Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33407 Publications

g-factor measurements on relativistic isomeric beams produced by fragmentation and U-fission: the g-Rising project at GSI

Neyens, G.; Atanasova, L.; Balabanski, D. L.; Becker, F.; Bednarczyk, P.; Caceres, L.; Doornenbal, P.; Gerl, J.; Gorska, M.; Grebosz, J.; Hass, M.; Ilie, G.; Kurz, N.; Kojouharov, I.; Lozeva, R.; Maj, A.; Pfutzner, M.; Pietri, S.; Podolyak, Z.; Prokopowicz, W.; Saitoh, T. R.; Schaffner, H.; Simpson, G.; Vermeulen, N.; Werner-Malento, E.; Walker, J.; Wollersheim, H. J.; Bazzacco, D.; Benzoni, G.; Blazhev, A.; Blasi, N.; Bracco, A.; Brandau, C.; Camera, F.; Chamoli, S. K.; Chmel, S.; Crespi, F. C. L.; Daugas, J. M.; de Rydt, M.; Detistov, P.; Fahlander, C.; Farnea, E.; Georgiev, G.; Gladnishki, K.; Hoischen, R.; Ionescu-Bujor, M.; Iordachescu, A.; Jolie, J.; Jungclaus, A.; Kmiecik, M.; Krasznahorkay, A.; Kulessa, R.; Lakshmi, S.; Lo Bianco, G.; Mallion, S.; Mazurek, K.; Meczynski, W.; Montanari, D.; Myalsky, S.; Perru, O.; Rudolph, D.; Rusev, G.; Saltarelli, A.; Schwengner, R.; Styczen, J.; Turzo, K.; Valiente-Dobon, J. J.; Wieland, O.; Zieblinski, M.
Within the RISING (Rare ISotope INvestigations @ GSI) Collabora-tion at GSI, g factor measurements have been performed on isomeric states in neutron-rich isotopes approaching 132 Sn and in the neutron deficient Pb-region (the g-RISING campaign). We present the experimental technique and some typical aspects related to such studies on relativistic beams selected with the FRS fragment separator. First results are presented for the (19/2+ ) 4.5 µs isomeric state in 127 Sn, which has been produced by means of fission of a relativistic 238 U beam on the one hand, and by the fragmentation of a relativistic 136 Xe beam on the other hand. Spin-alignment has been observed in both reactions. It was the first time that spin-alignment has been established in a relativistic fission reaction.
Keywords: Nuclear structure, radioactive beams, g-factor measurements
  • Contribution to proceedings
    Zakopane Conference on Nuclear Physics, 04.-10.10.2006, Zakopane, Poland
    Acta Physica Polonica B 38, 1237-1245

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Permalink: https://www.hzdr.de/publications/Publ-9668
Publ.-Id: 9668


U(VI) sorption on sandstone: Experiments and modeling

Richter, A.; Nebelung, C.; Brendler, V.
The sorption of U(VI) on natural and synthetic sandstone was investigated in batch sorption experiments (air atmosphere, 0.1M NaClO4, pH 3-11, [U(VI)] 10-9-10-4M. The synthetic sandstone was a mixture of quartz with muscovite and hematite. The surface area (N2-BET) of quartz was 0.047 m2/g, of muscovite 0.88 m2/g, of hematite 0.89 m2/g and of natural sandstone (mainly quartz) 0.69 m2/g.
The pH dependence shows a maximal sorption between pH 5.5-7.5. The U(VI) sorption varied between 95% (10-9M) and 7% (10-4) on natural sandstone, and between 80% (10-9M) and 2% (10-4M) on synthetic sandstone. Fig. 1 shows the comparison of sandstone with pure components (at similar conditions) quartz, muscovite, and hematite. More U(VI) was adsorbed on natural and on synthetic sandstone, than on quartz. The higher sorption are caused by the other components muscovite and hematite, and by the higher surface area.
The linear Freundlich sorption isotherms indicate one binding type. Sorption predicted by the Diffuse Double Layer Model (using the code FITEQL) agreed with the experimental sorption values within their uncertainty.
Keywords: sorption, uranium, sandstone, surface complexation, diffuse double layer model
  • Lecture (Conference)
    Goldschmidt 2007, 19.-24.08.2007, Köln, Germany
  • Abstract in refereed journal
    Geochimica et Cosmochimica Acta 71(2007), A838

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Permalink: https://www.hzdr.de/publications/Publ-9667
Publ.-Id: 9667


Ultra fast electron beam X-ray CT for two-phase flow measurements

Bieberle, M.; Schleicher, E.; Fischer, F.; Hampel, U.; Do Couto Aktay, K. S.; Koch, D.; Menz, H.-J.; Mayer, H.-G.
Nuclear reactor safety concerns for todays operated light water reactors are closely linked to thermal hydraulic phenomena in the primary and secondary coolant circuits of nuclear systems. To gain an improved understanding of phenomena associated with certain types of accidents as well as for the optimisation of fuel elements regarding the heat transfer in the reactor core simulation tools, such as system codes and more recently CFD codes are frequently applied. However, both types of tools today still exhibit some problems when treating two-phase flow scenarios. Therefore, in recent years much effort has been spent on further code development as well as on validation. This, however, was and is always accompanied by the requirement for reliable measurement data from two-phase flows under typical nuclear thermal hydraulic conditions. Experimental thermal hydraulic facilities, such as the TOPFLOW facility at FZD [1], may provide such data if they are equipped with sophisticated two-phase flow measurement sensors. One example is the wire-mesh sensor [2] that can provide phase and velocity data from steam-water two-phase flows at frame rates of up to 10 kHz and spatial resolution down to 2 mm. Since the wire mesh sensor is intrusive it has some influence on the flow. More appropriate would be tomographic imaging techniques based on either X-ray or gamma rays. However, classical CT systems, though being non-intrusive and sufficiently penetrative even for thicker metallic vessel walls, suffer from low temporal resolution, which is due to the requirement for taking different angular views of an object prior to reconstruction. So far this problem has been considered as intractable and unavoidable and tomographic techniques have almost exclusively been used to measure time averaged quantities, such as the gas hold-up.
We recently suggested [1] a computed tomography (CT) system which uses a fast moving electron beam X-ray source for the application in two-phase flow measurements. We have experimentally shown that frame rates of 10000 images per second can be reached. The static installation of the detector, however, limits the angular range of the source path which leads to so called limited-angle artefacts in the reconstructed images. Although these artefacts cannot be completely eliminated, because they are due to missing data, they can be reduced by maximizing the angular viewing range and by adequate image reconstruction algorithms [4].
Keywords: electron beam x-ray CT, two-phase flow
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2007, 22.-24.05.2007, Karlsruhe, Germany
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2007, 22.-24.05.2007, Karlsruhe, Germany
    Proc. Jahrestagung Kerntechnik 2007, CD-ROM plus, 27-30

Permalink: https://www.hzdr.de/publications/Publ-9666
Publ.-Id: 9666


Gründungsidee und Geschäftskonzept - BIOREM

Raff, J.
Im Rahmen der zweiten Phase des Businessplan-Wettbewerbs FutureSAX hat es die Geschäftsidee "BIOREM" erneut unter die besten Teams geschafft.
Vor der eigentlichen Prämierung muss die Geschäftsidee und die Marketingstrategie vor der Expertenjury der Branche Bio-/ Nanotechnologie verteidigt werden. Erst nach Prüfung aller Anträge werden die eigentlichen Gewinner gekürt.
  • Lecture (others)
    2. Phase FutureSAX-Businessplan-Wettbewerb, 19.04.2007, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-9665
Publ.-Id: 9665


Direct Time-of-Flight for Quantitative, Real-Time In-Beam PET: Concept and Feasibility Study

Crespo, P.; Shakirin, G.; Fiedler, F.; Enghardt, W.; Wagner, A.
We extrapolate the impact of recent detector and scintillator developments, enabling sub-nanosecond coincidence timing resolution t, onto in-beam positron emission tomography (in-beam PET) for monitoring charged-hadron radiation therapy. For t <= 200 ps full width at half maximum, the information given by the time-of-flight (TOF) difference between the two opposing gamma-rays enables shift-variant (fixed dual-head), artifact-free tomograms to be utilized for in-beam PET. We present the corresponding fast, TOF-based and backprojection-free, 3D reconstruction algorithm that, coupled with a real-time data acquisition and a fast detector encoding scheme, allows the sampled beta-plus-activity to be visualized in the object during the course of the irradiation. Despite the very low statistics scenario typical of in-beam PET, real-treatment simulations show that in-beam TOF-PET enables high-precision, quantified images to be obtained in real-time, either with closed-ring or with fixed, dual-head in-beam TOF-PET systems. The latter alleviates greatly the installation of in-beam PET at radiotherapeutic sites.
Keywords: TOF-PET, radiotherapy, proton therapy, ion therapy

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Permalink: https://www.hzdr.de/publications/Publ-9664
Publ.-Id: 9664


On projective Hilbert space structures at exceptional points

Günther, U.; Rotter, I.; Samsonov, B.
We consider a non-Hermitian complex symmetric 2×2 matrix toy model to study projective Hilbert space structures in the vicinity of exceptional points (EPs). After Puiseux-expanding the bi-orthogonal eigenvectors of a diagonalizable matrix in terms of the root vectors at the EP we resolve the apparent contradiction between the two incompatible normalization conditions with finite and singular behavior in the EP-limit by projectively extending the original Hilbert space. The complementary normalization conditions correspond then to two different affine charts of this enlarged projective Hilbert space. Geometric phase and phase jump behavior are analyzed and the usefulness of the phase rigidity as measure for the distance to EP configurations is demonstrated. Finally, EP-related aspects of PT-symmetrically extended Quantum Mechanics are discussed and the zero limit of the optimal passage time in non-Hermitian quantum brachistochrone problems is identified as an EP-related artifact.
Keywords: exceptional points, branch points, projective Hilbert space, geometric phase, singularities, PT-symmetric Quantum Mechanics, quantum brachistochrone problem
  • Invited lecture (Conferences)
    Many-body open quantum systems: From atomic nuclei to quantum dots, 14.-18.05.2007, Trento, Italy

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Permalink: https://www.hzdr.de/publications/Publ-9663
Publ.-Id: 9663


Projective Hilbert space structures at exceptional points

Günther, U.; Rotter, I.; Samsonov, B.
A non-Hermitian complex symmetric 2×2 matrix toy model is used to study projective Hilbert space structures in the vicinity of exceptional points (EPs). The bi-orthogonal eigenvectors of a diagonalizable matrix are Puiseux-expanded in terms of the root vectors at the EP. It is shown that the apparent contradiction between the two incompatible normalization conditions with finite and singular behavior in the EP-limit can be resolved by projectively extending the original Hilbert space. The complementary normalization conditions correspond then to two different affine charts of this enlarged projective Hilbert space. Geometric phase and phase jump behavior are analyzed and the usefulness of the phase rigidity as measure for the distance to EP configurations is demonstrated. Finally, EP-related aspects of PT-symmetrically extended Quantum Mechanics are discussed.
Keywords: exceptional points, branch points, projective Hilbert space, geometric phase, singularities, PT-symmetric Quantum Mechanics, quantum brachistochrone problem

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Publ.-Id: 9662


L-Type Amino Acid Transporters LAT1 and LAT4 in Cancer: Uptake of 3-O- Methyl-6-18F-Fluoro-L-Dopa (18F-OMFD) in Human Adenocarcinoma and Squamous Cell Carcinoma in vitro and in vivo

Haase, C.; Bergmann, R.; Füchtner, F.; Hoepping, A.; Pietzsch, J.
Expression of system L amino acid transporters (LAT) is strongly increased in many types of tumor cells. The purpose of this study was to demonstrate that 18F-labeled amino acids, e.g., 3-O-Methyl-6-18F-Fluoro-L-Dopa (18F-OMFD), that were accumulated in tumors via LAT, represent an important class of imaging agents for visualization of tumors in vivo by positron emission tomography (PET).
Methods:
In the present study 18F-OMFD uptake kinetics, transport inhibition, and the system L mRNA expression were studied in vitro in human adenocarcinoma (HT-29), squamous cell carcinoma (FaDu) cells, macrophages (THP-1) and primary aortic endothelial cells (HAEC), and in vivo in the corresponding mouse tumor xenograft models. Results: It was demonstrated that uptake of 18F-OMFD in all cell lines tested was mediated mainly by the sodium-independent high-capacity LAT. We found an increased uptake in FaDu cells (Vmax 10.6±1.1 nmol/min ´ mg cell protein) and in the corresponding FaDu tumor xenografts in comparison to the other cells and corresponding xenograft models studied. Quantitative mRNA analysis revealed that tumor cells and xenografts have a higher expression of LAT1 compared to HAEC and THP-1 macrophages. However, only in the FaDu tumor model an increased OMFD uptake seems to be explained by increased LAT expression. Furthermore, we demonstrated a high expression for LAT4, a recently new identified system L amino acid transporter.
Conclusion:
Our findings support the hypothesis that 18F-OMFD is a tracer for visualization of tumor cells, and, in particular, seems to be a suitable tracer for diagnostic imaging of amino acid transport in poorly differentiated squamous cell head and neck carcinoma with increased LAT1 and LAT4 expression.

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Publ.-Id: 9661


Aspects of 6-[18F]fluoro-L-DOPA preparation: Deuterochloroform as a substitute solvent for Freon 11

Füchtner, F.; Zessin, J.; Mäding, P.; Wüst, F.
Aim:
Replacement of the ecologically harmful solvent Freon 11 (CFCl3) by chloroform for the module-assisted preparation of 6-[18F]fluoro-L-DOPA based on the electrophilic radiofluorodestannylation of the precursor N-formyl-3,4-di-tert-butoxycarbonyloxy-6-(trimethylstannyl)-L-phenylalanine ethyl ester.

Materials and methods:
The TRACERlab Fx FDOPA module (GE Medical Systems) was used for the preparation of 6-[18F]fluoro-L-DOPA. Cyclotron-produced [18F]F2 gas (5 GBq) was passed through a cooled solution (5°C) of the stannyl precursor (45 mg) in CDCl3 (10 ml). After the [18F]fluorination step, HCl (2 ml, 6 M) was added to the solution. Then the reaction mixture was heated at 80°C for 5 min under vacuum to evaporate the chloroform. The hydrolysis to remove the protecting groups was completed by heating the closed reactor at 130°C for 8 min. After cooling to 20°C the reaction mixture was purified by HPLC with two polymer-based RP columns (PRP 1, 7 μm, 10×250 mm, Hamilton) using a solution of AcOH/AcONa (pH 4.7) as eluent. The [18F]fluoro-L-DOPA fraction was collected and sterile filtrated.

Results:
Three types of stabilised chloroform were tested for the radiofluorination of the precursor. Only by use of deuterochloroform stabilised with silver no significant losses of radioactivity were observed. Thus, 6 [18F]fluoro-L-DOPA purified by HPLC was obtained in decay-corrected radiochemical yields of 25±3%, ready for human use.

Conclusion:
CDCl3 has proved to be a convenient solvent for the module-assisted preparation of 6-[18F]fluoro-L-DOPA. In this way the use of the polluting Freon 11 can be avoided.
Keywords: 6-[18F]fluoro-L-DOPA, electrophilic radiofluorodestannylation, Freon 11 substitution, deuterochloroform

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Permalink: https://www.hzdr.de/publications/Publ-9660
Publ.-Id: 9660


Multimodal electronic–vibronic spectra of luminescence in ion-implanted silica layers

Fitting, H.-J.; Salh, R.; Schmidt, B.
Thermally oxidized SiO2 layers of 100 and 500 nm thickness have been implanted by oxygen and sulfur ions with a dose of 3x1016 and 5x1016 ions/cm2, respectively, leading to an atomic dopant fraction of about 4 at.% at the half depth of the SiO2 layers. The cathodoluminescence spectra of oxygen and sulfur implanted SiO2 layers show besides characteristic bands a sharp and intensive multimodal structure beginning in the green region at 500nm over the yellow-red region extending to the near IR measured up to 820 nm. The energy step differences of the sublevels amount on average 120meV and indicate vibration associated electronic states, probably of O2- interstitial molecules, as we could demonstrate by a respective configuration coordinate model.
Keywords: Cathodoluminescence; defect luminescence; vibronic spectra; photonic crystals

Permalink: https://www.hzdr.de/publications/Publ-9659
Publ.-Id: 9659


Multimodal Luminescence Spectra of Ion-Implanted Silica

Fitting, H.-J.; Salh, R.; Schmidt, B.
The main luminescence bands in silica SiO2 are the red luminescence R (650 nm, 1.9 eV) of the non-bridging oxygen hole center, and the blue band B (460 nm, 2.7 eV) and ultraviolet luminescence UV (290 nm, 4.3 eV), both commonly related to oxygen-deficient centers. In the present work, we will enhance or replace either the first or second constituent of SiO2, i.e., silicon or oxygen, isoelectronically by additional implantation of the respective ions. Thus, thermally oxidized SiO2 layers have been implanted by different ions of the IV group (C, Si, Ge, Sn, Pb) and of the VI group (O, S, Se) with doses up to 5x1016 cm-2, leading to an atomic dopant fraction of about 4 at % at the half depth of the SiO2 layers. Very surprisingly, the cathodoluminescence spectra of oxygen- and sulfur-implanted SiO 2 layers show, besides the characteristic bands, a sharp and intensive multimodal structure beginning at the green region at 500 nm up to the near infrared. The energy step differences of the sublevels equal on average 120 meV, and indicate vibration associated electronic states, probably of O2- interstitial molecules.
Keywords: Cathodoluminesence, silicon dioxide, ion implantation

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Permalink: https://www.hzdr.de/publications/Publ-9658
Publ.-Id: 9658


Nanosized allotropes of molybdenum disulfide

Enyashin, A. N.; Gemming, S.; Seifert, G.
The present review provides an overview of the rich polymorphism encountered on different length scales within the very versatile material class of transition metal chalcogenides. On the mesoscopic to nanoscopic scale such compounds exhibit a wide variety of nanostructured allotropes with varying dimensionality and competing internal structure, such as nanorods, nanostripes, nanotubes, fullerene-like particles and fullerenes. On the atomistic scale, competing local atomic arrangements within one type of allotrope determine crucially the stability, the chemical potential, and the electronic properties. Thus, any modeling of such structures can not be restricted to purely classical or quantum-mechanical approaches, but rather the development of classical models on the basis of electronic-structure calculations is required to fully account for all relevant nano- and meso-scale effects. The main part of this review is dedicated to the stability of such nanosystems in relation with the stable size regimes, with their electronic structure, and the derived analysis of the reactivity and application potential.
The calculations explain, why the nano-scale properties of the MoS allotropes can be quite different from the bulk ones, and predict novel effects both within and in addition to the established applications of MoS2 compounds in catalysis, tribology, electronics and electrochemistry.
Keywords: MoS2, nanostructures

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Permalink: https://www.hzdr.de/publications/Publ-9657
Publ.-Id: 9657


Finding polymorphic structures during vicinal surface growth

Radke De Cuba, M.; Emmerich, H.; Gemming, S.
A hybrid scheme is developed to describe vicinal surface growth during epitaxy on two different time and length scales. For this purpose this algorithm combines two modules based on a continuum and an atomistic approach. The continuum module is realized by a phase-field-model which traces back to the Burton-Cabrera-Frank theory, the atomistic module is based on the anisotropic Ising model which is mapped onto a lattice-gas model. The latter provides thermal density fluctuations resulting in adatom clustering. With increasing temperature the probability for island nucleation on the terraces decreases according to1-p where p is an Arrhenius-type activation probability which prevents clusters from becoming islands. Within this framework it is possible to find the transition from a rough surface at low temperatures to an evenly stepped surface at high temperatures where slight step meandering is observed. Furthermore two competing mechanisms of step bunching are investigated within this algorithm: alternating anisotropic diffusion and different Ehrlich-Schwoebel barriers at the step edges. Step bunching is found on two different time and length scales.
Keywords: self-assembly, patterning, phase-field, Ising, roughening, multi-scale modelling

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Permalink: https://www.hzdr.de/publications/Publ-9656
Publ.-Id: 9656


Modelling Ferroic Functional Elements

Gemming, S.; Luschtinetz, R.; Alsheimer, W.; Seifert, G.; Loppacher, C.; Eng, L. M.
The present study aims at the modelling of an organic field-effect transistor generated by the self-assembly of field-sensitive molecules on the surfaces of ferroic oxides. Electronic-structure-based methods for the microscopic properties of the surface, the molecules, and the respective interactions are combined with classical modelling on the self-assembly of larger adsorbate arrays on a scale-hopping basis. The structural and electronic characteristics of a realistic, stepped titanate surface as well as the electric field strength above such a surface are modelled quantum-mechanically by a combination of density-functional theory (DFT) and density-functional-based tight-binding (DF-TB). The effect of such fields on the electronic and optical properties of polarizable organic molecules is investigated by the time-dependent analogues of the DFT and DF-TB methods. For the integration of organic components via self-assembly a classical Ising Hamiltonian is developped for the coverage of stepped surfaces with molecules and parametrized on the basis of ab-initio and first-principles data.
Keywords: functional materials, ferroelectric, multi-scale modelling

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Permalink: https://www.hzdr.de/publications/Publ-9655
Publ.-Id: 9655


Simulation and AFM-Measurement Of PTCDA On Ag-supported KBr Films

Loppacher, C.; Zerweck, U.; Eng, L. M.; Gemming, S.; Seifert, G.; Olbrich, C.; Morawetz, K.; Schreiber, M.
Ordered growth of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) on Ag(111) partially covered by one or two monolayers of KBr was investigated by non-contact AFM and Monte-Carlo simulation. PTCDA grows partially ordered on pure Ag(111), smaller PTCDA aggregates occur on the first ML KBr, and large clusters and ordered planar growth are observed on the typical quadratic islands of the second KBr ML. In analogy to KBr covered Cu(111) we conclude that weak silver-bromine bonds are formed. In contrast, for a more weakly interacting substrate such as KBr|Au(111) PTCDA forms single crystals along step edges [1]. The delicate balance of vertical, adsorbate-substrate interactions and lateral, intermolecular ones was investigated by Metropolis-Monte-Carlo (MC) simulations with an extended Ising Hamiltonian on a periodically repeated 2D square lattice [2]. At fixed lateral interactions J12 = J13 the simulation reproduces the experimentally observed cluster formation by varying the adsorbate-substrate interaction H as the substrate changes from Ag(111) to 2 ML KBr|Ag(111): (i) on Ag(111) H dominantes (H >> J) (ii) on 2 ML KBr|Ag(111) J12 and J13 are dominant (J >> H) (iii) on 1 ML KBr|Ag(111) J12, J13, and H are competing (H ~ J) In the simulation the cases (i) and (ii) lead to the observed large and regular clusters, for case (iii) the competition of the different cluster stabilization mechanisms leads to the pinning of many smaller clusters. [1] Kunstmann T., Schlarb A., Fendrich M. et al., Phys. Rev. B, 71 (2005) 121403(R). [2] Loppacher C., Zerweck U., Eng L. M., Gemming S., et al., Nanotechnol., 17 (2006) 1-6.
Keywords: self-assembly, patterning, PTCDA, OLED
  • Poster
    E-MRS 2007 Spring Meeting, 27.05.-01.06.2007, Strasbourg, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-9654
Publ.-Id: 9654


Theory of DNA-wrapped Carbon Nanotubes

Enyashin, A. N.; Gemming, S.; Seifert, G.
Carbon nanotubes embedded in single-stranded DNA (CNT@DNA) were investigated by self-consistent density-functional-based tight-binding calculations (DFTB). A phenomenological model for the stability was derived, which gives the CNT-DNA interaction energy as a function of the nanotube radii and the number of DNA chains. Single CNTs are readily complexed by the DNA, but for CNT bundles an essential energy gain is only obtained, if multiple chains wrap around the tubes. Hence, the destruction of the CNT bundles, e.g. by sonication, can promote the CNT@DNA complex formation. Pyrimidine-based homopolymeric DNA more effectively wraps the DNA, whereas purine-based DNA exhibits the larger radius selectivity. The CNT-DNA interaction is not a genuine Van-der-Waals’ interaction. In general, the electronic structure is close to the superposition of the DOS curves of the “free” DNA and CNT fragments, but the most strongly bonding systems are characterized by a number of the mixed electronic states below Fermi level. Hence, magic matching occurs in conjunction with remarkable charge transfer.
Keywords: DNA, carbon nanotubes, nanoelectronics, functional materials
  • Lecture (Conference)
    E-MRS 2007 Spring Meeting, 27.05.-01.06.2007, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-9653
Publ.-Id: 9653


Molecular scale characterization of speciation of uranium(VI) associated with bacterial strains isolated form extreme habitats

Merroun, M.; Rossberg, A.; Hennig, C.; Selenska-Pobell, S.
This paper deals with the speciation of U(VI) associated with the cells of bacterial strains isolated from extreme habitats. For this propose, a combination of synchrotron-based X-ray absorption spectroscopy (XAS), time-resolved laser-induced fluorescence spectroscopy (TRLFS), transmission electron microscope (TEM) coupled with energy dispersive-X ray (EDX) analysis and electron diffraction were used. XAS analysis indicated that the effect of pH on the local coordination of U in the U-complexes formed by the different bacterial strains is species specific. No structural differences were found between the U complexes formed by three different eco-types of Acidothiobacillus ferrooxidans at pH 2, 3 and 4.5. In contrast, the cells of Bacillus sphaericus JG-B7, Microbacterium oxydans M2, and Sphingomonas sp. S15-S1 precipitate U(VI) as a meta-autunite-like phase at pH 4.5, probably due to the release of the inorganic phosphate from the cells. At pH 2, the U is coordinated to the organic phosphate groups of the cells of the listed bacteria. Both organic and inorganic uranyl/bacterial complexes were formed at pH 3. TEM/EDX analysis confirms these results and showed strain-specific extracellular and/or intracellular uranium accumulation to varying degrees. We applied Iterative Target Test Factor Analysis to determine the uranium speciation at different pH values quantitatively from the EXAFS spectra. Different hypothesis explaining the different coordination chemistry of uranium to bacteria as a function of pH of uranium solution in terms of solubility of m-autunite and/or microbial activity will be discussed.
  • Lecture (Conference)
    9th Symposium on Bacterial Genetics and Ecology (Bageco 9), 23.-27.06.2007, Wernigerode, Germany

Permalink: https://www.hzdr.de/publications/Publ-9652
Publ.-Id: 9652


Characterization of a novel Idiomarina loihiensis strain isolated from the westernmost Mediterranean: heavy-metal resistance and biomineralization capability

Gonzalez-Munoz, M.; de Linares, C.; Martinez-Ruiz, F.; Morcillo, F.; Merroun, M.; Arias, J.
This communication presents the identification of a bacterial strain, MAH1, isolated from a seawater sample collected from the westernmost Mediterranean surface waters. This strain was characterized using polyphasic taxonomy. It is Gram-negative, growing between 2--43 ºC (optimum 28-37 ºC), heterotrophic, aerobic and required NaCl for growth (0.7-20.0%, optimum being 2%). This strain is rod-shaped slightly curved with a single polar flagellum. Results of phylogenetic analyses evidenced that the strain belongs to Idiomarina loihiensis species (Donachie et al., 2003). The strain MAH1 displays a DNA base composition in G+C of the 48.2 mol%. The similarity of the 16S rDNA sequence and of the DNA-DNA hybridization to I. loihiensis (AF288370) is 100% and 96.1% respectively. Polar lipids were predominantly odd-numbered and iso-branched (15 and 17). According to these data we propose that the isolated MAH1 is a strain of the I. loihiensis species.
A preliminary study of the MAH1 strain mineralization capability and heavy metal resistance has also been performed. When the MAH1 strain is cultivated in a sea water solid medium (yeast extract 0.5%, triptone 1%, purified agar-agar 2% in seawater, pH 7.6) produces carbonates and phosphates. On the other hand, the minimal inhibitory concentrations of Ag, Cd, Pb, U, Ni, Cu, Cr, Mn and Zn for the growth of this bacterial strain are (concentration expressed as mM) 0.125, 0.125, 8.00, 8.00, 4.00, 4.00, 1.00, 8.00 and 2.00, respectively.
The obtained results are especially interesting in relation to the Idiomarina genus (Ivanova et al 2000), a member of the family Alteromonadaceae (Ivanova and Mikhailov, 2001) belonging to the subclases of the Proteobacteria.


Donachie, S. P., S. Hou, T. S. Gregory, A. Malahoff, and M. Alam. 2003. Int. J. Syst. Evol. Microbiol. 53:1873-1879
Ivanova, E. P., and V. V. Mikhailov. 2001. Mikrobiologia 70:15-23
Ivanova, E. P., L. A. Romanenko, J. Chun, M. H. Matte, G. R. Matte, V. V. Mikhailov, V. I. Svetashev, A. Huq, T. Maugel, and R. R. Colwell. 2000. Int. J. Syst. Evol. Microbiol. 50:901–907
  • Poster
    9th Symposium on Bacterial Genetics and Ecology (Bageco 9), 23.-27.06.2007, Wernigerode, Germany

Permalink: https://www.hzdr.de/publications/Publ-9651
Publ.-Id: 9651


Development of a high-speed capacitive surface sensor for fluid distribution imaging

Thiele, S.; Da Silva, M. J.; Hampel, U.
Experimental investigation of multiphase flows plays an important role in many research and industrial application areas. We introduce a novel surface sensor based on electrical capacitance (permittivity) measurements to imaging near-wall fluid distributions of multiphase flows. The sensor is formed by 32 x 32 interdigitated sensing structures and can be mounted on the edges of a pipe or vessel and thus has a minimal influence on the flow. An associated electronics measures the capacitance of the fluid overlaying each sensing structure in a multiplexed manner. This way, images of the fluid distribution can be achieved directly without the need for any reconstruction procedure. Images at up to 10,000 frames per second can be obtained. The system was evaluated showing good reproducibility and adequate accuracy. The system is able to well distinguish permittivity differences of up to one, which corresponds, for instance, to a two-phase flow of air and oil (rel. permittivity about 2).
Keywords: capacitance measurements, relative permittivity, multiphase flow
  • Contribution to proceedings
    IEEE SENSORS 2007 Conference, 28.-31.10.2007, Atlanta, USA
    Proceedings of the 6th Annual IEEE Conference on Sensors 2007 Atlanta, Stoughton, Wisconsin, USA: The Printing House, Inc., 1-4244-1262-5, 236-239
  • Poster
    IEEE SENSORS 2007 Conference, 28.-31.10.2007, Atlanta, USA

Permalink: https://www.hzdr.de/publications/Publ-9650
Publ.-Id: 9650


A new wire-mesh tomograph for multiphase flow measurement

Da Silva, M. J.; Schleicher, E.; Hampel, U.
We have developed and tested a new wire-mesh tomograph based on capacitance measurements, which may now be used for the investigation of non-conducting fluids. It can at the moment acquire up to 625 frames per second. For the experimental measurements we have employed a 16 x 16 laboratory wire-mesh sensor. The evaluation of the wire-mesh tomograph prototype has shown good reproducibility and accuracy in capacitance measurements, thus allowing the system to be employed in the investigation of a wide range of substances even with close relative permittivity values, such as for air and oil. Furthermore, time resolved measurements of different flow patterns for oil-air mixtures have been performed.
Keywords: capacitance measurement, multiphase flow, relative permittivity
  • Contribution to proceedings
    Multi-Phase Flow: Simulation, Experiment and Application, 25.-27.04.2007, Dresden, Germany
    Proceedings of FZR & ANSYS Multiphase Flow Workshop
  • Lecture (Conference)
    Multi-Phase Flow: Simulation, Experiment and Application, 25.-27.04.2007, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-9649
Publ.-Id: 9649


TRLFS: Analysing Spectra with an Expectation-Maximization (EM) Algorithm

Steinborn, A.; Taut, S.; Brendler, V.; Geipel, G.; Flach, B.
A new approach for fitting statistical models to time-resolved laser-induced fluorescence spectroscopy (TRLFS) spectra is presented. Such spectra result from counting emitted photons in defined intervals. Any photon can be described by emission time and wavelength as observable attributes and by component and peak affiliation as hidden ones. Understanding the attribute values of the emitted photons as drawn from a probability density distribution, the model estimation problem can be described as a statistical problem with incomplete data. To solve the maximum likelihood task, an expectation maximization (EM) algorithm is derived and tested. In contrast to the well known least squares method, the advantage of the new approach is the ability to decompose the spectrum into its components and peaks using the revealed hidden attributes of the photons. The simultaneous detection of temporal and spectral model parameters provides a mutually consistent description of TRLFS spectra. Theoretical aspects were investigated using simulated spectra and the applicability in practice is illustrated by spectra originating from uranyl species.
Keywords: Time-resolved laser-induced fluorescence spectroscopy, expectation maximization
  • Spectrochimica Acta Part A 71(2008)4, 1425-1432

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Publ.-Id: 9648


95 MeV neutron scattering on hydrogen, deuterium, carbon, and oxygen

Mermod, P.; Blomgren, J.; Johansson, C.; Ohrn, A.; Osterlund, M.; Pomp, S.; Bergenwall, B.; Klug, J.; Nilsson, L.; Olsson, N.; Tippawan, U.; Nadel-Turonski, P.; Jonsson, O.; Prokofiev, A.; Renberg, P.; Maeda, Y.; Sakai, H.; Tamii, A.; Amos, K.; Crespo, R.; Moro, A.
Three neutron-deuteron scattering experiments at 95 MeV have been performed recently at The Svedberg Laboratory in Uppsala. Subsets of the results of these experiments have been reported in two short articles, showing clear evidence for three-nucleon force effects. In this paper, we present a more detailed description of the experimental methods as well as further discussion of the results. In addition to neutron-deuteron scattering data, neutron-proton and C-12(n,n) elastic scattering data have been measured for normalization purposes, and O-16(n,n) data have been obtained for the first time at this energy.
It was possible to extract C-12(n,n(')) and O-16(n,n(')) inelastic scattering cross sections to excited states below 12 MeV excitation energy. The inelastic scattering data (for both carbon and oxygen) are shown to have a significant impact on the determination of nuclear recoil kerma coefficients.

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Publ.-Id: 9647


Dynamics of Molten Salt Reactors

Krepel, J.; Grundmann, U.; Rohde, U.; Weiss, F.-P.
Dynamics of the Molten Salt Reactor, one of the 'Generation IV International Forum' concepts, was studied in this paper. The graphite-moderated channel type MSR was selected for the numerical simulation. The MSR represents a liquid fueled reactor with very specific dynamics because of two physical peculiarities: the delayed neutrons precursors are drifted by the fuel flow and the fission energy is immediately released directly into the coolant. Presently, there are not many accessible numerical codes appropriate for the MSR simulation, therefore the DYN1D-MSR and DYN3D-MSR codes were developed based on the Light Water Reactor dynamics code DYN3D. It allows calculating of full 3D transient neutronics in combination with parallel channel type thermal-hydraulics. The codes were validated on experimental results of Molten Salt Reactor Experiment from Oak Ridge National Laboratory and applied to several transients typical for the liquid fuel system. Those transients were initiated by reactivity insertion, by overcooled or overfueled fuel slug, by the fuel pump start-up or coast-down, or by the blockage of single fuel channels. In these considered transients, the response of the MSR is characterized by the immediate change of the fuel temperature according to the power level. This causes fast feedback reactivity insertion, which is negative in the case of power increase. On the other hand, the graphite response is slower and its feedback coefficient is in some cases positive. The addition of erbium to the graphite can ensure the negative feedback and inherent safety features. The DYN1D-MSR and DYN3D-MSR codes have been shown as an effective tools for MSR dynamics studies.
Keywords: Molten Salt, Reactor, Dynamics, MSR, MSRE, MSBR.
  • Nuclear Technology 164(2008), 34-44

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Publ.-Id: 9645


Switchable two-color electroluminescence based on a Si metal-oxide-semiconductor structure doped with Eu

Prucnal, S.; Sun, J. M.; Skorupa, W.; Helm, M.
A Si metal-oxide-semiconductor (MOS) electroluminescent device structure is reported which emits two colors, while being doped with a single rare-earth element. Thermally grown SiO2 oxide layers were implanted with Eu and subseqently annealed. Depending on the electrical excitation current, the luminescence is red or blue, which can be ascribed to electronic transitions in tri- and di-valent europium (Eu3+ and Eu2+), respectively.
Keywords: electroluminescence, rare earth, Si MOS, light emitter

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Publ.-Id: 9644


Coherent structure eduction from PIV data of an electromagnetically forced separated flow

Weier, T.; Cierpka, C.; Gerbeth, G.
Periodic addition of momentum by wall–parallel electromagnetic forces has a strong influence on the separated region of a stalled airfoil. As in the case of periodic blowing and suction, actuation frequency and momentum input are the main factors of influence. However, the control authority depends as well on the actuation wave form. This latter aspect is investigated in the present paper by means of time resolved particle image velocimetry data from the suction side of an inclined flat plate. The control effect is rated by the size of the remaining recirculation region in the time averaged flow fields. The controlled flow possesses typically a small number of relatively large vortices, which are believed to be related to the control mechanism. Consequently, the time resolved flow fields have been analyzed by proper orthogonal decomposition and continuous wavelet transform to extract dominant features of the flow.
Keywords: active flow control, proper orthogonal decomposition, continuous wavelet transform, waveform, coherent structures
  • Lecture (Conference)
    IUTAM Symposium on Unsteady Separated Flows and Their Control, 18.-22.06.2007, Korfu, Greece
  • Contribution to proceedings
    IUTAM Symposium on Unsteady Separated Flows and Their Control, 18.-22.06.2007, Korfu, Greece
    IUTAM Symposium on Unsteady Separated Flows and their Control
  • Journal of Fluids and Structure 24(2008), 1339-1348
    DOI: 10.1016/j.jfluidstructs.2008.06.005

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Publ.-Id: 9643


Complex formation between UO2+2 and CO2-3: Studied by laser-inducted photoacoustic spectroscopy (LIPAS)

Geipel, G.; Bernhard, G.; Brendler, V.; Nitsche, H.
wird nachgereicht
  • Radiochimica Acta 82(1998), 59-62

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Publ.-Id: 9642


PT-symmetric Quantum Mechanics, the hydrodynamic Squire equation and UV-IR-duality

Günther, U.; Stefani, F.; Znojil, M.
Some facts about the spectrum of a PT-symmetric quantum mechanical (PTSQM) toy model with potential V(x)=Gx2(ix)ν in a box x∈[-L,L] are presented for the parameter region ν∈[-2,0]. The corresponding Hamiltonian is selfadjoint in an appropriately chosen Krein space and for ν=-1 the spectral problem maps into that of the hydrodynamic Squire equation. It is shown that in the limit L→∞ a spectral singularity occurs and that the PTSQM ⇄ Squire mapping can be interpreted as a special type of strong-coupling ⇄ weak-coupling (UV-IR) duality. Finally, the system behavior in the vicinity of a spectral triple point is sketched.
partially based on:
J. Math. Phys. 46, (2005), 063504, math-ph/0501069.
Czech. J. Phys. 55, (2005), 1099-1106, math-ph/0506021.
Keywords: PT-symmetric Quantum Mechanics, Krein space, spectral analysis, spectral triple point, UV-IR duality
  • Lecture (Conference)
    International conference "Modern Analysis and Applications (MAA 2007)" dedicated to the centenary of Mark Krein, 09.-14.04.2007, Odessa, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-9641
Publ.-Id: 9641


On the observation of vacuum birefringence

Heinzl, T.; Liesfeld, B.; Amthor, K.; Schwoerer, H.; Sauerbrey, R.; Wipf, A.
We suggest an experiment to observe vacuum birefringence induced by intense laser fields. A high-intensity laser pulse is focused to ultra-relativistic intensity and polarizes the vacuum which then acts like a birefringent medium. The latter is probed by a linearly polarized X-ray pulse. We calculate the resulting ellipticity signal within strong-field QED assuming Gaussian beams. The laser technology required for detecting the signal will be available within the next three years.
  • Optics Communications 267(2006)2, 318-321

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Publ.-Id: 9640


Self-induced transparency assisted by electromagnetically induced transparency

Nazarkin, A.; Netz, R.; Sauerbrey, R.
We show the possibility of transparency and soliton effects for an intense pulse propagating in a V-type medium in which two upper resonant sublevels experience fast field-induced decay due to incoherent coupling to an upper lying state or continuum. The transparency arises as a result of the combined action of population trapping on the sublevels leading to interference suppression of the relaxation channel, and coherent Rabi cycling induced by the laser field.
  • Physical Review A 7404(2006)4, 1806

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Publ.-Id: 9639


Fingerprinting of a thin secondary mineral film on DU

Baumann, N.; Arnold, T.; Foerstendorf, H.; Read, D.; Black, S.; Massanek, A.
Discs of depleted uranium (DU), obtained from a British pristine military tank shell were used in our experiments. One sample was placed in a solution containing 2.5 • 10−3 M Ca(NO3)2 and 1.05 • 10−3 M (NH4)3PO4. After a contact time of 360 days the sample was taken out of the solution. IR- and TRLFS measurements were made on the surface of the sample. The spectra obtained were compared with those of natural uranium minerals, formed under oxidising weathering conditions. Comparison of the IR-spectra from the DU surface with those of the reference minerals revealed that the newly formed secondary mineral on DU is a uranium (VI) phosphate. Further identification of the respective uranium phosphate mineral was not possible with IR. However, a comparison between the TRLFS spectra of the newly formed unknown uranium phase on the DU disc with well-known TRLFS spectra of uranium reference compounds clearly showed the presence of meta-autunite.
Keywords: depleted uranium, IR, TRLFS, uranium minerals
  • Abstract in refereed journal
    Geochimica et Cosmochimica Acta 71(2007)15S, A66-A66
  • Poster
    Goldschmidt 2007, 20.-24.08.2007, Köln, Germany

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Publ.-Id: 9638


Influence of humic colloids on the migration of U(VI) in compacted clay

Mibus, J.; Sachs, S.
Clay minerals and organic substances are widespread components of many soils, sediments, and rocks. As humic acids (HA) possess a strong ability for metal complexation, they can influence the migration of radioactive and toxic metal ions in clayey environments. However, the migration behavior of humic colloids and its impact on the actinide migration in clay formations is poorly understood.
Former studies discuss the influence of HA on the radionuclide migration in clays controversially. Wold and Eriksen [1] reported the diffusion of humic colloids through compacted bentonite without strong physical hindrance mobilizing metal ions. In contrast, Wang et al. [2] found a significant immobilization of Eu(III) by humic substances. Maes et al. [3] stressed the reversibility of the interaction between radionuclide, organic matter, and clay. The competition of the adsorbents for radionuclides is kinetic and determines their distribution between mobile and immobile phase.
In the present study we investigated the diffusion behavior of humic colloids in compacted clay as a function of compaction and pH. The impact on the uranium transport was studied by comparing the uranium diffusion in absence and presence of HA.
...
The migration of HA in clay is governed by diffusion. It is influenced by the colloidal behavior of HA. At higher clay bulk densities, size fractionation affects the diffusion parameters. In presence of HA colloids U(VI) is immobilized in association with HA near the high concentration boundary.
The German Federal Ministry of Economics and Technology funded this study under contract 02E9673. The technical assistance of Ch. Müller is gratefully acknowledged.
REFERENCES
[1] Wold, S., Eriksen, T.E. (2005) Proceedings of the 2nd International Symposium Clays in natural and engineered barriers for radioactive waste confinement. Tours, France, 14-18 March 2005, 547.
[2] Wang, X. et al. (2005) Adsorption Science and Technology, 23, 801-811.
[3] Maes, N. et al. (2004) Report SCK•CEN-BLG-988. SCK•CEN, Mol, Belgium.
[4] Sachs, S. et al. (2004) Report FZR-399, FZ Rossendorf, Dresden, Germany.
[5] Lead, et al. (2000) Environ. Sci. Technol. 34, 1365-1369.
  • Contribution to proceedings
    3rd International Meeting "Clays in natural and engineered barriers for radioactive waste confinement", 17.-20.09.2007, Lille, France
    Clays in Natural & Engineered Barriers for Radioactive Waste Confinement, 467-468
  • Poster
    3rd International Meeting "Clays in natural and engineered barriers for radioactive waste confinement", 17.-20.09.2007, Lille, France

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Permalink: https://www.hzdr.de/publications/Publ-9637
Publ.-Id: 9637


CFD application in nuclear engineering/industy

Höhne, T.; Krepper, E.; Weiss, F. P.; Stosic, Z.; Salnikova, T.
The last decade has seen an increasing use of three-dimensional CFD codes to predict steady state and transient flows in nuclear reactors. The reason for the increased use of multidimensional CFD methods is that a number of important phenomena such as pressurized thermal shocks, boron mixing, and thermal striping cannot be predicted by traditional one dimensional system codes with the required accuracy and spatial resolution.

CFD codes contain empirical models for simulating turbulence, heat transfer, multi-phase flows, and chemical reactions. Such models must be validated before they can be used with sufficient confidence in NRS applications. The necessary validation is performed by comparing model results against trustworthy data. However, in order to obtain a reliable model assessment, CFD simulations for validation purposes must satisfy strict quality criteria. For instance, numerical errors caused by too coarse numerical grids should be separated from shortcomings of the physical models to avoid wrong conclusions about model performance.

CFD simulations are shown with an emphasis on validation in areas such as: heat transfer, buoyancy, multi-phase flows, natural circulation, free-surface flows, turbulent mixing, and complex geometries. These topics are related to NRS-relevant issues such as: pressurized thermal shocks, boron dilution, hydrogen distribution, induced breaks, subcooled boiling, thermal striping, etc.
Keywords: Nuclear Engineering, CFD, Coolant Mixing, pressurized thermal shocks, boron dilution, hydrogen distribution, induced breaks, subcooled boiling
  • Invited lecture (Conferences)
    15th International Conference on Nuclear Engineering, 22.-26.04.2007, Nagoya, Japan

Permalink: https://www.hzdr.de/publications/Publ-9636
Publ.-Id: 9636


Density Functional Theory - Investigations of Vanadium Silicides

Thieme, M.; Gemming, S.
Vanadium and silicon form several binary compounds; the most well characterized structures have the compositions V:Si= 3:1, 6:5, 5:3, 1:2. Density-functional band-structure calculations with a plane-wave basis for the valence electrons and norm-conserving pseudopotentials for the core-valence interaction have been carried out to investigate the structural properties and the phase stability for the experimentally known binary crystals. As the early transition metal silicides belong to the class of refractory materials, also the elastic properties were determined. It is furthermore shown that the electronic properties of the compounds depend strongly on the composition.
  • Poster
    DPG-Frühjahrstagung Regensburg, 27.03.2007, Regensburg, Deutschland

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Publ.-Id: 9635


Tripodal polyamines as anion receptors: Extraction and structural studies

Wenzel, M.; Antonioli, B.; Gloe, K.; Gloe, K.; Sanchez, M. G.; Bernhard, G.; Bray, D. J.; Clegg, J. K.; Lindoy, L. F.
Tripodal polyamines based on the tris(2-aminoethyl)amine (tren) platform are useful complexing agents for cations or anions depending on the pH of the solution.[1,2] The binding properties of such compounds can be tuned by the addition of aromatic binding groups to the molecule.
A series of different substituted tren (1-4) derivatives were synthesised and characterised.
Here we present some recent solvent extraction and liquid membrane transport results that show a gradation in anion binding behaviour along I-, Cl-, Br-, CrO4
2-, SO4
2- and PO4
3-.
Finally, structural aspects of the anion complexes formed will be discussed, with the X-ray structure of the bromide complex of ligand 3 being presented.
[1] A.G. Blackman, Polyhedron, 2005, 24, 1-39
[2] K. Wichmann, B. Antonioli, T. Söhnel, M. Wenzel, K. Gloe, K. Gloe, J.R. Price, L. F.
Lindoy, A.J. Blake, M. Schröder, Coord. Chem. Rev., 2006, 250, 2987-3003
  • Contribution to proceedings
    ISMSC 2007, 2nd International Symposium on Macrocyclic and Supramolecular Chemistry, 24.-28.06.2007, Salice Therme (Pavia), Italy

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Publ.-Id: 9634


Cation and anion binding studies of a large N,O-donor macrocycle: Single ion extraction and synergistic enhancement

Wenzel, M.; Gloe, K.; Gloe, K.; Bernhard, G.; Clegg, J. K.; Ji, X.-K.; Lindoy, L. F.
Mixed N,O-donor macrocycles have been shown to result in interesting complexation properties towards both cations and anions (the latter on protonation of the macrocycle's nitrogen functions).[1-3]
In the present study the phase transfer properties of 1 toward selected transition metal ions and anions have been evaluated by liquid-liquid extraction studies under different pH conditions. The order of increasing extraction follows the Irving-Williams series Co(II) < Ni(II) < Cu(II) > Zn(II), while the anion extraction is contolled by the Hofmeister series. A synergistic enhancement of metal extraction was obtained on exploiting a dual host strategy [4] in which the tripodal thiourea host 2 was incorporated in the system. In this case atypical anti-Hofmeister behaviour was obtained in which significant metal extraction of chloride or sulfate was observed from solution.
[1] N.A. Bailey, D. E. Fenton, S.J. Kitchen, T.H. Lilley, M.G. Williams, P.A. Tasker, A.J.
Leong and L.F. Lindoy, J. Chem. Soc. Dalton Trans., 1991, 627-637.
[2] H. Adams, N.A. Bailey, D.E. Fenton, I.G. Ford, S.J. Kitchen, M.G. Williams, P.A.
Tasker, A.J. Leong and L.F. Lindoy, J. Chem. Soc. Dalton Trans., 1991,1665-1674.
[3] L. Tušek-Božić, A. Višnjevac, E. Marotta, B. Kojić-Prodic, Polyhedron 24, 2005, 97–
111.
[4] K. Kavallieratos, R.A. Sachleben, G.J. Van Berkel and B.A. Moyer, Chem. Commun.,
2000, 187-188.
  • Contribution to proceedings
    ISMSC 2007, 2nd International Symposium on Macrocyclic and Supramolecular Chemistry, 24.-28.06.2007, Salice Therme (Pavia), Italy

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Publ.-Id: 9633


Bacterial responses to uranyl and sodium nitrate treatments and fate of the added U(VI) in uranium mining waste piles

Geissler, A.; Merroun, M.; Geipel, G.; Reuther, H.; Selenska-Pobell, S.
The responses of the bacterial community of a uranium mining waste pile to increased concentrations of uranyl or sodium nitrate were studied in microcosm experiments under conditions corresponding to the natural. For this study, the 16S rRNA (Fig. 1) and the narG-gene retrievals were applied. Both retrievals demonstrated that at the early stages of the treatments with sodium nitrate a strong activation of nitrate reducing and denitrifying populations, mainly of Firmicutes and Betaproteobacteria, occurred; they had overgrown the Acidobacteria, Alpha-, and Deltaproteobacteria which originally predominated in the untreated samples. Due to the U(VI) toxicity only a few populations of the mentioned Firmicutes and betaproteobacterial nitrate reducers proliferated in the samples treated with uranyl nitrate. More significant for these samples was the stimulation of the gammaproteobacterial denitrifyers, able to effectively interact with the added uranium. After longer incubations both treatments resulted in an establishment of betaproteobacterial populations and also of populations characteristic for the original, non-treated sample. As measured by using Mössbauer spectroscopy, at these stages a strong reduction of Fe(III) to Fe(II) occurred in the samples. Time-resolved laser fluorescence spectroscopic analyses demonstrated that most of the added U(VI) was bound in uranyl-hydro-phosphate phases or was complexed by organic phosphate groups (Fig. 2). The phosphate groups were liberated by different kinds of bacteria due to the activity of their intrinsic acidic phosphatases or were supplied by the lysed cells of the dead parts of the numerically reduced populations. The latter was confirmed by X-ray structural analyses of the formed bacteria - uranium complexes in the studied samples. Our results demonstrate that bacteria in uranium mining waste piles possess a high potential to deal with increased, toxic concentrations of U(VI) and nitrate, which usually co-contaminate these environments.
  • Lecture (Conference)
    9th Symposium on Bacterial Genetics and Ecology (BAGECO 9), 23.-27.06.2007, Wernigerode, Germany

Permalink: https://www.hzdr.de/publications/Publ-9632
Publ.-Id: 9632


Bestimmung der Eigenfrequenzen von Brennelementen

Altstadt, E.
Mit Hilfe eines Finite Elemente Modells werden Eigenfrequenzen und Schwingungsformen eines DWR- Brennelements berechnet. Der Einfluss von Kontakt mit benachbarten Brennelementen wird untersucht. Der Bericht ist nicht öffentlich verfügbar (Industrieauftrag).
Keywords: Finite Element Model, Modal Analysis, Pressurized Water Reactor, Fuel Element Vibrations
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2007
    FZD\FWS\2007\04
    14 Seiten

Permalink: https://www.hzdr.de/publications/Publ-9631
Publ.-Id: 9631


Cluster Core Controlled Reactions of Substitution of Terminal Bromide Ligands by Triphenylphosphine in Octahedral Rhenium Chalcobromide Complexes

Shestopalov, M. A.; Brylev, K. A.; Kozlova, S. G.; Fedorov, V. E.; Spies, H.; Pietzsch, H.-J.; Stephan, H.; Geipel, G.; Bernhard, G.
Reactions of rhenium chalcobromides Cs4[{Re63-S)8}Br6].2H2O, Cs3[{Re63-Se)8}Br6].2H2O, Cs3[{Re63-Q)73-Br)}Br6].H2O (Q) S, Se), and K2[{Re63-S)63-Br)2}Br6] with molten triphenylphosphine (PPh3) have resulted in a family of novel molecular hybrid inorganic-organic cluster compounds. Six octahedral rhenium cluster complexes containing PPh3 ligands with general formula [{Re63-Q)8-n3-Br)n}(PPh3)4-nBrn+2] (Q ) S, n ) 0, 1, 2; Q ) Se, n ) 0, 1) have been synthesized and characterized by X-ray single-crystal diffraction and elemental analyses, 31P{1H} NMR, luminescent measurements, and quantum-chemical calculations. It was found that the number of terminal PPh3 ligands in the complexes is controlled by the composition and consequently by the charge of the cluster core {Re6Q8-nBrn}n+2. In crystal structures of the complexes with mixed chalcogen/bromine ligands in the cluster core all positions of a cube [Q8-nBrn] are ordered and occupied exclusively by Q or Br atoms. Luminescence characteristics of the compounds trans-[{Re6Q8}(PPh3)4Br2] and fac-[{Re6Se7Br}(PPh3)3Br3] (Q ) S, Se) have been investigated in CH2Cl2 solution and the broad emission spectra in the range of 600-850 nm were observed.
  • Journal of the American Chemical Society 129(2007), 3714-3721

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Publ.-Id: 9630


Beta decay of 101 Sn

Kavatsyuk, O.; Mazzocchi, C.; Janas, Z.; Banu, A.; Batist, L.; Becker, F.; Blazhev, A.; Brüchle, W.; Döring, J.; Faestermann, T.; Gorska, M.; Grawe, H.; Jungclaus, A.; Karny, M.; Kavatsyuk, M.; Klepper, O.; Kirchner, R.; La Commara, M.; Miernik, K.; Mukha, I.; Plettner, C.; Plochocki, A.; Roeckl, E.; Romoli, M.; Rykaczewski, K.; Schädel, M.; Schmidt, K.; Schwengner, R.; Zylicz, J.
The decay of the very neutron-deficient isotope 101 Sn was studied at the GSI on-line massseparator using silicon detectors for recording charged particles and germanium detectors for gamma-ray spectroscopy. Based on the beta-delayed proton data the production cross-section of 101 Sn in the 50 Cr+58 Ni fusion-evaporation reaction was determined to be about 60 nb. The half-life of 101 Sn was measured to be 1.9±0.3 s. For the first time beta-delayed gamma rays of 101 Sn were tentatively identified, yielding weak evidence for a cascade of 352 and 1065 keV transitions in 101 In. The results are discussed by comparing them to predictions obtained from shell-model calculations employing a new interaction in the 88Sr to 132Sn model space.
Keywords: Nuclear energy levels, Beta decay, double beta decay, electron capture, Lifetimes

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Publ.-Id: 9629


Cluster dynamics simulation of reactor pressure vessel steels under irradiation

Gokhman, A.; Bergner, F.; Ulbricht, A.; Birkenheuer, U.
The distance between irradiated features (precipitates, clusters and atmospheres) exceeds significantly the size of them in neutron irradiated reactor pressure vessel (RPV) steels. Therefore, cluster dynamics (CD) that originally has been suggested for small clusters and that can be applied to any ideal gas of clusters is found to be very effective to investigate the long-term behavior of the neutron stimulated changes of the microstructure of RPV steels.
In the present paper CD simulation have been carried out for model iron alloys with small and high copper content as well as for VVER 1000 steels R16, R17 and D under neutron irradiation. For this case CD simulations are needed for two sets of input parameters. The first one relates to the description of the local material damage at the cascade stage when the local temperature increases to the melting point and then decreases to a temperature of about 300°C over a time of some ps and CD is not applicable. The cascade stage is investigated by molecular dynamics (MD) and kinetic lattice Monte-Carlo (KLMC) methods that provide the data on the neutron cascade efficiency, rate of the vacancies (interstitials) that form the clusters, the planar or spherical or another shape of clusters, content and distribution of them by size at the end of cascade stage. The second set of input parameters contains the energy of formation and energy of migration, pre-exponential factor of diffusivity for vacancy and interstitial, copper, manganese, silicon and other alloying elements in iron; recombination radius for pair vacancy-interstitial; dislocation density, capture efficiency of vacancies (interstitials) by dislocations, surface tension for boundary between cluster and iron matrix; binding energy dependence on cluster size; lattice parameters of iron and precipitates. Some of these characteristics are well-known with some accuracy from the experiment and can be considered as materials constants for RPV steels.
It was found that the coupling between copper rich precipitates (CRP) and point defects in neutron irradiated iron alloys and VVER steels can be investigated by CD simulations using LSODA code as a solver of the stiff ordinary differential equations system. The additional consideration of the strain energy effect on CRP kinetics as well as the application of the regular solution model for the case of different fixed copper contents of CRP improves quantitatively the simulation results for considered model alloys. The additional accounting of the Ni effect in CD simulation is needed to study the kinetics in the investigated VVER steels under irradiation.
Keywords: cluster dynamics, reactor pressure vessel steels, neutron irradaition
  • Lecture (Conference)
    4th International Workshop "Diffusion and Diffusional Phase Transformations in Alloys" DIFTRANS-2007, 16.-21.07.2007, Sofiyivka (Uman), Cherkasy region, Ukraine
  • Defect and Diffusion Forum 277(2008), 75-80
  • Contribution to proceedings
    4th International Workshop "Diffusion and Diffusional Phase Transformations in Alloys" DIFTRANS-2007, 16.-21.07.2007, Sofiyivka (Uman), Cherkasy region, Ukraine
    Proceedings of the 4th International Workshop "Diffusion and Diffusional Phase Transformations in Alloys", 75-76

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Publ.-Id: 9628


Three-dimensional thermal-hydraulics analysis of ROCOM mixing experiment by RELAP5-3D© code

Frisani, A.; Del Nevo, A.; D’Auria, F.; Höhne, T.; Kliem, S.; Rohde, U.
The mixing phenomenon is relevant for the normal and off normal operation of the Nuclear Power Plant (NPP), because it influences the safety, mitigating the reactivity and structural consequences. The study of these issues was investigated performing experimental campaigns in large-scale test facilities and in real NPPs. In this framework ROCOM (Rossendorf Coolant Mixing Model) test facility was built with the purpose of investigating the coolant mixing phenomena occurring in the Reactor Pressure Vessel (RPV) of a Pressurizer Water Reactor (PWR). The experiments executed in this facility provide experimental data for code validation (CFD and TH-SYS codes). The purpose of this work is to address the capability of the RELAP5-3D© to reproduce ROCOM facility dynamic in simulating the mixing for a large range of operational and accident conditions. In particular, the attention is focused on the effects in the vessel downcomer, lower plenum and core inlet. Three experiments were selected for the analyses: two steady states and one transient. The ROCOM steady states are slug mixing experiments that analyze the mixing scalar trend inside the facility at different mass flow rates. The ROCOM transient represents the injection of a mixing scalar slug from one cold leg with an increasing mass flow rate in the same loop. A systematic comparison between ROCOM experimental data and the results of the simulations with the RELAP5-3D© is presented including a complete set of sensitivity analyses to find out the most relevant parameters which influence the results from nodalization and user effects points of view.
Keywords: Mixing, RELAP5-3D©, ROCOM facility, code assessment
  • Contribution to proceedings
    NURETH-12 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics, 30.09.-04.10.2007, Pittsburgh, USA
    CD-ROM, paper 159

Permalink: https://www.hzdr.de/publications/Publ-9626
Publ.-Id: 9626


Begleitende Untersuchungen zur Pilotierung eines Verfahrens zur elektrochemischen Aufbereitung saurer Wässer aus Tagebaurestseen (Zwischenbericht)

Kryk, H.; Schubert, M.; Hessel, G.
Das vom VKTA entwickelte elektrochemische Verfahren zur Aufbereitung schwefelsaurer Wässer aus Tagebau-Restseen befindet sich zurzeit in der Phase der Pilotierung. Hierzu wurde vom VKTA im Gebiet des Lausitzer Braunkohlen-Tagebaureviers eine Grubenwasserreinigungs-Pilotanlage errichtet. Durch das FZD wurden prozessbegleitende Untersuchungen sowohl zur Optimierung des Elektolyseprozesses als auch zur Aufbereitung der Koppelprodukte durchgeführt.
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2007
    FZD\FWS\2007\06
    86 Seiten

Permalink: https://www.hzdr.de/publications/Publ-9623
Publ.-Id: 9623


Experimental determination of the boron concentration distribution in the primary circuit of a PWR after a postulated cold leg small break loss-of-coolant-accident with cold leg safety injection

Kliem, S.; Prasser, H.-M.; Sühnel, T.; Weiss, F.-P.; Hansen, A.
It is known that under-borated coolant can accumulate in the loops and that it can be transported towards the reactor core during a loss of coolant accident. Therefore, the mixing of weakly borated water inside the reactor pressure vessel was investigated using the ROCOM test facility. Wire mesh sensors based on electrical conductivity measurement are used to measure in detail the spreading of a tracer solution in the facility. The mixing in the downcomer was observed with a measuring grid of 64 azimuthal and 32 vertical positions. The resulting distribution of the boron concentration at the core inlet was measured with a sensor integrated into the lower core support plate providing one measurement position at the entry into each fuel assembly.
The boundary conditions for this mixing experiment are taken from an experiment at the thermal hydraulic test facility PKL operated by AREVA Germany. The slugs, which have a lower density, accumulate in the upper part of the downcomer after entering the vessel. The ECC water injected into the reactor pressure vessel falls almost straight down through this weakly borated water layer and accelerates as it drops over the height of the downcomer. On the outer sides of the ECC streak, lower borated coolant admixes and flows together with the ECC water downwards. This has been found to be the only mechanism of transporting the lower borated water into the lower plenum. In the core inlet plane, a reduced boron concentration is detected only in the outer reaches of the core inlet. The minimum instantaneous boron concentration that was measured at a single fuel element inlet was found to be 66.3 % of the initial 2500 ppm.

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Publ.-Id: 9622


Investigation on thin films of new substituted quarterthiophene films of new substituted quarterthiophene

Zelenetskaya, K.; Jähne, E.; Adler, H.-J.; Loppacher, C.; Eng, L.; Grenzer, J.; Scholz, A.
alpha,beta-dicyano substituted beta, beta*-dibutylquarterthiophene (DCNDButQT) was synthesized and fully characterized by 1H-NMR and 13C-NMR, elemental analysis, UV-visible spectroscopy, DSC, TGA and cyclic voltammetry. The band gap energy (deltaEg) calculated from cyclic voltammetry data was found to be 1.97 eV, which is in the range of semiconductor materials (deltaEg < 3.0 eV). DCNDButQT was deposited on different substrates (Al2O3, SiO2, TiO2) by vacuum deposition and solution-cast methods. The structure of the thin films analysed by AFM and XRD showed different morphology depending on cast method. The spin-coating and drop-casting films showed amorphous structure, whereas the vacuum-deposition films exhibit a fine crystalline structure. AFM of vacuum-deposition film revealed the formation of well-ordered terrace structures, the step between adjacent terraces is about 1.5 nm.
Keywords: organic semiconductors
  • Poster
    DPG Jahrestagung und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 26.-30.03.2007, Regensburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-9621
Publ.-Id: 9621


Ion-induced surface ripples in silicon

Biermanns, A.; Grenzer, J.; Facsko, S.; Grigorian, S.; Pietsch, U.
The morphological evolution of surfaces during ion-beam irradiation has attracted a significant interest due to possibility of the development and the controlling of selforganization in nanostructures. Pattering and texture on nanometer length scale at metal and semiconductor surfaces has become a topic of intense research. In particular the surface and subsurface ripple formation under 40Ar+ ion-beam irradiation of Si (100) crystal has been studied recently. Strong ripple formation has been found for an irradiation energy of 60keV and incident angles around 60degree. During implantation a corrugated surface layer is formed, consisting of a strongly damaged, amorphous near-surface layer followed by a nearly sinusoidal shaped interface towards the crystalline material. In the present work, we investigate the onset and evolution of ripple-formation as function of implantation energy and incidence angle of the ion beam.
Keywords: ion beam induced rippling
  • Poster
    DPG Jahrestagung und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 26.-30.03.2007, Regensburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-9620
Publ.-Id: 9620


Glycoxidised LDL isolated from subjects with impaired glucose tolerance increases CD36 and peroxisome proliferator-activator receptor gamma gene expression in macrophages

Graessler, J.; Pietzsch, J.; Westendorf, T.; Julius, U.; Bornstein, S. R.; Kopprasch, S.
Aims/hypothesis: Glycoxidized low density lipoprotein (LDL) has been implicated in the pathogenesis of atherosclerosis, one of the major diabetic complications. Since atherogenesis may occur early at the onset of diabetes, we investigated whether circulating LDL isolated from subjects with impaired glucose tolerance (n=20, IGT-LDL) showed an increased glycoxidation status and explored their proatherogenic effects on macrophages.
Methods/Results: Using gas chromatography/mass spectrometry we could demonstrate a 3- to 5-fold higher oxidative apolipoprotein B-100 proline, arginine, lysine, and tyrosine modification as compared to LDL obtained from subjects with normal glucose tolerance (n=20, NGT-LDL). Moreover, LDL glycoxidation estimated by both N Epsilon-(carboxymethyl)lysine (CML) and N Epsilon-(carboxyethyl)lysine (CEL) residues was increased more than 9-fold in IGT-LDL when compared to NGT-LDL. After one hour incubation of murine macrophages with LDL mRNA expression rates of the scavenger receptors CD36 and SR-BI and transcription factor PPAR Gamma were quantified by reverse-transcription real-time PCR. In comparison to NGT-LDL, IGT-LDL elicited a significantly higher CD36 (p<0.05) and PPAR Gamma (p<0.05) gene expression, whereas SR-BI mRNA expression was not affected.
Conclusion: These data suggest that impaired glucose tolerance is associated with increased glycoxidation of circulating LDL that might contribute to conversion of macrophages into a proatherogenic phenotype.

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Permalink: https://www.hzdr.de/publications/Publ-9619
Publ.-Id: 9619


Forward and inverse problems in MHD: numerical and experimental results

Stefani, F.; Gailitis, A.; Gerbeth, G.; Gundrum, T.; Xu, M.
When a conducting fluid comes under the influence of a magnetic field, electrical currents are induced that give rise to a modification of this magnetic field. The ratio of induced magnetic field to applied magnetic field is characterized by the magnetic Reynolds number Rm of the flow. For large Rm, even self-excitation of a magnetic field can occur. This hydromagnetic dynamo effect is responsible for the maintenance of the magnetic fields of planets, stars and galaxies. In the present paper, we delineate some recent developments in the numerical treatment of induction effects in arbitrary geometry, and their application for dynamo experiments as well as for a Contactless Inductive Flow Tomography (CIFT).

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Publ.-Id: 9618


Mechanical and tribological properties of carbon and nitrogen consecutive ion implantation into aluminium

Szcancoski, J. C.; Foerster, C. E.; Serbena, F. C.; Fitz, T.; Kreissig, U.; Richter, E.; Möller, W.; Lepienski, C. M.; Soares, P. C.; Siqueira, C. J.
Mechanical and tribological properties of successive C and N ion implantation into Al were studied in the present work. Ion sequence, substrate temperature and subsequent thermal treatment were performed in order to understand the involved mechanisms on the surface hardening. The results showed that independent of the ion sequence, a higher surface hardness is obtained for room temperature ion implantation (≈ 10 GPa). At high substrate temperature the hardness decreases to 7 GPa. The hardening mechanisms are discussed in terms of: solid solution, hard embedded precipitates in the soft Al matrix and the damage produced by the ion implantation process. Adhesive and abrasive regimes are identified from the friction coefficient profiles and are function of the ion implantation parameters. Wear resistance is improved if subsequent thermal treatment at high temperature is performed. Wear improvement is correlated to the presence of a high concentration of carbon clusters in the Al matrix.
Keywords: Mechanical properties; Nanoindentation; Carburising; Nitriding; Aluminium; Wear
  • Surface & Coatings Technology 201(2006)3-4, 1488-1494

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Publ.-Id: 9616


Investigation of K+ meson production in C+C collisions at 2A GEV with HADES

Sadovsky, A.
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-464 2007

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Permalink: https://www.hzdr.de/publications/Publ-9615
Publ.-Id: 9615


Annual Report 2006 - Institute of Radiochemistry

Bernhard, G.; Foerstendorf, H.; Richter, A.; Viehweger, K.; (Editors)
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-459 2007

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Publ.-Id: 9614


Effects of irradiation damage on the back-scattering of electrons: silicon-implanted silicon

Nasdala, L.; Kronz, A.; Grambole, D.; Trullenque, G.
Radiation damage in an (initially crystalline) silicon wafer was generated by microbeam implantation with 600 keV Si+ ions (fluence 5 x 1014 ions/cm²). To produce micro-areas with different degrees of damage, 14 implantations at different temperatures (between 23 and 225 °C) were done. The structural state of irradiated areas was characterized using Raman spectroscopy and electron back-scatter diffraction. All irradiated areas showed strong structural damage in surficial regions (estimated depth <1 μm), and at implant substrate temperatures of below 130 °C, the treatment has caused complete amorphization. Back-scattered electron (BSE) images exhibited that observed BSE intensities correlate with the degree of irradiation damage; all irradiated areas were higher in BSE than the surrounding host. Because there were no variations in the chemical composition and, with that, no Z contrast in our sample, this observation again supports the hypothesis that structural radiation damage may strongly affect BSE images of solids.
Keywords: Back-scattered electron images, Raman spectroscopy, electron back-scatter diffraction, radiation damage, silicon
  • American Mineralogist 92(2007), 1768-1771

Permalink: https://www.hzdr.de/publications/Publ-9613
Publ.-Id: 9613


Gammatomographie zur Messung von Voidverteilungen im SWR-Bündel am KATHY-Versuchsstand in Karlstein Abschlussbericht 2007

Bieberle, A.; Hampel, U.; Hoppe, D.
Dieser Bericht beinhaltet insbesondere diejenigen durchgeführten Arbeiten und Untersuchungen, welche für die Planung zukünftiger Experimente am KATHY - Versuchsstand relevant sind. Der Bericht unterteilt sich in zwei voneinander weitgehend unabhängige Teile, zum einen die technische Weiterentwicklung des Tomographen (Abschnitt 2) und zum anderen methodisch orientierte Studien und Experimente (Abschnitt 3) betreffend. Konzeptionell basiert der Bericht auf Auswertungen der an KATHY im Oktober 2005 und Januar 2006 durchgeführten Experimente, wobei diese Auswertungen hier nicht noch einmal in ihrer Gesamtheit dargelegt werden, sondern nur auf ihre zukünftig relevanten Aspekte Bezug genommen wird.
Keywords: gamma tomography, determination of void distribution
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2007
    FZD\FWS\2007\07
    45 Seiten

Permalink: https://www.hzdr.de/publications/Publ-9612
Publ.-Id: 9612


Numerical simulation of coolant mixing in a pressurized water reactor with different CFD methods based on complex meshes

Höhne, T.
The work was aimed at the numerical simulation of coolant mixing in the downcomer and the lower plenum of the Rossendorf test facility ROCOM. ROCOM is a 1:5 scaled Plexiglas model of a German pressurized water reactor allowing conductivity measurements by wire mesh sensors and velocity measurements by LDA technique. The CFD calculations were carried out with the CFD-codes CFX-4 and CFX-5. In the case of stationary mixing, the maximum value of the averaged mixing scalar at the core inlet was found in the sector below the inlet nozzle, where the tracer was injected. The comparison of a very detailed mesh (CFX-5) and a mesh with simplifications and additional physical models (CFX-4) showed, that in the referred case the use of these models are allowed. For turbulent flows CFX-4 and CFX-5 were validated in accordance with the Best Practice Guidelines and can be used in the reactor safety analysis. A better description of the mixing processes inside the RPV is the basis of a more realistic safety assessment.
Keywords: Boron Dilution, CFD, Pressurized Water Reactor, Coolant Mixing

Permalink: https://www.hzdr.de/publications/Publ-9611
Publ.-Id: 9611


Complexation of uranium(VI) with aromatic acids such as hydroxamic and benzoic acid investigated by TRLFS

Glorius, M.; Moll, H.; Geipel, G.; Bernhard, G.
The complex formation of uranium(VI) with salicylhydroxamic, benzohydroxamic, and benzoic acid was investigated by time-resolved laser-induced fluorescence spectroscopy (TRLFS). We observed in all three systems a decrease in the fluorescence intensity with increasing ligand concentration. All identified complexed uranyl species are of the type MpLqHr. In the uranium(VI)-salicylhydroxamate system a 1:1 complex with a stability constant of log β111 = 17.34 ± 0.06 and a 1:2 complex with a stability constant of log β122 = 35.0 ± 0.11 was identified. Also in the uranium(VI)-benzohydroxamate system the stability constants are determined to be log β110 = 7.92 ± 0.11 and log β120 = 16.88 ± 0.49. In the uranium(VI)-benzoate system only a 1:1 complex is existent with a stability constant of log β110 = 3.56 ± 0.05.
Keywords: Uranyl; Hydroxamic acid; Spectroscopy; TRLFS; Complexation
  • Journal of Radioanalytical and Nuclear Chemistry 277(2008)2, 371-377

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Publ.-Id: 9610


Ferromagnetism in GaN induced by Fe ion implantation

Talut, G.; Reuther, H.; Stromberg, F.; Zhou, S.; Potzger, K.; Eichhorn, F.
We report about magnetic and structural studies on p-type GaN implanted with 57Fe with fuences from 1*10^16cm^-2 to 1.6*10^17cm^-2 at different temperatures and subsequently subjected to thermal treatment. X-ray diffraction, transmission electron microscopy, conversion electron Mössbauer spectroscopy and superconducting quantum interference device magnetometry were used for the crystallographic, electronic and magnetic characterization of the samples. Room temperature ferromagnetism was observed in GaN after implantation at 623 K with different fluences and is mainly ascribed to alpha-Fe precipitations. An additional contribution to ferromagnetic signal is observed in a Mössbauer spectrum and as a magnetization loop in SQUID in sample implanted with lowest fluence at 623 K which cannot be related to alpha-Fe. In samples implanted with low fluences at RT no ferromagnetism was observed by means of SQUID. However, in CEMS a 6.8 T magnetic hyperfine field was used to fit the experimental spectrum and is discussed in terms of possible origin. Samples implanted at 240 K do not exhibit ferromagnetic properties. Precipitation of alpha-Fe was successfully reduced by decreasing the implantation temperature, however this was accompanied by an enhanced crystal damage. Annealing between 973 K and 1123 K resulted in most cases predominantly in the formation of alpha-Fe-clusters. Thermal treatment brought no significant recover of the crystallinity as it was verified by RBS channeling measurements.
Keywords: Diluted magnetic semiconductor, GaN, ferromagnetism, Fe
  • Journal of Applied Physics 102(2007), 083909
  • Poster
    Nanospintronic Design and Realization 2007, 21.-25.05.2007, Dresden, Germany
  • Poster
    International Conference on the Applications of the Mössbauer Effect, 14.-19.10.2007, Kanpur, India

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Permalink: https://www.hzdr.de/publications/Publ-9609
Publ.-Id: 9609


Charakterisierung des Opalinus-Tones und erste Ergebnisse zur U(VI)-Komplexierung mit Huminsäure-Modellliganden

Joseph, C.
Eine homogenisierte Probe Opalinus-Ton wurde charakterisiert. Die erhaltenen Ergebnisse (CEC, BET, TOC, XRD, IR) stimmen mit denen in der Literatur beschriebenen Ergebnissen überein. Erste Untersuchungen der U(VI)-Komplexierung mit HS-Modellliganden wurden durchgeführt.
Keywords: Opalinus clay, characterization, U(VI)-complexation, HA
  • Lecture (others)
    Workshop des Verbundprojektes Wechselwirkung und Transport von Actiniden im natuerlichen Tongestein unter Beruecksichtigung von Huminstoffen und Tonorganika, 02.-03.04.2007, Potsdam, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-9608
Publ.-Id: 9608


Measurement of Mg-25(p, gamma)Al-26(g) resonance strengths via accelerator mass spectrometry

Arazi, A.; Faestermann, T.; Niello, J.; Knie, K.; Korschinek, G.; Poutivtsev, M.; Richter, E.; Rugel, G.; Wallner, A.
The strengths of resonances located at center-of-mass energies of E-c.m.=189, 304, 374, and 418 keV for the Mg-25(p,gamma) reaction have been measured for the first time with an off-line method: Mg targets were firstly activated with protons at the resonance energies and the produced Al-26(g) nuclei were counted by means of highly sensitive accelerator mass spectrometry (AMS). Thus, the production of Al-26 in its ground state is determined independently from the gamma-decay branching ratio. While the 304, 374, and 418 keV resonances show fair agreement with previous measurements, the 189 keV resonance yield a significantly less strength. In addition, an experimental upper limit for the E-c.m.=92 keV resonance was determined.
  • Physical Review C 7402(2006)2, 5802

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Publ.-Id: 9607


Superconducting regions and Kondo effect of MgB2 formed by implantation of magnesium ions into boron substrate

Trybula, Z.; Kempinska, W.; Andrzejewski, B.; Piekara-Sady, L.; Kaszynski, J.; Trybula, M.; Piekoszewski, J.; Stanislawski, J.; Barlak, M.; Richter, E.
The results of investigation of the polycrystalline boron implanted by magnesium and argon plasma pulse treatment are presented. The four-probe electric conductivity measurements and magnetically modulated microwave absorption showed the presence of superconducting islands below the temperature of 25 K. Below T = 23 K we detected the Kondo effect, a logarithmic increase in the resistivity as the temperature is lowered, due to iron impurity.
  • Open Access Logo Acta Physica Polonica A 109(2006)4-5, 657-660

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Permalink: https://www.hzdr.de/publications/Publ-9606
Publ.-Id: 9606


Einfluss von HS auf die U(VI)- und Am(III) Sorption an Kaolinit: TRLFS Untersuchungen

Krepelova, A.
We used time-resolved laser-induced fluorescence spectroscopy (TRLFS) in order to characterize the species of U(VI) adsorbed onto kaolinite in the absence and presence of HA. Two adsorbed U(VI) surface species on kaolinite were identified in the pH range of pH 5.0 to pH 8.5. Obtained results help to improve the understanding of the geochemical interactions of hexavalent actinides in environment.
Laser fluorescence spectroscopy measurements were carried out in the systems Am(III)-kaolinite and Am(III)-HA-kaolinite to study the surface complexes of Am(III) on kaolinite at different pH values (pH 5 - 8). HA decreases the fluorescence intensity of the samples. The shape of the measured fluorescence spectra in both systems, binary and ternary, differs from the spectrum observed in the solution. Further measurements are required to satisfactorily explain the obtained results.
Keywords: Sorption, kaolinite, HA, Am(III), U(VI), TRLFS
  • Lecture (others)
    Workshop zum Forschungsvorhaben "Wechselwirkung und Transport von Actiniden im natürlilchen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika", 02.-03.04.07, Potsdam, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-9605
Publ.-Id: 9605


Modeling of a Buoyancy-Driven Flow experiment in Pressurized Water Reactors using CFD-Methods

Höhne, T.; Kliem, S.
The influence of density differences on the mixing of the primary loop inventory and the Emergency Core Cooling (ECC) water in the downcomer of a Pressurised Water Reactor (PWR) was analyzed at the ROssendorf COolant Mixing (ROCOM) test facility. ROCOM is a 1:5 scaled model of a German PWR, and has been designed for coolant mixing studies. It is equipped with advanced instrumentation, which delivers high-resolution information for temperature or Boron concentration fields. This paper presents ROCOM experiments in which water with higher density was injected into a cold leg of the reactor model. Wire-mesh sensors measuring the concentration of a tracer in the injected water were installed in the upper and lower part of the downcomer. An experiment with 5 % of the design flow rate in one loop and 10 % density difference between the ECC and loop water was selected for validation of the CFD software ANSYS CFX. A mesh with two million control volumes was used for the calculations. The effects of turbulence on the mean flow were modelled with a Reynolds stress turbulence model. The results of the experiment and of the numerical calculations show that mixing is dominated by buoyancy effects: At higher mass flow rates (close to nominal conditions) the injected slug propagates in the circumferential direction around the core barrel. Buoyancy effects reduce this circumferential propagation. The ECC water falls in an almost vertical path and reaches the lower down¬comer sen¬sor directly below the inlet nozzle. Therefore, density effects play an important role during natural convection with ECC injection in PWRs. ANSYS CFX was able to predict the observed flow patterns and mixing phenomena quite well.
Keywords: Safety, Thermalhydraulics, Coolant Mixing, CFD
  • Open Access Logo Nuclear Engineering and Technology 39(2007)4, 327-336

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Permalink: https://www.hzdr.de/publications/Publ-9604
Publ.-Id: 9604


P implantation into pre-amorphized germanium and subsequent annealing: solid phase epitaxial regrowth, P diffusion and activation

Posselt, M.; Schmidt, B.; Anwand, W.; Grötzschel, R.; Heera, V.; Wündisch, C.; Skorupa, W.; Hortenbach, H.; Gennaro, S.; Bersani, M.; Giubertoni, D.; Möller, A.; Bracht, H.
High fluence P implantation (30 keV, 3x1015 cm-2) into pre-amorphized Ge and subsequent rapid thermal or flash lamp annealing is investigated. In contrast to previous assumptions a significant P diffusion in amorphous Ge is not observed. However, during the fast solid phase epitaxial regrowth a rapid redistribution of P occurs. After completion of the regrowth and at temperatures above 500 0C, a concentration-dependent diffusion of P in crystalline Ge takes place. An appreciable influence of implantation defects on the diffusion coefficient of P cannot be found. For 60 s rapid thermal annealing at 600 0C and for 20 ms flash lamp annealing at 900 0C, the junction depth and the sheet resistance vary between 140 and 200 nm and between 50 and 100 Ohm , respectively, and the maximum electrical activation of P is about 3 – 7x1019 cm-3.
Keywords: germanium implantation annealing doping
  • Contribution to proceedings
    International Workshop on INSIGHT in Semiconductor Device Fabrication, Metrology and Modeling (INSIGHT-2007), 06.-09.05.2007, Napa, United States
    Proceeding INSIGHT-2007 Workshop, 309-315
  • Lecture (Conference)
    International Workshop on INSIGHT in Semiconductor Device Fabrication, Metrology and Modeling (INSIGHT-2007), 06.-09.05.2007, Napa, United States

Permalink: https://www.hzdr.de/publications/Publ-9603
Publ.-Id: 9603


Experiments on the interface dynamics of stratified air/water flows

Vallee, C.
For the investigation of co-current two-phase flows, the Horizontal Air/Water Channel (HAWAC) was built at Forschungszentrum Dresden-Rossendorf. A special inlet device provides well-defined as well as variable boundary conditions for generic horizontal two-phase flow experiments. Optical measurements were performed with a high-speed video camera during slug flow. By an interface capture method, the water level can be measured in any observed cross-section. As a result, the water level history can be extracted from the image sequences. Furthermore, the profiles of the time-averaged water level bounded by the standard deviation were presented and show the evolution of the flow structure and of its dynamic component along the channel.
Keywords: horizontal two-phase flow, slug flow, image processing
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2007, 22.-24.05.2007, Karlsruhe, Germany
    Jahrestagung Kerntechnik 2007 - Fachsitzung, Berlin: INFORUM Verlags- und Verwaltungsgesellschaft, 23-26
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2007, 22.-24.05.2007, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-9602
Publ.-Id: 9602


Synthesis report on work package 2.1: Pressurized Thermal Shock (PTS) - T0+24

Lucas, D.
This report summarizes the results of the first 24 months period of the NURESIM project for the work package 2.1 “Pressurized Thermal Shock (PTS)”. It mainly bases on the deliverables supplied by the partners involved in this work package. In the Introduction chapter some more general information on the PTS issue is given, which should help to clarify the integration of the single activities. Since the PTS scenario involves different flow situations, for which also different modelling approaches are necessary, the contributions are sorted according to these flow situations. The relation of the work done to the general aim of the NURESIM project, which is to establish a new code platform, is indicated by assigning the activities to 6 different types. The present status PTS work package is in agreement with the planning of the NURESIM project, the expected results were met by the deliverables. The work done leads to an improvement of the simulation capabilities regarding a PTS flow situation, but caused by the complexity of the issue it will still be a long way to enable reliable predictions for the whole process from such simulations.
Keywords: PTS, CFD, Two-Phase Flow
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2007
    FZD\FWS\2007\05
    27 Seiten

Permalink: https://www.hzdr.de/publications/Publ-9601
Publ.-Id: 9601


On the simulation of two-phase flow pressurized thermal shock (PTS)

Lucas, D.; Bestion, D.; Bodèle, E.; Scheuerer, M.; F. D’Auria, D. M.; Smith, B.; Tiselj, I.; Martin, A.; Lakehal, D.; Seynhaeve, J.-M.; Kyrki-Rajamäki, R.; Ilvonen, M.; Macek, J.
This paper reports some activity about the Pressurized Thermal Shock (PTS) performed within the European Integrated Project NURESIM. The PTS phenomenon is expected to take place in some water cooled nuclear reactors equipped with pressure vessels during selected accident scenarios. The PTS implies the formation of temperature gradients in the thick vessel walls with consequent localized stresses and the potential for propagation of possible flaws present in the material. Current generation Pressurized Water Reactors, PWR (including the Russian VVER types), are primarily affected by the phenomenon which is investigated within three broad areas: material damage originated by irradiation, thermal-hydraulics (including single and two-phase flow conditions in the region of the ‘shock’) and structural mechanics with main reference to fracture mechanics. The present paper, in the area of thermal-hydraulics, focuses on the study of two-phase conditions that are potentially at the origin of PTS. Within the above context, the paper summarizes recent advances in the understanding of the two-phase phenomena occurring within the geometric region of the nuclear reactor, i.e. the cold leg and the downcomer, where the ‘PTS fluid-dynamics’ is relevant. Available experimental data for validation of two-phase CFD simulation tools are reviewed and the capabilities of such tools to capture each basic phenomenon are discussed. Key conclusions show that several two phase mechanisms (or sub-phenomena) are involved and can individually be simulated at least at a qualitative level, but the capability to simulate their interaction and the overall system performance (case of two phase flow) is presently not available.
Keywords: PTS, Two-Phase Flow, CFD
  • Contribution to proceedings
    NURETH-12 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics, paper [035], 30.09.-04.10.2007, Pittsburgh, Pennsylvania, United States
  • Lecture (Conference)
    NURETH-12 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics, 30.09.-04.10.2007, Pittsburgh, Pennsylvania, United States

Permalink: https://www.hzdr.de/publications/Publ-9600
Publ.-Id: 9600


CFD Modellierung in der Sicherheitstechnik - Möglichkeiten und Grenzen

Prasser, H.-M.; Frank, T.; Höhne, T.; Lucas, D.
Die CFD Modellierung hat Einzug gehalten in die nukleare Sicherheit. CFD-Codes werden erfolgreich eingesetzt, um komplexe Strömungsfelder in ganzen Druckwasserreaktoren zu berechnen. Dabei geht es vornehmlich um die Vermischung von Borsäure bei mit unboriertem Wasser und von kalten Notkühlwasser mit heißem Reaktorkühlmittel. Die Validierung anhand von Versuchen an verhätnismässig grossskaligen Testständen, die mit hochauflösender Leitfähigkeitsmesstechnik ausgestattet sind, zeigt die bereits erreichte hohe Zuverlässigkeit der Vorhersagen im Einphasenbereich. Diese Erkenntnisse können auf chemisch-verfahrenstechnische Anlagen übertragen werden. Beim Übergang zur Zweiphasenströmung treten zusätzliche Schwierigkeiten auf, die mit der Beschreibung der Prozesse an der Phasengrenze und der Modellierung der Topologie und Ausdehnung derselben zusammenhängen. Hierzu werden neuere Entwicklungen auf dem Gebiet der Zweifluidmodelle für Gas-Flüssigkeitsströmungen vorgestellt. Speziell handelt es sich um das Inhomogeneous MUSIG Model, das Bestandteil des Codes ANSYS CFX ist. Dieser Ansatz erlaubt die Beschreibung der Wechselwirkung mehrerer Blasenklassen unter Berücksichtigung der auf die Blasen wirkenden Kräfte und von Koaleszenz und Zerfall. Das Modell wurde ausgehend von Experimenten an vertikalen Rohrleitungen vorgeschlagen und dann anhand von Messergebnissen validiert. Auch hier kommen Leitfähigkeitssensoren zum Einsatz, die die Struktur der Phasengrenzfläche im gesamten Strömungsquerschnitt hochaufgelöst erfassen. Dabei wurden u.a. Strömungen mit Phasenübergang infolge Kondensation von Dampf an einer unterkühlten Flüssigphase untersucht. Mit solchen Gittersensoren wurden auch komplexe dreidimensionale Gas-Flüssigkeitsströmungen, z.T. bei Drücken bis zu 70 bar und Temperaturen bis 286 °C (Wasser-Dampf) vermessen, die charakteristische Merkmale von Strömungen in technisch relevanten Anlagenteilen aufweisen, wie Strömungsabriss, Staupunkte, Strahlausbildung, Rezirkulationsgebiete u.ä.. Der Vergleich zwischen Rechnungen und Experiment dokumentiert den erreichten Stand bei der dreidimensionalen Modellierung. Durch die Diskretisierung der zu untersuchenden Geometrie ist der CFD-Code in der Lage, die Einzelmodelle auch Geometrien zu übertragen, die bei der Validierung nicht betrachtetet wurden. Dies wird anhand von Rechenergebnissen für Sicherheitsventile demonstriert.
Keywords: CFD, Leitfähigkeitsmesstechnik, MUSIG
  • Lecture (Conference)
    ProcessNet-Jahrestagung 2007, 16.-18.10.2007, Aachen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-9599
Publ.-Id: 9599


R&D on RPC with CBM

Dohrmann, F.; Kotte, R.; Naumann, L.; Stach, D.; Sytcheva, A.; Wüstenfeld, J.
The talk summarizes the latest tests and results w.r.t. MRPCs with silicate glass resistive plates. These
have been tested in a high flux environment with a continous electron beam at ELBE.
  • Lecture (Conference)
    9. Collaboration Meeting of the CBM Experiment at FAIR, 27.02.-02.03.2007, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-9598
Publ.-Id: 9598


Dielectron detection capabilities of HADES at SIS100/300

Bannier, B.
The HADES experiment at SIS18 at GSI/Darmstadt is a dedicated experiment for studying medium modifications of hadrons, i.e. the light vector mesons rho, omega and phi, in pA, piA and AA collisions. Specifically, dileptonic decays of these vector mesons provide an direct probe for the properties of hadronic matter at high nuclear densities. The future FAIR facility at GSI/Darmstadt with SIS100/300 will provide heavy-ion beams with energies of up to 45 AGeV. It is planned to operate the HADES detector at these higher energies. In this work the principle possibilities of detecting dielectrons with an unmodified HADES detector are studied. Simulations of dielectron production for several beam energies have been performed using the UrQMDv1.3p1 transport code together with the PLUTO++ phase space generator. Future measurements of dileptons with HADES at FAIR are shown to be within reach of the current setup.
  • Lecture (Conference)
    Gießen 07 - DPG Frühjahrstagung, Hadronen und Kerne, 12.-16.03.2007, Giessen, Germany

Permalink: https://www.hzdr.de/publications/Publ-9597
Publ.-Id: 9597


Properties of Multigap RPC detectors tested with continuous electron beams at ELBE

Dohrmann, F.; Kotte, R.; Naumann, L.; Stach, D.; Sytcheva, A.; Wüstenfeld, J.
Multigap Resistive Plate Chambers (MRPC) provide the possibility for assembling high-granularity, large-area TOF sytems designed for modern nuclear and particle physics experiments. Currently, experiments like ALICE, STAR, FOPI, HADES prepare MRCP based TOF systems with time resolutions of less than 100 ps. The planned CBM experiment at the future FAIR facility at GSI/Darmstadt considers using an MRPC system provided sufficient time resolution and rate stability can be achieved. These properties of MRCP have been successfully demonstrated in prototype tests performed at the FZD electron linac ELBE, using continuous e− beams of 20-40 MeV. Typical time resolutions of 70 ps were achieved. The rate capabilities of MRCP using special low-resistive silicate glas were tested and stable efficiencies up to rates of 20 kHz/cm2 were observed.
  • Lecture (Conference)
    Gießen 07 - DPG Frühjahrstagung 2007, Hadronen und Kerne, 12.-16.03.2007, Giessen, Germany

Permalink: https://www.hzdr.de/publications/Publ-9596
Publ.-Id: 9596


Ion beam synthesis of 4H-(Si1-xC1-y)Gex+y solid solutions

Pezoldt, J.; Kups, T.; Voelskow, M.; Skorupa, W.
4H silicon carbide (Si1-xC1-y)Gex+y solid solutions with an average Ge incorporation on lattice sites ranging from 0.7 to 2.5 percent were formed by ion beam synthesis. RBS and RBS/C investigations revealed a decreasing Ge lattice incorporation with increasing implantation dose above 10%. The carried out rapid thermal annealing at 1300 °C reduces the residual damage, increases the lattice site occupation and led to negligible change in the concentration profiles.
Keywords: silicon carbide, germanium implantation, rapid thermal annealing, RBS

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Permalink: https://www.hzdr.de/publications/Publ-9595
Publ.-Id: 9595


DYN3D/ATHLET calculations of a boron dilution transient during natural circulation conditions

Kliem, S.; Rohde, U.
Slugs of under-borated, or even boron-free, coolant can be formed in the primary circuit during different accident scenarios, e. g. due to a malfunction of the chemical and volume control system, or due to an SBLOCA with partial failure of the safety injection system. An unintentional, or even unavoidable, decrease of boron concentration in the reactor core leads to a reactivity increase and may result in a power excursion, a so-called boron dilution transient. Whether re-criticality of the scrammed reactor occurs, and how high the power peak is, depends among other factors, in a sensitive manner, on the mixing of the too weakly borated water with the ambient coolant in the downcomer and the lower plenum on its way to the core. For an adequate simulation of such boron dilution transients, 3D neutron kinetic core models coupled with advanced thermal hydraulic system codes are necessary. Such analyses should be completed by a simulation of the above mentioned coolant mixing processes inside the reactor pressure vessel.

An earlier developed fast running semi-analytical coolant mixing model has been recently extended to natural circulation conditions. A parameter study, incorporating stationary and transient core calculations, was carried out for a hypothetical boron dilution event in a pressurized water reactor during the operation of the residual heat removal system, using the coupled 3D neutron kinetics/thermal hydraulics code system DYN3D/ATHLET in combination with this coolant mixing model. According to the boundary conditions, this analysis is carried out at atmospheric pressure conditions and a coolant temperature of 25 °C. By varying the initial slug volume, it was found in stationary calculations that, for the given core configuration, slugs of less than 6 m³ do not lead to re-criticality. Transient core calculations from 8 to the maximum initial slug volume of 15 m3 show a significant reactivity insertion and over-criticality. The resulting power excursion is mitigated and stopped by Doppler and moderator density feedback. The power increase in all calculations is accompanied by significant coolant boiling in single channels. It should be pointed out, that the thermal hydraulics simulations at low pressure are quite challenging because of the high density difference between water and steam and therefore, high sensitivity of void fraction versus coolant enthalpy. Although in all calculations local coolant boiling occurs over several tenths of seconds, the integrity of the fuel is always ensured according to the calculation results.
Keywords: boron dilution, natural circulation, neutron kinetics/thermal hydraulics coupling, coolant boiling
  • Contribution to proceedings
    NURETH-12 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics, 30.09.-04.10.2007, Pittsburgh, United States
    Proceedings of the 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, CDROM, paper 053, 0894480588
  • Lecture (Conference)
    NURETH-12 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics, 30.09.-04.10.2007, Pittsburgh, United States

Permalink: https://www.hzdr.de/publications/Publ-9594
Publ.-Id: 9594


Dilepton production in pp and CC collisions with HADES

Fröhlich, I.; Agakichiev, G.; Agodi, C.; Balanda, A.; Bellia, G.; Belver, D.; Belyaev, A.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Braun-Munziger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Diaz, J.; Dohrmann, F.; Duran, I.; Eberl, T.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Grosse, E.; Guber, F.; Hadjivasiliou, C.; Heilmann, M.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krizek, F.; Krücken, R.; Kugler, A.; Kühn, W.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, S.; Lopez, L.; Mangiarotti, A.; Marin, J.; Markert, J.; Metag, V.; Michalska, B.; Mishra, D.; Moriniere, E.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Novotny, J.; Otwinowski, J.; Pachmayer, Y.; Palka, M.; Pechenov, V.; Perez, T.; Pietraszko, J.; Pleskac, R.; Pospisil, V.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Senger, P.; Shileev, K.; Simon, R. S.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Veretenkin, I.; Wagner, V.; Wen, H.; Wisniovski, M.; Wojcik, T.; Wüstenfeld, J.; Zanevsky, Y.; Zumbruch, P.
e+e- production was studied using the High Acceptance DiElectron Spectrometer (HADES). In pp collisions at 2.2 GeV kinetic energy, the exclusive η production and the Dalitz decay η -> γe+e- have been reconstructed. The electromagnetic form factor of the latter decay was found to be in good agreement with the existing theoretical predictions. In addition, an inclusive e+e- invariant-mass spectrum from the 12C +12C reaction at 2 AGeV is presented and compared with a simplified thermal model.

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Permalink: https://www.hzdr.de/publications/Publ-9593
Publ.-Id: 9593


Nickel nanoparticle catalysed formation of fullerene like carbon nanostructures - a Raman analysis

Krause, M.; Abrasonis, G.; Kolitsch, A.; Mücklich, A.; Möller, W.
The catalytic effect of nickel nanoparticles on the formation and on the structure of fullerene-like carbon nanostructures prepared by ion beam sputtering at different temperatures was studied by wavelength dependent Raman spectroscopy. Compared to nickel-free reference films the formation of carbon nanostructures is enhanced in the whole range of deposition temperatures from 25°C =< T (°C) <= 500°C. Several phases characterized by different ratios of amorphous and graphite-like carbon, a different film transparency, and a different elastic Raman background intensity, were observed. Amorphous carbon structures are preferentially formed at lower deposition temperatures, whereas graphitic structures are dominant for higher growth temperatures. Based on data for different excitation wavelengths and using difference spectroscopy, a quantitative model for the composition of these nanostructured carbon materials is developed. The results are in full agreement with those obtained by TEM, XANES and XRD analysis.[1] The model might be used as well for the analysis of other pure carbon or carbon based composite materials like CN and BCN films.
[1] G. Abrasonis, A. Mücklich, K. Küpper, M. Krause, U. Kreissig, A. Kolitsch, W. Möller, K. Sedlackova, G. Radnoczi, R. Torres, and I. Jimenez, "Morphology and bonding structure of fullerene-like nanocomposite C:Ni (~30 at%.) thin films grown by ion beam sputtering", to be presented on XXI. IWEPNM, Kirchberg, 2007
Keywords: Carbon films, Nanocomposites, Nickel catalysis, Raman
  • Poster
    XXIst International Winterschool Molecular Nanostructures, 10.-17.03.2007, Kirchberg, Österreich

Permalink: https://www.hzdr.de/publications/Publ-9591
Publ.-Id: 9591


Superposition of quantum and classical rotational motions in Sc2C2@C84 fullerite

Michel, K. H.; Verberck, B.; Hulman, M.; Kuzmany, H.; Krause, M.
The superposition of the quantum rotational motion (tunneling) of the encapsulated Sc2C2 complex with the classical rotational motion of the surrounding C84 molecule in a powder crystal of Sc2C2@C84 fullerite is investigated by theory. Since the quantum rotor is dragged along by the C84 molecule, any detection method which couples to the quantum rotor (in casu the C2 bond of the Sc2C2 complex) also probes the thermally excited classical motion (uniaxial rotational diffusion and stochastic meroaxial jumps) of the surrounding fullerene. The dynamic rotation-rotation response functions in frequency space are obtained as convolutions of quantum and classical dynamic correlation functions. The corresponding Raman scattering laws are derived, and the overall shape of the spectra and the width of the resonance lines are studied as functions of temperature. The results of the theory are confronted with experimental low-frequency Raman spectra on powder crystals of Sc2C2@C84 [M. Krause et al., Phys. Rev. Lett. 93, 137403 (2004)]. The agreement of theory with experiment is very satisfactory in a broad temperature range.
Keywords: Fullerenes, Quantum Rotation

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Permalink: https://www.hzdr.de/publications/Publ-9590
Publ.-Id: 9590


Hydrogen peroxide treatment induced rectifying behavior of Au/n-ZnO contact

Gu, Q. L.; Ling, C. C.; Chen, X. D.; Cheng, C. K.; Ng, A. M. C.; Beling, C. D.; S. Fung, S.; DjurišIć, A. B.; Brauer, G.; Ong, H. C.
Conversion of the Au/n-ZnO contact from Ohmic to rectifying with H2O2 pretreatment was studied systematically using I-V measurements, x-ray photoemission spectroscopy, positron annihilation spectroscopy, and deep level transient spectroscopy. H2O2 treatment did not affect the carbon surface contamination or the EC–0.31 eV deep level, but it resulted in a significant decrease of the surface OH contamination and the formation of vacancy-type defects (Zn vacancy or vacancy cluster) close to the surface. The formation of a rectifying contact can be attributed to the reduced conductivity of the surface region due to the removal of OH and the formation of vacancy-type defects.
  • Applied Physics Letters 90(2007), 122101

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Permalink: https://www.hzdr.de/publications/Publ-9589
Publ.-Id: 9589


Dresden pulsed magnetic field facility

Wosnitza, J.; Bianchi, A. D.; Freudenberger, J.; Haase, J.; Herrmannsdörfer, T.; Kozlova, N.; Schultz, L.; Skourski, Y.; Zherlitsyn, S.; Zvyagin, S. A.
We report on the status quo of the Dresden High Magnetic Field Laboratory (HLD) that is being set up at the Forschungszentrum Dresden-Rossendorf in Dresden, Germany. First pulsed-field coils reaching up to 71T with a pulse duration of about 100 ms have been designed, constructed, and tested. A two-coil 100 T magnet and a long-pulse (1000 ms) 60T magnet are under construction. Electrical transport and magnetization experiments are running routinely in the pilot laboratory at the IFW Dresden. The feasibility of NMR experiments in pulsed-field environments has been proven.
  • Journal of Magnetism and Magnetic Materials 310(2007), 2728-2730

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Permalink: https://www.hzdr.de/publications/Publ-9588
Publ.-Id: 9588


Magnetism of the single molecule magnet system [(MnIIL2)3MnII](BF4)2

Prinz, M.; Voget, S.; Damnik, N.; Raekers, M.; Kuepper, K.; Chaudhuri, P.; George, S.; Coldea, M.; Neumann, M.
The single molecule magnet system [(MnIIL2)3MnII](BF4)2 containing four Mn2+ ions has been studied using X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy, and X-ray magnetic circular dichroism (XMCD). The XPS Mn 2p and Mn 3s spectra confirm the manganese 2+ valency. From XMCD measurements at a temperature of T = 2 K and a magnetic field of B = 5 T we obtained a high magnetic moment of 12 μB/f.u. This spin moment agrees in an excellent way with magnetic measurements which show a magnetization saturation of 10 μB/f.u. at 7 T and 2 K. From XMCD a quenching of the Mn orbital moments was observed (morb = 0.4 μB/f.u.).
Keywords: Molecular magnetism, Mn2+ complex, x-ray magnetic circular dischroism
  • Poster
    DPG Jahrestagung und DPG Frühjahrstagung des AKF, 26.-30.03.2007, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-9587
Publ.-Id: 9587


Investigation of high-k materials RScO3 (R=Sm,Gd,Dy) by XPS and band structure calculations

Raekers, M.; Bartkowski, S.; Kuepper, K.; Zhou, S.; Potzger, K.; Postnikov, A.; Uecker, R.; Neumann, M.
There has been considerable interest in high-k-dielectrics rare earth oxides as replacement for SiO2 in advanced field-effect transistors (FETs). Promising candidates are the perovskites SmScO3, GdScO3 and DyScO3. A tendency towards antiferromagnetic ordering at low temperatures is observed for the high magnetic moments at rare earth atoms. We analyse the electronic structure of the single crystalline samlpes by means of X-ray photoelectron spectroscopy and firstprinciples theory. The electronic structure calculations are performed with the augmented plane waves method (WIEN2k code) of the density functional theory, taking into account the spin-orbit interaction and orbital-dependent potential (LDA+U). The calculated positions of the main features in the valence band agree with the XPS data, the underlying chemical bonding can be analysed in detail. Small differences in the electronic structure, resulting in different stability of ferroand antiferromagnetic configurations, are discussed.
Keywords: high-k dielectrics, wide band gap insulators, perovskites, electronic structure calculations, x-ray photoelectron spectroscopy
  • Poster
    DPG Jahrestagung und DPG Frühjahrstagung des AKF, 26.-30.03.2007, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-9586
Publ.-Id: 9586


Magnetization dynamics of a single cross-tie wall

Kuepper, K.; Marko, D.; Buess, M.; Raabe, J.; Quitmann, C.; Fassbender, J.ORC
We report the imaging of the magnetic excitation spectrum of a single cross-tie wall by means of x-ray magnetic circular dichroism - photoemission electron microscopy (XMCD-PEEM). The permalloy rectangle was excited by a short magnetic in plane pulse with a maximum field value of about 20 Oe. The high temporal and lateral resolution allows a detailed quantitative analysis of the magnetodynamic excitations. We find new eigenmodes in the frequency domain which are characteristic for the vortex-antivortex interaction in a single cross-tie wall. We discuss our experiment along micromagnetic simulations.
Keywords: vortex, antivortex, cross-tie wall, magnetization dynamics
  • Lecture (Conference)
    DPG Jahrestagung und DPG Frühjahrstagung des AKF, 26.-30.03.2007, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-9585
Publ.-Id: 9585


Nanomagnetism at the Forschungszentrum Dresden-Rossendorf

Kuepper, K.
The activities of the nanomagnetism group at the Forschungszentrum Dresden-Rossendorf will be briefly presented.
Special emphasis will be given to lateral and time resolved x-ray microscopies in order to study the magnetization
dynamics of micromagnetic elements in detail.
Keywords: Nanomagnetism, vortex, antivortex, dynamics
  • Lecture (others)
    MSD Seminar, Argonne National Lab., Argonne, USA, 17.01.2007, Argonne, USA

Permalink: https://www.hzdr.de/publications/Publ-9584
Publ.-Id: 9584


Operational Experiences with Megawatt PV Plants in Central Germany

Rindelhardt, U.; Bodach, M.
Purpose
Stimulated by the German Feed-in-Law, a number of grid-connected Megawatt PV plants have been put into operation during the last 5 years. Because of the higher irradiance these plants were originally concentrated in the southern part of Germany (Bavaria and Baden-Wuerttemberg). Starting in 2004 some plants have been also installed in Central Germany. The paper describes design and operation results of seven plants operating in the region of Saxony and Thuringia.

Locations and design
The most plants are concentrated in a region earlier defined by the DWD as "solar island" around Leipzig and Chemnitz. One plant is located in north-west Thuringia.
All plants were built on heavily used or loaded areas (former industrial sites or waste sites). Different types of fundaments and rack support constructions (desks) were used for the module mounting. The connection with the grid was done in the 10 to 20 kV voltage level, the distance between the plants and the grid was several thousands meters in some cases. All plants started their operation before 2006. The operation of the plants is monitored by the owners or by professional service providers.

Results and conclusions
The operation results of the year 2006 are exemplarily presented. The solar irradiance in 2006 was higher than the long year average, similar to the years before. The final yield of the plants ranges between 950 and 1050 kWh/kW. These surprisingly high values are near the values which were only found in Germany south of 50° latitude so far. The final yield of the tracked plant in Borna surpasses the yield of the other plants by 25%.
The performance ratios were determined to be between 0.77 and 0.84. The sources of energy losses are analysed and discussed. Beside component failures in the plants also grid disconnections reduced the feed-in energy in some cases.
Finally a long term estimation of the yield for the different plants will be given. Based on the data of the year 2006 a mean yield between 900 and 1000 kWh/kW can be expected.
Keywords: photovoltaics, PV plants, performance
  • Contribution to proceedings
    22. European Photovoltaic Solar Energy Conference, 03.-07.09.2007, Milano, Italy
    Operational Experiences with Megawatt PV Plants in Central Germany, 3-936338-22-1, 2952-2955
  • Lecture (Conference)
    22. European Photovoltaic Solar Energy Conference, 03.-07.09.2007, Milano, Italy

Permalink: https://www.hzdr.de/publications/Publ-9581
Publ.-Id: 9581


Kernenergie im 21. Jahrhundert - Herausforderungen und Möglichkeiten

Rindelhardt, U.
Im Beitrag werden die Optionen und die Herausforderung für die Nutzung der Kernenergie im 21. Jahrhundert aufgezeigt. Ausgangspunkt sind die vorhandenen Vorräte an Kernbrennstoff und die Darstellung seiner derzeitigen Nutzung. Die Entwicklung der Kernkraftwerkstechnik seit 1960 wird beispielhaft dargestellt. Die Optionen und Entwicklungsziele der Kernreaktoren der 4. Generation (EInsatz etwa ab 2040) werden exemplarisch vorgestellt. Dabei wird besonders auf die zentrale Rolle der schnellen Brutreaktoren eingegangen.Ein besonderer Abschnitt ist der Wiederaufarbeitung und Endlagerung von Kernbrennstoff gewidmet.
Keywords: Kernenergie, Kernkraftwerke, Kernbrennstoff
  • Lecture (others)
    Informationsveranstaltung, 18.04.2007, Chemnitz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-9580
Publ.-Id: 9580


Laserinduzierte Breakdown-Detektion (LIBD)

Zänker, H.; Weiß, S.
Die LIBD ist eine Methode, die Kolloidpartikel in sehr niedrigen Konzentrationen zu vermessen vermag. Sie wurde bisher vorwiegend zur Untersuchung von Kolloidproblemen in der Umweltforschung eingesetzt. Wegen ihrer hohen Empfindlichkeit könnte die LIBD potentiell aber auch für die Überwachung von Reinst- und Prozesswässern in der Halbleiterindustrie interessant sein. Hier ist die etablierte Methode zur Überwachung der Partikelfreiheit von Wässern das Single Particle Counting (SPC), vor allem mit den kommerziellen Geräten von PMS und Horiba. Es wird gezeigt, dass (i) für Kolloidpartikel > 50 nm das SPC der LIBD bezüglich der Konzentrationsempfindlichkeit deutlich überlegen ist, (ii) für Kolloidpartikel < 50 nm die Konzentrationsempfindlichkeit der LIBD heute unbefriedigend ist (sie liegt über den zu vermutenden typischen Konzentrationen der Partikel < 50 nm in den Reinstwässern der Halbleiterindustrie), (iii) die LIBD die einzige Methode ist, die überhaupt eine Information über Partikel < 50 nm liefern kann und (iv) durch technische Weiterentwicklung die LIBD wahrscheinlich in den erforderlichen Bereich der Partikelkonzentrationsempfindlichkeit gebracht werden könnte. Die Methode würde (nach Weiterentwicklung) für die Halbleiterindustrie interessant, wenn Partikel der Größe < 50 nm als Verunreinigungen interessant werden.

Keywords: Particle-free waters, semiconductor industries, colloids, laser-induced breakdown detection (LIBD), single particle counting (SPC)
  • Invited lecture (Conferences)
    Seminar über Partikelmessung an Reinstwässern der Halbeiterindustrie, 20.03.2007, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-9579
Publ.-Id: 9579


K0 and Λ production in Ni+Ni collisions near threshold

Merschmeyer, M.; Lopez, X.; Bastid, N.; Crochet, P.; Herrmann, N.; Andronic, A.; Barret, V.; Basrak, Z.; Benabderrahmane, M. L.; Caplar, R.; Cordier, E.; Dupieux, P.; Dzelalija, M.; Fodor, Z.; Gasparic, I.; Grishkin, Y.; Hartmann, O. N.; Hildenbrand, K. D.; Hong, B.; Kang, T. I.; Kecskemeti, J.; Kim, Y. J.; Kirejczyk, M.; Kis, M.; Matulewicz, T.; Koczon, P.; Korolija, M.; Kotte, R.; Lebedev, A.; Leifels, Y.; Mangiarotti, A.; Pelte, D.; Petrovici, M.; Rami, F.; Reisdorf, W.; Ryu, M. S.; Schüttauf, A.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczynska, K.; Smolyankin, V.; Stoicea, G.; Tyminski, Z.; Wisniewski, K.; Xiao, Z.; Xu, H. S.; Yushmanov, I.; Zhang, X. Y.; Zhilin, A.
New results concerning the production of neutral strange particles, K0 and Λ in Ni+Ni collisions at 1.93 AGeV, measured with the FOPI detector at GSI Darmstadt, are presented. Rapidity density distributions and Boltzmann slope parameter distributions are measured in nearly the full phase space of the reaction. The observables are compared to existing K+ and proton data. While the K0 data agree with previously reported K+ measurements, the Λ distributions show a different behavior relative to that of protons. The strangeness balance and the production yield per participating nucleon as a function of the centrality of the reaction are discussed, for the first time at SIS energies.

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Permalink: https://www.hzdr.de/publications/Publ-9578
Publ.-Id: 9578


Confinement of strongly anisotropic hot-ion plasma in a compact mirror

Anikeev, A. V.; Bagryansky, P. A.; Ivanov, A. A.; Lizunov, A. A.; Murakhtin, S. V.; Prikhodko, V. V.; Solomakhin, A. L.; Noack, K.
The paper presents the results of recent study of anisotropic plasma with thermonuclear ions confined in the axially symmetric Gas Dynamic Trap (GDT) mirror. Anisotropic ions are produced by the perpendicular injection of two focused 18 keV neutral beams in the small mirror section attached to the GDT central cell. We observed build-up of density of anisotropic ions up to approximately 10^13cm^−3 with the localized spatial profile and the mean energy of 7 keV. The average fast ion density three times exceeded the background plasma density. Fast ion accumulation is accompanied by the decrease of the plasma flux from the central cell recorded outside the mirror, that was qualified as a potential barrier development causing confinement improvement. Analysis of measurement results compared with estimates of plasma parameters in the compact mirror allows to scale to the experiments with next generation neutral beams with increased power and pulse duration.
Keywords: Compact mirror, Anisotropic ions

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Permalink: https://www.hzdr.de/publications/Publ-9577
Publ.-Id: 9577


Practical experiences with the synthesis of [11C]CH3 trough gas phase iodination reaction using a TRACERlabFXC synthesis module

Knieß, T.; Rode, K.; Wüst, F.
The results of [11C]CH3I synthesis through hydrogen gas reduction of [11C]CO2 on different nickel catalysts (HARSHAW-nickel, SHIMALITE-nickel, nickel on silica/alumina, nickel nanosize 99.99%) followed by gas phase iodination using a TRACERlab FXC synthesis unit are reported. Further reaction parameters such as furnace temperatures, flow rate of hydrogen gas and reduction time were optimized. It was found that reduction of [11C]CO2 proceeded in 28-83% yield depending on the nickel catalyst and temperature. The gas phase iodination (methane conversion) gave 31-62% of [11C]CH3I depending on temperature and amount of iodine in the iodine furnace. [11C]CH3I was used for heteroatom methylation reactions exemplified by a piperazine and a phenol (1 and 3). The specific activity of the 11C-labelled products 2 and 4 was determined after HPLC purification and solid-phase extraction. Compounds 2 and 4 were obtained in 8-14% radiochemical yield (decay-corrected, based upon trapped [11C]CH4) within 30 minutes. The specific activity was determined to be in the range of 20-30 GBq/µmol at the end-of-synthesis. Nickel catalyst nanosize was found to be superior compared with other Ni catalysts tested. The relatively low specific activity may be mainly due to carbon contaminations originating from the long copper tubing (500m) between the cyclotron and the radiochemistry facility.
Keywords: [11C]CH4, [11C]CH3I, gas phase iodination, TRACERlabFXC

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Permalink: https://www.hzdr.de/publications/Publ-9576
Publ.-Id: 9576


Dielectron production in C+C and p+p collisions with HADES

Pietraszko, J.; Agakishiev, G.; Agodi, C.; Balanda, A.; Bellia, G.; Belver, D.; Belyaev, A.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Díaz, J.; Dohrmann, F.; Durán, I.; Eberl, T.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P. J. R.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Gilardi, C.; Golubeva, M.; González-Díaz, D.; Grosse, E.; Guber, F.; Hadjivasiliou, C.; Heilmann, M.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krizek, F.; Krücken, R.; Kugler, A.; Kühn, W.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, S.; Lopez, L.; Mangiarotti, A.; Marín, J.; Markert, J.; Metag, V.; Michalska, B.; Mishra, D.; Moriniere, E.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Novotny, R.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Pechenov, V.; Pérez, T.; Pleskac, R.; Pospísil, V.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Senger, P.; Shileev, K.; Simon, R.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Veretenkin, I.; Wagner, V.; Wen, H.; Wiśniowski, M.; Wójcik, T.; Wüstenfeld, J.; Zanevsky, Y.; Zumbruch, P.
The High Acceptance Di-Electron Spectrometer HADES has been constructed at the SIS accelerator (GSI Darmstadt) to investigate electron-positron pairs produced in proton, pion and heavy ion induced reactions. The main goal of these studies is to explore properties of hadrons in nuclear matter. The apparatus and the experimental results from C+C at 2.0 AGeV and 1.0 AGeV and p+p at 2.2 GeV compared with Monte-Carlo events from a generator based on known cross-sections and branching ratios are presented.
  • International Journal of Modern Physics A 22(2007), 388-396

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Publ.-Id: 9575


Experimental investigation of a flow driven by a combination of a rotating and a traveling magnetic field

Cramer, A.; Pal, J.; Gerbeth, G.
Velocity measurements in a liquid metal flow were performed in order to study the combined action of a rotating (RMF) and a traveling magnetic field (TMF). In a cylindrical container, an RMF as well as a TMF alone cause axisymmetric volume forces, which drive according axisymmetric base flows. The combination of both fields gives rise to an inherent three-dimensional part of the electromagnetic force distribution. In case of equal frequencies, this drives a three-dimensional flow consisting of a single large-scale helical motion, which implicates an intense mixing of the melt. The necessary admixture of a TMF to accomplish a qualitative change of the flow structure in a given RMF is shown to be two orders of magnitude smaller in case of equal field frequencies compared to the case of differing frequencies.
  • Physics of Fluids 19(2007)11, 118109

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Permalink: https://www.hzdr.de/publications/Publ-9574
Publ.-Id: 9574


The spherically symmetric α2-dynamo and some of its spectral peculiarities

Günther, U.; Kirillov, O.; Samsonov, B.; Stefani, F.
A brief overview is given over recent results on the spectral properties of spherically symmetric MHD α2-dynamos. In particular, the spectra of sphere-confined fluid or plasma configurations with physically realistic boundary conditions (BCs) (surrounding vacuum) and with idealized BCs (super-conducting surrounding) are discussed. The subjects comprise third-order branch points of the spectrum, self-adjointness of the dynamo operator in a Krein space as well as the resonant unfolding of diabolical points. It is sketched how certain classes of dynamos with a strongly localized α-profile embedded in a conducting surrounding can be mode decoupled by a diagonalization of the dynamo operator matrix. A mapping of the dynamo eigenvalue problem to that of a quantum mechanical Hamiltonian with energy dependent potential is used to obtain qualitative information about the spectral behavior. Links to supersymmetric Quantum Mechanics and to the Dirac equation are indicated.
Keywords: MHD dynamo, operator theory, spectrum, Krein space, boundary conditions, third-order branch points, Jordan structures, diabolical points, resonance, Korteveg-de Vries equation, supersymmetry, Quantum Mechanics, Dirac equation
  • Open Access Logo Acta Polytechnica 47(2007)2-3, 75-81

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Permalink: https://www.hzdr.de/publications/Publ-9573
Publ.-Id: 9573


High Performance Thermal Imaging Using Quantum Well Infrared Photodetector Arrays

Schneider, H.
Quantum well infrared photodetector (QWIP) technology has opened up new opportunities to realize focal plane arrays (FPA) for high-performance thermal imaging [1]. High thermal and spatial resolution, low 1/f noise, low fixed-pattern noise, and high pixel operability makes QWIP FPAs appropriate for many applications. Due to their narrow absorption bands with relative spectral widths of the order of 10%, QWIPs are particularly suitable for thermal imaging applications involving several atmospheric transmission bands or several colors within the same band. For dual-band/dual-color FPAs, QWIP technology has the unique property that the active region for the long-wavelength band is transparent for the short-wavelength band. In this talk, I will report on typical QWIP structures optimized for thermal imaging applications and on the performance of some state-of-the-art QWIP cameras which were jointly realized by the Fraunhofer-Institute for Applied Solid State Physics (Freiburg, Germany) and AIM Infrarot-Module GmbH (Heilbronn, Germany). Besides imagers for the 8 – 12 µm long-wavelength infrared (LWIR) and 3 – 5 µm mid-wavelength infrared (MWIR) regimes these include a LWIR/MWIR dual-band QWIP FPA with 384x288 pixels which, at 6.8 ms integration time, exhibits a noise-equivalent temperature difference as low as 20.6 mK in the LWIR and 26.7 mK in the MWIR spectral bands. A specially designed diffraction grating is used for optical coupling of both spectral regimes. The array, which is based on a photoconductive QWIP for the MWIR and a photovoltaic "low-noise" QWIP for the LWIR, allows for synchronous and pixel-registered image acquisition in both bands. This functionality yields several advantages, including better distinction between target and background clutter, operation in a much wider range of ambient conditions, and the ability of remote absolute temperature measurement.
[1] H. Schneider and H. C. Liu, Quantum Well Infrared Photodetectors: Physics and Applications, ISBN 3540363238, Springer Series in Optical Sciences Vol. 126, 2006.
Keywords: quantum well infrared photodetector, QWIP, focal plane array, thermal imaging, noise-equivalent temperature difference, GaAs/AlGaAs
  • Invited lecture (Conferences)
    March Meeting of the American Physical Society, 05.-09.03.2007, Denver, CO, USA

Permalink: https://www.hzdr.de/publications/Publ-9572
Publ.-Id: 9572


Four-Quark Condensates in Nucleon QCD Sum Rules

Thomas, R.; Hilger, T.; Kämpfer, B.
The in-medium behaviour of the nucleon spectral density including self-energies is revisited within the framework of QCD sum rules. Special emphasis is given to the density dependence of four-quark condensates. A complete catalog of four-quark condensates is presented and relations among them are derived. Generic differences of such four-quark condensates occuring in QCD sum rules for light baryons and light vector mesons are discussed.

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Permalink: https://www.hzdr.de/publications/Publ-9571
Publ.-Id: 9571


An analytical solution for a simple time dependent neutron transport problem with external source

Merk, B.
An analytical solution for the startup of an external source in a homogeneous subcritical reactor problem is developed. The problem is described through an approximation of the Boltzmann Transport equation, the Telegrapher's or time dependent P1 equation. The analytical solution to the problem is expressed in terms of a Green's function.
Keywords: Telegrapher's equation, Neutron Transport, Space-Time Dependent Transport
  • Contribution to proceedings
    20th International Conference on Transport Theory, 22.-28.07.07, Obninsk, Russia
    Book of Abstracts
  • Lecture (Conference)
    20th International Conference on Transport Theory, 22.-28.07.07, Obninsk, Russia

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Permalink: https://www.hzdr.de/publications/Publ-9570
Publ.-Id: 9570


High resolution gamma ray tomography scanner for flow measurement and non-destructive testing applications

Hampel, U.; Bieberle, A.; Hoppe, D.; Kronenberg, J.; Schleicher, E.; Sühnel, T.; Zimmermann, F.; Zippe, C.
We report on the development of a high resolution gamma ray tomography scanner that is operated with a Cs-137 isotopic source at 662 keV gamma photon energy and achieves a spatial image resolution of 0.2 lp/mm at 10% MTF for non-collimated detectors. It is primarily intended for the scientific study of flow regimes and phase fraction distributions in fuel element assemblies, chemical reactors, pipelines and hydrodynamic machines. Furthermore, it is applicable to non-destructive testing of larger radiologically dense objects. The radiation detector is based on advanced avalanche photo diode technology in conjunction with LYSO scintillation crystals. The detector arc comprises 320 single detector elements which are operated in pulse counting mode. For measurements at fixed vessels or plant components we built a CT scanner gantry that comprises rotational and translational stages, power supply via slip rings and data communication to the measurement PC via wireless LAN.
Keywords: Gamma ray tomography, gamma ray detector

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Permalink: https://www.hzdr.de/publications/Publ-9567
Publ.-Id: 9567


The suppression of temperature fluctuations by a rotating magnetic field in a high aspect ratio Czochralski configuration

Grants, I.; Gerbeth, G.
We demonstrate experimentally in a low temperature model that a rotating magnetic field (RMF) has the potential to stabilize the inverse temperature gradient in a medium scale Czochralski facility with a high initial melt level. This stabilization occurs as a result of a flow transition from large scale buoyancy driven to small scale magnetically driven turbulence. The dependency of the required field strength is found vs.\ the imposed temperature drop for an at least 10 times higher Grashof number than in earlier experiments. The observed scaling agrees well with previous results. It is observed that the flow transition becomes even more pronounced, i.e. occurs in a more narrow range of the magnetic forcing, as the Grashof number is increased. The influence of the RMF frequency is investigated. It is found that an increasing frequency of the RMF gradually eliminates the stabilizing effect. The optimum dimensionless frequency is found minimizing the required strength of the RMF. The characteristic azimuthal velocity of the flow is measured by the temperature correlation technique.
  • Journal of Crystal Growth 308(2007)2, 290-296

Permalink: https://www.hzdr.de/publications/Publ-9566
Publ.-Id: 9566


Thermophysical properties of Nd-, Er-, YNi- alloys

Plevachuk, Y.; Sklyarchuk, V.; Hermann, R.; Gerbeth, G.
Nd-Fe-B alloys are widely used in many technical applications due to their excellent permanent magnetic properties. YNi2B2C intermetallic compounds own much attention because of the coexistence of superconductivity and magnetic ordering phenomena. Er2PdSi3 alloys with hexagonal AlB2-type crystallographic structure are of special interest because of their complex magnetic ordering, Kondo and heavy fermion behaviour. The thermophysical properties (electrical conductivity, thermoelectric power, thermal conductivity and viscosity) of these liquid multicomponent intermetallic alloys have been measured in order to supply necessary information for crystal growth and casting processes. Good reproducibility of the results has been obtained.
  • International Journal of Materials Research 99(2008), 261-264

Permalink: https://www.hzdr.de/publications/Publ-9565
Publ.-Id: 9565


Thermal expansion of single-crystalline HoNi2B2C

Schneider, M.; Gladun, A.; Kreyssig, A.; Wosnitza, J.; Souptel, D.; Behr, G.
The thermal expansion a has been measured for single-crystalline HoNi2B2C in the range between 2 and 200 K. At low temperatures, a is dominated by magnetic contributions leading to a strongly anisotropic behaviour with different signs for the expansion coefficients near the antiferromagnetic phase transition. Analysing the magnetic and lattice contributions of a well above this temperature, a nearly isotropic behaviour of the latter one can be deduced. Using the Ehrenfest relation, a relatively weak pressure dependence of the superconducting transition temperature of dTc=dp ¼ 0:1K=GPa was determined for pressure applied along the c direction which points to a rather small pressure-induced lattice stiffening. The ratio between expansion coefficient and specific-heat features large values at the onset of magnetic order.
  • Journal of Magnetism and Magnetic Materials 311(2007), 489-493

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Publ.-Id: 9564


Structure and dielectric function of two- and single-domain ZnO epitaxial films

Vinnichenko, M.; Shevchenko, N.; Rogozin, A.; Grötzschel, R.; Mücklich, A.; Kolitsch, A.; Möller, W.
The differences between two- and single-domain ZnO epitaxial films, grown by reactive pulsed magnetron sputtering, have been studied with respect to their texture development and x-ray coherence length behavior at various substrate temperatures and oxygen partial pressures. The film in-plane ordering depends on the surface pretreatment of the sapphire substrate. After pretreatment in an oxygen radio-frequency plasma, single-domain films form even at a substrate temperature of 100 degrees C in a wide range of oxygen pressures, and at a growth rate up to 1.2 nm/s. The single-domain films show a linear dependence of the x-ray coherence length on the substrate temperature, while a steplike dependence is characteristic of the two-domain films. The ZnO complex dielectric function was obtained using a parametrized semiconductor oscillator model for spectroscopic ellipsometry data analysis. For the films grown at 550 degrees C, the band gap of 3.29 +/- 0.01 eV is independent of the type of in-plane ordering and variation of the texture. The oscillator broadening correlates with the width of (0002) diffraction peak rocking curve. Both parameters increase at high oxygen pressure and low substrate temperature, which is attributed to a higher defect (dislocation) density.
Keywords: ZnO, reactive pulsed magnetron sputtering, epitaxial growth, in-plane ordering, texture, spectroscopic ellipsometry, dielectric function

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Permalink: https://www.hzdr.de/publications/Publ-9563
Publ.-Id: 9563


Novel supported Pd hydrogenation bionanocatalyst for hybrid homogeneous/heterogeneous catalysis

Creamer, N.; Mikheenko, I.; Yong, P.; Deplanche, K.; Sanyahumbi, D.; Wood, J.; Pollmann, K.; Merroun, M.; Selenska-Pobell, S.; Macaskie, L.
Homogeneous and heterogeneous catalysis approaches to hydrogenation have different advantages and disadvantages and hybrid approaches are sought to maximise the advantages of both. Bacterial cells, of length 1-2 microns, present an economical alternative to conventional micro-scale supports such as graphite and alumina. Certain strains of bacteria can reduce soluble Pd(II), from stock solutions or acid extracts of spent catalysts, forming nanocrystals of Pd which are supported within the bacterial cell surface layers. The biologically-supported nano-Pd contains particles of size ~ 5nm and below, as determined using magnetic measurements (SQUID) and EXAFS. Bio-nano-Pd supported on exemplar Gram negative and Gram positive bacterial types catalysed the hydrogenation of itaconic acid (initial rates 1.1 and 1.2 × 10-4 mol gPd-1 s-1 ) comparing well with commercial 5% Pd-graphite (1.3 × 10-4 mol gPd-1 s-1).
Keywords: Bacillus sphaericus Desulfovibrio desulfuricans, heterogeneous catalyst, hydrogenation, itaconic acid, palladium

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Permalink: https://www.hzdr.de/publications/Publ-9562
Publ.-Id: 9562


A new FEFF-based wavelet for EXAFS data analysis

Funke, H.; Chukalina, M.; Scheinost, A.
A new mother wavelet function for extended X-ray absorption fine-structure (EXAFS) data analysis has been designed, combining a model EXAFS function derived from the ab initio EXAFS code FEFF8.20 and the complex Morlet wavelet. This new FEFF–Morlet mother wavelet routine allows the generation of wavelets well adapted to specific EXAFS problems. A substantial gain in resolution of the wavelet ridges in k and r space is achieved. The method is applied to a structural problem of Zn–Al double-layer hydroxides, demonstrating unequivocally the homogeneity of the metal cation distribution in the hydroxide layers.
Keywords: EXAFS; wavelet transform; data evaluation; layered double hydroxides

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Permalink: https://www.hzdr.de/publications/Publ-9561
Publ.-Id: 9561


Interactions of U(VI) with members of a microbial consortium recovered from a uranium mining waste pile

Reitz, T.; Geissler, A.; Merroun, M.; Selenska-Pobell, S.
Treatments of a soil sample from a uranium mining waste pile with uranyl nitrate led to a shifting in the crenarchaeal populations from subgroup 1.1a to 1.1b. Efforts to culture members of these Crenarchaeota resulted in an enrichment of a mixed microbial consortium consisting of representatives of 1.1b Crenarchaeota and Firmicutes.
In this study interactions of U(VI) with a pure culture of Paenibacillus sp. JG35+U4-B1 isolated from the mentioned consortium were studied by using a combination of wet chemistry and microscopic methods. Preliminary analyses on U sorption showed that the Paenibacillus strain studied accumulated up to 85 mg U/g dry biomass from a solution with an initial uranium concentration of 120 mg U/l. Live/Dead cell staining indicated that less than 10% of the U-treated cells were viable. Transmission electron microscope (TEM) analyses showed that the cells of the isolated strain accumulated uranium intracellularly as needle-like fibrils (Fig. 1A), and also at the cell surface (Fig. 2A). Energy dispersive X-ray (EDX) analysis of these U accumulates demonstrated the presence of U and P peaks (Figs. 1B and 2B) indicating that in both cases the phosphate groups are, probably, the main functional binding sites for U(VI).
  • Lecture (Conference)
    Journées des Actinides 2007, 24.-27.03.2007, Sesimbra, Portugal
  • Contribution to proceedings
    37ièmes Journées des Actinides, 24.-27.03.2007, Sesimbra, Portugal
    Programme and Abstracts, 56

Permalink: https://www.hzdr.de/publications/Publ-9560
Publ.-Id: 9560


Deviations from Vegard's rule in Al1-xInxN (0001) alloy thin films grown by magnetron sputter epitaxy

Seppänen, T.; Hultman, L.; Birch, J.; Beckers, M.; Kreißig, U.
Al1−xInxN (0001) thin films of the pseudobinary AlN–InN system were grown epitaxially onto (111)-oriented MgO wafers with seed layers of Ti1−yZryN by dual direct current magnetron
sputtering under ultrahigh vacuum conditions. The relaxed film c-axis lattice parameters determined
by x-ray diffraction were studied as a function of composition in the range of 0.07 < x < 0.82 measured by Rutherford backscattering spectrometry. We find a relative deviation by as much as
37% from the linear dependency described by Vegard’s rule for the lattice parameter versus film
composition. The highest relative deviations were found at low InN mole fractions, while the largest
absolute deviation was found at x=0.63. This shows that Vegard’s rule is not directly applicable to
determine the compositions in the wurtzite Al1−xInxN system. © 2007 American Institute of Physics.
[DOI: 10.1063/1.2450675 ]
  • Journal of Applied Physics 101(2007), 043519

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Publ.-Id: 9559


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