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39003 Publications

Ultrafast graphene-based broadband THz detector

Mittendorff, M.; Winnerl, S.; Kamann, J.; Eroms, J.; Weiss, D.; Schneider, H.; Helm, M.

We present an ultrafast graphene-based detector, working in the THz range at room temperature. A logarithmic-periodic antenna is coupled to a graphene flake that is produced by exfoliation on SiO2. The detector was characterized with the free-electron laser FELBE for wavelengths from 8 µm to 220 µm. The detector rise time is 50 ps in the wavelength range from 30 µm to 220 µm. Autocorrelation measurements exploiting the nonlinear photocurrent response at high intensities reveal an intrinsic response time below 10 ps. This detector has a high potential for characterizing temporal overlaps, e. g. in two-color pump-probe experiments.

Keywords: graphene; ultrafast detector; THz detection

Related publications

Publ.-Id: 18819

Switchable zero-bias anomaly in individual C60 molecules contacted with tunable aluminum electrodes

Scheer, E.; Böhler, T.; Edtbauer, A.; Egle, S.; Erbe, A.; Pietsch, T.

We report the observation of strong resonances at zero bias in the differential conductance through Al–C60–Al junctions with tunable electrode distance, measured above T 1⁄4 10 K. The conductance value at resonance ranges from a few percent up to eighty percent of the quantum of conductance. The resonances may disappear or reoccur completely and discontinuously upon very small changes of the electrode distance. However, once they are formed they are very robust with respect to changes of the electrode distance. We discuss similarities and differences to the common theories of the Kondo screening of a spontaneous spin polarization of the C60 molecule. We deduce Kondo temperatures in the range from 35 to 160 K and demonstrate that the temperature dependence is in agreement with the scaling behavior of the Kondo effect in the temperature range of our experiment.

Keywords: molecular electronics; mechanically controllable break junctions; Kondo effect

Publ.-Id: 18818

Fracture mechanics and mechanical characterization of the beltline welding seam of the decommissioned WWER-440 reactor pressure vessels of nuclear power plant Greifswald Unit 4

Viehrig, H.-W.; Altstadt, E.; Houska, M.; Valo, M.

The paper presents data measured for two trepans sampled from the beltline welding seam of the decommissioned WWER-440/V-230 reactor pressure vessel (RPV) of the nuclear power plant Greifswald Unit 4. Greifswald Unit 4 representing the first generation of this reactor type was shut down after 11 operating cycles in 1990. The aging of the RPV steels was not monitored by any surveillance program. The main focus of this work is put on fracture toughness characterization according to test standard ASTM E1921. Charpy size SE(B)-specimens were machined from different locations through the thickness of the multilayer beltline welding seam. SE(B) specimens machined from the same thickness are a set of specimens for which one reference temperature T0 was defined according to ASTM E1921. The pre-cracked and side-grooved Charpy-size SE(B) specimens were monotonically loaded until they failed by cleavage instability. T0 values were evaluated with the measured cleavage fracture toughness values, KJc, by applying the multi-temperature procedure. The neutron fluence at the RPV outer and inner RPV wall was determined with 4.1•1019 und 0.87•1019, respectively. That is a decrease for about 80% over the RPV wall.
Large variations in the evaluated T0 values across the wall of the multilayer beltline welding seams were observed. At the inner wall just beyond the cladding and in the welding root region comparatively low a T0 were evaluated with 28°C and 6°C, respectively. After the welding root towards the outer wall the average T0 amounts 81°C with a span (maximum value minus minimum value) of 57 K. It is demonstrated that the ductile-to-brittle transition temperature shift predicted by the Russian code for the existing content of deleterious elements P and Cu and the accumulated neutron fluences lies within the scatter of the measured T0 values. The irradiation induced shift of T0 expected due to the decrease of the neutron fluence by about 80% from the inner to the outer RPV wall is not visible. It is overlapped by the strong variation of KJc values caused by the intrinsic weld bead structure and the different filling materials used for weld root and the main weld.
In addition Charpy-V tests were performed to compare the results of fracture mechanics testing with the current integrity assessment code practice. The transition temperatures TT47J vary also through the thickness of the multilayer welding seam. At the inner wall just beyond the cladding and in the welding root region TT47J was measured with 73°C and 40°C, respectively. After the welding root the average TT47J amounts to 124°C with a span of 16 K. Compared with T0 the variation of TT47J within the filling layers after the welding root is considerably smaller.
Compact and reconstituted Charpy-V and SE(B) specimens were thermally annealed at 475°C for 152 h. This temperature time regime corresponds to the one applied to the Greifswald Units 1 to 3. The comparison of test of thermally annealed and non-annealed specimens provides irradiation induced shifts of 114 K for TT47J and 86 K for T0. The testing of annealed specimens confirms the results measured with samples from thermally annealed RPV of Greifswald Unit 2.

Keywords: decommissioned nuclear power plant; reactor pressure vessel; welding seam; annealing; fracture toughness; ductile-to-brittle transition; neutron embrittlement

  • Lecture (Conference)
    26th Symposium on the Effects of Radiation on Nuclear Materials, 12.-13.06.2013, Indianapolis, USA

Publ.-Id: 18817

Spheroid Control Probability as Analytical Endpoint for the Evaluation of a Radio-chemo-therapeutic Approach Combining External and Internal Irradiation

Ingargiola, M.; Runge, R.; Heldt, J.-M.; Pietzsch, H.-J.; Kotzerke, J.; Cordes, N.; Steinbach, J.; Baumann, M.; Kunz-Schughart, L. A.

kein Abstract verfügbar

  • Abstract in refereed journal
    European Journal of Cancer 48(2012), S272
    ISSN: 0959-8049
  • Poster
    22nd Biennial Congress of the European Association for Cancer Research, 07.-10.07.2012, Barcelona, Spain

Publ.-Id: 18816

From holes to sponge at irradiated Ge surfaces with increasing ion energy - an effect of defect kinetics?

Böttger, R.; Heinig, K.-H.; Bischoff, L.; Liedke, B.; Facsko, S.

We show that hole patterns and sponge-like layers at irradiated Ge surfaces originate from the same driving force, namely the kinetics of ion beam induced defects in the amorphous Ge surface layer. Ge hole Patterns reported earlier for irradiation with low energy (5 keV) Ga+ ions were reproduced for low energy Bi+ but also for Ge+ selfirradiation, which proves that the dominating driving force for morphology evolution cannot originate from the implanted impurities. At higher ion energies the well-known formation of sponge-like Ge surface layers after heavy ion irradiation was found for Bi+ irradiation and Ge+ self-irradiation too. The transition from smooth surfaces via hole patterns to sponge-like morphologies with increasing ion energies was studied in detail. A model based on the kinetics of ion beam induced defects was developed and implemented in 3D kinetic Monte Carlo simulations, which reproduce the transition from hole patterns to sponge-like layers with increasing ion energy.

Keywords: germanium; ion Irradiation; defect accumulation; self-organization; kinetic Monte Carlo simulations

Related publications

Publ.-Id: 18815

Optical Synchronization and Electron Bunch Diagnostic at ELBE

Kuntzsch, M.; Gensch, M.; Lehnert, U.; Roeser, F.; Schurig, R.; Bousonville, M.; Czwalinna, M. K.; Schlarb, H.; Schulz, S.; Vilcins, S.

The continuous wave electron accelerator ELBE is upgraded to generate short and highly charged electron bunches (~100fs duration, up to 1 nC) . In the last years a prototype of an optical synchronization system using a mode locked fiber laser has been build up which is now in commissioning phase. The stabilized pulse train can be used for new methods of electron bunch diagnostics like bunch arrival time measurements with femtosecond resolution. At ELBE a Bunch arrival time monitor (BAM) has been designed and tested at the accelerator. The contribution will show the design of the BAM and some measurement results.

Keywords: Synchronization

Related publications

  • Poster
    IPAC2013 - The 4th International Particle Accelerator Conference, 12.-17.05.2013, Shanghai, China
  • Open Access Logo Contribution to proceedings
    IPAC2013 - The 4th International Particle Accelerator Conference, 12.-17.05.2013, Shanghai, China
    Proceedings of the 4th International Particle Accelerator Conference, 978-3-95450-122-9, 2932-2934

Publ.-Id: 18814

Optische Synchronisation an der Strahlenquelle ELBE mit Femtosekunden Präzision

Kuntzsch, M.

Dieses wissenschaftliche Seminar an der Hochschule für Technik und Wirtschaft Dresden gibt einen Überblick zu der Strahlerzeugung und Diagnose am supraleitenden Elektronenbschleuniger ELBE im Helmholtz-Zentrum Dresden-Rossendorf. Besonders wird dabei auf die im Bau befindlichen Röntgenstrahlungs- und THz- Quellen eingegangen, die erhöhte Anforderungen an die Synchronisation und die Strahldiagnose stellen.
Um stabile Experimentierbedingungen zu schaffen, wird ein Synchronisationssystem mit einer Stabilität von mindestens 100 fs benötigt. Es wird beschrieben, wie dieses System funktioniert und erste Ergebnisse vom Betrieb des Prototyps vorgestellt.
Basierend auf dem optischen Synchronisationssystem wurde ein Gerät für die exakte Ermittlung der Ankunftszeit der Elektronenpulse an einer Stelle im Beschleuniger entwickelt. Es werden erste Messergebnisse dieser Einrichtung und deren Aufbau präsentiert.

Related publications

  • Invited lecture (Conferences)
    158. Wissenschaftliches Seminar, 19.03.2013, Dresden, Germany

Publ.-Id: 18813

Optical Synchronization and Electron Bunch Diagnostic at the quasi-CW accelerator ELBE

Kuntzsch, M.; Lehnert, U.; Röser, F.; Czwalinna, M. K.; Schulz, S.; Schlarb, H.; Vilcins, S.

The continuous wave electron accelerator ELBE is upgraded to generate short and highly charged electron bunches (~200fs duration, up to 1 nC) with an energy of up to 40 MeV. In the last years a prototype of an optical synchronization system using a mode locked fiber laser has been build up which is now in commissioning phase. The stabilized pulse train can be used for new methods of electron bunch diagnostics like bunch arrival time measurement with the resolution down to a few femtoseconds. At ELBE a bunch arrival time monitor (BAM) has been designed and tested at the accelerator. The contribution will show the concept of the femtosecond synchronization system, the design of the BAM and first measurement results.

Keywords: Synchronization ELBE

Related publications

  • Lecture (Conference)
    77. Jahrestagung der DPG und DPG-Frühjahrstagung, 04.-08.03.2013, Dresden, Germany

Publ.-Id: 18812

Semiconductor quantum well excitons in strong, narrowband terahertz fields

Teich, M.; Wagner, M.; Schneider, H.; Helm, M.

Optical transitions between exciton states in semiconductors – intraexcitonic transitions – usually fall into the terahertz (THz) range and can be resonantly excited with narrowband, intense THz radiation as provided by a free-electron laser. We investigate this situation for two different quantum well structures by probing the near-infrared excitonic absorption spectrum near the band edge. We observe the dynamical Stark – or Autler Townes – splitting of the 1s exciton ground state and follow its evolution for various THz photon energies and field strengths. The behavior is considerably more complex than in atomic systems. At the highest field strengths, where the Rabi energy is of the same order of magnitude as the exciton level separation, the system cannot be described within the standard framework of a two-level system in rotating wave approximation. When the ponderomotive energy approaches the exciton binding energy, signatures of exciton field ionization are observed.

Keywords: terahertz; Stark effect; quantum well; exciton; Autler-Townes; free electron laser

Related publications

Publ.-Id: 18811

Rare earth implanted MOS structures: Advantages and drawbacks for optoelectronic applications

Rebohle, L.

Integrated photonics is a key technology of the 21st century, and Si-based photonic components are of special interest as they propose an easy integration into the CMOS platform. An essential building block is the electrically driven light emitter (LE) which, however, is difficult to realize. Among the different approaches rare earth (RE) implanted MOS structures feature a high conformity with standard CMOS processes combined with the excellent optical properties of RE elements.
However, despite an intense research for more than 20 years in the field of Si-based light emission, the results are mixed. With respect to important key parameters like power efficien-cy, Si-based LE are not yet able to compete with their counterparts based on compound or organic semiconductors. The following contribution is focused on RE implanted MOS structures and discusses the different problems to turn them into long-living, efficient LE.
Such a LE typically consists of a Si substrate, a dielectric stack and a transparent electrode (Abb. 1). The layers of the dielectric stack fulfil several tasks like hosting the luminescence centres or providing a buffer against early electrical breakdowns. Usually, the injected charge carriers have to overcome substantial potential barriers requiring high electric fields for operation. The electroluminescence (EL) is based on radiative 4f intrashell transitions within the trivalent RE ion, although there are exceptions involving a 5d electron (e.g. Ce). For this reason oxidic materials, especially SiO2, are suitable as host matrices, but there are also successful reports where RE elements are embedded in other materials, e.g. silicon nitride.

Fig. 1: Basic scheme of a RE-implanted MOS device

At the beginning, a short view to the EL excitation mechanism may be helpful. From the physical point of view, there are two main types of excitation. At first, under favourable conditions electrons can be accelerated to high energies which can be transferred by inelastic scattering to the lumines¬cence centres. This mode can be fairly efficient, depending on the fraction of hot electrons in the average electron energy distribution, but inherently contains the seed of destruction: hot electrons are also efficient in creating new defects and degrading oxides. Different to this, charge carrier recombination releases the band gap energy of the host semiconductor at maximum, which prevents degradation and limits the different types of potential luminescence centres. In case of Si-based LE the efficiency is often less than in case of hot electron excitation, but there are ongoing research activities to improve the situation.
Starting the discussion with the quest for the most efficient RE-implanted MOS device, there are at least three strategies to be pursued: (i) to increase the excitation cross section, (ii) to increase the internal quantum efficiency, and (iii) to increase the outcoupling efficiency.
In most cases the first strategy was pursued, and indeed, this strategy probably offers the greatest potential if the efficiency is far away from reasonable levels. Among the most popular ideas is the use of Si nanoclusters to enhance the excitation cross section of RE ions, especially of Er. Although this recipe was quite successful in case of photoluminescence, it was found that often only a small percentage of Er is excited [1]. The problem was partially solved in the last years by substantial changes in the composition of the dielectric stack. The use of Ge nanoclusters gave the unexpected result that the RE ions were pumping the Ge nanoclusters instead vice versa [2]. At present, in case of EL the use of a second RE element pumping the first one was more efficient, as demonstrated for Gd pumping the EL of Ce [3].
In case of hot electron excitation another problem appears, namely the existence of a dark zone close to the injecting interface. This is the region where electrons are already accelerated but not yet have enough energy to excite the RE ions. In case of Tb-implanted MOS devices it was found that this zone extends up to 20 nm into the gate oxide [4] which limits the scalability to thinner devices and to lower operation voltages.
To improve operation lifetime, the use of LOCOS (LOCal Oxidation of Silicon) structures and dielectric buffer layers made of SiON [5] can prevent early electric breakdowns. However, these strategies cannot solve the fundamental problem of oxide degradation by hot electrons. In addition, the EL often exhibits degradation over lifetime due to the charging of defects and RE clusters [6]. Experiments with MOS structures, where SiO2 is replaced by materials with less hot electrons, show that in fact the operation lifetime is strongly enhanced, but unfortunately at the expense of efficiency. A possible solution could be the shift of the excitation mode to charge carrier recombination, e.g. if electrons and holes are both injected during AC excitation.
In summary, the advantages and drawbacks of RE-implanted MOS devices were discussed. At present, the current status of these devices allows only a few applications where efficiency and operation lifetime is not of major importance, as for some sensor applications. However, some possible solutions to reduce or overcome these problems were addressed.
[1] B. Garrido, C. García, P. Pellegrino, D. Navarro-Urrios, N. Daldosso, L. Pavesi, F. Gourbilleau, and R. Rizk, Appl. Phys. Lett. 89 (2006) 163103
[2] L. Rebohle, A. Kanjilal, W. Skorupa, and M. Helm, Opt. Mat. 33, Issue 7 (2011) 1075.
[3] J.M. Sun, S. Prucnal, W. Skorupa, M. Helm, L. Rebohle, and T. Gebel, Appl. Phys. Lett. 89, 091908 (2006)
[4] L. Rebohle, J. Lehmann, S. Prucnal, J. M. Sun, M. Helm and W. Skorupa, App. Phys. B 98:2 (2010) 439
[5] J.M. Sun, L. Rebohle, S. Prucnal, M. Helm, W. Skorupa, Appl. Phys. Lett. 92, 071103 (2008)
[6] A. N. Nazarov, S. I. Tiagulskyi, I. P. Tyagulskyy, V. S. Lysenko, L. Rebohle, J. Lehmann, S. Prucnal, M. Voelskow, and W. Skorupa, J. Appl. Phys. 107, 123112 (2010)

Keywords: electroluminescence; rare earth implantation; erbium

Related publications

  • Invited lecture (Conferences)
    7th International Workshop “Functional Nanomaterials and Devices”, 08.-11.04.2013, Kyiv, Ukraine
  • Book chapter
    Nazarov, A., Francis, B., Valeriya, K., Flandre, D: Functional Nanomaterials and Devices for Electronics, Sensors and Energy Harvesting, Berlin: Springer, 2014, 978-3-319-08803-7, 349-364
    DOI: 10.1007/978-3-319-08804-4_16

Publ.-Id: 18810

Interaction of uranium(VI) and neptunium(V) with Äspö diorite under anoxic conditions

Schmeide, K.; Gürtler, S.; Bok, F.; Brendler, V.

The interaction of uranium(VI) and neptunium(V) with diorite obtained from Äspö Hard Rock Laboratory (HRL, Sweden) has been studied by means of batch sorption experiments under anoxic conditions (N2) as a function of contact time (5 to 108 d) applying a synthetic Äspö groundwater (pH 7.8, I = 0.18 M) as background electrolyte. In the case of uranium(VI), sorption isotherms have been recorded by varying the total uranium(VI) concentration between 3•10−9 and 2•10−5 M. Distribution coefficients, Kd values, were determined. Desorption experiments have been performed using synthetic Äspö groundwater. For redox speciation of actinides in sample solution or desorbed from the diorite, solvent extraction has been applied.

Keywords: sorption; reduction; U(VI); Np(V); Np(IV)

  • Lecture (Conference)
    Final Workshop of the Project "Crystalline rock retention processes" (CROCK), 14.-16.05.2013, Karlsruhe, Germany
  • Poster
    Final Workshop of the Project "Crystalline rock retention processes" (CROCK), 14.-16.05.2013, Karlsruhe, Germany
  • Contribution to proceedings
    Final Workshop of the Project "Crystalline Rock Retention Processes" (CROCK), 14.-16.05.2013, Karlsruhe, Germany
    Final Workshop Proceedings of the Collaborative Project "Crystalline Rock Retention Processes" (7th EC FP CP CROCK), KIT Scientific Reports 7656, Karlsruhe: KIT Scientific Publishing, 211-223 (2014)

Publ.-Id: 18809

Accelerator based super-radiant THz sources: Challenges and opportunities

Gensch, M.

The past fifteen years have seen a rapid development of novel techniques to generate and detect ultra-short and high power THz pulses. The availability of these pulses with electric field strength in the few 10 to 100 MV/m regime has led to a number of exciting experiments in particular in the field of non-linear THz spectroscopy and THz control experiments. One class of these THz generation techniques utilizes highly charged, ultra short electron bunches accelerated to relativistic speed in linear particle accelerators [1]. A variety of different source concepts allows to shape the THz pulses from single cycle/broad band pulses to multicycle/narrowbandwidth pulses with polarizations ranging from radial to linear. One main attraction of accelerator-based THz originates from the fact that the THz generation process does not take place in a medium but in the ultra-high vacuum of the accelerator, so that the THz pulse energy can hence theoretically much easier up scaled than in any of the table top sources available today. Additionally it could recently be shown that coherent THz radiation can be generated residually and in parallel to the femtosecond X-ray pulses in 4th Generation X-ray Light sources such as FLASH [2,3,and 4] and LCLS [5]. This opens up the exciting opportunity to perform naturally synchronized THz pump X-ray probe experiments on few femtosecond time scales [2,3,and 5]. An overview over different THz facility projects will be presented and experimental opportunities and challenges will be discussed on the example of recent pilot experiments.
[1] G.L. Carr et. al., High power terahertz radiation from relativistic electrons, Nature 420 (2002), 153.
[2] M. Gensch et. al., New infrared undulator beamline at FLASH, Infrared Phys. Technol. 51 (2008), 423.
[3] U. Fruehling et. al., Single-Shot THz-field-driven X-ray streak camera, Nat. Photon. 3 (2009), 523.
[4] F. Tavella, N. Stojanovic, G. Geloni, M. Gensch, Few-Femtosecond timing at Fourth-Generation X-ray Light sources, Nat. Photon. 5 (2011), 162.
[5] D. Daranciang et. al., Single-cycle terahertz pulses with > 0.2 V/angstrom field amplitudes via coherent transition radiation, Appl. Phys. Lett. 99 (2011), 141117.

Related publications

  • Invited lecture (Conferences)
    Seminar, Lehrstuhl für Angewandte und Experimentelle Physik, Universität Regensburg, 28.05.2013, Universität Regensburg, Deutschland

Publ.-Id: 18808

A biochemical approach to single particle X-FEL studies on membrane proteins

Oertel, J.; Keller, A.; Weiss, S.; Stellato, F.; Barty, A.; Fahmy, K.

Membrane proteins are vital for making cells responsive to environmental stimuli as well as in controlling the exchange of ions between the cytoplasm and the extracellular space. Both processes depend on proteins containing multiple transmembrane helices that rearrange during function. The development of a technology that allows resolving structural transitions in single membrane proteins by the use of ultra-short X-ray pulses from X-ray free electron lasers (X-FELs) will represent a significant advance in studies of membrane protein structure and dynamics. The successful use of X-FEL radiation for Structural Biology has been proven for nanocrystals. In contrast, the potential for a fully crystallization-independent analysis of large protein structures at the single molecule level has not been explored experimentally.
Engineered phospholipid nanodiscs (NDs), which are lipid-protein complexes surrounded by a helical protein belt of two membrane scaffold proteins (MSPs) provide a completely soluble nanoscale section of a lipid bilayer designed for functional investigations of membrane proteins. Exploring their suitability for single particle X-ray diffraction will have a strong impact on X-FEL applications in Structural Biology, particular for the crystallization-independent structure determination of membrane proteins. Additionally, NDs will be labelled with small gold spheres of ~1.4nm diameter to aid particle identification and orientation. Sufficiently high concentrations of NDs have been obtained for preliminary X-ray diffraction experiments and aggregation can be prevented even at high concentrations (mg/ml).

Keywords: membrane proteins; structural biology; X-FEL

  • Poster
    Kick-off meeting for the HIBEF User Consortium, 02.-05.06.2013, Hamburg, Deutschland

Publ.-Id: 18807

Low-electrical resistivity polycrystalline TiO2-based transparent conductors by millisecond flash lamp annealing of magnetron sputtered films

Neubert, M.; Vinnichenko, M.; Cornelius, S.; Gebel, T.; Liepack, H.

Transparent conductive oxides (TCO), mainly In2O3:Sn (ITO), ZnO:Al (AZO) and SnO2:F (FTO) are widely used as transparent electrodes in flat panel displays, thin film solar cells and solid state lighting. In contrast to these TCOs, TiO2 –based films offer unique combination of low cost, high refractive index, stability against humidity, the high chemical stability and the non-toxicity. The Nb or Ta doped TiO2 films epitaxially grown on crystalline substrates already show electrical and optical properties which are comparable to those of conventional TCOs. However, it is still a challenge to achieve low electrical resistivity polycrystalline TiO2 - based films as required for most of applications. Furthermore, it is not possible to get low resistivity in polycrystalline films by direct growth at elevated substrate temperatures. Only a two-step approach, i.e. the deposition of amorphous films followed by annealing for minutes up to hours in vacuum or hydrogen delivers films with resistivity values in the range of 1•10-3 Ωcm. Both, the direct growth on crystalline substrates and the post deposition annealing of the amorphous films require substrate temperatures of about 400°C to ensure desired resistivity, which drastically limits applications. Furthermore, the high demand for energy for an annealing time of several minutes or even hour is almost unacceptable for a cost-efficient and environmental friendly replacement of conventional by TiO2 - based TCOs, especially for large area applications. In order to address this problem, we studied the films formed on glass substrates without heating by direct current magnetron sputtering (DC MS) of reduced TiO2:Ta ceramic targets followed by flash lamp annealing (FLA) in the millisecond range to crystallize as-deposited amorphous films. The Ti/O ratio of the as-deposited films was varied using a DC MS process in conjunction with a plasma feedback system to achieve an oxygen fine-tuning. Using FLA, the heat treatment is confined to the film and the substrate is only partly heated (several µm at the surface) which drastically lowers the energy consumption and allows the use of temperature sensitive substrates. In addition, the short annealing enables the film processing at atmospheric pressure in argon or even in air. The emerging electrical, optical and structural properties are strongly affected by the Ti/O ratio in the as-deposited films adjusted by the plasma feeback system Our approach delivered films with an electrical resistivity in the range of 1•10-3 Ωcm, optical transmittance above 80% for 400nm thick films and electrical activation of Ta dopants up to 60%. The reference films obtained combining deposition onto unheated substrate and subsequent conventional annealing in vacuum at 425°C for 1 hour show almost the same electrical and optical properties.

Keywords: transparent conductive oxide; TCO; titania; tantalum; flash lamp annealing

  • Lecture (Conference)
    2013 MRS Spring Meeting & Exhibit, 01.-05.04.2013, San Francisco, United States of America

Publ.-Id: 18806

PEnELOPE - a high peak-power diode-pumped laser system for laser-plasma experiments

Siebold, M.; Roeser, F.; Loeser, M.; Albach, D.; Schramm, U.

We introduce the directly diode-pumped PEnELOPE laser-system which is designed for a pulse energy of 150 J, a repetition rate of 1Hz and a pulse duration of 120 fs. The principle setup of amplifier and stretcher-compressor system as well as the pumping, energy extraction and cooling scheme of the power amplifiers will be reported. In this paper we focus on numerical modeling as well as design studies.

  • Contribution to proceedings
    SPIE Optics + Optoelectronics 2013, 15.-18.04.2013, Prag, Tschechien
    High-Power, High-Endergy and High_intensity Laser Technology: Proceedings of SPIE Vol. 8780, 878005
    DOI: 10.1117/12.2017522
    Cited 33 times in Scopus

Publ.-Id: 18805

Experimental investigations of two-phase flows in various liquid metal processes

Shevchenko, N.; Boden, S.; Vogt, T.; Timmel, K.; Röder, M.; Eckert, S.; Gerbeth, G.

Many technical applications in metallurgy and casting rely on liquid metal two-phase flows. Gas injection is routinely applied at various stages of melt preparation and refinement to promote chemical reactions and to stir the melt for reducing temperature and/or concentration gradients together with promoting an effective removal of impurities. In continuous steel casting, argon bubbles are injected to avoid solidification and to generate desired flow patterns directing impurities to the surface. In aluminium casting, on the other hand, uncontrolled entrapment of gas bubbles may cause serious casting defects.
Multi-phase flows with a compressible disperse phase, i.e. bubbles, are a particular challenge and substantially more difficult than corresponding single-phase flows. Different length and time scales coexist even in rather generic flow configurations such as a bubble plume and the stochastic nature of both the carrier-phase turbulence and the dispersed-phase distribution needs to be accounted for. The physical and numerical models still lack sophistication as they need reliable experiments for validation. Compared to the numerous experimental studies on the movement of bubbles in transparent liquids, especially in water, the number of publications dealing with gas bubbles rising in liquid metals is small. Measurements in liquid metals are substantially more difficult but are indispensable because of the distinct differences in material properties compared to water, in particular density and surface tension. Further specific problems concern the influence of surfactants at fluid-gas interfaces. All these conditions cause the gas bubbles to behave very differently in liquid metals compared to water, in particular with respect to bubble formation, dispersion, coalescence and breakup. Substantial work is still to be done in this respect.
We present experimental activities at HZDR for investigating liquid metal two-phase flows. Ultrasonic methods and X-ray radioscopy are used for detection and characterization of gas bubbles in the liquid metal flow. A series of measurements has been conducted for the configuration of a bubble plume rising in a liquid metal. Another study is concerned with the two-phase flow in a mockup for modeling the continuous casting process of steel. A specific experimental facility was designed and constructed at HZDR for visualizing two-phase flows in the mould and the submerged entry nozzle by means of X-ray radioscopy. This setup utilizes the low melting, eutectic alloy GaInSn as model liquid and operates under isothermal conditions. First results will be presented here accompanied by statistical analysis and a discussion of the advantages and limitations of the measuring techniques applied at these experiments.

Keywords: two-phase flows; bubbles; X-ray radioscopy; Ultrasonic methods

  • Poster
    The 3rd International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR2013), 20.-23.05.2013, Helsinki/ Stockholm, Finland/ Sweden

Publ.-Id: 18804

In situ X-ray radioscopy studies of microstructure and freckle formation in solidifying alloys

Shevchenko, N.; Boden, S.; Gerbeth, G.; Eckert, S.

In-situ observations of the solidification process of Ga-25wt%In alloy within a Hele-Shaw cell were obtained by means of X-ray radioscopy. This work is devoted to an experimental study of the initiation and development of segregation channels inside the mushy zone of a solidifying metal alloy under the influence of thermosolutal convection. We also focused on the analysis of dendrite formation and remelting, flow pattern and microstructure features, for instance, dendrite orientation, primary and secondary spacing. A series of directional bottom-up solidification experiments were carried out at a cooling rate of 0.01 K/s accompanied by vertical temperature gradients in the range between 0.5 and 2 K/mm. Because of the conical shape of the solidification cell there is no uniform cooling of the sample and an additional lateral temperature difference arises. The real time studies of solidification of Ga-In alloys deliver simultaneous data of both the structure of the solid fraction in the mushy zone and the flow pattern in the vicinity of the solidification front.
Different scenarios were observed concerning the formation of segregation channels in the mushy zone which can be related to variations of the vertical temperature gradient. A temperature gradient up to 1 K/mm results in the formation of various segregation channels, but a sustainable development of stable chimneys was observed only in 4 of 10 experiments. Stable chimneys occur mainly at positions with initial growth defects or grain boundaries, however, not every initial segregation channel evolves into a stable chimney. In the case of higher temperature gradients (up to 2 K/mm) we can identify a converging flow ahead of the mushy zone coming from the side walls and leading to a concentration of the rising plumes in the central part of the solidification cell. The continuous strengthening of the central plume causes a distinct solute accumulation in the mushy zone behind followed by a remelting of the solid fraction and the occurrence of a sustaining channel. In all solidification experiments performed under such conditions at least one stable chimney can be detected. This mechanism of chimney formation is different as compared to the case where the development of the segregation channel is linked with any initial growth defect. Our results reveal a clear impact of the flow field on the microstructure and the formation of chimneys.
In summary, the initiation and development of the chimneys and the probability of their surviving depend sensitively on the spatial and temporal properties of the flow field. Variations of the vertical temperature gradient along the solidification cell induce modifications of the melt flow pattern, which lead to different segregation structures. In situ characterizations of dendrite growth and chimney formation can give access to key parameters for modelling of freckle formation and its verification.

Keywords: solidification; in situ X-ray radioscopy; freckles; Ga-In alloy; flow pattern

  • Lecture (Conference)
    The 3rd International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR2013), 20.-23.05.2013, Helsinki/ Stockholm, Finland/ Sweden

Publ.-Id: 18803

Spin waves in a microstructured ion-implanted magnonic crystal

Chumak, A. V.; Obry, B.; Brächer, T.; Pirro, P.; Ciubotaru, F.; Serga, A. A.; Osten, J.; Fassbender, J.; Hillebrands, B.

In recent years the research on magnonic crystals (MC), which are magnetic materials with periodically-modulated properties, has experienced increasing attention due to their potential in manipulating the propagation properties of spin waves. However, up to date there are only few investigations of propagating spin waves in microscopic metallic magnonic crystals.

Keywords: magnonic crystals (MC)

Related publications

  • Lecture (Conference)
    International Symposium on Spin Waves, 09.-15.06.2013, St. Petersburg, Russia

Publ.-Id: 18802

XAS/XMCD studies of Ga+ ions irardiated of Pt/Co/Pt trilayers

Mazalski, P.; Maziewski, A.; Rogalev, A.; Wilhelm, F.; Fassbender, J.; Baczewski, L. T.; Wawro, A.

Investigation of the magnetic thin film structures with perpendicular magnetic anisotropy (PMA) is interesting task for both fundamental research and possible applications. New effect of Ga+ ion irradiation induced changes of magnetic and magnetooptical properties was reported in [1] where two branches of PMA were discovered on the 2D maps (dCo, F) of magnetic and magnetooptical parameters driven by ion fluence F and Co thickness. We shall report results of studies performed on Pt/(Co(dCo= 3.3nm)/Pt samples: nonirradiated and two irradiated with fluences corresponding to first (F1= 2.8*1014 ions/cm2) and second (F2= 6*1015 ions/cm2) PMA branches on Co K-edge and Pt L2,3-edges using XANES and XMCD techniques. XANES studies for both irradiated samples showed: (i) changes of the spectra profiles and (ii) big changes of the amplitude for the fluence F2 what is related with induced by irradiation modification of the local environment of Co(Pt) atoms and etching process, respectively. XMCD Co spectra on irradiated samples had similar shape as once for CoPt alloy. XMCD Pt L2,3-edges studies reveal increase of the magnetic moments of Pt atoms for both irradiated samples.
[1] A. Maziewski et al., Phys. Rev. B 85, 054427 (2012).

Keywords: XAS/XMCD studies of Ga+ ions irardiated of Pt/Co/Pt trilayers; PMA

Related publications

  • Lecture (Conference)
    Joint European Symposia on Magnetism (JEMS 2013), 25.-30.08.2013, Rhodos, Greece

Publ.-Id: 18801

Planar optical waveguide in SrTiO3 crystal fabricated by carbon ion irradiation

He, R.; Sun, S.; Xu, M.; Chen, F.; Akhmadaliev, S.; Zhou, S.

We report on the planar waveguide fabrication in SrTiO3 crystal by using carbon ion irradiation at energy of 15 MeV. The reconstructed refractive index profile of the waveguide shows the “barrier”-like distribution. The planar waveguide supports guidance along both of the TE and TM polarizations. The near-field mode distribution of the waveguide shows reasonable agreement with the simulated modal profile. After thermal annealing treatment at 260 °C in air, the propagation loss of waveguide is reduced to as low as 0.8 dB/cm.

Keywords: Optical waveguide; Ion irradiation; SrTiO3 crystal

Related publications

Publ.-Id: 18800

Microbial communities in flooded underground uranium mines of East Germany

Gagell, C.; Röske, K.; Arnold, T.

After the German reunification the Wismut GmbH, formerly the 3rd largest U producer of the world, started to remediate the legacies of their U mining activities. As a part of the remediation strategy, the pit body was flooded to induce reductive processes. Although flooding of the mines Pöhla and Schlema-Alberoda was already finished about ten years ago, the mine water still contains elevated concentrations of toxic metals such as U, As and Ra. Thus, expensive and long-lasting monitoring and waste water treatment is required. Since microorganisms can influence the toxicity of metals directly or indirectly, one alternative approach is to use them for bioremediation (Anderson and Lovley, 1997). To remediate U contaminated sites recent studies mainly focused on the applicaton of dissimilatory Fe(III) and sulfate-reducing microorganisms, which are capable to reduce U(VI) to U(IV) thus resulting in a decreased U mobility (Lovley and Philips, 1992; Lovley et al., 1993). Here, the diversity of the indigenous microbial community of the mine water from Pöhla, Schlema-Alberoda and an older uranium mine site, Zobes, is reported. Bacteria as well as Archaea were analyzed by state-of-the-art pyrosequencing of the 16S rRNA gene. Mine water samples were either filtrated (10 l) or harvested from an in situ flow cell. For the Zobes site natural biofilms grown on activated carbon were also collected. The analysis of the bacterial diversity of the Pöhla mine water resulted in 1196 sequences which represent members of the Proteobacteria, Verrumicrobia, Bacteriodetes, WS3, Chloroflexi, Firmicutes, Acidobacteria, SR1, Actinobacteria, Spirochaetes and OD1. For the Schlema-Alberoda mine water 1915 sequences were analysed which were divided into the nine following phyla Proteobacteria, Acidobacteria, WS3, Bacteriodetes, Chloroflexi, SR1, Chlorobi, TM7 and Actinobacteria. In comparison to the mine water of Pöhla and Schlema-Alberoda the bacterial composition of the Zobes mine water is very similar. The dominant bacterial phylum in all samples is the Proteobacteria. Interestingly, the analysis of biofilm samples of Zobes revealed a different bacterial community compared to the respective mine water. Geobacter, a known Fe(III)-reducing and U(VI)-reducing bacterium, was found to be the dominating genus in the bacterial biofilm community. For the investigation of the archaeal diversity of the mine water a dataset of 33658 (Pöhla), 19184 (Schlema-Alberoda) and 11401 (Zobes) sequences was analysed. In all samples the archaeal sequences mainly represent the three classes of Methanobacteria, Thermoprotei and Methanomicrobia.

Keywords: microbial community; diversity; uranium

  • Poster
    2nd International Conference on Microbial Diversity, 23.-25.10.2013, Turin, Italy
  • Contribution to proceedings
    2nd International Conference on Microbial Diversity, 23.-25.10.2013, Turin, Italy

Publ.-Id: 18799

Bacterial and archaeal community in a flooding uranium mine, Königstein (Germany)

Zirnstein, I.; Arnold, T.; Röske, K.; Röske, I.

The former uranium mine Königstein in Germany is currently in the process of remediation and represents an underground acid mine drainage (AMD) environment. Due to technical leaching with sulphuric acid, the mine water is characterized by low pH, high concentrations of toxic heavy metals and uranium (up to 3×10-4 M) (Arnold et al. 2011). Biofilms in the Königstein mine grew underground in the mine galleries in a depth of 250 m (50 above sea level) either as stalactite-like slime communities (snotites) or as acid streamers in the drainage channels (Zirnstein et al. 2012). Since 2010 the underground mine is no longer accessible because of flooding. Biomass of the mine water community was retrieved by three different in-situ systems: vacuum filtration of the mine water, flow cell with slides and reactor with PE carrier. The diversity of the planktonic microorganisms and of the biofilms of the Königstein samples of two consecutive years were characterized by catalysed reporter deposition fluorescence in-situ hybridization (CARD-FISH) and a bar-coded pyrosequencing approach.
The identified microbial communities showed low diversity. 24,630 archaeal sequences and 5,706 bacterial sequences could be classified into 5 classes (archaea) and 13 phyla (bacteria) including candidate divisions. CARD-FISH analysis showed that Bacteria were more abundant than Archaea. The dominating phylum of bacteria was Proteobacteria, especially Alphaproteobacteria and Gammaproteobacteria. Furthermore, sequences of Actinobacteria, Nitrospira, Firmicutes, Bacteroidetes, Verrucomicrobia, Acidobacteria, Chlorobi, Chloroflexi, Planctomyces, OD1, TM7 and Gemmatimonadetes were found. Most of the archaeal sequences belong to the class Thermoplasmata, especially Ferroplasma sp..
The obtained results for the microbial community in the flooded mine site is completely different in comparison to the microbial community observed in the underground environment before flooding. Before flooding the mine galleries were dominated by biofilms composed predominantly of Betaproteobacteria affiliated with Ferrovum myxofaciens, also designated “Ferribacter polymyxa”. Knowing more about the acidophiles in former uranium mines helps to explain how microorganisms live in such extreme environments and how they affect the water chemistry and how to use them for biomining and bioleaching technologies.

Keywords: microbial community; diversity; pyrosequencing

  • Poster
    2nd International Conference on microbial diversity, 23.-25.10.2013, Torino, Italy

Publ.-Id: 18798

Magneto-optical analysis of stripe elements embedded in a synthetic antiferromagnet

Langer, M.; Neudert, A.; Mönch, J. I.; Mattheis, R.; Lenz, K.; Fassbender, J.; McCord, J.

Domain structures and magnetic reversals of ferromagnetic micron stripe patterns embedded in an interlayer exchange coupled Co90Fe10 trilayer acting as a synthetic antiferromagnet were investigated. The patterning was achieved by means of ion irradiation through a lithographically processed mask, which changes the irradiated parts into ferromagnetic elements. The embedded stripes fabricated by this technique have been investigated and compared to stripes patterned by reactive ion etching. Using Kerr microscopy the domain structure and the shape of the magnetic reversal have been studied. Observed differences in the switching behavior will be explained by modifications of the magnetic material properties, e.g. anisotropy and saturation magnetization due to the ion irradiation. Irradiated 2 µm wide stripes show a collective switching with quasi-domains during the magnetic reversal. In this process interactions of the transversal magnetization component with the adjacent non-irradiated antiferromagnetically coupled trilayers are observed. Two possible mechanisms suspected to mediate these interactions are discussed. On the one hand a slight opening of the coupling angle between magnetization in top and bottom layer in the antiferromagnetic stripes leading to an effective magnetic moment. On the other hand a domain wall with its extended tail at the boundary between the two different kinds of stripes. The investigations are supported by micromagnetic simulations.

Keywords: magnetic patterning; Kerr microscopy; magnetic domains; magneto-optics; magnetic reversal; Co90Fe10; magnetic anisotropy

Related publications

Publ.-Id: 18797

Multiphase flow analysis using a compact gamma-ray CT system

Bieberle, A.; Härting, H.-U.; Schubert, M.; Hampel, U.

A new compact high-resolution gamma-ray computed tomography measurement system (CompaCT) has been developed for the determination of phase fraction distributions in multiphase flows occurring in technical devices with dense housings and inlets. The obtained data is used to understand fundamental physics behind flow processes and to validate flow simulation codes. The CompaCT contains a 137Cs isotopic source and a gamma-ray detector arc, whose single detectors are thermally stabilized. The entire analogue and digital signal processing are implemented within the detector arc. As examples, performance studies of qualitative and quantitative phase structure determination were accomplished in a steel rod bundle and a fixed bed reactor assembly.

Keywords: gamma-ray; computed tomography; multiphase flow

  • Contribution to proceedings
    7th World Congress on Industrial Process Tomography, 02.-05.09.2013, Krakau, Polen
  • Poster
    7th World Congress on Industrial Process Tomography, 02.-05.09.2013, Krakau, Polen

Publ.-Id: 18796

Fluorescence Resonance Energy Transfer by S-layer coupled fluorescence dyes

Weinert, U.; Pollmann, K.; Raff, J.

In this paper two fluorescence dyes were coupled to surface layer (S-layer) proteins of Lysinibacillus sphaericus A12 and Lysinibacillus sphaericus B53 to easily generate a fluorescence resonance energy transfer (FRET). S-layer proteins are structure proteins which self-assemble in aqueous solutions, on surfaces and at interfaces forming 2D-paracrystalline structures with a defined symmetry in nanometer range. These properties and the fact, that a lot of modifiable functional groups are available on their surface, make them a perfect coating and binding matrix for the generation of functionalized surfaces, e.g. needed for a sensor assembly. Here we chemically link two fluorescence dyes, which are able to perform a FRET, to S-layer proteins by carbodiimide-crosslinking chemistry. Fluorescence dyes were coupled to the protein with a yield of around 54 mol%, demonstrating a modification of every second protein monomer if fluorescence dyes are statistical distributed. A FRET could be detected between the two fluorescence dyes when linked to protein polymers whereas no FRET could be detected if fluorescence dyes are linked to protein monomers. This demonstrates, that the polymer structure is essential for FRET and that fluorescence dyes are statistical distributed on protein polymers with a close proximity of donor and acceptor dye. Due to the fact that the used S-layer proteins build a unit cell of p4 symmetry, it can be assumed that two fluorescence dyes are linked to one unit cell. In this paper the FRET pair arrangement and its optimization is described in which the FRET efficiency can be increased from 6 to 40 %, simple by varying the molar ratio of donor: acceptor. In result a sensory surface can be generated and used for detection of numerous substances in water like pharmaceuticals or heavy metals.

Keywords: Fluorescence Resonance Energy Transfer; Surface layer proteins; EDC; chemical modification; sensory layers; detection

Publ.-Id: 18795

Compact high-resolution gamma-ray computed tomography system for multiphase flow studies

Bieberle, A.; Nehring, H.; Berger, R.; Arlit, M.; Härting, H.-U.; Schubert, M.; Hampel, U.

In this paper, a compact high-resolution gamma-ray Computed Tomography (CompaCT) measurement system for multiphase flow studies and tomographic imaging of technical objects is presented. Its compact and robust design makes it particularly suitable for studies on industrial facilities and outdoor applications. Special care has been given to thermal ruggedness, shock resistance and radiation protection. Main components of the system are a collimated 137Cs isotopic source, a thermally stabilised modular high-resolution gamma-ray detector arc with 112 scintillation detector elements and a transportable rotary unit. The CompaCT allows full CT scans of objects with a diameter of up to 130 mm and can be operated with any tilting angle from 0° (horizontal) to 90° (vertical).

Keywords: computed tomography; gamma-ray tomography; flow measurement; non-destructive testing

Publ.-Id: 18794

Uranium(VI) sorption on montmorillonite at high ionic strengths

Fritsch, K.; Schmeide, K.

The current results of sorption and leaching experiments on montmorillonite in NaCl, KCl, and CaCl2 solutions of high ionic strength are presented.

Keywords: uranium sorption; argillaceous rock; clay; uranium; montmorillonite; high ionic strength

  • Lecture (others)
    4. Workshop des Verbundprojekts „Rückhaltung endlagerrelevanter Radionuklide im natürlichen Tongestein und in salinaren Systemen“, 12.04.2013, Karlsruhe, Deutschland

Publ.-Id: 18793

Nonlinear PT−symmetric plaquettes

Guenther, U.; Kevrekidis, P.; Li, K.; Malomed, B.

Nonlinear coupled gain-loss oscillator oligomers (plaquettes) of 4-node and 5-node type in a 2D-plane are studied. Their specific PT-symmetry properties are investigated, the occurrence of exceptional points (up to third-order) as well as their various nonlinear dynamical regimes.
based on: J Phys A 45 (2012) 444021

Keywords: PT-symmetry; coupled nonlinear oscillators; gain-loss regimes; exceptional points; PT phase transitions

  • Invited lecture (Conferences)
    Light-matter Interaction: Focus on Novel Observable non-Hermitian Phenomena. A Batsheva de Rothschild Seminar & ISF - Israel Science Foundation workshop., 21.-26.04.2013, Kibbutz Ein-Gedi, Israel

Publ.-Id: 18792

„risk management and the European Market Infrastructure Regulation (emir)”

Stiller, D.; Dammert, C.; Joehnk, P.


  • Invited lecture (Conferences)
    International Doctoral Seminar 2013, 13.-15.05.2013, Dubrovnik, Croatia

Publ.-Id: 18791

The impact of electromagnetic stirring on grain refinement and the mechanical properties of AlSi alloys

Räbiger, D.; Krößig, C.; Eckert, S.; Gerbeth, G.

The adjustment of fine grain morphologies has been approved to be a crucial issue for improving characteristics and properties of cast and wrought aluminium alloys. Several methods are known to achieve grain refinement in solidification processes: add-on of grain refiners, rapid cooling conditions, mechanical or electromagnetic stirring, or ultrasonic treatment.
AC magnetic fields provide a contactless method to control the flow inside a liquid metal and the grain size of the solidified ingot. However, the imposition of a rotating (RMF) or a travelling magnetic field (TMF) also causes problems like the occurrence of typical segregation pattern or a deflection of the upper free surface. Previous investigations considered the use of time-modulated rotating magnetic field to control the heat and mass transfer at the solidification front to avoid segregation effects.
This present study examines the directional solidification of AlSi7 alloys from a water cooled copper chill. A rotating magnetic field are used to agitate the melt. Different magnetic field intensities and time-modulated magnetic fields were considered to show the impact of diverse flow conditions on the resulting mechanical properties. The solidified structure was reviewed in comparison to an unaffected solidified ingot. Measurements of the phase distribution, the grain size, the hardness and the tensile strength were realized. Our results reveal the potential of magnetic fields to control the grain size, the formation of segregation freckles and the mechanical properties. In particular, time–modulated rotating fields demonstrated their capability to homogenize both the grain size distribution and the corresponding mechanical properties.

Keywords: grain refinement; mechanical properties; tailored magnetic field

  • Poster
    3rd International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining, 20.-23.05.2013, Hanasaari, Finnland

Publ.-Id: 18790

"after the Crisis: lessons learned? Responsibility and ethics of managers in large companies"

Joehnk, P.

Verantwortung und Moral der Manager in großen Unternehmen

  • Lecture (Conference)
    International Doctoral Seminar 2013, 13.-15.05.2013, Dubrovnik, Croatia

Publ.-Id: 18789

pK+Λ final state: towards the extraction of the ppK contribution

Fabbietti, L.; Agakishiev, G.; Behnke, C.; Belver, D.; Belyaev, A.; Berger-Chen, J. C.; Blanco, A.; Blume, C.; Böhmer, M.; Cabanelas, P.; Chernenko, S.; Dritsa, C.; Dybczak, A.; Epple, E.; Fateev, O.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garz´On, J. A.; Gill, K.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Höhne, C.; Holzmann, R.; Huck, P.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krasa, A.; Krebs, E.; Krizek, F.; Kuc, H.; Kugler, A.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lang, S.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.

The reaction p(@3.5GeV) + p -> p + Λ + K+ can be studied to search for the existence of kaonic bound states like ppK− leading to this final state. This effort has been motivated by the assumption that in p+p collisions the (1405) resonance can act as a doorway to the formation of the kaonic bound states. The status of this analysis within the HADES collaboration, with particular emphasis on the comparison to simulations, is shown in this work and the deviation method utilized by the DISTO collaboration in a similar analysis is discussed. The outcome suggests the employment of a partial wave analysis to disentangle the different contributions to the measured pK+Λ final state.

Publ.-Id: 18787

Magnetic field controlled floating-zone single crystal growth of intermetallic compounds

Herrmann, R.; Gerbeth, G.; Priede, J.

Radio-frequency (RF) floating zone single crystal growth is an important technique for the preparation of single bulk crystals. The advantage of the floating-zone method is the crucible-free growth of single crystals of reactive materials with high melting points. The strong heat diffusion on the surface, as well as the melt convection in the molten zone due to induction heating, often leads to an undesired solid-liquid interface geometry with a concave (towards the solid phase) outer rim. These concave parts aggravate the single crystal growth over the full cross-section. A two-phase stirrer was developed at IFW Dresden in order to avoid the problems connected with these concave parts. It acts as a magnetic field pump and changes the typical double vortex structure to a single roll structure, thus pushing hot melt into the regions where the concave parts may arise. The current in the secondary coil is induced by the primary coil, and the capacitor and the resistance of the secondary circuit are adjusted to get a stable 90 degree phase-shift between the coil currents. Single crystal growth of industrial relevant RuAl and TiAl intermetallic compounds was performed based on the material parameters and using the adjusted two-phase stirrer. Very recently, the magnetic system was applied to the crystal growth of biocompatible TiNb alloys and antiferromagnetic Heusler MnSi compounds.

Publ.-Id: 18786

Silicon nanodot Formation and self-ordering under bombardment with heavy Bi3 ions

Böttger, R.; Heinig, K.-H.; Bischoff, L.; Liedke, B.; Hübner, R.; Pilz, W.

Si nanodots of high density and hexagonal short-range order are observed upon normal-incidence bombardment of hot, crystalline Si with Bi3+ ions having a kinetic energy of a few tens of keV. The heights of nanodots are comparable to their widths of ~20 nm. The implanted Bi accumulates in tiny Bi nanocrystals in a thin Si top layer which is amorphous due to implantation damage. Light and heavy ions up to Xe cause smoothing of surfaces, but Bi3+ ions considered here have a much higher mass. Atomistic simulations prove that each Bi3+ impact deposits an extremely high energy density resulting in a several nanometer large melt pool, which resolidifies within a few hundreds of picoseconds. Experiments confirm that dot patterns form only if the deposited energy density exceeds the threshold for melting. Comparing monatomic and polyatomic Bi ion irradiation, Bi–Si phase separation and preferential ion erosion are ruled out as driving forces of pattern formation. A model based on capillary forces in the melt pool explains the pattern formation consistently.

Keywords: silicon; polyatomic ions; melting; nanodots; ion bombardment

Related publications

Publ.-Id: 18785

High-Speed PIXE – schnelle Multielementanalyse mit Ionenstrahlen

Ziegenrücker, R.; Hanf, D.; Gutzmer, J.; Ihle, S.; Merchel, S.; Renno, A. D.; Rugel, G.; Scharf, O.; Buchriegler, J.

Das Helmholtz-Institut Freiberg für Ressourcentechnolgie (HIF @ HZDR) entwickelt unter dem Schlagwort „Ressourcenanalytik“ neue Analysemethoden, um Technologien zur Erkundung, Gewinnung, Nutzung und dem Recycling von Rohstoffen entlang der Wertschöpfungskette zu bewerten und zu verbessern. Eines dieser neuen Verfahren ist eine weltweit unikale High-Speed PIXE, das ist die schnelle ortsaufgelöste Teilchen-induzierte Röntgenemissionspektrometrie (PIXE = Particle-Induced X-ray Emission). Mittels High-Speed PIXE wird die elementare Zusammensetzung großformatiger Erzproben in kurzer Zeit (min-h) quantitativ bestimmt. Neben den für die Ressourcentechnologie wichtigen geologischen und aufbereitungstechnischen Proben, sind Materialanalysen möglich und bei entsprechender Probenvorbereitung, da die Messung im Vakuum erfolgt, auch biologische oder medizinische Proben analysierbar.
Im Gegensatz zur Elektronen-induzierten EDX (EDX = Energy dispersive X-ray spectrometry) wird die spezifische Röntgenstrahlung bei der PIXE mit Protonen angeregt. Ein 6 MV Tandem-Teilchenbeschleuniger[1] erzeugt Protonen mit einer Energie von 4,2 MeV. Der 2 bis 3 mm große Teilchenstrahl wird anschließend aufgeweitet und regt simultan alle Atome über einer Probenfläche von 12x12 mm² an. Die dabei entstehende Röntgenstrahlung ist für die enthaltenen Elemente charakteristisch und kann quantitativ ausgewertet werden. Für die ortsaufgelöste Detektion wird eine sogenannte Röntgenfarbkamera SLcam®[2] verwendet, bestehend aus einer speziellen Röntgenkapillaroptik, die am IFG (IFG = Institut for Scientific Instruments) in Berlin entwickelt wurde in Verbindung mit einer pnCCD der Firma PNSensor. Der Detektorchip dieser Kamera ist aus 69696 48x48 µm² großen Pixeln aufgebaut, die alle ein komplettes energieaufgelöstes Röntgenspektrum messen können.
In der Abbildung sind mit der High-Speed PIXE gemessene Element-verteilungsbilder mit einer lateralen Ortsauflösung von 50 µm (bis ~10 µm möglich) dargestellt; links kumulativ alle Röntgenphotonen und rechts nur die K-alpha- und K-beta-Linien von As. Im Moment können alle Elemente ab Mg und zukünftig sogar ab B mit elementspezifischen Nachweisgrenzen bis in den µg/g-Bereich detektiert werden.


[1] S. Akhmadaliev et al., Nucl. Instr. Meth. B 294 2013, doi:10.1016/j.nimb.2012.01.053
[2] O. Scharf et al., Analyt. Chem. 83 2011, doi: 10.1021/ac102811p

Keywords: High-Speed PIXE; multi-element analysis; particle-induced X-ray emission; X-ray colorcam; X-ray-optics

Related publications

  • Poster
    Wissenschaftsforum Chemie 2013, 01.-04.09.2013, Darmstadt, Deutschland

Publ.-Id: 18784

Synthesis and radiopharmacological characterisation of a fluorine-18 labelled azadipeptide nitrile as potential PET Tracer for in vivo imaging of cysteine cathepsins

Löser, R.; Bergmann, R.; Frizler, M.; Mosch, B.; Dombrowski, L.; Kuchar, M.; Steinbach, J.; Gütschow, M.; Pietzsch, J.

A fluorinated cathepsin inhibitor based on the azadipeptide nitrile chemotype was prepared and selected for PET tracer development owing to its high affinity for the oncologically relevant cathepsins L, S, K and B. Labelling with fluorine-18 was accomplished in an efficient and reliable two-step, one-pot radiosynthesis using 2-[18F]fluoroethyl nosylate as prosthetic agent. The pharmacokinetic properties of the resulting radiotracer compound were studied in vitro, ex vivo and in vivo in normal rats by radiometabolite analysis and small animal positron emission tomography (PET). These investigations revealed the rapid conjugate formation of the tracer with glutathione in the blood associated with a slow blood clearance. The potential of the developed 18F-labelled probe to image tumour-associated cathepsin activity was investigated by dynamic small-animal PET imaging in nude mice bearing tumours derived from the human NCI-H292 lung carcinoma cell line. Computational analysis of the obtained image data indicated the time-dependent accumulation of the radiotracer in the tumours. The expression of the target enzymes in the tumours was confirmed by immunohistochemistry using specific antibodies. This indicates that azadipeptide nitriles have the potential to target thiol-dependent cathepsins in vivo despite their disadvantageous pharmacokinetics.

Keywords: cathepsins; glutathione; molecular imaging; small animal positron emission tomography; tumour-associated proteolysis

Publ.-Id: 18783

Use of 3-[18F]fluoropropanesulfonyl chloride as prosthetic agent for the radiolabelling of amines: Investigation of precursor molecules, labelling conditions and enzymatic stability of the corresponding sulfonamides

Löser, R.; Fischer, S.; Hiller, A.; Köckerling, M.; Funke, U.; Maisonial, A.; Brust, P.; Steinbach, J.

3-[18F]fluoropropanesulfonyl chloride, a recently proposed prosthetic agent for fluorine-18 labelling, was prepared in a two-step radiosynthesis via 3-[18F]fluoropropyl thiocyanate as intermediate. Two benzenesulfonate-based radiolabelling precursors were prepared by various routes. Comparing the reactivities of 3-thiocyanatopropyl nosylate and the corresponding tosylate towards [18F]fluoride the former proved to be superior accounting for labelling yields of up to 85%. Conditions for a reliable transformation of 3-[18F]fluoropropyl thiocyanate to the corresponding sulfonyl chloride with the potential for automation have been identified. The reaction of 3-[18F]fluoropropanesulfonyl chloride with eight different aliphatic and aromatic amines was investigated and the identity of the resulting 18F-labelled sulfonamides was confirmed chromatographically by comparison with their non-radioactive counterparts. Even for weakly nucleophilic amines such as 4-nitroaniline the desired radiolabelled sulfonamides were accessible in satisfactory yields owing to systematic variation of the reaction conditions. With respect to the application of the 18F-fluoropropansulfonyl group to the labelling of compounds relevant as imaging agents for positron emission tomography (PET), the stability of N-(4-fluorophenyl)-3-fluoropropanesulfonamide against degradation catalyzed by carboxylesterase was investigated and compared to that of the analogous fluoroacetamide.

Keywords: fluorine-18; hydrolytic metabolism; prosthetic groups; radiochemistry; sulfonamides

Publ.-Id: 18782

Experimental Study of the 22Ne(p,γ)23Na Reaction and its Implications for Novae Scenarios

Menzel, M.-L.

The 22Ne(p,γ)23Na reaction belongs to the catalytic neon-sodium cycle and has an important role in the explosive hydrogen burning. The neon-sodium cycle takes place at temperatures of T = 0:1 - 0:5GK and is assumed to occur in different astrophysical systems: e.g. in novae, in super novae of type Ia and during the shell-burning of red giant branch stars.

The implications of 22Ne(p,γ)23Na and the neon-sodium cycle in a nova scenario have been studied by using the nuclear network code libnucnet at GSI in Darmstadt. A nova is an outburst of matter in a binary system consisting of a white dwarf and a red giant star. It is therefore a representative phenomenon for explosive hydrogen burning. For the calculation of the nucleosynthesis during the nova outburst, the code libnucnet requires the initial mass composition of the novae partners, the temperature and density proles of the nova explosion and the thermonuclear reaction rates of the participating reactions. In the following, the code determined the ow and the nal atomic abundance in the neon-sodium cycle during the entire nova process. Additionally, the in uence of the temperature prole of the novae outburst as well as the thermonuclear reaction rate of the 22Ne(p,γ)23Na reaction on the nal atomic abundance in the outburst has been studied.

A characteristic measure for the reactions in astrophysical environments is the thermonuclear reaction rate. The reaction rate of 22Ne(p,γ)23Na has still strong uncertainties in the temperature range of T = 0:03-0:3 GK. These uncertainties are based on insucient upper limits of the resonance strengths as well as the possible existence of tentative states that are populated in the energy range of Elab p = 30 - 300 keV. The research presented in this thesis is dedicated to the experimental study of the 22Ne(p,γ)23Na reaction for an improved determination of the thermonuclear reaction rate. Furthermore, the implications of 22Ne(p,γ)23Na and the neon-sodium-cycle in novae scenarios are discussed. The data taking has been performed at the Laboratori Nazionali del Gran Sasso, Italy. This laboratory provides the LUNA facility (Laboratory for Underground Nuclear Astrophysics) for the measurement of small reaction cross sections. The LUNA facility includes a 400 kV ion accelerator, a windowless gas target system and a HPGe-detector. Based on the measurements of the 22Ne(p,γ)23Na reaction at LUNA, upper limits for the strengths of ve isolated resonances in the energy range of Elab p = 150 - 340 keV have been determined.

For the nuclear resonance at Elab res = 186 keV, a positive resonance strength has been measured for the rst time in literature.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-034 2013
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 18781

Strömungsprofilmessungen mittels PIV-Verfahren an einem Stabbündel

Franz, R.; Dominguez-Ontiveiro, E.; Barth, T.; Drapeau-Martin, S.; Hampel, U.

Umströmte Rohr- bzw. Stabbündel sind als Übertrager von Wärmeenergie in einem breiten Spektrum von Anwendungsgebieten zu finden. Beispiele sind Heizkörper, Kühlaggregate, Heizpatronen, industrielle Wärmetauscher und Brennelemente in Kernreaktoren. Für jede dieser Anwendungen besteht die Anforderung, die Wärmeübertragung an den Wärmeübertragerflächen zu optimieren. Dabei besteht eine enge Kopplung zwischen Wärmetransport und Strömungsstruktur. Eine besonders effiziente Form der Wärmeübertragung ist die Verdampfung. Diese wird unter anderem bei Brennelementen in Druckwasserreaktoren genutzt. Hier siedet das Kühlwasser an der Brennstaboberfläche. Durch Kondensation der Dampfblasen in der unterkühlten Kernströmung wird die Wärme dann effizient in die Flüssigphase übertragen. Durch die hohe Verdampfungsenthalpie des Wassers wird beim Strömungssieden ein viel höherer Wärmestrom in das Kühlwasser übertragen, als bei rein einphasig-konvektivem Wärmetransport. Sicherheitstechnisch relevant für Brennelemente in Leichtwasserreaktoren ist der Übergang vom Blasensieden zum Filmsieden (kritischer Wärmestrom). Dieser muss unter allen Umständen vermieden werden, um die Integrität der Brennstabhüllen zu gewährleisten, die bei Überschreiten der kritischen Heizflächenbelastung aufschmelzen bzw. reißen können. Aus diesem Grund werden im Rahmen eines vom Bundesministerium für Bildung und Forschung geförderten Projektes (Förderkennzeichen 02NUK010A) numerische Strömungsberechnungsmodelle entwickelt, die bei der Beschreibung und numerischen Behandlung der Siedephänomene helfen sollen. Zur Validierung dieser Modelle anhand von Experimenten wurde ein Strömungskanal konstruiert, in dem ein vertikales Stabbündel von einem Kältemittel (RC318) aufwärtig durchströmt wird. Der Versuchsstand ist so konzipiert, dass ein optischer und messtechnischer Zugang zu den umströmten Einbauten gegeben ist. Damit sind Messungen in Zweiphasenströmungen ebenso möglich, wie Untersuchungen zur einphasigen Durchströmung. Für später erfolgende Zweiphasen-Experimente mit Stabbeheizung wurden zunächst Voruntersuchungen zur einphasigen Durchströmungen durchgeführt, welche insbesondere Aufschluss über die Homogenität der Strömung in den Unterkanälen sowie die Existenz von Querströmungen geben sollten. Als Messverfahren dafür wurde die Particle Image Velocimetry (PIV) ausgewählt, welche es ermöglicht, zweidimensionale Strömungsfelder aufzuzeichnen. Die experimentellen Studien erfolgten am Optical Multi-Phase Flow Research Laboratory des Nuclear Engineering Department der Texas A&M University in College Station, USA.
Die Untersuchungen wurden für drei Volumenstromraten durchgeführt. Der vorliegende Bericht umfasst die Beschreibung des Versuchsstandes und der Messmethodik, eine Vorstellung des Auswerteverfahrens und relevanter Ergebnisse sowie eine Fehlerbetrachtung.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-033 2013
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 18780

Entwicklung und Validierung von Modellen für Blasenkoaleszenz und -zerfall

Liao, Y.; Lucas, D.

Ein neues, verallgemeinertes Modell für Blasenkoaleszenz und –zerfall wurde entwickelt. Es basiert auf physikalischen Überlegungen und berücksichtigt verschiedene Mechanismen, die zu Blasenkoaleszenz und –zerfall führen können. In einer ausführlichen Literaturrecherche wurden zunächst die verfügbaren Modelle zusammengestellt und analysiert. Es zeigte sich, dass viele widersprüchliche Modelle veröffentlicht wurden. Keins dieser Modelle erlaubt die Vorhersage der Entwicklung der Blasengrößenverteilungen entlang einer Rohrströmung für einen breiten Bereich an Kombinationen von Volumenströmen der Gas- und der Flüssigphase.
Das neue Modell wurde ausführlich in einem vereinfachten Testsolver untersucht. Dieser erfasst zwar nicht alle Einzelheiten einer sich entlang des Rohres entwickelten Strömungen, erlaubt aber im Gegensatz zu den CFD-Simulationen eine Vielzahl von Variationsrechnungen zur Untersuchung des Einflusses einzelner Größen und Modelle. Koaleszenz und Zerfall kann nicht getrennt von anderen Phänomenen und Modellen, die diese widerspiegeln, betrachtet werden. Es bestehen enge Wechselwirkungen mit der Turbulenz der Flüssigphase und dem Impulsaustausch zwischen den Phasen. Da die Dissipationsrate der turbulenten kinetischen Energie ein direkter Eingangsparameter für das neue Modell ist, wurde die Turbulenzmodellierung besonders genau untersucht.
Zur Validierung des Modells wurde eine TOPFLOW-Experimentalserie zur Luft-Wasser-Strömungen in einem 8 m langen DN200-Rohr genutzt. Die Daten zeichnen sich durch eine hohe Qualität aus und wurden im Rahmen des TOPFLOW-IIVorhabens mit dem Ziel eine Grundlage für die hier vorgestellten Arbeiten zu liefern, gewonnen. Die Vorhersage der Entwicklung der Blasengrößenverteilung entlang des Rohrs konnte im Vergleich zu den bisherigen Standardmodellen für Blasenkoaleszenz und -zerfall in CFX deutlich verbessert werden. Einige quantitative Abweichungen bleiben aber bestehen.
Die vollständigen Modellgleichungen sowie eine Implementierung über „User-FORTRAN“ in CFX stehen zur Verfügung und können für weitere Arbeiten zur Simulation polydisperser Blasenströmungen genutzt werden.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-032 2013
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 18779

Annual Report 2012 - Institute of Ion Beam Physics and Materials Research

Cordeiro, A. L.; Fassbender, J.; Heera, V.; Helm, M.

In 2012 the HZDR, and in consequence also the Institute of Ion Beam Physics and Materials Research (IIM) including its Ion Beam Center (IBC), has undergone a scientific evaluation. The evaluation committee composed of the Scientific Advisory Board and numerous external experts in our field of research concluded that “the overall quality of the scientific work is excellent”, that “there are an impressive number of young scientists working enthusiastically on a variety of high-level projects” and that “the choice of these projects represents a clear underlying strategy and vision”. We feel honored and are proud that the external view on our scientific achievements is that extraordinary. In view of this outstanding result we would like to express our gratitude to all our staff members for their commitment and efforts!
In the past year, we continued our integration into the Helmholtz Association of German Research Centers (HGF) with our Institute mostly active in the research area “Matter”, but also involved in a number of activities in the research area “Energy”. In this respect, many consultations were held with the Helmholtz centers contributing to common research areas to precisely define the role we will play in the newly established HGF program “From Matter to Materials and Life” (see schematic below). Our IBC has been recognized as a large-scale user facility for ion beam analysis and modification of materials, i.e., specializing on materials science. In particular, the IBC plays a prominent role in the recently approved Helmholtz Energy Materials Characterization Platform (HEMCP), which mainly concentrates on the development of dedicated analytical tools for the characterization of materials required for future energy technologies. The successes achieved by the IBC allows us to invest 7200 k€ to further improve and strengthen the ion beam capabilities at the Institute. In addition to this infrastructure-related grant, we were also successful in our funding application for the establishment of the International Helmholtz Research School for Nanoelectronic Networks (IHRS NANONET), aiming at promoting the next generation of leading scientists in the field of nanoelectronics. The IHRS NANONET is coordinated by our Institute and offers a well-structured PhD program to outstanding students of all nationalities with emphasis on interdisciplinary research and comprehensive training in technical and professional skills.

Related publications

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-031 2013
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 18778

Annual Report 2012 - Institute of Resource Ecology

Brendler, V.; Foerstendorf, H.; Bok, F.; Richter, A.; (Editors)

The Institute of Resource Ecology (IRE) is one of the currently eight institutes of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The research activities are fully integrated into the program “Nuclear Safety Research” of the Helmholtz Association and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”. With the integration of the division of “Reactor Safety” from the former “Institute of Safety Research” nuclear research at HZDR is now mainly concentrated within this institute.
In addition, various activities have been started investigating chemical and environmental aspects of processing and recycling of strategic metals, namely rare earth elements. Here, a knowledge transfer from the nuclear to the non-nuclear community, branching thermodynamics and spectroscopy, has been established. This also strengthens links to the recently established “Helmholtz-Institute Freiberg for Resource Technology”.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-030 2013
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 18777

Nanomaterialien – Einsatz in der Tumordiagnostik und Therapie

Stephan, H.

kein Abstract verfügbar

  • Invited lecture (Conferences)
    Kolloquium, Hochschule Zittau/Görlitz (FH), 08.05.2013, Zittau, Deutschland

Publ.-Id: 18776

Tumor imaging using copper-64 labeled peptides

Stephan, H.

kein Abstract verfügbar

  • Invited lecture (Conferences)
    Seminar, Beijing Normal University, College of Chemistry, 19.04.2013, Beijing, China

Publ.-Id: 18775

Instrument V4: Topic 1 - SANS investigation of irradiation-induced defects in RPV steels; Topic 2 - Characterization of nanoparticles in ODS Fe-Cr model alloys

Ulbricht, A.

Topic 1: Hardening combined with embrittlement of the reactor pressure vessel (RPV) due to the neutron irradiation during the operation of a nuclear power plant is one of the most safety-relevant phenomena. So far, design and safe operation have mainly relied on a predominantly empirical approach based on long-term irradiation programs in test reactors as well as on mechanical testing in specialized hot cells. However, the physical mechanism of radiation damage is not yet understood in detail. The microstructure that arise in RPV steels, primarily as a consequence of radiation-enhanced diffusion and defect clustering, are extremely fine-scaled, i.e. in magnitude of few nanometers. Among the experimental methods capable of detecting and characterizing irradiation-induced clusters small-angle neutron scattering is the only technique allowing a statistically representative size distribution of clusters to be calculated.
The measurements carried out on the instrument V4 have contributed to the understanding of the

  • cluster formation under different irradiation conditions (temperature, neutron fluence and flux),
  • effect of impurities and alloying elements on the formation of irradiation-induced clusters,
  • cluster dissolution and/or coarsening after post-irradiation annealing treatments,
  • reirradiation behaviour of materials.
The instrument V4 is particularly suitable for such kind of investigations because of the special equipment – an evacuated sample environment with electromagnet and a 14 position sample changer. This allows measurements with low background noise particularly important for the detection of very small scatterers such as irradiation-induced clusters.
Topic 2: Ferritic-martensitic chromium steels are candidate materials for future application in both Gen-IV fission and fusion technology. In order to improve irradiation-creep properties and to reduce detrimental helium effects oxide-dispersion strengthened (ODS) variants of these steels are of prime interest. Due to the complex microstructures of these ODS steels there is a multitude of hardening features, such as Y2O3 particles, carbides and alpha'-phase particles, that may also affect the brittle-to-ductile transition. Therefore, the fabrication and characterization of dedicated model alloys is an important means in order to separate individual effects and to improve mechanistic understanding.
The quality of the ODS material produced by means of a special procedure of powder metallurgy was checked and characteristics of ODS nanoparticles were determined by SANS.

Keywords: Small-angle neutron scattering; irradiation-induced cluster; reactor pressure vessel steel; Fe-Cr alloy; ODS; nanoparticle

  • Invited lecture (Conferences)
    Review of Neutron Scattering Instruments at BER II, 07.-08.05.2013, Berlin, Deutschland

Publ.-Id: 18774

Short note on the hydrolysis and complexation of neptunium(IV) in HEPES solution

Dahou, S.; Hennig, C.; Moisy, P.; Petit, S.; Scheinost, A. C.; Subra, G.; Vidaud, C.; Den Auwer, C.

The speciation of actinides in environmental or biological media is often difficult to assess because it involves complex media. We would like to report here on the properties of Np(IV) cation in the well known biological HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) buffer medium. HEPES has been targeted because the possibility to use this biological buffer in actinide toxicological studies presents several advantages although the possible effects of concentrated HEPES medium on the hydrolysis of the actinides (in particular at oxidation state +IV) has not been studied yet. A combination of spectrophotometric and EXAFS measurements at the Np L III edge shows that stable hydrolyzed neptunium(IV) clusters are obtained between pH 2.5 and 4. In a second step, in order to better understand the reactivity of these hydrolysis species formed in HEPES, the effect of a strong chelating ligands such as the hydroxamic acid (HA) or desferrioxamine (DFO) siderophores has been also investigated using spectrophotometry and EXAFS. Upon addition of HA or DFO, the hydrolyzed clusters of Np(IV) are unstable and monomeric complexes are formed and yield Np environments that are very similar to that of crystallized Pu-DFOE complex [Al(H2 O)6 ][Pu(DFE)(H2 O)3 ]2 (CF3 SO3 )5 ·10H2 O reported in the literature.

Keywords: Neptunium; HEPAS; EXAFS

Related publications

Publ.-Id: 18773

Comparison of simulations with PHITS and HIBRAC with experimental data in the context of particle therapy monitoring

Rohling, H.; Sihver, L.; Priegnitz, M.; Enghardt, W.; Fiedler, F.

Therapeutic irradiation with protons and ions is advantageous over radiotherapy with photons due to its favorable dose deposition. Additionally, ion beams provide a higher Relative Biological Effectiveness (RBE) than photons. For this reason an improved treatment of deep seated tumors is achieved and normal tissue is spared. However, small deviations from the treatment plan can have a large impact on the dose distribution. Therefore, a monitoring is required to assure the quality of the treatment. Particle Therapy Positron-Emission-Tomography (PT-PET) is the only clinically proven method which provides a non-invasive monitoring of dose delivery. It makes use of the ß+-activity produced by nuclear fragmentation during irradiation. In order to evaluate these PT-PET-measurements, simulations of the ß+-activity are necessary. Therefore, it is essential to know the yields of the ß+-emitting nuclides at every position of the beam path as exact as possible. We evaluated the 3D Monte-Carlo simulation tool PHITS (version 2.30) and the 1D deterministic simulation tool HIBRAC with respect to the production of ß+-emitting nuclides. The yields of the most important ß+-emitting nuclides for carbon, lithium, helium, and proton beams have been calculated. The results were then compared to experimental data obtained at GSI Helmholtzzentrum für Schwerionenforschung Darmstadt, Germany. GEANT4 simulations provide an additional benchmark. For PHITS the impact of different nuclear reaction models, total cross section models and evaporation models on the ß+-emitter production has been studied. In general, PHITS underestimates the yields of positron-emitters and cannot compete with GEANT4 so far. The ß+-emitters calculated with an extended HIBRAC code were in good agreement with the experimental data for carbon and proton beams and comparable to the GEANT4 results. Considering the simulation results and its speed compared with 3D Monte-Carlo tools, HIBRAC is a good candidate for the implementation in clinical routine PT PET.

Keywords: Simulation; Particle Therapy PET; PHITS; HIBRAC

  • Poster
    HITSRS2013 - Heavy Ion in Therapy and Space Radiation Symposium 2013, 15.-18.05.2013, Chiba, Japan
  • Open Access Logo Abstract in refereed journal
    Journal of Radiation Research 55 suppl1(2014), i43-i44
    Online First (2014) DOI: 10.1093/jrr/rrt151

Publ.-Id: 18772

Flüssigmetallbatterien als stationäre Speicher

Weier, T.; Weber, N.; Stefani, F.; Galindo, V.; Seilmayer, M.

Flüssigmetallbatterien, d.h. elektrochemische Hochtemperaturbatterien mit vollständig flüssigem Inventar, werden derzeit als preiswerte Regelenergiespeicher diskutiert. Das ursprünglich auf kleinere Zellen als Bestandteil thermisch regenerierbarer Systeme gerichtete Konzept soll auf Zellen mit Grundflächen im Quadratmeterbereich übertragen werden.

Eine elektrochemische Zelle mit vollständig flüssigem Inventar hat eine Reihe von Vorteilen: bei gut abgestimmten Dichten von Elektrolyt und aktiven Materialien ist die Batterie selbstassemblierend, eine stabile Dichteschichtung bildet sich aus. Die strukturlosen (flüssigen) Elektroden sind für Alterungserscheinungen unanfällig, versprechen somit gute Zyklierbarkeit, die Kinetik an den flüssig-flüssig Phasengrenzen und die Diffusionsprozesse sind vergleichsweise schnell, was hohe Stromdichten ermöglicht. Als aktive Materialien können breit und ökonomisch verfügbare Ausgangsstoffe eingesetzt werden. Natrium-Schwefel und Natrium-Nickelchlorid Zellen teilen eine Reihe der obengenannten Vorteile, erfordern wegen der komplexen Konstruktion jedoch ein beträchtliches Investitionsvolumen. Die Ausnutzung positiver Skaleneffekte ist ein wichtiges Mittel zur Kostensenkung und die einfache Skalierbarkeit eine der grundlegenden Annahmen bei der Entwicklung von Flüssigmetallbatterien.

Hohe Stromdichten und große Phasengrenzflächen resultieren jedoch in erheblichen Zellströmen. Diese generieren Magnetfelder und mithin beträchtliche elektromagnetische Kräfte. Das flüssige Inventar der Zelle kann auf diese elektromagnetischen Einwirkungen mit Instabilitäten reagieren. Eine dieser Instabilitäten ist die Tayler-Instabilität. Sie führt zu einer starken Strömung im Zellvolumen, die in der Lage ist, die Dichteschichtung zu destabilisieren. In der Folge käme es zu einem Direktkontakt der Elektroden und einem Versagen der Zelle. Der Tayler-Instabilität lässt sich durch konstruktive Maßnahmen begegnen, die in der Lage sind, die gewünschte Skalierbarkeit zu gewährleisten.

Keywords: liquid metal battery; Tayler instability; magnetohydrodynamics

  • Poster
    2.Dresdner Konferenz "Zukunft Energie", 28.-29.05.2013, Dresden, Deutschland

Publ.-Id: 18768

Fluid dynamic aspects of large liquid metal batteries

Weier, T.; Weber, N.; Stefani, F.; Galindo, V.; Seilmayer, M.

Liquid metal batteries (LMBs) are currently discussed as a means to provide economic grid-scale energy storage. LMBs are all-liquid electrochemical cells, typically containing an alkali metal as the negative, and a metal or half metal as the positive electrode. Due to their different densities, both metals form distinct horizontal layers separated by a molten salt with a density in between those of both metals. The molten salt acts as the electrolyte. Evidently, LMBs need elevated temperatures to function. However, they have a number of distinct advantages as, to name a few, self-assembly, ease of construction and scalability, high current densities, and potentially very long cycle life.
Due to the completely liquid inventory and the high total cell currents, fluid dynamics plays an important role for the operation of LMBs. We will focus on the occurrence and prevention of fluid dynamic instabilities in LMBs, especially the current driven Tayler instability (TI). Since the density differences between negative electrode and molten salt are typically small, fluid dynamic instabilities can provoke mixing of electrode and electrolyte material leading to an internal shorting of the cell. Both experimental as well as numerical results will be presented and discussed in relation to cell design and choice of active materials.

Keywords: liquid metal battery; Tayler instability; magnetohydrodynamics

  • Lecture (Conference)
    3rd International Conference on Energy Process Engineering, 03.-06.06.2013, Frankfurt am Main, Deutschland
  • Contribution to proceedings
    3rd International Conference on Energy Process Engineering, 03.-06.06.2013, Frankfurt am Main, Deutschland
    Proceedings of the 3rd International Conference on Energy Process Engineering

Publ.-Id: 18767

Theory of thermoelectric transport in layered structures

Hinsche, N. F.; Yavorsky, B. Y.; Mertig, I.; Zahn, P.

The thermoelectric transport properties of layered structures are analyzed by means of first-principles calculations and semi-classical Boltzmann theory. The electronic structure of the systems was calculated by means of a fully relativistic screened Korringa-Kohn-Rostoker Greens function method. The transport properties along in-plane and cross-plane direction were obtained within the relaxation time approximation of the Boltzmann theory.
We studied the change in thermoelectric properties due to symmetry breaking in Si and Si/Ge heterostructures. The anisotropy of the electrical conductivity, the thermopower and the resulting power factor are studied in dependence on doping level, temperature, and strain in [001] and [111] direction. Our results show that tetragonal [1] and rhombohedral [2] distortions have a strong influence on the thermoelectric transport properties.
Furthermore, we investigated the influence of strain and lattice period in Bi2Te3/Sb2Te3-heterostructures which show a remarkable enhancement of the thermoelectric figure of merit compared to the bulk materials [3]. To identify the physical origin, we studied the influence of composition, interfacial strain, and doping in detail. In addition, insights on the Lorenz function, the electronic contribution to the thermal conductivity, and the resulting figure of merit are given [4,5].


[1] N. F. Hinsche, I. Mertig, and P. Zahn, J. Phys.: Cond. Matt. 23, 295502 (2011)
[2] N. F. Hinsche, I. Mertig, and P. Zahn, Thermoelectric transport in strained Si and Si/Ge heterostructures, J. Phys.: Cond. Mat. 24, 275501 (2012)
[3] R. Venkatasubramanian, E. Siivola, T. Colpitts, and B. O’Quinn, Nature 413, 597 (2001)
[4] N. F. Hinsche, B. Yu. Yavorsky, M. Gradhand, M. Czerner, M. Winkler, J. König, H. Böttner, I. Mertig, and P. Zahn, Thermoelectric transport in Bi2Te3/Sb2Te3 superlattices, Phys. Rev. B 86, 085323 (2012)
[5] N. F. Hinsche, I. Mertig, and P. Zahn, Lorenz function of Bi2Te3/Sb2Te3 superlattices, J. Electronic Materials, 10.1007/s11664-012-2279-z (DOI) (2012)

Keywords: Thermo-electric transport; power factor; Seebeck coefficient; electrical conductivity; thermal conductivity; electronic contribution to thermal conductivity; figure of merit; multilayer; strain; Bi2Te3/Sb2Te3; Si(100); Si(111); Si/Ge(111)

  • Invited lecture (Conferences)
    529. WE-Heraeus-Seminar - Thermal transport at the nanoscale, 07.-10.04.2013, Bad Honnef, Deutschland

Publ.-Id: 18766

Spin Nernst Angle: Definition and qualitative Estimate for Cu Alloys

Zahn, P.; Gemming, S.

The spin Nernst effect describes the occurrence of a spin current perpendicular to an applied thermal gradient and the spin quantization axis in a non-magnetic material. To quantify the effect, the spin Nernst angle will be defined in a more general way than in ref. [1]. This allows for a clear separation of the transverse spin current into two opposite contributions proportional to the spin Hall angle and the spin Nernst angle, respectively. Qualitative trends for Cu alloys with 3d, 4d, and 5d defects extending a resonant scattering model by Fert and Levy [2] will be presented.

The work was supported by the Initiative and Networking Fund of the German Helmholtz Association, Helmholtz Virtual Institute MEMRIOX (VH-VI-442).

[1] K. Tauber et al., Phys. Rev. Lett. 109, 026601 (2012)

[2] A. Fert and P.M. Levy, Phys. Rev. Lett. 106, 157208 (2011)

Keywords: Spin-Nernst-effect; spin-caloric; thermo-electric; alloys; defect scattering; spin-orbit coupling; spin-dependent transport phenomena

  • Lecture (Conference)
    DPG Frühjahrstagung, 10.-15.03.2013, Regensburg, Deutschland

Publ.-Id: 18765

The “quiete Goldschmidt” - a mechanochemical, thermoanalytical, and spectroscopic study of selected steps of the aluminothermic reaction

Stößer, R.; Feist, M.; Willgeroth, C.; Emmerling, F.; Menzel, M.; Reuther, H.

The Goldschmidt reaction (2 Al + α-Fe2O3) was investigated both under mechanical and thermal activation by employing a combination of analytical methods such as ESR and Mössbauer spectroscopies, magnetic susceptibility, X-ray powder diffraction (XRD), and thermal analysis (TA). Both the mechanical treatment and the TA runs under air caused the reaction conditions of “quiete redox reactions” due to a retarding effect and enabled a reaction study in a “slow motion mode”. This allowed to establish distinct partial steps of the integral reaction process depending on the intensity of the mechanical impact, the educt composition, the gas phase composition, and, finally, the thermal excitation in the TA runs.

Publ.-Id: 18764

Mössbauer-spectroscopic study of the effect of He+ irradiation on model Fe-Cr alloys

Dubiel, S. M.; Cieslak, J.; Reuther, H.

Effect of 25 keV He ion irradiation on three model Fe100−xCrx alloys (x = 5.8, 10.75 and 15.15) was investigated by means of the conversion electron Mössbauer spectroscopy. A short-range ordering (SRO) parameter concerning a distribution of Cr atoms within the first-two neighbour shells, <α12>, for all three non-irradiated samples was positive, hence indicative of ordering, yet its amplitude, hence the degree of ordering, was decreasing with x. For the samples irradiated to the dose of 1.2·1017 He+/cm2 (7.5 dpa) <α12 > was unaffected for x = 5.8 and 10.75 but its value was negative for x = 15.15 i.e. an irradiation-induced inversion of the SRO-parameter occurred.

Keywords: Mösbauer spectroscopy; Fe–Cr alloys; Short-range ordering; He ion irradiation

Related publications

Publ.-Id: 18763

Cross-Section Measurements of the 86Kr(gamma,n) Reaction to Probe the s-Process Branching at 85Kr

Raut, R.; Tonchev, A. P.; Rusev, G.; Tornow, W.; Iliadis, C.; Lugaro, M.; Buntain, J.; Goriely, S.; Kelley, J. H.; Schwengner, R.; Banu, A.; Tsoneva, N.

We have carried out, for the first time, photodisintegration cross-section measurements on 86Kr using monoenergetic photon beams ranging from the neutron separation energy, Sn = 9.86 MeV, to 13 MeV. We combine our experimental 86Kr(,n)85Kr cross section with results from our recent 86Kr(gamma,gamma) measurement below the neutron separation energy to obtain the complete nuclear dipole response of 86Kr. The new experimental information is used to predict the neutron capture cross section of 85Kr, an important branching point nucleus on the abundance flow path during s-process nucleosynthesis. Our new and more precise 85Kr(n,)86Kr cross section allow us to consider models of asymptotic giant branch (AGB) stars. We find that models of mass smaller than the sun mass, where the 13 C neutron source burns convectively rather than radiatively, represent a possible solution for explaining the highest 86Kr/82Kr ratios observed in meteoritic stardust SiC grains.

Keywords: photodissociation; monoenergetic gamma rays; neutron detection; (gamma; n) cross section; s-process branching point

Related publications

Publ.-Id: 18762

Experimental and numerical study of flow in a precessing cylinder

Albrecht, T.; Gundrum, T.; Stefani, F.

Precession has long been discussed as a complementary energy source for homogeneous dynamo action. To that end, DRESDYN, a large scale, precession driven dynamo experiment, is currently in advanced planning stage at Helmholtz-Zentrum Dresden-Rossendorf. DRESDYN will consist of a variable axis, precessing cylinder of approximately 2m diameter filled with liquid sodium.

Preliminary studies using a 1:6 scale water experiment are currently performed, focussing on laminar-turbulent transition characteristics. A sudden jump in the motor's mesured electrical power suggests transition to occur at a precession rate of $\Gamma = 0.06$. We also conduct Direct Numerical Simulations, although, for the time being, limited to a Reynolds number Re = O(6000), which is ten times smaller than in the water experiment.

At the conference, we will introduce the planned setup of DRESDYN and show first experimental and numerical results for the 1:6 water model.

Keywords: precession; cylinder; DNS; water experiments; DRESDYN

  • Lecture (Conference)
    Bifurcations and Instabilities in Fluid Dynamics 2013, 08.-11.07.2013, Haifa, Israel

Publ.-Id: 18761

Bubble-driven liquid metal flows under the influence of AC magnetic fields

Vogt, T.; Zhang, C.; Andruszkiewicz, A.; Eckert, K.; Odenbach, S.; Eckert, S.; Gerbeth, G.

Mixing of liquid metals is an important issue in many industrial applications. In metallurgy, gas-bubbles are injected into furnaces, ladles or similar melt containing transfer vessels in order to homogenize the melt and their physical and chemical parameters. We present two experimental studies where a mixing enhancement in a gas-stirred ladle is achieved by the use of AC magnetic fields.

  • Lecture (Conference)
    The International Symposium on Electromagnetic Flow Control in Metallurgy, Crystal Growth and Electrochemistry, 25.-27.03.2013, Dresden, Deutschland

Publ.-Id: 18760

Transient Taylor-Görtler vortex flow in a spinning liquid metal

Vogt, T.; Grants, I.; Räbiger, D.; Eckert, S.; Gerbeth, G.

This paper is concerned with a liquid metal flow driven by a rotating magnetic field inside a stationary cylinder. We consider especially the secondary meridional flow during the time when the fluid spins up from rest.
Therefore, we filled a Perspex cylinder with the aspect ratio A=H0/D0=2 with the eutectic alloy GaInSn, which is liquid at room temperature. The filled cylinder is placed concentrically in the magnetic induction system PERM at the Helmholtz-Zentrum Dresden-Rossendorf. The PERM stirrer is equipped with six coils, arranged as pole pairs in order to create a rotating magnetic field with field strength up to 17 mT. The magnetic field frequency was fixed to 50 Hz. The developing flow is investigated experimentally and by direct numerical simulations. The fluid velocities are measured non-intrusively using the ultrasound Doppler velocimetry.
Evolving instabilities in the form of Taylor–Görtler vortices have been observed just above the instability threshold (Ta > 1.5*Tacr). They evolve from local spots near midplane that quickly spread around the whole circumference of the cylinder to form closed rings. Subsequently, the central TG-vortex ring is advected by the secondary flow towards the top or bottom of the vessel. In some cases, the central vortex pair is observed to remain stable at half height of the vessel for a long time. The rotational symmetry may survive over a distinct time even if a first Taylor–Görtler vortex pair has been formed as closed rings along the cylinder perimeter. The transition to a three dimensional flow in the side layers results from the advection or a precession and splitting of the Taylor–Görtler vortex rings. The predictable behaviour of the Taylor–Görtler vortices disappears with increasing magnetic field strength. The numerical simulations agree very well with the flow measurements.

Keywords: Transition; Tayler-Görtler; Vortices

  • Lecture (Conference)
    Bifurcations & Instabilities in Fluid Dynamics - 4th International Symposium, 08.-11.07.2013, Haifa, Israel

Publ.-Id: 18759

Persistent Current Reduction in Metal-Semiconductor FETs With a ZnCoO Channel in an External Magnetic Field

Kaspar, T.; Fiedler, J.; Skorupa, I.; Bürger, D.; Mücklich, A.; Fritzsche, M.; Schmidt, O. G.; Schmidt, H.

Transparent metal-semiconductor field-effect transistors (MESFETs) with a ZnCoO channel have been fabricated by pulsed laser deposition on c-plane sapphire substrates at a temperature of 550 degrees C. The paramagnetic properties have been confirmed by magnetotransport measurements on undepleted ZnCoO films without Schottky gate contacts.
The Au/AgxO Schottky gate contacts were processed by optical lithography and metallization. Below 50 K, the MESFET characteristics are persistently changed from a low resistance state (LRS) to high resistance state by an external magnetic field. The MESFET can be switched back into the LRS only by heating it up to room temperature.

Keywords: metal-semiconductor field-effect transistor

Related publications

Publ.-Id: 18758

Electromagnetic flow control in poor conductors

Albrecht, T.; Stiller, J.; Metzkes, H.; Weier, T.; Gerbeth, G.

Lorentz force-based flow control in materials with low electrical conductivity has a long history back to the first half of the 19th century. This review will focus on developments during the last two decades, collecting results from numerical simulations and laboratory experiments. Typically, the actuators consist of permanent magnets and electrodes flush-mounted with the surface, generating Lorentz forces in the fluid layers adjacent to the wall. We will discuss the application of Lorentz forces to reduce friction drag in turbulent boundary layers and to delay boundary layer transition. The control of separated flows and shear layers is another key aspect of the review. Energetic efficiency, one of the main criteria for flow control, and its relation to typical operating conditions will be analyzed as well. Lorentz forces can be successfully used to control a broad range of flow phenomena and are a versatile tool for basic fluid dynamics research. However their current applicability in large scale systems is hampered by the low electrical to mechanical efficiency intrinsic to actuators based on the magnetic fields delivered by today’s permanent magnets.

Keywords: EMHD; flow control; boundary layer control; separation control; transition control

Publ.-Id: 18757

Deriving forces from 2D velocity field measurements

Albrecht, T.; Del Campo, V.; Weier, T.; Metzkes, H.; Stiller, J.

We discuss how to derive a force or a force density from a measured velocity field. The first part focuses on the integral force a fluid exerts on a body, e.g. lift and drag on an airfoil. Obtaining the correct pressure is crucial; however, it cannot be measured within the flow non-intrusively. Using numerical and experimental test cases, we compare the accuracy achievable with three methods: pressure reconstruction from velocity fields via (1) the differential momentum equation, or (2) the Poisson equation, furthermore, (3) Noca’s momentum equation [Noca, JFS 13(5), 1999], which does not require pressure explicitly. The latter gives the best results for the lift, whereas the first or second approach should be used for the drag. The second part deals with obtaining the distribution of a body force density generated by an actuator. Using a stream function ansatz, we obtain a Laplace equation that allows us to compute the solenoidal part of the force distribution; however, the irrotational part is lost. Furthermore, the wall pressure must be known. We validate this approach using numerical data from a wall jet flow in a rectangular box, driven by a fictitious, solenoidal body force. Reconstructing the force distribution yields an error of less than 10−2 for most of the domain.

Keywords: PIV; force measurement

Publ.-Id: 18756

Synthesis of multi trace element doped Fe0.6Mn0.4Ta2O6 tantalite reference crystals by Czochralski method

Michalak, P.-P.; Uecker, R.; Galazka, Z.; Munnik, F.; Renno, A. D.; Merchel, S.

Quality assurance of natural raw materials (e.g. ores) with beam-based microanalytical methods requires a proper set of homogeneous, matrix-matched reference materials (RMs) doped with trace elements relevant to resource technology applications. Natural minerals usually exhibit chemical heterogeneity at μg/g sampling masses and are unsuitable as RMs for in-situ chemical microanalysis. On the other hand, available synthetic RMs (e.g. glasses, pressed pellets) fail to satisfy matrix-match criterion.
A novel strategy has been established to obtaining such RMs through the synthesis of multi trace element doped phases that would be subsequently tested for chemical and structural homogeneity with both microscopic and spectroscopic spatially-resolved microanalytical methods.
A dark brown tantalite crystal from the melt of composition Fe0.6Mn0.4Ta2O6 has been grown by the conventional Czochralski method (melting point of about 1600°C) with the use of an Ir crucible and a protective atmosphere consisting of 85% Ar, 10% CO2 and 5% CO. The growth rate of 1 mm/h and rotation rate of 10 rpm were applied. The boule was 17 mm in diameter and 30 mm in length (Fig. 1). Standard mineralogical thin sections were prepared for chemical analysis.
Back-scatter Electrons imaging (BSE) was implemented to check for the presence of impurities and other phases within the crystal. Electron Probe Microanalysis (EPMA) and Particle Induced X-ray Emission (PIXE) were used to determine the composition and homogeneity of the crystal. Compositional maps were prepared for each element for each method. As shown in Fig. 2 both BSE-EPMA and PIXE consistently proved stoichiometric composition of the crystal what is in agreement with stoichiometric composition of the melt. EPMA and PIXE compositional maps showed homogenous lateral distribution of all constituents of the crystal (Fig. 3).
The obtained tantalite phase turned out to be homogenous and stable. A matrix of the same stoichiometry will be used in further experiments – synthesis of tantalite crystals doped with different sets of technological trace elements - Sc, Ti; Y, Zr, W; La, Ce, Nd – each at concentration of 0.01 wt%.
Fig. 2
Mg wt% Ca wt% Fe wt% Mn wt% Ta wt% O wt% Total
EPMA 0.000048 0.00013 5.94 4.29 70.38 18.51 99.13
PIXE b.d. b.d. 6.44 4.08 70.98 18.50 100.00
b.d.= below limit of detection
Fig. 1 Tantalite boule
Fig. 3 PIXE Fe-Kα intensity distribution map

Keywords: IBA; reference material; EPMA; PIXE

Related publications

  • Poster
    17th International Conference on Crystal Growth and Epitaxy (ICCGE-17), 11.-16.08.2013, Warszawa, Polska

Publ.-Id: 18755

‘Freiberg Strategy’ for obtaining matrix-matched reference materials for resource-related microanalytical methods technology

Michalak, P.-P.; Renno, A. D.; Merchel, S.; Munnik, F.; Gutzmer, J.; Uecker, R.; Galazka, Z.; Heller, H.-P.; Radtke, M.; Reinholz, U.

Quality assurance of natural raw materials (e.g. ores) requires thorough studies on concentration and spatial distribution patterns of technologically relevant trace elements within the mineral matrix at the microscale. Obtaining such a goal is yet only possible with the use of beam-based microanalytical methods and a proper set of homogeneous, matrix-matched reference materials (RMs) doped with trace elements relevant to resource technology.
Natural minerals usually exhibit chemical heterogeneity at μg/g sampling masses and are unsuitable as RMs for in-situ chemical microanalysis. On the other hand, available synthetic RMs (e.g. glasses, pressed pellets) fail to satisfy matrix-match criterion.
A collaboration involving several German scientific institutions centered around TU Bergakademie Freiberg proposed a novel strategy for obtaining such RMs through the synthesis of multi trace element doped mineral matrices subsequently tested for chemical and structural homogeneity with both microscopic and spectroscopic (RMs-dependent and absolute) microanalytical methods.
Three mineral matrices vital to resource technology applications – pyrite, tantalite and feldspar – have been synthesized using flux method, Czochralski method and alkoxide-based sol-gel synthesis, respectively and doped with various sets of technologically important trace elements at the concentration range found in corresponding natural minerals. Their spatial chemical micro-homogeneity has been investigated using light and electron microscopy as well as RMs–dependent (EPMA, LA-ICP-MS) and absolute (PIXE, PIGE) analytical methods.
Quantitative and qualitative elemental spatial distribution maps have been obtained for major and trace elements for each matrix. Homogeneity of the matrices was evaluated using petrologically sensitive statistical analysis.
Established homogeneity testing protocol will be employed in the next stages of the project.

Keywords: reference material; microhomogeneity; pyrite; tantalite; feldspar; IBA; PIXE; PIGE

Related publications

  • Poster
    Goldschmidt 2013, 25.-30.08.2013, Firenze, Italia

Publ.-Id: 18754

The surface reactions of U(VI) on γ-Al2O3 - In situ spectroscopic evaluation of the transition from sorption complexation to surface precipitation

Müller, K.; Foerstendorf, H.; Brendler, V.; Rossberg, A.; Stolze, K.; Gröschel, A.

The surface reactions of U(VI) on γ-Al2O3 were comprehensively investigated by a combined approach of in situ vibrational spectroscopy and X-ray absorption spectroscopy. The focus was set to micromolar U(VI) concentrations and a variety of sorption parameters which are relevant to most environmental scenarios, such as pH, ionic strength, different aluminum oxides, and solid-to-liquid ratios. Time-resolved IR spectroscopic sorption experiments at the alumina-water interface evidence the formation of three different species as a function of surface loading: a monomeric carbonate surface complex, an oligomeric surface complex, and a surface precipitate. EXAFS experiments of batch sorption samples different in their U(VI) surface loading, provided consistent results. Aluminum oxides and oxyhydroxides represent an essential structural component of many minerals and play a decisive role in regulating the mobility of contaminants in rocks and soils. Thus, the results presented in this study are of interest for the assessment of water contamination characterized by near neutral solutions. Additionally, the molecular-scale knowledge of the sorption reactions occurring at the water-alumina interface substantiates basic thermodynamic ideas of the formation and transition of surface complexes from sorption of monomers and oligomers to surface precipitation.

Keywords: ATR FT-IR spectroscopy; EXAFS spectroscopy; time-resolved; alumina; uranium

Related publications

Publ.-Id: 18753

77Se-NMR spectroscopic investigations on aqueous selenium speciation at higher temperatures and in the presence of divalent metal ions

Kretzschmar, J.; Jordan, N.; Brendler, E.

The radioactive isotope selenium-79 is a long-lived fission product found in nuclear waste. Due to its half-life of 327,000 years, it is expected to be one of the important isotopes contributing to the potential radiation dose of nuclear waste underground repositories. High level and long-lived radioactive waste increases the temperature in the vicinity of the waste disposal site for at least 10,000 years. Thus, it is important to understand to what extent this temperature increase influences the aqueous speciation of the selenium itself and, hence, its sorption behaviour onto mineral phases.
With respect to the redox properties of selenium with its four main oxidation states (-II, ±0, +IV, +VI), the speciation may become quite complex depending on the prevailing environmental conditions.
The spin ½ nucleus of the inactive isotope Se-77 is well suited to be directly observed by NMR spectroscopy. This method provides a valuable tool for the discrimination of oxidation and protonation states of selenium compounds because of the high structural sensitivity of the selenium nucleus to its electronic environment. Thus, changes in speciation due to elevated temperatures or interactions with metal ions can be investigated.
The spectra clearly demonstrate that the aqueous speciation of Se(VI) is not changed within the investigated temperature range (20 °C – 60 °C). However, the interaction of selenium oxyanions with Ca2+ and Mg2+ can be tracked by changes in the selenium chemical shifts. These findings serve as reference data for further investigations addressing the mobility and the sorption behaviour in the presence of ubiquitous metal ions.

Keywords: selenium; aqueous speciation; NMR spectroscopy; nuclear safety research

  • Poster
    EURACT-NMR Workshop 2013, 17.-19.07.2013, Karlsruhe, Deutschland

Publ.-Id: 18752

Model experiments for the Czochralski crystal growth technique

Cramer, A.; Pal, J.; Gerbeth, G.

A lot of the physical and the numerical modeling of Czochralski crystal growth is done on the generic Rayleigh-B´enard system. To better approximate the conditions in a Czochralski puller, the influences of a rounded crucible bottom, deviations of the thermal boundary conditions from the generic case, crucible and/or crystal rotation, and the influence of magnetic fields are often studied separately. The present contribution reviews some of these topics while concentrating on studies of the flow and related temperature fluctuations in systems where a rotating magnetic field (RMF) was applied.
The three-dimensional convective patterns and the resulting temperature fluctuations will be discussed both for the mere buoyant case and for the application of an RMF. It is shown that a system between a Rayleigh-Benard and a more realistic configuration, which is still cylindrical but whose surface is partially covered by a crystal model, behaves much the same as a Rayleigh-Benard system. An RMF can be used to damp the temperature fluctuations. Secondly, a more Czochralski-like system is examined. It turns out that the RMF does not provide the desired damping of the temperature fluctutions in the parameter range considered.

Publ.-Id: 18751

A new solver for magnetohydrodynamic flow simulations

Weber, N.; Galindo, V.; Stefani, F.; Weier, T.

Numerical schemes for magnetized rotating flows often attempt to solve the induction equation directly. Due to numerical difficulties, this approach is limited to magnetic Prandtl numbers larger than 0.01, i.e., four orders of magnitude above the values typical for liquid metals. This makes a direct comparison of numerical results with liquid metal experiments difficult. Here we present an alternative approach based on a finite volume scheme for the Navier-Stokes and the Poisson equation describing the electric potential combined with a magnetic field calculation via Biot-Savart’s law. Using this integro-differential formulation, it is possible to circumvent the magnetic Prandtl number limitation mentioned above. First, we will discuss the implementation of this method in the framework of the open source library OpenFOAM. Second, calculations of the Tayler instability (TI), a kink-type current-driven instability, will be presented and compared to the data from a recent liquid metal TI experiment (Seilmayer et al., 2012). The computations faithfully reproduce the experimentally findings. Then, we will elaborate on further details of the TI in liquid metals, as the influence of the aspect ratio on the critical current, transient helical states, and possible implications for large-scale liquid metal batteries.

Keywords: OpenFOAM Tayler instability

  • Poster
    18th International Couette-Taylor Workshop, 24.-26.06.2013, Twente, Niederlande

Publ.-Id: 18750

Liquid metal flows driven by rotating and travelling magnetic fields

Stiller, J.; Koal, K.; Nagel, W. E.; Pal, J.; Cramer, A.

Alternating magnetic fields provide a comfortable means for non-intrusive flow control in conductive fluids. However, despite a long history of applications in metallurgy and crystal growth, detailed investigation of the practically important transitional and turbulent flow regimes has become possible only in the last dozen years. The present review gives an overview of this topic with focus on recent experimental and numerical studies of the flow driven by rotating and traveling magnetic fields. We discuss the three-dimensional, instantaneous flow structure as well as the resulting average transport properties for a broad range of parameters, including the superposition of both field types. In addition to the ideal case, the effect of a misalignment of the field with respect to the container axis will be considered, too.

Publ.-Id: 18749

Bildgebende Messverfahren für die Prozess- und Strömungsaufklärung in der Verfahrenstechnik

Hampel, U.

Verfahrenstechnische Prozesse sind zumeist mit mehrphasigen Stoffströmungen verbunden. Die Analyse und Vermessung solcher Mehrphasenströmungen ebenso wie räumlicher Verteilungen von Prozessparametern erfordern fortgeschrittene Mess- und Bildgebungsverfahren. Im Fokus des Interesses stehen dabei vor allem tomographische Bildgebungsverfahren, die heute bereits in der Medizin und in der zerstörungsfreien Prüfung verbreitet sind. Diese müssen allerdings an die oft vielfältigen Anwendungsbedingungen in der Verfahrenstechnik angepasst werden. Typische Probleme sind die optische und akustische Intransparenz von Stoffgemischen, hohe Betriebsdrücke, Temperaturen und aggressive Medien in Prozessanlagen und prozessnahen Versuchsständen sowie die bei vielen bekannten Messverfahren oft zu geringe zeitliche Auflösung bei der Untersuchung transienter Vorgänge. Der Beitrag gibt einen Überblick über neuere Entwicklungen im Bereich der Bildgebungsverfahren für Mehrphasenströmungen und erläutert deren Grundprinzipien und Anwendung.

Keywords: Bildgebende Messverfahren; Strömungsmesstechnik; Computertomographie; Mehrphasenströmungen; Verfahrenstechnik

  • Jubiläumsband 60 Jahre Dresdner Verfahrenstechnik (2013)

Publ.-Id: 18748

The production of K+K- pairs in proton-proton collisions below the φ meson threshold

Ye, Q. J.; Hartmann, M.; Chiladze, D.; Dymov, S.; Dzyuba, A.; Gao, H.; Gebel, R.; Hejny, V.; Kacharava, A.; Lorentz, B.; Mchedlishvili, D.; Merzliakov, S.; Mielke, M.; Mikirtytchiants, S.; Ohm, H.; Papenbrock, M.; Polyanskiy, A.; Serdyuk, V.; Stein, H. J.; Ströher, H.; Trusov, S.; Valdau, Y.; Wilkin, C.; Wüstner, P.

The pp -> ppK+K- reaction was measured below the phi threshold at a beam energy of 2.568 GeV using the COSY-ANKE magnetic spectrometer. By assuming that the four-body phase space is distorted only by the product of two-body final state interactions, fits to a variety of one-dimensional distributions permit the evaluation of differential and total cross sections. The shapes of the distributions in the Kp and Kpp invariant masses are reproduced only if the K-p interaction is even stronger than that found at higher energy. The cusp effect in the K+K- distribution at the K0K0bar threshold is much more clear and some evidence is also found for coupling between the K-p and K0bar n channels. However, the energy dependence of the total cross section cannot be reproduced by considering only a simple product of such pair-wise final state interactions.

Publ.-Id: 18747

Konzeption eines Experimentaufbaus zum Studium der Magneto-Rotationsinstabilität und der Tayler-Instabilität

Zscharschuch, J.

Auf der Grundlage eines methodisch konstruktiven Vorgehens wird die Suche nach Prinziplösungen für die Umsetzung eines Experimentaufbaus zum Studium der Magneto-Rotationsinstabilität und der Tayler-Instabilität beschrieben. Einer Kurzvorstellung des Zieles dieser Arbeit und des Experimentes folgt eine Übersicht artverwandter Experimente in der Magnetohydrodynamik. Der Fokus ist dabei auf Gestaltung und Funktion gerichtet. Ein Überblick zu den physikalischen Grundlagen und fluiddynamischen Phänomenen schließt sich an, bevor detailliert auf die angewandte Konstruktionsmethodik eingegangen wird. Anhand der Anforderungen zum Aufbau des Experimentes wird eine zweckdienliche Abstraktion zur technischen Hauptaufgabe durchgeführt. Schrittweise werden dadurch Flussbilder und darauf aufbauend Funktionsstrukturen abgeleitet. Ausgehend davon werden danach einzelne Funktionsgruppen näher betrachtet und Lösungskonzepte entwickelt. Mittels eines Vergleichs der Konzepte wird eine Vorzugsvariante gefunden. Eine Darstellung der Prinziplösung liegt als Ergebnis vor und bietet für den nachfolgenden Entwurfs- und Ausarbeitungsprozess die Basis.

Keywords: Fluiddynamik; Magnetohydrodynamik; Tayler-Instabilität; Magneto-rotationsinstabilität

  • Bachelor thesis
    HTW Berlin, 2013
    86 Seiten

Publ.-Id: 18746

Anti-tumor effects of peptide hormone analogs in pheochromocytoma cell lines and preclinical tumor imaging

Ullrich, M.; Ziegler, C. G.; Bergmann, R.; Pietzsch, J.; Ehrhart-Bornstein, M.; Schally, A. V.; Eisenhofer, G.; Bornstein, S. R.

Pheochromocytoma (PHEO) is a rare but potentially lethal neuroendocrine tumor arising from catecholamine producing chromaffin cells. Available treatment strategies are limited and, if the tumor has metastasized, not very effective. The abundant expression of peptide hormone receptors on endocrine tumor cells allows specific targeting by highly effective anti-tumor peptide analogs. The present study focuses on the preclinical evaluation of potential therapies in the treatment of pheochromocytoma targeting peptide hormone receptors.

Design and method
Our in vitro evaluation of peptide hormone receptor expression on the mouse pheochromocytoma (MPC) cell line and a more malignant mouse tumor tissue-derived (MTT) cell line was based on RT-PCR and immunohistological analysis. Based on these data, we evaluated the effects of cytotoxic peptide hormone analogs on cell viability, apoptosis and necrosis on MPC and MTT cells. For in vivo studies, we established a subcutaneous mouse model of MPC-derived PHEO and multimodal tumor imaging using PET, MRI, and CT, fluorescence and bioluminescence.

Results and conclusions
Our data reveal significant anti-tumor effects mediated by the cytotoxic peptide hormone analogs AN-162 and AN-238 targeting somatostatin receptor 2 (sst2), by the antagonist Cetrorelix and the cytotoxic analog AN-152 targeting luteinizing hormone-releasing hormone receptor (LHRH-R) as well as by the antagonist MIA-602 targeting growth hormone-releasing hormone receptors (GHRH-R) on MPC cells. Similar anti-tumor effects were evidenced for AN-152 and MIA-602 also on the more aggressive MTT cells. Using our newly established mouse model, we were able to visualize the growth of MPC cell-derived subcutaneous pheochromocytomas in vivo by multimodal molecular imaging including SSTR2 PET. Additionally, ex vivo tumor characterization demonstrated unaltered peptide hormone receptor expression during in vivo tumor growth in mice.
Our current investigation provides strong evidence for a possible future treatment of malignant pheochromocytoma using targeted peptide hormone receptor therapy.

  • Lecture (Conference)
    17th International AEK Cancer Congress, 20.-22.03.2013, Heidelberg, Deutschland
  • Contribution to proceedings
    17th International AEK Cancer Congress, 20.-22.03.2013, Heidelberg, Deutschland
    Congress Program and Abstracts: 17th International AEK Cancer Congress, Deutsche Krebsgesellschaft - Abteilung Experimentelle Krebsforschung. DKG. Heidelberg, 12

Publ.-Id: 18745

Anti-tumor effects of peptide hormone analogs in pheochromocytoma

Ullrich, M.; Ziegler, C. G.; Bergmann, R.; Pietzsch, J.; Ehrhart-Bornstein, M.; Schally, A. V.; Eisenhofer, G.; Bornstein, S. R.

Pheochromocytoma (PHEO) is a rare but potentially lethal neuroendocrine tumor arising from catecholamine producing chromaffin cells of the adrenal medulla. Especially for malignant pheochromoytoma the available treatment strategies are not very effective. Peptide hormone receptors are abundantly expressed on endocrine tumor cells and can be specifically targeted by highly effective anti-tumor peptide analogs. Our actual study focuses on the preclinical evaluation of potential peptide hormone receptor therapies for the treatment of pheochromocytoma.

Design and method
In our in vitro studies we evaluated peptide hormone receptor expression on a neuroendocrine tumors relevant mouse pheochromocytoma (MPC) cell line and a thereof established more malignant mouse tumor tissue-derived (MTT) cell line based on RT-PCR and immunohistological analysis. We also measured the effects of cytotoxic peptide hormone analogs on cell viability, apoptosis and necrosis on MPC and MTT cells. Furthermore, for our in vivo studies we established a subcutaneous mouse model of PHEO for optimization of multimodal tumor imaging using PET, MRI, and CT, fluorescence and bioluminescence imaging.

Results and conclusions
We could demonstrate significant anti-tumor effects mediated by the cytotoxic peptide hormone analogs AN-162 and AN-238 targeting somatostatin receptor 2 (sst2), by the antagonist Cetrorelix and cytotoxic analog AN-152 targeting luteinizing hormone-releasing hormone receptor (LHRH-R) as well as by the antagonist MIA-602 targeting growth hormone-releasing hormone receptors (GHRH-R) on MPC cells. Furthermore, similar anti-tumor effects were evidenced also for AN-152 and MIA-602 on more aggressive MTT cells. In our mouse model we were able to visualize tumor growth of MPC cell-derived subcutaneous pheochromocytomas in vivo by fluorescence imaging. Ex vivo tumor characterization demonstrated that peptide hormone receptors are still expressed during tumor growth in mice.
Our current investigation provides strong evidence for the usefulness of targeted peptide hormone receptor therapy for a possible future treatment of malignant pheochromocytoma.

  • Poster
    Fourth International Symposium on Adrenal Cancer, 22.-23.02.2013, Paris, France
  • Contribution to proceedings
    Fourth International Symposium on Adrenal Cancer, 22.-23.02.2013, Paris, France
    Fourth International Symposium on Adrenal Cancer: Final Program. European Science Foundation, Paris: European Science Foundation, 27

Publ.-Id: 18744

Novel therapeutic strategies for the treatment of pheochromocytoma

Ziegler, C. G.; Eisenhofer, G.; Ullrich, M.; Bergmann, R.; Pietzsch, J.; Schally, A. V.; Ehrhart-Bornstein, M.; Bornstein, S. R.

Pheochromocytoma is a rare but potentially lethal chromaffin cell tumor. The prognosis for malignant pheochromocytoma is particularly poor and there are currently no effective treatments. Interestingly, peptide hormone receptors are frequently overexpressed on endocrine tumor cells and can be specifically targeted by highly effective anti-tumor peptide analogs. Our actual study focuses on two endocrinologically relevant mouse pheochromocytoma cell lines, one more malignant and one more benign one as well as on mouse models of pheochromocytoma, which our group currently establishes.
First, we could demonstrate significant anti-tumor effects mediated by cytotoxic somatostatin analogs AN-162 and AN-238, by LHRH antagonist Cetrorelix and cytotoxic LHRH analog AN-152 as well as by GHRH antagonist MIA-602 targeting their respective receptors on mouse pheochromocytoma cells (MPC). Furthermore, similar anti-tumor effects were evidenced also for AN-152 and MIA-602 on more aggressive tumor tissue-derived (MTT) cells.
Second, we established a subcutaneous mouse model of pheochromocytoma for optimization of parametric tumor imaging in vivo. Tumor volume, morphology, metabolic activity and peptide receptors are evaluated using PET/MR and PET/CT imaging as well as fluorescence and bioluminescence imaging after injection of mCherry or luciferase transduced MPC cell lines. Furthermore, we are establishing an intravenous mouse model of pheochromocytoma to test the most effective peptide analogs in vivo. Ex vivo characterization of mouse pheochromocytomas demonstrated that peptide hormone receptors are still expressed during tumor growth in mice.
Altogether, our current investigation provides further evidence for the usefulness of targeted peptide hormone receptor therapy as a potential new option for future treatment of malignant pheochromocytoma

  • Lecture (Conference)
    56. Symposium der Deutschen Gesellschaft für Endokrinologie, 13.-16.03.2013, Düsseldorf, Deutschland
  • Abstract in refereed journal
    Experimental and Clinical Endocrinology & Diabetes 121(2013), OP5_32b
    DOI: 10.1055/s-0033-1336641

Publ.-Id: 18743

Novel aspects on the irradiation of HOPG surfaces with slow highly charged ions

Ritter, R.; Shen, Q.; Wilhelm, R. A.; Heller, R.; Ginzel, R.; Crespo López-Urrutia, J. R.; Facsko, S.; Teichert, C.; Aumayr, F.

As a continuation of our previous work, we present new results regarding the interaction of slow highly charged ions with HOPG. Lateral atomic force microscopy measurements with calibrated cantilevers were performed to investigate in more detail the locally enhanced friction at ion impact sites, which has been reported earlier. For very high charge states, apart from ever-present changes in frictional and electronic properties, we find evidence for true topographic surface modifications (hillocks). In complementary studies, we have investigated these structures regarding their conductivity by employing high-resolution conductive atomic force microscopy. In addition, we demonstrate the possibility to etch ion-induced surface structures by thermal annealing.

Keywords: HOPG; Highly charged ions; Nanostructuring; AFM; STM; Friction

Related publications

Publ.-Id: 18742

Di-pion and di-electron production in NN reactions with HADES at 1.25GeV incident beam energy

Kuc, H.; Agakishiev, G.; Behnke, C.; Belver, D.; Belyaev, A.; Berger-Chen, J. C.; Blanco, A.; Blume, C.; Böhmer, M.; Cabanelas, P.; Chernenko, S.; Dritsa, C.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; González-Díaz, D.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Höhne, C.; Holzmann, R.; Huck, P.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Krizek, F.; Kugler, A.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lang, S.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.

Significant isospin effects are observed by the HADES collaboration in inclusive dilepton production channels in the pp and quasi free np experiments at 1.25 GeV kinetic beam energy. Triggered by this observation, analyses of several exclusive channels within either dilepton or pion production have been started to shed more light on the possible explanations. Furthermore, the exclusive p+p production in np and pp collisions provide tests for a consistent description of double pion production in different isospin states, which is necessary to understand contributions of the double Δ(1232) and N*(1440) production. This is also important in the context of the recent results from the WASA collaboration on the ABC effect with reference to a d* dibaryon resonance in isospin 0 channel.

  • Open Access Logo Proceedings of Science (2013), PoS(BORMIO2013)060

Publ.-Id: 18741

Radiolabeling of modified recombinant epidermal growth factor (EGF) by Huisgen-Click reaction for multimodal imaging and therapy of tumors

Pietzsch, D.; Pretze, M.; Mamat, C.; Mosch, B.; Steinbach, J.; Pietzsch, J.

The epidermal growth factor receptor (EGFR) plays a critical role in epithelial tumors and, therefore, is a promising target for both tumor imaging and therapy. In order to develop novel EGFR-targeted radiotracers/radiotherapeutics the present work aims at synthesis of structurally modified recombinant EGF. One strategy implies incorporation of azidohomoalanine instead of methionine using supplementation-based incorporation by E. coli. Consequently, the biomolecule can be labeled site-selectively by Click reaction (Huisgen 1,3-dipolar cycloaddition) with fluorescence and radiolabeled building blocks, respectively.

Method and Results
The EGF gene motif was successfully ligated into vectors containing either a GST-tag or His6-tag. Resulting plasmids were transformed into methionine-auxotrophic E. coli (B834(DE3)pLysS), protein synthesis under addition of azidohomoalanine and protein purification were established. Purification of the GST fusion protein only resulted in the unmodified protein, but not in the azido-functionalized protein. In contrast, purification of His6-tagged azido-functionalized EGF was successfully established. This could be demonstrated by reaction with various alkynylated fluorescent dyes. Moreover, the modified EGF was radiolabeled with 1-(but-3-inyl)-4-(3-[18F]fluoropropyl)piperazine ([18F]BFP) as the alkyne with a radiochemical yield of about 0.5 % using Click reaction. First cell binding studies of [18F]BFP-labeled EGF demonstrated cellular association in EGFR-overexpressing A431 human epidermoid carcinoma cells. Cellular uptake amounted to about 25 % of injected dose/mg protein after 1 hour at 37°C.

Ongoing work focuses on the optimization of site-selective radiolabeling of EGF by Click reaction with higher radiochemical yield and specific activity. Afterwards, the radiolabeled protein will be radiopharmacologically tested concerning its properties as potential radiotracer.

  • Poster
    7th Conference on Recombinant Protein Production, 06.-08.03.2013, Laupheim, Deutschland
  • Contribution to proceedings
    7th Conference on Recombinant Protein Production., 06.-08.03.2013, Laupheim, Deutschland
    Programme & Abstracts. European Federation of Biotechnology, 104

Publ.-Id: 18740

Design, synthesis and surface engineering of ultrasmall iron oxide nanoparticles for cancer imaging

Pombo Garcia, K.; Zarschler, K.; Stephan, H.; Steinbach, J.

There is currently a great interest in the application of nanoparticles for molecular imaging. This results in the development of both, organic and inorganic nanoparticles functionalized in a way that radionuclides, targeting ligands, and different biopolymers can be attached in order to provide an imaging signal. Ultrasmall superparamagnetic iron oxide (Fe3O4) nanoparticles (USPIOs) are one of the most widely studied nanomaterials. USPIOs possess unique magnetic properties that make them attractive candidates as advanced biomedical materials (1).
Furthermore, the biocompatibility of USPIOs makes them suitable to be used as multifunctional agents. They can serve as contrast agents for clinical use in magnetic resonance imaging (MRI), positron emission tomography (PET) and optical imaging (OI) (2).
This work aims at the development of new nanotracers based on USPIOs coated with a biodegradable polymer that are also decorated with agents for radiochemical and/or fluorescence imaging and Epidermal Growth Factor Receptor-specific ligands as targeting units (3).
The production of hydrophobic USPIOs has been achieved using thermal decomposition and monodisperse nanocrystals within a size of 4-5 nm were observed with Transmission electron microscopy (TEM) (4). The main limitation of using USPIOs for in vivo applications is their instability in water. Different biocompatible polymers such as polyvinylalcohol and polyacrylic acid have been tested for the hydrophilic coating of the iron oxide core to make them stable in aqueous solution (5). After an intensive physicochemical characterization including studies of their stability in water and several buffers, carboxymethyl polyvinyl alcohol (CMPVA) was chosen as the most suitable coating agent for the surface modification of USPIOs (6). The stability of the CMPVA-coated USPIOs was studied using Dynamic Light Scattering (DLS, Zetasizer/ Malvern).
Our first goal was to engineer and functionalize the surface of the hydrophilic USPIOs. This included the attachment of a fluorescent label to the shell. This enabled the USPIOs to be suitable for fluorescence imaging. Furthermore, preliminary radiolabeling studies (64Cu) have been undertaken using USPIOs decorated with functional copper chelating agents, such as NOTA. Radio-HPLC and Radio-TLC have been applied to get information about the labelling efficiency and stability of the 64Cu-labeled USPIOs.
From our point of view, the generated nanoparticles possess promising features as novel imaging agents for in vivo cancer diagnostics.

1. Barreto, J.A., et al. Advanced Materials, 23(12): p. H18-H40, 2011.
2. Laurent, S., et al., Chemical Reviews, 108(6): p. 2064-211, 2008.
3. Li, Z., et al., The FASEB Journal, 19(14): p. 1978-1985, 2005..
4. Park, J., et al., Nat Mater, 3(12): p. 891-895, 2004.
5. Zhang, F., et al., Small, 7(22): p. 3113-3127, 2011.
6. Liong, M., et al., Advanced Materials, 22(45): p. 5168-5172, 2010.

  • Lecture (Conference)
    6th International Symposium on the Separation and Characterization of Natural and Synthetic Macromolecules (SCM-6), 06.-08.02.2013, Dresden, Deutschland

Publ.-Id: 18739

Single-domain antibodies as targeting moieties for nanomaterial-based cancer imaging

Witecy, S.; Zarschler, K.; Zscheppang, K.; Cordes, N.; Stephan, H.

kein Abstract verfügbar

  • Poster
    OncoRay-Retreat 2013, 07.-08.03.2013, Dresden-Rossendorf, Deutschland

Publ.-Id: 18738

Surface morphology and interface chemistry under ion irradiation - simultaneous atomistic simulation of collisional and thermal kinetics

Liedke, B.; Heinig, K.-H.; Möller, W.

A novel program package has been developed which allows for the simultaneous treatment of atomistic kinetics in collision cascades caused by energetic ion impacts and thermally activated relaxation and diffusion. In this 3D program named TRIDER (TRansport of Ions in matter with DEfect R}elaxation) the collision cascades treated in the framework of the Binary Collision Approximation has been combined with kinetic lattice Monte-Carlo simulations of the atomistic relaxation and diffusion. TRIDER simulations allow a more realistic description of ion-induced surface patterning because subsurface defect kinetics can be included in the simulations, which is demonstrated for low-energy Ar+ ion irradiation of silicon. The deeper understanding of ion beam mixing of bimetal interfaces can also be achieved: it is shown that the conventional Gaussian mixing profile is changed substantially for immiscible metals due to precipitation and for chemically active metals due to formation of intermetallics of different stoichiometry.

Keywords: Monte-Carlo; KMC; BCA; TRIM; TRIDYN; TRIDER; ripple formation; surface modification; large scale simulation; ion beam irradiation

Related publications

Publ.-Id: 18737

Synthesis and characterization of silicon nanoparticles

Licciardello, N.; Hsu, C.-W.; Hunoldt, S.; Viehweger, K.; Stephan, H.; de Cola, L.

kein Abstract verfügbar

  • Poster
    3rd International Conference on Multifunctional, Hybrid and Nanomaterials, 03.-07.03.2013, Sorrento, Italy

Publ.-Id: 18736

Production of large volume, strongly magnetized laser-produced plasmas by use of pulsed external magnetic fields

Albertazzi, B.; Béard, J.; Ciardi, A.; Vinci, T.; Albrecht, J.; Billette, J.; Burris-Mog, T.; Chen, S. N.; Da Silva, D.; Dittrich, S.; Herrmannsdörfer, T.; Hirardin, B.; Kroll, F.; Nakatsutsumi, M.; Nitsche, S.; Riconda, C.; Romagnagni, L.; Schlenvoigt, H.-P.; Simond, S.; Veuillot, E.; Cowan, T. E.; Portugall, O.; Pépin, H.; Fuchs, J.

The production of strongly magnetized laser plasmas, of interest for laboratory astrophysics and inertial confinement fusion studies, is presented. This is achieved by coupling a 16 kV pulse-power system. This is achieved by coupling a 16 kV pulse-power system, which generates a magnetic field by means of a split coil, with the ELFIE laser facility at Ecole Polytechnique. In order to influence the plasma dynamics in a significant manner, the system can generate, repetitively and without debris, high amplitude magnetic fields (40 T) in a manner compatible with a high-energy laser environment. A description of the system and preliminary results demonstrating the possibility to magnetically collimate plasma jets are given.

Related publications

Publ.-Id: 18735

Proton induced dielectron radiation off Nb: Pt and Y distributions

Lorenz, M.; Weber, M.; Agakishiev, G.; Behnke, C.; Belver, D.; Belyaev, A.; Berger-Chen, J. C.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Dohrmann, F.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Lalik, R.; Lang, S.; Lange, J. S.; Lapidus, K.; Liu, T.; Lopes, L.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Moriniere, E.; Mousa, J.; Müntz, C.; Naumann, L.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.

Following our recent letter [1] on inclusive e+e− pair production in proton induced reactions at Ekin = 3.5 GeV on the nucleus Nb, we present here in addition the transverse and rapidity distributions for various e+e− invariant mass bins and compare them to reference data measured in p+p reactions.

Publ.-Id: 18734

Reduction and immobilization processes of contaminants (Se, Tc, Pu) by Fe(II)-bearing minerals

Scheinost, A. C.

Fe(II)-bearing phases are naturally occuring in most anoxic aquifers, and form also at the surface of corroding steel containers under typical nuclear waste repository conditions. Due to their ability to reduce metal and metalloid contaminants, they are expected to play a key role for the migration behaviour of a wide range of radionuclides, including actinides and fission products. Using X-ray absorption spectroscopy as main tool, we have studied reaction end products, mechanisms and kinetics of redox processes at a range of water/mineral interfaces, including magnetite, green rust, mackinawite, chukanovite, and Fe2+-sorbed clays, but also in more redox-inert systems like cement.
Our results show that the electron transport within mineral structures and at the surface is controlling the extent and the kinetics of multi-electron redox reactions.

Keywords: XAFS; XANES; Redox

Related publications

  • Invited lecture (Conferences)
    Chemical and Radiochemical Processes in the Environment, 17.05.2013, Nice, France
  • Invited lecture (Conferences)
    Institutsseminar am Institut für Radioökologie und Strahlenschutz der Universität Hannover, 16.05.2013, Hannover, Germany

Publ.-Id: 18733

Is plutonium being incorporated by magnetite under anoxic conditions?

Dumas, T.; Fellhauer, D.; Gaona, X.; Altmaier, M.; Scheinost, A. C.

Magnetite, which forms under anoxic conditions on the surface of corroding steel containers, is able to reduce a range of elements, including radionuclides of high relevance in the context of nuclear waste disposal, e.g. Se, Tc, U, Np, Pu [1]. Aqueous Pu(V) is rapidly reduced by nanoparticulate magnetite to Pu(III), which then forms stable, tridentate sorption complexes on the {111} faces of magnetite [2]. Trivalent lanthanides have been shown to substitute for Fe(III) in magnetite, although their ionic radii are about 1.4 times larger than that of Fe(III) (1.15-1.17 vs. 0.79 Å in six-fold coordination) [3]. To investigate if such an incorporation is also possible for Pu(III) with a similar ionic radius as the lanthanides, we conducted coprecipitation experiments with two Pu loadings of 1000 and 3500 ppm. UV-VIS spectroscopy showed an immediate reduction of Pu(V) to Pu(III) in the initial Fe(II)/Fe(III) chloride solution. After formation of the black magnetite precipitate, Pu(III) concentration in solution was below 10-9 M. X-ray Absorption Near-Edge Structure (XANES) spectroscopy confirmed the trivalent oxidation state of solid phase-associated Pu. Extended X-ray Absorption Fine-Structure (EXAFS) spectroscopy was then used to investigate the molecular structure of incorporated Pu(III) in the fresh precipitate as well as after Fe(II)-induced aging [4]. The EXAFS spectra revealed two different spectral components. The first component represents the tridentate Pu(III) sorption complex also observed during sorption experiments. The second component represents Pu(III) in a highly distorted magnetite Oh site. The proportion of the incorporated Pu(III) decreased from about 75% to 40% with Fe(II)-induced aging, while the proportion of sorbed Pu(III) increased correspondingly. Our results suggest, therefore, that Pu can be incorporated by magnetite, but will convert to sorbed species on the long time scales relevant for nuclear waste disposal.

[1] Scheinost et al. (2008) J. Contam. Hydrol. 102, 228-245. [2] Kirsch et al. (2011), Environ. Sci. Technol. 45, 7267–7274. [3] Moon et al. (2007) Extremophiles 11, 859-867. [4] Boland et al. (2011) Environ. Sci. Technol. 45, 1327-1333.

Keywords: XAFS; XANES; Plutonium; Redox; magnetite

Related publications

  • Lecture (Conference)
    Goldschmidt 2013, 25.-30.08.2013, Firenze, Italy
  • Invited lecture (Conferences)
    248th ACS National Meeting, 10.-14.08.2014, San Francisco, USA

Publ.-Id: 18732

Interaction of plutonium with magnetite under anoxic conditions: Reduction, surface complexation, and structural incorporation

Scheinost, A. C.; Kirsch, R.; Dumas, T.; Fellhauer, D.; Gaona, X.; Altmaier, M.

For the redox-reactive fission products and actinides Se, Tc, U, and Np, it is assumed that the strongly reducing conditions in deep underground, anoxic nuclear waste repositories will reduce their mobility, since their lower-oxidation states commonly form solids of very low solubility. This is not necessarily the case for Pu, where the hexa- and pentavalent aquo-complexes prevalent at higher pe are replaced at lower pe by a tetravalent solid of low solubility, PuO2, but also by a trivalent aquocomplex at lower pH (Fig. 1) [1, 2]. Since the predominance field of Pu(III)aq overlaps with that obtained for the Fe(II)/Fe(III) redox couple as aqueous species or in equilibrium with Fe(II)-bearing minerals [3], one should assume that Pu(III) exists under anoxic nuclear waste conditions, where Fe(II) sources are provided by corroding steel containers and Fe(II)-bearing clays used as confinement, as well as by geogenic minerals. Although some studies have previously reported on trivalent lanthanides, little is known on the retention mechanisms of the trivalent Pu aquo complex by minerals, with implications for the safety case of nuclear waste repositories.

Keywords: Plutonium; Redox; XAFS; XANES; magnetite

Related publications

  • Invited lecture (Conferences)
    Actinides2013, 21.-26.07.2013, Karlsruhe, Deutschland

Publ.-Id: 18731

Recent trends in malignant melanoma biomarker research

Pietzsch, J.; Tandler, N.; Mosch, B.

Melanoma is the most malignant type of all skin neoplasms. Although current clinical, morphologic, pathologic, and biochemical methods provide insights into disease behavior and outcome, melanoma is still an unpredictable disease. Once in an advanced stage, it remains a fatal neoplasm with scarce therapeutic options. Therefore, significant efforts still need to be made in finding suitable biomarkers that could aid or improve its early diagnosis, its correct staging, the discrimination of other pathological conditions as well as indicate patients’ prognosis or the most appropriate therapeutic regimes. On the other hand, well-defined diagnostic markers are necessary to avoid the apparent overdiagnosis of melanoma.

  • Clinical Laboratory International 37(2013), 6-8

Publ.-Id: 18730

4-[18F]Fluoro-N-methyl-N-(propyl-2-yn-1-yl)benzenesulfonamide ([18F]F-SA): a versatile building block for labeling of peptides, proteins and oligonucleotides with fluorine-18 via Cu(I)-mediated click chemistry

Ramenda, T.; Steinbach, J.; Wuest, F.

Cu(I)-mediated [3+2]cycloaddition between azides and alkynes has evolved into a valuable bioconjugation tool in radiopharmaceutical chemistry. We have developed a simple, convenient and reliable radiosynthesis of 4-[18F]fluoro-N-methyl-N-(propyl-2-yn-1-yl)benzenesulfonamide ([18F]FSA) as a novel aromatic sulfonamide-based click chemistry building block. [18F]F-SA could be prepared in a remotely controlled synthesis unit in 32 ± 5 % decay-corrected radiochemical yield in a total synthesis time of 80 min. The determined lipophilicity of [18F]F-SA (logP = 1.7) allows handling of the radiotracer in aqueous solutions. The versatility of [18F]F-SA as click chemistry building blockwas demonstrated by the labeling of a model peptide (phosphopeptide), protein (HSA), and oligonucleotide (L-RNA). The obtained radiochemical yields were 77 % (phosphopeptide), 55–60 %(HSA), and 25 %(L-RNA), respectively. Despite the recent emergence of a multitude of highly innovative novel bioconjugation methods for 18F labeling of biopolymers, Cu(I)-mediated click chemistry with [18F]F-SA represents a reliable, robust and efficient radiolabeling technique for peptides, proteins, and oligonucleotides with the short-lived positron emitter 18F.

Keywords: Cu(I)-mediated click chemistry; Fluorine-18; Peptides; Proteins; Oligonucleotides; Positron emission tomography (PET)

Publ.-Id: 18729

Uranyl-Halide Complexation in N,N-Dimethylformamide: Halide Coordination Trend Manifests Hardness of [UO2]2+

Takao, K.; Takao, S.; Ikeda, Y.; Bernhard, G.; Hennig, C.

Complexation of [UO2]2+ with Cl−, Br−, and I− in N,N-dimethylformamide (DMF) was studied by UV-vis absorption spectroscopy and extended X-ray absorption fine structure (EXAFS) to clearly differentiate halide coordination strengths to [UO2]2+. In the Cl− system, it was clarified that the Cl− coordination to [UO2]2+ in DMF proceeds almost quantitatively. The coordination number of Cl− increases up to 4 with increasing its total concentration, i.e., the limiting complex is [UO2Cl4]2−. Logarithmic gross stability constants of [UO2Clx]2−x (x = 1-4) were evaluated as log 1 = 9.67, log 2 = 15.49, log 3 = 19.89, and log 4 = 24.63 from UV-vis titration experiment. The EXAFS results well demonstrated not only the Cl− coordination, but also the DMF solvation in the equatorial plane of [UO2]2+. The similar experiments were also performed for the Br− and I− systems. As a result, the Br− coordination to [UO2]2+ stops at the second step, i.e., only [UO2Br]+ and UO2Br2 were observed. The molecular structure of each occurring species was confirmed by EXAFS. The evaluated log x of [UO2Brx]2−x (x = 1, 2) are 3.45 and 5.42, respectively. The much smaller log x than those of [UO2Clx]2−x indicates that Br− is much weaker ligand to [UO2]2+ than Cl−. The EXAFS experiments revealed that the presence of I− in the test solution does not modify any coordination structure around [UO2]2+. Thus, I− does not form any stable [UO2]2+ complexes in DMF. Consequently, the stability of the halido complexes of [UO2]2+ in DMF is exactly in line with the hardness order of halides. This trend clearly manifests the hardness of [UO2]2+.

Keywords: EXAFS; UV-Vis; Uranium; Halides

Related publications

Publ.-Id: 18728

Crystal structure and solution species of Ce(III) and Ce(IV) formates-from mononuclear to hexanuclear complexes

Hennig, C.; Ikeda-Ohno, A.; Kraus, W.; Weiss, S.; Pattison, P.; Emerich, H.; Abdala, P.; Scheinost, A.

Cerium(III) and cerium(IV) form both formate complexes. However, their species in aqueous solution and the solid-state structures are surprisingly different. The species in aqueous solutions were investigated with Ce K-edge EXAFS spectroscopy. Ce(III) formate shows only mononuclear complexes, which is in agreement with the predicted mononuclear species of Ce(HCOO)2+ and Ce(HCOO)2+. In contrast, Ce(IV) formate forms in aqueous solution a stable hexanuclear complex of [Ce6(μ3-O)4(μ3-OH)4(HCOO)x(NO3)y]12-x-y. The structural differences reflect the different influence of hydrolysis, which is weak for Ce(III) and strong for Ce(IV). Hydrolysis of Ce(IV) ions causes initial polymerization while complexation through HCOO- results in 12 chelate rings stabilizing the hexanuclear Ce(IV) complex.
Crystals were grown from the above mentioned solutions. Two crystal structures of Ce(IV) formate were determined. Both form a hexanuclear complex with a [Ce6(µ3-O)4(µ3-OH)4]12+ core in aqueous HNO3 / HCOOH solution. The pH titration with NaOH resulted in a structure with the composition [Ce6(µ3-O)4(µ3-OH)4(HCOO)10(NO3)2(H2O)3] (H2O)9.5, while the pH adjustment with NH3 resulted in [Ce6(µ3-O)4(µ3-OH)4(HCOO)10(NO3)4] (NO3)3(NH3)3(H2O)5. Furthermore, the crystal structure of Ce(III) formate, Ce(HCOO)3, was determined. The coordination polyhedron is a tricapped trigonal prism which is formed exclusively by nine HCOO- ligands. The hexanuclear Ce(IV) formate species from aqueous solution is widely preserved in the crystal structure, whereas the mononuclear solution species of Ce(III) formate undergoes a polymerization during the crystallization process.

Keywords: EXAFS; XRD; aqueous solution; Ce(III); Ce(IV); formate

Related publications

Publ.-Id: 18727

Formation of actinide(IV) carboxylate complexes in aqueous solution – the unexpected predominance of hexanuclear species

Hennig, C.; Takao, K.; Takao, S.; Weiss, S.; Kraus, W.; Emerling, F.; Scheinost, A.

Tetravalent actinides form strong complexes with carboxyl containing ligands. Such complexes play an important role in technological processes as well as biological and environmental systems. The aqueous chemistry of such complexes is therefore of wide interest. So far, most of the thermodynamic data of actinide(IV) carboxylates are estimated assuming mononuclear solution species (see for example [1]). We applied comprehensive spectroscopic studies (EXAFS, UV-Vis-NIR spectroscopy and X-ray diffraction) to estimate the complex structure of actinide(IV) carboxylates with different actinides (Th4+, U4+ and Np4+) and carboxylates (RCOO–; R = H, CH3, CHR’NH2; R’ = H, CH3, CH2SH) in aqueous solution and solid state [2-4]. These studies show clearly that in all of the investigated systems hexanuclear complexes appear, which become predominant with increasing metal and ligand concentration as well as increasing pH, and comprise finally often close to 100% of the species distribution. The aim of our studies was to investigate the complex structure, stability constants, and the mechanism of complex formation.

Keywords: EXAFS; XRD; UV-Vis; Actinides; carboxyl groups

Related publications

  • Poster
    Actinides 2013, 21.-26.07.2013, Karlsruhe, Deutschland

Publ.-Id: 18726

Colorimetric As (V) Detection Based on S-Layer Functionalized Gold Nanoparticles

Lakatos, M.; Matys, S.; Raff, J.; Pompe, W.

Herein, we present simple and rapid colorimetric and UV/VIS spectroscopic methods for detecting anionic arsenic (V) complexes in aqueous media. The methods exploit the aggregation of S-layer-functionalized spherical gold nanoparticles of sizes between 20 and 50 nm in the presence of arsenic species. The gold nanoparticles were functionalized with oligomers of the S-layer protein of Lysinibacillus sphaericus JG-A12. The aggregation of the nanoparticles results in a color change from burgundy-red for widely dispersed nanoparticles to blue for aggregated nanoparticles. A detailed signal analysis was achieved by measuring the shift of the particle plasmon resonance signal with UV/VIS spectroscopy. To further improve signal sensitivity, the influence of larger nanoparticles was tested. In the case of 50 nm gold nanoparticles, a concentration of the anionic arsenic (V) complex lower than 24 ppb was detectable.

Keywords: arsenic; colorimetric; nanoparticle; S-layer; detection

Publ.-Id: 18724

Dual time point based quantification of metabolic uptake rates in 18F-FDG PET

van den Hoff, J.; Hofheinz, F.; Oehme, L.; Schramm, G.; Langner, J.; Beuthien-Baumann, B.; Steinbach, J.; Kotzerke, J.

Assessment of dual time point (DTP) positron emission tomography was carried out with the aim of a quantitative determination of Km, the metabolic uptake rate of [18F]fluorodeoxyglucose as a measure of glucose consumption.

Starting from the Patlak equation, it is shown that Km?mt/ca0 + Vr/?a, where mt is the secant slope of the tissue response function between the dual time point measurements centered at t=t0. ca0=ca(t0) denotes arterial tracer concentration, Vr is an estimate of the Patlak intercept, and ?a is the time constant of the ca(t) decrease. We compared the theoretical predictions with the observed relation between Ks=mt/ca0 and km in a group of nine patients with liver metastases of colorectal cancer for which dynamic scans were available, and Km was derived from conventional Patlak analysis. derived from conventional Patlak analysis. Twenty- two lesion regions of interest (ROIs) were evaluated. ca(t) was determined from a three-dimensional ROI in the aorta. Furthermore, the correlation between Km and late standard uptake value (SUV) as well as retention index was investigated. Additionally, feasibility of the approach was demonstrated in a whole-body investigation.

Patlak analysis yielded a mean Vr of Vr = 0.53?0.08 ml/ml. The patient averaged ?a was 99?23 min. Linear regression between Patlak-derived Km and DTP-derived Ks according to Ks = b ? Km + a yielded b = 0.98 ? 0.05 and a = -0.0054 ? 0.0013 ml/min/ml (r = 0.98) in full accordance with the theoretical predictions b = 1 and a ? -Vr=?a Ks exhibits better correlation with Km than late SUV and retention index, respectively. K(c)s = Ks + Vr=?a is proposed as a quantitative estimator of Km which is independent of patient weight, scan time, and scanner calibration.

Quantification of Km from dual time point measurements compatible with clinical routine is feasible. The proposed approach eliminates the issues of static SUV and conventional DTP imaging regarding influence of chosen scanning times and inter-study variability of the input function. Ks and K(c)s exhibit improved stability and better correlation with the true Km. These properties might prove especially relevant in the context of radiation treatment planning and therapy response control.

Publ.-Id: 18723

Anti-tumor effects of peptide analogues targeting neuropeptide hormone receptors on mouse pheochromocytoma cells

Ziegler, C. G.; Eisenhofer, G.; Schally, A. V.; Gebauer, L.; Gondek, K.; Ullrich, M.; Qin, N.; Bergmann, R.; Pietzsch, J.; Ehrhart-Bornstein, M.; Bornstein, S. R.

Pheochromocytoma is a rare but potentially lethal chromaffin cell tumor with currently no effective treatment. Peptide hormone receptors are frequently overexpressed on endocrine tumor cells and can be specifically targeted by various anti-tumor peptide analogs. The present study carried out on mouse pheochromocytoma cells (MPCs) and a more aggressive mouse tumor tissue-derived (MTT) cell line revealed that these cells are characterized by pronounced expression of the somatostatin receptor 2 (sst2), growth hormone-releasing hormone (GHRH) receptor and the luteinizing hormone-releasing hormone (LHRH) receptor. We further demonstrated significant anti-tumor effects mediated by cytotoxic somatostatin analogs, AN-162 and AN-238, by LHRH antagonist, Cetrorelix, by the cytotoxic LHRH analog, AN-152, and by recently developed GHRH antagonist, MIA-602, on MPC and for AN-152 and MIA-602 on MTT cells. Studies of novel anti-tumor compounds on these mouse cell lines serve as an important basis for mouse models of metastatic pheochromocytoma, which we are currently establishing.

Publ.-Id: 18721

Matching the 20 kW SSPA to ELBE

Büttig, H.; Arnold, A.

In January 2012 the 10 kW CW klystrons (CPI VKL7811St) used to operate the superconducting cavities of ELBE since 2001 have been replaced by pairs of 10 kW solid state amplifiers (SSPA) providing 20 kW RF power per cavity. The paper reviews the procedures and the problems during commissioning the new RF system.

Keywords: LINAC RF; Commissioning Linac RF-system; ELBE RF system

Related publications

  • Lecture (Conference)
    ARD Workshop “Pushing the ELBE CW RF-system to high average beam current”, 14.-15.03.2013, Dresden, Deutschland

Publ.-Id: 18719

Substitution of the Klystrons by Solid State Power Amplifiers (SSPA) at ELBE

Büttig, H.

In January 2012 the 10 kW CW klystrons (CPI VKL7811St) used to operate the superconducting cavities of ELBE since 2001 have been replaced by pairs of 10 kW solid state amplifiers (SSPA) providing 20 kW RF power per cavity. The paper gives an overview on the activities and the problems during high power CW operation.

Keywords: ELBE RF-system; 1.3GHz SSPA; SC-LINAC RF Power Generation

Related publications

  • Lecture (Conference)
    ARD Workshop “Pushing the ELBE CW RF-system to high average beam current”, 14.-15.03.2013, Dresden, Deutschland

Publ.-Id: 18718

Design and Performance of the Upgraded ELBE RF-System Based on Solid State Amplifiers

Büttig, H.; Arnold, A.; Büchner, A.; Justus, M.; Kuntzsch, M.; Lehnert, U.; Michel, P.; Schurig, R.; Staats, G.; Teichert, J.

With the expansion of the radiation source ELBE, a centre for high power radiation sources is being built until 2014 at the Helmholtz Zentrum Dresden Rossendorf. One part of this program is to double the beam current of the ELBE LINAC. In January 2012 the 10 kW CW klystrons, used to operate the superconducting cavities of ELBE since 2001, had been replaced by a pair of 10 kW solid state amplifiers. The paper gives an overview on the activities around this project and the first experience with the new RF-system.

Keywords: ELBE RF system; Superconducting LINAC RF; 1.3 GHz Solid State Power Amplifiers; Solid State Poer Amplifiers for Particle Accelerators

Related publications

  • Invited lecture (Conferences)
    TIARA Workshop on RF Power Generation for Accelerators, 17.-19.06.2013, Uppsala, Schweden

Publ.-Id: 18717

Effective Spin Meron Pairs In Ferromagnetic Multilayers

Wintz, S.; Bunce, C.; Neudert, A.; Körner, M.; Strache, T.; Buhl, M.; Erbe, A.; Gemming, S.; Raabe, J.; Quitmann, C.; Fassbender, J.

We report on pairs of diverging/converging spin vortices in Co/Rh/Ni81Fe19 trilayer disks. The lateral magnetization distribution of these effective spin merons is imaged directly by means of element-selective x-ray microscopy. By this method, both the divergence and circulation states of the individual layers are identified as antisymmetric. Reversal measurements on corresponding continuous films reveal that biquadratic interlayer exchange coupling is the origin for the formation of effective meron pairs. Furthermore, their three-dimensional magnetization structure is determined by micromagnetic simulations. Interestingly, the magnetic induction follows a kind of flux-closing torus. This toroidal topology enforces a symmetry break, which ties the core polarities to the divergence configuration.

Keywords: spin; texture; vortex; meron; topology

  • Lecture (Conference)
    Joint European Magnetic Symposia 2013, 25.-30.08.2013, Rhodos, Griechenland

Publ.-Id: 18716

Commisioning of the upgraded superconducting linac ELBE

Büttig, H.; Arnold, A.; Büchner, A.; Justus, M.; Kuntzsch, M.; Lehnert, U.; Michel, P.; Schurig, R.; Staats, G.; Teichert, J.

In January 2012 the 10 kW CW klystrons (CPI VKL7811St) used to operate the superconducting cavities of ELBE since 2001 have been replaced by pairs of 10 kW solid state amplifiers (SSPA) providing 20 kW RF power per cavity. The paper gives an overview on the activities and the problems during high power CW operation.

Keywords: Linac-RF; SSPA; High power solid state RF amplifiers; Accelerator RF systems; Superconducting Linac RF; CW Linac RF

Related publications

  • Open Access Logo Contribution to proceedings
    4th International Particle Accelerator Conference, IPAC13, 12.-17.05.2013, Shanghai, China
    IPAC2013-Proceedings , Paper WEPME007, page 2935, Geneva: JACoW, 2935
  • Poster
    4th International Particle Accelerator Conference, IPAC13, 12.-17.05.2013, Shanghai, China

Publ.-Id: 18715

X-ray diffraction studies during magnetron co-sputtering of Ni-Ti shape memory alloy films

Martins, R. M. S.; Schell, N.; Mahesh, K. K.; Silva, R. J. C.; Braz Fernandes, F. M.

The study of Ni-Ti shape memory alloy films is of great technological interest for applications in the field of microengineering. They can work as sensors and actuators at the same time. However, there are still important issues unresolved like formation of film crystallographic orientation and its control. Films exhibiting the two-way shape memory effect are also required.
A two-magnetron sputter deposition chamber mounted into the six-circle diffractometer of the Rossendorf Beamline at the European Synchrotron Radiation Facility was used for the processing of Ni-Ti films. The in-situ x-ray diffraction studies enabled to identify the different steps of the structural evolution during film growth.
Deposition conditions leading to Ni-Ti films mainly containing grains with (100) or (110) planes of the B2 phase parallel to the film surface were successfully defined. This is an important achievement since texture has a strong influence on the extent of the strain recovery. The deposition of films with a “two-way” actuation (films with a combination of superelasticity and shape memory characteristics) was also achieved. It will allow the development of smaller devices since no consideration has to be paid to a resetting spring.

Keywords: Shape Memory Alloy; Ni-Ti; Deposition by sputtering; In-situ X-ray diffraction; Texture development

Related publications

  • Open Access Logo Ciência & Tecnologia dos Materiais 24(2012)3/4, 161-169

Publ.-Id: 18714

Ein neuartiges Konzept zur Berechnung der Positronenemitter-Ausbeuten für die Reichweiteverifikation bei der Partikeltherapie mittels PET

Priegnitz, M.; Enghardt, W.; Laube, K.; Fiedler, F.

no abstract available

  • Lecture (Conference)
    44. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik, 18.-21.09.2013, Köln, Deutschland
  • Open Access Logo Contribution to proceedings
    44. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik, 18.-21.09.2013, Köln, Deutschland
    Medizinische Physik - Abstractband, 978-3-9816002-1-6, 119-121

Publ.-Id: 18713

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