Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32337 Publications
Experimental and numerical prediction of horizontal stratified flows using the HAWAC facility
Höhne, T.; Vallee, C.;
Slug flow is potentially hazardous to the structure of the system due to the strong oscillating pressure levels formed behind the liquid slugs. It is usually characterized by an acceleration of the gaseous phase and by the transition of fast liquid slugs, which carry out a significant amount of liquid with high kinetic energy. For the experimental investigation of air/water flows, a horizontal channel with rectangular cross-section was build at Forschungszentrum Dresden-Rossendorf (FZD). Experimental data were used to check the feasibility to predict the slugging phenomenon with the existing multiphase flow models build in ANSYS CFX. Further it is of interest to prove the understanding of the general fluid dynamic mechanism leading to slug flow and to identify the critical parameters affecting the main slug flow parameters (like e.g. slug length, frequency and propagation velocity; pressure drop).
A selected co-current test run that was carried out at a superficial water velocity of 0.69 m /s and a superficial air velocity of 2.2 m /s at ambient pressure and temperature conditions was analyzed using the software package ANSYS CFX. At these conditions, a slug flow is generated. For free surface simulations, the inhomogeneous multiphase model was used, where the gaseous and liquid phases can be partially mixed in certain areas of the flow domain. In this case the local phase demixing after a gas entrainment is controlled by buoyancy and interphase drag and is not hindered by the phase interface separating the two fluids. A further decision has to be made regarding the applied fluid morphology and interphase drag law for the multiphase flow. The fluid-dependent shear stress transport (SST) turbulence models were selected for each phase. Damping of turbulent diffusion at the interface has been considered. The k-ω based SST model accounts for the transport of the turbulent shear stress and gives highly accurate predictions of the onset and the amount of flow separation under adverse pressure gradients. The tail of the calculated slug and the flow behind it is in good agreement with the experiment. The entrainment of small bubbles in front of the slug could not be observed in the calculation. However, the front wave rolls over and breaks. It is created due to the high air velocity. In contrast to the measurement, the slug period is increasing with the time in the calculation. This could be a result of different amount of water in the channel at the beginning of experiment and CFD simulation. While in the simulation, the liquid phase covers 78% of the channel, it represents about 70% at the beginning of the experiment. Furthermore, in the experiment, this value is also reduced by a first slug which carries a significant amount of water out of the channel. This first slug could not be simulated. The behavior of slug propagation at the experimental setup was qualitatively reproduced, while quantitative deviations require a continuation of the work.
As some uncertainties were noticed at the inlet of this channel, the HAWAC (Horizontal Air/Water Channel) with well defined inlet boundary conditions dedicated to co-current flows was built. A picture sequence recorded during slug flow was compared with the equivalent CFD simulation made with the code ANSYS CFX. The two-fluid model was applied with a special free surface treatment. Due to an interfacial momentum transfer, it was possible to generate slugs based on instabilities. The behaviour of slug generation and propagation at the experimental setup was qualitatively reproduced, while deviations require a continuation of the work. The creation of small instabilities due to pressure surge or an increase of interfacial momentum should be analysed in the future. Furthermore, experiments like pressure and velocity measurements are planned and will allow quantitative comparisons, also at other superficial velocities.
Keywords: CFD, flow pattern, stratified flow, slug flow
  • Invited lecture (Conferences)
    ANSYS Conference & 25th CADFEM Users’ Meeting, 21.-23.11.2007, Dresden, Germany
  • Contribution to proceedings
    ANSYS Conference & 25th CADFEM Users’ Meeting, 21.-23.11.2007, Dresden, Germany
    CD-ROM, paper 679

Publ.-Id: 10810 - Permalink

Rare-earth implanted Y2O3 thin films
Peeva, A.; Dikovska, A. O.; Atanasov, P. A.; Jime´Nez De Castro, M.; Skorupa, W.;
Thin Er, Yb co–doped Y2O3 films were grown by pulsed laser deposition from ceramic target. Subsequent ion implantation with 1.1 MeV Er+
ions to a fluence of 6 x 10E14 at/cm2 at room temperature was performed in order to modify the structure of the as-deposited films. The as-depositedfilms have a polycrystalline column-like structure. Ion implantation induces defects into the as-deposited films. After annealing at 900 8C for 1 h inoxygen atmosphere, the films recrystallize in roundly shaped grain-like structure with grain size of about 100 nm. The Er3+ photoluminescence response was obtained for all the films by excitation through cross-relaxation of Yb3+ ions. The IR emission spectrum, consisting of two narrow peaks at 1415 and 1514 nm, differs from the typical spectra of Er-doped materials. The VIS emission spectrum observed in as-deposited films does not appear after implantation and subsequent 900 8C annealing.
Keywords: Rare-earth, erbium, ion implantation, thin films; Y2O3; Pulsed Laser Deposition

Publ.-Id: 10809 - Permalink

Investigation of flow development of co-current gas-liquid vertical slug flow
Kaji, R.; Azzopardi, B. J.; Lucas, D.;
Void fraction, Taylor bubble/liquid slug length, and slug frequency are parameters essential to understand the structure of slug flow. In the present study, these parameters were extracted from the time series of cross-sectionally averaged void fraction obtained from two vertical facilities having similar internal pipe diameter but significantly different axial lengths; 51.2mm/3.5m and 52.3mm/9m. To investigate the effect of flow development on slug characteristics measurements were carried out at several axial locations from the mixing section for both facilities. For slug frequency, a new correlation including the effect of the axial length has been proposed and assessed using previously published data.
Keywords: slug flow, vertical pipe, flow structure, flow development, frequency

Publ.-Id: 10807 - Permalink

Search of the origin of ferromagnetism in DMS
Talut, G.; Reuther, H.; Stromberg, F.; Zhou, S.; Potzger, K.; Grenzer, J.; Mücklich, A.; Eichhorn, F.;
Transition metal doped wide band gap semiconductors like GaN, ZnO and TiO2 are promising candidates to be diluted magnetic semiconductors (DMS) with Curie temperatures (Tc) above room temperature (RT). In most of the studies reported in literature the presence of metallic precipitates could not be excluded and may play an important role in the discussion of the origin of the ferromagnetism.
Hence, one of the main obstacles while creating a DMS is the formation of secondary phases. The detection of those is very problematic too.
Since solubility limits for the doping atoms, especially in GaN, are rather low, non-equilibrium doping techniques like low temperature film growth or ion implantation are commonly used.
Ion implantation gives the possibility of doping at different temperatures and with high dopand concentrations but is always connected with lattice damage of the target material. Subsequent annealing in a time scale of some minutes mostly results in phase separation. Combining ion implantation with faster techniques, i.e. rapid thermal annealing or flash lamp annealing, leads to a diluted state while the crystallinity of the target material can be partially restored.
Sample sets were implanted with 57Fe ions and concentrations up to 18 at. % and subsequently annealed at different temperatures and time scales.
Conversion electron Mössbauer spectroscopy (CEMS), superconducting quantum interference device (SQUID), x-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and Rutherford backscattering spectroscopy (RBS) were used to characterize the (micro)-structure, magnetic response and radiation damage of specimens as well as the charge state and site location of Fe. The origin of ferromagnetism is discussed on base of these results.
Keywords: DMS, Ferromagnetism, GaN, TiO2
  • Invited lecture (Conferences)
    Condensed Matter Seminar, University of Central Florida, 12.11.2007, Orlando, Florida, USA

Publ.-Id: 10806 - Permalink

Entwicklung und Validierung des Druckstoßprogramms DYVPRO Mod. 3
Neuhaus, T.; Schaffrath, A.; Ronneberger, R.; Altstadt, E.;
Druckstöße entstehen in Rohrleitungssystemen immer dann, wenn ein Fluid (z.B. eine Flüssigkeit oder ein Gas) durch das plötzliche Öffnen oder Schließen einer Armatur, die Änderung der Drehzahl einer Pumpe, in Folge von Rohrleitungsbrüchen usw. beschleunigt oder abgebremst wird. Hierbei entstehen Druckwellen, die erhöhte Innendrücke verbunden mit mechanischen Spannungen in den Rohrleitungswänden sowie zeitabhängige axiale Kräfte auf Rohrleitungen und deren Halterungen hervorrufen können. Durch Reflexionen der Druckwellen können Unterdrücke entstehen, die bei Unterschreiten des lokalen Sättigungsdrucks zur Bildung von Dampfblasen (Kavitation) führen können. Bei dem Zusammenfall der Dampfblasen können weitere, sekundäre Druckstöße auftreten, die die primären Druckwellen überlagern. Die Ausbreitungsgeschwindigkeit von Druckwellen hängt zum einen von den Eigenschaften des Fluids (speziell dessen Kompressibilität und Dichte) und zum anderen von den mechanischen Eigenschaften des Rohrleitungssystems (Elastizitätsmodul und Querkontraktionszahl) sowie dessen Geometrie (Durchmesser des Rohrs und Wanddicke) ab. Druckstöße sind oftmals die Ursache für Beschädigungen an Rohrleitungen und Rohrleitungshalterungen und stellen daher für viele verfahrenstechnische Anlagen ein Problem dar.

Die TÜV NORD SysTec GmbH & Co. KG beschäftigt sich seit vielen Jahren mit der Berechnung von Druckstößen in Kraftwerken und speziell in Kernkraftwerken. Hierzu hat sie das Druckstoßprogramm DYVRO entwickelt und qualifiziert. Der vorliegende Beitrag be¬schreibt die nun hinsichtlich des verwendeten partiellen Differentialgleichungssystems und der eingesetzten Numerik überarbeitete Programmversion DYVRO Mod. 3 und deren Validierung anhand repräsentativer Experimente (u.a. anhand des Simpson-Experiments sowie anhand eines Versuches an der Cold Water Hammer Test Facility). Die Ergebnisse der Validierungsrechnungen werden anschließend mit eigenen oder fremden Rechnungen mit Systemcodes (hier ATHLET und RELAP) sowie dem Druckstoßprogramm WAHA verglichen. Bei diesen Vergleichen werden u.a. die Ergebnisse des im 5. EU-Rahmenprogramm geförderten Forschungsvorhabens WAHALOADS mit einbezogen. Die Vergleiche zeigen eine sehr gute Übereinstimmung der Rechenergebnisse von DYVRO mit den Experimenten sowie den Ergebnissen des WAHA-Codes. Die Ergebnisse der Druckstoßcodes WAHA und DYVRO sind – sowohl im einphasigen als auch im zweiphasigen Bereich - deutlich besser als die der Systemcodes. Unsere Analysen belegen, dass DYVRO Mod. 3 dem aktuellen Stand von Wissenschaft und Technik entspricht.
Keywords: water hammer, pipe line, fluid dynamics, pressure wave
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany

Publ.-Id: 10805 - Permalink

(4-Methoxybenzenethiolato-κS)oxido-[2,2’-propylimino)-bis(ethanethiolato)- κ3S,N,S’]rhenium(V)
Kraus, W.; Emmerling, F.; Noll, B.; Noll, S.; Pietzsch, H.-J.;
The central Re atom of the mononuclear title complex, [Re(C8H18NS2)(C6H4OS)O], is five-coordinate (ReNOS3) with a square-pyramidal geometry comprising a tridentate 2,2 0-(propylimino)diethanethiolate ligand, a 4-methoxybenzenethiolate ligand and a doubly-bonded O atom.

Publ.-Id: 10804 - Permalink

Nachweis solarer Neutrinooszillationen an SNO
Wagner, A.;
Das Sudbury Neutrino Observatory wird vorgestellt, die Daten zur Flavour-Zusammensetzung des solaren Neutrinoflusses interpretiert und Schlüsse auf Neutrinooszillationen gezogen.
  • Invited lecture (Conferences)
    Vortrag an Fachbereich Physik der Technischen Universität Darmstadt, 31.10.2007, Darmstadt, Germany

Publ.-Id: 10803 - Permalink

The spectrum of a non-Hermitian two-mode Bose-Hubbard system
Graefe, E.-M.; Günther, U.; Niederle, A.; Korsch, H. J.;
We study an N-particle, two-mode Bose-Hubbard system, modelling a Bose-Einstein condensate in a double-well potential. By introducing effective complex energies to the modes we describe a coupling to a continuum. The eigenvalues of the resulting non-Hermitian matrix model are in general complex where the imaginary parts (resonance widths) describe the decay rate into the continuum. In dependence on the system parameters, the eigenvalues show intricate patterns of avoided and real crossings, as well as characteristic bifurcations. In the present talk the effect of the interplay between the particle interaction and the non-Hermiticity on characteristic features of the spectrum is analysed and its peculiarities are clarified by perturbational methods.
Keywords: Bose-Einstein condensate, Bose-Hubbard system, non-Hermitian matrix model, perturbation theory, exceptional point, spectral bifurcation
  • Lecture (Conference)
    DPG Frühjahrstagung, 10.-14.03.2008, Darmstadt, Germany

Publ.-Id: 10802 - Permalink

Reduzierung des Out-of-Field-of-View Einflusses auf die Event-basierte Bewegungskorrektur von Hirnuntersuchungen in der PET
Langner, J.;
Event-basierte Bewegungskorrekturverfahren erlauben durch räumliche Transformation jedes Koinzidenzereignisses auf einer line-of-response (LOR) eine exakte Korrektur von Patientenbewegungen in der PET. Die Integration dieser komplexen Verfahren in die klinische Routine setzt jedoch ein Bewegungsverfolgungssystem (Motion-Tracking) sowie einen vollautomatischen Verarbeitungsablauf voraus. Ein Schritt hierbei ist die Korrektur des Out-of-Field-of-View (OutFOV) Effektes. Bei diesem Effekt kommt es dazu, dass LORs zeitweise ausserhalb des FOV transformiert und somit nicht in den Emissions-Sinogrammen erfasst werden. Durch entsprechende Normierung der unterbewerteten Bins wird versucht, dies auszugleichen. Werden die Korrekturfaktoren jedoch zu groß, kommt es zu Bildartefakten, welche u.a. die quantitative Auswertung beeinträchtigen. Ziel dieser Arbeit war die Minimierung des OutFOV Einflusses und die Integration der Methode in einen automatisierten Untersuchungsablauf, welcher den Einsatz im klinischen Umfeld ermöglicht.

Meist wird bei event-basierter Korrektur ein einzelner Referenzzeitpunkt für alle Teilabschnitte (Frames) einer dynamischen Aufnahme benutzt – üblicherweise der Startzeitpunkt der Untersuchung. Ein solches Vorgehen führt jedoch i.a. zu den angesprochenen hohen statistischen Unsicherheiten bei der Normierung der OutFOV-Counts. Durch Analyse der Bewegungsdaten, wird für jeden Frame eine
Häufigkeitsverteilung der relativen Patientenbewegung erstellt. Anhand dieser werden optimale Zeitpunkte ermittelt, an denen die Normierungsfaktoren minimal sind. Diese Referenzpositionen erlauben es, jeden Frame einzeln mit ebenfalls räumlich angepassten Transmissionsdaten zu rekonstruieren. Die daraus resultierenden Bildvolumina werden abschließend auf eine gemeinsame
Orientierung transformiert. Hierbei wird die aus den Bewegungsdaten bekannte Orientierung der Bildvolumina zu den Referenzzeitpunkten genutzt.

Die Nutzung für jeden Frame angepasster Referenzzeitpunkte reduziert die OutFOV- Korrekturfaktoren erheblich und gewährleistet eine hinreichende Messstatistik für alle LORs im Gesichtsfeld des Tomographen. Die bewegungskorrigierten Bilddaten sind infolgedessen frei von den erwähnten Artefakten.

Es konnte gezeigt werden, dass durch die Einführung optimierter Referenzpositionen ein wichtiger limitierender Faktor der event-basierten Bewegungskorrektur eliminiert werden kann. Dies zeigt sich auch bei der Auswertung von klinischen Daten, wo das Verfahren in der Lage ist, bewegungsfreie sowie nunmehr quantitativ auswertbare Datensätze zu erzeugen. Nach Kombination dieser Methode mit bereits etablierten Methoden zeigt dies die Machtbarkeit einer klinischen Nutzung einer event-basierten Bewegungskorrektur und deren Potenzial.
  • Abstract in refereed journal
    Nuklearmedizin 47(2008)2, A59
  • Lecture (Conference)
    46. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 23.-26.04.2008, Leipzig, Germany

Publ.-Id: 10801 - Permalink

Helical MRI in MHD Taylor-Couette flow
Szklarski, J.;
Magnetorotational Instability (MRI) is believed to be one of the most important instabilities on astrophysical scales. However, it is very difficult to observe it in a laboratory experiment. One possibility is to use a Taylor-Couette setup (a flow between two concentric rotating cylinders) where a liquid metal alloy is used. Problems arise since such metals are characterized by very small magnetic Prandtl number and consequently vast rotation rates are necessary. In the PROMISE experiment a special helical configuration of the applied magnetic field was used in order to dramatically reduce rotation rates. We present numerical simulations and relate it to experimental results confirming the existence of MRI of this type.
  • Lecture (Conference)
    10th MHD Days, 26.-29.11.2007, Garching, Germany

Publ.-Id: 10800 - Permalink

Untersuchungen zur Kontrastabhängigkeit des untergrundbereinigten Schwellwertes bei der Volumenbestimmung in der PET
Dittrich, S.;
Bei der quantitativen Bewertung dreidimensionaler Strukturen (VOIs) innerhalb von PET-Bildvolumen wurde in (1) auch nach Untergrundsubtraktion eine Abhängigkeit des relativen Schwellwertes vom Bildkontrast nachgewiesen, welche aus theoretischer Sicht unerwartet ist. Für ein Verständnis dieser Abhängigkeit soll in der vorliegenden Arbeit der Einfluss verschiedener Faktoren wie Auflösung und Streukorrektur genauer untersucht werden. Es soll zudem ein effizientes Kalibrierungsverfahren entwickelt werden, welches für eine korrekte Volumenbestimmung bei einem automatischen Schwellwertverfahren notwendig wird.

Es wurden PET-Volumendatensätze mit unterschiedlichen Bildkontrasten ausgewertet, welche sowohl aus Phantommessungen als auch aus Monte Carlo Simulationen mit dem Programmpaket GATE (2) gewonnen wurden. Für die im rekonstruierten Bildvolumen dargestellten Kugeln wurde der Schwellwert, der zur bekannten wahren Objektgröße führt, bestimmt. Aus Least Squares Fits unter Nutzung des analytischen Ausdrucks für die Faltung der Objektfunktion (Aktivitätsverteilung) mit der Point Spread Function (PSF) wurden ferner die rekonstruierte Auflösung und die Kugelradien ermittelt.

Die aus den gemessenen Daten erhaltene Abhängigkeit des untergrundbereinigten, relativen Schwellwertes vom Bildkontrast konnte mit den simulierten Bilddaten bestätigt werden. Mit abnehmender Auflösung wird der relative Schwellwert zunehmend unabhängig vom Kontrast. Die aus den Least Squares Fits ermittelten Radien waren stets kleiner als die wahren Kugelradien. Diese scheinbare Reduktion der Objektgröße wies ebenfalls eine Abhängigkeit vom Bildkontrast auf, aus der sich wiederum der Zusammenhang zwischen relativen Schwellwert und Kontrast ableiten lässt. Dadurch konnte eine Kalibrierungsvorschrift für automatische Schwellwertverfahren entwickelt werden.

Für eine präzise Volumenbestimmung mittels automatischer Schwellwertanalyse in der PET muss auch nach erfolgter Untergrundsubtraktion die Kontrastabhängigkeit des relativen Schwellwertes beachtet werden. Die beobachtete Abhängigkeit konnte über eine Radiusreduktion erklärt werden, woraus eine allgemeine Kalibrierungsvorschrift für die Volumenbestimmung mit automatischen
Schwellwertverfahren entwickelt wurde.

(1) C. Pötzsch; F. Hofheinz; J. van den Hoff; Minimierung der Inter-Observer-Variabilität bei volumetrischen Auswertungen von onkologischen Ganzkörperstudien in der PET; Nuklearmedizin (2005) 44 p. A16
(2) S. Jan; G. Santin; D. Strul et al.; GATE: a simulation toolkit for PET and SPECT; Phys. Med. Biol. 49 (2004) 4543
  • Abstract in refereed journal
    Nuklearmedizin 47(2008)2, A58
  • Lecture (Conference)
    46. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 23.-26.04.2008, Leipzig, Germany

Publ.-Id: 10799 - Permalink

Multimere Neurotensin-Liganden: Synthese, Komplexbildung gegenüber Kupfer(II) und Affinität zum Neurotensin-Rezeptor 1
Stephan, H.; Röhrich, A.; Noll, S.; Bergmann, R.; Pietzsch, J.; Steinbach, J.;
Neben den eingeführten Radionukliden Tc-99m, Re-188 und Y-90 rücken Radionuklide wie Cu-64 und Cu-67 zunehmend in das Interesse für Diagnostik und Therapie von Tumor- und Stoffwechselerkrankungen. In Verbindung mit multifunktionale Liganden eröffnet dies einen neuen Zugang zu spezifischen Radiopharmaka und zwar vor allem dann, wenn die Verkapslung radioaktiver Metallnuklide im Kern topologisch so gelingt, dass diese unter physiologischen Bedingungen kinetisch und thermodynamisch stabil fixiert sind. Eine Modifizierung der Ligandstruktur mit Biomolekülen - wie Zucker oder Peptide - erlaubt dann die Einstellung definierter Löslichkeits- und selektiver Bindungseigenschaften. Ziel ist die Entwicklung metabolisch stabiler, radioaktiv markierter Neurotensin-Konjugate für die Tumordiagnostik und –therapie
  • Lecture (Conference)
    46. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 23.-26.04.2008, Leipzig, Germany
  • Abstract in refereed journal
    Nuklearmedizin 47(2008)2, A82

Publ.-Id: 10798 - Permalink

Nanoscaled silicon-based heterostructures formed by interface mediated endotaxy
Popov, V. P.; Tyschenko, I. E.; Cherkov, A. G.; Pokhil, G. P.; Fridman, V. M.; Voelskow, M.;
New types of substrates are needed for further scaling in CMOS microelectronics after 22 nm node. We speculate that this new type of materials can be semiconductor heterostructures on insulator (HOI) compatible with current silicon planar CMOS technology. In this work the effect of interface mediated endotaxial (IME) growth of thin Ge or InSb film at the Si/SiO2 bonded interface was experimentally observed and investigated. A joint semiconductor material stack obtained by hydrogen transfer of one layer material (silicon) and an endotaxially grown second one (germanium or indium antimonide) placed initially into an amorphous silicon dioxide film is presented. Thermodynamic, kinetic and lattice mismatch parameter influences on the IME process are considered.
Keywords: Nanoscaled, heterostructures
  • ECS Transactions 6(2007)1, 87-93

Publ.-Id: 10796 - Permalink

Advanced heterostructure Si-InSb on insulator formed by bonding of hydrogen transferred Si layer and implanted SiO2 film
Popov, V. P.; Tyschenko, I. E.; Cherkov, A. G.; Pokhil, G. P.; Fridman, V. M.; Voelskow, M.;
Using bulk silicon may be limited for 22 nm technological node due to silicon mobility limitation. New type of substrates needs for further scaling in CMOS microelectronics. We speculate that this new type of materials can be semiconductor heterostructure on insulator (HOI) compatible with current silicon planar CMOS technology. In this work an effect of interface mediated endotaxial (IME) growth of thin InSb film at Si/SiO2 bonded interface was experimentally observed and investigated for the first time. Joint semiconductor material stack obtained by hydrogen transfer of one layer material (silicon) and endotaxially grown second one (indium antimonide) placed initially into amorphous silicon dioxide film is presented. Thermodynamic, kinetic and lattice mismatch parameter influences on IME process are considered.
Keywords: silicon heterostructure InSb
  • ECS Transactions 6(2007)4, 345-350

Publ.-Id: 10794 - Permalink

Detection of intrinsic stress in cubic boron nitride films by x-ray absorption near-edge structure: Stress relaxation mechanisms by simultaneous ion implantation during growth
Gago, R.; Abendroth, B.; Cerda, J. I.; Jimenez, I.; Möller, W.;
The bonding structure of cubic boron nitride (cBN) films with different levels of intrinsic stress (1–10 GPa) has been studied from the K-shell x-ray absorption near-edge structure (XANES). The stress level was tuned by the damage induced from simultaneous medium-energy ion implantation (1–10 keV) during growth. The films show a dominant sp3 arrangement for damage values below a certain threshold, with an appreciable sp3 to sp2 transformation taking place above this limit. Interestingly, the degree of stress in sp3 structures is reflected in the B 1s spectral line shape, which progressively converges to that of stress-free cBN powder for increasing ion damage. These results indicate that stress buildup and release occur at a microscopic level. The changes in the spectral line shape are correlated with modifications in the electronic structure due to the presence of intrinsic stress and bond distortion within the cubic network, as predicted by density functional theory calculations. Our findings reveal the potential of XANES spectroscopy to detect stress in disordered BN systems.
Keywords: cubic boron nitride, intrinsic stress, ion implantation, XANES
  • Physical Review B 76(2007), 174111

Publ.-Id: 10793 - Permalink

Statistical properites and clustering of dynamo reversals observed from paleomagnetic records, experimental dynamo, numerical simulations and simplified models
Sorriso-Valvo, L.; Carbone, V.; Stefani, F.; Bourgoin, M.;
The statistical properites of the time sequence of the geodynamo reversals show interesting features, such as non-poisson statistics indicating presence of correlations, and clustering in time. Such properties can be used to compare the observed reversals sequence with different dynamos, both experimental and numerical. In this work an experimental Bullard-Von Karman dynamo, which reproduces the field reversal, is studied in comparison with the paleomagnetic data. Moreover, some numerical models (namely an alpha-alpha dynamo, a turbulent dynamo, a dissipative Rikitake dynamo, and a shell model MHD dynamo) are characaterized, and their capacity of reproducing the observed clustering properties are discussed, also allowing the fine tuning of the models parameters.
  • Lecture (Conference)
    AGU Fall Meeting, 10.-14.12.2007, San Francisco, USA
  • Abstract in refereed journal
    Eos, Transactions, American Geophysical Union 88(2007)52, GP33A-0921

Publ.-Id: 10792 - Permalink

On the Influence of Spatial Discretization on Cross Section Preparation with HELIOS 1.9
Merk, B.; Koch, R.;
An analysis of the influence of the spatial discretization strategy for cell- and lattice calculations on the neutron flux distribution and the kinf value in a single cell is performed. The analysis shows a significantly different neutron flux distribution and kinf value for different discretizations. In addtion the preparation of few group cross sections for 3D nodal full core simulators is analyzed. Especially these cross sections are very sensitive on an appropriate spatial discretization.
Keywords: Cell- and Lattice calculation, cross section preparation, HELIOS, Discretization
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany

Publ.-Id: 10791 - Permalink

Vergleich von Abbrandrechnungen mit HELIOS 1.9 und KAPROS/KARBUS mit zeitlich veränderlicher Leistung
Merk, B.;
Ein Vergleich des Zell- und Abbrandcodes HELIOS mit der im Programmsystem KAPROS entwickelten Prozedur KARBUS ist für Abbrandrechnungen mit zeitlich veränderlicher Leistung in einer Einheitszelle mit Uranoxid- (UOX) und Mischoxidbrennstoff (MOX) wird durchgeführt und die Ergebnisse für kinf und die Teilchendichten der Transurane analysiert.
A comparison of the cell and burnup code HELIOS with the program procedure KAPROS/KARBUS for burnup calcaultions with time dependent power in a unit cell for UOX and MOX fuel is performed. The results for kinf and the particle densities of transuranium elements are analyzed
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany

Publ.-Id: 10790 - Permalink

Laser accelerated particle beams
Kraft, S.; Zeil, K.; Kluge, T.; Debus, A.; Bock, S.; Sauerbrey, R.; Schramm, U.;
Laser driven particle acceleration has become a rapidly developing field in recent years. Laser pulses with a pulse duration of 10 - 100 fs and up to several Petawatt of power in each pulse are focussed onto either gas targets or thin foils where they create enormous electromagnetic fields. These fields operate as a mm scale accelerator producing quasimonoenergetic electron or ion beams with energies of 1 GeV and several MeV, respectively.

Although the lasers operate at very low repetition rates of around 1 Hz, such a system could become interesting for medical applications since a single bunch accelerated by the laser carries between 108 and 1010 particles.

In this talk, we want to present the current state of laser particle acceleration. Challenges and future developments for clinical applications in cancer therapy will be discussed.
  • Invited lecture (Conferences)
    Ion Beams in Biology and Medicine, 26.-29.09.2007, Heidelberg, Germany

Publ.-Id: 10789 - Permalink

A high-resolution time-of-flight mass spectrometer for the detection of ultracold molecules
Kraft, S. D.; Mikosch, J.; Staanum, P.; Deiglmayr, J.; Lange, J.; Fioretti, A.; Wester, R.; Weidemüller, M.;
We have realized a high-resolution time-of-flight mass spectrometer combined with a magneto-optical trap. The spectrometer enables excellent optical access to the trapped atomic cloud using specifically devised acceleration and deflection electrodes. The ions are extracted along a laser beam axis and deflected onto an off-axis detector. The setup is applied to detect atoms and molecules photoassociated from ultracold atoms. The detection is based on resonance-enhanced multiphoton ionization. Mass resolution up to m/Delta m = 1000 at the mass of 133^Cs is achieved. The performance of this spectrometer is demonstrated in the detection of photoassociated ultracold 7^Li133^Cs molecules near a large signal of 133^Cs ions.
  • Applied Physics B 89(2007), 453

Publ.-Id: 10788 - Permalink

Numerical Simulations of the onset of dynamo action with a hybrid finite volume/ boundary element method (FV-BEM)
Giesecke, A.; Stefani, F.;
The experimental realization of dynamo excitation as well as theoretical and numerical examinations of the induction equation have shown the relevance of boundary conditions and material properties for a self-sustaining dynamo. Generally, in non-spherical geometry typical insulating boundary conditions are described by elaborated schemes (e.g. solving of the Laplace equation in an extended domain) or by simplifying approximations (pseudo vacuum). A different approach is provided by a modified integral equation procedure, commonly known as the boundary element method (BEM). Integrating the Laplace equation on the boundaries allows to overcome the difficulties of the non-local character of insulating boundary conditions and the direct computation of the magnetic field next to an insulator becomes possible. However, within the interior of a field producing domain geometric constraints or varying material properties (e.g. electrical conductivity of the container walls or localized high-permeability material) might also play a role. For this problem, a more flexible approach utilizing a local discretization like the constraint transport (CT) method as a well known realization of a finite volume scheme is recommendable. The CT-scheme ensures a fast, robust and accurate solution of the kinematic dynamo problem and intrinsically maintains the solenoidal character of the magnetic field. Combining both methods in a hybrid FV-BEM scheme offers the flexibility of a local discretization with a stringent treatment of insulating magnetic boundary conditions in arbitrary geometries. Preliminary simulations of an alpha^2-Dynamo in a cartesian box and/or the decay of an initial magnetic field demonstrate the applicability of the approach.
Further examinations are intended to understand the behavior of the VKS-dynamo experiment where the field producing flow is driven by ferrous propellers and the dynamo mechanism probably is dominated by this high permeability material.
Other applications of the hybrid scheme may also be important for the evaluation of forthcoming dynamo experiments
for which a precise knowledge of the critical magnetic Reynolds number is essential.
  • Lecture (Conference)
    10th MHD Days, 26.-29.11.2007, Garching, Germany

Publ.-Id: 10787 - Permalink

Role of Four-Quark Condensates in QCD Sum Rules
Thomas, R.; Hilger, T.; Kämpfer, B.;
The QCD sum rule approach to the in-medium behavior of hadrons is discussed for omega meson, nucleon and D meson.
Emphasis is devoted to the impact of four-quark condensates and to order parameters of spontaneous symmetry breaking.

Publ.-Id: 10786 - Permalink

Characterization of hybrid amorphous-partially crystalline thin films
Martin, N.; Hamann, C.; McCord, J.; Fassbender, J.ORC; Quandt, E.; Gerber, A.; Bigall, N.; Eychmüller, A.; Schultz, L.
Amorphous FeCoBSi thin films with uniaxial anisotropy have been laterally structured by Co ion implantation into stripe arrays. The resulting multiphase samples were investigated regarding the magnetic properties. Hysteresis measurements revealed a large increase in coercivity of the implanted areas. By means of TEM investigations this could be attributed to formed crystallites in the amorphous matrix. Magneto-optical imaging was used to correlate the domain structure to the magnetic hysteresis. It is demonstrated that stripe orientation with respect to the magnetic easy axis governs the coupling between implanted and non implanted areas.
Keywords: magnetism, ion implantation, hybrid materials, crystalization, magnetic microscopy
  • Poster
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10785 - Permalink

The influence of non centric holes on the magnetization dynamics of Landau structures
Wintz, S.; Kuepper, K.; Buess, M.; Raabe, J.; Quitman, C.; Fassbender, J.ORC
Magnetic vortex cores are attracted and can be trapped by artificial defects. If more than one of such defects are created a switching between different vortex core trapped states, which might serve as discrete levels in a multivalent memory device, can be achieved. Up to now a number of studies of circular vortex structures comprising holes has been reported, e. g. [1,2,3]. We report the imaging of the magnetic excitation spectrum in presence of holes, fabricated by focussed ion beam milling, in the magnetic domains and domain walls of Landau structures by means of x-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM). Due to the very high lateral and temporal resolution the magnetization dynamics and the corresponding Eigen modes, which are characteristic for the vortexhole interaction, are investigated in detail. The experimental results are compared to micromagnetic simulations.

[1] M. Rahm et al., Appl. Phys. Lett. 85, 1553 (2004).
[2] T. Uhlig et al., Phys. Rev. Lett. 95, 237205 (2005).
[3] F. Hoffmann et al., Phys. Rev. B 76, 014416 (2007).
Keywords: magnetism, magnetization dynamics, vortex, Landau structure, holes, defects
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10784 - Permalink

Inclusive di-electron production in C+C collisions with HADES
Dohrmann, F.; Agakishiev, G.; Agodi, C.; Balanda, A.; Bellia, G.; Belver, D.; Belyaev, A.; Blanco, A.; Boehmer, M.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Diaz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Grosse, E.; Guber, F.; Heilmann, M.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kaempfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Krizek, F.; Kruecken, R.; Kuehn, W.; Kugler, A.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, J. S.; Lopes, L.; Maier, L.; Mangiarotti, A.; Marin, J.; Markert, J.; Metag, V.; Michalska, B.; Mishra, D.; Moriniere, E.; Mousa, J.; Muentz, C.; Naumann, L.; Novotny, R.; Otwinowski, J.; Pachmayer, Y. C.; Palk! A, M.; Pechenov, V.; Pechenova, O.; Cavalcanti, T. P.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Simon, R.; Spataro, S.; Spruck, B.; Stroebele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Veretenkin, I.; Wagner, V.; Wen, H.; Wisniowski, M.; Wojcik, T.; Wuestenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zumbruch, P.;
Inclusive di-electron production in C+C collisions at 1 and 2 AGeV has recently been measured by the HADES collaboration at GSI. Results are compared to a di-electron cocktail calculated from free hadron pi0, eta, omega decays after freeze-out. For the low invariant masses, M(e+e-) < 0.15 GeV/c2, the measured distributions are largely explained by the pi0 --> e+e- gamma Dalitz decay but for higher masses experimental yields significantly exceed expectations.
Keywords: In-medium properties of hadrons, heavy-ion collisions
  • Contribution to proceedings
    MENU2007 11th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon, 10.-14.09.2007, Jülich, Germany
    Proceedings of the 11th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon, SLAC, 67


Publ.-Id: 10783 - Permalink

Modification of magnetic order in Mn5Si3 and Mn5Ge3 by C ion implantation
Sürgers, C.; Joshi, N.; Montbrun, R.; von Löhneysen, H.; Potzger, K.; Möller, W.;
Antiferromagnetically ordered Mn5Si3 can be driven ferromagnetic by incorporation of carbon into the voids of Mn octahedra of the hexagonal structure. While for Mn5Si3Cx polycrystals the Curie temperature saturates for x > 0.22 at TC = 152 K [1], sputtered Mn5Si3C0.8 films exhibit a TC above room temperature [2]. An enhancement of TC is also found after C doping of the isostructural compound Mn5Ge3 which is currently in the focus of possible spintronic applications. In an alternative approach, Mn5Si3Cx and Mn5Ge3Cx films were prepared by implantation of 45 - 195 keV C+ ions into Mn5Si3 or Mn5Ge3 films at elevated temperatures. The carbon-implanted samples exhibit magnetic properties very similar to their respective magnetron-sputtered counterparts as inferred from magnetization and resistivity measurements.
Keywords: Magnetic semiconductors, Implantation, Mn5Ge3
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.2.2008, Berlin, Germany

Publ.-Id: 10782 - Permalink

Magnetic anisotropies in ferromagnetic and exchange-coupled systems on rippled surfaces
Liedke, M. O.; Liedke, B.; Marko, D.; Keller, A.; Muecklich, A.; Facsko, S.; Fassbender, J.ORC; Cizmar, E.; Zvyagin, S.; Wosnitza, J.
The influence of a surface and interface modulation on the magnetic properties of ferromagnetic materials (Py, Fe and Co) and an exchange bias system (Py/FeMn) is studied. A periodic surface modulation (the so-called ripples) is achieved by low energy ion erosion. Subsequently the magnetic stack is deposited. Due to the film morphology a strong uniaxial anisotropy is induced in the ferromagnetic layers, which is fixed in its orientation along ripples elongation. In the case of the exchange bias system the direction of the induced unidirectional anisotropy can be varied by means of different field annealing cycles. For all mutual orientations both anisotropy contributions are superimposed independently. The angular dependence of the magnetization reversal behavior can be described perfectly by a coherent rotation model [1]. In addition, the magnitude of the uniaxial and the unidirectional anisotropy scales with the step density or wave length of the rippled substrate, which is in full agreement with theoretical predictions.

[1] M. O. Liedke et al., Phys. Rev. B 75, 220407(R) (2007)
Keywords: exchange bias, ripples, ion erosion, exchange coupling, Py, FeMn, Co, Fe, magnetic anisotropy
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.02.2008, Berlin, Germany

Publ.-Id: 10781 - Permalink

Magnetic microstructures produced by local ion irradiation induced interfacial mixing
Strache, T.; Grenzer, J.; Fassbender, J.ORC; Möller, W.; Kaltofen, R.; Mönch, I.
Ion irradiation of Ni80Fe20/Ta multilayers induces an interfacial mixing of these two materials, which subsequently leads to a suppression of the ferromagnetic properties. In order to quantify the structural change grazing incidence x-ray reflectometry has been used. The ion irradiation induced intermixing has been studied by means of TRIDYN simulations. The broadening of the interfaces due to intermixing causes an enrichment of Ta in Ni80Fe20 and finally an amorphization of Ni80Fe20 above a Ta concentration of 10 to 20 percent [1]. Consequently the ferromagnetic properties are altered or even suppressed completely for high enough ion fluences. It is observed that the critical ion fluence for a complete suppression of the ferromagnetism depends sensitively on the number of interfaces. It is demonstrated that pure magnetic microstructures can be easily fabricated by local ion irradiation without changing the substrate topography.

[1] J. Fassbender et al., Nucl. Instr. and Meth. in Phys. Res. B 248, 343 (2006).
Keywords: magnetism, ion irradiation, amorphization, irradiation induced mixing, magnetic microstructures
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10780 - Permalink

Facile synthesis of various nitro-substituted derivatives of semaxinib (SU 5416)
Knieß, T.; Kuchar, M.; Wüst, F.;
The synthesis of novel nitro-substituted derivatives of the tyrosine kinase inhibitor SEMAXINIB (SU 5416) is described. The reaction of various substituted oxindoles with 3,5-dimethylpyrrol-2-carbaldehyde derivatives under Knoevenagel conditions gave an array of nitro-substituted derivatives of Semaxinib (SU 5416) in high yields of 72-87%.
Keywords: Nitration, semaxinib, tyrosine kinase

Publ.-Id: 10779 - Permalink

Surface improvement and biocompatibility of TiAl24Nb10 intermetallic alloy using rf plasma nitriding
Abd El-Rahman, A. M.; Maitz, M. F.; Kassem, M. A.; El-Hossary, F.; Prokert, F.; Reuther, H.; Pham, M. T.; Richter, E.;
The present work describes the surface improvement and biocompatibility of TiAl24Nb10 intermetallic alloy using rf plasma nitriding. The nitriding process was carried out at different plasma power from 400 W to 650 W where the other plasma conditions were fixed. Grazing incidence X-ray diffractometry (GIXRD), Auger electron spectroscopy (AES), tribometer and a nanohardness tester were employed to characterize the nitrided layer. Further potentiodynamic polarization method was used to describe the corrosion behavior of the un-nitrided and nitrided alloy. It has been found that the Vickers hardness (HV) and corrosion resistance values of the nitrided layers increase with increasing plasma power while the wear rates of the nitrided layers reduce by two orders of magnitude as compared to those of the un-nitrided layer. This improvement in surface properties of the intermetallic alloy is due to formation of a thin modified layer which is composed of titanium nitride in the alloy surface. Moreover, all modified layers were tested for their sustainability as a biocompatible material. Concerning the application area of biocompatibility, the present treated alloy show good surface properties especially for the nitrided alloy at low plasma power of 400 W.
  • Applied Surface Science 253(2007), 9067-9072

Publ.-Id: 10778 - Permalink

Radiolabeled glucocorticoids as molecular probes for imaging brain glucocorticoid receptors by means of positron-emission-tomography (PET)
Steiniger, B.; Knieß, T.; Bergmann, R.; Pietzsch, J.; Wüst, F.;
Over the last two decades, numerous attempts have been made to develop
11C- and 18F-labeled radiotracers in order to study glucocorticoid receptor (GR)-mediated abnormalities of the hypothalamus-pituitary-adrenocortical (HPA) axis function and regulation in vivo by means of positron emission tomography (PET). The present review wants to address the research efforts dealing with the design, radio-synthesis and radiopharmacological evaluation of PET radiotracers for brain GR im-aging. The underlying problems such as metabolic instability, insufficient blood-brain-barrier penetration and/or high non-specific binding will be discussed.
  • Mini-Reviews in Medicinal Chemistry 8(2008)7, 728-739

Publ.-Id: 10777 - Permalink

Ion irradiation induced local creation of ferromagnetism in Fe60Al40 alloys
Strache, T.; Liedke, M. O.; Fassbender, J.ORC; Möller, W.; Menendez, E.; Sort, J.; Gemming, T.; Weber, A.; Heyderman, L. J.; Rao, K. V.; Deevi, S. C.; Nogues, J.
Ion irradiation of Fe60Al40 alloys results in the phase transformation from the paramagnetic, chemically
ordered B2-phase to the ferromagnetic, chemically disordered A2-phase. The magnetic phase transformation is related to the number of displacements per atom (dpa) during the irradiation. For heavy ions (Ar+, Kr+, Xe+) a universal curve is observed with a steep increase in the fraction of ferromagnetic phase reaching saturation, i. e., a complete phase transformation, at about 0.5 dpa. This proves the purely ballistic nature of the disordering process. If light ions are used (He+, Ne+) a pronounced deviation from the universal curve is observed. This is attributed to bulk vacancy diffusion from dilute collision cascades, which leads to a partial recovery of the thermodynamically favored B2-phase. Comparing different noble gas ion irradiation experiments allows to asses the corresponding counteracting contributions. In addition, the potential to create local ferromagnetic areas embedded in a paramagnetic matrix is demonstrated.
Keywords: magnetism, ion irradiation, binary alloys, intermetallic, FIB, patterning
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10776 - Permalink

Self-organized surface ripples as a source of magnetic anisotropies
Fassbender, J.ORC; Liedke, M. O.; Keller, A.; Facsko, S.; Marko, D.; Hanisch, A.; Grenzer, J.; Cizmar, E.; Zvyagin, S.
In thin film magnetism surface and interfacemorphologies are important sources of magnetic anisotropy. This can be either due to the reduced coordination of step edge atoms (intrinsic contribution) or due to magnetic stray fields emanating from the film corrugation (extrinsic contribution). Low energy ion erosion is perfectly suited to create a periodic surface modulation (so-called ripples) on the nanoscale. By changing the primary energy of the ions the ripple periodicities can be varied from 20 to 150 nm. Subsequently, thin magnetic films are deposited on these template systems in order to investigate the influence of the surface morphology on the induced magnetic anisotropies. For small ripple periodicities a strong uniaxial magnetic anisotropy is found which rapidly decrease for larger ripple periodicities. In the case of Permalloy (Ni81Fe19) the induced anisotropy can be more than a factor of 20 larger compared to the intrinsic anisotropy of flat Permalloy. The microscopic origin of this effect will be discussed.
Keywords: magnetism, ion erosion, self-organization, magnetic anisotropies, ferromagnetic resonance
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10775 - Permalink

Magnetic thin film materials tailored by ion irradiation
Fassbender, J.ORC
In recent years the tailoring of magnetic properties by means of ion irradiation techniques has become fashionable.
Since the magnetic properties of multilayers depend sensitively on the mutual interfaces a modification of these interfaces by ion irradiation leads to a local modification of the magnetic anisotropy, the exchange bias or the interlayer exchange coupling [1,2]. Also structural phase transitions can be induced by ion irradiation. If these are accompanied by magnetic phase transformations ferromagnetic regions can immediately be written with a focused ion beam. In addition to pure radiation effects also doping effects can be exploited to achieve a pure magnetic patterning. Finally ion erosion of semiconductor substrates can be used as periodically modulated substrates which modify the magnetic anisotropies of subsequently deposited magnetic films.
Examples of all different approaches will be presented in order to demonstrate the large viability of ion beam technology to tailor magnetic materials.
Refs.: [1] J. Fassbender, D. Ravelosona,Y. Samson, J. Phys. D 37, R179 (2004). [2] J. Fassbender, J. McCord, J. Magn. Magn. Mater. 320, 579 (2008).
Keywords: magnetism, ion irradiation, FIB, self-organization, ripples
  • Invited lecture (Conferences)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Publ.-Id: 10774 - Permalink

Absence of superconductivity in boron-implanted diamond
Heera, V.; Höhne, R.; Ignatchik, O.; Reuther, H.; Esquinazi, P.;
Recently, superconductivity has been found in heavily boron doped diamond prepared by high temperature/ high pressure synthesis or chemical vapour deposition. An alternative doping method of technological relevance is ion implantation. It is an open question whether superconductivity can also be obtained in boron implanted diamond. Here we report on the transport and magnetic properties of high-dose (2.3x1016-1.7x1017 cm-2) boron-implanted natural IIa diamond samples doped at elevated temperature of 900°C and subsequently annealed at 1500°C and 1700°C. For comparison implantation at room temperature was also carried out. The samples were further characterized by Raman and infrared spectroscopy. No superconductivity could be detected in the samples at temperatures down to 40 mK. We discuss the possible origin for the absence of superconductivity.
Keywords: diamond, boron implantation, implantation damage, graphitization, resistance, superconductivity, magnetic and electrical properties

Publ.-Id: 10773 - Permalink

Combining theoretical chemistry and XANES multi-edge experiments to probe actinide valence states
Fillaux, C.; Berthet, J.-C.; Conradson, S. D.; Guilbaud, P.; Guillaumont, D.; Hennig, C.; Moisy, P.; Roques, J.; Simoni, E.; Shuh, D. K.; Tyliszczak, T.; Castro-Rodriguez, I.; Den Auwer, C.;
Both structural and electronic properties of the actinide cations are of fundamental interest in order to describe the intramolecular interactions. The 5f and 6d orbitals are the first partially or totally vacant states of these elements and their properties reflect the nature of the actinideeligand bond. Because of its chemical and orbital selectivities, XANES spectroscopy is useful to probe the actinides’ frontier orbitals and then understand the cation reactivity toward chelating ligands. The actinide L3 edge contains structural information on the coordination polyhedron because of important scattering features. But very little electronic information can be extracted, due to the short core-hole lifetime, broadening the edge signal. On the other hand, the actinide M4,5 edges provide a better resolution and allow one to achieve electronic and structural information. Furthermore, coupling simulations of the experimental spectra and quantum chemical calculations lead to quantitative information such as the determination of the actinide coordination sphere and its effective charge. To cite this article: C. Fillaux et al., C. R. Chimie 10 (2007). 2007 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Publ.-Id: 10772 - Permalink

RPV Material Investigation of the Former VVER-440 Greifswald NPP
Rindelhardt, U.; Viehrig, H.-W.; Konheiser, J.; Noack, K.; Schuhknecht, J.; Gleisberg, B.;
The real toughness response of RPV material can only be determined after the final shut down of the NPP. Such a chance is given now by investigating material from the former Greifswald NPP (VVER-440/230).
In the first part the paper deals with fast neutron fluence calculations and retrospective dosimetry based on Niobium. Unfortunately, a second neutron reaction besides 93Nb(n,n’) leading to 93mNb-activity is the reaction 92Mo(n,γ)93Mo. Based on the found Nb and Mo contents in the RPV material, it turns out that the 93mNb generation on the Mo path mostly dominates over the fast neutron induced generation from Nb.
The comparison between the calculated and the measured 93mNb activities typically resulted in deviations of 50%. Possible reasons for the observed differences are discussed.
In the second part first results of fracture mechanic investigations are reported. SE(B) specimens from three thickness positions were tested and evaluated according to the test standard ASTM E1921-05. Cleavage fracture toughness values, KJc, were determined and Master Curve based reference temperatures (T0) were evaluated. The T0 measured on the surface of this RPV does not show the highest value and, thus, reflect the conservative condition. The T0 of disc 1-1.3 located between the surface and ¼ thickness is about 40K higher compared with the surface.
The KJc values adjusted to a specimen thickness of 1T are enveloped by the WWER specific lower bound fracture toughness curve suggested in the VERLIFE procedure.
The measured KJc values are not enveloped by the 5% fractile indexed with T0 according to the Master Curve concept. However, the 5% fractile indexed with the VERLIFE reference temperature RTTo that includes an additional margin envelops the measured KJc values. Therefore the VERLIFE lower bound curve conservatively describes the fracture toughness of the investigated weld metal.
Keywords: VVER reactor, neutron fluence, Monte-Carlo calculation, retrospective dosimetry, neutron embrittlement, RPV material, Master Curve application.

Publ.-Id: 10771 - Permalink

P-Implantation in voramorphisiertes Ge und anschließende Temperung: Festphasen-Epitaxie, P-Diffusion und -Aktivierung
Posselt, M.; Schmidt, B.; Anwand, W.; Grötzschel, R.; Heera, V.; Wündisch, C.; Skorupa, W.; Hortenbach, H.; Gennaro, S.; Bersani, M.; Giubertoni, D.; Möller, A.; Bracht, H.;
For details please contact the first author
Keywords: germanium, ion implantation, annealing, phosphorus, diffusion, activation
  • Lecture (Conference)
    38. Treffen der Nutzergruppe Ionenimplantation, 09.11.2007, Dresden, Germany

Publ.-Id: 10770 - Permalink

The truth about ferromagnetic ZnO
Potzger, K.; Zhou, S.; Talut, G.; Kuepper, K.; Reuther, H.; Mücklich, A.; Grenzer, J.; Helm, M.; Fassbender, J.ORC; Schmidt, H.; Xu, Q.; Lorenz, M.
The combination of magnetic and semiconducting properties in oxides is currently one of most popular fields in materials research. Besides the expected gain of knowledge about basic physics, such materials have a large application potential in spin electronics. We present a summary of our results on transition metal doping of ZnO single crystals and thin films by means of ion implantation. We found that none of the samples investigated represents a diluted magnetic semiconductor as predicted by theory [1]. Nevertheless, transition metal ions can be dispersed within the ZnO matrix residing on different sites within the lattice depending on initial preparation conditions. The observed ferromagnetism mainly originates from secondary phase formation (metals or inverted spinels). We discuss the potential of those granular structures in spin-electronics. Moreover, we highlight the suppression of secondary phase formation by means of deliberately lowering the crystalline quality prior to the doping. In that case, purely defect induced ferromagnetic properties are observed. The effect of spin doping of such a defect induced ferromagnet is discussed.
[1] K. Sato and H. Katayama-Yoshida, Physica E 10, 251 (2001).
Keywords: Diluted magnetic semiconductors, ZnO, functional oxides
  • Invited lecture (Conferences)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.2.2008, Berlin, Germany

Publ.-Id: 10769 - Permalink

Fifty Years of radiopharmacy at Rossendorf
Spies, H.; Steinbach, J.;
The Central Institute of Nuclear Research was founded in Rossendorf near Dresden in 1956 and the production of radioactive materials and radiopharmaceuticals was started in 1958. The basis for the production was the irradiation of targets in the Rossendorf research reactor and, to a lower extent, at the Rossendorf cyclotron U-120.

This paper gives an account of the accomplishments of Rossendorf in the field of radiopharmacy from the early fifties, in the former department of 'Radioactive Isotopes', till to date. The production of radiopharmaceuticals is reviewed in brief. Investigations in technetium chemistry and pharmacology are discussed in more details, and efforts to set up positron emission tomography (PET) in Rossendorf, as the first PET centre in the former Eastern Block, are described. Nowadays, the research in radiopharmacy is carried out within the well-equipped Institute of Radiopharmacy, established in 1992.
  • Journal of Labelled Compounds and Radiopharmaceuticals 50(2007), 895-902
    DOI: 10.1002/jlcr.1431

Publ.-Id: 10768 - Permalink

Simultaneous determination of beta nuclides by liquid scintillation spectrometry
Nebelung, C.; Jähnigen, P.; Bernhard, G.;
The determination of radionuclides in environmental samples is of importance, because a large amount of hazardous radionuclides have been released into the biosphere and spread over large areas by weapon tests, releases from nuclear power plants or nuclear fuel reprocessing facilities. Many nuclides are radiotoxic even in small concentrations. Therefore, it is necessary to determine these nuclides at low levels. The usual way to analyze samples of several nuclides involves time-consuming chemical separations followed by activity measurement of the isolated nuclides. An alternative method is the simultaneous measurement of the nuclides by recording and analyzing the liquid scintillation spectra.
The nuclides 3H, 14C, 55Fe, 60Co, 90Sr, 99Tc, 137Cs were measured in various combinations of mixtures as well as with the TRICARB 3000 and Wallac1414a/b (both devices from PerkinElmer).
The TRICARB 3000 was used to measure up to three nuclides in one sample with the assay type dpm (triple) with a good accuracy even for large activity differences and beta energies close together. It is necessary to generate quench curves for each nuclide.
The multi nuclide spectra measured in the cpm mode in the Wallac1414 were deconvoluted with the knowledge of the shape of the single nuclide spectra [1]. In this case has to be considered the difference between the measured and fitted counts (cpm) and the real activity (dpm) subsequentlyThe spectra deconvolution allows to determine more than three nuclides in one sample but with a lower accuracy.
[1] C. Nebelung et al. 2007 Appl. Radiat. Isot. 65, 209-217
Keywords: liquid scintillation, beta-nuclide, beta-spectrum, deconvolution
  • Lecture (Conference)
    LSC 2008, Advances in Liquid Scintillation Spectrometry, 25.-30.05.2008, Davos, Switzerland
  • Contribution to proceedings
    LSC 2008, International Conference on Advances in Liquid Scintillation Spectrometry, 25.-30.05.2008, Davos, Switzerland
    Book of Abstracts, Villigen Schweiz: PSI Paul Scherrer Institut
  • Contribution to proceedings
    LSC 2008, International Conference on Advances in Liquid Scintillation Spectrometry, 25.-30.05.2008, Davos, Switzerland
    Radiocarbon 2009, Tucson, USA: University of Arizona, 978-0-9638314-6-0, 193-201

Publ.-Id: 10767 - Permalink

Das Hochfeld-Magnetlabor in Dresden – 100 Tesla für die Forschung
Herrmannsdörfer, T.; Wosnitza, J.;
  • Physik in unserer Zeit 38(2007), 242-248

Publ.-Id: 10766 - Permalink

Quasiparticle Model of Quark-Gluon Plasma at Imaginary Chemical Potential
Bluhm, M.; Kämpfer, B.;
A quasiparticle model of the quark-gluon plasma is compared with lattice QCD data for purely imaginary chemical potential. Net quark number density, susceptibility as well as the deconfinement border line in the phase diagram of strongly interacting matter are investigated. In addition, the impact of baryo-chemical potential dependent quasiparticle masses is discussed. This accomplishes a direct test of the model for non-zero baryon density. The found results are compared with lattice QCD data for real chemical potential by means of analytic continuation and with a different (independent) set of lattice QCD data at zero chemical potential.
Keywords: quasiparticle model, imaginary chemical potential
  • Physical Review D 77(2008), 034004

Publ.-Id: 10765 - Permalink

Photoactivation of 92Mo and investigation of the short-lived isomer in 91Mo with the new pneumatic delivery system at ELBE
Erhard, M.; Bemmerer, D.; Beyer, R.; Crespo, P.; Fauth, M.; Grosse, E.; Junghans, A. R.; Klug, J.; Kosev, K.; Rusev, G.; Schilling, K. D.; Schwengner, R.; Wagner, A.;
The photodisintegration cross section of the nucleus 92Mo is important for p-process nucleosynthesis. The superconducting electron accelerator ELBE at Forschungszentrum Dresden-Rossendorf provides the possibility to investigate photodisintegration with bremsstrahlung using the photoactivation technique. The reaction 92Mo(gamma,p)91Nb was studied using the decay of 91mNb with a 60.9 d half-life at ELBE [1]. Now the reaction 92Mo(gamma,n)91Mo has been probed using the new pneumatic delivery system to determine the activity of 91mMo (half-life: 65 s). Since the isomer 91mMo decays also into 91mNb it was necessary to measure this process to separate the (gamma,n) from (gamma,p) contributions.
[1] M. Erhard, C. Nair et al., PoS (NIC-IX) 056 (2006)
Keywords: photodisintegration, p-process, nucleosynthesis, bremsstrahlung, photoactivation, pneumatic delivery
  • Lecture (Conference)
    Frühjahrstagung der DPG, 2007, 13.03.2007, Gießen, Germany

Publ.-Id: 10764 - Permalink

Experimente mit reellen Photonen für die nukleare Astrophysik
Wagner, A.;
Experimente am ELBE Bescheuniger zur Photonenstreuung, Photoaktivierung wurden vorgestellt
  • Invited lecture (Conferences)
    Vortrag vor dem Fachbereich Physik der Technischen Universität Darmstadt, 31.10.2007, Darmstadt, Germany

Publ.-Id: 10763 - Permalink

Kerne und Sterne
Wagner, A.;
Vortrag vor der Astronomischen Arbeitsgemeinschaft Nürnberg e.V.
  • Lecture (others)
    Besuch der Nürnberger Astronomischen Arbeitsgemeinschaft, 02.11.2007, Dresden, Germany

Publ.-Id: 10762 - Permalink

Jahrestagung Kerntechnik - Sektionsbericht Sektion: Thermo- und Fluiddynamik
Stieglitz, R.; Kliem, S.;
Der Beitrag gibt einen Überblick über die in den Sitzungen der Sektion Thermo- und Fluiddynamik gehaltenen Vorträge.
  • atw - International Journal for Nuclear Power 52(2007)10, 652-654

Publ.-Id: 10761 - Permalink

Investigation of antimagnetic rotation in light Cadmium nuclei: Cd-106,Cd-108
Simons, A.; Wadsworth, R.; Jenkins, D.; Clark, R.; Cromaz, M.; Deleplanque, M.; Diamond, R.; Fallon, P.; Lane, G.; Lee, I.; Macchiavelli, A.; Stephens, F.; Svensson, C.; Vetter, K.; Ward, D.; Frauendorf, S.; Gu, Y.;
The lifetimes of excited states belonging to the lowest lying positive-parity bands in Cd-106,Cd-108 have been measured using the Doppler-shift attenuation method. The resulting B(E2) transition rates show a significant decrease with increasing spin in Cd-106, whereas in Cd-108 there is tentative evidence for a similar effect. The results are compared with cranking and semiclassical model calculations, which indicate that the structures have the properties expected from an "antimagnetic" rotational band resulting from the coupling of g(9/2) proton holes to aligned pairs of h(11/2) and g(7/2) neutron particles.
  • Physical Review C 72(2005), 024318

Publ.-Id: 10760 - Permalink

Evidence for Zn vacancy – hydrogen complexes in ZnO single crystals
Brauer, G.; Anwand, W.; Grambole, D.; Grenzer, J.; Skorupa, W.; Cizek, J.; Kuriplach, J.; Prochazka, I.; Ling, C. C.; So, C. K.; Schulz, D.; Klimm, D.;
A systematic study of various, nominally undoped ZnO single crystals, either hydrothermally grown (HTG) or melt grown (MG), has been performed. The crystal quality has been assessed by x-ray diffraction, and a comprehensive estimation of the detailed impurity and hydrogen contents by inductively coupled plasma mass spectrometry and nuclear reaction analysis, respectively, has been made also. High precision positron lifetime experiments show that a single positron lifetime is observed in all crystals investigated, which clusters at 180–182 ps and 165–167 ps for HTG and MG crystals, respectively. Furthermore, hydrogen is detected in all crystals in a bound state with a high concentration (at least 0.3 at. %), whereas the concentrations of other impurities are very small. From ab initio calculations it is suggested that the existence of Zn-vacancy–hydrogen complexes is the most natural explanation for the given experimental facts at present. Furthermore, the distribution of H at a metal/ZnO interface of a MG crystal, and the H content of a HTG crystal upon annealing and time afterward has been monitored, as this is most probably related to the properties of electrical contacts made at ZnO and the instability in p-type conductivity observed at ZnO nanorods in literature. All experimental findings and presented theoretical considerations support the conclusion that various types of Zn-vacancy–hydrogen complexes exist in ZnO and need to be taken into account in future studies, especially for HTG materials.
Keywords: zinc oxide, single crystal, positron lifetime, nuclear reaction analysis, X-ray diffraction, Inductively Coupled Plasma Mass Spectrometry, hydrogen, open volume defects, zinc vacancy-hydrogen complexes, ab initio calculations
  • Physical Review B 79(2009), 115212

Publ.-Id: 10759 - Permalink

Quantification of DNA double strand breaks
Beyreuther, E.;
Introduction and explanation of the quantification of DNA double strand breaks. First results measured for the time, dose and energy dependence for the induction of double strand breaks in cell line 184A1 are shown. Future plans are given.
  • Lecture (others)
    Seminar AG Mikrobiologie, 01.11.2007, Freiberg, Germany

Publ.-Id: 10758 - Permalink

Radiosynthesis of n.c.a. sodium [18F]fluoroacetate and radiopharmacological characterization in rats and tumour-xenografted mice
Richter, S.; Bergmann, R.; Pietzsch, J.; Beuthien-Baumann, B.; Wüst, F.;
A convenient remotely-controlled synthesis of no-carrier-added sodium [18F]fluoroacetate is described. Three ethyl esters 1a-1c and three tert.-butyl esters 3a-3c containing either a methanesulfonyloxy- (OMs), p-toluenesulfonyloxy- (OTs) or p-nitrobenzenesulfonyloxy (ONs) leaving group were investigated as labelling precursors. The optimized radiosynthesis of n.c.a. sodium [18F]fluoroacetate was performed in two steps: (1) Incorporation of fluorine into (methanesulfonyloxy)-acetic acid tert.-butyl ester 3a as the superior labelling precursor in acetonitrile at 100°C for 5 min followed by (2) acidic hydrolysis of the resulting [18F]fluoroacetic acid tert.-butyl ester at 100°C for 10 min to afford [18F]fluoroacetic acid. Several consecutive purification steps using anion exchange cartridges (Alltech Maxi-Clean SAX) and Sep-Pak neutral alumina cartridges gave sodium [18F]fluoroacetate in reproducible radiochemical yields of 20-25% (decay-corrected, n=20) in high radiochemical purity (>99%) within 50 min. Radiopharmacological characterization of sodium [18F]fluoroacetate was studied in Wistar rats and HT-29 tumour-bearing mice in comparison with [11C]acetate.
  • Current Radiopharmaceuticals 1(2008)2, 103-109

Publ.-Id: 10757 - Permalink

Characterization of sputtered Shape Memory Alloy Ni-Ti films by cross-sectional TEM and SEM
Martins, R. M. S.; Mücklich, A.; Schell, N.; Silva, R. J. C.; Mahesh, K. K.; Braz Fernandes, F. M.;
Characterization of sputtered Shape Memory Alloy Ni-Ti films by cross-sectional TEM and SEM
Keywords: shape memory alloy, Ni-Ti films TEM, SEM
  • Poster
    INCOMAM’07 - International Conference on Microscopy and Microanalysis - XLII Congress of the Portuguese Microscopy Society, 06.-07.12.2007, Coimbra, Portugal
  • Microscopy and Microanalysis 14(2008)supp 3, 85-86
    DOI: 10.1017/S1431927608089460

Publ.-Id: 10756 - Permalink

Spektroskopische Untersuchung der Uran(IV)- und Uran(VI)-Komplexierung mit organischen Modellliganden
Schmeide, K.; Joseph, C.; Raditzky, B.;
Spektroskopische Bestimmung von Stabilitätskonstanten für die U(VI)/U(IV)-Komplexierung durch Modellliganden
Keywords: Uran, hexavalent, tetravalent, Citronensäure, Benzolsulfonsäure, 4-Phenolsulfonsäure
  • Lecture (others)
    Workshop zum Forschungsvorhaben "Wechselwirkung und Transport von Actiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika", 11.-12.10.2007, Saarbrücken, Germany

Publ.-Id: 10755 - Permalink

Untersuchungen zur Isomerie des Komplexes [86Y((S) p NH2 bz DOTA)]-
Schlesinger, J.; Tamburini, S.; Bolzati, C.; Tisato, F.; Noll, B.; Bergmann, R.; Pietzsch, H.-J.;
Radioisotope des Yttriums und der Lanthaniden werden zu einer immer wichtigeren Komponente in medizinischen Applikationen, z. B. für die nicht-invasive in vivo-Bildgebung oder die Endoradionuklidtherapie von Tumorerkrankungen. Die Konjugation dieser dreiwertigen Metallionen an biologisch aktive Moleküle erfolgt in der Regel über bifunktionelle Chelatoren, z.B. 1,4,7,10-Tetraazacyclododecan-N,N’,N’’,N’’’-tetraessigsäure (DOTA). Die entsprechenden Metall-DOTA-Komplexe zeichnen sich durch eine hohe thermodynamische und kinetische in vivo Stabilität aus. Lanthaniden- und Yttrium-Komplexe optisch aktiver DOTA-Chelatoren treten jedoch als Konformationsisomere auf, über deren in vivo Verhalten, insbesondere über ihren Einfluss auf die markierten Moleküle nur wenig bekannt ist.

Zur Untersuchung der Isomerie des radioaktiven Komplexes [86Y((S) p NH2 bz DOTA)]- wurde der nicht-radioaktive, strukturell analoge Komplex [Y((S) p NH2 bz DOTA)]- synthetisiert und charakterisiert. Zwei Isomere des [Y((S) p NH2 bz DOTA)]- Komplexes wurden über die HPLC getrennt und mittels NMR- und CD-Messungen als Konformationsisomere identifiziert. Die Isomere liegen in einer quadratisch antiprismatischen (SAP) und einer verdrillt quadratisch antiprismatischen (TSAP) Geometrie vor.

Untersuchungen zur Bioverteilung der [86Y((S) p NH2 bz DOTA)]- Isomere in Wistar Ratten zeigten bereits nach 5 min unterschiedliche SUV-Werte (standardized uptake value) für beide Isomere in der Leber ((TSAP) 1,65 ± 0,45; (SAP) 0,50 ± 0,04). Der Vergleich der experimentell bestimmten logD7,0 Werte beider Isomere weist auf eine höhere Lipophilie des TSAP-Isomeren hin (logD7,0: (TSAP) -2,0 ± 0,029; (SAP) -2,3 ± 0,032). Bei der thermischen Behandlung der Isomere bei 90°C konnte auch nach 168 h keine gegenseitige Umwandlung beobachtet werden.

Die unterschiedlichen physikalischen Eigenschaften der [86Y((S) p NH2 bz DOTA)]- Konformationsisomere und deren unterschiedliche Bioverteilung zeigen, dass es unbedingt notwendig ist, den Einfluss der Chelateinheit auf das biologische Verhalten von Metallopharmaka zu berücksichtigen.
  • Poster
    Wissenschaftsforum Chemie 2007, GDCh-Jahrestagung, 16.-19.09.2007, Ulm, Germany

Publ.-Id: 10754 - Permalink

Growth and optical characterization of dielectric/metal nanocomposites
Baumgart, C.; Abendroth, B.; Abrasonis, G.; Kolitsch, A.; Möller, W.;
Thin films of Ag nanoclusters embedded in dielectric aC and SiO2 media have been prepared by pulsed cathodic arc and dual magnetron sputtering. The optical properties of the composite layers have been investigated by spectroscopic ellipsometry. The results show the dependence of the plasmon resonance band of the Ag particles from temperature and Ag concentration.
  • Lecture (Conference)
    VEIT 2007 - Fifttienth International Summer School on Vacuum, Electron and Ion Technologies, 17.-21.09.2007, Sozopol, Bulgaria

Publ.-Id: 10753 - Permalink

Quasifree Lambda, Sigma0, and Sigma- electroproduction from 1,2H, 3,4 He, and Carbon
Dohrmann, F.; Ahmidouch, A.; Armstrong, C. S.; Arrington, J.; Asaturyan, R.; Avery, S.; Bailey, K.; Baker, O. K.; Bitao, H.; Breuer, H.; Brown, D. S.; Carlini, R.; Cha, J.; Chant, N.; Christy, E.; Cochran, A.; Cole, L.; Crowder, J.; Danagoulian, S.; Elaasar, M.; Ent, R.; Fenker, H.; Fujii, Y.; Gan, L.; Garrow, K.; Geesaman, D. F.; Gueye, P.; Hafidi, K.; Hinton, W.; Juengst, H.; Keppel, C.; Liang, Y.; Liu, J. H.; Lung, A.; Mack, D.; Markowitz, P.; Mitchell, J.; Miyoshi, T.; Mkrtchyan, H.; Mtingwa, S. K.; Mueller, B.; Niculescu, G.; Niculescu, I.; Potterveld, D. H.; Raue, B. A.; Reimer, P. E.; Reinhold, J.; Roche, J.; Sarsour, M.; Sato, Y.; Segel, R. E.; Semenov, A. Y.; Stepanyan, S.; Tadevosian, V.; Tajima, S.; Tang, L.; Uzzle, A.; Wood, S.; Yamaguchi, H.; Yan, C.; Yuan, L.; Zeier, M.; Zeidman, B.; Zihlmann, B.;
Kaon electroproduction from light nuclei and hydrogen, using 1H, 2H, 3He, 4He, and carbon targets has been measured at Jefferson Laboratory. The quasifree angular distributions of Lambda and Sigma hyperons were determined at Q^2= 0.35 (GeV/c)^2 and W= 1.91 GeV. Electroproduction on hydrogen was measured at the same kinematics for reference.
Keywords: Electroproduction of Strangeness, Hyperons, Hypernuclear Physics

Publ.-Id: 10751 - Permalink

MOS light emitting devices based on rare-earth ion implantation
Rebohle, L.; Skorupa, W.;
In this article we will give an overview of our work to Si-based light emission which was done in the last years. Si-based light emitters were fabricated by ion implantation of rare earth elements into the oxide layer of a conventional MOS structure. Efficient electroluminescence was obtained for the wavelength range from UV to the visible by using a transparent top electrode made of indium-tin oxide. In the case of Tb-implantation the best devices reach an external quantum efficiency of 16 % which corresponds to a power efficiency in the order of 0.3 %. The properties of the microstructure, the IV characteristics and the electroluminescence spectra were evaluated. The electroluminescence was found to be caused by hot electron impact excitation of rare earth ions, and the electric phenomena of charge transport, luminescence centre excitation, quenching and degradation are explained in detail.
Keywords: Electroluminescence, Silicon-based light emission, Rare earth ion implantation
  • Contribution to external collection
    in: Advances in Light Emitting Materials, Stafa-Zurich: Trans Tech Publications Ltd, 2008, 117-138

Publ.-Id: 10749 - Permalink

The Influence of Natural and Manufactured Nanoparticles on Heavy Metal Behavior in Natural Waters
Zänker, H.; Schierz, A.;
A rapid development of the application of manufactured nanoparticles in science, technology, medicine and every day life is anticipated. Currently, there is still little knowledge about the behavior of manufactured nanoparticles in natural waters, their influences on the transport of organic pollutants, their effect on the behavior of toxic and radiotoxic heavy metals etc. Manufactured NPs are not yet present in the nature in significant amounts, i.e. “field studies” are not yet possible. However, conclusions by analogy based on the behavior of natural nanoparticles (natural colloids) can already be drawn. First, a very short introduction into the field of the detection of natural nanoparticles is given. The transport-impeding and the transport-facilitating effects of natural nanoparticles on heavy metal transport are analyzed. Examples are the immobilization of uranium by ferrihydrite nanoparticles in near-neutral mine waters during the flooding of an abandoned uranium mine and the mobilization of lead and arsenic by schwertmannite/H-jarosite nanoparticles in acid mine water from an abandoned Zn-Pb-Ag mine. The use of manufactured nanoparticles for the immobilization of heavy metals in natural waters is discussed. The adsorption of Pb2+, Cd2+, Cu2+ and UO22+ onto modified carbon nanotubes, synthetic ferrihydrite nanoparticles and titanium dioxide nanoparticles are considered with the focus on the carbon nanotubes. It is shown that all the nanoparticles considered have a potential for removing the above-mentioned heavy metal ions. A different point might be the challenge of gaining regulatory and public acceptance for using nanomaterials in water purification because of their still unknown or little known toxicity and environmental impact. The questions of the mobility of manufactured nanoparticles in natural waters and of potential transport-facilitating effects of artificial nanoparticles on heavy metals in case of accidental nanomaterial release are also addressed.
Keywords: Nanoparticles, carbon nanotubes, natural waters, contaminants, heavy metals, water purification
  • Lecture (Conference)
    Aquatic Nanoscience & Nanotechnology - bridging environmental nanosciences and nanotoxicology - 1st International workshop, 09.-11.12.2007, Wien, Austria

Publ.-Id: 10748 - Permalink

Generation of pulsed magnetic fields for synchrotron radiation experiments using a mobile pulsed-power supply
Herrmannsdörfer, T.;
no abstract available
Keywords: Pulsed magnetic fields, X-ray magnetic scattering
  • Invited lecture (Conferences)
    PETRA III Workshop: HighRes and RSD Beamlines, 27.-28.09.2007, DESY Hamburg, Germany

Publ.-Id: 10747 - Permalink

Switchable multi-color light emitter based on Eu implanted SiO2 layers confined in a MOS structure
Rebohle, L.; Prucnal, S.; Sun, J. M.; Helm, M.; Skorupa, W.;
Recent results regarding the electroluminescence properties of Si-based light emitters made by ion implantation are presented. The focus is on MOS structures either implanted with Eu or with Gd co-implanted with K or F.
  • Invited lecture (Conferences)
    Silicon to Light & Light to Silicon - Materials, Characterisation and Applications, 09.-10.07.2007, Halle, Deutschland

Publ.-Id: 10746 - Permalink

Switchable multi-color light emitter based on Eu-implanted SiO2 layers confined in a MOS structure
Rebohle, L.; Prucnal, S.; Sun, J. M.; Helm, M.; Skorupa, W.;
Si based light emitter become more and more important for the integration of optical and electrical function in one and the same chip. Among the various approaches rare earth (RE) implanted SiO2 layers confined in a MOS structure are especially promising due to the well-known optical properties of RE ions, the excellent material properties of the hosting SiO2 matrix and the full compatibility with current Si technology.
Here we report on the switchable multi-color electroluminescence (EL) from a MOS capacity doped with Eu. Depending on the electrical excitation conditions either the red narrow EL originating from a 4f inner shell transition of the Eu3+ ion or the blue broad emission from Eu2+ assigned to a 5d-4f electronic transition is dominant. The behavior of the EL spectrum as a function of the excitation and fabrication conditions is investigated, and the mechanisms behind will be discussed. The Si-based multi-color emitter introduces a new functionality into photonics and shows great potential for future micro-photonic applications.
  • Lecture (Conference)
    SEMINANO'07: 3rd International Workshop on Semiconductor Nanostructures, 13.-16.06.2007, Bad Honnef, Germany

Publ.-Id: 10745 - Permalink

Equation of State of Strongly Interacting Matter
Bluhm, M.;
Equation of State of Strongly Interacting Matter
  • Lecture (Conference)
    XXXVIII. Arbeitstreffen "Kernphysik", 22.02.-01.03.2007, Schleching, Germany

Publ.-Id: 10744 - Permalink

Complexation of uranium(VI) with aromatic acids in aqueous solution – A combined computational and experimental study
Wiebke, J.; Moritz, A.; Glorius, M.; Moll, H.; Bernhard, G.; Dolg, M.;
The complexes of uranium(VI) with salicylhydroxamate, benzohydroxamate, and benzoate have been investigated in a combined computational and experimental study using density functional theory methods and extended X-ray absorption fine structure spectroscopy, respectively. The calculated molecular structures, relative stabilities, as well as excitation spectra from time-dependent density functional theory calculations are in good agreement with experimental data. Furthermore, these calculations allow to identify the coordinating atoms in the uranium(VI)-salicylhydroxamate complex, i.e. salicylhydroxamate binds to the uranyl ion via the hydroxamic acid oxygen atoms and not via the phenolic oxygen and the nitrogen atom. Carefully addressing solvation effects has been found to be necessary to bring in line computational and experimental structures and excitation spectra.
Keywords: Uranyl - hydroxamic acid - density functional theory - EXAFS - spectroscopy
  • Inorganic Chemistry 47(2008)8, 3150-3157

Publ.-Id: 10743 - Permalink

QCD Equation of State - Impact on elliptic flow and transverse momentum spectra
Bluhm, M.;
QCD Equation of State - Impact on elliptic flow and transverse momentum spectra
  • Lecture (Conference)
    Heavy Ion Collisions at the LHC - Last Call for Predictions, 14.05.-08.06.2007, Genf, Switzerland

Publ.-Id: 10742 - Permalink

Dual-magnetron sputtering deposition of ferromagnetic FePt layers: in-situ x-ray investigations
Cantelli, V.; Grenzer, J.; von Borany, J.;
In this contribution it is discussed the use of the order parameter S as factor to judge the order degree of a L10 FePt layer grown at 350°C on a-SiO2. Because of the peculiar set-up of the deposition chamber, the FePt plasma is not thermalized, and energetic Ar ions allowed reducing the transition temperature, from the disorder to the order phase, to 350°C, for homogeneous 70 nm thick layers. The S parameter could be easily calculated by XRD measurements; therefore in-situ XRD could be applied to calculate the activation energy of the disorder order transformation. But, in the case of FePt layers deposited at low temperature, the evaluation of the degree of order (S parameter) in thin FePt layers is faulty and could cause to misleading data interpretations. Inconsistency was found between the high S values and the experimental FePt lattice parameters, which were showing a weaker deformation from the cubic to the tetragonal phase in respect to the theoretical values. This is explained in terms of low crystallinity degree and small grains size that are characteristic of the layer.
Keywords: Dual Magnetron sputtering, FePt, in-situ XRD
  • Lecture (others)
    Neue Entwicklungen in Röntgendiffraktometrie und -topographie, 24.04.2007, Frankfurt (Oder), Germany

Publ.-Id: 10741 - Permalink

Gluon Radiation of Heavy Quarks passing Deconfined Matter
Schade, H.;
Gluon Radiation of Heavy Quarks passing Deconfined Matter
  • Lecture (others)
    ITP, TU - Dresden, 23.06.2006, Dresden, Germany

Publ.-Id: 10740 - Permalink

Energy Loss of Charm Quarks Passing Hot Deconfined Matter
Schade, H.;
Energy Loss of Charm Quarks Passing Hot Deconfined Matter
  • Lecture (Conference)
    DPG Frühjahrstagung 2007, 13.03.2007, Gießen, Germany

Publ.-Id: 10739 - Permalink

Elemental analysis through X-ray techniques applied in archeological gold authentication — the case of Transylvanian gold and of the Dacian bracelets
Constantinescu, B.; Bugoi, R.; Cojocaru, V.; Simon, R.; Grambole, D.; Munnik, F.; Oberländer-Târnoveanu, E.;
To identify the provenance of gold archeological metallic artifacts, trace elements are more significant than the main components. The most promising elements are Platinum Group Elements (PGE), Sn, Sb, Hg, Pb, Te, and Cu. Several minute fragments of natural Transylvanian gold – placers and primary – were studied by micro Particle Induced X-ray Emission (micro-PIXE) at Forschungszentrum Dresden-Rossendorf, Germany and micro Synchrotron Radiation X-Ray Fluorescence (micro SR-XRF) at ANKA Synchrotron Radiation Facility of the Forschungszentrum Karlsruhe, Germany. The goal of the study was to identify the trace elements characterizing Transylvanian gold, especially Sn, Sb, Pb and Te. A spectacular application of these measurements to the authentication of nine Dacian gold bracelets is presented.
Keywords: micro-PIXE, micro SR-XRF, ED-XRF, archeological gold, Dacian bracelets, Transylvania
  • Poster
    ICXOM 2007, 19th International Congress on X-Ray Optics and Microanalysis, 16.-21.09.2007, Kyoto, Japan
  • Spectrochimica Acta Part B 64(2009), 1198-1203
    DOI: 10.1016/j.sab.2009.08.007

Publ.-Id: 10738 - Permalink

Quark mass dependence of 1-loop and HTL self-energies
Seipt, D.;
Quark mass dependence of 1-loop and HTL self-energies
  • Lecture (Conference)
    DPG Frühjahrstagung 2007, 13.03.2007, Gießen, Germany

Publ.-Id: 10737 - Permalink

Towards an EOS for the cold and dense QGP: plasmons, plasminos and Landau damping
Schulze, R.;
Towards an EOS for the cold and dense QGP: plasmons, plasminos and Landau damping
  • Lecture (Conference)
    Zimanyi 75 Memorial Workshop, 04.07.2007, Budapest, Hungary

Publ.-Id: 10736 - Permalink

QCD quasi-particle model with widths and Landau damping
Schulze, R.;
QCD quasi-particle model with widths and Landau damping
  • Lecture (Conference)
    DPG Frühjahrstagung 2007, 13.03.2007, Gießen, Germany

Publ.-Id: 10735 - Permalink

Density dependence of four-quark condensates: Impact on in-medium spectral properties
Kämpfer, B.;
Density dependence of four-quark condensates: Impact on in-medium spectral properties
  • Lecture (Conference)
    Quarks in Hadrons and Nuclei, 17.-23.09.2007, Erice, Italy

Publ.-Id: 10733 - Permalink

Non-perturbative aspects of QCD condensates
Hilger, T.;
Non-perturbative aspects of QCD condensates
  • Invited lecture (Conferences)
    Physics of Compressed Baryonic Matter - 10th CBM Collaboration Meeting, 25.-28.09.2007, Dresden, Germany

Publ.-Id: 10732 - Permalink

In-medium studies of omega, nucleon and open charm with QCD sum rules
Thomas, R.;
In-medium studies of omega, nucleon and open charm with QCD sum rules
  • Invited lecture (Conferences)
    Physics of Compressed Baryonic Matter - 10th CBM Collaboration Meeting, 25.-28.09.2007, Dresden, Germany

Publ.-Id: 10731 - Permalink

Nucleon and omega-Meson at Finite Density: The Role of Four-Quark Condensates in QCD Sum Rules
Thomas, R.;
Nucleon and omega-Meson at Finite Density: The Role of Four-Quark Condensates in QCD Sum Rules
  • Lecture (Conference)
    DPG Frühjahrstagung 2007, 13.03.2007, Gießen, Germany

Publ.-Id: 10730 - Permalink

Self-assembly FePt nanoislands: surface studies and magnetic properties
Cantelli, V.; von Borany, J.; Grenzer, J.;
L10 ordered, c-axis oriented FePt thin films belong to the most promising ferromagnetic materials for future magnetic storage media; but the coercive filed could be significantly improved if changing from homogeneous to granular films or even to FePt nanoislands arrays . This contribution describes the formation of self-assembled FePt nanoislands on amorphous SiO2/Si substrates by conventional DC magnetron sputtering. Ag is well known to follow the Volmer-Weber growth on SiO2: the as-deposited Ag islands are exploited as substrate for the FePt granular layer. If a characteristic ratio between Ag and FePt amonut is respected, no nano-islands agglomeration was observed after annealing at 450°C for 30 minutes. This effect is here explained in terms of thermal buget given to the system during deposition and the demand of a unimodal size distribution of the Ag nanoislands. From synchrotron x-ray GISAS investigations, the FePt islands have a pallet like shape with a 30 nm average diameter and 18 nm average height. SEM and AFM analysis didn't prove any order in the pallets placement over the SiO2. After annealing, the strong ferromagnetic L10 phase was detected by XRD. But, either SQUID or MFM measurements evidence no difference between a granular FePt layer without Ag and with Ag pallets as buffer, and an enhanced coercivity of FePt thin granular films has been confirmed, in comparison to thick homogeneous FePt layers.
Keywords: FePt, DC magnetron sputtering, Ag, nanoislands
  • Lecture (Conference)
    7th Autumn School on X-ray scattering from surfaces and thin layers, 04.-06.10.2007, Smolenice, Slovakia

Publ.-Id: 10729 - Permalink

Implantation of halogens to improve TiAl-components for high temperature applications,
Donchev, A.; Kolitsch, A.; Möller, W.; Schütze, M.; Yankov, R.;
No abstract available.
Keywords: TiAl alloys, halogen effect, oxidation resistance
  • Lecture (others)
    2nd Meeting of the International Advisory Committee of the Ion Beam Centre at FZD, 01.10.2007, Dresden, Germany

Publ.-Id: 10728 - Permalink

Fluorine surface treatment of TiAl alloys for aerospace applications
Donchev, A.; Kolitsch, A.; Schütze, M.; Yankov, R.;
No abstract available.
Keywords: TiAl alloys, halogen effect, oxidation resistance
  • Poster
    Euromat 2007 - European Congress on Advanced Materials and Processes, 10.-13.09.2007, Nürnberg, Germany

Publ.-Id: 10727 - Permalink

Oxidation-resistant TiAl alloys produced by plasma immersion ion implantation of fluorine
Yankov, R. A.; Kolitsch, A.; Steinert, M.; Donchev, A.; Schütze, M.;
Gamma-TiAl alloys (γ-TiAl) are a class of light-weight materials that hold great promise for advanced automobile, aerospace and power generation applications. Their use, however, has currently been limited to below 700°C because of inadequate resistance to oxidation at higher temperatures. Recent research work has established that dramatic enhancement in the high-temperature oxidation resistance of these alloys can be achieved by ion implanting halogens, notably fluorine. In the present study, samples of technical γ-TiAl alloys have been surface-modified by plasma immersion ion implantation (PIII) of fluorine using suitable F-containing precursor gases. Rutherford Backscattering Spectrometry, Elastic Recoil Detection Analysis and Auger Electron Spectrometry have been employed for sample characterization. The degree of oxidation protection has been assessed by testing F-implanted samples under conditions of isothermal oxidation in air at temperatures up to 1050°C. Optimum process parameters have been identified under which the modified alloys acquire a stable, adherent and highly protective alumina scale against high-temperature environmental oxidation.
Keywords: TiAl alloys, plasma immersion ion implantation, fluorine
  • Lecture (Conference)
    9th International Workshop on Plasma-Based Ion Implantation & Deposition, 02.-06.09.2007, Leipzig, Germany

Publ.-Id: 10726 - Permalink

Oxidation-resistant γ-TiAl alloys produced by ion implantation of fluorine
Yankov, R. A.; Kolitsch, A.; Rogozin, A.; Steinert, M.; Donchev, A.; Schütze, M.;
Gamma-TiAl alloys (γ-TiAl) are of great interest for advanced automobile, aerospace and power generation applications due to their light weight and high strength. However, destructive oxidation occurring in these materials at temperatures above 700°C has to date restricted their widespread use. It has recently been established that the high-temperature oxidation resistance of γ-TiAl alloys can be enhanced significantly by ion implanting halogens, notably fluorine. In this study, samples of technical γ-TiAl alloys have been surface-modified by either standard beamline ion implantation of fluorine or plasma immersion ion implantation using suitable fluorine-containing precursor gases. The degree of oxidation protection has been evaluated by testing ion implanted samples under conditions of both isothermal and thermal cyclic oxidation in air. Optimized ion implantation treatment produces marked improvement in the oxidation behavior of γ-TiAl. The alloys modified in this way acquire a stable, adherent and highly protective alumina scale against environmental oxidation while retaining the bulk mechanical properties of the starting material. Further improvements have been made in the oxidation resistance by co-implanting two additive elements, namely fluorine and silicon. Some of the most important process parameters that enable the formation of an efficient protective scale are considered and assessed.
Keywords: TiAl alloys, ion implantation, oxidation resistance, halogen effect
  • Poster
    E-MRS Spring Meeting, 28.05.-01.06.2007, Strasbourg, France

Publ.-Id: 10725 - Permalink

Improvement of the Oxidation Resistance of TiAl-Alloys with Fluorine
Donchev, A.; Richter, E.; Schütze, M.; Yankov, R.;
The technical TiAl-alloy γ-MET (Ti–46.5Al–4(Cr, Nb, Ta, B)) was oxidised thermocyclically (24 h-cycle-test) at 900 °C in wet and dry air. In this paper results of untreated and fluorine treated TiAl-samples are presented. Their oxidation behaviour will be shown. Several methods were used to apply the halogens to the surface, e.g. beamline ion implantation, spraying of or dipping into a halogen containing liquid. A pure protective alumina scale was found, e.g. after treatment with a fluorine containing polymer and thermocyclic oxidation up to 1 year at 900 °C in laboratory air. On the other side thick fast growing and non-protective mixed oxide scales were found on the untreated samples.
Keywords: Intermetallics; Oxidation; Metallography; Halogen effect; Titanium aluminides

Publ.-Id: 10724 - Permalink

Formation of a resonant microcavity in hydrogen ion-implanted silicon-on-insulator structures
Tyschenko, I. E.; Talochkin, A. B.; Bagaev, E. M.; Cherkov, A. G.; Popov, V. P.; Misiuk, A.; Yankov, R. A.;
Studies have been carried out on silicon-on-insulator (SOI) structures after the implantation of 24 keV, 3×10^17 cm−2 hydrogen ions, and annealing at temperatures of 200−1000 °C in an argon ambient at either atmospheric pressure or under conditions of hydrostatic compression at 6 and 12 kbar. Photoluminescence (PL), Raman spectroscopy, secondary ion mass spectrometry, and high-resolution electron microscopy have been used to characterize the optical and structural properties of the resulting SOI structures. It has been found that annealing at a pressure above 6 kbar leads to a wavelength-selective increase (up to 37×) in the intensity of the PL from hydrogen implanted SOI samples. The appearance of fine structure in the PL spectrum correlates with the impeded outdiffusion of hydrogen from the implanted top Si layer as well as with the suppressed process of hydrogen microbubble formation in the near-surface region as a result of the annealing at a pressure P>6 kbar. These processes enable one to fabricate an optical resonant microcavity with mirrors formed by the air/silicon and the top Si layer/SiO2 interfaces, and the optically active layer resulting from the implantation of hydrogen and the subsequent annealing. Theoretical calculations of the PL spectra in the resonator help explain some of the specific spectral features. The mechanism of the observed photoluminescence has been discussed in terms of recombination processes occurring in nanometer-sized amorphous silicon regions saturated with hydrogen.
Keywords: silicon-on-insulator, photoluminescence, optical resonant microcavity, hydrogen implantation
  • Journal of Applied Physics 102(2007), 074312

Publ.-Id: 10723 - Permalink

Slow-positron implantation spectroscopy in nanoscience
Prochazka, I.; Cizek, J.; Brauer, G.; Anwand, W.;
  • Lecture (Conference)
    NANO'07 - Nanostructured Materials for Functional, Structural and Bio-applications, 08.-10.10.2007, Brno, Czech Republic

Publ.-Id: 10722 - Permalink

Scouting the feasibility of Monte Carlo reactor dynamics simulations
Legrady, D.; Hoogenboom, J. E.;
Usual space dependent reactor dynamics simulations still rely on heavily simplified transport modelling, often restricted to two energy groups prepared with considerably debatable presumptions. The radical increase in computing power availability of recent times allows for more detailed modelling, more energy groups, better physics treatment or for choosing Monte Carlo (MC) methods. Developing MC methods for reactor dynamics are not supported up to now due to the lack of confidence of feasibility for realistic cases fearing unpractical computing times, but the capability of easy parallelization of the MC computing flow may offer hope of real applications. Our investigations here treat the options for performing and optimizing dynamic MC calculations including thermal feedback with the aim of determining the necessary computer resources for realistic simulations. We focus here on methodological questions as previous papers on the subject did not elaborate on such details.
Keywords: Monte Carlo, Reactor Dynamics, keff, variance reduction, Reactor Kinetics, feedback
  • Contribution to proceedings
    International Conference on the Physics of Nuclear Reactors, "Nuclear Power:a Sustainable Source", 14.-19.09.2008, Interlaken, Switzerland
    Proceedings of the International Conference on the Physics of Nuclear Reactors

Publ.-Id: 10721 - Permalink

Application of Wavelet Transform to Extended X-ray Absorption Spectroscopy
Funke, H.; Chukalina, M.; Scheinost, A.;
- wird nachgereicht
  • Contribution to external collection
    Dondon P., Mladenov V., Impedovo S., Cepisca S.: Mathematical Methods and Computational Techniques in Research and Education, ka: WSEAS Press, 2007, 978-960-6766-08-4, 117-121
  • Lecture (Conference)
    7th WSEAS International Conference on Wavelet Analysis & Multirate Systems (WAMUS07), 13.-15.10.2007, Arcachon, France

Publ.-Id: 10720 - Permalink

Influence of Acid Treatment of Multiwall Carbon Nanotubes on the Sorption of U(VI) and on the Stability of Aqueous Suspensions
Schierz, A.; Zaenker, H.; Bernhard, G.;
The unique properties of CNTs are being exploited in a growing number of products and applications [1]. The oxidation process is of great importance for CNT application since it is necessary for CNT purification and functionalization [2]. Acid treatment was recommended as a method of purification [2]. Additionally, the oxidation causes chemical and/or structural changes on CNTs which modify their properties.
Due to their hollow and nanosized structure the use of CNTs as adsorbent for pollutants such as dioxins and heavy metals such as Cd2+, Pb2+, Am3+ [3, 4, 5] for environmental remediation purposes has been considered. Different authors reported that CNTs treated with acid show a higher adsorption capacity for heavy metal ions and dioxins compared with other adsorbents such as activated carbon. These studies suggested that CNTs may be a promising adsorbent for use in environmental protection. The high cost of CNTs still limits their practical use. As these materials make their way to industrial and consumer products, their unintended release in the environment can not be excluded. However, not much research has been conducted to study the characteristics, the fate and behaviour of CNTs in the environment.
The aim of this study is gaining information on both the properties of the CNTs as a potential adsorbent material in water purification and the behaviour of the CNTs as potential carriers of pollutants in the case of their accidental release to the environment.
  • Contribution to proceedings
    NanoECO: Nanoparticles in Environment-Implications and Applications, 02.-07.03.08, Monte Verita, Schwitzerland
    Book of Abstracts, 127

Publ.-Id: 10719 - Permalink

Geplante PLEPS-Messungen an ZnO-Dünnfilmen
Brauer, G.; Schmidt, M.; von Wenckstern, H.; Anwand, W.; Skorupa, W.; Helm, M.; Grundmann, M.;
  • Lecture (Conference)
    2nd User Meeting at NEPOMUC, 30.10.2007, Garching, Germany

Publ.-Id: 10718 - Permalink

Positron Annihilation Spectroscopy – Its Basics and Application to ZnO single crystals
Brauer, G.; Anwand, W.;
  • Lecture (others)
    Seminar am Institute of Physics, Opole University, 25.10.2007, Opole, Poland
  • Lecture (others)
    Seminar am Institute of Experimental Physics, Wroclaw University, 26.10.2007, Wroclaw, Poland

Publ.-Id: 10717 - Permalink

Correlation between magnetic properties and lattice site location of Fe implanted TiO2 at different temperetures
Talut, G.; Reuther, H.; Zhou, S.; Potzger, K.;
Diluted magnetic semiconductors are materials which exhibit ferromagnetic and semiconducting properties simultaneously and are of great interest for spin injection. An interesting candidate is the transition metal doped TiO2 which has been reported to be ferromagnetic above room temperature (RT). It was found that nanometer-sized precipitates substantially contribute to the ferromagnetic properties.
In this study, rutile TiO2(110) single crystals were implanted with 100 keV 57Fe ions at 623 K with fluences between 1x10^16 and 4x10^16 cm^-2 and subsequently annealed at temperatures up to 1073 K. The maximum Fe concentration at the projected range Rp = 50 nm is about 8 at.%.
Virgin, implanted and post-annealed samples were investigated using conversion electron Mößbauer spectroscopy, channeling Rutherford backscattering spectrometry, x-ray diffraction, and super-conducting quantum interference device magnetometry.
Crystalline, imperfect bcc-Fe and FeO-TiO2 composites were detected already in the as-implanted state in the sample implanted at 623 K with 4x10^16 cm^-2. Besides secondary phases a small fraction of Fe^2+ is observed both in the as-implanted and at 923 K annealed sample and can be ascribed to Fe substituting Ti sites.
During annealing at 923 K, both phases grow in grain size, while the amount of FeO-TiO2 is drastically increased. After annealing at 1073 K, FeO-TiO2 composites are the predominant precipitates at the cost of metallic Fe. Both, bcc-Fe and FeO-TiO2 composites are textured. According to the CEMS and SQUID measurements the origin of ferromagnetism is attributed to bcc Fe clusters. The oxidization of metallic Fe with increasing annealing temperature results in the decrease of the saturation moment.
In order to prevent the formation of clusters another set of samples was implanted at RT and 230 K with same fluences. No cluster formation but also no ferromagnetism was observed in both cases.
Keywords: rutile TiO2, Fe, DMS
  • Lecture (Conference)
    52nd Magnetism and Magnetic Materials Conference, 05.-09.11.2007, Tampa, Florida, USA

Publ.-Id: 10716 - Permalink

Probing in-medium vector meson decays by double-differential di-electron spectra in heavy-ion collisions at SIS energies
Wolf, G.; Kämpfer, B.; Pavlenko, O. P.;
Within a transport code simulation for heavy-ion collisions at bombarding energies around 1 AGeV we demonstrate that double-differential di-electron spectra with suitable kinematical cuts are useful to isolate (i) the ρ meson peak even in case of strong broadening, and (ii) the in-medium ω decay contribution. The expected in-medium modifications of the vector meson spectral densities can thus b probed in this energy range via the di-electron channel.
Keywords: heavy-ion collisions, di-electrons, in-medium modifications of vector mesons

Publ.-Id: 10715 - Permalink

Ab-initio calculation of exchange interactions in YMnO3
Novak, P.; Chaplygin, I.; Seifert, G.; Gemming, S.; Laskowski, R.;
The density functional based calculations of the electronic structure of YMnO3 are performed for selected spin configurations and from the differences of the total energies the exchange integrals are determined. To improve the description of strongly correlated 3d electrons of Mn the LDA+U method is employed. The strongest exchange interaction is found between the nearest neighbor Mn spins, the interaction between the next nearest neighbors being more than order of magnitude weaker.
Exchange integrals are inversely proportional to the parameter U, pointing to the dominance of the superexchange interaction. Due to the triangular arrangement of the nearest Mn the magnetism is geometrically frustrated so that biquadratic or/and anisotropic exchange may be important. The calculation of noncollinear spin structures indicates the presence of the biquadratic exchange interaction.
Keywords: Exchange interaction, ab-initio calculation, yttrium manganite

Publ.-Id: 10714 - Permalink

Targetry upgrade at the Rossendorf CYCLONE 18/9
Preusche, S.; Mehaudens, M.;
kein Abstract verfügbar
  • Lecture (others)
    6th Workshop, CYCLONE 18/9 and 10/5 User Community, 23.-26.09.2007, Sevilla, Spain

Publ.-Id: 10713 - Permalink

Evaluation of 18F- L-DOPA PET-CT for surgery in focal congenital hyperinsulinism
Barthlen, W.; Mau, H.; Koch, M.; Höhne, C.; Blankenstein, O.; Mohnike, W.; Eberhard, T.; Füchtner, F.; Lorenz-Depiereux, B.; Mohnike, K.;
Context: In congenital hyperinsulinism (CHI), the identification and precise localization of a focal lesion is essential for successful surgery.
Objective: Our objective was to evaluate the predictive value and accuracy of integrated [F-18] fluoro-L-DOPA ([F-18]FDOPA) positron emission tomography (PET)-computed tomography (CT) for the surgical therapy of CHI.
Design: This was an observational study.
Setting: The study was performed in the Department of Pediatric Surgery at a university hospital.
Patients: From February 2005 to September 2007, 10 children with the clinical signs of CHI and an increased radiotracer uptake in a circumscribed area of the pancreas in the [F-18]FDOPA PET-CT were evaluated.
Interventions: Guided by the [F-18]FDOPA PET-CT report, all children underwent partial pancreatic resection, in two cases twice.
Main Outcome Measures: Correlation of the anatomical findings at surgery with the report of the [F-18] FDOPA PET-CT, and the results of surgery and clinical outcome were determined.
Results: In nine children the intraoperative situation corresponded exactly to the description of the [F-18] FDOPA PET-CT. A limited resection of the pancreas was curative in eight cases at the first surgery, in one case at the second intervention. We observed no diabetes mellitus or exocrine insufficiency in the follow up so far. In one child, hypoglycemia persisted even after two partial resections of the pancreatic head. Histological analysis finally revealed an atypical intermediate form of CHI.
Conclusions: The integrated [F-18]FDOPA PET-CT is accurate to localize the lesion in focal CHI and is a valuable tool to guide the surgeon in limited pancreatic resection.
  • Journal of Clinical Endocrinology and Metabolism 93(2008)3, 869-875

Publ.-Id: 10712 - Permalink

18F-DOPA Positron Emission Tomography for Preoperative Localization in Congenital Hyperinsulinism
Mohnike, K.; Blankenstein, O.; Minn, H.; Mohnike, W.; Füchtner, F.; Otonovski, T.;
In recent years, considerable progress has been made in the biochemical, morphological and molecular genetic differentiation of congenital hyperinsulinism (CHI). Fluorine-18 L -3,4-dihydroxyphenylalanine positron emission tomography
( 18 F-DOPA-PET) has been introduced for differentiation between focal and diffuse CHI. The ability to take up L -DOPA and convert it into dopamine is correlated with the activity of the aromatic amino acid decarboxylase and increased in the hyperfunctional affected pancreatic area in comparison to normally functioning pancreas. The high sensitivity of this method allows the surgeon to perform a curative limited resection of a focus without the risk of long-term diabetes. The exact preoperative planning by 18 F-DOPA-PET/CT computer tomography allows laparoscopic operation in selected cases with the focus in the tail and limits necessity to open the pancreatic duct in cases with focus in the head. Patients with persistent CHI should be managed within a strong network of diagnostic, treatment, and research institutions.
Keywords: [ 18 F]-DOPA-PET/CT, L -DOPA, Congenital hyperinsulinism , Positron emission tomography , Computer tomography

Publ.-Id: 10711 - Permalink

Formation and morphology control of nanostructures produced by PIII
Shevchenko, N.; Weber, J.; Kolitsch, A.;
Development of novel materials and structures for drug delivery systems is currently a very active field of research. For bare metal stents the in-stent restenosis was a serious problem for about 25 - 35% of the patients and this spurred the medical device companies to come up with a solution. Recently the drug-eluting stents were designed to deliver a drug locally from a surface layer to reduce restenosis.
High-fluence ion implantation of noble gas ions into metals can be used to create porous layers on metal surface. These void structures may show unique characteristics which offer potential for drug-eluting stents application. This application requires interconnected pores with the dimension in the range on the nano- to microscale.
The aim of the present work is to study the formation of nanostructures on stainless steel surfaces by means of plasma immersion ion implantation (PIII) using different noble gases. Argon and/or helium ion implantation was performed at following parameters: ion energies ranging from 5 to 35 keV, ion fluence of more than 1e18 cm-2, substrate temperature in the range 50 – 400°C. The modified steel surfaces have been analyzed by scanning electron microscopy, grazing incidence X-ray diffraction analysis (GIXRD), X-ray photoelectron spectroscopy, and elastic recoil detection analysis.
Varying the ion energy, fluences, and substrate temperature has been found to produce either void or sponge like structures on the nano- (~10 nm) to micro-scale (~1 µm). Argon PIII treatment at elevated temperatures leads to spongy structure formation (Fig. 1). Helium implantation results in a surface roughening and creation of voids in high concentration with size in the range 100 – 200 nm as well as nano-scale cavities (5-20 nm) (Fig. 2). Apart from the austenite iron peaks, the GIXRD patterns of the implanted samples display weak peaks of ferrite (bcc iron) as well as oxide phases.
Keywords: plasma immersion ion implantation, noble gases, void structures, modified steel surfaces
  • Lecture (Conference)
    Workshop: Beschichtung für Biotechnologie und Medizintechnik, 16.-17.10.2007, Dresden, Germany

Publ.-Id: 10710 - Permalink

Nanoporous metal surfaces produced by plasma immersion ion implantation
Shevchenko, N.; Weber, J.; Kolitsch, A.;
Development of novel materials and structures for drug delivery systems is currently a very active field of research. For bare metal stents the in-stent restenosis was a serious problem for about 25 - 35% of the patients and this spurred the medical device companies to come up with a solution. Recently the drug-eluting stents were designed to deliver a drug locally from a surface layer to reduce restenosis.
High-fluence ion implantation of noble gas ions into metals can be used to create porous layers on metal surface. These void structures may show unique characteristics which offer potential for medical applications such as metal-based drug-eluting stents. This application requires interconnected pores with the dimension in the range on the nano- to microscale. Systematic investigations of the influence of implantation parameters on the surface morphology and cavity characteristics (e.g. size, distribution, and degree of interconnection) have to date been rather limited.
The aim of the present work is to study the formation of nanostructures on stainless steel surfaces by means of plasma immersion ion implantation (PIII) using different gases (helium or argon).
Argon and/or helium ion implantation was performed at following parameters: ion energies ranging from 5 to 35 keV, ion fluence of more than 10e18 cm -2, substrate temperature in the range 50 – 400°C. The surface topography of the modified steel has been analyzed by scanning electron microscopy and atomic force microscopy. Focused ion beam (FIB) tool was used to prepare sections perpendicular to implanted surface (i.e. transverse section). The phase and element compositions have been examined by grazing incidence X-ray diffraction analysis (GIXRD), X-ray photoelectron spectroscopy, and elastic recoil detection analysis.
Varying the ion energy, fluences, and substrate temperature has been found to produce either void or sponge like structures on the nano- (~10 nm) to micro-scale (~1 µm). Argon PIII treatment at elevated temperatures leads to spongy structure formation. Helium implantation results in a surface roughening and creation of voids in high concentration with size in the range 300 – 500 nm as well as nano-scale cavities (5-50 nm). Apart from the austenite iron peaks, the GIXRD patterns of the implanted samples display weak peaks of ferrite (bcc iron) as well as oxide phases.
Keywords: drug-eluting stent, porous layer, stainless steel, PIII, argon, helium, nanostructure
  • Poster
    VEIT 2007 - 15th International Summer School on Vacuum, Electron and Ion Technologies, 17.-21.09.2007, Sozopol, Bulgaria

Publ.-Id: 10709 - Permalink

Realisation of a prototype superconducting CW cavity and cryomodule for energy recovery
Mcintosh, P. A.; Bate, R.; Beard, C. D.; Cordwell, M.; Dykes, D. M.; Pattalwar, S.; Strachan, J.; Wooldridge, E.; Belomestnykh, S.; Liepe, M.; Padamsee, H.; Buechner, A.; Gabriel, F.; Michel, P.; Kimura, T.; Smith, T. I.; Byrd, J.; Corlett, J. N.; Li, D.; Lidia, S.;
For Energy Recovery applications, the requirement for high-Q accelerating structures, operating in CW mode, at large beam currents, with precise phase & amplitude stability and modest accelerating gradients are all fundamental in achieving intense photon fluxes from the
synchronised FEL insertion devices. Both Daresbury Laboratory and Cornell University are developing designs for advanced Energy Recovery Linac (ERL) facilities which require accelerating Linacs which meet such demanding criteria. The specification for the main ERL accelerator for both facilities dictates a modest accelerating gradient of 20 MV/m, at a Qo of better than 10^10, with a Qext of up to 10^8. A collaborative R&D
program has been set-up to design and fabricate a ‘proofof-principle’ cryomodule (which is well underway) that can be tested on ERLP at Daresbury and also on the Cornell ERL injector. This paper details the new cryomodule design, provides an insight to the design solutions employed and reports on the present status of the project.
Keywords: Elbe; accelerator ; cryomodule; energy recovery; accelerator RF
  • Contribution to proceedings
    13th International Workshop on RF Superconductivity, 14.-19.10.2007, Beijing, China

Publ.-Id: 10708 - Permalink

Friction properties of implanted alumina for vacuum applications
Jagielski, J.; Piatkowska, A.; Merstallinger, A.; Librant, Z.; Aubert, P.; Groetzschel, R.; Suszko, T.;
The influence of ion irradiation on friction properties in vacuum of alumina ceramics was studied. The effects of irradiation fluence, ion energy, thickness of the modified layers and of the possible role of solid lubrication were analyzed. The tests performed under vacuum clearly show, that radiation damage-induced softening of the surface layer leads to significant, approximately two times, decrease of a friction coefficient. Further decrease of the friction force, down to about 1/3 of the initial value, was obtained when the implanted species revealed solid lubrication effect. The results obtained are discussed in the frames of theory of adhesive friction.
Keywords: Ion implantation; Ion irradiation; Friction properties; Alumina
  • Vacuum 81(2007)10, 1357-1362

Publ.-Id: 10707 - Permalink

Calorimetric Evidence for a Fulde–Ferrell–Larkin–Ovchinnikov Superconducting State in the Layered Organic Superconductor κ-(BEDT-TTF)2Cu(NCS)2
Lortz, R.; Wang, Y.; Demuer, A.; Böttger, P. H. M.; Bergk, B.; Zwicknagl, G.; Nakazawa, Y.; Wosnitza, J.;
The specific heat of the layered organic superconductor κ-(BEDT-TTF)2Cu(NCS)2, where BEDT-TTF is bisethylenedithio-tetrathiafulvalene, has been studied in magnetic fields up to 28 T applied perpendicular and parallel to the superconducting layers. In parallel fields above 21 T, the superconducting transition becomes first order, which signals that the Pauli-limiting field is reached. Instead of saturating at this field value, the upper critical field increases sharply and a second firstorder transition line appears within the superconducting phase. Our results give strong evidence that the phase, which separates the homogeneous superconducting state from the normal state is a realization of a Fulde-Ferrell-Larkin-Ovchinnikov state.
  • Physical Review Letters 99(2007), 187002

Publ.-Id: 10705 - Permalink

Interactions of U(VI) and Eu(III) with natural bacterial isolates
Merroun, M.; Geissler, A.; Nedelkova, M.; Selenska-Pobell, S.;
- wird nachgereicht
  • Poster
    Goldschmidt 2007, 19.-24.08.2007, Köln, Germany

Publ.-Id: 10704 - Permalink

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