Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31742 Publications
Mechanism of degradation of surface hardening at elevated temperature in TiAlV-alloys by in situ synchrotron radiation diffraction
Berberich, F.; Matz, W.; Kreißig, U.; Schell, N.; Mücklich, A.;
The surface hardness of the technically important alloy Ti–6Al–4V (wt.%) can be improved by nitrogen implantation. The structural mechanisms of hardening and of the stability of the improved hardness at elevated temperatures are studied. Ion implanted (II) and plasma immersion ion implanted (PII) samples were used. The formation of small TiN crystallites was detected in the as-implanted state, but only for the II samples a considerable surface hardness increase (factor 3) is observed. The in situ XRD experiments showed, that the TiN phase is stable up to temperatures of 650 °C for both types of implantation. At higher temperature Ti2N is formed which is stable up to 770 °C. ERDA results indicate a diffusion of nitrogen into the bulk material. The redistribution of N is responsible for the hardness changes: a slight decrease for II samples but an improvement by a factor of 2.5 for PII samples. The improvements/degradations of hardness and wear are discussed in correlation with the nitrogen depth distribution below the surface.
Keywords: Synchrotron radiation; Ion implantation; Hardening; Ti–6Al–4V
  • Nuclear Instruments & Methods B 199 (2003) 54-58

Publ.-Id: 5281 - Permalink


Development of nanosystems in TiO2 by ion implantation
Fromknecht, R.; Wang, L. M.; Zhu, S.; Sun, K.; van Veen, A.; van Huis, M. A.; Weimann, T.; Wang, J.; Niemeyer, J.; Eichhorn, F.; Wang, T.;
Au-ions were implanted into TiO2 single crystals with doses ranging from 2x1016Au+/cm2 to 6x1016Au+/cm2 at RT and 1000 K. At RT implanted samples were then thermally annealed at temperatures of 550 K to 1550 K. The Au-atoms precipitate to nanocrystals already during implantation at RT with an average particle size of 1.5 nm. HRTEM investigations revealed that the Au-nanocrystals, embedded in amorphous TiO2 regions, have a broad size and range distribution varying from large sizes in the near surface region to smaller sizes at larger depths. In the annealing process a reorientation of the Au-nanocrystals is observed, with the main effect of a decrease of the (111) peak and an increase of the (200)-peak in the XRD spectra. After annealing at 1000 K the particle size of the highly textured Au-implant was evaluated to ~ 6 nm; this means that during annealing the particles grow, leading to a partially coherent orientation in the disordered TiO2-matrix. Au implantation at RT performed through a metal mask with holes resulted in a narrow size distribution (2-6 nm) of the Au-nanocrystals in the near surface region.
Keywords: Au nanocrystals, ion implantation, rutile, x-ray diffraction
  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft, Frühjahrstagung des Arbeitskreises Festkörperphysik, Dresden, 24.-28.3.2003

Publ.-Id: 5280 - Permalink


Cu gettering in ion implanted and annealed silicon in regions before and beyond the main projected ion range
Kögler, R.; Peeva, A.; Lebedev, A.; Posselt, M.; Skorupa, W.; Özelt, G.; Hutter, H.; Behar, M.;
The strong gettering of Cu atoms in single-crystal Si implanted with 3.5 MeV P+ ions was studied after thermal treatment and contamination with low amount of Cu impurity. Cu decorates the remaining damage generated by ion implantation. Three separate Cu gettering layers were detected by secondary ion mass spectrometry: at the main projected ion range, RP, below RP (RP/2 effect) and beyond RP (trans-RP effect). The defects acting as gettering centers at RP/2 and RP are implantation induced excess vacancies and excess interstitials, respectively. Cu profiles fit very well with depth distributions of excess vacancies and excess interstitials simulated by binary collision model for random and channeled ion incidence. The RP/2 and RP gettering layer are implantation induced, whereas the trans-RP gettering layer is formed by thermal treatment. The Cu accumulation in the trans-RP region increases with increasing temperature and/or with increasing annealing time. The RP/2 effect for P+ implantation was found to be significantly reduced in comparison with Si+ implantation. It completely disappears for higher P+ ion fluences. The obtained results are in agreement with the assumption that interstitials carried by P diffusion are the origin of Cu gettering in the trans-RP region.
Keywords: Ion implantation (61.72.Q), Defect formation and annealing (61.72.C), Indirect evidence of defects (61.72.H), Defect diffusion (66.30.L),Cu gettering (61.72.T).

Publ.-Id: 5279 - Permalink


Atomistic simulation of ion-beam-induced defect production within 100 – 1000 ps after ion impact
Posselt, M.;
The formation and evolution of radiation damage by ion bombardment consists of three stages: (i) atomic displacements during ballistic processes, (ii) formation of a (meta)stable defect structure after fast relaxation, and (iii) long-term thermally activated defect rearrangement, migration, recombination and reduction. The first two stages occur on very short time scales and are hardly accessible by available experimental methods. Atomistic computer simulations can contribute to a better understanding of these processes and of their microscopic mechanisms.
In this talk, a combined simulation method is employed to study a relatively simple case, the defect production by a single ion impact in silicon. Processes in the collision cascade with energy transfers above about 100 eV are treated by computer simulations based on the binary collision approximation (BCA). Classical molecular dynamics (MD) calculations are applied to consider processes in certain parts of the cascade which start with energy transfers less than about 100 eV. Detailed investigations are performed to study the temporal evolution of the defect structure until the beginning of the thermally activated phase, and to determine the damage morphology obtained after the fast relaxation. The influence of nuclear energy deposition and target temperature is discussed. The combination of BCA and MD methods allows the effective calculation of the total number and the depth distribution of different defect species (isolated vacancies and self-intersitials as well as more complex defects) formed on average per incident ion after the fast relaxation processes are finished. The procedure yields more realistic initial conditions for the simulation of post-implantation annealing than hitherto used.




Keywords: computer simulation, defect formation, ion implantation
  • Invited lecture (Conferences)
    20th Int. Conf. on Atomic Collisions in Solids (ICACS 20), Puri, India, Jan. 19-24, 2003 (invited talk)

Publ.-Id: 5278 - Permalink


Betriebserfahrungen beim Batch-Monitoring mit adaptiven Stoff- und Wärmebilanzen
Hessel, G.; Heidrich, J.; Hilpert, R.; Roth, M.; Schmitt, W.; Seiler, T.; Weiß, F.-P.;
In der Feinchemie- und Pharmaindustrie werden Chemikalien kleinerer Menge meistens durch diskontinuierlich geführte Batch-Prozesse hergestellt. Zur Unterstützung des Bedienungspersonals bei der schwierigen Prozessführung von Batch-Reaktoren (Rührkesselreaktoren) wurde ein Online-Monitoring-System (MoSys) entwickelt, das auf adaptiven Stoff- und Wärmebilanzen basiert. Die Industrieerprobung erfolgte im Rahmen eines entwickelten Batch-Informations-Management-Systems (BIMS), das in einem separaten Industrie-PC implementiert und über den Terminalbus in die vorhandene Automatisierungstechnik einer Mehrzweckanlage der Degussa AG eingebunden wurde. Die Betriebserfahrungen von zwei Produktionskampagnen zeigten, dass das BIMS/MoSys stabil und zuverlässig arbeitete und die Konzentrationsprofile gut mit den erwarteten Konzentrationsverläufen übereinstimmten.

Mit BIMS/MoSys sind folgende praktische Nutzanwendungen möglich:

- Einsparung einer chemischen Online-Prozessanalytik,
- Erweiterung und Archivierung des bestehenden Prozesswissens,
- Verbesserung der Produktqualität bei komplexen Batch-Prozessen,
- Optimierung der Prozessführung durch die genauere Ermittlung von Anlagen- und Prozess- Kenngrößen,
- Fehler- und Ursachenanalyse anhand der archivierten Batches,
- Rückverfolgbarkeit von Batches bei Problemen (z. B. Qualitätsbeanstandungen),
- Aufbau eines automatisierten Batch-Reports.

Darüber hinaus können unerwünschte Betriebszustände mit erhöhter Zwischenproduktakkumulation und verringerter Raum-Zeit-Ausbeute frühzeitig erkannt und dadurch rechtzeitig Gegenmaßnahmen eingeleitet werden, um größere Verluste zu vermeiden. Das auf adaptiven Stoff- und Wärmebilanzen basierende Online-Monitoring-System ist bei allen ausreichend exothermen ( oder endothermen) Semibatch-Prozessen einsetzbar, wenn geeignete Informationen in den Stoff- und Wärmebilanzen enthalten sind.
  • Abstract in refereed journal
    Chemie Ingenieur Technik, (75), 8 (2003) 1141

Publ.-Id: 5277 - Permalink


INTERACTION OF URANIUM WITH Desulfovibrio äspöensis (DSM 10631T)
Moll, H.; Merroun, M.; Selenska-Pobell, S.; Bernhard, G.;
The FZR/IRC contributions are focussing on the interactions of actinides with indigenous bacteria in Äspö aquifer. We presenting the first results on interactions of the sulfate-reducing bacterium D. äspöensis (DSM 10631T) with uranium(VI). 80 % of the U(VI), solved initially in a concentration of 0.02 mM in a liquid medium supplemented with lactat (10 mM), was removed by the cells of this strain after 72 h of incubation at pH 5.
Keywords: uranium, desulfovibrio, reduction
  • Other report
    Äspö HRL Annual Report 2002 (2003)

Publ.-Id: 5276 - Permalink


Einführung von Facility Management in einer Forschungseinrichtung, Anforderungen, Probleme, Erfahrungen
Joehnk, P.; Keywords: Facility Management, Forschungseinrichtung
  • Lecture (others)
    Workshop Fa. Heinrich Nickel GmbH am 16.01.2003 in Berlin

Publ.-Id: 5274 - Permalink


New possibilities of characterizing growing sputter-deposited thin films
Schell, N.; Bottiger, J.; Matz, W.; Chevallier, J.; Petersen, J.; Andreasen, K. P.; Jensen, T.;
wird nachgereicht
  • Contribution to proceedings
    Proceedings of 9th Annual International Conference on Composite Engineering (ICCE/9), San Diego, USA, July 1-6, 2002, ed. Hui, D., p. 697-698

Publ.-Id: 5272 - Permalink


Institute of Ion Beam Physics and Materials Research: Annual Report 2002
von Borany, J.; Helm, M.; Jäger, H.-U.; Möller, W.; Wieser, E.; (Editors)
Summary of the scientific activities of the institute in 2002 including selected highlight reports, short research contributions and an extended statistics overview.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-362 Januar 2003

Downloads:

Publ.-Id: 5271 - Permalink


Influence of annealing on structural properties of metallic multilayers
Hecker, M.; van Loyen, L.; Tietjen, D.; Schell, N.; Schneider, C. M.;
wird nachgereicht
  • Materials Science Forum 378-381 (2001) 370-375

Publ.-Id: 5270 - Permalink


Thermal stability of grain structure and defects in submicrocrystalline and nanocrystalline nickel
Klemm, R.; Thiele, E.; Holste, C.; Eckert, J.; Schell, N.;
The grain and defect structure of submicrocrystalline and nanocrystalline nickel produced by equichannel angular pressing or by ball milling, respectively, has been studied by isochronal and isothermal annealing experiments, and Xray investigations. A detailed analysis of the thermal stability of the di.erent types of microstructures will be presented.
  • Scripta Materialica 46 (2002) 685-690

Publ.-Id: 5269 - Permalink


Internal strains in single grains of fatigued polycrystalline nickel
Thiele, E.; Bretschneider, J.; Buque, C.; Schell, N.; Schwab, A.; Holste, C.;
Bragg diffraction profiles were measured on single grains of different axial orientation in cyclically deformed Ni polycrystals. Diffraction profile parameters were determined and compared with results from profile measurements on fatigued single crystals, showing the same type of dislocation structure as the grains with corresponding axial orientation. Conclusions are drawn concerning the deformation processes in the grains taking into account the activated slip systems, the dislocation density and long-range residual strains.
  • Materials Science Forum 404-407 (2002) 823-828

Publ.-Id: 5268 - Permalink


Ion beam synthesized nanoclusters for silicon-based light emission
Rebohle, L.; von Borany, J.; Fröb, H.; Gebel, T.; Helm, M.; Skorupa, W.;
Strong blue and violet photoluminescence (PL) and electroluminescence (EL) at room temperature has been achieved from thin SiO2 layers implanted with group IV elements. Thermally grown SiO2 .lms with thicknesses between 130 and 500 nm were implanted with Si, Ge or Sn ions followed by di.erent annealing procedures. Based on PL and PL excitation spectra we tentatively interpret the blue–violet PL as due to a T1- S0 transition of an oxygen deficiency center. The strong EL is well visible with the naked eye and reaches a power e.ciency of up to 5E-3 for Ge. Whereas the EL intensity shows a linear dependence on the injection current for Ge-rich layers, the shape of the EL spectrum remains unchanged. It was found that the I–V characteristics shift to lower applied electric fields with increasing implantation
fuence. Furthermore, it is assumed that the luminescence centers will be excited either by field ionization or by the scattering of hot electrons. Finally, the suitability of ion implanted silicon dioxide layers for optoelectronic applications is discussed.
Keywords: Si, Ge, Sn implanted SiO2; Photoluminescence; Optoelectronic application
  • Nuclear Instruments and Methods in Physics Research B 188 (2002) 28–35

Publ.-Id: 5267 - Permalink


In situ high-temperature synchrotron-radiation diffraction studies of Ni and Co–Ni silicidation processes
Rinderknecht, J.; Prinz, H.; Kammler, T.; Berberich, F.; Zschech, E.;
Silicidation processes in nanoscale Ni and CoNi (5at.% Ni) layers on different silicon substrates were investigated using X-ray diffraction. The phase formation sequences as well as the formation and transition temperatures between 200 and 750°C were studied. The impact of different silicon substrates, i.e., polycrystalline Si and (100) oriented Si single-crystal substrates as well as the impact of different species of dopants (As, P) were analysed. The thermal range of the desired low resistance target phases NiSi and Co(0.95)Ni(0.05)Si(2) was determined. The temperatures for phase formation and phase transitions are significantly lowered on polycrystalline Silicon substrates.
Keywords: Ni silicide; Co–Ni silicides; Phase formation, transition temperatures; Impact of dopants, substrate
  • Microelectronic Engineering 64 (2002) 143-149

Publ.-Id: 5266 - Permalink


Plasma immersion ion implantation of nitrogen in Si: Formation of SiO2, Si3N4 and stressed layers under thermal and sputtering effects
Ueda, M.; Beloto, A. F.; Reuther, H.; Parascandola, S.;
Plasma immersion ion implantation of nitrogen in Si: Formation of SiO2,
Si3N4 and stressed layers under thermal and sputtering effects
  • Surface and Coatings Technology 136 (2001) 244-248

Publ.-Id: 5265 - Permalink


Sponge-like and columnar porous silicon implanted with nitrogen by plasma immersion ion implantation (PIII)
Beloto, A. F.; Ueda, M.; Abramof, E.; Senna, J. R.; Da Silva, M. D.; Kuranaga, C.; Reuther, H.; Ferreira Da Silva, A.; Pepe, I.;
Sponge-like and columnar porous silicon implanted with nitrogen by plasma immersion ion implantation (PIII)
  • Surface and Coatings Technology 156 (2002) 267 -271

Publ.-Id: 5264 - Permalink


Bacteria-Based Bioceramics for Bioremediation of Uranium Mining Waste Waters
Raff, J.; Soltmann, U.; Mattys, S.; Merroun, M.; Rossberg, A.; Hennig, C.; Böttcher, H.; Pompe, W.; Selenska-Pobell, S.;
Uranium mining waste piles are an enormous pool for heavy metal resistant bacteria. Many of these bacteria possess different mechanisms to detoxify metals, e.g. bioaccumulation, biotransformation, biomineralization or biosorption. The latter is of special interest for the development of bioremediation processes. We demonstrated that vegetative cells, spores and purified S-layer of Bacillus sphaericus JG-A12 which was recovered from a uranium mining waste pile near the town of Johanngeorgenstadt, Germany, bind selectively U, Cu, Pb, Al and Cd. In this work sol-gel techniques were used to immobilize cells, spores and stabilized S-layer of B. sphaericus JG-A12 in a porous silicate matrix. Processes of sorption and desorption of U and Cu by the produced biological ceramics (biocers) were investigated and compared with the binding properties of the single components. Localization of the bound metals was carried out using scanning electron microscopy and EDX analysis. Formed metal complexes were characterized by extended X-ray absorption fine structure spectroscopy (EXAFS). Our results demonstrate that spores followed by vegetative cells and the S-layer bind large amounts of U and Cu. The silicate matrix binds only small amounts of U and no Cu. The immobilization of the biocomponents in the bioceramics did not have any negative effect on the cells and S-layer but the metal binding capacity of the spores was strongly reduced. Binding capacity and binding kinetics of the biocers were positively influenced by adding water soluble additives as sorbitol or by freeze drying instead of air drying. The bound metals can be completely removed from the biocers by using aqueous citric acid what makes them reusable. EXAFS spectroscopy of the uranium complexes shows that uranium is bound via phosphate and carboxyl groups of the biocomponents as well as by the silicate and hydroxyl groups of the ceramic matrix. Because biocers possess high mechanical stability and metal binding capacity and are in addition reusable they are suitable for construction of intelligent filters for bioremediation.




Keywords: Keywords: Bacillus sphaericus, bioceramic, biosorption
  • Poster
    Abstrakt zur ASM-Jahrestagung (18.-22 Mai 2003), Washington Q10 Bioremediation of Metals and Bioremediation of Metal-Contaminated Soils

Publ.-Id: 5263 - Permalink


Hydrogen Embrittlement of Reactor Pressure Vessel Steels
Uhlemann, M.; Müller, G.; Böhmert, J.;
The embrittlement of reactor pressure vessel steels is mainly effected by the neutron field. However, recently results have pointed out an additional or coupled effect of hydrogen. The aim was to investigate the influence of hydrogen on mechanical behaviour of different unirradiated reactor pressure vessel steels up to the working temperature in dependence on cathodic hydrogen charging conditions in correlation to chemical composition, microstructure, and hydrogen diffusivity and solubility. Diffusivity and solubility of hydrogen were determined by means of permeation measurements, thermodesorption measurements, and hot extraction. Small differences are mainly caused by the chemical composition of the steels. Higher copper and phosphorus contents do not yield an expected higher hydrogen uptake of the unirradiated steels. The mechanical properties were determined by slow tensile tests up to 250°C with simultaneously hydrogen charging in simulated reactor pressure water dependent on strain rate and charging conditions, and by impact tensile tests. The results of the mechanical tests and the corresponding fractographic analysis showed hardly an effect of hydrogen and no significant differences of the steels under the applied charging conditions. The loss of ductility decreases with increasing strain rate and increasing temperature. These results are the staring point for further investigations on irradiated samples.
Keywords: diffusivity, hydrogen, embrittlement, mechanical properties, reactor pressure vessel steels, solubility
  • Lecture (Conference)
    EDEM 2003 - International Conference on Environmental Degradation of Engineering Materials, Bordeaux, 29.06-02.07.2003, Vollversion auf CD
  • Contribution to proceedings
    EDEM 2003 - International Conference on Environmental Degradation of Engineering Materials, Bordeaux, 29.06-02.07.2003, Vollversion auf CD

Publ.-Id: 5261 - Permalink


Analysis of a hypothetical boron dilution event by means of the neutron kinetic core model DYN3D using different cross section libraries
Kliem, S.; Mittag, S.;
Stationary and transient core calculations for a hypothetical boron dilution event have been carried out by the nodal code DYN3D. Two different two-group diffusion-parameter libraries, generated by the cell codes HELIOS and CASMO, have been used, in order to assess the influence of these data. Realistic core inlet boundary conditions have been applied using a validated semi-analytical coolant mixing model. The initial deborated-coolant-slug volumes, necessary for reaching recriticality in stationary calculations with both data libraries, differ by some 20 %. Differences are also observed in the height and time point of the power peak in transient calculations. The deviations between the applied data libraries are mainly due to different SCRAM reactivities and Doppler coefficients. Even when assuming a 36 m3 deborated slug, the core is brought back to subcriticality in all calculations.
  • Lecture (Conference)
    Fachtag der KTG-Fachgruppen "Betrieb" und "Reaktorphysik und Berechnungsmethoden" 13.-14.02.2003, Rossendorf, Proceedings CD-ROM
  • Contribution to external collection
    Fachtag der KTG-Fachgruppen "Betrieb" und "Reaktorphysik und Berechnungsmethoden" 13.-14.02.2003, Rossendorf, Proceedings CD-ROM

Publ.-Id: 5260 - Permalink


Electron Microscopy and X-ray Diffraction Study of AlN layers
Kowalczyk, A.; Jagoda, A.; Mücklich, A.; Matz, W.; Pawlowska, M.; Ratajczak, R.; Turos, A.;
AlN nanocrystalline layers and superstructures are used in the modern optoelectronic technology as reflecting mirrors in semiconductor lasers. In the present work the properties of AlN films prepared by sputtering methods from an AlN target in reactive Ar + N plasma were investigated. The characterisation was performed with HRTEM, SEM, glancing angle XRD and RBS methods. The present measurements confirmed the polycrystalline structure of AlN layers and enabled the evaluation of their grain size. The roughness and thickness of the layers were additionally determined by ellipsometric and profilometric measurements.
Keywords: Electron microscopy, X-ray diffraction, RBS
  • Acta Physica Polonica A 102 (2002) 221

Publ.-Id: 5259 - Permalink


RBS and ion channelling study of YBCO/STO and YBCO/LSMO/STO structures. Oxygen content estimated by X-ray diffraction
Grigorov, K.; Tsaneva, V.; Spasov, A.; Matz, W.; Groetzschel, R.; Reuther, H.;
The structure and the elemental depth distributions of Y1Ba2Cu3O7-d (YBCO) and La0.7Sr0.3MnO3 (LSMO) were examined by q-2q XRD, and by 1.7 MeV 4He+ Rutherford Backscattering Spectrometry (RBS) in random and channeling geometry. The YBCO layers were magnetron sputtered, where the only one varying parameters were the oxygen pressure and the annealing time. The layers have high crystalline qualitiy and an almost sharp interface with the substrate as revealed by the analysis. It is shown that the oxygen content influences considerably not only the superconducting behavior, but also the lattice parameters and the cmin parameter (the minimum yield which is the ratio of aligned to random Rutherford backscattering spectra). We have found by high-precision RBS simulation, that independent on the film quality, a disordered interface region of 20 to 30 nm is present in all structures. As a complementary study we have performed also AES depth profiling.
Keywords: HTSC, X-ray diffraction, RBS
  • Vacuum, 69 (2002) 315-319

Publ.-Id: 5257 - Permalink


YBCO/LSMO and LSMO/YBCO double-layer deposition by off-axis magnetron sputtering and strain effects
Donchev, T.; Tsaneva, V.; Nurgaliev, T.; Gravier, L.; Ansermet, J. P.; Petrov, I.; Petrova, V.; Matz, W.; Groetzschel, R.; Pignard, S.; Vincent, H.;
We report here on ferromagnetic/superconductor FM/SC and SC/FM double layers deposited without a buffer layer between FM and SC. Thin films of La0.7Sr0.3MnO3 (LSMO) are used for the FM, and YBa2Cu3O7-x (YBCO) for the SC. Both films can grow crystalline on SrTiO3 (STO) or LaAlO3 (LAO) substrates in high temperature and in oxygen atmosphere conditions. Magnetic and transport measurements and X-ray diffraction analysis are used to characterise film quality and properties. It is shown that off-axis magnetron sputtering can be used for high-quality double layer deposition. A prerequisite for this is the suppression of the interdiffusion process. This is achieved by lowering the deposition temperature and shortening the deposition time for the top layer. Lattice relaxation for LSMO films deposited on LAO substrates is seen. It is demonstrated that post-deposition annealing or additional top layer deposition enlarges the relaxed part of the lower LSMO film. LSMO films are smooth and free of imperfections and the stress is partly relieved by the formation of misfit dislocations. For YBCO films, SEM, XRD, EDX and magnetisation characterisations show that film lattice relaxation starts when single-element-oxide crystals start to grow into the film. Many experiments give evidence of a critical thickness of about 30 nm of a strained layer, after which the top part of the YBCO film relaxes. Despite the small compositional deviation due to the interdiffusion, the YBCO/LSMO double films demonstrate high enough transport and magnetic properties to allow their application in the investigation of the injection of spin-polarised quasiparticles from FM to SC film. The critical current for YBCO film is Jc~0.7×106 A/cm2 if it is a bottom layer, and Jc~1.7×106 A/cm2 if YBCO is a top layer, whilst our optimal single-layer YBCO films have Jc~(2.5¯5)×106 A/cm2 at 77 K.
Keywords: High Tc superconductor; Ferromagnetic film; Strain effects; Film relaxation
  • Vacuum, 69 (2002) 243-247

Publ.-Id: 5256 - Permalink


Analysis of the Boiling Water Reactor Turbine Trip Benchmark with the Codes DYN3D and ATHLET/DYN3D
Grundmann, U.; Kliem, S.; Rohde, U.;
The OECD/NRC BWR Turbine Trip Benchmark was analysed by the codes DYN3D and the coupled code system ATHLET/DYN3D. Considering the calculations with given thermal-hydraulic boundary conditions of the core for the Exercise 2 of the benchmark the analyses were performed with the core model DYN3D. Concerning the modelling of the BWR core in the DYN3D code several simplifications and their influence on the results were investigated. The standard calculations with DYN3D were performed with 764 coolant channels (1 channel per fuel assembly), the assembly discontinuity factors (ADF) and the phase slip model of MOLOCHNIKOV. Comparisons were performed with the results obtained by calculations with 33 thermal-hydraulic channels, without the ADF and with the slip model of ZUBER-FINDLAY. It is shown that the influence on core-averaged values of the steady state and the transient is small. Considering local parameters the influence of the ADF or the reduced number of coolant channels is not negligible. For the calculations of Exercise 3 the DYN3D-model validated during the Exercise 2 calculations in combination with the ATHLET system model, developed at GRS for Exercise 1 has been used. Calculations were performed for the basic scenario as well as for all specified extreme versions. They were carried out using a modified version of the external coupling of the codes, the ?parallel? coupling. This coupling shows a stable performance at the low time step sizes, which are necessary for an appropriate description of the feedback during the transient. The influence of assumed failures of different relevant safety systems on the plant and the core behaviour was investigated in the calculations of the extreme scenarios. The calculations of Exercise 2 and 3 contribute to the validation of DYN3D and ATHLET/DYN3D for boiling water reactor systems.
Keywords: neutron kinetics thermal hydraulics nuclear reactors boiling water reactors transients turbine trip benchmark measurements three-dimensional slip model
  • Nuclear Science and Engineering 148(2004), 226-234

Publ.-Id: 5255 - Permalink


The Integral Equation Method for a Steady Kinematic Dynamo Problem
Xu, M.; Stefani, F.; Gerbeth, G.;
With only a few exceptions, the numerical simulation of cosmic and laboratory hydromagnetic dynamos has been carried out in the framework of the differential equation method. However, the integral equation method is known to provide robust and accurate tools for the numerical solution of many problems in other fields of physics. The paper is intended to facilitate the use of integral equation solvers in dynamo theory. In concrete, the integral equation method is employed to solve the eigenvalue problem for a hydromagnetic dynamo model with a spherically symmetric, isotropic helical turbulence parameter alpha. Three examples of the function alpha(r) with steady and oscillatory solutions are considered. A convergence rate proportional to the inverse squared of the number of grid points is achieved. Based on this method, a convergence accelerating strategy is developed and the convergence rate is improved remarkably. Typically, quite accurate results can be obtained with a few tens of grid points.

Publ.-Id: 5254 - Permalink


The SHIP Experiment at GDT: Physical Concept and Pre-Calculations
Anikeev, A.; Bagryansky, P.; Ivanov, A.; Noack, K.;
At present, the GDT facility of the Budker Institute for Nuclear Physics Novosibirsk is being upgraded. The first stage of the upgrade is the Synthesised Hot Ion Plasmoid (SHIP) experiment. It aims, on the one hand, at the investigation of plasmas the parameters of which are expected to appear in the region of high neutron production in a GDT based fusion neutron source as proposed by the Budker Institute and, on the other hand, at the investigation of plasmas the parameters of which have never been achieved before in magnetic mirrors. The expected record values of plasma parameters and several peculiarities of the plasma offer a great field
for interesting investigations. In order to simulate the particle fields inside the GDT device and later in a GDT based neutron source an Integrated Transport Code System (ITCS) is being developed in collaboration between Forschungszentrum Rossendorf and Budker Institute. It consists of modules which allow the calculations of neutral gas, background plasma and of the fast ion component considering their mutual interactions. This contribution explains the concept of the SHIP experiment and presents the
results of first calculations by means of the ITCS modules.
Keywords: plasma physics, fusion, neutron source, magnetic mirror, gas dynamic trap, GDT facility, numerical calculation
  • Poster
    29th EPS Conference on Plasma Physics and Controlled Fusion, 17-21 June 2002, Montreux, Switzerland, Proceedings: ECA Vol. 26B, P-4.098 (2002)
  • Contribution to proceedings
    29th EPS Conference on Plasma Physics and Controlled Fusion, 17-21 June 2002, Montreux, Switzerland, Proceedings: ECA Vol. 26B, P-4.098 (2002)

Publ.-Id: 5253 - Permalink


Thin layer copper ISE for fluidic microsystem
Hüller, J.; Pham, M. T.; Howitz, S.;
A miniaturised ion selective electrode (ISE) for Cu2+ ions was developed, specially designed for application in a microfluidic system. The electrode was prepared on a silicon wafer substrate coated with a Cu deposit in the thickness range of 50 - 200 nm. The Cu layer was 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 proof and reversible, permitting an easy exchange of the chip electrodes. The effective electrode area contacting the liquid of the microsystem flow channel amounts to about 4 mm2.

Sensitivity measurements were performed stationary and in the flow through cell. There was found a good Nernstian response of 29 mV/pCu between pCu 5 and 1 agreeing very well with reference measurements carried out with a commercial ISE.

The rapid response observed even in the dilutest 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
  • Sensors & Actuators B. 91(2003) 17-20

Publ.-Id: 5252 - Permalink


Synthesis of 4-[18F]fluoroiodobenzene and its application in Sonogashira cross-coupling reactions
Wüst, F.; Knieß, T.;
The first application of a Sonogashira cross-coupling reaction in 18F chemistry has been developed. The reaction was exemplified by the cross-coupling of terminal alkynes (ethynylcyclopentyl carbinol 6, 17alpha-ethynyl-3,17beta-estradiol 7 and 17alpha-ethynyl-3-methoxy-3,17beta-estradiol 8) with 4-[18F]fluoroiodobenzene. 4,4'-Diiododiaryliodonium salts were used as precursors for the synthesis of 4-[18F]fluoroiodobenzene, enabling the convenient access to 4-[18F]fluoroiodobenzene in 13-70 % yield using conventional heating or microwave activation. The Sonogashira cross-coupling of 4-[18F]fluoroiodobenzene with terminal alkynes gave the corresponding 4-[18F]fluorophenylethynyl-substituted compounds [18F]-9, [18F]-10 and [18F]-13 in yields up to 88% within 20 min starting from 4-[18F]fluoroiodobenzene.
  • Journal of Labelled Compounds and Radiopharmaceuticals 2003, 46: 699-713
  • Lecture (Conference)
    15th International Symposium on Radiopharmaceutical Chemistry; Sydney, 07.-18.08.2003.

Publ.-Id: 5251 - Permalink


Efficient synthesis of the 18F-labelled amino acid 3-O-methyl-6-[18F]fluoro-L-DOPA
Füchtner, F.; Steinbach, J.;
The 18F-labelled amino acid derivative 3-O-methyl-6-[18F]fluoro-L-DOPA ([18F]OMFD) is a potential radiotracer to image tumour tissue using positron emission tomography. The precursor N-formyl-3-O-methyl-4-O-boc-6-trimethyl-stannyl-L-DOPA--ethyl ester enables the direct electrophilic radiofluorination by stereoselective destannylation. After partial hydrolysis, an optimized HPLC purification and sterile filtration the [18F]OMFD obtained with high radiochemical purity is ready for use. The total synthesis time is about 50 minutes and the radiochemical yield achieved is 20-25% (decay corrected, related to [18F]F2). It was demonstrated that [18F]OMFD can be produced routinely and reliably for clinical use. [18F]FDOPA - preparation devices can be used with minor modifications.
Keywords: 3-O-methyl-6-[18F]fluoro-L-DOPA, radiolabelled amino acid, electrophilic 18F-fluorination, PET-radiotracer
  • Applied Radiation and Isotopes 58 (2003) 575-578

Publ.-Id: 5250 - Permalink


Discontinuity factors for non-multiplying material in two-dimensional hexagonal reactor geometry
Mittag, S.; Petkov, P.; Grundmann, U.;
On the basis of methods developed recently for square-fuel-assembly reactor cores, discontinuity factors for hexagonal VVER (Russian PWR) control absorbers and reflector nodes have been derived. Partial currents from heterogeneous multi-group transport calculations are used for the determination of the discontinuity factors. As shown by suitable benchmark calculations, the application of these quantities in the two-group nodal diffusion code DYN3D clearly improves the results of assembly-power predictions. The advantage of reflector diffusion parameters, including discontinuity factors, over conventional albedos has also been demonstrated.
Keywords: albedo, baffle, benchmark problem, boundary condition, control rod, diffusion equation, discontinuity factor, DYN3D, equivalence theory, fine mesh, fuel assembly, heterogeneity, hexagonal geometry, homogenisation, MARIKO, neutron flux, neutron transport, nodal expansion method, non-multiplying material, nuclear reactor core, partial current, power distribution, reflector, PWR, VVER, VVER-440
  • Annals of Nuclear Energy 30/13 (2003) pp. 1347-1364

Publ.-Id: 5249 - Permalink


Synthetic Humic Acid Model Substances with Specific Functional Properties for the Use in Complexation and Sorption Experiments with Actinides
Sachs, S.; Heise, K.-H.; Bernhard, G.;
In order to improve the knowledge about the interaction processes between humic acids (HA) and metal ions, e.g., actinide ions, various HA model substances with different functional properties were developed at FZR-IfR. These include synthetic HA with different functional group contents and various structural elements, chemically modified HA with blocked phenolic OH groups as well as 14C-labeled HA. Since start of the project, synthetic HA with distinct redox functionalities are developed.
The report gives an overview about the synthesis, characterization and application of HA with various functional properties. It describes the synthesis and characterization of the melanoidin-based HA type M1 and M42, which are characterized by different carboxyl group contents. In addition, the synthesis and characterization of modified HA with blocked phenolic OH groups as well as of HA with distinct redox functionalities are discussed.
Keywords: Humic acids, Model substances, Synthesis, Characterization, Modification, Carbon-14 labeling, Application, Complexation, Migration, Actinides
  • Contribution to external collection
    Humic Substances in Performance Assessment of Nuclear Waste Disposal: Actinide and Iodine Migration in the Far-Field, First Technical Progress Report, Forschungszentrum Karlsruhe, Wissenschaftliche Berichte, FZKA 6800, Karlsruhe 2003, S. 51-64

Publ.-Id: 5246 - Permalink


Thermochromatographische Untersuchungen von Actinidenoxiden
Hübener, S.;
Die Flüchtigkeit von Oxiden der leichten Actiniden Th, Pa, U, Np und Pu im System O2-H2O(g)/SiO2(s) wurde mittels Thermochromatographie im Temperaturbereich 300 - 1475 K untersucht. Th und Pa bilden unter den experimentellen Bedingungen keine flüchtigen Verbindungen. Bei Temperaturen > 1250 K bilden U, Np und Pu flüchtige Oxidhydroxide, deren Flüchtigkeit in der Reihenfolge Pu<Np<U zunimmt. Die Flüchtigkeit des Plutoniums belegt die Oxidation von Plutoniumdioxid durch Sauerstoff/Wasser zum Trioxid.
Keywords: Actiniden, Plutoniumoxid, Thermochromatographie
  • Lecture (others)
    Seminar des Labors für Radio- und Umweltchemie der Universität Bern und des PSI, 24.01.2003, Universität Bern

Publ.-Id: 5245 - Permalink


Drug release from polyureaurethane coating modified by plasma immersion ion implantation
Kondyurin, A. V.; Maitz, M. F.; Romanova, V. A.; Begishev, V. P.; Kondyurina, I. V.; Guenzel, R.;
A crosslinked polyurethanurea (PUU) coating was synthesised from a solution on metal vascular stents. In the model system the glucocorticoid prednisolone was inserted into the film by the equilibrium swelling method; after this plasma immersion ion implantation (PIII) was applied to modify the coating for improved release kinetics. This treatment causes the formation of oxygencontaining and unsaturated carbon–carbon groups in the PUU and a destruction of the drug in the surface layer. As a consequence, the release rate of prednisolone to water becomes more stable with time than it is at the untreated coating. In this drug release system PIII treatment prevents an initial toxically high release of the drug. By this it allows the incorporation of a higher amount of the drug and an extended action.
Keywords: stent, polyurethane, drug release, plasma, ion implantation, PIII
  • Journal of Biomaterials Science, Polymer Edition 15(2004)2,145-159

Publ.-Id: 5244 - Permalink


Diamond formation in cubic silicon carbide
Pécz, B.; Weishart, H.; Heera, V.; Tóth, L.;
High-dose carbon implantation (3x10e17 and 1x10e18 ions/cm2) into cubic SiC on Si was carriedout at elevated temperatures (600 to 1200 °C) and different dose rates (1x10e13 to 1.5x10e14 cm-2 s-1). Transmission electron microscopy revealed the formation of either graphite or diamond precipitates, depending on the implantation parameters. In all cases, the diamond grains were epitaxial to the SiC lattice, while the graphite was textured. The minimum temperature for diamond formation was 900 °C, while graphite formed at 600 °C. The synthesized phase depends as well on the dose rate; graphite was formed at 900 °C with a high dose rate. Obviously, a criticaltemperature for diamond formation exists and increases with increasing dose rate. This behavior is explained by the competition between the accumulation and dynamic annealing of radiation defects in the SiC lattice, which acts as a template for diamond nucleation. Diamond grains with diametersas large as 10 nm have been observed after implantation at 1200 °C.
Keywords: Diamond, Silicon Carbide, Ion Beam Synthesis, Carbon Implantation, Transmission Electron Microscopy

Downloads:

Publ.-Id: 5243 - Permalink


On-line concentration estimation during chemical reactions using adaptive heat/ mass balances
Kryk, H.; Hessel, G.; Schmitt, W.; Seiler, T.; Weiß, F.-P.; Hilpert, R.; Roth, M.;
In the fine chemical industry, complex strongly exothermic reactions are usually carried out in semibatch mode in stirred tank reactors. These reactors are characterised by nonsteady-state conditions due to the discontinuous operation. Thus, it is difficult to estimate the actual conversion and to identify undesired process states during the chemical reaction, particularly, if the reactor is not equipped with expensive measuring systems for chemical on-line analysis. Therefore, an on-line monitoring system was developed that is able to estimate the concentration profiles without the need of chemical on-line analysis.
The on-line estimation of the concentration profiles is based on calculations of the thermal and chemical conversion courses during the chemical process using heat and mass balances. In order to consider factors of influence, such as heat losses, heat bridges and systematic measuring errors, adaptive model components are included. The adaptation of the complex model to the target plant is done by software-supported calculations of the adaptive parameters using process data of at least one normal batch course in the chemical plant.
The monitoring system was developed, optimised and tested by means of experiments in a miniplant at laboratory scale. As a test process, the strongly exothermic catalytic hydrogenation of an aromatic nitro compound was chosen. For industrial testing, the monitoring system was integrated into a batch-information-management system which was implemented into the process control system of a multipurpose reactor installation in the fine chemical factory at Radebeul (Degussa, Inc.). The tests showed good agreements of the estimated concentration profiles with analytical measurements in both, the laboratory and the industrial scale. Furthermore, it was found that deviant reaction courses and undesired process states can be recognised very earlier using the on-line monitoring system than with exclusive knowledge of process variables like temperatures, pressures and volume flows.
  • Lecture (Conference)
    4th European Congress of Chemical Engineering, 21-25 September 2003 Granada, Spain, Topic 10 Abstracts, O-10.2-001
  • Contribution to proceedings
    4th European Congress of Chemical Engineering, 21-25 September 2003 Granada, Spain, Topic 10 Abstracts, O-10.2-001

Publ.-Id: 5242 - Permalink


RPV Integrity Assessment by Operational Feedback: Post Service Investigations of VVER-type NPPs
Rindelhardt, U.; Böhmer, B.; Böhmert, J.;
The investigation of RPV material from decommissioned NPPs offers the unique opportunity to evaluate the real toughness response. By investigation of material from the decommissioned VVER 440-type Greifswald NPP the evaluation of a standard RPV design and the assessment of the quality of prediction rules and assessment tools will be possible. First results of the investigations are presented in the paper.
  • Lecture (Conference)
    ANS 2003 Annual Meeting, San Diego, June 2003
  • Transactions of ANS, Vol. 88,(2003)p. 547

Publ.-Id: 5241 - Permalink


First evidence for different freeze-out conditions for kaons and antikaons observed in heavy-ion collisions
Förster, A.; Uhlig, F.; Böttcher, I.; Debowski, M.; Dohrmann, F.; Grosse, E.; Koczon, P.; Kohlmeyer, B.; Laue, F.; Menzel, M.; Naumann, L.; Oeschler, H.; Scheinast, W.; Schwab, E.; Senger, P.; Shin, Y.; Ströbele, H.; Sturm, C.; Surowka, G.; Wagner, A.; Walus, W.;
Differential production cross sections of K- and K+ mesons have been measured in Ni+Ni and Au+Au collisions at a beam energy of 1.5 A·GeV. The K-/K+ ratio is found to be nearly constant as a function of the collision centrality. The spectral slopes and the polar emission pattern differ for K- and K+ mesons. These observations indicate that K+ mesons decouple earlier from the fireball than K- mesons.

Publ.-Id: 5240 - Permalink


Evolutionary aspects of the S-layers of Bacillus sphaericus
Schnorpfeil, M.; Raff, J.; Pollmann, K.; Merroun, M.; Selenska-Pobell, S.;
The primary structures of the S-layer proteins of the uranium mining waste pile isolate Bacillus sphaericus JG-A12 and of Bacillus sphaericus NTCC9602 were analysed. The amino acid sequences of the two proteins are almost identical but possess an abrupt homology to some of the other B. sphaericus S-layers studied up to date. This is an indication that a horizontal transfer of genetic information was involved in the evolution of the genes of the mentioned S-layers. An extensive comparative analysis of the S-layer proteins deposited to the GeneBanks demonstrated that several additional S-layers of B. sphaericus and of other Bacillus species were also subjected to late evolutionary events via lateral DNA transfer. The possible mechanism of these events in the case of B. sphaericus will be discussed.
Interestingly, the slight amino acid differences between the S-layer proteins of the strains JG-A12 and NTCC9692 lead to dramatic differences in their ability to interact with metals and also in their stability against proteases. As estimated by using EXAFS spectroscopy phosphorous residues, in addition to the carboxyl groups of the proteins, are involved in the binding of uranium (VI). ICP-MS analysis demonstrated that the two purified and recrystalized S-layer proteins contain phosphorous which indicates that they are phosphorylated. Moreover, the amount of phosphorous found in the S-layer of the strain JG-A12 was six times higher than those found in the S-layer of the reference strain NTCC 9602. This explains the higher ability of the S-layer of the uranium mining waste isolate to complex uranium and other metals. The latter seems to give an advantage to the strain JG-A12 to survive in the heavily polluted with uranium and other toxic metals environment from which it was recovered.













  • Lecture (Conference)
    Abstract in Proceedings of VAAM Jahrestagung 2003

Publ.-Id: 5238 - Permalink


Molecular analysis of the S-layer proteins of Bacillus sphaericus strains JG-A12 and NTCC 9602
Raff, J.; Schnorpfeil, M.; Pollmann, K.; Selenska-Pobell, S.;
Uranium mining waste pile isolate Bacillus sphaericus JG-A12 and it's closest relative B. sphaericus NTCC 9602 possess S-layer proteins with a similar size of about 135 kDa and with a square lattice symmetry. The two proteins differ significantly in their ability to interact with metals and in their stability against proteases and pH changes. By using ICP-MS, the "Stain-all" dye, and colourimetric method it was demonstrated that both proteins are phosphorylated but the S-layer of the strain JG-A12 contains six times more phosphorous than those of the reference strain NTCC9602. Surprisingly, the two proteins share an extremely high homology of 98 % in the region of the N-terminal S-layer homologous domains and of 91 % in the region of the central domains. It is noticeable that the minor amino acid differences between the S-layers of the studied strains consist of threonine and serine enrichments in the case of JG-A12. Bearing in mind that the majority of the phosphoproteins are usually modified at threonine and serine residues, our observation explains the higher level of phosphorylation of the S-layer of the uranium mining isolate JG-A12. The higher amount of phosphate groups of this protein explains also it's ability to complex more effectively uranium and other metals.
In addition, there are evidences that the two Bacillus sphaericus strains studied possess an additional S-layer or an S-layer-like copy which seems to be located on large indigenous plasmids.
  • Poster
    Abstract in Proceedings of VAAM Jahrestagung 2003

Publ.-Id: 5237 - Permalink


Bacteria-based bioremediation of uranium mining waste waters by using sol-gel ceramics
Raff, J.; Soltmann, U.; Matys, S.; Pompe, W.; Böttcher, H.; Selenska-Pobell, S.;
Sol-gel ceramics with high metal binding capacity were prepared via homogeneous dispersion and embedding of vegetative cells, spores and EDC stabilised surface proteins (S-layers) of Bacillus sphaericus JG-A12. The B. sphaericus JG-A12 strain was recovered from a uranium mining waste pile near the town of Johanngeorgen-stadt, Saxony, Germany (1). The whole cells as well as the purified S-layer protein of this strain possess an ability to bind selectively and very effectively uranium and several other metals such as Cu, Pb, Cd, Al, Pt and Pd (1, 2).
In this work the biosorption of U and Cu by the above mentioned three bacteria-based biological ceramics (biocers) was investigated. In addition, the metal binding capacity of the free SiO2 nanomatrix and of the three individual bacterial components (the vegetative cells, the spores and the S-layers) was studied as well.
Our results demonstrate that the high U and Cu binding capability of the three kinds of biocomponents is influenced by the sol-gel process in a different way. The metal binding properties of the vegetative cells and of the S-layers were not negatively influenced by the sol-gel treatments. The metal binding capacity of the embedded spores was, however, significantly lower than those of the non embedded spores. Very limited amounts of U and no Cu were bound by the silicate matrix alone.
The metal binding capacity of the biocers and also the kinetic of the biosorption were positively influenced by adding water soluble compounds such as sorbitol or by freeze drying instead of air drying. These results are connected to the higher porosity achieved by the mentioned treatments.
Both metals can be completely desorbed and washed from the biocers by using 0.5 M solution of citric acid. Afterwards the biocers can be reused for metal biosorption.
Due to their stability, high metal binding capacity and simple and complete removal of the bound metals described biocers are good candidates for construction of intelligent filters for cleaning of heavy metal contaminated liquid wastes.
The geographic origin of the source of the biocomponents, namely the strain B. sphaericus JG-A12, makes the constructed bioceramics promising for in situ bioremediation of the drain waters of the uranium mining waste piles and mill tailings.

References

1. Selenska-Pobell S., Miteva V., Boudakov I., Panak P., Bernhard G., and Nitsche H. (1999) Selective accumulation of heavy metals by three indigenous Bacillus isolates, B. cereus, B. megaterium and B. sphaericus in drain waters from a uranium waste pile.FEMS Microbiol Ecology 29, 59-67.
2. Raff J (2002) Wechselwirkungen der Hüllproteine von Bakterien aus Uran-abfallhalden mit Schwermetallen PhD Thesis, FZR-Report 358
  • Lecture (Conference)
    Abstract in Proceeding of 21. DECHEMA-Jahrestagung 2003, 2.-4.4.03

Publ.-Id: 5235 - Permalink


Uranium Mining Wastes as a Reservoir of Unusual Bacteria Prospective for Bioremediation and Nanotechnology
Selenska-Pobell, S.; Geißler, A.; Merroun, M.; Schnorpfeil, M.; Raff, J.; Radeva, G.; Flemming, K.;
Bacterial communities were studied in several uranium mining waste piles in Germany and in the USA by using 16S rDNA and RISA retrievals. Both approaches revealed extremely high and site-specific bacterial diversity. However, several bacterial groups including also novel lineages seem to be characteristic for the studied heavy-metal-polluted environments.
In parallel with the above mentioned direct molecular approaches, the method of enrichment culturing was applied in order to recover and study particular bacterial strains indigenous for the U wastes. Bacterial isolates belonging to different species representing diverse bacterial groups were recovered and characterized. The resistance and the interactions of these isolates with U and other heavy metals were demonstrated to be species- and even strain-specific. The atomic structures and the cellular location of the complexes formed by the isolates with U(VI) were studied using EXAFS spectroscopy, TEM, and EDX analyses. In all cases phosphate groups were predominantly implicated in the complexation of uranium but the structural parameters and the cellular location of the complexes differed between the studied bacterial groups.
Many of the studied strains possess unusual characteristics as the isolate JG-A12, for instance, which accumulates selectively U, Cu, Pb, Al, and Cd. This strain as well as it's intrinsic S-layer are forming U(VI)-complexes with identical structural parameters in which phosphorous residues in addition to the carboxyl groups are involved. ICP-MS and the "Stain-all" dye methods demonstrated that the S-layer of JG-A12 is phosphorylated. This can explain it's high ability to complex uranium and other metals. The latter seems to give an advantage to the strain to survive in the heavily polluted with uranium and other toxic metals environment from which it was recovered. Pd and Pt metallic nanoclusters were also successfully grown on the sheets of this S-layer. The latter is of interest for the nanotechnology. Interestingly, the S-layer of JG-A12 possesses unusual primary structure which indicates that lateral transfer was involved in the evolution of it's gene.
1848 words.
Keywords: bacterial diversity; S-layer, EXAFS, complexation of uranium

Keywords: Keywords: bacterial diversity; S-layer, EXAFS, complexation of uranium
  • Poster
    103rd ASM General Meeting, May 18 - May 22, 2003, Washington, DC, United States of America
  • Contribution to proceedings
    103rd ASM General Meeting, 18.-22.05.2003, Washington DC, United States of America

Publ.-Id: 5234 - Permalink


Elastic modulus of amorphous boron suboxide thin films studied by theoretical and experimental methods
Music, D.; Kreissig, U.; Chirita, V.; Schneider, J. M.; Helmersson, U.;
Boron suboxide BOx thin films have been deposited on Si (100) by reactive rf magnetron sputtering of B powders in an Ar/O2 atmosphere. Elastic recoil detection analysis and x-ray diffraction were used to study the influence of the O incorporation on the film composition and structure and relate them to mechanical properties, which were evaluated by nanoindentation. As x in BOx was increased from 0.08 to 0.18, the elastic modulus of the x-ray amorphous films decreased from 273 to 231 GPa, by 15%. This can be understood using classical molecular dynamics (MD) with a Buckingham-like interaction potential: The increase in the O concentration and corresponding formation of B–O bonds, shown to be longer than the B–B bonds, resulted in larger ionic contributions as well as a density reduction. This increased ionicity was responsible for the observed decrease in elastic modulus. As even more O was incorporated (x>0.18), the H concentration increased, exceeding 0.3 at. %. This may cause the formation of boric acid (H3BO3) as a result of the chemical reaction with H2O upon atmosphere exposure. The presence of van der Waals and hydrogen bonding, associated with H3BO3 formation, provides a reasonable explanation for the extensive decrease in elastic modulus from 231 to 15 GPa, by 94%. The parameterization for the Buckingham-like interaction potential, introduced in this study, can be used for MD simulations of amorphous BOx systems without H3BO3.

Publ.-Id: 5233 - Permalink


Investigations of the damage structure near the crack tip in Al-alloys by means of small angle x-ray scattering
van Ouytsel, K.; Böhmert, J.; Müller, G.; Roth, S.; Burghammer, M.;
Structural materials, such as bainitic and austenitic steels and aluminium alloys as
used in the nuclear and aircraft industry are subject to external stresses in different environments. Understanding the growth of an assumed preexisting crack under these conditions is of prime importance to prevent extensive crack propagation and failure of the component. The ongoing research aims to investigate the early stages of ductile fracture, the nucleation, growth and coalescence of microvoids and the evolution of the spatial dislocation distribution. Two commercial Al-alloys, alloys 2024-T351 and 6013-T6 used in the aircraft industry were investigated. Within the above framework, a small region around the crack tip of a 2024-T351 specimen was scanned using a microfocused beam of 5 µm in diameter (Esrf, ID13-Microfocus).
The major improvement lies in the strongly diminsihed influence of grain boundary scattering. Information from fracture toughness tests, from the simulation of the distribution of stresses and strains by means of finite element analysis, from scanning and transmission electron microscopy and positron annihilation microprobe experiments, will support the small angle X-ray scattering investigations.
  • Poster
    Posterbeitrag zur XII. International Conference on Small Angle Scattering, 25.-29.08.2002, Venice, Italy

Publ.-Id: 5229 - Permalink


Small Angle Scattering Research at FZ Rossendorf
van Ouytsel, K.;
Der Vortrag gab ein allgemeines Bild von den Kleinwinkelstreuuntersuchungen, die am FZ Rossendorf, Abt.Material-und Komponentensicherheit durchgeführt werden, ein Bild von den Materialien (Al-Legierungen und RDB-Stähle) und Techniken/Anlagen, die dazu erforscht/angewandt werden.

  • Lecture (others)
    Vortrag an der TU Delft, 31.10.2002, Delft, Niederlande

Publ.-Id: 5228 - Permalink


SAXS near the crack tip in metals
van Ouytsel, K.;
Der Vortrag gab das Ziel des Untersuchungsvorhabens wieder und erteilte allgemeine Informationen über den Stand der Röntgen-Kleinwinkelstreuungsforschung zur Charakterisierung der Rissspitze in Metallen.
  • Lecture (others)
    Vortrag am SCK.CEN, 12. März 2002, Mol, Belgien

Publ.-Id: 5227 - Permalink


Electric Field and Drift Characteristics Studies for the Multiwire Chambers of the Third Plane of HADES
Kanaki, K.; (Editor)
Aim of this report is the investigation of suitable operational conditions for the drif{}t chambers MDC III installed in the HADES setup. The simulations performed showed that operating the drif{}t chambers in a mode with nearly constant electron drif{}t velocity in a predominant part of the cell allows a more precise and fast tracking. This is particularly important for electrons and positrons; here the invariant dilepton mass must be reconstructed with high precision to get a resolution of $\Delta M/M\approx 1\%$ for the $\omega$ and $\phi$ mass peaks and thus a chance to verify also small in-medium mass shif{}ts. This helps to realize the physics program at HADES which focuses on the search for such mass shif{}ts to get insight into the in-medium behaviour of hadrons in dense strongly interacting matter.
Keywords: drift cell, drift chamber, drift velocity, equipotential contours, Garfield simulations, HADES, isochrones, Opera simulations
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-365 Januar 2003

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Publ.-Id: 5226 - Permalink


Die Simulation des Teilentlastungs-Compliance-Verfahrens mittels eines Finite-Element-Programms zur Rissfortschrittsberechnung an einer 3-Punkt-Biegeprobe
Werner, M.;
Das Verhalten einer 3-Punkt-Biegeprobe mit Anriss unter Belastung kann mittels einem Finite-Element-Modell nachgebildet werden. Das Modell ermöglicht die Berücksichtigung von elastisch-plastischem Materialverhalten entsprechend der jeweiligen materialspezifischen nichtlinearen Spannungs-Dehnungs-Kurve, welche mit dem Modell der multilinearen kinematischen Verfestigung (MKIN) umgesetzt wird. Weiterhin gestattet das Modell die Beschreibung der Rollenkinematik beim Biegevorgang. Unter Einbeziehung eines speziellen Damage-Modells für die Beschreibung des Bruchkriteriums ist das Modell in der Lage sowohl den Beginn des Risswachstums als auch den Rissfortschritt wiederzugeben.
Mit diesem Modell lässt sich auch das Teilentlastungs-Compliance-Verfahren nachbilden. Diese Simulation ermöglicht Korrekturansätze zur experimentellen Risslängenbestimmung über die Compliance-Methode.
Keywords: Compliance, Charpy-Probe, Risswachstum, crack extension
  • Poster
    DVM-Tagungsband "Werkstoffprüfung 2002", Wiley-VCH Verlag
  • Contribution to proceedings
    DVM-Tagungsband "Werkstoffprüfung 2002", Wiley-VCH Verlag

Publ.-Id: 5225 - Permalink


Evaluation of Irradiation Embrittlement of Reactor Pressure Vessels (RPV)
Ulbricht, A.; Strunz, P.;
The A533B Cl.1-type RPV steel, designated JRQ, has been used as IAEA reference steel and shows a high sensitivity against radiation embrittlement. Specimens from this material were irradiated to three different levels of neutron fluences. Thus, the investigation allows to realize the dependence of microstructural changes on the fluence and a comparison with results on VVER-type RPV steels, which differ from the Western RPV steel design.
Keywords: SANS radiation embrittlement microstructure
  • Contribution to external collection
    BENSC Experimental Reports 2001, Hahn-Meitner Institut Berlin, HMI-B 584, p. 208, May 2002

Publ.-Id: 5224 - Permalink


Kleinwinkelstreuung - ein vielversprechendes Werkzeug zum Nachweis von Strahlenschäden
Böhmert, J.; Große, M.; Ulbricht, A.;
Durch Bestrahlung mit Neutronen entstehen in Konstruktionswerkstoffen nanoskalige Strukturdefekte, die vielfach mit den hochauflösenden, direkt abbildenden Untersuchungsverfahren nicht oder nicht ausreichend nachweisbar sind. Diese Strukturdefekte führen aber zu einer erhöhten Streuung von Neutronen- und Röntgenstrahlen im Kleinwinkelbereich. Aus der Intensitätsverteilung der Kleinwinkelstreuung lassen sich, wenn vereinfachende Annahmen getroffen werden können oder Vorinformationen vorhanden sind, Größenverteilung und Anzahldichte bestimmen. Darüber hinaus sind Hinweise zum Typ und zur Zusammensetzung der Defekte ableitbar. Das Kleinwinkelstreuverfahren ist effektiv, volumenintegrierend, sensitiv im Größenbereich von ~ 1 nm ... 10 nm und unempfindlich gegenüber Präparationsfehlern. Es ist jedoch eine indirekte Methode der Strukturanalyse und sollte deshalb nicht alternativ, son-dern komplementär angewandt werden. Prozedur und Leistungsfähigkeit des Verfahrens wird am Beispiel von Untersuchungen an bestrahlten Reaktordruckbehälterstäh-len gezeigt.
  • Lecture (others)
    Werkstofftag 2002, TU Dresden, Dresden, 04. 10. 2002, eingeladener Vortrag

Publ.-Id: 5223 - Permalink


The SHIP Experiment at the GDT Facility - Concept and Results of Calculations
Anikeev, A. A.; Bagryansky, P. A.; Ivanov, A. A.; Noack, K.;
At present, the Gas Dynamic Trap (GDT) facility of the Budker Institute Novosibirsk is being upgraded. The first stage of the upgrade is the Synthesized Hot Ion Plasmoid (SHIP) experiment. It aims, on the one hand, at the investigation of plasmas which are expected to appear in the region of high neutron production in a GDT based fusion neutron source proposed by the Budker Institute and, on the other hand, at the investigation of plasmas the parameters of which have never been achieved before in magnetic mirrors. In parallel to experimental research at the GDT an Integrated Transport Code System (ITCS) is under development in collaboration with the Forschungszentrum Rossendorf. It is to calculate the relevant physical effects which are connected with neutral gas, background plasma and with the high-energetic ion component inside the central cell of the GDT and later inside the neutron source.
This contribution explains the concept of the SHIP experiment and presents the results of first calculations by means of ITCS modules.

Keywords: neutron source, fusion technology, mirror plasma facility, gas dynamic trap, material research, high-energetic ions
  • Lecture (Conference)
    4th Int. Conf. on Open Magnetic Systems for Plasma Confinement, July 1-4, Jeju Island, Korea, Proceedings in: Transactions of Fusion Technology, 43 (2003) 78
  • Contribution to external collection
    4th Int. Conf. on Open Magnetic Systems for Plasma Confinement, July 1-4, Jeju Island, Korea, Proceedings in: Transactions of Fusion Technology, 43 (2003) 78

Publ.-Id: 5222 - Permalink


Composition analysis of the insulating barrier in magnetic tunnel junctions by grazing angle of incidence RBS
Wei, P.; Barradas, N. P.; Soares, J. C.; Da Silva, M. F.; Kreissig, U.; Cardoso, S.; Freitas, P. P.;
Spin dependent tunnel junctions (Si/Al2O3/Ta/CoFe/AlNx/CoFe/Ta) were studied with grazing angle of incidence Rutherford backscattering spectrometry experiments using a 1.6 MeV He+ beam. While the sensitivity to light elements is too small to detect the N directly, the thickness and composition of the AlNx insulating barrier can be obtained by carefully simulating the signal of the Al and of two CoFe layers, which can be separated. From the observed Al signal the corresponding energy loss can be calculated, and the extra energy loss required to obtain the observed CoFe layer separation is assigned to the N. Eventual oxidation in the AlNx layer during film deposition can be further identified and quantified by analysing a similar tunnel junction, but deposited on a DLC substrate. A depth resolution of 25 Å at the CoFe layers ensures a highly precise measurement of this complex magnetic system.
Keywords: RBS; Tunnel junction; Insulating barrier; Ultra-thin oxynitrides
  • Nuclear Instruments and Methods B 190 (2002) 684-688

Publ.-Id: 5221 - Permalink


Ion beam studies of MBE grown GaN films on (111) silicon substrates
Alves, E.; Barradas, N. P.; Monteiro, T.; Correia, R.; Kreissig, U.;
GaN epitaxial films were grown on silicon substrates by molecular beam epitaxy under different conditions. Some of the films were doped with the rare earths (RE) Er, Eu or Tm during the growth, and were studied regarding its composition and crystalline quality. The Rutherford backscattering/channelling and heavy ion elastic recoil detection techniques were combined in order to get information on the depth distribution of all the elements present in the films. The results show that the single crystalline quality of the films improves with increasing substrate temperature and Ga flux. For these conditions the Ga concentration is the one expected for a stoichiometric film. A decrease of the Ga flux or increase in the RE cell temperature allows an increase of the concentration of the RE incorporated during the growth. The light impurity present in all the films studied, within our detection limits, was hydrogen. The angular scans along the <0 0 0 1> reveal that a fraction of the RE is incorporated into regular lattice sites of the wurtzite structure of GaN. Moreover, the optical properties of the films correlate well with the crystalline quality and the Eu doped samples show an intense red luminescence at room temperature.
Keywords: GaN epilayers; RE luminescence; RBS/channelling; ERDA
  • Nuclear Instruments and Methods B 188 (2002) 73-77

Publ.-Id: 5220 - Permalink


Experimental and numerical investigation of one and two phase natural convection
Krepper, E.; Prasser, H.-M.;
Experiments were performed to investigate heating up processes of fluids in storage tanks under the influence of an external heat source. Several tests were carried out both with heating from the bottom and with heating from the side walls. The test tank was equipped with thermocouples for measuring the temperature distribution and with needle probes for measuring of the local void fraction.
Calculations were performed using the CFD-code CFX-4. The simulation comprises two phase flow, subcooled boiling at the heated wall and steam release at the tank surface. The paper presents comparisons of measured and calculated temperatures and void fractions. CFX-4 simulations using the implemented boiling model reproduce and explain the observed physical phenomena. Convergence problems occurred with higher vapour volume fractions. As an application measures were investigated, to reduce the temperature stratification. It could be shown, that the insertion of buffle plates reduces and postpones the steam release.
Keywords: Natural convection, heating up, boiling, experiments, CFD simulations
  • Scientific Papers of the Kielce University of Technology, Series Mechanics,Vol. 77, 2003, pp. 33-39

Publ.-Id: 5219 - Permalink


Mechanical properties of thin films in the ternary triangle B-C-N
Linss, V.; Hermann, I.; Schwarzer, N.; Kreissig, U.; Richter, F.;
We report on thin films in the ternary system B–C–N deposited by reactive magnetron sputtering of targets with different B/C ratio in an Ar/N2 gas mixture. First, the proportion of nitrogen in the gas was varied from 0 to 100% with the substrate being at floating potential in order to change the incorporated amount of nitrogen in the films. Secondly, at 50% nitrogen in the gas a negative substrate potential was applied for ion bombardment of the growing film. The film composition was measured by elastic recoil detection analysis. The mechanical properties, Young's modulus and hardness, were determined from nanoindentation measurements. All films were also investigated by Fourier-transformed infrared spectroscopy (FTIR). The mechanical properties show a great variation range in dependence on the film composition (up to a factor of three) and ion bombardment (up to a factor of two), which can be related to the bonding characteristics derived from the FTIR spectra.
Keywords: Reactive magnetron sputtering; BCN; Mechanical properties
  • Surface and Coatings Technology 163-164 (2003) 220-226

Publ.-Id: 5218 - Permalink


Enhanced corrosion resistance of austenitic stainless steel by plasma immersion ion implantation of nitrogen
Pham, M. T.; Ram Mohan Rao, K.; Manna, I.; Richter, E.;
Surface coating on austenitic stainless steel 304 (ASS) was generated by plasma immersion ionimmplantation (PIII) of nitrogen. The corrosion resistance was shown to increase by ca. four orders of magnitude. A barrier layer produced by PIII was observed to restrict the underlaying alloy surface exposed to the corrosion environment.
Keywords: corrosion, stainless steel, surface coating, ion beam treatment
  • Journal of Materials Science Letters 22 (2003) 1099-1100

Publ.-Id: 5217 - Permalink


Strangeness saturation: energy- and system-size dependence
Cleymans, J.; Kämpfer, B.; Steinberg, P.; Wheaton, S.;
Relativistic heavy-ion collisions lead to a final state which has a higher degree of strangeness saturation than those of elementary collisions. A systematic analysis of this phenomenon, based on the strangeness saturation factor, is made for C+C, Si+Si and Pb+Pb collisions at the CERN SPS collider and for Au+Au collisions at RHIC energies. Strangeness saturation is shown to increase with the number of participants within a colliding system, at both CERN SPS and RHIC energies. The saturation observed in central collisions of lighter nuclei deviates from that seen in peripheral collisions of heavier nuclei with an equivalent participant number, which could be due to the difference in nuclear density.
Keywords: relativistic heavy-ion collisions, strangeness, hadron production
  • arXiv:hep-ph/0212335v1

Publ.-Id: 5216 - Permalink


Determination of Structural Parameters for Thorium(IV), Neptunium(IV), Neptunium(V) and Plutonium(III) Humate Complexes by Means of XAFS Spectroscopy
Schmeide, K.; Sachs, S.; Reich, T.; Heise, K. H.; Bernhard, G.;
Structural parameters for the near-neighbor surrounding of Pu(III), Th(IV), Np(IV) and Np(V) in complexes with various natural and synthetic humic and fulvic acids were determined by means of X-ray absorption fine structure (XAFS) spectroscopy. Furthermore, the interaction of the actinides with Bio-Rex70, a cation exchange resin having solely carboxylic groups as metal binding functional groups, was studied to determine structural parameters for the interaction of the respective actinide ions with carboxylic groups. Applying chemically modified humic acids with blocked phenolic/acidic OH groups, the influence of phenolic/acidic OH groups on the complexation of Np(V) by humic acids was studied in the neutral pH range. The structural parameters determined for actinide humate complexes were further compared with structural parameters of aqueous ions of the actinides and of solid actinide carboxylates given in the literature. The results indicate that the interaction between the actinide ions and humic acid is dominated by humic acid carboxylate groups. These carboxylate groups act predominantly as monodentate ligands. A contribution of phenolic/acidic OH groups to the complexation of Np(V) by humic acids at pH 7 cannot completely be excluded by EXAFS analysis.
Keywords: Thorium(IV), Neptunium(IV), Neptunium(V), Plutonium(III), Humic acid, Fulvic acid, EXAFS, XANES, Complexation, tetravalent
  • Contribution to external collection
    FZKA 6800, Wissenschaftliche Berichte, Forschungszentrum Karlsruhe, Karlsruhe 2003, S. 65-77.

Publ.-Id: 5215 - Permalink


Elastic modulus-density relationship for amorphous boron suboxide thin films
Music, D.; Kreissig, U.; Czigany, Z.; Helmersson, U.; Schneider, J. M.;
Boron suboxide thin films have been deposited on Si(100) substrates by reactive RF magnetron sputtering of a sintered B target in an Ar/O2 atmosphere. Elastic recoil detection analysis was applied to determine the film composition and density. Film structure was studied by X-ray diffraction and transmission electron microscopy. The elastic modulus, measured by nanoindentation, was found to decrease as the film density decreased. The relationship was affected by tuning the negative substrate bias potential and the substrate temperature during film growth. A decrease in film density, by a factor of 1.55, caused an elastic modulus reduction by a factor of 4.5, most likely due to formation of nano-pores containing Ar. It appears evident that the large scattering in the published data on elastic properties of films with identical chemical composition can readily be understood by density variations. These results are important for understanding the elastic properties of boron suboxide, but may also be qualitatively relevant for other B-based material systems.
  • Applied Physics A76 (2003) 269-271

Publ.-Id: 5214 - Permalink


Factors affecting an efficient sealing of porous low-k dielectrics by physical vapor deposition Ta(N) thin films
Iacopi, F.; Tökei, Z.; Le, Q. T.; Shamiryan, D.; Conard, T.; Brijs, B.; Kreissig, U.; van Hove, M.; Maex, K.;
The deposition of homogeneous thin films on porous substrates has been investigated. The thin film deposition of Ta(N) by physical vapor deposition on porous films with different average pore sizes and material compositions has been studied. The continuity of Ta(N) films on top of porous low-k dielectrics is evaluated by means of ellipsometric porosimetry combined with sheet resistance and atomic force microscopy measurements. Interface reactions are analyzed by x-ray photoelectron spectroscopy profiling. It has been observed that the minimal Ta(N) thickness required to obtain a continuous metal layer on top of the porous film depends, on the one hand, on the porosity and pore size and, on the other hand, on the chemical interaction of the thin film with the porous substrate. The sealing of pores is favored by the presence of carbon in the dielectric matrix. This is explained through a mechanism of local enhancement of the degree of crosslinking in the dielectric matrix, catalyzed by Ta.
  • Journal of Applied Physics 92 (2002) 1548

Publ.-Id: 5213 - Permalink


Sputterionenquelle
Friedrich, M.; Tyrroff, H.;
Der Erfindung liegt die Aufgabe zugrunde, die Lebensdauer einer Sputterionenquelle zu erhöhen, den Wartungsaufwand zu senken und die Zerstäubung der Teile der Ionenquelle, welche sich in der Nähe des für die Erzeugung der negativen Ionen erforderlichen Kathodeneinsatzes befinden, weitgehend zu verhindern.
Die Erfindung geht aus von den Bauteilen Ionisierer (2), Kathode (3), Sputtereinsatz (4), Formierungselektrode (5), Abschirmkappe (6) und Kathodenisolator (7) in einem vakuumdichten Gehäuse.
  • Patent
    Patentanmeldung 102 41 252.9
  • Patent
    DE 102 41 252 B4
  • Patent
    EP 1 396 870 A3

Publ.-Id: 5211 - Permalink


Verfahren zur Reinigung von Wasser mit hohen Uran-Konzentrationen
Walter, M.; Arnold, T.;
Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zu entwickeln, dass Uran(VI) aus stark belasteten bergbaulichen Abwässern, Haldensicker-, und kontaminierten Grundwässern kostengünstig und umweltfreundlich in großen Mengen entfernt, wobei zur Uranfixierung ein Barrierematerial eingesetzt werden soll, das eine Beschaffenheit aufweist, die eine langzeitstabile, sichere Endlagerung oder Wiedergewinnung des angereicherten Urans ermöglicht.
Die technische Lösung geht davon aus, dass das Uran(VI) überwiegend als Karbonat, Sulfat oder Hydroxy-Komplex vorliegt und elementspezifische Filtermaterialien in einer geochemischen Barriere eingesetzt werden.
  • Patent
    Patentanmeldung 102 38 957.8
  • Patent
    DE 102 38 957 A!

Publ.-Id: 5210 - Permalink


Verfahren zur tomographischen Bildrekonstruktion für ein aus zwei asynchron rotierenden komponeneten bestehendes Objekt
Hoppe, D.;
Die Erfindung betrifft ein Verfahren zur tomographischen Bildrekonstruktion für ein aus zwei asynchron rotierenden Komponenten bestehendes Objekt, wobei an einzelnen Drehwinkelpositionen der Objektkomponenten tomographische Projektionen vorgenommen werden.
Der Erfindung liegt die Aufgabe zugrunde, die beiden mit unterschiedlichen Winkelgeschwindigkeiten gegenüber ihrer Umgebung rotierenden Teilobjekte mit Hilfe eines Tomographen richtig abzubilden.
  • Patent
    Patentanmeldung 102 08 284.7
  • Patent
    DE-OS 102 38 540 A1

Publ.-Id: 5207 - Permalink


Bioaktives Material und Verfahren zu dessen Herstellung
Pham, M. T.; Maitz, M. F.;
Die Erfindung betrifft ein bioaktives Material sowie ein Verfahren zu dessen Herstellung. Potentielle Anwendungen sind medizinische Implantologie, Gewebezüchtung und Biotechnologie. Der Erfindung liegt ein von einer Schicht zellausgeschiedener Produkte umgebenes Festkörpermaterial zugrunde.
Der Erfindung liegt die Aufgabe zugrunde, ein Material für Anwendungen in medizinischer Implantologie, Gewebezüchtung und Biotechnologie zu schaffen, bei welchem die Oberfläche für eine breite Klasse von Festkörpermaterialien bei Kontakt mit zellulären Medien zellbiologisch spezifische Wechselwirkungen aktiv vermittelt. Der Erfindung obliegt auch die Aufgabe, ein anwendungswirksames Verfahren zur Herstellung des genannten bioaktiven Materials vorzuschlagen.
  • Patent
    Patentanmeldung 102 05 846.6
  • Patent
    DE 102 05 846 A1

Publ.-Id: 5206 - Permalink


P0111 - Biokompositmaterial
Selenska-Pobell, S.; Soltmann, U.; Raff, J.; Böttger, H.; Kallies, K.-H.; Quast, H.; Matys, S.;
Das Biokompositmaterial enthält ein anorganisches Gel und darin homogen verteilte, trocknungsstabile Zellprodukte wie Sporen, Zellwand-Proteine oder abgetötete Zellen. Das Biokompositmaterial ist als Biofilter in der Umwelttechnik zur Entfernung von Schwermetallionen aus wässrigen Lösungen geeignet.
  • Patent
    DE 101 46 375 B4 - 01. Okt. 2009
  • Patent
    DE 101 46 375 A 1

Publ.-Id: 5205 - Permalink


Influence of melt convection on the microstructure of levitated and undercooled Nd-Fe-B alloys
Fillip, O.; Hermann, R.; Gerbeth, G.; Priede, J.; Shatrov, V.; Güth, A.; Schultz, L.;
The influence of melt rotation on the microstructure formation of Nd-Fe-B alloys, mainly the volume fraction and grain size of the a-Fe phase, has been investigated using the electromagnetic levitation technique which allows the in-situ measurement of the solidification kinetics containerlessly. Samples were subjected to a strong rotation during levitation and compared to fixed samples without additional sample rotation in the levitation facility. Additionally, experiments have been carried out where specially sealed samples were subjected to a well-defined forced rotation. A distinct reduction of the a-Fe volume fraction in samples with strong rotation was observed by measuring the magnetic moment in a vibrating sample magnetometer (VSM). The influence of cooling rate and undercooling level on microstructure formation and phase distribution has been investigated as well. The melt flow in a levitated droplet is studied numerically under the additional effect of a global sample rotation which may give a strong suppression of internal motions.
  • Lecture (Conference)
    „Int. Conference on Magnetism“, Rom, Juli 2003
  • Journal of Magnetism and Magnetic Materials 272-276(2004)Suppl. 1, 1857-1858

Publ.-Id: 5203 - Permalink


Microstructure evolution of Nd-Fe-B alloys in consideration of magnetohydrodynamics
Hermann, R.; Filip, O.; Gerbeth, G.; Priede, J.; Schultz, L.;
The solidification process and the resulting microstructure of Nd-Fe-B alloys in consideration of melt convection has been investigated experimentally with a specially designed floating-zone arrangement. A controlled influence on the melt flow is possible via tailored magnetic fields which enable enhancement or suppression of the melt convection. A specially designed magnetic two-phase stirrer offers a strong influence on the melt flow in the floating-zone facility. As a result, the microstructure pattern, mainly the volume fraction and grain size of the a-Fe phase, vary strongly with the strength of the internal flow motion. The melt flow is studied numerically under the additional effect of the two-phase stirrer taking into account the coupled heat and fluid flow fields. The electromagnetically driven flow during the inductive heating turned out to be of strong influence on the resulting microstructure.
  • Lecture (Conference)
    „Int. Conference on Magnetism“, Rom, Juli 2003
  • Journal of Magnetism and Magnetic Materials 272-276(2004)Suppl. 1, 1855-1856

Publ.-Id: 5202 - Permalink


CFD simulation of a bubbly flow experiment with liquid PbBi eutectic alloy and Nitrogen
Mercurio, G.; Eckert, S.;
This study was carried out in the frame of the ADS European project aimed to the development of Accelerator Driven System technology for nuclear waste transmutation.
The scope is to verify the possibility to simulate a two phase HLM (Heavy Liquid Metal) bubbly flow using the commercial CFD code CFX4.4.
The first stage consisted of an experimental campaign for the measurement of the phase velocities by means of the ultrasound Doppler velocimetry (UDV) and local volume fractions using resistive probes. The eutectic alloy PbBi is located inside a cylindrical container made of stainless steel which is provided with an electrical heater. The measurements reported here were carried out at a fluid temperature of 180°C. Nitrogen (N2) gas was injected into the stagnant liquid metal by means of a single orifice with an inner diameter of 0.5 mm. The orifice is located in the centre of the cross-sectional area of the fluid container. The gas flow rate chosen for these experiments was restricted to values below 1.2 cm3/s in order to guarantee a single bubble flow regime.
The simulation of the experiment was performed using the two fluid Euler/Euler model of CFX-4.4. The implemented drag laws were tested and compared with other drag laws taken from literature. The influence of the "non-drag forces" like the turbulent dispersion force and the lift force was also tested. Finally an advanced interpolation method based on optimization techniques was adopted in order to get the best fitting of the simulated velocity curves with the experimental ones. The results shows in general a good qualitative agreement of the experiment and the calculations, but a much better agreement can be found using the drag law coefficients derived by the above mentioned optimization technique, especially in the cases where the mass flow rates and the bubble mean diameters are relatively small.

Keywords: two-phase flow, gas bubbles, heavy liquid metals, drag force, velocity measurements, UDV technique
  • Lecture (Conference)
    Computational Methods in Multiphase Flow II, A.A.Mammoli, C.A.Brebbia (Eds.), WIT Press 2004, Southampton pp.395-404, (Proc. of the Second International Conference on Computational Methods in Multiphase Flow, Santa Fe, New Mexico, USA, 2003)
  • Contribution to proceedings
    Computational Methods in Multiphase Flow II, A.A.Mammoli, C.A.Brebbia (Eds.), WIT Press 2004, Southampton pp.395-404, (Proc. of the Second International Conference on Computational Methods in Multiphase Flow, Santa Fe, New Mexico, USA, 2003)

Publ.-Id: 5201 - Permalink


Berechnung des Notkondensators des argentinischen Integralreaktors CAREM
Schaffrath, A.; Walter, D.; Delmastro, D.; Giménez, M.; Zanocco, P.;
In Argentinien wird das Integralreaktorkonzept CAREM als alternativer Einstieg in die Kerntechnik - speziell für Länder der dritten Welt - entwickelt. Diese sammelten bislang in der Regel ihre ersten Erfahrungen in der Nukleartechnik mit Forschungsreaktoren. Das beim Betrieb der Forschungsreaktoren gesammelte Wissen ist jedoch zu speziell und nicht umfassend genug, um hiermit allein Leistungsreaktoren betreiben zu können. Da das CAREM Konzept sämtliche in großen Leistungsreaktoren vorkommende Systeme beinhaltet, können mit dem CAREM Reaktor bei vergleichsweise ähnlichen - wenn nicht sogar niedrigeren - Kosten wie bei Forschungsreaktoren sämtliche zum Betrieb mittlerer und großer Reaktoren notwendigen Systemkenntnisse erworben werden.
Keywords: ATHLET, CAREM, KONWAR, Notkondensator
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2003, 2003 Tagungsband S. 501 - 506, Inforum Verlag, ISSN 0720-9207
  • atw Internationale Zeitschrift für Kernenergie 48 (2003), Nr. 2, S. 111-115

Publ.-Id: 5199 - Permalink


Tera-Hertz Radiation in Biological Research, Investigation on Diagnostics and Study on Potential Genotoxic Effects
Seidel, W.; Fahmy, K.; Furlinski, G.; Gippner, P.; Grosse, E.; Piest, H.; Sczepan, M.; Wohlfarth, D.; Wolf, A.; Wünsch, R.;
The radiation source ELBE at Dresden-Rossendorf is centered around a superconducting ELectron accelerator of high Brillance and low Emittance (ELBE) which produces electron beams up tu 40 MeV. This new facility delivers secondary radiation of diffrent kinds. Special emphasis will be given to the production of intense THz radiation from its Free-Electron-Lasers (FEL). This radiation will be used for various research activities including the life sciences. Two additional femtosecond Ti:sapphire lase system allow to exploid different methods of THz generation for such investigatin.
  • Poster
    Proc. Of the THZ-BRIDGE Workshop, Capri Italy Sept 2002
  • Contribution to proceedings
    Proc. Of the THZ-BRIDGE Workshop, Capri Italy Sept 2002

Publ.-Id: 5198 - Permalink


RBS and HIRBS studies of nanostructured AgSiO2 sol–gel thin coatings
Kokkoris, M.; Trapalis, C. C.; Kossionides, S.; Vlastou, R.; Nsoulid, B.; Grötzschel, R.; Spartalis, S.; Kordas, G.;
In the present work, composite AgSiO2 thin coatings, containing metal nanoparticles, were prepared on glass substrates by the sol–gel route. The coatings were thermally treated in oxidative and reductive conditions up to 500 °C for metal nanoparticle formation. The coating structure and the nanoparticle formation were studied by atomic force microscopy and Rutherford backscattering spectroscopy (RBS) techniques. In the case of RBS, 1.4 MeV 4He+ ions were used for all samples, and low energy 16O and 12C ions in selected ones (heavy ion RBS, HIRBS), in order to improve the depth resolution for the profiling of the metal component. The antibacterial activity against Escherichia coli is examined by antibacterial drop test. The coatings exhibited a high antibacterial activity, which was enhanced with the increase of the metal concentration and was reduced with the increase of the particle size of the metal nanoparticles. The possible correlation between the layer interdiffusion after the thermal treatment and the antibacterial activity is examined and analyzed. Although further studies are required, RBS and HIRBS seem to be excellent tools for the quality control in the production of sol–gel thin coatings.
Keywords: Rutherford backscattering spectroscopy; Heavy ion Rutherford backscattering spectroscopy; Sol–gel; Antibacterial; XRD; Thin coatings
  • Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Volume 188 , April 2002, 67-72

Publ.-Id: 5197 - Permalink


Post-Test Calculations of Medium Scaled Pressure Vessel Creep Failure Experiments
Willschütz, H.-G.; Altstadt, E.; Weiss, F.-P.; Sehgal, B. R.;
For the calculation of experiments simulating the behavior of the lower head in a core melt down scenario like FOREVER (performed at the Royal Institute of Technology, Stockholm) it is necessary to model the melt pool convection and the temperature field within the vessel as well as creep and plasticity processes. Therefore a 2D Finite Element Model is developed based on the code ANSYS®. The CFD module is used to calculate the thermodynamics. The resulting temperature field of the vessel wall is applied to the mechanical model. To describe the visco-plastic deformation 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. In this way the use of a single creep law, which employs constants derived from the data for a limited stress and temperature range, is avoided. For an evaluation of the failure times a damage model according to an approach of Lemaitre is applied.
After post-test calculations for the FOREVER-C2 experiment, pre-test calculations for the forthcoming experiments are performed. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios. After analyzing the results of the calculations, it seems to be advantageous to provide a vessel support, which can unburden the vessel from a part of the mechanical load and, therefore, avoid the vessel failure or at least prolong the time to failure. This can be a possible accident mitigation strategy. Additionally, it may be advantageous to install a passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in the event of a core melt down.
Keywords: core melt down accident, lower head behavior of the RPV, Finite Element Method, creep and damage modeling
  • Lecture (Conference)
    2003 International Congress on Advances in Nuclear Power Plants ICAPP '03 May 4-7, 2003; Congress Palais, Córdoba, SPAIN, Proceedings on CD
  • Contribution to proceedings
    2003 International Congress on Advances in Nuclear Power Plants ICAPP '03 May 4-7, 2003; Congress Palais, Córdoba, SPAIN, Proceedings on CD

Publ.-Id: 5196 - Permalink


Modulated CNx films prepared by IBAD
Safran, G.; Kolitsch, A.; Malhouitre, S.; Trasobares, S.; Kovacs, I.; Geszti, O.; Menyhard, M.; Colliex, C.; Radnoczi, G.;
CNx thin films have been prepared by IBAD varying the C-atom to N-ion ratio during deposition. The layers were studied by means of TEM and EELS investigation, ERDA and AES depth profiling. The obtained films were amorphous. The incorporation probality of N into the films was found to depend on the C/N arrival ratio. Large amount of N incorporation was found above and small amount below a N/C arrival rate of 0.3. Due to intentional change in the N/C arrival rate, modulated structures have been produced. The N concentration in the individual layers of modulated samples was found to exhibit distinct values of approximately 5 and 20 at.%. The erosion rate of the various CNx layers upon Ar ion bombardment depends on their N content. The relative erosion rate of the samples containing nitrogen of 20 and 5at.% was found to be r(rel)=1.6. It was determined by XTEM and EELS that the origin of the TEM image contrast marking out the individual sublayers is mainly due to density variations in the modulated structure and partly due to thickness differences of the cross sectional TEM samples as a result of Ar ion milling of layers of various compositions
Keywords: carbon-nitride, ion assited deposition, sputter erosion rate
  • Diamond and Related Materials 11 (2002) 1552-1559

Publ.-Id: 5195 - Permalink


Relativistic effects in proton-induced deuteron break-up at intermediate energies with forward emission of a fast proton pair
Kaptarii, L. P.; Kämpfer, B.; Semikh, S. S.; Dorkin, S. M.;
Recent data on the reaction pD -> (pp) n with a fast forward pp pair with very small excitation energy is analyzed within a covariant approach based on the Bethe-Salpeter formalism. It is demonstrated that the minimum non-relativistic amplitude is completely masked by relativistic effects, such as Lorentz boost and the negative-energy P components in the 1S0 Bethe-Salpeter amplitude of the pp pair.
Keywords: deuteron break-up, Bethe-Salpeter formalism

Publ.-Id: 5194 - Permalink


Anwendung des Master-Curve-Konzeptes zur Zähigkeitscharakterisierung von Druckbehälterstählen
Viehrig, H.-W.; Böhmert, J.;
Das „Master-Curve“ (MC)-Konzept nach Wallin empfiehlt sich als ein geeignetes Werkzeug zur bruchmechanischen Sprödbruchsicherheitsbewertung von Komponenten und Anlagen. Es hat mit dem ASTM Standard E 1921 bereits Eingang in die Regelwerke gefunden und steht unmittelbar vor einer breiteren internationalen Anwendung. MC-Referenztemperaturen T0 werden an russischern WWER-Druckbehälterstählen im un- und bestrahlten Zustand ermittelt und mit am gleichen Material gemessenen Charpy-V-Übergangstemperaturen TT verglichen. Die unterschiedliche Zähigkeit der verschiedenen Stähle lässt sich ebenso wie der Einfluss der Bestrahlung mit dem MC-Konzept nachweisen. T0 und TT zeigen eine gute Korrelation, wobei die T0 ca. 80 K niedriger liegen. Damit erniedrigen sich auch die Referenztemperaturen für die Reaktordruckbehälter Integritätsbewertung.
Keywords: Bruchzähigkeit, Master Curve, Referenztemperatur, Reaktordruckbehälter, Sprödbruchsicherheit
  • Lecture (Conference)
    Tagungsband der 35. Tagung des DVM-Arbeitskreises Bruchvorgänge, Fortschritte in der Bruch- und Schädigungsmechanik, 18. und 19. Februar 2003, Freiburg, S. 81 - 90
  • Contribution to proceedings
    Tagungsband der 35. Tagung des DVM-Arbeitskreises Bruchvorgänge, Fortschritte in der Bruch- und Schädigungsmechanik, 18. und 19. Februar 2003, Freiburg, S. 81 - 90

Publ.-Id: 5193 - Permalink


Krein space features of the MHD alpha² - dynamo operator matrix
Günther, U.;
The spherical MHD mean-field dynamo is considered from a mathematical viewpoint. It is shown that its 2x2 operator matrix is formally pseudo-Hermitian (J-symmetric), lives in a Krein space and has paired complex eigenvalues. 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 alpha²-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 alpha²-dynamo operator classes with the help of first-order differential intertwining operators.
  • Poster
    5. MHD-Tage, Forschungszentrum Rossendorf, 25-26. 11. 2002

Publ.-Id: 5192 - Permalink


Zusammenhang zwischen klinischen und neuropsychologischen Parametern und der regionalen Hirnfunktion bei der Major Depression
Triemer, A.; Lüdecke, S.; Beuthien-Baumann, B.; Zündorf, G.; Schwellong, J.; Spirling, S.; Felber, W.; Holthoff, V. A.;
  • Poster
    Kongress der Deutschen Gesellschaft für Psychiatrie und Nervenheilkunde, Berlin, 27.-30.11.2002
  • Abstract in refereed journal
    Nervenarzt 73(Suppl.1) (2002) S129

Publ.-Id: 5190 - Permalink


Major Depression: Regionale Hirnfunktion in Abhängigkeit vom Erkrankungsstadium
Lüdecke, S.; Beuthien-Baumann, B.; Zündorf, G.; Triemer, A.; Schellong, J.; Felber, W.; Holthoff, V. A.;
  • Poster
    Deutsche Gesellschaft für Psychiatrie und Nervenheilkunde Kongress, Berlin, 27.-30.11.2002
  • Abstract in refereed journal
    Nervenarzt 73 (Suppl.1) (2002) S129

Publ.-Id: 5189 - Permalink


Zerebrale Korrelate psychischer Symptome bei der frühen Demenz vom Alzheimertyp
Spirling, S.; Beuthien-Baumann, B.; Lüdecke, S.; Schellong, J.; Felber, W.; Holthoff, V. A.;
  • Poster
    Kongress der Deutschen Gesellschaft für Psychiatrie und Nervenheilkunde, Berlin, 27.-30.11.2002
  • Abstract in refereed journal
    Nervenarzt 73(Suppl.1) (2002) S128

Publ.-Id: 5188 - Permalink


Sarkoidose fünf Jahre nach Morbus Hodgkin
Bickhardt, J.; Gronke, K.; Beuthien-Baumann, B.; Aßmann, M.; Rolle, A.; Matthiesen, A. S.;
  • Poster
    43. Jahrestagung der Deutschen Gesellschaft für Pneumologie 2002 in Bochum
  • Abstract in refereed journal
    Pneumologie 56 (2002) 104

Publ.-Id: 5187 - Permalink


Glukosestoffwechsel, Intratumoraler pO2 und Tumorperfusion bei inoperablen Kopf-Hals-Tumoren vor Strahlentherapie
Beuthien-Baumann, B.; Appold, S.; Kittner, T.; Hietschold, V.; Baumann, M.;
Ziel/Aim: Prospektive Erfassung von Daten zur Charakterisierung des intratumoralen Mikromilieus mittels FDG-PET, interstitieller Messung des Sauerstoffpartialdruckes und MRT-Untersuchung der Tumorperfusion vor radikaler Radio- bzw. Radiochemotherapie und Evaluierung der prognostischen Wertigkeit der Parameter.

Methodik/Methods: 14 Patienten mit inoperablen Kopf-Hals-Tumoren (UICC Stadium IV) wurden untersucht. Der intratumorale p02-Gehalt wurde mit einer Eppendorf-Sonde polarographisch gemessen. Die Tumorperfusionsmessung wurde im MRT (1.5 T Siemens Vision mit Kopf-Hals-Spule) durch den gemessenen Signalverlust bei Kontrastmittel-Bolus-Passage ermittelt. Ferner wurden die Tumorvolumina im MRT bestimmt. Als Maß des Glukosestoffwechsels wurde der mittlere Standard uptake value (SUVmean) der Tumorregion im FDG-PET bestimmt (300 MBq 18F-FDG i.v., ECAT EXACT HR+, Siemens/CTI).

Ergebnisse/Results: Die Tumorvolumina reichten von 14 bis 220 cm3 (median 74 cm3). Die SUVmean betrugen im Median 9,7 und waren bis auf in einem Turnor deutlich erhöht (range 2,9 -12,0). Die medianen pO2-Werte der individuellen Tumoren zeigten eine weite Variabilität (range 0,1 - 33,1 mm Hg), der Median der Gruppe betrug 7,5 mm Hg. Korrelationsanalysen ergaben R2-Werten von 0,25 für Tumorvolumen versus pO2, 0,15 für SUVmean versus pO2, 0,13 für Perfusion versus pO2, 0,06 für SUVmean versus Tumorvolumen und 0,03 für Perfusion versus Tumorvolumen.

Schlussfolgerungen/Consequences: Die nicht vorhandenen bzw. sehr schwachen Korrelationen zwischen den gemessenen Parametern deuten an, dass mit den unterschiedlichen Messmethoden verschiedene Charakteristika des Tumormikromilieus erfasst werden und dass diese sich daher evtl. prognostisch ergänzen könnten. Die nur sehr schwache Korrelation zwischen Glukoseaufnahme und interstitiell gemessenem pO2 des Tumors weist darauf hin, dass neben anaerober Glykolyse weitere Faktoren die Zuckeraufnahme des Tumors beeinflussen. Derzeit werden weitere Patienten in diese Untersuchung aufgenommen und das Follow-up ergänzt, um die prognostische Relevanz der verschiedenen Messergebnisse, ggf. auch in Kombination, auf die Tumorkontrolle nach Strahlentherapie zu prüfen.
  • Lecture (Conference)
    40. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, Freiburg, 10.-13.04.2002
  • Abstract in refereed journal
    Nuklearmedizin 41 (2002) V173

Publ.-Id: 5186 - Permalink


Properties and planned use of the intense THz radiation from ELBE at Dresden-Rossendorf
Fahmy, K.; Furlinski, G.; Gippner, P.; Grosse, E.; Seidel, W.; Sczepan, M.; Wohlfahrt, D.; Wolf, A.; Wünsch, R.;
The radiation source ELBE at Dresden Rossendorf is centered around a superconducting ELectron accelerator of high Brilliance and low Emittance (ELBE) which produces electron beams up to 40 MeV. This new facility delivers secondary radiation of different kinds. Special emphasis will be given to the production of intense THz radiation form its Free-Electron Lasers (FEL). This radiation will be used for various research activities including the life sciences. Two additional femtosecond Ti:sapphire laser systems allow to exploit different methods of THz generation for such investigations
Keywords: THz-radiation, free-electron laser, dynamics in biomolecules, IR-beam diagnostic
  • Journal of Biological Physics 29:303 -307, 2003
  • Poster
    THz-Bridge Workshop, 29.09.-01.10.2002, Capri, Italy

Publ.-Id: 5185 - Permalink


In-medium spectral change of omega meson as a probe of QCD four-quark condensate
Zschocke, S.; Pavlenko, O. P.; Kämpfer, B.;
Within QCD sum rules at finite baryon density we show the crucial role of four-quark condensates, such as ‹(overline{q} γμλaq)2n, for the in-medium modification of the ωmeson spectral function. In particular, such a global property as the sign of the in-medium omega meson mass shift is found to be governed by a parameter which describes the strength of the density dependence of the four-quark condensate beyond mean-field approximation.
To study self-consistently the broadening of the omega meson resonance we employ a hadron spectral function based on the omega meson propagator delivered by a effective chiral Lagrangian. Measurements of the ωmeson spectral change in heavy-ion collisions with the HADES detector can reveal the yet unknown density dependence of the four-quark condensate.
Keywords: in-medium properties of hadrons, QCD sum rules, spectral function

Publ.-Id: 5184 - Permalink


THz radiation from free electron lasers and its potential for cell and tissue studies
Grosse, E.;
Free electron lasers (FELs) allow the generation of electromagnetic radiation (EM) in a wide field of frequencies (respectively wavelengths) throug the proper adjustment of energy of an electron beam and the field configuration of a magnetic undulator passed by this beam. Terahertz (THz) radiation covers the region of the electromagnetic spectrum between approximately 0.3 and 30 THz and thus can be considered a continuation of the optical spectrum beyond the far infrared (IR). The very interesting results obtained from various studies ot the interaction between IR radiation and biomolecules or tissue have stimulated increasing interest in the study of biological systems using THz radiation. This paper points out what role modern FELs can play in this research.
  • Phys, Med. Biol. 47 (2002) 3755-3760

Publ.-Id: 5183 - Permalink


Simulation of relaxation processes in amorphous carbon films
Belov, A.; Jäger, H.-U.;
The atomic mechanisms of relaxation processes in carbon films during ion beam deposition and post-deposition annealing are studied using the method of molecular-dynamics with a modified hydrocarbon potential of Brenner. Deposition of films was simulated for ion energies Eion=10-80 eV and for substrate temperatures Ts=100-900 K. Using a time-resolved analysis of atomic trajectories from the film deposition simulations, a short-term temperature-dependent relaxation stage (t~70-1000 fs), where the film formation is influenced by Ts, was identified. During this stage, depending on Ts, the carbon atoms at metastable four- or fivefold coordinated sites can relax into either three- or fourfold positions, giving rise to graphitic or tetrahedral (ta-C) amorphous carbon films, respectively. In agreement with experiment the simulations predict a sharp transition from ta-C to graphitic carbon as Ts exceeds a critical temperature Tc. Simulating post-deposition annealing, low-temperature structural relaxation of as-deposited ta-C was observed as evidenced by a reduction of potential energy and grown-in stress. The corresponding amorphous network rearrangements consist both in the sp3-to-sp2 conversion and in the
sp2-to-sp3 one. A nearly complete stress relief in ta-C with the sp3 content of ~80% and grown-in compressive stress of 11 GPa was simulated at an annealing temperature of ~1000 K.
Keywords: Ion beam deposition, structural relaxation, tetahedral amorphous carbon
  • Lecture (Conference)
    Annual Spring Meeting of the German Physical Society, Dresden, March 23-28, 2003

Publ.-Id: 5182 - Permalink


Trapping of negative and positive charges in Ge+ ion implanted silicon dioxide layers subjected to high-field electron injection
Nazarov, A.; Gebel, T.; Rebohle, L.; Skorupa, W.; Osiyuk, I.; Lysenko, V.;
Negative and positive charge trapping under constant current regime of high-field electron injection both from Al electrode and Si substrate in high-dose Ge+ ion implanted and then rapid thermal annealed thin-film dioxide has been studied. The negatively charged traps with >10-14 cm2, 1.8x10-15 cm2, 2x10-16 cm2 and 3x10-18 cm2 and generated positive charge with effective capture cross-section (5-7)x10-15 cm2 and 3.3x10-16 cm2 have been shown to be introduced into the oxide layer. A good correlation of the electron trap concentration with with a cross section of >10-14 cm2 and the concentration of the implanted Ge atoms, determined by RBS technique inside the oxide, have been observed. The decrease of Ge concentration within the oxide layer with increasing RTA duration have been associated with Ge atom outdiffision from the oxide at high-temperature annealing. The generated positive charge have been shown to be collected near the SiO2/Si interface during the high field electron injection, both from the Al and Si side. Correlation of the generated positive charge with the Ge atoms embedded in the SiO2/Si interface have been observed. The anode hole injection mechanism is suggested to be responsible for the observed generation of the positive charge.
Keywords: charge carrier trapping, nanocluster, germanium implantation, high-field electron injection, silicon based light emission, silicon dioxide layers
  • Journal Applied Physics 94 (7): 4440-4448 OCT 1 2003

Publ.-Id: 5181 - Permalink


Intersubband Absorption Saturation in InGaAs-AlAsSb Quantum Wells
Gopal, A. V.; Yoshida, H.; Neogi, A.; Georgiev, N.; Mozume, T.; Simoyama, T.; Wada, O.; Ishikawa, H.;
For realizing futuristic optical communications networks with greater than 100Gb/s transmission capability, highly efficient, ultra-fast all-optical devices are crucial at communication wavelengths (<2 mm). Such devices can be realized by making use of the large and fast intersubband transition (ISBT) non-linearity. However, for achieving ISBTs in the communication wavelength region, one requires a large conduction-band offset material. We reported the possibility of one of the crucial all-optical device, all-optical switch, based on ISBT absorption saturation, operating in the < 2 mm wavelength range using InGaAs-AlAsSb quantum well structures. The efficiency of such a device is defined in terms of the switching response time and the switching energy. While the relaxation time related to the switching response time can be estimated from a direct pump-probe measurement, estimation of the saturation intensity related to the switching energy is not that straightforward. In this work, we carry out a detailed study to estimate the saturation current in Sb-based quantum wells
Keywords: all-optical switch, antimony-based quantum wells, intersubband transitions, saturation intensity
  • IEEE Jornal of Quantum Electronics 38 (2002) 1515-1520

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Publ.-Id: 5180 - Permalink


Umweltgerechte Prozessführung und Zustandserkennung in Chemieanlagen: Teilvorhaben 1: Entwicklung und Validierung von Zustandserkennungswerkzeugen, Teilvorhaben2: Konzipierung und Erprobung des Zustandserkennungsverfahrens
Neumann, J.; Schwarze-Benning, K.; Wack, T.; Deerberg, G.; Schlüter, S.; Hessel, G.; Heidrich, J.; Hilpert, R.; Kryk, H.; Roth, M.; Schmitt, W.; Seiler, T.; Weiß, F.-P.;
Nach dem heutigen Stand der Technik wird zur Produktion in Batch-Chemieanlagen der Anlagenstatus im Betrieb vom Anlagenbediener beurteilt. Dies setzt ein hohes Maß an Erfahrungen voraus. Dennoch kommt es zu Fehlproduktionen, die umweltrelevante Entsorgungs- und Nachbearbeitungsaufwände verursachen. Durch eine Zusammenführung aller verfügbaren Informationen und durch deren Verdichtung soll dem Bediener eine Unterstützung bei der Beurteilung des Prozessablaufes gegeben werden, so dass Fehlproduktionen frühzeitig erkannt und vermieden werden können.
Im Teilvorhaben 1 wurden verschiedene Methoden zur Zustandsüberwachung durch neuronale Netze hinsichtlich ihrer Anwendbarkeit anhand von Technikumsversuchen für eine homogene exotherme Veresterungsreaktion geprüft. Hier zeigte sich, dass sowohl die Zustandsbeurteilung als auch die Prognose mit neuronalen Netzen vielversprechende Ansätze liefern. Hierzu ist allerdings ein hohes Maß an Systemwissen in Vorverarbeitungsstufen zu integrieren.
Im Teilvorhaben 2 wurde ein Online-Monitoring-System (MoSys) entwickelt, das auf dimensionslosen Stoff- und Wärmebilanzen mit adaptiven Komponenten basiert. MoSys muss zuerst mit den Prozessdaten von normalen und unerwünschten Batch-Verläufen angelernt werden, die im Miniplant unter den Bedingungen des Industrieprozesses durchgeführt wurden. Die Adaption der Bilanzmodelle an die Zielanlage erfolgt durch zweischichtige Perceptron-Netze. Um eine vollständige Maßstabsübertragung zu gewährleisten, sollte MoSys mit Prozessdaten von mindestens einem normalen Batch-Verlauf in der Chemieanlage angepasst und validiert werden. MoSys wurde sowohl für eine homogene exotherme Veresterungsreaktion als auch für einen komplexen heterogenen exothermen Hydrierprozess konzipiert. Experimentelle Tests wurden für die Veresterung in einer Pilotanlage und für die Hydrierung in einer industriellen Chemieanlage durchgeführt.
Zur Industrieerprobung wurde MoSys in ein Batch-Informations-Management-System (BIMS) integriert, das auch entwickelt und in das Prozessleitsystem (PLS) einer Mehrzweckanlage im Feinchemie-Werk Radebeul (Degussa AG) implementiert wurde. Dadurch konnten die MoSys-Ausgaben simultan mit wichtigen Prozesssignalen auf den Terminals des PLS visualisiert werden. Zum Beispiel werden der Hydrierungsfortschritt, das vorhergesagte Reaktionsende und die Konzentrationsverläufe des Edukts, Zwischenprodukts und Produkts auf den Terminals der Operatorstationen angezeigt. Wenn unerwünschte Betriebszustände auftreten, wird das Bedienungspersonal frühzeitig alarmiert und Empfehlungen für Gegenmaßnahmen, die nur vom Operator ausgeführt werden dürfen, werden auf den Terminals angezeigt. Die Leistungsfähigkeit von MoSys/BIMS konnte während zweier Hydrierungs-Produktionskampagnen nachgewiesen werden.
  • Contribution to WWW
    Deutsche Forschungsberichte, UB/TIB Hannover, Elektronische Bibliothek, www.tip.uni-hannover.de, Report 01RV9801 (2002)S. 1-95; www.tip.uni-hannover.de, Report 01RV9802 (2002) S. 1-137

Publ.-Id: 5178 - Permalink


Channeling doping profiles studies for small incident angle implantation into silicon wafers
Guo, B. N.; Variam, N.; Jeong, U.; Mehta, S.; Posselt, M.; Lebedev, A.;
Traditional dechanneling dopant profiles in the silicon crystal wafers have been achieved by tilting the wafer away the incident beam. As feature sizes of device shrink, the advantages for channeled doping profiles for implants with small
or near zero degree incident angles are being recognized. For example, high-energy CMOS well spacing limitations caused by shadowing and encroachment of the ion beam by photoresist mask can be avoided for near zero degree incident implants. Accurate models of channeled profiles are essential to predict the device performance more important. This paper will discuss the factors important for channeled dopant profiles, such as the acceptance angle, dopant species, energy, incident angle, dose and damage accumulation in the crystal based on SIMS and Crystal-TRIM simulation results. In addition, the control requirements on ion implantation parameters from a channeling perspective will also be discussed.
Keywords: ion implantation, channeling
  • Lecture (Conference)
    17th Int. Conf. on the Application of Accelerators in Research and Industry (CAARI 2002), Denton, USA, November 12-16, 2002
  • Contribution to proceedings
    AIP Conference Proceedings 680(2003) 658

Publ.-Id: 5177 - Permalink


Konzipierung und Erprobung des Zustandserkennungsverfahrens - Bedienungsanleitung von BIMS/MoSys (im Anhang)
Hessel, G.; Heidrich, J.; Hilpert, R.; Kryk, H.; Roth, M.; Schmitt, W.; Seiler, T.; Weiß, F.-P.;
Im internen Schlussbericht zum BMBF-Projekt 01RV9802/4 wird die Entwicklung des Online-Monitoring-System (MoSys) für homogene und heterogene exotherme chemische Reaktionen beschrieben. Zur Industrieerprobung wurde MoSys in ein neues Batch-Informations-Management-System (BIMS) integriert und in das Prozessleitsystem (PLS) einer Mehrzweckanlage im Feinchemie-Werk Radebeul (Degussa AG) implementiert. Die Betriebserfahrungen von zwei Hydrierungs-Produktionskampagnen werden vorgestellt.
Im Anhang ist eine Beschreibung der BIMS/MoSys-Bedienungsanleitung enthalten. Ferner sind die von BIMS/MoSys genutzten Daten und Informationen sowie ihre Tabellenstruktur in der BIMS-Datenbank zusammengestellt.
  • Other report
    Interner Schlussbericht zum BMBF-Fördervorhaben 01RV9802, Forschungszentrum Rossendorf, Dezember 2002

Publ.-Id: 5176 - Permalink


Hochdosis Si implantation in Diamant: Synthese von vergrabenen Siliziumkarbid-Nanokristallen
Weishart, H.; Heera, V.; Eichhorn, F.; Pecz, B.; Barna, A.; Wolfgang, S.;
Aufgrund ihrer hervorragenden Eigenschaften, wie große Bandlücke, hohe thermische Leitfähigkeit und gesättigte Elektronendriftgeschwindigkeit, sind sowohl Siliziumkarbid als auch Diamant vielversprechende Halbleitermaterialien für elektronische Bauelemente, die unter extremen Bedingungen noch einwandfrei funktionieren sollen. Allerdings ist es bislang noch nicht gelungen, Diamant in zufrieden stellender Weise mit flachen Donatoren zu versehen. Im Gegensatz hierzu ist die p-Dotierung von Siliziumkarbid noch nicht befriedigend gelöst. Da aber sowohl p-leitender Diamant, als auch n-leitendes SiC sehr einfach zu realisieren sind, könnten Heterostrukturen aus diesen so dotierten Materialien erfolgversprechend sein.
Frühere Experimente haben gezeigt, dass eine Hochdosisimplantation von Si in Diamant zur Bildung von ß-SiC führen kann. In dieser Arbeit wurden die Leitfähigkeit und strukturellen Eigenschaften von Diamantproben untersucht, die mit Si-Dosen im Bereich von 3×1017 cm-2 bis 1×1018 cm-2 implantiert worden sind. Die Implantation erfolgte bei 900 °C, um die Schädigung der Diamantmatrix zu reduzieren. Der Einfluß des Implantationsschadens wurde anhand von Vergleichsproben studiert, die mit Argon implantiert wurden. Röntgenbeugung (XRD), IR Absorptionsspectrometrie, hochauflösende cross-sectional Transmissionselektronenmicroscopie (HRTEM) sowie Vierpunktmessungen in van der Pauw Geometrie dienten zur Charakterisierung der implantierten Diamanten.

Keywords: Diamant, SiC, Implantation, Heterostrukturen
  • Lecture (Conference)
    Verhandlungen der Deutschen Physikalischen Gesellschaft

Publ.-Id: 5175 - Permalink


On the production of fullerene-like carbon nitride thin films by Ion Beam Assisted Deposition
Gago, R.; Kolitsch, A.; Möller, W.;
This communication addresses the production of carbon nitride thin films with fullerene-like structure (f-CNx), i.e. bent and cross-linked graphitic basal planes [1]. Normally, f-CNx thin films are produced by Magnetron Sputtering and a key parameter appears to be the use of low-energy ion bombardment (<100 eV) during the growth process [2]. The aim of the investigations is to obtain f-CNx by means of Ion Beam Assisted Deposition (IBAD), which will provide a better understanding of the growth process since the role of neutrals and ions can be studied separately. In order to reproduce the growth conditions of f-CNx, an IBAD device has been re-constructed, incorporating an End-Hall ion source to operate in the low-energy range (50-150 eV). Preliminary results on the deposition of our films will be shown.
1. H. Sjöstrom, et al. Phys. Rev. Lett. 75 (1995) 1336.
2. L.Hultman, et al. Phys. Lett. 87 (2001) 225503.

  • Poster
    MRS Fall Meeting, 2-6 December 2002, Boston (USA)

Publ.-Id: 5174 - Permalink


The 18F water target system - Useful improvements
Preusche, S.; Füchtner, F.; Roß, H.;
  • Poster
    IBA - SCX PET Users Meeting (CYCLONE 18/9 10/5 User Community, 4th Workshop), Milan Italy, 24.-27.11.2002

Publ.-Id: 5173 - Permalink


Procedure for rinsing the 18F water target with deionized water
Preusche, S.; Füchtner, F.; Roß, H.;
  • Lecture (others)
    IBA - SCX PET Users Meeting (CYCLONE 18/9 10/5 User Community, 4th Workshop), Milan Italy, 24.-27.11.2002

Publ.-Id: 5172 - Permalink


Six years experience in routine operation and maintenance of the Rossendorf CYCLONE 18/9 facility
Preusche, S.; Füchtner, F.; Roß, H.; Wüst, F.;
Our six years experience in routine operation and maintenance of the Rossendorf CYCLONE 18/9 facility is given here along with improvements for a stable and reliable cyclotron operation.
  • Contribution to proceedings
    IBA - SCX PET Users Meeting (CYCLONE 18/9 10/5 User Community, 4th Workshop), Milan Italy, 24.-27.11.2002

Publ.-Id: 5171 - Permalink


Partial Oxidation of Implanted Si by Humidity Penetrated into Damaged SiO2 Substrates
Müller, T.; Heinig, K.-H.; Schmidt, B.;
[no abstract available]
  • Lecture (others)
    Project Meeting, EU Growth Project "Nanoparticules for Electronics" (NEON), Toulouse, 3-6 December, 2002

Publ.-Id: 5170 - Permalink


Quasi-particle model for deconfined matter
Kämpfer, B.; Peshier, A.; Soff, G.;
Our quasi-particle model for deconfined matter near T_c is reviewed. The extrapolation of lattice QCD data to finite baryo-chemical is discussed. Determined by the chiral transition temperature T_c, the resulting equation of state of neutral and $\beta$ stable deconfined matter is soft and limits size and mass of pure quark stars.
Keywords: deconfinement, quark-gluon plasma, therodynamics, quark stars
  • Contribution to external collection
    arXiv:hep-ph/0212179

Publ.-Id: 5169 - Permalink


Molecular and spetroscopic characterization of uranium complexes formed bei different bacteria isolated form uranium mining wastes
Merroun, M.; Hennig, C.; Rossberg, A.; Geipel, G.; Reich, T.; Nicolai, R.; Heise, K. H.; Selenska-Pobell, S.;
Microorganisms have a potential to affect mobility and overall environmental behaviour of heavy metals and radionuclides through solubility and speciation changes, biosorption, bioaccumulation or other bio-transformations. In this study we used a combination of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, Infrared (IR) spectroscopy and Time Resolved Laser Induced Fluorescence Spectroscopy (TRLFS) to characterize the uranium complexes formed by different bacterial strains such as Acidithiobacillus ferrooxidans D2, Stenotrophomonas maltophilia JG-2, Bacillus sphaericus JG-A12 which were isolated from uranium mining wastes. In addition several reference strains namely Pseudomonas stutzeri ATCC 17588; 55595 and Pseudomonas migulae CIP 105470 which were demonstrated to be relevant to the bacterial populations in the uranium wastes were studied as well. The EXAFS analysis demonstrated that in the case of B. sphaericus JG-A12, the U(VI) is coordinated to carboxyl groups in a bidentate fashion with an average distance between the U atom and the C atom of 2.91 ± 0.02 Å and to phosphate groups in a monodentate fashion with an average distance between the U atom and the P atom of 3.59 ± 0.02 Å. In the case of the other bacteria, only phosphate groups are implicated in the complexation of uranium in a monodentate mode, with an average distance between the U atom and the P atom of 3.63 ± 0.02 Å. These results are consistent with those found by Infrared measurements. The latter demonstrates the complementary role which EXAFS spectroscopy can play in determining of metal distribution behaviour in the environment. In addition, we applied TRLFS in order to determine the energy and the shape of the emission bands and the fluorescence lifetime of the uranium complexes formed by the different bacterial biomass studied in this work.

  • Contribution to proceedings
    Int. Workshop on Biogeochemical Controls.., Ascona, 2.-7.3.2003

Publ.-Id: 5167 - Permalink


X-ray absorption spectroscopy characterization of uranium (VI) complexes formed by Bacillus sphaericus JG-A12 and NCTC 9602 and their recrystalized S-layers
Merroun, M.; Raff, J.; Hennig, C.; Rossberg, A.; Reich, T.; Selenska-Pobell, S.;
Mohamed Merroun1, Johannes Raff1, Christoph Hennig1, Andre Rossberg1, Tobias Reich2 and Sonja Selenska-Pobell1
1Institute of Radiochemistry, Forschungszentrum Rossendorf,D-01314 Dresden, Germany, 2Johannes Gutenberg Universität Mainz, Institut für Kernchemie, Mainz, Germany
Microorganisms have a potential to affect mobility and overall environmental behaviour of heavy metals and radionuclides via bio-transformations such as oxidation and reduction which can change metal's speciation and solubility and also via different biosorption, bioaccumulation, and biomineralisation processes. In this study Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy was used to determine the structural parameters of the uranium complexes formed by vegetative cells of B. sphaericus JG-A12 which was recovered from a uranium mining waste pile and it's genomic analogue, B. sphaericus NTCC 9602. The complexation of uranium (VI) by the purified and recrystalized S-layers of these two strains was studied as well. The EXAFS analysis demonstrated that in all cases studied the U(VI) was coordinated to carboxyl groups in a bidentate fashion with an average distance between the U atom and the C atom of 2.91 ± 0.02 Å and to phosphate groups in a monodentate fashion with an average distance between the U atom and the P atom of 3.59 ± 0.02 Å. By using ICP-MS, "Stain-all" analysis and colourimetric methods it was demonstrated that the S-layers of B. sphaericus NCTC 9602 and B. sphaericus JG-A12 are phosphorylated. The latter explains the atomic structures of the U-complexes formed at the surfaces of the strains.
Interestingly, the uranium complexes formed by both the bacterial cells and the purified S-layer proteins possess the same structural parameters. These results indicate that the S-layers play the main role in the binding of this radionuclide and that they are acting as a protective barrier against it in the polluted environments.




  • Poster
    VAAM 23.-26.3.2003, Berlin

Publ.-Id: 5165 - Permalink


Tagging the p n -> d phi reaction by backward protons in p d -> d phi p_{sp} processes
Kaptari, L. P.; Kämpfer, B.; Semikh, S. S.;
The reaction p d -> d phi p_{sp} is studied within the Bethe-Salpeter formalism. Under special kinematical conditions (slow backward spectator proton p_{sp} and fast forward deuteron) relevant for forthcoming experiments at COSY, the cross section and a set of polarization observables factorize in the contribution of the pure subprocess p n -> d phi and a contribution stemming from deuteron quantities and kinematical factors. This provides a theoretical basis for studying threshold-near processes at quasi-free neutrons.
Keywords: meson production, deuteron
  • nucl-th 0212066 2003
  • Journal of Physics G 30(2004)9, 1115-1126

Publ.-Id: 5164 - Permalink


Modifizierbare Tc(III)/Re(III) Gemischtligandkomplexe zur Kopplung an Biomoleküle
Pietzsch, H.-J.;
  • Lecture (others)
    10. Arbeitstreffen der Arbeitsgemeinschaft Radiochemie / Radiopharmazie, Wien, 12.-14.09.2002

Publ.-Id: 5163 - Permalink


Erste Ergebnisse zu 18F-Molekülen mittels Komplexierungsreaktion
Noll, B.; Noll, S.; Wester, H.-J.;
  • Lecture (others)
    10. Arbeitstreffen der Arbeitsgemeinschaft Radiochemie / Radiopharmazie, Wien, 12.-14.09.2002

Publ.-Id: 5162 - Permalink


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