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31738 Publications
The Sorption of Eu(III) on Opalinus Clay at elevated Temperatures and in Presence of Organics
Schott, J.; Acker, M.; Barkleit, A.; Brendler, V.; Bernhard, G.;
Presently, argillaceous rock formations are under investigation as potential host rocks for nuclear waste repositories. In addition to the diffusion the sorption of radionuclides on mineral phases is an important physicochemical process in a nuclear waste repository in the case of a water inleakage. Concerning the required long-term safety and risk assessment of the storage of high-level radioactive waste the understanding of these processes is essential. The investigations concentrated on the sorption of Eu(III) on OPA under realistic OPA pore water conditions (medium: pH 7.6; ionic strength 0.4 mol•L-1; presence of chloride, sulfate, carbonate) up to 50°C. In addition to the temperature dependent investigations the influence of tartrate and citrate (representatives of NOM) on the Eu(III) sorption was studied.
The sorption is characterized by a very strong binding of Eu(III) to the clay surface and a significant temperature dependency. With rising temperature the Rd value rises, showing that the Eu(III) sorption increases. In the presence of tartrate or citrate the Eu(III) sorption decreases with rising ligand concentration.
Keywords: Europium(III), sorption, Opalinus Clay, temperature, citrate, tartrate
  • Contribution to proceedings
    Workshop "Kompetenzerhaltung in der Kerntechnik", 23.-24.05.2012, Stuttgart, Germany
    Proceedings des Workshops "Kompetenzerhaltung in der Kerntechnik"
  • Lecture (Conference)
    The Sorption of Eu(III) on Opalinus Clay at elevated Temperatures and in Presence of Organics, 23.-24.05.2012, Stuttgart, Germany

Publ.-Id: 16913 - Permalink

Filtration and Catalytic Reaction in Trickle Beds: The Use of Solid Foam Guard Beds To Mitigate Fines Plugging
Wardag, A. R. K.; Hamidipour, M.; Schubert, M.; Edouard, D.; Larachi, F.;
The sensitivity of catalytic reactions to concurrent filtration and fines deposition in trickle-bed reactors (TBRs) was assessed by means of the catalytic hydrogenation of alpha-methylstyrene from kaolin-kerosene suspension flows. A negative correlation between catalytic conversion and the specific deposit of the bed resulted from the extra mass-transfer step that built up on the collectors in the course of filtration. The severity of the evolving extra mass-transfer step was sensitive to deposit compaction resulting from higher gas superficial velocities. Furthermore, irreversible catalyst activity losses were observed after catalyst cleanup and were ascribed to irretrievable active sites by catalyst intraparticle fines trapping. Fines accumulation in the catalyst bed was notably reduced by means of high-porosity solid-foam modules used as guard filters and placed upstream of, and adjacent to, the trickle bed. Hydrodynamic studies were carried out with alumina and silicon c!
arbide solid foams to assess their role on the distribution of suspension and the reduction of specific deposit and pressure drop in trickle beds. It was found that the foam capture efficiency critically depended on the open connectivity of foam cells and the physicochemical nature of foam materials. The numbering up of foam modules led to reduced overall specific deposits of the beds and pressure drops, foreseeing a prospect for prolonging the hydrotreatment TBR lifetime, using solid foam as guard beds.
  • Industrial & Engineering Chemistry Research 51(2012)4, 1729-1740
    DOI: 10.1021/ie200955v

Publ.-Id: 16912 - Permalink

Magnetization Reversal in Nanostructures with Graded Perpendicular Anisotropy
Greene, P. K.; Gilbert, D. A.; Kirby, B. J.; Borchers, J. A.; Lau, J. W.; Lai, C.-H.; Osten, J.; Fassbender, J.ORC; Davies, J. E.; Fitzsimmons, M. R.; Liu, K.
Magnetic nanostructures with graded anisotropy offer a solution to both thermal stability and writability challenges in advanced magnetic recording media. The interlayer exchange coupling lowers the overall coercivity, facilitating the writing process, while the magnetically hard layer provides pinning for the media and ensures its thermal stability. Magnetization reversal in such materials can be influenced by both the magnetic anisotropy gradient along the film depth and the lateral feature size. We have explored magnetization reversal in Co/Pd films and patterned structures. Perpendicular magnetic anisotropy is varied by changing the Co thicknesses or sputtering pressure during growth. Effects of deposition order and ion irradiation have been studied by x-ray diffraction, transmission electron microscopy, magnetometry, and first-order reversal curves. Structural integrity and amount of disorders are found to sensitively influence the magnetic properties. Reversal in highly ordered films is dominated by nucleation, propagation, and annihilation of domain walls while in disordered films magnetization reversal is largely by domain wall pinning and magnetization rotation. Depth-dependent magnetization profiles and magnetic anisotropy have been confirmed by polarized neutron reflectivity. Effects of lateral patterning have been investigated in patterned nanodots (down to 60nm diameter). An increase in coercivity and a modified switching field distribution are observed in patterned structures. This is due to the reduced lateral dimensions which limit the domain nucleation and propagation commonly found in unpatterned films. These results demonstrate attractive features of nanostructures with graded anisotropy towards future magnetic recording applications.

Work supported by the US NSF (DMR-1008791 & ECCS-0925626).
Keywords: Magnetic nanostructures
  • Invited lecture (Conferences)
    NordicSpin'12 - Third Nordic Workshop on Spintronics and Nanomagnetism, 22.-25.04.2012, Varberg, Schweden

Publ.-Id: 16911 - Permalink

Gas holdup of rotating foam reactors measured by γ-tomography - effect of solid foam pore size and liquid viscosity
Tschentscher, R.; Schubert, M.; Bieberle, A.; Nijhuis, T. A.; van der Schaaf, J.; Hampel, U.; Schouten, J. C.;
Rotating foam reactors have already shown to give high mass transfer rates compared to stirred tank reactors. For a deeper insight into the hydrodynamics of these reactors, the hydrodynamics of rotating foam reactors were studied using γ-ray tomography. The two-phase flow through the foam block stirrer is mainly influenced by the solid foam pore size and the liquid viscosity. For low viscosity, the optimal foam block pore size was identified in the range between 10 and 20 pores per inch (ppi). With smaller pore size, the gas holdup inside the foam block strongly increases due to bubble entrapment. For higher viscosity, pore sizes larger than 10 ppi have to be used to achieve a sufficient liquid flow rate through the foam block to avoid a strong gradient over the reactor height. The effect of the hydrodynamics on the gas–liquid and liquid–solid mass transfer and the reactor performance are discussed.
Keywords: multiphase reactors, gas holdup, tomography, solid foam

Publ.-Id: 16910 - Permalink

Investigation of various precursors for radiosynthesis of [F-18]flubatine, a novel radioligand for neuroimaging of α4β2-nAChR
Fischer, S.; Hiller, A.; Smits, R.; Hoepping, A.; Funke, U.; Sabri, O.; Steinbach, J.; Brust, P.;
Because specific subtypes of nicotinic acetylcholine receptors (nAChR) are involved in various neurodegenerative diseases, there is a continuing need for their visualization by PET. Compared to epibatidine and the 2-[F-18]F-A-85380, the novel homoepibatidine derivative [F-18]flubatine (formerly named as [F-18]NCFHEB) showed better pharmacological properties, promoting first studies in humans. The former radiosynthesis starting from a bromo precursor was hampered by very low radiochemical yields (RCY ~3%). Therefore, a highly improved approach, transferable to an automated module, was necessary. Herein, we report on comprehensive experiments to improve all steps of radiosynthesis.

The preparation of [F-18]flubatine is based on a two-step radiosynthesis: The nucleophilic aromatic radiofluorination followed by the cleavage of a protecting group. A variety of new precursors with various LGs and PGs was synthesized and tested under different labelling and purification conditions (such as precursor amount, solvent, temperature, thermal/microwave heating, SPE techniques). As LGs, -Cl, -NO2 and the -N(Me3)3 + group with iodide, triflate and other counter anions were tested. The protective function of ethoxycarbonyl, Fmoc, trityl und Boc at the NH-group was studied as well as their quantitative removal. Both SPE and ion exchange cartridges were tested for purification. Analytical and semi-preparative HPLC separation protocols were developed using RP18-AQ phases (isocratic/gradient method; aqueous MeCN as eluent). Furthermore, the stability of [F-18]flubatine was investigated under chemical and physiological conditions. For optimization, all radiochemical steps were controlled by radio-HPLC and radio-TLC.

Application of the -N(Me3)3 iodide precursor with a Boc-PG (0.5-1.0 mg, MeCN, 83°C) provided by far the best radiochemical results. For the final product labelling efficiencies of 90±5%, RCY 70±5% (n=25), spec. activity of >350 GBq/μmol were achieved within a total time of 2.0 h. Complete deprotection of the Boc-PG succeeded with 1M HCl (90°C, 5 min). Compared to results with other PGs, this enabled high labelling efficiencies without by-products, and thus, an easy, fast and quantitative separation. Prior to the deprotection step, the purification of the crude reaction mixture with a C18 cartridge and elution with 1% HOAc/MeCN increased the RCYs, too. The final product was isolated in very high purity by semi-preparative HPLC (tR ~30 min). [F-18]flubatine was stable in diluted HCl, NaOH and K2CO3 solutions as well as under physiological conditions.Furthermore, a chiral HPLC method was developed to prepare enantiomerically pure flubatine.

Various procedures were tested to get a validated [F-18]flubatine radiosynthesis as a prerequisite for an automated radiotracer production, applicable for human studies.

  • Lecture (Conference)
    NuklearMedizin 2012, 25.-28.04.2012, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), V62

Publ.-Id: 16909 - Permalink

Inkorporationsdosimetrische Untersuchung von F-18-Flubatine - Vergleich an Tiermodellen erhobener Daten mit first-in-man Ergebnissen
Sattler, B.; Kranz, M.; Patt, M.; Habermann, B.; Smits, R.; Hoepping, A.; Sattler, T.; Donat, C. K.; Deuther-Conrad, W.; Steinbach, J.; Brust, P.; Sabri, O.;
Ziel/Aim: F-18-Flubatine (früher F-18-NCFHEB) ist ein neuer und vielversprechender Radioligand für die Darstellung von alpha4beta2 nikotinischen Acetylcholinrezeptoren mit PET. Um das Strahlenrisikio durch diesen Tracer abzuschätzen, wurden die Organdosen (OD) und die effektive Dosis (ED) an Schweinen erhoben und mit den Ergebnissen aus Untersuchungen an CD1-Mäusen und Menschen verglichen. Der Ergebnis- und Methodenvergleich dient der Identifizierung des für die Verhältnisse am Menschen am ehesten repräsentativen Tiermodells und als Unterstützung bei der Interpretation der Ergebnisse präklinischer Inkorporationsdosimetrie von Radiotracern für die Hirn-PET. Methodik/Methods: Die inkorporationsdosimetrische Untersuchung von F-18-Flubatine wurde an 6 Ferkeln (weibliche Masthybriden, Alter 56±7d; Gewicht: 14±2kg) vorgenommen. Die narkotisierten Tiere (Einleitung mit 20 mg/kg Ketamin und 2 mg/kg Azaperon; 1.5% Isofluran in 70% N2O/30% O2) wurden nach i.v.- Injektion von 188,4±2,8 MBq F-18-Flubatine einer sequentiellen PET-CT-Untersuchung bis zu 4h nach Injektion an einem SIEMENS Biograph16 (6-7 Bettpositionen pro Frame, 1,5-6min/Bettposition, CT-Schwächungskorrektur, iterative Rekonstruktion) unterzogen. Bis zu 4h p.i. wurde Urin gesammelt und dessen Aktivitätskonzentration bestimmt. Die Gewichte der Organe wurden im Rahmen einer Sektion überprüft. Alle den Tracer aufnehmenden Organe wurden CT-geführt mit dreidimensionalen Regionen (VOIs) markiert und ihr Aktivitätsinhalt nach Recoverykorrektur als Zeit-Aktivitäts-Verlauf (TAC) dargestellt. Die Zeit- und Massenskalen wurden an die menschlichen Skalen angepasst [1]. Mit OLINDA [2] wurden TACs an diese Daten angepasst. ODs wurden unter Verwendung des 73,7kg-"adult male model" bestimmt. Die ED wurde unter Verwendung der Gewebewichtungsfaktoren in der ICRP 103 von 2007 berechnet. Ergebnisse/Results: Die präklinischen Untersuchungen ergaben eine ED für den Menschen von 14,0±0,9 μSv/MBq (extrapoliert v. Ferkel) bzw. 14,2μ μSv/MBq (extrapiliert v. CD1-Maus) Die frühklinischen Untersuchungen an gesunden Freiwilligen ergaben eine ED durch F-18-Flubatine von 22,6±0,7μSv/MBq. Schlussfolgerungen/Conclusions: Der Vergleich der Ergebnisse der präklinischen mit den klinischen Untersuchungen ergibt, dass erstere die Verhältnisse der Strahlenexposition des Menschen durch F-18-Flubatine um systematisch etwa 30-40% unterschätzen. Dieser Umstand ist bei der Abschätzung der Strahlenexposition des Menschen im Vorfeld frühklinischer Studien anhand präklinischer Daten zu berücksichtigen. Literatur/References: [1] Stabin MJ: Fundamentals of Nuclear Medicine Dosimetry, Springer 2008, ISBN 978-0-387-74578-7, 237P
[2] Stabin et. al.: OLINDA/EXM: The Second-Generation Personal Computer Software for Internal Dose Assessment in Nuclear Medicine; JNM 46/6, 2005Die Studie wird vom Bundesministerium für Bildung und Forschung (Nr. 01EZ0820) und vom Strahlenschutzseminar in Thüringen e.V. gefördert.
  • Lecture (Conference)
    NuklearMedizin 2012, 25.-28.04.2012, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), V173

Publ.-Id: 16908 - Permalink

On the T2 trap in zinc oxide thin films
Schmidt, M.; Ellguth, M.; Karsthof, R.; von Wenckstern, H.; Pickenhain, R.; Grundmann, M.; Brauer, G.; Ling, F. C. C.;
Weinvestigated the electronic properties of the T2 deep-level in zinc oxide thin films. It was found that T2 preferentially forms under zinc-rich conditions and can be generated by either annealing the samples at reduced oxygen partial pressures (pO2 < 1 bar) or implanting zinc or copper ions, respectively. A strong dependence of its activation energy and high temperature limit of its cross-section for electron capture on the T2 concentration in the sample is reported. Double DLTS measurements showed that the T2 activation energy decreases with increasing electric field due to phonon assisted tunnelling. Furthermore T2 can be photo-ionised with a threshold photon energy of about 700 meV. Depth-resolved concentration profiles of the T2 level in the samples were measured by optical capacitance–voltage spectroscopy.
Keywords: capacitance–voltage spectra, deep levels, DLTS, ZnO
  • Physica Status Solidi (B) 249(2012)3, 588-595
    DOI: 10.1002/pssb.201147271
  • Lecture (Conference)
    57th Annual Conference of the South African Institute of Physics, 09.-13.07.2012, Pretoria, South Africa

Publ.-Id: 16907 - Permalink

Redox behavior of uranium in biofilms and groundwater seeps, sampled from the granitic rock walls in the ONKALO tunnel (Finland)
Krawczyk-Bärsch, E.; Lünsdorf, H.; Pedersen, K.; Arnold, T.; Bok, F.; Steudtner, R.; Lehtinen, A.; Brendler, V.;
At a depth of 70 m of the ONKALO tunnel in Finland, 771 m from the tunnel entrance, massive biofilms were observed attached to the tunnel walls where groundwater was seeping from bedrock fractures. During a sample campaign 2010 samples of the biofilms and of the groundwater seeps were taken for laboratory experiments. Microelectrode measurements in the biofilms and in the groundwater seeps indicated that the studied biofilms constituted their own microenvironments, which differed significantly from that of the groundwater seeps. A pH of 5.37 was recorded inside the biofilm, approximately 3.5 units lower than the pH observed in the groundwater seeps. Similarly, the Eh of +73 mV inside the biofilm was approximately 420 mV lower than the Eh measured in the groundwater seeps. In flow cells with detached biofilms uranium was added to the circulating groundwater with a final uranium concentration of 4.25 × 10–5 M. After 42 h the pH increased in the biofilm to 7.27 and the Eh was reduced to –164 mV. The changes of Eh and pH influenced the bioavailability of uranium. EF-TEM investigations indicated that uranium in the biofilm was immobilized intracellularly in microorganisms by the formation of metabolically mediated uranyl phosphate, similar to needle-shaped Autunite (Ca[UO2]2[PO4]2•2-6 H2O) or meta-Autunite (Ca[UO2]2[PO4]2•10-12H2O).

In contrast, TRLFS studies of the uranium-contaminated groundwater identified aqueous uranium carbonate species, likely (Ca2UO2[CO3]3), formed due to the high concentration of carbonate in the uranium contaminated circulating groundwater. The results agreed with thermodynamic calculations of the theoretically predominant field of uranium species, formed in the uranium-contaminated groundwater at the measured geochemical parameters.
Keywords: biofilms, uranium, TEM, TRLFS, thermodynamic calculation
  • Contribution to proceedings
    4th Annual Workshop Proceedings of the Collaborative Project "Redox Phenomena Controlling Systems" (7EC FP CP ReCosy), 23.-26.01.2012, Karlsruhe, Deutschland
    KIT Scientific Reports 7626: KIT Scientific Publishing, 241-251

Publ.-Id: 16905 - Permalink

Instability types at ion-assisted alloy deposition: from surface to bulk nanopatterning
Abrasonis, G.; Morawetz, K.;
Ion irradiation assistance of the film growth has a strong impact on structural properties. Here, we demonstrate that ion irradiation of growing binary alloys leads to the formation of composition-modulated surface patterns. Be means of linear stability analysis we show that the ion-to-atom arrival ratio is the pattern control parameter. Close to the instability threshold we identify different regimes of instabilities driven by ion-induced surface roughness processes or roughness-composition feedback interactions. In particular, the synergistic effects of the curvature-dependent displacement coupling to the preferential sputtering or to the diffusivity are found to induce instabilities and pattern formation. Depending on the film growth and ion-irradiation conditions the instabilities show stationary or oscillating behavior. This presents opportunities to grow 3D laterally or vertically ordered nanostructures.
  • Poster
    76. Jahrestagung der DPG und DPG-Frühjahrstagung, 25.-30.03.2012, Berlin, Germany

Publ.-Id: 16904 - Permalink

Reactive High Impulse Power Magnetron Sputtering of Ti in Ar/O2 atmosphere
Audronis, M.; Abrasonis, G.; Heller, R.; Chapon, P.; Bellido-Gonzalez, V.;
High Power Impulse Magnetron Sputtering (HIPIMS) is a technologically important Physical Vapour Deposition (PVD) process that is able to provide a highly ionised flux of sputtered species. It is thought to be particularly important for applications where there is a need to coat 3D features. HIPIMS may have other added benefits, as compared to DC or medium frequency (MF) magnetron sputtering, that are related to improved coating structure-property relationship control through self-species ion/plasma assistance. Enhanced structure and properties of PVD thin film materials produced by reactive sputtering are also highly desirable. Significant progress related to providing control means for reactive HIPIMS processes and ensuring stability has been made recently. This paper reports some of the recent process (reactive HIPIMS of Ti in Ar/O2 atmosphere) and products analysis results. The recently developed Plasma Monitoring based method was used to investigate, monitor and control the deposition process. RBS, ERDA, GDOES and Spectroscopic Ellipsometry were used to characterise the samples produced.
  • Lecture (Conference)
    HIPIMS 2011 - 2nd International Conference on HIPIMS, 28.-29.06.2011, Braunschweig, Germany

Publ.-Id: 16903 - Permalink

Intraexcitonic Autler-Townes effect in terahertz-driven semiconductor quantum wells
Wagner, M.; Stehr, D.; Schneider, H.; Winnerl, S.; Teich, M.; Andrews, A. M.; Schartner, S.; Strasser, G.; Helm, M.;
When a two-level system is resonantly driven by intense light non-perturbative phenomena such as Rabi oscillations and their frequency equivalent, the AC Stark or Autler-Townes effect, can be observed. The latter one manifests itself in an absorption line splitting where the magnitude is linear in the light field strength and where the symmetry of the splitting is determined by the detuning from resonance. Known from molecular spectroscopy [1], the effect has also been observed in solid state structures with its much broader line widths, e.g. for intersubband transitions [2]. Here, we present the first unambigous evidence of this effect in undoped GaAs/AlGaAs quantum wells using the hydrogen atom like intraexcitonic 1s and 2p states of the heavy-hole exciton. These states with a transition energy of 9 meV are resonantly coupled by strong terahertz light from a free-electron laser. For low fields our findings are qualitatively explained by a simple two-level model whereas deviations occur in the 10 kV/cm field range where the rotating-wave approximation of the simplified model breaks down and exciton ionization occurs. Due to the small Rydberg energy we can easily reach a highly non-trivial regime where the Rabi energy and the transition energy become comparable to the photon energy.
[1] S. H. Autler and C. H. Townes, Phys. Rev. 100, 703 (1955).
[2] S. G. Carter et al., Science 310, 651 (2005).
[3] M. Wagner et al., Phys. Rev. Lett. 105, 167401 (2010).
Keywords: Intraexcitonic, Autler-Townes, terahertz, semiconductor quantum well, FEL
  • Lecture (Conference)
    APS March Meeting 2012, 27.02.-02.03.2012, Boston, Massachusetts, USA

Publ.-Id: 16902 - Permalink

Radiosynthese und Charakterisierung von [F-18]NS14490 als potentieller Radiotracer für die molekulare Bildgebung von α7 nikotinischen Acetylcholinrezeptoren (α7 nAChR) im Gehirn
Rötering, S.; Scheunemann, M.; Fischer, S.; Hiller, A.; Peters, D.; Steinbach, J.; Deuther-Conrad, W.; Brust, P.;
Ziel / Aim
Es existieren Hinweise auf Veränderungen von α7 nAChR bei neurodegenerativen Erkrankungen, die durch Radioliganden, die eine molekulare Bildgebung dieser Rezeptoren mit PET ermöglichen, erfasst und quantifiziert werden könnten. Wie früher bereits am Beispiel von [F-18]NS10743 (Ki,NS10743 = 11,6 nM) gezeigt, sind 1,4-Diaza-bicyclo[3.2.2]nonan-1,3,4-oxadiazole als Leitstrukturen dafür grundsätzlich geeignet [1].
In dieser Arbeit wird die Radiosynthese der strukturell modifizierten und höher affinen Verbindung [F-18]NS14490 ([F-18]-2-(1,4-Diaza-bicyclo[3.2.2]nonan-4-yl)-5-(1-(2-fluorethyl)-1H-indol-6-yl)-1,3,4-oxadiazol) vorgestellt.

Methodik / Methods
Eine zweistufige Synthese von [F-18]NS14490 erfolgte durch die Umsetzung von [F-18]Fluorethyltosylat, das aus [F-18]F- und Ethylenglykoldistosylat synthetisiert wurde, mit der Verbindung NS14540. Parallel wurde in einer Einstufensynthese [F-18]F- mit dem o-Tosylpräkursor I umgesetzt, der zuvor durch die Tosylierung des entsprechenden Alkohols erhalten wurde. Die Isolierung und Reinigung von [F-18]NS14490 wurde umfassend optimiert und erfolgte durch semipräparative RP-HPLC und anschließende Festphasenextraktion.
Zur physikochemischen Charakterisierung von [F-18]NS14490 wurden Stabilitätsuntersuchungen in verschiedenen wässrigen Pufferlösungen bei pH 7,4 und 40°C durchgeführt sowie der Verteilungskoeffizient logD7,1 in mehreren n-Octanol/Puffer-Extraktionssystemen bestimmt.

Ergebnisse / Results
Während in der Zweistufensynthese Markierungseffizienzen <10% (n = 3) erreicht wurden, war die Einstufensynthese mit einer Markierungseffizienz von bis zu 89% (n = 15) deutlich erfolgreicher.
Nach umfangreicher Optimierung aller Isolierungs- und Reinigungsschritte konnte das Zielprodukt [F-18]NS14490 mit einer radiochemischen Reinheit >98% und einer spezifischen Aktivität > 150 GBq µmol-1 innerhalb einer Gesamtsynthesedauer von zwei bis drei Stunden dargestellt werden (n = 3).
Bei der physikochemischen Charakterisierung zeigte [F-18]NS14490 in den physiologisch ähnlichen Pufferlösungen über einen Zeitraum von 120 Minuten eine Stabilität von >98% (n = 3). Der logD7,1-Wert betrug 1,20 ± 0,02 (n = 8).
Schlussfolgerungen / Conclusions
Die Ergebnisse stellen eine gute Voraussetzung für weiterführende In-vitro- und In-vivo-Studien dar, insbesondere zur Hirn-Aufnahme und zur Selektivität der Bindung von [F-18]NS14490 an α7 nAChR im Gehirn.
Darüber hinaus ist die erarbeitete Synthesevorschrift als Basis für die Entwicklung einer Herstellung von [F-18]NS14490 mit einem Synthesemodul geeignet.
Literatur / References
1. W. Deuther-Conrad et al. Eur J Nucl Med Mol Imaging (2009) 36:791–800
  • Lecture (Conference)
    NuklearMedizin 2012, 25.-28.04.2012, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), V108

Publ.-Id: 16901 - Permalink

Struktur-Affinitäts-Untersuchungen neuer Vesamicolanaloga zur Entwicklung eines PET-Liganden für den vesikulären Acetylcholintransporter
Barthel, C.; Wenzel, B.; Sorger, D.; Schweiger, S.; Deuther-Conrad, W.; Jäckel, P.; Brust, P.; Schüürmann, G.; Sabri, O.; Steinbach, J.;
Im Verlauf der Alzheimer Demenz kommt es zur Degeneration cholinerger Nervenzellen. Der präsynaptisch lokalisierte vesikuläre Acetylcholintransporter (VAChT) dient als Target, um diese Veränderungen im Gehirn mit Hilfe molekularer Bildgebung darzustellen. Vesamicol (2-(4-Phenylpiperidin-1-yl)cyclohexanol) ist ein hoch-affiner, nicht-kompetitiver Inhibitor des VAChT und dient als Leitstruktur für die Entwicklung eines PET-Liganden. Aufgrund seiner vorhandenen Affinität zu Sigma-Rezeptoren weist er eine unzureichende Selektivität für die In-vivo-Darstellung cholinerger Hirnareale auf. Systematisch strukturell modifizierte Vesamicolanaloga werden als Bestandteil einer Struktur-Affinitäts-Studie auf ihre Affinität zum VAChT und Sigma-Rezeptoren hin untersucht. Die Ergebnisse sollen zur Entwicklung eines selektiven PET-Liganden für den VAChT führen.
Ausgehend von geeigneten Epoxidvorläufern wurden die Vesamicolanaloga durch nukleophile Epoxidringöffnung mit strukturell verschiedenen Aminen synthetisiert. Ein Teil der Synthesen konnte durch den Einsatz von Lithiumsalzen regioselektiv durchgeführt werden. Die Regioisomere der nicht-regioselektiven Synthesen wurden mit Hilfe präparativer HPLC getrennt. Die isolierten Produkte wurden durch HPLC, NMR und MS charakterisiert. Mit Hilfe kompetitiver Bindungsassays wurden die Bindungsaffinitäten zum VAChT und zu den Sigma-Rezeptoren an mit Ratten-VAChT-cDNA stabil transfizierten PC12-Zellen, Rattencortex (σ1) und Rattenleber (σ2) mit den Radioliganden (-)-H-3-Vesamicol (VAChT), (+)-H-3-Pentazocin (σ1) und H-3-DTG (σ2) bestimmt.
Die drei neuen Gruppen der Vesamicole, F-Benzylether- und Aminobenzovesamicole wurden synthetisiert und im Hinblick auf ihre Affinitäten zum VAChT und den Sigma-Rezeptoren in vitro charakterisiert. Durch Einsatz verschiedener Epoxide konnte die Struktur des Cyclohexylrings (A) des Vesamicolgrundgerüsts variiert werden. Modifikationen am Piperidinylring (B) und Phenylring (C) wurden durch den Einsatz strukturell verschiedener Amine erhalten. Die VAChT-Bindungsaffinitäten reichen vom unteren nanomolaren bis in den mikromolaren Bereich. Dabei wurden erwartungsgemäß innerhalb der Klassen (Unterschied in B bzw. C) große Unterschiede beobachtet. Jedoch lieferten auch vergleichbare Derivate der verschiedenen Klassen (Unterschied in A) sehr unterschiedliche Werte. Die darauf basierenden Selektivitätsfaktoren (Ki(σ1)/Ki(VAChT) bzw. Ki(σ2)/Ki(VAChT)) variierten ebenfalls stark.
Die Ergebnisse zeigen, dass derzeit keine Vorhersage über das Affinitätsprofil einer Verbindung getroffen werden kann, da der Einfluss struktureller Veränderungen nicht sicher einschätzbar ist. Damit wird die Notwendigkeit zur Durchführung einer quantitativen Struktur-Affinitäts-Studie unterstrichen, die auf Grundlage der systematisch strukturell veränderten Vesamicolanaloga beruht.
  • Lecture (Conference)
    NuklearMedizin 2012, 25.-28.04.2012, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), V65

Publ.-Id: 16900 - Permalink

Relaxation dynamics in Landau quantized graphene
Mittendorff, M.; Winnerl, S.; Schneider, H.; Helm, M.; Orlita, M.; Potemski, M.; Winzer, T.; Malic, E.; Knorr, A.; Sprinkle, M.; Berger, C.; de Heer, W. A.;
To investigate the carrier relaxation dynamics in Landau quantized graphene, we performed pump-probe measurements on quasi-neutral sheets of multilayer epitaxial graphene in magnetic fields. Due to the linear dispersion for low energies in graphene, the Landau level (LL) spacing is not equidistant. Hence it is possible to investigate a single LL transition selectively. To this end we performed pump-probe measurements at a wavelength of 16.5 µm and applied a magnetic field of up to 7T. We varied the magnetic field for resonant measurements at three different LL transitions. For the transitions LL-1(-2) -> LL2(1) and LL-2(-3) -> LL3(2) we could observe a slight increase of the pump-probe signal while the relaxation time stayed constant. For the transition LL-1(0) -> LL0(1) the amplitude of the pump-probe signal increased by a factor of 2.5, the relaxation time decreased from 20 ps to 5 ps. To understand the processes, influencing the carrier relaxation, we performed measurements with linearly and circularly polarized radiation. This enables us to distinguish between the transition LL-1->LL0 and LL0->LL1. This revealed complex dynamics involving positive and negative signals. We suggest this to result from different relaxation channels including Auger processes.
  • Invited lecture (Conferences)
    THz dynamics in carbon based nanostructures, 07.03.2012, Dresden, Deutschland

Publ.-Id: 16899 - Permalink

Solid-state properties and colloidal stability of thorium(IV)-silica nanoparticles
Hennig, C.; Weiss, S.; Banerjee, D.; Brendler, E.; Honkimäki, V.; Cuello, G.; Ikeda-Ohno, A.; Scheinost, A.; Zänker, H.;
Thorium(IV) is able to form meta-stable colloids with silica in aqueous solution at pH ≥ 7 which results concentrations of colloid-borne Th(IV) of 10^-3 M. The colloid structure can be regarded as amorphous because it shows no long-range order, indicated by the absence of distinct structural periodicity > 4 Å. The internal structure of the colloid particles consists of [Th(O(H))n] polyhedra, n = 8-9, coordinated partly by [SiO4] polyhedra with Th-Si distances of 3.25±0.02Å, and partly by [Th(O(H))n] polyhedra with Th-Th distances of 3.98±0.02Å. The near-order coordination shows similarity with that of the orthosilicates thorite, α-ThSiO^4, and huttonite, β-ThSiO^4. XPS analysis of the oxygen bonds revealed the presence of O^2-, OH^- and H2O. The colloids can be classified as oxyhydroxo colloids [(Th,Si)On(OH)4-nxH2O]4-2n-(4-n). Silica occurs in the colloid structure either in mononuclear or oligomeric units, depending on the Si/Th ratio and the silica precursor formed in the initial solution. Silica is enriched at the colloid surface if the concentration of the initial solutions is increased. The solution behavior of the particles was analyzed by in-situ methods. With rising silica content, the particles gradually change from metal oxide type colloids to silica type colloids which can dramatically increase their colloidal stability.
Keywords: colloids, EXAFS, HEXS, XPS, neutron scattering, NMR

Publ.-Id: 16898 - Permalink

Multifunctional Schiff Base Ligands for UO22+ Binding and Extraction
Tanh Jeazet, H. B.; Gloe, K.; Doert, T.; Heine, A.; Mizera, J.; Kataeva, O. K.; Acker, M.; Tsushima, S.; Bernhard, G.; Gloe, K.;
no abstract for this material
  • Contribution to proceedings
    19th International Solvent Extraction Conference (ISEC 2011), 03.-07.10.2011, Santiago, Chile
    Proceedings of the 19th International Solvent Extraction Conference, Chapter 8, No. 200, 1-8

Publ.-Id: 16897 - Permalink

Untersuchungen transmutationsrelevanter Kernreaktionen im Rahmen des TRAKULA Verbundprojekts
Kögler, T.; Trakula-Kollaboration;
Für eine zukünftige Transmutation langlebiger hochradioaktiver Abfälle werden genaue Kernreaktionsdaten insbesonders von Kernreaktionen, wie der neutroneninduzierten Spaltung und der inelastischen Neutronenstreuung benötigt. Am neuen Zentrum fürr Hochleistungsstrahlungsquellen des HZDR wird für diese Messungen eine Photoneutronenquelle im Energiebereich von ca. 0.1 bis 10 MeV mit einer untergrundarmen Neutronenflugstrecke gebaut. Zum Nachweis der neutroneninduzierten Spaltung von Uran- und Plutonium-Isotopen befindet sich ein Experimentaufbau mit Spaltionisationskammern in Vorbereitung. Durch Verwendung dünner Probenschichten und separater digitaler Datenauslese soll eine Pulshöhenseparation der Spaltfragmente von den pile-up Ereignissen aus dem Alpha-Zerfall der Aktiniden erreicht werden. Aktinidenschichten aus U(238) und U(nat) sind bereits am Institut für Kernchemie der Universität Mainz hergestellt worden. Ausgewählte Aktivitäten des TRAKULA Verbundprojekts, wie Entwicklung einer Compton-Kamera zur hochaufgelösten MeV Gamma-Spektroskopie, Beschleunigermassenspektrometrie langlebiger Spaltprodukte, Entwicklung eines Untergrundlabors zur Messung sehr niedriger Alpha-Aktivitäten werden präsentiert. Das TRAKULA Projekt ( wird unterstützt durch das Bundesministerium für Bildung und Forschung (PTKA-WTE 02NUK13A).
Keywords: Transmutation, TRAKULA
  • Lecture (Conference)
    DPG Frühjahrstagung, 19.-23.03.2012, Mainz, Deutschland
  • Lecture (others)
    TRAKULA Seminar Mainz, 21.-23.05.2012, Mainz, Deutschland
  • Poster
    HZDR PhD Seminar 2011, 05.-07.10.2011, Breitenbrunn, Deutschland
  • Poster
    Tag des offenen Labors des HZDR 2012, 12.05.2012, Rossendorf, Deutschland

Publ.-Id: 16896 - Permalink

Coupled vortex pairs in magnetic multilayer elements
Wintz, S.; Raabe, J.; Banholzer, A.; Erbe, A.; Quitmann, C.; Fassbender, J.ORC
Spin vortices have attracted much attention due to their chiral nature and the variety of dynamic phenomena that they exhibit. In this contribution we present experimental findings on vortex coupling in trilayer elements, where two ferromagnetic layers are separated by a nonmagnetic interlayer. For such systems the relative configurations of the in-plane flux rotation senses (circulations) as well as the core orientations (polarities) of vortex pairs are identified by means of scanning transmission x-ray microscopy (STXM). The relevant coupling mechanisms here are the magneto-dipolar interaction and interlayer exchange coupling (IEC). Remarkably, a modification of the IEC, which can be induced by ion irradiation, allows to set the circulation configuration of a layered vortex pair to be either antiferromagnetic or ferromagnetic. In addition, time-resolved measurements of the response of interlayer coupled vortex pairs to an excitation by external magnetic fields will be shown.
Keywords: magnetism, vortex, coupling
  • Poster
    Annual Meeting of the Swiss Physical Society 2012, 21.-22.06.2012, Zürich, Schweiz

Publ.-Id: 16895 - Permalink

Pulsformdiskrimination und Lichtausbeutemessungen von LAB-basierten Flüssigszintillatoren
Kögler, T.;
Linear alkyl benzene (LAB, C6H5CnH2n+1, n = 10 - 13) is the proposed solvent for the SNO+, the Daya Bay Neutrino and LENA experiment. In solution with the commonly used scintillator PPO it is a colourless, odourless and cheap liquid scintillator with a high flash point and low health hazard compared to toluene based ones. The properties of LAB make this scintillator interesting also for nELBE, the neutron time-of-flight facility at Helmholtz-Zentrum Dresden-Rossendorf. A new approach to measure the light yield in the low-energy range using a combination of quasi-monoenergetic photon sources and a Compton-spectrometer is described. The latter allows the measurement of the light yield down to 5 keVee (electron equivalent). The Birks-Parameter was determined for a homemade solution (LAB + 3 g=l PPO) and for NE-213. The light yield (relative to this standard scintillator) was confirmed by measurements using a fluorescence spectrometer. The ability of pulse-shape-discrimination in a mixed n-gamma-field of a 252Cf source was tested using different digital and semi-analogue techniques.
Keywords: liquid scintillators, digital signal processing, digital pulse shape discrimination, Compton spectrometer
  • Diploma thesis
    HZDR / TU Dresden, 2012
    110 Seiten
  • Lecture (Conference)
    DPG Frühjahrstagung 2011 Münster, 21.-25.03.2011, Münster, Deutschland
  • Poster
    HZDR PhD Seminar, 05.-07.10.2011, Breitenbrunn, Deutschland

Publ.-Id: 16893 - Permalink

Light yield and n-gamma pulse-shape discrimination of liquid scintillators based on linear alkyl benzene
Kögler, T.; Junghans, A. R.; Beyer, R.; Hannaske, R.; Massarczyk, R.; Schwengner, R.; Wagner, A.;
The relative light yields of NE-213 and LAB-based liquid scintillators to electrons were determined in the electron energy range 5-1600 keV using a combination of monoenergetic photon sources and a Compton spectrometer. The light yield was found to be proportional to energy for both types of scintillator and expected deviations below 100 keV were described successfully applying Birks’ law. Digital pulse-shape discrimination in a mixed n-g field of a 252Cf source was investigated for LAB+PPO and LAB+PPO+bis-MSB and compared to NE-213. In combination with these two solutes, LAB shows poorer abilities to separate neutron-induced pulses from photon-induced ones.
Keywords: liquid scintillators, Compton spectrometer, digital data processing

Publ.-Id: 16892 - Permalink

Investigation of Uranium(VI) Speciation in Some German Mineral Waters
Osman, A. A. A.; Geipel, G.; Bernhard, G.;
A cryogenic time resolved laser induced fluorescence spectroscopy (cryo-TRLFS) was successfully used to identify uranium binding forms in some German mineral waters of exceptionally low concentrations (<3.0 µg/ L). The measurements were performed at 153 K. The spectroscopic data showed a prevalence of aquatic species Ca2UO2(CO3)3 in most of the waters, while UO2(CO3)34- dominates only in a very few samples. The influence of the pH and main water constituents on uranium speciation was discussed. Spectroscopy indicated a good agreement with the modelling results.
Keywords: Mineral water, cryo-TRLFS, uranium, speciation
  • Poster
    Uranium biogeochemistry: transformations and applications, 11.-16.03.2012, Ascona, Switzerland
  • Contribution to proceedings
    Uranium biogeochemistry: transformations and applications, 11.-16.03.2012, Ascona, Switzerland

Publ.-Id: 16891 - Permalink

Dynamics of the free surface of stratified two-phase flows in channels with rectangular cross-sections
Vallée, C.;
Stratified two-phase flows were investigated at different test facilities with horizontal test sections in order to provide an experimental database for the development and validation of computational fluid dynamics (CFD) codes. These channels were designed with rectangular cross-sections to enable optimal observation conditions for the application of optical measurement techniques. Consequently, the local flow structure was visualised with a high-speed video camera, delivering data with high-resolution in space and time as needed for CFD code validation.

Generic investigations were performed at atmospheric pressure and room temperature in two air/water channels made of acrylic glass. Divers preliminary experiments were conducted with various measuring systems in a test section mounted between two separators. The second test facility, the Horizontal Air/Water Channel (HAWAC), is dedicated to co-current flow investigations. The hydraulic jump as the quasi-stationary discontinuous transition between super- and subcritical flow was studied in this closed channel. Moreover, the instable wave growth leading to slug flow was investigated from the test section inlet. For quantitative analysis of the optical measurements, an algorithm was developed to recognise the stratified interface in the camera frames, allowing statistical treatments for comparison with CFD calculation results.

The third test apparatus was installed in the pressure chamber of the TOPFLOW test facility in order to be operated at reactor typical conditions under pressure equilibrium with the vessel atmosphere. The test section representing a flat model of the hot leg of the German Konvoi pressurised water reactor (PWR) scaled at 1:3 is equipped with large glass side walls in the region of the elbow and of the steam generator inlet chamber to allow visual observations. The experiments were conducted with air and water at room temperature and maximum pressures of 3 bar as well as with steam and water at boundary conditions of up to 50 bar and 264°C. Four types of experiments were performed, including generic test cases as well as transient validation cases of typical nuclear reactor safety issues. As an example, the co-current flow experiments simulate the two-phase natural circulation in the primary circuit of a PWR. The probability distribution of the water level measured in the reactor pressure vessel simulator was used to characterise the flow in the hot leg. Moreover, the flooding behaviour in this conduit was investigated with dedicated counter-current flow limitation experiments. A comparison of the flooding characteristics with similar experimental data and correlations available in the literature shows that the channel height is the characteristic length to be used in the Wallis parameter for channels with rectangular cross-sections. Furthermore, for the analysis of steam/water experiments, condensation effects had to be taken into account. Finally, the experimental results confirm that the Wallis similarity is appropriate to scale flooding in the hot leg of a PWR over a large range of pressure and temperature conditions.

Not least, different examples of comparison between experiment and simulation demonstrate the possibilities offered by the data to support the development and validation of CFD codes. Besides the comparison of qualitative aspects, it is shown exemplarily how to treat the CFD results in order to enable quantitative comparisons with the experiments.
Keywords: stratified two-phase flows, high-speed camera observation, videometry, HAWAC, TOPFLOW, steam/water experiments, hot leg model, counter-current flow limitation, CCFL, CFD validation
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-018 2012
    ISSN: 2191-8708


Publ.-Id: 16889 - Permalink

Analytical Solutions for ADS Experiments. Development and Application.
Glivici-Cotruta, V.; Merk, B.;
In recent years, the accelerator-driven subcritical reactors (ADSR or ADS) were proposed for the transmutation of the transuranic elements from spent nuclear fuel. ADS can be also used for the energy production from the abundant element thorium. An operation of ADS requires reliable online reactivity determination methods. The classical methods for reactivity calculation have demonstrated strong system dependence in the experimental campaigns (YALINA , MUSE). These methods are based on point kinetics equations. To overcome the problem in the analysis of the space-time behavior of the neutron flux in ADS, the solutions for the space and time dependent diffusion and P1 transport equations were developed analytically. The Green’s function method was applied. The results were compared with the experimental results for the YALINA-Booster facility. The analytical solutions are in a good agreement with the experimental ones. In this work the authors give an overview of the developed solutions and their application for the analysis of the ADS experiments.
Keywords: Accelerator-driven system, Green’s function, diffusion, P1 transport, YALINA-Booster
  • Contribution to proceedings
    International conference dedicated to the fiftieth anniversary of BFS critical facility, 28.02.-01.03.2012, Obninsk, Russia
    Proceedings of the International conference
  • Lecture (Conference)
    International conference dedicated to the fiftieth anniversary of BFS critical facility, 28.02.-01.03.2012, Obninsk, Russia

Publ.-Id: 16888 - Permalink

The linear and nonlinear optical response of native-oxide covered rippled Si templates with nanoscale periodicity
Persechini, L.; Ranjan, M.; Grossmann, F.; Facsko, S.; Mcgilp, J. F.;
Fabrication of dense arrays of nanowires by growth on nanostructured substrates appears to be a promising approach for producing functional nanoscale devices. Ion beam irradiation under carefully controlled conditions produces selforganized ripple patterns on silicon substrates, on which Ag nanowire arrays with nanoscale periodicity have been grown successfully. Here, the linear and nonlinear optical response from native-oxide-covered Si(001) templates, with ripple periodicity between 20 and 50 nm, is reported. Reflection anisotropy spectroscopy (RAS) shows a small, broad peak at 2.5 eV of1x10^-3 amplitude. The RAS response decreases as the periodicity of the ripple structure increases. The nonlinear second-harmonic (SH) response from the samples was also measured, using unamplified femtosecond excitation at 800 nm, by rotating the linear polarized input and detecting either the sor p-polarized SH output.Adecrease in response with increased ripple structure periodicity was observed for the p-in/p-out configuration, when the plane of incidence was orthogonal to the average ripple orientation. Possible origins of the response and future experiments are discussed.
Keywords: ion beam irradiation, nanowires, optical characterization, rippled silicon

Publ.-Id: 16887 - Permalink

Europium(III) Complexation with Salicylic Acid at Elevated Temperatures
Barkleit, A.; Acker, M.; Bernhard, G.;
The complex formation of europium(III) with salicylic acid was investigated with time-resolved laser-induced fluorescence spectroscopy (TRLFS) in aqueous solution at elevated temperatures. Three complexes with metal-to-ligand stoichiometries of 1:1, 1:2 and 1:3 could be identified. Stability constants have been calculated for these complexes at various temperatures between 25 and 60 °C. Using the van´t Hoff equation, thermodynamic data (reaction enthalpy ΔrH, reaction entropy ΔrS and reaction energy ΔrG) could be determined. The formation of the 1:1 complex with ΔrH = -2.1 ± 4.9 kJ • mol-1 is nearly temperature independent, whereas the formation of the 1:2 and 1:3 complexes with reaction enthalpies of 12.7 ± 4.8 kJ • mol-1 and 23.3 ± 3.7 kJ • mol-1, respectively, is clearly endothermic.
Keywords: Europium; salicylate; stability constants; thermodynamic data; TRLFS; potentiometry

Publ.-Id: 16886 - Permalink

Annual Report 2011 - Institute of Radiochemistry
Bernhard, G.; Foerstendorf, H.; Richter, A.; (Editors)
The Institute of Radiochemistry (IRC) is one of the seven institutes of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The research activities are fully integrated into the “Nuclear Safety Research Program” of the Helmholtz Association and focused on the topic “Safety of Nuclear Waste Disposal”.
The research objectives are to generate better process understanding and data for the long-term safety analysis of a nuclear waste disposal in the deep geological underground. A better knowledge about the dominating processes essential for radionuclide (actinide) mobilization and immobilization on the molecular level is needed for the assessment of the macroscopic processes which determine the transport and distribution of radioactivity in the environment.
Special emphasis is put on the biological mediated transport of long-lived radionuclides in the geosphere and their interaction with different biosystems like biota and human organism for a better calculation of environmental and health risks.
Advanced knowledge is needed for description of the processes dominating at the interfaces between geo- and bio-systems related to the distribution of long-lived radionuclides in various bio-systems along the food chain.
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-013 2012
    ISSN: 2191-8708


Publ.-Id: 16885 - Permalink

Neue photokatalytisch aktive Vervundmaterialien zur Eliminierung von pharmazeutischen Reststoffen - Teilprojekt: Herstellung und Charakterisierung von photokatalytischen S-Layer basierten Nanokompositen
Vogel, M.; Lehmann, F.; Bobeth, C.; Kutschke, S.; Pollmann, K.; Raff, J.;
Vorstellung der aktuellen Forschungsergebnisse und geplanten Arbeiten zum Thema Herstellung und Charakterisierung von photikatalytischen S-Layer Nanokompositen.
Keywords: S-Layer, Photokatalyse, Nanokomposit
  • Poster
    2. Clustertreffen der BMBF-Fördermaßnahmen NanoCare und NanoNature, 13.-14.03.2012, Frankfurt/Main, Deutschland

Publ.-Id: 16884 - Permalink

Entwicklung und Bewertung neuer photokatalytisch aktiver Verbundmaterialien zur Eliminierung von Arzneimittelreststoffen im Projekt NanoPharm
Raff, J.;
Vorstellung der wissenschaftlichen Arbeiten und erzielten Ergebnisse in dem NanoNature Verbundprojekt NanoPharm
  • Lecture (others)
    2. Clustertreffen der BMBF-Fördermaßnahmen NanoCare und NanoNature, 13.-14.03.2012, Frankfurt am Main, Deutschland

Publ.-Id: 16883 - Permalink

Thermal spin current and magnetothermopower by Seebeck spin tunneling
Jansen, R.; Deac, A. M.; Saito, H.; Yuasa, S.;
The recently observed Seebeck spin tunneling, the thermoelectric analog of spin-polarized tunneling, is described. The fundamental origin is the spin dependence of the Seebeck coefficient of a tunnel junction with at least one ferromagnetic electrode. Seebeck spin tunneling creates a thermal flow of spin-angular momentum across a tunnel barrier without a charge tunnel current. In ferromagnet/insulator/semiconductor tunnel junctions, this can be used to induce a spin accumulation Δμ in the semiconductor in response to a temperature difference ΔT between the electrodes. A phenomenological framework is presented to describe the thermal spin transport in terms of parameters that can be obtained from experiment or theory. Key ingredients are a spin-polarized thermoelectric tunnel conductance and a tunnel spin polarization with nonzero energy derivative, resulting in different Seebeck tunnel coefficients Sst ↑ and Sst ↓ for majority and minority spin electrons. We evaluate the thermal spin current, the induced spin accumulation and Δμ/ΔT, discuss limiting regimes, and compare thermal and electrical flow of spin across a tunnel barrier. A salient feature is that the thermally induced spin accumulation is maximal for smaller tunnel resistance, in contrast to the electrically induced spin accumulation that suffers from the impedance mismatch between a ferromagnetic metal and a semiconductor. The thermally induced spin accumulation produces an additional thermovoltage proportional to Δμ, which can significantly enhance the conventional charge thermopower. Owing to the Hanle effect, the thermopower can also be manipulated with a magnetic field, producing a Hanle magnetothermopower.
Keywords: spin current, spin injection, magnetothermopower

Publ.-Id: 16882 - Permalink

Structural analysis of surface species of U(VI) on gibbsite - A combined approach using ATR FT-IR, EXAFS spectroscopy and DFT-calculations
Gückel, K.;
The migration behavior of heavy metal contaminants like actinyl ions (U, Np) is mainly controlled by sorption processes at water-mineral interfaces. Hence, the investigation of the interactions of actinides with metal oxides such as Al(OH)3, Fe(OOH)x, TiO2, or SiO2, serving as model phases for more complex, naturally occurring minerals in aqueous solution, becomes essential for the safety assessment in the near and far field of nuclear repositories. In this study, gibbsite is used as a mineral model system because it the most common crystalline aluminum hydroxide and an ubiquitous weathering product of aluminosilicate minerals.
Spectroscopic data of surface complexes of uranium(VI) on gibbsite were obtained by in-situ Attenuated total reflection Fourier-transform (ATR FT-IR) and X-ray absorption spectroscopy.
The formation of a monomeric binary inner-sphere surface complex is derived from vibrational spectroscopic and EXAFS data irrespective of the prevailing atmospheric condition and surface loading. In addition, from infrared spectra it was found that U(VI) surface precipitation occurs at a micromolar concentration level after a relatively short contact time in an inert gas atmosphere. However, this is circumvented by lowering the initial U(VI) concentration or in the presence of atmospheric CO2 due to the formation of ternary uranyl carbonato surface complexes. The ternary complex was identified as a dimeric inner-sphere uranyl surface species containing a bidentately coordinated carbonate ligand.
Furthermore, DFT calculations were done to determine the structure and IR spectra of the aqueous dimeric uranyl-carbonate-hydroxo complex.
Keywords: uranium, ATR FT-IR, EXAFS, DFT
  • Poster
    ACTINET ThuL Spring School in Actinide Chemistry, 26.-30.03.2012, Karlsruhe, Deutschland

Publ.-Id: 16881 - Permalink

Magma storage and evolution in the Henties Bay-Outjo dyke swarm, Namibia –feeder systems of the Etendeka lavas
Keiding, J. K.; Frei, O.; Renno, A. D.; Veksler, I. V.; Trumbull, R. B.;
At the roots of continental flood basalts in the Paraná-Etendeka province are mafic dyke swarms that cover areas of several hundred kilometers. Studies of these dykes have focused mainly on the age, paleomagnetic properties and geochemistry, but less on pressure (P) and temperature (T) conditions of emplacement. However, the P and T conditions under which dyke magmas are stored are crucial for models of magma plumbing systems in flood basalt provinces. The erupted lavas are typically far from primitive compositions and generally show evidence for strong crustal assimilation in addition to magma fractionation. Unknown is where this magma modification took place in the crust. This is the kind of information that dyke studies can provide.
The Henties Bay Outjo dyke swarm (HOD) in NW Namibia is the subject of this study. This is inarguably the best exposed of major dyke swarms associated with South Atlantic rifting and breakup and its geochemical diversity is well documented but aspects relating to the magma dynamics in the dyke swarm have not been studied before. Our approach is to use geochemical data from selected dykes to assess the differentiation and assimilation history of the magmas, and combine that with petrologic constraints on the temperature-pressure conditions of crystallization derived from mineral-melt equilibria.
We have determined P-T estimates from olivine-melt and clinopyroxene-melt equilibria using analysis of phenocrysts by electron microprobe and applying the thermodynamic relations from Putirka (2008), who considered the standard error to be 1.7 kbar and 30 °C. The calculations reflect only mineral-melt (proxied by whole-rock) compositions that are consistent with equilibrium. Crystallization temperatures range from 1040 °C to 1350 °C with a mean (n=58) of 1170 °C. These T-variations are not random, the high-temperature results come from a specific region of dyke emplacement but the reason for this is not yet clear. Olivine-melt temperatures are higher than those from clinopyroxene-melt. The inferred crystallization sequence is in harmony with petrographic and geochemical observations. Pressures of clinopyroxene crystallization range from 0.7 to 7.1 kbar. The average pressure (n=12) is 4.9 kbar, few dykes yielded lower than 3 kbar, and the majority of dykes appear to have crystallized at 4-6 kbar. These estimates can be linked with bulk geochemistry to derive viscosity and melt densities to explore the mechanics of dyke emplacement.
Keywords: Namibia, Etendeka, Basalt, Henties Bay Outjo dyke swarm, Petrology, Geothermobarometer
  • Lecture (Conference)
    European Geosciences Union General Assembly 2012, 22.-27.04.2012, Wien, Österreich

Publ.-Id: 16880 - Permalink

Zircon and monazite patterns resulted from late- to postmagmatic fluid-interaction processes in granitoid pluton and related rhyolitic bodies
Lisowiec, K.; Budzýn, B.; Słaby, E.; Renno, A. D.; Götze, J.;
Zircon and monazite from the peraluminous Stolpen granite and related rhyolitic dyke show magmatic as well as post-magmatic textures. The magmatic textures represented mostly by subtle oscillatory zoning are overprinted by post-magmatic fluid interaction which is indicated by elevated contents of Y, P, Th, and U and dissolution textures in altered zircon domains. Late- to postmagmatic fluid-induced crystallization can be divided into two main stages separated by a strong dissolution event: 1st - the formation of Y-, P-, Th- and U-rich rims and 2nd - purification of these domains by trace element release which led to the formation of secondary xenotime and huttonite/thorite. This can be observed both in the granite and its aplitic parts and rhyolite. Patchy zoning in primary monazite from the granite also suggests fluid-induced alterations. Its formation could resulted from the coupled dissolution-reprecipitation processes. Dark patches are depleted in Th, U and Pb which is interpreted as a result of selective removal of these elements from the monazite structure. Beside modification of monazite composition, partial dissolution of monazite grains occurred as well indicating the aggressive character of the fluids. Monazite grains from the rhyolite show slightly different textures and composition. High Ca, Pb, and Si contents and depletion in Th, as well as porous, spongy textures are results of fluid-induced alterations that caused also crystallization of cheralite. Grains with pure monazite composition cannot be found.
Zircon and monazite from the granite are accompanied by fluorite, Y-rich and Nb-rich minerals. High abundance of fluorite suggests elevated fluorine concentration in the fluids which facilitated both the dissolution of zircon and monazite grains and removal of certain elements from their structure. The absence of fluorite in the rhyolite indicates a different nature of the fluids involved in the alteration processes however the porous textures of zircon and monazite suggest their high reactivity as well.
The alteration of primary, magmatic accessory minerals and formation of secondary minerals is interpreted as related to magmatic fluids, which origin cannot be defined precisely on the base of the present data. However their composition (high F-, Y- and Ca- activity) and the mineralogy of the accessory phases suggest that they weren’t derived only from the parental magma itself.
Keywords: zircon, monazite, accessory minerals, fluid interaction, Stolpen Granite, rhyolite
  • Poster
    European Geosciences Union General Assembly 2012, 22.-27.04.2012, Wien, Österreich

Publ.-Id: 16879 - Permalink

Magnetic domains and twin boundary movement of NiMnGa magnetic shape memory crystals
Neudert, A.; Lai, Y. W.; Schäfer, R.; Kustov, M.; Schultz, L.; McCord, J.;
Time-resolved metallographic optical microscopy techniques are used together with magnetic domain imaging to clarify the interaction between magnetic domains and twin boundary motion in magnetic shape memory NiMnGa single crystals. The magnetic field and stress induced magnetic domain formation is imaged by a magneto-optical indicator film technique. Reversible twin boundary motion is visualized up to high actuation speeds. From domain observation at adjacent crystal surfaces the fundamental volume magnetic processes during strain and field induced twin boundary motions are derived. For magnetic field induced structural reorientations a concurrent absence of magnetic domain wall motion is found. In contrast, for strain induced reorientations processes, a complete rearrangement of the magnetic domain structure by the moving twin boundary is observed. Dynamic actuation experiments on twin boundary motion reveal non-linear time effects on twin boundary mobility. In addition to training effects, the maximum field induced strain increases with actuation speed. Both effects can be interpreted as the interaction of moving twin boundaries with local non-fixed defects. The summarized results provide key information for the understanding of the connection of magnetic and crystallographic domains in magnetic shape memory alloys and for the optimization of devices for future technical applications.
Keywords: ferromagnetic shape memory alloys, stroboscopic microscopy

Publ.-Id: 16878 - Permalink

Interlayer coupled spin vortex pairs and their response to external magnetic fields
Wintz, S.; Bunce, C.; Banholzer, A.; Körner, M.; Strache, T.; Mattheis, R.; McCord, J.; Raabe, J.; Quitmann, C.; Erbe, A.; Fassbender, J.ORC
We report on the response of multilayer spin textures to static magnetic fields. Coupled magnetic vortex pairs in trilayer elements (ferromagnetic/nonmagnetic/ferromagnetic) are imaged directly by means of layer selective magnetic x-ray microscopy. We observe two different circulation configurations with parallel and opposing senses of magnetization rotation at remanence. Upon application of a field, all of the vortex pairs investigated react with a displacement of their cores. For purely dipolar coupled pairs, the individual core displacements are similar to those of an isolated single layer vortex but also a noticeable effect of the mutual stray fields is detected. Vortex pairs that are linked by an additional interlayer exchange coupling (IEC) mainly exhibit a layer-congruent response. We find that –apart from a possible decoupling at higher fields– these strict IEC vortex pairs can be described by a single layer model with effective material parameters. This result implies the possibility to design multilayer spin structures with arbitrary effective magnetization.
Keywords: magnetic vortex, multilayer, coupling, field, x-ray microscopy, effective magnetization

Publ.-Id: 16877 - Permalink

Diverging-converging spin vortex pairs in biquadratically interlayer exchange coupled elements
Wintz, S.; Bunce, C.; Banholzer, A.; Körner, M.; Gemming, S.; Erbe, A.; Raabe, J.; Quitmann, C.; Fassbender, J.ORC
Spin structures have been an interesting topic of magnetism research for many years. Within this field, magnetic vortices have attracted much attention, due to their non-trivial topology and the various dynamic modes they exhibit [1]. A magnetic vortex consists of a planar, flux-closing magnetization curl that turns out of the plane in the central nanoscopic core region. In a single layer structure, the curl’s radial components typically cancel each other out. Recent investigations show that this also holds true for multilayer vortex systems with bilinear interlayer exchange coupling [2]. Here we report on pairs of diverging-converging spin vortices occurring in biquadratically coupled systems. Using magnetic scanning transmission x-ray microscopy (STXM) we directly observe that the individual vortices of such pairs possess a residual radial magnetization component, i.e. ∇Mxy≠0. This implies an additional perpendicular magnetization divergence ∇Mz, for which we compare a continuous model with discrete micromagnetic simulations.
[1] S.-B. Choe et al., Science 304, 420 (2004). [2] S. Wintz et al., Appl. Phys. Lett. 98, 232511 (2011).
Keywords: magnetic vortex, biquadratic interlayer exchange coupling, multilayer, divergence
  • Poster
    19th international conference on magnetism (ICM 2012), 08.-13.07.2012, Busan, Korea

Publ.-Id: 16876 - Permalink

Interlayer coupled magnetic vortex pairs in trilayer disks
Wintz, S.; Banholzer, A.; Raabe, J.; Quitmann, C.; Erbe, A.; Fassbender, J.ORC
Micromagnetic structures have been a subject of magnetism research since many years. Among those structures, magnetic vortices are of special interest as they exhibit a non-trivial topology and various dynamic eigenmodes [1]. Such a vortex consists of a planar flux-closure magnetization curl that turns perpendicular to the plane only in the very small central core region. Both, the curl’s sense (circulation: c) and the core orientation (polarity: p) can be in either of two different states, giving rise to a binary handednes h=cp of the system. Extensive studies on the static and dynamic properties of single layer vortices led to the proposal of their application for memory cells and spin-transfer oscillators. From the viewpoint of these two concepts but also from a fundamental perspective, the coupling between spatially confined vortices is a key issue to address [2].
Keywords: magnetic vortex, x-ray microscopy, multilayer
  • Poster
    IEEE International Magnetics Conference (Intermag 2012), 07.-11.05.2012, Vancouver, Canada
  • Poster
    PNI in-house research workshop on "Magnetism and highly correlated electron systems", 11.-12.06.2012, Freising, Deutschland

Publ.-Id: 16875 - Permalink

Sorption of U(VI) onto Opalinus Clay: Effects of pH and humic acid
Joseph, C.; Stockmann, M.; Schmeide, K.; Sachs, S.; Brendler, V.; Bernhard, G.;
The U(VI) sorption onto Opalinus Clay, a natural clay rock from Mont Terri, Switzerland, was investigated as a function of pH in the absence and presence of humic acid (HA) under aerobic conditions using 0.1 M NaClO4 as background electrolyte ([U(VI)] = 1×10-6 M, [HA] = 50 mg/L, S/L = 4 g/L, pH 3-10). Due to leaching of Opalinus Clay, several competing ions are present in solution, where especially calcium and carbonate ions affect the speciation of U(VI) and HA in solution and consequently, their sorption properties. At pH > 7.5, the Ca2UO2(CO3)3(aq) complex is formed, which dominates the U(VI) speciation and sorbs only weakly onto Opalinus Clay. In the case of HA, the CaHA(II) complex dominates the HA speciation over a wide pH range. However, in the pH range 4.5-7.5, the presence of HA leads to the formation of the aquatic complex UO2(OH)HA(I), which causes a decreased U(VI) sorption. In the pH range from pH 7.5-8, HA seems to have no influence on the U(VI) sorption. The sorption characteristics of U(VI) on Opalinus Clay were predicted using PHREEQC. Thereby, the investigation was focused on the influence of the binding sites of the iron mineral goethite on U(VI) sorption onto Opalinus Clay.
Keywords: Opalinus Clay, uranium, humic acid, sorption, competing ions, surface complexation model

Publ.-Id: 16874 - Permalink

The impact of chirally odd condensates on the rho meson
Hilger, T.; Thomas, R.; Kämpfer, B.; Leupold, S.;
Based on QCD sum rules we explore the consequences of a scenario for the ρ meson, where the chiral symmetry breaking condensates are set to zero whereas the chirally symmetric condensates remain at their vacuum values. This clean-cut scenario causes a lowering of the ρ spectral moment by about 120 MeV. The complementarity of mass shift and broadening is discussed. A simple parametrization of the ρ spectral function leads to a width of about 280 MeV if no shift of the peak position is assumed.

Publ.-Id: 16873 - Permalink

Nonlinear Compton scattering of ultrahigh-intensity laser pulses
Seipt, D.; Kämpfer, B.;
We present results for the photon spectrum emitted in non-linear Compton scattering of pulsed ultra-strong laser fields off relativistic electrons for intensities up to a0 > 100 and pulse lengths of a few laser cycles. At ultrahigh laser intensity, it is appropriate to average over the sub- structures of the differential photon spectrum. Supplementing this procedure with a stationary phase approximation one can evaluate the total emission probability. We find the photon yield in pulsed fields to be up to a factor of ten larger than results obtained from a monochromatic wave calculation.

Publ.-Id: 16872 - Permalink

Width of the φ meson in nuclear matter
Polyanskiy, A.; Hartmann, M.; Kiselev, Y. T.; Paryev, E. Y.; Büscher, M.; Chiladze, D.; Dymov, S.; Dzyuba, A.; Gebel, R.; Hejny, V.; Kämpfer, B.; Keshelashvili, I.; Koptev, V.; Lorentz, B.; Maeda, Y.; Merzliakov, S.; Mikirtytchiant, S.; Nekipelov, M.; Ohm, H.; Schade, H.; Serdyuk, V.; Sibirtsev, A.; Sinitsyna, V. Y.; Stein, H. J.; Ströher, H.; Trusov, S.; Valdau, Y.; Wilkin, C.; Wüstner, P.;
The ratios of the cross sections for φ-meson production induced by 2.83-GeV protons on Cu, Ag, and Au nuclei to the respective cross section for C nuclei were measured at the ANKE-COSY facility in the momentum range of 0.6–1.6 GeV/c and the angular range of 0◦–8◦. The product φ mesons were identified by their decay φ → K+K−. The procedure used to separate kaon pairs was described in detail, and all sources of the background and their contribution to the resulting error in the values found for the above cross-section ratios were analyzed. The A dependence of the cross section for φ-meson production was shown to obey the A0.56±0.03 law. The total width of the φ meson at a normal nuclear density was extracted from a comparison of the measured cross-section ratios with the results of calculations based on two theoretical models. The resulting width value exceeds substantially both the vacuum width and the width expected in the absence of the nuclear-matter effect on the properties of the φ meson.

Publ.-Id: 16869 - Permalink

Ratio of bulk to shear viscosity in a quasigluon plasma: From weak to strong coupling
Bluhm, M.; Kämpfer, B.; Redlich, K.;
The ratio of bulk to shear viscosity is expected to exhibit a different behaviour in weakly and in strongly coupled systems. This can be expressed by its dependence on the squared sound velocity. In the high temperature QCD plasma at small running coupling, the viscosity ratio is uniquely determined by a quadratic dependence on the conformality measure, whereas in certain strongly coupled and nearly conformal theories this dependence is linear. Employing an effective kinetic theory of quasiparticle excitations with medium-modified dispersion relation, we analyze the ratio of bulk to shear viscosity of the gluon plasma. We show that in this approach, depending on the temperature, the viscosity ratio exhibits either of these dependencies found by means of weak coupling perturbative or strong coupling holographic techniques. The turning point between the two different dependencies is located around the maximum in the scaled interaction measure.

Publ.-Id: 16868 - Permalink

Momentum dependence of the phi-meson nuclear transparency
Hartmann, M.; Kiselev, Y. T.; Polyanskiy, A.; Paryev, E. Y.; Buescher, M.; Chiladze, D.; Dymov, S.; Dzyuba, A.; Gebel, R.; Hejny, V.; Kaempfer, B.; Keshelashvili, I.; Koptev, V.; Lorentz, B.; Maeda, Y.; Magas, V. K.; Merzliakov, S.; Mikirtytchiants, S.; Nekipelov, M.; Ohm, H.; Roca, L.; Schade, H.; Serdyuk, V.; Sibirtsev, A.; Sinitsyna, V. Y.; Stein, H. J.; Stroeher, H.; Trusov, S.; Valdau, Y.; Wilkin, C.; Wuestner, P.; Ye, Q. J.;
The production of phi mesons in proton collisions with C, Cu, Ag, and Au targets has been studied via the phi -> K+K- decay at an incident beam energy of 2.83 GeV using the ANKE detector system at COSY. For the first time, the momentum dependence of the nuclear transparency ratio, the in-medium phi width, and the differential cross section for phi meson production at forward angles have been determined for these targets over the momentum range of 0.6 - 1.6 GeV/c. There are indications of a significant momentum dependence in the value of the extracted phi width, which corresponds to an effective phi-N absorption cross section in the range of 14 - 21 mb.

Publ.-Id: 16865 - Permalink

The pK0Σ+ final state in proton-proton collisions
Abdel-Bary, M.; Abdel-Samad, S.; Brinkmann, K.-T.; Clement, H.; Dietrich, J.; Doroshkevich, E.; Dshemuchadse, S.; Ehrhardt, K.; Erhardt, A.; Eyrich, W.; Filippi, A.; Freiesleben, H.; Fritsch, M.; Gast, W.; Georgi, J.; Gillitzer, A.; Gottwald, J.; Hesselbarth, D.; Jäger, H.; Jakob, B.; Jäkel, R.; Karsch, L.; Kilian, K.; Koch, H.; Krapp, M.; Kreß, J.; Kuhlmann, E.; Lehmann, A.; Marcello, S.; Marwinski, S.; Mauro, S.; Meyer, W.; Michel, P.; Möller, K.; Morsch, H. P.; Mörtel, H.; Naumann, L.; Paul, N.; Pinna, L.; Pizzolotto, C.; Plettner, C.; Reimann, S.; Richter, M.; Ritman, J.; Roderburg, E.; Schamlott, A.; Schönmeier, P.; Schroeder, W.; Schulte-Wissermann, M.; Sefzick, T.; Stinzing, F.; Steinke, M.; Sun, G. Y.; Teufel, A.; Ullrich, W.; Wagner, G. J.; Wagner, M.; Wenzel, R.; Wilms, A.; Wintz, P.; Wirthand, S.; Wüstner, P.; Zupranski, P.;
This paper reports results from a study of the reaction pp->pK0\Sigma+ at beam momenta of p_{beam} = 2950, 3059, and 3200 MeV/c (excess energies of \epsilon= 126, 161, and 206 MeV). Total cross sections were determined for all energies; a set of differential cross sections (Dalitz plots; invariant mass spectra of all two-body subsystems; angular distributions of all final state particles; distributions in helicity and Jackson frames) are presented for \epsilon= 161 MeV. The total cross sections are proportional to the volume of available three-body phase-space indicating that the transition matrix element does not change significantly in this range of excess energies. It is concluded from the differential data that the reaction proceeds dominantly via the N(1710)P_{11} and/or N(1720)P_{13} resonance(s); N(1650)S_{11} and \Delta(1600)P_{33} could also contribute.

Publ.-Id: 16864 - Permalink

The production of K+K- pairs in proton-proton collisions at 2.83 GeV
Ye, Q. J.; Hartmann, M.; Maeda, Y.; Barsov, S.; Buescher, M.; Chiladze, D.; Dymov, S.; Dzyuba, A.; Gao, H.; Gebel, R.; Hejny, V.; Kacharava, A.; Keshelashvili, I.; Kiselev, Y. T.; Khoukaz, A.; Koptev, V. P.; Kulessa, P.; Kulikov, A.; Lorentz, B.; Mersmann, T.; Merzliakov, S.; Mikirtytchiants, S.; Nekipelov, M.; Ohm, H.; Paryev, E. Y.; Polyanskiy, A.; Serdyuk, V.; Stein, H. J.; Stroeher, H.; Trusov, S.; Valdau, Y.; Wilkin, C.; Wuestner, P.;
Differential and total cross sections for the pp -> ppK+K- reaction have been measured at a proton beam energy of 2.83 GeV using the COSY-ANKE magnetic spectrometer. Detailed model descriptions fitted to a variety of one-dimensional distributions permit the separation of the pp -> pp phi cross section from that of non-phi production. The differential spectra show that higher partial waves represent the majority of the pp -> pp phi total cross section at an excess energy of 76 MeV, whose energy dependence would then seem to require some s-wave phi-p enhancement near threshold. The non-phi data can be described in terms of the combined effects of two-body final state interactions using the same effective scattering parameters determined from lower energy data.

Publ.-Id: 16863 - Permalink

Binary and ternary surface complexes of U(VI) on the gibbsite/water interface studied by vibrational and EXAFS spectroscopy
Gückel, K.; Rossberg, A.; Brendler, V.; Foerstendorf, H.;
The retardation of contaminants in aquifers is mainly determined by chemical reactions occurring at the solid/liquid interface. For a more detailed understanding of the molecular reactions of uranium(VI) at Al-hydroxide surfaces, the surface speciation of the radionuclide on gibbsite was studied in aqueous medium by a combined spectroscopic approach using time-resolved Attenuated Total Reflection Fourier-Transform Infrared (ATR FT-IR) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. For the first time, the impact of the surface morphology and of atmospherically derived carbonate on the uranyl surface speciation was systematically investigated under environmentally relevant conditions, namely in the near neutral pH range, at maximum initial U(VI) concentrations of 20 µM, and at different surface loadings. Concordantly, the formation of a monomeric binary inner-sphere surface complex is derived from vibrational spectroscopic and EXAFS data irrespective of the prevailing atmospheric condition and surface loading. In addition, from infrared spectra it was found that U(VI) surface precipitation occurs at a micromolar concentration level after a relatively short contact time in an inert gas atmosphere. However, this is circumvented by lowering the initial U(VI) concentration or in the presence of atmospheric CO2 due to the formation of ternary uranyl carbonato surface complexes. The ternary complex was identified as a dimeric inner-sphere uranyl surface species containing a bidentately coordinated carbonate ligand. The results of this work might be of relevance for a comprehensive description of the dissemination of uranium in groundwater systems.
Keywords: uranyl, surface species, gibbsite, IR spectroscopy, EXAFS

Publ.-Id: 16862 - Permalink

Evidence for the formation of UO2(NO3)42- in an ionic liquid by EXAFS
Gaillard, C.; Klimchuk, O.; Ouadi, A.; Billard, I.; Hennig, C.;
The complexation between uranium(VI) and nitrate ions in a hydrophobic ionic liquid (IL), namely [BMI][NO3] (BMI = 1-butyl-3-methylimidazolium+), is investigated by EXAFS spectroscopy. It was performed by dissolution of uranyl nitrate UO2(NO3)2·6H2O or UO2(Tf2N)2 (Tf2N = bis(trifluoromethylsulfonyl) imide (CF3SO2)2N−). The formation of the complex UO2(NO3)4 2− is evidenced.
Keywords: EXAFS, UO2(NO3)42- , Ionic Liquids

Publ.-Id: 16861 - Permalink

Soft iron and axisymetric eigenmodes in the von-Karman-Sodium dynamo
Giesecke, A.; Stefani, F.; Gerbeth, G.;
In the Cadarache von-Karman-Sodium (VKS) dynamo experiment magnetic field excitation is generated by
a turbulent flow of liquid sodium. In the experiment this so called von-Karman-like flow is driven by two
counter-rotating impellers that are located close to the end-caps of a cylindrical vessel.
Despite of extensive numerical and experimental efforts the very nature of the VKS dynamo and its surprising properties still remain unclear. Firstly, dynamo action is obtained only when (at least one of) the flow driving impellers are made of soft iron with a relative permeability around 65. Moreover, and in apparent contradiction with Cowling’s anti-dynamo theorem, the geometric structure of the observed magnetic field is dominated by an axisymmetric field.
Our kinematic simulations of an axisymmetric model of the Cadarache dynamo show a close connection between the exclusive occurrence of dynamo action with soft iron impellers and the axisymmetry of the magnetic field. We observe two distinct classes of axisymmetric eigenmodes, a purely toroidal mode that is amplified by paramagnetic pumping at the fluid-disk interface and a mixed mode consisting of a poloidal and a toroidal contribution that is rather insensitive to the disk permeability. In the limit of large permeability, the purely toroidal mode is close to the onset of dynamo action with a growth-rate that is rather independent of the flow field.
This mode is located near to and in the high permeability disks and becomes the leading mode when the disk permeability exceeds a critical value. However, since in our axisymmetric configuration the purely toroidal mode is decoupled from any poloidal field component no dynamo action can be expected from this mode. The purely toroidal mode and its strong amplification by paramagnetic pumping at the fluid-disks interface can be obtained only by explicitly considering the internal permeability distribution. This mode does not exist in case of highly conducting disks or in simulations that only apply idealized boundary conditions.
The separation into purely toroidal and mixed mode can be overcome e.g. by a non-axisymmetric permeability distribution that resembles an assembly of blades attached to the disks. Such a coupled eigenmode is even more likely to facilitate the occurrence of dynamo action when a further source term like the alpha-effect is considered that is necessary to break the restriction imposed by Cowling’s theorem. The particular coupling mechanism provided by such a non-axisymmetric permeability distribution might give a hint why dynamo action is absent in experiments when the fluid flow is driven by an impeller system composed of soft iron disks and stainless steel blades.
Keywords: dynamo vks permeabilitaet
  • Lecture (Conference)
    European Geosciences Union General Assembly 2012, 23.-27.04.2012, Vienna, Austria
  • Open Access LogoAbstract in refereed journal
    Geophysical Research Abstracts 14(2012), EGU2012-1661

Publ.-Id: 16859 - Permalink

Fine Structure of the Giant M1 Resonance in 90Zr
Rusev, G.; Tsoneva, N.; Dönau, F.; Frauendorf, S.; Schwengner, R.; Tonchev, A. P.; Adekola, A. S.; Hammond, S. L.; Huibregtse, C.; Kelley, J. H.; Kwan, E.; Lenske, H.; Tornow, W.; Wagner, A.;
The M1 excitations in the nuclide 90Zr have been studied in a photon-scattering experiment with monoenergetic and linearly-polarized beams from 7 to 11 MeV. More than 40 J^pi = 1+ states have been identified from observed ground-state transitions, revealing the fine structure of the giant M1 resonance with centroid energy of 9 MeV and sum strength of 3.4(3) µ_N^2 . The result for the total M1 strength and its fragmentation are discussed in the framework of three-phonon quasi-particle model.
Keywords: Monoenergetic, polarized gamma rays. Photon scattering. M1 and E1 excitations. M1 strength. Magnetic giant resonance. Quasi-particle-phonon model.

Publ.-Id: 16858 - Permalink

Tomographic Reconstruction for In-Beam SPECT by Compton Camera
Schoene, S.; Enghardt, W.; Kormoll, T.; Rohling, H.; Fiedler, F.; Keywords: Cancer research, Ion therapy, Image reconstruction, Compton Camera
  • Poster
    OncoRay Retreat 2012, 07.-08.03.2012, Dresden, Deutschland

Publ.-Id: 16857 - Permalink

Reconstructing Compton Camera Images for Ion Therapy Monitoring
Schoene, S.;  Enghardt, W.; Kormoll, T.; Rohling, H.; Fiedler, F.;
Radiation therapy by means of protons or heavier ions can improve the performance of radiotherapy for cancer treatment by delivering dose more locally to tumor tissue. Due to the inherent precision of this irradiation modality a dose deposition monitoring is desirable. It has been shown that positron emission tomography (PET) can be used for that by exploiting the decay of positron emitters which arise from nuclear fragmentations of projectile and target nuclei. This monitoring was implemented and successfully applied to the treatment by carbon ions for more than 440 patients at the pilot facility at GSI Helmholtz Centre for Heavy Ion Research, Darmstadt, Germany. However, it comes with inherent drawbacks, e.g. spatial blurring of the reconstructed dose distribution due to unpredictable metabolically driven transport of the positron emitters within the patient.

Alternatively, the imaging of prompt gamma-rays -- photons emitted at time and location of the beam-tissue interaction -- is proposed to estimate dose deposition distributions more precisely and probably in real-time. Determined by their origin, these gamma-ray emission distributions have certain properties, i.e. smoothly extended in the order of a decimeter and a continuous energy spectrum up to 10 MeV.

A Compton camera is a single photon imaging device measuring position and energy deposition according to incoherent scattering (Compton scattering) of a photon, and its trajectory afterwards. Since the scattering angle is related to the photon energy before and after scattering a conical surface can be spanned in patient space which covers all possible source locations of the gamma-ray. This surface of response is the Compton camera equivalent to the well known line of response in PET.

Spanning this surface (which means performing a backprojection and constructing the system matrix) is the major part of the image reconstruction process of Compton camera imaging (CCI) in terms of design and implementation efforts, and computation time. As shown previously, its precision also strongly impacts the quality of the image reconstruction results. Furthermore, in CCI a realistic system matrix (SM) has to take into account the physical and technological characteristics of the camera like limited energy and spatial resolution as well as Compton camera specific features as: (i) the event and image space are of high dimensionality, i.e. due to the energy of the gamma-rays and multi attribute measurements, (ii) the backprojections are surfaces instead of lines (Anger SPECT, PET) and therefore the SM occupancy is high, and (iii) incompletely absorbed photons may lead to incorrect conclusions on the initial gamma energies and scattering angles and subsequently to misarranged backprojections.

These challenges of CCI including their impacts will be discussed. Approaches to overcome them will be proposed and evaluated. This is done by means of measurements using radioactive sources as well as via in-beam tests at the proton beam facility AGOR in at KVI Groningen, Netherlands. Complementary results by means of simulations will be shown.
Keywords: Image reconstruction Ion therapy Compton camera
  • Poster
    International Conference on Translational Research in Radio-Oncology and Physics for Health in Europe 2012, 27.02.-02.03.2012, Genève, Suisse

Publ.-Id: 16856 - Permalink

Work on a large-area MRPC-based time-of-flight detector for high energy neutrons
Yakorev, D.; Bemmerer, D.;
The NeuLAND detector at the R3B experiment of the future FAIR facility in Darmstadt aims to detect fast neutrons (0.2-1.0 GeV) with high time and spatial resolutions (σt<100 ps, σx,y,z<1 cm).

Here, development work on a possible NeuLAND solution based on the multigap resistive plate chamber (MRPC) technology is presented. In this hypothesis, the final detector consists of 50 consecutive MRPC stacks. Each stack contains a 4 mm thick anode made of iron converter material, with an additional 4mm of converter material between two stacks. The secondary charged particles stemming from hadronic interactions of the high energetic neutrons in the converter will be detected in the MRPC's. A number of prototypes have been developed and built. They have been tested with a beam of single electrons, with picosecond time resolution at the superconducting linac ELBE (Dresden, Germany).

The present prototypes show good time resolution and efficiency. However, much better multihit capability is expected for a fully active cube of 2.5 × 2.5 × 3 m scintillator material, so this is the solution adopted for the NeuLAND detector in the meantime.

Publ.-Id: 16855 - Permalink

Whole-body-PET/MRI a new way of imaging in soft tissue sarcomas
Richter, S.; Platzek, I.; Beuthien-Baumann, B.; Laniado, M.; Kotzerke, J.; Kroschinsky, F.; Ehninger, G.; Schuler, M.;
kein Abstract verfügbar
  • Abstract in refereed journal
    European Journal of Cancer 47(2011), 671-672
  • Lecture (Conference)
    The 2011 European Multidisciplinary Cancer Congress, 24.-27.09.2011, Stockholm, Schweden

Publ.-Id: 16854 - Permalink

Radiosynthesis and biological evaluation of novel receptor tyrosine kinase inhibitors for in vivo targeting of EGFR
Neto, C.; Fernandes, C.; Oliveira, C.; Gano, L.; Mendes, F.; Kniess, T.; Santos, I.;
Objectives: The overexpression of the epidermal growth factor receptor (EGFR) in tumours underlines the recent interest in EGFR as an attractive target for the development of new cancer imaging agents. EGFR-tyrosine kinase inhibitors (EGFR-TKI) based on the 4-anilinoquinazoline scaffold have been explored as potential probes for EGFR imaging [1, 2]. However up to now, no optimal radiotracer is still available. Herein, we report the synthesis, radiosynthesis (125I- and 18F) and biological evaluation of three novel halogenated 6-substituted 4-anilinoquinazoline based EGFR-TKI as potential biomarkers.
Methods: The halogenated 6-substituted-4-anilinoquinazolines (2a, 2b and 2c) were obtained by reaction of 6-amino-4-anilinoquinazoline (1) with 3-/4-iodobenzoyl and 4-fluorobenzoyl chlorides as depicted in Scheme 1 [3].
Studies to inhibit EGFR autophosphorylation and A431 cellular proliferation were performed by Western blot and MTT colorimetric assays, respectively. 125I-radiolabelled anilinoquinazolines, [125I]-2a/b were prepared via destannylation of the corresponding tributylstannyl precursors with [125I]NaI. Cellular uptake studies were conducted in intact A431 cells. Optimization of the radiosynthesis of the 18F-radiolabeld anilinoquinazoline [18F]-2c was attempted by nucleophilic substitution of the trimethylammonium- and nitro-6-substituted 4-anilinoquinazoline precursors using different reaction temperatures and solvents.
Results: The 6-substituted-4-anilinoquinazolines (2a, 2b and 2c) were synthesised in high chemical yield (>90%) and fully characterized. The fluorinated quinazoline 2c with IC50 < 0.1 μM was shown to be the most potent inhibitor of EGFR autophosphorylation. Furthermore the three compounds are potent inhibitors of A431 cell proliferation as demonstrated by IC50 values (0.78µM (2a), 3.37 (2b), 2.43 µM (2c)). The 125I-radioiodinated analogues, obtained in high radiochemical purity and specific activity, displayed a relative high celular uptake (>35%) in intact A431 cells. Despite of all attempts the radiofluorinated compound [18F]-2c was only formed in a modest labeling yield (4%) what, up to now has hampered further radiopharmacological investigation.
Conclusions: Three novel halogenated 4-anilinoquinazoline-based EGFR-TK inhibitors, 2a, 2b and 2c, have been successful prepared and radiolabelled. The in vivo inhibition study of EGFR autophosphorylation and A431 cell proliferation proved that all three compounds show inhibitory properties at the micromolar level. In summary, data from this study suggest that this class of quinazolines derivatives encompasses promising derivatives with the potential to act as EGFR-TKI and should be further explored as biomarkers for SPECT and PET.
Research Support: The authors acknowledge FCT and DAAD for financial support. C. Neto thanks FCT for a Ph.D. grant (SFRH/BD/31319/2006).
[1] Noble MEM. et al., (2004), Science, 303, 5665, 1800-5.
[2] Levitzki A. et al., (2003), Acc Chem Res, 36, 6, 462-9. [3] Hicks JW. et al., Molecules (2010), 15, 11, 8260-78.
[3] Fernandes C. et al., Bioorg Med Chem, (2007), 15, 12, 3974-80.
  • Poster
    19th International Symposium on Radiopharmaceutical Sciences, 28.08.-02.09.2011, Amsterdam, NL
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011), S171

Publ.-Id: 16851 - Permalink

Dual-labeled Anti-PSCA-antibody-based agent for PET and NIR Fluorescence imaging
Bergmann, R.; Pietzsch, J.; Steinbach, J.; Bachmann, M.;
Prostate stem-cell antigen (PSCA) is a cell-surface antigen expressed in the normal prostate and overexpressed in over 80% of prostate cancer tissues. PSCA overexpression is associated with increased tumor stage, grade, and bone metastasis, as well as androgen independence and higher resistance to treatment. The aim of this work was to prepare and characterize a humanized monoclonal anti PSCA antibody (anti-PSCA mAb) for near infrared fluorescence (NIRF) and PET imaging using a near infrared (NIR) dye Alexa Fluor 750 (AF) and [64Cu]Cu-NOTA as a prerequisite for combination of both imaging methods. We evaluated the imaging potential of the [64Cu]Cu-NOTA-AF-anti-PSCA mAb in human prostate cancer xenograft mouse models by using the androgenindependent recombinant cell line PC3-PSCA as target and the non-transfected cell line as control. anti-PSCA mAb was conjugated with the bifunctional chelator 2-(p-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (SCN-Bz-NOTA) and Alexa Fluor succinimidyl carboxic acid (Ex 752 nm; Em 776 nm; AF). NOTA-AF-anti-PSCA mAb was labeled with 64Cu within 30 min with high
radiolabeling yield and radiochemical purity. The [64Cu]Cu-NOTA- AF-anti-PSCA mAb showed high accumulation in xenotransplanted prostate carcinomas in mice after 24 hours demonstrated with both small animal PET and NIRF. The comparison of both methods in living animals showed the high signal intensity and accumulation of the probe in tumors; however only PET allowed the quantitative characterization of the probe distribution in vivo. Subsequent whole body cryosectioning of the animals into 40-micrometer sections permitted the direct comparison of the autoradiograms and NIRF images of the tissue cuts. The quantitative comparison of the registered autoradiograms and the NIRF images showed a good correlation of the pixel intensities, however, the different geometric resolution did not allow a pixel vise comparison. The NIRF images showed a higher differentiation than the autoradiograms. This was used to study the stability of the radio- and NIR-label on the mAbs. Dual labeling of antibodies is a promising tool for quantitative evaluation of the long time distribution in animals using also NIRF of cryosections beyond the decay of the radionuclide used.
Acknowledgement: This project was partially supported by FP7 project “GIPIO”, Project Reference: 223057
  • Poster
    World Molecular Imaging Congress 2011, 02.-10.09.2011, San Diego, USA
  • Contribution to proceedings
    World Molecular Imaging Congress, 02.-10.09.2011, San Diego, USA
    Proceedings of the 2011 World Molecular Imaging Congress, S82

Publ.-Id: 16850 - Permalink

Liquid metal alloy ion source based metal ion injection into a roomtemperature electron beam ion source
Thorn, A.; Ritter, E.; Ullmann, F.; Pilz, W.; Bischoff, L.; Zschornack, G.;
We have carried out a series of measurements demonstrating the feasibility of using the Dresden electron beam ion source (EBIS)-A, a table-top sized, permanent magnet technology based electron beam ion source, as a charge breeder. Low charged gold ions from an AuGe liquid metal alloy ion source were injected into the EBIS and re-extracted as highly charged ions, thereby producing charge states as high as Au60 +. The setup, the charge breeding technique, breeding efficiencies as well as acceptance and emittance studies are presented.
Keywords: Liquid Metal ion Source, Electron Ion Beam Source, Metal Ion Injection
  • Review of Scientific Instruments 83(2012), 02A511-1-02A511-3
    DOI: 10.1063/1.3673504

Publ.-Id: 16848 - Permalink

Study of dipole strength distributions in photon-scattering experimnets
Schwengner, R.; Keywords: photon scattering, nuclear resonance fluorescence, gamma-ray cascades, photoabsorption cross section
  • Invited lecture (Conferences)
    Workshop on Statistical Gamma Rays, 06.02.2012, Oslo, Norwegen

Publ.-Id: 16846 - Permalink

Radioiodinated sunitinib as a potential radiotracer for imaging angiogenesis - radiosynthesis and first radiopharmacological evaluation of 5-[125I]Iodo-sunitinib
Kuchar, M.; Oliveira, M. C.; Gano, L.; Santos, I.; Knieß, T.;
Sunitinib® (SU11248) is a highly potent tyrosine kinase inhibitor targeting vascular endothelial growth factor receptor (VEGFR). Radiolabeled inhibitors of RTKs might be useful tools for monitoring RTKs levels in tumour tissue giving valuable information for anti-angiogenic therapy. We report here the synthesis of a 125I-labeled derivative of sunitinib® and its first radiopharmaceutical characterization.
The non-radioactive reference compound 5-iodo-sunitinib 4 was prepared by Knoevenagel condensation of 5-iodo-oxindole with the corresponding substituted 5-formyl-1H-pyrrole. In a competition binding assay against VEGFR-2 a binding constant (Kd) of 16 nM for 4 was found. The ability of 4 to inhibit tyrosine kinase activity was demonstrated on RTK expressing cells suggesting this radiotracer as a useful tool for monitoring VEGFR expression. 5-[125I]lodo-sunitinib, [125I]-4 was obtained via destannylation of the corresponding tributylstannyl precursor with [125I]NaI in the presence of H2O2 in high radiochemical yield (>95%) and radiochemical purity (<98%) after HPLC purification. Determination of human plasma protein binding at time intervals of 0; 1; 2; 4 and 24h suggested a low non-specific binding of 5-10%. Preliminary biodistribution studies of [125I]-4 in healthy CD-1 mice showed a relatively high uptake in VEGFR-2 rich tissues like kidney and lung followed by rapid washout (9.6 and 9.7; 4.5 and 3.8% ID/g of kidney and lung at 1 and 4 h, respectively).
Keywords: sunitinib®, VEGFR, RTKs, iodine-125, radiolabeling

Publ.-Id: 16845 - Permalink

CFD modeling of free surface flow with and without condensation
Lucas, D.; Coste, P.; Höhne, T.; Lakehal, D.; Bartosiewicz, Y.; Bestion, D.; Scheuerer, M.; Galassi, M. C.;
This paper presents some recent developments on CFD models suitable to simulate free surface flows, which so far represented an unresolved matter for industrial nuclear reactors issues. While the general dynamics of such a large interface should be simulated in a CFD approach all sub-grid scale effects have to be modelled. Depending on choice of the general approach – one-fluid or multi-fluid models different closures are required. The momentum transfer between the phases is usually reflected by a drag model in a two-fluid approach. The drag force depends on the local morphology (free surface or dispersed bubbles/drops) and has to be anisotropic at the free surface. Surface tension has to be considered at wavy surfaces. The situation becomes even more complex if mass transfer occurs at the interface. Three approaches with different detailedness are presented. Examples for CFD simulations for free surface flow using different CFD codes and approaches are discussed.
Keywords: CFD, free surface flow, PTS

Publ.-Id: 16844 - Permalink

Fast neutron inelastic scattering at the nELBE facility
Beyer, R.; Bemmerer, D.; Grosse, E.; Hannaske, R.; Junghans, A. R.; Kempe, M.; Kögler, T.; Massarczyk, R.; Nolte, R.; Schwengner, R.; Wagner, A.;
At the superconducting electron accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf the compact neutron time-of-flight facility nELBE has been built. There, neutrons in the kinetic energy region from some tens of keV to a few MeV are produced by means of electrons impinging onto a liquid lead target. The emitted neutron spectrum is well suited for measurements of cross sections of fast-neutron nuclear interactions relevant to the transmutation of nuclear waste. To study inelastic neutron scattering a rather unique double-time-of-flight was developed measuring both emitted particles, i.e., the scattered neutron and the de-excitation photon, in coincidence. By this method the inelastic scattering cross section can be measured with a continuous neutron source without the knowledge of the decay scheme of the sample nucleus. Beside inelastic scattering also transmission experiments to measure the total neutron cross section were performed and for the future neutron fission experiments are under preparation.
Keywords: Instrumentation and methods for time-of-flight (TOF) spectroscopy Instrumentation for neutron sources Neutron detectors nELBE

Publ.-Id: 16843 - Permalink

Superconducting Ga-overdoped Ge layers capped with SiO2 – structural and transport investigations
Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Mücklich, A.; Facsko, S.; Reuther, H.; Perego, M.; Heinig, K.-H.; Schmidt, B.; Skorupa, W.; Gobsch, G.; Helm, M.;
Superconducting Ga-rich layers in Ge are fabricated by Ga implantation through a thin SiO2 cover layer. After annealing in a certain temperature window, Ga accumulation at the SiO2/Ge interface is observed. However, no Ga containing crystalline phases are identified. Thus it is suggested that the volatile Ga is stabilized in an amorphous mixture of all elements available at the interface. Electrical transport measurements reveal p-type metallic conductivity and superconducting transition. The superconducting properties of the samples with high Ga concentration at the interface change dramatically with etching the amorphous surface layer. A critical temperature of 6 K is measured before, whereas after etching it drops below 1 K. Therefore, one can conclude that the superconducting transport is based on two different layers: a Ga-rich amorphous phase at the interface and a heavily Ga-doped Ge layer. Finally, the comparison of the transport properties of Ga-rich Ge with those of Si demonstrates distinct differences between the interface layers and even the deeper lying doped regions.

Publ.-Id: 16842 - Permalink

High Proton Energies from Cone Targets: Electron Acceleration Mechanisms
Kluge, T.; Gaillard, S.; Flippo, K.; Burris-Mog, T.; Enghardt, W.; Gall, B.; Geissel, M.; Helm, A.; Kraft, S. D.; Lockard, T.; Metzkes, J.; Offermann, D. T.; Schollmeier, M.; Schramm, U.; Zeil, K.; Bussmann, M.; Cowan, T. E.;
Recent experiments in the Trident laser facility (Los Alamos National Laboratory) have shown that hollow conical targets with a flat top at the tip can enhance the maximum energy of proton beams created during the interaction of an ultra-intense short laser pulse with the target (Gaillard S A et al 2011 Phys. Plasmas 18 056710). The proton energies that have been seen in these experiments are the highest energies observed so far in laser-driven proton acceleration. This is attributed to a new acceleration mechanism, direct light pressure acceleration of electrons (DLLPA), which increases the number and energy of hot electrons that drive the proton acceleration. This acceleration process of protons due to a two-temperature sheath formed at the flat-top rear side is very robust and produces a large number of protons per shot, similar to what is regularly observed in target normal sheath acceleration (Hatchett S P et al 2000 Phys. Plasmas 7 2076, Maksimchuk A et al 2000 Phys. Rev. Lett. 84 4108, Snavely R A et al 2000 Phys. Rev. Lett. 85 2945) with flat foils. In this paper, we investigate the electron kinetics during DLLPA, showing that they are governed by two mechanisms, both of which lead to continuous electron acceleration along the inner cone wall. Based on our model, we predict the scaling of the hot electron temperature and ion maximum energy with both laser and target geometrical parameters. The scaling of T_e^{DLLPA}=m_e c_0 \frac {a_0^2} {4} with the laser strength parameter a0 leads to an ion energy scaling that surpasses that of some recently proposed acceleration mechanisms such as radiation pressure acceleration (RPA), while in addition the maximum electron energy is found to scale linearly with the length of the cone neck. We find that when optimizing parameters, high proton energies suitable for applications can be reached using compact short-pulse laser systems with pulse durations of only a few tens to hundreds of laser periods.
  • Open Access LogoNew Journal of Physics 14(2012), 023038
    DOI: 10.1088/1367-2630/14/2/023038
  • Lecture (Conference)
    SPIE Oprics+Optoelectronics, 18.-21.04.2011, Prag, Tschechische Republik

Publ.-Id: 16841 - Permalink

Was das Leben auf den Hinterlassenschaften des Uranerzbergbaus mit Zwergen zu tun hat
Raff, J.;
Die Natur ist ausgesprochen erfinderisch und erfolgreich in der Herstellung und Nutzung nanoskaliger Strukturen. Aus diesem Grund sind in der Nanotechnologie biomolekulare und biologisch erzeugte Strukturen eine interessante Alternative zu technisch erzeugten Nanomaterialien. Im Rahmen des Vortrags werden mikrobiologische Forschungsarbeiten im Zusammenhang mit den Hinterlassenschaften des Uranerzbergbaus vorgestellt und an verschiedenen Beispielen ihr hohes Anwendungspotenzial in der Bionanotechnologie aufgezeigt.
  • Invited lecture (Conferences)
    Vom Molekül zum Muster (Selbstorganisationsphänomene in der Biologie), Vortragsreihe vom COM-LABBIO, 08.05.2012, Dresden, Deutschland

Publ.-Id: 16840 - Permalink

A short description of the Rossendorf Beamline at ESRF – and one scientific example of French-German collaboration: The formation of polynuclear Actinide(IV) carboxylates
Hennig, C.; Meyer, M.;
The presentation will provide a short description of the Rossendorf Beamline at ESRF. Common results obtained with the University Burgundy will be discussed. The research is related with the formation of polynuclear Actinide(IV) carboxylates.
Keywords: EXAFS, Actinides
  • Invited lecture (Conferences)
    German-French research for nuclear safety: Chemistry of the f-elements, 22.-23.02.2012, Strasbourg, France

Publ.-Id: 16839 - Permalink

Standard and Helical Magnetorotational Instability: How Singularities Create Paradoxical Phenomena in MHD
Kirillov, O.; Stefani, F.;
The magnetorotational instability (MRI) triggers turbulence and enables outward transport of angular momentum in hydrodynamically stable rotating shear flows, e.g., in accretion disks. What laws of differential rotation are susceptible to the destabilization by axial, azimuthal, or helical magnetic field? The answer to this question, which is vital for astrophysical and experimental applications, inevitably leads to the study of spectral and geometrical singularities on the instability threshold. The singularities provide a connection between seemingly discontinuous stability criteria and thus explain several paradoxes in the theory of MRI that were poorly understood since the 1950s.
Keywords: Rotating shear flow, Couette-Taylor flow, Accretion disk, Magnetorotational instability, WKB, Plücker conoid, Exceptional point

Publ.-Id: 16838 - Permalink

A multi-field two-fluid concept for transitions between different scales of interfacial structures
Hänsch, S.; Lucas, D.; Krepper, E.; Höhne, T.;
This paper presents a concept for the CFD-modelling of multiphase flows where both segregated and dispersed flow structures occur simultaneously. Transitions between such morphologies, characterized by different scales of interfacial structures, are investigated and a new multi-field two-fluid strategy for a generalized two-phase flow (GENTOP) is presented. The GENTOP-approach extends the inhomogeneous Multiple Size Group (MUSIG) –model by adding an additional continuous gas phase. In the MUSIG-framework, mass transfers between different bubble size groups due to coalescence and –breakup as well as gas-liquid transfers are described. By modelling an additional mass transfer between the polydispersed and continuous gas phase, transitions between the different gas morphologies can be considered dependent on the flow situation. The continuous gas phase summarizes gas structures which are large enough to be resolved within the computed mesh. Therefore a free surface detection and generalized formulations for interfacial transfer models are introduced. The appearance of one particular gas phase due to mass transfer from another gaseous morphology is demonstrated by means of two demonstration cases: the impingement of a liquid jet on a free surface with an associated bubble entrainment as well as a vertical bubble column showing a wide spectrum of bubble sizes.
Keywords: multiphase flow, CMFD, MUSIG-model, AIAD-model, gas-liquid interface, impinging jet

Publ.-Id: 16837 - Permalink

Uranyl(VI) Complexation by Sulfonate Ligands: A Relativistic Density Functional and TRLFS Study
Kremleva, A.; Zhang, Y.; Shor, A. M.; Krüger, S.; Joseph, C.; Raditzky, B.; Schmeide, K.; Sachs, S.; Bernhard, G.; Rösch, N.;
To study the role of sulfonate functional groups of humic substances in uranyl(VI) complexation, all-electron density functional calculations and time-resolved laser-induced fluorescence spectroscopy (TRLFS) were applied using small sulfonate ligands as models. A thiolate ligand was explored for comparison. As in an earlier experiment, 4-hydroxy¬benzenesulfonic acid (HBSA) and benzenesulfonic acid (BSA) were examined and compared to methylsulfonic acid (MSA). Structural parameters as well as energetic aspects of uranyl complexes by BSA and HBSA ligands were determined to be rather similar, in contrast to earlier experimental findings. The present TRLFS measurements show complexation of uranyl by both ligands in agreement with the computational results. Overall, the combined computational and experimental results indicate that sulfonate groups play only a minor role in uranyl complexation by sulfonate groups of humic substances because of the rather low stability constants.
Keywords: Density functional calculations, time resolved spectroscopy, TRLFS, uranium, sulfonates

Publ.-Id: 16835 - Permalink

Local structure and charge distribution of Am bearing nuclear oxide fuels: (U,Am)O2±x and (U,Pu,Am)O2-x
Martin, P. M.; Belin, R. B.; Prieur, D.; Delahaye, T.; Gavilan, E.; Lebreton, F.; Robisson, A. C.; Dumas, J. C.; Scheinost, A. C.;
In the framework of recycling minor actinides (MA) in fast neutron reactors, americium can be transmuted either by adding it in a small amount to the fuel (e.g. (U,Pu,Am)O2-x) or by using dedicated blanket fuels (e.g. (U1-y,Amy)O2-x). In both strategies, the stoichiometry of the solid solution, commonly described as oxygen to metal atom ratio (O/M), is an important parameter affecting thermal, chemical, and physical properties of the fuel during irradiation. A thorough knowledge of its correlation with oxygen potential (µO2) during manufacturing and especially sintering is then of major interest. To better assess this issue, several thermodynamic descriptions have been developed1,2. Despite their differences, they all involve the valence state of actinide cations (e.g. U, Pu and Am) as an essential parameter. However, experimental data regarding actinide valence remains very limited in the literature.
As illustrated by our recent study of (U,Am)O2±x samples3, coupling X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) measurements allows to determine actinide valence states and to describe the solid solution at both long-range and short range order as a function of oxygen potential. From these data, O/M ratio is eventually calculated using the cation molar fractions determined by XAS. In the present work, we realized a complete XAS characterization on (U,Am)O2±x and (U,Pu,Am)O2-x samples.

Mixed oxide samples (U1-y,Amy)O2±x (y=0.10, 0.15, 0.20) and (U0.750Pu0.246Am0.004)O2-x were manufactured by conventional powder metallurgy process. By adding a controlled amount of either H2O or Ar/O2 to the furnace atmosphere (Ar/5%H2), oxygen potential were ranging from -520 kJ.mol-1 to -390 kJ.mol-1 during sintering. XAS measurements were performed at the ROssendorf Beam Line (BM20) located at the European Synchrotron Radiation Facility (ESRF, Grenoble, France). For each samples, U, Pu and Am LII,III edges were collected simultaneously in fluorescence and transmission modes at 15K using a helium cryostat.

Concerning americium, a complete reduction of Am4+ to Am3+ is observed for both (U,Am)O2 and (U,Pu,Am)O2 samples whatever the oxygen potential and the Am content. Unexpected results were obtained in the case of (U,Am)O2 solid solutions as, even for the lowest value of µO2 (-520 kJ.mol-1), pentavalent uranium is found, highlighting a charge compensation mechanism as the cause of this partial oxidation of uranium cations3. As a consequence, the expected hypo-stoichiometry was not observed and the solid solution can be described as .
For (U0.750Pu0.246Am0.004)O2-x samples, a radical difference is observed since uranium and americium cations remain respectively tetravalent and trivalent, regardless of the sintering conditions. On the other hand, a partial reduction of Pu4+ to Pu3+ as a function of µO2 is responsible for the continuous decrease in O/M (1.97≤O/M≤1.99). Furthermore, local environments given by EXAFS confirmed that the defects in hypo stoichiometric MOX are only located around Pu cations.
In the presentation, we will detail and compare these results and discuss their consequences on thermodynamical modeling, especially the actual temperature fixing the O/M ratio of the final material.

Using XAS measurement on (U,Am)O2±x and (U,Pu,Am)O2-x samples, O/M values were obtained as a function of oxygen potential at high temperature. Comparing these two materials, we evidenced (1) a distinct cation charge mechanism and (2) how the deviation from stoichiometry is supported in the solid solution structure. These results proved useful to better assess the thermodynamical models developed for actinides mixed oxides systems.

1 M. Osaka et al. (2005) J. Nucl. Mater., 344, 230-234.
2 M. Osaka et al. (2007) J. Alloys Compounds, 428, 355-361.
3 D. Prieur et al. (2011) Inorg. Chem., 50, 12437–12445
  • Invited lecture (Conferences)
    Plutonium Futures - The Science 2012, 15.-20.07.2012, Cambridge, United Kingdom

Publ.-Id: 16834 - Permalink

P1004 - Erzeugung kurzwelliger ultrakurzer Lichtpulse und deren Verwendung
Debus, A.; Bussmann, M.;
Die Erfindung beschreibt eine Anordnung zur Erzeugung ultrakurzer und kurzwelliger Lichtpulse mit Hilfe des Thomson-wave-scattering-Verfahrens, wobei dispersive Elemente zwischen einer Elektronen-, Teilchen- oder Strahlenquelle, die mit einem Lasersystem synchronisiert ist, und einem in einer Richtung fokussierendem optischen Element angeordnet sind und die Verwendung dieser Anordnung zur Überlagerung eines pulsfrontverkippten Lichtpulses hoher Leistung mit einem ultrakurzen Puls relativistischer Elektronen in einem Laserlinienfokus. Durch die Variierung der Laserpulsfrontverkippung erhält man schmalbandige Strahlungspulse hoher Photonenzahl in einem breiten Wellenlängenbereich von EUV bis zu Röntgenwellenlängen und kann zudem die Bandbreite und Kohärenzeigenschaften anpassen. Diese Anordnung kann u. a. bei der EUV-Lithographie, bei der Planung und optimalen Auslegung von Lasersystem und Elektronenquelle, bei der Materialanalyse mittels Phasen-Kontrast-Bildgebung (phase constrast imaging), der Supraleiterforschung verwendet werden. Die vorgeschlagene Anordnung ist kleiner und kostengünstiger als vergleichbare heutige Anordnungen realisierbar.
  • Patent
    DE102010028994 - Offenlegung 17.11.2011, Nachanmeldung: WO, US - Erteilung 23.02.2016

Publ.-Id: 16833 - Permalink

P1001 - Reaktorkern in natriumgekühlten schnellen Reaktoren
Merk, B.;
Hintergrund der Erfindung ist die Ausgestaltung von Reaktorkernen für natriumgekühlte schnelle Reaktoren wobei an verschiedenen Stellen im Reaktorkern feste Metall-Wasserstoff-Verbindungen eingefügt werden. Dadurch reduziert sich der Effekt der Verdampfung des Natriums deutlich und die Sicherheitskoeffizienten verbessern sich signifikant.
  • Patent
    DE102010003809A1: Offenlegung-13.10.2011
  • Patent
    WO2011123219A3: Offenlegung-15.03.2012; Nachanmeldung: EP, WO, IN, RU

Publ.-Id: 16832 - Permalink

P0908 - Verfahren zur Herstellung von SiC basierenden Dünnfilm-Solarzellen mit erhöhter Effizienz
Voelskow, M.; Kanjilal, A.; Skorupa, W.;
Die Erfindung beschreibt ein Herstellungsverfahren von auf Siliziumkarbid basierenden Dünnfilm-Solarzellen. Durch eine impulsartige, intensive Lichtbestrahlung können die Silizium oder Silizium/Germanium auf Silizium Grenzflächen der Substrate kurzzeitig und facettenartig aufgeschmolzen werden. Die dadurch entstehende reliefartige Grenzfläche führt zu einer erhöhten Lichtabsorbtion in der Siliziumkarbidschicht, wodurch die Effizienz der Solarzellen erhöht wird.
  • Patent
    DE 10200905515 A1 - 29.09.2011

Publ.-Id: 16831 - Permalink

P0906-Anordnung zur Kontrolle der Strahlentherapie und Verwendungsvorschrift
Kunath, D.; Shakirin, G.; Enghardt, W.; Baumann, M.;
Die Erfindung betrifft eine Anordnung zur Verbesserung der Kontrolle während der Strahlentherapie und deren Verwendung. Kern der Erfindung ist die Integration eines kombinierten PET/CT-Scanners in den Bestrahlungsplatz bzw. in unmittelbarer Nähe.

Vorteil dieser Erfindung ist, dass es zu einer Zeitersparnis für den Bestrahlungsablauf kommt, man erhält sicherere Werte für die Bestimmung des Bestrahlungserfolges. Die Positionierung des Patienten muss nur einmal vor Therapiefraktion durchgeführt werden.
  • Patent
    DE102009054676A1 - Offenlegung - 16.06.2011; Zurückweisung - 22.08.2012

Publ.-Id: 16830 - Permalink

P0901 - Koaxialer schlitzgekopplter Resonatordiplexer
Arnold, A.;
Die Erfindung beschreibt eine koaxialen schlitzgekoppelten Resonatordiplexer, basierend auf der Verwendung unterschiedlicher Eigenmoden eines elektromagnetischen Resonators für die Einkopplung von wenigstens zwei Hochfrequenzwellen hoher Leistung und unterschiedlicher Wellenlänge in einen koaxialen mehrmodigen Wellenleiter. Diese Funktion ist zum Beispiel an supraleitenden Hochfrequenzresonatoren zur Beschleunigung von Elementarteilchen von großem Interesse. Ein weiteres mögliches Anwendungsgebiet findet sich in der Radartechnik.
  • Patent
    DE 102009046463 A1 - Offenlegung 04.08.2011, Erteilung 05.06.2014

Publ.-Id: 16829 - Permalink

Joint Project: Interaction and transport of actinides in natural clay rock with consideration of humic substances and clay organics - Characterization and quantification of the influence of clay organics on the interaction and diffusion of uranium and americium in the clay
Schmeide, K.; Joseph, C.; Sachs, S.; Steudtner, R.; Raditzky, B.; Günther, A.; Bernhard, G.;
The objective of this project was the study of basic interaction processes in the systems actinide - clay organics - aquifer and actinide - natural clay - clay organics - aquifer. Thus, complexation, redox, sorption and diffusion studies were performed.
To evaluate the influence of nitrogen, phosphorus and sulfur containing functional groups of humic acid (HA) on the complexation of actinides in comparison to carboxylic groups, the Am(III) and U(VI) complexation by model ligands was studied by UV-Vis spectroscopy and TRLFS. The results show that Am(III) is mainly coordinated via carboxylic groups, however, probably stabilized by nitrogen groups. The U(VI) complexation is dominated by carboxylic groups, whereas nitrogen and sulfur containing groups play a minor role. Phosphorus containing groups may contribute to the U(VI) complexation by HA, however, due to their low concentration in HA they play only a subordinate role compared to carboxylic groups. Applying synthetic HA with varying sulfur contents (0 to 6.9 wt.%), the role of sulfur functionalities of HA for the U(VI) complexation and Np(V) reduction was studied. The results have shown that sulfur functionalities can be involved in U(VI) humate complexation and act as redox-active sites in HA for the Np(V) reduction. However, due to the low content of sulfur in natural HA, its influence is less pronounced.
In the presence of carbonate, the U(VI) complexation by HA was studied in the alkaline pH range by means of cryo-TRLFS (-120°C) and ATR FT-IR spectroscopy. The formation of the ternary UO2(CO3)2HA(II)4− complex was detected. The complex formation constant was determined with log β0.1 M = 24.57 ± 0.17.
For aqueous U(VI) citrate and oxalate species, luminescence emission properties were determined by cryo-TRLFS and used to determine stability constants. The existing data base could be validated.
The U(VI) complexation by lactate, studied in the temperature range 7 to 65°C, was found to be endothermic and entropy-driven. In contrast, the complex stability constants determined for U(VI) humate complexation at 20 and 40°C are comparable, however, decrease at 60°C.
For aqueous U(IV) citrate, succinate, mandelate and glycolate species stability constants were determined. These ligands, especially citrate, increase solubility and mobility of U(IV) in solution due to complexation.
The U(VI) sorption onto crushed Opalinus Clay (OPA, Mont Terri, Switzerland) was studied in the absence and presence of HA or low molecular weight organic acids, in dependence on temperature and CO2 presence using OPA pore water as background electrolyte. Distribution coefficients (Kd) were determined for the sorption of U(VI) and HA onto OPA with (0.0222 ± 0.0004) m3/kg and (0.129 ± 0.006) m3/kg, respectively. The U(VI) sorption is not influenced by HA (50 mg/L), however, decreased by low molecular weight organic acids (> 1×10-5 M), especially by citrate and tartrate. With increasing temperature, the U(VI) sorption increases both in the absence and in the presence of clay organics.
The U(VI) diffusion in compacted OPA is not influenced by HA at 25 and 60°C. Predictions of the U(VI) diffusion show that an increase of the temperature to 60°C does not accelerate the migration of U(VI). With regard to uranium-containing waste, it is concluded that OPA is suitable as host rock for a future nuclear waste repository since OPA has a good retardation potential for U(VI).
Keywords: Actinides, americium, uranium, neptunium, humic substances, clay organics, model ligands, Opalinus clay, complexation, reduction, sorption, diffusion, migration, repository
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-017 2012
    ISSN: 2191-8708
  • Contribution to external collection
    C.M. Marquardt: Interaction and transport of actinides in natural clay rock with consideration of humic substances and clay organic compounds, KIT Scientific Reports 7633, Karlsruhe: KIT Scientific Publishing, 2012, Annex B, Report No. 1


Publ.-Id: 16828 - Permalink

Stability of the flow between two hemispherical electrodes
Shatrov, V.; Gerbeth, G.;
The stability of the steady laminar flow driven by the meridional electromagnetic force due to an electric current from a hemispherical electrode to a hemispherical cavity surface is studied using a multi-domain pseudospectral method. The most unstable azimuthal wave number is found as m = 4. Even in a low external magnetic field, the meridional flow in the main toroidal eddy changes its direction from counter-clockwise to clockwise due to the rotation in the azimuthal direction.
  • Contribution to proceedings
    8th International pamir Conference on Fundamental and Applied MHD, 05.-09.09.2011, Borgo, Corsica, France
    Proceedings of the 8th PAMIR International Conference on Fundamental and Applied MHD, 235-239

Publ.-Id: 16826 - Permalink

Production of Σ±πpK+ in p+p reactions at 3.5 GeV beam energy
Agakishiev, G.; Balanda, A.; Belver, D.; Belyaev, A.; Berger-Chen, J. C.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Dohrmann, F.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Lalik, R.; Lang, S.; Lange, J. S.; Lapidus, K.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Moriniere, E.; Mousa, J.; Müntz, C.; Münzer, R.; Naumann, L.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.;
We study the production of Σ±πpK+ particle quartets in p+p reactions at 3.5 GeV kinetic beam energy. The data were taken with the HADES experiment at GSI. This report evaluates the contribution of resonances like Λ(1405), Σ(1385)0, Λ(1520), Δ(1232), N and K0 to the Σ±πpK+ final state. The resulting simulation model is compared to the experimental data in several angular distributions and it shows itself as suitable to evaluate the acceptance corrections properly.

Publ.-Id: 16825 - Permalink

Comparative study of wall-force models for the simulation of bubbly flows
Rzehak, R.; Krepper, E.; Lifante, C.;
Accurate numerical prediction of void-fraction profiles in bubbly multiphase-flow relies on suitable closure models for the momentum exchange between liquid and gas phases. We here consider forces acting on the bubbles in the vicinity of a wall. A number of different models for this so-called wall-force have been proposed in the literature and are implemented in widely-used CFD-codes. Simulations using a selection of these models are compared with a set of experimental data on bubbly air-water flow in round pipes of different diameter. Based on the results, recommendations on suitable closures are given.
Keywords: dispersed gas liquid multiphase flow, bubble forces, Euler Euler two fluid model, CFD simulation, model validation

Publ.-Id: 16824 - Permalink

The influence of the surface slope on ion induced mass drift
Kranz, A.; Heinig, K.-H.; Liedke, B.;

The irradiation of solids with energetic ions can lead to the formation of periodic ripples on the surface. Furthermore, the wavevector of the ripples turns from parallel to perpendicular to the projected ion beam direction as the incidence angle increases beyond a critical angle. Here, we want to investigate this phenonemon theoretically by examination of the so called crater function.

The crater function is the average surface height change per single ion impact averaged over a stochastically representative number of ion impacts, each hitting an undisturbed target. It describes a mean mass drift that is induced by the impingment. Obviously, the crater function is symmetric to the projected ion beam direction when it is incident on a horizontal plane. But, if the beam is incident on a tilted plane the crater function is rotated and becomes asymmetric resulting in a mass drift up or down the slope.

By mathematical treatment, we give a condition on that mass can drift up the slope leading to an instability. It is shown with the help of atomistic simulations that this condition is fulfilled for gracing incidence. This explains the change in ripple orientation for increasing incidence angle as the flank of longitudinal ripples can be seen as tilted planes in a first order approximation.

Keywords: Crater function, ripples, ion beam irradiation, atomistic simulation
  • Lecture (others)
    Spring meeting of the DFG FOR 845 "Selbstorganisierte Nanostrukturen durch niederenergetische Ionenstrahlerosion", 07.-08.02.2012, Kaiserslautern, Deutschland

Publ.-Id: 16823 - Permalink

CFD for subcooled flow boiling: Coupling wall boiling and population balance models
Krepper, E.; Rzehak, R.; Lifante, C.; Frank, T.;
In this work we investigate the present capabilities of CFD for wall boiling. The computational model used combines the Euler / Euler two-phase flow description with heat flux partitioning. Very similar modelling was previously applied to boiling water under high pressure conditions relevant to nuclear power systems. Similar conditions in terms of the relevant non-dimensional numbers have been realized in the DEBORA tests using Dichlorodifluoromethane (R12) as the working fluid. This facilitated measurements of radial profiles for gas volume fraction, gas velocity, liquid temperature and bubble size.
Essential for the momentum, mass and energy exchange between the phases is an adequate description of the interfacial area or respectively the bubble size. In a previous study (Krepper and Rzehak, 2011) it was shown that a monodisperse bubble size representation is not sufficient to this end. Therefore, in the present work a population balance approach is used, where bubbles are generated at the wall with a certain size that subsequently evolves due to both condensation / evaporation and coalescence / breakup processes. The results show the potential of this approach which is able to describe the observed bubble size increase after leaving the wall as well as the change of gas volume fraction profile from wall to core peaking with increasing inlet temperature.
Keywords: CFD, two phase flow, boiling, momentum exchange, population balance model

Publ.-Id: 16822 - Permalink

Entwicklung der Radionuklid-markierten Komponente eines Tumor-Pretargeting-Systems für die Endoradionuklidtherapie auf der Basis L-konfigurierter Oligonukleotide
Förster, C.;
kein Abstract verfügbar
  • Doctoral thesis
    TU Dresden, 2012
    165 Seiten

Publ.-Id: 16821 - Permalink

Chirped Auger electron emission due to field-assisted post-collision interaction
Schütte, B.; Bauch, S.; Frühling, U.; Wieland, M.; Gensch, M.; Plönjes, E.; Gaumnitz, T.; Azima, A.; Bonitz, M.; Drescher, M.;
We have investigated the Auger decay in xenon and krypton atoms in a terahertz streaking field. Linewidth asymmetries suggest a chirped Auger electron emission which can be understood by field-assisted post-collision interaction.
  • Contribution to proceedings
    XVIIIth International Conference on Ultrafast Phenomena, 08.-13.07.2012, Lausanne, Schweiz
    Proceedings of XVIIIth International Conference on Ultrafast Phenomena

Publ.-Id: 16820 - Permalink

How worms survive desiccation: Trehalose pro water
Erkut, C.; Penkov, S.; Fahmy, K.; Kurzchalia, T. V.;
While life requires water, many organisms, known as anhydrobiotes, can survive in the absence of water for extended periods of time. Although discovered 300 years ago, we know very little about the fascinating phenomenon of anhydrobiosis. In this paper, we summarize our previous findings on the desiccation tolerance of the Caenorhabditis elegans dauer larva. A special emphasis is given to the role of trehalose in protecting membranes against desiccation. We also propose a simple mechanism for this process.
Keywords: infrared spectroscopy anhydrobiosis C. elegans

Publ.-Id: 16819 - Permalink

Radiohalogenated 4-anilinoquinazoline-based EGFR-TK inhibitors as potential cancer imaging agents
Neto, C.; Fernandes, C.; Oliveira, M. C.; Gano, L.; Mendes, F.; Kniess, T.; Santos, I.;
Introduction: The overexpression of epidermal growth factor receptor (EGFR) in tumors underlines the recent interest in EGFR as attractive target for the development of new cancer imaging agents. EGFR-tyrosine kinase inhibitors (EGFR-TKIs) based on the anilinoquinazoline scaffold have been explored as potential probes for EGFR imaging. However, up to now, no optimal radiotracer is available. Herein, we report the synthesis and biological evaluation of three novel halogenated 6-substituted 4-anilinoquinazoline based EGFR-TKIs. Radiosynthesis (125I and 18F) of the corresponding analogues was also performed.
Methods: 6a, 6b and 8 were obtained by reaction of 6-amino-4-anilinoquinazoline (5) with 3-/4-iodobenzoyl and 4-fluorobenzoyl chlorides. Inhibition of EGFR autophosphorylation and A431 cellular proliferation were assessed by Western blot and MTT assays. 125I-anilinoquinazolines [125I]6a/b were prepared via destannylation of the corresponding tributylstannyl precursors with [125I]NaI. Cellular uptake studies were conducted in A431 cells. Optimization of the radiosynthesis of the 18F-anilinoquinazoline [18F]8 was attempted by nucleophilic substitution of the trimethylammonium- and nitro-6-substituted 4-anilinoquinazoline precursors.
Results: 6a, 6b and 8 were synthesized in high chemical yield. All of them are inhibitors of EGFR autophosphorylation (0.1bIC50b1 μM) and A431 cell proliferation (IC50<3.5 μM). [125I]6a/b, obtained in high radiochemical purity and specific activity, were highly taken up by A431 cells. Biodistribution profile in mice indicated fast blood clearance and hepatobiliary excretion. Despite all attempts, [18F]8 was only formed in 4% yield, hampering further biological evaluation.
Conclusions: This study suggests that these quinazoline derivatives can act as EGFR-TKI, warranting further modifications in the chemical structure in order to be explored as potential molecular imaging agents for single photon emission computerized tomography and positron emission tomography.
Keywords: 4-Anilinoquinazolines; EGFR-TK inhibitors; Radiohalogenation; SPECT; PET; Iodine-125; Fluorine-18

Publ.-Id: 16818 - Permalink

Investigations on bubble-Induced turbulence modeling for vertical pipe bubbly flows
Liao, Y.; Lucas, D.;
Recently, the effect of bubbles on the generation and destruction of turbulence in the liquid phase, the so-called Bubble-Induced Turbulence (BIT), is getting more and more attention in the numerical simulation of bubbly flows. There are several theories and models available in the literature, which helps much to understand the inherent characteristics of BIT. However, a systematic validation of these models is still missing. In the current work, popular models considering the additional BIT are implemented into a 1D Test Solver, where the standard k-epsilon model for traditional Shear-Induced Turbulence (SIT) is available. The Test Solver was developed specially for the case of vertical pipe flows by Lucas et al. (2001) and for the purpose of an efficient pre-test of closure models for CFD codes. Its applicability has been tested in an amount of previous work such as Lucas et al. (2005) and (2007).

In the current work, turbulence parameters as well as liquid velocity profiles, which are predicted by the modified k-epsilon model with the consideration of BIT, are compared with experimental data published by different investigators. To exclude other uncertainties, the k-epsilon model is tested firstly for several single-phase cases with different average velocities and pipe diameters. In general, satisfying agreements are achieved in these cases. Then the contribution of BIT and the effect of various models are investigated for mono-dispersed bubbly flows. The flow is assumed to be fully-developed and moreover, the radial gas volume fraction profile is taken from the measurement. The results prove that for test cases with high gas volume fractions (high superficial gas velocity or low superficial liquid velocity) the neglecting of BIT will lead to an obvious underestimation of turbulence parameters. Furthermore, noticeable inconsistency can be observed in the results delivered by different BIT models, which indicates a need for further improvement in this aspect.
Keywords: Bubble-Induced Turbulence (BIT), Shear-Induced Turbulence (SIT), Additional eddy viscosity, Additional k-epsilon source term, Test Solver
  • Open Access LogoContribution to proceedings
    20th International Conference on Nuclear Engineering, ICONE20, 30.07.-03.08.2012, Anaheim, USA
    Proceedings of the 20th International Conference on Nuclear Engineering
  • Lecture (Conference)
    20th International Conference on Nuclear Engineering, ICONE20, 30.07.-03.08.2012, Anaheim, USA

Publ.-Id: 16817 - Permalink

Adsorption mechanism of selenium(VI) onto maghemite
Jordan, N.; Ritter, A.; Foerstendorf, H.; Scheinost, A. C.; Weiß, S.; Heim, K.; Grenzer, J.; Mücklich, A.; Reuther, H.;
In this study, the sorption properties of maghemite (γ-Fe2O3) towards selenium(VI) were studied for the first time both on the macroscopic and the molecular level. Using batch experiments, we found that the retention reaction was very fast. Both increase of pH and ionic strength led to a decrease of selenium(VI) sorption. Electrophoretic mobility measurements showed that selenium(VI) sorption had no significant effect on the isoelectric point of maghemite. These macroscopic results strongly suggested the formation of outer-sphere complexes across the investigated pH range (3.5 – 8.0). At the molecular level, the structure of the sorbed surface species was elucidated in situ using Attenuated Total Reflection Fourier-Transform Infrared (ATR FT-IR) spectroscopy and Extended X-ray Absorption Fine-Structure (EXAFS) spectroscopy. The ATR FT-IR results suggested the formation of outer-sphere complexes showing an unexpected bidentate symmetry, which possibly revealed the lack of accuracy of the actual widely-used classification of inner- and outer-sphere coordination for anionic species. EXAFS results revealed, that in addition to outer-sphere complexes, there is also a small (15%) contribution of an inner-sphere complex in binuclear corner-sharing geometry present.
Keywords: sorption; selenium(VI); maghemite; ATR FT-IR; EXAFS

Publ.-Id: 16816 - Permalink

Probing origin of room temperature ferromagnetism in Ni ion implanted ZnO films with x-ray absorption spectroscop
Srivastava, P.; Ghosh, S.; Joshi, B.; Satyarthi, P.; Kumar, P.; Kanjilal, D.; Buerger, D.; Zhou, S.; Schmidt, H.; Rogalev, A.; Wilhelm, F.;
We report x-ray absorption at Zn and Ni K-edges in 200 keV Ni(2+) ion implanted ZnO/sapphire films. The implantation fluences are 6 x 10(15) and 2 x 10(16) ions/cm(2), corresponding to 2% and 7% Ni in a ZnO matrix. The measurements reveal a marginal substitution of Ni in ZnO in both the films and also rule out the presence of ferromagnetic Ni metal clusters. The M-H and field cooled-zero field cooled measurements performed via SQUID magnetometry show that the films are ferromagnetic at room temperature, and the saturation magnetization of 2% Ni film is appreciably higher than that of 7% Ni film. The origin of ferromagnetism is understood on the basis of the oxygen vacancy mediated bound magnetic polaron model.

Publ.-Id: 16815 - Permalink

Radiobiological effectiveness of laser accelerated electrons in comparison to electron beams from a conventional linear accelerator.
Laschinsky, L.; Baumann, M.; Beyreuther, E.; Enghardt, W.; Kaluza, M.; Karsch, L.; Lessmann, E.; Naumburger, D.; Nicolai, M.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H. P.; Pawelke, J.;
The notable progress in laser particle acceleration technology promises potential medical application in cancer therapy through compact and cost effective laser devices that are suitable for already existing clinics. Previously, consequences on the radiobiological response by laser driven particle beams characterised by an ultra high peak dose rate have to be investigated. Therefore, tumour and non-malignant cells were irradiated with pulsed laser accelerated electrons at the JETI facility for the comparison with continuous electrons of a conventional therapy LINAC. Dose response curves were measured for the biological endpoints clonogenic survival and residual DNA double strand breaks. The overall results show no significant differences in radiobiological response for in vitro cell experiments between laser accelerated pulsed and clinical used electron beams. These first systematic in vitro cell response studies with precise dosimetry to laser driven electron beams represent a first step toward the long term aim of the application of laser accelerated particles in radiotherapy.

Publ.-Id: 16814 - Permalink

Laserbeschleunigte Ionenstrahlen für die Krebstherapie
Pawelke, J.;
no abstract available
  • Invited lecture (Conferences)
    Vortragsforum Medica Vision, 16.-19.11.2011, Düsseldorf, Deutschland

Publ.-Id: 16813 - Permalink

Die Technologieplattform für translationale Forschung in der Protonentherapie am OncoRay Dresden..
Enghardt, W.; Bussmann, M.; Cowan, T.; Dersch, U.; Fiedler, F.; Pawelke, J.; Perrin, R.; Pieck, S.; Schramm, U.; Sauerbrey, R.; Baumann, M.;
Gemäß ihrer Wechselwirkung mit (belebter) Materie sollten Protonenund Ionenstrahlen das Potenzial besitzen, den Erfolg der Strahlentherapie deutlich zu erhöhen. Begründet wird dies durch physikalische Vorteile gegenüber konventionellen Strahlenarten (Photonen, Elektronen), welche i. a. zu einer reduzierten Normalgewebsdosis und zur Möglichkeit der Dosiseskalation im Tumor führen. Im Falle der leichten Ionen kommt zu diesen physikalischen Vorteilen eine Erhöhung der relativen biologischen Wirksamkeit, welche bei adäquater technologischer Umsetzung der Strahlführung (Rasteroder Spotscanning) nahezu auf das Tumorvolumen begrenzt werden kann. Bisher konnten diese physikalisch und biologisch offenkundigen Vorteile der Partikelstrahlen für viele Bestrahlungssituationen nicht in verbesserte Tumorheilung umgesetzt werden.
Dafür sind drei Gründe anzusprechen: (1) Die in der Partikeltherapie angewendeten Behandlungs- und Qualitätssicherungstechniken wurden zum überwiegenden Teil für die konventionellen Therapie an medizinischen Elektronen-Linearbeschleunigern entwickelt und von dort übernommen. Letzteres erscheint nicht adäquat, weil Dosisverteilungen von Partikelstrahlen, im Gegensatz zu Photonenstrahlen, nicht robust gegen Ungenauigkeiten in der gesamten Kette der Strahlentherapie von der CT-Diagnostik bis zur Dosisapplikation sind. (2) Die Zahl der bisher weltweit an technologisch ausgereiften Protonen- oder Ionen-Therapieanlagen in qualitativ hochwertigen klinischen Studien behandelten Patienten ist nach wie vor klein, so dass oftmals statistisch gut gesicherte Therapieergebnisse nicht vorliegen. Generelle Anforderungen der heutigen evidenzbasierten Medizin, insbesondere auch randomisierte Studien, finden nur geringe Berücksichtigung. (3) Die unter (1) und (2) genannten Gründe folgen zu einem großen Teil aus den hohen Investitions- und Betriebskosten für Partikeltherapie-Anlagen, welche jene mit konventioneller Bestrahlungstechnologie um ca. eine Größenordnung übersteigen.
Diese Analyse definiert die medizinischen, strahlenbiologischen und physikalisch-technischen Arbeitsfelder der im Aufbau befindlichen Hochtechnologieplattform am Nationalen Zentrum für Strahlenforschung in der Onkologie - OncoRay, Dresden: (1) Die Entwicklung von Technologien, welche auf die der Partikeltherapie inhärenten Präzision zugeschnitten sind (Bewegungskompensation, Bildführung, dreidimensionale Dosislokalisation, ortsaufgelöste in-vivo Dosimetrie in Echtzeit). (2) Den Einschluss aller Patienten in klinische Studien. (3) Die Entwicklung neuartiger auf der Laser-Teilchenbeschleunigung beruhender Partikeltherapie-Anlagen, die kompakt und kostengünstig sind.
Diese klinischen und wissenschaftlichen Zielstellungen bestimmen die Auslegung der Anlage. Sie wird auf dem Gelände des Universitätsklinikums Carl Gustav Carus Dresden errichtet und in die bestehende Klinik und Poliklinik für Strahlentherapie und Radioonkologie integriert. Sie wird mit einer konventionellen Zyklotron basierten Protonen-Bestrahlungsanlage (Hersteller: Fa. IBA, Louvain-la-Neuve, Belgien) ausgerüstet. Der Protonenstrahl bedient vorerst einen klinischen Bestrahlungsbunker mit isozentrischer Gantry, ausgestattet mit einer universellen Strahlführung für passive und aktive Bestrahlungsfeld-Formierung. Ferner wird für experimentelle Arbeiten der Protonenstrahl in einen Experimentalbunker geführt. Auf dessen Dach wird ein Reinraum für einen Dioden gepumpten Hochintensitäts-Laser der Petawatt-Klasse errichtet. Das Laserlicht wird in den Experimentalbunker geführt, so dass dort sowohl konventionell als auch Laser beschleunigte Protonenstrahlen zur Verfügung stehen werden. Dies wird für die Entwicklung und Validierung dedizierter Strahlführungssysteme, dosimetrischer Messverfahren, Echtzeit-Verifikations- und Qualitätssicherungs-Techniken sowie für die Durchführung strahlenbiologischer Experimente an Laser beschleunigten Protonenstrahlen ein bisher weltweit nicht vorhandenes Umfeld bieten.
  • Lecture (Conference)
    3 Ländertagung der ÖGMP, DGMP und SGSMP – 2011 Medizinische Physik, 28.09.-01.10.2011, Wien, Österreich

Publ.-Id: 16812 - Permalink

Dosimetrie und biologische Wirksamkeit Laser beschleunigter Protonen
Schürer, M.; Baumann, M.; Beyreuther, E.; Burris-Mog, T.; Dammene, Y.; Enghardt, W.; Karsch, L.; Kraft, S.; Kroll, F.; Laschinsky, L.; Lessmann, E.; Metzkes, J.; Naumburger, D.; Oppelt, M.; Richter, C.; Schramm, U.; Sobiella, M.; Zeil, K.; Pawelke, J.;
Einleitung: Bevor die neue Technologie der Laser Beschleunigung in der Strahlentherapie eingesetzt werden kann, müssen Beschleuniger einen stabilen, steuerbaren Strahl mit genügender Strahlstärke liefern. Ausserdem müssen die entstehenden ultra kurzen, sehr intensiven Strahlpulse auf ihre biologische Wirksamkeit und dosimetrische Erfassung hin untersucht werden.
Methoden: Es wurde ein integriertes Dosimetrie- und Zellbestrahlungssystem (IDOCIS) entwickelt, getestet und umfangreich kalibriert.
Die Kombination verschiedener Dosimeter erlaubt eine präzise Absolutdosimetrie und Strahlüberwachung in Echtzeit. Nach zusätzlicher Modifizierung und Optimierung des 150 TW Lasersystems DRACO (FZD) wurden Zellbestrahlungen mit Laser beschleunigten Protonen durchgeführt.
Ergebnisse: Der Laserbeschleuniger lieferte überWochen einen stabilen und reproduzierbaren Protonenstrahl. Zusammen mit der präzisen dosimetrischen Erfassung mit Hilfe des IDOCIS wurden Dosiseffektkurven bestimmt.
Schlussfolgerung: Vor einem Einsatz Laser beschleunigter Protonen in der Strahlentherapie sind verschiedene Verbesserungen der Lasertechnik und die Durchführung von tierexperimentellen Studien notwendig.
ST 1.4
  • Poster
    3 Ländertagung der ÖGMP, DGMP und SGSMP – 2011 Medizinische Physik, 28.09.-01.10.2011, Wien, Österreich

Publ.-Id: 16811 - Permalink

Bubble-induced Turbulence: Comparison of CFD Models
Rzehak, R.; Krepper, E.;
Modeling of bubble-induced turbulence in dispersed gas-liquid multiphase flow is an important but still unresolved issue. A common approach to its solution is to add source terms to the single phase two-equation turbulence models. We here report a comparison of different models of this type some of which have been used previously in the literature, some of which are new. Special care has been given to the selection of a set of reference data allowing to qualify the validity of the different models. Conclusions towards best practice guidelines for modeling bubbly turbulence are drawn and needs for further reasearch identified.
Keywords: dispersed gas liquid multiphase flow, bubble induced turbulence, Euler Euler two fluid model, CFD simulation, model validation
  • Contribution to proceedings
    International Symposium on Multiphase flow and Transport Phenomena, 22.-25.4.2012, Agadir, Morocco
  • Lecture (Conference)
    International Symposium on Multiphase flow and Transport Phenomena, 22.-25.4.2012, Agadir, Morocco

Publ.-Id: 16810 - Permalink

Biological effectiveness of laser accelerated protons: In vitro dose response studies
Oppelt, M.; Baumann, M.; Beyreuther, E.; Murris-Mog, T.; Enghardt, W.; Karsch, L.; Kraft, S.; Laschinsky, L.; Leßmann, E.; Metzkes, J.; Naumburger, D.; Richter, C.; Schramm, U.; Schürer, M.; Zeil, K.; Pawelke, J.;
The development of proton and ion acceleration by ultra-high intensity lasers for cancer therapy promises the realisation of compact and economic particle accelerators that can be integrated in already existing clinics. However, particle acceleration with high intensity lasers leads in comparison to the conventional used acceleration technique to ultra short beam pulses, generated with low pulse frequency, that apply a very high pulse dose. Prior to a clinical application the radiobiological consequences of laser accelerated and therewith ultra short pulsed particle beams have to be investigated.
For this in vitro dose effect curves have been determined, which required a high power laser system with a stable and reproducible acceleration of protons, precise beam monitoring and the technical ability to apply a prescribed dose to a cell sample and to determine the absolute dose received by the cells.
Systematic cell irradiations were performed at the 150 TW Ti:Sapphire laser system DRACO at HZDR that delivered laser pulseswith an energy of 3.5 J, a pulse duration of 30 fs and a frequency of 0.1 Hz. By focusing the laser on a 2 μm thin Ti foil, protons were accelerated from the target rear surface. The generated exponential energy spectrum was limited downwards to 6-20 MeV. An in-house developed integrated dosimetry and cell irradiation system was tested and calibrated, allowing precise dosimetry as well as the exact positioning of each cell sample.
In the present experiment radiosensitive head and neck tumour cells (SKX) were irradiated in a dose range from 0.5-4 Gy with an average pulse dose of 80 mGy and a mean dose rate of 0.5 Gy/min.
Investigated biological endpoints were the clonogenic cell survival and residual DNA-double strand breaks (DSB) 24 h post irradiation via γ-H2AX /p53BP1 assay.
Reference irradiation was performed with continuous, conventional accelerated 7.2 MeV proton beams at the Tandem accelerator at HZDR with a dose rate of 1.1 Gy/min.
The measured dose effect curves show no difference in biological effectiveness between laser accelerated ultra short pulsed and conventional continuous proton beams in clonogenic cell survival and residual DNA DSB.
  • Poster
    14th International Congress of Radiation Research (ICRR), 28.08.-01.09.2011, Warszawa, Poland

Publ.-Id: 16809 - Permalink

Dosimetry of laser-accelerated particle beams used for cell irradiation experiments
Pawelke, J.;
no abstract available
  • Invited lecture (Conferences)
    HEPTech Workshop, Industry meets Academia: Beam Monitoring Instrumentation and Quality Assurance, 10.-11.11.2011, Darmstadt, Deutschland

Publ.-Id: 16808 - Permalink

Towards radiotherapy application of laser driven particle beams
Pawelke, J.;
Abstract not available
  • Invited lecture (Conferences)
    International Conference on Medical Physics and Engineering, 21.-24.09.2011, Poznan, Poland
  • Abstract in refereed journal
    Polish Journal of Medical Physics and Engineering 17(2011)Suppl.1, 34

Publ.-Id: 16807 - Permalink

Laser driven accelerators for radiobiology experiment
Pawelke, J.; Beyreuther, E.; Burris-Mog, T.; Cowan, T.; Kraft, S.; Laschinsky, L.; Leßmann, E.; Metzkes, J.; Richter, C.; Schlenvoigt, H. P.; Schramm, U.; Zeil, K.; Baumann, M.; Dammene, Y.; Enghardt, W.; Karsch, L.; Naumburger, D.; Schürer, M.; Woithe, J.; Kaluza, M.; Nicolai, M.;
no abstract available
  • Invited lecture (Conferences)
    ESTRO Anniversary Congress, 08.-12.05.2011, London, United Kingdom

Publ.-Id: 16806 - Permalink

Impinging jet simulations using a multi-field approach with free surface detection
Hänsch, S.; Lucas, D.; Krepper, E.; Höhne, T.; Danciu, D.-V.;
The calculation of impinging liquid jets and the associated bubble entrainment is a challenging problem in two-fluid model applications. The various mechanisms behind these phenomena are not well understood and a better appreciation of them is vitally important for industrial and scientific issues. The difficulty of simulation arises from the fact that impinging jets show a mixture of both segregated and dispersed flow regimes. Therefore they demand a multi-fluid simulation to capture larger gas structures with resolved interfaces as well as many small bubbles of different sizes that require an averaged treatment. In order to deal with the complexity of these mechanisms a new CMFD-strategy of a generalized two-phase flow (GENTOP) is presented.
Currently, the GENTOP-concept combines a three-field simulation with the recently developed inhomogeneous Multiple Size Group (MUSIG)-approach. The flow is represented by a liquid phase, a polydispersed gas phase, containing different bubble size groups, and a continuous gas phase. Within the MUSIG-framework, transfers between the different bubble size groups due to bubble coalescence and -breakup are described. By modelling an additional mass transfer between the continuous and the polydispersed gas phase, transitions between different gas morphologies can be considered. The continuous gas phase summarizes all gas structures larger than a certain bubble diameter so that for these structures the gas-liquid interfaces are resolved. In order to blend the gaseous morphology basic ideas of the Algebraic Interfacial Area Density (AIAD)-model are used. Generalized formulations for interfacial area density and drag are introduced considering free surfaces within a multi-fluid simulation. This new concept can provide more detailed information about complex flow situations with higher gas fractions such as the impinging jet being just one particular application.
First results computed by the CFD-code CFX 13.0 are compared to experiments carried out at the HZDR and empirical correlations from literature. The flow field is adapted to the experiments considering inlet velocity of the jet v0=1.7m/s, jet length Lj=10mm and jet diameter d0=16mm as well as the dimensions of the water tank. The computational results show good qualitative agreement with the experiments regarding typical continuous and polydispersed gas structures. The values of air entrainment rate and bubble plume length are determined as quantitative values characterizing the results. Further developments consist of new generalized closure models for bubble coalescence and –breakup processes between continuous and dispersed gas phases.
Keywords: turbulent impinging jet, air entrainment, CMFD, gas-liquid interface, MUSIG-model, AIAD-model
  • Contribution to proceedings
    International Symposium on Multiphase Flow and Transport Phenomena, 22.-25.04.2012, Agadir, Marokko
  • Lecture (Conference)
    International Symposium on Multiphase Flow and Transport Phenomena, 22.-25.04.2012, Agadir, Marokko

Publ.-Id: 16805 - Permalink

Status der Protonentherapie auf Basis von Hochintensitätslasern – Erste Dosis-Effekt-Kurven Laser beschleunigter Protonen.
Karsch, L.; Baumann, M.; Beyreuther, E.; Burris-Mog, T.; Kraft, S.; Laschinsky, L.; Metzkes, J.; Naumburger, D.; Oppelt, M.; Richter, C.; Schramm, U.; Schürer, M.; Zeil, K.; Pawelke, J.;
no abstracts available
  • Lecture (Conference)
    17. Jahreskongress der Deutschen Gesellschaft für Radioonkologie, 02.-05.06.2011, Wiesbaden, Deutschland

Publ.-Id: 16803 - Permalink

Dosimetry and biological effectiveness of laser-accelerated particle beams
Karsch, L.; Baumann, M.; Beyreuther, E.; Burris-Mog, T.; Cowan, T.; Dammene, Y.; Enghardt, W.; Laschinsky, L.; Lessmann, E.; Kaluza, M. C.; Kraft, S.; Metzkes, J.; Naumburger, D.; Nicolai, M.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H. P.; Schramm, U.; Schürer, M.; Sobiella, M.; Woithe, J.; Zeil, K.; Pawelke, J.;
Purpose: Before laser particle accelerators can be used for radiation therapy, the supply of stable, reliable and reproducible beams with sufficient particle intensity and useable energy spectra is required. Moreover, consequences on dosimetry as well as on radiobiological effectiveness have to be investigated for laser-accelerated and therefore ultra-shortly pulsed particle beams with very high pulse dose rate.
Method and Materials: In vitro cell irradiations have been established and performed within the German multi-institutional research project onCOOPtics for both laser-accelerated electron and proton beams.
The experimental setups at two lasers, the 10 TW JETI laser for electron and the 150 TW DRACO laser for proton beams, includes a dedicated system for routine cell sample irradiation and precise determination of applied dose. After extensive tuning and optimization of the laser systems and particle beams as well as test and calibration of all dosimetric components, systematic radiobiological experiments with several tumor and normal tissue cell lines have been performed over the last three years measuring dose-effect-curves for cell survival and DNA double strand break induction.
Results: No significant differences in biological effectiveness between laser-accelerated and conventional electron beams were found, apart from one cell line at one end point. The evaluation of the recently finished proton irradiation campaign is in progress.
Conclusion: Laser accelerators can be used for radiobiological experiments, meeting all necessary requirements like homogeneity, stability and precise dose delivery. Nevertheless, before fulfilling the much higher requirements for clinical application, several improvements concerning i.e. proton energy, spectral shaping and patient safety are necessary.
  • Contribution to proceedings
    SPIE Optics and Optoelectronics 2011, 18.-21.04.2011, Prague, Czech Republic
    Proceedings of SPIE Optics and Optoelectronics 2011, 132-133
  • Lecture (Conference)
    Dosimetry and biological effectiveness of laser-accelerated particle beams, 18.-21.04.2011, Prague, Czech Republic

Publ.-Id: 16802 - Permalink

The Energy Dependence of the Electric Dipole Strength in Heavy Nuclei
Junghans, A. R.; Beyer, R.; Grosse, E.; Rusev, G.; Schwengner, R.; Wagner, A.;
We investigate on the basis of new photon scattering measurements and photoneutron and average neutron resonance capture data how well Lorentzians adjusted to photoneutron data in the giant dipole resonances give a good description of the photon strength also below the neutron threshold. If deformation effects are properly taken into account it is verified that down to about 4 MeV for various nuclei with A £¾ 80 the previously employed differentiation between deformed and non-deformed nuclei is no longer necessary.

Publ.-Id: 16801 - Permalink

Stable proton pulses for the measurement of the biological effectiveness of laser accelerated particle beams.
Zeil, K.; Metzkes, J.; Kraft, S.; Cowan, T.; Karsch, L.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schramm, U.;
The advent of high power laser systems providing pulse rates of a few pulses per minute in the field of laser ion acceleration has brought medical applications such as ion therapy of cancer closer into reach. Although the proton energies are still not high enough for patient treatment, they are sufficient to start first experiments on dosimetry and the biological effectiveness. In contrary to conventional accelerators, the laser ion acceleration delivers proton bunches with a very high charge in short times with a broad energy spectrum. Thus new concepts in dosimetry and irradiation are necessary.
It is evident, that applications with biological material have demanding requirements to the proton energy spectrum and its stability. In this paper we present a robust scheme to provide stable energy spectra for first cell irradiation experiments performed with the Dresden 150 TW laser system DRACO at a dose rate of about 1 Gy/min. A second paper will concentrate on the radiobiological aspects of the experiment and the complex dosimetry issues.
In addition to the production of a reproducible proton spectrum the scheme involves magnetic filtering. Based on a simple non-focusing magnetic dipole equipped with two apertures it makes use of an energy dependent angular asymmetry of the proton spectra and protons with energies above 7 MeV originating from a 2 μm thick Titanium foil are led to the cell sample.
S.D. Kraft, et al., Dose dependent biological damage of tumour cells by laser-accelerated proton beams, New Journal of Physics 12, 085003(2010)
  • Invited lecture (Conferences)
    SPIE Optics and Optoelectronics 2011, 18.-21.04.2011, Prague, Czech Republic
  • Contribution to proceedings
    SPIE Optics and Optoelectronics 2011, 18.-21.04.2011, Prague, Czech Republic
    Proceedings of SPIE Optics and Optoelectronics 2011, 132

Publ.-Id: 16800 - Permalink

Development of a Neutron TOF Facility at KAERI
Song, T.-Y.; Park, S.-H.; Lee, B. C.; Lee, Y.-O.; Junghans, A. R.;
KAERI (Korea Atomic Energy Research Institute) is developing a neutron TOF facility by using KAERI's electron accelerator. KAERI has a superconducting electron accelerator which can produce 17 MeV pulsed electron beams with a pulse width of 20 ps. The pulse current and maximum frequency of the electron accelerator are 20 A and 2 MHz respectively. Fast neutrons can be used for cross-section measurements. A short pulse width can provide a good neutron energy resolution for fast neutrons at relatively short flight lengths. The time resolution related to a neutron source target should be small enough to utilize the short pulse width. We adopted the liquid Pb target which was developed by FDZ (Forschungszentrum Dresden-Rossendorf). The first step of the neutron source development is to simulate a neutron production. MCNPX was used to simulate the neutron production when electron beams irradiate the Pb target. Those simulations were performed by varying beam energies and target sizes to find out optimal variables related to the beam and target. The information of heat deposition in the target was studied by MCNPX since a proper cooling system should be considered to operate the liquid Pb target safely. The thermal-hydraulic analysis was performed based on the result of heat deposition calculation. The study of the detection system is under progress. The design of an experimental hall and a collimator system is also being progressed with the development of the detection system.

Publ.-Id: 16799 - Permalink

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