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33403 Publications

Technical developments at ROBL

Oehme, W.; Pröhl, D.; Dienel, S.; Claußner, J.; Strauch, U.; Funke, H.; Scheinost, A. C.
The article describes the most important technical improvments which had been performed at the beamline ROBL in 2005 and 2006. These are new systems such a cryostat and a sample holder which unifies the adjustment of samples in the glove box. Additionally, there was an update of electronics and basic software to enhance the compatibility with the standard equipment used at ESRF beamlines (migration from OS9 to Linux operating systems, new instrumentation of beamposition monitors.) There was also a SMS-based warning system installed to inform the responsible beamline scientist in case of problems during unattended experiments.
  • Contribution to HZDR-Annual report
    Wissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-463 März 2007, 43-46

Permalink: https://www.hzdr.de/publications/Publ-9768
Publ.-Id: 9768


Concept of an ion implantation stage with atomistic resolution

Rangelow, I. W.; Ivanova, K.; Ivanov, T.; Meijer, J.; Burchard, B.; Park, S. J.; Persaud, A.; Schenkel, T.; Bischoff, L.
We propose a method for deterministic implantation of single atoms into solids which relies on a linear ion trap as an ion source. Our approach allows a deterministic control of the number of implanted atoms and a spatial resolution of less than 1 nm. Furthermore, the method is expected to work for almost all chemical elements. The deterministic implantation of single phosphor or nitrogen atoms is interesting for the realization of scalable solid state quantum computers, in particular for silicon and diamond based schemes. A wide range of further applications is expected for the fabrication of nano-electric devices.
Keywords: single ion implantation, AFM tip, FIB, stage
  • Lecture (Conference)
    9th International Conference on Nuclear Microprobe Technology and Applications, ICNMTA04, 13.-17.09.2004, Dubrovnik, Croatia

Permalink: https://www.hzdr.de/publications/Publ-9767
Publ.-Id: 9767


Surface plasmon propagation in metallic nanostructures

Seidel, J.; Grafström, S.; Bischoff, L.; Eng, L.
The generation of surface plasmon polaritons (SPPs) at isolated nanoholes in 100 nm thick Au films is studied using near-field scanning optical microscopy. Finite-difference time-domain calculations,some explicitly including a model of the scanning tip, are used to interpret the results. We find the holes act as point-like sources of SPPs and demonstrate that the interference between the SPP and a directly transmitted wave allows determination of the wavelength, phase, and decay length of the SPP. The near-field intensity patterns can be manipulated by varying the angle and polarization of the incident beam.
Keywords: surface plasmon polaritons, focused ion beam, nanostructures
  • Lecture (Conference)
    Int. Workshop and Seminar on Cooperative Phenomena in Optics and Transport in Nanostructures, 10.-20.06.2004, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-9765
Publ.-Id: 9765


Hard- und Software des Radiochemiemessplatzes ROBL an der ESRF/Grenoble

Oehme, W.; Scheinost, A. C.; Hennig, C.; Funke, H.; Roßberg, A.; Reich, T.; Claußner, J.; Dienel, S.
Der Messplatz des Instituts für Radiochemie am Synchrotron der ESRF in Grenoble/Frankreich wird aus der Sicht der elektronischen Instrumentierung beschrieben. Der Schwerpunkt liegt auf dem benutzten Messprinzip und der gewählten Hard- und insbesondere Softwarestruktur. Insbesonder wird auf das benutzte Messprogramm "xatros", das eine messplatzspezifische ROBL-Eigenentwicklung ist, eingegangen.
  • Contribution to external collection
    Dr.F.Wulf: Bericht Frühjahrstagung Studiengruppe Elektronische Instrumentierung 27.-29-März 2006, Berlin: Hahn-Meitner-Institut Berlin, 2006, 0936-0891, 197-212

Permalink: https://www.hzdr.de/publications/Publ-9764
Publ.-Id: 9764


Vibrational spectroscopic and DFT studies of the metal-nitride clusterfullerenes: cluster-cage interactions and molecular structures

Popov, A. A.; Dunsch, L.; Krause, M.; Yang, S.; Kalbac, M.
Significant progress in the synthesis and isolation of trimetallic-nitride (TNT) clusterfullerenes has been achieved in the recent years, with a variety of M3N (M=Sc, Y, Gd-Lu) being encapsulated in various C2n (n=34-44) cages (see Ref.[1] for review and references therein). However, structural information for many of the new structures remains limited because of the low available amounts, which often appear insufficient for X-ray crystallographic or 13C NMR spectroscopic studies. IR and Raman spectroscopy, which require substantially smaller amounts of the material, have been extensively used in our group for characterization of new clusterfullerenes.[2] In this work we develop the general methodology allowing elucidation of molecular structures of new clusterfullerenes based on the vibrational spectroscopy and DFT computations.
Keywords: fullerenes, cluster compounds, vibrational spectroscopy
  • Lecture (Conference)
    211th ECS Meeting, 06.-10.05.2007, Chicago, USA

Permalink: https://www.hzdr.de/publications/Publ-9763
Publ.-Id: 9763


Study on the formation of open-eye and slag entrainment in a gas stirred ladle

Thunman, M.; Eckert, S.; Hennig, O.; Björkvall, J.; Du, S.
Laboratory experiments were carried out to study the phenomena related to open-eye formation in ladle treatment. Ga-In-Sn alloy with a melting temperature of 283 K was used to simulate the liquid steel, while MgCl2-Glycerol(87%) solution as well as HCl solution were used to simulate the ladle slag. No open-eye was formed at lower gas flow rates, but, occurred when gas flow reached a critical rate. This critical gas flow rate was found to depend significantly on the height of the top liquid. No noticeable amount of top liquid was observed in any of the samples taken from the metal bulk during gas stirring. To confirm this aspect, samples of slag-metal interface were taken around the open-eye in an industrial gas stirred steel ladle. No entrapped slag droplet was found in the solidified steel within the region between the interface and 2 cm from the interface. The accordance of the laboratory and industrial results suggests that the entrainment of slag into the steel bulk around the open-eye cannot be considered as the major contribution to inclusion formation.
Keywords: cold model, inclusion, slag entrapment, Ga-In-Sn alloy, open-eye, steel-slag interface
  • Steel Research International 78(2007)12, 847-854

Permalink: https://www.hzdr.de/publications/Publ-9762
Publ.-Id: 9762


Proton-recoil detectors for time-of-flight measurements of neutrons with kinetic energies from some tens of keV to a few MeV

Beyer, R.; Grosse, E.; Heidel, K.; Hutsch, J.; Junghans, A. R.; Klug, J.; Legrady, D.; Nolte, R.; Röttger, S.; Sobiella, M.; Wagner, A.
For experiments at the superconducting electron accelerator ELBE, where neutrons in the kinetic energy region from some tens of keV to a few MeV will be produced by bremsstrahlung, neutron-time-of-flight detectors have been developed. These detectors are made from the plastic scintillator material EJ-200. Efficiency calibration showed more than 10% efficiency for kinetic energies down to 30 keV. The calibration was done at the “accelerator facility for fast neutron research” at Physikalisch-Technische Bundesanstalt in Braunschweig, using pulsed quasi-monoenergetic neutron fields with a well-determined fluence. The low detection threshold was obtained by coincident readout of two Hamamatsu R2059-01 photomultiplier tubes per scintillator and by triggering just below the single-photo-electron peak of these photomultiplier tubes, which additionally gives a well-reproduceable detection threshold.
Keywords: neutron detector proton-recoil detector, fast neutrons, neutron time of flight, nELBE
  • Nuclear Instruments and Methods in Physics Research A 575(2007), 449-455
    DOI: 10.1016/j.nima.2007.02.096
  • Poster
    2008 Nuclear Science Symposium, 12.-25.10.2008, Dresden, Deutschland
  • Contribution to proceedings
    2008 IEEE Nuclear Science Symposium, 19.-25.10.2008, Dresden, Deutschland
    Nuclear Science Symposium Conference Record, 2008. NSS '08.
    DOI: 10.1109/NSSMIC.2008.4774625

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Permalink: https://www.hzdr.de/publications/Publ-9761
Publ.-Id: 9761


CW Operation of the TTF-III Input Coupler

Knobloch, J.; Martin, M.; Anders, W.; Bauer, S.; Pekeler, M.; Belomestnykh, S.; Kostin, D.; Möller, W.; Büchner, A.; Büttig, H.; Gabriel, F.
Several newly proposed superconducting linacs are designed to use TESLA technology operating CW rather than pulsed for which the system was developed. It must therefore be demonstrated that CW operation is feasible. Here we describe a series of CW tests with the TTF-III power coupler to determine the average power limit. These tests were performed on a coupler test stand both at room temperature at the FZ Rossendorf and under cryogenic operating conditions in BESSY’s HOBICAT[1] facility. An extrapolation of the measurements suggests that the coupler can handle 5 kW CW standing wave. It was also demonstrated that even higher power levels are feasible if the cooling of the inner conductor is modified.
  • Contribution to proceedings
    PAC Particle Accelerator Conference 2005, 16.-20.05.2005, Knoxville, TN, USA
    Proceedings of 2005 Particle Accelerator Conference, 3292-3294

Permalink: https://www.hzdr.de/publications/Publ-9760
Publ.-Id: 9760


Radiochemische Synthesen von [F-18]-markierten bicyclischen Vesamicol-Derivaten als potentielle Radioliganden für den vesikulären Acetylcholin-Transporter (VAChT)

Fischer, S.; Vercouillie, J.; Scheunemann, M.; Hiller, A.; Sorger, D.; Sabri, O.; Steinbach, J.
Ziel/Aim:

Für den Transport von Acetylcholin in die präsynaptischen Vesikel im Hirn ist der vesikuläre Acetylcholintransporter (VAChT) verantwortlich. Zur Diagnose cholinerger Läsionen im Gehirn und deren Visualisierung mit Hilfe von PET sind insbesondere F-18-Radioliganden von großem Interesse, die spezifisch an den VAChT binden. Solche Tracer leiten sich von der Struktur des Vesamicols ab. Auf Basis von Untersuchungen zur Strukturoptimierung potentiell neuer Radiotracer werden Radiosynthesen ausgewählter bicyclischer Vesamicol-Derivate vorgestellt.

Methodik/Methods:

Zur Verbesserung der pharmakologischen Eigenschaften gegenüber Benzyloxyvesamicol-Derivaten wurden Verbindungen des 6-(4-Phenyl-piperidin-1-yl)-octahydro-benzo[1,4]oxazin-7-ols abgeleitet. Im Ergebnis von detaillierten Bindungsstudien wurden als Derivate [F-18]F-acetyl- ([F-18]VL115), 4-[F-18]F-benzoyl- ([F-18]VL112), 4-[F-18]F-benzyl- ([F-18]VL64) und [F-18]F-propyl für erste Radiosynthesen ausgewählt, wobei für [F-18]VL115 ein Br-, für [F-18]VL112 ein Nitro-Präkursor verfügbar war und für [F-18]VL64 eine Aufbausynthese mit 4-[F-18]Fluorbenzylbromid (FBBr) angestrebt wurde.

Ergebnisse/Results:

Die Synthese von [F-18]VL115 erfolgt durch nukleophile Radiofluorierung des Präkursors in DMF (145-155°C, 15 min) und nachfolgende Abtrennung des Zielproduktes durch SPE und anschließende HPLC. Das Endprodukt wurde mittels TLC, Radio-HPLC und GC charakterisiert: Radiochemische Reinheit 99,0 %, spezifische Aktivität: 34-100 GBq/#mikro#mol. Die Synthese konnte auf einen Automaten (TRACERlab, Fa. GE/Healthcare) übertragen werden (Synthesezeit ca. 1,6 h, Ausbeute 23 %). Zentraler Schritt der Synthese von [F-18]VL112 ist die nukleophile Substitution der Nitrogruppe durch nicht konventionelles Erhitzen mit Mikrowellen in DMF (150 Watt, 150-156°C, 15 min). Das Produktgemisch enthält noch Reste an nicht-abtrennbarem Präkursor. Die Separation gelingt nach Reduktion mit Pd/Ammoniumformiat in MeOH. Nach Feinreinigung mit SPE und HPLC ist der Radiotracer in hoher Reinheit und spez. Aktivität erhältlich (98,5 % bzw. 35-150 GBq/#mikro#mol), jedoch nur in moderater Ausbeute (≤15 %). Als Voraussetzung für die Darstellung von [F-18]VL64 wurde [F-18]FBBr in ausreichender Menge in einem verbesserten Verfahren erhalten. In ersten Versuchen wurden signifikante Unterschiede im Reaktionsverhalten zwischen nicht-radioaktiven Reaktionspartnern zum Umsatz mit [F-18]FBBr bei analoger Reaktionsführung festgestellt.

Schlussfolgerungen/Conclusions:

Die vorgestellten Radiosynthesen ermöglichen eine sichere reproduzierbare Herstellung der Radiotracer [F-18]VL115, [F-18]VL112 und deren Formulierung als sterile ethanolische Lösung. Zur Herstellung von [F-18]VL115 wurde eine automatisierte Synthese unter Nutzung eines kommerziellen Synthesemoduls entwickelt.
  • Lecture (Conference)
    45. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2007, Hannover, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 46(2007), A43

Permalink: https://www.hzdr.de/publications/Publ-9759
Publ.-Id: 9759


Helical magnetorotational instability in a liquid metal Taylor-Couette experiment

Gundrum, T.; Gerbeth, G.; Stefani, F.; Rüdiger, G.; Szklarski, J.; Hollerbach, R.
Cosmic magnetic fields are not only passive by-products of the hydromagnetic dynamo effect, they also play an active role in the formation of stars and black holes by virtue of the Magnetorotational Instability (MRI). By destabilizing Keplerian flows which are hydrodynamically stable due to Rayleighs criterion, the MRI enables outward transport of angular momentum in accretion discs. The effort to investigate the MRI in a liquid metal experiment can be dramatically reduced if the purely axial magnetic field is replaced by a helical magnetic field. We present results of a Taylor-Couette experiment with the liquid metallic alloy GaInSn under the influence of helical magnetic fields that show typical features of MRI at Reynolds numbers of the order 1000 and Hartmann numbers of the order 10.
  • Lecture (Conference)
    15th International Couette-Taylor Workshop, 09.-12.07.2007, Le Havres, France
  • Contribution to proceedings
    15th International Couette-Taylor Workshop, 09.-12.07.2007, Le Havre, France
    Proceedings of the 15th International Couette-Taylor Workshop, Le Havre, 266-269

Permalink: https://www.hzdr.de/publications/Publ-9758
Publ.-Id: 9758


Ionen in der Materialforschung und verdünnte magnetische Halbleiter

Talut, G.
Grundlagen der Ionenstrahlphysik und der verdünnten magnetischen Halbleiter
  • Lecture (others)
    Vortrag im Rahmen der Vorlesung zur Oberflächentechnik, 04.05.2007, Wildau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-9757
Publ.-Id: 9757


TiSi2-Nanostructures - Enhanced Conductivity at Nanoscale?

Enyashin, A. N.; Gemming, S.
The stability, the structural and the electronic properties of elongated titanium silicide nanostructures have been investigated by density-functional-based tight-binding calculations. Our results show that the strain energy in tubular form does not follow the trends observed for other layered materials; tubes from TiSi2 are more stable than the flat monolayer, because in nanotubes free valences of Ti and Si atoms can be saturated for geometric reasons. Multi-layered tubes are energetically favoured and exhibit a tendency towards facetting. All such nanostructures are metallic with a density of Ti(3d) states at the Fermi level, which is considerably higher than that of the bulk compound. Thus, nanostructured TiSi2 may exhibit a better conductivity than the bulk phase along the tube direction.
Keywords: inorganic nanotube, silicide, nanowire, electronic structure

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Permalink: https://www.hzdr.de/publications/Publ-9756
Publ.-Id: 9756


Oxidized and glycated LDL isolated from subjects with impaired glucose tolerance increases CD36 and PPARgamma gene expression in macrophages

Graessler, J.; Pietzsch, J.; Westendorf, T.; Julius, U.; Bornstein, S. R.; Kopprasch, S.
kein Abstract verfügbar
  • Poster
    113. Internistenkongreß, 15.-18.04.2007, Wiesbaden, Deutschland
  • Abstract in refereed journal
    Medizinische Klinik 102(2007)4, S94

Permalink: https://www.hzdr.de/publications/Publ-9755
Publ.-Id: 9755


In vivo glycoxidation of low density lipoprotein from subjects with impaired glucose tolerance increases CD36 and PPARgamma gene expression in macrophages

Kopprasch, S.; Pietzsch, J.; Bornstein, S. R.; Graessler, J.
kein Abstract verfügbar
  • Lecture (Conference)
    51. Jahrestagung der Gesellschaft für Thrombose- und Hämostaseforschung, 21.-24.02.2007, Dresden, Deutschland
  • Open Access Logo Abstract in refereed journal
    Hämostaseologie 27(2007)1, A7

Permalink: https://www.hzdr.de/publications/Publ-9754
Publ.-Id: 9754


Influence of glucose challenge on 2-deoxy-2-[18F]fluoro-D-glucose small animal positron emission tomography (PET) studies in rats

Bergmann, R.; Bergmann, S.; Pietzsch, J.
Imaging of regional glucose metabolism in small animals by dynamic PET Imaging of regional glucose metabolism in small animals by dynamic PET studies using 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) provides the unique possibility to study normal physiology and pathophysiological situations in various disease models in vivo. However, plasma glucose levels and other factors influence 18F-FDG PET studies. Therefore, we examined and compared the tissue-specific 18F-FDG uptake and kinetics in rats without and with a glucose challenge. 18F-FDG kinetics was studied for one hour in anesthetized rats using a dedicated small animal PET system. The animals were injected intravenously with 18F-FDG without (control) or simultaneously with glucose (270 mg/kg body weight). PET images were reconstructed and three-dimensional regions of interest were determined for subsequent data analysis. The plasma glucose concentrations one hour after injection were similar in the control and post challenge group. Tissue-specific 18F-FDG uptake, e.g., in brain, heart and liver, tends to be lower in the post challenge group as compared to the controls. Only with increasing body weight (>250 g) post challenge plasma glucose increased. However, in the post challenge group the kinetics of 18F-FDG was different only in the first 15 min after injection when compared to the controls, but subsequently converged to control kinetics within the following 45 min. In summary, glucose challenge did not influence the tissue-specific distribution pattern of 18F-FDG due to the high glycolysis rate of the rat. On the other hand, in diabetic models, older or larger animals the effects of increased plasma glucose levels should be taken into account for interpretation of PET data.
  • Poster
    2nd International Congress on Prediabetes and the Metabolic Syndrome, 25.-28.04.2007, Barcelona, Spain
  • Abstract in refereed journal
    Diabetes and Vascular Disease Research 4(2007)Suppl. 1, S219

Permalink: https://www.hzdr.de/publications/Publ-9753
Publ.-Id: 9753


High resolution magnetic resonance imaging and spectroscopy of adipose tissue deposits in mice

Strobel, K.; van den Hoff, J.; Pietzsch, J.
Adipose tissue (AT) plays a crucial role in the pathogenesis of the metabolic syndrome. In this line, for investigation of AT biology and disorder rodent models gain increasing importance. However, non-invasive differentiation and characterization of AT deposits in rodents in vivo is a current challenge. In the present study, high resolution magnetic resonance imaging (MRI) and spectroscopy (MRS) techniques were applied for quantitative in vivo evaluation of various brown adipose tissue (BAT) and white adipose tissue (WAT) deposits in mice. Experiments were carried out in NMRI and nude mice, respectively. Morphological differentiation between various AT deposits was obtained by 1H-MRI at 7 Tesla. Images were obtained with high spatial resolution of 156 microns. Furthermore, 1H-MRS has been performed to quantify in vivo different lipid patterns in BAT and WAT deposits using a volume selective PRESS sequence on 3 to 8 mm3 voxels. In both NMRI and nude mice various BAT and WAT deposits were clearly distinguished from the non-AT tissue with excellent contrast by T1-weighted MSME MRI sequences. High resolution spectra obtained at 7 Tesla allow identification of at least 9 different proton resonances specific for lipids, and, thus, for exact calculation of mono- to polyunsaturated fatty acid ratio in vivo. In this study, nude mice showed, e.g., a 4-fold higher degree of polyunsaturation of triglyceride fatty acids in BAT when compared to NMRI mice. High-resolution MRI and MRS are potentially useful tools for studying the biology of different BAT and WAT deposits non-invasively in rodent models in vivo.
  • Poster
    International Congress on Prediabetes and the Metabolic Syndrome, 25.-28.04.2007, Barcelona, Spain
  • Abstract in refereed journal
    Diabetes and Vascular Disease Research 4(2007)Suppl. 1, S195

Permalink: https://www.hzdr.de/publications/Publ-9752
Publ.-Id: 9752


Factors influencing the formation of small dense LDL particles

Julius, U. A.; Dittrich, M.; Pietzsch, J.
Aims:
We wanted to study factors influencing the size of LDL particles.

Material and methods:
752 persons (330 males, 422 females) have been studied. We performed an OGTT (plasma glucose, insulin, proinsulin). Triglycerides (TG), total cholesterol (TC) and protein (in whole plasma, in VLDL, in LDL) and HDL cholesterol have been measured. The size of the LDL particles has been estimated using a gel electrophoresis
(in LDL subclasses 1 – 3, mean LDL particle diameter, affiliation to phenotypes A or B). Probands have been subdivided into those with normal glucose tolerance (n 540), with an impaired glucose tolerance (n 137), with a newly discovered or known diabetes (n 51), or with a diabetes mellitus which was treated by insulin (n 24). The
Metabolic Syndrome (MS) has been defined according to the NCEP criteria.

Results:
In 29 % of all probands a MS was observed. These probands had a significantly smaller mean LDL particle diameter (25.5 nm) than those persons without a MS (26.2 nm). In univariate analysis (partially adjusted for fasting plasma glucose, proinsulin, insulin, gender, age, body mass index) the mean LDL diameter showed significant
correlations with the VLDL TG, plasma TG, VLDL cholesterol, VLDL proteins and HDL cholesterol. In a linear stepwise regression analysis in the different groups of glucose tolerance different independent factors of influence were seen. Conclusions: The data obtained show the significance of TG levels, of glucose intolerance and the presence of the MS for the formation of atherogenic small dense LDL particles.
  • Poster
    2nd International Congress on Prediabetes and the Metabolic Syndrome, 25.-28.04.2007, Barcelona, Spain
  • Abstract in refereed journal
    Diabetes and Vascular Disease Research 4(2007)Suppl. 1, S219

Permalink: https://www.hzdr.de/publications/Publ-9751
Publ.-Id: 9751


In vivo metabolism of glycated and glycoxidized LDL: insights from small animal positron emission tomography (PET) studies

Pietzsch, J.; Haase, C.; Hoppmann, S.; Bergmann, R.; Wüst, F.; van den Hoff, J.
Data concerning the role of circulating glycated (glycLDL) and glycoxidized LDL (glycoxLDL) in atherogenesis and other pathologies are scarce. One reason for this is the lack of suitable radiolabeling methods for direct assessment of metabolic pathways of modified LDL in vivo. We report a novel approach for specific labeling of human native LDL (nLDL), glycLDL, and glycoxLDL with the positron emitter fluorine-18 (18F) by either N-succinimidyl-4-[18F]fluorobenzoate or N-[6-(4-[18F]fluorobenzylidene)-aminooxyhexyl]maleimide (radiochemical yields, 15-40%; specific radioactivity, 150-400 GBq/µmol). Radiolabeling itself caused neither additional oxidative structural modifications of LDL constituents nor adverse alterations of their biological activity and functionality in vitro. The approach was evaluated with respect to binding and uptake of 18F-nLDL, 18F-glycLDL, and 18F-glycoxLDL in cells overexpressing various lipoprotein-recognizing receptors. The metabolic fate of 18F-labeled nLDL, glycLDL, and glycoxLDL in vivo was delineated by dynamic small animal PET studies in rats. Dynamic PET data demonstrated a significantly delayed catabolism of glycLDL when compared with nLDL. In contrast, glycoxLDL showed an enhanced catabolism when compared with nLDL. The in vivo distribution and kinetics of nLDL, glycLDL, and glycoxLDL correlated well with the anatomical localization and functional expression of LDL receptors, scavenger receptors, and receptors for advanced glycation end products. The study shows that LDL modification in part or fully blocks binding to the LDL receptor, and reroutes modified LDL to various tissue-specific pathways. In this line, 18F-labeling of LDL and the use of small animal PET provide a valuable tool for imaging and functional characterization of these pathways in animal models in vivo.
  • Poster
    2nd International Congress on Prediabetes and the Metabolic Syndrome, 25.-28.04.2007, Barcelona, Spain
  • Abstract in refereed journal
    Diabetes and Vascular Disease Research 4(2007)Suppl. 1, S220

Permalink: https://www.hzdr.de/publications/Publ-9750
Publ.-Id: 9750


Hydration and water exchange mechanism of the UO22+ ion revisited: The validity of the "n+1" model

Tsushima, S.
Hydration and water exchange mechanism of the UO22+ ion was studied by the B3LYP calculations. Relative Gibbs energies in aqueous phase of the 4-, 5-, and 6-fold uranyl(VI) hydrates were compared. A model with a complete first hydration shell and one water in the second shell was used (which is called "n+1" model) to compare the energy of the UO22+ ion with different hydration number. The "n+1" model tends to overestimate the overall stability of the complex, and this type of model should be carefully used for the determination of the coordination number or the coordination mode such as unidentate or bidentate. A stable 5-fold uranyl(VI) hydrate go through a very rapid water exchange process via an associative (A-) mechanism keeping the 5-fold uranyl(VI) being dominant species.

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Permalink: https://www.hzdr.de/publications/Publ-9749
Publ.-Id: 9749


Tc-99m labelled fatty acids for myocardial metabolism imaging

Walther, M.; Pietzsch, H.-J.; Pietzsch, J.; Bergmann, R.; Wunderlich, G.; Mirtschink, P.; Deussen, A.
Ziel/Aim:

Radiolabelled fatty acids displaying efficient myocardial uptake and adequate retention are attractive candidates for the clinical evaluation of regional discrepancies in the cardiac metabolism and energy turnover (1). The aim of this work is the substitution of the accelerator produced radiolabel I-123 for FA against the low price generator radionuclide Tc-99m (2).

Methodik/Methods:

Synthesis and physico-chemical characterization of the new Tc-99m labelled FA derivatives were followed by in vitro and in vivo experiments for their biological evaluation. Experiments on isolated perfused rat hearts provide a simple and well reproducible approach to detect promising Tc-99m compounds for biodistribution experiments. Biodistribution and metabolism studies in male Wistar rats after a single intravenous injection of various Tc-99m-labelled FA were investigated (3).

Ergebnisse/Results:

A very rapid disappearance of Tc-99m tracer concentration from the blood circulation was observed for all compounds. C11S FA showed the highest uptake with 2.0% ID/g tissue (alternatively 3.6% by addition of Tween 80) in the rat heart. Liver and kidneys are mainly responsible for fast removal of Tc-99m derivatives from the circulation. At 5 min after injection, approximately 50% of the injected dose is liver-associated. A substantial fraction is cleared by the kidneys and approximately 6% of the injected dose is kidney-associated at 5 min p.i. Overall, fast systemic clearance of Tc-99m species after injection of Tc-99m labelled FA in the rat is explained by the rapid hepatobiliary and renal elimination of Tc-99m species. On the other hand, the low mean accumulation of Tc-99m compounds in the thyroid gland (<0.07 %ID at 5 min; <0.07 %ID at 60 min) and the stomach (<1.7 %ID at 5 min; < 3.9% at 60 min), respectively, which express the sodium-iodide transporter is indicative of a very low abundance of pertechnetate in vivo.

Schlussfolgerungen/Conclusions:

Experiments on isolated perfused rat hearts showed very high ventricular extraction rates of the FA complexes, being in the order C11 compound (26.6% ± 3.7, n= 12), C12 (24.4% ± 4.9, n= 5), and C11S (23.4% ± 4.9, n= 5). These extraction rates exceed considerably those achieved with the established iodinated FA [I-123]IPPA (15.5% ± 1.1).The metabolic in vivo studies reveal the complete ß-oxidation within one hour. Condition precedent for the use of the described Tc-FA in heart imaging are the improvement of the heart : liver ratio of 0.25±0.1 at 5 min p.i., which may be achieved by alterations of the FA binding mode to the “4+1” chelate unit and variations of the chelate position in the FA chain.

Literatur/References:
(1) Knapp, F. F. Jr., Kropp, J. (1995) Eur. J. Nucl. Med. 22(4), 361-381.
(2) Mach, R. H., Kung, H. F., Jungwiwattanaporn, (1991) Nucl. Med. Biol. 18, 215-226.
(3) M. Walther, C. M. Jung, R. Bergmann, (2006) Bioconjugate Chem. submitted
  • Lecture (Conference)
    45. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2007, Hannover, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 46(2007), A16

Permalink: https://www.hzdr.de/publications/Publ-9748
Publ.-Id: 9748


Nierentumore zeigen nur vereinzelt einen erhöhten C-11-Azetat-Uptake in der Positronen-Emissions-Tomographie

Kotzerke, J.; Linne, C.; Meinhardt, M.; Steinbach, J.; Abolmaali, N.; Beuthien-Baumann, B.
Ziel:

Die vorliegende Arbeit untersucht das Potenzial von C-11-Azetat-Positronen-Emissions-Tomographie (PET) zur Darstellung von Nierentumoren am Menschen, da das Staging von Nierentumoren mit FDG-PET unzufriedenstellend ist.

Methodik:

Einundzwanzig Patienten mit Verdacht auf einen Nierentumor im CT/MRT wurden nach Injektion von 820±430 MBq C-11-Azetat dynamisch über 30 min untersucht (ECAT EXACT HR+, Siemens/CTI, Knoxville, USA). Die Azetat-Aufnahme wurde qualitativ auf einer 5-Punkte-Skala eingeschätzt. Die Aufnahme-Kinetik von Nierenparenchym und Tumor wurde qualitativ verglichen. Bei 18/21 Patienten erfolgte eine Operation und histologische Klassifizierung.

Ergebnisse:

Die Azetat-Aufnahme in die Tumore war geringer (n = 11), gleich (n = 8) oder höher (n = 2) als das umgebende Nierenparenchym. Bei den letztgenannten Tumoren zeigte die kinetische Analyse eine Radiotracerzunahme bis zur 10. min gefolgt von einer langsamen Tracerabnahme über den Untersuchungszeitraum. Die übrigen Tumore zeigten eine dem Nierenparenchym ähnlich Kinetik bei teilweise initial verminderter Traceraufnahme. Die Nierenfunktion war bei allen Patienten nur gering bis mäßig beeinträchtigt. Histologisch lagen klarzellige Nierenkarzinome (n = 14), zwei papilläre und zwei onkozytäre Nierentumore vor, was einer typischen Verteilung entspricht. Nur die beiden Onkozytome zeigten eine gesteigerte Azetat-Aufnahme. Diese Ergebnisse stehen im Widerspruch zur Untersuchung von Shreve et al. (1995), in der 3/3 klarzelligen Nierenkarzinomen eine erhöhte Azetat-Aufnahme aufwiesen.

Schlussfolgerungen:

Die meisten untersuchten Nierentumore zeigten keine gegenüber dem umgebenden Nierenparenchym erhöhte C-11-Azetat-Aufnahme. Die geringe C-11-Azetat-Aufnahme war nicht messtechnisch durch zu späte Akquisitionen bedingt. Auch Spätbilder zeigten keine wesentliche Kontrastzunahme. Daher kann C-11-Azetat-PET nicht routinemäßig zum Primärstaging von Nierentumoren empfohlen werden. Die Bedeutung von C-11-Azetat-PET für den Nachweis von Lymphknoten-, Fernmetastasen oder Rezidiven von Nierentumoren muß noch weiter untersucht werden.

Literatur:

Shreve P et al., J Nucl Med 36 (1995):1595-601
  • Lecture (Conference)
    45. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2007, Hannover, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 46(2007), A39-A40

Permalink: https://www.hzdr.de/publications/Publ-9747
Publ.-Id: 9747


Einfluss von Hypoxie und Proliferation auf die F-18-FDG-Aufnahme in 2 humanen Tumormodellen auf Nacktmäusen: Untersuchung mit PET, Autoradiographie und funktioneller Histologie

Beuthien-Baumann, B.; Gabrys, D.; Wüllrich, K.; Hofheinz, F.; Brüchner, K.; Bergmann, R.; Baumann, M.
Ziel/Aim:

Die Mehrzahl maligner Tumore weisen einen erhöhten Glukosestoffwechsel auf, ein Mechanismus der bei der Positronen-Emissions-Tomographie mit F-18-FDG in der Onkologie diagnostisch genutzt wird. Ziel dieser Untersuchung war es, die unterschiedlichen Einflüsse von Tumorhypoxie und Proliferation auf die intratumorale FDG-Aufnahme in 2 menschlichen Tumormodellen auf Nacktmäusen zu untersuchen.

Methodik/Methods:

Je 10 Nacktmäusen mit transplantiertem menschlichen Plattenepithel-Carcinom Fadu oder humanem Adeno-Carcinom HT29 wurden mit FDG und PET (MicroPET P4, CTI Molecular Imaging, gemessenen Transmission, 8 MBq FDG i.v., Untersuchung 30-60min p.i.) untersucht (Tumorvolumina 0,4 ± 0,2cc). Aus den PET-Aufnahmen wurde der SUVmax der Tumore bestimmt. Vor dem PET wurde den Mäusen Pimonidazol (Pimo) und Bromdesoxyuridin (BrdU) injiziert, die Mäuse wurden unmittelbar nach der PET getötet, die Tumore entnommen, tiefgefroren, serielle Schnitte von 20 µm angefertigt und die intratumorale FDG-Verteilung per Autoradiographie (BAS 5000, Fuji) bestimmt. Leberschnitte von 20µm dienten als Referenzgewebe. Anschließend erfolgte die Färbung der Schnitte mit Hämatoxylin/Eosin, Antikörper gegen Pimonidazol, BrdU oder Ki-67. Die Tumorschnitte wurden mit einer digitalen Kamera gescannt und per Bildanalyse wurden Masken für vitalen Tumor, Nekrose und funktionelle Färbungen (Pimo, BrdU, Ki-67) angefertigt. Die digitalen Histologien wurden mit der korrespondierenden Autoradiographie koregistriert und die quantitative FDG-Aufnahme in den definierten Tumorarealen bestimmt.

Ergebnisse/Results:

Der SUVmax in Fadu (1,55 ± 0,26) lag etwas höher als in HT29 (1,30 ± 0,17; p=0,03). Fadu bildet größere hypometabole Bereich aus, die sich in der Histologie als Nekrose identifizieren liessen. Bei ähnlicher Größe der Pimo-positiven Areale in Fadu und HT29 fand sich nur in Fadu eine signifikant höhere FDG-Aufnahme in den hypoxischen Arealen im Vergleich zu vitalem Pimo-negativem Tumorgewebe (Fadu: 3,1 ± 0,2 versus 2,2 ± 0,2 %ID/g, p=0,002, HT29: 2,4 ± 0,2 versus 2,2 ± 0,2%ID/g, p=0,4). In beiden Tumormodellen fand sich keine regional erhöhte FDG-Aufnahme in Tumorregionen mit proliferativer Aktivität im Vergleich zu nicht in Teilung begriffenen vitalen Tumorarealen.

Schlussfolgerungen/Conclusions:

In den zwei untersuchten Tumormodellen war nur bei dem Plattenepithel-Ca Fadu ein Einfluß der Hypoxie auf die FDG-Aufnahme zu erkennen, die höhere FDG-Aufnahme in Hypoxiearealen könnte sich in dem höheren SUVmax im Vergleich zum Adeno-Ca HT29 widerspiegeln. Weder in Fadu noch in HT29 fand sich eine Korrelation zwischen Proliferation (BrdU, Ki-67) und Intensität der FDG-Aufnahme.

Die Daten wurden im Rahmen des 6.Rahmenprogrammes der EU, Projekt Biocare, proposal Nr. 505785, erhoben.
  • Lecture (Conference)
    45. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2007, Hannover, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 46(2007), A14

Permalink: https://www.hzdr.de/publications/Publ-9746
Publ.-Id: 9746


Untersuchung des Einflusses von Kopfbewegungen auf die Quantifizierung von FDOPA-PET-Studien

Oehme, L.; Beuthien-Baumann, B.; Bühler, P.; Langner, J.; Pötzsch, C.; Hofheinz, F.; van den Hoff, J.
Ziel/Aim:

Ziel war die Bestimmung des Einflusses von Kopfbewegungen während einer dynamischen Untersuchung auf die Kompartmentmodell-gestützte Quantifizierung des FDOPA Uptakes durch den Vergleich von Auswertungen der bewegungskorrigierten und der unkorrigierten Daten.

Methodik/Methods:

Retrospektiv wurden Daten von 57 Patienten (32 m, 25 w, mittleres Alter 58,8 Jahre) analysiert, welche im Rahmen der Parkinson-Diagnostik mit F-18-FDOPA eine PET-Untersuchung (EXACT HR+, Siemens) erhielten. Die Messung erfolgte im Listmode, daraus wurde eine dynamische Studie von 21 Frames erstellt. Parallel zur Aufnahme wurde die Kopfbewegung mit einem Motion-Tracking-System (A.R.T.,München) aufgezeichnet. Die Bewegungsdaten wurden detailliert analysiert und zur Korrektur der Emissionsbilder verwendet. Dopamin-Einstromraten für die korrigierten und unkorrigierten Studien wurden mittels grafischer Patlak-Analyse sowohl für 8 manuell positionierte striatale VOIs (0,35ml, Software: ROVER, abx biochemicals) als auch voxelweise quantifiziert (Referenzregion okzipitaler Cortex, Regression 15-60min) und verglichen.

Ergebnisse/Results:

Bei 2 Patienten wurde ein Versagen der Bewegungskorrektur festgestellt, was auf eine ungenügende Fixierung des Targets für die Bewegungsmessung am Patientenkopf zurückgeführt wurde. Über das Kollektiv betrachtet sind die Bewegungen klein: Median und Quantilen (10%-90%) Translationen in mm für x;y;z 1,6 (0,8-3,4); 1,8 (1,0-4,7); 2,8 (1,0-8,0); Rotation in Grad um x;y;z-Achse 2,2 (1,2-4,9); 0,8 (0,4-1,7); 0,6 (0,3-1,7). Daraus ergeben sich maximale Voxelverschiebungen innerhalb des Gehirns von: weniger als 4mm bei 24 Patienten, zwischen 4 und 8mm bei 20 Patienten und 10mm bei einem Patienten. Die Verteilung des prozentualen Unterschiedes der Einstromraten ohne und mit Korrektur für die 440 VOIs hat einen Median von 1%. 80% der Werte liegen zwischen -4% und 13,6%. Bei 11 Patienten finden sich Abweichungen von mehr als 20% (Absolutbetrag), wobei bei 3 Patienten mehr als 3 VOIs betroffen sind. Dies sind Patienten, welche sich insbesondere in z-Richtung stark bewegt haben (>11mm). Kopfbewegung während der Aufnahme führt meist zu einer Überschätzung der Einstromraten, was sich auch in den Histogrammen der voxelweise korrelierten parametrischen Bilder zeigt. Artefakte in den parametrischen Bildern sind am ehesten in den kortikalen Bereichen erkennbar.

Schlussfolgerungen/Conclusions:

Bei der Quantifizierung der Dopamin-Einstromraten sollte eine Bewegungskorrektur angestrebt werden. Die hier angewandte framebasierte Methode ist einfach und schnell anwendbar, weitere Verbesserungen sollten durch eventbasierte Korrektur der Emission und Einrechnung von korrigierten Transmissionsdaten erreichbar sein.
  • Poster
    45. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2007, Hannover, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 46(2007), A118

Permalink: https://www.hzdr.de/publications/Publ-9745
Publ.-Id: 9745


Implementierung von Methoden zur Integration der PET in die Bestrahlungsplanung

Hofheinz, F.; Pötzsch, C.; Oehme, L.; van den Hoff, J.
Ziel/Aim:

Die Integration der PET in die Bestrahlungsplanung ist für die Strahlentherapie von zunehmendem Interesse. Folgende Voraussetzungen sind hierfür zu erfüllen: 1) adäquate DICOM-Integration der PET (Herstellerseitig für neuere Geräte i.w. erfüllt), 2) volumetrisch korrekte und routinefähige 3D ROI-Abgrenzung in den PET-Daten, 3) Transfer der 3D-ROIs in den DICOM-RT Standard, 4) Koregistrierung PET vs. Bestrahlungsplanungs-CT. Ziel dieser Arbeit war die vollständige Implementierung eines routinefähigen Workflows unter Nutzung existierender und neu entwickelter Methoden.

Methodik/Methods:

Die genutzten Verfahren zur benutzerunabhängigen 3D-ROI-Definition und Koregistrierung wurden anderweitig bereits vorgestellt (1-3). Umgesetzt wurde nunmehr die fehlende Übersetzung der resultierenden 3D-ROIs in den DICOM-RT Standard als Voraussetzung für den Import der ROIs in die Bestrahlungsplanungssysteme sowie die Kombination der verschiedenen Arbeitsschritte in einen routinefähigen Ablauf unter Nutzung einer eigenen DICOM-Schnittstelle. Das gesamte Verfahren wurde an verschiedenen Bestrahlungsplanungssystemen getestet.

Ergebnisse/Results:

Die PET-Information konnte in Planungssysteme verschiedenerer Hersteller integriert werden, wobei der Integrations-Workflow teilweise an das jeweilige Planungssystem angepasst werden musste. Unser Verfahren erlaubt insbesondere auch die Kombination der PET-ROIs und die Planungs-CT Konturen, was die Handhabung der kombinierten Information auf den Planungssystemen erleichtert. Der durch die Integration verursachte zusätzliche zeitliche Aufwand bei der Auswertung der PET-Aufnahmen ist vernachlässigbar.

Schlussfolgerungen/Conclusions:

Die vorgestellte Methode erlaubt eine routinemäßige Integration der PET-Information in die Bestrahlungsplanung.

Literatur/References:

1. C. Pötzsch;F. Hofheinz;J. van den Hoff; Nuklearmedizin (2005) 44 p. A16
2. C. Pötzsch;F. Hofheinz;J. van den Hoff; Nuklearmedizin (2006) 45 p. A42
3. F. Hofheinz;C. Pötzsch;J. van den Hoff; Nuklearmedizin (2005) 44 p. A162
  • Lecture (Conference)
    45. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2007, Hannover, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 46(2007), A10

Permalink: https://www.hzdr.de/publications/Publ-9744
Publ.-Id: 9744


Koregistrierung parametrischer PET-Daten mit CT-Datensätzen in der kardialen Diagnostik

Fricke, H.; Schwier, M.; Weise, R.; Fricke, E.; van den Hoff, J.; Domik, G.; Burchert, W.
Ziel/Aim:

Die kardiale PET zeichnet sich gegenüber der SPECT u.a. durch die Möglichkeit der absolut quantifizierenden Messung der myokardialen Perfusion aus. In der Diagnostik der KHK wird zunehmend eine Kombination von SPECT oder PET mit einer morphologischen Darstellung der Koronargefäße durch eine CT-Angiographie eingesetzt. Auch bei Einsatz von Hybridgeräten machen Unterschiede in der Datenakquisition und die Thoraxbewegung bei der Atmung eine Koregistrierung der Datensätze erforderlich. Von Seiten der Gerätehersteller wird derzeit jedoch nur eine Koregistrierung statischer Datensätze unterstützt. Der wesentliche Vorteil der PET, die Einschätzung einer koronaren 3-Gefäßerkrankung durch Beurteilung der absoluten Flusswerte, geht dadurch verloren. Ziel war daher die Koregistierung von CT und funktionellem PET-Datensatz.

Methodik/Methods:

Verwendet wurden dynamische PET-Studien mit N-13-Ammoniak und CT-Angiographien der Koronargefäße, die an unabhängigen Geräten akquiriert wurden. Die Koregistrierung von CT und PET erfolgte anhand des rekonstruierten CT-Datensatzes und des PET-Uptake-Bildes (letztes Frame der dynamischen Studie, 9.-16. Minute). Die Koregistrierung erfolgte manuell sowie durch automatische Detektion von Grenzflächen über Schwellenwerte. Im Rahmen der Kompartmentmodellierung dynamischer PET-Datensätze findet eine Reorientierung entsprechend der Herzachsen statt und die funktionellen Parameter können nur für Volumenelemente innerhalb des Myokards bestimmt werden. Daher gehen die ursprüngliche Orientierung der Datensätze und weitergehende anatomische Informationen zunächst verloren. Für eine kombinierte Darstellung der Morphologie der Koronargefäße und der quantitativen Flussinformation wurde daher in einem nächsten Schritt eine Rückprojektion der Flussinformation in die anatomisch korrekte Lokalisation durchgeführt.

Ergebnisse/Results:

Mit der vorliegenden Methode ist es möglich, quantitative Flussinformationen aus der PET mit CT-Angiographien der Koronargefäße zu koregistrieren und somit im Kontext anatomischer Daten darzustellen. Dies bedeutet für die klinische Anwendung, dass es im Vergleich zur myokardialen SPECT/CT möglich ist, relevante Hauptstammstenosen zu erkennen und auch bei koronarer Mehrgefäßerkrankung nicht nur die funktionelle Relevanz der führenden, sondern aller Stenosen zu beurteilen.

Schlussfolgerungen/Conclusions:

Die Weiterentwicklung von Software, die eine Koregistrierung von morphologischen Daten aus der CT und funktionellen Daten aus der PET ohne Informationsverluste ermöglicht, ist insbesondere im Hinblick auf die zunehmende Häufigkeit von Hybridgeräten dringend erforderlich.
  • Lecture (Conference)
    45. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2007, Hannover, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 46(2007), A32

Permalink: https://www.hzdr.de/publications/Publ-9743
Publ.-Id: 9743


First in-beam PET measurement of β+ radioactivity induced by hard photon beams

Kluge, T.; Möckel, D.; Pawelke, J.; Enghardt, W.
In this article we present the first experimental results of in-beam PET measurements during high energy photon phantom irradiation. An inhomogeneous phantom was irradiated with pulsed 34 MV bremsstrahlung. The measurements have been conducted with a dedicated double head photon camera. A high material contrast could be achieved and furthermore production rates of C-11 and O-15 were derived from the time dependent activity.

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Permalink: https://www.hzdr.de/publications/Publ-9742
Publ.-Id: 9742


Binding Studies of 14C-Caffeine to Artificial Receptors

Waldvogel, S. R.; Bomkamp, M.; Siering, C.; Malkowsky, I.; Landrock, K.; Stephan, H.
Caffeine is among the most frequently consumed alkaloidal compounds and is omnipresent in many plants. The traditional significant sources of caffeine in daily life are coffee, black tea and cocoa. Actually, the alkaloid is an ingredient of Cola beverages and energy drinks. Many analgesics sold-over-the-counter contain also caffeine. Because of the wide range of applications and the potential of new analytical tools caffeine is currently gathering an increasing attention. Recently, we reported the synthesis of functionalized triphenylene ketals which represent the rigid C3v symmetric scaffold of our novel receptors (1). The cleft like structure exhibits a high affinity to caffeine and does not interfere with the alkyl groups of the oxopurine system leading to a novel concept for the molecular recognition of caffeine and related compounds. Based on this concept several methods for the detection of caffeine in real life samples have been established. With extraction studies using 14C-labelled caffeine the potential of this receptor systems and their binding action could be elucidated. This is a key prerequisite for the further development of caffeine detection systems on a dip-stick model. Furthermore, first experiments were done in view of the development of controlled release systems for caffeine in aqueous media.
  • Lecture (Conference)
    14th Workshop der International Isotope Society, 21.-22.06.2007, Bad Soden, Germany
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 50(2007), 1280-1282

Permalink: https://www.hzdr.de/publications/Publ-9741
Publ.-Id: 9741


Efficient melt stirring using pulse sequences of a rotating magnetic field: I - Flow field in a liquid metal column

Eckert, S.; Nikrityuk, P. A.; Räbiger, D.; Eckert, K.; Gerbeth, G.
The utilization of a pulsed rotating magnetic field (RMF) is presented as an auspicious method to obtain an intensive stirring and mixing in a pool of liquid metal. The RMF pulses within a sequence have been applied with constant or alternating direction, respectively. The resulting flow structure in a cylindrical liquid metal column has been explored by numerical simulations and by model experiments using the ternary alloy GaInSn. The ultrasonic Doppler velocimetry (UDV) has been used to determine profiles of the vertical velocity. The numerical results as well as the velocity measurements demonstrate the capability of the proposed stirring regimes to overcome the limited mixing character of conventional rotary stirring. The application of a time-modulated RMF offers a considerable potential to provide optimal flow pattern in a solidifying melt for reasons of a well-aimed modification of casting properties.
Keywords: electromagnetic stirring, rotating magnetic field, Ultrasonic Doppler Velocimetry, solidification

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Permalink: https://www.hzdr.de/publications/Publ-9740
Publ.-Id: 9740


Synthesis of an 11C-labelled cyclooxygenase-2 (COX-2) inhibitor and PET imaging in HT-29 and FaDu tumor bearing mice

Knieß, T.; Bergmann, R.; Wüst, F.
Cyclooxygenase-2 (COX-2) is an enzyme induced during inflammation by various stimuli, but overexpression of COX-2 has been observed also in oncogenesis in a variety of tumors. Although several COX-2 inhibitors have recently been radiolabeled with isotopes for positron emission tomography (PET), their potential for tumor imaging has not been explored extensively. Herein we report the synthesis and radiopharmacological evaluation of 1-(4-[11C]methoxyphenyl)-2-(4-methylsulfonylphenyl)-1-cyclopentene as novel 11C-labelled radiotracer for PET imaging of COX-2.

Methods:
The radiolabeling was performed via a 11C-methylation reaction of the corresponding desmethyl precursor using [11C]MeI in a TRACERLab FXC module.
Biodistribution studies were performed in normal Wistar rats. Small animal PET studies were performed using xenografted HT-29 and FaDu tumors in mice using a micro-PET® P4 scanner.

Results:
The radiolabeling was achieved by the reaction of 1-(4-hydroxyphenyl)-2-(4-methylsulfonylphenyl)-1-cyclopentene at 60°C in DMF/aqueous NaOH with [11C]CH3I. After semi-preparative HPLC purification and solid phase extraction the 11C-labelled COX-2 inhibitor was obtained in 12-14 % decay-corrected radiochemical yield at a specific activity of 30 GBq/µmol at the end-of-synthesis. The radiochemical purity exceeded 97%. Biodistribution in normal rats showed high radioactivity accumulation in the liver, adrenals and brown adipose tissue, reaching 0.6±0.1, 0.7±0.2 and 0.8±0.1 %ID/g after 1 h post injection, respectively. Tumor-to-muscle ratios of 1.7±0.2 and 2.1±0.3, respectively, were determined with small animal PET-studies of xenografted HT-29 and FaDu tumors in mice after 1 h post injection.
  • Poster
    2nd International Conference of the European Society for Molecular Imaging, 14.-15.06.2007, Naples, Italy

Permalink: https://www.hzdr.de/publications/Publ-9739
Publ.-Id: 9739


Modified “4+1” Mixed Ligand Technetium Labeled Fatty Acids for Myocardial Imaging: Evaluation of Myocardial Uptake and Biodistribution

Mirtschink, P.; Stehr, S. N.; Pietzsch, H.-J.; Bergmann, R.; Pietzsch, J.; Wunderlich, G.; Heintz, A. C.; Kropp, J.; Spies, H.; Kraus, W.; Deussen, A.; Walther, M.
Our group previously synthesized 99mTc-labeled fatty acids suitable for myocardial metabolism and flow imaging. In this set of experiments 28 new analogues were synthesized according to the “4+1” mixed ligand approach with some specific differences. Conventional “4+1” 99mTc-fatty acids are built in the sequence Tc-chelate, alkyl chain and carboxylic group. We developed compounds with a new design with the sequence carboxylic group, alkyl chain, Tc-chelate, and lipophilic tail. Therefore the 99mTc-chelate was transferred to a more central position of the compound, aiming towards an improved myocardial profile and an accelerated liver clearance. In this context several functional groups incorporated in the lipophilic tail section were tested to evaluate their influence on the compound’s character. In addition to biodistribution studies in vivo the myocardial first-pass extraction of the compounds was tested in an isolated Langendorff rat heart model. A satisfactory myocardial uptake up to 20% of the injected dose (% ID) in the perfused heart and a fast liver clearance in vivo with only 0.29% ID/g at 60 min post injection demonstrates that the induced molecular modifications affect the kinetics of 99mTc-radiolabeled fatty acid compounds favorably. From the data set rules for estimating the biodistribution of fatty acids tracers are deduced.

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Permalink: https://www.hzdr.de/publications/Publ-9738
Publ.-Id: 9738


First results in 64Cu-production and copper complexation by new ligands derived from bispidine and 1,4,7-triazacyclononane

Walther, M.; Preusche, S.; Gasser, G.; Tjioe, L.; Graham, B.; Spiccia, L.; Juran, S.; Künstler, J.-U.; Stephan, H.; Steinbach, J.
Introduction:
64Cu (t1/2 = 12.7 h; ß+ 0.653 MeV, 17.4%; ß-: 0.578 MeV, 39%) [1,2] is the most used copper isotope in nuclear medicine due to its favorable decay characteristics and its ability to be produced with high specific activity. Bispidines and azamacrocycles containing pyridine pendant arms form thermodynamically stable complexes with copper(II) [1,2]. These chelating agents – possessing an additional linker group – provide an attractive lead for labelling biomolecules with copper radionuclides.

Experimental:
First experiments to adapt the described 64Cu-production process [3,4] at a biomedical cyclotron CYCLONE 18/9 were performed. A bombarding energy of 10 MeV and a proton beam current of 10 µA for 15 to 60 min were used. The yields of the 64Ni(p,n)64Cu reaction were comparable to reference values [179-331 MBq/µA/h versus 185-248 MBq/µA/h [3,4]].
Two novel ligands with carboxylic groups – a hexadentate bispidine 1 and a derivative of 1,4,7-triazacyclononane (TACN) 2 [5] were prepared. Labelling experiments of these ligands indicated the rapid formation of stable 64Cu-complexes under mild conditions. The bioconjugates 3 and 4 were obtained by coupling the bombesin (BBN) derivate βAla-βAla-[Cha13, Nle14]BBN(7-14) [6] to the ligands 1 and 2 (HBTU, DIPEA, DMF, r.t.).

Results and Discussion:
The bioconjugation of 1 and 2 to a bombesin derivative was successfully achieved via amide coupling to give 3 and 4. The free ligands and the bioconjugates were labelled with 64Cu and the resulting complexes were found to be stable in the presence of a large excess of competing ligands such as cyclam and even in rat plasma.

Conclusion:
The bispidine ligand 1, the TACN derivative 2 and their bombesin bioconjugates 3 and 4 are able to form complexes with high stability. These bifunctional chelating agents may be attractive candidates for the development of new copper radiopharmaceuticals for diagnosis (64Cu) and therapy (67Cu). Preliminary studies on the bio-distribution of 64Cu-complexes of 3 and 4 are currently underway [5].

[1] C. Bleiholder et al., Inorg. Chem. 2005, 44, 8145-8155.
[2] G. A. McLachlan et al., Inorg. Chem. 1994, 33, 4663-4668.
[3] F. Szelecsényi et al., Appl. Radiat. Isotopes 1993, 44, 575-580.
[4] D. W. McCarthy et al., Nucl. Med. Biol. 1997, 24, 35–43.
[5] G. Gasser et al., Bioconjugate Chemistry, 2007, in prep.
[6] E. Garcia Garayoa et al., Nucl. Med. Biol. 2007, 34, 17-28.
  • Lecture (Conference)
    2nd International Conference on Radiopharmaceutical Therapy, 03.-07.09.2007, Ulaanbaatar, Mongolia

Permalink: https://www.hzdr.de/publications/Publ-9737
Publ.-Id: 9737


Diagnostics Beamline for the SRF Gun Project

Kamps, T.; Dürr, V.; Goldammer, K.; Krämer, D.; Kuske, P.; Kuszynski, J.; Lipka, D.; Marhauser, F.; Quast, T.; Richter, D.; Lehnert, U.; Michel, P.; Teichert, J.; Evtushenko, P.
A superconducting radio-frequency photo electron injector (SRF gun) is currently under construction by a collaboration of BESSY, DESY, FZR and MBI. The project aims at the design and setup of a CW SRF gun including a diagnostics beamline for the ELBE FEL and to address R&D issues on low emittance injectors for future light sources such as the BESSY FEL. Of critical importance for the injector performance is the control of the electron beam parameters. For this reason a compact diagnostics beamline is under development serving a multitude of operation settings ranging from low-charge (77pC), low-emittance (1 mm mrad) mode to high-charge (2.5nC) operation of the gun. For these operation modes beam dynamics simulations are resulting in boundary conditions for the beam instrumentation. Proven and mature technology is projected wherever possible, for example for current and beam position monitoring. The layout of the beam profile and emittance measurement systems is described. For the bunch length, which varies between 5 ps and 50 ps, two schemes using electro-optical sampling and Cherenkov radiation are detailed. The beam energy and energy spread is measured with a 180o spectrometer.
  • Contribution to proceedings
    27th International Free Elektron Laser Conference FEL 2005, 21.-26.08.2005, Stanford, CA, USA
    Proceedings of the 27th International Free Electron Laser Conference 2005, 530-533

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Publ.-Id: 9736


Status of the 7Be(p,g)8B S-factor

Junghans, A.
We present new measurements of the 7Besp,gd8B cross section from Ec.m.=116 to 2460 keV (where c.m. means center-of-mass), which incorporate several improvements over our previously published experiment, also discussed here. Our new measurements lead to S17s0d=22.1±0.6sexptd±0.6stheord eV b based on data from Ec.m.=116 to 362 keV, where the central value is based on the theory of Descouvemont and Baye. The theoretical error estimate is based on the fit of 12 different theories to our low-energy data. We compare our results to other S17s0d values extracted from both direct f7Besp,gd8Bg and indirect (Coulomb-dissociation and heavy-ion reaction) measurements, and show that the results of these three types of experiments are not mutually compatible. We recommend a “best” value, S17s0d=21.4±0.5sexptd±0.6stheord eV b, based on the mean of all modern direct measurements below the 1+ resonance. We also present S factors at 20 keV which is near the center of the Gamow window: the result of our measurements is S17s20d =21.4±0.6sexptd±0.6stheord eV b, and the recommended value is S17s20d=20.6±0.5sexptd±0.6stheord eV b.
  • Invited lecture (Conferences)
    Advances and Challenges in Nuclear Astrophysics, 24.05.2004, Trento, Italy

Permalink: https://www.hzdr.de/publications/Publ-9735
Publ.-Id: 9735


Precise measurement of the 7Be(p,g)8B S-factor

Junghans, A.
We present new measurements of the 7Besp,gd8B cross section from Ec.m.=116 to 2460 keV (where c.m. means center-of-mass), which incorporate several improvements over our previously published experiment, also discussed here. Our new measurements lead to S17s0d=22.1±0.6sexptd±0.6stheord eV b based on data from Ec.m.=116 to 362 keV, where the central value is based on the theory of Descouvemont and Baye. The theoretical error estimate is based on the fit of 12 different theories to our low-energy data. We compare our results to other S17s0d values extracted from both direct f7Besp,gd8Bg and indirect (Coulomb-dissociation and heavy-ion reaction) measurements, and show that the results of these three types of experiments are not mutually compatible. We recommend a “best” value, S17s0d=21.4±0.5sexptd±0.6stheord eV b, based on the mean of all modern direct measurements below the 1+ resonance. We also present S factors at 20 keV which is near the center of the Gamow window: the result of our measurements is S17s20d =21.4±0.6sexptd±0.6stheord eV b, and the recommended value is S17s20d=20.6±0.5sexptd±0.6stheord eV b.
  • Invited lecture (Conferences)
    Bothe Kolloquium, 19.5.2004, Heidelberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-9734
Publ.-Id: 9734


Combined TEM, PAS and SANS investigation of neutron-irradiated pure iron

Bergner, F.; Al Mazouzi, A.; Hernandez-Mayoral, M.; Ulbricht, A.
Fission spectrum neutron irradiation of pure Fe at irradiation temperatures of about 300 °C gives rise to the formation of two populations of defects: planar dislocation loops and spherical vacancy-type clusters. Knowledge of the type and size distributions of these populations is important for the purpose of multi-scale modelling of the mechanical behaviour of Fe-based alloys. Among the experimental techniques with nanometer size resolution, transmission electron microscopy (TEM) and small-angle neutron scattering (SANS) allow to gain information on both nature and size distribution of particular types of defects. Furthermore, positron annihilation spectroscopy (PAS) is sensitive to sub-nanometer size open-volume defects. However, there is no single experimental technique capable of providing the full set of information required for calibration and validation of advanced models. The complementarity between the three techniques to identify and quantify the defects created by irradiation in pure Fe is emphasised in the paper. It is shown that while TEM allows direct size-resolved evidence of dislocation loops, PAS a qualitative appreciation of the existing sub-nanometer size vacancy-type clusters, SANS yields indirect size-resolved evidence of vacancy-type clusters, which form a sound basis for the quantification of the size distributions.
  • Lecture (Conference)
    Workshop on Structural Materials for Innovative Nuclear Systems (SMINS), 04.-06.06.2007, Karlsruhe, Germany
  • Contribution to proceedings
    Structural Materials for Innovative Nuclear Systems (SMINS), 04.-06.06.2007, Karlsruhe, Germany
    Workshop Proceedings: OECD 2008, 283-290

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Publ.-Id: 9733


Spallation residues in the reaction 56Fe+ p at 0.3A, 0.5A, 0.75A, 1.0A, and 1.5A GeV

Villagrasa-Canton, C.; Boudard, A.; Ducret, J.-E.; Fernandez, B.; Leray, S.; Volant, C.; Armbruster, P.; Enqvist, T.; Hammache, F.; Helariutta, K.; Jurado, B.; Ricciardi, M. V.; Schmidt, K.-H.; Sümmerer, K.; Vives, F.; Yordanov, O.; Audouin, L.; Bacri, C.-O.; Ferrant, L.; Napolitani, P.; Rejmund, F.; Stephan, C.; Tassan-Got, L.; Benlliure, J.; Casarejos, E.; Fernandez-Ordonez, M.; Pereira, J.; Czajkowski, S.; Karamanis, D.; Pravikoff, M.; George, J. S.; Mewaldt, R. A.; Yanasak, N.; Wiedenbeck, M.; Connell, J. J.; Faestermann, T.; Heinz, A.; Junghans, A.
The spallation residues produced in the bombardment of 56Fe at 1.5A, 1.0A, 0.75A, 0.5A, and 0.3A GeV on a liquid-hydrogen target have been measured using the reverse kinematics technique and the fragment separator at GSI (Darmstadt). This technique has permitted the full identification in charge and mass of all isotopes produced with cross sections larger than 10−2 mb down to Z = 8. Their individual production cross sections and recoil velocities at the five energies are presented. Production cross sections are compared with previously existing data and with empirical parametric formulas, often used in cosmic-ray astrophysics. The experimental data are also extensively compared with the results of different combinations of intranuclear cascade and deexcitation models. It is shown that the yields of the lightest isotopes cannot be accounted for by standard evaporation models. The GEMINI model, which includes an asymmetric fission decay mode, gives an overall good agreement with the data. These experimental data can be directly used for the estimation of composition modifications and damages in materials containing iron in spallation sources. They are also useful for improving high-precision cosmic-ray measurements.

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Publ.-Id: 9732


X-ray diffraction study of low-energy carbon-ion implanted Si(001)

Markwitz, A.; Barry, B.; Eichhorn, F.
In the search for Si- and C-based crystalline phases in low-energy ion implanted and electron-beam annealed Si surface layers, X-ray diffraction (XRD) measurements were performed at grazing incidence on samples of large SiC nanocrystals grown on a 90 nm thick Si layer containing C atoms. Diffraction patterns and reciprocal space maps did not reveal XRD patterns originating from the nanocrystals or the implanted layer, but did show that distortions of the Si crystal structure were introduced into the implanted layer. After annealing, the strain in the implanted layer is reduced, possibly by carbon atoms that have moved to locations close to dislocations and dislocation loops. This investigation underpins the growth theory of the SiC nanocrystals on Si, with carbon atoms migrating to form the nanostructures.
  • Surface and Interface Analysis 39(2007)5, 415-418

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Publ.-Id: 9731


Characterization of Ni-Ti (Shape Memory Alloy) thin film by in-situ XRD and complementary ex-situ techniques

Martins, R. M. S.; Schell, N.; Reuther, H.; Pereira, L.; Silva, R. J. C.; Mahesh, K. K.; Braz Fernandes, F. M.
Ni-Ti SMA are smart materials undergoing first order martensitic transformations driven by temperature and/or stress. In the form of film they are very attractive candidates for microelectro-mechanical system (MEMS) applications. Future directions include the production of functionally graded films by changing deliberately the ratio Ti/Ni across their thickness. However, for the successful development of this type of films, it is important to characterize, model and control the variations in composition, crystalline structure and transformation temperatures. Our approach is in-situ XRD study of the actual growth of the films of varying composition along the thickness carried out using a deposition chamber installed at a synchrotron radiation beamline. These studies were complemented with ex-situ analysis techniques. The results achieved on a Ni-Ti film co-sputtered from Ni-Ti and Ti targets on a TiN buffer layer are presented in this paper. The deposition started by using optimised parameters for a near equiatomic composition. After 1 h (≈330 nm thick film), the Ti power was increased from 20 to 25 W, leading to the precipitation of Ti2Ni. The evolution of the lattice parameter values of the B2 phase, calculated from the corresponding XRD data, is clearly linked with the increase of the Ti power. The depth profile of the atomic concentrations determined by Auger Electron Spectroscopy (AES) is in agreement with the in situ XRD results. The temperature dependence of the electrical resistivity was used to monitor phase transformations, Scanning Electron Microscopy (SEM) has shown the presence of twinned martensite on the film’s surface at room temperature.
  • Lecture (Conference)
    Materials 2007 (IV International Materials Symposium), 01.-04.04.2007, Porto, Portugal
  • Materials Science Forum 587-588(2008), 672-676

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Publ.-Id: 9730


The interfacial diffusion zone in magnetron sputtered Ni-Ti thin films deposited on different Si substrates studied by HR-TEM

Martins, R. M. S.; Beckers, M.; Mücklich, A.; Schell, N.; Silva, R. J. C.; Mahesh, K. K.; Braz Fernandes, F. M.
Ni-Ti Shape Memory Alloy thin films are suitable materials for microelectromechanical devices. During the deposition of Ni-Ti thin films on Si substrates, there exist interfacial diffusion and chemical interactions at the interface due to the high temperature processing necessary to crystallize the film. For the present study, Ni-Ti thin films were prepared by magnetron cosputtering from Ni-Ti and Ti targets in a specially designed chamber mounted on the 6-circle goniometer of the ROssendorf BeamLine (ROBL-CRG) at ESRF, Grenoble (France). The objective of this study has been to investigate the interfacial structure resulting from depositions (at a temperature of ≈ 470°C) on different substrates: naturally oxidized Si(100), Si(111) and poly-Si substrates. A detailed High-Resolution TEM analysis of the interfacial structure has been performed. When Ni-Ti is deposited on Si(100) substrate, a considerable diffusion of Ni into the substrate takes place, resulting in the growth of semi-octaeder A-NiSi2 silicide. In the case of Ni-Ti deposited on Si(111), there appears an uniform thickness plate, due to the alignment between substrate orientation and the [111]-growth front. For Ni-Ti deposited on poly-Si, the diffusion is inhomogeneous. Preferential diffusion is found along the columnar grains of poly-Si, which are favourably aligned for Ni diffusion. These results show that for the Ni-Ti/Si system, the morphology of the diffusion interface is strongly dependent on the type of substrates.
  • Poster
    Materiais 2007 (IV International Materials Symposium), 01.-04.04.2007, Porto, Portugal
  • Materials Science Forum 587-588(2008), 820-823

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Publ.-Id: 9729


Sputter deposition of high-temperature NiTiHf shape memory thin films

Martins, R. M. S.; Schell, N.; Zhou, S.; Beckers, M.; Silva, R. J. C.; Mahesh, K. K.; Braz Fernandes, F. M.
  • Poster
    Materiais 2007 (IV International Materials Symposium), 01.-04.04.2007, Porto, Portugal

Permalink: https://www.hzdr.de/publications/Publ-9728
Publ.-Id: 9728


In-situ study of the ion bombardment of Ni-Ti thin films

Martins, R. M. S.; Schell, N.; von Borany, J.; Braz Fernandes, F. M.
  • Poster
    ESRF Users' Meeting 2007, 07.02.2007, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-9727
Publ.-Id: 9727


Experiments with real photons for nuclear astrophysics

Wagner, A.
Research on experiments using real photons from bremsstrahlung production at ELBE is presented in an invited talk at the annual spring meeting of the german physical society.
Keywords: bremsstrahlung ELBE photons nuclear astrophysics
  • Invited lecture (Conferences)
    DPG Frühjahrstagung, 12.-16.03.2007, Giessen, Germany

Permalink: https://www.hzdr.de/publications/Publ-9726
Publ.-Id: 9726


Fast optical tomography for transient process diagnostics

Schleicher, E.; Hampel, U.; Da Silva, M. J.; Thiele, S.
Optical tomography is a potential technique for the visualisation of fast transient phenomena in multiphase flows. It can be applied for liquid-liquid, gas-liquid and gas-solid flows as long as the flow consists of a major transparent component/phase, such as a liquid or gas, and a minor component/phase that alters the intensity or light ray propagation path, such as solid particles or gas bubbles. The technique is also applicable in single phase flows with dye tracer marked fluid volumes. Recently we have built a fast optical tomography system that achieves frame rates up to 5 kfps and can be applied to study bubbly two-phase flows in pipes with an inner diameter of two inches. High frame rate at high spatial resolution in the range of 3 mm is obtained by application of a specially developed fully parallel 64 channel data logger with 1MSample simultaneous sampling frequency. The tomography system works similar to an X-ray computed tomography system. As radiation emitters we use 256 LEDs and as detector elements 32 avalanche photo diodes which are optically connected to the tomographic cross section be means of plastic optical fibres. For image reconstruction we use conventional CT algorithms. These algorithms, however, suffer to some degree from the non-linear attenuation of the light at phase boundaries due to total reflection or refraction. Therefore, we currently develop improved image reconstruction algorithms which use a binary reconstruction scheme together with a-priori information on the gas phase. With the new fast optical tomograph we have investigated different two and single phase flow phenomena and compared different image reconstruction algorithms concerning their quantitative accuracy. Especially for lower void fractions in bubble flow or lower particle numbers in liquids we get reliable high resolution images of the cross section at very high temporal resolution.
Keywords: Keywords Optical tomography, multiphase flow sensors
  • Contribution to proceedings
    5th World Congress on Industrial Process Tomography, 03.-06.09.2007, Bergen, Norway
  • Invited lecture (Conferences)
    5th World Congress on Industrial Process Tomography, 03.-06.09.2007, Bergen, Norway

Permalink: https://www.hzdr.de/publications/Publ-9725
Publ.-Id: 9725


A comparative experimental analysis of the a-C:H deposition processes using CH4 and C2H2 as precursors

Peter, S.; Graupner, K.; Grambole, D.; Richter, F.
The plasma enhanced chemical vapor deposition of a-C:H films using methane and acetylene as precursors was studied. Non-invasive in-situ techniques were used to analyze the plasma processes with respect to the self-bias voltage, the displacement currents to the grounded electrode, the neutral gas composition, the optical sheath thickness as well as current and energy of the ions hitting the powered electrode. The a-C:H films were characterized for their deposition rate, surface roughness, hardness, mass density and hydrogen content. Ion mean free paths, suitable for low pressure RF sheaths, have been quantified for both precursors. The film with the highest hardness of 25 GPa was formed in the C2H2 discharge when the mean energy per deposited carbon atom was about 50 eV. The hardness obtained with the CH4 discharge was lower at 17 GPa and less sensitive to changes in the process parameters. It was found that the creation of hard (hardness > 15 GPa) a-C:H films from both precursors is possible if the mean energy per deposited carbon atom exceeds only ~ 15 eV. Further film characteristics like surface roughness and hydrogen content show the interplay of ion flux and deposition from radicals to form the a-C:H structure and properties.
  • Journal of Applied Physics 102(2007)5, 53304

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Publ.-Id: 9724


Spectroscopic identifications of U(VI) species sorbed by the green algae Chlorella vulgaris

Günther, A.; Raff, J.; Geipel, G.; Bernhard, G.
The green algae Chlorella vulgaris has the ability to bind high amounts of uranium(VI) in the pH range from 3 to 6. At pH 3 up to 40 % of the uranium was bound by the algal cells. The uranium removal is almost complete at pH 5 and 6 under the given experimental conditions. Scanning electron microscopy and laser-induced fluorescence spectroscopy were used to characterize formed uranyl species in the selected pH range. Thus demonstrating the regular distribution of U(VI) on the cell surface. Fluorescence spectroscopic investigations of formed complexes outside/inside the cells indicate, the binding of U(VI) to carboxyl groups plays a dominating role at pH 3. Whereas a minor impact of organic phosphate compounds on the U(VI) sorption can not be excluded. In contrast the phosphate groups are mainly responsible for the removal and immobilization of U (VI) at pH 5 and 6 by formation of organic or/and inorganic uranyl phosphates.
Keywords: uranium(VI), green algae, sorption, complexation, TRLFS, REM-EDX

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Permalink: https://www.hzdr.de/publications/Publ-9723
Publ.-Id: 9723


Entrapped Bonded Hydrogen in a Fullerene - the five atomic Cluster Sc3CH in C80

Krause, M.; Ziegs, F.; Popov, A. A.; Dunsch, L.
The synthesis and characterisation of the new endohedral clusterfullerene Sc3CH@C80 is reported. The encapsulation of the first hydrocarbon cluster inside a fullerene was achieved by the arc burning method in a reactive CH4 atmosphere. The extensive characterisation by MS, HPLC, Sc-NMR, ESR, UV-Vis-NIR and Raman spectroscopy provided the experimental evidence for the caging of the five-atomic Sc3CH cluster inside the C80 cage isomer with icosahedral symmetry. The proposed new structure was confirmed by DFT calculations, which gave a closed shell and large energy gap structure. Thus a pyramidal Sc3CH cluster and the Ih-C80 cage were shown to be the most stable configuration for Sc3CH@C80 whereas alternative structures give a smaller bonding energy as well as a smaller energy gap.
Keywords: Endohedral Fullerenes Hydrogen Encapsulation in Carbon Nanostructures Molecular Clusters Mass Spectrometry NMR Spectroscopy

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Publ.-Id: 9721


Application of the small-punch-test to irradiated reactor vessel steels in the brittle-ductile transition region

Linse, T.; Kuna, M.; Schuhknecht, J.; Viehrig, H.-W.
The warranty of the high safety standards of existing nuclear power plants requires the assessment and characterization of the actual material state changing during service, e.g. embrittlement due to irradiation. In the brittle and brittle-ductile transition region, ferritic steels fail due to transcrystalline or intercrystalline cleavage fracture starting at flaws resulting from microplastic deformations. The large scatter of fracture mechanical properties in the transition region originating from statistically distributed flaws can be described by Weibull theory. Using the Beremin local approach model, the probability of cleavage fracture at a certain load state can be quantified.
In the small-punch-testing, a quadratical specimen lying on a die is loaded centrically and deformed vertically by a spherical punch, hence starting at plate-like bending and ending in a deep drawing process. Large parts of the specimen are exposed to a biaxial stress state, making the test rather suitable to represent the actual stress state observed in pressure vessel steels in service than other miniaturized methods such as tension or bending tests. Due to the tiny specimen size, material remnants of ongoing surveillance programs (slices of Charpy-specimen) can be used. A special small-punch device was manufactured to be installed into a testing machine in hot cells. To enable testing at temperatures down to -185°C, a cooling system based on liquid nitrogen is used. Neural networks are used to solve the inverse problem of finding material parameters from measured load-displacement-curves. Having identified the parameters describing hardening, Weibull-parameters are determined from both experimental data, e.g. displacement of the punch at fracture, and calculated stress distribution inside the specimen, obtained from FE calculations using the identified plastic properties. The reactor vessel steel A508 (IAEA JFL) is characterized at different levels of irradiation and different temperatures, covering brittle and brittle-ductile transition region of the steel.
Keywords: small specimen testing, small punch test, parameter identification, transition region, inverse method
  • Lecture (Conference)
    ASTM E10 Fifth Symposium on Small Specimen Test Techniques, 31.01.-01.02.2007, Anaheim, USA
  • Journal of ASTM International 5(2008)4
    DOI: 10.1520/JAI101008

Permalink: https://www.hzdr.de/publications/Publ-9720
Publ.-Id: 9720


Usage of small-punch-test for the characterisation of reactor vessel steels in the brittle-ductile transition region

Linse, T.; Kuna, M.; Schuhknecht, J.; Viehrig, H.-W.
This paper presents a method for the identification of hardening parameters in the brittle-ductile transition region and the determination of WEIBULL parameters in the brittle region. A small-punch-test device is developed for hot cells, where a miniaturised disk-like specimen is manufactured and deformed by a spherical punch. Its load-displacement-curve is analysed regarding its information about the material behaviour. Using Neural Networks, an identification routine is presented, which avoids time-consuming calculations with FEM during an optimisation algorithm. Identified material properties are compared with data from tensile tests. WEIBULL parameters are calculated for temperatures at which cleavage fracture occurs using the identified hardening parameters.
Keywords: small specimen testing, small punch test, parameter identification, transition region, inverse method

Permalink: https://www.hzdr.de/publications/Publ-9719
Publ.-Id: 9719


Photoluminescence from cadmium sulfide nanoclusters formed in the matrix of a Langmuir-Blodgett film

Bagaev, E. A.; Zhuravlev, K. S.; Sveshnikova, L. L.; Badmaeva, I. A.; Repinskii, S. M.; Voelskow, M.
Photoluminescence (PL) from CdS nanoclusters formed in the matrix of a Langmuir-Blodgett film and from the same clusters with the matrix removed has been studied. The PL spectrum of clusters in the matrix has the form of a broad band (full width at half-maximum (FWHM) ∼ 0.6 eV) peaked at 2.4 eV. After removing the matrix with hexane, the PL spectrum consists of a high-energy band at 2.9 eV (FWHM ∼ 0.2 eV) and two low-energy bands at 2.4 and 2.0 eV (FWHM ∼ 0.5 eV). The high-energy band is attributed to exciton recombination in the nanoclusters, and the bands at 2.4 and 2.0 eV, to recombination via levels related to defects in the bulk of the matrix and at the nanocluster-matrix interface, respectively.
Keywords: Photoluminescence, CdS, nanocluster
  • Semiconductors 37(2003)11, 1321-1325
  • Fizika i Tekhnika Poluprovodnikov 37(2003)11, 1358-1362

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Permalink: https://www.hzdr.de/publications/Publ-9718
Publ.-Id: 9718


Annealing studies of Al-implanted 6H-SiC in an induction furnace

Ottaviani, L.; Lazar, M.; Locatelli, M. L.; Chante, J. P.; Heera, V.; Skorupa, W.; Voelskow, M.; Torchio, P.
6H-SiC samples were amorphised by multiple Al implantations at room temperature, in order to study the annealing process. The paper deals with the influence of specific annealing conditions, such as furnace atmosphere and heating rate, on SiC reordering and Al profile. Below a certain deposited nuclear energy, solid phase epitaxy is possible and leads to recrystallisation under precise conditions (high heating rate, silicon partial pressure prescribed). Above it, material etching and dopant losses are observed, even though annealing has proven to be efficient for avoiding surface impairment (due to a specific cleaning process).
Keywords: Silicon carbide; Annealing; Surface roughness; SIMS
  • Materials Science and Engineering B 91-92(2002), 325-328

Permalink: https://www.hzdr.de/publications/Publ-9717
Publ.-Id: 9717


Post mortem investigations of the NPP Greifswald WWER-440 reactor pressure vessels

Viehrig, H.-W.; Rindelhardt, U.; Schuhknecht, J.
The investigation of reactor pressure vessel (RPV) materials from decommissioned NPPs offers the unique opportunity to scrutinize the irradiation behaviour under real conditions. Trepans taken from the whole RPV wall enable a comprehensive material characterisation. The paper describes the trepanning technology applied to the decommissioned WWER-440/230 RPVs of the Greifswald NPP. The Greifswald RPVs represent different material conditions such as irradiated, irradiated and recovery annealed and irradiated, recovery annealed and re-irradiated. The working program is focussed on the characterisation of the RPV steels (base and weld metal) through the RPV wall. The key part of the testing is aimed at the determination of the reference temperature T0 following the ASTM Test Standard E1921-05 to determine the fracture toughness of the RPV steel in different thickness locations. In a first step the material of the core welding seam was investigated. It could be shown that the Master Curve approach as adopted in E1921 is applicable to the investigated original RPV weld metal. The weld metal located in a distance of about 22 mm from the inner surface of the RPV wall yielded a T0 of 50°C which is about 40K higher than T0 close to the inner surface. This outcome is important for the assessment of results retrieved from so called boat samples taken directly from the RPV surface after the recovery annealing. It shows that boat samples do not represent the material with the lowest toughness.
Keywords: nuclear power plant, WWER type, reactor pressure vessel, weld metal, integrity assessment, neutron embrittlement, mechanical testing, fracture toughness, Master Curve concept
  • Contribution to proceedings
    19th International Conference on Structural Mechanics in Reactor Technology (SMiRT-19), 12.-17.08.2007, Toronto, Canada
    Proceedings of the 19th International Conference on Structural Mechanics in Reactor Technology
  • Lecture (Conference)
    19th International Conference on Structural Mechanics in Reactor Technology (SMiRT-19), 12.-17.08.2007, Toronto, Canada

Permalink: https://www.hzdr.de/publications/Publ-9716
Publ.-Id: 9716


Properties of Ge nanocrystals formed by implantation of Ge+ ions into SiO2 films with subsequent annealing under hydrostatic pressure

Tyschenko, I. E.; Talochkin, A. B.; Cherkov, A. G.; Zhuravlev, K. S.; Misiuk, A.; Voelskow, M.; Skorupa, W.
The influence of hydrostatic compression on the implantation-induced synthesis of Ge nanocrystals in SiO2 host was studied. It is found that high-temperature annealing under pressure leads to retardation of Ge diffusion in SiO2. It is shown that unstressed Ge nanocrystals are formed as a result of conventional annealing (under atmospheric pressure). Annealing under pressure is accompanied by formation of hydrostatically stressed Ge nanocrystals. The stress in Ge nanocrystals was determined from optical-phonon frequencies in the Raman spectra. The shift of Raman resonance energy (E 1, E 1 + Δ1) corresponds to the quantization of the ground-state energy for a two-dimensional exciton at the critical point M 1 of germanium. It is ascertained that a photoluminescence band peaked at 520 nm is observed only in the spectra of the films which contain stressed Ge nanocrystals.
Keywords: Ge, Ion implantation, SiO2, diffusion, nanocrystals
  • Semiconductors 37(2003)4, 462-467
  • Fizika i Tekhnika Poluprovodnikov 37(2003)4, 479-484

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Permalink: https://www.hzdr.de/publications/Publ-9715
Publ.-Id: 9715


Curium(III) complexation with pyoverdins secreted by a groundwater strain of Pseudomonas fluorescens

Moll, H.; Johnsson, A.; Schäfer, M.; Pedersen, K.; Budzikiewicz, H.; Bernhard, G.
Pyoverdins, bacterial siderophores produced by ubiquitous fluorescent Pseudomonas species, have great potential to bind and thus transport actinides in the environment. Therefore, the influence of pyoverdins secreted by microbes on the migration processes of actinides must be taken into account in strategies for the risk assessment of potential nuclear waste disposal sites. The unknown interaction between curium(III) and the pyoverdins released by Pseudomonas fluorescens (CCUG 32456) isolated from the granitic rock aquifers at the Äspö Hard Rock Laboratory (Äspö HRL), Sweden, is the subject of this paper.
The interaction between soluble species of curium(III) and pyoverdins was studied at trace curium(III) concentrations (3  10 -7 M) using time-resolved laser-induced fluorescence spectroscopy (TRLFS). Three Cm3+  P. fluorescens (CCUG 32456) pyoverdin species, MpHqLr, could be identified from the fluorescence emission spectra, CmH2L+, CmHL, and CmL-, having peak maxima at 601, 607, and 611 nm, respectively. The large formation constants, log β121 = 32.50 ± 0.06, log β111 = 27.40 ± 0.11, and log β101 = 19.30 ± 0.17, compared to those of other chelating agents illustrate the unique complexation properties of pyoverdin-type siderophores. An indirect excitation mechanism for the curium(III) fluorescence was observed in the presence of the pyoverdin molecules.
Keywords: Curium; Pyoverdin; Fluorescence spectroscopy; TRLFS; Complexation

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Publ.-Id: 9714


Real-time spectroscopic ellipsometry of silver nanoparticle formation in poly(vinyl alcohol) thin films

Oates, T. W. H.; Christalle, E.
Silver nanoparticle formation in poly(vinyl alcohol) thin films is analyzed in real time by spectroscopic ellipsometry. Modeling the data using the Maxwell-Garnett theory shows that the silver content predicted by the model depends of the film thickness. This is conjectured to be due to the absence of plasmon resonances in very small particles affecting the model. The size dependence of the free electron relaxation frequency is used to analyze the particle size during nucleation and growth. Evaporation of the polymer matrix is also monitored by real time ellipsometry and the plasmon resonance is observed to shift from 3.0 to 2.2 eV as the particles are liberated from the polymer. The particle density on the surface can be controlled by the silver concentration and the initial polymer thickness. The exposed particles are easily imaged with scanning electron microscopy, and the particle sizes are compared to the parameters predicted from the Maxwell-Garnett theory.
  • Journal of Physical Chemistry C 111(2007), 182-187

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Publ.-Id: 9713


Heating of the edge of a metal sheet in the container-less melt extraction of fibres

Cramer, A.; Priede, J.; Galindo, V.; Gerbeth, G.; Andersen, O.; Kostmann, C.
The present work is concerned with the metallurgical process of melt extraction. Certain industrial requirements, e.g. high purity and small cross-sectional area of the extracted fibres, require a geometrically strictly confined melt volume that is not in contact with any other material being a potential source of pollution. Hitherto, the pending drop method is embodied on small scale facilities. It suffers from low productivity because only one edge can be used to tear a filament out off the molten droplet forming at the tip of a heated rod. Here, a modification is proposed that uses extraction from a pending molten edge at the lower end of a metal sheet. Being a trivial task by all appearances, closer examination shows that it is not. Almost any embodiment of the pending drop technique makes use of locally confined sources of heat, i.e. an acetylene-oxygen torch, or, in the case of high valued materials, laser or electron beams. As attempts to employ induction heating to a single drop did not work even there, it is all the more difficult to melt a sheet along its entire edge rather than between the two opposing branches of an inductor. Tailoring of the induction heating magnetic field, the basic feature of which is the same direction of the electric current in both branches of the inductor, solved the problem. A proper choice of geometry, electrical conductivities of both extraction and substrate material, and the frequency of the alternating magnetic field have proven to be essential for the extraction process. Melting a platinum sheet at the edge and extraction of fibres only 25 micron in effective cross-section from a tin sheet was successfully demonstrated in model experiments.
  • Contribution to proceedings
    HES-07 International Symposium on Heating by Electromagnetic Sources, 20.-22.06.2007, Padua, Italy, 88-89884-07-X, 445-452
  • Lecture (Conference)
    HES-07 International Symposium on Heating by Electromagnetic Sources, 20.-22.06.2007, Padua, Italy

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Publ.-Id: 9712


Magnetization of RuSr2GdCu2O8 in pulsed magnetic fields up to 47 T

Papageorgiou, T. P.; Casini, E.; Skourski, Y.; Herrmannsdörfer, T.; Freudenberger, J.; Braun, H. F.; Wosnitza, J.
Magnetization measurements in pulsed magnetic fields up to 47 T were utilized to estimate the average Ru moment in polycrystalline RuSr2GdCu2O8. A NbSr2GdCu2O8 sample was used as reference. The extracted Ru moment of about 1.8µB at 4.2 K and 47 T is indicative of a mixed-valence state of Ru involving Ru5+ and Ru4+ ions with magnetic moments of 2µB/Ru5+ and 0.9µB/Ru4+. The estimated ratio of Ru5+:Ru4+≈ 87%:13% corresponds to a hole concentration p≈0.065 in the CuO2 planes suggesting an underdoped nature of the superconducting state. We propose that the magnetic structure of the Ru moments corresponds to an antiferromagnetic phase, involving only Ru5+ ions, interrupted by ferromagnetic stripes, where charge transfer between Ru4+and Ru5+ ions takes place.
  • Physical Review B 75(2007), 104513

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Publ.-Id: 9711


Topotaxial growth of Ti2AlN by solid state reaction in AlN/Ti(0001)multilayer thin films

Höglund, C.; Beckers, M.; Schell, N.; von Borany, J.; Birch, J.; Hultman, L.
The formation of Ti2AlN by solid state reaction between layers of wurtzite-AlN and alpha-Ti was characterized by in situ x-ray scattering. The sequential deposition of these layers by dual magnetron sputtering onto Al2O3 (0001) at 200°C yielded smooth, heteroepitaxial (0001) oriented films, with abrupt AlN/Ti interfaces as shown by x-ray reflectivity and Rutherford backscattering spectroscopy. Annealing at 400°C led to AlN decomposition and diffusion of released Al and N into the Ti layers, with formation of Ti3AlN. Further annealing at 500°C resulted in a phase transformation into Ti2AlN(0001) after only 5 min.

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Publ.-Id: 9709


Ultra-shallow junctions produced by plasma doping and flash lamp annealing

Skorupa, W.; Yankov, R. A.; Anwand, W.; Voelskow, M.; Gebel, T.; Downeyc, D. F.; Arevaloc, E. A.
The capabilities of plasma doping (PLAD) and flash lamp annealing (FLA) for use in ultra-shallow junction (USJ) fabrication have been evaluated. Silicon wafers have been doped in a BF3 plasma using wafer biases ranging from 0.6 to 1 kV and a dose of 4 × 1015 cm−2. The wafers so implanted have been heat-treated by FLA using pre-heating temperatures in the range of 500–700 °C, peak temperatures of 1100–1350 °C, and effective anneal times of 20 and 3 ms. Secondary ion mass spectrometry (SIMS) and sheet resistance measurements have been undertaken to determine the junction depth and the sheet resistance, respectively. Optimum processing conditions have been identified under which both high electrical activation and insignificant dopant diffusion occur compared to the as-implanted state. In this way, one can obtain combinations of junction depth and sheet resistance that meet the 45 nm technology node requirements.
Keywords: Flash lamp annealing; Plasma doping; Ultra-shallow junctions
  • Materials Science and Engineering B 114-115(2004), 358-361

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Publ.-Id: 9707


Comparative Study of Scintillators for PET/CT Detectors

Nassalski, A.; Kapusta, M.; Batsch, T.; Wolski, D.; Möckel, D.; Enghardt, W.; Moszynski, M.
A growing interest in the development of dual modality PET/CT scanners prompts the comparative study of numerous scintillators to select the best one, which could be used simultaneously in PET detectors working in the pulsing mode and in the CT detectors working in the current mode. In the comparative measurements, done in the same experimental conditions, various samples of BGO, GSO, GSO:Ce,Zr, LGSO, LSO, LYSO, MLS, LaCl3, LaBr3 and CWO scintillators were tested. The measurements covered a determination of the light output, energy resolution, non-proportionality of the light yield, decay times of the light pulses and for the selected crystals their time resolution for 511 keV annihilation quanta. Moreover, a comparative study of afterglow, induced by 60 keV gamma-rays from a strong 241-Am source (13.9 GBq), was done in the second range of time. The LSO-like crystals are best in the PET scanners application. However, they do not fit to the CT requirements, due to a high afterglow. The studies conclude that besides of the well known BGO, only GSO:Ce and most likely LaBr3 might be considered for the simultaneous PET/CT detectors.
Keywords: Image analysis and processing, NMIS, PET instrumentation, reconstruction algorithms

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Publ.-Id: 9706


Behavior of germanium ion-implanted into SiO2 near the bonding interface of a silicon-on-insulator structure

Tyschenko, I. E.; Voelskow, M.; Cherkov, A. G.; Popov, V. P.
The properties of germanium implanted into the SiO2 layers in the vicinity of the bonding interface of silicon-on-insulator structures are studied. It is shown that, under conditions of high-temperature (1100 degrees C) annealing, germanium nanocrystals are not formed, while the implanted Ge atoms segregate at the Si/SiO2 bonding interface. It is established that, in this case, Ge atoms are found at sites that are coherent with the lattice of the top silicon layer. In this situation, the main type of traps is the positive-charge traps; their effect is interpreted in the context of an increase in the surface-state density due to the formation of weaker Ge-O bonds. It is found that the slope of the drain-gate characteristics of the back MIS transistors increases; this increase is attributed to an increased mobility of holes due to the contribution of an intermediate germanium layer formed at the Si/SiO2 interface.
Keywords: SOI SiO2
  • Semiconductors 41(2007)3, 291-296

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Publ.-Id: 9705


Scanning spreading resistance microscopy of defect engineered low dose SIMOX samples

Vines, L.; Kögler, R.; Kuznetsov, A. Y.
SIMOX (separation by implanted oxygen) process was studied using cross section scanning spreading resistance microscopy (SSRM). Firstly, open volume defects, nanocavities, have been introduced by He+ ion implantation in the region, where SiO2 precipitates were subsequently formed. Secondly, dual (simultaneous) oxygen (O+) and silicon (Si+) implantation was used to modify SiO2 reaction kinetics too. The results show that the He-induced nanocavities enhance the SiO2 formation presumably releasing excess strain associated with Si oxidation, while the use of a dual O+/Si+ beam do not influence significantly the oxidation kinetics in the initial state of the SIMOX process in our samples. Overall, SSRM was shown to be a suitable method for observation of the early stage of buried oxide formation in Si, since it measures the local resistivity, the main functional parameter of a SIMOX structure.
Keywords: Silicon on insulator, ion beam synthesis, SIMOX, simultaneous dual implantation
  • Microelectronic Engineering 84(2007), 547-550

Permalink: https://www.hzdr.de/publications/Publ-9704
Publ.-Id: 9704


Magnetic order in the S=1/2 two-dimensional molecular antiferromagnet copper pyrazine perchlorate Cu(Pz)2(ClO4)2

Lancaster, T.; Blundell, S. J.; Brooks, M. L.; Baker, P. J.; Pratt, F. L.; Manson, J. L.; Conner, M. M.; Xiao, F.; Landee, C. P.; Chaves, F. A.; Soriano, S.; Novak, M. A.; Papageorgiou, T. P.; Bianchi, A. D.; Herrmannsdörfer, T.; Wosnitza, J.; Schlueter, J. A.
We present an investigation of magnetic ordering in the two-dimensional S=1/2 quantum magnet Cu(Pz)2(ClO)4)2 using specific heat and zero-field muon-spin relaxation (µ+SR). The magnetic contribution to the specific heat is consistent with an exchange strength of 17.7(3) K. We find unambiguous evidence for a transition to a state of three-dimensional long-range order below a critical temperature TN=4.21(1) K using µ+SR even though there is no feature in the specific heat at that temperature. The absence of a specific heat anomaly at TN is consistent with recent theoretical predictions. The ratio of TN/J=0.24 corresponds to a ratio of intralayer to interlayer exchange constants of |J´ /J| =6.8x10−4, indicative of excellent two-dimensional isolation. The scaled magnetic specific heat of [Cu(Pz)2(HF2)]BF4, a compound with an analogous structure, is very similar to that of Cu(Pz)2(ClO)4)2 although both differ slightly from the predicted value for an ideal 2D S=1/2 Heisenberg antiferromagnet.
  • Physical Review B 75(2007), 094421

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Publ.-Id: 9703


Electron spin resonance in S = 1/2 Heisenberg chains with alternating g-tensor and the Dzyaloshinskii–Moriya interaction

Zvyagin, S. A.; Wosnitza, J.; Kolezhuk, A. K.; Krzystek, J.; Feyerherm, R.
Low-temperature ESR studies of copper pyrimidine dinitrate, a spin-1/2 antiferromagnetic chain with alternating g-tensor and the Dzyaloshinskii–Moriya interaction, are presented. The ESR linewidth and g-factor shift are investigated as function of temperature. The data are interpreted in frame of a new theoretical concept proposed recently by Oshikawa and Affleck [Phys. Rev. Lett. 82 (1999) 5136] and applied for precise calculations of the ESR parameters in S ¼ 1/2 antiferromagnetic chains in the perturbative spinon regime. Excellent quantitative agreement between the theoretical predictions and experiment is obtained.
  • Journal of Magnetism and Magnetic Materials 310(2007), 1209-1211

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Publ.-Id: 9702


Spin-triplet excitons and anisotropy effects in the S = 1/2 gapped antiferromagnet BaCuSi2O6

Zvyagin, S. A.; Wosnitza, J.; Krzystek, J.; Stern, R.; Jaime, M.; Sasago, Y.; Uchinokura, K.
BaCuSi2O6 can be regarded as an almost ideal realization of an S = 1/2 system of weakly interacting spin dimers with spin-singlet ground state and gapped excitation spectrum. We argue that the fine structure observed in low-temperature EPR spectra of BaCuSi2O6 is a fingerprint of triplet excitations (excitons). Analyzing the angular dependence of the exciton modes allows us to precisely calculate the zero-field splitting within the triplet states and, correspondingly, the anisotropy parameter, D = 0.07cm-1. The proposed procedure can be applied for studying anisotropy effects in a large number of S = 1/2 gapped quantum antiferromagnets with dimerized or alternating spin structure.
  • Journal of Magnetism and Magnetic Materials 310(2007), 1206-1208

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Publ.-Id: 9701


An intense channeling radiation source

Wagner, W.; Pawelke, J.; Azadegan, B.; Sobiella, M.; Steiner, J.; Zeil, K.
A nonconventional x-ray source based on the production of electron channeling radiation in a diamond crystal has been installed at the Radiation source ELBE. The brilliant electron beam with an average current up to 100 microA available in the radiation physics cave allows to reach photon rates of quasi-monochromatic channeling radiation of the order of 10^(11) s^(-1) per 10% bandwidth. On-line x-ray monitoring was realised using a Compton spectrometer. The photon energy can be tuned by variation of the beam energy. Monochromisation of channeling radiation and bremsstrahlung background reduction have been investigated applying x-ray diffraction on a HOPG crystal.
Keywords: channeling radiation, x-ray source, Compton spectrometer, HOPG crystal
  • Nuclear Instruments and Methods in Physics Research B 266(2008)2, 327-334

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Publ.-Id: 9700


Fermi surfaces of the half-Heusler compounds Ce1-xLaxBiPt

Bianchi, A. D.; Wosnitza, J.; Kozlova, N.; Freudenberger, J.; Schultz, L.; Opahle, I.; Elgazzar, S.; Richter, M.; Goll, G.; von Löhneysen, H.; Yoshino, T.; Takabatake, T.
We report on the Fermi surface in the correlated half-Heusler compounds Ce1xLaxBiPt. In CeBiPt, as well as in Ce0:95La0:05BiPt, we find a temperature-dependent Fermi-surface topology. In addition, we observe a field-induced change of the electronic band structure as discovered by electrical-transport measurements in pulsed magnetic fields. For magnetic fields above 25 T, in a simple one band picture, the charge-carrier concentration determined from Hall-effect measurements increases nearly 30%, whereas the Shubnikov-de Haas (SdH) signal disappears at the same field. In the non-4f compound LaBiPt the Fermi surface remains unaffected, suggesting that these features are intimately related to the Ce 4f electrons. Electronic band–structure calculations point to a 4f-polarization-induced change of the Fermi-surface topology.
  • Journal of Magnetism and Magnetic Materials 310(2007), e261-e263

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Publ.-Id: 9699


From Thermodynamically Driven Phase Transitions to Quantum Critical Phenomena

Wosnitza, J.
In this short review some basic concepts of phase transitions at non-zero and zero temperature are highlighted. For that the critical behavior of classical, thermodynamically driven magnetic phase transitions is exemplified for conventional universality classes as well as for systems reflecting chiral order. Finally the quantum critical phenomena for two magnetic-field-driven phase transitions are presented.
  • Journal of Low Temperature Physics 147(2007), 249-278

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Publ.-Id: 9698


Intrinsic vs. extrinsic inelastic scattering contributions in κ-(BEDT-TTF)2Cu[N(CN)2]Br - Transport measurements under hydrostatic pressure

Strack, C.; Akinci, C.; Paschenko, V.; Wolf, B.; Uhrig, E.; Assmus, W.; Schreuer, J.; Wiehl, L.; Schlueter, J.; Wosnitza, J.; Schweitzer, D.; Lang, M.
Interlayer-resistivity measurements have been performed on a variety of single crystals of the quasi-two-dimensional organic superconductor k-(BEDT-TTF)2Cu[N(CN)2]Br. These crystals, which have been synthesized along two somewhat different routes, reveal strongly sample-dependent resistivity profiles: while the majority of samples shows a more or less pronounced r(T) maximum around 90 K with a semiconducting behaviour above, some crystals remain metallic at all temperatures T 300 K. In the absence of significant differences in the crystals’ structural parameters and chemical compositions, as proved by high-resolution X-ray and electron-probe-microanalysis [C. Strack et al., Phys. Rev. B 72 (2005) 054511], these results indicate that real structure phenomena, i.e. disorder and/or defects, may strongly affect the inelastic scattering. Comparative resistivity measurements under He-gas pressure on two crystals with strongly differing r(T) profiles indicate that these additional, sample-dependent scattering contributions are characterized by an extraordinarily strong pressure response which is highly non-monotonous as a function of temperature. No correlations have been found between the strength of these scattering contributions and other characteristic properties such as the glass transition at Tg ¼ 77 K, the temperature T*z40 K, where the temperature dependence of the resistivity changes rather abruptly, or the superconducting transition temperature Tc.
  • Comptes Rendus Chimie 10(2007), 96-100

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Publ.-Id: 9697


Flavonoids affect actin functions in cytoplasm and nucleus

Boehl, M.; Tietze, S.; Sokoll, A.; Madathil, S.; Pfennig, F.; Apostolakis, J.; Fahmy, K.; Gutzeit, H. O.
Based on the identification of actin as a target protein for the flavonol quercetin, the binding affinities of quercetin and structurally related flavonoids were determined by flavonoid-dependent quenching of tryptophan fluorescence from actin. Irrespective of differences in the hydroxyl pattern, similar Kd values in the 20 µM range were observed for six flavonoids encompassing members of the flavonol, isoflavone, flavanone, and flavane group. The potential biological relevance of the flavonoid/actin interaction in the cytoplasm and the nucleus was addressed using an actin polymerization and a transcription assay, respectively. In contrast to the similar binding affinities, the flavonoids exert distinct and partially opposing biological effects: while flavonols inhibit actin functions, the structurally related flavane epigallocatechin promotes actin activity in both test systems. Infrared spectroscopic evidence reveals flavonoid-specific conformational changes in actin which may mediate the different biological effects. Docking studies provide models of flavonoid binding to the known small molecule-binding sites in actin. Among these, the mostly hydrophobic tetramethylrhodamine-binding site is a prime candidate for flavonoid binding and rationalizes the high efficiency of quenching of the two closely located fluorescent tryptophans. The experimental and theoretical data consistently indicate the importance of hydrophobic, rather than H-bond-mediated actin-flavonoid interactions. Depending on the rigidity of the flavonoid structures, different functionally relevant conformational changes are evoked through an induced fit.
Keywords: binding studies, fluorescence spectroscopy, infrared spectroscopy, molecular modelling

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Publ.-Id: 9696


Tollmien-Schlichting wave cancellation using an oscillating Lorentz force

Albrecht, T.; Metzkes, H.; Mutschke, G.; Grundmann, R.; Gerbeth, G.
Oscillating Lorentz forces are used to control transition in a flat-plate boundary layer.
Keywords: boundary layer, transition, control, Lorentz force
  • Lecture (Conference)
    5th International Symposium on Turbulence and Shear Flow Phenomena, 27.-29.08.2007, München, Germany
  • Contribution to proceedings
    5th International Symposium on Turbulence and Shear Flow Phenomena, 27.-29.08.2007, München, Germany
    Proceedings of the 5th International Symposium on Turbulence and Shear Flow Phenomena, vol. 2, 419-423

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Publ.-Id: 9695


Tollmien-Schlichting wave cancellation using an oscillating Lorentz force

Albrecht, T.; Metzkes, H.; Mutschke, G.; Grundmann, R.; Gerbeth, G.
Oscillating Lorentz forces are used to control the development of Tollmien-Schlichting waves in a flat-plate boundary layer
Keywords: boundary layer, transition control, Lorentz force
  • Lecture (Conference)
    ETC11 - EUROMECH European Turbulence Conference, 25.-28.06.2007, Porto, Portugal
  • Contribution to proceedings
    ETC11 - EUROMECH European Turbulence Conference, 25.-28.06.2007, Porto, Portugal
    ADVANCES IN TURBULENCE XI. Springer Proceedings in Physics vol. 117. Proceedings of the 11th EUROMECH European Turbulence Conference, Heidelberg: Springer, 978-3-540-72603-6, 218-220

Permalink: https://www.hzdr.de/publications/Publ-9694
Publ.-Id: 9694


Electromagnetic control of separation at hydrofoils

Mutschke, G.; Weier, T.; Albrecht, T.; Gerbeth, G.; Grundmann, R.
Lorentz forces originating from surface-mounted actuators of permanent magnets and electrodes in weakly conducting fluids like seawater provide a convenient tool for separation control at hydrofoils. A well-known actuator design of alternating stripes of permanent magnets and externally fed electrodes is considered which creates a mainly streamwise Lorentz force that is exponentially decaying in wall-normal direction. Separation control by steady forcing at the suction side and by oscillatory forcing near the leading edge of a symmetric foil is investigated numerically, mostly in the post-stall regime. The results are based on direct numerical simulations in the laminar flow regime in order to reveal basic control phenomena as well as on simulations using turbulence modelling at higher Reynolds numbers which are closer to possible naval application.
By applying a strong enough steady control, separation can always be completely suppressed. The scaling behaviour of the maximum lift gain Delta C_L^{max} in the turbulent regime nicely agrees with experimental results. - Oscillatory forcing always has to compete with the natural shedding process, lock-in behavior may occur. Lift-optimum control for strong amplitudes is found in a frequency band around the natural shedding frequency. In terms of the momentum coefficient describing the control effort, appropriate excitation frequencies in relation to the natural vortex shedding frequency allow for a more effective lift control than steady forcing for small lift gains; for large lift enhancement the energetic effort seems to approach the level of steady control.
Keywords: electromagnetic flow control, separation control, wings, numerical simulation, incompressible flow.
  • Lecture (Conference)
    IUTAM Symposium on Unsteady Separated Flows and their Control, 18.-22.06.2007, Kerkyra (Corfu), Greece

Permalink: https://www.hzdr.de/publications/Publ-9693
Publ.-Id: 9693


Inhomogeneous MUSIG model – a population balance approach for polydispersed bubbly flows

Krepper, E.; Frank, T.; Lucas, D.; Prasser, H.-M.; Zwart, P. J.
A generalized inhomogeneous Multiple Size Group (MUSIG) Model based on the Eulerian modeling framework was developed in close cooperation of ANSYS-CFX and Forschungszentrum Dresden-Rossendorf and implemented into CFX-10. Simulating a poly-dispersed gaseous liquid two phase flow along with the mass exchanged between bubble size classes by bubble coalescence and bubble fragmentation and the momentum exchange of bubble size dependent bubble forces have to be considered. Particularly the lift force has been proved to play an important role establishing a certain flow regime.
The derived model has been validated against experimental data from the TOPFLOW test facility at the Forschungszentrum Dresden (FZD). The wire mesh measuring technology measuring local gas volume fractions, bubble size distributions and velocities of gas and liquid was applied. Numerous tests investigating air water flow and steam water flow at saturation conditions in vertical pipes having a length up to 8 m and a diameter up to 200 mm were performed and used for model validation. To check the model framework for a more complex flow situation in further experiments on the flow field around a half moon shaped asymmetric obstacle were performed and simulated by applying the inhomogeneous MUSIG model.
The paper describes the main concepts of the model approach and presents model validation and application cases. The inhomogeneous MUSIG model approach was shown to be able to describe of bubbly flow with higher gas content. Particularly the separation phenomenon of small and large bubbles which was proven to be a key phenomenon for the establishment of the corresponding flow regime is well described. Weaknesses in this approach can be attributed to the characterization of bubble coalescence and bubble fragmentation, which must be further investigated.
Keywords: Bubbly flow, CFD, Non-drag forces, bubble break up, bubble coalescence, population balance, validation
  • Contribution to proceedings
    NURETH-12 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics, 30.09.-04.10.2007, Pittsburgh, USA
  • Lecture (Conference)
    NURETH-12 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics, 30.09.-04.10.2007, Pittsburgh, USA

Permalink: https://www.hzdr.de/publications/Publ-9692
Publ.-Id: 9692


CFD-modelling of insulation debris transport phenomena in water flow

Krepper, E.; Cartland-Glover, G.; Grahn, A.; Weiss, F.-P.; Alt, S.; Hampel, R.; Kästner, W.; Seeliger, A.
The investigation of insulation debris generation, transport and sedimentation becomes more important with regard to reactor safety research for PWR and BWR, when considering the long-term behavior of emergency core coolant systems during all types of loss of coolant accidents (LOCA). The insulation debris released near the break during a LOCA incident consists of a mixture of disparate particle population that varies with size, shape, consistency and other properties. Some fractions of the released insulation debris can be transported into the reactor sump, where it may perturb/impinge on the emergency core cooling systems.
Open questions of generic interest are for example the particle load on strainers and corresponding pressure drop, the sedimentation of the insulation debris in a water pool, its possible re-suspension and transport in the sump water flow. A joint research project on such questions is being performed in cooperation with Institute of Process Technology, Process Automation and Measuring Technology (IPM) Zittau. The project deals with the experimental investigation and the development of CFD models for the description of particle transport phenomena in coolant flow. While the experiments are performed at the IPM-Zittau, the theoretical work is concentrated at Forschungszentrum Dresden-Rossendorf.
Whereas the paper Alt et al. is focused on the experiments in the current paper the basic concepts for CFD modeling are described and feasibility studies including the conceptual design of the experiments are presented.
Keywords: CFD, two-fluid approach, fiber flows
  • Contribution to proceedings
    NURETH-12 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics, 30.09.-04.10.2007, Pittsburgh, USA
  • Lecture (Conference)
    NURETH-12 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics, 30.09.-04.12.2007, Pittsburgh, USA

Permalink: https://www.hzdr.de/publications/Publ-9691
Publ.-Id: 9691


Review of available data for validation of nuresim two-phase CFD software applied to CHF investigations

Bestion, D.; Anglart, H.; Peturaud, P.; Smith, B.; Krepper, E.; Moretti, F.; Macek, J.
The NURESIM Integrated Project of the 6th European Framework Program is envisaged to initiate the development of the next-generation common European Standard Software Platform for simulating nuclear reactors. The overall objective of NURESIM Thermalhydraulic sub-project is to improve the understanding and the predictive capabilities of the simulation tools for key two-phase flow thermal-hydraulic processes such as the Critical Heat Flux (CHF). A multi-scale analysis of reactor thermalhydraulics is envisaged and two-phase CFD is developed to allow some zoom on local processes when the resolution of system codes is not sufficient.
Current industrial methods for CHF mainly use the sub-channel analysis and empirical CHF correlations based on large scale experiments having the real geometry of the reactor assembly. The NURESIM-TH activities regarding CHF aim at using two-phase CFD as a tool for understanding boiling flow processes, in order to subsequently help new fuel assembly design and to develop better CHF predictions in both PWR and BWR. A “Local Predictive Approach” may be envisaged for the long term where CHF empirical correlations would be based on local T/H parameters provided by CFD.
This paper presents a review of existing experimental data bases which can be used for validation of the two-phase CFD application to Critical Heat Flux (CHF) investigations with respect to nuclear reactors. The phenomenology of DNB and Dry-Out are detailed identifying all basic flow processes which require a specific modeling in CFD tool. The resulting program of work is given and the current state of the art of the modeling is presented.
The resulting program of work is presented and the present state of the art in the modeling is detailed.
Keywords: Critical heat flux, experimenbtal data, CFD simulation
  • Contribution to proceedings
    NURETH-12 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics, 30.09.-04.10.2007, Pittsburgh, USA
  • Lecture (Conference)
    NURETH-12 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics, 30.09.-04.10.2007, Pittsburgh, USA

Permalink: https://www.hzdr.de/publications/Publ-9690
Publ.-Id: 9690


Application of the moment-density method in CFD code to model bubble size distribution

Ruyer, P.; Seiler, N.; Beyer, M.; Weiß, F.-P.
This study, carried out at Institut de Radioprotection et de Sûreté Nucléaire, concerns the model of a polydispersed bubble population in the frame of an ensemble averaged two-phase flow formulation. We consider the ability of the moment density approach, e.g. Kamp et al. (2001), to represent bubble population size distribution within a multi-dimensional CFD code based on the two-fluid model. Special attention is given to the closure issue of the method. We consider in particular the influence of the polydispersion on (i) coalescence and break-up phenomena and on (ii) momentum inter-phase transfers related to drag and lift forces. A first approach formulation is developed allowing to represent a full spectrum of bubble size with a very reduced number of parameters. The latter property constitutes one of the main advantages of the moment density method with regard to alternative methods for polydispersion representation like population balance. The system of transport equations and corresponding main closure terms are derived in the case of adiabatic flows with spherical bubbles of an incompressible fluid that is immiscible in the continuous phase. Air-water polydispersed bubbly flows in a vertical pipe with obstacle of the TOPFLOW experiments series performed at FZD, e.g. Prasser et al. (2006), are then used as simulations test cases. The numerical results, obtained with NEPTUNE_CFD, e.g. Guelfi et al. (2005), allow to attest the validity of the approach. Perspectives concerning the improvement of the model, its validation, as well as the extension of its applicability range are discussed.
Keywords: two-phase flow, NEPTUNE_CFD, bubble size distribution, moment density
  • Lecture (Conference)
    European Two-Phase Flow Group Meeting 2007, 29.-31.05.2007, Toulouse, France

Permalink: https://www.hzdr.de/publications/Publ-9689
Publ.-Id: 9689


Numerical investigations of the transport of submerged insulation particle

Cartland-Glover, G.; Alt, S.; Kästner, W.; Krepper, E.
A numerical investigation of insulation debris transport and sedimentation is being performed as part of a joint research project with the Institute of Process Technology, Process Automation and Measuring Technology (IPM) Zittau. The study considers the impact of the transport of insulation wool debris on the long-term behaviour of emergency core coolant systems during all types of LOCA that occur in PWR and BWR. In order to implement models into computational fluid dynamic codes (CFD), the models that characterize insulation debris (particle buoyancy, drag, turbulent dispersion and the fluid-particle mixture viscosity) must be tested. Experimental investigations are being performed at the IPM-Zittau to provide detailed information with which the numerical models can be validated.
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2007, 22.-24.05.2007, Karlsruhe, Germany
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2007, 22.-24.05.2007, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-9688
Publ.-Id: 9688


Application of multiphase flow modeling techniques to the transport of submerged mineral wool fibers

Cartland-Glover, G.; Alt, S.; Kästner, W.; Krepper, E.
The transport of mineral wool insulation debris, which is generated during all types of loss of coolant accidents (LOCA) could impede the long-term operation of emergency core coolant systems (ECCS) in nuclear power plants. Therefore, a combined experimental and numerical investigation of mineral wool fibers is being pursued to improve the understanding of how ECCS can be undermined by the transport, sedimentation and resuspension of mineral wool fibers.
The application of the Eulerian-Eulerian multiphase flow model to the transport of the fibers is discussed here with regard to the transport of fibers in a racetrack type channel. The study examines the application of closure models such as the Favre-Averaged turbulence dispersion force and the mixture viscosity and the impact that they have on fiber transport. The intention of the study is to aid the experimental part of the study by determining which parameters influence the particle forces and which conditions can be used in analyzing the parameters for further model development and evaluation. The phenomena observed in the calculations correspond qualitatively to preliminary experimental observations.
Keywords: CFD, Eulerian-Eulerian Multiphase, Nuclear Reactor Containment Sump, Mineral Wool Fibers, Sedimentation and Resuspension
  • Contribution to proceedings
    International Conference on Multiphase Flow - ICMF 2007, 09.-13.07.2007, Leipzig, Germany
  • Lecture (Conference)
    International Conference on Multiphase Flow - ICMF 2007, 09.-13.07.2007, Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-9687
Publ.-Id: 9687


Application of a population balance approach for polydispersed bubbly flows

Krepper, E.; Beyer, M.; Frank, T.; Lucas, D.; Prasser, H.-M.
A population balance model was developed in close cooperation of ANSYS-CFX and Forschungszentrum Dresden-Rossendorf and implemented into CFX-10 (Frank et al. 2005, Krepper et al. 2007). The current paper presents the application of the model to upward flow in vertical pipes for air/water and for steam/water bubbly flow. Finally the application to a bubbly flow around a half moon shaped obstacle arranged in a 200 mm pipe is shown (see Frank et al. 2007).
Applying the inhomogeneous MUSIG approach a more deep understanding of the flow structure is possible. For upward two phase flow in vertical pipes the core peak in the cross sectional gas fraction distribution could be reproduced very well. For complex flows the general structure of the flow could be well reproduced in the simulations. This test case of the obstacle demonstrates the complicated relationship between size dependent bubble migration and bubble coalescence and break-up effects for real flows. While the closure models for bubble forces, which are responsible for the simulation of bubble migration are in agreement with the experimental observations, clear deviations occur for bubble coalescence and fragmentation. The presently applied models describing bubble fragmentation and coalescence could be proved as weak points in numerous CFD analyses of vertical upward two phase pipe flow. Further work on this topic is considered for future investigations.
Keywords: Bubbly flow, CFD, Non drag forces, bubble break up, bubble coalescence, population balance, validation
  • Contribution to proceedings
    International Conference on Multiphase Flow - ICMF 2007, 09.-13.07.2007, Leipzig, Germany
    Poster No PS6_6
  • Poster
    International Conference on Multiphase Flow - ICMF 2007, 09.-13.07.2007, Leipzig, Germany

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Publ.-Id: 9686


Inhomogeneous MUSIG model – a population balance approach for polydispersed bubbly flows

Krepper, E.; Frank, T.; Lucas, D.; Prasser, H.-M.; Zwart, P. J.
A generalized inhomogeneous Multiple Size Group (MUSIG) Model based on the Eulerian modeling framework was developed in close cooperation of ANSYS-CFX and Forschungszentrum Dresden-Rossendorf and implemented into CFX-10. Simulating a poly-dispersed gaseous liquid two phase flow along with the mass exchanged between bubble size classes by bubble coalescence and bubble break-up and the momentum exchange of bubble size dependent bubble forces have to be considered. Particularly the lift force has been proved to play an important role establishing a certain flow regime. The paper describes the main concepts of the model approach and presents a model validation case. Further application test cases are presented by Krepper et al. 2007.
The inhomogeneous MUSIG model approach was shown to be able to describe of bubbly flow with higher gas content. Particularly the separation phenomenon of small and large bubbles which was proven to be a key phenomenon for the establishment of the corresponding flow regime is well described. Weaknesses in this approach can be attributed to the characterization of bubble coalescence and bubble break-up, which must be further investigated.
Keywords: Bubbly flow, CFD, Non drag forces, bubble break up, bubble coalescence, population balance, validation
  • Contribution to proceedings
    International Conference on Multiphase Flow - ICMF 2007, 09.-13.07.2007, Leipzig, Germany
    Paper No S_6_Thu_B_51
  • Lecture (Conference)
    International Conference on Multiphase Flow - ICMF 2007, 09.-13.07.2007, Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-9685
Publ.-Id: 9685


Compositional and structural changes in ZrOxNy films depending on growth condition

Carvalho, P.; Fernandes, A. C.; Rebouta, L.; Vaz, F.; Cunha, L.; Kreissig, U.; Barradas, N. P.; Ramos, A. R.; Alves, E.
The present work focuses on the analysis of ZrOxNy thin films, the composition evolution with changing growth conditions and its relation with the structural and morphological properties of the films. The films were prepared by rf reactive magnetron sputtering, using different reactive gas flows. Composition and structure were measured combining ion beam analysis (IBA) and X-ray diffraction (XRD) techniques. The depth profiles of nitrogen and oxygen have been obtained by elastic recoil detection analysis (ERDA). Results showed that the oxygen fraction in the films increases with gas flow, reaching a value of x ~ 0.33 for a reactive gas flow mixture of 6.25 sccm. During growth mixed zirconium nitride and oxide phases form. Furthermore, the deposition rate correlates with the oxygen content variations, showing a continuous decrease with reactive gas flow.
Keywords: Decorative films; XRD; Nitrides; Oxides; Ion beams
  • Nuclear Instruments and Methods in Physics Research B 249(2006), 458-461

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Publ.-Id: 9684


Study of anomalous behaviour of LiTaO3 during the annealed proton exchange process of optical waveguide´s formation - comparison with LiNbO3

Salavcova, L.; Spirkova, J.; Ondracek, F.; Mackova, A.; Vacik, J.; Kreissig, U.; Eichhorn, F.; Groetzschel, R.
This paper deals with detailed study of changes that lithium tantalate (LT) and lithium niobate (LN) single crystals undergo during the APE (Annealed Proton Exchange) process of optical waveguides´ formation. It is a well-known fact that several cases of anomalous behaviour are connected to the APE:LT samples, bringing thus serious limitations for the practical utilization of the APE:LT waveguides. As the LT crystal posseses even better optical properties than the LN (e.g., it is less susceptible to optical damage), it is highly desirable to provide research focused on its behaviour during the APE in order to get a control over fabrication of the APE:LT devices.
Neutron Depth Profiling (NDP), Elastic Recoil Detection Analysis (ERDA) and High Ion Energy ERDA (HIERDA) were performed to study changes in the surface of the LT and LN Z-cut wafers caused by the APE treatment and to determine the concentration depth profiles of the exchanged ions (lithium and hydrogen). Information on modifications of the crystals during the APE were obtained using X-Ray Diffraction (XRD) analysis. Optical/waveguiding properties of the samples were obtained by means of the standard mode spectroscopy at 633 nm.
The experiments proved that the LT is significantly less affected by the APE process compared to the LN and that most characteristics of the APE:LT layers are relatively easily restored back towards that of the virgin crystal by the annealing process.
Keywords: APE; Ion exchange; Lithium niobate; Lithium tantalate
  • Optical Materials 29(2007), 913-918

Permalink: https://www.hzdr.de/publications/Publ-9683
Publ.-Id: 9683


Das Komplexbildungsverhalten von Uran(IV) mit Phosphat – Untersuchungen mittels Zeitaufgelöster Fluoreszenzspektroskopie

Lehmann, S.; Geipel, G.
Die Zeitaufgelöste Fluoreszenzspektroskopie erlaubt die unmittelbare Untersuchung fester und flüssiger Systeme in mikro- und submikromolaren Stoffmengenkonzentrationen. Dies prädestiniert die Etablierung und den Einsatz der Fluoreszenzspektroskopie als analytische Methode für Untersuchungen von Festphasen- und aquatischen Umweltsystemen in ihren entsprechenden relevanten Konzentrationsbereichen. Die hier gezeigten Forschungsergebnisse repräsentieren die ersten Resultate zur Komplexbildung von Uran(IV) im Phosphatsystem, welche mit Hilfe der Zeitaufgelösten Fluoreszenzspektroskopie ermittelt wurden.
Zur Untersuchung der Komplexbildung zwischen Uran(IV) und Phosphat wurde die Konzentration des Uran(IV) im perchlorsauren Medium konstant gehalten und die Konzentration des zugegebenen Phosphat in einem Bereich zwischen einem 5fachen Unterschuss und einem 5fachen Überschuss variiert. Fluoreszenzspektroskopische Aufnahmen des Uran(IV) ohne Zusatz von Phosphat zeigen die Übereinstimmung der Peakpositionen mit [1] und [2]. Die Positionen der 5 Hauptpeaks wurden wie folgt ermittelt: 291, 320, 335, 394 and 409 nm. Die Auswertung der aufgenommenen zeitaufgelösten Spektren von Uran(IV) mit Phosphatzusatz zeigt insbesondere an den intensivsten Peaks bei 320 und 409nm, dass mit zunehmender Phosphatkonzentration die Fluoreszenzintensität abnimmt, freies Uran(IV) folglich im Komplex gebunden wird, bis freies Uran(IV) bei äquimolaren Stoffmengenkonzentrationen von Uran(IV) und Phosphat nicht mehr nachweisbar ist und somit vollständig mit Phosphat reagiert hat.
Die über die äquimolare Konzentration hinaus bis hin zum 5fachen Überschuss an Phosphat aufgenommenen Spektren sind gegenüber den zuvor beschriebenen gänzlich verändert und zeigen nur eine einzige breite Bande zwischen 290 und 400nm mit einem Peak schwacher Intensität bei 374nm. Die undefinierte Bande lässt sich möglicherweise auf die gelartigen Ausfällungen zurückführen, welche bei stöchiometrischen Konzentrationen und bei Phosphatüberschuss unter den hier gewählten Versuchsbe-dingungen zu beobachten sind.

Weitergehende Untersuchungen haben als Ziel, die Natur des Peaks bei 374nm zu klären und die gebildeten Uran(IV)-Phosphatspezies sowie die entsprechenden Komplexbildungskonstanten zu bestimmen.
Keywords: uranium(IV) phosphate, TRLFS, complex formation constant
  • Poster
    GDCh - Wissenschaftsforum Chemie 2007, 16.-19.09.2007, Ulm, Germany

Permalink: https://www.hzdr.de/publications/Publ-9682
Publ.-Id: 9682


Gas-liquid flow around an obstacle in a vertical pipe – CFD simulation & comparison to experimental data

Frank, T.; Prasser, H.-M.; Beyer, M.; Al Issa, S.
A novel technique to study the two-phase flow field around an asymmetric diaphragm in a vertical pipe is presented, that allows to obtain detailed 3-dimensional data for CFD code validation in complex geometries. The investigated validation test case consists of an air-water two-phase bubbly flow around a half-moon shaped obstacle in a DN200 vertical pipe (TOPFLOW test facility), where the 3-dimensional flow field shows flow phenomena like curved stream lines, flow separation at sharp edges and
recirculation zones in the obstacle wake, like they are common to complex flow situations in bends, T-junctions, valves, safety valves and other components of power plant and other industrial equipment. Pre-test calculations with the commercial flow solver ANSYS CFX have been performed using an Eulerian two-phase flow model with a monodisperse bubble diameter assumption and by taking into account all significant drag and non-drag forces contributing to the interphase momentum transfer. Results of the CFD simulation have been compared to the 3-dimensional air volume fraction and water velocity fields, which were obtained from the wire-mesh sensor data, where the comparison showed a general very good agreement. Therefore CFD code validation on this type of complex 3-dimensional flow geometries permits the assessment of flow solver accuracy for other industrial type applications and contributes to further multiphase flow model development for ANSYS CFX.
Keywords: bubbly flows, CFD, wire-mesh sensor, 3-dimensional validation
  • Lecture (Conference)
    International Conference on Multiphase Flow, ICMF 2007, 09.-13.07.2007, Leipzig, Germany
  • Contribution to proceedings
    International Conference on Multiphase Flow, ICMF 2007, 09.-13.07.2007, Leipzig, Germany
    paper:S6_Thu_B_50

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Publ.-Id: 9681


[18F]FBAM and [18F]FBOM: Novel Thiol-reactive prosthetic groups derived from 4-[18F]fluorobenzaldehyde

Vogler, L.; Berndt, M.; Pietzsch, J.; Wüst, F.
The incorporation of 18F into peptides and proteins usually takes advantage of prosthetic groups, also referred to as bifunctional labeling agents. This approach comprises 18F incorporation into a small organic molecule capable of being linked to peptides and proteins under mild conditions.
Two new prosthetic groups derived from 4-[18F]fluorobenzaldehyde for the mild and selective conjugation to thiol-group containing biomacromolecules are described: N-[6-(4-[18F]fluorobenzylidene)aminooxyhexyl]-maleimide ([18F]FBAM) and 4-[18F]fluorobenzaldehyde-O-(2-{2-[2-(pyrol-2,5-dion-1-yl)ethoxy]ethoxy}ethyl)oxim ([18F]FBOM.
The aminooxy-functionalized labeling precursor for radiosynthesis of [18F]FBAM was prepared in a convenient three-step synthesis sequence in a total yield of 59%. The corresponding labeling precursor for the radiosynthesis of [18F]FBOM succeeded in a four-step reaction sequence in 14% total yield. Formation of the prosthetic groups [18F]FBAM and [18F]FBOM was achieved through condensation reaction with [18F]fluorobenzaldehyde to form the desired oximes in radiochemical yields of 20-30% ([18F]FBAM) and of 14-19% ([18F]FBOM), respectively. The syntheses were carried out in a remotely-controlled radiofluorination module allowing the convenient and reliable performance of the radiolabeling reactions. The radiochemical purity exceeded 95% and the specific activity ranged from 50 to 80 GBq/μmol. The total synthesis time was 70 to 80 min. The lipophilicity was determined to be logP=2.71 for [18F]FBAM and logP=0.84 for [18F]FBOM. Both prosthetic groups could successfully be used in the radiolabeling of thiol-group containing compounds such as glutathion, low density lipoproteins (LDL) and modified neurotensin derivatives.
  • Lecture (Conference)
    14th Workshop der International Isotope Society, 21.-22.06.2007, Bad Soden, Germany
  • Journal of Labelled Compounds and Radiopharmaceuticals 50(2007), 1276-1286

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Publ.-Id: 9680


Mobilisation and speciation of depleted uranium in water and soils

Geipel, G.; Baumann, N.; Arnold, T.; Bernhard, G.; Gerstmann, U.; Schimmack, K.; Read, D.
Depleted uranium (DU) from penetrating ammunition was exposed to several environmental conditions in order to determine the binding forms of uranium as well as in its dissolved and solid forms.
In a first series fresh disks of DU were treated with a calcium phosphate solution. The results from time-resolved laser-induced fluorescence spectroscopy clearly show that metaautunite Ca(UO2)2(PO4)2 x 2-6(H2O) has formed during alteration [1].
In a second experiment the corrosion and leaching of used up DU was investigated for three years in a column with a soil core. The columns were irrigated with synthetic rainwater.
The luminescence spectrum of a yellow material, which was crystallized at the soil surface was assigned clearly to be the mineral sabugalite AlH(UO2)(PO4)4 x 16(H2O).
In contrast to the luminescence spectra of the solid material the spectra of the uranium species in the dissolved samples could only obtained at temperatures below 220 K. From the shape of the spectrum and the emission maxima of the luminescence of seepage water samples it could be clearly concluded that the solution species are mostly uranyl carbonate species UO2(CO3)34- [2].
Keywords: Depleted uranium, TRLFS, Binding form
  • Contribution to proceedings
    Goldschmidt 2007, 19.-24.08.2007, Köln, Germany

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Publ.-Id: 9679


Model studies with DU to assess the mobilisation and speciation of U in soils

Geipel, G.; Baumann, N.; Arnold, T.; Bernhard, G.; Gerstmann, U.; Schimmack, K.; Read, D.
Since the 1990th, depleted uranium (DU) was used in several conflict regions as 'penetrator' in munition rounds designed to pierce battle tanks. Lots of this amunition undergo wheatering processes under environmental conditions. One goal of our studies was the determination of the binding forms of uranium, if the DU is exposed to several environmental conditions.
The formed uranium species were detected by time-resolved laser-induced fluorescence spectroscopy (Geipel 2005). By use of spectroscopic databases including U(VI)-oxides, U(VI)-hydroxides, U(VI)-sulphates and U(VI)-phosphates the different formed uranium species in solution as well as solid species can be clearly assigned.
In a first series disks of DU were treated with a calcium phosphate solution at ambient temperature for 182 days. The weathering solution contained 2.49 mM calcium and 1.05 mM phosphate, representing enhanced pore water concentrations of agricultural soils. The TRLFS results clearly show that metaautunite, a U(VI) phosphate, has formed during low temperature alteration of the DU disc. The TRLFS spectrum is characterized by six fluorescence emission bands at 486, 501, 522, 546, 573, and 601 nm, and two fluorescence life times of 50±5 ns and 700±25 ns (Baumann et.al., 2006).
In a second experiment the corrosion and leaching of depleted uranium (DU) was investigated for three years in a column with a soil core. The columns were installed in a laboratory with controlled temperature of (21 ± 1) °C and a relative humidity of (55 ± 10) %. The columns were irrigated weekly with 16 mm synthetic rainwater of pH 6 consisting mainly of 0.09 mM NH4NO3, 0.08 mM (NH4)2SO4 and 0.05 mM CaSO4.
The luminescence spectrum of a yellow material, which was crystallized at the soil surface was measured and the comparison with the TRLFS database assigned this luminescence spectrum clearly to be the mineral sabugalite AlH(UO2)(PO4)4 x 16(H2O).
In contrast to the luminescence spectra of the solid material the spectra of the uranium species in the dissolved samples could only obtained at temperatures below 220 K. From the shape of the spectrum and the emission maxima of the luminescence of seepage water samples it could be clearly concluded that the solution species are mostly uranyl carbonate species UO2(CO3)34- (Schimmack et.al.submitted, Schimmack et.al. 2007).
Keywords: Depleted uranium, binding form
  • Invited lecture (Conferences)
    International Symposium Protecting Water Bodies from Negative Impacts of Agriculture, 04.-06.06.2007, Braunschweig, Germany

Permalink: https://www.hzdr.de/publications/Publ-9678
Publ.-Id: 9678


FT-IR investigation of the uranium S-layer interaction in aqueous solutions

Li, B.; Foerstendorf, H.; Raff, J.; Bernhard, G.
Many bacteria possess so-called surface layer (S-layer) proteins, forming paracrystalline lattice structures on the cell wall (1). Beside its ecological relevance for the retention of toxic metals, they are a good model system for investigations of the interaction of bio-ligands, e.g. proteins, with uranium in aqueous solutions. Several S-layers from different Bacillus strains were proved to have high binding capacity to uranium. But there is still little knowledge of the interactions between the functional groups of the protein with the actinyl ions at a molecular level (2).
In this work we present results of batch experiments where the uranium binding capacities of different S-layer protein from different Bacilllus strains were determined. The experiments were carried out at different pH values (pH 4, 6, and 8) for each isolated S-layer protein. It was found that the uranium binding capacities of each gram S-layer range from 5.0 mg and 63.9 mg, from 11.1 mg and 561.1 mg, and from 14.2 mg and 33.5 mg at pH 4, 6, and 8, respectively, depending on the respective S-layer.
For a deeper understanding of the molecular binding of the uranyl ion to the protein we used Attenuated Total Reflectance Fourier-transform Infrared spectroscopy (ATR-FTIR) which allows vibrational spectroscopic investigations of aqueous solutions containing actinide ions and disolved proteins as well (3, 4). The spectra clearly demonstrate carboxyl groups are the major functional groups which interact with the uranyl ions at pH 4. Additionally, the infrared spectra suggest the formation of different uranium-protein complexes depending on the incubation period (1 h vs. 48 h) which can be observed by a peak shift of the absorption band representing the antisymetric uranyl stretch to lower wavenumbers.
This spectroscopic approach constitutes the foundation of more detailed investigations on the impact of the pH value and of other functional groups (e.g. phosphate or amino groups) on the uranium complexation by bio-systems.


REFERENCES
(1) Sleytr, U.B., Beveridge T.J., Trends Microbiol. 1999 7(6), 253-260
(2) Merroun, M.L., et al. Appl. Environ. Microbiol. 2005, 71(9), 5532–5543
(3) Quilès, F.; Burneau, A. Vib. Spec. 2000, 23, 231-241.
(4) Fahmy, K. et al. Biophys. J. 2006, 91(3), 996-1007
  • Contribution to proceedings
    17th Annual Goldschmidt Conference, Cologne, Germany, 19.-24.08.2007, Köln, Germany
    FT-IR investigation of the uranium S-layer interaction in aqueous solutions

Permalink: https://www.hzdr.de/publications/Publ-9677
Publ.-Id: 9677


Complexation of Uranium(VI) with Nitrate in Nonaqueous and Aqueous solutions: Speciation and Structural Studies

Ikeda, A.; Hennig, C.; Rossberg, A.; Tsushima, S.; Scheinost, A. C.; Bernhard, G.
Understanding the complexation behavior of uranium(VI) with nitrate ions in solution is important for the assessment of environmental impact on the geological disposal of radioactive wastes or for the development of nuclear fuel reprocessing since the present reprocessing plants employ PUREX process, that separates uranium and plutonium from other actinides and fission products in nitric acid solution and, as a result, produces radioactive liquid wastes in nitrate solution. In this study, the chemical speciation and the structure of uranium(VI) nitrate complexes have been investigated in nonaqueous (acetonitrile) and aqueous (nitric acid) solutions by UV-visible absorption spectroscopy, U LIII-edge x-ray absorption spectroscopy, and quantum chemical calculations.

In acetonitrile, the complexation between uranium(VI) and nitrate ions is very strong and the trinitrato complex, [UO2(NO3)3]-, becomes the dominant species when [NO3]/[U] is above 3. The extended x-ray absorption fine structure (EXAFS) spectrum of this trinitrato species indicates that the nitrate ions coordinate to the uranyl ion in a bidentate mode and the average U-Oax, U-Oeq, and U-N distances are 1.77, 2.50, and 2.95 Å, respectively. These values are in good agreement with the results of DFT calculations in acetonitrile (i.e. 1.76, 2.50, and 2.96 Å for U-Oax, U-Oeq, and U-N distances, respectively). By varying the [NO3]/[U] ratio from 0 to 3, we observe a complex speciation diagram composed of four species (UO22+, [UO2NO3(H2O)n]+, [UO2(NO3)2(H2O)m]0, and [UO2(NO3)3]-). However, it is impossible to determine the complex structures of these species directly by EXAFS. In order to estimate their structure, we have isolated their individual EXAFS spectra from the spectra of the mixtures by performing factor analysis [1] on the basis of the speciation diagram obtained from the UV-visible spectral titration. The data analysis of the isolated EXAFS spectra demonstrates that the dinitrato complex has a coordination number of 6 in the equatorial plane of the uranyl ion and forms the complex [UO2(NO3)2(H2O)2]0. On the other hand, the estimated EXAFS spectrum for the mononitrato complex indicates that it has a coordination number of 5 and forms the complex [UO2NO3(H2O)3]+. These results are supported by DFT calculations. The same data treatment (i.e. factor analysis combined with the speciation diagram from spectral titration) has also applied to the EXAFS spectra in aqueous solutions of nitric acid. The results suggest that the nitrate complexation of uranium(VI) is far weaker in aqueous solution than that in acetonitrile and almost no trinitrato complex is formed even when the [NO3]/[U] ratio exceeds 360.
Keywords: uranium(VI), nitrate, solution, acetonitrile, nitric acid, XAFS, UV-visible absorption, DFT, factor alanysis, speciation
  • Poster
    Migration 2007, 26.-31.08.2007, Arabella Sheraton Grand Hotel, Munich, Germany
  • Contribution to proceedings
    Migration 2007, 26.-31.08.2007, München, Germany
    11th Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 178

Permalink: https://www.hzdr.de/publications/Publ-9676
Publ.-Id: 9676


Infrared spectroscopic identification of aqueous uranium(VI) species

Müller, K.; Foerstendorf, H.; Bernhard, G.
Migration of uranium(VI), the most stable form of uranium in environmental waters, is largely controlled by its geochemical reactions, both in solution and at the mineral-water interface. Current knowledge about U(VI) speciation is mainly based on thermodynamic calculations using data obtained by non-structural experiments, i.e. potentiometric titration [1]. A spectroscopic verification of the speciation of aqueous U(VI) is still insufficient. For the identification of different molecular species previous studies applied primarily EXAFS and Raman spectroscopy at very high uranyl concentrations (>100 mM) unreasonably in an environmental context [2-4].
In this study we used Attenuated Total Reflectance Fourier-transform Infrared (ATR-FTIR) spectroscopy, that allows the direct measurement of liquid samples. Our aim was to obtain additional vibrational spectroscopic information on the U(VI) species and especially to verify the U(VI) speciation throughout a wide pH range (pH 2-10) at a micromolar concentration level. The obtained spectral information was compared to previously reported thermodynamic data [1].
ATR-FTIR spectra were recorded at UO22+ concentrations ranging from 5 to 0.005 mM at pH 4. The spectroscopic results indicate distinctly that dimer and trimer hydroxo complexes become dominant upon lowering the uranyl concentration at pH 4. The thermodynamic data predict an absolute predominance of the free uranyl species UO22+ until pH 5 at these conditions.
At the micromolar concentration level the calculations predict the dominance of the uncomplexed uranyl ion until pH 5 and the formation of uranyl hydroxo complexes at neutral pH. Uranyl complexes with atmospheric carbonate in alkaline solutions are proposed above pH 6.5. However, the obtained ATR-FTIR spectra of low concentrated 0.02 mM uranyl solutions already show the coexistence of free and hydroxo complexed uranyl at pH 2.5. The appearance of carbonate complexes in solution becomes noticeable at the spectra of solutions at pH 7. Since the results are partially contradictionary to previous predictions of U(VI) speciation a critical review of the present knowledge of uranium migration in the environment is required.

[1] Guillaumont, R. et al. (2003) Update on the Chemical Thermodynamics of U, Np, Pu, Am and Tc. (Elsevier, Amsterdam)
[2] Moll, H. et al. (2000) Radiochim. Acta 88, 411-415.
[3] Nguyen-Trung, C. et al. (1992) Inorg. Chem. 31, 5280-5287.
[4] Quiles, F. et al. (2000) Vib. Spec. 23, 231-241.
  • Lecture (Conference)
    Goldschmidt 2007, 19.-24.08.2007, Köln, Germany
  • Abstract in refereed journal
    Geochimica et Cosmochimica Acta 71(2007)15S, A694

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Additional FDG PET-CT in week 5-6 of radiotherapy for patients with NSCLC as a means of dose escalation planning

Gillham, C.; Zips, D.; Pönisch, F.; Evers, C.; Enghardt, W.; Abolmaali, N.; Zöphel, K.; Appold, S.; Hölscher, T.; Steinbach, J.; Kotzerke, J.; Herrmann, T.; Baumann, M.
Aims:
To detect a reduction in disease volume during radical radiotherapy for non-small cell lung cancer (NSCLC) using PET-CT and to determine whether this would facilitate dose escalation.

Methods:
Ten patients with localised inoperable NSCLC were prospectively enrolled. Each received conformally planned radiotherapy to a dose of 66Gy/33# over 6.5 weeks using 6-15MV photons and prescribed to the 100% isodose. PET-CT imaging was performed just prior to and following 50 or 60Gy. Target volume definition was performed by one senior radiation oncologist with the help of a senior radiologist and nuclear medicine physician. For all patients and at both time points CT and PET-delineated gross tumour volumes were generated (GTVCT, GTVPET). A composite GTV was then created (GTVCT+PET) and 15mm added in all planes to form the planning target volume (PTV). No correction for organ movement was incorporated and no elective nodal irradiation performed. Each of the different volumes were compared before and after 50-60 Gray. Two plans were then created and compared: 78Gy delivered to the initial PTV and 66Gy to the initial PTV with a 12Gy boost to the post 50/60Gy PTV.

Results:
All patients (mean age 64 years) had stage III disease (4 IIIA and 6 IIIB). There were 4 squamous cell and 6 adeno-carcinomas. After 50/60 Gray the GTVCT, GTVPET, GTVCT+PET and PTV reduced by a mean of 22%, 43%, 30% and 22% respectively. The delivery of 78 Gray to the initial PTV could have been safely achieved in 4/10 patients. Of these delivering treatment in two phases would have substantially spared normal tissue in 2 patients. In the remaining 6 patients, delivering 78 Gray to the initial PTV would have exceeded normal tissue constraints
and no benefit was seen when planned in 2 phases.

Conclusions:
The PTV, consequent on changes seen on PET-CT, reduces during a course of radical radiotherapy for NSCLC. Such a reduction permits dose escalation in a subset of patients and may lead to improved therapeutic outcomes.
  • Lecture (Conference)
    14th European Cancer Conference, 23.-27.09.2007, Barcelona, Spanien

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Publ.-Id: 9674


Rising gas bubbles in a liquid metal under the influence of external magnetic fields

Zhang, C.; Eckert, S.; Gerbeth, G.
In the present paper we consider the impact of various external DC magnetic fields on the motion of a single bubble rising in a cylindrical column of stagnant liquid metal and the flow structure of a bubble plume, respectively. The ultrasound Doppler method (UDV) has been used to measure the velocity non-intrusively. The motion of single Argon bubbles rising in the eutectic alloy GaInSn under the influence of a DC vertical magnetic field was examined. The bubble terminal velocity showed oscillations indicating a zizag movement of ellipsoidal bubbles. The measurements revealed a distinct electromagnetic damping of the bubble induced liquid velocity leading to more rectilinear bubble trajectories. A global damping of the flow field was also observed if a vertical magnetic field has been imposed on a bubble plume. By contrast, a restructuring of the flow pattern being typical for a bubble plume was observed in the case of a horizontal magnetic field. The DC field gave rise to non-steady, non-isotropic and large-scale flow structures which was rather unknown until now and therefore not sufficiently considered for electromagnetic processing of materials.
Keywords: single bubble, bubble plume, liquid metal, magnetic field, ultrasound Doppler velocity measurements
  • Lecture (Conference)
    International Conference on Multiphase Flow - ICMF2007, 09.-13.07.2007, Leipzig, Germany
  • Contribution to proceedings
    International Conference on Multiphase Flow - ICMF2007, 09.-13.07.2007, Leipzig, Germany, No. 279

Permalink: https://www.hzdr.de/publications/Publ-9673
Publ.-Id: 9673


Diagnostic impact of PET with 18F-FDG, 18F-DOPA and 3-O-methyl-6-[18F]fluoro-DOPA in recurrent or metastatic medullary thyroid carcinoma

Beuthien-Baumann, B.; Strumpf, A.; Zessin, J.; Bredow, J.; Kotzerke, J.
Purpose
In patients with medullary thyroid carcinoma (MTC), rising levels of the tumour markers calcitonin and CEA after primary surgery indicate tumour recurrence or metastases. The only chance of cure is the resection of localised tumour tissue. For positron emission tomography (PET) with 18F-fluorodeoxyglucose (18F-FDG) and 18F-dihydroxyphenylalanine (18F-DOPA), sensitivities of 78% and 63% have been reported, but in a considerable percentage of MTC patients the source of tumour marker elevation is not detected. The aim of this retrospective data evaluation was to compare the value of PET with 18F-FDG, 18F-DOPA and the amino acid tracer 3-O-methyl-6-[18F] fluoro-DOPA (18F-OMFD) in the detection of MTC recurrence.

Methods
Fifteen patients with elevated calcitonin were investigated with PET as part of their individual clinical work-up. All patients underwent 18F-FDG PET and 18FDOPA PET, and ten patients underwent 18F-OMFD PET.

Results
With 18F-FDG, seven patients showed foci in the neck, mediastinum, upper abdomen or bone. In seven patients, 18F-DOPA revealed suspicious foci; five of these seven patients showed partially corresponding uptake of 18F-FDG in the neck and mediastinum. Two of these patients underwent surgery and metastases were verified. With 18F-OMFD, a small focus in the liver was suspected in one patient without a correlate on 18F-FDG PET, 18FDOPA PET or conventional imaging.

Conclusion
18F-FDG and 18F-DOPA showed foci that were highly suspicious for local recurrence or metastasis of MTC, although histological verification in these patients with numerous previous surgical interventions was performed in only two patients. The amino acid tracer 18FOMFD had no diagnostic impact in these patients.
Keywords: Medullary thyroid carcinoma . Positron emission tomography . 18F-fluorodeoxyglucose . 18F-DOPA. 3-O-methyl-6-[18F]fluoro-DOPA

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Data acquisition system for angle synchronized gamma-ray tomography of rapidly rotating objects

Bieberle, A.; Schleicher, E.; Hampel, U.
We developed a fast read-out electronics which is used in conjunction with a radiation detector for gamma ray computed tomography. The detector comprises 320 single scintillation detector elements and is operated in pulse counting mode. Digital pulses corresponding to gamma or x-ray absorption events in the scintillation crystals are counted by a counter bank implemented fully parallel in FPGA electronics. The counter data may be read-out at a maximum rate of 5 MHz via micro controller and USB 2.0 interface. This enables to take full projection data within intervals of down to 23 µs which in turn gives the opportunity to produce sharp tomographic slice images of objects rotating with more than 1000 rotations per minute. As an example we demonstrate the reconstruction of the gas distribution in the turbine region of a stirred tank reactor.
Keywords: high-resolution gamma ray tomography, multi-phase flow
  • Measurement Science and Technology 18(2007), MST/248418/PAP/167103

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Uranium(VI) complexation studies with selected aromatic acids - a comparison of different spectroscopic techniques

Glorius, M.; Moll, H.; Geipel, G.; Bernhard, G.
To understand the actinide interaction processes in biological systems on a molecular level it is necessary to explore the complexation behaviour of actinides with selected bioligands of relevant functionalities as model compounds. We used salicylhydroxamic acid (SHA), benzohydroxamic acid (BHA) and benzoic acid (BA) as model compounds for pyoverdins, which are natural bioligands secreted from Pseudomonas ssp. possessing a high potential to bind actinides [1]. The different U(VI) species, MpLqHr, were characterized by UV-vis spectroscopy and laser-induced spectroscopic techniques (TRLFS, fs-TRLFS).
From the UV-vis measurements different coordination modes of uranyl can be postulated [2]. If uranyl is coordinated to hydroxamic acids this results in a blue shift of the absorption maxima in comparison to the bands of the free uranyl ion of app. 25 nm. Whereas in the case of coordination to the carboxylic acid group of benzoic acid, a red shift of the absorption maxima of app. 2.5 nm was observed.
The U(VI)-TRLFS measurements show, that all uranyl ligand species emit no fluorescence light. In all three systems a static quench process of the uranyl fluorescence due to the complex formation was observed.
In the U(VI)-SHA system the stability constant for the 1:1 complex, UO2[HOC6H4CONHO]+, is log β 0111 = 16.33 0.16 and for the 1:2 complex, UO2[HOC6H4CONHO]2, log β 0122 = 33.43 0.11. In the U(VI)-BHA system the stability constants results to log β 0110 = 7.49 0.03 for UO2C6H4CONHO+ and log β 0120 = 15.40 1.15 for UO2[C6H4CONHO]2. In the U(VI)-BA system the stability constant for the 1:1 complex, UO2C6H4COO+, was determined to log β 0110 = 3.02 0.13. All stability constants were averaged from the measurements by UV-vis and TRLFS.
The higher formation constants of uranyl with the aromatic hydroxamate compounds compared to benzoic acid points to the high potential of the pyoverdins to bind and mobilize uranium(VI) in the environment.

[1] M. Bouby, I. Billard, H. J. Maccordick, Czechoslovak. J. Phys. 49, 769-772 (1999).
[2] M. Glorius, H. Moll, G. Bernhard, Complexation of uranium(VI) with aromatic acids in aqueous solution – A comparison of hydroxamic acids and benzoic acid, Radiochimica Acta, in press (2007).

This work was funded by the BMWi under contract number 02E9985.
Keywords: Uranium; aromatic acids; spectroscopy; TRLFS; complexation
  • Poster
    Migration 2007, 26.-31.08.2007, München, Germany
  • Contribution to proceedings
    Migration 2007, 26.-31.08.2007, München, Germany
    11th Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 175-176

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Publ.-Id: 9670


3He(alpha,gamma)7Be cross section at low energies

Gyürky, G.; Confortola, F.; Costantini, H.; Formicola, A.; Bemmerer, D.; Bonetti, R.; Broggini, C.; Corvisiero, P.; Elekes, Z.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Imbriani, G.; Junker, M.; Laubenstein, M.; Lemut, A.; Limata, B.; Lozza, V.; Marta, M.; Menegazzo, R.; Prati, P.; Roca, V.; Rolfs, C.; Rossi Alvarez, C.; Somorjai, E.; Straniero, O.; Strieder, F.; Terrasi, F.; Trautvetter, H. P.
The flux of 7Be and 8B neutrinos from the Sun and the production of 7Li via primordial nucleosynthesis depend on the rate of the 3He(alpha,gamma)7Be reaction. In extension of a previous study showing cross section data at 127 - 167 keV center of mass energy, the present work reports on a measurement of the 3He(alpha,gamma)7Be cross section at 106 keV performed at Italy's Gran Sasso underground laboratory by the activation method. This energy is closer to the solar Gamow energy than ever reached before. The result is sigma = 0.567 +- 0.029(stat) +- 0.016(syst) nbarn. The data are compared with previous activation studies at high energy, and a recommended S(0) value for all 3He(alpha,gamma)7Be activation studies, including the present work, is given.

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g-factor measurements on relativistic isomeric beams produced by fragmentation and U-fission: the g-Rising project at GSI

Neyens, G.; Atanasova, L.; Balabanski, D. L.; Becker, F.; Bednarczyk, P.; Caceres, L.; Doornenbal, P.; Gerl, J.; Gorska, M.; Grebosz, J.; Hass, M.; Ilie, G.; Kurz, N.; Kojouharov, I.; Lozeva, R.; Maj, A.; Pfutzner, M.; Pietri, S.; Podolyak, Z.; Prokopowicz, W.; Saitoh, T. R.; Schaffner, H.; Simpson, G.; Vermeulen, N.; Werner-Malento, E.; Walker, J.; Wollersheim, H. J.; Bazzacco, D.; Benzoni, G.; Blazhev, A.; Blasi, N.; Bracco, A.; Brandau, C.; Camera, F.; Chamoli, S. K.; Chmel, S.; Crespi, F. C. L.; Daugas, J. M.; de Rydt, M.; Detistov, P.; Fahlander, C.; Farnea, E.; Georgiev, G.; Gladnishki, K.; Hoischen, R.; Ionescu-Bujor, M.; Iordachescu, A.; Jolie, J.; Jungclaus, A.; Kmiecik, M.; Krasznahorkay, A.; Kulessa, R.; Lakshmi, S.; Lo Bianco, G.; Mallion, S.; Mazurek, K.; Meczynski, W.; Montanari, D.; Myalsky, S.; Perru, O.; Rudolph, D.; Rusev, G.; Saltarelli, A.; Schwengner, R.; Styczen, J.; Turzo, K.; Valiente-Dobon, J. J.; Wieland, O.; Zieblinski, M.
Within the RISING (Rare ISotope INvestigations @ GSI) Collabora-tion at GSI, g factor measurements have been performed on isomeric states in neutron-rich isotopes approaching 132 Sn and in the neutron deficient Pb-region (the g-RISING campaign). We present the experimental technique and some typical aspects related to such studies on relativistic beams selected with the FRS fragment separator. First results are presented for the (19/2+ ) 4.5 µs isomeric state in 127 Sn, which has been produced by means of fission of a relativistic 238 U beam on the one hand, and by the fragmentation of a relativistic 136 Xe beam on the other hand. Spin-alignment has been observed in both reactions. It was the first time that spin-alignment has been established in a relativistic fission reaction.
Keywords: Nuclear structure, radioactive beams, g-factor measurements
  • Contribution to proceedings
    Zakopane Conference on Nuclear Physics, 04.-10.10.2006, Zakopane, Poland
    Acta Physica Polonica B 38, 1237-1245

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U(VI) sorption on sandstone: Experiments and modeling

Richter, A.; Nebelung, C.; Brendler, V.
The sorption of U(VI) on natural and synthetic sandstone was investigated in batch sorption experiments (air atmosphere, 0.1M NaClO4, pH 3-11, [U(VI)] 10-9-10-4M. The synthetic sandstone was a mixture of quartz with muscovite and hematite. The surface area (N2-BET) of quartz was 0.047 m2/g, of muscovite 0.88 m2/g, of hematite 0.89 m2/g and of natural sandstone (mainly quartz) 0.69 m2/g.
The pH dependence shows a maximal sorption between pH 5.5-7.5. The U(VI) sorption varied between 95% (10-9M) and 7% (10-4) on natural sandstone, and between 80% (10-9M) and 2% (10-4M) on synthetic sandstone. Fig. 1 shows the comparison of sandstone with pure components (at similar conditions) quartz, muscovite, and hematite. More U(VI) was adsorbed on natural and on synthetic sandstone, than on quartz. The higher sorption are caused by the other components muscovite and hematite, and by the higher surface area.
The linear Freundlich sorption isotherms indicate one binding type. Sorption predicted by the Diffuse Double Layer Model (using the code FITEQL) agreed with the experimental sorption values within their uncertainty.
Keywords: sorption, uranium, sandstone, surface complexation, diffuse double layer model
  • Lecture (Conference)
    Goldschmidt 2007, 19.-24.08.2007, Köln, Germany
  • Abstract in refereed journal
    Geochimica et Cosmochimica Acta 71(2007), A838

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Ultra fast electron beam X-ray CT for two-phase flow measurements

Bieberle, M.; Schleicher, E.; Fischer, F.; Hampel, U.; Do Couto Aktay, K. S.; Koch, D.; Menz, H.-J.; Mayer, H.-G.
Nuclear reactor safety concerns for todays operated light water reactors are closely linked to thermal hydraulic phenomena in the primary and secondary coolant circuits of nuclear systems. To gain an improved understanding of phenomena associated with certain types of accidents as well as for the optimisation of fuel elements regarding the heat transfer in the reactor core simulation tools, such as system codes and more recently CFD codes are frequently applied. However, both types of tools today still exhibit some problems when treating two-phase flow scenarios. Therefore, in recent years much effort has been spent on further code development as well as on validation. This, however, was and is always accompanied by the requirement for reliable measurement data from two-phase flows under typical nuclear thermal hydraulic conditions. Experimental thermal hydraulic facilities, such as the TOPFLOW facility at FZD [1], may provide such data if they are equipped with sophisticated two-phase flow measurement sensors. One example is the wire-mesh sensor [2] that can provide phase and velocity data from steam-water two-phase flows at frame rates of up to 10 kHz and spatial resolution down to 2 mm. Since the wire mesh sensor is intrusive it has some influence on the flow. More appropriate would be tomographic imaging techniques based on either X-ray or gamma rays. However, classical CT systems, though being non-intrusive and sufficiently penetrative even for thicker metallic vessel walls, suffer from low temporal resolution, which is due to the requirement for taking different angular views of an object prior to reconstruction. So far this problem has been considered as intractable and unavoidable and tomographic techniques have almost exclusively been used to measure time averaged quantities, such as the gas hold-up.
We recently suggested [1] a computed tomography (CT) system which uses a fast moving electron beam X-ray source for the application in two-phase flow measurements. We have experimentally shown that frame rates of 10000 images per second can be reached. The static installation of the detector, however, limits the angular range of the source path which leads to so called limited-angle artefacts in the reconstructed images. Although these artefacts cannot be completely eliminated, because they are due to missing data, they can be reduced by maximizing the angular viewing range and by adequate image reconstruction algorithms [4].
Keywords: electron beam x-ray CT, two-phase flow
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2007, 22.-24.05.2007, Karlsruhe, Germany
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2007, 22.-24.05.2007, Karlsruhe, Germany
    Proc. Jahrestagung Kerntechnik 2007, CD-ROM plus, 27-30

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Publ.-Id: 9666


Gründungsidee und Geschäftskonzept - BIOREM

Raff, J.
Im Rahmen der zweiten Phase des Businessplan-Wettbewerbs FutureSAX hat es die Geschäftsidee "BIOREM" erneut unter die besten Teams geschafft.
Vor der eigentlichen Prämierung muss die Geschäftsidee und die Marketingstrategie vor der Expertenjury der Branche Bio-/ Nanotechnologie verteidigt werden. Erst nach Prüfung aller Anträge werden die eigentlichen Gewinner gekürt.
  • Lecture (others)
    2. Phase FutureSAX-Businessplan-Wettbewerb, 19.04.2007, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-9665
Publ.-Id: 9665


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