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32228 Publications
A brief comparison of Pitzer databases for nuclear waste disposal modeling
Bok, F.; Voigt, W.; Bube, C.; Wilhelm, S.; Moog, H.;
For the modeling of different chemical aspects of a salt repository for nuclear waste, the Pitzer formalism is necessary. Therefore, a comprehensive database with the relevant aqueous and mineral species, the corresponding reaction constants and associated ion-ion interaction parameters are required.
A number of different Pitzer databases are available for, or even delivered with various geochemical speciation codes such as EQ3/6, PHREEQC, Geochemist’s Workbench® (GWB) or ChemApp. In this work we performed comparative calculations for well-defined chemical systems on the base of these Pitzer databases. In Addition, for a more comprehensive view experimentally measured values from the literature were included in the comparisons.
Keywords: THEREDA, Thermodynamic Reference Database, Benchmark calculation, Pitzer, databases, geochemical modeling, nuclear waste disposal
  • Lecture (Conference)
    Actinide and Brine Chemistry in a Salt Repository Workshop (III), 15.-17.04.2013, Santa Fe, USA

Publ.-Id: 18493 - Permalink


Small-angle neutron scattering of low-Cu RPV steels neutron-irradiated at 255 degrees C and post-irradiation annealed at 290 degrees C
Wagner, A.; Bergner, F.; Ulbricht, A.; Dewhurst, C. D.;
Fast neutron irradiation of low-Cu reactor pressure vessel (RPV) steels gives rise to the formation of solute clusters and a degradation of mechanical properties. A remarkable acceleration of cluster formation was identified in a previous investigation of low-Cu steels irradiated at 255 degrees C. The thermal stability of the observed features at a typical RPV operation temperature (290 degrees C) is of particular interest. Small-angle neutron scattering experiments for three low-Cu materials irradiated at 255 degrees C and exposed to post-irradiation annealing at 290 degrees C are reported. The results indicate stability of the irradiation-induced features at a temperature of 290 degrees C for all three materials. In two cases, even an increase in scattering intensity upon post-irradiation annealing has been observed. The effect of the annealing treatment on the nature of clusters is discussed and a model of the cluster-matrix interface is introduced to rationalize the observed increase in scattering intensity. The role of the residual elements is discussed.
  • Poster
    NuMat 2012: The Nuclear Materials Conference, 21.-25.10.2012, Osaka, Japan
  • Journal of Nuclear Materials 441(2013), 487-492
    DOI: 10.1016/j.jnucmat.2013.06.032

Publ.-Id: 18492 - Permalink


Robust Monte-Carlo fitting of small-angle neutron scattering curves for determining cluster-size distributions
Wagner, A.; Ulbricht, A.; Bergner, F.;
Reactor pressure vessel (RPV) steel, when exposed to fast neutron irradiation, leads to the formation of nano-sized clusters [1]. These clusters can cause an overall degradation in mechanical properties, which is a safety issue. Small-angle neutron scattering (SANS) is a commonly used technique to determine the irradiation-induced cluster volume fraction and cluster size distribution in the material.
However, in the case of modern RPV steels, standard data treatment [2] for back-transforming the SANS scattering curves to real space can lead to unstable results. These are highly dependent on renormalisation parameters to be chosen by the user.
Here, a Monte Carlo fitting (MCF) algorithm based on [3] is presented. No renormalisation parameter is needed. The algorithm is optimized to get a robust determination of small cluster volume fractions (≈ 0.01 %) and cluster radii (≈ 0.7 nm), which are typical for modern RPV steels. The significance of the resulting data can be evaluated by an automatic error analysis. Using simulated scattering curves, the MCF is able to deliver a good reconstruction of the cluster size distribution and volume fraction in the vicinity of the SANS detection limit. Furthermore, the algorithm is tested with experimental scattering curves of neutron-irradiated RPV steels. The MCF transformation yields in physical meaningful, non-divergent results. Comparisons between analyses performed by the standard methods [2] and the MCF algorithm are drawn. The stability of the results and the limits of information to be extracted from the experimental data are discussed.

References
[1] G.R. Odette, B.D. Wirth, Handbook of Materials Modeling, Springer Netherlands, 999–1037 (2005)
[2] S. Hansen, J.S. Pedersen, J.Appl.Crystallogr. 24, 541–548 (1991)
[3] S. Martelli, P.E. Di Nunzio, Part.Part.Syst.Char. 19, 247–255 (2002)
  • Poster
    German Neutron Scattering Conference, 24.-26.09.2012, Bonn, Deutschland

Publ.-Id: 18491 - Permalink


Microstructural properties of Spark Plasma Sintered ODS Fe-14Cr steels
Schönitz, I.; Heintze, C.; Bergner, F.; García-Junceda, A.; Weißgärber, T.;
Fe-14 Cr based ODS alloys are candidates for nuclear applications such as cladding tubes. One of the main issues is the fabrication of dense material with uniformly dispersed nanometer-size oxide particles. In order to investigate the influence of the fabrication route on the microstructure of the material the samples with Yttria contents of 0…0.6wt% were produced by mechanical alloying and subsequent consolidation via spark plasma sintering (SPS). The microstructure was characterized concerning the grain and particle size by means of electron backscatter diffraction (EBSD) and atom probe tomography (APT).
Keywords: EBSD, spark plasma sintering, APT, ODS, ferritic steel
  • Poster
    ODS Alloys workshop, 24.-26.09.2012, Oxford, United Kingdom

Publ.-Id: 18490 - Permalink


Fabrication and Characterization of ODS Fe14Cr-Alloys for Nuclear Applications
Schönitz, I.; Bergner, F.; Weißgärber, T.; Shariq, A.;
Ferritic Fe14Cr based oxide dispersion strengthened (ODS) alloys are promising candidates for components of GEN IV reactors. Due to their high Cr content high corrosion resistance is provided and the austenite phase transformation is prevented. Matrix compositions containing Ti in combination with yttria as reinforcing constituent tend to the formation of complex Y-Ti oxides that are known for their small particle sizes. High creep resistance and yield strength as well as an improved resistance against radiation induced He embrittlement are expected improvements to be achieved by ODS.
The considered fabrication process consists of a mechanical alloying step and the subsequent consolidation. During these steps an evolution of the added yttria particles (≈30 nm) towards much smaller Ti-Y-O nanoclusters (2-5 nm) has been observed [ ; ]. However, the mechanisms of dissolution and especially the re-precipitation during the consolidation process are not well known yet.
In order to evaluate the influence of the processing parameters, powders of different compositions (0….0.6wt% Y2O3) are fabricated applying different milling times (20h; 30h). These powders are consolidated via spark plasma sintering (SPS). The sintered material has been characterized with respect to porosity, microstructure, spatial distribution of composition and Vickers hardness. Ongoing research is focussed on the characterization of the oxide particles at the nanometre scale.
Keywords: ODS, ferritic steel, spark plasma sintering, nanoclusters
  • Poster
    International School on Materials UNder Extreme COnditions (MUNECO), 11.-15.06.2012, Madrid, Spain

Publ.-Id: 18489 - Permalink


Interfacial reactions of Sn(II) with anatase (TiO2): EXAFS and surface complexation modeling
Dulnee, S.; Merkel, B.; Scheinost, A. C.;
Sn(II) is a contaminant of general environmental interest, but little is known about its interaction and retention by mineral surfaces. We have selected the redox-inactive mineral anatase (TiO2) to study the surface complexation mechanism by combining EXAFSderived surface structures with surface complexation modeling to model the macroscopic sorption behavior. Three adjustable parameters required for diffuse double layer model were determined in this study: the surface site density (16 sites/nm2), and two log K+ values (4.76 ± 0.36 and −9.90 ± 0.42) of the protolysis reactions. EXAFS spectra show Sn(II)–Ti distances at 3.26 and 3.60 Å indicating the formation of monodentate and bidentate inner-sphere sorption complexes. Four surface complexes, Anat_sOSn+, Anat_sSnOH,
Anat_sOH(Anat_sO)Sn+, and (Anat_sO)2Sn, with log K values of 3.66, 3.68, 4.63, and 4.41, respectively,
were required to model the sorption data.
Keywords: Sn(II) surface complexation; surface complexation models; anatase (TiO2); adsorption
  • Contribution to HZDR-Annual report
    Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-030 Januar 2013, 44-44

Publ.-Id: 18488 - Permalink


Anticorrosion studies for pipe organ-related materials using plasma processing
Pelic, B.; Skorupa, W.;
The present historical organs are musical instruments, which provide sound impression of divine music spanning six centuries. Unfortunately, organ pipes, traditionally made of PbSn alloys, have been severely affected by corrosion in the last couple of centuries, and particularly over the last decades. A major threat to the historical organs is harmful indoor environments. Thus, it is necessary to develop a method of protecting the organ pipes, so that the significant cultural heritage obtained over many centuries does not get lost. A new conservation concept based on nanotechnology using plasma immersion ion implantation (PIII) is proposed here for the protection of PbSn alloys exposed to high levels of acetic acid vapors.
Keywords: Plasma immersion ion implantation, PbSn alloys, corrosion of organ pipes
  • Lecture (Conference)
    Internationale Konferenz zur Korrosion in Pfeifen von historischen Orgeln, 21.02.2013, Bremen, Germany

Publ.-Id: 18487 - Permalink


Millisecond flash lamp annealing for LaLuO3 and LaScO3 high-k dielectrics
Lehmann, J.; Hübner, R.; Skorupa, W.; von Borany, J.; Mikolajick, T.; Schäfer, A.; Schubert, J.; Mantl, S.;
LaLuO3 and LaScO3 high-k layers were treated by flash lamp annealing (FLA) at temperatures between 1000°C and 1200°C for 3 or 20 ms. This procedure mimics the effect of an source/drain activation annealing by FLA on the electrical and microstructural properties of these alternative high-k dielectrics in a gate-first processing sheme. Related MOS capacitors with a TiN metal gate were processed in a gate first like processing scheme. It is shown that 3 nm thick oxide layers resist crystallization even at 1200°C for 3 ms, while nanocrystallites are formed in thicker layers. The influence of the FLA treatment on capacitance-voltage (C-V) and current-voltage (I-V) characteristics are investigated. From these measurements, the effects on the relative dielectric constant (k), the fixed oxide charge density (Qox) as well as the leakage current through the insulators are deduced.
Keywords: High-k gate dielectrics, Higher-k gate dielectrics, Ternary high-k oxides, Rare-earth based gate oxides, Electrical properties
  • Microelectronic Engineering 109(2013), 381-384
    DOI: 10.1016/j.mee.2013.04.021
  • Lecture (Conference)
    18th Conference of "Insulating Films on Semiconductors", 25.-28.06.2013, Kraków, Polen

Publ.-Id: 18485 - Permalink


CFD-Simulation of Bubble Columns
Ziegenhein, T.; Rzehak, R.; Krepper, E.; Lucas, D.;
CFD simulations of dispersed bubbly flow on the scale of technical equipment are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, accurate numerical predictions rely on suitable closure models. A large body of work using different closure relations of varying degree of sophistication exists, but no complete, reliable, and robust formulation has been achieved so far.
As a step towards this goal, an attempt is made here to collect the best available description for all aspects known to be relevant for adiabatic bubbly flows where only momentum is exchanged between liquid and gas phases. Apart from interest in its own right, results obtained for this restricted problem also provide a good starting point for the investigation of more complex situations including heat and mass transport and possibly phase change or chemical reactions.
Aspects requiring closure for the case under consideration are: (i) the exchange of momentum between liquid and gas phases, (ii) the effects of the dispersed bubbles on the turbulence of the liquid carrier phase, and (iii) processes of bubble coalescence and breakup that determine the distribution of bubble sizes. All of these aspects are coupled and therefore in principle have to be considered as a whole.
To validate the overall model, simulation results are compared against experimental data taken from the literature for bubble columns in various settings. In the present study the focus is on the homogeneous regime where the assumption of a monodisperse bubble size distribution is reasonable and coalescence and breakup need not be considered. From the observed level of agreement between simulation and experiment, issues requiring further investigation will be identified. Necessary extensions to the heterogeneous regime will be discussed but remain to be worked out in the future.
Keywords: bubble column, CFD simulation, gas liquid multiphase flow, Euler Euler two fluid model, model validation
  • Lecture (Conference)
    Jahrestreffen der Fachgruppen Agglomerations- und Schüttguttechnik und Computational Fluid Dynamics, 04.-06.03.2013, Weimar, Deutschland

Publ.-Id: 18484 - Permalink


Ion Beam Shaping of Nanomaterials
Schmidt, B.;
The talk gives an overview about high energy ion-induced anisotropic deformation of nanostructures, also called ion beam shaping, especially of different nanoparticles embedded in silica. For selected examples, swift-heavy-ion-induced deformation of spherical Au and Ge nanoclusters (NCs) embedded in SiO2 was studied experimentally and theoretically. Ge NC shaping is size dependent under irradiation with 38 MeV iodine ions and with 89 and 185 MeV gold ions. Large NCs don’t deform, smaller ones become discus-shaped, and very small ones show Ge loss at their equator. Small Au NCs deform into rods and wires, and, rather exotic, at critical NC size Au wires are squeezed out of the poles of the Au spheres.
Experimental results are compared with modeling and atomistic computer simulations. The model describes the ion-induced shape evolution of different elements for different ion species, energies and fluences even quantitatively, where only one fit parameter describes all experiments. It is based on classical thermodynamics and hydrodynamics only.
  • Lecture (Conference)
    3rd SPIRIT Workshop “Ion Beams as a Tool for Nanotechnology”, 19.-20.07.2012, Lisbon, Portugal

Publ.-Id: 18483 - Permalink


Feasibility studies with GeoPET: microbial processes tomography in geological environments
Mickein, K.; Kutschke, S.; Pollmann, K.; Kulenkampff, J.; Lippmann-Pipke, J.;
Positron emission tomography (PET) is widely used in radiology to visualized cancer cells and infections in human tissue. This functional imaging technique is commonly used in order to visualize processes in the body with the help of radioactive substances. In addition, this method has been used for the investigation of transport processes in geological materials [1].
The aim of our work is the development of a method for the application of PET for geo-microbial research. We will use this technique for the spatio-temporal visualization of the mobility of bacteria in geological matrices. The visualization of the formation of biofilms and their influence on flow paths in different matrices is an important aspect as well. In addition, it offers the possibility to get insights into microbial processes (e.g. bioleaching) in opaque materials.
Some basic investigations for the experimental set-up are necessary. First, the method requires an efficient non-toxic method that allows the selective labeling of bacteria without interfering with the geological matrix. Currently, we are investigating a selection of antimicrobial peptides for their use as appropriate marker. Second, appropriate bacteria are selected for further investigation. Pseudomonas fluorescens and Lysinibacillus sphaericus JG-A12 were chosen as typical organisms living in soil. Third, the interactions of the different compounds and the influence of experimental parameters need to be tested. For further experiments it is very important to examine the stability of the label as well as adsorption and desorption processes of the PET nuclides and of the labeled substances in conjunction with different matrices. The characterisation of model columns that are filled with quartz gravel or copper ore needs to be investigated as well. Fluid dynamics and structural parameters like porosity and the internal surface area have to be investigated.
In this study we present our recent results on the development of a PET-method that allows the in-situ labeling of bacteria and the visualization of their mobility in geological matrices.

[1] Gründig, M., M. Richter, et al. (2003). Positron Emission Tomography for investigation of water flow in soil columns. Geochemical Processes in Soil and Groundwater. H. D. Schulz. Weinheim, Wiley-VCH: 550-559.
  • Poster
    Annual Conference of the Association for General and Applied Microbiology (VAAM), 11.-13.03.2013, Bremen, Deutschland

Publ.-Id: 18482 - Permalink


Interactions of the Mont Terri Opalinus Clay isolate Sporomusa sp. MT-2.99 with curium(III) and europium(III)
Moll, H.; Lütke, L.; Geissler, A.; Selenska-Pobell, S.; Bernhard, G.; Bachvarova, V.;
Bacterial cell walls have great potential to influence the speciation and mobility of actinides and lanthanides in the environment. This study explores the unknown interaction between Cm(III)/Eu(III) and cell-suspensions of Sporomusa sp. MT-2.99, a novel isolate originating from Opalinus Clay (Mont Terri, Switzerland).
The Cm(III)/Eu(III) binding by the cell surface functional groups was studied by potentiometry combined with time-resolved laser-induced fluorescence spectroscopy (TRLFS). This paper provides stability constants of Cm(III)/Eu(III) complexed by cell surface functional groups. It could be shown that as a function of pH Cm(III)/Eu(III) binding occurred to hydrogen phosphoryl, carboxyl and deprotonated phosphoryl sites. Both metals showed a similar interaction process consisting of surface complexation (major) with high thermodynamic stability and immobilization within the cell envelope (minor).
Keywords: curium; europium; Sporomusa sp.; bacteria; TRLFS; potentiometry; complexation

Publ.-Id: 18481 - Permalink


A fluoro versus a nitro derivative - a high-performance liquid chromatography study of two basic analytes with different RP and silica phases as basis for the separation of a positron emission tomography radiotracer
Wenzel, B.; Günther, R.; Brust, P.; Steinbach, J.;
To optimize the semi-preparative separation of a 18F-labeled PET radiotracer from its nitro precursor in a recently developed radiosynthesis, we performed an analytical HPLC study using the unlabeled reference compound and the corresponding nitro precursor. Several RP phases as well as a bare silica column were investigated with ACN and MeOH as organic modifiers and aqueous NH4OAc because of the basic character of the analytes. Four types of separation were observed based on different interaction mechanisms. When ACN/20 mM NH4OAc aq. was used mainly cationic-exchange and hydrophobic interactions contribute to the retention. A reversal of elution order could be observed starting from 95% ACN and subsequent increasing of the water content. This phenomenon was observed for all RP phases and seems to be independent of the different spacers bound to the silica. By contrast, using MeOH/20 mM NH4OAc aq. the elution order depends on the phase material. Two columns with the potential to perform π-π interactions showed different separation behavior compared to the other RP phases.
Keywords: Basic analytes, Cationic-exchange, RP phases, Silanol sites, VAChT

Publ.-Id: 18479 - Permalink


Wear in tetrahedral amorphous carbon induced by sp3/sp2 phase transition
Kunze, T.; Seifert, G.; Posselt, M.; Gemming, S.; von Lautz, J.; Pastewka, L.; Moseler, M.;
Tetrahedral amorphous carbon (ta-C) coatings have attracted high scientific attention in recent years due to their outstanding low friction coefficients in lubricated environments and their superior resistance to abrasive as well as adhesive wear. Consequently, they are highly suitable as protective coatings in automotive components such as combustion engines to reduce wear and friction. Nevertheless, ta-C abrade under extreme conditions and an atomistic understanding of the wear processes in ta-C is crucial for optimizing its wear resistance. The present study employs atomic-scale simulations to investigate the basic principles of wear between hydrogen- free tetrahedral-amorphous carbon (ta-C) films, which are modeled state-of-the-art by an improved version of the well-known Brenner bond-order potential. During tribological contact, these mainly sp3 hybridized films tend to form an amorphous carbon (a-C) tribomaterial mainly consisting of carbon atoms in sp2 configuration. Furthermore, the observed tribolayer grows faster than the a-C between diamond surfaces under similar conditions, which can be explained by easy breaking of weak bonds in a finite ta-C region triggered by plasticity in the adjacent a-C while the diamond/a-C transition occurs at an atomically sharp interface. The difference in the a-C tribofilm formation between ta-C and diamond is in agreement with near-edge x-ray absorption fine structure spectroscopy (NEXAFS) studies published recently.
  • Poster
    PSI-K ADGLASS Workshop 2012 - Atomistic modelling for Industrial product development, 14.-16.11.2012, Bremen, Deutschland

Publ.-Id: 18478 - Permalink


Tribosimulation of ta-C nanocoatings - Friction and wear on the atomic scale
Kunze, T.; Posselt, M.; Gemming, S.; von Lautz, J.; Pastewka, L.; Moseler, M.; Seifert, G.;
Nanocoatings have the potential to improve the surface properties of various materials. They are of extreme importance for surfaces in sliding contact such as highly stressed automotive engine parts. Here, nanocoatings have to be optimized with respect to low friction properties and a high wear resistance to enhance the energetic and environmental efficiency. The present study employs atomic-scale simulations to investigate the basic principles of wear and friction between hydrogen-free tetrahedral-amorphous carbon (ta-C) films. The ta-C films are modeled state-of-the-art by an improved version of the well-known Brenner bond-order potential, which had been successfully applied to elucidate the wear processes during diamond polishing.

We start our work by the preparation of the ta-C film structure, which is then characterized with respect to local and global film properties in comparison to experiments. After validating our ta-C nanocoatings with the help of experimental data, we perform computational sliding experiments to investigate mechanisms of friction and wear between interacting ta-C surfaces. During tribological contact, these diamond-like films (mainly sp3 hybridized) tend to form a soft-amorphous or graphite-like tribomaterial mainly consisting of carbon atoms in sp2 configuration. The sp3 to sp2 transition originates from atom-by-atom extraction events occurring at the sp3/sp2 interface. We discuss the underlying mechanisms by focusing on associated triboreactions and tribological properties such as shear forces.
  • Poster
    Gordon Research Conference 2012 - Tribology, 08.-13.07.2012, Waterville, USA

Publ.-Id: 18477 - Permalink


Ultrasensitive Bestimmung von Radionukliden Mittels Beschleunigermassenspektrometrie bei DREAMS am Beispiel von 36Cl
Pavetich, S.; Akhmadaliev, S.; Merchel, S.; Rugel, G.;
Beschleunigermassenspektrometrie (AMS - Accelerator Mass Spectrometry) ist eine hochsensitive Methode zur Bestimmung der Häufigkeit von Radioisotopen. Dabei werden Radionuklide immer relativ zu den stabilen Isotopen des jeweiligen Elements gemessen. Da bei der AMS radioaktive Atome nicht durch ihren Zerfall detektiert werden, sondern direkt gezählt werden, eignet sich die Methode in erster Linie für langlebige Radionuklide (t1/2 > 100 a). Dabei können je nach Element Isotopenverhältnisse von 10-15-10-16 (entspricht nBq) gemessen werden, wobei die Messzeit ca. 1 h pro Probe beträgt. Im Wesentlichen besteht eine AMS-Anlage aus einer Ionenquelle (üblicherweise Cs-Ionensputterquelle) zur Extraktion negativer Ionen aus dem Probenmaterial (< 10 mg), zwei Massenspekrometern (Injektormagnet und Analysiermagnet) zum Filtern der Ionen nach ihrer Energie, ihrem Impuls und Ladungszustand, einem Beschleuniger der die Ionen auf die für die finale Separation notwendigen Energien (MeV) beschleunigt und durch das sogenannte „Stripping“ für eine totale Unterdrückung des molekularen Isobarenhintergrundes sorgt und einem Detektor zum Zählen der Radioisotope bzw. Faraday-Cups zur Messung des Stromes der Stabilisotope.

Die AMS-Anlage DREAMS (DREsden AMS) ist seit August 2011 in Betrieb [1]. Momentan werden bei DREAMS Routinemessungen der Nuklide 10Be, 26Al und 41Ca durchgeführt [2]. Bei den volatilen Element Cl und I werden Präzisionsmessungen noch durch Langzeit- und Probe-zu-Probe-Kontaminationseffekte in der Ionenquelle verhindert [3]. Kooperationen mit der TU Bergakademie Freiberg einerseits und dem UFZ Leipzig (Helmholtz-Zentrum für Umweltforschung) andererseits bei denen Proben aus der Salar de Uyuni (Salzwüste in Bolivien) und von unterirdischen Wasserläufen im Oman untersucht wurden, haben gezeigt, dass die Bestimmung von 36Cl-Konzentrationen dennoch auf einem Level von einigen 100 nBq zurzeit schon möglich ist. Die Entwicklung einer neuen Ionenquelle für volatile Elemente, die in ersten Versuchen vielversprechende Ergebnisse geliefert hat, wird noch präzisere AMS-Messungen von 36Cl bei DREAMS ermöglichen.

Danksagungen: Prof. Dr. Broder J. Merkel und Anna Seither, TU Bergakademie Freiberg
Dr. Gerhard Strauch und Thomas Müller, Helmholtz-Zentrum für Umweltforschung Leipzig

[1] S. Akhmadaliev et al., Nucl. Instr. Meth. B 294 (2013) 5
[2] G. Rugel, Vortrag, 7. Workshop RCA
[3] R. Finkel et al., Nucl. Instr. Meth. B 294 (2013) 121
Keywords: AMS, DREAMS, 36Cl, langlebige Radionuklide
  • Poster
    7. Workshop RCA, 10.-11.06.2013, Dresden, Deutschland

Publ.-Id: 18476 - Permalink


36Cl-AMS at the DREAMS facility
Pavetich, S.; Akhmadaliev, S.; Arnold, M.; Aumaître, G.; Bourlès, D.; Buchriegler, J.; Golser, R.; Keddadouche, K.; Martschini, M.; Merchel, S.; Rugel, G.; Steier, P.;
The DREAMS (DREsden Accelerator Mass Spectrometry) facility [1] went operational in August 2011. It is based on a state-of-the-art 6 MV Tandetron. The target wheels of the two Cs sputter ion sources can be loaded with up to 200 samples each. A fast bouncing system at the 90° injection magnet allows almost simultaneous measurements of the radioisotope and its stable isotope(s). For the measurement of 10Be and 36Cl a 1 µm Si3N4-post-acceleration stripping-foil in combination with a 35° ESA suppresses their stable isobars 10B and 36S. An ionization chamber with four anodes is used for the final identification of the radioisotopes.

At the moment routine measurements of 10Be, 26Al and 41Ca are performed at DREAMS. In the case of volatile elements like Cl and I, the key issue for precise AMS-measurements is the understanding and minimization of ion source memory effects [2,3]. For this purpose the main focus for 36Cl-measurements at DREAMS was set to the mechanical modification and improvement of the original SO110 ion source from High Voltage Engineering (HVE) [4]. The new DREAMS design has a more open geometry to improve the vacuum level and a modified target loading and positioning system, which allows exchanging the individual cathode aperture with each target.

In order to evaluate this improvement in comparison to other up-to-date ion sources, an interlaboratory comparison with three AMS labs had been initiated. The long-term memory effect in the four Cs sputter ion sources of VERA [5] (Vienna Environmental Research Accelerator, NEC ion source: MC-SNICS), ASTER [3] (Accélérateur pour les Sciences de la Terre, Environnement, Risques, modified HVE SO110) and DREAMS (original HVE SO110 and modified HVE SO110 ion source) had been investigated by running samples of natural 35Cl/37Cl-ratio and samples containing highly-enriched 35Cl (35Cl/37Cl > 500). We choose to perform these measurements with the two stable Cl isotopes instead of using 36Cl standards and blanks to avoid limitations of accuracy by counting statistics on low level 36Cl samples.

The primary goals of these experiments are the determination of the time constants of the recovery from the contaminated sample ratio to the initial ratio of the sample and the level of the long-term memory effect in the sources.

[1] S. Akhmadaliev et al., Nucl. Instr. Meth. B 294 (2013) 5.
[2] R. Finkel et al., Nucl. Instr. Meth. B 294 (2013) 121.
[3] M. Arnold et al., Nucl. Instr. Meth. B 294 (2013) 24.
[4] M.G. Klein et al., Nucl. Instr. Meth. B 249 (2006) 764.
[5] M. Martschini et al., Nucl. Instr. Meth. B 269 (2011) 3188.
Keywords: accelerator mass spectrometry, DREAMS, 36Cl, volatile elements, long-term-memory-effect, ion source
  • Lecture (others)
    Departmental seminar at the Nuclear Physics Department of the Australian National University, 04.04.2013, Canberra, Australia

Publ.-Id: 18475 - Permalink


Formic acid interaction with uranyl(VI) ion: structural and photochemical characterization
Lucks, C.; Roßberg, A.; Tsushima, S.; Foerstendorf, H.; Fahmy, K.; Bernhard, G.;
Complex formation between uranyl(VI) ion and formic acid was studied by infrared absorption (IR) and X–ray absorption (EXAFS) spectroscopy as well as density functional theory (DFT) calculations. In contrast to the acetate ion which forms exclusively bidentate complex with uranyl(VI), formate ion binds to uranyl(VI) in unidentate fashion. The photochemistry of the uranyl(VI)–formic acid system was explored by DFT calculations and photoreduction of uranyl(VI) in the presence of formic acid was found to occur via an intermolecular process, that is hydrogen abstraction from hydrogenformate by the photo–excited uranyl(VI). There is no photo–induced decarboxylation of uranyl(VI) formate via an intramolecular process, presumably due to lack of a C=C double bond.

Publ.-Id: 18474 - Permalink


Impact of a revised Mg-25(p, gamma)Al-26 Reaction Rate on the Operation of the Mg-Al Cycle
Straniero, O.; Imbriani, G.; Strieder, F.; Bemmerer, D.; Broggini, C.; Caciolli, A.; Corvisiero, P.; Costantini, H.; Cristallo, S.; Dileva, A.; Formicola, A.; Elekes, Z.; Fulop, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyurky, G.; Junker, M.; Lemut, A.; Limata, B.; Marta, M.; Mazzocchi, C.; Menegazzo, R.; Piersanti, L.; Prati, P.; Roca, V.; Rolfs, C.; Alvarez, C.; Somorjai, E.; Terrasi, F.; Trautvetter, H.;
Proton captures on Mg isotopes play an important role in the Mg-Al cycle active in stellar H-burning regions. In particular, low-energy nuclear resonances in the Mg-25(p,gamma)Al-26 reaction affect the production of radioactive Al-26(gs) as well as the resulting Mg/Al abundance ratio. Reliable estimations of these quantities require precise measurements of the strengths of low-energy resonances. Based on a new experimental study performed at the Laboratory for Underground Nuclear Astrophysics, we provide revised rates of the Mg-25(p,gamma)Al-26(gs) and the Mg-25(p,gamma)Al-26(m) reactions with corresponding uncertainties. In the temperature range 50-150 MK, the new recommended rate of Al-26(m) production is up to five times higher than previously assumed. In addition, at T = 100 MK, the revised total reaction rate is a factor of two higher. Note that this is the range of temperature at which the Mg-Al cycle operates in a H-burning zone. The effects of this revision are discu!
ssed. Due to the significantly larger Mg-25(p,gamma)Al-26(m) rate, the estimated production of Al-26(gs) in H-burning regions is less efficient than previously obtained. As a result, the new rates should imply a smaller contribution from Wolf-Rayet stars to the galactic Al-26 budget. Similarly, we show that the asymptotic giant branch (AGB) extra-mixing scenario does not appear able to explain the most extreme values of Al-26/Al-27, i.e., > 10(-2), found in some O-rich presolar grains. Finally, the substantial increase of the total reaction rate makes the hypothesis of self-pollution by massive AGBs a more robust explanation for the Mg-Al anticorrelation observed in globular-cluster stars.
Keywords: globular clusters: general; nuclear reactions, nucleosynthesis, abundances; stars: AGB and post-AGB; stars: Wolf-Rayet

Publ.-Id: 18473 - Permalink


Long spin relaxation time of holes in InGaAs/GaAs quantum wells probed by cyclotron resonance spectroscopy
Drachenko, O.; Kozlov, D.; Ikonnikov, A. V.; Spirin, K. E.; Gavrilenko, V.; Schneider, H.; Helm, M.; Wosnitza, J.;
In this paper, we report on a long, ms range, hole spin relaxation time in InGaAs/GaAs quantum wells probed by cyclotron resonance spectroscopy in pulsed magnetic fields. In our experiments, we found strong hysteresis in the spectral weights of cyclotron resonance absorption lines when rapidly changing magnetic field is used for the experiment. The hysteresis vanishes when a much slower changing magnetic field is used. We attribute this behavior to a long energy relaxation time between the two lowest spin-split hole Landau levels, i.e., a long hole spin relaxation time. We also present transition frequencies calculated using a 4×4 Luttinger Hamiltonian, which confirm our findings.
Keywords: Cyclotron resonace, spin relaxation time, spintronics, InGaAs, high magnetic fields

Publ.-Id: 18472 - Permalink


New insight into physics of the holes in semiconductors through Terahertz studies in ultra-high magnetic fields
Drachenko, O.;
This talk summarizes recent magneto-optical activities at Dresden high magnetic field laboratory. The first part reports a correction to the model potential of the Ga acceptor in germanium, evidenced by high-magnetic-field photoconductivity measurements. It was found that under high magnetic fields the chemical shift of the binding energy of Ga acceptors vanishes, contrary to the results given by the generally accepted theory. To fit our data, we found that the central-cell correction should contain a repulsive part (i.e., it must be bipolar), in contrast to the purely attractive screened point-charge potential widely used in the literature.
In the second part, we report long, ms range, hole spin relaxation time in InGaAs/GaAs quantum wells probed by cyclotron- resonance spectroscopy in pulsed magnetic fields. In our experiments, we found strong hysteresis in the spectral weights of cyclotron resonance absorption lines when rapidly changing magnetic field is used for the experiment. The hysteresis vanishes when a much slower changing magnetic field is used. We attribute this behavior to a long energy relaxation time between two lowest spin-split hole Landau levels, i.e. a long hole spin relaxation time. We also present transition frequencies calculated using a 4x4 Luttinger Hamiltonian, which confirm our findings.
Keywords: Semiconductors, cyclotron resonance, magnetic fields, holes, spin relaxation
  • Lecture (others)
    Seminar at Laboratory Charles Coulomb &TERALAB, Université Montpellier 2 &CNRS, 22.02.2013, Montpellier, France

Publ.-Id: 18471 - Permalink


Modelling turbulence dynamics at the free surface of horizontal two phase flows
Höhne, T.;
- Limits today in simulating horizontal two phase flow: no special turbulence treatment at the surface Turbulence Damping,
- Introduction of a symmetric damping procedure (Egorov) for the solid wall-like damping of turbulence in both gas and liquid phases Subgrid wave turbulence (SWT),
- Waves created by Kelvin-Helmholtz instabilities that are smaller than the grid size are neglected - Influence on the turbulence kinetic energy of the liquid side can be significantly large,
- A region of marginal breaking is defined according Brocchini and Peregrine (2001) and added as a source term in the turbulent kinetic energy equation,
- Verification and Validation is going on – more experimental data are required for the validation
Keywords: AIAD, CFD, Horizontal Flow, SWT
  • Lecture (Conference)
    CFD-Verbundtreffen, 06.-07.03.2013, Garching, Deutschland

Publ.-Id: 18470 - Permalink


Uptake of multi-disperse starch by anion exchangers
Pürschel, M.; Sachs, S.; Bernhard, G.; Ender, V.;
Demineralisation plants of power stations are not able to remove organics in all cases to a satisfied degree. The present work focuses on natural organic matter (NOM) and its interaction with anion exchanger and adsorber resins to optimize organics uptake. In this study, four different starches (one of them 14C-labelled) with different molecular size distributions were selected as model substances for the biopolymer fraction of NOM. Their uptake by various anion exchangers and adsorbers was measured in column experiments. Results are discussed in terms of size exclusion, anion exchange, adsorption, and hydrophilic/hydrophobic repulsion. In summary, at neutral pH, starch has been removed preferably by size-exclusion followed by adsorption, whereas anion exchange resins show higher uptake capacities than “pure” adsorber resins caused by stronger attraction between starch and polar functional groups of the anion exchangers. At acidic pH, the uptake of sulphate, as competitive adsorptive, leads to an earlier starch breakthrough at anion exchangers. Therefore, adsorbers are more effective. It was found, that the higher the water content of the resins, the more effective the uptake is.
Keywords: water treatment, natural organic matter (NOM), anion exchange, adsorption
  • Open Access LogoJournal of Physical Science and Application 3(2013)3, 147-155

Publ.-Id: 18469 - Permalink


Functional DNA origami nanostructures
Keller, A.;
Functional DNA origami nanostructures for single-molecule experiments and novel nanomaterials
  • Lecture (others)
    B CUBE Seminar, 30.01.2013, Dresden, Deutschland
  • Lecture (others)
    Seminar Physikalische Chemie, 09.04.2013, Potsdam, Deutschland

Publ.-Id: 18468 - Permalink


Optical measurement of the longitudinal ion distribution of bunched ion beams in the ESR
Wen, W. Q.; Lochmann, M.; Ma, X.; Bussmann, M.; Winters, D. F. A.; Nörtershäuser, W.; Botermann, B.; Geppert, C.; Frömmgen, N.; Hammen, M.; Hannen, V.; Jöhren, R.; Kühl, T.; Litvinov, Y.; Sánchez, R.; Stöhlker, T.; Vollbrecht, J.; Weinheimer, C.; Dimopoulou, C.; Nolden, F.; Steck, M.;
An optical technique to study the longitudinal distribution of ions in a bunched ion beam circulating in a storage ring is presented. It is based on the arrival-time analysis of photons emitted after collisional excitation of residual gas molecules. The beam-induced fluorescence was investigated in the ultraviolet regime with a channeltron and in the visible region using a photomultiplier tube. Both were applied to investigate the longitudinal shape of bunched and electron-cooled 209Bi80+ ion beams at about 400 MeV/u in the experimental storage ring (ESR) at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Bunch lengths were determined with an uncertainty of about 0.5 m using the UV-sensitive channeltron and with slightly lower accuracy from the photomultiplier data due to the slower transitions in the red region of the spectrum. The Gaussian shape of the longitudinal distribution of ions inside the bunch was confirmed. With the information of the transverse beam size that can be measured simultaneously by a newly installed ionization profile monitor (IPM) at the ESR, an accurate determination of the ion density in the bunched beam will be allowed.
Keywords: optical, bunch, length, measurement, ion, storage, ring

Publ.-Id: 18467 - Permalink


Characterization of primary and secondary magnetite in marine sediment by combining chemical and magnetic unmixing techniques
Ludwig, P.; Egli, R.; Bishop, S.; Chernenko, V.; Frederichs, T.; Rugel, G.; Merchel, S.; Orgeira, M. J.;
We present a novel technique for quantitative unmixing of primary and secondary ferrimagnetic minerals in sediments. Hysteresis and high-resolution first-order reversal curve (FORC) measurements are performed on sediment samples before and after digestion in a citrate-bicarbonate-dithionite (CBD) solution optimized for maximum selective extraction of secondary fine-grained iron oxides. The difference between magnetic measurements of untreated and CBD-treated sample materials is used to calculate the original magnetic signature of CBD-extractable minerals. Combination of selective chemical extraction and magnetic measurements suited for the detection of single-domain particles provides a cross-check between chemical and magnetic unmixing of primary and secondary iron-oxides and resolves the non-uniqueness of numerical unmixing methods. A fully quantitative magnetic characerization of secondary ferrimagnetic minerals in a magnetofossil-rich pelagic carbonate is presented for the first time. It can be used for calibartion of recently developed fast magentic unmixing techniques. CBD-based Fe extraction from sediments with minimal clascic and/or aeolian inputs, such as pelagic carbonates, is partcularly suited for the detection of cosmogenic 60Fe signatures from supernova explosions, because 60Fe dilution by dissolved primary Fe-bearing minerals is minimized.
Keywords: accelerator mass spectrometry, supernova, ferrimagnetic minerals, FORC, radiochemical separation

Publ.-Id: 18466 - Permalink


Experimental investigation of multilayer particle deposition and resuspension between periodic steps in turbulent flows
Barth, T.; Reiche, M.; Banowski, M.; Oppermann, M.; Hampel, U.;
Multilayer particle deposition and resuspension between periodic steps in a turbulent channel flow was experimentally studied. A particle laden turbulent flow in a horizontal channel was generated by means of a small-scale wind tunnel. Periodic steps were placed on the channel floor to induce a complex flow field characterized by flow separations, recirculation and reattachment zones.
The turbulent flow field was recorded by means of a stereoscopic Particle Image Velocimetry system. The dimensions of the flow field structures agree well with the specifications from comparable studies. Polydisperse graphite particles were injected into the flow field during a pure deposition regime. The multilayer build up between the periodic steps was measured using a laser distance sensor coupled with a linear stage. The particle layer build up shows a linear tendency against time and the deposition velocities are in good agreement with similar investigations. After the deposition scenario the particle dispersion was switched off and particle resuspension was induced by the stepwise increase of the fluid velocity. The particle resuspension was found to begin in clusters close to the recirculation zones and was accomplished at lower friction velocities than necessary for single particle resuspension. Surface roughness analysis of the multilayer interface characterizes the growth of the loose particle agglomerates during particle deposition and the instant removal of these structures during particle resuspension. Furthermore, particle bed porosity measurements were performed by gravimetrical and x-ray methods to characterize the packing properties. Spatial correlations between the turbulent flow field and the multilayer thickness distribution indicate the influence of inertia impaction, turbulent dispersion and gravitational settling on the particle deposition process. The multilayer particle resuspension seems to be influenced by the mean and fluctuating flow field structures. The results indicate similarities between single particle and multilayer particle formation during particle deposition and resuspension processes.
Keywords: multilayer, graphite particle, deposition, resuspension, turbulent duct flow, periodic steps, high temperature reactor, design basis accident, particle image velocimetry

Publ.-Id: 18465 - Permalink


Metal interaction processes with cell wall components of Gram-positive bacteria studied by QCM-D
Suhr, M.; Matys, S.; Raff, J.; Pollmann, K.;
Bacterial isolates from the uranium mining waste pile Haberland (Johanngeorgenstadt, Saxony) possess high affinities for heavy metals [1]. Binding sites are predominantly provided by the components of the bacterial cell wall, mainly by surface layer proteins, but also from other parts of the cell wall e.g. membrane lipids.

A deeper understanding of the metal interaction with the biosphere is important not only from an ecological point of view but also from an application oriented one.
Parts of our investigations focused on surface layer proteins (S-layers). They represent the outermost cell envelope of many eubacteria and archaea forming highly ordered paracrystalline lattices not only on the living cell, but also after isolation on various technical surfaces by self-assembling processes [2]. Such biological structures can be used e.g. as filter materials for waste water treatment and as templates for synthesis of bio-based sensory layer or chemical catalysts [3]. Nevertheless, the investigation of interactions of the cell wall components like S-layer, peptidoglycan, lipids and secondary cell wall polymers (SCWP) with metals and nanoparticles both as molecules and as intact layers on a molecular level remains challenging.

In addition, to standard bio-analytical methods the quartz crystal microbalance with dissipation monitoring (QCM-D) represents a versatile tool to track and control the biological layer formation, metal interaction and nanoparticle deposition as well as adsorption kinetics. This method allows the real time detection of sorption processes on a molecular level and gives further information of the viscoelasticity [4].

Aim of our study was the investigation of layer adsorption of isolated cell wall components on technical surfaces such as glass or silicon using a simplified model derived from Gram-positive bacteria in order to get basic information about multilevel processes in complex natural systems. The sorption behavior of metals with these components will be investigated by QCM-D. The results were evaluated by supporting atomic force microscopy (AFM).

[1] J. Raff et al. (2003), Chem. Mater. 15, 240-244.
[2] Sleytr, U. B. et al. (2007), FEMS Microbiology Letters 267(2), 131-144.
[3] K. Pollmann et al. (2006), Biotechnol. Adv. 24, 58– 68.
[4] A. E. Lopez et al. (2010), Small 6 (3), 396 -403.
Keywords: Bacteria, QCM-D, Biosorption, sorption, heavy metal, metal binding, AFM, cell wall
  • Lecture (Conference)
    Annual Conference of the Association for General and Applied Microbiology (VAAM), 10.-13.03.2013, Bremen, Deutschland

Publ.-Id: 18464 - Permalink


To Develop a High Brightness SRF Photo Injector for Electron-Laser Interaction
Lu, P.; Vennekate, H.; Teichert, J.; Arnold, A.; Murcek, P.; Xiang, R.;
Background:
- a 3½-cell SRF gun was developed and commissioned in HZDR
- the SRF gun needs further optimization and refinement
  • Poster
    First International School on Laser Applications at Accelerators, 14.-17.10.2012, Caen, France

Publ.-Id: 18463 - Permalink


Performance and Workflow of a new sequential PET/MR System, the Mediso nanoScan®
Kranz, M.; Will, E.; Bergmann, R.; Meister, S.; Hóbor, S.; Donat, C.; Brust, P.;
Aim:
In this study we describe the performance and workflow of the commercially available small animal sequential PET/MR system, the Mediso nanoScan®.

Material and Methods:
The system consists of a PET scanner (Mediso Ltd. Budapest, Hungary) based on LYSO crystals (1.12 x 1.12 x 13mm) with an axially FOV of 94.7mm and a 1 tesla permanent magnet (Aspect Imaging, Toronto, Canada). The fringe fields of this magnet enable the use of Position Sensitive PMTs (PSPMTs) for the PET gantry.
The PET performance was assessed by using NEMA NU 4-2008 standard to derive the sensitivity and spatial resolution. The MR based attenuation correction for this device is tested by using different homogenous volumes (syringes); the activity is reconstructed and compared to the uncorrected data to determine the impact of this method. The image quality of the system is presented in through different MR scans of rat and mice as well as in coregistered PET/MR images.

Conclusion:
The PET performance has no visible influence by the MRI system. The first results deliver an absolute sensitivity of 8.4% and an axial resolution of 1.1mm FWHM (radial 1.5, tangential 1.3). Anatomic good quality brain images are obtained in 20 minutes and a basic 3D scout in 4.5 minutes. The reproduced activity of the attenuation corrected data verifies the efficiency of the implemented method, while the residual deviation in homogenous phantoms is +1.3% (5ml, 10ml and 20ml syringes).
The nanoScan® PET/MR scanner allows fast, high resolution anatomical MR- and precise PET-imaging with a special regard to brain studies.
  • Poster
    Marburger 7Tesla MRT-Symposium, 12.04.2013, Marburg, Deutschland

Publ.-Id: 18462 - Permalink


Laser-driven High-Energy-Density Physics
Schlenvoigt, H.-P.; Schramm, U.; Cowan, T.;
Research fields for the HED Instrument at the European XFEL
with the Helmholtz-Beamline add-on
Keywords: European XFEL, laser compression, shock compression, warm dense matter, WDM
  • Poster
    European XFEL & DESY Photon Science User's Meeting 2013, 23.-25.01.2013, Hamburg, Deutschland

Publ.-Id: 18461 - Permalink


Relativistic Laser-Matter-Interaction
Schlenvoigt, H.-P.; Schramm, U.; Cowan, T.;
Research fields for the HED Instrument at the European XFEL with the Helmholtz-Beamline add-on
Keywords: European XFEL, laser particle acceleration, relativistic electron transport, SAXS
  • Poster
    European XFEL & DESY Photon Science User's Meeting 2013, 23.-25.01.2013, Hamburg, Deutschland

Publ.-Id: 18460 - Permalink


The HELMHOLTZ-BEAMLINE at the European XFEL
Schlenvoigt, H.-P.; Schramm, U.; Cowan, T.;
Providing additional instrumentation to the HED instrument via a User-Consortium to a world-unique combination.
Keywords: European XFEL, HED, HEDP, Helmholtz Beamline
  • Poster
    European XFEL & DESY Photon Science User's Meeting 2013, 23.-25.01.2013, Hamburg, Deutschland

Publ.-Id: 18459 - Permalink


Risk management:corporate governance and compliance
Stiller, D.; Joehnk, P.;
  • Contribution to proceedings
    20th International Scientific Conference. Global Crises - Opportunities and Threats, 10.-12.10.2012, Trnava, Slovak Republic
    CO-MAT-Tech 2012, Trnava: AlumniPress, 978-80-8096-180-0

Publ.-Id: 18458 - Permalink


Risk management for companies factors for an effective risk management
Stiller, D.; Joehnk, P.;
The article deals with the formal reguirements for an effective risk management system. After summing up the definition of risk and risk management and the description of the objectives and tasks, the idea of the process steps of a risk management system with significant methods and instruments follows. Finally, an organizational integration will be shown.
Keywords: risk, risk management, ris identification, risk assessment, risk regulation, risk control, risk reporting, risk portfolio
  • Open Access LogoJournal of International Scientific Publications: Economy & Business 5(2011)1, 223-232

Publ.-Id: 18457 - Permalink


Reactive crisis management
Stiller, D.; Joehnk, P.;
The article describes the different aspects of crisis management. The term corporate crisis and its typical phases will be defined as well as the essential measures, which can be used to avoid or manage a crisis situation in a company. A particular focus is placed on measures of reorganisation as a part of reactive crisis management. Three particular measures of reorganisation management will be present.
Keywords: corporate crises, crisis management, active and reactive crisis management, reorganisation management
  • Open Access LogoJournal of International Scientific Publications: Economy & Business 6(2012)1, 231-239
  • Invited lecture (Conferences)
    Economy & Business – 11th Annual International Symposium, 03.09.2012, Sunny Beach, Bulgaria

Publ.-Id: 18456 - Permalink


The influence of defects on the structural and electronic properties of oxides
Gemming, S.; Zschornak, M.; Weißbach, T.; Meyer, D. C.; Lubk, A.; Riedl, T.; Gemming, T.;
Seminarvortrag zu:
- Switching – Electrostatic field at interfaces
- Strontium Titanate & Defects
- Aluminium Oxide Boundaries - Quantification by DFT – EELS – HRTEM
Keywords: density-finctional theory, oxides, transmission electron microscopy, titanates, Ruddlesden-Popper
  • Lecture (others)
    Eingeladener Seminarvortrag am HZ Berlin, 26.11.2012, Berlin, Deutschland

Publ.-Id: 18455 - Permalink


Nanoscale Metal-Molecule Contacts
Berger, S.; Gemming, S.; Erdogan, E.; Seifert, G.; Sendler, T.; Erbe, A.;
Several differently substituted 1,4-bis(phenylethynyl)benzene molecules have been analyzed regarding their suitability as nano-electrical devices. Since the molecules have the same fully conjugated backbone and only differ in their side groups it has been possible to study the influence of such side groups. First, the contact stability of the molecules was investigated by molecular dynamics simulations. Not only the energetically optimized contact geometries, but also energetically less favorable contract geometries remained contacted. In the next step, the density-functional-based tight-binding method was employed to analyze the density of states as well as the charge transport properties of both molecules. This investigation showed that the side group effect reduces the energy gap between the highest occupied and the lowest unoccupied molecular orbital. However, the charge transport was lowered by the influence of the side group. Furthermore, the molecular density of states gets significantly changed if the molecule is contacted by metallic leads.
Keywords: molecular electronics, nanoelectronics, density-functional
  • Invited lecture (Conferences)
    JaDe - Joint Dresden-Japan Workshop on Molecular Scale and Organic Electronic Materials, 11.-14.12.2012, Dresden, Deutschland

Publ.-Id: 18454 - Permalink


Tribosimulation of ta-C nanocoatings
Kunze, T.; Posselt, M.; Gemming, S.; von Lautz, J.; Pastewka, L.; Moseler, M.; Seifert, G.;
Nanocoatings have the potential to improve the surface properties of various materials. They are of extreme importance for surfaces in sliding contact such as highly stressed automotive engine parts. Here, nanocoatings have to be optimized with respect to low friction properties and a high wear resistance to enhance the energetic and environmental efficiency.
The present study employs atomic-scale simulations to investigate the basic principles of wear and friction between hydrogen-free tetrahedral-amorphous carbon (ta-C) films. The ta-C films are modeled state-of-the-art by an improved version of the well-known Brenner bond-order potential [1,2], which had been successfully applied to elucidate the wear processes during diamond polishing[3].

Our work starts with the preparation of ta-C film structures with different atomic densities, which are then characterized with respect to local and global film properties in comparison to experimental data. With these prepared nanocoatings, we perform computational sliding experiments to investigate mechanisms of friction and wear between interacting ta-C surfaces. Dry and lubricated sliding is considered. Especially for dry sliding and during tribological contact, these diamond-like films (mainly sp3 hybridized) tend to form a soft-amorphous or graphite-like tribomaterial mainly consisting of carbon atoms in sp2 configuration. We discuss underlying mechanisms of the dynamic triboreactions and investigate tribological properties such as shear forces at the sliding interface.
Keywords: nanotribology, molecular dynamics, molecular modeling, density-functional theory, scale-bridging
  • Poster
    MSE - Materials Science and Engineering, 25.-27.09.2012, Darmstadt, Deutschland

Publ.-Id: 18453 - Permalink


Nanoscale metal-molecule contacts
Berger, S.; Gemming, S.; Erbe, A.; Erdogan, E.; Seifert, G.;
Several differently substituted 1,4-bis(phenylethynyl)benzene molecules have been analyzed regarding their suitability as nano-electrical devices. Since the molecules have the same fully conjugated backbone and only differ in their side groups it has been possible to study the influence of such side groups. First, the contact stability of the molecules was investigated by molecular dynamics simulations. Not only the energetically optimized contact geometries, but also energetically less favorable contract geometries remained contacted. In the next step, the density-functional-based tight-binding method was employed to analyze the density of states as well as the charge transport properties of both molecules. This investigation showed that the side group effect reduces the energy gap between the highest occupied and the lowest unoccupied molecular orbital. However, the charge transport was lowered by the influence of the side group. Furthermore, the molecular density of states gets significantly changed if the molecule is contacted by metallic leads.
Keywords: molecular electronics, nanoscale electronics, contacts, interfaces, density-functional theory, scale-bridging
  • Lecture (Conference)
    MSE 2012 - Materials Science and Engineering, 25.-27.09.2012, Darmstadt, Deutschland

Publ.-Id: 18452 - Permalink


How to build a positron beam
Brauer, G.;
A story of personal experience is presented which will be illustrated by several photographs taken in the course of design, construction and final use of the positron beam "SPONSOR" at Rossendorf. In particular, the important role of and very fruitful cooperation with Professor Paul Coleman will be outlined and honoured.
Keywords: design, construction, slow positron beam
  • Invited lecture (Conferences)
    The recent history of positron physics (Colemanfest), 18.08.2012, Bristol, United Kingdom

Publ.-Id: 18451 - Permalink


Uranium(VI) sorption on mineral phases studied by in situ laser fluorescence spectroscopy
Steudtner, R.; Berger, M.; Müller, K.; Brendler, V.;
The determination and verification of thermodynamic and kinetic parameters of complexation, redox and sorption processes will improve the safety assessment of nuclear waste disposal sites. Sorption processes of U(VI) on mineral surface were traditionally investigated as a function of different reaction parameters (pH, I, T, Eh, c, atm., gs) by employing batch sorption experiments and surface complexation modeling (SCM). In the last decades, the batch sorption experiments were additionally investigated by the application of different spectroscopic techniques (TRLFS, EXAFS, ATR FT-IR). Especially the in situ ATR FT-IR experiments provide an online monitoring of the absorption changes of the sorption processes by the formation of the U(VI) surface complexes. The main objective of this study is to demonstrate the possibility of laser fluorescence spectroscopy for in situ monitoring and characterization of U(VI) sorption reactions. Therefore we investigated the sorption of an aqueous solution of U(VI) onto SiO2. In analogy to the in situ ATR FT-IR measurements, three subprocesses (conditioning, sorption, flushing) are performed in in situ laser fluorescence experiments, as shown in Fig. 1. The resulting fluorescence spectra showed significantly different fluorescence characteristics between the aquoues U(VI) and the sorbed U(VI) species. These preliminary results show that the application of the in situ laser fluorescence spectroscopy is a new alternative technique for identification and characterization of U(VI) complexes at mineral-water interfaces on a molecular level. Furthermore, the time-resolution in the sub-minute range allows kinetic studies of the surface reactions.
Keywords: TRLFS, ATR FT-IR, surface complexation
  • Lecture (Conference)
    GDCh-Wissenschaftsforum Chemie 2013, 01.-04.09.2013, Darmstadt, Deutschland

Publ.-Id: 18450 - Permalink


3-D dose determination using scintillator blocks and optical tomography.
Kroll, F.; Karsch, L.; Enghardt, W.; Schürer, M.; Zuber, K.; Pawelke, J.;
Kein Abstrakt vorhanden
  • Poster
    Retreat and 7th Meeting of the Scientific Advisory Board of OncoRay, 07.-08.03.2012, Dresden, Deutschland

Publ.-Id: 18449 - Permalink


Krein space related physics (I+II)
Günther, U.;
Physical models with anti-linear symmetries can often be described by differential operators self-adjoint in suitably chosen Krein spaces.
In the first lecture, we briefly comment on the spectral properties of some specific operators self-adjoint in Krein spaces and related effects:
1) the operator of the Bender-Boettcher model of PT Quantum Mechanics and its historical background in the 2D Ising model, the Lee-Yang model, Yang-Lee edge singularities, conformal field theory and the theory of phase transitions
2) the operator of the hydrodynamic Squire equation, its scaling behavior and mapping to the operator of the Bender-Boettcher model of PT Quantum Mechanics,
3) the cusp-type spectral properties in the vicinity of third-order exceptional points (algebraic branch points),
4) the unfolding of higher-order exceptional points of the spectrum of Hamiltonians in PT-symmetric Bose-Hubbard models described with the help of Puiseux series expansions and Newton polygon techniques.
The second lecture comprises the following three main subjects:
1) the eigenvector isotropization in the vicinity of exceptional points (algebraic branch points) of the spectra of parameter dependent operators and matrices, and underlying Lie group structures of such isotropizations. For simple toy model matrix Hamiltonians we demonstrate the structural analogy to Lorentz boost transformations of chiral spinors and the naturally emerging SO(N,C) group structure of these boosts. It will be shown that normalization divergencies of the eigenvectors can be simply resolved via projective extensions and the use of different affine charts of the corresponding projective spaces. For gauged PT-symmetric systems we demonstrate the occurrence of Lie triple systems (ternary Lie algebraic structures) as well as of a hidden Clifford algebra.
2) We briefly explain the basic features of the so-called quantum brachistochrone problem for Hamiltonians self-adjoint in Hilbert spaces and in Krein spaces and demonstrate their interrelation geometrically in terms of contraction-dilation maps in projective Hilbert spaces and via positive operator-valued measures (POVMs) and Naimark dilation.
3) Finally, we briefly comment on recent experimental findings in PT-symmetric (i.e. Krein-space related) physics, especially in optical wave-guide systems and microwave cavities.
Keywords: Krein spaces, Yang-Lee edge singularity, exceptional points, algebraic branch points, Jordan blocks, non-Hermitian operators, PT quantum mechanics, Bose-Hubbard model, Bose-Einstein condensate, Puiseux series, Newton polygon technique, eigenvector isotropization, chiral spinors, Lorentz boosts, Lie group structure, Lie triple system, Clifford algebra, projective Hilbert space, affine charts, quantum brachistochrone, positive operator valued measure, POVM, Naimark dilation, optical waveguides
  • Lecture (others)
    Lectures presented at the Department of Theoretical Physics. Nuclear Physics Institute of the Academy of Sciences of the Czech Republic, 08.02.2013, Rez near Prague, Czech Republic

Publ.-Id: 18447 - Permalink


Numerical Modeling of Turbulent Melt Flow in a Continuous Casting Mold Affected by an Electromagnetic Brake
Miao, X.; Timmel, K.; Lucas, D.; Ren, Z.; Eckert, S.; Gerbeth, G.;
The current work combines numerical and experimental investigations based on a small-scale mockup using the eutectic alloy GaInSn. The jet flow discharging from the submerged entry nozzle was exposed perpendicularly to a DC magnetic field across the entire wide face of the mold. Numerical calculations were performed by using the commercial package CFX with an implemented RANS-SST turbulence model. The anisotropic properties of the MHD turbulence were taken into account by specific modifications of the turbulence model. The comparison between our numerical calculations and the experimental results shows a very well agreement. In particular, the modified RANS-SST turbulence model is capable to reconstruct the peculiar phenomenon of the excitation of non-steady, non-isotropic large-scale flow perturbations caused by the application of the DC magnetic field. Another important finding of our study is the feature that the electrical boundary conditions, namely the wall conductivity ratio, have a great impact on the mold flow subjected to an external magnetic field.
Keywords: continuous casting; electromagnetic brake; RANS-SST turbulence model; MHD turbulence
  • Open Access LogoContribution to proceedings
    7th International Conference on Electromagnetic Processing of Materials (EPM2012), 22.-26.10.2012, Peking, China
    Proceedings of the 7th International Conference on Electromagnetic Processing of Materials
  • Open Access LogoJournal of Iron and Steel Research International 19(2012)Suppl.1, 845-848

Publ.-Id: 18446 - Permalink


In vivo dose response studies for laser driven particle beams
Oppelt, M.; Baumann, M.; Bergmann, R.; Beyreuther, E.; Brüchner, K.; Kaluza, M.; Karsch, L.; Krause, M.; Laschinsky, L.; Leßmann, E.; Nicolai, M.; Reuter, M.; Sävert, A.; Schnell, M.; Schürer, M.; Pawelke, J.;
Purpose: The development of proton and ion acceleration by ultra high intensity lasers for cancer therapy promises the realization of compact and economic particle accelerators that can be integrated in already existing clinics. For translational research towards clinical application the radiobiological consequences of laser accelerated and therewith ultra-short pulsed particle beams with high pulse dose have to be investigated. After extensive in vitro dose response studies with laser driven electron and proton beams, in vivo experiments have been performed within the joint research project “onCOOPtics” as next translational step.

Material/Methods: A mouse tumor model suitable for currently available low energy laser protons was developed, tested and successfully used. The already in vitro established laser based irradiation technology was further developed for the animal model in terms of beam transport, beam monitoring, dose delivery and dosimetry allowing to apply a prescribed dose to each tumor and to determine the absolute dose received. For precise and reproducible positioning at the irradiation site a system for mouse fixation, tumor positioning and position verification was implemented as described in [Schürer et al 2012]. Experiments were carried out at the 30 Terawatt Jena Titanium:Sapphire (JeTi) laser system. Laser pulses of 28 fs duration were focused into a hydrogen gas jet accelerating electrons to energies of up to a few 10 MeV. In vivo tumor irradiation was realized for murine sarcoma KHT and human squamous cell carcinoma FaDu. Doses up to 14 Gy were applied at mean dose rates of 1-2 Gy/min and irradiation induced tumor growth delay was investigated. Comparison irradiations were performed at a conventional therapy LINAC with the same setup for irradiation and absolute dose determination.
Results: The reliability and stability of all implemented setup components and methods were proven by numerous irradiations over a period of several months. Dose response curves of tumor growth delay were generated for direct comparison of ultra short pulsed laser accelerated and conventional continuous electron beam. The ongoing data evaluation by now shows no significant difference in RBE for laser driven electrons.
Conclusion: The successful establishment of all technical requirements for and the world wide first performance of systematic animal studies with laser accelerated electrons mark an important step towards the clinical application of laser accelerated particle beams. The realization of in vivo studies with laser driven proton beams is now feasible.
The authors thank for the contribution of the Jeti accelerator crew at Friedrich-Schiller-University Jena, Ralf Bergmann (HZDR) and for the support by the German Ministry of Education and Research (BMBF) Grant Nr 03Z1N511.
  • Lecture (Conference)
    2nd ESTRO Forum, 19.-23.04.2013, Geneva, Switzerland
  • Abstract in refereed journal
    Radiotherapy and Oncology 106(2013)Suppl 2, 566

Publ.-Id: 18445 - Permalink


First order concept beamline design for particle therapy with laser accelerated protons
Masood, U.; Bussmann, M.; Enghardt, W.; Karsch, L.; Kroll, F.; Pawelke, J.;
Kein Abstrakt vorhanden
  • Lecture (Conference)
    SPIE Optics and Optoelectronics Conferences, 15.-18.04.2013, Prague, Czech Republic
  • Contribution to proceedings
    SPIE Optics and Optoelectronics Conferences, 15.-18.04.2013, Prague, Czech Republic
    Book of Abstracts (2013)

Publ.-Id: 18444 - Permalink


Konzept einer Strahlführung für Laser basierte Protonentherapien
Karsch, L.; Bussmann, M.; Enghardt, W.; Kroll, F.; Masood, U.; Pawelke, J.;
Kein Abstrakt vorhanden
  • Lecture (Conference)
    Frühjahrstagung des Fachverbandes Strahlen- und Medizinphysik der Deutschen Physikalischen Gesellschaft, 10.-15.03.2013, Regensburg, Deutschland
  • Contribution to proceedings
    Frühjahrstagung des Fachverbandes Strahlen- und Medizinphysik der Deutschen Physikalischen Gesellschaft, 10.-15.03.2013, Regensburg, Deutschland
    Verhandl. DPG 48(VI)(2013)

Publ.-Id: 18443 - Permalink


In vivo dose response studies at laser driven particle beams.
Oppelt, M.; Baumann, M.; Bergmann, R.; Beyreuther, E.; Brüchner, K.; Hartmann, J.; Kaluza, M.; Karsch, L.; Krause, M.; Laschinsky, L.; Leßmann, E.; Nicolai, M.; Reuter, M.; Sävert, A.; Schnell, M.; Schürer, M.; Pawelke, J.;
Kein Abstrakt vorhanden
  • Lecture (Conference)
    22. Symposium Experimentelle Strahlentherapie und Klinische Strahlenbiologie, 21.-23.02.2013, Dresden, Deutschland
  • Contribution to proceedings
    22. Symposium Experimentelle Strahlentherapie und Klinische Strahlenbiologie, 21.-23.02.2013, Dresden, Deutschland
    Experimentelle Strahlentherapie und Klinische Strahlenbiologie 22(2013)

Publ.-Id: 18442 - Permalink


Laser driven accelerators for proton therapy: Physical, technological and radiobiological aspects.
Pawelke, J.;
Kein Abstrakt vorhanden
  • Invited lecture (Conferences)
    28th Conference on Clinical and Experimental Research in Radiation Oncology (CERRO 28), 19.-26.01.2013, Les Menuires, France

Publ.-Id: 18441 - Permalink


Physics of ionising radiation (regardinng radiation oncology aspects).
Pawelke, J.;
Kein Abstrakt vorhanden
  • Lecture (others)
    OncoRay Radiobiology Seminar, 13.12.2012, Dresden, Deutschland

Publ.-Id: 18440 - Permalink


Ein szintillatorbasierter Detektorprototyp zur schnellen Bestimmung dreidimensionaler Dosisverteilungen.
Kroll, F.; Karsch, L.; Pawelke, J.;
Kein Abstrakt vorhanden
  • Poster
    43. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP), 26.-29.09.2012, Jena, Deutschland
  • Contribution to proceedings
    43. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP), 26.-29.09.2012, Jena, Deutschland
    Abstractband der 43. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (2012) 551

Publ.-Id: 18439 - Permalink


Neutron induced reactions at nELBE
Beyer, R.;
The principles and data needs of nuclear transmutation are explained. The nELBE neutron time-of-flight facility and the different types of experiments with fast neutrons are presented.
Keywords: nuclear transmutation, nELBE, fast neutrons, time-of-flight, inelastic scattering, transmission
  • Lecture (Conference)
    4th TRAKULA graduate seminar - “Radiochemistry of the Actinides”, 21.-23.05.2012, Mainz, Deutschland

Publ.-Id: 18438 - Permalink


First approximation concept design of a gantry beamline for proton therapy with laser accelerated protons
Masood, U.; Bussmann, M.; Enghardt, W.; Karsch, L.; Pawelke, J.;
  • Lecture (Conference)
    43. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP), 26.-29.09.2012, Jena, Germany
  • Contribution to proceedings
    43. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP), 26.-30.09.2012, Jena, Germany
    Abstraktband der 43. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik

Publ.-Id: 18437 - Permalink


Laserbeschleunigte Ionen für die Strahlentherapie.
Pawelke, J.;
Kein Abstrakt vorhanden
  • Invited lecture (Conferences)
    43. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP), 26.-29.09.2012, Jena, Deutschland
  • Contribution to proceedings
    43. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP), 26.-29.09.2012, Jena, Deutschland
    Abstractband der 43. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (2012) 277

Publ.-Id: 18436 - Permalink


Biological effectiveness of laser driven particle beams: In vivo dose response studies.
Oppelt, M.; Brüchner, K.; Baumann, M.; Bergmann, R.; Beyreuther, E.; Kaluza, M.; Karsch, L.; Krause, M.; Laschinsky, L.; Leßmann, E.; Nicolai, M.; Reuter, M.; Säbert, A.; Schnell, M.; Schürer, M.; Pawelke, J.;
The development of proton and ion acceleration by ultra-high intensity lasers for cancer therapy promises the realization of compact and economic particle accelerators that can be integrated in already existing clinics. However, particle acceleration with high intensity lasers, in comparison to the conventional used acceleration technique, leads to ultra-short beam pulses, generated with low pulse frequency, that apply a very high pulse dose. Prior to a clinical application the radiobiological consequences of laser accelerated and therewith ultra-short pulsed particle beams have to be investigated.
After extensive in vitro dose response studies, for several cell lines and endpoints with laser driven electron and proton beams, the translational step to perform in vivo experiments has been taken. A tumor model suitable for currently available low energy laser protons was developed, tested and successfully used. The already in vitro established laser based irradiation technology was further developed for the animal model in terms of beam transport, beam monitoring, dose delivery and dosimetry, allowing to apply a prescribed dose to each tumor and to determine the absolute dose received. The utilized high power laser system delivered a stable and reproducible particle beam over a period of months to allow systematic in vivo dose response studies of a human xenograft line. 300 mice hosting two different tumor lines were irradiated with various defined doses and monitored for several weeks to determine tumor growth delay.
In parallel irradiation by a continuous beam of a conventional accelerator has been performed. Results of the still ongoing data evaluation will be presented and discussed.

Experiments were carried out within the onCOOPtics project in cooperation between Oncoray Dresden and Ultraoptics Jena. The work was supported by the German Ministry of Education and Research (BMBF), grant no. 03ZIK445
  • Poster
    15. Jahrestagung der Gesellschaft für Biologische Strahlenforschung (GBS), 17.-20.09.2012, München, Deutschland

Publ.-Id: 18435 - Permalink


Laser in der Strahlentherapie der Zukunft
Pawelke, J.;
Kein Abstrakt vorhanden
  • Invited lecture (Conferences)
    Tag des offenen Labors, Helmholtz-Zentrum Dresden-Rossendorf, 12.05.2012, Dresden, Deutschland

Publ.-Id: 18434 - Permalink


Ein neues Detektorsystem zur schnellen Bestimmung von 3D-Dosisverteilungen
Karsch, L.; Kroll, F.; Pawelke, J.;
Kein Abstrakt vorhanden
  • Lecture (Conference)
    76th Annual Conference of the DPG and DPG Spring Meeting 2012, Radiation and Medical Physics Division, 25.-30.03.2012, Berlin, Deutschland
  • Contribution to proceedings
    76th Annual Conference of the DPG and DPG Spring Meeting 2012, Radiation and Medical Physics Division, 25.-30.03.2012, Berlin, Deutschland
    Verhandl. DPG 47(VI, No. 4), 406

Publ.-Id: 18433 - Permalink


P1011 - Verwendung eines Biokompositmaterials zur Entfernung von Arsenverunreinigungen aus Wasser und Verfahren
Raff, J.; Pollmann, K.; Günther, T.; Marquard, A.; Katzschner, B.; Matys, S.; Pompe, W.;
Die vorliegende Erfindung betrifft die Verwendung ne und Nanopartikel umfasst, sowie ein Verfahren zur Entfernung von Arsenverunreinigungen aus Wasser. Die erfindungsgemäße Verwendung bzw. das erfindungsgemäße Verfahren eignen sich zur Verwendung in der Grund-, Trink-, Brauch- und Abwasseraufbereitung. In Versuchen der Erfinder konnten Abtrennleistungen von bis zu 5,3 mg Arsen/g Biokompositmateria erzielt werden. Dies entspricht nahezu der doppelten Menge im Vergleich zum kommerziellen Arsen-Adsorbens Ferrosorp®, einem Eisenhydroxidgranulat. Damit übersteigt die Bindungsfähigkeit des erfindungsgemäß verwendeten Biokompositmaterial für Arsen (V) deutlich die Summe der Bindungswerte der Einzelkomponenten (S-Layer und Nanopartikel).
  • Patent
    DE102011006753B3 - Offenlegung - 24.05.2012
  • Patent
    WO002012175080A2 - Offenlegung - 27.12.2012
  • Patent
    DE102011006753B3 - Erteilung - 25.04.2013
  • Patent
    WO2012175080A2 - tot - 27.09.2013

Publ.-Id: 18432 - Permalink


Progress Report March 2011 - Feb. 2012: Laser-Radiooncology (onCOOPtics).
Pawelke, J.;
Kein Abstrakt vorhanden
  • Invited lecture (Conferences)
    Retreat and 7th Meeting of the Scientific Advisory Board of OncoRay, 07.-08.03.2012, Dresden, Deutschland

Publ.-Id: 18431 - Permalink


P1014 - Neue Halogenalkoxychinazoline, deren Herstellung und Verwendung
Nieber, K.; Erdmann, S.; Briel, D.; Schwan, G.; Barbar, A. G.; Sträter, N.; Zahn, M.; Funke, U.; Scheunemann, M.; Fischer, S.; Brust, P.;
Die Erfindung betrifft neue Chinazolinderivate, die als Diagnostika sowie Therapeutika geeignet sind und insbesondere zur Diagnose und Behandlung neurodegenerativer und psychiatrischer Erkrankungen, z. B. Schizophrenie verwenden werden können. Die neuen Chinazolinderivate zeichnen sich durch eine hohe Affinität und Selektivität für PDE10A aus und dadurch dass sie mindestens einen Halogensubstituierten Substituenten am Chinazolinrest aufweisen.
  • Patent
    DE102010042833A1 - Offenlegung - 26.04.2012; Nachanmeldung WO
  • Patent
    WO002012052556A1 - 26.04.2012

Publ.-Id: 18430 - Permalink


Hochintensitätslaser für die Radioonkologie
Pawelke, J.;
Kein Abstrakt vorhanden
  • Lecture (others)
    Fachgespräch Protonentherapie, 25.11.2010, Dresden, Deutschland

Publ.-Id: 18429 - Permalink


High power ultra-short laser pulses interacting with solid density plasmas – probing ultra-fast, micron-scale plasma dynamics with XFEL
Huang, L.; Kluge, T.; Schlenvoigt, H. P.; Gutt, C.; Lei, A.; Yu, W.; Bussmann, M.; Cowan, T. E.;
Plasma heating and ionization are important processes during the interaction of high power ultra-short laser pulses with solid density targets. In order to understand the relevant physics, particle-in-cell simulations including collisions and ionization were run to study ion heating dynamics in buried layer targets illuminated by high-intensity, ultra-short laser pulses. Our results show that bulk ions can be heated to above 1keV temperature. When studying the ionization dynamics strong filaments have been observed which depend on preplasma on the target front side, laser pulse duration and intensity. In order to study the evolution of ionization and ion bulk heating in experiment, ultra-bright X-ray free electron lasers - such as the European XFEL - are a very promising and strong tool to resolve the spatial and temporal scales of these processes inside the solid target.
Keywords: Laer plasma physcis,ion heating,ionization,XFEL
  • Poster
    International Conference on High Energy Density Physics, 18.-21.10.2012, Beijing, China

Publ.-Id: 18428 - Permalink


Dosimetrie laserbeschleunigter Teilchenstrahlen: Strahlenbiologische in vitro Experimente.
Pawelke, J.;
Kein Abstrakt vorhanden.
  • Invited lecture (Conferences)
    Workshop „Detektorentwicklung für laserbeschleunigte Teilchen“, FZD, 19.11.2010, Dresden, Deutschland

Publ.-Id: 18427 - Permalink


Laserbasierte Technologien zur Strahlenapplikation
Pawelke, J.;
Kein Abstrakt vorhanden.
  • Invited lecture (Conferences)
    15. Dresdner Weiterbildungsveranstaltung „Klinische Strahlenbiologie für Ärzte in der Weiterbildung zum Radioonkologen“, 10.-13.11.2010, Dresden, Germany

Publ.-Id: 18426 - Permalink


P1018 - Pharmakologische Wirkstoffe und Radiodiagnotika mit 18F-markierter 3-Aryl- oder 3-Heteroaryl-1,2,4-oxadiazoleinheit und Verfahren zu deren Herstellung
Rühl, T.; Deuther-Conrad, W.; Brust, P.; Fischer, S. H.; Steinbach, J.;
Die Erfindung betrifft neue 3-Aryl- oder 3-Heteroaryl-1,2,4-Oxadiazole, die insbesondere Cannabinoid-Rezeptor-Liganden sind und als diagnostische und therapeutische Mittel eingesetzt werden können, insbesondere bei neurologischen, neurodegenerativen und psychiatrischern Erkrankungen, sowie ein Verfahren zu deren Herstellung. Die Liganden eignen sich insbesondere als Radiodiagnostika zum Nachweis von Cannabinoid-Rezeptor mittels Positronen-Emissions-Tomographie (PET). Bevorzugte erfindungsgemäße 3-Aryl- oder 3-Heteroaryl-1,2,4-Oxadiazole zeichnen sich durch eine hohe Affinität und Selektivität für den humanen CB2-Rezeptor aus. Das erfindungsgemäße Verfahren zeichnet sich durch eine bisher im Stand der Technik nicht beschriebene nucleophile aromatische Substitution eines Aromaten oder Heteroaromaten in 3-Position eines 1,2,4-Oxadiazolringes aus.
  • Patent
    Anmeldung DE102010063974A1 - 28.06.2012

Publ.-Id: 18425 - Permalink


Extremely Large Scale Simulation of Surface Growth and Lattice Gases
Ódor, G.; Schulz, H.; Kelling, J.; Heinig, K.-H.; Máté Ferenc, N.;
Learn how to do efficient simulations of interface growth and Kinetic Monte Carlo on GPUs. Due to a mapping of the surface dynamics onto a binary lattices gas bit-coding permits to achieve simulations of unprecedentedly large sizes (2^17 x 2^17) and large speedups (~430 with respect to a single CPU). Explore new techniques in different implementations on GPUs using CUDA and OpenCL. Dive deep into the run-time and scaling analysis on different architectures to find optimal solutions for solving current simulation problems in the field of statistical physics and materials science.
Keywords: Computational Physics; Manufacturing Technical
  • Lecture (Conference)
    GPU Technology Conference, 18.-21.03.2013, San Jose, USA

Publ.-Id: 18424 - Permalink


Influence of magnetic fields on the behavior of bubbles in liquid metals
Fröhlich, J.; Schwarz, S.; Heitkam, S.; Santarelli, C.; Zhang, C.; Vogt, T.; Boden, S.; Andruszkiewicz, A.; Eckert, K.; Odenbach, S.; Eckert, S.;
The paper reviews numerical and experimental investigations concerned with the physics of rising bubbles in conducting liquid metals under the action of a magnetic field. Different situations, characterized by different void fractions ranging from single bubbles to bubble swarms, are considered. The impact of the geometrical arrangement is addressed covering large containers with bubbles far from the walls and narrow containers with bubbles interacting with the walls. It is demonstrated that magnetic fields offer a convenient means to influence bubble dynamics, which makes them interesting for technological applications.
Keywords: liquid metal, two-phase flows, bubbly flows, bubble detection, bubble agglomeration
  • European Physical Journal - Special Topics 220(2013), 167-184

Publ.-Id: 18423 - Permalink


Electromagnetic melt flow control during solidification of metallic alloys
Eckert, S.; Nikrityuk, P. A.; Willers, B.; Räbiger, D.; Shevchenko, N.; Neumann-Heyme, H.; Travnikov, V.; Odenbach, S.; Voigt, A.; Eckert, K.;
In this minireview, we summarize experimental and numerical studies particularly concerned with applications of rotating magnetic fields (RMF) or travelling magnetic fields (TMF) to directional solidification of metal alloys. After introducing some fundamentals of electromagnetic stirring, we review the insights gained into flow-induced modifications of microstructure and the formation of freckles and macrosegregations. We further discuss recent strategies, using time-modulated RMF and TMF, which aim to overcome the deficiencies of conventional stirring, in particular flow-induced macrosegregation, by effectively controlling the flow field. On the microscale, we show that time-varying flows are able to alter the sidebranch characteristics vital to the potential of fragmentation.
Keywords: solidification, electromagnetic stirring, rotating magnetic field, traveling magnetic field, grain refinement, macrosegregation

Publ.-Id: 18422 - Permalink


(T)ELBE: ARD Testanlage für Diagnose an quasi - cw Elektronenstrahlen.
Gensch, M.;
Die Kooperation zwischen DESY und HZDR sieht den Austausch von Personal, technischen Lösungen und wissenschaftlichen Geräten vor sowie gemeinsame Experimente und Messzeiten an den Freie-Elektronen-Lasern FLASH und FELBE. Im Rahmen der Kooperation sollen Methoden zur Elektronenstrahl-Diagnostik an supraleitenden Beschleunigern noch weiter optimiert werden, so dass die Lichtquellen in beiden Zentren mit noch besseren Eigenschaften betrieben werden können.
Die Entwicklungen fließen in Dresden beispielsweise in den Aufbau eines neuen Terahertz-Labors namens TELBE mit einer Kombination aus einer schmalbandigen und einer breitbandigen Terahertz-Quelle ein, die dieses Jahr in Betrieb gehen soll. Die Entwicklungen sind aber auch enorm wichtig, um die Voraussetzungen zur Erzeugung brillanten Röntgenlichts zu schaffen. Dazu wird künftig der Dresdner Hochleistungslaser DRACO mit dem Elektronenstrahl aus dem Teilchenbeschleuniger ELBE gekoppelt.
  • Invited lecture (Conferences)
    MDI techn. Forum / DESY, 15.02.2013, Hamburg, Deutschland

Publ.-Id: 18421 - Permalink


Application of X-ray radioscopic methods for characterization of two-phase phenomena and solidification processes in metallic melts
Shevchenko, N.; Boden, S.; Eckert, S.; Borin, D.; Heinze, M.; Odenbach, S.;
X-ray attenuation techniques are an important diagnostic tool for investigating liquid metal two-phase flows or solidification studies in metallic alloys. X-ray visualization enables a general, intuitive understanding of flow phenomena or pattern formation in opaque liquid metal systems. Real-time and in-situ observations of the density distribution within thin solidifying samples achieve a spatial resolution of a few microns and contribute significantly to an improved understanding of dendritic growth processes. Moreover, X-ray radioscopy is a useful tool for a non-invasive, in-situ visualization and characterization of gas bubbles in nontransparent melts or for observations of the formation of metal foams. In this paper we consider three different fields of application which are under intensive investigation at HZDR and TUD: the bottom-up solidication of Ga-In alloys under the influence of buoyancy-driven and electromagnetically driven convection, the injection of Ar gas into liquid GaInSn, the study of Al foams with respect to foam formation and the characterization of their internal structure.
Keywords: X-ray radioscopy, liquid metal, melt flow, solidification, metal foams, two-phase flows

Publ.-Id: 18420 - Permalink


P0016 - Verfahren und Vorrichtung zur Aktivierung der Radioaktivität von Atomkernen, insbesondere zur Aktivierung kurzlebiger radioaktiver Isotope für medizinische Zwecke
Sauerbrey, R.; Schwoerer, H.;
Aufgabe war es, auf möglichst einfache und aufwandgeringe Weise radioaktive Strahlung mit kurzer Halbwertszeit zu erzeugen. Insbesondere sollen für Nutzer, die lediglich kurzlebige Isotope für eigene Anwendungen benötigen, aufwendige Vorrichtungen, wie Reaktoren und Teilchenbeschleuniger, bzw. auch besondere Vorkehrungen zur Aufbewahrung, Entsorgung und/oder für den Transport von radioaktiv strahlenden Materialien vermieden werden. Erfindungsgemäß wird die Radioaktivität der Atomkerne durch Neutronen aktiviert, die durch eine photoinitiierte Kernspaltung eines Neutronendonators gewonnen, und im Fangbereich der Isotope sanft moderiert werden, wobei die zur Kernspaltung eingesetzten Röntgenstrahlen aus einem lasererzeugten Plasma emittiert werden. Anwendungsmöglichkeiten ergeben sich beispielsweise für die radiologische Diagnostik und Therapie: Tumorlokalisation (Schilddrüse, Nieren, Skelett, Gehirn, Blut, Leber, Spinalkanal, Herz u. a.), Tumorbestrahlung (Schilddrüse, Prostata, Ovarien, Leukämie u. a.), sowie lokale Bestrahlung von Arterien nach Öffnung von Stenosen zur Verhinderung von Restenosen.
  • Patent
    DE10037439B4

Publ.-Id: 18419 - Permalink


P0604 - Verfahren und Anordnung zur kontaktlosen Messung des Durchflusses elektrisch leitfähiger Medien
Priede, J.; Buchenau, D.; Gerbeth, G.; Eckert, S.;
Die Aufgabe der vorliegenden Erfindung besteht darin, eine Durchflussmessung zu ermöglichen, die ohne mechanischen oder elektrischen Kontakt zum fließenden Medium auskommt, keine Vielzahl von Magnetfeldmessstellen erfordert, eine Durchflussmessung hoher zeitlicher Auflösung liefert, gegenüber äußeren Einflüssen möglichst unempfindlich ist und nicht die lageempfindlichen Amplituden in Empfängerspulen bei Wechselstromerregung benutzt. Die Erfindung geht aus von einem magnetischen Wechselfeld außerhalb des elektrisch leitfähigen Mediums und beinhaltet, dass der Einfluss des strömenden Mediums auf das angelegte Magnetfeld zu einer Phasenverschiebung in den Magnetfeldsignalen an zwei verschiedenen Messorten führt, die als direktes Maß für die mittlere Durchflussgeschwindigkeit des Mediums verwendet wird. Die Phasenverschiebung kann auch mittels zweier Empfängerspulen entlang des Strömungskanals gemessen werden.
  • Patent
    EP 1847813B1 - 21.03.2012
  • Patent
    EP 1847813A2 - 24.10.2007
  • Patent
    DE102006018623A1 - 25.10.2007
  • Patent
    DE102006018623B4 - 15.05.2008

Publ.-Id: 18418 - Permalink


P1012 - Supraleitende Strukturen auf Schaltungen oder Schaltungselementen, Herstellung dieser Strukturen und deren Verwendung
Skrotzki, R.; Heera, V.; Hermannsdörfer, T.; Fiedler, J.; Schmidt, B.; Helm, M.;
Die Erfindung beschreibt die Herstellung integrierter supraleitender Strukturen in Schaltungen und Schaltungselementen auf der Basis von Silizium- bzw. Germanium-Wafern durch Implementieren von Ausscheidungen, neuen chemischen Verbindungen oder einer Dotierung via Ionenimplantation und anschließender Kurzzeitausheilung. Vorteil dieser Strukturen ist die kostengünstige Produktion, und der höheren Leistungsdichte dieser Schaltungen bezüglich Transistorschaltungen. Diese Strukturen ermöglichen die Steuerung quantenmechanischer Interferenzerscheinungen mit Hilfe eines äußeren Magnetfeldes oder auf dem Chip erzeugten Magnetfeldes. Eine weitere Einsatzmöglichkeit bieten Logikschaltungen für das Quantum Computing.
  • Patent
    WO 2012037936A1 - 29.03.2012
  • Patent
    DE102010039911A1 - Offenlegung - 01.03.2012, Zurückweisung - 22.01.2013; Nachanmeldung WO

Publ.-Id: 18416 - Permalink


Gas bubble detection in liquid metals by means of the ultrasound transit-time-technique
Andruszkiewicz, A.; Eckert, K.; Eckert, S.; Odenbach, S.;
In this work the ultrasound-transit time technique is introduced as a versatile method to analyze the bubble dynamics in liquid metal-gas flows. After discussing the principle of operation and the implementation of the technique, the methods used to extract the positions of the bubbles, their velocities, or their diameters are explained. Finally, the performance of the method is demonstrated for a liquid metal-gas flow with and without a magnetic field.
Keywords: liquid metal, two-phase flow, bubbly flow, bubble detection, ultrasound transit-time technique

Publ.-Id: 18415 - Permalink


P1019 - Verfahren zur hochgenauen Messung der Strahlungsschwächung von veränderlichen Materialverteilungen mit Photonen- oder Teilchenstrahlung
Hampel, U.;
Verfahren zur hochgenauen Messung der Strahlungsschwächung von veränderlichen Materialverteilungen mit Photonen- oder Teilchenstrahlung, verwendend eine Anordnung umfassend eine kollimierte Strahlungsquelle 1, mindestens einen Detektor 2 und einer dem Detektor 2 nachgeordneten Datenerfassungs- und Verarbeitungseinheit 3, dadurch gekennzeichnet, dass a) die Photonen- oder Teilchenstrahlung ausgehend von der Strahlungsquelle 1 das zu untersuchende Material 4 durchdringt und anschließend auf den Detektor 2 fällt, wobei der Detektor 2 die eintreffenden Photonen bzw. Teilchen zählt; b) die Datenerfassungs- und -verarbeitungseinheit 3 aufeinander folgend eine Anzahl von Zählwerten K des Detektors 2 für hinreichend kurze Zeitintervalle &Dgr;Tkurz erfasst, in denen die Materialverteilung in ausreichender Näherung als unveränderlich angesehen werden kann; c) die Datenerfassungs- und -verarbeitungseinheit 3 die aufeinander folgend aufgenommenen Zählwerte als Häufigkeitsverteilung in einem Datenfeld F abspeichert; d) die Datenerfassungs- und -verarbeitungseinheit 3 durch nacheinander folgende Berechnung des algebraischen Gleichungssystems Q = P+ F und den mittleren Schwächungswert A...
  • Patent
    DE 102010061440A1 - 21.06.2012

Publ.-Id: 18414 - Permalink


Flow measurements in liquid metals by means of the ultrasonic Doppler method and local potential probes
Cramer, A.; Eckert, S.; Gerbeth, G.;
Substantial research activities have been carried out at HZDR during the last 15 years on the development and qualification of various methods to measure the velocity field in liquid metal flows. In this paper we report on two complementary methods for measuring the local velocity. The potential difference probe is a local sensor which is immersed into the liquid. Such sensors are very effective for investigations of the turbulent fluctuations at a local point. However, the installation of the probe in the bulk of the liquid might disturb the flow to be measured. Ultrasonic techniques are non-invasive, but need a continuous path from the ultrasonic transducer to the liquid under investigation. The ultrasound Doppler method delivers instantaneous profiles of the local velocity. Experimental applications of these measuring techniques in diverse liquid metal flows under the influence of magnetic fields will be presented here showing the capabilities and limitations of both methods.
Keywords: liquid metal, flow measurements, ultrasound Doppler velocimetry, potential difference probe

Publ.-Id: 18413 - Permalink


Experimental demonstration of gas entrainment into liquid metals
Eckert, S.; Vogt, T.; Boden, S.; Shevchenko, N.; Gerbeth, G.;
Entrainment of cover gas into the liquid metal coolant is one of the essential safety issues in the design of innovative liquid metal-cooled fast reactors. We present experimental studies of this phenomenon in low-melting metals. Ultrasonic and X-ray were considered as diagnostic tools for a visualization of gas entrainment at the free surface of the melt. Laboratory experiments were conducted using the eutectic alloy GaInSn which is liquid at room temperature. The vortex activated entrainment of air at the free surface of a rotating flow was disclosed by means of ultrasonic techniques. The X-ray radioscopy was used to visualize the behaviour of Argon bubbles inside a slit geometry. The measurements reveal distinct differences between water and GaInSn especially with respect to the process of bubble formation, the coalescence and the breakup of bubbles. Our results emphasize the importance of liquid metal experiments which are able to provide a suitable data base for numerical code validation.
Keywords: liquid metal fast reactor, gas entrainment, two-phase flow, ultrasound Doppler method, X-ray radioscopy
  • Lecture (Conference)
    International Conference on Fast Reactors and Related Fuel Cycles: Safe Technologies and Sustainable Scenarios (FR13), 04.-07.03.2013, Paris, France
  • Contribution to proceedings
    International Conference on Fast Reactors and Related Fuel Cycles: Safe Technologies and Sustainable Scenarios (FR13), 04.-07.03.2013, Paris, France
    IAEA-CN-199/289

Publ.-Id: 18412 - Permalink


P1108 - Integriertes nichtflüchtiges Speicherbauelement, Herstellung und Verwendung
Schmidt, H.; Shuai, Y.; Skorupa, I.; Zhou, S.;
Die Erfindung beschreibt die Herstellung, den Aufbau eines integrierten Speicherbauelementes, umfassend mindestens einen gleichrichtenden Bottom-Kontakt oder einen Top-Kontakt und eine ferrroelektrische Schicht als leitfähigen Kanal zwischen den Kontakten. Weiterhin wird die Verwendung des integrierten Speicherbauelementes in einem integrierten Feldeffekttransistor beschrieben.
  • Patent
    DE 102011051767A1 - Offenlegung - 17.01.2013; Nachanmeldung WO, US

Publ.-Id: 18411 - Permalink


P1015 - Anordnung und Verfahren zur Erfassung des räumlichen Geschwindigkeitsprofils
Hampel, U.; Reinecke, S.;
Die Erfindung beschreibt eine Anordnung zur Bestimmung des dreidimensionalen räumlichen Geschwindigkeitsprofils rheologischer Medien, wobei die Anordnung in einem Prozessbehälter untergebracht ist und aus im Prozessbehälter drehbar und beweglich angeordneten Messlanzen mit mindestens einer Detektoreinheit besteht. In das Prozessmedium eingebrachte Tracer werden von den Detektoren erfasst und die gemessenen Signale zur Bestimmung des räumlichen Geschwindigkeitsprofiles herangezogen. Die für die Geschwindigkeitsprofilmessung benutzten Tracer können im Anschluss für die Bestimmung des Verweilzeitspektrums des Prozessgemischs im Prozessbehälter verwendet werden.
  • Patent
    DE 102010060131A1 - 26.04.2012

Publ.-Id: 18410 - Permalink


P1101 - Sensoranordnung und Verfahren zur berührungslosen Bestimmung des wirksamen Drehmomentes in einer Welle
Buchenau, D.; Schmidt, G.; Wustmann, B.;
Die Erfindung betrifft ein auf der Grundlage des magnetoelastischen Effektes basierendes, berührungsloses Messprinzip zur Bestimmung des Drehmomentes, welches auf ein magnetisierbares, rotationssymmetrisches Bauteil wirkt. Der Vorteil der erfindungsgemäßen Anordnung und des erfindungsgemäßen Messverfahrens ist die Überwindung der bisher ungelösten Problematik von materialspezifischen, eigenspannungsbedingten Hystereseeffekten, sowie der Begrenzung von Drift- und Störeinflüssen im dynamischen Betrieb. Lösung Die erfindungsgemäße Anordnung besteht aus einer Senderspule die mit symmetrisch oder asymmetrisch zur Senderspule angeordneten Empfängerspulen zusammenwirkt, wobei die Spulenlängsachsen der verwendeten Sender- und Empfängerspulen senkrecht zur Wellenlängsachse angeordnet sind. Erfindungsgemäß stehen sich Senderspule und Empfängerspulen bezogen auf das Messobjekt (Welle) diametral gegenüber, wobei speziell eine der Empfängerspulen auf der gleichen Längsachse zur Senderspule diametral gegenübersteht. Die verbleibenden beiden weiteren (äußeren) Empfängerspulen sind in der symmetrischen Anordnung in äquidistanten Abständen zur mittleren Empfängerspule angeordnet.
  • Patent
    EP2549255A2 - Offenlegung - 23.01.2013

Publ.-Id: 18409 - Permalink


P1009 - Magnetisierbare Einzel- und Mehrschichtstrukturen, deren Herstellung und Verwendung
Schmidt, H.; Mok, K. M.; Scarlat, C.; Weber, I.;
Die Erfindung beschreibt die Auslegung einer Anordnung eines magnetooptischen Systems, bei dem für eine vorgegebene Wellenlänge der einfallenden elektromagnetischen Welle eine bestimmte Polarisation der reflektierten oder transmittierten Welle erreicht wird. Die erfindungsgemäße Anordnung und das Verwendungsverfahren ermöglicht den Einsatz zur Optimierung der Auslegung eines magnetooptischen Systems um die „Ziel“-Polarisation der reflektierten oder transmittierten Welle zu erreichen oder eines magnetooptischen Speichers oder eines Magnetfeldsensors. Weiterhin werden mit der Erfindung der Aufbau eines magnetooptischen Modulators oder eines Multiplexers mit magnetooptischen Komponente ermöglicht.
  • Patent
    Anmeldung: DE102011052217A1 31.01.2013
  • Patent
    Anmeldung WO2013013674A1 - 31.01.2013

Publ.-Id: 18408 - Permalink


Setting-up a Super-SIMS at DREAMS
Rugel, G.; Akhmadaliev, S.; Merchel, S.; Pavetich, S.; Renno, A.; Ziegenrücker, R.;
At the Helmholtz-Zentrum Dresden-Rossendorf a new AMS (accelerator mass spectrometry) facility, DREsden AMS (DREAMS), with a 6-MV tandem accelerator has been successfully installed [1]. The range of applications will be broaden by setting up a Super-SIMS (SIMS = Secondary ion mass spectrometry) as an ultrasensitive analytical method for the determination of stable elements and isotopes. A commercial SIMS (from CAMECA) is connected to the accelerator and the high-energy setup of DREAMS, which will be additionally equipped with a time-of-flight detector system. The spatial resolution (x,y: ∼ 3μm; z: ∼ 5nm) of the SIMS will be kept as the SIMS is utilized as the negative ion source for the accelerator-based mass spectrometry. By the complete destruction of molecules detection limits some orders of magnitude better than for traditional dynamic SIMS are expected, i.e. ∼10-9-10-12, see e.g. [2]. The focus of applications will be geological samples in the framework of resource technology research.
Ref.: [1] S.\ Akhmadaliev et al., NIMB 294 (2013) 5. [2] C. Maden, Dissertation. ETH Zürich 2003.
Keywords: AMS, SIMS, sensitive analytical method
  • Poster
    DPG-Frühjahrstagung der Sektion AMOP (SAMOP), 18.-22.03.2013, Hannover, Deutschland

Publ.-Id: 18407 - Permalink


Amorphous Li-Al-based compounds: Novel approach for designing high performance electrode materials for Li-ion batteries
Thoss, F.; Thomas, J.; Oswald, S.; Potzger, K.; Reuther, H.; Ehrenberg, H.; Eckert, J.; Giebeler, L.;
A new amorphous compound with the atomic composition Al43Li43Y6Ni8 applied as electrode material for Li-ion batteries is investigated. Unlike other amorphous compounds so-far investigated as anode materials it already contains Li as a base element in the uncycled state. The amorphous compound powder is prepared by high energy ball milling of a master alloy. It shows a strongly enhanced specific capacity in contrast to amorphous alloys without Li in the initial state and furthermore to conventional graphite anodes. According to the charge rate (C-rate) the specific capacity is reversible over 20 cycles at minimum in contrast to conventional crystalline intermetallic phases failing by volume changes. The delithiation process occurs quasi-continuously over a voltage range of nearly 4 V, while the lithiation is mainly observed between 0.1 V and 1.5 V. That way, the electrode is applicable for different potential needs. We suggest the application as anode. The electrode stays amorphous during cycling, thus avoiding volume changes. The cycling performance is further enhanced by a significant amount of Fe introduced as wear debris from the milling tools, which acts as a promoting element.
Keywords: high energy ball milling; pre-lithiation; anode; intermetallic phase

Publ.-Id: 18406 - Permalink


P1114 - Extraktion von Edelmetall(ionen) mittels ionischer Flüssigkeiten
Straßner, T.; Schulz, T.; Bernhard, G.; Raff, J.; Lehmann, F.;
Die vorliegende Erfindung betrifft ein Verfahren zur Extraktion von Metallen aus einer wässrigen Phase mit Hilfe spezifischer ionischer Flüssigkeiten.
  • Patent
    DE102011080230 - Offenlegung 07.02.2013, Nachanmeldungen: WO, EP, US

Publ.-Id: 18405 - Permalink


P1117 - Präkursorverbindungen für die Radiosynthese von [18F]Norchlor-fluor-homoepibatidin
Brust, P.; Deuther-Conrad, W.; Fischer, S.; Hiller, A.; Hoepping, A.; Patt, J. T.; Patt, M.; Sabri, O.; Smits, R.; Steinbach, J.;
Die Erfindung betrifft eine Verbindung der Formel Ia oder Ibworin R1-CO2R3, -COR4 oder -R5 darstellt, worin R3 unsubstituiertes oder substituiertes C1-C6-Alkyl darstellt, R4 Wasserstoff, unsubstituiertes oder substituiertes C1-C6-Alkyl darstellt und R5 Wasserstoff, unsubstituiertes oder substituiertes C1-C6-Alkyl darstellt, R2-N+(R6)(R7)(R8)X– oder eine Nitrogruppe darstellt, worin R6, R7, R8 unabhängig von einander unsubstituiertes oder substituiertes C1-C6-Alkyl oder unsubstituiertes oder substituiertes -(CH)n- mit n = 1 bis 12 darstellen mit der Maßgabe, dass zumindest zwei der Substituenten R6, R7 und R8 C1-C6-Alkyl sind, und X– ein Halogenid, Sulfonat, unsubstituiertes oder substituiertes Acetat, Sulfat, Hydrogensulfat, Nitrat, Perchlorat oder Oxalat darstellt.
  • Patent
    DE102011052348 - Erteilung 07.02.2013, Nachanmeldung: WO, AU, BR, CA, CN, EP, JP, KR, US

Publ.-Id: 18404 - Permalink


Feasibility study of in vivo MRI based dosimetric verification of proton end-of-range for liver cancer patients
Yuan, Y.; Andronesi, O. C.; Bortfeld, T. R.; Richter, C.; Wolf, R.; Guimaraes, A. R.; Hong, T. S.; Seco, J.;
Purpose: To investigate the feasibility of using MRI to verify proton beam distal range for liver tumor treatment in a retrospective study.
Methods and Materials: Because the follow-up hepatocyte-specific functional MR imaging can detect the radiobiological change of liver tissue after radiation, we firstly registered the contrast-enhanced MR images to the planning CT images from 5 liver patients, then overlaid the prescribed dose distribution on the MR images. Since dose calculation is most accurate at the penumbra dose region, we correlated the MR signal intensity (SI) to the radiation dose at the superior/inferior penumbra region. This dose-SI correlation was finally employed on registered MR images to estimate the proton end-of-range.
Results: Statistically significant correlations between radiation dose and MR SI were observed in superior/inferior penumbrae regions, with correlation coefficient ranging from 0.93 to 0.99. By applying the dose-SI correlation to the distal region of each proton beam, the mean difference between MR-estimated and the planned dose range was -2.18±4.89 mm for anterior-posterior beams and -3.90±5.87 mm for lateral beams.
Conclusions: This feasibility study proved the principle that proton dose range can be verified in vivo by follow-up MR images after proton liver treatment.
Keywords: Proton therapy, liver tumor, radiation effects on liver, magnetic resonance imaging, in vivo dosimetry, distal proton range verification

Publ.-Id: 18403 - Permalink


EXAFS and X-ray scattering as complementary techniques to determine metal coordination in solutions
Hennig, C.;
The determination of stability constants of metal complexes in aqueous solutions requires at least an estimate of the complex stoichiometry or better the determination of the complex structure. The structure analyses of metal complexes in solution is restricted to near-order sensitive techniques like X-ray scattering and X-ray absorption spectroscopy. X-ray scattering provide important structure information, but summarizes scattering contributions from all scattering pairs whose separation becomes difficult in real space with increasing number of involved elements. EXAFS is an element selective technique und provides structural information from the direct neighborhood of the absorbing atom. A statistical analysis of a sample series of solutions with pH variation provides furthermore direct access to the species distribution function. The advantages of both techniques will be discussed and typical applications will be demonstated.
Keywords: X-ray absorption, X-ray scattering, EXAFS, HEXS, XRD, structure analysis, aqueous solutions, actinides
  • Lecture (Conference)
    School and Conference on Analysis of Diffraction Data in Real Space, 18.-22.03.2013, Grenoble, France

Publ.-Id: 18402 - Permalink


Fabrication of nanopores in 1 nm thick carbon nanomembranes with slow highly charged ions
Ritter, R.; Wilhelm, R. A.; Stöger-Pollach, M.; Heller, R.; Mücklich, A.; Werner, U.; Vieker, H.; Beyer, A.; Facsko, S.; Gölzhäuser, A.; Aumayr, F.;
We describe the use of slow highly charged ions as a simple tool for the fabrication of nanopores with well-defined diameters typically between 10 and 20 nm in freestanding, 1 nm thick carbon nanomembranes (CNMs). When CNMs are exposed to a flux of highly charged ions, for example Xe40+, each individual ion creates a circular nanopore, the size of which depends on the kinetic and potential energy of the impinging ion. The controlled fabrication of nanopores with a
uniform size opens a path for the application of CNM based filters in nanobiotechnology.

Publ.-Id: 18401 - Permalink


Investigations to the Eu(III)-B(OH)3-Organic System at increased salt concentrations
Schott, J.; Acker, M.; Kretzschmar, J.; Barkleit, A.; Taut, S.; Brendler, V.; Bernhard, G.;
Boric acid (B(OH)3) and (poly)borates are of great interest regarding the mobilization of trivalent actinides in nuclear waste repositories, particularly in salt deposits.
This work describes the influence of boric acid on the Eu salicylate complexation due to the formation of a borate ester of salicylate, which could be the key to determine the stability constants of Eu-borate complexes.
Furthermore, at pH 6 the formation of a solid Eu borate species in presence of polyborates is observed. The formation progress of the solid Eu borate species depends on the polyborate concentration and salt concentration. The solid formation could be an interesting possibility for the immobilization of trivalent actinides in a nuclear waste repository.
Keywords: lanthanides, actinides, europium, boric acid, borates, polyborates
  • Contribution to proceedings
    Actinide and Brine Chemistry in a Salt Repository Workshop (III), ABC-Salt(III), 15.-17.04.2013, Santa Fe, New Mexico, USA
  • Lecture (Conference)
    Actinide and Brine Chemistry in a Salt Repository Workshop (III), ABC Salt III, 15.-17.04.2013, Santa Fe, New Mexico, USA

Publ.-Id: 18400 - Permalink


Spinwaves in Nanostructures: The Transition from Periodical Perturbations to Magnonic Crystals
Lenz, K.; Gallardo, R. A.; Bali, R.; Neudert, A.; Banholzer, A.; Wagner, K.; Langer, M.; Körner, M.; Grebing, J.; Lindner, J.; Landeros, P.; Fassbender, J.ORC
Two-magnon scattering is a well-known effect e.g. in ferromagnetic resonance (FMR) experiments leading to a linewidth broadening. Available theory so far was based on random defects acting as scattering centers for spin waves. Recently it was shown by Landeros and Mills [1] that this theory can be extended to handle two-magnon scattering in periodically perturbed films, which can be easily created by lithographical patterning processes. We present, that the uniform resonance mode splits into several modes and we compare the experimental results with analytical theory and simulations.
The periodically perturbed films are the intermediate step in the transition from a planar film towards full magnonic crystals. Small magnetic perturbations can be achieved by magnetic patterning using ion beam implantation [2]. A lithographically defined mask (stripes, dots, squares, …) covers part of the sample. Thus, these areas are protected from the ion beam changing the magnetic properties in the surface region of the sample creating magnetic defects. Another method we apply is to use ion etching to mill the pattern into the magnetic film to create geometric defects. Both techniques allow for precise control of the defect depth. With the latter approach the defect depth can be increased reaching the substrate, such that the structures are finally separated resembling a 1D or 2D magnonic crystal.
The evolution of spinwave modes and magnon bands in this transition from just a perturbation to a magnonic crystal has not been investigated so far.The extended model allows for analytically calculating the response function of 1D and 2D periodically perturbed ferromagnetic films in almost perfect agreement to FMR experiments as it will be shown. A striking feature e.g. is the level splitting due to the two-magnon scattering, which even leads to magnonic band gaps in full magnonics crystals. Exactly this splitting can be tailored by the geometric and magnetic sample parameters as described above.

This work was supported by the DFG grants FA 314/6-1 and FA314/3-2, as well as by CONICYT and MECESUP FSM0806.
Keywords: spin waves, ferromagnetic resonance, magnonic crystals, nanostructures, damping, relaxation, dispersion relation
  • Poster
    Yamada Conference LXVII -The 8th International Symposium on Metallic Multilayers (MML2013), 19.-24.05.2013, Kyoto, Japan

Publ.-Id: 18399 - Permalink


Splitting of spin-wave modes in thin films with Arrays of periodic perturbations: theory and experiment
Gallardo, R. A.; Lenz, K.; Banholzer, A.; Körner, M.; Lindner, J.; Fassbender, J.ORC; Landeros, P.
We present an analytical theory focused on the description of the ferromagnetic resonance (FMR) response of thin lms in the case that periodic surface perturbations are introduced. These perturbations can be any kind of one- or two-dimensional rectangular arrays of defects patterned onto one surface of the magnetic lm. Our theory allows us to describe their influence in such a way that the periodic defect structure can have any given shape. We calculate the response functions that are the components of the dynamic susceptibility tensor of the lm exposed to the FMR microwave excitation. These allow us to obtain the resonant response of the system, trough relevant quantities as the microwave absorption, the FMR linewidth, and resonance eld. We show examples where the periodic defects have the shape of stripes, dots, and rectangles. In our framework the perturbations may be considered either as bumps or pits. Finally, we compare our results with recent experimental FMR results, which manifest a very good agreement with the theory.
Keywords: spin relaxation, ferromagnetic resonance, two-magnon scattering, periodic perturbations, magnonic crystals

Publ.-Id: 18398 - Permalink


Linear and non-linear stability of melt flows in magnetic fields
Grants, I.; Galindo, V.; Gerbeth, G.;
This review considers the stability of melt motion in two simplified models of semiconductor crystal growth by either vertical gradient freeze (VGF) or Czochralski (Cz) processes under the influence of various magnetic fields. In VGF the crystal is grown at the bottom of the crucible, resulting in a stable thermal stratification of the melt. The presence of a stabilizing temperature gradient surprisingly decreases the stability of the flow driven by a rotating magnetic field (RMF). The instability of the travelling magnetic field (TMF)-driven flow, in contrast, is significantly delayed by thermal stratification in VGF. The TMF may, thus, be used in VGF to control the shape of the solidification interface or the radial dopant distribution without causing undesirable flow oscillations. The crystal is pulled out from the melt in the Cz process, producing an unstable temperature gradient below the crystal. The RMF is able to force the resulting unstable buoyant flow into a state of small-scale, high-frequency turbulence that may be regarded as stable for practical purposes. This effect is experimentally observed over a wide range of Grashof numbers, up to 10^9, characteristic for a large Cz system.
Keywords: crystall grwoth, vertical gradient freeze, Czochralski, Linear and non-linear stability, liquid metal flows, magnetic fields

Publ.-Id: 18397 - Permalink


The Use of Magnetic Fields in vertical Bridgman/Gradient Freeze-type Crystal Growth
Pätzold, O.; Niemietz, K.; Lantzsch, R.; Galindo, V.; Grants, I.; Bellmann, M.; Gerbeth, G.;
This paper outlines advanced vertical Bridgman/Gradient Freeze techniques with flow control using magnetic fields developed for the growth of semiconductor crystals. Low-temperature flow modelling, as well as laboratory-scaled crystal growth under the influence of rotating, travelling, and static magnetic fields are presented. Experimental and numerical flow modelling demonstrate the potential of the magnetic fields to establish a well-dened flow for tailoring heat and mass transfer in the melt during growth. The results of the growth experiments are discussed with a focus on the influence of a rotating field on the segregation of dopants, the influence of a travelling field on the temperature field and thermal stresses, and the potential of rotating and static fields for a stabilization of the melt flow.
Keywords: crystal growth, vertical Bridgman technique, Gradient Freeze technique, magnetic fields

Publ.-Id: 18396 - Permalink


Advances in Principal Balances for Compositional Data
Martin-Fernandez, J. A.; Pawlowsky-Glahn, V.; Egozcue, J. J.; Tolosana-Delgado, R.;
A prior reduction of dimension is often a necessary step when dealing with largedimensional data sets (geochemical surveys, microarray data, genetic Compositional data analysis requires selecting an orthonormal basis with which to work on coordinates. In most cases this selection is based on a data driven criterion. Principal component analysis provides bases that are, in general, functions of all the original parts, each with a different weight hindering their interpretation. For interpretative purposes, it would be better to have each basis component as a ratio or balance of the geometric means of two groups of parts, leaving irrelevant parts with a zero weight. This is the role of principal balances, defined as a sequence of orthonormal balances which successively maximize the explained variance in a data set. The new algorithm to compute principal balances requires an exhaustive search along all the possible sets of orthonormal balances. To reduce computational time, the sets of possible partitions for up to 15 parts are stored. Two other suboptimal, but feasible, algorithms are also introduced: (i) a new search for balances following a constrained principal component approach and (ii) the hierarchical cluster analysis of variables. The latter is a new approach based on the relation between the variation matrix and the Aitchison distance. The properties and performance of these three algorithms are illustrated using a typical data set of geochemical compositions and a simulation exercise.
Keywords: Aitchison norm; Cluster analysis; Compositions; Isometric logratio coordinates; Principal component analysis; Simplex

Publ.-Id: 18394 - Permalink


CFD Modeling of Bubble-induced Turbulence
Rzehak, R.; Krepper, E.;
Modeling of bubble-induced turbulence in dispersed gas-liquid multiphase flow is an important but still unresolved issue. Aside from its intrinsic interest, turbulence in this type of flow has a strong impact on other important processes like turbulent dispersion of the bubbles and bubble-coalescence and -breakup and thus is a central part of the overall model. Especially the latter require as input values of turbulent kinetic energy and dissipation, which as shown subsequently are not readily obtained from the most common approach to add a bubble-induced contribution to the effective viscosity. This may be overcome by including source terms in the single phase two-equation turbulence models that describe the bubble effects on the liquid turbulence. However, no consensus on the precise form of these terms has been reached yet. We here report a comparison of different models of this type. Special care has been given to the selection of a rather comprehensive set of reference data allowing to qualify the validity of the different models. Conclusions towards best practice guidelines for modeling bubbly turbulence are drawn and needs for further research identified.

Publ.-Id: 18393 - Permalink


Room temperature ferromagnetism in Ti Dioxide DMS
Smekhova, A.; Orlov, A. F.; Balagurov, L. A.; Perov, N. S.; Ganshina, E. A.; Semisalova, A. S.; Novikov, A.; Potzger, K.; Butterling, M.; Cornelius, S.; Yildirim, O.;
Abstract: A detailed study of a room-temperature ferromagnetism in diluted magnetic semiconductors on the basis of Titanium dioxide thin films with incorporated Co and V atoms has been performed. The relations between the structure, magnetization, transport and magneto-optical properties as well as evolution of defects and some peculiarities of preliminary element-specific XANES spectra are presented.
A continues interest to diluted magnetic semiconductors (DMS) during the last decade caused by an ambitious idea to get spin-polarized carriers in transparent semiconductor materials.1 A new physics exhibited by such materials could be exploited in fast developed information processing, storage and other diverse spintronic technologies. Up to now lot of systems have been already studied 2,3,4,5,6; and among them a particular interest to the DMS on the basis of Titanium Dioxide with incorporated 3d impurities (Co, V and Mn) have been ascertained.
The main goal of our present research is the study of the influence of structural properties such as point defects or defect complexes linked to oxygen deficiency on the magnetic, magneto-optical and magneto-transport properties of V (Mn) doped TiO2 anatase thin films. According to preliminary basic researches, magnetism in doped oxides is strongly influenced by defects and represents so far not-understood kind of magnetic phenomenon.
The TiO2 anatase thin films (200÷500 nm) with several percents (3 and 8%) of 3d transition metals with unpaired electrons (Co and V) have been prepared by rf magnetron deposition technique as well as ion-beam implantation (for samples with Vanadium). The presence of room temperature ferromagnetism in the samples has been initially checked by VSM and SQUID magnetometry measurements. The further magneto-optical (Transversal Kerr Effect) and transport (Hall Effect) measurements have been performed to obtain a more detailed picture of magnetism and concentration of carries. The special attention has been applied to verify an absence of any additional phases and magnetic impurities as metallic clusters insight the samples: in addition to a standard XRD analysis the element-specific XANES measurements at the Ti and 3d transition metal K- absorption edges have been done. The positron annihilation spectroscopy (PAS) has been used in order to investigate open volume defects on a very local scale and the first preliminary results will be presented.
The relationship of observed hysteresis loop in the sample magnetization, carrier concentration and characteristic features of magneto-optical spectra depending on film thicknesses, preparation route and structural defects is discussed. The difference in magnetic behaviour of TiO2:V and previously studied TiO2:Co is established.
This work is supported by the Initiative and Networking Fund of the German Helmholtz Association, Helmholtz-Russia Joint Research Group HRJRG-314 and RFBR #12-02-91321-SIG_а
References
1. Y. Matsumoto et al., Science 291, pp. 854 - 856 (2001).
2. H. Ohno et al., Appl. Phys. Lett. 69, 363 - 365 (1996).
3. H. Akai, Phys. Rev. Lett. 81, pp. 3002 - 3005 (1998).
4. S. Sonada et al., J. Cryst. Growth 237–239, 1358 (2002).
5. S.Q. Zhou et al., Appl. Phys. Lett. 93, pp. 232507 (2008).
6. A. F. Orlov et al., Phys. Solid State 53, pp. 482 - 484 (2011).
Keywords: diluted magnetic semiconductors
  • Lecture (Conference)
    ETOPIM (Electrical, Transport and Optical Properties of Inhomogeneous Media), 02.-07.09.2012, Marseille, Frankreich

Publ.-Id: 18392 - Permalink


Experimental Investigation of Horizontal Gas-Liquid Stratified and Annular Flow using Wire Mesh Sensor
Vieira, R. E.; Kesana, N. R.; Torres, C. F.; Mclaury, B. S.; Shirazi, S. A.; Schleicher, E.; Hampel, U.;
Stratified and annular gas-liquid flow patterns are commonly encountered in oil and gas transportation pipelines. The measurement and visualization of two-phase flow characteristics is of great importance as two-phase flows persist in many fluids engineering applications. A Wire Mesh Sensor technique based on conductance measurements was applied to investigate two-phase horizontal pipe flow. The horizontal flow test section consisting of a 76 mm ID pipe, 18 m long was employed to generate stratified and annular flow conditions. A 16×16 wire configuration sensor, installed at 17 m from the inlet test section, is used to determine the void fraction within the cross-section of the pipe. Physical flow parameters were extracted based on processed raw measured data obtained by the sensors using signal processing techniques. In this work, the principle of wire mesh sensors and the methodology of flow parameter extraction are described. From the obtained raw data time series of void fraction, mean void fraction and characteristic liquid film velocities are determined for different liquid and gas superficial velocities that ranged from 0.03m/s to 0.2 m/s and from 9 m/s to 34 m/s, respectively. The effects of liquid viscosity on the measured parameters are also investigated using three different viscosities.
Keywords: Wire Mesh Sensor, two-phase flow, flow visualization, void fraction.
  • Contribution to proceedings
    ASME 2013 Fluids Engineering Division Summer Meeting (FEDSM 2013), 07.-11.07.2013, Incline Village, Nevada, United States
    ASME 2013 Fluids Engineering Division Summer Meeting Volume 1C: ASME, 978-0-7918-5556-0, V01CT17A0
  • Journal of Fluids Engineering - Transactions of the ASME 136(2014)12, 121301
    DOI: 10.1115/1.4027799

Publ.-Id: 18391 - Permalink


Simulation of instabilities in liquid metal batteries
Weber, N.; Galindo, V.; Weier, T.; Stefani, F.; Wondrak, T.;
Liquid metal batteries, i.e. batteries in which both electrodes as well as the electrolyte are in the liquid state are usable for grid-scale energy storage and have received considerable attention recently. However, in completely liquid systems, fluid dynamic instabilities have to be considered. We focus here on the current driven Tayler instability and present results of a numerical study using a finite volume code for the calculation of the fluid flow coupled to a Biot-Savart integration to obtain the magnetic field. Growth rates of the instability as well as the magnetic field structure of the saturated instability fit very well to the experimental findings.
Keywords: Liquid metal battery, Tayler instability, finite volume method
  • Lecture (Conference)
    ERCOFTAC WORKSHOP Direct and Large-Eddy Simulation 9 (DLES 9), 03.-05.04.2013, Dresden, Deutschland
  • Contribution to proceedings
    ERCOFTAC WORKSHOP Direct and Large-Eddy Simulation 9 (DLES 9), 03.-05.04.2013, Dresden, Deutschland
    ERCOFTAC Series Volume 20: Springer, 978-3-319-14447-4, 585-594
    DOI: 10.1007/978-3-319-14448-1_74

Publ.-Id: 18390 - Permalink


Interaction of Selected Actinides (U, Cm) with Bacteria Relevant to Nuclear Waste Disposal
Lütke, L.;
To assess the safety of a site destined for storage of nuclear waste enhanced research effort is demanded to investigate the complex interactions of released radionuclides with parts of the environment that includes indigenous microorganisms.
As part of a BMWi-funded project this work aimed at assessing the interactions of two bacterial strains with the actinides uranium and curium with a focus on thermodynamics to provide stability constants of the actinide bacteria species formed usable for modelling the distribution of these actinides in the environment. The influences of Pseudomonas fluorescens (CCUG 32456A) isolated from the granitic aquifers at Äspö (Sweden) and a novel isolate from Mont Terri Opalinus clay (Switzerland), Paenibacillus sp. MT-2.2, were investigated. A combined approach using microbiological and spectroscopic techniques as well as potentiometry was employed to characterize the U(VI) and Cm(III) binding onto the cell surface functional groups structurally and thermodynamically. Further, due to its similar ionic radius to Cm(III) also Eu(III) was studied as non-radioactive analog.
The results evidenced that U(VI) and Cm(III) binding onto the cells is strongly pH-dependent. Both strains displayed high U(VI) binding capacities. In view of the versatile possible interaction mechanisms between microbes and actinides, it was found that both investigated strains display besides direct also indirect interaction in the form of a pronounced pH-dependent phosphatase activity and concomitant phosphate release which was drastically decreased in presence of U(VI). A moderate to strong interaction of U(VI) and Cm(III) (Eu(III)) with carboxylic and phosphoryl sites of the bacterial surfaces could be proven. Based on the determined stability constants of the different U(VI) phosphoryl and the U(VI) carboxyl surface complexes it could be shown that U(VI) is bound thermodynamically more stable to phosphoryl sites than to carboxylic ones. U(VI) speciation calculations indicated a dominant binding of U(VI) to the bacterial surface functional groups up to pH 7. For Eu(III) interaction with the bacterial surfaces the complexes R-O-PO3H-Eu2+ and R-COO-Eu2+ were identified and characterized thermodynamically. Spectroscopic results on Cm(III) binding onto Paenibacillus sp. cells indicated that binding occurred to H-phosphoryl surface sites over a wide pH range while sorption was found to be fully reversible. The identified complex R­-O-­PO3H-­Cm2+ was characterized spectroscopically and thermodynamically.
The stability constants calculated in the present work are valuable for modelling the U(VI), Cm(III) and Eu(III) speciation and distribution in the environment.
Keywords: U(VI), Cm(III), Eu(III), Pseudomonas fluorescens, Paenibacillus sp., Äspö, Mont Terri, Opalinus clay, potentiometry, TRLFS, EXAFS
  • Doctoral thesis
    TU Dresden, 2013
    133 Seiten

Publ.-Id: 18389 - Permalink


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