Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34122 Publications

Microorganisms in potential host rocks for geological disposal of nuclear waste and their interactions with radionuclides

Cherkouk, A.; Liebe, M.; Lütke, L.; Moll, H.; Stumpf, T.

The long-term safety of nuclear waste in a deep geological repository is an important issue in our society. Microorganisms indigenous to potential host rocks are able to influence the oxidation state, speciation and therefore the mobility of radionuclides as well as gas generation or canister corrosion. Therefore, for the safety assessment of such a repository it is necessary to know which microorganisms are present in the potential host rocks (e.g., clay, salt) and if these microorganisms can influence the performance of a repository.
Microbial diversity in potential host rocks for geological disposal of nuclear waste was analyzed by culture-independent molecular biological methods (e.g., 16S rRNA gene retrieval) as well as enrichment and isolation of indigenous microbes.
Among other isolates, a Paenibacillus strain, as a representative of Firmicutes, was recovered in R2A media under anaerobic conditions from Opalinus clay from the Mont Terri in Switzerland. Accumulation experiments and potentiometric titrations showed a strong interaction of Paenibacillus sp. cells with U(VI) within a broad pH range (3-7) [1].
Additionally, the interactions of the halophilic archaeal strain Halobacterium noricense DSM 15987, a salt rock representative reference strain, with U(VI) at high ionic strength was investigated. After 48 h the cells were still alive at uranium concentrations up to 60 μM, which demonstrates that Halobacterium noricense can tolerate uranium concentrations up to this level. The formed uranium sorption species were examined with time-resolved laser-induced fluorescence spectroscopy (TRLFS).
The results about the microbial communities present in potential host rocks for nuclear waste repositories and their interactions with radionuclides contribute to the safety assessment of a prospective nuclear waste repository.

  • Poster
    Key topics on deep geological disposal, 24.-26.09.2014, Köln, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20722
Publ.-Id: 20722


Growth of separated individual SWCNTs from metal:matrix templates

Melkhanova, S.; Kunze, T.; Haluska, M.; Hübner, R.; Keller, A.; Gemming, S.; Krause, M.

Metal: matrix templates deposited by physical vapor deposition (PVD) were used to grow separated, individual single-walled carbon nanotubes (SWCNTs). The templates are thin films of 2 nm thickness, where the metal is either segregated as nanoparticles (NPs) or diluted in the matrix. The upper limit of the NP diameter was confined by the film thickness. The function of the matrix is to prevent the metal particle from coalescence during nanotube growth by chemical vapor deposition. SEM, TEM, AFM, and Raman mapping were used for template and carbon nanotube characterization. SWCNTs with a narrow, monomodal diameter distribution are obtained from templates with NPs of 2 nm diameter. About 50 % of the SWCNTs detected by Raman mapping have a diameter between 1.3 nm and 1.5 nm. Smaller SWCNT diameters down to 0.8 nm are obtained from templates where the metal is diluted in the matrix. For these templates a bimodal SWCNT diameter distribution was observed. The two maxima of the CNT diameter distribution were found at about 0.8 nm to 1.0 nm and at about 1.2 nm to 1.4 nm, respectively. The CNTs are in their majority separated each from other.

Keywords: Nanocomposites; Carbon Nanotubes; SEM; TEM; AFM; Raman

  • Poster
    XXVIII. International Winterschool on Electronic Properties of Novel Materials, 08.-15.03.2014, Kirchberg, Österreich

Permalink: https://www.hzdr.de/publications/Publ-20721
Publ.-Id: 20721


Periacetabular bone metabolism following hip revision surgery. PET-based evaluation of allograft osteointegration.

Bernstein, P.; Beuthien-Baumann, B.; Kotzerke, J.; Hofheinz, F.; Zessin, J.; Stiehler, M.; Günther, K.-P.

The treatment of loosened total hip replacement (THR) acetabular components may require the management of severe bone defects. Although being applied for decades, there is only limited scientific data about the osteointegration of cancellous bone allografts (CBA) and other void fillers. Monitoring of periprosthetic bone regeneration could possibly help to optimize this process thereby reducing late failure rates. The aim of this study was to show osteometabolic changes in periprosthetic CBA after THR revision with the use of sodium-[18F]-fluoride (NaF) and positron emission tomography (PET). Patients, methods: Twelve patients undergoing THR revision with the use of CBA were prospectively enrolled in the study. Nine patients completed all necessary examinations and were included in the evaluation. The temporal pattern of osteointegration was assessed via NaF-PET at one (PET1) and six weeks (PET2) after surgery. CBA, tantalum implants, supraacetabular regions ipsilateral and contralateral, and parasymphyseal pubic bones were delineated as volumes of interest (VOI) in postop CT scans, which were then merged with the PET data. Results: In comparison to the contralateral supraacetabular reference bone, a significant 1.5-fold increase of osteometabolic activity from PET1 to PET2 was seen in the CBA region. Also, the ipsilateral supraacetabular host bone showed a higher NaF-influx in week 6, compared to the first postoperative week. The supraacetabular site exhibited a significantly 1.8- to 2-fold higher influx and uptake than bone regions in non-operated sites. Tantalum implants had a low NaF influx at both time points investigated.

Conclusion: Using NaF-PET osteometabolic changes of CBA and implant-bone-interfaces can be monitored. Applying this method we demonstrated early periprosthetic temporal bone regeneration patterns in THR cup revision patients.

Keywords: Allograft; NaF-PET, bone metabolism; endoprothesis; acetabular

Permalink: https://www.hzdr.de/publications/Publ-20720
Publ.-Id: 20720


Zwitterionic-Coated "Stealth" Nanoparticles for Biomedical Applications: Recent Advances in Countering Biomolecular Corona Formation and Uptake by the Mononuclear Phagocyte System

Pombo Garcia, K.; Zarschler, K.; Barbaro, L.; Barreto, J. A.; O'Malley, W.; Spiccia, L.; Stephan, H.; Graham, B.

Nanoparticles represent highly promising platforms for the development of imaging and therapeutic agents, including those that can either be detected via more than one imaging technique (multi-modal imaging agents) or used for both diagnosis and therapy (theranostics). A major obstacle to their medical application and translation to the clinic, however, is the fact that many accumulate in the liver and spleen as a result of opsonization and scavenging by the mononuclear phagocyte system. This focused Review summarizes recent efforts to develop zwitterionic-coatings to counter this issue and render nanoparticles more biocompatible. Such coatings have been found to greatly reduce the rate and/or extent of non-specific adsorption of proteins and lipids to the nanoparticle surface, thereby inhibiting production of the "biomolecular corona" that is proposed to be a universal feature of nanoparticles within a biological environment. Additionally, in vivo studies have demonstrated that larger-sized nanoparticles with a zwitterionic coating have extended circulatory lifetimes, while those with hydrodynamic diameters of <= 5 nm exhibit small-molecule-like pharmacokinetics, remaining sufficiently small to pass through the fenestrae and slit pores during glomerular filtration within the kidneys, and enabling efficient excretion via the urine. The larger particles represent ideal candidates for use as blood pool imaging agents, whilst the small ones provide a highly promising platform for the future development of theranostics with reduced side effect profiles and superior dose delivery and image contrast capabilities.

Permalink: https://www.hzdr.de/publications/Publ-20719
Publ.-Id: 20719


Development of Radiotracers for Neuroimaging with PET: Challenges and Problems.

Brust, P.

Es ist kein Abstract vorhanden.

  • Invited lecture (Conferences)
    5th INBR International Neuroscience Conference 2014, Satellite Meeting on Neuroimaging – the PET Experience, 01.08.2014, Owerri, Nigeria

Permalink: https://www.hzdr.de/publications/Publ-20717
Publ.-Id: 20717


Introduction into Autoradiography and Radioligand Binding Assays.

Brust, P.

Es ist kein Abstract vorhanden.

  • Invited lecture (Conferences)
    5th Biennial International Neuroscience Conference (INBR2014), Advanced school on Improving Neuroscience Research in the Third World, 28.-31.07.2014, Owerri, Nigeria

Permalink: https://www.hzdr.de/publications/Publ-20716
Publ.-Id: 20716


Nonlinear PT−symmetric plaquettes --- and beyond

Günther, U.; Kevrekidis, P.; Li, K.; Malomed, B.

Nonlinear 2-dimensional PT-symmetric plaquettes of various types are considered. A technique is developed to obtain explicit matrix representations for the parity (P) and for the time-reversal (T) operators starting from initially heuristically designed gain-loss setups of general 2D-type. The threshold behavior of the corresponding linear sub-systems is analyzed near PT-phase transition points in parameter space, the concrete type of exceptional point is established and the analytical construction of stationary solutions for the nonlinear setups is made explicit. The presentation is based on common work with Panayotis Kevrekidis, Kai Li and Boris Malomed [J. Phys. A 45, 444021 (2012)]. Next possible steps of technical extensions towards higher-dimensional soliton setups and required integrability tests via the search for Lax pairs of Zakharov-Shabat and Fordy-Kulish type are briefly sketched.

Keywords: PT symmetry; nonlinear 2-dimensional plaquettes; parity operator; time reversal operator; PT phase transition; exceptional point; Lax pair

  • Invited lecture (Conferences)
    SIAM Conference on Nonlinear Waves and Coherent Structures (SIAM-NW14), Churchill College, University of Cambridge, 11.-14.08.2014, Cambridge, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-20715
Publ.-Id: 20715


Hydrothermal carbonate chimneys from a continental rift (Afar Rift): Mineralogy, geochemistry, and mode of formation

Dekov, V. M.; Egueh, N. M.; Kamenov, G. D.; Bayon, G.; Lalonde, S. V.; Schmidt, M.; Liebetrau, V.; Munnik, F.; Fouquet, Y.; Tanimizu, M.; Awaleh, M. O.; Guirreh, I.; Le Gall, B.

Carbonate chimney-like structures up to 60 m high are scattered or arranged in rows at the shores of a desiccating hypersaline and alkaline lake from a continental rift setting (Lake Abhé, Afar Rift, Djibouti). The chimneys apparently formed sub-aqueously in the lake water body at a higher water level than observed today. Alternating calcite and low-Mg calcite + silica concentric layers compose the chimney structures. Mineralogical and geochemical investigations of the chimneys, lake water, and hot spring (hydrothermal) fluids suggest that the chimneys are a result of rapid carbonate precipitation during the mixing of hydrothermal fluids with lake water. In contrast to hot spring fluid, lake water is enriched in HREE and possesses a pronounced positive Ce anomaly, features that are preserved in the carbonate chimney layers. Mixing calculations based on Sr- isotope and concentration data indicate a hydrothermal fluid contribution of ~45 % in the chimney interior, which decreases to ~4 % in the external chimney layer. Sr in the hydrothermal fluids is predominantly leached from the underlying volcanic rocks, whereas the lake’s Sr budget is dominated by riverine input. Considering the fluid mixing ratios calculated by Sr-data, the measured C and O isotope compositions indicate that chimney carbonates precipitated at temperatures between 14°C (internal part) and 22°C (external part) with a carbon source that was most likely atmospheric.
The low-Mg calcite layers, including the outermost layer, appear to have enhanced signals of lake water inheritance based on elevated concentrations of immobile elements, ΣREE, and Sr and Ca isotope compositions. Ca-isotope data reveal that internal chimney layers formed by non-equilibrium calcite precipitation with a predominantly hydrothermal Ca source. The external low-Mg calcite layer received Ca contributions from both hydrothermal fluid and lake water, with the latter being the dominant Ca source. Highly positive δ44/40Ca of lake water likely reflects non-equilibrium Ca-carbonate precipitation during lake water evaporation with resulting 44Ca enrichment of residual lake water. The strong degree of 44Ca enrichment may point towards multiple lake drying and Ca-reservoir depletion events. Coupled C-O-Ca-isotope data of the sampled carbonate chimney suggest late-stage (low-temperature) hydrothermal carbonate chimney formation during strongly evaporative lake conditions at the time of low-Mg calcite precipitation. U-Th age dating suggests the chimneys formed no earlier than 0.82 kyr BP (0.28 ± 0.54).

Keywords: carbonate; chimney; continental rift; H-C-O-Ca-Sr-Nd-Pb-Th-U-isotopes; hydrothermalism

Permalink: https://www.hzdr.de/publications/Publ-20714
Publ.-Id: 20714


Entwicklung, Synthese und F-18-Markierung von fluoralkylierten Triazinderivaten zur bildgebenden Darstellung der Phosphodiesterase 2A mittels PET

Schröder, S.; Wenzel, B.; Kranz, M.; Egerland, U.; Teodoro, R.; Deuther-Conrad, W.; Fischer, S.; Höfgen, N.; Steinbach, J.; Brust, P.

Ziel:
Phosphodiesterasen (PDE) hydrolysieren die zyklischen Nucleotide cAMP und/oder cGMP. PDE-Inhibitoren verzögern den Abbau dieser sekundären Botenstoffe und beeinflussen physiologische Prozesse. Die PDE2A zeigt eine hohe, spezifische Expression im Gehirn sowie in bestimmten Tumoren und ist vermutlich an der Pathophysiologie entsprechender Erkrankungen beteiligt. Ziel ist die Darstellung eines F-18-Radioliganden für die Bildgebung der PDE2A mittels PET.

Methodik:
Ausgehend von der Leitstruktur TA1 wurden neue Fluoralkyl-Derivate TA2-4 entwickelt
(Abb. 1). Für potentielle PDE2A-Inhibitoren ist neben der Affinität v. a. die Selektivität zwischen der PDE2A und der PDE10A aufgrund ähnlicher Verteilungsmuster entscheidend.
Abb. 1
Zu den Derivaten TA3/4 wurden Tosylat-Präkursoren für einstufige F-18-Markierungen synthetisiert, wobei folgend der Radioligand [F-18]TA3 vorgestellt wird.
Die F-18-Fluorierung erfolgte in Acetonitril bei 80°C in 15 Minuten. [F-18]TA3 wurde mittels semi-präparativer HPLC isoliert, über eine Sep-Pak® C18 Kartusche gereinigt und in 0,9%iger NaCl-Lösung formuliert. Die Analytik des Endproduktes erfolgte mittels Radio-DC und -HPLC. Für in-vitro-Autoradiographien wurden sagittale Rattenhirnschnitte mit 1 MBq [F-18]TA3 für 60 Minuten bei Raumtemperatur inkubiert.

Ergebnisse:
[F-18]TA3 wurde mit einer Markierungsausbeute von 75,4 ± 4,9%, einer radiochemischen Ausbeute von 57,2 ± 0,4%, einer spezifischen Aktivität von 60,4 ± 11,6 GBq/µmol (EOS) und einer radiochemischen Reinheit von ≥ 99,5% synthetisiert.
Entsprechend dem PDE2A-Verteilungsmuster zeigten erste in-vitro-Autoradiographien eine hohe und spezifische Anreicherung von [F-18]TA3 im Cortex und Striatum (Abb. 2).

Abb. 2
Schlussfolgerungen:
Die Ergebnisse zu [F-18]TA3 zeigen, dass ein neuartiger und hochaffiner PDE2A-Radioligand erfolgreich dargestellt werden kann. Die Radiosynthese von [F-18]TA4 wird derzeit bearbeitet. Die Charakterisierung dieser F-18-Alkyl-Derivate mittels TierPET/MR, Autoradiographie und Studien zum Metabolismus ist geplant.

  • Lecture (Conference)
    AGRR2014 - 22. Jahrestagung der Arbeitsgemeinschaft Radiochemie/Radiopharmazie, 11.-13.09.2014, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20713
Publ.-Id: 20713


Spectroscopic study on uranyl carboxylate complexes formed at the surface layer of Sulfolobus acidocaldarius

Reitz, T.; Rossberg, A.; Barkleit, A.; Steudtner, R.; Selenska-Pobell, S.; Merroun, M. L.

The complexation of U(VI) at the proteinaceous surface layer (S-Layer) of the archaeal strain Sulfolobus acidocaldarius was investigated over a pH range from pH 1.5 to 6 at the molecular scale using time-resolved laser-induced fluorescence spectroscopy (TRLFS) and U LIII-edge extended X-ray absorption fine structure (EXAFS). The S-layer, which represents the interface between the cell and its environment, is very stable against high temperatures, proteases, and detergents. This allowed the isolation and purification of S-layer ghosts (=empty cells) that maintain the size and shape of the cells. In contrast to many other cell envelope compounds the studied S-layer is not phosphorylated, which enabled the investigation of uranyl carboxylate complexes, which are usually masked by uranyl phosphate complexes. We demonstrated that at highly acidic conditions (pH 1.5 to 3) no uranium was bound by the S layer. In contrast to that, at moderate acidic pH conditions (pH 4.5 and 6) a complexation of U(VI) at the S layer via deprotonated carboxylic groups was stimulated. Titration studies revealed dissociation constants for the carboxylic groups of glutamic and aspartic acid residues of pKa = 4.78 and 6.31. The uranyl carboxylate complexes formed at the S-layer did not show luminescence properties at room temperature, but only under cryogenic conditions. The obtained luminescence maxima are similar to those of uranyl acetate. EXAFS spectroscopy demonstrated that U(VI) in these complexes is mainly coordinated to carbon in a bidentate binding mode. The elucidation of the molecular structure of these complexes was facilitated by the absence of phosphate groups in the studied S-layer protein.

Keywords: Sulfolobus acidocaldarius; S-Layer; Uranium; Interactions; uranyl carboxylate complexes; XANES; EXAFS; TRLFS

Permalink: https://www.hzdr.de/publications/Publ-20712
Publ.-Id: 20712


Decrease of U(VI) immobilization capability of the facultative anaerobic strain Paenibacillus sp. JG TB8 under anoxic conditions due to strongly reduced phosphatase activity.

Reitz, T.; Rossberg, A.; Barkleit, A.; Selenska-Pobell, S.; Merroun, M. L.

Interactions of a facultative anaerobic bacterial isolate named Paenibacillus sp. JG-TB8 with U(VI) were studied under oxic and anoxic conditions in order to assess the influence of the oxygen-dependent cell metabolism on microbial uranium mobilization and immobilization. We demonstrated that aerobically and anaerobically grown cells of Paenibacillus sp. JG-TB8 accumulate uranium from aqueous solutions under acidic conditions (pH 2 to 6), under oxic and anoxic conditions. A combination of spectroscopic and microscopic methods revealed that the speciation of U(VI) associated with the cells of the strain depend on the pH as well as on the aeration conditions. At pH 2 and pH 3, uranium was exclusively bound by organic phosphate groups provided by cellular components, independently on the aeration conditions. At higher pH values, a part (pH 4.5) or the total amount (pH 6) of the dissolved uranium was precipitated under oxic conditions in a meta autunite-like uranyl phosphate mineral phase without supplying an additional organic phosphate substrate. In contrast to that, under anoxic conditions no mineral formation was observed at pH 4.5 and pH 6, which was clearly assigned to decreased orthophosphate release by the cells. This in turn was caused by a suppression of the indigenous phosphatase activity of the strain. The results demonstrate that changes in the metabolism of facultative anaerobic microorganisms caused by the presence or absence of oxygen can decisively influence U(VI) biomineralization.

Keywords: Paenibacillus; Uranium; Biomineralization; XAS; TRLFS; TEM; Phosphatase activity

Permalink: https://www.hzdr.de/publications/Publ-20711
Publ.-Id: 20711


Neuroimaging the PET experience

Brust, P.

Positron Emission Tomography (PET) is an in vivo molecular imaging tool which is widely used in nuclear medicine for early diagnosis and treatment follow-up of many brain diseases. PET uses biomolecules as probes which are labeled with radionuclides of short half-lives, synthesized prior to the imaging studies. These probes are called radiotracers. Fluorine-18 is a radionuclide that is routinely used in radiolabeling of neuroreceptor ligands for PET because of its favorable half-life of 109,8 min. The administration of such radiotracers into the brain provides images of transport, metaboic and neurotransmission processes on the molecular level. After a short introduction into the principles of PET this talk will mainly focus on the strategy of radiotracer development bridging from basic science to biomedical application. Successful radiotracer design as discussed in this talk provides molecular probes which are not only useful for imaging of human brain diseases. They allow also molecular neuroreceptor imaging studies in various small-animal models of disease including genetically engineerd animals. Futhermore, they provide a powerful tool for in vivo pharmacology during the process of preclinical drug development to identify new drug targets, to investigate pathophysiology, to discover potential drug candidates, and to evaluate the phramacokinetics and pharmacodynamics of drugs in vivo.

  • Invited lecture (Conferences)
    5th Biennial International Neuroscience Conference (INBR2014), 28.-31.07.2014, Owerri, Nigeria

Permalink: https://www.hzdr.de/publications/Publ-20710
Publ.-Id: 20710


Plasma based nanotechnology against corrosion of CuZn and TiAl alloys.

Pelic, B.; Bregolin, F. L.; Prucnal, S.; Yankov, R.; Skorupa, W.

Experiments have been undertaken to explore the improvement of the aqueous corrosion and high temperature oxidation of CuZn and TiAl, respectively, by applying plasma immersion ion implantation (PI3).
The atmospheric corrosion of the tongues within the reed pipes which consist of a Cu-Zn alloy (namely brass) is strongly enhanced by traces of VOC (acetic acid vapors) and also the alloy’s instability caused by dezincification. A significant improvement in corrosion resistance has been achieved by applying a 30 nm aluminum oxide film using pulsed laser deposition (PLD) and implanting nitrogen ions into the near surface and the interface regions. In the case of γ-TiAl alloys which exhibit poor oxidation resistance, despite their good mechanical properties at elevated temperatures, this limits the replacement of the nowadays used heavy components made of Ni-alloys. A significant improvement in high temperature oxidation resistance of TiAl alloys (up to 900 °C) has been achieved by implanting fluorine ions (1017 cm-2) at 30 keV into the alloy’s subsurface using PI3 process. A TiAl alloy modified in this way has been shown to acquire a stable, adherent and highly protective alumina scale (Al2O3) under high temperature oxidation in air. The influence of the implanted N+ into CuZn and F+ into TiAl samples on the corrosion process has been investigated. For the sample evaluation, different characterization methods including scanning electron microscope with energy dispersive X-ray spectroscopy (SEM / EDX), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), Elastic recoil detection analysis (ERDA), and Dektak stylus profiling have been applied to determine the chemical composition, the elemental depth profiles, roughness and defect formation of the samples before and after exposure.

Keywords: Plasma immersion ion implantation (PI3); Pulsed laser deposition (PLD); corrosion of reed organ pipes; CuZn alloys; TiAl alloys; oxidation protection

  • Lecture (Conference)
    ION 2014 X-th INTERNATIONAL CONFERENCE on Ion Implantation and Other Applications of Ions and Electrons, 23.-26.06.2014, Kazimierz Dolny, Poland

Permalink: https://www.hzdr.de/publications/Publ-20709
Publ.-Id: 20709


Importance of the blood-brain barrier for neuroimaging studies

Brust, P.

The blood-brain barrier (BBB) is a control system to preserve homeostasis in the nervous system, facilitating the entry of necessary metabolites, but blocking the entry or facilitating the removal of unnecessary metabolites or toxic substances. For any solute the efficacy of the exclusion or transport is determined by the morphological and functional characteristics of the brain capillaries and by the biochemical and biophysical characteristics of the solute. This applies also for radiotracers which are used for brain imaging. Several transport routes across the BBB exist. Therfore, the transport of radiotracers depends on the functional status of the brain endothelium. Studies were performed to investigate the expression and function of various transport systems at the BBB, such as ABC transporters, aquaporins, glucose, amino acid, choline and serotonin transporters. The influence of drugs, hormones and brain development on transport processes has been explored. Our main findins are: (1) The brain uptake of certain 99m/99Tc-labelled radiotracers is reduced by the presence of drug efflux transporters, e.g: P-glycoprotein. (2) Peptide hormones selectively alter the water permeability and the transport of neutral amino acids at the BBB. (3) The BBB transport of neutral amino acids decreases during development. (4) The transport of basic drugs from blood to brain is partly mediated by the BBB choline transporter. (5) The transport of the PET radiotracer [11C]McN5652 is mediated by the serotonin transporter at the BBB but of no relevance for human PET studies. It is concluded that the transport of radiotracers across the BBB does not solely depend on the lipophilicity of the compounds. Active and regulated efflux systems need to be considered. For many radiotracers specific transport systems exist, which underlie developmental changes and physiological regulation. Nutrient transporter, e. g. for glucose, amino acids and choline, are of special importance.

  • Invited lecture (Conferences)
    5th Biennial Inernational Neuroscience Conference (INBR2014), 28.-31.07.2014, Owerri, Nigeria

Permalink: https://www.hzdr.de/publications/Publ-20708
Publ.-Id: 20708


Molecular Imaging of Neurodegeneration

Brust, P.

Molecular imaging (MI) originated from the field of radiopharmacology due to the need to better understand the fundamental molecular pathways inside organisms in a noninvasive manner. It emerged in the early twenty-first century as a discipline at the intersection of molecular biology and in vivo imaging and enables the visualization of the cellular function and the follow-up of the molecular process in living organisms without perturbing them. Basic requirements for MI are probes whose concentration and/or spectral properties are altered by the specific biological process under investigation technology to monitor these probes in living organisms and to reconstruct images from their distribution patterns. Positron Emission Tomography (PET) ist the most sensitive molecular imaging tool and a well-established method for neuroimaging of neurodegeneration such as Alzheimer's disease (AD). An ideal PET biomarker for AD should allow a reliable estimation of disease risk and rate of disease progression long before first symptoms are clinically diagnosed. The main pathologic processes of AD, deposition of beta-amyloid, hyperphosphorylated tau protein, degeneration of cholinergic and other neurons, precede clinical symptoms by years providing potential targets for the identification of individuals at risk for AD. In the last few years, several PET tracers targeting beta-amyloid in AD have been developed. The suitability of these PET radiopharmaceuticals to differentiate AD patients and patients with mild cognitive impairment (MCI) from control subjects has been demonstrated and will be discussed. However beta-amyloid deposition has been found in about 20% of normal elderly subjects.

  • Invited lecture (Conferences)
    5th Biennial International Neuroscience Conference (INBR2014), 28.-31.07.2014, Owerri, Nigeria

Permalink: https://www.hzdr.de/publications/Publ-20707
Publ.-Id: 20707


Systematic analysis on the achievable accuracy of PT-PET through automated evaluation techniques

Helmbrecht, S.; Kuess, P.; Birkfellner, W.; Enghardt, W.; Stützer, K.; Georg, D.; Fiedler, F.

Introduction: Particle Therapy - Positron Emission Tomography (PT-PET) is currently the only clinically applied method for in vivo verication of ion-beam radiotherapy during or close in time to the treatment.
Since a direct deduction of the delivered dose from the measured activity is not feasible, images are compared to a reference distribution. The achievable accuracy of two image analysis approaches was investigated by means of reproducible phantom benchmark tests. This is an objective method that exclude patient related factors of influence.
Material and Methods: Two types of phantoms were designed to produce well dened deviations in the activity distributions. Pure range dierences were simulated using the rst phantom type while the other emulated cavity structures. The phantoms were irradiated with 12C-ions. PT-PET measurements were performed by means of a camera system installed at the beamline. Dierent measurement time scenarios were investigated, assuming a PET scanner directly at the irradiation site or placed within the treatment room.
The images were analyzed by means of the Pearson Correlation Coecient (PCC) and a range calculation algorithm combined with a dedicated cavity lling detection method.
Results: Range dierences could be measured with an error of less than 2 mm. The range comparison algorithm yielded slightly better results than the PCC method. The lling of a cavity structure could be safely detected if its inner diameter was at least 5 mm.
Conclusion: Both approaches evaluate the PT-PET data in an objective way and deliver promising results for in-beam and in-room PET for clinical realistic dose rates.

Permalink: https://www.hzdr.de/publications/Publ-20706
Publ.-Id: 20706


Leaching of copper from Kupferschiefer by organic acid and heterotrophic bacteria

Kostudis, S.; Bachmann, K.; Kutschke, S.; Pollmann, K.; Gutzmer, J.

Polymetallic Cu-Ag ores of the Central European Kupferschiefer deposits are one of the most important sources of Cu in Europe. Because the ores are typically complex and often exceptionally fine-grained the development of efficient alternatives to conventional beneficiation strategies are an important target of current research. Biomining – the use of biological components for metal extraction - may offer solutions that are both efficient and environmentally benign. As conventional bioleaching with acidophilic microorganisms is impeded by the high carbonate content of the Kupferschiefer ores, heterotrophic microorganisms and glutamic acid are investigated as a possible alternative in the present study. The focus of this investigation is solely on the recovery of copper from the Kupferschiefer sensu strictu. Bioleaching experiments were carried out using such material from the Polkowice Mine in Poland. This material is marked by high grade (3.8 wt% Cu), complex ore mineralogy (chalcocite, bornite, chalcopyrite and covellite in significant quantity) and a gangue mineralogy that is rich in carbonate, organic carbon and clay minerals that together form a very fine-grained matrix. (Bio)-leaching experiments yield best results when glutamic acid alone is used – reaching Cu recoveries up to 44 %. Recoveries are consistently lower in experiments in which glutamic acids and microbiological metabolites are both present. The leaching of chalcocite renders the greatest contribution to the Cu recovered to the leach solution in all experiments. It can be concluded that glutamic acid solubilise copper efficiently from Kupferschiefer, mainly from chalcocite.

Keywords: sulphide ores; bacteria; bioleaching; liberation analysis; ore mineralogy

  • Minerals Engineering (2015)

Permalink: https://www.hzdr.de/publications/Publ-20705
Publ.-Id: 20705


Determination of Uranium (VI)-Speciation in Natural Occurring Waters by Time-resolved Laser-induced Fluorescence Spectroscopy

Baumann, N.; Geipel, G.

Method of Time-resolved Laser-induced Fluorescence Spectroscopy (TRLFS) is explained, and illustrated with U(VI) measuring results gained from surface water and soil water samples originated from the area of the former uranium mining heap "Gessenhalde" close to Ronneburg in Eastern Thuringia. Comparative former TRLFS measuring results gained from several uranium mining tailing waters and from further water samples are shown.

  • Invited lecture (Conferences)
    Special lecture at the Department of Applied Radiation and Isotopes, Faculty of Science, Kasetsart University, 27.08.2014, Bangkok, Thailand

Permalink: https://www.hzdr.de/publications/Publ-20704
Publ.-Id: 20704


Speciation of uranyl(VI) using combined theoretical and luminescence spectroscopic methods

Drobot, B.; Tsushima, S.; Steudtner, R.; Raff, J.

Speciation constitutes the basis for actinide complexation studies. These systems can be very complex and challenging especially because of the polynuclear species. An advanced combination of theoretical and experimental methods is proposed here. Continuous wave (CW) and time-resolved laser-induced fluorescence spectroscopy (TRLFS) data of uranyl(VI) hydrolysis were analyzed using parallel factor analysis (PARAFAC). Distribution patterns of five major species were thereby derived under a fixed uranyl concentration (10-5) over a wide pH range from 2 to 11. UV (180 nm to 370 nm) excitation spectra were extracted for individual species. Time-dependent density functional theory (TD-DFT) calculations revealed ligand excitation (water, hydroxo, oxo) in this region and ligand-to-metal charge transfer (LMCT) responsible for luminescence. Thus excitation in the UV is extreme ligand sensitive and highly specific. Combining findings from PARAFAC and DFT the [UO2(H2O)5]2+} cation (aquo complex, 1:0) and four hydroxo complexes (1:1, 3:5, 3:7 and 1:3) were identified. Refined structural and thermodynamical data of uranyl(VI) hydrolysis is thus acquired.

  • Lecture (others)
    PSI meeting, 25.08.2014, Villigen, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-20703
Publ.-Id: 20703


Geobiotechnologie: „Grüne“ Technologie zur Metallgewinnung?

Pollmann, K.

Perspektiven der Geobiotechnologie

  • Invited lecture (Conferences)
    Seminar zum Stipendienprogramm der Deutschen Bundesstiftung Umwelt, 02.09.2014, Ostritz/Kloster Marienthal, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20702
Publ.-Id: 20702


Biologische Bausteine für Materialien der Zukunft

Drobot, B.

Auf der Suche nach umwelt- und ressourcenschonenden industriellen Prozessen richtet sich der Fokus zunehmend auf die Biologie. Unzählige Organsimen haben im Laufe der Evolution vielfältige Mechanismen entwickelt, die sowohl spezifisch als auch effizient sind. Damit reicht der potentielle Anwendungsbereich von antimikrobiellen Oberflächen über Filtration bis hin zu hochempfindlichen Sensoren.

  • Lecture (others)
    Tage der Wissenschaften, 02.07.2014, Radebeul, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20701
Publ.-Id: 20701


Polyoxometalates as potent inhibitors of P2X receptors

Spanier, C.; Stephan, H.; Kortz, U.; Haider, A.; Hausmann, R.; Abdelrahman, A.; Müller, C. E.

P2X receptors are trimeric ion channels that are activated by ATP and are permeable for the cations Na+, K+ and Ca2+. Seven different subunits exist, which are assembled as homo- or heterotrimers of various stoichiometry.1,2 Polyoxometalates (POMs) are discrete, polynuclear metal-oxo anions of early transition metals in high oxidation states (e. g. W6+, Mo6+, V5+), comprising edge- and corner-shared MO6 octahedra. They exhibit enormous flexibility with respect to shape, size, composition and charge.3 POMs are relatively large molecules (> 1 nm) and bear several negative charges. In this respect they bear similarity to ATP, which binds to P2X2 and P2X4 in its tetraanionic form (ATP4-) and to P2X1 and P2X3 possibly also in its dianionic state as a Mg2+ complex (MgATP2-).4 We previously found that certain POMs can inhibit alkaline phosphatase5 and ectonucleotidases,6, 7 enzymes that are capable of hydrolyzing nucleotides such as ATP and ADP. In the present study we investigated whether POMs can interact with P2X receptors. A series of POMs was investigated for their effects to inhibit ATP-induced calcium influx in recombinant 1321N1 astrocytoma cells stably transfected with P2X1, P2X2, P2X3, P2X4 or P2X7 receptors. Several POMs were found to be highly potent inhibitors of P2X receptors with potency in the low nanomolar range. The compounds were found to be non-cytotoxic at pharmacologically active concentrations, whereas some POMs showed cytotoxic effects in an MTT assay at concentrations typically higher than 1 µM.


1 Young, MT (2010), Trends Biochem. Sci. 35: 83-90
2 Torres, GE, Egan, TM, Voigt, MM (1999), J Biol. Chem. 274: 6653-6659
3 Hasenknopf, B (2005), Front Biosci. 10: 275-28
4 Li, M, Silberberg, SD, Swartz, KJ (2013), Proc. Natl. Acad. Sci. USA: 110: E3455-E3463
5 Raza, R, Matin, A, Sarwar, S, Barsukova-Stuckart, M, Ibrahim, M, Kortz, U, Iqbal, J (2012), Dalton Trans. 41: 14329-14336
6 Müller, CE, Iqbal, J, Baqi, Y, Zimmermann, H, Röllich, A, Stephan, H (2006), Bioorg. Med. Chem. Lett. 16: 5943-5947
7 Stephan, H, Kubeil, M, Emmerling, F, Müller, CE (2013), Eur. J. Inorg. Chem. 1585-1594

  • Poster
    Purines International Conference on Nucleotides Nucleosides and Nucleobases, 23.-27.07.2014, Bonn, Deutschland
  • Open Access Logo Abstract in refereed journal
    Purinergic Signalling 10(2014), 779-780
    DOI: 10.1007/s11302-014-9430-7

Permalink: https://www.hzdr.de/publications/Publ-20700
Publ.-Id: 20700


Bioleaching of Kupferschiefer blackshale – A review including perspectives of the Ecometals project

Kutschke, S.; Guézennec, A.-G.; Hedrich, S.; Schippers, A.; Borg, G.; Kamradt, A.; Gouin, J.; Giebner, F.; Schopf, S.; Schlömann, M.; Rahfeld, A.; Gutzmer, J.; D’Hugues, P.; Pollmann, K.; Dirlich, S.; Bodénan, F.

In Europe, most of the primary copper resources that possess a high or moderate amount of metals, have a reasonable accessibility and are easy to process are exhausted. In this context, low grade and complex ores as well as old waste deposits related to past mining activities are receiving increasing attention. For an economic exploitation of such ores and resources, with quite different mineral matrix, new and efficient methods need to be developed. Bioleaching is a reliable and promising option .
Among the different kinds of copper mineralisation that can be found in Europe, sulphidic Kupferschiefer deposits have been explored and exploited for years in Germany and Poland. They are Europe’s largest copper reserve with more than 60 Mill. tons of Cu, and contain additional associated metals such as Ag, Pb, Zn and possibly other high-value metals. Kupferschiefer deposits are currently under exploitation in Poland, but process operations are more and more penalised by the significant amounts of organic matter and arsenic present in this type of ores. Therefore bioleaching is more and more considered as a credible alternative to the pyrometallurgical technology which may no longer be feasible in future given the concentrate chemistry.
In this context, this paper provides an overview of the previous work on the geology, mineralogy, and (bio)processing of the Kupferschiefer. It will also present new opportunities and challenges related to the development of innovative methods for metal recovery by means of biotechnology.
Generally, bioleaching of Kupferschiefer is influenced by the mineralogical nature of sulphides and organic matter contained in the ores. For example, recalcitrance of chalcopyrite during leaching is a major limitation of biohydrometallurgy applied to copper ores in general and blackshales in particular. Organic matter, moreover, causes also flotation problems. However, the organic materials especially the metallorganic compounds containing platinum group (PGE) or rare earth elements (REE) may make processing of Kupferschiefer economically interesting.
The first works dealing with Kupferschiefer bioleaching in Europe date back more than three decades, and were pursued again beginning of the 21st century in the European Bioshale project. This project demonstrated the overall efficiency of continuous stirred tank reactors (CSTR) bioleaching of a blackshale concentrate with an extraction rate above 90 %. Nevertheless, two possible improvement paths were identified: reducing the tank size or improving chalcopyrite dissolution affecting the operation efficiency. These challenges were then further addressed in ProMine project opening new perspectives for bioleaching of Kupferschiefer ores which will be dealt with in the French-German project Ecometals.

Keywords: copper; blackshale; chalcopyrite; organic matter; bioleaching

Permalink: https://www.hzdr.de/publications/Publ-20699
Publ.-Id: 20699


Potential mapping from geochemical surveys using a Cox process

Tolosana-Delgado, R.; van den Boogaart, K. G.; Schaeben, H.

Punctual occurrence phenomena are often modeled as Poisson point processes, sometimes with an inhomogeneous, unknown intensity, that is desired to be estimated from some covariables. Within this setting, we study the case in which the covariables form a regionalized geochemical composition of stream sediments, and the known punctual occurrences are existing mineral deposits, not collocated with the available explanatory data. This is modeled by assuming a two-layer stochastic process, where the observed Poisson log-intensity is taken as a balanced log-linear function of the geochemical composition of stream sediments, which coefficients must be estimated. Estimation is possible through a pseudolikelihood device based on generalized loglinear models, though the result intensity function appears to be valid only up to arbitrary scaling and addition of constants.

  • Contribution to proceedings
    GeoENV 2014 - 10th Conference on Geostatistics for Environmental Applications, 09.-11.07.2014, Paris, France
    Proceedings of geoENV 2014

Permalink: https://www.hzdr.de/publications/Publ-20698
Publ.-Id: 20698


Applications in Compositional Data Analysis

Tolosana-Delgado, R.; van den Boogaart, K. G.

Compositional data occur in all fields of science: from politics to materials engineering, from biomedical sciences to geochemistry. In all these fields, variables representing the relative contribution of some parts forming a whole are routinely acquired. Actually, compositions form their own scale, essentially characterized by their intrinsic multivariate nature and the closure to constant sum to 100%. Statistical techniques used with these data must then conform to that scale.

This contribution presents a comprehensive summary of how to adapt the most common statistical techniques, based on the principle of working on coordinates within the log-ratio approach. In application of this principle, data are represented in an one-to-one set of logratios of the original components, the scores are analysed with classical multivariate tools, and results are eventually back-transformed for interpretation. In particular, this contribution explores the uses of cluster analysis, principal components and linear regression to explain the natural variability on several data sets from the Earth sciences.

Keywords: biplot; PCA; linear model; geochemical survey; clr; ilr

  • Lecture (Conference)
    Joint Statistical Meeting, 02.-07.08.2014, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-20697
Publ.-Id: 20697


Spatial Analysis of Compositional Data

Pawlowsky-Glahn, V.; Tolosana-Delgado, R.; van den Boogaart, K. G.

Spurious correlation is known to be a problem in statistics since Pearson's early warnings in 1897. The same problems arise in spatial statistics: bias towards negative values and non-zero cross-covariances and cross-covariograms; singular matrices of intrinsic co-dispersion; co-kriged regionalised vectors of proportions that do not satisfy the constant sum constraint. A way out is to use log-ratio transformations: the spatial structure can be described in terms of direct variograms of each possible pairwise logratio; variation-variograms can be estimated even in case of missing components; they can be modelled with standard tools; both the data and the spatial structure model can be expressed in isometric logratio coordinates, and standard co-kriging techniques can be applied to obtain interpolated logratios. These can be back-transformed to compositions, delivering interpolated maps of each component that satisfy the required constraints. Moreover, the result does not depend on which logratio transformation was used for the computations. This approach and its potentialities is illustrated with a data set of soil geochemistry.

Keywords: Aitchison geometry of the simplex; co-kriging; compositional data; spurious spatial covariance; variation-variogram

  • Lecture (Conference)
    Joint Statistical Meeting, 02.-07.08.2014, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-20696
Publ.-Id: 20696


Multi-functional bispidine derivatives as versatile imaging agents

Stephan, H.; Coma, P.

The development of multi-functional complexing agents for radiometal nuclides with a view of nuclear medical application represents a fast developing field of intensive research [1]. A requirement for ligands in this field is fast complexation kinetics and high complex stabilities with specific radiometal ions and ligands which are easy to functionalize with several different groups for linking to biological vectors, nanoparticles and/or fluorescence molecules.

Ligands based on 3,7-diazabicyclo[3.3.1]nonane (bispidine) form very stable transition metal complexes [2]. Due to the formation of thermodynamically and kinetically stable CuII complexes, pentadentate and hexadentate bispidines are very well suited for in vivo application, i.e. for tumor imaging (64CuII) using positron emission tomography (PET) and tumor therapy (64CuII, 67CuII) [3, 4]. The bispidine scaffold has various sites for functionalization that permit the introduction of biomolecules for pharmaceutical targeting and fluorescent units for optical imaging (see Figure 1).

Several bispidine ligands have been developed in order to improve the radiopharmaceutical behavior as well as possibilities for further beneficial functionalization. These ligands and the important properties of their CuII complexes, e.g., stabilities, ligand exchange kinetics, serum stability, partition coefficients ([64Cu]Cu-bispidine: n-octanol/water) and biodistribution studies 64Cu-labeled bispidines will be reported.

References
1. C. S. Cutler, M. H. Hemmkens, N. Sisay, S. Markai-Huclier. S. S. Jurisson, Chem. Rev. 113, 858 (2013).
2. P. Comba, M. Kerscher, W. Schiek, Prog. Inorg. Chem. 55, 613 (2007).
3. S. Juran, M. Walther, H. Stephan, R. Bergmann, J. Steinbach, W. Kraus, F. Emmerling, P. Comba, Bioconjugate Chem. 20, 347, (2009).
4. P. Comba, S. Hunoldt, M. Morgen, J. Pietzsch, H. Stephan, H. Wadepohl, Inorg. Chem. 52, 8131 (2013).

  • Lecture (Conference)
    5th EuCheMS Chemistry Congress, 31.08.-04.09.2014, Istanbul, Turkey

Permalink: https://www.hzdr.de/publications/Publ-20695
Publ.-Id: 20695


Single-domain antibodies as targeting moieties for nanomaterial-based cancer imaging

Zarschler, K.; Zscheppang, K.; Cordes, N.; Stephan, H.; Steinbach, J.

ken Abstract verfügbar

  • Poster
    DKTK Retreat 2014, 12.-13.05.2014, Heidelberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20694
Publ.-Id: 20694


Ultrasmall silicon nanoparticles: preparation strategies and bioapplications

Licciardello, N.; Hsu, C.-W.; Prasetyanto, E. A.; Hunoldt, S.; Viehweger, K.; Stephan, H.; de Cola, L.

The use of nanoparticles in multimodal bio-imaging is attracting increasing interest, but toxicity and accumulation in organs still limit their in vivo applications. Silicon nanoparticles (Si NPs) are very promising in this respect as their size, 1.5 - 4 nm, can allow body excretion. In addition Si NPs are photo- and chemical stable, possess bright tunable luminescence and can be covalently functionalized with desired molecules. Indeed several techniques have been described to obtain Si NPs [1-3] with different sizes and bearing various functional groups.
Here we report on some optimized wet chemistry techniques to prepare ultrasmall (< 5 nm) Si NPs and, in particular, the focus is on microemulsion methods and hydrothermal synthesis. The obtained Si NPs can bear different functional groups, allowing a wide spectrum of subsequent conjugations. Once functionalized and purified, Si NPs were characterized by HR-TEM and IR spectroscopy, and their photophysical properties were investigated. Reactivity and properties of the NPs obtained by various methods will be compared and the results of in vitro and in vivo experiments will be shown to demonstrate the great potentialities of such ultrasmall Si NPs.
This work was financially supported by Helmholtz Virtual Institute “Nano-Tracking”, Agreement No. VH-VI-421

1. J. H. Warner et al., Angew. Chem. Int. Ed. 2005, 44, 4550 –4554
2. M. Rosso-Vasic et al., Small, 2008, 4, 1835–1841
3. Y. Zhong et al., J. Am. Chem. Soc., 2013, 135, 8350-8356

  • Lecture (Conference)
    E-MRS Spring Meeting, 26.-30.05.2014, Lille, France

Permalink: https://www.hzdr.de/publications/Publ-20693
Publ.-Id: 20693


Morphological transformations of top electrodes on YMnO3 caused by filamentary resistive switching in the oxide matrix

Bogusz, A.; Blaschke, D.; Skorupa, I.; Bürger, D.; Schmidt, O. G.; Schmidt, H.

Unipolar resistive switching in YMnO3 with large-scale bottom and small-scale top electrodes is analyzed in detail by tracking the morphological transformations of the top electrodes induced by applied writing voltages. Micro-scale digital images are taken after each subsequent quasi-static current-voltage sweep. Current mapping after electrical investigations indicates a shift in the conductivity at the localized areas of the morphologically transformed top electrodes. Those changes are assigned to the heat induced structural and compositional changes within YMnO3 which lead to the formation and rupture of conductive filaments observed as unipolar resistive switching. Presented results underline the importance of Joule heating in the fostering of resistive switching and its adverse impact on the device endurance.

Keywords: resistive switching; Joule heating; morphological changes of electrode; multiferroic YMnO₃

  • Lecture (Conference)
    3rd International Conference on Material Science and Engineering Technology (ICMSET 2014), 24.-26.10.2014, Beijing, China
  • Advanced Materials Research 1101(2015), 120-123
    DOI: 10.4028/www.scientific.net/AMR.1101.120

Permalink: https://www.hzdr.de/publications/Publ-20692
Publ.-Id: 20692


Transport in Nanoelectronic Systems

Grebing, J.; Deb, D.; Grube, M.; Trommer, J.; Teshome, B.; Sendler, T.; Wieser, M.; Helm, M.; Weber, W.; Keller, A.; Erbe, A.

Microelectronics today is still based on the silicon technology it has been employing for the past 40 years even though it has been highly optimised and iteratively refined. Yet, it will come to a point where new concepts will be needed when “More Moore” has been extended to its ultimate limits. This is why there is a high interest in researching different approaches, e.g., with added functionality (“More-than-Moore”) [1] or even completely different concepts going “beyond Moore” like molecular electronics.

In the first part of this paper we present recent work on the top-down fabrication of silicon nano wire field effect transistors (FET) with two gates allowing not only for the control of the current through the device as it is done in a conventional FET but also to switch between the conduction mechanism, i.e., p- or n-type behaviour. It has been demonstrated previously that this kind of device can be used to build circuits [2,3]. However, we want to extend the principle from single nano wire devices to complex integrated circuits.

The second part will then go “beyond Moore” to illustrate results from our research on two challenges in the field of molecular electronics: Joining bottom-up with top-down techniques to form electrical contacts to nano objects on the one hand. We employ ion beam treatment of the substrate to form a preferential alignment for DNA templated wires. These will ultimately be used for DNA templated quantum dot transistors. On the other hand we will present a single molecular switch sensitive to light in the UV/VIS regime [4].

[1] ITRS “More-than-Moore” White Paper (2010) – http://www.itrs.net/papers.html
[2] A. Heinzig et al., Nano Lett. 12 (1) 119–124 (2012)
[3] T. Mikolajick et al., Phys. Status Solidi Rapid Res. Lett. 7 (10), 793–799
[4] Y. Kim et al., Nano Lett. 12 (7) 3736–3742 (2012)

Keywords: nanoelectronics; DNA template; nanowire; molecular electronics

  • Invited lecture (Conferences)
    9. Silicon Saxony Day, 03.07.2014, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20691
Publ.-Id: 20691


HASEonGPU - An Open-Source ASE code for calculating the gain in high power laser media on GPU clusters

Zenker, E.; Eckert, C.; Albach, D.; Bussmann, M.; Debus, A.

We present an adaptive Monte Carlo approach for computing the amplified spontaneous emission (ASE) flux in large size laser gain media pumped by pulsed lasers. Computations are based on a GPU algorithm with large speedup compared to previously existing solutions, capable of simulating the upcoming generation of high-power laser systems.

Keywords: GPU; MPI; Monte Carlo; laser; ASE flux; CUDA; HPC; parallel; gain media; high-power laser systems

  • Poster
    16th Advanced Accelerator Concepts Workshop, 13.-18.07.2014, San Jose, USA

Permalink: https://www.hzdr.de/publications/Publ-20690
Publ.-Id: 20690


An adaptive, load-balanced MPI/GPU-Code for calculating the gain in High Power Laser media

Zenker, E.; Eckert, C.; Albach, D.; Bussmann, M.

We present an adaptive Monte Carlo approach for computing the amplified spontaneous emission (ASE) flux in a laser medium pumped by pulsed lasers. For high energy laser systems with large apertures sufficient spatial resolution requires high computational power. We have developed an adaptive multi-node GPU algorithm with load balancing that shows close to perfect strong scaling that allows for large speedups compared to previously existing CPU implementations. This code will allow to calculate the ASE flux in large size gain media as they will be used in the upcoming generation of high-power laser systems.

Keywords: CUDA; MPI; Monte Carlo; ASE flux; HPC; Cluster; laser; parallel; GPU

  • Lecture (Conference)
    Workshop Programming of Heterogeneous Systems in Physics, 14.-15.07.2014, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20689
Publ.-Id: 20689


Spectroscopic investigation of the complexation of trivalent actinides/lanthanides in body fluids

Wilke, C.; Barkleit, A.; Stumpf, T.

The lanthanide and actinide elements are exogenous metals, which have no essential role in normal biochemistry. Through different processes these heavy metals can be potentially released into the environment where they can be incorporated into the food chain. There are executed Laser-Fluorescence measurements to possible complexes of Eu(III) in body fluids of the human gastrointestinal tract.

Keywords: trivalent lanthanides/actinides; TRLFS; body fluids

  • Poster
    Wilhelm and Else Heraeus Physics School on "Ionizing Radiation and Protection of Man", 10.-22.08.2014, Bad Honnef, Deutschland
  • Poster
    Aufbereitung von Wasserproben und Nachweis von Radionukliden in Wasserproben, 25.-27.11.2014, KIT, Karlsruhe, Deutschland
  • Lecture (others)
    Workshop zum Verbund "Transfer von Radionukliden in aquatischen Ökosystemen", 20.-21.04.2015, Bremen, Deutschland
  • Poster
    GDCh-Wissenschaftsforum Chemie 2015 Chemie verbindet, 30.08.-02.09.2015, Dresden, Deutschland
  • Lecture (others)
    10th HZDR PhD Seminar, 02.-04.11.2015, Altenberg, Deutschland
  • Lecture (others)
    2. Workshop TransAqua zum Thema „Verhalten von Radionukliden im Wasserpfad“, 16.-17.11.2015, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20688
Publ.-Id: 20688


Do microorganisms help to clean up uranium polluted waters?

Gerber, U.; Krawczyk-Bärsch, E.; Arnold, T.; Stumpf, T.

The well examined uranium mining waste piles Königstein (Germany) is heavily polluted with uranium and also other toxic metals. Despite it is a reservoir for a high diversity of microorganisms that have evolved special strategies to survive in these extreme environments. Microorganisms are the beginning of the food chain and therefor the transfer of bound uranium along this food chain could rise to a serious threat to human health. The aim of the study should be to characterize the quantitative and structural interactions of different microorganisms with uranium in environmental concentrations and pH ranges. Bodo saltans a eukaryotic flagellate and it´s feeder bacterium Acidovorax facilis should be the representatives of this biodiversity.

Keywords: uranium; microorganisms; sorption

  • Poster
    WE-Heraeus Physics School in Ionizing Radiation and Protection of Man, 10.-22.08.2014, Bad Honnef, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20687
Publ.-Id: 20687


Contactless inductive flow tomography: brief history and recent developments in its application to continuous casting

Ratajczak, M.; Gundrum, T.; Stefani, F.; Wondrak, T.

The contactless inductive flow tomography (CIFT) aims at reconstructing the velocity field of electrically conducting fluids, with special focus on applications in metallurgy and crystal growth technologies The method relies on the induction of secondary magnetic fields if the moving fluid is exposed to a primary magnetic field. The theoretical foundation of the method is delineated, and some early experiments on the reconstruction of the three-dimensional flow in a cylinder are sketched. Then, the recent efforts to apply CIFT to various model problems in connection with the continuous casting of steel are summarized.

Permalink: https://www.hzdr.de/publications/Publ-20686
Publ.-Id: 20686


P1401WO-Komplementärer Widerstandsschalter, Kontaktierte Polykristalline Piezo- oder Ferroelektrische Dünnschicht, Verfahren zum Verschlüsseln einer Bitfolge

Schmdit, H.; Kolitsch, A.; Manjunath, N.; Ou, X.; Shuai, Y.; Skorupa, I.; You, T.; Bürger, D.; Du, N.

Gemäß verschiedenen Ausführungsformen kann ein komplementärer Widerstandsschalter aufweisen: zwei äußere Kontakte (T1, T2 ), zwischen denen zwei piezo- oder ferroelektrische Schichten (11a und 11b) liegen, die durch einen inneren gemeinsamen Kontakt voneinander getrennt sind, dadurch gekennzeichnet, dass mindestens ein Bereich der piezo- oder ferroelektrischen Schicht (11a und 11b) mindestens einmal derart modifiziert ist, dass in der piezo- oder ferroelektrischen Schicht (11a und 11b) jeweils zwischen dem inneren Kontakt und dem zugehörigen äußeren Kontakt ein Bereich (11') der Dicke (d ') entsteht, weicher mindestens zusätzlich in einem Bereich (11") der Dicke (d") modifiziert sein kann, wobei a) die äußeren Kontakte Oberflächenkontakte (Sa) und (Sb) und der innere Kontakt ein gemeinsamer zugehöriger Gegenkontakt (O) oder die äußeren Kontakte Gegenkontakte (Oa) und (Ob) und der innere Kontakt ein gemeinsamer zugehöriger Oberflächenkontakt (S) sind, b) die Oberflächenkontakte (S), (Sa) und (Sb) gleichrichtend und die Gegenkontakte (O) bzw. (Oa) und (Ob) nicht-gleichrichtend sind, c) sich die modifizierten Bereiche in der piezo- oder ferroelektrischen Schicht (11a und 11b) an den Oberflächenkontakten (S) bzw. (Sa) und (Sb) ausbilden, d) die piezo- oder ferroelektrische Schichten (11, 11', 11") verschiedene verspannungsabhängige strukturelle Phasen mit unterschiedlicher Bandlücke und/oder unterschiedlicher Polarisationsladung aufweisen, und e) die elektrische Leitfähigkeit der piezo- oder ferroelektrischen Schichten (11, 11', 11") unterschiedlich ist.

  • Patent
    PCT/EP2014/050829 - Offenlegung: 14.07.2014;

Permalink: https://www.hzdr.de/publications/Publ-20685
Publ.-Id: 20685


Evaluation of metabolism, plasma protein binding and other biological parameters after administration of (−)-[18 F]Flubatine in humans

Patt, M.; Becker, G. A.; Grossmann, U.; Habermann, B.; Schildan, A.; Wilke, S.; Deuther-Conrad, W.; Graefe, S.; Fischer, S.; Smits, R.; Wagenknecht, G.; Steinbach, J.; Gertze, H.-J.; Hesse, S.; Schönknecht, P.; Brust, P.; Sabri, O.

Introduction
(−)-[18 F]Flubatine is a PET tracer with high affinity and selectivity for the nicotinic acetylcholine α4β2 receptor subtype. A clinical trial assessing the availability of this subtype of nAChRs was performed. From a total participant number of 21 Alzheimer’s disease (AD) patients and 20 healthy controls (HCs), the following parameters were determined: plasma protein binding, metabolism and activity distribution between plasma and whole blood.

Methods
Plasma protein binding and fraction of unchanged parent compound were assessed by ultracentrifugation and HPLC, respectively. The distribution of radioactivity (parent compound + metabolites) between plasma and whole blood was determined ex vivo at different time-points after injection by gamma counting after separation of whole blood by centrifugation into the cellular and non-cellular components. In additional experiments in vitro, tracer distribution between these blood components was assessed for up to 90 min.

Results
A fraction of 15% ± 2% of (−)-[18F]Flubatine was found to be bound to plasma proteins. Metabolic degradation of (−)-[18F]Flubatine was very low, resulting in almost 90% unchanged parent compound at 90 min p.i. with no significant difference between AD and HC. The radioactivity distribution between plasma and whole blood changed in vivo only slightly over time from 0.82 ± 0.03 at 3 min p.i. to 0.87 ± 0.03 at 270 min p.i. indicating the contribution of only a small amount of metabolites. In vitro studies revealed that (−)-[18F]Flubatine was instantaneously distributed between cellular and non-cellular blood parts.

Discussion
(−)-[18F]Flubatine exhibits very favourable characteristics for a PET radiotracer such as slow metabolic degradation and moderate plasma protein binding. Equilibrium of radioactivity distribution between plasma and whole blood is reached instantaneously and remains almost constant over time allowing both convenient sample handling and facilitated fractional blood volume contribution assessment.

Keywords: Flubatine; Plasma protein binding; Metabolism; Clinical trial; PET; Fluorine-18

Permalink: https://www.hzdr.de/publications/Publ-20684
Publ.-Id: 20684


The influence of metallic brazing materials on the strain formation of internally water-cooled X-ray optics

Oberta, P.; Kittler, M.; Áč, V.; Hrdý, J.; Iragashi, N.; Scheinost, A. C.; Uchida, Y.

An extended study of metallic bonding material for internally cooled optics is presented. The study shows the influence of the different material properties on the final quality of the bond in terms of diffracted wave-front distortion, i.e. enlargement of the rocking curve. By choosing the proper bonding material and applying the proper bonding conditions, the influence of the bonding material can be fully eliminated. Furthermore the degradation of some bonding material due to the extreme working conditions of the optics is presented. Measurement results from ESRF and KEK confirm the importance of the proper bonding material choice.

Keywords: x-ray optics; silica; bonding; XAS

Permalink: https://www.hzdr.de/publications/Publ-20683
Publ.-Id: 20683


Frequency dependence of an alternating magnetic field driven flow

Cramer, A.; Galindo, V.

The flow induced by a single-phase alternating magnetic field (AMF) is studied mainly numerically, and by experiments at mains frequency. For validation, the well-known dependence of the characteristic velocity uc on the magnetic induction B in the turbulent case when the mean velocity scales with the shear velocity, υc ∝ B, is reproduced experimentally and in the simulations. Ultrasonic flow mapping reveals that the eddies in the well believed flow structure of two toroidal vortices one on top of another do not only simply oscillate, but rather the topology of the flow changes slowly on a large scale. Besides such turbulence characteristics, it will be shown that the global flow structure depends strongly also on the frequency of the AMF. An investigation of the change of the characteristic velocity with frequency suggests a quantitative difference of flows in an AMF compared to rotating and travelling magnetic fields.

  • Contribution to proceedings
    MEP 2014 Modelling for Electromagnetic Processing, 16.-19.09.2014, Hannover, Deutschland
  • Lecture (Conference)
    MEP 2014 Modelling for Electormagnetic Processing, 16.-19.09.2014, Hannover, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20682
Publ.-Id: 20682


Automated recognition of quasi-planar ignimbrite sheets as paleosurfaces via robust segmentation of digital elevation models: an example from the Central Andes

Székely, B.; Koma, Z.; Karátson, D.; Dorninger, P.; Wörner, G.; Brandmeier, M.; Nothegger, C.

Quasi-planar morphological surfaces may become dissected or degraded with time, but still retain original features related to their geologic-geomorphic origin. To decipher the information hidden in the relief, recognition of such features is required, possibly in an automated manner. In our study, using Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM), an existing algorithm has been adapted to recognize quasi-planar features fulfilling specified criteria. The method has been applied to a study area of the Central Andes with Miocene to Quaternary volcanic edifices, tilted ignimbrite surfaces, and basin-filling sediments. The result is a surface segmentation, whereas non-planar features (gullies, tectonic faults, etc.) are sorted out. The main types of geomorphic features that can be distinguished and interpreted are as follows. (1) The west-dipping western margin of the Altiplano is differentiated into segments of the lower sedimentary cover that of increased erosion by tectonic steepening at intermediate levels, and an upper plane with limited erosion. (2) In the central part of the Western Cordillera, the Oxaya ignimbrite block shows a ‘striped’ bulging pattern that results from a smoothly changing surface dip. This pattern is due to continuous folding/warping of the ignimbrite block possibly related to gravitational movements. (3) To the west, large, uniform planes correspond to flat, smooth, tectonically undisturbed surfaces of young sedimentary cover of the Central Basin. (4) The evolution of Taapaca volcanoes with sector collapse events and cone-building phases is shown by several segments with overlapping clastic aprons. (5) To the east, on the western margin of the Altiplano, young intermontane basins filled by Upper Miocene sediments show progressively increasing dip toward basin margins, reflected by a circular pattern of the segmentation planes. We show that the segmentation models provide meaningful images and additional information for geomorphometric analysis that can be interpreted in terms of geological and surface evolution models.

Keywords: geomorphometry; dissected surfaces; robust segmentation; digital elevation model; paleosurfaces

  • Earth Surface Processes and Landforms 39(2014)10, 1386-1399
    DOI: 10.1002/esp.3606

Permalink: https://www.hzdr.de/publications/Publ-20681
Publ.-Id: 20681


Plasma based nanotechnology against corrosion of CuZn and TiAl alloys

Bregolin, F.; Pelic, B.; Prucnal, S.; Yankov, R.; Skorupa, W.

Experiments have been undertaken to explore the improvement of the aqueous corrosion and high temperature oxidation of CuZn and TiAl, respectively, by applying plasma immersion ion implantation (PI3).
The atmospheric corrosion of the tongues within the reed pipes which consist of a Cu-Zn alloy (namely brass) is strongly enhanced by traces of VOC (acetic acid vapors) and also the alloy’s instability caused by dezincification. A significant improvement in corrosion resistance has been achieved by applying a 30 nm aluminum oxide film using pulsed laser deposition (PLD) and implanting nitrogen ions into the near surface and the interface regions. In the case of γ-TiAl alloys which exhibit poor oxidation resistance, despite their good mechanical properties at elevated temperatures, this limits the replacement of the nowadays used heavy components made of Ni-alloys. A significant improvement in high temperature oxidation resistance of TiAl alloys (up to 900 °C) has been achieved by implanting fluorine ions (1017 cm-2) at 30 keV into the alloy’s subsurface using PI3 process. A TiAl alloy modified in this way has been shown to acquire a stable, adherent and highly protective alumina scale (Al2O3) under high temperature oxidation in air. The influence of the implanted N+ into CuZn and F+ into TiAl samples on the corrosion process has been investigated. For the sample evaluation, different characterization methods including scanning electron microscope with energy dispersive X-ray spectroscopy (SEM / EDX), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), Elastic recoil detection analysis (ERDA), and Dektak stylus profiling have been applied to determine the chemical composition, the elemental depth profiles, roughness and defect formation of the samples before and after exposure.

Keywords: Plasma immersion ion implantation (PI3); Pulsed laser deposition (PLD); corrosion of reed organ pipes; CuZn alloys; TiAl alloys; oxidation protection

  • Lecture (Conference)
    X-th INTERNATIONAL CONFERENCE - Ion Implantation and Other Applications of Ions and Electrons, 23.-26.06.2014, Kazimierz Dolny, Poland

Permalink: https://www.hzdr.de/publications/Publ-20680
Publ.-Id: 20680


TRLFS studies on biosorption of uranium on halophilic archaea at high ionic strength (3 M NaCl)

Bader, M.; Cherkouk, A.; Drobot, B.; Stumpf, T.

Salt rock is one of the three potential host rock types for long-term storage of radioactive waste in a deep geological repository in Germany. To date little is known about the interactions of halophilic microorganisms which are indigenous in salt rock and radionuclides under these extreme conditions. The microorganisms can impact the oxidation state, speciation and solubility of radionuclides and hence their mobility. These information are necessary to improve the safety assessment of a geological repository.
To characterize the interactions between radionuclides and microorganisms under high saline conditions biosorption experiments with Halobacterium noricense DSM 15987 and uranium were done. This halophilic archaea is used because of its ubiquitous occurrence in salt rock [1] .
Due to its halophilicity the working concentration of NaCl was 3 M. The batch experiments have shown that 90% of U(VI) was bound to the cells after 48 h. The formed uranium complexes were characterized by the use of infrared-spectroscopy and time-resolved laser-induced fluorescence spectroscopy (TRLFS). Despite the high concentration of chloride a luminescence spectrum could be recorded. The spectra of the salt solutions (3 M NaCl) with different uranium concentrations (10 µM, 50 µM, 100 µM; pH 6) without cells have the same emission maxima (512, 536, 560 nm; see Fig.1). Comparing the position of this bands with literature they can be assigned to the (UO2)3(OH)5+ complex [2]. In contrast, the suspension consisting of Halobacterium noricense cells and U(VI) in 3 M NaCl lead to a red-shift of the spectra where the emission bands (501, 522, 550 nm; see Fig. 1) indicate the uranyl phosphate complex UO2PO4- [3]. It can be concluded that uranium binds to phosphate groups which are located on the cell wall or inside the cells. Further investigations (e.g. TEM/EDX) are required for differentiation. These first results show that the characterization of the formed complexes is possible with TRLFS despite the high chloride concentration and can be used for further examinations.

1. Swanson, J.S., et al. (2012) Status Report Los Alamos National Laboratory
2. Moulin, C., et al. (1998) Appl. Spectrosc. 52, 528-535.
3. Bonhoure, I., et al.(2007) Radiochim. Acta. 95, 165-172.

  • Lecture (Conference)
    Advanced Techniques in Actinide Spectroscopy 2014 (ATAS 2014), 03.-07.11.2014, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20679
Publ.-Id: 20679


Thermal evolution of defects in undoped zinc oxide grown by pulsed laser deposition

Wang, Z.; Su, S.; Ling, F. C. C.; Anwand, W.; Wagner, A.

Undoped ZnO films are grown by pulsed laser deposition on c-plane sapphire with different Oxygen pressures. Thermal evolutions of defects in the ZnO films are studied by secondary ion mass spectroscopy (SIMS), Raman spectroscopy, and positron annihilation spectroscopy (PAS), and with the electrical properties characterized by the room temperature Hall measurement. Oxygen deficient defect related Raman lines 560 cm^-1 and 584 cm^-1 are identified and their origins are discussed. Thermal annealing induces extensive Zn out-diffusion at the ZnO/sapphire interface and leaves out Zn-vacancy in the ZnO film. Two types of Zn-vacancy related defects with different microstructures are identified in the films. One of them dominates in the samples grown without oxygen. Annealing the sample grown without oxygen or growing the samples in oxygen would favor the Zn-vacancy with another microstructure, and this Zn-vacancy defect persists after 1100 °C annealing.

Keywords: undoped ZnO films; Raman spectroscopy; positron annihilation; green luminescence

Permalink: https://www.hzdr.de/publications/Publ-20678
Publ.-Id: 20678


Nature of red luminescence band in research-grade ZnO single crystals: A “self-activated” configurational transition

Chen, Y. N.; Xu, S. J.; Zheng, C. C.; Ning, J. Q.; Ling, F. C. C.; Anwand, W.; Brauer, G.; Skorupa, W.

By implanting Zn+ ions into research-grade intentionally undoped ZnO single crystal for facilitating Zn interstitials (Zni) and O vacancies (VO) which is revealed by precise X-Ray diffraction rocking curves, we observe an apparent broad red luminescence band with a nearly perfect Gaussian lineshape. This red luminescence band has the zero phonon line at ~2.4 eV and shows distinctive lattice temperature dependence which is well interpreted with the configurational coordinate model. It also shows a low “kick out” thermal energy and small thermal quenching energy. A “selfactivated” optical transition between a shallow donor and the defect center of Zni-VO complex or VZnVO di-vacancies is proposed to be responsible for the red luminescence band. Accompanied with the optical transition, large lattice relaxation simultaneously occurs around the center, as indicated by the generation of multiphonons.

Keywords: ZnO; Zn Implantation; red luminescence; Zn interstitials; O vacancies

Permalink: https://www.hzdr.de/publications/Publ-20677
Publ.-Id: 20677


Quantification of brittle-ductile failure behavior of ferritic reactor pressure vessel steels using the Small-Punch-Test and micromechanical damage models

Linse, T.; Kuna, M.; Viehrig, H.-W.

Two German ferritic pressure vessel steels are examined in the brittle to ductile transition regime as a function of temperature and irradiation.The experiments are done by a miniaturized Small-Punch-Test in hot cells within the temperature range of -185 °C up to 70 °C. From the load–displacement curve of the SPT,the yield curves and parameters of both a non-local GURSON-TVERGAARD-NEEDLEMAN ductile damage model and a modified BEREMIN model are identified. The influence of temperature and irradiation on the model parameters is analyzed. All parameters are verified by comparison with results from standard test methods. The parameters, identified from SPT, are used to simulate the failure behavior in standard fracture mechanics specimens.In the uppershelf, the non-local GTN-model is applied to simulate crack resistance curves,from where the fracture toughness data could be successfully predicted. In the lower shelf, the WEIBULL-stress of the specimens was computed to find out the statistics of fracture toughness values.Finally, the modified BEREMIN model and the non-local ductile damage model were combined to evaluate the failure of fracture specimens in the brittle-ductile transition region.This way, an acceptable agreement with Master-Curve data for non-irradiated steels could be achieved in the whole temperature range.

Keywords: Non-local ductiledamagemodel; Beremin-Model; Small-Punch-Test; Brittle-ductile transition

Permalink: https://www.hzdr.de/publications/Publ-20676
Publ.-Id: 20676


Numerical simulations of two-phase stratified turbulent flow in a channel

Apanasevich, P.; Lucas, D.; Sato, Y.; Ničeno, B.

The main goal of the current research project is numerical investigation of steam condensation on a subcooled water interface. The Direct Numerical (DNS) and Large Eddy Simulation (LES) methods are used to study physical mechanisms determining the interfacial heat and mass transfer. The paper presents a part of this work that deals with the evaluation of the Sub-Grid Scale (SGS) modeling within the LES framework. For that purpose two simulations of a stratified turbulent counter-current steam-water flow in a channel were conducted using the Wall-Adapting Local Eddy-Viscosity (WALE) SGS model. To exclude the phase change and to focus on the turbulence in the vicinity of the interface, both phases were assumed to be at saturation tem-perature. The simulations have shown that the variation of the WALE model constant has a significant influence on the mean velocity and velocity fluctuations and should be calibrated using the DNS data. It was also shown that the deformable steam-water interface has a strong damping effect on the near-interfacial turbulent field in the liquid phase.

Keywords: Computational fluid dynamics; free surface flows; large eddy simulation; turbulent flows

  • Contribution to proceedings
    2nd International Symposium on Multiscale Multiphase Process Engineering (MMPE2014), 24.-27.09.2014, Hamburg, Deutschland
    2nd International Symposium on Multiscale Multiphase Process Engineering
  • Poster
    2nd International Symposium on Multiscale Multiphase Process Engineering (MMPE2014), 24.-27.09.2014, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20673
Publ.-Id: 20673


Isobar separation of 93Zr and 93Nb at 24MeV with a new multi-anode ionization chamber

Martschini, M.; Buchriegler, J.; Collon, P.; Kutschera, W.; Lachner, J.; Lu, W.; Priller, A.; Steier, P.; Golser, R.

93Zr with a half-life of 1.6 Ma is produced with high yield in nuclear fission, and thus should be present as a natural or anthropogenic trace isotope in all compartments of the general environment. This isotope would immediately find numerous applications, however, its detection at sufficiently low levels has not yet been achieved. AMS measurements of 93Zr suffer from the interference of the stable isobar 93Nb. At the Vienna Environmental Research Accelerator VERA a new multi-anode ionization chamber was built. It is optimized for isobar separation in the medium mass range and is based on the experience from AMS experiments of 36Cl at our 3MV-facility. The design provides high flexibility in anode configuration and detector geometry. After validating the excellent energy resolution of the detector with 36Cl, it was recently used to study Iron-Nickel and Zirconium-Niobium-Molybdenum isobar separation. To our surprise, the separation of 94Zr (Z=40) from 94Mo (Z=42) was found to be much better than that of 58Fe (Z=26) from 58Ni (Z=28), despite the significantly larger deltaZ/Z of the latter pair. This clearly contradicts results from SRIM-simulations and suggests that differences in the stopping behavior may unexpectedly favor identification of 93Zr. At 24 MeV particle energy, a 93Nb (Z=41) suppression factor of 1000 was achieved based on a 93Zr spectrum obtained by interpolation between experimental spectra from the two neighboring stable isotopes 92Zr and 94Zr. Assuming realistic numbers for chemical Niobium reduction, a detection level of 93Zr/Zr below 10^9 seems feasible.

Keywords: accelerator mass spectrometry; isobar separation; isobar suppression; anthropogenic trace isotope; VERA; SRIM; Niobium; Zirconium

  • Lecture (Conference)
    AMS-13 The Thirteenth International Conference on Accelerator Mass Spectrometry, 24.-29.08.2014, Aix en Provence, France

Permalink: https://www.hzdr.de/publications/Publ-20672
Publ.-Id: 20672


Investigations on the Discrimination of Nuclear Reactor Core State Changes by the external Gamma Radiation Field

Brachem, C.; Konheiser, J.; Hampel, U.

Monte Carlo Simulations have been carried out to estimate the gamma radiation distributions outside the reactor pressure vessel of a generic pressurized water reactor for a set of simplified accident-like reactor states.
This is done as a first step towards the development of a non-invasive core monitoring system for light water reactors.
The results show a change in the shape of the gamma ray distributions for decreasing coolant levels as well as a vast increase in flux for corium accumulating inside the lower head.

Keywords: gamma radiation; Monte Carlo simulation; PWR; accident

  • Lecture (Conference)
    46th Annual Meeting on Nuclear Technology, 05.-07.05.2014, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-20671
Publ.-Id: 20671


The Gamma Radiation emitted by a PWR Core under severe Accident Conditions

Brachem, C.; Konheiser, J.; Hampel, U.

The gamma radiation emitted by a nuclear reactor core might contain information about the reactor state. This information may be used in a monitoring system for severe accidents.
The Technische Universit¨at Dresden and the Zittau/G¨orlitz University of Applied Sciences are currently carrying out feasibility studies for the development of such a system in a collaborative effort. As one part of such feasibility studies we performed Monte Carlo simulations on a simplified model of a generic pressurized water reactor. For a set of states which represent scenarios of a coolant level decrease and core melt, the gamma radiation distribution outside the reactor pressure vessel has been computed.
The results are presented in this paper.
They indicate that different coolant levels yield different gamma radiation distributions, and that an accumulation of corium inside the lower head is detectable from the outside.

Keywords: gamma radiation; Monte Carlo simulation; PWR; accident

  • Lecture (Conference)
    22nd International Conference on Nuclear Engineering (ICONE22), 07.-11.07.2014, Prague, Czech Republic
  • Contribution to proceedings
    22nd International Conference on Nuclear Engineering (ICONE22), 07.-11.07.2014, Prague, Czech Republic
    Proceedings of the 22nd International Conference on Nuclear Engineering, ICONE22

Permalink: https://www.hzdr.de/publications/Publ-20670
Publ.-Id: 20670


Development of a Joule-class Yb:YAG amplifier and its implementation in a CPA system generating 1TW pulses

Wandt, C.; Klingebiel, S.; Keppler, S.; Hornung, M.; Loeser, M.; Siebold, M.; Skrobol, C.; Kessel, A.; Trushin, S. A.; Major, Z.; Hein, J.; Kaluza, M. C.; Krausz, F.; Karsch, S.

In this paper the development and implementation of a novel amplifier setup as an additional stage for the CPA pump laser of the Petawatt Field Synthesizer, currently developed at the Max-Planck-Institute of Quantum Optics, is resented. This amplifier design comprises 20 relay-imaged passes through the active medium which are arranged in rotational symmetry. As the gain material, an in-house-developed Yb:YAG active-mirror is used. With this setup, stretched 4 ns seed pulses are amplified to output energies exceeding 1 J with repetition rates of up to 2 Hz. Furthermore, a spectral bandwidth of 3.5nm (FWHM) is maintained during amplification and the compression of the pulses down to their Fourier-limit of 740 fs is achieved. To the best of our knowledge, this is the first demonstration of 1TW pulses generated via CPA in diode-pumped Yb:YAG.

Permalink: https://www.hzdr.de/publications/Publ-20669
Publ.-Id: 20669


Sponge-like Si-SiO2 nanocomposite for PV applications

Liedke, B.; Heinig, K.-H.; Friedrich, D.; Schmidt, B.; Mücklich, A.; Keles, U.; Bulutay, C.

The aim of this talk is to explain method of fabrication, modification and optimization of Sponge-like Si-SiO2 nanocomposite.
It consists of Si embedded in SiO2 fabricated by spinodal decomposition of sputter-deposited silicon-rich oxide SiOx≈1. Thermal treatment using rapid thermal processing and oven annealing requires annealing times of few tens of sec. up to few tens of min. However, in a thin film technology the phase separation of SiOx at high temperatures requires a very rapid thermal processing of few tens of ms in order to avoid substrate damage.
Here, the structure of the Si-SiO2 nanocomposite was investigated by energy-filtered transmission electron microscopy (EFTEM), EFTEM tomography and atom probe tomography, which revealed a percolated Si morphology. This is in excellent agreement with atomistic simulations using kinetic Monte-Carlo method. Depending on the annealing time and temperature a feature size in the range of 2...5 nm was found, which is small enough for band gap widening due to quantum confinement.
We show that the favorable properties of Si-SiO2 nanocomposite, e.g. quantum size effect and percolated morphology, make it a suitable material for PV absorber.

Keywords: sponge-like nanocomposite; SiOx; photovoltaic; absorber; phase separation; band-gap engineering

  • Lecture (others)
    Seminar an der TU Bergakademie Freiberg, 15.07.2014, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-20668
Publ.-Id: 20668


Optimization of magnetic amplification by flow constraints in turbulent liquid sodium

Nornberg, M. D.; Taylor, N. Z.; Forest, C. B.; Rahbarnia, K.; Kaplan, E.

Direct measurements of the vector turbulent emf in a driven two-vortex flow of liquid sodium were performed in the Madison Dynamo Experiment [K. Rahbarnia et al., Astrophys. J. 759, 80 (2012)]. The measured turbulent emf is anti-parallel with the mean current and is almost entirely described by an enhanced resistivity, which increases the threshold for a kinematic dynamo. We have demonstrated that this enhanced resistivity can be mitigated by eliminating the largest-scale eddies through the introduction of baffles. By tailoring the flow to reduce large-scale components and control the helical pitch, we have reduced the power required to drive the impellers, doubled the magnetic flux generated by differential rotation, and increased the decay time of externally applied magnetic fields. Despite these improvements, the flows remain sub-critical to the dynamo instability due to the reemergence of turbulent fluctuations at high flow speeds.

Keywords: Magnetic fields; Magnetic field measurements; Rotating flows; Diffusion; Flow Instabilities

Permalink: https://www.hzdr.de/publications/Publ-20666
Publ.-Id: 20666


Stand-alone modelling of the high burnup structure formation and burst release during design basis accidents

Holt, L.; Schubert, A.; van de Laar, J.; van Uffelen, P.

In the first part of the paper, experimental results for the Xe depletion in the matrix of high burn-up fuel are analysed from the High Burnup Rim Project (HBRP). The influence of the burn-up and irradiation temperature on the Xe concentration was investigated using a multi-physics approach involving various simulation tools. The temperature influence was accounted for by means of the temperature dependent effective burn-up. Good agreement was found between the modelled temperature threshold of the effective burn-up and the experimental temperature threshold between un- and restructured fuel in the HBRP. However, a systematic difference was observed between the onset burn-up derived from the Xe measurements in highly enriched discs such as those of HBRP and the corresponding values derived from irradiated Light Water Reactor fuel rods and reported in the open literature. A sensitivity study identified the neutron flux spectrum and the fission product yields as the main reasons for the observed differences.

In the second part of the paper, we present a new model for dealing with release of fission gas from nuclear fuel containing a high burnup structure (HBS) during design basis accidents such as loss of coolant accident. The fission gas release from the HBS during an accident is assumed to be caused by crack formation. The empirical model is developed on the basis of out-of-pile annealing tests carried out with samples from HBRP discs irradiated in Halden, and then subsequently applied to an integral in-pile test in IFA-650. In addition to the comparison with the experimental data, the new model is also compared with some models available in the open literature. Finally, from the discussion we also outline the experimental and modelling work needed for further model refinements.

  • Contribution to proceedings
    Enlarged Halden Programme Group Meeting, 07.-12.09.2014, Røros, Norway

Permalink: https://www.hzdr.de/publications/Publ-20665
Publ.-Id: 20665


Stabilität des Hypoxietracers [18F]-FMISO während sequentieller PET-Untersuchungen bei Patienten mit radiochemotherapierten HNO-Tumoren und Korrelation von funktionellen Tumor-Subvolumina zur Rezidivlokalisation

Zschaeck, S.; Haase, R.; Zöphel, K.; Abolmaali, N.; Perrin, R.; Kotzerke, J.; Steinbach, J.; Zips, D.; Krause, M.; Baumann, M.

Fragestellung.
Untersucht wurde die Verteilung der Aktivitätskonzentration des Hypoxietracers FMISO in sequentiellen PET-Untersuchungen bei Patienten mit primär radiochemotherapierten Kopf-Hals-Tumoren. Patienten mit residueller Hypoxie während der zweiten Behandlungswoche erleiden fast immer ein Lokalrezidiv im Hochdosis-Bereich. Zur Erhöhung der Strahlendosis werden unter anderem FMISO-PET-basiert adaptierte Dosisverschreibungen (Dose-painting) diskutiert. Für eine erste Plausibilitätsprüfung dieses Ansatzes wurde die Stabilität der FMISO-Verteilung und die Lokalisation von Lokalrezidiven mit, während der Therapie erfassten, PET-Parametern untersucht.
Methodik.
Von 25 Patienten, die während der primären Radiochemotherapie sequentielle FMISO Aufnahmen erhielten (FMISO1 vor Therapie, FMISO2 in der ersten, FMISO3 in der zweiten und FMISO4 in der fünften Woche) zeigten 12 eine ausgeprägte residuelle Hypoxie (bestimmt als TBRmax>1,9). Sechs dieser Patienten hatten ein auswertbares Lokalrezidiv (2 x in der CT und 4 x in der FDG-PET-CT). Die Rezidivbildgebung und darauf basierende Konturen wurden auf die FMISO- und FDG PET-Untersuchungen vor Therapie fusioniert und die PET-Konturen auf ein Überlappen überprüft.
Ergebnis.
Die wiederholten FMISO-PET-Untersuchungen während der Radiochemotherapie zeigten ein sehr heterogenes volumetrisches Verhalten der hypoxischen Subvolumina zu Beginn der Therapie. In der FMISO4-Bildgebung war nur noch selten Hypoxie nachzuweisen. Trotz der Größenvariationen innerhalb der ersten beiden Wochen war die Überlappung der sequentiellen Sub-Volumina ausgeprägt, bestimmt als mittlerer Dice-Index von 62% zwischen FMISO1 und FMISO2 und 58% zwischen FMISO2 und FMISO3. Die Lokalisation des Aktivitäts-Hot-Spots SUVmax zeigte demgegenüber dramatische Veränderungen, der mittlere Abstand betrug zwischen FMISO2 und FMISO3 13,5
mm. Die vorhandenen, registrierten Rezidive zeigten sowohl ein Überlappen mit dem initialen FDG-PET, als auch mit FMISO1 und FMISO3 (medianer Dice-Index 27, 24 und 28%). Zur Überprüfung ob es wirklich eine reproduzierbare und stabile FMISO-PET-positive Region gibt, die sich zur Dosiseskalation eignet, wurden die überlappenden Konturen verschiedener FDG und FMISO-Konturen zu einer gemeinsamen Kontur zusammengefasst (FDG, FMISO1, FMISO3). Nur in 2 Fällen trat das Rezidiv in der so eingegrenzten Region auf.
Schlussfolgerung.
Die FMISO-Verteilung variiert während der ersten beiden Therapiewochen erheblich, es erfolgt jedoch keine komplette Verschiebung des hypoxischen Subvolumens sondern eine unterschiedlich ausgeprägte Volumenveränderung. Die Überlappung der FMISO-PET-basierten Subvolumina mit dem Lokalrezidiv stärken die Hypothese, dass radioresistente Zellen in diesen Regionen das Rezidiv verursachen können. Die Variabilität des SUVmax und die geringe Rate an Rezidiven innerhalb einer reproduzierbar abgrenzbaren FDG und FMISO aviden Region sprechen jedoch gegen eine, rein voxelbasierte, Dosisverschreibung.

  • Poster
    20. Jahrestagung der Deutschen Gesellschaft für Radioonkologie (DEGRO), 03.-06.07.2014, Düsseldorf, D
  • Abstract in refereed journal
    Strahlentherapie und Onkologie 190(2014)Suppl. 1, 52

Permalink: https://www.hzdr.de/publications/Publ-20664
Publ.-Id: 20664


Spin dynamics in triangular-lattice antiferromagnets Cs2CuBr4 and Cs2CuCl4: high-field ESR studies

Zvyagin, S.

A spin-1/2 Heisenberg antiferromagnet (AF) on a triangular lattice is the paradigmatic model in quantum magnetism, which was intensively studied. In spite of numerous theoretical studies (which predict a rich variety of grounds states, ranging from a gapless spin liquid to Néel order), many important details of the phase diagram of triangular-lattice AFs remain controversial or even missing. In order to test the theory experimentally, a precise information on the spin-Hamiltonian parameters for the materials of interest is highly demanded. Here, we present results of high-field electron spin resonance (ESR) studies of spin-1/2 Heisenberg AFs Cs2CuCl4 and Cs2CuBr4 with distorted triangular-lattice structures in magnetic fields up to 50 T [1]. In the magnetically saturated phase (H>Hsat), quantum fluctuations are fully suppressed, and the spin dynamics is defined by ordinary magnons. This allows us to accurately describe the magnetic excitation spectra in both materials and, using the harmonic spin-wave theory, to determine their exchange parameters. The viability of the proposed method was first proven by applying it to Cs2CuCl4, revealing good agreement with inelastic neutron-scattering results. For the isostructural Cs2CuBr4 we obtain J/kB=14.9(7) K, J'/kB=6.1(3) K, [J'/J~0.41], providing exact and conclusive information on the exchange coupling parameters in this frustrated spin system. The approach has a broader impact and can be potentially used for any quantum magnet with reduced (e.g., by the staggered Dzyaloshinskii-Moriya interaction) translational symmetry, resulting, as predicted, in emergence of a new exchange mode above Hsat

  • Invited lecture (Conferences)
    Fifth Workshop on Current Trends in Molecular and Nanoscale Magnetism, 26.-29.05.2014, Larnaca, Cyprus

Permalink: https://www.hzdr.de/publications/Publ-20662
Publ.-Id: 20662


Site-selective TRLFS of Eu(III) doped rare earth phosphates for conditioning of radioactive wastes

Huittinen, N.; Arinicheva, Y.; Holthausen, J.; Holliday, K.; Neumeier, S.; Stumpf, T.

Crystalline ceramic materials show promise as potential waste forms for immobilization of high-level radioactive wastes. Rare earth (RE) phosphate ceramics have been found to be extremely stable over geological time scales and they show good tolerance to high radiation doses. These ceramics are able to incorporate radionuclides in well-defined atomic positions within the crystal lattice up to high (~25%) loadings, which will reduce the volume of waste in the radionuclide conditioning process. The dehydrated RE phosphates are known to crystallize in two distinct structures, depending on the ionic radius of the cation: the larger lanthanides from La3+ to Gd3+ crystallize in the nine-fold coordinated monazite structure, while the smaller lanthanides such as Lu3+ form eight-fold coordinated xenotime structures.
Structural information on the radionuclide substitution in these RE phophates can be obtained by site-selective time-resolved laser fluorescence spectroscopy (TRLFS). In our previous work we studied the structural incorporation of Eu(III), taken as an analogue for the long-lived trivalent actinides Pu(III), Am(III) and Cm(III) found in spent nuclear fuel, in the monazite LaPO4. Eu3+ was found to incorporate on the La3+ site in LaPO4 as expected, despite slight discrepancies between the ionic radii of the host and dopant cations.
In the present work we study synthetic Eu(III) doped LaPO4, GdPO4, and LuPO4, as well as mixtures thereof, to investigate the influence of the ionic radius and crystalline structure on Eu(III) substitution in the ceramic material. Results on Eu(III) substitution in the monazite and xenotime materials will be presented and influences of the ionic radii on Eu(III) substitution within the host cation sites will be discussed.

  • Poster
    Goldschmidt 2014, 08.-13.06.2014, Sacramento, USA

Permalink: https://www.hzdr.de/publications/Publ-20661
Publ.-Id: 20661


Experimentelle Untersuchungen zur Ablagerung und Remobilisierung von Aerosolpartikeln in turbulenten Strömungen

Barth, T.

Im Rahmen dieser Dissertation werden eine Serie von Grundlagenexperimenten zur Ablagerung (Deposition) und Remobilisierung (Resuspension) von Aerosolpartikeln in turbulenten Strömungen beschrieben. Die Kernmotivation stellt die Quelltermanalyse von Druckentlastungsstörfällen von Hochtemperaturreaktoren (HTR) dar. Im Primärkreislauf früherer HTR-Forschungsanlagen wurden größere Mengen an radiologisch belastetem Graphitstaub gefunden. Dieser Staub scheint größtenteils durch Abrieb zwischen den graphitischen Kernstrukturen entstanden zu sein und verteilte sich während des fortlaufenden Reaktorbetriebs über sämtliche Oberflächen des Primärkreislaufs. Während eines Druckentlastungsstörfalls kann dieser Staub durch die Gasströmung remobilisiert und aus dem Primärkreislauf ausgetragen werden. Eine Quelltermanalyse solch eines Störfallszenarios erfordert die Kenntnis über die Menge und die räumliche Verteilung des Staubs, die radiologische Belastung sowie das Remobilisierungsverhalten in Bezug auf die zu erwartenden Strömungstransienten. Nach dem heutigen Stand von Wissenschaft und Technik kann die räumlich-zeitliche Verteilung des Staubs im Primärkreislauf für stationären Reaktorbetrieb unter Verwendung eindimensionaler Systemcodes abgeschätzt werden. Jedoch ist unbekannt, welcher Anteil des Staubinventars durch die Gasströmung remobilisiert und aus dem Primärkreislauf ausgetragen werden würde.
Zur systematischen Untersuchung des Staubtransportverhaltens in turbulenten Strömungen wurden zwei kleinskalige Versuchsanlagen entwickelt und eine Serie von Depositions- und Resuspensionsexperimenten durchgeführt. Die partikelbeladene Strömung in der Heißgasumgebung des HTR-Primärkreislaufs wurde über die Verwendung von Ähnlichkeitskennzahlen auf eine Luftströmung bei Umgebungsbedingungen herunterskaliert. Die Strömung und die Partikel wurden mittels hochauflösender, bildgebender und nichtinvasiver Messverfahren räumlich und zeitlich vermessen, um eine umfangreiche Datenbasis für die Analyse der Partikeltransportprozesse zu erstellen. Inhaltlich lassen sich die durchgeführten Untersuchungen in drei Teile gliedern. Der erste Teil besteht aus zwei Studien über die Deposition und Resuspension monodisperser, sphärischer Einzelpartikel in einer ungestörten, horizontalen Kanalströmung. Die systematische Variation experimenteller Randbedingungen wie der Partikelgröße, der Oberflächenrauheit und der Strömungsgeschwindigkeit ermöglichte die Quantifizierung der einzelnen Einflussgrößen. Im zweiten und dritten Teil der Dissertation wurden die Deposition und Resuspension einer mehrschichtigen Ablagerung (Partikel-Multilayer) zwischen periodischen Stufen und in einer Kugelschüttung untersucht, um die komplexe Interaktion zwischen der turbulenten Strömung und der Multilayer-Ablagerung weiter zu erforschen.
Die gewonnenen Erkenntnisse leisten einen Beitrag für die Quelltermanalyse des Staubtransports im HTR-Primärkreislauf und können für die Weiterentwicklung numerischer Strömungssimulationen des Partikeltransports in turbulenten Strömungen verwendet werden.

Keywords: turbulent flows; aerosol particle; deposition; resuspension; high temperature reactor

  • Doctoral thesis
    TU Dresden, 2014
    Mentor: Prof. Dr.-Ing. habil. Uwe Hampel
    155 Seiten

Permalink: https://www.hzdr.de/publications/Publ-20660
Publ.-Id: 20660


Development of substrate-based radiotracers for imaging of tumour-associated lysyl oxidase activity by positron emission tomography

Kuchar, M.; Bergmann, R.; Wodtke, R.; Mosch, B.; Lenk, J.; Steinbach, J.; Pietzsch, J.; Löser, R.

kein Abstract verfügbar

  • Poster
    23rd Biennial Congress of the European Association for Cancer Research (EACR), 05.-08.07.2014, München, D
  • Abstract in refereed journal
    European Journal of Cancer 50(2014)Suppl. 5, S204

Permalink: https://www.hzdr.de/publications/Publ-20659
Publ.-Id: 20659


EphB4 negatively regulates blood vessel network formation and perfusion in human A375 melanoma xenografts

Neuber, C.; Hofheinz, F.; Bergmann, R.; Meister, S.; Steinbach, J.; Mosch, B.; Pietzsch, J.

kein Abstract verfügbar

  • Poster
    23rd Biennial Congress of the European Association for Cancer Research (EACR), 05.-08.07.2014, München, D
  • Abstract in refereed journal
    European Journal of Cancer 50(2014)Suppl. 5, S62-S63

Permalink: https://www.hzdr.de/publications/Publ-20658
Publ.-Id: 20658


A novel animal model of phaeochromocytoma for preclinical therapy evaluation

Ullrich, M.; Bergmann, R.; Pietzsch, J.; Cartellieri, M.; Peitzsch, M.; Eisenhofer, G.; Bornstein, S. R.; Ziegler, C. G.

kein Abstract verfügbar

  • Poster
    23rd Biennial Congress of the European Association for Cancer Research (EACR), 05.-08.07.2014, München, D
  • Abstract in refereed journal
    European Journal of Cancer 50(2014)Suppl. 5, S53

Permalink: https://www.hzdr.de/publications/Publ-20657
Publ.-Id: 20657


Role of extracellular S100A4 in stimulation of melanoma cells crossing the blood-brain barrier in vitro and in vivo

Herwig, N.; Wolf, S.; Haase-Kohn, C.; Steinbach, J.; Pietzsch, J.

kein Abstract verfügbar

  • Poster
    23rd Biennial Congress of the European Association for Cancer Research (EACR), 05.-08.07.2014, München, D
  • Abstract in refereed journal
    European Journal of Cancer 50(2014)Suppl. 5, S49

Permalink: https://www.hzdr.de/publications/Publ-20656
Publ.-Id: 20656


Effect of notch acuity on the apparent fracture toughness

Schindler, H.-J.; Kalkhof, D.; Viehrig, H.-W.

The fracture behaviour of a component or specimen that contains a sharp notch is governed essentially by the same theoretical relations known from cracks. The blunt notch root only causes an increase of the resistance against crack initiation, which depends on the fracture mechanism. In the present paper, the relation between fracture toughness and notch toughness is investigated by simple analytical models. The derived formulas were compared with experimental results obtained from fracture toughness tests on RPV-steel 24 NiCrMo 3-7 at various temperatures. 1T-CT- and 0.4T-SEB-specimens that contained a sharp notch with a root radius of 0.06 mm introduced by spark erosion (EDM) instead of the standard fatigue crack were used. The predictions were found to agree well with the experimental data. The effect of the notch radius on fracture toughness is most pronounced in the brittle to ductile transition regime, where fracture toughness can be characterized by the master curve and the corresponding reference temperature T0 according to ASTM E1921. Accordingly, the effect of the notch radius can be quantified by a shift of T0. Since the shape of the transition curve depends on the notch radius, the procedure of ASTM E1921 to determine T0 is not applicable. An alternative is suggested. As limiting cases, ductile tearing and brittle fracture are also considered.

Keywords: Ductile to brittle transition; reference temperature; notch; toughness; root radius; ferritic steel

Permalink: https://www.hzdr.de/publications/Publ-20654
Publ.-Id: 20654


Uniaxial anisotropy and its manipulation in amorphous Co68Fe24Zr8 thin films

Fu, Y.; Barsukov, I.; Meckenstock, R.; Lindner, J.; Zhai, Y.; Hjörvarsson, B.; Farle, M.

We have proven that the growth of Co68Fe24Zr 8 layers under external field yields a uniaxial anisotropy, defined by the direction of the field. No magnetic coupling is present between Co 68Fe24Zr8 layers when separated by a 3nm of Al70Zr30. The anisotropy axis can therefore be manipulated at will and the direction can be tailored, layer by layer in multilayers, by the choice of the direction of the applied field during growth. The g-factor (2.13) and the anisotropy constant, obtained from ferromagnetic resonance, support the existence of short-range order. The relation between the temperature dependences of magnetic anisotropy and magnetization are partially captured by Callen-Callen power law.

Permalink: https://www.hzdr.de/publications/Publ-20653
Publ.-Id: 20653


Strong Auger scattering in Landau-quantized graphene investigated by infrared pump-probe experiments

Mittendorff, M.; Wendler, F.; Malic, E.; Knorr, A.; Orlita, M.; Potemski, M.; Berger, C.; de Heer, W. A.; Schneider, H.; Helm, M.; Winnerl, S.

The non-equidistant Landau-level (LL) spectrum of graphene enables the investigation of the carrier dynamics of distinct LL transitions. We present pump-probe measurements on multilayer epitaxial graphene, complemented by microscopic modelling. The free-electron laser (FEL) FELBE served as radiation source at a wavelength of 16.5 µm, which corresponds to a photon energy of 75 meV. At a magnetic field of 4.2 T, the photon energy gets resonant with the energetically degenerate LL transitions LL-1 → LL0 and LL0 → LL1. Circularly polarized radiation allows one to address one of these transitions selectively.
Besides a strong increase of the pump-probe signal at 4.2 T, we observe a complex set of pump-probe signals for all four combinations of pump and probe polarization. For contrarily polarized pump and probe radiation, one would expect negative pump-probe signals, as the initial state of the probed transition is populated (pump: σ+; probe: σ-) or the final state of the probe gets depopulated.
Our measurements show the counterintuitive result of positive pump-probe signals for the case of σ+-polarized pump radiation. The experimental findings are well described by microscopic calculations based on the density matrix formalism, which helped to reveal the origin of this behavior.

Keywords: Landau quantization; relaxation dynamics; graphene

  • Lecture (Conference)
    High Magnetic Fields in Semiconductor Physics, 03.-08.08.2014, Panama City Beach, USA

Permalink: https://www.hzdr.de/publications/Publ-20652
Publ.-Id: 20652


Kurzzeitspektroskopie: Kürzeste Laserpulse für Materialuntersuchungen

Mittendorff, M.

Mit Hilfe der Kurzzeitspektroskopie ist es möglich die Ladungsträgerdynamik in unterschiedlichen Materialsystemen direkt zu untersuchen. Bei sog. „Pump-Probe-Messungen“ werden z.B. Ladungsträger oder Moleküle mit einem sehr intensiven, aber auch sehr kurzen Laserpuls angeregt. Ein zweiter, wesentlich schwächerer Puls wird verwendet um die verursachte Änderung zu messen. Durch eine zeitliche Verschiebung des zweiten Pulses kann gemessen werden, wie lange das System braucht um die Energie wieder abzugeben. Eine einfache Skizze eines Aufbaus für Pump-Probe-Messungen, sowie ein Beispiel für das Ergebnis einer Messung sind in Abb. 1 gezeigt. Diese Untersuchungen sind beispielsweise besonders wichtig zur Entwicklung und Optimierung elektro-optischer Bauelemente wie z. B. Detektoren oder optische Modulatoren.
Die erreichbare zeitliche Auflösung bei diesen Messungen hängt im Wesentlichen von der Pulsdauer des Lasersystems ab. In diesem Vortrag werden verschieden Lasersysteme zur Erzeugung ultra-kurzer Laserpulse in einem breiten Spektralbereich vom nahen bis zum fernen Infrarot vorgestellt (800 nm – 250 µm). Zu jedem vorgestellten System wird als Beispiel eine Messung der Ladungsträgerdynamik in Graphen gezeigt, das aus einem zweidimensionalen Gitter aus Kohlenstoffatomen besteht. Dieses relativ neue Material, für dessen Untersuchung der Nobelpreis für Physik 2010 verliehen wurde, ist neben der Verwendung in der Elektronik speziell für Anwendungen in der Optoelektronik interessant. Durch die Verwendung verschiedener Wellenlängen können in diesem Material unterschiedliche physikalische Effekte untersucht werden.

  • Lecture (others)
    2. Fortbildungsveranstaltung zu Optotechnik und Bildverarbeitung, 27.06.2014, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20651
Publ.-Id: 20651


Radiobiological response to ultra-short pulsed megavoltage electron beams of ultra-high pulse dose rate

Beyreuther, E.; Karsch, L.; Laschinsky, L.; Lessmann, E.; Naumburger, D.; Oppelt, M.; Richter, C.; Schürer, M.; Woithe, J.; Pawelke, J.

Purpose: In line with the long-term aim of establishing the laser based particle acceleration for future medical application the radiobiological consequences of electron delivery with the typical ultra-short pulses of ultra-high pulse dose rate have to be investigated.
Materials and methods: The radiation source ELBE (Electron Linac for beams with high Brilliance and low Emittance) was used to mimic the quasi-continuous electron beam of a clinical linear accelerator (LINAC) and to deliver electron pulses at the ultra-high pulse dose rate of 10^10 Gy min-1 either at the low frequency of a laser accelerator or at 13 MHz avoiding effects of prolonged dose delivery. The impact of pulse structure was analysed by clonogenic survival assay and by the number of residual DNA double-strand breaks remaining 24 h after irradiation of two human squamous cell carcinoma lines of differing radiosensitivity.
Results: The radiation response of both cell lines was found to be independent from electron pulse structure for the two endpoints under investigation.
Conclusions: The results reveal, that ultra-high pulse dose rate of 10^10 Gy min-1 and the low repetition rate of laser accelerated electrons have no additional influence on the radiobiological effectiveness of megavoltage electrons.

Keywords: pulsed electron treatment; laser particle acceleration; ultra-high pulse dose rate; in vitro dose response

Permalink: https://www.hzdr.de/publications/Publ-20650
Publ.-Id: 20650


Microscopic Description of Intraband Absorption in Graphene: The Occurrence of Transient Negative Differential Transmission

Kadi, F.; Winzer, T.; Malic, E.; Knorr, A.; Göttfert, F.; Mittendorff, M.; Winnerl, S.; Helm, M.

We present a microscopic explanation of the controversially discussed transient negative differential transmission observed in degenerate optical pump-probe measurements in graphene. Our approach is based on the density matrix formalism allowing a time- and momentum-resolved study of carrier-light, carrier-carrier, and carrier-phonon interaction on microscopic footing. We show that phonon-assisted optical intraband transitions give rise to transient absorption in the optically excited hot carrier system counteracting pure absorption bleaching of interband transitions. While interband transition bleaching is relevant in the first hundreds of fs after the excitation, intraband absorption sets in at later times. In particular, in the low excitation regime, these intraband absorption processes prevail over the absorption bleaching resulting in a zero crossing of the differential transmission. Our findings are in good qualitative agreement with recent experimental pump-probe studies.

Keywords: graphene; carrier-dynamics; ultrafast spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-20649
Publ.-Id: 20649


Magnetization reversal in Co zigzag nanocolumns grown by glancing angle deposition

Buchta, K.; Lewandowski, M.; Bischoff, L.; Synoradzki, K.; Błaszyk, M.; Toliński, T.; Luciński, T.

A Co zigzag nanocolumn sample was grown by glancing angle deposition using molecular beam epitaxy. A structural study was carried out using scanning electron microscopy and the magnetic properties and the magnetoresistance were investigated at room temperature. Each zigzag consisted of six arms tilted with respect to each other by approx. 60°, had a club-like shape, diameter in the range of 20-100 nm, a single arm length of about 150 nm and a total height of approx. 370 nm. The magnetization hard axis was observed for the magnetic field oriented parallel to the zigzag long axis and the easy axis for the field oriented perpendicular to the long axis. The system exhibited very high maximum coercivity values, which could find potential applications. The angular dependences of the coercive field and the remanent to saturation magnetization ratio, as well as magnetoresistance curves, indicated the presence of curling magnetization reversal mode.

Keywords: Glancing Angle Deposition; Magnetization Reversal Mechanisms; Magnetic Anisotropy; Magnetic Properties; Zigzag Nanostructures; Sculptured Thin Films

Permalink: https://www.hzdr.de/publications/Publ-20648
Publ.-Id: 20648


A Survivin-XIAP regulates Complexity of the Signaling Molecules FAK and Aktl Radiation Sensitivity as well as Motility of Colorectal Tumor Cells

Hehlgans, S.; Petraki, C.; Cordes, N.; Oppermann, J.; Rodel, C.; Rodel, F.

kein Abstract vorhanden

  • Abstract in refereed journal
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 35-35

Permalink: https://www.hzdr.de/publications/Publ-20647
Publ.-Id: 20647


Effect of EGF Receptor and beta 1-Integrin Inhibition on the Radiosensitivity three dimensions growing colorectal Cancer cells / Einfluss von EGF Rezeptor und β1-Integrin Hemmung auf die Strahlenempfindlichkeit dreidimensional wachsender kolorektaler Karzinomzellen

Poschau, M.; Zscheppang, K.; Cordes, N.

kein Abstract vorhanden

  • Abstract in refereed journal
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 44-44

Permalink: https://www.hzdr.de/publications/Publ-20646
Publ.-Id: 20646


Pharmacological Inhibition of Focal Adhesion Kinase affects Cell Survival and Cell death but not Radiosensitivity of human Glioblastoma Cells / Pharmakologische Hemmung der Fokalen Adhäsionskinase beeinflusst Zellüberleben und Zelltod aber nicht Strahlenempfindlichkeit von humanen Glioblastomzellen

Sagerer, A.; Storch, K.; Cordes, N.

kein Abstract vorhanden

  • Abstract in refereed journal
    Strahlentherapie und Onkologie 190(2014)Suppl. 1, 35-35

Permalink: https://www.hzdr.de/publications/Publ-20645
Publ.-Id: 20645


Fractionated radiotherapy and cetuximab: EGFR amplification and histological markers as potential biomarkers / Fraktionierte Bestrahlung und Cetuximab: EGFR-Amplifikation und histologische Marker als potenzielle Biomarker

Gurtner, K.; Thurow, C.; Koi, L.; Yaromina, A.; Eicheler, W.; Baumann, M.; Krause, M.

kein Abstract vorhanden

  • Abstract in refereed journal
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 27-27

Permalink: https://www.hzdr.de/publications/Publ-20644
Publ.-Id: 20644


Effects of a Combined Radio (chemo) therapy and HMG-CoA Reductase-Inhibition in Patients with Head-and-neck-Cancer / Effekte einer kombinierten Radio(chemo)therapie und HMG-CoAReduktase-Inhibition bei Patienten mit Kopf-Hals-Tumoren

Ebert, N.; Thiele, C.; Gurtner, K.; Dorr, W.; Lock, S.; Baumann, M.; Krause, M.

kein Abstract vorhanden

  • Abstract in refereed journal
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 144-144

Permalink: https://www.hzdr.de/publications/Publ-20643
Publ.-Id: 20643


Influence of Chromatin Condensation on cellular Radiosensitivity in three dimensions growing human Tumor Cells / Einfluss der Chromatinkondensierung auf die zelluläre Strahlenempfindlichkeit dreidimensional wachsender humaner Tumorzellen

Storch, K.; Borgmann, K.; Eke, I.; Krause, M.; Becker, K.; Schrock, E.; Cordes, N.

kein Abstract vorhanden

  • Abstract in refereed journal
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 45-45

Permalink: https://www.hzdr.de/publications/Publ-20642
Publ.-Id: 20642


Radiation sensitization of human squamous by alpha3 integrin Inhibition / Strahlensensibilisierung humaner Plattenepithelkarzinomzellen durch alpha3 Integrin Hemmung

Steglich, A.; Eke, I.; Vehlow, A.; Cordes, N.

kein Abstract vorhanden

  • Abstract in refereed journal
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 22-22

Permalink: https://www.hzdr.de/publications/Publ-20641
Publ.-Id: 20641


The LIM only Protein FHL2 modulates the MAPK Signal Pathways and influences the Radiation Sensitivity of growing 3D Pancreatic Carcinoma Cells / Das LIM only Protein FHL2 moduliert MAPK Signalwege und beeinflusst die Strahlenempfindlichkeit von 3D wachsenden Pankreaskarzinomzellen

Zienert, E.; Eke, I.; Cordes, N.

kein Abstract vorhanden

  • Abstract in refereed journal
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 14-15

Permalink: https://www.hzdr.de/publications/Publ-20640
Publ.-Id: 20640


From a non-magnet to a ferromagnet: Mn implantation into different TiO2 structures

Yildirim, O.; Cornelius, S.; Butterling, M.; Anwand, W.; Wagner, A.; Smekhova, A.; Baehtz, C.; Potzger, K.

As one of the most promising candidates for a diluted magnetic oxide material for spintronic and magneto optic applications, transition metal (TM) doped titanium dioxide (TiO2) has been extensively studied for last two decades. Up to date room temperature ferromagnetism (RTFM) has been reported for different types of TM dopants and also different types of preparation methods, such as ion implantation [1] or magnetron sputtering [2]. There is an ongoing debate on the origin of the ferromagnetic properties of TiO2, whether RTFM arises from unwanted clustering of the TM atoms, magnetic contamination from sample handling or the desired substitution of Ti by the TM dopants.
We have investigated Mn implanted TiO2 films with respect to the effect of the crystalline structure of the pristine film on the magnetic properties of the doped films. The films were prepared by DC magnetron sputtering using a high purity oxygen deficient ceramic TiO2-x target in Ar/O2 atmosphere. SrTiO3 (100) single crystals were used as substrates. In order to achieve different structures of TiO2, namely amorphous, polycrystalline anatase and epitaxial anatase, different substrate temperatures and post-growth annealing were applied. The as-prepared TiO2 samples have been implanted with Mn ions of 30 keV to 190 keV kinetic energy and variable fluence resulting in a homogenous Mn concentration of 5 at.% within a 150 nm thin layer below the film surface.
The structural changes upon implantation were followed by means of X-ray diffraction (XRD) measurements. Comparison of the diffraction patterns indicates ion-induced damage in the epitaxial film and the formation of Mn containing secondary phases in the polycrystalline material. Depth resolved defect concentration profiles of as-grown and Mn implanted films were determined by means positron annihilation spectroscopy (PAS) measurements based on Doppler broadening spectroscopy. Magnetometry measurements of Mn implanted films reveal ferromagnetism for amorphous and polycrystalline films whereas paramagnetism is observed for epitaxial films. The local environments of implanted Mn ions in different TiO2 structures were probed by X-ray absorption spectroscopy (XAS) in fluorescence mode.
In summary, we have found a significant influence of the as-grown film structure on the magnetic properties of Mn:TiO2. During the presentation the PAS and XAS data will be discussed with respect to the presence of defects and secondary phases in the Mn doped TiO2 films.

  • Lecture (Conference)
    Moscow International Symposium on Magnetism MISM-2014, 29.06.-03.07.2014, Moscow, Russia
  • Lecture (Conference)
    The 59th Annual Magnetism and Magnetic Materials (MMM) Conference, 03.-07.11.2014, Honolulu, Hawaii, United States of America

Permalink: https://www.hzdr.de/publications/Publ-20639
Publ.-Id: 20639


Angular dependent ferromagnetic resonance analysis in a single micron sized cobalt stripe

Schoeppner, C.; Wagner, K.; Stienen, S.; Meckenstock, R.; Farle, M.; Narkowicz, R.; Suter, D.; Lindner, J.

We demonstrate how planar microresonators (PMRs) can be utilized to investigate the angular dependent magnetic resonance response of single magnetic nanostructures. In contrast to alternative detection schemes like electrical or optical detection, the PMR approach provides a classical means of investigating the high frequency dynamics of single magnetic entities, enabling the use of well-established analysis methods of ferromagnetic resonance (FMR) spectroscopy. To demonstrate the performance of the PMR-based FMR setup for angular dependent measurements, we investigate the microwave excited magnons in a single Co stripe of 5x1x0.02 µm^3 and compare the results to micromagnetic simulations. The evolution of excited magnons under rotation of one individual stripe with respect to a static magnetic field is investigated. Besides quasi uniform excitations, we observe magneto-static as well as localized excitations. We find a strong influence of inhomogeneous dynamic and static demagnetizing fields for all modes.

Permalink: https://www.hzdr.de/publications/Publ-20638
Publ.-Id: 20638


Efficiency determination of resistive plate chambers for fast quasi-monoenergetic neutrons

Röder, M.; Elekes, Z.; Aumann, T.; Bemmerer, D.; Boretzky, K.; Caesar, C.; Cowan, T. E.; Hehner, J.; Heil, M.; Kempe, M.; Maroussov, V.; Nusair, O.; Prokofiev, A. V.; Reifarth, R.; Sobiella, M.; Stach, D.; Wagner, A.; Yakorev, D.; Zilges, A.; Zuber, K.; for the R3B Collaboration

Composite detectors made of stainless-steel converters and multigap resistive plate chambers have been irradiated with quasi-monoenergetic neutrons with a peak energy of 175 MeV. The neutron detection efficiency has been determined using two different methods. The data are in agreement with the output of Monte Carlo simulations. The simulations are then extended to study the response of a hypothetical array made of these detectors to energetic neutrons from a radioactive ion beam experiment.

Permalink: https://www.hzdr.de/publications/Publ-20637
Publ.-Id: 20637


Nanofiltration of uranium-contaminated water – focus on separation mechanisms

Hoyer, M.; Haseneder, R.; Steudtner, R.; Brendler, V.; Repke, J.-U.

Nanofiltration offers new perspectives for the treatment of mine drainage from former uranium mines, e.g. in East Germany. In this study the perfor-mance of various commercial nanofiltration membranes for a real mine water sample was determined experimentally and modelled. Experimental data is key to membrane selection and is necessary to validate modelling results. Mathematical modelling offers deeper insights into the interaction of uranium species with solid surfaces which also has the potential to extrapolate to other research fields.

  • Contribution to proceedings
    Uranium Mining and Hydrogeology 2014, 21.-25.09.2014, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-20633
Publ.-Id: 20633


Interfacial heat transfer models for flashing flows: a review

Liao, Y.; Lucas, D.

An extensive literature review on existing models for interfacial heat transfer in flashing of pure liquids was carried out. It reveals that recent numerical simulations rely still on empirical closures. A correlation in terms of the Jakob number, Reynolds number and Prandtl number might be the most promising one. However, all the validation against experiment is limited to single spherical droplet or bubble. For large deformed bubbles and high void fractions, there are still no direct validation due to the lack of experimental data and complicated intervening physics. Improvement regarding the effect of bubble interaction, interfacial morphology and turbulence is necessary.

Keywords: Flashing flow; Heat transfer; Models; Review

  • Contribution to proceedings
    13th international conference Multiphase Flow in Industrial Plant, 17.-19.09.2014, Genova, Italy
  • Lecture (Conference)
    13th international conference Multiphase Flow in Industrial Plant, 17.-19.09.2014, Genova, Italy

Permalink: https://www.hzdr.de/publications/Publ-20632
Publ.-Id: 20632


Assessment of CFD predictive capacity for flash boiling

Liao, Y.; Lucas, D.; Krepper, E.; Rzehak, R.

Flash boiling of water inside a converging-diverging nozzle and a vertical pipe under pressure release transients is investigated. Some representative assumptions and simplifications encountered in the literature are assessed. It is shown that a fully non-equilibrium model with two velocity fields and two temperature fields should be applied. Non-drag forces are necessary to predict the lateral distribution of bubbles, which is usually non-uniform. For large bubbles (dg>1mm), bubble translation has a significant contribution to the interphase heat transfer, and thus heat conduction would give a significant under-prediction. The most important point in the assessment of these interphase exchange closures is to have a reliable prediction of bubble size. On this topic there is still much to do, since a realistic modelling of bubble number density transport is still missing. Great efforts need to be invested in the development of generally applicable closure models for nucleation, bubble growth, coalescence and breakup, etc.

Keywords: CFD; Flash boiling; phase change; heat transfer

  • Contribution to proceedings
    CFD4NRS-5, 09.-11.09.2014, Zürich, Schweiz
  • Lecture (Conference)
    CFD4NRS-5, 09.-11.09.2014, Zürich, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-20631
Publ.-Id: 20631


CFD simulations on TOPFLOW-PTS tests

Apanasevich, P.; Coste, P.; Merigoux, N.

Pressurized Thermal Shock (PTS) has been identified as one of the most important industrial needs related to nuclear reactor safety. The PTS analysis is required to assure the integrity of the Reactor Pressure Vessel (RPV) throughout the reactor life. One important part of the PTS analysis is the thermal hydraulic analysis which must predict the local temperature fields experienced by the structural parts of the cold leg and especially of the RPV wall close to the cold leg nozzle. Such results are applied as the input data for further structural analyses. Several scenarios that describe what could occur in Small Break Loss Of Coolant Accidents (SB-LOCA) result in an Emergency Core Cooling (ECC) water injection into the cold leg of a Pressurized Water Reactor (PWR). The cold water mixes there with the hot coolant, which is present in the primary circuit. The mixture flows to the downcomer where further mixing of the fluids takes place. Single-phase as well as two-phase PTS situations have to be considered. In case of two-phase PTS situations the water level in the RPV has dropped down to or below the height of the cold leg nozzle, which leads to a partially filled or totally uncovered cold leg. Pressurized Thermal Shock implies the occurrence of thermal loads on the Reactor Pressure Vessel wall. In order to predict thermal gradients in the structural components of the Reactor Pressure Vessel (RPV) wall, knowledge of transient temperature distribution in the downcomer is needed. The prediction of the temperature distribution requires reliable Computational Fluid Dynamic simulations. The CFD models should be able to model the complex mixing processes taking place in the cold leg and the downcomer of the reactor pressure vessel (IAEA, 2001; Lucas et al., 2008, 2009).

In the framework of the NURESAFE project attempts have been made to continue improvement and validation of CFD modeling for two-phase PTS situations. The NEPTUNE_CFD, ANSYS CFX and TransAT codes are used in the project for PTS investigations. A CFD benchmark test on a reference TOPFLOW-PTS steam-water experiment is a part of these activities within the project.

Keywords: TOPFLOW-PTS experiments; direct contact condensation; CFD

  • Lecture (Conference)
    NURESAFE 1st Open Seminar, 16.-17.06.2014, Budapest, Hungary

Permalink: https://www.hzdr.de/publications/Publ-20630
Publ.-Id: 20630


Ge(1-x)Sn(x) alloys synthesized by ion implantation and pulsed laser melting

Gao, K.; Prucnal, S.; Huebner, R.; Baehtz, C.; Skorupa, I.; Wang, Y.; Skorupa, W.; Helm, M.; Zhou, S.

The tunable bandgap and the high carrier mobility of Ge(1-x)Sn(x) alloys stimulate a large effort for bandgap and strain engineering for Ge based materials using silicon compatible technology. In this letter we present the fabrication of highly mismatched Ge(1-x)Sn(x) alloys by ion implantation and pulsed laser melting with Sn concentration ranging from 0.5 at. % up to 1.5 at. %. According to the structural investigations, the formed Ge(1-x)Sn(x) alloys are monocrystalline with high Sn-incorporation rate. The shrinkage of the bandgap of Ge(1-x)Sn(x) alloys with increasing Sn content is proven by the red-shift of the E1 and E1+Δ1 critical points in spectroscopic ellipsometry. Our investigation provides a chip technology compatible route to prepare high quality monocrystalline Ge(1-x)Sn(x) alloys.

Keywords: Ge(1-x)Sn(x) alloys; ion implantation; pulsed laser melting

Permalink: https://www.hzdr.de/publications/Publ-20629
Publ.-Id: 20629


Uncertainties in the fluence determination in the surveillance samples of VVER-440

Konheiser, J.; Grahn, A.; Borodkin, P.; Borodkin, G.

The reactor pressure vessel (RPV) represents one of the most important safety components in a nuclear power plant. Therefore, surveillance specimen (SS) programs for the RPV material exist to deliver a reliable assessment of RPV residual lifetime. This report will present neutron fluence calculations for SS. These calculations were carried out by the codes TRAMO and DORT [1, 2]. This study was accompanied by ex-vessel neutron dosimetry experiments at Kola NPP. The main neutron activation monitoring reactions were Fe-54(n,p)Mn-54 and Ni-58(n,p)Co-85. Good agreement was found between the deterministic and stochastic calculation results and between the calculations and the ex-vessel measurements. The different influences on the monitors were studied. In order to exclude the possible healing effects of the samples due to excessive temperatures, the heat release in the surveillance specimens was determined based on the calculated gamma fluences. Under comparatively realistic conditions, the heating was up to 6 K.

Keywords: VVER440; reactor pressure vessel; surveillance specimen; activation monitors; Fe-54(n; p)Mn-54; Ni-58(n; p)Co-85

  • Lecture (Conference)
    Fifteenth International Symposium on Reactor Dosimetry, 18.-23.05.2014, Aix-en-Provence, France
  • Open Access Logo Contribution to proceedings
    Fifteenth International Symposium on Reactor Dosimetry, 18.-23.05.2014, Aix-en-Provence, France
    EPJ Web of Conferences, Les Ulis Cedex: EDP Sciences, 978-2-7598-1929-4
    DOI: 10.1051/epjconf/201610602006

Permalink: https://www.hzdr.de/publications/Publ-20627
Publ.-Id: 20627


Assessment of the best N3− donors in preparation of [M(N)(PNP)]-based (M = 99mTc-; 188Re) target-specific radiopharmaceuticals: Comparison among succinic dihydrazide (SDH), N-methyl-S-methyl dithiocarbazate (HDTCZ) and PEGylated N-methyl-S-methyl dithiocarbazate (HO2C-PEG600-DTCZ)

Carta, D.; Jentschel, C.; Thieme, S.; Salvarese, N.; Morellato, N.; Refosco, F.; Ruzza, P.; Bergmann, R.; Pietzsch, H.-J.; Bolzati, C.

Succinic dihydrazide (SDH), N-methyl-S-methyl dithiocarbazate (HDTCZ) and PEGylated N-methyl-S-methyl dithiocarbazate (HO2C-PEG600-DTCZ) are nitrido nitrogen atom donors employed for the preparation of nitride [M(N)]‐complexes (M = 99mTc and 188Re).
This study aims to compare the capability and the efficiency of these three N3− group donors, in the preparation of [M(N)PNP]-based target-specific compounds (M = 99mTc, 188Re; PNP = aminodiphosphine). For this purpose, three different kit formulations (SDH kit; HO2C-PEG600-DTCZ kit; HDTCZ kit) were assembled and used in the preparation of [M(N)(cys~)(PNP3)]0/+ complexes (cys~ = cysteine derivate ligands).
For each formulation, the radiochemical yield (RCY) of the [M(N)(~cys)(PNP3)] compounds, was determined by HPLC. The deviation of the percentage of RCY, due to changes in concentration of the N3− donors and of the
exchanging ligand, was determined.
For 99mTc, data clearly show that HDTCZ is the most efficient donor of N3−; however, SDH is the most suitable nitrido nitrogen atom donor for the preparation of [99mTc(N)(PNP)]-based target-specific agents with high specific activity. When HO2C-PEG600-DTCZ or HDTCZ are used in N3− donation, high amounts of the exchanging ligand (10−4 M) were required for the formation of the final complex in acceptable yield.
The possibility to usemicrogram amounts of HDTCZ also in [188Re(N)] preparation (0.050 mg) reduces its ability to compete in ligand exchange reactions, minimizing the quantity of chelators required to obtain the final complex in high yield. This finding can be exploit for increasing the radiolabeling efficiency in [188Re(N)]-radiopharmaceutical preparations compared to the previously reported HDTCZ-based procedure, notwithstanding a purification process could be necessary to improve the specific activity of the complexes.

Keywords: Rhenium; Technetium; 188Re; Diphosphinoamines; Peptide; Therapy

Permalink: https://www.hzdr.de/publications/Publ-20626
Publ.-Id: 20626


Influence of riboflavin on the reduction of radionuclides by Shewanella oneidenis MR-1

Cherkouk, A.; Law, G. T. W.; Rizoulis, A.; Law, K.; Renshaw, J. C.; Morris, K.; Livens, F. R.; Lloyd, J. R.

Uranium (as UO22+), technetium (as TcO4-) and neptunium (as NpO2+) are highly mobile radionuclides that can be reduced enzymatically by a range of anaerobic and facultatively anaerobic microorganisms, including Shewanella oneidensis MR-1, to poorly soluble analogues. The redox chemistry of Pu is more complicated, but the dominant oxidation state in most environments is poorly soluble Pu(IV), which can be reduced to the potentially more soluble Pu(III), which could enhance migration of Pu in the environment. Recently it was shown that flavins (riboflavin and flavin mononucleotide (FMN)) secreted by Shewanella oneidensis MR-1 can act as electron shuttles, promoting anoxic growth coupled to the accelerated reduction of poorly-crystalline Fe(III) oxides. Here we studied the role of riboflavin in mediating the reduction of radionuclides in cultures of Shewanella oneidensis MR-1. Our results demonstrate that the addition of 10 µM riboflavin enhances the reduction rate of Tc(VII) to Tc(IV) and Np(V) to Np(IV), but has no significant influence on the reduction rate of U(VI) by Shewanella oneidensis MR-1. The presence of riboflavin also accelerated Pu(IV) reduction, demonstrated by an increase in the percentage of Pu(IV) reduced to Pu(III), with and without riboflavin present (17 and 3%, respectively). Thus riboflavin can act as an extracellular electron shuttle to enhance rates of Tc(VII), Np(V) and Pu(IV) reduction, and may therefore play a role in controlling the oxidation state of key redox active actinides and fission products in natural and engineered environments. These results also suggest that the addition of riboflavin could be used to accelerate the bioremediation of radionuclide-contaminated environments.

Permalink: https://www.hzdr.de/publications/Publ-20625
Publ.-Id: 20625


Scalable, interactive 3D in-situ visualization of large-scale Simulations

Pausch, R.; Schneider, B.; Hettmanczyk, D.; Burau, H.; Huebl, A.; Schmitt, F.; Widera, R.; Grottel, S.; Gumhold, S.; Bussmann, M.

We present scalable, in-situ visualization of large-scale plasma simulations that allows for remote live visualization. We discuss the GPU rendering implementation, its interface to the simulation, scalable image composition on large clusters and the use of low-power visualisation clients attached to a server located at the HPC system. Such a setup challenges current HPC visualization paradigms and will potentially allow for explorative simulation surveys of large parameter spaces with strongly reduced storage footprint.

Keywords: in-situ visualization; PIConGPU; live visualization; GPU; HPC

  • Lecture (Conference)
    Workshop Programming of Heterogeneous Systems in Physics, 14.-15.07.2014, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20624
Publ.-Id: 20624


Computing Angularly-resolved Far Field Emission Spectra in Particle-in-cell Codes using GPUs

Pausch, R.; Burau, H.; Bussmann, M.; Couperus, J. P.; Cowan, T.; Debus, A.; Huebl, A.; Irman, A.; Köhler, A.; Schramm, U.; Steiniger, K.; Widera, R.

Angularly resolved far field radiation spectra computed from the Lienard Wiechert Potentials of accelerated electrons give information on the microscopic particle dynamics. We present recent results using our many-GPU, fully relativistic 3D3V particle-in-cell code PIConGPU for which we have developed fully synthetic radiation diagnostics that is capable of computing angularly-resolved radiation spectra of more than 10^10 electrons for several hundred to a thousand wavelengths and directions in a single simulation in less than a day on large-scale supercomputers. With such a technique it is possible to use precision spectroscopic methods for understanding the dynamics of electron acceleration in scenarios where other diagnostics fail. We present studies on laser-driven wakefield acceleration and astrophysical jet dynamics to underline the power of this new technique.

Keywords: far field radiation spectra; Lienard Wiechert potentials; PIConGPU; many-GPU; synthetic radiation diagnostics

  • Poster
    5th International Particle Accelerator Conference (IPAC 2014), 15.-20.06.2014, Dresden, Deutschland
  • Contribution to proceedings
    5th International Particle Accelerator Conference (IPAC 2014), 15.-20.06.2014, Dresden, Deutschland
    Proceedings of IPAC2014, 978-3-95450-132-8, MOPRI069

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-20623
Publ.-Id: 20623


Charakterisierung von anisotropen Magnetowiderstandseffekten in Nanostrukturen aus Permalloy und Eisenaluminium

Warnatz, T.

Magnetic field induced resistance effects are used in digital storage media - like hard- disk read heads [1]. To produce commercial devices it is of utmost importance to understand and tune the effect. The ion beam induced change of ferromagnetic or paramagnetic effects is known since 1986 [2,3]. However, most of the research was done on bulk material. Due to the increasing miniaturization of digital storage devices it is essential to investigate also the behavior in thin films. Taking into account that a commercial use of the devices is favored, it was focused on easy and reproducible sample geometries. The aim of this thesis was to produce, tune and character- ize magnetic field induced resistance changes in thin films of permalloy and iron-aluminum. Af- terwards, the results have been used to create well-defined nanostructures with potential giant magnetoresistance effects. It is shown, that magnetoresistance effects can be created (iron- aluminum) or reduced (permalloy) by ion beam irradiation. The measurements were performed by a self-programmed LabVIEW program with a precise four-terminal sensing setup at low tempera- tures and with a variable magnetic field up to 2.5 T. The variation of the angle between current flow and the magnetic field as well as measurements at different temperatures led to a very good understanding of the occurring phenomena.

Keywords: FeAl; anisotropic magnetoresistance

  • Bachelor thesis
    Westsächsische Hochschule Zwickau, 2013

Permalink: https://www.hzdr.de/publications/Publ-20622
Publ.-Id: 20622


Herstellung und Charakterisierung eines Spinventils zur Untersuchung der Spindiffusionslänge von FeAl

Liersch, V.

Spintronic devices hold great potential for future applilcations in information technology. In this work, the design and fabrication of a lateral spin valve for investigating the spin diffusion length of paramagnetic Fe60Al40 will be discussed. Samples were prepared by defining polycrystalline circuits using electron beam lithography, thin film deposition, and lift-off processing. The developed sample layout allows for both local and non-local measurement routines. Cobalt was employed as ferromagnetic polarizing material, while aluminium holds for reference measurements of the spin diffusion length. The determination of the so far unknown spin diffusion length of paramagnetic Fe60Al40 shall then be performed by detecting resistance changes at different temperatures and for different polarizer distances. Highly sensitive electric transport measurements were carried out in a so-called probe station, which allows for achieving very low temperatures via liquid He cooling. Additionally, paramagnetic ferromagnetic heterostructures were investigated with respect to possible giant magneto resistance effects.

Keywords: FeAl; spin valve; spin diffusion length

  • Bachelor thesis
    Westsächsische Hochschule Zwickau, 2014

Permalink: https://www.hzdr.de/publications/Publ-20621
Publ.-Id: 20621


Transverse Emittance Compensation for the Rossendorf SRF GUN II

Vennekate, H.; Lu, P.; Arnold, A.; Murcek, P.; Teichert, J.; Xiang, R.; Kneisel, P.; Kamps, T.

Superconducting RF particle sources combine the advantages of normal conducting RF sources and high duty cycle non-RF sources. The Rossendorf SRF gun was the first to demonstrate this injecting electrons into the ELBE accelerator at 13MHz. Recently, a new 3-1/2-gun cavity has been prepared at Jefferson Lab for its use in an updated injector which is expected to increase the electron energy from 2:4 to 7:5 MeV. Along with this new cavity, a new gun cryostat has been introduced. It combines several minor updates to the setup with the installation of a superconducting solenoid right at the exit of the gun, compensating the emittance growth of the electron bunch at an early stage. Hereby, the results of the commissioning of the new cryostat including the solenoid are concluded and compared to the prior concept of using a normal conducting solenoid outside the cryostat. As it is of great importance to this subject, studies of the magnetic shielding are going to be presented as well.

Keywords: SRF; superconducting radio frequency; injector; Rossendorf SRF Gun; ELBE; emittance

  • Open Access Logo Contribution to proceedings
    5th International Particle Accelerator Conference (IPAC'14), 15.-20.06.2014, Dresden, Deutschland
    Proceedings of IPAC2014, JACoW, 978-3-95450-132-8, TUPRI015

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-20620
Publ.-Id: 20620


Simulation d ́écoulement multiphasique couplé aux effets magnétiques des batteries à métaux liquides

Barry, L.

Le stockage d’énergie électrique devient une nécessité avec le développement des énergies renouvelables en Allemagne. Dans cette perspective un nouveau type de batterie, composée de trois phases de métal liquide maintenues à plus de 500°C, semble prometteur pour une future utilisation. Cependant ces batteries sont le siège d’instabilités qui peuvent mener à un mélange non voulu des trois phases liquides. Ce projet étudie une instabilité particulière appelée instabilité de Tayler, et cherchera à savoir si celle-ci peut mener à une destruction de la batterie. Pour cela, un nouveau solveur numérique est utilisé, combinant à la fois les lois de l’électromagnétique et de la mécanique des fluides. Des simulations seront lancées à partir de diverses conditions initiales, et nous verrons qu’il est en effet possible d’arriver à une destruction de la batterie, sous réserves de conditions initiales particulières.

Keywords: Tayler instability; liquid metal battery; multiphase simulation; OpenFOAM

  • Master thesis
    Arts et Métiers Paristech Bordeaux-Talence, 2014
    Mentor: Azita Ahmadi, Tom Weier

Permalink: https://www.hzdr.de/publications/Publ-20619
Publ.-Id: 20619


Experimental evidence for nonaxisymmetric magnetorotational instability in a rotating liquid metal exposed to an azimuthal magnetic field

Seilmayer, M.; Galindo, V.; Gerbeth, G.; Gundrum, T.; Stefani, F.; Gellert, M.; Rüdiger, G.; Schultz, M.; Hollerbach, R.

The azimuthal version of the magnetorotational instability (MRI) is a nonaxisymmetric instability of a hydrodynamically stable differentially rotating flow under the influence of a purely or predominantly azimuthal magnetic field. It may be of considerable importance for destabilizing accretion disks, and plays a central role in the concept of the MRI dynamo. We report the results of a liquid metal Taylor-Couette experiment that shows the occurrence of an azimuthal MRI in the expected range of Hartmann numbers.

Permalink: https://www.hzdr.de/publications/Publ-20618
Publ.-Id: 20618


Magnetic fields in space: phenomena and related lab experiments

Stefani, F.

The magnetic fields of cosmic bodies are generated by the homogeneous dynamo effect in moving electrically conducting fluids. Cosmic magnetic fields also play an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. In 1999 the threshold of magnetic-field self-excitation was exceeded in the two liquid sodium experiments in Riga and Karlsruhe. Since 2006, the Cadarache dynamo experiment has successfully reproduced many features of geophysical interest such as reversals and excursions. In the same year, the helical version of the magnetorotational instability was observed in the PROMISE facility in Dresden-Rossendorf.
The lecture gives an overview about liquid metal experiments on dynamo action and magnetically triggered instabilities, and it concludes with an overview about future experiments, including a precession driven dynamo and a large-scale Tayler-Couette experiment to be set-up in the framework of the DRESDYN project.

  • Invited lecture (Conferences)
    Space trips summer school on thermo-acoustic and space technologies, 17.-20.06.2014, Riga, Latvia

Permalink: https://www.hzdr.de/publications/Publ-20617
Publ.-Id: 20617


The azimuthal MRI in experiment: confirmations and surprises

Stefani, F.

The azimuthal magnetorotational instability (AMRI) may be of considerable importance for destabilizing accretion disks and plays also a central role in the concept of the MRI dynamo. We report the results of a liquid metal Taylor-Couette experiment that shows the occurrence of an azimuthal MRI in the expected range of Hartmann numbers. We also discuss some peculiarities of the experimental results which are connected with the slight symmetry breaking of the applied magnetic field.

  • Invited lecture (Conferences)
    General Meeting of the Max Planck/Princeton Center for Plasma Physics, 28.06.-01.07.2014, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-20616
Publ.-Id: 20616


Simulation of the ELBE SRF Gun II

Lu, P.; Arnold, A.; Lehnert, U.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.

By combining the code of ASTRA and elegant in a user-friendly interface, a simulation tool is developed for the ELBE SRF Gun II. The photoelectric emission and first acceleration to several MeV in the gun cavity are simulated by ASTRA with a 1D Model, where the space charge effect is considered. The dependence of the beam quality on key parameters is studied, and a compromised optimization for a 77 pC beam is used for further elegant simulation of the beam transport through a dogleg and ELBE Linacs. Proper settings of the magnets and RF phases are the main targets of improving the beam quality. Up to now the best simulation result is an electron bunch with the energy of 47 MeV, energy spread of 66 keV, bunch length of 0.35 ps and transverse emittance of 1.9 μm and 2.7 μm in the two perpendicular directions.

  • Open Access Logo Contribution to proceedings
    IPAC2014 - 5th International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Germany
    Proceedings of IPAC2014, MOPRI023

Permalink: https://www.hzdr.de/publications/Publ-20615
Publ.-Id: 20615


Dynamo action and related magnetic instabilities in the liquid metal lab

Stefani, F.

Magnetic fields of cosmic bodies are generated by the hydromagnetic dynamo effect in moving electrically conducting fluids, such as liquid metals or plasmas. Once produced, cosmic magnetic fields are able to act back on moving fluids. This back-reaction may have dramatic consequences for cosmic structure formation, with the magnetorotational instability (MRI) in accretions disks as the most prominent example. Considerable theoretical and computational progress has been made in understanding both the dynamo effect as well as magnetically triggered flow instabilities. Complementary to this, the last fifteen years have seen much effort in studying both effects in liquid metal experiments.
In the talk, we summarize the history of these experiments, discuss their main results and their limitations, and give an outlook on future activities. As for dynamo action, we focus on the Riga, Karlsruhe and Cadarache experiments, and discuss the present status of a large-scale precession-driven dynamo experiment to be set-up in the framework of the DRESDYN project. As for magnetically triggered instabilities, we review the recent experiments on the helical and azimuthal versions of the MRI, as well as on the current-driven Tayler instability (TI). After discussing the astrophysical relevance of those basically induction-less instabilities, we motivate the set-up of a large-scale liquid sodium experiment for studying the continuous transition to the standard version of MRI.

  • Invited lecture (Conferences)
    EUROMECH Colloquium 561: Dimensionality of Turbulence, 19.-21.05.2014, Coventry, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-20614
Publ.-Id: 20614


Liquid metal experiments on dynamo action and related magnetic instabilities

Stefani, F.

The magnetic fields of planets, stars and galaxies are generated by self-excitation in moving electrically conducting fluids. Once produced, cosmic magnetic fields can play an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. For a long time, both effects, i.e. hydromagnetic dynamo action and the magnetorotational instability, have been the subject of purely theoretical investigations. This situation changed in 1999 when the threshold of magnetic-field self-excitation was exceeded in the two liquid sodium experiments in Riga and Karlsruhe. Since 2006, the Cadarache dynamo experiment has successfully reproduced many features of geophysical interest such as reversals and excursions. In the same year, the helical version of the magnetorotational instability was observed in the PROMISE facility in Dresden-Rossendorf. The lecture gives an overview about liquid metal experiments on dynamo action and magnetically triggered instabilities, it asks for the lessons they have taught us about real cosmic dynamos and accretion disks, and it concludes with an overview about future experiments, including a precession driven dynamo and a large-scale Tayler-Couette experiment to be set-up in the framework of the DRESDYN project.

  • Invited lecture (Conferences)
    LSTM Fluid Mechanics Seminar, 07.02.2014, Erlangen, Germany

Permalink: https://www.hzdr.de/publications/Publ-20613
Publ.-Id: 20613


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