Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

31745 Publications
Multilayer porous silicon structures for optical devices
Torres-Costa, V.; Martín-Palma, R. J.; Gago-Fernández, R.; Vinnichenko, M.; Martínez-Duart, J. M.;
Porous silicon (PS) has a great potential in optical applications due to its tuneable refractive index. In particular, multilayer structures consisting on PS layers with different refractive indexes can be used as interference filters. Due to the characteristics of PS and its production process, many types of interence filters can be produced: Bragg reflectors, monochromatic filters for light emitting devices (which can also be based on PS), microcavities for biosensing applications, Fabry-Pérot resonators, photonic crystals, etc.

In the present work the optical properties of porous silicon single layers and multilayer structures have been studied. PS is formed by the electrochemical etch of monocrystalline silicon wafers. Since PS can be modelled as an homogeneous mixture of silicon and air (and, eventually, silicon dioxide), its refractive index varies depending on the air content of the porous structure, according to the effective medium theories (EMTs). The electrochemical process gives a perfect control over the porosity –and hence, over the index of refraction- and thickness of the porous silicon layer, since both parameters are highly sensitive to the formation conditions, mainly current density and etching time. In addition, when the current density applied is periodically varied, a multilayer structure is formed. By simply adjusting the refractive index and thickness of each individual layer we can obtain a stack of porous silicon layers with the desired optical properties, resulting in an interference filter of predetermined band width.

The optical characterization has been carried out by spectrophotometric and spectroscopic ellipsommetry measurements. In addition, compositional analysis has been performed by means of Ion Beam Analysis (IBA) techniques, with special interest devoted to oxygen and hydrogen, in order to correlate the optical parameters and the chemical composition. Finally, multilayers structures have been produced and their operation has been checked.
  • Lecture (Conference)
    European Congress on Advanced Materials and Processes (EUROMAT 2003), 1-5 September 2003, Lausanne (Switzerland)

Publ.-Id: 5848 - Permalink

Surface patterning by low-energy ion irradiation
Gago, R.; Vázquez, L.; Cuerno, R.; Albella, J. M.; Facsko, S.; Moeller, W.;
The modification of the surface morphology by means of low-energy (0.1-10 keV) ion irradiation is a fascinating process that has been devoted to intense study during the last decades. The first implications of this process were considered due to secondary effects derived from the ion-modified roughness, such as secondary ion emission (SIMS). However, the ability to produce regular and self-organized patternings in the nanoscale range, related to the typical size of the ion collision cascade, has recently attracted the interest on this process due to its potential applications in Nanotechnology. Depending on the ion incidence angle, different morphologies can be induced on the surface, namely ripples and dots [1]. The universality of the process has been demonstrated by the production of patterns either on metals (Ag, Cu), semimetals (graphite), semiconductors (GaSb, GaAs, InP, Si, Ge) and insulators (glass, SiO2). The mechanisms leading to the formation of these patternings have also attracted intense theoretical studies [3]. The successful approach considers continuum equations where an instability results from the interplay between roughening, due to the dependence of the ion sputtering yield on the local surface curvature, and smoothing processes (thermal and ion-induced). Finally, the applications of these nanostructures are still to be exploited. Several applications as optical filters, quantum wires, quantum dots, magnetic nanostructures, and templates have been addressed. In addition, the latter application has been already realized, transferring the pattern from Si surfaces to polymeric and metallic films [4]. Complementary, the possible functionalization of the surface for biological or catalytic processes can also open a wide range of potential applications.

[1] Navez et al. C.R. Acad. Sci, Paris 254 (1962) 240; Facsko et al. Science 285 (1999) 1551.
[2] Gago et al. Appl. Phys. Lett. 78 (2001) 3316; Gago et al. Nanothecnology 13 (2002) 304.
[3] Bradley et al. J. Vac. Sci. Technol. A 6 (1988) 2390; Cuerno et al. Phy. Rev. Lett. 74 (1995) 4746.
[4] Azzaroni et al. Appl. Phys. Lett. 82 (2003) 457; Azzaroni et al. Nanotechnology (submitted)
  • Lecture (Conference)
    International Summer School on Vacuum, Electron and Ion Technologies (VEIT 2003), 15-19 September, Varna (Bulgaria)

Publ.-Id: 5847 - Permalink

Surface Nanopatterning of Metal Thin Films by Physical Vapor Deposition onto Surface-Modified Silicon Nanodots
Azzaroni, O.; Fonticelli, M.; Schilardi, P. L.; Caretti, I.; Gago, R.; Vázquez, L.; Salvarezza, R. C.;
One of the most active research topics within the nanoscience and nanotechnology fields are those related to large-scale fabrication, in an accurate manner, of nanostructured metal thin films [1]. This interest is due to their potential applications for different technological purposes such as electrocatalysis [2] and optical devices [3]. In order to obtain these nanostructured films different techniques, such as ion sandblasting [4] or nanotransfer printing [5], have been developed. In this work we present results on the largescale preparation of nanostructured metal thin films from surface-modified silicon nanodots templates [6]. The nanopatterning process is based on the deposition of a copper thin film (approximately 300nm thick) by physical vapor deposition on nanostructured silicon substrates [7], which were previously surface-modified with an octadecyltrichlorosilane (OTS) self-assembled monolayer in order to promote an easy metal film detachment after deposition. Once the 300 nm thick film has been deposited, a thick (10 mm approximately) film of copper is electrodeposited onto it to improve the mechanical properties of the physically-deposited nanostructured thin film. Thanks to the very low adhesion of OTS layer to the metal film the latter is easily mechanically detached from the template, leading to a surface nanostructure corresponding to the negative replica of the original nanopatterned silicon template. This metal nanopatterning strategy shows potential applications for accurate large-scale fabrication of nanostructured metal thin films.

[1] G.L. Egan, J.-S. Yu, C.H. Kimm, S.J. Lee, R.E. Schaak, T.E. Mallouk, Adv.Mater. 12,1040 (2000)
[2] G.S. Attard, et al., Science, 278, 838 (1997)
[3] M.B. Sobnack, et al., Phys.Rev.Lett. 80, 5667 (1998)
[4] S. Rusponi, G. Constantini, F. Buatier de Mongeot, C. Borago, U. Valvusa, Appl. Phys. Lett. 75, 3318 (1999).
[5] Y.-L. Loo, et al., J.Am.Chem.Soc. 124, 7654 (2002).
[6] O. Azzaroni, P.L. Schilardi, R.C. Salvarezza, R. Gago, L. Vázquez, Appl. Phys. Lett. 82, 457 (2003).
[7] R. Gago, L. Vázquez, R. Cuerno, M. Varela, C. Ballesteros, J.M. Albella, Appl.Phys.Lett. 178, 3316 (2001).
  • Poster
    Trends in Nanotechnology (TNT2003), 15-19 September 2003, Salamanca (Spain)

Publ.-Id: 5846 - Permalink

Untersuchung der Metabolisierung von Neurotensin(8-13) mit 99mTc- und 18F-Markierung
Pawelke, B.; Bergmann, R.; Künstler, J.-U.; Kretzschmar, M.; Wittrisch, H.; Johannsen, B.;
  • Poster
    41. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, Essen, 02.-05.04.2003
  • Abstract in refereed journal
    41. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, Essen, 02.-05.04.2003 Nuklearmedizin (2003) 42: A94

Publ.-Id: 5845 - Permalink

Spectroscopic ellipsometry investigation of amorphous carbon films with different sp3 content: relation with protein adsorption
Vinnichenko, M.; Gago, R.; Huang, N.; Leng, Y. X.; Sun, H.; Kreissig, U.; Kulish, M. P.; Maitz, M.;
The albumin adsorption on non-hydrogenated amorphous carbon films with different diamond-like character (i.e. sp3 content) is addressed. The films were produced by ion beam assisted deposition and by filtered cathodic vacuum arc deposition to obtain a wide range of sp3 contents. A combination of the spectroscopic ellipsometry, Raman spectroscopy and elastic recoil detection analysis was used for characterization of the films. It is shown that an increase of the deposition temperature leads to a decrease of the film band gap, density and a shift of the Raman G-band position. The wettability of the film is not influenced by its sp3 content. Albumin adsorption on the surface depends more on its wetting behavior than on the sp3 content. In addition, Ar ion treatment of the layers can be used to reduce the amount of adsorbed proteins.
Keywords: spectroscopic ellipsometry; Raman scattering; ion bombardment; coatings

Publ.-Id: 5844 - Permalink

Biodistribution and Catabolism Studies of 18F-labeled Amino Acid and Peptide Derivatives
Pawelke, B.; Bergmann, R.; Helling, R.; Wittrisch, H.; Wüst, F.; Johannsen, B.;
  • Poster
    6. Deutsches Peptidsymposium, Berlin, 23.-26.03.2003

Publ.-Id: 5843 - Permalink

Diagnostik von Ein- und Mehrphasenströmungen mit Leitfähigkeits-Gittersensoren
Hampel, U.; Zschau, J.; Prasser, H.-M.;
Leitfähigkeits-Gittersensoren ermöglichen die Untersuchung von Strömungen mit und ohne Gasanteil (Ein- und Zweiphasenströmungen) mit hoher räumlicher und zeitlicher Auflösung. Sie können damit für viele strömungsdiagnostische Probleme eingesetzt werden. Der Beitrag gibt einen Überblick über das Funktionsprinzip, die Gewinnung physikalischer Strömungsparameter aus den elektrischen Messsignalen sowie über Anwendungsgebiete solcher Sensoren.
Keywords: Leitfähigkeitsmessung, Gittersensor, Strömungsdiagnostik
  • Contribution to proceedings
    Proceedings 6. Dresdner Sensor-Symposium - Sensoren für zukünftige Hochtechnologien und Neuentwicklungen für die Verfahrenstechnik, Band 20, G. Gerlach Hrsg., pp. 33-36, w.e.b. Universitätsverlag, 2003

Publ.-Id: 5842 - Permalink

Complexation of uranium(VI) with glycerol 1-phosphate
Koban, A.; Bernhard, G.;
The complex formation of uranium(VI) with glycerol 1-phosphate was determined by potentiometric titration, UV-vis and TRLFS spectroscopy. Three complexes were found by potentiometry in the pH range 3 - 8, and the stability constants were calculated for I = 0.1 M: 1 : 1 complex UO2(C3H7O3PO3) (log beta11 = 6.23 ± 0.09); 1 : 2 complex UO2(C3H7O3PO3)22- (log beta12 = 10.22 ± 0.13); 2 : 3 complex (UO2)2(C3H7O3PO3)32- (log beta23 = 20.28 ± 0.03). The UV-vis spectra at pH 2 to 4 show an increase of the absorption intensity with increasing ligand concentration, connected with a red shift of the main absorption bands. The three complexes could be isolated by deconvolution of the measured spectra and the stability constants were determined (at I = 0.5 M) to be: log beta11 = 6.15 ± 0.20, log beta12 = 10.38 ± 0.39, and log beta23 = 19.34 ± 0.65. The TRLFS spectra at pH = 4 show also an increase of the fluorescence intensity connected with a red shift of the emission spectra. But contrary to the both above mentioned methods only the 1 : 1 complex UO2(C3H7O3PO3) could be detected under the specific experimental conditions. The main fluorescence emission bands and the lifetime of this complex were determined. The complex stability constant at I = 0.1 M was calculated to be log beta11 = 6.15 ± 0.05.
Keywords: Uranium; glycerol phosphate; complex formation; potentiometric titration; UV-vis; TRLFS

Publ.-Id: 5841 - Permalink

Uran(VI) complexes with sugar phosphates in aqueous solution
Koban, A.; Geipel, G.; Roßberg, A.; Bernhard, G.;
The complex formation in the aqueous systems of uran(VI) with glucose 6-phosphate (G6P) and fructose 6-phosphate (F6P), respectively, were studied by means of potentiometric titration, TRLFS, and EXAFS. In each case two complexes with a metal-to-ligand ratio of 1 : 1 and 1 : 2 could be observed. Complex stability constants were determined by potentiometric titration for both complexes to be log beta11(G6P) = 5.89 ± 0.40, log beta12(G6P) = 9.45 ± 0.08, log beta11(F6P) = 5.72 ± 0.21, and log beta12(F6P) = 9.54 ± 0.09. By TRLFS stability constants could be calculated under the specific experimental conditions only for the 1 : 1 complexes (log beta11(G6P) = 6.35 ± 0.28, and log beta11(F6P) = 5.66 ± 0.17).
The TRLFS measurements resulted in that the UO2G6P complex shows no fluorescence properties. For this system only a decrease of the fluorescence intensity with increasing ligand concentration could be observed. For the uranyl fructose 6-phosphate system a red shift of the fluorescence emission bands of about 8 to 9 nm compared to the free uranyl ion was observed. The fluorescence emission wavelengths of the UO2F6P complex were determined to be 483, 496, 518, 542, and 567 nm, and the lifetime of this complex is 0.13 ± 0.05 µs.
Uranium LIII-edge EXAFS measurements at different pH values yielded a shortened U - Oeq bond distance (2.31 ± 0.02 to 2.37 ± 0.02 Angström) compared to the UO22+(H2O)5 ion (2.40 ± 0.02 Angström) due to a monodentate coordination via the oxygen atoms of the phosphate group.
Keywords: Uranium; sugar phosphate; complex formation; TRLFS; EXAFS; potentiometric titration

Publ.-Id: 5840 - Permalink

Positron Emission Tomography Imaging of the Serotonin Transporter in the Pig Brain Using [11C](+)-McN5652 and S-([18F]fluoromethyl)-(+)-McN5652
Brust, P.; Zessin, J.; Kuwabara, H.; Pawelke, B.; Kretzschmar, M.; Hinz, R.; Bergman, J.; Eskola, O.; Solin, O.; Steinbach, J.; Johannsen, B.;
S-([18F]fluoromethyl)-(+)-McN5652 ([18F](+)-FMe-McN5652) has recently been synthesized as a new potential radiotracer for positron emission tomography (PET) imaging of the 5-HT transporter. It is an analog of [11C](+)-McN5652, which has been used in clinical PET studies for 5-HT transporter imaging. This article describes the comparison of these two radiotracers in pigs with respect to their in vivo binding characteristics. PET images revealed that the highest accumulation of both radiotracers was found in the ventral midbrain, thalamus, olfactory lobe, and pons which is consistent with the known density of 5-HT transporters. The specific binding was determined by subtracting the values of the inactive (-) enantiomers or of the occipital cortex from those obtained with [11C](+)-McN5652 or [18F](+)-FMe-McN5652 in the time period between 75 and 115 min after radiotracer injection. The specific binding of the 18F-labeled derivative was about 40 % higher than that of the 11C-labeled derivative. A strong inhibition of the specific binding was observed for both radiotracers after pre-treatment with the selective 5-HT uptake inhibitor citalopram. [18F](+)-FMe-McN5652 showed faster kinetics than [11C](+)-McN5652. It reached the binding equilibrium during a study length of 120 min, which was not the case for [11C](+)-McN5652. It is concluded that [18F](+)-FMe-McN5652 is suitable for 5-HT transporter imaging with PET.
Keywords: serotonin transporter; receptor imaging; positron emission tomography; porcine brain; [18F](+)-FMe-McN5652; citalopram
  • Synapse (2003) 47: 143-151

Publ.-Id: 5839 - Permalink

Nuclear stopping from 0.09A GeV to 1.93A GeV and its correlation to flow
Reisdorf, W.; Andronic, A.; Gobbi, A.; Hartmann, O. N.; Herrmann, N.; Hildenbrand, K. D.; Kim, Y. J.; Kirejczyk, M.; Koczon, P.; Kress, T.; Leifels, Y.; Schüttauf, A.; Tyminski, Z.; Xiao, Z. G.; Alard, J. P.; Barret, V.; Basrak, Z.; Bastid, N.; Benabderrahmane, M. L.; Caplar, R.; Crochet, P.; Dupieux, P.; Dzelalija, M.; Fodor, Z.; Grishkin, Y.; Hong, B.; Kecskemeti, J.; Korolija, M.; Kotte, R.; Lebedev, A.; Lopez, X.; Merschmeyer, M.; Mösner, J.; Neubert, W.; Pelte, D.; Petrovici, M.; Rami, F.; de Schauenburg, B.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczynska, K.; Smolyankin, S.; Stockmeier, M.; Stoicea, G.; Wagner, P.; Wisniewski, K.; Wohlfarth, D.; Yushmanov, I.; Zhilin, A.;
We present a complete systematics (excitation functions and system-size dependences) of global stopping and sideflow for heavy ion reactions in the energy range between 0.09A GeV and 1.93A GeV. For the heaviest system, Au+Au, we observe a plateau of maximal stopping extending from about 0.2A to 0.8A GeV with a fast drop on both sides. The degree of stopping, which is shown to remain significantly below the expectations of a full stopping scenario, is found to be highly correlated to the amount of sideflow.

Publ.-Id: 5838 - Permalink

Hochauflösende RBS an ultradünnen Multischichten
in Russian
Mäder, M.; Grötzschel, R.; Klein, C.;
Die hochauflösende Rutherford Rückstreu-Spektrometrie (HRBS) hat ein großes Potential bei der Charakterisierung von dünnen Schichten mit Dicken im Nanometer-Bereich bis hin zu Dicken im Monolagen-Bereich. Der Bedarf der Materialforschung an quantitativen, schnellen und zuverlässigen Tiefenprofilen solcher Proben wächst ständig. Der wesentliche Unterschied zur weit verbreiteten Standard-RBS besteht dabei im Einsatz von Spektrometern in Verbindung mit ortsauflösenden Detektoren. Diese Konfiguration bietet zum einen die Möglichkeit einer verbesserten Energieauflösung bei der Detektion der gestreuten Ionen. Zum anderen ist die Verwendung schwerer Primärionen, deren größeres Bremsvermögen eine bessere Tiefenauflösung erlaubt, damit erst ohne nennenswerte Einschränkungen der Energieauflösung möglich. Die Verwendung von Spektrometern bringt es allerdings mit sich, dass Ionen mit verschiedenen Ladungszuständen getrennt gemessen werden müssen.
Messungen an Mehrfachschichtsystemen mit Li und C als Primärionen illustrieren die Tiefenauflösung im Tiefenbereich bis 20 nm, die mit der HRBS am Rossendorfer Browne-Buechner-Spektrometer erreicht werden kann. An einem einfachen Schichtsystem mit sehr dünnen Einzelschichten werden die exzellenten Möglichkeiten der HRBS im Vergleich zur Standard-RBS und zur MEIS vorgeführt. Die Auswertung der HRBS-Spektren liefert auch Aussagen über das Straggling und den Energieverlust schwerer Ionen in den untersuchten Materialien. Für C-Ionen wurde der Einfluss der Schädigung während der Messung untersucht. Eine Verwendung von Ionen, welche schwerer als C sind, erweist sich bei den am Rossendorfer Tandetron zur Verfügung stehenden Energien auf Grund der erhöhten Schädigung ohne gleichzeitige Verbesserung der Tiefenauflösung als nicht sinnvoll.
  • Lecture (others)
    Arbeitstreffen "Forschung mit nuklearen Sonden und Ionenstrahlen" FSI-2003, Berlin, 30.09. bis 1.10.2003

Publ.-Id: 5837 - Permalink

Hochauflösende Rutherford-Rückstreu-Spektrometrie mit schweren Ionen
Klein, C.;
no abstract
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-390 Oktober 2003


Publ.-Id: 5836 - Permalink

Short-wavelength intersubband absorption in InP-based material systems
Helm, M.;
kein abstract
Keywords: intersubband absorption, quantum cascade laser
  • Lecture (others)
    Seminarvortrag am Institute of Industrial Science, University of Tokyo, Japan (22.9.2003)

Publ.-Id: 5835 - Permalink

Short-wavelength intersubband absorption in InP-based material systems
Georgiev, N.; Dekorsy, T.; Helm, M.; Semtsiv, M. P.; Masselink, W. T.; Biermann, K.; Künzel, H.;
In recent years, several novel material systems (such as II-VI’s and nitrides) have been explored with the goal of achieving intersubband absorption in the 1.5 micron telecommunication wavelength region. This could lead to novel near-infrared modulators, detectors and (quantum cascade) lasers with high modulation frequencies.
We have investigated two different material systems grown on InP substrates:
(1) Heavily strained, but overall strain compensated InxGa1-xAs/AlAs/InyAl1-yAs structures grown by gas-source MBE. Here the conduction band offset between the In0.7Ga0.3As and the pure AlAs is approximately 1.23 eV.
(2) Lattice matched In0.53Ga0.47As/AlAs0.56Sb0.44 structures grown by solid-source MBE, with a conduction band offset of approximately 1.6 eV.
In both systems, absorption wavelengths shorter than 2 micron (0.62 eV photon energy) were observed. In the strained system, we investigated multiple quantum wells (MQW) as well as short-period superlattices. The absorption strength in the MQWs (Fig.1) diminishes dramatically for wells narrower than 20 Å, either due to problems in dopant activation (although the doping was put into the wells), or because the second subband has already moved into the continuum. The short-period superlattices show clear evidence of dispersive minibands as well as a small, but non-negligible s-polarized absorption. X-ray diffraction data show that the individual layers are elastically strained, with an overall strain compensation better than 0.2%.
The MQW structures of the antimonide system (modulation doped) exhibit very strong absorption, not degrading for wells down to 27 Å thickness (Fig. 2). Due to the high barriers, a wavelength shorter than 2 microns can be reached already with this thickness value.
Keywords: intersubband absorption, quantum cascade laser
  • Lecture (Conference)
    7th Int. Conference on Intersubband Transitions in Quantum Wells, 1.-5. Sept. 2003, Evolene, Switzerland (auf CD-ROM publiziert)

Publ.-Id: 5834 - Permalink

A modified ion sputter source with increased lifetime
Friedrich, M.; Tyrroff, H.;
The Cs sputter ion source HVEE 860-C has shown significant erosion of inner parts after an operation time of some thousand hours. This is caused by Cs ions generated at hot surfaces outside the spherical ioniser surface. The calculated trajectories of these ions and the erosion patterns show an excellent correspondence. The suppression of the disturbing ions has resulted in increased lifetimes of the ion source and an improved focus of the primary Cs ions on the sputter target. The modified sputter ion source is still in operation without any maintenance (about 3000 operating hours at October 2003).
Keywords: Ion Sources, Negative Ions, Electrostatic Accelerators.
  • Lecture (Conference)
    37th Symposium of Northeastern Accelerator Personnel, Strasbourg, 2003
  • Contribution to proceedings
    37th Symposium of Northeastern Accelerator Personnel, Strasbourg, 2003 (auf CD-ROM)

Publ.-Id: 5833 - Permalink

Autoradiographic analyses of 5-HT1A and 5-HT2A receptors after social isolation in mice
Schiller, L.; Jähkel, M.; Kretzschmar, M.; Brust, P.; Oehler, J.;
Social isolation of rodents is used to model human psychopathological processes. In the present study, the effects of intermediate and long term isolation housing on postsynaptic 5-HT1A and 5-HT2A receptors were analyzed in male mice housed in groups or isolation for 4 and 12 weeks. [3H]8-OH-DPAT and [3H]ketanserin were used to label 5-HT1A and 5-HT2A receptors. Four representative sagittal sections (planes 1–4) were scored by in vitro autoradiography. Whereas after 4 weeks of housing both receptor densities were lowered significantly in isolated mice, after 12 weeks of housing only marginal isolation effects were seen. Intermediate isolation reduced 5-HT1A receptors especially in the lateral frontal, parietal and entorhinal cortex (-63%), in the lateral CA1–3 and dentate gyrus region of the hippocampus (-68%), in the basolateral, basomedial, central and medial amygdaloid nuclei (between -38 and -66%), and in the hypothalamus (–28%). 5-HT2A receptors were strongly reduced in the frontal cortex (between -47 and -74%), in the hippocampus (between -47 and -95%), in the striatum (between -66 and -76%), and in the accumbens nucleus (between -59 and -73%) in comparison to group housed control mice. After 12 weeks of isolation in the hippocampus continuously decreased 5-HT1A receptor densities were demonstrated (between -24 and -61%). But increased 5-HT2A receptor densities were seen in the lateral striatum (+86%) compared to control mice. Age-dependent effects were also found. After 12 weeks of group housing the 5-HT1A and 5-HT2A receptor densities were decreased (between -28 and -54%) in all analyzed brain regions in comparison to 4 weeks of group housing. Isolated animals showed diminished 5-HT1A receptor densities in the cortex (-14%) and hippocampus (-15%), but increased 5-HT1A receptor densities in the amygdala (+33%) after 12 weeks. The 5-HT2A receptor densities were increased in all analyzed regions (between +31 and +96%) after 12 weeks of isolation compared to 4 weeks. To explain these dynamic, time-dependent pattern of isolation-induced changes different regulation processes are supposed regarding 5-HT1A and 5-HT2A receptors. Besides metabolism-related adaptation processes also neurotransmitter and hormonal (e.g., glucocorticoid) interactions especially in limbic regions have to be considered.
  • Brain Research 980 (2003) 169-178

Publ.-Id: 5832 - Permalink

On the Dynamic Behaviour of a Charging System of a Van de Graaff Belt Generator
Bürger, W.;
The dynamic stability of the voltage of Van de Graaff belt generators depends to a great extend on the internal impedance of the charging current supply and on the dynamic precision of the current measurement. A charging stabilizer with increased dynamic precision based on guard technique was developed. The arrangement and results are explained, a disturbance compensation is discussed.
Keywords: Van de Graaff belt generator, current stabilisation, dynamic behaviour, modellation, disturbance compensation
  • Lecture (Conference)
    Proceedings of the 37th Symposium of North Eastern Accelerator PersonnelIReS Strasbourg 13 - 16 October 2003
  • Contribution to proceedings
    Proceedings of the 37th Symposium of North Eastern Accelerator PersonnelIReS Strasbourg 13 - 16 October 2003

Publ.-Id: 5831 - Permalink

Advanced thermal processing of ultrashallow implanted junctionsusing flash lamp annealing
Skorupa, W.; Gebel, T.; Yankov, R. A.; Paul, S.; Lerch, W.; Downey, D. F.; Arevalo, E. A.;
The use of flash lamp annealing for ultra-shallow junction formation in silicon has been described. Low energy boron and arsenic implants have been heat-treated in this way using peak temperatures in the range of 1100o to 1300oC and effective anneal times of 20 ms and 3 ms. Secondary ion mass spectrometry and four point probe measurements have been undertaken to determine the junction depth and the sheet resistance, respectively. Optimum processing conditions have been identified, under which one can obtain combinations of junction depth and sheet resistance values that meet the 90 nm technology node requirements and beyond.
Keywords: semiconductor, silicon, low energy boron implantation, low energy arsenic implantation, flash lamp annealing, ultra shallow junction, thermal processing
  • Journal Electrochemical Society 152(2005)6, G436-G440

Publ.-Id: 5830 - Permalink

Comparison of the updated solutions of the 6th dynamic AER benchmark - main steam line break in a NPP with VVER-440
Kliem, S.;
The 6th dynamic AER Benchmark is used for the systematic validation of coupled 3D neutron kinetic/thermal hydraulic system codes. It was defined at the 10th AER-Symposium. In this benchmark, a hypothetical double ended break of one main steam line at full power in a VVER-440 plant is investigated. The main thermal hydraulic features are the consideration of incomplete coolant mixing in the lower and upper plenum of the reactor pressure vessel and an asymmetric operation of the feed water system. For the tuning of the different nuclear cross section data used by the participants, an isothermal re-criticality temperature was defined.
First solutions of the benchmark were compared during the 11th AER-Symposium. Due to the considerable spreading of these first results, the participants continued the work on the calculation of the benchmark. Updated solutions were received from VTT Processes Espoo (HEXTRAN/SMABRE), Kurchatov Institute Moscow (BIPR8/ATHLET), NRI Rez (RELAP5-3D) and Forschungszentrum Rossendorf (DYN3D/ATHLET). The solution of KFKI AEKI Budapest (KIKO3D/ATLET) remained unchanged.
The paper gives an overview on the behaviour of the main thermal hydraulic and neutron kinetic parameters in the provided solutions. The differences in the updated solution in comparison to the previous ones are described. Improvements in the modelling of the transient led to a better agreement of a part of the results while for another part the deviations rose up. The sensitivity of the core power behaviour on the secondary side modelling is discussed in detail.
  • Lecture (Conference)
    XIII. AER-Symposium on VVER Physics and Reactor Safety, Dresden, Germany, September 23-26, 2003, Proceedings pp. 413-444
  • Contribution to proceedings
    XIII. AER-Symposium on VVER Physics and Reactor Safety, Dresden, Germany, September 23-26, 2003, Proceedings pp. 413-444

Publ.-Id: 5828 - Permalink

Phi meson production in near threshold proton-nucleus collisions
Barz, H.-W.; Zetenyi, M.;
The cross section for production of phi mesons inproton-nucleus reactions is calculatedas a function of the target mass. The decay width of the phi meson is affected by the change of the masses of the phi, K+ and K- mesons in the medium. A strong attractive K- potential leads to a measurable change of the behavior of the cross section as a function of the target mass. Comparison between the kaon and electron decay modes are made.
Keywords: Phi meson production, proton-nucleus collisions, mass dependence of cross section

Publ.-Id: 5827 - Permalink

Electroproduction of Strangeness on Light Nuclei
Dohrmann, F.; Abbott, D.; Ahmidouch, A.; Ambrozewicz, P.; Armstrong, C. S.; Arrington, J.; Asaturyan, R.; Assamagan, K.; Avery, S.; Bailey, K.; Baker, O. K.; Beedoe, S.; Bitao, H.; Breuer, H.; Brown, D. S.; Carlini, R.; Cha, J.; Chant, N.; Christy, E.; Cochran, A.; Cole, L.; Collins, G.; Cothran, C.; Crowder, J.; Cummings, W. J.; Danagoulian, S.; Duncan, F.; Dunne, J.; Dutta, D.; Eden, T.; Elaasar, M.; Ent, R.; Ewell, L.; Fenker, H.; Fortune, H. T.; Fujii, Y.; Gan, L.; Gao, H.; Garrow, K.; Geesaman, D. F.; Gueye, P.; Gustafsson, K.; Hafidi, K.; Hansen, J. O.; Hinton, W.; Jackson, H. E.; Juengst, H.; Keppel, C.; Klein, A.; Koltenuk, D.; Liang, Y.; Liu, J. H.; Lung, A.; Mack, D.; Madey, R.; Markowitz, P.; Martoff, C. J.; Meekins, D.; Mitchell, J.; Miyoshi, T.; Mkrtchyan, H.; Mohring, R.; Mtingwa, S. K.; Mueller, B.; O'Neill, T. J.; Niculescu, G.; Niculescu, I.; Potterveld, D. H.; Price, J. W.; Raue, B. A.; Reimer, P. E.; Reinhold, J.; Roche, J.; Roos, P.; Sarsour, M.; Sato, Y.; Savage, G.; Sawafta, R.; Segel, R. E.; Semenov, A. Y.; Stepanyan, S.; Tadevosian, V.; Tajima, S.; Tang, L.; Terburg, B.; Uzzle, A.; Wood, S.; Yamaguchi, H.; Yan-1, C.; Yan-2, C.; Yuan, L.; Zeier, M.; Zeidman, B.; Zihlmann, B.;
The A(e,e'K+)YX reaction has been investigated in Hall C at Jefferson Laboratory. Data were taken for Q^2= 0.35 and 0.5 GeV^2 at a beam energy of 3.245 GeV for 1H,2H,3He, 4He targets. The missing mass spectra are fitted with Monte Carlo simulations taking into account the production of Lambda and Sigma0 hyperon production off the proton, and Sigma- off the neutron. Models for quasifree production are compared to the data, excess yields close to threshold are attributed to FSI. Evidence for Lambda-hypernuclear bound states is seen for 3,4 He targets. This is the first time, the electroproduction of these hypernuclei has been measured.
Keywords: Electroproduction, Strangeness, Hyperons, Hypernuclear boundstates
  • Lecture (Conference)
    SENDAI 03, International Symposium on Electrophoto-production of Strangeness on Nucleons and Nuclei, June 16-18 2003, Sendai. Japan
  • Contribution to proceedings
    Proceedings of SENDAI 03, International Symposium on Electrophoto-production of Strangeness on Nucleons and Nuclei, 16.-18.06. 2003, Sendai, Japan - Singapore World Scientific 2004, 146-151

Publ.-Id: 5826 - Permalink

Multi-component clustering in VVER-type pressure vessel steels - Thermodynamic aspects and impact on SANS
Gokhman, A.; Böhmert, J.; Ulbricht, A.;
APFIM investigation of irradiated VVER 440-type reactor pressure vessel steels suggests the appearance of multi-component clusters. The effect is surprising from the thermodynamic point of view. Numerical estimations of the negative minimum of the thermodynamic driving forces for a multi-component system are carried out considering a quasi-quaternary system consisting of Fe, Mn, Si and vacancies. A relative minimum was only found for a composite model of the multi-component clusters composed from a Fe containing core and a vacancies-rich shell. Such structures can agree with the small angle neutron scattering curves measured. On the other hand, the scattering curves do not provide features which prove the existence of core-shell-structures.
Keywords: Radiation, neutron embrittlement, small angle neutron scattering, radiation defects

Publ.-Id: 5825 - Permalink

Depth-related microstructure of Rf plasma nitrocarburized austenitic stainless steel
Abd El-Rahman, A. M.; Negm, N. Z.; Prokert, F.; El-Hossary, F. M.; Richter, E.; Möller, W.;
The depth dependence of elemental composition, phase distribution, and cross sectional morphology of rf plasma nitrocarburized 304 austenitic stainless steel were investigated using glow discharge optical spectroscopy (GDOS), grazing incidence X-ray
diffraction (GIXRD), and optical microscope (OM), respectively. A step-wise mechanically polishing method was used to remove successive sublayers of the treated surface. It is found that the properties of the nitrocarburized layer depend critically on the plasma gas composition, which controls the supersaturation of nitrogen and carbon through the compound layer depth. Iron nitride phases and/or nitrogen expanded austenite phase (gN) were detected in the nitrocarburized layer prepared at high plasma nitrogen (N2) content. In the compound layer processed at high plasma carbon (C2H2) content, besides the carbon expanded austenite phase (gC), carbide phases were found predominantly in the top-layer, in which the carbon concentration has a maximum value of ~2 wt. %. The lattice expansion of the expanded austenite phases depends on the depth with the variation of the local nitrogen and carbon content. The plasma processing power has enormous influence on the nitrogen and carbon distribution in treated sublayers.

Keywords: Nitrocarburising; 304 austenitic stainless steel; GDOS; Depth microstructure.

Publ.-Id: 5824 - Permalink

Enhancement in redox and electrocatalytic activity observed on Si ion-implanted Ni
Pham, M. T.; Maitz, M.; Richter, E.; Reuther, H.; Mücklich, A.; Prokert, F.;
Ni was surface-alloyed with Si by ion implantation. The material was examined for its redox and electrocatalytic behaviour in NaOH by cyclic voltammetry. The surface war characterized by X-ray photoelectron spectroscopy, X-ray and electron diffraction, and electron and atomic force microscopy. The activity toward the redox conversion of Ni(OH)2 " NiOOH and the anodic oxidation of glucose was enhanced by ca. 3.5 times and ca. 2.8 times, respectively. The material is an amorphous mixed oxide of Ni and Si. The effect was discussed considering the true surface area and the generation of active surface sites in relation to the oxygen evolution.
Keywords: Si-Ni alloy electrodes, electrocatalysis, glucose, surface alloying, ion implantation
  • Journal of Materials Research 19(2004)2, 616-622

Publ.-Id: 5823 - Permalink

Analysis of a PWR core baffle considering irradiation induced creep
Altstadt, E.; Kumpf, H.; Weiß, F.-P.; Fischer, E.; Nagel, G.; Sgarz, G.;
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.
Keywords: Pressurized water rector, Core baffle, Irradiation induced creep, Gamma heating
  • Annals of Nuclear Energy 31(2004)7, 723-736

Publ.-Id: 5822 - Permalink

Equipment for beam diagnostics
Friedrich, M.;
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.
Keywords: Accelerator, Beam diagnostics
  • Contribution to external collection
    R. Hellborg: Electrostatic Accelerators - Fundamentals and Applications, Berlin Heidelberg: Springer, 2005, 3-540-23983-9, 317-327

Publ.-Id: 5821 - Permalink

Superconducting RF guns for FELs
Janssen, D.; Büttig, H.; Evtushenko, P.; Lehnert, U.; Michel, P.; Möller, K.; Schneider, C.; Stephan, J.; Teichert, J.; Kruchkov, S.; Myskin, O.; Tribendis, A.; Volkov, V.; Sandner, W.; Will, I.; Quast, T.; Goldammer, K.; Marhauser, F.; Ylä-Oijala, P.;
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.
Keywords: Cavity; Superconductivity; Photocathode; Laser; Electron gun
  • Lecture (Conference)
    AES Meeting,13.01.2004, Medford, USA
  • Nuclear Instruments and Methods in Physics Research Section A, 528(2004)1-2, 305-311
    DOI: 10.1016/j.nima.2004.04.076
  • Contribution to proceedings
    25th International Free Electron Laser Conference, and the 10th FEL Users Workshop, 08.-12.09.2003, Tsukuba, Ibaraki, Japan
    41.60.Cr; 41.75.Fr; 42.55.Xi; 82.25.-j

Publ.-Id: 5820 - Permalink

Chirality of rotating nuclei
Dimitrov, V. I.; Frauendorf, S.;
kein Abstract
  • Contribution to proceedings
    Proceedings of the third International Conference on Fission and Properties of Neutron-Rich Nuclei, Sanibel Island, Florida, 2002, World Science Pub., 1(2003), p. 93

Publ.-Id: 5819 - Permalink

Temperature-induced pair correlations in cluster and nuclei
Frauendorf, S.; Kuzmenko, N. K.; Mikhailov, V. M.; Sheikh, J. A.;
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.

Publ.-Id: 5818 - Permalink

Cranked relativistic Hartree-Bogoliubov theory: probing the gateway to superheavy nuclei
Afanasjev, A. V.; Khoo, T. L.; Frauendorf, S. G.; Lalazissis, G. A.; Ahmad, I.;
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.

Publ.-Id: 5817 - Permalink

Evidence for isovector neutron-proton pairing from high-spin states in N = Z 74Rb
O´Leary, C. D.; Svensson, C. E.; Frauendorf, S. G.; Afanasjev, A. V.; Appelbe, D. E.; Austin, R. A. E.; Ball, G. C.; Cameron, J. A.; Clark, R. M.; Cromaz, M.; Fallon, P.; Hodgson, D. F.; Kelsall, N. S.; Macciavelli, A. O.; Ragnarsson, I.; Sarantites, D.; Waddington, J. C.; Wadsworth, R.;
kein Abstract
  • Phys. Rev. C67, 021301 (R) (2003)

Publ.-Id: 5816 - Permalink

Monitoring postradiotherapeutic changes of lung tissue with CTR, PET and SPECT
Beuthien-Baumann, B.; Eckhardt, M.; Herrmann, T.; Hliscs, R.; van den Hoff, J.; Kumpf, R.; Blank, H.; Baumann, M.;
  • Abstract in refereed journal
    12th International Congress of Radiation Research, 17.-22.08.2003 in Brisbane, Australia; Abstract book (2003) p270
  • Poster
    12th International Congress of Radiation Research; Brisbane, Australia, 17.-22.08.2003

Publ.-Id: 5815 - Permalink

In-band and inter-band B (E2) values within the triaxial projected shell model
Boutachkov, P.; Aprahamian, A.; Sun, Y.; Sheikh, J. A.; Frauendorf, S.;
kein Abstract
  • Eur. Phys. Journal A 15, 455 (2002)

Publ.-Id: 5814 - Permalink

Regional cerebral metabolism in unipolar depression: the relationship with clinical characteristics
Beuthien-Baumann, B.; Zündorf, G.; Lüdecke, S.; Triemer, A.; Schierz, K.; Herholz, K.; Holthoff, V. A.;
  • Abstract in refereed journal
    Brain and BrainPET 2003, 29.06.-03.07.2003 in Calgary, Canada; J Cereb Blood Flow Metabol (2003) 23 Suppl1 p642
  • Poster
    Brain and BrainPET 2003; Calgary, Canada, 29.06.-03.07.2003

Publ.-Id: 5813 - Permalink

Observation of a doublet band in the nucleus 128Pr
Petrache, C. M.; Lo Bianco, G.; Bazzacco, D.; Menegazzo, R.; Nespolo, M.; de Angelis, G.; Blasi, N.; Dimitrov, V. I.; Frauendorf, S. G.; Semmes, P.;
kein Abstract
  • Phys. Rev. C65, 054324 (2002)

Publ.-Id: 5812 - Permalink

Behavioral disturbances and regional cerebral metabolism in probable Alzheimer´s Disease
Holthoff, V. A.; Herholz, K.; Lüdecke, S.; Spirling, S.; Kalbe, E.; Lenz, O.; Zündorf, G.; Beuthien-Baumann, B.;
  • Abstract in refereed journal
    Brain and BrainPET 2003, 29.06.-03.07.2003 in Calgary, Canada; J Cereb Blood Flow Metabol (2003) 23 Suppl1 p631
  • Poster
    Brain and BrainPET 2003; Calgary, Canada, 29.06.-03.07.2003

Publ.-Id: 5811 - Permalink

Monitoring postradiotherapeutic changes of lung tissue with PET and SPECT
Beuthien-Baumann, B.; Eckhardt, M.; Herrmann, T.; Hliscs, R.; Oehme, L.; van den Hoff, J.; Kumpf, R.; Geyer, P.; Blank, H.; Baumann, M.;
  • Abstract in refereed journal
    International Congress of Translational Research, 16.-18.03.2003 in Lugano, Int J Radiat Oncol Biol Physics (Suppl.) (2003): 499
  • Poster
    International Congress of Translation Research; Lugano, 16.-18.03.2003

Publ.-Id: 5810 - Permalink

Major-Depression im höheren Lebensalter: Regionale Hirnfunktion und kognitive Leistungsfähigkeit in Abhängigkeit vom Erkrankungsalter
Holthoff, V. A.; Lüdecke, S.; Beuthien-Baumann, B.; Zündorf, G.; Triemer, A.; Schellong, J.;
  • Abstract in refereed journal
    6. Jahrestagung der Deutschen Gesellschaft für Gerontopsychiatrie und -psychotherapie e. V. 2.-5. April 2003 in München
  • Lecture (Conference)
    6. Jahrestagung der Deutschen Gesellschaft für Gerontopsychiatrie und -psychotherapie e. V. 2.-5. April 2003 in München

Publ.-Id: 5809 - Permalink

High-spin studies of N ~ Z Nuclei in the mass 70 region
Kelsall, N. S.; Svensson, C. E.; Fisher, S.; Appelbe, D. E.; Austin, R. A. E.; Balamuth, D. P.; Ball, G. C.; Cameron, J. A.; Carpenter, M. P.; Clark, R. M.; Cromaz, M.; Deleplanque, M. A.; Diamond, R. M.; Durell, J. L.; Fallon, P.; Freeman, S. J.; Hausladen, P. A.; Hodgson, D. F.; Janssens, R. V. F.; Jenkins, D. G.; Lane, G. J.; Leddy, M. J.; Lister, C. J.; Macchiavelli, A. O.; O`Leary, C. D.; Sarantites, D. G.; Stephens, F. S.; Schmidt, D. C.; Seweryniak, D.; Varley, B. J.; Vincent, S.; Vetter, K.; Waddington, J. C.; Warsworth, R.; Ward, D.; Wilson, A. N.; Afanasjev, A. V.; Frauendorf, S. G.; Ragnarsson, I.; Wyss, R.;
kein Abstract
  • Contribution to proceedings
    Proceedings of the Conference on Frontiers of Nuclear Structure, Berkeley, California, 2002, UC Berkeley, Clark Kerr Campus, 261 (2003)

Publ.-Id: 5808 - Permalink

Gross shell structure of moments of inertia
Deleplanque, M. A.; Frauendorf, S.; Pashkevich, V. V.; Chu, S. Y.; Unzhakova, A.;
kein Abstract
  • Contribution to proceedings
    Proceedings of the Conference on Frontiers of Nuclear Structure, Berkeley, California, 2002, UC Berkeley, Clark Kerr Campus, 105 (2003)

Publ.-Id: 5806 - Permalink

Left-handed nuclei
Dimitrov, V.; Dönau, F.; Frauendorf, S.; Zhang, J.;
kein Abstract
  • Contribution to proceedings
    Proceedings of the Conference on Frontiers of Nuclear Structures, Berkeley, California, 2002, UC Berkeley, Clark Kerr Campus, 105 (2003)
  • Lecture (Conference)
    Colloquium, Dep. Phys. and Astronomy, 27.10.2005, Nashville, USA

Publ.-Id: 5805 - Permalink

Probing the gateway to superheavy nuclei in cranked relativistic Hartree-Bogoliubov theory
Afanasjev, A. V.; Khoo, T. L.; Frauendorf, S.; Lalazissis, G. A.; Ahmad, I.;
kein Abstract
  • Contribution to proceedings
    Proceedings of the Conference on Frontiers of Nuclear Structure, Berkeley, California, 2002, UC Berkeley, Clark Kerr Campus, 379 (2003)

Publ.-Id: 5804 - Permalink

Rotating nuclei in the relativistic mean field theory: Microscopic nature of nuclear magnetism
Afanasjev, A. V.; Frauendorf, S. G.; Ring, P.;
kein Abstract
  • Contribution to proceedings
    Proceedings of the NATO Advanced Research Workshop on "The Nuclear Many-Body Problem 2001", Brijuni, Pula, Croatia, 2001, Eds. W. Nazarewicz and D. Vretenar, NATO Science Series II-Math., Phys. and Chem. (Kluwer Academic Publ.) v. 53 (2002) 103-111

Publ.-Id: 5803 - Permalink

Evidence for magnetic rotation in the light tin region
Wadsworth, R.; Camaron, J. A.; Clark, R. M.; Frauendorf, S.; (Editors)
kein Abstract
  • Phys. Scripta T88 (2000) 49

Publ.-Id: 5802 - Permalink

A hybrid version of the tilted axis cranking model and its application to 128Ba
Dimitrov, V. I.; Dönau, F.; Frauendorf, S.;
kein Abstract
  • Phys. Rev. C62 (2000) 024315

Publ.-Id: 5801 - Permalink

Chirality of nuclear rotation
Dimitrov, V. I.; Frauendorf, S. G.; Dönau, F.;
kein Abstract
  • Physical Review Letters 84 (2000) 5732
  • Lecture (Conference)
    Annual meeting of the Division of Nuclear Physics, 01.04.2004, Bejing, China

Publ.-Id: 5800 - Permalink

Symmetry breaking by neutron-proton pairing
Frauendorf, S. G.; Sheikh, J.;
kein Abstract
  • Phys. Scripta T88(2000)162

Publ.-Id: 5799 - Permalink

Description of multi quasiparticle bands by the tilted axis cranking
Frauendorf, S. G.;
kein Abstract
  • Nucl. Phys. A677 (2000) 115

Publ.-Id: 5797 - Permalink

Moment of inertia for multi-quasiparticle configurations
Frauendorf, S. G.; Sheikh, J. A.; Walker, P. M.; Neergard, K.;
kein Abstract
  • Phys. Rev. C61 (2000) 064324

Publ.-Id: 5796 - Permalink

Shears mechanism in 109Cd
Chiara, C. J.; Asztalos, S. J.; Busse, B.; Clark, R. M.; Cromaz, M.; Deleplanque, M. A.; Diamond, R. M.; Fallon, P.; Fossan, D. B.; Jenkins, D. G.; Juutinen, S.; Kelsall, N. S.; Krücken, R.; Lane, G. J.; Lee, I. Y.; Macchiavelli, A. O.; Macleod, R. W.; Schmid, G.; Sears, J. M.; Smith, J. F.; Stephens, F. S.; Vetter, K.; Wadsworth, R.; Frauendorf, S. G.;
kein Abstract
  • Phys. Rev. C61(2000) 034318

Publ.-Id: 5795 - Permalink

Evidence for Shears Bands in 108Cd
Kelsall, N. S.; Wadsworth, R.; Asztalos, S. J.; Busse, B.; Chiara, C. J.; Clark, R. M.; Deleplanque, M. A.; Diamond, R. M.; Fallon, P.; Fossan, D. B.; Jenkins, D. G.; Juutinen, S.; Krücken, R.; Lane, G. J.; Lee, I. Y.; Macchiavelli, A. O.; Parry, C. M.; Schmid, R. W.; Sears, J. M.; Stephens, F. S.; Smith, J. F.; Vetter, K.; Frauendorf, S. G.;
kein Abstract
  • Phys. Rev. C61(2000) 011301(R)

Publ.-Id: 5794 - Permalink

Evidence for Shears Bands in 108Cd
Kelsall, N. S.; Wadsworth, R.; Asztalos, S. J.; Busse, B.; Chiara, C. J.; Clark, R. M.; Deleplanque, M. A.; Diamond, R. M.; Fallon, P.; Fossan, D. B.;
kein Abstract
  • Phys. Rev. C61 (2000) 034318

Publ.-Id: 5792 - Permalink

Oxidativ modifizierte Lipoproteine und deren Antikörper bei Patienten mit Antiphospholipid-Syndrom
Roch, B.; Kopprasch, S.; Pietzsch, J.; Schröder, H.;
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.

Publ.-Id: 5791 - Permalink

The pivotal role of scavenger receptor CD36 and phagocyte-derived oxidants in oxidized low density lipoprotein-induced adhesion to endothelial cells
Kopprasch, S.; Pietzsch, J.; Westendorf, T.; Kruse, H.-J.; Graessler, J.;
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.
Keywords: Phagocyte, Adhesion, Reactive oxygen species, Oxidized LDL, Endothelial, Cell, HDL, CD36
  • International Journal of Biochemistry and Cell Biology 36(2004)3, 460-471

Publ.-Id: 5790 - Permalink

Validation of different chemilumigenic substrates for detecting extracellular generation of reactive oxygen species by phagocytes and endothelial cells
Kopprasch, S.; Pietzsch, J.; Graessler, J.;
  • Luminescence (2003) 18: 268-273

Publ.-Id: 5789 - Permalink

The protective effects of HDL and its constituents against neutrophil respiratory bust activation by hypochlirite-oxidized LDL
Kopprasch, S.; Pietzsch, J.; Graessler, J.;
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.
Keywords: atherosclerosis, oxidized low-density lipoprotein, hypochlorite, high-density lipoprotein, neutrophils, respiratory burst
  • Molecular and Cellular Biochemistry 258(2004), 121-127

Publ.-Id: 5788 - Permalink

Analysis of non-protein amino acids as specific markers of low density lipoprotein apolipoprotein B-100 oxidation in human atherosclerotic lesions: the use of N(O,S)-ethoxycarbonyl trifluoroethyl ester derivatives and GC-MS
Pietzsch, J.; Bergmann, R.; Kopprasch, S.;
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.
  • Spectroscopy 18(2004),177-183

Publ.-Id: 5787 - Permalink

Analysis of 6-hydroxy-2-aminocaproic acid (HACA) as a specific marker of protein oxidation: The use of N(O,S)-ethoxycarbonyl trifluoroethyl ester derivatives and gas chromatography/mass spectrometry
Pietzsch, J.; Bergmann, R.;
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.
Keywords: Amino acids, Hemin, Low density lipoprotein, Protein oxidations, Gas chromatography/mass spectrometry
  • Amino Acids 26(2004), 45-51

Publ.-Id: 5786 - Permalink

Fortschritte in der Aminosäureanalytik: N(O,S)-Ethoxycarbonyl-(trifluoro)ethylester-Derivate
Pietzsch, J.;
  • Bioforum 10/2003, 643-645

Publ.-Id: 5785 - Permalink

Assessment of metabolism of native and oxidized low density lipoprotein in vivo: insights from animal positron emission tomography (PET) studies
Pietzsch, J.; Bergmann, R.; Wüst, F.; Grote, M.; Hultsch, C.; Pawelke, B.; van den Hoff, J.;
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.
  • Lecture (Conference)
    8th International Congress on Proteins and Amino Acids, Rome, Italy, 5-9 September 2003
  • Abstract in refereed journal
    Amino Acids (2003) 25: 120

Publ.-Id: 5784 - Permalink

Electromagnetic flow control leading to a strong drag reduction of a sphere
Shatrov, V.; Gerbeth, G.;
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.
  • Fluid Dynamics Research 36(2005), 153-173

Publ.-Id: 5782 - Permalink

Separation control by electromagnetic forces - applications at ships
Gerbeth, G.; Weier, T.;
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.
  • Lecture (others)
    Seoul National University, 07.10.2003

Publ.-Id: 5781 - Permalink

Review of the Status of SRF Photo-Injectors
Teichert, J.; Büttig, H.; Evtushenko, P.; Janssen, D.; Lehnert, U.; Michel, P.; Schneider, C.;
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.
Keywords: photoelectron-injector electron source superconductivity superconducting cavity rf-photogun srf-photo-injector
  • Lecture (Conference)
    11th Workshop on RF-Sperconductivity SRF 2003, 5 pages, 08. – 12. September 2003, Lübeck/Travemünde, Germany
  • Contribution to proceedings
    11th Workshop on RF-Sperconductivity SRF 2003, 5 pages, 08. – 12. September 2003, Lübeck/Travemünde, Germany

Publ.-Id: 5779 - Permalink

Two-dimensional heterogeneous transport theory hot zero-power benchmarks for the WWER-1000 reactors
Petkov, P. T.; Mittag, S.;
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.
  • Lecture (Conference)
    13. Symposium of AER, Dresden, 22-26 September, 2003, pp. 77-88
  • Contribution to proceedings
    13. Symposium of AER, Dresden, 22-26 September, 2003, pp. 77-88

Publ.-Id: 5778 - Permalink

A new DYN3D library for the WWER-1000 reactors
Petkov, P. T.; Mittag, S.; Christoskov, I.; Kamenov, K.; Antov, A.; Bakalov, I.; Wehner, H.;
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.
  • Lecture (Conference)
    13. Symposium of AER, Dresden, 22-26 September, 2003, pp. 109-122
  • Contribution to proceedings
    13. Symposium of AER, Dresden, 22-26 September, 2003, pp. 109-122

Publ.-Id: 5777 - Permalink

Validation of Coupled Neutronics / Thermal Hydraulics Codes for VVER Reactors (VALCO)
Weiss, F.-P.; Mittag, S.; Langenbuch, S.; Vanttola, T.; Hämäläinen, A.; Keresztúri, A.; Hádek, J.; Darilek, P.; Petkov, P. T.; Kuchin, A.; Hlbocky, P.; Sico, D.; Danilin, S.; Powney, D.;
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.
  • Lecture (Conference)
    Symposium FISA-2003 - EU research in reactor safety, European Commission, Luxembourg, 10-13 November 2003, Pre-proceedings pp. 490-495
  • Contribution to proceedings
    Symposium FISA-2003 - EU research in reactor safety, European Commission, Luxembourg, 10-13 November 2003, Pre-proceedings pp. 490-495

Publ.-Id: 5776 - Permalink

Specific hemin catalyzed low density lipoprotein ocidation reactions: implications for metabolic and inflammatory diseases
Pietzsch, J.;
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.
  • Abstract in refereed journal
    Amino Acids (2003) 25: 120
  • Lecture (Conference)
    8th International Congress on Proteins and Amino Acids, Rome, Italy, 5-9 September 2003

Publ.-Id: 5775 - Permalink

Discontinuity factors for non-multiplying hexagonal nodes in VVER reactors
Mittag, S.; Petkov, P. T.; Grundmann, U.;
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.
  • Lecture (Conference)
    13. Symposium of AER, Dresden, 22-26 September, 2003, pp. 89-108
  • Contribution to proceedings
    13. Symposium of AER, Dresden, 22-26 September, 2003, pp. 89-108

Publ.-Id: 5774 - Permalink

DYN3D Calculations for the V-1000 Test Facility and Comparisons with the Measurements
Grundmann, U.; Mittag, S.;
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.

Keywords: neutron transport nuclear reactors research reactors neutron kinetics diffusion equation nodal methods measurementss code validation
  • Lecture (Conference)
    Proceedings of 13. Symposium of AER,p. 521-539, Dresden, 22-26. September, 2003
  • Contribution to proceedings
    Proceedings of 13. Symposium of AER,p. 521-539, Dresden, 22-26. September, 2003

Publ.-Id: 5773 - Permalink

Therapy of malignant ascites in vivo by 211At-labelled microspheres
Bredow, J.; Kretzschmar, M.; Wunderlich, G.; Dörr, W.; Pohl, T.; Franke, W.-G.; Kotzerke, J.;
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.
  • Nuklearmedizin 43(2004), 63-68

Publ.-Id: 5771 - Permalink

Phase composition and properties of iron nanocrystals and clusters embended in MgO matrix
Schneeweiss, O.; Pizúrová, N.; Jirásková, Y.; ŽÁk, T.; Bezdicka, P.; Reuther, H.;
Phase composition and properties of iron nanocrystals and clusters embended in MgO matrix
  • Poster
    Int. Conference on the Applications of the Mössbauer Effect, Muscat, Oman, 21.-25.9.2003

Publ.-Id: 5770 - Permalink

Low temperature Mössbauereffect studies of c-FeSi films synthesized by molecular beam epitaxy and by ion implantation
Walterfang, M.; Reuther, H.; Keune, W.;
Low temperature Mössbauereffect studies of c-FeSi films synthesized by molecular beam epitaxy and by ion implantation
  • Poster
    Int. Conference on the Applications of the Mössbauer Effect, Muscat, Oman, 21.-25.9.2003

Publ.-Id: 5769 - Permalink

Anorganische Kolloide im Wasser der Elbe
Opel, K.; Hüttig, G.; Zänker, H.;
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.
Keywords: colloids, particles, river water, contaminants, photon correlation spectroscopy, centrifugation, filtration, REM, EDX
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-395 Januar 2004


Publ.-Id: 5766 - Permalink

Identification of isomers in the N = Z+1 nucleus 95Ag
Döring, J.; Grawe, K.; Schmidt, K.; Borcea, R.; Galanopoulos, S.; Gorska, M.; Harissopulos, S.; Hellström, M.; Janas, Z.; Kirchner, R.; La Commara, M.; Mazzocchi, C.; Roeckl, E.; Schwengner, R.;
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.

Publ.-Id: 5765 - Permalink

A hadron nucleus collision event generator for simulations of intermediate energies
Ackerstaff, K.; Bisplinghoff, J.; Bollmann, R.; Cloth, P.; Diehl, O.; Dohrmann, F.; Drueke, V.; Eisenhardt, S.; Engelhardt, H. P.; Ernst, J.; Eversheim, P. D.; Filges, D.; Fritz, S.; Gasthuber, M.; Gebel, R.; Greiff, J.; Gross, A.; Gross-Hardt, R.; Hinterberger, F.; Jahn, R.; Lahr, U.; Langkau, R.; Lippert, G.; Maschuw, R.; Mayer-Kuckuk, T.; Mertler, G.; Metsch, B.; Mosel, F.; Paetz, H.; Petry, H. R.; Prasuhn, D.; von Przewoski, B.; Rohdjess, H.; Rosendaal, D.; Ross, U.; von Rossen, P.; Scheid, H.; Schirm, N.; Schulz-Rojahn, M.; Schwandt, F.; Scobel, W.; Sterzenbach, G.; Theis, D.; Weber, J.; Wellinghausen, A.; Wiedmann, W.; Woller, K.; Ziegler, R.;
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.
  • Nucl. Instrum. Meth. A491 (2002)424

Publ.-Id: 5764 - Permalink

Kaon and antikaon production in dense nuclear matter
Sturm, C.; Böttcher, I.; Debowski, M.; Forster, A.; Grosse, E.; Koczon, P.; Kohlmeyer, B.; Laue, F.; Mang, M.; Naumann, L.; Oeschler, H.; Pühlhofer, F.; Schwab, E.; Senger, P.; Shin, Y.; Speer, J.; Strobele, H.; Surowka, G.; Uhlig, F.; Wagner, A.; Walus, W.;
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.
  • J. Phys. G: Nucl. Part. Phys. 28 (2002) 1895-1902

Publ.-Id: 5763 - Permalink

Quantification of secondary Fe-phases formed during sorption experiments on chlorites
Reuther, H.; Arnold, T.; Krawczyk-Bärsch, E.;
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.
  • Hyperfine Interactions 156/157(2004), 439-443
  • Poster
    Int. Conference on the Applications of the Mössbauer Effect, 21.-25.09.2003, Muscat, Oman

Publ.-Id: 5762 - Permalink

Large area deposition of hydrogenated amorphous carbon films for optical storage disks
Piazza, F.; Grambole, D.; Zhou, L.; Talke, F.; Casiraghi, C.; Ferrari, A. C.; Robertson, J.;
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.
Keywords: Diamond Like carbon, hydrogenated amorphous carbon, ECWR plasma beam source, protective coatings
  • Lecture (Conference)
    14th European Conference on Diamand, Diamand-like Materials, Carbon Nanotubes, Nitrides and Silicon Carbid, Sept. 7 - 12, 2003, Salzburg, Austria
  • Diamond and Related Materials 13(2004), 1505-1510
    DOI: 10.1016/j.diamond.2003.08.030

Publ.-Id: 5761 - Permalink

Investigation of steel surfaces treated by a hybrid ion implantation technique
Reuther, H.; Richter, E.; Prokert, F.; Ueda, M.; Beloto, A. F.; Gomes, G. F.;
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.
  • Hyperfine Interactions 156(2004), 575-579

Publ.-Id: 5758 - Permalink

Surface modified NiTi alloy for biomedical application
Shevchenko, N.; Pham, M. T.; Maitz, M. F.;
no abstract delivered from author
Keywords: TiNi, surface modified, plasma ion implantation
  • Poster
    13th International Summer School on Vacuum, Electron and Ion Technologies, 15-19 September 2003, Varna, Bulgaria

Publ.-Id: 5757 - Permalink

Structure studies of oxygen buried layers in titanium by synchrotron X-ray scattering
Shevchenko, N.; Prokert, F.; von Borany, J.;
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.

Keywords: Buried layers, ion implantation, XRD
  • Poster
    European Vacuum Congress, Berlin, June 23-26, 2003

Publ.-Id: 5756 - Permalink

Studies of surface modified NiTi alloy
Shevchenko, N.; Pham, M. T.; Maitz, M. F.;
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.

Keywords: NiTi, surface modified, biocompatibility, plasma ion implantation
  • Lecture (Conference)
    European Vacuum Congress, Berlin, June 23-26, 2003
  • Applied Surface Science 235(2004), 126-131

Publ.-Id: 5755 - Permalink

Limits of complete equilibration of fragments produced in central Au on Au collisions at intermediate energies
Neubert, W.; Botvina, A. S.;
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.

Publ.-Id: 5754 - Permalink

Temporal evolution of dot patterns during ion sputtering
Bobek, T.; Facsko, S.; Kurz, H.; Dekorsy, T.; Xu, M.; Teichert, C.;
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.
Keywords: ion sputtering, pattern formation, continuum equations, Kuramoto-Sivashinsky equation
  • Physical Review B 68 (2003) 085324

Publ.-Id: 5753 - Permalink

Status of the ELBE accelerator - a driver for different radiation sources
Michel, P.; Gabriel, F.; Grosse, E.;
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
  • Lecture (Conference)
    FEL-Conferenz 2000

Publ.-Id: 5752 - Permalink

An internal friction working model to advance the understanding of effects of radiation and thermal ageing on reactor pressure-vessel steel
van Ouytsel, K.; de Batist, R.; Schaller, R.;
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.
Keywords: Pressure vessel stee; Neutron irradiation; Thermal ageing, Dislocations, Embrittlement; Internal friction
  • International Journal of Pressure Vessels and Piping 80 (2003) 275-284

Publ.-Id: 5751 - Permalink

Development of Ti based coatings using plasma immersion ion implantation assisted deposition techniques and their properties
Mukherjee, S.; Richter, E.; Pham, M. T.; Maitz, M. F.; Prokert, F.; Möller, W.;
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.
Keywords: Biocompatibility, Cell adhesion, Titanium, coating, Titanium nitride
  • Lecture (Conference)
    XIIIth International Conference on Surface Modification of Materials by Ion Beams (SMMIB), San Antonio, Texas, 21.-26.09.2003

Publ.-Id: 5750 - Permalink

r0meson production in the pp->ppp+p-reaction at 3.67 GeV/c
Balestra, F.; Bedfer, Y.; Bertini, R.; Bland, L. C.; Brenschede, A.; Brochard, F.; Bussa, M. P.; Seon-Ho, C.; Colantoni, M. L.; Dressler, R.; Dzemidzic, M.; Faivre, J. C.; Ferrero, A.; Ferrero, L.; Foryciarz, J.; Frohlich, I.; Frolov, V.; Garfagnini, R.; Grasso, A.; Heinz, S.; Jacobs, W. W.; Kuhn, W.; Maggiora, A.; Maggiora, M.; Manara, A.; Panzieri, D.; Pfaff, H. W.; Piragino, G.; Popov, A.; Ritman, J.; Salabura, P.; Tchalyshev, V.; Tosello, F.; Vigdor, S. E.; Zosi, G.;
kein Abstract
  • Physical Review Letters 89 (2002) 092001

Publ.-Id: 5749 - Permalink

Surface properties of NiTi alloy modified by plasma immersion ion implantation
Shevchenko, N.; Pham, M. T.; Maitz, M. F.;
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.

Keywords: Nitinol, Plasmaimmersionsionenimplantation, PIII, Stickstoff
  • Lecture (Conference)
    XIIIth International Conference on Surface Modification of Materials by Ion Beams (SMMIB), San Antonio, Texas, 21.-26.09.2003

Publ.-Id: 5748 - Permalink

Forward K+ Production in Subthreshold pA Collisions at 1.0 GeV
Zolnierczuk, P.; Zwoll, K.; Zychor, I.; Debowski, M.; Müller, H.; Prietzschk, B.; Rimarzig, B.; Schneider, C.; Schneider, H.; Schneider, A.; Schleichert, R.; Schug, G.;
kein Abstract
  • Phys. Rev. Lett. 87(2001)022301

Publ.-Id: 5747 - Permalink

Time-resolved dynamics of ta-C film deposition as predicted by molecular-dynamics simulations
Jäger, H. U.; Belov, A. Y.;
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 Eion=10-80 eV and for substrate temperatures Ts =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 byTs. During this stage, depending on Ts, 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 Ts exceeds a critical temperature Tc. The behaviour of the sp3 content, density and the film stress near the transition temperature is discussed. For super-critical substrate temperatures (Ts > Tc), 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 (Ts <Tc).

Keywords: diamond-like carbon, deposition simulations, substrate temperature, critical temperature
  • Lecture (Conference)
    14th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, Nitrides & Silicon Carbide, 7-12 Sept. 2003, Salzburg, Austria

Publ.-Id: 5746 - Permalink

Titanium Oxide Layers prepared by Metal Plasma Immersion Ion Implantation and Deposition (MePIID) as Hemocompatible Surfaces
Tsyganov, I.; Wieser, E.; Prokert, F.; Richter, E.; Rogozin, A.; Maitz, M. F.;
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.
Keywords: Blutkompatibilität, Titanoxyd, Kristallstruktur, Dotierung
  • Poster
    XIIIth International Conference on Surface Modification of Materials by Ion Beams (SMMIB), San Antonio (Texas), 21.-26.09.2003
  • Contribution to proceedings
    XIIIth International Conference on Surface Modification of Materials by Ion Beams (SMMIB), San Antonio (Texas), 21.-26.09.2003

Publ.-Id: 5745 - Permalink

Proton beam examination of glass – an analytical contribution for preventive conservation
Mäder, M.; Neelmeijer, C.;
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.
Keywords: glass corrosion, ion beam analysis, external beam, PIGE, PIXE, RBS, conservation, preservation
  • Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Volume 226, Issues 1-2 , November 2004, Pages 110-118
    DOI: 10.1016/j.nimb.2004.03.086

Publ.-Id: 5744 - Permalink

Electrochemical behaviour of bimetallic Ni-Ti surface generated by ion implantation
Pham, M. T.; Maitz, M. F.; Richter, E.; Reuther, H.; Prokert, F.; Mücklich, A.;
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.
  • Journal of Materials Science 19(2004)2, 439-446

Publ.-Id: 5741 - Permalink

Iridescent Art Nouveau glass - IBA and XPS for the characterisation of thin iridescent layers
Jembrih, D.; Neelmeijer, C.; Schreiner, M.; Mäder, M.; Ebel, M.; Svagera, R.; Peev, M.;
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.
Keywords: IBA, XPS, iridescent layers, Art Nouveau glass, Tiffany, Loetz
  • Nuclear Instruments and Methods in Physics Research B 181 (2001) 698-702

Publ.-Id: 5739 - Permalink

Comissioning of the ELBE Superconducting Electron Linac
Michel, P.; Büchner, A.; Evtushenko, P.; Gabriel, F.; Lehnert, U.; Teichert, J.; Voigtländer, J.;
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.
  • Lecture (Conference)
    EPAC 2002, Paris, Frankreich, 03.06. - 07.06.2002
  • Contribution to proceedings
    EPAC 2002, 03.-07.06.2002, Paris, Frankreich
    Proceedings of EPAC 2002

Publ.-Id: 5738 - Permalink

Zerstörungsfreie Röntgenfluoreszenzanalyse von Kunstwerken
Schreiner, M.; Mantler, M.; Neelmeijer, C.;
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.
Keywords: RFA, RFA an Luft, zerstörungsfreie Analyse, Kunstwerke
  • Contribution to proceedings
    Archäometrie und Denkmalpflege 2000, Jahrestagung der Arbeitskreise: deutscher Chemiker, deutsche mineralogische Gesellschaft, Landesamt für archäologie Dresden, Kurzberichte 2000, S. 201-204

Publ.-Id: 5737 - Permalink

Irisierende Jugendstilgläser - mit Röntgenfluoreszenz- und Ionenstrahlmethoden auf der Spur ihrer Geheimnisse
Jembrih, D.; Schreiner, M.; Neelmeijer, C.; Mäder, M.; Peev, M.; Krejsa, P.; Clausen, C.;
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.
Keywords: Jugendstilgläser, Irisierung, zerstörungsfreie Identifizierung, Herstellungstechnologie, Tiffany, Lötz, RFA, PIGE, PIXE, RBS
  • Contribution to proceedings
    Archäometrie und Denkmalpflege, Jahrestagung der Arbeitskreise Achäometrie: deutsche Chemiker, deutsche Mineralogen, Landesamt für Archäologie Dresden, Kurzberichte (2000) pp. 116-119

Publ.-Id: 5736 - Permalink

Welche Ursachen haben die Schäden an Emailkunstwerken?
Müller, W.; Adam, K.; Neelmeijer, C.; Mäder, M.;
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.
Keywords: Email, Kunstwerke, Schäden, Ursachen, zerstörungsfreie Analyse
  • Restauro 6 (2000) pp. 414-418

Publ.-Id: 5735 - Permalink

Pages: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] [105] [106] [107] [108] [109] [110] [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128] [129] [130] [131] [132] [133] [134] [135] [136] [137] [138] [139] [140] [141] [142] [143] [144] [145] [146] [147] [148] [149] [150] [151] [152] [153] [154] [155] [156] [157] [158] [159] [160] [161] [162] [163] [164] [165] [166] [167] [168] [169] [170] [171] [172] [173] [174] [175] [176] [177] [178] [179] [180] [181] [182] [183] [184] [185] [186] [187] [188] [189] [190] [191] [192] [193] [194] [195] [196] [197] [198] [199] [200] [201] [202] [203] [204] [205] [206] [207] [208] [209] [210] [211] [212] [213] [214] [215] [216] [217] [218] [219] [220] [221] [222] [223] [224] [225] [226] [227] [228] [229] [230] [231] [232] [233] [234] [235] [236] [237] [238] [239] [240] [241] [242] [243] [244] [245] [246] [247] [248] [249] [250] [251] [252] [253] [254] [255] [256] [257] [258] [259] [260] [261] [262]