Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33168 Publications

Dose Assessment and Comparison in Mice, Piglets and Humans

Kranz, M.; Sattler, B.; Patt, M.; Fischer, S.; Hiller, A.; Donat, C. K.; Deuther-Conrad, W.; Hoepping, A.; Sattler, T.; Wünsch, B.; Steinbach, J.; Sabri, O.; Brust, P.;
  • Lecture (others)
    3. Dresdner Workshop "Molekulare Bildgebung in den Lebenswissenschaften", 05.06.2013, Rossendorf, Deutschland
  • Invited lecture (Conferences)
    Weiterbildungsveranstaltung für Ärzte am Universitätsklinikum Carl Gustav Carus der Technischen Universität Dresden, 28.01.2014, Dresden, Deutschland
  • Lecture (others)
    Doktoranden-Kolloquium des BBZ, 03.12.2014, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-19861
Publ.-Id: 19861


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

Cherkouk, A.; Lütke, L.; Moll, H.; Bachvarova, V.; Selenska-Pobell, S.; Bernhard, G.;
The long-term safety of nuclear waste in a deep geological repository is an important issue in our society. For the safety assessment of such a repository it is necessary to know what microorganisms are present in the potential host rocks (e.g. clay, salt) and how these microorganisms can influence the performance of a repository to potentially reduce their activity.
In this study, the analysis of bacterial diversity in a sample from the Mont Terri Opalinus clay demonstrated the predominance of representatives of Firmicutes, Betaproteobacteria, and Bacteriodetes. Alpha-, Beta- and Gammaproteobacteria were detected in the porewater samples from the Mont Terri rock laboratory, whereas Gammaproteobacteria especially Pseudomonas sp. dominated the bacterial community.
Among other isolates, a Paenibacillus sp., as a representative of Firmicutes, was isolated from the clay under anaerobic conditions. 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, we will present a study on the interactions of the halophilic archaea Halobacterium noricense DSM 15987, an salt rock representative reference strain, with U(VI) at high ionic strength. These results contribute to the safety assessment of a prospective nuclear waste repository.
  • Poster
    IGD-TP Geodisposal 2014, 24.-26.06.2014, Manchester, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-19860
Publ.-Id: 19860


Efficient laser-driven proton acceleration in the ultra short pulse regime

Zeil, K.;
The work described in this thesis is concerned with the experimental investigation of the acceleration of high energy proton pulses generated by relativistic laser-plasma interaction and their application. Using the high intensity 150TW Ti:sapphire based ultra-short pulse laser Draco, a laser-driven proton source was set up and characterized. Conducting experiments on the basis of the established target-normal sheath acceleration (TNSA) process, proton energies of up to 20MeV were obtained. The reliable performance of the proton source was demonstrated in the first direct and dose controlled comparison of the radiobiological effectiveness of intense proton pulses with that of conventionally generated continuous proton beams for the irradiation of in vitro tumour cells. As potential application radiation therapy calls for proton energies exceeding 200MeV. Therefore the scaling of the maximum proton energy with laser power was investigated and observed to be near-linear for the case of ultra-short laser pulses. This result is attributed to the efficient predominantly quasi-static acceleration in the short acceleration period close to the target rear surface. This assumption is furthermore confirmed by the observation of prominent non-target-normal emission of energetic protons reflecting an asymmetry in the field distribution of promptly accelerated electrons generated by using oblique laser incidence or angularly chirped laser pulses. Supported by numerical simulations, this novel diagnostic reveals the relevance of the initial prethermal phase of the acceleration process preceding the thermal plasma heath expansion of TNSA. During the plasma expansion phase, the efficiency of the proton acceleration can be improved using so called reduced mass targets (RMT). By confining the lateral target size which avoids the dilution of the expanding sheath and thus increases the strength of the accelerating sheath fields a significant increase of the proton energy and the proton yield was observed.
  • Doctoral thesis
    TU Dresden, 2013
    127 Seiten

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Permalink: https://www.hzdr.de/publications/Publ-19859
Publ.-Id: 19859


Pu interaction studies with a typical bacterial isolate from Mont Terri Opalinus clay

Moll, H.; Lütke, L.; Cherkouk, A.; Bernhard, G.;
Nuclear waste is supposed to be stored in deep geological formations. An example is the Opalinus clay formation located in the North-Western part of Switzerland (Mont Terri URL) which is currently studied in terms of its suitability as host rock for future nuclear waste storage. In this talk, results will be presented and discussed describing the interactions of a specific novel Sporomusa sp. isolate with plutonium. Results from accumulation experiments as well as detailed plutonium oxidation state changes in the presence and absence of an electron donor will be discussed.
Keywords: plutonium, Mont Terri, Opalinus Clay, Sporomusa sp., solvent extractions
  • Lecture (Conference)
    TD-246 Joint BN, GD, HT, MA Mont Terri Meeting, 10.-11.02.2014, St. Ursanne, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-19858
Publ.-Id: 19858


Disentangling defect-induced ferromagnetism in SiC

Wang, Y.; Li, L.; Prucnal, S.; Chen, X.; Tong, W.; Yang, Z.; Munnik, F.; Potzger, K.; Skorupa, W.; Gemming, S.; Helm, M.; Zhou, S.;
We present a detailed investigation of the magnetic properties in SiC single crystals bombarded with neon ions. Through careful measuring of the magnetization of virgin and irradiated SiC, we decompose the magnetization of SiC into paramagnetic, superparamagnetic, and ferromagnetic contributions. The ferromagnetic contribution persists well above room temperature and exhibits a pronounced magnetic anisotropy. We qualitatively explain the magnetic properties as a result of the intrinsic clustering tendency of defects.

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Permalink: https://www.hzdr.de/publications/Publ-19857
Publ.-Id: 19857


Search for Supernova-produced 60Fe in the Earth's Fossil Record

Bishop, S.; Ludwig, P.; Egli, R.; Chernenko, V.; Faestermann, T.; Famulok, N.; Fimiani, L.; Frederichs, T.; Gomez, J.; Hain, K.; Hazlik, M.; Korschinek, G.; Merchel, S.; Rugel, G.;
Approximately 1.8 to 2.8 Myr before the present our planet was subjected to the debris of a supernova explosion. The terrestrial proxy for this event was the discovery of live atoms of 60Fe in a deep-sea ferromanganese crust [Knie et al., Phys. Rev. Lett. (2004)]. The signature for this supernova event should also reside in magnetite (Fe3O4) magnetofossils produced by magnetotactic bacteria extant at the time of the Earth-supernova interaction; these bacteria were and are ubiquitous in all ocean sediments. We have conducted accelerator mass spectrometry (AMS) measurements, searching for live 60Fe in the magnetofossil component of a Pacific Ocean sediment core (ODP Core 848); additional AMS measurements are now ongoing with a second Sediment core (ODP Core 851) in which we expect to find a higher 60Fe signal. This talk will present the current preliminary status of our 60Fe search results for both sediment cores.
Keywords: accelerator mass spectrometry, supernova, AMS, cosmogenic nuclide
  • Lecture (Conference)
    DPG Frühjahrstagung der Fachverbände Physik der Hadronen und Kerne, Didaktik der Physik, 17.-21.03.2014, Frankfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-19856
Publ.-Id: 19856


Comparing OSL and CN techniques for dating fluvial terraces and estimating surface process rates in Pamir

Fuchs, M. C.; Gloaguen, R.; Pohl, E.; Sulaymonova, V.; Merchel, S.; Rugel, G.;
The quantification of surface process rates is crucial for understanding the topographic evolution of high mountains. Spatial and temporal variations in fluvial incision and basin-wide erosion enable to decipher the role of tectonic and climatic drivers. The Pamir is peculiar in both aspects because of its location at the western end of the India-Asia collision zone, and its position at the edge of two atmospheric circulation systems, the Westerlies and the Indian Summer Monsoon. The architecture of the Panj river network indicates prominent variations across the main tectonic structures of the Pamir. The trunk stream, deflects from the predominantly westward river orientation and cuts across the southern and central Pamir domes before doubling back to the west and leaving the orogen.
Optically stimulated luminescence (OSL) dating of fluvial terraces reveals short-term sedimentation along the trunk stream during the last ~25 kyr. The agreement of OSL results to new exposure ages based on the cosmogenic nuclide (CN) 10Be confirms accurate terrace age modelling and treatment of incomplete bleaching. The consistent terrace sedimentation and exposure ages suggest also fast terrace abandonment and rapid onset of incision. Considerable differences in terrace heights reflect high spatial variations of fluvial incision, independent of time interval, change in rock type or catchment increase. Highest rates of (5.9 + 1.1) mm/yr to (10.0 + 2.0) mm/yr describe the fluvial dynamic across the Shakhdara Dome and that related to the Darvaz Fault Zone. Lower rates of (3.9 + 0.6) mm/yr to (4.5 + 0.7) mm/yr indicate a transient stage north of the Yazgulom Dome. Fluvial incision decreases to rates ranging from (1.7 + 0.3) mm/yr to (3.9 + 0.7) mm/yr in graded river reaches associated to southern dome boundaries. The pattern agrees to the interpretation of successive upstream river captures across the southern and central Pamir domes inferred from morphometric analyses of river and valley profiles.
Basin-wide erosion rates based on 10Be concentrations in modern fluvial sediments yield relatively consistent rates between (0.61 + 0.1) mm/yr and (0.75 + 0.14) mm/yr along the Panj. The increasing Panj catchment averages variations of tributary basins, but minor variations in erosion rates of along-stream sub-basins resemble the pattern of OSL-based incision rates. In contrast, basin-wide erosion rates of tributary basins clearly differentiate between plateau-related sub-basins of (0.05 + 0.01) mm/yr to (0.17 + 0.03) mm/yr, and plateau margin-related sub-basins of (0.38 + 0.06) mm/yr to (1.43 + 0.26) mm/yr. The differentiation in plateau-related and marginal sub-basins and the northward increase in erosion rates correlate with the 75-percentile of the slope distribution within respective basins and to a minor degree to cumulative annual precipitation.
Keywords: cosmogenic nuclides, erosion
  • Poster
    European Geosciences Union (EGU) General Assembly, 27.04.-02.05.2014, Wien, Österreich

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Permalink: https://www.hzdr.de/publications/Publ-19855
Publ.-Id: 19855


Silica-stabilised actinide(IV) colloids in neutral and slightly alkaline solutions

Zänker, H.; Hennig, C.; Weiss, S.;
Due to their low solubility, tetravalent actinides, An(IV), are usually assumed to be immobile in natural waters. However, insoluble precipitation products can also be mobile if they occur as colloids. For An(IV) oxyhydroxides this phenomenon has thoroughly been studied. The formation of a further type of An(IV) colloids is described (cf. [1]): Silica-containing U(IV), Th(IV) and Np(IV) colloids formed in near-neutral to slightly alkaline solutions of background chemicals of geogenic nature (carbonate, silicic acid, Na+). Whereas the silica-containig colloids addressed in the BELBaR project are formed by the adsorption of radionuclides onto pre-existing silica particles, the colloids here under discussion result from a reaction of dissolved An(IV) with dissolved silicic acid (co-precipitation). An-O-Si bonds, which increasingly replace the An-O-An bonds of the amorphous actinide(IV) oxyhydroxide with increasing silica concentration, make up the internal structure of these colloids as was elucidated by EXAFS spectroscopy and further spectroscopic methods. A strong shift of the particles’ isoelectric point by silica incorporation is observed. The particles remain stable in aqueous suspension over years. A concentration of up to 10-3 M of colloid-borne An(IV) was observed. The prevailing size of the particles is below 20 nm (about 10 to 100 kDa). The question if such An(IV) colloids may contribute to the mobility of the actinides in the near-field or the far-field of a nuclear waste repository is discussed.
Keywords: tetravalent actinides, silica, colloids, particle size, isoelectric point, EXAFS
  • Lecture (Conference)
    IGDTP-Geodisposal 2014, 24.-26.6.2014, Manchester, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-19854
Publ.-Id: 19854


Quantifying ages of river terraces and basin wide denudation rates in Pamir

Sulaymonova, V. A.; Fuchs, M. C.; Gloaguen, R.; Merchel, S.; Rugel, G.;
The Pamir is located at the western edge of the Indian indenter and results from the India-Asia collision. The Pamir also lies at the transition between zones dominated either by the Westerlies or the Indian Summer Monsoon. The ongoing tectonic deformation together with the climatic gradients from the two prevailing atmospheric circulation systems provide a natural laboratory to study surface processes and their rates. To determine and quantify the interaction between tectonics and the drainage system in the Tajik Pamir we use cosmogenic nuclide based techniques.
We measured 10Be and 26Al concentrations of modern fluvial sediments sampled from drainage system of Pamirs. Depth profiles enable to determine exposure ages of fluvial terraces, while the modern river sediments reveal basin-wide erosion rates.
However, accurate measurement results depend on the quality of the sample preparation. The samples from Pamir contain a high amount of various feldspars that are very difficult to separate from quartz using standard procedures such as magnetic or density separation. Unclean samples cause uncertainties in chemical procedures, especially in the case of combined 10Be and 26Al analysis. We developed a feldspar flotation in addition to our sample preparation procedure that allowed an almost complete separation of the quartz, up to 95%. Several depth profiles were analyzed to determine the exposure age of fluvial terraces. The first results of one terrace along the southern Panj River east of Langar, and one along the Shakhdara River are promising. The AMS results demonstrated that the depth profiles are consistent, with 10Be and 26Al concentrations decreasing with depth. The results of both fluvial terraces show similar denudation rates 0.5 mm/yr., while exposure age analysis yields 3.5 ka for the Langar and 19 ka Shakhdara terrace. Further analyses are ongoing. These ages are validated by OSL dates at or nearby the same sites. 10Be denudation rates on modern river samples refine the picture produced by one of us (see Fuchs et al., same session).
Keywords: cosmogenic nuclides, fluvial terraces, erosion rate
  • Poster
    European Geosciences Union (EGU) General Assembly, 27.04.-02.05.2014, Wien, Österreich

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Permalink: https://www.hzdr.de/publications/Publ-19853
Publ.-Id: 19853


Application of the method for uncertainty and sensitivity evaluation to results of PWR LBLOCA analysis calculated with the code ATHLET. Part 2: Sensitivity analysis

Kozmenkov, Y.; Rohde, U.;
In the previously published part 1 of the paper the uncertainty analysis of the large break loss-of-coolant accident (LBLOCA) for German PWR Konvoi was performed using a statistical method, which is based on the Wilks’ theory. The evaluated output parameter is the peak cladding temperature (PCT). The primary goal of this (second) part of the paper is a ranking of the input uncertainties, according to their contributions to the PCT uncertainty in the ATHLET simulation of PWR LBLOCA, by performing a sensitivity analysis. It was shown, that the first extended set of varied parameters used in part 1 can be considerably reduced without any statistically significant influence on the uncertainty analysis results. Thus, it can be shown that the input uncertainty vector based on the LBLOCA PIRT of AREVA GmbH was complete.
To minimize the number of varied parameters the statistical t-test was used and, thus, a set of uncertainty parameters with significant impact on the uncertainty of the PCT was identified. The main contribution to the uncertainty of the first cladding temperature maximum during the blowdown phase of the accident is produced by the core parameters that affect the fuel’s stored energy at the beginning of the accident. However, the major contributors to the uncertainty of the second PCT maximum are the uncertainties in the code models, and first of all the uncertainties in the heat transfer coefficients for dispersed and pure steam flows.
Keywords: LBLOCA, PWR, blowdown phase, reflood phase, ATHLET code, input uncertainties, peak cladding temperature, sensitivity analysis, t-test, PIRT completeness

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Permalink: https://www.hzdr.de/publications/Publ-19852
Publ.-Id: 19852


Experimental Investigation of the Effect of 90 Degrees Standard Elbow on Horizontal Gas-Liquid Stratified and Annular Flow Characteristics using Dual Wire Mesh Sensors

Vieira, R. E.; Kesana, N. R.; Torres, C. F.; Mclaury, B. S.; Shirazi, S. A.; Schleicher, E.; Hampel, U.;
Fluid flowing through pipelines often encounters fittings such as elbows. Although it is true that two-phase flow patterns observed in elbows are qualitatively the same as those seen in straight pipes, the presence of a pipe elbow can modify relative positions and local velocities of the two phases as they are subjected to forces in addition to those encountered in a straight pipe. That redistribution can affect pressure drop values, chemical inhibitor concentration and distribution to the top of the pipe, as well as the erosion pattern occurring from solid particles such as sand that is entrained in oil and gas transportation pipelines. In this work, a Wire-Mesh Sensor technique based on conductance measurements of void fraction was applied to investigate two-phase pipe flow through a standard elbow. The horizontal flow test section, consisting of a 76 mm ID, 18 m long pipe, was employed to generate stratified-wavy and annular flow conditions. Two 16×16 Wire-Mesh configuration sensors were positioned either 0.9 m upstream or 0.6 m downstream of the bend. The experiments were conducted at different liquid and gas superficial velocities that ranged from 0.03 m/s to 0.2 m/s and from 9 m/s to 34 m/s, respectively. The effects of liquid viscosity on the measured parameters are also investigated using two different viscosities of 1 and 10 cP. Stratified-slug transition, stratified wavy and annular flow patterns were observed visually in the clear section placed upstream of the Wire-Mesh sensors. Analysis of time series void fraction data from the dual Wire-Mesh sensors allows the determination of mean void fraction, local time average void fraction distribution, liquid phase distribution around the tube periphery, interfacial structure velocities, as well as Probability Density Function characteristic signatures within the cross-section of pipe before and after the elbow. The results indicate that the distribution of gas and liquid phases and interfacial velocities are significantly altered even 20 diameters downstream of the elbow.
Keywords: Wire-Mesh Sensor, two-phase flow, flow visualization, void fraction

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Permalink: https://www.hzdr.de/publications/Publ-19850
Publ.-Id: 19850


Experimental Investigation of Slug Characteristics through a Standard Pipe Bend

Kesana, N. R.; Vieira, R. E.; Mclaury, B. S.; Shirazi, S. A.; Schleicher, E.; Hampel, U.;
Slug flow is a very common flow pattern encountered during the production of petroleum fluids. Likewise, pipe bends are often used to change the direction of the fluids during transportation. This work focuses on comparing various slug characteristics before and after a pipe bend. For this investigation, a dual Wire Mesh Sensor (WMS) is utilized. Measurements are made by placing the sensor before and after the bend. In order to obtain higher spatial and temporal resolution of the signals, a sampling frequency of 10,000 Hz is used. Experiments were conducted in a 76.2 mm (3-inch) diameter pipe utilizing air and water as fluids. Effect of fluid viscosity is also studied by conducting the experiments using three different liquid viscosities: 1, 10 and 40 cP. The experiments were conducted with superficial gas velocity ranging from 9.1 m/s to 35 m/s, and superficial liquid velocity ranged from 0.45 to 0.76 m/s. The three-dimensional time series void data from the Wire-Mesh sensor before and after the bend are analyzed to obtain averaged void fractions, structure of the slugs, void in liquid slugs, bubble size distributions, and radial profiles of gas velocity. Also, this study presents the differences in the void fraction distributions in slugs and pseudo slugs. Since pseudo slugs occur between slug and annular regimes, this information can further the understanding of the effect of flow characteristics on erosion occurring from solid particles for this flow pattern. Finally, from this comprehensive analysis the influence of the bend on the gas and liquid distributions over the cross-section has been discussed.
Keywords: Solid particle erosion, Multiphase slug flow, Wire Mesh Sensor
  • Contribution to proceedings
    22nd Symposium on Industrial Flows, ASME International Mechanical Engineering Congress & Exposition, 15.-21.11.2013, San Diego, California, USA
    Proceedings of ASME 2013 International Mechanical Engineering Congress & Exposition 2013

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Permalink: https://www.hzdr.de/publications/Publ-19848
Publ.-Id: 19848


Hypoxia-inducible factor pathway inhibition resolves tumor hypoxia and improves local tumor control after single-dose irradiation

Helbig, L.; Koi, L.; Brüchner, K.; Gurtner, K.; Hess-Stumpp, H.; Unterschemmann, K.; Pruschy, M.; Baumann, M.; Yaromina, A.; Zips, D.;
Purpose To study the effects of BAY-84-7296, a novel orally bioavailable inhibitor of mitochondrial complex I and hypoxia-inducible factor 1 (HIF-1) activity, on hypoxia, microenvironment, and radiation response of tumors. Methods and Materials UT-SCC-5 and UT-SCC-14 human squamous cell carcinomas were transplanted subcutaneously in nude mice. When tumors reached 4 mm in diameter BAY-84-7296 (Bayer Pharma AG) or carrier was daily administered to the animals. At 7 mm tumors were either excised for Western blot and immunohistologic investigations or were irradiated with single doses. After irradiation animals were randomized to receive BAY-84-7296 maintenance or carrier. Local tumor control was evaluated 150 days after irradiation, and the dose to control 50% of tumors (TCD50) was calculated. Results BAY-84-7296 decreased nuclear HIF-1α expression. Daily administration of inhibitor for approximately 2 weeks resulted in a marked decrease of pimonidazole hypoxic fraction in UT-SCC-5 (0.5% vs 21%, P<.0001) and in UT-SCC-14 (0.3% vs 19%, P<.0001). This decrease was accompanied by a significant increase in fraction of perfused vessels in UT-SCC-14 but not in UT-SCC-5. Bromodeoxyuridine and Ki67 labeling indices were significantly reduced only in UT-SCC-5. No significant changes were observed in vascular area or necrosis. BAY-84-7296 before single-dose irradiation significantly decreased TCD50, with an enhancement ratio of 1.37 (95% confidence interval [CI] 1.13-1.72) in UT-SCC-5 and of 1.55 (95% CI 1.26-1.94) in UT-SCC-14. BAY-84-7296 maintenance after irradiation did not further decrease TCD50. Conclusions BAY-84-7296 resulted in a marked decrease in tumor hypoxia and substantially reduced radioresistance of tumor cells with the capacity to cause a local recurrence after irradiation. The data suggest that reduction of cellular hypoxia tolerance by BAY-84-7296 may represent the primary biological mechanism underlying the observed enhancement of radiation response. Whether this mechanism contributes to the improved outcome of fractionated chemoradiation therapy warrants further investigation.

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Permalink: https://www.hzdr.de/publications/Publ-19847
Publ.-Id: 19847


Plasmonic off-axis unidirectional beaming of quantum-well luminescence

Dimaria, J.; Dimakis, E.; Moustakas, T. D.; Paiella, R.;
Plasmonic off-axis unidirectional beaming of luminescence is demonstrated using nitride semiconductor quantum wells. The underlying mechanism involves the near-field excitation of surface plasmon polaritons on an ultrathin metal film, which are then diffractively scattered by an adjacent periodic array of asymmetric metallic nanoparticles. By tailoring the nanoparticles shape, we show that forward scattering can be suppressed in favor of backward diffraction (or vice versa), thereby enabling unidirectional beaming at geometrically tunable oblique angles. These nanostructures can be used to control the output light directionality of arbitrary planar luminescent devices, with a spatial resolution that would be unattainable with bulk optics.

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Permalink: https://www.hzdr.de/publications/Publ-19846
Publ.-Id: 19846


Application of a three-feature dispersed-barrier hardening model to neutron-irradiated Fe-Cr model alloys

Bergner, F.; Pareige, C.; Hernández-Mayoral, M.; Malerba, L.; Heintze, C.;
An attempt is made to quantify the contributions of different types of defect-solute clusters to the total irradiation-induced yield stress increase in neutron-irradiated (300 °C, 0.6 dpa), commercial-purity Fe-Cr alloys (target Cr contents of 2.5, 5, 9 and 12 at% Cr). Former work based on the application of transmission electron microscopy, atom probe tomography, and small-angle neutron scattering revealed the formation of dislocation loops, NiSiPCr-enriched clusters and alpha’-phase particles, which act as obstacles to dislocation glide. The values of the dimensionless obstacle strength are estimated in the framework of a three-feature dispersed-barrier hardening model. Special attention is paid to the effect of measuring errors, experimental details and model details on the estimates. The three families of obstacles and the hardening model are well capable of reproducing the observed yield stress increase as a function of Cr content, suggesting that the nanostructural features identified experimentally are the main, if not the only, causes of irradiation hardening in these alloys.
Keywords: Radiation hardening, Fe-Cr alloys

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Permalink: https://www.hzdr.de/publications/Publ-19845
Publ.-Id: 19845


Polynuclear complexes of tetravalent actinides and lanthanides with simple carboxylate ligands

Hennig, C.;
Polyanuclear An(IV) carboxylate complex were identified in aqueous solution. The related complex species were preserved in crystals and their structures were determined. The structural identity of the species in solution and in solid state was tested by EXAFS spectroscopy.
Keywords: actinides, carboxylates, EXAFS, XRD
  • Lecture (others)
    Forschungszentrum Juelich, Institute of Energy and Climate Research, 06.02.2014, Jülich, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-19844
Publ.-Id: 19844


Robust energy enhancement of ultra-short pulse laser accelerated protons from reduced mass targets

Zeil, K.; Bussmann, M.; Cowan, T. E.; Kluge, T.; Kraft, S. D.; Metzkes, J.; Schramm, U.;
We present a systematic study of the ultrashort pulse laser driven acceleration of protons from thin targets of finite lateral size, so-called reduced mass targets (RMTs). Reproducible series of targets, manufactured with lithographic techniques, and varying in size, thickness, and mounting geometry were irradiated at the 150 TW Draco Laser facility of the Helmhotz-Zentrum Dresden-Rossendorf with ultrashort (30 fs) laser pulses of intensities of about 8 • 10^20 W/cm^2. A robust maximum energy enhancement of almost a factor of two was found when compared to reference irradiations of plain foils of the same thickness and material. Furthermore, these targets exhibit a reduced performance dependence on target thickness compared to standard foils, which, based on detailed PIC simulations can be explained by the influence of the RMT geometry on the electron sheath. The performance gain was, however, restricted to lateral target sizes of about 50 μm which was attributed to edge and mounting structure influences. The contribution of the large electric fields at the target edges to the proton acceleration performance was investigated with measurements of the proton beam profile as well as optical pump and probe experiments.
  • Lecture (Conference)
    Laser and Plasma Accelerator Workshop 2013, 04.09.2013, Goa, India

Permalink: https://www.hzdr.de/publications/Publ-19843
Publ.-Id: 19843


CFD simulations of steam-water flow with condensation

Apanasevich, P.; Lucas, D.;
Gas-liquid two-phase flows have become increasingly important in engineering equipment and technology (e.g. in chemical or process industries). Depending on mass flow rates, geometry and the fluid properties, different flow regimes can occur (e.g. bubble flow, stratified flow, droplet flow etc.). The current project focuses on stratified two-phase flows with heat and mass transfer across a moving interface due to direct contact condensation (DCC) in horizontal pipes or channels. In case of direct contact condensation, the resistance to condensation heat transfer considerably lower compared to film-wise condensation. Hence, DCC allows a considerably better heat exchange between the phases. Direct contact condensation is used in a variety of heat transfer devices (such as direct contact condensers), which offer the possibility of increased per-formance. DCC has also been of major importance in connection with the analysis of nuclear reactor safety systems, in particular during two-phase pressurized thermal shock (PTS) scenari-os. PTS occurs when there are large thermal loads on the Reactor Pressure Vessel wall during an accident. Therefore, the modeling of direct contact condensation is a task of considerable im-portance. Condensation phenomena depend on the turbulence in the liquid phase. To consider pronounced 3D effects and local phenomena CFD methods need to be used. Generally, two-phase CFD models are not yet mature and have to be qualified for two-phase flows. The work aims at the development and validation of CFD models for two-phase stratified flows including heat and mass exchange between the phases. A promising model development strategy implies experimental data with high resolution both in space and time for the entire domain of interest. To investigate two-phase PTS scenarios with DCC, the TOPFLOW-PTS experiments were carried out at the TOPFLOW test facility of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) [1]. The goal of the paper is to present the CFD simulations of a TOPFLOW-PTS steam-water experiment and to discuss the limits of the models used.
Keywords: CFD, pressurized thermal shock, direct contact condensation, TOPFLOW-PTS experiments
  • Lecture (Conference)
    International Colloquim 150th Birthday of Richard Mollier Heat transfer phenomena in external fields: Basis research for next generation energy machines, 21.-22.11.2013, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-19842
Publ.-Id: 19842


Carbon Cage Vibrations of M@C82 and M2@C2n (M = La, Ce; 2n = 72, 78, 80): The Role of the Metal Atoms

Popov, A. A.; Kästner, C.; Krause, M.; Dunsch, L.;
Infrared spectra of La2@C80 and a series of Ce-based endohedral metallofullerenes (EMFs), including Ce@C82, Ce2@C72, Ce2@C78, and Ce2@C80 are reported. DFT calculations are used for their thorough analysis and assignment. The vibrations of the fullerene cages in all studied EMFs differ from those of their empty, charged cage analogues. Furthermore, EMFs with the same carbon cage but different type of encapsulated species also show significant differences in their cage vibrational patterns. These phenomena are explained by a different coupling of the vibrational modes as well as by the different charge distributions in EMFs and empty, isostructural fullerene anions.
Keywords: Endohedral fullerene, metallofullerene, vibrational spectroscopy, density functional theory

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Permalink: https://www.hzdr.de/publications/Publ-19841
Publ.-Id: 19841


Development of a transport solver for DYN3D on the basis of CCCP with orthonormal flux expansion

Litskevich, D.; Merk, B.;
DYN3D is a well-known and widely used computer code for reactor physics simulation of nuclear power plants, in particular for reactors with hexagonal fuel assembly structures. It has been developed in Helmholtz-Zentrum Dresden-Rossendorf, Germany. The standard version of the DYN3D code can be used for investigations of transients in light water reactors cores with hexagonal or quadratic fuel assemblies. In order to determine the pin with the maximum power in selected assemblies, a two-dimensional pin power reconstruction can be performed based on the node homogenized neutron flux. A superposition of global diffusion solution of the full core calculation with the assembly pin powers obtained in the cell calculations is used therefore. This method is implemented in DYN3D for reconstruction of power inside selected assemblies. An improved onset would be a hybrid solution, the coupling of the full core diffusion solver with an advanced transport solver on fuel assembly base. This method can be used to directly determine the power distribution for each rod inside fuel assemblies by applying a transport solver using unstructured mesh and boundary conditions extracted from the full core diffusion solution. Nowadays, this mentioned methodology is under development. In the present work an advanced multigroup transport method of current coupling collision probability (CCCP) with orthonormal flux expansion inside the calculation regions is being developed and tested for cylindrical, hexagonal geometries and for assemblies of hexagonal cells. The results of test calculations demonstrate very good agreement with the results obtained from Monte Carlo calculations. Multigroup calculations for hexagonal assemblies with cross-sections prepared using the HELIOS code show good agreement with HELIOS reference solution, too. These convincing results encourage the implementation of this advanced pin power calculation method into DYN3D as future pin-power determination method using currents from nodal solution as boundary conditions.
Keywords: Transport equation, current coupling collision probability method, DYN3D
  • Open Access Logo Contribution to proceedings
    23rd Symposium of AER on VVER Reactor Physics and Reactor Safety, 30.09.-04.10.2013, Štrbské pleso, Slovakia
    Proceedings of the 23rd Symposium of AER on VVER Reactor Physics and Reactor Safety, Budapest: MTA Energoatom, 38-48
  • Lecture (Conference)
    23rd Symposium of AER on VVER Reactor Physics and Reactor Safety, 30.09.-04.10.2013, Štrbské pleso, Slovakia

Permalink: https://www.hzdr.de/publications/Publ-19840
Publ.-Id: 19840


Sintering and Crystallization during the Production of Strontium-Anortite Glass Ceramic

Sarkisov, P. D.; Orlova, L. A.; Popovich, N. V.; Bruntsch, R.; Chainikova, A. S.; Klinkmueller, K.; Shchegoleva, N. E.;
Crystallization and sintering, which occur during firing, during the production of strontium-anortite glass ceramics by means of powder metallurgy are studied. It is shown that the dispersity of the initial glass powder and the temperature–time firing regimes affect the crystallization temperature and heat, the nature of the precipitating phases and the sintering temperature interval and kinetics of the particles. It is determined that for ceramizing glass compositions there exists a narrow powder dispersity interval in which densely sintered materials with the required composition and high mechanical properties can be obtained using multistep heat-treatment.
Keywords: glass ceramic, sintering, dispersity, strontium anortite, SrO–Al2O3–SiO2

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Permalink: https://www.hzdr.de/publications/Publ-19839
Publ.-Id: 19839


Importance of nuclear triaxiality for electromagnetic strength, level density and neutron capture cross sections in heavy nuclei

Grosse, E.; Massarczyk, R.; Junghans, A. R.;
Cross sections for neutron capture in heavy nuclei in the energy range of unresolved resonances are predicted simultaneously to data on level densities at the neutron threshold and average photon widths from 132 spin-0 target nuclei with 70
  • Open Access Logo Contribution to proceedings
    Final ERINDA User Meeting and Scientific Workshop, 01.-03.10.2013, Geneva, Switzerland
    Proceedings of the ERINDA Workshop, CERN, edited by Enrico Chiaveri CERN Proceedings 2014-002, Geneva: CERN, 978-92-9083-403-8, 135-144
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    Permalink: https://www.hzdr.de/publications/Publ-19838
    Publ.-Id: 19838


    Transmutation of high-level radioactive waste - Perspectives

    Junghans, A.; Beyer, R.; Grosse, E.; Hannaske, R.; Kögler, T.; Massarczyk, R.; Schwengner, R.; Wagner, A.;
    In a fast neutron spectrum essentially all long-lived actinides (e.g. Plutonium) undergo fission and thus can be transmuted into generally short lived fission products. Innovative nuclear reactor concepts e.g. accelerator driven systems (ADS) are currently in development that foresee a closed fuel cycle. The majority of the fissile nuclides (uranium, plutonium) shall be used for power generation and only fission products will be put into final disposal that needs to last for a historical time scale of only 1000 years. For the transmutation of high-level radioactive waste a lot of research and development is still required. One aspect is the precise knowledge of nuclear data for reactions with fast neutrons. Nuclear reactions relevant for transmutation are being investigated in the framework of the european project ERINDA. First results from the new neutron time-of-flight facility nELBE at Helmholtz-Zentrum Dresden-Rossendorf will be presented.
    • Open Access Logo Contribution to proceedings
      Final ERINDA User Meeting and Scientific Workshop, 01.-03.10.2013, Geneva, Switzerland
      Proceedings of the ERINDA Workshop, CERN, edited by Enrico Chiaveri CERN Proceedings 2014-002, Geneva: CERN, 978-92-9083-403-8, 175-181

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    Permalink: https://www.hzdr.de/publications/Publ-19837
    Publ.-Id: 19837


    Kinetics and activation parameters of the reaction of organoarsenic(V) compounds with glutathione

    Kretzschmar, J.; Brendler, E.; Wagler, J.; Schmidt, A.-C.;
    In this work the kinetics of the reaction of glutathione (GSH) with different organoarsenic(V) compounds is investigated. This includes phenylarsonic acid (PAA), 4-hydroxy-3-nitrophenylarsonic acid (HNPAA), p-aminophenylarsonic acid (p-APAA) and o-aminophenylarsonic acid (o-APAA) as well as monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA). The reaction progress was monitored in real time by 1H-NMR, which allowed the determination of rate coefficients and half-lives as well as activation energies, enthalpies and entropies of activation and, eventually, Gibbs free energies of activation. The reaction consists of two steps: redox reaction and conjugation. In all investigated systems, the conjugation is fast compared to the redox reaction, which therefore is rate determining. All investigated phenylarsonic acids are subject to the same rate law, showing overall reaction orders of 3 and half-life values between 47.7 ± 0.2 and 71.0 ± 3.6 min, corresponding to reaction rates between 1330 ± 10 L2 mol-2 min-1 and 850 ± 5 L2 mol-2 min-1, respectively. The methylated compounds react slower, showing half-lives of 76.6 ± 0.4 and 444 ± 10 min for DMAA and MMAA, respectively. The obtained enthalpies of activation range from 20 to 36 (± 2) kJ mol-1 and the entropies of activation are within −154 and −97 (± 7) J mol-1 K-1. The results reveal a correlation of the toxicity of the arsenic compound and the reaction rate with GSH. This may pave the way for the estimation of the toxicity of such compounds by simple kinetic studies.
    Keywords: glutathione, roxarsone, phenylarsonic acid, arsanilic acid, arsenic detoxification, kinetics, NMR

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    Permalink: https://www.hzdr.de/publications/Publ-19836
    Publ.-Id: 19836


    All-optical helicity dependent magnetic switching in Tb-Fe thin films with a MHz laser oscillator

    Hassdenteufel, A.; Schubert, C.; Hebler, B.; Schultheiss, H.; Fassbender, J.ORC; Albrecht, M.; Bratschitsch, R.
    We demonstrate all-optical magnetic switching (AOS) in an amorphous Tb30Fe70 thin film, triggered by a 5.1 MHz laser oscillator. The magnetic layer is grown on a SiO2/Si substrate. An identical magnetic film deposited on a microscope glass slide shows no AOS and only exhibits thermally induced demagnetization. This effect is due to heat accumulation by multiple laser pulses because of the low thermal conductivity of the glass substrate. In contrast, the use of a proper heat sink (e.g. SiO2/Si) abolishes need for low repetitive laser amplifier systems to induce AOS and paves the way for a cheap and easy to use technological implementation with conventional laser oscillators.
    Keywords: Ultrafast technology; Ultrafast phenomena; Ultrafast processes in condensed matter, including semiconductors; Optical data storage; Magneto-optical materials; Optical storage-recording materials
    • Open Access Logo Optics Express 22(2014)8, 10017-10025
      DOI: 10.1364/OE.22.010017
    • Lecture (Conference)
      CLEO 2014, 08.-13.06.2014, San Jose, Kalifornien, USA

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    Permalink: https://www.hzdr.de/publications/Publ-19835
    Publ.-Id: 19835


    Electromagnetic method for detection of gas bubbles in two phase liquid metals flows

    Andreew, O.; Gundrum, T.; Wondrak, T.; Eckert, S.; Gerbeth, G.; Dekdouk, B.; Peyton, A.;
    We present a combined numerical and experimental investigation of an electromagnetic system dedicated for an operative detection of non-metallic enclosures (gas bubbles) into the liquid metal flows. The method is based on the generation of eddy currents in the electrically conducting medium by applying AC magnetic field and the detection of the electromagnetic distortions caused by heterogeneity of electrical conductivity of the medium. We defined an optimal position and configuration of detector and excitation coil in order to get maximal sensitivity of the system to the spatial distribution of admixture.
    Keywords: two-phase flow; electromagnetic tomography; gas bubbles.
    • Lecture (Conference)
      7th World Congress on Industrial Process Tomography, WCIPT7, 02.-05.09.2013, Krakow, Poland
    • Lecture (Conference)
      2013 International Congress on Advances in Nuclear Power Plants (ICAPP2013) & The 28th Korea Atomic Industrial Forum Inc., 14.-18.04.2013, Jeju, Korea

    Permalink: https://www.hzdr.de/publications/Publ-19834
    Publ.-Id: 19834


    Liquid metal experiments with strong magnetic fields and high electrical currents

    Seilmayer, M.;
    To measure the fluid motion in liquid metal experiments Ultrasound Doppler Velocimetry (UDV) is used very often. The very small UDV signals can be disturbed by high direct current sources due to electromagnetic noise coming from these devices. The presentation will give some ideas and work around to common problems arising with magnetic field generation. All this will be explained on an ongoing experiment to the magneto rotatorical instability (MRI) in our laboratory. Finally some concepts and results will be given to rise measurement quality.
    Keywords: EMV, magnetic field, Switching mode power supply, UDV, ultrasound doppler
    • Invited lecture (Conferences)
      Mitarbeiter Seminar, 10.04.-10.09.2013, Illmenau, Thüringen

    Permalink: https://www.hzdr.de/publications/Publ-19833
    Publ.-Id: 19833


    Electromagnetic method for gas bubble detection in liquid metal flows

    Andreew, O.; Gundrum, T.; Wondrak, T.; Eckert, S.; Gerbeth, G.; Dekdouk, B.; Peyton, A.;
    We present a combined numerical and experimental investigation of an electromagnetic system dedicated for an operative detection of non-metallic enclosures (gas bubbles) into the liquid metal flows. The method is based on generation of eddy currents in the electrically conducting medium by applying of ac magnetic field and detection of the electromagnetic distortions caused by inhomogeneity of electrical conductivity of the medium. We defined an optimal position and configuration of detector in order to get maximal sensitivity of the system to the spatial distribution of admixture.
    Keywords: Electromagnetic Thomogpaphy, Gas Bubbles, Liquid Metal
    • Lecture (Conference)
      2013 International Congress on Advances in Nuclear Power Plants & 28th KAIF/KNS Annual conference - ICAPP 2013, 14.-18.04.2013, Jeju Island, South Korea

    Permalink: https://www.hzdr.de/publications/Publ-19832
    Publ.-Id: 19832


    Development and application of digital image analysis technique to gas-liquid flows in a pseudo-2D bubble

    Thiruvalluvan Sujatha, K.; Lau, Y. M.; Deen, N. G.; Kuipers, J. A. M.;
    Bubble columns are widely used in the chemical industry for gas-liquid operations. In-spite of the wide spread use of bubble column reactors, fundamental understanding of interactions between hydrodynamics, mass transfer and chemical reaction in dense systems is still lacking. Several experimental techniques are available to study gas-liquid flows: photographic imaging, particle image velocimetry, X-ray tomography, wire mesh sensors, etc. We developed a digital image analysis technique (DIA) to study the gas-liquid flows in bubble column reactor.
    • Lecture (Conference)
      Joint HZDR & ANSYS Conference - 11th Multiphase Flow Conference & Short Course, 26.-28.11.2013, Dresden, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19831
    Publ.-Id: 19831


    New possibilities for investigation of the technological texture based on electric Parameters: theoretical Analysis and experimental verification

    Kozik, T.; Minarik, S.;
    Texture is preferred orientation of crystallites in some polycrystalline materials. Different methods are applied to characterize the orientation patterns and determine the orientation distribution. Most of these methods rely on diffraction. This paper introduces the principle of a method used for characterization of ceramics texture based on anisotropy of electrical properties of crystallites in ceramics. The mathematical framework of this method is presented in theoretical part of our work. In experimental section we demonstrate how the theoretical result could be used to evaluate technology texture of ceramic material intended for the production of electronic insulators.
    Keywords: ceramics texture, scalar potential, Laplace equation, Bessel function, Bessel differential equation

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    Permalink: https://www.hzdr.de/publications/Publ-19830
    Publ.-Id: 19830


    Structural modifications of thin magnetic Permalloy films induced by ion implantation and thermal annealing, a comparison

    Roshchupkina, O. D.; Strache, T.; McCord, J.; Muecklich, A.; Baehtz, C.; Grenzer, J.;
    We report the structural properties of thin magnetic Permalloy films treated by two different methods: broad-beam Ga+ ion implantation at an energy of 30keV as well as annealing at different temperatures under ultra-high vacuum. Transmission electron microscope imaging and X-ray diffraction measurements have demonstrated that both ion implantation and annealing (above 300°C) lead to further material crystallization and crystallite growth. Whereas, annealing (above 400°C) leads to a strain-free state with an almost constant lattice parameter and to a further enhancement of the initial (111) texture, ion beam implantation boosts the growth of small arbitrary oriented crystallites and leads to an linear increase of the lattice parameter introducing mirco-strain to the sample. The observed decrease of the saturation magnetization for the implanted samples is mainly attributed to the presence of the non-magnetic Ga atoms incorporated in the Permalloy film itself. The rise of the saturation magnetization for the samples annealed at temperatures above 500°C is explained by an arising de-wetting effect since no ordered FeNi3 phase was detected with anomalous X-ray diffraction.
    Keywords: ion beam implantation, microstructure, XRD

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    Permalink: https://www.hzdr.de/publications/Publ-19829
    Publ.-Id: 19829


    Flow measurements in a continuous steel casting model using low temperature liquid metal

    Willers, B.; Timmel, K.; Eckert, S.; Gerbeth, G.;
    Model experiments with low melting point liquid metals are used to evaluate the flow structure and its related transport processes in metallurgical applications in melt flows. Water model experiments are less important, in particular, in case of strong temperature gradients, two-phase flows or flows exposed to electromagnetic fields. Here we present the Mini-LIMMCAST experimental facility to illustrate the continuous steel casting process using a GalnSn room-temperature liquid metal alloy. The parameters of the facility and the dimensions of the test sections will be given and possibilities to evaluate the flow in the mold will be discussed.
    The effect which the magnetic field has on the flow structure turned out to be complex. The flow measurements do not show a general braking effect which would be expected as an overall damping of the flow velocity and its resulting fluctuations in the mold. Not only different magnetic field intensities had a big influence on the flow field, but also the variation of the electromagnetic field position had a striking impact on the resulting flow structures. The flow intensity in the upper part of the mold is also significantly influenced by the movement on the free surface of the metal. During continuous casting, this movement of the free surface is an important parameter to indicate the quality of steel. The experiments provide a substantial database for the validation of respective numerical simulations.
    Keywords: magnetic field, liquid metal, flow, flow structure, flow measurement, flow velocity, flow control, continuous casting, magnetic brake, Ruler EMBr, GaInSn
    • Lecture (Conference)
      The 5th International Conference STEELSIM 2013, 10.-12.09.2013, Ostrava, Czech Republic

    Permalink: https://www.hzdr.de/publications/Publ-19828
    Publ.-Id: 19828


    Simulation of positron energy spectra generated by channeling radiation of GeV electrons in a tungsten single crystal

    Azadegan, B.; Mahdipour, S. A.; Wagner, W.;
    Positron production based on the generation of channeling radiation by relativistic electrons channeled along the (110) crystallographic plane of a W crystal and the subsequent conversion of radiation into e+e−-pairs in an amorphous tungsten target is described. Electron dechanneling is considered by solving of the Fokker-Planck equation. The continuous potential of the channeling plane is calculated using the Doyle–Turner approximation to the atomic scattering factor taking into account thermal vibrations of the crystal atoms. The trajectories, velocities and accelerations of planar channeled electrons are obtained by solving the classical equation of motion. In the framework of classical electrodynamics, the spectral-energy distribution of radiation is obtained from the Fourier transforms of realistic electron trajectories, velocities and accelerations within the W crystal. The calculations of channeling radiation and dechanneling are carried out by means of our Mathematica codes. The conversion of radiation into e+e− -pairs and the energy distributions of produced positrons are simulated using the GEANT4 package.
    Keywords: channeling radiation, dechanneling, positrons, positron source
    • Open Access Logo Contribution to proceedings
      RREPS-13 and Meghri-13, 22.-28.09.2013, Yerevan, Lake Sevan, Armenia
      Proceedings of RREPS-13 and Meghri-13, Bristol: IOP Publishing
    • Open Access Logo Journal of Physics: Conference Series 517(2014), 012039
      DOI: 10.1088/1742-6596/517/1/012039

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    Permalink: https://www.hzdr.de/publications/Publ-19827
    Publ.-Id: 19827


    Contact-less Magneto-Elastic Torsional Sensor based on Phase-Shift Measurements

    Buchenau, D.; Schmidt, G.; Eckert, S.;
    We report on the development of a contactless measurement technique for torsional shear stress τ in ferromagnetic axles or hollow shafts, based on the magneto-elastic effect. In general two different measuring principles for ferromagnetic materials can be realised, based on: the evaluation of the change of magnetic polarisation influenced by mechanical stress ΔJ(τ ) or, the change of the magnetic susceptibility ΔχA(τ). The comprehension of the magnetic polarisation or the magnetic susceptibility in a sensor concept requires an external magnetic field. Preferably alternating magnetic fields were used as mechanical stress can disturb the amplitude but also the phase distribution of the applied magnetic field. As a result of a torsional moment acting on an axle or hollow shaft an angle of twist η appears, which is constant over the length of the twisted object. This angle of twist can be understood as a shift of infinitesimal thin cross-sections in which the whole length of the axle is separated. Beside the macroscopic deformation effect, shear forces taking also effect on the Weiss domains in the microscale of the ferromagnetic material. The effects in the microscale are the base of the magneto-eleastic effect. The combination of the deformation effect in the macro-scale with the deformation of the Weiss domains in the microscale leading to a sophisticated measurement principle for torsional stress in axles or hollow shafts. Magneto-sensitive detectors along or around the measurement object open the possibility for a contactless detection of torsional stress in ferromagnetic materials. Beside a strong measuring signal, free from electromagnetic interference, the introduced contactless measurement principle offers different advantages, like an independence from compression strength, nominal tensile stress, impact load, ferromagnetic hysteresis effects and an independence from the temperature dependent electrical conductivity of the axle or hollow shaft. The characteristics of such a type of sensor are analysed by an electrotechnical model based on Maxwells equations. Beside the chosen design of a contactless torsion sensor and an experimental set-up, the obtained test results are illustrated and reported in the present paper.
    Keywords: Magneto-elasticity, magnetic susceptibility and anisotropy, torsional stress, phase-shift

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    Permalink: https://www.hzdr.de/publications/Publ-19826
    Publ.-Id: 19826


    Invasion as target for therapy of glioblastoma multiforme

    Vehlow, A.; Cordes, N.;
    The survival of cancer patients suffering from glioblastoma multiforme is limited to just a few months even after treatment with the most advanced techniques. The indefinable borders of glioblastoma cell infiltration into the surrounding healthy tissue prevent complete surgical removal. In addition, genetic mutations, epigenetic modifications and microenvironmental heterogeneity cause resistance to radio- and chemotherapy altogether resulting in a hardly to overcome therapeutic scenario. Therefore, the development of efficient therapeutic strategies to combat these tumors requires a better knowledge of genetic and proteomic alterations as well as the infiltrative behavior of glioblastoma cells and how this can be targeted. Among many cell surface receptors, members of the integrin family are known to regulate glioblastoma cell invasion in concert with extracellular matrix degrading proteases. While preclinical and early clinical trials suggested specific integrin targeting as a promising therapeutic approach, clinical trials failed to deliver improved cure rates up to now. Little is known about glioblastoma cell motility, but switches in invasion modes and adaption to specific microenvironmental cues as a consequence of treatment may maintain tumor cell resistance to therapy. Thus, understanding the molecular basis of integrin and protease function for glioblastoma cell invasion in the context of radiochemotherapy is a pressing issue and may be beneficial for the design of efficient therapeutic approaches. This review article summarizes the latest findings on integrins and extracellular matrix in glioblastoma and adds some perspective thoughts on how this knowledge might be exploited for optimized multimodal therapy approaches.

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    Permalink: https://www.hzdr.de/publications/Publ-19825
    Publ.-Id: 19825


    Contactless flow rate measurements in metallic melts
    Kontaktlose Durchflussmessung in Metallschmelzen

    Buchenau, D.; Eckert, S.; Lenk, S.;
    Control of the flow rate of liquid metals is required in a number of technological processes such as the cooling of nuclear reactors, transmutation systems and the dosing and casting of liquid metals. Electromagnetic flow meters play an important role in the diagnostics and automatic control of such processes. For example, the electromagnetic control of casting processes can be used to improve the quality of products by reducing their brittleness and increasing durability at high production efficiency, especially for complex shape components. A number of different electromagnetic flow meter designs have been developed starting from the end of the forties of the last century. One such flowmeter - themagnetic flywheel,which is described in the textbook of Shercliff uses the electromagnetic force exerted by the flow on a close magnet. Commercial electromagnetic flow meters are typically based on the flow-induced electrical voltage measurements by electrodes in direct contact to the melt in a steady magnetic field. In view of the typical problems coming along with applications at liquid metal flows such as high temperatures, interfacial effects and corrosion, the main disadvantage of this type of flow meter is the electrical contact to the liquidmetal, which is necessary to measure the electric potential difference. Therefore, contactless operating measurement techniques are very attractive for liquid metal applications.
    Keywords: Contactless electromagnetic flow meter, liquid metal, phase-shift, EMD.ps, rotational frequency.

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    Permalink: https://www.hzdr.de/publications/Publ-19824
    Publ.-Id: 19824


    Visualisation of the Ludford column

    Andreew, O.; Kolesnikov, Y.; Thess, A.;
    When a liquid metal flows around a truncated cylinder in the presence of a magnetic field which is parallel to the axis of the cylinder, a stagnant region develops above the cylinder. This region is called Ludford column. The Ludford column represents the magnetohydrodynamic (MHD) analogue to the well-known Taylor columns in rotating flows. Whereas Taylor columns can be easily visualised using dye, the visualisation of Ludford columns remained elusive up to now because liquid metals are opaque. We demonstrate that this fundamental limitation of experimental MHD can be overcome by using a superconducting 5-Tesla magnet. This facility permits us to perform MHD experiments in which the opaque liquid metals are replaced with a transparent electrolyte while maintaining the key MHD-effects. We report results of a series of flow experiments in which an aqueous solution of sulphuric acid flows around a bar with square cross section. We vary the Reynolds number in the range 5 < Re < 100 and the Hartmann number in the range 0 < Ha < 14. The experimental procedure involves flow visualisations using tracer particles as well as velocity measurements using particle image velocimetry (PIV). Our experiments provide direct access to the Ludford columns for the first time and reveal the spatial structure of this basic feature of MHD flows.
    Keywords: Magneto hydrodynamics, truncated cylinder, PIV, optical visualisation of flow patterns

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    Permalink: https://www.hzdr.de/publications/Publ-19823
    Publ.-Id: 19823


    Nutzung der intrinsischen Eigenschaften bakterieller S-Layer zur Herstellung funktioneller Beschichtungen

    Döge, S.;
    The intention of this work was to get a distinct conformation of the s-layer Lysinibacillus sphaericus JG-A12. S-layers are interesting for e.g. functional surfaces and filtration media. A distinct conformation of the proteins is important to optimize processes and the range of applications.
    The conformation is influenced by different solution compositions for e.g. the pH-value, the buffer concentration and different concentrations of salt. This work summarizes some strategies to achieve a solution of s-layer monomers.
    • Study thesis
      HTW Dresden, 2013
      98 Seiten

    Permalink: https://www.hzdr.de/publications/Publ-19822
    Publ.-Id: 19822


    Actinide/Lanthanide interaction studies with a typical bacterial isolate from Mont Terri Opalinus Clay a potential host rock for nuclear waste disposal

    Moll, H.; Lütke, L.; Cherkouk, A.; Bernhard, G.;
    The Opalinus clay layer of the Mont Terri Underground Rock Laboratory (Switzerland) is one potential host rock tested for nuclear waste disposal [1]. It is well known that bacteria indigenous to such subterranean environments can affect the speciation and hence the mobility of actinides [2]. The unknown interactions between U(VI), Cm(III)/Eu(III) and Pu with Sporomusa sp. MT-2.99 cells was explored. This bacterium was recently isolated from Mont Terri Opalinus clay core samples by our group. Strong An/Ln interactions of this clay isolate within a broad pH range (2-8) were detected. Thermodynamic stability constants of bacterial U(VI)/Cm(III)/Eu(III) surface species were determined and will be discussed. The biosorption process of U(VI)/Cm(III)/Eu(III) can be described as a pH-dependent binding on phosphoryl and carboxyl sites of the cell membrane. For Pu a complex interaction mechanism was identified. Besides biosorption strong abiotic and biotic plutonium reduction processes were observed. The information obtained in our study is of great importance for predicting the safety of a planned nuclear waste repository.

    Acknowledgements. The authors thank the BMWi for financial support (contract no.: 02E10618 and 02E10971) and the BGR for providing the clay samples.

    References
    [1] M. Thury, P. Bossart (1999). The Mont Terri Rock Laboratory, a new international research project in a Mesozoic shale formation, in Switzerland. Eng. Geol. 52,347-359.
    [2] J.R. Lloyd, G.M. Gadd (2011). The Geomicrobiology of Radionuclides. Geomicrobiol. J. 28, 383-386.
    Keywords: uranium, curium, europium, plutonium, bacteria, clay rock, biosorption, bioreduction
    • Contribution to proceedings
      IGD-TP Geodisposal 2014 Conference, 24.-26.06.2014, Manchester, United Kingdom
    • Lecture (Conference)
      IGD-TP Geodisposal 2014 Conference, 24.-26.06.2014, Manchester, United Kingdom

    Permalink: https://www.hzdr.de/publications/Publ-19821
    Publ.-Id: 19821


    Hydrodynamics and transport processes in structured reactor devices

    Schubert, M.; Zalucky, J.; Rabha, S.; Hampel, U.;
    In the contribution, the recent activites on mass transfer and hydrodynamics in structured packings are presented
    • Lecture (others)
      Half-year-meeting: Helmholtz Energy-Alliance „Energy efficient chemical multiphase processes“, 21.-23.03.2013, Karlsruhe, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19820
    Publ.-Id: 19820


    Silicide induced ion beam patterning of Si(001)

    Engler, M.; Frost, F.; Müller, S.; Macko, S.; Will, M.; Feder, R.; Spemann, D.; Hübner, R.; Facsko, S.; Michely, T.;
    Low energy ion beam pattern formation on Si with simultaneous co- deposition of Ag, Pd, Pb, Ir, Fe or C impurities was investigated by in-situ scanning tunneling microscopy as well as ex-situ atomic force microscopy, scanning electron microscopy, transmission electron microscopy and Rutherford backscattering spectrometry. The impurities were supplied by sputter deposition. Additional insight into the mechanism of pattern formation was obtained by more controlled supply through e-beam evaporation. For the situations investigated, the ability of the impurity to react with Si, i.e. to form a silicide, appears to be a necessary, but not a sufficient condition for pattern formation. Comparing the effects of impurities with similar mass and nuclear charge the collision kinetics is shown to be not of primary importance for pattern formation. To understand the observed phenomena, it is necessary to assume a bi-directional coupling of composition and height fluctuations. This coupling gives rise to a sensitive dependence of the final morphology on the conditions of impurity supply. Because of this history dependence the final morphology cannot be uniquely characterized by a steady state impurity concentration.
    Keywords: ion irradiation, pattern formation, silides

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    Permalink: https://www.hzdr.de/publications/Publ-19819
    Publ.-Id: 19819


    Hydrodynamische Charakterisierung von Blasensäulen

    Schubert, M.;
    Mehrphasenreaktoren wie Blasensäulen, Festbetten und Wirbelschichten sind das Herzstück der chemischen und biochemischen Industrie. Trotz der weitgefächerten Anwendungsgebiete, stellen Auslegung und Skalierung von Mehrphasenreaktoren immer noch große Herausforderungen dar, insbesondere aufgrund fehlender Messdaten unter industriell relevanten Betriebsbedingungen. Darüber hinaus liegen in industriellen Prozessen meist lichtundurchlässige Strömungen vor – beispielsweise bei hohen Gas- und Flüssigkeitsleerrohrgeschwindigkeiten – die mit bloßem Auge aber auch mit herkömmlicher optischer Messtechnik nicht erfasst werden können. Der Beitrag fast Ergebnisse hydrodynamischer Studien in Blasensäulen mittels gering-invasiver Gittersensorik zusammen. Insbesondere werden Übergänge von Strömungsregimen, Blasengrößenverteilungen und Gasgehalte in Abhängigkeit vom Blasensäulendurchmesser als wesentliche Auslegungsparameter analysiert.
    • Contribution to proceedings
      Proceedings-Paper zur Festschrift zum Kolloquium 60 Jahre Verfahrenstechnikausbildung an der TU Dresden, 24.05.2013, Dresden, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19818
    Publ.-Id: 19818


    Wetting Efficiency in Tubular Reactors with Solid Foam Packings

    Mohammed, I.; Bauer, T.; Schubert, M.; Lange, R.;
    In the recent years, the performance of gas-liquid-solid fixed bed reactors with structured catalysts instead of catalyst particles has been intensively discussed. Structured catalysts based on solid foams with an open cell structure are in particular very promising. Such porous structures combine high specific surface area up to 2000 m²/m³, low single-phase and two-phase pressure drop due to bed porosities between 75 and 95 %, and interconnected pores for enhanced heat and mass transfer (Stemmet et al., 2005; Grosse and Kind, 2011). The performance of fixed bed reactors with structured catalysts depends heavily on the gas-liquid-solid contacting pattern. For a broad range of flow conditions, the liquid phase does not cover the solid surface homogeneously, which is known as partial wetting. The externally wetted fraction, which is defined as fraction of the external solid foam area covered by the liquid phase to the total external solid foam area, is directly linked to the liquid-solid and gas-solid mass transfer and thus, to the overall rate of reaction. The wetting fraction is a function of the superficial gas and liquid velocity and depends also on the physical properties of the liquid phase as well as catalyst shape, surface, porosity, etc. (Nigam and Larachi, 2005). However, studies on the wetting efficiency in trickle bed reactors also indicated the impact of the pre-wetting mode (Joubert and Nicol, 2012).
    The aim of this work was to adopt an electrochemical method for: (a) measuring the wetting fraction in tubular reactors with solid foam packings and (b) to study the effect of pre-wetting.
    • Lecture (Conference)
      AIChE Annual Meeting, 03.-08.11.2013, San Francisco, USA

    Permalink: https://www.hzdr.de/publications/Publ-19817
    Publ.-Id: 19817


    Gas-Liquid Distribution in Tubular Reactors with Solid Foam Packing

    Mohammed, I.; Bauer, T.; Schubert, M.; Lange, R.;
    Solid foam catalysts are a potential replacement for conventional catalyst particles such as extrudates, tablets, hollow cylinders and spheres. They improve the fixed-bed reactor performance in gas-liquid-solid reactions due to their high specific surface area and low pressure drop. Furthermore foam has very narrow residence time distribution which enhances the selectivity. However, there is still a lack of knowledge on the evolving flow patterns in solid foams and the proper design of liquid-phase distributors for industrial applications and conditions. In our contribution, gas-liquid distribution of downward two-phase flow with solid foam packings was studied experimentally. The packings varied in solid foam pore density.
    The measurements in a column with 0.1 m inner diameter are based on a combination of a segmented collector (25 compartments of same size) and imaging wire-mesh sensors with 16×16 wires and a pixel resolution of 6.25 mm. Both techniques provided the same results regarding the quality assessment of the flow distribution. The setup was applied to investigate the effect of: different liquid distributors, gas and liquid flow rates, and pre-wetting conditions. The experiments revealed information on liquid spreading along the reactor axis. The flow patterns inside the column are quantified by a maldistribution factor. The results indicate that foam packings cannot effectively counterbalance initial liquid maldistribution. Based on this study results, the design of packed-bed reactors can be improved towards much higher productivity and energy efficiency.
    • Poster
      9th World Congress of Chemical Engineering, 19.-22.08.2013, Seoul, South Korea

    Permalink: https://www.hzdr.de/publications/Publ-19815
    Publ.-Id: 19815


    Charakterisierung der Siebboden-Fluiddynamik mittels Gittersensor

    Schubert, M.; Hampel, U.;
    Kolonnen mit Siebböden als trennwirksame Einbauten werden vielfältig zur intensiven Phasenkontaktierung und Stofftrennung eingesetzt. Eine verlässliche Beschreibung der Fluiddynamik auf Kolonnenböden ist die Grundlage für eine effiziente Gestaltung der Trennprozesse, erfolgt jedoch gegenwärtig hauptsächlich erfahrungsbasiert. Voraussetzung zur modellunterstützten Auslegung von Siebböden, vor allem im Hinblick auf die Optimierung von Strömungsmustern, sind Bodenprüfstände mit hochauflösender Spezialmesstechnik. Zur Charakterisierung der Strömungsverhältnisse (z.B. Totzonen, Wirbeln, Kurzschluss- und Rückströmungen) und zur Extraktion fluiddynamischer Kenngrößen (z.B. Verweilzeit) in einem 800 mm Kolonnenprüfstand mit Siebböden (4 % Öffnungsverhältnis, 5 mm Lochdurchmesser) wurde u.a. ein leitfähigkeitsbasierter Gittersensor implementiert. Der Gittersensor besteht aus zwei um 90° versetzt angeordneten Drahtebenen aus 64×51 Drähten mit einem Ebenenabstand von 10 mm. In den Kreuzungspunkten wird in Abhängigkeit der lokalen Leifähigkeit ein Strom mit hoher Abtastfrequenz gemessen, der Aussagen über die transienten Strömungszustände (z.B. Tracermenge, Gas-/Flüssigkeitsanteil) erlaubt. Im Beitrag werden Tracerstudien zur Bestimmung der Flüssigphasenverweilzeit und der Strömungsmuster in Abhängigkeit der hydraulischen Belastungen und der Wehrhöhen vorgestellt.
    • Poster
      Jahrestreffen der Fachgruppen Fluidverfahrenstechnik und Wärme- und Stoffübertragung, 20.-21.03.2013, Baden Baden, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19814
    Publ.-Id: 19814


    Low temperature and decay lifetime photoluminescence of Eu and Tb nanoparticles embedded into SiO2

    Lipp Bregolin, F.; Franzen, P.; Boudinov, H.; Sias, U. S.; Behar, M.;
    In the present work, we have studied the photoluminescence (PL) and decay lifetime of Tb and Eu nanoparticles (NPs) at low temperatures. The NPs were obtained by ion implantation into a SiO2 matrix. Concerning the PL yield of Tb, it has a maximum at 12 K and decreases with increasing temperatures reaching a minimum at 300 K. On the other hand, the PL lifetime of the PL band centered at 542 nm remains almost constant at a value of 1.6 ms. Concerning Eu, two bands are observed, one narrow centered around 618 nm and the other in the blue-green region (from 400 up to 550 nm). Both PL bands show a minimum yield at 12 K, and then they start to increase with increasing temperatures, reaching their maximum at around 100 K. Then, they start to decrease their yield reaching a minimum at 300 K, being this yield similar to the one obtained at 12 K. For the Eu PL lifetime, two different results were obtained. The narrow PL band centered at 618 nm shows a lifetime of the order of 1.6 ms independent of the temperature. Conversely, the blue-green PL band is strongly temperature dependent, being of the order of several ms for temperatures lower than 100 K down to 500 µs at 300 K.
    Keywords: rare-earth photoluminescence Tb nanoparticles Eu nanoparticles Ion implantation Decay lifetime

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    Permalink: https://www.hzdr.de/publications/Publ-19813
    Publ.-Id: 19813


    Hydrogen engineering via plasma immersion ion implantation and flash lamp annealing in silicon-based solar cell substrates

    Lipp Bregolin, F.; Krockert, K.; Prucnal, S.; Vines, L.; Hübner, R.; Svensson, B. G.; Wiesenhütter, K.; Möller, H.-J.; Skorupa, W.;
    Higher conversion efficiencies while reducing costs at the same time is the ultimate goal driving the advancement of solar cell development. In this work, solar cell emitters are formed in Si substrates by plasma immersion ion implantation (PIII) of phosphine and posterior millisecond-range flash lamp annealing (FLA). In Si-based solar cells, hydrogen plays a fundamental role due to its excellent passivation properties and the optical and electrical properties of the fabricated emitters will be studied, with particular interest in their dependence on the hydrogen content present in the samples. The influence of different FLA annealing parameters and a comparison with traditional thermal treatments such as rapid thermal annealing (RTA) and furnace annealing (FA) will be presented. The samples treated by FLA at 1200 °C for 20 ms in forming gas shows sheet resistance values of the order of 60 Ω/□, and minority carrier diffusion lengths in the range of ~ 200 µm without the use of a capping layer for surface passivation. Those results are significantly better than the ones observed from RTA or FA annealed samples. The simultaneous implantation of hydrogen during the doping process combined with optimal FLA annealing parameters gave promising results for the application of this technology in replacing the conventional POCl3 deposition and diffusion.
    Keywords: plasma immersion ion implantation hydrogen engineering emmiter formation flash lamp annealing photovoltaics solar cell

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    Permalink: https://www.hzdr.de/publications/Publ-19812
    Publ.-Id: 19812


    Liquid-solid mass transfer in solid foam packed tubular reactors

    Mohammed, I.; Bauer, T.; Schubert, M.; Lange, R.;
    Solid foams were found to be promising replacements of conventional fixed bed reactor catalysts due to their high specific surface area, high porosity and low pressure drop. Especially, high gas-liquid mass transfer rates were observed in solid foams (Stemmet et al., 2008). However, for liquid limited reactions, high liquid-solid mass transfer rates are required. The liquid-solid mass transfer is strongly affected by the wetting of the packing surface and thus, depends also on the pre-wetting mode. For example Joubert and Nicol (2012) found that solid-liquid mass transfer coefficients in trickle bed reactors exhibit significant multiplicity behavior due to different flow textures. However, to the best of our knowledge, studies on the liquid-solid mass transfer in down flow solid foam tubular reactors are not yet available. To determine liquid-solid mass transfer coefficient we applied the electrochemical diffusion current method (ferricyanide system with excess of NaOH) The method is based on the measurement of current (i.e. electron transfer from cathode to anode) at mass transfer diffusion limited condition, pure nickel foam (Alantum Europe) of same foam density was applied as cathode.
    The aim of this study is to determine the effective liquid-solid mass transfer coefficient in tubular solid foam reactors at different axial positions in down-flow trickle mode taking “LEVEC” and “KAN-LIQUID” pre-wetting mode into account.
    • Poster
      9th European Congress of Chemical Engineering (ECCE), 21.-25.04.2013, Den Haag, Netherland

    Permalink: https://www.hzdr.de/publications/Publ-19811
    Publ.-Id: 19811


    Tomographic and numerical distributor studies in bubble column reactors

    Bieberle, A.; Rabha, S.; Schubert, M.; Hampel, U.;
    Bubble column reactors are widely preferred in the petro/chemical industries due to flexible residence time, excellent heat and mass transfer characteristics and the absence of moving parts. Here, proper sparger design is essential to tune bubble size and bubble rise velocity and to provide optimal holdup and mixing behavior (Kulkarni and Joshi, 2011). Information pertaining to bubble size distribution, pressure distribution in various distributor is scantily available. Therefore, we provide a comparative study on different gas distributors in terms of gas hold-up and bubble size distribution using gamma-ray computed tomography and wire-mesh sensor techniques. Four different types of gas distributor were used, e.g. sieve plate, ring sparger, spider and radial sparger. In addition, the influence of the gas distributor on the above mentioned parameters is also predicted using Euler-Euler approached and validated with the experimental results.
    Keywords: Bubble colums reactors, gamma-ray CT, wire-mesh sensor
    • Lecture (Conference)
      Jahrestreffen der Fachgruppen Extraktion und Mehrphasenströmungen, 19.-20.03.2013, Baden Baden, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19810
    Publ.-Id: 19810


    Experimental observation of transverse modulations in laser-driven proton beams

    Metzkes, J.; Kluge, T.; Zeil, K.; Bussmann, M.; Kraft, S. D.; Cowan, T. E.; Schramm, U.;
    We report on the experimental observation of transverse modulations in proton beams accelerated from micrometer thick targets which were irradiated with ultra-short (30 fs) laser pulses of a peak intensity of 5·10^20 W/cm^2. The net-like proton beam modulations were recorded using radiochromic film and the data suggest a dependence on laser energy and target thickness for their onset and strength. Numerical simulations suggest that intensity-dependent instabilities in the laser-produced plasma at the target front side lead to electron beam break-up or filamentation, then serving as the source of the observed proton beam modulations.
    • Open Access Logo New Journal of Physics 16(2014), 023008-1-023008-12
      DOI: 10.1088/1367-2630/16/2/023008
    • Poster
      41st EPS Conference on Plasma Physics, 23.-27.06.2014, Berlin, Deutschland

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    Permalink: https://www.hzdr.de/publications/Publ-19809
    Publ.-Id: 19809


    A volume of intersection approach for on-the-fly system matrix calculation in 3D PET image reconstruction

    Lougovski, A.; Hofheinz, F.; Langner, J.; Schramm, G.; Will, E.; van den Hoff, J.;
    The aim of this study is the evaluation of on-the-fly volume of intersection computation for system’s geometry modelling in 3D PET image reconstruction. For this purpose we propose a simple geometrical model in which the cubic image voxels on the given Cartesian grid are approximated with spheres and the rectangular tubes of response (ToRs) are approximated with cylinders. The model was integrated into a fully 3D list-mode PET reconstruction for performance evaluation. In our model the volume of intersection between a voxel and the ToR is only a function of the impact parameter (the distance between voxel centre to ToR axis) but is independent of the relative orientation of voxel and ToR. This substantially reduces the computational complexity of the system matrix calculation. Based on phantom measurements it was determined that adjusting the diameters of the spherical voxel size and the ToR in such a way that the actual voxel and ToR volumes are conserved leads to the best compromise between high spatial resolution, low noise, and suppression of Gibbs artefacts in the reconstructed images. Phantom as well as clinical datasets from two different PET systems (Siemens ECAT HR+ and Philips Ingenuity-TF PET/MR) were processed using the developed and the respective vendor-provided (line of intersection related) reconstruction algorithms. A comparison of the reconstructed images demonstrated very good performance of the new approach. The evaluation showed the respective vendor-provided reconstruction algorithms to possess 34–41% lower resolution compared to the developed one while exhibiting comparable noise levels.
    Contrary to explicit point spread function modelling our model has a simple straight-forward implementation and it should be easy to integrate into existing reconstruction software, making it competitive to other existing resolution recovery techniques.

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    Permalink: https://www.hzdr.de/publications/Publ-19808
    Publ.-Id: 19808


    Entwicklung eines Stoffsystems zur Durchführung elektrochemischer Stofftransportmessungen in organischen Medien

    Rüdiger, K.;
    Die Bestimmung von Stofftransportraten mittels der Grenzstrommethode hat in der Vergangenheit bereits häufig Anwendung in der Untersuchung von Mehrphasenströmungen durch strukturierte Packungen und regellose Schüttungen gefunden. Bis auf eine Ausnahme beschränkten sich bisherige Untersuchungen aber auf wässrige Stoffsysteme, die hinsichtlich ihrer physikalischen Eigenschaften (Dichte, Oberflächenspannung und Viskosität) eher einen Spezialfall in der Durchströmung von Packungen darstellen und sich kaum auf industriell relevante, organische Systeme übertragen lassen. Zur Adaption der Grenzstrommethode auf organische Systeme befasst sich die vorliegende Belegarbeit mit der Suche, Synthese und Langzeitbeständigkeit verschiedener organischer Redoxsysteme und Lösungsmittel sowie potenziell geeigneter Leitelektrolyte für die organische Grenzstrommethode. Untersucht werden hierbei die organometallischen Metallkomplex-Systeme des Eisens mit Bipyridin sowie des Ferrocens in verschiedenen Oxidationsstufen. Weiterhin kommt ein Tetraalkylammoniumsalz als Leitfähigkeitverbesserer in verschiedenen organischen Lösungsmitteln zum Einsatz. In Langzeittests zeigten UV-VIS-Messungen, dass lediglich das Ferrocen-System unter Argonatmosphäre über längere Zeit hinweg seine Zusammensetzung nicht ändert. Lichteinfluss zeigte dabei eine stabilisierende Wirkung. In ersten Vortests wird die Einsetzbarkeit des Systems für die organische Grenzstrommethode unter bestimmten Bedingungen bewiesen.
    Betreuer: Johannes Zalucky
    Keywords: organo-electrochemical method, mass transfer, ferrocen, organo-metallic complexes, tetraalkyl ammonium salt, stabilizing light, UV-VIS
    • Study thesis
      TU-Dresden, 2013
      63 Seiten

    Permalink: https://www.hzdr.de/publications/Publ-19807
    Publ.-Id: 19807


    PET/MRI Imaging in High-Risk Sarcoma: First Findings and Solving Clinical Problems

    Schuler, M. K.; Richter, S.; Beuthien-Baumann, B.; Platzek, I.; Kotzerke, J.; van den Hoff, J.; Ehninger, G.; Reichardt, P.;
    Simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) is a new whole-body hybrid PET/MR imaging technique that combines metabolic and cross-sectional diagnostic imaging. Since the use of MRI in imaging of soft-tissue sarcoma is extremely beneficial, investigation of the combined PET/MRI is of great interest. In this paper, we present three cases and first data. Combined PET/MRI technique can support the process of clinical decision-making and give answers to some meaningful questions when treating patients with STS. Therefore, the combined modality of simultaneous PET/MRI offers new pieces to the puzzle of sarcoma treatment.

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    Permalink: https://www.hzdr.de/publications/Publ-19806
    Publ.-Id: 19806


    Hydrodynamics and transport processes in structured reactor devices: Project status report

    Zalucky, J.; Rabha, S.; Schubert, M.; Hampel, U.;
    On the occasion of annual project status report, work package progress is presented. The first part includes demarcation of work topics of hydrodynamic groups, status of setup construction and preliminary experimental matrix for CT measurements. The second part is related to actions in mass transfer investigations and reports progress and upcoming investigations with the electrochemical method as well as first successes in zeolite coating of SiSiC foams.
    Keywords: annual project status report, energy efficient chemical multiphase processes, hydrodynamic CT investigations, mass transfer
    • Lecture (others)
      Jahrestreffen Helmholtz-Energie-Allianz "Energieeffiziente chemische Mehrphasenprozesse", 30.09.-02.10.2013, Bochum, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19805
    Publ.-Id: 19805


    Chemical reaction related mass transfer measurements in organic environments under industrial relevant conditions

    Zalucky, J.;
    Within HZDR annual PhD seminar, the PhD motivation, conception, approaches and first results are presented.
    Keywords: mass transfer, organo-electrochemical method, zeolite coating, dynamic oxygen sorption technique
    • Poster
      HZDR Doktoranden-Seminar, 07.-09.10.2013, Bautzen, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19804
    Publ.-Id: 19804


    Hydrodynamics and transport processes in structured reactor devices - PhD meeting status report TU Hamburg-Harburg

    Zalucky, J.;
    On the occasion of half-annual PhD meeting of projekt group at TU Hamburg-Harburg, the status of hydrodynamic setup and current research subproject SiSiC zeolite coating which were investigated under SEM are orally presented.
    Keywords: Hydrodynamic setup, SiSiC zeolite coating
    • Lecture (others)
      Half-annual meeting of PhD students within Helmholtz Energy Alliance "Energy Efficient Chemical Multiphase Processes", 26.07.2013, Hamburg, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19803
    Publ.-Id: 19803


    Formation of regularly arranged large grain silicon islands by using embedded micro mirrors in the flash crystallization of amorphous silicon

    Henke, T.; Bartha, J. W.; Rebohle, L.; Merkel, U.; Hübner, R.; Albert, M.; Skorupa, W.;
    The well-controlled formation of large silicon grains on predetermined positions is a key issue in order to produce single-grain thin film transistors on insulating substrates and thus to enable monolithic 3D integration. One way to achieve this is to artificially control the solidification of molten silicon during the flash crystallization of amorphous silicon. In this work, we present such an approach in which we used patterned metal layers below the amorphous silicon. The metal spots act as embedded micro mirrors and consequently introduce a lateral temperature gradient into the silicon film during flash crystallization. As a result, the grain growth from molten silicon is seeded from the predefined regions with the lowest temperature and thus the formation of large crystal silicon islands proceeds in a controlled manner. In the scope of this study, we evaluated a variety of different mirror patterns with respect to their suitability for this approach and observed that patterns of both circular and line-shaped mirrors are the most promising variants. The resulting silicon islands have pillow-like shapes and are located exclusively in regions between neighboring mirrors. They exhibit dimensions of a few tens of micrometers and consist of grains with sizes up to 28 µm. The formation of single-grain silicon pillow-like structures was observed for particular mirror patterns having circular mirrors. On the other hand, the application of mirror patterns with line-shaped mirrors resulted in the formation of elongated silicon grains which we explained in terms of lateral solidification starting from one edge. Furthermore, this approach exhibits grain filter characteristics leading to the controlled growth of large single grains at predetermined positions.
    Keywords: flash lamp annealing, crystallization, liquid phase epitaxy

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    Permalink: https://www.hzdr.de/publications/Publ-19802
    Publ.-Id: 19802


    Inclined rotating fixed bed reactors for process intensification

    Härting, H.-U.; Schubert, M.;
    After an introduction of the research activities at the Institue of Fluid Dynamics, especially of the Experimental Thermal Fluid Dynamics Department, process intensification is illustrated by working examles from science and industry.
    The new reactor concept "inclined rotating fixed bed reactor" is introduced with detailed explanations of the idea, the benefits as well as aspects of the design.
    Selected results from hydrodynamic experiments coupled with tomographic imaging are presented.
    Keywords: Process intensification, fixed bed reactor, tomographic imaging, rotation, inclination
    • Lecture (Conference)
      HZDR PhD-Seminar 2013, 07.-09.10.2013, Bautzen, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19801
    Publ.-Id: 19801


    Hindered magnetic order from mixed dimensionalities in CuP2O6

    Nath, R.; Ranjith, K. M.; Sichelschmidt, J.; Baenitz, M.; Skourski, Y.; Alet, F.; Rousochatzakis, I.; Tsirlin, A. A.;
    We present a combined experimental and theoretical study of the spin-½ compound CuP2O6 that features a network of two-dimensional (2D) antiferromagnetic (AFM) square planes, interconnected via one-dimensional (1D) AFM spin chains. Magnetic susceptibility, high-field magnetization, and electron spin resonance (ESR) data, as well as microscopic density-functional band-structure calculations and subsequent quantum Monte Carlo simulations, show that the coupling J2D ≃ 40 K in the layers is an order of magnitude larger than J1D ≃ 3 K in the chains. Below TN ≃ 8 K, CuP2O6 develops long-range order, as evidenced by a weak net moment on the 2D planes induced by anisotropic magnetic interactions of Dzyaloshinsky-Moriya type. A striking feature of this 3D ordering transition is that the 1D moments grow significantly slower than the ones on the 2D units, which is evidenced by the persistent paramagnetic ESR signal below TN. Compared to typical quasi-2D magnets, the ordering temperature of CuP2O6 TN/J2D ≃ 0.2 is unusually low, showing that weakly coupled spins sandwiched between 2D magnetic units effectively decouple these units and impede the long-range ordering.

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    Permalink: https://www.hzdr.de/publications/Publ-19800
    Publ.-Id: 19800


    Size-effects in 2D Transition Metal Chalcogenides

    Gemming, S.; Seifert, G.;
    Nanoscale Mo_mS_n compounds exist in a large variety of compositions with many different characteristic structural elements and related electronic properties. The structural wealth of Mo_mS_n compounds comprises finite structures such as small clusters and hollow inorganic fullerenes, one-dimensionally extended wires and stripes, or two-dimensional platelets. The structural elements are based either on a three-dimensional Mo_m framework or on platelet-shaped elements derived from the layered MoS_2 bulk structure. The electronic features range from large energy gaps in closed-shell systems over the semiconducting two-dimensional MoS_2 sheet to the metallic conductivity of the brim state in platelets or along the Mo core of wires.
    With the help of density-functional calculations the preferred structural elements and the relative stabilities could be correlated with the chemical potentials of sulfur and molybdenum in the system. As structural elements and electronic features are related, this result is the basis for a further tailoring of electronic properties via the preparation conditions. For very small systems Mo_mS_n, with m <= 4, n <= 14 the cluster-platelet transition depends on a sulfur excess of the system of at least one additional S atom per MoS_2 formula unit, i.e. to MoS_3. In the small size regime the most important species are the extremely stable large-gap Mo_4S_6 cluster, Mo_3S_6 as smallest member of (MoS_2)_n platelet family and Mo_3S_3 and Mo_3S_5 as stable building blocks of wires. For one-dimensionally extended conducting structures the termination exhibits a length-dependent crossover of the termination group from (Mo_3S_3)_nS_2 to (Mo_3S_3)_n-1(MoS_4)_2 provided that the chemical potential of sulfur is low and constant. Sulfur-terminated two-dimensional (MoS_2)_nS_m platelets are stable only at the enhanced sulfur chemical potential required to saturate the platelet edges with sulfur up to a stoichiometry of Mo:S = 1:3 in the smallest clusters. In even more sulfur-rich conditions all systems tend to form chemically active, but electronically inert S_2^2- ions.
    Keywords: density-functional, molybdenum sulfide, 2D electronics, molecular electronics, inorganic nanotubes, nanotubes, platelet
    • Invited lecture (Conferences)
      Flatlands Beyond Graphene, 17.-21.06.2013, Bremen, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19799
    Publ.-Id: 19799


    Microscopic Processes in Energy and Data Storage

    Gemming, S.;
    DGK Symposium MS17 - Materials for Electronics:
    Energy and Data Storage through the Eyes of Crystallographers
    Keywords: multiscale modeling, density-functional, Heisenberg, Ising, multiferroic
    • Invited lecture (Conferences)
      21st Annual Conference of the German Crystallographic Society, 19.-22.03.2013, Freiberg (S), Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19798
    Publ.-Id: 19798


    The nELBE (n,fis) experiment

    Kögler, T.; Beyer, R.; Hannaske, R.; Junghans, A.; Massarczyk, R.; Schwengner, R.; Wagner, A.;
    At the Center for High-Power Radiation Sources at Helmholtz-Zentrum Dresden-Rossendorf fast neutron-induced fission cross section experiments on U(235) and Pu(242) will be investigated by a parallel plate fission ionization chamber. An optimization of chamber parameters was performed using extensive Geant4 simulations with GEF code generated fission observable inputs. Pile-up effects due to the high alpha activity of the plutonium targets have been considered in a realistic geometry. Beyond that, a setup for the determination of the areal density and homogeneity of targets will be presented with a focus on current simulation work.
    Keywords: nELBE, parallel plate fission ionization chamber, Geant 4 simulations
    • Lecture (Conference)
      Final ERINDA User Meeting and Scientific Workshop, 01.-03.10.2013, Geneva, Switzerland
    • Open Access Logo Contribution to proceedings
      Final ERINDA User Meeting and Scientific Workshop, 01.-03.10.2013, Geneva, Switzerland
      Proceedings of the ERINDA Workshop, CERN, edited by Enrico Chiaveri CERN Proceedings 2014-002: CERN, 978-92-9083-403-8, 25-30

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    Permalink: https://www.hzdr.de/publications/Publ-19797
    Publ.-Id: 19797


    Nanomaterials for Biomedical Applications

    Stephan, H.;
    kein Abstract verfügbar
    • Invited lecture (Conferences)
      Seminar, Jacobs University Bremen, 08.01.2014, Bremen, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19796
    Publ.-Id: 19796


    Synthesis and biological evaluation of both enantiomers of [18F]flubatine, promising radiotracers with fas kinetics for the imaging of α4β2-nicotinic acetylcholine receptors

    Smits, R.; Fischer, S.; Hiller, A.; Deuther-Conrad, W.; Wenzel, B.; Patt, M.; Cumming, P.; Steinbach, J.; Sabri, O.; Brust, P.; Hoepping, A.;
    Both enantiomers of the epibatidine analogue flubatine display high affinity towards the α4β2 nicotinic acetylcholine receptor (nAChR) in vitro, accompanied by negligible interactions with diverse off-target proteins. Extended single dose toxicity studies in rodent indicated a NOEL (No Observed Effect Level) of 6.2μg/kg for (-)-flubatine and 1.55μg/kg for (+)-flubatine. We developed syntheses for both flubatine enantiomers and their corresponding precursors for radiolabeling. The newly synthesized trimethylammonium precursors allowed for highly efficient (18)F-radiolabelling in radiochemical yields >60% and specific activities >750GBq/μmol, thus making the radioligands practical for clinical investigation.
    Keywords: Alzheimers’s disease (AD), Nicotinic acetylcholine receptor (nAChR), Flubatine, PET, Fluorine-18

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    Permalink: https://www.hzdr.de/publications/Publ-19795
    Publ.-Id: 19795


    Development of 18F-labeled radiotracers for neuroreceptor imaging with positron emission tomography

    Brust, P.; van den Hoff, J.; Steinbach, J.;
    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 routinely used in the radiolabeling of neuroreceptor ligands for PET because of its favorable half-life of 109.8 min. The delivery of such radiotracers into the brain provides images of transport, metabolic, and neutotransmission processes on the molecular level.
    After a short introduction into the principles of PET, the review mainly focuses on the strategy of radiotracer development bridging from basic science to biomedical application. Successful radiotracer design as described here provides molecular probes which not only are useful for imaging of huma brain diseases, but also allow molecular neuroreceptor imaging studies in various small-animal models of diseases, including genetically-engineered animals. Furthermore, they provide a powerful tool for in vivo pharmacology during the process of pre-clinical drug development to identify new drug targets, to investigate phathophysiology, to discover potential drug candidates, and to evaluate the pharmacokinetics and pharmacodynamics of drugs in vivo.
    Keywords: Alzheimer's disease; autoradiography; blood-brain barrier; brain tumor; cholinergic system; kinetic modeling; metabolism; molecular imaging; neurodegeneration; positron emission tomography; precursor; psychiatric disorder; radiotracer; sigma receptor

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    Permalink: https://www.hzdr.de/publications/Publ-19794
    Publ.-Id: 19794


    Brief review on high-field ESR at the EMFL: facilities and applications

    Zvyagin, S.;
    • Invited lecture (Conferences)
      Round table on NMR and EPR in ultra-high magnetic fiels (Satellite workshop to EUROMAR 2013), 02.07.2013, Herssonisos, Greece

    Permalink: https://www.hzdr.de/publications/Publ-19793
    Publ.-Id: 19793


    Analysen zum Neutronenflussrauschen mit Hilfe des Rechenprogramms DYN3D - Abschlußbericht -

    Rohde, U.; Bilodid, Y.;
    In Computersimulationen wurden Schwankungen der Kühlmitteltemperatur (KMT) am Kerneintritt und des Kühlmittelmassenstromes als mögliche Ursache für erhöhtes Neutronenflussrauschen in Druckwasserreaktoren untersucht. Das Ziel ist die Vermeidung von Neutronenflußschwankungen in einer Größenordnung, die zu einer unbeabsichtigten Auslösung von Signalen zur Reaktorschnellabschaltungführen können.
    Als Simulationstool wurde dafür der Rossendorfer Reaktordynamikcode DYN3D eingesetzt. Es wurden transiente Rechnungen mit verschiedenen aufgeprägten Randbedingungen für die Kühlmitteleintrittstemperatur oder den Kühlmittelmassenstrom durchgeführt, in denen dreidimensional die zeitlich variierenden lokalen linearen Stableistungen berechnet wurden. Diese lokalen linearen Stableistungen werden als In-Core-Detektorsignale interpretiert. Dabei wurden zunächst harmonische Oszillationen, dann auch stochastische Fluktuationen der lokalen Kühlmitteleintrittstemperatur oder des Massenstroms betrachtet, die zwischen den einzelnen Brennelementen oder Bereichen des Reaktorkerns auf unterschiedliche Weise korreliert sein können. Mittels Fast Fourier Transformation (FFT) wurden Übertragungsfunktionen zwischen Temperaturstörung und Responsesignal (lokale lineare Stableistung) ermittelt und ausgewertet.
    Um den Einfluss von unterkühltem Sieden des Kühlmittels und der Wärmeleitung im Brennstab zu klären, wurden Variantenrechnungen mit verstärktem unterkühltem Sieden sowie mit verändertem Wärmedurchgangskoeffizienten im Gasspalt zwischen Brennstoff und Hülle durchgeführt. Unterkühltes Sieden wurde durch eine Reduzierung des Massenstroms bzw. Erhöhung der Eintrittstemperatur generiert. Weiterhin wurden für einen Referenzfall Untersuchungen zum Einfluss der numerischen Diffusion durchgeführt.
    Der größte Teil der Rechnungen wurde für eine generische Kernbeladung eines DWR vom Typ Konvoi durchgeführt. Teilweise wurden auch konkrete, reaktor- und zyklusspezifische thermohydraulische Randbedingungen sowie neutronenphysikalische Wirkungsquerschnitte (WQS) benutzt, um quantitativ belastbare Aussagen zu erhalten.
    Die Ergebnisse der DYN3D-Simulationen zum können wie folgt zusammengefasst werden:
    • Stochastische, unkorrelierte Schwankungen der KMT am Eintritt in die einzelnen Brennelemente (BE) führen bei realistischer Amplitude nur zu sehr kleinen Schwankungen in der Leistungsdichte, die für eie eventuelle unbeabsichtigte Auslösung eines Signals zur Reaktorschnellabschaltung nicht relevant sind.
    • Stochastische Temperaturschwankungen mit Korrelationen zwischen den BE (z.B. bedingt durch Schwankungen der Kaltstrangtemperaturen) können Leistungsdichteschwankungen mit relevanten Amplituden generieren (je nach Grad der Korrelation).
    • Schwankungen der Leistungsdichte, die durch Schwankungen der Eintrittstemperatur oder durch Massenstromschwankungen hervorgerufen werden, zeigen ein deutlich unterschiedliches Signalverhalten.
    • Unterkühltes Sieden und Variation des WÜ im Gasspalt Brennstoff-Hülle haben nur geringen Einfluss auf das Neutronenflussrauschen.
    Aufgrund dieser Ergebnisse können Temperaturschwankungen als Ursache für überhöhtes Neutronenrauschen praktisch ausgeschlossen werden.
    Keywords: neutronic noise, temperature fluctuations, statistical analysis, transfer functions, reactor dynamics simulations
    • Article, self-published (no contribution to HZDR-Annual report)
      Helmholtz-Zentrum Rossendorf 2014
      HZDR\FWO\2014\02
      46 Seiten

    Permalink: https://www.hzdr.de/publications/Publ-19792
    Publ.-Id: 19792


    Optimization of magneto-resistive response of ion-irradiated Exchange biased films through zigzag arrangement of magnetization

    Trützschler, J.; Sentosun, K.; Langer, M.; Mönch, I.; Mattheis, R.; Fassbender, J.ORC; McCord, J.
    Exchange coupled ferromagnetic-antiferromagnetic Ni81Fe19/Ir23Mn77 films with a zigzag alignment of magnetization are prepared by local ion irradiation in order to shape the anisotropic magneto-resistive behavior of the magnetic thin film structures. A unique uniaxial field sensitivity along the net magnetization alignment is obtained through the orthogonally modulated and magnetic domain wall stabilized magnetic ground state. Controlling local thin film magnetization distributions and thus the overall magnetization response opens unique ways to tailor the magneto-resistive sensitivity of functional magnetic thin film devices.
    Keywords: exchange bias, field sensor, ion irradiation, anisotropic magneto-resistance

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    Permalink: https://www.hzdr.de/publications/Publ-19791
    Publ.-Id: 19791


    Design of Radioligands for PET Imaging of Brain Diseases

    Brust, P.;
    Es ist kein Abstract vorhanden.
    • Invited lecture (Conferences)
      Partnership: Vanderbilt University - Leipzig University - Leipzig University: 5th Scientific Symposium, 30.10.-03.11.2013, Nashville, USA

    Permalink: https://www.hzdr.de/publications/Publ-19790
    Publ.-Id: 19790


    Synthesis and development of metabolic PSY receptor ligands for imaging

    Brust, P.;
    • Invited lecture (Conferences)
      Partnership Vanderbilt University - Leipzig University: 4th Scientific Symposium and Kick-off Meeting, 06.-12.07.2013, Leipzig, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19789
    Publ.-Id: 19789


    Development of Radioligands for Imaging of nAChR

    Brust, P.;
    • Invited lecture (Conferences)
      COGNITO Meeting, 27.09.2013, Kopenhagen, Dänemark

    Permalink: https://www.hzdr.de/publications/Publ-19788
    Publ.-Id: 19788


    Development of 18F-labelled radiopharmaceuticals for brain and tumor imaging

    Brust, P.;
    • Invited lecture (Conferences)
      Colloquium series Zhenjiang University, 27.05.2013, Hangzhou, Zhejiang, China

    Permalink: https://www.hzdr.de/publications/Publ-19787
    Publ.-Id: 19787


    Spin dynamics in the spin-1/2 triangular-lattice antiferromagnet Cs2CuBr4

    Zvyagin, S.;
    • Invited lecture (Conferences)
      EUROMAR 2013, 30.06.-05.07.2013, Hersonissos, Greece

    Permalink: https://www.hzdr.de/publications/Publ-19786
    Publ.-Id: 19786


    Recent development of the High Field ESR facility at HLD Dresden

    Zvyagin, S.;
    • Invited lecture (Conferences)
      Evaluation of research finding applications ETAG (The Estonian Research Council), 21.09.2013, Tallinn, Estonia

    Permalink: https://www.hzdr.de/publications/Publ-19785
    Publ.-Id: 19785


    Recent development of the high-field ESR facility at the Dresden High Magnetic Field Laboratory

    Zvyagin, S.;
    • Invited lecture (Conferences)
      Annual Meeting SPP1601, 12.-14.09.2013, Frauenchiemsee, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19784
    Publ.-Id: 19784


    Unconventional spin dynamics in Cs2CuBr4

    Zvyagin, S.;
    • Invited lecture (Conferences)
      ETH Zürich, 26.09.2013, Zürich, Switzerland

    Permalink: https://www.hzdr.de/publications/Publ-19783
    Publ.-Id: 19783


    Spin dynamics in the spin-1/2 triangular-lattice antiferromagnet Cs2CuBr4

    Zvyagin, S.;
    • Lecture (Conference)
      JEMS2013 - Joint European Magnetic Symposia, 25.-30.08.2013, Rhodos, Greece

    Permalink: https://www.hzdr.de/publications/Publ-19782
    Publ.-Id: 19782


    Superconductivity in highly Ga-doped germanium and silicon

    Skrotzki, R.;
    • Lecture (others)
      Institutsseminar TU Dresden, 08.01.2013, Dresden, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19781
    Publ.-Id: 19781


    Evidence of Field-Induced Ordering in the Dynamic Spin Ice Compund Pr2Sn2O7

    Green, E.;
    • Invited lecture (Conferences)
      Ss. Cyril and Methodius University, 27.04.2013, Skopje, Macedonia

    Permalink: https://www.hzdr.de/publications/Publ-19780
    Publ.-Id: 19780


    Magnetoelastic properties of some uranium intermetallic antiferromagnets as studied by high-field ultrasound measurements

    Zherlitsyn, S.;
    • Poster
      2013 Joint UFFC, EFTF, and PFM Symposium, 21.-23.07.2013, Prague, Czech Republic

    Permalink: https://www.hzdr.de/publications/Publ-19779
    Publ.-Id: 19779


    Pulsed-magnet upgrades at the Dresden High Magnetic Field Laboratory

    Zherlitsyn, S.;
    • Lecture (Conference)
      MT 23 - International Conference on Magnet Technology, 14.-19.07.2013, Boston, USA

    Permalink: https://www.hzdr.de/publications/Publ-19778
    Publ.-Id: 19778


    Strongly correlated electron physics at high magnetic fields: recent science highlights at the HLD

    Herrmannsdörfer, T.;
    • Invited lecture (Conferences)
      Institutsseminar Hochfeld Magnetlabor Wroclaw, 16.-17.05.2013, Wroclaw, Poland

    Permalink: https://www.hzdr.de/publications/Publ-19777
    Publ.-Id: 19777


    Hydrogenation of α-methylstyrene in an inclined rotating fixed bed reactor

    Härting, H.-U.; Schubert, M.;
    Trickle bed reactors are widespread in the chemical industry for the implementation of heterogeneous catalytic processes, especially for the production of bulk chemicals. Nevertheless, the reactor performance may be limited by liquid maldistribution as well as by poor mass and heat transfer rates. Furthermore, the rather simple reactor design and operation is accompanied by limited degrees of freedom for manipulation of local conditions to enhance the reactor performance.
    Dynamic operation strategies, like the periodic inlet flow rate modulation, have been proposed for process intensification of trickle bed reactors [1]. These strategies have been proven to result in increased space-time-yields at lab-scale, however, their positive effects are strongly dampened with increasing reactor length.
    The inclined rotating fixed bed reactor is an alternative reactor concept, that aims to transform the temporal periodic operation into a spatial periodic one, which holds for the whole length of the reactor. The inclination of the reactor, with the catalyst fixed between two retaining grates, results in a phase separation, whereas the superimposed slow rotation ensures a periodic wetting and draining of the catalyst and will therefore enhance the access of the gas phase to the active sites (see Figure 1).
    By adjustment of the reactor inclination and rotation, the performance of the reactor can be adapted to a given reaction system (e. g. fast or slow kinetics, high or low viscous liquid etc.) to optimize the local conditions with respect to flow regime and subsequently to mass and heat transfer performance for a specific process.
    For the evaluation of the new reactor concept, the space-time-yield of the hydrogenation of α-methylstyrene to cumene (C9H10 + H2  C9H12) is investigated in the trickle bed reactor as well as in the inclined rotating fixed bed reactor. The reaction already exhibits mass transfer limititations of the gas phase at moderate conditions, which allows for attributing changes in the space-time-yield directly to the operational conditions [2].
    The reactor (dR = 0.1 m, LR = 1.6 m) is operated like a differential loop reactor with a layer of the palladium egg-shell catalyst (Pd/γ-Al2O3, dP = 4 mm, w = 0,1 wt-% Pd) placed in the middle of the otherwise inert fixed bed. The reaction studies are performed at varying pressure (p = 1 and 6 bar) and temperature (θ = 25°C and 40°C) at isothermal conditions. The rotational speed and the inclination angle are adjusted to identify optimal hydrodynamic conditions regarding the space-time-yield.
    The results of the reaction studies are discussed with respect to the prevailing flow regimes obtained by additional tomographic imaging studies for the same setup and operating conditions.
    Keywords: Hydrogenation, process intensification, fixed bed reactor, inclination, rotation
    • Lecture (Conference)
      "CHEMREACTOR-21" XXI International Conference on Chemical Reactors, 22.-25.09.2014, Delft, The Netherlands

    Permalink: https://www.hzdr.de/publications/Publ-19776
    Publ.-Id: 19776


    Hydrierung von alpha-Methylstyrol in einem geneigt rotierenden Festbettreaktor

    Härting, H.-U.; Lange, R.; Schubert, M.;
    Rieselbettreaktoren finden in der chemischen Industrie breite Anwendung zur Realisierung heterogen-katalysierter Reaktionen insbesondere bei hohen Eduktdurchsätzen. Allerding ist die Reaktorleistung durch geringe Stoff- und Wärmeübertragungsraten begrenzt. Zusätzlich können sich Fehlverteilungen der Flüssigphase nachteilig auf Transportprozesse, Katalysatorausnutzungsgrad und -aktivität auswirken. Konzepte mit dynamischer Betriebsweise, wie beispielsweise die periodische Variation des Flüssigphasendurchsatzes am Reaktoreingang, wurden vorgeschlagen, bei denen die zeitgemittelten Raum-Zeit-Ausbeuten gesteigert werden konnten. Dispersionsvorgänge schwächen die positiven Effekte jedoch mit zunehmender Länge des Festbetts ab.
    Ein alternatives quasi-periodisches Reaktorkonzept ist der geneigt rotierende Festbettreaktor, bei dem die zeitliche in eine örtliche periodische Betriebsweise überführt wird. Die Reaktorneigung führt zur Separation der Gas- und Flüssigphase; die überlagerte Reaktorrotation resultiert in einer periodischen Be- und Entnetzung der im Reaktor fixierten Katalysatorschüttung, wodurch die Zugänglichkeit der aktiven Zentren für die Edukte, insbesondere der Gasphase, über die gesamte Reaktorlänge verbessert wird. Beim neuen Reaktorkonzept können sowohl die Drehzahl als auch die Neigung in Abhängigkeit vom Reaktionssystem (Reaktionsrate, Flüssigkeitseigenschaften, Katalysator etc.) angepasst werden, um die Strömung (siehe Abbildung 1) für den jeweiligen Prozess zu optimieren.
    Zur Leistungsbewertung des neuen Reaktorkonzepts wurde zusätzlich zur hydrodynamischen Charakterisierung die jeweilige Strömung hinsichtlich der Raum-Zeit-Ausbeute einer Modellreaktion vergleichend zum Rieselbettreaktor untersucht. Als Modellreaktion wurde die irreversible unselektive Hydrierung von α-Methystyrol zu Cumol (C9H10+H2 --> C9H12) verwendet, bei der bereits bei moderaten Prozessbedingungen Stoffübertragungs¬limitierungen der Gasphase auftreten (Khadilkar et al., 1999). Die Veränderungen beim Reaktionsumsatz in Abhängigkeit von den Betriebsbedingungen (p = 1 bar und 6 bar, T = 25 °C und 40 °C, isotherm) können damit direkt der Stoffübertragung zugeordnet werden. Für die reaktionstechnischen Studien wurde der Reaktor mit einer dünnen Schicht Palladium-Katalysator (kugelförmiges γ-Al2O3-Trägermaterial, Ø 4 mm, egg-shell, 0,1 Ma.-% Pd) in der Mittelebene des Reaktors (L = 1,6 m, D = 0,1 m) zwischen Inertmaterial befüllt.
    Keywords: Hydrogenation, process intensification, fixed bed reactor, alpha-methylstyrene, inclination, rotation
    • Poster
      Jahrestreffen Reaktionstechnik 2014, 28.-30.04.2014, Würzburg, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19775
    Publ.-Id: 19775


    Residence time distribution in an inclined rotating fixed-bed reactor

    Härting, H.-U.; Lange, R.; Schubert, M.;
    Trickle bed reactors (TBR) are widely applied in the chemical industry for heterogeneous catalytic reactions. Besides their wide application, their performance often suffers from inherent drawbacks, like liquid maldistribution and poor mass and heat transfer rates; and are therefore a promising target for process intensification (PI). PI in such reactors can be realised by a periodic operation of the reactor, which is usually implemented by the modulation of liquid flow rate or liquid inlet concentration. Flow rate modulation is known to increase the mass and heat transfer rates and to significantly increase the time-averaged reaction rates compared to steady state results. On the other hand, the positive effects of the flow rate modulation vanish rapidly along the reactor length due to the fading pulse shape.
    An alternative reactor concept for PI is the inclined rotating fixed-bed reactor, which retains the positive effects of flow rate modulation but eludes the deficiencies. The reactor inclination results in phase segregation, whereas the superimposed reactor rotation generates a periodic wetting and draining of the particles in the co-rotating fixed-bed (see Figure 1), thus, transforming the temporal periodic operation into a spatial periodic operation, which is present along the whole reactor length.
    To optimize the reactor performance for a given chemical reaction, a reactor model is required, which considers the macro-mixing behaviour. Thus, the aim of this study is the systematic investigation of the influence of reactor inclination and rotation on the residence time distribution (RTD) for selected combinations of gas and liquid superficial velocities. The RTD is examined by the imperfect pulse method, whereat inhouse developed wire-mesh sensors are applied to measure the tracer concentration as well as the in-plane spatial phase distribution at two axial positions in the reactor. The experimental data are fitted to the axial dispersion model with open-open boundary conditions, from which the mean residence time and the Péclet number are extracted.
    The results will be discussed with respect to flow regime maps that are based on tomographic imaging. Furthermore, the mean residence time and the Péclet number will be compared with data for the vertical reactor configuration (TBR) and with correlations from the literature.
    Keywords: Residence time distribution, process intensification, fixed bed reactor, inclination, rotation
    • Lecture (Conference)
      21st International Congress of Chemical and Process Engineering (CHISA 2014), 23.-27.08.2014, Praha, Česká republika

    Permalink: https://www.hzdr.de/publications/Publ-19774
    Publ.-Id: 19774


    Analyse des hydrodynamischen und reaktionstechnischen Verhaltens geneigt rotierender Festbettreaktoren für heterogene Mehrphasenreaktionen

    Härting, H.-U.;
    Der geneigt rotierende Festbettreaktor stellt ein neuartiges Reaktorkonzept mit dem Ziel der Prozessintensivierung dar. Anders als bei bisherigen Ansätzen zur Prozessintensivierung, bei denen dem Reaktor üblicherweise durch Strömungsmodulation eine zeitliche Periodizität aufgeprägt wird, erfolgt hier durch die geneigte Rotation die Aufprägung einer örtlichen Periodizität unter gleichzeitiger quasistationärer Durchströmung des Reaktors.
    In der Forschungsarbeit wird die Hydrodynamik des neuen Reaktorkonzepts mittels nichtinvasiver bildgebender Verfahren (Gammastrahlen-Computertomographie) aufgeklärt. Zur Leistungsbewertung wird weiterhin der Einfluss der neuen Betriebsparameter Reaktorneigung und –rotation auf die Raum-Zeit-Ausbeute der Hydrierung von alpha-Methylstyrol zu Cumol untersucht. Klassische Methoden der Verfahrenstechnik, wie die Ermittlung der Verweilzeitverteilung durch Aufgabe von Stoßmarkierungen sowie die Bestimmung von Stoffüber-tragungskoeffizienten werden ebenfalls angewandt. Erste Ergebnisse belegen die Eignung des neuen Reaktorkonzepts zur Einstellung definierter Strömungsformen, z. B. einer stratifizierten Strömung, bei konstanten Durchsätzen.
    Keywords: Process intensification, inclined rotating fixed bed reactor
    • Contribution to external collection
      in: Jubiläumsband 60 Jahre Dresdner Verfahrenstechnik, Dresden: Inst. für VT und UT, TU Dresden, 2014, 140-140

    Permalink: https://www.hzdr.de/publications/Publ-19773
    Publ.-Id: 19773


    Experimental observation of spatially modulated laser-driven proton beams from micrometer thick targets

    Metzkes, J.; Kluge, T.; Zeil, K.; Bussmann, M.; Kraft, S. D.; Cowan, T. E.; Schramm, U.;
    • Lecture (Conference)
      Laser and Plasma Accelerator Workshop 2013, 02.-06.09.2013, Goa, India

    Permalink: https://www.hzdr.de/publications/Publ-19772
    Publ.-Id: 19772


    ISR precision measurements of the 2 pi cross section below 1 GeV with the KLOE experiment and their impact on (g-2)_mu

    Müller, S. E.;
    During the last 10 years, the use of initial state radiation (ISR) has changed from being a novel method to an established technique for precision measurements of hadronic cross sections at e+e- -colliders. By means of a dispersion integral, these measurements enter the hadronic contribution to the theoretical value of the anomalous magnetic moment of the muon, which still shows a 2-3sigma discrepancy with the experimental value measured at the Brookhaven National Laboratory.

    The KLOE collaboration, operating the KLOE experiment at the DAPHNE e+e- -collider in Frascati, has published 4 measurements of the cross section for the process e+e- ->pi+pi- in the energy region below 1 GeV, covering ~70% of the total hadronic contribution to the muon anomaly.

    I will present the ISR method in detail using the KLOE measurements as examples, and show how these measurements contribute to the current status of the theoretical evaluation of (g-2)mu.
    Keywords: (g-2)_mu, ISR, 2pi cross section, KLOE
    • Lecture (others)
      Institutskolloquium, 09.01.2014, Dresden, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19771
    Publ.-Id: 19771


    Mini-Proceedings of the 14th Meeting of the Working Group on Rad. Corrections and MC Generators for Low Energies

    Czyż, H.; Eidelman, S.; Fedotovich, G. V.; Korobov, A.; Müller, S. E.; Nyffeler, A.; Roig, P.; Shekhovtsova, O.; Teubner, T.; Venanzoni, G.; (Editors)
    The mini-proceedings of the 14th Meeting of the "Working Group on Rad. Corrections and MC Generators for Low Energies" held in Frascati on September 13, 2013, as a satellite meeting of the PHIPSI13 conference in Rome, are presented. These meetings, started in 2006, have as aim to bring together experimentalists and theorists working in the fields of meson transition form factors, hadronic contributions to (g-2)_\mu and the effective fine structure constant, and development of MonteCarlo generators and Radiative Corrections for precision e+e- and tau physics.
    Keywords: | energy: low | electron: energy: low | form factor: transition | fundamental constant: fine structure | radiative correction | magnetic moment | meson
    • Open Access Logo Contribution to proceedings
      14th Meeting of the Working Group on Rad. Corrections and MC Generators for Low Energies, 13.09.2013, Frascati, Italy
      Mini-Proceedings of the 14th meeting of the Working Group on Rad. Corrections and MC Generators for Low Energies arXiv:1312.0454 [hep-ph]

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    Permalink: https://www.hzdr.de/publications/Publ-19770
    Publ.-Id: 19770


    Constraining the Hadronic Contributions to the Muon Anomalous Magnetic Moment

    Masjuan, P.; Venanzoni, G.; Czyż, H.; Denig, A.; Vanderhaeghen, M.; Eidelman, S.; Hu, H.; Kloss, B.; Kupsc, A.; Pettersson, J.; Ahmadov, A. I.; Kuraev, E. A.; Volkov, M. K.; Voskresenskaja, O. O.; Zemlyanaya, E. V.; Müller, S. E.; Ping, R. G.; Redmer, C. F.; Sanchez-Puertas, P.; Nugent, I.; Przedzinski, T.; Roig, P.; Shekhovtsova, O.; Was, Z.; Spiesberger, H.; Tomasi-Gustafsson, E.; Wang, Y.;
    The mini-proceedings of the Workshop on "Constraining the hadronic contributions to the muon anomalous magnetic moment" which included the "13th meeting of the Radio MonteCarLow WG" and the "Satellite meeting R-Measurements at BES-III" held in Trento from April 10th to 12th, 2013, are presented. This collaboration meeting aims to bring together the experimental e+e- collider communities from BaBar, Belle, BESIII, CMD2, KLOE, and SND, with theorists working in the fields of meson transitions form factors, hadronic contributions to (g-2)_\mu and effective fine structure constant, and development of Monte Carlo generator and Radiative Corrections for precision e+e- and tau physics.
    Keywords: muon: magnetic moment | form factor: transition | fundamental constant: fine structure | electron: pair production | BES | radiative correction | Monte Carlo | BaBar | CMD-2 | BELLE | KLOE | SND | t | eta | pi0 | radiation: initial-state interaction | electron positron: annihilation | photon photon: scattering | tau-: semileptonic decay | eta(958) | effective Lagrangian: chiral | quantum chromodynamics: sum rule | anti-p p: annihilation
    • Open Access Logo Contribution to proceedings
      Workshop on "Constraining the hadronic contributions to the muon anomalous magnetic moment" which included the "13th meeting of the Radio MonteCarLow WG" and the "Satellite meeting R-Measurements at BES-III", 10.-12.04.2013, Trento, Italy
      Constraining the Hadronic Contributions to the Muon Anomalous Magnetic Moment arXiv:1306.2045 [hep-ph]

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    Permalink: https://www.hzdr.de/publications/Publ-19769
    Publ.-Id: 19769


    First Test of Lorentz Invariance in the Weak Decay of Polarized Nuclei

    Dijck, E. A.; Bekker, H.; van den Berg, J. E.; Böll, O.; Hoekstra, S.; Jungmann, K.; Meinema, C.; Noordmans, J. P.; Nunez Portela, M.; Onderwater, C. J. G.; Pijpker, C.; van der Poel, A. P. P.; Santra, B.; Sytema, A.; Timmermans, R. G. E.; Versolato, O. O.; Willmann, L.; Wilschut, H. W.; Yai, K.; Müller, S. E.;
    A new test of Lorentz invariance in the weak interactions has been made by searching for variations in the decay rate of spin-polarized 20Na nuclei. This test is unique to Gamow-Teller transitions, as was shown in the framework of a recently developed theory that assumes a Lorentz symmetry breaking background field of tensor nature. The nuclear spins were polarized in the up and down direction, putting a limit on the amplitude of sidereal variations of the form |(Γup − Γdown)|/(Γup + Γdown) < 3 × 10−3. This measurement shows a possible route toward a more detailed testing of Lorentz symmetry in weak interactions.
    Keywords: PACS numbers: 11.30.Cp, 24.80.+y, 23.40.Bw

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    Publ.-Id: 19768


    Thermophysical properties of the liquid GaInSn eutectic alloys

    Plevachuk, Y.; Sklyarchuk, V.; Eckert, S.; Gerbeth, G.; Novakovic, R.;
    Among different Ga-based alloys the overall properties of the Ga In Sn eutectic alloy make it particularly suitable for many applications. However, the experimental data on its thermophysical properties are rather discrepant. In this work, the electrical and thermal conductivity, thermoelectric power, viscosity, surface tension and density of the Ga In Sn eutectic have been investigated in the temperature range between the melting temperature and 700 K. The experimental results obtained were compared with the data available in the literature. New information from scaling properties of the Ga In Sn eutectic liquid alloy can be used as input for thermodynamic simulations or for the modeling of casting processes.
    Keywords: thermophysical properties, liquid metals, GaInSn alloy

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    Publ.-Id: 19767


    U(VI) retention by potential host rocks: Comparison of clay and crystalline rock

    Schmeide, K.; Joseph, C.; Brendler, V.;
    The long-term disposal of high-level nuclear waste in deep geological formations is discussed worldwide as main strategy for nuclear waste management. This approach requires the use of a multiple barrier system consisting of engineered, geo-engineered, and geological barriers to prevent any release of radionuclides into the geo- and biosphere. Sorption of radionuclides on the host rock of a repository is one important process for retarding their migration. Potential host rocks for nuclear waste repositories that are investigated internationally are salt domes, clay rock, and crystalline rock.
    In the present work, the retention behavior of clay and crystalline rock towards U(VI) is compared. For this, sorption of U(VI) onto Opalinus clay from the Mont Terri rock laboratory (Switzerland) was studied in the presence of Opalinus clay pore water (pH = 7.6; I = 0.36 M) [1]. This is compared to U(VI) sorption onto anoxic diorite from Äspö Hard Rock Laboratory (Sweden) that was studied in the presence of Äspö groundwater (pH = 7.8; I = 0.18 M) [2]. The impact of various parameters, such as solid-to-liquid ratio, initial U(VI) concentration, temperature and atmosphere, on U(VI) sorption was studied.
    Distribution coefficients, Kd values, determined for the U(VI) sorption onto Opalinus clay and diorite at 25 °C, amount to 22.2 ± 0.4 L/kg [1] and 3.8 ± 0.6 L/kg [2], respectively. This shows that U(VI) sorption onto Opalinus clay is stronger than onto diorite, which can be attributed to its larger surface area. TRLFS and ATR FT-IR spectroscopic measurements showed that the U(VI) speciation in Opalinus clay pore water as well as in diorite groundwater is predominated by the weakly sorbing Ca2UO2(CO3)3(aq) complex. Reduction processes of U play only a subordinate role. The U(VI) sorption increases with increasing temperature.
    U(VI) diffusion experiments with intact Opalinus clay bore cores [3] also showed that Opalinus clay has a good retardation potential for U(VI) since the molecular diffusion process through Opalinus clay retards the migration of Ca2UO2(CO3)3(aq).
    Generally, it can be concluded that U(VI) retention by clay rock is stronger than that by crystalline rock. This supports decisions to use clay rock not only as host rock but also as backfill material. In case of crystalline rock the natural retention capacity for U is insufficient and has to be strengthened by additional geo-technical and technical barriers that preserve their enclosing capabilities over very long time scales.

    [1] Joseph, C., Schmeide, K., Sachs, S., Brendler, V., Geipel, G., Bernhard, G.: Sorption of uranium(VI) onto Opalinus clay in the absence and presence of humic acid in Opalinus clay pore water. Chem. Geology 284, 240-250 (2011).
    [2] Schmeide, K., Gürtler, S., Müller, K., Steudtner, R., Bok, F., Joseph, C., Brendler, V.: Interaction of U(VI) with Äspö diorite: A batch and in situ ATR FT-IR sorption study. Appl. Geochem., under review (2014).
    [3] Joseph, C., Van Loon, L.R., Jakob, A., Steudtner, R., Schmeide, K., Sachs, S., Bernhard, G.: Diffusion of U(VI) in Opalinus clay: Influence of temperature and humic acid. Geochim. Cosmochim. Acta 109, 74-89 (2013).
    Keywords: Uranium, sorption, retention, clay rock, crystalline rock
    • Contribution to proceedings
      RadChem 2014 - 17th Radiochemical Conference, 11.-16.05.2014, Mariánské Lázně, Czech Republic
    • Invited lecture (Conferences)
      RadChem 2014 - 17th Radiochemical Conference, 11.-16.05.2014, Mariánské Lázně, Czech Republic

    Permalink: https://www.hzdr.de/publications/Publ-19766
    Publ.-Id: 19766


    Nanostructuring Ge Surfaces by Ion Irradiation

    Facsko, S.; Fritzsche, M.; Ou, X.; Keller, A.;
    Low energy ion irradiation induces the formation of periodic surface patterns. These struc-tured surfaces exhibit periodicities in the range of a few tens to hundreds of nanometers and are promising templates for producing nanostructured thin films. Periodic ripple patterns with wave vector parallel to the ion beam direction are observed frequently for ion irradiation at incidence angles between 50° and 70° to the surface normal. At normal incidence dot or hole patterns with hexagonal symmetry are observed only under special irradiation conditions.
    The formation of hexagonally arranged hole patterns on Ge(001) surfaces induced by irradia-tion at normal incidence was studied with a scanned focused Ga+ ion beam (FIB). Hole pat-terns with characteristic length of about 50 nm are observed in a narrow energy range of 4 - 6 keV. Hole patterns induced by FIB irradiations were compared to broad beam Ga+ and Ge+ irradiations with the same ion energy. No differences were found demonstrating that FIB irra-diations with a large overlap of the scanned beam are identical to conventional broad beam irradiations.
    Furthermore, ion the formation of checkerboard patterns on Ge surfaces was observed dur-ing 1 keV Ar+ irradiation at normal incidence and higher substrate temperature. Similar to the case of ion irradiated crystalline metal surfaces on the crystalline Ge surface a new instability appears at temperatures above the recrystallization temperature due to the Ehrlich-Schwoebel barrier. In this case, we observe regular checkerboard or hole patterns with the symmetry of the patterns reflecting the crystal structure of the irradiated surface.
    Keywords: ion irradiation, surface patterning, Ge, nanostructures
    • Lecture (Conference)
      18th International Conference on Surface Modification of Materials by Ion Beams (SMMIB 2013), 15.-20.09.2013, Kusadasi, Türkiye

    Permalink: https://www.hzdr.de/publications/Publ-19765
    Publ.-Id: 19765


    Reverse epitaxy: patterns on crystalline Ge surfaces

    Facsko, S.; Ou, X.; Keller, A.;
    Low energy ion irradiation induces the formation of periodic surface patterns. These structured surfaces exhibit periodicities in the range of a few tens to hundreds of nanometers and are promising templates for producing nanostructured thin films. Periodic ripple patterns with wave vector parallel to the ion beam direction are observed frequently for ion irradiation at incidence angles between 50° and 70° to the surface normal. At normal incidence dot or hole patterns with hexagonal symmetry are observed only under special irradiation conditions.
    At room temperature semiconductor surfaces are amorphized by ion irradiation. However, at temperatures higher than the recrystallization temperature the surface remains crystalline and novel ion induced patterns appear with the symmetry of the crystal structure of the material. We present pattern formation on Ge surfaces during 1 keV Ar+ ion irradiation under normal incidence at temperature above the recrystallization temperature of Ge. Similar to the case of ion irradiated crystalline metal surfaces on the crystalline Ge surface a new instability appears at higher temperature due to the Ehrlich-Schwoebel barrier. In this case, regular checkerboard or hole patterns with the symmetry of the patterns reflecting the crystal structure of the irradiated surface are observed.
    Keywords: ion irradiation, surface patterning, homoepitaxy
    • Lecture (Conference)
      Symposium on „Nanoscale Pattern Formation at Surfaces“, 26.-30.05.2013, Copenhagen, Danmark

    Permalink: https://www.hzdr.de/publications/Publ-19764
    Publ.-Id: 19764


    Ion Irradiation of Ge: From Sponge-Like Structures to Periodic Patterns

    Böttger, R.; Ou, X.; Fritzsche, M.; Keller, A.; Heinig, K. H.; Bischoff, L.; Liedke, B.; Facsko, S.;
    Ion irradiation of Ge surfaces leads to a variety of different morphologies depending on the irradiation conditions. In the energy range of few MeV down to a few tens of keV swelling and the formation of sponge like structures are observed. When lowering the energy these porous structures turn into self-organized periodic surface patterns: at off-normal incidence angles well-known ripple patterns with wave vector parallel or perpendicular to the ion beam direction appear, whereas at normal incidence angles hexagonally ordered dot or hole patterns can be formed. The structure size of the patterns is in the range of 10 to 100 nm and, occa-sionally, a high degree of ordering is achieved.
    On materials which turn amorphous during ion irradiation the formation of periodic patterns relies on at least two inter-playing processes: surface roughening due to local variation of ero-sion rate and smoothing via diffusional processes. In addition, atomic relocations on the sur-face and in the bulk resulting from the collision cascade have been identified as equally im-portant or even dominating. At the atomic level the creation of surface and bulk defects, sput-tering, and the influence of the ion beam on surface diffusion processes play a decisive role in the morphology evolution.
    At high temperature, when amorphization of the Ge surface is prevented by recrystallization, novel surface patterns are developing during ion irradiation. Similar to the case of ion irradia-tions of crystalline metal surfaces a new instability appears on the crystalline Ge surface due to a Ehrlich-Schwoebel barrier for ascending ion induced vacancies. In this case, regular checkerboard patterns are evolving on the Ge (001) surface with structures oriented along the <100> direction.
    Moreover, a new mechanism for pattern formation on Ge has been discovered recently: by polyatomic Bi ion irradiation or monoatomic Bi ion irradiation of hot Ge melt pools are in-duced at the Ge surface by the incident ions. These melt pools can also lead to a surface insta-bility and thus to the formation of periodic dot patterns at normal incidence.
    We will present an overview of the different morphologies induced by ion irradiation on Ge surfaces and analyze the dominant formation mechanism.
    Keywords: ion irradiation, surface patterning, vacancy diffusion
    • Lecture (Conference)
      Workshop on "Particle - surface interactions: from surface analysis to materials processing" (PASI 2013), 03.-5.05.2013, Luxembourg, Luxembourg

    Permalink: https://www.hzdr.de/publications/Publ-19763
    Publ.-Id: 19763


    Interaction of highly charged ions with surfaces

    Facsko, S.;
    Highly charged ions (HCI) release a large amount of potential energy during their neutralization when interacting with solid surfaces. This energy is mostly retained in the solid leading to local phase transformations on a nanometer scale. The study of modifications on surfaces and thin foils as a function of potential and kinetic energy gives insight into the interaction of HCIs with surfaces as well as into phase transformations under these non-equilibrium conditions.
    Keywords: Highly charge ions, surfaces, nanostructures
    • Invited lecture (Conferences)
      11th European Conference on Atoms, Molecules and Photons, 24.-28.06.2013, Aarhus, Danmark

    Permalink: https://www.hzdr.de/publications/Publ-19762
    Publ.-Id: 19762


    Spin Nernst Angle: Definition and qualitative Estimation for Cu Alloys

    Zahn, P.; Gemming, S.;
    The spin Nernst effect describes the occurrence of a spin current perpendicular to an applied thermal gradient and the spin quantization axis in a non-magnetic material. To quantify the effect, the spin Nernst angle will be defined in a more general way than in ref. [1]. This allows for a clear separation of the transverse spin current into two opposite contributions proportional to the spin Hall angle and the spin Nernst angle, respectively. Qualitative trends for Cu alloys with 3d, 4d and 5d defects extending a resonant scattering model by Fert and Levy [2] will be presented.
    The work was partially supported by the Initiative and Networking Fund of the German Helmholtz Association, Helmholtz Virtual Institute MEMRIOX (VH-VI-442) and the DFG Priority Program 'Nanostructured Thermoelectrics' (ZA264/3-2).
    [1] K. Tauber et al., Phys. Rev. Lett. 109, 026601 (2012)
    [2] A. Fert and P.M. Levy, Phys. Rev. Lett. 106, 157208 (2011)
    • Poster
      550. WE-Heraeus-Seminar 'Spin Transport beyond Boltzmann', 08.-10.01.2014, Bad Honnef, Deutschland

    Permalink: https://www.hzdr.de/publications/Publ-19761
    Publ.-Id: 19761


    Memory Effects in Resistive Ion-beam Modified Oxides

    Zahn, P.; Gemming, S.; Potzger, K.; Schmidt, H.; Mikolajick, T.; Slesazeck, S.; Stöcker, H.; Abendroth, B.; Meyer, D. C.; Dittmann, R.; Rana, V.; Waser, R.; Ronning, C.; Spaldin, N. A.; Basov, D.;
    The Virtual Institute MEMRIOX establishes a joint research initiative in the field of ion-tailored oxide-based memristive elements, to be pursued within a novel and unique combination of core competences from the Helmholtz centers Dresden-Rossendorf and Jülich and their university partners in Dresden, Freiberg, Jena, San Diego, and Zürich.
    A nanoscale memristive element may prove the concept of the ultimate future non-volatile memory cell with a resistance set directly by electric currents. The Virtual Institute aims at stepping beyond the established layer-by-layer control of intrinsic defects during the synthesis of memristive elements. The project is financed by the Initiative and Networking Funds of the Helmholtz Association (VH-VI-442).
    • Poster
      E-MRS Spring Meeting, 27.-31.05.2013, Strasbourg, France

    Permalink: https://www.hzdr.de/publications/Publ-19760
    Publ.-Id: 19760


    Gelatin-based biomaterials with tailorable mechanical properties as promising matrices for soft-tissue replacement

    Ullm, S.; Tondera, C.; Gebauer, T.; Neffe, A. T.; Lendlein, A.; Pietzsch, J.;
    Objectives
    Gelatin-based hydrogels are promising degradable materials for soft tissue regeneration. Our approach aims at biopolymer-based polymer networks with tailorable elastic properties and degradation behavior due to different degrees of crosslinking with lysine diisocyanate ethyl ester. Two gelatin-based hydrogel films were compared regarding their influence on vitality, adhesion and proinflammatory activation of both endothelial cells and human macrophages, to investigate representative cells being responsible for tissue integration and degradation of the material.
    Materials & methods
    10 wt% gelatin solutions were crosslinked with three- (G10LNCO3) or eight-fold (G10LNCO8) excess of isocyanate groups, resulting in hydrogels with tailored Young’s moduli (13 and 55 kPa), swelling (1200 and 350 vol%) and degradation time [1]. For experiments on cell vitality, human leukemia HL-60 cells differentiated to macrophages (MΦ), and primary human aortic endothelial cells (HAEC) were incubated with material eluates for 24 and 48 h. Furthermore, these cells were seeded directly on swollen hydrogels for adhesion assays at 2 or 4 h, as well as for microscopic studies on their infiltration ability into the hydrogels after 48 h and 7 days. In order to characterize the ability of hydrogels to induce proinflammatory effects in cells, expression of COX-2 and the receptor for advanced glycation endproducts was quantified by western blotting after 48 h.
    Results
    MΦ showed a higher vitality and HAEC showed a lower vitality after incubation with material eluates, which can only be related to fragments formed by partial degradation. Interestingly, the strong difference in degradation rate, with G10LNCO3 showing a mass loss of 60 wt% within 6 days, while G10LNCO8 showed only 5–10 wt% mass loss, did not have an influence on the vitality. The adhesion ability of MΦ to swollen hydrogels was significantly decreased to 30% (p<0.05, ANOVA) for G10LNCO3 and to 38% for G10LNCO8, respectively, when compared with adhesion on normal cell culture plastic. By contrast, HAEC in part showed enhanced adhesion to the materials (116% for G10LNCO3, n.s.; 145% for G10LNCO8, p<0.05). This suggests that gelatin offers adhesion sequences for HAEC, but not for MΦ. A higher degree of crosslinking resulted in higher adhesion of both cell types. Additionally, both cell types infiltrated the materials within 4 days, which highlights the degradability of the material, putatively supported by cell-mediated mechanisms. Direct contact with the materials resulted in an increment of COX-2 expression in both cell lines, with a higher degree of hydrogel crosslinking leading to elevated COX-2 expression. Receptor for advanced glycation endproducts synthesis remained unaffected in both MΦ and HAEC.
    Conclusion
    The hydrogels provide both a surface preventing adhesion of macrophages and supporting adhesion of endothelial cells, which might lead to good tissue integration. However, the materials or their degradation products induced proinflammatory effects on MΦ depending on the degree of crosslinking. In further studies, these hydrogel films will be studied in animal models concerning their initial interaction with the organism after implantation and their degradation.
    Financial & competing interests disclosure
    This work is part of a research initiative within the Helmholtz-Portfoliotheme “Technologie und Medizin - Multimodale Bildgebung zur Aufklaerung des In vivo -Verhaltens von polymeren Biomaterialien”.
    Reference
    1 Tronci G, Neffe AT, Piercea BF, Lendlein A. An entropy–elastic gelatin-based hydrogel system. J. Mater. Chem. 20, 8875–8884
    • Abstract in refereed journal
      Regenerative Medicine 8(2013), S201
    • Poster
      World Conference on Regenerative Medicine, 23.-25.10.2013, Leipzig, Deutschland

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