Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33168 Publications

Bulk Properties of Strongly Interacting Matter

Leupold, S.; Redlich, K.; Stephanov, M.; Andronic, A.; Blaschke, D.; Bluhm, M.; Dumitru, A.; Fodor, Z.; Friman, B.; Fuchs, C.; Kämpfer, B.; Karsch, F.; Katz, S. D.; Klähn, T.; Randrup, J.; Ratti, C.; Rebhan, A.; Rischke, D.; Rummukainen, K.; Sasaki, C.; Schaefer, B.-J.; Shuryak, E.; Thaler, M.; Wambach, J.; Weber, F.; Weise, W.; Typel, S.;
"Bulk Properties of Strongly Interacting Matter" is part of the CBM Physics Book.

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Permalink: https://www.hzdr.de/publications/Publ-15553
Publ.-Id: 15553


P0904 - E. coli-Sekretionssystem auf der Basis von S-Layer-Proteinen

Pollmann, K.; Lederer, F.; Raff, J.;
Die vorliegende Erfindung betrifft ein E. coli-Sekretionssystem auf Basis einer S-Layer-Gensequenz, deren Expressionsprodukt die Sekretion von rekombinanten Proteinen aus E. coli-Zellen vermittelt. Das Sekretionssystem eignet sich für die Anwendung in der Molekularbiologie und in der Biotechnologie. Das erfindungsgemäße Sekretionssystem basiert auf der Verwendung eines S-Layer-Proteins, einer Teilsequenz davon oder einer dazu homologen Sequenz als Sekretionssignal. Die Erfindung umfasst weiter ein Fusionsprotein, welches ein zu exprimierendes Zielprotein und das erfinungsgemäße Sekretionssignal enthält, eine Nukleinsäuresequenz, welche für ein erfindungsgemäßes Fusionsprotein kodiert, einen Expressionsvektor oder einen Klonierungsvektor für die Herstellung eines erfindungsgemäßen Fusionsproteins, eine Wirtszelle für die Expression eines erfindungsgemäßen Fusionsproteins und einen Kit sows erfindungsgemäßen Fusionsproteins aus einer Wirtszelle.
  • Patent
    DE102009032646A1: Offenlegung-05.01.2011
  • Patent
    EP2270029A1: Offenlegung - 05.01.2011; Erteilung-19.11.2014 (Validierung in AT, CH, DE, FR, GB)

Permalink: https://www.hzdr.de/publications/Publ-15552
Publ.-Id: 15552


P0905 - Hochfrequenz-Fotoelektronenquelle mit supraleitendem Hohlraumresonatorsystem stabilisierter Eigenfrequenz

Teichert, J.; Murcek, T.; Möller, K.; Arnold, A.;
Die Erfindung betrifft das Hohlraumresonatorsystem (HRS) supraleitender Hochfrequenz-Fotoelektronenquellen (SHFE), die in Elektronenbeschleunigern eingesetzt werden können. Die beschleunigten Elektronen können direkt genutzt oder mittels nachgelagerter Anordnungen zur Erzeugung von Sekundärstrahlen, wie Gamma-, Röntgen- oder Laserstrahlung dienen. Der Erfindung liegt die Aufgabe zugrunde, die bei den bisherigen supraleitenden Hochfrequenz-Fotoelektronenquellen unbefriedigende Frequenzstabilität wesentlich zu erhöhen. Die Aufgabe wird durch eine spezielle Konstruktion zur mechanischen Stabilisierung des Hohlraumresonanzsystems gelöst, wobei die für das supraleitende System erforderliche hohe Effektivität für die Kühlung weiterhin gewährleistet wird und eine einfache Montage des Systems unterstützt wird.
  • Patent
    DE102009028182B3 - 24.02.2011

Permalink: https://www.hzdr.de/publications/Publ-15551
Publ.-Id: 15551


P0903 - Mikroröhren, umfassend Bestandteile der äußeren Membran von E. coli Zellen und rekombinant exprimierte S-Layer-Proteine, Verfahren zu ihrer Herstellung und Verwendung

Pollmann, K.; Raff, J.; Lederer, F.;
Die vorliegende Erfindung betrifft röhrenartige biologische Strukturen, die sich aus der äußeren Membran von E. coli zusammensetzen und durch heterolog exprimierte rekombinante S-Layer-Proteine stabilisiert werden. Die neuartigen Mikroröhren eignen sich für die Anwendung in der Biotechnologie, Pharmazie, in der chemischen Katalyse und in der Nanotechnologie. Die erfindungsgemäßen Mikroröhren umfassen Bestandteile der äußeren Membran von E. coli Zellen und rekombinant exprimierte S-Layer-Proteine. Die Erfindung umfasst weiter ein Verfahren zur Herstellung der erfindungsgemäßen Mikroröhren, bei dem S-Layer-Proteine in E. coli-Zellen exprimiert werden und anschließend die E. coli-Zellen ggf. aus den gebildeten Mikroröhren entfernt werden, die E. coli-Zellen, welche die rekombinanten S-Layer-Proteine exprimieren, und die Verwendung der erfindungsgemäßen Mikroröhren zur Bindung von Metall aus einer wässrigen Lösung, zur Herstellung funktionalisierter Schichten, als Carrier für Enzyme oder für pharmazeutische Wirkstoffe oder als Katalysator.
  • Patent
    DE102009032645 - Erteilung 17.03.2011, Nachanmeldungen: EP (validiert in AT, DE, GB)

Permalink: https://www.hzdr.de/publications/Publ-15550
Publ.-Id: 15550


Sump simulations

Cartland Glover, G.;
Mineral wool insulation material applied to the primary cooling circuit of a nuclear reactor maybe damaged in the course of a loss of coolant accident (LOCA). The insulation material released by the leak may compromise the operation of the emergency core cooling system (ECCS), as it maybe transported together with the coolant in the form of mineral wool fiber agglomerates (MWFA) suspensions to the containment sump strainers, which are mounted at the inlet of the ECCS to keep any debris away from the emergency cooling pumps. In the further course of the LOCA, the MWFA may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Therefore, it is essential to understand the transport characteristics of the insulation materials in order to determine the long-term operability of nuclear reactors, which
undergo LOCA.
An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz1 is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effects that particles formed due to corrosion of metallic containment internals by the coolant medium have on the strainer pressure drop.
The focus of this presentation is on the numerical models that are used to predict the transport of MWFA by CFD simulations in the containment sump. Two dispersed phases were conditions to determine the influence of entrained air from a jet on the transport of fibre agglomerates through the sump. The strainer model of A. Grahn was implemented to observe the impact that the accumulation of the fibres have on the pressure drop across the strainers. The geometry considered is similar to the containment sump configurations found in Nuclear Power Plants.
Keywords: Mineral Wool Fiber Agglomerates, Loss of Coolant Accidents, Containment Sump, Computational Fluid Dynamics, Multiphase Flow
  • Contribution to proceedings
    Fachkolloquium "Partikelströmung" CD Rom, 17.-18.03.2011, Zittau and Dresden, Dresden
    Fachkolloquium "Partikelströmung" CD Rom

Permalink: https://www.hzdr.de/publications/Publ-15549
Publ.-Id: 15549


Simulations of agglomerate sedimentation and suspension

Cartland Glover, G.;
Mineral wool insulation material applied to the primary cooling circuit of a nuclear reactor maybe damaged in the course of a loss of coolant accident (LOCA). The insulation material released by the leak may compromise the operation of the emergency core cooling system (ECCS), as it maybe transported together with the coolant in the form of mineral wool fiber agglomerates (MWFA) suspensions to the containment sump strainers, which are mounted at the inlet of the ECCS to keep any debris away from the emergency cooling pumps. In the further course of the LOCA, the MWFA may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Therefore, it is essential to understand the transport characteristics of the insulation materials in order to determine the long-term operability of nuclear reactors, which undergo LOCA.
An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effects that particles formed due to corrosion of metallic containment internals by the coolant medium have on the strainer pressure drop.
The focus of this presentation is on the numerical models that are used to predict the transport of MWFA by CFD simulations. A number of pseudo-continuous dispersed phases of spherical wetted agglomerates can represent the MWFA. The size, density, the relative viscosity of the fluid-fiber agglomerate mixture and the turbulent dispersion all affect how the fiber agglomerates are transported. In the cases described here, the size is kept constant while the density is modified. This definition affects both the terminal velocity and volume fraction of the dispersed phases. Application of such a model to sedimentation in a quiescent column and a horizontal flow are examined. The scenario also presents the suspension and horizontal transport of a single fiber agglomerate phase in a racetrack type channel.
Keywords: Mineral Wool Fiber Agglomerates, Loss of Coolant Accidents, Containment Sump, Computational Fluid Dynamics, Multiphase Flow
  • Lecture (others)
    Fachkolloquium "Partikelströmung", 17.-18.03.2011, Zittau and Dresden, Germany
  • Contribution to proceedings
    Fachkolloquium "Partikelströmung", 17.-18.03.2011, Zittau and Dresden, Germany
    Fachkolloquium "Partikelströmung"

Permalink: https://www.hzdr.de/publications/Publ-15548
Publ.-Id: 15548


Numerical models used for the modelling of the transport of fibrous insulation debris

Cartland Glover, G. M.; Krepper, E.; Renger, S.; Seeliger, A.; Kästner, W.; Kryk, H.;
Mineral wool insulation material applied to the primary cooling circuit of a nuclear reactor maybe damaged in the course of a loss of coolant accident (LOCA). The insulation material released by the leak may compromise the operation of the emergency core cooling system (ECCS), as it maybe transported together with the coolant in the form of mineral wool fiber agglomerates (MWFA) suspensions to the containment sump strainers, which are mounted at the inlet of the ECCS to keep any debris away from the emergency cooling pumps. In the further course of the LOCA, the MWFA may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Therefore, it is essential to understand the transport characteristics of the insulation materials in order to determine the long-term operability of nuclear reactors, which undergo LOCA.
An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz1 is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effects that particles formed due to corrosion of metallic containment internals by the coolant medium have on the strainer pressure drop.
The focus of this presentation is on the numerical models that are used to predict the transport of MWFA by CFD simulations. A number of pseudo-continuous dispersed phases of spherical wetted agglomerates can represent the MWFA. The size, density, the relative viscosity of the fluid-fiber agglomerate mixture and the turbulent dispersion all affect how the fiber agglomerates are transported. In the cases described here, the size is kept constant while the density is modified. This definition affects both the terminal velocity and volume fraction of the dispersed phases. Only one of the single effect experimental scenarios is described here that are used in validation of the numerical models. The scenario examines the suspension and horizontal transport of the fiber agglomerates in a racetrack type channel. The corresponding experiments will be described in an accompanying presentation (see abstract of Seeliger et al.).
Keywords: Mineral Wool Fiber Agglomerates, Loss of Coolant Accidents, Containment Sump, Computational Fluid Dynamics, Multiphase Flow
  • Lecture (Conference)
    Euromech Coloquium 513 on non-spherical particles in fluid turbulence, 06.-08.04.2011, Udine, Italy
  • Contribution to WWW
    http://158.110.32.35/Euromech/PRESENTATIONS/CartlandGlover.pdf
  • Lecture (Conference)
    Euromech Coloquium 513 on non-spherical particles in fluid turbulence, 06.-08.04.2011, Udine, Italy

Permalink: https://www.hzdr.de/publications/Publ-15547
Publ.-Id: 15547


Experiments to assess the transport of fibrous insulation debris

Seeliger, A.; Cartland Glover, G. M.; Renger, S.; Krepper, E.; Kästner, W.; Kryk, H.;
Loss of coolant accidents (LOCA) in the primary cooling circuit of a nuclear reactor may result in damage to insulation materials that are located near to the leak. The insulation materials released may compromise the operation of the emergency core cooling system (ECCS). Insulation material in the form of mineral wool fibre agglomerates (MWFA) maybe transported to the containment sump strainers mounted at the inlet of the emergency cooling pumps, where the insulation fibres may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fibre cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Thus, knowledge of transport characteristics of the damaged insulation materials in various scenarios is required to help plan for the long-term operability of nuclear reactors, which undergo LOCA.
An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz1 is investigating the phenomena that maybe observed in the containment vessel during a LOCA. The study entails the generation of fibre agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effect that corrosion of the containment internals by the coolant has on the strainer pressure drop.
The focus of this presentation is on the experiments performed that characterize the horizontal transport of MWFA, whereas the corresponding CFD simulations are described in an accompanying contribution (see abstract of Cartland Glover et al.). The experiments were performed a racetrack type channel that provided a near uniform horizontal flow. The channel is 0.1 wide by 1.2 m high with a straight length of 5 m and two bends of 0.5 m. The measurement techniques include particle imaging (both wide-angle and macro lens), concurrent particle image velocimetry, ultravelocimetry, laser detection sensors to sense the presence of absence of MWFA and pertinent measurements of the MWFA concentration and quiescent settling characteristics. The transport of the MWFA was observed at velocities of 0.1 and 0.25 m s-1 to verify numerical model behaviour in and just beyond expected velocities in the containment sump of a nuclear reactor.
Keywords: Mineral Wool Fibre Agglomerates, Loss of Coolant Accidents, Containment Sump, Particle Imaging, Particle Image Velocimetry

Permalink: https://www.hzdr.de/publications/Publ-15546
Publ.-Id: 15546


F-18 Labelled cathepsin inhibitors as potential radiotracers for tumour imaging

Löser, R.; Frizler, M.; Bergmann, R.; Dombrowski, L.; Knieß, T.; Gütschow, M.; Steinbach, J.;
Ziel/Aim:
The enzyme class of thiol-dependent cathepsins has been shown to be linked to the progression of cancer in multiple ways. Particularly crucial is their involvement in proteolytic pathways that are related to tumour invasion and metastasis (1).
The aim was the design of a fluorine-containing inhibitor of the azadipeptide nitrile chemotype (2) and the labelling with the radionuclide F-18 to evaluate the potential of this inhibitor class for functional tumour imaging by PET and to gain insight into the pharmacokinetic behaviour of these inhibitors.

Methodik/Methods:
The fluorine atom was connected by an ethylene bridge to the inhibitor core structure and the affinities of the resulting compound to its targets were determined in kinetic enzyme assays. Labelling with F-18 was achieved by fluoroethylation with different substituted [18F]2-fluoroethyl benzenesulfonates (3). The stability of the tracer against chemical and enzymatic degradation as well as its metabolic fate in rat blood was investigated and its biodistribution was studied in vivo by small animal PET.

Ergebnisse/Results:
The fluorine containing azadipeptide nitrile Gue2011 exhibits inhibition constant in the single-digit to subnanomolar range against the oncologically relevant cathepsins L, S, and B. Among the various F-18 fluoroethylating agents tested, [18F]2-fluoroethyl nosylate revealed as the most efficient one. This enabled the two-step radiosynthesis of [18F]Gue2011 in an average RCY (dc) of 24 % (n = 6). Metabolite analysis in rat blood showed the rapid conversion of the tracer into its glutathione conjugate as indicated by HPLC. Studies towards the pharmacological prevention of this conjugate formation are under current investigation.

Schlussfolgerungen/Conclusions:
With Gue2011 a highly potent fluorine-containing cathepsin inhibitor was found and its labelling with fluorine-18 could be successfully established. The compounds suitability as PET tracer for functional tumour imaging seems to be limited due to its inherent thiol reactivity. The radiolabelling of other cathepsin inhibitors is underway.

Literatur/References:
(1) Mohamed, M. M.; Sloane B. F. Nat. Rev. Cancer 2006, 6, 764-775
(2) Löser, R. et al. Angew. Chem. Int. Ed. 2008, 47, 4331-4334
(3) Musachio, J. L.; Shah, J.; Pike V. W. J. Label. Compd. Radiopharm. 2005, 48, 735-747
  • Poster
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A118

Permalink: https://www.hzdr.de/publications/Publ-15545
Publ.-Id: 15545


Einfluss der Datenfilterung auf die Bestimmung von Tumor-Volumen und SUVmax in der PET: Vergleich von einfacher Glättung und lokal adaptiver Filterung.

Beuthien-Baumann, B.; Hofheinz, F.; Oehme, L.; Langner, J.; van den Hoff, J.;
Ziel/Aim:
Bei der FDG-PET kann die Bildqualität bzg. des Signal/Rausch-Verhältnisses (SN-ratio) deutlich eingeschränkt sein (z.B. Adipositas, Atemgating). Der Einsatz üblicher glättender Filter (MAF: „Moving Average Filter“) verbessert das SN-ratio, reduziert aber die räumliche Auflösung, woraus verminderte Detailerkennbarkeit und Kontrastverlust v.a. bei Strukturen nahe der Auflösungsgrenze resultieren. Eine Alternative zu MAF sind lokal adaptive Filter, welche eine Rauschunterdrückung kombiniert mit Kantenerhaltung in den Bildern bewirken, aber bisher wenig verbreitet sind. Ziel: Einfluß der Bildbearbeitung mittels MAF und einem lokalen adaptiven Filter (LAF ) auf das abgegrenzte Tumorvolumen und den maximalen Standard Uptake Value (SUVmax) zu ermitteln.

Methodik/Methods:
10 Patienten mit nicht-kleinzelligem Bronchial-Karzinom und mind. einer Metastase, BMI 29,5 (23,9 – 40,4), mittl. injizierte Aktivität 384 MBq F18-FDG. Akquisition ab 60 min p.i., PET-Scanner ECAT EXACT HR+ (Siemens/ CTI). Iterative Rekonstruktion OSEM 6/16, Gauss 6mm. Vergleich von 5 Datensätzen: Original-Daten, MAF (3x3x3 Gaussfilter, FWHM = 8 mm) sowie LAF optimiert für 3 Rauschamplituden (NR20, NR40, NR60). Ermittlung von Tumorvolumen und SUVmax über 3D Regions Of Interest mittels ROVER (ABX, Radeberg). Ausgewertet wurde die Änderung des Volumens und des SUVmax in Abhängigkeit von der Filterung.

Ergebnisse/Results:
Es wurden insgesamt 29 Läsionen ausgewertet. 9 Läsionen zeigten eine Volumen < 3 ccm, 12 Läsionen zwischen >3 ccm und < 10c cm, 5 Läsionen <10 und >20 ccm, und 5 Läsionen > 20 ccm. Der SUVmax lag im Mittel bei 6,5 für Läsionen < 3 ccm, SUVmax 8,3 bei Läsionen zwischen >3 und < 10 ccm, SUVmax 12,1 bei Läsionen <10 und >20 ccm und SUVmax 19,4 bei Läsionen > 20 ccm. MAF führte zu einer Zunahme des ermittelten Volumens zwischen 2 und 18%, wobei die kleinen Läsionen eine relativ größere Volumenzunahme aufwiesen. Der SUVmax sank auf 85% bis 95% des Ausgangswertes, wobei kleine Läsionen eine deutlichere Reduktion des SUVmax zeigten. LAF führte zu keiner wesentlichen Volumenänderung im Vergleich zum Originaldatensatz. Der SUVmax lag bei einer noise reduction von 60% zwischen 92% und 98% des Ausgangswertes, bei NR20 und NR40 waren die Abweichunegn noch geringer.

Schlussfolgerungen/Conclusions:
Der Einsatz glättender Filter reduziert die effektive räumliche Auflösung der Bilddaten und ist problematisch im Hinblick auf die visuelle und quantitative Bewertung von kleinen Läsionen nahe der Auflösungsgrenze, selbst bei nur geringfügiger Glättung. Kantenerhaltende lokal adaptive Filter bieten eine vielversprechende Alternative und führen visuell wie quantitativ zu überlegenen Ergebnissen. Dies erscheint insbesondere von Bedeutung für Verlaufsuntersuchungen, bei denen möglicherweise die prozentuale Änderung des SUVmax nach Chemotherapie für eine weitere Therapiestratifizierung genutzt wird.
  • Poster
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A104

Permalink: https://www.hzdr.de/publications/Publ-15544
Publ.-Id: 15544


A new segmentation approach for F-18-fluoromisonidazole positron emission tomography data based on Ant Colony Optimization: Considering Reproducibility

Haase, R.; Hietschold, V.; Andreeff, M.; Böhme, H. J.; Kotzerke, J.; Steinbach, J.; Zips, D.; Baumann, M.; Abolmaali, N.;
Ziel/Aim:
Hypoxia imaging using F-18-fluoromisonidazole (FMISO) positron emission tomography (PET) is of increasing interest in the field of radiation oncology. But for analysis of FMISO PET data a reliable and accurate delineation technique of hypoxic subvolumes is still needed. Due to the inability of threshold based segmentation approaches to deliver reliable results when applied to data sets with small, inhomogeneous or non spherical target volumes, more complex algorithms may be preferred (1). We propose an Ant-Colony-Optimization (ACO) approach for segmentation of FMISO PET data sets. This investigation was performed to validate the reproducibility of the algorithm processing patient data sets.

Methodik/Methods:
Our analysis included 28 patients from an ongoing prospective study on head and neck cancers. FMISO PET images were acquired 4 hours p.i. of ~266 MBq. Patients were investigated by FMISO PET before radiochemotherapy (RCT) and the resulting data sets were further processed by the proposed ACO approach. Virtual ants were operating autonomously in the PET volume searching for regions with signal intensity above average. When an ant is located in such a region, it emits pheromone, attracting more ants to go to the marked region. More ants emit more pheromone and in that way the pheromone field shows the target objects with higher contrast than the original data set. Afterwards the pheromone fields were segmented into positive and negative regions using a histogram based threshold algorithm. Each data set was processed for 3 times and the resulting delineations were compared pair wise using the Jaccard-Index (JI). Mean JI and standard deviation were calculated from the resulting three JI values for each data set.

Ergebnisse/Results:
The JI over all data sets was 0.81 (+- 0.1) indicating highly reproducible volume delineations. The mean segmented volume was 182 ml with a mean deviation of 10 %. In 19 patient data sets volumes outside the presumptive tumour volume were segmented as positive, especially in the cerebellar region. This finding is well comparable to the clinical experience and these volumes were also segmented with high reproducibility.

Schlussfolgerungen/Conclusions:
The results show that the ACO approach delivers reproducible volume delineations when applied to FMISO PET patient data sets. Further development of the proposed algorithm will face excluding positive regions outside the presumptive tumour volume and comparison of automatically generated delineations with manual segmentations by experienced physicians.

Literatur/References:
(1) Lee J.A. (2010) Segmentation of positron emission tomography images: Some recommendations for target delineation in radiation oncology.
Radiotherapy & Oncology, Vol. 96, Issue 3, pp 302-307
  • Poster
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A95

Permalink: https://www.hzdr.de/publications/Publ-15543
Publ.-Id: 15543


Dynamics of PBF changes in regions of aspiration-induced acute lung injury

Bergmann, R.; Richter, T.; Ragaller, M.; Pietzsch, J.;
Ziel/Aim:
Aspiration of gastric contents is the second most common clinical event associated with the development of the adult respiratory distress syndrome (ARDS) and the mortality for ARDS resulting from acid aspiration ranges from 40-50%. Regions of aspiration induced injury matches regions of high pulmonary blood flow (PBF) in the early stage of acute lung injury, as recently shown by us. The aim of this project was to characterize the dynamics of regional PBF distribution in dependence on time after injury.

Methodik/Methods:
The protocol was approved by the Animal Study Committee of the Landesdirektion Dresden. In 11 desflurane anesthetized, spontaneously breathing male Wistar rats the lung injury was achieved by instillation of 0.1 HCl (0.4 ml/kg body weight) through a tracheostomy tube. The animals were scanned with a dedicated small animal CT scanner before and after injury. The pulmonary blood flow in the lungs was imaged by dedicated positron emission tomography (PET) using intravenously infused Ga-68-labeled DOTA-modified microspheres (diameter 20 µm) at 10 (6 animals) and 120 min (5 animals) after aspiration. CT- and PET-images were co-registered. Areas of injury, identified as new high density regions in lung CT-images after aspiration, were marked with a spherical mask and regions of interest (ROI) were derived using a threshold of 80% of maximum activity in the mask. Identical masks were used at the contralateral lung as reference. PBF in the injury ROI was calculated as activity fraction of the reference PBF region. The PBF in injury was compared with the reference side using the Wilcoxon matched-pairs signed rank test. The PBF-fraction at different time points was compared between the groups by unpaired t-test with Welch's correction.

Ergebnisse/Results:
CT images after aspiration showed areas of lung injury different in location and size within the two groups. Fraction of PBF in injured regions was higher at 10 min {1.34 (1.15-1.45) (median (interquartile range)} compared to 120 min (0.9 (0.85-1.06); P=0.0014) after aspiration. The intra-individual difference was determined by a high PBF in injured lung regions compared to the contralateral reference side at 10 min after injury (P = 0.03), whereas at 120 min after aspiration, injured regions have shown similar PBF compared to the contralateral reference side (P=0.81).

Schlussfolgerungen/Conclusions:
Regional PBF was increased 10 minutes after acid aspiration in regions of injury. This effect disappears within two hours after injury in anesthetized rats. This observed change in PBF after aspiration-induced acute lung injury seems to be important in early targeted treatment of acid aspiration.
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizn 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A76-A77

Permalink: https://www.hzdr.de/publications/Publ-15542
Publ.-Id: 15542


Optimierung der Pharmakokinetik radioaktiv markierbarer L-Oligonukleotide durch PEGylierung

Pietzsch, H.-J.; Förster, C.; Schubert, M.; Bergmann, R.; Vonhoff, S.; Klussmann, S.; Steinbach, J.;
Ziel/Aim:
Komplementäre L-Oligonukleotide (L-ON) stellen einen alternativen Ansatz zur Realisierung von Pretargeting-Technologien dar. Im Vergleich zu natürlichen D‑Oligonukleotiden besitzen L-Oligonukleotide eine sehr hohe metabolische Stabilität; allerdings werden sie sehr schnell aus der Blutbahn entfernt und in hohem Maße in den Nieren angereichert.Ziel des Forschungsvorhabens ist die gezielte Einflussnahme auf die Pharmakokinetik durch systematische PEGylierung einer L-ON-Leitstruktur. Schwerpunkte sind die Erhöhung der Bioverfügbarkeit durch Reduzierung der Blutclearance sowie die Verringerung der Nierenakkumulation.

Methodik/Methods:
Als Leitstruktur wurde das L-Oligonukleotid HO-C6H12-S-S-C6H12-5’GCG-GCT-GTG-CGG-TGC-GG3’ verwendet. Das 3’-Ende wurde mit PEG unterschiedlicher Größen (2, 5, 10, 20 kDa) derivatisiert. Nach Spaltung der Disulfidbindung und Funktionalisierung der PEG-L-ON-Konjugate mit maleinimidfunktionalisierten NOTA- bzw. DOTA-Chelatoren wurden die resultierenden Konstrukte mit Ga-68 bzw. Cu-64 markiert. Die Pharmakokinetik der Radiotracer wurde durch dynamische PET-Scans und simultane Organverteilungsstudien in Wistar-Ratten bestimmt.

Ergebnisse/Results:
Die Zunahme der PEG-Molmassen bewirkte eine stetige Reduzierung der Nierenaufnahme nach 60 min von 56,3 ± 4,1 %ID (Cu-64; 2 kDa PEG) und 52,4 ± 6,1 %ID (Ga-68; 2 kDa PEG) zu 6,5 ± 0,4 %ID (Cu-64; 20 kDa PEG) und 6,9 ± 0,6 % (Ga-68; 20 kDa PEG).Mit zunehmender PEG-Größe zeigte sich eine ansteigende Leberaufnahme nach 60 min p.i. von 4,8 ± 0,2 %ID (Cu-64; 2 kDa PEG) und 2,6 ± 0,4 %ID (Ga-68; 2 kDa PEG) zu 13,3 ± 2,1 %ID (Cu-64; 20 kDa PEG) und 10,7 ± 2,7 %ID (Ga-68; 20 kDa PEG). In den restlichen Organen, mit Ausnahme des Blutes, war die Radiotraceraufnahme nach 60 min p.i. sehr gering (<0,5 %ID/g bzw. <1 SUV). Aus den dynamischen PET-Untersuchungen wurden die Halbwertszeiten der einzelnen Radiotracer im Blutkreislauf bestimmt, diese betrugen 10,8 min (2 kDa PEG), 9,6 min (5 kDa PEG), 27,7 min (10 kDa PEG) und 39,4 min (20 kDa PEG).

Schlussfolgerungen/Conclusions:
Die Modifikation des pharmakokinetischen Profils der L-ON-Leitstruktur ist durch sukzessive PEGylierung möglich. Im optimalen Fall verringerte sich die Nierenanreicherung der PEG-L-ON nach 60 min auf ein Neuntel des Wertes der nicht-PEGylierten L-ON, bei gleichzeitiger Erhöhung der Verweilzeiten im Blut. Weiterhin bewirkte die PEGylierung eine Erhöhung der Leberaufnahme, während alle anderen Gewebe und Organe auf sehr niedrigem Radioaktivitätsniveau blieben. Durch PEGylierung von L-ON ist eine gezielte Beeinflussung der Pharmakokinetik möglich, jedoch ergeben sich entgegengesetzte Effekte bezüglich der Nieren- und Leberaufnahme. Die absoluten Anreicherungen in den genannten Organen müssen noch weiter reduziert werden, um die L-ON in Pretargeting-Technologien für Diagnostik und Therapie anwenden zu können.
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A74

Permalink: https://www.hzdr.de/publications/Publ-15541
Publ.-Id: 15541


Molecular imaging of radio- and NIR-labeled EGFR-antibody in tumor bearing mice

Bergmann, R.; Zenker, M.; Pietzsch, J.; Walther, M.; Heldt, J.-M.; Pietzsch, H.-J.; Steinbach, J.;
Ziel/Aim:
The epidermal growth factor receptor (EGFR) is often overexpressed in human malignancies. This phenotype is associated with tumor aggressiveness, treatment resistance, and biological heterogeneity with potential to bypass the blockade of the EGFR signaling pathways. Cetuximab (C225) as a chimeric monoclonal antibody specifically targets the EGFR was modified for radio- and near infrared fluorescence (NIRF) imaging as well as for potential applications in radiotherapy using DTPA-, DOTA-, NOTA-modification, radio-labeling with Cu-64, Y-86, Y-90, Lu-177, and for modification with X-SIGHT Large Stokes Shift Dye (X-SIGHT 670 LSS Dye).

Methodik/Methods:
C225 was conjugated with bifunctional chelators based on SCN-Bz and -DTPA, -DOTA, -NOTA, and the C225-NOTA derivative was additionally modified with the X-SIGHT 670 Large Stokes Shift Dye, TFP Ester (XS670). The receptor binding and cell (A431 cells expressing high amounts of EGFR) uptake of Cu-64-NOTA-XS670-C225 was studied in vitro. The EGFR-affinity of the immune-conjugates was measured by a competitive radio-ligand binding assay. The conjugates were labeled with Cu-64, Y-86, Y-90, Lu-177 within 30 min with high radiolabeling yield and radiochemical purity. The biodistribution and –kinetics in vivo were studied by small animal PET or SPECT and ex vivo by autoradiography. Whole body cryo-sectioning of the animals into 40 micrometer sections permitted the direct comparison of the autoradiograms and NIRF images of the tissue sections.

Ergebnisse/Results:
C225 was conjugated with bifunctional chelators based on SCN-Bz and -DTPA, -DOTA, -NOTA, and the C225-NOTA derivative was additionally modified with the X-SIGHT 670 Large Stokes Shift Dye, TFP Ester (XS670). The receptor binding and cell (A431 cells expressing high amounts of EGFR) uptake of Cu-64-NOTA-XS670-C225 was studied in vitro. The EGFR-affinity of the immune-conjugates was measured by a competitive radio-ligand binding assay. The conjugates were labeled with Cu-64, Y-86, Y-90, Lu-177 within 30 min with high radiolabeling yield and radiochemical purity. The biodistribution and –kinetics in vivo were studied by small animal PET or SPECT and ex vivo by autoradiography. Whole body cryo-sectioning of the animals into 40 micrometer sections permitted the direct comparison of the autoradiograms and NIRF images of the tissue sections.

Schlussfolgerungen/Conclusions:
PET allows the quantitative kinetic characterization of biodistribution in small animals, which will be a prerequisite to estimate the dosimetry in animals. SPECT and autoradiography allowed the fine distribution imaging. The dual-labeling of antibodies is a promising tool for quantitative evaluation of the long time distribution in animals using NIRF of cryo-sections beyond the decay of the radionuclide used. Dual-labeled immune-conjugates represent a potential probe for translational application in tumor detection.
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A41-A42

Permalink: https://www.hzdr.de/publications/Publ-15540
Publ.-Id: 15540


Erste Ergebnisse zur Untersuchung des Uptakes von Y-90-Cetuximab in vitro an FaDu-Monolayer-Zellen

Runge, R.; Ingargiola, M.; Förster, C.; Freudenberg, R.; Wunderlich, G.; Heldt, J.-M.; Zenker, M.; Steinbach, J.; Cordes, N.; Kunz-Schughart, L.; Kotzerke, J.;
Ziel/Aim:
In einer Vielzahl menschlicher Tumore ist die Expression des Epidermal-Growth-Factor-Receptor (EGFR) nachweisbar und geht mit einer schlechteren Prognose onkologisch behandelter Patienten einher. Der EGFR wird durch seine natürlichen Liganden oder ligandenunabhängig durch Bestrahlung aktiviert. Zu den Substanzen, die den EGFR hemmen gehören monoklonale Antikörper (mAb) z.B. Cetuximab (C225). Die Markierung des C-225 mit dem Beta-Strahler Y-90 ermöglicht eine zielgerichtete Induktion von DNA-Schäden. Es sollte untersucht werden, welchen Einfluss der Zusatz von kaltem C225 auf den Uptake von Y-90-C225 in FaDu-Monolayer-Zellen hat.

Methodik/Methods:
FaDu-Zellen wurden in 6-Well-Mikrotiterplatten (MTP) ausgesät (1x105 und 3x105 Zellen pro well). Die Inkubation erfolgte mit Y-90-C225 über 24 h bei 37°C mit unterschiedlichen Dosen (0-6 Gy, Geant4 Monte Carlo Toolkits). Y-90-C225 wurde mit unmarkiertem C225 auf C225-Konzentrationen von 1 µg/ml und 5 µg/ml eingestellt und Proben ohne Zusatz von unmarkiertem C225 mitgeführt. Die Bestimmung des zellulär gebundenen Y-90-C225 (Uptake) erfolgte durch Messung der Radioaktivität des ungebunden Y-90-C225 sowie des gebundenen Y-90-C225 im Zelllysat an einem Gammacounter (CobraTM II).

Ergebnisse/Results:
Der Uptake von Y-90-C225 in FaDu-Zellen zeigte eine Abhängigkeit von der Zellzahl. Der absolute Uptake von Y-90-C225 ohne Zusatz von unmarkiertem C-225 stieg bei Dosissteigerung bzw. Konzentrationserhöhung des mAb nur marginal an, die relativen Werte (bezogen auf die eingesetzte Radioaktivität) zeigten bei 1 Gy den höchsten Uptake (1 Gy: 18,63%, 6 Gy: 3,6 %). Die Kompetition von Y-90-C225 und unmarkiertem C225 um die Bindungsstellen auf der Zellmembran konnte durch die Reduzierung des Y-90-C225-Uptakes mit zunehmendem Anteil von unmarkiertem C225 an der Gesamtantikörperkonzentration nachgewiesen werden.

Schlussfolgerungen/Conclusions:
Bei höheren Dosen bzw. Antikörperkonzentrationen wurde kein höherer Y-90-C225-Uptake erzielt, was auf eine Sättigung der Rezeptoren/Bindungsstellen hinweist. Die lineare Abnahme der zellulären Bindung des Y-90-C225 bei Erhöhung der Konzentration des unmarkierten C225 deutet auf die gleiche Affinität des markierten und unmarkierten Antikörpers an die EGFR-Bindungsstellen der FaDu-Zellen hin.Zur Verifizierung der Ergebnisse sind weitere Experimente geplant.
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A37

Permalink: https://www.hzdr.de/publications/Publ-15539
Publ.-Id: 15539


Inkorporationsdosimetrie mit (-)-F18-NCFHEB, einem neuen PET-Tracer zur Darstellung von zerebralen α4β2 nikotinischen Acetylcholinrezeptoren.

Sattler, B.; Wilke, S.; Starke, A.; Seese, A.; Patt, M.; Schildan, A.; Smits, R.; Hoepping, A.; Brust, P.; Steinbach, J.; Gräf, S.; Gertz, H. J.; Sabri, O.;
Ziel/Aim:
(-)-F18-Norchloro-fluoro-homoepibatidin ((-)-F18-NCFHEB) ist ein neuer und vielversprechender Radioligand für die Darstellung von alpha4beta2 nikotinischen Acetylcholinrezeptoren mit PET. Um das Strahlenrisikio durch diesen Tracer abzuschätzen, wurden die resultierenden Organdosen (OD) und die effektive Dosis (ED) im Rahmen einer Machbarkeitsstudie inkorporationsdosimetrisch ermittelt.

Methodik/Methods:
Die inkorporationsdosimetrische Untersuchung von (-)-F18-NCFHEB wurde an 3 Probanden (2 männlich, 1 weiblich; Alter: 59,6±3,9a; Gewicht: 74,3±3,1Kg) vorgenommen. Die Probanden unterzogen sich nach intravenöser Injektion von 353,7±10,2 MBq (-)-F18-NCFHEB einer sequentiellen PET-CT-Untersuchung bis zu 7h nach Injektion an einem SIEMENS Biograph16 PET-CT-System (9 Bettpositionen pro Frame, 1,5-6min/Bettposition, CT-Schwächungskorrektur, iterative Rekonstruktion). Bis zu 7h p.i. wurde sämtlicher Urin gesammelt und dessen Aktivitätskonzentration bestimmt. Alle den Tracer aufnehmenden Organe wurden CT-geführt mit dreidimensionalen Regionen (VOIs) markiert, und ihr Aktivitätsinhalt als Zeit-Aktivitäts-Verlauf dargestellt. Mit dem EXM-Modul von OLINDA [1] wurden Zeit-Aktivitäts-Kurven an diese Daten angepasst. Der Aktivitätsverlauf in der Blase wurde anhand der Urinabgaben bestimmt. ODs wurden unter Verwendung des 73,7kg-"adult male model" mit OLINDA bestimmt. Die ED wurde unter Verwendung der Gewebewichtungsfaktoren in der ICRP 103 von 2007 berechnet [2].

Ergebnisse/Results:
Die Harnblaseblase erhält die höchste OD (80,2±37,8µSv/MBq), gefolgt von der Leber (44,7±5,4µSv/MBq), den Nieren (38,6±5,1µSv/MBq), der Milz (38,4±11,6µSv/MBq), der Schilddrüse (32,8±11,9µSv/MBq) und den Lungen (31,1±5,3µSv/MBq). Die höchsten Beiträge zur ED leisten die Lunge (3,7±0,6µSv/MBq), die Harnblase (3,2±1,5µSv/MBq), der Magen (2,9±0,7µSv/MBq), das rote KM (2,3±0,2µSv/MBq), der absteigende Dickdarm (1,9±0,2µSv/MBq) und die Leber (1,8±0,2µSv/MBq). Die ED durch i.v. Applikation von (-)-F18-NCFHEB ergibt sich zu 22,9±0,7µSv/MBq.

Schlussfolgerungen/Conclusions:
Die effektive Dosis als Maß für das summarische Risiko durch i.v. Applikation von 300 MBq (-)-F18-NCFHEB) ergibt sich zu 6,8±0,2mSv. Dies liegt im Bereich der Strahlenexposition durch andere F18-markierte Radioliganden. Diese günstigen dosimetrischen Ergebnisse unterstützen die weitere Entwicklung von (-)-F18-NCFHEB) als klinischen Hirn-PET-Tracer.

Literatur/References:
[1] Stabin et. al.: OLINDA/EXM: The Second-Generation Personal Computer Software for Internal Dose Assessment in Nuclear Medicine; JNM 46/6, 2005
[2] International Commission on Radiological Protection. Recommendations of the International Commission on Radiological Protection. ICRP Publication 103, Pergamon Press, New York, 2007
Die Studie wird vom Bundesministerium für Bildung und Forschung gefördert (Nr. 01EZ0820)
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutsche, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A36

Permalink: https://www.hzdr.de/publications/Publ-15538
Publ.-Id: 15538


Ein Verfahren zur modellfreien Recovery-Korrektur fokaler Strukturen in der PET

Hofheinz, F.; Langner, J.; Will, E.; Oehme, L.; Beuthien-Baumann, B.; van den Hoff, J.;
Ziel/Aim:
Der Partialvolumeneffekt beeinträchtigt die Bestimmung der wahren Aktivitätskonzentration einer Zielstruktur (sowie hiervon abgeleiteter Größen, wie z.B. SUV-Werte). Bereits bei Strukturabmessungen, die noch deutlich größer als die rekonstruierte räumliche Auflösung der Bilddaten sind, tritt eine gravierende Unterschätzung der wahren Werte auf, insbesondere, wenn ROI-Mittelwerte betrachtet werden (beschränkte Signal-Recovery). Werden quantitative Parameter wie SUV-Werte zur Beurteilung des Therapieansprechens herangezogen, muss daher eine Recovery-Korrektur durchgeführt werden Ziel dieser Arbeit war es, eine routinefähige modellfreie Methode zur Recovery-Korrektur zu entwickeln und diese anhand von Phantommessungen zu validieren.

Methodik/Methods:
Die entwickelte Methode arbeitet in 2 Schritten. Schritt 1: Bestimmung des wahren Objektvolumens V unter Benutzung eines automatischen thresholdbasierten Verfahrens inklusive einer Berücksichtigung des lokalen Untergrundes (ROVER, ABX) und der entsprechenden Gesamtaktivität A innerhalb von V. Schitt 2: Bestimmung des infolge des Partialvolumeneffektes ausserhalb der Objektgrenze abgebildeten untergrundbereinigten(!) Aktivtätsanteils B. Der Recoverykoeffizient
ergibt sich hiermit zu R = A/(A+B). Es wurden Messungen mit einem Zylinderphantom (Durchmesser: 20 cm, Höhe: 18 cm) durchgeführt. Die im Zylinder befindlichen 6 Kugeleinsätze besitzen Volumina von 2,5 ml bis 27 ml. In 3 Phantommessungen mit einem ECAT EXACT HR+ (Siemens/CTI, Knoxville, Tennessee) wurden der Zylinder und die Kugeln mit unterschiedlichen Aktivitätsmengen (Fluor-18) befüllt, um das Signal-Untergrund-Verhältnis und damit den Bildkontrast zu variieren. Zum Vergleich wurden die Recovery-Koeffizienten aus der Faltung der Objektfunktion (homogene Kugel) mit der bekannten/gemessenen Point Spread Function der Bilddaten berechnet. Die berechneten Recovery-Koeffizienten wurden mit den aus den Bilddaten gewonnenen Koeffizienten verglichen.

Ergebnisse/Results:
Die in den Bilddaten mit dem beschriebenen Verfahren bestimmten Recovery-Koeffizienten stimmmen bei praktisch relevanten Target/Background Kontrastverhältnissen sehr gut mit den berechneten Koeffizienten überein (Abweichungen im Mittel 5%).

Schlussfolgerungen/Conclusions:
Die vorgestellte Methode liefert bei praktisch relevanten Kontrastverhältnissen und homogenem Untergrund gute Ergebnisse. Die genauen Gültigkeitsgrenzen des Verfahren (inhomogener Untergrund, geringer Kontrast usw.) müssen noch genauer untersucht werden.
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A28

Permalink: https://www.hzdr.de/publications/Publ-15537
Publ.-Id: 15537


Perfusion measurements using Arterial Spin Labeling and MRI in small animals: comparison with radioactive and fluorescent microspheres

Bos, A.; Bergmann, R.; Hofheinz, F.; van den Hoff, J.;
Ziel/Aim:
Regional tissue perfusion is a fundamental physiological parameter controlling delivery of oxygen and nutrients to tissue. Arterial Spin Labeling (ASL) is a Magnetic Resonance Imaging (MRI) technique used for perfusion quantification. ASL has been shown to work reasonably well in human brain investigations. In other organs and especially in small animal imaging, however, ASL is not yet well established and validation against other methods is missing. The purpose of this work was to evaluate ASL in the brain of the rat by comparison with microspheres-derived regional perfusion using dedicated small animal PET and Optical Imaging (OI) systems.

Methodik/Methods:
Catheters were implanted through the right carotid artery in the left ventricle of the heart for administration of labeled microspheres (20μm) and in the left femoral artery for blood sampling. Microspheres were double-labeled with Cu-64 (or Ga-68) for PET (microPET P4, Siemens) and and X-sight 670 LSS for OI (Kodak FX). ASL measurements were performed in a 7T small animal MRI system (BioSpec 70/30, BRUKER) using a FAIR (Flow-sensitive Alternating Inversion Recovery) sequence with an adiabatic hyperbolic secant inversion pulse (length-bandwidth product: 80) and EPI (Echo Planar Imaging) acquisition. Global and selective T1 images were used for calculation of the perfusion values.

Ergebnisse/Results:
Perfusion in two brain slices was determined in three different ways (PET, MRI, OI). For the catheterized rat under anesthesia the whole brain perfusion values range from 0.2 to 1.19 ml/min/g for PET measurements and from 0.3 to 1.15 ml/min/g for OI calculations. In the normal rat brain (no catheter) under anesthesia perfusion values from FAIR-ASL ranged from 0.8 to 1.4 ml/min/g in both hemispheres (caudate putamen region). Catheter implantation created left/right differences between hemispheres of 10-30 %. The Pearson correlation factor varies between 0.88 and 0.9 for ASL vs. PET.

Schlussfolgerungen/Conclusions:
Overall the regional perfusion contrast is concordant between ASL and microspheres measurements. However, substantial quantitative deviations exist and are currently investigated. In order to become a useful routine applications in small animal imaging, ASL data acquisition and data evaluation needs to be further optimized. A thorough calibration via a quantitative comparison with radio- and fluorescent-labeled microspheres is mandatory. Altogether, perfusion quantification in the rat brain with ASL seems possible.
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A10

Permalink: https://www.hzdr.de/publications/Publ-15536
Publ.-Id: 15536


Countercurrent gas-liquid flow in a PWR hot leg (Effects of channel shape and size)

Kinoshita, I.; Murase, M.; Utanohara, Y.; Lucas, D.; Vallée, C.; Tomiyama, A.;
A numerical study is presented to examine the effects on countercurrent flow limitation (CCFL) of shape and size of hot leg models with rectangular cross-section. Using the CFD software FLUENT 6.3.26, numerical simulations were conducted for CCFL experiments in a 1/3 scale rectangular channel (HxW = 0.25x0.05 m2), and results were compared with CCFL data and simulation results in a 1/5 scale rectangular channel (HxW = 0.15x0.01 m2). Comparing CCFL characteristics in rectangular channels with those in circular channels, the hydraulic diameter was turned out to be a major factor of cross-section geometry influencing the CCFL characteristics in hot legs.
Keywords: PWR hot leg, countercurrent gas-liquid flow, CCFL, rectangular channel, numerical simulation
  • Contribution to proceedings
    Japan Society of Multiphase Flow (JSMF) Annual Meeting 2011, 06.-08.08.2011, Koto, Japan

Permalink: https://www.hzdr.de/publications/Publ-15535
Publ.-Id: 15535


Radiolabelling of engineered nanomaterials as a tool for sensitive particle tracking

Hildebrand, H.; Franke, K.;
Engineered nanoparticles (NPs) are present in a wide variety of consumer products, occasionally in significant quantities. During aging, abrasion or disposal of such products, NPs-release is likely - accompanied with effects for the environment that have to be investigated in more detail. The aim of this study is to quantify the amount of NPs (TiO2 and Ag0) released from composite coatings due to weathering, aging or mechanical stress and to follow the NPs along their further fate in the environment.
Generally, particle tracking may provide information on the transport behavoir of the particles in aqueous media or on their interactions with biota. Since NPs are possibly released in tiny amounts and into very complex natural systems, we suggest the radiolabelling of NPs as a tool for their very sensitive detection throughout their life cycle including complex media such as aquifer sands, soil or cells.
Within this study, a novel radiolabelling technique for TiO2 (P 25, Evonik Degussa) and Ag0 (Sigma-Aldrich) NPs is under development. During this labelling process, significant changes of the chemical composition and properties of the particles are avoided to the greatest possible extend.
Stability of the NPs in different media has been studied and results contribute to first estimates concerning their transport behaviour in the aquatic environment. Batch tests including sediment materials were conducted to describe interactions of Ag0 and TiO2 NPs with natural matrices.
Interactions of engineered NPs and natural colloids have been studied as well. Results show that natural colloids have a strong influence on stability and transport of engineered NPs under environmental conditions.
Based on these data, radiolabelling of engineered NPs may open up the chance for sensitive tracking of particles not only in environmental media but also in other complex systems.
  • Lecture (Conference)
    Goldschmidt2011, 14.-19.08.2011, Prag, Tschechische Republik

Permalink: https://www.hzdr.de/publications/Publ-15534
Publ.-Id: 15534


Interdiffusion in Fe/Pt Multilayers: In-situ high-temperature synchrotron radiation reflectivity study

Zotov, N.; Feydt, J.; Savan, A.; Ludwig, A.; von Borany, J.;
Thermal annealing of Fe/Pt multilayers (ML) is reported to reduce significantly the formation temperature of FePt hard magnetic thin films. The transformation mechanisms of [Fe 1.38 nm/Pt 2.24 nm]50 ML, prepared by magnetron sputtering, is investigated in the present communication by high temperature X-ray reflectivity using synchrotron radiation. Complete degradation of the ML periodic structure is observed at about 610 K. The variation with annealing temperature of the intensity of the first Bragg peak, the correlated vertical roughness, and the lateral correlation length of the ML show that the ML transform in two stages with a cross-over temperature of about 515 ± 15 K. This behavior cannot be simply explained by the change in the measured interdiffusion coefficient below and above the cross-over temperature, suggesting the formation of FePt nanograins along the interfaces.

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Permalink: https://www.hzdr.de/publications/Publ-15533
Publ.-Id: 15533


Die Nutzung der Hochenergie-Ionenimplantation für die Verbesserung des Schaltverhaltens von Leistungshalbleiter- Bauelementen

von Borany, J.;
Im Vortrag werden die Möglichkeiten zur Verbesserung des Schaltverhaltens von Leistungshalbleiter-Bauelementen mittels einer Ionenbestrahlung vorgestellt. Die grundlegenden physikalischen Effekte und gerätetechnischen Voraussetzungen werden diskutiert und die anwendungsrelevanten Vorteile am Bespiel von schnellen Schaltdioden aufgezeigt.
Keywords: Ion-beam irradiation, Power electronics, Fast Switching Diodes
  • Lecture (others)
    2. Mitteldeutscher Innovationstag, 14.04.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15532
Publ.-Id: 15532


Superconductivity in quasi-two-dimensional organic charge-transfer salts

Wosnitza, J.;
Since the discovery of the first organic superconductor, more than 30 years ago, these materials revealed many fascinating properties and allowed to study fundamental low-dimensional physics. Besides superconductivity, the organic metals show a wealth of different ground states such as antiferromagnetic, spin-Peierls, spin-density-wave, and charge-density-wave phases. These ground states are accessible by tuning the structure, counter anion, magnetic field, temperature, and pressure. The study of these fertile phase diagrams has led to new theoretical concepts; however, a solid understanding of some of these states still remains a challenge and especially the nature of the superconducting state is a controversially discussed issue since many years. Even the normal metallic phase of these electronically low-dimensional metals reveals unusual properties sometimes not in line with conventional Fermi-liquid theory. Here, a review on selected normal-state and superconducting properties of the layered quasi-two-dimensional organic superconductors will be given. Thereby, the focus will be laid on the superconducting properties of the charge-transfer salts based on bisethylenedithio-tetrathiafulvalene, BEDT-TTF or ET for short, the building block of most of the to-date known organic superconductors. Some basic features of the crystallographic structure, the highly anisotropic electronic properties, and of the superconductivity in the organics will be highlighted. In more detail the recently reported evidence for the existence of a Fulde Ferrell Larkin Ovchinnikov state for exactly aligned in-plane magnetic fields will be presented
  • Invited lecture (Conferences)
    477. Wilhelm und Else Heraeus Seminar, 11.-13.04.2011, Bad Honnef, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15531
Publ.-Id: 15531


Spectroscopic study of influence of silica on the stability of actinide(IV) colloids at near-neutral pH

Banerjee, D.; Weiss, S.; Zaenker, H.; Scheinost, A. C.; Hennig, C.;
The migration of tetravalent actinides in natural waters occurs predominantly as sorption complexes at the surface of colloidal particles like clay, but also by the formation of actinide oxyhydroxide colloids (MOn(OH)4-2n•mH2O where M = Th or U [1]). Colloid-facilitated migration of plutonium has also been documented in subsurface groundwater conditions [2]. In a recent study it was observed that the stability of U(IV) and Th(IV) oxyhydroxide colloids is dramatically enhanced by the presence of silica [3]. In this study we investigate the influence of silica on the formation and stability of U and Th colloids at near-neutral pH conditions, which might have important environmental implications due to the uniquitous nature of silica in aquifers and surface waters.
U and Th colloids with varying U/Si and Th/Si ratios were synthesized and characterized using a range of spectroscopic and microscopic techniques. TEM and XRD measurements indicated that the structure of thorium/silica colloids is highly amorphous, which is clearly different from the ordered actinide(IV) oxyhydroxide colloids which are stable at pH < 3 but agglomerate and precipitate at near neutral pH within minutes. Comparison of O 1s X-ray photoelectron spectra (XPS) of actinide(IV)-silica and actinide(IV)-oxyhydroxide colloids revealed that two types of oxygen bonds (oxo and hydroxo) occur in presence of silica, which may explain the high degree of structural disorder. Moreover, the presence of O-Si bonds at near-neutral pH values suggest that silica is able to stabilize such colloids through modification of the structure by replacing the An-O(H)-An bonds of the oxyhydroxide structure with An-O(H)-Si bonds and consequently influencing the surface charge. These observations are consistent with X-ray absorption spectroscopy (XAS) data which demonstrate higher An-Si interaction and lower An-An interaction with increasing silica content in these colloids.

[1] Rothe et al. (2002) Inorg. Chem. 41, 249-258.
[2] Kersting et al. (1999) Nature 397, 56-59.
[3] Dreissig et al. (2011) GCA 75, 352-367.
  • Abstract in refereed journal
    Mineralogical Magazine 75(2011)3, 478-478
  • Lecture (Conference)
    Goldschmidt2011, 14.-19.08.2011, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-15530
Publ.-Id: 15530


Wechselwirkung von wasserlöslichen Calixarenen mit divalenten Kationen (85Sr, 56Co)

Paulik, S.; Mansel, A.; Schnorr, R.; Haupt, S.; Bernhard, G.; Kersting, B.;
Das vom BMBF (Bundesministerium für Bildung und Forschung) geförderte Forschungsprojekt „Multifunktionelle Komplexbildner mit N, O, S-Donorfunktionen für d- und f-Elemente: Synthese, Komplexbildung, Struktur und Transportverhalten“ beschäftigt sich im Teilprojekt II mit der „Steuerung des Migrationsverhaltens von Radionukliden mit Hilfe makrozyklischer, multifunktionaler Chelatliganden“. Die Arbeitspakete Radionukliderzeugung, Radiomarkierung, Komplexbildungs- und Transportstudien in Geosystemen des Teilprojekts II werden in der Abteilung Reaktiver Transport des Instituts für Radiochemie untersucht.

Für die Sicherheitsbewertung von Schadstoffen in Untertagedeponien bestehen teilweise Defizite – insbesondere das Sorptions- und Komplexierungsverhalten von langlebigen radiotoxischen Schwermetallen unter naturnahen Bedingungen bedarf noch genauerer Aufklärung, was auch anhand fehlender Einträge in der RES3T-Datenbank zu sehen ist.[1] Das Sorptions- und Komplexierungsverhalten der Radionuklide wird sowohl durch das Milieu des Wirtsgesteins, als auch durch die Präsenz von anorganischen Komplexbildnern bestimmt.[2]

Für die Trennung von schwach-radioaktivem und hoch-radioaktivem Abfall werden hauptsächlich organische Komplexierungsverbindungen eingesetzt, die durch ihre teilweise hohe Elementselektivität mittels Extraktion oder Ionenaustausch diese Trennung ermöglichen. Für diese Trennung haben sich auch die Stoffgruppe der Calixarene als sehr nützlich erwiesen.[3] Die Calixarene werden nun so modifiziert, dass sie einerseits eine gute Wasserlöslichkeit und andererseits eine selektive Komplexierung von 85Sr bzw. 56Co aufweisen. Somit sollte eine gezielte Steuerung des Transports von Radionukliden mit Hilfe von Calixarenen ermöglicht werden.

Literatur:

[1] RES3T-Datenbank, URL: http://www.hzdr.de/db/res3t.login [13.04.2011] [2] M. Dozol, Pure & Appl. Chem. 1993, 65, 1081-1102. [3] J. F. Dozol, J. Incl. Phenom. Macrocycl. Chem. 2000, 38, 1-22.
  • Lecture (Conference)
    GDCh-Wissenschaftsforum Chemie 2011, 04.-07.09.2011, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15529
Publ.-Id: 15529


Magneto-acoustic study of single crystalline UCu0.95Ge

Yasin, S.; Andreev, A. V.; Skourski, Y.; Wosnitza, J.; Zherlitsyn, S.; Zvyagin, A. A.;
We present results of a magneto-acoustic study of UCu0.95Ge. This compound exhibits antiferromagnetic ordering at 48 K and shows a metamagnetic phase transition at 38 T for the magnetic field applied along the c direction, seen as a jump in themagnetization. The sound velocity and sound attenuation demonstrate pronounced anomalies in the vicinity of both magnetic phase transitions proving the important role of magnetoelastic interactions in the physics of this actinide compound.
  • Physical Review B 83(2011), 134401

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Publ.-Id: 15528


Novel Phase Transition Probed by Sound Velocity in Quasi-One-Dimensional Ising-Like Antiferromagnet BaCo2V2O8

Yamaguchi, H.; Yasin, S.; Zherlitsyn, S.; Omura, K.; Kimura, S.; Yoshii, S.; Okunishi, K.; He, Z.; Taniyama, T.; Itoh, M.; Hagiwara, M.;
We have performed magnetostriction and ultrasound measurements on the quasi-one-dimensional S ¼ 1=2 Ising-like antiferromagnet BaCo2V2O8 in high magnetic fields of up to 51 T. The magnetostriction shows lattice shrinking along the c-axis, and we interpret it as the lattice distortion caused by exchange striction and Van-Vleck paramagnetism. It is clarified that the field dependence of sound velocity is correlated to the magnetostriction. We observed a pronounced softening in the sound velocity of the longitudinal-acoustic c33 mode and found a novel phase transition.
  • Journal of the Physical Society of Japan 80(2011), 033701

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Publ.-Id: 15527


Microstructure of superconducting films fabricated by high-fluence Ga implantation in Si

Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Mücklich, A.; Skorupa, W.; Gobsch, G.; Helm, M.; Wosnitza, J.;
The feasibility of embedding extrinsic superconducting nanolayers in commercial (100) silicon due to Ga precipitation is presented. To be far beyond the solid solubility limit of 0.1 at.% a high Ga fluence of 4x1016cm-2 is introduced in silicon by the ion-implantation technique. This leads to 100 nm thick amorphous silicon layers with a Ga peak concentration of 16 at.%. Subsequent recrystallization and Ga precipitation is initiated via rapid thermal annealing (RTA) for 60 seconds at temperatures of 500 – 800°C. A 30 nm sputter deposited SiO2 cover layer is used to protect the silicon surface during implantation and prevent Ga out-diffusion during annealing. It was shown that optimized annealing conditions (600 – 700°C) lead to superconducting layers with critical temperatures of 7 K and in plane critical fields up to 14 T [1]. Details of the layer microstructure investigations using of RBS/C and TEM as well as depth dependent XPS will be presented. The presented structural investigations reveal poly-crystalline silicon layers and show a strong Ga enrichment at the Si/SiO2 interface. Even if no crystalline Ga clusters were detected it is shown that the superconductivity arises due to a high density of amorphous Ga-rich precipitates at the Si/SiO2 interface. Since all involved processing steps are fully compatible with standard microelectronic technology and high criti-cal current densities of more than 2 kA/cm2 are reached, the proposed material system may implicate a high potential for future microelectronic applications.
[1] Skrotzki R. et al., Appl. Phys. Lett. 97 (2010) 192505
  • Lecture (Conference)
    Workshop Ionen- und Positronenstrahlen, 04.-05.07.2011, Neubiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15526
Publ.-Id: 15526


Uranium(VI) Complexation with Lactate and Citrate in Dependence on Temperature (7-65°C)

Steudtner, R.; Schmeide, K.; Bernhard, G.;
After disposal in nuclear waste repositories the chemical and migration behavior of actinides depends on many factors. It is estimated that maximum temperatures in the near field of a repository could reach 300°C in dependence on the waste forms [1] and the host rock [2]. Thus, for the long-term safety assessment, knowledge of the interaction of actinides such as uranium with inorganic and organic ligands at elevated temperatures is required. The amount of organic matter in a repository can be separated in humic substances and in low molecular weight organic substances. A not negligible component of low molecular weight organic substances is the group of carboxylic acid. For example, citric acid is used in nuclear reprocessing [3] and acetic, lactic and formic acid were identified in rock extracts and pore water of Opalinus Clay [4]. Reliable experimental data on the complexation of U(VI) in solution at elevated temperatures are still needed.
Therefore, we studied the U(VI) complexation by lactic acid (pH 3) and citric acid (pH 0-10) in the temperature range from 7 to 65°C. Species distribution and complex formation constants were determined by means of UV-Vis and time-resolved laser-induced fluorescence spectroscopy. In the U(VI) lactate system, we identified the formation of 1:1- and 1:2-complexes. In the presence of citrate, we could characterize five U(VI) complexes in dependence on pH value. The complex formation between U(VI) and these both ligands was found to be endothermic and entropy-driven. The complex stability constants of the U(VI) complexes increase with increasing temperature. This could lead to an increased mobility of U(VI) at higher temperatures.
Keywords: Uranium(VI), Lactate, Citrate, Complexation, higher Temperatures
  • Contribution to proceedings
    Goldschmidt 2011, 14.-19.08.2011, Prag, Czech Republic
    Mineralogical Magazine 75, 1940
  • Poster
    Goldschmidt 2011, 14.-19.08.2011, Prag, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-15525
Publ.-Id: 15525


High Efficiency Nanosecond Pulse Amplication Based on Diode-Pumped Cryogenic-Cooled Yb:YAG

Koerner, J.; Hein, J.; Kahle, M.; Liebtrau, H.; Kaluza, M.; Siebold, M.;
An output energy of 1.1 J of amplified nanosecond pulses was obtained by utilizing a diode-pumped Yb:YAG laser amplifier with the crystal cooled to 125 K. An all-mirror relay imaging was implemented to accomplish a low loss multi-pass scheme, where a three dimensional folding compensates the astigmatism of spherical mirrors at non-normal incidence. Without the need of diode-wavelength stabilization a for this type of amplifier record high total diode output to amplifier efficiency of 45 % was achieved.
Keywords: Lasers and laser optics
  • Lecture (Conference)
    Advanced Solid-State Photonics (ASSP), 13.-16.02.2011, Istanbul, Turkey

Permalink: https://www.hzdr.de/publications/Publ-15524
Publ.-Id: 15524


Broadband, diode-pumped Yb:SiO2 multicomponent glass laser

Roeser, F.; Reichelt, A.; Kroll, F.; Siebold, M.; Schramm, U.; Grimm, S.; Kirchhof, J.; Litzkendorf, D.;
We successfully demonstrated cw lasing of ytterbium-doped silica multicomponent glass bulk material. A slope efficiency of 43% and a tuning range from 1010-1080 nm have been achieved.
Keywords: Lasers, diode-pumped; Lasers, ytterbium; Lasers, tunable; Lasers, solid-state; Laser materials; Rare earth and transition metal solid-state lasers
  • Lecture (Conference)
    Advanced Solid-State Photonics (ASSP), 13.-16.02.2011, Istanbul, Turkey

Permalink: https://www.hzdr.de/publications/Publ-15523
Publ.-Id: 15523


Analysis of a high-energy, diode-pumped Yb:CaF2 disk laser

Loeser, M.; Siebold, M.; Kroll, F.; Roeser, F.; Koerner, J.; Hein, J.; Schramm, U.;
We present gain measurements and a time-resolved thermal lens analysis of a diode pumped, joule-class Yb:CaF2 disk laser. A thermal lens power of 0.05dpt at a single disk and small-signal gain of 5.2 in a two-disk amplifier were achieved at full pump power.
Keywords: Lasers, diode-pumped; Lasers Ytterbium; Laser amplifiers
  • Lecture (Conference)
    Advanced Solid-State Photonics ASSP, 13.-16.02.2011, Istanbul, Turkey

Permalink: https://www.hzdr.de/publications/Publ-15522
Publ.-Id: 15522


Adsorption of thallium(I) onto geological materials: Effect of pH and humic matter

Liu, J.; Lippold, H.; Wang, J.; Lippmann-Pipke, J.; Chen, Y. H.;
Thallium (Tl) is a typical toxic heavy metal, with higher toxicity than Hg, Cd, Pb. Anthropogenic sources such as coal combustion or mining/smelting activities generated high enrichments of Tl in some areas. For long-term risk assessments, the mobility in geochemical systems is a topic of major interest. Adsorption onto mineral surfaces can be considerably affected by dissolved humic acids (HAs), which are ubiquitous in natural waters. By using radioactive tracers, we were able to investigate co-adsorption of Tl and HAs at low concentration levels to be considered in real scenarios.
Two natural HAs were extracted from river sediments collected in a contaminated mining area in South China (regions of Guangzhou and Yunfu City). They were radiolabeled by an azo-coupling reaction with 14C-aniline. 204Tl(I) was employed as a radiotracer for Tl(I). The geological materials used in this study were goethite, pyrolusite and a natural sediment sample taken from Yunfu City.
For all these substrates, metal adsorption was found to be promoted with increasing pH since more binding sites are provided by deprotonation of surface hydroxyl groups. In contrast, adsorption of HAs was counteracted with increasing pH, which is explained by increasing electrostatic repulsion as a consequence of deprotonation. As expected, the extent of Tl(I)-HA complexation turned out to be very low, with a slight increase at higher pH.
Based on these data, a combined distribution model (Linear Additive Model) was tested for suitability in predicting the pH-dependent influence of HAs on Tl(I) adsorption. Our experimental results could not be reproduced in this way. In view of the fact that the approach worked well in other studies, criteria for its applicability need to be identified. Selectivities within the multicomponent system of humic material, regarding adsorption as well as complexation, are one possible reason for a failure of the model.
  • Lecture (Conference)
    Goldschmidt 2011, 14.-19.08.2011, Praha, Ceska Republika

Permalink: https://www.hzdr.de/publications/Publ-15521
Publ.-Id: 15521


Time-of-flight detection of fast neutrons

Bemmerer, D.;
The methods of time of flight detection of fast neutrons are reviewed, with an emphasis on the planned NeuLAND detector at FAIR.
  • Invited lecture (Conferences)
    XLII. Arbeitstreffen "Kernphysik" in Schleching/Obb., 24.02.-03.03.2011, Schleching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15520
Publ.-Id: 15520


Prototyping and design for a time-of-flight detector for 1 GeV neutrons at R3B/FAIR

Bemmerer, D.;
At the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, uniquely intensive beams of radioactive ions will become available, enabling many experiments of astrophysical relevance. The Reactions with Relativistic Radioactive Beams (R3B) setup at FAIR will study reactions of such projectiles at energies up to 1 GeV/A. As part of R3B, the planned NeuLAND (New Large Area Neutron Detector) time-of-flight detector shall detect emitted neutrons with a time resolution of sigma < 100 ps and efficiency >90%. Two possible solutions are currently under study for NeuLAND: a pure scintillator concept and a design based on passive converters and multigap resistive plate chambers (MRPC's). The poster will outline the design work on the MRPC-based solution. The measured properties of a 200 cm * 50 cm large MRPC-based neutron detector prototype will be shown, the first device of such a size with thick passive converters inside the MRPC structure.
  • Poster
    European Physical Society 24th Nuclear Physics Divisional Conference: Nuclear Physics in Astrophysics – V, 04.-08.04.2011, Eilat, Israel

Permalink: https://www.hzdr.de/publications/Publ-15519
Publ.-Id: 15519


A possible underground accelerator in the Dresden Felsenkeller

Bemmerer, D.; Cowan, T.; Szücs, T.; Zuber, K.;
Due to the suppression by the Coulomb barrier, the cross sections of astrophysically relevant nuclear reactions are very low at the stellar energy. Therefore they can only be directly measured in a low-background environment. For more than a decade, the LUNA collaboration has pursued this approach with a 0.4\,MV accelerator in the Gran Sasso underground laboratory in Italy. It was highly successful in studying the nuclear physics of the Sun and of the Big Bang. However, the energy range of LUNA is not sufficient to address the nuclear reactions of stellar helium burning and the neutron source reactions for the astrophysical s-process. Therefore, in the NuPECC 2010 long range plan it is recommended to install one or more accelerators with higher energy underground. A comparison of the background at LUNA (1400\,m rock cover) and the Dresden Felsenkeller (45\,m) has shown that with an anti-muon veto the background counting rates in a $\gamma$-detector differ only by a factor of three. The feasibility of installing a 2-3\,MV accelerator for intense $\alpha$-beams in Felsenkeller will be discussed.
  • Poster
    European Physical Society 24th Nuclear Physics Divisional Conference: Nuclear Physics in Astrophysics V., 04.-08.04.2011, Eilat, Israel
  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft, Frühjahrstagung 2011, 21.-25.03.2011, Münster, Deutschland
  • Open Access Logo Journal of Physics: Conference Series 337(2012), 012032
    DOI: 10.1088/1742-6596/337/1/012032

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Permalink: https://www.hzdr.de/publications/Publ-15518
Publ.-Id: 15518


Characterisation and calibration of weak 44Ti sources for astrophysical applications

Schumann, D.; Schmidt, K.; Bemmerer, D.;
Five Ti-44 calibration sources supplied by Paul-Scherrer-Institute have been characterized concerning their activity distribution as well as the absolute activities. Now, calibration sources for nuclear astrophysics experiments with an uncertainty of +/-1.2% are available
Keywords: Ti-44, supernova, alpha-rich freezeout, nuclear astrophysics, activation, low-level counting
  • Contribution to external collection
    A. Türler, M. Schwikowski, and A. Blattmann: Annual Report 2010, Labor für Radio- und Umweltchemie der Universität Bern und des Paul-Scherrer-Instituts, Villigen/Schweiz: Paul-Scherrer-Institut, 2011, 52

Permalink: https://www.hzdr.de/publications/Publ-15517
Publ.-Id: 15517


Realitätsnahe Einbindung von Sorptionsprozessen in Sicherheitsanalysen

Stockmann, M.; Brendler, V.; Schikora, J.; Noseck, U.; Flügge, J.;
Als Teil eines Langzeitsicherheitsnachweises für Endlager mit radioaktiven Abfällen sind auch Szenarien zu betrachten, bei denen es zu einer Mobilisierung von Radionukliden aus den Abfällen und damit zu deren Transport durch das Endlagersystem kommen kann. Eine wichtige Barriere im System eines Endlagers stellt neben dem Wirtsgestein auch das darüberliegende Deckgebirge dar. Der Transport durch die Geosphäre wird für viele Radionuklide durch Sorption an Oberflächen vorhandener Mineralphasen verlangsamt. In bisher verwendeten Transportprogrammen wird die Rückhaltung der Radionuklide über zeitlich und räumlich konstante Verteilungskoeffizienten (Kd Werte) beschrieben.
Im Rahmen des Vortrages wird das Verbundprojekt ESTRAL (Realitätsnahe Einbindung von Sorptionsprozessen in Transportprogramme für die Langzeitsicherheitsanalyse) (Kooperations-partner: HZDR Dresden-Rossendorf und GRS Braunschweig) vorgestellt. Ziel des Projektes ist es, eine neue Methodik zur Berücksichtigung der Sorption im bestehenden reaktiven Transportcode r³t (radionuclide, reaction, retardation, and transport, GRS) zu entwickeln und zu erproben. Dabei werden die bisher konditionellen Kd-Werte durch so genannte smart Kd-Werte ersetzt, welche auf Basis mechanistischer Modelle (Oberflächenkomplexierungsmodelle) als Funktion wichtiger Einflussgrößen Ei (z.B. pH, Ionenstärke, pCO2, Konzentration Ca2+ und Al3+) im geochemischen Speziationscode PHREEQC berechnet werden. Mit dieser Weiterentwicklung von r3t wird ein Instrumentarium zur Verfügung gestellt, mit dem der Radionuklidtransport unter sich verändernden geochemischen Bedingungen (z.B. infolge Klimaänderungen) realitätsnäher beschrieben werden kann. Eine solche Vorgehensweise wird exemplarisch für den Radionuklidtransport im Deckgebirge des möglichen Endlagers im Salzstock Gorleben entwickelt. Einzelne Einflussgrößen Ei sind bislang im Transportcode r³t nicht verfügbar. Hierzu werden geeignete Methoden zum Transport dieser Parameter sowie Gleichungen zur Beschreibung des pH-Wertes und der Ionenkonzentrationen als Funktion der verfügbaren Mineralphasen in r³t implementiert. Anschließend kann r³t für jeden Raum-Zeit-Punkt vorberechnete Verteilungs-koeffizienten aus einer mehrdimensionalen Matrix in Abhängigkeit von den jeweiligen geochemischen Bedingungen abrufen.
Anhand von Anwendungsrechnungen wird das weiterentwickelte Programm erprobt. Dafür werden zwei verschiedene Prozesse, die als Folge klimatischer Veränderungen auftreten können, untersucht: (1) Der Eintrag von Nordseewasser in das Deckgebirge für den Fall einer Meerestransgression während eines Klimaoptimums, und (2) Die Entwicklung des Deckgebirges in einer Warmzeit nach einer Kaltzeit mit lang andauerndem Permafrost. Bei beiden Prozessen werden sich die geochemischen Bedingungen erheblich verändern, was zu einer gravierenden Veränderung des Sorptionsverhaltens vieler Radionuklide führen wird.
  • Invited lecture (Conferences)
    Jahrestagung Kerntechnik, 17.-19.05.2011, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15516
Publ.-Id: 15516


The special case of Actinide(IV) complexation by the carboxylic function of small and large organic ligands

Hennig, C.; Takao, K.; Takao, S.; Meyer, M.; Jeanson, A.; Dahou, S.; Den Auwer, C.;
Accidental release of radionuclides from mining activities, nuclear energy production, and radioactive waste storage sites requires research to predict the fate and mobility of these contaminants in the environment and more specific in organisms. To date, the interaction of actinides with biological systems is widely unkown, due to the lack of structural information on the molecular level. The aim of this presentation is to summarize recently explored coordination principles of tetravalent actinides with small carboxylic and aminocarboxylic ligands as well as the interaction with proteins.
Tetravalent actinides form with carboxylate ligands in aqueous solutions at low pH values usually monomeric complexes. They show at the other hand a strong tendency toward hydrolysis already at low pH. As the pH reaches the onset of An(IV) hydrolysis, olation and oxolation occur as competing reactions to the carboxylate complexation. We observed under these circumstances the formation of several well-defined polynuclear species. The carboxylic group acts in such systems as a terminating ligand and stabilizes nanosized polynuclear clusters in solution and in the solid state. It is important to note that this reaction prevents widely the formation of polynuclear hydrolysis species as well as the formation of An(IV) hydrous oxide colloids.
Keywords: tetravalent actinides, carboxylic ligands, proteins, EXAFS, XRD
  • Invited lecture (Conferences)
    Goldschmidt 2011, 14.-19.08.2011, Prague, Czech Republic
  • Abstract in refereed journal
    Mineralogical Magazine (2011), 1010-1010

Permalink: https://www.hzdr.de/publications/Publ-15515
Publ.-Id: 15515


Comparative study of the U(VI) complexation onto γ-Al2O3 by ATR FT-IR and EXAFS spectroscopy

Müller, K.; Foerstendorf, H.; Rossberg, A.; Stolze, K.; Gückel, K.;
Aluminates, representing an essential component of clay minerals, play a decisive role in regulating the mobility of contaminants in rock and soil formations, in particular due to their tendency to form coatings on mineral surfaces [1].
In this work, U(VI) sorption on γ-Al2O3 is comparatively investigated using in situ vibrational and X-ray absorption spectroscopy. The focus was set to micromolar U(VI) concentrations and a variety of environmentally relevant sorption parameters in order to resolve discrepancies reported earlier [2-4].
Time-resolved (TR) IR spectroscopic sorption experiments at the alumina-water interface evidence the formation of three different species as a function of surface loading (c.f. Fig.): a monomeric carbonate complex, an oligomeric surface complex and a surface precipitate. These results are confirmed by IR experiments performed at different flow rates, pH values, ionic strengths, U(VI) concentrations, and in inert gas atmosphere. Results of EXAFS experiments of batch samples are consistent to these findings.
[1] Guillaumont, R. (1994) Radiochimica Acta 66-7, 231-242. [2] Catalano, J. G. et al. (2005) Geochim. Cosmochim. Acta 69, 3555-3572. [3] Moskaleva, L.V. et al. (2006) Langmuir 22, 2141-2145. [4] Sylwester, E. R. et al. (2000) Geochim. Cosmochim. Acta 64, 2431-2438.
  • Contribution to proceedings
    Goldschmidt conference 2011, 14.-19.08.2011, Prague, Czech Republic
    Mineralogical Magazine, Vol. 75 (3), 1513
  • Poster
    Goldschmidt conference 2011, 14.-19.08.2011, Prague, Czech Republic
  • Lecture (Conference)
    Goldschmidt conference 2011, 14.-19.08.2011, Prague, Czech Republic

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Permalink: https://www.hzdr.de/publications/Publ-15514
Publ.-Id: 15514


Scaling law for the photon spectral density in the nonlinear Thomson-Compton scattering

Seipt, D.; Kämpfer, B.;
We derive a new scaling law for the photon spectral density in nonlinear Thomson/Compton scattering, extending the findings of Heinzl, Seipt, and Kämpfer [Phys. Rev. A 81, 022125 (2010)]. This allows one to easily include the effects of general scattering geometries, e.g., side injection, and of a finite-size detector on the photon spectrum. The scaling law is employed to study substructures emerging in the nonlinear Thomson/Compton spectra due to temporally shaped laser pulses scattering off relativistic electrons. We determine optimum scattering geometries for an experimental verification of these substructures.
Keywords: Thomson scattering, scaling law, electron phase space, photon spectrum
  • Open Access Logo Physical Review Special Topics - Accelerators and Beams 14(2011)4, 040704

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Publ.-Id: 15513


Dosimetry of laser-accelerated electron beams used for in vitro cell irradiation experiments

Richter, C.; Kaluza, M.; Karsch, L.; Schlenvoigt, H.-P.; Schürer, M.; Sobiella, M.; Woithe, J.; Pawelke, J.;
The dosimetric characterization of laser-accelerated electrons applied for the worldwide first systematic radiobiological in vitro cell irradiations will be presented. The laser-accelerated electron beam at the JeTi laser system has been optimized, monitored and controlled in terms of dose homogeneity, stability and absolute dose delivery. A combination of different dosimetric components were used to provide both an online beam as well as dose monitoring and a precise absolute dosimetry. In detail, the electron beam was controlled and monitored by means of an ionization chamber and an in-house produced Faraday Cup for a defined delivery of the prescribed dose. Moreover, the precise absolute dose delivered to each cell sample was determined by an radiochromic EBT film positioned in front of the cell sample. Furthermore, the energy spectrum of the laser-accelerated electron beam was determined. As presented in a previous work of the authors, also for laser-accelerated protons a precise dosimetric characterization was performed that enabled initial radiobiological cell irradiation experiments with laser- accelerated protons. Therefore, a precise dosimetric characterization, optimization and control of laseraccelerated and therefore ultra-short pulsed, intense particle beams for both electrons and protons is possible, allowing radiobiological experiments and meeting all necessary requirements like homogeneity, stability and precise dose delivery. In order to fulfil the much higher dosimetric requirements for clinical application, several improvements concerning, i.e., particle energy and spectral shaping as well as patient safety are necessary.
Keywords: laser particle acceleration, laser-accelerated electrons, dosimetry, radiobiology, radiochromic films, faraday cup, ionization chamber, EBT films

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Permalink: https://www.hzdr.de/publications/Publ-15512
Publ.-Id: 15512


Terahertz nonlinear optics of exciton states

Helm, M.;
Excitons in semiconductor exhibit a hydrogenic energy spectrum, scaled down into the THz range. By pumping the 1s-2p intra-excitonic transition in GaAs/AlGaAs quantum wells with the Dresden free-electron laser, we induce an AC Stark effect, namely the famous Autler-Townes splitting reflecting exciton states dressed by THz photons [1]. The spectrum is probed via band-gap absorption. Under similar conditions, we also observe resonantly enhanced THz sideband generation by mixing the THz and band gap radiation [2].
[1] M. Wagner et al., Phys. Rev. Lett. 105, 167401 (2010)
[2] M. Wagner et al., Appl. Phys. Lett. 94, 241105 (2009)
Keywords: terahertz, exciton, free-electron laser
  • Invited lecture (Conferences)
    Workshop of the GDRI-CNRS: Semiconductors Sources and Detectors of THz Radiation, 29.03.-01.04.2011, Tignes, France

Permalink: https://www.hzdr.de/publications/Publ-15511
Publ.-Id: 15511


THz spectroscopy of semiconductors at high electric and magnetic fields

Helm, M.;
THz spectroscopy of semiconductors at high electric and magnetic fields
Keywords: terahertz, semiconductors
  • Invited lecture (Conferences)
    4th Annual Meeting of the German Terahertz Center, 28.03.2011, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15510
Publ.-Id: 15510


High resolution RBS investigations of ZrO2 layer growth in the initial stage on native silicon oxide and titanium nitride

Vieluf, M.; Munnik, F.; Neelmeijer, C.; Kosmata, M.; Teichert, S.;
High Resolution Rutherford Backscattering Spectrometry (HR-RBS) with a depth resolution of about 0.3 nm near the surface was used to analyse the interface between ultrathin high-k ZrO2-layers and the substrate. In order to improve the quality of the analysis, a method was developed that takes local thickness variations, obtained by atomic force microscopy (AFM), into account during simulation of the HR-RBS spectra. The aim was to study atomic layer deposition (ALD) growth processes on Si(100) covered with native silicon oxide (SiO2) or with TiN. In the first case the interface is sharp, except for a small intermediate ZrSiO4-layer, and no diffusion of Zr-atoms in SiO2 could be detected. A quite different behaviour could be derived from high resolution spectra for the growth of ZrO2 on TiN. In addition, measurements of the surface topography of the TiN-layer revealed non-negligible surface roughness. Diffusion of Zr into polycrystalline TiN was demonstrated for the first time after correction for surface roughness. This observation indicates that already during the first ALD reaction cycle a small proportion of the deposited Zr-atoms diffuses – probably along grain boundaries – into the TiN-layer up to a depth of 3 nm.
Keywords: High Resolution Rutherford Backscattering Spectrometry (HR-RBS); High-k dielectric; Atomic Layer Deposition (ALD)

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Permalink: https://www.hzdr.de/publications/Publ-15509
Publ.-Id: 15509


CFD modelling of adiabatic bubbly flow

Krepper, E.; Morel, C.; Niceno, B.; Ruyer, P.;
The paper describes the simulation of adiabatic gas-liquid flow based on the Euler/Eulerian approach. An adequate characterisation of the momentum exchange between the phases is necessary. The basic experiment investigating the momentum exchange is the vertical upward flow in a pipe. This report describes the main CFD approaches for momentum exchange and the comparison to experimental results for several test conditions. For large gas injection rates, a bubble size distribution including bubble coalescence and fragmentation has to be considered. The paper describes the concept of the inhomogeneous MUSIG model, developed by ANSYS/CFX and HZDR which is implemented in CFX and a comparable concept of a population balance model implemented in NEPTUNE_CFD (CEA, EDF, IRSN and AREVA). Measurements performed in HZDR are used for model validation. Crucial for the quality of the described models are the base approaches for bubble coalescence and fragmentation. Among other influences these phenomena depend on the liquid turbulence. Therefore special attention was devoted on CFD simulation of bubbly turbulent flow based on different model concepts. Concepts based on Reynolds averaged turbulence models are described. In PSI Large Eddy based studies were performed and compared to DEDALE experiments. The work was performed within the NURESIM and the NURISP projects in the frame of sixth and the seventh European Framework Program.
Keywords: CFD, multiphase-flow, adiabatic flow, polydispersed flow, turbulence, experiments, simulations

Permalink: https://www.hzdr.de/publications/Publ-15508
Publ.-Id: 15508


Weiterentwicklung des Siebmodells und Experimente zum Anlagerungs- und Penetrationsverhalten

Grahn, A.;
Im Vortrag wird der aktuelle Bearbeitungsstand zur Modellierung von Rückhaltevorrichtungen im Notkühlkreislauf von Kernreaktoren berichtet. Die Modellierung unterteilt sich in ein Basismodell zur Berechnung der im Verlauf des Prozesses akkumulierten Isoliermaterialmasse und des daraus resultierenden Druckverlusts über der kompressiblen Packung, sowie in ein erweitertes Modell, das den weiteren Anstieg des Druckverlusts durch Einlagerung von Korrosionspartikeln infolge der Tiefenfiltrationswirkung der Packung in der Spätphase des Kühlmittelverluststörfalls beschreibt. Im Vortrag werden experimentelle und theoretische Arbeiten zur Parametrierung der Modellgleichungen sowie Beispielrechnungen vorgestellt.
Keywords: loss of coolant accident, nuclear reactor safety, pressure loss
  • Lecture (others)
    Fachkolloquium zum BMWi-Projekt 150 1360/150 1363, 17.-18.03.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15507
Publ.-Id: 15507


Bildgestützte in-vivo Dosimetrie: Von PET zu in-beam SPECT

Fiedler, F.;
No abstract availabe
  • Invited lecture (Conferences)
    23. Weiterbildungsveranstaltung Mitteldeutscher Medizinphysiker in Dresden, 08.-09.04.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15506
Publ.-Id: 15506


Electron transport and anisotropy of the upper critical magnetic field in a Ba0.68K0.32Fe2As2 single crystals

Gasparov, V. A.; Wolff-Fabris, F.; Sun, D. L.; Lin, C. T.; Wosnita, J.;
Early work on the iron-arsenide compounds supported the view, that a reduced dimensionality might be a necessary prerequisite for high–Tc superconductivity. Later, however, it was found that the zero-temperature upper critical magnetic field, Hc2(0), for the 122 iron pnictides is in fact rather isotropic. Here, we report measurements of the temperature dependence of the electrical resistivity, rho(T), in Ba0.5K0.32Fe2As2 and Ba0.68K0.32Fe2As2 single crystals in zero magnetic field and for Ba0.68K0.32Fe2As2 as well in static and pulsed magnetic fields up to 60 T. We find that the resistivity of both compounds in zero field is well described by an exponential term due to inter-sheet umklapp electron-phonon scattering between light electrons around the M point to heavy hole sheets at the Г point in reciprocal space. From our data, we construct an H–T phase diagram for the inter-plane (H || c) and in-plane (H || ab) directions for Ba0.68K0.32Fe2As2. Contrary to published data for underdoped 122 FeAs compounds, we find that Hc2(T) is in fact anisotropic in optimally doped samples down to low temperatures. The anisotropy parameter, γ = Habc2/Hcc2, is about 2.2 at Tc. For both field orientations we find a concave curvature of the Hc2 lines with decreasing anisotropy and saturation towards lower temperature. Taking into account Pauli spin paramagnetism we perfectly can describe Hc2(T) and its anisotropy.
  • JETP Letters 93(2011), 26-30

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Permalink: https://www.hzdr.de/publications/Publ-15505
Publ.-Id: 15505


Magneto-acoustic study of single crystalline UCu0.95Ge

Yasin, S.; Andreev, A. V.; Skourski, Y.; Wosnitza, J.; Zherlitsyn, S.; Zvyagin, A. A.;
We present results of a magneto-acoustic study on a UCu0.95Ge single crystal. This compound exhibits antiferromagnetic ordering at 48 K and shows a first-order metamagnetic phase transition at 38 T to a spin-polarized state, i.e., when the magnetic field is applied along the c direction a sharp jump in the magnetization appears. The sound velocity and sound attenuation demonstrate pronounced anomalies in the vicinity of both magnetic phase transitions proving the important role of magneto-elastic interactions in the physics of this actinide compound. Above TN, the acoustic characteristics show some unusual frequency-dependent features which presumably can be related to the dynamics of Cu vacancies in UCu0.95Ge. Our results are discussed in frame of a phenomenological model, which describes qualitatively the main experimental observations.
  • Poster
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 13.-18.03.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15504
Publ.-Id: 15504


Fermi-surface topology of Ce1−xYbxCoIn5

Polyakov, A.; Ignatchik, O.; Bianchi, A. D.; Prevost, B.; Seyfarth, G.; Fisk, Z.; Hurt, D.; Goodrich, R. G.; Wosnitza, J.;
The heavy-fermion (HF) metals are very susceptible to chemical substitution. In these compounds the Kondo coupling between a lattice of local moments and the conduction band creates quasiparticle excitations with large effective masses and the dopants disrupt the coherent Kondo coupling. We study the effect of Yb doping on the Pauli-limited, HF superconductor, CeCoIn5 via de Haas-van Alphen (dHvA) measurements. Yb acts as a non-magnetic divalent substitution for Ce, equivalent to hole doping on the rare-earth site. Our main goal consists in the systematic investigation of the dHvA oscillations on Ce1−xYbxCoIn5 in order to elucidate the evolution of the Fermi surface as a function of Yb. The dHvA data were obtained on high-quality single crystals with different concentrations of Yb atoms. The experiment was performed in a top-loading dilution refrigerator by use of a capacitive torque cantilever technique at temperatures down to 20 mK in magnetic fields up to 18 T.
  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 13.-18.03.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15503
Publ.-Id: 15503


Gallium nanolayers featuring on-chip superconductivity in silicon

Skrotzki, R.; Herrmannsdörfer, T.; Fiedler, J.; Heera, V.; Voelskow, M.; Mücklich, A.; Schmidt, B.; Skorupa, W.; Gobsch, G.; Helm, M.; Wosnitza, J.;
We demonstrate the feasibility of embedding superconducting Ga nanolayers in commercial (100) oriented silicon wafers and discuss the possibility of potential device applications [1]. Ion implantation and rapid thermal annealing, known as versatile tools of microelectronic technology, have been used for inserting and distributing a gallium dose of up to 4 × 1016 cm2. As proven by structural analysis, a 10 nm thin layer of amorphous Ga-rich precipitates forms during annealing at 600 - 700°C. These structures exhibit a superconducting transition at 7 K. Extended resistivity and magnetization measurements reveal in-plane critical fields around 14 T and critical current densities exceeding 2 kA/cm2. In summary, we proceed with an optimistic outlook concerning the implementation of prospective microstructuring. After all, this would be the next step towards the development of novel semiconductor-based superconducting devices.
  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 13.-18.03.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15502
Publ.-Id: 15502


Thermodynamic, magnetic and transport properties of Rh17S15

Uhlarz, M.; Ignatchik, O.; Wosnitza, J.; Haase, A.; Doerr, M.; Daou, R.; Rosner, H.; Naren, H. R.; Thamizhavel, A.; Ramakrishnan, S.;
We determined thermodynamic (specific heat), magnetic (magnetization, magnetostriction and susceptibility) and transport (electrical resistivity) properties of the 4d-electron superconductor Rh17S15 (Tc = 5.3 K). The upper critical field is 19.2 T at T = 0.07 K. We investigated both a polycrystal and a single crystal. Specific heat gives (B = 0) = 107 mJ/molK2, meff = 35 m0, and a superconducting energy gap Δ0 = 0.94 meV. The magnetic properties are dominated by flux-line pinning; resistivity likely reveals an amplification of electron-phonon coupling by weak disorder. Additionally, band-structure calculations are presented and interpreted in the context of our own experiments and other recently published results.We interpret our findings in order to find the origin of the strong electronic correlations in Rh17S15 both in the superconducting and in the normal-conducting state.
  • Poster
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 13.-18.03.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15501
Publ.-Id: 15501


Field-induced gap in a quantum spin-1/2 chain in a strong magnetic field

Ozerov, M.; Wosnitza, J.; Čižmár, E.; Feyerherm, R.; Manmana, S. R.; Mila, F.; Zvyagin, S. A.;
Magnetic excitations in copper pyrimidine dinitrate, a spin-1/2 antiferromagnetic chain with alternating g-tensor and Dzyaloshinskii-Moriya interaction, that exhibits a field-induced spin gap, are probed by means of pulsed-field electron spin resonance spectroscopy. In particular, we report on a minimum of the gap in the vicinity of the saturation field Bsat = 48.5 T associated with a transition from the sine-Gordon region (with soliton-breather elementary excitations) to a fully spin-polarized state (with magnon excitations). This interpretation is fully confirmed by quantitative the agreement with DMRG calculations for a spin-1/2 Heisenberg chain with staggered transverse field
  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 13.-18.03.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15500
Publ.-Id: 15500


Ergebnisse von Korrosionsuntersuchungen an der Korrosionsversuchsanlage „KorrVA“ des HZDR

Kryk, H.; Hoffmann, W.;
Inhalt der Arbeiten des HZDR im Rahmen des BMWi-Forschungsvorhabens 150 1363 ist u. A. die Untersuchung des Einflusses von Korrosionsprodukten auf das Differenzdruckverhalten von Mineralwolleablagerungen an den Sumpfansaugsieben der Notkühlsysteme von Leichtwasserreaktoren bei Kühlmittelverluststörfällen.
Zur Aufklärung der Korrosionsprozesse und deren Auswirkungen auf die Verstopfung der Sumpfsiebe wurden zahlreiche Experimente in der Korrosionsversuchsanlage „KorrVA“ unter Nutzung von feuerverzinkten Stahlproben durchgeführt. Die Ergebnisse der Langzeit-Korrosionsexperimente lassen auf einen mehrstufigen Korrosionsmechanismus schließen. Zunächst erfolgt eine Auflösung der Zinkschicht in der Borsäure-Lösung. Die dabei entstehenden Zink-Ionen gehen in Lösung und tragen somit nicht signifikant zur Erhöhung des Druckverlustes an den Sumpfsieben bei. Während der zweiten Stufe erfolgt die Auflösung des Basismaterials, welches in weiterer Folge zu unlöslichen Korrosionspartikeln (Rost) reagiert. Diese lagern sich an den mit Isoliermaterial-Fasern belegten Sumpfsieben ab und führen so zu einem weiteren Differenzdruckaufbau. Als Haupteinflussfaktoren des Gesamtprozesses wurden die Aufprallkraft des Leckstrahls auf die Materialoberfläche, die Kühlwasserchemie sowie das Verhältnis der Korrosions-Oberfläche zum Kühlmittel-Volumen und das Verhältnis von Zink-Oberflächen im Leckstrahl zu unter dem Wasserspiegel liegenden verzinkten Oberflächen identifiziert.
Keywords: LWR, LOCA, corrosion, hot-dip galvanised steel, zinc, boric acid
  • Lecture (Conference)
    Fachkolloquium "Partikelströmung", 17.-18.03.2011, Zittau und Dresden, Deutschland
  • Contribution to proceedings
    Fachkolloquium "Partikelströmung", 17.-18.03.2011, Zittau und Dresden, Deutschland
    CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-15499
Publ.-Id: 15499


Peculiar high-field quantum magnetism in the frustrated S = 1/2 spin chain cuprate linarite

Schäpers, M.; Wolter, A. U. B.; Drechsler, S.-L.; Nishimoto, S.; Skourski, Y.; Uhlarz, M.; Schmitt, M.; Rosner, H.; Rule, K. C.; Süllow, S.; Heide, G.; Büchner, B.;
We present an experimental and theoretical study of the quasi-onedimensional S = 1/2 Heisenberg magnet linarite PbCuSO4(OH)2, with competing ferromagnetic nearest-neighbor and antiferromagnetic nextnearest- neighbor exchange interactions. It includes magnetization and NMR studies as well as theoretical simulations for the determination of the leading exchange couplings, which are about an order of magnitude higher as determined previously [1]. Furthermore, a manifold of field-induced phases are probed, from which we draw a preliminary phase diagram. Notably, spin-lattice relaxation investigations indicate that linarite might undergo a magnetic quadrupolar spin liquid phase transition as recently predicted for such materials.
  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 13.-18.03.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15498
Publ.-Id: 15498


Investigation of spin- lattice interactions in Ho2Ti2O7 and Dy2Ti2O7

Erfanifam, S.; Zherlytsin, S.; Wosnitza, J.; Petrenko, O.;
Ho2Ti2O7 and Dy2Ti2O7 belong to the family of rare-earth titanates with pyrochlore structure which have attracted much interest in recent years because of their spin-ice ground state and unusual magnetic excitations. Ultrasound experiments have been carried out on Ho2Ti2O7 and Dy2Ti2O7 at low temperatures down to 0.3 K and applied magnetic fields of up to 17.5 T. The temperature as well as field dependences of the relative change of the sound velocity demonstrate some pronounced anomalies below 2 K for the acoustic modes c11 and cL. In addition we have performed magnetization measurements of these two compounds. The observed anomalies and features in the sound velocity and magnetization provide additional information about the spin-lattice interactions in these spin-ice compounds. The role of the lattice degrees of freedom in connection with the emergent quasiparticles (magnetic monopoles) is discussed.
  • Poster
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 13.-18.03.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15497
Publ.-Id: 15497


Investigatons of modified interlayer coupling in the anisotropic antiferromangnet [Cu(pyz)2(HF2)]SbF6

Beyer, R.; Manson, J. L.; Schlueter, J. A.; Wosnitza, J.;
In recent years, many synthetic strategies have emerged with regard to the crystal engineering of functional magnetic materials. The group of J.L. Manson et al. were able to grow single crystals of a quasi-2D antiferromagnet [Cu(pyz)2(HF2)]SbF6 and a defective polymorphic pendant [Cu2(pyz)4F(HF)(HF2)](SbF6)2 where 50% of the HF2- links are broken, leading to two crystallographically unique Cu2+ sites. The chemical composition remains unchanged, the structural configuration indicates a minor Jahn-Teller distortion. We studied the two branches of this compound by means of magnetization and specific heat measurements, in order to get a better understanding of the importance of H-F hydrogen bonds for establishing long-range magnetic ordering in polymeric quantum magnets.
  • Poster
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 13.-18.03.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15496
Publ.-Id: 15496


Development of a new methodology for realistic describing radionuclide retardation in safety assessment

Stockmann, M.; Brendler, V.; Schikora, J.; Noseck, U.; Flügge, J.;
Conceptual model of the new methodology
In previous safety assessments the Kd concept with temporally constant values was applied to describe the radionuclide retardation in the far field of a repository.
Here, the existing transport program r3t [1] used for large model areas and very long time scales has been improved by a new methodology. Implementing the smart Kd concept based on surface complexation allows to consider varying realistic geochemical conditions.
The methodology is based on a description of the sorption of radionuclides as a function of selected, important environmental parameters Ei such as pH, pCO2, ionic strength, concentration of the cations Ca2+ and Al3+ and presence of mineral phases. Exemplarily for a potential repository site in Germany, the Gorleben site has been selected as application case for a proof-of-concept.
Most of the individual parameters Ei are not available in r³t so far. Thus the transport of these influence factors as well as equations describing pH and concentrations of ions as a function of accessible mineral phases had to be implemented. Then the reactive transport model r³t can call for each time-space point pre-calculated Kd values for selected sediments. They are stored in a multidimensional matrix depending on the respective geochemical conditions. Figure 1 shows the frequency distribution of the pre-calculated Kd-values for Am3+ and U6+ and their classification.

Figure 1: Frequency distribution of the pre-calculated Kd values for Am3+ and U6+.

[1] Fein (2004) Report GRS-192.
  • Contribution to proceedings
    Goldschmidt2011, 14.-19.08.2011, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-15495
Publ.-Id: 15495


Intraexciton terahertz nonlinear optics in semiconductor quantum wells: sideband generation and AC Stark splitting

Wagner, M.; Schneider, H.; Stehr, D.; Winnerl, S.; Andrews, A. M.; Schartner, S.; Strasser, G.; Helm, M.;
We investigate nonlinear optics related to the intraexcitonic 1s-2p heavy-hole transition in GaAs/AlGaAs quantum wells. Tuning intense terahertz (THz) light around this resonance we report (i) efficient second order sideband generation and (ii) first clear evidence of the Autler-Townes effect.
Keywords: intraexciton, exciton, AC Stark, Autler-Townes, terahertz, free-electron laser
  • Lecture (Conference)
    35th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THZ 2010), 05.-10.09.2010, Rom, Italien
  • Contribution to proceedings
    35th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THZ 2010), 05.-10.09.2010, Rom, Italien
    IEEE conference proceedings, 978-1-4244-6657-3

Permalink: https://www.hzdr.de/publications/Publ-15494
Publ.-Id: 15494


Microstructural Evaluation of Ti-6Al-4V alloy after Plasma Immersion Ion Implantation (PIII)

Oliveira, V.; Silva, M. M.; Ueda, M.; Yogi, L.; Zepka, S.; Reis, D. A. P.; Reuther, H.;
Microstructural Evaluation of Ti-6Al-4V alloy after Plasma Immersion Ion Implantation (PIII)
  • Poster
    IX Encontro da SBPMat 2010, IX Brazilian MRS Meeting 2010, 24.-28.10.2010, Ouro Preto, Brasilien

Permalink: https://www.hzdr.de/publications/Publ-15493
Publ.-Id: 15493


Surface Modification of Ni-Ti SMA by Nitrogen Plasma Immersion Ion Implantation – Tribology Preliminary Results

Camargo, E. N.; Silva, M. M.; Ueda, M.; Mello, C. B.; Otubo, J.; Rigo, O. D.; Reuther, H.;
Surface Modification of Ni-Ti SMA by Nitrogen Plasma Immersion Ion Implantation – Tribology Preliminary Results
  • Poster
    IX Encontro da SBPMat 2010, IX Brazilian MRS Meeting 2010, 24.-28.10.2010, Ouro Preto, Brasilien

Permalink: https://www.hzdr.de/publications/Publ-15492
Publ.-Id: 15492


Structure and Tribological Properties of the Aged Inconel 718 Superalloy by Plasma Immersion Ion Implantation

Silva, M. M.; Hirschmann, A. C. O.; Moura Neto, C.; Ueda, M.; Reuther, H.; Mello, C. B.;
Structure and Tribological Properties of the Aged Inconel 718 Superalloy by Plasma Immersion Ion Implantation
  • Poster
    5th Int. Conf. on Surfaces, Coatings and Nanostructured Materials, NANOSMAT-5,, 19.-21.10.2010, Reims, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-15491
Publ.-Id: 15491


Synthesis and evaluation of 1,5-diaryl-substituted tetrazoles as novel selective cyclooxygenase-2 (COX-2) inhibitors

Al-Hourani, B. J.; Sharma, S. K.; Mane, J. Y.; Tuszynski, J.; Baracos, V.; Kniess, T.; Suresh, M.; Pietzsch, J.; Wuest, F.;
A series of 1,5-diaryl-substituted tetrazole derivatives was synthesized via conversion of readily available diaryl amides into corresponding imidoylchlorides followed by reaction with sodium azide. All compounds were evaluated by cyclooxygenase (COX) assays in vitro to determine COX-1 and COX-2 inhibitory potency and selectivity. Tetrazoles 3a–e showed IC50 values ranging from 0.42 to 8.1 mM for COX-1 and 2.0 to 200 lM for COX-2. Most potent compound 3c (IC50 (COX-2) = 2.0 lM) was further used in molecular modeling docking studies.
Keywords: Cyclooxygenase; COX-2 inhibitors; 1,5-Diaryl-tetrazoles

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Permalink: https://www.hzdr.de/publications/Publ-15490
Publ.-Id: 15490


Thermal hydraulic reactor core calculations based on coupling the CFD code ANSYS CFX with the 3D neutron kinetic core model DYN3D

Grahn, A.; Kliem, S.; Rohde, U.; Schütze, J.; Frank, T.;
In order to get the correct feedback on the core reactivity, analyses of postulated reactivity initiated accidents in nuclear reactors require the coupled solution of the neutron transport equation, the equations of heat conduction in the fuel and the heat and momentum transport in the coolant. The paper gives an overview on the coupling of the neutron kinetics code DYN3D with the general purpose fluid dynamics code ANSYS CFX which was carried out to improve the thermal hydraulic part of reactor dynamics simulations. Two steady state simulations of Convoi and VVER type reactors demonstrate that the coupled code system allows for analyses with more plausible results of coupled thermal hydraulics - neutron kinetics problems because three-dimensional coolant flow and heat transport can now be simulated.
Keywords: neutron kinetics, thermal hydraulics, coupled codes
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2011, 16.-19.05.2011, Berlin, Deutschland
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2011, 16.-19.05.2011, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15489
Publ.-Id: 15489


Uranium immobilization in biofilms from a granitic nuclear waste repository research tunnel. - A microsensor and spectroscopic study.

Krawczyk-Bärsch, E.; Pedersen, K.; Lehtinen, A.; Arnold, T.;
At the depth of 70 m (tunnel chainage 771) of the nuclear waste repository research tunnel ONKALO (Finland), which will be part of the nuclear waste repository in the future, massive biofilms are growing next to a fracture zone in a granitic rock environment. They were described as a pink and solid slime, consisting of Pseudomonas anguilliseptica, Arthrobacter bergeri, Hydrogenophaga sp., Methylobacter tundripaludum, Rhodoferrax ferrireducens, and Haliscomenobacter hydrossis. The samples were removed from the tunnel wall together with the fracture water for uranium sorption experiments in a flow cell. A uranium concentration of 4×10-5 M was adjusted in the fracture water by adding UO2(ClO4)2. The water was pumped through the flow cell in a closed circuit for 42 hours. Microsensor measurements of the redox potential, pH and oxygen were performed in the several millimeters thick biofilms before and after the addition of uranium in order to record the effect of uranium. The obtained data showed significant changes of redox potential, pH and oxygen. The redox potential decreased after the addition of uranium during the experiment from 70  2 mV to -164 mV  2 mV with an increase of the pH from 5.4  0.1 to 7.3  0.1 at the same time, indicating reducing conditions in the microenvironment of the biofilm. The decrease in the oxygen concentration showed that the bacteria in the top region of the biofilms, i.e. the metabolically most active biofilms zone, battled the toxic effects of aqueous uranium with an increased respiratory activity, which resulted in oxygen depleted zones. Redox processes may have been triggered, leading to a removal of uranium from the aqueous phase. Analysis, which were performed before and after the sorption experiment, clearly showed, that 63 % of the added uranium was immobilized.

The retardation of uranium in the biofilm was determined by Energy-filtered Transmission Electron Microscopy (EF-TEM) and Electron Energy Loss Spectroscopy (EELS). Elongated particles of high electron density were observed in the cytoplasm of some rod shaped gram negative bacteria, which were often found associated with large rod shaped bacteria. Analysis of the elongated particles by EELS provided spectroscopic evidence for the presence of uranium immobilization, showing unequivocally uranium ionization intensity peaks of O4,5- and N6,7-edges. Distribution analysis of uranium, phosphorus and calcium clearly showed, that a solid uranium mineral has formed intracellular, which indicates the presence of a solid U-phosphate mineral similar to Autunite (Ca[UO2]2[PO4]2•10-12H2O).

Acknowledgments:
The European Atomic Energy Community Seventh Framework Programme [FP7/2007-2013] under grant agreement n° 212287, Collaborative Project ReCosy is thanked for funding.
Keywords: retardation, uranium, biofilm, nuclear waste repository
  • Lecture (Conference)
    3rd Annual Workshop of ReCosy, 21.-24.03.2011, Balaruc-les-Bains, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-15488
Publ.-Id: 15488


A 3D heat conduction model for block-type High Temperature Reactors and its implementation into the Code DYN3D

Baier, S.; Kliem, S.; Rohde, S.;
The code DYN3D, devoloped at the Helmholtzzentrum Dresden-Rossendorf, is extended for application of block-type High Temperature Reactors.
It involves a 3D heat conduction model to deal with higher-(than one)-dimensional effects of heat transfer and heat conduction in a block-type HTR. The heat conduction model is coupled with the existing thermal-hydraulic channel model of DYN3D. Fully-coupled (hexagonal) neutron kinetics and thermal hydraulics calculations are performed. It is shown that the model is appropriate to simulate both stationary states and short-time transients (sudden change of reactivity, sudden increase of the inlet coolant temperature) in a block-type HTR.
Keywords: high temperature gas cooled reactor, heat conduction model, transient analysis, computer code, temperature reactivity feedback
  • Lecture (Conference)
    Jahrestagung Kerntechnik, 17.-19.05.2011, Berlin, BRD
  • Contribution to proceedings
    Jahrestagung Kerntechnik, 17.-19.05.2011, Berlin, BRD

Permalink: https://www.hzdr.de/publications/Publ-15486
Publ.-Id: 15486


The first candidate for chiral nuclei in the A=80 mass region: 80Br

Wang, S. Y.; Qi, B.; Zhang, S. Q.; Hua, H.; Li, X. Q.; Zhu, L. H.; Meng, J.; Liu, L.; Wyngaardt, S. M.; Papka, P.; Ibrahim, T. T.; Bark, R. A.; Datta, P.; Lawrie, E. A.; Lawrie, J. J.; Majola, S. N. T.; Masiteng, L. P.; Mullins, S. M.; Gal, J.; Kalinka, G.; Molnar, J.; Nyako, B. M.; Timar, J.; Juhasz, K.; Schwengner, R.;
Excited states of 80Br have been investigated via the 76Ge(11B, 3n) and 76Ge(7Li, 3n) reactions and a new I = 1 band has been identified which resides 400 keV above the yrast band. Based on the comparison between the experimental results and the triaxial particle rotor model calculations, a chiral character of the two bands within the pi g9/2 X nu g9/2 configuration is proposed, which provides the first evidence for chirality in the A 80 region.
Keywords: Nuclear structure, in-beam spectroscopy, chiral rotation, particle-rotor model

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Permalink: https://www.hzdr.de/publications/Publ-15485
Publ.-Id: 15485


Magnetic moments of the first excited 2+ states in the semi-magic A=112,114,116,122,124 Sn isotopes

Walker, J.; Jungclaus, A.; Leske, J.; Speidel, K.-H.; Ekström, A.; Boutachkov, P.; Cederkäll, J.; Doornenbal, P.; Gerl, J.; Gernhäuser, R.; Goel, N.; Gorska, M.; Kojouharov, I.; Maier-Komor, P.; Modamio, V.; Naqvi, F.; Pietralla, N.; Pietri, S.; Prokopowicz, W.; Schaffner, H.; Schwengner, R.; Wollersheim, H.-J.;
The g factors of the first excited 2+ states in the A=112,114,116,122,124 Sn isotopes have been measured with high accuracy using the transient field technique in combination with Coulomb excitation in inverse kinematics. The experimental results are discussed in a qualitative way on the basis of empirical single particle g factors of the relevant proton and neutron orbitals and compared to a number of different theoretical calculations. The results are found to be best described by shell-model calculations in an extended configuration space. Clear evidence for the contribution of neutron pair excitations from the 1d3/2 to the 0h11/2 orbital to the wave function of the 2+ state in 122,124Sn has been obtained.
Keywords: Nuclear structure, in-beam spectroscopy, magnetic moments, shell model.

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Permalink: https://www.hzdr.de/publications/Publ-15484
Publ.-Id: 15484


Field- and current-induced domain-wall motion in permalloy nanowires with magnetic soft spots

Vogel, A.; Wintz, S.; Gerhardt, T.; Bocklage, L.; Strache, T.; Im, M.-Y.; Fischer, P.; Fassbender, J.ORC; McCord, J.; Meier, G.
We study field- and current-induced domain-wall motion in permalloy nanowires comprising a square-shaped magnetically softened region. Implantation of chromium ions is used to induce pinning sites via a local reduction of the saturation magnetization. Micromagnetic simulations, magnetic transmission soft X-ray microscopy, and electrical measurements are employed to char- acterize the pinning potential which significantly differs for transverse and vortex walls. Reliable domain-wall depinning from a so-called magnetic soft spot by single current pulses is observed. This demonstrates the suitability of these pinning sites for applications.
Keywords: magnetic nanowires, spin transfer torque, magnetic soft spot, x-ray microscopy

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Permalink: https://www.hzdr.de/publications/Publ-15483
Publ.-Id: 15483


Plutonium redox chemistry under anoxic conditions in the presence of iron(II) bearing minerals

Kirsch, R.; Fellhauer, D.; Altmaier, M.; Charlet, L.; Fanghänel, T.; Scheinost, A. C.;
The environmental fate of plutonium, the major transuranium actinide in nuclear waste, is largely impacted by its sorption onto and redox reactions with iron oxide, carbonate or sulfide minerals that form as corrosion products of steel in the "near field" and occur widely in sediments. To obtain information on oxidation state and local structure of Pu in the presence of Fe(II) bearing minerals, electrolytically prepared Pu(V) or Pu(III) (242Pu, 1-3·10-5 M) were, under anoxic conditions, reacted with magnetite (FeIIFeIII2O4) (pH 6-8.5), chukanovite (Fe2(CO3)(OH)2) (pH 8.5) and mackinawite (FeS) (pH 6-8.5). Pu-LIII-edge X-ray absorption spectra (XAS) were collected after 40 d and 8 months of reaction.
In all 14 samples, more than 98 % of Pu was associated with the solid phase and its redox speciation thus accessible by XAS. With magnetite, only the sample prepared at the highest pH and highest Pu loading contained Pu(IV)O2 while in all others Pu was solely present as a tridentate Pu(III) surface complex [1]. The three chukanovite samples all contained both Pu(III) (15 to 40 %) and PuO2. With mackinawite at pH 6 only Pu(III) was present, while all samples prepared at pH7 and higher contained mostly PuO2 and up to approx. 10 % Pu(III).
Through comparison of the different types of minerals (oxide, carbonate, sulfide), reaction pH and Pu/mineral ratios, it becomes apparent that the type of surface complexation (e.g. inner-sphere on magnetite vs. outer-sphere on mackinawite) and total mineral surface area are key parameters in controlling concentrations of dissolved Pu and in determining whether a PuO2 solid phase precipitates. While PuO2 provides an upper limit for concentrations of dissolved Pu, the available mineral surface area and sorption complex stability control what percentage of Pu is present in surface complexes. Under reducing conditions as established through the Fe(II) bearing minerals used here, this mineral surface associated Pu was found to be trivalent. Surface complexed Pu(III) and PuO2 can be thought of being in equilibrium with each other via two processes: a sorption reaction between dissolved and surface complexed Pu(III) and a heterogeneous redox reaction between dissolved Pu(III) and solid phase Pu(IV)O2. It remains to be investigated if and through what mechanisms the Pu solid phase speciation (sorbed Pu(III) vs. solid phase PuO2) might impact the migration behavior of Pu and how, for risk assessment purposes, Pu(III) surface complexes with iron minerals can be implemented into geochemical models.
Keywords: plutonium, redox, EXAFS, XANES, Fe(II)-bearing minerals, mackinawite, magnetite, chukanovite
  • Lecture (Conference)
    Goldschmidt Conference 2012, 24.-29.06.2012, Montreal, Canada
  • Abstract in refereed journal
    Mineralogical Magazine (2012), 1942-1942

Permalink: https://www.hzdr.de/publications/Publ-15482
Publ.-Id: 15482


Molecular imaging of α7 nicotinic acetycholine receptors in vivo: current status and perspectives

Brust, P.; Deuther-Conrad, W.;
Es ist kein Abstract vorhanden.
  • Open Access Logo Book chapter
    Peter Bright: Neuroimaging-Clinical Applications, Rijeka, Croatia: InTech - Open Access Publisher, 2012, 978-953-51-0200-7, 533-558

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Permalink: https://www.hzdr.de/publications/Publ-15481
Publ.-Id: 15481


Frequency dependence of spin relaxation in periodic systems

Barsukov, I.; Römer, F. M.; Meckenstock, R.; Lenz, K.; Lindner, J.; Hemken To Krax, S.; Banholzer, A.; Körner, M.; Grebing, J.; Fassbender, J.ORC; Farle, M.
As a common method to separate intrinsic and extrinsic spin relaxation processes in a ferromagnet, their frequency dependence is employed. We show, that this current approach may be insufficient for a large class of ferromagnetic systems, since the extrinsic spin relaxation can exhibit non-monotonous, periodic frequency dependence, as demonstrated by a good agreement of ferromagnetic resonance experiment and phenomenologic theory.
Keywords: ferromagnet, magnetic relaxation, magnon-magnon scattering, magnetic resonance, thin films, ion beam irradiation

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Permalink: https://www.hzdr.de/publications/Publ-15480
Publ.-Id: 15480


High-Field ESR in Spin Systems with Reduced Dimensionality

Zvyagin, S.;
Quantum fluctuations in low-dimensional magnets give rise to a variety of exotic strongly correlated states, making those systems an extremely attractive ground for testing various theoretical concepts. In this presentation I will focus on high-frequency and high-field Electron Spin Resonance (ESR) studies of two low-dimensional quantum magnets: copper pyrimidine dinitrate (Cu-PM), a spin-1/2 antiferromagnetic chain system with alternating g-tensor and Dzyaloshinskii-Moriya interactions, and the spin-ladder system (C5H12N)2CuBr4 (known as BPCB). In Cu-PM, the observation of a minimum of the spin gap in the vicinity of the saturation field, Hsat = 48.5 T, is associated with a transition from the sine-Gordon region (with soliton-breather elementary excitations) to a spin-polarized magnon state. This interpretation is fully confirmed by the quantitative agreement over the entire field range of the experimental data with the DMRG calculations for spin-1/2 Heisenberg chain with a staggered transverse field. In BPCB, the zero-field gap in the excitation spectrum, Δ = 16.5 K, is observed directly. In addition, our studies provide straightforward evidence of a pronounced anisotropy in this compound (~ 5% of the rung interaction), which is in contrast to an isotropic spin-ladder model, employed for this system previously. It is argued that such an anisotropy in BPCB is determined by the substantial spin-orbit coupling, which appears to be very important for describing magnetic properties of BPCB. The talk will give also a brief introduction into the recent development of the high-field ESR program at the Dresden High Magnetic Field Laboratory.
  • Invited lecture (Conferences)
    International School and Symposium on Multifunctional Molecule-based Materials, 13.-18.03.2011, Argonne, Illinois, USA

Permalink: https://www.hzdr.de/publications/Publ-15479
Publ.-Id: 15479


Field-Induced Gap in a Quantum Spin-1/2 Chain in a Strong Magnetic Field

Zvyagin, S.; Ozerov, M.; Wosnitza, J.; Cizmar, E.; Feyerherm, R.; Manmana, S. R.; Mila, F.;
Magnetic excitations in copper pyrimidine dinitrate, a spin-1/2 antiferromagnetic chain with alternating g-tensor and Dzyaloshinskii-Moriya interactions that exhibits a field-induced spin gap, are probed by means of pulsedfield electron spin resonance spectroscopy. In particular, we report on a minimum of the gap in the vicinity of the saturation field Hsat = 48.5 T associated with a transition from the sine-Gordon region (with solitonbreather elementary excitations) to a spin-polarized state (with magnon excitations). This interpretation is fully confirmed by the quantitative agreement over the entire field range of the experimental data with the DMRG investigation of the spin-1/2 Heisenberg chain with a staggered transverse field.
  • Lecture (Conference)
    MAR11 Meeting of The American Physical Society, 21.-25.03.2011, Dallas, Texas, USA

Permalink: https://www.hzdr.de/publications/Publ-15478
Publ.-Id: 15478


Direct Observation of Band-Gap Closure for a Semiconducting Carbon Nanotube in a Large Parallel Magnetic Field

Jhang, S. H.; Marganska, M.; Skourski, Y.; Preusche, D.; Grifoni, M.; Wosnitza, J.; Strunk, C.;
We have investigated the magnetoconductance of semiconducting carbon nanotubes (CNTs) in pulsed, parallel magnetic fields up to 60 T, and report the direct observation of the predicted band-gap closure and the reopening of the gap under variation of the applied magnetic field. We also highlight the important influence of mechanical strain on the magnetoconductance of the CNTs.
  • Physical Review Letters 106(2011), 096802

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Permalink: https://www.hzdr.de/publications/Publ-15477
Publ.-Id: 15477


Damping of de Haas-van Alphen oscillations and vortex-lattice disorder in the peak-effect region of extreme type-II borocarbide superconductors

Maniv, A.; Maniv, T.; Zhuravlev, V.; Bergk, B.; Wosnitza, J.; Köhler, A.; Behr, G.; Canfield, P. C.; Sonier, J. E.;
The study of magnetic quantum oscillations in the superconducting state is of fundamental importance for understanding the nature of superconductivity under high magnetic fields. However, although studied for more than three decades, this phenomenon poses several basic questions that still defy satisfactory answers. A key controversial issue concerns the additional damping observed in the vortex state of many strong type-II superconductors. Here, we show results of μSR, dHvA, and superconducting quantum interference device magnetization measurements on borocarbide superconductors, initially aimed at investigating the “phase-smearing” effect due to inhomogeneous field broadening. It is found, however, that a sharp drop observed in the dHvA amplitude just below Hc2 is correlated with enhanced disorder of the vortex lattice in the peak-effect region, where the phase-smearing effect is negligible. It is concluded that quasiparticle scattering by the pair potential is significantly enhanced due to vortex-lattice disorder, thus generating additional damping in the dHvA amplitude.
  • Physical Review B 83(2011), 104505

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Permalink: https://www.hzdr.de/publications/Publ-15476
Publ.-Id: 15476


Duration measurement of laser-accelerated electron bunches using single-shot THz time-domain interferometry

Debus, A.; Bussmann, M.; Schramm, U.; Sauerbrey, R.; Karsch, S.;
Laser-plasma wakefield based electron accelerators are expected to deliver ultrashort electron bunches of unprecedented peak currents. However, their actual pulse duration has never been directly measured in a single-shot experiment. We present measurements of the ultrashort duration of such electron bunches by means of THz time-domain interferometry from coherent transition radiation. Using a ZnTe-based electro-optical setup and a 0.5J, 45fs, 800nm laser beam, we demonstrate that the duration of quasi-monoenergetic electron bunches from laser-wakefield acceleration is 32fs (FWHM) at a best fit and below 38fs at a 90% confidence level.
Keywords: laser-wakefield acceleration, pulse length measurement, electro-optic sampling, time-domain interferometry
  • Poster
    DPG Frühjahrstagung Münster 2011, 21.-25.03.2011, Münster, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15475
Publ.-Id: 15475


Traveling-wave Thomson Scattering towards tunable, high-yield sources in the hard X-ray range

Debus, A.; Steiniger, K.; Siebold, M.; Jochmann, A.; Irman, A.; Bussmann, M.; Schramm, U.; Cowan, T.; Sauerbrey, R.;
Thomson sources are compact in size and can provide ultrashort, hard X-ray pulses of high brilliance. However, the finite Rayleigh length at small interaction diameters, makes it increasingly difficult in head-on (180°) Thomson scenarios to avoid higher laser intensities and thus the onset of the nonlinear regime. Effectively, such a geometry limits the peak brilliance of all future Thomson sources. We present a novel concept, Traveling-wave Thomson scattering (TWTS), which allows to obtain centimeter to meter long optical undulators, where interaction length and diameter are independent of each other. With an ultrashort, high-power laser pulse in an oblique angle scattering geometry using tilted pulse fronts, electrons and laser remain overlapped while both beams travel over distances much longer than the Rayleigh length. TWTS offers per pulse photon yields that are 2-3 orders of magnitudes beyond current designs, a minimum scattered bandwidth independent of the ultrashort laser pulse duration and tunability of photon energy without requiring a change in electron energy.
Keywords: Traveling-Wave Thomson Scattering, X-ray, VLS grating, Thomson source
  • Lecture (Conference)
    DPG Frühjahrstagung Kiel 2011, 28.-31.3.2011, Kiel, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15474
Publ.-Id: 15474


Design and scaling considerations of Traveling-wave Thomson sources

Debus, A.; Steiniger, K.; Siebold, M.; Jochmann, A.; Irman, A.; Bussmann, M.; Schramm, U.; Cowan, T.; Sauerbrey, R.;
Thomson sources, driven by small linacs or laser-wakefield accelerated (LWFA) electrons are compact in size and can provide ultrashort, hard X-ray pulses of high brilliance. Traveling-wave Thomson scattering (TWTS) is particularly interesting for “pink beam” experiments at hard X-rays in which high photon yields in a single, ultrashort pulses are needed. Above 100keV photon energy, this approach potentially leads to peak brilliances that are beyond the capabilities of existing synchrotron radiation sources. Towards experimental realization, we show how such a Traveling-wave setup has to be implemented. An emphasis is put on the use of varied-line spacing (VLS) gratings for dispersion precompensation of the laser beam at large interaction angles to achieve the required overlap between laser and electrons within the interaction region.
Keywords: Traveling-Wave Thomson Scattering, X-ray, VLS grating, Thomson source
  • Poster
    DPG Frühjahrstagung Kiel 2011, 28.-31.3.2011, Kiel, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15473
Publ.-Id: 15473


Long optical undulators with Traveling-Wave Thomson Scattering

Debus, A.; Steiniger, K.; Siebold, M.; Jochmann, A.; Irman, A.; Bussmann, M.; Schramm, U.; Cowan, T.; Sauerbrey, R.;
We present a novel concept for optical undulators that avoids the restrictions by the Rayleigh limit of the laser, which allows to define interaction length and diameter independent of each other. With an
ultrashort, high-power laser pulse in an oblique angle scattering geometry using tilted pulse fronts, electrons and laser remain overlapped while both beams travel over distances much longer than the Rayleigh length. This allows to realize side-scattering in laser-electron beam interactions, without compromises with regard to luminosity or overlap.
This is of particular interest for linac-driven Thomson sources, where this Traveling-wave Thomson scattering (TWTS) setup could increase per pulse photon yields 2-3 orders of magnitudes beyond current headon (180°) scattering designs. Also, the smallest achievable scattered bandwidth is controlled by the width of a cylindrically focused laser beam and thus is independent of the ultrashort laser bandwidth. Due to the flexibility in side-scattering angle, photon energies become tunable over a large spectral range without requiring a change in electron energy.
Keywords: Traveling-Wave Thomson Scattering, X-ray, VLS grating, Thomson source
  • Lecture (Conference)
    DPG Frühjahrstagung Münster 2011, 21.-25.03.2011, Münster, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15472
Publ.-Id: 15472


Experimental challenges of Traveling-wave Thomson Scattering

Debus, A.; Steiniger, K.; Siebold, M.; Jochmann, A.; Irman, A.; Bussmann, M.; Schramm, U.; Cowan, T.; Sauerbrey, R.;
Traveling-wave Thomson scattering is a novel interaction design that allows circumventing the Rayleigh limit in optical undulators, which is interesting for possible realizations of Thomson scattering sources with photon yields per pulse that are 2-3 orders of magnitudes beyond current designs. Here we present details on how a Traveling-wave setup has to be implemented in experiment. An emphasis is put on the use of varied-line spacing (VLS) gratings for spatio-temporal beam shaping at large interaction angles to achieve optimal overlap. At the FZD we are using the high-power laser system DRACO (250TW) to realize a Thomson source with electrons from the linear accelerator ELBE or laser-plasma accelerated electrons. We present the current status and further progress towards a head-on Thomson source and a Traveling-Wave Thomson scattering source aiming for high photon yields per pulse.
Keywords: Traveling-wave Thomson scattering, TWTS, X-ray, VLS gratings, Thomson source
  • Poster
    DPG Frühjahrstagung Münster 2011, 21.-25.03.2011, Münster, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15471
Publ.-Id: 15471


Space-time couplings at the DRACO laser

Debus, A.;
The effect of spatio-temporal distortions in the DRACO laser potentially leads to pulse-front tilts in the laser focus on the order of tens of degrees. It is emphasized, that for controlling the focal pulse-front tilt, it is not only necessary to analyze angular dispersion, but additionally spatial and group delay dispersion. A qualitative picture of the space-time couplings is presented and quantitatively discussed at the example of an imperfectly aligned DRACO compressor. The results suggest that the focal pulse front tilt is currently unknown and that more precise measurements of both spatial and group delay are required.
Keywords: spatio-temporal distortions, DRACO, pulse-front tilt
  • Lecture (others)
    Gruppenklausur in Gries, Austria / HZDR retreat, 27.02.-3.3.2011, Gries, Austria

Permalink: https://www.hzdr.de/publications/Publ-15470
Publ.-Id: 15470


Imidazole Containing Bispidine Ligands: Synthesis, Structure and Cu(II)-Complexation

Walther, M.; Matterna, M.; Juran, S.; Fähnemann, S.; Stephan, H.; Kraus, W.; Emmerling, F.;
The preparation and characterization of tris-pyridyl bispidine (3,7-diazabicyclo[3.3.1]nonane) derivatives with benzimidazole and imidazole donor groups at the N3 position of the bispidine skeleton and their copper(II) complexes are reported. The impact of the hetaryl substituents on the configuration isomerism of piperidones and their corresponding bispidones has been studied by 1H NMR spectroscopy. The di-pyridyl piperidones with benzimidazole, imidazole and the Cu(II) complex of the benzimidazole containing bispidone have been characterized by X-ray single crystal diffraction.
  • Zeitschrift für Naturforschung Section B - A Journal of Chemical Sciences 66b(2011), 721-728

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Permalink: https://www.hzdr.de/publications/Publ-15469
Publ.-Id: 15469


Preparation and Characterization of Magnetic Tunnel Junctions with Spin Transfer Torque

Höwler, M.; Bernert, K.; McCord, J.; Potzger, K.; Fritzsche, M.; Mücklich, A.; Fassbender, J.ORC; Kirsch, K.; Mattheis, R.; Slesazeck, S.
Current-perpendicular-to-plane (CPP) magnetic tunnel junctions (MgO-MTJ) have been prepared using electron beam lithography as well as argon ion beam etching. A tantalum hardmask was utilized for pattern transfer. The size of the elliptical nanopillars could be decreased down to 90nm x 150 nm while preserving a TMR ratio of 92.5 %. TEM images proof the absence of redepositions at the MgO layer edge and give an insight into the interface quality. Magnetization switching was performed using either static magnetic fields and/or dc current (spin torque). The nanopillars could be characterized at temperatures ranging from 5 K to 150 K and room temperature. The analysis of magnetization dynamics included single-shot time-resolved magnetoresistance measurements as well as dc current induced oscillations of the free-layer magnetization.
Keywords: magnetic tunnel junction, MgO, spin transfer torque effect, preparation, electron beam lithography, ion beam etching
  • Poster
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 13.-18.03.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15468
Publ.-Id: 15468


Bestimmung langlebiger Radionuklide mit Beschleunigermassenspektrometrie (AMS) mit DREAMS: Von Bergstürzen über Klimaforschung bis Rückbau

Merchel, S.; Akhmadaliev, S.; Rugel, G.;
Das Helmholtz-Zentrum Dresden-Rossendorf (HZDR) hat sein Spektrum ionenanalytischer Verfahren um eine weitere hochsensitive Methode erweitert: die Beschleunigermassenspektrometrie (accelerator mass spectrometry = AMS). Diese AMS ist prädestiniert zur Bestimmung langlebiger Radionuklide (t1/2 ≥ 100 a), die entgegen der allgemein üblichen Zerfallszählung, nicht durch den eigentlichen Zerfall detektiert werden. Vielmehr werden die noch nicht zerfallenen Nuklide wesentlich effizienter massenspektrometrisch bestimmt. Dabei besitzt die AMS gegenüber der konventionellen Massenspektrometrie den Vorteil, dass sie Störsignale von Molekülionen und Isobaren effektiver unterdrücken kann. Die AMS liefert somit weitaus niedrigere Nachweisgrenzen (20000 Atome/g oder 10-9 Bq) als die konventionellen Methoden.
Im Gegensatz zu den in Europa gängigen niederenergetischen AMS-Anlagen, die sich weitgehend auf die Bestimmung von 14C spezialisiert haben, wird die AMS-Anlage des HZDR - DREAMS (DREsden AMS) - als erste moderne Anlage in der EU mit einer Terminalspannung von 6 MV betrieben. Aufgrund der instrumentellen Weiterentwicklungen der AMS, die die Bestimmung von Isotopenverhältnissen im Bereich von 10-16 nun ermöglichen [1], haben sich die interdisziplinären Applikationsgebiete stark ausgeweitet. Anfänglich bevorzugt untersuchte Proben aus Kosmochemie, Astrophysik und nukleare Daten, werden zunehmend von Proben aus Strahlenschutz, Nuklearsicherheit, Nuklearentsorgung, Radioökologie, Phytologie, Ernährungswissenschaften, Toxikologie und Pharmakologie verdrängt. DREAMS fördert nicht nur die interne Vernetzung der HZDR-Forschungsaktivitäten in der Materialforschung, Strahlenphysik, Radiochemie und Radiopharmazie. Zudem steht DREAMS auch externen Nutzern, insbesondere denen von anderen Helmholtz-Zentren und Universitäten, zur Verfügung. Kommerzielle Proben aus dem Rückbau und der Hydrogeologie runden das DREAMS-Profil ab.
Eine zwingende Voraussetzung für ein erfolgreiches AMS-Labor ist allerdings die Installation radiochemischer Probenpräparationslabore. Die Ansprüche an die chemische bzw. Nuklidreinheit der AMS-Proben sind zwar wesentlich geringer als z.B. die der alpha- oder beta-Spektrometrie und die stark verringerten Probenmengen erleichtern grundsätzlich die Aufbereitung, jedoch muss aufgrund der Nachweisstärke der AMS ein besonderes Augenmerk auf (Kreuz-)Kontaminationen gelegt werden. Erste Projekte aus den Geo- und Umweltwissenschaften mit der TUBA Freiberg, der Uni Rennes, der Uni Bayreuth, der BGR Hannover, dem Alfred-Wegener-Institut, dem GFZ und der Uni Potsdam zeigen, dass der Erfolg etablierter radiochemischer Trennungsgänge u.a. proportional der Laborerfahrung der Probenpräparatoren ist.
Referenzen [1] S. Merchel et al, Nucl. Instr. and Meth. B 266 (2008) 4921.
Keywords: accelerator mass spectrometry
  • Lecture (Conference)
    GDCh-Wissenschaftsforum Chemie 2011, 04.-07.09.2011, Bremen, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-15467
Publ.-Id: 15467


Entwicklung nanoskaliger funktionaler Schichten auf Basis von bakteriellen Hüllproteinen

Weinert, U.; Günther, T.; Müller, N.; Pollmann, K.; Raff, J.;
Bakterielle Hüllproteine stellen die äußerste Abgrenzung von vielen Bakterien und fast allen Archaeen zu ihrer Umwelt dar. Isoliert sind diese Proteine in der Lage, in wässrigen Systemen oder auf Oberflächen zu rekristallisieren und regelmäßige Gitterstrukturen auszubilden. Ihre Fähigkeit hochstrukturierte Nanoschichten zu bilden und das Vorhandensein von zahlreichen frei zugänglichen funktionellen Gruppen qualifizieren diese Proteine als Matrix für die Herstellung nanoskaliger funktioneller Schichten, wie z.B. sensorischen Schichten. Ziel unserer Arbeit ist die Entwicklung von Sensoren für die Detektion kleinster Mengen an Pharmaka, z. B. Canamycin A und von Metallen in wässrigen Systemen.

Dabei ist es möglich, verschiedene Komponenten wie optische Signalgeber und einen spezifischen Rezeptor für bestimmte Substanzen, sequentiell an das Protein zu koppeln. Für die Signalgebung werden Fluoreszenzfarbstoffe genutzt, die in der Lage sind, einen Fluoreszenz Resonanz Energietransfer (FRET) zu erzeugen. Bei diesem Effekt wird Energie von einem Donor-Farbstoff auf einen Akzeptor-Farbstoff übertragen. Im Resultat wird die Fluoreszenz des Donors vermindert und die des Akzeptors erhöht. Da dieser Energietransfer sehr empfindlich auf äußere Veränderungen reagiert, soll der zu detektierende Analyt diesen durch Quenching stören.
Als spezifische Rezeptoren dienen Aptamere. Aptamere sind kurze Oligonukleotide, die ähnlich wie Antikörper nach dem Schlüssel-Schloss-Prinzip funktionieren, jedoch aufgrund ihrer chemischen Eigenschaften weitaus stabiler sind. Mittels dieser chemischen Antikörper lassen sich eine Vielzahl verschiedener Targetmoleküle spezifisch an die sensorische Schicht binden.

Die Erzeugung eines FRET zwischen zwei S-Layer-gebundenen Fluoreszenzfarbstoffen konnte bereits mittels Bestimmung der Fluoreszenzlebensdauer nachgewiesen werden. Ebenso konnten Anti-Thrombin-Aptamere als Modell erfolgreich gebunden werden und deren Funktionalität mittels Affinitätsmessungen nachgewiesen werden. Somit wurden bereits wichtige Zwischenziele für den Aufbau einer sensorischen Schicht erreicht. In einem nächsten Schritt sollen beide Komponenten auf dem Protein gekoppelt werden und so eine nanoskalige sensorische Schicht erzeugt werden.
Keywords: S-layer proteins, sensory layer, FRET, aptamers
  • Lecture (Conference)
    7. Deutsches BioSensor Symposium, 03.-06.04.2011, Heilbad Heiligenstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15466
Publ.-Id: 15466


Magnetic domain structure evolution in NiMnGa magnetic shape memory alloy

Neudert, A.; McCord, J.;
We have investigated the magnetic domain structure evolution due to twin boundary motion in single crystalline NiMnGa (10M) magnetic shape memory samples. Due to the high mobility of the twin boundaries they can be moved by applying a magnetic field or mechanical stress. In general, the equilibrium domain width in magnetic samples depends on the interplay of demagnetization and anisotropy energy. Depending on the orientation of the easy axis within a magnetic sample different equilibrium widths can be found. We investigated the magnetic domain structure using optical polarization microscopy and magnetic indicator film technique. We found that the qualitative domain structure depends on whether the sample was subjected to magnetic fields or mechanical stresses. In both cases the twin boundary is moved and therefore the orientation of the magnetic easy axis is changing. During the field induced motion the variants are partially saturated, whereas during the stress induced motion the net magnetization in the variants is unchanged. This results in a completely different remagnetization process and magnetic domain structure. Using domain theory the equilibrium domain width can be calculated and is compared with the experimental values. We greatly acknowledge support by DFG priority program SPP 1239.
Keywords: magnetic shape memory alloy, magnetic domains
  • Poster
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 15.03.2011, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-15465
Publ.-Id: 15465


CFD for subcooled flow boiling: Simulation of DEBORA experiments

Krepper, E.; Rzehak, R.;
In this work we investigate the present capabilities of CFD for wall boiling. The computational model used combines the Euler / Euler two-phase flow description with heat flux partitioning. Very similar modelling was previously applied to boiling water under high pressure conditions relevant to nuclear power systems. Similar conditions in terms of the relevant non-dimensional numbers have been realized in the DEBORA tests using Dichlorodifluoromethane (R12) as the working fluid. This facilitated measurements of radial profiles for gas volume fraction, gas velocity, liquid temperature and bubble size.
After reviewing the theoretical and experimental basis of correlations used in the model, give a careful assessment of the necessary recalibrations to describe the DEBORA tests. It is then shown that within a certain range of conditions different tests can be simulated with a single set of model parameters. As the subcooling is decreased and the amount of generated vapour increases the gas fraction profile changes from wall to core peaking. This is a major effect not captured by the present modelling. Some quantitative deviations are assessed as well and directions for further model improvement are outlined.
Keywords: CFD, two phase flow, boiling, momentum exchange

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Permalink: https://www.hzdr.de/publications/Publ-15464
Publ.-Id: 15464


Rise and fall of defect induced ferromagnetism in SiC single crystals

Li, L.; Prucnal, S.; Yao, S. D.; Potzger, K.; Anwand, W.; Wagner, A.; Zhou, S.;
6H-SiC single crystals containing VSi-VC divacancies are investigated with respect to magnetic and structural properties. We found that an initial increase of structural disorder leads to pronounced ferromagnetic properties at room temperature. Further introduction of disorder lowers the saturation magnetization and is accompanied with the onset of lattice amorphization. Close to the threshold of full amorphization, also divacancy clusters are formed and the saturation magnetization nearly drops to zero.
Keywords: Silicon carbide, defect induced magnetism
  • Applied Physics Letters 98(2011)22, 222508

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Publ.-Id: 15463


Corrosion Resistance of NiTi SMA Modified by Nitrogen Plasma Immersion Ion Implantation

Camargo, E. N.; Silva, M. M.; Ueda, M.; Otubo, J.; Baldissera, S. C.; Pichon, L.; Reuther, H.;
Corrosion Resistance of NiTi SMA Modified by Nitrogen Plasma Immersion Ion Implantation
  • Poster
    5th Int. Conf. On Surfaces, Coatings and Nanostructured Materials, NANOSMAT-5, 19.-21.10.2010, Reims, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-15462
Publ.-Id: 15462


Modification of Surface Properties of Ti-16Si-4B Powder Alloy by Plasma Immersion Ion Implantation

Fernandes, B. B.; Ueda, M.; Mello, C. B.; Fernandes, P. B.; Reuther, H.; Ramos, A. S.;
Results of the surface modification of Tie16Sie4B powder alloy by nitrogen ion implantation are presented, together with the experimental description of the preparation of that powder by high-energy ball milling and hot pressing. The phase structure, chemical composition and morphology of sample surfaces were observed by utilizing X-ray diffractometer (XRD), atomic force microscope (AFM) and scanning electron microscopy (SEM). A tribological characterization was carried out with a ball-on-disc tribometer and an SEM. Friction coefficient is compared with the one obtained for Tie6Ale4V alloy and the wear scars characterized by SEM/EDS (energy dispersive spectroscopy). The concentration profile of the detected elements have been investigated using Auger electron spectroscopy (AES) depth profiling. Our results show that a shallow implanted layer of oxygen and nitrogen ions were obtained at the Tie16Si e4B alloy surface, sufficient to modify slightly its tribological properties.

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Publ.-Id: 15461


Magnetic Au Nanoparticles on Archaeal S-layer Ghosts as Templates

Selenska-Pobell, S.; Reitz, T.; Schönemann, R.; Herrmannsdörfer, T.; Merroun, M.; Geißler, A.; Bartolomé, J.; Bartolomé, F.; Garcia, L. M.; Wilhelm, F.; Rogalev, A.;
Gold nanoparticles with a size of 2.5 nm were produced using the SlaA-layer ghosts of the archaeon Sulfolobus acidocaldarius as a template. These archaeal bio-Au nanoparticles differ significantly from those of the bacterial bio-Au nanoparticles produced on the S-layer of Bacillus sphaericus. The archaeal Au nanoparticles consist exclusively of Au(0), while the bacterial ones represent a mixture of Au(0) and Au(III). The most impressive feature of the archaeal Au nanoparticles is that they are paramagnetic, in contrast to the bacterial ones and also to bulk gold. As demonstrated by SQUID magnetometry, the archaeal bio-Au possess an unusually large magnetic moment of about 0.1 µB/Au atom. HR-TEM combined with EDX analysis revealed that the archaeal Au nanoparticles are linked to sulfur atoms. The latter originate from the thiol groups of the cystein amino acid residues which are characteristic for the SlaA-layer of S. acidocaldarius but absent in the S-layer of B. sphaericus.
Keywords: Magnetic gold nanoparticles, Sulfolobus acidocaldarius, surface layer (S-layer)
  • Open Access Logo Nanomaterials and Nanotechnology 1(2011)2, 8-16

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Permalink: https://www.hzdr.de/publications/Publ-15460
Publ.-Id: 15460


Dipole-strength functions in 86Kr and 136Ba

Massarczyk, R.;
This talk was a presentation about my diploma thesis. A overview over the ELBEfacility, photon scattering experiments and GEANT4 simulations was presented.
Keywords: Photon scattering, nuclear spectroscopy, nuclear structure, gamma strength function
  • Lecture (others)
    Mini-Workshop on Applications of Electron Bremsstrahlung, 17.-18.01.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15459
Publ.-Id: 15459


Bestimmung der elektromagnetischen Dipolstärkeverteilung in mittelschweren Atomkernen mittels Kernresonanzfluoreszenz

Massarczyk, R.;
Im Rahmen der Arbeit wurden Experimente aus den Jahren 2008/09 für die Kerne 86Kr und 136Ba analysiert. Zur Auswertung mussten neben Photonenfluss- und Effizienzbestimmung auch Simulationen durchgeführt werden, welche die experimentellen Bedingungen widerspiegeln. Nicht am Kern gestreute Ereignisse und Detektorantwortfunktionen wurden mit Hilfe des Programmpaketes GEANT4 simuliert, um in den gemessenen Daten berücksichtigt zu werden. Daraus zeigt sich, dass neben diskreten Energiezuständen auch ein beachtlicher Teil des ermittelten Anregungsquerschnitts in einer Art Quasikontinuum aus unauflösbaren Peaks liegt. Die ermittelten Wirkungsquerschnitte werden mit Hilfe eines statistischen Ansatzes auf Verzweigung in mögliche Zerfallskanäle und auf Fütterung durch Zustände höherer Energie korrigiert.
Keywords: Photon scattering, nuclear spectroscopy, nuclear structure, gamma strength function
  • Diploma thesis
    TU Dresden und Helmholtz-Zentrum Dresden-Rossendorf, 2011
    88 Seiten
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-047 2014

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Permalink: https://www.hzdr.de/publications/Publ-15458
Publ.-Id: 15458


Molecular identification of xenobiotic degrading bacteria via the 16S rDNA approach

Satschanska, G.; Selenska-Pobell, S.;
Molecular identification of five xenobiotic degrading bacteria was performed by using the16S rDNA approach. The strains KCM-R10 and KCM-R11 were isolated from polluted environments near the biggest Pb-Zn smelter on the Balkan Peninsula - KCM. AP9 strain was isolated from activated sludge of the Sofia waste water treatment plant and BT271 - from a phenol-polluted soil in the region of the petrochemical plant near the town of Burgas. The “U”-strain is a bacterial culture of the laboratory microbial collection of Sofia University. All strains are transforming or degrading xenobiotics such as heavy metals, phenol and its derivatives. PCR amplification of their 16S rRNA genes, RFLP analysis of the obtained amplicons with MspI and HaeIII endonucleases and sequencing were conducted. The isolate KCM R10 was affiliated with Pseudomonas sp., the isolates KCM R11 and BT271 – with Bacillus sp., the isolate AP9 - with Pseudomonas putida, and the isolate called “U” - with Bacilluis amyloliquifaciens. The strains are promising for application as mixed cultures in the industrial waste water purification
  • Lecture (Conference)
    Ecology, 28.-29.04.2011, Sofia, Bulgaria

Permalink: https://www.hzdr.de/publications/Publ-15457
Publ.-Id: 15457


Bestimmung der elektromagnetischen Dipolstärkeverteilung in Atomkernen mittels Kernresonanzfluoreszenz an ELBE

Massarczyk, R.; Cowan, T.; Junghans, A. R.; Grosse, E.; Schramm, G.; Schwengner, R.; Wagner, A.;
Beitrag zum Barkhausenposterpreis 2011
  • Poster
    Dresdner Barkhausen-Poster-Preis 2011 für Studenten und Nachwuchswissenschaftler, 28.01.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15456
Publ.-Id: 15456


Dipole strength in 86Kr up to the neutron-separation energy

Massarczyk, R.; Schwengner, R.; Junghans, A. R.; Rusev, G.; Schramm, G.; Wagner, A.;
For the firrst time a high-pressure gas target has been investigatetd at the bremsstrahlung facility at the ELBE accelerator of the Forschungszentrum Dresden-Rossendorf. The experiment was carried out at an electron beam energy of 12MeV in order to study the energy region up to the neutron separation. GEANT4 simulations were performed to subtract the atomic background from the measured spectrum and deduce the intensity of the resonantly scattered gamma-rays. Considering also transitions from states in the quasicontinuum, simulations of gamma-ray cascades were carried out with a new code to estimate branching ratios. As a result the photoabsorption cross section obtained from transitions to the ground state is calculated. The data will be presented in the context of further photon-scattering experiments performed in Rossendorf on the stable isotopes at the closed neutron shell N = 50.
Keywords: Photon scattering, nuclear spectroscopy, nuclear structure, gamma strength function
  • Lecture (Conference)
    DPG Frühjahrstagung 2011 Münster, 21.-25.03.2011, Münster, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15455
Publ.-Id: 15455


Investigating fluorinated cycloalkyl groups for increased metabolic stability using a Tyrosine model system

Franck, D.; Kniess, T.; Steinbach, J.; Zitzmann-Kolbe, S.; Friebe, M.; Dinkelborg, L. M.; Graham, K.;
Objectives:
The aim was to investigate whether fluorocyclobutyl rings can be introduced into targeting probes to improve metabolic stability, while maintaining its binding affinity, using tyrosine as a model system for the LAT transporters.

Methods:
The precursor, cis-cyclobutane-1,3-diol ditosylate, its corresponding F-19 reference compound trans-3-fluorocyclobutanol (FCB), along with the cis-(3-fluorocyclobutyl)-tyrosine (3FCBT), were synthesized using standard organic chemistry methodologies. The non-radioactive 3FCBT was tested in competition and efflux stimulation cell assays using A549 human lung carcinoma cells with [3H]-D-Tyrosine. The metabolic stability of reference compound 3FCBT was studied in both rat hepatocytes and human plasma. Radiosynthesis methods using standard radiofluorination of the prosthetic group [18F]FCB and its conjugation to tyrosine gave the desired 3[18F]FCBT after chromatographic purification. In vitro studies were performed in A549 cells using 3[18F]FCBT and incubated at 37°C for 10, 20, 30 and 60 minutes with and without inhibitors fluoroethyl-tyrosine (FET) and non-radioactive
3FCBT.

Results:
The syntheses of cis-cyclobutane-1,3-diol ditosylate, trans-3-fluorocyclobutanol (FCB), along with the cis-(3-fluorocyclobutyl)-tyrosine (3FCBT) were established. 3FCBT was shown to block the uptake of [3H]-D-tyrosine in the competition cell assay and could stimulate the release of 3H]-D-Tyrosine from the cell in an efflux stimulation cell assay. 3FCBT showed very high stability in both rat hepatocytes (> 95%) and human plasma (> 95%). The unoptimized radiosynthesis gave the desired 3[18F]FCBT, via the prosthetic group [18F]FCB, in moderate yield (12%) with high radiochemical purity (> 99%). The cell uptake showed an increase of 3[18F]FCBT over time and reached a plateau of 5.87% after 30 minutes.

Conclusions:
The radiosynthesis of the prosthetic group [18F]FCB and its conjugation to tyrosine to give 3[18F]FCBT were successfully established. The introduction of 3[18F]FCBT into the LAT-targeting vector D-Tyr was characterized by a significant in vitro uptake in A549 cells and was actively transported into these cells. The encouraging results warrant further investigations of this tracer in the in vivo setting.
  • Lecture (Conference)
    SNM 58th Annual Meeting, 04.-08.06.2011, San Antonio, USA

Permalink: https://www.hzdr.de/publications/Publ-15453
Publ.-Id: 15453


Experiments on evaporating pipe flow

Lucas, D.; Beyer, M.; Szalinski, L.;
Evaporating two-phase flows were investigated in an 8 m long vertical pipe with an inner diameter of 195.3 mm. The phase transfer was induced by depressurization of the pipe starting from 1, 2, 4 and 6.5 MPa. The pressure relief was done for an upward liquid flow in the test section as well as for stagnant liquid. These experiments complete the extensive CFD-grade database obtained at the same test section for adiabatic two-phase flows and flows with bubble condensation along the pipe. Detailed information on the structure of the steam-water interface was obtained using a pair of wire-mesh sensors. The established database is suitable for the development and validation of CFD.
Keywords: poly-disperse flow, evaporation, pressure relief, phase transfer, bubble size
  • Contribution to proceedings
    The 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics, NURETH-14, paper NURETH14-061, 25.-30.09.2011, Toronto, Ontario, Canada
    Proceedings of the 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics (NURETH-14), paper 061
  • Lecture (Conference)
    The 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics, NURETH-14, 25.-30.09.2011, Toronto, Ontario, Canada

Permalink: https://www.hzdr.de/publications/Publ-15452
Publ.-Id: 15452


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