Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41397 Publications

2-Carbaborane-3-phenyl-1H-indoles—Synthesis via McMurry Reaction and Cyclooxygenase (COX) Inhibition Activity

Laube, M.; Neumann, W.; Scholz, M.; Lönnecke, P.; Crews, B.; Marnett, L. J.; Pietzsch, J.; Kniess, T.; Hey-Hawkins, E.

Cyclooxygenase-2 (COX-2) inhibitors have been in the focus of medicinal chemistry for years and many compounds exhibiting high selectivity and affinity were developed. As carbaboranes represent interesting pharmacophores as phenyl mimetics in drug development, this paper presents the synthesis of carbaboranyl derivatives of COX-2-selective 2,3-disubstituted indoles. Despite the lability of carbaboranes under reducing conditions, 2-carbaborane-3-phenyl-1H-indoles could be synthesized by McMurry cyclization of the corresponding amides. While the meta-carbaboranyl-substituted derivatives (3a-c) lacked COX inhibition activity, the orthocarbaboranyl analog (3d) was active but showed a selectivity shift towards COX-1.

Permalink: https://www.hzdr.de/publications/Publ-17851
Publ.-Id: 17851


Microbial life in flooded underground uranium mines in Saxony

Gagell, C.; Arnold, T.; Röske, I.

First results with regard to microbial life in flooded underground uranium mines in Saxony are presented.

  • Poster
    HZDR Doktorandenseminar, 10.10.2012, Schöneck, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17850
Publ.-Id: 17850


Laser-induced spectroscopy - A method for the determination of complexation behaviour of metals by organic ligands

Lindner, K.; Günther, A.; Bernhard, G.

Presentation of the complexation of Uranium(VI) with selected Schiff bases in methanol investigated by cryo-TRLFS and fs-TRLFS.

Keywords: cryo-TRLFS; fs-TRLFS; Uranium(VI); Schiff Bases

  • Poster
    PhD seminar 2012, 08.-10.10.2012, Schöneck, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17849
Publ.-Id: 17849


Investigation of the mobility of uranium (VI) in argillaceous rock at higher salinity

Fritsch, K.; Schmeide, K.

Three types of rock are considered for nuclear waste repositories: salt domes, crystalline rock and argillaceous rock. In this work, clay minerals and natural argillaceous rock are the subject of interest. North German clay deposits have high ionic strength pore water, up to 4 mol L-1. Therefore in the event of container failure, the nuclear waste will be in an environment of high salinity. To study the retention of radionuclides in clays in salinar systems, the experiments in the current project are carried out at high ionic strengths. Previous research(1) at HZDR investigated U(VI) sorption and diffusion at Opalinus clay and kaolinite in natural pore water and sodium perchlorate at low ionic strengths.

Keywords: nuclear waste repositories; uranium sorption; argillaceous rock; clay; uranium

  • Poster
    PhD seminar 2012, 08.-10.10.2012, Schöneck, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17848
Publ.-Id: 17848


Krein spaces and PT Quantum Mechanics

Günther, U.

A few basic facts about PT Quantum Mechanics (PTQM) are presented. Specifically, the underlying mathematical structures are briefly sketched, including Krein spaces (Hilbert spaces endowed with indefinite metric structures), J-selfadjointness, spectral singularities and PT phase transitions, the C-operator and the mapping between local PTQM and, in general, nonlocal conventional QM. The features are illustrated by following expamples: PT-symmetric Bose-Hubbard models (which may describe e.g. Bose-Einstein condensates with well balanced particle injection and extraction) and PT-symmetric brachistochrones and tachistochrones. Finally, recent realizations and applications in optical systems and microwave billiards are discussed --- including corresponding experiments.

Keywords: PT quantum mechanics; Krein spaces; spectral singularities; phase transitions; nonlocal quantum mechanics; Bose-Hubbard model; Bose-Einstein condensate; quantum brachistochrone; tachistochrone; optical systems; microwave billiards

  • Invited lecture (Conferences)
    Physics Meeting in Amazonia, 24.-28.09.2012, Belem, Brazil

Permalink: https://www.hzdr.de/publications/Publ-17847
Publ.-Id: 17847


Stabilization of prolate deformation at high spin in 75Kr

Steinhardt, T.; Eberth, J.; Skoda, S.; Thelen, O.; Schwengner, R.; Dönau, F.; Plettner, C.; Schnare, H.; de Angelis, G.; Napoli, D. R.; Farnea, E.; Gadea, A.; Jungclaus, A.; Lieb, K. P.; Wadsworth, R.

The neutron-deficient nucleus 75Kr has been studied in two EUROBALL experiments. The analysis yielded a considerably extended level scheme including two newly observed excited high spin bands. The results are interpreted in the framework of the cranked Nilsson-Strutinsky approach. The calculations compare well to the experimentally established level scheme and predict the nucleus to be mainly prolate or triaxially deformed at high spin. Evidence for an oblate-prolate shape coexistence could not be found at high spin.

Keywords: Nuclear structure; silicon detectors; cranked Nilsson-Strutinsky model; neutron detectors; EUROBALL; HPGe detectors; gamma-ray spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-17846
Publ.-Id: 17846


Synthesis and characterization of a percolating, ferromagnetic, Mn-rich Ge:Mn nanonet with hysteretic transport properties

Bürger, D.; Zhou, S.; Höwler, M.; Ou, X.; Kovacs, G. J.; Reuther, H.; Mücklich, A.; Skorupa, W.; Helm, M.; Schmidt, H.

The coupling of the magnetization state with the electrical transport properties of a magnetic semiconductor is one big step to new spintronics devices. The coupling can be proved by SQUID magnetization and Hall resistance measurements. In a previous work we fabricated ferromagnetic Ge:Mn by Mn ion implantation and pulsed laser annealing (PLA) and observed a clear hysteretic Hall resistance correlated with the magnetization below 10 K [1]. Recently, by applying optimized PLA conditions, we fabricated a percolating, Mn-rich Ge:Mn nanonet with hysteretic Hall resistance up to 30 K [2]. This nanonet is embedded in crystalline Ge:Mn between 5 nm and 40 nm under the sample surface. The reason for the formation of the nanonet is a constitutional undercooling of the liquid Ge-Mn-alloy during the recrystallization process using a relatively long pulse length of 300 ns which helped to imprint an optimal temperature profile during PLA [3]. We applied etching to confirm the contribution of the nanonet to the electrical transport properties. In the future such nanonets may be used to spin-polarize free charge carriers in magnetic semiconductors at room temperature. Because the nanonet can be selectively etched, substrates with ordered “nano-channels” can be fabricated which may be also useful in the field of nanoimprint-lithography. [1] S. Zhou et al., Phys. Rev. B 81, 165204 (2010) [2] D. Bürger et al., Appl. Phys. Lett. 100, 012406 (2012) [3] J. Narayan, J. Appl. Phys. 52, 1289 (1981)

Keywords: pulsed laser annealing; pulsed laser melting; ion implantation; Hall resistance; ferromagnetism; constitutional supercooling; nanonet

Related publications

  • Lecture (Conference)
    E-MRS 2012 Fall Meeting, 17.-21.09.2012, Warschau, Polen

Permalink: https://www.hzdr.de/publications/Publ-17845
Publ.-Id: 17845


Hydrogen interaction with defects in ZnO

Lukac, F.; Cizek, J.; Vlcek, M.; Prochazka, I.; Vlach, M.; Anwand, W.; Brauer, G.; Traeger, F.; Rogalla, D.; Becker, H.-W.; Wagner, S.; Uchida, H.; Bähtz, C.

In the present work hydrothermally grown ZnO single crystals were electrochemically charged with hydrogen. The influence of hydrogen on ZnO microstructure was investigated by positron annihilation spectroscopy (PAS) combined with X-ray diffraction (XRD) using synchrotron radiation. Hydrogen concentration in the samples was determined by nuclear reaction analysis (NRA). It was found that a high concentration of hydrogen can be introduced into ZnO by electrochemical loading. At low concentrations absorbed hydrogen causes elastic volume expansion of ZnO crystal. At higher concentration, hydrogen-induced stresses exceed the yield stress in ZnO and plastic deformation of the crystal takes place leading to formation a defected subsurface layer in the crystals.

Keywords: zinc oxide; hydrogen defects; positron annihilation spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-17844
Publ.-Id: 17844


Synthesis, in silico, in vitro, and in vivo investigation of 5-[11C]methoxy-substituted sunitinib, a tyrosine kinase inhibitor of VEGFR-2

Caballero, J.; Muñoz, C.; Alzate-Morales, J. H.; Cunha, S.; Gano, L.; Bergmann, R.; Steinbach, J.; Kniess, T.

Sunitinib® (SU11248) is a highly potent tyrosine kinase inhibitor targeting vascular endothelial growth factor receptor (VEGFR). Radiolabeled inhibitors of receptor tyrosine kinases (RTKs) might be useful tools for monitoring RTKs levels in tumor tissue giving valuable information for anti-angiogenic therapy. Herein we report the synthesis of 5-methoxy-sunitinib 5 and its 11C-radiolabeled analogue [11C]-5. The non-radioactive reference compound 5 was prepared by Knoevenagel condensation of 5-methoxy-2-oxindole with the corresponding substituted 5-formyl-1H-pyrrole. A binding constant (Kd) of 20 nM for 5 was determined by competition binding assay against VEGFR-2. In addition, the binding mode of sunitinib® and its 5-methoxy substituted derivative was studied by flexible docking simulations. These studies revealed that the substitution of the fluorine at position 5 of the oxindole scaffold by a methoxy group did not affect the inhibitor orientation, but affected the electrostatic and van der Waals interactions of the ligand with residues near the DFG motif of VEGFR-2. 5-[11C]methoxy-sunitinib ([11C]-5) was synthesized by reaction of the desmethyl precursor with [11C]CH3I in the presence of DMF and NaOH in 17±3% decay-corrected radiochemical yield at a specific activity of 162-205 GBq/µmol (EOS). In vivo stability studies of [11C]-5 in rat blood showed that more than 70% of the injected compound was in blood stream, 60 min after administration.

Keywords: sunitinib®; VEGFR; docking; molecular dynamics; MM-GBSA; carbon-11; radiolabeling

Permalink: https://www.hzdr.de/publications/Publ-17843
Publ.-Id: 17843


High-field magnetism and magnetoacoustics in uranium intermetallic antiferromagnets

Andreev, A. V.; Skourski, Y.; Yasin, S.; Zherlitsyn, S.; Wosnitza, J.

We report on studies on the magnetic and magnetoacoustic properties of uranium intermetallic antiferromagnets UCo2Si2, UCu0.95Ge, UIrGe and U2Ni2Sn in pulsed magnetic fields up to 60 T, where they undergo metamagnetic transitions. The measurements were performed in the temperature range from 1.4 to 100 K. The magnetic ordering and the metamagnetic transitions are accompanied by pronounced anomalies in the ultrasound velocity and the ultrasound attenuation. All studies were performed on single crystals grown by the Czochralski method in a tri-arc furnace.

Permalink: https://www.hzdr.de/publications/Publ-17842
Publ.-Id: 17842


Interplay between crystal field splitting and Kondo effect in CeNi9Ge4-xSix

Gold, C.; Gross, P.; Peyker, L.; Eickerling, G.; Simeoni, G. G.; Stockert, O.; Kampert, E.; Wolff-Fabris, F.; Michor, H.; Scheidt, E.-W.

The pseudo-ternary solid solution CeNi9Ge4-xSix (0 ≤ x ≤ 4) has been investigated by means of x-ray diffraction, magnetic susceptibility, specific heat, electrical resistivity, thermopower and inelastic neutron scattering studies. The isoelectronic substitution of germanium by silicon atoms causes a dramatic change of the relative strength of competing Kondo, RKKY an crystal field (CF) energy scales. The strongest effect is the continuous elevation of the Kondo temperature TK from approximately 3.5 K for CeNi9Ge4 to about 70 K for CeNi9Si4. This increase of the Kondo temperature is attended by a change of the CF level scheme of the Ce ions. The interplay of the different energy scales results in an incipient reduction of the ground state degeneracy from an effectively fourfold degenerate non-magnetic Kondo ground state with unusual non-Fermi-liquid features of CeNi9Ge4 to a lower one, followed by an increase towards a sixfold, fully degenerate ground state multiplet in CeNi9Si4 (TK ~ ΔCF).

Permalink: https://www.hzdr.de/publications/Publ-17841
Publ.-Id: 17841


Advanced biotechnology for extraction and recovery of metals

Raff, J.; Lehmann, F.; Moll, H.; Kutschke, S.; Pollmann, K.

In an era of dwindling resources and rising prices new procedures for the exploitation, beneficiation and recycling of especially industrial relevant metals are in demand. Such elements are essential for modern high tech industry and development of future techno¬logies. Interestingly, nature itself offers promising approaches in these fields. Some organisms are thusly able to mobilize metals not only from ores but also from electrical and electronical equipment waste by bioleaching [Bosecker K. 1997, Brantley et al. 2001, Brandl H. et al. 2001]. Bioleaching is already used for the large scale production of copper especially in ores with low metal content. Furthermore, other species or biomolecules are able to selectively bind and accumulate metals [Pollmann et al. 2006], allowing the con-struction of metal selective filter materials. In addition, some organisms trigger the formation of minerals or are able to form different kinds of biominerals by themselves, representing also a way to separate metals [Wang X. and W.E.G. Müller 2009]. In combination with established physical and chemical processes, such biotechnological approaches have a high potential to improved metal beneficiation and recycling.
Within the biotechnology group at the Helmholtz Institute Freiberg for Resource Technology such new procedures for extracting, treating and recycling metals such as copper or rare earths using microbes are under development. Whereas the bioleaching related research is just at the beginning and the investigation of biomineralization pro¬cesses for metal separation is planned for the future, the group has long-term experience in the investigation of the interaction of metals with biomass and especially in the selective metal binding by proteins and other bioligands. Within radioecological research, bacterial isolates were investigated that possess so called surface-layer (S-layer) proteins, forming a closed protein lattice on many bacteria and archaea protecting the cells from being affected by environ¬mental influences. In case of such bacteria living in highly heavy metals contaminated environments, their S-layers have high metal binding capacity and high stability. Furthermore, they possess different metal binding sites. There are many less specific binding sites, binding large amounts of precious metals such as Pt, Pd and Au as well as radioactive metals such as U. Metals such as Fe, Co, Ni, Cu and Zn are not bound or only in small quantities. In addition, there are several highly specific binding sites, binding Ca, Cm and Eu. First results indicates, that the binding affinity of these metals differs significantly. As the metal binding additionally depends on the pH and differs from metal to metal, S-layer proteins possess a high application potential for the specific separation of industry relevant metals.

Keywords: Biotechnology; biosorption; bioleaching; metals

Related publications

  • Lecture (Conference)
    GeoHannover 2012, 01.-03.10.2012, Hannover, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17840
Publ.-Id: 17840


QCM-D a versatile tool for biosorption processes

Suhr, M.; Drechsel, N.; Günther, T.; Matys, S.; Raff, J.; Pollmann, K.

Bacterial isolates from the uranium mining waste pile Haberland (Johanngeorgenstadt, Saxony) possess high affinities to heavy metals e.g. uranium. This binding effect is caused by the components of the bacterial cell wall, mainly affected by surface layer proteins.
Aim of this work is to investigate metal interaction processes like biosorption with Gram-positive bacteria and their main cell wall components.
In addition to the standard analytical methods, the quartz crystal microbalance with dissipation monitoring is used to track and control the biological layer formation and metal deposition. This method allows the real time detection of sorption processes on a molecular level and gives further information to viscoelastic properties. Subsequent atomic force microscopy (AFM) studies enable the imaging of bio nanostructures and reveal complex information of structural properties.
Some selected results of these experiments will be shown on this poster.

Keywords: QCM-D; bacteria; Biosorption; metals; S-layer; lipids; interaction; AFM

  • Poster
    7th Annual Ph.D. seminar, 08.-10.10.2012, Schöneck, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17839
Publ.-Id: 17839


Do microorganisms influence the transport of radionuclides in Uranium-contaminated underground mines?

Zirnstein, I.; Arnold, T.; Röske, I.

Microorganisms are ubiquitous, also in extreme environments e.g. in environments with high salinity, in very hot and acid waters or underneath thick slides of ice. In the former uranium mine Königstein exist also an extreme environment, due to the very low pH (2.7), the high concentrations of heavy metals and uranium. Nevertheless microorganisms in form of biofilms exist in a depth of 250 meters in this mine. Since 2010 the underground mine was flooded and is no longer accessible for sampling. For investigations in mine biofilms the microorganisms in the mine water have to be cultivated above ground in flow cells or in a biofilm reactor. The microorganisms in the mine water should grow on special biofilm carriers in the reactor. Our studies may contribute to new remediation measures for heavy metal contaminated mine waters.

  • Lecture (Conference)
    7th PhD Seminar, 08.-10.10.2012, Schöneck, Germany

Permalink: https://www.hzdr.de/publications/Publ-17838
Publ.-Id: 17838


Biofilms in a Uranium contaminated acid mine drainage environment

Zirnstein, I.; Arnold, T.; Krawczyk-Bärsch, E.; Wobus, A.; Röske, I.

The Königstein mine is currently in the process of remediation and represents an underground acid mine drainage (AMD) environment. Due to technical leaching with sulphuric acid, the mine water is characterized by low pH, high concentrations of toxic heavy metals and uranium (up to 3×10-4 M). Biofilms in the Königstein mine grew underground in the mine galleries in a depth of 250 m (50 above sea level) either as stalactite-like slime communities (snottites) or as acid streamers in the drainage channels. Previously conducted studies on the bacterial diversity in both biofilm communities showed that beta-proteobacterium affiliated with Ferrovum myxofaciens, also designated “Ferribacter polymyxa” were identified as dominating bacterial species. The eukaryotic diversity of the Königstein biofilms was analysed by molecular methods, i.e. 18S rDNA PCR, cloning and sequencing and by microscopic investigations. It was found that the eukaryotic biofilm communities of the Königstein environment showed a limited number of different heterotrophic species and consist of a variety of lineages belonging to nine major taxa: Ciliates, Flagellates, Amoebae, Heterolobosea, Fungi, Apicomplexa, Stramenopiles, Rotifers and Arthropoda and in addition a large number of uncultured eukaryotes, denoted as acidophilic eukaryotic cluster (AEC).
Since 2010 the underground mine was flooded and is no longer accessible for sampling. For investigations in mine biofilms the microorganisms in the mine water have to be cultivated above ground in flow cells or in a biofilm reactor. The microorganisms in the mine water should grow on special biofilm carriers in the reactor. Our studies may contribute to new remediation measures for heavy metal contaminated mine waters.

  • Poster
    1st Transnational Workshop "GETGEOWEB": Genomics and Transcriptomics in Geobiotechnolgy and White Biotechnology, 29.-30.10.2012, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-17837
Publ.-Id: 17837


Optical Excitation of Josephson Plasma Solitons in a Cuprate Superconductor

Dienst, A.; Casandruc, E.; Zhang, L.; Eckstein, M.; Fausti, D.; Hoffmann, M.; Khanna, V.; Dean, N.; Gensch, M.; Winnerl, S.; Seidel, W.; Pyon, S.; Takayama, T.; Takagi, H.; Cavalleri, A.

Josephson Plasma Waves are linear electromagnetic modes that propagate along the planes of cuprate superconductors, sustained by oscillatory tunnelling supercurrents. These waves exhibit a plasmonic resonance in the GHz , to THz frequency range, depending on the interlayer coupling strength. For strong electromagnetic fields, the supercurrents approach their critical value and the electrodynamics become highly nonlinear , . Josephson Plasma Solitons (JPS) are breather excitations , that emerge in this regime, bound vortex/antivortex pairs that self-localize , , and propagate without dispersion. We experimentally excite such solitons using intense narrowband radiation from an infrared Free Electron Laser, tuned to the 2-THz Josephson Plasma Resonance of La1.84Sr0.16CuO4. The JPS is revealed by the appearance of long-lived transparency window in the spectral region immediately below the plasma resonance, which is opaque to small-amplitude waves. This reshaping of the optical properties originates from Fano-type coupling between probe waves and the JPS. Optical control of solitonic excitations in superconductors opens up possibilities in THz opto-plasmonics or in the manipulation of high-Tc superconductivity.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-17836
Publ.-Id: 17836


Das Metallbindungsverhalten von Membranen Gram-positiver Bakterien

Drechsel, N.

Für das Verständnis von Mobilität und Stabilität von Metallen, wie z. B. Schwermetallen, in der Umwelt, stellt die Untersuchung der Metallsorption einen wichtigen Faktor dar. Für die weiterführende Erforschung von Wechselwirkungsprozessen der Mikroorganis-men und deren Metallbindungseigenschaften ist es notwendig, die Sorption verschie-dener Metalle durch Mikroorganismen und zellulären Bestandteilen zu untersuchen.
In der vorliegenden Bachelorarbeit werden die Wechselwirkungen von umweltrele-vanten Metallen mit biologischen Komponenten untersucht. Dazu dienen die bak-teriellen Haldenisolate Lysinibacillus sphaericus JG-A12 und Lysinibacillus sp. JG-B53. Diese zeigten bereits in vorangegangenen Untersuchungen sehr hohe Metallbindungs-kapazitäten. Für die Sorptionsversuche werden die Schwer- und Edelmetalle Platin, Palladium, Blei, Cadmium, Europium und Gold und das Halbmetall Arsen verwendet. Durch die Einbeziehung von isolierten Zellwandbestandteilen der Gram-positiven Mikroorganismen, wie z. B. S-Layer-Proteine und Membranlipide sollen genauere Kenntnisse der Sorptionseigenschaften der biologischen Komponenten erlangt werden. Als analytische Verfahren werden die ICP-MS und die QCM-D eingesetzt. Durch einen Vergleich der zwei Bakterien werden unterschiedliche Metallselektivitäten aufgedeckt, die in weiteren Forschungsvorhaben und Anwendungsgebieten Einsatz finden können.

Keywords: Biosorption; QCM-D; Bakterien; S-Layer; Lipide; Metalle; Metallinteraktionen

  • Bachelor thesis
    HZDR und Hochschule Mittweida, 2012
    98 Seiten

Permalink: https://www.hzdr.de/publications/Publ-17835
Publ.-Id: 17835


Electromagnetic dipole strength up to the neutron separation energy from 196Pt(γ,γ′) and 195Pt(n,γ) reactions

Massarczyk, R.; Schramm, G.; Junghans, A. R.; Schwengner, R.; Anders, M.; Belgya, T.; Beyer, R.; Birgersson, E.; Ferrari, A.; Grosse, E.; Hannaske, R.; Kis, Z.; Kögler, T.; Kosev, K.; Marta, M.; Szentmiklosi, L.; Wagner, A.; Weil, J. L.

The dipole strength in the nucleus 196-Pt was investigated using two different experimental methods. The photon spectrum from the deexcitation of a state after cold neutron capture in 195-Pt is influenced by the dipole strength and nuclear level density in 196-Pt as is also the gamma-ray spectrum from photon scattering on 196-Pt. In a combined analysis of data from the research reactor in Budapest and the bremsstrahlung facility at the ELBE accelerator in Dresden, the GEANT4 code was used to calculate detector response and efficiency. Also the influence of non-nuclear scattered photons was determined and allows us to take into account the continuum of unresolved states. The statistical code gammaDEX was used to estimate branching ratios and compare simulated and experimental spectra. Using information from both experiments it was possible to obtain a temperature parameter of 600\,keV for the constant temperature level density model. For the dipole strength a small extra strength over tail of the Giant Dipole Resonance in the region below the neutron energy separation was found.

Keywords: neutron capture; strength functions; nuclear structure; statistical calculations

Related publications

Permalink: https://www.hzdr.de/publications/Publ-17833
Publ.-Id: 17833


From terahertz science and technology to semiconductor quantum structures and back

Helm, M.

I will give an overview about modern terahertz science and technology and discuss some applications of THz radiation. Then I will present the physics of semiconductor quantum wells and show how such structures can be developed into a so-called quantum cascade laser working in the THz range

Keywords: terahertz; laser; semiconductor

  • Invited lecture (Conferences)
    Lecture at Southeastern University, 18.09.2012, Nanjing, China

Permalink: https://www.hzdr.de/publications/Publ-17832
Publ.-Id: 17832


Process Monitoring of tracer transport through artificial soil with GeoPET

Kulenkampff, J.; Gründig, M.; Lippmann-Pipke, J.; Enzmann, F.; Khan, F.; Kersten, M.; Stoll, M.; Ritschel, T.; Totsche, K. U.

Positron-Emission-Tomography (PET) enables direct and quantitative monitoring of the spatiotemporal distributions of dissolved inert and/or reactive PET-nuclides and PET-nuclide-labelled compounds during their passage through decimeter-scaled material samples. We apply our biomedical PET-scanner (ClearPET, Raytest) exclusively to geomaterial samples and reach the physical limit of spatial resolution of nearly 1 mm with pico-molar sensitivity.
Artificial soil columns (68.5% fine-medium sand, 25.5% coarse silt, 5% Illit, 1% Goethit) have been prepared in Jena. µCT-images have been produced at the Bundesanstalt für Materialforschung und –prüfung (BAM) and analysed in Mainz. They show layering and inhomogeneous water saturation, yet a roughly homogeneous grain distribution. PET-imaging was conducted during flow-through experiments into the upright column, which is perpendicular to the scanner axis.
First flow experiments have been conducted with – presumably – conservative tracers ([18F]KF (decay time 109.77 min) and Eosin). Conventional break-through curves (BTCs) have been recorded both by fluorescence detection of Eosin and with a Gamma Radioactivity Flow-Through Monitor (Gabi Star, Raytest). From the transport process observation by sequential PET-imaging we could derive longitudinal BTCs during the tracer propagation through the column. Further, it could be shown that 18F- was slightly retarded and - more significantly - the effective pore volume was inhomogeneous (preferential transport through the sample).
These experiments will be repeated on newly constructed columns with plastic endplates (instead of the original stainless steel ones) and an optimized dead volume.
To preliminarily conclude, we demonstrated that the combined tomographic information on pore structure and spatio-temporal transport process observation in a soil model column yields an essential gain in information for describing and parameterizing transport processes, compared to input-output experiments. Such measurements represent the experimental control of ab-initio model simulations of conservative and reactive transport, e.g. [64Cu]MCPA), and of the interpretation of conventional input-output transport experiments, conducted by the partners.

Keywords: Reactive Transport; PET; Process Observation

  • Poster
    Annual Meeting DFG Priority Programme SPP1315 "Biogeochemical Interfaces in Soil", 10.-12.10.2012, Dornburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17830
Publ.-Id: 17830


Verification of the trigonal-geometry diffusion and SP3 models of the code DYN3D

Duerigen, S.; Nikitin, E.; Mittag, S.

DYN3D is a three-dimensional nodal diffusion code for steady-state and transient analyses of Light-Water Reactors with square and hexagonal fuel assembly geometries, applicable also to innovative reactor concepts. Currently, several versions of the DYN3D code are available including a multi-group diffusion and simplified P3 (SP3) neutron transport option.
In this work, both the diffusion and SP3 method in trigonal geometry are verified by means of fine-mesh homogenized reference solutions. Good agreement is observed for eigenvalues, neutron flux and power distributions. Mesh refinement studies show that the trigonal nodal DYN3D methods converge well to the fine-mesh references. Furthermore, an anisotropic-scattering benchmark problem was chosen to show the advantage of the SP3 method over the diffusion approach.

Keywords: simplified P3; SP3; nodal method; trigonal; triangular; hexagonal; DYN3D; mesh refinement

  • Open Access Logo Contribution to proceedings
    22nd SYMPOSIUM of ATOMIC ENERGY RESEARCH (AER) on VVER Reactor Physics and Reactor Safety, 01.-05.10.2012, Pruhonice, Czech Republic
  • Lecture (Conference)
    22nd SYMPOSIUM of ATOMIC ENERGY RESEARCH (AER) on VVER Reactor Physics and Reactor Safety, 01.-05.10.2012, Pruhonice, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-17829
Publ.-Id: 17829


Femtosecond Level Synchronization of a Linac Based super-radiant THz Facility

Kuntzsch, M.; Röser, F.; Lehnert, U.; Gensch, M.; Bousonville, M.; Schlarb, H.; Stojanovic, N.; Vilcins-Czvitkovits, S.

The superconducting radiofrequency (SRF) electron accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is currently upgraded with an SRF Gun and a femtosecond (fs) electron beamline to enable continuous wave operation with bunch charges of up to 1 nC and bunch durations down to 100 fs (RMS). The new femtosecond electron beamline will be used to drive two coherent THz sources and one X-ray source based on Thomson scattering. The two different THz sources, one narrow bandwidth undulator source and one broad bandwidth coherent transition/diffraction source, are guided into a dedicated THz Laboratory where they can be combined with various fs-laser systems. For the planned THz pump laser probe experiments, synchronization of the external pump-probe lasers on the fs- level is essential. Our approach is based on an optical synchronization system, adapted from a similar system installed at FLASH [*]. That system will be installed in collaboration between DESY and HZDR. In this contribution we will discuss the layout of the synchronization scheme and first ideas for measurements of the arrival time jitter of the THz pulses to evaluate the achieved degree of timing stability.

Keywords: ELBE Synchronization THz

Related publications

  • Poster
    Free-Electron Laser Conference, 26.-31.08.2012, Nara, Japan

Permalink: https://www.hzdr.de/publications/Publ-17828
Publ.-Id: 17828


Optical Synchronization at HZDR

Kuntzsch, M.

The superconducting electron accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf is currently upgraded to enable continuous wave operation with bunch charges of up to 1 nC and durations down to 200 fs (RMS). The new beamline will drive a THz source and an X-ray source based on Thomson scattering. In collaboration with DESY, Hamburg, an optical synchronization system based on a mode locked master laser is currently being set up to ensure timing stability on the few 10 fs level. This talk is giving an overview on different synchronization concepts, the implementation at ELBE and the first comissioning results.

Keywords: ELBE Synchronization

Related publications

  • Invited lecture (Conferences)
    1st ARD Workshop ST3 “ps-fs Electron and Photon Beams”, 21.-23.08.2012, Hamburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-17827
Publ.-Id: 17827


Temperature grid sensor for the measurement of spatial temperature distributions

Schäfer, T.; Schubert, M.; Hampel, U.

This paper presents results of the development and application of a new temperature grid sensor based on the wire-mesh sensor principle. The grid sensor consists of a matrix of 256 Pt1000 platinum chip resistors and an associated electronics that measures the grid resistances with a multiplexing scheme at high speed. The individual sensor elements can be spatially distributed on an object surface and measure transient temperature distributions in real time. The advantage, compared to other temperature field measurement approaches, such as infrared cameras, is that the object under investigation can be thermally insulated and radiation properties of the surface do not play a role for measurement accuracy. The sensor principle is therefore suited for various industrial monitoring applications. Its applicability for surface temperature monitoring has been demonstrated by conduction and analysis of heating and mixing experiments in a vessel.

Keywords: temperature grid sensor; temperature measurement; wire-mesh sensor; thermal surface monitoring

Permalink: https://www.hzdr.de/publications/Publ-17826
Publ.-Id: 17826


REECOB: 20 Years of Rare Earth Element Calcium Oxoborates Crystal Growth Research

Möckel, R.; Reuther, C.; Götze, J.

Rare earth element calcium oxoborates (REECOB, REECa4O[BO3]3) represent a group of materials for non-linear optics and with useful piezoelectric properties under high-pressure and high-temperature conditions making it applicable as sensor materials in extreme environments. High-quality crystals with appropriate size are generally grown from a melt by the Czochralski method. This article presents a compilation and comparison of crystal growth parameters and properties of members of the REECOB group from the literature with those of own growth experiments. Recent studies provided new data concerning the melting temperature of REECOB members, such as ca. 1475°C for SmCa4O(BO3)3 (SmCOB). In addition, first data on the change of thermal expansion coefficients of SmCOB are presented and discussed.

Keywords: REECOB; oxoborate; Czochralski

Permalink: https://www.hzdr.de/publications/Publ-17825
Publ.-Id: 17825


Investigation of the Eu(III)-B(OH)3-Organic System

Schott, J.; Barkleit, A.; Acker, M.; Brendler, V.

Borates and organic matter (humic and fulvic acids, small organic molecules) are ubiquitous compounds in the environment (rocks, soils, natural waters).
Concerning the safety and risk assessment for a nuclear waste repository the interaction between trivalent lanthanides and actinides and borates is interesting to study. Borates occur in salt deposits (possible host rock for nuclear waste repositories) and can be release due to corrosion of vitrified waste block (borosilicate glass) and storage containers.
The investigations concentrate on the reaction between Eu(III) and borates in aqueous solution.
For boric acid (B(OH)3) no and for polyborates weak complexation properties concerning Eu(III) are observed.
The complexation between Eu(III) and salicylate is influenced by boric acid due to the formation of a borate ester.
Furthermore at pH 6 the formation of a solid Eu borate species in presence of polyborates is observed. The formation of the solid Eu borate species depends on the polyborate concentration and ionic strength.

Keywords: lanthanides; actinides; europium; boric acid; borates; polyborates

  • Poster
    Annual Ph.D. seminar, 08.-10.10.2012, Schöneck, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17824
Publ.-Id: 17824


Broadband, diode pumped Yb:SiO2 multicomponent glass laser

Loeser, M.; Röser, F.; Reichelt, A.; Siebold, M.; Grimm, S.; Litzkendorf, D.; Schwuchow, A.; Kirchhof, J.; Schramm, U.

Fabrication, spectroscopic properties, and laser performance of a Yb:SiO2 multicomponent glass have been investigated in this paper. The glass system composed of SiO2, Al2O3, and La2O3 excels in terms of a high thermal stress resistance compared to other laser glasses. The laser experiments were conducted with a 3.4 mm thick and 0.9 mol. % Y2O3 doped sample. A maximum slope efficiency of 51%, a maximum optical to optical efficiency of 42%, and a tuning range from 1010–1090 nm was realized. Due to the promising laser properties and a straightforward fabrication technique it may well qualify as an alternative gain medium in high-energy, ultrashort pulse laser systems.

Keywords: Lasers, diode-pumped; Lasers, solid-state; Lasers, tunable; Rare earth and transition metal solid-state lasers; Laser materials; Lasers, ytterbium

  • Optics Letters 37(2012)19, 4029-4031

Permalink: https://www.hzdr.de/publications/Publ-17823
Publ.-Id: 17823


Hades experiments: investigation of hadron in-medium properties

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

Hadron modications in nuclear matter are discussed in connection to chiral symmetry restoration and/or hadronic many body eects. Experiments with photon, proton and heavy ion beams are used to probe properties of hadrons embedded in nuclear matter at different temperatures and densities. Most of the information has been gathered for the light vector mesons ρ, ω and φ. HADES is a second generation experiment operating at GSI with the main aim to study in-medium mass modication by means of dielectron production at SIS18/Bevelac energy range. Large acceptance and excellent particle identication capabilities allows also for measurement of strangeness production. These abilities combined with the variety of beams provided by the SIS18 allows for characterization of properties of the dense baryonic matter properties created in heavy ion collisions at these energies. A review of recent experimental results obtained by HADES is presented, with main emphasis on hadron properties in nuclear matter.

Permalink: https://www.hzdr.de/publications/Publ-17822
Publ.-Id: 17822


High rate deposition of amorphous hydrogenated carbon films by hollow cathode arc PECVD

Zimmermann, B.; Fietzke, F.; Klostermann, H.; Lehmann, J.; Munnik, F.; Möller, W.

Amorphous hydrogenated carbon films (a-C:H) are of increasing importance in science and applications. However, most deposition techniques applied suffer from a low deposition rate. In this paper, a high rate process based on hollow cathode arc PECVD is presented. A magnetically enhanced hollow cathode arc plasma has been used to activate the precursor acetylene. The argon-acetylene plasma has been characterized by energy-resolved mass spectrometry revealing a large variety of dissociation and polymerization products as well as their kinetic energy distributions, which are related to the spatial distribution of ion generation. A-C:H layers have been deposited on flat substrates with rates of up to 1 µm/min. Depending on the deposition conditions, polymeric, graphitic, and diamond-like carbon films with a nanoindentation hardness of 18.2 GPa have been produced and analyzed by Raman spectroscopy and scanning electron microscopy. In order to obtain the film composition, elastic recoil detection analysis and Rutherford backscattering spectrometry have been applied.

Keywords: hollow cathode arc; plasma diagnostics; amorphous hydrogenated carbon; diamond-like carbon; plasma-enhanced chemical vapor deposition; elastic recoil detection analysis

Related publications

Permalink: https://www.hzdr.de/publications/Publ-17821
Publ.-Id: 17821


Investigation of upward cocurrent gas-liquid pipe flow using ultrafast X-ray tomography and wire-mesh sensor

Zhang, Z.; Bieberle, M.; Barthel, F.; Szalinski, L.; Hampel, U.

Ultrafast X-ray tomography and wire-mesh sensor as two high-speed imaging modalities were applied to study upward gas-liquid flow in a vertical pipe of 50 mm inner diameter. High speed scanning of the flow cross-section was performed with 2500 frames per second with both modalities. Sequences of two-dimensional distributions of local gas fraction were acquired and further analyzed. Radial profiles of time averaged gas fraction distributions show a good agreement for both imaging techniques. Furthermore radial gas velocity profiles were obtained from a temporal cross-correlation of the image data of both measurement techniques and also bubble size distributions from binarized image data were compared.

Keywords: gas-liquid flow; ultrafast X-ray tomography; wire-mesh sensor

Permalink: https://www.hzdr.de/publications/Publ-17820
Publ.-Id: 17820


Insider 6 / 2012

Weigl, A.

Mitarbeiterzeitung des HZDR

Keywords: HZDR in-house paper

  • Communication & Media Relations
    Mitarbeiterzeitung 31.07.2012
    8 Seiten

Permalink: https://www.hzdr.de/publications/Publ-17819
Publ.-Id: 17819


Kelvin probe force microscopy for characterizing functionalized semiconductor surfaces for nano and biotechnologies

Baumgart, C.; Habicht, S.; Feste, S.; Helm, M.; Müller, A.-D.; Schmidt, H.

Kelvin probe force microscopy (KPFM) is one of the most promising non-contact electrical nanometrology technique to characterize functionalized semiconductor. We present its applicability to determine surface-near electrostatic forces in locally doped silicon structures. Those electrostatic forces may be used to position and control nano and biomaterials on doped semiconductor carriers. Furthermore, quantitative dopant profiling by means of KPFM measurements [1] is successfully demonstrated on a conventional static random access memory (SRAM) cell, on cross-sectionally prepared Si epilayers, and on arrays of horizontal Si nanowires [2] by applying a recently introduced new explanation of the measured KPFM signal. Additionally, the influence of local, carrier-depleted space charge regions and of the electric fields across them is discussed. It is explained how drift and diffusion of injected charge carriers in intrinsic electric fields influence the surface-near electrostatic forces [3]. Surface-near electrostatic forces may be enhanced above pn junctions and KPFM is successfully employed to locate pn junctions in doped silicon structures, e.g. along the B-doped and As-doped Si nanowires. [1] C. Baumgart, M. Helm, H. Schmidt, Phys. Rev. B, 80, 085305 (2009). [2] S. F. Feste, J. Knoch, S. Habicht, D. Buca, Q.-T. Zhao, S. Mantl, Solid-State Electronics, 53, 1257 (2009). [3] C. Baumgart, A.-D. Müller, F. Müller, and H. Schmidt, Phys. Stat. Sol. A, 208, 777 (2011) (editor’s choice).

Related publications

  • Lecture (Conference)
    E-MRS Fall Meeting 2012, 17.-21.09.2012, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-17818
Publ.-Id: 17818


Optical probing of TNSA acceleration conditions

Metzkes, J.; Zeil, K.; Kluge, T.; Kraft, S. D.; Bussmann, M.; Cowan, T. E.; Schramm, U.

Laser-plasma based accelerators, where a high intensity laser interacts with a solid target, represent a promising concept for compact and cost-efficient ion sources.
As the acceleration takes place on ultra-fast timescales and very small spatial scales of only a few µm, information about the acceleration processes in the plasma are generally derived indirectly, e.g. through particle or radiation diagnostics. Optical probing techniques however can give direct access to the plasma dynamics on the fs to ps timescale.
In this poster we will present pump-probe experiments performed at the high-intensity laser DRACO at the HZDR, Germany. Seeking information about the conditions of the critical density surface in the plasma, we simply image the probe reflected from the target surface without doing tomography. The curvature of the reflecting critical surface translates into characteristic angular patterns in the reflected probe beam which can be traced back to the original surface shape using a ray-tracing model of the experiment.
In our experiments, the pump beam was the 150 TW DRACO beam with a pulse length of 30 fs and a central wavelength of 800 nm. The probe beam was derived from the mean beam, frequency doubled, and had a pulse duration of ~100fs. Both beams were synchronized and the probe could be delayed with respect to the main beam with a resolution of ~200 fs. The imaging of the probe was performed with a large-aperture objective yielding a high spatial resolution of ~2µm.
As a result, we compared the critical surface deformation and dynamics for different target materials (metal and silicon) and target shapes, observing a strong influence of the lateral target size.

  • Poster
    32nd European Conference on Laser Interaction with Matter (ECLIM 2012), 10.-14.09.2012, Warschau, Polen

Permalink: https://www.hzdr.de/publications/Publ-17817
Publ.-Id: 17817


Time resolved FT-IR difference spectroscopy of vibrational control experiments on bacteriorhodopsin

Bauer, C.; Gensch, M.; Heberle, J.

Our goal is to investigate how photoreactions of proteins can be controlled by intense THz radiation tuned in resonance to specific vibrational modes, in analogy to coherent control experiments conducted by femtosecond (fs) NIR laser pulses [1]. For this we combine a time-resolved IR difference spectroscopic setup with uniquely intense, tunable narrow bandwidth THz radiation at the picosecond (ps) beamline of the THz free electron laser FELBE [2].

Related publications

  • Poster
    Jahrestagung der Deutschen Gesellschaft für Biophysik (DGfB), 24.-29.09.2012, Göttingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17816
Publ.-Id: 17816


Direct observation of prompt pre-thermal laser ion sheath acceleration

Metzkes, J.; Zeil, K.; Kluge, T.; Bussmann, M.; Cowan, T.; Kraft, S.; Sauerbrey, R.; Schramm, U.

High-intensity laser-plasma ion generation is promising as a compact, low-cost proton source for applications like ion beam therapy. Using a femtosecond table-top laser system, we study the intra-pulse phase of the laser driven proton acceleration and show that protons efficiently gain energy in these early times [1].

In recent laser-ion acceleration experiments performed at the 150 TW Draco laser in Dresden, Germany, we have demonstrated the importance of a precise understanding of the electron dynamics in solids on an ultra-short time scale. For example, with ultra-short laser pulses a description based purely on the evolution of a thermal electron ensemble, as in standard TNSA models, is not sufficient anymore. Rather, non-thermal effects during the ultra-short intra-pulse phase of laser-electron interaction in solids become important for the acceleration of ions when the laser pulse duration is in the order of only a few 10s of femtoseconds. While the established maximum ion energy scaling in the TNSA regime goes with the square root of the laser intensity, for such ultra short pulse durations the maximum ion energy is found to scale linear with laser intensity [2], motivating the interest in such laser systems.
Investigating the influence of laser pulse contrast, laser polarization and laser incidence angle on the proton maximum energy and angular distribution, we present recent advances in the description of the laser interaction with solids, focusing on the implications of intra-pulse non-thermal phenomena on the ion acceleration.

References

1. K. Zeil, J. Metzkes, T. Kluge, M. Bussmann, T.E. Cowan, S. D. Kraft, R. Sauerbrey and U. Schramm, Direct observation of prompt pre-thermal laser ion sheath acceleration, Nature Communications 3 (874), 2012

2. K. Zeil, S. D. Kraft, S. Bock, M. Bussmann, T.E. Cowan, T. Kluge, J. Metzkes, T. Richter, R. Sauerbrey and U. Schramm, Scaling of proton energies in ultrashort pulse laser plasma acceleration, New Journal of Physics 12 (045015), 2010

  • Lecture (Conference)
    32nd European Conference on Laser Interaction with Matter (ECLIM 2012), 10.-14.09.2012, Warschau, Polen
  • Lecture (Conference)
    SPIE Optics + Optoelectronics 2013, 15.-18.04.2013, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-17815
Publ.-Id: 17815


Segmentierung von Gasblasen aus Röntgentomographiedaten von zweiphasigen Rohrströmungen

Banowski, M.; Bieberle, M.; Wagner, M.; Lucas, D.; Hoppe, D.; Harnisch, J.; Hampel, U.

In der Präsentation wird das bildgebende Messverfahren „ultraschnelle Röntgentomographie“ vorgestellt sowie die Versuchsanlage TOPFLOW kurz erläutert. Die verschiedenen, zur Segmentierung von Gasblasen entwickelten und getesteten Algorithmen werden ebenfalls vorgestellt und deren Ergebnisse anhand von Phantommessungen qualitativ und quantitativ verglichen. Die jeweiligen Vor- und Nachteile der Algorithmen werden beispielhaft gezeigt und mögliche weitere Lösungsansätze diskutiert.

Keywords: two-phase; measuring technique; X-ray; tomography; pipe flow; bubble detection

  • Lecture (Conference)
    DBV-Workshop - Workshop für Digitale Bildverarbeitung, 04.09.2012, Zittau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17814
Publ.-Id: 17814


Ion mass and energy distributions in the DC magnetron sputtering of AZO from metallic and ceramic targets

Wilde, C.; Cornelius, S.; Vinnichenko, M.

technique to fabricate transparent conductive oxides. Especially in large-scale solar cell production a combination of good electrical and optical properties along with low production costs is of crucial importance. AZO can be sputter-deposited reactively (i.e. with addition of O2) using a metallic target or non-reactively using a ceramic target. On the one hand, non reactive processes are easy to control and they provide high-quality films with high reproducibility, but on the other hand, ceramic Al-doped ZnO targets are much more expensive compared to the metallic ones. Therefore, the understanding of differences between these two techniques is of vital importance for the improvement of process control, stability and, finally, properties of reactively sputtered AZO, especially in large-scale fabrication. In this contribution we report results of systematic comparison of ion mass and energy distributions in magnetron plasma using reactive and non reactive DC process of AZO film growth. The measurements were performed with the orifice of mass-spectrometer facing the magnetron target race track. We present the results of comparison in a broad range of particles’ energy for different deposition conditions with a main focus on high energetic ions and fragments. It is shown that in case of sputtering of ceramic target the ratio of high to low energetic ions is substantially higher than that of metallic target. The contribution from high energetic particle fragments is also more pronounced in that case. Therefore, from point of ion energy distributions, a well established reactive process has a potential to provide better properties for AZO layer.

Keywords: AZO; TCO; mass spectrometry; ion energy distribution; DC magnetron sputtering

  • Poster
    13th International Conference on Plasma Surface Engineering (PSE 2012), 09.-14.09.2012, Garmisch-Partenkirchen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17813
Publ.-Id: 17813


Resonance production in p+p, p+A and A+A collisions measured with HADES

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

The knowledge of baryonic resonance properties and production cross sections plays an important role for the extraction and understanding of medium modications of mesons in hot and/or dense nuclear matter. We present and discuss systematics on dielectron and strangeness production obtained with HADES on p+p, p+A and A+A collisions in the few GeV energy regime with respect to these resonances.

Permalink: https://www.hzdr.de/publications/Publ-17812
Publ.-Id: 17812


Dipole strength on the tail of the giant dipole resonance

Schwengner, R.

http://www.hzdr.de/FWK/MITARB/rs/Tours2012-Schwengner.pdf

Keywords: Photon scattering; bremsstrahlung; monoenergetic polarized gamma rays; photoabsorption; dipole strength; reaction rates; statistical models; RPA; QPM

Related publications

  • Invited lecture (Conferences)
    VIII. Tours Symposium on Nuclear Physics and Astrophysics, 02.-07.09.2012, Black Forest, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17811
Publ.-Id: 17811


Morphology induced two-magnon scattering in thin NiFe films

Körner, M.; Lenz, K.; Fritzsche, M.; Facsko, S.; Fassbender, J.

When studying magnetization dynamics of thin magnetic films, intrinsic as well as extrinsic spin relaxation processes have to be taken into account. While intrinsic processes, summarized as Gilbert damping, are well known and studied for the last decades, the focus now has shifted to extrinsic contributions. In this context the two-magnon scattering (TMS) is of particular interest. This type of scattering is induced within thin magnetic films by defects and inhomogeneities. It was shown that periodic magnetic patterns can serve as defect structure, e.g. by periodically varying the magnetization saturation using ion beam irradiation combined with periodic sample patterning by electron beam lithography. Due to irradiation of the material a local variation of the magnetic properties can be achieved [1], where the TMS strength is set by the periodicity of the modification. However, directly patterning the material is time consuming and not suitable for large scale manufacturing. Hence a self-organized nanoscale patterning is more favorable. Broad ion beam erosion is a well-established technique for structuring large surface areas. By varying the irradiation parameters, e.g. ion energy, fluence, and incident angle sinusoidally modulated surfaces (ripples) can be created with a periodicity tuneable over a wide range [2]. Growing magnetic materials on these ripples imprints the corrugation to the material and induces by dipolar effects a wavelength dependent uniaxial magnetic anisotropy (UMA). Furthermore the imprinted corrugation can serve as a spin wave scattering center, modifying the two-magnon damping contribution. Here we present the influence of the substrate surface corrugation on the magnetic damping properties of 30 nm thin Ni80Fe20 (Py) films grown by molecular beam epitaxy at room temperature on rippled Si substrates. Due to ion beam erosion of flat Si as well as natural oxidation of the substrate prior to film deposition, Py films grown on top exhibit a polycrystalline structure that suppresses the intrinsic magneto-crystalline anisotropy almost completely. The in-plane magnetostatic and dynamic properties of these samples were investigated by means of angular and frequency dependent vector network analyzer ferromagnetic resonance (VNA-FMR).
Starting with a planar reference sample the angular together with the frequency dependent linewidth measurements reveal a Gilbert dominated relaxation process, whereby no TMS can be observed. Due to the polycrystalline film structure, only a very weak magnetic anisotropy is observed. This uniaxial magnetic anisotropy (UMA) has a two-fold symmetry and is randomly aligned with respect to the sample edges. Changing to rippled substrates the grown Py film maintains its polycrystalline structure. Depending on the ripple wavelength λ, ranging from 25 nm to 230 nm, an UMA is induced with its easy axis always aligned parallel to the ripple ridges. The strength of the UMA decays with increasing wavelength and is strongest for λ=25 nm. In this case no influence of the corrugation on the damping is observed. This changes drastically for samples with a higher wavelength of λ=230 nm. While the UMA is reduced to the value of the planar reference sample the linewidth measurements now show clear indications for defect induced TMS. This is shown in Fig. 1a, where the peak-to-peak linewidth is plotted as a function of the in-plane magnetic field angle (open circles). Modeling the linewidth results in a Gilbert contribution that is constant for all in-plane field orientations. Additionally an angle dependent TMS contribution is found, which consists of a small four-fold and a dominating two-fold (uniaxial) part. Thereby the direction of minimal linewidth aligns parallel with the ripple ridges, which in turn defines the uniaxial symmetry of the damping. Fig. 1b depicts the frequency dependent measurements parallel (red squares) and perpendicular (green circles) to the ripple ridges. In parallel configuration the damping is purely Gilbert-like, as already observed in the reference measurement. The monotonous increase of the linewidth with applied microwave frequency is instead lost in case of the perpendicular geometry. Here, a preeminent peak is observed with its center at f=10 GHz. Following the description of Barsukov et al. [1] this excessive linewidth increase is a result of defect induced TMS, where the width and frequency position of the peak is determined by the scattering potential, created by the corrugation of the film. The origin and wavelength dependence of these morphology induced linewidth manipulation will be discussed in detail.
We thank I. Barsukov, J. Lindner, and P. Landeros for fruitful discussions. This work is supported
by DFG grant no. FA 314/6-1.
1) I. Barsukov et al., Phys. Rev. B 84, 140410(R) (2011)
2) J. Fassbender et al., New J. Phys. 11, 125002 (2009)

Related publications

  • Poster
    International Colloquium on Magnetic Films and Surfaces (ICMFS) 2012, 24.-28.09.2012, Shanghai, China

Permalink: https://www.hzdr.de/publications/Publ-17810
Publ.-Id: 17810


Frequency dependence of spin relaxation in periodic systems

Körner, M.; Barsukov, I.; Römer, F. M.; Lenz, K.; Meckenstock, R.; Hemken To Krax, S.; Banholzer, A.; Grebing, J.; Lindner, J.; Farle, M.; Fassbender, J.

In the presence of a periodic scattering potential the spin relaxation in ultrathin ferromagnets is not a monotonous function of the frequency. The spin relaxation rate is found to substantially increase at characteristic frequencies related to the periodicity of the magnon scattering potential (see Fig. 1). This is experimentally confirmed in Ni80Fe20 thin films by artificially introducing different scattering periodicities [1]. The lateral struvturing of the thin film is achieved by Cr+ ion implantation with at an energy of 5 keV and a fluence of 5 × 10E15 ions/cm2 through a 100 nm thick polymethyl methacrylate (PMMA) resist covering the whole sample area. Electron beam lithography was used to fabricate 1 mm long-stripes of width s0 and spacing s1 (i.e., with periodicity l = s0 + s1) within the PMMA resist so that the surface becomes Cr-implanted in a stripewise manner. Frequency dependent Ferromagnetic resonance spectroscopy reveals that the magnetic damping may be increased at specific frequencies by a factor of up to 100%.
This work is supported by the DFG, SFB 491, Grants No. FA 314/6-1 and No. FA 314/3-2.
[1] I. Barsukov et al., Phys. Rev. B 84, 140410(R) (2011)

Related publications

  • Poster
    International Colloquium on Magnetic Films and Surfaces (ICMFS) 2012, 24.-28.09.2012, Shanghai, China

Permalink: https://www.hzdr.de/publications/Publ-17809
Publ.-Id: 17809


Magnonic Crystals By Means Of Patterned Ion Implantation

Fassbender, J.; Körner, M.; Lenz, K.; Strache, T.; Banholzer, A.; Grebin, J.; Lindner, J.; Barsukov, I.; Römer, F.; Meckenstock, R.; Hemken To Krax, S.; Farle, M.; McCord, J.; Mönch, I.; Mattheis, R.

Ion implantation is a standard process in semiconductor tech¬nology. However, since a doping of metals typically does not have such a tremendous effect as compared to semiconductors ion implantation in metals to achieve a desired electrical, optical or magnetic property is much less explored. A combination of litho-graphy and ion implantation to achieve a lateral ion implantation pattern is a novel route to design and construct artificial materials like photonic or magnonic crystal which rely on the local band gap or spin wave dispersion engineering [1].
The contribution will provide an overview over the different physical mechanisms which allow modifying and tailoring the dynamical magnetic properties, i. e., magnetic damping even in an anisotropic fashion, aiming at the creation of new functional materials. In one example [2] it is demonstrated that the mag¬netic damping parameter in a ferromagnetic/antiferromag¬ne¬tic/ferro¬magnetic trilayer stack can be continuously and spatially varied between two extremal values (see Fig. 1). In a second example [3] the creation of a lateral magnetization pattern by ion implantation gives rise to additional and anisotropic relaxation channels. Potential areas of application are magnonic crystals and band-stop filters in the GHz range.

Acknowledgement: This work was supported by Deutsche Forschungsgemeinschaft SFB491, FA 314/3, FA314/6-1 and MC 9/7.

[1] J. Fassbender, J. McCord, J. Magn. Magn. Mater. 320, 579 (2008).
[2] J. McCord, T. Strache, I. Mönch, R. Mattheis, J. Fassbender, Phys. Rev. B 83, 224407 (2011).
[3] I. Barsukov, F. M. Römer, R. Meckenstock, K. Lenz, J. Lindner, S. Hemken to Krax, A. Banholzer, M. Körner, J. Grebing, J. Fassbender, M. Farle, Phys. Rev. B 84, 140410(R) (2011).

Keywords: ion irradiation; ion implantation; magnetic films; modification; magnonics; dynamics

Related publications

  • Lecture (Conference)
    18th International Conference on Ion Beam Modification of Materials (IBMM2012), 02.-07.09.2012, Qingdao, China

Permalink: https://www.hzdr.de/publications/Publ-17808
Publ.-Id: 17808


Tailoring perpendicular anisotropy in Co/Pd multilayers by ion irradiation

Osten, J.; Greene, P.; Ende, T.; Iwata, N.; Lenz, K.; Liu, K.; Fassbender, J.

A major obstacle towards the increase in areal magnetic recording density and the decrease in bit size is the retention of thermal stability while maintaining reasonable write fields. Materials with graded magnetic anisotropy are promising candidates to solve this problem. Here we demonstrate the approach of using post-deposition ion irradiation to tailor the perpendicular anisotropy in Co/Pd multilayer thin films. The films, with uniform as well as graded perpendicular anisotropy, were synthesized by magnetron sputtering. Based on TRIDYN simulations, different primary ion energies are chosen to achieve varying penetration depths of the ions creating a depth dependent anisotropy grading. Before and after ion irradiation, MOKE as well as magnetometry measurements were employed to detect the changes of the magnetic properties. In the irradiated layer of the film domain nucleation is promoted (Fig. 1). Upon ion irradiation, the Co/Pd films exhibit reduced coercivity and remanence with increasing energies. Higher ion energies have a more pronounced effect on reducing the perpendicular anisotropy. The archived anisotropy grading also depends on the original film stack.

Keywords: ion irradiation; magnetism; magnetic recording; thermal stability; graded media

Related publications

  • Poster
    18th International Conference on Ion Beam Modification of Materials (IBMM 2012), 02.-07.09.2012, Qingdao, China

Permalink: https://www.hzdr.de/publications/Publ-17807
Publ.-Id: 17807


Self-consistent isotopic comparative method used to determine dependence of secondary-yields on oxygen concentration in Si-O system up to 33%

Dupuy, J. C.; Prudon, G.; Dubois, C.; Kögler, R.; Akhmadaliev, S.; Perrat-Mabilon, A.

Yields of B+,O+,Si+, B-, O-, and Si- versus oxygen concentration were determined in Si under Ar+ bombardment using the isotopic comparative method (ICM). Samples containing a near-uniform low concentration of 18O and a Gaussian-like profile of 16O with high concentration were fabricated by multi-energy ion implantation. ICM allows to determine the oxygen concentration profile by secondary-ion mass spectrometry. The ion yield can be measured as a function of the oxygen concentration up to 33 at%. Whatever the charge of the secondary ions, all relative ion yields are enhanced with increasing oxygen concentration. Very strong matrix effects due to oxygen are found for B+ (>100), whereas moderate or slight matrix effects are found for Si+ and O- (>10) and for Si-, B-, and O+ (<4). Relative ion yields of B+ and Si+ differ versus oxygen, whereas they are identical for B- and Si-. The relative ionization probability versus oxygen for Si+ agrees very well with the results of William´s group.

Keywords: SIMS; matrix effect; ion yield; silicon-oxygen system; ICM

Related publications

  • Surface and Interface Analysis 45(2013)1, 369-372
    Online First (2012) DOI: 10.1002/sia.5108

Permalink: https://www.hzdr.de/publications/Publ-17806
Publ.-Id: 17806


Zeitaufgelöste (4D) Rekonstruktion von in-beam PET Daten für das Dosismonitoring bei der Bestrahlung bewegter Zielvolumina in der Ionentherapie

Laube, K.; Bert, C.; Fiedler, F.; Helmbrecht, S.; Priegnitz, M.; Saito, N.; Enghardt, W.

no abstract available

Keywords: in-beam PET; moving targets; ion beam therapy

  • Lecture (Conference)
    43. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik e. V. (DGMP), 26.-29.09.2012, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17805
Publ.-Id: 17805


Time resolved (4D) reconstruction of in-beam PET data for the dose monitoring of intra-fractionally moving target volumes in ion beam therapy

Laube, K.; Bert, C.; Fiedler, F.; Helmbrecht, S.; Parodi, K.; Priegnitz, M.; Saito, N.; Enghardt, W.

In-beam positron emission tomography (PET) with a double-head PET scanner has been successfully applied for the in situ dose monitoring of about 440 patients with static tumour entities within a pilot project at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. For future treatment of intra-fractionally moving tumours, mainly located in the lung or liver, a dose monitoring is highly desired since complex beam delivery strategies and continuous respiration-related density changes in the irradiated tissue increase the risk for dose errors. Conventional three-dimensional (3D) in-beam PET measurements taken from moving structures would result in a reproduction of a blurred activity distribution and would, therefore, impede correct dose verification. An implemented motion compensated (4D) reconstruction routine based on the existing 3D Maximum Likelihood Expectation Maximization (MLEM) algorithm has been tested by phantom experiments performed at the GSI facility. Homogeneous polymethyl methacrylate (PMMA) phantoms of dedicated geometries have been irradiated with 12C pencil beams and in-beam PET data acquisition was performed throughout irradiation and additional time beyond to gain better statistics. Motion mitigation techniques of rescanning, gating or tracking have been used for a homogeneous dose deposition in the PMMA targets which performed a one-dimensional cos2- or cos4-shaped motion perpendicular to the beam direction. 4D reconstruction results have been compared to static reference measurements and to reconstruction results without consideration of the
target motion. Evaluation outcome with respect to the conservation of lateral and distal gradients in the reconstructed activity distributions will be shown at the workshop. Furthermore, the acquisition of required input parameters from the accelerator, the motion acquisition and the motion compensation systems and the data handling before reconstruction, like the temporal synchronization of all signals, as well as the necessary improvements for clinical usage of the 4D in-beam PET dose monitoring will be discussed.

Keywords: in-beam PET; moving targets; ion beam therapy; reconstruction

  • Lecture (Conference)
    Tomography, data processing and image reconstruction for medicine and engineering, 10.-12.09.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17804
Publ.-Id: 17804


Generalizations of Matérn's hard-core point processes

Teichmann, J.; Ballani, F.; van den Boogaart, K. G.

Matérn’s hard-core processes are valuable point process models in spatial statistics. In order to extend their field of application, Matérn’s original models are generalized here, both as point processes and particle processes. The thinning rule uses a distancedependent probability function, which controls deletion of points close together. For this general setting, explicit formulas for first- and second-order characteristics can be given. Two examples from materials science illustrate the application of the models.

Keywords: Point process; marked Poisson process; Matérn hard-core process; dependent thinning; independent thinning; pair correlation function

Permalink: https://www.hzdr.de/publications/Publ-17803
Publ.-Id: 17803


Entwicklung und Synthese von [18F]Flubatine für die Visualisierung von α4β2 nikotinischen Acetylcholinrezeptoren (nAChRs)

Smits, R.; Hoepping, A.; Fischer, S.; Hiller, A.; Funke, U.; Deuther-Conrad, W.; Steinbach, J.; Sabri, O.; Brust, P.

Ziel: Bei Patienten mit Alzheimer-Demenz (AD) ist die Verfügbarkeit nikotinischer Acetylcholinrezeptoren (nAChR), insbesondere des α4β2 Subtyps im Gehirn reduziert [1]. Die Visualisierung dieser Rezeptoren könnte zu einer frühzeitigen Diagnose der AD beitragen. Die zur Zeit zur Verfügung stehenden Radioliganden haben entweder eine unzureichende Affinität zum Rezeptor oder weisen eine sehr langsame Bindungskinetik auf. Der neue Ligand [18F]Flubatine bietet wesentliche Vorteile. Beide Enantiomere besitzen eine hohe in vitro Affinität [2] und zeigen eine schnelle cerebrale Bindungskinetik in der Maus [3] und im Schwein [4]. Erste humane PET-Studien bestätigen eine hohe Aufnahme im Thalamus, eine geringe unspezifische Bindung und das Erreichen des Bindungsgleichgewichtes in weniger als zwei Stunden. Für die Durchführung von klinischen Studien und für eine potentielle routinemäßige Anwendung war es notwendig, die bestehende Präkursorsynthese zu optimieren. Ein neuer enantiomerenreiner Präkursor soll eine einfache, robuste und effiziente Radiosynthese erlauben, mit dem Ziel der Automatisierung der Tracerproduktion. Zu diesem Zweck wurden eine kleine Bibliothek von Präkursoren mit verschiedenen Schutzgruppen und Abgangsgruppen synthetisiert und getestet.

Methodik: Als Startmaterial für die Synthese der neuen Präkursoren diente das Cbz-geschützte 8-Aza-bicyclo[3.2.1]oct-6-en-3-on, das nach literaturbekannten Verfahren dargestellt wurde. Nach einer reduktiven Heck-Reaktion zur Einführung des Pyridylrestes konnte die C3-Ketofunktion in einer dreistufigen Sequenz deoxygeniert werden. Die Abspaltung der Cbz-Schutzgruppe lieferte den [18F]Flubatine-Standard, dessen Racematspaltung mittels chiraler HPLC gelang. Im Anschluss wurden verschiedene Schutzgruppen und Fluchtgruppen eingeführt, deren [18F]-Markierung untersucht und optimiert wurde. Die Radiomarkierung der verschiedenen Präkursoren erfolgte über ein zweistufiges Verfahren bestehend aus trägerfreier, nucleophiler Radiofluorierung und Abspaltung der Schutzgruppe.

Ergebnisse: Die besten Resultate wurden mit dem Boc-geschützten Trimethylammonium-Präkursor erzielt. Die Ausbeute der unter Phasentransfer-Bedingungen durchgeführten Radiomarkierung betrug 90±5%. Nach Abspaltung der Schutzgruppe mit 1N HCl und Aufreinigung mittels semipräparativer HPLC konnte enantiomerenreines [18F]Flubatine in einer radiochemischen Ausbeute von 70±5% und einer spezifischen Aktivität >750 GBq/µmol erhalten werden.

Schlussfolgerungen: Die Radiosynthese von [18F]Flubatine konnte durch den Einsatz des neuen, enantiomerenreinen Präkursors entscheidend verbessert werden und ermöglicht eine automatisierte Produktion zur klinischen Evaluierung des Radioliganden.

  • Lecture (Conference)
    20. Jahrestagung der AG Radiochemie/Radiopharmazie der DGN, 04.-06.10.2012, Bad Honnef, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17802
Publ.-Id: 17802


Severe accident research in the core degradation area: An example of effective international cooperation between the European Union (EU) and the Commonwealth of Independent States (CIS) by the International Science and Technology Center

Bottomleya, D.; Stuckert, J.; Hofmann, P.; Tocheny, L.; Hugon, M.; Journeau, C.; Clément, B.; Weber, S.; Guentay, S.; Hozer, Z.; Herranz, L.; Schumm, A.; Oriolo, F.; Altstadt, E.; Krause, M.; Fischer, M.; Khabensky, V. B.; Bechta, S. V.; Veshchunov, M. S.; Palagin, A. V.; Kiselev, A. E.; Nalivaev, V. I.; Goryachev, A. V.; Zhdanov, V.; Baklanov, V.

The International Science and Technology Center (ISTC) was set up in Moscow to support nonproliferation of sensitive knowledge and technologies in biological, chemical and nuclear domains by engaging scientists in peaceful research programmes with a broad international cooperation. The paper has two following objectives:

1) to describe the organization of complex, international, experimental and analytical research of material processes under extreme conditions similar to those of severe accidents in nuclear reactors and,
2) to inform briefly about some results of these studies.
The main forms of ISTC activity are Research Projects and Supporting Programs. In the Research Projects informal contact expert groups (CEGs) were set up by ISTC to improve coordination between adjacent projects and to encourage international collaboration. The European Commission was the first to use this. The CEG members – experts from the national institutes and industry – evaluated and managed the projects’ scientific results from initial stage of proposal formulation until the final reporting. They were often involved directly in the project’s details by joining the Steering Committees of the project. The Contact Expert Group for Severe Accidents and Management (CEG-SAM) is one of these groups, five project groups from this area from the total of 30 funded projects during 10 years of activity are detailed to demonstrate this: (1) QUENCH-VVER from RIAR, Dimitrovgrad and IBRAE, Moscow, and PARAMETER projects (SF1–SF4) from LUCH, Podolsk and IBRAE, Moscow; these concerned a detailed study of bundle quenching from high temperature; (2) Reactor Core Degradation; a modelling project simulating the fuel
rod degradation and loss of geometry from IBRAE, Moscow; (3) METCOR projects from NITI, St. Petersburg on the interaction of core melt with reactor vessel steel; (4) INVECOR project, NNE Kurchatov City, Kazakhstan; this is a large-scale facility to examine the vessel steel retention of 60 kg corium during the decay heat; and finally, (5) CORPHAD and PRECOS projects, NITI, St. Petersburg undertook a systematic examination of refractory ceramics relevant to in-vessel and ex-vessel coria, particularly examining poorly characterised, limited data or experimentally difficult systems.

Keywords: Severe accident management; core melt down; nuclear reactors; in-vessel melt retention

Permalink: https://www.hzdr.de/publications/Publ-17801
Publ.-Id: 17801


Impact of 5-lipoxygenase inhibitors on the spatiotemporal distribution of inflammatory cells and neuronal COX-2 expression following experimental traumatic brain injury in rats

Härtig, W.; Michalski, D.; Seeger, G.; Voigt, C.; Donat, C. K.; Dulin, J.; Kacza, J.; Meixensberger, J.; Arendt, T.; Schuhmann, M. U.

Inflammation induced by traumatic brain injury (TBI) is considered as contributor to neuronal death with poor outcome. Although anti-inflammatory strategies were beneficial in experimental TBI, clinical translations mostly failed, probably caused by the complexity of involved cells and mediators. We recently showed in a rat model of controlled cortical impact (CCI) that leukotriene inhibitors (LIs) attenuate contusion growth and improve neuronal survival. This study focuses on spatiotemporal characteristics of macrophages and granulocytes, typically involved in inflammatory processes, and neuronal COX-2 expression. Further, effects of LIs (Boscari/MK-886) were evaluated by quantifying CD68+, CD43+ and COX-2+ cells 24 and 72 h post-CCI in the parietal cortex (PC), CA3 region (CA3r), dentate gyrus (DG) and visual/auditory cortex (v/aC). Correlations were applied to identify inter-cellular relationships. At 24 h, untreated animals showed granulocytes in all regions investigated, decreasing towards 72 h. In contrast, macrophages increased from 24 to 72 h post-CCI in the PC and v/aC. COX-2+ neurones showed no temporal dynamics, except of an increase in the CA3r towards 72 h. Treatment reduced granulocytes at 24 h in the pericontusional penumbra and hippocampus, and reduced macrophages at 72 h in the PC and v/aC. COX-2 expression remained unaffected by LIs, except of time-specific reactions in the DG (increase/decrease at 24/72 h). Interrelations confirmed concomitant cellular reactions beyond initial trauma site. In conclusion, LIs attenuated the cellular inflammatory response following CCI and therefore become attractive as potential treatment strategy. Future studies should clarify region-specific effects and feasible time windows for applying LIs after CCI.

Keywords: Traumatic brain injury; Neuronal death; Macrophage; Granulocyte; COX-2

Permalink: https://www.hzdr.de/publications/Publ-17800
Publ.-Id: 17800


Reconstruction of Gebel Kamil’s irradiation history

Merchel, S.; Akhmadaliev, S.; Fimiani, L.; Haubold, R.; Herrmann, S.; Korschinek, G.; Ott, U.; Pavetich, S.; Rugel, G.

Data of the lighter cosmogenic radionuclides 10Be, 26Al, 36Cl, and 41Ca are now easily attainable at the accelerator mass spectrometry facility DREAMS [1]. Accompanied by the heavier radionuclides 53Mn and 60Fe, which are measured at the 14 MV tandem at Munich, and stable noble gas nuclides from MPI Mainz, complete and unique exposure histories of extraterrestrial material can be reconstructed.
One of the first meteorites investigated by this team is Gebel Kamil, an ungrouped Ni-rich ataxite that produced an impact crater (Ø: 45 m) in southern Egypt. Two neighboured shrapnel (S) samples and two from the only individual (I) fragment (~83 kg) have been analysed. Comparison with Monte-Carlo calculations of production rates indicate that Gebel Kamil was exposed as a meteoroid body of >120 cm radius. Samples I originate from a moderate shielding of 18-25 cm, whereas samples S are from a deeper position of 53-65 cm. Most reliable 36Cl-36Ar ages of I and S are ~450 Ma calculated after [3].
Ackn.: L. Folco (meteorite) & accelerator crews (support AMS). Ref.: [1] Akhmadaliev et al. (2012) NIMB, in print. [2] Folco et al., Science 329 (2010) 804. [3] Ammon et al., MAPS 44 (2009) 485.

Keywords: cosmogenic; AMS; meteorite

Related publications

  • Lecture (Conference)
    Joint meeting “Paneth Kolloquium”, “The first 10 million years of the solar system” (DFG SPP 1385) & “MEMIN” (DFG FOR 887), 09.-12.10.2012, Nördlingen, Duetschland

Permalink: https://www.hzdr.de/publications/Publ-17799
Publ.-Id: 17799


Growth mode and texture development in Ni-Ti shape memory alloy (SMA) films during co-sputtering deposition – An in situ synchrotron radiation study

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

In-situ X-ray scattering measurements were carried out during Ni-Ti shape memory alloy film processing at the Rossendorf Beamline (BM20-ESRF). The experiments performed with a two-magnetron sputter deposition chamber mounted into the six-circle diffractometer of the beamline enabled us to identify the different steps of the structural evolution during deposition with a set of parameters as well as to evaluate the effect of changing parameters (Ti target power) during film growth. The results show that the type of substrate plays an important role for the preferential orientation of sputtered Ni-Ti films. Amorphous SiO2 and TiN buffer layers were used to successfully control their crystallographic orientations. The deposition conditions leading to films mainly containing grains with (100) or (110) planes of the B2 phase parallel to the film surface are presented. The control of texture is an important achievement since it has a strong influence on the extent of the strain recovery of the Ni-Ti films. The deposition of graded Ni-Ti films by deliberately changing the Ti:Ni ratio, thereby altering microstructure and transformation temperatures across the film thickness, provided significant data for the optimisation of the deposition parameters in order to fabricate films with a “two-way” actuation (films with a combination of superelasticity and shape memory characteristics). This is a plus for the miniaturization of Ni–Ti films based devices in the field of micro-electro-mechanical systems since no consideration has to be paid to a resetting spring.

Related publications

  • Poster
    MPA 2012 – 6th International Meeting on Developments in Materials, Processes and Applications of Emerging Technologies, 02.-04.07.2012, Alvor, Portugal

Permalink: https://www.hzdr.de/publications/Publ-17798
Publ.-Id: 17798


Terahertz nonlinear optics of excitons in quantum wells using a free-electron laser

Helm, M.

Keywords: terahertz; quantum well; free electron laser; exciton

Related publications

  • Invited lecture (Conferences)
    Viennese Symposium on Heterostructures, 07.09.2012, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-17797
Publ.-Id: 17797


Modification of Ni-Ti surface composition and morphology by plasma immersion ion implantation for biomedical applications

Martins, R. M. S.; Barradas, N.; Alves, E.; Henke, D.; Reuther, H.; Schell, N.; Carmezim, M. J.; Silva, T. M.; Fernandes, J. C. S.

The shape memory effect and superelasticity of Ni-Ti (Nitinol) make it very attractive for biomedical applications. The Ni-Ti alloy (~ 50.4 at.% Ni) selected for this work is austenitic (superelastic) at body temperature. In the frame of the AIM-74 and SPIRIT-77 projects, plasma immersion ion implantation (PIII) has been employed to modify and improve the superficial region of the alloy. The formation of titanium oxynitride (TiNxOy) was achieved by ion implantation of nitrogen. A Ti-rich oxide layer was obtained during the experiments carried out with oxygen. Thus, the parameters to obtain a Ni-depleted surface, which serves as a barrier to out-diffusion of Ni ions from the bulk material, have been successfully established. Furthermore, nanostructured Ni-Ti surfaces have been produced. Synchrotron radiation-based X-ray diffraction data acquired in transmission mode show that the PIII technique only changes the structure of the Ni-Ti alloy top layer preserving superelastic behaviour at body temperature (PIII experiments carried out without intentional heating of the substrate holder). Techniques like thermal oxidation and nitriding also lead to an improved corrosion resistance and Ni-depleted Ni-Ti surface but require high processing temperatures leading to modification of the phase transformation characteristics and loss of specific mechanical properties.

Related publications

  • Lecture (Conference)
    MPA 2012 - 6th International Meeting on Developments in Materials, Processes and Applications of Emering Technologies, 02.-04.07.2012, Alvor, Portugal

Permalink: https://www.hzdr.de/publications/Publ-17796
Publ.-Id: 17796


Supernova Dust in Terrestrial Deep-Sea Archives

Feige, J.; Wallner, A.; Fifield, L. K.; Korschinek, G.; Merchel, S.; Rugel, G.; Winkler, S. R.

The long-lived radionuclides 26Al, 53Mn and 60Fe are produced in the late burning phases and during a supernova explosion of a massive star. These nuclides are then ejected into space, condensed into dust and, if the supernova occurs in a close distance to the solar system, might be able to reach the Earth. An indication for a close-by supernova in the past, deduced from a signal about 2 Myr ago, has already been identified in a ferromanganese crust [1]. Deep-sea sediments, with higher accumulation rates, provide a higher time resolution and allows therefore a more precise dating of the signal.
Here, samples of two sediment cores originating from the Indian Ocean are analyzed to search for supernova signals. Currently, the only method sensitive enough to detect these signals is accelerator mass spectrometry. Additionally to the supernova-produced nuclides, 10Be, which is constantly produced by cosmic rays in the Earth's atmosphere, is measured to date the sediment cores. First 10Be and 26Al data are presented and discussed.
[1] Knie, K., et al. (2004), Phys. Rev. Lett. 93, 17.

Keywords: supernovae; AMS; radionuclide

Related publications

  • Poster
    Joint meeting “Paneth Kolloquium”, “The first 10 million years of the solar system” (DFG SPP 1385) & “MEMIN” (DFG FOR 887), 09.-12.10.2012, Nördlingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17795
Publ.-Id: 17795


Radiosynthesis of racemic and enantiomerically pure (–)-[18F]flubatine – A promising PET radiotracer for neuroimaging of α4β2 nicotinic acetylcholine receptors

Fischer, S.; Hiller, A.; Smits, R.; Hoepping, A.; Funke, U.; Wenzel, B.; Cumming, P.; Sabri, O.; Steinbach, J.; Brust, P.

(–)-[18F]flubatine is a promising agent for visualization by PET of cerebral α4β2 nicotinic acetylcholine receptors (nAChRs), which are implicated in psychiatric and neurodegenerative disorders. Here, we describe a substantially improved two-step radiosynthesis strategy for (–)-[18F]flubatine, based on the nucleophilic radiofluorination of an enantiomerically pure precursor followed by deprotection of the intermediate. An extensive leaving group/protecting group library of precursors was tested. Application of a trimethylammonium-iodide precursor with a Boc protecting group provided the best results: Labeling efficiencies of 80-95%, RCY of 60±5%, radiochemical purity of >98%, and a specific activity of >350 GBq/µmol. The radiosynthesis is easily transferable to an automated synthesis module.

Keywords: Fluorine-18; Positron emission tomography; Neuroimaging; α4β2 nicotinic acetylcholine receptors; α4β2 ligands; Radiosynthesis; Leaving groups; Protecting groups

Permalink: https://www.hzdr.de/publications/Publ-17794
Publ.-Id: 17794


PET/MR for therapy response evaluation in malignant lymphoma: initial experience

Platzek, I.; Beuthien-Baumann, B.; Langner, J.; Popp, M.; Schramm, G.; Ordemann, R.; Laniado, M.; Kotzerke, J.; van den Hoff, J.

Object: To evaluate the feasibility of positron emission tomography/magnetic resonance imaging (PET/MR) with 18fluoro-2-deoxyglucose (FDG) for therapy response evaluation of malignant lymphoma.
Materials and methods: Nine patients with malignant lymphoma who underwent FDG-PET/MR before and after chemotherapy were included in this retrospective study. Average time between the two scans was 70 days. The scans were evaluated independently by two nuclear medicine physicians. The Ann Arbor classification was used to describe lymphoma stage. Furthermore, the readers also rated PET image quality using a five point scale. Weighted kappa was used to calculate interrater agreement.
Results: The initial scan showed foci of increased FDG uptake in all patients, with Ann Arbor stage varying between I and IV. In the follow-up examination, all but one patient showed complete response to chemotherapy. PET image quality was rated as very good or excellent for all scans. Interrater agreement was excellent regarding Ann Arbor stage (kappa = 0.97) and good regarding image quality (kappa = 0.41). Conclusion PET/MR shows promising initial results for therapy response evaluation in lymphoma patients.

Keywords: PET; MRI; Lymphoma

Permalink: https://www.hzdr.de/publications/Publ-17793
Publ.-Id: 17793


PET/MR in head and neck cancer: initial experience

Platzek, I.; Beuthien-Baumann, B.; Schneider, M.; Gudziol, V.; Langner, J.; Schramm, G.; Laniado, M.; Kotzerke, J.; van den Hoff, J.

Purpose: To evaluate the feasibility of PET/MRI (positron emission tomography/magnetic resonance imaging) with FDG (18F-fluorodeoxyglucose) for initial staging of head and neck cancer.
Methods: The study group comprised 20 patients (16 men, 4 women) aged between 52 and 81 years (median 64 years) with histologically proven squamous cell carcinoma of the head and neck region. The patients underwent a PET scan on a conventional scanner and a subsequent PET/MRI examination on a whole-body hybrid system. FDG was administered intravenously prior to the conventional PET scan (267–395 MBq FDG, 348 MBq on average). The maximum standardized uptake values (SUVmax) of the tumour and of both cerebellar hemispheres were determined for both PET datasets. The numbers of lymph nodes with increased FDG uptake were compared between the two PET datasets.
Results: No MRI-induced artefacts where observed in the PET images. The tumour was detected by PET/MRI in 17 of the 20 patients, by PET in 16 and by MRI in 14. The PET/MRI examination yielded significantly higher SUVmax than the conventional PET scanner for both the tumour (p<0.0001) and the cerebellum (p00.0009). The number of lymph nodes with increased FDG uptake detected using the PET dataset from the PET/MRI system was significantly higher the number detected by the stand-alone PET system (64 vs. 39, p00.001).
Conclusion: The current study demonstrated that PET/MRI of the whole head and neck region is feasible with a wholebody PET/MRI system without impairment of PET or MR image quality.

Keywords: PET/MRI; Head and neck cancer

Permalink: https://www.hzdr.de/publications/Publ-17792
Publ.-Id: 17792


Intraband carrier dynamics in quantum dots and quantum wells

Bhattacharyya, J.; Zybell, S.; Winnerl, S.; Hopkinson, M.; Wilson, L. R.; Andrews, A. M.; Strasser, G.; Helm, M.; Schneider, H.

Optical properties of self assembled quantum dots (QDs) have dominant inhomogeneous broadening due to the distribution of size and composition of the QDs in the ensemble. The carrier dynamics in such systems is affected by the neighboring dots due to interdot diffusion of carriers. In this work we investigate the intraband relaxation mechanisms in the QDs. We performed time-resolved photoluminescence (PL) quenching measurements on InAs/GaAs self assembled QDs. The samples were excited by near infrared laser pulses and the time and wavelength resolved PL was measured by a streak camera. During the decay of the PL, a THz pulse from a free electron laser, tuned to the intersublevel transition energy of the QDs, was made incident on the sample. This THz pulse induced quenching of the PL, shown by the dip in Fig.1, by re-exciting carriers to higher levels within the QDs. These carriers eventually relaxed back to the ground state (s-state) resulting in the recovery of the s-state PL intensity. Thus, the recovery of the PL was directly related to carrier relaxation dynamics in the QDs. The mechanisms involved were (i) ISL relaxation, where the excited carriers in the QDs directly fell back into the s-state of the same dot and (ii) transfer to adjacent dots via the wetting layer by multiphoton absorption or tunneling. To distinguish these two effects we performed measurements on two samples grown simultaneously but post-growth annealed at different temperatures resulting in different ISL relaxation times of 60 ps and 1.5 ns. From rate equation model fit of the measured data we found that the recovery time of the quenched PL was independent of the ISL relaxation times. This implied that the carrier relaxation within the dots was dominated by mechanisms other than ISL transition. Comparison of the amount of recovered PL signals for different emission energies showed that there was loss of carriers at higher PL energies, as showed in Fig.1(a), and gain of carriers after recovery for lower emission energies [Fig.1(b)]. This indicates carrier transfer among adjacent QDs. Therefore, even for quite low QD densities (4 x 10^10 cm-2 for our samples), interdot carrier transfer plays an important role in intraband carrier relaxation in self assembled QDs.

Keywords: Photoluminescence quenching; FEL; Intraband transition; quantum dots; quantum well

Related publications

  • Lecture (Conference)
    International conference on superlattices, nanostructures and nanodevices, 22.-27.07.2012, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-17791
Publ.-Id: 17791


Alpha self-irradiation effect on the local structure of the U0.85Am0.15O2+x solid solution

Prieur, D.; Martin, P. M.; Lebreton, F.; Delahaye, T.; Jankowiak, A.; Laval, J.-P.; Scheinost, A. C.; Dehaudt, P.; Blanchart, P.

Uranium–americium mixed oxides are promising fuels for achieving an efficient Am recycling. Previous studies on U0.85Am0.15O27x materials showed that the high a activity of 241Am induces pellet swelling which is a major issue for cladding materials design. In this context, X-ray Diffraction and X-ray Absorption Spectroscopy measurements were used to study self-irradiation effects on U0.85Am0.15O27x local structure and to correlate these results with those obtained at the macroscopic scale. For a cumulative a decay dose equal to 0.28 dpa, it was shown that non-defective fluorite solid solutions were achieved and therefore, that the fluorite structure is stable for the studied doses. In addition, both interatomic distance and lattice parameter expansions were observed, which only partially explains the macroscopic swelling. As expected, an increase of the structural disorder with self-irradiation was also observed.

Keywords: XAFS; self-irradiation; nuclear fuel; nuclear waste; Am

Related publications

Permalink: https://www.hzdr.de/publications/Publ-17790
Publ.-Id: 17790


Moderating material to compensate the drawback of high minor actinide containing transmutation fuel on the feedback effects in SFR cores

Merk, B.

The use of fine distributed moderating material to enhance the feedback effects and to reduce the sodium void effecting SFRs is described. The drawback on the feedback effects due to the introduction of minor actinides into SFR fuel is analyzed. The possibility of compensation of the effect of the minor actinides on the feedback effects by the use of fine distributed moderating material is demonstrated. The consequences of the introduction of fine distributed moderating material into fuel assemblies with fuel configurations foreseen for minor actinide transmutation is analyzed and the positive effects on the transmutation efficiency are shown. Finally, the possible increase of the Americium content to improve the transmutation efficiency is discussed, the limit value of Americium is determined and the possibilities given by an increase of the Hydrogen content are analyzed.

Keywords: enhanced feedback; transmutation; fast reactror; Americium; Curium

Permalink: https://www.hzdr.de/publications/Publ-17789
Publ.-Id: 17789


Thermal stability of moderating material used to enhance the feedback coefficients in SFR cores

Merk, B.

Recently, the use of moderating materials in fuel assemblies for Sodium cooled fast reactors has been investigated and published in several papers (e. g. Annals of Nuclear Energy 38, 5, Annals of Nuclear Energy 38, 11 (2011)). Especially the fine distribution of the moderating material in a layer inside the fuel rod or inside the wire spacer has shown very promising results for the enhancement of the feedback coefficients. Additionally, this arrangement is very attractive since it causes only a very limited influence on the safety relevant fuel assembly structure and on the operational parameters. A detailed investigation on the use of moderating material for transmutation fuels has proven that a compensation of the negative influence on the feedback coefficients caused by the Minor Actinides is possible. The critics on the limited thermal stability of the suggested ZrH based moderating material has been a major issue in the discussion of all up to now published publications. In this work the problem will be solved with the help of t change of the hydrogen bearing metal compound. In a first step an overview on possible metal materials will be given and properties as well as manufacturing issues will be discussed. Additionally, an insight will be given into the relationship of the hydrogen content of the compound and the resulting thermal stability. Based on this relation the reasons for the choice of Yttrium are described. In a second step the transferability of the old results gained for ZrH will be proven by a detailed comparison of different important reactor physical parameters for cases using identical amounts of ZrH and YH.
Thermal stability of the moderating material up to more than 1300°C can be ensured by the use of Yttrium-mono-hydride as moderating material. The topic will be closed by a survey on the existing operation experience with YH in fast reactors and a comparison of the raw material costs for Zirconium and Yttrium.

Keywords: fast reactor; enhanced feedback effects; moderating material; Yttrium hydride; thermal stability

  • Contribution to proceedings
    International Conference on Fast Reactors and Related Fuel Cycles: Safe Technologies and Sustainable Scenarios (FR13), 04.-07.03.2013, Paris, France
  • Lecture (Conference)
    International Conference on Fast Reactors and Related Fuel Cycles: Safe Technologies and Sustainable Scenarios (FR13), 04.-07.03.2013, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-17788
Publ.-Id: 17788


The Molten Salt Fast Reactor as Transmutation System

Merk, B.; Rohde, U.; Scholl, S.

The basic development and design of a molten salt reactor with fast neutron spectrum (Molten Salt Fast Reactor – MSFR) is the target of the EVOL project in FP7. The MSFR offers certain advantages in the view of transmutation compared to solid fuelled reactor types. In the first part, these advantages will be discussed in a comparison with the sodium cooled fast reactor technology and the research challenges will be analyzed. In the second part, cycle studies for the MSFR, based on the EVOL benchmark design, will be given for different configurations – core with U-238 fertile, a fertile free core and a core with Th-232 as fertile material. For all cases, the transmutation potential will be determined and a significant improvement in the transmutation performance for the case with Th as fertile will be demonstrated. The time evolution of different important isotopes will be analyzed. Additionally, the used tool HELIOS 1.10 and the adaptations needed for the simulation of a MSFR will be described.

Keywords: molten salt fast reactor; molten salt reactor; fast reactor; transmutation

  • Contribution to proceedings
    International Conference on Fast Reactors and Related Fuel Cycles: Safe Technologies and Sustainable Scenarios (FR13), 04.-07.03.2013, Paris, France
  • Lecture (Conference)
    International Conference on Fast Reactors and Related Fuel Cycles: Safe Technologies and Sustainable Scenarios (FR13), 04.-07.03.2013, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-17786
Publ.-Id: 17786


Progress in fast reactor operation and new trends to increased inherent safety

Merk, B.; Stanculescu, A.; Chellapandi, P.; Hill, R.

The reasons for the renewed interest in fast reactors and an overview of the progress in sodium cooled fast reactor operation and design in the last ten years is given. The relevance of feedback effects for safe reactor design is described, and a new method for the enhancement of feedback effects in fast reactors is proposed. The excellent operational performance of sodium cooled fast reactors in this period is highlighted as a sound basis for the development of new fast reactors. Experimental reactors demonstrating the inherent safety of advanced sodium cooled fast reactor designs are described and the potential safety improvements resulting from the use of fine distributed moderating material are demonstrated. Finally, the fast reactor specifics are analysed with regard to the Fukushima accident.

Keywords: fast reactor history; fast reactor technology; enhanced feedback; inherent safety

Permalink: https://www.hzdr.de/publications/Publ-17785
Publ.-Id: 17785


Sorption of Se(VI) and Se(IV) oxyanions onto maghemite: a macroscopic and spectroscopic study

Jordan, N.; Ritter, A.; Foerstendorf, H.; Scheinost, A. C.; Heim, K.; Weiß, S.; Brendler, V.

79Se, a long-lived (t1/2 ~ 3.27 × 105 years) and radiotoxic fission product, was identified by safety performance assessments to be one of the most contributing isotopes to the total radioactivity that could be potentially released to the biosphere. Selenium has a quite complex speciation, with four main oxidation states, depending on both the pH and the redox potential of the surrounding environment. Sorption of selenium oxyanions onto mineral surfaces (iron, alumina, titanium oxides and clays) has been extensively investigated based on batch experiments and spectroscopic studies. However, the sorption processes of selenium oxyanions onto maghemite was not explicitly studied before and thus the potential ability of maghemite to significantly retard selenium migration in the environment is therefore still unknown. Maghemite was identified as a corrosion product of steel waste canisters and iron archaeological analogues, and is also a ubiquitous mineral in the environment.
In this work, we investigated in detail the sorption of selenium(VI) and selenium(IV) onto maghemite (γ-Fe2O3), for the first time. The effect of pH and ionic strength was studied by batch experiments. Sorption of both oxyanions onto maghemite was found to decrease with increasing pH. An increase of the ionic strength (from 0.01 M to 0.1 M) impacted the sorption of selenium(VI), while it had no significant effect for selenium(IV) uptake. Electrophoretic mobility measurements revealed that the isoelectric point (pHIEP) of maghemite was shifted to lower pH values upon selenium(IV) sorption, while it was not significantly modified upon selenium(VI) sorption. By combining EXAFS and in situ ATR FT-IR spectroscopic measurements, the formation of inner-sphere complexes during selenium(IV) sorption onto maghemite was observed. Selenium(VI) sorption proceeded via the formation of predominant outer-sphere complexes (together with a small amount of inner-sphere complexes).

Keywords: selenium; sorption; EXAFS; IR; maghemite

Related publications

  • Lecture (Conference)
    Selen2012 - Selenium in geological, hydrological and biological systems, 08.-09.10.2012, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-17784
Publ.-Id: 17784


Inertial wave observations in liquid metal by means of ultrasound Doppler velocimetry

Räbiger, D.; Vogt, T.; Franke, S.; Eckert, S.; Gerbeth, G.; Czarske, J.

This experimental study considers the transient flow inside a liquid metal column exposed to a pulsed rotating magnetic field. To measure two-dimensional velocity fields of the secondary flow in the radial-meridional plane a novel ultrasound Doppler system was used. A linear ultrasound transducer array equipped with 25 transducer elements is used to measure the flow field in a square plane of 67 x 67 mm². The application of advanced processing techniques like a simultaneous excitation of multiple transducer elements and a segmented array technique enable high data acquisition rates as well as a high spatial resolution. The measurements revealed transient flow regimes showing distinct inertial oscillations and coherent vortex structures.

Keywords: Ultrasound Doppler method; flow field measurements; electromagnetic stirring; rotating magnetic field; inertial waves; flow control

  • Lecture (Conference)
    ISUD8 - 8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 19.-21.09.2012, Dresden, Deutschland
  • Contribution to proceedings
    ISUD8 - 8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 19.-21.09.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17783
Publ.-Id: 17783


Magnetic properties of Co/Pd multilayers films deposited on GaSb nanocones

Ball, D. K.; Günther, S.; Fritzsche, M.; Lenz, K.; Varvaro, G.; Makarov, D.; Mücklich, A.; Facsko, S.; Fassbender, J.; Albrecht, M.

The magnetic properties of ferromagnetic thin films fabricated on nanostructured templates is strongly affected by the surface morphology. Low energy ion irradiation of GaSb yields to a self organized hexagonal pattern that can serve as templates for subsequent deposition of magnetic films.
In this respect, curvature effects and influence of pattern symmetry result in a substantial modification of the magnetization reversal behavior of individual magnetic nanostructures and their assemblies.
Curvature-driven changes can be beneficial to reduce the switching field, which is advantageous for magnetic data storage applications, especially for the recording concept known as bit patterned media (BPM). In the BPM concept, an individual bit will be stored in a single magnetic nanostructure. Candidates for a recording layer are films with strong out-of-plane magnetic anisotropy (Ku) such as hard magnetic FePt alloys and [Co/Pd(Pt)]n multilayers.
Here, we aim at the fabrication of arrays of magnetic [Co/Pd]n multilayers on top of selfassembled nanocone templates created on GaSb(100) single crystal using a Ar+ ion erosion technique. By tailoring the irradiation conditions, the self-organized assemblies of nanocones were modified in size and periodicity. Due to the self-organization, large patterned areas can be fabricated which is challenging using e-beam lithography.
Macroscopic magnetic measurements performed using vector-VSM magnetometry (vVSM) indicate that all samples possess the magnetic easy axis perpendicular to the cone surface. The remanence as well as the coercivity decreases with increasing cone size, as the letter leads to a larger angular spread of easy axis following the morphology of the pattern. Additionally, MFM characterization shows that in the case of small cone structures the underlying cone pattern results in a pinning of magnetic domain walls on cone locations as there is a clear correlation between the morphology and positions of magnetic domain walls. For larger cone sizes, exchange decoupled magnetic caps are achieved with single domain areas confined to the cones apexes.

Related publications

  • Poster
    Joint European Magnetic Symposia (JEMS 2012), 09.-14.09.2012, Parma, Italien

Permalink: https://www.hzdr.de/publications/Publ-17782
Publ.-Id: 17782


NMR Investigations of the intra- and intermolecular exchange phenomena of the 3,5-dimethylpyrazolylsilane ClSi(pz*) and related compounds

Bitto, F.; Kretzschmar, J.; Brendler, E.; Kroke, E.

Chlorine substituted 3,5-dimethylpyrazolyl (pz*) silanes exhibit interesting inter- and intramolecular exchange phenomena. Intermolecular reactions involving Si-N vs. Si-Cl dismutation cause equilibria between the three species Cl2Si(pz*)2, ClSi(pz*)3 (main component) and Si(pz*)4. Intramolecular exchange is interpreted as a “dangling” of the pz*-moieties in every pyrazolyl silane molecule itself.[1] These phenomena were investigated with one and two dimensional NMR spectroscopic methods at variable temperatures. The “dangling” of the pz*-moieties is slowed down with decreasing temperature and are best visible in the spectra recorded at -40°C. The use of 1H-29Si-HMBC spectroscopy (heteronuclear multiple bond correlation) allows to assign the olefinic protons to the corresponding silicon species. In the EXSY (exchange spectroscopy) spectra the exchange between the pz*-methyl groups and the NOE (nuclear overhauser effect) correlation between the methyl groups and the olefinic protons are observed at the same time in one spectrum. The data obtained with EXSY and HMBC-spectroscopy in combination with variable temperature 1H NMR allows qualitative conclusions concerning the rate of exchange and the dependence on the silicon corresponding species.

[1] F. Bitto, J. Wagler, E. Kroke, Eur. J. Inorg. Chem. 2012, in press, doi:10.1002/ejic.201101409.

Keywords: NMR spectroscopy; H,Si-HMBC; H,H-NOESY, H,H-EXSY; 3,5-dimethylpyrazolyl silanes

  • Poster
    4th EuCheMS Chemistry Congress, 26.-30.08.2012, Prag, Tschechische Republik

Permalink: https://www.hzdr.de/publications/Publ-17781
Publ.-Id: 17781


Dual-beam irradiation of friction stir spot welding of nanostructured ferritic oxide dispersion strengthened alloy

Chen, C.-L.; Richter, A.; Kögler, R.; Wu, L.-T.

Friction stir spot welding (FSSW) is a very promising technique for the joining of oxide dispersion strengthened (ODS) materials without oxide particle agglomeration and loss in mechanical properties in the weld zone. Heating and severe plastic deformation can significantly alter the originally as-received material. The local microstructure determines the weld mechanical properties, which are analyzed by nanointendation. The FSSW region consists of three different zones: the base material, the thermo-mechanically affected zone and the heat affected zone. Irradiation of the FSSW area was performed with a Fe+/He+ dual ion beam. Hardness changes within the welding zones and variation with irradiation damage are discussed.

Keywords: Nanostructured material; oxide dispersion strengthened (ODS) alloys; friction stir welding; nanoindentation; irradiation damage

Related publications

Permalink: https://www.hzdr.de/publications/Publ-17780
Publ.-Id: 17780


Neutronic analysis of SFR core with HELIOS-2, SERPENT, and DYN3D codes

Rachamin, R.; Wemple, C.; Fridman, E.

In this study, HELIOS-2 deterministic transport code and Serpent Monte-Carlo (MC) reactor physics code were considered as tools for preparation of few-group constants for sodium cooled fast reactor (SFR) analysis. Initially, applicability of the mainly LWR-oriented HELIOS-2 code to the modeling of SFR lattices was investigated and recommendations for methodological modifications were given. At the next stage the methodology for few-group cross section generation for fuel and non-multiplying regions of SFR core was proposed. Afterward, few-group constants produced by HELIOS-2 and Serpent employing the proposed methodology were used by nodal diffusion code DYN3D for the analysis of a reference SFR core. Finally, the DYN3D results were verified against the full core Serpent MC solution. The full core DYN3D results obtained using few-group constants produced by Serpent agreed very well with that of the reference full core MC simulations. The use of HELIOS-2 based few-group constants led to somewhat reduced agreement between reference MC and DYN3D results. The implementation of the suggested modifications to the HELIOS-2 methodology can potentially improve its modeling accuracy for SFR lattices.

Keywords: HELIOS-2; Serpent; Monte Carlo; DYN3D; few-group cross section generation; sodium cooled fast reactor

Permalink: https://www.hzdr.de/publications/Publ-17779
Publ.-Id: 17779


AMS Measurements of Supernova-Produced Radionuclides in Deep-Sea Sediment Cores

Feige, J.; Wallner, A.; Winkler, S. R.; Merchel, S.; Fifield, L. K.; Korschinek, G.; Rugel, G.

Accelerator Mass Spectrometry (AMS) provides the highest sensitivity for measurements of long-lived radionuclides with half-lives in the order of million years. We will apply this method to search for live supernova (SN)-produced radionuclides on Earth.
An indication to recent SN activity in our solar neighborhood is the existence of a thin, hot cavity in the local interstellar medium, embedding our solar system. This so called superbubble, the Local Bubble, was produced by multiple SN explosions, starting ~14 Myr ago. Nuclides, which are synthesized in massive stars and during their explosions, are then entrained in the SN shell and may be transported to the solar system, if such an event happens within a short distance.
Two deep-sea sediment cores originating from the Indian Ocean have been selected to search for the SN-produced radionuclides 26Al, 53Mn, 60Fe and 244Pu in the time range of 2-3 Myr. We aim to measure these isotopes at different laboratories with high time resolution with the goal to confirm a previously found SN signal in a ferromanganese crust from the Pacific Ocean.

Keywords: supernovae; radionuclide; AMS; sediments

Related publications

  • Poster
    62. Jahrestagung der Österreichischen Physikalischen Gesellschaft, 18.-21.09.2012, Graz, Österreich

Permalink: https://www.hzdr.de/publications/Publ-17778
Publ.-Id: 17778


The Search for Supernova-Produced Radionuclides in Deep-Sea Sediments with AMS

Feige, J.; Wallner, A.; Winkler, S. R.; Merchel, S.; Fifield, K. L.; Korschinek, G.

We will search for supernova-produced radionuclides in deep-sea sediment cores originating from the Indian Ocean. We aim to measure the long-lived radionuclides 26Al (t1/2 = 0.7 Myr), 60Fe (t1/2 = 2.6 Myr), 53Mn (t1/2 = 3.7 Myr) and 244Pu (t1/2= 80 Myr) at different laboratories in sediment samples with high time resolution.
A positive signal will also confirm a previous finding of an enhanced 60Fe content in a ferromanganese crust [1]. The above mentioned radionuclides are commonly synthesized in massive stars and ejected by supernova (SN) explosions. If such a SN event happens in the solar vicinity, the expanding SN envelope might hit the solar system and leave certain traces in terrestrial archives. An indication to recent SN activity is the existence of a cavity consisting of thin, hot gas in the local interstellar medium, embedding our solar system. This superbubble, called the Local Bubble, was presumably produced by 14-20 SN explosions starting 14 Myr ago [2].
Because SNe and their ejecta are a site for dust formation, there might be a chance of finding such radionuclides in dust particles deposited in such terrestrial archives, like deep-sea sediments. The measurements will be carried out with accelerator mass spectrometry (AMS) utilizing laboratories with the highest sensitivities for these long-lived radionuclides.
[1] K. Knie, et al., Physical Review Letters 93, 17 (2004).
[2] B. Fuchs et al., Monthly Notices of the Royal Astronomical Society 373, 993-1003 (2006).

Keywords: supernovae; AMS; radionuclide; sediments

Related publications

  • Poster
    496. Wilhelm und Else Heraeus-Seminar - Astrophysics with modern small-scale accelerators, 06.-10.02.2012, Bad Honnef, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17777
Publ.-Id: 17777


Supernova-Dust in Deep-Sea Sediment Cores

Feige, J.; Wallner, A.; Winkler, S. R.; Merchel, S.; Fifield, L. K.; Korschinek, G.; Rugel, G.

Because supernovae (SNe) and their ejecta are a site for dust formation, there might be a chance of finding supernova-produced radionuclides in dust particles deposited in terrestrial archives, like deepsea sediments. Measurements will be carried out with Accelerator Mass Spectrometry (AMS), which provides the highest sensitivity for measurements of long-lived radionuclides with half-lifes in the order of million years.
An indication to recent SN activity in our solar neighborhood is the existence of a thin, hot cavity in the local insterstellar medium, embedding our solar system. This so called superbubble, the Local Bubble, was produced by multiple SN explosions, starting ~14 Myr ago (Fuchs et al. 2006). Nuclides, which are synthesized in massive stars and during their explosions, are then entrained in the SN shell, condensed into dust, and may be transported to the solar system and thus into Earth archives, if such an event happens within a short distance.
Two deep-sea sediment cores originating from the Indian Ocean have been selected to search for the SN-produced radionuclides 26Al, 53Mn, 60Fe and 244Pu in the time range of 2-3 Myr. We aim to measure these isotopes at different laboratories with high time resolution with the goal to confirm a previously found SN signal in a ferromanganese crust from the Pacific Ocean (Knie et al. 2004),

Keywords: supernovae; AMS; radionuclide; sediments

Related publications

  • Poster
    International conference of the European Science Foundation EuroGENESIS CoDustMas network action, 05.-08.11.2012, Ascona, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-17776
Publ.-Id: 17776


AMS within CoDustMas: Nanodiamonds and SN-signatures

Wallner, A.; Vockenhuber, C.; Güttler, D.; Feige, J.; Fifield, L. K.; Korschinek, G.; Melber, K.; Merchel, S.; Ott, U.; Paul, M.; Rugel, G.; Steier, P.; Tims, S.

Via accelerator mass spectrometry (AMS) two relevant aspects to dust formation and evolution are studied in the laboratory: First, the measurement of trace element isotope ratios in presolar nanodiamonds isolated from meteorites, e.g. isotope ratios of stable Pt isotopes to extract r-process nucleosynthesis signatures. Recent experiments demonstrate the applicability of AMS for measuring Pt isotope signatures in material from the Allende meteorite [1,2]. The second aspect relates to the search for live supernova (SN)-produced radionuclides in terrestrial deep-sea archives [3-5]. In particular, we focus on longer-lived isotopes with half-lives of the order of million years. Previous time-resolved measurements of a deep-sea manganese crust identified a clear 60Fe enrichment about 2.5 Ma in the past [6]. This anomaly is interpreted as evidence for a nearby SN. With improved time resolution we continue this search by investigating two deep-sea sediment cores from the Indian Ocean for a possible signal of the SN-candidates 26Al, 53Mn, 60Fe, and potentially 244Pu [7].
An overview of the technique of AMS will be given and its potential for such studies and some selected applications will be discussed. In particular, the experimental proof of r-process scenarios via the direct observation of nuclides generated in the r-process such as the significance of new data for Pt isotope ratios measured in nanodiamonds will be presented and new technical approaches will be detailed [1,2]. We will exemplify the high sensitivity of AMS via the search of r-process 244Pu complementing the recent finding of live 60Fe in a manganese crust.
References: [1] U. Ott et al. PASA 29 (2012) 90; [2] A. Wallner et al. NIMB (2012); [3] J. Ellis et al., AstrophysJ. 470 (1996) 1227; [4] G. Korschinek et al., Radiocarbon 38 (1996) 68; [5] M. Paul et al., J.Radioanal.Nucl.Chem. 272, (2007) 243; [6] K. Knie et al. PRL 93 (2004) 171103; [7] J. Feige et al. PASA 29 (2012) 109.

Keywords: AMS; supernova; radionuclide; presolar grains; nanodiamonds; deep-sea sediments; meteorite

Related publications

  • Poster
    International conference of the European Science Foundation EuroGENESIS CoDustMas network action, 05.-08.11.2012, Ascona, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-17775
Publ.-Id: 17775


Evidences for a more restricted Icelandic Ice cap re-advance after the Bølling warming period

Meriaux, A.-S.; Delunel, R.; Merchel, S.; Finkel, R. C.

Moraines dated north of Vatnajökull by cosmogenic surface exposure dating show that the Icelandic Ice cap (IIS) was less extended during the Younger Dryas than previously suggested. The data imply that this glacial advance was more complex and restricted in some glacial valleys in NE Iceland. While the IIS margins are relatively well constrained offshore by marine or coastal evidences, little is known about their onshore characteristics and rates of recession during the warmer Holocene periods. This is especially the case in the NE of Iceland where volcanic activity and major outburst floods (jökulhlaups) have removed a large amount of morphological evidences of past ice margins. Our study aimed at filling this chronological gap of the IIS inland during the late Quaternary deglaciation by dating past preserved ice margins using 36Cl and 3He cosmogenic nuclides. We studied moraines and outwash located 44 km, 48 km and 60 km north of Vatnajökull, between the Jökulsà à Fjöllum and Jökulsà à Brú, the main northern glacial river systems draining the icecap. Preliminary 36Cl ages of the northernmost moraine at Skessugardur, 60 km north of present-day IIS and 65 km away from the coastline, indicate that the minimum exposure ages derived from Ca-rich plagioclases range from 11.0 ± 1.2 ka to 13.4 ± 1.4 ka with an average at 12.2 ± 1.0 ka (±1 sigma=6), using the local Icelandic production rates for Ca spallation of Licciardi et al. (2008). These ages are close to the Younger Dryas at a time when the Icelandic Ice Sheet is thought to have re-advanced further north toward the coastline. Overall, our results call for a revision of our understanding of the IIS deglaciation history and provide new tie-points for the calibration of the IIS models.
References: Licciardi et al., EPSL 267 (2008) 365–377.

Keywords: Ice sheets; Quaternary geochronology; Cosmogenic-nuclide exposure dating; AMS; TCN; radionuclide

  • Poster
    American Geophysical Union, Fall Meeting 2012, 03.-07.12.2012, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-17774
Publ.-Id: 17774


Decadal to Millennial scale erosion rates in the Nepal Himalayas

Andermann, C.; Bonnet, S.; Gloaguen, R.; Crave, A.; Merchel, S.; Braucher, R.; Bourlès, D. L.

On a sub-millennial time scale the spatial distribution of erosion is controlled to first order by tectonics, relief, and possibly precipitation, and secondly by vegetation, lithology, temperature and human activity. The Himalayas form a very distinct orographic barrier with a pronounced rainfall gradient from the South to the North and have a very rugged terrain, causing highly dynamic surface processes and fast erosion rates. Thus, the Himalayas provide an ideal site of investigation to study erosion and constrain its controlling factors. In this contribution we present an integrated comparison of mean catchment erosion rates, calculated from in-situ produced 10Be cosmogenic isotope concentration in river sands (representative for millennial time scales) and suspended sediment measurements (integrating the annual to decadal time spans). We discuss erosion rates and patterns in the context of precipitation-landscape features of the studied catchments. The samples cover all major rivers, and several minor tributaries of the Narayani watershed (30,000 km2) in central Nepal. They represent all lithologies, topographic units and climate regimes across the Himalayan range. The erosion rates, both from cosmogenic nuclide analysis and suspended sediment measurements, range from 0.1 to 4 mm/yr. These agree well between the two methods and also with already published data for the major outlet stations at the Himalayan front. However, in the Middle and High Himalayas the cosmogenic erosion rates are significantly higher than those from suspended sediment measurements. While on the short term (intra-annual) a clear relation between precipitation and erosion can be observed, the cosmogenic erosion rates show no clear dependency with the basin wide precipitation pattern. Furthermore, no relation could be observed with the dominant lithological units and the degree of glaciation.
Our observations confirm the overall established relationship between erosion rates, relief and slope, showing clearly that topography exerts a predominant control on spatial erosion rates on the millennial timescale. However, we observe a different relationship between main stream basins (> 250 km2) and small tributary basins (< 250 km2). Small basins show in general lower erosion rates than larger basins for respectively the same topographic characteristics.

Keywords: Hydrology; Erosion; Geomorphological geochronology; hillslope; AMS; TCN; radionuclide

Related publications

  • Poster
    American Geophysical Union, Fall Meeting 2012., 03.-07.12.2012, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-17773
Publ.-Id: 17773


Ion-irradiation induced damage in FeCr alloys characterized by nanoindentation

Heintze, C.; Bergner, F.; Hernández-Mayoral, M.

Self-ion irradiation in combination with nanoindentation offers the possibility to characterize irradiation damage in a broad range of irradiation temperature and fluence. Nanoindentation results are reported for binary FeCr alloys of commercial purity with nominal chromium contents of 2.5, 9 and 12 at%. The irradiation conditions considered include irradiations at room temperature, 300°C and 500°C. Special features of this work are roughly rectangular damage profiles produced by multi-step irradiations with different ion energies and exploitation of the load dependence of hardness for indentation loads in the range of 2 to 500 mN. The effects of Cr content, fluence and irradiation temperature are discussed. Irradiation-induced changes of the microstructure were characterized by means of transmission electron microscopy (TEM). Hardening features and their contribution to the observed irradiation-induced hardness changes will be discussed in the framework of a tentative two-feature hardening model. Small-angle neutron scattering (SANS) data reported for neutron-irradiated conditions of the same alloys will be taken into account.

Keywords: Self-ion irradiation; nanoindentation; TEM; irradiation hardening; FeCr alloys

  • Invited lecture (Conferences)
    CAARI 2012 - 22nd International Conference on the Application of Accelerators in Research and Industry, 05.-10.08.2012, Fort Worth, USA

Permalink: https://www.hzdr.de/publications/Publ-17772
Publ.-Id: 17772


Complexation behaviour of U(VI) and Eu(III) with Schiff Bases investigated by laserinduced spectroscopy

Lindner, K.; Günther, A.; Bernhard, G.

Actinides and lanthanides play an increasing important role in present time. Actinides can be released into the natural environment especially from mining areas by weathering, erosion and anthropogenic activities as well as by nuclear incidents and thus represents a hazard potential for humans. Lantha-nides occur in nature rarely, but they are significant in the glass and ceramics industries, metallurgy and the cracking of petroleum. New supramolecular complexing agents with N, O, S donor function are developed to separate the metals of the d- and f-block and enriched rare earths. Schiff Bases are essential basic components of these new organic ligands. In this study the complexation of uranium(VI) and europium(III) with the Schiff bases N-benzylideneaniline (NBA), 2-(2-hydroxybenzyliden-amino)phenol (HBAP) and alpha-(4-hydroxyphenyl-imino)-p-cresol (HPIC) was investigated in methanolic solution using time-resolved laserinduced fluorescence spectroscopy (TRLFS) at room and cryogenic temperature and in the case of the uranium(VI)-Schiff bases systems by applying of TRLFS with ultrashort laser pulses (fs-TRLFS).
The measurements of the uranyl luminescence in alcoholic solution at room temperature show strong quenching effects by solvent. These quenching effects could be minimized by measurements at cryogenic temperature (153 K). There is a decrease in fluorescence of the uranium(VI) with the addition of the Schiff Base. A wavelength shift can not be observed, which indicate that the complex seems not to fluoresce.
The europium(III) fluorescence at room temperature is not affected by the methanol. But it turns out that the europium(III) in methanol solution forms an asymmetric complex in comparison to the Eu(III)-water complex. The europium(III) fluorescence decrease with addition of Schiff Base. The observed splitting of the peaks indicates that two different europium(III) species exist in the system.
The fs-TRLFS as a sensitive speciation technique was used to determine the luminescence properties of formed complexes in the uranium(VI)-NBA, uranium(VI)-HBAP and uranium(VI)-HPIC systems. The emission signals show hypsochromic, bathochromic or hypsochromic shifts in comparison to the emission maxima of the uncomplexed ligand. The intensity of the ligand fluorescence increase with the increasing uranium(VI) concentration. The fs-TRLFS investigation opens up the possibilities for the determination of very short-lived complex species via the fluores-cence of the organic compounds by delocalized p-electron systems. Corresponding to the first analyses of the time resolved measurements the luminescence lifetimes of the free ligand and the uranium(VI) complex species are in the range from 2-4 ns. Through the change of the emission properties of organic ligands or metals can be observed the complexation with uranium(VI) and europium(III) and calculated corresponding complex formation constants.

Keywords: fs-TRLFS; Cryo TRLFS; uranium(VI); europium(III); Schiff Bases

  • Poster
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.11.-07.12.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17771
Publ.-Id: 17771


Lower head failure

Altstadt, E.

During a severe accident in a pressurized water reactor with core melt, the reactor pressure vessel integrity may be threatened by the relocation of molten corium into the lower head and the formation of a molten pool.This book section describes the thermal and mechanical phenomena in the reactor pressure vessel.

Keywords: Reactor pressure vessel failure; core melt down; in-vessel melt retention; nuclear reactor

  • Book chapter
    Bal Raj Sehgal: Nuclear Safety in Light Water Reactors: Severe Accident Phenomenology, Amsterdam etc.: Academic Press Elsevier, 2012, 978-0-12-3888446-6, 145-155

Permalink: https://www.hzdr.de/publications/Publ-17770
Publ.-Id: 17770


Combination of spectroscopic methods for the identification of U(VI) spezies formed by selected bacteria, algae and fungi

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

Microorganisms like bacteria, algae and fungi have a significant influence on the immobilization, mo-bilization and transport of radionuclides like uranium and other heavy metals in the biological and geological environment via the soil and water path. To understand the mechanisms of uptake, trans-port, deposition, degradation and the behavior of actinides in different biological and geological sys-tems structural knowledge about the formed actinides species are of great importance and are essential for a reliable assessment of these processes.
Arthrobacter (bacteria), Chlorella vulgaris (green algae) and Schizophyllum commune (fungi) bind significant amounts of uranium(VI) in the pH range from 4 to 7 and contact time of two days. Trans-mission electron microscopy and scanning electron microscopy investigations showed mainly interac-tions of uranium with parts of cell walls of the selected biomass. By investigations of transparent fun-gal cells were identified additionally uranium containing accumulates inside originally living cells.For the determination of the functionalities, which are important for the binding and mobilization or immobilization of uranium, the interaction of uranium(VI) with metabolic active bacterial, algal and fungal cells was investigated by means of time-resolved laser-induced fluorescence spectroscopy (TRLFS) and X-ray absorption fine structure spectroscopy (EXAFS). The measured luminescence spectra of uranyl containing cell species of all investigated organisms show bathochromic shifts of the uranyl emission bands in comparison to the corresponding emission signals of the uranyl species in the initial solution independent of the uranium concentration and the pH value of the solution. The com-parison of the obtained biomass spectra with luminescence properties of uranyl model compounds demonstrated the carboxylic and organic/inorganic phosphate groups are responsible for uranium binding on the biomass with varying contributions dependent on the microbial biomass, cell status and uranium concentration in the initial sorption solution. The dominant interaction of uranium(VI) with organic/inorganic phosphate groups could be verified by corresponding EXAFS investigations.

Keywords: Bacteria; algae; fungi; uranium; TRLFS; EXAFS

Related publications

  • Poster
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17769
Publ.-Id: 17769


Transient magneto-photoluminescence quenching by intra-excitonic THz absorption

Bhattacharyya, J.; Zybell, S.; Helm, M.; Andrews, A. M.; Strasser, G.; Schneider, H.

Optical properties of III-V semiconductor heterostructures are strongly influenced by excitons. With increasing carrier confinement, as in quantum wells and quantum dots, the exciton binding energy increases. This results in distinct features in absorption and emission spectra arising from the excitonic transitions and recombinations. The temporal behavior of the optical properties of these systems is also influenced by the exciton dynamics. Recently, there has been an increasing interest on the study of intraexcitonic transitions. The energy separations of the excitonic states (1s, 2s, 2p, and so on) fall in the terahertz (THz) frequency range. Intense and tunable THz sources like free electron lasers have been used to probe these transitions. However, most experiments like optically detected magnetic resonance measurements, were done in the time integrated mode and the intraexcitonic carrier dynamics could not be probed.
Here we present our work on time resolved measurements of photoluminescence (PL) quenching in presence of a varying external magnetic field. We performed measurements on GaAs/AlGaAs multiple quantum well sample with a narrow PL line width (2 meV) associated with the 1s heavy-hole exciton. THz pulses from a free electron laser were used to induce intraexcitonic transitions resulting in the quenching of the PL. The quench manifested itself as a dip in the PL transient during the incidence of the THz pulse and the depth of the dip was proportional to the THz absorption. The intraexcitonic transition energies were tuned using an external magnetic field. Excitonic 1s-2p and cyclotron resonances appeared as maxima in the plot of the dip depth vs. magnetic field. Time resolved measurement enabled us to investigate the relaxation dynamics of the 2p state which does not undergo radiative recombination and thus cannot be observed directly in the PL spectra. The carriers excited to the 2p state, by the THz pulse, eventually relaxed back to the 1s-state resulting in the gradual recovery of the 1s PL intensity after the quench. Some of the carriers in the 2p state however got scattered to the 2s state resulting in the enhancement of the 2s emission during the incidence of the THz pulse. This is a direct consequence of intraexcitonic carrier transfer between the 2p and 2s states. From magnetic field dependence of the THz induced 2s emission intensity we showed the possibility of externally controlling intraexcitonic transitions.

Keywords: excitons; terahertz; GaAs quantum wells; transient photoluminescence

Related publications

  • Poster
    ICPS2012 - 31st International Conference on the Physics of Semiconductors, 29.07.-03.08.2012, Zürich, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-17766
Publ.-Id: 17766


Untersuchungen zur magnetfeldkontrollierten Auftriebskonvektion in einem Czochralski-Tiegel

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

Die Untersuchungen zur physikalischen Modellierung der Strömung in einer Czochralski-Geometrie umfassen Ultraschall-Doppler Geschwindigkeits- und Temperaturmessungen, Letztere mit dünnen, und damit hinreichend schnell ansprechenden, Thermoelementen. Um ähnliche Wärmetransporteigenschaften, wie sie bspw. bei der Züchtung von Siliziumkristallen vorliegen, zu haben, wurde die niedrig-schmelzende ternäre Legierung GaInSn eingesetzt. Die kleine Prandtlzahl Pr « 1 dieses de facto Standard-Modellfluids für derartige Untersuchungen liegt im Bereich der Halbleiterschmelzen und sorgt für die Dominanz von Wärmeleitung über konvektiven Transport. Das Strömungsfeld zeigt eine komplexe nicht achsen­sym­metrische Topologie. Reine Moden mit einer bestimmten azimuthalen Wellenzahl, über die in der Literatur oftmals berichtet wird, wurden nicht gefunden. Vielmehr manifestiert sich die Konvektionsstruktur in der Überlagerung der achsen­symmetrischen (azimuthale Wellenzahl m = 0) mit einer monozellulären (m = 1) Mode. Die Temperaturmessungen zeigen, dass die in vielen anderen Arbeiten gefundene Dämpfung der unerwünschten auftriebsinduzierten Tempe­ra­tur­fluk­tu­ationen durch Anwendung eines rotierenden Magnetfeldes nicht reproduziert werden können.

Keywords: Crystal growth; Czochralski technique; electromagnetic flow control; damping of turbulence; rotating magnetic field

  • Lecture (Conference)
    Elektroprozesstechnik, 06.-07.09.2012, Ilmenau-Heyda, Deutschland
  • Contribution to proceedings
    Elektroprozesstechnik, 06.-07.09.2012, Ilmenau-Heyda, Deutschland
    Tagungsband Elektroprozesstechnik 2012

Permalink: https://www.hzdr.de/publications/Publ-17765
Publ.-Id: 17765


A tool for semiautomatic evaluation of PET data for range verification in ion beam therapy

Helmbrecht, S.; Enghardt, W.; Georg, D.; Kuess, P.; Schubert, M.; Fiedler, F.

Introduction:

The positron emission tomography (PET) is a clinically proven method for verification of ion beam therapy. Due to fundamentally different physical processes leading to dose and activity the evaluation is based upon a comparison between the β+-emitter distribution measured during or after irradiation and a Monte-Carlo prediction from the treatment plan. A visual comparison slice by slice requires well trained personnel and is very time consuming. Furthermore, the reproducibility is low.
A software is presented that allows a semi-automatic and guided comparison of prediction an measurement to overcome the mentioned difficulties.

Material and Methods:

The range of the primary particles is the crucial parameter affecting the position of dose deposition and also the activity distribution. A direct extraction of the range from a β+-emitter distribution is not feasible, however, the range difference between two data sets can be determined. Therefore, a one dimensional range comparison algorithm was enhanced and extended to three dimensions. It generates a two dimensional matrix of range deviations, that represents the complete activity distribution.
A comprehensive software has been developed providing an intuitive graphical user interface to perform different evaluation methods. A statistical evaluation provides information about the overall agreement between measurement and prediction. System inherent fluctuations can be easily taken into account by using the statistic criterion. However, small deviations can be overlooked.
Hence the software provides different methods for analysis of local deviations. The matrix of range deviations is projected into the CT images to allow a fast localization of possible critical areas.
The gamma index is used to take stochastic fluctuations into account that are caused by the relatively low cont rates compared to the classic diagnostic usage of PET.
A common issue during fractionated ion beam therapy is the filling of cavities in the beam path due to physiological processes between two fractions. Such a change in the filling status can cause severe changes in the particle range and thereby a failure in dose deposition. Hence the filling of cavities is automatically evaluated, the result is presented graphically to the user.
For the development in-beam PET data captured at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany during patient treatment from 1997 to 2008 was used. All fractions from 6 patients were evaluated visually to check the performance of the range comparison algorithm and the feasibility of the different displaying possibilities of the software.
The feasibility of the statistical criterion has been tested on artificial range modifications. In simulated β+ -emitter distributions of 6 patients the range was shifted in the shape of a truncated quadratic pyramid with a maximum change of ± 4 mm, ± 6 mm and ± 10 mm water equivalent path length. These modified distributions have been compared to the measurement. By applying the statistical criterion a classification of the data sets was performed, i.e. the system had to decide whether a distribution was range modified.

Results:

From the classification results of the data sets the true positive and false positive rate was calculated to quantify the quality of the algorithm. For ±10 mm a true positive rate (TPR) of 90 % and a false positive rate (FPR) of 12 % and was reached, for ±6 mm a TPR of 82 % and a FPR of 26 % and for ± 4 mm a TPR of 72 % and an FPR of 26 %, respectively. This shows the abilities of the statistical criterion but also the limitations in the case of small deviations that make a local evaluation necessary. The comparison of the visual evaluation and the local results of the algorithm shows a good correlation. Differences in the result of the range comparison algorithm and the valuation of a human evaluator are rare.

Conclusion:

Despite system inherent difficulties like low count rates and physiological washout effects that blur the obtainable images, PET is a powerful tool for range verification in ion beam therapy. For a routine application a systematic and easy usable software tool is required. The developed tool combines a statistical approach to gain information about the overall agreement between measurement and prediction with local criterion. An intuitive graphical user interface allows also less trained personnel to evaluate the PET data.

Keywords: PT-PET; ion-beam therapy

  • Contribution to proceedings
    ICTR-PHE 2012 - International Conference on Translational Research in Radiation Oncology, 01.03.2012, Genf, Schweiz: Elsevier
  • Open Access Logo Abstract in refereed journal
    Radiotherapy and Oncology 102(2012)Suppl., S42-S43
    DOI: 10.1016/S0167-8140(12)70080-4

Permalink: https://www.hzdr.de/publications/Publ-17764
Publ.-Id: 17764


Fano effect due to ponderomotive coupling in intersubband response of semiconductor quantum wells

Baudisch, M.; Wagner, M.; Schneider, H.; Stehr, D.; Helm, M.; Atkinson, P.; Huo, Y.; Schmidt, O. G.; Andrews, A. M.; Strasser, G.

Using terahertz-time-domain spectroscopy, it has been demonstrated before that an intersubband transition in photoexcited undoped quantum wells reveals a Fano-like line shape in transmission spectra due to the phase-sensitive coupling of ponderomotive and intersubband currents [ D. Golde et al. Phys. Rev. Lett. 102 127403 (2009)]. In the present experimental study on GaAs/AlGaAs quantum wells we attempt to delineate the observability conditions of this phenomenon. We find that intensity-based Fourier-transform infrared (FTIR) spectroscopy cannot uncover these ponderomotive effects. However, for time-domain spectroscopy they are shown not to be limited to the case of optically excited electrons, but can be seen in doped samples as well.

Keywords: intersubband transition; terahertz; Fano; ponderomotive; quantum well; GaAs/AlGaAs

Permalink: https://www.hzdr.de/publications/Publ-17763
Publ.-Id: 17763


Terahertz nonlinear optics using intra-excitonic quantum well transitions: Sideband generation and AC Stark splitting

Wagner, M.; Schneider, H.; Stehr, D.; Winnerl, S.; Andrews, A. M.; Schartner, S.; Strasser, G.; Helm, M.

We present experiments investigating nonlinear optics in the terahertz (THz) range related to the 1s–2p intra-excitonic heavy-hole transition in GaAs/AlGaAs multiquantum wells (MQWs). Driven by intense THz fields of the Dresden free-electron laser the system exhibits two different phenomena: (i) we observe efficient near-infrared (NIR) sideband generation as a perturbative effect in the transmission of a narrowband NIR laser, and (ii) we present unambiguous evidence for the intra-excitonic Autler–Townes splitting, a non-perturbative effect.

Keywords: AC Stark effect; Autler–Townes effect; excitons; sidebands; terahertz

Related publications

Permalink: https://www.hzdr.de/publications/Publ-17762
Publ.-Id: 17762


Pt(II) and Pd(II) Pyrrolidine-Dithiocarbamates Investigated by XPS

Wenisch, R.; Montagner, D.; Helm, M.; Forrer, D.; Tondello, E.; Gross, S.

In the present contribution, a series of four metal dithiocarbamates, namely 1-pyrrolidinecarbodithioate methyl ester (PyDTM) of Pd(II) and Pt(II), PtCl2(PyDTM), PtBr2(PyDTM), PdBr2(PyDTM), PdCl2(PyDTM), were analysed by x-ray Photoelectron Spectroscopy (XPS). Besides the wide scan spectra, detailed spectra for the C 1s, O 1s, N 1s, S 2s, S 2p, Pt 4f (for Pt-based compounds), Pd 3d (for Pd-based compounds), Cl 2p (for Cl containing compounds), Br 3p (for Br containing compounds) regions were acquired and the related data are presented and discussed.

Keywords: organic compounds; palladium compounds; X-ray photoelectron spectra; dithiocarbamates; coordination compounds; metal-sulphur bond; platinum; palladium; sulphur

Permalink: https://www.hzdr.de/publications/Publ-17761
Publ.-Id: 17761


Reconstruction of 4D in-beam PET data for quality control of moving target irradiation in ion beam therapy

Laube, K.; Fiedler, F.; Bert, C.; Saito, N.; Enghardt, W.

no abstract available

Permalink: https://www.hzdr.de/publications/Publ-17760
Publ.-Id: 17760


GaAs photocathode status in Dresden-Rossendorf

Xiang, R.; Arnold, A.; Murcek, P.; Teichert, J.

We introduce in this talk the developing status of GaAs photocathode for SRF gun. A new preparation chamber and transfer system has been designed. The test result of unactived bulk GaAs in SRF gun is reported here. Some experience for NEA-photocathode activation through GaN experiments is discussed.

Keywords: GaAs; photocathode; SRF gun

Related publications

  • Invited lecture (Conferences)
    EuCARD SRF Annual Review, 29.-30.03.2012, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-17759
Publ.-Id: 17759


Curium(III) as intrinsic luminescence probe for direct speciation studies in biogeochemical systems

Moll, H.; Lütke, L.; Raff, J.; Brendler, V.; Bernhard, G.

Knowledge concerning the speciation of actinides is essential to understand their fate and behavior in the environment. Moreover, the speciation of actinides influences their behavior in biological systems (e.g., microbes) in terms of chemical toxicity and radiotoxicity. Since many years we are successfully operating a unique pulsed flash lamp pumped Nd:YAG-­OPO laser system (Powerlite Precision II 9020 laser equipped with a Green PANTHER EX OPO from Continuum, Santa Clara, CA, USA) designed especially to detect the luminescence of trivalent actinides and lanthanides (e.g., Cm, Eu). The luminescence spectra were detected using an optical multi-channel analyzer-system, consisting of an Oriel MS 257 monochromator and spectrograph with a 300 or 1200 line mm-1 grating and an Andor iStar ICCD camera (Lot-Oriel Group, Darmstadt, Germany). The potential of this system for direct speciation studies of Curium(III) in biogeochemical systems will be presented on the basis of selected examples. These examples cover geochemical systems: the aqueous Cm(III) phosphate system [1] and biological systems: (a) Cm(III) speciation studies with cells of a groundwater strain of Pseudomonas fluorescens [2] and (b) Cm(III) complexation with bacterial surface-layer proteins [3].

Acknowledgement: This work was partly funded by BMWi under contract number 02E10618. The authors are indebted to the U.S. Department of Energy, Office of Basic Energy Sciences, for the use of 248Cm via the transplutonium element production facilities at Oak Ridge National Laboratory; 248Cm was made available as part of collaboration between HZDR and the Lawrence Berkeley National Laboratory (LBNL).

[1] Moll, H. et al. (2011) Radiochim. Acta 99, 775-782.
[2] Moll, H. et al. (2012) Geomicrobiol. J., in press.
[3] Moll, H. et al. (2011) Poster at the 13th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products (MIGRATION 2011), 18.-23.09.2011, Beijing, PR China.

Keywords: curium; TRLFS; speciation; biogeochemical systems

  • Contribution to proceedings
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland
  • Poster
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17758
Publ.-Id: 17758


Cellular and molecular properties of 90Y-labeled cetuximab in combination with radiotherapy on human tumor cells in vitro

Saki, M.; Toulany, M.; Sihver, W.; Zenker, M.; Heldt, J.-M.; Mosch, B.; Pietzsch, H.-J.; Baumann, M.; Steinbach, J.; Rodemann, H. P.

Purpose. Anti-EGFR antibody cetuximab (C225) is used in combination with radiotherapy of head and neck squamous cell carcinoma (HNSCC) patients. We investigated whether conjugation of cetuximab with trans-cyclohexyl-diethylene-triamine-pentaacetic acid (CHX-A″-DTPA) and radiolabeling with 90Yttrium affect the molecular and cellular function of cetuximab and improve its combined effect with external-beam irradiation (EBI).Methods. The following cell lines were used: HNSCC UT5, SAS, FaDu, as well as A43, Chinese hamster ovary cells (CHO), and human skin fibroblast HSF7. Binding affinity and kinetics, specificity, retention, and the combination of 90Y-cetuximab with EBI were evaluated.Results. Control cetuximab and CHX-A″-DTPA-cetuximab blocked the proliferation activity of UT5 cells. In combination with EBI, CHX-A″-DTPA-cetuximab increased the radiosensitivity of UT5 to a similar degree as control cetuximab did. In contrast, in SAS and HSF7 cells neither proliferation nor radiosensitivity was affected by either of the antibodies. Binding [90Y]Y-CHX-A″-DTPA-cetuximab (90Y-cetuximab) to EGFR in HNSCC cells occurred time dependently with a maximum binding at 24 h. Retention of 90Y-cetuximab was similar in both HNSCC cell lines; 24 h after treatment, approximately 90% of bound activity remained in the cell layer. Competition assays, using cell membranes in the absence of an internalized fraction of cetuximab, showed that the cetuximab affinity is not lost as a result of conjugation with CHX-A″-DTPA. Cetuximab and CHX-A″-DTPA-cetuximab blocked EGF-induced Y1068 phosphorylation of EGFR. The lack of an effect of cetuximab on EGF-induced Akt and ERK1/2 phosphorylation and the inhibition of irradiation (IR)-induced Akt and ERK1/2 phosphorylation by cetuximab were not affected by DTPA conjugation. 90Y-cetuximab in combination with EBI resulted in a pronounced inhibition of colony formation of HNSCC cells.Conclusions. Conjugation of CHX-A″-DTPA to cetuximab does not alter the cellular and biological function of cetuximab. 90Y-labeling of cetuximab in combination with EBI may improve radiotherapy outcome.

Keywords: Head and neck squamous cell carcinoma; EGFR; Cetuximab; 90Yittrium; 90Y-cetuximab

Permalink: https://www.hzdr.de/publications/Publ-17756
Publ.-Id: 17756


Prozess und Ergebnisse der Visions- und Zielbildung in einem komplexen Forschungsprojekt am Beispiel des ProSIN Projekts DER

Klossek, A.

Die identifizierte Forschungslücke wird im vorliegenden Arbeitspapier aufgegriffen und konkret anhand des Fallbeispiels der Kooperationsplattform „Deutsches EnergieRohstoff-Zentrum Freiberg (DER)“ analysiert. Ziel des vorliegenden Arbeitspapieres ist es dementsprechend, den Entstehungs- und Gestaltungsprozess einer Vision, von Zielen und von Strategien in komplexen Forschungsprojekten strukturiert und fallstudienbasiert anhand des DER Projektes zu beschreiben. Aus der Fallstudienanalyse sollen ferner Gestaltungs- und Optimierungsansätze für zukünftige Kooperationsplattformen ähnlicher Art abgeleitet werden.

  • Open Access Logo Contribution to external collection
    in: DER Working Papier Series Nr. 1/2012, Freiberg: Deutsches EnergieRohstoff-Zentrum, 2013

Permalink: https://www.hzdr.de/publications/Publ-17755
Publ.-Id: 17755


EtherCAT Feldbusknoten: Entwicklung, Systemunterstützung und -kompatibilität

Kaever, P.

Die Verwendung selbst entwickelter Feldbusknoten und deren Einbindung in kommerzielle Automatisierungssysteme erfordert in der frühen Phase des Produktlebenszyklus einen erhöhten Entwicklungsaufwand. Nach erfolgreicher Integration bieten Hersteller von Automatisierungssystemen eine langfristig stabile und leistungsfähige Umgebung zur Projektierung und Programmierung von Anlagen, welche langfristig den Aufwand zur Pflege minimiert. Zur Überprüfung der Funktionsfähigkeit des Gesamtsystems ist die durch Testwerkzeuge unterstützte Systemkompatibilität eine entscheidende Voraussetzung. Die Vorgehensweise bei der Systemintegration eines Slave Device und der Prüfung der Systemkompatibilität wird im Folgenden vorgestellt.

Keywords: Fieldbus; slave devices; product life cycle; industrial Ethernet; EtherCAT; system integration; device test

  • Open Access Logo Contribution to proceedings
    103. Tagung der Studiengruppe elektronische Instrumentierung im Frühjahr 2012, 12.-14.3.2012, Dresden, Deutschland
    103. Tagung der Studiengruppe elektronische Instrumentierung im Frühjahr 2012, ed.: Peter Göttlicher, 22607 Hamburg, Germany: Verlag Deutsches Elektronen-Synchrotron, 978-3-935702-65-2, 47-53
  • Lecture (Conference)
    103. Tagung der Studiengruppe elektronische Instrumentierung im Frühjahr 2012, 12.-14.3.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17754
Publ.-Id: 17754


Diffusive racetrack oxidation in a Ti sputter target by reactive high power impulse magnetron sputtering

Audronis, M.; Abrasonis, G.; Munnik, F.; Heller, R.; Chapon, P.; Bellido-Gonzalez, V.

This paper reports experimental results for near-surface Ti sputter target oxidation in a magnetron racetrack during reactive high power impulse magnetron sputtering (HIPIMS) at various optical plasma monitoring set-points in the transition region between ‘metal’ and ‘poisoned’ target states. Oxygen depth profiles were obtained by nuclear reaction analysis and glow discharge optical emission spectroscopy. Ti target surface oxidation depth as induced by reactive HIPIMS was found to depend on the process set-point as well as discharge conditions. Deepest oxidation was observed when operating close to ‘fully poisoned (FP)’ or in ‘FP’ regime with oxygen profiles extending as deep as ∼0.5μm (oxygen concentration >=5 at%). Oxygen profiles obtained indicate the occurrence of oxygen bulk diffusion. Process induced elevated target surface temperature, magnetic field and plasma assistance are suggested to contribute substantially to these profiles. Based on these findings it is proposed that ion-bombardment-assisted thermal diffusion is a third target poisoning mechanism that can be taking place and is therefore important in reactive HIPIMS in addition to the two currently accepted mechanisms—ion implantation and chemisorption. Under the conditions investigated in this work, diffusive oxidation was most significant when operating in the lower part of the hysteresis loop. Reactive HIPIMS processes that will facilitate significant diffusive sputter target surface oxidation will also be expected to exhibit wider hysteresis and longer target cleaning times after substantial target poisoning.

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Permalink: https://www.hzdr.de/publications/Publ-17753
Publ.-Id: 17753


Position-resolved Positron Annihilation Lifetime Spectroscopy

Wagner, A.; Butterling, M.; Fiedler, F.; Fritz, F.; Kempe, M.; Cowan, T. E.

A new method which allows for position-resolved positron lifetime spectroscopy studies in extended volume samples is presented. In addition to the existing technique of in-situ production of positrons inside large (cm3) bulk samples using high-energy photons up to 16 MeV from bremsstrahlung production, granular position-sensitive photon detectors have been employed. A beam of intense bremsstrahlung is provided by the superconducting electron linear accelerator ELBE (Electron Linear Accelerator with high Brilliance and low Emittance) which delivers electron bunches of less than 10 ps temporal width and an adjustable bunch separation of multiples of 38 ns, average beam currents of 1 mA, and energies up to 40 MeV. Since the generation of bremsstrahlung and the transport to the sample preserves the sharp timing of the electron beam, positrons generated inside the entire sample volume by pair production feature a sharp start time stamp for positron annihilation lifetime studies with high timing resolutions and high signal to background ratios due to the coincident detection of two annihilation photons. Two commercially available detectors from a high-resolution medial positron-emission tomography system are being employed with 169 individual Lu2SiO5:Ce scintillation crystals, each. In first experiments, a positron-lifetime gated image of a planar Si/SiO2 (pieces of 1 cm × 2 cm size) sample and a 3-D structured metal in Teflon target could be obtained proving the feasibility of a three dimensional lifetime-gated tomographic system.

Keywords: position-resolved positron lifetime spectroscopy; superconducting LINAC

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Permalink: https://www.hzdr.de/publications/Publ-17752
Publ.-Id: 17752


Isospin observables from fragment energy spectra

Liu, T. X.; Lynch, W. G.; Tsang, M. B.; Hodges, R. K.; Liu, X. D.; Tan, W. P.; van Goethem, M. J.; Verde, G.; Wagner, A.; Xi, H. F.; Xu, H. S.; Famiano, M.; de Souza, R. T.; Charity, R. J.; Sobotka, L. G.; Showalter, R. H.

The energy spectra of light charged particles and intermediate mass fragments from 112Sn+112Sn and 124Sn+124Sn collisions at an incident energy of E/A=50 MeV have been measured with a large array of Silicon strip detectors. We used charged particle multiplicities detected in a near-4 array to select data from the central collision events. We study isospin observables analogous to ratios of neutron and proton spectra, including double ratios and yield ratios of t/3He and of asymmetries constructed from fragments with Z=3-8. Using the energy spectra, we can construct these observables as functions of kinetic energy and observe a large difference in the fragment observables if fragments contributing to sequential decays are included.

Keywords: intermediate mass fragment; nuclear multifragmentation; silicon strip detector; CsI detector; light charged particle spectra

Permalink: https://www.hzdr.de/publications/Publ-17751
Publ.-Id: 17751


Visualisierung der Cyclooxygenase-2 mittels optischer Bildgebung in vitro und in vivo bei tumorassoziierten Prozessen

Tondera, C.

kein Abstract verfügbar

  • Diploma thesis
    Friedrich-Schiller-Universität Jena, Biologisch-Pharmazeutische Fakultät, 2012
    100 Seiten

Permalink: https://www.hzdr.de/publications/Publ-17750
Publ.-Id: 17750


Photobiology: the biological impact of sunlight in carcinogenesis

Pietzsch, J.

kein Abstract verfügbar

  • Invited lecture (Conferences)
    1st Klixx Solar Workshop on Photophysics, Photochemistry and Photobiology, 13.-14.07.2012, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-17749
Publ.-Id: 17749


Targeting cyclooxygenase-2 and oxidant stress pathways for attenuation of radiation-induced vascular dysfunction

Pietzsch, J.; Laube, M.; Ullm, S.; Sehn, F.; Pietzsch, F.-J.; Knieß, T.

Radiotherapy of various cancers is closely associated with increased cardiovascular morbidity and mortality. Arachidonic acid metabolites are supposed to play a key role in radiation-induced vascular dysfunction.
This investigation was performed in order to evaluate the effects of novel selective cyclooxygenase-2 (Cox-2) inhibitors (coxibs) on radiation-induced formation of eicosanoids via Cox-2 and oxidant stress pathways in both human arterial endothelial cells (EC model) and rat aortic rings (AR model), respectively. In order to assess acute effects (24 h) of X-ray radiation at moderate doses (2, 4, and 10 Gy) without or with presence of coxibs (EC model: cyclopentene/indole/indomethacin derivatives; AR model: indole derivatives; celecoxib as reference) compared to sham-irradiated controls, the following parameters were measured: Cox-2 protein induction, release of prostaglandins, release of isoprostanes, and formation of lipid and protein oxidation products (LO/PO). Irradiation of EC and AR without presence of coxibs resulted in a dose-dependent augmentation of all parameters studied. When EC and AR were exposed to Cox-2 inhibitors (0.1, 1, and 10 µM), during and for 24 h post irradiation, indole derivatives showed highest potency to inhibit release of both prostaglandins and isoprostanes. Furthermore, indole derivatives significantly decreased LO/PO formation, indicating a direct interaction with oxidant stress-pathways. By contrast, both cyclopentene and indomethacin derivatives (and celecoxib) mainly inhibited prostaglandin release, but showed only slight effects on formation of isoprostanes and LO/PO. Model experiments using human low density lipoproteins showed that indole derivatives differently interact with oxidation of polyunsaturated fatty acids and protein amino acid side chains, than the cyclopentene/indomethacin derivatives, suggesting a physico-chemical rationale for observed antioxidative activity. The reduction of radiation-induced vascular dysfunction by antioxidative coxibs may widen the therapeutic window of Cox-2 targeted treatment.

  • Lecture (Conference)
    6th European Congress of Pharmacology (Ephar 2012), 17.-20.07.2012, Granada, Spain
  • Contribution to proceedings
    6th European Congress of Pharmacology (Ephar 2012), 17.-20.07.2012, Granada, Spain
    Proceedings of the 6th European Congress of Pharmacology, Bologna: Medimond, 978-88-7587-670-8, 87-90

Permalink: https://www.hzdr.de/publications/Publ-17748
Publ.-Id: 17748


18F-Labeled phosphopeptide-cell-penetrating peptide dimers with enhanced cell uptake properties in human cancer cells

Richter, S.; Bouvet, V.; Wuest, M.; Bergmann, R.; Steinbach, J.; Pietzsch, J.; Neundorf, I.; Wuest, F.

Introduction
Phosphopeptides represent interesting compounds to study and elucidate cellular protein phosphorylation/dephosphorylation processes underlying various signal transduction pathways. However, studies of phosphopeptide action in cells are severely constrained by the negatively charged phosphate moiety of the phosphopeptide resulting in poor transport through the cell membrane. The following study describes the synthesis and radiopharmacological evaluation of two 18F-labeled phosphopeptide-cell-penetrating peptide dimers. The polo-like kinase-1-binding hexaphosphopeptide H-Met-Gln-Ser-pThr-Pro-Leu-OH was coupled to cell-penetrating peptides (CPPs), either sC18, a cathelicidin-derived peptide, or the human calcitonin derivative hCT(18-32)-k7.

Methods
Radiolabeling was accomplished with the prosthetic group N-succinimidyl 4-[18F]fluorobenzoate ([18F]SFB) using both, conventional and microfluidic-based bioconjugation of [18F]SFB to N-terminal end of phosphopeptide part of the peptide dimers. Cellular uptake studies in human cancer cell lines HT-29 and FaDu cells at 4 °C and 37 °C and small animal PET in BALB/c mice were utilized for radiopharmacological characterization.

Results
Isolated radiochemical yields ranged from 2% to 4% for conventional bioconjugation with [18F]SFB. Significantly improved isolated radiochemical yields of up to 26% were achieved using microfluidic technology. Cellular uptake studies of radiolabeled phosphopeptide and phosphopeptide-CPP dimers indicate enhanced internalization of 50% ID/mg protein after 2 h for both phosphopeptide dimers compared to the phosphopeptide alone (< 1% ID/mg protein). In vivo biodistribution of 18F-labeled peptide dimers was determined with small animal PET revealing a superior biodistribution pattern of sC18-containing peptide dimer MQSpTPL-sC18 [18F]4.

Conclusion
[18F]SFB labeling of the phosphopeptide-CPP dimers using a microfluidic system leads to an improved chemoselectivity towards the N-terminal NH2 group compared to the conventional labeling approach. Cell-penetrating peptide sC18 can be considered as an ideal molecular shuttle for intracellular delivery of the Plk1-PBD-binding hexaphosphopeptide as demonstrated by its favourable radiopharmacological profile.

Keywords: 18F; Phosphopeptides; Cell-penetrating peptides (CPP); Microfluidic; Positron emission tomography (PET)

Permalink: https://www.hzdr.de/publications/Publ-17747
Publ.-Id: 17747


Experimente zur Entstehung von Titan-44 in Supernovae

Schmidt, K.

In dieser Diplomarbeit wurde das astrophysikalisch interessante Resonanztriplett der Reaktion 40Ca(α,γ)44Ti bei 4,5MeV untersucht. Am 3-MV-Tandetron des Helmholtz-Zentrums Dresden-Rossendorf wurden dafür die Energien von Protonen- und -Strahlen kalibriert, Anregungsfunktionen im Energiebereich der drei Resonanzen aufgenommen, vier CaOTargets aktiviert und deren Struktur mittels der Reaktion 40Ca(p,γ)41Sc überprüft. Im Felsenkeller-Niederniveaumesslabor wurde anschließend die Aktivität der Proben gemessen. Schließlich konnte die Summe der Resonanzstärken bei 4497 und 4510 keV -Energie im Laborsystem zu (12;8 2;3) eV und die Summe der Resonanzstärken des gesamten Tripletts, d.h. zusätzlich bei 4523 keV, zu (12;0 2;0) eV bestimmt werden. Bei der ersten Resonanzstärke konnte die Unsicherheit im Vergleich zur Literatur von 19% auf 18% verbessert werden. Außerdem bieten die Daten der vorliegenden Arbeit die Grundlage, zukünftig die Unsicherheiten noch erheblich weiter zu reduzieren.

In this thesis the astrophysically interesting resonance triplet of the 40Ca(α,γ)44Ti reaction at 4.5MeV has been studied. For this purpose energies of proton and beams provided by 3MVTandetron at Helmholtz-Zentrum Dresden-Rossendorf have been calibrated. Excitation functions of energy regions near the resonances and in-beam spectra of four different targets have been measured. The 40Ca(p,γ)41Sc reaction has been used to scan the structure of the activated targets. Afterwards their activity has been measured in the underground laboratory Felsenkeller Dresden. Hence the sum of resonance strengths at laboratory energies of 4497 and 4510 keV of (12:8 2:3) eV has been determined as well as the sum of the total triplet strength, including 4523 keV, of (12:0 2:0) eV. In the case of the first resonance, the uncertainty was decreased from 19% to 18 %. Furthermore the results of this work establish a basis for reaching much lower uncertainties in the future.

Keywords: Ti-44; supernova; nuclear astrophysics; activation; 40Ca(alpha; gamma)44Ti; Tandetron; Felsenkeller

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-020 2012
    ISSN: 2191-8708, eISSN: 2191-8716

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Publ.-Id: 17746


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