Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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

35173 Publications

Stabilization of internal spaces in multidimensional cosmology

Günther, U.; Zhuk, A.

Effective 4-dimensional theories are investigated which were obtained under dimensional reduction of multidimensional cosmological models with a minimal coupled scalar field as matter source. Conditions for the internal space stabilization are considered and the possibility for inflation in the external space is discussed. The electroweak as well as the Planck fundamental scale approaches are investigated and compared with each other. It is shown that there exists a rescaling for the effective cosmological constant as well as for gravitational exciton masses in the different approaches.

Keywords: moduli stabilization; scalar-tensor theory; higher dimensional gravity; dimensional reduction

Publ.-Id: 11040

Multidimensional perfect fluid cosmology with stable compactified internal dimensions

Günther, U.; Zhuk, A.

Multidimensional cosmological models in the presence of a bare cosmological constant and a perfect fluid are investigated under dimensional reduction to 4-dimensional effective models. Stable compactification of the internal spaces is achieved for a special class of perfect fluids. The external space behaves in accordance with the standard Friedmann model. Necessary restrictions on the parameters of the models are found to ensure dynamical behavior of the external (our) universe in agreement with observations.

Keywords: moduli stabilization; scalar-tensor theory; higher dimensional gravity; dimensional reduction

Publ.-Id: 11039

On stable compactification with Casimir-like potential

Günther, U.; Kriskiv, S.; Zhuk, A.

Multidimensional cosmological models with a higher dimensional space-time manifold are investigated under dimensional reduction. In the Einstein conformal frame, the effective potential for the internal scale factors is obtained. The stable compactification of the internal spaces is achieved due to the Casimir effect. In the case of more than one internal space a Casimir-like ansatz for the energy density of the massless scalar field fluctuations is proposed. Stable configurations with respect to the internal scale factor excitations are found in the cases of one and two internal spaces.

Keywords: string theory; moduli stabilization; scalar-tensor theory; higher dimensional gravity; dimensional reduction

  • Gravitation and Cosmology 4(1998), 1-16

Publ.-Id: 11038

Stable compactification and gravitational excitons from extra dimensions

Günther, U.; Zhuk, A.

We study inhomogeneous multidimensional cosmological models with a higher dimensional space-time manifold under dimensional reduction. Stability due to different types of effective potentials is analyzed for specific configurations of internal spaces. Necessary restrictions on the parameters of the models are found and masses of gravitational excitons (small inhomogeneous excitations of the scale factors of the internal spaces near minima of effective potentials) are calculated.

Keywords: string theory; moduli stabilization; scalar-tensor theory; higher dimensional gravity; dimensional reduction

  • Hadronic Journal 21(1998), 279-318

Publ.-Id: 11037

Gravitational excitons from extra dimensions

Günther, U.; Zhuk, A.

We study inhomogeneous multidimensional cosmological models with a higher dimensional space-time manifold under dimensional reduction and show that small inhomogeneous excitations of the scale factors of the internal spaces near minima of effective potentials should be observable as massive scalar particles (gravitational excitons) in the external space-time.

Keywords: string theory; moduli stabilization; scalar-tensor theory; higher dimensional gravity; dimensional reduction

  • Contribution to proceedings
    8th Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories (MG 8), Jerusalem, Israel, 22-27 June 1997, 22.-27.06.1997, Jerusalem, Israel
    8th Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories (MG 8), Singapore: World Scientific, 981-02-3793-6, 517-519

Publ.-Id: 11036

Gravitational excitons from extra dimensions

Günther, U.; Zhuk, A.

nhomogeneous multidimensional cosmological models with a higher-dimensional space-time manifold M=M0×∏i=1 nMi (n>~1) are investigated under dimensional reduction to D0-dimensional effective models. In the Einstein conformal frame, small excitations of the scale factors of the internal spaces near minima of an effective potential can be observed as massive scalar fields in the external space-time. Parameters of models that ensure minima of the effective potentials are obtained for particular cases and masses of gravitational excitons are estimated.

Keywords: string theory; moduli stabilization; scalar-tensor theory; higher dimensional gravity; dimensional reduction

Publ.-Id: 11035

Experimental Study on the Air/water Counter-current Flow Limitation in a Model of the Hot Leg of a Pressurised Water Reactor

Deendarlianto; Vallee, C.; Lucas, D.; Beyer, M.; Pietruske, H.; Carl, H.

An experimental investigation on the air/water counter-current two-phase flow in a horizontal rectangular channel connected to an inclined riser has been conducted. This test-section representing a model of the hot leg of a pressurized water reactor is mounted between two separators in a pressurized experimental vessel. The cross-section and length of the horizontal part of the test-section are (0.25 m × 0.05 m) and 2.59 m, respectively, whereas the inclination angle of the riser is 50°. The flow was captured by a high-speed camera in the bended region of the hot leg, delivering a detailed view of the stratified interface as well as of dispersed structures like bubbles and droplets. Countercurrent flow limitation (CCFL), or the onset of flooding, was found by analyzing the water levels measured in the separators. The counter-current flow limitation is defined as the maximum air mass flow rate at which the discharged water mass flow rate is equal to the inlet water mass flow rate.
From the high-speed observations it was found that the initiation of flooding coincides with the formation of slug flow. Furthermore, a hysteresis was noticed between flooding and deflooding. The CCFL data was compared with similar experiments and empirical correlations available in the literature. Therefore, the Wallis-parameter was calculated for the rectangular cross-sections by using the channel height as length, instead of the diameter. The agreement of the CCFL curve is good, but the zero liquid penetration was found at lower values of the Wallis parameter than in most of the previous work. This deviation can be attributed to the special rectangular geometry of the hot leg model of FZD, since the other investigations were done for pipes.

Keywords: Two-phase flow; counter-current flow; CCFL; flooding; deflooding; PWR; hot leg; rectangular channel; TOPFLOW

Publ.-Id: 11033

Counter-current flow limitation experiments in a model of the hot leg of a pressurised water reactor

Vallee, C.; Deendarlianto; Lucas, D.; Beyer, M.; Pietruske, H.; Carl, H.

The counter-current flow limitation was investigated experimentally in a flat model of the hot leg of a pressurised water reactor. Counter-current flow limitation, or the onset of flooding, was found by analysing the water levels measured in the separators. A confrontation with high-speed observation images indicates that the initiation of flooding coincides with the reversal of the flow in the horizontal part of the hot leg due to high air velocities.

Furthermore, the CCFL data was compared with empirical correlations for analogue geometries available in the literature. This comparison shows that the Wallis-parameter can be applied to rectangular cross-sections by using the channel height as length, instead of the diameter. The obtained flooding curve is similar to those reported by other investigators, but its slope and the gaseous Wallis parameter for zero penetration are lower. This is attributed to the geometry of the hot leg model.

Keywords: hot leg; pressurised water reactor; PWR; two-phase flow; counter-current flow; counter-current flow limitation; CCFL

  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Deutschland
    Jahrestagung Kerntechnik 2008 - Fachsitzungen / Topical Sessions, Berlin: INFORUM Verlags- und Verwaltungsgesellschaft
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Deutschland
  • atw - International Journal for Nuclear Power 53(2008)8/9, 546-549

Publ.-Id: 11032

Modeling free surface flows relevant to a PTS scenario: comparison between experimental data and three RANS based CFD-codes - Comments on the CFD-experiment integration and best practice guideline

Bartosiewicz, Y.; Seynhaeve, J.-M.; Vallee, C.; Höhne, T.; Laviéville, J.

This paper presents some results concerning a benchmark for stratified two-phase flows conducted in the frame of the European Platform for NUclear REactor SIMulations (NURESIM). This benchmark relies on the FZD slug flow experiment performed in the Horizontal Air/Water Channel (HAWAC). For this test bench, special experimental arrangements have been taken in order to be able to properly model the boundary and initial conditions with CFD. A picture sequence recorded with a high-speed camera was used as reference for comparison with the simulations. For this benchmark, three different codes have been tried out. CFX was used with a turbulent two-fluid model in which a special turbulence damping function was implemented in the specific dissipation rate of the turbulent kinetic energy. This allowed a good qualitative representation of the slug dynamics, even though quantitative comparison were less relevant because of difficulties in modelling the inlet instabilities. The VOF approach in its laminar and turbulent form was also tried out trough the FLUENT code and was found to be inappropriate for those conditions due to the high velocity slip between phases. Moreover, NEPTUNE_CFD was tested with a new implemented model allowing free surface location and the computation of momentum transfer across this interface. This Large Interface Model (LIM) enables to detect "stratified cells" from the other and hence to apply local closure law. With this model, the results agreed well with experimental data qualitatively and quantitatively. This benchmark experience also allowed to draw basis concerning a best practice guideline in numerical simulation related to those flows in nuclear thermal hydraulics.

Keywords: stratified two-phase flow; free surface flow; slug flow; CFD; benchmark

  • Contribution to proceedings
    XCFD4NRS - Experiments and CFD Code Applications to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, France
    Paper HOR-01
  • Lecture (Conference)
    XCFD4NRS - Experiments and CFD Code Applications to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, France
  • Nuclear Engineering and Design 240(2010), 2375-2381
    DOI: doi:10.1016/j.nucengdes.2010.04.032

Publ.-Id: 11031

A comparison of the magnetic properties of proton- and iron-implanted graphite

Barzola-Quiquia, J.; Höhne, R.; Rothermel, M.; Setzer, A.; Esquinazi, P.; Heera, V.

In this work we have investigated the changes of the magnetic properties of highly oriented pyrolytic graphite samples after irradiation either with ~3×1014 protons or 3.5×1013 ... 3.5×1014 iron ions with energies in the MeV range. Our results show that iron and proton irradiations can produce similar paramagnetic contributions depending on the implantation temperature. However, only protons induce a ferromagnetic effect.

Keywords: Magnetic semiconductors; Interactions of particles and radiation with matter; Carbon; diamond; graphite

Publ.-Id: 11030

Assessment of CFD codes for nuclear reactor safety problems

Smith, B. L.; Bieder, U.; Graffard, E.; Heitsch, M.; Henriksson, M.; Höhne, T.; Komen, E.; Mahaffy, J.; Moretti, F.; Morii, T.; Mühlbauer, P.; Rohde, U.; Scheuerer, M.; Song, C.-H.; Zigh, G.

This report is a consolidation of document NEA/SEN/SIN/AMA(2005)3, which aimed to evaluate the existing CFD assessment basis, identify gaps that need to be filled in order to adequately validate CFD codes for application to NRS problems, and propose a methodology for establishing assessment matrices relevant to NRS needs. The document is a revision of the original, and has been compiled by members of an expert Writing Group, WG2, under the auspices of the OECD/NEA secretariat. The group met three times during the period January 2005 to August 2007, the dates chosen to coordinate with the activities of the sister groups WG1 (Best Practice Guidelines) and WG3 (Multiphase Extensions).
The group has concentrated on single-phase phenomena, considering that two-phase CFD is not yet of sufficient maturity for a useful assessment basis to be constructed and that identification of the development areas (the task of Writing Group 3) should be undertaken first. The organisation of the report reflects the tasks the Group set itself.
To review critically the NRS problems where the use of CFD is needed for the analysis or where its use is expected to result in major benefits.
To review critically the existing assessment basis for CFD application to NRS issues.
To identify the gaps in the technology base, and the need for further development effort.
To organise a web-based NRS assessment database, regulated by an NEA webmaster.
To continue to look for suitable experiments that could form the basis of benchmarking exercises that are specifically tailored to NRS needs.
To organise an International Workshop, with OECD/NEA sponsorship, to promote the availability and distribution of experimental data suitable for NRS benchmarking, and to monitor the current status of CFD validation exercises relevant to NRS issues.
Beyond 2007, an amalgamation of Writing Groups WG1, WG2 and WG3, together with the NEA web-master and secretariat, is proposed to drive the activities further. This would be a core group of no more than five persons, meeting once per year.
This document is now submitted to the Working Group on the Analysis and Management of Accidents (GAMA) for evaluation.

Keywords: OECD; CFD; NEA; WG2

  • Other report
    Paris: NEA/CSNI/R(2007)13, 2008
    136 Seiten

Publ.-Id: 11028

Spectroscopic characterization of Pt complexation and nanocluster formation on Bacillus sphaericus JG-A12 S-layer

Jankowski, U.; Fahmy, K.; Hennig, C.; Selenska-Pobell, S.; Merroun, M.

In this study, a combination of X-ray absorption spectroscopy (XAS) and Fourier transformed infrared (FT-IR) was used to investigate at molecular scale the coordination of Pt(II) to the S-layer sheets B. sphaericus JG-A12, and to characterize the formation of Pt nanoacluster using this protein layer as template.

  • Contribution to HZDR-Annual report
    Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZD-489 Februar 2008, 43-43
    ISSN: 1437-322X

Publ.-Id: 11027

Interactions of Paenibacillus sp. JG-TB8 and Sulfolobus acidocaldarius with U(VI): spectroscopic and microscopic studies.

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

In this work, a combination of wet chemistry, spectroscopic and microscopic techniques was used to investigate and compare the interactions of uranium(VI) with one representative each of the domains Bacteria and Archaea. The bacterial strain Paenibacillus sp. JG-TB8 was isolated from a microbial consortium cultured from a uranium mining waste pile near the town of Johanngeorgenstadt, Germany. This consortium consisted not only of bacteria of the division Firmicutes but also of mesophilic 1.1b-Crenarchaeota. Because isolation approaches of these archaeal strains failed until now, the thermophilic relative Sulfolobus acidocaldius, which has already been found in comparable soil samples, was used for this study.
The U(VI) sorption studies showed that the cells of both microbial strains accumulated significant amounts of uranium.X-ray absorption spectroscopy was used to characterize, at molecular scale, the local coordination of uranium associated with the cells of the studied microorganisms. XANES analysis showed that in both cases the oxidation state of the U(VI) added to the cells was unchanged indicating that U(VI) was not reduced. The EXAFS spectrum of the U(VI) complexes formed by the cells of Paenibacillus sp. JG-TB8 showed a high similarity to that of meta-autunite, indicating that this radionuclide is precipitated by the cells as a meta-autunite-like phase. These uranium precipitates were located at the cell surface and intracellularly as needle-like fibrils as was demonstrated by transmission electron microscope analyses. In the case of Sulfolobus acidocaldarius, EXAFS analysis showed that the structural parameters of the uranium complexes formed by this archaeon are similar to those arising from the complexation of uranium with organic phosphate compounds such as fructose 6-phosphate.

  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 703-710
  • Lecture (Conference)
    5th International Conference Uranium Mining and Hydrology (UMH V), 14.-18.09.2008, Freiberg, Germany

Publ.-Id: 11025

Spectroscopic characterization of Pt-complexation and nanoparticle formation on S-layer protein of bacillus sphaericus JG-A12

Jankowski, U.; Fahmy, K.; Hennig, C.; Selenska-Pobell, S.; Merroun, M.

The strain Bacillus sphaericus JG-A12, isolated from the uranium mining waste pile called Haberland in Saxony, Germany, is capable of selective and reversible accumulation of radionuclides and toxic metals. It was demonstrated that the main role by metal binding is played by the surface of protein layer.
The S-layer possesses a highly ordered lattice structure and can serve as a template for production transportation of noble metals.
The aim of this study was the characterization of the secondary structure and the stability of the protein after complexation Pt and also after the formation of nanoclusters by reduction.
The measurements by Fourier transformed infrared spectroscopy (FT-IR), revealed that the structure of the S-layer protein is stabilized after both sorption or reduction of Pt(II) against acidification.
An aspect for this conclusion is pH induced infrared absorption changes of the Pt(II)-bound S-layer. An effect of different pH-values is the protonation of carboxylic acids caused the reduction of the COO- stretching modes. The denaturation occurs near by pH of 0.8. This is shown by the downshift of amid I absorption.
The aim of the EXAFS measurement was the identification of functional groups of the s-layer protein which are involved in binding Pt(II) or Pt(0). The analysis which has been carried out at synchrotron beam line at ESRF in Grenoble approves the results of IR measurements for identification of functional groups. The first shell contains at a distance of 2.01 ± 0.02 Å oxygen and nitrogen whereas the system can not distinguish between this elements. In the second were found Pt-Pt bindings and the third was dominated by Pt-C bindings.

  • Poster
    School on synchrotron X-ray and IR Methods Focusing on Environmental Sciences, 21.-23.01.2008, Karlsruhe, Deutschland

Publ.-Id: 11024

Interactions of U(VI) with members of a microbial consortium recovered from a uranium mining waste pile: spectroscopic and microscopic studies.

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

In this work, a combination of wet chemistry, spectroscopic and microscopic techniques was used to investigate the interactions of U(VI) with the cells of Paenibacillus sp. JG-TB8, a bacterial strain enriched from a microbial consortium isolated from a uranium mining waste pile near the town of Johanngeorgenstadt, Germany. This consortium consisted of mesophilic 1.1b-Crenarchaeota and bacteria of the division Firmicutes.
The U(VI) sorption studies showed that cells of the studied Paenibacillus strain accumulated up to 85 mg U/g dry biomass from a solution with an uranium concentration of 120 mg U/l.
X-ray absorption spectroscopy was used to characterize, at molecular scale, the local coordination of uranium associated with the cells of the studied bacterium. XANES analysis showed that the oxidation state of the U(VI) added to the cells was unchanged indicating that U(VI) was not reduced. The EXAFS spectrum of the U(VI) complexes formed by the cells of Paenibacillus sp. JG-TB8 showed a high similarity to that of meta-autunite, indicating that this radionuclide is precipitated by the cells as a meta-autunite-like phase. These uranium precipitates were located at the cell surface and intracellularly as needle-like fibrils as was demonstrated by transmission electron microscope analyses.
The results found in this study indicated that the cells of Paenibacillus sp. JG-TB8 are involved in the biomineralization of uranium at aerobic and acidic conditions.

  • Poster
    School on Synchrotron X-ray and IR Methods Focusing on Environmental Sciences, 21.-23.01.2008, Karlsruhe, Germany

Publ.-Id: 11023

VOF-Simulation des freien Aufstiegs von Öltropfen in Wasser

Schmidtke, M.; Bothe, D.

Die Resultate von VoF-Simulationen zum freien Aufstieg von Öltropfen in Wasser werden mit experimentellen Beobachtungen verglichen. Kleine Öltropfen steigen geradlinig mit einem stationären Nachlauf auf. Große Tropfen steigen in den Simulationen zunächst geradlinig auf mit einem stabilem Nachlauf, dessen Länge mit der Zeit anwächst. Der Tropfen beschleunigt, bis der Nachlauf instabil wird. Mit dem Einsetzen periodischer Wirbelablösung sinkt die Aufstiegsgeschwindigkeit ab auf die Endgeschwindigkeit. Die periodische Wirbelablösung im Nachlauf großer Tropfen geht einher mit einer Formoszillation und einer zickzackförmigen Trajektorie. Es werden Aufstiegsgeschwindigkeit, Tropfenform und Bewegungsverhalten in Abhängigkeit von der Tropfengröße ermittelt und mit experimentellen Resultaten verglichen. Der Dragkoeffizient für zickzackförmig aufsteigende Tropfen ist deutlich höher als für geradlinig aufsteigende Tropfen.

Keywords: Oil drops; drag coefficient; vortex shedding; volume of fluid

  • Lecture (Conference)
    "Mehrphasenströmungen", Jahrestagung des ProcessNet Fachausschusses, 10.-14.03.2008, Weihenstephan / Freising, Deutschland

Publ.-Id: 11022

FTIR study of the photoinduced processes of plant phytochrome phyA using isotope-labeled bilins and DFT calculations

Schwinté, P.; Foerstendorf, H.; Hussain, Z.; Gärtner, W.; Mroginski, M.-A.; Hildebrandt, P.; Siebert, F.

FTIR spectroscopy was employed to analyse the chromophore structure in the parent states Pr and Pfr of plant phytochrome phyA and the respective photoproducts lumi-R and lumi-F. The spectra were obtained from phyA adducts assembled with either uniformly or selectively isotope-labeled phytochromobilin and phycocyanobilin. The interpretation of the experimental spectra is based on the spectra of chromophore models calculated by density functional theory. Global 13C-labelling of the tetrapyrrole allows for the discrimination between chromophore and protein bands in the FTIR difference spectra. All IR difference spectra display a prominent difference band attributable to a stretching mode with large contributions from the methine bridge between the inner pyrrole rings (B-C stretching). Due to mode coupling, frequencies and isotopic shifts of this mode suggest that the Pr chromophore may adopt a distorted ZZZssa geometry with a twisted A-B methine bridge. The transition to lumi-R is associated with only minor changes of the amide I bands indicating limited protein structural changes during the isomerization site of the C-D methine bridge. Major protein structural changes occur upon the transition to Pfr in which the chromophore adopts a ZZEssa-like state. In addition, specific interactions with the protein alter the structure of the B-C methine bridge as concluded from the substantial downshift of the respective stretching mode. These interactions are removed during the photoreaction to lumi-F which affords a ZZZssa-like structure of the chromophore and involves only small protein structural changes.

Keywords: vibrational spectroscopy; chromophore-protein interaction; photoisomerization; isotope- labelling; conformational changes; resonance Raman

Publ.-Id: 11021

Computation of the lift force for single bubbles in a simple shear flow

Schmidtke, M.; Bothe, D.; Warnecke, H.-J.

Bubbles in shear flows experience a lift force, causing them to migrate sideward while they are rising. This lateral migration is also observed in numerical simulations, which are carried out with an extended version of the highly parallelized code FS3D, employing an advanced Volume-of-Fluid method. The movement of single bubbles in linear shear flows is simulated to obtain the magnitude of the lift force – expressed by the lift force coefficient – for various bubble diameters and material data. Simulation results are in good agreement with experiments for medium liquid phase viscosities. The pressure and the velocity fields near the interface are investigated and the contribution of dynamic pressure and the circulation of the lift force are discussed.

Keywords: rise of bubbles; lift coefficient; Volume of Fluid method; shear flow

  • Lecture (Conference)
    Fachausschußsitzung VDI-GVC "Mehrphasenströmungen", 07.-08.03.2007, Baden-Baden, Deutschland

Publ.-Id: 11020

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

Skorupa, W.

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

Keywords: flash lamp annealing; short time thermal processing; ion implantation; annealing; silicon; transient enhanced diffusion; germanium; silicon dioxide; zinc oxide; indium tin oxide; silicon carbide; silicon based light emission; MOS structures; lead casting; organ pipe materials

  • Invited lecture (Conferences)
    Seminar des Walter-Schottky-Institutes der TU München, 12.02.2008, Garching, Deutschland

Publ.-Id: 11019

Measurements of transient flow fields driven by a discontinuously applied rotating magnetic field

Räbiger, D.; Eckert, S.; Gerbeth, G.

This experimental study considers the transient liquid metal flow which is generated inside a cylindrical container by discontinuously applying a rotating magnetic field (RMF). The focus is on the fluid motion arising from the impulsive spin-up from the resting state, a single pulse or a sequence of RMF pulses. The ultrasonic Doppler velocimetry (UDV) has been used to determine profiles of the fluid velocity in the ternary alloy GaInSn. The azimuthal and vertical velocity components have been measured allowing for an analysis of both the primary, swirling flow and the secondary flow in the radial-meridional plane. The experimental results show an excellent agreement with recently published numerical results. The investigations reveal that the recirculating flow in the radial- meridional plane undergoes characteristic oscillations. Periodic reversals of the meridional flow direction can be observed for a specific length of the RMF pulses.
Our results demonstrate that the utilisation of a time-modulated rotating magnetic field (RMF) offers a considerable potential to provide optimal flow pattern for an efficient melt mixing. For instance, such tailored methods of electromagnetic stirring can be applied during the solidification of metal alloys, where a well-aimed modification of casting properties is achieved by controlling the melt flow in the bulk and adjacent to the solidification front.

Keywords: liquid metal; rotating magnetic field; spin-up; flow measurements; Ultrasound Doppler method

  • Lecture (Conference)
    GAMM 2008, 31.03.-04.04.2008, Bremen, Germany

Publ.-Id: 11018

Giant stability enhancement of rare-earth implanted SiO2 light-emitting devices by an additional SiON protection layer

Sun, J. M.; Rebohle, L.; Prucnal, S.; Helm, M.; Skorupa, W.

The electrical stability of rare-earth implanted SiO2 light emitting devices was improved by using a SiON dielectric buffer layer in an indium-tin-oxide/SiON/SiO2:Tb /Si device structure. At the expense of a small increase of the electroluminescence threshold voltage, a large increase of the breakdown electric field from 7.5 to 10.5 MV/cm was obtained in the SiO2:Tb layer, and the maximum injection current density was increased by three orders of magnitude from 4 mA/cm2 to 4 A/cm2 . The operation time of the electroluminescence devices was increased by more than three orders of magnitude at an injection current density of ~4 mA/cm2. Our experimental results are consistent with a theoretical model proposed for designing a stable and efficient thin-film light emitting device containing double-stacked dielectric layers.

Keywords: rare earth; electroluminescence; MOS; Terbium; Si-based light emission

  • Applied Physics Letters 92(2008)7, 071103

Publ.-Id: 11017

Synthesis of a Se0/calcite composite using hydrothermal carbonation of Ca(OH)2 coupled with a complex selenocystine fragmentation.

Montes-Hernandez, G.; Charlet, L.; Renard, F.; Scheinost, A. C.; Bueno, M.; Fernández-Martínez, A.

In this study, the hydrothermal carbonation of calcium hydroxide under high CO2-Ar pressure (90 bar) coupled with a complex selenocystine fragmentation under O2-poor and O2-rich conditions was carried out by using a semi-batch
system (sampling with time) in order to synthesize an elemental selenium (Se0)/calcite composite. Under O2-poor conditions (i.e. with purge stage), the composite was mainly characterized by spherical selenium nanoparticles
(<500nm) deposed on the calcite matrix. The carbonate matrix was constituted by nano- and micro rhombohedral crystals (<2µm) and micrometric agglomerates and/or aggregates (<5mµ). For this case, the spherical Se nanoparticles give
a stable red coloration to the composite. In contrast, under O2-rich conditions (i.e. without purge stage), the composite was characterized by hexagonal selenium microparticles (<25µm) dispersed in the calcite matrix. For this case, a gray coloration of composite was observed. In conclusion, the gas purge in the system and the selenocystine dose (mg/kgwater) play a crucial role on the selenocystine fragmentation mechanism during Ca(OH)2 suspension heating (at 90°C) and carbonation stages, this leading the precipitation/growth of elemental selenium with different morphologies and particles sizes. Consequently, it was noticed that the selenocystine fragmentation participates to the precipitation/growth of calcite with unusual morphologies. Finally, the results presented here demonstrate that Se0/calcite composite, with spherical or hexagonal morphologies for elemental selenium can be produced, this composite possibly with a high potential for medical (ex. dietary supplement) or industrial (ex. pigments) applications.

  • Crystal Growth & Design 8(2008)7, 2497-2504

Publ.-Id: 11015

X-ray absorption and photoelectron spectroscopy investigation of selenite reduction by FeII–bearing minerals

Scheinost, A. C.; Kirsch, R.; Banerjee, D.; Fernandez-Martinez, A.; Zaenker, H.; Funke, H.; Charlet, L.

The long-lived radionuclide 79Se is one of the elements of concern for the safe storage of high-level nuclear waste, since clay minerals in engineered barriers and natural aquifer sediments strongly adsorb cationic species, but to lesser extent anions like selenate (SeVIO42−) and selenite (SeIVO32−). Previous investigations have demonstrated, however, that SeIV and SeVI are reduced by surface-associated FeII, thereby forming insoluble Se0 and Fe selenides. Here we show that the mixed FeII/III (hydr)oxides green rust and magnetite, and the FeII sulfide mackinawite reduce selenite rapidly (< 1 day) to FeSe, while the slightly slower reduction by the FeII carbonate siderite produces elemental Se. In the case of mackinawite, both S−II and FeII surface atoms are oxidized at a ratio of one to four by producing a defective mackinawite surface. Comparison of these spectroscopic results with thermodynamic equilibrium modeling provides evidence that the nature of reduction end product in these FeII systems is controlled by the concentration of HSe−; Se0 forms only at lower HSe− concentrations related to slower HSeO3− reduction kinetics. Even under thermodynamically unstable conditions, the initially formed Se solid phases may remain stable for longer periods since their low solubility prevents the dissolution required for a phase transformation into more stable solids. The reduction by Fe2+-montmorillonite is generally much slower and restricted to a pH range, where selenite is adsorbed (pH < 7), stressing the importance of a heterogeneous, surface-enhanced electron transfer reaction. Although the solids precipitated by the redox reaction are nanocrystalline, their solubility remains below 6.3 × 10− 8 M. No evidence for aqueous metal selenide colloids nor for Se sorption to colloidal phases was found. Since FeII phases like the ones investigated here should be ubiquitous in the near field of nuclear waste disposals as well as in the surrounding aquifers, mobility of the fission product 79Se may be much lower than previously assumed.

Keywords: Selenium redox nuclear waste XAFS XANES

  • Journal of Contaminant Hydrology 102(2008), 228-245
  • Lecture (Conference)
    Migration ´09 - 12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, USA

Publ.-Id: 11013

Pressure independence of intensity clamping during filamentation: theory and experiment

Bernhardt, J.; Liu, W.; Chin, S. L.; Sauerbrey, R.

Because of the dynamic equilibrium between Kerr self-focussing and plasma induced defocusing
and the inexistence of collisional ionization the critical intensity during femtosecond laser
filamentation in air is independent of pressure. An analytical analysis is given which is justified
by a direct experimental verification.
PACS: 42.65.Jx, 52.38.Hb, 52.70.Kz

Keywords: Pressure independence of intensity clamping during filamentation; Theory and experiment

  • Applied Physics B 91(2008)1, 45-48

Publ.-Id: 11012


Sauerbrey, R.; Schramm, U.

Keywords: Laser-Particle-Acceleration; Electron laser field; Laser ion acceleration; Applications

  • Invited lecture (Conferences)
    GSI Kolloquium, 22.01.2008, Darmstadt, Deutschland

Publ.-Id: 11011

Laser-driven proton oncology - a unique new cancer therapy?

Ledingham, K. W. D.; Galster, W.; Sauerbrey, R.

In 2000, the University of Strathclyde, collaborating with the Rutherford Appleton Laboratory, organized the first workshop dealing with the potential of highpower laser technology in medicine. Two areas of potential were identified: firstly the production of positron emission tomography (PET) isotopes; and secondly, the potential for laser-accelerated proton and heavy ion beams for therapy. The attendees, mainly clinicians and radiation physicists, emphasised that the laser community should concentrate on developing laser and target technology for therapy rather than isotope production because of the potential advantages over conventional accelerator technology for that purpose. On the 30 March 2007, the universities of Strathclyde and Paisley organized a follow-up meeting to identify the progress made in laser-driven proton and ion beam technology with applications leading to proton and ion beam therapy for deep-seated tumours. The meeting was supported by the Scottish Uni!
versities Physics Alliance (SUPA) - an organization set up in Scotland to bring together all of the physics departments collaborating with life scientists to work on ground-breaking new science which no single university could attempt. This is a summary of the meeting.

Keywords: highpower laser technology in medicine; positron emission tomography (PET); laser-accelerated proton and heavy ion beams for therapy; laser-driven proton and ion beam technology

Publ.-Id: 11009

Yttrium-86-labelled human serum albumin microspheres: relation of surface structure with in vivo stability

Schiller, E.; Bergmann, R.; Pietzsch, J.; Noll, B.; Sterger, A.; Johannsen, B.; Wunderlich, G.; Pietzsch, H.-J.

Radiolabelled particles are an attractive tool in the therapy of malignancies of the liver. We consider particles manufactured from denatured human serum albumin (HSA) as useful carriers of therapeutic radionuclides. Covalent attachment of suitable chelators onto the surface of the spheres promises an easy access to radiolabelled HSA microspheres.

We synthesized 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid (DOTA) bearing smooth, medium-rough and rough surfaced HSA microspheres (mean diameter: 25 μm). In vitro stability of 86Y-labelled particles was determined after incubation in human plasma and in a DTPA challenge experiment. In vivo stability of 86Y DOTA-HSA microspheres was determined after single intravenous application in rats. Subsequently, the particles were completely trapped in the lung microvasculature. Thus, the lung serves in our experiments as target organ.

DOTA-HSA microspheres were 86Y labelled in reproducible high yields (N95%). No differences between smooth and rough surfaced spheres were found for both DOTA coupling and 86Y labelling. Labelled microspheres showed high in vitro stability in human plasma and in DTPA solution with only 8±1% and 2±0% loss of radioactivity from the surface, respectively, 48 h postinjection (pi). The three batches (smooth, medium-rough and rough surfaced microspheres) differed considerably in their radioactivity recovery in the lungs of rats 48 h pi. Smooth particles showed the highest in vivo stability of the radiolabel on the surface of the spheres, presumably because of slower proteolytic degradation.

We found that for the preparation of HSA-derived microspheres for radiotherapeutic application, smooth surfaced spheres are superior to rough spheres due to their higher in vivo stability of the radionuclide fixation.

Keywords: Human serum albumin microspheres; Yttrium-86; In vivo stability; Radiolabelled particles; Radiotherapy

Publ.-Id: 11008

Präparative Reinigung polarer, mehrfunktionaler Liganden

Röhrich, A.

kein Abstract verfügbar

  • Lecture (others)
    Workshop - Möglichkeiten und Grenzen der HPLC in den Lebenswissenschaften, 01.02.2008, Dresden, Deutschland

Publ.-Id: 11007

Soft X-ray Absorption and Emission Spectroscopic Investigation of Carbon and Carbon:Transition Metal Composite Films

Abrasonis, G.; Berndt, M.; Krause, M.; Kuepper, K.; Munnik, F.; Kolitsch, A.; Möller, W.

Carbon and C:V, C:Co, C:Cu nanocomposite films grown by ion beam cosputtering in the temperature range from room temperature (RT) to 500 °C are investigated. Soft X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) have been used to determine electronic structure of the occupied and unoccupied electronic states of the coexisting carbon and transition metal (TM) constituents. The results from the spectroscopy are supplemented by the film composition data and TM inclusion phase structural information obtained by elastic recoil detection analysis and X-ray diffraction, respectively. The TM(2p) XAS shows that V (Cu) is in carbidic (metallic) state over the whole temperature range, while Co shows a transition from a carbidic toward a metallic state when the growth temperature increases from RT to 500 °C. The C(1s) XAS demonstrates that the increase in the growth temperature favors the formation of graphite-like structures in carbon films. On the other hand, the TM metal incorporation strongly promotes the sp3 admixture in the surrounding carbon phase which manifests itself through a significant increase in the intensity of a feature in the C(1s) XAS spectra positioned at ~291 eV resulting from 1s → σ* transitions. In addition, the codeposition of TM atoms with carbon enhances the formation of carbon structures with the prominent peak between π* and σ* regions in the C(1s) XAS spectra positioned at ~288.5 eV. The effect is independent of the TM tendency to form carbides or TM state (carbidic metallic) while its magnitude increases concomitantly with the TM content and decreases when the crystallinity degree of the inclusion phase increases. The results are discussed on the basis of the nanoparticle imposed curvature on the surrounding carbon network and interactions at the atomic level at the C−TM interfaces.

Publ.-Id: 11005

Question of dynamic chirality in nuclei: The case of 134Pr

Tonev, D.; de Angelis, G.; Brant, S.; Petkov, P.; Dewald, A.; Dönau, F.; Balabanski, D. L.; Zhong, Q.; Pejovic, P.; Bazzacco, D.; Bednarczyk, P.; Camera, F.; Curien, D.; Della Vedova, F.; Fitzler, A.; Gadea, A.; Lo Bianco, G.; Lenzi, S.; Lunardi, S.; Marginean, N.; Möller, O.; Napoli, D. R.; Orlandi, R.; Sahin, E.; Saltarelli, A.; Valiente Dobon, J.; Zell, K. O.; Zhang, J.-Y.; Zhang, Y. H.; Frauendorf, S.

Lifetimes of exited states in 134Pr were measured by means of the recoil distance Doppler-shift and Doppler-shift attenuation techniques. The branching ratios and the electric or magnetic character of the transitions were also investigated. The experiments were performed at IReS, Strasbourg, using the EUROBALL IV spectrometer, in conjunction with the inner bismuth germanate ball and the Cologne coincidence plunger apparatus. Exited states in 134Pr were populated in the fusion-evaporation reaction 119Sn(19F, 4n)134Pr. The possible chiral interpretation of twin bands was investigated in the two-quasiparticle triaxial rotor and interacting boson-fermion-fermion models. The analysis of the wave functions has shown that the possibility for the angular momenta of the proton, neutron, and core to find themselves in the favorable, almost orthogonal geometry, is present but is far from being dominant. The structure is characterized by large beta and gamma fluctuations. The existence of doublets of bands in 134Pr can be attributed to weak chirality dominated by shape fluctuations.

Publ.-Id: 11004

n+ doping of Ge by P implantation and subsequent RTA or FLA

Posselt, M.; Wündisch, C.; Schmidt, B.; Anwand, W.; Grötzschel, R.; Mücklich, A.; Skorupa, W.; Hortenbach, H.; Gennaro, S.; Bersani, M.; Guibertoni, D.; Möller, A.; Pelzing, P.; Clarysse, T.; Simoen, E.; Satta, A.; Bracht, H.

Abstract not available. For details, please contact the first author.

Keywords: Electrical doping; Germanium; Ion Implantation; Diffusion; Activation

  • Lecture (others)
    Seminar talk at IMEC Leuven (Belgium), 07.02.2008, Leuven, Belgium

Publ.-Id: 11003

Neptunium(V) reduction by humic substances of varying functionality

Schmeide, K.; Bernhard, G.

The time dependence of the reduction of Np(V) to Np(IV) by humic substances of varying functionality has been studied under anaerobic conditions between pH 3.5 and pH 9.0. Synthetic humic acids with pronounced redox functionality were studied in comparison to natural humic substances. For Np redox speciation in solution solvent extraction, NIR absorption spectroscopy and ultrafiltration were applied. Exemplary, the application of a synthetic HA is shown for the study of the Np(IV) sorption onto kaolinite in the presence of HA.

Keywords: neptunium; pentavalent; tetravalent; humic acid; sorption; reduction

  • Contribution to proceedings
    Plutonium Futures “The Science” 2008, 07.-11.07.2008, Dijon, France
  • Poster
    Plutonium Futures “The Science” 2008, 07.-11.07.2008, Dijon, France

Publ.-Id: 11002

Hydrophile, macrocyclische Amine: Reinigung mit Problemen

Ruffani, A.

kein Abstract verfügbar

  • Lecture (others)
    Workshop „Möglichkeiten und Grenzen der HPLC in den Lebenswissenschaften“, 01.02.2008, Dresden-Rossendorf, Deutschland

Publ.-Id: 11001

Bis(2-pyridylmethyl) derivatives of 1,4,7-triazacyclononane: promising ligands for radiolabeling of biomolecules

Ruffani, A.

kein Abstract verfügbar

  • Lecture (Conference)
    5th SUPRAPHONE Meeting, 29.05.-01.06.2008, Prague, Czech Republic

Publ.-Id: 11000

1,4,7-Triazacyclononane (TACN) ligands with pendant pyridyl arms - New versatile bifunctional chelating agents (BFCAs)

Ruffani, A.; Stephan, H.; Steinbach, J.; Gasser, G.; Spiccia, L.; Graham, B.

Radiopharmaceuticals based on metallic radionuclides, such as 64/67Cu, 99mTc, 186/188Re and 86/90Y, are often used for diagnostic and therapeutic purposes (1, 2). These nuclides are usually enveloped in organic ligands, such as heteromacrocyclic systems. To be effective, the ligands have to show fast metal complexation kinetics, form complexes with high in vitro and in vivo stability and contain a group that can be linked to biomolecules. We have developed a new ligand scaffold - based on bis(2-pyridylmethyl)triazacyclononane (DMPTACN) – that satisfies these requirements. This structure allows for the introduction of linker groups, such as carboxylic acids, maleinimide or isothiocyanate, thereby facilitating coupling of targeting molecules.

A new TACN derivative, containing two pyridyl pendant arms as well as a carboxylic group for coupling to biomolecules has been synthesized and its copper(II) binding properties investigated. Conjugation of a stabilized octapeptide (bombesin βAla-βAla-[Cha13, Nle14]) was successfully achieved via amide coupling (3). Both the free ligand and the bombesin bioconjugate can rapidly form very stable radiocopper complexes. In vitro ligand competition experiments and stability studies in rat plasma medium gave no evidence of transchelation or demetalation. Biodistribution studies of the bombesin conjugate revealed an accumulation of the compound in the pancreas, which is the organ with highest levels of gastrin-releasing peptide receptor (GRPR) targeted by bombesin.
Our radiopharmalogical data indicate that bifunctional chelating TACN agents are attractive candidates for developing new copper radiotherapeutics. In this perspective, particular BFCAs will be attached to carrier molecules, such as oligonucleotides, antibodies and synthetic polymers, to deliver radiocopper isotopes to target tissues.

1. Anderson C.J., Welch M.J. (1999) Metal complexes as diagnostic tools. Coord. Chem. Rev. 184, 3-66.
2. Volkert W.A., Hoffman T.J. (1999) Therapeutic radiopharmaceuticals. Chem. Rev. 99, 2269-2292.
3. Gasser G., Tjioe L., Graham B., Belousoff M. J., Juran S., Walther M., Künstler J.U., Bergmann R., Stephan H., Spiccia L. (2008)
Synthesis, Copper(II) Complexation, 64Cu-Labeling, and Bioconjugation of a New Bis(2-pyridylmethyl) Derivative of 1,4,7-
Triazacyclononane. Bioconjugate Chem. In press

  • Lecture (Conference)
    7th International Symposium on Polymer Therapeutics: from Laboratory to Clinical Practice, 26.-28.05.2008, Valencia, Spain

Publ.-Id: 10999

Patterning of magnetic structures on austenitic stainless steel by ion beam nitriding

Menendez, E.; Martinavicius, A.; Liedke, M. O.; Abrasonis, G.; Fassbender, J.; Sort, J.; Surinach, S.; Baro, M. D.; Nogues, J.

Nitriding of austenitic stainless steel (ASS) at moderate temperatures (~400ºC) leads to the formation of the supersaturated nitrogen solid solution often called in the literature “expanded austenite” or γN phase [1,2]. This causes an enhancement of the microhardness and the wear resistance without loss of the corrosion resistance. Moreover, this phase shows ferromagnetic behavior, whose origin is linked to the expansion of the austenite (γ) lattice due to the incorporation of nitrogen atoms into interstitial positions [3,4]. Actually, since there is a nitrogen depth profile and the onset of ferromagnetism is connected with nitrogen concentrations of ~15 at.%, the nitrided layer consists of two magnetically different parts (paramagnetic and ferromagnetic) determined by the obtained nitrogen concentration.

In this study, we report the influence of the nitriding temperature and time on the ASS ferromagnetic properties. AISI 304L ASS polycrystalline samples (discs of 10 mm diameter and 2 mm thickness) have been ion beam nitrided in the temperature range of 300-400ºC. The ion energy and the ion current density were ~1 keV and 0.5 mA/cm2 (the corresponding ion flux of ~5•1015 ions•cm-2•s-1), respectively. The processing times were 5 and/or 30 minutes [2]. Periodic arrays of ferromagnetic structures in the micrometer range have been prepared at the surface of the samples using a 2000 mesh Cu transmission electron microscopy grid as a shadow mask (mesh size of 7.5 x 7.5 µm2, 12.5 µm pitch, 20 µm thickness and 3.05 mm diameter). The structure was characterized by X-ray diffraction (XRD) and nuclear reaction analysis (NRA). The magnetic properties were determined by magneto-optical Kerr effect (MOKE) and magnetic force microscopy (MFM).
The XRD patterns of the nitrided ASS samples are presented in Figure 1. The XRD pattern consistent with the FCC lattice structure can be identified for the virgin ASS sample (not shown). For the nitrided samples, each austenite peak exhibits a satellite peak, located at lower diffraction angles which is related with the formation of the “expanded austenite”. The amount of this “expanded” phase increases with the processing temperature, as it is evidenced by the increase of intensity of the γN XRD peaks in detriment to the γ ones.
This is consistent with NRA observations. For instance, a nitrided layer of around 1 µm depth is obtained in the sample nitrided at 400ºC for 30 min, whereas ~15 at.% of nitrogen is obtained around 0.5 µm of depth.
MOKE measurement results of the virgin and the nitrided sample at 400°C for 5 min are compared in Figures 2(a) and 2(b) (patterned area).
It can be seen that the virgin sample does not show any hysteretic behavior, i.e. it is non-ferromagnetic. Conversely, the nitrided samples show clear hysteresis loops indicating the existence of ferromagnetic constituents in the nitrided layer. Figure 2(c) shows the AFM image of a patterned area of the nitrided sample which shows that a moderate sputtering process of the surface has taken place during nitriding resulting in the formation of the periodic array of squared pits. Figure 2 (d) is the corresponding MFM image in an applied magnetic field of 70 mT, where a magnetic dipolar contrast can be clearly seen in each entity, confirming the feasibility of the production of periodic arrays of isolated ferromagnetic structures. It is worth noting that the hysteresis behavior of the continuously nitrided areas and the patterned ones are quite similar due to the fact that the induced ferromagnetic structures are relatively large (micrometer range), leading to entities with magnetic multi-domain configurations.

[1] M.P. Fewell et al., Surf. Coat. Technol. 131, 300 (2000)
[2] G. Abrasonis, et al., J. Appl. Phys. 97, 083531 (2005)
[3] O. Öztürk and D.L. Williamson, J. Appl. Phys. 77, 3839 (1995)
[4] J. Baranowska, Vacuum 81, 1216 (2007)

Keywords: magnetism; stainless steel; nitriding; patterning; ion

  • Poster
    International Conference on Magnetics, Intermag 2008, 04.-08.05.2008, Madrid, Spain

Publ.-Id: 10998

Sc3AlN - A New Perovskite

Höglund, C.; Birch, J.; Beckers, M.; Alling, B.; Czigány, Z.; Mücklich, A.; Hultman, L.

Sc3AlN with perovskite structure has been synthesized as the first ternary phase in the Sc-Al-N system. Magnetron sputter epitaxy at 650 °C was used to grow single-crystal, stoichiometric Sc3AlN(111) thin films onto MgO(111) substrates with ScN(111) seed layers as shown by elastic recoil detection analysis, X-ray diffraction, and transmission electron microscopy. The Sc3AlN phase has a lattice parameter of 4.40 Å, which is in good agreement with the theoretically predicted 4.42 Å. Comparisons of total formation energies show that Sc3AlN is thermodynamically stable with respect to all known binary compounds. Sc3AlN(111) films of 1.75 µm thickness exhibit a nanoindentation hardness of 14.2 GPa, an elastic modulus of 249 GPa, and a room-temperature electrical resistivity of 41.2 µΩ cm.

Publ.-Id: 10997

Entwicklung des Neutronentransportcodes TransRay und Untersuchungen zur zwei- und dreidimensionalen Berechnung effektiver Gruppenwirkungsquerschnitte

Beckert, C.

Standardmäßig erfolgt die Datenaufbereitung der Neutronenwirkungsquerschnitte für Reaktorkernrechnungen mit 2D-Zellcodes. Ziel dieser Arbeit war es, einen 3D-Zellcode zu entwickeln, mit diesem Code 3D-Effekte zu untersuchen und die Notwendigkeit einer 3D-Datenaufbereitung der Neutronenwirkungsquerschnitte zu bewerten. Zur Berechnung des Neutronentransports wurde die Methode der Erststoßwahrscheinlichkeiten, die mit der Ray-Tracing-Methode berechnet werden, gewählt. Die mathematischen Algorithmen wurden in den 2D/3D-Zellcode TransRay umgesetzt. Für den Geometrieteil des Programms wurde das Geometriemodul eines Monte-Carlo-Codes genutzt. Das Ray-Tracing in 3D wurde auf Grund der hohen Rechenzeiten parallelisiert. Das Programm TransRay wurde an 2D-Testaufgaben verifiziert.
Für einen Druckwasser-Referenzreaktor wurden folgende 3D-Probleme untersucht: Ein teilweise eingetauchter Regelstab und Void (Vakuum oder Dampf) um einen Brennstab als Modell einer Dampfblase. Alle Probleme wurden zum Vergleich auch mit den Programmen HELIOS (2D) und MCNP (3D) nachgerechnet. Die Abhängigkeit des Multiplikationsfaktors und der gemittelten Zweigruppenquerschnitte von der Eintauchtiefe des Regelstabes bzw. von der Höhe der Dampfblase wurden untersucht. Die 3D berechneten Zweigruppenquerschnitte wurden mit drei üblichen Näherungen verglichen: Lineare Interpolation, Interpolation mit Flusswichtung und Homogenisierung. Am 3D-Problem des Regelstabes zeigte sich, dass die Interpolation mit Flusswichtung eine gute Näherung ist. Demnach ist hier eine 3D-Datenaufbereitung nicht notwendig. Beim Testfall des einzelnen Brennstabs, der von Void umgeben ist, erwiesen sich die drei Näherungen für die Zweigruppenquerschnitte als unzureichend. Demnach ist eine 3D-Datenaufbereitung notwendig. Die einzelne Brennstabzelle mit Void kann als der Grenzfall eines Reaktors angesehen werden, in dem sich eine Phasengrenzfläche herausgebildet hat.

Keywords: Reactor physics; calculational methods; neutron transport; transport methods; ray tracing; cross sections; cell calculation; absorber rod; void

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZD-492 2008
    ISSN: 1437-322X


Publ.-Id: 10996

Radiation damage in helium-implanted diamond

Nasdala, L.; Grambole, D.; Harris, J. W.; Wildner, M.; Hofmeister, W.

Diamond platelets were implanted with 8.8 MeV He2+ ions, the equivalent of alpha particles generated in the natural 212Po ---> 208Pb decay (Th decay chain). Implantation densities were varied in the range 1012 - 1017 ions per cm². Visible green colouration was produced at He2+ fluences _>1015 cm-2. The radioinduced colour is mainly due to a broad absorption band at ca. 16000 cm-1, which is assigned to the GR1 centre. Raman line scans showed that a narrow, stongly damaged area is formed ca. 29 µm below the sample surface. This corresponds very well with the distribution of Frenkel-type defects as predicted by Monte Carlo simulations using the SRIM program 1. Raman data obtained from naturally radiocoloured diamonds are discussed in light of our new results.
1 Ziegler JF, Biersack JP, Littmark U. The stopping and range of ions in solids. Pergamon Press, New York, 1985.

  • Lecture (Conference)
    8th International Conference on Raman Spectroscopy Applied to the Earth Sciences (GeoRaman08), 02.-06.06.2008, Ghent, Belgium
  • Contribution to proceedings
    8th International Conference on Raman Spectroscopy Applied to the Earth Sciences (GeoRaman08), 02.-06.06.2008, Ghent, Belgium
    Book of abstracts, 52

Publ.-Id: 10995

The origin of the Energy-Dose window in Separartion-by-Implanted-Oxygen (SIMOX) materials processing

Koegler, R.; Ou, X.; Skorupa, W.; Moeller, W.

Separation-by-Implantated-Oxygen (SIMOX) is an established technique to manufacture a buried oxide layer in silicon (SOI) by ion implantation and annealing. The so called energy-dose window defines implantation parameters suitable for the formation of a continuous buried oxide layer with the lowest ion dose. The study concerns the reason why defined combinations of ion energy and ion dose result in a high quality oxide layer. Excess defects induced by the O implantation are shown to influence the oxide layer formation. The depth distribution of excess defects fits very well with the final depth position of the oxide layer for O implants in the energy-dose window.

Keywords: Ion implantation; silicon-on-insulator; SIMOX; defects; oxygen

Publ.-Id: 10994

Comparative investigation of the interaction of uranium with lipopolysaccharide and peptidoglycan

Barkleit, A.; Moll, H.; Bernhard, G.

Microorganisms are very important for the bioremediation of the environment because they are able to adsorb radionuclides and other heavy metals. They significantly influence mobilization and immobilization of metal ions in soils.
We investigated representative the complexation of the uranyl ion with main parts of bacterial cell walls. Lipopolysaccharide (LPS) is the principal component of the cell wall of gram-negative bacteria, whereas peptidoglycan (PGN) represents the basis of the cell wall of gram-positve bacteria. Both biomolecules contain a high density of metal-binding functionalities like carboxyl, amino, and hydroxyl groups. LPS offers additionally a high amount on phosphoryl groups, which are missing in PGN.
We investigated the interaction of the uranyl cation (UO22+) with the biopolymers LPS and PGN by using potentiometric titration and time-resolved laser-induced fluorescence spectroscopy (TRLFS) over a wide pH range (2.4 – 9) and at environmentally relevant low uranium concentrations (10-4 – 10-5 M).
Using potentiometric titration, the dissociation constants of the respective functional groups were determined. Furthermore essential uranyl complexes and their stability constants were identified.
With the aid of time-resolved laser-induced fluorescence spectroscopy (TRLFS) the luminescence properties of uranyl complexes with the biopolymers and the associated stability constants were investigated. At low pH values both biomolecules effect an increase of the luminescence intensity and a red-shift of about 8-10 nm, compared to the free UO22+ ion. With LPS the luminescence intensity increases up to pH 8. In contrast to LPS, the PGN polymer causes a decrease of the luminescence intensity over pH 4.5, indicating, that a non-luminescent complex has built.
As a result from both methods, we found that the uranyl ion prefers with LPS phosphoryl coordination, whereas PGN, with a lack of phosphoryl groups, forms stable carboxylate complexes.

  • Lecture (Conference)
    5th International Conference Uranium Mining Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 753-754

Publ.-Id: 10993

Theoretical study on the highest oxidation states of Pu

Tsushima, S.

It has been demonstrated recently that quantum chemical calculations can accurately perdict redox potentials of An(VI)/An(V) couples (An = U, Np, Pu, Am) if multireference effect and spin-orbit effects are treated properly [1,2]. The An(VI)/An(V) redox potentials obtained at the multireference CASPT2 level calculations with spin-orbit corrections were found to have fairly good agreement with those obtained by experiments.
Here, I extend such calculations to the higher oxidation states of actinide, namely Pu(VII) and Pu(VIII). Pu(VII) is known to be meta-stable in aqueous solution. Recently, Nikonov et al. have suggested that Pu(VIII) may be obtained by the ozonation of Pu(VI), although they were not able to find a direct evidence for the presence of Pu(VIII) [3]. The present work aims to discuss from a theoretical point of view whether or not Pu(VIII) may exist in water. Geometry optimizations and energy calculations of the complexes were performed at the B3LYP level, and spin-orbit effects were calculated separately at the CASSCF level.
The redox potential of the PuVIIIO4(OH)2 2-/ PuVIIO4(OH)2 3- couple was found to be as high as ~1.7V. At very high pH, Pu(VII) may exist as a penta-oxo complex, PuVIIO5(OH)4-. The redox potential of PuVIIIO5(OH)3-/ PuVIIO5(OH)4- couple was found to be ~1.3V. Spin-orbit effect was found to play a very important role for the total redox potential because the ground state energy lowering of Pu(VII) due to the spin-orbit splitting depends highly on the number of coordinating oxo ligands. The effect of coordinating ligands (OH-, CO3 2- etc.) and coordination number on the total redox potential was also studied. The calculations suggest that Pu(VIII) is unlikely to exist in both acidic and alkaline aqueous solutions, while Pu(VIII) may be present in non-aqueous solvents with a large redox window.

[1] Tsushima,S; Wahlgren, U.; Grenthe, I. J. Phys. Chem. A 2006, 110, 9175.
[2] Shamov, G.A.; Schreckenbach, G. J. Phys. Chem. A 2005, 109, 10961.
[3] Nikonov, M.V.; Gogolev, A.V.; Tananaev, I.G.; Myasoedov, B.F. Radiochemsitry 2004, 46, 340.

Keywords: Plutonium; quantum chemistry; redox potential

  • Lecture (Conference)
    Plutonium Futures "The Science" 2008, 07.-11.7.2008, Dijon, France

Publ.-Id: 10992

Natural and Engineered Nanoparticles in the Environment: A presentation of current activities of the AK Aquatic Nanoscience & Nanotechnology

von der Kammer, F.; Baalousha, M.; Baun, A.; Hassellov, M.; Delay, M.; Thieme, J.; Zänker, H.; Neumann-Hensel, H.; Handy, R.; Hochella, M.

For more than two decades aquatic chemistry is constantly gaining knowledge about nanoscale processes in the environment. While in early years the co-transport of contaminants in the saturated zone of aquifers has been in the focus of aquatic nanosciences and nanogeosciences, nowadays the research activities have broadened and span across several disciplines. In the course of R & D activities on nanomaterials the question of the behavior, fate and useful or adverse effects of nanoparticles in the environment arose and has boosted the activities quite substantially. The working group Aquatic Nanosciences and Nanotechnology has responded to the current development by inviting European scientists from different fields to contribute their expertise into the group’s discussions and activities while still keeping the core expertise on characterization techniques inherited from the former working group “Colloids”. In 2007 the working group organized an international workshop which was held in Vienna during the 10th and 11th December. The aim of the event was to offer a platform for bridging the different disciplines and exchange the current knowledge in the fields. Scientists from aquatic and environmental chemistry, nanogeosciences, nano-engineering, eco-toxicology and risk assessment presented their contributions to the current state of the art. The overall conclusions drawn from 29 presentations are given.

Keywords: Natural nanoparticles; engineered nanoparticles; environment; natural waters

  • Lecture (Conference)
    Wasser 2008. Jahrestagung der Wasserchemischen Gesellschaft, 28.-30.04.2008, Trier, Germany

Publ.-Id: 10991

Dipole-strength functions studied in photon-scattering experiments at ELBE

Schwengner, R.

Dipole-strength functions studied in photon-scattering experiments at ELBE

  • Invited lecture (Conferences)
    Seminar, 15.01.2008, Durham, North Carolina, USA

Publ.-Id: 10990

P implantation into preamorphized germanium and subsequent annealing: Solid phase epitaxial regrowth, P diffusion, and activation

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

Phosphorus implantation (30 keV, 3x1015 cm−2) into preamorphized Ge and subsequent rapid thermal or flash lamp annealing is investigated. During annealing a significant P diffusion in amorphous Ge is not observed. However, the fast solid phase epitaxial regrowth causes a rapid redistribution of P. After completion of the regrowth and at temperatures above 500 °C, a concentration-dependent diffusion of P in crystalline Ge takes place and leads to considerable loss of P toward the surface. An appreciable influence of implantation defects on the diffusion coefficient of P is not detected. For 60 s rapid thermal annealing at 600 °C and for 20 ms flash lamp annealing at 900 °C, the junction depth and the sheet resistance vary between 140 and 200 nm and between
50 and 100 Ohm, respectively, and the maximum electrical activation of P is about 3–7 x1019 cm−3

Keywords: Germanium; electrical doping; ion implantation; annealing; diffusion; activation; solid-phase epitaxial regrowth

  • Journal of Vacuum Science & Technology B 26(2008), 430-434

Publ.-Id: 10989

Beschleunigen mit Licht

Schramm, U.

Keywords: Laserplasma Beschleuniger

  • Invited lecture (Conferences)
    Physikalisches Kolloquium, 23.10.2007, Dresden, Germany

Publ.-Id: 10988

Equation of state for strongly interacting matter: collective effects, Landau damping and predictions for LHC

Schulze, R.; Bluhm, M.; Kämpfer, B.

Abstract for the description of the hydrodynamic phase of strongly interacting matter in relativistic HIC the equation of state (EOS) is of utmost importance. Lattice QCD can provide useful information on the EOS, mainly for small net baryon densities. The QCD quasiparticle model (QPM) provides a means to map lattice results into regions relevant for a variety of experiments. Recent work has enabled us to include collectives modes and damping effects into the QPM. Among physical implications are predictions for forthcoming heavy-ion collisions at LHC/ALICE.

Keywords: QCD; equation of state; EOS; quasiparticle; model; plasmon; plasmino; plasmons; plasminos; quark; gluon; plasma; Landau; damping; characteristics

  • Contribution to proceedings
    XLVI International Winter Meeting on Nuclear Physics, 20.-26.1.2008, Bormio, Italy
    Proceedings of the XLVI International Winter Meeting on Nuclear Physics, Milano: Università degli Studi di Milano, 63-69
  • Contribution to WWW
  • Lecture (Conference)
    XLVI International Winter Meeting on Nuclear Physics, 22.01.2008, Bormio, Italien

Publ.-Id: 10987

Prospects for Applications of Laser-Accelerated Particles

Schramm, U.; Sauerbrey, R.

Invited talk on possible medical applications of laser accelerated particle beams

Keywords: laser ion acceleration; FELs

  • Invited lecture (Conferences)
    International Symposium on Ultrafast Intense Laser Science ISUILS 07, 24.-27.9.2007, Pisa, Italy

Publ.-Id: 10986

Focusing and transport of laser-accelerated protons with quadrupoles

Schollmeier, M.; Geißel, M.; Flippo, K.; Becker, S.; Blazevic, A.; Grüner, F.; Harres, K.; Nürnberg, F.; Rambo, P.; Schramm, U.; Schreiber, J.; Schwarz, J.; Atherton, B.; Habs, D.; Hegelich, B. M.; Roth, M.

Focusing and transport of laser-accelerated protons with quadrupoles

Keywords: Laser acceleration of ions; beam transport; quadrupole lenses PMQ

  • Contribution to external collection
    in: GSI Jahresbericht, Darmstadt: GSI, 2008

Publ.-Id: 10985

Laser-Particle-Acceleration and Prospects of the application of laser-accelerated particles

Schramm, U.

Tutorial on laserparticle acceleration and applications of such beams.

Keywords: Tutorial lectures

  • Invited lecture (Conferences)
    International Workshop on Prospectives of High Density Short Pulse Lasers, 07.-11.1.2008, Cairo, Egypt

Publ.-Id: 10984

Complexation studies of Uranium(VI) by Sulfur and Nitrogen Containing Model Ligands in Aqueous Solution

Raditzky, B.; Schmeide, K.; Geipel, G.; Bernhard, G.

The long-term safety assessment of nuclear waste disposals requires detailed knowledge of the transport and interaction behavior of actinides within the technical, geotechnical and geological barriers. The migration and interaction behavior of actinides can be effectively influenced by humic substances, biopolymers ubiquitous in natural environments, due to their ability for complex and colloid formation and their redox properties. It is known, that especially their carboxylic and phenolic OH groups are able to complex metal ions. In addition to these oxygen containing functional groups, humic substances also offer sulfur and nitrogen containing functionalities.

The aim of this work is to determine the influence of various sulfur and nitrogen containing functional groups on the uranium(VI) complexation and to evaluate their contribution in comparison to oxygen containing functional groups. For this, simple organic model ligands that can occur as building blocks for humic substances are used in the first instance with the objective to transfer the results to humic substances. In this study, results are presented for the uranium(VI) complexation by the organic ligands benzenesulfonic acid and 4-hydrxybenzenesulfonic acid as well as anthranilic and nicotinic acid. The complex formation constants for the uranium(VI) complexation were determined applying time-resolved laser-induced fluorescence spectroscopy (TRLFS) as a function of pH.

Keywords: uranium(VI); fs-TRLFS; TRLFS; benzenesulfonic acid; 4-hydroxybenzenesulfonic acid; anthranilic acid; nicotinic acid; complexation

  • Contribution to proceedings
    Seventh International Conference on Nuclear and Radiochemistry (NRC7), 24.-29.08.2008, Budapest, Hungary
  • Lecture (Conference)
    Seventh International Conference on Nuclear and Radiochemistry (NRC7), 24.-29.08.2008, Budapest, Hungary

Publ.-Id: 10983

Qualitätssicherung bei der PET/CT für die Bestrahlungsplanung

Zips, D.; Richter, C.

kein Abstract vorhanden, da Vortrag

  • Lecture (others)
    Strahlenschutz und Qualitätssicherung bei modernen strahlentherapeutischen Verfahren und in der klinisch-strahlentherapeutischen Forschung, 08.12.2007, Dresden, Deutschland
  • Lecture (others)
    Strahlenschutz und Qualitätssicherung bei modernen strahlentherapeutischen Verfahren und in der klinisch-strahlentherapeutischen Forschung, 03.-04.04.2009, Dresden, Deutschland

Publ.-Id: 10982

4D-PET/4D-CT Bildgebung und ihre Anwendung in der Strahlentherapie

Richter, C.

kein Abstract vorhanden, da Vortrag.

  • Lecture (others)
    OncoRay Seminar, 06.12.2007, Dresden, Deutschland

Publ.-Id: 10981

Momentum Control of Charged Particles with Light

Schramm, U.

Laser cooling at ESR and laserplasma particle acceleration.

Keywords: laser cooling; laser plasma acceleration

  • Invited lecture (Conferences)
    GSI Atomic Physics Seminar, 30.1.2008, Darmstadt, Germany

Publ.-Id: 10980

On three-dimensional magnetic field effects during metal deposition in cuboid cells

Mutschke, G.; Cierpka, C.; Weier, T.; Bund, A.; Eckert, K.; Mühlenhoff, S.; Yang, X. G.; Hess, A.

This paper will discuss recent experimental and numerical results from the authors' labs on the effects of moderate magnetic fields in electrochemical reactions. It is well established that the influence of the Lorentz force due to external homogeneous magnetic fields, known as magnetohydrodynamic (MHD) effect, manifests itself in the majority of cases in increased mass transport. However, a careful analysis of the governing equations shows that often a three-dimensional modeling of this effect is necessary. We will present numerical simulations of copper electrolysis in cuboid cells under the influence of homogeneous magnetic fields of different directions in the limiting current regime. In most cases there is a complex interplay of natural and magnetically driven convection. A comparison with recent experimental results (flow and concentration gradient visualization) will be given.

Acknowledgments: This work was supported by the German Science Foundation in frame of the collaborative research center 609 "Electromagnetic flow control in metallurgy, crystal growth and electrochemistry"


1) K. Kim & T.Z. Fahidy, "An analysis of free-convective magnetoelectrolysis in constant magnetic fields", J. Electrochem. Soc. 142 (1995) 4196-4204
2) A.Bund, S.Koehler, H.Kuehnlein, W.Plieth, "Magnetic field effects on electrochemical processes", Electrochimica Acta 49 (2003) 147—152.
3) A. Bund, A. Ispas, G. Mutschke, "Magnetic field effects on electrochemical metal depositions", submitted to: Science and Technology of Advanced Materials, 2007
4) T. Weier, K. Eckert, S. Muehlenhoff, C. Cierpka, A. Bund, M. Uhlemann, Electrochem. Commun., 9 (2007) 2479.

Keywords: Magnetoelectrochemistry; Electrolytic metal deposition; magnetic field; Lorentz force

  • Lecture (Conference)
    213th ECS Meeting, 18.-22.05.2008, Phoenix, Arizona, United States
  • ECS Transactions 13(2008)16, 9-13

Publ.-Id: 10979

Minimization of topological defects in ion-induced ripple patterns on silicon

Keller, A.; Facsko, S.; Möller, W.

The evolution of self-organized nanoscale ripple patterns induced by low energy ion sputtering of silicon was investigated. The quality of the patterns was monitored by calculating a normalized density of topological defects from atomic force microscopy images. A strong dependence of the normalized defect density on the applied ion fluence is observed with a well pronounced minimum at intermediate fluences. Simulations using the damped Kuramoto-Sivashinsky equation yield good agreement with the experiments and are further used to study the dynamics of single pattern defects.

Publ.-Id: 10978

THEREDA – Thermodynamic Reference Database for Nuclear Waste Disposal in Germany

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

The disposal of radioactive waste including the assessment of long-term safety is an open question in Germany. In addition to the choice of the repository host rock (salt, granite, clay) the basic necessity of a consistent and bindingly used reference database exists. Only by means of such a database it is possible to assess potential failure scenarios accurately and to make well-founded predictions about the long-term safety. Specific needs for waste repository and remediation projects in Germany are comprehensive datasets also covering high temperatures and high salinities. Against this background, available databases (NEA-TDB, IUPAC, NAGRA-PSI) do not suffice all these requests and are limited in their use, partly because of high restrictions and resulting incompleteness of thermodynamic datasets. Other databases rely on heterogeneous and therefore inconsistent data yielding in inadequately reproducible and plausible model calculations. Due to these deficiencies THEREDA, a joint project of institutions leading in the field of safety research for nuclear waste disposal in Germany, was started. It will provide consistent thermodynamic datasets and enhance the transparency and reliability of safety analyses.
Within the project THEREDA we seek to compile data of high quality, accordance and traceability, mainly from existing databases, and to complement this basis particularly with datasets for high saline systems (Pitzer and SIT parameters) and systems at elevated temperatures. Persistent data gaps are closed via estimated values. The identification of such gaps can also aid decisions about the scheduling of experimental programs. Each dataset included in THEREDA is documented in detail and gets a grade of quality attached. Higher grades of quality are allocated to thermodynamic parameters derived from experimental data, namely from non-thermochemical experiments, whereas estimated values determined from systematic trends in thermodynamical behavior or from studies of chemical analogs get lower ratings. Furthermore, numerical data uncertainties and the quality of data sources (primary or secondary literature, peer-reviewed or non-certified) are categorized.
THEREDA will represent a source of information on thermodynamic data that will be publicly accessible and free of charge via Internet ( and set up on a SQL-database. A broad use of the database is ensured by export functions tailored to important geochemical codes such as EQ3/6, PHREEQC, GWB and ChemApp.

Keywords: THEREDA; database; nuclear waste disposal; long-term safety; thermodynamic data; quality assurance; high saline systems; Pitzer; SIT

  • Contribution to proceedings
    2008 International High-Level Radioactive Waste Management Conference (2008 IHLRW), 07.-11.09.2008, Las Vegas, Nevada, United States
    Steps Toward Reality for Safe Disposal, 978-0-89448-062-1, 287-290
  • Lecture (Conference)
    2008 International High-Level Radioactive Waste Management Conference (2008 IHLRW), 07.-11.09.2008, Las Vegas, Nevada, United States

Publ.-Id: 10977

Sorption of uranium(VI) on ferrihydrite – Influence of atmospheric carbonate on surface complex formation investigated by ATR-FT-IR spectroscopy

Foerstendorf, H.; Heim, K.

The migration behaviour of uranium in the geosphere is generally influenced by sorption processes in aqueous media. The solubility, mobility and bioavailability is determined by the molecular interactions between the dissolved actinide species and mineral surfaces in groundwater aquifers. In its hexavalent form, uranium usually exists in the environment as the dioxouranyl cation (UO22+) which can form highly soluble complexes with a variety of anionic species commonly increasing the solubility of uranium. However, since there is a high affinity of the UO22+ ion to hydrous iron oxides the mobility of U(VI) can be considerably reduced in the environment. The affinity of U(VI) to hydrous ferric oxides is strongest in the pH range from 5 to 8. But it is also dependent on the composition of the liquid phase. Strong complexing ligands such as carbonate potentially inhibit adsorption of U(VI) onto the mineral phase (1). Therefore, the structures of the uranyl surface complexes at iron hydroxide mineral phases such as hematite and ferrihydrite (Fh) in the presence of CO2 are still in the focus of recent spectroscopic investigations (2,3).
In this work we present results from sorption experiments of U(VI) on Fh using Attenuated Total Reflection Fourier-transform Infrared (ATR-FT-IR) spectroscopy which provide in situ spectral information of the sorption processes in aqueous solution. The sorption of the UO22+ ion was investigated at mildly acidic conditions in atmospheric equilibrium and under an inert gas atmosphere in order to study the influence of dissolved CO2 on the sorption process. The infrared spectra show a similar surface complex of the uranyl ion at the Fh-phase irrespective of the presence of atmospheric CO2. However, the binding of the carbonate ligand to the mineral phase changes considerably upon sorption of the actinide ion and a change from a monodentate to a bidentate binding upon sorption of UO22+ is concluded. Furthermore, we investigated the sorption and desorption behavior of carbonate ions on pristine Fh and after sorption of UO22+ onto the iron oxide phase.

(1) Hsi, C. D.; Langmuir, D. Geochim. Cosmochim. Acta 1985, 49, 1931-1941.
(2) Bargar, J. R.; Reitmeyer, R.; Davis, J. A. Environ. Sci. Technol. 1999, 33, 2481-2484.
(3) Ulrich, K. U.; Rossberg, A.; Foerstendorf, H.; Zänker, H.; Scheinost, A. C. Geochim. Cosmochim. Acta 2006, 70, 5469-5487.

Keywords: Ferrihydrite; ATR FTIR spectroscopy; uranium(VI); carbonate; sorption

  • Poster
    7th International Conference on Nuclear and Radiochemistry, 24.-29.08.2008, Budapest, Hungria

Publ.-Id: 10976

Infrared spectroscopic comparison of the aqueous species of uranium(VI) and neptunium(VI)

Müller, K.; Foerstendorf, H.; Brendler, V.; Bernhard, G.

The distribution of aqueous species of actinide(VI) ions primarily defines their geochemical reactions, e.g. complexation in solution, sorption onto mineral and biological phases, and the formation of colloids, and thus, influences the migration behaviour in the environment. In aqueous solution under normal conditions both uranium and neptunium exist as dioxoactinyl ions AnO2n+ (An = U, Np). They form different complexed species depending on their concentration level, pH range and the presence of potential ligands, such as carbonate.
In recent years, the aqueous U(VI) system has been investigated intensively, in contrast to Np(VI). However, the stability constants used for thermodynamic calculations often arise from non-structural experiments, such as potentiometry and ion exchange, performed at defined sample parameters (1,2). Up to now, a spectroscopic verification of uranyl and neptunyl species is lacking in particular at low concentrations and at neutral pH conditions, reasonably in an environmental context. Thus, speciation modelling using extrapolated data, might be inadequate for the assessment of actinide migration.
In this study we used Attenuated Total Reflectance Fourier-transform Infrared (ATR-FTIR) spectroscopy to compare hydrolysis and carbonate complexation reactions of both U(VI) and Np(VI). Such comparative vibrational study is feasible since the ions NpO22+ and UO22+ are linear and symmetrical. The results are relevant for a comprehensive understanding of actinyl(VI) complexation in aqueous solution.
The experiments were performed at a micromolar concentration level (≤ 100 µM) and in the pH range 2 – 7 under both oxic and anoxic atmosphere. In the infrared spectra the asymmetric stretching vibrations ν3 of the free ions, UO22+ and NpO22+, found in solutions at very acidic pH, are observed at similar wavenumbers, 961 and 964 cm–1. Upon increasing the pH the IR spectra provide evidence for the formation of hydroxo complexes of both actinyl(VI) ions at pH ≥ 3, which is contradictive to current thermodynamic speciation modelling. Since the comparison of the spectral differences between the two actinides show red-shifted bands to a similar extent it can be assumed that analogous hydrolysis species are formed.

(1) Guillaumont, R.; Fanghänel, T.; Fuger, J.; Grenthe, I.; Neck, V.; Palmer, D. A.; Rand, M. H. Update on the Chemical Thermodynamics of U, Np, Pu, Am and Tc.; Elsevier: Amsterdam, 2003.
(2) Grenthe, I.; Fuger, J.; Lemire, R. J.; Muller, A. B.; Nguyen-Trung, C.; Wanner, H. Chemical Thermodynamics of Uranium. ; 1st ed.; Elsevier Science Publishers B. V.: Amsterdam, 1992.

  • Contribution to proceedings
    NRC 7 - Seventh International Conference on Nuclear and Radiochemistry, 24.-29.08.2008, Budapest, Hungary
    Book of Abstracts, 978-963-9319-80-6, 275
  • Poster
    NRC7 - Seventh International Conference on Nuclear and Radiochemistry, 24.-29.08.2008, Budapest, Hungary

Publ.-Id: 10975

U(VI) species sorbed on the green algae Chlorella vulgaris - a TRLFS and EXAFS study

Günther, A.; Roßberg, A.; Raff, J.; Geipel, G.; Bernhard, G.

Algae in soil and water can have a significant influence on the transport of actinides in the biological and geological environment in particular on the load pathway soil - plant - animal - human. The chemical characterization of the radionuclide species is essential for a reliable assessment of the migration. Due to the relative simple structure of mono-cellular green algal cells and their properties to bind high amounts of heavy metals and actinides they are used as model organisms for the investigations of different biosorption and bioaccumulation processes.
Sorption studies with Chlorella vulgaris cells have shown that up to 40 % of the initial uranium is bound by the algal cells at pH 3. The uranium removal is almost complete at pH 5 and 6 in our experiments. The use of the time-resolved laser-induced fluorescence spectroscopy (TRLFS) and X-ray absorption spectroscopy (XAS) is an effort to obtain information about the possible structure and the spectroscopic properties of the sorbed U(VI) species on the algal cells in comparison to those of the initial uranyl species in the contact solution.
The luminescence spectroscopic investigations of formed algal uranyl complexes indicate that the binding of U(VI) to carboxyl groups plays a dominating role at pH 3, whereas a minor impact of organic phosphate compounds on the U(VI) sorption can not be excluded. In contrast, at pH 5 and 6 the phosphate groups are mainly responsible for the removal and binding of U(VI) by formation of organic and/or inorganic uranyl phosphates. The results of the uranium LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopic measurements support these evidence.

  • Contribution to proceedings
    NRC7 - 7th International Conference on Nuclear and Radiochemistry, 24.-29.08.2008, Budapest, Hungary
  • Lecture (Conference)
    NRC7 - 7th International Conference on Nuclear and Radiochemistry, 24.-29.08.2008, Budapest, Hungary

Publ.-Id: 10974

Einfluss der Oberflächeneigenschaften von Kohlenstoffnanotubes auf ihr Verhalten in der Umwelt

Schierz, A.; Zaenker, H.; Bernhard, G.

Kohlenstoffnanotubes (CNTs) weisen einzigartige mechanische, elektronische und chemische Eigenschaften auf. Mit dem zunehmendem Einsatz dieser Materialien in Industrie- und Konsumgütern kann, realistisch betrachtet, ein unbeabsichtigter Eintrag in die Umwelt nicht ausgeschlossen werden. Bislang veröffentlichte Studien zum Verhalten und zum Lebenszyklus von CNTs in der Umwelt sind unzureichend.
Im Rahmen der Arbeit wird der Zusammenhang zwischen Oberflächeneigenschaften, Suspensionsstabilität und Sorptionseigenschaften von CNTs diskutiert, um Vorhersagen über das Verhalten dieser Materialien nach einer unbeabsichtigten Freisetzung in die Umwelt zu treffen.

  • Contribution to proceedings
    2. Symposium "Nanotechnology and Toxocology in Environment and Health, 02.-03.04.07, Leipzig, Deutschland

Publ.-Id: 10973

Microscopic and spectroscopic investigation of the U(VI) interaction with monocellular green algae

Vogel, M.; Günther, A.; Raff, J.; Bernhard, G.

The green alga Chlorella vulgaris has the ability to bind high amounts of uranium(VI) in the pH range from 3 to 6 and to a lesser extend at higher pH values. The uranium removal is almost complete at pH 4.4 and 6 by metabolic active and inactive cells under the given experimental conditions. Laser-induced fluorescence spectroscopy was used for the characterization of uranyl species formed in solutions and biomass. Fluorescence spectroscopic investigations indicate differences of the formed algal uranyl complexes in dependence of the metabolic activity of cells and the uranyl speciation. Scanning electron microscopy demonstrates that the algal cell wall is involved in the binding of U(VI).

  • Lecture (Conference)
    5th International Conference Uranium Mining Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 693-702

Publ.-Id: 10972

Complexation of Curium(III) and Europium(III) with Urea

Heller, A.; Barkleit, A.; Bernhard, G.

To understand the toxicity, transport, deposition and elimination of man-made radioactive elements in the human organism, it is crucial to elucidate their chemical behavior and properties on a molecular level. The present work is part of a project to determine the speciation of curium(III) and its lanthanide analog europium(III) in human urine in order to identify potential decontamination agents, to discover possible metabolism pathways in the organism and to detect differences and similarities in the chemistry of trivalent lanthanides and actinides. The aim of this work was to investigate the complexation of curium(III) and europium(III) with urea, the main component of mammal urine. Since both elements exhibit unique luminescence properties, the complexation was studied by time-resolved laser-induced fluorescence spectroscopy with an excitation wavelength of 395 nm. The europium(III) and curium(III) concentration was 3x10-5 M and 3x10-7¬ M, respectively, in all series. The urea concentration was varied between 0.001 and 5 M, the pH ranged from 1 to 8. All measurements were carried out in a glove box under nitrogen atmosphere.

In aqueous solution the luminescence spectrum of europium(III) shows two typical peaks at 585-595 and 610-620 nm, respectively. Each of these peaks is slightly split, the first one into two peaks with emission maxima at 588 and 591nm, respectively, the second one into two peaks with luminescence maxima at 612 and 616 nm, respectively. Upon complexation with urea the position of all peaks remains unaltered but the ratio of the split peaks in the 610-620 nm range changes. Furthermore luminescence in this wavelength range is significantly increased by complexation. The lifetime of the europium(III)-aqua-ion was determined to be 110 µs. In contrast the complex exhibits a considerably longer lifetime (> 120 µs). Analysis of the time-resolved spectra indicated the formation of a 1:1 complex. At an urea concentration of 1 M the complex is stable till pH 6 but starting at pH 7 the luminescence spectrum changes due to formation of europium(III) hydroxides. Using the factor analysis program SPECFIT the stability constant of the complex log ß110 was determined to be -0.08.

In contrast to europium(III), the luminescence spectrum of curium(III) in aqueous solution shows only one emission peak at 593 nm. Upon complexation with urea the peak is red-shifted to 598 nm and the luminescence intensity decreases. The lifetime of the curium(III)-aqua-ion was determined to be 68 µs but the lifetime of the complex is considerably longer (> 75 µs). Analysis of the time-resolved spectra indicated the formation of a 1:1 complex. At an urea concentration of 1.5 M the complex is already formed at pH 1 and till pH 5 the luminescence spectra are identical. Starting at pH 6 the luminescence intensity decreases significantly due to the formation of curium(III) hydroxides. Using the factor analysis program SPECFIT the single spectra of the different species were calculated and the stability constant of the complex log ß110 was determined to be between -0.8 and -0.9.

Comparing the complexation of urea with europium(III) and curium(III), it seems that the latter is complexed inferior to the first one although it is obvious that both form very weak complexes. This can be explained with the structure of urea in aqueous solution over the whole pH range investigated in this study. The results obtained indicate that urea unlikely plays a role in heavy metal binding in urine and that other substances will have greater complexing potential.

Keywords: europium(III); curium(III); complexation

  • Poster
    Seventh International Conference on Nuclear and Radiochemistry, 24.-29.08.2008, Budapest, Hungary

Publ.-Id: 10971

Helical magnetorotational instability in a liquid metal experiment with reduced Ekman pumping

Stefani, F.; Gerbeth, G.; Gundrum, T.; Szklarski, J.; Rüdiger, G.; Hollerbach, R.

The magnetorotational instability (MRI) is one of the most promising candidates to explain turbulence and angular momentum transport in accretion disks which is essential to understand the mass accumulation of stars and black holes. Only recently, a possible connection of MRI with the dynamo process in the Earth's core was discussed. We study a special type of MRI in a Taylor-Couette experiment with the liquid metal alloy GaInSn under the influence of a helical magnetic field (Phys. Rev. Lett. 97, 184502; Astrophys. J. 649, L145-L147; New J. Phys. 9, 295). This helical MRI sets in at Reynolds numbers of the order 1000 and Hartmann numbers of the order 10, quite in contrast to the standard MRI with an purely axial magnetic field which would require much larger values. Particular focus is laid on recent results of a modified experiment with strongly reduced Ekman pumping at the endplates in which sharper transitions between stable and unstable regimes are observed.

  • Open Access Logo Abstract in refereed journal
    Geophysical Research Abstracts 10(2008), 01989

Publ.-Id: 10969

Stochastic resonance in a noise triggered relaxation oscillation model of Earth's magnetic field reversals

Stefani, F.; Fischer, M.; Gerbeth, G.; Günther, U.; Sorriso-Valvo, L.

One of the most interesting features of Earth's magnetic field reversals is their pronounced asymmetry, including a slow dipole decay and a fast recreation of the reversed dipole. This asymmetry indicates a possible connection with relaxation oscillations as they were early studied by van der Pol. A simple mean-field dynamo model (Phys. Rev. Lett. 94 (2005), 184506) is analysed with view on this similarity, and a comparison of the time series and the phase space trajectories with those of paleomagnetic measurements is carried out. For the case of highly supercritical dynamos a very good agreement with the paleomagnetic data is achieved (Earth Planet. Sci. Lett. 143 (2006), 828; Geophys. Astrophys. Fluid Dyn. 101 (2007), 227). Deviations of both numerical and paleomagnetic reversal sequences from Poisson statistics are touched upon (Phys. Earth Planet. Inter. 164 (2007), 197). The observed clustering property of reversals is interpreted as a feature of ''punctuated equilibrium'' which is, in turn, typical for metastable systems. We show that both metastability and the relaxation oscillation character have their common root in the typical spectral behaviour of the non-selfadjoint dynamo operator. In addition, we try to constrain the most essential parameters of the dynamo model by the typical time scale of individual reversals, the clustering characteristics, and the stochastic resonance phenomenon ( The latter was recently shown to appear with a time period typical for the Milankovitch cycle of the Earth's orbit eccentricity.

  • Open Access Logo Abstract in refereed journal
    Geophysical Research Abstracts 10(2008), 02003

Publ.-Id: 10968

Optical contrast in ion-implanted amorphous silicon carbide nanostructures

Takahashi, S.; Dawson, P.; Zayats, A. V.; Bischoff, L.; Angelov, O.; Dimova-Malinovska, D.; Tsvetkova, T.; Townsend, P. D.

Topographic and optical contrasts formed by Ga+ ion irradiation of thin films of amorphous silicon carbide have been investigated with scanning near-field optical microscopy. The influence of ion-irradiation dose has been studied in a pattern of sub-micrometre stripes. While the film thickness decreases monotonically with ion dose, the optical contrast rapidly increases to a maximum value and then decreases gradually. The results are discussed in terms of the competition between the effects of ion implantation and surface milling by the ion beam. The observed effects are important for uses of amorphous silicon carbide thin films as permanent archives in optical data storage applications.

Keywords: amorphous silicon carbide; Ga+ ion irradiation; SNOM; optical data storage application

  • Journal of Physics D: Applied Physics 40(2007)23, 7492-7496

Publ.-Id: 10967

Thermodynamical Data of uranyl carbonate complexes from Absorption Spectroscopy

Götz, C.; Geipel, G.; Bernhard, G.

Aqueous uranyl carbonate complexes play an important role in the hydrogeology of uranium mining areas and nuclear waste disposals. Many publications are available for the stability of uranyl carbonate complexes, but thermodynamical data like the enthalpy or entropy are rare. We determined thermodynamical data from spectroscopic studies for the uranyl carbonate complex UO2(CO3)34- in the temperature range from 5°C to 70°C. We found for the reaction enthalpy the value 36.25 ± 4.31 kJ/mol and for the reaction entropy a value of 297.082 ± 13.839 J/(K∙mol).

Keywords: Uranyl; Carbonates; uranylcarbonate; thermodynamics; equilibrium constant

  • Poster
    5th International Conference Uranium Mining and Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 907-914

Publ.-Id: 10966

P0607-Verfahren zum Bestimmen einer Materialzusammensetzung einer Materialprobe

Kraft, G.; Enghardt, W.; Würschig, T.

Verfahren zum Bestimmen der Materialzusammensetzung einer Strahlung abstrahlenden Materialprobe (12) mit den folgenden Verfahrensschritten: Aufnehmen (P2) eines Spektrums der in einem Detektormaterial durch die Strahlung deponierten Energie; Bestimmen einer in einem ersten Energiebereich deponierten ersten Energie (F1), einer in einem zweiten Energiebereich deponierten zweiten Energie (F2) und einer in einem dritten Energiebereich deponierten dritten Energie (F3); Zuordnen (P4) eines ersten Farbparameters (F1) zu der ersten deponierten Energie, eines zweiten Farbparameters (F2) zu der zweiten deponierten Energie und eines dritten Farbparameters (F3) zu der dritten deponierten Energie und Vergleichen (P5) der zugeordneten Farbparameter (F1, F2, F3) mit vorgegebenen Werten für die Farbparameter (R1, R2, R3), wobei die vorgegebenen Werte (R1, R2, R3) typischen Farbparametern einer vorbestimmten Materialzusammensetzung entsprechen.

  • Patent
    DE 10 2006 033 662 A1 - 24 Jan. 2008

Publ.-Id: 10965

Detektoranordung zur winkelauflösenden Detektion von Strahlung und Verfahren zum Betrieb desselben

Kraft, G.; Enghardt, W.; Würsching, T.

Detektoranordnung (1) zur winkelauflösenden Detektion von Strahlung mit mindestens einem Detektorelement (2), welches eine Vorderseite (3) und eine Rückseite (4), ein erstes Detektormaterial und ein zweites Detektormaterial zwischen der Vorderseite (3) und der Rückseite (4) aufweist, wobei ein Raum zwischen der Vorderseite (3) und der Rückseite (4) des Detektorelementes (2) von mehreren Bereichen (6) aus dem ersten Detektormaterial und mindestens einem Bereich (5) aus dem zweiten Detektormaterial ausgefüllt ist und jeder Bereich die Vorderseite (3) mit der Rückseite (4) des Detektorelementes (2) verbindet und wobei eine Kollimation von durch die Vorderseite (3) in das Detektorelement (2) eintretender Strahlung (γ) durch die Detektormaterialien erfolgt.

  • Patent
    DE 10 2006 033 661 A1 - 24 Jan. 2008

Publ.-Id: 10964

Complexation of Uranium(VI) by Sulfur and Nitrogen Containing Model Ligands in Aqueous Solution

Joseph, C.; Raditzky, B.; Schmeide, K.; Geipel, G.; Bernhard, G.

The long-term safety assessment of nuclear waste disposals requires detailed knowledge of the transport and interaction behavior of actinides within the technical, geotechnical and geological barriers. Humic substances, ubiquitous in natural environments, are able to influence the migration of actinides due to their ability for complex and colloid formation and their redox properties. It is known, that especially their carboxylic and phenolic OH groups are able to complex metal ions. In addition to these oxygen containing functional groups, humic substances also offer sulfur and nitrogen containing functionalities.
The aim of this work is to determine the influence of various sulfur and nitrogen containing functional groups on the uranium(VI) complexation and to evaluate their contribution in comparison to oxygen containing functional groups. For this, simple organic model ligands that can occur as building blocks for humic substances are used in the first instance with the objective to transfer the results to humic substances.
In this study, results are presented for the uranium(VI) complexation by the organic ligands benzenesulfonic and 4-hydroxybenzenesulfonic acid as well as for nicotinic and anthranilic acid. The complex formation constants for the uranium(VI) complexation were determined applying UV-vis absorption spectroscopy and time-resolved laser-induced fluorescence spectroscopy (TRLFS) as a function of pH.
Interestingly, we did not see any interaction of the uranyl ion with benzenesulfonic acid (BSA). In contrast, for the uranium(VI) complexation by 4-hydroxybenzenesulfonic acid (HBSA) the formation of a 1:1 complex was detected. The stability constant for this complex of the type MpHqLr was determined with log ß101 = 3.9 ± 0.03.

Keywords: Uranium; complexation; benzenesulfonic acid; 4-hydroxybenzenesulfonic acid; nicotinic acid; anthranilic acid

  • Poster
    5th International Conference Uranium Mining Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 539-548

Publ.-Id: 10963

Interaction of uranium(VI) with peptidoglycan

Barkleit, A.; Moll, H.; Bernhard, G.

Bacteria have a great influence on the migration behaviour of heavy metals in the environment. Peptidoglycan (PGN) forms the main part of the outer membrane of Gram-positive bacteria. We investigated the interaction of the uranyl cation (UO22+) with PGN from Bacillus subtilis by using potentiometric titration and time-resolved laser-induced fluorescence spectroscopy (TRLFS) over a wide pH range (2.4 – 9) and at environmentally relevant low uranium concentrations (10-4 – 10-5 M). The PGN polymer contains a high density of functional groups for metal ion binding, like carboxyl, amino and hydroxyl groups.
With potentiometric titration the dissociation constants of the functional groups and the corresponding site densities could be detected. We found four functional groups, which can be dedicated to two different carboxyl functionalities, amino and hydroxyl groups. Using the same technique, two different uranyl PGN complexes could be identified, one complex with a carboxyl ligand (R-COO-UO2+) and a second complex with additional hydroxyl coordination (R-COO-UO2+-HO-R). The complex stability constants were determined to be log beta = 5.16 ± 0.13 for the first, and log beta = 13.00 ± 0.05 for the second complex, respectively.
TRLFS measurements show from pH 2.4 to 4.5 a red shift of the peak maxima of about 8 – 10 nm, in comparison to the free uranyl ion, connected with an increase of the luminescence intensity. Over pH 4.5 up to pH 9 the luminescence intensity decreases. The time resolved measurements show beneath the lifetimes of the free uranyl ion (1800 ± 200 ns) and the known uranyl hydroxides only one additional lifetime (224 ± 54 ns) which can be dedicated to a uranyl PGN complex species. From these we conclude that the two uranyl PGN complex species found by potentiometry can also be identified with TRLFS. The first complex (R-COO-UO2+) shows luminescence activity, but the second complex (R-COO-UO2+-HO-R) not. Complex stability constants for these two complexes were determined using the computer program SPECFIT. They are in good accordance to those calculated from potentiometric titrations.

  • Lecture (Conference)
    7th International Conference on Nuclear and Radiochemistry (NRC7), 24.-29.08.2008, Budapest, Hungary

Publ.-Id: 10962

On the three-dimensional character of the magnetohydrodynamic effect during metal electrodeposition in cuboid cells

Mutschke, G.; Bund, A.

The influence of external homogeneous magnetic fields during electrochemical metal deposition in cuboid cells is shortly reviewed. By analytical means, supported by numerical simulations, it is shown that a simplified two-dimensional approach is often misleading and has to be replaced by a more complex three-dimensional treatment as only the solenoidal part of the Lorentz force can cause convection.

Keywords: Magnetoelectrochemistry; electrochemistry; Lorentz force; metal deposition; limiting current; numerical simulation

Publ.-Id: 10961

Temperature-Jump-Induced Structural Transition in DNA Monitored by Rapid Scan FTIR-Difference-Spectroscopy

Fahmy, K.; Savchuk, O.; Khesbak, H.

Conformational substates of B-DNA have been reported to be involved in DNA recognition by proteins [1]. BI and BII substates, that co-exist in B-DNA, differ in the phosphate backbone conformation about the C3'-O3'-P segment related to the variability of the dihedral e and z angles (see figure left [2]). Typical IR marker bands have previously been identified which allow assessing the relative population of BI and BII conformers by FTIR spectroscopy for DNA from salmon testes, poly(dG-dC) and the d(CGCGAATTCGCG)2 dodecamer [3]. So far, BI/BII dynamics studies were restricted to static FTIR spectroscopy under isothermal relaxation at low temperatures . We have attempted to monitor the BI/BII transition under defined native-like conditions using rapid scan FTIR-difference-spectroscopy at a time resolution of 70 ms. An ATR-cell accessory was designed that allows both, the application of flashes to induce small temperature jumps and the adjustment of constant humidity of the sample. The latter is critical to address the role of backbone hydration in the dynamics of the BI/BII transition.

  • Poster
    XIIth European Conference on the Spectroscopy of Biological Molecules, 01.-06.09.2007, Bobigny, France

Publ.-Id: 10960

Flavor Diagonal and Off-Diagonal Susceptibilities in a Quasiparticle Model of the Quark-Gluon Plasma

Bluhm, M.; Kämpfer, B.

The Taylor coefficients of flavor diagonal and off-diagonal susceptibilities as well as baryon number, isovector and electric charge susceptibilities are considered within a phenomenological quasiparticle model of the quark-gluon plasma and successfully compared with lattice QCD data for two degenerate quark flavors. These susceptibility coefficients represent sensible probes of baryon density effects in the equation of state. The baryon charge is carried, in our model, by quark-quasiparticle excitations for hard momenta.

Keywords: quark-gluon plasma; susceptibility; quasiparticle model

Publ.-Id: 10959

D(E)RY Motif- A Conserved Proton Dependent Modular Switch In Class-1 GPCRs

Madathi, S.; Fahmy, K.

Activation of G protein-coupled receptors (GPCRs) orginates in ligand-induced structural changes that are transmitted across the plasma membrane to the cytosolic receptor surface. In rhodopsin-like class-1GPCRs, protonation of a carboxylic acid (Glu134 in rhodopsin) in the conserved cytosolic D(E)RY motif in transmembrane helix 3 (TM3) is coupled to receptor activation. Here, we have investigated the proton-sensitivity of the structure of synthetic peptides consisting of 30amino acids derived from TM3 of bovine rhodopsin (rho) and the chemokine receptor CCR3. ATR- Fourier-transform-infrared (FTIR) spectroscopy reveals a helical structure of the rho-TM3 peptide in PC vesicles and detergent micelles, where Glu134 exchanges protons with the solvent at a pKa of 5.5-6.0 as determined from the pH sensitivity of the COO- stretching mode. The amide I modes reveal a proton-induced helical turn formation in rho-TM3 and CCR3-TM3. The conformational change in the ERY motif is affects also the Tyr136 fluorescence which exhibits a strong pH sensitivity (pKa of 6) which is abolished upon replacement of Glu134 by Gln in rho-TM3. Förster-Resonance-Energy-transfer from a C-terminal Trp to DANSYL-labelled lipids in mixed micelles and lipid vesicles evidences that the D(E)RY motif constitutes an autonomous proton-driven conformational switch which couples protonation to helical turn formation and probably helix insertion depth. We propose that the protonation-controlled hydrophobicity profile at the cytosolic end of TM3 provides a pH-sensitive module that couples helix packing in the active receptor conformation of class I GPCRs to proton exchange reactions with the cytosol.

  • Poster
    FEBS Workshop The Biology of Modular Protein Domains, 08.-13.09.2007, Seefeld in Tirol, Austria

Publ.-Id: 10958

Curium(III) Speciation in Aqueous Solutions of Bacterial Siderophores

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

Actinides have been and will be introduced into shallow and deep groundwater environments via various human activities. The process of interaction between naturally occurring chelating substances and metals may influence the migration behavior of hazardous actinides in the environment once they have been released. Siderophores are chelating substances produced by microorganisms under iron-deficient conditions. For example, Powell et al. [1] demonstrated the occurrence of hydroxamate siderophores produced by microorganisms in concentrations ranging from 10-7 to 10-8 M in a variety of soils. In general catechol and hydroxamate groups in siderophores are the main functional groups involved in binding with actinides. As an example, Pseudomonas species are ubiquitous soil and groundwater bacteria that synthesize bacterial pyoverdin-type [2-5] and hydroxamate siderophores [6]. The observed mobilization effects of siderophore molecules on radionuclides probably due to the formation of strong soluble species motivated detailed investigation of their complexation characteristics, using a radionuclide suitable for spectroscopic methods.
To overcome the lack of information about actinide(III) siderophore interactions, we thus present findings regarding the complexation of curium(III) with pyoverdins (PYO) and desferrioxamine B (DFO), obtained using time-resolved laser-induced fluorescence spectroscopy (TRLFS). The excellent luminescence properties of curium(III) were used to explore its complexation behavior with the two different bioligands at environmentally relevant curium(III) concentrations.
(A) PYO: Pseudomonas fluorescens (CCUG 32456) cells isolated from the granitic rock aquifers at the Äspö Hard Rock Laboratory (Äspö HRL), Sweden, secreted a pyoverdin mixture containing 4 main components [5].
(B) DFO: Desferrioxamine B (DFO) is a microbial produced trihydroxamate siderophore which is commercially available and could occur naturally in soils. Recently Essen et al. [6] could show the production of desferrioxamine siderophors by Pseudomonas stutzeri (CCUG 36651). This strain was also isolated at the Äspö Hard Rock Laboratory.

We explored the unknown luminescence properties, lifetimes and individual luminescence emission spectra of the formed Cm(III) species. The strength of the complex formation of the two bioligands will be discussed on the basis of the spectroscopic properties obtained in their individual systems. The results of this study increase our understanding of the mobilization of actinides by siderophores secreted by resident bacteria in a natural environment.

[1] Powell, P.E., et al., Nature 287 (1980) 833-834.
[2] Budzikiewicz H., Fortschr. Chem. Org. Naturst. 87 (2004) 83-237 .
[3] Kalinowski B.E., et al., Geomicrobiol. J. 23 (2006) 157-164.
[4] Moll, H., et al., BioMetals 21 (2008) 219-228.
[5] Moll, H., et al., Geomicrobiol. J. 25 (2008) 157-166.
[6] Essen, S.A., et al., Appl. Environ. Microbiol. 73 (2007) 5857-5864.

Keywords: Curium; Pyoverdin; Desferrioxamine B; Fluorescence spectroscopy; TRLFS; Complexation

  • Contribution to proceedings
    7th International Conference on Nuclear and Radiochemistry (NRC7), 24.-29.08.2008, Budapest, Hungary
  • Poster
    7th International Conference on Nuclear and Radiochemistry (NRC7), 24.-29.08.2008, Budapest, Hungary

Publ.-Id: 10957

Results of a 20 minutes decay measurement of a patient irradiation by the in-beam PET scanner

Fiedler, F.; Parodi, K.; Pawelke, J.; Pönisch, F.; Priegnitz, M.; Shakirin, G.; Enghardt, W.; Möckel, D.

no abstract available

Keywords: in-beam PET

  • Open Access Logo Contribution to external collection
    in: GSI Jahresbericht, Darmstadt: GSI, 2008

Publ.-Id: 10956

Alpha-irradiation effects in SiO2

Krickl, R.; Nasdala, L.; Götze, J.; Grambole, D.; Wirth, R.

Natural and synthetic crystalline α-quartz, as well as synthetic SiO2 glass, were irradiated with different doses of 8.8 MeV He2+ ions. The irradiation-induced alteration was characterised using Raman and cathodoluminescence (CL) spectroscopy, optical microscopy, transmission electron microscopy (TEM) and CL and electron microscope imaging. The initially dull bluishviolet CL colour of the two α-quartz samples was found to be transformed to bright yellow in the irradiated areas. The emission maximum was observed 45 μm below the surface, which corresponds well with correlated helium trajectory lengths and defect density distribution. Both, total intensity and radial intensity distribution of the CL emission change with the irradiation dose. Observations suggest a nonlinear, approximately logarithmic increase of the CL intensity depending on the alpha dose. Significant broadening of Raman bands is only observed near the far end of helium trajectories. This broadening is not only caused by the structural radiation damage but also by strain between strongly and lowly damaged areas.

Keywords: Alpha-quartz; radiohalo; cathodoluminescence; Raman spectroscopy; He implantation; irradiation; radiation damage; transmission electron microscopy

Publ.-Id: 10955

Effects of alpha-irradiation on SiO2 phases

Krickl, R.; Grambole, D.; Götze, J.; Wirth, R.; Nasdala, L.

Aureoles surrounding radioactive inclusions – so called radiohaloes – are a common feature often observed in several rock-forming minerals. These alterations are caused by the action of alpha-particles (i.e. He2+ ions) emitted into the host mineral.
While in some cases (e.g. biotite, cordierite) the most striking feature of radiohaloes is a strongly enhanced absorption of light, there are commonly no visible changes found in quartz. In this mineral, alpha irradiation leads to a marked change in the emission behaviour, which can be very well observed using cathodoluminescence (CL) imaging.
In the present study several micro- and nano-techniques [i.e., Raman spectroscopy, CL spectroscopy, and transmission electron microscopy (TEM)] were used to study the alteration in synthetic radiohaloes, produced by artificial alpha irradiation of various SiO2 samples. Alpha-quartz of natural and synthetic origin as well as synthetic SiO2 glass were implanted with different doses of 8.8 MeV He2+ ions (fluences in the range from 1013 to 1017 ions/cm²).
The initially dull bluish-violet CL colour of the crystalline quartz samples was found to be transformed to bright yellow in irradiated areas. Monte Carlo simulations predicted that the observed depth of alteration is in very good agreement with the calculated range of alpha particles in quartz. Both, total intensity and radial intensity distribution of the CL emission change with the irradiation dose. Observations suggest a non-linear, approximately logarithmic increase of the CL intensity depending on the alpha dose. In contrast, no significant change in CL emission was observed in the case of He-irradiated amorphous SiO2.
The changed emission behaviour of He-irradiated areas in alpha-quartz is accompanied by structural damage, caused by the impact of the alpha particles. Significant broadening of Raman bands is only observed near the far end of helium trajectories. This broadening is not only caused by the structural radiation damage but also by strain, inter alia due to (locally heterogeneous) volume expansion of irradiated micro-areas.
Restricted to the end of the helium trajectories, there is a clearly defined, lense-shaped zone, characterised by changed optical and BSE behaviour. The structural state of this region, as investigated by TEM, will be discussed.

  • Lecture (Conference)
    European Geosciences Union General Assembly, 13.-18.04.2008, Vienna, Austria
  • Contribution to proceedings
    European Geosciences Union General Assembly, 13.-18.04.2008, Vienna, Austria
    Geophysical Research Abstracts, EGU2008-A-09731, 10

Publ.-Id: 10954

Component Additivity Approach for Uranium Retardation in Sandstone Host Rocks

Richter, A.; Nebelung, C.; Brendler, V.

Sandstone is one of the most important host rocks for uranium ore deposits, e.g. in Germany (Königstein) or the Czech Republic (Pribram). Any remediation efforts of respective mining legacies thus require a detailed understanding of this system. Namely the sorption in this complex rock is not well enough investigated yet.
One widely accepted approach (Component Additivity – CA, cf. [1]) to describe the sorption is based on the assumption that the surface of a complex mineral assemblage is composed of a mixture of one or more phases whose surface properties are known from independent studies. An internally consistent SCM database can be developed that describes the adsorption reactions of solutes to each phase. The fitting of data of the complex system is not necessary.
We predicted the sorption of uranium(VI) on sandstone using the results of the surface characterization of the assemblage and published data for adsorption onto the pure mineral constituents. The results were compared with batch sorption experiments using natural and synthetic sandstone (mixture of the main components quartz, muscovite, and hematite).
The sorption of U(VI) on natural and two synthetic sandstone (I and II) was investigated in batch sorption experiments (air atmosphere, 0.1M NaClO4, pH 3-11, [U(VI)] 10-9-10-3M). We had to consider the natural uranium concentration dissolved from the sandstone at low concentrations.
The synthetic sandstone was a mixture of quartz with muscovite and hematite. The surface area (N2-BET) of quartz was 0.047 m2/g, of muscovite 0.88 m2/g, of hematite 0.89 m2/g and of natural sandstone (mainly quartz) 0.69 m2/g.
The pH dependence shows a maximal sorption between pH 6 and 7. The U(VI) sorption varies between 95% (10-9M) and 7% (10-4) on natural sandstone, and between 80% (10-9M) and 2% (10-4M) on synthetic sandstone.
The modeling of U(VI) sorption on sandstone was performed using the CA approach. We assumed just one type of surface sites and applied a model with simple electrostatics, the Diffuse Double Layer Model (DDLM). For the modeling the code MINTEQA2 (Version 4.03, US EPA, May 2006) was used. The aqueous species were taken from the NEA-TDB [2].
As surface reactions we considered the protolysis of quartz, hematite, muscovite, the U(VI) surface complexes of quartz, hematite, muscovite (monomer, dimer) and the ternary U(VI) surface complexes of quartz and hematite with carbonate. The surface area was considered according to the mineral fraction. Despite of a slight shift of the predicted curve to lower pH in both systems, a good accordance with experimental values were found. Obviously, the sorption is strongly influenced by the small amount (0.5%) of hematite.
For the sorption behavior at varying U(VI) initial concentration, a precipitation of schoepite was predicted. As schoepite is an aged mineral, it is unlikely to be formed within the experimental duration of five days. A subsequent exclusion from the list of allowed phases led to a predicted precipitation of both soddyite and metaschoepite.
[1] Davis, J.A. et al. (1998) Application of the surface complexation concept to complex mineral assemblages. Environ. Sci. Technol. 32, 2820-2828.
[2] Guillaumont, R. et al. (2003) Update on the chemical thermodynamics of U, Np, Pu, Am, Tc. Elsevier, Amsterdam.

Keywords: Component Additivity Approach; Sorption; Surface Complexation; Uranium; MINTEQA2

  • Lecture (Conference)
    XVII International Conference on Computational Methods in Water Resources (CMWR 2008), 06.-10.07.2008, San Francisco, USA
  • Contribution to proceedings
    XVII International Conference on Computational Methods in Water Resources (CMWR 2008), 06.-10.07.2008, San Francisco, USA
    Proceedings of Computational Methods in Water Resources


Publ.-Id: 10953

Diode-pumped lasers for ultra-high peak power

Siebold, M.; Hein, J.; Hornung, M.; Podleska, S.; Kaluza, M. C.; Bock, S.; Sauerbrey, R.

The generation of the highest laser peak intensities at a high degree of system compactness can be achieved by combining modern diode-pump technologies with the chirped pulse amplification technique. In principle, the spectroscopic properties of the gain medium determine the scaling laws of both high output pulse energy and short pulse duration. Here we introduce a novel criterion classifying laser materials with respect to their ability to generate pulses of highest peak power in a diode-pumped solid state laser system. Furthermore, amplified spontaneous emission as well as laser damage issues affecting the efficiency and compactness of a laser amplifier system are discussed.

Publ.-Id: 10952

Broad-band regenerative laser amplification in ytterbium-doped calcium fluoride (Yb:CaF2)

Siebold, M.; Hornung, M.; Bock, S.; Hein, J.; Kaluza, M. C.; Wemans, J.; Uecker, R.

An output pulse energy of 17.3 mJ has been achieved with a diodepumped Yb:CaF2) regenerative laser amplifier. The bandwidth of the output pulse spectrum was 7.3 nm, being seeded with femtosecond pulses stretched to 2.2 ns. In cw operation a tuning range of 80 nm has been observed. A maximum pulse energy of 44mJ at a repetition rate of 1 Hz has been obtained in Q-switched mode. The laser damage threshold of a Yb:CaF2) crystal has been determined at a wavelength of 1064 nm and a pulse duration of 10 ns.

Publ.-Id: 10951

Flow structure and concentration distribution measurements in seemingly parallel magnetic and electric fields

Cierpka, C.; Weier, T.; Mutschke, G.; Eckert, K.; Uhlemann, M.; Bund, A.

Characterized by the interplay of Lorentz forces, flow and concentration distributions, magnetoelectrochemical processes are typically quite complex. We aim to show that flow field and concentration measurements by means of Particle Image Velocimetry (PIV) and the relatively new technique Background Oriented Schlieren (BOS) are a valuable aid in understanding the observed phenomena. Two examples, the flow field in a cylindrical cell and the concentration distribution near a circular millielectrode, will be discussed in detail.

Keywords: Background Oriented Schlieren; Particle Image Velocimetry; Electrochemistry; Flow Control

  • Lecture (Conference)
    213th ECS Meeting, 18.-23.05.2008, Phoenix, USA

Publ.-Id: 10950

Hydrogen incorporation in ultrananocrystalline diamond/amorphous carbon films

Kulisch, W.; Sasaki, T.; Rossi, F.; Popov, C.; Sippel, C.; Grambole, D.

The incorporation of hydrogen within ultrananocrystalline diamond/amorphous carbon composite films has been investigated by nuclear reaction analysis (NRA) and Fourier transform infrared spectroscopy (FTIR). The film bulk contains ca. 7.5-8 % H (for a deposition temperature of 600°C), while the H concentration in the surface region is considerably higher. FTIR measurements show that the hydrogen-rich surface is formed right at the beginning of the deposition process and grows outward as the film thickness increases. It can thus be concluded that surface hydrogen species play an active role in the formation of ultrananocrystalline diamond/amorphous carbon films.

Publ.-Id: 10949

Yrast studies of 80,82 Se using deep-inelastic reactions

Jones, G. A.; Regan, P. H.; Podolyak, Z.; Yoshinaga, N.; Higashiyama, K.; de Angelis, G.; Zhang, Y. H.; Gadea, A.; Ur, C. A.; Axiotis, M.; Bazzacco, D.; Bucurescu, D.; Farnea, E.; Gelletly, W.; Ionescu-Bujor, M.; Iordachescu, A.; Kröll, T.; Langdown, S. D.; Lenzi, S.; Lunardi, S.; Marginean, N.; Martinez, T.; Medina, N. H.; Menegazzo, R.; Napoli, D. R.; Quintana, B.; Rubio, B.; Rusu, C.; Schwengner, R.; Tonev, D.; Valiente Dobon, J. J.; von Oertzen, W.

We report the results of an experiment in which we studied the near-yrast states in selenium isotopes approaching N = 50 following their population in multinucleon transfer reactions between a 82Se beam and a 192Os target. The level schemes for 80,82Se derived from the current work are compared with restricted-basis shell-model calculations and pair-truncated shell-model calculations. These provide a good description of the yrast sequences in these nuclei using a basis space limited to excitations in the (p3/2 , p1/2 , g9/2 ) and (f5/2 , p3/2 , p1/2 ) orbitals.

Keywords: nuclear Structure; gamma-ray spectroscopy; deep-inelastic reactions; shell model

  • Physical Review C 76(2007), 054317-1-054317-5

Publ.-Id: 10948

Evolution of ion-induced ripple patterns on SiO2 surfaces

Keller, A.; Facsko, S.; Möller, W.

The evolution of nanoscale ripple patterns during sub-keV ion sputtering of thermally grown, fused, and single crystalline SiO2 surfaces has been investigated by means of atomic force microscopy. For all three materials, different dependencies of the ripple wavelength and the surface roughness on the ion fluence have been found. Within the Bradley-Harper model of pattern formation, the observed differences are consistent with different amounts of surface and near-surface mass transport by ion-enhanced viscous flow which might result from different surface energies of the SiO2 specimens.

  • Nuclear Instruments and Methods in Physics Research B 267(2009)4, 656-659
  • Lecture (Conference)
    17th International Workshop on Inelastic Ion-Surface Collisions, 21.-26.09.2008, Porquerolles, France

Publ.-Id: 10947

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

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

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

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

  • Contribution to external collection
    in: GSI Scientific Report 2007, Darmstadt: GSI, 2008

Publ.-Id: 10946

Zellschädigung nach Röntgenbestrahlung

Beyreuther, E.; Lessmann, E.; Pawelke, J.

Zusammenfassung über die Arbeiten zur Bestimmung des RBW von weicher Röntgenstrahlung

  • Poster
    OncoRay, Strategie-Meeting, 08.-09.01.2008, Gröditz, Germany

Publ.-Id: 10945

In-beam PET monitoring of phantom irradiation with 7Li-ions

Priegnitz, M.; Möckel, D.; Parodi, K.; Fiedler, F.; Sommerer, F.; Enghardt, W.

No abstract available.

  • Contribution to external collection
    in: GSI Scientific Report 2007, GSI Report 2008-1, Darmstadt: Gesellschaft für Schwerionenforschung mbH, 2008, 381

Publ.-Id: 10944

Uranium(VI) complexation with pyoverdins secreted by a subsurface strain of Pseudomonas fluorescens and Complexation of curium(III) with pyoverdin model compounds – salicylhydroxamic (SHA) and benzohydroxamic acid (BHA)

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

The contributions of the Forschungszentrum Dresden-Rossendorf (FZD)/Institute of Radiochemistry (IRC) within the microbe project as part of the international co-operation of the Äspö HRL (Sweden) with the BMWi (Germany) are concentrated in a project addressing the indirect interaction mechanism of a mobilization of actinides by released bioligands in the aquifer system from relevant Äspö bacteria. The ongoing study is focused on: (i) isolation and characterization of microbial ligands produced from a subsurface strain of Pseudomonas fluorescens isolated at Äspö, (ii) interaction of U(VI), Np(V), and Cm(III) with the microbial ligands including compounds simulating the functionality of the microbial ligands and the surface of the bacteria and (iii) spectroscopic characterization of the formed actinide complexes/compounds. The formation constants determined will be used directly in speciation and transport models. This project should help to identify the dominating process of the interaction between actinides and microbes (direct or indirect ones). The research performed in our project improves the understanding of the behavior of colloids and microbes and their respective interaction with radionuclides.
The activities in 2007 were concentrated on (a) complexation studies of U(VI) with the secreted bioligand mixture of P. fluorescens found at Äspö HRL, (b) complexation studies of Cm(III) with relevant pyoverdin model compounds, and (c) complexation studies of U(VI) and Cm(III) with model molecules simulating the functionality of bacterial cell envelopes to explain the interactions of actinides in biologically systems on a molecular level. Selected results of the topics (a) and (b) will be reported here.

Keywords: uranyl; Complexation; TRLFS; Hydroxamic acids; Cm(III); complexation; fs-TRLFS spectra; UV-vis spectra; pyoverdins

  • Other report
    Stockholm: Äspö HRL Annual Report 2007, 2008
    8 Seiten

Publ.-Id: 10943

Measurement of the spatio-temporal distribution of harmonic and transient eddy currents in a liquid metal

Forbriger, J.; Galindo, V.; Gerbeth, G.; Stefani, F.

Harmonic and transient eddy currents in the eutectic liquid metal alloy GaInSn positioned above an excitation coil are determined by measuring the corresponding voltage drop in an electric potential probe. The resulting spatio-temporal eddy current field is compared with the corresponding analytical expressions for a conducting half-space. Further, a deformation of the eddy current distribution due to a non-conducting torus immersed into the liquid metal is measured and compared with numerical results. The method can be generalized to arbitrary geometries, and might help to validate numerical models for non-destructive testing and magnetic inductance tomography.

Keywords: Eddy currents; Magnetic induction tomography; Nondestructive testing; Liquid metals

  • Measurement Science and Technology 19(2008)4, 045704

Publ.-Id: 10942

Density, viscosity and electrical conductivity of hypoeutectic Al-Cu liquid alloys

Plevachuk, Y.; Sklyarchuk, V.; Yakymovych, A.; Eckert, S.; Willers, B.; Eigenfeld, K.

New workable aluminium-based light alloys are a key issue in current materials science. In this work, thermophysical properties (density, viscosity and electrical conductivity) of liquid Al96Cu4, Al80Cu20, Al70Cu30, and AlCu4TiMg (wt.%) alloys have been measured in a wide temperature range.
The anomalies with respect to the concentration dependence of the electrical conductivity are explained in terms of the s–d hybridization model. A comparison with data and scaling relations being available in the literature is given.

Keywords: Al-Cu alloys; density; viscosity; electrical conductivity

  • Metallurgical and Materials Transactions A 39(2008)12, 3040-3045

Publ.-Id: 10940

ERDA and Structural Characterization of Oriented Multiwalled Carbon Nanotubes

Gohier, A.; Point, S.; Djouadi, M. A.; Granier, A.; Minea, T. M.; Kreissig, U.; Abrasonis, G.; Kolitsch, A.; Möller, W.

Oriented multiwalled carbon nanotubes have been synthesized by distributed electron cyclotron resonance plasma enhanced chemical vapor deposition. Elastic recoil detection analysis measurements on multiwalled carbon nanotubes are reported here for the first time. On the basis of the recorded depth profiles, we have developed a simple model to estimate the surface densities of as-grown nanotubes. Besides, nitrogen and hydrogen contents into MWNT, typically less than 6.5 and 8 atom %, respectively, have been characterized as a function of the chemical nature of the catalyst, the synthesis temperature, and the hydrogen carrying diluent gas. These results are discussed with respect to the structural characterization performed by electron energy loss spectroscopy measurements, transmission electron microscopy and X-ray photoelectron spectroscopy.

  • Journal of Physical Chemistry C 111(2008)28, 10353-10358

Publ.-Id: 10939

A new high-quality database for air-water flow in a DN200 vertical duct

Lucas, D.; Beyer, M.; Kussin, J.

This presentation reports about a new experimental series on air-water upwards pipe flow. The generated database is suitable for investigations on bubble coalescence and fragmentation.

Keywords: two-phase flow; pipe flow

  • Lecture (others)
    Meeting of the German CFD Network for Nuclear Reactor Safety, 23.-24.01.2008, Grosshartpenning, Deutschland

Publ.-Id: 10938

Analyse von Borverdünnungstransienten in Druckwasserreaktoren

Kliem, S.

Der Vortrag gibt eine Einführung in die Problematik der Borverdünnungstransienten in Druckwasserreaktoren. An einem konkreten Fall werden die Möglichkeiten gekoppelter neutronenkinetisch/thermohydraulischer Rechenprogramme, diese Art von Transienten zu berechnen, gezeigt.

  • Invited lecture (Conferences)
    Seminar für Energieverfahrenstechnik, 18.12.2007, Dresden, Germany

Publ.-Id: 10937

Experimente zu Zweiphasenströmungen an der Versuchsanlage TOPFLOW

Lucas, D.

Im Vortrag wird ein Überblick zu den durchgeführten Experimenten an der TOPFLOW-Anlage sowie der Nutzung der gewonnen Daten für die CFD-Code-Entwicklung und -validierung gegeben.

Keywords: Zweiphasenströmung; CFD

  • Invited lecture (Conferences)
    Seminar für Energieverfahrenstechnik, 15.01.2008, Dresden, Germany

Publ.-Id: 10936

Linear stability of an alternating magnetic field driven flow in a spinning cylindrical container

Shatrov, V.; Gerbeth, G.; Hermann, R.

We present a numerical analysis of the free surface liquid metal flow and its three-dimensional linear stability. The flow is driven by an alternating magnetic field in a spinning cylindrical container. The electromagnetic and hydrodynamic fields are fully coupled via the shape of the liquid free surface. The hydrodynamic equations are solved by a spectral collocation method, and the alternating magnetic field distribution is found by a boundary-integral method. The flow stability is analyzed for various magnetohydrodynamic interaction parameter and Ekman numbers assuming a flat free surface. We find that only a sufficiently fast spinning suppresses and stabilizes the flow, but a moderate spinning can significantly destabilize it.

  • Physical Review E 77(2008)4, 046307

Publ.-Id: 10935

Ferromagnetism of Fe implanted ZnO – a phenomenon related to defects?

Zhou, S.; Potzger, K.; Talut, G.; Reuther, H.; Kuepper, K.; Grenzer, J.; Xu, Q.; Helm, M.; Fassbender, J.; Arenholz, E.

ZnO(0001) single crystals annealed in high vacuum have been investigated with respect to their magnetic properties. Annealing at mild temperatures up to 773 K leads to ferromagnetic properties without any transition metal doping. Fe ion implantation at low temperatures leads to similar results. However, no evidence for the relevance of the Fe magnetic moment for the generation of ferromagnetism was observed. Nevertheless, the degradation of the magnetization with time is much less pronounced for the implanted crystals with respect to the purely annealed samples.

Keywords: ZnO; Diluted Magnetic Semiconductors; ion implantation

  • Journal of Physics D: Applied Physics 41(2008), 105011

Publ.-Id: 10934

Curium(III) complexation with desferrioxamine B (DFO) investigated using fluorescence spectroscopy

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

Hydroxamate-type siderophores like desferrioxamine B (DFO) are the most common siderophores ubiquitously found in the environment. These naturally occurring chelating substances have the potential to enhance the solubility and mobility of actinides by forming soluble complexes. The unknown interaction between curium(III) and the aqueous DFO species is the subject of this paper. The interaction between soluble species of curium(III) and DFO was studied at trace curium(III) concentrations (3 x 10-7 M) using time-resolved laser-induced fluorescence spectroscopy (TRLFS). Three Cm3+ - DFO species, MpHqLr, could be identified from the luminescence spectra, CmH2DFO2+, CmHDFO+, and CmDFB, having emission maxima at 599, 611, and 614 nm, respectively. The as well large formation constants, log β121 = 31.62 ± 0.23, log β111 = 25.70 ± 0.17, and log β101 = 16.80 ± 0.40, compared to those of other chelating agents illustrate the unique complexation properties of hydroxamate-type siderophores. An indirect excitation mechanism for the curium(III) luminescence was observed in the presence of the DFO molecules.

Keywords: Curium; Desferrioxamine B; Fluorescence spectroscopy; TRLFS; Complexation

  • Bulletin of the Chemical Society of Japan 81(2008)7, 857-862

Publ.-Id: 10933

Photovoltaik-Anlagen im Netzparallelbetrieb: Erfahrungen eines Regionalversorgers

Rindelhardt, U.; Nitzschner, F.

Die ENSO Strom AG ist der ostsächsische Regionalversorger. Das Netzgebiet reicht von Riesa im Westen bis zur polnischen Grenze im Osten und vom Erzgebirge im Süden bis zur Landesgrenze zu Brandenburg. Die ENSO Strom AG betreibt seit 1998 eine eigene PV-Anlage und veranstaltet seit dieser Zeit jährlich im Frühjahr einen „Solartag“, der zur Information und zum Erfahrungsaustausch der Anlagenbetreiber genutzt wird.
Im ENSO-Netzgebiet wurde 1990 die erste PV-Anlage der damaligen DDR in Betrieb genommen. Größere Zuwächse waren an die folgenden Förderprogramme gebunden. Mit dem 1000-Dächer-Programm erfolgte der erste wesentliche Schritt, nach einer Phase geringen Wachstums begann ab 2000 mit dem 100000-Dächer-Programm und dem EEG ein steiler Aufschwung. Das Leistungsspektrum der Anlagen reicht von 1 kW bis zu 1 MW, die durchschnittliche Leistung der etwa 1100 Anlagen lag Ende 2006 bei knapp 8 kW.
Die Netzintegration der meist kleinen Anlagen gestaltet sich unproblematisch, nur in Ausnahmefällen (Stichleitungen in ländlichen Netzen) waren Netzberechnungen und gegebenenfalls Festlegung anderer Verknüpfungspunkte erforderlich.
Die Ertragsentwicklung der PV-Anlagen im ENSO-Netzgebiet wird seit einigen Jahren verfolgt und auf den genannten Solartagen ausgewertet. Zwei Hauptergebnisse werden hier detailliert vorgestellt. Zum einen wird seit einigen Jahren der Zusammenhang zwischen der Einstrahlung im Netzgebiet und den Standorten der ertragsstärksten Anlagen untersucht. Diese Anlagen sind per se optimal ausgelegt und ausgerichtet. Es ist deutlich, dass zwischen den Standorten der besten Anlagen (Erträge 2006 > 1080 kWh/kW) und den vom DWD ermittelten Gebieten mit unterschiedlicher Einstrahlung kein nachweisbarer Zusammenhang besteht.
Dies deutet darauf hin, dass die den Ertrag bestimmenden technischen Unterschiede zwischen den einzelnen Anlagen größer sind als die Einstrahlungsdifferenzen im Netzgebiet.
Ein zweites interessantes Ergebnis ist die Ertragsentwicklung der besten Anlagen im Verlauf der letzten 4 Jahre. Seit 2003 wurden jährlich die jeweils besten 20 Anlagen ermittelt und deren gemittelter Ertrag (in kWh/kW) mit den entsprechenden Werten der Vorjahre verglichen. Es zeigte sich, dass in den Folgejahren jeweils neu errichtete Anlagen die älteren „Spitzenanlagen“ übertrafen: Das höheren Erträge neu errichteter Anlagen spiegeln offensichtlich technische Fortschritte in Komponentenqualität und Auslegung wider. Die Erträge erreichen Werte, die bisher nur von Anlagen aus dem süddeutschen Raum bekannt wurden.

Keywords: Photovoltaik; Netzintegration; Performance

  • Contribution to proceedings
    23. Symposium Photovoltaische Solarenergie, 05.-07.03.2008, Bad Staffelstein, Germany
  • Poster
    23. Symposium Photovoltaische Solarenergie, 05.-07.03.2008, Bad Staffelstein, Germany

Publ.-Id: 10931

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