Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41421 Publications

Design and commissioning of a small-scale gas/aerosol test facility for investigation of deposition and resuspension of nulcear aerosol particles

Barth, T.; Banowski, M.; Hampel, U.

Nuclear aerosol deposition and the assessment of its resuspension during a design basis accident in the primary circuit are a key issue in the development and certification of advanced (Very) High Temperature Reactors ((V)HTRs). It is of general interest how much of these nuclear aerosol particles escape from the primary circuit into the containment during a depressurization scenario. The knowledge about the amount of resuspended material will allow detailed estimate
of dose escaping the primary circuit (Fontanet et al. (2009)).
Kissane (2009) and Moormann (2008) list different sources of radioactive graphite dust production. Regarding pebble bed HTRs, there is mechanical movement and thereby friction between the pebbles due to loading and unloading of the core. Furthermore, different kind of impurities such as oil, water and air ingresses lead to dust production due to oxidation and peeling of the pebble surfaces. Referring to VAMPYR filter experiments at AVR J¨ulich, Moormann (2008) reports about airborne concentration (C = 0..50 μg/m3), geometrical size distribution (dP = 0.1..50 μm) and chemical composition of graphite dust. Annual amount of dust production in the AVR is estimated to be around 5 kg/yr and surface loading is calculated to be approximately 10 g/m2 after 16 years operation. Furthermore, Kissane (2009) expects that the partially graphitized binder is a major source of carbonaceous dust production. Scaling these dust production contributions up to a 400 MWt pebble bed core, the annual dust production is around 100 kg/yr. The graphite dust particles circulate in helium pressure boundary (HPB) which is characterized by a cooling pressure of about 11 to 55 bar and coolant temperature up to 950°C. Flow conditions range from laminar flows in the recuperator to turbulent high Reynolds number flows in pipes and ducts. Depending on the local conditions, there is deposition and esuspension of graphite dust mainly moderated by diffusion, thermophoresis, turbophoresis, particle inertia, gravitational settling and electrostatic precipitation. In order to investigate transport, deposition and resuspension phenomena, we focus on single effect studies of nuclear aerosol particles in a well developed turbulent flow field.

Keywords: nuclear aerosol particles; particle image velocimetry; VHTR; deposition; resuspension

  • Lecture (Conference)
    THINS - Students Course & Workshop - 2011, 07.-11.02.2011, Zurich, Swiss

Permalink: https://www.hzdr.de/publications/Publ-15330
Publ.-Id: 15330


Hochauflösende Zweiphasenmesstechnik

Hampel, U.

Der Vortrag gibt einen Einblick in hochauflösende Zweiphasenmesstechnik mit dem Schwerpunkt Gas-Flüssig-Systeme. Vorgestellt werden Nadelsonden, Gittersensoren, Gammadensitometrie sowie Gammastrahlen- und Röntgentomographie-Verfahren. Neben den physikalischen Messprinzipien werden Einsatzgebiete und Grenzen sowie Methoden zur Datenverarbeitung und Datenanalyse vorgestellt.

Keywords: Zweiphasen-Instrumentierung

  • Invited lecture (Conferences)
    CIWA Druckstoßseminar, 24.-25.02.2011, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15329
Publ.-Id: 15329


High-end gamma and X-ray tomography

Hampel, U.

The presentation introduces into gamma ray and x-ray tomography as sophisticated tomographic imaging techniques applicable in multiphase flow studies and process imaging. Both techniques have recently been developed at HZDR and have been usedin different scientific applications, such as steam-water two phase flow studies in nuclear safety research and multiphase flow studies in process technology. The presentation both gives an overview over physical measuring principles along with different and unique applications in science and industry.

Keywords: gamma ray tomography; x-ray tomography; process tromography; multiphase flow

  • Invited lecture (Conferences)
    Thermal Hydraulics of Innovative Nuclear Reactor Systems, 07.-11.02.2011, Zürich, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-15328
Publ.-Id: 15328


Tomographische Bildgebungsverfahren für Mehrphasenströmungen

Hampel, U.

Mehrphasenströmungen finden sich in einer Vielzahl von Prozessen und Apparaten der chemischen Industrie. Sie treten in vielfältigen Formen, wie etwa als disperse Gas-Flüssigkeits-Strömungen in Blasensäulenreaktoren, Gas-Feststoff-Strömungen in Wirbelschichtapparaten oder Blasen-, Schwall- und Filmströmungen in Destillationskolonnen auf. Charakteristisch für Mehrphasenströmungen ist, dass sie messtechnisch schwer erfassbar, theoretisch schwer modellierbar und numerisch schwer berechenbar sind. Ihre Beobachtung und Beschreibung in sowohl industriellen Apparaten als auch in kleinskaligen Versuchsanlagen erfordert Messverfahren, die in der Lage sind, mit hoher räumlicher und zeitlicher Auflösung Phasenverteilungen, Phasengrenzflächendichten, Turbulenz- und Geschwindigkeitsparameter in Kontinuumsphasen, als auch Wärme-, Stoff- und Impulstransport zwischen den beteiligten Phasen abzubilden. Da Mehrphasenströmungen im Allgemeinen opak sind, ist dies mit den sonst in der Strömungsmechanik üblichen optischen Messverfahren nur begrenzt möglich. Dazu kommt, dass gerade in der Verfahrenstechnik viele Prozesse bei hohen Drücken und Temperaturen und in Gefäßen mit dicken Metallwänden und Einbauten ablaufen, was die Möglichkeiten der Instrumentierung einschränkt und hohe Anforderungen an die Robustheit von Messsystemen stellt.

In der jüngeren Vergangenheit wurden am Helmholtz-Zentrum Dresden-Rossendorf verstärkt Anstrengungen unternommen, tomographische bildgebende Messverfahren zu entwickeln, mit denen eine Aufklärung von Mehrphasenströmungen mit hoher räumlicher und zeitlicher Auflösung möglich ist. Ergebnisse dieser Entwicklungen, wie die Gittersensortechnik, die Gamma- und Röntgentomographie, werden im Vortrag vorgestellt. Mit dem Gittersensor wurde erstmalig die Untersuchung transienter Gas-Flüssigkeits-Strömungen mit Bildraten von bis zu 10.000 Bildern pro Sekunde bei einer räumlichen Auflösung von ca. 2 mm möglich. Für druckführende Apparate und Apparate mit Einbauten steht die hochauflösende Gammatomographie zur Verfügung, die eine räumliche Auflösung von ebenfalls ca. 2 mm erreicht. Schließlich vereint die ultraschnelle Röntgentomographie einige vorteilhafte Eigenschaften, wie die berührungsfreien Messung mit hoher räumlicher (~1 mm) und zeitlicher (~10.000 Bilder pro Sekunde) Auflösung sowie die Abbildung opaker und sowie feststoffhaltiger Medien. Der Vortrag stellt die genannten Messverfahren hinsichtlich ihrer physikalischen und messtechnischen Grundprinzipien dar und gibt einen Einblick in potenzielle Anwendungen und Methoden für die Bilddatenanalyse.

Keywords: Bildgebende Messverfahren; Tomographie; Mehrphasenströmungen

  • Invited lecture (Conferences)
    Reaktionstomographie und Chemical Imaging, 17.02.2011, Frankfurt, Germany

Permalink: https://www.hzdr.de/publications/Publ-15327
Publ.-Id: 15327


Biomineralization and biotransformations of actinide materials

Neu, M.; Boukhalfa, H.; Merroun, M. L.

Microorganisms moderate local chemical conditions and alter forms of metals indirectly or directly to meet their cellular, species, and consortia needs. The diversity of microorganisms and the complexity of biogeochemical systems ensures that bacterially mediated processes yield a wide range of products, which await discovery by material scientists. Few types of materials produced by environmental bacteria have been analyzed by modern chemical and material science methods. Research on actinide biomaterials has focused on the biomineralization of a few chemical forms of uranium, neptunium, and plutonium. The materials produced are molecular complexes, microcrystalline minerals (most commonly oxides and phosphates) within cells and biofilms, and mineral adsorbates. The actinide biomaterials that emerge from this new research area will impact nuclear waste isolation and increase our understanding of environmental and geological metal cycles and may yield new bioremediation methods and industrially useful materials.

Permalink: https://www.hzdr.de/publications/Publ-15326
Publ.-Id: 15326


Modulation of Adrenal Aldosterone Release by Oxidative Modification of Low-Density Lipoprotein

Ansurudeen, I.; Pietzsch, J.; Graessler, J.; Ehrhart-Bornstein, M.; Saha, S.; Bornstein, S. R.; Kopprasch, S.

BACKGROUND
Serum aldosterone is a causative factor for various metabolic and cardiovascular disorders. Low-density lipoprotein (LDL) is a major cholesterol source for aldosterone steroidogenesis; however, the effect of oxidative modification of LDL on aldosterone release is not known. We studied the effect of hypochlorite-oxidized LDL (oxLDL) on adrenal aldosterone secretion.
METHODS
LDL (native LDL (natLDL)) was obtained from healthy volunteers and oxidatively modified in vitro. NCI-H295R cells were stimulated with natLDL and oxLDL, and the aldosterone release was quantified by radioimmunoassay. Molecular changes were studied with western blot analysis and quantitative RT-PCR analysis.
RESULTS NatLDL and oxLDL caused dose-dependent increase in aldosterone release up to threefold. However, the stimulatory effects of modified LDL on aldosterone secretion decreased with increasing degree of LDL oxidation. 24-h incubations with natLDL, mild- and medium-oxidized LDL sensitized the adrenocortical cells to subsequent angiotensin II (Ang II) stimulations by 2.9-, 2.8-, and 2.5-folds, respectively. Heavily oxidized LDL did not sensitize the cells to Ang II stimulations to a similar extent. At the molecular level, the ERK pathway was activated within a minute by both natLDL and oxLDL; however, oxLDL showed a stronger (2.75-fold at 1 and 15 min) and longer (15 min) activation of ERK than natLDL (twofold).
CONCLUSIONS This study demonstrates the following: (i) both natLDL and hypochlorite-oxidized LDL utilize ERK pathway to mediate aldosterone release; (ii) mildly oxidized LDL sensitizes the adrenocortical cells to further stimulations by Ang II similar to natLDL that may have a role in pathological processes; (iii) extensive LDL oxidation counteracts adrenocortical aldosterone release.

Permalink: https://www.hzdr.de/publications/Publ-15324
Publ.-Id: 15324


Phase Composition of 316L Stainless Steel after Electron-Beam Irradiation Followed by Chromium Ion Implantation

Pryadko, E. L.; Reuther, H.; Shevchenko, N.; Markov, A. B.; Kolitsch, A.

In this work, samples of 316L, an austenite stainless steel, have been irradiated with a low-energy high-current electron beam of microsecond duration after that these samples were implanted at 150 keV by chromium ions. Implantation doses varied between 2.0 ⋅ 1016 and 2.0 ⋅ 1017 ions/cm2. The structure of the irradiated and implanted layer was examined by grazing incidence X-ray diffraction analysis. At 2.0 ⋅ 1016 ions/cm2 X-ray diffraction analysis of the phase composition in the surface layer revealed no difference between initial and irradiated-implanted samples. Above 2.0 ⋅ 1016 ions/cm2 a new bcc ferrite structure appeared. Higher implantation dose leads to a larger fraction of the ferritic phase. Irradiation with a low-energy high-current electron beam (LEHCEB) followed by ion beam implantation results in complete dissolution of inclusions and leads to the formation of ompletely homogeneous surface layer. It was also revealed that the surface layer homogeneity doesn't depend on implantation dose.

Related publications

  • Lecture (Conference)
    10th Int. Conf. on Modification of Materials with Particle Beams and Plasma Flows, 19.-24.09.2010, Tomsk, Russland
  • Contribution to proceedings
    10th Int. Conf. on Modification of Materials with Particle Beams and Plasma Flows, 19.-24.09.2010, Tomsk, Russland
    Proc. 10th Int. Conf. on Modification of Materials with Particle Beams and Plasma Flows: Publishing House of the IOA SB RAS, 153-155

Permalink: https://www.hzdr.de/publications/Publ-15323
Publ.-Id: 15323


Erratum to “Experimental study on the air/water counter-current flow limitation in a model of the hot leg of a pressurised water reactor”

Deendarlianto; Vallée, C.; Lucas, D.; Beyer, M.; Pietruske, H.; Carl, H.

This paper replaces the paper published in the journal by Deendarlianto et al. (2008). Because of an error in the implementation of the air flow meter some of the data given by Deendarlianto et al. (2008) are wrong. They are corrected within the present paper. The general results and conclusions remain unchanged.
An experimental investigation on the air/water counter-current two-phase flow in a horizontal rectangular channel connected to an inclined riser has been conducted. This test-section representing a model of the hot leg of a pressurized water reactor is mounted between two separators in a pressurized experimental vessel. The cross-section and length of the horizontal part of the test-section are (0.25 m × 0.05 m) and 2.59 m, respectively, whereas the inclination angle of the riser is 50. The flow was captured by a high speed camera in the bended region of the hot leg, delivering a detailed view of the stratified interface as well as of dispersed structures like bubbles and droplets. Countercurrent flow limitation (CCFL), or the onset of flooding, was found by analyzing the water levels measured in the separators. The counter-current flow limitation is defined as the maximum air mass flow rate at which the discharged water mass flow rate is equal to the inlet water mass flow rate.
From the high-speed observations it was found that the initiation of flooding coincides with the formation of slug flow. Furthermore, a hysteresis was noticed between flooding and deflooding. The CCFL data was compared with similar experiments and empirical correlations available in the literature. Therefore, the Wallis-parameter was calculated for the rectangular cross-sections by using the channel height as length, instead of the diameter. The agreement of the CCFL curve is good, but the zero liquid penetration was found at lower values of the Wallis parameter than in most of the previous work. This deviation can be attributed to the special rectangular geometry of the hot leg model of FZD, since the other investigations were done for pipes.

Keywords: Counter-current flow limitation (CCFL); pressurized water reactor (PWR); Hot leg; Flooding

Permalink: https://www.hzdr.de/publications/Publ-15322
Publ.-Id: 15322


Gas-liquid countercurrent two-phase flow in a PWR hot leg: a comprehensive research review

Deendarlianto; Höhne, T.; Lucas, D.; Vierow, K.

Research into gas-liquid countercurrent two-phase flow in a model of pressurized water reactor (PWR) hot leg has been carried out over the last several decades. An extensive experimental data base has been accumulated from these studies, leading to the development of phenomenological correlations and scaling parameters of the countercurrent flow limitation (CCFL). However, most the proposed correlations apply under a relatively narrow range of conditions, generally limited to the test section conditions and/or geometry. Moreover the development of mechanistic models based on the underlying physical processes has been limited. In contrast to this mechanistic form of modelling, the implementation of computational fluid dynamic (CFD) techniques has also been pursued, but the numerical approach for this application should be improved to reduce the computational cost.

This paper presents a comprehensive review of research work on countercurrent gas-liquid two-phase flow in a PWR hot leg and provides direction regarding future research on this topic. In the introductory section, the problems facing current research are described. In the following sections, recent experimental as well as theoretical research achievements are overviewed. In the last section, the problems that remain unsolved are discussed, along with some concluding remarks. It was found that only limited theoretical developments exist in the literature, however highly reliable experimental data are needed to support this effort. Additional work, both analytical and experimental, needs to be carried out on the effects of mass transfer on countercurrent flow limitation to improve the existing correlations and analytical models.

Keywords: Pressurized water reactor (PWR); Countercurrent flow limitation (CCFL); Experiment; Analytical studies; Computational fluid dynamics (CFD)

Permalink: https://www.hzdr.de/publications/Publ-15321
Publ.-Id: 15321


Simulation von Isoliermaterialtransport bei Sumpfkühlung

Höhne, T.

In 1992, strainers on the suction side of the ECCS pumps in Barsebäck NPP Unit 2 became partially clogged with mineral wool because after a safety valve opened the steam impinged on thermally-insulated equipment and released mineral wool. This event pointed out that strainer clogging is an issue in the course of a loss-of-coolant accident. Modifications of the insulation material, the strainer area and mesh size were carried out in most of the German NPPs. Moreover, back flushing procedures to remove the mineral wool from the strainers and differential pressure measurements were implemented to assure the performance of emergency core cooling during the containment sump recirculation mode. Nevertheless, it cannot be completely ruled out, that a limited amount of small fractions of the insulation material is transported into the RPV. During a postulated cold leg LOCA with hot leg ECC injection, the fibers enter the upper plenum and can accumulate at the fuel element spacer grids, preferably at the uppermost grid level. This effect might affect the ECC flow into the core and could result in degradation of core cooling.
It was the aim of the numerical simulations presented to study where and how many mineral wool fibers are deposited at the upper spacer grid. The 3D, time dependent, multi-phase flow problem was modelled applying the CFD code ANSYS CFX. The CFD calculation does not yet include steam production in the core and also does not include re-suspension of the insulation material during reverse flow. This will certainly further improve the coolability of the core.
The spacer grids were modelled as a strainer, which completely retains all the insulation material reaching the uppermost spacer level. There, the accumulation of the insulation material gives rise to the formation of a compressible fibrous cake, the permeability of which to the coolant flow is calculated in terms of the local amount of deposited material and the local value of the superficial liquid velocity.
Before the switch over of the ECC injection from the flooding mode to the sump mode, the coolant circulates in an inner convection loop in the core extending from the lower plenum to the upper plenum. The CFD simulations have shown that after starting the sump mode, the ECC water injected through the hot legs flows down into the core at so-called “breakthrough channels” located at the outer core region where the downward leg of the convection roll had established. The hotter, lighter coolant rises in the centre of the core. As a consequence, the insulation material is preferably deposited at the uppermost spacer grids positioned in the breakthrough zones. This means that the fibers are not uniformly deposited over the core cross section.
When the inner recirculation stops later in the transient, insulation material can also be collected in other regions of the core. Nevertheless, with a total of 2.7 kg fiber material deposited at the uppermost spacer level, the pressure drop over the fiber cake is not higher than 8 kPa and all the ECC water could still enter the core.

Keywords: CFD; Sump Cooling; Isolation Material

  • Contribution to proceedings
    Jahrestagung Kerntechnik 2011, 16.-19.05.2011, Berlin, Deutschland
    CD-Rom
  • Invited lecture (Conferences)
    Jahrestagung Kerntechnik 2011, 16.-19.05.2011, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15319
Publ.-Id: 15319


Numerical simulation of an horizontal counter-current two-phase flow experiment using an interfacial area density model

Höhne, T.; Deen, D.; Lucas, D.

In order to improve the understanding of counter-current two-phase flows, a CFD simulation of 1/3rd scale model of the hot leg of a German Konvoi PWR with rectangular cross section was performed. A selected air-water counter-current flow limitation (CCFL) experiment at the Forschungszentrum Dresden-Rossendorf (FZD) at 0.306 MPa and room temperature (experimental running of 30-05) was calculated with three-dimensional two-fluid models of computer code ANSYS CFX 13. It was simulated using the multi-fluid Euler-Euler modeling approach. The transient calculation was carried out using a gas/liquid inhomogeneous multiphase flow model coupled with a SST turbulence model for each phase. In the simulation, the surface drag was approached by a new correlation inside the Algebraic Interfacial Area Density (AIAD) model. The AIAD model allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface using the local liquid phase volume fraction value. A comparison with the high-speed video observations shows also a good qualitative agreement (Fig. 1). The results indicated also that quantitative agreement of the CCFL characteristics between calculation and experimental data was obtained.

Keywords: CFD; multiphase flow; horizontal flow; CCFL; AIAD model

  • Contribution to proceedings
    8th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, 21.-23.06.2011, Trondheim, Norwegen
    Proceedings of the 8th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, CD-ROM, paper 083
  • Lecture (Conference)
    8th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, 21.-23.06.2011, Trondheim, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15317
Publ.-Id: 15317


Numerical simulations of counter-current two-phase flow experiments in a PWR hot leg model using an interfacial area density model

Höhne, T.; Deen, D.; Vallee, C.; Lucas, D.; Beyer, M.

In order to improve the understanding of counter-current two-phase flows and to validate new physical models, CFD simulations of 1/3rd scale model of the hot leg of a German Konvoi PWR with rectangular cross section was performed. Selected counter-current flow limitation (CCFL) experiments at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) were calculated with ANSYS CFX 12.1 using the multi-fluid Euler-Euler modeling approach. The transient calculations were carried out using a gas/liquid inhomogeneous multiphase flow model coupled with a SST turbulence model for each phase. In the simulation, the surface drag was approached by a new correlation inside the Algebraic Interfacial Area Density (AIAD) model. The AIAD model allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface using the local liquid phase volume fraction value. A comparison with the high-speed video observations shows a good qualitative agreement. The results indicated that quantitative agreement of the CCFL characteristics between calculation and experimental data was obtained.

Keywords: Numerical simulation; CFD; CCFL; AIAD model; reflux condensation; PWR hot leg; air-water experiment

  • Contribution to proceedings
    The 14th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-14), 25.-29.09.2011, Toronto, Kanada
    Proceedings of the 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics (NURETH-14), CD-ROM
  • Lecture (Conference)
    The 14th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-14), 25.-29.09.2011, Toronto, Kanada

Permalink: https://www.hzdr.de/publications/Publ-15316
Publ.-Id: 15316


CFD-Simulation von Vermischungsvorgängen

Höhne, T.; Kliem, S.; Rohde, U.

Coolant mixing in the cold leg, downcomer and the lower plenum of pressurized water reactors is an important phenomenon mitigating the reactivity insertion into the core. Therefore, mixing of the deborated slugs with the ambient coolant in the reactor pressure vessel was investigated at the four loop 1:5 scaled ROCOM mixing test facility. Thermal hydraulics analysis showed, that weakly borated condensate can accumulate in the pump loop seal of the loops. After refilling of the primary circuit, natural circulation in the stagnant loops which do not receive safety injection can re-establish and the deborated slugs are shifted towards the reactor pressure vessel (RPV). In the ROCOM experiments, the length of the flow ramp and the initial density difference between the slugs and the ambient coolant was varied. From the test matrix experiments with 0-2% density difference between the deborated slugs and the ambient coolant were used to validate the CFD software ANSYS CFX. To model the effects of turbulence on the mean flow a higher order Reynolds stress turbulence model was employed and a mesh consisting of 6.4 million hybrid elements was utilized. Only the experiments and CFD calculations with modeling density differences show stratification in the downcomer. Depending on the degree of density differences the less dense slugs flow around the core barrel at the top of the downcomer. On the opposite side the lower borated coolant is entrained and borated by the colder safety injection water and transported to the core. The validation proves that ANSYS CFX is able to simulate appropriately the flow field and mixing effects of coolant with different densities.

Keywords: CFD; ROCOM; boron dilution; PWR

  • Poster
    Jahrestreffen der Fachausschüsse Computational Fluid Dynamics und Mischvorgänge, 21.-23.02.2011, Dortmund, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15315
Publ.-Id: 15315


Superconducting films fabricated by high fluence Ga implantation in Si

Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Mücklich, A.; Oswald, S.; Schmidt, B.; Skorupa, W.; Gobsch, G.; Wosnitza, J.; Helm, M.

Ga-rich layers in Si were fabricated by 80 keV Ga implantation through a 30 nm SiO2 cover layer and subsequent rapid thermal annealing for 60 s in a temperature range between 500°C and 1000°C. Fluences of 2x1016cm-2 and 4x1016cm-2, leading to Ga peak concentrations of 8 at.% and 16 at.%, are chosen. Residual damage in the implanted layers and the Ga distribution were investigated by Rutherford-backscattering spectrometry in combination with ion channeling, cross-sectional electron microscopy and X-ray photoelectron spectroscopy. Temperature dependent Hall-effect measurements were carried out in order to determine the electrical properties of the implanted layers. It is shown that annealing at temperatures up to 800°C leads to the formation of poly-crystalline layers containing random distributed amorphous clusters. At the Si/SiO2 interface a dense and narrow band of Ga-rich clusters is observed. For 4x1016cm-2 the amount of mobile Ga is higher than for 2x1016cm-2 and an increase of the cluster density at the Si/SiO2 interface was found. Due to the higher cluster density for 4x1016cm-2 this interface layer can become superconducting below 7 K with critical fields exceeding 9 T at optimized annealing conditions. Critical currents are above 1 kA/cm2 and therefore this seems to be a possible material system for future microelectronic applications. After annealing at 900°C and above, the implanted layers are single crystalline and no amorphous precipitates were found.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-15314
Publ.-Id: 15314


Laser cooling of relativistic C3+ ions at the ESR

Bussmann, M.; Kroll, F.; Loeser, M.; Siebold, M.; Schramm, U.; Novotny, C.; Nörtershäuser, W.; Dimopoulou, C.; Nolden, F.; Steck, M.; Kozhuharov, C.; Kühl, T.; Stöhlker, T.; Winters, D. F. A.; Tichelmann, S.; Birkl, G.; Beck, T.; Rein, B.; Walther, T.; Ma, X.; Wen, W.

Recent experiments at the Experimental Storage Ring (ESR) at GSI have shown that relativistic Li-like carbon (C3+) ion beams can be laser-cooled to an un-precedented momentum spread of Δp/p ≈ 10-7. Here, a single-frequency laser was tuned to the Doppler-shifted 1s22s → 1s22p (2P1/2 and 2P3/2) transitions. These results encourage the application of laser cooling to beams of other Li- and Na-like ions at even higher energies, as will e.g. be available at FAIR.

Keywords: storage ring; ion beam; relativistic energy; laser cooling; optical detection; fluorescence; strong coupling

  • Contribution to external collection
    K. Große: GSI Scientific Report, Darmstadt: GSI Helmholtzzentrum für Schwerionenforschung, 2011, 1-582

Permalink: https://www.hzdr.de/publications/Publ-15313
Publ.-Id: 15313


Nanomaterials: applications in cancer imaging and therapy

Barreto, J. A.; O'Malley, W.; Kubeil, M.; Graham, B.; Stephan, H.; Spiccia, L.

The application of nanomaterials (NMs) in biomedicine is increasing rapidly and offers excellent prospects for the development of new non-invasive strategies for the diagnosis and treatment of cancer. In this review, we provide a brief description of cancer pathology and the characteristics which are important for tumor-targeted NM design, followed by an overview of the different types of NMs explored to date, covering synthetic aspects and approaches explored for their application in unimodal and multi-modal imaging, diagnosis and therapy. Significant synthetic advances now allow for the preparation of NMs with highly controlled geometry, surface charge and physicochemical properties, and the decoration of their surfaces with polymers and bioactive molecules in order to improve biocompatibility and achieve active targeting. This is stimulating the development of a diverse range of nano-sized objects that can recognize cancer tissue, enabling visualization of tumors, delivery of anti-cancer drugs and/or the destruction of tumors by different therapeutic techniques.

Permalink: https://www.hzdr.de/publications/Publ-15312
Publ.-Id: 15312


Ultra-thin resistors for piezoresistive sensors

Schmidt, B.; Zier, M.; Philipp, P.; Potfajova, J.

Different ion implantation techniques for the fabrication of shallow boron doped layers used as piezoresistors have been evaluated. In the present case the corresponding process parameters have been optimized to meet demands for high deflection sensitivity of piezoresistive AFM cantilevers. Boron doped layers with decreased pn-junction depths down to ~ 20 nm has been fabricated showing increased deflection sensitivities of (10-20)x106 Ωm-1 compared to conventional implanted resistors. The used ion beam technique fulfills requirements for pn-junctions in terms of small junction depth and low sheet resistance. Additionally, the piezoresistor fabrication processes was evaluated in combination with other ion implanted elements integrated in AFM cantilevers.

Keywords: ion implantation; ultra-shallow pn-junction; piezoresistor; AFM cantilever probe

Related publications

  • Lecture (Conference)
    SENSOR+TEST Conference 2011, 07.-09.06.2011, Nürnberg, Deutschland
  • Open Access Logo Contribution to proceedings
    SENSOR+TEST Conference 2011, 07.-09.06.2011, Nürnberg, Deutschland
    SENSOR+TEST Conference 2011 Proceedings, Wunstorf: AMA Service GmbH, 978-3-9810993-9-3, 222-227

Permalink: https://www.hzdr.de/publications/Publ-15311
Publ.-Id: 15311


Die Bildung von Uran(IV)-Silica-Kolloiden im nahneutralen pH-Bereich

Zänker, H.; Weiss, S.; Hennig, C.; Dreissig, I.; Bernhard, G.

Gewöhnlich wird davon ausgegangen, dass tetravalente Actiniden, An(IV), wegen ihrer Schwerlöslichkeit in natürlichen Wässern immobil sind. Es ist jedoch auch gut bekannt, dass unlösliche Fällungsprodukte mobil sein können, wenn sie als Kolloide auftreten. Für An(IV)-Oxyhydroxide wurde dieses Phänomen umfassend studiert.Hier beschreiben wir einen neuen Typ von An(IV)-Kolloiden. Mit Hilfe von Photonenkorrelationsspektroskopie (PCS), Ultrafiltration und Ultrazentrifugation wird nachgewiesen, dass Uran(IV) silikathaltige Kolloide bilden kann. Diese U(IV)-Silica-Partikel entstehen in nahneutralen bis leicht alkalischen Lösungen mit Inhaltsstoffen geogener Natur (Carbonat, Silikat, Natriumionen). Unter Luftausschluss bleiben sie über Jahre in wässriger Suspension stabil. Es wurde eine Konzentration von bis zu 10 hoch -3 M an kolloidgetragenem U(IV) beobachtet, was eine deutlich höhere Konzentration als die bisher für den nahneutralen pH-Bereich berichteten Konzentrationen echt gelöster oder kolloidal suspendierter An(IV)-Spezies darstellt. Die vorherrschende Größe der Nanopartikel hängt von der Silikatkonzentration sowie vom pH-Wert ab und liegt unter 20 nm. Mit Laser-Doppler-Velocimetrie wurde gefunden, dass die Partikel durch elektrostatische Abstoßung infolge eines durch das Silikat negativeren Zetapotenzials im wassergetragenen Zustand stabilisiert werden. Messungen mittels Extended X-ray absorption fine structure (EXAFS) spectroscopy zeigten, dass U-O-Si-Bindungen, welche mit steigender Silikatkonzentration die U-O-U-Bindungen des amorphen U(IV)-Oxyhydroxids ersetzen, die innere Struktur der Kolloide bilden. Die Next-neighbor-Koordination des U(IV) ist vergleichbar mit der des Coffinits, USiO4.

Keywords: uranium(IV); silica; colloids; PCS; zeta potential; EXAFS

Related publications

  • Lecture (Conference)
    Jahrestagung Nuklearchemie. Wissenschaftsforum Chemie 2011, 04.-07.09.2011, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15310
Publ.-Id: 15310


Lasergetriebene Protonenbeschleuniger auf dem Weg zur Strahlentherapie

Schramm, U.

Eingeladener Key Note Vortrag: 20. Symposium zur Experimetellen Strahlentherapie und Klinischen Strahlenbiologie

  • Invited lecture (Conferences)
    20. Symposium Experimentelle Strahlentherapie und Klinische Strahlenbiologie, 11.02.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15309
Publ.-Id: 15309


Nuclear Transmutation Research at nELBE

Junghans, A. R.

Nuclear Transmutation Research at nELBE

Related publications

  • Invited lecture (Conferences)
    Institute Seminar, 03.05.2010, Daejeon, Korea

Permalink: https://www.hzdr.de/publications/Publ-15308
Publ.-Id: 15308


In-Vivo Dosimetry for Photon Radiotherapy Based on Pair Production

Kormoll, T.; Kunath, D.; Enghardt, W.

Experience during percutaneous ion beam therapy at Gesellschaft für Schwerionenforschung showed that the treatment can be improved by in-vivo dose monitoring that is independent of the irradiation device and based on positron emission tomography. It has been studied whether a similar technique can be implemented for high energy photon therapy. Simulation shows that the dose is closely related to the distribution of the annihilation points of positrons emerging from pair production. Design parameters of a detector system have been assessed which is capable of registering annihilation radiation during treatment. A test system has been assembled which can be operated with various scintillator crystals and avalanche photodiodes. A custom digital signal processing
system has been implemented. Phantom experiments at a clinical linear accelerator disclosed a severe background that does not solely stem from scattered primary photons but from radiation directly emitted from the treatment head. It was not possible to shield the detectors sufficiently and thus there was no success in identifying annihilation radiation.

Keywords: Biomedical applications of radiation; dosimetry; gamma-ray detectors; nuclear imaging; positron emission tomography

  • IEEE Transactions on Nuclear Science 57(2010)3, 1125-1131
    DOI: 10.1109/TNS.2010.2044516
  • Contribution to proceedings
    IEEE Nuclear Science Symposium and Madical Imaging Conference, 25.-31.10.2009, Orlando, Florida, USA

Permalink: https://www.hzdr.de/publications/Publ-15307
Publ.-Id: 15307


Study of Cu+, Ag+ and Au+ ion implantation into silicate glasses

Svecova, B.; Nekvindova, P.; Mackova, A.; Malinsky, P.; Kolitsch, A.; Machovic, V.; Stara, S.; Mika, M.; Spirkova, J.

A study of the ion implantation of Cu+, Ag+ or Au+ ions into different types of silicate glasses is reported. The energy of the implanted ions was 330 key and the implantation fluence was kept at 1 x 1016 cm-2. The samples were characterised by various analytical methods: Rutherford backscattering spectrometry for the concentration depth profiles of the implanted atoms, Raman spectroscopy for the structure of the samples and also by UV-VIS absorption spectroscopy. The obtained data were evaluated on the bases of the structure of the glass matrix and the relations between the structural changes and optical properties, important for photonics applications, were formulated.
The main focus was the impact of various types and concentrations of glass network modifiers (e.g. Li, Na, K, Mg, Ca or Zn) as well as glass network formers (Si, and B) on the projected range of the implanted ions. Interesting results were also provided by a study of the annealing of the as-implanted samples in various types of glass substrates. The study showed that each of the implanted ions migrated in the substrates with different glass structures via unique mechanisms.

Keywords: glass; ion implantation; RBS; Raman; UV-VIS

Related publications

Permalink: https://www.hzdr.de/publications/Publ-15306
Publ.-Id: 15306


Measurement of the sound velocity in fluids using the echo signals from scattering particles

Lenz, M.; Bock, M.; Kühnicke, E.; Pal, J.; Cramer, A.

With conventional methods the sound velocity c in fluids can be determined using the back wall echo. This paper proposes a novel technique, in which the signals reflected by scattering particles suspended in the fluid are analysed instead. The basic idea is that the particles generate the strongest echo signal when being located in the sound field maximum. Therefore the position of the echo signal maximum is a measure for the sound propagation time to the sound field maximum. Provided that calibration data or sound field simulations for the ultrasonic transducer are available, this propagation time suffices to determine both the sound velocity and the location of the sound field maximum. The feasibility of the new approach is demonstrated by different kinds of experiments: (i) Measurements of the sound velocity in four fluids covering the wide range between c = 1116 m/s and 2740 m/s. The results show good agreement with values published elsewhere. (ii) Using the dependence of the sound velocity on temperature, it is possible to vary c over the comparatively small range between 1431 m/s and 1555 m/s with increments of less than 10 m/s. The measured statistical variation of 1.4 m/s corresponds to a relative uncertainty not worse than 0.1%. (iii) The focus position, i. e. the distance of the maximum of the sound field from the transducer, was varied by time-shifted superposition of the receive signals belonging to the different elements of an annular array. The results indicate that the novel method is even capable of measuring profiles of the sound velocity along the ultrasonic beam non-invasively.

Keywords: sound velocity; sound field; non-invasive measurement; scatterers; annular array; sparse array

  • Ultrasonics 52(2011)1, 117-124

Permalink: https://www.hzdr.de/publications/Publ-15305
Publ.-Id: 15305


Accurate stopping power determination of 15N ions for hydrogen depth profiling by a unique combination of ion beams and synchrotron radiation

Zier, M.; Reinholz, U.; Riesemeier, H.; Radtke, M.; Munnik, F.

Hydrogen plays an important role in many areas of material sciences. For example, hydrogen is an abundant impurity in thin-film materials - depending on the deposition process - and has great influence on the chemical, physical and electrical properties of many materials. Therefore, hydrogen analysis is of particular importance and it is often necessary to obtain a depth profile of the H-concentration. Best-suited methods for depth-resolved hydrogen analysis are ion beam techniques such as elastic recoil detection (ERD) and nuclear reaction analysis (NRA). In principle, both methods can be performed as primary - reference material free - methods.

The method with the best depth resolution is NRA using the 6385 keV resonance of the 1H(15N,αγ)12C nuclear reaction. The correct quantification of the depth scale in the measured hydrogen profiles essentially relies on accurate stopping power values. The most commonly used stopping power values are from the SRIM program [1]. Here, the stopping power for heavy ions is calculated using the stopping power for hydrogen and an effective charge. The parameters for the effective charge are based on a fit of experimental data. Due to the lack of reliable experimental data, the uncertainty in the stopping powers, thus obtained, can be quite large and is only known in the widest sense (as the average deviation between experiment and SRIM for all elements or all ions). Therefore, we present a new method to deduce these values from a unique combination of two techniques: NRA and X-ray reflectometry (XRR), also a primary method. This method is applied to the determination of the accurate stopping power of ~6.4 MeV 15N ions in H-containing amorphous Si-layers (a-Si:H).

The samples are prepared by magnetron sputtering of a-Si in an Ar/H2-atmosphere on a Cr-layer, which is needed as contrast material for XRR. The energy loss in the layers is measured by NRA at HZDR and the H-content has also been determined by NRA [2]. The layer thickness, density and roughness are determined by XRR using synchrotron radiation. XRR measurements were performed at the electron storage ring BESSY at the hard X-ray beamline BAMline [3]. The beam was monochromatised to 10 keV using a Si[111]-double-crystal monochromator. The reflected photons of the θ-2θ-scans from the 6-circle goniometer are counted by a scintillation detector and a photodiode, respectively. Data analysis is performed by the IMD 4.1 software package [4].

The combination of results from NRA and XRR allows the accurate calculation of the mass stopping power independent of the density of the material. The results for the H-containing amorphous Si-layers are presented, including a discussion of the uncertainty budget. Stopping powers at different H concentrations, ranging from 6 at.% to 14 at.%, are determined with an overall uncertainty of 3%. The preliminary results show a reasonable agreement with the SRIM values, thereby increasing the confidence in the results obtained by NRA.
[1] J. F. Ziegler, J. P. Biersack and U. Littmark, “The Stopping and Range of Ions in Solids", Pergamon Press, New York, 2009, http://www.srim.org.
[2] D. Grambole et al, Nucl. Instr. Meth. B 210 (2003) 526.
[3] W. Görner et al., Insight-Non-Destr. Test. Cond. Monit. 48 (2006) 540.
[4] D.L. Windt, Comp. in Physics 12 (1998) 360.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-15304
Publ.-Id: 15304


The nELBE neutron time-of-flight facility

Junghans, A. R.; Altstadt, E.; Beckert, C.; Beyer, R.; Galindo, V.; Grosse, E.; Hannaske, R.; Matic, A.; Mosconi, M.; Naumann, B.; Nolte, R.; Röttger, S.; Schilling, K. D.; Schlenk, R.; Schneider, S.; Schwengner, R.; Wagner, A.; Weiss, F.-P.

At the superconducting electron linear accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf the neutron time-of-flight facility nELBE has become operational. Fast neutrons in the energy range from 200 keV to 10 MeV are produced by the pulsed electron beam from ELBE impinging on a liquid lead circuit as a radiator. The short beam pulses of 10 ps provide the basis for an excellent time resolution for neutron time-of-flight experiments, giving an energy resolution of about <1% at 1 MeV with a short ight path of 5 m. The neutron intensity on target is ≈ 4*10^4 n/(cm2s) using an electron bunch charge of 77 pC and 100 kHz pulse repetition rate. The energy range of the neutrons produced is well suited for neutron cross section measurements relevant for the development of Generation IV reactor systems and for the transmutation of nuclear waste. First measurements of inelastic neutron scattering cross sections have been performed and will be presented.

Related publications

  • Contribution to proceedings
    IEEE Nuclear Science Symposium 2008, 19.-25.10.2008, Dresden, Deutschland
    The nELBE neutron time-of-flight facility, 2909
    DOI: 10.1109/NSSMIC.2008.4774974
    Cited 1 times in Scopus
  • Lecture (Conference)
    IEEE Nuclear Science Symposium, 19.-25.10.2008, Dresden, Deutschland
  • Journal of the Korean Physical Society 59(2011), 1593-1596
    DOI: 10.3938/jkps.59.1593

Permalink: https://www.hzdr.de/publications/Publ-15303
Publ.-Id: 15303


Electromagnetic strength in heavy nuclei – experiments and a global fit

Beyer, R.; Birgersson, E.; Junghans, A. R.; Massarczyk, R.; Schramm, G.; Schwengner, R.; Grosse, E.

A global parameterization is presented for the electromagnetic strength in heavy nuclei which gives a rather good fit to respective data in nuclei with mass numbers A between 50 and 240. It relies on a Lorentzian description of the isovector giant dipole resonance and it needs only a very small number of parameters to describe the electric dipole strength down to low excitation energy of importance for radiative capture processes. The resonance energies are chosen to be in accordance to liquid drop model parameters adjusted to ground state masses and to rotation invariant determinations of ground state deformation and triaxiality. By a straightforward use of this information a surprisingly smooth variation of the GDR width with A and Z is found and a full agreement to the predictions of the electromagnetic sum rule is assured. Predictions for radiative neutron capture cross sections compare well to respective data, when the proposed photon strength function is combined with standard prescriptions for the level density in the product nuclei.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-15302
Publ.-Id: 15302


The Electron-Ion Scattering experiment ELISe at the International Facility for Antiproton and Ion Research (FAIR) – a conceptual design study

Antonov, A. N.; Gaidarov, M. K.; Ivanov, M. V.; Kadrev, D. N.; Aïche, M.; Barreau, G.; Czajkowski, S.; Jurado, B.; Belier, G.; Chatillon, A.; Granier, T.; Taieb, J.; Dor´C, D.; Letourneaux, A.; Ridikas, D.; Dupont, E.; Berthoumieux, E.; Panebianco, S.; Reymund, F.; Schmitt, C.; Audouin, L.; Khan, E.; Tassan-Got, L.; Aumann, T.; Beller, P.; Boretzky, K.; Dolinskii, A.; Egelhof, P.; Emling, H.; Franzke, B.; Geissel, H.; Kelic-Heil, A.; Kester, O.; Kurz, N.; Litvinov, Y.; Münzenberg, G.; Nolden, F.; Schmidt, K.-H.; Simon, H.; Steck, M.; Weick, H.; Enders, J.; Pietralla, N.; Richter, A.; Schrieder, G.; Zilges, A.; Distler, M. O.; Merkel, H.; Müller, U.; Junghans, A.; Lenske, H.; Fujiwara, M.; Suda, T.; Kato, S.; Adachi, T.; Hamieh, S.; Harakeh, M. N.; Kalantar-Nayestanaki, N.; Wörtche, H.; Berg, G. P. A.; Koop, I. A.; Logatchov, P. V.; Otboev, A. V.; Parkhomchuk, V. V.; Shatilov, D. N.; Shatunov, P. Y.; Shatunov, Y. M.; Shiyankov, S. V.; Shvartz, D. I.; Skrinsky, A. N.; Chulkov, L. V.; Danilin, B. V.; Korsheninnikov, A. A.; Kuzmin, E. A.; Ogloblin, A. A.; Volkov, V. A.; Grishkin, Y.; Lisin, V. P.; Mushkarenkov, A. N.; Nedorezov, V.; Polonski, A. L.; Rudnev, N. V.; Turinge, A. A.; Artukh, A.; Ershov, S. N.; Fomichev, A.; Golovkov, M.; Gorshkov, A. V.; Grigorenko, L.; Klygin, S.; Krupko, S.; Meshkov, I. N.; Rodin, A.; Sereda, Y.; Seleznev, I.; Sidorchuk, S.; Syresin, E.; Stepantsov, S.; Ter-Akopian, G.; Teterev, Y.; Vorontsov, A. N.; Kamerdzhiev, S. P.; Litvinova, E. V.; Karataglidis, S.; Alvarezrodriguez, R.; Borge, M. J. G.; Fernandezramirez, C.; Garrido, E.; Sarriguren, P.; Vignote, J. R.; Fraileprieto, L. M.; Lopezherraiz, J.; Moyadeguera, E.; Udias-Moinelo, J.; Amarosoriano, J. E.; Lallena Rojo, A. M.; Caballero, J. A.; Johansson, H. T.; Jonson, B.; Nilsson, T.; Nyman, G.; Zhukov, M.; Avdeichikov, V.; Hencken, K.; Jourdan, J.; Krusche, B.; Rauscher, T.; Kiselev, D.; Trautmann, D.; Al-Khalili, J.; Catford, W.; Johnson, R.; Stevenson, P.; Barton, C.; Jenkins, D.; Lemmon, R.; Chartier, M.; Cullen, D.; Heinz, A.; Bertulani, C. A.

The Electron-Ion Scattering experiment ELISe at the International Facility for Antiproton and Ion Research (FAIR) – a conceptual design study

Permalink: https://www.hzdr.de/publications/Publ-15301
Publ.-Id: 15301


Production of new neutron rich isotopes of heavy elements in fragmentation reactions of 238U projectiles at 1 AGeV

Alvarez Pol, H.; Benlliure, J.; Audouin, L.; Casarejos, E.; Cortina Gil, D.; Enqvist, T.; Fernandez Dominguez, B.; Junghans, A. R.; Jurado, B.; Napolitani, P.; Pereira, J.; Rejmund, F.; Schmidt, K. H.; Yordanov, O.

The production of heavy neutron-rich nuclei has been investigated using cold-fragmentation reactions of U 238 projectiles at relativistic energies. The experiment performed at the high-resolving-power magnetic spectrometer Fragment Separator at GSI made it possible to identify 40 new heavy neutron-rich nuclei: Pt 205 , Au 207−210 , Hg 211−216 , Tl 214−217 , Pb 215−220 , Bi 219−224 , Po 223−227 , At 225−229 , Rn 230,231 , and Fr 233 . The production cross sections of these nuclei were also determined and used to benchmark reaction codes that predict the production of nuclei far from stability.

Permalink: https://www.hzdr.de/publications/Publ-15300
Publ.-Id: 15300


Measurement of the inelastic neutron scattering cross section of 56Fe

Beyer, R.; Birgersson, E.; Ferrari, A.; Gehre, D.; Grosse, E.; Hannaske, R.; Junghans, A. R.; Massarczyk, R.; Matic, A.; Nolte, R.; Schilling, K.-D.; Schwengner, R.; Wagner, A.

Measurement of the inelastic neutron scattering cross section of 56Fe

Related publications

  • Lecture (Conference)
    EFNUDAT Measurements and Models of Nuclear Reactions, 25.-27.05.2010, Paris, France
  • Open Access Logo Contribution to proceedings
    EFNUDAT Measurements and Models of Nuclear Reactions, 25.-27.05.2010, Paris, France
    EPJ web of conferences 8 (2010) 07007
    DOI: 10.1051/epjconf/20100807007

Permalink: https://www.hzdr.de/publications/Publ-15299
Publ.-Id: 15299


Operation of the liquid lead loop at nELBE

Junghans, A. R.

Operation of the liquid lead loop at nELBE

Related publications

  • Lecture (Conference)
    Scientific workshop on Neutron measurements , Theory and Applications Nuclear Data for Sustainable Nuclear Energy, 28.-30.04.2009, Geel, Belgium
  • Contribution to proceedings
    Scientific workshop on Neutron measurements , Theory and Applications Nuclear Data for Sustainable Nuclear Energy, 28.-30.04.2009, Geel, Belgium
    EFNUDAT Fast Neutrons - Proceedings of the Scientific Workshop on Neutron Measurements, 978-92-79-11705-3, 73-77

Permalink: https://www.hzdr.de/publications/Publ-15298
Publ.-Id: 15298


The nELBE neutron time of flight facility

Junghans, A. R.

The nELBE neutron time of flight facility

Related publications

  • Lecture (Conference)
    International Conference on Nuclear Data for Science and Technology 2010, 26.-30.04.2010, Jaju Island, Korea
  • Contribution to proceedings
    International Conference on Nuclear Data for Science and Technology 2010, 26.-30.04.2010, Jeju Island, Korea
    Journal of the Korean Physical Society 59, 1593-1596

Permalink: https://www.hzdr.de/publications/Publ-15297
Publ.-Id: 15297


Inelastic neutron scattering measurements at the photoneutron source nELBE

Junghans, A. R.

Inelastic neutron scattering measurements at the photoneutron source nELBE

Related publications

  • Lecture (Conference)
    Workshop on (in)elastic neutron scattering, 06.-07.12.2010, Strasbourg, France
  • Lecture (Conference)
    Workshop on Gamma Strength and Level Density in Nuclear Physics and Nuclear Technology, 30.08.-03.12.2010, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15296
Publ.-Id: 15296


Transmutation radioaktiven Abfalls - Grundlagen, Methoden, Perspektiven

Junghans, A. R.

Transmutation radioaktiven Abfalls - Grundlagen, Methoden, Perspektiven

Related publications

  • Invited lecture (Conferences)
    Physikalische Kolloquium, 14.01.2011, Darmstadt, Deutschland
  • Invited lecture (Conferences)
    74. Jahrestagung der DPG und DPG Frühjahrstagung der Fachverbände 2010, 15.-19.03.2010, Bonn, Deutschland
  • Invited lecture (Conferences)
    Jährliches Behördenseminar, 18.11.2010, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15295
Publ.-Id: 15295


Mechanische Analyse für den Sumpf des SHB des Kernkraftwerks Brunsbüttel (KKB)

Werner, M.; Altstadt, E.

Es handelt sich um einen vertraulichen Bericht, deshalb kein Abstract.

  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2011
    HZDR\FWS\2011\01
    7 Seiten
    ISSN: 1437-322X

Permalink: https://www.hzdr.de/publications/Publ-15294
Publ.-Id: 15294


Cross section in deuteron-proton elastic scattering at 1.25 GeV/u

Kurilkin, P. K.; Agakishiev, G.; Balanda, A.; Belver, D.; Belyaev, A.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Castro, E.; Chernenko, S.; Díaz, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gil, A.; Golubeva, M.; González-Díaz, D.; Guber, F.; Hennino, T.; Holzmann, R.; Huck, P.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kopp, A.; Korcyl, G.; Kornakov, G. K.; Kotte, R.; Kozuch, A.; Krása, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Kurilkin, A.; Kählitz, P.; Ladygin, V.; Lamas-Valverde, J.; Lang, S.; Lapidus, K.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Müntz, C.; Naumann, L.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roskoss, J.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Weber, M.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.

First results of the differential cross section in dp elastic scattering at 1.25 GeV/u measured with the HADES over a large angular range are reported. The obtained data corresponds to large transverse momenta, where a high sensitivity to the two-nucleon and three-nucleon short-range correlations is expected.

  • Contribution to WWW
    Proc. XXth Int. Baldin Seminar on High Energy Physics Problems "Relativistic Nuclear Physics and Quantum Chromodynamics", JINR, Dubna, Russia, October 4-9, 2010: http://de.arxiv.org/abs/1102.1610

Permalink: https://www.hzdr.de/publications/Publ-15292
Publ.-Id: 15292


Sorption of U(VI) at the TiO2 – water interface: An in situ vibrational spectroscopic study.

Müller, K.; Foerstendorf, H.; Meusel, T.; Brendler, V.; Comarmond, M. J.; Lefèvre, G.; Payne, T. E.

Molecular-scale knowledge of U(VI) sorption reactions at the water-mineral interface is important for predicting U(VI) transport processes in the environment. In this work, in situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy was used in a comprehensive investigation of the sorption processes of U(VI) onto TiO2. The high sensitivity of the in situ ATR FT-IR technique allows the study of U(VI) concentrations down to the low micromolar range, which is relevant to most environmental scenarios.
A set of highly purified and well characterized TiO2 phases differing in their origin, the ratio of the most stable polymorphs (anatase and rutile), in specific surface area, isoelectric points and in particle size distribution was investigated. Irrespective of the composition of the mineral phase, it was shown that U(VI) forms similar surface complexes, which was derived from the antisymmetric stretching mode υ3(UO2) showing a characteristic shift to lower wavenumbers compared to the respective aqueous species at a similar low concentration level.
The availability of a fast scanning IR device makes it feasible to perform time-resolved experiments of the sorption processes with a time resolution in the sub-minute range. It is shown that during the early stages of the U(VI) uptake a surface species on the mineral phase is formed characterized by a significantly red-shifted absorption maximum which is interpreted as a bidendate inner-sphere complex. After prolonged sorption, the IR spectra indicate the formation of a second surface species showing a smaller shift compared to the aqueous species. These findings were verified by a series of spectroscopic experiments performed on a U(VI)-saturated surfaces.
Further ATR FT-IR spectroscopic experiments focused on the impact of the U(VI) concentration, the pH value and the exclusion of atmospheric carbonate on the sorption process. The results confirm the presence of two surface species, occurring sequentially as a function of U(VI) surface loading.
This work provides new insights into the sorption processes of U(VI) on titanium dioxide on a molecular level. Basic thermodynamic ideas of surface complexation are substantiated by in situ infrared spectroscopy.

Permalink: https://www.hzdr.de/publications/Publ-15291
Publ.-Id: 15291


FEL's @ ELBE

Seidel, W.

Two free-electron lasers (FELBE; 4-21 μm and 18-250 μm, respectively) have been in routine user operation for a wide range of IR experiments at the radiation source ELBE in the Forschungszentrum Dresden-Rossendorf for several years. The lasers are driven by a superconducting RF linac that permits the generation of a cw-beam with a repetition rate of 13 MHz and a high average beam power. In addition, operation in a macropulse modus (pulse duration >100 µs, repetition rate ≤ 25 Hz) is possible. A few important experiments using the cw-operation are discussed.

Related publications

  • Lecture (Conference)
    German-Turkish Workshop on Superconducting Accelerators for FEL- and Bremsstrahlung Applications, 31.01.-03.02.2011, Antalya, Turkey

Permalink: https://www.hzdr.de/publications/Publ-15290
Publ.-Id: 15290


Realization of the Nijmegen THz-FEL

Jongma, R. T.; Engels, A. C. N.; Lof, R. W.; Wijnen, F. J. P.; Wulterkens, G. F. A. J.; Zhaunerchyk, V.; van Dael, P. A. W.; van Roij, A. J. A.; van Vliet, A. P.; van der Zande, W. J.; Dunkel, K.; Piel, C.; Lehnert, U.; Michel, P.; Seidel, W.; Wuensch, R.; van der Meer, A. F. G.

The Radboud University in Nijmegen received funding to realize a narrow-band THz laser system and a 45 T hybrid magnet system. In this paper we present the technical solutions for realization of the main system components. We present the details of the RI Research Instruments GmbH (a former ACCEL Instruments GmbH activity) LINAC system. Operation of the full system (including the electron source) at 3 GHz is desirable and deemed feasible after first experimental studies. As the Nijmegen FEL will operate at wavelength up to 1.5 mm, the cavity will be fully waveguided, complicating the incorporation of an intra-cavity Fox-Smith interferometer required to induce coherence between micropulses and a Michelson interferometer as most ideal outcoupler. The optical distribution system comprises 150 m of vacuum tubing with 25 cm effective diameter (planar and refocusing) mirrors. A robust yet cost efficient realization taking boundary conditions on optical beam parameters at diagnostics station and user stations into account is foreseen.

Related publications

  • Poster
    31st International Free Electron Laser Conference 2009, 23.-28.08.2009, Liverpool, UK
  • Contribution to proceedings
    31st International Free Electron Laser Conference 2009, 23.-28.08.2009, Liverpool, UK

Permalink: https://www.hzdr.de/publications/Publ-15289
Publ.-Id: 15289


In-vivo dosimetry for proton and ion therapy

Fiedler, F.

no abstract available

Keywords: in-vivo dosimetry

  • Invited lecture (Conferences)
    6th Meeting of the Scientific Advisory Board of OncoRay, 10.02.2011, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-15288
Publ.-Id: 15288


PM-IRRAS mapping of ultrathin molecular films with high spatial resolution

Steiner, G.; Sablinskas, V.; Seidel, W.; Salzer, R.

Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) is a very sensitive technique to characterize the degree of molecular ordering in thin films on metallic surfaces. This is the first report of the coupling of a PM-IRRAS microscope to a free electron laser (FEL), a light source of highest brilliance. Some FELs emit in the infrared region and permit the mapping of molecular properties at high lateral resolution. We studied the molecular orientation of octadecanephosphonic acid (OPA) attached to a gold surface with microstructured aluminum oxide islands on the gold. The spatial resolution achieved is 12 μm which corresponds to the diffraction limit of the infrared light used in this study. This is a substantial improvement compared to previous studies using a PM-IRRA accessory together with a commercial Fourier transform infrared spectrometer, where the lateral resolution is noise-limited rather than diffraction-limited. The spectral maps reveal that OPA is preferably attached to the aluminum oxide islands via the bidentate binding mode whereas the tridentate mode is dominating in case of OPA attached to the gold areas.

Keywords: PM-IRRAS; Mapping; Free electron laser; Self-assembly monolayer

Related publications

  • Analytical and Bioanalytical Chemistry 395(2009), 1641-1650

Permalink: https://www.hzdr.de/publications/Publ-15287
Publ.-Id: 15287


Interaction of Chlorella vulgaris and Schizophyllum commune with U(VI)

Vogel, M.; Günther, A.; Gube, M.; Raff, J.; Kothe, E.; Bernhard, G.

For a risk assessment for released radionuclides a comprehensive elucidation of the migration behavior of uranium is necessary. Therefore not only the uranium interactions with the geosphere but also with the biosphere have to be investigated.
The aim of the study was to characterize the sorption of U(VI) by living Chlorella vulgaris and Schizophyllum commune and the molecular structure of formed complexes.
Both organisms bind significant amounts of U(VI) dependent on applied uranium concentration and pH in the range from 4 to 7. At uranium concentration of 0.2 mM Schizophyllum shows binding capacities of around 130 mg U/g dry weight independent of pH value. A higher initial uranium concentration leads to higher binding capacities of 230-280 mg U/g dry weight at pH 5 and 6 for still living Schizophyllum biomass. In contrast to that, Chlorella binds at a uranium concentration of 0.5 mM 75 mg U/g dry weight (pH 4.4). Furthermore, Chlorella cells die at concentration higher than 0.1 mM within 48 h. Therefore further experiments were carried out at a concentration of 5 µM. Under this condition living algae firstly bind almost all uranium within 5 min of incubation, but then again mobilize up to 80% of the bound uranium during ongoing incubation. The release of metabolism related substances is suggested to cause this mobilization of uranium. As potential leachates for algal-bound uranium oxalate, citrate and ATP were tested and found to be able to mobilize 55-87% of the algal-bound uranium within 24 h.
Differences in complexation of uranium by active and inactive algae cells as well as fungal biomass were investigated with a combination of different spectroscopic techniques. Obtained results demonstrated an involvement of carboxylic and organic/inorganic phosphate groups in the uranium complexation with varying contributions dependent on microbial biomass, cell status, uranium concentration and pH.

Keywords: uranium; sorption; Chlorella; Schizophyllum

Related publications

  • Lecture (Conference)
    6th International Conference Uranium Mining and Hydrogeology, 18.-22.09.2011, Freiberg, Deutschland
  • Contribution to proceedings
    6th International Conference Uranium Mining and Hydrogeology, 18.-22.09.2011, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15285
Publ.-Id: 15285


A simple method to prepare microorganisms for AFM analysis

Günther, T.; Raff, J.; Pollmann, K.

Nowadays AFM becomes a more and more attractive method for microbiologists to investigate Microorganisms. The technique allows imaging over a broad magnitude scale and is not confined by the diffraction limit. Sometimes it is interesting to measure the dimensions of an organism. The other time the question is about surface properties of a cell. The scanning principle makes the AFM technique comparatively slow and the specimen has to be fixed on a flat surface during the scans. It is quite simple to dry the samples on a surface. Drying leads to a good immobilization but also to drying artifacts like denaturation of Proteins and shrinkage of the whole cell due to the loss of water. Therefore it is advantageous for most biological questions to do the imaging in liquids. Immobilization is not trivial as result of the heterogeneous surface properties of different micro organisms. Existing preparation methods are mostly utilizing coated surfaces or lithographicaly prepared surfaces. While lithography is not an option for everyone there is a variety of coatings available for instance poly-L-lysine or gelatine which work quite good with some microorganisms. A new method based on polyelectrolyte coated surfaces combined with centrifugal sedimentation shows promising results regarding the efficiency of immobilization. A variety of micro organisms were tested with the new method showing universality for many organisms. The samples were prepared with and without fixation. Of course fixation simplifies the imaging by enhancing the stability of the samples. But even unfixed Microorganisms can be imaged which opens the field for investigations in respect to cell division or other dynamic processes of living cells.

  • Lecture (Conference)
    Jahrestagung der Vereinigung für allgemeine und angewandte Mikrobiologie, 03.-06.04.2011, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15284
Publ.-Id: 15284


Effect of temperature and humic acid on the U(VI) diffusion in compacted Opalinus Clay

Joseph, C.; van Loon, L. R.; Jakob, A.; Schmeide, K.; Sachs, S.; Bernhard, G.

Beside salt dome and granite rock, argillaceous rock is discussed as host rock for a nuclear waste repository. For safety assessment, knowledge about the migration behavior of the actinides is required. In this study, the interaction of U(VI) (110-6 M) with the natural clay rock Opalinus Clay (OPA) from Mont Terri, Switzerland was investigated by diffusion experiments under anaerobic conditions using synthetic OPA pore water [1] as background electrolyte and intact bore cores (diameter: 2.57 cm, thickness: 1.1 cm, density: 2.4 g/cm3).
Due to radioactive decay of the radionuclides, temperatures in the near-field of a nuclear waste repository in argillaceous rock are likely to be increased to ≤ 100°C [2], which can impact the migration behavior of actinides. Thus, the U(VI) diffusion in OPA was investigated in dependence on temperature (25 and 60°C).
Humic acids (HA) occur ubiquitously in nature. They are able to influence the migration of actinides due to their ability for complex and colloid formation and their redox properties. Thus, the influence of HA (10 mg/L) on the U(VI) diffusion was also studied.
At first, HTO diffusion experiments were performed for determination of the diffusion parameters of the OPA samples. The obtained HTO diffusion coefficients and porosities agreed with literature values.
After three months of diffusion time the U(VI) diffusion profiles in the OPA bore core samples were determined. The U(VI) diffusion profiles showed that, compared to the experiment at 25°C, the U(VI) diffusion is increased within the first 1.5 mm at 60°C. After 1.5 mm this effect levels off, which can be attributed to the increased sorption of U(VI) at 60°C. In the presence of HA, at 60°C and diffusion distances ≥ 800 µm, a lower amount of U(VI) was detected in the clay. That means, the U(VI) diffusion was hindered by the presence of HA.
Currently, diffusion and distribution coefficients are determined by fitting of the U(VI) and HA diffusion profiles using the modeling software COMSOL Multiphysics 3.3 [3]. The results will be compared to results of sorption experiments with OPA [4].

[1] F.J. Pearson (1998) PSI Internal report TM-44-98-07, PSI, Villigen, Switzerland.
[2] T. Brasser, et al. (2008), GRS-247, GRS, Braunschweig, Germany.
[3] Finite-element software package. http://www.comsol.com.
[4] C. Joseph, et al. (2011), Chem. Geol., accepted.

Keywords: Opalinus Clay; diffusion; uranium(VI); humic acid; temperature

  • Contribution to proceedings
    6th International Conference Uranium Mining Hydrogeology (UMH VI), 18.-22.09.2011, Freiberg, Germany
  • Lecture (Conference)
    6th International Conference Uranium Mining Hydrogeology (UMH VI), 18.-22.09.2011, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-15283
Publ.-Id: 15283


Two-dimensional ultrasound Doppler velocimeter for investigations of liquid metal flows

Franke, S.; Lieske, H.; Fischer, A.; Büttner, L.; Czarske, J.; Räbiger, D.; Eckert, S.

In the research area of magnetohydrodynamics (MHD) the pulsed-wave ultrasound Doppler velocimetry (UDV) is a worthwhile measurement technique for flow field investigations of liquid metal flows. Thereto, several UDV instruments are available on the market. However, their capability for two-dimensional mapping of flows is highly limited due to restricted number of scanning elements (max. 20 transducers) and low temporal resolution. Hence, an ultrasound Doppler velocimeter based on ultrasound arrays is developed which allows the measurement of both flow field vectors in the measuring plane of 67 x 67 mm². Thereby, it provides high measurement rates and a high spatial resolution with a significant increased number of scanning lines simultaneously.
The linear ultrasound transducer arrays are arranged orthogonally to each other. There each array measures one flow field component by electronic traversing.
The ultrasound arrays comprise 2x 25 transducer elements each with a centre frequency of 8 MHz and a piezo element size of 2.5 x 5 mm². In operation two adjacent elements are combined to a square transducer pair of 5 x 5 mm² allowing a small lateral scanning step width of 2.5 mm on the one hand and a low divergence of the ultrasound beam and according to this a high lateral resolution up to 2 mm on the other hand.
The requirements for a high temporal resolution and a high number of scanning lines are opponent. To achieve a high measurement rate nevertheless, the measurement is parallelized as much as possible by simultaneous operation of four transducer pairs. Thereby a specific distance between the active transducer pairs avoids spatial crosstalk. For the same reason both arrays are actuated alternatively. This excitation scheme is implemented by a fast multiplex electronics which is a proprietary development. Depending on the averaging time frame rates up to 33 Hz are achieved at pulse repetition rates of 1.5 kHz.

Keywords: ultrasound Doppler velocimetry; array sensor; flow mapping; rotating magnetic field; electromagnetic stirring

  • Lecture (Conference)
    Sensor+Test 2011, 07.-09.06.2011, Nürnberg, Deutschland
  • Contribution to proceedings
    Sensor+Test 2011, 07.-09.06.2011, Nürnberg, Deutschland
    Sensor Proceedings, 165-170

Permalink: https://www.hzdr.de/publications/Publ-15282
Publ.-Id: 15282


Two-dimensional ultrasound Doppler velocimeter for velocity field measurements of liquid metal flows

Franke, S.; Lieske, H.; Fischer, A.; Büttner, L.; Czarske, J.; Räbiger, D.; Eckert, S.

In the research area of magnetohydrodynamics (MHD) the pulsed-wave ultrasound Doppler velocimetry (UDV) is a worthwhile measurement technique for flow field investigations of liquid metal flows. Thereto, several UDV instruments are available on the market. However, their capability for two-dimensional mapping of flows is highly limited due to restricted number of scanning elements (max. 20 transducers) and low temporal resolution. Hence, an ultrasound Doppler velocimeter based on ultrasound arrays is developed which allows the measurement of both flow field vectors in the measuring plane of 67 x 67 mm². Thereby, it provides high measurement rates and a high spatial resolution with a significant increased number of scanning lines simultaneously.
The linear ultrasound transducer arrays are arranged orthogonally to each other. There each array measures one flow field component by electronic traversing.
The ultrasound arrays comprise 2x 25 transducer elements each with a centre frequency of 8 MHz and a piezo element size of 2.5 x 5 mm². In operation two adjacent elements are combined to a square transducer pair of 5 x 5 mm² allowing a small lateral scanning step width of 2.5 mm on the one hand and a low divergence of the ultrasound beam and according to this a high lateral resolution up to 2 mm on the other hand.
The requirements for a high temporal resolution and a high number of scanning lines are opponent. To achieve a high measurement rate nevertheless, the measurement is parallelized as much as possible by simultaneous operation of four transducer pairs. Thereby a specific distance between the active transducer pairs avoids spatial crosstalk. For the same reason both arrays are actuated alternatively. This excitation scheme is implemented by a fast multiplex electronics which is a proprietary development. Depending on the averaging time frame rates up to 33 Hz are achieved at pulse repetition rates of 1.5 kHz.

Keywords: ultrasound Doppler velocimetry; array sensor; flow mapping; rotating magnetic field; electromagnetic stirring

  • Lecture (Conference)
    Jahrestagung der Gesellschaft für angewandte Mathematik und Mechanik (GAMM 2011), 18.-21.04.2011, Graz, Österreich
  • Contribution to proceedings
    Jahrestagung der Gesellschaft für angewandte Mathematik und Mechanik (GAMM 2011), 18.-21.04.2011, Graz, Österreich
    Proceedings in Applied Mathematics and Mechanics (PAMM), 649-650

Permalink: https://www.hzdr.de/publications/Publ-15281
Publ.-Id: 15281


Efficiency of a DC magnetic field used for braking the flow within a continuous casting mould

Miao, X.; Timmel, K.; Eckert, S.; Lucas, D.; Gerbeth, G.

The continuous casting technology provides about 90% of the world steel production. The application of DC magnetic fields in form of so-called electromagnetic brakes is considered for an effective flow control with substantial capabilities to improve the product quality or to enhance the productivity of the process. The main effect of the DC field is supposed to result in a uniform reduction of the maximum velocities in the discharging jet from the submerged entry nozzle and to damp violent turbulent fluctuations. However, the electromagnetic braking of such highly turbulent and complex flows is a complicated phenomenon and has not been understood fully until now.
We present numerical and experimental investigations focusing on the fluid flow in the continuous casting mold under the influence of a transverse magnetic field. Numerical calculations were performed using the software package CFX with an implemented RANS-SST turbulence model. The non-isotropic nature of the MHD turbulence was taken into account by specific modifications of the turbulence model.
Corresponding experimental investigations were carried out at the mockup LIMMCAST at HZDR. The comparison between our numerical calculations and the experimental results display a very well agreement. An important outcome of this study is the feature that the magnetic field does not provide a continuous reduction of the velocity fluctuations at the nozzle port.

Keywords: continuous casting; mould flow; flow measurements; DC magnetic field; electromagnetic brake

  • Lecture (Conference)
    Jahrestagung der Gesellschaft für angewandte Mathematik und Mechanik (GAMM 2011), 18.-21.04.2011, Graz, Österreich

Permalink: https://www.hzdr.de/publications/Publ-15280
Publ.-Id: 15280


Taylor-Görtler vortex flows driven by a rotating magnetic field inside a liquid metal column

Vogt, T.; Räbiger, D.; Grants, I.; Eckert, S.; Gerbeth, G.

The spin-up of a fluid in a rotating axisymmetric container is a classical problem in fluiddynamics. Considering a spinning cylinder the viscous forces are responsible to convey the angular momentum from the container walls into the liquid. Therefore, the fluid rotates faster in the boundary layers near the horizontal walls. In those Ekman layers the centrifugal force exceeds the radial pressure gradient and the fluid is driven radial outward. A secondary flow is established which effectively transports the angular momentum to the bulk of the liquid. We consider a circular cylinder filled with a liquid metal which is exposed to a rotating magnetic field (RMF). The magnetic field strength is suddenly increased to B0 and maintained at that value. The magnetic field induces a mainly azimuthal body force, the Lorentz force. This experimental study is concerned with the secondary meridional flow during the time if the fluid spins up from rest. Vertical profiles of the axial velocity have been measured by means of the ultrasound Doppler method. The flow measurements show the existence of two stages during the RMF-driven spin-up, in particular the so-called initial adjustment phase followed by an inertial phase which is dominated by inertial oscillations of the secondary flow. Evolving instabilities in form of Taylor-Görtler vortices have been observed just above the instability threshold.

Keywords: spin-up; rotating magnetic field; Taylor-Görtler vortices; flow measurements; ultrasound Doppler velocimetry

  • Lecture (Conference)
    Jahrestagung der Gesellschaft für angewandte Mathematik und Mechanik (GAMM 2011), 18.-21.04.2011, Graz, Österreich

Permalink: https://www.hzdr.de/publications/Publ-15279
Publ.-Id: 15279


Curium(III) complexation with surface-layer (S-layer) proteins from a uranium mining waste pile isolate

Moll, H.; Raff, J.; Li, B.; Bernhard, G.

During the last years the interaction of U(VI) with the isolate Lysinibacillus sphaericus JG-A12, recovered from the uranium mining waste pile “Haberland” near Johanngeorgenstadt (JG), Saxony, Germany, was intensively studied [1, 2]. It could be demonstrated that L. sphaericus JG-A12 shows the ability to form S-layer proteins. This outermost subcellular structure plays an important role for selective binding of heavy metals, for example U(VI) [2]. The interaction of trivalent actinides (e.g., curium) with bacterial S-layer proteins is unknown. This knowledge is essential for the understanding of An(III) interactions at biological solid-water interfaces. Dependent on pH and [Ca] S-layer proteins occur as monomers and polymers in aqueous solution. The main aim of this study is to explore the unknown Cm(III) binding on different S-layers and S-layer protein structures.
The direct speciation technique time-resolved laser-induced fluorescence spectroscopy (TRLFS) has been applied at trace Cm(III) concentrations. Two S-layer suspensions a) Ca-reduced protein containing 195 mmol Ca/mol protein and b) Ca-purified protein were investigated. As a result and illustrated in Figure 1, both S­layers have a high affinity to bind Cm(III) over a broad pH range between 3 and 9. The Ca-reduced S­layer proteins can associate Cm(III) in two coordination environments characterized by individual emission spectra and luminescence lifetimes (e.g., 140 and 300 µs). The results can be interpreted by an intensive Cm(III) interaction with S-layer monomers between pH 3 and 5 with monomer concentrations of 100, 60, and 17 %, respectively; and a dominating interaction with S-layer polymers between pH 6 to 9 with polymer concentrations of 84, 91, 91, and 75 %, respectively. Whereas in the Ca-purified S-layer protein suspension only one Cm(III) coordination environment occurs with a long lifetime of 300 µs. Here the S-layer monomers dominate the whole pH range. The Cm(III)-S-layer species with monomers identified in both protein suspensions is characterized by an intensive and sharp emission band at 602.6 nm. This suggests an incorporation of Cm(III) into the S-layer protein structure. There is high evidence that the main functionality of the S-layer proteins in Cm(III) binding are the carboxyl groups. A Ca titration of the Cm(III) loaded Ca-purified S-layer protein suspension at pH 9 gave evidence for a change of the S­layer speciation probably by forming polymers. This affects the Cm(III) speciation according to the results detected in the Ca-reduced S­layer suspension. In contrast at pH 3 no indications were observed for an coordination change of Cm(III) bound to the Ca-purified S-layer proteins.
This study presents the first speciation results of Cm(III) with S-layer proteins isolated from bacteria recovered from an actinide contaminated environment. This helps to increase our understanding regarding the speciation of Cm(III) at biological solid-water interfaces. The results of the present study are the basis for a detailed investigation of Ca(II) exchange reactions by Cm(III) in proteins in order to understand the important impact of trivalent actinides on the Ca-metabolism in bacterial cells. Also with respect to a possible An(III) transport in living cells.

[1] J. Raff, U. Soltmann, S. Matys, S. Selenska-Pobell, W. Pompe, H. Böttcher (2003). "Biosorption of Uranium and Copper by Biocers." Chem. Mater. 15: 240-244.
[2] M. Merroun, J. Raff, A. Rossberg, C. Hennig, T. Reich, S. Selenska-Pobell (2005). "Complexation of Uranium by Cells and S-layer Sheets of Bacillus sphaericus JG-A12." Appl. Environ. Microbiol. 71: 5532-5543.

The authors are indebted for the use of the 248Cm to the U.S. Department of Energy, Office of Basic Energy Sciences, through the transplutonium element production facilities at Oak Ridge National Laboratory which was made available as part of a collaboration between the HZDR and the Lawrence Berkeley National Laboratory (LBNL).

Keywords: Curium(III); TRLFS; S-layer; Speciation; Lysinibacillus sphaericus JG-A12

  • Contribution to proceedings
    13th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere 2011, 18.-23.09.2011, Beijing, PR China
  • Poster
    13th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products (MIGRATION 2011), 18.-23.09.2011, Beijing, PR China

Permalink: https://www.hzdr.de/publications/Publ-15278
Publ.-Id: 15278


Speciation of curium(III) bound by bacteria found in rocks considered for nuclear waste disposals

Moll, H.; Bachvarova, V.; Frost, L.; Geissler, A.; Selenska-Pobell, S.; Bernhard, G.

Bacteria occur ubiquitously in the environment and can significantly affect the migration behavior of actinides released e.g. after an accidental leakage from current and future underground radioactive waste repositories. Curium causes many of the long term radiological and thermal problems associated with nuclear waste disposal. Moreover, Cm(III) is worthwhile to study because it is a representative of the trivalent actinides with excellent luminescence properties and there is limited knowledge of its behavior in biological systems. The aim of our study is to characterize the Cm(III)-bacteria species formed and to elucidate the underlying interaction mechanisms. This knowledge is essential for the prediction of the migration behavior of Cm(III).
This new study is focused on the interaction processes of Cm(III) with bacteria isolated from two geochemical formations considered for nuclear waste disposals a) Pseudomonas fluorescens from granite rocks at the Äspö Hard Rock Laboratory (Äspö HRL), Sweden, and b) Sporomusa sp. from opalinus clay of the Mont Terri Rock Laboratory, Switzerland.
The direct speciation technique time-resolved laser-induced fluorescence spectroscopy (TRLFS) has been applied at trace Cm(III) concentrations. The unknown Cm(III) speciation in the two studied biological systems (P. fluorescens and Sporomusa sp.) was determined in terms of luminescence spectra and lifetimes of: a) original cell suspensions with Cm(III); b) Cm(III) in the supernatants after discarding the cells; c) desorbed Cm(III) from the cell envelopes; and d) irreversibly bound Cm(III) on the biomass. An overview of the emission spectra of Cm(III) in original cell suspensions of P. fluorescens and Sporomusa sp in 0.1 M NaClO4 is presented in Figure 1. Our results demonstrate that both bacteria have a high affinity to bind Cm(III) over a broad pH range between 2 and 8. Moreover, biomass dependent experiments at pH 6 indicate that already at a very low cell concentration of 0.01 mgdry weight/L all Cm(III) is bound by P. fluorescens and Sporomusa sp.. Both strains can associate Cm(III) in two coordination environments characterized by individual emission bands and luminescence lifetimes. Factor analyses of the emission data indicate interactions with carboxyl groups in the acidic pH up to pH 5.5 followed by interactions with phosphoryl groups of the cell surfaces at higher pH values. In the Cm(III)-P. fluorescens system, almost 100 % of the adsorbed Cm(III) was easily desorbed with 0.01 M EDTA solution. This clearly shows that Cm(III) is bound extracellularly on the cell surface via a pure biosorption process. In the Cm(III)-Sporomusa sp. system, however, only 70 % of the bound Cm(III) was easily desorbed by washing with 0.01 M EDTA. Hence, only 70 % of the added Cm(III) was adsorbed in this case in away similar to those of P. fluorescens, i.e. on the cell surface of the Sporomusa sp. isolate. In contrast to the cells of P. fluorescens, the cells of the Sporomusa sp. bind a significant amount of Cm(III), 30 %, irreversibly, that indicates that this part of the added Cm(III) is more strongly bound. Our results demonstrate that there is an evidence for differences between the Cm(III) interaction mechanisms observed in both bacterial systems. In addition, excitation spectra of Cm(III) associated with these bacteria will be discussed to support our conclusions drawn from the luminescence emission measurements.
The results of this study contribute to increase our understanding of the Cm(III) speciation in bacterial systems. This knowledge is necessary for a fundamental understanding of An(III) reactions under natural conditions.

This work was funded by the BMWi under contract number: 02E10618. The authors are indebted for the use of the 248Cm to the U.S. Department of Energy, Office of Basic Energy Sciences, through the transplutonium element production facilities at Oak Ridge National Laboratory which was made available as part of a collaboration between the HZDR and the Lawrence Berkeley National Laboratory (LBNL).

Keywords: Curium(III); Bacteria; Speciation; TRLFS

  • Contribution to proceedings
    13th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere 2011, 18.-23.09.2011, Beijing, PR China
  • Poster
    13th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products (MIGRATION 2011), 18.-23.09.2011, Beijing, PR China

Permalink: https://www.hzdr.de/publications/Publ-15277
Publ.-Id: 15277


Synthesis, structure determination and (radio-) fluorination of novel functionalized phosphanes suitable for the traceless Staudinger ligation

Mamat, C.; Franke, M.; Peppel, T.; Köckerling, M.; Steinbach, J.

An elegant and efficient synthesis approach for the preparation of novel benzoate and nicotinate containing phosphanes is presented. This reaction path has a broad substrate scope. Thus, various functionalized phosphanes were obtained in high yields using an esterification procedure under Steglich conditions. A facile blocking of the phosphorus with BH3 as protecting group enables a further derivatization of the benzoate residue. The prepared phosphane derivatives proved to be valuable labeling building blocks for the implementation of a (radio-)fluorination strategy. For this case, these compounds were applied for these labeling purposes using the traceless Staudinger Ligation. In this case, the preparation of a selection of azide-functionalized small organic and bioactive sample molecules and subsequent mild and selective (radio-) fluorination of these derivatives is demonstrated adopting this bioorthogonal ligation method.

Permalink: https://www.hzdr.de/publications/Publ-15275
Publ.-Id: 15275


Application of quantum chemical calculations to actinide solution chemistry: spectroscopy and photochemistry

Tsushima, S.

Three examples will be presented at the talk. (1) DFT application to the structural determination of aqueous actinide species. Role of 5f electron to the An-O bond distance and to the selection of monodentate/bidentate will be discussed. (2) Calculation of redox potential of An(VI)/ An(V) for An=U, Np, Pu, Am. (3) Uranyl(VI) luminescence and photochemistry. The mechanisms of uranyl(VI) luminescence quenching and photochemical reduction of uranyl(VI) complexes will be discussed.

Related publications

  • Invited lecture (Conferences)
    Tokai Research and Development Center of the Japan Atomic Energy Agency (JAEA), 09.03.2011, Tokai, Japan

Permalink: https://www.hzdr.de/publications/Publ-15274
Publ.-Id: 15274


Retention of uranium in biofilms of a granitic nuclear waste repository research tunnel

Krawczyk-Bärsch, E.; Lünsdorf, H.; Pedersen, K.; Lehtinen, A.; Arnold, T.

Several mechanisms of interactions of microorganisms with actinides under aerobic conditions are known, e.g. biosorption, interactions with S-layers or bioprecipitation. Some of them have the potential of a substantial retention of actinides, like uranium. However, little is known about the retention processes in a microbial community, such as biofilms. Since bacteria do not usually occur as single individual cells in nature but as multicellular communities, we have to draw our attention on the biofilms. They are characterized by building up their own microenvironment, which can differ significantly from that of the bulk solution with the consequence that biofilms are becoming more important in potential retention processes for actinides.

At the depth of 70 m (tunnel chainage 771) of the nuclear waste repository research tunnel ONKALO (Finland), which will be part of the nuclear waste repository in the future, massive biofilms are growing next to a fracture zone in a granitic rock environment. They were described by Pedersen et al. (2008) as a pink and solid slime, consisting of Pseudomonas anguilliseptica, Arthrobacter bergeri, Hydrogenophaga sp., Methylobacter tundripaludum, Rhodoferrax ferrireducens, and Haliscomenobacter hydrossis. The samples were removed from the tunnel wall together with the fracture water for uranium sorption experiments in a flow cell. A uranium concentration of 4×10-5 M was adjusted in the fracture water by adding UO2(ClO4)2. The water was pumped through the flow cell in a closed circuit for 42 hours. Microsensor measurements of the redox potential, pH and oxygen were performed in the several millimeters thick biofilms before and after the addition of uranium in order to record the effect of uranium. The obtained data showed significant changes of redox potential, pH and oxygen. The redox potential decreased after the addition of uranium during the experiment from 70 ± 2 mV to -164 mV with an increase of the pH from 5.4 ± 0.1 to 7.3 ± 0.1 at the same time, indicating reducing conditions in the microenvironment of the biofilm. The decrease in the oxygen concentration showed that the bacteria in the top region of the biofilms, i.e. the metabolically most active biofilms zone, battled the toxic effects of aqueous uranium with an increased respiratory activity, which resulted in oxygen depleted zones. Redox processes may have been triggered, leading to a removal of uranium from the aqueous phase. Analysis, which were performed before and after the sorption experiment, clearly showed, that 63 % of the added uranium was immobilized.

The retardation of uranium in the biofilm was determined by Energy-filtered Transmission Electron Microscopy (EF-TEM) and Electron Energy Loss Spectroscopy (EELS). Elongated particles of high electron density were observed in the cytoplasm of some rod shaped gram negative bacteria, which were often found associated with large rod shaped bacteria. Analysis of the elongated particles by EELS provided spectroscopic evidence for the presence of uranium immobilization, showing unequivocally uranium ionization intensity peaks of O4,5- and N6,7-edges. Distribution analysis of uranium, phosphorus and calcium clearly showed, that a solid uranium mineral has formed intracellular, which indicates the presence of a solid U-phosphate mineral similar to Autunite (Ca[UO2]2[PO4]2•10-12H2O).

Pedersen K, Arlinger J, Eriksson S, Hallbeck M, Johansson J, Jägevall S, Karlsson L. Microbiology of Olkiluoto Groundwater. Results and Interpretations 2007. POSIVA Working Report 2008-34. Olkiluoto, Finland.

Keywords: biofilm; uranium; retention; nuclear waste repository

  • Lecture (Conference)
    13th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere, 18.-23.09.2011, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-15273
Publ.-Id: 15273


Uptake of Np(IV) by C-S-H Phases and Cement Paste: An EXAFS Study

Gaona, X.; Dähn, R.; Tits, J.; Scheinost, A. C.; Wieland, E.

In many nuclear waste disposal concepts cementitious materials are foreseen to be used for the immobilization of long-lived intermediate level wastes (ILW). ILW may contain significant amounts of neptunium-237, which is expected as Np(IV) under the reducing conditions developing after the closure of the repository. Predicting the release of Np(IV) from this environment requires a sufficiently detailed understanding of its interaction with the main sorbing components of cement. In this study, the uptake of Np(IV) by calcium silicate hydrates (C-S-H) and hardened cement paste (HCP) has been investigated using extended X-ray absorption spectroscopy (EXAFS).

Evaluation of EXAFS data from Np(IV)-doped C-S-H and HCP indicates the predominant incorporation of Np in the C-S-H structure throughout the complete sequence of cement degradation. Two species were identified, corresponding to Np(IV) in C-S-H with Ca:Si 1.65 (fresh cement) and 0.75 (highly degraded cement). The coordination environment of Np(IV) was found to depend on the Ca:Si ratio but not on pH, consistently with the aqueous speciation of Np(IV) in the pH range 10 – 13.3 (with predominance of Np(OH)4(aq)). These results unequivocally show that C-S-H are responsible for Np(IV) immobilization in cementitious materials, whilst incorporation in the interlayer of the C-S-H structure is regarded as the predominant uptake mechanism.

Keywords: Neptunium; EXAFS; cement

Related publications

Permalink: https://www.hzdr.de/publications/Publ-15272
Publ.-Id: 15272


S-Layer protein from Lysinibacillus sphaericus JG-A12 as matrix for Au-III sorption and Au-nanoparticle formation

Jankowski, U.; Merroun, M.; Selenska-Pobell, S.; Fahmy, K.

The strain Lysinibacillus sphaericus JG-A12, isolated from the uranium mining site at Haberland. Saxony (Germany) selectively and reversibly accumulates radionuclides and toxic metals. Metal binding occurs to its surface layer (S-layer) surrounding the cells. Here, we have studied by Fourier-transform infrared (FTIR) spectroscopy the protein structure and stability as a function of Au-III binding and the subsequent reductively induced formation of Au-nanoclusters. Similar to previously studied complexes with Pd-II. Au-treated S-layers become resistant to acid denaturation evidenced by little response of their amide I absorption frequency. However, the strong effect of Pd-II on the side chain carboxylate IR absorption intensity is not observed with gold. Particularly after reduction, the carboxyl absorption responds little to acidification and a fraction appears to be protonated already at neutral pH. We ascribe this to a hydrophobic environment of the carboxyl groups after formation of Au-nanoclusters. EXAFS spectra agree with the metallic Au-Au distance but the reduced coordination number indicates that the Au-nanoclusters do not exceed similar to 2 nm. Thus, the S-layer of L. sphaericus JG-A12 provides a biotemplate for efficient Au-nanocluster formation in an acid-resistant matrix and independently of cysteins.

Permalink: https://www.hzdr.de/publications/Publ-15271
Publ.-Id: 15271


Dismantling of the Cyclotron U-120 at the Research Center Dresden-Rossendorf

Naumann, B.; Friedrich, M.; Matz, W.

Status report about the dismantling and disposal of the Rossendorf cyclotron U-120.

Keywords: dismantling; disposal; circular accelerator; activation of large-volume components

  • Poster
    10th International Symposium "Conditioning of Radioactive Operational & Decommissioning Wastes", 06.-08.04.2011, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15270
Publ.-Id: 15270


Uranium(IV)-Silica colloids at near-neutral pH

Zänker, H.; Weiss, S.; Hennig, C.; Dreissig, I.; Bernhard, G.

Evidence is provided by photon correlation spectroscopy, ultrafiltration and ultracentrifugation that uranium(IV) can form silicate-containing colloids. The particles are generated in near-neutral to slightly alkaline solutions containing background chemicals of geogenic nature (carbonate, silicate, sodium ions). They remain stable in aqueous suspension over years. A concentration of up to 10-3 M of colloid-borne U(IV) was observed which is a concentration much higher than the concentrations of truly dissolved or colloidally suspended waterborne An(IV) species hitherto reported for the near-neutral pH range. The prevailing size of the particles is below 20 nm. Laser Doppler velocimetry reveals that the nanoparticles are stabilized in solution by electrostatic repulsion due to a negative zeta potential caused by the silicate. The isoelectric point of the nanoparticles is shifted toward lower pH values by the silicate. Extended X-ray absorption fine structure (EXAFS) spectroscopy showed that U-O-Si bonds, which increasingly replace the U-O-U bonds of the amorphous uranium(IV) oxyhydroxide with increasing silicate concentrations, make up the internal structure of the colloids.

Keywords: uranium(IV); silicate; colloids; near-neutral pH

Related publications

  • Contribution to proceedings
    41ièmes Journees des Actinides, 09.-12.04.2011, Stara Lesna, Slovakia
    Proceedings ot the 41ièmes Journees des Actinides
  • Lecture (Conference)
    Journees des Actinides, 09.-12.04.2011, Stara Lesna, Slovakia

Permalink: https://www.hzdr.de/publications/Publ-15269
Publ.-Id: 15269


U(VI) sorption on montmorillonite: A macroscopic and microscopic study

Marques Fernandes, M.; Baeyens, B.; Dähn, R.; Scheinost, A. C.; Macé, N.; Bradbury, M. H.

The mechanism of U(VI) sorption on montmorillonite (Na-SWy-2) in the absence and the presence of carbonate was investigated through a combination of different approaches: macroscopic sorption experiments, modelling with the 2 Site Protolysis Non Electrostatic Surface Complexation and Cation Exchange model and Extended X-ray absorption fine structure (EXAFS) spectroscopy. U(VI) sorption measurements were performed both in the absence and in the presence of carbonate at fixed ionic strength (0.1 M NaClO4) as a function of pH at U(VI) trace concentration (~ 9x10-8 M) and as a function of U(VI) concentration (5x10-8-10-4 M) at pH ~ 8. In the presence of carbonate, experiments were carried out in equilibrium with atmospheric pCO2 and in 1, 3 and 5 mM NaHCO3. The sorption edge data in the absence of carbonate were modelled by considering the formation of the following surface species, ≡SSOUO2+, ≡SSOUO2OH0, ≡SSOUO2(OH)2-, ≡SSOUO2(OH)32-, and ≡SSOUO2(OH)32- on the strong sites. From the isotherm the formation of ≡SW1OUO2+ and ≡SW1OUO2OH0 on the weak sites were derived. Two additional surface complexes on the strong sites, ≡SSOUO2CO3- and ≡SSOUO2(CO3)23- and one surface complex on the weak sites, ºSW1OUO2CO3-, were necessary to reproduce the sorption data in the presence of carbonate. The EXAFS measurements did not allow to verify the formation of ternary uranyl-carbonate complexes on the montmorillonite surface. However the obtained fit parameters, splitting of the equatorial oxygen shell, two Si/Al shells at ~3.09 Å and 3.85 Å and one Fe shell at ~ 3.43 Å clearly indicate that U(VI) forms a mononuclear edge-sharing surface complex, sharing one octahedral Fe, one octahedral Al and one tetrahedral Si/Al. The lack of angular dependence of the Polarized–EXAFS spectra confirms that U(VI) is not sorbed to the montmorillonite surface in the continuity of the octahedral sheet.

Keywords: EXAFS; montmorillonite; sorption U(VI)

Related publications

Permalink: https://www.hzdr.de/publications/Publ-15268
Publ.-Id: 15268


Interaction of U(VI) with Some Bioligands or the Influence of Different Functional Groups on Complex Formation

Frost, L.; Osman, A. A. A.; Geipel, G.; Viehweger, K.; Moll, H.; Bernhard, G.

U(VI) released anthropogenically, e.g. through mining activities, can be accumulated for instance in plants and consequently can enter further parts of the food chain. Hence it is of crucial importance to study the interaction of U(VI) with cellular ligands, like glutathione, uric acid and benzoic acid. Glutathione, the most abundant thiol compound of a cell, has a well known affinity for heavy metal ions. It is a precursor for phytochelatin synthesis and thus also a model substance for the study on U(VI) phytochelatin interaction. Uric acid (UA) was investigated as a further ligand being potentially capable of chelate formation with U(VI). It is present e.g. in bio-fluids such as urine and sweat. Benzoic acid occurs naturally free and bound as benzoic acid esters in many plant and animal species. Furthermore it is a model ligand to study the interaction with bacterial siderophores and humic acids.
UV-vis and time-resolved laser-induced fluorescence spectroscopy (TRLFS) were applied to investigate complex formation between U(VI) and glutathione, uric acid and benzoic acid. Additionally one of the four major potential binding sites of glutathione, the thiol group, was blocked by derivatization to assess the coordination chemistry more detailed.
In the U(VI)-glutathione system a 1:1 complex with a large stability constant of 39.07 ± 0.15 (at zero ionic strength) could be identified. On the contrary, in the U(VI)-urate and -benzoic acid systems a comparably weak complexation was found.
What are the structure-related reasons for such a considerable discrepancy in complex stability? Investigating the interaction of U(VI) with glutathione-S-conjugates, no decrease in complex stability in comparison to U(VI) complexation by glutathione was found. Thus here a significant involvement of the thiol group in coordination can be excluded. Since benzoic acid offers one carboxyl functionality but exhibits a very weak U(VI) coordination, for U(VI) complexation by glutathione a chelate-like coordination with an involvement of at least one carboxyl functionality can be assumed. Since uric acid coordinates as a bidentate ligand and is suggested to undergo a chelation with U(VI) as well, specifically by its 7-amine and 6-carbonyl group, it follows that chelate formation must not necessarily result in strong complexation.
In general, these results contribute to a better understanding of the intricate U(VI) interactions in biological systems on a molecular level.

Keywords: U(VI); Glutathione; Uric Acid; Benzoic Acid; Complexation; UV-vis spectroscopy; TRLFS

  • Contribution to proceedings
    Uranium Mining and Hydrogeology VI, 18.-22.09.2011, Freiberg, Deutschland
    The New Uranium Mining Boom, Berlin: Springer, 978-3-642-22121-7, 595-606
  • Lecture (Conference)
    Uranium Mining and Hydrogeology VI, 18.-22.09.2011, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15267
Publ.-Id: 15267


The geochemical fate of Se(IV) in the Boom Clay system - XAS based solid phase speciation

Breynaert, E.; Scheinost, A.; Dom, D.; Rossberg, A.; Vancluysen, J.; Gobechiya, E.; Kirschhock, C.; Maes, A.

For more than 30 years the Boom Clay formation is studied as a reference host formation for methodological research concerning clay-based geological disposal of HLRW in Belgium and Europe. Boom Clay provides good sorption capacity, very low permeability and chemically reducing conditions due to the anoxic conditions and the presence of pyrite and siderite. Performance Assessment calculations have indicated Se79 (t1/2 = 2.95×105 y) to be one of the critical radionuclides for the geological disposal of HLRW [1]. Aqueous selenite [Se(+IV)] and selenate [Se(+VI)] are the dominant species in mildly and strongly oxidizing environments. Under reducing conditions the solubility of Se is theoretically controlled by the formation of sparsely soluble selenium phases such as elemental Se or transition metalselenide salts (e.g. FeSe or FeSe2) [2, 3]. Slow kinetic reactions between the different redox states have been observed [4] and proposed to explain different redox phases observed within a single reducing environment. Se oxyanions, such as SeO4 2- and SeO32-, are generally considered as the most mobile forms of Se [5] and their migration through Boom Clay thus is considered as “worst case scenario”. In order to assess their long-term fate it is imperative to understand the influence of different geochemical phases present in the Boom Clay matrix on selenium speciation and mobility. A multidisciplinary approach combining long-term batch sorption experiments with linear combination XANES and ITFA-based EXAFS analysis on different fractions isolated from Boom Clay batch systems equilibrated with Se(IV), identified Se0 as the dominant in situ solid phase speciation of Se in Boom Clay conditions.
[1] SAFIR-2, 2001. Brussels, Belgium. p. 288. [2] Breynaert, E. et al., ES&T. 42 (10): p. 3595. [3] Scheinost, A.C. et al., J. Contam. Hydrol. 102 p. 228. [4] Masscheleyn, P.H. et al., ES&T. 24 (1): p. 91. [5] Elrashidi, M.A. et al., Soil Science 144 (2): p. 141.

Keywords: selenium; redox; Boom clay

Related publications

  • Lecture (Conference)
    Goldschmidt Conference, 13.06.2010, Knoxville, Tennessee, USA
  • Abstract in refereed journal
    Geochimica et Cosmochimica Acta 74(2010)12, A122

Permalink: https://www.hzdr.de/publications/Publ-15266
Publ.-Id: 15266


Ultraschnelle Elektronenstrahl-Röntgencomputertomographie als Verfahren zur zerstörungsfreien Qualitätskontrolle

Pöpping, U.; Barthel, F.; Tietze, H.; Hampel, U.

Qualitätskontrollen von Nahrungsmitteln haben eine besondere Bedeutung sowohl zur Sicherstellung eines unbedenklichen Verzehrs als auch zur Feststellung der Güte. Neben der Untersuchung von äußeren Qualitätsmerkmalen sowie chemisch-biologischen Analysen spielt dabei auch die Beschaffenheit im Inneren eine wesentliche Rolle. Die Untersuchung hier kann aber in vielen Fällen nur in Stichproben erfolgen, da das Untersuchungsobjekt dazu zerstört werden muss. Zudem ist die Qualitätsprüfung in der Regel auch nur manuell möglich.

Am Institut für Sicherheitsforschung im Helmholtz-Zentrum Dresden-Rossendorf (HZDR) wurde eine ultraschnelle Elektronenstrahl Röntgencomputertomographie entwickelt. Hierbei handelt es sich um ein bildgebendes Messverfahren, bei dem von einem Untersuchungsobjekt bis zu 7.000 Schnittbilder pro Sekunde bei einer räumlichen Auflösung von ca. 1 mm erzeugt werden können. Dabei wird die für die Rekonstruktion von überlagerungsfreien Schnittbildern benötigte Aufnahme von Durchstrahlungsprojektionen aus unterschiedlichen Blickwinkeln nicht durch die mechanische Drehung von Objekt oder Messsystem erreicht, stattdessen wird ein Elektronenstrahl, der den die Röntgenstrahlung emittierenden Brennfleck auf einem ringförmigen Target erzeugt, elektronisch abgelenkt. Auf diese Weise wird die Untersuchung einer großen Stückzahl von Untersuchungsobjekten innerhalb kurzer Zeit möglich.

Erste Untersuchungen haben die prinzipielle Eignung der - ursprünglich für die Messung in mehrphasigen Strömungen entwickelten - Technologie auch zur zerstörungsfreien Qualitätskontrolle gezeigt. Es konnte für verschiedenste Untersuchungsobjekte wie beispielsweise Wallnüsse, Esskastanien aber auch Paprikaschoten die Rekonstruktion des Inneren in einer prinzipiell für die Qualitätssicherung mehr als ausreichender Güte gezeigt werden.

Die Ergebnisse der ersten Studien lassen auf ein großes Potenzial dieser Technologie für dieses Anwendungsfeld schließen. Allerdings liegt die Expertise am HZDR vor allem in der Entwicklung solcher Messsysteme und nicht in der fachlichen Bewertung von Qualitätsmerkmalen von Nahrungsmitteln. Weitere Forschungs- und Entwicklungsarbeiten, die gemeinsam mit einer Forschungseinrichtung mit notwendiger Expertise auf dem Gebiet der Landwirtschaft bzw. des Gartenbaus angestrebt werden, sind vor allem zur erheblichen Verkürzung der notwendigen Rekonstruktionszeit sowie zur Automatisierung dieser Technologie und des Prozesses selbst notwendig.

Keywords: Ultrafast X-ray computed tomography; quality inspection

  • Poster
    47. Jahrestagung der Deutschen Gartenbauwissenschaftlichen Gesellschaft (DGG) und des Bundesverbandes der Hochschulabsolventen/Ingenieure Gartenbau u. Landschaftsarchitektur (BHGL), 23.-26.02.2011, Hannover, Deutschland
  • Contribution to proceedings
    47. Jahrestagung der Deutschen Gartenbauwissenschaftlichen Gesellschaft (DGG) und des Bundesverbandes der Hochschulabsolventen/Ingenieure Gartenbau u. Landschaftsarchitektur (BHGL), 23.-26.02.2011, Hannover, Deutschland
    Ultraschnelle Elektronenstrahl-Röntgencomputertomographie als Verfahren zur zerstörungsfreien Qualitätskontrolle, Hannover: BHGL & DGG, 1613-088X

Permalink: https://www.hzdr.de/publications/Publ-15265
Publ.-Id: 15265


Geogases in the Kaapvaal Craton – Origin and modes of transport

Lippmann-Pipke, J.; Sherwood Lollar, B.; Niedermann, S.; Stroncik, N. A.; Naumann, R.; van Heerden, E.; Onstott, T. C.; Erzinger, J.; Zimmer, M.; Kujawa, C.; Boettcher, M.; Bester, A.; Moller, H.; Reches, Z.

Introduction The deep gold mines of the Witwatersrand Basin, South Africa, have gained recent attention because of reports of deep microbial communities persisting to depths of >3 kilometers - an exotic outpost of the Earth's deep biosphere [1,2]. Prerequisites of such investigations are studies on the age of the deep fracture water [3] and the origin of associated abiogenic CH4- [4] and H2-rich gases [5]. Here we report about insights obtained from two new gas data sets (I, II) with respect to the dynamic of the ultra-deep fluid system [6,7].
Methods (I) The isotopic composition of neon dissolved in deep fracture water and in fluid inclusions of quartz host rock was analyzed, and the results correlated with the isotopic signatures of the biogenic and abiogenic H2- and CH4-rich sample aliquots. (II) In the other project the geogas composition of the free gas was monitored by means of a mass spectrometer and gas sensitive sensors installed just inside the Pretorius Fault Zone at 3.45 km depth in the TauTona Mine. Data from a 4-year observation period are cross-correlated on the minute-by-minute basis with seismic data obtained from a 3-dimensional array of highly sensitive seismometers.
Results (I) Highest ever observed 21Ne/22Ne ratios combined with an anomalous 21Ne/22Ne production ratio imply that the dissolved neon is a 2 Ga metamorphic signal stored in fluid inclusions and accumulating in fracture water since geological times as a result of water rock reaction processes. (II) Geogas concentration variations (4He, H2, CH4, CO2) strongly correlate with seismic signals resulting from mining related blasts and induced earthquakes in the TauTona Mine. The fracture gas permeability of ~ 5*10e-10 m² is estimated on the basis of observed gas flux rates.
Conclusion (I) 21Ne/22Ne ratios may serve as search proxy for regions of the Archean Earth's crust where investigations of the deep biosphere might be focused. (II) Methodological improvements enabled the simultaneous gas geochemical and seismic signal recording in the world deepest operating mine, reflecting the near-field at earthquake focal depths.

[1] Lin et al., Science 2006, 314(5798): 479-482; [2] Chivian et al., Science 2008, 322(5899): 275-278 ; [3] Lippmann et al., GCA 2003, 67(23): 4597-4619; [4] Sherwood Lollar et al., Chem. Geol. 2006, 226(3-4): 328-339; [5] Lin et al., GGG 2005, 6: Q07003; [6] Lippmann-Pipke et al. Chem. Geol., submitted; [7] Lippmann-Pipke et al., Appl. Geol., submitted

  • Invited lecture (Conferences)
    New Horizons for International Investigations into Carbon Cycing in the Deep Crustal Biosphere, 18.-23.01.2011, Bloemfontein, South Africa

Permalink: https://www.hzdr.de/publications/Publ-15264
Publ.-Id: 15264


Vibrational characteristics of outer-sphere surface complexes: example of sulfate ions adsorbed onto metal (hydr)oxides

Müller, K.; Lefèvre, G.

The vibrational characteristics of outer-sphere complexes of sulfate at several mineral oxide – water interfaces were investigated by in situ attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy. In the IR spectra obtained from surface outer-sphere complexes only one peak of the antisymmetric stretching vibrational mode υ3 similar to the free sulfate ion SO4 2− in aqueous solution is observed. However, on the investigated (hydr)oxide surfaces of Al3+, Ti4+, Fe2+/3+, Cr3+, Ni2+, Ce4+, Cu2+, Y3+, Zn2+, and Nd3+ a shift of up to 14 cm−1 was found, correlated to the polarizing power of the metal cations. A high polarizing power was found to result in a stronger shift of υ3 compared to the aqueous SO4 2− ion. Furthermore, the impact of the metal oxide structure on the characteristics of the formed outer-sphere complex was negligible, since different Al and Fe (hydr)oxides did not show any changes in the respective IR spectra. A variation of ionic strength (1 – 10-4 M) and pH (6.8 – 3.1) during the formation of SO4 2− outer-sphere complexes on g-Al2O3 showed that those changes directly influence the surface potential, without modifying the geometry of the outer-sphere complex.

Permalink: https://www.hzdr.de/publications/Publ-15263
Publ.-Id: 15263


Synthesis and biological evaluation of new [Tc(N)(PS)]-based mixed-ligand compounds useful in design of target-specific radiopharmaceuticas: the 2-methoxyphenylpiperazine dithiocarbamate derivatives as example

Bolzati, C.; Salvarese, N.; Carta, D.; Refosco, F.; Dolmella, A.; Pietzsch, H.-J.; Bergmann, R.; Bandoli, G.

This study presents the first application of a general procedure based on the use of the [Tc(N)Cl(PS) (PPh3)] species (PS is an alkyl phosphinothiolate ligand) for the preparation of Tc(N) target-specific compounds. [Tc(N)Cl(PS)(PPh3)] selectively reacts with an appropriate dithiocarbamate ligand (S^Y) to give [Tc(N)(PS)(S^Y)] compounds. 1-(2-Methoxyphenyl)piperazine, which displays a potent and specific affinity for 5HT1A receptors,
was selected as a functional group and conjugated to the dithiocarbamate unit through different spacers (Ln). [99mTc(N)(PS)(Ln)] complexes were prepared in high yield (more than 90%). The chemical identity of 99mTc complexes was determined by high performance liquid chromatography comparison with the corresponding 99gTc complexes. All complexes were found to be inert toward transchelation with an excess of glutathione and cysteine. No notable biotransformation of the native compound into different species by the in vitro action of the serum and liver enzymes was shown. Nanomolar affinity for the 5HT1A receptor was obtained for [99mTc(N)(PSiso)L3] (IC50 = 1.5 nM); a reduction of the affinity was observed for the other complexes as a function of the shortening of the alkyl chain interposed between the dithiocarbamate and the pharmacophore. Negligible brain uptake was found from in vivo distribution data of [99mTc(N)(PSiso)L3]. The key finding of this study is that the complexes maintained good affinity and selectivity for 5HT1A receptors, and the IC50 value for [99gTc(N)(PSiso)L3] being comparable to the IC50 value found for WAY 100635. This result confirmed the possibility of preparing [99mTc(N)(PS)]-based targetspecific compounds without affecting the affinity and selectivity of the bioactive molecules for the corresponding receptors.

Keywords: Technetium; Phosphinothiolate; Dithiocarbamate; 5HT1A receptor; Brain

Permalink: https://www.hzdr.de/publications/Publ-15262
Publ.-Id: 15262


[18F]1-(3-fluoropropyl)piperazines as model compounds for the radiofluorination of pyrido[2,3-d]pyrimidines

Grosse-Gehling, P.; Wuest, F. R.; Peppel, T.; Köckerling, M.; Mamat, C.

The visualization of cyclin-dependent kinases (CDKs), which are overexpressed in multiple tumor types, with radiolabeled CDK inhibitors by means of positron emission tomography in vivo is a promising approach for tumor imaging.
Pyrido[2,3-d]pyrimidines belong to a class of inhibitors, which bind with high affinity to CDK4 and CDK6. [18F]1-(3-Fluoropropyl)-4-(4-nitrophenyl)piperazine and [18F]1-(3-fluoropropyl)-4-(4-nitropyridin-3-yl)piperazine represent
structural elements of the appropriate CDK inhibitors and were therefore chosen as model compounds for the incorporation of fluorine-18 into pyrido[2,3-d]pyrimidines. Three methods are known for the preparation of tertiary [18F]3-fluoropropyl-amines:
1) the direct substitution of a good leaving group,
2) the two-step reaction synthesizing a [18F]3-fluoropropyl intermediate,
and 3) the utilization of aziridinium or azetidinium salts. In general, radiofluorinations using azetidinium salts lead to
excellent radiochemical yields in short periods of time. For these reasons we developed a synthesis route to tosylated piperazine precursors and establish a radiolabeling approach based on the incorporation of fluorine-18 into open-chained
tosylates as well as the respective azetidinium spiro compounds to yield the desired radiofluorinated piperazines successfully.

Keywords: Radiofluorination; Spiro compounds; CDK inhibitor; Pyrido[2; 3-d]pyrimidines

Permalink: https://www.hzdr.de/publications/Publ-15261
Publ.-Id: 15261


Radioiodination of humic substances

Franke, K.; Kupsch, H.

The known IODO-GEN™-method [1] was adapted for radiolabeling of humic and fulvic acids with 131I. The water insoluble oxidizing agent 1,3,4,6tetrachloro-3α,6α-diphenylglycoluril (IODO-GEN™) forms an iodous ion species (I+), which undergoes an electrophilic I/H-substitution on aromatic moieties of the humic and fulvic acids. This method offers mild conditions with a lesser extent of oxidative alterations of the target molecule, accompanied by an easy handling due to the virtual water-insolubility of the oxidizing agent. The method was optimized and different techniques were tested for the purification of the radioiodinated humic material. The yield of the labeling procedure varies between 45 and 75% depending on the provenance of the humic material and the applied purification method. A specific activity up to 40 MBq/mg was achieved. Furthermore, the known inherent photo-susceptibility of the iodinated humic substance and the influence of reducing agents were verified. An additional release of 131I up to 20% and up to 35%, respectively were observed.

Permalink: https://www.hzdr.de/publications/Publ-15260
Publ.-Id: 15260


Twin boundary motion and magnetic domain distribution investigated by optical polarization microscopy

Neudert, A.; McCord, J.

An overview of optical studies of magnetic and structural transformation in magnetic shape memory materials is given. The magnetic domain behavior and the motion of twin boundaries in single crystalline bulk samples of the shape memory alloy NiMnGa are investigated by optical polarization microscopy and magnetic indicator film technique. During stress induced twin boundary motion the magnetization reversal takes place by rotation of magnetization, leading to a total rearrangement of the magnetic domain distribution. Time-resolved studies of twin boundary motion induced by pulsed magnetic fields show that the distance traveled by the twin boundary is enhanced with increasing sample temperature. An overview of these and complementary experiments and the obtained results will be given.

Keywords: magnetic shape memory alloy; optical polarization microscopy; time-resolved microscopy

  • Invited lecture (Conferences)
    International Conference on Ferromagnetic Shape Memory Alloys, 18.-22.07.2011, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-15259
Publ.-Id: 15259


The influence of biofilms on the migration of uranium in acid mine drainage (AMD) waters

Krawczyk-Bärsch, E.; Lünsdorf, H.; Arnold, T.; Brendler, V.; Eisbein, E.; Jenk, U.; Zimmermann, U.

The uranium mine in Konigstein (Germany) is currently in the process of being flooded. Huge mass of Ferrovum myxofaciens dominated biofilms are growing in the acid mine drainage (AMD) water as macroscopic streamers and as stalactite-like snottites hanging from the ceiling of the galleries. Microsensor measurements were performed in the AMD water as well as in the biofilms from the drainage channel on-site and in the laboratory. The analytical data of the AMD water was used for the thermodynamic calculation of the predominance fields of the aquatic uranium sulfate (UO2SO4) and UO2++ speciation as well as of the solid uranium species Uranophane [Ca(UO2)(2)(SiO3OH)(2)center dot 5H(2)O] and Coffinite [U(SiO4)(1-x)(OH)(4x)], which are defined in the stability field of pH>4.8 and Eh < 960 mV and pH>0 and Eh<300 mV, respectively. The plotting of the measured redox potential and pH of the AMD water and the biofilm into the calculated pH Eh diagram showed that an aqueous uranium(VI) sulfate complex exists under the ambient conditions. According to thermodynamic calculations a retention of uranium from the AMD water by forming solid uranium(VI) or uranium(IV) species will be inhibited until the pH will increase to >4.8. Even analysis by Energy-filtered Transmission Electron Microscopy (EF-TEM) and electron energy loss spectroscopy (EELS) within the biofilms did not provide any microscopic or spectroscopic evidence for the presence of uranium immobilization. In laboratory experiments the first phase of the flooding process was simulated by increasing the pH of the AMD water. The results of the experiments indicated that the F. myxofaciens dominated biofilms may have a substantial impact on the migration of uranium. The AMD water remained acid although it was permanently neutralized with the consequence that the retention of uranium from the aqueous solution by the formation of solid uranium species will be inhibited.

Keywords: AMD water; Uranium; Biofilm; Ferrovum myxofaciens; microsensor measurement; thermodynamically calculation

Permalink: https://www.hzdr.de/publications/Publ-15258
Publ.-Id: 15258


Nuclear Astrophysics and Nuclear Transmutation

Wagner, A.

Albeit their quite disjoint research history, the research areas of nuclear astrophysics and transmutation of nuclear waste show striking similarities resembling the same basics in nuclear physics. In both fields, the electromagnetic response function of nuclei and the nuclear level density play a key role in the explosive stellar burning as in the reduction of long-lived actinides produced in nuclear power plants. In the talk, I will present recent results on the electromagnetic strength function in medium-mass nuclei studied at the superconducting electron linear accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf. Neutron-induced reactions on various nuclei, like neutron capture, neutron inelastic scattering are studied at a new neutron time-of-flight facility, as well.

Related publications

  • Invited lecture (Conferences)
    Kernphysikalisches Kolloquium, 27.01.2011, Bonn, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15256
Publ.-Id: 15256


Recombinant S-layer production induces disordered cell division in E. coli filaments

Lederer, F.; Günther, T.; Raff, J.; Pollmann, K.

The rod-shaped bacterium Escherichia coli is one of the best studied microorganism with a size of 1.1-1.5 µm x 2.0-6.0 µm. We used E. coli BL21(DE3), one of the most widely used host in genetic engineering, for heterologous expression of surface layer (S-layer) proteins to enable a fast and efficient protein production.
S-layer are proteins which cover the outermost of many prokaryotes and are probably the basic and oldest forms of bacterial envelopes. These proteins are mostly composed of protein and glycoprotein monomers and have the ability to self-assemble into two-dimensional arrays on interfaces. Several characteristics like their work as molecular sieve, as virulence factor or the protection of the cell from toxic heavy metal ions make S-layer proteins interesting for their usage as filter materials or patterning structures in nanotechnology.
Surprisingly, the heterologous expression of S-layer proteins of the uranium mining waste pile isolate Lysinibacillus sphaericus JG-A12 induced drastic morphological changes of E. coli BL21(DE3) single cells to filaments and tubes enclosing single cells of >100 µm in length. The S-layer expressing E. coli cultures reached a high optical density and cells showed a high viability as well as strong expression of S-layer proteins. The drastically changed cell morphology was investigated by light microscope, AFM and TEM. Analyses with S-layer-GFP expressing cells, which were stained with DAPI and membrane stain, present a disordered cell division process. Our results give a new insight in the morphology and the cell division process in E. coli induced by recombinant proteins.

Lederer et al. (2010) Heterologous expression of the surface-layer-like protein SllB induces the formation of long filaments of Escherichia coli consisting of protein-stabilized outer membrane. Microbiology 156,3584-95.

  • Poster
    FEMS (Federation of European Microbiological Societies), 26.-30.06.2011, Geneva, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-15255
Publ.-Id: 15255


Recombinant S-layer production induces disordered cell division in E. coli filaments

Lederer, F.; Günther, T.; Raff, J.; Pollmann, K.

The rod-shaped bacterium Escherichia coli is one of the best studied microorganism with a size of 1.1-1.5 µm x 2.0-6.0 µm. We used E. coli BL21 (DE3), one of the most widely used host in genetic engineering, for heterologous expression of surface layer (S-layer) proteins to enable fast and efficient protein production.
S-layer are proteins which cover the outermost of many prokaryotes and are probably the basic and oldest forms of bacterial envelope. These proteins are mostly composed of protein and glycoprotein monomers and have the ability to self-assemble into two-dimensional arrays on interfaces. Several characteristics like their work as molecular sieve, as virulence factor or the protection of the cell from toxic heavy metal ions make S-layer proteins interesting for their usage as ultrafiltration membranes, drug microcontainers, filter materials or patterning structures in nanotechnology.
Surprisingly, the heterologous expression of S-layer proteins of the uranium mining waste pile isolate Lysinibacillus sphaericus JG-A12 induced drastic morphological changes of E. coli BL21 (DE3) single cells to filaments and single cell enclosing tubes of >100 µm in length. The assumed secretion of tube-stabilizing S-layer proteins was investigated with SDS-PAGE and ß-galactosidase assay. These analyses result in a high S-layer appearance without significant ß-galactosidase activity in the supernatant and the periplasm. The origin and composition of filaments and tubes were analysed by membrane stain studies. We identified that filaments in the exponential growth phase form a continuous intracellular space without partitioning. To investigate the mechanism of filament and tube formation we analyzed GFP/S-layer expressing E. coli with DAPI-stain. The staining showed >50 µm long DNA-fibres that cross the filaments and “DNA-free” areas, the latter exhibiting strong GFP-expression. Our results point to a disordered cell division in E. coli filaments which is effected by recombinant S-layer expression.

[1] Lederer et al. (2010) Heterologous expression of the surface-layer-like protein SllB induces the formation of long filaments of Escherichia coli consisting of protein-stabilized outer membrane. Microbiology 156,3584-95.

  • Poster
    VAAM (Jahrestagung der Vereinigung für Allgemeine und Angewandte Mirkobiologie), 03.-06.04.2011, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15254
Publ.-Id: 15254


Bulk diffusion induced structural modifications of carbon-transition metal nanocomposite films

Berndt, M.; Abrasonis, G.; Kovacs, G. J.; Krause, M.; Munnik, F.; Heller, R.; Kolitsch, A.; Möller, W.

The influence of transition metal (TM=V,Co,Cu) type on the bulk diffusion induced structural changes in carbon:TM nanocomposite films is investigated. The TMs have been incorporated into the carbon matrix via ion beam co-sputtering, and subsequently the films have been vacuum annealed in the temperature range of 300-700°C. The structure of both the dispersed metal rich and the carbon matrix phases has been determined by a combination of elastic recoil detection analysis, X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The as-grown films consist of carbidic (V and Co) and metallic (Cu) nanoparticles dispersed in the carbon matrix. Thermal annealing induces surface segregation of Co and Cu starting at >=500°C, preceded by carbide-metal transformation of Co-carbide nanoparticles at ~300°C. No considerable morphological changes occur in C:V films. In contrast to the surface diffusion dominated regime where all the metals enhance the six-fold ring clustering of C, in the bulk diffusion controlled regime only Co acts as a catalyst for the carbon graphitization. The results are consistent with the metal-mediated crystallization mechanism in the C:Co films. The results are discussed on the basis of the metal-carbide phase stability, carbon solubility in metals or their carbides and interface species.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-15253
Publ.-Id: 15253


The Dresden High Magnetic Field Laboratory (HLD) - a User Facility for Advanced Pulsed-Field Experiments

Wosnitza, J.; Herrmannsdörfer, T.; Zherlitsyn, S.; Zvyagin, S.

es liegt kein Abstract vor.

  • Invited lecture (Conferences)
    Physical Phenomena at High Magnetic Fields (PPHMF VII), 04.-08.12.2010, Tallahassee, Florida, USA

Permalink: https://www.hzdr.de/publications/Publ-15252
Publ.-Id: 15252


The role of water H-bond imbalances in B-DNA substate transitions and peptide recognition revealed by time-resolved FTIR spectroscopy

Khesbak, H.; Savchuk, O.; Tsushima, S.; Fahmy, K.

The conformational substates BI and BII of the phosphodiester backbone in B-DNA are thought to contribute to DNA flexibility and protein recognition. We have studied by rapid scan FTIR spectroscopy the isothermal BI-BII transition on its intrinsic time scale. Correlation analysis of IR absorption changes occurring within seconds after a reversible incremental growth of the DNA hydration shell identifies water populations w1 (PO2--bound) and w2 (non-PO2--bound) exhibiting weaker and stronger H-bonds, respectively, than those dominating in bulk water. The BII substate is stabilized by w2. The water H-bond imbalance of 3-4 kJ mol-1 is equalized at little enthalpic cost upon formation of a contiguous water network (at 12-14 H2O molecules per DNA phosphate) of reduced n(OH) band width. In this state, hydration water cooperatively stabilizes the BI conformer via the entropically favored replacement of w2-DNA interactions by additional w2-water contacts, rather than binding to BI-specific hydration sites. Such water rearrangements contribute to the recognition of DNA by indolicidin, an antimicrobial 13-mer peptide from bovine neutrophils which, despite little intrinsic structure, preferentially binds to the BI conformer in a water-mediated induced fit. The FTIR spectra resolve sequential steps leading from PO2--solvation to substate transition and eventually to base stacking changes in the complex. In combination with CD-spectral titrations, the data indicate that in the absence of a bulk aqueous phase, as in molecular crowded environments, water relocation within the DNA hydration shell allows for entropic contributions similar to those assigned to water upon DNA ligand recognition in solution.

Keywords: indolicidin; netropsin; DNA conformation; hydration; infrared; 2D correlation

  • Journal of the American Chemical Society 133(2011), 5834-5842

Permalink: https://www.hzdr.de/publications/Publ-15251
Publ.-Id: 15251


Fermi surface of the electron-doped cuprate superconductor Nd2−xCexCuO4 probed by high-field magnetotransport

Kartsovnik, M. V.; Helm, T.; Putzke, C.; Wolff-Fabris, F.; Sheikin, I.; Lepault, S.; Proust, C.; Vignolles, D.; Bittner, N.; Biberacher, W.; Erb, A.; Wosnitza, J.; Gross, R.

We report on the study of the Fermi surface of the electrondoped cuprate superconductor Nd2−xCexCuO4 by measuring the interlayer magnetoresistance as a function of the strength and orientation of the applied magnetic field. We performed experiments in both steady and pulsed magnetic fields on high-quality single crystals with Ce concentrations of x = 0.13–0.17. In the overdoped regime of x > 0.15, we found both semiclassical angledependent magnetoresistance oscillations (AMROs) and Shubnikov–de Haas (SdH) oscillations. The combined AMROs and SdH data clearly show that the appearance of fast SdH oscillations in strongly overdoped samples is caused by magnetic breakdown. This observation provides clear evidence for a reconstructed multiply connected Fermi surface up to the very end of the overdoped regime at x ~ 0.17. The strength of the superlattice potential responsible for the reconstructed Fermi surface is found to decrease with increasing doping level and likely vanishes at the same carrier concentration as superconductivity, suggesting a close relation between translational symmetry breaking and superconducting pairing. A detailed analysis of the high-resolution SdH data allowed us to determine the effective cyclotron mass and Dingle temperature, as well as to estimate the magnetic breakdown field in the overdoped regime.

  • Open Access Logo New Journal of Physics 13(2011), 015001

Permalink: https://www.hzdr.de/publications/Publ-15250
Publ.-Id: 15250


High-field ESR in low-dimensional spin systems

Zvyagin, S. A.

es hat kein Abstract vorgelegen!

  • Invited lecture (Conferences)
    Einladung an die University of Heraklion and the FORTH (Institut für Forschung und Technologie), 10.-15.05.2010, Heraklion, Greece
  • Invited lecture (Conferences)
    2016 Hefei Conference on Novel Phenomena in High Magnetic Fields, 29.10.-01.11.2016, Hefei, China

Permalink: https://www.hzdr.de/publications/Publ-15248
Publ.-Id: 15248


Implementation and workflow for PET monitoring of therapeutic ion irradiation: a comparison of in-beam, in-room, and off-line techniques

Shakirin, G.; Braess, H.; Fiedler, F.; Kunath, D.; Laube, K.; Parodi, K.; Priegnitz, M.; Enghardt, W.

Abstract
An independent assessment of the dose delivery in ion therapy can be performed using positron emission tomography (PET). For that a distribution of positron emitters which appear as the result of interaction between ions of the therapeutic beam and the irradiated tissue is measured during or after the irradiation. Three concepts for PET monitoring implemented in various therapy facilities are considered in this paper. The in-beam PET concept relies on the PET measurement performed simultaneously to the irradiation by means of a PET scanner which is completely integrated into the irradiation site. The in-room PET concept allows measurement immediately after irradiation by a standalone PET scanner which is installed very close to the irradiation site. In the off-line PET scenario themeasurement is performed by means of a standalone PET/CT scanner 10–30 min after the irradiation. These three concepts were evaluated according to image quality criteria, integration costs, and their influence onto the workflow of radiotherapy. In-beam PET showed the best performance. However, the integration costs were estimated as very high for this modality. Moreover, the performance of in-beam PET depends heavily on type and duty cycle of the accelerator. The in-room PET is proposed for planned therapy 5 Present address: Philips Research, HTC11, 5656 AE Eindhoven, The Netherlands.
0031-9155/

Keywords: in-beam PET; PET monitoring; ion therapy; in-vivo dosimetry

Permalink: https://www.hzdr.de/publications/Publ-15247
Publ.-Id: 15247


Infrared/terahertz applications in physical sciences

Schneider, H.

Starting with a brief survey on infrared/THz applications and systems, this talk concentrates on specific research opportunities in physics offered by free-electron lasers (FEL) at infrared/THz wavelengths. Unique properties of FEL radiation are (i) continuous spectral tunability at narrow spectral bandwidth, (ii) high power, (ii) spatial coherence, and (iv) short pulse length. Corresponding experimental techniques include linear, nonlinear/high-field, near-field, and time resolved spectroscopy. After describing the free-electron laser facility FELBE at HZDR, a few recent studies in solid-state physics covering these techniques will be reported.

Keywords: mid-infrared and terahertz (THz) spectroscopy; free-electron laser; semiconductor quantum structures

Related publications

  • Invited lecture (Conferences)
    Free Electron Laser IR to THz Applications Workshop, 28.01.2011, Bangkok, Thailand

Permalink: https://www.hzdr.de/publications/Publ-15246
Publ.-Id: 15246


A Markov chain model of classified atomistic transition states for discrete kinetic Monte-Carlo simulations

Numazawa, S.; Smith, R.

Classical harmonic transition state theory is considered and applied in discrete lattice cells with hierarchical transition levels. The scheme is then used to determine transitions which can be applied in a lattice-based kinetic Monte Carlo (KMC) atomistic simulation model.
The model results in an effective reduction of KMC simulation steps by utilizing a classification scheme of transition levels for thermally activated atomistic diffusion processes. Thermally activated atomistic movements are considered as local transition events constrained in potential energy wells over certain local time periods. These processes are represented by Markov chains of multi-dimensional Boolean valued functions in three dimensional lattice space.
The events inhibited by the barriers under a certain level are regarded as thermal fluctuations of the canonical ensemble and accepted freely.
Consequently, the fluctuating system evolution process is implemented as a Markov chain of equivalence class objects.
It is shown that the process can be characterized by the acceptance of metastable local transitions.
The method is applied to a problem of Au and Ag cluster growth on a rippled surface. The simulation predicts the existence of a morphology dependent transition time limit from a local metastable to stable state for subsequent cluster growth by accretion. Excellent agreement with observed experimental results is obtained.

Keywords: Kinetic Monte-Carlo

  • Physical Review E 84(2011), 046714

Permalink: https://www.hzdr.de/publications/Publ-15245
Publ.-Id: 15245


A population balance approach considering heat and mass transfer - experiments and CFD simulations

Krepper, E.; Beyer, M.; Lucas, D.; Schmidtke, M.

Bubble condensation in sub-cooled water is a complex process, to which various phenomena contribute. Since the condensation rate depends on the interfacial area density, bubble size distribution changes caused by breakup and coalescence play a crucial role.
Experiments on steam bubble condensation in vertical co-current steam/water flows have been carried out in an 8m long vertical DN200 pipe. Steam is injected into the pipe and the development of the bubbly flow is measured at different distances to the injection using a pair of wire mesh sensors. By varying the steam nozzle diameter the initial bubble size can be influenced. Larger bubbles come along with a lower interfacial area density and therefore condensate slower. Steam pressures between 1-6.5 MPa and sub-cooling temperatures from 2 to 6 K were applied. Due to the drop of hydrostatic pressure along the pipe, the saturation temperature falls towards the upper pipe end. This affects the sub-cooling temperature and can even cause re-evaporation in the upper part of the test section. The experimental configurations are simulated with the CFD code CFX using an extended MUSIG approach, which includes the bubble shrinking or growth due to condensation or re-evaporation. The development of the vapour phase along the pipe with respect to vapour void fractions and bubble sizes is qualitatively well reproduced in the simulations. For a better quantitative reproduction, reliable models for the heat transfer at high Reynolds number as well as for bubble breakup and coalescence are needed.

Keywords: two phase flow; experiments; CFD; population balance model; bubble coalescence; bubble breakupo; condensation; evaporation

Permalink: https://www.hzdr.de/publications/Publ-15244
Publ.-Id: 15244


Biokinetics, metabolism and PET imaging with Cu-64 and Ga-68 labeled ghrelin analogues in rats

Bergmann, R.; Chollet, C.; Pietzsch, J.; Beck-Sickinger, A. G.; Steinbach, J.

Ghrelin is a gastric peptide involved in food intake control, and growth hormone release. Besides its well-defined orexigenic role, ghrelin is likely involved in tumor development and growth. Therefore, non-invasive imaging agents for determining ghrelin receptors are desirable. However, ghrelin receptors are expressed in low level making detection via imaging difficult. The labeling using activated esters like 4-(F-18-fluoro)benzoyl-succinimide (2) was not possible due to the existence of three primary amino groups per peptide. Therefore, human ghrelin1-28 [Lys16(NODAGA)]-ghrelin1-28 and a short ghrelin inverse agonist NODAGA-KwFwLL-NH2 were synthesised on solid-phase. Subsequently, radiolabeling yielded Cu-64- and Ga-68-NODAGA-peptides in high radiochemical purity (>98%) with a specific activity >10 GBq/Gmol. For basic radiopharmacological characterization biodistribution, small animal PET, and metabolite analysis in arterial blood plasma were carried out in Wistar rats with all 4 radiotracers. The ghrelin analogues were in high amounts taken up by the kidneys. The Cu-64- and Ga-68-NODAGA-KwFwLL-NH2 were for the most part hepathobilliary eliminated. The metabolite analysis showed the well-known des acyl ghrelin as the main metabolite in vivo reaching 90% in blood plasma after one hour. On the other site the NODAGAKwFwLL-NH2 peptides were highly stabile; only 5% metabolites were observed after one hour in rat plasma. Interestingly, the biodistribution and kinetics were similar for the pairs of peptide labeled ether with Cu-64 or Ga-68. This shows the small effect of the different ionization of the Ga-68 (neutral) or Cu-64 (one negative charge) NODAGA complexes on the biodistribution. The blood clearance of these peptides was relative low, with about 50% of starting amount after one hour. The high stability and low blood clearance are important prerequisites for further studies of ghrelin receptor imaging. These results indicate that further in vivo evaluation of radiolabeled ghrelin inverse agonists as potential PET tracers for ghrelin receptors is warranted.

Reference: (1) Holst, B., et al. (2003) High constitutive signaling of the ghrelin receptor--identification of a potent inverse agonist. Mol Endocrinol 17, 2201-10. (2) Bergmann, R., et al. (2002) Biodistribution and catabolism of (18)F-labeled neurotensin(8-13) analogs. Nucl Med Biol 29, 61-72.

Acknowledgement: This project was partially supported by FP7 project “GIPIO”, Project Reference: 223057

  • Poster
    2010 World Molecular Imaging Congress, 08.-11.09.2010, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-15243
Publ.-Id: 15243


Dual-labeled Cetuximab-based imaging agent for NIR Fluorescence and PET

Bergmann, R.; Zenker, M.; Walther, M.; Pietzsch, H.-J.; Hofheinz, F.; van den Hoff, J.; Pietzsch, J.; Steinbach, J.

Cetuximab (C225) as a chimeric monoclonal antibody specifically targets the epidermal growth factor receptor (EGFR) that often is overexpressed in human malignancies. This phenotype is associated with tumor aggressiveness, treatment resistance, and biological heterogeneity with potential to bypass the blockade of the EGFR signaling pathways. The aim of this work was to prepare and characterize the C225 for near infrared fluorescence (NIRF) and PET imaging using a X-SIGHT Large Stokes Shift Dye (X-SIGHT 670 LSS Dye) and [64Cu]Cu-NOTA as a prerequisite for combination of both imaging methods. C225 was conjugated with the bifunctional chelator 2-(p-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (SCN-Bz-NOTA) and the X-SIGHT 670 Large Stokes Shift Dye, TFP Ester (XS670). The EGFR-affinity of the immunoconjugate resulted in 94% versus 100% of the unmodified C225 measured with specific enzyme-linked immunosorbent assay (ELISA) on EGFR-positive tumor cell line A431. C225-SCNBz-NOTA was labeled with 64Cu within 30 min with high radiolabeling yield and radiochemical purity. The [64Cu]Cu-NOTA-C225-XS670 showed high accumulation in xenotransplanted squamous cell carcinoma tumors in mice after 24 hours imaged with small animal PET and NIRF. The comparison of both methods in living animals showed the high signal intensity and accumulation of the probe in tumors; however only PET allowed the quantitative characterization of the probe distribution in vivo. The subsequent whole body cryosectioning of the animals into 40 µm sections permitted the direct comparison of the autoradiograms and NIRF images of the tissue cuts. The quantitative comparison of the autoradiograms and the NIRF images after coregistration of the corresponding images yielded a good correlation of the pixel intensities, but the different geometric resolution did not allow a pixel vise comparison. The NIRF images showed a higher differentiation than the autoradiograms. The dual-labeled C225 demonstrated the higher resolution and comparable concentration values of the antibody distribution in whole body cryosections of tumor bearing mice using the combination of 64Cu-radioluminography and NIRF imaging. The dual labeling of antibodies is a promising tool for quantitative evaluation of the long time distribution in animals using NIRF of cryosections beyond the decay of the radionuclide used.

Acknowledgement: This project was partially supported by FP7 project “GIPIO”, Project Reference: 223057

  • Poster
    2010 World Molecular Imaging Congress, 08.-11.09.2010, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-15242
Publ.-Id: 15242


Multimodality imaging in preclinical cancer research

Bergmann, R.

kein Abstract verfügbar

  • Invited lecture (Conferences)
    4th Bioscan Imaging Users Meeting (European part), 10.10.2010, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-15241
Publ.-Id: 15241


Identification of transport processes in bioirrigated muddy sediments by [18F]fluoride PET (Positron Emission Tomography)

Roskosch, A.; Lewandowski, J.; Bergmann, R.; Wilke, F.; Brenner, W.; Burchert, R.

In aquatic environments transport processes across the sediment–water interface are intensified by bioirrigating macrozoobenthos. Transport processes caused by Chironomus plumosus larvae dwelling in U-tubes were investigated by dynamic small animal Positron Emission Tomography (PET) with [18F]fluoride. Significant tracer transport from the burrows into the sediment was detected; penetration was deeper at the outlet branch of the burrow than at the inlet branch. Hence, advection plays a significant role in exchange between water in the burrows and muddy sediment.

Permalink: https://www.hzdr.de/publications/Publ-15240
Publ.-Id: 15240


Small animal PET for evaluation of tumor therapy

Bergmann, R.

kein Abstract verfügbar

  • Lecture (others)
    Oncoray Retreat, 28.01.2010, Bautzen, D

Permalink: https://www.hzdr.de/publications/Publ-15239
Publ.-Id: 15239


Biodistribution, -kinetics, metabolic stability, and imaging with radioactive ghrelin analogues

Bergmann, R.

kein Abstract verfügbar

  • Lecture (Conference)
    2nd GIPIO meeting, 02.-03.06.2010, Copenhagen, Danmark

Permalink: https://www.hzdr.de/publications/Publ-15238
Publ.-Id: 15238


Small animal molecular imaging in cancer research

Bergmann, R.

Quantitative small animal imaging plays a key role in preclinical research and drug development. However, no single imaging modality is perfect and sufficient to gain all the necessary morphologic, physiologic, metabolic or genetic information. For instance, optical fluorescence imaging is difficult to quantify - especially in tissue more than a few millimetres in depth within a subject; magnetic resonance imaging of protons (MRI) has superb resolution but low sensitivity, positron emission tomography (PET) has very high sensitivity but poor resolution, single photon emission tomography (SPECT) has good resolution but low sensitivity and X-ray tomography (CT) has good resolution of bones but cannot good resolve tissues. The combination of multiple molecular imaging techniques can therefore offer synergistic advantages over any modality alone. The multimodal approach by combination of the methods and development of multimodal probes is far from trivial and a challenge for the interdisciplinary work and collaboration of scientists.
In the presentation we provide an overview of the small animal imaging in the Forschungszentrum Dresden-Rossendorf, recent developments of probes and applications in multimodal cancer research. We will show examples of quantitative imaging using low and high molecular weight probes and microspheres labeled for PET, SPECT and optical imaging. The especial developed animal bed system helps us to register the 3D data from different dedicated modalities for combining and comparing the methods. The development of imaging probes is embedded a combination of in vitro and ex vivo evaluation of gene expression, cell uptake and binding studies.
The molecular imaging in mouse and rat models allows us to ‘see’ the biological complexities of tumors for the treatment of this disease. This is one of the most exciting and growing areas in our research.

  • Invited lecture (Conferences)
    International workshop on bio-medical applications of micro-PET, 20.-21.09.2010, Seville, Spain

Permalink: https://www.hzdr.de/publications/Publ-15237
Publ.-Id: 15237


Small animal imaging in Cancer Research

Bergmann, R.

kein Abstract verfügbar

  • Invited lecture (Conferences)
    Workshop Molecular Imaging, Budapest, 28.04.2010, Budapest, Hungary
  • Invited lecture (Conferences)
    Workshop Molecular Imaging, Veterinärmedizinische und Pharmazeutische Universität Brno, 27.04.2010, Brno, Czech Republic
  • Invited lecture (Conferences)
    Workshop Molecular Imaging, Karls-University Prague, 26.04.2010, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-15236
Publ.-Id: 15236


Multimodality small animal imaging in tumor biology

Bergmann, R.

kein Abstract verfügbar

  • Invited lecture (Conferences)
    Seminar Semmelweis University of Medicine, Faculty of Medicine, Institute of Human Physiology and Clinical Experimental Research, 28.04.2010, Budapest, Hungary

Permalink: https://www.hzdr.de/publications/Publ-15235
Publ.-Id: 15235


Synthesis and biological evaluation of novel 4-benzylpiperazine ligands for sigma-1 receptor imaging

Li, Z.-J.; Ren, H.-Y.; Cui, M.-C.; Deuther-Conrad, W.; Tang, R.-K.; Steinbach, J.; Brust, P.; Liu, B.-L.; Jia, H.-M.

We report the synthesis and evaluation of 4-benzylpiperazine ligands (BP-CH3, BP-F, BP-Br, BP-I, and BPNO2) as potential r1 receptor ligands. The X-ray crystal structure of BP-Br, which crystallized with monoclinic space group P21/c, has been determined. In vitro competition binding assays showed that all the five ligands exhibit low nanomolar affinity for r1 receptors (Ki = 0.43–0.91 nM) and high subtype selectivity (r2 receptor: Ki = 40–61 nM; Kir2/Kir1 = 52–94). [125I]BP-I (1-(1,3-benzodioxol-5-ylmethyl)-4-(4-iodobenzyl)piperazine) was prepared in 53 ± 10% isolated radiochemical yield, with radiochemical purity of >99% by HPLC analysis after purification, via iododestannylation of the corresponding tributyltin precursor. The log D value of [125I]BP-I was found to be 2.98 ± 0.17, which is within the range expected to give high brain uptake. Biodistribution studies in mice demonstrated relatively high concentration of radiolabeled substances in organs known to contain r1 receptors, including the brain, lung, kidney, heart, and spleen. Administration of haloperidol 5 min prior to injection of [125I]BP-I significantly reduced the concentration of radioactivity in the above-mentioned organs. The accumulation of radiolabeled substance in the thyroid was quite low suggesting that [125I]BP-I is relatively stable to in vivo deiodination. These findings suggest that the binding of [125I]BP-I to r1 receptors in vivo is specific.

Permalink: https://www.hzdr.de/publications/Publ-15234
Publ.-Id: 15234


Micro-structured copper electrodeposition in inhomogeneous magnetic fields

Mutschke, G.; Tschulik, K.; Weier, T.; Uhlemann, M.; Bund, A.; Fröhlich, J.

It is well known that in various electrochemical systems the mass transfer and also the morphology and the structure of the electrodeposits can be influenced by the proper application of magnetic fields. One of the main reasons seems to be the convection induced by the resulting magnetic forces. Lorentz forces have been used to tailor the electrodeposition of metals for quite a while. Only recently, an improved understanding of the convection forced was gained that turned out to be more complex than expected, even in simple geometries [1]. Additionally, the influence of magnetic gradient forces on the preparation of micro-structured metal deposits on field-gradient electrodes has been discussed in the literature [2]. These electrodes consist of magnetic elements such as permanent magnets or magnetized ferromagnetic materials which are arranged beneath the surface of the working electrode. Here, however, besides the magnetic gradient force, also the Lorentz force might influence the deposition process. The presentation will summarize new numerical simulations, analytical findings and experimental results in order to discuss the influence of the different magnetic forces involved and will discuss the prospects towards smaller deposition structures [3,4].

[1] G. Mutschke et al., Electrochim. Acta 55 (2010) 1543.

[2] K. Tschulik et al., Electrochem. Comm. 11 (2009) 2241.

[3] G. Mutschke et al., Electrochim. Acta 55 (2010) 9060.

[4] K. Tschulik et al., Electrochim. Acta 56 (2010) 297.

Keywords: Magnetoelectrochemistry; electrodeposition

  • Lecture (Conference)
    Jahrestagung der Gesellschaft für angewandte Mathematik und Mechanik (GAMM 2011), 18.-21.04.2011, Graz, Österreich

Permalink: https://www.hzdr.de/publications/Publ-15233
Publ.-Id: 15233


Future aspects of X-ray emission from crystalline undulators at positron channeling

Backe, H.; Krambrich, D.; Lauth, W.; Buonomo, B.; Dabagov, S. B.; Mazzitelli, G.; Quintieri, L.; Lundsgaard Hansen, J.; Uggerhoj, U. I.; Azadegan, B.; Dizdar, A.; Wagner, W.

In connection with ideas to produce undulator-like radiation in the hundreds of keV up to the MeV region by means of positron and electron channeling, there is renewed interest to study various channeling phenomena also experimentally. With electrons experiments have been performed at the Mainz Microtron MAMI to explore channeling-radiation emission by a 4-period epitaxially grown strained layer SiGe undulator. Unfortunately, high quality positron beams of sufficient intensity are not easily accessible. The only serious candidate in Europe seems to be the Beam Test Facility at INFN LNF Frascati, Italy. Some requirements to extend BTF in a facility which is also well suited for positron channeling-radiation experiments will be outlined.

Keywords: undulator radiation; crystal undulator; positron channeling; channeling radiation

  • Contribution to proceedings
    4th International Conference Charged and Neutral Particles Channeling Phenomena, Channeling 2010, 03.-08.10.2010, Ferrara, Italy
    Future aspects of X-ray emission from crystalline undulators at positron channeling, Bologna: Societa Italiana di Fisica, 175-180
  • Nuovo Cimento C 34(2011)04, 175-180
    DOI: 10.1393/ncc/i2011-10983-9
    Cited 14 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-15232
Publ.-Id: 15232


Simulation of axial channeling radiation on a thin Ge single crystal

Azadegan, B.; Dabagov, S. B.; Wagner, W.

Based on classical electrodynamics the radiation emitted by axially channeled electrons has been investigated by means of computer simulations. Using the Doyle-Turner approximation for the atomic scattering factor and taking thermal vibrations of atoms into account, we calculated the two-dimensional continuum potential of the <110> crystallographic axis of a thin Ge single crystal. The trajectories, velocities and accelerations of electrons are obtained by solving the equations of motion in three dimensions, and the spectral-angular distribution of radiation has been calculated in the classical way.

Keywords: axial channeling; channeling radiation; Germanium single crystal

  • Contribution to proceedings
    4th International Conference Charged and Neutral Particles Channeling Phenomena, Channeling 2010, 03.-08.10.2010, Ferrara, Italy
    Simulation of axial channeling radiation on a thin Ge single crystal, Bologna: Societa Italiana di Fisica, 149-156
  • Nuovo Cimento C 34(2011)04, 149-156
    DOI: 10.1393/ncc/i2011-10919-5
    Cited 5 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-15231
Publ.-Id: 15231


Ion erosion induced surface patterning studied by combined trim and kinetic monte-carlo simulations

Liedke, B.; Heinig, K.-H.; Facsko, S.; Möller, W.

Understanding of surface morphology evolution induced by ion erosion is still limited. Continuum models cannot explain microscopic processes. On the other hand, so far atomistic simulations could not describe pattern evolution on experimental spatiotemporal scales. Therefore, recently continuum equations were feeded with MD simulation results, which allows the understanding of smoothing mechanisms like an effective mass ‘downhill’ current induced by ballistic drift.

We developed a novel program package which unifies the collision cascade with kinetic Monte-Carlo simulations. This allows a fully atomistic description on experimental spatiotemporal scales. 3D atom relocations were calculated using the binary collision approximation, whereas the thermally activated relaxation as well as diffusive processes were simulated by a bit-coded kinetic 3D Monte Carlo program. Effects like ballistic mass drift or dependence of local morphology on sputtering yield are automatically included by this approach.

The mechanism of ripple formation induced by a local surface currents is studied. The quantitative description of current vectors for different environmental parameters, and initial surface condition of sinusoidal structure, can be analized in time and space, following the local atomic drift. Different driving forces can be distinguished. Without ion irradiation the mass current vectors are always parallel to the surface plane with down-hill direction. Collision-cascade-induced defects change the mass currents significantly. Up-hill currents induce self-organization for certain obligue ion incidence angles. This driving forces causes patterning even without sputtering events.

Keywords: ripples; ion beam sputtering; pattern formation; kinetic Monte-Carlo; TRIM; crater formation; surface mass current

  • Poster
    17th International Conference on Ion Beam Modification of Materials (IBMM 10), 22.-27.08.2010, Montreal, Canada

Permalink: https://www.hzdr.de/publications/Publ-15230
Publ.-Id: 15230


Channeling radiation on quartz stimulated by acoustic waves

Wagner, W.; Azadegan, B.; Büttig, H.; Grigoryan, L. S.; Mkrtchyan, A. R.; Pawelke, J.

The stimulation of channeling radiation by acoustic waves excited in the single crystal has been predicted in early works of the 1980's. Based on quantum calculations, the described experiment aimed at verification of theoretical considerations. Making use of the reverse piezoelectric effect, hypersonic waves of frequency 12 GHz, which corresponds to a dedicated transition between bound states of planar channelled relativistic electrons, were excited in a single-crystal quartz plate. The spectrum of channeling radiation measured under the influence of acoustic waves reveals enhanced radiation intensity. The obtained results are discussed and may be phenomenologically understood assuming electron diffraction on an acoustic superlattice.

Keywords: channeling radiation; quartz single crystal; ultrasound

Related publications

  • Contribution to proceedings
    4th International Conference Charged and Neutral Particles Channeling Phenomena, Channeling 2010, 03.-08.10.2010, Ferrara, Italy
    Channeling radiation on quartz stimulated by acoustic waves, Bologna: Societa Italiana di Fisica, 133-140
  • Nuovo Cimento C 34(2011)04, 133-140
    DOI: 10.1393/ncc/i2011-10899-4
    Cited 5 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-15229
Publ.-Id: 15229


Ion-beam-induced interface mixing: unified atomistic simulations of collisional and thermal processes

Liedke, B.; Heinig, K.-H.; Facsko, S.; Möller, W.

Ion beam processing of materials at elevated temperature, which can be room temperature for metals, is controlled simultaneously by both, collisional and thermally activated processes. So far, large scale process simulations separate these processes, calculating all collision cascades of the complete ion irradiation in the binary collision approximation like the TRIDYN code, and simulating then the defect relaxation/impurity nucleation by kinetic Monte Carlo.

Here we present and apply a unified computer simulation program package which unifies both programs, i.e. after each calculated 3D collisional cascade some kinetic Monte Carlo steps allow relaxation, diffusion, phase separation etc. in the whole volume. Contrary to molecular dynamics simulations, our approach allows studies on experimental spatiotemporal scales. In this presentation we focus on the evolution of interfaces under ion irradiation, where collisional mixing is in competition with thermally activated diffusion and phase separation. He+ irradiations for two extreme cases were studied: (i) Irradiation of interfaces made by immiscible elements, here Al and Pb. Ballistic interface mixing is accompanied by phase separation. Al and Pb nanoclusters form and show self-ordering (banding) parallel to the interface. (ii) Irradiation of interfaces made by intermetallics forming species, here Pt and Co. Well-ordered layers of phases of intermetallics appear in the sequence Pt/Pt3Co/PtCo/PtCo3/Co, resulting in a stepwise changing Pt/Co concentration depth profile. Novel magnetic properties of such sandwiched phases are predicted and can explain the transition between out of plane and in-plane magnetic anisotropy caused by ion irradiation.

Keywords: interface; mixing; bi-layer; kinetic monte-carlo; KMC; TRIM; TRIDYN; phase transition; crystal ordering

  • Lecture (Conference)
    17th International Conference on Ion Beam Modification of Materials (IBMM 10), 22.-27.08.2010, Montreal, Canada

Permalink: https://www.hzdr.de/publications/Publ-15228
Publ.-Id: 15228


Quantum uncertainties in the energy of transverse oscillations of planar channeled particle

Mkrtchyan, A. R.; Grigoryan, L. S.; Mkrtchyan, A. H.; Khachatryan, H. F.; Wagner, W.; Azadegan, B.

It is shown that quantum uncertainties in the energy of transverse oscillations of planar channeled particle become significant at definite values of the crystal period in the direction of channeling. The possibility of producing superlattices with periodical potential is discussed.

Keywords: channeling radiation; quantum uncertainties

  • Contribution to proceedings
    International conference on electrons, positrons, neutrons and X-rays scattering under external influences, 26.-30.10.2009, Yerevan-Meghri, Armenia
    Quantum uncertainties in the energy of transverse oscillations of planar channeled particle, Yerevan, Armenia, 978-99941-2-486-2

Permalink: https://www.hzdr.de/publications/Publ-15226
Publ.-Id: 15226


Channeling radiation on quartz influenced by acoustic waves

Wagner, W.; Azadegan, B.; Büttig, H.; Mkrtchyan, A. R.; Grigoryan, L. S.; Pawelke, J.

The influence of acoustic waves excited in a single quartz crystal on the emission of channeling radiation by relativistic electrons has been proved experimentally.

Keywords: channeling radiation; quartz single crystal; ultrasound

Related publications

  • Contribution to proceedings
    International conference on electrons, positrons, neutrons and X-rays scattering under external influences, 26.-30.10.2009, Yerevan-Meghri, Armenia
    Proceedings of the International conference on electrons, positrons, neutrons and X-rays scattering under external influences, Yerevan, Armenia, 978-99941-2-486-2

Permalink: https://www.hzdr.de/publications/Publ-15225
Publ.-Id: 15225


Warum Ge und Si durch Ionenimplantation zu Supraleitern werden

Fiedler, J.

Es konnte gezeigt werden, dass neben Diamant auch die technologisch relevanten Gruppe-IV-Halbleiter Si und Ge im extrem hochdotierten Zustand supraleitend werden. Am Helmholtz – Zentrum Dresden – Rossendorf ist es erstmalig gelungen, supraleitfähige Ge-Schichten in einem zu Fertigungsverfahren der Mikroelektronik kompatiblen Dotierprozess, bestehend aus Ga-Ionenimplantation und Kurzzeitausheilung, herzustellen. Die hochdotierten Ge-Schichten zeigen intrinsische Supraleitung mit kritischen Temperaturen bis zu 1 K. Eine weitere Erhöhung der Dotierkonzentration und damit der kritischen Temperatur ist aufgrund der begrenzten Löslichkeit von Ga in Ge (1 at.%) sehr schwierig. Um dennoch höhere Sprungtemperaturen zu erreichen, wurden die geringe Löslichkeit von Ga in Si (0.1 at.%) sowie die supraleitenden Eigenschaften von Ga ausgenutzt. In Ga implantiertem Si bilden sich Ausscheidungen, wodurch vergrabene, extrinsisch supraleitende Ga reiche Schichten hergestellt werden können. Die kritische Temperatur ist mit 7 K deutlich höher als in dotiertem Ge.
Die Struktur der Proben wurde mit Rutherford Rückstreuspektrometrie (RBS), Transmissionselektronenmikroskopie (TEM) sowie Sekundärionen-Massenspektrometrie (SIMS) untersucht. Für die elektrische Charakterisierung wurden Temperaturen zwischen 100 mK und 400 K sowie Magnetfelder bis 9 T verwendet. Im Vortrag werden die Grundzüge der Dotierung mittels Ionenimplantation sowie die Ergebnisse elektrischer und struktureller Untersuchung beider Materialsysteme vorgestellt.

Related publications

  • Lecture (others)
    Institutsseminar SS 2011, Institut für Physik, TU Ilmenau, 18.05.2011, Ilmenau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-15224
Publ.-Id: 15224


ROBL: The first European actinide XAS beamline in its second decade of operation

Scheinost, A. C.; Hennig, C.; Rossberg, A.; Banerjee, D.

The Rossendorf Beamline at ESRF (ROBL) in operation since 1998 [1] is together with the INE Beamline at ANKA and the micro-XAS beamline at SLS one of three dedicated radionuclide XAS beamlines in Europe. ROBL is specialized in handling actinide nuclides up to Cf with a total activity to 185 MBq. The wide energy range (5 to 35 keV) permits to run actinide L1, L2 and L3 edges, important for the investigation of mixed actinide systems. Both the high photon flux (6 1011 ph/s on the sample) and the high-performance fluorescence detection makes ROBL suited for very low concentrations (according to XAS standards,  1 ppm XANES,  20 ppm EXAFS). Research at ROBL encompasses basic actinide chemistry, biogeochemistry, environmental chemistry and materials sciences, with applications for the improvement of nuclear waste repositories, remediation of uranium mining areas and other contaminated sites, development of fourth generation nuclear fuels, minor actinide waste forms and transmutation targets. The ROBL team supports users before, during and after the experiments. Own research specializes on the development of new data analysis tools (statistical tools, wavelets, Monte-Carlo simulations, PDF) as well as on actinide redox chemistry (structure of aqueous and non-aqueous complexes, redox mechanisms at water/mineral interfaces). From 2012 on, a major upgrade of the ROBL optics will further increase photon flux, energy range, and spectral resolution; and reduce spot size and data acquisition time; while maintaining reliable and relatively easy operation.

[1] W. Matz et al., Journal of Synchrotron Radiation 6, 1076-1085 (1999).

Keywords: xafs; robl; xanes; xas; synchrotron; beamline

Related publications

  • Invited lecture (Conferences)
    Actinide-XAS 2011, 02.02.2011, Harima Science Garden City, Japan

Permalink: https://www.hzdr.de/publications/Publ-15223
Publ.-Id: 15223


AcXAS, a reference data base for XAS spectra of actinides and other radionuclides

Scheinost, A. C.; Schmeisser, N.; Denecke, M.; Banerjee, D.; Dardenne, K.; Hennig, C.; Rossberg, A.; Rothe, J.; Daehn, R.

Reference spectra of well characterized samples are crucial for the analysis of x-ray absorption spectra (XAS). In order to avoid that experimentalists have to repeat XAS measurements of standard actinide compounds/species, thereby making more efficient use of costly radionculides, sample preparation, beamtime, radioprotection measures, transport, administration, etc., we are in the process of establishing a public database of actinide XAS reference spectra. The spectra are retrieved from the large data inventory of the three current European radionuclide beamlines, the Rossendorf Beamline at ESRF (France), the INE beamline at ANKA (Germany), and the micro-XAS beamline at SLS (Switzerland), but will also include data from other beamlines. This effort is supported by the European Commission through the ACTINET-I3 project. An overview on data base structure, criteria for data entry and use, as well as on the current status of data will be given.

Keywords: actinides; xas; xanes; exafs; data base

Related publications

  • Poster
    Actinide-XAS 2011, 02.02.2011, Harima Science Garden City, Japan
  • Invited lecture (Conferences)
    ACTINET Plenary Meeting, 01.02.2011, Marcoule, France

Permalink: https://www.hzdr.de/publications/Publ-15222
Publ.-Id: 15222


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