Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf
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42029 Publications
The effect of flash lamp annealing on Fe implanted ZnO single crystals
Potzger, K.; Anwand, W.; Reuther, H.; Zhou, S.; Talut, G.; Fassbender, J.; Brauer, G.; Skorupa, W.
Abstract
The effect of flash lamp annealing applied to ZnO single crystals implanted with 3.6 at. % Fe has been studied. For intermediate light power, the implantation induced surface defects could be annealed without creation of secondary phases within the implanted region. At the same annealing temperatures, however, ion beam induced open volume defects start to increase in size. Recrystallization is initiated for the highest light power applied, i.e. the ion beam induced lattice disorder reflected by the minimum channelling yield of Rutherford backscattering spectroscopy decreases from 76 % to 46 % and the open volume defects are annealed. At the same time, the Fe3+ fraction increases at the cost of the Fe2+ states. Weak ferromagnetic properties are induced, that are mainly associated with nanoparticles
Keywords: ZnO; Diluted magnetic semiconductors; ion implantation; flash lamp annealing
- Journal of Applied Physics 101(2007)3, 033906
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Lecture (Conference)
71. Jahrestagung der Deutschen Physikalischen Gesellschaft und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 26.-30.3.2007, Regensburg, Germany
Permalink: https://www.hzdr.de/publications/Publ-9023
Resonance effects in α2-dynamos
Kirillov, O.; Günther, U.
Abstract
First results on a perturbation theory for α2-dynamos with non-constant spherically symmetric α-profiles are presented. The basics of the mathematical technique is demonstrated on a simplified model with idealized boundary conditions (BCs). Such BCs allow for a full semi-analytical treatment of the problem due to the selfadjointness of the dynamo operator in a so called Krein space --- a Hilbert space with an additional indefinite metric structure.
Starting point of the consideration is the model with constant α-profile α₀ which is exactly solvable. The eigenvalues λ of such a model form a mesh-like branch structure in the (α₀,Re λ)-plane. The nodes of this mesh (the intersection points of the branches) are double semi-simple eigenvalues (diabolical points) of algebraic and geometric multiplicity 2.
A Krein space related perturbation theory as well as a Galerkin technique for the numerical treatment of inhomogeneous perturbations of the α-profile have been developed. With the help of these tools, a very pronounced α-resonance pattern has been found in the deformations of the spectral mesh as well as in the unfolding of the diabolical points. The selection rules of this resonance pattern are defined by the Fourier coefficients of the perturbations leading to a strong correspondence between the characteristic length scale of the α-perturbations and the decay rates of the coherently induced field excitations. Such correlations will exist also in models with realistic BCs and may provide a qualitative explanation for some specifics of field reversal processes --- supporting corresponding numerical simulations on more realistic dynamo setups.
Furthermore, an estimation technique has been developed for obtaining optimal α-profiles for which α2-dynamos can become overcritical in oscillatory regimes. This basic technique is demonstrated explicitly for a simplified monopole (l=0) model, where it leads to a bound on the Fourier components of the α-profile. The capability of the used Galerkin approach is demonstrated in extending the strength of the α-perturbations from weakly perturbed regimes to strongly perturbed ones.
Extensions of the presented techniques to spherically symmetric α2-dynamos with realistic boundary conditions are in preparation.
Keywords: MHD dynamo; Krein space; perturbation theory; spectral analysis; spectral singularities; diabolical points; exceptional points
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Lecture (Conference)
9th MHD Days 2006, 04.-05.12.2006, Heidelberg, Germany
Permalink: https://www.hzdr.de/publications/Publ-9022
Boron dilution analyses at reactor shutdown conditions using the coupled code DYN3D/ATHLET
Kliem, S.; Rohde, U.
Abstract
A parameter study of a hypothetical boron dilution event during the work of the RHRS was performed. Based on a validated coolant mixing model for the lower plenum of the RPV, realistic boron concentration curves at the inlet into each fuel assembly were obtained and used for a number of stationary and transient core calculations. For the generic core loading pattern used in the calculations, in the stationary calcu-lations recriticality is reached for slug volumes of about 8 m3 if the realistic core inlet boron concentration distribution is used. Transient core calculations from 8 to the maximum initial slug volume of 15 m3 showed, that the maximum calculated fuel and cladding temperature values are below critical values. 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.
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Lecture (Conference)
Annual Meeting on Nuclear Technology 2007, 22.-24.05.2007, Karlsruhe, Germany -
Contribution to proceedings
Annual Meeting on Nuclear Technology 2007, 22.-24.05.2007, Karlsruhe, Germany
Proceedings of the Annual Meeting on Nuclear Technology 2007: INFORUM GmbH, 51-57
Permalink: https://www.hzdr.de/publications/Publ-9018
Silicon-on-insulator microcavity light emitting diodes with two Si/SiO2 Bragg reflectors
Potfajova, J.; Sun, J. M.; Schmidt, B.; Dekorsy, T.; Skorupa, W.; Helm, M.
Abstract
Light emitting pn-diodes were fabricated on a 5.8 µm thick n-type Si device layer of a silicon-on-insulator (SOI) wafer using standard silicon technology and boron implantation. The thickness of the Si device layer was reduced to 1.3 µm, corresponding to a 4λ-cavity for λ = 1150nm light. Electroluminescence spectra of these low Q-factor microcavities are presented. Addition of Si/SiO2 Bragg reflectors on the top and bottom of the device (3.5 and 5.5 pairs, respectively) is predicted to lead to spectral emission enhancement by ∼270.
Keywords: Silicon; Electroluminescence; Resonant cavity
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Journal of Luminescence 121(2006)2, 290-292
DOI: 10.1016/j.jlumin.2006.08.006
ISSN: 0022-2313
Cited 8 times in Scopus -
Poster
E-MRS 2006 Spring Meeting, 29.05.-02.06.2006, Nizza, Frenkreich
Permalink: https://www.hzdr.de/publications/Publ-9017
Asymptotic methods for spherically symmetric MHD α2-dynamos
Kirillov, O.; Günther, U.
Abstract
We consider two models of spherically-symmetric MHD α2-dynamos --- one with idealized boundary conditions (BCs) and one with physically realistic BCs. As it has been shown in our previous work, the eigenvalues λ of a model with idealized BCs and constant α-profile α₀ are linear functions of α₀ and form a mesh in the (α₀,Re λ)-plane. The nodes of the spectral mesh correspond to double-degenerate eigenvalues of algebraic and geometric multiplicity 2 (diabolical points). It was found that perturbations of the constant α-profile lead to a resonant unfolding of the diabolical points with selection rules of the resonant unfolding defined by the Fourier coefficients of the perturbations. In the present contribution we present new exact results on the spectrum of the model with physically realistic BCs and constant α₀. For non-degenerate (simple) eigenvalues perturbation gradients are found at any particular α₀. We present a detailed study of the spectral behavior of the α2-dynamo operator over a family of homotopic deformations of the BCs between idealized ones and physically realistic ones. Furthermore, we demonstrate that although the spectral singularities are lifted, a memory about their locations remains deeply imprinted in the homotopic family of the spectral deformations due to a hidden underlying invariance.
Keywords: MHD dynamo; homotopic deformation; homotopic invariance; non-Hermitian operator; spectral analysis
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Lecture (Conference)
6th International Congress on Industrial and Applied Mathematics (iciam 07), 16.-20.07.2007, Zürich, Switzerland
Permalink: https://www.hzdr.de/publications/Publ-9016
Single-pion production in pp collisions at 0.95 GeV/c (I)
Abd El-Samad, S.; Bilger, R.; Brinkmann, K.-T.; Clement, H.; Dietrich, M.; Doroshkevich, E.; Dshemuchadse, S.; Erhardt, A.; Eyrich, W.; Filippi, A.; Freiesleben, H.; Fritsch, M.; Geyer, R.; Gillitzer, A.; Hauffe, J.; Hesselbarth, D.; Jaekel, R.; Jakob, B.; Karsch, L.; Kilian, K.; Koch, H.; Kress, J.; Kuhlmann, E.; Marcello, S.; Marwinski, S.; Meier, R.; Möller, K.; Morsch, H. P.; Naumann, L.; Roderburg, E.; Schönmeier, P.; Schulte-Wissermann, M.; Schroeder, W.; Steinke, M.; Stinzing, F.; Sun, G. Y.; Wächter, J.; Wagner, G. J.; Wagner, M.; Weidlich, U.; Wilms, A.; Wirth, S.; Zhang, G.; Zupranski, P.
Abstract
The single-pion production reactions pp → dπ+, pp → npπ+ and pp → ppπ0 were measured at a beam momentum of 0.95GeV/c ( T p ≈ 400MeV) using the short version of the COSY-TOF spectrometer. The implementation of a central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements. Thus, all pion production channels were recorded with 1-4 overconstraints. The total and differential cross-sections obtained are compared to previous data and theoretical calculations. Main emphasis is put on the discussion of the ppπ0 channel, where we obtain angular distributions different from previous experimental results, however, partly in good agreement with recent phenomenological and theoretical predictions. In particular, we observe very large anisotropies for the π0 angular distributions in the kinematical region of small relative proton momenta revealing there a dominance of proton spinflip transitions associated with π0 s and d partial waves and emphasizing the important role of π0 d-waves.
Keywords: PACS. 13.75.Cs Nucleon-nucleon interactions; 25.10.+s Nuclear reactions involving few-nucleon systems; 25.40.Ep Inelastic proton scattering; 29.20.Dh Storage rings
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European Physical Journal A 30(2006)2, 443-453
DOI: 10.1140/epja/i2006-10133-6
Cited 22 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-9015
Study of spectator tagging in the reaction np → ppπ- with a deuteron beam
Abdel-Bary, M.; Brinkmann, K.-T.; Clement, H.; Doroshkevich, E.; Dshemuchadse, S.; Erhardt, A.; Eyrich, W.; Freiesleben, H.; Gillitzer, A.; Jäkel, R.; Karsch, L.; Kilian, K.; Kuhlmann, E.; Möller, K.; Morsch, H. P.; Naumann, L.; Paul, N.; Pizzolotto, C.; Ritman, J.; Roderburg, E.; Schönmeier, P.; Schroeder, W.; Schulte-Wissermann, M.; Sun, G. Y.; Teufel, A.; Ucar, A.; Wagner, G. J.; Wagner, M.; Wintz, P.; Wüstner, P.; Zupranski, P.
Abstract
The reaction dp → pppπ- has been studied in a kinematically complete experiment at a single beam momentum pd
=1.85 GeV/c (T = 759MeV). All four ejectiles have been detected in the large-acceptance time-of-flight spectrometer COSY-TOF. We analyzed the data along the lines of the spectator model as a means to isolate the quasi-free np → pppπ- reaction. The spectator proton was identified by its momentum and flight direction thus yielding access to the associated Fermi motion of the bound neutron. A comparison is carried out with Monte Carlo simulations based on two different parameterizations of the deuteron wave function. Up to a Fermi momentum of roughly 150MeV/c no significant deviations between experimental and simulated data of various observables were found from which we conclude that the deuteron can indeed be taken as a valid substitute for the neutron.
Keywords: .Cs Nucleon-nucleon interactions; Nuclear reactions involving few-nucleon systems; Dh Storage rings
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European Physical Journal A 29(2006)3, 353-361
DOI: 10.1140/epja/i2006-10099-3
Cited 14 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-9014
Scanning probe microscopy with cantilever arrays
Rangelow, I.; Ivanov, T.; Volland, B.; Dontsov, D.; Sarov, Y.; Ivanova, K.; Persaud, A.; Filenko, D.; Nikolov, N.; Schmidt, B.; Zier, M.; Gotszalk, T.; Sulzbach, T.
Abstract
This paper reports on to the realization of piezoresistive cantilever-Arrays used in scanning probe microscopy (SPM). Sensors for the SPM are peculiar microsystems since the combination of physical and microtechnological principles allows to gain an insight into the material science at nanoscale. Moreover SPM technology is opening new horizons in fundamental research and gives a chance to employ new interaction principles for the realization of new sensors and sensor arrays. Physical, biological, and chemical values and interactions can effectively be detected and analyzed using cantilevers, where the nanomechanical interactions can be transformed into an electric signal. The basic issues for the realization of a complete system of self-actuated, piezoresistive cantilever arrays are described.
Keywords: Piezoresistive cantilever arrays; scanning force microscopy; microsystems; nanosystems
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Technisches Messen 73(2006)9, 485-492
DOI: 10.1524/teme.2006.73.9.485
Cited 7 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-9013
Bubble recognition algorithms for the processing of wire-mesh sensor data
Prasser, H.-M.; Beyer, M.
Abstract
Wire-mesh sensors deliver sequences of instantaneous, two-dimensional gas fraction distributions from a measuring cross-section. The spatial and temporal resolutions are high enough to reflect individual bubbles in much more than one measuring frame during their passage through the sensor plane. The bubbles can therefore be detected by a pattern recognition method based on the identifications of connected areas of gas-filled elements in the array of local instantaneous gas fractions, available as a function of the lateral co-ordinates x,y and as function of time. Algorithms were presented in earlier publications, which are based on a recursive fill procedure that assigns individual bubble numbers to the elements of the gas fraction array. This procedure has to rely on a threshold for the cancellation of the recursive fill, because the gas fraction data are affected by noise. The choice of the correct threshold is difficult, since a too high gas fraction threshold leads to unrealistic bubble fragmentation, while a too low threshold provokes unrealistic unification of bubbles. In previous papers an optimum approach was found by introducing a differential threshold determined for each bubble individually from the maximum gas fraction inside the given bubble to identify the cores of the bubbles. This is combined with an agglomeration step, where elements with a gas fraction below the threshold are assigned to already existing bubble cores, if these elements were not yet assigned to a bubble in the recursive fill step.
In the present paper, the algorithm will be analysed by applying it to synthetic measuring data, which is generated by placing bubbles of known geometrical parameters into the discretization measuring grid defined by the wire-mesh geometry. The discretization is performed with due care to reflect the fact that the gas-liquid interface at the periphery of the bubbles crosses control volumes of the measuring grid, producing local instantaneous void fractions of intermediate values. The synthetic signals are furthermore superposed by synthetic white noise. It is shown that the original bubble recognition algorithm needs to be improved in certain cases: (a) Unrealistic fragmentation in axial (time) direction may occur, when bubbles cross the sensor plane with a low velocity. (b) non-realistic coalescence becomes dominating at very high gas fractions, where bubbles of complex shape occur. Different improvements were tested. Unrealistic coalescence is avoided by introducing a criterion to terminate the recursive fill algorithm, which are based on the local gradient of the gas fraction. A second approach relies on a repair algorithm, which unites unrealistic fragments in an additional processing step after the preliminary bubble recognition. This repair algorithm takes benefit from a-priory knowledge to distinguish realistic close neighbour bubbles from unrealistic bubble fragments divided by an early truncation of the bubble recognition. After the check against synthetic bubbles, the algorithms are applied to real measuring data from gas-liquid flows in vertical pipes and the results obtained by the different algorithms are compared.
Keywords: wire-mesh sensor; measurement technique; bubble identifikation; bubble recognition algorithm
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Contribution to proceedings
International Conference on Multiphase Flow, ICMF 2007, 09.-13.07.2007, Leipzig, Germany
paper:S7_Thu_B_50 -
Lecture (Conference)
International Conference on Multiphase flow, ICMF 2007, 09.-13.07.2007, Leipzig, Germany
Permalink: https://www.hzdr.de/publications/Publ-9012
A globally diagonalizable α2-dynamo operator, SUSY QM and the Dirac equation
Günther, U.; Samsonov, B.; Stefani, F.
Abstract
A new class of semi-analytically solvable MHD α2-dynamos is found based on a global diagonalization of the matrix part of the dynamo differential operator. Close parallels to SUSY QM are used to relate these models to the Dirac equation and to extract non-numerical information about the dynamo spectrum.
Keywords: MHD dynamo; Krein space; operator theroy; supersymmetric Quantum Mechanics; Dirac equation; quasi-exactly solvable model; perturbation theory; Jordan structure
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Journal of Physics A 40(2007), F169-F176
DOI: 10.1088/1751-8113/40/5/F04
ISSN: 1751-8121
Cited 15 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-9011
A bubble size distribution model for the numerical simulation of bubbly flows
Ruyer, P.; Seiler, N.; Beyer, M.; Weiss, F.-P.
Abstract
This study carried out at the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) concerns the bubbly flow numerical simulation. One of the determining features of the two-phase flow is the topology of the flow. Local interfacial area concentration, say ai, allows to determine the exchange surface for momentum, heat and mass transfers between liquid and vapor. In the case of bubbly flow the size of the inclusion, say D, (through the non-dimensional Eötvös number) determines essential liquidvapor momentum transfers such as the lift force (e.g. (Tomiyama et al. 1995)). The corresponding fields ai and D are functions of history, flow conditions, as well as local events such as coalescence, break-up and phase change. This justifies to model their evolution thanks to additional transport equations (in addition to momentum, mass and energy balance equations). Several approaches can then be distinguished, namely the population balance (Coulaloglou and Tavlarides 1977), the two-group interfacial area transport (Fu and Ishii 2002) or the moment densities (Kamp et al. 2001). The purpose of the present study is to examine the ability of the NEPTUNE_CFD code to predict bubble size distribution in complex flow configurations.
A series of experiments performed at FZD in the frame of the TOPFLOW project allows to determine the local structure of the two-phase flow including the bubble size local distribution. We focus more particularly on bubbly air-water flows around an asymmetric obstacle in the section of a vertical pipe (see (Prasser et al. 2006)). The presence of the obstacle induces a pronounced three-dimensional effect as well as coalescence events. We perform numerical simulations with the NEPTUNE_CFD code of these experiments. The NEPTUNE_CFD code (see (Guelfi et al. 2005)) is based on the two-fluid model formulation. It is developed in the frame of a research program supported by EDF, CEA, IRSN and AREVA_NP. In the present study, two different levels of description of the bubble size distribution in space and time are considered. At the first level of description, the bubble size distribution is determined thanks to an interfacial area equation allowing to define locally a single bubble size (monodisperse flow). At the second level we consider locally a spectrum of bubble sizes (polydisperse flow) with the help of a moment densities approach. We incorporate the model within NEPTUNE_CFD and present the resulting gain in accuracy of the simulation. Perspectives concerning improvement of the numerical modelling of bubble size distribution are discussed.
Keywords: two-phase flow; NEPTUNE_CFD; bubble size distribution
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Lecture (Conference)
International Conference on Multiphase Flow, ICMF 2007, 09.-13.07.2007, Leipzig, Germany -
Contribution to proceedings
International Conference on Multiphase Flow, ICMF 2007, 09.-13.07.2007, Leipzig, Germany
paper: S6_Thu_A_48
Permalink: https://www.hzdr.de/publications/Publ-9009
Crystallographically oriented magnetic ZnFe2O4 nanoparticles synthesized by Fe implantation into ZnO
Zhou, S.; Potzger, K.; Reuther, H.; Talut, G.; Eichhorn, F.; von Borany, J.; Skorupa, W.; Helm, M.; Fassbender, J.
Abstract
In this paper, a correlation between structural and magnetic properties of Fe-implanted ZnO is presented. High fluence Fe+ implantation into ZnO leads to the formation of superparamagnetic α-Fe nanoparticles. High vacuum annealing at 823 K results in the growth of α-Fe particles, but the annealing at 1073 K oxidizes the majority of the Fe nanoparticles. After a long term annealing at 1073 K, crystallographically oriented ZnFe2O4 nanoparticles are formed inside ZnO with the orientation relationship of ZnFe2O4(1 1 1)[1 1 0]//ZnO(0 0 0 1)[11 2 0]. These ZnFe2O4 nanoparticles show a hysteretic behaviour upon magnetization reversal at 5 K.
Keywords: ZnO; Magnetism of nanostructures; Ferrite
- Journal of Physics D: Applied Physics 40(2007), 964-969
Permalink: https://www.hzdr.de/publications/Publ-9008
Annual Report 2005 - Institute of Safety Research
Weiss, F.-P.; Rindelhardt, U.; (Editors)
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Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZR-457 2006
ISSN: 1437-322X
Downloads
Permalink: https://www.hzdr.de/publications/Publ-9007
Synthesis of 18F-labeled neurotensin(8-13) via copper-mediated 1,3-dipolar [3+2]cycloaddition reaction
Ramenda, T.; Bergmann, R.; Wüst, F.
Abstract
The copper(I)-mediated 1,3 dipolar [3+2]cycloaddition between terminal alkynes and azides, also referred to as click-chemistry, was used to synthesize a 18F-labeled neurotensin(8-13) (NT(8-13)). 4-[18F]Fluoro-N-(prop-2-ynyl)benzamide [18F]1 as novel terminal alkyne building block could successfully be coupled with azide-functionalized NT(8-13) 4 to give the corresponding 18F-labeled NT(8-13) derivative [18F]5 product in 66% yield as determined by radio-HPLC. The in vitro binding affinity of 18F-labeled NT(8-13) derivative [18F]5 was determined to be 66 nM.
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Letters in Drug Design & Discovery 4(2007)4, 279-285
ISSN: 1570-1808
Permalink: https://www.hzdr.de/publications/Publ-9005
Investigations into the Formation of Intrinsic Colloids and Pseudocolloids of Uranium(IV)
Zänker, H.; Opel, K.; Weiß, S.; Hübener, S.; Bernhard, G.
Abstract
Investigations into the formation of intrinsic colloids and pseudocolloids of uranium(IV) were performed. Coulometric titrations of strongly acidic U(IV) solutions in HClO4/NaClO4 medium were carried out in order to find the pH of first colloid formation. Laser-induced breakdown detection (LIBD) was applied for the detection of traces of uranium colloids as the pH was increased. The pH values at the onset of colloid formation were used for thermodynamic calculations aimed at determining the solubility products of crystalline and amorphous uranium dioxide. Furthermore, the UO2·xH2O(am) colloids were investigated for their colloidal stability. Zeta potentials of ≥ 30 mV were found for pH values of less than 4. The point of zero charge was found at pH ~ 6.9. Colloidal suspensions of 1 mMol/L UO2·xH2O(am) at a pH value of 2.5 proved to be stable over > 1.5 years. The interaction of the forming UO2·xH2O(am) colloids with other colloid-forming species was tested. Therefore, coulometric titrations of U(IV) solutions in the presence of (a) dissolved Al(III) and (b) dissolved silicate were carried out. The presence of Al(III) does not significantly influence the formation of the UO2·xH2O(am) colloids, and the presence of U(IV) does not significantly influence the behaviour of Al(III). Also silicate does not significantly influence the pH of UO2·xH2O(am) colloid formation. However, the presence of U(IV) significantly influences the behaviour of the silicate (formation of pseudocolloids). The nature of the interaction between the silicate and the U(IV) is not yet known (adsorption? formation of a coffinite precursor?). EXAFS experiments to elucidate the local structure around the U(IV) atoms in the pseudocolloids are under preparation.
Keywords: Uranium(IV); uranium dioxide; intrinsic colloids; pseudocolloids; aluminum; silicate
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Lecture (Conference)
2nd Annual Workshop of the IP FUNMIG, 21.-23.11.2006, Stockholm, Sweden
Permalink: https://www.hzdr.de/publications/Publ-9004
Mixed-ligand 68Ga complexes with tetradentate/monodentate NS3/N ('4+1') coordination: Relation of structure with in vitro stability
Noll, B.; Smuda, C.; Hecht, M.; Kraus, W.; Pietzsch, H.-J.
Abstract
Gallium forms complexes of the general formula [Ga(NS3)NHR2], where NS3 is the tripodal ligand tris(2-mercaptoethyl) amine and secondary amines (NHR2) are co-ligands. Structure determinations reveal trigonal-bipyramidal structure of the mononuclear species and the tendency of solvent-coordinated species [Ga(NS3)solv] (solv: water, methanol) to condensate to trinuclear species. Challenge experiments with the plasma protein transferrin, performed with the respective Ga-68 complexes, show enhanced stability of the aminederived species [Ga(NS3)NHR2] with piperidine and imidazole derivatives as the most stable complexes.
Keywords: Ga complexes; tris(2-mercaptoethyl) amine; in vitro stability; challenge experiments
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Poster
7th International Symposium on Technetium in Chemistry and Nuclear Medicine, 06.-09.09.2006, Bressanone, Italy -
Contribution to external collection
U. Mazzi: Technetium, Rhenium and Other Metals in Chemistry and Nuclear Medicine, Padova: SGE Editoriali, 2006, 88-89884-04-5, 227-228
Permalink: https://www.hzdr.de/publications/Publ-9003
Relativistic approaches to investigations of few-nucleon systems
Dorkin, S. M.; Kaptari, L. P.; Kämpfer, B.; Semikh, S. S.
Abstract
Theoretical approaches used in investigations of relativistic effects in high energy lepton and hadron collisions with few nucleon systems are analyzed. The Bethe-Salpeter formalism for describing interacting systems of two spinor particles both in the continuum and bound state is described in detail. Special attention is paid to partial expansions taking into account the analytic properties of Bethe-Salpeter amplitudes and unitary transformations correlating different representations of partial amplitudes. Mathematical methods of numerical solution of equations are considered. Results of calculation of relativistic corrections and effects of interactions in the final state in particular reactions with the deuteron, namely, inelastic pD backward scattering and in reactions of deuteron break-up with production of correlated pairs, are presented.
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Physics of Particles and Nuclei 37(2006), 867-898
ISSN: 1063-7796
Permalink: https://www.hzdr.de/publications/Publ-9002
Theta+ formation in inclusive gamma D to pK-X
Titov, A. I.; Kämpfer, B.; Date, S.; Ohashi, Y.
Abstract
We analyze the possibility to produce an intermediate Tp via a KN to Tp formation process in gamma D to pK-X (X=nK+,pK0) reactions at some specific kinematical conditions, in which a pK- pair is knocked out in the forward direction and its invariant mass is close to the mass of Ls (Ls equiv Lambda(1520)). The Theta+ signal may appear in the [gamma D,pK-] missing mass distribution. The ratio of the signal (cross section at the Theta+ peak position) to the smooth background processes varies from 0.7 to 2.5 depending on the spin and parity of Tp, and it decreases correspondingly if the pK- invariant mass is outside of the Ls-resonance region. We analyze the recent CLAS search for the Tp in the gamma D to pK-nK+ reaction and show that the conditions of this experiment greatly reduce the Tp formation process making it difficult to extract a Tp peak from the data.
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Physical Review C 74(2006), 055206
ISSN: 0556-2813
Permalink: https://www.hzdr.de/publications/Publ-9001
omega - pi gamma* transition form factor in proton-proton collisions
Kaptari, L. P.; Kämpfer, B.
Abstract
Dalitz decays of omega and rho mesons, omega to pi0gamma* topi0 e+e- and rho0 to pi0gamma* to pi0 e+e-, produced in pp collisions are calculated within a covariant effective meson-nucleon theory.
We argue that the omega transition form factor F_{omega to pi0gamma*} is experimentally accessible in a fairly model independent way in the reaction pp to pp pi0 e+ e- for invariant masses of the pi0 e+ e- subsystem near the omega pole.
Numerical results are presented for the intermediate energy kinematics of envisaged HADES experiments.
- European Physical Journal A 31(2007)2, 233-243
Permalink: https://www.hzdr.de/publications/Publ-9000
Rhenium complexes of dimercaptosuccinic acid derivatives for targeted radiotherapy
Pietzsch, H.-J.; Heinrich, T.; Kraus, W.; Jentschel, C.; Seifert, S.; Spies, H.
Abstract
This work is part of efforts to develop chelating agents for stable binding and easy conjugation of Re-188 to biologically interesting structures. Starting from the high in vivo stability of [188ReO(DMSA)2]- we want to exploit this coordination system for the design of 188ReO(V) chelates which are stable towards re-oxidation to perrhenate under conditions of radiopharmaceutical procedures. Therefore a new type of tetradentate ligand has been synthesized by bridging two molecules on N-N'-diisobutyl-2,3-dimercaptosuccinamide with N-(3-aminopropyl)propane-1,3diamine. The resulting stereoisomeric tetrathiolato S4ligand forms anionic five-coordinated oxorhenium(V) complexes by ligand exchange reaction of NBu4[ReOCl4]in methanol. Without addition of base the compounds will be isolated as "betain", [ReO(S4)], with the protonated nitrogen of the bridge as a internal "counter ion".
Two representatives have been characterized in solid state and found to adopt the expected square-pyramidal coordination geometry. The equatorial plane is formed by four thiolate sulfur atoms, whereas the oxygen occupies the apical position. The orientation of the metal oxo group is exo in relation to the carbamido groups in both isomers. The complexes are stereoisomeric regarding the junction of the triamine chain. The Re-188 labelling procedure runs fast, in good yields and under mild conditions, making the new complexes interesting as access to stable Re-188 radiotherapeutics.
T. Heinrich, W. Kraus, H.-J. Pietzsch et al. Inorg. Chem., 44, 9930-9937 (2005).
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Lecture (Conference)
37. International Conference on Coordination Chemistry, 13.-18.09.2006, Cape Town, South Africa -
Contribution to proceedings
37. International Conference on Coordination Chemistry, 13.-18.09.2006, Cape Town, South Africa
37th International Conference on Coordination Chemistry (ICCC) eds: D.J. Robinson, I.M. Robinson, 1-920-01705-4, 52
Permalink: https://www.hzdr.de/publications/Publ-8999
Uranium - an unique luminescent element - New observations in different oxidation states -
Geipel, G.
Abstract
Vortrag über Lumineszenzeigenschaften des Urans in verschiedenen Oxidationsstufen
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Invited lecture (Conferences)
Kolloqium an der Nukleartechnischen Fakultät der Czech Technical University, 09.11.2006, Prague, Czech Republic
Permalink: https://www.hzdr.de/publications/Publ-8998
Hypochlorite-induced oxidation of low-density lipoproteins and high-density lipoprotein modifies their potential role in atherogenesis
Kopprasch, S.; Grässler, J.; Pietzsch, J.
Abstract
Substantial evidence has accumulated that the myeloperoxidase (MPO)/hydrogen peroxide/hypochlorite system of phagocytes plays a critical role not only in antimicrobial defence but also in chronic inflammatory conditions like atherosclerosis. Oxidation of low-density lipoproteins (LDL) by hypochlorite (OCl-LDL) results in physico-chemical modifications of both the protein and lipid moiety of the lipoprotein molecule. Following oxidation OCl-LDL display a number of proatherogenic and proinflammatory properties including stimulation of phagocyte oxidant generation, induction of leukocyte degranulation, and increase of phagocyte adhesion to endothelial cells. Importantly, the class B scavenger receptors CD36 and SR-BI are receptors for OCl-LDL. This fact may explain the high uptake of OCl-LDL in macrophages, leading to the formation of foam cells. Our investigations revealed that OCl-LDL upregulates the gene expression of CD36 and PPAR in macrophages dose- and time-dependently while modulating SR-BI expression differently in dependence on incubation conditions. The antiatherogenic properties of high-density lipoproteins (HDL) are suggested to be mainly associated with its SR-BI-mediated reverse cholesterol transport. In addition we could demonstrate that HDL possesses anti-inflammatory actions by inhibiting OCl-LDL-induced increase in phagocyte respiratory burst and adhesion to endothelial cells. The protective role of HDL was substantially attenuated when HDL apolipoproteins were oxidized by hypochlorite. Our in vitro data show that hypochlorite-oxidized lipoproteins could mimic fundamental atherogenic and inflammatory processes therefore underlying the potential role of hypochlorite oxidation as pathogenetic factor in vivo.
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Contribution to external collection
Pietzsch, J.: Protein Oxidation and Disease, Recent Research Developments in Pathological Biochemistry 1, Trivandrum, Kerala, India: Research Signpost, 2006, 81-308-0028-4, 179-196
Permalink: https://www.hzdr.de/publications/Publ-8997
Protein oxidation in diabetes mellitus
Julius, U.; Obrosova, I. G.; Pietzsch, J.
Abstract
Growing evidence indicates that diabetes mellitus is accompanied by oxidative stress. In addition to lipids and nucleic acids, proteins also undergo oxidation. Diabetic patients have several groups of oxidatively modified proteins, i.e., advanced glycation end-products, carbonylated proteins, and advanced oxidation protein products, in the circulation. Oxidized proteins have also been detected in tissues of animals with experimental diabetes. Oxidative modifications of mitochondrial proteins are blunted in diabetic conditions. Of special interest is the oxidation of apolipoprotein B-100, the structural protein of low density lipoproteins. Oxidatively modified apolipoprotein B-100 molecules had been detected in atherosclerotic lesions as well as in the circulation. Oxidatively altered proteins lead to vascular damage. Increased oxidative stress was also observed in gestational diabetes. Protein oxidation plays a major role in the development of diabetes complications and has been implicated in the pathogenesis of diabetic nephropathy, neuropathy and retinopathy. In diabetic nephropathy which develops as a result of complex interplay of hemodynamic and metabolic factors, oxidative protein modifications contribute to albuminuria, mesangial expansion, glomerulosclerosis and tubulo-interstitial fibrosis. There is also strong experimental evidence that morphological abnormalities of diabetic retinopathy, such as pericyte dropout, formation of acellular capillaries, are associated with non-enzymatic glycosylation (glycation) and accumulation of advanced glycation end-products. Protein oxidation also takes place in the lens and plays a central role in the development of cataract. Growing evidence implicates advanced protein glycoxidation and lipoxidation in the pathogenesis of both somatic and autonomic diabetic neuropathy, and, in particular, motor and sensory nerve conduction deficits, neurovascular dysfunction, diabetic neuropathic pain and loss of sensory function, and morphological abnormalities characteristic for peripheral and autonomic neuropathy.
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Contribution to external collection
Pietzsch, J.: Protein Oxidation and Disease, Recent Research Developments in Pathological Biochemistry 1, Trivandrum, Kerala, India: Research Signpost, 2006, 81-308-0028-4, 293-325
Permalink: https://www.hzdr.de/publications/Publ-8996
In vivo catabolism of hypochlorite-modified low density lipoproteins (LDL): insights from small animal positron emission tomography studies
Hoppmann, S.; Steiniger, B.; Strobel, K.; Haase, C.; Pietzsch, J.
Abstract
Oxidative modification of LDL apolipoprotein (apo) B-100 by myeloperoxidase-generated hypochlorous acid (HOCl) is regarded as a crucial event in atherogenesis. Exemplarily, HOCl-modified LDL (OCl-LDL) apoB-100 has been shown to be present in the human aortic vessel wall from various stages of atherosclerotic lesion evolution. On the other hand, data concerning the role of circulating OCl-LDL in the development of atherosclerosis are scarce. One reason for this is the shortage of methods for direct assessment of metabolism of oxidatively modified LDL in vivo. We report an improved methodology for radiolabeling of both native LDL (nLDL) and HOCl-LDL with the positron-emitter fluorine-18 (18F) by N-succinimidyl 4-[18F]fluorobenzoate ([18F]SFB) and the use of [18F]fluorobenzoylated LDL particles in dynamic positron emission tomography (PET) studies in rats. As model reactions, nLDL were modified in vitro by 3 mM NaOCl. For radiolabeling, pools of chemically and biochemically well characterized human nLDL and OCl-LDL were used. Preparation of [18F]SFB was achieved by module-assisted synthesis within 68 min with radiochemical yields of 36±2% (corrected for decay) and purity of >95%. LDL labeling with [18F]SFB resulted in radiochemical yield of 30±10% (nLDL; corrected for decay) and 10±5% (OCl-LDL), respectively, with specific radioactivity of 50-400 GBq/µmol. Radiolabeling of native and modified LDL using [18F]SFB caused neither additional oxidative structural modifications of LDL lipids and proteins nor alteration of their biological activity and functionality in vitro, respectively. The method was further evaluated with respect to the uptake of [18F]fluorobenzoylated native and modified LDL particles, respectively, in various human cells. Biodistribution studies in rats revealed high in vivo stability for the [18F]fluorobenzoylated LDL particles. The metabolic fate of [18F]fluorobenzoylated nLDL and OCl-LDL particles in vivo was delineated by dynamic PET studies using a dedicated small animal positron emission tomograph. Dynamic PET data demonstrated a significantly enhanced catabolism of OCl-LDL when compared with nLDL. The in vivo distribution and kinetics of both native and modified LDL particles in the rat correlated well with the anatomical localization of LDL receptors and scavenger receptors. In conclusion, [18F]SFB-labeling of LDL and the use of small animal PET provide a valuable tool to discriminate the kinetics and the metabolic fate of both native and oxidatively modified LDL in animal models in vivo.
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Contribution to external collection
Pietzsch, J.: Protein Oxidation and Disease, Recent Research Developments in Pathological Biochemistry 1, Trivandrum, Kerala, India: Research Signpost, 2006, 81-308-0028-4, 197-219
Permalink: https://www.hzdr.de/publications/Publ-8995
Technetium coupled to biologically active moieties
Pietzsch, H.-J.; Künstler, J.-U.; Spies, H.
Abstract
Many 99mTc pharmaceuticals were designed for the measurement of organ function, based on regional blood flows, ion transport, and cellular rentention. Organ specificity is governed by molecular characteristics (e.g., size, shape, charge) and physiological factors.
Primarily, these radiotracers are coordination complexes of technetium leaving either a positive or a negative charge; neutral, lipophilic complexes pass the blood-brain barrier. Organ function is related to regional perfusion (e.g., brain, heart). Hepatocyte function is measured by the excretion of iminodiacetic acid (IDA) derivatives into bile, simulating the active transport of bilirubin. Increased osteogenic activity correlates with increased regional uptake of 99mTc-diphosphonate complexes in bone structures, delineating tumor and metastatic growth. The functional state of the kidneys as measured by active tubular secretion requires a negatively charged complex with a carboxylate anion.
99mTc pharmaceuticals based on coordination complexes with functionalized ligands are also known as "Tc essentials"; those concerning labeled particles and macromolecules are called "Tc-tagged" radiopharmaceuticals. A variety of chelating agents have been developed for complex formation with certain oxidation states of technetium, providing the structural requirements for uptake and rentention (Schwochau 1000). Examples of Tc essentials are shown in Fig. 2.3.1.
The outstanding interest in the development of novel 99mTc pharmaceuticals is documented in recent reviews (Hom and Katzenellenbogen 1997; Johannsen and Pietzsch 2002a; Jurisson and Lydon 1999)
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Contribution to external collection
Zolle, I.: Tc-99m Pharmaceuticals - Preparation and Quality Control in Nuclear Medicine, Berlin Heidelberg New York: Springer-Verlag, 2007, 10: 3-540-33989-2, 40-58
Permalink: https://www.hzdr.de/publications/Publ-8994
Stannous chloride in the preparation of 99mTc radiopharmaceuticals
Spies, H.; Pietzsch, H.-J.
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Contribution to external collection
Zolle, I.: Tc-99m Pharmaceuticals - Preparation and Quality Control in Nuclear Medicine, Berlin Heidelberg New York: Springer-Verlag, 2007, 10: 3-540-33989-2, 59-66
Permalink: https://www.hzdr.de/publications/Publ-8993
C78 cage isomerism defined by trimetallic nitride cluster size: a computational and vibrational spectroscopic study
Popov, A. A.; Krause, M.; Yang, S.; Wong, J.; Dunsch, L.
Abstract
Molecular structure of Dy3N@C78 and Tm3N@C78 clusterfullerenes are addressed by the IR and Raman vibrational spectroscopic studies and DFT computations. Firstly, extensive semiempirical calculations of 2927 isomers of C78 hexaanions followed by DFT optimization were applied to establish their relative stability. Then, DFT calculations of a series of M3N@C78 (M=Sc, Y, Lu, La) isomers were performed which have shown that the stability order of the isomers depends on the cluster size. While the Sc3N cluster is planar in the earlier reported Sc3N@C78 (D3h: 24109) clusterfullerene, relatively large Y3N and Lu3N clusters would be forced to be pyramidal inside this cage, which would result in their destabilization. Instead, these clusters remain planar in the non-IPR C2: 22010 isomer making Y3N@C78 and Lu3N@C78 clusterfullerenes with this cage structure the most stable ones. Finally, on the basis of a detailed analysis of their IR and Raman spectra supplemented with DFT vibrational calculations, the recently isolated Tm3N@C78 and the major isomer of Dy3N@C78 are assigned to the non-IPR C2: 22010 cage structure. A detailed assignment of their experimental and computed IR and Raman spectra is provided to support this conclusion and to exclude other cage isomers.
Keywords: Endohedral Fullerenes; Structure Determination; Vibrational Spectroscopy
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Journal of Physical Chemistry B 111(2007)13, 3363-3369
DOI: 10.1021/jp068661r
Cited 83 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8992
Deviation from the Planarity - a Large Dy3N Cluster Encapsulated in an Ih-C80 Cage: An X-ray Crystallographic and Vibrational Spectroscopic Study
Yang, S.; Troyanov, S. I.; Popov, A. A.; Krause, M.; Dunsch, L.
Abstract
The high-yield synthesis of Dy3N@C80 (I) opens the possibility of characterizing its molecular and vibrational structures. We report on the structure determination of Dy3N@C80 (I) by X-ray crystallographic study of single crystal of Dy3N@C80 (I)Ni(OEP)2C6H6, revealing a nearly planar Dy3N cluster encapsulated in an Ih-C80 cage. The vibrational structure of Dy3N@C80 (I) is studied by FTIR and Raman spectroscopy in combination with force-field calculations. A correlation was found between the antisymmetric metal-nitrogen stretching vibration and the structure of the M3N cluster of M3N@C80 (I) (M = Y, Gd, Tb, Dy, Ho, Tm). Moreover, a stronger interaction between the encaged nitride cluster and the C80 carbon cage was found in the class II M3N@C80(I) (M=Y, Gd, Tb, Dy, Ho, Tm) than in Sc3N@C80 (I). This study demonstrates that the cluster size (determined by the ionic radius of the metals involved) plays the dominating role in the structure of the M3N cluster in M3N@C80 (I).
Keywords: endohedral fullerenes; nitride clusters; vibrational spectroscopy; structure elucidation; X-ray crystallography
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Journal of the American Chemical Society 128(2006)51, 16733-16739
DOI: 10.1021/ja066814i
Cited 125 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8990
Nanocluster Memories by Ion Beam Synthesis of Si in SiO2
Schmidt, B.
Abstract
Self-assembling of Si-nanocrystals (NCs) in gate oxides, with special emphasis on size and position tailoring and their application as discrete charge storage centers in nanocrystal memories area great challange to materials research with ion beams. The Si NCs for these multi-dot floating-gate memories have been produced by ion irradiation through SiO2/Si-interfaces. Si excess within SiO2 is formed by ion beam mixing of Si from the Si substrate and from the poly-Si capping layer into the gate oxide. Ion irradiation with 3x1015 -10x1015 Si+ cm-2 at 50-100 keV through 50 nm poly-Si and 15 nm SiO2 on (001)Si results in a considerable Si excess. At the upper and lower interfaces of the gate oxide, this ion irradiation forms a metastable SiOx composition. Si NCs are formed by phase separation into Si and SiO2 during post-irradiation thermal treatment. Adjacent to the recovering interfaces, narrow SiO2 zones becomes denuded of excess Si. More distant excess Si precipitates as Si NCs in the gate oxide. This approach was applied to nMOSFET-NC-memory fabrication in the standard CMOS line at ZMD. MOSFET characteristics in terms of write/erase voltage, duration of the programming time, endurance and retention have been evaluated.
Keywords: Ion beam irradiation; Si nanocrystals; MOSFET-nanocrystal memory
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Lecture (Conference)
2nd Workshop "Hybrid Nanostructured Materials - Synthesis, Properties, Applications", 08.-09.11.2006, Dresden, Germany - Materials Science - Poland 25(2007)4, 1213-1222
Permalink: https://www.hzdr.de/publications/Publ-8989
Image reconstruction for fast X-ray computed tomography of multiphase flows
Bieberle, M.; Hampel, U.
Abstract
Electron beam X-ray computed tomography is a measurement method, which allows imaging of cross sectional density distributions of an object of interest with a frame rate of more than 1000 images per second. This is very attractive for multiphase flow measurements because flow velocities of 1 m/s and more can be resolved without influencing the flow.
Contrary to conventional tomography, electron beam X-ray CT comprises no mechanical rotated components but a fast moving X-ray source generated by a deflected electron beam. Unfortunately, the static arrangement of the system impedes the acquisition of a complete tomography data set of one imaging plane. Either, there is an offset between source and detector plane or the data acquisition is limited to an angular range smaller than 180°. In the first case, the image resolution in flow direction is reduced depending on the offset, whereas the image reconstruction of the second case tends to limited-angle artifacts in form of skewed object structures.
To minimize the artifacts in image reconstruction the algorithms were adapted to this special limited-angle case. They are mostly based on the iterative reconstruction algorithms ART and MART (additive and multiplicative algebraic reconstruction technique), because they are more flexible and modifiable than common filtered backprojection methods. Especially the reconstruction of two-phase flows permits the incorporation of a priori knowledge into the reconstruction process because only the phase distribution of one known attenuation coefficient has to be recovered.
We will explain the measurement setup and our reconstruction methods in detail. Furthermore, we will present the results of the reconstruction of simulated 2D and 3D two-phase flow data as well as measured data from static and dynamic phantoms imitating real flow scenarios.
Keywords: multiphase flow imaging; x-ray computed tomography
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Contribution to proceedings
6th International Conference on Multiphase Flow, ICMF 2007, 09.-13.07.2007, Leipzig, Germany
Proceedings of ICMF 2007, Paper S7_Thu_C_55 -
Lecture (Conference)
International Conference on Multiphase Flow, ICMF 2007, 09.-13.07.2007, Leipzig, Germany
Permalink: https://www.hzdr.de/publications/Publ-8988
Synthesis, in vitro stability studies, and bioconjugation of Rhenium-188 complexes with tetradentate/monodentate NS3/P ('4+1')coordination
Schiller, E.; Pietzsch, H.-J.; Tisato, F.; Refosco, F.; Seifert, S.; Spies, H.
Abstract
Rhenium(III) mixed-ligand complexes with tetradentate/monodentate (4 + 1) coordination of the general formula [Re(NS3)(PRRR)] (NS3 = tris-(2-mercaptoethyl)amine and derivatives thereof, PRRR = tertiary phosphine) are promising candidates for the development of rhenium-188 complexes for radiotherapeutic applications. In order to understand relationships between the structure of 188Re 4+1 complexes and their in vitro stability we synthesized a series of rhenium model complexes using various combinations of NS3 derivatives and monodentate phosphorus(III) ligands and determined their stability at MBq activity level in human plasma. As an outcome of these investigations we are able to roughly estimate which ligands are suitable for a rational complex design with regard to high in vitro and in vivo stability. Subsequently, the most stable representative was investigated at GBq activity level showing no detectable degradation of the rhenium-188 complex in pharmaceutical preparation up to 2 hours after preparation. This stable 188Re 4+1 complex was furthermore successfully conjugated to the model peptide arginine-tyrosine using the water-soluble N-hydroxy-sulfosuccinimidyl activated ester of the monodentate phosphine ligand. In summary, our results show the great potential of 188Re 4+1 complexes for labelling biomolecules for therapeutic purposes.
Keywords: rhenium-188 complexes; in vitro Stability; peptide labelling
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Poster
7th International Symposium on Technetium in Chemistry and Nuclear Medicine, 06.-09.09.2006, Bressanone, Italy -
Contribution to external collection
U. Mazzi: Technetium, Rhenium and Other Metals in Chemistry and Nuclear Medicine, Padova: SGE Editoriali, 2006, 88-89884-04-5, 479-482
Permalink: https://www.hzdr.de/publications/Publ-8987
Simulation study on multilayer limited angle scanned electron beam X-ray CT arrangements for two-phase flow measurements
Bieberle, M.; Hampel, U.; Prasser, H.-M.; Schleicher, E.
Abstract
Recently, we presented a limited angle computed tomography approach that utilises a scanned electron beam X-ray source to produce multiple projections of an object. From these projections cross sectional images of the object are reconstructed by using iterative reconstruction algorithms. Tests with static as well as dynamic objects proved that the scan rate of the electron beam allows tomographic imaging with 1000 frames per second at an in-plane resolution of 1 mm. In a simulation study on three-dimensional flow data sets obtained with a fast and high-resolution conductivity wire-mesh sensor under real two-phase flow conditions we have shown, that this approach is capable to recover the in-plane phase structure of the flow. However, two problems arise when this measuring method is utilized for quantitative analysis of two-phase flows. Firstly, by acquiring a time sequence of cross sectional images of one plane in the flow no information about the volumetric structure of the flow can be obtained without knowing the different phase velocities. Secondly, the static arrangement of the X-ray focal spot path and the detector arc in one plane allows only a limited angular range from which projections are available. The missing data leads to artefacts in the reconstructed images which increase with the size and complexity of the imaged structures. For these reasons, simulation studies on different extended measurement arrangements with a two-dimensional beam deflection unit including multilayer imaging have been performed. The presentation will be focused on these different arrangements and their influence on the phase structure recovery of two-phase flows.
Keywords: limited angle X-ray CT; two-phase flow measurements
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Contribution to proceedings
5th World Congress on Industrial Process Tomography (WCIPT5), 03.-06.09.2007, Bergen, Norway
Proceedings of the 5th World Congress on Industrial Process Tomography, 259-264 -
Lecture (Conference)
5th World Congress on Industrial Process Tomography (WCIPT5), 03.09.2007, Bergen, Norway
Permalink: https://www.hzdr.de/publications/Publ-8986
Interactions of microbes found at Äspö underground lab with actinides such as curium, plutonium and uranium
Moll, H.
Abstract
Sulfate-reducing bacteria (SRB) frequently occur in the deep granitic rock aquifers at the Äspö Hard Rock Laboratory (Äspö HRL), Sweden. The new SRB strain Desulfovibrio äspöensis could be isolated. Results describing the basic interaction mechanisms of uranium, curium, and plutonium with cells of D. äspöensis DSM 10631T will be presented. The interaction experiments with the actinides showed that the cells are able to remove all three actinides from the surrounding solution. The amount of removed actinide and the interaction mechanism varied among the different actinides.
The main U(VI) removal occurred after the first 24 h. The contact time, pH and [U(VI)]initial influence the U removal efficiency. The presence of uranium caused a damaging of the cell membranes. TEM revealed an accumulation of U inside the bacterial cell. D. äspöensis are able to form U(IV). A complex interaction mechanism takes place consisting of biosorption, bioreduction and bioaccumulation.
In the case of 242Pu, solvent extractions, UV-vis- and XANES spectroscopy were used to determine the speciation of the Pu oxidation states. In the first step, the Pu(VI) and Pu(IV)-polymers are bound to the biomass. Solvent extractions showed that 97 % of the initially present Pu(VI) is reduced to Pu(V) due to the activity of the cells within the first 24 h of contact time. Most of the formed Pu(V) dissolves from the cell envelope back to the aqueous solution due to the weak complexing properties of this plutonium oxidation state. Indications were found for a penetration of Pu species inside the bacterial cells.
In the case of curium at a much lower metal concentration of 3x10-7 M, a pure biosorption of Cm(III) on the cell envelope forming an inner-sphere surface complex most likely with organic phosphate groups was detected.
To summarize, the strength of the interaction of D. äspöensis with the selected actinides at pH 5 and actinide concentrations ≥ 10 mg/L ([Cm] 0.07 mg/L) follows the pattern: Cm > U > Pu.
Keywords: microbial interactions; Desulfovibrio äspöensis; actinides
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Lecture (Conference)
2nd Annual Workshop of the IP FUNMIG, 21.-23.11.2006, Stockholm, Sweden -
Contribution to proceedings
2nd Annual Workshop of the IP FUNMIG, 21.-23.11.2006, Stockholm, Schweden
Interactions of microbes found at Äspö underground lab with actinides such as Curium, Plutonium and Uranium, Bromma: CM Digitaltryck AB,, 1404-0344, 131-137
Permalink: https://www.hzdr.de/publications/Publ-8985
A novel approach for 99mTc labelling of peptides organometallic Tc(III) complexes for conjugation of bombesin derivatives
Künstler, J.-U.; Veerendra, B.; Sieckman, G. L.; Smith, C. J.; Pietzsch, H.-J.
Abstract
Among peptides for tumour targeting bombesin (BBS), binding to gastrin releasing peptide receptors (GRPR) and overexpressed by e.g. prostate and breast carcinomas has a great potential. Thus, various labelled bombesins were described in the literature showing a varying pharmacokinetic behaviour depending on the labelling approach, the spacer between the radiometal moiety and the N-terminus as well as modifications in the peptide sequence.
In this study, the bioactive minimal sequence BBS(7-14) was labelled by the Tc-4+1 mixed-ligand system, where Tc(III) is coordinated by a monodentate isocyanide bearing the peptide and the tetradentate tripodal chelator tris(2-mercaptoethyl)-amine (NS3).
BBS(7-14) was N-terminally modified with Gly-Gly-Gly, β-Ala and Ser-Ser-Ser as spacer groups and functionalized with 4-isocyanomethyl benzoic acid or 4-isocyanobutyric acid. 99mTc labelling was performed in a two-step ligand exchange procedure starting from 99mTc-EDTA/mannitol. The Re analogues were used as references for chemical characterization and in receptor-binding studies. Complex bearing β-Ala-BBN(7-14) exhibited a GRPR-affinity in the subnanomolar range and high uptake in human prostate (PC-3) cancer cells, whereas pancreatic uptake in biodistribution studies using normal mice was low.
Keywords: Technetium; '4+1' Mixed-ligand Complexes; Organometallic; Bombesin; Peptide Labelling
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Poster
7th International Symposium on Technetium in Chemistry and Nuclear Medicine, 06.-09.09.2006, Bressanone, Italy -
Contribution to external collection
U. Mazzi: Technetium, Rhenium and Other Metals in Chemistry and Nuclear Medicine, Padova: SGE Editoriali, 2006, 88-89884-04-5, 317-318
Permalink: https://www.hzdr.de/publications/Publ-8984
99mTc-labelled RGD-Peptide using the "4+1" mixed-ligand approach
Giglio, J.; León, E.; Rey, A.; Künstler, J.-U.; Gniazdowska, E.; Pietzsch, H.-J.
Abstract
This paper presents the 99mTc-labelling and evaluation of two isocyanide (4-isocyanomethylbenzoic acid = L1, 4-isocyanobutanoic acid= L2) derivatives of the peptide c(RGDyK) using the "4+1" mixed-ligand chelate system. Starting from the precursor 99mTc-EDTA labelling was achieved by reaction of the isocyanide-bearing peptide and the tetradentate ligand containing three non-coordinating carboxyl groups (NS3(COOH)3) resulting in 99mTc(NS3(COOH)3)(L1-c(RGDyK)), 1 and 99mTc(NS3(COOH)3)(L2-c(RGDyK)), 2. A radiochemical purity (RP) of 60% was obtained for both peptides and HPLC purification resulted in RP>95% and stability was >90% after 24h. Plasma protein binding was 27% for 1 and 15% for 2. Both complexes showed preferential renal excretion. Uptake in induced B16F1 murine melanoma was moderate for both compounds but higher tumour/muscle ratios were achieved for 1 at all time points.
Keywords: Tc "4+1" mixed-ligand complexes; 99mTc labelled peptides; RGD peptides
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Poster
7th International Symposium on Technetium in Chemistry and Nuclear Medicine, 06.-09.09.2006, Bressanone, Italy -
Contribution to external collection
U. Mazzi: Technetium, Rhenium and Other Metals in Chemistry and Nuclear Medicine, Padova: SGE Editoriali, 2006, 88-89884-04-5, 331-332
Permalink: https://www.hzdr.de/publications/Publ-8983
86Y-labelled L RNA oligonucleotides as Molecular Probes for Positron Emission Tomography (PET)
Schlesinger, J.; Bergmann, R.; Klußmann, S.; Wüst, F.; Pietzsch, H.-J.
Abstract
A short 5-aminohexyl-functionalised L RNA oligonucleotide 1 (sequence: UGA CUG ACU GAC 3, MW 3975) was used to study the influence of two different 86Y DOTA chelates on the biodistribution in Wistar rats. The L-oligonucleotide 1 was conjugated with 1,4,7,10 tetraazacyclododecane-N,N,N,N-tetraacetic acid (DOTA) using N-succinimide ester (DOTA-NHS) 2 and isothiocyanate derivative (p SCN bz DOTA) 4 to afford the corresponding amide 3 and thiourea 5, respectively. Both DOTA-functionalised L RNA oligonucleotides 3 and 5 were labelled with the medium half-life positron-emitting radiometal 86Y (t1/2 = 14.7 h) in 76 % and 85 % radiochemical yield. 86Y-Complexes 3a and 5a represent the first examples of L-oligonucleotides labelled with the positron emitter 86Y.
The in vivo biodistribution of 86Y-complex 3a showed a faster elimination from the body via the kidneys compared to thiourea-containing 86Y-complex 5a. Transient accumulation of radioactivity in the kidneys and the adrenals was found for both 86Y-complexes 3a and 5a. After incubation of 86Y-complex 5a in whole rat blood at 37°C no noticeable decomposition could be observed over 12 h as confirmed by HPLC-analysis
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Poster
7th International Symposium on Technetium in Chemistry and Nuclear Medicine, 06.-09.09.2006, Bressanone, Italy -
Contribution to external collection
U.Mazzi: Rhenium and Other Metals in Chemistry and Nuclear Medicine, Padova: SGEditoriali, 2006, 88-89884-04-5, 211-214
Permalink: https://www.hzdr.de/publications/Publ-8982
Positron Emission Tomography
van den Hoff, J.
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Contribution to external collection
D. Ganten and K. Ruckpaul: Encyclopedic Reference of Genomics and Proteomics in Molecular Medicine, ed., Heidelberg, New York: Springer Verlag, 2006, 3-540-44244-8, 1446-1449
Permalink: https://www.hzdr.de/publications/Publ-8981
Reversals made simple: some new results
Stefani, F.; Gerbeth, G.; Günther, U.; Xu, M.; Sorriso-Valvo, L.
Abstract
We present new results of a very simple model of Earth's magnetic field reversals which is based on an alpha^2 dynamo under the influence of noise. This reversal model relies on the existence of exceptional points of the spectrum of the non-selfadjoint dynamo operator. As new aspects of this model, we delineate its connection with the van der Pol oscillator, we demonstrate a remarkable agreement with the characteristic time scales and the well-known asymmetry of real reversals, and we discuss the deviation from Poissonian statistics in real reversal sequences and in our model. Finally, we present some speculations on the influence of the size of the inner core on the spectral properties of the dynamo operator and on the reversal rate.
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Lecture (Conference)
9th MHD Days 2006, 04.-05.12.2006, Heidelberg, Germany
Permalink: https://www.hzdr.de/publications/Publ-8980
Observation of magnetorotational instability in a liquid metal Taylor-Couette experiment
Gundrum, T.; Gerbeth, G.; Stefani, F.; Rüdiger, G.; Hollerbach, R.
Abstract
Magnetic fields can play an active role in the formation of stars and black holes by virtue of the Magnetorotational Instability (MRI) which enables outward transport of angular momentum in accretion discs. Using a combination of axial and azimuthal magnetic fields, we provide experimental evidence of the MRI in a liquid metal Taylor-Couette experiment with Reynolds numbers of the order 1000 and Hartmann nubers of the order 10. The MRI mode in the liquid metal alloy GaInSn is measured by Ultrasonic Doppler Velocimetry.
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Lecture (Conference)
9th MHD Days 2006, 04.-05.12.2006, Heidelberg, Germany
Permalink: https://www.hzdr.de/publications/Publ-8979
Proton single voxel spectroscopy of different adipose tissue deposits in mice
Strobel, K.; van den Hoff, J.; Pietzsch, J.
Abstract
Accumulation of excess abdominal visceral fat has been shown to play crucial roles in the development of cardiovascular disease as well as the development of obesity-related disorders like Diabetes mellitus, hyperlipidemia, and hypertension.
In the last years, rodent models have gained an important role in the investigation of adipose tissue (AT) biology and disorder. In this line, non-invasive differentiation and characterization of various AT deposits in the living animal is a current challenge. Magnetic resonance spectroscopy (MRS) at high magnetic field strength can help us to learn more about lipids in vivo. MRS is applied for brown adipose tissue (BAT), as well as intra-abdominal white adipose tissue (WAT) deposits in mice.
All experiments were carried out in NMRI mice and nude mice. Morphological differentiation between various BAT and WAT deposits was obtained by 1H-MRI at 7 Tesla using a Biospec 70/30 (Bruker, Germany). 1H-MRS has been performed to quantify in vivo the different lipid patterns in BAT and WAT deposits using a volume selective PRESS sequence on 1 to 8 mm3 voxels.
In both nude mice and NMRI mice the various BAT and WAT deposits were clearly distinguished from the non-AT tissue with excellent contrast by T1-weighted MSME MRI sequences. The high resolution spectra obtained at 7 T allow identification of at least 9 different proton resonances specific for lipids, and, thus, for calculation of mono- to polyunsaturated fatty acid ratio in vivo. In this study, nude mice showed a 3-fold higher degree of polyunsaturation of triglyceride fatty acid acyl chains in BAT when compared to NMRI mice. No significant differences were observed in WAT deposits.
High-resolution MRS is a potentially useful tool for studying the biology of different BAT and WAT deposits non-invasively in small experimental animals in vivo.
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Lecture (others)
User Meeting 2006 der Fa. Bruker Biospin MRI GmbH, 09.-12.10.2006, Ettlingen, Germany
Permalink: https://www.hzdr.de/publications/Publ-8978
Impact of tumour hypoxia on the FDG uptake in two human tumour models on nude mice investigated with PET, autoradiography and functional histology
Beuthien-Baumann, B.; Gabrys, D.; Wüllrich, K.; Hofheinz, F.; Krause, M.; Bergmann, R.; Hessel, F.; Yaromina, A.; Eicheler, W.; Baumann, M.
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Abstract in refereed journal
Radiotherapy and Oncology Suppl. 1(2006), S142 -
Lecture (Conference)
ESTRO-Conference, 09.-12.10.2006, Leipzig, Germany
Permalink: https://www.hzdr.de/publications/Publ-8977
PET-based investigation of cerebral activation following intransal trigeminal stimulation
Hummel, T.; Beuthien-Baumann, B.; Heinke, M.; Oehme, L.; van den Hoff, J.; Gerber, J. C.
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Abstract in refereed journal
Chemical Senses 31(2006), A60-A61 -
Lecture (Conference)
AChems 28th Annual Meeting, 26.-30.04.2006, Sarasota/Florida, USA
Permalink: https://www.hzdr.de/publications/Publ-8976
Labeling of low-density lipoproteins using the 18F-labeled thiol-reactive reagent N-[6-(4-[18F]fluorobenzylidene)aminooxyhexyl]maleimide [18F]FBAM
Berndt, M.; Pietzsch, J.; Wüst, F.
Abstract
The novel thiol group-selective bifunctional 18F-labeling agent N-[6-(4-[18F]fluoro-benzylidene)aminooxyhexyl]maleimide ([18F]FBAM) has been developed. The bifunctional labeling precursor 4 containing a thiol-reactive maleimide group and a carbonyl group-reactive aminooxy group was prepared in only three steps in a total chemical yield of 59%.
Subsequent radiolabeling with 4-[18F]fluorobenzaldehyde gave the bifunctional 18F-labeling agent [18F]FBAM in 29% radiochemical yield. In a typical experiment 3.88 GBq of [18F]fluoride could be converted into 723 MBq of [18F]FBAM within 69 min. Conjugation of [18F]FBAM with thiol groups was exemplified with the cystein-containing tripeptide glutathione and with various apolipoproteins of human low density lipoproteins (LDL) subfractions. The latter one was evaluated with respect to uptake of [18F]FBAM-LDL subfractions in human hepatoma cells (HepG2) in vitro. In vivo biodistribution studies in rats revealed high stability for the [18F]FBAM-LDL subfractions. Moreover, the metabolic fate of the [18F]FBAM-LDL subfractions in vivo was delineated by dynamic PET studies using a dedicated small animal tomograph. Data were compared to former studies using the NH2-reactive 18F-labeling agent N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB). Compound [18F]FBAM can be considered to be an excellent prosthetic group for the selective and mild 18F-labeling of thiol group-containing biomolecules suitable for subsequent investigations in vitro and in vivo.
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Nuclear Medicine and Biology 34(2007), 5-15
DOI: 10.1016/j.nucmedbio.2006.09.009
Cited 79 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8975
Advances in the Production, Processing and MicroPET Image Quality of Technetium-94m
Bigott, H. M.; Laforest, R.; Liu, X.; Ruangma, A.; Wüst, F.; Welch, M.
Abstract
This work involves the production, processing and imaging of the short-lived, rarely used positron emission tomography (PET) radionuclide technetium-94m (94mTc). Our procedures are an extension of methods reported in the literature and are detailed within. A key modification was the development of a single step that combines purification and concentration of an aqueous 94mTc-pertechnetate solution, which both reduces processing time and increases the final concentration of the solution. Additionally, a convenient method for the direct recovery of 94mTc into an organic solvent was developed, eliminating the solvent transfer step needed for organic syntheses using 94mTc.
Each of these advances potentially extends the scope of syntheses possible with this short-lived radionuclide. To explore the imaging potential of 94mTc, we carried out phantom imaging studies on small-scale high-resolution PET scanners to estimate the limitations of detection associated with 94mTc and PET. Preliminary studies demonstrate that useful images can be obtained with modern image reconstruction algorithms when using a correction for the cascade gamma ray contamination.
- Nuclear Medicine and Biology 33(2006)7, 923-933
Permalink: https://www.hzdr.de/publications/Publ-8974
Excitation dynamics in La0.875Sr0.125MnO3 measured by resonant Auger electron and resonant x-ray emission spectroscopies
Mentes, T. O.; Bondino, F.; Magnano, E.; Zangrando, M.; Kuepper, K.; Galakhov, V. R.; Mukovskii, Y. M.; Neumann, M.; Parmigiani, F.
Abstract
The charge transfer dynamics of an underdoped manganite is probed by resonant x-ray emission and Auger electron spectroscopies at the Mn L3 edge. The dispersion of peak positions, as the incident photon energy is tuned through the absorption threshold, gives direct information on the relaxation rate in terms of the core-hole lifetime and the localization behavior of the states involved. The charge transfer time is found to be around 0.45 fs, with a dependency on the final state d-band occupancy.
Keywords: PACS: 79.60.-i; 72.15.Lh; 71.70.Ch; 78.70.En
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Physical Review B 74(2006), 205409
DOI: 10.1103/PhysRevB.74.205409
Cited 3 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8973
CFD-Analysen der Kühlmittelvermischung in Druckwasserreaktoren
Höhne, T.
Abstract
Buoyancy driven mixing was investigated under simulated natural circulation conditions at the test facility ROCOM.
Experiments with density differences between the ECC water (higher density) resp. the de-borated slugs (lower density) and the ambient coolant was used to validate the CFD software CFX.
A Reynolds stress turbulence model was employed to model the effects of turbulence on the mean flow.
Hybrid meshes consisting at least of 2 million nodes and 4 million elements were used.
The experiment and CFD calculations show in both cases significant mixing effects due to the density differences.
The CFX-5 calculations show a good qualitative agreement with the data. At some local positions differences in the predicted and measured concentration fields occur. The obtained experimental and numerical results can be used for further studies of the core behavior using coupled thermo-hydraulic and neutron-kinetic code systems.
Next Steps: Improvement of turbulence models, calculation with different Reynolds Stress models or DES
Keywords: CFD; Coolant Mixing
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Lecture (others)
DECHEMA/GVC-Arbeitsausschuß Sicherheitsgerechtes Auslegen von Chemieapparaten, 22.11.2006, Lampertheim, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-8972
Strahlentherapieplanung bei Hirntumoren mit 18F-3-O-methyl-fluordopa (18F-OMFD) und Positronen-Emissions-Tomographie (PET)
Ahlheit, H.; Oehme, L.; Winkler, C.; Blank, H.; Grabowski, J.; Füchtner, F.; Hoepping, A.; Kotzerke, J.; Beuthien-Baumann, B.
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Abstract in refereed journal
Strahlentherapie und Onkologie 182(2006)1, V11-3 -
Lecture (Conference)
12. Jahreskongress der Deutschen Gesellschaft für Radioonkologie, 25.-28.05.2006, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-8971
Structure and Stability of Molybdenum Sulfide Fullerenes
Bar-Sadan, M.; Enyashin, A. N.; Gemming, S.; Popovits-Biro, R.; Hong, S. Y.; Prior, Y.; Tenne, R.; Seifert, G.
Abstract
MoS2 nanooctahedra are the smallest stable close-cage structures of MoS2, i.e. the genuine inorganic fullerenes. Here, a combination of experiments and density-functional tight-binding calculations with molecular dynamics annealing are used to elucidate the structures and electronic properties of octahedral MoS2 fullerenes. The calculations show that the octahedra are stable beyond n(Mo)>100, but with the loss of 12 S atoms at the six corners. In contrast to the semi-conducting bulk and nanotubular structures, the Fermi level of the octahedra is situated within a band, hence the nano-octahedra are metalloid. A model derived from these calculations for the treatment of larger structures shows that, in agreement with experiment, multiwall nanooctahedra are stable over a limited size range of about 10^4 to 10^5 atoms; beyond that size, the clusters are converted into spherical nanoparticles. These theoretical findings concerning the critical size for the structural transition, the under-stoichiometry in S, and the electronic nature of the nanooctahedra are confirmed by TEM experiments on particles synthesized by laser ablation.
Keywords: inorganic fullerenes; molybdenum sulfide; density-functional
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Journal of Physical Chemistry B 110(2006), 25399-25410
DOI: 10.1021/jp0644560
ISSN: 1520-6106
Cited 57 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8969
Quasi-Particle Perspective on Equation of State
Bluhm, M.; Schulze, R.; Seipt, D.; Kämpfer, B.
Abstract
We propose a procedure for determining the equation of state of strongly interacting matter needed in a
hydrodynamical description of relativistic heavy-ion collisions.
Keywords: QCD equation of state; elliptic flow; quasi-particle model
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Contribution to proceedings
Quark Confinement and Hadron Spectrum VII, 02.-07.09.2006, Ponta Delgada Acores, Portugal, 387-390 - AIP Conference Proceedings 892(2007), 387-390
Permalink: https://www.hzdr.de/publications/Publ-8968
Quasi-particle perspective on critical end-point
Bluhm, M.; Kämpfer, B.
Abstract
Within a quasi-particle model for the equation of state of strongly interacting matter for two quark flavors we include phenomenologically features of the QCD critical point and discuss its impact on the equation of state. In particular, we investigate the influence on the quark number susceptibility and the pattern of isentropic trajectories which describe the evolutionary paths of matter during the hydrodynamical expansion of a heavy-ion collision.
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Contribution to proceedings
Critical Point and Onset of Deconfinement, 03.-06.07.2006, Florence, Italy
Proceedings of Science CPOD 2006, 004
Permalink: https://www.hzdr.de/publications/Publ-8967
Orbitofrontal Dysfunction Related to Both Apathy and Disinhibition in Frontotemporal Dementia
Peters, F.; Perani, D.; Herholz, K.; Holthoff, V.; Beuthien-Baumann, B.; Sorbi, S.; Pupi, A.; Degueldre, C.; Lemaire, C.; Collette, F.; Salmon, E.
Abstract
Orbitofrontal metabolic impairment is characteristic of the frontal variant of frontotemporal dementia (fv-FTD), as are early changes in emotional and social conduct. Two main types of behavioral disturbances have been distinguished in fv-FTD patients: apathetic and disinhibited manifestations. In this study, we searched for relationships between brain metabolism and presence of apathetic or disinhibited behavior. Metabolic activity and behavioral data were collected in 41 fv-FTD patients from European PET centers. A conjunction analysis of the PET data showed an expected impairment of metabolic activity in the anterior cingulate, ventromedial and orbital prefrontal cortex, the dorsolateral prefrontal cortex and the left anterior insula in fv-FTD subjects compared to matched controls. A correlation was observed between disinhibition scores on the Neuropsychiatric Inventory scale and a cluster of voxels located in the posterior orbitofrontal cortex (6, 28, -24). Comparison of brain activity between apathetic and nonapathetic fv-FTD patients from two centers also revealed a specific involvement of the posterior orbitofrontal cortex in apathetic subjects (4, 22, -22). The results confirm that the main cerebral metabolic impairment in fv-FTD patients affects areas specializing in emotional evaluation and demonstrate that decreased orbitofrontal activity is related to both disinhibited and apathetic syndromes in fv-FTD.
Keywords: Frontotemporal dementia; Positron emission tomography; Apathy; Disinhibition; Social conduct
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Dementia and Geriatric Cognitive Disorders 21(2006), 373-379
DOI: 10.1159/000091898
Cited 168 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8966
11C-Acetat positron-emission-tomography for occult prostate cancer
Froehner, M.; Beuthien-Baumann, B.; Wirth, M. P.
Abstract
We report, to our knowledge previously not described, a case of occult prostate cancer, in which 11C-acetate positron emission tomography disclosed tumor manifestation after failure of conventional diagnostic procedures.
Keywords: Prostate cancer; Occult; Positron emission tomography; Bone scan; Metastases
- Urologic Oncology 24(2006), 410-411
Permalink: https://www.hzdr.de/publications/Publ-8965
Decomposition of metabolic brain clusters in the frontal variant of frontotemporal dementia
Salmon, E.; Kerrouche, N.; Herholz, K.; Perani, D.; Holthoff, V.; Beuthien-Baumann, B.; Degueldre, C.; Lemaire, C.; Luxen, A.; Baron, J.-C.; Collette, F.; Garraux, G.
Abstract
Previous studies that measured brain activity in frontotemporal dementia (FTD) used univariate analyses, examining each region of interest separately. We explored in a multicenter European research program the principal brain clusters characterized by a common variability in cerebral metabolism in FTD. Seventy patients with frontal variant (fv) FTD were selected according to international clinical recommendations; principal component analysis (PCA) was performed on FDG-PET metabolic images, looking for covariance clusters in this large population. A first metabolic cluster included most of the lateral and medial prefrontal cortex, bilaterally; PC1 scores correlated with performances on memory and executive neuropsychological tasks. Moreover, FDG-PET images in fv-FTD were further characterized by a metabolic covariance in two clusters comprising the subcallosal medial frontal region, the temporal pole, medial temporal structures and the striatum, separately in the left and in the right hemisphere. The study provides original data-driven arguments for metabolic involvement of separate brain clusters in the rostral limbic system, corresponding to pathological poles differentially affected in each FTD patient.
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NeuroImage 30(2006)3, 871-878
DOI: 10.1016/j.neuroimage.2005.10.016
Cited 40 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8964
Experimental and numerical results on the fluid flow driven by a traveling magnetic field
Lantzsch, R.; Galindo, V.; Grants, I.; Zhang, C.; Pätzold, O.; Gerbeth, G.; Stelter, M.
Abstract
A traveling magnetic field (TMF) driven convection and its transition from a laminar to a time-dependent flow is studied by means of ultrasonic Doppler velocimetry and numerical simulations. The experimental setup comprises a cylindrical cavity containing the electrically conducting model fluid GaInSn and a system of six equidistant coils, which are fed by an out-of-phase current to create an up- or downward directed TMF. Hence, a Lorentz force is induced in the melt which leads to meridional flow patterns. For numerical simulations commercial codes (Opera/Fidap) and a spectral code are used. The characteristic parameters of the magnetohydrodynamic model system are chosen close to the conditions used for Vertical Gradient Freeze (VGF) crystal growth. The axisymmetric basic flow and its dependence on the dimensionless shielding parameter S are examined. It is shown that, for S>10, the flow velocity decreases significantly, whereas almost no influence is found for a smaller shielding parameter. The critical Reynolds number for the onset of instability is found in the range of 300-450. Good agreement between experimental results and the numerical simulations is achieved.
Keywords: Fluid Flows; Magnetic Fields; Stirring; Growth from melt
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Journal of Crystal Growth 305(2007), 249-256
DOI: 10.1016/j.jcrysgro.2007.03.047
ISSN: 0022-0248
Cited 55 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8963
Effect of pseudophosphorylation and cross-linking by lipid peroxidation and advanced glycation end product precursors on tau aggregation and filament formation
Kuhla, B.; Haase, C.; Flach, K.; Lüth, H.-J.; Arendt, T.; Münch, G.
Abstract
Accumulation of hyperphosphorylated tau protein as paired helical filaments (PHFs) in pyramidal neurons is a major hallmark of Alzheimers disease. Besides hyperphosphorylation, other modifications of the tau protein such as crosslinking are likely to contribute to the characteristic features of PHFs, including their insolubility and resistance against proteolytic degradation. In this study, we have investigated if the four reactive carbonyl compounds acrolein, malondialdehyde, glyoxal and methylglyoxal accelerate the formation of tau oligomers, thioflavin T positive aggregates and fibrils using wild-type and seven pseudophosphorylated mutant tau proteins. Acrolein and methylglyoxal were the most reactive compounds, followed by glyoxal and malondialdehyde in terms of formation of tau dimers and higher molecular weight oligomers. Furthermore, acrolein and methylglyoxal induced the formation of thioflavin T fluorescent aggregates in a triple pseudophosphorylation mimicking mutant to a slightly higher degree than wild type tau. Analysis of the tau aggregates by electron microscopy study showed that formation of fibrils using wild type tau and several tau mutants could be observed with acrolein and methylglyoxal but not with glyoxal and malondialdehyde. Our results suggest that reactive carbonyl compounds, particularly methylglyoxal and acrolein, could accelerate tangle formation in vivo, and that this process could be slightly accelerated, at least in the case of methylglyoxal and acrolein, by hyperphosphorylation. Interference with the formation or the reaction of these reactive carbonyl compounds could be a promising way of inhibiting tangle formation and neuronal dysfunction in Alzheimers disease and other tauopathies.
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Journal of Biological Chemistry 282(2007)10, 6984-6991
DOI: 10.1074/jbc.M609521200
Cited 103 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8962
Ion implantation-induced damage depth profile determination in SiC by means of RBS/C and bevelling technique
Romanek, J.; Grambole, D.; Herrmann, F.; Voelskow, M.; Posselt, M.; Skorupa, W.; Zuk, J.
Abstract
Ion implantation-induced damage depth profiles of 450 keV Al+ ion-implanted 6H-SiC were studied using RBS/C technique for implantations along channeling direction and non-channeling direction with fluence of 3.4 1015 cm2. Bevelling method of sample preparation was used to get access to the deeper situated layers over the whole damaged region and below. To determine damage degree at the specific depth of the bevelled sample, RBS/C technique combined with a 3 MeV Li2+ ion beam of size of about 30 micrometer x 30 micrometer was utilized (micro-RBS/C). The micro-RBS/C method combined with the bevelling technique gave us a possibility to probe deeper reaching damage regions than in the case of conventional RBS/C investigations. It also utilizes a near-surface part of backscattered spectra, which is slightly influenced by damage created by probing ions and a random fraction of probing beam. Additionally, there is no need to perform energy calibration of detector for backscattered particles. Due to much smaller sample area hit by probing ions of micro-beam, the required fluence, comparable to that at conventional RBS/C measurements is obtained at much lower charge. Negligibly small effect of bevelling-induced mechanical damage has been observed in this study. The obtained results by micro-RBS/C method validate the results of computer simulations (Crystal-TRIM software).
Keywords: Ion implantation damage; SiC; micro-RBS
- Nuclear Instruments and Methods in Physics Research B 251(2006), 148-156
Permalink: https://www.hzdr.de/publications/Publ-8960
Uranmunition im Boden: - Spektroskopische Untersuchungen zur Sekundärphasenbildung auf abgereichertem Uran
Baumann, N.
Abstract
Zusammenfassung und Interpretation der Ergebnisse von TRLFS-Messungen an einer Probe von abgereichertem Uran (DU), welches zuvor 182 Tage bei Raumtemperatur einer Calziumphosphatlösung ausgesetzt war. Durch diese Messung konnte die Bildung der Sekundärphase Meta-Autunit und damit eine Reaktion von DU mit der Lösung spektroskopisch nachgewiesen werden.
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Invited lecture (Conferences)
Vortragsreihe des Schwerpunktes Bio-Geo der Friedrich-Schiller-Universität Jena, 07.11.2006, Jena, Germany
Permalink: https://www.hzdr.de/publications/Publ-8959
Quantification of beta+ activity generated by hard photons by means of PET
Möckel, D.; Müller, H.; Pawelke, J.; Sommer, M.; Will, E.; Enghardt, W.
Abstract
Positron emission tomography (PET) as a method for quality assurance in radiotherapy is well-investigated in the case of therapy with carbon ion beams and successfully applied at the Heavy Ion Medical Accelerator at Chiba (HIMAC), Japan, and the Gesellschaft für Schwerionenforschung (GSI), Germany. By measuring the beta{}^+ activity distribution during the irradiation (in-beam PET) valuable information on the precision of the dose deposition can be obtained. To extend this efficient technique to other radiation treatment modalities may be worthwhile. For example, since positron emitters are generated by high energy photons with energies above 20~MeV due to (gamma{},~n) reactions (predominantly {11}C and {15}O in tissue) in-beam PET seems to be feasible for the radiation therapy with high-energy photons as also shown in Geant4 simulations. Quantitative results on the activation of tissue-equivalent materials at hard photon beams were obtained by performing off-beam PET experiments. Homogeneous PMMA phantoms as well as inhomogeneous phantoms were irradiated with high energy bremsstrahlung. After the irradiation the distributions of the generated positron emitters in the phantoms were measured using a conventional PET scanner. Furthermore, the depth-dose-distributions were determined by means of optically stimulated luminescence detectors. In the experiments an activity per dose comparable to that produced in a typical patient irradiation with carbon ions could be achieved for 34~MV bremsstrahlung. In addition, a high contrast in the PET images for materials with different density and stoichiometry could be detected. Thus, further research concerning the development of in-beam PET seems to be worthwhile.
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Physics in Medicine and Biology 52(2007), 2515-2530
DOI: 10.1088/0031-9155/52/9/012
Cited 13 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8958
RBE of 10 kV X-rays determined for the Human Mammary Epithelial Cell Line MCF-12A
Lehnert, A.; Lessmann, E.; Pawelke, J.; Dörr, W.
Abstract
Presently, an extended discussion about the dependence of the relative biological effectiveness (RBE) on photon energy takes place. The increasing amount of in vitro data in the low-energy region indicates this is a complex dependence which is influenced by the endpoint and cell line studied. In the present investigation, the RBE of 10 kV rays (W anode) was determined relative to 200 kV X-rays (W anode, 0.5 mm Cu filter) for cell survival in the dose range 1 - 10 Gy and induction of micronuclei in the range 0.5 - 3.6 Gy for the human mammary epithelial cells MCF-12A. The RBE for cell survival was found to increase with decreasing dose, being 1.21 ± 0.03 at the 10 % survival rate. Considerably higher values were obtained for the micronucleus induction, where RBEM obtained from the ratio of the linear coefficients of the dose-effect curves was equal to 2.6 ± 0.4 for the fraction of binucleated cells (BNC) with micronuclei (MN) and 4.1 ± 1.0 for the number of MN per BNC. These values, together with our previous data, support a monotonic increase in RBE with decreasing photon energy down to the mean energy of 7.3 keV used in the present study.
Keywords: soft X-rays; RBE; X-ray tube; clonogenic survival; micronucleus test; human mammary epithelial cells; MCF-12A
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Radiation Research 169(2008), 330-336
DOI: 10.1667/RR0874.1
Cited 24 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8957
Radiolabelling of multimeric neurotensin(8-13) analogues with the short-lived positron emitter fluorine-18
Hultsch, C.; Berndt, M.; Bergmann, R.; Wüst, F.
Abstract
Neurotensin receptors are expressed with high incidence in several human tumour entities. Thus, radiolabelled neurotensin derivatives might be used for tumour targeting. However, its application is limited by insufficient metabolic stability. Metabolic stability might be improved by the synthesis of multivalent peptides.
Three methods for 18F-labelling of dimeric and tetrameric
neurotensin(8-13) derivatives were evaluated with respect to the labelling yield and the required peptide amounts. Labelling using N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB) gave low radiochemical yield for the dimeric peptides. Coupling of the tetramer with [18F]SFB was not successful. Furthermore, labelling of aminooxy-functionalized neurotensin(8-13) derivatives using 4-[18F]fluorobenzaldehyde ([18F]FBA) was investigated. High yields were obtained for the dimer whilst coupling of the tetramer only gave low yields.
In contrast to these findings, labelling of sulfhydryl-functionalized
neurotensin(8-13) derivatives using the maleinimide 4-[18F]fluorobenzaldehyde O-[6-(2,5-dioxo-2,5-dihydro-pyrrol-1-yl)-hexyl]-oxime ([18F]FBAM) resulted in high radiochemical yields for both, the dimer and the tetramer. Therefore, [18F]FBAM seems to be the most suitable 18F-labelling agent for multivalent neurotensin(8-13) derivatives.
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Applied Radiation and Isotopes 65(2007), 818-826
DOI: 10.1016/j.apradiso.2007.02.004
Cited 29 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8956
Synthesis of 18F-labelled stilbenes from 4-[18F]fluorobenzaldehyde using the Horner-Wadsworth-Emmons reaction
Gester, S.; Pietzsch, J.; Wüst, F.
Abstract
The first application of the Horner-Wadsworth-Emmons reaction in 18F-chemistry is described. This carbonyl-olefination reaction was performed via a multi-step/one-pot reaction by the coupling of benzylic phosphonic acid esters (3,5-bis-methoxymethoxybenzyl)-phosphonic acid diethyl ester 2e, (4-methoxymethoxybenzyl)-phosphonic acid diethyl ester 3e and (4-dimethyl-aminobenzyl)phosphonic acid diethyl ester 4d) with 4-[18F]fluorobenzaldehyde to give the corresponding 18F-labelled stilbenes [18F]2g, [18F]3g and [18F]4e exclusively as the expected E-isomers. The radiochemical yields ranged from 9 to 22% (based upon [18F]fluoride, including HPLC purification). The specific activity reached up to 90 GBq/µmol.
Keywords: 18F-labelled stilbenes; [18F]fluorobenzaldehyde; Horner-Wadsworth-Emmons reaction
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Journal of Labelled Compounds and Radiopharmaceuticals 50(2007)2, 105-113
DOI: 10.1002/jlcr.1172
Cited 12 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8955
Neurotensin Receptors in Adeno- and Squamous Cell Carcinoma
Haase, C.; Bergmann, R.; Oswald, J.; Zips, D.; Pietzsch, J.
Abstract
Background: Peptide receptors seem to be good markers for receptor targeting because of their overexpression in human cancer. Understanding the role of receptors and their cognate ligands is currently used for both diagnosis and therapy. Candidates playing a key role in tumor biology are the neurotensin receptors (NTR). The expression of NTR in HT-29 cells (human colon adenocarcinoma cell line) and FaDu cells (human squamous cell carcinoma cell line) and in corresponding tumor xenografts on nude mice, was investigated. Materials and Methods: Quantitative RT-PCR of the three receptor subtypes was carried out to study mRNA expression. Receptor protein expression was analyzed by immunohistochemistry with specific antibodies for the three known neurotensin receptors NTR1, NTR2 and NTR3. Results: Analysis of receptor mRNA revealed a strong expression of NTR3 and a weak expression of NTR1 and NTR2 in cultured cells and xenografts. Examining the protein levels, a strong signal for NTR1 was detected in tumor cells and xenografts and only a weak signal was detected for NTR3. Conclusion: Since the receptor protein is targeted in vivo, the enhanced protein expression of NTR1 in xenografts could be a useful tool for molecular targeting with radioligands and for further characterization of carcinogenic processes.
Keywords: Neurotensin; neurotensin receptor; Tumor xenograft model; HT-29; FaDu
- Anticancer Research 26(2006), 3527-3534
Permalink: https://www.hzdr.de/publications/Publ-8954
Synthesis and radiopharmacological characterization of [11C]AL-438 as a nonsteroidal ligand for imaging brain glucocorticoid receptors
Wüst, F.; Knieß, T.; Bergmann, R.; Henry, B.; Pietzsch, J.
Abstract
The radiosynthesis and the radiopharmacological characterization of [11C]AL-438 as a nonsteroidal ligand for the glucocorticoid receptor (GR) is described. Radiolabelling of the corresponding desmethyl precursor 10 with [11C]MeI gave [11C]AL-438 in decay-corrected radiochemical yields of 30±4% (based upon [11C]CO2) within 35 min at a specific radioactivity of 10-15 GBq/µmol at the end-of-synthesis. The radiopharmacological evaluation of [11C]AL-438 involved biodistribution and small animal PET imaging in rats, and autoradiography studies using rat brain sections.
Biodistribution studies were performed in male Wistar rats and demonstrated high radio-activity uptake in pituitary and brain. However, the inability of high dose corticosterone to block binding would suggest that the radioactivity accumulation in the brain was not receptor-mediated.
- Bioorganic & Medicinal Chemistry Letters 17(2007), 4035-4039
Permalink: https://www.hzdr.de/publications/Publ-8953
Bispidine - Ein neues Chelatsystem zur stabilen Bindung von Radiokupfernukliden
Juran, S.; Walther, M.; Stephan, H.; Steinbach, J.
Abstract
Ziel/Aim:
Die Arbeiten zielen auf die Entwicklung von radioaktiven Kupfer(II)-Komplexen mit hoher thermodynamischer Stabilität und schneller Komplexbildungskinetik auf der Basis des 3,7-Diazabicyclo[3.3.1]nonans (Bispidin). Voruntersuchungen haben gezeigt, dass sechszähnige Derivate, die Pyridinfunktionen enthalten, am aussichtsreichsten sind (1). Durch Einführen von Kopplungsstellen am Bispidin soll die Anknüpfung an Biomoleküle ermöglicht werden.
Es wird über die Darstellung von hexadentaten Bispidinderivaten berichtet sowie deren Möglichkeiten zur Kopplung an Biomoleküle diskutiert. Des Weiteren werden Ergebnisse radiopharmakologischer Untersuchungen mit Cu-64 und Cu-67 präsentiert. Schwerpunkt dabei werden in vitro Stabilitätsuntersuchungen und Bioverteilungsstudien sein.
Methodik/Methods:
Die Synthese der Bispidinliganden erfolgt durch zwei aufeinanderfolgende Mannich-Kondensationen, wobei Pyridin- und Imidazol-Edukte eingesetzt wurden. An ausgewählten Vertretern wurden Möglichkeiten zur Kopplung an Biomoleküle erprobt. Die entsprechenden Biokonjugate wurden mittels semipräparativer HPLC gereinigt und radioaktiv markiert. Stabilitätstests im Rattenplasma und in Anwesenheit von Konkurrenzliganden (Glutathion, Cyclam) erfolgten.
Ergebnisse/Results:
Es wurden eine Reihe neuer Bispidinliganden dargestellt und die in vitro Stabilität entsprechender Kupfer(II)-Komplexe getestet. Das Bispidingrundgerüst wurde so modifiziert, dass Biomoleküle über eine Carboxylfunktion angekoppelt werden können. Für eine Peptidkopplung erwies sich der Einsatz von HBTU als Reagenz in Anwesenheit von DIPEA am geeignesten. Die dargestellten Konjugate weisen eine günstige Kinetik der Komplexierung sowie eine hohe Stabilität sowohl im Rattenplasma als auch in Anwesenheit von Konkurrenzliganden auf. Es konnte keine Transchelatisierung des Kupfers nachgewiesen werden.
Schlussfolgerungen/Conclusions:
Die dargestellten Kupfer(II)-Komplexe mit sechszähnigen Bispidinliganden weisen eine sehr hohe Stabilität auf und verfügen damit über ein hohes inhärentes Anwendungspotential für radiopharmazeutische Anwendungen in Diagnostik (Cu-64, PET) und Therapie (Cu-67, Endoradionuklidtherapie). Zum Erzielen eines selektiven Anreicherns der radioaktiven Kupferkomplexe im Zielgewebe, sollen sich weitere Untersuchungen insbesondere mit der Kopplung von Antikörpern an das Grundgerüst hexadentater Bispidin-Derivate befassen. Kleintier-PET-Untersuchungen ausgewählter Konjugate sollen sich anschließen.
Literatur/References:
(1) H. Stephan, S. Juran, M. Walther, J. Steinbach, K. Born, P. Comba
Synthesis, characterization and evaluation of novel chelating agents for copper radionuclides in Technetium, Rhenium and other Metals in Chemistry and Nuclear Medicine, U. Mazzi (Ed.), SGE Editoriali, Padova, Italy, 2006, 7, 219-222.
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Lecture (Conference)
45. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2007, Hannover, D -
Abstract in refereed journal
Nuklearmedizin 46(2007), A42
ISSN: 0029-5566
Permalink: https://www.hzdr.de/publications/Publ-8952
Validation of CFD models for mono- and polydisperse air-water two-phase flows in pipes
Frank, T.; Zwart, P.; Krepper, E.; Prasser, H.-M.; Lucas, D.
Abstract
Many flow regimes in Nuclear Reactor Safety (NRS) Research are characterized by multiphase flows, where one of the phases is continuous and the other phase consists of gas or vapor of the liquid phase. The validation of the CFD multiphase flow models against detailed experimental data for simplified flow configurations is a basic requirement for the accurate prediction of more complex flows, like e.g. multiphase flow in fuel rod assemblies with spacer grids under the conditions from ONB to DNB including bulk and wall boiling in a pressurized polydisperse liquid-vapor flow. This paper is therefore aimed on validation of the underlying multiphase flow modeling concepts for gas-liquid monodisperse and polydisperse bubbly flows. CFD predictions using ANSYS CFX and taking into account interphase momentum transfer (drag and non-drag forces) as well as bubble break-up and coalescence are compared to experiments of MT-Loop and TOPFLOW test facilities (FZ Rossendorf, Germany). Best Practice Guidelines have been applied in order to allow for a systematic error quantification and thoroughly assessment of model formulations.
Keywords: CFD; Multiphase flow; experiments; bubble forces; monodispersed flow; polydispersed flow; multiple bubble size classes; model validation; best practice guidelines
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Lecture (Conference)
OECD/NEA International Workshop on The Benchmarking of CFD Codes for Application to Nuclear Reactor Safety (CFD4NRS, 05.-09.09.2006, Garching, Germany -
Contribution to proceedings
OECD/NEA International Workshop on The Benchmarking of CFD Codes for Application to Nuclear Reactor Safety (CFD4NRS, 05.-09.09.2006, Garching, Germany
Proceedings paper B6-32 -
Nuclear Engineering and Design 238(2008), 647-659
DOI: 10.1016/j.nucengdes.2007.02.056
Cited 203 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8951
Capacitance wire-mesh tomograph for multiphase flow applications
Da Silva, M. J.; Schleicher, E.; Hampel, U.
Abstract
We present a novel wire-mesh tomography system based on electrical capacitance (permittivity) measurements for multiphase flow applications. The system measures with high spatial and high temporal resolution the phase distribution in a flow cross section and can be used to investigate phases having different relative permittivity (dielectric constant) values. A prototype system has been developed and manufactured comprising of a sensor with two layers of 16 wires each and associated electronics. The system achieves 3 mm spatial resolution and can measure up to 625 frames per second. The evaluation of the prototype has shown good accuracy and reproducibility. Initial tests have been performance including an air-oil bubbly flow measurement and the static measurement of a stratified air-oil-water flow.
Keywords: wire-mesh sensor; capacitance; permittivity; non-conducting fluids; multiphase flow
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Contribution to proceedings
5th World Congress on Industrial Process Tomography, 03.-06.09.2007, Bergen, Norway
Proceedings of the 5th World Congress on Industrial Process Tomography: VCIPT, 978 0 85316 265 0, 624-629 -
Lecture (Conference)
5th World Congress on Industrial Process Tomography, 03.-06.09.2007, Bergen, Norway
Permalink: https://www.hzdr.de/publications/Publ-8950
Ereignis an der Versuchsanlage TOPFLOW-Heißstrang des Forschungszentrums Dresden - Rossendorf
Kryk, H.; Hessel, G.; Beyer, M.; Carl, H.; Hampel, U.; Strobel, H.
Abstract
Zur Untersuchung von Zweiphasenströmungen in horizontalen Geometrien wurde am FZD eine neue Versuchsanlage aufgebaut. Sie besteht im Wesentlichen aus einem Druckbehälter mit einem Schnellverschlussdeckel, einer Umluftkühlung sowie einer Kompressorenanlage. Bei einem Test der Wärmeisolierung der Testsektionen kam es zu einem Brand im Druckbehälter. Der damit verbundene Temperatur- und Druckanstieg im Behälter führte zum Abriss der zum Sicherheitsventil führenden Leitung. Personen kamen nicht zu Schaden. Im Zuge der Brand-Ursachenermittlung wurden vom FZD und dem Institut Fresenius u. a. thermische und chemische Analysen des neuen und havarierten Isoliermaterials (Polysiloxan-Schaum) sowie Pyrolyseuntersuchungen mit Gasanalysen durchgeführt. Im Ergebnis der Untersuchungen wurden brennbare Substanzen identifiziert (z. B. niedermolekulare zyklische Siloxane), die bei thermischer Belastung des Isoliermaterials innerhalb der Polysiloxanschaum-Poren entstehen und bei Kontakt mit Luftsauerstoff ein zündfähiges Gemisch bilden können. Ausgegangen wird von einer lokalen Anreicherung brennbarer Substanzen im Isoliermaterial und einer Zündung vorzugsweise am heißesten Anlagenteil. Begünstigt wurde der Zündprozess durch die druckbedingte Herabsetzung der Zündtemperatur, die temperaturbedingte Verringerung von Sauerstoffgrenzkonzentration und UEG sowie der Präsenz eines Platin-Katalysators. Die Brandausbreitung über die gesamte Oberfläche des Isolationsmaterials erfolgte durch Erhitzung umliegender Isolationsmaterial-Bereiche durch Wärmeleitung und Konvektion, Reaktionsbeschleunigung durch Erwärmung unter Bildung weiterer brennbarer Stoffe in den umliegenden Isoliermaterial-Bereichen sowie wärmebedingten Transport der Substanzen an die Oberfläche des Materials. Zur Verhinderung weiterer Störfälle erfolgte ein Austausch des Polysiloxan-Schaumes durch ein anorganisches Isoliermaterial, welches vor dem Einsatz thermischen und chemischen Analysen unterzogen wurde. Da der Einsatz von organischen Substanzen im weiteren Versuchsbetrieb nicht ausgeschlossen werden kann, ist weiterhin eine Anlage zur Inertisierung des Druckbehälters mit Stickstoff geplant.
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Lecture (others)
DECHEMA/GVC-Arbeitsausschuss "Sicherheitsgerechtes Auslegen von Chemieanlagen", 22.-23.11.2006, Lampertheim, Germany
Permalink: https://www.hzdr.de/publications/Publ-8949
Scale-hopping Modelling of Ferroic Functional Elements
Gemming, S.
Abstract
The modelling concepts of a nanoscale organic field effect transistor on a ferroelectric substrate are presented. The device consists of a ferroelectric substrate with a switchable, macroscopic electric polarisation, an electric-field-sensitive organic molecule, and suitable connectors. The structural and electronic properties of the single components and the major interactions between them are modelled by first-priciples electronic structure calculations. For the influence of the electric field on the optical and the conductivity properties of the larger organic molecules, a related density-functional-based tight-binding scheme was employed, which focusses on the salient features of the electronic system. For the self-assembly of the transistor building blocks, mesoscale approaches based on atomistic pair potentials and on a supramolecular Ising-type modelling have been developped and successfully applied.
Keywords: multi-scale modelling; multifunctional material
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Invited lecture (Conferences)
ITF-Seminar, 07.11.2006, Dresden, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-8948
Intersubband transitions in GaPAlP heterostructures
Semtsiv, M. P.; Müller, U.; Masselink, W. T.; Georgiev, N.; Dekorsy, T.; Helm, M.
Abstract
Intersubband optical transitions in doped AlPGaP multiple quantum wells are investigated using midinfrared absorption. Strong p-polarized absorption corresponding to the transition from the first to the fourth electronic subband in the Xz valley is measured at wavelengths between 5 and 8 microns. Additional absorption peaks related to transitions between confined donor states are also observed. The measured intersubband transition energies are consistent with an X valley conduction band offset between AlP and GaP of 280 meV and a value of 1.1m0 for the longitudinal effective mass for the X valleys of AlP (where m0 is a free electron mass). These values, the role of donors and confined two-dimensional continuum states, and applications of this system for terahertz intersubband devices are discussed.
Keywords: intersubband; infrared GaP; AlP; quantum well
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Applied Physics Letters 89(2006), 184102
DOI: 10.1063/1.2372709
ISSN: 0003-6951
Cited 15 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8947
Impact of Four-Quark Condensates on In-Medium Effects of Hadrons
Thomas, R.; Hilger, T.; Zschocke, S.; Kämpfer, B.
Abstract
Spectral properties of hadrons in nuclear matter are treated in the framework of QCD sum rules. The influence of the ambient strongly interacting medium is encoded in various condensates. Especially, the structure of different four-quark condensates and their density dependencies in light quark systems are exemplified for the omega meson and the nucleon.
Keywords: Medium modifications; Four-quark condensates; QCD sum rules
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Contribution to proceedings
Quark Confinement and the Hadron Spectrum VII, 02.-07.09.2006, Ponta Delgada, Portugal: AIP, 978-0-7354-0396-3, 274-277
Permalink: https://www.hzdr.de/publications/Publ-8946
Stability of 188Re Complexes Prepared with Highly Concentrated [188Re]Perrhenate Eluates from 188W/188Re Generators
Seifert, S.; Schiller, E.; Jentschel, C.; Bergmann, R.; Pietzsch, H.-J.; Wunderlich, G.; Kotzerke, J.; Steinbach, J.
Abstract
The preparation and stability of a novel 188Re-S4-complex (S4 = bridged DMSA ligand) was studied at therapeutic relevant radioactive concentrations. The results were compared with an 188Re-MAG3 and an 188Re-DMSA preparation which were obtained from 188Re-EDTA by a combined re-oxidation/ligand exchange reaction. The highly concentrated [188Re]perrhenate solution (12-15 GBq/ml) used for preparations was received by successive elution of several 188W/188Re generators connected in series. The preparations were performed under nitrogen, stabilized by adding 15 mg of ascorbic acid and analyzed after 1, 2, and 24 hours by TLC and HPLC. Only about 8 % of perrhenate were detected after 24 h in the 188Re-S4-complex samples. The 188Re-DMSA preparations were only marginally re-oxidized during this time, whereas the stabilized 188Re-MAG3 samples remained nearly stable. Additionally, in vitro and in vivo stability studies at radioactive concentrations of 30-50 MBq/ml were performed with all the complexes. Therefore, the preparations were purified by HPLC and incubated in phosphate buffer as well as rat and human plasma. The in-vivo-stability was determined in rats. Samples of plasma, urine, liver, and intestine were taken off 1 h after application of the 188Re complex solutions. Results from these studies demonstrated that only the 188Re-S4-complex was completely stable in vitro and in all investigated in vivo samples.
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Poster
7th International Symposium on Technetium in Chemistry and Nuclear Medicine, 06.-09.09.2006, Bressanone, Italy -
Contribution to external collection
U. Mazzi: Technetium, Rhenium and Other Metals in Chemistry and Nuclear Medicine, Padova: SGEditoriali, 2006, 88-89884-04-5, 605-606
Permalink: https://www.hzdr.de/publications/Publ-8945
Preparation and biological characterization of 188Re(V) oxocomplexes with tetradentate S4-ligands derived from DMSA for labeling of biomolecules
Seifert, S.; Heinrich, T.; Jentschel, C.; Bergmann, R.; Pietzsch, H.-J.
Abstract
A new type of tetradentate S4-ligands has been synthesized by bridging two molecules of 2,3-dimercaptosuccinic acid for stable binding and easy conjugation of rhenium-188 to biologically interesting structures. The stereoisomeric tetrathiolato S4-ligands form very robust anionic five-coordinated oxorhenium(V) complexes. Two routes for the preparation of the 188Re(V) oxocomplexes I and II with (R)2N(O)C-CH(SH)-CH(SH)-C(O)NH-(CH2)3NH-(CH2)3NHC(O)-CH(SH)-CH(SH)-C(O)N(R)2 (ligand 1, R = iBu) and its hydrophilic derivative 2 (R = 1-aza-18-crown-6) were tested and optimized. Several isomers were separated by HPLC from the preparation solutions and characterized in vitro and in vivo. The identity of the species obtained was determined by comparison with the HPLC profiles of reference 185/187Re analogues which were characterized by ESI-MS. All of them were absolutely stable in rat and human plasma solutions. Challenge experiments with cysteine corroborated the high inertness of the isomers towards ligand exchange reactions. Various in vivo samples, taken off at different times from blood, intestine and urine of rats, confirmed the high in vivo stability of the 188Re-S4 complexes. Biodistribution studies using male Wistar rats were performed and resulted in a high uptake and fast clearance from the liver of the more lipophilic cis and trans isomers of complex I (log Po/w between 1.5 and 1.7), whereas the hydrophilic isomers of complex II (log Po/w about -1.75) were preferentially excreted via the renal pathway. The low level of radioactivity in the stomach indicated good in vivo stability.
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Poster
7th International Symposium on Technetium in Chemistry and Nuclear Medicine, 06.-09.09.2006, Bressanone, Italy -
Contribution to external collection
U. Mazzi: Technetium, Rhenium and Other Metals in Chemistry and Nuclear Medicine, Padova: SGEditoriali, 2006, 88-89884-04-5, 411-414
Permalink: https://www.hzdr.de/publications/Publ-8944
Dynamics of charged fluids and 1/l perturbation expansions
Znojil, M.; Günther, U.
Abstract
Some features of the calculation of fluid dynamo systems (spherically symmetric α2-dynamos) in magnetohydrodynamics are studied, the problem connected with the presence of mixed (Robin) boundary conditions is addressed and a new treatment for it is proposed. The perturbation formalism of large l expansions is shown applicable and its main technical steps are outlined.
Keywords: large l expansion; perturbation theory; MHD dynamos; Robin boundary conditions; anharmonic oscillator
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Journal of Physics A 40(2007), 7375-7388
DOI: 10.1088/1751-8113/40/26/018
ISSN: 1751-8113
Cited 6 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8943
Absence of ferromagnetism in V-implanted ZnO single crystals
Zhou, S.; Potzger, K.; Reuther, H.; Skorupa, W.; Helm, M.; Fassbender, J.
Abstract
The structural and magnetic properties of V doped ZnO are presented. V ions were introduced into hydrothermal ZnO single crystals by ion implantation with fluences of 1.2×10^16 to 6×10^16 cm^-2. Post-implantation annealing was performed in high vacuum from 823 K to 1023 K. The ZnO host material still partly remains in a crystalline state after irradiation, and is partly recovered by annealing. The V ions show a thermal mobility as revealed by depth profile Auger electron spectroscopy. Synchrotron radiation x-ray diffraction revealed no secondary phase formation which indicates the substitution of V onto Zn site. However in all samples no ferromagnetism was observed down to 5 K by a superconducting quantum interference device magnetometer.
Keywords: ZnO; magnetic semiconductor
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Contribution to proceedings
10th Joint MMM/Intermag Conference, 07.-11.01.2007, Baltimore, Maryland, United States -
Journal of Applied Physics 101(2007), 09H109
DOI: 10.1063/1.2710802
Cited 39 times in Scopus -
Poster
71. Jahrestagung der Deutschen Physikalischen Gesellschaft und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 26.-30.03.2007, Regensburg, Germany
Downloads
Permalink: https://www.hzdr.de/publications/Publ-8942
Spectroscopic study of defects and inclusions in bulk poly- and nanocrystalline diamond aggregates
Shiryaev, A. A.; Iakoubovskii, K.; Grambole, D.; Dubrovinskaia, N.
Abstract
Recently, a novel form of nanodiamond exhibiting unusual mechanical properties has been synthesized by high-pressure high-temperature (HPHT) treatment of C60 fullerene, amorphous carbon and diamond powder. In this study, we have characterized the dominant defects in this nanodiamond by a combination of optical absorption, luminescence, Raman, electron spin resonance and elastic recoil detection techniques. Unusually high concentrations (~0.4 at.%) of hydrogen and very low concentrations of nitrogen (~1E-5 at.%) have been detected in diamond grown from C60. Although most of hydrogen is shown to originate from inclusions of foreign phases, such as water, significant concentrations (~0.01 at.%) of hydrogen were also detected as a point defect in the nanodiamond grains. Observed structural differences between the samples made from various carbonaceous materials are attributed to different behaviour of the starting compounds during HPHT treatment.
- Journal of Physics: Condensed Matter 18(2006), L493-L501
Permalink: https://www.hzdr.de/publications/Publ-8940
Femtosecond pump-probe spectroscopy of intersubband relaxation dynamics in narrow InGaAs/AlAsSb quantum well structures
Tribuzy, C. V.-B.; Ohser, S.; Winnerl, S.; Grenzer, J.; Schneider, H.; Helm, M.; Neuhaus, J.; Dekorsy, T.; Biermann, K.; Künzel, H.
Abstract
Intersubband relaxation dynamics in InGaAs/AlAsSb multiquantum wells (QWs) is studied by single-color femtosecond pump-probe measurements. At early delay times, all samples show an exponential decay of the transient transmission occurring with time constants of the order of a picosecond. The relaxation dynamics at later delay times strongly depend on both QW thickness and doping location. A non-single-exponential decay behavior indicates extra competing relaxation channels, as further confirmed by solving three-level rate equations. It is shown that slowly decaying components are due to electron transfer to states related to indirect valleys in the wells or in the barriers.
Keywords: Intersubband relaxation; InGaAs/AlAsSb quantum wells
- Applied Physics Letters 89(2006), 171104-1-171104-3
Permalink: https://www.hzdr.de/publications/Publ-8939
Modellierung der Wechselwirkung zwischen Corium und RDB-Stahl im Rahmen von Schmelzerückhaltungsszenarien
Altstadt, E.; Willschütz, H.-G.
Abstract
Bei einem schweren Störfall mit anschließender Schmelzeverlagerung in das untere Plenum stellt der Reaktordruckbehälter die letzte Sicherheitsbarriere vor einer direkten Belastung des Containments dar. Für eine genauere Einordnung der Vorgänge und Phänomene in diesem Szenario wurden von der EU bzw. der OECD finanzierte Experimente zum Behälterversagen durch Kriechbruch durchgeführt.
Am FZR wurden Modelle entwickelt, die sowohl die Temperaturfeldberechnung als auch die viskoplastische Mechanik des RDB umfassen und geeignet sind, den Versagensmodus und die Versagenszeit des Behälters zu ermitteln. Die Validierung der Modelle erfolgte an Hand von Voraus- und Nachrechnungen zu den Experimenten. Ein Schwerpunkt der Modellierung von prototypischen LWR-Szenarien ist die Berücksichtigung der thermo-chemischen Wechselwirkung der Coriumschmelze mit der RDB-Wand.
Im Rahmen der METCOR-Experimente am Alexandrov-Research Institute (NITI) in Sosnovy Bor wird die Schmelze-Metall-Wechselwirkung im kleinen Maßstab untersucht. Die Ergebnisse zeigen, dass die Ablation des Stahls je nach Zusammensetzung der Schmelze durch Bildung von Eutektika schon deutlich unterhalb der Schmelztemperatur des Stahls einsetzt. Entsprechende Abschmelzmodelle sind in die Finite-Elemente-Modelle zur Simulation der Schmelzerückhaltungsszenarien integriert worden. Die Anwendung dieser Modelle führt zu deutlich reduzierten Restwanddicken.
Keywords: In-vessel melt retention; corrosion damage; finite element analysis; reactor pressure vessel
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Contribution to proceedings
MPA Seminar, 05.-06.10.2006, Stuttgart, Germany
Proceedings on CD-ROM, paper 16.1 -
Lecture (Conference)
MPA Seminar, 05.-06.10.2006, Stuttgart, Germany
Permalink: https://www.hzdr.de/publications/Publ-8938
Nachrechnung der Leistungsparameter eines Vollhub-Feder Sicherheitsventils mit ANSYS CFX
Höhne, T.; Friedel, L.
Abstract
Mit dem CFX-Code wurden Nachrechnungen von Durchsatzparametern eines Leser Sicherheitsventils mit einem Gitter von 1 Million Hexaeder Zellen vorgestellt. Sehr gute Übereinstimmung wurde bei den Durchsatzkennlinien der vom Hersteller angegebenen Charakteristiken für Luft und Wasser erzielt, es existierte jedoch eine systematische Abweichung bei Luft im Falle hoher Ansprechdrücke durch Realgasverhalten und das Auftreten hohe Ma-Zahlen. Eine CFX-Rechnung mit einem Zweiphasengemisch bei 2 bar Überdruck, 1 mm Blasendurchmesser und 4% Gasanteil ergab eine realistische Erhöhung des Volumenanteils der Gasphase in Abhängigkeit von der Druckabsenkung. Weitere Untersuchungen, insbesondere das Verhalten bei Sattdampf und bei Stoffgemischen im Vergleich mit Experimenten sind geplant.
Keywords: Sicherheitsventil; CFD
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Invited lecture (Conferences)
24th CADFEM & ANSYS Germany Users Meeting, 26.10.2006, Stuttgart/Fellbach, Germany
Permalink: https://www.hzdr.de/publications/Publ-8937
The origin of ferromagnetism in 57Fe ion-implanted semiconducting 6H-polytype silicon carbide
Stromberg, F.; Keune, W.; Chen, X.; Bedanta, S.; Reuther, H.; Mücklich, A.
Abstract
Semiconducting (mostly p-doped) single crystals of the 6H-polytype of α-SiC(0001) were implanted with 57Fe ions with a nominal dose of 1.0 × 1016, 2.0 × 1016, 3.0 × 1016 or 2.0 × 1017 cm−2 (high-dose sample phd) at 100 or 200 keV ion energy in order to produce diluted magnetic semiconductors (DMSs). After implantation all samples (except p-hd) were subject to rapid thermal annealing at 1000 ◦C for 2 min. The structure was investigated by x-ray diffraction, high-resolution cross-sectional transmission electron microscopy and sputter-Auger depth profiling. The magnetic properties were obtained from superconducting quantum interference device (SQUID) magnetometry and 57Fe conversion electron M¨ossbauer spectroscopy (CEMS) at room temperature (RT) and 4.2 K. Our combined results obtained by several techniques prove unambiguously that ferromagnetism in 57Fe-implanted SiC for Fe concentrations above 3%originatesmostly from epitaxial superparamagnetic Fe3Si (and possibly a small fraction of Fe nanoparticles) in the SiC matrix. We find a wide range of blocking temperatures, TB, which start from 400 K for a dose of 2.0 ×1016 cm−2, and shift downwards to ∼220 K for 3.0× 1016 cm−2. For the lowest dose of 1.0 × 1016 cm−2 at 200 keV, we find evidence of ferromagnetism below 20 K via weak magnetic hyperfine interaction. Our measurements suggest that for a maximum Fe concentration in the range of 13%, which corresponds to this lowest Fe dose, the possibility exists to obtain a DMS in Fe-implanted SiC, prepared at lower or equal implantation doses.
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Journal of Physics: Condensed Matter 18(2006), 9881-9900
DOI: 10.1088/0953-8984/18/43/010
Cited 60 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8936
FELBE Free-Electron Laser: Status and Application for Time Resolved Spectroscopy Experiments
Winnerl, S.; Stehr, D.; Drachenko, O.; Schneider, H.; Helm, M.; Seidel, W.; Michel, P.; Schneider, S.; Seidel, J.; Grafström, S.; Eng, L.-M.; Roch, T.; Strasser, G.; Maier, T.; Walther, M.
Abstract
This paper reviews the basic properties of the infrared free-electron laser FELBE at the Forschungszentrum Rossendorf. At present FELBE delivers pulses with typical durations of 0.95 ps in the wavelength range 422 µm, which soon will be extended to 150 µm. Furthermore we report on recent experiments using FELBE, namely the study of phonon resonances in ferroelectric domains using a newly designed scattering scanning near-field optical microscope (s-SNOM), as well as pump-probe spectroscopy on doped semiconductor superlattices. The pump-probe signal reflects, apart from a component due to the bleaching of the interminiband transition, the temperature of the miniband electrons on a picosecond timescale.
Involved research facilities
- F-ELBE
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Invited lecture (Conferences)
Joint 31st International Conference on Infrared and Millimter Waves and 14th International Conference on Terahertz Electronics, 18.-22.09.2006, Shanghai, China -
Contribution to proceedings
Joint 31st International Conference on Infrared and Millimeter Waves and 14th International Conference on Terahertz Electronics, 18.-22.09.2006, Shanghai, China
Conference digest of the 2006 IRMMW-THz 2006: Piscataway, NJ : IEEE Operations Center, 1-4244-0399-5, 159-159
Permalink: https://www.hzdr.de/publications/Publ-8935
RPV material investigations of the former VVER-440 Greifswald NPP
Rindelhardt, U.; Viehrig, H.-W.; Konheiser, J.; Noack, K.; Gleisberg, B.
Abstract
The Greifswald NPP was operated between 1973 and 1990. The units are of Russian WWER-440-230 type. Now trepans from the RPV were gained to investigate the post mortem properties of the material.
The paper describes the results of weld metal originating from the critical weld of the RPV of unit 1. The RPV of this unit was annealed after 14 years of operation, followed by two additional years of operation.
The neutron dosimetry was based on fluence calculations as well as retrospective Nb dosimetry. Both approaches are shortly described. A decrease of 60% through the thickness of the RPV was found by both methods.
The material test results comprise Charpy-V, tensile and fracture toughness parameters. The main interest is focussed on the comparison of assessment codes applied in Russia and other European countries where WWER-440 reactors are operated. An additional aspect is the comparison of results determined on sub-size Charpy specimens immediately after the annealing procedure.
The first results show, that the material properties are near the predicted values.
Keywords: RPV; neutron dosimetry; neutron embrittlement; material properties
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Contribution to proceedings
15th International Conference on Nuclear Energy (ICONE15), 22.-26.04.2006, Nagoya, Japan
Proceedings of ICONE-15, JSME No 07-202, Contribution 15-1035 -
Lecture (Conference)
15th International Conference on Nuclear Energy (ICONE15), 22.-26.04.2006, Nagoya, Japan
Permalink: https://www.hzdr.de/publications/Publ-8934
Radiochemische Analysen von 93mNb in Druckkesselstahl und Vergleiche mit Fluenzberechnungen
Gleisberg, B.; Rindelhardt, U.; Konheiser, J.
Abstract
Zur Untersuchung der Materialeigenschaften wurden aus dem Reaktordruckbehälter des Blockes 1 des ehemaligen KKW Greifswald Materialproben entnommen. Die interessierenden Eigenschaften werden durch die während des Betriebes auftretende Neutronenstrahlung bestimmt.
Im Beitrag wird dargestellt, wie durch Messungen der Nb-Aktivität die Neutronenfluenz bestimmt wurde. Niob ist im im untersuchten Material nur als Spurenmetall erhalten. Die vorgenommenen Trennverfahren zur Isolation von Nb werden dargestellt.Die Messergebnisse werden mit Rechenergebnissen verglichen.
Keywords: Neutron fluence; reactor pressure vessel material; neutron embrittlement
-
Lecture (Conference)
Radiochemische Analytik bei Betrieb und Rückbau kerntechnischer Anlagen, der Deklaration von Abfällen und im Strahlenschutz, 19.-20.06.2006, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-8933
High resolution gamma ray tomography of a rotating hydrodynamic coupling
Hampel, U.; Bieberle, A.; Schleicher, E.; Zippe, C.; Hoppe, D.
Abstract
Hydrodynamic couplings are being used for torque transfer in heavy duty systems, such as naval vessels, power plants, locomotives or other transport vehicles. A hydrodynamic coupling essentially consists of two rotating bladed wheels, the pump and the turbine wheel, which are placed inside a metal enclosure. In operation the coupling is partially filled with a fluid and this fluid realises the momentum transfer from the driving side (pump) to the load side (turbine). The flow conditions in the coupling determine its operational behaviour. A known problem of such devices is the sudden change of slip during a continuous increase or decrease of either load or angular velocity of the pump. To investigate the behaviour of a hydrodynamic coupling the flow structure inside the coupling must be disclosed. But there only few measurement techniques which are applicable. Thus, the flow inside the pump is a heavily turbulent two-phase flow that is hardly accessible to optical or other measurement techniques. Gamma ray tomography provides a convenient method to measure the time integrated phase distribution within such a coupling. We performed such measurements in the past with the help of a low resolution gamma ray tomography system. Now we continued to use a high resolution gamma ray tomograph for that purpose. The measurements were carried out using a Cs-137 isotopic source and a detector arc with 2 mm spatial resolution. The test coupling mostly consists of aluminium and has an outer diameter of approximately 500 mm. For the measurement we employed the angle resolved data acquisition scheme that allows us to image rotating distributions with a fixed tomography setup. In the paper we will discuss the application of gamma ray tomography to this particular industrial problem.
Keywords: gamma ray tomography; hydrodynamic coupling; flow measurement
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Contribution to proceedings
5th World Congress on Industrial Process Tomography (WCIPT5), 03.-06.09.2007, Bergen, Norway
Proceedings of the 5th World Congress on Industrial Process Tomography, 978 0 85316 265 0, 683-689 -
Lecture (Conference)
5th World Congress on Industrial Process Tomography (WCIPT5), 03.-06.09.2007, Bergen, Norway
Permalink: https://www.hzdr.de/publications/Publ-8932
High resolution gamma ray tomography and its application to the measurement of phase fractions in chemical reactors
Hampel, U.; Bieberle, A.; Schleicher, E.; Hessel, G.; Zippe, C.; Friedrich, H.-J.
Abstract
We applied gamma ray tomography to the problem of phase fraction measurement in chemical reactors. Therefore, we used a new tomography device that is operated with a Cs-137 source and a high resolution gamma ray detector. One application example is the reconstruction of the fluid distribution and the measurement of radial gas fraction profiles in a laboratory scale stirred vessel. The tomograph was used to obtain radiographic projections of the averaged gamma ray attenuation for different stirrer speeds along the height of the vessel. With tomographic reconstruction techniques we calculated the angularly averaged radial distribution of the attenuation coefficient for as many as 150 single cross-sectional planes and synthesised from this data set the axial and radial fluid distribution pattern. Further, we exemplarily reconstructed the radial gas fraction distributions induced by the stirrer in the area of the stirrer blades. In a second application the gamma ray measurement system was used to visualise gas inclusions in a water cleaning column that is used to remove hazardous heavy metal species from water.
Keywords: gamma ray tomography; chemical reactor; flow measurement; gas hold-up; liquid hold-up
-
Lecture (Conference)
The 5th International Symposium on Measurement Techniques for Multiphase Flows, 10.-13.12.2006, Macao, China -
Contribution to proceedings
The 5th International Symposium on Measurement Techniques for Multiphase Flows, 10.-13.12.2006, Macao, China
Multiphase Flow: The Ultimate Measurement Challange, 942-948 -
Contribution to proceedings
Multiphase Flow - the Ultimate Measurement Challenge, 10.-13.12.2006, Macao, China
Proceedings of the 5th International Symposium on Measurement Techniques for Multiphase Flows and 2nd International Workshop on Process Tomography: American Institute of Physics, 753-759
Permalink: https://www.hzdr.de/publications/Publ-8931
Wasserkraftnutzung in Ostdeutschland
Rindelhardt, U.
Abstract
Im Beitrag werden der aktuelle Stand und die Potenziale der Wasserkraftnutzung in Ostdeutschland beschrieben. Ausgehend von der historischen Entwicklung im letzten Jahrhundert wird insbesondere die Reaktivierung von Wasserkraftanlagen nach der Wiedervereinigung diskutiert. Die bestehenden Wasserkraftanlagen und die ausbauwürdigen Potenziale liegen vor allem an den Nebenflüssen der Elbe, die Leistung übersteigt nur bei wenigen Anlagen 1 MW. Das bis zum Jahr 2010 nutzbare Potenzial liegt bei 650 GWh/a, eine Nutzung des größeren Potenzials der Elbe (1 TWh/a) ist gegenwärtig nicht absehbar.
Keywords: Wasserkraft; Erneuerbare Energien
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Wasserwirtschaft 97(2007)6, 33-36
ISSN: 0043-0978
Permalink: https://www.hzdr.de/publications/Publ-8930
Einsatz spektroskopischer Methoden zur Abschätzung der Stabilität dentritischer Metallkomplexe
Röhrich, A.
-
Invited lecture (Conferences)
SFB-624 Workshop "Affinität zu supramolekularen Templaten", 13.10.2006, Bonn, Germany
Permalink: https://www.hzdr.de/publications/Publ-8929
Untersuchungen zur in vitro Stabilität von Kupfer(II)-Komplexen sechszähniger Bispidinderivate
Juran, S.
-
Invited lecture (Conferences)
SFB-624 Workshop "Affinität zu supramolekularen Templaten", 13.10.2006, Bonn, Germany
Permalink: https://www.hzdr.de/publications/Publ-8928
Charakterisierung supramolekularer Rezeptoren mittels der Radiotracertechnik
Stephan, H.
-
Invited lecture (Conferences)
SFB-624 Workshop "Affinität zu supramolekularen Templaten", 13.10.2006, Bonn, Germany
Permalink: https://www.hzdr.de/publications/Publ-8927
Dissociation of Si+ ion implanted and as-grown thin SiO2 layers during annealing in ultra-pure neutral ambient by emanation of SiO
Beyer, V.; von Borany, J.; Heinig, K.-H.
Abstract
We have observed a very inhomogeneous dissociation of stoichiometric and non-stoichiometric thin SiO2 layers (thermally grown on Si substrates) during high temperature annealing at a low partial pressure of oxygen. During this process some silicon of the (100)Si substrate and, in case of Si ion implantation, additionally excess Si is consumed. The SiO2 dissociation has been studied by electron microscopy and Rutherford backscattering spectrometry. Large holes (>1µm) in non-implanted oxide layers have been observed which evolve probably from defects located at the Si/SiO2 interface. For Si implanted SiO2 additionally the formation of voids within the oxide during annealing has been observed preferably at the position of the implanted Si excess. Oxygen vacancies are possibly emitted from Si/SiO2 interfaces into the oxide and migrate through SiO2 with long-range distortions of the oxide network. In that way the hole and void formation in the oxide can be explained by oxygen-vacancy formation, migration and silicon-monoxide (SiO) emanation. As a driving force for growth of the large holes we identified oxygen diffusion from the Si/SiO2 interface to the bare Si surface. This surface is a sink of oxygen diffusion due to the emanation of volatile SiO, whereas the Si/SiO2 interface serves as an oxygen source. The predicted mechanism is consistent with the geometry of the holes in the SiO2 layer.
Keywords: oxygen-vacancy; Si self-diffusion; SiO; dissociation; SiO2
- Journal of Applied Physics 101(2007), 053516
Permalink: https://www.hzdr.de/publications/Publ-8926
Identification of actinide molecule complexes: A new vibrational spectroscopic approach at the free electron laser facility FELBE
Foerstendorf, H.; Seidel, W.; Heim, K.; Bernhard, G.
Abstract
The free electron laser (FEL) facility at the electron linear accelerator ELBE of the Forschungszentrum Rossendorf, Dresden, Germany, provides an optical laboratory which is suitable for spectroscopic investigations in actinide research. For the first time a great number of actinide elements which are currently in the focus of scientific work in the field of radioecology can now be investigated with laser spectroscopic techniques using infrared FEL radiation. The facility is also open for external users. In this work we present our first results of vibrational spectroscopic experiments for the identification of actinide molecule complexes by Photothermal Beam Deflection (PTBD) spectroscopy using an FEL as a coherent pulsed pump source which can be tuned throughout a broad wavelength range of interest. We demonstrate that reliable absorption spectra of test samples containing uranyl and neptunyl compounds can be obtained which was verified by conventional FT-IR spectroscopy. A prominent feature of photothermal techniques is the capability of detection of low absorptions. Therefore we tried to evaluate the minimum content of actinide ions which can still be detected by our setup of the vibrational PTBD spectroscopic experiment. It was found that the limit is obviously given by the background absorption of the hygroscopic KBr matrix of the samples which is originated by residual water. Furthermore, we present an overview about the technical equipment of the laboratory.
-
Journal of Nuclear Materials 366(2007)1-2, 248-255
DOI: 10.1016/j.jnucmat.2007.01.242
ISSN: 0022-3115
Permalink: https://www.hzdr.de/publications/Publ-8923
Identification of fluorescent U(V) and U(VI) microparticles in a multispecies biofilm by confocal laser scanning microscopy and fluorescence spectroscopy
Großmann, K.; Arnold, T.; Krawczyk-Bärsch, E.; Diessner, S.; Wobus, A.; Bernhard, G.; Krawitz, R.
Abstract
Fluorescent uranium(V) and uranium(VI) particles were observed for the first time in vivo by a combined laser fluorescence spectroscopy and confocal laser scanning microscopy approach in a 43 µm thick living multispecies biofilm grown on biotite plates. These particles differ between 1-7 µm in diameter and were located at the bottom of the biofilm in the boundary region of high and low bacterial density. Laser fluorescence spectroscopy was used to identify these particles. The particles showed either a characteristic fluorescence spectrum in the wavelength range of 415 to 475 nm, indicative for uranium(V), or in the range of 480 to 560 nm, which is typical for uranium(VI). Particles of uranium(V) as well as uranium(VI) were simultaneously observed in the biofilm. These uranium particles were attributed for uranium(VI) to biologically mediated precipitation and for uranium(V) to redox processes taking place within the biofilm. The detection of uranium(V) in a multispecies biofilm was interpreted as a short-lived intermediate of the uranium(VI) to uranium(IV) redox reaction. Its presence clearly documents that the uranium(VI) reduction is not a two electron step but that only one electron was involved.
- Environmental Science & Technology 41(2007)18, 6498-6504
Permalink: https://www.hzdr.de/publications/Publ-8922
Materials for Tomorrow
Gemming, S.; Schreiber, M.; Suck, J.-B.; (Editors)
Abstract
Material science has taken a key position for new technical developments, and is therefore strongly supported by industry and governments. It has nowadays a position between physics, chemistry and engineering and extends from basic science in physics and chemistry on atomic scale to large scale applications in industry. An increasing number of material science study courses at
universities underlines the present and future importance of understanding and developing materials for the future. Looking at
the industry with one of the fastest development at present, the communication industry, it is obvious that a large part of the actual research for future materials is devoted to the understanding of materials to be used in devises developed on the nanometer (nm) scale.
The contributions to this book grew out of the lectures given at the Heraeus Ferien Kurs on materials for today, tomorrow and beyond, held at the University of Technology Chemnitz in October 2004. As the lectures were given to students of different origin (physics, chemistry, material science), the articles not only contain our todays knowledge in each of the fields, but make reference also to basic facts needed for their understanding. Thus the articles combine a presentation of the present research in the field with some basis information on a text book level; they bridge the gap between specialized reviews and study books. In addition, lectures on material simulation, a very fast advancing discipline, are combined with lectures on experimental research in material science, and the techniques used in both of these disciplines.
Keywords: materials design; materials modelling; measuring materials properties
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Book (Editorship)
Berlin - Heidelberg - New York: Springer, 2007
212 Seiten
ISBN: 978-3-540-47970-3
Permalink: https://www.hzdr.de/publications/Publ-8921
Simulation of Inorganic Nanotubes
Enyashin, A. N.; Gemming, S.; Seifert, G.
Abstract
Motivated by the high application potential of carbon nanotubes, the search for other quasi one-dimensional nanostructures has been pursued both by theoretical and experimental approaches. The investigations soon concentrated on layered inorganic materials, which may be exfoliated and rolled up to tubular and scroll-type forms. The present chapter reviews the basic design principles, which govern the search for novel inorganic nanostructures on the basis of energy- and strain-related stability criteria.
These principles are then applied to the prediction and characterisation of the properties of non-carbon, elemental and binary nanotubes derived from layered boride, nitride, and sulfide bulk phases. Finally, the present chapter introduces examples, where one-dimensional nanostructures such as tubes and scrolls have successfully been constructed from non-layered materials, especially from oxides. Examples for the experimental verification of the predicted structures are given throughout the discussion and impressively underline the predictive power of today's materials modelling.
Keywords: nanostructures; quantum-mechanical methods; materials design; nanotubes
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Contribution to external collection
Sibylle Gemming, Michael Schreiber, Jens-Boie Suck: Materials for Tomorrow, Berlin - Heidelberg - New York: Springer, 2007, 978-3-540-47970-3, 33-57
Permalink: https://www.hzdr.de/publications/Publ-8920
Theoretical Investigation of Interfaces
Gemming, S.; Schreiber, M.
Abstract
The proper treatment of defects is one of the major tasks in materials design, because defects are responsible for the either desirable or detrimental deviations between the characteristics of the material to be tuned and the well-known properties of an ideal crystal. Microelectronic devices work because of clever point defect engineering, line defects govern plastic deformation processes, and interfaces determine the mechanical stability of composite materials. Especially interfaces gain importance with the current trend towards nanoscale materials; first, the surface-to-volume ratio is strongly increased in nanocrystalline material, and, second, stable arrangements of point or line defects require a minimum crystallite size, which can be larger than the actual nanocrystallites. Thus, the present chapter gives an introduction into the most common approaches for modeling interface properties. We introduce the basic concepts of interface symmetry, structure and analysis with a strong focus on the theoretical methods and give an overview of currently available techniques for the modeling and simulation of the interface properties at an atomic-scale level. Two fundamentally different interface types are distinguished: The discussion of the homophase boundary properties is focussed on oxide grain boundaries, which we studied extensively in comparison with amply available experimental observations. For the heterophase boundaries examples of non-reactive, reactively doped, and inherently reactive boundaries are presented. A special focus lies on the interfaces between metals and oxides where the discrepancy of the material properties across the interface is most prominent and all three bonding situations can occur: weak adhesion between inert fragments, activated adhesion upon doping, and strong adhesion.
Keywords: interface; grain boundary; numerical methods; materials desgin
-
Contribution to external collection
Sibylle Gemming, Michael Schreiber, Jens-Boie Suck: Materials for Tomorrow, Berlin - Heidelberg - New York: Springer, 2007, 978-3-540-47970-3, 91-122
Permalink: https://www.hzdr.de/publications/Publ-8919
Structural and Electronic Properties of a Mo6S8 Cluster deposited on a Au(111) Surface
Popov, I.; Gemming, S.; Seifert, G.
Abstract
Atomic and electronic properties of the Mo6S8 cluster are investigated using DFT band structure calculations with pseudopotentials and a plane-wave basis set. The calculations showed that these clusters can be well bound on the surface in a potential well with degenerate local energy minima, despite a negligible net electron transfer between the two subsystems. The cluster may move freely inside this well on the surface. The cluster-surface binding is via S-Au bonds, with additional contributions of the Mo atom in the vicinity of the surface.
Keywords: adsorption; DFT; density-functional theory; cluster; metal surface
- Physical Review B 75(2007), 245436
Permalink: https://www.hzdr.de/publications/Publ-8918
Biodistribution and catabolism of 18F-labeled N-epsilon-fructoselysine as a model of Amadori products
Hultsch, C.; Hellwig, M.; Pawelke, B.; Bergmann, R.; Rode, K.; Pietzsch, J.; Krause, R.; Henle, T.
Abstract
Amadori products are formed in the early stage of the so-called Maillard reaction between reducing sugars and amino acids or proteins. Such nonenzymatic glycosylation may occur during the heating or storage of foods, but also under physiological conditions. N-epslion-fructoselysine is formed via this reaction between the epsilon-amino group of peptide-bound lysine and glucose. Despite the fact that, in certain heated foods, up to 50% of lysyl moieties may be modified to such lysine derivatives, up to now, very little is known about the metabolic fate of alimentary administered Amadori compounds. In the present study, N-succinimidyl-4-[18F]fluorobenzoate was used to modify N-epsilon-fructoselysine at the a-amino group of the lysyl moiety. The in vitro stability of the resulting 4-[18F]fluorobenzoylated derivative was tested in different tissue homogenates. Furthermore, the 4-[18F]fluorobenzoylated N-epsilon-fructoselysine was used in positron emission tomography studies, as well as in studies concerning biodistribution and catabolism. The results show that the 4-[18F]fluorobenzoylated N-epsilon-fructoselysine is phosphorylated in vitro, as well as in vivo. This phosphorylation is caused by fructosamine 3-kinases and occurs in vivo, particularly in the kidneys. Despite the action of these enzymes, it was shown that a large part of the intravenously applied radiolabeled N-epsilon-fructoselysine was excreted nearly unchanged in the urine. Therefore, it was concluded that the predominant part of peptide-bound lysine that was fructosylated during food processing is not available for nutrition.
Keywords: N-epsilon-fructoselysine; Maillard reaction; Amadori products; Fructosamine 3-kinase; Positron emission tomography
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Nuclear Medicine and Biology 33(2006), 865-873
DOI: 10.1016/j.nucmedbio.2006.07.007
Cited 19 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8917
The Rossendorf Beamline at ESRF: An XAS Experimental Station for Actinide Research
Scheinost, A.; Hennig, C.; Funke, H.; Rossberg, A.; Bernhard, G.
Abstract
The Rossendorf Beamline with its X-ray absorption spectroscopy (XAS) station dedicated to actinide research was the first of its kind at a European synchrotron. Since its opening in 1999, it serves for about 30 experiments each year. An overview on the current status of operation modes, the technical details and on access conditions is presented.
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Contribution to proceedings
Actinide XAS 2006, 18.-20.09.2006, Karlsruhe, Germany
Speciation Techniques and Facilities for Radioactive Materials at Synchrotron Light Sources: OECD, 978-92-64-99006-7, 141-149
Permalink: https://www.hzdr.de/publications/Publ-8916
SANS investigation of neutron-irradiated pressure vessel steels and model alloys
Bergner, F.; Ulbricht, A.
Abstract
Application of small angle neutron scattering to RPV steels had to be reconsidered, when it was discovered by Atom Probe investigations that irradiation-induced clusters in RPV steels do contain Fe. It was no longer justified in general to determine the total volume fraction of clusters, as long as the magnetic moment of the Fe atoms inside the clusters is not known for sure. The aim of the talk is to compile ways out from this dilemma. The first part is devoted to selected SANS results obtained assuming non-magnetic clusters. The second part is a compilation of 5 ways to solve the questions that arise, if this assumption is not justified. In the third part it will be analyzed, which conclusions remain valid and which have to be modified. If the magnetic character of scatterers is not known in advance, SANS and 3DAP can be combined synergistically: 3DAP yields cluster composition, but sensitivity to vacancies is low. SANS (A-ratio) is particularly sensitive to the vacancy fraction.
Keywords: SANS; RPV steel
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Invited lecture (Conferences)
13th Meeting of the International Group on Radiation Damage Mechanisms in Pressure Vessel Steels (IGRDM 13), 16.-20.10.2006, Tsukuba, Japan -
Contribution to proceedings
13th Meeting of the International Group on Radiation Damage Mechanisms in Pressure Vessel Steels (IGRDM 13), 16.-20.10.2006, Tsukuba, Japan
Proceedings of IGRDM 13
Permalink: https://www.hzdr.de/publications/Publ-8915
Proteomic Insights into Metabolic Adaptations in Alcanivorax borkumensis Induced by Alkane Utilization
Sabirova, J.; Ferrer, M.; Regenhardt, D.; Timmis, K.; Golyshin, P.
Abstract
Alcanivorax borkumensis is a ubiquitous marine petroleum oil-degrading bacterium with an unusual physiology specialized for alkane metabolism. This hydrocarbonoclastic bacterium degrades an exceptionally broad range of alkane hydrocarbons but few other substrates. The proteomic analysis presented here reveals metabolic features of the hydrocarbonoclastic lifestyle. Specifically, hexadecane-grown and pyruvate-grown cells differed in the expression of 97 cytoplasmic and membrane-associated proteins whose genes appeared to be components of 46 putative operon structures. Membrane proteins up-regulated in alkane-grown cells included three enzyme systems able to convert alkanes via terminal oxidation to fatty acids, namely, enzymes encoded by the well-known alkB1 gene cluster and two new alkane hydroxylating systems, a P450 cytochrome monooxygenase and a putative flavin-binding monooxygenase, and enzymes mediating -oxidation of fatty acids. Cytoplasmic proteins up-regulated in hexadecane-grown cells reflect a central metabolism based on a fatty acid diet, namely, enzymes of the glyoxylate bypass and of the gluconeogenesis pathway, able to provide key metabolic intermediates, like phosphoenolpyruvate, from fatty acids. They also include enzymes for synthesis of riboflavin and of unsaturated fatty acids and cardiolipin, which presumably reflect membrane restructuring required for membranes to adapt to perturbations induced by the massive influx of alkane oxidation enzymes. Ancillary functions up-regulated included the lipoprotein releasing system (Lol), presumably associated with biosurfactant release, and polyhydroxyalkanoate synthesis enzymes associated with carbon storage under conditions of carbon surfeit. The existence of three different alkane-oxidizing systems is consistent with the broad range of oil hydrocarbons degraded by A. borkumensis and its ecological success in oil-contaminated marine habitats.
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Journal of Bacteriology 188(2006)11, 3763-3773
DOI: 10.1128/JB.00072-06
Cited 112 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8914
Genome sequence of the ubiquitous hydrocarbon-degrading marine bacterium Alcanivorax borkumensis
Schneiker, S.; Martins Dos Santos, V.; Bartels, D.; Bekel, T.; Brecht, M.; Buhrmester, J.; Chernikova, T.; Denaro, R.; Ferrer, M.; Gertler, C.; Regenhardt, D.
Abstract
AAlcanivorax borkumensis is a cosmopolitan marine bacterium that uses oil hydrocarbons as its exclusive source of carbon and energy. Although barely detectable in unpolluted environments, A. borkumensis becomes the dominant microbe in oil-polluted waters. A. borkumensis SK2 has a streamlined genome with a paucity of mobile genetic elements and energy generationrelated genes, but with a plethora of genes accounting for its wide hydrocarbon substrate range and efficient oil-degradation capabilities. The genome further specifies systems for scavenging of nutrients, particularly organic and inorganic nitrogen and oligo-elements, biofilm formation at the oil-water interface, biosurfactant production and niche-specific stress responses. The unique combination of these features provides A. borkumensis SK2 with a competitive edge in oil-polluted environments. This genome sequence provides the basis for the future design of strategies to mitigate the ecological damage caused by oil spills.
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Nature Biotechnology 24(2006)8, 997-1004
DOI: 10.1038/nbt1232
Cited 354 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-8913
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