Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

31861 Publications
Quantitative Auswertemethoden für die Beurteilung von Patientenbewegungen in der klinischen PET
Langner, J.; Oehme, L.; Beuthien-Baumann, B.; van den Hoff, J.;
Ziel/Aim:
Aufgrund der kontinuierlich gestiegenen Auflösung der Geräte stellen Patientenbewegungen während einer PET-Aufnahme vor allem bei der Analyse kleiner Strukturen ein wachsendes Problem dar. Dies macht immer häufiger den Einsatz von Bewegungskorrekturmethoden notwendig. Um den Zeitbedarf für die Berechnungen in einem vertretbaren Rahmen zu halten, müssen geeignete Schwellwerte aus den Bewegungsdaten ermittelt werden, unterhalb derer eine Bewegungskorrektur vermieden werden kann. Die sechs die Bewegung beschreibenden Transformationsparameter sind hierzu nur bedingt geeignet, da der kombinierte Einfluss aller Parameter auf die Bewegung nicht einfach abschätzbar ist. Unsere Studie greift dies auf und zeigt am Beispiel von Hirnuntersuchungen wie aus den Daten eines externen Bewegungsmesssystems aussagefähige Schwellwerte abgeleitet werden können. Wir zeigen ferner wie eine routinemäßige Nutzung der Bewegungsanalyse für die Qualitätskontrolle genutzt werden kann.

Methodik/Methods:
Die bei einer PET-Aufnahme von einem Bewegungstracker aufgezeichneten Daten werden automatisch mittels des statistischen Analysewerkzeuges ‚R’ verarbeitet. Es werden statistische Kenngrößen bzgl. der Stabilität der Bewegungsmessung berechnet, sowie die Daten der sechs Translations-/Rotations-Freiheitsgrade graphisch dargestellt und hieraus Transformationsmatrizen berechnet. Zur Analyse des Bewegungseinflusses innerhalb des relevanten Bildvolumens werden die (zeitabhängigen) Transformationsmatrizen auf die Oberfläche einer Kugel von ; 20 cm angewandt. Hierbei wird jeder Punkt eines Gitternetzes transformiert und die euklidische Längen der
Differenzvektoren zwischen ursprünglichem und transformiertem Gitternetz berechnet. Anhand eines Schwellwertes für diese Verschiebung werden die Transformationsmatrizen ausgewählt, die für eine Bewegungskorrektur relevant sind. Zusätzlich ist es möglich, Zielkoordinaten wie z.B. die des Striatums einzugeben, um die berechneten Bewegungsmatrizen auf eine beliebige ROI anzuwenden und somit unmittelbar Bewegungsinformationen für dieses Areal zu erhalten.

Ergebnisse/Results:
Die entwickelten Methoden generieren nach einer Bewegungsmessung automatisch Auswertungen in Form einer PDF-Datei. Diese beinhaltet neben verschiedenen graphischen Statistiken eine Zusammenfassung über die als relevant eingestuften Bewegungen des Patienten und lokalisiert Areale, welche kritisch von Bewegungen betroffen sind.

Schlussfolgerungen/Conclusions:
Durch die Integration der vorgestellten Auswertemethoden in die klinische PET lässt sich die Qualität einer Untersuchung in Hinblick auf den Einfluss der Patientenbewegung objektiver beurteilen. Es ist hiermit möglich, routinemäßige Bewegungsanalysen für PET-Untersuchungen durchzuführen und diese für eine akkurate, in Hinblick auf den Rechenaufwand optimierte Bewegungskorrektur zu nutzen.
  • Lecture (Conference)
    45. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2007, Hannover, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 46(2007), A34

Publ.-Id: 9507 - Permalink


Hydraulic jump in a closed horizontal two-phase flow channel
Vallee, C.;
The hydraulic jump in a co-current two-phase flow was investigated in the Horizontal Air/Water Channel (HAWAC) of Forschungszentrum Dresden-Rossendorf. The hydraulic jump is the discontinuous transition between super- and subcritical flow and is characterised by a steep rising of the water surface with high turbulence production.
High-speed video observations were performed in the channel and an algorithm was developed to recognise the interface in the camera frames. This allows a water level measurement in any cross-section. Since the interface is very dynamic due to the high turbulence in the jump, a statistical approach is proposed in order to reflect the structure of the interface over the time. The probability distribution of the water levels was calculated in each vertical cross-section and is shown in pictures of the test-section.
Furthermore, experiments were performed to point out the influence of the air flow rate on the hydraulic jump in a closed channel. Due to the momentum exchange between the phases, the position of the hydraulic jump from the inlet increases sensibly with the air flow rate. Moreover, an increasing smearing of the probability distributions was observed with higher air flow rate. This indicates that the oscillations of the interface are increasing with the air flow rate, which can be attributed to the flow regime downstream of the hydraulic jump, in particular to the transition to slug flow.
Keywords: hydraulic jump, stratified two-phase flow, horizontal channel
  • Contribution to proceedings
    International Conference on Multiphase Flow 2007, 09.-13.07.2007, Leipzig, Germany
    Paper N° S5_Fri_A_63
  • Lecture (Conference)
    International Conference on Multiphase Flow 2007, 09.-13.07.2007, Leipzig, Germany

Publ.-Id: 9506 - Permalink


Experimental investigation of time-dependent flow driven by a travelling magnetic field
Cramer, A.; Pal, J.; Zhang, C.; Eckert, S.; Gerbeth, G.;
Recently, the flow generated by a travelling magnetic field (TMF) has received increasing attention. This comprises industrial applications in crystal growth as well as basic research on stability and on time-dependent flow for higher values of the forcing parameter, the latter aiming at metallurgical processes. Whereas the flow driven by rotating magnetic fields (RMF) might be said to be fairly understood, this does not hold for the TMF. Moreover, there exist experimental investigations on RMFs but studies on TMF almost restrict to numerical simulations. Also in the case of an RMF, most experiments dealt only with the mean flow. The present work is devoted to both mean flow and turbulence in an electrically conducting melt subjected to a TMF.
  • Contribution to proceedings
    11th EUROMECH European Turbulence Conference, 25.-28.06.2007, Porto, Portugal
    Springer Proceedings in Physics 117: Advances in Turbulence XI, Berlin: Springer, 978-3-540-72603-6, p.750
  • Poster
    11th EUROMECH European Turbulence Conference, 25.-28.06.2007, Porto, Portugal

Publ.-Id: 9505 - Permalink


Extraktionsuntersuchungen mit radiomarkierten Verbindungen zur Charakterisierung neuer Wirt/Gast-Systeme
Stephan, H.;
Die thermodynamische Behandlung von Extraktionsgleichgewichten in flüssigen Zweiphasensystemen gestattet Aussagen zur stöchiometrischen Zusammensetzung extrahierter Komplexe sowie die Ableitung thermodynamischer Daten wie Extraktions-, Komplexstabilitäts-, Verteilungs- und Assoziationskonstanten. Bei Einsatz von radioaktiv markierten Verbindungen zur Konzentrationsbestimmung ergeben sich Vorteile hinsichtlich Substanzbedarf, Reproduzierbarkeit, Genauigkeit und Schnelligkeit gegenüber einer Reihe von anderen Methoden wie NMR-, ICP- und UV/VIS-Spektroskopie, die häufig zur Charakterisierung der Bindungseigenschaften von neuen organischen Liganden herangezogen werden.[1]
Untersuchungen zur Flüssig-Flüssig-Extraktion radioaktiver Kupferkomplexe mit lipophilen Oxobathophenanthrolin-Liganden I werden vorgestellt, die Aussagen zur Komplex-bildungskinetik und Stöchiometrie der gebildeten Komplexe gestatten.[2] Am Beispiel trifunktionalisierter Triphenylketalrezeptoren II wird die Bestimmung von Assoziations-konstanten für Koffein, Theophyllin und Trimethylharnsäure mithilfe der Extraktions-methode diskutiert.[3] Verteilungsuntersuchungen im Zweiphasensystem 1-Octanol/Wasser werden häufig zur Abschätzung der Lipophilie pharmazeutisch relevanter Verbindungen herangezogen, um Vorhersagen zur Bioverteilung treffen zu können. In diesem Zusammenhang werden Ergebnisse zur Charakterisierung von neuen radioaktiv markierten Kupferkomplexen vorgestellt, die für einen Einsatz in der Nuklearmedizin von Interesse sind.

[1] H. Stephan, S. Juran, B. Antonioli, K. Gloe, K. Gloe, Extraction Methods in Analytical Methods in Supramolecular Chemistry, C. Schalley (ed.), Wiley-VCH, Weinheim, 2007, 79-103.
[2] H. Stephan, G. Geipel, G. Bernhard, P. Comba, G. Rajaraman, U. Hahn, F. Vögtle, Eur. J. Inorg. Chem. 2005, 4501-4508
[3] M. Bomkamp, C. Siering, K. Landrock, H. Stephan, R. Fröhlich, S. Waldvogel, Chem. Eur. J. 2007, im Druck (DOI: 10.1002/chem.200601231)
  • Lecture (Conference)
    Wissenschaftsforum Chemie 2007, 16.-19.09.2007, Ulm, Germany

Publ.-Id: 9504 - Permalink


Entwicklung von radioaktiven Kupferkomplexen auf der Basis hexadentater Bispidinliganden
Juran, S.; Walther, M.; Stephan, H.; Bergmann, R.; Steinbach, J.; Comba, P.;
Die Entwicklung von Chelatbildnern für Kupferradionuklide im Hinblick auf einen Einsatz in der Nuklearmedizin (64Cu: PET, 67Cu: Endoradionuklidtherapie) ist ein intensiv bearbeitetes Forschungsgebiet. [1, 2] In diesem Zusammenhang stellen Liganden auf der Basis des Bispidins – Derivate des 3,7-Diazabicyclo[3.3.1]nonans – eine neue interessante Stoffklasse dar, weil sie sehr stabile Kupfer(II)-Komplexe bilden. [3] Darüber hinaus weisen Bispidinliganden weitere günstige Eigenschaften wie eine schnelle Komplexbildungskinetik sowie vielfältige Modifizierungsmöglichkeiten auf, und sind damit für die Entwicklung zielsuchender Radioliganden prädestiniert. [4] Es wird über die Synthese verschiedener hexadentater Bispidine berichtet und über Möglichkeiten zur Einführung kopplungsfähiger Ankergruppen, die eine Verknüpfung mit biologisch relevanten Molekülen gestatten, diskutiert (Bild 1). An ausgewählte Bispidinliganden wurden Biomoleküle wie Neurotensin NT(8-13) und Bombesin BBN(7-13) gekoppelt. Untersuchungen zur Radiochemie und auch zur Radiopharmakologie entsprechender 64Cu-markierter Biokonjugate werden vorgestellt. Dafür werden in vitro- (Challengeversuche in Anwesenheit von Konkurrenzliganden, Plasmastabilität) und in vivo-Studien an Wistar-Ratten (Bioverteilung, Kleintier-PET) herangezogen.

[1] S. V. Smith, J. Inorg. Biochem. 2004, 98, 1874-1901.
[2] S. J. DeNardo, Semin. Nucl. Med. 2005, 35, 143-151
[3] P. Comba, M. Kerscher, W. Schiek, Prog. Inorg. Chem. 2007, in press
[4] H. Stephan, S. Juran, M. Walther, J. Steinbach, K. Born, P. Comba, in „Technetium, Rhenium, and other
Metals in Chemistry and Nuclear Medicine“, U. Mazzi (Ed.), SGE Editoriali, Padova, Italy, 2006, 7, 219-222.
  • Lecture (Conference)
    Wissenschaftsforum Chemie 2007, 16.-19.09.2007, Ulm, Germany

Publ.-Id: 9503 - Permalink


Das Auflösungsvermögen optischer Mikroskope - wo liegt die Grenze?
Winnerl, S.;
Das Abbe´sche Prinzip und das Rayleigh-Kriterium werden eingeführt. Weiterhin werden wichtige Mikroskoptypen wie Konfokalmikroskop und Fluoreszenzmikroskop vorgestellt. Modene Varianten mit hoher Auflösung wie das Zwei-Photon-Fluoreszenzmikroskop und das Stimulated-Emission-Depletion Mikroskop werden besprochen. Im letzten Teil werden verschiedene Bauformen von Nahfeldmikroskopen und ihre Funktionsweise erläutert, schließlich wird ein Experiment mit einem IR-Nahfeldmikroskop diskutiert, bei dem der Rossendorfer FEL als durchstimmbare Lichtquelle eingesetzt wird.
  • Lecture (others)
    Lehrerfortbildung "Bildgebende Verfahren", 16.02.2007, Dresden, Deutschland

Publ.-Id: 9502 - Permalink


Bonding Network in Filtered-Arc-Deposited Carbon Films: Simulation and Characterization
Gago, R.; Jiménez, I.; Vinnichenko, M.; Jäger, H. U.; Belov, A. Y.;
This work address the bonding structure of amorphous carbon films (a-C) with varying sp2 content deposited by filtered-cathodic-vacuum arc (FCVA) at different substrate temperatures (up to 700 K). Experimentally, the arrangement of carbon atoms within the atomic network is assesed by the combination of x-ray absorption near edge spectroscopy (XANES) and spectroscopic ellipsometry (SE) studies. The experimental evolution of sp2 hybrids with temperature is contrasted with theoretical predictions from molecular-dynamics (MD) deposition simulations.
Keywords: amorphous carbon , filtered-cathodic-vacuum arc (FCVA), substrate temperature, sp2 content , x-ray absorption near edge spectroscopy (XANES), spectroscopic ellipsometry (SE), molecular-dynamics (MD)
  • Invited lecture (Conferences)
    International Conference on Metallurgical Coatings and Thin Films (ICMCTF 2007), 23.-27.04.2007, San Diego, California, USA

Publ.-Id: 9501 - Permalink


An octahedral rhenium cluster compound K4[Re6S8(CN)6]: synthesis, structural characterization and biodistribution
Fedorov, V.; Mironov, Y.; Kim, S.-J.; Gaidash, A.; Trunova, V.; Röhrich, A.; Stephan, H.; Pietzsch, H.-J.;
Polynuclear metal compounds may have considerable potential as metallic drugs. Some types of polyoxometalates, derived from Mo, W, Re and others, are able to be transported into cells and mitochondria. Certain representatives show antiviral and anti-tumour properties.[1-3] Deposited in target cells, metal clusters have promising properties to be used in photon activation therapy (PAT) or photodynamic therapy. In this nexus, octahedral cluster rhenium compounds possess bright red luminescence to make them interesting for medical treatment of cancer.[4] Furthermore, the combination of anti-tumour activity and photodynamic therapy can provide synergetic medical efficacy.
We want to present the synthesis, structural characterization and preliminary pharmacological properties of an octahedral rhenium cluster compound. In the latter concern, it is important to know its biodistribution, metabolism and toxicity. So, the goal of the work presented was the determination of biodistribution of K4[Re6S8(CN)6] and lethal dose LD100 in rats. Experiments were carried out on male rats. As formulation the cluster compound K4[Re6S8(CN)6], dissolved in water (different concentrations in the range from 0.01 to 0.5%), was intra-peritoneally administered. The animals were distributed into 5 groups, each group had 5 rats; one rat was control. The formulation has been injected (one mL of solution every one hour during the day). It was determined that 0.5 mg of K4[Re6S8(CN)6] per one gram of live weight of the rats provokes 100% fatal outcome of experimental animals during first day. This value was accepted as the lethal dose LD100 at intraperitoneal administration of the compound.
Biodistribution experiments were carried out in the format of acute toxicity with single injecting preparation of 1/5LD50 dose. The data of biodistribution are shown that the cluster compound is mainly accumulated in the liver the kidney and spleen. No correlation between the concentrations of rhenium and iron in the internal was found. This can be evidenced of the fact that cyanide groups of compound K4[Re6S8(CN)6] are indifferent to molecular forms of iron in which it is presented in organism. Accumulation in spleen may be interpreted as a location of cluster compound in immune structures. This allows to consider cluster rhenium complexes as promising compounds for treatment of lymphoma proliferation sicknesses and first of all the lymphomas.

REFERENCES
[1] J. T. Rhule, C. L. Hill, D. A. Judd, R. F. Schinazi, Chem. Rev. 1998, 98, 327-357.
[2] B. Hasenknopf, Front. Biosci. 2005, 10, 275-287.
[3] C. E. Müller, J. Iqbal, Y. Baqi, H. Zimmermann, A. Röllich, H. Stephan, Bioorg. Med. Chem. Lett. 2006, 16, 5943-5947.
[4] Y. V. Mironov, M. A. Shestopalov, K. A. Brylev, A. S. Yarovoi, G. V. Romanenko, V. E. Fedorov, H. Spies, H.-J. Pietzsch, H. Stephan, G. Geipel, G. Bernhard, W. Kraus, Eur. J. Inorg. Chem. 2005, 657-661.
  • Poster
    International Symposium on Polymer Therapeutics, 19.-21.02.2007, Berlin, Deutschland

Publ.-Id: 9500 - Permalink


Carbohydration of branches ligands with a cyclam-core
Röhrich, A.; Noll, S.; Stephan, H.; Steinbach, J.; Kirchner, R.; Seidel, J.;
Radiopharmaceuticals based on the metallic radionuclides 64/67Cu, 99mTc, 186/188Re and 90Y are often used for diagnostic and therapeutic purposes. Cyclam and its derivatives are one of the most important ligands for the radionuclides mentioned above.[1] A 99mTc-labelled cyclam derivative with attached nitro-triazole units has the potential to be utilized as a marker for tumor hypoxia.[2] Promising tumor accumulation properties have been found for a 99mTc complex of a water-soluble cyclam-containing porphyrin.[3] Recently, we could show that a star-like cyclam ligand appended with four PEG-arms rapidly forms stable copper(II) complexes.[4] Currently, we are focusing our attention on the development of dendritic ligands having both enhanced complex stability and improved bio-availability. In this nexus, we built up two glycodendrimers possessing a cyclam core modified with thiourea-linked sugar residues at the periphery of the molecule (see scheme). Dendrons possessing such sugar moieties show both unique cell uptake behaviour and specific carbohydrate-protein interaction.[5, 6]

We want to report the 99mTc-labelling of the dendritic ligands synthesized. Furthermore, the interaction of these ligands with concanavalin A has been studied using isothermal titration microcalorimetry. In this nexus, a cluster glycoside effect could be clearly shown.[7]

REFERENCES
[1] X. Liang, P. Sadler, Chem. Soc. Rev. 2004, 33, 246-266.
[2] S. Murugesan, S. J. Shetty, O. P. D. Noronha, A. M. Samuel, T. S. Srivastava, C. K. K. Nair, L. Kothari, Appl. Radiat. Isot. 2001, 54, 81-88.
[3] S. Murugesan, S. J. Shetty, T. S. Srivastava, O. P. D. Noronha, A. M. Samuel, Appl. Radiat. Isot. 2001, 55, 641-646.
[4] H. Stephan, G. Geipel, D. Appelhans, G. Bernhard, D. Tabuani, H. Komber, B. Voit, Tetrahedron Lett. 2005, 46, 3209-3212.
[5] L. Vannucci, A. Fiserova, K. Sadalapure, T. K. Lindhorst, M. Kuldova,, P. Rossmann, O. Horvath, V. Kren, P. Krist, K. Bezouska, M. Luptovcova, F. Mosca, M. Pospisil, Int. J. Oncology 2003, 23, 285-296.
[6] P. Krist, L. Vannucci, M. Kuzma, P. Man, K. Sadalapure, A. Patel, K. Bezouska, M. Pospisil, L. Petrus, T. K. Lindhorst, V. Kren, CHEMBIOCHEM 2004, 5, 445-452.
  • Poster
    International Symposium on Polymer Therapeutics, 19.-21.02.2007, Berlin, Deutschland

Publ.-Id: 9499 - Permalink


„TRLFS fingerprinting for uranyl(VI) surface species on clay model substances“
Brendler, V.; Trepte, P.; Krepelova, A.; Baumann, N.;
The U(VI) binding to complex systems such as clays, which play an important role in nuclear waste disposal design, is still to be clarified. An efficient tool to study the relevant speciation in-situ is required, thus TRLFS (time-resolved laser-induced fluorescence spectroscopy) was applied. Silica gel (providing higher binding site concentrations as quartz) and gibbsite were used as model substances for the investigation of silianol and aluminol binding sites, respectively, in clays. Kaolinite, offering both types of surface groups, served as a further model system.

All measurements were using 10 mg silica gel in 40 ml 0.1 M NaClO4 and a uranium concentration of 5•10-6 mol/l. The pH was varied between 4.5 and 9. For the TRLFS measurements the solid phase was centrifuged and resuspended with a NaClO4 solution with pH and ionic strength identical to the original but without uranium. A Nd:YAG diode laser with an excitation wavelength of 266 nm was used to study the sorbed species. Spectra were recorded by a diode array in the wavelength range between 460 and 620 nm. The delay times covered 30 ns up to 200 µs. For further details of the experimental set-up see [1]. All measurements were performed under oxygen atmosphere and at room temperature.

For silica gel, at least three U(VI) surface complexes with fluorescence decay constants  of 47 µs, 185 µs and 299 µs were observable. Peak maxima were red-shifted by 10-16 nm compared to the free uranyl cation. Concerning gibbsite, two species with fluorescence lifetimes of 2.4 and 13.2 µs were present throughout the whole pH range, with a third surface species occurring at pH > 7 ( = 51 µs). Finally, the investigation with kaolinite yielded two surface species with lifetimes of 5.9 and 42.5 µs. For pH values below 7 this is closer to the gibbsite results, indicating that aluminol sites dominate uranyl sorption onto alumosilicates.

[1] Sachs, S. et al. (2007) Radiochim. Acta 95, 103-110.
  • Contribution to proceedings
    Migration 2007, 26.-31.08.2007, München, Germany
    11th Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 72-73
  • Poster
    Migration 2007, 26.-31.08.2007, München, Germany

Publ.-Id: 9498 - Permalink


Terahertz spectroscopy of electron-doped superconductors in magnetic field
Pronin, A.; Pimenov, A.; Loidl, A.; Tsukada, A.; Naito, M.;
In the terahertz and infrared regions we measured the optical conductivity and penetration depth of the electron-doped cuprate superconductor La2-xCexCuO4. In the frequencytemperature behavior of conductivity we observe remarkable differences between the samples with different Ce content, suggesting the gap anisotropy to be a function of the doping level. At terahertz frequencies, we performed measurements in high magnetic fields to suppress superconductivity below Tc. From the conductivity spectra we extract the quasiparticle scattering rate as a function of temperature, and compare its behavior in the superconducting and normal states below Tc. We find a small but measurable optical magnetoresistance at all doping levels, and no signatures for the pseudogap. We also discuss the applicability of ‘universal scaling laws’ to our data on conductivity and penetration depth.
  • Lecture (Conference)
    71. Jahrestagung der Deutschen Physikalischen Gesellschaft und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 26.-30.03.2007, Regensburg, Germany

Publ.-Id: 9497 - Permalink


Magnetic-field-induced Change of the Fermi Surface in CeBiPt
Bartkowiak, M.; Bergk, B.; Skourski, Y.; Wosnitza, J.; Opahle, I.; Elgazzar, S.; Richter, M.; Löhneysen, H. V.; Yoshino, T.; Takabatake, T.;
Comparative experiments between the two semimetals CeBiPt and LaBiPt reveal changes of the Fermi surface in CeBiPt with respect to temperature, applied magnetic, field and chemical composition. It must be concluded that the strong temperature dependence of the Shubnikov-de Haas (SdH) frequency as well as the change of carrier concentration above a sample dependent critical field are associated with the 4f electrons introduced by the Ce atoms. We present Hall and magnetoresistance measurements up to 70T obtained at our new pulsed high magnetic field laboratory in Dresden. We observe the disappearance of the SdH signal and a change of the Hall coefficient above a sample-dependent threshold field. Rather than at 25 T, as reported previously, we measured a threshold field of ~40 T demonstrating the strong dependence of the Fermi surface on stoichiometry.
  • Poster
    Frühjahrstagung DPG, 26.-30.03.2007, Regensburg, Deutschland

Publ.-Id: 9496 - Permalink


Determination of the band structure of LuNi2B2C
Bergk, B.; Bartkowiak, M.; Ignatchik, O.; Jäckel, M.; Wosnitza, J.; Rosner, H.; Petzold, V.; Canfield, P.;
We present de Haas-van Alphen (dHvA) investigations on the nonmagnetic borocarbide superconductor LuNi2B2C which have been performed by use of the torque method in high magnetic fields up to 32 T and at low temperatures down to 50 mK. The complex band structure is extracted from the quantum oscillations in the normal state. In comparison with full-potential-local-orbital calculations of the band structure we are able to assign the observed dHvA frequencies to the different bands. Temperature dependent dHvA investigations allowed the extraction of the effective band masses for the several Fermi-surface sheets. We observe an enhancement of the effective masses compared to the theoretical calculations which is due to electron-phonon interaction. Finally, we are able to examine the angular dependence of the electron-phonon coupling for the different Fermi-surface sheets.
  • Poster
    Frühjahrstagung der DPG, 26.-30.03.2007, Regensburg, Deutschland

Publ.-Id: 9495 - Permalink


The spherically symmetric α2-dynamo, resonant unfolding of diabolical points and third-order exceptional points in Krein space related setups
Günther, U.; Kirillov, O.; Stefani, F.;
In the first part of the talk we consider the spectral behavior of the spherically symmetric α2-dynamo with idealized boundary conditions. The corresponding operator is self-adjoint in a Krein space and therefore it shares many features with Hamiltonians of PT-symmetric Quantum Mechanics. The spectrum of a dynamo with constant α-profile contains a countably infinite number of diabolical points which under inhomogeneous perturbations unfold in a very specific and resonant way. We describe this mechanism in detail and discuss its physical implications.

In the second part of the talk we discuss coalescing second-order exceptional points in Krein space related models and the emergence of third-order Jordan structures. We demonstrate the basic mechanism on a most simple PT-symmetric 4x4 matrix model and use the obtained results to identify similar structures in the spectral decomposition of α2-dynamo operators.
Keywords: Krein space, MHD dynamo, diabolical point, exceptional point, triple point, Jordan structure, resonance
  • Invited lecture (Conferences)
    Analytic and algebraic methods in physics., 20.02.2007, Prague, Czech Republic

Publ.-Id: 9494 - Permalink


U(VI)-Kaolinite Surface Complexation in Absence and Presence of Humic Acid Studied by TRLFS
Krepelova, A.; Brendler, V.; Sachs, S.; Baumann, N.; Bernhard, G.;
Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was applied to study the U(VI) surface complexes on kaolinite in presence and absence of humic acid (HA). Two uranyl surface species with fluorescence lifetimes of 5900  700 and 42500  1700 ns and 4400  600 and 30900  3600 ns were identified in the binary (U(VI)-kaolinite) and ternary system (U(VI)-HA-kaolinite), respectively. The fluorescence spectra of adsorbed uranyl surface species were described with six and five fluorescence emission bands in the binary and ternary system, respectively. Positions of peak maxima are shifted significantly to higher wavelengths compared to the free uranyl ion in perchlorate medium. HA has no influence on positions of the fluorescence emission bands. In the binary system, both surface species can be attributed to adsorbed bidentate mononuclear surface complexes, which differ in the number of water molecules in their coordination environment. In the ternary system, U(VI) prefers direct binding on kaolinite rather than via HA, but it is sorbed as a uranyl-humate complex. Thus, the hydration shell of the U(VI) surface complexes is partly displaced with complexed HA, which is simultaneously partly distributed between kaolinite particles. Aluminol binding sites are assumed to control the sorption of U(VI) onto kaolinite.
Keywords: U(VI), Kaolinite, Surface, Complexation, Humic Acid, TRLFS, Sorption
  • Environmental Science & Technology 41(2007)17, 6142-6147

Publ.-Id: 9493 - Permalink


Influence of Humic Acid on the Am(III) Sorption onto Kaolinite
Krepelova, A.; Sachs, S.; Geipel, G.; Bernhard, G.;
The influence of humic acid (HA) on the sorption of Am(III) onto kaolinite KGa-1b (Clay Minerals Society Source Repository) as a model mineral was studied by batch experiments. The sorption experiments were performed under ambient atmosphere (pCO2 = 10-3.5 atm) in a glove box, for a Am(III) concentration of 110-6 M and a HA concentration of 10 mg/L in 0.01 M NaClO4 solution. The solid/solution ratio was 4 g/L and the pH values were varied between pH 3 and 10.
In the absence of HA, Am(III) exhibits a very strong sorption onto kaolinite, which is almost independent on the pH value. The percentage of sorbed Am(III) amounts to 98% at pH 3 and to almost 100% at higher pH values. Presumably the high solid/solution ratio used in the sorption experiments represents the reason for no observation of a sorption edge at lower pH values. In the presence of HA, there are small changes in the Am(III) sorption in comparison to the system without HA. At pH < 5, HA enhances very slightly the sorption of Am(III). At pH ≥ 5.5, the sorption of Am(III) decreases in comparison to the HA-free system due to the formation of dissolved Am(III)-humate complexes. The formation of such binary and ternary Am(III)-humate complexes was reported by Kim et al. [1] and Morgenstern et al. [2]. However, the drop of the Am(III) sorption onto kaolinite observed in this study is very small. Generally, the trend in the sorption behavior of Am(III) in the presence of HA is consistent with the results reported in literature for trivalent actinides. At low pH values the sorption is enhanced by the presence of HA, while at high pH the presence of HA lowers the sorption. At pH > 8.5, HA has no influence on the Am(III) sorption onto kaolinite. Further batch experiments with varying experimental conditions will be performed.
First laser-induced fluorescence spectroscopic measurements were carried out in the systems Am(III)-kaolinite and Am(III)-HA-kaolinite to study the surface complexes of Am(III) on kaolinite. HA decreases the fluorescence intensity of the samples. The shape of the measured fluorescence spectra in both systems, binary and ternary, differs from the spectrum observed in the solution.

[1] J.I. Kim et al., Radiochim. Acta 48, 135 (1989).
[2] M. Morgenstern et al., Radiochim. Acta 88, 7 (2000).

Keywords: Sorption, Kaolinite, Humic Acid, Am(III), Fluorescence Spectroscopy
  • Contribution to proceedings
    Migration 2007, 26.-31.08.2007, München, Germany
    11th Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 65
  • Poster
    Migration 2007, 26.-31.08.2007, München, Germany

Publ.-Id: 9492 - Permalink


Mixed complexes of alkaline earth uranyl cabonates: A laser-induced time-resolved fluorescence spectroscopic study
Geipel, G.; Amayri, S.; Bernhard, G.;
The interaction of the alkaline earth ions Mg2+, Sr2+ and Ba2+ with the uranyl tricarbonate complex has been studied by time resolved laser-induced fluorescence spectroscopy. In contrast to the non-luminescent uranyl tricarbonate complex the formed products show slight luminescence properties. These have been used to determine the stoichiometry and complex stabilities of the formed compounds. As the alkaline earth elements are located in an outer shell of the complex the influence of the type of the alkaline earth element on the stability constant is not very drastic. Therefore all obtained data were averaged in order to derive an common stability constant for the described complexes. These stability constants result in log β°113 = 26.24 ± 0.08 for the first reaction step and in log β°213 = 30.42 ± 0.23 for the overall complex formation with two alkaline earth ions.
Keywords: Alkaline earth elements, uranium, carbonate, luminescence, complex formation

Publ.-Id: 9491 - Permalink


Probing the phase separation in transition metal implanted semiconductors using synchrotron radiation x-ray diffraction
Zhou, S.; Potzger, K.; von Borany, J.; Skorupa, W.; Helm, M.; Fassbender, J.ORC
Traditional electronics can be greatly stimulated by a combination of magnetic and semiconducting properties where spins provide an additional freedom degree. Recently theoretical works predict that some semiconductors (e.g. ZnO, GaN, TiO2, and Si) doped with transition metal (TM) are diluted magnetic semiconductors (DMS) [1]. In DMS materials, TM ions are substituted onto cation sites of the host semiconductor and are coupled with free carriers via indirect interaction resulting in ferromagnetism. However most experimental works have only concentrated on reporting high Tc and interpreted the observed ferromagnetism in terms of DMS without detail structural characterization. In this work, we have prepared magnetic ZnO, TiO2 and Si samples doped with TM by implantation, and correlated their magnetic and structural properties [2-5]. By synchrotron radiation x-ray diffraction, phase separations (Fe, Ni, Co and Mn-silicide nanocrystals) are observed in our samples, and are responsible for the magnetism. Depending on their crystalline structure, those nanocrystals are crystallographically oriented with respect to the host matrix. The structural information is well agreeable with the magnetic properties measured by SQUID. Additionally due to their orientation nature (crystallographically oriented or randomly oriented with respect to the host crystal), these nanocrystals in some cases are very difficult to detect by a simple Bragg-Brentano scan. This nature results in the pitfall of using XRD to exclude secondary phase in DMS materials.
[1] T. Dietl, et al, Science 287, 1019 (2000).
[2] K. Potzger, Shengqiang Zhou , et al, Appl. Phys. Lett. 88, 052508 (2006).
[3] Shengqiang Zhou, et al., J. Appl. Phys. 100, 114304 (2006).
[4] Shengqiang Zhou, et al., to be published at Phys. Rev. B75, 085203 (2007).
[5] Shengqiang Zhou, et al., to be published at J. Phys. D: Appl. Phys. 40, 964 (2007).
  • Lecture (Conference)
    Work shop on "Ion beam processing and magnetic properties of semiconductors", 13.02.2007, Leuven, Belgium

Publ.-Id: 9490 - Permalink


Schwingungsspektroskopische Analyse von Actinylkomplexen in wässrigen Lösungen und an festen Oberflächen
Foerstendorf, H.;
Die Molekülstrukturen von Actinidenkomplexen können mittels der FT-IR-Spektroskopie identifiziert werden. Die ATR-Technik erlaubt Untersuchungen von wässrigen Lösungen gelöster Komplexe. Damit sind in situ Experimente unter naturnahen Bedingungen mit definierten Parametern (pH, Konzentration, Ionenstärke) möglich. Es werden aktuelle Ergebnisse zur Hydrolysespeziation von U(VI) und zur Komplexbildung mit organischen Liganden und an mineralischen Phasen präsentiert. Die Anwendung des Freie Elektronen Lasers am Beschleuniger ELBE erlaubt die Anwendung oberflächenspezifischer IR-Techniken. Erste Resultate zeigen potentielle Anwendungsmöglichkeiten für Sorptionsproben von Actiniden an definierten Mineraloberflächen.
Keywords: FT-IR spectroscopy; ATR; uranyl(VI); neptunyl(V); FEL; photothermal techniques
  • Lecture (others)
    Institutskolloquium des Instituts für Interdisziplinäre Isotopenforschung Leipzig, 26.02.2007, Leipzig, Germany

Publ.-Id: 9489 - Permalink


Reaction of uranium(VI) with lipopolysaccharide - a laser spectroscopic study
Barkleit, A.; Moll, H.; Bernhard, G.;
Bacteria in the environment have a significant influence on the transport of heavy metals in nature. To estimate the mobility of actinides in natural systems, studies on the molecular level are essential to understand the accumulation and metabolism processes. The bacterial cell surfaces consists of various components which represent a wide range of reactive groups like phosphonate, carboxylate and hydroxyl groups, which are able to bind heavy metals, such as lipopolysaccharides [1].
We investigated the complex behaviour of the lipopolysaccharide (LPS) of pseudomonas aeruginosa serotype 10 with uranium(VI) in the aqueous system at pH 2 to 9 by time-resolved laser-induced fluorescence spectroscopy (TRLFS). The complexation of uranium(VI) by LPS effects a strong red shift of the fluorescence emission bands, connected with an increase of the fluorescence intensity, compared to the free uranyl ion, even at low pH ranges.
The shift of the emission bands shows clearly two different types of complexes. One complex appears only at very low pH (2 to 3) with a red shift of 8-9 nm compared to UO22+(aq). At higher pH the emission bands are even shifted 11-12 nm. This kind of red shift is clearly caused by phosphate groups [2,3]. The complex with the lower red shift at very low pH range can be assigned to a hydrogen phosphonate species, and the complex with the stronger red shift can be dedicated to a dehydrogenated phosphonate species.
The evaluation of the time-resolved measurement shows at least three different lifetimes, indicating more than two uranyl-LPS complex types, which are not to distinguish by the shift of the emission bands, but only by lifetime. Two lifetimes of about 8 and 15 µs can be associated with the two uranyl phosphonate complex types.
The complexation of the uranyl ion was completed even at a lesser molar extent of phosphonate groups over a wide pH range (2 to 7). This indicates a participation of carboxyl or hydroxyl groups, which can describe a further form of uranyl-LPS complex type, associated with a lifetime of about 100 µs.

[1] T.J. Beveridge, R.J. Doyle, Metal Ion and Bacteria, John Wiley & Sons Inc., New York, NY, 1989.
[2] A. Koban, G. Bernhard, J. Inorg. Biochem., in press, DOI: 10.1016/j.jinorgbio.2007.01.001 (2007).
[3] S. Scapolan, E. Ansoborlo, C. Moulin, C. Madic, J. Alloys Comp. 271-273, 106-111 (1998).
Keywords: Uranyl, TRLFS, Lipopolysaccharides, Complexation
  • Lecture (Conference)
    Migration 2007, 26.-31.08.2007, München, Germany
  • Contribution to proceedings
    Migration 2007, 26.-31.08.2007, München, Germany
    11th Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 288-289

Publ.-Id: 9488 - Permalink


Electromagnetic Excitations in Nuclei: From Photon Scattering to Photo-dissociation
Junghans, A.;
In explosive nucleosynthesis temperatures are high enough for photo dissociation reaction to occur, e.g. leading to the production of p- process nuclei. In order to understand the details of element production and element disruption we started an experimental program at the new bremsstrahlung facility of the superconducting electron accelerator ELBE of FZ-Rossendorf, Dresden. The bremsstrahlung facility and the detector setup are designed such that the scattering of photons from nuclei and the photo dissociation of nuclei around the particle separation energies can be studied under optimized background conditions. The results of photon scattering experiments from the Z=42 nuclei 92,98,100-Mo and the N=50 nuclei 88-Sr, 89-Y,Land 90 Zr will be shown and compared to calculations based on a random-phase approximation method for deformed nuclei. In activation measurements with bremsstrahlung at end point energy from 10.5 to 16 MeV (gamma, p), (gamma, n) and (gamma,alpha) reactions of 92,100-Mo. have been studied. The results are compared to recent astrophysical network calculations to investigate if the underproduction of Mo, Ru isotopes in the p- process is due to incorrect nuclear reaction rates.
  • Lecture (others)
    Seminar bei Konan Universität, Kobe, Japan, 14.03.2006, Kobe, Japan

Publ.-Id: 9487 - Permalink


Photodissociation studies of p-process nuclei with bremsstrahlung at ELBE
Junghans, A.;
Photodissociation studies of p-process nuclei with bremsstrahlung at ELBE
  • Invited lecture (Conferences)
    International Workshop XXXIV on Gross Properties of Nuclei and Nuclear Excitations, 15.-21.01.2006, Hirschegg, Kleinwalsertal, Austria

Publ.-Id: 9486 - Permalink


Effect of visible and UV illumination on the water contact angle of TiO2 thin films with incorperated nitrogen
Borras, A.; Lopez, C.; Rico, V.; Gonzalez-Elipe, A. R.; Richter, E.; Battiston, G.; Gerbasi, R.; Mcsporran, N.; Sauthier, G.; György, E.;
kein Abstract vorhanden
  • Journal of Physical Chemistry C 111(2007)4, 1801-1808

Publ.-Id: 9485 - Permalink


Possible magnetic-field-induced Lifshitz transition in Ce1−xLaxBiPt
Wosnitza, J.; Bartkowiak, M.; Bergk, B.; Bianchi, A. D.; Goll, G.; von Löhneysen, H.; Yoshino, T.; Takabatake, T.;
Usually the electronic band structure is a rather robust property of the metallic state, especially when applying magnetic fields. For the half-Heusler compounds Ce1−xLaxBiPt, however, we observe magnetic-field-induced band-structure changes in strong magnetic fields. This is evidenced by Shubnikov-de Haas (SdH) and Hall-effect measurements performed in pulsed magnetic fields up to 70 Tesla. Above sample-dependent threshold fields, both in CeBiPt as well as in Ce0.95La0.05BiPt single crystals, the SdH signals vanish and the Hall coefficients change drastically. Such kind of effects are absent in the non-4f compound LaBiPt. Electronic-band-structure calculations can well explain the observed behavior by a 4f-polarization-induced Fermi-surface modification, i.e., a fieldinduced
Lifshitz transition.1,2

1 N. Kozlova et al., Phys. Rev. Lett. 95, 086403 (2005).
2 J. Wosnitza et al., New J. Phys. 8, 174 (2006).
  • Lecture (Conference)
    The International Conference on Strongly Correlated Electron Systems, 13.-18.05.2007, Houston, USA

Publ.-Id: 9484 - Permalink


Binary-collision modeling of ion-induced stress relaxation in cubic BN and amorphous C thin films
Abendroth, B.; Jäger, H. U.; Möller, W.; Bilek, M.;
It is demonstrated that ion-bombardment-induced stress release during physical vapor deposition of cubic boron nitride cBN and amorphous carbon aC films is related to collisional relocation of atoms. A model based on TRIM and molecular dynamics computer simulations is presented.
Experimental results obtained using pulsed substrate bias are in good agreement with the model predictions at adequately chosen threshold energies of atomic relocation. The collisional relaxation model describes the experimental data significantly better than the widely applied thermal spike model.
Keywords: stress relief, ion implantation, cubic boron nitride, amorphous carbon, binary collision approximation, thermal spike
  • Applied Physics Letters 90(2007), 181910

Publ.-Id: 9483 - Permalink


An elementary model of Earth's magnetic field reversals
Stefani, F.; Gerbeth, G.; Günther, U.; Xu, M.; Sorriso-Valvo, L.;
The Earth's magnetic field undergoes polarity reversals with a mean reversal rate that varies from zero during superchrons to 4 per Myr in the present. Typically, these reversals have a strongly asymmetric shape with a decay time of around 50 kyr and a recreation time of around 5 kyr. Despite the recent successes of three-dimensional fully coupled dynamo models, there is no agreement yet on the basic principle of reversal. We investigate a simple mean-field dynamo model and compare the resulting time series and the phase space trajectories with those of paleomagnetic measurements. In the case of highly supercritical dynamos a very good agreement with recent paleomagnetic data is achieved. We show that the typical reversal dynamics traces back to the spectral properties of non-selfadjoint dynamo operators which exhibit so-called exceptional points where two real eigenvalues coalesce and continue as a complex conjugated pair of eigenvalues. Within this picture we can also explain the observed general tendency of highly supercritical dynamos to self-tune into reversal prone states. We conclude with a speculation on the possible role of the inner core growth for the long term changes
of the reversal rate and for the occurrence of superchrons.
  • Invited lecture (Conferences)
    LGIT Research Seminar, 22.03.2007, Grenoble, France

Publ.-Id: 9482 - Permalink


Non-destructive characterization of vertical ZnO nanowire arrays by slow positron implantation spectroscopy, atomic force microscopy, and nuclear reaction analysis
Brauer, G.; Anwand, W.; Grambole, D.; Skorupa, W.; Hou, Y.; Andreev, A.; Teichert, C.; Tam, K. H.; Djurisic, A. B.;
ZnO nanorods, grown by a hydrothermal method, have been characterized by slow positron implantation spectroscopy (SPIS) and atomic force microscopy (AFM). It has been demonstrated that such non-destructive characterization techniques can provide a comprehensive picture of the nanorod structure (including its length, shape, orientation, and seed layer thickness), as well as provide additional information about defects present in the structure. Nanorods were also characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), and it was found that the combination SPIS/AFM is more sensitive to the nanorod orientation and the thickness of the seed layer. To obtain still more information about defects in the nanorods, as well as to confirm the findings on the sample structure, nuclear reaction analysis (NRA) was performed and a large concentration of bound hydrogen was found. The results obtained by different characterization techniques are discussed.
Keywords: zinc oxide, nanorods, slow positron implantation spectroscopy, atomic force microscopy, scanning electron microscopy, X-ray diffraction, nuclear reaction analysis
  • Nanotechnology 18(2007), 195301

Publ.-Id: 9481 - Permalink


Some physical data of the near eutectic liquid lead-bismuth
Plevachuk, Y.; Sklyarchuk, V.; Eckert, S.; Gerbeth, G.;
Lead-bismuth alloys are under intense consideration as target material of spallation sources. The thermohydraulic design of such a target or related coolant systems requires a reliable data basis regarding the temperature dependent physical properties of such alloys. We present measurements of the electrical conductivity and thermoelectric power up to about one hundred degree above the melting point for various alloy compositions. For the eutectic alloy the measurements were performed up to much higher temperatures including, in addition, viscosity and thermal conductivity. A comparison with data and scaling relations available in literature is given.
  • Journal of Nuclear Materials 373(2008), 335-342

Publ.-Id: 9480 - Permalink


Experimental results on magnetorotational instability
Gerbeth, G.; Gundrum, T.; Stefani, F.; Hollerbach, R.; Rüdiger, G.;
The magnetorotational instability (MRI) plays a key role in the formation of stars and black holes, by enabling outward angular momentum transport in accretion disks. A recent paper [R. Hollerbach and G. Rüdiger, Phys. Rev. Lett., Vol. 95, 124501 (2005)] has shown that the threshold for the onset of the MRI in a liquid metal Taylor-Couette flow is dramatically reduced if both axial and azimuthal magnetic fields are imposed. In agreement with this prediction, a variety of experimental results of a Taylor-Couette experiment with the liquid metal alloy GaInSn is presented, showing evidence for the existence of the MRI at Reynolds numbers of order 1000 and Hartmann numbers of order 10.
  • Invited lecture (Conferences)
    Julius Hartmann Meeting, 15.-16.02.2007, Coventry, UK

Publ.-Id: 9479 - Permalink


XAFS Study of Uranyl Carbonate Complexes in Aqueous Solution
Ikeda, A.; Hennig, C.; Tsushima, S.; Rossberg, A.; Scheinost, A.; Bernhard, G.;
The carbonate complex of uranium is one of the most fundamental chemical species for the migration study on the geological disposal of radioactive wastes or the remediation study of closed uranium mining. In this study, the carbonate complexes of uranyl(VI)- and uranyl(V) ions were investigated in aqueous solution by using electrochemical (cyclic voltammetry and electrolysis) and spectroscopic (UV-visible and XAFS) techniques.
From the electrochemical study, it was found that the UVO2+-carbonate complex was stable only in the limited concentration range of 0.8 M < [Na2CO3] < 1.4 M. Therefore, the UVO2+ samples for XAFS measurements were prepared in 1.4 M-Na2CO3 solution by using a Pt-mesh working electrode. The results of XAFS measurement indicated that both uranyl(V) and uranyl(VI) ions form the tricarbonate complex, [UO2(CO3)3]n- (n = 5 for uranyl(V) and 4 for uranyl(VI)). The coordination occurs in a bidentate manner and, in general, all bond lengths for the uranyl(V) complex were longer than those for the uranyl(VI) complex. These results are in good agreement with the DFT calculations at least for the uranyl(VI) complex. Additionally, a chemical shift was also observed in the U LI- and LIII-XANES spectra, which can be interpreted as the combination of electronic transitions and multiple scattering features.
  • Poster
    ESRF Users Meeting 2007, 07.02.2007, Grenoble, France

Publ.-Id: 9478 - Permalink


Photoresponse in the visible range from Cr doped TiO2 nanotubes
Ghicov, A.; Schmidt, B.; Kunze, J.; Schmuki, P.;
Layers of TiO2 nanotubes have been fabricated by electrochemical anodization of Ti. After annealing the tubes to an anatase structure Cr doping was carried out by ion implantation at an energy of 60 keV and at two nominal fluences, 5x1015 cm-2 and 5x1016 cm-2. XRD measurements reveal that the anatase structure shows a certain degree of amorphization after ion implantation. However, this effect can be reversed by subsequent thermal annealing. Photoelectrochemical measurements show a visible photoresponse for the Cr+ implanted tubes. Reannealing the tubes, leads to an increase in the photoresponce magnitude in the visible range of the solar spectrum.
Keywords: Nanotubes, ion implantation, photoelectrochemical measurement
  • Chemical Physics Letters 433(2007), 323-326

Publ.-Id: 9477 - Permalink


Gas-liquid flow around an obstacle in a vertical pipe
Prasser, H.-M.; Beyer, M.; Al Issa, S.; Carl, H.; Pietruske, H.; Schütz, P.;
This paper presents a novel technique to study the two-phase flow field around an asymmetric diaphragm in a vertical pipe with a nominal diameter of DN200. Main feature of the experiments is a translocation of the diaphragm to scan the 3D void field with a stationary wire-mesh sensor that supplies data with a spatial resolution of 3 mm over the cross-section and a frequency of 2.5 kHz in axial direction. Besides the measurement of time-averaged void fraction fields, novel data evaluation methods were developed to extract estimated liquid velocity profiles as well as lateral components of bubble velocities from the wire-mesh sensor data. The combination of void fraction fields and velocity profiles offer the possibility to analyse the complex flow around an obstacle in order to learn more about similar flow situations in components of power and chemical plant equipment. Selected plots reveal the behaviour of the flow, e.g. at sharp edges and within recirculation areas.
This paper based on air-water and steam-water (6.5 MPa) test runs which were performed with liquid superficial velocities (JW) between 0.1 and 1.6 m/s. The JG was changed in the range of 0.04 to 0.84 m/s.
A detailed uncertainty analyse of the velocity assessments finishes the presented paper. Among others, it includes remarks about a comparison with a second method for calculating radial gas velocity profiles – the cross-correlation.
Keywords: Two-phase flow, flow around an obstacle, gas fraction distribution, axial and lateral velocity fields, wire-mesh sensors
  • Nuclear Engineering and Design 238 (7)(2008), 1802-1819

Publ.-Id: 9476 - Permalink


Di-electrons from eta meson Dalitz decay in proton-proton collisions
Kaptari, L. P.; Kämpfer, B.;
The reaction pp to pp eta to pp gamma e^+ e^- is discussed within a covariant effective meson-nucleon theory.
The model is adjusted to data of the subreaction pp to pp eta.
Our focus is on di-electrons from Dalitz decays of eta mesons, eta to gamma gamma^* to gamma e^+e^-, and the role of the corresponding transition form factor F_{eta gamma gamma^*}.
Numerical results are presented for the intermediate energy kinematics of HADES experiments.
Keywords: di-electron, Dalitz decay, hadron reaction

Publ.-Id: 9475 - Permalink


A computational model for the formation of (SiC)1-x(AlN)x structures by hot, high dose N+ and Al+ co-implants in 6H-SiC
Trushin, Y.; Yankov, R. A.; Kharlamov, V. S.; Kulikov, D. V.; Tsigankov, D. N.; Kreissig, U.; Voelskow, M.; Pezoldt, J.; Skorupa, W.;
This work is an attempt to model the fundamental processes that occur when 6H-SiC is implanted at elevated substrate temperatures with high doses of N+ and Al+ ions to synthesise thin buried layers of (SiC)1-x(AlN)x.
Keywords: ion-beam synthesis, computer simulation, defect production, kinetics of defects
  • Materials Science Forum 264-268(1998), 757-760

Publ.-Id: 9474 - Permalink


Semiconductor spectroscopy with free-electron and tabletop pulsed lasers at FZD
Schneider, H.;
No abstract available.
  • Lecture (others)
    Seminar Talk, 30.01.2007, Santa Barbara, CA, USA

Publ.-Id: 9473 - Permalink


Intersubband relaxation dynamics in short-wavelength InGaAs/AlAsSb quantum well structures
Grimm, C. V.-B.; Ohser, S.; Winnerl, S.; Grenzer, J.; Schneider, H.; Helm, M.; Neuhaus, J.; Dekorsy, T.; Biermann, K.; Künzel, H.;
Intersubband transitions in semiconductor quantum wells (QW) are crucial for mid-infrared lasers, detectors, and modulators. New compound materials such as lattice matched InGaAs/AlAsSb and strain compensated InGaAs/AlAs, both grown on InP, feature large conduction band discontinuities (>1eV) and allow the extension of the available wavelength range into the near infrared. Such short wavelengths require narrow QWs (<3 nm) where the first excited state inside the QW may be raised above indirect (X or L) valleys within the Brillouin zone.
We have studied intersubband relaxation dynamics in In0.53Ga0.47As/AlAs0.56Sb0.44 multiple QWs with thicknesses between 2 and 4.6 nm (corresponding to absorption wavelengths of 1.9 to 3.2 µm) by femtosecond pump-probe experiments. The high repetition rate (78 MHz) of our 280 fs pulses in combination with a rapid-scanning technique results in a detectable transmission change as low as 10^-5. At early delay times, all samples show an exponential decay of the transient transmission occurring with time constants of 1 to 1.5 ps. The relaxation dynamics at later delay times strongly depends on the QW thickness and doping. For very narrow QWs the observed bi-exponential decay indicates several competing relaxation channels. Here transfer of electrons to X- and L-states in the wells or in the barriers is energetically possible. States localized in the barrier exist due to strong band bending resulting from the n-type modulation doping. Finally, we will also show rate-equation simulations to study possible relaxation scenarios within a three level system.
Keywords: Intersubband absorption, intersubband relaxation, femtosecond pump-probe, indirect valleys, InGaAs/AlAsSb
  • Lecture (Conference)
    PHOTONICS WEST 2007, Symposium on Physics and Simulation of Optoelectronic Devices XV, 20.-25.01.2007, San José, CA, USA

Publ.-Id: 9472 - Permalink


Isolation and characterization of the bioligands secreted by P. fluorescens (CCUG 32456 A) and Complexation of uranium(VI) with aromatic acids having different functionalities studied by different spectroscopic techniques (UV-vis spectroscopy and time-resolved laser-induced fluorescence spectroscopy (TRLFS))
Moll, H.; Glorius, M.; Bernhard, G.;
The FZD/IRC contributions within the microbe project as part of the international co-operation of the Äspö HRL (Sweden) with the BMWi (Germany) are concentrated in a project addressing the indirect interaction mechanism of a mobilization of actinides by released bioligands in the aquifer system from relevant Äspö bacteria. The ongoing study is focused on: (i) isolation and characterization of microbial ligands produced from a subsurface strain of Pseudomonas fluorescence isolated at Äspö, (ii) interaction of U(VI), Np(V), and Cm(III) with the microbial ligands including compounds simulating the functionality of the microbial ligands and the surface of the bacteria and (iii) spectroscopic characterization of the formed actinide complexes/compounds. The formation constants determined will be used directly in speciation and transport models. This project should help to identify the dominating process of the interaction between actinides and microbes (direct or indirect ones). The research performed in our project improves the understanding of the behavior of colloids and microbes and their respective interaction with radionuclides.

The activities in 2006 were concentrated on a) the isolation and characterization of bioligands secreted by a subsurface strain of P. fluorescence found at Äspö HRL and b) complexation studies of actinides with relevant model compounds to explain the interactions of actinides in biologically systems on a molecular level. Main results of these subjects will be reported here.
Keywords: Actinides, Bioligands, Pseudomonads, Complexation, Aromatic acids, Spectroscopy
  • Other report
    Stockholm, Sweden: Äspö HRL Annual Report 2006, 2007
    10 Seiten

Publ.-Id: 9471 - Permalink


Uranium (VI) Sorption an natürlichem und synthetischem Sandstein
Nebelung, C.; Brendler, V.; Richter, A.; Bernhard, G.;
Die Wechselwirkung von Radionukliden an der Schnittstelle Wasser Gestein ist bei Fragen der Endlagerung oder bei der Umweltüberwachung von Interesse. Ein Ver-gleich von Einzelmineralien und Mineralgemischen wird für die mögliche Vorhersa-ge der Sorption an nicht untersuchten Mineralgemischen benötigt. Die Abschät-zung der Sorption beruht auf dem Oberflächenkomplexierungsmodell DDL (Diffuse Double Layer).
Das System natürlicher Sandstein – synthetischer Sandstein wurde mittels Batch Versuchen und potentiometrischer Titration untersucht. Der natürliche Sandstein besteht hauptsächlich aus Quarz mit Anteilen von Muskowit. Der künstliche Sand-stein besteht aus Quarz, Muskowit und Hämatit. Der natürliche Sandstein zeigt eine höhere Aufnahmekapazität für Uran (VI) als der synthetische Sandstein. Ur-sache dafür kann die höhere spezifische Oberfläche (damit mehr Bindungsstellen) des natürlichen Sandsteins oder zusätzliche aufnahmefähige Bestandteile sein, z.B. geringe Anteile durch XRD nicht quantifizierbare Fe- und Ca-haltige Minerale. Auf Grund der linearen Sorptionsisotherme wird nur ein Bindungstyp vermutet. Aus den Sorptionsdaten wurden mit FITEQL die allgemeiner anzuwendenden Protoly-sekonstanten und Komplexbildungskonstanten errechnet und mit Literaturdaten von Einzelmineralien [1] verglichen, die mehrere Bindungstypen für Uran an den Einzelmineralien angeben.

Literatur
[1] V. Brendler, et al., J. Contam. Hydrol. 2003. 61, 281-291. [2]

Förderung: BMBF und BMWA 02C1144
Keywords: sorption, uranium, sandstone, quartz, muscovite, hematite, surface complexation model, diffuse double layer
  • Lecture (Conference)
    Wissenschaftsforum Chemie 2007, 16.-19.09.2007, Ulm, Germany
  • Contribution to proceedings
    Wissenschaftsforum Chemie 2007, 16.-19.09.2007, Ulm, Germany
    Wissenschaftsforum Chemie 2007- Energie Materialien Synthese, Frankfurt am Main: Gesellschaft Deutscher Chemiker, 3-936028-47-8
  • Lecture (others)
    PSI-FZR Meeting, 05.-06.11.2007, Villigen, Switzerland

Publ.-Id: 9470 - Permalink


Photon-scattering and photoactivation experiments at the electron accelerator ELBE
Schwengner, R.;
Photon-scattering and photoactivation experiments at the electron
accelerator ELBE
  • Invited lecture (Conferences)
    Seminar, 06.11.2006, Madrid, Spain

Publ.-Id: 9469 - Permalink


Photon-scattering and photoactivation experiments at the electron accelerator ELBE
Schwengner, R.;
Photon-scattering and photoactivation experiments at the electron
accelerator ELBE
  • Invited lecture (Conferences)
    Workshop AP.G.RA.D(E) 2006, Applications of Gamma-Ray Diffraction, 26.-28.10.2006, Grenoble, France

Publ.-Id: 9468 - Permalink


Dipole-strength distributions up to the particle-separation energies and photodissociation of Mo isotopes
Schwengner, R.;
Dipole-strength distributions up to the particle-separation energies
and photodissociation of Mo isotopes
  • Lecture (Conference)
    Second International Conference on Collective Motion in Nuclei Under Extreme Conditions (COMEX2), 20.-23.06.2006, Sankt Goar, Deutschland

Publ.-Id: 9467 - Permalink


The Big Bang, our Sun and the 3He(α,γ)7Be Reaction
Bemmerer, D.;
Unmittelbar nach dem Urknall, noch vor der Bildung der ersten Sterne, wurden die leichten chemischen Elemente bis 7Li erzeugt. Die 3He(α,γ)7Be-Reaktion war dabei für die 7Li-Produktion mit verantwortlich. Weiterhin spielt sie auch heute noch eine wichtige Rolle, und zwar in unserer Sonne: Der Fluss von solaren 7Be- und 8B-Neutrinos hängt direkt vom 3He(α,γ)7Be-Wirkungsquerschnitt ab. Tief unter Tage im Gran-Sasso-Labor (Italien) wurde dieser Wirkungsquerschnitt mit bisher unerreichter Präzision gemessen. Diese neuen Daten und ihre Auswirkungen auf die Kosmologie und unser Verständnis der Sonne werden in dem Vortrag vorgestellt.
Keywords: big bang, sun
  • Lecture (others)
    Seminar Nukleare Astrophysik, 30.10.2006, Berlin, Deutschland

Publ.-Id: 9464 - Permalink


Isotope ratios and isoscaling of spallation products in p(1 GeV) + A reactions
Neubert, W.; Andonenko, M. N.; Andonenko, L. N.;
An analysis of experimental yields concerning isotopically resolved spallation products from 1 GeV-proton nucleus interactions with targets from Fe to Cs is presented. It was found that the yield ratios of isotopes classified by the difference of the neutron numbers are compatible with relations derived in the grand-canonical approach. The independence of isotope temperatures from the target mass was demonstrated for spallation products. The spallation residues exhibit isoscaling behaviour. The high sensitivity of the isoscaling parameters to the nucleonic composition (N/Z) of the disassembling nuclei is analysed. A unified isoscaling for a common description of similar reactions is discussed.

Publ.-Id: 9463 - Permalink


Experiments with real photons for nuclear astrophysics
Wagner, A.;
Experiments with real photons for nuclear astrophysics
  • Invited lecture (Conferences)
    NuSTAR Seminar, 24.01.2007, Darmstadt, Deutschland

Publ.-Id: 9462 - Permalink


Die Dipolstärke in Kernen und der Kernphotoeffekt im Kosmos
Wagner, A.;
  • Lecture (others)
    Physikalisches Kolloquium, 04.07.2006, Dresden, Deutschland

Publ.-Id: 9461 - Permalink


Dipolstärke in Kernen und der Kernphotoeffekt im Kosmos
Wagner, A.;
  • Invited lecture (Conferences)
    Seminar des SFB 634, 04.05.2006, Darmstadt, Deutschland

Publ.-Id: 9460 - Permalink


Planar channeled relativistic electrons and positrons in the field of resonant hypersonic wave
Grigoryan, L. S.; Mkrtchyan, A. H.; Khachatryan, H. F.; Tonoyan, V. U.; Wagner, W.;
The wave function of a planar channeled relativistic particle (electron, positron) in a single crystal excited by longitudinal hypersonic vibrations (HVs) is determined. The obtained expression is valid for periodic (not necessarily harmonic) HV of desired profile and single crystals with an arbitrary periodic continuous potential. A revised formula for the wave number of HV that exerts resonance influence on the state of a channeled particle was deduced to allow for non-linear effects due to the influence of HV.-
Keywords: channelin radiation, ultrasonic vibrations, hypersound
  • Nuclear Instruments and Methods in Physics Research B 201(2003), 25-33

Publ.-Id: 9459 - Permalink


On the amplification of radiant energy during channeling in acoustically excited single crystal
Grigoryan, L. S.; Mkrtchyan, A. H.; Khachatryan, H. F.; Wagner, W.; Saharian, A. A.; Baghdasaryan, K. S.;
Numerical solutions of classical equations of motion and of total radiant energy from a relativistic electron/positron in planar channeling in a single crystal excited by longitudinal standing hypersonic (HS) wave are given. The limit on the radiant energy increase from the channeled particle at parametric resonance is determined by nonlinear effects and the amplitude of HS vibrations. The relative increase of radiant energy due to the transverse oscillations near the minima of potential energy of particle may reach ~100% if HS vibrations are in phase with the instants of particle incidence on the crystal. For particles with energies E < 100 MeV the achieved fit is only qualitative, because for description of channeling in this case the application of the methods of quantum theory is needed.
Keywords: channeling radiation, ultrasonic vibrations, hypersound
  • Nuclear Instruments and Methods in Physics Research B 212(2003), 51-55

Publ.-Id: 9458 - Permalink


Experimental Facilities at ELBE
Wagner, A.;
  • Lecture (others)
    Seminar, 17.03.2006, Sayo-Gun, Japan

Publ.-Id: 9457 - Permalink


Vom Mikrokosmos zum Makrokosmos
Wagner, A.;
  • Lecture (others)
    Tag des offenen Labors, 24.09.2005, Dresden, Deutschland

Publ.-Id: 9456 - Permalink


Activation of p-process nuclei by photodissociation
Wagner, A.;
  • Lecture (Conference)
    International Conference on Frontiers in Nuclear Structures, Astrophysics and Reactions, 12.09.2005, Kos, Greece

Publ.-Id: 9455 - Permalink


Kerne und Sterne
Wagner, A.;
  • Lecture (others)
    Lange Nacht der Wissenschaften, 01.07.2005, Dresden, Deutschland

Publ.-Id: 9454 - Permalink


Kernphysikalische Experimente an ELBE
Wagner, A.;
  • Invited lecture (Conferences)
    Kernphysik Kolloquium, 26.01.2005, Dresden, Deutschland

Publ.-Id: 9453 - Permalink


Photon scattering from heavy nuclei up to energies well above particle threshold (group report)
Wagner, A.;
  • Lecture (Conference)
    DPG Frühjahrstagung, 11.03.2004, Köln, Deutschland

Publ.-Id: 9452 - Permalink


A position-sensitive heavy-ion detector for time-of-flight applications
Wagner, A.;
  • Lecture (Conference)
    Annual NUSTAR Meeting, 19.02.2004, Darmstadt, Deutschland

Publ.-Id: 9451 - Permalink


Erste Experimente mit Bremsstrahlung an ELBE
Wagner, A.;
  • Lecture (others)
    ELBE-Palaver, 07.02.2003, Dresden, Deutschland

Publ.-Id: 9450 - Permalink


Der Coulomb-Aufbruch von 8-B und das solare Neutrino-Problem
Wagner, A.;
  • Lecture (others)
    Seminar im Institut für Kern- und Teilchenphysik, 02.05.2002, Dresden, Deutschland

Publ.-Id: 9449 - Permalink


Experimente zur Kernphysik an ELBE
Wagner, A.;
  • Lecture (Conference)
    Spring Meeting of the German Physical Society, 20.03.2001, Erlangen, Deutschland

Publ.-Id: 9448 - Permalink


Experimente zur nuklearen Astrophysik an ELBE
Wagner, A.;
  • Lecture (others)
    ELBE-Palaver, 11.09.2000, Dresden, Deutschland

Publ.-Id: 9447 - Permalink


Kerne und Sterne
Wagner, A.;
  • Lecture (others)
    Tag der offenen Tür, 16.09.2000, Dresden, Deutschland

Publ.-Id: 9446 - Permalink


The Isospin Degree-of-Freedom in Nuclear Multfragmentation
Wagner, A.;
  • Lecture (Conference)
    Spring Meeting of the German Physical Society, 20.03.2000, Dresden, Deutschland

Publ.-Id: 9445 - Permalink


Detector Simulations with GEANT
Wagner, A.;
  • Lecture (Conference)
    Workshop on a New High Resolution Array, 11.11.1999, East Lansing / MI, USA

Publ.-Id: 9444 - Permalink


Pionen als Sonden der Reaktionsdynamik in Schwerionenstößen
Wagner, A.;
  • Lecture (Conference)
    Arbeitstreffen Hadronen- und Kernphysik, Struktur stark wechselwirkender Teilchen, 10.06.1999, Endingen, Deutschland

Publ.-Id: 9443 - Permalink


Coulomb Dissociation of B-8 and the Solar Neutrino Flux
Wagner, A.;
  • Lecture (others)
    Group Seminar, 29.06.1999, Dresden, Deutschland

Publ.-Id: 9442 - Permalink


Die Produktion geladener Pionen in Schwerionenstößen bei 1 GeV/u
Wagner, A.;
  • Lecture (Conference)
    Spring Meeting of the German Physical Society, 03.04.1994, München, Deutschland

Publ.-Id: 9441 - Permalink


Dipole response of Sr-88 up to the neutron-separation energy
Schwengner, R.; Rusev, G.; Benouaret, N.; Beyer, R.; Erhard, M.; Grosse, E.; Junghans, A. R.; Klug, J.; Kosev, K.; Kostov, L.; Nair, C.; Nankov, N.; Schilling, K. D.; Wagner, A.;
The dipole response of the magic N=50 nucleus ^{88}Sr was studied in photon-scattering experiments at the electron linear accelerator ELBE with bremsstrahlung produced at kinetic electron energies of 9.0, 13.2, and 16.0 MeV. 160 levels were identified up to an excitation energy of 12 MeV.
By using polarized photons linear polarizations of about 50 gamma transitions were measured that enabled parity assignments to the corresponding states. In the energy range of 6 -- 12 MeV we identified only one M1 transition while all other transitions have E1 character. Thus, E1 character was proven for 63\% of the total dipole strength found for the observed levels in the given energy range. Statistical methods were applied in order to filter out inelastic transitions and to correct the intensities of the ground-state transitions for their branching ratios. In this way we obtained the photoabsorption cross section up to the neutron-separation energy. This cross section matches well the photoabsorption cross section obtained from (gamma,n) data and thus provides information about the extension of the dipole-strength distribution towards energies below the neutron-separation energy. An enhancement of E1 strength at 6 -- 11 MeV may be considered as an indication for a Pygmy Dipole Resonance.
Keywords: Photon scattering, Polarised photons, Dipole excitations, Photoabsorption cross section, Giant Dipole Resonance

Publ.-Id: 9440 - Permalink


Tailoring and Imaging the Magnetization Dynamics in Microstructures
Fassbender, J.ORC
It will be shown how the magnetization dynamics can be modified and tailored by means of either ion implantation or ion beam milling. Integral measurement techniques like pulsed inductive microwave magnetometry are used. In addition element specific time-resolved imaging is performed by means of photoemission electron microscopy or transmission x-ray microscopy making use of the magnetic x-ray dichroism effect.
Keywords: magnetism, magnetization dynamics, ion implantation, focused ion beam, XMCD, PEEM, TXM
  • Lecture (others)
    Seminarvortrag am 2. Physikalischen Institut der RWTH Aachen, 12.02.2007, Aachen, Deutschland
  • Lecture (others)
    Seminarvortrag am Institut für Festkörperforschung des FZ Jülich, 14.02.2007, Jülich, Deutschland

Publ.-Id: 9438 - Permalink


A high-resolution time-of-flight spectrometer with tracking capabilities for fission fragments and beams of exotic nuclei
Kosev, K.; Nankov, N.; Friedrich, M.; Grosse, E.; Hartmann, A.; Heidel, K.; Junghans, A. R.; Schilling, K. D.; Schwengner, R.; Sobiella, M.; Wagner, A.;
Bremsstrahlung photons produced at the superconducting electron accelerator ELBE at the FZ Dresden-Rossendorf will be used for the production of neutron-rich nuclei by photon-induced fission. The properties of such exotic nuclei will be studied by decay spectroscopy. The mass and the charge identifications will be based on a double time-of-flight (TOF) method for both fission fragments. Currently, an experimental TOF spectrometer consisting of two micro-channel plate (MCP) detectors with two-dimensional position-sensitive delay-line anodes has achieved a position resolution of 1.8 (0.3) mm (FWHM) and a time resolution of 240 ps (FWHM) with a foil thickness of 163 mug/cm^2. The spectrometer will also be applied to track beams of exotic nuclei for experiments at the heavy ion synchrotron at GSI, Darmstadt.
Keywords: Nuclear Structure, Nuclear Astrophysics, Time-of-Flight Spectrometry

Publ.-Id: 9437 - Permalink


The Role of Colloids in Uranium Transport: A Comparison of Nuclear Waste Repositories and Abandoned Uranium Mines
Zänker, H.; Ulrich, K.-U.; Opel, K.; Brendler, V.;
The formation of colloids containing U(IV) or U(VI) was studied by experiments simulating colloid formation under unoxic and oxic conditions. It is concluded that both transport-facilitating effects of colloids on “immobile” radiotoxic contaminants such as U(IV) and transport-impeding effects on “mobile” radiotoxic contaminants such as U(VI) can play a part in the surroundings of nuclear waste repositories and abandoned uranium mines. The differences between the two geochemical settings are discussed.
Keywords: Colloids, uranium, solubility, nuclear waste repositories, abandoned uranium mines
  • Contribution to proceedings
    IMWA Symposium 2007 Water in Mining Environments, 27.-31.05.2007, Cagliari, Italy
    IMWA Symposium 2007 Proceeding: MakoEdizioni, ISBN 978 88 90 295 5 0 8 330, 127-131
  • Lecture (Conference)
    IMWA Symposium 2007 Water in Mining Environments, 27.-31.05.2007, Cagliari, Italy

Publ.-Id: 9436 - Permalink


Complexation of actinides with bioligands sectreted by a subsurface strain of Pseudomonas fluorescens
Moll, H.; Johnsson, A.; Schäfer, M.; Glorius, M.; Pedersen, K.; Budzikiewicz, H.; Bernhard, G.;
Microbes secrete chelating agents in the surrounding aquifer system. These bioligands, in the case of the ubiquitous fluorescent Pseudomonas spp. pyoverdin-type siderophores, possess a high potential to bind besides Fe(III) also other metals like actinides [1]. The unknown interaction of actinides (U(VI), Cm(III)) with pyoverdin-type bioligands released from the aerobic soil bacterium Pseudomonas fluorescens (CCUG 32456 A) isolated from the aquifers at the Äspö Hard Rock Laboratory, Sweden is the subject of this study. The cells synthesized a bioligand mixture which consists of ferribactin (biogenetic precursors of the pyoverdin) and pyoverdin here in a ratio of 2:1.
The complexation studies were performed at pyoverdin concentrations below 0.1 mM and at an ionic strength of 0.1 M by applying different spectroscopic techniques. Differences in the complexation behavior depending on the nature of the actinide element will be discussed on the basis of the determined complex formation constants.
Two UO22+ -P. fluorescens (CCUG 32456 A) pyoverdin species could be identified due to their individual absorption spectra and molar extinction coefficients.
The Cm(III)-borne pyoverdin species were investigated by fluorescence emission at different excitation wavelengths (360 and 395 nm), i.e. directly at the absorption maxima of Cm(III) or indirectly by energy transfer from the pyoverdin molecule. A strong red shift of the emission signal of app. 7 nm compared to the Cm(III) aquo ion was already observed at low pyoverdin concentrations of 3x10-7 M and at pH 4. Three different Cm- P. fluorescens (CCUG 32456 A) pyoverdin species could be distinguished on the basis of their individual fluorescence emission spectra and lifetimes.
This study helps to improve the understanding of the actinide coordination chemistry with natural pyoverdin-type siderophores in aqueous solution. Such investigations with selected bioligands are essential to explain the overall interaction process of actinides with microbes on a molecular level.

[1] M. Bouby, I. Billard, H.J. Maccordick, Czechoslovak J. Phys. 49, 147-150 (1999).

This work was funded by the BMWi under contract number: 02E9985.
Keywords: Uranyl; Curium; Pyoverdins; Spectroscopy; Complexation
  • Poster
    Migration 2007, 26.-31.08.2007, München, Germany
  • Contribution to proceedings
    Migration 2007, 26.-31.08.2007, München, Germany
    11th Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 141

Publ.-Id: 9435 - Permalink


The superconducting RF Photo Injector for ELBE
Teichert, J.; Arnold, A.; Buettig, H.; Hempel, R.; Janssen, D.; Lehnert, U.; Michel, P.; Moeller, K.; Murcek, P.; Schneider, C.; Schurig, R.; Staufenbiel, F.; Xiang, R.; Kamps, T.; Stephan, J.; Lehmann, W.-D.; Klemz, G.; Will, I.; Lipka, D.; Matheisen, A.; van der Horst, B.; vom Stein, P.; Beard, C. D.; Rogers, J. H. P.; Militsyn, B. L.;
  • Poster
    2nd Annual EUROFEL Workshop 2006, 06.-08.11.2006, Daresbury,, UK

Publ.-Id: 9434 - Permalink


Thickness inhomogeneity effect in EXAFS spectroscopy
Ryazhkin, A. V.; Babanov, Y. A.; Miyanaga, T.; Crozier, E. D.; Gordon, R. A.; Reich, T.; Funke, H.;
In many cases x-ray absorption spectra measured in transmission mode are degraded by an inhomogeneity in thickness of the samples. As a result, the EXAFS amplitude is decreased and information about the coordination numbers is distorted. To avoid this influence, it is necessary to prepare a homogeneous sample. But, for powder samples, thick inhomogeneous foils, and sputtered films this is not possible. Absorption spectra on these samples should be corrected for the thickness inhomogeneity effect.To correct an absorption spectrum it is necessary to know the sample thickness distribution function. We propose a method of solving an integral equation for a distribution function as an inverse problem. We use and compare the experimental pre-edge absorption behaviour with the theoretical Victoreen function. We apply the Tikhonov regularization algorithm to determine the distribution function. Model calculations are carried out to check the reproducibility of the calculations. This method is applied to preliminary procession of x-ray absorption spectra for high quality foils of crystalline Cu, crystalline Cu powder samples, and an inhomogeneous foil of ordered Ni50Mn50 alloy. We estimate the thickness inhomogeneity effect on the coordination numbers in the cases before and after correcting the spectra.
  • Physica Scripta T115(2005), 197

Publ.-Id: 9433 - Permalink


Status of ELBE radio frequency system
Büttig, H.;
The radiation source ELBE is based on a superconducting linear accelerator that can be operated in high average power mode (quasi continous wave mode, cw). Electrons are preaccelerated in a 250 keV-thermionic DC electron-gun and prebunched in a two stage RF-buncher section. Main acceleration is accompished in two 20 MeV-superconducting linear accelerator modules operating at 1,3 GHz which are cooled with liquid helium. The RF-power comes from 10 kW clystrons controled by the low level RF-system.
  • Lecture (others)
    MSL Seminar, 27.07.2006, Stockholm, Sweden

Publ.-Id: 9432 - Permalink


Cs2Te photocathode for SRF gun in Rossendorf
Teichert, J.; Xiang, R.;
  • Lecture (Conference)
    1st WorkShop on High Quantum Efficiency Photocathodes for RF Guns, 04.-06.10.2006, Milano, Italy
  • Contribution to proceedings
    1st Workshop on High Quantum Efficieny Photocathodes for RF guns, 04.-06.10.2006, Milano, Italy
    Proceedings of the 1st WorkShop on High Quantum Efficiency Photocathodes for RF Guns

Publ.-Id: 9431 - Permalink


Very stable 188Re-S4 chelates for labelling biomolecules, prepared with highly concentrated perrhenate eluates
Seifert, S.; Jentschel, C.; Bergmann, R.; Pietzsch, H.-J.; Wunderlich, G.; Kotzerke, J.; Steinbach, J.;
Aim:
The preparation and stability of a new 188Re-S4-complex (S4 = (1-aza-18-crown-6)(O)C-C(SH)-C(SH)-C(O)NH-(CH2)3–NH-(CH2)3–NHC(O)-C(SH)-C(SH)-C(O)(1-aza-18-crown-6) was studied at therapeutic relevant radioactive concentrations. The results were compared with 188Re-MAG3 (MAG3 = mercaptoacetyltriglycine) and 188Re-DMSA preparations (DMSA = dimercaptosuccinic acid) performed with the same highly concentrated [188Re]perrhenate solution (12-15 GBq/ml).

Methods:
The 188Re complexes were prepared by direct reduction of perrhenate (188Re-S4-complex) as well as via the 188Re-EDTA precursor complex (188Re-MAG3, 188Re-DMSA). The preparations were stabilised with 15 mg of ascorbic acid and analysed after 1, 2, and 24 hours by TLC and HPLC. Additionally, in vitro and in vivo stability studies were performed with the purified complexes. Results: After stabilisation with 15 mg of ascorbic acid, all of the complexes were nearly stable under nitrogen for hours, and only 2-8 % of perrhenate was observed after 24 h. In contrast, only the 188Re-S4 complex was completely stable in vitro and in all investigated in vivo samples after separation of ligand excess and reducing agent by HPLC.

Conclusion:
The bridging amine group or free carboxylic groups of the S4-ligand framework make available reactive positions for coupling biomolecules to the chelate. Thus it appears that the new 188Re-S4 complexes offer the possibility of stable and high specific activity labelling of biomolecules for therapeutic application.
Keywords: Rhenium-188 complexes, radiotherapy, stability, radiolysis
  • Nuklearmedizin 5(2007), 181-184

Publ.-Id: 9430 - Permalink


Capacitance wire-mesh sensor for fast measurement of phase fraction distributions
Da Silva, M. J.; Schleicher, E.; Hampel, U.;
We introduce a new wire-mesh sensor based on capacitance (permittivity) measurements. The sensor can be used to measure transient phase fraction distributions in a flow cross-section, such as in a pipe or other vessel, and is able to discriminate fluids having different relative permittivity (dielectric constant) values in a multiphase flow. We designed and manufactured a prototype sensor which comprises two planes of 16 wires each. The wires are evenly distributed across the measuring cross-section, and measurement is performed at the wire crossings. Time resolution of the prototype sensor is 625 frames per second. Sensor and measuring electronics were evaluated showing good stability and accuracy in the capacitance measurement. The wire-mesh sensor was tested in a silicone oil/water two-phase bubbly flow.
Keywords: wire-mesh sensor, capacitance measurement, permittivity, two-phase flow, phase fraction
  • Measurement Science and Technology 18(2007)7, 2245-2251

Downloads:

Publ.-Id: 9429 - Permalink


An intense channeling radiation X-ray source
Wagner, W.; Azadegan, B.; Pawelke, J.;
Already in the first publications about channeling radiation (CR), it has been declared as a unique quasi-monochromatic photon source. Numerous investigations devoted to the fundamental properties of CR have been carried out up to now at research centers all around the world. New perspectives for the application of CR as a non-conventional intense tunable X-ray source opened with the construction of brilliant superconducting cw electron sources.
At the Radiation source ELBE, systematic measurements of planar electron CR have been performed on diamond crystals. A water-cooled radiation production target has been constructed. The crystal alignment with respect to the beam axis is performed by means of an inventive remotely controlled goniometer.
Intense CR from 14.6 MeV electrons channeled along the (110) plane of a 150 micrometer thick diamond crystal has for the first time been produced at average beam currents of up to 100 microA. On-line monitoring the of CR X-rays at primary counting rates of the order of 10^11 photons per second and per 10% band width was realised by the use of a Compton spectrometer. Applying X-ray diffraction on a HOPG crystal, monochromatisation of CR and bremsstrahlung-background reduction has been investigated.
Keywords: channeling radiation, X-ray source
  • Lecture (Conference)
    9th European Conference on Atoms Molecules & Photons - ECAMP IX, 06.-11.05.2007, Crete, Greece
  • Other report
    Heraklion, Crete, Greece: European Physical Society (EPS), 31C, 2007
    600 Seiten

Publ.-Id: 9428 - Permalink


Experimente an der Versuchsanlage ROCOM zum Einfluss der Dichtedifferenz auf die Kühlmittelvermischung bei postulierten Störfällen mit kleinem Leck im heißen Strang
Kliem, S.; Sühnel, T.;
Die in diesem Bericht dokumentierten Ergebnisse sind vertraulich.
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2007
    FZD\FWS\2007\02
    53 Seiten

Publ.-Id: 9427 - Permalink


Performance of RPC with low-resistive silicate glass electrodes exposed to an intense continuous electron beam
Ammosov, V.; Ciobanu, M.; Dohrmann, F.; Gapienko, V.; Guber, F.; Herrmann, N.; Hildenbrand, K. D.; Ivashkin, A.; Kotte, R.; Müller, W. F. J.; Naumann, L.; Schüttauf, A.; Semak, A.; Senger, P.; Sviridov, Y.; Sytcheva, A.; Stach, D.; Tiflov, V.; Wüstenfeld, J.; Zaets, V.;
Four-gap Resistive Plate Chamber (RPC) prototypes with silicate glass electrodes (bulk resistivity ~10^8-10^9Ohm cm) were studied for suitability in time-of-flight applications at high rates. These studies were performed using a continuous electron beam of 34 MeV at the FZ Dresden-Rossendorf electron linac ELBE. Time resolutions of about 100 ps and efficiencies larger than 95% were obtained for rate densities up to 20 kHz/cm².
Keywords: Gaseous detectors, Multi-gap RPC, Bulk resistivity, Rate capability, Detection efficiency, Time resolution

Publ.-Id: 9426 - Permalink


Integration of DYN3D into the SALOME platform
Gommlich, A.;
The computer code DYN3D is integrated into the SALOME platform within the NURSIM project. The first phase of implementation were presented. This phase contains the pre processing of a DYN3D calculation by using of SALOME platform.
Keywords: DYN3D NURESIM SALOME pre processor nuclear reactor reactor core code implementation calculation
  • Invited lecture (Conferences)
    First NURESIM Seminar, Paris, November 7-8, 2006, 07.-08.11.2006, Paris, France

Publ.-Id: 9425 - Permalink


Asymmetrical metallodendrimers with biocompatible surface units
Röhrich, A.;
  • Lecture (Conference)
    3nd SUPRAPHONE Meeting, 04.-06.05.2006, Lisbon, Portugal

Publ.-Id: 9424 - Permalink


Multigroup kinetic methods RTD in DYN3D
Grundmann, U.;
A nodal expansion method of the multigroup diffusion equation was implemented in the computer code DYN3D. The results were compared with reference results for steady states of international benchmarks. Hexagonal and rectangular geometry of fuel assemblies was considered. The results show a good agreeement with the references.
Keywords: neutron diffusion equation multigroups nodal expansion method benchmarks comparisons NURESIM DYN3D
  • Invited lecture (Conferences)
    First NURESIM Seminar, Paris, November 7-8, 2006, 07.-08.11.2006, Paris, France

Publ.-Id: 9423 - Permalink


Dynamic vortex − antivortex interaction in a single cross-tie wall
Kuepper, K.; Buess, M.; Raabe, J.; Quitmann, C.; Fassbender, J.ORC
A fascinating property of micromagnetism comes from the possibility to control the domain and vortex configuration through the sample shape and size. For instance, in a rectangular platelet a configuration containing a stable combination of vortices and an antivortex can be created. Such a single cross-tie wall can be understood as being a coupled micromagnetic system with three static solitons. Here we report on its magnetization dynamics including the vortex-antivortex interactions. The spectrum of eigenmodes is investigated as well as the effect of different vortex core orientations. We show that the vortex dynamics can be used to identify the core configuration which is not directly accessible to x-ray microscopy because of its limited spatial resolution.
Keywords: PABS numbers: 75.40.Gb, 75.60.-d, 75.60.Ch, 75.75.+a
  • Physical Review Letters 99(2007)16, 167202
    DOI: 10.1103/PhysRevLett.99.167202
  • Lecture (others)
    Workshop "New Concepts in Spin Dynamics", 07.-09.01.2008, Bad Honnef, Germany
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 9422 - Permalink


Improvement of process safety and efficiency of Grignard reactions by real-time monitoring
Kryk, H.; Hessel, G.; Schmitt, W.;
Grignard reactions possess considerable hazard potentials due to the spontaneous heat release during the initiation of these strongly exothermic reactions and the high reactivity of the Grignard compounds. To establish an industrially applicable method for an objective real-time detection of the reaction start-up and for the accumulation of the organic halide during the process, a heat/ mass balance-based real-time monitoring approach was developed and tested by miniplant experiments. Additionally to the concentration profiles provided by the approach, the real-time estimation of the safety-relevant parameters, like adiabatic temperature rises and corresponding pressures, enables application of advanced control strategies up to the point of a safety-oriented fully automated control of Grignard reactions. In the same time, such systems can contribute to improve process efficiency by increasing the space-time yield as well as to enhance the inherent process safety.
  • Organic Process Research & Development 11(2007)6, 1135-1140

Publ.-Id: 9420 - Permalink


Benchmarking of reactor physics codes for VVER
Rohde, U.; Petkov, P.; Hadek, J.; Kereszturi, A.; Hegyi, G.; Kolev, N.;
An overview on benchmarking activities for reactor physics codes for VVER type reactors within the European code platform NURESIM is given. Different levels of benchmarks were calculated - mathematical benchmarks for diffusion codes with given cross section data and with neutron transport reference solutions as well as benchmarks based on experimental data. Benchmarking is performed at different levels - fuel rod lattice and reactor core, static and kinetics calculations. Validation calculations are performed using the codes APOLLO, CRONOS and DYN3D.
Keywords: reactor physics, numerical codes, validation, benchmarking, VVER reactors, neutron diffusion, neutron transport, European code platform
  • Invited lecture (Conferences)
    1st NURESIM Seminar, 07.-08.11.2006, Paris, France

Publ.-Id: 9419 - Permalink


Application of high resolution gamma ray tomography to the measurement of gas hold-up distributions in a stirred chemical reactor
Hampel, U.; Hristov, H. V.; Bieberle, A.; Zippe, C.;
We employed high resolution gamma ray tomography to measure radial and axial phase distributions in a laboratory type chemical reactor with a gas inducing turbine stirrer. Therefore, we used a recently developed gamma ray CT system which is operated with a Cs-137 source and a detector that achieves approximately 2 mm spatial resolution. The measured data has been compared to computational fluid dynamics predictions obtained with CFX 10.0.
Keywords: gamma ray tomography, stirred reactor, two-phase flow measurement, CFD simulation

Publ.-Id: 9418 - Permalink


Flash Lamp Annealing vs Rapid Thermal and Furnace Annealing for Optimized Metal-Oxide-Silicon-Based Light-Emitting Diodes
Prucnal, S.; Sun, J. M.; Muecklich, A.; Skorupa, W.;
Conventional annealing processes such as furnace annealing (FA) and rapid thermal annealing (RTA) are compared to the more advanced technique of flash lamp annealing (FLA) regarding the electroluminescence (EL) efficiency, electrical stability, defect formation, and rare-earth nanocluster (RE-nc) creation in metal-oxide-silicon-based light-emitting diodes with Gd implanted SiO2 layers. We observed strong correlation between the electroluminescence efficiency, the nanocluster size, and the annealing technique for Gd implanted oxides. The increase of the annealing temperature and time leads to an increase of the RE-nc size and decreases the EL efficiency. Therefore, short-pulse high-temperature annealing (FLA) has a large advantage over the different annealing techniques (FA and RTA) from the point of view of stable and efficient metal oxide semiconductor light emitters.
Keywords: flash lamp annealing, ion implantation, electroluminescence, light emitter, Gadolinium
  • Electrochemical and Solid State Letters 10(2007)2, H50-H52

Publ.-Id: 9417 - Permalink


Si-based Materials for Advanced Microelectronic Devices: Synthesis, Defects and Diffusion
Napolitani, E.; Kuznetsov, A.; Skorupa, W.; Foad, M.;
This volume contains the proceedings of Symposium U “Si-based Materials for Advanced Microelectronic Devices: Synthesis, Defects and Diffusion” that was held in Nice (France) from the 29th of May to the 2nd of June 2006 during the E-MRS IUMRS ICEM 2006 Spring Meeting. The Symposium was organized by Enrico Napolitani (MATIS – CNR-INFM, Padova, Italy), Andrej Kuznetsov (University of Oslo, Norway), Wolfgang Skorupa (Forschungszentrum Rossendorf, Dresden, Germany), and Majeed Foad (Applied Materials, Sunnyvale CA, USA).
As classical scaling of CMOS devices is slowing down, being progressively replaced by ‘performance engineering’, new approaches are becoming object of more and more intense research, such as strain engineering, new materials, and advanced annealing methods. Topics of the Symposium were new materials such as strained Si, Si1−xGex, concerning issues on defects, diffusion, ion implantation and on their synthesis. But also, and mainly, research on ultra shallow junctions for future Si CMOS devices, spanning from the investigation of new methods for their formation to the fundamental understanding of dopants and defects. 113 contributions were selected from about 30 countries around the world (including Europe, Americas, Africa and Asia). The presentations were organized in 10 oral technical sessions and two poster sessions, including 14 invited speakers, 37 oral presentations and 62 posters.
The organizers of Symposium U would like to thank all participants for their valuable contribution and their active participation, which made the Symposium a very stimulating and lively forum for academic and industrial researchers. Special thanks are due to all the invited speakers for the excellent reviews of their recent work and the state-of-the-art of the actual research activities, and for their brilliant chairing of the sessions. We acknowledge also the significant sponsorship of Applied Materials, which make us capable to provide financial support to some participants and grants to the award winners.
Keywords: Ion implantation, Millisecond annealing, Synthesis, Defects, Diffusion, Doping, Si CMOS devices, Ultra shallow junctions, Boron clustering, Process simulation, Characterization
  • Contribution to proceedings
    ICEM 2006 Spring Meeting - Symposium U, 29.05.-02.06.2006, Nice, France, Amsterdam: Elsevier

Publ.-Id: 9416 - Permalink


Uran - Bindungsform und Toxizität
Bernhard, G.; Geipel, G.;
Neben dem Eintrag des Urans durch seine Gewinnung und die Anwendung von Uranmunition, ist auch der Eintrag in die Biosphäre über Industrieprodukte wie Zement, Dünger und Trinkwässer zu berücksichtigen. Durch den erhöhten Umwelteintrag ist eine mögliche Akkumulation des Urans in den Biosystemen in Betracht zu ziehen. Bisher war es nicht möglich, in den notwendigen niedrigen Konzentrationsbereichen, die unterschiedlichen Bindungsformen des Urans zu bestimmen und damit Aussagen über die Abhängigkeit der Toxizität von der Bindungsform abzuleiten. Vor der Problematik des Urangehaltes des Wassers der Nürtinger Heinrichs-Quelle, wird aktuell über erste Ergebnisse der Unterschiede der Bindungsform des Urans im aufgenommenen Wasser und im entsprechenden metabolischen Urin berichtet.
  • Invited lecture (Conferences)
    Workshop "Heinrichsquelle Nürtingen", 19.03.2007, Nürtingen, Deutschland

Publ.-Id: 9415 - Permalink


Bestimmung der Bindungsform des Urans in kontaminierten Wässern
Geipel, G.; Bernhard, G.;
Spektroskopische Methoden erlauben grundsätzlich die Bestimmung der Bindungsform von Schwermetallen, ohne einen chemischen Eingriff in das System selbst vornehmen zu müssen. Je niedriger die Konzentration des Schwermetalls ist, desto komplizierter und spezifischer werden die angewandten Methoden. Im Fall des Urans hilft die besondere Eigenschaft der Lumineszenz, um zu niedrigsten Konzentrationen vorzudringen. Durch die Anregung dieser Lumineszenz mit sehr intensiven Lichtquellen, wie z.B. Lasern, wird eine weitere Empfindlichkeitssteigerung erzielt. An ausgewählten uranhaltigen Wässern werden die heute vorhandenen Möglichkeiten der Bestimmung der Bindungsformen des Urans bis hin zum Spurenbereich erläutert.
  • Invited lecture (Conferences)
    Workshop "Heinrichsquelle Nürtingen", 19.03.2007, Nürtingen, Deutschland

Publ.-Id: 9414 - Permalink


Neurotensin Receptor Expression in Human Adeno- and Squamous Cell Carcinoma
Haase, C.; Bergmann, R.; Oswald, J.; Pietzsch, J.;
There is increasing interest in targeting peptide receptors and their ligands for tumor diagnostics and therapy since there is evidence that various of these receptors are overexpressed in tumors compared to their expression in normal tissues. Among these receptors playing a key role in tumor progression is the neurotensin receptor (NTR) family. The present study investigated the expression of NTR in HT29 cells (human colon adenocarcinoma), in FaDu cells (human squamous cell carcinoma), and in the corresponding HT-29 and FaDu xenografts in nude mice as a well characterized animal tumor model. Quantitative RT-PCR with specific primers for the three NTR subtypes was done to study mRNA expression. Receptor protein expression was analysed by in vitro autoradiography using [3H]neurotensin(8-13) and by immunohistochemistry with specific antibodies against the three neurotensin receptors NTR1, NTR2, and NTR3. Analysis of receptor mRNA revealed a strong expression of NTR3 and a weaker expression of NTR1 and NTR2. Looking at protein levels, strong signals for NTR1 and NTR2 (NTR1 > NTR2) were detected immunohistochemically both in tumor cells and the corresponding xenografts. In contrast, expression of NTR3 revealed only a very weak immunopositive staining in tumors. Because it is the receptor protein that is targeted in vivo, the enhanced expression of NTR1 and NTR2 in these tumor entities could be a useful target for diagnostics, e.g., with radioligands suitable for single photon or positron emission tomography.
  • Poster
    Fourth International Conference on Tumor Microenvironment: Progression, Therapy and Prevention, 06.-10.03.2007, Florence, Italy

Publ.-Id: 9413 - Permalink


Preclinical PET studies in BIOCARE
Beuthien-Baumann, B.;
  • Invited lecture (Conferences)
    Clinical and experimental research in radiation oncology (CERRO), 21.-26.01.2007, Les Menuires, France

Publ.-Id: 9412 - Permalink


PET in Oncology
Beuthien-Baumann, B.; Kotzerke, J.;
  • Lecture (others)
    Postgraduate Diploma Course: Radiopharmaceutical Chemistry /Radiopharmacy. Course Module III Pharmacy II and Nuclear Medicine, 04.09.2006, Leipzig, Germany

Publ.-Id: 9411 - Permalink


MicroPET in mice – status and problems
Beuthien-Baumann, B.;
  • Invited lecture (Conferences)
    Pre-Meeting on New Tech and normal toxicity Primer, 11.03.2006, Lugano, Switzerland

Publ.-Id: 9410 - Permalink


Comparison of PET imaging and histology
Beuthien-Baumann, B.;
  • Invited lecture (Conferences)
    Clinical and experimental research in radiation oncology (CERRO), 22.-27.01.2006, Les Menuires, France

Publ.-Id: 9409 - Permalink


Prefrontal Cortex Dysfunction and Depression in Atypical Parkinsonian Syndromes
Herting, B.; Beuthien-Baumann, B.; Pöttrich, K.; Donix, M.; Triemer, A.; Lampe, J. B.; von Kummer, R.; Herholz, K.; Reichmann, H.; Holthoff, V. A.;
Depressive symptoms are common in patients with neurodegenerative disorders. Imaging studies suggest that a
disruption of frontal–subcortical pathways may underlie depression associated with basal ganglia disease. This pilot study tested the hypothesis that frontal dysfunction contributes to depression associated with multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). Depressed patients with MSA (n = 11), PSA (n = 9), and age-matched controls (n = 25) underwent measures of cerebral glucose metabolism applying positron emission tomography with 18F-fluorodeoxyglucose. Regional metabolism in the patient groups was compared
to the normal subjects using the voxel-based statistical parametric mapping. Depressive symptom severity (Hamilton Depression Rating) and degree of locomotor disability (Hoehn & Yahr) were assessed in the patient groups. The association between prefrontal metabolism and the occurrence of depressive symptoms and the degree of locomotor disability was investigated. When compared to controls, MSA patients revealed
significant metabolic decreases in bilateral frontal, parietal, and cerebellar cortex and in the left putamen. In PSP
patients, significant hypometabolism was demonstrated in bilateral frontal cortex, right thalamus, and midbrain. Depression severity but not the patients’ functional condition was significantly associated with dorsolateral prefrontal glucose metabolism in both patient groups. The findings of this pilot study support the hypothesis that depressive symptoms in MSA and PSP are associated with prefrontal dysfunction.
Keywords: multiple system atrophy; progressive supranuclear palsy; depression; tomography; emission-computed; frontal lobe

Publ.-Id: 9408 - Permalink


CFX simulations of ROCOM slug mixing experiments
Moretti, F.; Melideo, D.; D’Auria, F.; Höhne, T.; Kliem, S.;
The present paper documents the CFD code validation activity carried out at the University of Pisa. In particular, the ANSYS CFX-10.0 code has been used to simulate one of the experiments conducted at the ROCOM mixing test facility (FZD, Germany), that reproduced the injection of a de-borated slug in one cold leg of a pressurized water reactor (simulated by a salt tracer) with all circulation pumps at steady-state operation. The calculations were run on several grids obtained through different meshing strategies and having different sizes. The numerical results, in terms ofnormalized concentration of the transported passive scalar in the downcomer and at the core inlet, were compared against corresponding values obtained through experimental measurements of electrical conductivity in the ROCOM facility. Such comparison resulted in a general good qualitative agreement between simulations and experiments, while some discrepancies were evidenced from a quantitative point of view, mainly due to grid coarseness and low order numerical schemes.
Keywords: ROCOM, CFD
  • Contribution to proceedings
    15th International Conference on Nuclear Engineering (ICONE15), 22.-26.04.2007, Nagoya, Japan
    ICONE15-10461
  • Lecture (Conference)
    15th International Conference on Nuclear Engineering (ICONE15), 22.-26.04.2007, Nagoya, Japan
  • Open Access LogoJournal of Power and Energy Systems 2(2008)2, 720-733
    DOI: 10.1299/jpes.2.720

Publ.-Id: 9407 - Permalink


Anisotropy of ion-induced amorphous-crystalline ripples in silicon
Grigorian, S.; Grenzer, J.; Biermanns, A.; Hazra, S.; Datta, D. P.; Chini, T. K.; Sanyal, M. K.; Pietsch, U.;
The morphological evolution of surfaces during ion-beam irradiation has attracted significant interest due to possibility of the evelopment and the controlling of self-organization in nanostructures. Pattering and texture on nanometer length scale at metal and semiconductor surfaces has become a topic of intense research. In particular the surface and subsurface ripple formation under 40Ar+ ion-beam irradiation of Si (100) crystal has been studied recently. Based on transmission electron microscopy (TEM), atomic force microscopy (AFM) and x-ray analysis a dramatic effect of the ripple formation was found at an irradiation energy of 60 keV.
Apart from the crystalline part, the amorphization process is very important for understanding the amorphous-crystalline interface and the ripple formation mechanism. The dose of the ion beam was varied in the range from low 3e16 up to high 7e17 ions/cm^2 at an incident angle of 60° and an energy of 60 keV. Keeping the optimized irradiation parameters constant we have measured the degree of amorphization as a function of Ar+ dose by means of x-ray grazing incidence amorphous scattering (GIAS). For irradiated samples we found two broad peaks indicating a short-range ordering of amorphous material which does what with the penetration depth of probing x-ray. GIAS profiles probed at different azimuthal angles display a strong anisotropy of the amorphous scattering. The strong damage of the crystalline structure takes place along particular crystallographic directions. This is for the directional anisotropy: and strongly reveal for low doses, before it becomes completly amorphous and mostly uniform at high doses of implantation.
Such behavior can be explained taking into account the anisotropy of the crystalline material and orientation of the ion beam with respect crystallographic orientation of the substrate material. This work was supported by the DST-DAAD India-Germany Collaborative Program. We are grateful to ID1 beamline staff for the support at ESRF.
  • Lecture (Conference)
    8th Biennial Conference on High Resolution Diffraction and Imaging, XTOP 2006, 19.-22.09.2006, Baden-Baden/Karlsruhe, Deutschland

Publ.-Id: 9406 - Permalink


Linkage between the intramembrane H-bond network around aspartic acid 83 and the cytosolic environment of helix 8 in photoactivated rhodopsin
Lehmann, N.; Alexiev, U.; Fahmy, K.;
Understanding the coupling between conformational changes in the intramembrane domain and at the membrane-exposed surface of the bovine photoreceptor rhodopsin, a prototypical G protein-coupled receptor (GPCR), is crucial for the elucidation of molecular mechanisms in GPCR activation. Here, we have combined FTIR- and fluorescence spectroscopy to address the coupling between conformational changes in the intramembrane region around the retinal and the environment of helix 8, a putative cytosolic surface switch region in class-I GPCRs. Using FTIR / fluorescence cross-correlation we show specifically that surface alterations monitored by emission changes of fluorescein bound to Cys316 in helix 8 of rhodopsin are highly correlated with (i) H-bonding to Asp83 proximal of the retinal Schiff base but not to Glu122 close to the -ionone and (ii) with a MII-specific 1643 cm-1 IR absorption change, indicative of a partial loss of secondary structure in helix 8 upon MII formation. These correlations are disrupted by limited C-terminal proteolysis but are maintained upon binding of a transducin -subunit (Gt -derived peptide, which stabilizes the MII state. Our results suggest that additional C-terminal cytosolic loop contacts monitored by an amide II absorption at 1557 cm-1 play a functionally crucial role in keeping helix 8 in the position in which its environment is strongly coupled to the retinal-binding site near the Schiff base. In the intramembrane region, this coupling is mediated by the H-bonding network that connects Asp83 to the NPxxY(x)F motif preceding helix 8.
Keywords: long-range coupling in rhodopsin, FTIR spectroscopy, site-directed fluorescence labeling, heterospectral cross correlation, conformational switch, GPCR signaling

Publ.-Id: 9405 - Permalink


[1-11C]Acetate uptake is not increased in renal cell carcinoma
Kotzerke, J.; Linné, C.; Meinhardt, M.; Steinbach, J.; Wirth, M.; Baretton, G.; Abolmaali, N.; Beuthien-Baumann, B.;
Purpose
The purpose of this study was to investigate the potential of [1-11C]acetate (AC) as a metabolic tracer for renal cell cancer in human subjects.
Methods
Twenty-one patients with suspected kidney tumours were investigated with AC and dynamic PET. AC uptake was scored on a five-step scale. Tumour localisation was known from CT/MRI. Histology was available in 18/21 patients. The results in these 18 patients are reported.
Results
AC uptake by the tumour was less than (n=11), equal to (n=5) or higher than (n=2) uptake in the surrounding renal parenchyma. Histological tumour types showed a typical distribution, with a predominance of clear cell carcinomas (n=14) and only a small number of papillary cell carcinomas (n=2) and oncocytomas (n=2). Only the benign oncocytomas were highly positive with AC.
Conclusion
In most kidney tumours the AC accumulation was not higher than in normal kidney parenchyma. Therefore, AC PET cannot be recommend for the characterisation of a renal mass.
Keywords: [1-11C]acetate, Kidney tumour, Positron emission tomography

Publ.-Id: 9404 - Permalink


Pages: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] [105] [106] [107] [108] [109] [110] [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128] [129] [130] [131] [132] [133] [134] [135] [136] [137] [138] [139] [140] [141] [142] [143] [144] [145] [146] [147] [148] [149] [150] [151] [152] [153] [154] [155] [156] [157] [158] [159] [160] [161] [162] [163] [164] [165] [166] [167] [168] [169] [170] [171] [172] [173] [174] [175] [176] [177] [178] [179] [180] [181] [182] [183] [184] [185] [186] [187] [188] [189] [190] [191] [192] [193] [194] [195] [196] [197] [198] [199] [200] [201] [202] [203] [204] [205] [206] [207] [208] [209] [210] [211] [212] [213] [214] [215] [216] [217] [218] [219] [220] [221] [222] [223] [224] [225] [226] [227] [228] [229] [230] [231] [232] [233] [234] [235] [236] [237] [238] [239] [240] [241] [242] [243] [244] [245] [246] [247] [248] [249] [250] [251] [252] [253] [254] [255] [256] [257] [258] [259] [260] [261] [262] [263]