Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31735 Publications
Hydrodynamics of co-current two-phase flows in slanted porous media - modulation of pulse flow via bed obliquity
Schubert, M.; Hamidipour, M.; Duchesne, C.; Larachi, F.;
A packed bed operated with descending gas-liquid co-current flows in slanted configuration to force trickle flow pattern to segregate due to gravity was studied, in addition to dependences to inclination angle of liquid saturation and pressure drop. Inception of pulse flow regime could take place regardless of inclination angle and the transition from segregated/trickle regime to pulse flow regime was experimentally determined. The Grosser et al.1 flow regime transition model was modified by considering only axial components of the gas and liquid superficial velocities to predict the slant-dependent shifts in transition from segregated/trickle to pulse flow and was found to agree with experimental data. Pulse flow regime at different inclinations was characterized with respect to frequency, velocity and shape of pulses. Bed obliquity was unveiled as a new artifice to pulse flow modulation with possible prospects for catalytic reactions requiring antagonistically high-interaction regime mass transfer coefficients and partial catalyst wetting.
Keywords: Packed bed hydrodynamics; inclination; segregation; electrical capacitance tomography; flow regime transition; transition model

Publ.-Id: 13262 - Permalink


KKW Krümmel: Spannungs- und Ermüdungsanalyse des Kernmantels für die Transiente am 28.06.2007
Altstadt, E.; Werner, M.;
Es handelt sich um einen vertraulichen Bericht, kein Abstract.
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2008
    FZD\FWS\2008\09
    20 Seiten

Publ.-Id: 13261 - Permalink


Dynamics of Mesoscopic Magnetic Objects
Quitmann, C.; Raabe, J.; Puzic, A.; Kuepper, K.; Wintz, S.;
We report on the dynamic properties of mesoscopic magnetic objects. Such objects have dimensions somewhat larger than the magnetic exchange length ξ. This leads to relatively simple and stable patterns of the magnetization which can be excited using magnetic field pulses. The subsequent dynamics can be studied using x-ray based magnetic microscopy. We show examples of high symmetry structures where the dynamics is relatively simple and can be analyzed quantitatively in terms of amplitude, frequency, damping and symmetry. Intentional defects allow modifying specific modes. When using high amplitude excitations the magnetization in such structures can be switched.
Keywords: magnetism, dynamics, vortex, XMCD
  • Contribution to external collection
    Beaurepaire, E.; Bulou, H.; Scheurer, F.; Kappler, J.-P.: Magnetism and Synchrotron Radiation - New Trends; Springer Proceedings in Physics, Vol. 133, Berlin, Heidelberg: Springer, 2010, 978-3-642-04497-7

Publ.-Id: 13260 - Permalink


Implantation, Diffusion, Activation, and Recrystallization of Gallium Implanted in Preamorphized and Crystalline Germanium
Hellings, G.; Wündisch, C.; Eneman, G.; Simoen, E.; Clarysse, T.; Meuris, M.; Vandervorst, W.; Posselt, M.; de Meyer, K.;
We investigated the as-implanted profiles, electrical activation, diffusion, and recrystallization of gallium implanted in germanium samples through the combination of secondary-ion mass spectrometry, transmission electron microscopy, and sheet resistance measurement. Because of their high activation level (4.4 x 1020 cm−3) without preamorphization, low activation temperature (400°C), and absence of diffusion (up to 700°C), Ga junctions in crystalline Ge are very promising candidates for implementation in germanium technology. In the amorphous Ge phase, an increased diffusivity of Ga was observed at temperatures above 400°C.
Keywords: germanium gallium diffusion activation recrystallization
  • Electrochemical and Solid State Letters 12(2009), H417-H419

Publ.-Id: 13259 - Permalink


Millisecond flash lamp annealing of ultra-shallow implanted layers in Ge
Posselt, M.; Wündisch, C.; Schmidt, B.; Schumann, T.; Mücklich, A.; Skorupa, W.; Clarysse, T.; Simoen, E.; Hortenbach, H.;
In the past the lack of a stable native germanium oxide for surface passivation and gate dielectrics as well as the inability to epitaxially grow sufficiently thick defect-free germanium layers on silicon hindered the integration of germanium into the mainstream Si-based technology. Recent developments, such as high-k dielectrics and germanium-on-insulator substrates have made germanium a promising candidate for future high-mobility and low-power consumption devices. Therefore, electrical doping of germanium by ion implantation and subsequent annealing has drawn a renewed interest. Investigations on the formation of ultra shallow junctions by ion beam processing have shown that p+-doping using B yields junctions that meet the requirements for the 22 nm technology node, whereas the formation of n+-junctions by P or As is complicated by the high diffusivity and the low solubility of the dopants. Recently, the concentration-dependent diffusion of n-dopants like P, As and Sb has been explored, and it has been found that doubly negatively charged vacancies are the mobile species responsible for the migration of the dopant atoms. The application of conventional rapid thermal annealing (RTA) with durations of some seconds and temperatures above about 500 °C leads to the activation of the n-dopants but their fast concentration-dependent diffusion can generally be not prevented. On the other hand it has been shown that both the diffusion and the activation of the dopants does not depend significantly on the implantation damage, i.e. using the defect engineering schemes known from Si technology seems to be not promising. Therefore, in order to control junction depth and dopant activation ultra-short annealing by flash lamps or lasers are currently under investigation.
The present work deals with the application of millisecond flash lamp annealing (FLA) to samples containing an implanted surface layer of about 100 nm thickness. P or As ions were implanted at an energy of 30 or 90 keV, respectively, and a fluence of 3x1015 cm-2. The investigations are focused on solid phase recrystallization, dopant redistribution and dopant activation. The dependence of these effects on the heat transfer to the sample during FLA as well as on pre-amorphization and pre-annealing treatment is discussed. The results are compared to typical data achievable by RTA. Different characterization methods were employed. Channeling Rutherford backscattering spectrometry and cross-sectional transmission electron microscopy (XTEM) were used to monitor the recrystallization of the amorphous layers formed during implantation. The depth distributions of P and As were measured by secondary ion mass spectrometry. In order to determine the sheet resistance variable probe spacing and micro four point probe measurements were utilized. Selected samples were studied by XTEM to search for precipitates and end-of-range defects. While in RTA the concentration dependent dopant diffusion hinders the formation of ultra-shallow n+ layers, FLA does not cause any diffusion. The maximum activation obtained by FLA is about 4x1019 and 2x1019 cm-3 for P and As, respectively. This is about 3-4 times higher than under typical RTA conditions. However, the activation and the sheet resistance achieved by FLA do not yet fulfill the ITRS requirements for the 22 nm technology node. Possible mechanisms responsible for dopant deactivation are discussed.
Keywords: germanium flash lamp annealing ion implantation
  • Invited lecture (Conferences)
    216th Meeting of the Electrochemical Society, Symposium E10: ULSI Process Integration 6, 04.-09.10.2009, Vienna, Austria

Publ.-Id: 13258 - Permalink


Atomistic simulation of recrystallization of amorphous Si and Ge
Posselt, M.; Gabriel, A.;
Recrystallization of amorphous Si and Ge is an important issue both in the formation of ultra-shallow junctions and in photovoltaics. In the former case the relatively high fluences applied in dopant implantation or the use of pre-amorphization implantation lead to the formation of an amorphous layer. In the first stage of annealing the solid phase epitaxial regrowth (SPER) of the amorphous layer takes place. SPER leads to redistribution of dopants, and they are incorporated into the crystal either substitutionally or within clusters containing self-interstitials or vacancies. In Si the SPER process leaves beyond the original amorphous-crystalline interface the end-of-range damage which contains an excess of self-interstitials. During further annealing, free self-interstitials are emitted from the end-of-range damage and may cause an enhanced diffusion of the dopants. It is highly desirable to understand the processes occurring during SPER on the atomic level. This work presents results of classical molecular dynamics simulations of SPER in pure Si and Ge. While in the last decade several authors investigated SPER in Si, the regrowth of amorphous Ge layers has not been considered yet.

First of all a realistic atomic system with two amorphous-crystalline interfaces which are nearly parallel to a {100} plane is prepared and characterized. The structural properties of the amorphous and crystalline parts are in very good agreement with experimental data from literature. After preparation at 300 K the system is heated to a given temperature and the regrowth of the amorphous layer is monitored by different methods including visualization and statistical analysis. Two stages are found: The initial stage (0 - 3 ns) corresponds to the SPER process. Here, the amorphous part is contiguous and its thickness is large enough so that the two interfaces do not influence each other. In the final stage (4 - 5 ns) the amorphous region becomes thinner, and finally isolated amorphous regions may exist and recrystallize independently of each other. This may lead to the generation of stacking faults and defects. For a wide temperature range regrowth velocities are calculated for the SPER process and the results are drawn in an Arrhenius plot. From this presentation the effective activation energy of SPER and the corresponding pre-exponential factor are determined. The results are compared to experimental data from literature. Furthermore, the evolution of the roughness and the morphology of the amorphous-crystalline interface are investigated.
Keywords: silicon germanium recrystallization atomistic simulation
  • Lecture (Conference)
    XIIIth International Autumn Meeting on Gettering and Defect Engineering in Semiconductor Technology (GADEST 2009), 26.09.-02.10.2009, Döllnsee-Schorfheide, Germany

Publ.-Id: 13257 - Permalink


Intrinsic and extrinsic diffusion of indium in germanium
Kube, R.; Bracht, H.; Chroneos, A.; Posselt, M.; Schmidt, B.;
Diffusion experiments with indium (In) in germanium (Ge) were performed in the temperature range between 550 and 900 °C. Intrinsic and extrinsic doping levels were achieved by utilizing various implantation doses. Indium concentration profiles were recorded by means of secondary ion mass spectrometry and spreading resistance profiling. The observed concentration independent diffusion profiles are accurately described based on the vacancy mechanism with a singly negatively charged mobile In-vacancy complex. In accord with the experiment, the diffusion model predicts an effective In diffusion coefficient under extrinsic conditions that is a factor of 2 higher than under intrinsic conditions. The temperature dependence of intrinsic In diffusion yields an activation enthalpy of 3.51 eV and confirms earlier results of Dorner et al. [Z. Metallk. 73, 325 (1982)]. The value clearly exceeds the activation enthalpy of Ge self-diffusion and indicates that the attractive interaction between In and a vacancy does not extend to third nearest neighbor sites which confirms recent theoretical calculations. At low temperatures and high doping levels, the In profiles show an extended tail that could reflect an enhanced diffusion at the beginning of the annealing.
Keywords: diffusion indium germanium
  • Journal of Applied Physics 106(2009), 063534

Publ.-Id: 13256 - Permalink


Tests of ELBE RF-Components with Increased RF-Power
Büttig, H.; Arnold, A.; Büchner, A.; Freitag, M.; Lehnert, U.; Michel, P.; Schurig, R.; Staats, G.; Teichert, J.; Voigtländer, J.; Winter, A.;
The RF-system of the superconducting electron linac ELBE (40 MeV, 1 mA CW) is in permanent operation since 2001, but it is not completely free of RF-trips. Experience gained within eight years of operation shows that the better the RF-components were conditioned the better is their electrical stability during long time operation. To be prepared for the planned ELBE upgrade with 16 kW of RF-power per cavity several test benches have been built to study the performance of RF-couplers and waveguide windows. In cooperation with Bruker BioSpin / France and CPI / USA the prototype of a 30 kW RF-amplifier based on an IOT had been tested with beam at ELBE. This paper gives an overview about tests of RF-components with increased RF-power at ELBE.
Keywords: ELBE-RF System, Superconducting Radio Frequency, RF 1.3 GHz, RF-Power Coupler, 1.3GHz Waveguide Window, RF-Coupler Test Bench, Resonant Ring (1.3GHz), 1.3GHz CW-RF
  • Poster
    14-th International Conference on RF Superconductivity,SRF09 20.-25.09.2009, 20.-25.09.2009, Berlin, Dresden, Deutschland
  • Contribution to proceedings
    14th International conference on RF Superconductivity, SRF09, 20.-25.09.2009, Berlin, Dresden, Deutschland
    Proceedings SRF 2009

Publ.-Id: 13255 - Permalink


Side Effects on the Heart and Skeleton of Growing Mice Attributed to Chronic Imatinib Exposure
Suttorp, M.; Boehme, J.; Vaitl, J.; Mosch, B.; Pursche, S.; Jung, R.; Bergmann, R.; Fischer, R.; Pietzsch, J.; Bornhaeuser, M.; Gasser, J. A.;
Objectives: Chronic myeloid leukemia (CML) is effectively treated by Imatinib (IM) via inhibition of the BCR-ABL tyrosine kinase. However, also related tyrosine kinases like abl, c-Kit, PDGF-R, and c-FMS are blocked by IM. As shown in adult humans and mice, abl-controlled protein folding as part of the endoplasmatic stress response in heart myoblasts as well as bone "remodeling" depending on PDGF-R and c-FMS is impaired under imatinib exposure (Dewar AL et al 2005, Kerkelä R et al 2006, Fitter S et al 2008). The influence of IM on the growing heart and skeleton of immature animals has not been studied so far. With respect to treatment of pediatric CML we report alterations in these organs of juvenile mice chronically exposed to IM during the growth period.
Methods: From the age of 4–14 weeks (w) [development milestones of mice: weaning 3 w; puberty 7 w; epiphysial lines closure 18 w] C3H/Neu male and female wild-type mice were chronically exposed to IM via the drinking water at concentrations of 500 mg/l (group A), 750 mg/l (group B), and 1000mg/l (group C). Femur length and overall skeletal development was analysed by whole body X-ray analysis using a mammography device. Bone metabolic activity was assessed by total body Na18F PET and CT after 5w and 10w of exposure using dedicated small animal tomographs. Bone mineral density and microstructure of tibiae were analysed by pQCT and microCT (resolution 12.5µ m) while the number of osteoclasts and resorption lacunae in femora and vertebrae was assessed by histomorphometry. Plasma concentration of IM, osteocalcin, and activity of the tartrate resistant acid phosphatase (TRAP5b) was also determined. The heart was examined histologically and ultrastructurally by electron microscopy.
Results: IM was tolerated well and mean uptake of 80 mg/kg/d
A. 110 mg/kg/d
B. and 150 mg/kg/d
C. resulted in serum levels of 60–674 ng/ml, 36–242 ng/ml and 51–534 ng/ml, respectively.
Body weight gain was delayed in groups B and C until the age of 8 w while no change in overall growth, development and behaviour was observed at 14 w. At higher doses of IM and at younger age there was a non-significant trend to a reduction in femur length. Heart morphological examination exhibited an increased number (p<0.05) of hypertrophic cardiomyocytes (toxic damage) paralleled by ultrastructural alterations in mitochondria, myofibrils, and nucleus. In the skeleton, no significant differences compared to controls concerning 18F-kinetics and uptake in vertebrae and femura could be demonstrated. However, IM dose-dependently reduced the number of osteoclasts and resorption lacunae (p<0.05); these effects were less pronounced in female mice. Tibia cortical thickness was increased significantly in males by 6.1% (B) and 11.2% (C), respectively, and 7.5% in females (C). By microCT cancellous bone exhibited a significant increase in trabecular bone mass density and volume and number resulting in an increase in trabecular connectivity in males by 63% (B) and 64% (C), respectively, and in females by 22% (B) and 38% (C), respectively. Bone biomarkers indicated a significant reduction of TRAP5b activity while osteocalcin levels remained unchanged.
Conclusion: In juvenile mice, a chronic exposure of IM resulted in toxic damage of the cardiomyocytes at higher dose rates. However, these alterations do not necessarily imply also a functional impairment which can only be studied in vivo. In the skeleton, IM reduced the number of osteoclasts and resorption lacunae in long bones but not in vertebrae. IM showed an antiresorptive effect in cancellous bone and increased cortical thickness and trabecular number by inhibiting the expansion of the marrow cavity. The effects were more pronounced in male mice and at younger age.
  • Poster
    Annual Meeting American Society of Hematology, 06.-09.12.2008, San Francisco, USA
  • Abstract in refereed journal
    BLOOD 112(2008), 402

Publ.-Id: 13254 - Permalink


NMR Studies and Crystal Structure Determinations of CF3 Group-containing Bicyclic phenolates
Mamat, C.; Reinke, H.; Langer, P.;
Three new CF3-substituted bicyclic Salicylate derivatives were synthesized by the TiCl4-mediated cyclization Of trifluoromethyl-containing ketones with 1,3-bis(silyl enol ethers) and characterized by NMR and IR, spectroscopy, Mass spectrometry and elemental analysis. The crystal structures of the bicyclic derivatives have been determined by single crystal X-ray analysis. All structures exhibit hydrogen bonding.
  • Zeitschrift für Naturforschung Section B - A Journal of Chemical Sciences 64(2009)4, 423-426

Publ.-Id: 13252 - Permalink


Luminescence properties of uranium(VI) citrate and uranium(VI) oxalate species and their application for the determination of complex formation constants
Günther, A.; Steudtner, R.; Schmeide, K.; Bernhard, G.;
For the first time, the interaction of uranium(VI) with citric acid and oxalic acid in aqueous solution was investigated using time-resolved laser-induced fluorescence spectroscopy (TRLFS) between pH 2 and 4. The complex species UO2cit− and (UO2)2(cit)22− formed in citrate medium as well as UO2ox and UO2(ox)22- formed in oxalate medium show no luminescence emissions at room temperature. However, by coupling the fluorescence measurement technique with a low temperature system (-120 °C, cryo-TRLFS), emission signals of the various complex species could be detected. The emission signals are bathochromic shifted in comparison to the emission maxima of the uncomplexed uranyl(VI) cation. Using the spectroscopic data, the corresponding complex formation constants were calculated, which corroborate literature data.
Keywords: uranium(VI), citric acid, oxalic acid, time-resolved laser-induced fluorescence spectroscopy, cryogenic measurement technique

Publ.-Id: 13251 - Permalink


QCD Sum Rules for D and Ds Mesons in Dense and Hot Nuclear Matter
Hilger, T.;
Tool: QCD sum rules, Goal: D mesons → CBM / FAIR, Outlook: charm near Tc
  • Lecture (Conference)
    International Conference on Strangeness in Quarkmatter 09 (SQM 09), 27.09.-02.10.2009, Buzios, Brazil

Publ.-Id: 13250 - Permalink


Radiokupfer-markierte Peptide auf der Basis neuer bifunktioneller Chelatliganden
Stephan, H.; Bergmann, R.; Steinbach, J.;
Die erfolgreiche klinische Anwendung von radioaktiv markierten Somatostatin-Peptid-Analogen für die Bildgebung von rezeptorexprimierenden Tumoren hat die Modifizierung anderer Regulatorpeptide wie Neurotensin, RGD-Peptide oder Bombesin als mögliche Tumordiagnostika und –therapeutika vorangetrieben.[1] Auf dem Weg zu diesen neuen radioaktiven Arzneimitteln sind eine Reihe unterschiedlicher Aufgaben zu lösen. Das betrifft insbesondere die Entwicklung von chemisch und radiolytisch stabilen Verbindungen, die eine unkomplizierte Markierung der Peptide mit geeigneten Radionukliden erlauben. 99mTc-, 64Cu- und 68Ga-markierte Peptide eignen sich dabei prinzipiell zur Tumordiagnostik. Analoge Verbindungen mit den Partikelstrahlern 67Cu und 188Re weisen ein großes Potenzial zur Therapie von Tumoren auf. Zur stabilen Fixierung von radioaktiven Kupfernukliden sind beispielsweise Pyridin-haltige makrocyclische Amine I und Bispidin-Liganden II entwickelt worden, die gleichzeitig eine Konjugation von Peptiden erlauben. Auf der Basis stabilisierter Bombesinderivate konnten durch Anwendung geeigneter Peptidkupplungsreaktionen entsprechende Biokonjugate hergestellt werden. Diese Verbindungen bilden unter physiologischen Bedingungen mit schneller Kinetik sehr stabile Radiokupferkomplexe. Ligandenaustauschexperimente und radiopharmakologische in-vitro- und in-vivo-Untersuchungen belegen eine sehr hohe Komplexstabilität. Studien zur Bioverteilung eines Bombesinkonjugates mit I ergaben eine hohe Anreicherung im Pankreas, dem Zielorgan mit der höchsten Dichte am Gastrin Releasing Peptidrezeptor.[2] PET-Studien an PC3-Tumor-Mäusen unter Einsatz des 64Cu markierten Bispidin-Bombesin-Derivates belegen eine gute Tumoranreicherung dieser Verbindung sowie eine klare Visualisierung des Tumors.[3]
  • Lecture (Conference)
    GDCh-Wissenschaftsforum Chemie 2009, 30.08.-02.09.2009, Frankfurt/M., Deutschland

Publ.-Id: 13249 - Permalink


Autoradiographic studies of rhenium-188-hydroxyethylidine diphosphonate in normal skeleton and osteoblastic bone metastases in a rat model of metastatic prostate cancer
Liepe, K.; Geidel, H. H.; Bergmann, R.; Haase, M.; Runge, R.; Kotzerke, J.;
Aim
The quantitative distribution of bone-seeking radiopharmaceuticals in trabecular bone, cortical bone and in skeletal metastases is required for calculation of radiation-absorbed dose in radionuclide therapy. An animal model of intraosseous tumor cell administration was developed to simulate osteoblastic metastases for autoradiographic study of radionuclide localization.
Methods In 45 Copenhagen rats R3327-MATLyLu syngeneic prostate cancer cells were given intraosseously in both the femori. Rhenium-188-hydroxyethylidine diphosphonate (HEDP) was administered intravenously 17 +/- 1 days after cells instillation and these animals were euthanized at 4, 24 and 48 h after injection of the radiopharmaceutical. The uptake of radiopharmaceutical was estimated in normal skeleton and the bone metastases by means of region of interest analysis using autoradiography. The tumor to nontumor ratio and the fractional uptake in cortical bone and trabecular bone were quantified.

Results
The uptake of rhenium-188-HEDP in cortical bone was 33.5% and in trabecular bones was 66.5% after 4 h, 34.6 and 65.4% after 24 h, and 35.9 and 64.1% after 48 h, respectively. Assuming a theoretic cortical-trabecular distribution of 50-50%, (MIRDOSE) calculation, radiation-absorbed dose to bone marrow was underestimated by 26%. In bone metastases, an inhomogeneous distribution with a minimal and maximal tumor to nontumor ratio of 3:1 and 14:1 after 4 h, 5: 1 and 14: 1 after 24 h, and 5:1 and 16:1 after 48 h was observed.

Conclusion
The MIRDOSE model underestimates the radiation-absorbed dose to the bone marrow because of demonstrable differences in the uptake of rhenium-188-HEDP in cortical and trabecular bone and inhomogeneous uptake in skeletal metastases.

Publ.-Id: 13248 - Permalink


Prätherapeutisches [18F]FMISO hypoxisches Volumen ist ein signifikanter prognostischer Faktor für die lokale Tumorkontrolle nach Einzeldosisbestrahlung von FaDu-Tumoren in Nacktmäusen/Pretherapeutic [F-18]FMISO hypoxic volume is a significant prognostic factor for local tumour control after single dose radiation of FaDu- tumours in night mouse
Schütze, C.; Bergmann, R.; Mosch, B.; Yaromina, A.; Zips, D.; Hessel, F.; Thames, H. D.; Mäding, P.; Kotzerke, J.; Baumann, M.; Beuthien-Baumann, B.;
Hintergrund:
Präklinische und klinische Untersuchungen haben gezeigt, dass das Ausmaß der prätherapeutischen Tumorhypoxie das Ergebnis einer Strahlentherapie solider Tumoren beeinflusst. Derzeit werden strahlentherapeutische Interventionen wie z.B. Dosis-Eskalation partieller hypoxischer Subvolumina untersucht. In dieser Studie wurde in einer einzelnen, in Nacktmäusen transplantierten humanen Tumorzelllinie untersucht, ob das prätherapeutische [18F]FMISO hypoxische Tumorvolumen (HV) oder die Intensität des Tracer-uptakes (maximaler Standard uptake
value SUVmax) mit der lokalen Tumorkontrolle nach Einzeldosisbestrahlung korreliert.

Methoden:
Die hSCC Zelllinie FaDu wurde subkutan auf das rechte Hinterbein von NMRI Nacktmäusen transplantiert. 70 Tiere wurden bei einem Tumorvolumen von 165-343 mm³ in das Experiment aufgenommen. Jedes Tier erhielt am Tag 0 eine PET-Untersuchung (MicroPET® P4, CTI Molecular Imaging Inc) mit dem Hypoxie-Marker 18F]FMISO ([18F]Fluormisonidazol) unter Anästhesie. Die Auswertung erfolgte mittels 3D-regions of interest über dem Tumor (ROVER software, ABX GmbH, Radeberg, Germany). Bestimmt wurde das [18F]FMISO hypoxische Volumen (HV) und der SUVmax. Anschließend wurden die Tumoren entsprechend des medianen hypoxischen Volumens für Einzeldosisbestrahlungen mit 25 Gy oder 35 Gy unter normalem Blutfluss randomisiert. Die Einzeldosisbestrahlungen erfolgten mit 200 kV Röntgenstrahlen (0.5 mm Cu, ~ 1 Gy min-1). Der experimentelle Endpunkt war die lokale Tumorkontrolle am Tag 120 nach Bestrahlung.

Ergebnisse:
Die lokalen Tumorkontrollraten nach Bestrahlung mit 25 Gy waren niedriger als nach Bestrahlung mit 35 Gy (22% vs. 69%, Logrank-Test p< 0.0001). Die Spanne der HV reichte von 38-353 mm³, der Median HV betrug 112 mm³ (95%CI: 92; 128 mm³). Für Tumoren < Median HV betrug die lokale Kontrollrate 33% nach 25 Gy vs. 82% nach 35 Gy (p=0.001). In Tumoren > Median HV betrug die lokale Kontrollrate 15% nach 25 Gy vs. 53% nach 35 Gy (p=0.0005). In der multivariaten Cox-Analyse konnte nach Korrektur für Dosis und Tumorvolumeneffekte ein signifikanter Effekt des HV als kontinuierliche Variable (p=0.009) oder dichotome Variable (Stratifikation entsprechend des Median HV) (p=0.039) nachgewiesen werden. Der SUVmax war bezüglich der Prognose der Heilungswahrscheinlichkeit nicht relevant.

Schlussfolgerungen:
Das [18F]FMISO hypoxische Tumorvolumen ist ein signifikanter unabhängiger Prädiktor für das Ergebnis einer Bestrahlung mit hohen Einzeldosen in FaDu hSCC. Diese Ergebnisse unterstützen die Hypothese, dass ein prätherapeutisches [18F]FMISO-PET wichtige Informationen für die Verschreibung einer heterogenen Bestrahlungsdosis in
hypoxischen Subvolumina individueller Tumoren liefern kann. Weitere Experimente mit anderen Tumormodellen und fraktionierter Bestrahlung sind notwendig.

Gefördert im Rahmen des EU-Projektes „BioCare“ Molecular Imaging for Biologically Optimized Cancer Therapy proposal# 505785 und DFG Projekt Ba 1433.
  • Lecture (Conference)
    DEGRO 2009 - 15. Jahreskongress der Deutschen Gesellschaft für Radioonkologie, 11.-14.06.2009, Bremen, Deutschland
  • Abstract in refereed journal
    Strahlentherapie und Onkologie 185(2009)Suppl. 1, 22-23

Publ.-Id: 13247 - Permalink


InIII and GaIII Complexes of Sugar-Substituted Tripodal Trisalicylidene Imines: The First 68Ga-Labelled Sugar Derivative
Gottschaldt, M.; Bohlender, C.; Pospiech, A.; Görls, H.; Walther, M.; Müller, D.; Klette, I.; Baum, R. P.; Schubert, U. S.;
Gallium and indium complexes derived from salicylaldimines of 1,1,1-tris(aminomethyl)ethane (TAME) with pendantxylose, glucose and galactose units have been synthesised as model compounds for potential application as radiotracers. The formed neutral complexes have been characterised by NMR spectroscopy, elemental analysis, mass spectrometry and, in the case of the galactose-bearing InIII complex, by single-crystal X-ray structure analysis. Octahedral coordination was observed with the appearance of an equilibrium of - and -isomers at the metal centre. The glucose-appended ligand was radiolabelled with 68GaIII ions in up to 98 % yield depending on the prevailing pH value. The in vitro stability of the radioactive complex was examined by challenge experiments against apo-transferrin and blood plasma. Very high stability was observed; even after a period of 2 h, 90 % of the complex could still be detected.

Publ.-Id: 13246 - Permalink


Circulating S100A12: a novel player in atherosclerosis?
Pietzsch, J.;
S100A12 is a member of the S100 family of EF-hand calcium-binding proteins. Besides calcium binding S100A12 also shows high affinity for zinc and copper ions. Extracellular S100A12 is predominantly secreted by granulocytes and monocytes and is part of the innate immune response.
S100A12 is markedly overexpressed in inflammatory compartments, and elevated serum levels of S100A12 are found in patients suffering from various inflammatory and metabolic disorders. In this regard, binding of copper by S100A12 is assumed to play a pathogenic role. In vitro experiments show that copper-bound S100A12 can function as a pro-oxidant agent by supporting both copper reduction and copper redox-cycling, respectively. As a consequence, copper-bound S100A12 enhances and accelerates oxidation of human low density lipoprotein lipids and apolipoproteins, respectively. Furthermore, copper-bound S100A12 stimulates proinflammatory activation of endothelial cells, granulocytes, and monocytes. These processes were substantially suppressed in the presence of redox-inert copper-chelating or radical-scavenging agents. Clinical examinations show significantly elevated plasma S100A12 levels in subjects with impaired glucose tolerance, newly-diagnosed diabetes mellitus Type 2, and acute rheumatoid arthritis (1.5 to 3-fold higher than in control subjects). In the patient groups, plasma S100A12 is strongly associated with plasma markers of both LDL oxidation and inflammation, and, additionally, with ultrasonically measured carotid atherosclerosis. It is suggested that oxidation processes mediated by copper-bound S100A12 are involved in accelerated atherogenesis in proinflammatory states.
Supported by Deutsche Forschungsgemeinschaft (Pi 304/1-1)
  • Invited lecture (Conferences)
    11th International Congress on Amino Acids, Peptides and Proteins, 03.-07.08.2009, Wien, Österreich
  • Abstract in refereed journal
    Amino Acids 37(2009)Suppl. 1, S78
    DOI: 10.1007/s00726-009-0320-1

Publ.-Id: 13245 - Permalink


Molecular imaging of the receptor for advanced glycation endproducts
Pietzsch, J.; Hoppmann, S.;
The receptor for advanced glycation endproducts (RAGE) is a member of the immunoglobulin superfamily and has been implicated in the pathogenesis of various disorders including inflammatory processes and cancerogenesis. However, data concerning the functional expression of RAGE in inflammatory compartments and other pathologies in vivo are scarce. We report a multi-radiotracer approach using radiolabeling of various RAGE ligands, including glycated low-density lipoproteins (glycLDL), glycated albumin (glycBSA), and S100 proteins (S100B and S100A12) with the positron emitter fluorine-18 (18F) and the application of 18F-labeled RAGE ligands in dynamic small animal positron emission tomography (PET) studies. Radiolabeling of proteins was performed by conjugation with N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB) causing no adverse alterations of the biological functionality of the proteins in vitro. Biodistribution and metabolite studies in rodent normal, inflammatory, and tumor models revealed high stability for the 18F-RAGE ligands in vivo. The in vivo kinetics of 18F-RAGE ligands, with or without presence of specific ligands or inhibitors of RAGE and, additionally, various scavenger receptors, in rodent models was quantified by PET, and correlated well with the anatomical localization of RAGE, e.g., in lung, endothelium, inflammatory lesions, and tumors.
18F-radiolabeling of glycLDL, glycBSA, and S100 proteins and the use of small animal PET provide a potential approach to measure the functional expression of RAGE under normal and pathophysiological conditions in vivo.
Supported by Deutsche Forschungsgemeinschaft (Pi 304/1-1)
  • Invited lecture (Conferences)
    11th International Congress on Amino Acids, Peptides and Proteins, 03.-07.08.2009, Wien, Österreich
  • Abstract in refereed journal
    Amino Acids 37(2009)Suppl. 1, S39
    DOI: 10.1007/s00726-009-0320-1

Publ.-Id: 13244 - Permalink


Fluorine-18 radiolabeling of S100/calgranulins: potential probes for molecular imaging of receptor for advanced glycation endproducts
Hoppmann, S.; Haase, C.; Richter, S.; Strobel, K.; Steinbach, J.; Pietzsch, J.;
The interaction of S100/calgranulins, a multigenic family of Ca2+-modulated proteins, with the receptor for advanced glycation endproducts (RAGE) is hypothesized to be of high relevance in the pathogenesis of various diseases including cardiovascular diseases, inflammatory processes, and cancerogenesis. However, data concerning the role of circulating S100 proteins in these pathologies are scarce. Furthermore, it is currently not known whether RAGE is an universal S100 receptor. One reason for this is the shortage of suitable radiolabeling methods for direct assessment of the metabolic fate of circulating S100 proteins in vivo. We report a novel radiotracer approach using radiolabeling of recombinant human S100A1 with the positron emitter-fluorine-18 (18F) by conjugation with N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB) and the use of [18F]fluorobenzoylated S100A1 (18F-S100A1) in dynamic small animal positron emission tomography (PET) studies in rats. Human S100A1 was cloned as a fusion protein in the bacterial expression vector pGEX-6P-1 and expressed in E. coli strain BL21. Radiolabeling of S100A1 with [18F]SFB at pH 7.4 resulted in 18F-S100A1 specifically labeled at the N-terminal glycine residue with radiochemical yields of 2-6% (decay-corrected) and effective specific activities of 0.5-1 GBq/µmol, respectively. In vitro experiments, and biodistribution and metabolite studies in rats in vivo revealed high stability for the 18F-S100A1. The metabolic fate of 18F-S100A1 in rats in vivo was delineated by dynamic PET studies using a dedicated small animal PET system. The organ-specific in vivo distribution and kinetics of 18F-S100A1 correlated well with the anatomical localization of RAGE, e.g., in lungs and in the vascular system. In the presence of molar excess of glycated human low density lipoprotein (glycLDL), a well characterized RAGE ligand, the mean plasma residence time of circulating 18F-S100A1 increased by 40% from 29.6 ± 1.5 min to 41.3 ± 2.1 min and, vice versa, tissue-associated retention of 18F-S100A1 decreased by approximately 50% in lungs and 32% in large blood vessels, respectively. These findings indicate first circulating S100A1 to be a specific ligand for RAGE in rats in vivo. In conclusion, radiolabeling of S100/calgranulins with 18F and the use of small animal PET provide novel probes to delineate functional expression of RAGE under normal and pathophysiological conditions in rodent models of disease in vivo.
Keywords: multiligand receptors; pattern recognition; S100 proteins; 18F-labeled prosthetic group; small animal positron emission tomography; animal models
  • Contribution to external collection
    Xiaoyuan Chen: Recent Advances of Bioconjugation Chemistry in Molecular Imaging, Kerala (India): Trivandrum: Research Signpost, 2008, 978-81-308-0210-7, 329-351

Publ.-Id: 13243 - Permalink


Synthesis, 64Cu-Labeling and Biodistribution of DOTA-Glycodendrimers
Jäger, K.; Stephan, H.; Bergmann, R.; Steinbach, J.; Appelhans, J.; Voit, D.;
The utilization of dendrimers in medicine holds great potential in emerging applications of diagnostic imaging, as well as the promise of new capabilities for delivering therapies tailored and targeted for specific diseases. In this perspective, radiolabeled dendritic frameworks are gaining in importance, particularly for the use in tumor imaging and therapy.[1] Pegylation as well as carbohydration of radiolabeled compounds is of considerable interest to improve the pharmacokinetics, biocompatibility, and tumor accumulation.[2,3]
In this context, DOTA-modified glycodendrimers with dense maltose shell (Figure: structure of 4th generation dendrimer) were selected from the point of view to use the highly homogenous dendritic structure for improved tumor imaging and therapy and to enhance the biocompatibility of dendrimers by the decoration with carbohydrates. The outcome of the synthetic effort was the synthesis of 4th and 5th generation glycodendrimers with the variation of chemically attached DOTA chelators (1, 3, 9 DOTA units/4th generation dendrimer; 9 and 18 DOTA units/5th generation dendrimer), which form stable complexes with a large number of radiometals. The multivalent decoration with DOTA on dendrimer surface was also stimulated by the facts that radiolabeling kinetics can be accelerated and to achieve enhanced specific activity.
The labeling conditions of the glycodendrimers synthesized with 64Cu were optimized, and the influence of reaction time, temperature, buffer conditions and the dendrimer amount on the radiochemical yield were studied using Radio-TLC and Radio-SEC. The radiocopper(II) complexes of the DOTA-functionalized glycodendrimers show a high in vitro stability. Preliminary biodistribution studies of 64Cu-labeled 4th generation dendrimers with maltose shell in healthy Wistar rats indicate the preferred accumulation in the liver.
  • Poster
    GDCh-Wissenschaftsforum Chemie 2009, 30.08.-02.09.2009, Frankfurt am Main, Deutschland

Publ.-Id: 13242 - Permalink


Visualizing inflammation activity in rheumatoid arthritis with Tc-99m Anti-CD4-mAb fragment scintigraphy - First results of a proof of principle study
Steinhoff, K.-G.; Pierer, M.; Sorger, D.; Seese, A.; Künstler, J. U.; Emmrich, F.; Sabri, O.; Hesse, W.; Siegert, J.; Piegla, U.; Pietzsch, H.-J.; Seidel, W.; Laub, R.;
T‐cell‐located CD4 antigen represents one of the therapeutic targets in rheumatoid arthritis (RA). However, up to now it has not been possible to visualize this target in vivo. The aim of our study was to assess the safety and tolerability of a Technetium 99 labelled anti‐CD4 antibody fragment (Tc‐99m‐anti‐CD4) in patients with active synovitis due to rheumatoid arthritis and to evaluate its potential as a marker of disease activity. Methods: In the present phase I proof of principle study 5 patients (3 female, 2 male, 58 to 71 years) with RA were examined. Planar whole body scans as well as separate hand and feet scintigraphies were taken 30 minutes, 1, 2, 4, 8 and 24 hours after application of 585 +/‐ 115 MBq Tc‐99m‐anti‐CD4. The obtained scintigramms were analysed visually and compared with clinical data in 68 joints per patient. Active inflammation was clinically defined by swelling and tenderness in at least one joint (gold standard). Patients were clinically re‐evaluated 7 days p.i. Results: Neither infusion related adverse events nor adverse events during follow up were observed. No increase in HAMA titres was seen. All 5 patients had positive scans in 25 of 37 clinically affected joints. Positive scans were also found in 19 out of 227 joints without evidence of swelling or tenderness yielding a 7% rate of false positive joints and a 32% rate of false negative joints. Conclusion: Scintigraphy with Tc‐99m‐anti‐CD4 is a new promising technique for evaluation of inflammatory activity in patients with RA. Tracer uptake in clinically inconspicuous joints strongly indicates diagnostic potential of 99Tc anti CD4. Based on the few patients investigated, it seems that inflammation is detected with apparently higher specificity than sensitivity. Whether this technique is eligible for prognostic disease evaluation needs to be analysed in further studies as well as the pathophysiological background of clinically affected joints lacking tracer uptake.
  • Lecture (Conference)
    Annual Congress of the European Association of Nuclear Medicine 2009 (EANM), 10.-14.10.2009, Barcelona, Spain
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 36(2009)Suppl. 2, S210

Publ.-Id: 13241 - Permalink


Synthesis and biological evaluation of new [Tc(N)(R2PS)]-based mixed compounds as analogues of WAY 100635
Bolzati, C.; Cavazza-Ceccato, M.; Refosco, F.; Salvarese, N.; Pietzsch, H.-J.; Bergmann, R.; Bandoli, G.;
Aim: This study was focused on evaluating the applicability of a new labelling procedure to the preparation of Tc(N)‐based target specific compounds. The chemistry is based on the use of the [Tc(N)Cl(R2PS)(PPh3)] species (R2PS = alkyl‐phosphino‐thiolate ligand), which selectively reacts with an appropriate mono‐negative chelate, such as a dithiocarbamate (DTC), to give neutral [Tc(N)(R2PS)(DTC)] compounds. The 2‐methoxyphenylpiperazine (2‐MPP) pharmacophore, which displays a potent and specific affinity for 5HT1A receptors, was selected as functional group and conjugated to the dithiocarbamate unit through different spacers. Method: The synthesis of [99m/99gTc(N)(R2PS)(Ln)] complexes, and their in vitro stability as well as their biological in‐vitro and in‐vivo assays were investigated. Stability studies were performed by considering: i) stability toward transchelation with Cysteine and Glutatione ii) binding to the serum proteins; ii) stability in rat serum, human serum and rat liver homogenates. The in vitro affinity for the 5HT1A receptors of the technetium complexes was assessed by measuring the ability of the compounds to compete with [3H]‐8‐OH‐DPAT binding in isolated membranes from rat cerebral cortex. The biodistribution profile of the best radiolabeled compound and its in vivo stability were evaluated in Sprague‐Dawley rats. Results: [99mTc(N)(R2PS)(Ln)] complexes were prepared in high yield (>90%) using a multi‐step procedure. The chemical identity of 99mTc‐complexes was determined by HPLC comparison with the corresponding 99gTc‐complexes. All complexes were found to be inert toward transchelation with an excess of free Glutathione and Cysteine. No significant in vitro serum protein binding and no notable biotransformation of the native compound into different species by the in vitro action of the serum and liver enzymes were shown. Nanomolar affinities for the 5‐HT1A receptor were obtained for [99mTc(N)(PSiso)L3] (IC50 = 1.5 nM), a reduction of the affinity were observed for the other complexes as a function of the reduction of the alkyl chain length interposed between the DTC group and the bioactive molecule. A negligible brain uptake was displayed from in vivo distribution data of [99mTc(N)(PSiso)L3]. Conclusion This work describes the application of a new labelling procedure for incorporating a bioactive molecule into a stable dissymmetric 99mTc(N)‐complex. Despite the favourable binding properties, the lack of BBB penetration indicates that these particular complexes may not be useful for CNS‐receptor mapping. Further studies should be performed in order to clarify the reason for this behaviour and to evaluate the usefulness in peripheral applications.
  • Lecture (Conference)
    Annual Congress of the European Association of Nuclear Medicine (EANM) 2009, 10.-14.10.2009, Barcelona, Spain
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 36(2009)Suppl. 2, S220

Publ.-Id: 13240 - Permalink


Photochemistry of uranium(VI) revisited: A density functional theory study
Tsushima, S.; Fahmy, K.;
Photochemical reduction of uranium(VI) in the presence of organic substances is a well known and well studied process, but its reaction mechanism has not yet been fully verified. One of the difficulties in studying uranium photochemistry is the involvement of photo-excited states which is difficult to assess solely by experiments. Quantum chemical calculation is capable of predicting the properties of excited state uranium(VI), and therefore can provide possible photochemical reaction mechanisms and reaction pathways. Here, we have studied the photochemical reduction of uranium(VI) in the presence of several organic ligands, namely methanol, ethanol, and oxalic acid, by density functional theory (DFT) calculations. We were able to reproduce entire reaction pathways which demonstrates the validity of the DFT approach in further exploring uranium(VI) photochemistry.
  • Lecture (Conference)
    Spring 2010 National Meeting and Exposition, Symposium on "Lanthanides and Actinides: a Chemist's Perspective", 21.-25.03.2010, San Francisco, U.S.A.

Publ.-Id: 13239 - Permalink


Aptamer modifizierte bakterielle Oberflächenstrukturen für die Entwicklung neuer Sensoren (AptaSens)
Pollmann, K.;
Bakterielle Hüllproteine (S-Layer) werden als Grundlage für die Entwicklung von Biosensoren für die Detektion von Spurenstoffen in Wässern genutzt. Im April startete dazu ein BMBF-Verbundprojekt im Rahmen der Fördermaßnahme Biona. Dieses Projekt wird vorgestellt.
  • Lecture (others)
    Vortragsreihe GMBU, Arbeitsgruppenberatung, 11.11.2009, Dresden, Deutschland

Publ.-Id: 13238 - Permalink


Bispidine als Radiokupferchelatoren - Konfigurationsisomerie Imidazol-haltiger Derivate
Fähnemann, S.; Juran, S.; Matterna, M.; Walther, M.; Stephan, H.; Emmerling, F.; Kraus, W.;
Derivate des 3,7-Diazabicyclo[3.3.1]nonans (Bispidin) bilden insbesondere mit Cu2+ sehr stabile Koordinationsverbindungen, wobei die Komplexstabilität im Bereich jener mit makrocyclischen Liganden liegt.[1] Für Bispidin-Derivate ergeben sich drei unterschiedliche Konformationsisomere, wobei die abgeflachte Doppel-Sessel-Form die thermodynamisch stabilste Konformation repräsentiert. Dabei sind die beiden Aminstickstoff-Donoratome (N3- und N7-Position) des Bispidin-Grundgerüstes für die Koordination mit Metallionen optimal vororganisiert.
Die Einführung von weiteren Donoreinheiten, wie Pyridyl- oder Imidazolyl-Substituenten, an den Positionen C2 und C4 kann zu Konfigurations-isomeren mit cis- und trans-Stellung führen. Hexadentate Bispidin-Liganden mit vier Pyridin-Einheiten lassen sich mit hoher Ausbeute in der für die Komplexbildung mit Cu2+ gewünschten cis-Isomerie (endo/endo) darstellen. Die entsprechenden 64Cu-Komplexe zeigen sehr interessante radiopharmakologische Eigenschaften.[2] Aufgrund der Komplexbildungs- und Löslichkeitseigenschaften erscheinen in diesem Zusammenhang auch Radiokupfer-komplexe von Imidazol-haltigen Bispidin-Derivaten aussichtsreich.
Es wird darüber berichtet, wie sich die Einführung von Imidazolyl-Substituenten auf die Konfigurationsisomerie von Bispidin-Derivaten auswirkt. Dazu werden insbesondere NMR-spektroskopische Daten und Röntgenkristallstrukturen herangezogen.
  • Poster
    GDCh-Wissenschaftsforum Chemie 2009, 30.08.-02.09.2009, Frankfurt am Main, Deutschland

Publ.-Id: 13237 - Permalink


Imaging and functional characterization of the receptor for advanced glycation endproducts (RAGE) in vivo
Pietzsch, J.; Hoppmann, S.; Richter, S.; Strobel, K.; Steinbach, J.;
RAGE has been implicated in the pathogenesis of various disorders including inflammatory processes and cancerogenesis. However, data concerning the functional expression of RAGE in inflammatory lesions and other pathologies in vivo are scarce. We report a novel radiotracer approach using radiolabeling of various RAGE ligands, including S100 proteins (S100B/S100A12), glycated low-density lipoproteins (glycLDL), and glycated albumin (glycBSA) with the positron emitter fluorine-18
(18F) and the application of 18F-labeled RAGE ligands in dynamic small animal positron emission tomography (PET) studies. Radiolabeling of proteins was performed by conjugation with no-carrier added N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB) causing no adverse alterations of the biological functionality of the proteins in vitro.
Biodistribution and metabolite studies in rodent normal, inflammatory, and tumor models revealed high in vivo-stability for the 18F-RAGE ligands. The in vivo-kinetics of 18F-RAGE ligands, with or without presence of specific ligands/inhibitors of RAGE and various scavenger receptors, in rodent models was quantified by PET, and correlated well with the anatomical localization of RAGE, e.g., in blood vessels, lungs, inflammatory lesions, and tumors. 18F-radiolabeling of S100 proteins, glycLDL and glycBSA and the use of small animal PET provide potential probes to measure functional expression of RAGE under normal and pathophysiological conditions in vivo.
  • Poster
    XXXVI International Congress of Physiological Sciences, 27.07.-01.08.2009, Kyoto, Japan
  • Abstract in refereed journal
    Journal of Physiological Sciences 59(2009)Suppl. 1, 325

Publ.-Id: 13236 - Permalink


The inhomogeneous MUSIG model for upward polydisperse flows with new constitutive models for bubble coalescence and breakup
Liao, Y.; Lucas, D.;
In the present study we propose new coalescence and breakup closures for the inhomogeneous multiple bubble size group (MUSIG) model. The major purpose is to consider bubble coalescence and breakup due to different mechanisms and to develop a general applicable constitutive model for CFD applications. For bubble coalescence the new model includes coalescence due to turbulence, laminar shear, wake entrainment and eddy capture. Bubble breakup mechanisms encompass turbulent fluctuation, laminar shear and interfacial slip velocity. The new models were implemented in ANSYS-CFX and applied to the case of turbulent air-water mixtures in a large vertical pipe (DN 200). Simulation results for the evolution of radial gas volume fraction, bubble size distribution were compared to as default used closure models of Luo & Svendsen and Prince & Blanch [1, 2] as well as TOPFLOW experimental data. Better prediction of bubble size distribution is accomplished.
Keywords: Inhomogeneous MUSIG model; New constitutive models; Bubble coalescence and breakup; TOPFLOW test facility
  • Contribution to proceedings
    International Conference Nuclear Energy for New Europe 2009, 14.-17.09.2009, Bled, Slovenia
  • Poster
    International Conference Nuclear Energy for New Europe 2009, 14.-17.09.2009, Bled, Slovenia

Publ.-Id: 13235 - Permalink


Development and validation of bubble coalescence and breakup models : status of KEK project
Liao, Y.; Lucas, D.;
Bubble coalescence and breakup is an important phenomenon in gas-liquid mixtures. The application of existing models is limited and they are usually not transferable from one case to another. The objective of the work is to develop a generally applicable new model for bubble coalescence and breakup. Based on an extensive literature study, a basis model is proposed which encompasses all important mechanisms. The model is implemented into the Test Solver and CFX code and applied to a case of air-water flow in a vertical pipe. The comparison with the experimental data from TOPFLOW facility shows substantial difference between the results given by Test Solver and CFX. Test Solver with the new model can provide a much better agreement than CFX. This might be caused by the turbulence modeling. The influence of two-phase turbulence parameters will be investigated in future work.
Keywords: Test Solver; Inhomogeneous MUSIG model; New model; Bubble coalescence and breakup; TOPFLOW test facility
  • Lecture (Conference)
    German CFD Network 16th Meeting, 07.-08.10.2009, Garching, Germany

Publ.-Id: 13234 - Permalink


Further developments of the thermodynamic reference database THEREDA and the thermodynamic sorption database RES3T
Richter, A.; Altmaier, M.; Brendler, V.; Marquardt, C.; Moog, H.; Scharge, T.; Voigt, W.; Wilhelm, S.; Wollmann, G.;
The THEREDA project aims at a consistent and quality assured thermodynamic reference database for modeling geochemical processes in waste disposal sites. It offers evaluated thermodynamic data for all relevant elements, covering both radioactive waste and chemo-toxic substances, and with full bibliographic tracking. Parameters for a variety of models describing interactions in mixed phases are included, too. All host rocks currently discussed as candidates for waste repositories in Germany are considered. THEREDA is freely accessible (www.thereda.de).
The RES³T database (Rossendorf Expert System for Surface and Sorption Thermodynamics) supplies complementary information based on the concept of surface complexation models (SCM). Recently, a portal (www.fzd.de/RES3T) started to provide open public access.
Next steps are the integration of SCM data from RES³T into the THEREDA framework, the provision of data export tools (with speciation-code specific formatting), and the development of a web-based data input and editing interface.
Keywords: THEREDA RES3T thermodynamic database sorption radioactive waste chemo-toxic substances modelling
  • Lecture (Conference)
    239th ACS National Meeting, 21.-25.03.2010, San Francisco, USA
  • Abstract in refereed journal
    American Chemical society: Abstracts of scientific papers 239(2010), GEOC-112

Publ.-Id: 13230 - Permalink


A Three-Scale Expansion Solution for a Time-Dependent P1 Neutron Transport Problem with External Source
Merk, B.; Weiß, F. P.;
This work presents the development of an analytical approximation solution for a space-time–dependent neutron transport problem in a one-dimensional system consisting of a homogenized medium with a central external source with Green’s functions. The delayed neutron production is implemented in two additional timescales with the multiple-scale expansion method. Qualitative results for a given system are analyzed, and a detailed comparison of the developed analytical approximation solution with results gained by the point-kinetics equation and the time-dependent diffusion equation without separation of space and time is given.
Keywords: Time Dependent Neutron Transport, Multiple Scale Expansion, Green's Functions, Accelerator Driven Systems
  • Nuclear Science and Engineering 163(2009), 152-174

Publ.-Id: 13229 - Permalink


Influence of humic acid functionalities on uranium complexation and influence of humic acid on uranium(VI) migration in opalinus clay
Schmeide, K.; Sachs, S.; Joseph, C.; Raditzky, B.; Bernhard, G.;
Results are reported to the influence of different humic acid functionalities (nitrogen, sulfur and phosphorus containing functionalities) on the uranium(VI) complexation, to the uranium(IV) complexation by small organic model ligands, to the sorption of uranium(VI) onto opalinus clay in the absence and presence of humic acid and to the uranium(VI) diffusion in opalinus clay in the absence and presence of humic acid.
Keywords: Uranium, humic substances, complexation, functional groups, sorption, opalinus clay
  • Lecture (others)
    Workshop zum Forschungsvorhaben "Wechselwirkung und Transport von Actiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika", 06.-07.10.2009, Mainz, Germany

Publ.-Id: 13228 - Permalink


Anomalous Hall resistance in Ge:Mn systems with low Mn concentrations
Zhou, S.; Bürger, D.; Helm, M.; Schmidt, H.;
Taking Mn doped Germanium as an example, we evoke the consideration of a two-band-like conduction in diluted ferromagnetic semiconductor (FMS). The main argument for claiming Ge:Mn as a FMS is the occurrence of the anomalous Hall effect (AHE). Usually, the reported AHE (1) is observable at temperatures above 10 K, (2) exhibits no hysteresis, and (3) changes the sign of slope. We observed a similar Hall resistance in Mn implanted Ge with the Mn concentration as low as 0.004%. We show that the puzzling AHE features can be explained by considering a two-band-like conduction in Ge:Mn.

Publ.-Id: 13227 - Permalink


Quantitative myocardial perfusion PET combined with coronary anatomy derived from CT angiography: Validation of a new fusion and visualisation software
Fricke, H.; Elsner, A.; Weise, R.; Bolte, M.; van den Hoff, J.; Burchert, W.; Domik, G.; Fricke, E.;
Aim
Dynamic perfusion PET offers a clinical relevant advantage over myocardial perfusion scintigraphy due to its ability to measure myocardial blood flow quantitatively. This leads to an improved detection of multivessel disease and the possibility to assess not only the culprit lesion but lower grade stenoses as well. For appropriate revascularization, perfusion defects must be matched to coronary lesions. It has been shown that image fusion of morphological and functional images is superior to side-by-side analysis. Still, software for quantitative perfusion PET combined with CT angiography is rare. In this paper we present a new software tool for image fusion and visualization of quantitative perfusion PET and coronary morphology derived from CT angiography.

Methods
In our software, a PET uptake image is used for manual co-registration. Co-registration results are then applied to the functional data derived from compartment modelling. To evaluate the reproducibility of the manual co-registration, we calculated the deviation between a series of manual co-registrations performed on nine pairs of unregistered PET and CT datasets by five trained participants. Two dimensional transfer functions were used to highlight the coronary arteries from the CT study in the combined data sets.

Results
The average Euclidian distances for three references points were between 3.7 and 4.1 mm. The maximum distance was 10.6 mm. By the use of the two dimensional transfer functions, coronary anatomy could be easily visualised either by user-interaction or automatically by use of neuronal networks.

Conclusions
With this approach it is possible to combine quantitative perfusion PET with coronary anatomy derived from CT angiography. Our first experiences indicate that manual image fusion with our tool is reproducible and that visualisation of the combined datasets is achieved within short time.


Ziel
Die dynamische Perfusions-PET bietet gegenüber der Myokardszintigraphie den klinisch relevanten Vorteil einer quantitativen Perfusionsmessung. Dies führt zu einer besseren Erkennung von Mehrgefäßerkrankungen sowie dazu, dass nicht nur die führenden, sondern auch niedriggradigere Stenosen bezüglich ihrer Relevanz beurteilt werden können. Revaskularisierende Maßnahmen erfordern die korrekte Zuordnung von Perfusionsdefekt und verursachendem Gefäß. Es konnte gezeigt werden, dass die Bildfusion von morphologischer und funktioneller Information einer getrennten Beurteilung überlegen ist. In dieser Arbeit stellen wir eine neue Software zur Koregistrierung und Visualisierung von quantitativen PET-Perfusionsbildern mit der Koronarmorphologie aus einer CT-Angiographie vor.

Methodik
In unserer Software verwenden wir ein PET-Uptake-Bild für die Koregistrierung mit dem CT-Datensatz. Die Ergebnisse der Koregistrierung werden dann auf die parametrische Oberfläche aus der Kompartmentmodellierung übertragen. Um die Reproduzierbarkeit der manuellen Koregistrierung zu evaluieren, berechneten wir die Abweichung der Ergebnisse von fünf erfahrenen Untersuchern an neun Paaren unregistrierter PET und CT-Datensätze. Wir verwenden zweidimensionale Transferfunktionen, um die Koronarien aus einer CT-Angiographie im kombinierten Datensatz hervorzuheben.

Ergebnisse
Der mittlere Abstand im Raum betrug für drei Referenzpunkte zwischen 3,7 und 4,1 mm, der maximale Abstand 10,6 mm. Durch Einsatz der zweidimensionalen Transferfunktionen konnten die Koronarien problemlos in den kombinierten Datensätzen visualisiert werden.

Schlussfolgerungen
Mit der von uns vorgestellten Methode ist es möglich, eine quantitative Perfusions-PET kombiniert mit der Koronaranatomie aus einer CT-Angiographie darzustellen. Unsere ersten Ergebnisse zeigen, dass die manuelle Koregistrierung mit unserem Werkzeug reproduzierbar und eine kombinierte Visualisierung der kombinierten Datensätze in kurzer Zeit möglich ist.
Keywords: Coronary artery disease; CT angiography; cardiac PET; quantitative perfusion measurement Koronare Herzerkrankung; CT-Angiographie; PET; quantitative Perfusionsmessung

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Publ.-Id: 13226 - Permalink


Comparison of [18F]FDG uptake and distribution with hypoxia and proliferation in FaDu human squamous cell carcinoma (hSCC) xenografts after single dose irradiation
Bruechner, K.; Bergmann, R.; Santiago, A.; Mosch, B.; Yaromina, A.; Hessel, F.; Hofheinz, F.; van den Hoff, J.; Baumann, M.; Beuthien-Baumann, B.;
Purpose: This study investigated the uptake of [18F]2-fluoro-2-deoxy-glucose ([18F]FDG) in the human tumour xenograft FaDu at early time points after single dose irradiation with Positron-Emission-Tomography (PET), autoradiography and functional histology. Materials and methods: [18F]FDG-PET of FaDu hSCC xenografts on nude mice was performed before 25 Gy or 35 Gy single dose irradiation and one, seven or 11 days post irradiation (p.irr.). Before the second PET, mice were injected with pimonidazole (pimo) and bromodeoxyuridine (BrdU). After the PET tumours were excised, sliced and subjected to autoradiography and functional histology staining (pimo, BrdU, Ki67). [18F]FDG tumour uptake was quantified in the PET scans by maximal standard uptake value (SUVmax) and in the autoradiography after co-registration to the histology slices. Results: No differences in the overall [18F]FDG uptake between the two dose groups and time points were found with PET or autoradiography. Comparing!
autoradiography and histology, the [18F]FDG uptake was constant in tumour necrosis over time, while it decreased in vital tumour areas and particularly in hypoxic regions. No differences in the [18F]FDG uptake between positive and negative areas of Ki67 and BrdU were found. Conclusions: The decline of [18F]FDG uptake in vital tumour and in pimopositive areas as seen in autoradiography, was not reflected by evaluation of SUVmax determined by PET. These findings suggest that the SUVmax does not necessarily reflect changes in tumour biology after irradiation.
Keywords: Positron emission tomography; FDG; human tumour xenografts; single dose irradiation; hypoxia; proliferation

Publ.-Id: 13225 - Permalink


Synthesis and characterization of rhenium and technetium-99m tricarbonyl complexes bearing the 4-[3-bromophenyl]quinazoline moiety as a biomarker for EGFR-TK imaging
Bourkoula, A.; Paravatou-Petsotas, M.; Papadopoulos, A.; Santos, I.; Pietzsch, H.-J.; Livaniou, E.; Pelecanou, M.; Papadopoulos, M.; Pirmettis, I.;
Aiming at the development of technetium-99m (99mTc) complexes for early detection and staging of EGFR positive tumors, the tyrosine kinase inhibitor 6-amino-4-[(3-bromophenyl)amino]quinazoline was derivatized with pyridine-2-carboxaldehyde to generate the imine 6-(pyridine-2-methylimine)-4-[(3-bromophenyl) amino]quinazoline suitable for reacting with the fac-[99mTc(CO)3]+ core as an N,N bidentate ligand. The labelling was performed in high yield (>90%) by ligand exchange reaction using fac-[99mTc(OH2)3(CO)3]+ as precursor. The 99mTc complex was characterized by comparative HPLC analysis using the analogous rhenium (Re) complex as reference. The Re complex was prepared by ligand exchange reaction using the fac-[ReBr3(CO)3]2- as precursor and was fully characterized by NMR and IR spectroscopies and elemental analysis. In vitro studies indicate that both the ligand and its Re complex
inhibit the EGFR autophosphorylation (IC50: 17± 3.7 and 114 ± 23 nM respectively) in intact A431 cells, bind the receptor in a reversible mode, and inhibit A431 cell growth (IC50: 5.2 ± 1.1 and 2.0 ± 0.98 µM respectively). Biodistribution of the 99mTc complex in healthy animals showed a rather fast blood and soft tissue clearance between 1 and 15 min p.i. with excretion occurring mainly via the hepatobiliary system.
Keywords: Technetium; Rhenium; 4-Anilinoquinazoline; Tyrosine kinase inhibitors; Epidermal growth factor receptor

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Publ.-Id: 13224 - Permalink


Isomerism in tetrahedral rhenium cluster complexes [Re4Q4(PMe2sub>Ph)4X8]·nCH2Cl2 (Q = Se, X = Br; Q = Te, X = Cl, Br).
Efremova, O. A.; Mironov, Y. V.; Brylev, K. A.; Fedorov, V. E.; Pietzsch, H.-J.; Stephan, H.;
Three new tetrahedral rhenium cluster compounds [Re4Se4(PMe2Ph)4Br8].1.5CH2Cl2 (1), [Re4Te4(PMe2Ph) 4Br8].CH2Cl2 (2), and [Re4Te4(PMe2Ph)4Cl8].CH2Cl2 (3) have been synthesized by the reaction of the corresponding precursor chalcohalide complexes [Re4Q4(TeX2)4X8] (X = Br, Q = Se (for 1), Te (for 2); X = Cl, Q = Te (for 3)) with dimethylphenylphosphine in CH2Cl2. All compounds have been characterized by X-ray single-crystal diffraction and elemental analyses, IR and 31P NMR spectroscopy. 31P NMR spectroscopy indicates the formation of isomers in solution, confirmed by single-crystal X-ray analysis.
Keywords: Rhenium tetrahedral cluster complexes; Synthesis; Crystal structure; Isomerism; Organic ligands

Publ.-Id: 13223 - Permalink


High-peak power diode-pumped Yb:CaF2 laser
Siebold, M.; Hornung, M.; Hein, J.; Reinhard, U.; Kaluza, M.;
Recent result of a 1 TW directly diode-pumped laser using Yb:Ca2 as amplifying medium.
  • Lecture (Conference)
    Conference on Lasers and Electro-Optics Europe (CLEO), 14.-19.06.2009, München, Deutschland

Publ.-Id: 13222 - Permalink


Gittersensortechnologie und ihr Einsatzpotenzial in der Chemieindustrie
Hampel, U.;
Die experimentelle Untersuchung von Mehrphasenströmungen erlangt eine zunehmende Bedeutung in der Optimierung chemischer und verfahrenstechnischer Prozesse sowie bei der Überprüfung thermohydraulischer Modelle für Mehrphasenströmungen. Zur Untersuchung von Flüssigkeitsströmungen mit und ohne Gasanteil wurden am Institut für Sicherheitsforschung des Forschungszentrums Dresden-Rossendorf Gittersensoren entwickelt, die eine schnelle Visualisierung der Phasenzusammensetzung von Stoffgemischen ermöglichen. Die Einsatzbreite von Gittersensoren in der Chemieindustrie reicht von der Überwachung und Prozesskontrolle in chemischen Reaktoren, wie Kolonnen, Säulenreaktoren und Rieselbettreaktoren, über die Mehrphasendurchflussmessung, bildgebende Füllstands- und Separationsmessung bis hin zur Validierung von Rechenmodellen für verfahrenstechnische Prozesse. Der Vortrag gibt einen Einlick in die Technologie sowie potenzielle Anwendungsfelder.
Keywords: wire mesh sensors, chemical engineering
  • Lecture (others)
    Seminar "Sensoranwendung in der Chemieindustrie" der BASF Ludwigshafen, 14.10.2009, Ludwigshafen, Germany

Publ.-Id: 13221 - Permalink


Wire mesh sensor technology - on the road towards three-phase flow measurement
Hampel, U.;
Wire mesh sensors are tools for ultrafast cross-sectional imaging of gas-liquid two-phase flows. They are helpful measurement devices for flow studies in fundamental chemical, nuclear and process engineering research problems, where multiphase flows play a role. A recent development of this technology is the capacitance wire-mesh sensor, which may be used to study phase fraction distributions in electrically non-conducting liquids. This is of particular importance for problems related to mineral oil processing. The presentation gives an overview on the current state-of-the-art in wire mesh sensor technology and discusses its potential for the studiy of complex and transient liquid-liquid-gas three-phase flows.
Keywords: wire mesh sensor, multiphase flow
  • Invited lecture (Conferences)
    Multiphase Club, 13.-14.10.2009, London, UK

Publ.-Id: 13220 - Permalink


High-efficiency, room-temperature nanosecond Yb:YAG laser
Siebold, M.; Loeser, M.; Schramm, U.; Koerner, J.; Wolf, M.; Hellwing, M.; Hein, J.; Ertel, K.;
Yb3+-doped gain media offer favorable properties for diode-pumped laser amplifiers for high-energy ns-pulses. To reach high optical-to-optical conversion efficiencies at room temperature however, very high and often impractical fluences are required both for pumping and extraction. Low temperature operation offers a solution, but the required cryogenic cooling systems add considerable complexity, bulkiness and cost. Multi-passing both pump and extraction beams through the gain medium is an alternative approach to overcome efficiency limitations at room temperature. In this article we present numerical and experimental results to this effect.We demonstrated ns-pulse output from a diode-pumped Yb:YAG amplifier at an energy of 566 mJ and an optical-to-optical efficiency of 20 %, which is almost a doubling of the efficiency achieved with ns-lasers employing Yb3+-doped gain media at this energy level.
Keywords: Laser amplifiers Lasers, ytterbium Lasers, diode-pumped

Publ.-Id: 13219 - Permalink


Synthesis of Benzoate-Functionalized Phosphanes as Novel Building Blocks for the Traceless Staudinger Ligation
Mamat, C.; Flemming, A.; Köckerling, M.; Steinbach, J.; Wuest, F.;
A new synthetic pathway for the preparation of benzoate-functionalized phosphanes for microwave-mediated traceless Staudinger ligations is described. Novel phosphane derivatives based on 4-substituted iodophenyl benzoates were prepared via palladium(II)-catalyzed P–C cross-coupling reaction strategy in high yields. The application of microwave conditions for the ligation reactions reduced the reaction time considerably. An approach to fast and facile labeling strategies using this ligation was established.
Keywords: Staudinger ligation, traceless, click chemistry, P–C cross-coupling, palladium-catalyzed

Publ.-Id: 13218 - Permalink


Reduction of Arteriosclerotic Nanoplaque Formation and Size by n-3 Fatty Acids in Patients after Valvular Defect Operation
Koppe, C.; Rodriguez, M.; Winkler, K.; Pietzsch, J.; Neumann, K.; Hiemann, N. H.; Hetzer, R.; Malmsten, M.; Siegel, G.;
Summary
Background/Methods: Coating a silica surface with the isolated lipoprotein receptor heparan sulfate proteoglycan (HS-PG) from arterial endothelium and vascular matrices, we could observe the very earliest stages of arteriosclerotic plaque development by ellipsometric techniques in vitro (patent EP 0 946 876). This so-called nanoplaque formation is represented by the ternary aggregational complex of the HS-PG receptor, lipoprotein particles and calcium ions. The model was validated in several clinical studies on statins in cardiovascular high-risk patients applying their native blood lipoprotein fractions.
Results: In 7 patients who had undergone a valvular defect operation, the reduction of arteriosclerotic nanoplaque formation in normal Krebs solution amounted to 6.1 ± 2.3% (p < 0.0156) and of nanoplaque size to 37.5 ± 13.2% (p < 0.0312), respectively, after a 3-month therapy with n-3 fatty acids (3 × 3 g daily, Ameu® 500 mg). Additionally, the quotient oxLDL/LDL was lowered by 6.8 ± 2.1% (p < 0.0166), the MDA concentration remained unchanged and the lipoprotein(a) concentration decreased by 15.8 ± 5.6% (p < 0.0469) in the patients’ blood. The concentration of the nanoplaque promoting particles VLDL and total triglycerides was diminished by 34.1 ± 11.6% (p < 0.0469) and 26.7 ± 10.8% (p < 0.0156), respectively. Furthermore, the ratio of the strongly atherogenic small dense to the total LDL cholesterol (LDL5+LDL6)/LDLtot decreased by 9.9 ± 3.0% (p < 0.0174).
Conclusions: A combinatorial regression analysis revealed a basis for a mechanistic explanation of nanoplaque reduction under n-3 fatty acid treatment. This effect was possibly due to the beneficial changes in lipid concentrations and an attenuation of the risk factors oxLDL/LDL and (LDL5+LDL6)/LDLtot.

Zusammenfassung
Hintergrund/Methode: Durch Beschichtung einer Silikatoberfläche mit dem Lipoproteinrezeptor Heparansulfat-Proteoglykan (HS-PG), der aus arteriellem Endothel und der Gefäßmatrix isoliert wurde, konnten wir mithilfe ellipsometrischer Techniken die ersten Anfangsstadien arteriosklerotischer Plaques in vitro beobachten (Patent EP 0 946 876). Die sogenannten Nanoplaques werden durch den ternären Aggregatkomplex aus HS-PGRezeptor, Lipoproteinpartikeln und Kalziumionen gebildet. Das Modell wurde in mehreren klinischen Studien zur Wirkung von Statinen bei kardiovaskulären Hochrisikopatienten bestätigt, wobei deren natürliche Blut-Lipoprotein-Fraktionen eingesetzt wurden.

Ergebnisse: Bei 7 Patienten nach Herzklappenoperation betrug die Reduktion der arteriosklerotischen Nanoplaquebildung und -größe nach 3-monatiger Therapie mit ω-3-Fettsäuren (3 × 3 g/d Ameu® 500 mg) in normaler Krebslösung 6,1 ± 2,3% (p < 0,0156) bzw. 37,5 ± 13,2% (p < 0,0312). Zusätzlich wurde im Patientenblut der oxLDL/LDL-Quotient um 6,8 ± 2,1% (p < 0,0166) gesenkt, die MDA-Konzentration blieb unverändert und die Lipoprotein(a)-Konzentration nahm um 15,8 ± 5,6% (p < 0,0469) ab. Die Konzentration der Nanoplaque fördernden VLDLs und Gesamttriglyzeride wurde um 34,1 ± 11,6% (p < 0,0469) sowie 26,7 ± 10,8% (p < 0,0156) reduziert. Ferner verringerte sich das Verhältnis der stark atherogenen, kleinen dichten LDL-Fraktionen zum Gesamt-LDL (LDL5+LDL6)/LDLtot um 9,9 ± 3,0% (p < 0,0174).

Schlussfolgerungen: Eine mehrfache Regressionsanalyse ergab eine Grundlage für eine mechanistische Erklärung der Nanoplaquereduktion unter ω-3-Fettsäure-Behandlung. Dieser Effekt beruht möglicherweise auf günstigen Veränderungen der Lipidkonzentrationen und einer Verminderung der Risikofaktoren oxLDL/LDL und (LDL5+LDL6)/LDLtot.
Keywords: Proteoglycan receptor · Lipoproteins · Nanoplaque formation · n-3 Fatty acids · Clinical trial Proteoglykanrezeptor · Lipoproteine · Nanoplaquebildung · ω-3-Fettsäuren · Klinische Studie
  • Forschende Komplementärmedizin / Research in Complementary Medicine 16(2009), 237-245
    DOI: 10.1159/000229786

Publ.-Id: 13217 - Permalink


Direct labelling of peptides with 2-[F-18]fluoro-2-deoxy-D-glucose ([F-18]FDG)
Wuest, F.; Hultsch, C.; Berndt, M.; Bergmann, R.;
The study describes the use of [F-18]FDG as F-18 building block for the direct labelling of various aminooxy-functionalised peptides via chemoselective oxime formation.

Publ.-Id: 13216 - Permalink


Properties of Transparent Conductive Oxides Deposited by Magnetron Sputtering
Vinnichenko, M.; Cornelius, S.; Rogozin, A.; Shevchenko, N.; Gago, R.; Kolitsch, A.; Möller, W.;
Transparent conductive oxides (TCOs) are attracting an increasing attention as materials for transparent electrodes in thin film solar cells. The characteristic features of TCOs are low formation energy of defects, which enables n-type doping, and low probability of compensating defects formation. These materials are mainly based on In2O3, SnO2 and ZnO, wide band gap (>3 eV) semiconductors, which may be easily converted by doping to degenerate semiconductors with electrical resistivity as low as ~10-4 Ohm cm and high transmittance (>80%) in the visible spectral range. In addition to these properties, photovoltaic applications require TCO materials with increased near-IR transmittance, adjustable work function and defined surface morphology, which improves light trapping in PV absorber layer (e.g. a-Si:H-based cells). The need to decrease TCO production costs has stimulated research activity on reactive pulsed magnetron sputtering (RPMS) as a versatile deposition method.
In order to explore potential advantages of RPMS, the relationship between the deposition parameters and structure, phase composition, and physical properties of TCOs should be established. Understanding the mechanisms of donor impurity incorporation and its electrical activation is of special importance. For this purpose, indium oxide (IO), ITO, ZnO, and AZO films (with Al concentrations 0.7-8.7 at. %) were grown by RPMS with a precise control of the oxygen partial pressure at substrate temperatures ranging from ~40 °C to 580 °C. The magnetron plasma parameters were determined by a Langmuir probe. The resulting films were characterized by spectroscopic ellipsometry, Hall effect measurements, X-ray diffraction (XRD) and, in case of ZnO and AZO films, by X-ray absorption near edge spectroscopy (XANES). The Sn concentration in ITO was determined by Auger analysis, while the Al concentration in ZnO matrix was estimated by elastic recoil detection analysis.
The comparison of the real-time behavior of the IO and ITO film structure and electrical properties during annealing provides a direct evidence of Sn donor activation (with an estimated efficiency of 40%) in ITO due to amorphous-to-crystalline transition. The ITO film crystallinity always improves with increasing substrate temperature or during isothermal annealing, with the electrical resistivity decreasing. In contrast, the electrical resistivity of ZnO:Al films shows a clear minimum at a certain substrate temperature (250-400 °C), which depends on Zn/O2 flux ratio and correlates with a maximum in crystallinity (grain size). In this case, the highest mobility value of 46 cm2 V-1 s-1 is comparable to the best values achieved in AZO films grown by less cost-efficient techniques. This value is achieved at the free electron density of 6x1020 cm-3 which corresponds to maximum ~30% electrical activation of Al impurity. At higher temperatures, the AZO electrical properties and crystalline quality deteriorate abruptly. This is likely due to formation of a new metastable phase, which is identified by XANES as homologous (ZnO)3(Al2O3). Its formation is triggered by an increase of the Al/Zn ratio in the film, and leads to electrical deactivation of the Al impurity in AZO. In order to improve electrical activation of the donor impurity and to extend the functionality of TCOs, the formation of epitaxial AZO and TiO2:Nb films by RPMS is proposed.
Keywords: transparent conductive oxides, Al-doped ZnO, tin-doped indium oxide
  • Invited lecture (Conferences)
    16th International Summer School on Vacuum, Electron and Ion Technologies (VEIT 2009), 28.09.-02.10.2009, Sunny Beach, Bulgaria

Publ.-Id: 13215 - Permalink


Radiopharmacological investigation of 3-[4’-[F]fluorobenzylidenyl]-indolin-2-one
Bergmann, R.; Knieß, T.; Kuchar, M.; Steinbach, J.; Wüst, F.;
Introduction and Aim:
The radiopharmacological evaluation of the new compound 3-[4’-[18F]fluorobenzylidenyl]-indolin-2-one is described. The compound is a radiolabeled derivative of an inhibitor of the VEGF-mediated signaling through the Flk-1/KDR (VEGFR-2) tyrosine kinase receptor pathway (SU5416 (NSC 696819) [3-(3,5-dimethyl-1H-pyrrol-2-ylmethylene)-1,3-dihydro-indol-2-one]).

Materials and Methods:
The radiosynthesis was accomplished by Knoevenagel condensation of 4-[18F]fluorobenzaldehyde with oxindole in a remotely controlled synthesis module. The radiotracer was obtained after a two-step labeling procedure in 4% decay-corrected radiochemical yield at a specific activity of 48-61 GBq/µmol within 90 min. The radiochemical purity after semi-preparative HPLC purification exceeded 98%. The biodistribution, metabolism and excretion were studied in Wistar rats. Small animal PET studies in rats and FaDu tumor bearing nude mice were carried out. Results: After distribution the radiotracer was rapidly accumulated in the adrenals, liver and kidneys, however, it was cleared from these and the most other organs. Only the adipose tissue retained the activity over 60 min. Unexpected high transient uptake was observed in the brain, pancreas, heart and lung. The fast blood clearance of 3-[4’-[18F]fluorobenzylidenyl]-indolin-2-one was caused by excretion, approximately one half each was renal and biliary excreted and other metabolic processes. Only the original compound was entering the brain. In arterial blood plasma were two more polar radiometabolites detected. The blood clearance was fast and could be described by a two phase elimination with half-lifes of 8 and 267 s. Consequently, in small animal PET studies with FaDu tumor bearing mice - no specific uptake in the tumors could be detected.

Conclusion:
The investigation of the 3-[4’-[18F]fluorobenzylidenyl]-indolin-2-one revealed that the uptake in high perfused organs was transiently, and only in the adipose tissue the compound was accumulated. However, it seems to be it is not applicable for angiogenesis imaging.
  • Poster
    World Molecular Imaging Congress 2009, 23.-26.09.2009, Montreal, Canada

Publ.-Id: 13214 - Permalink


Cell uptake studies of fluorescent labeled phophopeptide-cell-penetrating peptide hybrids
Richter, S.; Bergmann, R.; Neundorf, I.; Beck-Sickinger, A.; Pietzsch, J.; Steinbach, J.; Wüst, F.;
Introduction and Aim:
Phosphopeptides are very useful reagents to study signal transduction pathways related with cellular protein phosphorylation/dephosphorylation processes. Phosphopeptides also have been identified as important drug candidates to modulate intracellular signal transduction pathways. The present study describes the use of cell-penetrating peptides (CPPs) sC18 and hCT(18-32)-k7 coupled to Polo-like kinase-1 (Plk-1)-binding hexaphosphopeptide H-Met-Gln-Ser-pThr-Pro-Leu-OH to investigate cell uptake of the corresponding phosphopeptide-CPP hybrids.

Materials and Methods:
Peptide syntheses were accomplished using a combination of automated and manual solid-phase peptide syntheses following standard Fmoc chemistry. Fluorescence labeling was carried out via coupling 5(6)-carboxyfluoresceine (CF) to the N-terminal end of the phosphopeptide using HATU as the activation agent, DIPEA as the base, and DMF as the solvent. Cell uptake studies of CF-Met-Gln-Ser-pThr-Pro-Leu-sC18 (CF-I) and CF-Met-Gln-Ser-pThr-Pro-Leu-hCT(18-32)-k7 (CF-II) were performed using the human breast cancer cell line MCF-7 and human cervical carcinoma epithelial (HeLa) cells on a Zeiss Axio fluorescence confocal microscope. Results: Peptide hybrids CF-I and CF-II showed cellular uptake in both cell lines after incubation at 37°C for 60 min. Cell uptake was more pronounced in HeLa cells compared to MCF-7 cells. Phosphopeptide conjugated to sC18 showed higher cell uptake compared to phosphopeptide-hCT(18-32)-k7 conjugate. As expected, CF-labeled phosphopeptide without being conjugated to CPPs as molecular shuttles was not internalized into both cell lines. Quantification of cellular uptake using flow cytometry analysis and fluorine-18 labeled phosphopeptide-CPP hybrids are currently in progress.

Conclusion:
Cell-penetrating peptides sC18 and hCT(18-32)-k7 are useful drug delivery systems enabling sufficient membrane transport of phosphopeptides to further promote studies on intracellular metabolic pathways involving phosphopeptides.
  • Poster
    World Molecular Imaging Congress 2009, 23.-26.09.2009, Montreal, Canada

Publ.-Id: 13213 - Permalink


Deep Subthreshold Xi- Production in Ar+KCl Reactions at 1.76A GeV
Agakishiev, G.; Balanda, A.; Bassini, R.; Belver, D.; Belyaev, A. V.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Díaz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Fabbietti, L.; Fateev, O. V.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; González-Díaz, D.; Guber, F.; Hennino, T.; Holzmann, R.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krizek, F.; Krücken, R.; Kühn, W.; Kugler, A.; Kurepin, A.; 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.; Mishra, D.; Morinière, E.; Mousa, J.; Müntz, C.; Naumann, L.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Weber, M.; Wisniowski, M.; Wojcik, T.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y. V.; Zhou, P.; Zumbruch, P.;
We report first results on a deep subthreshold production of the doubly strange hyperon Xi- in a heavy-ion reaction. At a beam energy of 1.76A GeV the reaction Ar+KCl was studied with the High Acceptance Di-Electron Spectrometer at SIS18/GSI. A high-statistics and high-purity Lambda sample was collected, allowing for the investigation of the decay channel Xi--->Lambdapi-. The deduced Xi-/(Lambda+Sigma0) production ratio of (5.6±1.2-1.7+1.8)×10-3 is significantly larger than available model predictions.

Publ.-Id: 13212 - Permalink


Quantum oscillations in the normal and superconducting state of LuNi2B2C
Bergk, B.; Maniv, T.; Zhuravlev, V.; Canfield, P. C.; Wosnitza, J.;
We present de Haas-van Alphen (dHvA) investigations in the nonmagnetic borocarbide superconductor LuNi2B2C both in the normal and in the superconducting state. The measurements have been carried out by use of the torque method as well as by the field-modulation method. The quantum oscillations in the normal state give information on the elaborated Fermi surfaces which consists of several open and closed parts [1]. In the superconducting state we observe dHvA oscillations that belong to a spheroidal Fermi surface deep into the superconducting state down to B = 2.5 T far below the upper critical field, Bc2. We find only a minor additional damping of the dHvA oscillation amplitude in the superconducting state compared to the normal state. Only close to Bc2 the oscillations appear to be more strongly damped. There, the background signal shows a strong peak effect which complicates the analysis of the dHvA signal in this region. However, the apparent increase of the additional damping in the peak-effect range hints at the influence of increased flux-line pinning in this region
  • Poster
    9th International Conference on Materials and Mechanisms of Superconductivity (M2S-IX), 07.-12.09.2009, Tokyo, Japan

Publ.-Id: 13211 - Permalink


Magnetic Order and Magnetic Exchange Interactions in the Quasi-Two-Dimensional Magnets [Cu(pyz)2(HF2)]X with X = BF4 and PF6
Wosnitza, J.; Beyer, R.; Cizmar, E.; Ozerov, M.; Skourski, Y.; Uhlarz, M.; Zvyagin, S. A.; Gemming, S.; Sengupta, P.; Batista, C.; Schlueter, J. A.; Manson, J. L.;
We report on combined experimental and theoretical efforts to elucidate the magnetic properties of the organic magnets [Cu(HF2)(pyz)2]X with X = BF4 and PF6. By use of high-resolution specific-heat measurements on high-quality single crystals we were able to resolve small lambda-type anomalies indicative for a phase transition into a long-range ordered state. First-principles density-functional calculations allow to estimate the exchange couplings and confirm a three-dimensional antiferromagnetic order between ad-jacent Cu centers with a stronger coupling within the layers of pyz-bridged Cu and a much weaker cou-pling across the HF2 linker units. Specific-heat data in magnetic field, B,reveal a slightly anisotropic nonmonotonic dependence of the Néel temperature TN with B. The increase of TN at low fields can be un-derstood by the reduction of phase fluctuations that are prominent in these highly anisotropic quasi-two-dimensional magnets. Towards higher fields, B suppresses the amplitude of the antiferromag-netic order parameter, and correspondingly TN, by aligning the spins parallel to B. This nonmonotonic be-havior of TN, as well as the magnetic part of the specific heat, cannot be described by a mean field theory that neglects the crucial role played by phase fluctuations. In contrast, we show that both properties are very well reproduced by Quantum Monte Carlo simulations. Pulsed-field magnetization data corroborate the strong anisotropy of the exchange interactions. The ratio of the inter- to intralayer exchange interac-tion is estimated as 0.0025 (for X = BF4) and 0.009 (X = PF6). High-field electron spin resonance meas-urements reveal a magnetic easy-plane anisotropy.
  • Invited lecture (Conferences)
    The 8th International Symposium on Crystalline Organic Metals, Superconductors and Ferromagnets (ISCOM 2009), 12.-17.09.2009, Hokkaido, Japan

Publ.-Id: 13210 - Permalink


Magnetic quantum oscillations in borocarbide superconductors
Bergk, B.; Wosnitza, J.;
We report systematic de Haas–van Alphen (dHvA) investigations in the normal and superconducting state of RNi2B2C (R = Y and Lu). The observed rich frequency spectrum of the dHvA signals results from a rather complex electronic band structure with different open and closed Fermi-surface sheets. From our data in combination with full-potential local-orbital calculations we are able to extract the angular-resolved mass-enhancement factors, lambda, for different bands. We find a strong anisotropy and band dependence of lambda, clearly reflecting the multiband character of the superconductivity in RNi2B2C. We further were able to resolve dHvA oscillations deep into the superconducting state. The observed additional damping of the dHvA amplitudes is much less than expected from most theories. This hints at a reduced or even zero superconducting gap for the detected Fermi surface
  • Low Temperature Physics 35(2009)8/9, 872-878

Downloads:

Publ.-Id: 13209 - Permalink


Status of the Umbrella project LONGLIFE
Altstadt, E.;
In view of the increasing age of the European NPPs and envisaged life time extensions up to an EOL of 80 years, there is a need for an improved understanding and prediction of RPV irradiation embrittlement effects connected with long term operation (LTO). Effects caused by high neutron fluences such as the possible formation of Late Blooming Phases and as yet unknown defects must be considered adequately in safety assessments. However, the surveillance database for long irradiation times (>20 years) and low neutron flux is sparse, which leads to uncertainties in the treatment of LTO irradiation effects. In this context microstructural data are essential for the understanding of the involved mechanisms. The proposed project aims at: 1) improved knowledge on LTO phenomena relevant for European reactors; 2) assessment and proposed improvements of prediction tools, codes and standards; 3) elaboration of best practice guidelines for irradiation embrittlement surveillance.
The suggested scope of work is:
i) Summary of boundary conditions for LTO and systematic (re)evaluation of the international prediction procedures of irradiation embrittlement
ii) Generation of microstructural data of irradiated representative or original RPV materials; demonstration that damage models are (or not) consistent with the mechanisms of irradiation damage in the LTO (use of PERFORM60 prediction tools)
iii) Investigation of specific LTO relevant phenomena like late blooming phases and flux effect from available results; role of Cu, Ni, Mn, P, Si under the aspect of LTO;
iv) Correlation of microstructural data with mechanical properties and identification of the most important influencing factors (link with PERFORM60)
v) Influence of high neutron fluences on fracture toughness curves shape
vi) Comparison of embrittlement results from decommissioned plants with surveillance data
vii) Elaboration of recommendations for RPV embrittlement surveillance under LTO conditions
Keywords: Reactor Pressure Vessel, Irradiation defects, Long term operation, FP7 Project
  • Lecture (others)
    5-th NULIFE Network meeting, 15.-17.09.2009, Les Renardieres, France

Publ.-Id: 13208 - Permalink


KKW Krümmel – Ermüdungsbeitrag der Transiente vom 28.06.2007 für den RDB-Boden
Altstadt, E.;
Kein Abstract, da vertraulicher Bericht.
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2009
    FZD\FWS\2009\04
    18 Seiten

Publ.-Id: 13207 - Permalink


Mechanische Analyse für die RDB-Deckel-Verbindung des Kernkraftwerks Brunsbüttel
Altstadt, E.; Werner, M.;
Kein Abstract, da Bericht vertraulich.
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2009
    FZD\FWS\2009\05
    22 Seiten

Publ.-Id: 13206 - Permalink


VVER vessel steel corrosion at interaction with molten corium in oxidizing atmosphere
Bechta, S. V.; Granovsky, V. S.; Khabensky, V. B.; Krushinov, E. V.; Vitol, S. A.; Sulatsky, A. A.; Gusarov, V. V.; Almiashev, V. I.; Lopukh, D. B.; Bottomley, D.; Fischer, M.; Piluso, P.; Miassoedov, A.; Tromm, W.; Altstadt, E.; Fichot, F.; Kymalainen, O.;
The long-term in-vessel corium retention (IVR) in the lower head bears a risk of the vessel wall deterioration caused by steel corrosion. The ISTC METCOR Project has studied physicochemical impact of prototypic coria having different compositions in air and steam and has generated valuable experimental data on vessel steel corrosion. It is found that the corrosion rate is sensitive to corium composition, but the composition of oxidizing above-melt atmosphere (air, steam) has practically no influence on it. A model of the corrosion process that integrates the experimental data, is proposed and used for development of correlations.
Keywords: Corium-steel interaction, in-vessel melt retention, physiochemical properties

Publ.-Id: 13205 - Permalink


Studying the astrophysical r-process: Multigap resistive plate chamber prototypes for NeuLAND
Bemmerer, D.;
At the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, uniquely intensive beams of radioactive ions will become available. One of the experiments at FAIR, called Reactions with Relativistic Radioactive Beams (R3B), will study reactions of such projectiles at energies up to 1 GeV/A. The planned NeuLAND time-of-flight detector will detect the emitted neutrons with a time resolution of sigma = 50 ps and efficiency of better than 90 %. The poster will discuss recent progress in the development of multigap resistive plate chamber based prototypes for NeuLAND. Using the ELBE electron beam facility in Dresden, the time resolution of the prototypes has been shown to fulfill the design criteria.
Keywords: Nuclear astrophysics neutron time-of-flight detector multigap resistive plate chamber MRPC NeuLAND R3B FAIR
  • Poster
    Nuclear Physics in Astrophysics IV, 08.-12.06.2009, Frascati, Italien

Publ.-Id: 13204 - Permalink


The sorption processes of Np(V) and U(VI) onto metal oxide phases. The formation of sorption complexes and mechanistic aspects studied by in situ ATR FT-IR spectroscopy
Foerstendorf, H.; Müller, K.; Heim, K.;
The migration behaviour of actinide ions in the geosphere is generally influenced by sorption processes in aqueous media. These processes occurring at solid/liquid interfaces can be monitored by in situ Attenuated Total Reflection Fourier-transform Infrared (ATR FT-IR) spectroscopy providing structural information on a molecular level.[1]
In this work, the sorption of neptunium(V) onto metal oxides was investigated for the first time. From the Np(V) sorption studies on the metal oxides, stable surface species of NpO2+ are derived. The type of the sorbed species can be elucidated by a spectral shift (~ 30 cm−1) to lower wavenumbers of the antisymmetric stretching vibration υ3(NpO2+) compared to the aqueous species suggesting an inner-sphere complexation. Outer-sphere complexation is found to play a minor role due to the pH independence of the sorption species throughout the pH range 4 – 7.6. The comparative spectroscopic experiments of Np(V) sorption onto TiO2, SiO2 and ZnO indicate structurally similar bidentate surface complexes.[2]
A detailed insight into the molecular mechanisms occurring during the formation of ternary actinide complexes at the solid/liquid interface is provided upon formation of uranyl carbonato complexes on ferrihydrite (Fh). The influence of the presence of atmospheric carbon dioxide during the sorption processes of the actinide ions was studied by sorption experiments which were carried out under inert gas conditions and in an ambient atmosphere. From the results, the formation of bidentate [Fh•••UO2•••O2CO] complexes can be derived under mildly acid conditions which is in agreement from recent EXAFS results obtained from batch samples.[3]
Furthermore, experiments with 13C labelled carbonate provide an unequivocal assignment of the spectral features reflecting the structural alterations of the carbonate ions upon sorption of uranyl cations onto Fh. From these assignments, the formation of the ternary uranyl complexes can be described at a molecular level.

References
[1] Lefèvre, G. (2004) Adv. Colloid Interface Sci. 107, 109-123.
[2] Müller, K. et al. (2009) Environ. Sci. Technol., in press.
[3] Rossberg, A. et al. (2009) Environ. Sci. Technol. 43, 1400-1406.
  • Contribution to proceedings
    16th Radiochemical Conference, 18.-23.04.2010, Marianske Lazne, Czech Republic
    Chemicke listy, Vol. 104, Praha: Czech Chemical Society, 0009-2770, s178-s178
  • Lecture (Conference)
    RadChem 2010 - 16th Radiochemical Conference, 18.-23.04.2010, Mariánske Lázne, Czech Republic

Publ.-Id: 13203 - Permalink


Enhancement Of Electrical And Chemical Surface Properties Of Titanium And Iron-Carbon Alloys Irradiated With A Low-Energy Intense Pulsed Electron Beam
in Russian
Markov, A. B.; Reuther, H.; Shevchenko, N.; Kolitsch, A.;
Processes leading to homogenization of chemical and phase composition of near-surface layers materials made from titanium and iron-carbon alloys under irradiation of a low energy intense pulsed electron beam have been investigated. It has been shown that preliminary heating leads to appearance of a more homogeneous chemical composition of surface alloy. It has been determined that an electron-beam polishing took place during irradiation. Irradiation results in dissolution of secondary phase inclusions, decreasing of roughness, and as a result in the enhancement of electrical and chemical surface properties of titanium and iron-carbon alloys.
  • Contribution to proceedings
    19th Int. Crimean Conference Microwave & Telecommunication Technology, 14.-18.09.2009, Sevastopol, Ukraine
    Enhancement Of Electrical And Chemical Surface Properties Of Titanium And Iron-Carbon Alloys Irradiated With A Low-Energy Intense Pulsed Electron Beam, 978-966-335-244-594 2., 593-594

Publ.-Id: 13202 - Permalink


Phase-sensitive terahertz spectroscopy with BWOs in reflection mode
Pronin, A. V.; Goncharov, Y. G.; Fischer, T.; Wosnitza, J.;
We report on a method, which allows accurate measurements of complex reflection coefficient of a solid at frequencies 1 to 50 cm-1 (30 GHz - 1.5 THz). Backward-wave oscillators (BWOs) are used as sources of monochromatic coherent radiation, tunable in frequency. The amplitude of the complex reflection (the reflectivity) is measured in a standard way, while the phase shift, introduced by the reflection from the sample surface, is measured using a polarizing Michelson interferometer. This method is particular useful for not-transparent samples (such as metals, superconductors, etc.), where phase-sensitive transmission measurements are not possible.
The method requires no Kramers-Kronig transformation in order to extract the sample's electrodynamic properties (such as complex dielectric function or complex conductivity). Another area of application of this method is the study of magnetic materials with complex dynamic permeability different from unity at the measurement frequencies (for example, metamaterials). Measuring both, the phase-sensitive transmission and the phase-sensitive reflection, would allow a straight-forward model-independent determination of the dielectric permittivity and magnetic permeability of such materials.
  • Poster
    The 34th International Conference on Infrared, Millimeter, and Terahertz Waves, 21.-25.09.2009, Busan, Korea

Publ.-Id: 13201 - Permalink


Memory effect of Mn5Ge3 nanomagnets embedded inside a Mn-diluted Ge matrix
Zhou, S.; Shalimov, A.; Potzger, K.; Helm, M.; Fassbender, J.ORC; Schmidt, H.
Crystalline Mn5Ge3 nanomagnets are formed inside a Mn-diluted Ge matrix using Mn ion implantation. A temperature-dependent memory effect and slow magnetic relaxation are observed below the superparamagnetic blocking temperature of Mn5Ge3. Our findings corroborate that the observed spin-glass-like features are caused by the size distribution of Mn5Ge3 nanomagnets, rather than by the inter-particle interaction through the Mn-diluted Ge matrix.

Publ.-Id: 13200 - Permalink


Bruchmechanische Werkstoffcharakterisierung zur Überwachung der Neutronenversprödung von Reaktordruckbehältern für den Langzeitbetrieb von Kernkraftwerken
Zurbuchen, C.; Viehrig, H.-W.;
Die Schweizer Richtlinie HSK-AN-425 dient der bruchmechanische Werkstoffcharakterisierung zur Überwachung der Neutronenversprödung von Reaktordruckbehältern für den Langzeitbetrieb von Kernkraftwerken. Eine Besonderheit ist, dass nicht quasistatische, sondern dynamische Bruchzähigkeitskennwerte ermittelt werden. Die Richtlinie deckt den gesamten Bereich der Zähigkeit ferritischer Stähle ab, also vom instabilen Spaltbruch in der Tieflage (tiefe Temperaturen) bis zum duktilen Reissen in der Hochlage (hohe Temperaturen) und dem dazwischen liegenden Bereich des Steilabfalls der Zähigkeit.
Ziel des Forschungsprojektes HSK-AN-6305 war, die zentralen Elemente der neuen Richtlinie HSK-AN-425 Rev. 5 durch experimentelle Überprüfung an vergleichbaren Werkstoffen aus dem RDB Biblis C zu validieren (Einfluss der Risslänge, Fortsetzung der MC im oberen ZSÜ-Bereich). Allfällige Schwachstellen der Richtlinie HSK-AN-425 sind zu korrigieren, bevor sie in der Überwachung der Kernanlagen freigegeben werden kann. Der Einfluss der Probendicke und der Probenart auf die quasistatische MC-Referenztemperatur T0 nach ASTM E 1921 sowie auf die dynamische MC-Referenztemperatur T0d nach HSK-AN-425 ist zu bestimmen (Übertragbarkeit der Ergebnisse auf Bauteile und Komponenten), und ob bei den Bruchmechanikproben der herkömmliche Ermüdungsanriss durch EDM-Kerben ersetzbar ist.
In dieser Publikation werden die Ergebnisse des Forschungsprojektes HSK-AN-6305 ausführlich vorgestellt.
Keywords: fracture mechanics, quasistatic, dynamic, Master Curve, crack growth resistance curve, R curve, ASTM E 1921, ASTM E 1820, NM method, HSK-AN-425, HSK AN 425, stretch zone
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2009
    FZD\FWS\2009\07
    166 Seiten

Publ.-Id: 13199 - Permalink


Bruchmechanische Werkstoffcharakterisierung zur Überwachung der Neutronenversprödung von Reaktordruckbehältern für den Langzeitbetrieb von Kernkraftwerken- Kurzfassung
Zurbuchen, C.;
Die Schweizer Richtlinie HSK-AN-425 dient der bruchmechanische Werkstoffcharakterisierung zur Überwachung der Neutronenversprödung von Reaktordruckbehältern für den Langzeitbetrieb von Kernkraftwerken. Eine Besonderheit ist, dass nicht quasistatische, sondern dynamische Bruchzähigkeitskennwerte ermittelt werden. Die Richtlinie deckt den gesamten Bereich der Zähigkeit ferritischer Stähle ab, also vom instabilen Spaltbruch in der Tieflage (tiefe Temperaturen) bis zum duktilen Reissen in der Hochlage (hohe Temperaturen) und dem dazwischen liegenden Bereich des Steilabfalls der Zähigkeit.
Ziel des Forschungsprojektes HSK-AN-6305 war, die zentralen Elemente der neuen Richtlinie HSK-AN-425 Rev. 5 durch experimentelle Überprüfung an vergleichbaren Werkstoffen aus dem RDB Biblis C zu validieren (Einfluss der Risslänge, Fortsetzung der MC im oberen ZSÜ-Bereich). Allfällige Schwachstellen der Richtlinie HSK-AN-425 sind zu korrigieren, bevor sie in der Überwachung der Kernanlagen freigegeben werden kann. Der Einfluss der Probendicke und der Probenart auf die MC-Referenztemperatur T0 ist zu bestimmen (Übertragbarkeit der Ergebnisse auf Bauteile und Komponenten), und ob bei den Bruchmechanikproben der herkömmliche Ermüdungsanriss durch EDM-Kerben ersetzbar ist.
In dieser Publikation werden die Hauptergebnisse des Forschungsprojektes HSK-AN-6305 vorgestellt.
Keywords: fracture mechanics, quasistatic, dynamic, Master Curve, crack growth resistance curve, R curve, ASTM E 1921, ASTM E 1820, NM method, HSK-AN-425, HSK AN 425, stretch zone
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2009
    FZD\FWS\2009\08
    16 Seiten

Publ.-Id: 13198 - Permalink


Complexation of U(VI) with Nitrogen and Phosphorous Containing Ligands in Aqueous Solution
Raditzky, B.; Schmeide, K.; Sachs, S.; Bernhard, G.;
The long-term safety assessment of nuclear waste disposals requires detailed knowledge of the transport and interaction behavior of actinides within the technical, geotechnical and geological barriers. In the case of accidental release of radionuclides into the surrounding environment, their migration behavior can be effectively influenced by the ambient conditions like pH, temperature, ionic strength and especially the presence of inorganic and organic complexing ligands, e.g. bioligands like humic acids, amino acids or phospholipids. Due to their high complexing capacity towards metal ions these ligands may influence the mobility of actinides.

We studied the U(VI) complexation with nitrogen and phosphorous containing model ligands in order to simulate the functionalities of bioligands. The aim of this work is to determine the influence of various nitrogen and phosphorous containing functional groups on the U(VI) complexation and to evaluate their contribution in comparison to oxygen containing functional groups. As nitrogen containing ligands we used the biologically important substances anthranilic acid (AA) and nicotinic acid (NA). Furthermore, phenylphosphonic acid (PPA) was used as aromatic phosphorous containing ligand.

The complexation studies in aqueous solution were performed as a function of pH using time-resolved laser-induced fluorescence spectroscopy (TRLFS). All ligands show a complex formation with U(VI) under the given experimental conditions ([U(VI)] = 0.05 mM, [ligand] = 0 – 0.5 mM, pH 2-4, I = 0.1 M, T = 25°C). The binding of U(VI) by AA and NA takes place via the carboxylic group of the ligands. It can be concluded, that oxygen containing functional groups dominate the U(VI) complexation in the investigated pH range. The nitrogen functionalities of the ligands play only a subordinate role. AA forms a 1:1 complex, with a corresponding stability constant of log ß11 = 3.14 +/- 0.17 [1]. The formation of 1:1 and 1:2 complexes was detected for the U(VI)-nicotinate system (log ß11 = 3.73 +/- 0.30, log ß12 = 7.46 +/- 0.17 [1]) as well as for the U(VI)-phenylphosphonate system (log ß11 = 3.58 +/- 0.17, log ß12 = 6.81 +/- 0.10). At high U(VI) concentrations (1 mM), a precipitation of the formed complexes was observed for the U(VI) complexation by AA and PPA. The precipitates were analyzed with FT-IR spectroscopy and X-ray diffraction. To study the influence of different functional groups on the complexation of actinides in different oxidation states, comparable complexation studies are performed with Am(III).

References:
[1] B. Raditzky, K. Schmeide, S. Sachs, G. Geipel, G. Bernhard, Polyhedron (2009), doi:10.1016/j.poly.2009.08.010.
  • Contribution to proceedings
    RadChem 2010 - 16th Radiochemical Conference, 18.-23.04.2010, Marianske Lazne, Czech Republic
  • Lecture (Conference)
    RadChem 2010 - 16th Radiochemical Conference, 18.-23.04.2010, Marianske Lazne, Czech Republic

Publ.-Id: 13197 - Permalink


Effect of Ca2+ on the Sorption of Uranium(VI) and Humic Acid on Natural Clay
Joseph, C.; Schmeide, K.; Sachs, S.; Bernhard, G.;
In various countries clay is discussed as possible host rock for a nuclear waste repository. The interaction of the clay with actinides, especially U(VI), is the focus of our work. Sorption experiments were performed to estimate the actinide migration in clay formations. Also the influence of humic acid (HA) is investigated. HA are ubiquitously found in natural environments and can interact with e.g. actinides of the nuclear waste. Natural clay contains HA and fulvic acid like organic matter, which can be released from the clay [1]. HA also forms stable colloids. Due to this behavior HA can influence the mobility of actinides, e.g. U(VI), in a nuclear waste repository.

Opalinus clay (OPA) from Mont Terri, Switzerland was studied. Batch sorption experiments were performed in order to determine the sorption ability of U(VI) ([U] = 1x10-6 M) onto OPA in the absence and presence of HA ([HA] = 10 mg/L, 50 mg/L) and of HA in the absence and presence of U(VI) using synthetic OPA pore water (OPAWA, [2], pH 7.6, I = 0.39 M) and NaClO4 (pH 3-10, I = 0.1 M) as background electrolyte. During these studies a large influence of calcite on the sorption behavior of U(VI) and HA was determined. Calcite presents a fraction of 13% in OPA and its ions occur also in the OPAWA ([Ca2+] = 0.03 M, [CO32-] = 5x10-4 M). In OPAWA, U(VI) forms with the ions in solution the neutral aquatic complex Ca2UO2(CO3)3 [3]. This complex dominates the speciation with a fraction of 99%. In sorption experiments it was shown, that this complex adsorbs weakly onto OPA. Normalized to the specific surface area of OPA (BET = 41.6 m2/g) the U(VI) sorption was determined with 0.05 ± 0.002 µg U/m2 clay. In further sorption studies it was shown that HA has no influence on the U(VI) sorption onto OPA. This was also proved by speciation calculations, which showed that also in the presence of HA the Ca2UO2(CO3)3(aq) complex is the dominating species in solution. In order to interpret the sorption data onto OPA, additional zeta potential measurements were performed, where between pH 0 and 7.5 a negative zeta potential for OPA was determined.

The HA sorption onto OPA in OPAWA was determined with 3.57±0.01 µg HA/m2 (10 mg/L) and 17.28±0.15 µg HA/m2 (50 mg/L). In the presence of U(VI), a slight increase of HA sorption (D = 0.3 µg HA/m2) was observed for [HA] = 50 mg/L. Species calculations showed that Ca2+ ions influence also the HA speciation, because Ca2+ is complexed by HA. Ca2+ is present in such a high concentration, that it saturates the binding sites of HA. Thus, only few binding sites, about 0.1% according to speciation calculations, are available for the complexation of U(VI). Consequently, U(VI) and HA have no effect on each other during the sorption studies. These experiments show the large influence of the calcite fraction of the OPA and thus the resulting composition of the OPAWA on the U(VI) and HA sorption. Thus, calcite should be taken into account for the safety case analysis of a nuclear waste repository.

[1] F. Claret et al., Sci. Total Environ. 317, 2003, 189.
[2] F.J. Pearson, PSI Internal Report TM-44-98-07, Switzerland, 1998.
[3] G. Bernhard et al., Radiochim. Acta 89, 2001, 511.
Keywords: opalinus clay, calcium, uranium(VI), humic acid, sorption, pore water, zeta potential
  • Contribution to proceedings
    RadChem 2010 - 16th Radiochemical Conference, 18.-23.04.2010, Mariánské Lázne, Czech Republic
  • Lecture (Conference)
    RadChem 2010 - 16th Radiochemical Conference, 18.-23.04.2010, Mariánské Lázne, Czech Republic

Publ.-Id: 13195 - Permalink


Defect-induced ferromagnetism in crystalline SrTiO3
Potzger, K.; Levin, A. A.; Shalimov, A.; Osten, J.; Meyer, D. C.;
Plasma irradiation of high-quality SrTiO3 single crystals leads to room-temperature ferromagnetism. The saturation magnetization is about two orders of magnitude larger than in the pristine material. Structural analysis revealed a polycrystalline layer at the sample surface induced by the plasma irradiation. The results are discussed in the frame of grain-boundary-induced defect ferromagnetism.
Keywords: SrTiO3, defect induced ferromagnetism, plasma irradiation
  • Journal of Magnetism and Magnetic Materials 323(2011)11, 1551-1562
    DOI: 10.1016/j.jmmm.2011.01.018
  • Lecture (Conference)
    75. Jahrestagung der DPG und DPG Frühjahrstagung, 13.-18.03.2011, Dresden, Deutschland

Publ.-Id: 13194 - Permalink


The influence of magnetic field on the two-dimensional quantum antiferromagnet Cu(tn)Cl2: an intriguing magnetic phase diagram
Orendacova, A.; Cizmar, E.; Sedlakova, L.; Hanko, J.; Kajnakova, M.; Zelenak, V.; Xia, J. S.; Yin, L.; Pajerowski, D. M.; Zvyagin, S. A.; Wosnitza, J.; Orendac, M.; Feher, A.; Meisel, M. W.;
Specic heat and magnetic susceptibility measurements, spanning low temperatures (T ≥ 40 mK) and high magnetic elds (B ≤ 14 T), have been performed on Cu(tn)Cl2 (tn = C3H10N2), a two-dimensional (2D) S = 1/2 spatially anisotropic triangular antiferromagnet realized by a square lattice with nearest- neighbor (J=kB = 3 K), frustrating next-nearest-neighbor (0 < J'/J < 0.6), and interlayer (|J''/kB| <3 mK) interactions [1]. The absence of long-range magnetic order down to T = 60 mK in B = 0 and the T2 behavior of the specific heat for T ≤ 0.4 K and B ≥ 0 are considered evidence of 2D magnetic correlations. In fields lower than the saturation field, Bsat = 6.6 T, a specific heat anomaly, appearing near 0.8 K, is interpreted as a Berezinski-Kosterlitz-Thouless (BKT) phase transition. The magnetic phase diagram is remarkably consistent with the theoretical predictions [2], except for the point that Bsat(T -> 0) is shifted to values significantly lower than expected. Potential explanations for this observation will be discussed.
  • Invited lecture (Conferences)
    QFS2009 - International Symposium on Fluids and Solids, 05.-11.08.2009, Evanston, Illinois, USA

Publ.-Id: 13193 - Permalink


Teilchenbeschleunigung mit Laserlicht - Chancen für kompakte Strahlungsquellen für medizinische Anwendungen
Schramm, U.;
Anwendungsmöglichkeiten laserbeschleunigter Teilchenstrahlen in der Medizin
  • Invited lecture (Conferences)
    17. Jahrestagung der AG Radiochemie / Radiopharmazie, 24.-26.9.2009, Schellerhau, Sachsen, Deutschland

Publ.-Id: 13192 - Permalink


Polarisationsinduzierte Oberflächenfunktionalität an Ferroelektrika
Eng, L. M.; Grafström, S.; Seifert, G.; Gemming, S.;
In structured or self-organized materials spatial confinement effects lead to structure- and interface-controlled modifications of the bulk transport properties. In part, such modifications can be accounted for by a classical master equation approach for the transport of the different charge carrier species. The rather large quantity of parameters, which enter such an approach, can more or less easily be adjusted to the dimensional characteristics, local potential changes at interfaces, and the electronic settings of the system as well as to temperature effects. On the other hand, a microscopically more detailed and mostly parameter-free picture is obtained from a quantum-mechanical treatment on the basis of the density-functional theory. An extension by a Green's function formalism allows the determination and analysis of electronic transport through contacted nanostructures. Examples will be given to demonstrate the applicability of the different approaches for dissipative and hopping transport through a regular array of nanostructures, for a mechanically triggered metal-insulator transition in nanowires, and for the enhanced conductivity at multiferroic domain walls.
Keywords: conduction, conductivity, OFET, FerroFET, transport, SAM, self-assembled, polarization, density-functional
  • Lecture (Conference)
    Abschlusskolloquium des SPP 1157, 21.-22.09.2009, Bonn, Deutschland

Publ.-Id: 13190 - Permalink


Novel Concepts for Anisotropic Heisenberg Modeling of Multiferroic Oxides
Gemming, S.; Kunze, T.; Numazawa, S.; Schreiber, M.;
Thermodynamic equilibration of complex systems like spin glasses or (degenerate) anisotropic spin crystals by numerical methods can be challenging due to the presence of multiple minima on the potential energy surface. This problem becomes pronounced especially at low temperature, where the system remains mainly in few states. We employ the anisotropic Heisenberg model in two dimensions to simulate and analyze the domain formation and the domain structure of multiferroic oxides. In particular, we discuss various techniques to improve the low-temperature equilibration behavior by means of a trigonal antiferromagnet with single-ion anisotropy. Furthermore, we present a localized sampling method for the Metropolis algorithm, which increases the acceptance ratio significantly.
Keywords: Monte-Carlo, Heisenberg, frustrated antiferromagnet, triangular lattice, Metropolis, importance sampling
  • Lecture (Conference)
    45th Symposium on Theoretical Chemisrty, 08.-12.09.2009, Neuss, Deutschland

Publ.-Id: 13189 - Permalink


First-principles investigation of metal/oxide contacts and related metal/group-IV interfaces
Gemming, S.;
Density-functional band-structure calculations have been carried out for two types of material combinations at heterophase boundaries in order to characterise the main influence factors on adhesion.
Strong binding at heterophase interfaces is often related to a favourable and directed electron redistribution in the vicinity of the boundary plane.
The propensity for such redistributions is reflected in materials parameters such as electronegativities, polarisabilities and the differences between the values of the two sides of the interface. Strong adhesion is indirectly also related to the lattice matching or mismatch, because that influences the density of suitable in-teraction sites in the boundary plane.
Finally, fixed local charges, which are characteristic for ionic compounds, introduce additional Coulomb and image charge interactions. The present comparison aims at assessing those latter interactions by comparing material combinations with one ionic partner to completely non-ionic combinations.
Keywords: interfaces, density-functional, metal-ceramic, ferroic, semiconductor
  • Invited lecture (Conferences)
    CECAM-Workshop on Metal-Ceramic Interfaces, 20.-22.07.2009, Zürich, Schweiz

Publ.-Id: 13188 - Permalink


Multi-scale approaches for structure and conductivity of complex materials
Gemming, S.;
In nanostructured materials spatial confinement effects lead to structure-dependent modifications of the bulk transport properties. In part, such modifications can be accounted for by a classical master equation approach for the transport of the different charge carrier species. The rather large quantity of parameters, which enter such an approach, can more or less easily be adjusted to the dimensional characteristics and the electronic settings of the system as well as to temperature effects. On the other hand, a microscopically more detailed and mostly parameter-free picture is obtained from a quantum-mechanical treatment on the basis of the density-functional theory. An extension by a Green's function formalism allows the determination and analysis of electronic transport through contacted nanostructures. Examples will be given to demonstrate the applicability of the different approaches for dissipative and hopping transport through a regular array of nanostructures, for a mechanically triggered metal-insulator transition in nanowires, and for the enhanced conductivity at multiferroic domain walls.
Keywords: conduction, density-functional, multi-scale
  • Invited lecture (Conferences)
    Colloquium on Multi-Scale Modeling, 04.05.2009, Wien, Österreich

Publ.-Id: 13187 - Permalink


Transport through nanostructures
Gemming, S.;
In nanostructured materials spatial confinement effects lead to structure-dependent modifications of the bulk transport properties. In part, such modifications can be accounted for by a classical master equation approach for the transport of the different charge carrier species. The rather large quantity of parameters, which enter such an approach, can more or less easily be adjusted to the dimensional characteristics and the electronic settings of the system as well as to temperature effects. On the other hand, a microscopically more detailed and mostly parameter-free picture is obtained from a quantum-mechanical treatment on the basis of the density-functional theory. An extension by a Green's function formalism allows the determination and analysis of electronic transport through contacted nanostructures. Examples will be given to demonstrate the applicability of the different approaches for dissipative and hopping transport through a regular array of nanostructures, for a mechanically triggered metal-insulator transition in nanowires, and for the enhanced conductivity at multiferroic domain walls.
Keywords: transport, conduction, conductivity, multi-scale, calculation, density-functional
  • Lecture (Conference)
    Sächsisches Landesseminar Theoretische Chemie, 26.02.2009, Leipzig, Deutschland

Publ.-Id: 13186 - Permalink


The role of homophase and heterophase interfaces on transport properties in structured material
Gemming, S.; Kunze, T.; Morawetz, K.; Pankoke, V.; Luschtinetz, R.; Seifert, G.;
In structured or self-organized materials spatial confinement effects lead to structure- and interface-controlled modifications of the bulk transport properties. In part, such modifications can be accounted for by a classical master equation approach for the transport of the different charge carrier species. The rather large quantity of parameters, which enter such an approach, can more or less easily be adjusted to the dimensional characteristics, local potential changes at interfaces, and the electronic settings of the system as well as to temperature effects. On the other hand, a microscopically more detailed and mostly parameter-free picture is obtained from a quantum-mechanical treatment on the basis of the density-functional theory. An extension by a Green's function formalism allows the determination and analysis of electronic transport through contacted nanostructures. Examples will be given to demonstrate the applicability of the different approaches for dissipative and hopping transport through a regular array of nanostructures, for a mechanically triggered metal-insulator transition in nanowires, and for the enhanced conductivity at multiferroic domain walls.
Keywords: conduction, calculation, OFET, ferroic, FerroFET, ferrorganics

Publ.-Id: 13185 - Permalink


First-principles study of ferroelectric domain walls in multiferroic bismuth ferrite
Lubk, A.; Gemming, S.; Spaldin, N. A.;
We present a first-principles density-functional study of the structural, electronic, and magnetic properties of the ferroelectric domain walls in multiferroic BiFeO3. We find that domain walls in which the rotations of the oxygen octahedra do not change their phase when the polarization reorients are the most favorable and of these, the 109° domain wall centered around the BiO plane has the lowest energy. The 109° and 180° walls have a significant change in the component of their polarization perpendicular to the wall; the corresponding step in the electrostatic potential is consistent with a recent report of electrical conductivity at the domain walls. Finally, we show that changes in the Fe-O-Fe bond angles at the domain walls cause changes in the canting of the Fe magnetic moments which can enhance the local magnetization at the domain walls.
Keywords: Bismuth ferrite, multiferroic, ferroic, domain wall, boundary, density-functional, calculation, conductivity
  • Physical Review B 80(2009), 104110
    DOI: 10.1103/PhysRevB.80.104110
  • Poster
    DPG Frühjahrstagung der Sektion Kondensierte Materie (SKM) 2010, 21.-26.03.2010, Regensburg, Deutschland

Publ.-Id: 13184 - Permalink


Effect of low nitrogen concentrations on the electronic properties of InAs1−xNx
Patanè, A.; Feu, W. H. M.; Makarovsky, O.; Drachenko, O.; Eaves, L.; Krier, A.; Zhuang, Q. D.; Helm, M.; Goiran, M.; Hill, G.;
We report cyclotron resonance (CR), transverse magnetoresistance (MR), and Hall effect studies of a series of n-type InAs1−xNx epilayers grown on GaAs with x up to 1%. The well-resolved CR absorption lines, the classical linear MR, Shubnikov–de Haas magneto-oscillations, and negative MR revealed in our experiments provide a means of probing the effect of the N atoms on the electronic properties of this alloy system and reveal qualitative differences compared to the case of the wider gap III-N-V compounds, such as GaAs1−xNx. In GaAs1−xNx electron localization by N levels that are resonant with the extended band states of the host crystal act to degrade the electrical conductivity at small x (~0.1%). These phenomena are significantly weaker in InAs1−xNx due to the smaller energy gap and higher energy of the N levels relative to the conduction band minimum. In InAs1−xNx the electrical conductivity retains the characteristic features of transport through extended states, with electron coherence lengths (l~100 nm at 2 K) and electron mobilities (µ=6×103 cm2 V−1 s−1 at 300 K) that remain relatively large even at x=1%.
Keywords: InAsN, dilute nitride, magnetotransport, cyclotron resonance

Publ.-Id: 13183 - Permalink


U(VI) biosorption and biomineralization by Sulfolobus acidocaldarius
Reitz, T.; Merroun, M. L.; Li, B.; Foerstendorf, H.; Rossberg, A.; Steudtner, R.; Selenska-Pobell, S.;
Microorganisms, along with the abiotic physicochemical factors, strongly influence migration of uranium in nature. In contrast to the well investigated interactions of bacteria with uranium, the influence of archaea on the natural behaviour of this radionuclide is still not well studied. In this work the interactions of the acidothermophilic archaeon Sulfolobus acidocaldarius DSM 639 with U(VI) at acidic conditions (pH 1.5, 3, 4.5 and 6) were investigated. These pH values are relevant for some heavy metal and uranium polluted environments where S. acidocaldarius is also distributed. After the contact with the archaeal cells, U(VI) was rapidly complexed, whereby the binding capacity was strongly influenced by the pH value and the biomass concentration. A combination of X-ray absorption spectroscopy, Fourier-transform infrared spectroscopy, and time-resolved laser-induced fluorescence spectroscopy revealed that at highly acidic conditions (pH 1.5 and 3) U(VI) is predominantly bound to organic phosphate groups. At pH 4.5 carboxylic groups are involved in the U(VI) complexation as well. However, at this pH part of the added U(VI) was precipitated in inorganic uranyl phosphate mineral phases. The latter were the most predominant uranium complexes found after the treatment of the cells with U(VI) for 48 hours at pH 6. Transmission electron microscopic analysis of the cells treated at pH 4.5 showed extracellular and intracellular U(VI) accumulates. The extracellular complexes represented mainly inorganic uranyl phosphate complexes, which were formed due to the liberation of orthophosphate by the cells. The formation of the intracellular uranyl phosphate deposits is attributed to uncontrolled uptake of U(VI) as a result of the increased cell permeability due to the stress of the non-optimal pH and uranium toxicity. Our results demonstrate that at moderate acidic conditions S. acidocaldarius immobilizes U(VI) via biosorption and biomineralization.
  • Lecture (Conference)
    8th Symposium on remediation in Jena - “Jenaer Sanierungskolloqium”, 28.-29.09.2009, Jena, Deutschland
  • Lecture (others)
    Internes Seminar (Angewandte Naturwissenschaft), 22.11.2009, Freiberg, Deutschland

Publ.-Id: 13182 - Permalink


The role of Ge-related oxygen-deficiency centers in controlling the blueviolet photo- and electroluminescence in Ge-rich SiO2 via Er doping
Kanjilal, A.; Tsushima, S.; Götz, C.; Rebohle, L.; Voelskow, M.; Skorupa, W.; Helm, M.;
Using combined electroluminescence (EL) and photoluminescence (PL) studies we establish that the energy transfer process from the Er3+ to the Ge-related oxygen-deficiency centers (GeODCs) plays the key role in enhancing the 404 nm EL intensity in Ge-rich SiO2. Er doping induced structural modification does not appear to be relevant, which is deduced from the 404 nm PL quenching with increasing Er concentration, implying a gradual loss of GeODCs. In contrast to PL, the 404 nm EL intensity increases by 0.3% Er doping followed by a gradual decrease in intensity for higher Er concentrations, which is described in terms of a competition between the energy transfer process and the gradual segregation of Er due to the destruction of GeODCs with Er doping. This fact is further discussed in the light of ab initio molecular orbital calculations.
Keywords: Ge, Er, EL, PL

Publ.-Id: 13181 - Permalink


Implantation-assisted Co-doped CdS thin films: Structural, optical, and vibrational properties
Chandramohan, S.; Kanjilal, A.; Sarangi, S. N.; Majumder, S.; Sathyamoorthy, R.; Som, T.;
This paper reports on structural, optical, vibrational, and morphological properties of cobalt-doped CdS thin films, prepared by 90 keV Co+ implantation at room temperature. In this work, we have used cobalt concentration in the range of 0.34–10.8 at. %. Cobalt doping does not lead to the formation of any secondary phase, either in the form of metallic clusters or impurity complexes. However, with increasing cobalt concentration a decrease in the optical band gap, from 2.39 to 2.26 eV, is observed. This reduction is addressed on the basis of band tailing due to the creation of localized energy states in association with Urbach energy calculations. In addition, implantation gives rise to grain growth and increase in the surface roughness. Size and shape fluctuations of individual CdS grains, at higher fluences, give rise to inhomogeneity in strain. The results are discussed in the light of ion-matter interaction in the keV regime.
Keywords: CdS, Co doping

Publ.-Id: 13180 - Permalink


Domain-wall pinning and depinning at magnetic soft spots in nanowires
Wintz, S.; Vogel, A.; Moser, J.; Bolte, M.; Strache, T.; Fritzsche, M.; Im, M.-Y.; Fischer, P.; Meier, G.; Fassbender, J.ORC
The controlled motion of magnetic domain walls (DWs) in nanowires is one of the fundamental issues for the realization of new concepts of high-density and ultrafast non-volatile data-storage devices. Locally welldefined confining potentials, e.g., created by notches, act as pinning sites for individual DWs . A spin polarized current, driven through the nanowire, yields the possibility to manipulate the magnetic configuration due to a transfer of spin-angular momentum. For a reliable spin-torque induced domain-wall depinning, low threshold currents are required in order to reduce stochastic temperature effects, caused by Joule heating as well as to avoid damage to the nanowire.

Here we present a concept to create pinning sites for DWs in magnetic nanowires without geometric constrictions:
The local modification of magnetic properties by means of ion irradiation (magnetic soft spots). Implantation of chromium ions into Ni80Fe20 causes a reduction of the saturation magnetization (Ms) and changes the crystalline magnetic anisotropy. The application of electron beam lithography (EBL) or focused ion beam (FIB) on the other hand enables a spatial resolution below 50 nm for this kind of magnetic patterning process. Pinning of DWs in magnetic soft spots is expected to be preferred compared to the environment, as the locally reduced Ms causes a decrease of the exchange energy associated with the DW. In order to verify the suitability of our concept, we fabricate magnetic soft spots into Ni80Fe20 nanowires by means of 15 kV Cr ion irradiation through an EBL shadow mask and examine the pinning characteristics for DWs.

In conclusion, magnetic soft spots realized via implantation of chromium are suitable as pinning sites for domain walls, avoiding a local increase of the current density in the nanowire due to supplementary spatial constriction.
Keywords: Magnetism, Domain Wall, Nanowire, Pinning, Soft-Spots
  • Poster
    11th Joint MMM-Intermag Conference, 18.-22.01.2010, Washington D.C., USA

Publ.-Id: 13179 - Permalink


Laser Particle Acceleration for Radiotherapy: A first radiobiological characterization of laser accelerated electrons
Pawelke, J.; Beyreuther, E.; Enghardt, W.; Kaluza, M.; Karsch, L.; Laschinsky, L.; Leßmann, E.; Naumburger, D.; Nicolai, M.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H.-P.; Baumann, M.;
In recent years, the technology of laser-based particle acceleration has developed at such a rate that compact and potentially more cost-effective accelerators are promised for medical application, e.g. for high precision hadron radiotherapy. Necessary requirements are the supply of stable and reliable particle beams with reproducible properties, sufficient particle intensities and monoenergetic spectra. Additionally, a precise dose delivery in an appropriate time and the exposure of a desired irradiation field are needed. Beside these physical demands, the consequences on detection and dosimetry as well as the radiobiological effect on living cells have to be investigated for the ultra-short pulsed laser-based particle beams. As a first step, the laser accelerator facility at the Jena Titanium:Sapphire system was customized for in vitro cell irradiation experiments and the delivered electron beam was im-proved with regard to its spectrum, diameter, dose rate and dose homogeneity. Furthermore, a custom-designed beam and dose monitoring system was established that enables real-time monitoring of the irradiation experiments and a precise determination of the dose delivered to the cells. Moreover, stable and reproducible beam properties were achieved during the whole three month experiment campaign. Dose-effect-curves were obtained for four cell lines and two endpoints, generally displaying a lower biological effectiveness for short-pulsed laser-accelerated electrons relative to the continuous 200 kV X-ray reference irradiation. Possible reasons will be discussed.
  • Lecture (Conference)
    World Congress on Medical Physics and Biomedical Engineering 2009, 07.-12.09.2009, München, Deutschland
  • Contribution to proceedings
    World Congress on Medical Physics and Biomedical Engineering 2009, 07.-12.09.2009, München, Deutschland
    WC 2009, IFMBE Proceedings 25/III: Springer, 502-504

Publ.-Id: 13178 - Permalink


Laser particle accelerators for radiotherapy – first radiobiological in vitro cell characterisation
Naumburger, D.; Beyreuther, E.; Enghardt, W.; Kaluza, M.; Karsch, L.; Laschinsky, L.; Leßmann, E.; Nicolai, M.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H.-P.; Baumann, M.;
The novel technology of particle acceleration based on high intensity laser systems promises radiotherapy accelerators of compact size and reasonable costs. Laser acceleration results in ultra-short pulsed particle beams (in the region of 100 fs) with very high pulse dose rate (more than 1012 Gy/min) and is used in single shot physics experiments so far. Before a conceivable clinical application such particle beams have to be characterized in terms of their radiobiological properties and dosimetric detection and must allow a stable and reliable dose delivery. First in vitro cell irradiations with laser accelerated electron beams were performed and dose-effect-curves were obtained for four cell lines and two endpoints. Experiments have been performed at the Jena Titanium:Sapphire 10 terawatt laser system JETI, accelerating electrons to energies of up to 20 MeV. Before cell irradiation, the JETI system was optimized, adjusting the electron energy and beam spot size and improving the dose rate and homogeneity. Cell irradiations with doses in the range of 0.3 to 10 Gy have been performed for two squamous cell carcinoma cell lines with different radiosensitivity (FaDu, SKX) and two normal tissue cell lines (mammary gland epithelial cells 184A1, human skin fibroblasts HSF2). Each sample was equipped with radiochromic films used for retrospective precise dose determination. A Roos ionization chamber and a Faraday Cup monitored the beam providing online dose information necessary for irradiation control. Following to the irradiation the cell survival fraction was determined using clonogenic survival assay. Furthermore DNA double strand breaks were analyzed by immunochemical detection of the colocalized γH2AX and 53BP1 proteins 24 h after irradiation. Reference irradiation with a conventional X-ray tube (200 kV) was performed in parallel with experiments at JETI.
Samples were irradiated over a period of 3 months with described doses in which a reasonably stable and reproducible beam could be achieved monitored by the reliable accurate dosimetry system. The dose-effect-curves obtained indicate a lower biological effectiveness for the ultra-short pulsed laser accelerated electron beams in comparison with continuous X-rays. Possible reasons could be the different energy spectra impacting on cells as well as the low mean and ultra-high pulse dose rate of the electron beam. The effects will be discussed based on further experimental results.
This work has been supported by the German Federal Ministry of Education and Research (BMBF), grant no. 03ZIK445.
  • Lecture (Conference)
    37th Annual Meeting of the European Radiation Research Society, 26.08.-29.09.2009, Prague, Tschechische Republik

Publ.-Id: 13177 - Permalink


Does the high pulse dose rate affect the biological efficiency of laser accelerated electrons?
Beyreuther, E.; Karsch, L.; Laschinsky, L.; Leßmann, E.; Naumburger, D.; Richter, C.; Pawelke, J.;
In recent years, the technology of laser-based particle acceleration was rapidly developed promising compact and potentially more cost-effective accelerators for medical applications, especially for hadron therapy. Beside specific physical requirements, e.g. stability and reliability of the particle beam as well as sufficient particle intensities, these ultra-short pulsed particle beams have to be investigated with regard to their radiobiological characteristics.
As a first step, in vitro cell irradiation experiments were performed using laser accelerated electron beams generated at the Jena Titanium:Sapphire laser system (JETI). Two biological endpoints, the clonogenic survival and remaining DNA double-strand breaks, were analyzed revealing in general a lower biological effectiveness for laser accelerated electrons relative to the continuous 200 kV X-ray reference source. Possible reasons might be the low mean and ultra-high pulse dose rate as well as the different electron spectra delivered to the cells.
The influence of the ultra-high pulse dose rate was assessed using pulsed electrons produced by the electron accelerator ELBE (Electron Linac for beams with high Brilliance and low Emittance) at the Forschungszentrum Dresden-Rossendorf. Based on a superconducting linear accelerator ELBE provides monoenergetic electrons of 20 MeV with a micropulse repetition rate of 13 MHz, a variable time structure that allows for single pulse or continuous irradiations and pulse doses tuneable over more than six orders of magnitude. Consequently, the ELBE beam can be used to mimic laser accelerated ultra-short pulses or for a continuous electron beam generated in a conventional radiotherapy linac.
Both pulse regimes were applied in the present study in order to investigate the influence of the pulse dose rate on the biological effectiveness independent on electron spectra, irradiation setup and dosimetry approach. The biological endpoints assessed at the JETI experiments were also analysed in two normal human cell lines (fibroblast, epithelial). In parallel, the clonogenic survival and DNA double-strand breaks remaining 24 hours post irradiation were also determined at the 200 kV X-ray reference source. To sum up the preliminary results, no significant differences were found for the biological effectiveness of continuous and ultra-short pulsed ELBE electrons relative to 200 kV X-rays. Further results and possible explanations will be discussed.
This work has been supported by the German Federal Ministry of Education and Research (BMBF) under contract 03ZIK445.
  • Lecture (Conference)
    37th Annual Meeting of the European Radiation Research Society, 26.08.-29.09.2009, Prague, Tschechische Republik

Publ.-Id: 13176 - Permalink


Laser particle accelerators for radiotherapy: first in vitro cell experiments with laser accelerated electron beams
Laschinsky, L.; Beyreuther, E.; Enghardt, W.; Karsch, L.; Leßmann, E.; Naumburger, D.; Nicolai, M.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H.-P.; Baumann, M.;
Objective
The novel technology of particle acceleration based on high intensity laser systems promises accelerators of compact size and reasonable costs and may significantly contribute to a widespread use of high precision hadron radiotherapy. Although some basic properties of laser acceleration are reasonably well known from theory, simulations and fundamental physical experiments, several further requests have to be fulfilled for its medical application such as supply of a stable and reliable particle beam with reproducible properties and precise delivery of dose in an appropriate irradiation time with required exposure of a desired irradiation field. Moreover, the ultra-short pulsed (in the region of 100 fs) particle beams with resulting high pulse dose-rate (more than 1012 Gy/min) have to be characterized with regard to there radiobiological properties. First in-vitro cell irradiations with laser accelerated electron beams were performed and dose-effect-curves were obtained for four cell lines and two endpoints.

Material and Methods
Experiments have been performed at the Jena Titanium:Sapphire 10 terawatt laser system JeTi. Laser pulses (80 fs duration, 2.5 Hz repetition rate) were focused into a helium gas jet, accelerating electrons to energies of up to few ten MeV. Before irradiation, the JeTi system was optimized for cell experiments: the electron spectrum was limited to a minimum energy of 3 MeV, the beam spot size was adjusted and the dose rate and homogeneity were improved. Cell irradiations with doses in the range of 0.3 to 10 Gy have been performed for two squamous cell carcinoma (FaDu, SKX) and two normal tissue (mammary gland epithelial cells 184A1, human skin fibroblasts HSF2) cell lines. Each sample was equipped with two Gafchromic EBT radiochromic films, one in front and one behind the cell monolayer, used for retrospective precise dose determination. A Roos ionization chamber and a Faraday Cup monitored the beam providing on-line dose information necessary for irradiation control.
Following to the irradiation the cell survival fraction was determined using clonogenic survival assay. In addition, DNA double strand breaks present in cell 24 h after irradiation were analyzed by immunochemical detection of co-localized gamma-H2AX and 53BP1 molecules. Reference irradiation with a conventional X-ray tube (200 kV) was performed in parallel with experiments at JeTi.

Results
Normally used for physical single-shot experiments, the JeTi was customized for a long-time cell irradiation. Samples were irradiated at 13 experiment days over a period of 10 weeks. A reasonably stable and reproducible beam was achieved. Reviewed as average out of all cell irradiations a mean dose per pulse of 2.4 mGy was obtained. Comparing all samples, a variation in beam intensity of up to 40 % within one day and up to 130 % within all days was observed, but was compensated during cell irradiations by means of the on-line dose monitoring system. Dose homogeneity was examined for all samples within the target area and the inhomogeneity obtained was less than 10 % for all days and all applied doses. Although still preliminary, the dose-effect-curves obtained show in general a lower biological effectiveness for the laser accelerated electron beams in comparison with conventional X-rays. Possible reasons will be discussed.

Conclusions
Further experiments are prepared at a 100 terawatt laser system, which will lead to enhanced energy and intensity of the electron beam but also provide laser accelerated proton beams for cell irradiation studies.

The work was supported by the BMBF, grant no. 03ZIK445
Keywords: radiotherapy
  • Lecture (Conference)
    Fourth International Conference on Translational Research and Pre-Clinical Strategies in Radiation Oncology, 11.-13.03.2009, Geneva, Switzerland
  • Abstract in refereed journal
    Radiotherapy and Oncology 90(2009)Suppl 3

Publ.-Id: 13175 - Permalink


Systematic in vitro cell experiments with laser accelerated electron beams
Laschinsky, L.; Beyreuther, E.; Enghardt, W.; Karsch, L.; Leßmann, E.; Kaluza, M.; Naumburger, D.; Nicolai, M.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H.-P.; Baumann, M.;
Purpose: The novel technology of particle acceleration based on high intensity laser systems promises ion radiotherapy accelerators of compact size and reasonable costs. Laser acceleration results in ultra-short pulsed particle beams with very high pulse dose-rate and is used in single shot physics experiments so far. Such particle beams have to be characterized in terms of their radiobiological properties and dosimetric detection and must allow a stable and reliable dose delivery before a conceivable clinical application. In a first step, systematic in vitro cell irradiations with laser accelerated electron beams were performed and dose-effect-curves were obtained.

Material: Experiments have been performed at the Jena Titanium:Sapphire (JeTi) 10 terawatt laser system. Laser pulses (80 fs duration) were focused into a helium gas jet, accelerating electrons to energies of up to 20 MeV. Before cell irradiation, the JeTi system was optimized, adjusting the electron energy and beam spot size and improving the dose rate and homogeneity. Cell irradiations were realized for two squamous cell carcinoma (FaDu, SKX) and two normal tissue (184A1, HSF2) cell lines in a dose range from 0.3 Gy to 10 Gy. For irradiation control a Roos ionization chamber and a Faraday Cup monitored the beam providing on-line dose information. Additional Gafchromic EBT radiochromic films were used for retrospective exact dose determination at the cell site. Referring to irradiation the survival fraction was determined and furthermore DNA double strand breaks were analyzed by immunochemical detection of the co-localized γH2AX and 53BP1 molecules 24 h after irradiation. A conventional X-ray tube (200 kV) was used for reference irradiation.

Results: The JeTi laser accelerator was successfully customized for long-time irradiation of cell samples with prescribed doses. Samples were irradiated at 13 experiment days over a period of 3 months. A reasonably stable and reproducible beam was achieved. Dose homogeneity was examined for all samples inside the target area and the inhomogeneity obtained was less than 10 % for all days and all applied doses. The determined dose-effect-curves show in general a reduced biological effectiveness for the laser accelerated electron beams in comparison with conventional X-rays. The effect of the high pulse dose-rate among the possible reasons will be discussed.

Conclusion: Further experiments are prepared at a 100 terawatt laser system, which will provide laser accelerated proton beams for cell irradiation studies.

This work was supported by the BMBF, grant no. 03ZIK445
  • Lecture (Conference)
    10th BIENNIAL ESTRO CONFERENCE ON PHYSICS AND RADIATION TECHNOLOGY FOR CLINICAL RADIOTHERAPY, 30.08.-03.09.2009, Maastricht, Netherlands
  • Contribution to proceedings
    10th BIENNIAL ESTRO CONFERENCE ON PHYSICS AND RADIATION TECHNOLOGY FOR CLINICAL RADIOTHERAPY, 30.08.-03.09.2009, Maastricht, Netherlands
    Radiother. Oncol. 92 (Suppl. 1)(2009) S89

Publ.-Id: 13174 - Permalink


Mit laserbeschleunigten Teilchen gegen Tumore – erste in vitro Experimente an laserbeschleunigten Elektronentrahlen
Naumburger, D.; Beyreuther, E.; Enghardt, W.; Karsch, L.; Lessmann, E.; Messner, L.; Nicolai, M.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H.-P.; Baumann, M.;
Mit der neuartigen Technologie der Laser-Beschleunigung von Ionen werden kürzere Teilchenpakete (einige 10 Femtosekunden) mit wesentlich geringerer Pulsfrequenz und damit einhergehend einer viel höheren Puls-Dosisleistung erzeugt. Ziel ist es, durch Einsatz dieser Technologie die bisherige Strahlentherapie zu verbessern.
In einem ersten Schritt bei der Ermittlung einer möglicherweise veränderten biologischen Wirksamkeit dieser neuen Strahlenqualität wurden in vitro Bestrahlungsexperimente von Tumor- und Normalgewebszellen mit laserbeschleunigten Elektronen durchgeführt. Für die Experimente wurde das 10-Terawatt-Lasersystem JETI in Jena genutzt. Voraussetzung für die Zellbestrahlung war die Anpassung des Lasersystems und der Aufbau eines geeigneten Bestrahlungsplatzes einschließlich eines Dosimetriesystems. Im Anschluss an die Bestrahlung wurde das klonogene Zellüberleben mittels Koloniebildungstests bestimmt. Ergänzend hierzu wurde als weiterer biologischer Endpunkt der Nachweis der mit der DNA-Reparatur assoziierten Proteine g-H2AX und p53BP1 gewählt. g-H2AX reguliert als Histon die Zugänglichkeit der DNA für Reparaturmechanismen und ist mitverantwortlich für die Arretierung der Zelle in einer Phase des Zellzyklus als zelluläre Antwort auf niedrige Strahlendosen. Zusammen mit p53BP1 bildet es unmittelbar nach der Bestrahlung diskrete Foci an DNA-Doppelstrangbrüchen. Das verglichen mit unbestrahlten Proben erhöhte Auftreten von g-H2AX/p53BP1 Foci 24 h nach Bestrahlung ist ein Maß für residuelle, Dosis vermittelte DNA-Doppelstrangbrüche. Der Nachweis erfolgte mit dem g-H2AX/p53BP1 Foci Assay. Die Dosis-Effekt Kurven für beide Endpunkte werden präsentiert und diskutiert.
Die Genauigkeit beider Assays soll künftig durch Teilautomatisierung (z.B. FACS) verbessert werden. Des Weiteren wurde mit der Vorbereitung von Zellbestrahlungsexperimenten mit laserbeschleunigten Protonenstrahlen begonnen.
  • Lecture (Conference)
    11. Jahrestagung der Gesellschaft für Biologische Strahlenforschung GBS Tübingen, 06.-08.10.2008, Tübingen, Deutschland

Publ.-Id: 13173 - Permalink


Realistic integration of sorption processes in transport programs for long-term safety analysis
Brendler, V.; Stockmann, M.; Noseck, U.; Püschel, A.;
Safety assessment of radioactive waste repositories in salt rock formations considers the overlying sedimentary rock above the salt domes as important barrier. Sorption on mineral surfaces of the sediment can retard the transport of many contaminants, namely radionuclides, considerably. Previously, the retention of radionuclides has been described in respective computer programs by temporally constant distribution coefficients.
In the present study, an existing transport program r3t [1] is extended towards a more realistic description of the radionuclide migration under changing geochemical conditions. The methodology developed here is based on a description of the sorption of radionuclides as a function of important influence factors such as pH, pCO2, ionic strength, and the mineral phases being present. Applying surface complexation models, multidimensional matrices of “smart Kd”-values can be computed a-priori. The reactive transport model r3t then can call for each time-space point Kd values adapted for the correct geochemical conditions. The biggest challenge here was finding a fast and robust algorithm for search and averaging in multidimensional matrices with non-equidistant population (see e.g. [2]). First results are presented for a test case where respective site-specific geochemical conditions in the overlying rock have been evaluated, mainly consisting of tertiary and quaternary sands and clays [3].
References:
[1] Fein, E., Software Package r3t. Model for Transport and Retention in Porous Media. Final Report. Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) mbH, Report GRS-192, Braunschweig 2004.
[2] McNames, J.: A fast nearest neighbor algorithm based on a principal axis search tree. IEEE Trans. Pattern Analysis Machine Intell. 23 (2001), 964-976.
[3] Klinge, H., Köthe, A., Ludwig, R.-R., Zwirner, R., Geologie und Hydrogeologie des Deckgebirges über dem Salzstock Gorleben. Z. Angew. Geol. 2 (2002), 7-15.
  • Poster
    ICEM'09, 11.-16.10.2009, Liverpool, Great Britain

Publ.-Id: 13171 - Permalink


P0802 - Hochgeordnete Nanostruktur und Sensor und deren Verwendung
Pollmann, K.; Raff, J.; Fahmy, K.;
Die vorliegende Erfindung betrifft eine hochgeordnete Nanostruktur und Sensor, in der bzw. dem organische Molekülgruppen, die spezifische Bindungseigenschaften für ein Zielmolekül haben, geordnet gebunden sind, und deren Verwendung. Anwendungsgebiet dafür finden sich in der Biotechnologie, Verfahrenstechnik, Umwelttechnik und Pharmazie, insbesondere bei der Herstellung von Biosensoren, in der biomedizinischen Analytik, bei der Beseitigung von Schadstoffen und Pathogenen, in der DNA-Analytik, für die Herstellung von Filtermaterialien, für Separationsverfahren, für Katalysatoren und in der medizinischen Therapie. Die Aufgabe der Erfin-dung ist es, eine Struktur zur Verfügung zu stellen, in der organische Molekülgruppen, insbesondere Molekülgruppen, die spezifische Bindungseigenschaften haben, geordnet gebunden sind, und dadurch die von den organischen Molekülgruppen gebundenen Substanzen in die Nähe funktioneller Bestandteile zu bringen. Dies wird gelöst durch eine Nanostruktur, die selbstorganisierende Prote-ine, an die Aptamere oder andere organische Molekülgruppen, die spezifische Bindungseigenschaften für ein Zielmolekül aufweisen, gebunden sind, und an die selbst-organisierenden Proteine gebundene anorganische Nanopartikel enthält.
  • Patent
    DE 2008014298 A1 - 24 09. 2009
  • Patent
    EP 2101 175 A1 - 16. 09. 2009
  • Patent
    EP 2101175 B1 - 16.09. 2012

Publ.-Id: 13170 - Permalink


ESR in low-dimensional quantum magnets
Zvyagin, S. A.;
hat nicht vorgelegen
  • Invited lecture (Conferences)
    National High Magnetic Field Laboratory, Tallahassee, 15.09.2009, Tallahassee, USA

Publ.-Id: 13169 - Permalink


On the long way to laser particle therapy: Results of radiobiological experiments with laser accelerated electrons and future experiments with laser accelerated protons
Richter, C.; Beyreuther, E.; Enghardt, W.; Kaluza, M.; Karsch, L.; Laschinsky, L.; Leßmann, E.; Naumburger, D.; Nicolai, M.; Pawelke, J.; Sobiella, M.; Sauerbrey, R.; Schlenvoigt, H.-P.; Schürer, M.; Baumann, M.;
Background: The novel technology of particle acceleration based on high intensity laser systems promises proton therapy accelerators of compact size and reasonable costs. Laser acceleration results in ultra-short pulsed (≈100 fs) particle beams with very high pulse dose-rate (in the order of 1012 Gy/min). These beams have to be characterized with regard to their radiobiological and dosimetric properties and must allow a stable and reliable dose delivery before a conceivable clinical application is possible. The results of the worldwide first systematic in vitro cell irradiation experiments with laser accelerated electrons will be presented. Moreover, the developed dosimetric requirements for cell irradiation experiments with laser accelerated protons of low energy will be presented.

Material and Methods: The experiments with laser accelerated electrons have been performed at the Jena Titanium:Sapphire (JeTi) 10 TW laser system. Laser pulses were focused into a helium gas jet, accelerating electrons to energies of up to 20 MeV. Cell irradiations were realized for two squamous cell carcinoma and two normal tissue cell lines in a dose range from 0.3 Gy to 10 Gy. For irradiation control an ionization chamber and a Faraday Cup provided online dose information. Additional Gafchromic EBT radiochromic films were used for retrospective exact dose determination at the cell site. Referring to irradiation the survival fraction was determined and furthermore DNA double strand breaks 24 h after irradiation were analyzed.
Moreover, an integrated dosimetry and cell irradiation device (IDCID) has been designed and optimized for laser accelerated proton beams of low energy. It integrates an online- and absolute dosimeter system in combination with an in vitro cell irradiation device. Furthermore, the different detectors and dosimeters of the IDCID have been tested and cross calibrated at the tandem accelerator of the Forschungszentrum Dresden-Rossendorf. For the application of radiochromic films within the IDCID, EBT films have been calibrated for different proton spectra at the eye irradiation facility of the Helmholtz Zentrum Berlin.

Results:
The determined dose-effect-curves for laser accelerated electrons show in general a reduced biological effectiveness in comparison with conventional X-rays. The effect of the high pulse dose-rate among the possible reasons will be discussed. Furthermore, calibration curves for EBT films have been determined for 6 energies between 5 and 62 MeV. For energies between 10 and 62 MeV no significant energy dependence was found. Moreover, results of the optimization and cross calibration of the detectors included in the IDCID will be shown.

Conclusion: A laser particle accelerator was successfully used to perform long-time systematic in vitro cell irradiations. Further cell irradiation experiments with laser accelerated protons from a 100 TW laser system are prepared.

This work was supported by the BMBF, grant no. 03ZIK445
  • Poster
    PTCOG 48, 28.09.-03.10.2009, Heidelberg, Dresden

Publ.-Id: 13168 - Permalink


Energy dependence of EBT-1 radiochromic film response for photon (10 kVp - 15 MVp) and electron beams (6 - 18 MeV) readout by a flatbed scanner
Richter, C.; Karsch, L.; Woithe, J.; Pawelke, J.;
Purpose: The aim of this paper is to investigate the energy dependence of the radiochromic film type, Gafchromic EBT-1, when scanned with a flatbed scanner for film readout.

Methods: Dose response curves were determined for 12 different beam qualities ranging from a 10 kVp x-ray beam to a 15 MVp x-ray beam and include also two high energy electron beam qualities (6 and 18 MeV). The dose responses measured as net optical density (netOD) for the different beam qualities were normalized to the response of a reference beam quality (6 MVp).

Results: A strong systematic energy dependence of the film response was found. The lower the effective beam energy the less sensitive the EBT-1 films get. The maximum decrease in dose for the same film response between the 25 kVp and 6 MVp beam qualities was 44 %. Additionally, a difference in energy dependence for different doses was discovered, meaning that higher doses show a smaller dependency on energy than lower doses. The maximum decrease in normalized netOD was found to be 25 % for a dose of 0.5 Gy relative to the normalized netOD for 10 Gy. Moreover, a scaling procedure is introduced, allowing the correction of the energy dependence for the investigated beam qualities and also for comparable x-ray beam qualities within the energy range studied.

Conclusions: A strong energy dependence for EBT-1 radiochromic films was found. The films were readout with a flatbed scanner. If the effective beam energy is known, the energy dependence can be corrected with the introduced scaling procedure. Further investigation of the influence of the spectral band of the readout device on energy dependence is needed to understand the reason for the different energy dependence found in this and previous works.
Keywords: flatbed scanner, radiochromic film, energy dependence, dosimetry

Publ.-Id: 13167 - Permalink


An integrated dosimetry and cell irradiation device for in vitro cell experiments withlaser accelerated protons
Richter, C.; Karsch, L.; Sobiella, M.; Weber, A.; Pawelke, J.; Baumann, M.;
Background: The novel technology of particle acceleration based on high intensity laser systems promises accelerators of compact size and reasonable costs and may significantly contribute to a widespread use of hadron radiotherapy. Although some basic properties of laser acceleration are reasonably well known from theory, simulations and fundamental physical experiments, several requests have to be fulfilled for its medical application. Moreover, the ultra-short pulsed (≈100 fs) particle beams with resulting high pulse dose-rate (in the order of 1012 Gy/min) have to be characterized with regard to their radiobiological properties. Therefore a precise dosimetry is necessary that takes into account the special characteristics of the laser accelerated protons. Special attention has to be drawn on the low energy (<10 MeV) of the available laser accelerated proton beams.

Material and Methods: An integrated dosimetry and cell irradiation device has been designed and optimized for the use with a laser accelerated proton beam of low energy. The device consists of a kapton vacuum window, an ultra-thin (25 µm) ionisation chamber for online dose information, a faraday cup inset for absolute dosimetry that can be replaced with a cell holder inset for cell irradiations. Moreover radiochromic films, i.e. Gafchromic EBT, can be placed in the cell holder inset matching the plane of the cell mono layer. Radiochromic films can be used to determine the two dimensional dose distribution and also for absolute dosimetry. For these purposes Gafchromic EBT films have been calibrated for different proton spectra at the eye irradiation facility of the Helmholtz Zentrum Berlin. Moreover first tests of the Faraday cup and the ionisation chamber have been carried out at the tandem accelerator of the Forschungszentrum Dresden-Rossendorf to characterize these detectors.
Fig 1: Integrated dosimetry and cell irradiation device

Results: Calibration curves for EBT films have been determined for 6 energies between 5 and 62 MeV and doses between 0.5 and 15 Gy. For energies between 10 and 62 MeV no significant energy dependence was found, whereas for 5 MeV protons the film response is reduced by up to 25 % compared to the 62 MeV proton beam quality. Moreover, this reduction in film sensitivity is dose depend. At the tandem accelerator the dependency of the Faraday cup signal from air pressure and guard ring voltage was determined. A more detailed cross calibration of Faraday Cup, ionization chamber and radiochromic films is ongoing and will be presented.

Conclusion: An integrated dosimetry and cell irradiation device for in vivo cell irradiation experiments with laser accelerated protons of low energy was designed, built and started to characterize. This includes the calibration of radiochromic films (Gafchromic EBT) and first characterizations of the different detectors.
  • Poster
    440. Wilhelm and Else Heraeus Seminar - Lasergetriebene Teilchen- und Röntgen-Stahlung für die Medizin, 13.-17.09.2009, Frauenwörth, Deutschland

Publ.-Id: 13166 - Permalink


4D in-beam positron emission tomography for verification of motion-compensated ion beam therapy
Parodi, K.; Saito, N.; Chaudhri, N.; Richter, C.; Durante, M.; Enghardt, W.; Rietzel, E.; Bert, C.;
Purpose: Clinically safe and effective treatment of intra-fractionally moving targets with scanned ion beams requires dedicated delivery techniques such as beam tracking. Apart from treatment delivery, also appropriate methods for validation of the actual tumor irradiation are highly desirable. In this contribution the feasibility of four-dimensionally (space and time) resolved, motion-compensated in-beam positron-emission-tomography (4DibPET) was addressed in experimental studies with scanned carbon ion beams.
Methods: A polymethyl methracrylate (PMMA) block sinusoidally moving left-right in beam's eye view was used as target, radiological depth changes were introduced by placing a stationary ramp-shaped absorber proximal of the moving target. Treatment delivery was compensated for motion by beam tracking. Time-resolved, motion-correlated in-beam PET data acquisition was performed during beam delivery with tracking the moving target, and prolonged after beam delivery first with the activated target still in motion and, finally, with the target at rest. Motion-compensated 4DibPET imaging was implemented and the results were compared to a stationary reference irradiation of the same treatment field. Data were used to determine feasibility of 4DibPET but also to evaluate offline in comparison to in-beam PET acquisition.
Results: 4D in-beam as well as offline PET imaging was found to be feasible and offers the possibility to verify the correct functioning of beam tracking. Motion-compensation of the imaged b+-activity distribution allows recovery of the volumetric extension of the delivered field for direct comparison with the reference stationary condition. Observed differences in terms of lateral field extension and penumbra in the direction of motion were typically less than 1 mm for both imaging strategies in comparison to the corresponding reference distributions. However, in-beam imaging retained a better spatial correlation of the measured activity with the delivered dose.
Conclusions: 4DibPET is a feasible and promising method to validate treatment delivery of scanned ion beams to moving targets. Further investigations will focus on more complex geometries and treatment planning studies with clinical data.
Keywords: in-beam PET, ion therapy, treatment verification, 4D, target motion

Publ.-Id: 13165 - Permalink


Nanostructuring of surfaces for biosensing and other "nano" applications
Günther, T.; Weinert, U.; Raff, J.; Pollmann, K.;
Many bacteria are covered with a protein envelope. These surface layer (s-layer) proteins are closely attached and anchored to the secondary cell wall polymer. The proteins used in our group derive from strains of Lysinibacillus species isolated from a uranium mining waste pile near Johanngeorgenstadt, Saxony, Germany. Once purified the disassembled S-layer keep the ability of self-organizing and self-assembling on interfaces. In vitro they form a paracrystalline protein lattice with defined pores and cavities as it can be naturally found on the bacterial surface. These protein sheets either coil up to tube-like structures or attach to surfaces. In addition to the self- assembling and organizing properties these proteins can bind high amounts of heavy metals. The ability to form monomolecular layers at interfaces qualifies them as tool for nano-patterning of surfaces. We are able to cover various surfaces with these proteins with nearly full coverage. This is possible due to recrystallization of monomers on polyelectrolyte coated surfaces. The recrystallization process can be monitored by AFM. AFM-images show the periodic nature of the protein lattice. The monomolecular character of the attached protein lattice was proven during the growth and afterwards by nanolithographic removal of the proteins. Different functional groups of the proteins are provided as binding sites for modifications such as crosslinking of molecules or binding or nucleation of inorganic particles. Therefore the lattice is a perfect immobilization matrix for different compounds as well as the assembly of sensory surfaces. A recently started project aims the development of a sensor for the optical readout of a chemical signal.
The efficient metal binding combined with the periodic alignment is used in other applications to create nanoparticles with a narrow size distribution. Currently we are optimizing the composition of the particles for photocatalysis. The high metal binding capacity itself turns the proteins into a promising material for filtering solutions as it is naturally used by the bacteria.
Keywords: nanoparticles, S-layer, surface layer, biosensor, AFM, FRET, photocatalysis
  • Poster
    Natural and Biomimetic Mechanosensing, 26.-28.09.2009, Dresden, Deutschland

Publ.-Id: 13164 - Permalink


Retention of selenium oxyanions onto kaolinite and illite
Jordan, N.; Foerstendorf, H.; Brendler, V.;
In the context of nuclear waste management, long-term safety assessments have shown that selenium-79, released from the solid waste matrix, could be one of the major isotopes contributing to the global radioactivity potentially reaching the biosphere. Selenium has a quite complex speciation, with four main oxidation states, depending on both the pH and the redox potential of the surrounding environment. Sorption onto minerals can strongly affect the availability and the mobility of selenium. It is thus of great importance to be able to characterize both at a macroscopic and a microscopic level the different processes (retention, reduction, surface precipitation, …) that can potentially take place.
Regarding the multi-barrier concept considered for deep underground storage of high level and long-lived radionuclides, clays are candidates as host rock as well as backfill materials. The main phases constituting clay rocks are minerals such as montmorillonite, bentonite, or illite, but also other compounds like iron oxides, titanium oxide, pyrite, calcite and organic matter. It has already been shown that clays and iron oxides can sorb and reduce selenium(VI) and selenium(IV) (Nguyen et al. (2005), Scheinost and Charlet (2008), Charlet et al. (2007)).
Thus, sorption experiments of selenium(VI) and selenium(IV) onto kaolinite and illite have been performed. Kaolinite and illite have been investigated since they are abundant and well crystallized clay mineral in soils. To get a better understanding of involved sorption mechanisms, a combination of both macroscopic and microscopic measurements have been used.
Kaolinite KGa1-b from the Clay Mineral Society repository has been used without further pretreatment. Illite du Puy (France) has been purified in order to remove auxiliary and minor phases to get a homo-ionic “Na-illite” clay. Then, batch experiments aiming at studying the sorption behaviour of selenium(IV) onto kaolinite and illite have been performed in NaCl and NaClO4. Preliminary results show that clays have higher affinity towards selenium(IV) compared to selenium(VI), which is an agreement with former studies on iron and aluminium oxides (Rovira et al. (2008). The influence of the suspensions´pH, as well as the ionic strength effect has been investigated. All the experiments have been performed under anoxic conditions in a glove box under N2 atmosphere (O2 < 1 ppm). Selenium speciation in solution has been checked using Hydride Generation-Atomic Absorption Spectroscopy measurements. The oxidation state of the selenium species once sorbed onto the kaolinite and illite surface has been evidenced using X-Ray Photoelectron Spectroscopy.
Electrophoresis measurements have also been performed during this work. Comparison between the zeta potential of the kaolinite and illite surfaces before and after selenium oxyanions retention has been done, to check whether the sorption takes place by chemical bonding formation or rather by electrostatic attraction.
Finally, ATR-FTIR measurements have been performed using an ATR ZnSe crystal. By comparison with former IR measurements concerning selenato and selenito-ligands containing complexes as well as phases with sorbed selenium species, the fashion binding of selenium(VI) and selenium(IV) onto illite has been evidenced.
  • Contribution to proceedings
    Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, 29.03.-01.04.2010, Nantes, France, 413-414

Publ.-Id: 13163 - Permalink


Experiments and numerical simulations of horizontal two phase flow regimes
Höhne, T.; Vallee, C.;
Stratified two-phase flow regimes can occur in the main cooling lines of Pressurized Water Reactors, Chemical plants and Oil pipelines. A relevant problem occurring is the development of wavy stratified flows which can lead to slug generation. Because slug flow cannot be predicted with the required accuracy and spatial resolution by the one-dimensional system codes, the stratified flows are increasingly modelled with computational fluid dynamics (CFD) codes. In CFD, closure models are required that must be validated. The recent improvements of the multiphase flow modelling in the ANSYS CFX code make it now possible to simulate these mechanisms in detail. In order to validate existing and further developed multiphase flow models, high-resolution measurement data is needed in time and also in space. For the experimental investigation of co-current air/water flows, the HAWAC (Horizontal Air/Water Channel) was built. The channel allows in particular the study of air/water slug flow under atmospheric pressure. Parallel to the experiments, CFD calculations were carried out. The two-fluid model was applied with a special turbulence damping procedure at the free surface. An Algebraic Interfacial Area Density (AIAD) model on the basis of the implemented mixture model was introduced, which allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface using the local liquid phase volume fraction value. The behaviour of slug generation and propagation at the experimental setup was qualitatively reproduced by the simulation, while local deviations require a continuation of the work. The creation of small instabilities due to pressure surge or an increase of interfacial momentum should be analysed in the future. Furthermore, experiments with pressure and velocity measurements are planned and will allow quantitative comparisons, also at other superficial velocities.
Keywords: CFD, horizontal flow, Multiphase flow, HAWAC
  • Contribution to proceedings
    Seventh International Conference on CFD in the Minerals and Process Industries, 09.-12.12.2009, Melbourne, Australia
    CD-ROM
  • Invited lecture (Conferences)
    Seventh International Conference on CFD in the Minerals and Process Industries, 09.-12.12.2009, Melbourne, Australia

Publ.-Id: 13162 - Permalink


Validation of CFD codes and applications in NRS
Höhne, T.;
Strong increase of usage of three-dimensional Computational Fluid Dynamics (CFD) in industrial applications because for instance
slugging,
pressurized thermal shocks,
coolant mixing,
thermal striping
cannot be predicted by traditional one-dimensional system codes with the required accuracy and spatial resolution.
Keywords: slugging, CFD, pressurized thermal shocks, coolant mixing
  • Invited lecture (Conferences)
    3rd Nordic Conference on Fluid Dynamics in the Power Industry, 15.-16.09.2009, Copenhagen, Danmark

Publ.-Id: 13161 - Permalink


On the formation of mixed vacancy-copper clusters in neutron-irradiated Fe-Cu alloys
Birkenheuer, U.; Ulbricht, A.; Bergner, F.; Gokhman, A.;
To investigate the irradiation-induced degradation of the mechanical properties of Cu-containing reactor pressure vessel steels, a set of model alloys was fabricated and neutron-irradiated up to four different doses, 0.026, 0.052, 0.10, and 0.19 dpa, using the same neutron flux (140 x10-9 dpa/s). A series of complementary experimental techniques have been applied to these samples, including PAS and SANS. We report here the analyses the of small-angle neutron scattering (SANS) experiments for the two binary Fe-Cu model alloys: Fe-0.3%Cu and Fe-0.1%Cu. Size-resolved cluster distributions functions were extracted from the scattering data and characterized by the peak radius of the distribution and the total volume fraction of the detectable precipitate clusters. A significant difference in the results for the Cu-rich and the Cu-poor model alloys could be observed. The aim of the present study is to understand the observed trends on the base of rate theoretical (RT) cluster dynamic simulations.
To this end, the time evolution of the precipitate clusters under the given irradiation conditions were simulated using standard rate theory models for pure Cu clusters. While reasonable model parameters could be found to describe the experimental data of the Fe-0.3%Cu alloy, it was impossible to reproduce the data for the Cu-poor model alloy this way. By linking the rate theory models to classical nucleation theory it could be demonstrated that no RT model could do so – no matter how involved the point defect dynamics – as long as the Cu precipitation process itself is not changed. Different mechanisms can be thought off to result in such modifications, among them heterogeneous nucleation with nanovoids as nucleus for further Cu growth, or the formation of mixed vacancy-copper aggregates throughout.
We therefore augmented our rate theory model to allow for the additional absorption of vacancies by the Cu-rich precipitates and an accompanied change in the interface energy between iron matrix and mixed clusters. Adjusting the model parameters properly the entire set of data point for all four doses and both compositions could be reproduced giving confidence that the basic idea of our RT model are reasonable. In addition, it was possible to provide some estimates on the time evolution of the average composition of the precipitate clusters. They exhibit – without any re-fitting – the same trends as the experimental cluster compositions deduced from the A-ratio of the SANS signals.
Keywords: rate theory, Fe-Cu alloys, SANS
  • Poster
    XIV International Conference on Small-Angle Scattering, 13.-18.09.2009, Oxford, United Kingdom
  • Open Access LogoJournal of Physics: Conference Series 247(2010), 012011
    DOI: 10.1088/1742-6596/247/1/012011

Publ.-Id: 13160 - Permalink


SANS investigation of neutron-irradiated Fe-Cr alloys
Ulbricht, A.; Heintze, C.; Bergner, F.; Eckerlebe, H.;
Ferritic-martensitic chromium steels are candidate materials for future applications in both Gen-IV fission and fusion technology. Experimental investigation of Fe-Cr alloys is important for the understanding of the effect of chromium on the irradiation behaviour of more complex alloys.
The materials investigated in this work are four binary Fe-Cr alloys of commercial purity with chromium contents between 2.5 and 12.5at%. Neutron irradiation was performed in the reactor BR2 at Mol (Belgium) at a temperature of 300°C and neutron flux of 9x1013 cm-2s-1 (E > 1 MeV). The neutron exposures expressed in units of displacements per atom correspond to 0.6 and 1.5 dpa.
In the SANS experiments carried out at the SANS-2 facility of GKSS, a wavelength of 0.58 nm and three detector-sample distances of 1, 4 and 16 m were used. The samples were placed in a saturation magnetic field. Special details related to the analysis of the SANS results (e.g. interference for concentrated solutions, bimodal distribution of scatterers) will be discussed in the full paper. The scattering curves obtained for the unirradiated conditions of the four Fe-Cr alloys were taken as reference in order to calculate difference scattering curves for the irradiated conditions.
We have found that (1) the volume fraction of scatterers slightly increases with neutron exposure (Fe-9at%Cr) or exhibits a saturation (Fe-2.5, 5 and 12.5at%Cr), (2) the volume fraction at 1.5 dpa is an increasing function of the chromium level with a slight increase up to Fe-9at%Cr and an abrupt increase between 9 and 12.5at%Cr, (3) the radii of irradiation-induced scatterers are essentially less than 8 nm and the size distributions can be reasonably described by a monomodal (Fe-2.5, 5 and 12.5at%Cr) or a bimodal (Fe-9at%Cr) distribution, (4) the A-ratio of 2.05 obtained for Fe-12.5at%Cr corresponds with the expectation for the alpha’-phase, (5) for the lower chromium levels the A-ratio can be explained neither as alpha’ nor as vacancy clusters alone, clusters composed of chromium and impurity carbon are possible candidates.
Conclusions will be drawn on the effect of the chromium content and the neutron exposure on the concentration and nature of the irradiation-induced scatterers. For the special case of Fe-12.5at%Cr the volume fraction of alpha’ and the solubility limit for chromium in iron at the irradiation temperature can be estimated.
Keywords: SANS, Fe-Cr alloys, neutron irradiation
  • Poster
    XIV International Conference on Small-Angle Scattering, 13.-18.09.2009, Oxford, United Kingdom
  • Open Access LogoJournal of Physics: Conference Series 247(2010), 012035
    DOI: doi:10.1088/1742-6596/247/1/012035

Publ.-Id: 13159 - Permalink


laser proton acceleration … aiming for cancer therapy
Schramm, U.;
Invited talk at 440th WE Heraeus Seminar, Frauenwörth 2009, Laser driven particle and x-ray sources for medical applications
Keywords: laser proton acceleration, cancer ion therapy
  • Invited lecture (Conferences)
    Laser driven particle and x-ray sources for medical applications, 13.-17.09.2009, Kloster Frauenwörth, Chiemsee, Deutschland

Publ.-Id: 13158 - Permalink


Laser-accelerated ion beams for future medical applications
Kraft, S.;
Recent success in laser-driven particle acceleration has increased interest in laser-generated “accelerator-quality” beams, for example, protons and ions have been produced with up to several tens of MeV per nucleon, and with extremely low emittance (<0.01 mm mrad, normalized). Compact, high-gradient laser-accelerators are therefore now being discussed as a potentially viable technology for a host of particle-beam applications, including future compact medical accelerators for medical diagnostics and therapy. After commissioning of a 150 TW laser system at the FZD, a joint research center for radiation therapy with laser-accelerator ions is being established together with the OncoRay Center for Radiation Research in Oncology, and the University Clinic of the Technical University of Dresden. The present status and future plans of the center, and the results from first proton acceleration experiments at FZD will be presented.
  • Lecture (Conference)
    World Congress on Medical Physics and Biomedical Engineering, 12.09.2009, München, Deutschland

Publ.-Id: 13157 - Permalink


Selenium(IV) retention onto ilite
Jordan, N.; Foerstendorf, H.; Brendler, V.;
In the context of nuclear waste management, long-term safety assessments have shown that selenium-79, released from the solid waste matrix, could be one of the major isotopes contributing to the global radioactivity potentially reaching the biosphere. Selenium has a quite complex speciation, with four main oxidation states, depending on both the pH and the redox potential of the surrounding environment. Sorption onto minerals can strongly affect the availability and the mobility of selenium. It is thus of great importance to be able to characterize both at a macroscopic and a microscopic level the different processes (retention, reduction, surface precipitation, …) that can potentially take place.
Regarding the multi-barrier concept considered for deep underground storage of high level and long-lived radionuclides, clays are candidates as host rock as well as backfill materials. Clays like illite, kaolinite, montmorillonite and bentonite constitute the main phases of clay rocks, together with other compounds like iron oxides, titanium oxide, pyrite, calcite and organic matter. We decided to focus our work on Illite since it is an abundant and well crystallized clay mineral in soils.
Thus, retention properties of illite towards selenium(IV) have been investigated during this study, using a combination of both macroscopic and microscopic measurements.
Illite du Puy (France) has been used as the sorbing phase. It has been purified in order to remove auxiliary and minor phases to get a homo-ionic “Na-illite” clay. Then, batch experiments aiming at studying the sorption behaviour of selenium(IV) onto illite have been performed in NaClO4. The influence of the suspensions´pH, as well as the ionic strength effect has been investigated. All the experiments have been performed under anoxic conditions in a glove box under N2 atmosphere (O2 < 1 ppm). Selenium speciation in solution has been checked using Hydride Generation-Atomic Absorption Spectroscopy measurements. The oxidation state of the selenium species once sorbed onto the illite surface has been evidenced using X-Ray Photoelectron Spectroscopy.
Electrophoresis measurements have also been performed during this work. Comparison between the zeta potential of the illite surfaces before and after selenium(IV) sorption has been done, to check whether the sorption takes place by chemical bonding formation or rather by electrostatic attraction.
Finally, ATR-FTIR measurements have been performed using an ATR ZnSe crystal. By comparison with former IR measurements concerning selenito-ligands containing complexes as well as phases with sorbed selenium species, the fashion binding of selenium(IV) onto illite has been evidenced.
  • Contribution to proceedings
    16th Radiochemical Conference, 18.-23.04.2010, Mariánské Lázne, Czech Republic, 0009-2770, s115

Publ.-Id: 13156 - Permalink


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