Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35818 Publications

Morphology analysis of sponge-like Si-SiO2 nanocomposites using energy-filtered electron tomography and electron holographic tomography

Hübner, R.; Wolf, D.; Friedrich, D.; Liedke, B.; Schmidt, B.; Heinig, K.-H.

Due to the possibility of band-gap engineering by quantum confinement, Si nanosponge structures embedded in SiO2 formed by spinodal decomposition of metastable silicon-rich silicon oxide are promising absorbers for 3rd generation solar cells. High-temperature annealing of thermodynamically metastable, silicon-rich oxide SiOx with x < 2 leads to phase separation of elemental Si from stoichiometric SiO2. While this phase separation results in disconnected Si nanoclusters for 1.2 ≤ x < 2, percolated Si nanostructures with a sponge-like morphology are observed for x < 1.2 [1].
To visualize the sponge-like morphology in SiOx films for x around 1 after thermal treatment, energy-filtered transmission electron microscopy (EFTEM) imaging, EFTEM tomography, and electron holographic tomography (EHT) [2] were carried out. To this end, 200 nm thick SiOx layers were prepared on p type (100) Si wafers by magnetron sputtering in Ar plasma from two simultaneously operating Si and SiO2 targets. During subsequent annealing, samples were heated up to 1150 °C. Sponge-like nanostructures were investigated by EFTEM imaging using an image-corrected FEI Titan 80-300 microscope equipped with a GIF 863. For EFTEM tomography, a tilt series between ±70° was acquired in a Philips CM200 FEG microscope with a GIF 678, and for EHT, a tilt series from -74° to +79° was recorded in an image-corrected FEI Tecnai TF20 microscope. Tomographic reconstruction of the Si 3D morphology was performed with the Weighted Simultaneous Iterative Reconstruction Technique [3].
Valence-band plasmon energy-loss imaging is an appropriate approach to visualize the Si morphology in phase-separated Si-SiO2 nanocomposites [4]. As an example, Figure 1 shows the Si plasmon EFTEM images (Eloss = 17 eV) of a SiOx≈1 layer decomposed into Si and SiO2 after thermal treatment at 1100 °C for 3 min (left) and 3 h (right). As indicated by the selected area electron diffraction patterns, coarsening of the Si nanostructure is accompanied by Si crystallite growth. Although Si plasmon EFTEM imaging can show the Si phase distribution in a planar projection, it does not provide 3D information. Therefore, EFTEM tomography was applied, revealing that a spinodal sponge-like morphology of Si is only partially visible in a volume of ca. (30 nm)³ (Figure 2). However, in a larger volume of ca. (140 nm)³ - as demonstrated by applying EHT on a needle-shaped specimen prepared by FIB - both isolated nanoparticles and percolated Si nanostructures with a sponge-like morphology are observed (Figure 3).

[1] T. Müller et al., Appl Phys Lett 85 (2004) 12.
[2] D. Wolf et al., Curr Opin Solid St M 17 (2013) 126.
[3] D. Wolf et al., Ultramicroscopy 136 (2014) 15.
[4] D. Friedrich et al., Appl Phys Lett 103 (2013) 131911.

The authors kindly acknowledge TEM sample preparation by Annette Kunz and Martina Missbach.

Keywords: silicon-rich silicon oxide; EFTEM imaging; EFTEM tomography; electron holographic tomography

  • Poster
    18th International Microscopy Congress, 07.-12.09.2014, Prague, Czech Republic
  • Contribution to proceedings
    18th International Microscopy Congress, 07.-12.09.2014, Prague, Czech Republic

Publ.-Id: 20883

Contributions of Cu-rich clusters, dislocation loops and nanovoids to the irradiation-induced hardening of Cu-bearing low-Ni reactor pressure vessel steels

Bergner, F.; Gillemot, F.; Hernández-Mayoral, M.; Serrano, M.; Török, G.; Ulbricht, A.; Altstadt, E.

Dislocation loops, nanovoids and Cu-rich clusters (CRPs) are known to represent obstacles for dislocation glide in neutron-irradiated reactor pressure vessel (RPV) steels, but a consistent experimental determination of the respective obstacle strengths is still missing. A set of Cu-bearing low-Ni RPV steels and model alloys was characterized by means of SANS and TEM in order to specify mean size and number density of loops, nanovoids and CRPs. The obstacle strengths of these families were estimated by solving an over-determined set of linear equations. We have found that nanovoids are stronger than loops and loops are stronger than CRPs. Nevertheless, CRPs contribute most to irradiation hardening because of their high number density. Nanovoids were only observed for neutron fluences beyond typical end-of-life conditions of RPVs. The estimates of the obstacle strength are critically compared with reported literature data.

Keywords: pressure vessel steels; electron microscopy; neutron scattering; hardening; precipitation; dislocations

Publ.-Id: 20882

Biologische Bausteine für Materialien der Zukunft

Kostudis, S.; Weinert, U.; Raff, J.

Der Vortrag stellt das Helmholtz-Zentrum Dresden-Rossendorf sowie das Helmholtz-Institut Freiberg für Ressourcentechnologie vor und gibt Einblick in Arbeiten der Arbeitsgruppe Biotechnologie. Mithilfe mikrobiologischer Organismen, Bausteine und Prozesse können neue umweltfreundliche und nachhaltige industrielle Anwendungen wie Filter und Sensoren entwickelt werden.

  • Lecture (others)
    Vortragsreihe "Werte-Wege-Welt", 13.12.2013, Bautzen, Deutschland

Publ.-Id: 20880

Spectral and geochemical characterization of onshore hydrocarbon seep-induced alteration in the Dezful Embayment, SW Iran

Salati, S.; van Ruitenbeek, F.; de Smeth, B.; van der Meer, F.

The presence of hydrocarbon seeps at the surface is indirect evidence of the presence of mature source rocks within a geologi- cal system at depth. Chemical changes in the environment of sur- face rocks caused by hydrocarbon seeps cause mineralogical alterations. To determine the nature of the alterations and the influences of lithology and type of seep, rock samples were col- lected from altered and unaltered evaporite and marly limestone formations in the Dezful embayment, southwest Iran. Reflectance spectroscopy, bulk rock/wet chemical analyses, and sulfur, carbon, and oxygen isotopic analyses were used to delin- eate surficial alterations and relate alterations to hydrocarbons seeping from underlying reservoirs. In addition, the boosted regression trees (BRT) method was used to predict the presence of alterations from spectral indices. Comparisons of geochemical data and spectral data of altered evaporites and altered marly lime- stones showed that the minerals within alteration facies have dis- tinctive spectral, chemical, and isotopic signatures. Gas-induced alterations were characterized by the formation of gypsum and native sulfur and depletion in 34S. The released H2S in natural gas reacted with gypsum in the evaporite sediments and calcite in the marly limestone formations, which led to precipitation of secondary gypsum and native sulfur. Oil-induced alterations were characterized by formation of secondary calcite and depletion in 13C. The oxidation of seeping oil and reactions between this oil and host rocks caused precipitation of secondary calcite within both formations. The combination of fieldwork data and spectral-geochemical data showed a connection exists between surficial alterations and underlying petroleum reservoirs, which can be used in exploration campaigns.

Keywords: Hydrocarbon seeps; Alterations; Spectroscopy; Geochemistry; Isotopic analysis; Boosted Regression Trees (BRT)

Publ.-Id: 20879

Detection of Alteration Induced by Onshore Gas Seeps from ASTER and WorldView-2 Data

Salati, S.; van Ruitenbeek, F.; van der Meer, F.; Naimi, B.

Hydrocarbon seeps cause chemical and mineralogical changes at the surface, which can be detected by remote sensing. This paper aims at the detection of mineral alteration induced by gas seeps in a marly limestone formation, SW Iran. For this purpose, the multispectral Advance Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the high spatial resolution WorldView-2 (WV-2) data were utilized for mapping surficial rock alteration. In addition, the potential of Visible Near Infrared (VNIR) bands of the WV-2 and its high spatial resolution for mapping alterations was determined. Band ratioing, principal component analysis (PCA), data fusion and the boosted regression trees (BRT) were applied to enhance and classify the altered and unaltered marly limestone formation. The alteration zones were identified and mapped by remote sensing analyses. Integrating the WV-2 into the ASTER data improved the spatial accuracy of the BRT classifications. The results showed that the BRT classification of the multiple band imagery (created from ASTER and WV-2) using regions of interest (ROIs) around field data provides the best discrimination between altered and unaltered areas. It is suggested that the WV-2 dataset can provide a potential tool along higher spectral resolution data for mapping alteration minerals related to hydrocarbon seeps in arid and semi-arid areas.

Keywords: hydrocarbon seep; alteration mineral; ASTER; WorldView-2; boosted regression trees (BRT) classification

Publ.-Id: 20878

Near surface silicide formation after off-normal Fe-implantation of Si(001) surfaces

Khanbabaee, B.; Lützenkirchen-Hecht, D.; Hübner, R.; Grenzer, J.; Facsko, S.; Pietsch, U.

We report on formation of non-crystalline Fe-silicides of various stoichiometries below the amorphized surface of crystalline Si(001) after irradiation with 5 keV Fe+ ions under off-normal incidence. We examined samples prepared with ion fluences of 0.1 × 1017 and 5 × 1017 ions cm−2 exhibiting a flat and patterned surface morphology, respectively. Whereas the iron silicides are found across the whole surface of the flat sample, they are concentrated at the top of ridges at the rippled surface. A depth resolved analysis of the chemical states of Si and Fe atoms in the near surface region was performed by combining X-ray photoelectron spectroscopy and X-ray absorption spectroscopy (XAS) using synchrotron radiation. The chemical shift and the line shape of the Si 2p core levels and valence bands were measured and associated with the formation of silicide bonds of different stoichiometric composition changing from an Fe-rich silicides (Fe3Si) close to the surface into a Si-rich silicide (FeSi2) towards the inner interface to the Si(001) substrate. This finding is supported by XAS analysis at the Fe K-edge which shows changes of the chemical environment and the near order atomic coordination of the Fe atoms in the region close to surface. Because a similar Fe depth profile has been found for samples co-sputtered with Fe during Kr+ ion irradiation, our results suggest the importance of chemically bonded Fe in the surface region for the process of ripple formation.

Publ.-Id: 20877

Biologische Bausteine für Materialien der Zukunft

Kostudis, S.; Weinert, U.; Raff, J.

Der Vortrag stellt das Helmholtz-Zentrum Dresden-Rossendorf sowie das Helmholtz-Institut Freiberg für Ressourcentechnologie vor und gibt Einblick in Arbeiten der Arbeitsgruppe Biotechnologie. Mithilfe mikrobiologischer Organismen, Bausteine und Prozesse können neue umweltfreundliche und nachhaltige industrielle Anwendungen wie Filter und Sensoren entwickelt werden.

  • Lecture (others)
    Tag der Wissenschaften 2013, 13.06.2013, Radebeul, Deutschland

Publ.-Id: 20876

Bioleaching of copper from Kupferschiefer by organic acid and heterotrophic bacteria

Kostudis, S.; Bachmann, K.; Kutschke, S.; Pollmann, K.

Increasing prices of metals and strategic issues such as independent resource access force reconsideration of European Kupferschiefer deposits in Germany. For the mode of exploitation is cost-intensive and the copper content does hardly exceed four percent the processing has to be all the more efficient. This advantage of efficiency as well as ecological friendliness is brought along by biomining – the usage of biological components for metal extraction. For Kupferschiefer (Polkowice, Poland) bears carbonates up to 10 % commonly used bioleaching with acidophilic microorganisms is an issue. Therefore heterotrophic microbes and their metabolites were investigated. Results show copper yields up to nearly 48 % in undirected proof-of-principle batches.

Keywords: sulphide ores; bacteria; bioleaching; liberation analysis; environmental

  • Lecture (Conference)
    Biohydrometallurgy '14, 09.-11.06.2014, Falmouth, United Kingdom

Publ.-Id: 20875

Visualization and quantitative analysis of dispersive mixing by a helical static mixer in upward co-current gas-liquid flow

Rabha, S.; Schubert, M.; Grugel, F.; Banowski, M.; Hampel, U.

Growing interest towards process intensification in chemical industries over the last decade promotes static mixers as an attractive contactor alternative to the bubble column and mechanically stirred vessels. In the present work, the dispersion provided by a helical static mixer in a vertical pipe at turbulent gas-liquid flow conditions was studied using ultrafast electron beam X-ray tomography. Dispersive mixing was quantified upstream and downstream of three, six and nine helical static mixer elements in terms of bubble size distribution and gas holdup. Bubble breakup within the mixer elements was visualized and quantified via bubble size distribution and interfacial area density. Moreover, the power dissipation per unit mass of liquid was calculated for different number of static mixer elements and slip. The results provide a new insight into the development of the gas phase distribution within helical static mixers and a sound basis for design improvement, optimization of flow conditions and CFD validation.

Keywords: Helical static mixer; Ultrafast electron beam X-ray tomography; Gas-liquid flows; Specific interfacial area

Publ.-Id: 20874

PGE geochemistry of the Fengshan porphyry–skarn Cu–Mo deposit, Hubei Province, Eastern China

Wang, M.; Gutzmer, J.; Michalak, P. P.; Guo, X.; Xiao, F.; Wang, W.; Liu, K.

The Fengshan Cu–Mo deposit is located in the western part of the Jiurui Cu–Au–Mo district in the Late Mesozoic Middle–Lower Yangtze River Metallogenic Belt (YRMB), Eastern China. The mineralization is spatially associated with the Fengshan granodiorite porphyry stock (149–138 Ma), where two types of ore bodies (porphyry, skarn) occur. The Fengshan deposit is located on the Yangtze Craton, i.e., in an intracontinental extensional environment, a geological setting not considered by previous studies of PGE abundance and distribution in porphyry systems. For the present investigation the PGE geochemistry of fourteen samples of the granodiorite, ore and flotation concentrates were determined by ICP-MS, after preconcentration by the Lead Fire Assay technique from large (30 g) samples. A maximum of 32 ppb Pd and 81.2 ppb Pt is reported for the molybdenum flotation concentrate. Cu, Au, Pt, Pd contents from flotation concentrate samples are almost 1 to 2 orders of magnitude higher than those reported for ore samples; this is especially true for the Pt content. Covariant diagrams of Cu and Mo with noble metals (Au, Ag, Pt and Pd) reveal weak correlation between Cu vs. Au, Ag, and Mo vs. Pt. Also, Au shows a slightly positive relationship with Pt and Pd.

It is apparent that Pd and Pt contents of flotation concentrate from the Fengshan deposit are considerably lower than those reported for porphyry deposits in an island arc setting. However, Au and Ag appear to be elevated in the Fengshan deposit. The intrusion derived from an enriched mantle source, high oxygen fugacity (fO2), and liberation of mantle sulfates during partial melting, are the first steps for PGE enrichment in porphyry Cu deposits. However, the Fengshan granodiorite was most likely generated by partial melting of enriched mantle that was previously metasomatized by slab melts related to an ancient subduction system. Au, Pt, and Pd in potassic alteration zones and/or endocontact zones are transported as an aqueous chloride complex in high temperature, hypersaline fluid. In contrast, Au, Pt and Pd would be transported by bisulfide complex in low temperature, intermediate salinity fluid in phyllic alteration zones and/or exocontact marble. That is distinctly different from the porphyry Cu deposits in an island arc environment, where intrusion derived directly from slab melting and Pd and Pt are transported only as chloride complexes.

Keywords: Platinum group elements; Porphyry–skarn Cu–Mo deposit; Fengshan; Eastern China

Publ.-Id: 20873

New lithogeochemical and mineralogical exploration of Li-Sn greisen mineralisation in old mining adits of the Zinnwald deposit, Germany

Neßler, J.; Seifert, T.; Gutzmer, J.; Müller, A.; Henker, J.; Kühn, K.

The polymetallic Zinnwald-Cínovec deposit is represented by greisen-type mineralisation hosted within the apical portion of a small granite intrusion. Similar to other granitic stocks with Sn-W mineralisation in the Erzgebirge, the Zinnwald granite intruded during the post-collisional stage of the late-Variscan (Permo-Carboniferous) magmatic evolution. These intrusions are characterised by the prominent enrichment of incompatible elements (F, Li, Rb, Cs, Sn, Nb and Ta) and the depletion of P2O5. The deposit is located in the eastern part of the Erzgebirge region, Germany and straddles the border between Germany and the Czech Republic. It is characterised by flat dipping, sheet-like greisen ore bodies (up to 40 m in thickness) and veins (up to 1 m in thickness) located in the apical part and along the quaquaversal dipping edges of the granite stock. The greisen bodies predominantly consist of quartz, Li-Rb-Cs-bearing mica (named zinnwaldite), topaz, fluorite and accessory kaolinite and cassiterite. Historically mined for its cassiterite and wolframite ores since the 16th and 19th century, respectively, the deposit still provides access to a wide spread system of drifts and adits. Selected parts of the underground mine are now presented by the visitor's mine "Vereinigt Zwitterfeld zu Zinnwald". These local conditions are favourable for the re-examination of the exhibited greisen mineralisation. Within the framework of the ongoing Li and Sn exploration project of the SolarWorld Solicium GmbH in the German part of the deposit, an underground sampling campaign has been conducted, incorporating a series of 88 channel samples gained at two different levels (Tiefer Bünau adit = 750 m a.s.l.; Tiefe Hilfe Gottes adit = 720 m a.s.l.). Equally spaced channels of 2 m intervals and approximate dimensions of 180 x 5 x 2.5 cm have been created on pre-selected and detailed mapped walls of two different adits within the mine. The sample material has been gained for mineralogical and geochemical investigation using optical light microscopy and ICP-MS. The herein presented work aims to provide information about the horizontal distribution of selected elements (Li, Rb, Cs, Sn, W, Sc, Nb, Ta and Zn) and to assess historic data on mineralogy and geochemistry. Furthermore, the question of a sufficient sampling distance is tried to answer with the help of statistical exclusion principles. Investigations on the chemical composition of the greisen ore yielded homogeneous concentration of elements contained in micas (Li, Rb, Cs, Zn and Sc!) with Li concentration of about 0.3 wt. %, whereas concentrations of Sn and W (but also Nb and Ta) are more heterogenic distributed with some high-grade values connected to local mica-nests, veins and/or joint planes. Moreover, results of investigated elements from this campaign are in good agreement with the overall geochemical pattern obtained by past investigations. Compared with geochemical whole rock data from drill core samples of surrounding drill holes, the mean Li grades of channel samples are consistent for different areas within the mine. In case of Li, the application of statistical exclusion principles can provide a good estimation of the sufficient maximum sampling distance (about 5 m).

  • Open Access Logo Contribution to proceedings
    EGU General Assembly, 27.04.-02.05.2014, Vienna, Austria
    Geophysical Research Abstracts 16(2014), Vienna: Copernicus

Publ.-Id: 20872

Provenance of the Neoproterozoic rocks of the Gifberg Group (Western South Africa)

van Staden, A.; Zimmermann, U.; Gutzmer, J.; Germs, G. J. B.

New petrographic and lithogeochemical data are presented for siliciclastic units of the Gifberg Group (western South Africa), a succession rarely studied in the past. The main detrital source for the oldest succession of the Gifberg Group, the Karoetjes Kop Formation, has been identified as sourced by local metamorphic rocks with a felsic geochemical composition. Nearly unweathered detritus (Chemical index of alteration: 50 to 60; K/Cs >>5000) occurs in the metadiamictite of this formation and is interpreted as palaeovalley infill, deposited only a short distance from its sources. The provenance signature of the overlying Aties Formation indicates significant mafic and/or intermediate sources. Possible sources are rocks of the Bushmanland Group and an unknown unmetamorphosed mafic to intermediate rock succession, which might have been exposed during the deposition of the Aties Formation. The overlying Bloupoort Formation is characterised by a geochemically homogenous metadiamictite (Swartleikrans Bed) with only slightly weathered detritus (K/Cs >10000) and overlying mature silica-rich metarenites and metaconglomerates. It is proposed that the Gifberg basin formed as a small-scale rift basin and then widened through time with subsequent longer sedimentary transport of the detritus which have caused the higher compositional maturity. The predominance of detrital input from local sources in the Karoetjes Kop Formation hinders correlation based on its mineralogical and geochemical content alone. A glacial origin for the Swartleikrans Bed was proposed previously based on the occurrence of possible dropstones. Certain criteria for a glacial depositional environment as outlined by Arnaud and Etienne (2011) were met in our study and include poor sorting, rapid lateral facies changes, crude stratification, variable thicknesses, compositional immaturity, and a gradational contact plus a chaotic texture with large boulders. While these observations point to a ‘rainout’ deposit, there is still a lack of evidence for glacial transport on grain surfaces or in the form of faceted clasts and pebbles.

Publ.-Id: 20871

P1309 - Magnetooptik mit strukturierten unmagnetischen Metallen

Schmidt, H.; Kaspar, T.; Schmidt, O. G.; Brunner, R.

Die Erfindung beschreibt die Auslegung einer Anordnung eines regelmäßig strukturierten unmagnetischen Einzel- oder Mehrschichtsystems mit mehreren Basiselementen in der Einheitszellen, bei dem für eine vorgegebene Wellenlänge der einfallenden elektromagnetischen Welle eine bestimmte Polarisation der reflektierten oder transmittierten Welle in Abhängigkeit von einem von außen angelegten Magnetfeld erreicht wird.

  • Patent
    DE102013203761 - Offenlegung 11.09.2014, Nachanmeldung: WO, DE

Publ.-Id: 20870

Magnetic Characterization and Electrical Field-Induced Switching of Magnetite Thin Films Synthesized by Atomic Layer Deposition and Subsequent Thermal Reduction

Zierold, R.; Le Lam, C.; Dendooven, J.; Gooth, J.; Böhnert, T.; Sergelius, P.; Munnik, F.; Montero Moreno, J. M.; Görlitz, D.; Detavernier, C.; Nielsch, K.

Magnetite (Fe3O4) of high quality was prepared by combining atomic layer deposition (ALD) with a subsequent thermal reduction process. The reduction process in hydrogen atmosphere was investigated by in situ X-ray diffraction studies as a function of temperature. A complete reduction to Fe3O4 was confirmed within a narrow temperature window during the thermal treatment. Magnetic characterization of magnetite thin films as a function of temperature, applied magnetic field, and magnetic field orientation were performed. The highly stoichiometry- and impurity-sensitive Verwey transition was observed in magnetic and electrical measurements. Moreover, the isotropic point at which the magnetocrystalline anisotropy of magnetite vanishes was unveiled. Both findings prove, first, the formation of the magnetite phase against the undesired maghemite and, second, the quality of the ALD thin films to be comparable with samples grown by molecular beam epitaxy. The magnetic easy- and hard-axis could be found to be in-plane and out-of-plane, respectively. Consistent with angular-dependent studies of the coercive field, additionally performed first-order reversal curve measurements revealed a complex micromagnetic structure with different magnetization reversal path for both configurations. Finally, electric field-induced resistive switching was studied in detail being in perfect agreement with results of single-crystalline samples. The presented data and its analysis support the assumption of previous works of the magnetization reversal in magnetite nanotubes, suggest improvement for future magnetization studies of nanostructures by exploiting the isotropic point, and might open new paths for low-cost resistive switching devices.

Publ.-Id: 20869

Kupferlaugung aus Kupferschiefer mit organischer Säure

Kostudis, S.; Bachmann, K.; Kutschke, S.; Pollmann, K.; Gutzmer, J.

Die steigende Nachfrage an Basismetallen wie Kupfer, aber auch strategischen Elementen wie Gallium oder Molybdän, steht einer verringerten Qualität und erhöhter Komplexität vorhandener Erzressourcen gegenüber. Biotechnologische Ansätze wie die Biolaugung können auch mit diesem Ausgangsmaterial effiziente Abbauprozesse liefern. So konnten mithilfe von Schimmelpilzen und organischen Säuren vielversprechende Ergebnisse in der Kupferlaugung aus Kupferschiefer (Polkovice/Lubin, Polen) erzielt werden. Der europäische Kupferschiefer ist eine potente lokale Ressource und zeichnet sich durch hohe Anteile organischer Verbindungen und Carbonate, eine komplexe Matrix und maximalen Kupferkonzentrationen von ca. 5 % aus. Insbesondere der hohe Carbonatgehalt von ca. 18 % bringt die herkömmlichen Biolaugungsverfahren mit säureliebenden Bakterien an ihre Grenzen.
Der Beitrag zeigt die Auswirkungen der Säureeinwirkung auf die Mineralogie des Kupferschiefers. Vornehmlich wird Chalkosin gelaugt, aber auch Kupfereisensulfide wie Bornit und Chalkopyrit. Die Gesamtkupferausbeute liegt bei durchschnittlich 44 % in einfachen Ansätzen in Schüttelkolben.

  • Lecture (Conference)
    Aufbereitung und Recycling 2014, 12.-13.11.2014, Freiberg, Deutschland

Publ.-Id: 20868

Interfacial Reaction of SnII on Mackinawite (FeS)

Dulnee, S.; Scheinost, A. C.

The interaction of SnII with metastable, highly reactive mackinawite is a complex process due to transient changes of the mackinawite surface in the sorption process. In this work, we show that tin redox state and local structure as investigated by Sn-K X-ray absorption spectroscopy (XAS) change with pH. We observe at pH <7 that SnII forms two short (2.38 Å) Sn-S bonds, the S atoms being part of the S-terminated surface of mackinawite. Two longer Sn-S bonds of 2.59 Å point most likely towards the solution phase, completing the tetragonal SnS4 innersphere sorption complex, while precipitation of SnS or formation of a solid solution with mackinawite could be excluded. At pH > 9, SnII is completely oxidized by an FeII/FeIII (hydr)oxide, most likely green rust, forming on the surface of mackinawite. Six O atoms at 2.04 Å and 6 Fe atoms at 3.29 Å demonstrate a structural incorporation by green rust, where SnIV substitutes for Fe in the crystal structure. The transition between SnII and SnIV and between sulfur and oxygen coordination takes place between pH 7 and 8, in accordance with the transition from the mackinawite stability field to more oxidized Fe-bearing minerals. The uptake processes of SnII by mackinawite are largely in line with the uptake processes of divalent cations of other soft Lewis-acid metals like Cd, Hg and Pb.

Keywords: mackinawite; nuclear waste; Sn; EXAFS; redox

Publ.-Id: 20867

Raman spectroscopy - casting (laser) light on microbe - mineral interactions

Kostudis, S.; Bachmann, K.; Kutschke, S.; Pollmann, K.

Highly efficient and sustainable mining strategies gain importance due to the fact that available resources of base metals like copper but strategic elements such as gallium and molybdenum as well face a steadily decreasing grade. This issue is enhanced by the increased demand and production amounts of those metal compounds. Biohydrometallurgy – the use of microorganisms or related substances in metal extraction - provides the potential of processing low grade ores efficiently. Thus it is applied yet in some gold and uranium mining.
Also due to strategic reasons mining of regional resources such as the European Kupferschiefer come to the fore. Its complex composition including sulphide rich ores, carbonates and organic compounds challenges biotechnological approaches. Nevertheless promising approaches have been reported. We examine heterotrophic bioleaching of copper from Kupferschiefer ores. To investigate the interactions between mineral surface and microorganisms Raman spectroscopy offers a versatile applicability: Identification of minerals and differentiation of microorganisms is nicely provided and is accompanied by imaging opportunities in a two or even three dimensional manner. Thus biofilms, for example, can be analysed with respect to microbial diversity or preferences of minerals during the attaching process.

  • Poster
    Microbiology and Infection 2014, 05.-08.10.2014, Dresden, Deutschland

Publ.-Id: 20866

Dynamo action driven by a periodically perturbed Beltrami-flow.

Giesecke, A.; Stefani, F.

We apply kinematic simulations of the induction equations in order to examine the ability of a Beltrami flow (with curl(V) ~V) generating dynamo action. In the basic state we find a surprisingly complex behavior of the leading azimuthal modes that have a wavenumber up to m=3. Depending on the relation of poloidal to toroidal flow the eigenmodes show slow amplitude modulations and a azimuthal drift of the field pattern.

In a more complex model we add a non-axisymmetric time-dependent flow perturbation. In extension of a previous study we change the (azimuthal) pattern and amplitude of the perturbation flow. Consequently, the magnetic field growth rates are enhanced when the frequency of the perturbation is in the appropriate regime. We find small windows of perturbation frequencies with strong enhancement of the growth rates as well as broader regimes for rather fast drifting perturbations when the perturbation amplitude is sufficient to alter structure of the basic axisymmetric flow.

The effect may be relevant for forthcoming dynamo experiments conducted in Madison or in the precession dynamo experiment at HZDR, where, however, the basic flow will look quite different.

Keywords: Dynamo

  • Lecture (Conference)
    IGDR Annual Meeting Cambridge, 01.-04.09.2014, Cambridge, Great Britain

Publ.-Id: 20865

How to identify groundwater-caused thermal anomalies in lakes based on multi-temporal satellite data in semi-arid regions

Mallast, U.; Gloaguen, R.; Friesen, J.; Roediger, T.; Geyer, S.; Merz, R.; Siebert, C.

The deduction by conventional means of qualitative and quantitative information about groundwater discharge into lakes is complicated.
Nevertheless, at least for semi-arid regions with limited surface water availability, this information is crucial to ensure future water availability for drinking and irrigation purposes.
Overcoming this lack of discharge information, we present a satellite-based multi-temporal sea-surface-temperature (SST) approach.
It exploits the occurrence of thermal anomalies to outline groundwater discharge locations using the example of the Dead Sea. Based on a set of 19 Landsat Enhanced Thematic Mapper (ETM+) images 6.2 (high gain), recorded between 2000 and 2002, we developed a novel approach which includes (i) an objective exclusion of surface-runoff-influenced data which would otherwise lead to erroneous results and (ii) a temporal SST variability analysis based on six statistical measures amplifying thermal anomalies caused by groundwater.
After excluding data influenced by surface runoff, we concluded that spatial anomaly patterns of the standard deviation and range of the SST data series spatially fit best to in situ observed discharge locations and, hence, are most suitable for detecting groundwater discharge sites.

Publ.-Id: 20864

Sulfur sources of sedimentary "buckshot" pyrite in the Auriferous Conglomerates of the Mesoarchean Witwatersrand and Ventersdorp Supergroups, Kaapvaal Craton, South Africa

Guy, B. M.; Ono, S.; Gutzmer, J.; Lin, Y.; Beukes, N. J.

Large rounded pyrite grains (> 1 mm), commonly referred to as "buckshot" pyrite grains, are a characteristic feature of the auriferous conglomerates (reefs) in the Witwatersrand and Ventersdorp supergroups, Kaapvaal Craton, South Africa. Detailed petrographic analyses of the reefs indicated that the vast majority of the buckshot pyrite grains are of reworked sedimentary origin, i.e., that the pyrite grains originally formed in the sedimentary environment during sedimentation and diagenesis. Forty-one of these reworked sedimentary pyrite grains from the Main, Vaal, Basal, Kalkoenkrans, Beatrix, and Ventersdorp Contact reefs were analyzed for their multiple sulfur isotope compositions (delta S-34, Delta S-33, and Delta S-36) to determine the source of the pyrite sulfur. In addition, five epigenetic pyrite samples (pyrite formed after sedimentation and lithification) from the Middelvlei and the Ventersdorp Contact reefs were measured for comparison. The delta S-34, Delta S-33, and Delta S-36 values of all 41 reworked sedimentary pyrite grains indicate clear signatures of mass-dependent and mass-independent fractionation and range from -6.8 to +13.8 aEuro degrees, -1.7 to +1.7 aEuro degrees, and -3.9 to +0.9 aEuro degrees, respectively. In contrast, the five epigenetic pyrite samples display a very limited range of delta S-34, Delta S-33, and Delta S-36 values (+0.7 to +4.0 aEuro degrees, -0.3 to +0.0 aEuro degrees. and -0.3 to +0.1 aEuro degrees, respectively). Despite the clear signatures of mass-independent sulfur isotope fractionation, very few data points plot along the primary Archean photochemical array suggesting a weak photolytic control over the data set. Instead, other factors command a greater degree of influence such as pyrite paragenesis, the prevailing depositional environment, and non-photolytic sulfur sources. In relation to pyrite paragenesis, reworked syngenetic sedimentary pyrite grains (pyrite originally precipitated along the sediment-water interface) are characterized by negative delta S-34 and Delta S-33 values, suggesting open system conditions with respect to sulfate supply and the presence of microbial sulfate reducers. On the contrary, most reworked diagenetic sedimentary pyrite grains (pyrite originally precipitated below the sediment-water interface) show positive delta S-34 and negative Delta S-33 values, suggesting closed system conditions. Negligible Delta S-33 anomalies from epigenetic pyrite suggest that the sulfur was sourced from a mass-dependent or isotopically homogenous metamorphic/hydrothermal fluid. Contrasting sulfur isotope compositions were also observed from different depositional environments, namely fluvial conglomerates and marine-modified fluvial conglomerates. The bulk of the pyrite grains from fluvial conglomerates are characterized by a wide range of delta S-34 values (-6.2 to +4.8 aEuro degrees) and small Delta S-33 values (+/- 0.3 aEuro degrees). This signature likely represents a crustal sulfate reservoir derived from either volcanic degassing or from weathering of sulfide minerals in the hinterland.
Reworked sedimentary pyrite grains from marine-modified fluvial conglomerates share similar isotope compositions, but also produce a positive Delta S-33/delta S-34 array that overlaps with the composition of Archean barite, suggesting the introduction of marine sulfur.
These results demonstrate the presence of multiple sources of sulfur, which include atmospheric, crustal, and marine reservoirs. The prevalence of the mass-dependent crustal sulfur isotope signature in fluvial conglomerates suggests that sulfate concentrations were probably much higher in terrestrial settings in comparison to marine environments, which were sulfate-deficient. However, the optimum conditions for forming terrestrial sedimentary pyrite were probably not during fluvial progradation but rather during the early phases of flooding of low angle unconformities, i.e., during retrogradational fluvial deposition, coupled in some cases with marine transgressions, immediately following inflection points of maximum rate of relative sea level fall.

Publ.-Id: 20863

P1308 - Anordnung zur Bestimmung der Phasenverteilung in mehrphasigen Medien mit mindestens einer hochleitfähigen Phase

Schleicher, E.; Löschau, M.; van Campen, L.

Die Erfindung betrifft einen Gittersensor zur Messung der Phasenverteilung eines mehrphasigen Stoffgemisches mit gasförmigen und flüssigen Komponenten unter Vorhandensein einer hochleitfähigen Phase (wie Salzwasser oder Flüssigmetall). Anwendungsgebiete sind die Bestimmung der Flüssigkeitsverteilung und des Füllstands in Gefäßen sowie die Untersuchung von Gas-Flüssigkeits-Mehrphasenströmungen, insbesondere in Rohrleitungen z. B. in der Erdölproduktion und -verarbeitung.

  • Patent
    DE102013203437 - Offenlegung 28.08.2014, Erteilung 28.05.2015, Nachanmeldung: WO, BR, CA, EP, RU, US

Publ.-Id: 20862

Redirection of CD4+ and CD8+ T lymphocytes via a novel antibody-based modular targeting system triggers efficient killing of PSCA+ prostate tumor cells

Arndt, C.; Feldmann, A.; Töpfer, K.; Koristka, S.; Cartellieri, M.; Temme, A.; Ehninger, A.; Ehninger, G.; Bachmann, M.

There is still a need for new therapeutic options against prostate cancer. Conventional single-chain bispecific antibodies (bsAbs), that directly cross-link T cells and tumor cells, hold great potential for efficient tumor treatment. However, rapid development of novel bsAbs is hampered by laborious optimization to improve their efficacy and reduce potential side effects. To accelerate the development of a novel antibody tool for the redirection of T cells to different tumor-associated antigens, we recently introduced a modular targeting system.
We here describe a novel modular system for treatment of prostate cancer by retargeting of T cells to the prostate stem cell antigen (PSCA). Functionality of the novel PSCA-specific modular system was investigated in vitro by T cell activation and chromium release assays as well as in immunodeficient mice.
Similar to a conventional bsAb CD3-PSCA, the novel PSCA-specific modular system induces activation of both CD4+ and CD8+ T cells leading to secretion of pro-inflammatory cytokines and highly efficient target-specific tumor cell lysis. The novel TM was ready-to-use from the time point of construction and functional at low E:T ratios and picomolar concentrations without further optimization. In addition, the PSCA-specific modular system delays outgrowth of s.c. tumors in mice comparable to bsAb CD3-PSCA.
We have developed a novel PSCA-specific modular system which triggers an efficient T cell-mediated killing of PSCA+ tumor cells in vitro and in vivo. The new Ab-based targeting strategy can functionally replace conventional bsAbs and allows a flexible redirection of T cells to different tumor-associated antigens.

Publ.-Id: 20861

Ion-surface interaction in plasma processing

Möller, W.

Whereas the studies of ion-surface interaction have been a significant issue in nuclear fusion research through about four decades, corresponding knowledge in the area of low-pressure plasma processing can still be considered as marginal. Qualitatively, it is well accepted that energetic ion bombardment is essential for several processes of plasma surface treatment or plasma-assisted deposition of thin films. For the latter, it plays an important role in determining the growing thin film structure and stoichiometry. However, more quantitative models are only available for a few selected processes and for specific materials.
The lecture will briefly review the state of knowledge. It will particularly focus on the process physics of non-reactive and reactive sputtering. Open questions will be addressed in connection with recent experimental findings and computer simulation results, such as describing self-organized topographical and stoichiometric pattern formation under ion bombardment, and the characteristics of sputtering from such modified surfaces.

Keywords: Ion-surface interaction; Hard coatings; Magnetron sputtering; Plasma processing

  • Invited lecture (Conferences)
    PSE 2014 - International Conference on Plasma Surface Engineering, 15.-20.09.2014, Garmisch-Partenkirchen, Deutschland

Publ.-Id: 20860

Sputtering of nanospheres - a computer simulation study

Möller, W.; Nietiadi, M. L.; Urbassek, H. M.; Sandoval, L.

The sputtering of spherical objects – such as clusters, nanoparticles or aerosol particles – being exposed to energetic ion irradiation has been studied using both Monte Carlo simulation in the binary collisions approximation (MC) and molecular dynamics simulation (MD). 20 keV Ar impact on a-Si has been chosen as a typical example. With a denoting the mean depth of energy deposition in a planar target, inverse scaled cluster radii a/R ranging from 0 to 20 have been investigated, both addressing the impact parameter dependence and the average sputtering yield. For large radii (a/R < 0.2) sphere sputtering follows closely the sputtering of planar targets, if the variation of the incidence angle on the sphere surface is taken into account. For smaller radii, the yield increases due to the influence of sphere curvature. For a/R > 1, pronounced forward sputtering leads to a maximum in the sputter yield. In the limit of small radii, sputter emission becomes largely isotropic, but decreases in yield since the projectile energy is only partly deposited in the sphere and the surface area shrinks. However, for all spheres studied, the average sputter yield is larger than for the planar surface. Within the uncertainties of the modelling, there is an excellent agreement between the planar surface sputtering yields as obtained by MC and MD. For small spheres, however, the MD yields are significantly larger which is attributed to the influence of collisional spikes.

Keywords: Sputtering; Nanostructures; Computer Simulation

  • Lecture (Conference)
    IBMM 2014 - International Conference on Ion Beam Modification of Materials, 15.-19.09.2014, Leuven, Belgien

Publ.-Id: 20859

Ion beam synthesis of InAs, InGaAs and GaAs nanocrystals in Silicon

Rebohle, L.; Wutzler, R.; Prucnal, S.; Hübner, R.; Grenzer, J.; Helm, M.; Skorupa, W.

InAs, InGaAs and GaAs nanocrystals (NCs) were fabricated by sequential ion implantation and flash lamp annealing. In detail, silicon-SiO2-silicon structures were provided with a SiO2 capping layer followed by the sequential implantation of In, Ga and As ions with fluences in the range of a few 1016 at./cm2. In the following step of flash lamp annealing the NCs will be formed in the Si device layer by liquid phase epitaxy. The resulting III-V NCs are mostly single-crystalline with sizes in the range of a few to a few tens of nm. Depending on the specific segregation coefficients and melting temperatures, elemental In clusters can be also formed. The proposed qualitative model for the NC formation is based on Transmission electron microscopy (TEM), Raman spectroscopy, and X-ray diffraction (XRD) measurements.

Keywords: InAs; InGaAs and GaAs nanocrystals; ion implantation; flash lamp annealing; III-V integration into silicon

  • Poster
    EMRS Fall Meeting 2014, 15.-18.09.2014, Warschau, Polen

Publ.-Id: 20858

Sputtering of Si nanospheres

Nietiadi, M. L.; Sandoval, L.; Urbassek, H. M.; Möller, W.

Spherical objects, such as clusters, nanoparticles, or aerosol particles, are sputtered when exposed to energetic irradiation.We use Monte Carlo (MC) and molecular dynamics (MD) computer simulation to study this process, with 20 keV Ar impact on a-Si clusters as a prototypical example. The sputter yield is quantified as being influenced by oblique incidence and target curvature. Cluster radii R are scaled to the energy deposition depth, a. For large R (R/a > 5) sphere sputtering follows closely the sputtering of planar targets, if the variation of the incidence angle on the sphere surface is taken into account. For smaller radii, the yield increases due to the influence of curvature. For radii R/a 1 pronounced forward sputtering leads to a maximum in the sputter yield. For smaller R, sputter emission becomes isotropic, but decreases in magnitude since not all the projectile energy is deposited in the sphere. However, for all spheres studied (R > 0.05a) the average sputter yield is larger than for infinitely large spheres (R→∞). A simple model based on linear collision cascade theory and assuming that the energy deposition profile is independent of the sphere size predicts sputtering for large spheres well, but fails for small spheres where it strongly underestimates sputtering. The MC data for the smaller spheres are supplemented by MD calculations, which indicate a significant additional contribution caused by spike sputtering.

Keywords: Sputtering; Nanostructures; Computer Simulation; Binary Collision Approximation; Molecular Dynamics

Publ.-Id: 20857

The electroluminescence mechanism of Er3+ in different silicon oxide and silicon nitride environments

Rebohle, L.; Berencén, Y.; Wutzler, R.; Braun, M.; Hiller, D.; Ramírez, J. M.; Garrido, B.; Skorupa, W.; Helm, M.

Rare earth doped metal-oxide-semiconductor (MOS) structures are of great interest for Si-based light emission. However, several physical limitations make it difficult to achieve the performance of light emitters based on compound semiconductors. To address this point, in this work the electroluminescence (EL) excitation and quenching mechanism of Er-implanted MOS structures with different designs of the dielectric stack are investigated. The devices usually consist of an injection layer made of SiO2 and an Er-implanted layer made of SiO2, Si-rich SiO2, silicon nitride or Si-rich silicon nitride. All structures implanted with Er show intense EL around 1540 nm with EL power efficiencies in the order of 2×10-3 (for SiO2:Er) or 2×10-4 (all other matrices) for lower current densities. The EL is excited by the impact of hot electrons with an excitation cross section in the range of 0.5-1.5×10-15 cm-2. Whereas the fraction of potentially excitable Er ions in SiO2 can reach values up to 50%, five times lower values were observed for other matrices. The decrease of the EL decay time for devices with Si-rich SiO2 or Si nitride compared to SiO2 as host matrix implies an increase of the number of defects adding additional non-radiative de-excitation paths for Er3+. For all investigated devices EL quenching cross sections in the 10-20 cm2 range and charge-to-breakdown values in the range of 1-10 Ccm-2 were measured. For the present design with a SiO2 acceleration layer, thickness reduction and the use of different host matrices did not improve the EL power efficiency or the operation lifetime, but strongly lowered the operation voltage needed to achieve intense EL.

Keywords: electroluminescence; ion implantation; erbium; MOS structure; decay time

Publ.-Id: 20856

Electromagnetic fields of a vertical magnetic dipole above and within a horizontal stratified earth in due consideration of the electrical permittivity

Scheunert, M.; Börner, R.-U.; Siemon, B.

Our poster is motivated by the helicopter electromagnetic forward and inversion problem. In this context, we use the secondary field approach to evaluate the total electromagnetic fields of a vertical magnetic dipole (VMD) by a numerical discretization scheme. This approach requires the calculation of an analytic solution of the primary field at every receiver position, located within the air half-space. Furthermore, in order to calculate the Jacobian matrix using the sensitivity equation approach, these primary fields have to be calculated at every degree of freedom within the stratified media. The primary fields are the solution of the Helmholtz equation for a 1-D conductivity distribution.
We show the complete derivation of the electromagnetic fields of a VMD for the magnetic vector potential based on the spatial Hankel transformation. To avoid inaccuracies at high frequencies, varying electrical permittivities are incorporated. We furthermore explain the recursion algorithm that is used to find general expressions at arbitrary depths and which allows us to easily derive the different electromagnetic field components. The calculations start with the simple two layer case and are subsequently expanded to the more general N-layer case. Special attention is payed to a singularity problem arising at the derivation of the horizontal electrical and vertical magnetic fields in the air layer which is resolved by an integration by parts approach.

Keywords: fields of a VMD; stratified earth; HEM; vector potential; Fourier transform

  • Poster
    22nd EM Induction Workshop, 24.-30.08.2014, Weimar, Deutschland

Publ.-Id: 20855

A Concept for 3-D Inversion of Helicopter Electromagnetic Data Using a Tensor-based Problem Formulation

Scheunert, M.; Afanasjew, M.; Börner, R.-U.; Eiermann, M.; Ernst, O. G.; Spitzer, K.

Helicopter electromagnetic (HEM) measurements allow to manage huge surveys in a very short time. Due to the enormous data and model sizes, laterally constrained 1-D inversion schemes for the entire survey are still state of the art, even for those parts of the survey where 3-D conductivity anomalies are expected.

We introduce a new strategy that is based on the precedent localization of the entire HEM survey to parts which are actually affected by an expected local 3-D anomalies. A full 3-D inversion scheme capable of revealing those anomalous conductivity structures is presented that directly benefits from a-priori information, resulting from the localization procedure. We therefore reformulate the discrete forward problem in terms of the secondary electric field, employing either finite difference or finite element methods. For solving the inverse problem, we apply a straightforward Gauss-Newton method and a Tikhonov-type regularization scheme. The concept allows us to additionally restrict the domain where the inverse problem is solved, acting as an implicit regularization. The derived linear least squares problem is solved with Krylov subspace methods, such as LSQR, that are able to deal with the inherent ill-conditioning. The resulting systems of linear equations subsequently yield expressions for the gradient and approximate Hessian of the minimization problem. Resulting from the unique transmitter-receiver relation of the HEM problem, an explicit representation of the Jacobian matrix is used. We further introduce a tensor-based problem formulation that provides a fast update of the linear system of the forward problem and an effective handling of the sensitivity related algebraic quantities, respectively.

Keywords: HEM; 3-D inversion; cut-&-paste strategy; field data; explicit Jacobian

  • Poster
    74. Jahrestagung der Deutschen Geophysikalischen Gesellschaft (DGG), 10.-13.03.2014, Karlsruhe, Deutschland

Publ.-Id: 20854

EM fields of a VMD calculated at arbitrary points within a layered half-space

Scheunert, M.; Börner, R.-U.; Siemon, B.

In this paper, we derive expressions for all electromagnetic (EM) field components which can be observed, when a vertical magnetic dipole (VMD) is located at z = −h, h > 0 over a stratified earth, i.e., when the electrical conductivity is a piecewise constant function of depth z. We further allow a non-vanishing but small electrical conductivity in the air layer, and let the electrical permittivity vary from its vacuum value. Apart from traditional approaches, we use a non-vanishing air conductivity to be consistent with our 3-D discretizations which would otherwise yield singular mass matrices. The basic ideas of the derivation within the following paragraphs emanate from Ward and Hohmann (1988) and Zhdanov (2009). While the first sections of this paper concern the two-layer (i.e., the nearly non-conductive air and the conductive homogeneous half-space) case we expand the concept to the general N-layer case in the last section. This work has been motivated by the one-dimensional forward and inverse problem of helicopter electromagnetics (HEM). To evaluate the observed total fields by a numerical discretization scheme, the secondary field approach requires the calculation of the analytical solution of the EM fields at the receiver positions within the air half-space. Furthermore, in order to calculate the Jacobian matrix, these fields are required at arbitrary points within the conductive layered half-space.

Keywords: electromagnetic fields; vertical magnetic dipole; stratified earth; magnetic vector potential; Fourier transform

  • Open Access Logo Contribution to proceedings
    25. Schmucker-Weidelt-Kolloquium für Elektromagnetische Tiefenforschung, 23.-27.09.2013, Kirchhundem-Rahrbach, Deutschland
    Protokoll über das 25. Schmucker-Weidelt-Kolloquium für Elektromagnetische Tiefenforschung : Kirchhundem-Rahrbach 23.-27. September 2013, Potsdam: Deutsche Geophysikalische Gesellschaft e. V., 5-20


Publ.-Id: 20853

Investigation of the effects of a variation of fuel assembly position on the ex-core neutron flux detection in a PWR

Konheiser, J.; Brachem, C.; Seidl, M.

This work shows the impact of potential displacements of the fuel assembly positions in the reactor core on the signal values of the ex-core instrumentation of a KWU – type pressurized water reactor in order to understand in detail the impact on the calibration factor of excore detectors. This was done with a range of Monte Carlo calculations which simulated the detailed geometrical effect by stepwise changing the positions of fuel assemblies for selected, conservative scenarios. First, criticality calculations were carried out for the chosen core configurations and corresponding surface sources on the core barrel were determined. In these calculations, the distances were varied between the fuel assemblies which were in the line of sight of the ex-core instrumentation. A maximal change of the fluxes on the surface of the core barrel of 4%/mm could be calculated under conservative assumptions for the combination of displaced fuel assemblies. In addition, a dependence of this effect as a function of cycle burnup was analyzed. In a second step transport calculations for the ionization chambers were performed using the surface sources. An increase of the reaction rate at the chambers of up to 3%/mm has been calculated.

Keywords: PWR type reactor; Ex-core instrumentation; Monte Carlo calculation

Publ.-Id: 20852

Hyperspectral remote sensing of carbonatite hosted REE deposits in Namibia

Zimmermann, R.; Salati, S.; Andreani, L.; Brandmeier, M.; Gloaguen, R.

High spectral and spatial resolution of hyperspectral images allow mapping and determination of minerals on the earth surface. It also provide valuable information about ore deposits and their alteration zoning.
Carbonatites are well known for hosting economic concentrations of REE-bearing minerals like bastnäsite, monazite and apatite among others (WINTER 2001). They show signifcant spectral characteristics, even REE-absorption bands (ROWAN et al. 1986).
The aim of our study is to apply recent advances in hyperspectral imaging and to develop new tools in order to map these rocks. A refnement of the geological map by lithological mapping, image classifcation, mineral mapping and tectonic geomorphology is also done.
Our research mainly focuses on carbonatites from Namibia. We selected two sites with well known occurrences in Northern Namibia: the Epembe and the Lofdal dykes. Both yield signifcant REE- concentrations and being under exploration. In these areas LANDSAT 8, SRTM, EO-1 Hyperion and airborne hyperspectral (HyMap) data overlap giving an excellent coverage.
The data had been processed for atmospherical and geometric corrections frst. For the EO-1 Hyperion data a more carefully pre-processing had to be applied due to streaking and smiling effects. Results of LANDSAT 8 classifcation had been used for validation and classifcation purposes. Detailed spectral signatures and mineral maps are extracted by hyperspectral imaging. The results confrm former observations by BEDINI (2009) on the Sarfartoq carbonatite complex in West Greenland. Secondly the structural controls of emplacement of the selected carbonatite dykes had been carried out using tectonic geomorphology and feld observation. For this purpose the TecDEM-toolbox (SHAHZAD & GLOAGUEN 2011) was applied to the SRTM-data for drainage- network and stream-profle analysis.
Combining all these information with geological knowledge of carbonatites and their occurrences, it is possible to explore new, unknown deposits by remote sensing applications.

  • Poster
    GeoFrankfurt 2014, 22.-24.09.2014, Frankfurt/Main, Deutschland

Publ.-Id: 20851

Cockade breccia: Product of mineralisation along dilational faults

Frenzel, M.; Woodcock, N. H.

Cockade breccias are fault fills in which individual clasts are completely surrounded by concentric layers of cement. They occur particularly in low-temperature near-surface hydrothermal veins. At least six mechanisms have been proposed for the formation of cockade breccia-like textures, but only two – repeated rotation-accretion, and partial metasomatic replacement of clast minerals – have been supported by detailed evidence. A typical example of cockade breccia from the Gower Peninsula (South Wales) shows clear evidence for the rotation-accretion mechanism: in particular, overgrown breakage points in cement layers – where cockades were previously touching each other – and rotated geopetal infills of haematitic sediment. Based on the available evidence, it is proposed that cockade textures result from low rates of cement growth compared to high rates of dilational fault slip. Seven criteria are given for the correct identification of cockade breccias.

Keywords: cockade ore; ring ore; syntectonic mineralisation; dilational faulting; epithermal veins

  • Journal of Structural Geology 68(2014), 194-206
    Online First (2014) DOI: 10.1016/j.jsg.2014.09.001
  • Lecture (Conference)
    UK Tectonic Studies Group Annual Meeting, 06.-08.01.2015, Edinburgh, United Kingdom

Publ.-Id: 20850

Strongly Non-Reciprocal Dipole-Exchange Spin Wave Mode in Antiferromagnetically Coupled Magnetic Bilayers

Tyberkevych, V.; Slavin, A.; Wintz, S.; Slobodianiuk, D.; Melkov, G.

  • Lecture (Conference)
    59th Annual Magnetism & Magnetic Materials Conference, 03.-07.11.2014, Honolulu, USA

Publ.-Id: 20849

Laser pulse-shape dependence of Compton scattering

Titov, A.; Kämpfer, B.; Shibata, T.; Hosaka, A.; Takabe, H.

Compton scattering of short and ultra short (sub-cycle) laser pulses off mildly relativistic electrons is considered within a QED framework. The temporal shape of the pulse is essential for the differential cross section as a function of the energy of the scattered photon at fixed observation angle. The partly integrated cross section is sensitive to the non-linear dynamics resulting in a large enhancement of the cross section for short and, in particular, for ultra-short flat-top pulse envelopes which can reach several orders of magnitude, as compared with the case of a long pulse. Such effects can be studied experimentally and must be taken into account in Monte-Carlo/transport simulations of %e+e− pair production in the interaction of electrons and photons in a strong laser field.

Publ.-Id: 20847

Defining medium-specific condensates in QCD sum rules for D and B mesons

Buchheim, T.; Hilger, T.; Kämpfer, B.

QCD sum rules for D and B mesons in a strongly interacting environment require the decomposition of Gibbs averaged operators related to tensor structures. We present a procedure to decompose these operators into vacuum and medium-specific parts, thus defining plain medium-specific condensates with coefficients vanishing in vacuum. Our decomposition allows for an identification of potential elements of order parameters for chiral restoration, in particular for higher mass-dimension quark-condensates which would be masked otherwise if operators with uncontracted Lorentz indices would be linked to DIS amplitudes.

Publ.-Id: 20846

Recent results from the high magnetic field laboratory Dresden: Probing the 1D or 2D nature of M2+Ta2O6 (M2+=Ni,Co)

Law, J. M.

es hat kein Abstract vorgelegen

  • Invited lecture (Conferences)
    Moscow International Symposium on Magnetism MISM-2014, 29.06.-03.07.2014, Moscow, Russia

Publ.-Id: 20844

ESR Studies of the Spin-1/2 Heisenberg Antiferromagnet Copper Pyrazine Dinitrate

Ozerov, M.

Copper pyrazine dinitrate, Cu(C4H4N2)(NO3), is one of the best known model spin-1/2 Heisenberg antiferromagnet chain system. Here, we present electron spin resonance (ESR) studies of this material. Angular, temperature and field dependences of ESR parameters are studied. We evidence the inequivalence of Cu sites belonging to adjacent spin chains in the ac planes. It is revealed that the dominating interchain interaction in this compound is of zig-zag-type. This interaction gives rise to geometrical frustration strongly affecting the character of antiferromagnetic ordering. Combining our experimental findings with the results of a quasiclassical approach we predict that at low temperatures the system orders in an incommensurate spiral state.

  • Poster
    International Conference on Strongly Correlated Electron Systems, 07.-11.07.2014, Grenoble, France

Publ.-Id: 20843

Simulation of Channel Segregation During Directional Solidification of In—75 wt pct Ga. Qualitative Comparison with In Situ Observations

Saad, A.; Gandin, C.-A.; Bellet, M.; Shevchenko, N.; Eckert, S.

Freckles are common defects in industrial casting. They result from thermosolutal convection due to buoyancy forces generated from density variations in the liquid. The present paper proposes a numerical analysis for the formation of freckles using the three dimensional (3D) cellular automaton (CA) - finite element (FE) model [1]. The model integrates kinetics laws for the nucleation and growth of a microstructure to the solution of the conservation equations for the casting, while introducing an intermediate modeling scale for a direct representation of the envelope of the dendritic grains. Directional solidification of a cuboid cell is studied. Its geometry, the alloy chosen as well as the process parameters are inspired from experimental observations recently reported in the literature [2]. Snapshots of the convective pattern, the solute distribution and the morphology of the growth front are qualitatively compared. Similitudes are found when considering the coupled 3D CAFE simulations. Limitations of the model to reach direct simulation of the experiments are discussed.

Keywords: Solidification; Natural convection; Segregation; Freckle; Dendritic growth; Grain structure

Publ.-Id: 20842

A 3D microstructural model of freckle initiation from pre-existing imperfections

Karagadde, S.; Yuan, L.; Shevchenko, N.; Eckert, S.; Lee, P. D.

The quality and lifing of high performance turbine blades are severely hampered by presence of freckles, which are initiated by presence of enriched solute plumes during solidification [1]. Nickel based turbine blades can be cast as equiaxed, directionally solidified or single crystals. Several types of perturbations may occur during these casting techniques, which can eventually lead to freckles.
In this work, a 3D microstructural numerical model of freckle formation is presented [2]. A typical simulation of stabilized solute plume formation leading to a freckle channel is shown in Fig. 1. The model is validated with in situ x-ray radiographic measurements [3], comparing solute partitioning, convection and freckle channel width. This model was then used to investigate freckle formation under a range of solidification conditions. Using the dendrite tip growth and solute profiles, freckle onset was observed to occur in two distinct stages. The influence of imperfections that occur in primary arm spacing and grain boundary was investigated from the proposed model. It was found that the freckles initiate from these irregularities, with a higher propensity for converging grain boundaries. In addition, the effect of dendrite orientation angle on freckle formation is studied.

Keywords: 3D microstructural model; freckle; x-ray radiography; model validation; dendrite tip growth

  • Lecture (Conference)
    4th International Conference on Advances in Solidification Processes, 08.-11.07.2014, Old Windsor, United Kingdom

Publ.-Id: 20841

Melt flow and temperature gradient effects on freckle formation

Shevchenko, N.; Roshchupkina, O.; Eckert, S.

A visualization of the segregation freckle formation and the main convection pattern in solidifying Ga - In alloys was obtained by using the X-ray imaging technique [1, 2]. A Ga - In alloy was used because its density variation and thermo-physical properties are similar to many commercial alloys. Furthermore, it has a very good X-ray contrast and shows a melting point near room temperature. Recently, formation of stable chimney at several solidification conditions and captured the solute distribution and flow velocities were reported [2]. Variations of the vertical and lateral temperature gradients induce modifications of the melt flow pattern, which lead to different segregation structures.
In the case of solidification at higher vertical temperature gradients (up to 2 K/mm), we identified a converging flow ahead of the mushy zone coming from the side walls. Such flow patterns are driven by the lateral temperature gradient and the convex shape of the solidification front. This leads to a continuous accumulation of solute in the central part of the solidification cell followed by a remelting of the solid fraction and the occurrence of a sustaining chimney. This mechanism of chimney formation is different as compared to the case where the evolution of the segregation channel is related to any initial growth defect.
Variations of the lateral temperature gradient by additional side cooling lead to a collapse of the double-vortex convection over entire cell volume. A more complicated flow pattern occurs consisting of multiple convection rolls along the solid - liquid interface. At such solidification conditions a sustainable development of stable chimneys was rarely observed.

Keywords: Visualization; X-ray radioscopy; freckle formation; solid liquid interface; flow patterns; temperature gradient

  • Lecture (Conference)
    4th International Conference on Advances in Solidification Processes, 08.-11.07.2014, Old Windsor, United Kingdom

Publ.-Id: 20840

In situ X-ray radiography study on the impact of forced melt convection on solidification processes

Shevchenko, N.; Roshchupkina, O.; Eckert, S.

In this paper, we present experimental investigations focusing on the question how natural and forced convection influence the microstructure formation in solidifying alloys.
In situ visualization of the solidification of Ga–25wt%In alloys was carried out by means of X-ray radioscopy. An electromagnetically driven flow was produced inside the solidifying liquid by a rotating wheel with two parallel disks containing at their inner sides a set of permanent NdFeB magnets with alternating polarisation [1, 2]. Rotation speeds of the magnetic wheel were chosen in the range of 10 – 80 revolutions per minute resulting in local flow velocities between 0.5 and 1.5 mm/s in the area just ahead of the solidification front. The melt flow is almost perpendicular with respect to the growth direction of the dendrites.
The forced convection induces a redistribution of solute concentration, re-orientation of the dendritic structure, changes of primary and secondary branching, and leads to a formation of segregation channels. Flow patterns, dendrite morphologies and tip velocities were quantified by image analysis and related to the experimental conditions. In principle, the forced flow is an external operational parameter that can be used to control the final microstructure. However, the optimization of the microstructure by electromagnetic flow control is a complex task which requires a deep understanding of the complex interplay between melt flow and solidification process.

Keywords: X-ray radiography; Solidification; Ga-In alloy; Forced convection; Dendritic structure; Tip velocity

  • Lecture (Conference)
    4th International Conference on Advances in Solidification Processes, 08.-11.07.2014, Old Windsor, United Kingdom

Publ.-Id: 20839

Dependence of all-optical magnetic switching on the sublattice magnetization orientation in Tb-Fe thin films

Hassdenteufel, A.; Schubert, C.; Schmidt, J.; Richter, P.; Zahn, D. R. T.; Salvan, G.; Helm, M.; Bratschitsch, R.; Albrecht, M.

We demonstrate that the direction of all-optical switching (AOS) in rare-earth transition-metal (RE-TM) alloy Tb-Fe thin films depends on the orientation of the sublattice magnetization and not on the direction of the resulting net magnetization. For this purpose, we investigated the AOS ability for a sample dominated by the Fe sublattice magnetization (Tb24Fe76) and another dominated by the Tb sublattice (Tb30Fe70). This finding of the sublattice dependence of AOS contributes to the understanding of switching in RE-TM multilayered thin films and heterostructures.

Keywords: all-optical magnetic switching; AOS; sublattice magnetization; rare earth metal alloy

Publ.-Id: 20838

Why Do Strategic Alliances Persist? A Behavioral Decision Model

Klossek, A.; Meyer, K. E.; Nippa, M.

Strategic alliances are considered a flexible form of organizing, yet they are often long-lived. Even when systematic benefit–cost analysis suggests that their organizational form should be changed or terminated, some alliances still persist. Drawing on behavioral decision theory, we propose a theoretical model that explains this phenomenon. Decision makers are subject to a variety of biases that can lead to the overvaluation of the net benefits of an alliance and, hence, inhibit the change or discontinuation of underperforming alliances. Our model illustrates how decision-making biases at the individual, interpersonal, organizational, and interorganizational levels are moderated by the design of an alliance and the tools employed in the decision-making process. This behavioral decision perspective advances our theoretical understanding of the longevity of strategic alliances and their embeddedness in complex decision-making contexts.

  • Managerial and Decision Economics 36(2015)7, 470-486
    Online First (2014) DOI: 10.1002/mde.2682

Publ.-Id: 20837

Visualization of liquid metal two-phase flows in a physical model of the continuous casting process of steel

Timmel, K.; Shevchenko, N.; Röder, M.; Anderhuber, M.; Gardin, P.; Eckert, S.; Gerbeth, G.

We present an experimental study concerned with investigations of the two-phase flow in a mockup of the continuous casting process of steel. A specific experimental facility was designed and constructed at HZDR for visualizing liquid metal two-phase flows in the mold and the submerged entry nozzle (SEN) by means of X-ray radioscopy. This setup operates with the low melting, eutectic alloy GaInSn as model liquid. The argon gas is injected through the tip of the stopper rod into the liquid metal flow. The system operates continuously under isothermal conditions. First results will be presented here revealing complex flow structures in the SEN widely differing from a homogeneously dispersed bubbly flow. The patterns are mainly dominated by large bubbles and large-area detachments of the liquid metal flow from the inner nozzle wall. Various flow regimes can be distinguished depending on the ratio between the liquid and the gas flow rate. Smaller gas bubbles are produced by strong shear flows near the nozzle ports. The small bubbles are entrained by the submerged jet and mainly entrapped by the lower circulation roll in the mold. Larger bubbles develop by coalescence and ascend towards the free surface.

Keywords: continuous casting; liquid metal model; two-phase flow; x-ray imaging

Publ.-Id: 20836

Decision-making criteria in rare earths exploration projects: An interview study

Klossek, P.; van den Boogaart, K. G.

When the rare earth prices skyrocketed in 2011, over 400 exploration projects appeared in the rest of the world. Before any of these exploration projects comes into production, it has to pass various stages of the project development and face multiple challenges at each of these stages. According to the Cooper’s stage-gate system, a decision about whether to move on to the next project stage should be based on the evaluation of certain criteria. The case of rare earth elements, however, differs from other metals in terms of mineralogy, market, technology, environmental issues, strategic importance etc. Therefore, the decision criteria might also partly differ. To find these criteria for the case of rare earths, interviews with decision- makers from several rare earths projects at different stages of development were conducted. In the paper, obtained criteria are listed, explained, and analysed for each stage/gate. Suggestions about their application to project management are made.

Keywords: exploration; mining; project development process; project management; project evaluation; decision-making; stage-gate system; decision-making criteria; rare earth elements; interview study; project realisability; project economics; project externalities; project uncertainty

Publ.-Id: 20835

High-magnetic-field properties of frustrated magnets

Wosnitza, J.

es hat kein Abstract vorgelegen

  • Invited lecture (Conferences)
    13th Japanese-German Symposium “Interplay of Spin- and Orbital Degrees of Freedom in Strongly Correlated Electron Systems”, 13.-16.07.2014, Rottach-Egern, Deutschland

Publ.-Id: 20834

Emerging evidence for FFLO states in layered organic superconductors

Wosnitza, J.

es hat kein Abstract vorgelegen

  • Invited lecture (Conferences)
    2nd International Symposium of the SFB/TR 49 on “Novel states in correlated condensed matter – from model systems to real materials”, 08.-10.04.2014, Königstein, Deutschland
  • Invited lecture (Conferences)
    The 11th International Conference on Materials & Mechanisms of Superconductivity, 23.-28.08.2015, Geneva, Switzerland
  • Invited lecture (Conferences)
    Workshop on "Interference of Magnetism and Superconductivity", 18.07.-02.09.2016, Natal, Brasilien
  • Invited lecture (Conferences)
    Gordon Research Conference on Conductivity & Magnetism in Molecular Materials, 14.-19.08.2016, South Hadley, USA
  • Invited lecture (Conferences)
    3rd International Workshop GRK 1621, 26.-27.05.2016, Meissen, Deutschland
  • Invited lecture (Conferences)
    10th Workshop "Control of Quantum Correlations in Tailored Matter", 03.-06.04.2017, Loveno di Menaggio, Italien

Publ.-Id: 20833

The Fulde-Ferrell-Larkin-Ovchinnikov state in layered organic superconductors

Wosnitza, J.

es hat kein Abstract vorgelegen

  • Invited lecture (Conferences)
    International Workshop on Topological quantum matter and two-dimensional superconductors, 11.-14.01.2014, Kuming, China

Publ.-Id: 20832

Observation of the hyperfine transition in lithium-like bismuth Bi20980+ : Towards a test of QED in strong magnetic fields

Lochmann, M.; Jöhren, R.; Geppert, C.; Andelkovic, Z.; Anielski, D.; Botermann, B.; Bussmann, M.; Dax, A.; Frömmgen, N.; Hammen, M.; Hannen, V.; Kühl, T.; Litvinov, Y. A.; López-Coto, R.; Stöhlker, T.; Thompson, R. C.; Vollbrecht, J.; Volotka, A.; Weinheimer, C.; Wen, W.; Will, E.; Winters, D.; Sánchez, R.; Nörtershäuser, W.

We performed a laser spectroscopic determination of the 2s hyperfine splitting (HFS) of Li-like 209Bi80+ and repeated the measurement of the 1s HFS of H-like 209Bi82+. Both ion species were subsequently stored in the Experimental Storage Ring at the GSI Helmholtzzentrum für Schwerionenforschung Darmstadt and cooled with an electron cooler at a velocity of ≈0.71c. Pulsed laser excitation of the M1 hyperfine transition was performed in anticollinear and collinear geometry for Bi82+ and Bi80+, respectively, and observed by fluorescence detection. We obtain ΔE(1s)=5086.3(11)meV for Bi82+, different from the literature value, and ΔE(2s)=797.50(18)meV for Bi80+. These values provide experimental evidence that a specific difference between the two splitting energies can be used to test QED calculations in the strongest static magnetic fields available in the laboratory independent of nuclear structure effects. The experimental result is in excellent agreement with the theoretical prediction and confirms the sum of the Dirac term and the relativistic interelectronic-interaction correction at a level of 0.5%, confirming the importance of accounting for the Breit interaction.

Keywords: laser spectroscopy; qed; storage ring; esr; bismuth; li-like

Publ.-Id: 20831

Synthesis and evaluation of a 18F-labeled spirocyclic piperidine derivative as promising σ1 receptor imaging agent

Chen, Y.-Y.; Wang, X.; Zhang, J.-M.; Deuther-Conrad, W.; Zhang, X.-J.; Huang, Y.; Li, Y.; Ye, J.-J.; Cui, M.-C.; Steinbach, J.; Brust, P.; Liu, B.-L.

Several spirocyclic piperidine derivatives were designed and synthesized as σ1 receptor ligands. In vitro competition binding assays showed that the fluoroalkoxy analogues with small substituents possessed high affinity towards σ1 receptors and subtype selectivity. Particularly for ligand 1'-((6-(2-fluoro-ethoxy)pyridin-3-yl)methyl)-3H-spiro[2-benzofuran-1,4'-piperidine] (2), high σ1 receptor affinity (Ki = 2.30 nM) and high σ12 subtype selectivity (142-fold) as well as high σ1/VAChT selectivity (234-fold) were observed. [18F]2 was synthesized using an efficient one-pot, two-step reaction method in a home-made automated synthesis module, with an overall isolated radiochemical yield of 8-10%, a radiochemical purity of higher than 99%, and specific activity of 56-78 GBq/µmol. Biodistribution studies of [18F]2 in ICR mice indicated high initial brain uptake and a relatively fast washout. Administration of haloperidol, compound 1 and different concentrations of SA4503 (3, 5, or 10 µmol/kg) 5 min prior to injection of [18F]2 significantly decreased the accumulation of radiotracer in organs known to contain σ1 receptors. Ex vivo autoradiography in Sprague-Dawley rats demonstrated high accumulation of radiotracer in brain areas with high expression of σ1 receptors. These encouraging results prove that [18F]2 is a suitable candidate for σ1 receptor imaging with PET in humans.

Keywords: PET; 18F; Sigma-1 receptors; Imaging agent; Spirocyclic piperidine derivatives

Publ.-Id: 20830

Adsorption of zinc by biogenic elemental selenium nanoparticles

Jain, R.; Jordan, N.; Schild, D.; van Hullebusch, E. D.; Weiss, S.; Franzen, C.; Farges, F.; Hübner, R.; Lens, P. N. L.

The adsorption of Zn2+ ions onto biogenic elemental selenium nanoparticles (BioSeNPs) was investigated. BioSeNPs were produced by reduction of selenite (SeO32−) in the presence of anaerobic granules from a full scale upflow anaerobic sludge blanket (UASB) reactor treating paper mill wastewater. The BioSeNPs have an iso-electric point at pH 3.8 at 5 mM background electrolyte concentration. X-ray photoelectron spectroscopy showed the presence of a layer of extracellular polymeric substances on the surface of BioSeNPs providing colloidal stability. Batch adsorption experiments showed that the uptake of Zn2+ ions by BioSeNPs was fast and occurred at a pH as low as 3.9. The maximum adsorption capacity observed was 60 mg of zinc adsorbed per g of BioSeNPs. The Zn2+ ions adsorption on the BioSeNPs was largely unaffected by the presence of Na+ and Mg2+, but was impacted by the presence of Ca2+ and Fe2+ ions. The colloidal stability of BioSeNPs decreased with the increasing Zn2+ ions loading on BioSeNPs (increase in mg of zinc adsorbed per g of BioSeNPs), corresponding to the neutralization of the negative surface charge of the BioSeNPs, suggesting gravity settling as a technique for solid-liquid separation after adsorption. This study proposes a novel technology for removal of divalent cationic heavy metals by their adsorption on the BioSeNPs present in the effluent of an UASB reactor treating selenium oxyanions containing wastewaters.

Keywords: adsorption; selenium nanoparticles; zinc removal; XPS analysis; ζ-potential; colloidal stability

Publ.-Id: 20829

Spin-lattice effects in selected magnetic materials

Zherlitsyn, S.

  • Invited lecture (Conferences)
    V International Conference of Young Scientists LOW TEMPERATURE PHYSICS (ICYS–LTP–2014), 02.-06.06.2014, Kharkov, Ukraine

Publ.-Id: 20828

Direct determination of exchange parameters in spin-1/2 Heisenberg triangular-lattice antiferromagnets: high-field ESR studies

Zvyagin, S.

Spin-1/2 Heisenberg antiferromagnets Cs2CuCl4 and Cs2CuBr4 with distorted triangular-lattice structures are studied by means of electron spin resonance spectroscopy in magnetic fields up to the saturation field and above. In the magnetically saturated spin polarized phase, quantum fluctuations are fully suppressed, and the spin dynamics is defined by ordinary magnons. This allows us to accurately describe the magnetic excitation spectra in both materials and, using the harmonic spin-wave theory, to determine their exchange parameters. The proposed approach has a broader impact and can be potentially used for any quantum magnet with reduced (e.g., by the staggered DM interaction) translational symmetry, resulting, as predicted, in emergence of a new exchange mode in the magnetically saturated phase.

  • Invited lecture (Conferences)
    International Conference Magnetic Resonance: fundamental research and pioneering applications (MR 70), 23.-27.06.2014, Kazan, Russia

Publ.-Id: 20827

Magnetic fields in Europe

Wosnitza, J.

  • Invited lecture (Conferences)
    Farewell Symposium of Jan Kees Maan, 23.05.2014, Nijmegen, The Netherlands

Publ.-Id: 20826

Measurement of the quasi free np -> npπ+π- and np ->ppπ-π0 reactions at 1.25 GeV with HADES

Kurilkin, A.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; 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.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, K.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Krizek, F.; Kuc, H.; Kugler, A.; Kunz, T.; Kurepin, 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.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; 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.; Wendisch, C.; Wirth, J.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.

We present the results of two-pion production in tagged quasi-free np collisions at a proton incident beam energy of 1.25 GeV measured with the High-Acceptance Di-Electron Spectrometer (HADES) installed at GSI. The specific acceptance of HADES allowed for the first time to obtain high-precision data on π+π- and π-π0 production in np collisions in a region corresponding to large transverse momenta of the secondary particles. The obtained differential cross section data provide strong constraints on the production mechanisms and on the various baryon resonance contributions (, N(1440), N(1520), Δ(1600)). The invariant mass and angular distributions from the np->npπ+π- and np->ppπ-π0 reactions are compared with dierent theoretical model predictions.

Publ.-Id: 20825

Application of computational fluid dynamics in nuclear reactor safety analysis

Höhne, T.

The last decade has seen an increasing use of three-dimensional CFD codes to predict steady state and transient flows in nuclear reactors because a number of important phenomena such as pressurized thermal shocks, coolant mixing, and thermal striping cannot be predicted by traditional one-dimensional system codes with the required accuracy and spatial resolution. CFD codes contain models for simulating turbulence, heat transfer, multi-phase flows, and chemical reactions. Such models must be validated before they can be used with sufficient confidence in NRS applications.

Numerical investigations on single phase coolant mixing in Pressurized Water Reactors (PWR) have been performed at the HZDR for more than a decade. The work is aimed at describing the mixing phenomena relevant for both safety analysis, particularly in steam line break and boron dilution scenarios, and mixing phenomena of interest for economical operation and the structural integrity.

On the other hand slug flow as a multiphase flow regime can occur in the cold legs of pressurized water reactors, for instance after a small break Loss of Coolant Accident (SB-LOCA). Slug flow is potentially hazardous to the structure of the system due to the strong oscillating pressure levels formed behind the liquid slugs. For the experimental investigation of horizontal two phase flows, different non pressurized channels and the TOPFLOW Hot Leg model in a pressure chamber was build and simulated with ANSYS CFX.

The behavior of insulation material released by a LOCA into the containment and the reactor core might compromise the long term emergency cooling systems. Subsequently, if the ECCS is operating in the sump recirculation mode, the debris suspended in the containment sump would begin to accumulate on the sump strainers. A small part could penetrate through the strainers and could be transported towards the reactor core. It was the aim of the numerical simulations to study where and how many mineral wool fibres are deposited at the upper spacer grid of a core.


  • Contribution to proceedings
    24th SYMPOSIUM of AER on VVER Reactor Physics and Reactor Safety, 14.-18.10.2014, Sotschi, Russland
  • Lecture (Conference)
    24th SYMPOSIUM of AER on VVER Reactor Physics and Reactor Safety, 14.-18.10.2014, Sotschi, Russland

Publ.-Id: 20824

Validation of closure models for interfacial drag and turbulence of horizontal segregated flows

Höhne, T.

In the last decade, applications of Computational Fluid Dynamic (CFD) methods for nuclear applications received more and more attention, as they proved to be a valuable complementary tool for design and safety. The main interest towards CFD consists in fact in the possibility of obtaining detailed 3D complete flow-field information on relevant physical phenomena at lower cost than experiments. Typically free surfaces manifest as stratified and wavy flows in horizontal flow domain where gas and liquid are separated by gravity. Stratified two-phase flows are relevant in many nuclear applications, e.g. pipelines, main coolant lines, horizontal heat exchangers and storage tanks.

CFD simulations for free surface flows require the modeling of the non-resolved scales. For modeling of interfacial transfers it is necessary to select the adequate interfacial transfer models and to determine the interfacial area. The numerical solution can resolve the statistically averaged motion of the free surface (including waves) which may not be too small relatively to the channel height and to the characteristic length of the spatial discretization. However, the detailed structure of interacting boundary layers of the separated continuous phases and surface ripples cannot be resolved. Instead, its influence on the average flow must be modeled.

The development of a general model closer to physics and including less empiricism is a long-term objective of the activities of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) research programs. Such models are an essential precondition for the application of CFD codes to the modeling of flow related phenomena in nuclear facilities. Here local geometry independent models for mass, momentum, heat transfer, and scalar transport are developed and validated. The new formulation for the drag force at the free surface within the algebraic interfacial area density model (the FSD model inside AIAD) is one result of these activities.

A further step of improvement of modeling the turbulence is the consideration of sub-grid wave turbulence (SWT) that means waves created by Kelvin-Helmholtz instabilities that are smaller than the grid size. So fare in the present code versions they are neglected. However, the influence on the turbulence kinetic energy of the liquid side can be significantly large. A region of marginal breaking is defined according Brocchini and Peregrine (2001). In addition turbulence damping functions should cover all the free surface flow regimes, from weak to strong turbulence.

CFD validation of the new approach was done using experiments of the HZDR HAWAC channel. A discussion of the general requirements of such CFD grade experiments was performed. The CFD calculations were done using the Best Practice Guidelines for two-phase flow modeling. One result of the simulations was that the sub-grid wave turbulence which exists in the area of the free surface follows the slug formations. At the wavy front and back of the slugs the value of the sub-grid wave turbulence is the highest in the channel. The slug frequency analysis was done using fast Fourier transform (FFT). The characteristic slug frequency of the simulation was around 2.0 Hz, which corresponds roughly to the experimental value of approximately 2.4 Hz. The model improves the physics of the existing two fluid approaches and is already applicable for a wide range of industrial two phase flows.

More verification and validation of the approach is still necessary – more CFD grade experimental data are required for the validation.

Keywords: CFD; AIAD; HZDR; two-phase flow

  • Contribution to proceedings
    CFD4NRS-5, Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation, Joint OECD/NEA & IAEA Workshop, 09.-11.09.2014, Zürich, Schweiz
  • Lecture (Conference)
    CFD4NRS-5, Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation, Joint OECD/NEA & IAEA Workshop, 09.-11.09.2014, Zürich, Schweiz

Publ.-Id: 20823

Uranium retention by montmorillonite at high ionic strengths

Fritsch, K.; Schmeide, K.

Clay and clay minerals are viewed as potential host rock as well as backfill material for nuclear waste disposal in deep geological formations. While South German clay deposits have pore waters with ionic strengths below 0.5 mol l-1, North German clay deposits exhibit high ionic strengths up to 4 mol l-1 in the depth relevant for repositories.[1] Such high ionic strength conditions are rarely investigated and are thus in the focus of the present work. Montmorillonite is used as model clay for uranium sorption experiments in sodium and calcium chloride. Additionally, a mixed electrolyte was prepared that resembles the groundwater composition at the Konrad site, which serves as a reference site. Surface complexation modelling is employed to gain thermodynamic data from the sorption experiments.

Sorption experiments were conducted with Na montmorillonite SWy-2, which was purified according to Poinssot et al. [2] and Bradbury et al. [3]. Sorption edges were determined with an initial U(VI) concentration of 1.10-6 mol kg-1 and a solid-liquid ratio of 4 g kg-1 in a pH range of 4 to 10 with electrolyte concentrations from 0.1 to 3 mol kg-1. The U(VI) concentration for sorption isotherms ranged from 1.10-8 to 1.10-5 mol kg-1. The mixed electrolyte was composed of cNaCl = 2.52 mol kg-1, cCaCl2 = 0.12 mol kg-1 and cMgCl2 = 0.048 mol kg-1 (overall I = 3.02 mol kg-1).

The classic ionic strength effect describes the decrease of sorption with increasing ionic strength and is generally only observed in the acidic pH range, where cation exchange is the predominant sorption mechanism. Natural groundwaters at the Konrad site have pH values above 5.5, where cation exchange is not the dominant sorption mechanism anymore, which in turn causes a smaller influence of ionic strength on sorption. The sorption maxima in the different salt systems usually lie just below the neutral point and well within the pH range of groundwaters at the reference site. The sorption edge in NaCl is observed at pH 4.1. In the mixed electrolyte, sorption is increased in the alkaline pH range when compared to pure electrolytes. This is due to the magnesium content in this electrolyte, which forms hydroxide precipitates that influence uranium retention by co-precipitation.

Surface complexation modelling with the 2 site protolysis non-electrostatic surface complexation and cation exchange model (2SPNE SC/CE)[4] in conjunction with spectroscopic investigation of the sorption phenomena can be used to identify the surface species involved. The results show that ≡SOUO2 + is the dominant surface complex below pH 6 Uranium hydroxide complexes become the dominant surface complexes above pH 7 in absence of CO2. In presence of CO2, sorption above pH 7 is decreased due to aqueous uranium carbonate complexes.

In general, there is no influence of ionic strength on U(VI) retention by montmorillonite at environmentally relevant pH values. The classic ionic strength effect can only be observed in the acidic pH range, and only up to a sodium concentration of 2 mol kg-1. However, in the presence of calcium or magnesium, uranium retention is promoted by secondary phase formation which leads to partial irreversibility of immobilisation at high ionic strengths in the alkaline pH range.

[1] Brewitz, W. et al. Eignungsprüfung der Schachtanlage Konrad für die Endlagerung radioaktiver Abfälle. GSF-T 136; 1982.
[2] Poinssot, C. et al. Experimental studies of Cs, Sr, Ni, and Eu sorption on Na-illite and the modelling of Cs sorption. NTB 99-04; 1999.
[3] Bradbury, M.; Baeyens, B. Geochim Cosmochim Acta 2009, 73, 990–1003.
[4] Bradbury, M.; Baeyens, B. J Contam Hydrol 1997, 27, 223–248.

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

  • Contribution to proceedings
    Clays in natural and engineered barriers for radioactive waste confinement, 23.-26.03.2015, Brussels, Belgium
    Proceedings of Clays in natural and engineered barriers for radioactive waste confinement
  • Poster
    Clays in natural and engineered barriers for radioactive waste confinement, 23.-26.03.2015, Brussels, Belgium

Publ.-Id: 20822

Parameter Estimation of anisotropic diffusion in Clay with COMSOL Multiphysics

Gerasch, R.; Kulenkampff, J.; Lippmann-Pipke, J.

Our GeoPET camera is explicitly dedicated for and well capable of 4D monitoring of solute transport in dense geological material, c = c(x,y,z,t) (Richter et al., 2005; Gründig et al., 2007; Kulenkampff et al., 2008; Zakhnini et al., 2013). We apply COMSOL Multiphysics for reproducing our experiments and extracting parameter sets for our 4D problems (Lippmann-Pipke et al., 2011; Schikora, 2012). By aligning simulated results of anisotropic diffusion in clay to our observations we are able to clearly differentiate and evaluate likely explicit sample features and transport processes.

Use of COMSOL Multiphysics: A quarter section of a cylinder (3D geometry) is representing our clay core. The bedding of the clay is about vertical. A central bore allows for the application of a labelled pore water solution to diffuse into the material. Isotropic diffusion is assigned to the fluid in the bore hole, while anisotropic diffusion is assigned to the porous media (both with cdeq). From our non-invasive, spatio-temporal PET observations of the diffusion process in a real clay sample two 2D sets ci(x,z) and ci(y,z), are extracted and provided to the Optimization Module for the parameter estimation for Dxx=Dyy and Dzz. A sensitivity analysis quantifies the effects on uncertainties regarding porosity n, initial concentration c0 and spatial resolution.

The 4D simulation results quantitatively nicely match with our 4D experimental results obtained in GeoPET experiments.

  • Lecture (Conference)
    COMSOL Conference 2014, 17.-19.09.2014, Cambridge, UK

Publ.-Id: 20821

FP7 Project LONGLIFE: Overview of Results and Implications

Altstadt, E.; Keim, E.; Hein, H.; Serrano, M.; Bergner, F.; Viehrig, H.-W.; Ballesteros, A.; Chaouadi, R.; Wilford, K.

LONGLIFE (“Treatment of long term irradiation embrittlement effects in RPV safety assessment”) was a collaborative project of the 7th Framework Programme of EURATOM under the umbrella of NULIFE/NUGENIA, aiming at an improved understanding of irradiation effects in reactor pressure vessel steels under conditions representative of long term operation. The LONGLIFE project was completed by end of January 2014. The paper gives an overview of the main project results and their implications for future research, as discussed at the final project workshop. The microstructural database for neutron-irradiated RPV steels was extended considerably and existing gaps on mechanical property data were closed. Indications of late blooming effects (LBE) were found in some cases, but clear criteria for the occurrence/exclusion in terms of irradiation conditions and chemical composition have still to be developed. The commonly accepted trend, that low flux and low irradiation temperature promotes LBE, is supported. A significant flux effect on the size of defect clusters was observed in two high Cu weld materials, while the changes of mechanical properties are not affected by the neutron flux. The database requires completion in particular for low-Cu RPV steels. The shift of reference temperature T0 over the thickness location of a VVER-440 welding seam does not follow the prediction Russian code, because of the strong variation of the intrinsic weld bead structure. Therefore, the effect of the initial microstructure and of the heterogeneity on the radiation behaviour has to be addressed in future works. Existing embrittlement trend curves models were applied to the LONGLIFE data base. None of the trend curves could predict the behaviour of the entirety of the LONGLIFE materials sufficiently. A guideline for monitoring radiation embrittlement during life extension periods was developed.

Keywords: Reactor pressure vessel steel; radiation induced defects; embrittlement; hardening; flux effect; late blooming; trend curves

Publ.-Id: 20818

Novel Cyclopentadienyl Tricarbonyl 99mTc Complexes Containing 1‑Piperonylpiperazine Moiety: Potential Imaging Probes for Sigma‑1 Receptors

Wang, X.; Li, D.; Deuther-Conrad, W.; Lu, J.; Xie, Y.; Jia, B.; Cui, M.; Steinbach, J.; Brust, P.; Liu, B.; Jia, H.

We report the design, synthesis, and evaluation of a series of novel cyclopentadienyl tricarbonyl 99mTc complexes as potent σ1 receptor radioligands. Rhenium compounds 3-(4-(1,3-benzodioxol-5-ylmethyl)piperazin-1-yl)-propylcarbonylcyclopentadienyl tricarbonyl rhenium (10a) and 4-(4-(1,3-benzodioxol-5-ylmethyl)piperazin-1-yl)-butylcarbonylcyclopentadienyl tricarbonyl rhenium (10b) possessed high in vitro affinity for σ1 receptors and moderate to high selectivity for σ2 receptors and the vesicular acetylcholine transporter. Biodistribution studies in mice demonstrated high initial brain uptake for corresponding 99mTc derivatives [99mTc] 23 and [99mTc]24 of 2.94 and 2.13% injected dose (ID)/g, respectively, at 2 min postinjection. Pretreatment of haloperidol significantly reduced the radiotracer accumulation of [99mTc]23 or [99mTc]24 in the brain. Studies of the cellular uptake of [99mTc]23 in C6 and DU145 tumor cells demonstrated a reduction of accumulation by incubation with haloperidol, 1-(3,4-dimethoxyphenethyl)-4-(3-phenylpropyl)piperazine (SA4503), or 1,3-di-otolyl-guanidine (DTG). Furthermore, blocking studies in C6 glioma-bearing mice confirmed the specific binding of [99mTc]23 to σ1 receptors in the tumor.

Publ.-Id: 20817

Cyclotron based production of high specific activity [197(m)Hg]HgCl2

Walther, M.; Preusche, S.; Pietzsch, H.-J.; Bergmann, R.; Steinbach, J.

197mHg (T1/2 = 23.8 h, Eγ 133.98 keV, 33.5%) and 197Hg (T1/2 = 64.14 h, Eγ 77.4 keV, 18.7%) are gamma-emitting radionuclides suitable for SPECT imaging and of additional interest because of the potential therapeutic us of their Auger- and conversion electron emission. The unique chemical and physical properties as metal which forms water-stable carbon-metal bonds and the easy volatility awakened interest on mercury decades ago. The medical use of mercury was virtually complete after the scientific determination of the high toxicity and long biological half life of mercury compounds in vivo. From this follows that the condition precedent to develop new radiopharmaceuticals based on mercury radionuclides is their high specific activity. The production of nca 197Hg radionuclide together with the short lived 197mHg isomer is possible by proton or deuteron irradiation of natural gold using a cyclotron. The 197Au(p,n)197Hg reaction was applied until now only for small scale tracer production, beam monitoring or stacked foil measurements. The main goal of the research project is the evaluation of the cyclotron-based radionuclides 197Hg/197mHg regarding their suitability for diagnostics and therapy of tumors. First results of investigations concerning nca 197Hg/197mHg production and the development of bifunctional mercury chelate complexes stable in vivo will be reported.

  • Abstract in refereed journal
    Nuclear Medicine and Biology 41(2014)7, 646
    DOI: 10.1016/j.nucmedbio.2014.05.018
  • Lecture (Conference)
    2nd International Symposium on TECHNETIUM and other RADIOMETALS in CHEMISTRY and MEDICINE (Terachem 2014), 10.-13.09.2014, Bressanone, Italy

Publ.-Id: 20816

Pharmacological characterization of α-MSH-derivatives

Sihver, W.; Gao, F.; Jurischka, C.; Haase-Kohn, C.; Steinbach, J.; Carta, D.; Bolzati, C.; Calderan, A.; Pietzsch, J.; Pietzsch, H.-J.

The melanocortin-1 receptor is known to be overexpressed in melanoma. Thus, it is a potential target for novel α-MSH peptide derivatives aiming at diagnosis and therapy of melanoma. In this study, NOTA-NCS was conjugated with two peptides: NAP-NS1, a linear peptide with 9 amino acids (Ahx-βAla-Nle-Asp-His-D-Phe-Arg-Trp-Gly-NH2) and NAP-NS2, a lactam bridge-cyclized peptide with 12 amino acids (ε-Ahx-β-Ala-cyclo(Lys-Glu-His-D-Phe-Arg-Trp-Glu)-Arg-Pro-Val-NH2) each with the sequence His-Phe-Arg-Trp for biological activity. Four α-MSH derivatives were investigated in competition assays in murine B16-F10 and human MeWo melanoma cells. (S)-p-NH2-Bn-NOTA (NOTA-NAP-NS1) labeled with 64Cu and 68Ga, showing no transchelation in the cysteine and histidine challenge, was applied in saturation assays. Determination of octanol/water partition coefficients suggested that [64Cu]Cu-NOTA-NAP-NS1 had high hydrophilicity, and in buffer and serum it was stable after 1 h and 24 h. NAP-NS1 and NOTA-NAP-NS1 showed higher affinity than the cyclic derivatives. Linking the chelate unit at the peptide was accompanied by some loss of affinity. Saturation studies with the labeled peptide resulted in Kd values in the lower nanomolar range for [64Cu]Cu-NOTA-NAP-NS1 and [68Ga]Ga-NOTA-NAP-NS1, respectively. Thus, both radiolabeled peptides appear to be promising for further investigations in animal melanoma models.

This research was supported by MIUR (PRIN 2008F5A3AF_002).

  • Abstract in refereed journal
    Nuclear Medicine and Biology 41(2014)7, 637-638
    DOI: 10.1016/j.nucmedbio.2014.05.038
  • Lecture (Conference)
    2nd International Symposium on TECHNETIUM and other RADIOMETALS in CHEMISTRY and MEDICINE (Terachem 2014), 10.-13.09.2014, Bressanone, Italy

Publ.-Id: 20815

Single-domain antibodies: Next-generation targeting vectors for molecular imaging

Zarschler, K.; Zscheppang, K.; Kapplusch, F.; Cordes, N.; Stephan, H.

Single-domain antibodies (sdAbs) provide significant benefits over conventional antibodies and fragments thereof in terms of size, stability, solubility as well as tumour uptake and blood clearance. Thus, sdAbs have been identified as valuable next-generation targeting moieties for molecular imaging and drug delivery in the past years. Since these probes are much less complex than conventional antibody fragments, bacterial expression represents a facile method for production of sdAbs in large amounts as soluble and functional proteins. Herein we report on heterologous high-yield expression of substantial amounts of soluble and functional sdAbs, which have an antagonistic effect on their molecular target, the epidermal growth factor receptor (EGFR). Upon radiolabeling with Tc-99m using the tricarbonyl method, we evaluated binding specificity and affinity to human EGFR-expressing tumor cells. Furthermore, we describe bioconjugation of sdAbs to fluorescent nanoparticles and characterization of sdAb-nanoparticles conjugates covering in vitro cancer cell imaging, cell proliferation as well as EGFR phosphorylation and signaling. The herein highlighted valuable properties of radiolabeled sdAbs combined with tailored effector functions may result in innovative next-generation theranostics.

  • Abstract in refereed journal
    Nuclear Medicine and Biology 41(2014)7, 628
    DOI: 10.1016/j.nucmedbio.2014.05.015
  • Poster
    2nd International Symposium on TECHNETIUM and other RADIOMETALS in CHEMISTRY and MEDICINE (Terachem 2014), 10.-13.09.2014, Bressanone, Italy

Publ.-Id: 20814

Peptide conjugates for EGFR-targeting

Viehweger, K.; Hesse, J.; Stephan, H.; Spiccia, L.; Graham, B.

We have synthesized 64Cu-labelled peptide conjugates based on a 1,4,7-triazacyclononane (TACN) framework that may be applied for in vivo PET imaging. A peptide sequence (LARLLT, “D4”) was used to target the epidermal growth factor receptor (EGFR). Overexpression and mutations of this cell-surface receptor are involved in carcinogenesis and progression of many human cancers.

Four different linker groups were introduced to influence solubility and lipophilicity. The TACN-peptide conjugates are obtained in high yields after purification by RP-HPLC. Radiolabelling with 64Cu(II) was rapidly achieved under mild conditions (pH = 5.5; 22 °C). The receptor binding abilities of the labelled conjugates have been evaluated using immunoprecipitation and by determination of the dissociation constants, revealing only weak interactions (Kd > 100 nM) compared to its native ligand epidermal growth factor (EGF; Kd = 0.04 ± 0.002 nM). However, it was not determined if the “D4” peptide alone could target the EGFR.

  • Abstract in refereed journal
    Nuclear Medicine and Biology 41(2014)7, 636
    DOI: 10.1016/j.nucmedbio.2014.05.045
  • Poster
    2nd International Symposium on TECHNETIUM and other RADIOMETALS in CHEMISTRY and MEDICINE (Terachem 2014), 10.-13.09.2014, Bressanone, Italy

Publ.-Id: 20813

Binding properties of radiolabeled cetuximab conjugates

Sihver, W.; Schubert, M.; Stephan, H.; Graham, B.; Spiccia, L.; Baumann, M.; Pietzsch, J.; Steinbach, J.; Pietzsch, H.-J.

The monoclonal antibody cetuximab (C225) binds with high affinity to the epidermal growth factor receptor (EGFR), which is a major molecular target for treatment of different types of cancer. Radiolabeled C225 has been proven to be appropriate for cancer imaging and treatment. This study comprises an affinity comparison of different C225 conjugates incorporating p-SCN-Bn-NOTA (1), p-SCN-Bn-dipicolyl-TACN (2) and p-SCN-Bn-CHX-A″-DTPA (3). Evaluation of the Ki values using homogenates of A431 cells (EGFRhigh/Her2high expression) revealed minimal loss of affinity for these conjugates compared to unchanged C225. Saturation assays have been applied to compare the binding properties of ([64Cu]Cu-1)3-C225, ([64Cu]Cu-2)2-C225, ([90Y]Y-3)3-C225 and ([111In]In-3)3-C225 on homogenates of different cancer cell lines. The labeled conjugates were found to bind with high specificity and affinity to both the A431 and FaDu (EGFRmedium/Her2low expression) cells, however, the affinity for the FaDu was higher than for the A431 cells. The affinity of ([64Cu]Cu-1)3-C225 and ([64Cu]Cu-2)4-C225 for both EGFR expressing cell lines was somewhat higher than that displayed by ([90Y]Y-3)4-C225 and ([111In]In-3)3-C225. No specific binding was observed in the case of the EGFR-negative MDA-MB-453S cells. Moreover, immunoreactive fractions of more than 80% were determined, indicating that the conjugates are promising candidates for further in vivo evaluation.

  • Abstract in refereed journal
    Nuclear Medicine and Biology 41(2014)7, 635
    DOI: 10.1016/j.nucmedbio.2014.05.037
  • Poster
    2nd International Symposium on TECHNETIUM and other RADIOMETALS in CHEMISTRY and MEDICINE (Terachem 2014), 10.-13.09.2014, Bressanone, Italy

Publ.-Id: 20812

In vitro evaluation of 64Cu-labeled GE11-conjugates

Oertel, F.; Starke, F.; Sihver, W.; Steinbach, J.; Pietzsch, H.-J.

The epidermal growth factor receptor (EGFR) is frequently overexpressed in epithelial tumors and consequently represents an important target for cancer diagnosis and therapy. Recently, a novel peptide sequence (GE11, YHWYGYTPQNVI) was identified to bind the EGFR with high affinity in vitro (Kd = 22 nM) as well as in vivo [1]. These promising data suggest that a GE11-conjugate, which is radiolabeled with a positron-emitting radionuclide, may be used for the assessment of EGFR-levels of tumors and metastases by positron emission tomography, thus, identifying patients which can be medicated by anti-EGFR therapy. Therefore, the peptide-conjugates NOTA-linker-GE11, NOTA-linker-GE11-NH2 and TACN-(linker-GE11-NH2)3 (linker = NH-((CH2)2-O)2-(CH2)2-NH-CO-CH2-O-CH2-CO-βAla) were synthesized and radiolabeled with 64Cu at a radiochemical purity of at least 95%. All three radiolabeled GE11-conjugates were stable in buffer as well as in human blood serum. The binding properties of the radiolabeled conjugates were then evaluated in vitro using EGFR-rich (A431, FaDu) and EGFR-negative (MDA-MB-435s) cell preparations. However, as a result of the in vitro studies for all three GE11-conjugates no binding affinity could be determined. These findings may be explained by the highly hydrophobic character of the produced GE11-conjugates with accompanying tendency for aggregation.

[1] Z. Li, R. Zhao, X. Wu, et al.
FASEB J, 19 (2005), pp. 1978–1985

  • Abstract in refereed journal
    Nuclear Medicine and Biology 41(2014)7, 634-635
    DOI: 10.1016/j.nucmedbio.2014.05.035
  • Poster
    2nd International Symposium on TECHNETIUM and other RADIOMETALS in CHEMISTRY and MEDICINE (Terachem 2014), 10.-13.09.2014, Bressanone, Italy

Publ.-Id: 20811

Bispidines as a platform for targeted multimodal imaging

Comba, P.; Hunoldt, S.; Morgen, M.; Pietzsch, J.; Steinbach, J.; Stephan, H.; Walther, M.

Ligands based on 3,7-diazabicyclo[3.3.1]nonane (bispidine) form very stable coordination compounds, in particular with first row transition metal ions. Considering multiple functionalization, bispidines are promising candidates for pharmaceutical targeting and multimodal imaging. Due to the formation of thermodynamically stable and kinetically inert CuII complexes, penta- and hexadentate bispidine ligands are well suited for 64Cu positron emission tomography imaging and radiotherapy (64Cu/67Cu). The bispidine scaffold paves the way for introducing further functionalities, such as targeting units and fluorescence labels, which broadens the scope regarding pharmaceutical targeting and dual labelling (PET and optical imaging). Several bispidine ligands have been developed in order to improve the radiopharmaceutical behavior as well as possibilities for further beneficial functionalization. Variable denticity (tetra-, penta- and hexadentate) with different donor groups, such as amino, amido, pyridine and/or methoxypyridine functionalities allows for tuning properties such as complexation and lipophilicity. These ligands and the important properties of their CuII complexes, e.g., stabilities, ligand exchange kinetics, serum stability, partition coefficients ([64Cu]Cu-bispidine: n-octanol/water) and biodistribution studies will be reported.

  • Abstract in refereed journal
    Nuclear Medicine and Biology 41(2014)7, 632-633
    DOI: 10.1016/j.nucmedbio.2014.05.047
  • Poster
    2nd International Symposium on TECHNETIUM and other RADIOMETALS in CHEMISTRY and MEDICINE (Terachem 2014), 10.-13.09.2014, Bressanone, Italy

Publ.-Id: 20810

Corporate governance and compliance of companies: changes in risk management?

Stiller, D.; Joehnk, P.

The concept of corporate governance in enterprises is an important topic in business administration. The topic is gaining on importance in the last years through the economic and financial crisis in 2007 and the crisis of public deficit and governmental debt in Europe in 2010. This paper describes current national and international legal provisions and standards of corporate governance. A particular emphasis is placed on the differences and influence factors in risk management between Europe and the United States of America.

Keywords: corporate governance; compliance; risk management; regulation; automotive industry

  • Open Access Logo Journal of International Scientific Publications: Economy & Business 8(2014)547, 554
  • Lecture (Conference)
    13th International Conference Economy & Business, 01.-05.09.2014, Elenite, Bulgaria

Publ.-Id: 20809

Scintillator Characterization at Energies Relevant for a Prompt Gamma Detection System in Particle Therapy

Römer, K.; Pausch, G.; Berthel, M.; Dreyer, A.; Enghardt, W.; Golnik, C.; Hueso-González, F.; Kormoll, T.; Petzoldt, J.; Fiedler, F.

The proton therapy in oncology requires instantaneous and reliable particle range verification, which can be done using prompt gamma emissions. The characteristic requirements of prompt gamma detection include the energy range of up to several MeV, increased background due to secondary emissions and high counting rates. Different concepts make use of these prompt gammas for dose verification like collimated systems or Compton cameras. Additionally to prompt gamma imaging, the prompt gamma timing method has been proposed, utilizing the proton time-of-flight inside the body. Those approaches imply different needs on energy-, spatial- or timing-resolution of the detection system. Various scintillator materials with multiple shapes have been characterized with respect to those requirements using classical photomultiplier tubes (PMT) and different experimental setups and locations. The light output, non-linearity and energy resolution were measured using gamma sources. The timing was characterized at the ELBE facility at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), using the bremsstrahlung beam with photons up to 12.5 MeV. Planned measurements at the 3 MV Tandetron accelerator at HZDR will provide information at the energy resolution at therapy relevant energies of 4.4 MeV.

Keywords: Scintillation; Characterization

  • Poster
    2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (2014 NSS/MIC), 08.-15.11.2014, Seattle, USA
  • Contribution to proceedings
    2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (2014 NSS/MIC), 08.-15.11.2014, Seattle, USA
    Proceedings of 2014 NSS/MIC

Publ.-Id: 20808

Model for the Design of a Prompt Gamma Detection System Using Large Scintillators and Digital Silicon Photomultipliers

Römer, K.; Pausch, G.; Rohling, H.; Schöne, S.; Enghardt, W.; Golnik, C.; Hueso-González, F.; Kormoll, T.; Petzoldt, J.; Fiedler, F.

Proton therapy is, due to the well defined penetration depth, advantageous compared to classical radiation therapy in oncology. But range uncertainties can arise easily and have to be corrected for, preferably immediately during irradiation. Prompt gammas are a good means of instantaneous determination of the dose deposition. Detection systems have to cope with the high counting rates, energy region of up to several MeV and increased background due to secondary emissions, while providing reliable information on energy, timing and location of the detected gamma ray. Various concepts utilize these prompt gammas for dose verification like collimated systems, Compton cameras or prompt gamma timing. The digital silicon photomultiplier (dSiPM), as a favorable alternative to PMTs because of good timing performances and no requirement of further electronics, has been modelled in order to understand the complex behavior when working with monolithic scintillation crystals. Especially, the selection of trigger- and validation-parameters may lead to different spectrum shapes. This model will be helpful for finding best parameter settings for the required task, because it determines the photons lost in various processes, the trigger timing information and the spatial map. Comparison of modelled spectra and measured spectra are presented.

Keywords: Scintillation; digital Silicon PMT

  • Poster
    2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (2014 NSS/MIC), 08.-15.11.2014, Seattle, USA
  • Contribution to proceedings
    2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (2014 NSS/MIC), 08.-15.11.2014, Seattle, USA
    Proceedings of 2014 NSS/MIC

Publ.-Id: 20807

Kinetic inertness evaluation of copper complexes using gel electrophoresis techniques

Kubeil, M.; Zarschler, K.; Steinbach, J.; Stephan, H.

The development of highly stable radiocopper complexes is one major challenge that seeks to further improved radiopharmaceuticals for medicinal applications. In many cases, radiocopper complexes suffer the fate of dissociation in vivo which is contributed to loss of the radionuclide resulting amongst others in an unspecific accumulation in non-target tissues and thus in poor target-to-background ratios. The kinetic lability has been addressed as major issue for transchelation or dissociation in vivo. Valuable information of kinetic inertness can be derived from non-physiological and non-radiotracer conditions e.g., ligand or metal ion challenge experiments, acid-assisted dissociation studies. Serum stability experiments are more suitable, since they are associated with in vivo conditions. Usually, the method of choice to measure the kinetic inertness involves a time-consuming radio-HPLC procedure. In contrast, we describe two reliable in vitro assays using standard gel electrophoresis techniques which provide a timesaving work-flow for measuring simultaneously a variety of copper-containing chelates. With this procedure, different radiocopper chelates can be evaluated and compared concerning their kinetic inertness using protein challenge assays. Moreover, both experiments are transferable not only to newly designed chelates, but also to conjugates containing targeting molecules such as peptides or proteins.

Keywords: copper complexes; radiocopper; Cu-64; kinetic inertness; transchelation; chelate; chelator; gel electrophoresis; SDS-PAGE; native PAGE; human serum; superoxide dismutase

  • Poster
    2nd International Symposium on TECHNETIUM and OTHER RADIOMETALS in CHEMISTRY and MEDICINE (TERACHEM 2014), 10.-13.09.2014, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 41(2014)7, 633-634
    DOI: 10.1016/j.nucmedbio.2014.05.028

Publ.-Id: 20806

Cyclam with N-carbonxyethyl pendant arms as suitable radiocopper chelates

Kubeil, M.; Zarschler, K.; Pietzsch, J.; Stephan, H.; Comba, P.

Cyclam (1,4,8,11-Tetraazacyclotetradecane) and its derivatives are powerful ligands for very stable complexes with (radio)copper(II) [1]. These chelators allow the functionalization of targeting molecules, e.g. peptides and/or fluorescence units, to construct effective radiopharmaceuticals for diagnostic and therapeutic purposes. In this context, 1,4,8,11-tetra(carboxymethyl)-1,4,8,11-tetraazacyclotetradecane (TETA) is used for the development of copper-based target-specific radiopharmaceuticals, although dissociation and transchelation occur in biological systems. In contrast, radiolabeling of the pentadentate cyclam ligands with a different number of N-carboxyethyl groups have not been reported so far. As a consequence, their copper(II) complexes have been synthesized [2]. Herein, we present a comprehensive study, dealing with the influence of the pendant arm length on structural properties, radiolabelling conditions, in vitro and in vivo stability, and compare these results with cyclam ligands bearing N-carboxymethyl pendant arms e.g., CuII-TETA.
The different number of N-carboxyethyl pendant arms at the cyclam backbone strongly influences the structure and stability of the copper complexes. TE2P is ideally suited as a copper(II)-chelating agent due to its fast complexation with radiocopper, the high kinetic inertness towards SOD and human serum as well as the excellent biodistribution behaviour. The facile N-functionalization of TE2P with a specific peptide produces an imaging tool with improved pharmaceutical targeting.

1. T. J. Wadas, E. H. Wong,G. R. Weisman,C. J. Anderson, Chem. Rev. 110, 2858 (2010).
2. P. Comba, F. Emmerling, M. Jakob, W. Kraus, M. Kubeil, M. Morgen, J. Pietzsch, H.
Stephan, Dalton Trans. 42, 6142 (2013).

  • Lecture (Conference)
    5th EuCheMS Chemistry Congress, 31.08.-04.09.2014, Istanbul, Turkey

Publ.-Id: 20805

Characterization of circulating microparticle-associated CD39 family ecto-nucleotidases in human plasma

Jiang, Z. G.; Wu, Y.; Csizmadia, E.; Feldbrügge, L.; Enjyoji, K.; Tigges, J.; Toxavidis, V.; Stephan, H.; Müller, C. E.; Mcknight, C. J.; Moss, A.; Robson, S. C.

Phosphohydrolysis of extracellular ATP and ADP is an essential step in purinergic signaling that regulates key pathophysiological processes, such as those linked to inflammation. Classically, this reaction has been known to occur in the pericellular milieu catalyzed by membrane bound cellular ecto-nucleotidases, which can be released in the form of both soluble ecto-enzymes as well as being associated with exosomes. Circulating ecto-nucleoside triphosphate diphosphohydrolase 1 (NTPDase 1/CD39) and adenylate kinase 1 (AK1) activities have been shown to be present in plasma. However, other ecto-nucleotidases have not been characterized in depth. An in vitro ADPase assay was developed to probe the ecto-enzymes responsible for the ectonucleotidase activity in human platelet-free plasma, in combination with various specific biochemical inhibitors. Identities of ecto-nucleotidases were further characterized by chromatography, immunoblotting, and flow cytometry of circulating exosomes. We noted that microparticle-bound ENTPDases and soluble AK1 constitute the highest levels of ecto-nucleotidase activity in human plasma. All four cell membrane expressed E-NTPDases are also found in circulating microparticles in human plasma, inclusive of: CD39, NTPDase 2 (CD39L1), NTPDase 3 (CD39L3), and NTPDase 8. CD39 family members and other ecto-nucleotidases are found on distinct microparticle populations. A significant proportion of the microparticle-associated ecto-nucleotidase activity is sensitive to POM6, inferring the presence of NTPDases, either −2 or/and −3. We have refined ADPase assays of human plasma from healthy volunteers and have found that CD39, NTPDases 2, 3, and 8 to be associated with circulating microparticles, whereas soluble AK1 is present in human plasma. These ecto-enzymes constitute the bulk circulating ADPase activity, suggesting a broader implication of CD39 family and other ecto-enzymes in the regulation of extracellular nucleotide metabolism.

Keywords: Ecto-nucleotidase; CD39; ATP; ADP; Adenosine; Purinergic signaling; TLC

Publ.-Id: 20804

The Ti7-Containing, Tetrahedral 36-Tungsto-4-Arsenate(III)[Ti6(TiO6)(AsW9O33)4]20-

Wang, K.-Y.; Bassil, B. S.; Lin, Z. G.; Haider, A.; Cao, J.; Stephan, H.; Viehweger, K.; Kortz, U.

We have prepared the Ti7-containing, tetrahedral 36-tungsto-4-arsenate(III) [Ti6(TiO6)(AsW9O33)4]20- (1) in a simple, one pot procedure. Polyanion 1 contains a novel Ti7-core, comprising a central TiO6 octahedron surrounded by six TiO5 square-pyramids, capped by four {AsIIIW9} trilacunary fragments. The title polyanion is solution-stable, as shown by 183W NMR and mass spectrometry, and exhibits interesting biological properties.

Publ.-Id: 20803

Bispidines for dual imaging

Stephan, H.; Walther, M.; Fähnemann, S.; Ceroni, P.; Molloy, J.; Bergamini, G.; Heisig, F.; Müller, C. E.; Kraus, W.; Comba, P.

The efficient transformation of the hexadentate bispidinol 1 into carbamate derivatives yields functional bispidines for the convenient functionalization for targeted imaging. The BODIPY-substituted bispidine 3 combines the coordination site for metal ions (e.g., radioactive 64CuII) with a fluorescent unit. Product 3 was thoroughly characterized by standard analytical methods, single crystal diffraction, radiolabeling and photophysical analysis. The luminescence of ligand 3 was found to be strongly dependent on metal ion coordination: CuII quenches the BODIPY fluorescence, while NiII and ZnII ions do not affect it. It follows that, in imaging applications with the positron emitter 64CuII, residues of its origin from enriched 64Ni and the decay products 64NiII and 64ZnII, efficiently restore the fluorescence of the ligand. This allows for monitoring of the emitted radiation as well as the fluorescence signal. The stability of the 64CuII-3 complex was investigated by transmetalation experiments with ZnII and NiII, using fluorescence and radioactivity detection and the results confirm the high stability of 64CuII-3. In addition, metal complexes of ligand 3 with the lanthanide ions TbIII, EuIII and NdIII are shown to exhibit emission of the BODIPY ligand and the lanthanide ion, thus enabling dual emission detection.

Publ.-Id: 20802

2,3-Diaryl-substituted indole based COX-2 inhibitors as leads for imaging tracer development

Laube, M.; Tondera, C.; Sharma, S. K.; Bechmann, N.; Pietzsch, F.-J.; Pigorsch, A.; Köckerling, M.; Wuest, F.; Pietzsch, J.; Kniess, T.

A series of 2,3-diaryl-substituted indoles containing a fluorine or methoxy group was synthesized via Fischer indole synthesis, McMurry cyclization, or Bischler–Möhlau reaction to identify potential leads for positron emission tomography (PET) radiotracer development as well as for optical imaging. All 2,3-diaryl-substituted indoles possess autofluorescent properties with an emission maximum in a range of 443–492 nm, which is acceptable for biological studies in vitro and, in part, in vivo. The molecular structure of compounds 3a and 3j was confirmed by X-ray crystal structure analysis. COX inhibitory activity was evaluated by a fluorescence-based and enzyme immunoassay-based assay. Redox activity of all target compounds was also determined. All synthesized 2,3-diaryl-substituted indoles are inhibitors of COX-2 enzyme in the low micromolar range. Compounds 3e, 3f, 3g and 3m displayed a 30–40% inhibition of COX-2 at 0.1 µM concentration while compounds 3f and 3g also exhibited COX-1 inhibitory activity. Various compounds like 3g showed substantial antioxidative potential (RDIENE=2.85, RHAVA=1.98), an effect that was most measurable with methoxy-substituted compounds. With respect to PET radiotracer synthesis, OMe-containing compound 3j was selected as a promising candidate for carbon-11 labeling, and F-containing compound 3m as a lead for the development of a fluorine-18 labeled derivative.

Publ.-Id: 20801

Effects of pulmonary acid aspiration on the regional pulmonary blood flow within the first hour after injury: an observational study in rats

Richter, T.; Bergmann, R.; Pietzsch, J.; Mueller, M. P.; Koch, T.

Gastric aspiration events are recognized as a major cause of pneumonitis and the development of acute respiratory distress syndrome. The first peak in the inflammatory response has been observed one hour after acid-induced lung injury in rats. The spatial pulmonary blood flow (PBF) distribution after an acid aspiration event within this time frame has not been adequately studied. We determined therefore PBF pattern within the first hour after acid aspiration.
Anesthetized, spontaneous breathing rats (n= 8) underwent unilateral endobronchial hydrochlorid acid instillation so that the PBF distributions between the injured and non-injured lungs could be compared. The signal intensity of the lung parenchyma after injury was measured by magnetic resonance tomography. PBF distribution was determined by measuring the concentration of [68Ga]-radiolabeled microspheres using positron emission tomography.
Following acid aspiration, magnetic resonance images revealed increased signal intensity in the injured regions accompanied by reduced oxygenation. PBF was increased in all injured lungs (171 [150; 196], median [25%; 75%]) compared to the blood flow in all uninjured lungs (141 [122; 159], P= 0.0078).
From the first minute until fifty minutes after acid-induced acute lung injury, the PBF was consistently increased in the injured lung. These blood flow elevation was accompanied by significant hypoxemia

Keywords: Acute lung injury; respiratory aspiration; positron emission tomography; pulmonary blood flow; magnetic resonance imaging

  • Clinical Hemorheology and Microcirculation 60(2015), 253-262
    Online First (2014) DOI: 10.3233/CH-141867

Publ.-Id: 20800

In Vivo Fluorescence Imaging and Urinary Monoamines as Surrogate Biomarkers of Disease Progression in a Mouse Model of Pheochromocytoma

Ullrich, M.; Bergmann, R.; Peitzsch, M.; Cartellieri, M.; Quin, N.; Erhart-Bornstein, M.; Block, N. L.; Schalley, A. V.; Pietzsch, J.; Eisenhofer, G.; Bornstein, S. R.; Ziegler, C. G.

Pheochromocytoma is a rare but potentially lethal neuroendocrine tumor arising from catecholamine producing chromaffin cells.Especially for metastatic pheochromocytoma,the availability of animal models is essential for developing novel therapies. For evaluating therapeutic outcome in rodent pheochromocytoma models reliable quantification of multiple organ lesions depends on dedicated small animal in vivo imaging, which is still challenging and only available at specialized research facilities. Here, we investigated whether whole-body fluorescence imaging and monitoring of urinary free monoamines provide suitable parameters for measuring tumor progression in a murine allograft model of pheochromocytoma. We generated an mCherry-expressing mouse pheochromocytoma cell line by lentiviral gene transfer. These cells were injected subcutaneously into nude mice to perform whole-body fluorescence imaging of tumor development. Urinary free monoamines were measured by liquid chromatography with tandem mass spectrometry. Tumor fluorescence intensity and urinary outputs of monoamines showed tumor growth-dependent increases (<0.001) over the 30 days of monitoring post tumor engraftment. Concomitantly, systolic blood pressure was increased significantly during tumor growth. Tumor volume correlated significantly (<0.001) and strongly with tumor fluorescence intensity (=0.946) and urinary outputs of dopamine (=0.952), methoxytyramine (=0.947), norepinephrine (=0.756) and normeta-nephrine (=0.949). Dopamine and methoxytyramine outputs allowed for detection of lesions at diameters below 2.3 mm. Our results demonstrate that MPC-mCherry cell tumors are functionally similar to human pheochromocytoma. Both tumor fluorescence intensity and urinary outputs of free monoamines provide precise parameters of tumor progression in this subcutaneous mouse model of pheochromocytoma. This animal model will allow for testing new treatment strategies for chromaffin cell tumors.

Keywords: Pheochromocytoma; Catecholamines; Metanephrines; LC-MS/MS; In vivo fluorescence imaging; Mouse pheochromocytoma cells

Publ.-Id: 20799

Biocompatibility and inflammatory response in vitro and in vivo to gelatin-based biomaterials with tailorable elastic properties

Ullm, S.; Krüger, A.; Tondera, C.; Gebauer, T. P.; Neffe, A. T.; Lendlein, A.; Jung, F.; Pietzsch, J.

Hydrogels prepared from gelatin and lysine diisocyanate ethyl ester provide tailorable elastic properties and degradation behavior. Their interaction with human aortic endothelial cells (HAEC) as well as human macrophages (Mɸ) and granulocytes (Gɸ) were explored. The experiments revealed a good biocompatibility, appropriate cell adhesion, and cell infiltration. Direct contact to hydrogels, but not contact to hydrolytic or enzymatic hydrogel degradation products, resulted in enhanced cyclooxygenase-2 (COX-2) expression in all cell types, indicating a weak inflammatory activation in vitro. Only Mɸ altered their cytokine secretion profile after direct hydrogel contact, indicating a comparably pronounced inflammatory activation. On the other hand, in HAEC the expression of tight junction proteins, as well as cytokine and matrix metalloproteinase secretion were not influenced by the hydrogels, suggesting a maintained endothelial cell function. This was in line with the finding that in HAEC increased thrombomodulin synthesis but no thrombomodulin membrane shedding occurred. First in vivo data obtained after subcutaneous implantation of the materials in immunocompetent mice revealed good integration of implants in the surrounding tissue, no progredient fibrous capsule formation, and no inflammatory tissue reaction in vivo. Overall, the study demonstrates the potential of gelatin-based hydrogels for temporal replacement and functional regeneration of damaged soft tissue.

Keywords: Cyclooxygenases; Cytokines; Endothelial cells; Macrophages; Matrix metalloproteinases; Thrombomodulin

Publ.-Id: 20798

The Feasibility of direct measurement of the 44Ti(α, p)47V and 40Ca(α, p)43Sc reactions in forward kinematics at astrophysically relevant temperatures

Al-Abdullah, T.; Akhmadaliev, S.; Ayranov, M.; Bemmerer, D.; Dressler, R.; Elekes, Z.; Kivel, N.; Schmidt, K.; Schumann, D.; Sobiella, M.; Stowasser, T.; Takacs, M. P.; Zuber, K.

Understanding the synthesis of radioactive 44Ti in the α-rich freeze-out following core-collapse supernovae may help to better interpret such explosive events. The γ-ray lines from the decay of 44Ti have been observed by space-based γ-ray telescopes from two supernova remnants. It is believed that the 44Ti(α,p)47V reaction dominates the destruction of 44Ti, while the 40Ca(α,p)43Sc reaction removes fuel from the main 44Ti production reaction 40Ca(α,γ)44Ti. Here we report on a possible technique to determine both reaction rates at astrophysically relevant energies in forward kinematics. The first reaction will be performed using a 1–10 MBq 44Ti target. Two important concerns are considered to make this study possible: The amount of stable Ti in the radioactive target, which will be prepared via spallation reactions at Paul Scherrer Institute (PSI), and the degree of radioactive contaminations in the experimental setup due to sputtered 44Ti atoms after intensive irradiations. Several online and offline measurements in parallel with Monte Carlo simulations were performed to investigate these issues.

Publ.-Id: 20797

Interaction of Slow Highly Charged Ions with Ultrathin Membranes

Wilhelm, R. A.; Gruber, E.; Ritter, R.; Heller, R.; Facsko, S.; Aumayr, F.

Slow highly charged ions (HCI) are known as an efficient tool for surface nano structuring of various insulating and semi-conducting surfaces. We show here that slow HCI can also be used to perforate a free-standing carbon nano membrane (CNM) with a thickness of only 1 nm. In Fig. 1 (left) a helium ion microscopy (HIM) image shows ion induced pores with sizes of up to 15 nm in diameter and corresponding sputter yields of up to a few thousand atoms. Recent energy loss and charge exchange measurements on ions transmitted through a 1 nm thick CNM and free-standing Graphene reveal a strong dependence of the ion energy loss on charge exchange (see Fig. 1 (right)). Surprisingly two distinct exit charge state distributions are observed, i.e. one part of the ions is almost neutralized and the other part remains in very high charge states after transmission.
A simple model for charge state dependent energy loss of slow ions is compared to the mea- sured transmission data. The ions potential and kinetic energy dependence on pore formation is discussed in terms of charge exchange and energy loss.

  • Invited lecture (Conferences)
    17th International Conference Physics of Highly Charged Ions (HCI2014), 31.08.-05.09.2014, San Carlos de Bariloche, Argentinien
  • Lecture (others)
    Institutsseminar, Institut für Angewandte Physik der TU Wien, 20.02.2015, Wien, Österreich

Publ.-Id: 20795

Driving Plasmas with Lasers - from Fundamental Physics to Killing Tumors

Bussmann, M.

Overview on Laser Particle Acceleration fundamentals and related work at HZDR.

Keywords: laser acceleration; overview; summer student program

  • Lecture (others)
    Lecture Series HZDR Summer Student Program, 04.08.2014, Dresden, Deutschland

Publ.-Id: 20794

Vom Experimentalphysiker zum Theoretiker - Warum geradlinige Lebensläufe langweilig sind

Bussmann, M.

Der Vortrag behandelt die Frage, wie und ob man seine Karriere in der Wissenschaft planen kann und sollte.

Keywords: carreer; science; cv

  • Lecture (others)
    Praktikerseminar des Fachschaftsrats Physik der TU Dresden, 26.06.2014, Dresden, Deutschland

Publ.-Id: 20793

Beyond “single-shot” simulations - Can we simulate what is measured?

Bussmann, M.; Widera, R.; Huebl, A.; Burau, H.; Pausch, R.; Debus, A.; Schmitt, F.

We present PIConGPU, a highly-scalable particle-in-cell simulation code which allows for large-scale simulation surveys that includes synthetic diagnostics which produce simulation results similar to what is measured in experiments.

Keywords: picong; particle-in-cell; simulation; laser; plasma; synthetic diagnostics

  • Invited lecture (Conferences)
    3rd Topical Workshop on Novel Acceleration Techniques, 27.-30.04.2014, Dresden, Deutschland

Publ.-Id: 20792

Laser cooling of stored relativistic ion beams with large momentum spreads using a laser system with a wide scanning range

Wen, W.; Winters, D.; Beck, T.; Rein, B.; Walther, T.; Tichelmann, S.; Birkl, G.; Sanchez-Alarcon, R.; Ullmann, J.; Lochmann, M.; Nörtershäuser, W.; Clark, C.; Kozhuharov, C.; Kühl, T.; Sanjari, S.; Litvinov, Y.; Giacomini, T.; Steck, M.; Dimopoulou, C.; Nolden, F.; Stöhlker, T.; Yang, J.; Zhang, D.; Ma, X.; Seltmann, M.; Siebold, M.; Schramm, U.; Bussmann, M.

New results on laser cooling of stored, bunched, relativistic ion beams are presented. For the first time it has been possible to cool an ion beam with large momentum spread without initial electron cooling or scanning of the bunching frequency by using a single cw laser system.

Keywords: laser cooling; ion beams; relativistic; cw laser; scanning; broadband

Publ.-Id: 20791

Cooling of Bunched Relativistic Ion Beams using a CW Laser with a Frequency Scanning Range Greater than the Bucket Acceptance

Bussmann, M. H.; Schramm, U.; Seltmann, M.; Siebold, M.; Beck, T.; Birkl, G.; Rein, B.; Tichelmann, S.; Walther, T.; Dimopoulou, C.; Giacomini, T.; Kozhuharov, C.; Kühl, T.; Litvinov, Y. A.; Lochmann, M.; Nörtershäuser, W.; Nolden, F.; Sanchez Alarcon, R. M.; Sanjari, M. S.; Steck, M.; Stöhlker, T.; Ullmann, J.; Winters, D. F. A.; Ma, X.; Wen, W. Q.; Zhang, D.

With new, all solid-state cw laser sources cooling of relativistic ion beams with a large momentum spread has become possible. We present results on laser cooling of relativistic C3+ ion beams at the Experimental Storage Ring at GSI. In the experiment we used a frequency-quadrupled external-cavity diode laser for scanning over a relative ion momentum spread of dp/p ~ 10-5. We could show that laser cooling with such a system is almost independent of beam current and that the momentum spread reached for various bunching harmonics, bucket depths and beam currents always was found to be comparable to the resolution of the resonant Schottky pickup at ESR. We further found a decrease in Schottky power with decreasing momentum spread and that cooling times were only limited by the scanning time of the laser. The laser cooling technique presented here is of great interest for future heavy ion storage rings as it allows to address ion beams with an initially large momentum spread, thus not requiring initial electron cooling.

Keywords: laser cooling; ion beams; relativistic; esr; fair

  • Poster
    5th International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Deutschland

Publ.-Id: 20790

Cooling Relativistic Ion Beams of initially large Momentum Spread with a fast scanning cw Laser System

Bussmann, M.; Winters, D.; Wen, W.; Dimopoulou, C.; Giacomini, T.; Kozhuharov, C.; Kühl, T.; Litvinov, Y.; Lochmann, M.; Nörtershäuser, W.; Nolden, F.; Sánchez, R.; Sanjari, S.; Steck, M.; Stöhlker, T.; Ullmann, J.; Beck, T.; Birkl, G.; Rein, B.; Tichelmann, S.; Walther, T.; Ma, X.; Zhang, D.; Loeser, M.; Seltmann, M.; Siebold, M.; Schramm, U.

We present new results from a recent experiment on laser cooling of relativistic bunched ion beams at the Experimental Storage Ring at GSI. Our results show laser cooling with a single solid-state cw laser system with a laser frequency scanning range larger than the bucket acceptance. This technique is of great importance for future storage ring facilities such as FAIR and HIAF, as it allows for all-optical beam cooling of initially hot ion beams without the need for pre-electron cooling or stochastic cooling.

Keywords: laser cooling; ion beams; relativistic; esr; fair

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion AMOP (SAMOP), 17.-21.03.2014, Berlin, Deutschland

Publ.-Id: 20789

Laser Cooling of Relativistic Ion Beams with Large Momentum Spreads

Bussmann, M.; Winters, D.; Wen, W.; Dimopoulou, C.; Giacomini, T.; Kozhuharov, C.; Kühl, T.; Litvinov, Y.; Lochmann, M.; Nörtershäuser, W.; Nolden, F.; Sánchez, R.; Sanjari, S.; Steck, M.; Stöhlker, T.; Ullmann, J.; Beck, T.; Birkl, G.; Rein, B.; Tichelmann, S.; Walther, T.; Ma, X.; Zhang, D.; Loeser, M.; Seltmann, M.; Siebold, M.; Schramm, U.

We present new results from a recent experiment on laser cooling of relativistic bunched ion beams at the Experimental Storage Ring at GSI. Our results show laser cooling with a single solid-state cw laser system with a laser frequency scanning range larger than the bucket acceptance. This technique is of great importance for future storage ring facilities such as FAIR and HIRFL, as it allows for all-optical beam cooling of initially hot ion beams without the need for pre-electron cooling.

Keywords: laser cooling; ion beams; relativistic; esr; fair

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 30.03.-04.04.2014, Dresden, Deutschland

Publ.-Id: 20788

The Helmholtz Beamline at XFEL - Probing solid density laser-plasma physics with XFELs on the femtosecond scale

Bussmann, M.; Kluge, T.; Huang, L.; Cowan, T. E.

We show that probing the ionization evolution and plasma dynamics in high power laser interaction with matter on the femtosecond and nanometer scale is in reach with state of the art X-ray lasers at facilities such as LCLS, SACLA and the European XFEL.
We have conducted particle-in-cell simulations including radiative and collisional atomic processes to generate absolute predictions for synthetic scattering images using SAXS and RCXDI techniques. We could show that plasma dynamics from the target front side and bulk can be distinguished and plasma instabilities identified and their development could be temporarily involved. Inclduing atomic physics models from SCFly we could furthermore show that the temporal evolution of the ionization dynamics can be probed by resonant scattering.

Keywords: xfel; hibef; helmholtz beamline; scattering; x-ray; laser; plasma; imaging; simulation

  • Lecture (Conference)
    Strongly Coupled Coulomb Systems, 27.07.-01.08.2014, Santa Fe, NM, United States of America

Publ.-Id: 20787

Direct measurement of the magnetic anisotropy field in Mn-Ga and Mn-Co-Ga Heusler films

Fowley, C.; Ouardi, S.; Kubota, T.; Oguz, Y.; Neudert, A.; Lenz, K.; Sluka, V.; Lindner, J.; Law, J. M.; Mizukami, S.; Fecher, G. H.; Felser, C.; Deac, A. M.

The static and dynamic properties of tetragonally distorted Mn–Ga based alloys were investigated. Static magnetic properties are determined in magnetic fields up to 6.5 T using SQUID magnetometry. For the pure Mn1.6Ga film, the saturation magnetisation is 0.36 MA/m and the coercivity is 0.29 T. Partial substitution of Mn by Co results in Mn2.6Co0.3Ga1.1. The saturation magnetisation of those films drops to 0.2 MA/m and the coercivity is increased to 1 T. Time-resolved magneto-optical Kerr effect (TR-MOKE) is used to probe the high-frequency dynamics of Mn–Ga. The ferromagnetic resonance frequency extrapolated to zero-field is found to be 125 GHz with a Gilbert damping, $\alpha$, of 0.019. The anisotropy field is determined from both SQUID and TR-MOKE to be 4.5 T, corresponding to an effective anisotropy density of 0.81 MJ/m3. Given the large anisotropy field of the Mn2.6Co0.3Ga1.1 film, pulsed magnetic fields up to 60 T are used to determine the field strength required to saturate the film in the plane. For this, the extraordinary Hall effect was employed as a probe of the local magnetisation. By integrating the reconstructed in–plane magnetisation curve, the effective anisotropy energy density for Mn2.6Co0.3Ga1.1 is determined to be 1.23 MJ/m3.

Keywords: Heusler alloys; Mn-Ga; Hall Effect; Time resolved MOKE; magneto-optics; magnetotransport; high magnetic fields; anisotropy; perpendicular magnetic anisotropy

Publ.-Id: 20786

The influence of current collectors on Tayler instability and electro-vortex flows in liquid metal batteries

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

The Tayler instability is a kink-type flow instability which occurs when the electrical current through a conducting fluid exceeds a certain critical value. Originally studied in the astrophysical context, the instability was recently shown to be also a limiting factor for the upward scalability of liquid metal batteries. In this paper, we continue our efforts to simulate this instability for liquid metals within the framework of an integro-differential equation approach. The original solver is enhanced by multi-domain support with Dirichlet-Neumann partitioning for the static boundaries. Particular focus is laid on the detailed influence of the axial electrical boundary conditions on the characteristic features of the Tayler instability, and, secondly, on the occurrence of electro-vortex flows and their relevance for okliquid metal batteries.

Keywords: liquid metal battery; simulation; OpenFOAM; magnetohydrodynamics; Tayler instability; electro-vortex flow

Publ.-Id: 20785

Plasma-based nanotechnology against corrosion of organ pipes

Pelic, B.; Skorupa, W.

Experiments have been undertaken to explore the improvement of aqueous corrosion of Cu-Zn, by applying plasma immersion ion implantation (PI3).
The atmospheric corrosion of the tongues within the reed pipes which consist of a Cu-20Zn alloy (namely brass) is strongly enhanced by traces of acid vapors (from wooden parts and glue) and also the alloy’s instability caused by dezincification. A significant improvement in corrosion resistance has been achieved by applying a 30 nm aluminum oxide film using pulsed laser deposition (PLD) and implanting nitrogen ions into the near surface and the interface regions. The influence of the implanted N+ into CuZn and F+ into TiAl samples on the corrosion process has been investigated. For the sample evaluation, different characterization methods including scanning electron microscope with energy dispersive X-ray spectroscopy (SEM / EDX), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), and Dektak stylus profiling have been applied to determine the chemical composition, the elemental depth profiles, roughness and defect formation of the samples before and after exposure.

Keywords: Plasma immersion ion implantation (PI3); Pulsed laser deposition (PLD); corrosion of organ pipes; Cu-Zn alloys; PbSn alloys

  • Invited lecture (Conferences)
    Final conference of the EU research project ''EU-PANNA'', 04.09.2014, Berlin, Germany

Publ.-Id: 20782

Investigation of the interactions between selected bacteria and selenium oxyanions

Luthardt, P.; Fischer, S.; Fischer, S.; Vogel, M.; Steudtner, R.; Henle, T.

The microbial reduction of soluble selenium cations into its insoluble elemental form presents a unique opportunity to decontaminate industrial waste. We tested two strains of Bacillus sp. (JG-B5T, JG-B41) isolated from a uranium mining waste pile in Johanngeorgenstadt (Saxony) for their potential capacity to reduce selenium. A third species (Shewanella oneidensis) with a known reduction capacity is used as reference organism.
The microbial behavior of the bacteria under the influence of sodium selenite and selenate was observed. This included recording growth curves, pH alteration and changes in redox potential. The bacteria displayed differential growth when confronted with 2.5 mM selenite (Fig. 1) and selenate compared to controls. The content of the water soluble oxyanions was analyzed in the supernatant using inductively coupled plasma optical emission spectrometry. All selected strains have the ability to reduce selenite, whereas a reaction with selenate was not observed.
In addition we have observed and characterized the extracellular matrix focused on organic acids via High Performance Liquid Chromatography during the trial period. So far, the results indicate that two of the selected strains rely on different mechanisms.
The produced particles (Fig. 2) were isolated from the bacterial matrix and analyzed with Scanning electron microscopy with energy dispersive X-ray spectroscopy, by Raman spectroscopy, and Dynamic Light Scattering. With that we can determine their particle size, the type of bonding involved and their elemental compositions. The Raman spectra have already given indications for Se8-ring formation. X-ray analyses will reveal if other elements, like sulfur, are incorporated.After investigating the interaction of the selected strains with selenium in a defined medium, we will perform trials with real wastewater to test and validate our laboratory results under industrial conditions.
Reactions between selenium and microorganisms can significantly influence its transport behavior in the bio- and geosphere. Furthermore these metalloid-bacteria interactions can be used for various biotechnological applications.

Keywords: Selenium; Microbial Reduction; Shewanella oneidensis; Bacillus; Selenite; Selenate

  • Poster
    Selen2014 - Selenium in geological, hydrological and biological systems, 13.-14.10.2014, Karlsruhe, Deutschland

Publ.-Id: 20781

Convenient recycling and reuse of bombarded [18O]H2O for the production and the application of [18F]F

Rötering, S.; Franke, K.; Zessin, J.; Brust, P.; Füchtner, F.; Fischer, S.; Steinbach, J.

The limited availability and the increasing demands of [18O]H2O force the reuse of bombarded [18O]H2O for the production of [18F]F at least for the purposes of research. Therefore inorganic and organic contaminants have to be removed from the [18O]water. We present a simple and effective method of [18O]water purification including oxidation and distillation. The obtained recycled [18O]water has comparable properties to unused [18O]water. This was confirmed by a detailed comparison of produced radionuclides and their activities and the application of [18F]F in standardised radiotracer synthesis.

Keywords: purification of used [18O]water; recycling and reuse; production of [18F]fluoride; radiosynthesis; analysis methods

Publ.-Id: 20780

Photoemission studies of niobium and lead photocathodes using picosecond UV laser

Xiang, R.; Arnold, A.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Barday, R.

We present the results of our investigations on superconducting photocathodes for supercondcuting rf injectors. Bulk niobium and lead film on niobium have been considered as the best candidates. The quantum efficiency (QE) at room temperature has been measured with 258 nm UV laser pulses of 14 ps duration. A QE of 10-4 has been obtained for the lead film. In order to improve the photoemission yield of niobium, new treatment methods, like Cs-activation and implantation with alkali metals, have been applied and the results are reported.

Keywords: photocathode; niobium; lead; quantum efficiency (QE)

  • Open Access Logo Contribution to proceedings
    the 36th International Free Electron Laser Conference (FEL 2014), 25.-29.08.2014, Basel, Switzerland
    Proceedings of FEL2014
  • Poster
    the 36th International Free Electron Laser Conference (FEL 2014), 25.-29.08.2014, Basel, Switzerland

Publ.-Id: 20779

The challenges of regional geochemistry to compositional data analysis from a methodological viewpoint

van den Boogaart, K. G.; Tolosana-Delgado, R.

Regional Geochemistry is an important tool for the detect on of geopotenials (e.g. deposits) and risks (e.g. polution sources) and is an important source of geological insight on large scale. It is mainly concerned with geochemical data, which is inherently compositional. Modern compositional data analysis (CoDa) provides a lot of tools like distribution models, transforms, graphics, compositional geostatistics, imputation, compositional regression and linear models, outlier detection and robustness. However it does not yet provide tools for typical tasks in regional geochemistry, which among others are: maps of single components, anomaly detection and background definition, dealing with below detection limit, dealing with spatially varying geology and land use, working with surveys with too many components to explore all pairwise log ratios, calibration of instruments, collocated compositions, etc.. Ideally CoDa methods should be superior to classical statistical methods for geochemical data and it should thus be possible to simply replace the statistical methods in state-of-the-art geochemical practice by corresponding CoDa tools.The aim of the talk is to give a systematic account of how and why this is not yet occuring. For instance, single components maps are considered a key information in geochemistry, but spurious according to the doctrine of the Aitchison simplex. The compositional alternative would be to work with pairwise log ratios. However such compositional tools have other drawbacks, like e.g. too many pairs, mixing of different information on and no standard literature on their interpretation. Anomaly detection and spa! al factors are not yet sufficiently developed in the methodology research on CoDa. O$ en the application on of standard CoDa tools generates practical problems, like e.g. the identification of anomalies in a multivariate compositon will show a multitude of kinds of anomalies and we are confronted with many different sources and reasons for their occurrence. Par! ally CoDa methods need to be developed for tasks specific to geochemistry, and partly geochemists need to to develop a new thinking for interpreting the results of CoDa methods.From this systematic analysis we have deduced a set of key issues:

  • The composition as a whole holds too much information at once. We need efficient methods to extract informative summaries with respect to geochemical tasks. This includes developing readable CoDa graphics and summaries for more than 30 components and multiple layers.
  • The single component is understood in a completely different way by geochemists and CoDa-statistians. It is necessary to generate a joint view of this problem and then solve it.
  • Enabling CoDa methods for below detection limit and measurement error issues including taylored callibration on for the needs of regional geochemistry.
  • High level key publications of the proper use of compositional methods in a regional geochemistry context as reference for future geochemical publications.
  • Specialized CoDa based so$ ware for geochemistry powerful enough to replace the existing tools.

Keywords: geochemical exploration; CODA; anomaly detection

  • Lecture (Conference)
    GeoMap Workshop, 17.06.-20.09.2014, Olomouc, Česká republika
  • Contribution to proceedings
    Geomap Workshop, 17.-20.6.2014, Olmouc, Česká republika
    GeoMap Workshop Proceedings, Oulmouc: Univerzita Palackého in Olomouc, 978-80-244-4149-8, 14-15


Publ.-Id: 20778

New Insight into the Photochemical Reaction Mechanism of Uranyl Citrate by Combining NMR Experiment and DFT Calculation

Tsushima, S.; Kretzschmar, J.; Steudtner, R.

A sound understanding of the major reaction mechanisms is crucial to handle uranium containing waste appropriately. This means both the synthesis of unique compounds and the treatment of uranium occurring in or released into the environment. In an environmental context, uranium occurs in two main redox states: mobile U(VI) and immobile U(IV).
Due to both its model character in U(VI) complexation by chelating polycarboxylates and the citrate being a ubiquitous occurring ligand, particularly being important in the citric acid cycle in vivo, the uranyl citrate system itself [1–4] and also its photoreaction [5,6] is already repeatedly investigated, but still not fully understood.
This investigation provides not only further insight into the U(VI)-citrate complexation, but also a better understanding of the (photo-)redox chemistry of uranium in general.
Here we want to present the reaction pathway of the U(VI) citrate complex photooxidation to its degradation products ketoglutaric acid, acetoacetic acid and acetone with concomitant CO2 formation by several decarboxylation steps and the formation of U(IV). The oxidation state of the latter is indicated by NMR showing 1H chemical shifts > 50 ppm and proven by UV-vis. Moreover, the yielded U(IV) appears as soluble complexes of citrate and its degradation products. The identity of the formed compounds was experimentally proven by one- and twodimensional NMR methods and confirmed by DFT calculations.
The photoreaction starts by irradiating the sample with light from a simple light source such as the sun or a commercial mercury lamp. Interestingly, the initial chemical alteration starts by a single electron transfer from a citrate molecule, being hydrogen bonded to the fifth remaining coordination site not occupied by U(VI)–coordinating citrate. Most likely the intermediate, i.e., not observable U(V) disproportionates fast to U(VI) and the aforementioned U(IV).

[1] R. Bramley, W. F. Reynolds, I. Feldman, J. Am. Chem. Soc. 1965, 87, 3329–3332.
[2] E. Ohyoshi, J. Oda, A. Ohyoshi, Bull. Chem. Soc. Jap. 1975, 48, 227–229.
[3] S. P. Pasilis and J. E. Pemberton, Inorg. Chem. 2003, 42, 6793–6800.
[4] A. Günther, R. Steudtner, K. Schmeide, G. Bernhard, Radiochim. Acta 2011, 99, 535–541.
[5] H. D. Burrows and T. J. Kemp, Chem. Soc. Rev. 1974, 3, 139–165.
[6] A. J. Francis and C. J. Dodge, DAE-BRNS Biennial Symposium on Emerging Trends in Separation Science and Technology (SESTEC) 2008 (BNL-80322-2008-CP).

Keywords: uranium; citrate; photoreaction; reaction mechanism; NMR spectroscopy; DFT calculation

  • Poster
    Advanced Techniques in Actinide Spectroscopy 2014 (ATAS 2014), 03.-07.11.2014, Dresden-Rossendorf, Deutschland

Publ.-Id: 20777

Nuclear Magnetic Resonance Spectroscopy in Ln/An Research

Kretzschmar, J.; Schott, J.; Tsushima, S.; Barkleit, A.; Paasch, S.; Brunner, E.; Scholz, G.; Brendler, V.

Since signal separation by lanthanide shift reagents [1,2] has been replaced by elaborate pulse sequences and high-field spectrometers, lanthanides have advanced from auxiliaries to real objects of interest, also as inactive analogues for trivalent actinides in consequence of their similar chemistry.
Here we want to report on interactions and structures of the Ln(III) (La3+, Eu3+ and, where applicable, Y3+) with selected systems, i.e., L-lactate [3], inorganic (poly)borates [4] and organoborates [5]. Small organic molecules such as lactate are important as model molecules and potential complexing agents found throughout the biosphere. Borates are ubiquitous in nature. In the context of nuclear waste disposal they occur in remarkable amounts in salt formations being potential host rocks for nuclear waste repositories, but also in boron containing cooling water or borosilicate glass coquilles for spent nuclear fuel. Organoborates are considered due to possible reaction of the former compounds and, additionally, suggested as analogues to model the interaction between Ln/An and borates in general.
Among several possible structures, infrared (IR) and NMR measurements, supported by density functional theory (DFT) calculation, revealed that lactate forms Ln(III) (and Am3+) complexes with both the carboxyl and hydroxyl group involved. Polyborates, i.e., triborate and pentaborate form soluble weak aqueous Ln(III) complexes prior to precipitation as amorphous white solids, whereas condensation to higher polyborates can be excluded. Two signals in both the 89Y and the 11B NMR spectra probably arise from two coordination sites, which may reflect the polyborate species found in the supernatant solution. The organoborates formed by the reaction of boric acid and, e.g., lactate or salicylate also possess a tetra-coordinated boron atom [BO4], considered as the responsible site for Ln(III) interaction in inorganic (poly)borates. Since the (poly)borate/boric acid equilibrium is strongly concentration and pH dependent, their replacement by organic analogues allows investigations at both lower total boron concentrations and pH values.

[1] Hinckley, C. C. J. Am. Chem. Soc. 1969, 91, 5160–5162.
[2] Gansow, O. A.; Willcott, M. R.; Lenkinski, R. E. J. Am. Chem. Soc. 1971, 93, 4295–4297.
[3] Barkleit, A.; Kretzschmar, J.; Tsushima, S.; Acker, M. Dalton Trans. 2014, 43, 11221–11232.
[4] Schott, J.; Kretzschmar, J.; Acker, M.; Eidner, S.; Kumke, M. U.; Drobot, B.; Barkleit, A.; Taut, S.; Brendler, V.; Stumpf, T. Dalton Trans. 2014, 43, 11516–11528.
[5] Schott, J; Kretzschmar, J; Acker, M.; Tsushima, S.; Barkleit, A.; Taut, S.; Brendler, V.; Stumpf, T., Dalton Trans., in preparation.

Keywords: lanthanides; actinides; lanthanum; europium; yttrium; phosphorylated amino acid; boric acid; polyborate; NMR spectroscopy

  • Lecture (Conference)
    Advanced Techniques in Actinide Spectroscopy 2014 (ATAS 2014), 03.-07.11.2014, Dresden-Rossendorf, Deutschland

Publ.-Id: 20776

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