, S.; Pompe, W.; Böttcher, H.

Biological ceramic composites (biocers) made according to an aqueous sol-gel protocol were used as selective metal binding filters. The biological component of the biocers Bacillus sphaericus JG-A12 was isolated from a uranium mining waste pile. Vegetative cells and spores of this strain are known to bind selectively U, Cu, Al, Cd and Pb in large amounts. Sol-gel ceramics were prepared by dispersing vegetative cells, spores and stabilized surface-layer proteins (S-layer) in aqueous silica nanosols, gelling and drying. The biosorption of uranium and copper by the three kinds of biocers and by their single components was investigated in dependence on time, concentration and preparing conditions. Biocers with cells possess the highest binding capacity compared to matrices with spores and S-layer. Freeze drying of prepared biocers or adding water soluble additives as sorbitol lead to higher porosity and faster metal binding. Uranium was bound mainly to the biological component but also to the SiO2 network. In contrast, copper was only bound by the cells, spores or S-layer. Bound uranium and copper were completely removed by washing with aqueous citric acid.

  • Chemistry of Materials, 15 (1), 240-244, Jan. 2003

Permalink: https://www.hzdr.de/publications/Publ-4489
Publ.-Id: 4489


Complexation of trivalent actinide and lanthanide ions by glycolic acid: A TRLFS study.

Stumpf, T.; Fanghänel, T.; Grenthe, I.

The complexation in the Cm(III) and Eu(III) glycolate systems have been studied by time-resolved laser fluorescence spectroscopy (TRLFS). The measurements have been performed at trace Cm(III) and Eu(III) concentrations (about 10-7 and 10-6 mol/L, respectively) at different concentrations of glycolic acid and at different pH using NaClO4 as background electrolyte. Measurements at higher Eu(III) concentrations (10-3 mol/L) have also been performed in order to study the influence of metal ion concentration on the complexation reaction.
By varying the glycolic acid concentration from 0.1 to 0.5 mol/L at low pH ([H+]=10-3) the stepwise formation of glycolate complexes [Cm(HOCH2COO-)n(H2O)9-2n]3-n with n=1-4 were confirmed spectroscopically. By varying the pH between 4.5 and 12.0 in 1 M glycolate the following three Cm(III) species were identified from the fluorescence emission spectra
- a hydrated tetraglycolate complex [Cm(HOCH2COO-)4(H2O)]- (Cm/complex 1) with a peak maximum at 602.3 nm and a fluorescence emission lifetime of 206 ± 3 µs,
- a mixed hydroxide-glycolate complex [Cm(HOCH2COO-)4(OH)]2- (Cm/complex 2) with a peak maximum at 605.6 nm and the same lifetime as Cm/complex 1 and
- a chelate complex [Cm(HOCH2COO-)3(-OCH2COO-)(OH)]3- or [Cm(HOCH2COO-)2(-OCH2COO-)2(H2O)]3- (Cm/complex 3 ) (peak maximum 611.3 nm) which is generated after deprotonation of one or two of the coordinated a-OH groups of the glycolate with a fluorescence emission lifetime of 295 ± 15 µs. In the europium system there is evidence only for the corresponding Eu/complex 1 and 3. The corresponding europium mixed hydroxide-glycolate complex is not detectable spectroscopically. The fluorescence decay is different in the Cm and Eu systems in the pH range from 7.8 up to 10.5; a bi-exponential decay behaviour was observed for the Cm system, while the Eu system shows mono-exponential decay. This indicates that the kinetics of the chelating process is much slower for Cm(III) than for Eu(III). The rate of protonation of the coordinated a-O- group in the Eu/complex 3 is much faster than in case of Cm/complex 3. Different spectra were observed for Eu(III)/glycolate complexes at europium concentrations of 3x10-6 mol/L and 1x10-3 mol/L indicating the formation of poly-nuclear Eu(III)/glycolate complexes at high metal ion concentration.

  • Journal of the Chemical Society - Dalton Transactions, (20): 3799-3804, 2002

Permalink: https://www.hzdr.de/publications/Publ-4488
Publ.-Id: 4488


Laserinduzierte Fluoreszenzspektroskopie - Untersuchung der Wechselwirkung von Actiniden mit organischen Liganden

Geipel, G.

Die laserinduzierte Fluoreszenzspektroskopie wird häufig genutzt, um in der Actinidenchemie Untersuchungen bei sehr geringen Konzentrationen durchzuführen. Während dies beispielsweise für Curium(III) und Uran(VI) mit Nachweisgrenzen um 10-9 mol/L bzw. 10-7 mol/L kein Problem ist, sind andere Actinidenelemente auf Grund ihrer fehlenden Fluoreszenzeigenschaften derartigen Untersuchungen nicht zugänglich.
Einen Ausweg bieten Methoden, bei denen nicht die spektroskopischen Eigenschaften des Actinidelementes, sondern die des Liganden im Vordergrund stehen. Als Liganden kommen Verbindungen in Frage, die auf Grund ihrer p-Elektronensysteme über ausgeprägte Fluoreszenzeigenschaften verfügen. Anhand der verschiedenen isomeren Dihydroxybenzoe-säuren kann zudem der Einfluss der phenolischen OH-Gruppe auf die Komplexbildung ermittelt werden. Dies ist von besonderer Bedeutung für das Verständnis der Komplexbildung von Huminstoffen und Holzabbauprodukten.
Berichtet wird über die Komplexbildung von Neptunium(V) und Uran(VI) mit 2,3-Dihydroxybenzoesäure. Da Uran(VI) selbst fluoresziert kann in diesem Fall die Komplexbildung sowohl über die Veränderung der Uranfluoreszenz, als auch über Veränderung der Ligandfluoreszenz beschrieben werden. In diesem Zusammenhang wird die Frage diskutiert, inwieweit andere Prozesse Einfluss auf die ermittelten Komplexkonstanten haben.

  • Lecture (Conference)
    Kolloquium TU Mainz, 10.7.02, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-4487
Publ.-Id: 4487


Size and Location Control of Si Nanocrystals at Ion Beam Synthesis in Thin SiO2 Films

Müller, T.; Heinig, K.-H.; Möller, W.

Binary collision simulations of high-fluence 1 keV Si+ ion implantation into 8 nm thick SiO2 films on (001)Si were combined with kinetic Monte Carlo simulations of Si nanocrystal (NC) formation by phase separation during annealing. For nonvolatile memory applications, these simulations help to control size and location of NCs. For low concentrations of implanted Si, NCs form via nucleation, growth and Ostwald ripening, whereas for high concentrations Si separates by spinodal decomposition. In both regimes, a self-adjusted oxide layer denuded of NCs forms at the SiO2/Si interface, which has just the right thickness for NC charging by direct electron tunneling. However, only in the nucleation regime the width of the tunneling oxide and the mean NC diameter remain constant during annealing. This stability originates in the competition of Ostwald ripening and Si loss to the Si/SiO2 interface. Based on the process simulations, its is predicted that the technological demands on the NC synthesis for nonvolatile memories are fulfilled best in the nucleation regime.

Keywords: non-volatile memories; Si nanocrystals; phase separation; spinodal decomposition

  • Applied Physics Letters 81 (2002) 3049

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Permalink: https://www.hzdr.de/publications/Publ-4485
Publ.-Id: 4485


Experimental and Numerical Investigation of Boron Dilution Transients in Pressurized Water Reactors

Hertlein, R.; Umminger, K.; Kliem, S.; Prasser, H.-M.; Höhne, T.; Weiß, F.-P.

Within the PWR safety analyses, attention has increasingly focussed in recent years on boron dilution events which could potentially lead to reactivity transients. Mixing of the diluted water with the ambient coolant of higher boron content provides an important mitigation mechanism before the diluted water enters the core.
Experimental support is needed to validate the computational tools to be applied to analyze the mixing of the low-boron water. Experiments were performed in the three test facilities UPTF, PKL and ROCOM in Germany.
The relevant PKL and UPTF tests were focussed on small break loss of coolant accident (SB-LOCA) scenarios with reflux-condenser mode and restart of natural circulation. The two test facilities represent a typical western-type PWR and are/were operated by Siemens/KWU now Framatome ANP in Germany. While the restart of natural circulation was investigated in the PKL system test facility (volume 1:145, height 1:1), the UPTF experiments dealt with the mixing of water flows with different boron concentration in the cold legs, reactor pressure vessel (RPV) downcomer and the lower plenum (all these components were full-scale models).
The results from the PKL test facility demonstrate, that in case of a postulated SB-LOCA with reflux condensation phase, natural circulation does not start up simultaneously in all loops. This means, that slugs of condensate, that might have accumulated in the pump seal during reflux condenser mode of operation, would reach the RPV at different points in time. The UPTF tests showed an almost ideal mixing of water flows with different boron concentration in the RPV downcomer.
The ROCOM test facility has been built in a linear scale of 1:5 for the investigation of coolant mixing phenomena in a wide range of flow conditions in the RPV of the German KONVOI type PWR. The test results presented are focussed on the mixing of a slug of deborated water during the start-up of the first reactor coolant pump. Based on experimentally determined pulse responses, a semi-analytical model for the description of coolant mixing inside the KONVOI RPV has been developed. Calculations for a presumed boron dilution event during the start-up of the first reactor coolant pump have been carried out by means of the semi-analytical model and independently by means of the CFD-code CFX-4. The semi-analytical model is able to describe the time dependent behaviour of the deboration front at each fuel element position in a good agreement with the experiment. All main mixing effects, observed in the experiment, are also reproduced by the CFX-calculation.

Keywords: Boron dilution; Mixing; SB-LOCA; Pump Startup; PKL-; UPTF-; ROCOM-Test Facility

  • Nuclear Technology, vol. 141,January 2003, pp. 88-107

Permalink: https://www.hzdr.de/publications/Publ-4484
Publ.-Id: 4484


Bestimmung der Aktivitätsverteilung in Gebinden mit geringfügig radioaktivem, Material unter Verwendung großflächiger, unkollimierter, feststehender Gamma-Szintillationsdetektoren

Franke, E.; Hoppe, D.

Die Verwendung von großflächigen Gamma-Detektoren zeichnet sich durch hohe Effektivität und damit geringe Messzeit aus. Dagegen sind mit ihnen keine hohen Ortsauflösungen bei der Rekonstruktion der Aktivitätsverteilung möglich. Zur Untersuchung der Rekonstruierbarkeit unbekannter Aktivitätsverteilungen werden zwei in der Tomographie gebräuchliche Verfahren verglichen, ein algebraisches (iterativ) und ein analytisches (gefilterte Rückprojektion). Beide Verfahren erbringen qualitativ ähnliche Ergebnisse. Reale Aktivitätsverteilungen werden nach beiden Verfahren zufriedenstellend rekonstruiert.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-347 Juni 2002
    ISSN: 1437-322X

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Permalink: https://www.hzdr.de/publications/Publ-4482
Publ.-Id: 4482


Bestimmung der Aktivitätsverteilung in Gebinden mit geringfügig redioaktivem Material unter Verwendung großflächiger, unkollimierter, feststehender Gamma-Szintillationsdetektoren

Franke, E.; Hoppe, D.; (Editors)

Die Verwendung von großflächigen Gamma-Detektoren zeichnet sich durch hohe Effektivität und damit geringe Messzeit aus. Dagegen sind mit ihnen keine hohen Ortsauflösungen bei der Rekonstruktion der Aktivitätsverteilung möglich. Zur Untersuchung der Rekonstruierbarkeit unbekannter Aktivitätsverteilungen werden zwei in der Tomographie gebräuchliche Verfahren verglichen, ein algebraisches (iterativ) und ein analytisches (gefilterte Rückprojektion). Beide Verfahren erbringen qualitativ ähnliche Ergebnisse. Reale Aktivitätsverteilungen werden nach beiden Verfahren zufriedenstellend rekonstruiert.

Keywords: Freimessung; Kalibriergebinde; Emissions-Tomographie; Aktivitätsverteilung; Strahlungsdichte

  • Technisches Messen 6/2002, 306-313

Permalink: https://www.hzdr.de/publications/Publ-4481
Publ.-Id: 4481


Analysis of microstructures using the ion acoustic effect

Akhmadaliev, C.; Bischoff, L.

The interaction of a pulsed ion beam with a solid leads to a small temperature variation in the near subsurface region. Due to the local heating of the target thermal elastic waves were generated. The measurement of these waves gives informations about the internal structure and properties of the sample. Experiments were carried out using an intensity modulated beam of high energy ions from a TANDETRON accelerator for the investigation of elastic waves in aluminum, steel, copper and silicon samples as well as for a pulsed low energy focused ion beam (FIB) for acoustic imaging from structures on different targets. The detection of the acoustic signal was provided by piezoelectric transducers based on lead zirconium titanium (PZT) ceramic or on polyvinylidene fluoride (PVDF) films which can be applied in the scanning ion acoustic microscopy. In this case the modulation frequency was varied in the range from 60 kHz to 2 MHz. A lateral resolution of the ion acoustic images near the samples surface of a few micrometers could be obtained.

Keywords: modulated ion beam; thermal elastic wave; ion acoustic microscopy; piezoelectric sensor

  • Lecture (Conference)
    E-MRS 2002 Spring Meeting June 18-21, 2002, Strasbourg, France
  • Materials Science and Engineering B102 (2003) 8-11

Permalink: https://www.hzdr.de/publications/Publ-4480
Publ.-Id: 4480


Hyperon-Nucleon Bound States and Electroproduction of Strangeness on Light Nuclei

Dohrmann, F.; Abbott, D.; Ahmidouch, A.; Ambrozewicz, P.; Armstrong, C. S.; Arrington, J.; Asaturyan, R.; Assamagan, K.; Avery, S.; Bailey, K.; Baker, O. K.; Beedoe, S.; Bitao, H.; Breuer, H.; Brown, D. S.; Carlini, R.; Cha, J.; Chant, N.; Christy, E.; Cochran, A.; Cole, L.; Collins, G.; Cothran, C.; Crowder, J.; Cummings, W. J.; Danagoulian, S.; Duncan, F.; Dunne, J.; Dutta, D.; Eden, T.; Elaasar, M.; Ent, R.; Ewell, L.; Fenker, H.; Fortune, H. T.; Fujii, Y.; Gan, L.; Gao, H.; Garrow, K.; Geesaman, D. F.; Gueye, P.; Gustafsson, K.; Hafidi, K.; Hansen, J. O.; Hinton, W.; Jackson, H. E.; Juengst, H.; Keppel, C.; Klein, A.; Koltenuk, D.; Liang, Y.; Liu, J. H.; Lung, A.; Mack, D.; Madey, R.; Markowitz, P.; Martoff, C. J.; Meekins, D.; Mitchell, J.; Miyoshi, T.; Mkrtchyan, H.; Mohring, R.; Mtingwa, S. K.; Mueller, B.; O'Neill, T. J.; Niculescu, G.; Niculescu, I.; Potterveld, D. H.; Price, J. W.; Raue, B. A.; Reimer, P. E.; Reinhold, J.; Roche, J.; Roos, P.; Sarsour, M.; Sato, Y.; Savage, G.; Sawafta, R.; Segel, R. E.; Semenov, A. Y.; Stepanyan, S.; Tadevosian, V.; Tajima, S.; Tang, L.; Terburg, B.; Uzzle, A.; Wood, S.; Yamaguchi, H.; Yan-1, C.; Yan-2, C.; Yuan, L.; Zeier, M.; Zeidman, B.; Zihlmann, B.

The A(e,e'K+)YX reaction has been investigated in Hall C at Jefferson Laboratory for 6 different targets. Data were taken for Q2ࣈ 0.35 and 0.5 GeV2 at a beam energy of 3.245 GeV for 3H, 2H, 2He, C and Al targets. The missing mass spectra are fitted with Monte Carlo simulations taking into account the production of Lambda and Sigma0 hyperon production off the proton, and Sigma- off the neutron. Models for quasifree production are compared to the data, excess yields close to threshold are attributed to FSI. Evidence for Lambda-hypernuclear bound states is seen for
3,4He targets.

Keywords: Electroproduction of strangeness; Nuclear targets; Spectral function

  • Lecture (Conference)
    MESON 2002: 7th International Conference on Meson Production, Properties and Interaction of Mesons, Crakow, Poland, May 24-28 May 2002, World Scientific, New Jersey, 2003, 427-429
  • Prog. Part. Nucl. Phys. 50, 587 (2003)
  • Contribution to proceedings
    MESON 2002: 7th International Conference on Meson Production, Properties and Interaction of Mesons, Crakow, Poland, May 24-28 May 2002, World Scientific, New Jersey, 2003, 427-429

Permalink: https://www.hzdr.de/publications/Publ-4479
Publ.-Id: 4479


Bulk-limited conduction of Ge-implanted thermally grown SiO2 layers

Zhao, J.; Rebohle, L.; Gebel, T.; von Borany, J.; Skorupa, W.

The electrical conduction mechanism of Ge-implanted SiO2 films exhibiting room-temperature blue electroluminescence with a power efficiency of up to 0,5 % [Appl.Phys.Lett.71(1997)2809] is investigated. In detail it will be shown that the current–voltage characteristic of Ge-implanted SiO2 layers for applied electric fields between 4.5 and 7 MV/cm can be modeled very well with the space charge limited (SCL)conduction mechanism in the trap-filled-limited (TFL) region.The current density j shows a power law dependence j ~ Ea of the applied electric field E, and the temperature dependence of a exhibits the typical behavior of TFL injection currents. For applied electric fields above 7 MV/cm the charge transport mechanism is explained by SCL currents which are superimposed by effects of field emission, impact ionization, and electron–hole recombination.

  • Solid-State Electronics 46 (2002) 661-664

Permalink: https://www.hzdr.de/publications/Publ-4477
Publ.-Id: 4477


MHD Dynamo-Operatoren

Günther, U.


The spherical MHD mean-field dynamo is considered from a mathematical
viewpoint. It is shown that the corresponding 2x2 operator matrix lives in a Krein
space (a Hilbert space with indefinite metric) and has paired complex
eigenvalues.
A no-go theorem is discussed which forbids isospectral classes of dynamo
operators for a linear factorization ansatz in a supersymmetric intertwining
approach.
A detailed compatibility analysis is presented for the associated matrix
Riccati differential equations.



  • Lecture (others)
    Lecture given at Bremen University, Department of Mathematics, Applied Analysis Group, June 12-13, 2002, Bremen, Germany

Permalink: https://www.hzdr.de/publications/Publ-4476
Publ.-Id: 4476


Die Stellung der Sekretärin nach dem BAT - eine moderne Form der Leibeigenschaften?

Joehnk, P.

no abstract delivered from author

  • Lecture (others)
    Bundesverband Sekretariat und Büromanagement e. V., Dresden, 03.06.2002

Permalink: https://www.hzdr.de/publications/Publ-4475
Publ.-Id: 4475


Directed flow in Au+Au, Xe+CsI and Ni+Ni collisions and the nuclear equation of state

Andronic, A.; Reisdorf, W.; Herrmann, N.; Crochet, P.; Barret, V.; Basrak, Z.; Bastid, N.; Berek, G.; Caplar, R.; Devismes, A.; Dupieux, P.; Dzelalija, M.; Finck, C.; Fodor, Z.; Gobbi, A.; Grishkin, Y.; Hartmann, O. N.; Hildenbrand, K. D.; Hong, B.; Kecskemeti, J.; Kim, Y. J.; Kirejczyk, M.; Koczon, P.; Korolija, M.; Kotte, R.; Kress, T.; Lebedev, A.; Lee, K. S.; Leifels, Y.; Lopez, X.; Merschmeyer, M.; Neubert, W.; Pelte, D.; Petrovici, M.; Rami, F.; de Schauenburg, B.; Schuettauf, A.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczynska, K.; Smolyankin, V.; Stockmeier, M.; Stoicea, G.; Tyminski, Z.; Wagner, P.; Wisniewski, K.; Wohlfarth, D.; Yushmanov, I.; Zhilin, A.

We present new experimental data on directed flow in collisions of Au+Au, Xe+CsI and Ni+Ni at incident energies from 90 to 400 A MeV. We study the centrality and system dependence of integral and differential directed flow for particles selected according to charge. All the features of the experimental data are compared with Isospin Quantum Molecular Dymnamics (IQMD) model calculations in an attempt to extract information about the nuclear matter equation of state (EoS). We show that the combination of rapidity and transverse momentum analysis of directed flow allows to disentangle various parametrizations in the model. At 400 A MeV, a soft EoS with momentum dependent interactions is best suited to explain the experimental data in Au+Au and Xe+CsI, but in case of Ni+Ni the model underpredicts flow for any EoS. At 90 A MeV beam energy, none of the IQMD parametrizations studied is able to consistently explain the experimental data.

  • Phys. Rev. C 67 (2003) 034907

Permalink: https://www.hzdr.de/publications/Publ-4474
Publ.-Id: 4474


Application of mass separated focused ion beams

Bischoff, L.

With the invention of the liquid metal ion source (LMIS) in the sixties the focused ion beam (FIB) technique started an impressive development from the laboratory level to high performance industrial equipments. At present, the FIB is a very useful and versatile tool in microelectronics industry for mask and integrated circuit repair and modification, failure analysis or TEM specimen preparation, as well as in the material science for radiation damage and sputtering investigations, for grain size and distribution analysis in metals and alloys, for the formation of silicides or the fabrication of micro-tools. For special purposes in the field of research and development, like writing ion implantation or ion mixing in the µm- or sub-µm range different ion species are needed. Therefore alloy LMIS are used. The energy distribution of the ions from an alloy LMIS is one of the determining factors for the performance of the FIB equipment. Different source materials like Au73Ge27, Au77Ge14Si9, Co36Nd64, Er69Ni31, and Er70Fe22Ni5Cr3 were investigated with respect to the energy spread of the different ion species as a function of emission current I, ion mass m and temperature T. For single charged ions the predicted dependence of the energy spread according to DE µ I2/3 m1/3 T1/2 found for Ga could be confirmed. The alloy LMIS`s discussed above have been used in the Rossendorf FIB system IMSA-100 especially for writing implantation to fabricate sub-µm pattern without any lithographic steps. So a Co-FIB was applied for the ion beam synthesis of CoSi2 micro-structures. Additionally, the possibility of varying the current density with the FIB by changing the pixel dwell-time was used for radiation damage investigations in Si and SiC at elevated implantation temperatures. Furthermore, a broad spectrum of ions was employed to study the sputtering process depending on temperature, angle of incidence and ion mass on a couple of target materials using the volume loss method. All these examples underline the importance of a FIB in modern research and the new possibilities given by a mass separated system applying a broad spectrum of ion species.

Keywords: Focused ion beam; alloy liquid metal ion source; energy distribution; mass spectra; application

  • Lecture (Conference)
    IV-th International Scientific Symposium "Ion Implantation and Other Applications of Ions and Electrons ION 2002" Kazimierz Dolny, Poland, June 10 - 13, 2002

Permalink: https://www.hzdr.de/publications/Publ-4473
Publ.-Id: 4473


Development and application of a fast running model for the description of coolant mixing inside the pressure vessel of pressurized water reactors

Kliem, S.; Prasser, H.-M.; Höhne, T.; Rohde, U.

An efficient semi-analytical model for the description of the coolant mixing during stationary and transient processes inside the reactor pressure vessel (RPV) of pressurised water reactors (PWR) has been developed. This model is based on the technique of linear superposition of response functions on Dirac impulse shaped perturbation functions. In the model, the RPV is represented formally by a group of transfer systems (for each combination of inlet nozzle position and fuel element position one) with one input and one output each. An experimental way of obtaining the transfer properties is shown on the example of the German PWR KONVOI. The validation of the model against experimental data from the 1:5 scaled coolant mixing test facility ROCOM is presented.
The semi-analytical model for the description of coolant mixing has been used in combination with the 3D reactor dynamics code DYN3D for the analysis of a hypothetical boron dilution event after start-up of the first main coolant pump in a generic four-loop PWR. The model provides realistic time-dependent boron concentration fields at the core inlet. By varying the initial slug volume it was found, that for the given core configuration slugs of less than 20 m3 do not lead to a re-criticality of the shut-off reactor. Calculations with the bounding slug volume of 36 m3 show, that the corresponding reactivity insertion does not lead the safety relevant consequences.

  • Lecture (Conference)
    Int. Conf. on the Physics of Reactors PHYSOR 2002,Seoul, Korea, 6.-10.10.2002, Proc. CD-ROM paper 5D-04
  • Contribution to external collection
    Int. Conf. on the Physics of Reactors PHYSOR 2002,Seoul, Korea, 6.-10.10.2002, Proc. CD-ROM paper 5D-04

Permalink: https://www.hzdr.de/publications/Publ-4472
Publ.-Id: 4472


The electron accelerator facility ELBE at Rossendorf/Dresden and its applications

Helm, M.

At the Research Center Rossendorf near Dresden a superconducting electron accelerator is under construction and will start its operation in the course of this year. The electron beam with an energy of 20 (later up to 40) MeV is intended to provide the "source" for several types of secondary radiation: (1) gamma photons for nuclear spectroscopy, (2) X-rays for studies of cell damage, (3) neutrons for fusion-related research, (4) positrons for applications mostly in solid state physics, and finally (5) intense, coherent infrared radiation by means of two free-electron lasers, which will span the wavelength range between 5 and 150 microns. While giving a brief overview about all the above topics, I will concentrate on the free-electron lasers and the solid state spectroscopy we are planning to use them for. A focus will be time resolved studies of semiconductor quantum structures. It is intended to develop ELBE into a user facility, open to users worldwide, but of course in particular to researchers in central Europe.

Keywords: electron accelerator; free electron laser; ELBE; semiconductor quantum structures

  • Lecture (others)
    Vortrag an der Karls-Universität Prag, Tschechische Republik, 27.5.2002

Permalink: https://www.hzdr.de/publications/Publ-4471
Publ.-Id: 4471


Experimental high-resolution database for co-current air-water flow in a vertical pipe

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

Measurements were conducted in a vertical pipe with an inner diameter of 51.2 mm and a length of about 3 m for air/water bubble and slug flow. The use of a wire-mesh sensor allows a high resolution of the gas fraction data in space as well as in time. From these data time averaged values for the two-dimensional gas fraction profiles decomposed according to a large number of bubble size classes were calculated. This allows to extract data for the radial gas fraction profiles for a given range of bubble sizes as well as data for local bubble size distributions. The measurements were done for up to 10 different inlet lengths and for about 100 combinations of gas and liquid volume flow rates. Further experiments are planned. The data will be used for the development of models for the forces acting on a bubble in a shear field of the liquid flow and models for bubble coalescence and break-up.

Keywords: database; experiment; pipe flow; two-phase flow; bubble

  • Lecture (Conference)
    40th European Two-Phase Flow Group meeting, Stockholm, Sweden, June 10-13, 2002, Paper C4
  • Contribution to proceedings
    40th European Two-Phase Flow Group meeting, Stockholm, Sweden, June 10-13, 2002, Paper C4

Permalink: https://www.hzdr.de/publications/Publ-4470
Publ.-Id: 4470


Velocity measurements at high temperatures by ultrasound Doppler velocimetry using an acoustic wave guide

Eckert, S.; Gerbeth, G.; Melnikov, V. I.

The ultrasound Doppler velocimetry (UDV) has been used to measure flow velocities at temperatures up to 620°C. To overcome the thermal restriction of the ultrasonic transducers an acoustic wave guide has been used. The acoustic wave guide and the piezoelectric element are combined in form of an integrated sensor. This approach allowed the first successful application of the ultrasound Doppler technique in liquid metals at temperatures above 200°C. The feasibility of this integrated sensor concept was demonstrated in experiments with metallic melts. Measurements were performed in a PbBi bubbly flow and in CuSn.

Keywords: flow measurement technique; ultrasound Doppler technique; fluid velocity; opaque fluids; liquid metal

  • Experiments in Fluids, Vol.35/5 (2003), 381-388

Permalink: https://www.hzdr.de/publications/Publ-4469
Publ.-Id: 4469


Analysis of the Boiling Water Reactor Turbine Trip Benchmark with the Code DYN3D

Grundmann, U.; Rohde, U.; (Editors)

Considering the phase 2 of the OECD/NRC BWR Turbine Trip Benchmark several analyses were performed with the help of the DYN3D code. Thermal-hydraulic boundary conditions of the core are given for this part of the benchmark. Concerning the modelling of the BWR in the DYN3D code several simplifications and their influence on the results were investigated. The standard calculations with DYN3D were performed with 764 coolant channels (1 channel per fuel assembly). It is shown that the power peak obtained for the given boundary conditions is close to the measured value. For numerical stability reasons, preliminary calculations were carried out neglecting the instationary mass balance equation. This approximation provided a stronger reduction of the core void that results in a higher power peak. The impact of the assembly discontinuity factors (ADF) was studied. It is shown that the influence on core-averaged values of the steady state and the transient is small. Considering local parameters the influence is not negligible. Several participants of the benchmark perform calculations with 33 thermal-hydraulic channels. The influence of the number of coolant channels has also a small effect on the core averaged values, but local parameters as axial power distribution in single fuel assemblies are affected. The phase slip model of MOLOCHNIKOV is the standard model of DYN3D for void fraction calculation. The ZUBER-FINDLAY model shows only small deviations from the standard case for both global and local values, however not in the direction of the measurement. Using the thermal-hydraulic boundary conditions the best agreement with the experiment was obtained for the standard model.

Keywords: nuclear reactors; transients; benchmarks; boiling water reactor; turbine trip; measurements; simulation; three-dimensional

  • Lecture (Conference)
    PHYSOR 2002 International Conference on the New Frontiers of Nuclear Technology: Reactor Physics, Safety and High-Performance Computing, October 7-10, 2002, Seoul, Korea
  • Contribution to proceedings
    PHYSOR 2002 International Conference on the New Frontiers of Nuclear Technology: Reactor Physics, Safety and High-Performance Computing, October 7-10, 2002, Seoul, Korea

Permalink: https://www.hzdr.de/publications/Publ-4468
Publ.-Id: 4468


Dynamic Master Curve Issues

Viehrig, H.-W.; Böhmert, J.; Dzugan, J.

The paper links the Master Curve (MC) concept and the Charpy-V impact test to determine dynamic fracture mechanical parameters of ASTM A 533 B Cl. 1 nuclear pressure vessel steel. Pre-cracked and side-grooved Charpy size specimens were tested under impact loading using the instrumented impact pendulum test. J-integral based fracture toughness values, KJc, were determined at cleavage failure of the specimen. MC based reference temperatures, T0dy, were determined on the basis of measured KJc values.
The change in T0dy was determined in dependence on the thickness position of a steel plate and compared with the quasi-static reference temperature, T0st, and the Charpy-V transition temperature (TT). All three parameters increased from the surface towards the middle of the steel plate in the same course. However, in the middle section of the plate T0dy is in average approximately 26 K higher than TT41J and 72 K higher than T0st. Different T0 were found when tested at different temperatures, but the trend is ambiguous.
The results show that the MC based T0 is sensitive to reflect rather small microstructural differences by testing small Charpy size specimens and, thus it is applicable for the fracture mechanical characterisation of materials.

Keywords: instrumented impact testing; cleavage failure; fracture toughness; Master Curve; ductile-to brittle transition; reference temperature; reactor pressure vessel steel

  • Lecture (Conference)
    Proceedings, MASC 2002: Use and Applications of the Master Curve for Determining Fracture Toughness, June 12 - 14, 2002, Helsinki - Stockholm - Helsinki
  • Contribution to external collection
    Proceedings, MASC 2002: Use and Applications of the Master Curve for Determining Fracture Toughness, June 12 - 14, 2002, Helsinki - Stockholm - Helsinki

Permalink: https://www.hzdr.de/publications/Publ-4466
Publ.-Id: 4466


Scanning Force Microscopy of Spin-coated Humic Acid

Mertig, M.; Klemm, D.; Pompe, W.; Zänker, H.; Böttger, M.

We report on investigations of spin-coated peat humic acid solutions by scanning force microscopy allowing, for the first
time, direct imaging of individual single humic acid molecules with a minimum diameter of 1.5-3.5 nm. The measured
height of the molecules deposited onto a mica substrate increases with decreasing pH value of the solution. This behaviour
can be explained by means of the random coil model if one takes the existence of charge carriers in organic macromolecules
into consideration. With increasing humic acid concentration the molecules arrange into a few monolayer-thick
agglomerates formed during the process of film deposition. In unfiltered solutions and in 1000 nm filtrates we find
additional particles well distinct from the above-mentioned molecules in size and properties. They possess an equivalent
spherical diameter of 70-160 nm and behave inert when the ambient conditions are changed.

Keywords: humic acid; random coil model; film formation; scanning force microscopy

  • Surface and Interface Analysis 27, 426-432 (1999)

Permalink: https://www.hzdr.de/publications/Publ-4465
Publ.-Id: 4465


Influence of dynamic annealing on the shape of channeling implantation profiles in Si and SiC

Posselt, M.; Bischoff, L.; Teichert, J.; Ster, A.

The influence of dose rate and temperature on the dose dependence of the shape of Ge depth profiles obtained by channeling implantation into Si and SiC is investigated. A focused ion beam system is employed which enables the application of two widely different dose rates (1011 and 1018 cm-2 s-1). Implantations into Si are performed at room temperature (RT) and 250 0C. SiC is implanted at RT, 225, 450, and 580 0C. The Ge depth distributions are measured by secondary ion mass spectrometry. The shape of the channeling implantation profiles is affected by the formation and evolution of complex defects formed during ion bombardment, since these defects cause significant dechanneling of the implanted particles. The competing influence of dose rate and temperature on the shape of Ge depth profiles is explained in terms of intracascade defect relaxation. The time scale for the reduction of complex defects is estimated. At RT, in Si some defect relaxation occurs within the first 100 s after an ion impact. At temperatures of 225 and 250 0C, in SiC and Si, a considerable defect reduction is found within the first 10 ms as well as between 10 ms and 100 s after an ion impact. The complex defects in Si vanish entirely between 10 ms and 100 s, whereas in SiC some of them survive. At 450 and 580 0C, defects in SiC relax mainly within the first 10 ms after an ion impact. The defect reduction increases with growing implantation temperature. Different mechanisms which may be responsible for the dynamic annealing in Si and SiC are discussed. A phenomenological model is developed in order to treat the dose rate and temperature dependence of the defect-induced dechanneling within the framework of atomistic computer simulations of ion implantation. The simulated Ge depth profiles agree very well with the measured data.

Keywords: ion implantation into Si and SiC; radiation damage; channeling; computer simulation

Permalink: https://www.hzdr.de/publications/Publ-4464
Publ.-Id: 4464


Alternative Flüssigmetall-Ionenquellen

Bischoff, L.

Als alternative Ionenquellen für Feinstrahlanlagen werden zur Ga-LMIS (liquid metal ion source) Flüssigmetall-Ionenquellen vorgestellt, die mit metallischen Legierungen arbeiten und so das Spektrum verfügbarer Ionen erweitern. Die Wirkungsweise sowie die Herstellungstechnologie werden diskutiert sowie vielfältige Anwendungen eines massenseparierten Ionenfeinstrahls (FIB = focused ion beam) dargestellt.

Keywords: Focused Ion Beam; Legierungs-Flüssigmetallionenquelle; Parameter; Massenspektrum; Wien-Filter; Applikationen

  • Lecture (others)
    LEO CrossBeam Workshop Dresden, 14.-16.05.2002

Permalink: https://www.hzdr.de/publications/Publ-4463
Publ.-Id: 4463


Transport of Reacting Solutes Through the Unsaturated Zone

Kuechler, R.; Noack, K.

Unsaturated flows within subsurface regions control many large-scale hydrological and environmental processes. This contribution presents and discusses the results of numerical calculations dealing with the flow of water, the chemical reaction at the water-mineral interface and the transport of chemical species caused by such flows. The source of the water flow through the soil is solely the rainfall. The water motion is calculated for two different soil classes and for a typical annual precipitation. The codes which were used are based on the following model: The transport of chemical species is described by a set of partial differential equations, and the homogeneous chemical processes, under the assumption of equilibrium, are described by a set of nonlinear algebraic equations. The source terms of these partial differential equations are given by rate laws of the chemical weathering. Rainfall and chemical weathering are therefore the sources of the transport of reactive multispecies in this model.

Keywords: Rainfall; unsaturated zone; seepage water; weathering; geochemistry; aqueous solution; reactive solute transport

  • Transport In Porous Media 49 (2002) 361

Permalink: https://www.hzdr.de/publications/Publ-4462
Publ.-Id: 4462


Formation of Fe-oxyhydroxide particles during the dissolution of Fe-rich chlorite: Fate and behavior of heavy metals in the environment

Krawczyk-Bärsch, E.; Arnold, T.; Brandt, F.; Bosbach, D.; Bernhard, G.

The rock phyllite is commonly encountered in uranium tailings associated with the former uranium mining activities in the Western Erzgebirge in Germany. Currently, many of these mines are being flooded. The flood water, which contains concen-tration of uranium penetrates through cracks and fissures of the phyllite and leads to a dissolution of several minerals. One of the major components in the phyllite is an iron-rich chlorite [1], which dominates the sorption behaviour for heavy metals.
During the dissolution of the chlorite a reaction causes the loss of octahedral layer cations, primarily Fe. Ferrous iron is released in the aqueous solution, where it is oxidized rapidly to ferric iron. Hydro-lysis of ferric iron leads to Fe-oxyhydroxide, which precipitates from the solution as due to the low solubility of iron in the pH region higher 4. By scanning electron microscopy, these precipitates of Fe-oxyhydroxide are detected as small spherical particles of ferrihydrite that are preferentially situated as immobile coatings on the most reactive edge surfaces of the chlorite crystals [2]. During the dissolution of chlorite a mobile component of ferrihydrite is formed, too. These are colloids, which are found under similar geochemical conditions. The mobile colloids are aqueous species that do not adsorb to rock surfaces. The adsorption of contaminants, for example uranium onto the colloidal particles of ferrihydrite influences and enhances the rate of contaminant transport. In previous investigations the uptake of uranium on ferrihydrite reaches almost 95-100 % in a pH range from 5.0 to 7.5 [1]. Conclusively, the formation of secondarily formed ferrihydrite as mobile colloids and as immobile coatings during the dissolution of chlorite in the rock phyllite is an important process which has to be considered in risk management.

References:
[1] Arnold, T. et al. (1998): Chemical Geology 151,
129-141.
[2] Krawczyk-Bärsch, E. et al. (2002): Chemical
Geology (submitted).





  • Lecture (Conference)
    80. Jahrestagung der Deutschen Mineralogischen Gesellschaft vom 8.9. - 12.9.02 in Hamburg
  • Beiheft zum European Journal of Mineralogy (2002)14, 92

Permalink: https://www.hzdr.de/publications/Publ-4460
Publ.-Id: 4460


Facility Management in Forschungseinrichtungen - unmöglich möglich?

Joehnk, P.

  • Lecture (others)
    Workshop: "Technische Betriebsführung von A-Z", Heinrich Nickel GmbH, Bonn, 7.5.2002

Permalink: https://www.hzdr.de/publications/Publ-4459
Publ.-Id: 4459


Evaluation of QCD sum rules for light vector mesons at finite density and temperature

Zschocke, S.; Pavlenko, O. P.; Kämpfer, B.

QCD sum rules are evaluated at finite nucleon densities and temperatures to determine the change of mass parameters
for the lightest vector mesons ρ, ω and Φ in a strongly interacting medium. For conditions relevant for the starting experiments at HADES we find that the in-medium mass shifts of the ͦ and ω mesons are governed, within the Borel QCD sum rule approach, by the density and temperature dependence of the four-quark condensate. In particular, the variation of the strength of the density dependence of the four-quark condensate reflects directly the decreasing mass of the ρ meson and can lead to a change of the sign of the ω meson mass shift as a function of the density. In contrast, the in-medium mass of the Φ-meson is directly related to the chiral strange quark condensate which seems correspondingly accessible.

Keywords: QCD sum rules; vector meson properties

Permalink: https://www.hzdr.de/publications/Publ-4454
Publ.-Id: 4454


Chlorite dissolution relevant to environmental processes in Uranium tailings: influence on the Uranium(VI) migration

Krawczyk-Bärsch, E.; Arnold, T.; Walther, M.; Brandt, F.; Bosbach, D.; Bernhard, G.

In flow-through reactor experiments the dissolution of a ripidolite chlorite (CCa-2) from Flagstaff Hill (El Dorado County, California, USA) was studied with the intention to approach mineral dissolution conditions occuring in the unsaturated zone of an uranium tailing. The experiments were conducted under atmospheric conditions, a temperature of 25 °C, an ionic strength of 0.1 M, and a pH of 7. In addition the experiments were conducted with and without 1.10-6 M uranium and also with and without a humic acid concentration of 5 mg/L.
During the first eight hours of the experiments high initial dissolution rates calculated from Mg, Si, Al and Fe concentrations were determined. These initial dissolution rates are attributed to reactive surface sites on the freshly crushed chlorite platelets /1/. High initial dissolution rates were obtained when using an aqueous solution with a humic acid or uranium concentration. The initial dissolution rates for Mg and Si are 250 times and 400 times greater than the initial dissolution rates determined in experiments with solutions free of humic acid. In uranium containing solutions an initial dissolution rate for Al was 50 times greater than in solutions free of uranium. It seems that humic acid as well as uranium ions initiate a fast dissolution of the chlorite mineral. A constant dissolution rate was obtained after 8 hours which is almost similar to experiments with solutions free of humic acid and uranium. Average dissolution rates of 3,18.10-12 and 1,86.10-11 mol.m-2.sec-1 were calculated for Mg and Si, respectively. The average dissolution rates for Fe and Al of 7,86.10-13 and 2,87.10-12 mol.m-2.sec-1 respectively seem to be very low. In fact they are primarily higher. But however, they are based on the concentration of Fe and Al in solution and do not consider precipitated Fe and Al phases. Due to the low solubility of Fe and Al in aqueous solutions with a pH > 5 Fe-oxyhydroxides and Al(OH)-phases are precipitating. Fe-oxyhydroxide particles have been detected on the {hk0}-faces of chlorite crystals and as well as immobile colloids in the surrounding solution /2/. Due to their very high specific surface area and their affinity to bind heavy metals the formation of secondary Fe-minerals may significantly influence as Fe-coatings and Fe-colloids the migration of uranium and other toxic heavy metals in uranium tailings. Additional EXAFS investigations of sorbed uranium on chlorite platelets were performed to find out if chlorite or the newly formed Fe-phases are responsible for the immobilization of uranium in the environment of uranium tailings.

/1/ Rochelle, C.A. et al., 1995. Mat. Res. Soc. Symp. Vol. 353, p. 149-156.
/2/ Krawczyk-Bärsch et al.: Formation of secondary iron oxyhydoxide phases during the
dissolution of chlorite - effect on uranium sorption. In: Chemical Geology (submitted).


  • Lecture (Conference)
    39th Annual Meeting of The Clay Minerals Society, June 8-13, 2002, Boulder, Colorado, USA

Permalink: https://www.hzdr.de/publications/Publ-4453
Publ.-Id: 4453


Füllstandswächter zur diversitären Grenzwertmeldung an Siedewasserreaktoren - Entwicklung und Erprobung

Prasser, H.-M.; Böttger, A.; Schütz, P.; Zschau, J.; Fleischer, S.; Gocht, T.; Hampel, R.

Das Standardverfahren für die Füllstandsmessung von Flüssigkeiten in druckführenden Anlagenkomponenten von Kraftwerksanlagen basiert seit vielen Jahrzehnten auf einer Differenzdruckmessung. Am Siedewasserreaktor hat die Füllstandsmessung eine besonders hohe sicherheitstechnische Relevanz. Daher empfiehlt die Reaktorsicherheitskommission, eine diversitären Füllstandsmessung vorzusehen. Diversität bedeutet, dass das angewandte Verfahren nach einem andersartigen physikalischen Wirkprinzip funktionieren muss. Als diversitäres Messprinzip wurde die lokale Leitfähigkeitsmessung gewählt, mit der eine binär arbeitende Füllstandsdetektion zu realisieren war. Der Messwertgeber des vorgestellten Füllstandswächters ist für den Einbau in ein Standrohr vorgesehen. Der Nachweis der Flüssigphase geschieht durch Detektion deren elektrischer Leitfähigkeit. Der Füllstandswächter wurde entsprechend den Anforderungen an störfallfeste Instrumentierung für die Einbindung in den Reaktorsicherheitskreis entsprechend KTA 3505 ausgelegt. Weiterhin wurde er mit einem Selbsttest ausgestattet, die den Ausfall infolge Isolationsabfall oder Leitungsbruch signalisiert. Wesentliches Element des Messwertgebers ist eine isolierte Durchführung aus Aluminiumoxid-Sinterkeramik. Der Füllstandswächter wurde an einem Teststand der Hochschule Zittau/Görlitz unter Einsatznahen Bedingungen erprobt. Bei diesen und weiteren Tests wurde eine Standzeit von mindestens 5 Jahren bereits jetzt experimentell nachgewiesen. Die Qualifizierung des Füllstandswächters für den Einsatz im Kernkraftwerk ist im Gange. Sie umfasst hauptsächlich abschließende Entwicklungsschritte, die Durchführung der theoretischen und praktischen Prüfungen zur Bauartzulassung gem. KTA 3505 /3507 sowie die Untersuchung des Zusammenhangs von Füllstand im Standrohr und Füllstand im Reaktor zur Erarbeitung einer Konzeption zur Einbindung der Signale. Die Arbeiten zur Qualifizierung werden von Framatome ANP durchgeführt.

Keywords: coolant level; boilung water reactor; diversified level measurement system; conductivity probes

  • Lecture (Conference)
    Jahrestagung Kerntechnik 2002, Stuttgart, 14.-16. Mai 2002
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2002, Stuttgart, 14.-16. Mai 2002

Permalink: https://www.hzdr.de/publications/Publ-4452
Publ.-Id: 4452


Charge trapping in light-emitting SiO2-layers implanted with Ge+ ions

Gebel, T.; Rebohle, L.; Skorupa, W.; Nazarov, A. N.; Osiyuk, I. N.; Lysenko, V. S.

The trapping effects of negative and positive charges in Ge-enriched SiO2 layers during high-field electron injection from the Si-substrate of Al-SiO2-Si structures are studied. The capture cross-section and the concentration of negatively and positively charged traps are estimated and the location of the positively charged traps is determined. It is shown that increasing rapid thermal annealing (RTA) time from 6 s to 150 s at 1000°C leads to an enhanced diffusion of Ge towards the SiO2-Si interface and the increase of negatively and positively charged trap concentration. The mechanisms of the trap generation are discussed.

Keywords: silicon based light emission; charge trapping; nanocluster; electroluminescence

  • Applied Physics Letters 81 (2002) 1575

Permalink: https://www.hzdr.de/publications/Publ-4451
Publ.-Id: 4451


Observation of a hysteretic pseudogap behavior via coherent phonons in high temperature superconductors

Dekorsy, T.; Georgiev, N.; Helm, M.; Misochko, O. V.

We investigate ultrafast reflectivity changes of a near-optimally doped YBa2Cu3O7-x (123) superconductor. The amplitude of coherently excited phonons show strong changes as a function of temperature above the superconducting transition temperature. These changes give evidence for two crossover temperatures within the pseudogap regime. In addition, these crossover temperatures exhibit a clear hysteretic behavior as a function of temperature.

Keywords: time-resolved spectroscopy; high temperature superconductivity; coherent phonons; quasi particle dynamics

  • Contribution to external collection
    Springer Series in Chemical Physics 71 (2003) 368-370

Permalink: https://www.hzdr.de/publications/Publ-4450
Publ.-Id: 4450


Structural studies of ion beam synthesized nanocrystals: diamond in SiC and SiC in diamond

Eichhorn, F.; Heera, V.; Weishart, H.; Schell, N.

SiC and diamond are semiconductor materials with unique physical properties for very promising applications for high frequencies, high power and extreme environment (radiation, high temperature). However, the possibility of doping these materials are limited and complementary to each other. Only n-doped SiC and p-doped diamond can be produced in a reliable way [1]. It is found that p-n-junctions can be formed by ion beam synthesis of buried nanocrystallites, especially diamond in SiC [2] and SiC in diamond [3].
The materials studied were 6H-SiC(0001) implanted with 1x1018 cm-2 C+ (60 keV) at 900 °C and diamond(001) implanted with 5.3x1017 cm-2 Si+ (120 … 170 keV) at 900 °C. In this high temperature implantation processes nanocrystals of diamond are grown in 6H-SiC at a depth of (110 ± 30) nm below the surface and 3C-SiC nanocrystals in diamond at a depth of (90 … 130 ± 30) nm, respectively. At lower implantation temperatures it was not possible to grow diamond in 6H-SiC.
Various x-ray scattering techniques like coplanar diffraction, grazing incidence diffraction, texture studies, measurement of specular reflectivity, and reciprocal space mapping were used at laboratory and synchrotron (ROBL at ESRF) sources to study structural details of the material.
The nanocrystals of diamond have a diameter of 5 … 6 nm, and those of 3C-SiC a diameter of 7 … 8 nm. They are oriented completely heteroepitaxially according to
diamond < 1 1 1 > || substrate 6H-SiC < 0 0 0 1 >
diamond < 1 1 0 > || substrate 6H-SiC < 1 1 -2 0 >
3C-SiC < 0 0 1 > || substrate diamond < 0 0 1 >: all crystallographic directions of both cubic materials coincide.
The mosaicity (angular fluctuation of the alignment) is anisotropic to the surface and lies for diamond crystals in 6H-SiC in the range from 2° (220) to 6° (111) and for 3C-SiC crystallites in diamond in the range from 5° (111) to 12° (002), respectively.
The heteroepitactic growth is favoured by a partial coherence of the neighbouring crystal lattices: in both systems a 4:5 coherence between the crystal lattices of synthesized crystallites and substrate is observed:
5 x ddiamond(111) » 4 x d6H-SiC(0006) (1.027 nm » 1.004 nm)
5 x ddiamond(220) » 4 x d6H-SiC(11-20) (0.629 nm » 0.615 nm)
4 x a3C-SiC » 5 x adiamond (1.744 nm » 1.780 nm).
In all cases the strain does not exceed 2.3 %.
In conclusion it can be stated that well aligned nanocrystals can be grown by the ion beam synthesis at high temperatures in 6H-SiC as well as in diamond.


References
[1] - R. Kalish, Diamond and Related Materials 10, 1749 (2001)
[2] - V. Heera, W. Skorupa, B. Pécz and L. Dobos, Applied Physics Letters 76, 2847 (2000)
[3] - V. Heera, F. Fontaine, W. Skorupa, B. Pécz and A. Barna, Applied Physics Letters 77, 226 (2000)

Keywords: nanocrystals; x-ray diffraction; synchrotron x-rays; SiC; diamon

  • Poster
    X-TOP 2002 “6th Biennial Conference on High Resolution X-Ray Diffraction and Imaging” September 10–14, 2002 Grenoble-Aussois, France

Permalink: https://www.hzdr.de/publications/Publ-4449
Publ.-Id: 4449


AlN growth kinetics during ion nitriding of aluminum

Fitz, T.; Möller, W.

To study the kinetics of Al ion nitriding, a series of experiments have been performed at an ion energy of 1.6 keV, an ion current density of 0.2 mA/cm2 and substrate temperatures varied from 250 °C to 400 °C. The nitride layers have been analyzed by nuclear reaction analysis (NRA) and scanning electron microscopy (SEM). Binary collision computer simulations have been performed to calculate the sputtering yields of N and Al. Depending on the experimental conditions, the nitriding kinetics is either controlled by the supply of N atoms from the ion beam or by the diffusion of Al atoms trough the growing nitride layer. Solutions of rate equations describing the growth of the nitride layer are fitted to the experimental data, from which diffusion and activation parameters are obtained for the transport of the Al atoms.

Keywords: Aluminium; nitriding; diffusion; AlN

  • J.Appl.Phys. Vol. 92, No. 11, (2002) p.6862-6867

Permalink: https://www.hzdr.de/publications/Publ-4448
Publ.-Id: 4448


An in-depth investigation of the energy distribution of doubly charged ions emitted from a liquid metal alloy ion source

Mair, G.; Bischoff, L.; Mair, A.; Aidinis, C.; Ganetsos, T.; Aleiev, C.

We investigate the energy spread, dE½, vs emission current, i, of the doubly-charged ions emitted by a Au77Ge14Si9 Liquid Metal Alloy Ion Source (LMAIS). For the ionic species of main interest, namely Ge++, two modes were found with regard to the dependence of dE½ on i. In the first mode dE½ ~ i^ 0.3 and in the second dE½ ~ i . The difference is attributed to changes in the composition of the alloy during field-evaporation. Au++ an Si++ were also found to obey a dE½ ~ i^ 0.3 law; in the case of Si++ however, there is a deviation from this law at high currents.

Keywords: alloy liquid metal ion source; energy spread; doubly charged ions

  • Journal of Physics D: Applied Physics 35 (2002) L33 - L36

Permalink: https://www.hzdr.de/publications/Publ-4446
Publ.-Id: 4446


Electroproduction of Strangeness on Light Nuclei

Dohrmann, F.; Abbott, D.; Ahmidouch, A.; Ambrozewicz, P.; Armstrong, C. S.; Arrington, J.; Asaturyan, R.; Assamagan, K.; Avery, S.; Bailey, K.; Baker, O. K.; Beedoe, S.; Bitao, H.; Breuer, H.; Brown, D. S.; Carlini, R.; Cha, J.; Chant, N.; Christy, E.; Cochran, A.; Cole, L.; Collins, G.; Cothran, C.; Crowder, J.; Cummings, W. J.; Danagoulian, S.; Duncan, F.; Dunne, J.; Dutta, D.; Eden, T.; Elaasar, M.; Ent, R.; Ewell, L.; Fenker, H.; Fortune, H. T.; Fujii, Y.; Gan, L.; Gao, H.; Garrow, K.; Geesaman, D. F.; Gueye, P.; Gustafsson, K.; Hafidi, K.; Hansen, J. O.; Hinton, W.; Jackson, H. E.; Juengst, H.; Keppel, C.; Klein, A.; Koltenuk, D.; Liang, Y.; Liu, J. H.; Lung, A.; Mack, D.; Madey, R.; Markowitz, P.; Martoff, C. J.; Meekins, D.; Mitchell, J.; Miyoshi, T.; Mkrtchyan, H.; Mohring, R.; Mtingwa, S. K.; Mueller, B.; O'Neill, T. J.; Niculescu, G.; Niculescu, I.; Potterveld, D. H.; Price, J. W.; Raue, B. A.; Reimer, P. E.; Reinhold, J.; Roche, J.; Roos, P.; Sarsour, M.; Sato, Y.; Savage, G.; Sawafta, R.; Segel, R. E.; Semenov, A. Y.; Stepanyan, S.; Tadevosian, V.; Tajima, S.; Tang, L.; Terburg, B.; Uzzle, A.; Wood, S.; Yamaguchi, H.; Yan-1, C.; Yan-2, C.; Yuan, L.; Zeier, M.; Zeidman, B.; Zihlmann, B.

The A(e,e'K+)YX reaction has been investigated in Hall C at Jefferson Laboratory for 6 different targets. Data were taken for Q2)approx 0.35 and 0.5 GeV2) at a beam energy of 3.245GeV for 1)H, 2)H, 3)He, 4)He, C and Al targets. The missing mass spectra are fitted with Monte Carlo simulations taking into account the production of Lambda and Sigma0) hyperon production off the proton, and Sigma-) off the neutron. Models for quasifree production are compared to the data, excess yields close to threshold are attributed to FSI. Evidence for Lambda-hypernuclear bound states is seen for 3,4)He targets.

Keywords: Electroproduction of strangeness; Nuclear targets; Spectral function

  • Lecture (Conference)
    B.A. Mecking and C.E. Carlson(eds.) Proceedings of the 9th International Conference on the Structure of Baryons, Baryons 2002, March 3-8 2002, Jefferson Lab, Newport News, VA, USA World Scientific, New Jersey, 2003 , 585-588
  • Contribution to proceedings
    B.A. Mecking and C.E. Carlson(eds.) Proceedings of the 9th International Conference on the Structure of Baryons, Baryons 2002, March 3-8 2002, Jefferson Lab, Newport News, VA, USA World Scientific, New Jersey, 2003 , 585-588

Permalink: https://www.hzdr.de/publications/Publ-4445
Publ.-Id: 4445


Transition from amorphous boron carbide to hexagonal boron carbon nitride thin films induced by nitrogen ion assistance

Gago, R.; Jiménez, I.; Agullo-Rueda, F.; Albella, J. M.; Czigány, Z.; Hultman, L.

Boron carbon nitride films (BCN) were grown by B4C evaporation under concurrent N2 ion beam assistance (IBAD). The films were characterized by x-ray absorption near edge spectroscopy, IR and Raman spectroscopy and high-resolution transmission electron microscopy. The bonding structure and film composition correlate with the momentum transfer per incoming atom during deposition. As the momentum transfer is increased, the film structure evolves from an amorphous boron carbide network towards a hexagonal ternary compound (h-BCN) with standing basal planes. The growth of h-BCN takes place for momentum transfer in the window between 80 and 250 (eVxamu)1/2. The characteristic vibrational features of the h-BCN compounds have also been studied. Finally, the solubility limit of carbon in the hexagonal BN structure, under the working conditions of this report, is found to be ~15 at. %.

Keywords: Boron carbon nitride; IBAD; XANES; IR and Raman

  • Journal of Applied Physics 92 (2002) 5177-5182

Permalink: https://www.hzdr.de/publications/Publ-4444
Publ.-Id: 4444


N1-Methyl-9-[(4-[18F]fluoro-3-hydroxymethylbutyl]guanine [18F]MFHBG as new substrate of HSV-1-thymidine kinase to monitor gene expression?

Noll, B.; Grote, M.; Noll, S.; Bergmann, R.; Wolkersdorfer, G.; Johannsen, B.

Aim
Gene therapy with the transfer of Herpes simplex virus type 1 thymidine kinase gene (HSV1-tk) has shown significant potential in treating several cancers. Many nucleoside analogues are known to localize selectively HSV1-tk transfected cells and show a high specificity for the viral enzyme, especially acyclic nucleosides such as ganciclovir or penciclovir. The penciclovir derivative [18F]FHBG is one of the proposed tracer for monitoring the gene expression by positron emission tomography. In order to improve the tracer properties, we modified the lipophilicity of [18F]FHBG by introduction of a methyl group into the N1-position to get N1-methyl-9-[(4-[18F]fluoro-3-hydroxymethylbutyl]guanine 3.

Materials and methods
The precursor 1 and the nonradioactive reference substance (MFHBG) were prepared by methylation of N1-Methyl-N2-(p-anisyldiphenylmethyl)-9-[(4-(p-toluene-sulphonyloxy))-3-(p-anisyldiphenylmethoxy)-methyl-butyl]guanine with methyl iodide in the N1 position. The precursor 1 reacts with a [18F]KF kryptofix complex to the intermediate 2 in a 65-75 % radiochemical yield. In a second step the protecting groups are removed from 2 by heating in methanolic HCl solution. The tracer is purified by RP HPLC separation. The identity of the tracer [18F]MFHBG with the nonradioactive reference compound was also proved by HPLC. The in vitro uptake of [18F]FHBG and [18F]MFHBG was evaluated into transduced and non-transduced human MC 38 cells.

Results
The labelling yield amounts to 70%, and the radiochemical purity of the tracer is greater than 98 %. Biodis-tribution data of [18F]MFHBG show a fast blood clearance without remarkable erythrocyte binding. An ini-tial high uptake of the tracer was found in the spleen, kindney and liver, which decreased rapidly in time. No metabolites were found. The rapid blood and organ clearance (faster than for [18F]FHBG) and the high in vivo stability of [18F]MFHBG are considered advantageous for in vivo monitoring of the gene transfer in tumours. The uptake of [18F]MFHBG is however lower than the uptake of [18F]FHBG in HSV1-tk trans-fected cell lines.

Conclusion
The novel tracer 9-[(4-[18F]fluoro-3-hydroxymethyl-butyl]-guanine ([18F]MFHBG) seems to be inferior to [18F]FHBG because of lower uptake in the target cells. It is assumed that the molecule position chosen for methylation is unsuitable for the anticipated improvement of the tracer.

  • Poster
    Annual Congress of the European Association of Nuclear Medicine, Vienna, 31.08.-04.09.2002

Permalink: https://www.hzdr.de/publications/Publ-4443
Publ.-Id: 4443


A new approach for a C-11-C bond formation: Synthesis and biodistribution studies of 17a-(3'-[11C]prop-1-ynyl)-3-methoxy-3,17b-estradiol

Wüst, F.; Zessin, J.; Bergmann, R.; Pawelke, B.

AIMS: To expand the scope of 11C-labelled compounds, novel 11C-C bond forming reactions gain more and more attention. In this context, technically simple, high-yielding and functional group tolerating reactions are of particular interest. The Sonogashira copper-palladium catalysed coupling of terminal alkynes with aromatic and vinylic halides represents such a reaction. To the best of our knowledge, the Sonogashira-reaction has not yet been employed in 11C-chemistry. In this work we describe a modified Sonogashira-like reaction for labelling the terminal alkyne group of the potent contra-ceptive steroid mestranol with [11C]methyl iodide and biodistribution studies of the title compound.
METHODS: Pd2(dba)3/AsPh3/TBAF as catalyst/co-ligand/base combination was used to form the desired cross-coupling product in sufficient radiochemical yield. The labelling position was verified by the synthesis of the corresponding 13C-labelled compound using the same cross-coupling protocol. Biodistribution studies were performed with immature female Wistar rats. One group of animals was pre-treated with 1 mg/kg body weight 17a-ethynyl-estradiol 10 minutes before injecting the 11C-labelled compound. Radioactivity distribution in organs of interst was studies after 5 and 60 minutes after injection. Blood plasma samples were taken for metabolite analysis by means of radio-HPLC.
RESULTS: A new approach for a 11C-C bond formation via a Sonogashira-like cross-coupling reaction of terminal acetylenes with [11C]MeI was exemplified by the synthesis of 17a-(3'-[11C]prop-1-ynyl)-3-methoxy-3,17b-estradiol. Classical conditions of the Sonogashira reaction (Pd0, CuI and TEA or DIPA as the base) can not be employed for 11C-labelling with [11C]methyl iodide due to the rapid quaternization of the amine base. Using optimized alternative reaction conditions (Pd2(dba)3/AsPh3/TBAF/[11C]MeI/ steroid in THF, 5 minutes at 60°C) the title compound was obtained in decay-corrected radiochemical yields of 27-47% (n=8) based on [11C]MeI within 21-27 minutes after EOB. In a typical synthesis, 1-2 GBq of 17a-(3'-[11C]prop-1-ynyl)-3-methoxy-3,17b-estradiol could be synthesized in radiochemical purity >99%. The specific activity ranged between 10-19 GBq/µmol, and the labeling position was verified by the synthesis of the corresponding 13C-labeled compound. Biodistribution studies after 5 min. and 60 minutes exhibited no specific binding in target organs (uterus, ovaries). The highest uptake of radioactivity was observed in the fat (4.7% ID/g tissue nomalized to 100 g body weight at 60 minutes). The compound was fast metabolized and biliary eliminated.
CONCLUSION: We developed a new method for a 11C-C bond formation employing the cross-coupling of terminal alkynes with [11C]methyl iodide via a Sonogashira-like reaction in sufficient radiochemical yields. The biodistribution data of the title compound are consistent with the high lipophilicity of the compound.

  • Lecture (Conference)
    Turku PET Symposium, May 2002

Permalink: https://www.hzdr.de/publications/Publ-4442
Publ.-Id: 4442


Effect of hypoxia/hypercapnia on metabolism of 6-[18F]fluoro-L-DOPA in newborn piglets

Bauer, R.; Brust, P.; Walter, B.; Vorwieger, G.; Bergmann, R.; Elhalag, E.; Fritz, A.; Steinbach, J.; Füchtner, F.; Hinz, R.; Zwiener, U.; Johannsen, B.

There is evidence that the dopaminergic system is sensitive to altered pO2 in the immature brain. However, the respective enzyme activities have not been measured in the living neonatal brain together with brain oxidative metabolism. Therefore 18F-labelled 6-fluoro-L-3,4-dihydroxyphenylalanine (FDOPA) together with positron emission tomography (PET) was used to estimate the activity of the aromatic amino acid decarboxylase (AADC) in the brain of fifteen newborn piglets (2 - 5 days old). Two PET scans were performed in each piglet. Eleven animals underwent a period of normoxia and moderate hypoxia/hypercapnia (H/H). The remaining four animals were used as an untreated control group. Simultaneously, the brain tissue pO2 was recorded, the regional cerebral blood flow (CBF) was measured with colored microspheres and the cerebral metabolic rate of oxygen (CMRO2) was determined. In addition, in four untreated and six H/H treated piglets the relative amounts of fluorodopamine and the respective metabolites were determined in brain tissue samples using HPLC analysis. H/H conditions were induced by lowering the inspired fraction of oxygen from 0.35 to 0.10 and adding CO2 to the inspired gas resulting in an arterial pO2 between 74 and 79 mmHg. H/H elicited a more than 3-fold increase of the CBF(P < 0.05) so that CMRO2 remained unchanged throughout the H/H period. Despite this, the brain tissue pO2 was reduced from 19 ± 4 to 6 ± 3 mmHg /P < 0.05). The permeability-surface area product of FDOPA (PSFDOPA) was unchanged. However, the transfer rate of FDOPA (k3FDOPA of the nigrostriatal dopaminergic system and the relative amounts of fluorodopamine and the respective metabolites were significantly increased (P < 0.05). It is suggested that H/H induces an increase of AADC activity. However, an H/H-induced CBF increase maintains bulk O2 delivery and preserves CMRO2.

Keywords: FDOPA; Aromatic amino acid decarboxylase; Dopamine metabolism; Positron emission tomography; Colored microspheres; Newborn piglets

  • Brain Research 934 (2002) 22-33

Permalink: https://www.hzdr.de/publications/Publ-4441
Publ.-Id: 4441


Kombinierter Einsatz von FCKW und Tritium als Tracer

Mibus, J.; Szymczak, P.; Hebert, D.; Oster, H.

Zur Bewertung der Grundwassergeschütztheit werden neben hydrogeologischen und hydrochemischen Untersuchungen auch die Altersdatierung der Grundwässer anhand der Konzentration des Tritiums (³H) herangezogen. Rückläufige Tritiumkonzentrationen im Niederschlag und eine im Modell-ansatz begründete, häufig auftretende Ambiguität der Ergebnisse schränken die Anwendbarkeit ein oder erfordern Zusatzinformationen. Eine Möglichkeit zum Informationsgewinn stellt die Messung von im low-level Konzentrationsbereich auftretenden FCKW dar. Die kombinierte Anwendung beider Umwelttracer wird in einem Gemeinschaftsprojekt bei der Untersuchung einer Trinkwasserfassung in der Jahna-Aue (Nordwest-Sachsen) gezeigt.
Aus dem Zusammenhang zwischen Tritium-Konzentration und dem aus FCKW-Gehalten berechneten Jungwasseranteil konnten Rückschlüsse über die Verweilzeit der Wässer in der Aerationszone gezogen werden. Damit war es möglich, das mehrdeutige Ergebnis der Simulation der Output-Funktion des Tritiums eindeutig zu interpretieren. Die Grundwässer weisen bei mittleren Verweilzeiten von ca. 50 Jahren eine gute Geschütztheit auf.

  • Contribution to external collection
    Isotopen und Tracer in der Wasserforschung, TU BA Freiberg, 21.6.2002

Permalink: https://www.hzdr.de/publications/Publ-4440
Publ.-Id: 4440


Validation of a creep and plasticity model for French and German RPV-steels

Willschütz, H.-G.; Altstadt, E.; Sehgal, B. R.; Weiß, F.-P.

For pre- and post-test calculations of Lower Head Failure experiments like FOREVER or OLHF it is necessary to model creep and plasticity processes. Therefore a Finite Element Model is developed using a numerical approach which avoids the use of a single creep law employing constants derived from the data for a limited stress and temperature range. Instead of this a numerical creep data base (CDB) is developed where the creep strain rate is evaluated in dependence on the current total strain, temperature and equivalent stress. The CDB includes the primary, secondary and tertiary creep stage. A main task for this approach is the generation and validation of the CDB. The source for the CDB are uniaxial creep tests, like the REVISA-experiments.
For an evaluation of the failure times a damage model is necessary. The applied damage model accounts for the triaxiality of the mechanical stresses according to an approach of Lemaitre.
The validation of the numerical model is performed by the simulation of and comparison with experiments. This is done in 3 levels: starting with the simulation of single uniaxial creep tests, which is considered as a 1D-problem. In the next level so called “tube-failure-experiments” are modeled: the RUPTHER-14 and the “MPA-Meppen”-experiment. These experiments are considered as 2D-problems. The last level considers the application of the numerical model to scaled 3D-experiments, where the lower head of a PWR is represented in its hemispherical shape, like in the FOREVER-experiments.

Keywords: creep and plasticity; Finite Element Model; French and German RPV-steel

  • Lecture (Conference)
    OLHF Seminar 2002, Madrid, Spain, June 2002; OECD Nuclear Energy Agency Proceedings February 2003, NEA/CSNI/R(2003)1, pp 117-136
  • Contribution to proceedings
    OLHF Seminar 2002, Madrid, Spain, June 2002; OECD Nuclear Energy Agency Proceedings February 2003, NEA/CSNI/R(2003)1, pp 117-136

Permalink: https://www.hzdr.de/publications/Publ-4439
Publ.-Id: 4439


Cavitation behind a fast acting flap valve and prevention of water hammers

Prasser, H.-M.; Böttger, A.; Zschau, J.; Dudlik, A.; Schlüter, S.

Fast shut-off experiments were carried out at a 200 m long experimental pipeline of the Fraunhofer Institute for Environmental, Safety, and Energy Technology (UMSICHT) in Oberhausen, Germany. The cavitation bubbles occurring at the fast acting valve were recorded by means of mesh sensors. Primarily these sensors record distributions of the electrical conductivity in the measuring cross section, which are converted into void fraction distributions, stored with a rate of 1024 frames per second. An excentrical butterfly valve was used to shut off the pipeline. The sensor was located at different positions up- and downstream the valve. In a pipe of 100 mm nominal diameter the cavitation bubble was recorded at distances of 0,15 m and 1,5 m downstream the valve. In the presentation, computer animations of the measured signals will be shown, in which the appearance and the collapse of the bubbles are visible in high temporal and spatial resolution. Furthermore, the influence of a pipe bridge located behind the valve as well as the damping effect of injected air to the amplitude of the pressure peaks will be discussed on the basis of such visualisations. Special cavitation patterns occurred during partial closing of the valve. In another experiment two sensors were directly flanged to a flap valve of 50 mm nominal diameter, located in the rear section of the pipeline. It was found that cavitation appeared also upstream the valve as well as at the edge of the flap of the valve. With the help of the obtained information it was possible to design measures for water hammer prevention. A back valve put at a certain distance downstream the shut-off valve closes in the moment of flow reverse. In this way, the cavitation bubble is captured and the cavitation collapse cannot occur. The closure of the back valve itself is not accompanied with a pressure peak. Water hammers upstream the main valve are prevented by a second measure: a disc brake acting at the shaft of the flap valve, which is interrupting the closing movement of the flap when the upstream pressure starts to grow. A combination of both methods allows to cut off the liquid flow without pressure peaks in the smallest possible time.

Keywords: water hammers; mesh sensors; void measurement; fast acting valve; cavitation

  • Lecture (Conference)
    XXXIV. Kraftwerkstechnisches Kolloquium, TU Dresden, 24.-26. September 2002, Vortrag VM8, Kurzfassung in Beitragsmanusskripte, S. 184.

Permalink: https://www.hzdr.de/publications/Publ-4438
Publ.-Id: 4438


Sorption of Uranium(VI) onto ferric oxides in sulfate-rich acid waters

Walter, M.; Arnold, T.; Reich, T.; Bernhard, G.

The Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy was used to study the sorption of uranium(VI) on schwertmannite and goethite. Samples for EXAFS analysis were prepared under N2 atmosphere with initial uranium(VI) concentrations of 1x10-5 (pH 6.5) to 5x10-5 M (pH 4.2). The ionic strength was adjusted to 0.02 N Na2SO4 or 0.01 N NaClO4, respectively. The results from EXAFS spectroscopy of uranium(VI) sorbed on goethite in sulfate-rich, acid and near-neutral solutions indicate that uranium(VI) is sorbed as an inner-sphere mononuclear bidentate surface complex which is coordinated to ferric iron at a distance of 3.44 Å. The uranium(VI) sorbed onto schwertmannite in acid and sulfate-rich solution is coordinated to one or two sulfate molecules at a distance of 3.66 Å. The EXAFS results indicate the formation of mononuclear-monodentate surface complexes and partly, of binuclear-bidentate surface complexes coordinated to the structural sulfate of schwertmannite. Considering the uncertainty in assigning the sulfate either to the bulk structure or to adsorption reactions, the formation of ternary uranium(VI)-sulfate surface complexes could not be excluded. Due to the release of sulfate from schwertmannite in perchlorate solution, the uranium(VI) adsorption occurs predominantly as a mononuclear bidentate complexation with the ferric iron.

Keywords: uranium; schwertmannite; goethite; EXAFS; acid mine drainage; sorption

Permalink: https://www.hzdr.de/publications/Publ-4437
Publ.-Id: 4437


Einfluss des Gefüges auf die Neutronenversprödung von Reaktordruckbehälterstählen

Böhmert, J.; Viehrig, H.-W.; Ulbricht, A.

Neutronenstrahlen führen zu einer Degradation der mechanischen Eigenschaften niedriglegierter Stähle, die als Neutronenversprödung bezeichnet wird. Sie wirkt sich vorzugsweise als Erhöhung der Übergangstemperatur zwischen sprödem und duktilem Bruchverhalten und in einer Absenkung der Hochlagenbruchenergie aus. Die Größe des Effektes ist von der Neutronendosis abhängig, wird aber darüber hinaus vor allem mit dem Gehalt an bestimmten, versprödungsfördernden Elementen in Verbindung gebracht. Vergleichende Untersuchungen an Proben aus der Wand eines Druckbehälters, aus der Schweiße und der Wärmeeinflusszone oder an Proben aus unterschiedlichen Tiefenlagen eines Druckbehälters zeigen jedoch klar, dass die Gefügeausbildung einen dominierenden Einfluss ausübt. Es werden die Ergebnisse von mechanischen Prüfungen (Charpy-Versuche, Zugversuche, Bruchzähigkeitsbestimmung) nach Bestrahlungen bis 5 x 10 19 n/cm2 [E < 1 MeV] bei 255 °C vorgestellt. Die strahleninduzierten Strukturdefekte werden mit Hilfe der Neutronenkleinwinkelstreuung analysiert. Die erhaltenen Korrelationen zwischen den Änderungen der mechanischen Eigenschaften und den Strukturparametern werden unter dem Aspekt der unterschiedlichen Ausgangsgefüge klassifiziert und hinsichtlich ihrer Verträglichkeit mit bekannten Modellen zum Mechanismus der Neutronenversprödung bewertet.

  • Poster
    7. Tagung "Gefüge und Bruch", Tagungsband, Leoben (Österreich), April 2002, S. 129
  • Contribution to proceedings
    7. Tagung "Gefüge und Bruch", Tagungsband, Leoben (Österreich), April 2002, S. 129

Permalink: https://www.hzdr.de/publications/Publ-4436
Publ.-Id: 4436


Thermal Parameters in Heavy Ion Collisions at SPS and RHIC: Centrality Dependence

Kämpfer, B.; Cleymans, J.; Gallmeister, K.; Wheaton, S.

The centrality dependence of thermal parameters describing hadron multiplicities and intermediate-mass dilepton spectra in heavy-ion collisions at SPS and RHIC is analyzed. From hadron multiplicities we deduce evidence for strangeness saturation at high energy and maximum centrality. The dilepton spectra can be parameterized by a centrality independent temperature.

Keywords: relativistic heavy-ion collisions; thermal models; hadron yields; dileptons

  • Acta Phys Hung NS-H 18(1):1-10 2003

Permalink: https://www.hzdr.de/publications/Publ-4435
Publ.-Id: 4435


Synthetische und modifizierte Huminsäuren zur Untersuchung des Wechselwirkungsverhaltens von Huminsäuren mit Metallionen

Sachs, S.; Heise, K.-H.; Bernhard, G.

Huminstoffe sind aufgrund ihrer ausgeprägten Eigenschaft, Metallionen zu komplexieren, in der Lage, die Speziation von Metallionen in der Umwelt und somit auch deren Ausbreitungsverhalten zu beeinflussen. Bedingt durch ihre große strukturelle und funktionelle Heterogenität in Abhängigkeit von ihrer Herkunft ergeben sich Probleme bei der Beschreibung ihres Wechselwirkungsverhaltens mit Metallionen in natürlichen Systemen. Zur detaillierten Untersuchung des Wechselwirkungsverhaltens von Huminsäuren mit Metallionen wurden am Institut für Radiochemie des Forschungszentrums Rossendorf Huminsäuremodellverbindungen mit unterschiedlichen strukturellen und funktionellen Eigenschaften, basierend auf dem Melanoidinkonzept, entwickelt [1,2]. Darüber hinaus wurde ein Verfahren zur Synthese von chemisch modifizierten Huminsäuren, Huminsäuren mit blockierten phenolischen OH-Gruppen, erarbeitet [3]. Mit diesen Huminsäuren kann der Einfluß phenolischer OH-Gruppen auf das Wechselwirkungsverhalten von Huminsäuren mit Metallionen untersucht werden. Zur Untersuchung der Redoxeigenschaften von Huminsäuren sowie der Redoxstabilität von Metall-Humat-Komplexen werden Huminsäuremodellverbindungen mit ausgeprägter Redoxfunktionalität entwickelt.
Der Vortrag gibt einen Überblick zur Synthese und Anwendung von Huminsäuremodellverbindungen. Anhand der synthetischen Huminsäure vom Typ M1 [1] wird die Präparation von chemisch modifizierten Huminsäuren mit blockierten phenolischen OH-Gruppen erläutert. Ergebnisse NMR-spektroskopischer Untersuchungen, die den Verlauf des Modifzierungsprozesses bestätigen [4], werden diskutiert. Die Synthese von Huminsäuren mit ausgeprägt reduzierenden Eigenschaften wird vorgestellt und das Fe(III)-Reduktionsvermögen dieser Huminsäuremodellverbindungen mit dem natürlicher und anderer synthetischer Huminsäuren verglichen.

Literatur
[1] Pompe (Sachs), S. et al., Radiochim. Acta 74, 135 (1996).
[2] Pompe (Sachs), S. et al., Wissenschaftlich-Technische Berichte FZR-290, Rossendorf 2000.
[3] Pompe (Sachs), S. et. al., Radiochim. Acta 88, 553 (2000).
[4] Sachs, S. et al., Talanta, zur Publikation angenommen.

Keywords: Huminsäuren; Modellverbindungen; Modifizierung; Komplexierung; Redoxfunktionalität

  • Lecture (others)
    Symposium über Torfpräparate in der Medizin, Veterinärmedizin und Körperpflege, Bad Langensalza, 23.-24.Mai 2002
  • Contribution to external collection
    Sitzungsberichte der Mathematisch-Naturwissenschaftlichen Klasse der Akademie gemeinnütziger Wissenschaften zu Erfurt 2002. Sitzungsberichte der Mathematisch-Naturwissenschaftlichen Klasse 12 (2003) 125-137, ISBN 3-932295-62-5

Permalink: https://www.hzdr.de/publications/Publ-4434
Publ.-Id: 4434


Endangered glass objects identified by ion beam analysis

Neelmeijer, C.; Mäder, M.

Art objects of glass are subjected to ageing processes even under air conditioning of museums. Glass surfaces are decomposed and sometimes their transparency is considerably reduced. This is the consequence of chemical processes which take place between the silicate network and the humidity of the ambient atmosphere. In particular, potassium-calcium-silica glasses are affected. Degradation takes place via ion exchange reactions where potassium and calcium are leached out and hydrogen-bearing species are incorporated into the silicate structure. Endangered glass objects of museums should be indicated by means of non-destructive composition analysis. Simultaneous use of the ion beam methods PIXE, PIGE and RBS at a non-vacuum facility proves ideal to determine both the corrosion state of the glass surface and the composition of the glass bulk. The results allow recommendations to museums regarding demands of special storage conditions. Art scientists may deduce details on the glass prove-nience or on special manufacturing technologies.

Keywords: glass corrosion; glass deterioration; glass disease; museum glass objects; non-destructive glass analysis; preventive ion beam analysis; PIXE; PIGE

  • Lecture (Conference)
    Art2002, 7th Int. Conf. on Non-destructive Testing and Microanalysis for the Diagnostics and Conservation of the Cultural and Environmental Heritage, Antwerpen, Belgien, 2.-6. Juni 2002, Conference Proceedings
  • Contribution to external collection
    René Van Grieken, Koen Janssens, A.A. Balkema Publishers: Cultural Heritage Conservation and Environmental Impact Assessment by Non-Destructive Testing and Micro-Analysis, London: Taylor & Francis Group, 2005, 211-222

Permalink: https://www.hzdr.de/publications/Publ-4433
Publ.-Id: 4433


Strahlende Stützen - Radioaktiv markierte Stents verhindern die Re-Stenose von Blutgefäßen

Ottow, S.; Noll, B.

Das Forschungszentrum Rossendorf (FZR) wurde am 1. Januar 1992 aus dem Zentralinstitut für Kernforschung der Akademie der Wissenschaften der DDR gegründet. Im neu gewonnenen Profil des FZR bilden nunmehr seit zehn Jahren Materialforschung, Biochemie-Medizin, Umwelt- und Sicherheitsforschung sowie Kernphysik die Schwerpunkte.
Durch seine Vergangenheit hat die Forschung rund um die Radioaktivität im FZR eine lange Tradition. Und genau dieser Tradition folgt der Beitrag "Strahlende Stützen". Er befasst sich mit dem Einsatz von Radioaktivität in der Medizin, die nicht nur zur Bekämpfung von Krebs ein unerlässliches Hilfsmittel ist. Mediziner setzen Radioaktivität zur Behandlung der unterschiedlichsten Krankheiten ein, so auch zur Behandlung von Arteriosklerose.

  • Leibniz 1 (2002) 13-14

Permalink: https://www.hzdr.de/publications/Publ-4432
Publ.-Id: 4432


Tc and Re chelates of 8alpha-amino-6-methyl-ergoline: synthesis and affinity to the dopamine D2 receptor

Spies, H.; Noll, B.; Noll, S.; Findeisen, M.; Brust, P.; Syhre, R.; Berger, R.

The influence of structural changes at the 8alpha-amino position of 8alpha-amino-6-methyl-ergoline on the lipophilicity and affinity to the D2 receptor was studied.8alpha-amino- 6-methyl-ergoline (1) was converted into the derivatives (2a-f) by mercaptoacylation of the amino group to make it possible to prepare the rhenium and technetium complexes (3, 4a,b). Binding tests on cloned human dopamine D2 receptors show that the affinities of the coordination compounds (IC50 values between 50 and 240 nM) are less than those of the derivatives 2a-f (IC50= 3 to 50 nM) but more than those of the parent compound 1. Biodistribution studies of the Tc complexes 4a,b performed on Wistar rats show a slow blood clearance with substantial accumulation and retention in the liver and kidneys and low brain uptake.

  • Bioorganic and Medicinal Chemistry 10 (2002) 3523-3528

Permalink: https://www.hzdr.de/publications/Publ-4430
Publ.-Id: 4430


5HT1A- and 5HT2A-receptors during social isolation in mice

Oehler, J.; Schiller, L.; Kretzschmar, M.; Brust, P.

Social isolation is an animal model for analysing behavioural and neurobiological processes caused by impairment of organism
environment relationships. In previous studies we found time dependent changes in behaviour and central transmitter metabolism
especially in the serotonergic and dopaminergic systems (Rilke et al. 1998a, Rilke et al. 1998b).
The aim of the study was to find out time-dependent effects of social isolation after 4 and 12 weeks at serotonin receptor 5HT1A- and
5HT2A-subtypes. Autoradiographic studies in distinct brain regions were carried out and the Bmax-values were determined.
After 4 weeks Bmax-values for both subtypes were diminished in all analysed brain regions. After 12 weeks of isolation weaker alterations were found. Only the Bmax-values for the 5HT1A-receptor in the hippocampus were significantly decreased. Furthermore up-regulations for both receptors were found in some regions.
The results we-re discussed in relation to biochemical and behavioural changes.

  • Poster
    7th World Congress of Biological Psychiatry, Berlin, 01.-06.07.2001
  • Abstract in refereed journal
    World J. Biol. Psychiatry 2 (2001) 221S

Permalink: https://www.hzdr.de/publications/Publ-4429
Publ.-Id: 4429


5HT1A- and 5HT2A-receptors during social isolation in mice

Schiller, L.; Kretzschmar, M.; Oehler, J.; Brust, P.

Social isolation is an animal model for analysing behavioural and neurobiological processes caused by impairment of organism environment relationships. In previous studies we found time dependent changes in behaviour and central transmitter metabolism especially in the serotonergic and dopaminergic systems (Rilke et al. 1998a, Rilke et al. 1998b).
The aim of the study was to find out time-dependent effects of social isolation after 4 and 12 weeks at serotonin receptor 5HT1A- and 5HT2A-subtypes. Autoradiographic studies in distinct brain regions were carried out and the specific binding [fmol/mg protein] was determined. After 4 weeks specific binding for both receptor subtypes was diminished in all analysed brain regions of isolated mice in comparison to group housed animals. After 12 weeks of isolation, weaker alterations were found. Only the specific [3H]8-OH-DPAT binding for the 5HT1A-receptor in the hippocampus was significantly decreased. Furthermore up-regulations for both receptors were found in some regions. The results are discussed in relation to biochemical and behavioural changes.

  • Poster
    28th Göttingen Neurobiology Conference, Göttingen, 07.-10.06.2001
  • Contribution to proceedings
    Procceedings of the 4th Meeting of the German Neuroscience Society 2001, Volume II 28th Göttingen Neurobiology Conference (edited by Norbert Elsner and Georg W. Kreutzberg)

Permalink: https://www.hzdr.de/publications/Publ-4428
Publ.-Id: 4428


Untersuchung der Tumoraffinität, der Aufnahmekinetik und des Transportmechanismus von 3-O-methyl-6-[123I]iodo-L-DOPA (OMID) in HT-29 Zellen und Tumoren

Bergmann, R.; Wunderlich, G.; Füchtner, F.; Runge, R.; Steinbach, J.; Bredow, J.; Johannsen, B.

Ziel:
Die deutliche Darstellung von Hirntumoren mit 3-O-methyl-6[18F]fluoro-L-DOPA (OMFD) in der PET lässt erwarten, dass auch der analoge, iodsubstituierte Radiotracer OMID von Tumoren mit erhöhtem Aminosäuretransport aufgenommen wird. Deshalb wurde die Aufnahmekinetik und der Transportmechanismus in Zellkulturen und die Bioverteilung von OMID in Nacktmäusen mit transplantierten Tumoren untersucht.

Methodik:
Ausgehend vom Precursor für das 3-O-methyl-6-[18F]fluoro-L-DOPA (OMFD) wurde das analoge 123I synthetisiert. Die Aufnahmekinetik von OMID in HT-29 Zellen wurde in Na+-haltigem und Na+-freiem Puffer und in Anwesenheit verschiedener Transportinhibitoren, wie 2-Aminobicyclo-[2,2,2]heptan-2-carbonsäure (BCH), L-Leucin, L-Phenylalanin und alpha-(Methylamino)-isobuttersäure (MeAIB) gemessen. Die Bioverteilung von OMID wurde an tumortragenden (HT-29) Nacktmäusen (5, 10, 30, 60, 120 min p.i.) untersucht.

Ergebnisse:
Die Aufnahme von OMID in HT-29-Zellen konnte durch Inhibitoren der L-Aminosäuretransporter gehemmt werden, von anderen Transportinhibitoren dagegen kaum. Der Influx des Tracers ist dabei unabhängig von Na-Ionen. Nach Inkubation (60 min) von OMID mit HT-29 Zellen und anschließender Proteinfällung konnte keine signifikante Aktivität in der Proteinfraktion gefunden werden. Die HPLC-Analyse der im Urin nach einer Stunde ausgeschiedenen Aktivität (39,5±4,9%ID) ergab einen Aktivitätspeak, der zur gleichen Zeit wie OMID eluiert wurde. Die Aktivität in der Schilddrüse war zu allen Zeiten kleiner 0,5%ID. 3,6±0,7%ID/g Gewebe wurden nach einer Stunde im Tumor gefunden. Dadurch ergaben sich Tumor zu Gewebsverhältnis (%ID/g Tumor/%ID/g Gewebe) von 3,5 (Blut), 2,9 (Hirn) und 1,9 (Muskel), die auch eine szintigraphische Darstellung der Tumore zuließen.

Schlussfolgerungen:
OMID wurde durch L-Aminosäuretransporter selektiv in Tumorzellen aufgenommen, in HT-29 Zellen nicht in Proteine eingebaut, in vivo kaum metabolisiert und hauptsächlich renal ausgeschieden. Diese Eigenschaften und die lange Retention im Tumorgewebe lassen OMID als SPECT-Tracer für die Tumordarstellung geeignet erscheinen, was in weiteren Untersuchungen geprüft wird.

  • Lecture (Conference)
    40. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, Freiburg, 10.-13.04.2002
  • Abstract in refereed journal
    Nuklearmedizin 41 (2002) V204

Permalink: https://www.hzdr.de/publications/Publ-4427
Publ.-Id: 4427


Ti based coatings on stainless steel for bone integrated implants

Mukherjee, S.; Pham, M.-T.; Maitz, M. F.

Various titanium based coatings have been produced by metal plasma immersion ion implantation assisted deposition (PIIIAD) technique on stainless steel. TiN coatings with some Al substitution for Ti exhibit good mechanical properties and their use for implant coating is considered. Therefore the adherence of rat bone marrow cells as osteoblast progenitor cells to these coatings was investigated in correlation with deposition parameters and surface morphology. For comparison of the above coating's performance with other coat-ings (Ti, TiAl), all these coatings were developed using PIIIAD technique on stainless steel with the bias voltages 0 kV, -1 kV, -2 kV. Apart from increasing the bonding strength between the coating and the stainless steel substrate, the bias can also be used to manipulate the surface roughness of the coatings (10 - 80 nm). Rat bone marrow cells at the first passage were seeded out on the samples in medium with or without serum, allowed to adhere for 6 hours, fixed with paraformaldehyde, fluorescent stained for the adhesion protein vinculin, the cytoskeleton protein actin, the nuclei were couterstained. No difference in cell behaviour in the different surfaces was seen in medium with serum, indicating that adsorbed serum pro-teins equalise differences between surfaces. In the serum free medium there was a general trend of a bet-ter adherence of the cells and better organisation of the cytoskeleton on coatings produced at 0 kV bias voltage compared to those with -1 kV or -2 kV bias voltage. There have been no signs of necrotic cell death but a high rate (5 to 25%) of pyknotic, fragmented nuclei has been found as hint for apoptotic cell death in serum free medium. This rate has been different for the different substrates, but there was no correlation to surface chemistry or surface roughness. As a reason an effect of the serum free medium, direct effect of the coating or inhibition of the adherence cells to the coating are discussed. For further research and possible applications gradient layers produced from -2 kV at the substrate to 0 kV at the top are suggested.

Keywords: Titanium; Titanium Nitride; Titanium Aluminum Nitride; Cell culture; biomaterial; hard coating

  • Lecture (Conference)
    International Conference for Surface Engineering, Chengdu (China) 10.-13.10.2002 Z. Siwei, Z. Zhongrong, L. Liajun and Z. Minhao (Eds.), Contributions of Surface Engineering to Modern Manufacturing and Remanufacturing. Southwest Jiaotong Unive...
  • Contribution to proceedings
    International Conference for Surface Engineering, Chengdu (China) 10.-13.10.2002 Z. Siwei, Z. Zhongrong, L. Liajun and Z. Minhao (Eds.), Contributions of Surface Engineering to Modern Manufacturing and Remanufacturing. Southwest Jiaotong Unive...

Permalink: https://www.hzdr.de/publications/Publ-4426
Publ.-Id: 4426


3-O-methyl-6-[123I]iodo-L-DOPA (OMID) - ein Aminosäurederivat zur Tumordarstellung mit SPECT

Wunderlich, G.; Füchtner, F.; Bergmann, R.; Bredow, J.; Steinbach, J.; Johannsen, B.; Franke, W.-G.

Ziel:
Seit der Einführung von PET in die klinische Anwendung werden 11C markierte Aminosäuren vor allem für die Hirndarstellung verwendet. Im Sinne breiterer Anwendbarkeit wurden Aminosäuren auch mit 18F und 123I markiert. Ausgehend vom Precursor für das 3-O-methyl-6-[18F]fluoro-L-DOPA (OMFD) synthetisierten wir das analoge Iodprodukt OMID, mit dem Ziel die guten Ergebnisse, die im PET erreicht wurden, zukünftig auf das breiter verfügbare SPECT zu übertragen.

Methodik:
Die stereoselektive Synthese basiert auf der elektrophilen Substitution des entsprechenden zinnorganischen Precursors. Die Markierung wird mit 1 mg Substanz in Acetonitril und N-chlorosuccinimid als Oxidationsmittel innerhalb von 10 min bei Raumtemperatur durchgeführt. Es schließt sich eine Hydrolyse der Schutzgruppen mit konzentrierter HCl bei 80°C und eine Reinigung mittels HPLC (PRP1 Säule, Laufmittel: Ethanol/Phosphatpuffer 70/30) an. Die Bioverteilung wurde nach Injektion von [123I]OMID und [18F]OMFD in Wistarratten verglichen.

Ergebnisse:
Der [123I]NaI Umsatz zu [123I]OMID erfolgt quantitativ. Nach abschließender Abspaltung der Schutzgruppen und Reinigung wird nach ca. 90 min eine Ausbeute von 50% bezogen auf das eingesetzte Iod erreicht. Das Endprodukt ist in vitro stabil markiert und auch nach Injektion in Wistarratten ist nur eine geringe Iodabspaltung (<5%) und -aufnahme in die Schilddrüse nachweisbar. Die Verteilungsbilder der Substanzen [123I]OMID und [18F]OMFD ähneln sich, wobei nach 1 h die Aufnahme von OMID in Hirn und Muskel geringer ist als die Aufnahme von OMFD. Erste Untersuchungen an tumortragenden (FaDu) Nacktmäusen zeigten eine brauchbare Darstellung der Tumore isb. 10-30 min p.i..

Schlussfolgerung:
Das Verfahren zur Herstellung von [123I]OMID ist einfach und ergibt in kurzer Zeit gute Ausbeuten. Die Verwendung von Iod an Stelle von Fluor führt zur Lipophilieerhöhung und zu Unterschieden in der Bioverteilung der markierten Substanzen. Weitere Untersuchungen zur Abschätzung der Potenzen von OMID bei der Tumordarstellung sind notwendig.

  • Poster
    40. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, Freiburg, 10.-13.04.2002
  • Abstract in refereed journal
    Nuklearmedizin 41 (2002) P55

Permalink: https://www.hzdr.de/publications/Publ-4425
Publ.-Id: 4425


Autoradiografische Darstellung des Serotonin Transporters mit S- ([18F]Fluoromethyl)-(+)-McN5652 ([18F]FMe-McN) in verschiedenen Tierspecies

Kretzschmar, M.; Zessin, J.; Brust, P.; Cumming, P.; Bergmann, R.; Johannsen, B.

Ziel:
Eine veränderte Serotonin-Transporter (SERT) Dichte im Hirn wird als Ursache zahlreicher neuropsychiatrischer Erkrankungen angesehen. Für Untersuchungen des Serotonin -Transporters mittels PET gilt derzeit (+)-[11C]McN5652 als Tracer der Wahl. Die kurze Halbwertszeit (HWZ) von 11C (20,4 min ) begrenzt jedoch seinen klinischen Einsatz. Es wurde deshalb S-([18F]Fluoromethyl)-(+)-McN5652 (HWZ 18F 109,8 min) synthetisiert und dessen regionale Hirnaufnahme in vitro an Hirnschnitten des Schweines und der Ratte sowie in vivo an Schnitten von Ratten und Mäusen bewertet. Zum Vergleich dienten dabei die SERT Liganden [3H]-Citalopram und (+)-[11C]McN5652.

Methodik:
Die regionale Hirnaufnahme der Radiotracer wurde mit quantitativer digitaler Autoradiographie (BAS 2000 Bildauswertesystem FUJI Co) in vitro nach Inkubation der Hirnschnitte und ex vivo 60 und 90 min nach Applikation der Verbindungen erfasst. Zur Bestimmung der Spezifität der Bindung an den SERT wurden die SERT-Inhibitoren Citalopram bzw. Fluoxetin eingesetzt.

Ergebnisse:
Das S-([18F]Fluoromethyl)-(+)-McN5652 wies eine ähnliche Affinität (Ki 2,3 nM) zum SERT wie (+)-McN5652 (Ki 0,72 nM) auf. Die regionale Hirnaufnahme von S-([18F]Fluoromethyl)-(+)-McN5652 im Hirn korrelierte gut mit der Aufnahme des hochaffinen SERT-Liganden [3H]-Citalopram, d.h. die höchste Aktivität zeigte sich in Amygdala ,Hypothalamus, einigen Nuklei des Thalamus, Substantia nigra und superfizieller Schicht der Colliculi superiores. Das Gewebe/Cerebellum Verhältnis in den SERT-reichen Hirnregionen lag in vitro und in vivo zwischen 3 und 5, welches dem Gewebe/Cerebellum Verhältnis nach in vivo Applikation von (+)-[11C]McN5652 entsprach, für [3H]-Citalopram wurden in vitro Werte von 8 bis 20 erreicht. Die Aufnahme war bei allen Verbindungen mit SERT Inhibitoren hemmbar. Der Blut/Hirnschranken Transfer des S-([18F]Fluoromethyl)-(+)-McN5652 war niedriger als der des (+)-[11C]McN5652.

Schlussfolgerungen:
In vitro und in vivo wurde S-([18F]Fluoromethyl)-(+)-McN5652 spezifisch in den Hirnregionen mit einer hohen SERT-Dichte bei verschiedenen Tierspecies angereichert. S-([18F]Fluoromethyl)-(+)-McN5652 erscheint somit als potentieller PET-Tracer für den SERT im Hirn geeignet.

  • Poster
    40. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, Freiburg, 10.-13.4.2002
  • Abstract in refereed journal
    Nuklearmedizin 41 (2002) P23

Permalink: https://www.hzdr.de/publications/Publ-4424
Publ.-Id: 4424


Impaired glucose tolerance is not associated with lipid intolerance

Henkel, E.; Temelkova-Kurtschiev, T.; Köhler, C.; Pietzsch, J.; Leonhardt, W.; Hanefeld, M.

Post-prandial (pp) hypertriglyceridaemia (HTG) plays an important role in the development of atherosclerosis in Type 2 diabetes. Impaired glucose tolerance (IGT) is associated with an increased risk of atherosclerosis and increased level of fasting triglycerides (TG). The aim of this study was to analyse pp HTG and the composition of TG-rich lipoproteins in carefully selected subjects with IGT in comparison to controls with normal glucose tolerance (NGT). Fifteen men with IGT and 27 men with NGT, aged 44 to 70 yr, were examined. All study participants were non-smokers and had fasting TG <4.6 mmol/l. The subjects underwent an oral glucose tolerance test (75 g glucose) and a lipid-glucose tolerance test (LGTT; 92 g fat, 126 g carbohydrate), that allowed the assessment of lipid and glucose tolerance in one test. HbA1c, plasma glucose and lipids were measured by routine methods. Lipoprotein subfraction analysis of VLDL (VLDL1: Sf 60-400 and VLDL2: Sf 20-60) was conducted in a fasting state, as well as 4 hr after the LGTT using a density gradient ultracentrifugation with a subsequent compositional analysis. No significant difference was found either for fasting or pp TG, nor for area under curve (AUC)-TG (12.21±4.27 mmol/l*6 hr vs 13.95±6.74 mmol/l*6 hr; p>0.05) between the IGT and NGT. A highly significant correlation was found between the fasting TG and the AUC-TG (r=0.925; p<0.01). To avoid bias by differences in fasting plasma TG known to affect lipid tolerance we investigated 11 matched pairs for fasting TG. Also, the matched-pairs evaluation pp TG course did not differ significantly from the IGT and NGT. No significant difference for fasting or pp levels of VLDL1 and VLDL2, or for the TG content of chylomicron, VLDL1 and VLDL2, and for the percentage of TG in VLDL1 and VLDL2 was found between the IGT and NGT group. In conclusion, IGT subjects with a similar level of fasting TG do not exhibit lipid intolerance. Our data suggest that glucose intolerance should precede lipid intolerance.

  • Diab Nutr Metab 15 (2002) 84-90

Permalink: https://www.hzdr.de/publications/Publ-4422
Publ.-Id: 4422


Institute of Bioinorganic and Radiopharmaceutical Chemistry; Annual Report 2001

Johannsen, B.; Seifert, S.; (Editors)

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-340 Januar 2002
    ISSN: 1437-322X

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Permalink: https://www.hzdr.de/publications/Publ-4420
Publ.-Id: 4420


Synthese, Struktur, physikochemische und biologische Eigenschaften einiger schwefelhaltiger "3+1" Oxorhenium(V)-Komplexe

in Russian

Zablotskaya, A.; Segal, I.; Kemme, A.; Germane, S.; Popelis, J.; Lukevics, E.; Berger, R.; Spies, H.

  • Chem. Heterocycl. Compds. 4 (2002) 543-555

Permalink: https://www.hzdr.de/publications/Publ-4418
Publ.-Id: 4418


Quadrupole Moment of the 11- Intruder Isomer in 196Pb and Its Implications for the 16- Shears Band Head

Vyvey, K.; Chmel, S.; Neyens, G.; Hübel, H.; Balabanski, D. L.; Borremans, D.; Coulier, N.; Coussement, R.; Georgiev, G.; Nenoff, N.; Pancholi, S.; Rossbach, D.; Schwengner, R.; Teughels, S.; Frauendorf, S.

The quadrupole moment of the 11- isomer in 196Pb has been measured by the level mixing spectroscopy method.
This state has a pi (3s_1/2^-2 1h_9/2 1i_13/2)11- configuration which is involved in most of the shears band
heads in the Pb region. The first directly measured value of Qs(11-) = (-) 3.41(66) b, coupled to the previously known quadrupole moment of the nu (1i_13/2 )12+ isomer allows us to estimate the quadrupole moment of the 16- shears band head as Qs(16-) = -0.32(10) b. The experimental values are compared to tilted axis cranking calculations, giving insight into the validity of the additivity approach to couple quadrupole moments and on the amount of deformation in the shears bands.

Keywords: Quadrupole moment; LEMS technique; Shears bands; Tilted-Axis-Cranking Model

  • Physical Review Letters 88 (2002) 102502

Permalink: https://www.hzdr.de/publications/Publ-4417
Publ.-Id: 4417


Erzeugung und Nutzung von Bibliotheken von Zwei-Gruppen-Diffusionsparametern zur Berechnung eines KWU-Konvoi-Reaktors mit dem Reaktordynamik-Programm DYN3D

Mittag, S.; Grundmann, U.; Koch, R.; Semmrich, J.

Libraries of two-group neutron-diffusion parameters for a Siemens-KWU-Konvoi Pressurized Water Reactor have been generated at Forschungszentrum Rossendorf and TÜV Bau und Betrieb GmbH by using the codes HELIOS and CASMO, respectively. The libraries have been coupled to the reactor-dynamics code DYN3D. For a generic PWR core containing MOX fuel elements, DYN3D macro-burnup calculations and the calculation of different operation states have been carried out. The results will be used for the investigation of possible accident scenarios. Reactivity coefficients calculated by DYN3D are needed for accident analyses by the 1-D thermal-hydraulic code ATHLET. Using the cross section data, more detailed analyses can be carried out by applying the coupled-code system DYN3D-ATHLET, considering 3D neutron kinetics. The comparison of the results calculated by DYN3D with two different diffusion-parameter libraries can give an idea of how uncertainties in diffusion data influence the accuracy of reactor simulation.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-346 April 2002
    ISSN: 1437-322X

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Permalink: https://www.hzdr.de/publications/Publ-4416
Publ.-Id: 4416


Institute of Ion Beam Physics and Materials Research: Annual Report 2001

von Borany, J.; Helm, M.; Jäger, H.-U.; Möller, W.; Wieser, E.; (Editors)

Summary of the scientific activities of the institute in 2001 including selected highlight reports, short research contributions and an extended statistics overview.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-338 März 2002
    ISSN: 1437-322X

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Permalink: https://www.hzdr.de/publications/Publ-4412
Publ.-Id: 4412


Magnetic rotation in 82Rb and 84Rb

Schwengner, R.; Rainovski, G.; Schnare, H.; Wagner, A.; Dönau, F.; Jungclaus, A.; Hausmann, M.; Iordanov, O.; Lieb, K. P.; Napoli, D. R.; de Angelis, G.; Axiotis, M.; Marginean, N.; Brandolini, F.; Rossi Alvarez, C.

High-spin states in 82Rb and 84Rb were populated in the reaction 11B + 76Ge at beam energies of 45 and 50 MeV. Gamma rays were detected with the spectrometer GASP. The level schemes of 82Rb and 84Rb were extended up to 6.0 and 7.4 MeV, respectively. Mean lifetimes of five levels in 82Rb and eleven levels in 84Rb were determined using the Doppler-shift-attenuation method. Regular magnetic dipole bands including strong M1 and weak E2 transitions observed in both nuclei show the characteristic features of magnetic rotation. These bands have been successfully described in the tilted-axis cranking model on the basis of the four-quasiparticle configuration pi(fp) pi(g_{9/2}^2) \nu(g_{9/2}). The calculations reproduce the band-like properties as well as absolute B(M1) and B(E2) transition strengths in both nuclei, which supports the concept of
magnetic rotation. Excited states in 84Rb were also interpreted in terms of the shell model using the model space
pi(0f_{5/2},1p_{3/2},1p_{1/2},0g_{9/2}) nu(1p_{1/2},0g_{9/2}).
These calculations reproduce the low-spin states. Moreover, calculated states with the main configuration
pi(0f_{5/2}^{-2}1p_{3/2}^{-1} 0g_{9/2}^2) nu(0g_{9/2}^{-3}) can be combined to M1 sequences that reproduce roughly
the experimental transition strengths, but do not describe the features of magnetic rotation, as regular level spacings and B(M1) values decreasing with increasing rotational frequency.

Keywords: Nuclear Structure; in-beam gamma-ray spectroscopy; magnetic rotation; tilted-axis cranking model; shell model

  • Physical Review C 66, 024310, (2002)

Permalink: https://www.hzdr.de/publications/Publ-4411
Publ.-Id: 4411


Experimental and numerical investigation of one and two-phase natural convection

Krepper, E.; Prasser, H.-M.

Experiments were performed to investigate heating up processes of fluids in storage tanks under the influence of an external heat source. Several tests were carried out both with heating from the bottom and with heating from the side walls. The test tank was equipped with thermocouples for measuring the temperature distribution and with needle probes for measuring of the local void fraction.
Calculations were performed using the CFD-code CFX-4. The simulation comprises two phase flow, subcooled boiling at the heated wall and steam release at the tank surface. The paper presents comparisons of measured and calculated temperatures and void fractions. CFX-4 simulations using the implemented boiling model reproduce and explain the observed physical phenomena. Convergence problems occurred with higher vapour volume fractions.

Keywords: Natural convection; heating up; boiling; experiments; CFD simulations

  • Lecture (Conference)
    HEAT 2002: Third International Conference Transport Phenomena in Multiphase Systems, Baranow Sandomierski, Poland, June 24-27, 2002, pp. 333-339
  • Contribution to proceedings
    HEAT 2002: Third International Conference Transport Phenomena in Multiphase Systems, Baranow Sandomierski, Poland, June 24-27, 2002, pp. 333-339

Permalink: https://www.hzdr.de/publications/Publ-4408
Publ.-Id: 4408


Annealing behavior of magnesium and aluminum implanted with iron ions

Reuther, H.

Magnesium and aluminum were alloyed by implantation with iron ions. The implantation energy was 200 keV while the ion doses ranged over several decades from 1x1015 up to 9x1017 cm-2. In this way highly disordered alloyed layers with up to 90 at.% iron were obtained [1]. To study possible ordering, stabilization and redistribution processes samples were annealed in vacuum at subsequently increasing temperatures up to 600 °C for aluminum and up to 400 °C for magnesium. The annealing process was observed by conversion electron Mössbauer spectroscopy, Auger electron depth profiling, and X-ray diffraction. In the case of the Fe-Al system different iron aluminides are formed. In the case of the Fe-Mg system (insoluble with each other), a-iron is precipitated in small clusters in the final state.

  • Journal of Applied Physics 92 (2002) 7056-7061

Permalink: https://www.hzdr.de/publications/Publ-4407
Publ.-Id: 4407


Experimental Investigation of the Potential of In-Beam PET for the Monitoring of Proton Therapy

Parodi, K.; Enghardt, W.; Haberer, T.

Keywords: Proton Therapy; PET

  • Lecture (Conference)
    XXXVI PTCOG-Meeting, Catania, Italy, 29-31 May 2002
    Book of Abstract (2002) 12
  • Contribution to proceedings
    XXXVI PTCOG-Meeting, Catania, Italy, 29-31 May 2002
    Book of Abstract (2002) 12

Permalink: https://www.hzdr.de/publications/Publ-4406
Publ.-Id: 4406


Positron Emission Tomography for Quality Assurance of Carbon Ion Therapy

Enghardt, W.; Crespo, P.; Fiedler, F.; Parodi, K.; Pawelke, J.; Pönisch, F.; Haberer, T.; Kausch, C.; Krämer, M.; Schardt, D.

Keywords: Heavy-Ion-Therapy; PET

  • Lecture (Conference)
    XXXVI PTCOG-Meeting, Catania, Italy, 29-31 May 2002
    Book of Abstracts (2002) 12
  • Contribution to proceedings
    XXXVI PTCOG-Meeting, Catania, Italy, 29-31 May 2002
    Book of Abstracts (2002) 12

Permalink: https://www.hzdr.de/publications/Publ-4405
Publ.-Id: 4405


Evolution of flow patterns, gas fraction profiles and bubble size distributions in gas-liquid flows in vertical tubes

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

Air-water flow at ambient conditions in a vertical pipe with an inner diameter of 51.2mm is investigated. An electrode wire-mesh sensor enables the measurement of the phase distribution with a very high resolution in space and in time. Local bubble size distributions are calculated from the data. The measurements were done in different distances from the gas injection device. As a result the development of bubble size distributions as well as the development of the radial gas fraction profiles can be studied. It was found, that the bubble size distribution as well as local effects determine the transition from bubble flow to slug flow. The data are used for the development of a model, which predicts the development of the bubble size distribution and the transition from bubble flow to slug flow in case of stationary flow in a vertical pipe.

Keywords: Two-phase flow; Flow pattern transition; Bubble Flow; Slug flow

  • Lecture (Conference)
    HEAT 2002: Third International Conference Transport Phenomena in Multiphase Systems, Baranow Sandomierski, Poland, June 24-27, 2002, pp. 341 - 348
  • Transactions of the Institute of Fluid-Flow Machinery 112(2003)37-46
  • Contribution to proceedings
    HEAT 2002: Third International Conference Transport Phenomena in Multiphase Systems, Baranow Sandomierski, Poland, June 24-27, 2002, pp. 341 - 348

Permalink: https://www.hzdr.de/publications/Publ-4404
Publ.-Id: 4404


Application of Master Curve Approach for Rector Pressure Vessel Integrity Assessment

Viehrig, H.-W.; Langer, R.

The state-of-the-art of structural integrity assessment of reactor pressure vessels (RPV) uses universal and experimentally verified reference fracture toughness curves. These curves are constructed as the lower boundary to an available plain strain fracture toughness, KIC, database.
Recent industry attention has been focussed on the direct use of measured fracture toughness properties in the RPV integrity assessment. The Master Curve Concept (MC)is a new methodology to characterise the fracture toughness in the transition region. The MC methodology provides a reference temperature, T0, that directly relates the reference toughness curve to the measured fracture toughness values.
The utilities and licensing authorities establish short and long-range objectives in implementing MC technology. The short range objective is to develop an alternative method of indexing the universal plain strain fracture toughness curves using measured fracture toughness T0 instead of the existing drop weight and Charpy-based methodology. The long range objective is to implement a statistically defined MC as an alternative fracture toughness curve in place of the KIC lower bound curves.
The paper introduces the state-of-the-art and future trend of the RPV integrity assessment in Germany. In the second part the MC approach is demonstrated for Russian WWER-type RPV steels.

Keywords: reactor pressure vessel; integrity assessment; reference temperature; fracture toughness; Master Curve

  • Lecture (Conference)
    Proceedings of the NATO Advanced Research Workshop On Scientific Fundamentals for the life Time Extension of Reactor Pressure Vessels, held in Kiev, Ukraine, from 22 to 25 April 2002.
  • Contribution to proceedings
    Proceedings of the NATO Advanced Research Workshop On Scientific Fundamentals for the life Time Extension of Reactor Pressure Vessels, held in Kiev, Ukraine, from 22 to 25 April 2002.

Permalink: https://www.hzdr.de/publications/Publ-4403
Publ.-Id: 4403


Approach towards spatial phase reconstruction in transient bubbly flow using a wire-mesh sensor

Richter, S.; Aritomi, M.; Prasser, H.-M.; Hampel, R.

A wire-mesh sensor, which is based on local conductivity measurement, has been applied to studies on the characteristics of bubböe flow in a rectangular channel (20 x 100 mm²). Special design of the sensor allowed the measurement of the local instantaneous true gas velocity besides the measurement of the local instantaneous void fraction. A review of an already published method for true gas velocity measurement under consideration of the uncertainty caused by limitations in the sampling frequency is presented. A cluster-algorithm is proposed for the evaluation of bubble size distribution and volume flow reconstruction. The validity of this algorithm for spatial field reconstruction was benchmarked by theoretical considerations as well as comparison of the calculated with alternatively measured data. Good agreement was stated. The achieved information was used to obtain plots showing the bubble/slug velocity (up to the second statistical momentum) depending on the spherical-equivalent bubble diameter. This information was measured inside a transient bubble flow with void fraction of up to 20 %. Occurring phenomena are explained by presented Fourier spectra of the cross-sectional averaged void fraction and the gas volume flow.

Keywords: gas-liquid flow; two-phase flow; wire-mesh sensor; void fraction; gas velocity; bubble size

  • International Journal of Heat and Mass Transfer 45 (2002) 1063-1075.

Permalink: https://www.hzdr.de/publications/Publ-4402
Publ.-Id: 4402


Inverse Problems in MHD

Stefani, F.; Gerbeth, G.

We consider inverse problems in MHD that are related to the reconstruction of velocity fields from external measurements of electromagnetic fields. Possible applications are contactless flow measurements in metallurgical and crystal growth facilities as well as velocity reconstructions for cosmic and laboratory hydromagnetic dynamos. In the case of small magnetic Reynolds numbers it is necessary to apply external magnetic field and to measure the flow induced electromagnetic fields. Analytical results concernig the uniqueness problem of velocity reconstruction and the need for regularization are discussed. First results for inverse dynamo theory, i.e. the region of high magnetic Reynolds number, are also presented.

  • Lecture (Conference)
    Jahrestagung der Gesellschaft für Angewandte Mathematik und Mechanik (GAMM) 2002, Universität Augsburg, 25.-28. März 2002

Permalink: https://www.hzdr.de/publications/Publ-4401
Publ.-Id: 4401


Surface structuring and phase formation in thin metallic layers deposited at various temperatures

Markwitz, A.; Matz, W.; Short, K.; Waldschmidt, M.

Scanning electron microscopy, atomic force microscopy and XRD analyses were performed for the study of the influence of the substrate temperature during deposition on the surface structuring and phase formation on thin metallic double layers. Thin layers of Au, Cr, Al and Cr were deposited at 150 and 300 °C on 30-nm Cu layers evaporated on (100) wafer Si substrates. Possible applications of such layers are Raman active surfaces and model layers for diffusion experiments. The topographical investigation revealed an increase with temperature of surface structuring that is related to the formation of intermetallic and oxide phases. At 150 °C deposition temperature, the average roughness of the films was determined to 2 – 3 nm and the surfaces appeared smooth. In agreement with previous ion beam analysis measurements, a significant surface roughness occurred at 300 °C depending on the type of the metallic films. The lowest average surface roughness value was measured for the Al/Cu/Si system (Ra = 14.1 nm). About double the roughness was measured for the Au/Cu/Si and Cr/Cu/Si layer systems. In contrast, single Cu layers a high value of Ra = 93.0 nm was determined. The combined analyses showed that the formation of intermetallic phases, such as AlCu and CuAl2, reduces a surface roughening. However, the formation of oxide phases, such as CuO2, increase the average surface roughness.

Keywords: multilayers; metallic compounds; surface structuring; nanotechnology; diffusion; surface artefacts

  • Surface and Interface Analysis 33 (2002) 1-6

Permalink: https://www.hzdr.de/publications/Publ-4399
Publ.-Id: 4399


A Kinetic Study of Clusters Evolution under VVER-type Reactor Condition

Gokhman, A.; Böhmert, J.; Ulbricht, A.

The evolution of copper rich clusters and vacancy clusters in the neutron irradiated VVEER steels is investigated beginning at the nucleation stage. For this, typical VVER-type reactor conditions are considered. Cluster dynamics approach is used for calculation of the size distribution function, mean radius, number density of copper precipitates and the concentration of free Cu-atoms in dependence on the irradiation time. The results for time of one year are compared with the results of small angle neutron experiments which were carried out at specimens irradiated at surveillance position of VVER reactors.

  • Lecture (Conference)
    Nucleation Theory and Applications, J. W. P. Schmelzer, G. Röpke, Y. B. Priezzhev (Eds.), Dubna, April 14-21, 2002, pp. 81-107
  • Contribution to external collection
    Nucleation Theory and Applications, J. W. P. Schmelzer, G. Röpke, Y. B. Priezzhev (Eds.), Dubna, April 14-21, 2002, pp. 81-107

Permalink: https://www.hzdr.de/publications/Publ-4398
Publ.-Id: 4398


Determination of velocity profiles in liquid metal flows by means of Ultrasound Doppler Velocimetry

Eckert, S.; Gerbeth, G.; Melnikov, V.

The Ultrasound Doppler Velocimetry (UDV) is a non-intrusive technique to measure velocities of liquid flows. Because of the ability to work in opaque fluids and to deliver complete velocity profiles in real time it becomes very attractive for liquid metal applications. But, in case of hot metallic melts the user is confronted with a number of specific problems: First of all the application of the ultrasonic transducers is usually restricted to maximum temperatures of 150°C. The transmission of a sufficient amount of ultrasonic energy from the transducer to the fluid has to be guaranteed. Here, the acoustic coupling and the wetting conditions have to be considered as important issues. Moreover, the flow has to be seeded with reflecting particles to obtain Doppler signals from the fluid.
The feasibility of velocity profile measurements by UDV has already been demonstrated for low temperature liquid metals as mercury [1] and gallium [2]. Now, first successful measurements in liquid sodium at 150°C are published [3]. We will present mean profiles of a flow in a rectangular exposed to an external, transverse magnetic field. To demonstrate the capability of UDV the transformation of a well-known turbulent, piston-like profile to a M-shaped velocity profile with growing magnetic field strength was observed. The significance of artefacts such as caused the existence of reflecting interfaces in the measuring domain will be discussed.
An integrated ultrasonic sensor with acoustic wave guide has been developed to overcome the limitation of ultrasonic transducers to temperatures lower than 200°C. This sensor can be applied at maximum temperatures up to 400°C, but an extension up to 800°C can reasonably be expected.. In this presentation we show some experimental results obtained in a PbBi bubbly flow at 250...300°C. Ar bubbles were injected through a single orifice in a cylindrical container filled with stagnant PbBi. Velocity profiles were measured in the bubble plume. Mean values of the liquid as well as the bubble velocity were extracted from the data and will be presented as function of the gas flow rate.


[1] Y. Takeda: Measurement of velocity profile of mercury flow by ultrasound Doppler shift method. Nucl. Techn. 79 (1987), 120-124
[2] D. Brito, H.-C. Nataf, P. Cardin, J. Aubert, J.-P. Masson: Ultrasonic Doppler velocimetry in liquid gallium. Exp. Fluids 31 (2001) 6, 653-663
[3] S. Eckert, G.Gerbeth: Velocity measurements in liquid sodium by means of Ultrasound Doppler Velocimetry. accepted for publication in Exp. Fluids (2002)

Keywords: Ultrasonic Doppler Velocimetry; acoustic wave guide; liquid metals; flow velocity measurements; two-phase flow; bubbles

  • Lecture (Conference)
    5th International Conference on Fundamental and Applied MHD (PAMIR), September 16-20, 2002, Ramatuelle, France, Proceedings I 119-124
  • Contribution to proceedings
    5th International Conference on Fundamental and Applied MHD (PAMIR), September 16-20, 2002, Ramatuelle, France, Proceedings I 119-124

Permalink: https://www.hzdr.de/publications/Publ-4397
Publ.-Id: 4397


Application of Ultrasound Doppler Velocimetry to flows of hot metallic melts

Eckert, S.; Gerbeth, G.; Melnikov, V.; Lefhalm, C.-H.; Knebel, J.

During the last decades the Ultrasound Doppler Velocimetry (UDV) became a very powerful tool to measure the velocity structure of liquid flows. Because of the ability to work in opaque fluids and to deliver complete velocity profiles in real time it becomes very attractive for liquid metal applications. But, in case of hot metallic melts the user is confronted with a number of specific problems: First of all, the application of the ultrasonic transducers is usually restricted to maximum temperatures of 150°C. The transmission of a sufficient amount of ultrasonic energy from the transducer to the fluid has to be guaranteed. Here, the acoustic coupling and the wetting conditions have to be considered as important issues. Moreover, the flow has to be seeded with reflecting particles to obtain Doppler signals from the fluid.
The feasibility of velocity profile measurements by UDV has already been demonstrated for low temperature liquid metals as mercury [1] and gallium [2]. Now, first successful measurements in liquid sodium at 150°C are published [3]. We will present mean profiles of a sodium flow in a rectangular duct exposed to an external, transverse magnetic field. To demonstrate the capability of UDV the transformation of a well-known turbulent, piston-like profile to a M-shaped velocity profile with growing magnetic field strength was observed. The significance of artefacts such as caused by the existence of reflecting interfaces in the measuring domain will be discussed.
An integrated ultrasonic sensor with acoustic wave guide has been developed to overcome the limitation of ultrasonic transducers to temperatures lower than 200°C. This sensor can presently be applied at maximum temperatures up to 400°C, but an extension up to 800°C can reasonably be expected. In this presentation we show some experimental results obtained in PbBi bubbly flows at temperatures up to 350°C. Ar bubbles were injected through a single orifice in a cylindrical container filled with stagnant PbBi. Velocity profiles were measured in the bubble plume. Mean values of the liquid as well as the bubble velocity were extracted from the data and will be presented as function of the gas flow rate.
Velocity profiles of a single-phase PbBi flow in a tube were successfully obtained at the KALLA laboratory of FZK. By means of the integrated sensor stable velocity signals could be received over a period of about 72 hours at temperatures between 180°C and 350°C.


[1] Y. Takeda: Measurement of velocity profile of mercury flow by ultrasound Doppler shift method. Nucl. Techn. 79 (1987), 120-124
[2] D. Brito, H.-C. Nataf, P. Cardin, J. Aubert, J.-P. Masson: Ultrasonic Doppler velocimetry in liquid gallium. Exp. Fluids 31 (2001) 6, 653-663
[3] S. Eckert, G.Gerbeth: Velocity measurements in liquid sodium by means of Ultrasound Doppler Velocimetry. accepted for publication in Exp. Fluids (2002)

Keywords: Ultrasonic Doppler Velocimetry; acoustic wave guide; liquid metals; flow velocity measurement; two-phase flow; bubbles

  • Lecture (Conference)
    3rd International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, September 9-11, 2002, Lausanne, Switzerland PSI-Proceedings 02-01, 77-82, ISSN 1019-6447
  • Contribution to proceedings
    3rd International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, September 9-11, 2002, Lausanne, Switzerland PSI-Proceedings 02-01, 77-82, ISSN 1019-6447

Permalink: https://www.hzdr.de/publications/Publ-4396
Publ.-Id: 4396


Dynamical moment of inertia and quadrupole vibrations in rotating nuclei

Nazmitdinov, R. G.; Almehed, D.; Dönau, F.

The contribution of quantum shape fluctuations to inertial properties of rotating nuclei has been analysed within the self-consistent one-dimensional cranking oscillator model. It is numerically proven that for even-even nuclei the dynamical moment of inertia calculated in mean field approximation in the intrinsic frame is equivalent to the
Thouless-Valatin moment of inertia. If the contribution of the quantum fluctuations
to the total energy is taken into account, the dynamical moment of inertia differs from the Thouless-Valatin value.

Keywords: Cranking model; Random Phase Approximation; Moments of inertia

  • Physical Review C, Rapid Communication, Volume 65, 041307 (R), 2002

Permalink: https://www.hzdr.de/publications/Publ-4395
Publ.-Id: 4395


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