Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The core baffle of a PWR is loaded by the pressure difference between bypass and core and by temperature profiles developing from gamma and neutron heating and heat transfer into the coolant. Strain, deformation and gaps between the sheets resulting from this load are determined considering the effect of neutron irradiation induced creep of the core baf-fle bolts. The finite element code ANSYS is applied for the thermal and mechanical analyses. The FE-model comprises a complete 45° sector of the core baffle structure in-cluding the core barrel, the formers, the core baffle sheets and about 230 bolt connections with non-linear contact between the single components and the effect of friction. The com-plete analysis requires three major steps:

1. Evaluation of the three dimensional distribution of neutron flux and gamma in-duced internal heating with the Monte Carlo code MCNP®. These calculations are based on pin wise power distributions at the core edge for typical loading patterns.
2. Calculation of the temperature distribution in the core baffle for different opera-tional conditions and core loading patterns, considering heat conduction in the components with internal heat sources and convectional boundary conditions (heat transfer coefficients and bulk temperature of the coolant).
3. Calculation of time dependent deformation, stresses and strains taking into account weight, pressure loads, temperature fields for different load situations, prestressing, irradiation induced creep of the bolts as correlated to neutron flux.
The results show the equalizing effect of redistribution of bolt loads from high flux to lower flux exposure locations in a self controlled process, keeping the mechanical and geometrical stability of the core baffle structure and leaving the gaps between sheet edges unaffected.

In the paper the experiences of more than 30 years operation and development at the electrostatic accelerators at the Forschungszentrum Rossendorf, Dresden/Germany are summarized and focused on the necessary equipment for beam diagnostics at electrostatic accelerators, especially for measurement and monitoring of the current, position, stability and profile of the ion beam.

The paper provides an overview of the advantages and problems of superconducting RF guns. The results of the Rossendorf experiments are presented here. These results are integrated in the design of a new 3.4 cell superconducting RF gun. The beam parameters of this gun correspond to the demands of the new generation of high current, high brightness injectors.

kein Abstract

The pair correlations in mesoscopic systems such as nanometer-size superconducting clusters and nuclei are studied at a finite temperature for the canonical ensemble of fermions in model spaces with a fixed particle number: (i) a degenerate spherical shell (strong-coupling limit), (ii) an equidistantly spaced deformed shell (weak-coupling limit). It is shown that after the destruction of the pair correlations at T = 0 by a strong magnetic field or rapid rotation, heating can bring them back. This phenomenon is a consequence of the fixed number of fermions in the canonical ensemble.

The cranked relativistic Hartree-Bogoliubov theory has been applied for a systematic study of the nuclei around ²⁵⁴No, the heaviest element for which detailed spectroscopic data are available. The deformation, rotational response, pairing correlations, quasiparticle, and other properties of these nuclei have been studied with different parametrizations for the effective mean-field Lagrangian. Pairing correlations are taken into account by a finite range two-body force of Gogny type. While the deformation properties are well reproduced, the calculations reveal some deficiencies of the effective forces both in the particle-hole and particle-particle channels. For the first time, the quasiparticle spectra of odd deformed nuclei have been calculated in a fully self-consistent way within the framework of the relativistic mean field (RMF) theory. The energies of the spherical subshells, from which active deformed states of these nuclei emerge, are described with an accuracy better than 0.5 MeV for most of the subshells with the NL1 and NL3 parametrizations. However, for a few subshells the discrepancies reach 0.7¿1.0 MeV. In very heavy systems, where the level density is high, this level of accuracy is not sufficient for reliable predictions of the location of relatively small deformed shell gaps. The calculated moments of inertia reveal only small sensitivity to the RMF parametrization and, thus, to differences in the single-particle structure. However, in contrast to lighter systems, it is necessary to decrease the strength of the D1S Gogny force in the pairing channel in order to reproduce the moments of inertia.

kein Abstract

kein Abstract

kein Abstract

kein Abstract

kein Abstract

kein Abstract

kein Abstract

kein Abstract

kein Abstract

kein Abstract

kein Abstract

kein Abstract

kein Abstract

kein Abstract

kein Abstract

kein Abstract

kein Abstract

Das Antiphospholipidsyndrom (APS), mit den typischen klinischen Manifestationen von rezidivierenden Thrombosen und Aborten, wird laborchemisch durch das Vorkommen von Antiphospholipidantikörpern (aPL) definiert. Das Krankheitsbild gewinnt in letzter Zeit als mögliches Bindeglied zwischen Autoimmunität und Atherosklerose zunehmend an Bedeutung. Sowohl aPL, als auch oxidierten low-density Lipoproteinen (oxLDL) und deren Antikörpern (Anti-oxLDL) wird eine pathogenetische Bedeutung in der Atherogenese zugesprochen. In unserer Studie verglichen wir die Serumspiegel von oxLDL und AntioxLDL bei APS-Patienten (20 Patienten primäres/14 sekundäres APS) und nonAPS-Patienten (24 phänotypisch gesunde Kontrollpersonen und 12 Patienten mit Systemischem Lupus erythematodes/ SLE/) und untersuchten Assoziationen dieser Parameter zur Intima-Media-Dicke (IMT), einem klinischen Surrogatparameter der Atherosklerose.
SLE-Patienten mit und ohne APS wiesen signifikant erhöhte Anti-oxLDL-Spiegel im Vergleich zur Kontrollgruppe auf (p = 0,038 bzw. p = 0,007). Dahingegen unterschieden sich die oxLDL-Konzentrationen nicht signifikant bei Kontrollen und Patienten. DieAntioxLDL- Spiegel korrelierten signifikant mit Anticardiolipin- (p = 0,002) und 2-Glykoprotein-IAntikörpern (p < 0,048), jeweils vomIgG-Isotyp. Nur SLE-Patienten ohne APS wiesen eine signifikant erhöhte Produktion reaktiver Sauerstoffspezies (ROS) als Zeichen eines proatherogenen oxidativen Stresses in der Zirkulation auf (p < 0,002). Sowohl die zirkulierenden oxLDL- als auch die AntioxLDL- Spiegel wiesen keine Assoziation zur Atherosklerose, gemessen an der IMT, bei den Patientengruppen auf. Zusammenfassend ergibt sich aus unseren experimentellen Daten kein Hinweis darauf, dass bei APS-Patienten eine durch oxidativen Stress beschleunigte Atherosklerose auftritt.

Adhesion of phagocytes to endothelial cells constitutes a crucial step in atherogenesis. Oxidized low density lipoproteins (LDL) are supposed to facilitate the adhesion process. We investigated the molecular mechanisms by which mildly and extensively hypochlorite-oxidized LDL force adhesion of murine macrophages and human neutrophils to human umbilical venous endothelial cells. After 1 h of co-incubation of macrophages, endothelial cells, and lipoproteins adhesion significantly increased to 160 ± 13 % (S.E.M., n=5) in the presence of mildly oxidized lipoprotein, and 210 ± 11 % (S.E.M., n=5) in the presence of extensively oxidized lipoprotein. Similar results were obtained with neutrophils. CD36 antibody (FA6-152) significantly reduced adhesion to 102 ± 7 % (S.E.M., n=5) using mildly oxidized low density lipoprotein and to 179 ± 16 % (S.E.M., n=5) using extensively oxidized low density lipoprotein. Native high density lipoprotein and to a lesser extent methionine-oxidized high density lipoprotein significantly counteracted the effects of low density lipoprotein. Prior incubation of endothelial cells with modified lipoproteins followed by their removal and subsequent incubation with macrophages or neutrophils resulted in only minor changes of adhesion. This suggests that the direct contact of low density lipoprotein with phagocytes followed by activation of a respiratory burst with release of reactive oxygen species facilitates the adhesion process. Accordingly, the addition of antioxidants (superoxide dismutase and catalase) to the co-incubation medium was followed by a significant decrease in phagocyte adhesion. It is concluded that oxidized low density lipoprotein-induced respiratory burst activation of phagocytes with subsequent release of oxidants constitutes a crucial step in promoting the adhesion of phagocytes to endothelial cells.

Hypochlorite-oxidized low-density lipoprotein (oxLDL) possesses a substantial proinflammatory potential by modulating respiratory burst activities of polymorphonuclear neutrophils (PMN). As evaluated by luminol-amplified chemiluminescence (CL) incubation of 10⁶ PMN/ml with 70 nM oxLDL was followed by substantial induction of neutrophil oxidant (ROS) generation. We evaluated the inhibitory capacity of high-density lipoprotein (HDL) and its lipid and protein constituents against the activating effects of oxLDL. At a HDL or apolipoprotein AI/LDL protein ratio of 1.0, native HDL decreased the respiratory burst activation by 64 %, followed by trypsinized HDL (57 %) and native apoAI (43 %). The inhibitory effects of native HDL did not require prior incubation with PMN or with oxLDL suggesting an instantaneously acting protective mechanism in the minute range. OxLDL modulated ROS production not only of resting PMN but also that of activated PMN, as indicated by a 14-fold increase in FMLP-stimulated CL response and a 50 % decreased in zymosan-mediated CL answer. HDL itself did not protect PMN from activation by FMLP and zymosan. However, it clearly reduced effects of oxLDL on FMLP-activation and slightly counteracted the oxLDL-mediated decrease in zymosan-induced ROS generation. Taken together, these findings may offer new insight into atheroprotective mechanisms of HDL.

Oxidative modification of proteins can interfere with critical cellular functions, and is widely regarded as a crucial event in the pathogenesis of various diseases ranging from rheumatoid arthritis to atherosclerosis and cancer. In this line, a new GC-MS methodology using N(O)-ethoxycarbonyl trifluoroethyl amino acid esters (ECEE-F-3) for rapid and sensitive determination of 3-chlorotyrosine, 5-hydroxy-2-aminovaleric acid (HAVA), and 6-hydroxy-2-aminocaproic acid (HACA) in proteins has been developed. 3-Chlorotyrosine is a highly specific marker of myeloperoxidase catalyzed protein oxidation, whereas gamma-glutamyl semialdehyde (gammaGSA) and alpha-aminoadipyl semialdehyde (alphaASA), which by reduction form HAVA and HACA, respectively, are specifically formed by metal catalyzed oxidation processes. ECEE-F3 derivatives are formed by the unlabored reaction of amino acids with ethylchloroformate plus trifluoroethanol plus pyridine. The key steps of the methodology employed are (i) enzymatic hydrolysis of target proteins to prevent decomposition of oxidation products during hydrolysis and (ii) an uniquely rapid derivatization of amino acids completing sample preparation for GC within a few minutes in aqueous solution at room temperature. The use of these stable products of protein amino acid side chain oxidation as potential markers for assessing oxidative damage in LDL apoB-100 recovered from human aortic vascular lesions is demonstrated. These observations provide quantitative chemical evidence for metal catalyzed oxidative processes in the human artery wall.

Summary. An alteration of low density lipoprotein (LDL) apolipoprotein (apo) B-100 structure by direct oxidative modification is an important mechanism involved in atherogenesis. There is difficulty in quantifying this type of modification because a lack of specific assays. The use of N(O,S)-ethoxycarbonyl trifluoroethyl amino acid esters for a rapid and sensitive determination of 6-hydroxy-2-aminocaproic acid (HACA), a highly specific marker of metal catalyzed protein oxidation, by using standard gas chromatography/electron impact mass spectrometry, is discussed. The derivatives are formed by the unlabored reaction of amino acids with ethylchloroformate plus trifluoroethanol plus pyridine. Femtomole levels of HACA can be reproducible measured in different LDL preparations subjected to oxidative damage in the presence of iron or copper. HACA determination compares well with the measurement of carbonyl groups that are generally accepted as a nonspecific index of protein oxidation. Thus, the method could prove to be a sensitive assay for studying specific apoB-100 modification.

Oxidative modification of low density lipoprotein (LDL) is regarded as a crucial event in athergenesis. Data concerning the role of circulating oxidized LDL (oxLDL) in the development of atherosclerosis are scarce. One reason for this is the shortage of methaods for direct assessment of metabolism of oxLDL in vivo. We reprot an improved methodology for labelling of both native LDL (nLDL) and oxLDL with fluorine-18 (¹⁸F) by N-succinimidyl 4-[¹⁸F]fluorobenzoate ([¹⁸F]SFB) and the use of LDL-[¹⁸]FB-conjugates in dynamic PET studies in Wistar rats. For labelling experiments, pools of chemically well characterized human nLDL and oxLDL, respectively, were used. Preparation of [¹⁸F]SFB was achieved within 40 min with radiochemical yields of 50±5% and purity of >95% using O-(N-succinimidyl)-N-N,N´,N´-tetramethyluronium tetrafluoroborate (TSTU) as activating reagent. LDL labelling with [¹⁸F]SFB resulted in radiochemical yields of 30±10%. The method was evaluated with respect to uptake of FB-conjugated nLDL in HepG2 cells and of FB-conjugated oxLDL in primary human macrophages, respectively. Biodistribution studies revealed high in vivo stability for the LDL-[¹⁸F]FB conjugates. The metabolic fate of LDL-[¹⁸F]FB conjugates in vivo was delineated by PET using a dedicated small animal tomograph (microPET; spatial resolution of 2 mm). In conclusion, [¹⁸F]SFB-labelling of LDL and the use of PET provide a valuable tool for assessment of metabolism of nLDL and oxLDL in vivo.

We consider the flow of an electrically conducting fluid around a sphere with some internal source of alternating magnetic field. The resulting electromagnetic forces of this inductive scheme lead to a thrust of the sphere and a changed drag coefficient which balance each other in the self-moved regime. Allowing for a free choice of physically meaningful field distributions, the inverse problem is addressed of looking for such magnetic fields which result in a low drag. Without claiming to have found a global minimum, we present some examples of electromagnetic forces providing strong reductions of the sphere drag. Numerical results up to Re=1000 are given, the corresponding modifications of surface pressure and vorticity are discussed. The energetic balance is not yet analysed as it requires to consider the coupled hydrodynamic and electromagnetic problems.

The flow of electrically conducting fluids can be controlled by electromagnetic forces. Whereas this concept is already in industrial use in metallurgical or crystal growth technologies, its application to flows of electrolytes is less developed yet. For seawater flows around ship components, flow separation is an important phenomenon limiting the operation of, e.g., rudders or stabilizing foils. We present experimental and numerical results on the prevention of flow separation by means of a stream-wise, wall parallel Lorentz force acting on the suction side of inclined flat plates and hydrofoils. The use of steady as well as oscillatory Lorentz forces is considered. The results for oscillating Lorentz forces will be compared to recent literature results for periodic suction/blowing. Scaling relations for an extrapolation to application relevant Reynolds numbers will be given, and the related energy consumption will be analysed.

Superconducting radio frequency photoelectron injectors open the way to low-emittance electron beams in continuous-wave operation mode. Their progress is essential for future projects of high-power free electron lasers, energy recovery linacs and next generation light sources. In this presentation, the technical issues associated with the design, construction and operation of SRF photo-injectors will be reviewed together with the progress in several laboratories during the past few years. Results of the operation of the Rossendorf SRF photo-injector with an 1.3 GHz niobium half cell and the future projects are discussed in detail.

The Mariko code, based on the method of characteristics, has been used to calculate several two-dimensional full core heterogeneous 23-group transport theory solutions for hot zero power states of the WWER-1000 reactor. The initial loading for the three-year fuel cycle is considered. Helios-1.5 has been used to prepare 23-group cross-section data. The benchmarks differ by the positions (up or down) of the control rods groups. The asymptotic assembly-averaged and cell-averaged two-group diffusion parameters for all assembly types, the group-to-group albedos on the radial reflector boundary, and the effective diffusion parameters, including reference discontinuity factors, for the radial reflector nodes are all calculated by Mariko. The accuracy of the SPPS-1.6 and DYN3D nodal diffusion codes and the HEX2DA/B pin-by-pin diffusion codes have been tested. The benchmark with all control rods down poses a great problem for the nodal diffusion codes, the maximum error in the relative assembly-wise power distribution reaching 18% for SPPS-1.6. The pin-by-pin codes perform well in all cases.

A new library of two-group diffusion and kinetics parameters has been generated for the neutron kinetics code DYN3D, intended for analysis of reactivity initiated accidents for the WWER-1000 reactors. All assembly types for the 3-year fuel cycle are included. The Helios-1.5 code and its adapted 190-group library have been used at the stage of the lattice calculations. A generalised code for preparation of Helios input for both types of WWER reactors has been developed. The approximation methodology is based on a combination between interpolation over the moderator temperature and density, and approximation over the rest of the independent state parameters. High accuracy is achieved by applying square interpolation over the moderator temperature and cubical interpolation over the moderator density. The axial/radial reflectors are described by effective diffusion parameters, including reference discontinuity factors, calculated on the base of one/two-dimensional heterogeneous 23-group transport theory solutions by Mariko. DYN3D has been modified in order to use the new library. BIPR-7 results, used for operational neutronics calculations of the WWER-1000 reactors at the Kozloduy NPP, have been used to validate the new library. The kinetics parameters have been validated as well.

The VALCO project aims at the improvement of the validation of coupled neutron-kinetics / thermal-hydraulics codes for VVER reactors. VALCO was started on January 1, 2002 and will be completed December 31, 2003. The project is split into three Work Packages.

In Work Package 1, lead by VTT, the existing data base, containing measured VVER transient data from the former EU Phare project SRR1/95, has been extended by five new transients. Two of these transients were used for the validation of different coupled codes suitable for VVER. The comparison between the codes and the validation against the measurements was successful. The obtained deviations from the experimental data are well understood and mostly caused by missing information about the operational regime during the transient.

A comprehensive uncertainty analysis for the two SRR1/95 transients, one for each a VVER-440 and a VVER-1000, has been carried out in Work Package 2 under the leadership of GRS. An essential result of the analysis is the identification of the input parameters, such as the secondary-circuit pressure, the control-assembly position (as a function of time), and the control-assembly efficiency, that most sensitively affect the safety-relevant output parameters.

In Work Package 3, lead by FZR, stand-alone three-dimensional neutronics codes have been validated against measurements in the Russian V-1000 zero power test facility. After correcting the geometrical input data, a good agreement between calculated and measured steady-state power distributions could be achieved, both for assembly-averaged powers and pin powers. The real time behavior of local power measured during transients is well modeled by the reactor-dynamic codes.

Oxidation of LDL and lipids by transition metal catalyzed processes is a key factor in atherogenesis. Clinical and experimental evidence suggests that these processes involve binding of hemin, a product of hemoglobin degradation, to descrete binding sites of LDL thus forming centers for redox cycling and repeated radical production. The mechanisms for these observations remain unclear. In the present study, we found that hemin binds rapidly to low density lipoprotein subfractions (LDL1, 1.019-1.044 kg/L; LDL2, 1.044-1.063 kg/L) with binding rates in the nM range. Spectrosphotometric and fluorescence experinemts indicated that the amphiphilic hemin molecule is buried in the lipoprotein surface monolayer with the carboxylic groups in contact with positively charged surface regions. In vitro, in the presence of H2O2, hemin oxidizes both LDL1 and LDL2 with formation of specific products of oxidation of positively charged protein amino acid residues (gamma-glutamyl semialdehyde and alpha-aminoadipic semialdehyde) and phospholipids (1-palmitoyl-2-oxovaleroyl-sn-glycero-3-phosphorylcholine). The formation of these products was more than twofold higher (p<0.01) when compared with oxidation systems containing free iron or copper. Hemin catalyzed LDL oxidation was inhibited by the iron-chelating agents 1,2-Dimethyl-3-hydroxypyrid-4-one and N,N-bis(2-hydroxybenzyl)ethylenediamine-N,N-diacetic acid, respectively. In vivo, a significantly increased formation of all three specific oxidation products could be confirmed in circulating plasma LDL1 and LDL2 particles obtained from patients with impaired glucose tolerance (p<0.05), Type 2 diabetes mellitus (p<0.05), and rheumatoid arthritis (p<0.01) when compared with healthy controls. The rsults provide further evidence on pathophysiological relevance of hemin catalyzed LDL oxidation in metabolic an inflammatory diseases.

On the basis of methods developed recently for square-fuel-assembly reactor cores, discontinuity factors for hexagonal control absorbers (VVER-440) and reflector nodes have been derived. Partial currents from heterogeneous multi-group transport calculations are used for the determination of the discontinuity factors. As shown by suitable benchmark calculations, the application of these quantities in the two-group nodal diffusion code DYN3D clearly improves the results of assembly powers and effective multiplication factors. The advantage of reflector diffusion parameters, including discontinuity factors, over conventional albedos has been demonstrated.

In the framework of the EU project VALCO, measurements at the V-1000 test facility of the Russian Research Centre ?Kurtschatov Institute? are used for the validation of three-dimensional neutronic calculations. Experimental results of steady states and kinetic experi-ments are available for comparisons with calculations. Respective DYN3D calculations have been performed by using the cross section libraries generated with the codes HELIOS, CASMO and WIMS.
Results obtained by the DYN3D code are compared with steady-state measurements for two different configurations of the V-1000 facility. Pin-power distributions measured within one fuel assembly are compared to the results of the pin power reconstruction implemented in DYN3D.
Two kinetic experiments performed in the V-1000 facility were calculated with DYN3D. Comparisons of the calculated results with the measurements at the in-core detector positions are given. The calculated fast flux of the nodes, situated near to the ionisation chambers of the two reactimeters, is compared with the detector signal. The reactivities obtained from the core-averaged flux by inverse point kinetics and the reactivity curves, provided by the reac-timeters, are presented and discussed.

Aim: Determination of the biological effect of the alpha emiter ²¹¹At on cellular level as well as the assessment of dosimetric data in a tumor model in vivo.
Methods: Transplantation of malignant ascitic cells in mice intraperitoneally and estimation of tumor characteristics (doubling time of the cells, mean survival of the animals following an i.p. applicatin of a defined tumor cell number). ²¹¹At labelled human serum albumine microspheres B-20 (MSP) of different activity were injected into tumor bearing mice intraperitoneally. The effectiveness of the therapy was evaluated by means of determination of the duration of cell cycle arrest as well as the microscopic analysis of the rate of abnormal mitotic cells due to radiation induced damage. Furthermore, dose dependence of survival was evaluated.
Results: Three days following the intraperitoneally application of 8 x 10⁶ tumor cells, 50 - 600 kBq ²¹¹At-MSP were applied into the abdominal cavity. Derived from the volume of ascites at this time and the administered activity, dese calculations were performed. An activity of 50 kBq caused a dose of 0.84 Gy. The increase of radiation induced effect on ascitic tumor cells was correlated with the dose. Between the duration of the cell cycle arrest and the administered activity, a dirctly proportional correlation was found. The mean survival of non treated animals was 16.9 ± 3.7 days. Teh prolongation of the survival was proportional to the activity administered. Using a dosage of 10 Gy, five animals out of 16 survived.
Conclusion: Therapy of malignant ascitic cells using ²¹¹At-MSP was effective in vivo. For tumor therapy, teh alpha emitter ²¹¹At represents a highly effective alternative to usually employed beta emitters.

Phase composition and properties of iron nanocrystals and clusters embended in MgO matrix

Low temperature Mössbauereffect studies of c-FeSi films synthesized by molecular beam epitaxy and by ion implantation

Das Wasser der Elbe auf der Höhe von Dresden enthält anorganische Kolloidpartikel, deren Partikelgrößenverteilung nahezu den gesamten kolloidalen Definitionsbereich (1 nm bis 1 µm) überstreicht und die vor allem aus sekundär ausgeschiedener amorpher Kieselsäure sowie aus Oxyhydroxiden des Fe, Al und Mn bestehen. Als wichtigstes Schwermetall führen sie Zn. Ihre Konzentration liegt unter 5×10^-1 mg/l, um etwa Faktor 30 unter der Konzentration der Schwebstoffe des Elbwassers (Partikel >1 µm). Wegen ihrer hohen spezifischen Oberfläche sind die Kolloidpartikel als potentielle Träger für Schadstoffe trotz dieser geringeren Massekonzentration nicht gegenüber den Schwebstoffen zu vernachlässigen. Die in der Elbe gemessene Partikelgrößenverteilung ähnelt derjenigen, die zu einem früheren Zeitpunkt im Rhein gefunden worden war. Auch die chemische Zusammensetzung der Kolloidpartikel in der Elbe ist der der Partikel des Rheins ähnlich. Die Konzentration der Kolloidpartikel in der Elbe war aber um Faktor 5 bis 10 höher als im Rhein. Grund für letzteres ist wahrscheinlich der höhere Gehalt des Elbwassers an gelöstem Kohlenstoff (DOC). Im „Bulk“ eines Flusses sind kolloidgetragene Schadstoffe - anders als schwebstoffgetragene - vermutlich fast genauso mobil wie echt gelöste. Unterschiede zwischen den Transportgeschwindigkeiten der kolloidgetragenen und der echt gelösten Spurenstoffe treten in bestimmten Situationen auf, in denen das Wasser den „Bulk“ eines Flusses verlässt (Sickerbereich unter dem Fluss, Ästuar). Es werden Schlussfolgerungen über die Rolle von Kolloidpartikeln im Ökosystem eines Flusses gezogen und noch bestehende Forschungsdesiderate benannt.

Three γ-decaying isomers in the N=Z+1 nucleus ⁹⁵Ag have been identified for the first time. The ⁹⁵Ag nuclei were produced via the ⁵⁸Ni(⁴⁰ca, p2n) reaction and separated by using the GSI on-line mass separator. The emitted γ rays were measured with a multi-Ge detector setup in anticoincidence with positrons. Three individual γ-decay cascades have been identified and assigned to ⁹⁵Ag, representing the depopulation of isomers at 344-, 2531-, and 4859- keV excitation energy with tentative spin-parity assignments of (1/2^-), (23/2⁺), and (37/2⁺), respectively. The spin and parity assignments are based on a comparison with shell-model predictions employing empirical interactions.

Several available codes for hadronic event generation and shower simulation are discussed and their predictions are compared to experimental data in order to obtain a satisfactory description of hadronic processes in Monte Carlo studies of detector systems for medium energy experiments. The most reasonable description is found for the intranuclear-cascade (INC) model of Bertini which employs microscopic description of the INC, taking into account elastic
and inelastic pion–nucleon and nucleon–nucleon scattering. The isobar model of Sternheimer and Lindenbaum is used to simulate the inelastic elementary collisions inside the nucleus via formation and decay of the D33-resonance which, however, limits the model at higher energies.
To overcome this limitation, the INC model has been extended by using the resonance model of the HADRIN code, considering all resonances in elementary collisions contributing more than 2% to the total cross-section up to kinetic energies of 5 GeV. In addition, angular distributions based on phase shift analysis are used for elastic nucleon–nucleon as well as elastic and charge exchange pion–nucleon scattering. Also kaons and antinucleons can be treated as projectiles. Good agreement with experimental data is found predominantly for lower projectile energies, i.e. in the regime of the Bertini code.

The production and propagation of kaons and antikaons in relativistic heavy-ion collisions have been systematically investigated with the Kaon spectrometer at SIS/GSI. Experimental results on the K⁺ and K^- yiels and on the azimuthal emission pattern of K⁺ mesons are presented. Within the framework of transport models the data can be explained assuming in-medium kaon-nucleon potentials. The comparison of K⁺production excitation functions obtained for Au+Au and C+C collisions with results of transport model calculations favours a soft nuclear equation-of-state.

During batch sorption experiments of heavy metals on chlorite not only sorption reactions take place, but also reactions of chemical weathering leading to mineral dissolution and the formation of secondary phases, in particular the Fe-oxy-hydroxide ferrihydrite. Despite of its minor mass, ferrihydrite plays a major role in removing aqueous uranium(VI) from solution, because of its large specific surface area which it introduces into the system. To accurately model the sorption and transport on or through geological materials it is necessary to precisely determine the mass of the newly-formed Fe-phase. As the relative mass of the ferrihydrite within the geological matrix was too small, it proved impossible to use powder X-ray diffraction or some other spectroscopic technique, e.g. Raman spectroscopy, for its identification and quantification.
Because of the ability to discriminate different sites and oxidation states of iron, Mössbauer spectroscopy was the method of choice. At first spectra of pure chlorite and pure ferrihydrite were measured. In a second step, simulated spectra were compared with spectra from powders with known chlorite/ ferrihydrite ratios. There was a good agreement between the predicted values and those obtained by the spectrum fit. Finally, the calibration spectra were used to investigate real geological material and to estimate the fraction of the secondary Fe-phase, which has formed during the sorption experiments. Changes of less than 2 % (absolute) could be detected. It should be noted that there is a strong overlap between the different subspectra and that a good counting statistics is required.

Homogenous wear resistant carbon coatings with an optical gap of 3 eV but low stress are needed to increase the storage density in optical storage disks in order to reach 100 GB in 12 cm diameter disks. Here, a-C:H films are deposited at room temperature using a large area Electron Cyclotron Wave Resonance (ECWR) plasma beam source of 14.2" diameter. Methane is used as the precursor. The ion flux and energy, plasma pressure, distance between the extraction grid and the surface were varied. The films are characterized in terms of hydrogen content, stress, optical gap, refractive index, wear resistance, surface roughness, and homogeneity by a variety of characterization techniques. Resonant Raman spectroscopy is used in order to non-destructively monitor the disk quality. We show how it is possible to produce homogenous, wear resistant a-C:H coatings with an optical gap of 3 eV and low stress (<500 MPa), without damaging the plastic disks.

Implantation of nitrogen ions into stainless steel in combination with oxidation often results in a decrease or even complete removal of the chromium in the nitrogen containing outermost surface layer. While iron nitrides can be formed easily by this method, due to the absence of chromium, the formation of chromium nitrides is impossible and the beneficial influence of chromium in the steel for corrosion resistance cannot be used. To overcome this problem we use the following hybrid technique. A thin chromium layer is deposited on steel and subsequently implanted with nitrogen ions. Chromium can be implanted by recoil into the steel surface and thus the formation of iron/chromium nitrides should be possible. Both beam line ion implantation and plasma immersion ion implantation are used. Due to the variation of the process parameters, different implantation profiles and different compounds are produced. The produced layers are characterized by Auger electron spectroscopy, conversion electron Mössbauer spectroscopy and X-ray diffraction. The obtained results show that due to the variation of the implantation parameters, the formation of iron/chromium nitrides can be achieved and that plasma immersion ion implantation is the most suitable technique for the enrichment of chromium in the outermost surface layer of the steel when compared to the beam line implantation.

no abstract delivered from author

Thin buried layers of titanium oxides have received great attention due to their possible use for optoelectronic components and as a diffusion barrier in semiconductor technology. Ion implantation is a very versa-tile method to produce such buried layers whereas the physical properties of the oxide in the host matrix can be tailored by the variation of e.g. the implan-tation temperature and/or the fluence. The structure and phase transformation in such buried im-plan-ted layers were not investigated in details up to now.
The contribution reports an investigation of buried layers fabricated by means of high-fluence (10 17…10 18 cm-2) oxygen ion implantation into titanium. The implantation was performed at an energy of 200 or 450 keV, leading to a buried implanted profile in a depth of 270 nm or 600 nm, respectively.
The structure of the buried layers was examined by different X-ray diffraction (XRD) techni-ques at a standard diffractometer and with synchrotron radia-tion at the Rossendorf Beamline at ESRF. The elemental composition of the implanted samples was studied by Auger electron spectroscopy. The microstructural properties of modified near-surface titanium and oxygen buried layers were investigated as a function of the ion energy, the fluence and the influence of post-annealing treatment. Structural changes in the titanium lattice due to an increase of oxygen content and formation of Ti3O (or Ti6O) (with oxygen content up to 30 at.%) were found. Depending on the implantation fluence a phase transition process in the buried layers of a-Ti - Ti3O (or Ti6O) - TiO was detected.

The superelastic titanium-nickel alloy NiTi is already in use in medical applications as vascular stents and for osteosynthetic devices mainly in craniosurgery. However there are still concerns because of the high nickel content and a possible release of nickel ions, where toxicity, carcinogenicity and allergic hazards are well documented.
Bone forming cells were grown on NiTi from two suppliers, titanium, pure nickel and stainless steel. The cell adherence and the organisation of the actin cytoskeleton was severely disturbed both on the NiTi of one supplier and on pure nickel, compared with the reference material. These changes did not exist on the other NiTi preparation, the effect also could not be reproduced by nickel ions in solution. This indicates that by different preparation of the material and different surface treatment of the material its biocompatibility can be improved.
Ion implantation of Ar+ and N+ ions in NiTi with energy of 20-40 keV and fluences of (3-5)x10 17 cm-2 by means of plasma immersion ion implantation with the intention to perform preferential sputtering of Ni and to seal the surface with a TiN layer. The near surface layer was analysed by grazing incidence X-ray diffraction analysis (GIXRD), Auger electron spectroscopy (AES), scanning electron microscopy (SEM).
The surface morphology, microstructural properties, phase composition, elemental depth distribution of NiTi after implantation and an analysis of the biocompatibility of these surfaces will be shown.

Experimental data related to fragment production in central Au on Au collisions were analysed in the framework of a modified statistical model which considers cluster production both prior and at the equilibrated stage. The analysis provides limits to the number of nubleons and to the temperature of the equilibrated source. The rather moderate temperatures obtained from experimental double-yield ratios of d, t, ³He and ⁴He are in agreement with the model calculations. A phenomenological relation was established between the collective flow and the chemical temperature in these reactions. It is shown that dynamical mechanisms of fragment production, e.g. coalescence, dominate at high energies. It is demonstrated that coalescence may be consistent with chemical equilibrium between the produced fragments. The different meaning of chemical and kinetic temperatures is discussed.

The temporal evolution of the morphology of GaSb surfaces induced by ion bombardment is investigated.
The erosion process with normal incident argon ions forms a regular dot pattern that shows an increase of
ordering among the dots with increasing sputtering time. The pattern stabilizes to a highly uniform, hexagonally
ordered dot pattern for very long times. The degree of ordering is determined by quantitative analysis of
the surface roughness and the power spectral density of the surface pattern using atomic force microscopy. A
comparison of the experimental results with numerical integrations of the unstabilized Kuramoto-Sivashinsky
equation shows that this equation cannot reproduce essential details of the experimental pattern observed.

At the Forschungszentrum Rossendorf (FZR) the new facility ELBE for research with various kinds of radiation (IR from FEL´s, quasi-monochomatic channeling X-rays, bremsstrahlung in the MeV range, neutrons) is presently under construction. ELBE is centered around a superconducting Electron Linac which will produce quasi-continuous beams of high Brilliance and low Emittance. Electron beams with variable bunch charges up to 80 pC and variable repetition rates up to 260 MHz are produced in a pulsed thermionic DC gun followed by a two-stage RF bunching system. Two cryomodules each containing two 9-cell RF-cavities (1.3 Gz) accelerate the electrons t 40 MeV. At present the 250 keV injector has been installed and tested. The accelerator is planned to deliver a 20 MeV beam at the end of 2000. First results of beam parameter measurements at the 250 keV injector will be shown. Detailed transverse emittance studies by multi-slit techniques and investigations concerning the longitudinal phase space will be discussed

Temperature- and amplitude-dependent internal-friction measurements have been carried out on JRQ A533B Cl. 1 steel, in order to investigate the influence of neutron irradiation and thermal ageing on this material. Neutron irradiation decreases the internal friction maximum observed in the vicinity of 315 K; this decrease is attributed to a reduction in the dislocation mobility by copper-rich clustering. Thermal ageing (3 years, 300 °C) clearly influences the internal friction highlighting the sensitivity of the technique.
A new working model - referred to as the new interpretation, based on a linear combination of seven dislocation-related relaxations - is introduced to provide a basis from which to explain more in detail the qualitative effects of thermal ageing and irradiation.
Amplitude-dependent results provide a measure of the yield stress which is compared with static tensile data and with a model for the yield stress comprising long- and short-range interactions. Neutron irradiation results in an athermal increase in the yield stress, while thermal ageing influences only the thermally activated part of the yield stress. The model is refined to explain the effects of thermal ageing and irradiation.

Various Ti based coatings have been produced by plasma immersion ion implantation assisted deposition (PIIIAD) technique on a wide variety of substrates. In PIIIAD, the substrate is exposed to cathodic arc plasma comprising of metallic ions corresponding to the cathode composition, and the substrate is biased pulsed negative. The pulsed bias of the substrate gives alternate phases of deposition (during the bias off time) and implantation and deposition (during bias on time). Thus the deposition temperature can be controlled and simultaneously the compressive stress can be reduced, enhancing adhesion of the coating with the substrate. The deposition has been carried out in a neutral as well as reactive nitrogen environment, which leads to nitrogen bearing coatings. The coatings investigated are Ti, TiN, TiAl, TiAlN. It has been observed that the TiAl composition on the substrate depends on the bias and is different from the cathode composition. TiN and TiAlN coatings are hard coatings and show an enhanced wear resistance. All the coatings are tested for their suitability as biocompatible coatings on stainless steel substrates, and hence the adherence of osteoblast progenitor cells to these coatings was investigated in correlation with deposition parameters and surface morphology. The results indicate that these coatings can suitably be used as inert wear resistant coatings for orthopaedic implants.

kein Abstract

The titanium-nickel NiTi alloys is already in use in medical applications due to a good combination of shape memory or superelastic characteristics, biocompatibility and corrosion resistance. However, there are still concerns because of the high nickel content and a possible release of nickel ions, where toxicity and allergic hazards are well documented and carcinogenicity is under discussion. At present the influence of nickel on biocompatibility of the titanium - nickel alloys is an actual and open question for biomedical applications.

The aim of this work is to investigate surface modifications of nickel-titanium alloys and its influence on a biocompatibility and corrosion resistance.

Ar+ and/or N+ implantation in superelastic NiTi alloy with energy of 20-40 keV and fluences of (3-5) x 1017 cm-2 by means of plasma immersion ion implantation was performed.
The near surface layers were studied by grazing incidence X-ray diffraction analysis, Auger electron spectroscopy (AES), scanning electron microscopy and an analysis of the biocompatibility and corrosion resistance of these layers were performed.

The AES analysis of the implanted NiTi showed a reduced Ni content in the near surface (approx. 100 nm). Due to preferential sputtering of Ni and a Ni diffusion in the deeper layers a nickel depleted surface layer was produced, which was sealed by formation of a TiN layer. The deeper layers with a high Ni concentration contain mainly the Ni3Ti or Ni4Ti3 phases. Electrochemical corrosion experiments showed a significantly improved corrosion stability of the ion implanted surfaces.

Bone forming cells grown on untreated NiTi showed in several cases a disturbed cytoskeleton organisation as it was found also on pure nickel. As the effect could not be completely reproduced by nickel ions in the solution, it seems to be a surface effect. On the ion implanted surfaces the cell adherence always was undisturbed.

The results show that by Ar and N ion implantation the corrosion stability and biocompatibility of NiTi can be further improved.

kein Abstract

The temporal pattern for ion beam deposition of amorphous carbon films is presented on the basis of molecular-dynamics simulations. An analytic interatomic potential of Brenner was adopted, but with an increased C-C interaction range. Deposition of films with a thickness of up to 10 nm was simulated for ion energies E_ion =10-80 eV and for substrate temperatures T_s =100-900 K. The approach used describes quite accurately the properties (including sp² clustering) of highly tetrahedral amorphous carbon (ta-C) films, overestimating, however, density of graphitic films, since the potential does not account for the long-range repulsion between non-bonded pi-orbitals.

A time-resolved analysis of atomic trajectories from the film deposition simulations revealed a short-term temperature-dependent relaxation stage (t~70-1000 fs), where the film formation is considerably influenced byT_s . During this stage, depending on T_s , the carbon atoms at metastable highly coordinated sites can relax into either three- or fourfold coordinated positions. In agreement with experiment the molecular-dynamics simulations predict a sharp (within the range of about 50 K) transition from ta-C to graphitic carbon as T_s exceeds a critical temperature T_c . The behaviour of the sp³ content, density and the film stress near the transition temperature is discussed. For super-critical substrate temperatures (T_s > T_c ), the kinetic energy of the atoms is high enough to overcome the barrier in cohesive energy between a diamond-like and graphite-like film region. As a result, the relaxation processes lead finally to the energetically more favoured graphitic amorphous network. The diamond-like network remains stable in the case of deposition at sub-critical substrate temperatures (T_s <T_c ).

BACKGROUND: Titanium oxide is known for a good bio- and hemocompatibility, but this has not yet been correlated with crystal structure or electronic properties of this semiconductor. These physical features may be interesting because surface charges interact with charges of the protein and induce conformational changes of the protein with a change of function. Also chemical oxidation of proteins on the surface is under discussion for blood clotting activation.
METHOD: For this study Titanium oxide layers were deposited on oxidised Si as model substrate from a plasma produced by cathodic arc evaporation under addition of oxygen to the ambient near the substrate. The redox state of amorphous titanium oxide was additionally changed by ion implantation of Chromium, the electronic prop-erties of rutile TiO2 were changed by low dose implantation of the n-doping element Phosphorous. Both types of ion implantation should prevent an electron transfer from the protein to the surface. Blood platelet adherence and activation as well as clotting time were determined as parameters of hemocompatibility.
RESULTS: In dependence of the deposition parameters amorphous and nanocrystal-line structures, crystalline layers composed of anatase and brookite as well as layers dominated by the rutile phase have been obtained. The activation of the plasmatic clotting cascade was only minimally influenced by the crystal size and the crystallite structure of the titanium oxide films. As a trend, amorphous, nanocrystalline and fine-grained layers showed higher clotting times than well crystallized rutile films. Ion im-plantation of Cr or P strongly prolongated the clotting time, indicating a lower clotting activation. Only for P+-doped rutile both, enhanced clotting time and improved platelet adhesion, are observed. Contrasting tendencies in the dependence of clotting time and platelet adhesion on the Cr implanted Ti oxide have been stated.
CONCLUSION: Low dose P+ implantation into TiO2 can improve its blood compatibility, but it has to be worked out whether this effect really is due to modifications in the electronic properties of the TiO2 or due to biochemical effects. There was almost no effect of the crystal structure on the blood compatibility.

Historic glass objects belong to the valuable artistic and cultural heritage that suffers a progressive deterioration due to atmospheric effects. For predicting the chemical stability of a glass object showing no visible alteration or corrosion damage, the three ion beam techniques PIGE, PIXE and RBS have been combined in simultaneous measurements at the Rossendorf external proton beam. Non-destructive determination of the glass bulk composition despite a thin corrosion layer on the glass surface facilitate the identification of glasses which are sensitive to environmental degradation, hence require specific storage conditions. The complete analytical reproduction of the chemical composition of unaffected glass using the combination of PIGE and PIXE is also discussed.

Ni was surface-alloyed with Cu, Ti or Cu + Ti by ion implantation. The redox and catalytic activity of the materials was studied in NaOH by cyclic voltammetry. The surface was characterized by X-ray photoelectron spectroscopy, X-ray and electron diffraction, and electron and atomic force microscopy. All three materials exhibited a unique voltammetric response of Ni and were shown to stabilize the ß modification of the Ni oxide/hydroxide. Cu modified the anodic oxidation of glucose and the oxygen evolution to a higher degree than Ti. The morphology and microstructure differed from those of bulk materials.

The external proton beam of the Tandem accelerator on the research Centre in Rossendorf/Germany was used to carry out non-destructive particle-induced X-ray emission (PIXE) particle-induced gamma-ray emission (PIGE) and Rutherford backscattering (RBS) measurements simultaneously on Art Nouveau artefacts produced around 1900 by Tiffany/USA and Loetz/Austria. These studies should proof the technology of producing an iridescent layer on a glass surface. By means of the yield ratio Y(Si-K)/g(Si-g) of both characteristic X-radiation (Si-K) and g-radiation (Si-g) of the element silicon it could be shown that a thin top layer is present on the glass surface due to the treatment of the heated artefacts (about 500°C) with an alcoholic solution of SnCl2 [1]. Combined evaluation of the PIXE and RBS spectra resulted in a thickness of 20-300 nm for this top layer. In addition, a transition region between the iridescent layer and the bulk glass was obtained by RUMP simulations. XPS studies showed that the outermost layer consists of SnO2. The formation of other Sn compounds in the outermost near-surface region based on Sn-Si-O during the manufacturing process can be excluded.

The radiation source ELBE at Forschungszentrum Rossendorf is based on a superconducting linear accelerator that produces a cw electron beam up to 40 MeV and 1 mA. In 2001 first stage of the ELBE-linac was put into operation. The main electron beam parameters like energy, energy spread, transverse emittance and bunch length were specified and several online diagnostic tools for ELBE routine high-power operation were tested, such as λ/4-stripline monitors and beam-loss detectors.

Für die zerstörungsfreie Analyse von Kunstwerken ist die Messdatenerfassung an Luft erforderlich. RFA liefert hohe Signalintensitäten hauptsächlich für die schwereren und mittelschweren Elemente im PSE. Die geringe Nachweisempfindlichkeit für leichte Elemente, z. B. Si, wird durch starke Schwächung der niederenergetischen Röntgenstrahlung in Luft noch weiter herabgesetzt. Eine spezielle Messdüse mit Heliumdurchfluss verhindert diesen Effekt und macht den Nachweis leichter Elemente für RFA an Atmosphäre zugänglich.

Irisierende Jugendstilgläser zählen heute zu sehr kostbaren und beliebten Sammelobjekten zahlreicher Museen und Privatsammler. Die Geheimnisse der Herstellungstechnologie, die nur wenige Glasmanufakturen wie Tiffany (USA) und Lötz (Österreich-Ungarn) bis zu deren Perfektion entwickelt haben, beschäftigen heute viele Kunsthistoriker und Wissenschaftler, da die bekannten Patente oft Lücken enthalten. Auch die steigende Zahl der Fälschungen solcher Glasobjekte kommt immer mehr zum Tragen und dadurch wird häufig die Frage nach der eindeutigen Identifizierung sowie der Zuordnung der irisierenden Jugendstilgläser gestellt.

Emails bestehen aus dem „Materialverbund“ Edelmetalllegierung und als dünne Schicht aufgebrachter farbiger Glasfluss. Thermomechanische Eigenschaften, chemische Zusammensetzung, Herstellungsprozess, aber auch die Geometrie der Objekte bestimmen die Schadensursachen.

The aim of this interdisciplinary research project is the non-destructive analysis of glass/enamel objects of the Medieval and Baroque periods. For medieval stained glass, medieval goblets decorated with émail en ronde bosse, and artefacts of the baroque gold work, which are highly endangered by environmental effects, specific storage conditions shall be recommended in order to avoid further degeneration processes. The analytical procedure can be applied to museum objects as well as in situ artefacts with initial corrosion phenomena.

PIXE, proton induced X-ray emission, is a proven method for non-destructive substantial analysis of art objects. By varying the proton energy this technique succeeds also in the non-destructive identification of layer sequences. Very thin surface layers can be characterised by simultaneous RBS, the detection of backscattered protons.

Pigment studies on porcelain painting may help to support the attribution of a special artefact made from porcelain to a certain artist. Examinations of a variety of decoration details allow a representative image of the paint materials used. Non-destructive substantial analysis is guaranteed by X-ray (PIXE) and gamma-ray (PIGE) emission plus particle backscattering (RBS), induced by the proton beam at atmospheric pressure.

Diamond like carbon (DLC) is known to posses high mechanical hardness and chemical inertness along with good bloodcompatibility. The latter is determined by protein - DLC surface interaction that is not properly addressed in the literature. These properties of DLC are determined to a large extent by sp3 bonds fraction and hydrogen content. Therefore, DLC films with different sp3 content have been produced by Ion Beam Assisted Deposition (IBAD) (low sp3) and Filtered Cathodic Vacuum Arc (FCVA) (high sp3) by changing deposition parameters.
The films were characterized by spectrocopic ellipsometry (SE) within the wavelength range l=300-1700 nm after deposition. The spectral dependences of ellipsometric parameters, D and Y, were acquired in autoretarder mode of VASE spectroscopic ellipsometer (J.A. Woolam Co., Inc., USA). To improve the quality of SE data reduction, multiple sample analysis was carried out for set of different thickness DLC samples produced by IBAD at the same deposition parameters on different substrates. The optical constants of DLC both with low and high content of sp3 bonds were parameterized in semiconductor model approach [2]. The SE data reduction yielded refraction and absorption index values, film thickness, band gap values of the DLC and surface roughness. Relation of SE results for samples produced by FCVA with Raman scattering data, which demonstrate D and G bands displacements, allowed proper characterization of the bonding structure of DLCs and estimation of sp3/sp2 fraction ratio. By using film thickness from SE results DLC film densities were estimated due to elastic recoil detection analysis (ERDA). ERDA also demonstrated only low amount of hydrogen mainly near film-substrate interface in DCLs produced by FCVA technique. Thus, it demonstrates that DLC properties modification is due to sp3/sp2 ratio variation and are not caused by variation of hydrogen content.
Deposition of human serum albumin labeled by fluorescein on DLC layers with different sp3 fraction was investigated. Selective binding of polyclonal antibody to the adsorbed albumin was quantified. The ratio of antibody binding to total adsorbed protein as measured by florescence gives the information about availability of epitopes and protein deformation.

Osteoblast-like SAOS-2 cells were allowed to synthesize and assemble their extracellular matrix (ECM) on titanium surfaces. After the selective removal of cells, Ti coated with a native ECM was obtained (ECM-Ti). The responses of SAOS-2 cells to ECM-Ti compared with those to peptide sequence RGDS- or fibronectin-immobilized Ti were examined,
demonstrating the compositional and structural effects needed to trigger the native cell behavior.

Titanium with its natural oxide is known to be generally good biocompatible; and therefore, the suitability of some Ti-based coatings as coating for blood-contacting implants is analyzed. Layers of pure Ti, Ti oxynitrides (TiN1-xOx with x = 0.25, 0.50, and 0.75), and Ti oxides were deposited on oxidized Si from a plasma produced by cathodic arc evaporation under addition of N-2 and/or O-2 to the ambient near the substrate. The oxynitrides are crystalline with the fcc structure of TiN up to x = 0.25. For x = 0.5, a two-phase system of fcc TiN and fcc TiO has been found. In dependence on the deposition parameters, amorphous and crystalline layers (anatase + brookite or rutile) of TiO2 have been obtained. The rutile layers were doped by implantation of P. The amorphous TiO2 layers were implanted with Cr. To study the correlation between structure of the coating and blood compatibility, the clotting time of blood plasma as well as the adhesion and activation of blood platelets o! n the surface was investigated. TiN and oxynitrides showed the longest clotting time compared to rutile. Minimum platelet adhesion has been observed for pure TiO2. Contrasting tendencies in the dependence of clotting time and platelet adhesion on the microstructure have been stated. However, for P+-doped rutile, both enhanced clotting time and improved platelet adhesion were observed. Platelet adherence and activation always showed similar trends. (C) 2004 Elsevier B.V. All rights reserved.

Conventional pigment analysis of paintings requires the removal of micro-samples followed by the preparation of cross-sections. There are also requirements for investigating several locations within a painting in order to obtain information about dating and provenance or the reason for aesthetic impressions of the paint materials. The need to carry out such work without removing samples prompted the present project, in which the authors aimed to examine the possibility of applying XRF and PIXE methods in a complementary manner. The ion beam techniques of external PIXE plus Rutherford backscattering could distinguish painting techniques, i.e. paint layer arrangements and pigment admixtures, whereas portable XRF represents a valuable tool for preselecting the objects of interest which could be transported to the ion beam laboratory. This procedure was tested using samples of prepared paint layers. It is shown that it is possible to distinguish between two or three layers. The situation would be more difficult for more complex paint layer arrangements.

Die zerstörungsfreie Identifizierung von Malschichten mittels Protonenstrahlen an Luft wird exemplarisch an der Torgauer Tafel "14 Nothelfer" (Lucas Cranach der Ältere) vorgestellt. Durch Variation der Protonenenergie lassen sich Abfolgen von Malschichten sichtbar machen.

Externe PIXE, protoneninduzierte Röntgenemission an Luft, hat sich als zerstörungsfreie Methode zur Substanzanalyse von Kunstwerken bewährt. Durch Variation der Protonenenergie gelingt es jetzt auch, Schichtenabfolgen zerstörungsfrei zu identifizieren. Extrem dünne Oberflächenschichten können durch RBS, die Detektion der rückgestreuten Protonen, charakterisiert werden.

Restorers, art scientists and criminalogists are interested in the material composition of historic paintings. The substantial and structural analysis of details of paint layers are helpful and necessary to distinguish originals from forgeries, to decide on original states and later additives, to support statements on age and provenance and to understand aging phenomena. The basic idea of non-destructive paint layer analysis is demonstrated using PIXE at different proton energies.

An dem Reliquienkästchen aus der Stiftskirche in Quedlinburg, das derzeit im Berliner Kunstgewerbemuseum ausgestellt ist, wurde für die Untersuchung von Metall die zerstörungsfreie Röntgendiagnostik am Teilchenbeschleuniger (PIXE) gewählt. Sie soll Aufschluss über die zeitliche Einordnung der verschiedenen Fassungen geben. Die hohe Bedeutung und Einmaligkeit des Objekts rechtfertigte den apparativen und finanziellen Aufwand dieser Methode. Ein Bericht über die Restaurierung des Kästchens wird folgen.

Der a-Fe-Volumenanteil in den Magnetlegierungen auf Nd-Fe-B-Basis wird reduziert.

Les résultats analytiques par faisceaux des protons à pression atmosphérique et par la combination PIXE-RBS sont presentées pour charactériser la stratification des pigments sur le retable "Quatorze Intercesseurs" de Lucas cranach l'Ancien.

Es wird der a-Fe-Volumenanteil in den Magnetlegierungen auf Nd-Fe-B-Basis reduziert.

Es wird die verbesserte Stabilität des Züchtungsprozesses und eine verbesserte Qualität des Einkristalls erreicht.

Die Nitinol-Oberfläche wird so modifiziert, dass sie durch Nickel-Armut oder -freiheit gut biovertäglich ist, ohne die gewünschten mechanischen Eigenschaften des Materials an sich zu verändern. Die Oberflächen-Schicht ist mechanisch stabil, kratzunempfindlich und fest haftend.

Es wird die Phasenverteilung des Strömungsmediums mit Hilfe von Sender-Empfangsstrecken ohne tomographische Nachberechnung mit hoher örtlicher, zeitlicher und stofflicher Auflösung für mehrphasige Medien auch nichtleitender Art zweidimensional bestimmt.

Es werden Substanzen vorgeschlagen, die nach Applikation in den Körper metabolisch stabil hinsichtlich des Chelats sind und vom Herzmuskel aufgenommen werden. Die Herstellung der Substanzen wird angegeben.

Oxidative modification of proteins can interfere with critical cellular functions, and is widely regarded as a crucial event in the pathogenesis of various diseases ranging from rheumatoid arthritis to atherosclerosis and cancer. The mechanisms of formation and the nature of the altered amino acid side chain residues formed on proteins subjected to oxidant attack are reviewed. In this line, a new GC-MS method using N(O,S)-ethoxycarbonyltrifluoroethyl amino acid esters (ECEE-F₃) for rapid and sensitive determination of 3-chlorotyrosine, 5-hydroxy-2-aminovaleric acid (HAVA), and 6-hydroxy-2-aminocaproic acid (HACA) in proteins is discussed. 3-Chlorotyrosine is a highly specific marker of myeloperoxidase-catalyzed protein oxidation, whereas HAVA and HACA are specifically formed by metal-catalyzed oxidation processes. ECEE-F₃ derivatives are formed by the unlabored reaction of amino acids with ethylchloroformate plus trifluoroethanol plus pyridine. The key steps of the methodology employed are i) enzymatic hydrolysis of target proteins to prevent decomposition of oxidation products during hydrolysis and ii) an uniquely rapid derivatization of amino acids completing sample preparation for GC within a few minutes in aqueous solution at room temperature. Femtomole levels of 3-chlorotyrosine, HAVA, and HACA can be reproducible measured in different protein preparations subjected to oxidative damage in vitro. Furthermore, the use of these stable products of protein amino acid side chain oxidation as potential markers for assessing oxidative damage in patients with inflammatory and metabolic disorders ex vivo and in vivo is demonstrated. Evidence is presented to show that the pattern of products detected may yield information as to the nature of the original oxidative insult.

Die Oxiddegradation wird vermindert.

Es wird der Messaufwand für die Bestimmung der elektrischen Parameter bei der ITO-Abscheidung gesenkt.

Gamma-Glutamyl-semialdehyde (Gamma-GSA) is a major product of the metal catalysed oxidation of apolipoprotein B-100 (apoB-100) proline and arginine residues. On reduction, Gamma-GSA forms 5-hydroxy-2-aminovaleric acid (HAVA). This report describes the application of HAVA measurement to characterise the formation of Gamma-GSA in low density lipoprotein (LDL) recovered from human atherosclerotic lesions. HAVA concentrations were greatly increased in LDL from early (mean, 10.25; SD, 3.49 mol/mol apoB-100; p < 0.01), intermediate (mean, 11.18; SD, 2.37 mol/mol apoB-100; p < 0.01), and advanced (mean, 9.91; SD, 2.15 mol/mol apoB-100; p < 0.01) lesions, when compared with LDL from normal aortic tissue (mean, 0.05; SD, 0.01 mol/mol apoB-100). These findings support the hypothesis that pathways involving metal catalysed oxidation of LDL apoB-100 are of pathological importance in atherogenesis. LDL apoB-100 recovered from human aortic vascular lesions. These observations provide quantitative chemical evidence for metal catalysed oxidative processes in the human artery wall.

Die in Nahrungspflanzen enthaltenen Flavonoide umfassen eine sehr umfangreiche Gruppe von Molekülen, die über verschiedene Wirkmechanismen einen Einfluss auf die Entstehung und Progression von Tumoren, die Atherogenese und andere chronische Erkrankungen nehmen können (BIOforum 5/2003, S. 289-291). Die zugrundeliegenden zellulären Prozesse sind bisher nur ansatzweise geklärt und wurden erst für wenige ausgewählte Verbindungen dieser umfangreichen Stoffgruppe untersucht.
Noch ist man vorsichtig mit Aussagen über klinische Wirkungen der Flavonoide, da viele Studien rein experimentell sind bzw. nur an Tiermodellen durchgeführt wurden. Einige epidemiologische Studien (Copenhagen City Heart Study, Physician´s Health Study, Nancy Study, Mainzer Weinstudie, u. a.) lassen aber bereits annehmen, dass durch die Aufnahme von Flavonoiden Herz-Kreislauf-Krankheiten und vermutlich auch anderen chronischen Krankheiten vorgebeugt werden kann [1,6]. Ob die Befunde dieser zuletzt genannten Studien tatsächlich auf der Wirkung bestimmter Flayonoide beruhen, erfordert detailliertere Untersuchungen über das Flavonoidspektrum in verschiedenen Lebensmitteln und Lebensmittelzubereitungen, ihre Bioverfügbarkeit im menschlichen Organismus und ihre spezifischen zellulären Wechselwirkungen.