Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

35179 Publications

Ion beam induced nanocrystallization of SiC

Höfgen, A.; Heera, V.; Mücklich, A.; Skorupa, W.

Ion-beam-induced crystallization (IBIC) was used to produce nanocrystals in the preamorphized region of a 6H-SiC bulk crystal. The precipitation was stimulated by high dose implantation with Al and Si at temperatures between 300 °C and 700 °C. The morphology of the nanocrystalline phase and its dependence on the implantation parameters were investigated by cross-sectional transmission electron microscopy (XTEM). Above a certain threshold dose, randomly oriented grains of 3C-SiC with almost spherical shape and mean diameters ranging from 4 to 25 nm are formed. The recrystallization is completed within a very narrow time window. Therefore, in our experiments the nucleation and growth process could not be observed directly. From the extrapolation of the kinetics of the secondary grain growth to zero time the window of suitable parameters for the observation of nucleation and primary grain growth was estimated. A critical temperature (TC 300 °C) as well as an incubation time (tI 300 s below 700°C) for the beginning of the recrystallization were found.

Keywords: ion implantation; amorphization; recrystallization

  • Mat. Sci. Forum 388 (2000) 897

Publ.-Id: 2911

XPS investigation with factor analysis for the study of Ge clustering in SiO2

Oswald, S.; Schmidt, B.; Heinig, K.-H.

The change of the depth profile and chemical bond character of Ge in Ge+ ion implanted SiO2 layers during annealing in O2 atmophere has been studied by x-ray photoelectron spectroscopy (XPS). The Ge depth profiles in as-implanted and annealed samples as measured by XPS are in agreement with profiles measured by Rutherford backscattering spectroscopy (RBS). At interfaces XPS gives more information about the Ge depth distribution than RBS. Thus, other than RBS, XPS could proof that the fraction of implanted Ge, with moves during annealing to the SiO2/Si interface region, resides on the Si side of this interface. Additionally, the high and low contrast nanoclusters in Ge implanted samples, which have been found recently in cross-section transmission electron microscopy (XTEM) images, could be identified by XPS, in combination with data analysis by factor analysis, to consist mainly of elemental Ge and GeO2, respectively.

Keywords: XPS; depth profiling; factor analysis; Ge; cluster formation; nanocrystals

  • Surface and Interface Analysis 29 (2000) 249-254

Publ.-Id: 2910

Institute of Safety Research; Report January 1998-June 1999

Weiß, F.-P.; Rindelhardt, U.; (Editors)

The report gives an overview on the scientific work of the Institute of Safety Research between January 1998 and June 1999.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-273 September 1999
    ISSN: 1437-322X


Publ.-Id: 2909

High concentration doping of 6H-SiC by ion implantation: flash versus furnace annealing

Panknin, D.; Wirth, H.; Anwand, W.; Brauer, G.; Skorupa, W.

The electrical properties of high concentration aluminum and nitrogen implanted layers have been investigated after furnace as well as flash lamp annealing. For Al doped layers the electrical efficiency is enhanced using flash lamp annealing. For highest Al concentrations the doped layer shows metal like conductivity. For N doped layers the flash lamp annealing effects no increase of the carrier concentration. Due to the short annealing time only the nitrogen on hexagonal sites is electrically active. Flash lamp annealing produced no extra damage of the vacancy type as proved by Positron Annihilation Spectroscopy.

Keywords: aluminum; nitrogen; ion implantation; annealing; electrical activation

  • Mat. Sci. Forum 338-342 (2000) 877

Publ.-Id: 2908

Q-Band single-crystal EPR study and molecular orbital calculations of [C6H5)4As][ReVINCl4/ReVOCl4]

Voigt, A.; Abram, U.; Böttcher, R.; Richter, U.; Reinhold, J.; Kirmse, R.

A Q-band single-crystal EPR study of tetraphenylarsoniumtetrachloro-nitridorhenate(VI), [(C6H5)4As][ReVINCl4], diamagnetically diluted by the isoelectronic oxorhenate(V) complex is reported. The EPR spectra are typical of an ion with 5d1 (S = 1/2) configuration and are influenced by large rhenium hyperfine coupling constants and nuclear quadrupole interactions. They are characterized by well-resolved 185,187Re hyperfine patterns with almost equal spacings and the occurrence of "forbidden" transitions (DmI = ± 1, DmI = ± 2).
The 185,187Re hyperfine parameters as well as the data obtained from density functional theory (DFT) and extended Hückel theory (EHT) molecular orbital calculations are used to analyze the spin-density distribution in the system under study. Thereby, the negative sign found for the spin-density at the nitrogen from DFT is mainly determined by spin polarization. In addition, both MO methods are used to calculate the electric field gradient being responsible for the 185,187Re nuclear quadrupole coupling.

Keywords: Rhenium (VI) Complex; Single-Crystal EPR; DFT Calculation; EHT Calculation; 185; 187RE Nuclear Quadrupole Interaction

  • Abstract in refereed journal
    Chemische Physik

Publ.-Id: 2907

Resolved dipole strength below the giant resonance in 138Ba

Herzberg, R.-D.; Fransen, C.; von Brentano, P.; Eberth, J.; Enders, J.; Fitzler, A.; Käubler, L.; Kaiser, H.; von Neumann-Cosel, P.; Pietralla, N.; Ponomarev, V. Y.; Prade, H.; Richter, A.; Schnare, H.; Schwengner, R.; Skoda, S.; Thomas, H. G.; Tiesler, H.; Weisshaar, D.; Wiedenhöver, I.

  • Physical Review C, Volume 60, 051307

Publ.-Id: 2906

Assessment and Identification of Undesired States in Chemical Semibatch Reactors Using Neural Networks

Hessel, G.; Kryk, H.; Schmitt, W.; Seiler, T.; Weiß, F.-P.; Deerberg, G.; Neumann, J.

This paper presents a neural-network approach to operator-independent assessing the operational states of chemical semibatch reactors. The suitability of neural networks for process monitoring was investigated in a miniplant in which strongly exothermic chemical reference processes were carried out. Before being applied to state classification, the neural network classifiers first have be trained using process data of normal and abnormal sequences of reaction to establish a nonlinear decision model between process parameters and state classification. Afterwards, the trained classifiers can be used for process monitoring. Best results were reached with three-layer perceptron networks. For assessing the danger potential of fault states, separate perceptron networks for danger classification and for fault isolation were used.

Keywords: Fault diagnosis; Process identification; Supervision; Artificial intelligence; Classifiers; Neural networks; Chemical industry

  • Lecture (Conference)
    Proceedings of IFAC Symposium on Fault Detection, Supervision and Safety for Technical Processes - SAFEPROCESS'2000, Budapest, 14-16 June, 2000, pp. 458-461
  • Contribution to proceedings
    Proceedings of IFAC Symposium on Fault Detection, Supervision and Safety for Technical Processes - SAFEPROCESS'2000, Budapest, 14-16 June, 2000, pp. 458-461

Publ.-Id: 2905

BRICK - a one-dimensional simulation tool for multiphase flow in vessels

Lucas, D.

A new one-dimensional model suitable for practically orientated simulations of transient multiphase flows within vessels was developed. The model bases on a new developed specific Particle-In-Cell method. The equations of transport are solved free of numerical diffusion. This property and the distinction between continuous and dispersed phases make an implicit reflection of discontinuities as e.g. the top level of the mixture possible. Flexible interfaces allow a convenient coupling of this model with constitutive correlations and models for special phenomena. There is also an interface, which enables the implementation of foam models. By such a model the generation decay of foam at the top level of the mixture may be simulated. A special goal of the code is the transient simulation of emergency relief from chemical reactors. For this reason the code was equipped with models for pressure calculation, conservation of energy, phase transfer, bubble generation, bubble growth, coalescence, drift of the phases, heat release from the vessel wall, discharge and homogeneous chemical reactions.

Keywords: multiphase flow; simulation; batch reactor; bubble column; pressure relief; foam; numerical diffusion

  • Chemical Engineering and Technology 23(2000)845-849

Publ.-Id: 2903

Bis{2-[1-(thiosemicarbazono)ethyl]-pyridinium} hexakis(nitrato-0,0')-thorate(IV) tetramethanol solvate

Abram, U.; Bonfada, E.; Schulz-Lang, E.

  • Acta crystallographica (1999) C55, 1479-1482

Publ.-Id: 2900

Oxidation of carbon based materials for innovative energy systems (HTR, fusion reactor): Status and further needs

Moormann, R.; Hinssen, H.-K.; Latge, C.; Dumesnil, J.; Veltkamp, A. C.; Grabon, V.; Beech, D.; Buckthorpe, D.; Dominguez, T.; Krüssenberg, A.-K.; Wu, C. H.

Following an overview on kinetics of carbon/gas-reactions, status and further needs in selected safety relevant fields of graphite oxidation in HTR and fusion reactors are outlined: Considering severe air ingress, lack of experimental data on Boudouard reaction and in the field of advanced oxidation kinetics was detected. Development of coatings, protecting against oxidation, has to focus on stability under neutron irradiation and on general feasability of coatings on HTR pebble fuel graphite. Oxidation in normal operation of direct-cycle HTR requires examinations on gas atmospheres and on catalytic effects. Advanced carbon materials like CFCs and mixed materials should be developed and tested with respect to their oxidation resistance in a common HTR/fusion task. In an interim HTR fuel storage radiolytic oxidation in normal operation and thermal oxidation in accidents have to be considered. Plans for future work in these fields are described.

Keywords: Oxidation of carbon based materials

  • Contribution to proceedings
    Proc. First Meeting: Survey on Basic Studies in the Field of High Temperature Engineering (including Safety Studies), Paris, France, 27-29 September 1999, 161-172

Publ.-Id: 2899

Supramolekulare Rezeptoren zur Bindung von Pertechnetat und Perrhenat

Stephan, H.; Spies, H.

Die Entwicklung von supramolekularen Komplexbildnern für Pertechnetat und Perrhenat eröffnet den Zugang zu bisher nicht bekannten Tc(VII)- bzw. Re(VII)-Spezies und bietet damit eine realistische Alternative zu den gegenwärtig in der Diagnostik angewendeten Tc(V)-, Tc(III)- und Tc(I)-Koordinationsverbindungen.
Möglichkeiten der selektiven Bindung und des Phasentransfers für die tetraedrischen Oxoanionen Pertechnetat und Perrhenat werden am Beispiel von bicyclischen Guanidiniumverbindungen sowie photo- und pH-schaltbarer Dendrimere diskutiert.

  • Lecture (others)
    Universität Potsdam, Institut für Anorganische Chemie (Institutskolloquium), 29.9.1999

Publ.-Id: 2898

EXAFS Structural Analysis of Aqueous Uranium(VI) Complexes with Wood Degradation Products

Roßberg, A.; Baraniak, L.; Reich, T.; Hennig, C.; Bernhard, G.; Nitsche, H.

To study the role of carboxylic and phenolic hydroxyl groups in the complexation of uranium(VI) with phenolic wood degradation products in aqueous solution, we prepared 1 mMol/L U(VI) complexes with the following simple model compounds in two pH ranges, i.e., 4-5 and 8-10: protocatechuic acid (3,4-dihydroxybenzenecarboxylic acid), catechol (1,2-dihydroxybenzene), pyrogallol (1,2,3-trihydroxybenzene), and vanillic acid (4-hydroxy-3-methoxybenzenecarboxylic acid). The structural parameters of these complexes were measured by uranium LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy.
In acid solutions containing 1:1 complexes with ligands having both carboxylic and hydroxyl groups, the uranium is surrounded by 5 equatorial oxygen (Oeq) at a distance of 2.44 Å and 2.46 Å for vanillic acid and protocatechuic acid, respectively. This relatively long U-Oeq bond distance is characteristic for bidentate coordination of the carboxylic group to the uranyl cation [Denecke et al., J. Phys. IV France 7, C2-637 (1997)]. If the ligands have only neighbouring hydroxyl groups as in case of catechol and pyrogallol the uranium is surrounded by 5-6 oxygen atoms at a shorter U-Oeq distance (2.39 Å). This shows that in the pH range of 4-5, the coordination behaviour of the acids is dominated by the carboxylic groups and not the hydroxyl groups. In the pH range of 8-10, the neighbouring phenolic hydroxyl groups dominate the com-plexation. This is in agreement with the observed similarities in the EXAFS structural parameters of the corresponding 1:2 and 1:3 complexes. In all these complexes the measured U-Oeq bond distance is 2.38 Å. It can be concluded that this relatively short U-Oeq bond distance is characteristic for the complexation of the uranyl ion with two or three ligands having neighbouring phenolic hydroxyl groups.

  • Poster
    Migration 99, Nevada, USA 26.09.-1.10.1999

Publ.-Id: 2897


Baraniak, L.; Abraham, A.; Mack, B.; Geipel, G.; Bernhard, G.; Nitsche, H.

Large underground mines are beiing flooded by surface and groundwater during the restoration of the East German uranium mining sites. The mine shafts and galleries are heavily reinforced with wood, and the flooding process isolates the wood from exposure to air. In conjunction with the wood degradation, this may cause potentially reducing conditions.

To study this effect, redox potential measurements and redox titrations with potassium hexacyanoferrate(III) were carried out on hydrothermal wood leachates, lignin and humic acid using a platinum electrode in combination with a silver-silver chloride electrode in a cell with liquid junction. The redox potentials of spruce lignin and humic acid, extrapolated to pH 0 and infinite dilution, were determined to be 570"5 mV for both with a negative pH gradient of 54.0"1 mV/pH. The potential indicates that the organic matter produced by the wood degradation can reduce U(VI) to U(IV). We identified U(IV) as the reduction product by spectrophotometry of the U(IV)-arsenazo(III) complex . The capacity for lignin to reduce U(VI) in-creases from pH 5 to 8 from 1.3@10-2 to 0.5 µeq/g, respectively. For comparison, iron(III) was reduced at pH 4.5 with a capacity of 0.15 meq/g.

We also studied how reducing conditions were generated by the decay of wood in a highland bog . We measured the redox potential in the field as a function of depth, and found that the redox potential de-creased by more than 800 mV from the surface to the depth of one meter. In comparison, the redox potential in deeper layers of the flooded mines was diminished by about 700 mV. This is ascribed to the oxidation of sulfidic and arsenic min-erals, especially of pyrite, markasite and arsenopyrite. This lowering of the redox potential causes the UO22+ to be immobilized as UO2. Our results show that the degradation of the large quantities of wood in the mines also contribute to establish, maintain and enhance reducing conditions and, hence, to immobilize significant parts of the 100 tons of urani-um and 50 tons of arsenic that are dissolved in Saxony=s largest underground mine at Schlema.

  • Poster
    Migration 99, Nevada

Publ.-Id: 2896

Aerosol Formation by UV Irradiation of Paraffin and Silicone Vapors

Rettig, D.; Adam, R.; Merker, P.

  • Poster
    European Aerosol Conference EAC´99, Prag

Publ.-Id: 2895

Thermal Particle Production at SIS

Wolf, G.; Barz, H. W.; Kämpfer, B.

In a transport model calculation we study some of the basic assumptions of thermal models. We find at SIS energies the particles are mainly produced in a highly non-equilibrium situation. At freeze-out only nucleons are thermalized.

  • Prog. Part. Nucl. Phys. 42 (1999) 157c

Publ.-Id: 2893

Detailed Angular Correlation Analysis with 4π Spectrometers: Spin Determinations and Multipolarity Mixing Measurements in 128Ba

Wiedenhöver, I.; Vogel, O.; Klein, H.; Dewald, A.; von Brentano, P.; Gableske, J.; Krücken, R.; Nicolay, N.; Gelberg, A.; Petkov, P.; Gizon, A.; Gizon, J.; Bazzacco, D.; Rossi Alvarez, C.; de Angelis, G.; Lunardi, S.; Pavan, P.; Napoli, D. R.; Frauendorf, S.; Dönau, F.; Janssens, R. V. F.; Carpenter, M. P.

We analyze for the first time the full γγ directional correlations from oriented states (DCO) in an experiment performed with the GASP detector array. Our analysis based on a transformation of the directional information into expansion coefficients of an orthogonal basis. With this method, which we call SpeeDCO (spectral expansion of DCO), the complete DCO information is concentrated in 12 γγ coincidence spectra. The analysis is applicable to all detector arrays which uniformly cover the solid angle. We show that the complete DCO information can be used for a reliable and unique determination of spins and multipolarity mixing ratios in weakly populated bands. We were able to establish the spins and the positive parity of the Δ I=1 ''M1 band'' in 128Ba and multipolarity mixing ratios of M1/E2 in-band transitions were derived as well. The measured values are in good agreement with those expected for a high-K rotational band.

  • Phys. Rev. C 58 (1998) 721-728

Publ.-Id: 2892

Lowest Four-Quasiparticle Magnetic Dipole Band in 128Ba

Vogel, O.; Dewald, D.; von Brentano, P.; Gableske, J.; Krücken, R.; Nicolay, N.; Gelberg, A.; Petkov, P.; Gizon, A.; Gizon, J.; Bazzacco, D.; Rossi Alvarez, C.; Lunardi, S.; Pavan, P.; Napoli, D. R.; Frauendorf, S.; Dönau, F.

The four-quasiparticle magnetic dipole band in 128Ba has been investigated with the 96Zr(36S,4n)128Ba reaction at the GASP spectrometer of the Laboratori Nazionali di Legnaro. Linking transitions to the previously known positive parity states have been observed for the first time in this mass region and new transitions on top of the band have been found. The experimental results are compared to previously made tilted axis cranking calculations.

  • Phys. Rev. C 56 (1998) 1338-1343

Publ.-Id: 2890

Polarization Observables in the Reaction NN ® NN f

Titov, A. I.; Kämpfer, B.; Shklyar, V. V.

The sensitivity of polarization observables in the reaction NN NN slightly above the threshold is studied with respect to the details of the one-boson exchange model and a possible admixture of hidden strangeness in the nucleon. It is shown that the finite-energy predictions differ strongly from the threshold predictions. A measurement of the beam-target asymmetry and the decay anisotropy can help to disentangle the role of various reaction mechanisms.

  • Phys. Rev. C 59 (1999) 999-1008

Publ.-Id: 2889

Temperatures of Exploding Nuclei

Serfling, V.; Schwarz, C.; Bassini, R.; Begemann-Blaich, M.; Fritz, S.; Gaff, S. J.; Groß, C.; Immé, G.; Iori, I.; Kleinevoß, U.; Kunde, G. J.; Kunze, W. D.; Lynen, U.; Maddalena, V.; Mahi, M.; Möhlenkamp, T.; Moroni, A.; Müller, W. F. J.; Nociforo, C.; Ocker, B.; Odeh, T.; Petruzzelli, F.; Pochodzalla, J.; Raciti, G.; Riccobene, G.; Romano, F. P.; Saija, A.; Schnittker, M.; Schüttauf, A.; Seidel, W.; Sfienti, C.; Trautmann, W.; Trzcinski, A.; Verde, G.; Wörner, A.; Hongfei, X.; Zwieglinski, B.

Breakup temperatures in central collisions of 197 Au + 197Au at bombarding energies E/A = 50 to 200 MeV were determined with two methods. Isotope temperatures, deduced from double ratios of hydrogen, helium, and lithium isotopic yields, increase monotonically with bombarding energy from 5 to 12 MeV, in qualitative agreement with a scenario of chemical freeze-out after adiabatic expansion. Excited-state temperatures, derived from yield ratios of states in 4He, 5,6Li, and 8Be, are about 5 MeV, independent of projectile energy, and seem to reflect the internal temperature of fragments at their final separation from system.

  • Phys. Rev. Lett. 80 (1998) 3928-3931

Publ.-Id: 2888

Strange Mesons as Probe for Dense Nuclear Matter

Senger, P.

The production and propagation of kaons and antikaons has been studied in symmetric nucleus-nucleus collisions in the SIS energy range. The ratio of the excitation function of K+ production in Au+Au and C+C collisions increases with decreasing beam energy. This effect was predicated for a soft nuclear equation-of-state. In noncentral Au+Au collisions, the K+ mesons are preferentially emitted perpendicular to the reaction plane. The K-/K+ ratio from A+A collisions at beam energies which are equivalent with respect to the threshold is found to be about two orders of magnitude larger than the corresponding ratio from proton-proton collisions. Both effects are considered to be experimental signatures for a modification of kaon properties in the dense nuclear medium.

  • Prog. Part. Nucl. Phys. 42 (1999) 209c

Publ.-Id: 2887

Flow Angle from Intermediate Mass Fragments

Rami, F.; Crochet, P.; Dona, R.; de Schauenburg, B.; Wagner, P.; Alard, J. P.; Andronic, A.; Basrak, Z.; Bastid, N.; Belyaev, I.; Bendarag, A.; Berek, G.; Best, D.; Caplar, R.; Devismes, A.; Dupieux, P.; Dzelalija, M.; Eskef, M.; Fodor, Z.; Gobbi, A.; Grishkin, Y.; Herrmann, N.; Hildenbrand, K. D.; Hong, B.; Kecskemeti, J.; Kirejczyk, M.; Korolija, M.; Kotte, R.; Lebedev, A.; Leifels, Y.; Merlitz, H.; Mohren, S.; Moisa, D.; Neubert, W.; Pelte, D.; Petrovici, M.; Pinkenburg, C.; Plettner, C.; Reisdorf, W.; Schüll, D.; Seres, Z.; Sikora, B.; Simion, V.; Siwek-Wilczynska, K.; Stoicea, G.; Stockmeier, M.; Vasiliev, M.; Wisniewski, K.; Wohlfarth, D.; Yushmanov, I.; Zhilin, A.

Directed sideward flow of light charged particles and intermediate mass fragments was measured in different symmetric reactions at bombarding energies from 90 to 800 AMeV. The flow parameter is found to increase with the charge of the detected fragment up to Z=3-4 and turns into saturation for heavier fragments. Guided by simple simulations of an anisotropic expanding thermal source, we show that the value at saturation can provide a good estimate of the flow angle, Θflow, in the participant region. It is found that Θflow, depends strongly on the impact parameter. The excitation function of Θflow, reveals striking deviations from the ideal hydrodynamical scaling. The data exhibit a steep rise of Θflow, to a maximum at around 250-400 AMeV, followed by a moderate decrease as the bombarding energy increases further.

  • Nucl. Phys. A 646 (1999) 367

Publ.-Id: 2886

High-Fold γ-ray spectroscopy of 117I: Coexistence of Collective and Noncollective Structures

Paul, E. S.; Fossan, D. B.; Hauschild, K.; Hibbert, I. M.; Nolan, P. J.; Schnare, H.; Sears, J. M.; Thorslund, I.; Wadsworth, R.; Wilson, A. N.; Wilson, J. N.; Ragnarsson, I.

High spin states have been populated in 117  53I via the 90Zr(31P,2p2n) reaction at 150 MeV, using the EUROGAM II γ-ray spectrometer to record high-fold γ-ray coincidences. A quadruples γ-ray analysis (γ4) has been used to extend the known level scheme. In addition to several aligned noncollective states, a new high-spin band showing characteristics of smooth termination has been established at and linked into the low-spin level scheme. Its structure has been inferred through comparison with cranked Nilsson-Strutinsky calculations.

  • Phys. Rev. C 59 (1999) 1984-1998

Publ.-Id: 2885

Velocity reconstruction in electrically conducting fluids from external electromagnetic measurements

Stefani, F.; Gerbeth, G.

A possibility for the determination of velocity fields in electrically conducting fluids is presented. Applying an external magnetic field, electric and magnetic fields are induced by the fluid motion. The electric potential can be measured at the walls and the magnetic field outside the fluid volume. The inverse problem of reconstructing the velocity from the measured quantities is solved using Tikhonov regularization. Several examples will be given to illustrate the potential of such type of velocity reconstruction. The problem of uniqueness is treated in detail for the spherical geometry. Our ultimate aim is to develop a fully contactless velocity measurement technique whereby measuring the electric potential at the wall can be avoided.

  • Contribution to external collection
    APS Bulletin vol. 44, no. 4, pp. 106 (1999)

Publ.-Id: 2884

Die Strahlungsquelle ELBE am Forschungszentrum Rossendorf

Grosse, E.

In einigen Wochen wird der Grundstein für die Strahlungsquelle ELBE am Forschungszentrum Rossendorf (FZR) bei Dresden gelegt. Das Kernstück dieser neuen Anlage wird ein supraleitender Elektronen-Linearbeschleuniger hoher Brillanz sein, der in seiner kombination von hoher Strahlintensität und guter Strahlqualität (d. h. niedriger Emittanz) alle in Europa existierenden Anlagen übertreffen soll (das Akronym ELBE wurde aber nicht nur deshalb gewählt).

  • Phys. Bl. 54 (1998) 342-344

Publ.-Id: 2883

Three-Particle Final States Measured at the Pion threshold with COSY-TOF

Brinkmann, K.-T.; Bilger, R.; Böhm, A.; Clement, H.; Dennert, H.; Dshemuchadse, S.; Dutz, H.; Eyrich, W.; Fanara, C.; Filges, D.; Filippi, A.; Freiesleben, H.; Fritsch, M.; Geyer, R.; Hassan, A.; Hauffe, J.; Herrmann, P.; Hesselbarth, D.; Hübner, B.; Jahn, P.; Kilian, K.; Koch, H.; Kress, J.; Krug, J.; Kuhlmann, E.; Marcello, S.; Marwinski, S.; Metzger, A.; Meyer, W.; Michel, P.; Möller, K.; Morsch, H. P.; Nann, H.; Naumann, B.; Naumann, L.; Raimondo, A.; Roderburg, E.; Rogge, M.; Schamlott, A.; Schönmeier, P.; Schröder, W.; Schulte-Wissermann, M.; Steinke, M.; Stinzing, F.; Sun, G. Y.; Wächter, J.; Wagner, G. J.; Wagner, M.; Wirth, S.; Zielinski, U.

The production of pions in pp collisions at beam energies of ≤ 300 MeV has been studied with the COSY-TOF spectrometer, which was recently extended to flight paths of ~ 3 m for charged particles through the addition of a barrel section. Together with the bremsstrahlung channel, which was investigated in an earlier
experiment, pion production exhausts the inelastic pp cross section at these energies. TOF allows the simultaneous study of
all channels, the measurement of pnπ+ being facilitated by the neutron detector COSYnus. In this contribution, preliminary results on the pionic three-body final states are discussed.

  • Acta Phys. Polon. B 29 (1998) 2993

Publ.-Id: 2882

An inverse problems approach to velocity reconstruction from measurements of electromagnetic fields

Stefani, F.; Gerbeth, G.

If a moving electrically conducting fluid is exposed to an external magnetic field electrical currents are induced. These currents give rise
to an additional magnetic field which can be measured outside the fluid volume and to an electric potential measurable at the fluid
boundary. From the viewpoint of inverse problems, we consider the possibility of velocity reconstruction from the measured
electromagnetic fields. Possible applications for a contactless measuring technique are delineated.

  • Lecture (Conference)
    International Workshop on Measuring Techniques for Liquid Metal Flows (MTLM) Dresden, October 11-13, 1999

Publ.-Id: 2881

Strangeness Production in the Reaction pp→ pK+λ in the Threshold Region

Bilger, R.; Böhm, A.; Brand, S.; Brand, H.; Brinkmann, K.-T.; Clement, H.; Cloth, P.; Dahmen, M.; Dellert, M.; Dennert, H.; Dshemuchadse, S.; Eyrich, W.; Filges, D.; Freiesleben, H.; Fritsch, M.; Geyer, R.; Hassan, A.; Hauffe, J.; Herrmann, P.; Hübner, B.; Jahn, P.; Kilian, K.; Kirsch, M.; Koch, H.; Kress, J.; Krug, J.; Kuhlmann, E.; Lange, J. S.; Metzger, A.; Michel, P.; Möller, K.; Morsch, H. P.; Moosburger, M.; Nake, C.; Nann, H.; Naumann, B.; Naumann, L.; Ringe, P.; Roderburg, E.; Rogge, M.; Schamlott, A.; Schönmeier, P.; Schülke, A.; Sperl, R.; Steinke, M.; Stinzing, F.; Turek, P.; Wagner, G. J.; Wirth, S.; Zielinski, U.

The reaction pp → K+ λ,p was measured exclusively at the cooler synchrotron COSY at beam momenta of pBeam = 2.50 GeV/c and pBeam = 2.75 GeV/c using the TOF detector. Angular and momentum distributions were obtained for the full phase space of the reaction products. Total cross sections were extracted to be (2.7 ± 0.3)μ b and (12.0 ± 0.4) μ b,
respectively. The polarization of the λ-hyperon was determined as a function of its transversal momentum and was found to be negative for transverse momentum transfers of pT ≥ 0.3 GeV/c. The results together with existing data are compared with phenomenological parameterizations and model calculations on the basis of meson exchange.

  • Phys. Lett. B 420 (1998) 217

Publ.-Id: 2880

Proton-Proton Bremsstrahlung at 797 MeV/c

Bilger, R.; Böhm, A.; Brand, H.; Brand, S.; Brinkmann, K.-T.; Clement, H.; Cloth, P.; Dahmen, M.; Dshemuchadse, S.; Eyrich, W.; Filges, D.; Freiesleben, H.; Fritsch, M.; Geyer, R.; Hassan, A.; Hauffe, J.; Herrmann, P.; Hübner, B.; Jahn, P.; Kilian, K.; Koch, H.; Kress, J.; Krug, J.; Kuhlmann, E.; Lange, J. S.; Metzger, A.; Michel, P.; Möller, K.; Morsch, H. P.; Nake, C.; Nann, H.; Naumann, B.; Naumann, L.; Ringe, P.; Roderburg, E.; Rogge, M.; Schamlott, A.; Schönmeier, P.; Schülke, A.; Steinke, M.; Stinzing, F.; Turek, P.; Wagner, G. J.; Wirth, S.; Zielinski, U.

At COSY pp-bremsstrahlung was measured at a beam momentum of 797 MeV/c using an external proton beam. Data were taken with a wide angle spectrometer covering a solid angle of approximately 1 sr. The complete data set is presented in a series of c.m. angular distributions as well as a single Dalitz plot. The absence of final state interaction effects is understood as being due to a general insensitivity of the pp γ reaction to the spin-singlet component of the NN interaction. Coplanar angular distributions (in the laboratory system) are well reproduced by recent model calculations; also good agreement is found with the original TRIUMF data [K. Michaelian et al., Phys. Rev. D 41 (1990) 286] when omitting the rescaling factor of 2/3.

  • Phys. Lett. B. 429 (1998) 195-200

Publ.-Id: 2879

Coulomb Effects on Particle Spectra in Relativistic Nuclear Collisions

Barz, H. W.; Bondorf, J. P.; Gaardhøje, J. J.; Heiselberg, H.

Coulomb effects on π± and K± spectra in relativistic nuclear collisions are investigated. At collision energies around 1 GeV the ratio of π- to π+ is enhanced several times at low transverse momenta but less at ultrarelativistic energies. We describe the ratios at SIS, AGS, and SPS energies with simple analytic models as well as more elaborate numerical models incorporating the expansion dynamics. The Coulomb effect
depends on the properties of the source after the violent collision phase and provides information on source sizes, freeze-out times, and expansion velocities. Comparison with results from HBT analyses are made. Predictions for π± and K± at RHIC and LHC energies are given.

  • Phys. Rev. C 57 (1998) 2536

Publ.-Id: 2878

A Large Acceptance Multiparticle Spectrometer for 1-3 GeV Proton Beams

Balestra, F.; Bedfer, Y.; Bertini, R.; Bland, L. C.; Brenschede, A.; Brochard, F.; Bussa, M. P.; Chalyshev, V.; Seonho, C.; Debowski, M.; Dzemidzic, M.; Faivre, J. C.; Falomkin, I. V.; Fava, L.; Ferrero, L.; Foryciarz, J.; Frolov, V.; Garfagnini, R.; Gill, D.; Grasso, A.; Grosse, E.; Heinz, S.; 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.; Senger, P.; Stroth, J.; Tosello, F.; Vigdor, S. E.; Zalikhanov, B.; Zosi, G.

A magnetic spectrometer system has been constructed for the study of reactions with multiple charged particles in the final state, induced by polarized proton beams of few GeV energy. The system is based on a large-gap dipole magnet, with a liquid hydrogen target and scintillating fiber tracking detectors embedded inside the magnet. Multiwire proportional chambers, plastic scintillator hodoscopes, and threshold Cerenkov detectors placed outside the magnet provide additional tracking, triggering and particle identification capabilities. The system has been applied to study exclusive hyperon as well as pseudoscalar and vector meson production reactions at bombarding energies below 3 GeV. Additionally, it has been used to monitor the proton beam polarization at Laboratoire National Saturne. The components and performance of the system are reported.

  • Nuclear Instruments and Methods in Physics Research A 426 (1998) 385-404

Publ.-Id: 2877

Production of Φ and ω Mesons in Near Threshold pp Reactions

Balestra, F.; Bedfer, Y.; Bertini, R.; Bland, L. C.; Brenschede, A.; Brochard, F.; Bussa, M. P.; Chalyshev, V.; Seonho, C.; Debowski, M.; Dzemidzic, M.; Faivre, J.-C.; Falomkin, I. V.; Fava, L.; Ferrero, L.; Foryciarz, J.; Frolov, V.; Garfagnini, R.; Gill, D.; 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.; Senger, P.; Stroth, J.; Tosello, F.; Vigdor, S. E.; Zosi, G.

The ratio of the exclusive production cross sections for Φ and ω mesons has been measured in pp reactions at Tbeam = 2.85 GeV. The observed f/w ratio is (3.7±0.7+1.2-0.9)×10-3. After phase space corrections, this ratio is about a factor 10 enhanced 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 energies. 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.
  • Physical Review Letters 81 (1998) 4572-4575

Publ.-Id: 2876

Betrieb und Wartung des Rossendorfer PET-Zyklotrons "CYCLONE 18/9"

Preusche, S.; Füchtner, F.; Steinbach, J.; Roß, H.

Übersicht über Routinebetrieb, Verbesserungen am PET-Zyklotron, Erfahrungen beim Betrieb und bei der Wartung des PET-Zyklotrons, Vorstellung der "CYCLONE 18/9 & 10/5 USER COMMUNITY"

  • Lecture (others)
    Zyklotron-Workshop 1999 der Betreiber kleiner deutscher Zyklotrons, Rossendorf, 9./10.9.1999

Publ.-Id: 2875

Spezifische und selektive Bindung von 99mTc-Verbindungen an den Serotonin-(5HT2A) Rezeptor des Gehirns

Kretzschmar, M.; Brust, P.; Pietzsch, H.-J.; Scheunemann, M.; Seifert, S.; Gupta, A.; Zessin, J.; Syhre, R.; Johannsen, B.

Bei vielen neurologischen und psychiatrischen Erkrankungen wie Alzheimer-Krankheit, Depression, Schizophrenie, Migräne usw. sind postmortem veränderte Serotonin Rezeptor-dichten im Gehirn nachweisbar. Die Entwicklung von spezifischen SUP>99mTc-Tracern für SPECT (Single- Photonen- Emissions- Tomo-graphie), mit denen derartige Veränderungen bereits im lebenden Organismus erkennbar wären, stellt daher einen wesentlichen Beitrag zur Diagnose dieser pathophysiologischen Veränderungen des serotoninergen Systems dar.

Ketanserin ist eine Leitsubstanz mit hoher Affinität zum Serotonin-(5-HT2A) Rezeptor. In struktureller Analogie zu dieser Leitsubstanz wurde in den letzten Jahren eine Reihe von Tc-Koordinationsverbindungen synthetisiert, welche in Hemmexperimenten an Homogenaten des Rattenhirns Affinitäten mit Ki-Werten ( = Hemmkonstanten) unter 10 nM aufwiesen.

In dieser Arbeit wird die spezifische Bindung eines neuen hochaffinen 99mTc Komplexes, der in Hirnregionen mit bekanntermaßen hoher 5-HT2A Rezeptordichte eine subnanomolare Affinität (Ki = 0,5 nM) zum Rezeptor aufweist, autoradiografisch in verschiedenen Tierarten dargestellt. Als Methode wurde die Radioluminografie eingesetzt. Als Referenz für die autoradiografische Darstellung der 5-HT2A-Rezeptordichte diente die In-vitro-Verteilung von [3H]Ketanserin und [18F]Altanserin in Hirnschnitten von Ratte und Schwein. Zur Bestimmung der Spezifität und Selektivität der Rezeptorbindung des untersuchten Tc-Komplexes wurden In-vitro-Hemmversuche mit den spezifischen 5-HT2A Antagonisten Mianserin und Ketanserin, dem D2 Antagonisten Haloperidol, dem 5-HT1A Agonisten 8-OH-DPAT sowie dem alpha- und beta1- adrenergen Rezeptoragonisten (±) Norepinephrin durchgeführt.

Die an Hirnhomogenaten bestimmte hohe Affinität und Spezifität für den 5-HT2A Rezeptor wurde auch im Autoradiogramm bestätigt. Es zeigte sich die Anreicherung in 5-HT2A rezeptorreichen Regionen wie Cortex frontalis, Nucleus olfactorius anterior und Nucleus caudatus-Putamen sowie eine Verdrängung der totalen Bindung durch Mianserin zwischen 38 und 42 % im Gesamtschnitt, 48 und 51 % im frontalen Cortex und 31 und 42 % im Striatum. Diese Werte entsprechen der mit [3H]Ketanserin erfaßbaren spezifischen Bindung an den 5-HT2A Rezeptor. Eine hohe Selektivität des 99mTc Komplexes besteht gegenüber dem 5-HT1A Rezeptor, dem 5-HT- und dem Dopamin Transporter. Durch Verdrängungsexperimente mit Haloperidol wurde allerdings festgestellt,daß der Komplex auch eine Affinität für den D2 Rezeptor aufweist.

Mit diesen Arbeiten gelang erstmals überhaupt,wenn auch In vitro, mit einem Tc-Komplex eine Bildgebung des 5-HT2A -Rezeptors zu erreichen. Die Hirnaufnahme in der Ratte erwies sich allerdings noch als zu gering, um eine In-vivo-Darstellung erwarten zu lassen. Durch geeignete Modifikation der Verbindung wird ein besseres In-vivo-Verhalten angestrebt.

  • Poster
    Jahrestagung der WGL, München, 13.10.1999

Publ.-Id: 2874

Improvement of the wear properties of cutting tools implanted with nitrogen ions

Werner, Z.; Jagielski, J.; Piekoszewski, J.; Kubiak, L.; Günzel, R.

  • Nukleonika, Vol. 44, No. 2, p. 261-264, 1999

Publ.-Id: 2873

Surface layer destruction during ion beam analysis

Behrisch, R.; von der Linden, W.; von Toussaint, U.; Grambole, D.

In ion beam analysis the decrease of the measuring signal with a number of incident ions, due to a destruction of the surface layer being analysed, depends critically
on the lateral intensity distribution in the analysing ion beam. For the assumption of destruction in one step, the decrease was calculated and the obtained analytical
formulae was fitted to the decrease as measured in ERDA and PIXE analyses. This allows to obtain values for the destruction cross sections for the ions and the
samples in the analysis, as well as information about the lateral intensity distribution in the analysing ion beam.

Keywords: Hydrogen

  • Nuclear Instruments and Methods in Physics Research B 155 (1999) 440-446

Publ.-Id: 2872

Molecular-dynamics simulations of steady-state growth of ion-deposited tetrahedral amorphous carbon films

Jäger, H.-U.; Albe, K.

Molecular-dynamics calculations were performed to simulate ion beam deposition of diamond-like carbon films. Using the computationally efficient analytical potentials of Tersoff and Brenner we are able to simulate more than 103 carbon atom impacts on {111} diamond, so that steady-state film properties can be computed and analyzed. For the Tersoff potential, we achieve sp3 fractions of approximately half of the experimentally observed values. For the more refined hydrocarbon potentials of Brenner the fraction of tetrahedrally coordinated atoms is much too low, even if structures with densities close to diamond are obtained. We show, that the sp3 contents calculated with Tersoff's potential are an artifact related to the overbinding of specific bonding configurations between three- and fourfold coordinated sites. On the other hand we can prove, that the range for the binding orbitals represented by the cutoff-function is too short in Brenner's parametrization. If an increased C-C interaction cutoff value is chosen, we achieve a distinct improvement in modeling the sp3 content of deposited ta-C films. As a result, we compute sp3 fractions which lie between 52 and 95% for the C+ ion energies E = 30-80eV and are in reasonable agreement to recent experimental studies.

  • Lecture (Conference)
    TRANSDIAM", 5 - 7 June 2000, Amiens, France
  • Journal of Applied Physics 88 (2000) 1129-35

Publ.-Id: 2871

"Schnelles Freimeßverfahren für alpha - aktive Nuklide in Bauschutt durch Direktmessung großflächiger dünner Meßpräparate" (BMWi und BMBF Förderkennzeichen: 02S7768)

Nebelung, C.; Henniger, J.

Bei der Freimessung von Bauschutt aus dem Abriß von Nuklearanlagen sind für die Bestimmung der (gamma-und beta-Aktivivtät in-situ Messungen verfügbar. Eine direkte Messung der alpha-aktiven Nuklide im stehenden Gebäude ist auf Grund der geringen Reichweite der alpha-Strahlung und ihrer Absorption im Beton nicht möglich. Die im Rahmen dieses und der vorhergehenden Projekte entwickelten Methode der direkten alpha-Spektrometrie nach nur mechanischer Präparation des Betons ermöglicht eine Bestimmung der Actinide bis zu 0,02Bq/g in Multielementspektren. In einem aus zwei Schritten bestehendem Zerkleinerungsprozeß wurden mittlere Partikeldurchmesser von 0,5µm erreicht. Die Meßproben mit einem Durchmesser von 20cm und Schichtdicken zwischen 0,6 und 5µm wurden durch Sprühen aus der Betonsuspension auf Probenträger und anschließendes Trocknen hergestellt. Die Suspensionsstabilität (nachgewiesen durch Zeta-Potentialmessungen) wurde durch verschiedene Dispergatoren erreicht. Die Spektren der Meßproben wurden in einer Gitterionisationskammer aufgenommen. Durch die Verwendung von Standardbeton mit zugefügten Actiniden konnten die Selbstabsorption der alpha-Strahlung und die Peakform in Abhängigkeit der Probendicke ermittelt werden. Somit konnten die Spektren unbekannter Betonproben gleicher Geometrie entfaltet werden. Das für diese Arbeit entwickelte Programm WINKRUM basiert auf einem geometrischen Modell für Partikelgröße, Partikelverteilung und Packungsdichte. Mit Strahlungstransportberechnungen können Spektren simuliert werden, die ebenfalls eine Peakentfaltung von Multielementspektren ermöglichen.

Keywords: Freimessung; Beton; alpha-Spektrometrie; Actinide

  • Lecture (Conference)
    "VI. Stillegungskolloquium Hannover und 5. Statusbericht Stillegung und Rückbau kerntechnischer Anlagen", Hannover, 13.und 14. 04.2000
  • Contribution to external collection
    "VI. Stillegungskolloquium Hannover und 5. Statusbericht Stillegung und Rückbau kerntechnischer Anlagen", Hannover, 13.und 14. 04.2000

Publ.-Id: 2870

Conformational Influence of Dithiocarbazinic Acid Bishydrazone Ligands on the Structure of Zinc(II) Complexes: A Comparative XANES Study

Hennig, C.; Hallmeier, K. H.; Zahn, G.; Tschwatschal, F.; Hennig, H.

  • Inorganic Chemistry 1999, 38, 38-43

Publ.-Id: 2868

Kristallographische Untersuchungen an meteoritischem (Fe,Ni)-Phosphid

Geist, V.; Hennig, C.

  • Zeitschrift für Kristallographie, Suppl. 15, 106 (1998)

Publ.-Id: 2867

In situ measurement of stress during deposition of boron nitride films

Fukarek, W.; Fitz, C.; Kolitsch, A.; Möller, W.

A two-beam laser deflection system has been setup for real-time measurement of the stress in thin films during processing. The curvature of a Si-cantilever, laser reflectivity and real time spectroscopic ellipsometry data are recorded simultaneously. Reliable real time film thickness data are essential for the calculation of the instantaneous stress from the bending force per unit width measured. Instantaneous stress data with a depth resolution in the nanometer range provide detailed information on growth processes. It is demonstrated that force per unit width or global stress data, as calculated by applying the simple form of Stoney's equation, are not appropriate for the analysis of the stress in layered structures like boron nitride films.
The depth distribution of the instantaneous stress in boron nitride films recorded during growth by ion beam assisted deposition has been analyzed. The layer sequence of interfacial turbostratic BN layer / mixed (t-BN+c-BN) transition layer / cubic BN can be clearly identified in the instantaneous stress data. The instantaneous stress has been found to depend sensitively upon fluctuations in the boron deposition rate which in turn cause variations in the ion/atom arrival ratio. Real time global stress data recorded during ion implantation into c-BN films have revealed for the first time two mechanisms being involved.

Keywords: instantaneous stress; laser deflection; ellipsometry; boron nitride; ion implantation

  • Contribution to proceedings
    Material Science Forum, Proceedings of the 5th European Conference on Residual Stress, 28-30 September 1999, Noorwijkerhout, The Netherlands, Vol. 347-349 (2000) pp. 156-160

Publ.-Id: 2866

Trinuclear rhenium complexes with bridging nitrido ligands

Abram, U.

Trinuclear complexes with bridging nitrido ligands between the rhenium atoms are formed when [ReN(Et2dtc)2(Me2PhP)] (Et2dtc- = N,N-diethyldithio-carbamate) reacts with TlCl or Pr(O3SCF3)3. [Cl(Me2PhP)2(Et2dtc)ReºN-Re(N)Cl2(Me2PhP)-NºRe(Et2dtc)(Me2PhP)2Cl] and [(Et2dtc)2(Me2PhP)ReºN-Re(N)-(Et2dtc)(Me2PhP)-NºRe(Me2PhP)(Et2dtc)2]+ contain two almost linear, asymmetric nitrido bridges. Additional, terminal nitrido ligands are located at the middle rhenium atoms.

Keywords: Keywords: Rhenium complexes; Nitrido bridges; Crystal structure; Oligomerization

  • Anorganische allg. Chemie

Publ.-Id: 2864

Benzeneselenolates of Mercury(II). Crystal and Molecular Structures of [Hg(SePh)2] and (nBu4N)[Hg(SePh)3]

Schulz Lang, E.; Müller Dias, M.; Abram, U.

The reaction of dibenzenediselenide, (SePh)2, with mercury in refluxing xylene gives bis(benzeneselenolato)mercury(II), [Hg(SePh)2], in a good yield. (nBu4N)[Hg(SePh)3] is obtained by the reaction of [Hg(SePh)2] with a solution of [SePh]- and (nBu4N)Br in ethanol. The solid state structures of both compounds have been determined by X-ray diffraction.
The mercury atom in [Hg(SePh)2] (space group C2, a = 7.428(2), b = 5.670(1), c = 14.796(4) Å, b = 103.61(1)°) is linearly co-ordinated by two selenium atoms (Hg-Se = 2.471(2) Å, Se-Hg-Se = 178.0(3)°). Additional weak interactions between the metal and selenium atoms of neighbouring molecules (Hg···Se = 3.4 - 3.6 Å) associate the [Hg(SePh)2] units to layers.
The crystal structure of (nBu4N)[Hg(SePh)3] (space group P21/c, a = 9.741(1), b = 17.334(1), c = 21.785(11) Å, b = 95.27(5)°) consists of discrete complex anions and (nBu4N)+ counter ions. The coordination geometry of mercury is distorted trigonal-planar with Hg-Se distances ranging between 2.5 and 2.6 Å.

Keywords: Keywords: Mercury; Benzeneselenolates; Selenolates; Crystal structure

  • Anorganische allg. Chemie

Publ.-Id: 2863

Ring Transformations of Heterocyclic Compounds. XIX Spiro[dihydropyridine-indolines] - Novel Heterocycles with Two Spiro-Condensed N-Containing Subunits Easy Accessible by 1,3-Oxazinium Ring Transformation

Zimmermann, T.; Abram, U.

The synthesis of hitherto unknown 1-benzoyl-1´,3´,3´-trimethyl-4,6-diphenylspiro[1,2-dihydropyridine-2,2´-indolines] 5 from 2,4,6-triphenyl-1,3-oxazinium tetrafluoroborate (1b) and 1,3,3-trimethyl-2-methylene-indolines 2 (used as such or generated in situ from the corresponding 3H-indolium salts 4) in the presence of triethylamine in anhydrous acetonitrile by a 3,6-[C3N+C2] 1,3-oxazinium ring transformation is reported. Structure elucidation is performed by an X-ray structure determination of the spiro[dihydropyridine-indoline] 5a. Spectroscopic data of the transformation products and their mode of formation are discussed.

  • J. Heterocyclic Chem. 35, 787 (1998)

Publ.-Id: 2862

Measurement of Fragment Production Cross Sections in 1 GeV Proton Interactions with Carbon, Preprint

Andronenko, L.; Andronenko, M.; Kotov, A.; Neubert, W.; Petrov, G.; Seliverstov, D.; Vaishnene, L.; Yatsoura, V.

Double differential cross sections of fragment production in 1 GeV proton interactions with carbon were measured with a two-arm spectrometer installed at 30° and 126° with respect to the proton beam line of the PNIP synchrocyclotron. Mass and charge identifications of the fragments were performed by time-of-flight and Bragg spectroscopy methods for both registration angles. The obtained kinetic energy spectra were reproduced by moving source fits with a Maxelllian-like emission pattern.

Keywords: Cross sections; isotopes; Bragg spectroscopy

  • Other report
    Preprint PNPI NP-3-1998 Nr. 2217

Publ.-Id: 2861

Early Detection and Identification of Undesirable States in Chemical Plants Using Neural Networks

Neumann, J.; Deerberg, G.; Schlüter, S.; Schmitt, W.; Hessel, G.

The suitability of pattern recognition for safety diagnosis of chemical plants is discussed. Experiments in a miniplant and with a process simulator are carried out. The process characteristics are treated with different recognition methods and classified with the aid of expert know how. Afterwards, the trained system can be used for process diagnosis. The capability of neural networks for this problem can be shown.

  • Contribution to external collection
    Keil, F., Mackens, W., Voß, H., Werther, J. (eds): Scientific Computing in Chemical Engineering II - Simulation, Image Processing, Optimization and Control, Springer-Verlag Berlin, Heidelberg, New York, 1999, S. 380-387, LSBN: 3-540-65851-3

Publ.-Id: 2860


Pompe, S.; Schmeide, K.; Bubner, M.; Geipel, G.; Reich, T.; Heise, K.-H.; Bernhard, G.

Huminsäuren (HS) spielen aufgrund ihrer guten Löslichkeit im pH-Bereich natürlicher Wässer sowie aufgrund ihres hohen Komplexierungsvermögens eine entscheidende Rolle innerhalb von natürlichen Wechselwirkungsvorgängen. Dazu gehören Wechselwirkungs-prozesse von HS mit Metallionen, z.B. Actinidionen, welche die Speziation der Actinidionen und daraus folgend das Migrations- bzw. Retardationsverhalten dieser Schadstoffe beeinflussen. Die Untersuchung der Wechselwirkung von HS und Actinidionen ist unbedingt erforderlich, z.B. für die Erstellung von Langzeitsicherheitsabschätzungen potentieller Endlager für nuklearen Abfall sowie für unter- und obertägige Einrichtungen des früheren Uranerzbergbaus in Sachsen und Thüringen. Aufgrund der heterogenen Natur der HS ist jedoch die genaue Beschreibung ihres Komplexbildungsverhaltens mit Metallionen schwierig.
In Fortsetzung unserer früheren Untersuchungen1,2 wollen wir die Kenntnisse zur Wechselwirkung von HS mit Metallionen erweitern. Dazu untersuchten wir den Einfluß phenolischer OH-Gruppen auf das Komplexbildungsverhalten von HS mit Uran(VI). Ausgehend von einer synthetischen HS (Typ M11) und zwei natürlichen HS (Aldrich, Kranichsee3) synthetisierten wir modifizierte HS mit blockierten phenolischen OH-Gruppen. Die partielle Blockierung der phenolischen OH-Gruppen wurde mit einer radiometrischen Methode zur Bestimmung der Huminsäurefunktionalität sowie FTIR-spektroskopisch nachgewiesen. Mittels zeitaufgelöster laserinduzierter Fluoreszenzspektroskopie untersuchten wir in Lösung das Komplexbildungsverhalten der modifizierten HS mit blockierten phenolischen OH-Gruppen mit UO22+-Ionen im Vergleich zu den nicht modifizierten HS. Für die modifizierten HS vom Typ M1 und Aldrich bestimmten wir signifikant kleinere Beladungskapazitäten mit UO22+-Ionen als für die entsprechenden originalen HS. Dieses Ergebnis weist daraufhin, daß die Blockierung der phenolischen OH-Gruppen das Komplexbildungsverhalten der HS in Lösung verändert.
Weiterhin führten wir mittels FTIR- und EXAFS-Spektroskopie Strukturuntersuchungen an festen Uranyl-Humat-Komplexen der modifizierten und nicht modifizierten HS durch. Mit der FTIR-Spektroskopie erbrachten wir den Nachweis für die Komplexierung von UO22+-Ionen durch die HS. Als Ergebnis der EXAFS-Untersuchungen bestimmten wir für die festen Uranyl-Humat-Komplexe Strukturparameter, d.h. axiale und äquatoriale Bindungsabstände zwischen Uran und Sauerstoff.

  • Lecture (Conference)
    Arbeitstagung der Sektion IV der Deutschen Gesellschaft für Moor- und Torfkunde 7.-8.10.1999, Bad Elster

Publ.-Id: 2859

Study on the formation of mixed ligand oxorhenium and oxotechnetium complexes (SNS/S combination)

Papadopoulos, M.; Pirmettis, I.; Tsoukalas, C.; Nock, B.; Maina, T.; Raptopoulou, C. P.; Terzis, A.; Pietzsch, H.-J.; Friebe, M.; Spies, H.; Johannsen, B.; Chiotellis, E.

Theoretically, the reaction of the tridentate aminedithiol ligand EtN(CH2CH2SH)2, L1H2, and the monodentate thiol 4-ClC6H4SH, L2H, with the ReVOCl3(PPh3)2 may lead to the formation of the following complexes: (i) neutral mixed ligand complexes ReOL1L2 (the syn isomer, complex 1 and the anti isomer, complex 2, (ii) binuclear complex of the tridentate ligand, (MO)2(L1)3, complex 3, and (iii) anionic complex of the monothiol [MO(L2)4]-, complex 4. When a mixture of L1H2/L2H, 1/1 ratio, is applied, the major product of the reaction is the syn isomer 1. A small amount of the anti isomer 2 is also isolated (yield < 2 %) while none of the complexes 3 and 4 form during the reaction under the above conditions. The oxorhenium complexes 3 and 4 have been synthesized by the reaction of L1H2 or L2H with the precursor ReOCl3(PPh3)2. The crystal structure of 1, 3, and 4 is determined by X-ray crystallography. The corresponding Tc-99m complexes have been prepared by exchange reaction using Tc-99m glucoheptonate as precursor. Similarly the major reaction product is the syn isomer, complex 1´, while none of the other complexes form during the reaction at tracer level. The above studies demonstrate that simultaneous action of a tridentate SNS ligand and a monodentate thiol in equimolar quantities on ReVOCl3(PPh3)2 or Tc-99m glucoheptonate leads to a single rhenium or technetium-99m species, the syn MOL1L2.

  • Inorg. Chim. Acta 295 (1999) 1-8

Publ.-Id: 2858


Schuster, G.; Bubner, M.; Henkel, K.; Pompe, S.; Schmeide, K.; Jander, R.; Heise, K.-H.; Bernhard, G.

Thermoanalytische Untersuchungen (TG, DTA, DSC) haben sich als Methoden zur qualitativen Identifizierung und strukturellen Charakterisierung der Huminstoffe bewährt. In der vorliegenden Arbeit werden der exotherme, oxiadative Abbau unter Sauerstoff und die endotherme, thermische Zersetzung unter Stickstoff untersucht.
Die auf die Änderungen des thermischen Verhaltens empfindlich reagierenden DTA Diagramme zeigen für die Huminsäuren (HS) und ihre Metallkomplexe den ähnlichen strukturellen Aufbau eines endothermen Peaks bis 150°C und von zwei bzw. drei exothermen Peaks bis 500°C mit individuellen Unterschieden der Temperaturlagen und der Umsatzraten der einzelnen Teilreaktionen. Auf diese Weise wurden z.B. HS von Aldrich®, HS aus Gartentorf und HS aus dem Wasser des Hochmoors "Kleiner Kranichsee" bei Johann-georgenstadt deutlich differenziert. Mit Hilfe der ermittelten H : C und O : C Verhältnisse der gasförmigen Thermolyseprodukte konnten die in den Teilreaktionen abgebauten Gruppen hinsichtlich ihrer atomaren Zusammensetzung näher spezifiziert werden. So sind z.B. die Fulvinsäuren gegenüber den HS gleicher Herkunft durch einen höheren Gehalt an wasserstoff- und sauerstoffreichen Gruppen gekennzeichnet.
Die von uns präparierten synthetischen HS vom Melanoidintyp wurden thermoanalytisch mit natürlichen HS verglichen und als geeignete Funktionsmodelle für die natürlichen HS bestätigt. Die DTA Diagramme sind bei beiden ähnlich strukturiert. Auffällige Analogien wurden dabei zwischen der HS aus Torf und den synthetischen HS festgestellt, während die HS aus dem Wasser des Hochmoors "Kleiner Kranichsee" mehr der Aldrich HS ähnlich ist.
Chemische Eingriffe in das Makromolekül verändern das thermische Verhalten in charakteristischer Weise. Bereits das übliche Abtrennungs- und Reinigungsverfahren für HS durch Lösen in Natronlauge und Fällung mit HCI erhöht ganz entscheidend deren Reaktionsfähigkeit und setzt die thermische Stabilität stark herab. Die Methylierung der phenolischen OH Gruppen und der Carboxylgruppen der HS dokumentiert sich in einer signifikanten Verstärkung des ersten exothermen Peaks bis 350°C, der für den Abbau der wasserstoffreichen, aliphatischen Gruppen charakteristisch ist. Zugleich wird die thermische Stabilität dieser Huminstoffe durch den Eingriff geringfügig erhöht.
Deutliche Veränderungen der DTA Diagramme werden durch die Bindung von Metallionen über die Carboxylgruppen der HS bewirkt. Dabei wird die thermische Stabilität des Makromoleküls stark herabgesetzt. Dieser Effekt ist für den Fe(III)-HS-Komplex deutlich stärker als für den UO22+-HS-Komplex. In beiden Fällen ist er konzentrationsabhängig und wächst mit steigender Menge des gebundenen Metalls, die ebenfalls thermoanalytisch bestimmt wurde. Da dieser Effekt den Komplexbildungskonstanten direkt proportional ist, ist anzunehmen, daß intramolekulare Spannungen für die thermische Destabilisierung verantwortlich sind, die durch die Bindung der Metallionen in das Makromolekül eingebracht werden. Sie sind um so stärker, je fester das Metall gebunden ist.

  • Lecture (Conference)
    Tagung der Deutschen Gesellschaft für Torf- und Moorkunde

Publ.-Id: 2857

Untersuchungen zur Bildung fester Metall-Huminsäure-Komplexe

Bubner, M.; Pompe, S.; Schmeide, K.; Amayri, S.; Reich, T.; Nevedov, V.; Heise, K.-H.; Bernhard, G.

Durch Reaktion fester, vorwiegend ungelöster natürlicher und synthetischer Huminsäuren mit wässerigen Metallsalzlösungen wurden in heterogener Phase feste Huminsäurekomplexe synthetisiert. Hierfür wurden als natürliche Huminsäuren die aufgereinigte Huminsäure der Fa. Aldrich und die aus dem "Kleinen Kranichsee" (Johanngeorgenstadt, Erzgebirge) gewonnene, aquatische Huminsäure eingesetzt. Als synthetische Huminsäure wurde eine Melanoidinfraktion mit huminsäureartigen Eigenschaften (M1) verwendet /1/. Die Komplexierungen erfolgten mit den umweltrelevanten Metallionen UO22+, Fe3+, Ca+ und Mg2+ sowie mit natürlich vorkommenden Mineralen, in denen Uran(VI), Calcium und Magnesium als Carbonatokomplex vorliegt.
Es wurden Humate mit unterschiedlicher Metallbeladung gewonnen, indem der pH-Wert des Reaktionsgemisches und die stöchiometrischen Verhältnisse der Reaktionspartner variiert wurden. Die Konzentration der Huminsäure wurde dabei auf die COOH-Äquivalente bezogen. Durch Konkurrenzreaktionen mit Gemischen unterschiedlicher Metallkationen und Kationenaustausch-reaktionen an definierten Metallhumaten mit "freien" Kationen konnte die unterschiedliche Affinität von Eisen gegenüber natürlichen und synthetischen Huminsäuren nachgewiesen werden.
Am Beispiel der Umsetzung freier Huminsäuren mit den gemischten Carbonatokomplexen von Uran(VI) und Calcium (Liebigit) bzw. Uran(VI) und Magnesium (Bayleyit) wurden natürliche Komplexierungsvorgänge simuliert.
An den synthetisierten Metall-Humat-Komplexen wurden Strukturuntersuchungen mit Hilfe von FTIR /2/ sowie EXAFS /3/ und ESCA /4/ durchgeführt und die thermische Stabilität durch Thermische Analyse /5/ bestimmt.

  • Lecture (Conference)
    Arbeitstagung der Sekt. IV der DGMT 7.-8.10.1999 Bad Elster

Publ.-Id: 2856

Chemische Reaktion an der Phasengrenze nichtmischbarer Flüssigkeiten

Grahn, A.

Im Vortrag werden Versuche zum reaktiven Stoffübergang über die Phasengrenze zweier nicht mischbarer Lösungsmittel und die dabei auftretenden hydrodynamischen Instabilitäten sowie die numerische Simulation dieser Vorgänge in einer vertikalen Spaltgeometrie vorgestellt.

Keywords: hydrodynamische Instabilität; fluide Phasengrenze; Grenzflächenreaktion

  • Lecture (others)
    29. Sitzung des DECHEMA/GVC-Arbeitsausschusses "Reaktionstechnik sicherheitstechnisch schwieriger Prozesse"

Publ.-Id: 2855

Experimentelle und numerische Untersuchungen zu Instabilitäten beim reaktiven Stoffübergang an einer ebenen fluiden Phasengrenze im vertikalen Spalt

Grahn, A.; Eckert, K.

Spontane Grenzflächenkonvektionen an fluiden Phasengrenzen führen beim Stoffübergang zu einer signifikanten Erhöhung der pro Zeiteinheit übertragenen Stoffmenge. Zwei Mechanismen, die Rayleigh-Bénard- und die Marangoniinstabilität, sind für die Entstehung dieser Konvektionen verantwortlich. Gegenstand der Arbeit sind Stoffaustauschvorgänge, die von exothermen chemischen Reaktion begleitet werden. Diese führen zur Ausbildung von Konzentrations- und Temperaturgradienten im Bereich der fluiden Phasengrenze. Grenzflächenkonvektionen treten als Folge der Kopplung von Stoff-, Energie- und Impulstransport auf. Bei einfachen Neutralisationsreaktionen an der Phasengrenze konnte eine Vielzahl unterschiedlicher Konvektionsstrukturen festgestellt werden.

In einem vertikalen Spalt (Breite=1mm) wurden zwei miteinander begrenzt mischbare Lösungsmittel (Wasser und Isobutanol bzw. Cyclohexan) übereinandergeschichtet. In der leichteren organischen Phase liegt eine Fettsäure (Ameisen-, Essig- oder Propionsäure), in der schwereren wässrigen Phase Natronlauge vor. Der Stoffübergang der Fettsäure erfolgt von der organischen an die wässrige Phase. Daran schließt sich unter Wärmefreisetzung die Neutralisationsreaktion in unmittelbarer Nachbarschaft der Phasengrenze an.

Im Verlauf des reaktiven Stoffübergangs durchläuft das System 3 Stadien. Das Anfangsstadium ist von aufsteigenden Plumes (pilzförmige Bereiche von Fluid geringerer Dichte) in der organischen Phase gekennzeichnet. Das Zwischenstadium wird von Plumes in der oberen Phase und der unregelmäßigen Bildung von Fingern in der unteren Phase bestimmt. Das Plume-Regime der oberen Phase wird zunehmend ungeordneter und löst sich im weiteren Verlauf auf. Im Endstadium hat sich in der unteren Phase ein regelmäßiges Fingerregime ausgebildet. Dieses Regime ist charakteristisch für die doppelt-diffusive Instabilität, die hier durch die unterschiedlichen Diffusivitäten von Wärme und Stoff sowie die Überlagerung zweier die Stabilität gegensätzlich beeinflussender Gradienten verursacht wird. Die Fingerinstabilität ist von der thermohalinen Konvektion, dem Transport von Salz und Wärme in Ozeanen her bekannt und stellt einen sehr effizienten Mischungsvorgang dar. Sowohl Plume- als auch Fingerinstabilität sind verantwortlich für die sich selbst erhaltende Dynamik des Systems, die im Experiment über 2 Stunden lang beobachtet werden konnte.

Numerische Untersuchungen werden mit dem Ziel durchgeführt, die beobachteten Transportvorgänge durch ein 2D-Modell, das die Bilanzgleichungen für Stoff, Energie und Impuls berücksichtigt, nachzubilden. Die Abbildung zeigt die zeitliche Entwicklung des Stoffstroms durch die Phasengrenze für den reaktiven und den reaktionsfreien Stoffübergang von Essigsäure. Nach anfänglich diffusivem Stoffübergang werden die Konzentrationsgrenzschichten instabil und es setzen Konvektionsbewegungen ein. Diese führen zum sprunghaften Ansteigen des Stoffstroms. Durch die Kombination solutaler und thermischer Effekte fällt dieser Anstieg beim reaktiven Stoffübergang wesentlich stärker als beim nichtreaktiven aus. Die Fluktuationen der dargestellten Größe resultieren aus dem instationären Charakter des konvektiven Stoffübergangs.

Keywords: hydrodynamische Instabilitäten; fluide Phasengrenzen; Grenzflächenreaktion

  • Lecture (Conference)
    GVC-Jahrestagung, Leipzig 1999
  • Abstract in refereed journal
    Chemie Ingenieur Technik 71 (1999) 945

Publ.-Id: 2854

Colloid-Borne Uranium and Other Heavy Metals in the Water of a Mine Drainage Gallery

Zänker, H.; Richter, W.; Brendler, V.; Nitsche, H.

The water of a mine drainage gallery was investigated for its contents of colloid-borne heavy metals with empha-sis on uranium. About 1 mg/L of colloid particles of 100 to 300 nm in size were found. They consist of a matrix of Fe and Al oxyhydroxides and are formed when anoxic slightly acidic shaft waters mix with oxic near-neutral gal-lery water. The colloid matrix bears toxic trace elements metals such as As, Pb, and Cu. Carbonato and aquo complexes prevent the uranyl from being adsorbed to the colloids in the unaltered gallery water. Acidification destroys these complexes: up to 50 mass percent of the uranium is attached to the colloids in the slightly acidic pH region. Further acidification converts the uranyl again to a "non-colloidal" form. The heavy metals are most likely bound to the Fe and Al colloids as inner sphere surface complexes.

  • Lecture (Conference)
    Vortrag auf "Migration 99", Incline Village, USA
  • Radiochimica Acta 88, 619-624 (2000)

Publ.-Id: 2853

Bericht der Frühjahrstagung der Studiengruppe für Elektronische Instrumentierung vom 7.-9. April 1997 in Darmstadt (GSI)

Gabriel, F.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-185
    ISSN: 1436-3976


Publ.-Id: 2852

A theoretical search for possible high efficiency semiconductor based field assisted positron moderators

Beling, C. D.; Fung, S.; Ming, L.; Gong, M.; Panda, B. K.

  • Applied Surface Science 149 (1999) 253-259

Publ.-Id: 2851

Investigation on stress evolution in boron nitride films

Fitz, C.; Fukarek, W.; Kolitsch, A.; Möller, W.

Boron nitride films have been grown by ion beam assisted deposition (IBAD) using a Kaufman ion source and an electron beam evaporator. Cantilevers made from <100> Si have been used as substrates. Instantaneous stress data are derived from dynamic simultaneous measurement of cantilever bending and film thickness during growth. The instantaneous stress in t-BN layers is found to increase with film thickness and to be in the range between 1.6 and 4.2 GPa. At the nucleation of c-BN the stress increases up to about 10 GPa and remains constant during c-BN growth. Correlations between the ion to atom arrival ratio and the Ar/N2 ratio and the instantaneous stress are discussed. The stress relaxation during Ar+-ion post implantation has been measured.

Keywords: boron nitride; thin films; intrinsic stress

  • Surface and Coatings Technology 128-129 (2000) 292-297

Publ.-Id: 2847

An instrument for in-situ stress measurement in thin films during growth

Fitz, C.; Fukarek, W.; Kolitsch, A.; Möller, W.

An improved stress-measuring technique based on the cantilever bending principle is presented. Thermal shift of the sample holder position that results in errors in the stress data is minimised by evaluating the difference in the deflection of two laser beams. The film thickness is calculated from the reflected laser intensity or from ellipsometry data recorded simultaneously during film growth. Without using a lock-in technique or image processing, the resolution in bending force-per-unit-width is 0.02 N/m for a 50 µm thick cantilever. The system represents an easy, versatile and cheap technique to measure intrinsic and thermal stresses in thin films. The system has been employed to record the instantaneous stress during ion beam assisted deposition of BN films and the global stress during ion induced amorphisation of silicon.

Keywords: cantilever; intrinsic stress; thin films

  • Surface and Coatings Technology 128-129 (2000) 474-478

Publ.-Id: 2846

Growth and characterization of hard and elastic carbon nitride thin films

Kolitsch, A.; Möller, W.; Malkow, T.; Bull, S. J.; Magula, V.; Domankova, M.

Hard CNx films were prepared by nitrogen ion beam assisted deposition (IBAD) of evaporated carbon on silicon wafers with a nitrogen ion energy of 100 to 1200eV, ion/neutral transport ratios from 0.7 to 1.7, and deposition temperatures from RT to 1000°C. The films were characterised by ERDA, XPS, TEM, ED, EELS, and nanoindentation.
By varying the deposition parameters a maximum nitrogen content of < 33 at.% was found at N/C transport ratios of about 1.2. Further increase of this ratio did not result in a higher nitrogen content in the films. XPS measurement reflects a shift of the main chemical state of the nitrogen bonds with changing nitrogen content of the films and with increasing deposition temperature. The nitrogen content of the films was drastic decreased with increasing temperatures > 600°C.
EELS investigations have shown weak changes of the plasmon peak position and the sp2/sp3 ratio with increasing deposition temperature in correlation to the nitrogen content of the carbon films.
Nanoindentation techniques have been used to investigate the mechanical properties such as hardness and elastic modulus of the films. High hardness and elastic modulus values for those composites have been found. All measured structural and mechanical properties correlate with the analysed nitrogen content.

Keywords: carbon nitride; ion beam assisted deposition; IBAD; ERD; EELS; XPS; thin film deposition

  • Surface and Coatings Technology 128-129 (2000) 126-132

Publ.-Id: 2845

Microstructure and Oxidation Kinetics of Intermetallic TiAl after Si- and Mo- Ion-Implantation

Hornauer, U.; Richter, E.; Matz, W.; Reuther, H.; Mücklich, A.; Wieser, E.; Möller, W.; Schumacher, G.; Schütze, M.

Titanium aluminide alloys based on gamma-TiAl have a substantial potential for high temperature application. However, there are still problems concerning the high temperature oxidation behavior. Ion implantation is a promising tool to improve the oxidation resistance without disturbing the mechanical properties. A systematic investigation of the microstructure and phase development of silicon and molybdenum implanted gamma-TiAl is presented. For Si, the fluence is varied from 2.5·1016 cm-2 to 8·1017 cm-2 at an implantation energy of 1 MeV resulting in a local con-centration of Si between 1 at% and 35 at% at a projected range of 1 µm measured by AES depth profiling. Grazing incidence XRD and transmission electron microscopy show the formation of a buried Ti5Si3 enriched layer at 650 °C, which acts as a diffusion barrier for oxygen. Long term TGA oxidation tests at 900 °C in air show a positive effect in the beginning of oxi-dation for the fluence of 8·1017 cm-2. After a few hours the oxidation kinetic is similar to unimplanted Ti50Al, but the mass gain after 100 h is still 30 % smaller. The influence of the local Si concentration on the oxidation behavior is discussed. Implantation of Mo at 180 keV (2·1016 cm-2 and 1·1017 cm-2) has only minor influence on the oxidation at 900 °C. After implantation, Mo precipitates are found for the high fluence.

Keywords: implantation; TiAl; oxidation; silicon; molybdenum

  • Poster
    Surface and Coatings Technology 128-129 (2000) 418-422
  • Contribution to external collection
    Surface and Coatings Technology 128-129 (2000) 418-422

Publ.-Id: 2843

Erste Ergebnisse aus Säulenexperimenten zur Untersuchung des Migrationsverhaltens von U(VI) im System Gohy 532 / Gorlebensand

Pompe, S.

  • Poster
    Workshop Institut für Kernchemie der Universität Mainz, Mainz, Germany, 13. 03. 1998

Publ.-Id: 2841

Einfluß von Huminstoffen auf das Migrationsverhalten von Schadstoffen

Trautmann, N.; Pompe, S.; Heise, K.-H.; Bernhard, G.; Bubner, M.; Nitsche, H.; Beck, H. P.; Wagner, H.; Keuth, U.; Schank, M.; Mansel, A.; Seibert, A.; Keller, H.

  • Contribution to external collection
    Forschungszentrum Karlsruhe, Report FZKA-PTE Nr. 5, 147-172 (1998)

Publ.-Id: 2840

EPR evidence of tetrahalogeno(triphenylmethylimido)rhenium(VI) complexes [Re{NC(C6H5)3}X4] (X = Cl, Br)

Voigt, A.; Kirmse, R.; Abram, U.

  • Inorg. Chem. Communications 1, 203 (1998)

Publ.-Id: 2835

An electron paramagnetic resonance study of tetrabutylammoniumtetrabromonitridorhenate(VI), [(n-C4H9)4N] [ReNBr4]

Voigt, A.; Abram, U.; Strauch, P.; Kirmse, R.

  • Inorg. Chim. Acta 271,199 (1998)

Publ.-Id: 2834

Evidence for Relativistic Effects in the Chemistry of Element 104

Türler, A.; Buklanov, G. V.; Eichler, B.; Gäggeler, H. W.; Grantz, M.; Hübener, S.; Jost, D. T.; Lebedev, V. Y.; Piguet, D.; Timokhin, S. N.; Yakushev, A. B.; Zvara, I.

  • J. Alloys Comp. 271-273, 287 (1998)

Publ.-Id: 2833

Zur Problematik der Bestimmung dynamischer Festigkeitswerte im instrumentierten Kerbschlagbiegeversuch

Richter, H.

Zur Bewertung der strukturellen Integrität von Bauteilen werden auch Festigkeitskennwerte unter schlagartigen Belastungsbedingungen benötigt.
Eine Möglichkeit dynamische Festigkeitskennwerte abzuschätzen, bietet die Berechnung der dynamischen Fließ- und Biegebruchspannungen aus den nach ISO/CD 14 556 im instrumentierten Kerbschlagbiegeversuch bestimmten charakteristischen Kräften. Üblicherweise werden die Festigkeitswerte unter Schlagbiegebelastung nach einem Vorschlag von SERVER (1978) berechnet. Dieser Vorschlag wurde aus einer Lösung der Fließlinientheorie nach EWING (1968) abgeleitet.
SERVERs Formalismus gilt für ISO-V-Proben, die mit einer ASTM-Finne belastet werden, da die Zusammenhänge durch EWING (1968) für diese Belastung hergeleitet wurden. Bei Anwendung einer DIN/ISO-Hammerfinne (r=2 mm) ist aber davon auszugehen, dass sich für gekerbte Proben ungefähr 5 % und bei zusätzlicher Berücksichtigung einer größeren Stützweite 9 % höhere Festigkeitswerte ergeben können.

  • Lecture (others)
    Vortrag zur Jahressitzung 1999 der DVM-Arbeitsgruppe "Instrumentierter Kerbschlagbiegeversuch", 24.09.1999, TU Bergakademie Freiberg

Publ.-Id: 2832

Decay properties of 256Sg(Z=106) and 266Sg(Z=106)

Türler, A.; Dressler, R.; Eichler, B.; Gäggeler, H. W.; Jost, D. T.; Schädel, M.; Brüchle, W.; Gregorich, K. E.; Trautmann, N.; Taut, S.

  • Phys. Rev. C 57, 1648 (1998)

Publ.-Id: 2831

Sorption behaviour of rutherfordium and thorium from HCl/Hf containing aqueous solution

Schumann, D.; Nitsche, H.; Taut, S.; Jost, D. T.; Gäggeler, H. W.; Yakushev, A. B.; Buklanov, G. V.; Domanov, V. P.; Din, T. L.; Kubica, B.; Misiak, R.; Szeglowski, Z.

  • J. Alloys and Compounds 271-273, 307 (1998)

Publ.-Id: 2830

Sorption behaviour of W, Hf, Lu, U, and Th on ion exchangers from HCl/H2O2 solutions. Model experiments for chemical studies of Seaborgium (Sg)

Schumann, D.; Andrassy, M.; Nitsche, H.; Novgorodov, A. F.; Misiak, R.; Schädel, M.; Brüchle, W.; Schausten, B.; Kratz, J. V.; Bruchertseifer, H.

  • Radiochim. Acta 80, 1 (1998)

Publ.-Id: 2829

Coordination Behavior of the fac-[Tc(CO)3]+ Moiety towards Macrocyclic Thioethers of Various Ring Size: Synthesis and Structure of the Complexes fac-[Tc(9-ane-S3)(CO)3]Br, fac-[Tc2(tos)2(18-ane-S6)(CO)6] and fac-[Tc2(20-ane-S6-OH)(CO)6][tos]2

Schibli, R.; Alberto, R.; Abram, S.; Abram, S.; Egli, A.; Schubiger, P. A.; Kaden, T. A.

  • Inorg. Chem. 37, 3509 (1998)

Publ.-Id: 2828

Use of Instrumented Charpy Impact Tests for the Determination of Fracture Toughness Values

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

A number of techniques has been under development to estimate fracture mechanics parameters using the instrumented Charpy impact test. The evolution of elastic-plastic fracture mechanics has led to the use of small test specimens to achieve valid cleavage fracture toughness values based on the J-Integral concept, KJc, in the lower ductile-to-brittle transition temperature (DBTT) range. A successful concept bases on the statistical data treatment methodology with the Weibull-type statistic. It has been demonstrated that the probabilistic-based estimates of the median fracture toughness of ferritic steels tend to form transition curves of the same shape, the so-called "master curve", normalized to one common specimen size, namely the 1T (i.e. 25 mm thick) specimen. This method covers the determination of a reference temperature, T0, at a median fracture toughness, KJc, of 100 MPa m1/2. Furthermore toughness parameters in terms of J-Integral based ductile crack initiation toughness, KJi, have been also used for the integrity assessment of structures. The determination of KJi values by the instrumented impact test requires the detection of the ductile crack initiation on the dynamic load vs. displacement curve.

Keywords: instrumented impact test; master curve concept; fracture toughness; crack initiation; acoustic emission

  • Lecture (Conference)
    From Charpy to Present Impact Testing, ESIS-Publication 30, D. Francois, A. Pineau, Eds., Charpy Centenary Conference, 2-5 October 2001, Poitiers, France, Elsevier Science Ltd. and ESIS, 2002, p. 245
  • Contribution to proceedings
    From Charpy to Present Impact Testing, ESIS-Publication 30, D. Francois, A. Pineau, Eds., Charpy Centenary Conference, 2-5 October 2001, Poitiers, France, Elsevier Science Ltd. and ESIS, 2002, p. 245

Publ.-Id: 2827

Sequences around the fragmentation sites of the large subunit rRNA in the family Rhizobiaceae

Selenska-Pobell, S.; Döring, H.

  • Antonie van Leewenhoek 73, 55-67 (1998)

Publ.-Id: 2826

Sorption of Uranium (VI) onto Phyllite and its Mineral Constituents

Zorn, T.; Arnold, T.; Bernhard, G.; Nitsche, H.

  • Poster
    GDCh-Fachtagung, FG Nuklearchemie Dresden, Germany, 07.-09.09.1998

Publ.-Id: 2825

Wechselwirkung von Moorwasserkolloiden mit Uranyl(VI)-Ionen

Zänker, H.; Hüttig, G.; Richter, W.; Schmeide, K.; Nitsche, H.

  • Poster
    GDCh-Fachtagung, FG Nuklearchemie Dresden, Germany, 07.-09.09.1998

Publ.-Id: 2824

Colloid Characterization in a Humic-Rich Environmental Water Containing Varying Concentrations of Uranyl(VI) Ions

Zänker, H.; Hüttig, G.; Richter, W.; Schmeide, K.; Nitsche, H.

  • Poster
    13th Radiochemical Conference Mariánske Lázne-Jachymov, Czech Republic, 20.-24.04.1998

Publ.-Id: 2823

Einsteinium: Entropien und Enthalpien der Adsorption auf Niobium, Tantal und Titanium

Taut, S.; Hübener, S.; Eichler, B.; Türler, A.; Gäggeler, H. W.; Timokhin, S. N.; Zvara, I.

  • Poster
    GDCh-Fachtagung, FG Nuklearchemie Dresden, Germany, 07.-09.09.1998

Publ.-Id: 2822

Thermoanalytische Untersuchungen an Huminsäuren und ihren Uran(VI)- und Eisen(III)- Komplexen

Schuster, G.; Bubner, M.; Pompe, S.; Jander, R.; Henkel, K.; Heise, K.-H.; Nitsche, H.

  • Poster
    GDCh-Fachtagung, FG Nuklearchemie Dresden, Germany, 07.-09.09.1998

Publ.-Id: 2821

Microstructural investigation of Sn nanoclusters in double-energy implanted and annealed SiO2 layers with cross-sectional TEM

Markwitz, A.; Grötzschel, R.; Heinig, K.-H.; Rebohle, L.; Skorupa, W.

  • Nuclear Instruments and Methods in Physics Research B 152 (1999) 319-324

Publ.-Id: 2820

Complexation of U(VI) with Aquatic Humic Acid Isolated from Bog Water

Schmeide, K.; Geipel, G.; Zänker, H.; Heise, K.-H.

  • Poster
    13th Radiochemical Conference Mariánske Lázne-Jachymov, Czech Republic, 20.-24.04.1998

Publ.-Id: 2819

Molekulare Untersuchungen bakterieller Diversität in Erdproben aus uranhaltigen Abfallhalden

Satschanska, G.; Kampf, G.; Flemming, K.; Selenska-Pobell, S.

  • Poster
    Wissenschaftliche Konferenz: BIODIVERSITÄT der WGL Berlin, Germany, 17.-19.11.1998

Publ.-Id: 2818

Molecular bacterial diversity in soils of two East German uranium waste piles

Satschanska, G.; Kampf, G.; Flemming, K.; Selenska-Pobell, S.

  • Poster
    Euroconference: Bacterial-Metal/Radionuclide Interaction Rossendorf/Dresden, Germany, 02.-04.12.1998

Publ.-Id: 2817

Komplexierung von Uran(VI) mit Arsen

Rutsch, M.; Geipel, G.; Brendler, V.; Bernhard, G.; Nitsche, H.

  • Poster
    GDCh-Fachtagung, FG Nuklearchemie Dresden, Germany, 07.-09.09.1998

Publ.-Id: 2816

Charakterisierung anorganischer und organischer Kolloide in bergbaurelevanten Wässern.

Richter, W.; Zänker, H.; Nitsche, H.

  • Poster
    4. Kolloquium des DFG-Schwerpunktprogramms "Geochemische Prozesse mit Langzeitfolgen im anthropogen beeinflußten Sickerwasser und Grundwasser" Freiberg, Germany, 26.-27.03.1998.

Publ.-Id: 2815

Structural Analysis of the Interaction of Uranium(VI) with Humic Acid and Simple Carboxylic Acids Using EXAFS

Reich, T.; Denecke, M. A.; Pompe, S.; Otto, A.; Brendler, V.; Bubner, M.; Heise, K.-H.; Nitsche, H.; Allen, P. G.; Bucher, J. J.; Edelstein, N. M.; Shuh, D. K.

  • Poster
    Euroconference and NEA Workshop: Actinide-XAS-98 Grenoble, France, 04.-06.10.1998

Publ.-Id: 2814

Characterization of the surface layer of the Bacillus sphaericus isolate JG-A12 from a uranium waste pile

Raff, J.; Kirsch, R.; Kutschke, S.; Maier, T.; Mertig, M.; Selenska-Pobell, S.; Bernhard, G.; Hahn, U.; Pompe, W.

  • Poster
    Euroconference: Bacterial-Metal/Radionuclide Interaction Rossendorf/Dresden, Germany, 02.-04.12.1998

Publ.-Id: 2813

Selective accumulation of heavy metals in drain waters of a uranium waste pile by indigenous Bacilli

Panak, P.; Selenska-Pobell, S.; Boudakov, I.; Miteva, V.; Bernhard, G.; Nitsche, H.

  • Poster
    Euroconference: Bacterial-Metal/Radionuclide Interaction Rossendorf/Dresden, Germany, 02.-04.12.1998

Publ.-Id: 2812

Bacteria from a uranium mining waste pile: interaction with U(VI)

Panak, P.; Kutschke, S.; Selenska-Pobell, S.; Geipel, G.; Bernhard, G.; Nitsche, H.

  • Poster
    Euroconference: Bacterial-Metal/Radionuclide Interaction Rossendorf/Dresden, Germany, 02.-04.12.1998

Publ.-Id: 2811

Wechselwirkung von U(VI) mt Bakterien aus Uranhalden

Panak, P.; Kutschke, S.; Selenska-Pobell, S.; Geipel, G.; Bernhard, G.; Nitsche, H.

  • Poster
    GDCh-Tagung, FG Nuklearchemie Dresden, Germany, 07.-09.09.1998

Publ.-Id: 2810

RAPD and Rep-APD analysis of Bacillus sphaericus

Miteva, V.; Mitev, V.; Selenska-Pobell, S.

  • Poster
    8th Int. Symposium on Genetics of Industrial Microorganisms Israel, 28.06.-03.07.1998

Publ.-Id: 2809

Molecular and radiochemical analysis of Thiobacillus ferrooxidans strains recovered from a uranium waste pile in Saxony

Kutschke, S.; Panak, P.; Groudeva, V.; Selenska-Pobell, S.; Bernhard, G.; Nitsche, H.

  • Poster
    Euroconference: Bacterial-Metal/Radionuclide Interaction Rossendorf/Dresden, Germany, 02.-04.12.1998

Publ.-Id: 2808

Seaborgium: Charakterisierung als Oxidhydroxid

Hübener, S.; Brüchle, W.; Dressler, R.; Eichler, B.; Gäggeler, H. W.; Grantz, M.; Heyne, H.; Jäger, E.; Jost, D. T.; Kirbach, U.; Nitsche, H.; Piguet, D.; Schädel, M.; Schimpf, E.; Taut, S.; Trautmann, N.; Türler, A.; Vahle, A.; Yakushev, A. B.

  • Poster
    GDCh-Tagung, FG Nuklearchemie Dresden, Germany, 07.-09.09.1998

Publ.-Id: 2807

EXAFS Investigations of Uranyl Sorption on Ferrihydrite

Hennig, C.; Reich, T.; Arnold, T.; Roßberg, A.; Nitsche, H.

  • Poster
    Euroconference and NEA Workshop: Actinide-XAS-98 Grenoble, France, 04.-06.10.1998

Publ.-Id: 2806

Implantation of boron ions into hard metals

Mrochek, I.; Günzel, R.; Matz, W.; Möller, W.; Anishchik, V.

  • Nukleonika 44(1999)2, 217-224

Publ.-Id: 2805

The Problem of Preferred Orientation in EXAFS Measurements - Solvable with X-ray Diffraction?

Hennig, C.; Kraus, W.; Nolze, G.

  • Poster
    Euroconference and NEA Workshop: Actinide-XAS-98 Grenoble, France, 04.-06.10.1998

Publ.-Id: 2804

Korrektur der Koordinationszahlbestimmung für die Uranylgruppe aus EXAFS-Messungen pulverförmiger Proben

Hennig, C.

  • Poster
    GDCh-Fachtagung, FG Nuklearchemie Dresden, Germany, 07.-09.09.1998

Publ.-Id: 2803

Humic Acid Research at FZR

Heise, K.-H.; Pompe, S.; Schmeide, K.; Bubner, M.; Schuster, G.; Nicolai, R.; Zänker, H.; Reich, T.; Geipel, G.; Baraniak, L.; Bernhard, G.; Nitsche, H.

  • Poster
    Uranium Mining and Hydrogeology II Freiberg, Germany, 15.-17.09.1998

Publ.-Id: 2802

Huminsäureforschung im FZR - Melanoidine als Modell-Huminsäuren

Heise, K.-H.; Pompe, S.; Nicolai, R.; Schmeide, K.; Bubner, M.; Reich, T.; Nitsche, H.

  • Poster
    Uranium Mining and Hydrogeology II Freiberg, Germany, 15.-17.09.1998

Publ.-Id: 2801

FTIR-Untersuchungen zur Komplexierung von Uran(V) durch huminsäureähnliche Melanoidine

Heise, K.-H.; Nicolai, R.; Pompe, S.; Bubner, M.; Nitsche, H.

  • Poster
    GDCh-Fachtagung, FG Nuklearchemie Dresden, Germany, 07.-09.09.1998

Publ.-Id: 2800

Mineralisierung von Kohlenstoff-14-haltigen Reststoffen durch anodische Oxidation

Förster, E.; Heller, S.; Heise, K.-H.; Nitsche, H.

  • Poster
    GDCh-Fachtagung, FG Nuclearchemie Dresden, Germany, 07.-09.09.1998

Publ.-Id: 2794

Die Synthese isotopmarkierter Modellhuminsäuren

Bubner, M.; Pompe, S.; Meyer, M.; Heise, K.-H.; Nitsche, H.

  • Poster
    GDCh-Fachtagung, FG Nuklearchemie Dresden, Germany, 07.-09.09.1998

Publ.-Id: 2793

Vergleich der Sorption von Eisen und Uran an Erzgebirgsmetamorphiten und Elbtalsedimenten unter aeroben und anaeroben Bedingungen und unter dem Einfluß organischer Grubenwasserinhaltsstoffe

Abraham, A.; Mack, B.; Baraniak, L.; Nitsche, H.

  • Poster
    GDCh-Fachtagung, FG Nuklearchemie Dresden, Germany, 07.-09.09.1998

Publ.-Id: 2792

Forschungszentrum Rossendorf; Jahresbericht 1996

Leib, J.

  • Open Access Logo Forschungszentrum Rossendorf, Jahresbericht 1996
    ISSN: 1436-3976


Publ.-Id: 2791

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