Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32228 Publications
Laboratory -unit investigations of palladium treated titanium foil for dry scrubber application
Piekoszewski, J.; Chmielewski, A. G.; Licki, J.; Sartowska, B.; Werner, Z.; Barson, S. D.; Skeldon, P.; Thompson, G. E.; Richter, E.; Wieser, E.;
Titanium foil is employed for electron transparent windows in the electron beam dry scrubber process. The foil suffers corrosion, which limits the window life. Here, the examination of palladium-coated window, prepared by ion beam assisted deposition and plasma source ion assisted deposition (PSIAD), after service in a pilot-scale plant is reported. Most significantly, the adhesion of the coating was reduced by the flue gas. Where the coating remained adherent, corrosion was negligible. Elswhere, generalmintergranular and pitting corrosin occured. A PSIAD coating provided the best performance.
Keywords: Electron beam treatment, Flue gases, Ttanium, Palladiumn, Corrosion, Coatings
  • Radiation Physics and Chemistry 62 (2001) 253-260

Publ.-Id: 4621 - Permalink


Reflektivitätsuntersuchungen mittels Synchrotronstrahlung an durch MBE erzeugten Fe/Cr-Multischichten
Prokert, F.; Kravtsov, E.; Milayev, M.; Romashev, L.; Ustinov, V.; Schell, N.;
Fe/Cr-Multischichten zeigen GMR (giant magnetoresistance) Effekte, die in der Anwendungstechnik (Magnetoelektrik, Sensorik, Speichertechnologie) von besonderer Bedeutung sind. Magnetische Multischichten werden deshalb gegenwärtig vielerorts untersucht. In diesem Zusammenhang werden die Einflüsse der unterschiedlichen Verfahren der Schichtabscheidung studiert.
Durch die Reflektivitätsuntersuchungen mittels Synchrotronstrahlung können die durch MBE abgeschiedenen Einzelschichten auch im Fe/Cr-Multischichtsystem hinsichtlich Schichtdicke, Dichte, Rauhigkeit und Interface-Morphologie recht genau charakterisiert werden.
Keywords: Fe/Cr- Multischichten; SR-Reflektometrie; Anomale Streuung
  • Poster
    Zeitschrift für Kristallographie, Supplement Issue No. 19, S. 58 Referate, 10. Jahrestagung der Deutschen Gesellschaft für Kristallographie (DGK) vom 4. bis 7. März 2002 in Kiel
  • Contribution to proceedings
    Zeitschrift für Kristallographie, Supplement Issue No. 19, S. 58 Referate, 10. Jahrestagung der Deutschen Gesellschaft für Kristallographie (DGK) vom 4. bis 7. März 2002 in Kiel

Publ.-Id: 4620 - Permalink


Use of anomalous scattering for synchrotron X-ray reflectivity studies of Fe-Cr and Co-Cu double layers
Prokert, F.; Schell, N.; Gorbunov, A.;
Double layers of Fe-Cr and Co-Cu, respectively, were prepared on oxidized Si substrates by pulsed laser deposition (PLD). The interfacial roughness structure was studied by synchrotron X-ray reflectivity measurements at the absorption K-edges using the contrast enhancement due to resonant scattering. The results are determined from simulations of the measured specular and diffuse scans. Whereas in Fe-Cr double layers the rms-interface width for Fe deposition on Cr (sigma_Cr = 0.70 ± 0.1 nm) is not very different from that of Cr deposition on Fe (sigma_Fe = 0.85 ± 0.1 nm), in Co-Cu double layers, in contrast, for Cu deposition on Co, the width (sigma_Co = 0.65 ± 0.1 nm) is much smaller than for Co deposition on Cu (sigma_Cu = 1.5 ± 0.15 nm). On the basis of the fractal model to describe the interface roughness morphology, from the off-specular scans the lateral roughness correlation length, xi, and the roughness exponent, h, were determined. For both types of double layers extremely high xi-values (larger than 2 µm) were found. However, the flatness is accompanied by a high short-scale roughness (jaggedness), expressed by a small h-parameter (h = 0.25 ± 0.05). Both facts were found to be characteristic for the 'as-deposited' state of such metal/metal layers prepared by PLD.
Keywords: X-ray reflectometry; interfaces; anomalous scattering
  • Nuclear Instruments and Methods in Physics Research B 199 (2003) 123-127

Publ.-Id: 4619 - Permalink


Φ and ω Meson Production in pp Reactions at plab=3.67 GeV/c
Balestra, F.; Bedfer, Y.; Bertini, R.; Bland, L. C.; Brenschede, A.; Brochard, F.; Bussa, M. P.; Choi, S.; Debowski, M.; Dressler, R.; Dzemidzic, M.; Faivre, J.-C.; Falomkin, I. V.; Fava, L.; Ferrero, L.; Foryciarz, J.; Fröhlich, I.; Frolov, V.; Garfagnini, R.; Grasso, A.; Grosse, E.; Heinz, S.; Ivanov, V. V.; Jacobs, W. W.; Kühn, W.; Maggiora, A.; Maggiora, M.; Manara, A.; Panzieri, D.; Pfaff, H.-W.; Piragino, G.; Pontecorvo, G. B.; Popov, A.; Ritman, J.; Salabura, P.; Tchalyshev, V.; Tosello, F.; Vigdor, S. E.; Zosi, G.;
The exclusive production cross sections for ω and Φ mesons have been measured in proton-proton reactions at plab=3.67 GeV/c.
The observed Φ/ω cross section ratio is (3.8±0.2+1.2-0.9)×10-3.
After phase space corrections, this ratio is enhanced by about an order of magnitude relative to naive predictions based upon the Okubo-Zweig-Iizuka (OZI) rule, in comparison to an enhancement by a factor ~ 3 previously observed at higher beam momenta. The modest increase of this enhancement near the production threshold is compared to the much larger increase of the Φ/ω ratio observed in specific channels of pp annihilation experiments.
Furthermore, differential cross section results are also presented which indicate that although the Φ meson is predominantly produced from a 3P1 proton-proton entrance channel, other partial waves contribute significantly to the production mechanism at this beam momentum.

Publ.-Id: 4618 - Permalink


YSO, LSO, GSO and LGSO. A study of energy resolution and nonproportionality.
Balcerzyk, M.; Moszynski, M.; Kapusta, M.; Wolski, D.; Pawelke, J.; Melcher, M.;
We have studied the nonproportionality and intrinsic energy resolution of cerium doped YSO, GSO, LSO and LGSO crystals. While LSO and YSO have similar light output, GSO and LGSO have ca. 70% and 20% lower light output than LSO, respectively. YSO, a compound containing fairly light elements, was expected to have proportional light output vs. energy, like YAP:Ce. Surprisingly it has almost the same nonproportional as LSO and GSO. The nonproportionality of YSO is followed by large values of intrinsic energy resolution. The comparison of the nonproportionality of YSO-LSO and YAP-LuAP pairs indicates that high proportionality is connected with the structure of the crystal and not with the presence of light elements. To our knowledge, this is the first study of nonproportionality and intrinsic resolution for LGSO.
  • IEEE Transactions on Nuclear Science, Vol. 47, No. 4 (2000) 1319-1323

Publ.-Id: 4617 - Permalink


Synthese und Verwendung uranophiler Calicarene
Keil, D.; Schmeide, K.;
kein Abstract
  • Lecture (others)
    Mikrosymposium FCS im Technologie- und Gründerzentrum Bitterfeld-Wolfen 27.11.2001

Publ.-Id: 4616 - Permalink


Double injection of charge carriers in chemical vapor deposited diamond-based diodes
Weima, J. A.; von Borany, J.; Messinger, K.; Horstmann, J.; Fahrner, W. R.;
Boron ion implantation of thermochemically polished chemical vapor deposited diamond films with multienergies ranging between 24 and 150 keV and a total dose of about 2E16 cm-2 is used to get p-type conductivity. n-type conductivity is achieved by lithium ion implantation of the diamond films with a single energy of 50 keV and a dose of 2E16 cm-2. The intrinsic areas separating the p- and n-doped regions form the active areas of the diodes into which charge carriers are simultaneously injected upon bias. Onset voltages of < 10 V are due to the low concentration (~1E14 cm-3) of nitrogen related centers in the diamond films. The current–voltage (I–V) characteristics of the p-i-n diodes manifest trap filling, Frenkel–Poole emission, thermionic emission, and space charge limited current regimes. At 300°C, currents as high as 12 mA are measured at a forward bias of 100 V. Rectification ratios of up to about four orders of magnitude are achieved. They increase with increasing width of the i-region within the measured i-region of 3–10 µm, as a result of the considerable decrease of the reverse bias current relative to the forward bias current.
Keywords: diamond, pin-diodes, conduction mechanism
  • Journal of Applied Physics 92(7)(2002) 4047-4052

Publ.-Id: 4615 - Permalink


Static Quadrupole Moment of the Five-Quasiparticle K=35/2 Isomer in 179W Studied with the Level-Mixing Spectroscopy Method
Balabanski, D. L.; Vyvey, K.; Neyens, G.; Coulier, N.; Coussement, R.; Georgiev, G.; Lépine-Szily, A.; Ternier, S.; Teughels, S.; Mineva, M.; Walker, P. M.; Blaha, P.; Almehed, D.; Frauendorf, S.;
The spectroscopic quadrupole moment of the high-spin, high-K five-quasiparticle isomer (Kπ=[(35-)/2], T1/2=750(80) ns, Ei = 3349 keV) in 179W has been determined using the level mixing spectroscopy method.
A value Qs = 4.00([(+0.83) || (-1.06)])e b was derived, which corresponds to an intrinsic quadrupole moment Q0 = 4.73([(+0.98) || (-1.25)])e b and to a quadrupole deformation β2 = 0.185([(+0.038) || (-0.049)]).
These values differ significantly from the deduced ground-state quadrupole moments and are in disagreement with the current theoretical predictions in this mass region.

Publ.-Id: 4614 - Permalink


Development of a Tritium AMS Detection Method for Biomedical Applications
Kiisk, M.; Friedrich, M.; Hellborg, R.; Mattson, S.; Pilz, W.; Vesanen, R.;
There are numerous applications for tritium (3H) as a tracer isotope in biomedicine commonly combined with the liquid scintillation counting method. The use of accelerator mass spectrometry (AMS), a rather new detection method, would enlarge and open new possibilities for tritium applications in biomedicine, especially when sample volumes are small. The tritium in the samples has to be transformed to solid form yielding high output of negative hydrogen current. The sample preparation for tritiated water is done in two steps: firstly extracting water from the biological sample and secondly, extracting hydrogen/tritium from the water and forming a chemically suitable compound for the AMS system.
In this paper a chemical procedure for the sample preparation is described. The results of the first measurements of tritiated water with known activity using AMS detection technique will also be presented.

Keywords: AMS, tritium AMS, Biomedical applications
  • Contribution to external collection
    HIPAN-02, Neptun, Romania, September 2-6, 2002

Publ.-Id: 4613 - Permalink


Untersuchungen über die Komplexierung und die Migration von Actiniden und nichtradioaktiven Stoffen mit Huminsäuren unter geogenen Bedingungen
Bernhard, G.; Pompe, S.; Schmeide, K.; Heise, K. H.; Brendler, V.; Trautmann, N.; Kuczewski, B.; Seibert, A.; Kratz, J. V.; Beck, H. P.;
kein Abstract
  • Lecture (others)
    5. Projektstatusgespräch zu F+E-Vorhaben auf dem Gebiet der Entsorgung gefährlicher Abfälle in tiefen geologischen Formationen, Leipzig 15.-16.5.2001

Publ.-Id: 4611 - Permalink


Magnetic Dipole Rotational Bands in Odd-A Rb Isotopes
Amita, A.; Jain, K.; Dimitrov, V. I.; Frauendorf, S.;
The hybrid version of tilted axis cranking has been used to study the existence of magnetic rotation in the ΔI = 1 bands of odd-A 79,81,83,85Rb isotopes.
The bands are found to be built on prolate three quasiparticle π(g9/2) Ä n[g9/2(fp)1] configuration.
The results exhibit a rapid onset and decline of magnetic rotation as we go from N = 42 to 48.
The 83Rb appears to be a better case of magnetic rotation among these four Rb isotopes.

Publ.-Id: 4610 - Permalink


Contribution of the FZR to the HUPA Project
Schmeide, K.; Sachs, S.;
Humic Substances in Performance Assessment of Nuclear Waste Disposal: Actinide and Iodine Migration in the Far-Field
  • Lecture (others)
    Workshop zum Forschungsvorhaben FZK 3.-4.12.2001

Publ.-Id: 4609 - Permalink


EXAFS-Untersuchungen an Pu(III)-Humaten sowie erste Ergebnisse zur Np(V)-Sorption an Granit in Ab- und Anwesenheit von Huminsäure.
Schmeide, K.;
Untersuchungen über die Komplexierung und die Migration von Actiniden und nichtradioaktiven Stoffen mit Huminsäuren unter geogenen Bedingungen - Komplexierung von Huminsäuren mit Actiniden in der Oxidationsstufe IV Th, U, Np
  • Lecture (others)
    Workshop zum Forschungsvorhaben FZK 15.-16.11.2001

Publ.-Id: 4607 - Permalink


Huminsäureforschung im FZR/IfR - Synthetische Huminsäuren
Schmeide, K.; Pompe, S.;
kein Abstract
  • Lecture (others)
    Vortrag anläßlich des Besuchs von Vertretern der HS Zittau-Görlitz im FZR, 30.4.2001

Publ.-Id: 4605 - Permalink


Quantum Correlations in Rotating Nuclei
Almehed, D.; Dönau, F.; Nazmitdinov, R. G.;
Using the Hamiltonian that consists of the separable quadrupole + pairing forces and the cranking term, we analyze the correlations associated with shape, orientation, and particle-number fluctuations in rotating nuclei. Quantum fluctuations around mean field solutions are treated in the random phase approximation (RPA), with special emphasis on the restoration of
rotational symmetry and particle number conservation. The mean field calculations have been made within the self-consistent cranking model. The effect of the RPA correlation energy for the moment of inertia is studied with the integral representation method proposed.
  • Physics of Atomic Nuclei 64 (2001) 1076

Publ.-Id: 4604 - Permalink


NIR-Untersuchungen an Np(V)-Humaten modifizierter und nicht modifizierter Huminsäuren sowie erste Ergebnisse zur Synthese von Huminsäuren mit ausgeprägter Redoxfunktionalität.
Pompe, S.;
Untersuchungen über die Komplexierung und die Migration von Actiniden und nichtradioaktiven Stoffen mit Huminsäuren unter geogenen Bedingungen - Komplexierung von Huminsäuren mit Actiniden in der Oxidationsstufe IV Th, U, Np
  • Lecture (others)
    Workshop zum Forschungsvorhaben, FZK 15.-16.11.2001

Publ.-Id: 4603 - Permalink


Markierung und Modifizierung von Huminsäuren und deren Komplexierung mit Neptunium(V)
Pompe, S.;
Untersuchung über die Komplexierung und die Migration von Aktiniden und nichtradioaktiven Stoffen mit Huminsäuren unter geogenen Bedingungen - Komplexierung von Huminsäuren mit Aktiniden in der Oxidationsstufe IV Th, U, Np.
  • Lecture (others)
    Workshop zum Forschungsvorhaben Saarbrücken 2001, 26.-27.4.2001

Publ.-Id: 4601 - Permalink


Rhizobium sullae sp. nov. (formerly "Rhizobium hedysari"), the root-nodule microsymbiont of Hedysarum coronarium L.
Squartini, A.; Struffi, P.; Döring, H.; Selenska-Pobell, S.; Tola, A.; Giacomini, A.; Vendramin, E.; Velazques, E.; Mateos, P.; Martinez-Molina, E.;
This work is the completion of a series of reports describing the nitrogen-fixing bacterial symbionts of sulla (Hedyzarum coronarium L., Leguminosae) and providing the grounds for their proposal as a new taxon. The introduction summarizes a large amount of previous evidence gathered on the physiology, genetics and ecology of such organisms, which have in the past been referred to provisionally as "Rhizobium hedysari". Upon adding 16S rRNA sequencing, amplified rDNA restriction analysis of the rrn operon, DNA-DNA hybridization homology and analysis of low-molecular-mass RNA species, it is concluded that the group of strains that specifically nodulate sulla consists of a coherent set of isolates that differ from previously described rhizobia to an extend that warrants the construction of the species boundary. The name Rhizobium sullae sp. nov. is proposed, with isolate IS123T (=USDA4950T = DSM 14623T) as the type strain.

Autor/Institut
Dipartimento di Biotecnologie Agrarie, Universita di Padova, Agripolis, Strada Romea16, 35020 Legnaro, Padova, Italy; Molecular Microbiology Group, Institute of Radiochemistry, Forschungszentrum Rossendorf, D-01314 Dresden, Germany; Departamento de Microbio-logia y Genetica, Universidad de Salamanca, Avda del Campo Charro s/n, 37007 Salamanca, Spain; Department of Microbiology, Michigan State University, East Lansing, MI 48824, USA; Dipartimento di Chimica e Biotecnologie Agrarie, Universita di Pisa, via del Borghetto 80, Pisa, Italy
  • Int. I. Syst. Evol. Microbiologie 52, 1267-1276

Publ.-Id: 4599 - Permalink


Diversity and activity of bacteria in uranium waste piles
Selenska-Pobell, S.;
The pollution of the environment with toxic metals is one of the most severe problems of our industrial age. Uranium mining waste piles are a subject of particular attention, because in the soils, sediments, and drainage waters of these environments significant amounts of many hazardous metals are present, such as uranium, selenium, molybdenum, arsenic, cadmium, chromium, mercury, lead, copper, nickel and zinc (Francis, 1990). In addition, significant amounts of thorium, radium, polonium and other decay products may also be present in the so-called uranium 'mill tailings' where the extraction of uranium from the ores was performed.

Even in the most heavily polluted uranium wastes, large numbers of bacteria are present (Cerda et al., 1993; Goebel & Stackebrandt, 1994; Shippers et al., 1994). Moreover, different groups of bacteria can interact in different ways with metals and radionuclides (see Chapters ????). Some of the most important mechanisms by which bacteria can biotransform and influence the mobilization and/or immobilisation of metals are listed below:
i) direct oxidation and/or reduction of metals, which affect their solubility (DiSpirito & Tuovinen, 1982; Lovley, 1993; Nelson et al., 1999; Sharma et al. 2000; Wildung et al., 2000);
ii) direct or indirect oxidation of metal sulfides and the associated solubilization of certain elements (Bosecker, 1997; Krebs & Brandl, 1997);
iii) indirect alteration of metal speciation caused by microbially-induced pH and Eh changes in the medium (Bosecker, 1997; Bacelar-Nicolau & Johnson, 1999);
iv) bioaccumulation [biosorption by cell surface polymers (DiSpirito et al., 1983; Douglas & Beveridge, 1998; Macaskie et al., 1992; Panak et al., 1999; Selenska-Pobell et al., 1999; Valentive et al., 1996) and/or uptake of metals inside the cells (Klaus et al., 1999; Marques et al., 1991; Purchase et al., 1997)];
v) bio-mineralization, including induction of metal precipitation by specific metabolic functions and the consequent generation of minerals (Brown and Beveridge, 1998; Douglas and Beveridge, 1998; Francis, 1998);
vi) release of biosorbed metals by chelation, alkylation, or decomposition (Bosecker, 1997; Francis, 1990; Francis et al., 1998).
It is clear that the bacterial activities described above strongly influence the fate and migration of toxic metals in and outside the sites where uranium mining has been performed. In addition to the living cells, significant amounts of different bacterial metabolites are present in the wastes and these also interact with the heavy metals and influence their behaviour. For these reasons, knowledge of the diversity and activity of the indigenous bacteria in the uranium waste piles is of fundamental importance for understanding the biogeochemical processes occurring in these environments and especially for modelling the migration of the heavy metals and radionuclides.

Until recently, information about bacterial diversity in uranium waste piles was limited to several studies dealing with culturable bacteria (Berthelot et al., 1997; Cerda et al., 1993; Francis et al., 1991; Goebel & Stackebrandt, 1994; Shippers et al., 1994). This, however, is not sufficient because only a few percent of natural bacterial populations can be cultured and studied in the laboratory (Chapter 2) due to our limited knowledge of the nutrient requirements and other life-necessities for most bacterial species in nature (Pace, 1997; Service, 1997; Ward et al., 1990). The development and application of molecular approaches in bacterial ecology during the last decade has revealed a tremendous prokaryotic diversity which was overlooked by traditional culture enrichment techniques (Byers et al., 1998; Chandler et al., 1997; Dojka et al., 2000; Pace, 1997; Service, 1997).

One of these approaches, 16S rDNA retrieval, has been applied to analysis of bacterial diversity in deep granitic rocks and in an aquifer around a nuclear fuel repository in Sweden (chap...
  • Book (Authorship)
    Interactions of Bacteria with Radionuclides Elsevier Sciences, Oxford, UK pp. 225-253

Publ.-Id: 4596 - Permalink


Synthesis of hydroxyl silylated rhenium and (99mTc)technetium ‚3+1'mixed ligand complexes
Knieß, T.; Spies, H.; Santos, I.; Zablotskaya, A.;
The synthesis of hydroxyl silylated thiols as monodentate ligands is described. These monodentates were used to build with Re and 99mTc trimethyl-, triethyl- and triphenyl-silylated ‚3+1' mixed ligand complexes, using 3thiapentane-1,5-dithiol as co-ligand. The Re complexes were characterized by 1H NMR and elemental analysis, the 99mTc complexes were detected by radio HPLC. While the trimethyl silylated derivatives hydrolysed in aqueous media, the triethyl- and triphenyl silylated complexes have proved to be stable in neutral solutions.
Keywords: hydroxyl silylated thiols; Re and Tc complexes
  • J Label Compd Radiopharm 45 (2002) 629-636

Publ.-Id: 4594 - Permalink


Bacterial diversity and activity in uranium mining wastes
Selenska-Pobell, S.;
Bacterial diversity was studied in several uranium mining waste piles and mill-tailings in Germany (Johanngeorgenstadt, Schlema/Alberoda, Gittersee/Coschütz) and in the USA (Shiprock, New Mexico and Gunnison, Colorado) using direct molecular approaches. Significant differences were found between bacterial communities distributed in the uranium mill-tailings and in the uranium mining waste piles. The predominant bacterial groups in the water and soil samples collected from the mill-tailings were gamma-, beta-, and delta-Proteobacteria, representatives of Cytophaga/Flavobacterium/Bacteroides (CFB) group and also Gram-positive bacteria with low G+C content. In contrary, in the uranium mining waste piles representatives of alpha-Proteobacteria and such of Holophaga/Acidobacterium division were predominant. In both environments, however, presence of related groups of gamma-Proteobacteria was demonstrated.
In parallel, the method of enrichment culturing was applied and particular indigenous bacterial strains were cultured from the uranium wastes and their interactions with U and some other metals were studied. In particular, microdiverse bacterial isolates belonging to Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, Desulfovibrio vulgaris (oxamicus), Bacillus sphaericus, B. cereus, B. thuringiensis, B. megaterium, Clostridium sp., and Pseudomonas sp. were recovered and characterized.
Vegetative cells, spores and S-layers of one uranium mining waste pile isolate, namely Bacillus sphaericus JG-A12, able to accumulate reversibly high amounts of toxic metals from drain waters of the U wastes, were used for construction of bacteria-based biological ceramics (biocers) for bioremediation. Biosorption and desorption of U and Cu by the constructed biocers were studied in model experiments and it was demonstrated that they possess very high metal binding capacity and are suitable for reversible usage. The latter demonstrates that uranium mining waste piles are a reservoir of bacteria prospective for in situ bioremediation of these environments.
  • Lecture (Conference)
    Konferenz in Hiroshima, Japan 21.8.2002

Publ.-Id: 4593 - Permalink


Bacterial communities in uranium mining waste piles and their interaction with heavy metals
Selenska-Pobell, S.;
kein Abstract, nur Folien
  • Lecture (Conference)
    Konferenz in Hiroshima 21.8.2002

Publ.-Id: 4592 - Permalink


Production of w mesons in proton-proton collisions
Abd El-Samad, S.; Abdel-Bary, M.; Brinkmann, K.-T.; Clement, H.; Dshemuchadse, S.; Dutz, H.; Eyrich, W.; Erhardt, A.; Filges, D.; Filippi, A.; Freiesleben, H.; Fritsch, M.; Georgi, J.; Gillitzer, A.; Hesselbarth, D.; Jakob, B.; Karsch, L.; Kilian, K.; Koch, H.; Kress, J.; Kuhlmann, E.; Marcello, S.; Marwinski, S.; Mauro, S.; Meyer, W.; Michel, P.; Möller, K.; Mortel, H.; Morsch, H. P.; Naumann, L.; Plettner, C.; Richter, M.; Roderburg, E.; Schamlott, A.; Schönmeier, P.; Schulte-Wissermann, M.; Schroeder, W.; Stinzing, F.; Steinke, M.; Sun, G. Y.; Wagner, G. J.; Wagner, M.; Wilms, A.; Wirth, S.;
The cross section for the production of ω mesons in proton-proton collisions has been measured in a previously unexplored region of incident energies. Cross sections were extracted at 92 MeV and 173 MeV excess energy,
respectively. The angular distribution of the ω at ε=173 MeV is strongly anisotropic, demonstrating the importance of partial waves beyond pure s-wave production at this energy.
  • Physics Letters B 522 (2001) 16-21

Publ.-Id: 4591 - Permalink


Experimental investigations and modelling on the transition from bubble to slug flow in vertical pipes
Lucas, D.; Krepper, E.; Prasser, H.-M.;
To qualify CFD codes for two-phase flows, they have to be equipped with constitutive laws describing the interaction between the gaseous and the liquid phases. In the case of bubble flow this particularly concerns the forces acting on the bubbles and bubble coalescence and break-up. To obtain detailed experimental data, an electrode wire-mesh sensor was used, which enables the measurement of the phase distribution with a very high resolution in space and in time. Air-water flow at ambient conditions in a vertical pipe (51.2 mm inner diameter) is investigated to have well defined boundary conditions. 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, Bubble Flow, Slug Flow
  • Lecture (Conference)
    Proceedings of the German-Japanese Workshop on Multiphase Flow, Karlsruhe, August 25-27, 2002, FZKA 6759(http://www.emsi.fzk.de/gjwmf2002/pdf/Proceedings_FZKA6759.pdf), pp. C-1 - C-12
  • Contribution to proceedings
    Proceedings of the German-Japanese Workshop on Multiphase Flow, Karlsruhe, August 25-27, 2002, FZKA 6759(http://www.emsi.fzk.de/gjwmf2002/pdf/Proceedings_FZKA6759.pdf), pp. C-1 - C-12

Publ.-Id: 4589 - Permalink


Synthetische Huminsäuren und deren Einsatz.
Pompe, S.; Schmeide, K.;
kein Abstract
  • Lecture (others)
    Vortrag anläßlich des Besuchs der AG Gleixner vom Max Planck Institut für Biochemie Jena, Rossendorf 30.1.01

Publ.-Id: 4588 - Permalink


Untersuchungen über das Komplexierungsverhalten von Huminsäuren und deren Einfluß auf die Migration von radioaktiven und nichtradioaktiven Stoffen unter geogenen Bedingungen.
Pompe, S.; Schmeide, K.; Brendler, V.; Heise, K. H.; Bernhard, G.;
kein Abstract
  • Other report
    FZKA-PTE Nr. 7, Wissenschaftlicher Bericht, Forschungszentrum Karlsruhe 2001, pp 473-480

Publ.-Id: 4587 - Permalink


Characterization of U(VI)-Acidithiobacillus ferrooxidans complexes by using EXAFS, transmission electron microscopy and energy-dispersive X-ray analysis
Merroun, M.; Hennig, C.; Rossberg, A.; Reich, T.; Selenska-Pobell, S.;
Summary. We used a combination of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, Transmission Electron Microscopy (TEM) and Energy-Dispersive X-ray (EDX) analysis to conduct molecular scale studies on U(VI) interaction with three recently described eco-types of A. ferrooxidans. On the basis of the information obtained by using these methods, we conclude that uranyl phosphate complexes were formed by the cells of the three eco-types studied. The uranium accumulated by A. ferrooxidans cells was located mainly within the extracellular polysaccharides and on the cell wall. We suggest that at toxic levels when uranium enters the bacterial cells A. ferrooxidans can detoxify and efflux this metal by a process in which its polyphosphate bodies are involved.
  • Radiochimica Acta 91, 583-591 (2003)

Publ.-Id: 4586 - Permalink


Generation of a High Temperature Material Data Base and its Application to Creep Tests with French or German RPV-steel
Willschütz, H.-G.; Altstadt, E.;
Considering the hypothetical core melt down scenario for a light water reactor (LWR) a possible failure mode of the reactor pressure vessel (RPV) and its failure time has to be investigated for a determination of the loadings on the containment. Numerous experiments have been performed accompanied with material properties evaluation, theoretical, and numerical work /REM 1993/, /THF 1997/, /CHU 1999/.
For pre- and post-test calculations of Lower Head Failure experiments like OLHF or FOREVER it is necessary to model creep and plasticity processes. Therefore a Fi-nite Element Model is developed at the FZR 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. Additionally the implementation of all relevant temperature dependent material properties has been performed. 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 com-parison with experiments. This is done in 3 levels: starting with the simulation of sin-gle 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. This report deals with the 1D- and 2D-simulations.
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. Since these 2 steels show a similar behavior, it should be allowed on a lim-ited scale to transfer experimental and numerical data from one to the other.

Keywords: Creep and Plasticity of RPV-steel, Tube failure experiments FEM-Simulation
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-353 August 2002

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Publ.-Id: 4583 - Permalink


Analysis of the S-Layer from the uranium mining waste pile isolate Bacillus sphaericus JG-A12 and its interaction with metals
Raff, J.;
Institutsseminar, in der Universität Leipzig ,
Institut für Biochemie; no abstract delivered from author
  • Lecture (others)
    Seminar am Institut für Biochemie, Universität Leipzig am 17.12.2001

Publ.-Id: 4581 - Permalink


A novel surface layer protein of the uranium waste pile isolate Bacillus sphaericus JG-A 12 and its interaction with metals
Raff, J.; Flemmig, K.; Mathys, S.; Wahl, R.; Pompe, W.; Soltmann, U.; Nicolai, R.; Heise, K. H.;
Bacteria in uranium waste piles are of special interest for bioremediation, because they are adapted to high concentrations of heavy metals in these environments. One bacterial isolate from a uranium mining waste pile "Haberland" near the town of Johanngeorgenstadt in Saxony, Germany, Bacillus sphaericus JG-A 12, possesses a surface layer (S-layer) protein which differs significantly from the other S-layers studied up to date. Interestingly, the N-terminal domain (182 amino acid residues) of this S-layer is almost identical to that of B. sphaericus NCTC 9602 which was also analyzed in our laboratory. Vegetative cells and spores of the two B. sphaericus strains accumulate selectively large amounts of U, Pb, Cd, Cu and Al from the highly polluted drain waters of the uranium waste. The interaction of the S-layers of the two strains with U, Pt and Pd were studied in particular, using IR spectroscopy and EXAFS spectroscopy. The ability of the vegetative cells, spores and S-layers of the two B. sphaericus strains to interact with metal ions makes them prospective for bioremediation. Results on entrapping of vegetative cells of B. sphaericus JG-A 12 and B. sphaericus 9602 in SiO2 ceramics using the sol-gel process, will be presented.
  • Poster
    VAAM Jahrestagung Oldenburg 25.-28.3.2001

Publ.-Id: 4580 - Permalink


Schnelles Freimeßverfahren für alpha-aktive Nuklide in Bauschutt durch Direktmessung von großflächigen dünnen Meßpräparaten - Automatisierung des Verfahrens -
Nebelung, C.;
Beim Abriß von Nuklearanlagen fallen große Mengen Bauschutt an, die mit Radionukliden kontaminiert sein können. Da diese Kontaminationen häufig nahe der Freigabewerte liegen, ist für die Entscheidung, ob das Material als radioaktiver Abfall behandelt werden muß oder freigegeben werden kann, eine schnelle und exakte Meßmethode notwendig. Eine direkte Messung der a-aktiven Nuklide im stehenden Gebäude ist auf Grund der geringen Reichweite der a-Strahlung und ihrer Absorption im Beton nicht möglich. Die übliche chemische Analyse der a-aktiven Nuklide ist sehr arbeits- und zeitaufwendig und somit ungeeignet.
Im Rahmen dieses Projektes wurde die Methode der direkten a-Spektrometrie nach nur mechanischer Präparation des Betons bis zur technischen Anwendungsreife weiterentwickelt. In einem aus zwei Schritten bestehenden Zerkleinerungsprozeß wurden Suspensionen mit mittleren Partikeldurchmessern von 0,5 µm hergestellt. Die Meßproben mit einem Durchmesser von 20 cm und Schichtdicken zwischen 1 und 2,5 µm wurden durch Sprühen auf die Probenträger und anschließendes Trocknen hergestellt. Für die Stabilität der Suspensionen wurden Peptisatoren und Tenside getestet, die agglomeratfreie Suspensionen und damit gleichmäßige Schichten garantieren. Die Spektren dieser Proben wurden in einer Gitterionisationskammer (GIK) aufgenommen. Es wurden Untersuchungen zur Verringerung des Nulleffektes der GIK durchgeführt, um die Nachweisgrenze der Methode zu verringern. Die Spektrenauswertung erfolgte durch Peakfitting mit einer der Peakform angepaßten kombinierten Gaußschen und exponentiellen Funktion. Eine zweite Methode zur Spektrenanalyse ist das verbesserte Programm WINKRUM, basierend auf Strahlungstransportberechnungen. Dieses Modell berücksichtigt Partikelgrößenverteilung und Packungsdichte, spezifische Dichte, Schichtdicke, Parameter der GIK und die Energie der Actiniden.
Mit dieser Direktmessung dünner Meßproben können a-aktive Nuklide bis zu einer Nachweisgrenze von 0,005 bis 0,02 Bq/g (abhängig von der a-Energie) in Multielementspektren innerhalb von 28 h bestimmt werden.


Fördernde Institution
Bundesministerium für Bildung und Forschung (BMBF)
53170 Bonn

BMBF 02S 7768 6
  • Contribution to external collection
    BMBF-Schlussbericht 2001

Publ.-Id: 4579 - Permalink


Rückbau von Nuklearanlagen Minimierung des Sondermülls Schnelle Bestimmung von Alpha-Strahlern
Nebelung, C.;
Rückbau von Nuklearanlagen:
große Mengen Bauschutt z.B. KKW Greifswald 1.800.000Mg

Abfallminimierung: Trennung von kontaminiertem und unbelastetem Material.
1m³ Abfall kosten (ohne Behälter, Analytik, Transport)
Morsleben 12.500DM
Schacht Konrad 25.000DM

hohe Anforderung an die Freimessung nach den gesetzlichen Freigabekriterien - Bestimmung alpha-strahlender Nuklide bisher zeit- und arbeitsaufwendig

neu: Entwicklung einer schnellen Direktmeßmethode zur Einzelnuklidbestimmung von Alpha-Strahlern
- rein mechanische Probenaufbereitung
- dünne großflächige Meßproben
- Spektrenmessung und Peakentfaltung Bestimmung aller Nuklide in einer Meßprobe
- Vergleich mit unbelastetem Material (natürliche Radioaktivität in vergleichbarer Größenordnung)

Förderung:
Bundesministerium für Bildung und Forschung
02 S 7442 2, 02 S 7655 8, 02 S 7768
  • Poster
    Hannover-Messe 2001

Publ.-Id: 4578 - Permalink


Isospectrality of spherical MHD dynamo operators: Pseudo-Hermiticity and a no-go theorem
Günther, U.; Stefani, F.;
The isospectrality problem is studied for the operator of the spherical hydromagnetic alpha^2-dynamo. It is shown that this operator is formally pseudo-Hermitian (J-symmetric) and lives in a Krein space. Based on the J-symmetry, an operator intertwining Ansatz with first-order differential intertwining operators is tested for its compatibility with the structure of the alpha^2-dynamo operator matrix. An intrinsic structural inconsistency is obtained in the set of associated matrix Riccati equations. This inconsistency is interpreted as a no-go theorem which forbids the construction of isospectral alpha^2-dynamo operator classes with the help of first-order differential intertwining operators.
  • Journal of Mathematical Physics 44 (2003) 3097-3111

Publ.-Id: 4577 - Permalink


Finite Element Based Stress Analysis of BWR Internals Exposed to Accident Loads
Altstadt, E.; Weiß, F.-P.; Werner, M.; Willschütz, H.-G.;
During a hypothetical accident the reactor pressure vessel internals of boiling water reactors can be exposed to considerable loads resulting from temperature gradients and pressure waves. The finite element (FE) analysis is an efficient tool to evaluate the consequences of those loads by computing the maximum mechanical stresses in the components. 3 dimensional FE models were developed for the core shroud, the upper and the lower core supporting structure, the steam separator pipes and the feed water distributor. The models of core shroud, upper core support structure and lower core support structure were coupled by means of the substructure technique. All FE models can be used for thermal and for structural mechanical analyses. As an example the FE analysis for the case of a station black-out scenario (loss of power supply for the main circulating pumps) with subsequent emergency core cooling is demonstrated. The transient temperature distributions within the core shroud and within the steam dryer pipes as well were calculated based on the fluid temperatures and the heat transfer coefficients provided by thermo-hydraulic codes. At the maximum temperature gradients in the core shroud, the mechanical stress distribution was computed in a static analysis with the actual temperature field being the load. It could be shown that the maximum resulting material stresses do not exceed the permissible thresholds fixed in the appropriate regulations. Another scenario which was investigated is the break of a feed water line leading to a non-symmetric subpressure wave within the reactor pressure vessel. The dynamic structural response of the core shroud was assessed in a transient analysis. Even for this load case the maximum resulting stresses remain within the allowed limits at any time.
Keywords: FEM-Analysis, BWR Internals, temperature field and stress calculation
  • Lecture (Conference)
    Paper ICONE-6508 on CD of the conference proceedings of the 6th International Conference on Nuclear Engineering, ICONE-6, San Diego, California, USA, May 10-15, 1998
  • Contribution to proceedings
    Paper ICONE-6508 on CD of the conference proceedings of the 6th International Conference on Nuclear Engineering, ICONE-6, San Diego, California, USA, May 10-15, 1998

Publ.-Id: 4576 - Permalink


Entwicklung und Erprobung einer Schnittstelle zwischen der Messdatenerfassungs- und Automatisierungssoftware DIAdem von National Instruments und der Wasser/Dampf Stoffwertedaten-Unterbibliothek Libl97
Pietruske, H.; Schaffrath, A.;
The Institute of Safety Research (IfS) of the Forschungszentrum Rossendorf (FZR) e.V. is constructing a new large-scale multipurpose test facility TOPFLOW (Transient Two Phase Flow Test Facility). This facility will be probably put into operation in the next two months. For an effective evaluation of the start up experiments and the acceptance trials against the vendors FZR starts with the preparation of automated software tools for the measurement data logging and automation software DIAdem, which is distributed by National Instruments (NI). In a first step an interface for the coupling of a water/steam material property library LiblF97 of the university of applied science Zittau/Görlitz was developed.
This report describes the programming of the General Control Interface (GPI) and its coupling with DIAdem. Additionally the capability of this coupling in connection with autosequences for data evaluation was investigated. Further on effective methods for the TOPFLOW data evaluation were demonstrated and tested against a concrete example. Currently no TOPFLOW data are available. Therefore one selected NOKO experiment was evaluated and first practical experiences were collected. Even this example is easy understandable and clearly seen, it contains every step, which is necessary for the TOPFLOW data evaluation. This contains the opening of files, determination of water/steam material properties with the Dynamic-Link-Library LibIF97.dll, the linkage of different data channels and the generation of layouts for graphics and reports.

The tools presented in this report are an important steps for the evaluation of the experimental data of TOPFLOW. These tools will be adapted now for the assessment of the acceptance trails. Further on now the generation of the automated software sequences for the first scientific tests are developed.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-352 August 2002

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Publ.-Id: 4575 - Permalink


Synthesis and properties of triethyl(triphenyl)siloxyalkyl(aryl)thiolato(3-thiapentane-1,5-dithialato)oxorhenium(V)- potential brain seeking agents
Abedin, M. Z.; Spies, H.; Pietzsch, H.-J.; Zablotskaya, A.;
Four triethyl(triphenyl)siloxyalkyl(aryl)thiolato(3-thiapentane-1,5-dithialato)oxorhenium(V) complexes viz. triethylsiloxyethylthiolato-(3-thiapentane-1,5-dithialato)oxorhenium(5), triethylsiloxypropylthiolato-(3-thiapentane-1,5-dithialato)oxorhenium(6), triethylsiloxyphenylthiolato-(3-thiapentane-1,5-dithialato)oxorhenium(8) and triphenylsiloxyethylthiolato-(3-thiapentane-1,5-dithialato)oxorhenium(7) were synthesized by a new route reacting chloro-(3-thiapentane-1,5-dithialato)oxorhenium(V) with bis silylated mercaptoalkanols or mercaptophenol. Stability of the compounds in acetonitrile-water (1:1) solution at different temperature and pH was studied by reverse phase HPLC method. Compound 5 was found to be the most stable in acetonitrile-water system with respect to both temperature and pH changes.
  • Bangladesh Journal of Nuclear Medicine (2001) 1-6.

Publ.-Id: 4574 - Permalink


Synthesis and physico-chemical characterization of triorganylsiloxyalkyl monodentate ligands with free mercapto group.
Zablotskaya, A.; Segal, I.; Lukevics, E.; Knieß, T.; Spies, H.;
no abstract delivered from author
  • Latv. Kim. Z. N4 (2001) 339-342

Publ.-Id: 4573 - Permalink


Energy loss of quarks in deconfined matter at RHIC: photon-tagged jets, single electron and dilepton spectra from open charm
Gallmeister, K.; Kämpfer, B.; Pavlenko, O. P.;
We report a first attempt
(i) to derive constraints on the energy loss of charm quarks in a deconfined medium from the recent PHENIX data of single-electron transverse momentum spectra and
(ii) to estimate the resulting suppression of dileptons from correlated semi-leptonic decays of open charmed mesons.
The momentum imbalance of photon-tagged light-quark jetsis also considered.
Keywords: gluon radion, energy loss, charm quarks
  • Nucl. Phys. A 715 (2003) 705c nucl-th

Publ.-Id: 4572 - Permalink


Berechnung des Notkondensators des Integralreaktors CAREM
Walter, D.; Schaffrath, A.;
CAREM is an Argentine project to achieve the development, design and construction of an innovative, simple and small Nuclear Power Plant (NPP). This NPP has an indirect cycle reactor with some distinctive and characteristic features (e.g. integrated primary cooling system by natural circulation, self-pressurized primary system and passive safety systems, etc.). In the frame of an IAEA forwarded HUMAN RESOURCES DEVELOPMENT - “Advice on CAREM passive emergency condenser” at the Centro Atómico in San Carlos de Bariloche (Argentina) German experimental as well analytical investigation of passive safety systems - mainly performed at the research centers Jülich and Rossendorf were presented. During this visit it was decided that FZR should determine the emergency condenser capacity by using the ATHLET code with and without the condensation module extension KONWAR (condensation inside horizontal tube). These results should be compared and assessed with existing RELAP calculations.
The ATHLET and ATHLET/KONWAR calculations of the emergency condenser were used for minimizing the user influence performed with exactly the same nodalization scheme and the same initial and boundary conditions than the RELAP calculations. The comparison of all three computational results shows that the required condenser capacities were achieved. The magnitudes were in order of up to 12%. An additionally performed evaluation of local flow parameters show large deviations especially for the heat transfer coefficients at the inner and outer tube wall. Due to the good validation progress of KONWAR by an extensive module validation against NOKO and HORUS experiments, the focus of the further investigation were concentrated on the boiling heat transfer. A comparison of the ATHLET boiling model (according to Forster and Zuber in combination with the equation of Thom for the determination of temperature difference between wall and saturated fluid) with other models from literature (Borishansky, Fritz, Gormenflo, Stefan and Abdelsalam) shows a strong underestimation of heat transfer coefficients in low pressure conditions. Therefore the model of Forster and Zuber is replaced against the model of Stefan and Abdelsalam. The calculations with ATHELT/KONWAR were repeated and show now a better agreement (deviations less equal than 3 %) with the RELAP results.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-351 August 2002

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Publ.-Id: 4571 - Permalink


A small and compact AMS facility for tritium depth profiling
Friedrich, M.; Pilz, W.; Bekris, N.; Glugla, M.; Kiisk, M.; Liechtenstein, V.;
A dedicated AMS facility for depth profiling of tritium in carbon samples containing higher quantities of tritium has been installed, tested and applied for routine measurements in the Forschungszentrum Rossendorf. It is based on an SF6-insulated 100 kV tandem accelerator equipped with a thin diamond-like carbon (DLC) stripper foil of about 1 µg/cm2. The carbon samples have been cut from tiles of the inner wall of the fusion experiments ASDEX-upgrade Garching/Germany, JET Culham/GB and TFTR Princeton/USA. Depth profiles of deuterium and other light elements can be measured simultaneously using the Faraday cup at the entrance of the accelerator (SIMS mode of the facility) or in the case of very low concentrations after acceleration using a particle detector (AMS mode).


Keywords: Mass Spectrometry, Tritium, Fusion, Electrostatic Accelerators
  • Lecture (Conference)
    Ninth International Conference on Accelerator Mass Spectrometry, 09.-13.09.2002, Nagoya, Japan
  • Nuclear Instruments and Methods in Physics Research B 223-224(2004), 21-25
    DOI: 10.1016/j.nimb.2004.04.008
  • Contribution to proceedings
    Ninth International Conference on Accelerator Mass Spectrometry, 09.-13.09.2002, Nagoya, Japan

Publ.-Id: 4568 - Permalink


Thin layer copper ISE for fluidic microsystem
Hüller, J.; Pham, M. T.; Howitz, S.;
A miniaturized ion selective electrode (ISE) for Cu2+ ions was developed, specially for application in a microfluidic system. The electrode preparation is based on a silicon wafer substrate which is coated with a Cu deposit in the range of 50 - 200 nm. The Cu layer is quantitatively converted into CuS by treatment in a sulphidic ambient. The chip electrode has a size of 5x5 mm2 and was mounted on a spacer chip coupled to the fluidic microcell using a chip clip technology. The coupling is liquid tight and reversible, admitting an easy exchange of the chip electrodes. The effective electrode area in contact with the liquid of the microsystems flow channel amounts to about 4 mm2.
Sensitivity measurements were performed stationary and in the flow through cell. Good Nernstian response of 29 mV/pCu between pCu 5 and 1 has been found and is in agreement with reference measurements carried out with a commercial ISE.
The rapid response observed also in the most diluted solutions used, is related to the thin, non porous structure of the CuS layer, minimizing diffusion effects during changing the test solutions. The adhesion of the sensitive CuS layer is different for the substrates Si, SiO2 and Si3N4 and depends on their history, roughness and evaporation conditions.
Keywords: micro electrode, ion selective electrode, copper ion sensor, fluidic micro system, solid state membrane
  • Lecture (Conference)
    9th International Meeting on Chemical Sensors, 7-10 July 2002, Boston USA, Abstract book p. 173
  • Contribution to proceedings
    9th International Meeting on Chemical Sensors, 7-10 July 2002, Boston USA, Abstract book p. 173

Publ.-Id: 4567 - Permalink


Improved p-type Conductivity in Heavily, Al-doped SiC by Ion-Beam- Induced Nano-Crystallization
Heera, V.; Madhusoodanan, K. N.; Mücklich, A.; Panknin, D.; Skorupa, W.;
Low-resistivity ( < 0.1 Ohm cm at room temperature), p-type SiC layers were produced by the combination of high dose Al implantation in n-type, 6H-SiC at low temperature, subsequent ion-beam-induced crystallization by means of Si irradiation at 500°C and high temperature annealing at 1500°C. The implanted SiC layers have a nanocrystalline structure consisting of randomly oriented grains of 3C-SiC. The electrical properties of the nanocrystalline and single-crystalline reference samples were investigated by sheet resistance and Hall measurements in dependence on temperature. In comparison with the standard doping process the hole concentration is enhanced by more than one order of magnitude. This can be explained by a higher solid solubility of Al in nanocrystalline SiC. Current-voltage measurements across the vertical p-n-junction in the heavily doped nanocrystalline and single-crystalline samples demonstrated the equivalence of the diode quality.
Keywords: p-type doping, nanocrystalline SiC, ion-beam-induced crystallization, Al implantation
  • Poster
    European Conference on SiC and Related Materials, Linköping, Sept. 1-5, 2002 (ECSCRM2002) Materials Science Forum vols. 433-436 (2003) 395-398, Trans Tech Publications
  • Mat. Sci. Forum 433-436 (2003) 395
  • Contribution to proceedings
    European Conference on SiC and Related Materials, Linköping, Sept. 1-5, 2002 (ECSCRM2002) Materials Science Forum vols. 433-436 (2003) 395-398, Trans Tech Publications

Publ.-Id: 4566 - Permalink


Nanocluster-rich SiO2 layers produced by ion beam synthesis: electrical and optoelectronic properties
Gebel, T.;
The aim of this work was to find a correlation between the electrical, optical and microstructural properties of thin SiO2 layers containing group IV nanostructures produced by ion beam synthesis. The investigations were focused on two main topics: The electrical properties of Ge- and Si-rich oxide layers were studied in order to check their suitability for non-volatile memory applications. Secondly, photo- and electroluminescence (PL and EL) results of Ge-, Si/C- and Sn-rich SiO2 layers were compared to electrical properties to get a better understanding of the luminescence mechanism.
Keywords: nanocluster, electroluminescence, photoluminescence, non-volatile memory, charge trapping, retention, endurance, CV, IV, EL, PL, RBS, TEM, defect luminescence, silicon dioxide, SiO2, Fowler-Nordheim
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-350 Juli 2002

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Publ.-Id: 4564 - Permalink


Subthreshold Phi-meson yield in central 58Ni+58Ni collisions at 1.93 AGeV
Mangiarotti, A.; Herrmann, N.; Maurenzig, P. R.; Gobbi, A.; Kotte, R.; Keczkemeti, J.; Leifels, Y.; Alard, J. P.; Andronic, A.; Averbeck, R.; Barret, V.; Basrak, Z.; Bastid, N.; Belyaev, I.; Bendarag, A.; Berek, G.; Caplar, R.; Crochet, P.; Devismes, A.; Dupieux, P.; Dzelalija, M.; Finck, C.; Fodor, Z.; Grishkin, Y.; Hartmann, O.; Hildenbrand, K. D.; Hong, B.; Kim, Y. J.; Kirejczyk, M.; Koczon, P.; Korolija, M.; Kress, T.; Kutsche, R.; Lebedev, A.; Lee, K. S.; Manko, V.; Merschmeyer, M.; Moisa, D.; Nianine, A.; Neubert, W.; Pelte, D.; Petrovici, M.; Plettner, C.; Rami, F.; Reisdorf, W.; de Schauenburg, B.; Schüll, D.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczynska, K.; Smolyankin, V.; Stockmeier, M.; Stoicea, G.; Vasiliev, M.; Wagner, P.; Wisniewski, K.; Wohlfarth, D.; Yang, J. T.; Yushmanov, I.; Zhilin, A.;
The Phi-meson production cross section is measured for the first time at a sub-threshold energy of 1.93 AGeV in 58Ni+58Ni collisions. The Phi data were obtained within the acceptance of the CDC/Barrel subsystem of the FOPI detector. For a sample of 4.7x106 central events, after background subtraction, 23 Phi candidates were observed. Extensive simulation calculations of the detector performance are shown in a detailed comparison to the data, aiming at a good understanding of the apparatus response and at a reliable determination of the efficiencies, production probability and possible systematic errors. A filter procedure is elaborated, which is meant to facilitate the comparison of any theoretical calculation with the data in the detector acceptance. How to extrapolate the result to a Phi-meson cross section in 4\pi is also discussed. This first result on pseudo-vector mesons can now be compared to existing data for the same reaction at the same incident energy for various outgoing channels, K+ and K- included. It suggests that a significant fraction (at least 20%) of the K--mesons is originating in the decay of the Phi showing that the two channels are strongly correlated. A first comparison to existing model calculations indicates the possible role of the Rho-meson channels in Phi production.

Publ.-Id: 4563 - Permalink


Control of the solid-liquid interface during RF-floating zone crystal growth by means of a two-phase inductor
Priede, J.; Gerbeth, G.; Hermann, R.; Behr, G.;
The quality of single crystals grown by the floating-zone method is strongly determined by the geometry of the solid-liquid phase boundary which, in turn, can be significantly influenced by the convection in the molten zone.
We describe a novel inductor design which allows a strong influence on the flow filed. Numerical simulations are presented for the design of such a two-phase inductor.
  • Poster
    5th International Conference on Fundamental and Applied MHD, Ramatuelle (France), Sept.16-20, 2002, Proceedings V 49-54
  • Contribution to proceedings
    5th International Conference on Fundamental and Applied MHD, Ramatuelle (France), Sept.16-20, 2002, Proceedings V 49-54

Publ.-Id: 4562 - Permalink


Three-dimensional linear stability analysis of LID-driven MHD cavity flow
Shatrov, V.; Mutschke, G.; Gerbeth, G.;
We present numerical results of a linear 3-D stability analysis of a square lid-driven cavity flow under the influence of an external magnetic field which is directed parallel to the lid. The Lorentz force has a strong influence on the flow structure, thereby changing number, shape and strength of the eddies inside. Although increasing magnetic fields are able to damp 3-D instability, in a parameter region around Re=3000, several branches of the neutral stabiliy curve do exist. This leads to a non-monotonic behaviour of receptivity to 3-D disturbances as the strength of the magnetic field is increased.
  • Poster
    5th International Conference on Fundamental and Applied MHD, Ramatuelle (France), Sept.16-20, 2002, Proceedings I 237-242
  • Contribution to proceedings
    5th International Conference on Fundamental and Applied MHD, Ramatuelle (France), Sept.16-20, 2002, Proceedings I 237-242

Publ.-Id: 4561 - Permalink


Lenz's rule liquefied: Understanding magnetic field saturation in the Riga dynamo experiment
Stefani, F.; Gerbeth, G.; Gailitis, A.;
We present the main observable features connected with magnetic field saturation in the Riga dynamo experiment, and try to explain them in terms of a simplified numerical model of back-reaction.
  • Poster
    5th International Conference on Fundamental and Applied MHD, Ramatuelle (France), Sept.16-20, 2002, Proceedings VI 53-58
  • Contribution to proceedings
    5th International Conference on Fundamental and Applied MHD, Ramatuelle (France), Sept.16-20, 2002, Proceedings VI 53-58

Publ.-Id: 4560 - Permalink


New results from the Riga dynamo experiment
Gailitis, A.; Lielausis, O.; Platacis, E.; Gerbeth, G.; Gundrum, T.; Stefani, F.;
In June 2002, a new series of experimental runs was carried out at the Riga dynamo facility. Compared with the experiments in November 1999 and July 2000, the new experiments have delivered much more magnetic field data with higher radial resolution and with sampling rates up to 10 kHz. The range of propeller rotation rates has been extended to higher values, giving new
information on the kinematic and the saturation regime for higher magnetic Reynolds numbers.
  • Lecture (Conference)
    5th International Conference on Fundamental and Applied MHD, Ramatuelle (France), Sept.16-20, 2002, Proceedings V17-12
  • Contribution to proceedings
    5th International Conference on Fundamental and Applied MHD, Ramatuelle (France), Sept.16-20, 2002, Proceedings V17-12

Publ.-Id: 4559 - Permalink


Contactless methods of velocity determination in conducting fluids
Stefani, F.; Gerbeth, G.;
The possibility of velocity reconstruction in electrically conducting fluids from external measurements of different induced magnetic fields is studied numerically. It is shown that for a reliable velocity reconstruction the effect of the electric potential at the fluid boundary on the induced magnetic field should be taken into account.
  • Lecture (Conference)
    5th International Conference on Fundamental and Applied MHD, Ramatuelle (France), Sept.16-20, 2002, Proceedings I 131-136
  • Contribution to proceedings
    5th International Conference on Fundamental and Applied MHD, Ramatuelle (France), Sept.16-20, 2002, Proceedings I 131-136

Publ.-Id: 4557 - Permalink


Intermittency route to turbulence in a rotating magnetic field driven flow
Grants, I.; Gerbeth, G.;
Stability and transition to turbulence in a flow driven by a rotating magnetic field is studied experimentally. Intermittent signals have been obtained clearly below the linear stability threshold.
  • Lecture (Conference)
    5th International Conference on Fundamental and Applied MHD, Ramatuelle (France), Sept.16-20, 2002, Proceedings I 179-183
  • Contribution to proceedings
    5th International Conference on Fundamental and Applied MHD, Ramatuelle (France), Sept.16-20, 2002, Proceedings I 179-183

Publ.-Id: 4556 - Permalink


Strömungskontrolle mit Magnetfeldern
Gerbeth, G.;
Strömungen elektrisch leitfähiger Flüssigkeiten, insbesondere von flüssigen
Metallen und Halbleiterschmelzen, lassen sich mit Magnetfeldern in
kontaktloser Weise stark beeinflussen. Es wird eine Übersicht gegeben zu
diesen Arbeiten im Rahmen des SFB 609 "Elektromagnetische
Strömungsbeeinflussung in Metallurgie, Kristallzüchtung und Elektrochemie"
und am FZR. Die inverse Herangehensweise, maßgeschneiderte Magnetfelder für
die im jeweiligen Prozeß wünschenswerten Strömungen bzw. Wärme- und
Stofftransporte zu entwickeln, wird vorgestellt. Es werden Möglichkeiten zur
Magnetfeldbeeinflussung metallischer Strahlen aufgezeigt, die für das
Sprühkompaktieren interessant sein könnten.
  • Lecture (others)
    Institut für Werkstofftechnik der Universität Bremen, 02.08.2002

Publ.-Id: 4555 - Permalink


Annual Report 2001 Institute of Safety Research
Weiss, F.-P.; Rindelhardt, U.; (Editors)
The report gives an overview on the activities of the Institute of Safety Research in 2001.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-342 Juni 2002

Downloads:

Publ.-Id: 4554 - Permalink


Bloch-Oszillationen: ein Faszinosum der Festkörperphysik seit 70 Jahren
Helm, M.;
Bei Anlegen eines elektrischen Feldes an einen Kristall würde der Strom ohne Streuung nicht auf unendlich anwachsen, sondern (fast) auf Null absinken. Dieses im ersten Moment paradoxe Phänomen, das mit der periodischen Struktur des Kristallgitters zusammenhängt, kann semiklassisch als sogenannte Bloch-Oszillation und quantenmechanisch durch die Ausbildung einer Wannier-Stark-Leiter verstanden werden. Beide Beschreibungsweisen führen zu einer Lokalisierung der Elektronen.
Nach einer grundlegenden Darstellung dieses Phänomens möchte ich einen Streifzug durch seine lange Geschichte unternehmen, die ihren Ausgangspunkt in einer Arbeit von Zener aus dem Jahre 1934 hat. Die „Gegenwart“ hat erst um 1990 durch den experimentellen Nachweis in Halbleiterübergittern begonnen. Vieles wurde seither verstanden, viele andere Dinge sind noch offen, wie zum Beispiel die Realisierung eines elektrisch getriebenen Bloch-Oszillators als THz-Quelle oder -Verstärker, wie 1970 von Esaki und Tsu vorgeschlagen. Ich werde aktuelle Experimente, Theorien, Probleme und neue Konzepte diskutieren.

Keywords: Bloch oscillations, superlattices
  • Lecture (others)
    Kolloquium an der Universität Würzburg, 15.7.2002

Publ.-Id: 4553 - Permalink


Proton and deuteron rapidity distributions and nuclear stopping in 96Ru(96Zr)+96Ru(96Zr) collisions at 400A MeV
Hong, B.; Kim, Y. J.; Kang, D. H.; Leifels, Y.; Rami, F.; de Schauenburg, B.; Sim, K. S.; Alard, J. P.; Andronic, A.; Barret, V.; Basrak, Z.; Bastid, N.; Berek, G.; Caplar, R.; Crochet, P.; Devismes, A.; Dupieux, P.; Dzelalija, M.; Finck, C.; Fodor, Z.; Gobbi, A.; Grishkin, Y.; Hartmann, O. N.; Herrmann, N.; Hildenbrand, K. D.; Kecskemeti, J.; Kirejczyk, M.; Koczon, P.; Korolija, M.; Kotte, R.; Kress, T.; Kutsche, R.; Lebedev, A.; Lopez, X.; Neubert, W.; Pelte, D.; Petrovici, M.; Reisdorf, W.; Schüll, D.; Seres, Z.; Sikora, B.; Simion, V.; Siwek-Wilczynska, K.; Smolyankin, V.; Stockmeier, M. R.; Stoicea, G.; Wagner, P.; Wisniewski, K.; Wohlfarth, D.; Yushmanov, I.; Zhilin, A.;
We present the centrality dependence of proton and deuteron rapidity distributions in Ru+Ru collisions at 400A MeV. Data are compared with Isospin Quantum Molecular Dynamics calculations (IQMD) under various assumptions on the nucleon-nucleon cross-section in the medium. The rapidity spectra of both particles can be reproduced by IQMD with a free nucleon-nucleon cross-section for the most central collisions. The ratio of baryon rapidity distributions in isospin asymmetric collision systems shows incomplete mixing and partial transparency of both the projectile and target nuclei at this beam energy.
  • Phys. Rev. C 66 (2002) 034901

Publ.-Id: 4551 - Permalink


Der EFF-Fonds - eine Fördermöglichkeit für Mitarbeiterausgründungen
Joehnk, P.;
  • Lecture (others)
    Vortrag IFW Dresden, Workshop "Neue Impulse für die Verwertung von Forschungsergebnissen" am 14.05.2002

Publ.-Id: 4549 - Permalink


Synthesis, characterization and biological evaluation of technetium(III) complexes with tridendate/bidendate S,E,S/P,S coordination (E = O, N(CH3), S): A novel approach to robust technetium chelates suitable for linking the metal to biomolecules
Pietzsch, H.-J.; Seifert, S.; Syhre, R.; Tisato, F.; Refosco, F.; Leibnitz, P.; Spies, H.;
A novel type of mixed-ligand Tc(III) complexes, [Tc(SCH2CH2-E-CH2CH2S)(PR2S)] (E = S, N(CH3); PR2S = phosphinothiolate with R = aryl, alkyl) is described. These "3+2"-coordinated complexes can be prepared in a two-step reduction/substitution procedure via the appropriate chloro-containing oxotechnetium(V) complex [TcO(SES)Cl] (E = S, N(CH3). Tc(III) compounds have been fully characterized both in solid and solution states and found to adopt the trigonal-bipyramidal coordination geometry. The equatorial trigonal plane is formed by three thiolate sulfurs atoms, whereas the phosphorus of the bidendate P,S ligand and the neutral donor of the tridendate chelator occupy the apical positions. The 99Tc(III) complexes have been proven to be identical with the 99mTc-agents prepared at the no-carrier-added level by comparison of the corresponding UV-Vis and radiometric HPLC profiles. Challenge experiments with glutathione clearly indicated that this tripeptide has no effect on the stability of the 99mTc complexes in solutions. Biodistribution studies were carried out in rats at 5 and 120 minutes post injection. The substituents at the bidendate P,S ligand significantly influenced the biodistribution pattern. Remarkable differences were observed especially in brain, blood, lungs and liver. All the complexes were able to penetrate the blood-brain-barrier of rat brain and showed a relatively fast washout from the brain.
Keywords: Tc(III) mixed ligand complexes, 3+2 complexes, X-ray structural analysis, biodistribution studies
  • Bioconjugate Chemistry 14 (2003) 136-143

Publ.-Id: 4548 - Permalink


Optical properties of N - implanted GaAs
Sinning, S.; Dekorsy, T.; Helm, M.;
Poster of experimental results of time resolved investigations of nitrogen implanted GaAs
Keywords: GaNAs time resolved implantation nitrogen III-V
  • Poster
    Poster for presentation at the 56th Scottish Universities Summer School in Physics "Ultrafast-Photonics" 1. - 14.9.2002 at the University of St Andrews, Scotland

Publ.-Id: 4547 - Permalink


Ion Beam Synthesis of Diamond-SiC-Heterostructures
Weishart, H.; Heera, V.; Eichhorn, F.; Pecz, B.; Barna, A.; Skorupa, W.;
Nanocrystals of silicon carbide were synthesized inside natural diamond using high dose silicon implantation. In order to retain the diamond structure, however, implantation was done at 900 °C. The samples were subsequently annealed in an rf-heated furnace at 1500 °C for 10 minutes. X-ray diffraction (XRD), IR absorption spectrometry and high-resolution cross-sectional transmission electron microscopy (HRTEM) are used to investigate formation and structure of SiC nanocrystallites in the implanted diamond. Raman spectroscopy contributed to trace implantation-induced destruction of the diamond. A first characterization of the electrical properties of the implanted and annealed samples is done by four point probe measurements. The results indicate a highly conductive, buried layer inside the diamond. This layer contains cubic SiC nanocrystals, which are perfectly aligned with the diamond lattice. However, when fluence exceeds a critical value of 5.3×1017 Si+cm-2, the diamond is irreversibly damaged and defect conduction type dominates.
Keywords: diamond, doping, silicon carbide, ion beam synthesis
  • Diamond & Related Materials 12/3-7 (2003) pp. 1241-1245

Publ.-Id: 4546 - Permalink


Nanocrystalline SiC layers produced by ion-beam-induced crystallization - morphology and resistivity
Heera, V.; Madhusoodanan, K. N.; Mücklich, A.; Skorupa, W.;
Ion beam induced crystallization was used to transform amorphized, heavily Al doped SiC layers to nanocrystalline material. The morphology of the as-implanted and the annealed layers was studied by XTEM. The electrical properties were analyzed by sheet resistance and Hall measurements and compared with crystalline reference samples. A high-temperature annealing step is necessary to activate the implanted Al acceptor atoms. During annealing the mean grain size of the nanocrystals grow from 3 nm to 37 nm. The Al doped, nanocrystalline SiC has a much lower sheet resistance than the crystalline reference samples. It was found that this is due to the enhanced hole concentration which could be explained by a higher solid solubility of Al in the nc SiC.
Keywords: Silicon Carbide, SiC, nanocrystalline, implantation, doping, morphology, resistivity
  • Diamond and Related Materials 12 (2003) 1190-1193

Publ.-Id: 4545 - Permalink


Interfaces under ion irradiation: Growth and taming of nanostructures
Heinig, K.-H.; Müller, T.; Schmidt, B.; Strobel, M.; Möller, W.;
We have investigated the synthesis of nanostructures as well as the control of their size and location by means of ion beams. The phase separation and interface kinetics under ion irradiation give new possibilities to control the growth of nanostructures. Additionally, the chemical decomposition of the host matrix by collisional mixing may contribute to self-organization of nanostructures, especially at interfaces. It is shown how collisional mixing during ion implantation affects nanocrystal (NC) synthesis and how ion irradiation through NCs modifies their size and size distribution. An analytical expression for solute concentration around an ion-irradiated NC were found which may be written like the well-known Gibbs-Thomson relation. However, parameters have modified meanings which has a tremendous impact on the evolution of NC ensembles. Thus, inverse Ostwald ripening of NCs resulting in an unimodal NC size distribution is predicted, which has been confirmed experimentally for Au NCs in SiO2 and by kinetic lattice Monte-Carlo simulations. At interfaces, the same ion-irradiation induced mechanism may result in self-organization of NCs in a thin d-layer. Collisional decomposition of SiO2 may enhances the NC d-layer formation in SiO2 at the Si/SiO2 interface. The distance of the self-organized NC d-layer from the SiO2/Si interface makes it interesting for non-volatile memory applications.
Keywords: Nanocrystals, Ion Beams, Phase Separation
  • Applied Physics A 77, 2003, 17-25

Publ.-Id: 4544 - Permalink


Targeting of renal tumors with mAb 138H11 against human gamma-glutamyltransferase in a novel syngeneic mouse model and cloning of recombinant 138H11 derivatives
Fischer, P.; Zimmermann, J.; Sachsinger, J.; Ivancevic, V.; Künstler, J.-U.; Schmiedl, A.; Michael, R.; Knoll, K.; Rezska, R.; Seifert, S.; Krause, H.; Munz, D. L.; Heicappell, R.; Miller, K.; Johannsen, B.; Scherberich, J. E.; Duebel, S.;
Continuing our strategy for a targeted therapy of metastatic renal cell carcinoma (RCC), a tumor which resists chemo- or radiotherapy, we now determined the primary structure of the antigen binding region of the monoclonal antibody 138H11. MAb 138H11, produced against human renal gamma-glutamyltransferase (GGT), stained over 99% clear cell and papillary RCC as well as other carcinomas on frozen sections, showing a membranous expression of the target antigen. In contrast, in normal kidneys GGT is restricted to the brush-border in the lumen of proximal tubules and thus not accessible to the circulation. Human tumor-bearing kidneys perfused in an
extra-corporeal system with 99mTc-138H11 revealed a high, specific uptake into the tumor. In vivo, a 138H11-Calicheamicin theta conjugate was very effective in reducing the tumor size and preventing or significantly delaying the regrowth of residual tumor cells in xenografted nude mice (Cancer Res. 2000, 60, 6089-6094). However, these nude mice are not useful for evaluating ADCC of naked 138H11 or immunoactivating conjugates. For creating a syngenic, immunocompetent mouse model bearing a tumor sensitive to mAb 138H11, we stably transfected the murine RCC RENCA cell line with the human GGT-gene. FACS-analysis revealed that transfected cells were positive for mAb 138H11, in contrast to wild type cells. The transfected cells were growing s.c. in
Balb/c mice without signs of rejection by the host. The mice showed a higher uptake of 99m-Tc-labelled 138H11 into the GGT positive RENCA tumors compared to the wild type tumors. This new model will be usful in the future for evaluating therapeutic effects of potential constructs made with the newly cloned recombinant 138H11-derivatives such as stabilized scFv, diabodies and triabodies.
  • Poster
    International Workshop Immunotherapy for the new century: Back and forth between basic science and clinical trials. Havana, Cuba, 05.-08.12.2002

Publ.-Id: 4543 - Permalink


Identification of tumor tissue by FTIR spectroscopy in combination with positron emission tomography
Richter, T.; Steiner, G.; Abu-Id, M. H.; Salzer, R.; Bergmann, R.; Rodig, H.; Johannsen, B.;
A method is described for identifying tumor tissue by means of FTIR microspectroscopy and positron emission tomography (PET). Thin tissue sections of human squamous carcinoma from hypopharynx (FaDu) and human colon adenocarcinoma (HT-29) grown in nude mice were investigated. FTIR spectroscopic maps of the thin tissue sections were generated and evaluated by Fuzzy C-Means (FCM) clustering and principal component analysis (PCA). The processed data were reassembled into images and compared to stained tissue samples and to PET. Tumor tissue could successfully be identified by this FTIR microspectroscopic method, while it was not possible to accomplish this with PET alone. On the other hand, PET permitted the non-invasive screening for suspicious tissue inside the body, which could not be achieved by FTIR.
Keywords: FTIR spectroscopy; Positron emission tomography; PET; Autoradiography; Tumor; PCA; FCM
  • Vibrational Spectroscopy 28 (2002) 103-110

Publ.-Id: 4542 - Permalink


Insulin secretion and insulin sensitivity in persons with different degrees of glucose tolerance.
Fischer, S.; Metzler, W.; Hanefeld, M.; Pietzsch, J.; Schwanebeck, U.; Julius, U.;
  • Poster
    62nd Scientific Sessions of the American Diabetes Association, San Francisco, California, USA; June 14-18, 2002
  • Abstract in refereed journal
    Diabetes 51, Suppl. 2 (2002) A561.

Publ.-Id: 4541 - Permalink


Heritability of the metabolic syndrome.
Julius, U.; Pietzsch, J.; Fuecker, K.;
no abstract delivered from author
  • Poster
    62nd Scientific Sessions of the American Diabetes Association, San Francisco, California, USA; June 14-18, 2002
  • Abstract in refereed journal
    Diabetes 51, Suppl. 2 (2002) A532.

Publ.-Id: 4540 - Permalink


Pro12Ala polymorphism of the peroxisome proliferator-activated receptor-gamma-2 : Association to Type 2 diabetes and response to a glucose tolerance test in a risk population for diabetes.
Temelkova-Kurktschiev, T.; Hanefeld, M.; Koehler, C.; Henkel, E.; Leonardt, W.; Pietzsch, J.; Laakso, M.;
  • Poster
    62nd Scientific Sessions of the American Diabetes Association, San Francisco, California, USA; June 14-18, 2002
  • Abstract in refereed journal
    Diabetes 51, Suppl. 2 (2002) A269.

Publ.-Id: 4539 - Permalink


The Ala12Ala variant of the PPAR-gamma-2 gene is associated with decreased insulin sensitivity.
Fischer, S.; Pihlajamäki, J.; Fuecker, K.; Hanefeld, M.; Laakso, M.; Julius, U.; Pietzsch, J.;
  • Poster
    62nd Scientific Sessions of the American Diabetes Association, San Francisco, California, USA; June 14-18, 2002
  • Abstract in refereed journal
    Diabetes 51,Suppl. 2 (2002) A264

Publ.-Id: 4538 - Permalink


Luminescence studies of blood phagocyte oxygenation activities in patients with antiphospholipid syndrome.
Kopprasch, S.; Roch, B.; Pietzsch, J.; Graessler, J.;
  • Poster
    XIIth International Symposium on Bioluminescence and Chemiluminescence, Cambridge, England; April 5 - 9, 2002
  • Abstract in refereed journal
    Luminescence 17 (2002) 96.

Publ.-Id: 4537 - Permalink


Chemiluminescence as a tool to assess hyperglycemia-induced systemic oxidative stress in different insulin-resistant states.
Kopprasch, S.; Pietzsch, J.; Kuhlisch, E.; Graessler, J.;
  • Poster
    XIIth International Symposium on Bioluminescence and Chemiluminescence, Cambridge, England; April 5 - 9, 2002
  • Abstract in refereed journal
    Luminescence 17 (2002) 96

Publ.-Id: 4536 - Permalink


Oxidative stress in impaired glucose tolerance
Kopprasch, S.; Pietzsch, J.; Kuhlisch, E.; Temelkova-Kurktschiev, T.; Hanefeld, M.; Fuecker, K.; Julius, U.; Gräßler, J.;
  • Poster
    37. Jahrestagung der Deutschen Diabetes-Gesellschaft, Dresden, 8.- 11. Mai 2002
  • Abstract in refereed journal
    Diabetes und Stoffwechsel 11 Suppl. 1 (2002) S103-104

Publ.-Id: 4535 - Permalink


Frequency spectra and electrohydrodynamic phenomena in a liquid gallium field-ion- emission source
Akhmadaliev, C.; Mair, G. L. R.; Aidinis, C. J.; Bischoff, L.;
A detailed investigation of the emission frequency spectra of a gallium Liquid Metal Ion Source (LMIS) is presented. The spectra are correlated with current oscillograms. The current for which pulses appear superimposed on the d.c. level of current is well predicted by existing theory. The pulses are believed to be the result of droplet emission, and their terminal frequency appears to coincide with the frequency of vibrations of the sides of the liquid cone at high currents. Better understanding of the instabilities that develop on the liquid anode can be useful for deposition purposes.
Keywords: Liquid metal ion source, frequency spectra, electrohydrodynamic phenomena
  • Journal of Physics D: Applied Physics 35 (2002) L91

Publ.-Id: 4534 - Permalink


Time Resolving Gamma-Tomography for Periodically Changing Gas Fraction Fields
Prasser, H.-M.; Baldauf, D.; Fietz, J.; Hampel, U.; Hoppe, D.; Zippe, C.; Zschau, J.; Christen, M.; Will, G.;
In the paper a novel non-intrusive tomographic method is presented to visualise the gas fraction distribution inside the rotating impeller of an axial pump delivering a two-phase flow. The device has been developed for an axial pump (inducer), which has an impeller with three helical blades rotating at 1500 revolutions per minute. Model fluid is air-water mixture created by a gas distributor upstream the pump inlet nozzle. The developed gamma-tomography set-up consists of a Cs-137 source and an arc of 64 scintillation detectors. Each of the detectors is connected to a number of counters grouped into banks. Each bank is active only during a 100 µs long interval of the rotation period, which corresponds to a well-defined angular interval of the impeller rotation. A trigger pulse, generated at the beginning of each revolution, forces the control unit to restart the counting process from the first bank. In this way, the device is able to measure ensemble averaged projections of the gamma absorption density distribution, which are resolved according to the rotating angle of the impeller. An image reconstruction by filtered back-projection provides density distributions inside the impeller. Void fraction distributions are visualised by means of differential tomography. i.e. by subtracting sets of projections obtained for two-phase operation and for plain liquid.
Keywords: Two-phase flow, axial pump, tomography, void fraction measurement
  • Poster
    HEAT 2002: Third International Conference Transport Phenomena in Multiphase Systems, Baranow Sandomierski, Poland, June 24-27, 2002, proc. pp. 425-434.
  • Flow Measurement and Instrumentation 14 (2003)3 pp. 119-125
  • Contribution to proceedings
    HEAT 2002: Third International Conference Transport Phenomena in Multiphase Systems, Baranow Sandomierski, Poland, June 24-27, 2002, proc. pp. 425-434.

Publ.-Id: 4533 - Permalink


Simulation of the non-equilibrium processes for tetrahedal amorphous carbon: Deposition and structural relaxation
Belov, A.; Jäger, H.-U.;
The processes of deposition and structural relaxation of tetrahedral amorphous carbon (ta-C) films are investigated using atomistic computer simulations. Applying classical molecular dynamics with a modified hydrocarbon potential of Brenner, ion-beam deposition of carbon films 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 ~80-85% of sp3 bonding at E > 30 eV. Above 200 °C simulations with the Brenner potential predict a sharp transition from ta-C to graphitic carbon with dominating sp2 bonding. Simulating thermal annealing, we show that low-temperature structural relaxation in ta-C is accompanied by a considerable stress reduction with only minor changes in the short-range order.
Keywords: Molecular dynamics; Ion-beam deposition; Tetrahedral amorphous carbon; Intrinsic stress, Structural relaxation
  • Nuclear Instruments and Methods in Physics Research B 202 (2003) 242-248

Publ.-Id: 4532 - Permalink


Quo vadis Anionenextraktion?
Gloe, K.; Stephan, H.; Grotjahn, M.;
Reaktivextraktionsverfahren stellen sehr effektive und elegante Trenn- und Anreicherungsverfahren für Metallionen in Lösung dar, die in vielfältiger Weise industriell genutzt werden. Trotz der großen Bedeutung von Anionen in Biologie, Medizin, Umwelt und Technik sind die praktischen Beispiele zur Anionenextraktion relativ begrenzt. Im wesentlichen basieren derartige Prozesse auf einer unspezifischen Ionenpaarbildung mit hydrophoben Ammonium-Kationen, wobei der Phasenübergang durch die Lipophilie der Anionen dominiert wird. Ursache für diese Unterschiede sind eine Reihe von Besonderheiten, die Anionen im Vergleich zu Kationen auszeichnen. Neue Ansätze zu spezifischer Bindung und selektivem Transport anionischer Komponenten beruhen auf einem fortschreitenden Verständnis der biologischen Rolle von Anionen und der dabei wirksamen Prinzipien sowie auf Möglichkeiten, die die supramolekulare Chemie durch Aufbau von vielfältigen Rezeptorarchitekturen mit spezifischen Bindungsstellen für Anionen eröffnet. Ziel der vorliegenden Übersicht ist es, ausgehend von den typischen Eigenschaften der Anionen gegenwärtige Entwicklungstendenzen sowie Einsatzpotentiale neuer potentieller Extraktionsmittel zu diskutieren.
  • Chemie Ingenieur Technik 74 (2002) 767-777

Publ.-Id: 4531 - Permalink


Annual Report 2001 Institute of Radiochemistry
Fanghänel, T.;
entfällt
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-343 Mai 2002

Downloads:

Publ.-Id: 4530 - Permalink


Probing in-medium vector meson decays by double-differential di-electron spectra in heavy-ion collisions at SIS energies
Kämpfer, B.; Pavlenko, O.; Wolf, G.;
Within a transport code simulation for heavy-ion collisions at bombarding energies around 1 AGeV we demonstrate that double-differential di-electron spectra with suitable kinematical cuts are useful to isolate
(i) the ρ meson peak even in case of strong broadening, and
(ii) the in-medium ω decay contribution,
which probe via the di-electron channel the expected in-medium modifications of the vector meson spectral densities.
Keywords: heavy-ion collisions, di-electrons, in-medium modifications of vector mesons
  • Phys. Lett. B nucl-th/0306029 (2003)

Publ.-Id: 4529 - Permalink


Low capacitance point diodes fabricated with focused ion beam implantation
Bischoff, L.; Schmidt, B.;
Low capacitance p+n point diodes were fabricated by combination of sputtering and implantation of a Ga focused ion beam through a thin oxide layer on a silicon substrate. The capacitance of the diodes were determined to be in the range of aF. The current-voltage characteristics show a tendency to a generation / recombination controlled behaviour with increasing dose i.e. with increasing depth of the sputter crater. This is correlated to the big amount of inactive Ga atoms of about 70% in the Si lattice after an annealing of 900°C; 20 min, N2.
Keywords: focused ion beam, point diodes, Ga implantation, sputtering, I-V characteristics
  • Solid State Electronics 47 (2003) 989

Publ.-Id: 4528 - Permalink


Atomic scale simulation of structural relaxation processes in tetrahedal amorphous carbon
Belov, A.;
Structural relaxation processes in tetrahedral amorphous carbon (ta-C) are examined at the atomic scale using computer simulation techniques and Brenner's bond-order potential. The amorphous carbon networks generated by ion-beam deposition simulation are employed as structural models of as-prepared ta-C. The models possess high intrinsic compressive stresses (~10 GPa) typical of as-grown ta-C films. Simulating annealing by the molecular-dynamics method, structural changes due to the relaxation of the ta-C networks were observed. In agreement with experiment, it is shown that low-temperature structural relaxation in ta-C is accompanied by a considerable stress reduction with only minor changes in the structural disorder and density. A complete stress relief is found to occur at Ta~1000 K. The stress relief mechanism discussed on the basis of the molecular-dynamics simulations includes structural transformations within the sp3-bonded constituent of ta-C networks and doesn't require oriented clustering of sp2-bonded atoms.
Keywords: Structural relaxation, molecular dynamics, tetrahedral amorphous carbon, intrinsic stress
  • Computational Materials Science 27 (2003) 30-35

Publ.-Id: 4527 - Permalink


Three-dimensional linear stability analysis of the flow in a liquid spherical droplet driven by an alternating magnetic field
Shatrov, V.; Priede, J.; Gerbeth, G.;
The paper presents a numerical stability analysis of the flow driven by an alternating (AC) magnetic field in an electromagnetically levitated liquid metal droplet. The basic axisymmetric flow is found to become unstable at Reynolds numbers in the order of 100. The critical Reynolds number Rec and the corresponding most unstable azimuthal wave number m are found for several configurations of the magnetic field depending on the skin-depth d. For a uniform external AC magnetic field the azimuthal wave number of the most unstable mode is m=3. An additional steady (DC) magnetic field imposed along the axis of symmetry increases the stability of the flow.
  • Physics of Fluids, March 2003, Vol. 15, Number 3, pp 668-678

Publ.-Id: 4526 - Permalink


Nanocrystal Formation in Si Implanted Thin SiO2 Layers under the Influence of an Absorbing Interface
Müller, T.; Heinig, K.-H.; Möller, W.;
Kinetic 3D lattice Monte Carlo studies are presented on Si nanocrystal (NC) formation by phase separation in 1 keV Si+ implanted thin SiO2 films. The simulation start from Si depth profiles calculated using the dynamic, high-fluence binary collision code TRIDYN. From the initial Si supersaturation, NCs are found to form either by nucleation, growth and Ostwald ripening at low Si concentrations. Or at higher concentrations, non-spherical, elongated Si structures form by spinodal decomposition, which spheroidize by interface minimization during longer annealing. In both cases, the close SiO2/Si interface is a strong sink for diffusing Si atoms. The NCs align above a thin NC free oxide layer at the SiO2/Si interface. Hence, the width of this zone denuded of NCs has just the right thickness for NC charging by direct electron tunneling, which is crucial for non-volatile memory applications. Moreover, the competition of Ostwald ripening and Si loss to the interface leads at low Si concentrations (nucleation regime) to a constant width of the denuded zone and a constant mean NC size over a long period of annealing.
Keywords: Nanocrystals, Nucleation, Spinodal Decomposition, Kinetic Monte Carlo, TRIDYN
  • Materials Science and Engineering B 101/1-3 (2003) 49-54

Publ.-Id: 4525 - Permalink


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

Publ.-Id: 4524 - Permalink


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

Publ.-Id: 4523 - Permalink


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

Publ.-Id: 4522 - Permalink


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

Publ.-Id: 4521 - Permalink


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

Publ.-Id: 4520 - Permalink


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

Publ.-Id: 4519 - Permalink


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

Publ.-Id: 4518 - Permalink


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

Publ.-Id: 4517 - Permalink


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

Publ.-Id: 4516 - Permalink


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

Publ.-Id: 4515 - Permalink


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

Publ.-Id: 4514 - Permalink


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

Publ.-Id: 4513 - Permalink


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

Publ.-Id: 4502 - Permalink


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

Publ.-Id: 4501 - Permalink


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

Publ.-Id: 4500 - Permalink


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

Publ.-Id: 4499 - Permalink


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

Publ.-Id: 4498 - Permalink


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

Publ.-Id: 4497 - Permalink


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

Publ.-Id: 4496 - Permalink


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

Publ.-Id: 4495 - Permalink


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

Publ.-Id: 4494 - Permalink


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