Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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39563 Publications

Decomposition of gas fraction profiles according to bubble size classes

Prasser, H.-M.; Lucas, D.; Krepper, E.

Drag and non-drag forces acting on a bubble depend on the bubble diameter. Recently it was found that the lift force occurring in shear flows changes its sign, when the bubble diameter exceeds a certain critical value. This is probably the main reason for the change from a wall-peaked gas fraction profile to a central-peaked one. The paper presents a new method to obtain bubble size distributions and radial gas fraction profiles decomposed according to bubble size classes. It is based on a wire-mesh sensor, capable in resolving individual bubbles. The sensor delivers time sequences of two-dimensional instantaneous gas fraction distributions in a 51.2 mm diameter pipe with a time resolution of 1200 frames per second. After identifying the bubbles in this data, and after quantifying their effective diameter, the data is decomposed according to given bubble size classes. Partial gas fraction distributions are created by checking each element of the measured data array whether it belongs to a bubble the diameter of which is within a given range, or not. Radial profiles calculated from this partial distributions reflect the quantity of gas carried by the selected bub-ble size class. By varying the axial position of a sensor, the evolution of the bubble size distribution and the decomposed radial profiles in an air-water flow along a vertical pipe was studied. It could be confirmed in a real multi-disperse flow, that bubbles larger than a critical diameter are accumulated in the centre of the pipe, while small bubbles tend to move towards the wall.

Keywords: two-phase flow; gas fraction; wire-mesh sensor; bubble size; gas fraction profiles; gas-liquid flow

  • Lecture (Conference)
    4th International Conference on Multiphase Flow, New Orleans, Lousiana, USA - May 27 to June 1, 2001, proc. CD-ROM, paper 159.
  • Contribution to proceedings
    4th International Conference on Multiphase Flow, New Orleans, Lousiana, USA - May 27 to June 1, 2001, proc. CD-ROM, paper 159.

Publ.-Id: 3437

Can we look inside a dynamo?

Stefani, F.; Gerbeth, G.

For mean-field dynamos, we investigate the possibility of determining the radial dependence of alpha which is assumed to be spherically symmetric. Growth rates for magnetic field spherical harmonics with different orders l are supposed to be known by measurement.
An evolutionary strategy (ES) is used for the solution of the inverse problem. Numerically, we find quite different solutions giving nearly the same eigenvalues. The ES is also applied to find functions alpha(r) yielding zero growth rates for the lowest four l-modes. Additionally, a slight modification of the ES is utilized for an ''energetic'' optimization. The consequences of our findings for inverse dynamo theory and for the design of future dynamo experiments are discussed.

  • Astronomische Nachrichten (2000) 235-248

Publ.-Id: 3436

Phenomenological model of reactive r.f.-magnetron sputtering of Si in Ar/O2 atmosphere for the prediction of SiOx thin film stoichiometry from process parameters

Seifarth, H.; Schmidt, J. U.; Grötzschel, R.; Klimenkov, M.

The process of reactive sputtering from a silicon target in an Ar/O2 gas mixture is investigated. An optical plasma regulating circuit using the intensity of the 251.9 nm Si I line as setpoint is employed to stabilize the sputtering process. A phenomenological model of the process is derived that, in contrast to previous models, allows to calculate the composition of the growing SiOx film exclusively from measurable process parameters and accounts for the non-uniform deposition at the substrate. Film compositions X predicted this way for different setpoints were verified by Rutherford back-scattering spectroscopy.
As an example, a SiO2/SiO1.5/SiO2 layer stack was prepared applying an appropriate setpoint sequence. During a subsequent high temperature anneal the stack transformes into an ultrathin layer of nanocrystalline silicon embedded in an oxide matrix, a structure that has high potential for applications in novel optoelectronic and non-volatile MOSFET memory devices (nanocrystal memories).

Keywords: nanostructures; plasma processing and deposition; reactive rf magnetron sputtering; silicon; metal oxide semiconductor structure(MOS); semiconductors

  • Thin Solid Films 389 (2001) 108-115

Publ.-Id: 3435

Anwendung des Ultraschall-Doppler Verfahrens zur Bestimmung von Geschwindigkeitsprofilen in Flüssigmetallströmungen

Eckert, S.; Gerbeth, G.

Aufgrund der spezifischen Eigenschaften metallischer Schmelzen ist die Bestimmung lokaler Strömungseigenschaften wesentlich diffiziler als in Luft oder Wasser. Gegenwärtig gibt es auf dem Markt kaum zuverlässige Meßtechnik, um Geschwindigkeiten in Flüssigmetallströmungen speziell bei höheren Temperaturen zu bestimmen, obwohl gerade für Anwendungen in der Industrie (Stahl, Aluminium, Magnesium, ...) ein großer Bedarf festzustellen ist. Eine weitere Optimierung einschlägiger Produktionstechnologien setzt ein umfassendes Wissen über die Struktur und Transporteigenschaften der Strömung voraus.
Die Ultraschall-Doppler Methode wird bereits kommerziell zur Geschwindigkeitsmessung in Fluiden genutzt. Ein wesentlicher Vorteil des Ultraschall-Doppler Verfahrens besteht in der Möglichkeit, nicht-transparente Fluide zu untersuchen, ohne die Strömung durch den Sensor zu stören. Andererseits ist die heute verfügbare Technik auf Anwendungen bei kleinen Temperaturen (T < 150°C) beschränkt. Aus diesem Grund wurden Anstrengungen unternommen, diese Methode für Flüssigmetallanwendungen bei höheren Temperaturen zu qualifizieren. In unserem Labor wurde die Eignung des Ultraschall Doppler Verfahrens für Strömungen von InGaSn, PbBi, SnPb und Natrium bis zu Temperaturen von 250°C demonstriert, wobei es gelang, die Ultraschallenergie in das Fluid einzukoppeln und verwertbare Echosignale aufzunehmen. Mit einem optimierten Meßaufbau wurden Geschwindigkeitsprofile einer Natriumkanalströmung gemessen.

Keywords: Strömungsmechanik; Meßtechnik; Ultraschall-Doppler-Methode; Geschwindigkeitsprofile; Flüssigmetalle

  • Lecture (Conference)
    5. Seminar für Strömungssensorik an der Universität Rostock, 28./29.09.2000, Shaker-Verlag ISBN 3-8265-8163-6
  • Contribution to proceedings
    5. Seminar für Strömungssensorik an der Universität Rostock, 28./29.09.2000, Shaker-Verlag ISBN 3-8265-8163-6

Publ.-Id: 3434

Labelling of aromatic compounds with carbon-11

Steinbach, J.

The rapid development of life sciences connected with biochemical investigations of living processes initiated the research for labelling organic compounds during the fifties of the 20th century. The need for inserting radioactive carbon-14 atoms into aromatic rings became a matter of interest as more than 50% of naturally occurring and biologically active compounds contain benzenoid and heteroaromatic rings. The radionuclide of choice for labelling was 14C in many cases due to the need for stable isotopic labelling. A number of useful labelling methods was developed.

For reflecting in vivo processes in man and animal the radionuclide of choice changed: the positron emitter carbon-11 became of interest since the external measurement of biochemical processes using Positron Emission Tomography was developed.
The labelling procedures of carbon-14 radiochemistry could not be transferred to carbon-11 chemistry due to the different radionuclide and radiochemical properties as short half life, low substance amounts and high doses rates. New labelling methods for syntheses of 11C-labelled compounds had to be developed.
Initial investigations from 1982 for 11C-labelling of aromatic compounds were unsatisfactory. First in our systematic work a number of suitable labelling syntheses were developed for carbon-11 introduction into benzenoid and heteroaromatic rings (Figure 1, Steinbach at al. J. Labelled Cpd. Radiopharm., 36 (1995) 33-41, Mäding et al. J. Labelled Cpd. Radiopharm., 41 (1998) 647-656, Zessin et al. J. Labelled Cpd. Radiopharm., 42 (1999) 725-736). The labelling position was determined by 11C/13C co-labelling experiments and appropriate 13C-NMR investigations for the reaction path 1 and 2.

Not all derivatives of choice are available by this synthetic routes so far. An overall view will be given and the chances and limitations of this methods will be discussed.

  • Lecture (Conference)
    7th International Symposium on The Synthesis and Applications of Isotopes and Isotopically Labelled Compounds of the International Isotope Society, Dresden, 18.-22.06.2000
  • Contribution to external collection
    Synthesis and Application of Isotopically Labelled Compounds, Vol. 7, U. Pleiss, R. Voges (eds.), John Wiley & Sons, Ltd., 2001, 333-342

Publ.-Id: 3433

Rapid module-assisted synthesis of 16alpha-[18F]fluorestradiol-3,17beta-disulfamate

Römer, J.; Füchtner, F.; Steinbach, J.; Kasch, H.

16alpha-Fluoroestradiol-3,17beta-disulphamate has proven to be a very strong sulphatase inhibitor. Because the sulphatase activity is high in breast cancer tissue there was much hope to image human mammary tumours by using 16alpha-[18F]fluoroestradiol-3,17beta-disulphamate ([18F]FESDS) in PET investigations. For biological characterizing, the new radiotracer had to be made available in high specific activity and in radiochemically pure form. Thus, the module-assisted procedure was developed.

The synthesis of [18F]FESDS consists of two steps. In a first step, 3-methoxymethyloxy-16beta,17beta- sulphuryldioxy-estra-1,3,5(10)-triene (1) reacted with n.c.a. [18F]fluoride. The labelled product was deprotected by acid hydrolysis to give 16alpha-[18F]fluoroestradiol ([18F]FES). In a second step, [18F]FES was sulphamoylated to [18F]FESDS by using sulphamoyl chloride in presence of equivalent amounts of Kryptofix 2.2.2 and potassium carbonate. HPLC purification allowed to obtain pure [18F]FESDS. The synthesis shown in Figure 1 can be carried out in an automated module as a one-pot procedure.

Results: The synthesis required about 90 min from end of bombardment to the final [18F]FESDS ready for use. The time was composed of the time of synthesis (60 min) and the time of column purification (about 30 min). The decay-corrected yield of [18F]FESDS was 22 - 26%. The chemical and radiochemical purity was better than 98%. The specific radioactivity was found to be between 250 and 450 GBq/µmol. When starting with 70 GBq n.c.a. [18F]fluoride, about 8 - 10 GBq [18F]FESDS can be produced. A typical radiochromatogram of the HPLC purification is shown in Fig. 2.

  • Poster
    7th International Symposium on The Synthesis and Applications of Isotopes and Isotopically Labelled Compounds of the International Isotope Society, Dresden, 18.-22.06.2000

Publ.-Id: 3432

Imaging of the serotonin transporter with the [18F]fluoromethyl analogue of (+)-McN5652

Zessin, J.; Eskola, O.; Steinbach, J.; Marjamäki, P.; Bergman, J.; Brust, P.; Solin, O.; Johannsen, B.

Dysfunctions of the serotonin transporter (SERT) may cause numerous psychiatric and neurological diseases. The radiotracer (+)-[11C]McN5652 has the best biological properties for PET investigations of the serotonin transporter state (Suehiro et al., 1993, 53:883-892). Unfortunately, sufficient target-to-nontarget ratios in the human brain were obtained after 115 min (Szabo et al., 1995, 20:37-43), which is out of proportion to the half-life of carbon-11 (20.4 min). Our efforts are therefore directed to develop an 18F-analogue of (+)-McN5652.
The fluoromethyl analogue of (+)-McN5652 (1) has a similar binding affinity (IC50 1.5 nM) as ((+)-McN5652. For this reason, we developed a synthesis of the [18F]fluoromethyl analogue of McN5652 ([18F]FMe-McN, [18F]1).
The required fluoromethylation agent [18F]bromofluoromethane 2 was prepared from[18F]fluoride and dibromomethane (Eq. 1, decay-corrected radiochemical yield 40%, related to [18F]F-). The thioester precursor 3 was hydrolyzed by treatment with TBAH. The resulting thiol 4 was reacted with 2 to yield [18F]FMe-McN 1 with decay-corrected radiochemical yields of 3-5 % (related to [18F]F-) and a specific radioactivity of 1100 - 2400 GBq/µmol.

First autoradiographic ex vivo investigations in rats demonstrated that [18F]FMe-McN is concentrated in brain regions with a high density of the SERT as raphe nucleus and hypothalamus. After preinjection of the SERT inhibitor fluoxetine, a nonspecific distribution of the radiotracer was observed.
These results indicated that the 18F-labelled fluoromethyl analogue of (+)-McN5652 has a high potential to be the tracer of choice for imaging of the serotonin transporter.

  • Poster
    7th International Symposium on The Synthesis and Applications of Isotopes and Isotopically Labelled Compounds of the International Isotope Society, Dresden, 18.-22.06.2000
  • Contribution to external collection
    Synthesis and Application of Isotopically Labelled Compounds, Vol. 7, U. Pleiss, R. Voges (eds.), John Wiley & Sons, Ltd., 2001, 377-379

Publ.-Id: 3431

F-18 peptide labelling: Neurotensin derivatives

Scheunemann, M.; Mäding, P.; Bergmann, R.; Steinbach, J.; Iterbeke, K.; Tourwé, D.; Johannsen, B.

The tridecapeptide Neurotensin (NT) exhibits a high specific affinity to receptors located on various tumours like small cell lung carcinoma or human colon carcinoma. The purpose of this study was to evaluate the potential of using succinimidyl-4-[18F]fluorobenzoate ([18F]SFB) for the specific radiolabelling of a non-lysine containing oligopeptide. This was demonstrated using the C-terminal bioactive hexapeptide NT(8-13) as well as its partially reduced stabilised congeners [Arg8ps(CH2NH)Arg9]NT(8-13), [Arg8ps(CH2NH)Arg9, Tle12]NT(8-13). The radiosynthesis of [18F]SFB started from ethyl trimethylammonium benzoate via a standard three-step procedure. Finally O-(N-succinimidyl) N,N,N',N'-tetramethyluronium tetrafluoroborate was used as activating agent to give [18F]SFB in 40 % overall radiochemical yield related to [18F]F- within 100 min (Wester et al. Nucl. Med. Biol. 1996, 23, 365).
Our labelling experiments revealed that [18F]SFB reacts with selected N-terminal Arg-peptides with moderate to good chemoselectivities in aqueous buffered solutions (phosphate-borate buffer; pH 7.1 - 8.3). To shorten the period of time necessary for a complete consumption of [18F]SFB we found it advisable to heat the mixture to 40 - 50 °C for 20 min. The desired products were obtained after HPLC purification in radiochemical yields of 10 to 43 % (80 - 120 min) related to [18F]SFB. The conditions mentioned above allow the active ester to react specifically with the a-amino group of the N-terminal arginine unit. The radioactive product was identified by chromatographic comparison with a reference compound. The reactions carried out with nonradioactive SFB were shown to give the corresponding 4-FB peptides of which their structural identity was confirmed by proton NMR and MS studies.

The labelled peptides display in vitro affinities to the Neurotensin receptor NTR1 in the nanomolar range (KD values: 1-9 nM). The accumulation of radioactivity in tumour tissue of tumour bearing mice in vivo is still moderate, demonstrated by tumour/blood and tumour/muscle relations of 2-8 after 30 min (calculated from % D/g tissue).

This work is supported by the European Community (BMH4-CT98-3198)

  • Poster
    7th International Symposium on The Synthesis and Applications of Isotopes and Isotopically Labelled Compounds of the International Isotope Society, Dresden, 18.-22.06.2000
  • Contribution to external collection
    Synthesis and Application of Isotopically Labelled Compounds, Vol. 7, U. Pleiss, R. Voges (eds.), John Wiley & Sons, Ltd., 2001, 380-383

Publ.-Id: 3430

pH-controlled inclusion and release of oxyanions by denrimers bearing methyl orange moieties

Stephan, H.; Spies, H.; Johannsen, B.; Kaufmann, C.; Vögtle, F.

We report the synthesis of POPAM-dendrimers, bearing up to 64 chromophores at their periphery. For these dendrimers radiotracer technique was used to study the liquid-liquid partition of pertechnetate and 14C-labeled nucleotides in trichloromethane-aqueous systems. Inclusion and release of guest molecules can be controlled by changing the pH. The extraction efficacy increases with rising generation number.

  • Organic Letters 2 (15) (2000) 2343-2346

Publ.-Id: 3429

Magnetfeldeinsatz bei Kristallzüchtungen aus der Schmelze - Beispiele und Perspektiven

Gerbeth, G.

Es wird eine Übersicht gegeben zu den am FZR durchgeführten Arbeiten zur Nutzung von Magnetfeldern in Kristallzüchtungstechnologien. Auf den bei der Si-Cz-Züchtung erreichten Stand des industriellen Magnetfeldeinsatzes wird
hingewiesen, ohne jedoch auf Einzelheiten einzugehen. Ausführlich dargestellt wird der Einsatz eines rotierenden Magnetfeldes bei der GaAs-Züchtung nach dem VGF-Verfahren, und es werden Verallgemeinerungen zu einem optimalen Rühren der Schmelze, z. B. für das Floating-Zone-Verfahren, diskutiert.

  • Lecture (others)
    Einladungsvortrag am 19.05.2000 am Institut für Kristallzüchtung Berlin

Publ.-Id: 3428

Stabilisation of the melt extraction process by magnetic fields

Cramer, A.; Gerbeth, G.; Bojarevics, A.; Gelfgat, Y.

When a quickly rotating wheel is brought in touching contact with the surface of a liquid metal pool which may contain any pure metal or alloy it draws material out of the melt. The molten metal solidifies at the, usually water-cooled, wheel, shrinks, and is flinged away by centrifugal forces. The shape of this rapidly quenched metal is determined by the geometry of the chill wheel. In the direct melt extraction of metallic and intermetallic fibres the extraction wheel is equipped with one or more edges aligned around the circumference of the wheel, the length of the fibres is determined by the distance of the grooves made into these edges.
The industrial production of melt-extracted fibres has two certain limitations which are inevitably coupled with the circumferential speed of the wheel. Besides the production rate most of the applications of such fibres demands them to have diameters in the range of 50mm to 100mm. Increasing the rotation rate decreases their cross-section, but far beyond the desired diameter respectively wheel speed the extraction process becomes unstable due to turbulence within the melt and a wavy motion on the surface.
Many patents are concerned with the stabilisation of the melt pool. They propose submersing mechanical parts directly into the melt to avoid the non-stationary conditions produced by the turbulence within the liquid metal pool. Even made of heat resistant ceramics they suffer from corrosion or cracks and do not work at all.
The present work describes contact-less control mechanism by means of steady magnetic fields of different strength and orientation. They can either be applied globally to damp the flow within the whole melt volume or locally to the meniscus region where the fibre is formed, to reach higher Lorentz forces in this very sensitive region.
Model experiments (In-Ga-Sn, liquid at room temperature; no extraction) with global stabilisation were carried out to study the calm down of the turbulent surface of an inductively stirred melt. The influence of the globally applied field onto the fibres has been investigated in a second model experiment using the low melting Sn-Pb and under real hazardous industrial conditions like induction heating and vacuum. Though the otherwise wavy surface was damped down to a nearly mirror-like plane the goal of significant smaller fibre cross-section could not be reached by the global stabilisation alone.
The clearly observable positive tendency towards smaller fibres is presently investigated with two series of model experiments with additional local stabilisation. The smaller volume which needs to be magnetised allows for a 5 times stronger field which can be achieved either by rare earth permanent magnets or a concentration of the globally applied field with magnetic field guides. First results using the second alternative of field concentration show a significant reduction of the fibre cross-section. Using a global field of 0.14T only we have been able to reach 0.7T at the edge of the wheel the outer parts of which including the edges were made of magnetic iron. The widespread range of extraction parameters, most of which have even been not mentioned here, is far from being investigated. As one typical result Sn-Pb fibres have been extracted with and without the locally concentrated magnetic field at a temperature of T=245oC, keeping even the circumferential speed of 7m/sec constant. The amount of fibres with diameter below 80mm increased from 9% to 51% by applying the magnetic field.

  • Lecture (Conference)
    International Workshop "Electromagnetic Control of Free Surface Flows in Materials Processing" (EFMP 2000) June 4-7, 2000, Ilmenau, Germany

Publ.-Id: 3427

Experimental and numerical study of anomalous thermocapillary convection in liquid gallium

Priede, J.; Cramer, A.; Bojarevics, A.; Gerbeth, G.

Thermocapillary Marangoni convection of liquid gallium was studied experimentally and analytically. Using a sophisticated high-vacuum technique, liquid gallium was filled into the container with an optical window. The main idea was to obtain an oxide-free surface. For this purpose the working container was made as small as possible, so as to minimize the number of residual gas molecules. The amount of gallium introduced into the container was such as to form a layer of 2 mm thickness. This finite-volume technique is the principal advantage and innovation versus all other methods used before. It worked so well that no deterioration of the surface quality was noticeable over 6 months after preparation of the facility. This enabled us to monitor the motion of tracer particles along the free surface and to measure the corresponding velocity profiles.
It turned out that the movement along the free surface is directed from the cold toward the hot area for some temperature range just above the melting temperature. This finding was quite unexpected, since it means that surface tension increases with temperature. In the most investigations, however, the surface tension of gallium is found to decrease with increasing temperature.
This anomalous direction of the thermocapillary flow could be explained by the presence of a small amount of a surface-active contaminant. Despite the high purity of the gallium, laser-ablation analysis of the solidified sample of gallium done after opening of the container revealed 0.5% of lead in the layer of 50 microns depth at the free surface, but no lead in the bulk of the sample was found. Lead is known to be strongly surface-active with respect to gallium, and even a very small admixture can significantly change the surface tension of the latter.
A novel physical model was devised for the flow driven by the gradient of the surface tension induced additionally by the concentration of the adsorbed layer of contaminant, which in turn depends on the temperature. The observed anomalous direction of the flow can be explained as follows: In the hot region of the container the adsorbed layer partly dissolves and its concentration decreases, so that the surface tension increases, driving the surface towards the hot region of the container. This centripetal flow advects the adsorbed layer and restores its concentration, and at the same time reduces the gradient of the surface tension. When the surface concentration exceeds its equilibrium level, the surfactant on the surface begins to dissolve, increasing the bulk concentration. The resulting non-uniformity of the latter is smoothed out by diffusion and advection of the impurity in the liquid bulk. Thus there is a balance between contraction and stretching of the adsorbed layer, as well as between adsorption and desorption of the impurity - which is controlled by its diffusion from and to the surface. Since the diffusion of the impurity is much slower than the thermal or even the viscous one, the flow has a very strong feedback on the driving force. This is different from pure thermocapillary convection in low-Prandtl-number fluids where the coupling between the velocity and the driving temperature field is weak. The strong coupling in the present case could account for the heavily concave surface velocity profile observed in the experiment.

  • Lecture (Conference)
    International Workshop "Electromagnetic Control of Free Surface Flows in Materials Processing" (EFMP 2000) June 4-7, 2000, Ilmenau, Germany

Publ.-Id: 3426

Riga Dynamo Experiment

Gailitis, A.; Lielausis, O.; Platacis, E.; Gerbeth, G.; Stefani, F.

In the first run of the Riga Dynamo experiment an intense flow of liquid sodium produced by an outside driven propeller has generated a slowly growing magnetic field eigenmode. For a slightly decreased flowrate the observed field is slowly decaying. The measured results correspond satisfactorily with theoretical predictions for the growth rates and frequencies. In the report will be presented computational base, optimisation, the detailed design of the experiment, current results and next experimental steps.

  • Lecture (Conference)
    Dynamo and Dynamics, a Mathematical Challenge, NATO Science Series II: Mathematics, Physics and Chemistry, Vol. 26, Edited by P. Chossat, D. Armbruster, I. Oprea, Kluwer, Dordrecht, 2001, pp. 9-16
  • Contribution to external collection
    Dynamo and Dynamics, a Mathematical Challenge, NATO Science Series II: Mathematics, Physics and Chemistry, Vol. 26, Edited by P. Chossat, D. Armbruster, I. Oprea, Kluwer, Dordrecht, 2001, pp. 9-16

Publ.-Id: 3425

Ion Implantation Induced Defects in 6H-SiC and Their Annealing Behaviour

Anwand, W.; Brauer, G.; Panknin, D.; Skorupa, W.

Fourfold Al+ implantations into 6H-SiC have been carried out in order to create a laterally structured p-doped layer. This way, a 400 nm thick box-shaped Al profile with a concentration plateau of 5x1019 cm-3 buried 200 nm below the SiC surface could be realized. The defects caused by the ion implantation should be minimized by implantation at higher substrate temperatures and post implantation annealing. In addition to the traditional furnace annealing a flash lamp annealing has been used. The defect structure after implantation and annealing has been investigated by Slow Positron Implantation Spectroscopy (SPIS). It could be shown that vacancies and vacancy agglomerates can be removed using furnace annealing at 1650 0C. However, dislocation loops in the implantation region remain stable at this temperature. Using flash lamp annealing a further defect removal could be observed.

Keywords: 6H-SiC; ion implantation; radiation damage; post implantation heat treatment

  • Materials Science Forum 363-365 (2001) 442
  • Lecture (Conference)
    12th International Conference on Positron Annihilation, München, Germany, August 6-12, 2000

Publ.-Id: 3424

Structural Investigation of the Interaction of Uranium(VI) with Modified and Unmodified Humic Substances by EXAFS and FTIR Spectroscopy

Schmeide, K.; Pompe, S.; Bubner, M.; Reich, T.; Heise, K. H.; Bernhard, G.

We studied the interaction of uranium(VI) with humic and fulvic acids to obtain information on the binding of uranium(VI) onto functional groups of humic substances. Therefore, various natural and synthetic humic acids (HAs) were chemically modified resulting in HAs with blocked phenolic OH groups. From the original and modified HAs, solid uranyl humate complexes were prepared at pH 2. FTIR spectroscopy and U LIII-edge extended X-ray absorption fine structure (EXAFS) analysis were applied to study the derivatization process of HAs, to study the structure of the uranyl humates and to evaluate the effect of HA functional groups (carboxylic and phenolic OH groups) on the uranyl complexation.
By FTIR spectroscopy it could be shown that the synthesis of modified HAs with blocked phenolic OH groups was successful. These modified HAs are suitable model substances to study the complexation of actinides by humic substances, especially to study the role of phenolic OH groups in dependence on pH.
By EXAFS, identical structural parameters were determined for all uranyl humates. Axial U-O bond distances of 1.78 Å were determined. In the equatorial plane approximately five oxygen atoms were found at a mean distance of 2.39 Å. The blocking of phenolic OH groups of HAs did not change the near-neighbor surrounding of uranium(VI).
The comparison of results obtained by FTIR spectroscopy and EXAFS analyses for uranyl humates prepared from original and modified HAs confirmed that predominantly HA carboxylate groups are responsible for binding of uranyl ions at pH 2. These carboxylate groups are monodentate coordinated to uranyl ions. The influence of phenolic OH groups is insignificant.

Keywords: uranium; humic acid; complexation; modification; FTIR spectroscopy; EXAFS

  • Contribution to external collection
    FZKA 6524, Wissenschaftliche Berichte Forschungszentrum Karlsruhe, (G. Buckau, ed.). Karlsruhe 2000, pp. 189-209.

Publ.-Id: 3423

Influence of neutron-core excitations on high-spin states in $^{88}$Sr

Stefanova, E.; Schwengner, R.; Reif, J.; Schnare, H.; D\Önau, F.; Wilhelm, M.; Fitzler, A.; Kasemann, S.; von Brentano, P.

High-spin states of the nucleus $^{88}$Sr have been studied via the
reaction $^{80}$Se($^{11}$B,$p$2$n$) at a beam energy of 45 MeV. Gamma-rays
were detected with the six-detector array OSIRIS CUBE. The level scheme of
$^{88}$Sr has been extended up to $E \approx$ 11 MeV and $J = 17$.
Mean lifetimes of three levels have been determined using the
Doppler-shift-attenuation method. The level structures in $^{88}$Sr have
been interpreted in terms of the shell model. The calculations were performed
in the configuration space $(0f_{5/2}, 1p_{3/2}, 1p_{1/2}, 0g_{9/2})$ for
the protons and $(1p_{1/2}, 0g_{9/2}, 1d_{5/2})$ for the neutrons. These
calculations describe the high-spin level sequences linked by $M1$ transitions
with strengths of $B(M1) \leq 1.4$ W.u. as multiplets of seniority
$\upsilon$ = 4 and 6 states including proton configurations and neutron-core

Keywords: Nuclear Structure; In-beam spectroscopy; Cologne OSIRIS cube; Shell-model calculations

  • Physical Review C, Vol. 62, 054314, 1-10

Publ.-Id: 3422

High-energy ion-implantation-induced copper gettering in silicon beyond the projected ion range: the trans-projected range effect

Gueorguiev, Y.; Kögler, R.; Peeva, A.; Mücklich, A.; Panknin, D.; Yankov, R. A.; Skorupa, W.

Five different species, namely B, Si, P, Ge, and As, have been implanted at MeV energies into (100)-oriented n-type CZ-Si, in order to form deep gettering layers during the subsequent annealing. Then the samples have been contaminated with Cu by implanting the impurity on the backface and an additional annealing. The resulting Cu depth distributions have been measured by secondary ion mass spectrometry. Surprisingly, strong gettering of Cu atoms beyond the projected ion range RP and formation of a well-defined separate Cu gettering band therein has been found for P and As implants. We call this phenomenon the "trans-RP effect". It is an indication of a significant amount of defects in the regions much deeper than RP. Their gettering ability is higher than that of the extended defects around RP, since the amount of Cu atoms gettered beyond RP is, especially for the P implants, much greater than that in the implanted gettering layer at RP. These deep defects have not been detected by transmission electron microscopy and we suggest that they are small interstitial clusters. A mechanism responsible for the migration of self-interstitials from RP into the trans-RP region and their clustering therein is proposed. An explanation is given of the possible reasons for the differences in the results for the phosphorous and arsenic implants.

Keywords: Ion implantation (61.72.Q); Defect formation and annealing (61.72.C); Indirect evidence of defects (61.72.H); Defects diffusion (66.30.L); Gettering (61.72.T)

  • Journal of Applied Physics 88 (2000) 5645

Publ.-Id: 3420

Bacteria from uranium waste piles and their interactions with uranium

Selenska-Pobell, S.; Radeva, G.; Merroun, M.; Reich, T.; Tzvetcova, T.; Flemming, K.; Hennig, C.

Bacterial diversity was studied in drain waters and soil samples drawn from different sites and depths of three uranium mill-tailings - Schlema/Alberoda, Gittersee/Coschütz (Germany), and Shiprock, New Mexico (USA) as well as in samples drawn from a uranium mining waste pile called "Haberlandhalde" situated near the town of Johanngeorgenstadt, Germany. For this study both culture-dependent and direct (culture-independent) molecular approaches were applied.

  • Lecture (Conference)
    Biotechnology 2000 Berlin 3.-8.9.2000

Publ.-Id: 3418

Microdiverse types of Acidithiobacillus ferrooxidans and their interactions with uranium

Merroun, M. L.; Flemming, K.; Tzvetkova, T.; Reich, T.; Hennig, C.; Selenska-Pobell, S.

In uranium mining waste piles a number of acidophilic chemolithoautotrophic bacteria have been identified, which are able to oxidise sulphide minerals, elemental sulfur, ferrous iron, and in presence of uranium minerals, also U(IV). Especially one representative of this group, Acidithiobacillus ferrooxidans, is of particular interest. This organism has been used industrially in metal leaching from ores and decontamination of industrial wastes.
Sequence analysis of the 16S rRNA genes of several reference strains and uranium mining waste pile isolates of this bacterium revealed specific signatures which distinguish three types within the species. This allowed to develop a technique for analysis of the distribution of the A. ferrooxidans eco-types in the soil samples of a uranium mining waste pile.
The technique is based on amplification of 16S rDNA fragments in total soil DNA by the use of two A. ferrooxidans species specific primers 16S458F and 16S1473R [1]. The resulting amplicons were then digested with a frequently cutting enzyme RsaI which produced three different type-specific profiles [2; 3]. Using this direct approach we have demonstrated that one of the A. ferrooxidans types (type I) was predominant in the soil samples studied and was found in more polluted sites, whereas the type II was found in less contaminated samples. The type III was found mostly to coexist with the type II.
The objectives of this work were to determine whether these eco-types differ in their capability to tolerate and accumulate uranium, and also to study the structural complexes formed at the surfaces of A. ferrooxidans eco-types using spectroscopic techniques as Extended X-ray Absorption Fine Structure (EXAFS), Infra Red (IR) and Raman Spectroscopy. In addition, the most efficient desorbing agent for the accumulated uranium was selected.
The uranium accumulation by the three types of A. ferrooxidans was studied at different metal concentrations and at pH 1.5 and 4. The results obtained (Fig.1) demonstrated that the strains from the three different types possess different capability to accumulate uranium. The amount of uranium biosorbed by the three types increased with increasing concentration of uranium and pH.

Fig.1: Biosorption of uranium by three types of A. ferrooxidans

On the basis of the results obtained studying the uranium tolerance by the three eco-types by the determination of the Minimum Inhibitory concentrations (MICs) of uranium for the growth of the strains studied, one may speculate that the strains of the types I and III are more resistant to uranium, probably because they possess a mechanism which limits the uranium binding below the lethal amounts.
The recovery of accumulated uranium by desorption was investigated using different desorbing agents as sodium carbonate, sodium citrate and EDTA at different concentrations. The results obtained demonstrated that sodium carbonate is able to recuperate up to 97% of the uranium sorbed from the cells of A. ferrooxidans type III, and 88.3 and 88.5 % from the cells of the types I and II, respectively.
Using EXAFS analysis we have found that no significant structural differences were observed between the uranium complexes formed by the thee types of A. ferrooxidans. However, the EXAFS spectra are indicating formation of uranium complexes which are different from those formed by bacilli [4; 5] and other bacteria.
[1] De Wulf-Durand, P. et al., (1997) Appl. Environ. Microbiol. 63, 2944-2948
[2] Selenska-Pobell, S. et al., (2000) Antonie van Leewenhuek (in press)
[3] Selenska-Pobell, S. et al., (1999) Report FZR-285, p. 52
[4] Hennig, C. et al., (2000) Radiochemica Acta. (submitted)
[5] Hennig, C. et al., (1999) Report FZR-285, p. 70

  • Poster
    Biotechnology 2000, Berlin, 3.-8.9.2000

Publ.-Id: 3417

Interactions of the S-layer protein of the uranium waste pile isolate Bacillus Sphaericus SG A12 with metals

Raff, J.; Wahl, R.; Mertig, M.; Selenska-Pobell, S.; Pompe, W.

Bacteria in uranium waste piles are of special interest for bioremediation, because they are adapted to the high concentrations of radionuclides and heavy metals which occur in those environments. A large number of Bacillus strains was recovered from the uranium mining waste pile "Haberland" near the town of Johanngeorgenstadt in Saxony, Germany. One isolate, Bacillus sphaericus JG-A 12, possesses a surface layer protein with a molecular weight of 135 kDa [1]. Sequence analyses of this protein show that its primary structure differs significantly from those described for the B. sphaericus strains 2362, P-1 and CCM 2177 (EMBL Ac. Nos. M28361, A45814 and AF211170, respectively). However, the B. sphaericus JG-A 12 S-layer protein shares the N-terminal surface layer homology domain with the S-layer protein of B. stearothermophilus PV 72 p2 [2].
Fig. 1: TEM micrograph of the negatively stained na-tive surface layer, isolated from the uranium waste pile isolate Bacillus sphae-ricus JG-A 12.
Additionally one can see fragments of the bacterial flagellum (see the arrow).

The S-layer of B. sphaericus JG-A 12 has a p4 symmetry with a lattice constant of 12.5 nm [1]. S-layers may interact with different metal ions by forming metal clusters [3; 4; 5; 6]. We have demonstrated that the treatment of the native S-layer sheets of B. sphaericus JG-A 12 with Pt- or Pd-salt solutions leads to metal nanocluster formation. The latter is of great interest for the nanotechnology.
Vegetative cells and spores of B. sphaericus JG-A 12 are selectively accumulating large amounts of U, Pb, Cd, Cu and Al from the highly polluted drain waters of the above mentioned waste pile [7]. Using a sol-gel-process we have prepared a nanoscale bio-ceramic, which contains intact bacterial cells or extracted S-layer proteins. First results on heavy metal binding properties of this bio-ceramic will be presented.
[1] Raff, J. et al. (1999) 99TH General Meeting of the American Society for Microbiology,
May 30 - June 3, 1999, Chicago, Illinois, USA, J-12, p. 398
[2] Engelhardt, H. et al. (1998) Journal of Structural Biology 124, 276-302
[3] Brown A. D. et al. (1998) FEMS Microbiology Ecology 26, 297-310
[4] Diluweit, S. et al. (1998) Supramolecular Science 5, 15-19
[5] Pompe W. et al. (1999) Zeitschrift für Metallkunde 90 (12), 1085-1091
[6] Shenton W. et al. (1997) Nature 389, 585-587

  • Poster
    Biotechnology 2000, Berlin

Publ.-Id: 3416

Molecular analysis of bacterial communities in uranium polluted waste piles

Selenska-Pobell, S.; Flemming, K.; Tzvetkova, I.; Radeva, G.

Bacterial diversity was studied in soil and water samples drawn from different sites and depths of several uranium mining waste piles, mill-tailings and disposal sites by the use of 16S rDNA and RISA retrievals. These studies demonstrated significant differences in the structure of the natural communities and in the degree of bacterial variability between the environments studied. The predominant bacterial groups in the samples analysed were in general site-specific. However, many samples share common bacterial groups, belonging mainly to the g subgroup of Pseudomonas; to the sulfate and metal reducing genera such as Desulfovibrio and Geobacter (d-Proteobacteria); to the Gram-positive bacteria with a low DNA G+C content (Bacillus/Clostridium); to the aerobic chemolithoautotrophs oxidising iron and/or sulfur compounds (Acidithiobacillus); or to those oxidising nitrite (Nitrospina) and ammonium (Nitrosomonas) b-Proteobacteria. Interestingly, 16S rDNA sequences indicating the presence of the recently discovered anaerobic chemolithotrophic ammonium oxidising bacteria named Anammox were found to be ubiquitous in many of the uranium waste samples studied [1]. The Anammox was identified as a novel autotrophic member of the order Planctomycetales, one of the major distinct divisions of Bacteria [2].
In all three kinds of uranium polluted wastes the presence of a large variety of not yet cultured representatives belonging to Holophaga/Acidomicrobium and Cytophaga/Flexibacter clusters was also shown. In addition, many 16S rDNA sequences were affiliated with various undefined so called "candidate" bacterial divisions.

In parallel to the above described culture independent approach, the classical method of enrichment culturing was applied to analyse the bacteria present in the uranium polluted environments. The aim was to culture and study particular bacterial groups which are of interest because of their ability to biotransform heavy metals and radionuclides.
Among the cultured bacterial strains predominant were those belonging to the genera Acidithiobacillus, Agrobacterium, Bacillus, Desulfovibrio, Desulfotomaculum, Leptospirillum, Pseudomonas, Rhizobium, and Stenotrophomonas. Many of the strains cultured are representing novel species within the above mentioned genera.
These natural bacterial isolates are prospective for in situ bioremediation of the uranium mining wastes piles, because they are well adapted to the extremely complex conditions in those heavily polluted environments.


[1] Radeva, G., et al., (1999) Annual Report FZR 285, 56

  • Poster
    Biotechnology 2000, Berlin

Publ.-Id: 3415

Bubble size measurement using wire-mesh sensors

Prasser, H.-M.; Scholz, D.; Zippe, C.

A wire-mesh sensor with a time resolution of 1.2 kHz is used to measure bubble size distributions in a gas-liquid flow. The sensor consists of two electrode grids with 16 electrodes each, put in flow direction behind each other. The local instantaneous electrical conductivity is directly measured between all pairs of crossing wires, a tomographic image reconstruction is not necessary. The resulting 16 x 16 sensitive points are equally distributed over the cross section. This resolution is sufficient to detect individual bubbles, which are imaged in several successive frames during its transition through the measuring plane of the sensor. A comparison with high-speed video observations has shown that the sensor causes a significant fragmentation of bubbles. Nevertheless, the measured signals still represent the structure of the two-phase flow before it is disturbed by the sensor. Bubble sizes can therefore be determined by integrating local instantaneous gas fractions over an area of measuring points occupied by the bubble. Bubble size distributions can be obtained if large assemblies of bubbles are analysed. The method was applied to study the establishing slug flow along a vertical tube. The obtained bubble size distributions show the effect of coalescence as well as bubble fragmentation.

Keywords: two-phase flow; gas-liquid flow; wire-mesh sensor; gas fraction; bubble size; bubble flow; slug flow

  • Flow Measurement and Instrumentation 12/4 (2001) 299-312

Publ.-Id: 3414

A unique parameterization of the shapes of secondary dilepton spectra observed in heavy-ion collisions at CERN-SPS energies

Gallmeister, K.; Kämpfer, B.; Pavlenko, O. P.

A unique parameterization of secondary dilepton yields in heavy-ion experiments at CERN-SPS is proposed.
This parameterization resembles a thermal q \bar q annihilation rate and is supported by the ''dual'' description of hot, strongly interacting matter within either a hadronic or partonic base. Adding the thermal yield and the background contributions (hadronic cocktail, Drell-Yan, correlated semileptonic decays of open charm) the spectral shapes of the CERES/NA45, NA38, NA50 and HELIOS/3 data in experiments with lead and sulfur beams can be well described.

Keywords: relativistic heavy-ion collisons; dileptons; deconfinement; chiral symmetry restoration

  • Nuclear Physics A 688 (2001) 935-955

Publ.-Id: 3413

A unique large thermal source of real and virtual photons in the reactions Pb(158 AGeV) + Pb, Au

Gallmeister, K.; Kämpfer, B.; Pavlenko, O. P.

The data of direct single-photon measurements of the WA98 collaboration in the reaction Pb(158 AGeV) + Pb are analyzed within a thermal model with a minimum number of parameters adjusted to the dilepton data obtained by the CERES and
NA50 collaborations in the reactions Pb(158 AGeV) + Au, Pb.
The agreement of our model with the WA98 data points to a unique large thermal source emitting electromagnetic radiation observable in both the real and virtual photon channels.

Keywords: relativistic heavy-ion collisions; electromagnetic radiation; chiral symmetry restoration; deconfinement

  • Physical Review C , Vol. 62 (2000), 057901
  • Contribution to WWW
    HEP-Ph Server

Publ.-Id: 3412

Elastic properties of diamond-like amorphous carbon films grown by computer simulation of ion-beam deposition process

Belov, A.; Jäger, H.-U.

The unique mechanical properties of ta-C films such as high hardness and Young modulus are directly related to the atomic structure of amorphous carbon. Atomic-scale modeling is a valuable tool to study both growth mechanisms of amorphous carbon films and the properties sensitive to details of their structure, primarily to the content of sp 3-bonded atoms. As it has been recently demonstrated, the steady-state growth of ta-C thin films can be modeled using the molecular dynamics method with realistic empirical interatomic potentials. It was shown that the experimentally observed high contents of i>sp 3-bonded atoms ( up to 90%) can be achieved using a potential function of Brenner with a slightly increased interaction radius. This provides a possibility to investigate the mechanical properties of amorphous carbon networks generated by a realistic growth process simulation, rather than by quenching the liquid carbon at high pressures as was done in previous

In this contribution we present results of the investigation of average and atomic-level elastic moduli of amorphous carbon networks with different sp 3-contents, corresponding to C+ ion energies of E = 30-80 eV in the ion-beam deposition process.
For the sake of comparison, the calculation of the elastic moduli was performed using not only the potential functions of Brenner, but also the potential function of Tersoff. The relaxational part of elastic moduli was computed using 3D-supercells with about
1000 atoms and an accurate iterative method for the solution of large linear systems. The elastic moduli tensor was found to show only small deviations from the elastic isotropy. Taking into account that the Brenner potential functions underestimate the bulk modulus of crystalline diamond, the results are in an agreement with experimental measurements.

Keywords: amorphous carbon; mechanical properties; molecular dynamics

  • Poster
    MRS 2000 Fall Meeting, Nov. 27 - Dec. 1, Boston, Sym. P: Growth, Evolution, and Properties of Surfaces, Thin Films, and Self-Organized Structures

Publ.-Id: 3410

The Dresden high-magnetic field laboratory - overview and first results

Krug, H.; Doerr, M.; Eckert, D.; Eschrig, H.; Fischer, F.; Fulde, P.; Groessinger, R.; Handstein, A.; Herlach, F.; Hinz, D.; Kratz, R.; Loewenhaupt, M.; Müller, K.-H.; Pobell, F.; Schultz, L.; Siegel, H.; Steglich, F.; Verges, P.

It is planned to build a 50 MJ pulsed field laboratory at the Forschungszentrum Rossendorf (near Dresden) to obtain magnetic fields up to 100 T with 10 ms pulse duration. This facility would provide the appealing possibility to have access to Zeeman energies in the energy range of the infrared free electron lasers (5m to 250m) now under construction at the radiation source ELBE in Rossendorf. For gaining experience in the construction and operation of pulsed magnets, a smaller pulsed field laboratory was established at the Institute for Solid State Physics and Materials Research Dresden (IFW Dresden) in 1999. The laboratory includes pulse magnets with peak fields up to 50 T in a 24 mm bore and a rise time of about 10 ms, and a 40 T long pulse magnet with a 24 mm bore and rise time of about 80 ms. The coils are energized by a 1 MJ, 10 kV capacitor bank with thyristor switches. The bank is subdivided into four identical and independent units. A particular advantage is the possibility to reverse the polarity of the magnetic field pulse by means of a novel circuit with industrial circuit breakers. The design of the power supply is explained in detail. High precision measurements of magnetization and magnetotransport in the temperature range of 1.5 to 300 K have been performed.

Keywords: Pulsed field; capacitor bank; high energy density capacitor; field reversal; modular capacitor bank

  • Physica B 294-295 (2001) 605-611
  • Poster
    RHMF 2000 Conference, Porto

Publ.-Id: 3408

Transition from in-plane to out-of-plane azimuthal enhancement in Au+Au collisions

Andronic, A.; Stoicea, G.; Petrovici, M.; Simion, V.; Alard, J. P.; Averbeck, R.; Basrak, Z.; Bastid, N.; Belyaev, I.; Berek, G.; Best, D.; Caplar, R.; Crochet, P.; Devismes, A.; Dupieux, P.; Dzelalija, M.; Eskef, M.; Fodor, Z.; Gobbi, A.; Herrmann, N.; Hildenbrand, K. D.; Hong, B.; Kecskemeti, J.; Kim, Y. J.; Kirejczyk, M.; Korolija, M.; Kotte, R.; Kress, T.; Kutsche, R.; Lebedev, A.; Leifels, Y.; Merlitz, H.; Mohren, S.; Neubert, W.; Pelte, D.; Pinkenburg, C.; Plettner, C.; Rami, F.; Reisdorf, W.; Ritman, J.; de Schauenburg, B.; Schüll, D.; Seres, Z.; Sikora, B.; Sim, K. S.; Siwek-Wilczynska, K.; Stockmeier, M.; Wagner, P.; Wisniewski, K.; Wohlfarth, D.; Yushmanov, I.; Zhilin, A.

The incident energy at which the azimuthal distributions in semi-central heavy ion collisions change from in-plane to out-of-plane enhancement is studied as a function of mass of emitted particles, their transverse momentum and centrality for Au+au collisions. The analysis is performed in a reference frame rotated with the sideward flow angle relative to the beam axis.

Keywords: Nuclear reactions; E=90-400 AMeV; semi-central collisions; flow angle; azimuthal distributions; transition energy; comparison to quantum molecular Dynamics model; nuclear matter Eqation of State

  • Nucl. Phys. A 679 (2001) 765

Publ.-Id: 3406

Direct comparison of phase-space distributions of K- and K+ mesons in heavy-ion collisions at SIS energies -- evidence for in-medium modifications of kaons?

Wisniewski, K.; Crochet, P.; Herrmann, N.; Andronic, A.; Averbeck, R.; Devismes, A.; Finck, C.; Gobbi, A.; Hartmann, O.; Hildenbrand, K. D.; Koczon, P.; Kress, T.; Kutsche, R.; Leifels, Y.; Reisdorf, W.; Schüll, D.; Alard, J. P.; Barret, V.; Basrak, Z.; Bastid, N.; Belyaev, I.; Benderag, A.; Berek, G.; Caplar, R.; Cindro, N.; Dupieux, P.; Dzelalija, M.; Eskef, M.; Fodor, Z.; Grishkin, Y.; Hong, B.; Kecskemeti, J.; Kim, Y. J.; Kirejczyk, M.; Korolija, M.; Kotte, R.; Kowalczyk, M.; Lebedev, A.; Lee, K. S.; Manko, V.; Merlitz, H.; Mohren, S.; Moisa, D.; Neubert, W.; Nianine, A.; Pelte, D.; Petrovici, M.; Plettner, C.; Rami, F.; de Schauenburg, B.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczynska, K.; Smolyankin, V.; Somov, A.; Stockmeier, M.; Stoicea, G.; Vasiliev, M.; Wagner, P.; Wohlfarth, D.; Yang, J. T.; Yushmanov, I.; Zhilin, A.

The ratio of K- and K+ meson yields has been measured in the systems 96Ru+96Ru at 1.69 AGeV, 96Ru+96Zr at 1.69 AGeV, and 58Ni+58Ni at 1.93 AGeV incident beam kinetic energy. The yield ratio is observed to vary across the measured phase space. Relativistic transport-model calculations indicate that the data are best understood if in-medium modifications of the kaons are taken into account.

Keywords: heavy-ion reactions; strange mesons; in-medium effects

  • The European Physical Journal A 9 (2000) 515

Publ.-Id: 3404

Entdeckung und Charakterisierung der schwersten Elemente

Hübener, S.

Ausgehend von der Entdeckung der Elemente 114, 116 und 118 im Jahre 1999 in Dubna und Berkeley [1, 2] wird ein Überblick über die experimentellen Techniken und die Ergebnisse der letzten 20 Jahre gegeben, die die Entdeckung der Elemente 107 bis 112 in Darmstadt einschließen [3]. Anhand des jahrelangen Prioritätsstreites über die Entdeckung der Elemente 102 bis 105, der durch die verbindliche Namensgebung durch die IUPAC bis einschließlich Element 109 im Jahre 1997 beendet wurde [4], werden die Kriterien für die Entdeckung eines neuen Elementes erläutert.
Im Hauptteil des Vortrages werden anhand eigener experimenteller Arbeiten zur physikochemischen Charakterisierung des Seaborgiums die Grundprinzipien, Methoden und Probleme der Erforschung der chemischen Eigenschaften der schwersten Elemente erläutert [5-7].
In einem Ausblick werden Konzepte zur chemischen Identifizierung der superschweren Elemente 112 und 114 vorgestellt [8,9].

[1] Yu. Ts. Oganessian et al., Physical Review Letters 83 (1999) 3154
[2] V. Ninov et al., Physical Review Letters 83 (1999) 1104
[3] S. Hofmann, G. Münzenberg, GSI Preprint 2000 - 02, submitted to Rev. Mod. Phys.
[4] Pure & Appl. Chem., 69 (1997) 2471
[5] M. Schädel et al., Nature 388 (1997) 55
[6] A. Türler et al., Angew. Chem. 111 (1999) 2349
[7] S. Hübener et al., TAN 99, Seeheim 1999, Extended Abstracts
[8] H.W. Gäggeler et al., GSI UNILAC Proposal, 2000
[9] S. Hübener et al., unveröffentlichte Mitteilung

  • Lecture (Conference)
    Seminarvortrag im Institut für Werkstoffwissenschaften der TU Dresden 15.6.2000

Publ.-Id: 3403

Über die Möglichkeit der reduktiven Uran- und Arsenimmobilisierung in Bergbauwässern als Folge des natürlichen Holzabbaus

Baraniak, L.; Abraham, A.; Mack, B.; Geipel, G.; Bernhard, G.; Nitsche, H.

Eine wesentliche Sanierungsaufgabe in der sächsischen und thüringischen Uranbergbauregion ist die Flutung von ausgedehnten Untertagebergwerken, die in hohem Maße mit Holz ausgebaut sind. Im Flutungsprozess wird das Grubenholz zunehmend vom Luftzutritt abgeschnitten und der natürliche Holzabbau unter der Einwirkung des Grubenwassers findet statt. Bei diesem Vorgang wird Sauerstoff verbraucht und es entstehen reduzierende Bedingungen [1].
Um diesen Prozess zu untersuchen, wurden Redoxpotenzialmessungen und Redoxtitrationen mit Kaliumhexacyanoferrat(III) an hydrothermalen Holzauszügen, Fichtenlignin und Huminsäu-ren unter Verwendung einer Platinelektrode in Kombination mit einer Silber-Silberchloridelek-trode in einer Zelle mit Überführung ausgeführt. Die Redoxpotenziale des Lignins und der Huminsäure wurden in Abhängigkeit vom pH-Wert und der Konzentration untersucht. Nach Extrapolation auf pH 0 und unendliche Verdünnung wurde für beide ein Redoxpotenzial (Eh) von 570"5 mV mit einem negativen pH-Gradienten von 54,0"1 mV/pH erhalten. Dieses Potenzial zeigt, dass organische Zersetzungsprodukte des Holzes Uran(VI) zu Uran(IV) reduzieren können.
Das Reduktionsprodukt Uran(IV) wurde sowohl spektrophotometrisch als U(IV)-arsenazo(III)-Komplex als auch mit Hilfe der laserinduzierten photoakustischen Spektroskopie (LIPAS) nachgewiesen. Photoakustisch fanden wir die für U(IV) typischen Absorptionsbanden bei 630, 650 and 670 nm. Das Vermögen des Lignins Uran(VI) zu reduzieren stieg im pH-Bereich 5-8 von 0,13@10-4 auf 5@10-4 mval/g. Im Falle von Eisen(III) erhielten wir bei pH 4,5 eine Reduktions-kapazität von 0,15 mval/g.
Um die durch den natürlichen Holzabbau im wässrigen Milieu verursachten reduzierenden Eigenschaften zu charakterisieren, wurden Untersuchungen im Hochmoor AKleiner Kranischsee@ am Erzgebirgskamm bei Johanngeorgenstadt durchgeführt. Bei Feldmessungen fanden wir, dass das Redoxpotenzial von der Oberfläche bis zu einer Tiefe von einem Meter um mehr als 800 mV abfiel. Aus der Analyse des Sumpfgases (49,6% CH4, 3,28% CO2, 1,65@10-3% H2S) konnte für das Redoxpotenzial im Moorgrund (pH 5,3, 4°C) ein Eh-Wert von -120 mV hergeleitet werden. Schließt man hiervon auf das Flutungswasser mit seinem höheren pH und seiner höheren Temperatur, so müssten Redoxpotenziale unter -200 mV möglich sein. Würde als Folge des Holzabbaus die Sulfatreduktion in Gang kommen und Sulfid in mikro-molarer Konzen-tration auftreten, so entspräche das einem Redoxpotenzial von -220 mV. Das würde bedeuten, dass so stark anoxische Bedingungen auftreten, das zur Uran(VI)-Reduktion die reduktive Immobilisierung von Arsen(V) als As2S3 (Auripigment) hinzu kommen kann [2].
In tieferen Wasserschichten gefluteter Bergwerke wurden Potenzialerniedrigungen um etwa 700 mV gemessen. Dies wird aber ausschließlich der Oxidation sulfidischer und arsenidischer Erze und Mineralien, wie beispielsweise Pyrit, Markasit und Arsenopyrit zu geschrieben. Diese Potenzialverminderung bewirkt, dass Uran(VI), als Carbonatokomplex vorliegend, unter Gruben-wasserbedingungen zu Uran(IV) reduziert wird, das als Uran(IV)-hydroxid ausfällt und sedimen-tiert.
Die vorliegenden Ergebnisse zeigen, dass die Zersetzung großer Holzmengen in den gefluteten Gruben mithilft reduzierende Bedingungen zu erzeugen und aufrecht zu erhalten. Der natürli-chen Holzabbau im Grubenwasser der zur Uranimmobilisierung beiträgt und u.U. weitergehende reduktive Ausscheidungen verursacht, entspricht damit einem eminent wichtigen natürlichen Reinigungsprozess.

[1] SMWK-Projektbericht 4-7541.83-FZR/512, Juni 1998: AUntersuchung des Einflusses der in Gruben- wässern gelösten organischen Verbindungen auf den Valenzzustand von Radionukliden@

[2] Baraniak et al.: ARedox Reaction Sequence in Flooded Wood-Supported Mines@, Report FZR-272 (1999) p. 51

  • Poster
    Internationale Konferenz Bergbausanierung Schlema/Sachsen 11.-14.7.2000
  • Contribution to proceedings
    Internationale Konferenz Bergbausanierung Schlema/Sachsen 11.-14.7.2000

Publ.-Id: 3401

EXAFS investigation of uranium(VI) complexes formed at Bacillus cereus and Bacillus sphaericus surfaces

Hennig, C.; Selenska-Pobell, S.; Matz, W.; Panak, P.; Reich, T.; Roßberg, A.; Raff, J.; Bucher, J.; Bernhard, G.; Nitsche, H.

Uranium(VI) complex formation at vegetative cells and spores of Bacillus cereus and Bacillus sphaericus was studied using uranium LII-edge and LIII-edge extended x-ray absorption fine structure (EXAFS) spectroscopy. A comparison of the measured equatorial U-O distances and other EXAFS structural parameters of uranyl complexes formed at the Bacillus strains with those of the uranyl structure family indicates that the uranium is predominantly bound as uranyl phosphate.

Keywords: EXAFS; uranium complexation; bioaccumulation; Bacillus cereus; Bacillus sphaericus

  • Radiochimica Acta 89 (2001), 625-631

Publ.-Id: 3400

Grundlagen der Röntgenabsorptionsspektroskopie (EXAFS) und ihre Anwendung auf die Untersuchung der Chrom-Kollagen-Wechselwirkung

Reich, T.

Es werden die Grundlagen, Möglichkeiten und Grenzen von EXAFS-Untersuchungen erläutert. Die für derartige Messungen erforderlichen leistungsfähigen Röntgenquellen stehen u. a. an der European Synchrotron Radiation Facility (ESRF) in Grenoble zur Verfügung. Dort unterhält das FZR ein eigenes Strahlrohr, die Rossendorfer Beamline (ROBL). Deren Aufbau und Anwendungsgebiete werden kurz beschrieben. Am Beispiel mittels Chromgerbstoffen quervernetzten Kollagens wird die Nützlichkeit von EXAFS-Untersuchungen auch auf gerbereichemischen Gebiet nachgewiesen. So konnte erstmalig experimentell bestätigt werden, dass die Chromgerbung durch zweikernige Chromkomplexe erfolgt. Dies war bisher nur postuliert oder durch Computermodelling wahrscheinlich gemacht worden.

  • Lecture (Conference)
    Freiberger Kollagensymposium
  • Contribution to proceedings
    Freiberger Kollagensymposium

Publ.-Id: 3399

Modelle zur Bestimmung der Relativbewegung der Phasen in einer Zweiphasenstroemung - Stand der Technik

Schaffrath, A.; Ringel, H.

Für zahlreiche technische Prozesse ist die Kenntnis des Schlupfes bzw. des Drift-Fluxes in Zweiphasenströmungen notwendig. Beispiele sind die Bestimmung der Druckverluste sowie der Wärme- und Stoffübertragungsvorgänge in Verdampfern oder Kondensatoren, der Phasenverweilzeit in chemischen Reaktoren sowie der Moderatorwirkung des zweiphasigen Kühlmittels innerhalb des Kerns eines Siedewasserreaktors.

Keywords: Zweiphasenstroemung; Drift-Flux; Schlupfmodelle; Dampfgehalt

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf, FZR-294 Juni 2000
    ISSN: 1437-322X


Publ.-Id: 3398

Sub-picosecond electro-optic measurement of relativistic electron pulses

Yan, X.; Macleod, A. M.; Gillespie, W. A.; Knippels, G. M. H.; Oepts, D.; van der Meer, A. F. G.; Seidel, W.

Time-resolved measurements of the transverse electric field associated with relativistic electron bunches are presented. Using an ultra-fast electro-optic sensor close to the electron beam, the longitudinal profile of the electric field could be measured with sub-picosecond time resolution and without time-reversal abiguity. Results are shown for two cases: inside the vacuum beam line in the presence of wake fields, and in air behind a Be window, effectively probing the near-field transition radiation. Especially in the later case, reconstruction of the longitudinal electron bunch shape is straightforward.

  • Phys. Rev. Lett., 85 (2000) 3404-3407

Publ.-Id: 3397

A toy model for inverse dynamo theory

Stefani, F.; Gerbeth, G.

For a simple spherically symmetric mean-field dynamo model the radial dependence of $\alpha$ is determined from eigenvalues of some spherical harmonics by means of an evolutionary strategy code. The same code is used for "energetic" optimization as well as for constructing dynamo models with level-crossing. The connection with isospectrality problems in quantum mechanics is outlined. Consequences for a general inverse dynamo theory are discussed.

  • Poster
    SEDI2000 The 7th Symposium of the Study of the Earth's Deep Interior University of Exeter, UK, 30th July - 4th August 2000

Publ.-Id: 3396

The Riga Dynamo Experiment: Prognoses, Results, Interpretation

Gailitis, A.; Lielausis, O.; Platacis, E.; Stefani, F.; Gerbeth, G.

We present the results of the Riga dynamo experiment where magnetic field self-excitation was detected in November 1999 (Gailitis et al., Phys. Rev. Lett. 84, 4365, 8 May 2000). The observed growth rates, frequencies and spatial structures of the magnetic field are compared in some detail with the numerical prognoses.

  • Poster
    SEDI2000 The 7th Symposium of the Study of the Earth's Deep Interior University of Exeter, UK, 30th July - 4th August 2000

Publ.-Id: 3395

Bericht der Frühjahrstagung der Studiengruppe für Elektronische Instrumentierung vom 27. bis 29. März 2000 im Physikalischen Institut der Universität Heidelberg

Gabriel, F.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-293 Mai 2000
    ISSN: 1437-322X


Publ.-Id: 3394

The Rossendorf radiation source ELBE and its FEL projects

Gabriel, F.; Gippner, P.; Grosse, E.; Janssen, D.; Michel, P.; Prade, H.; Schamlott, A.; Seidel, W.; Wolf, A.; Wünsch, R.

The Forschungszentrum Rossendorf (FZR) is constructing a superconducting Electron Linac [F. Gabriel, J. Voigtländer, et al.,
ELBE Design Report 1998,; Annual Report 1996, FZR-179 (1997) 3; Annual
Report 1997, FZR-215 (1998) 3] with high Brilliance and low Emittance (ELBE) which can deliver a 1 mA cw beam of 40
MeV. ELBE will be equipped with a free-electron laser (FEL) system for the production of infrared (IR) light in the range 5¯300
um and will thus cover the range from the infrared to the THz regime. The electron beam can also be used to generate X-rays,
bremsstrahlung, positrons or fast neutrons.

Keywords: Free-electron laser; Undulator magnet; Infrared; Superconducting RF linac

  • Nucl. Instr. Meth. B 161(2000)1143-1147 PACS classification codes: 41.60.Cr; 41.85.Lc

Publ.-Id: 3392

3-125I-4-HO-Phenylacetyl-[Lys-Psi(CH2=NH)-Arg-Phe11-t-Leu12-]NT(10-13): Radiosynthesis and characterisation

Chavatte, K.; Bergmann, R.; Terriere, D.; Iterbeke, K.; Tourwé, D.; Mertens, J.; Bossuyt, A.

4-HO-Phenylacetyl-[Lys-Psi(CH2=NH)-Arg-Phe11-t-Leu12-]NT(10-13) is a Neurotensin (NT) derivative with a Ki of 25 nM and is a good candidate for labelling with radio iodine. A fast and efficient radio iodination procedure by electrophilic substitution is proposed. 0.1 µmol of peptide together with 200 MBq of Na125I in 1 ml of PBS of pH 7.4 were added to an Iodogen coated vial. Labelling was performed at 20°C for 5 min. QC by HPLC and Sep Pak showed labelling yields >98%. The pure n.c.a. (75 GBq/mmol) compound was obtained after semipreparative HPLC purification followed by recovery from a RPC-18 Bonda Pak column. Overall synthesis yields were over 80%. Biodistribution of 150 kBq of the n.c.a. compound in HT29 bearing nude mice revealed tumour uptake to ±5% of the I.D./g 10 min p.i. which could be inhibited for 75% by competition with native NT. The in vitro half-life of the pure peptide in human blood is 67 h. Due to its excellent biological half-life and its acceptable biological properties, the proposed 123I labelled peptide is a good candidate as a new peptidergic SPECT tracer for NT receptor expressing pathologies.

  • Lecture (Conference)
    International Congress on Peptide Radiopharmaceuticals in Diagnosis and Therapy, Rome, 25.-28.05.2000
  • Abstract in refereed journal
    Nuclear Medicine Communications 21 (2000) 568

Publ.-Id: 3391

Geschlossen-analytische Modellierung der Längsvermischung von Kühlmittelpfropfen auf dem Weg vom Reaktoreintrittsstutzen zum Kerneintritt in Druckwasserreaktoren

Grunwald, G.; Höhne, T.

Messungen an der Versuchsanlage ROCOM mit der in Rossendorf entwickelten Gittersensortechnik lieferten auch zeitabhängige mittlere Vermischungen an verschiedenen Modellpositionen. Der Versuch, diese mit Hilfe eines aufgestellten geschlossen-analytischen 1D-Rechenmodells der turbulenten Diffusion in einer stationären und symmetrischen Modellströmung nachzurechnen, erwies sich auch für den Fall einfachster Annahmen und einer Anpassung an nur einen Fluidmassenstrom, der bis auf das 6-fache erhöht wurde, als erfolgreich.

Zum Vergleich mit den Messungen und den Ergebnissen aus den analytischen Rechnungen werden auch CFX-4 Simulationen herangezogen, welche eine gute Übereinstimmung aller angewandten Verfahren zur Bestimmung der mittleren Vermischungen an der Modellanlage ROCOM bestätigen.

Insbesondere konnten auch in Abhängigkeit von der dimensionslosen Pfropfenlänge der Tracerdosierungen nicht nur die Maxima der mittleren Vermischungsverteilungen berechnet, sondern auch die zu erwartenden Maximalwerte selbst abgeschätzt werden.

Eine Anwendung des beschriebenen analytischen Verfahrens und der CFX-4 Simulationen auf prinzipiell beliebige Modelle und Originalkomponenten bei vergleichbaren turbulenten stationären und symmetrischen Strömungen läßt ebenso gute Ergebnisse erwarten.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-333 Oktober 2001
    ISSN: 1437-322X


Publ.-Id: 3389

Optimization of a neurotensin(8-13) analogue for radioiodination

Iterbeke, K.; Chavatte, K.; Terriere, D.; Bergmann, R.; Johannsen, B.; Tourwe, D.; Mertens, J.

2-123I-phenylacetyl-NT(8-13)-OH (1) and 4-HO-2-123I-phenylacetyl-[Phe11]-NT(8-13)-OH (2) were developed as potential SPECT tracers for NT-receptor expressing tumors. The precursor compounds showed high affinity for NT-receptors on bulbus olfactorius membranes of rodent (Ki in the Mn range). (1) Was obtained by Cu1 assisted non-isotopic exchange on 1 mg of the 2-Br-phenylacetyl analogue, with a labeling yield of 70%. (2) Was obtained by direct electrophilic substitution during 5 min at Rt using Iodogen on 0.1 mg 4-HO-phenylacetyl-[Phe11]-NT(8-13)-OH with a yield >98%. The second method allows a two component kit application. In vivo in the rat fast degradation (t1/2: 1.5 min) was observed coupled to high long-acting liver uptake. This is probably caused by radioiodo-phenylacetyl-Arg, a compound that mimics MIBG. 4-HO-phenylacetyl-[Lys8Y(CH2NH)Arg9]-[tLeu12]-NT(8-13)-OH, a double stabilized NT(8-13) analogue of type (2), from which high in vivo stability is expected, was synthesised.

  • Lecture (Conference)
    International Conference on Peptide Radiopharmaceuticals in Diagnosis and Therapy, Rome, 25.-28.05.2000
  • Abstract in refereed journal
    Nuclear Medicine Communications 21 (2000) 588-589

Publ.-Id: 3388

Fast, uniform, and large scale heat treatment by plasma-based electrons

Günzel, R.; Rogozin, A. I.; Astrelin, V. T.

Heat treatment of steels by electron beams with an energy density ranging from 1 to 10 kW/cm2 results in a considerable hardness improvement and wear reduction. Hence, electron beam treatment is a typical line-of-sight process and demands a complicated target manipulation and beam rastering system.
A new method is presented, circumventing the limitations inherent in the scanning electron beam treatment. The workpiece to be treated is immersed into a plasma and surrounded by a negatively biased grid, preventing the penetration of plasma electrons. Further the workpiece is connected to a positive DC high voltage source of about 20 kV and a capacitor, acting as an energy storage. Changing the grid bias, electrons are extracted from the plasma and accelerated by the positive potential towards the workpiece. During the pulsed electron bombardment power densities of about 10 kW/cm2 can be achieved resulting in a rapid thermal heating and self quenching, occurring after the electron pulse. Detailed investigations are presented on the response of a plasma if electrons are extracted by a large electrode with special emphasis on the processes near the wall and near the control grid.

Keywords: heat treatment; electron saturation current; plasma

  • Lecture (Conference)
    Vacuum 65 (2002) 59-65
  • Contribution to external collection
    Vacuum 65 (2002) 59-65

Publ.-Id: 3387

186Re labeled stents for prophylaxis of restenosis: First animal results

Dinkelborg, L. M.; Tepe, G.; Noll, B.; Muschick, P.; Duda, S. H.

OBJECTIVES: Restenosis is a major problem occuring after angioplasty, atherectomy and implantation of stents. It has been shown, that external beam teletherapy (X-rays) and intravascular brachytherapy (e.g. 192Iridium ribbon seeds, 188Re filled catheters, P-32-coated stents) prevents restenosis by inhibition of the proliferation of medial smooth muscle cells. The aim of this study was to investigate the potential of 186Rhenium labeled stents to prevent restenosis in an animal model.

METHODS: New Zealand White rabbits were fed a 0.5% cholesterol diet four weeks prior to intervention. 186Re (T = 3.8 d) labeled Palmaz-stents with an activity of 25.6 ± 2.5 MBq (n = 11) were placed in the infrarenal aorta of rabbits after balloon denudation. Animals with implanted unlabeled stents served as controls (n = 11). Whole body scintigrams were obtained after 1, 4, 24 hours and after 7 and 14 days to determine the bleaching of 186Re from the stents in vivo. Seven weeks later, the animals were sacrified and morphometry and immunohistology was performed.

RESULTS: More than 80% of the 186Re remained on the stent 14 days after implantation as determined by ROI analysis of the scintigrams. The neointimal area inducted seven weeks after implantation of the unlabeled stents was 2.2 ± 0.2 mm2. No neointima was detectable in the aorta of animals with implanted radiolabeled stents. No intraluminal accumulation of fibrin and fibroblasts directly at the stent struts implies that the delivered dose can even be reduced.

CONCLUSION: Arterial implantation of 186Re labeled stents was feasible and stable in vivo. The activity of 25.6 ± 2.5 MBq totally inhibited neointimal formation. In further studies we will reduce the stent activity in order to determine the therapeutic window of 186Re labeled stents

  • Lecture (Conference)
    47th Annual Meeting of the Society of Nuclear Medicine, St. Louis, USA, 03.-07.06.2000
  • Abstract in refereed journal
    J. Nucl. Med. 41 (Suppl. 5) (2000) 7P

Publ.-Id: 3386

N,N-(Dialkylamino)-alkyl substituted 99mTc-amineamidedithiol (AADT) complexes as diagnostic probes for melanoma

Friebe, M.; Mahmood, A.; Bolzati, C.; Spies, H.; Johannsen, B.; Mohammed, A.; Eisenhut, M.; Davison, A.; Jones, A. G.

In our effort to develop small molecular 99mTc diagnostic probes to image malignant melanoma, tetradentate N2S2(AADT) 99mTc-complexes of the general formula AADT-X-NR2 (X = -(CH 2) n-, R = Et, Bu) were synthesized. The N-substituted AADT-X-NR2 ligands were radiolabeled with 99mTc(V) via transmetallation with [99mTc]technetium(V)-glucoheptonate resulting in 99mTc complexes in high radiochemical yield (86%-98%). These complexes were further characterized via HPLC coelution with similarly synthesized rhenium analogues. In-vitro evaluation in B16 murine melanoma cells revealed a distinct pattern of cell accumulation. The more lipophilic complex 2 [n = 2, R = Bu] displayed only an 8% melanoma uptake, whereas complex 1 [n = 2, R = Et] displayed a 44% cell uptake in 60 min. Complexes 3 [n = 3, R = Et] and 4 [n = 3, R = Bu] showed a 62% and 68% cell uptake at 60 min, respectively. In-vivo biodistribution studies in the C57B16/B16 mouse melanoma tumor model revealed a tumor accumulation of 7.6% ID/g at 60 min post injection (p.i.) and high melanoma/blood (10.8), melanoma/spleen (10.1) and melanoma/lung (7.3) ratios for complex 1. Although the tumor uptake of compound 3 was significantly lower (3.7% ID/g) at 60 min p.i., the melanoma/blood (19.1), melanoma/spleen (19.1) and melanoma /lung (12.7) ratios were considerably high. These results demonstrate the feasibility of developing N-substituted [99mTc-AADT] complexes as small molecular probes for potential diagnostic imaging of malignant melanoma via SPECT.

  • Lecture (Conference)
    47th Annual Meeting of the Society of Nuclear Medicine, St. Louis, USA, 03.-07.06.2000
  • Abstract in refereed journal
    J. Nucl. Med. 41 (Suppl. 5) (2000) 120P

Publ.-Id: 3385

3-O-Methyl-6-[18F]fluoro-L.DOPA ([18F]OMFD): Development and first application of a new tracer for tumor detection with PET.

Alheit, H.; Bergmann, R.; Beuthien-Baumann, B.; Bredow, J.; Burchert, W.; Franke, W. G.; Füchtner, F.; Steinbach, J.; Syhre, R.; Zips, D.

OBJECTIVES: Development (synthesis, biologic evaluation and first results in humans) of a [18F]-labeled synthetic amino acid for tumor detection with PET.

METHODS: Synthesis of [18F]OMFD based on a new precursor (N-formyl-3-O-methyl-4-O-Boc-6-trimethylstannyl-L-DOPA-ethyl-ester). The biologic evaluation was performed in cell culture (HT-29;RBE-4) and tumor bearing nude mice (SC-Ca). First application in humans were obtained in 4 patients with recurrent glioblastoma multiforme with inconclusive CT and MRI. [18F]OMFD was used to identify localization and extent of recurrent tumor for treatment planning with stereotactic radiotherapy, which was the last treatment option for the individual patient.

RESULTS: The radiochemical yield of [18F]OMFD was 20-25% (decay corrected, related to [18F]F2) in 50 min synthesis time. Cell culture experiments showed a high tracer uptake in tumor cells via the L-amino acid transporter without evidence for any metabolism or protein incorporation. Biodistribution in mice 60 min p.i. showed a high tumor uptake (12.4 ± 1.8%ID/g) with a high tumor/blood ratio (9.2 ± 0.845 min p.i.). In all patients an increased tracer uptake in the area of the suspected recurrence (lesion to non-lesion 2.2 ± 0.5) was found. In the whole body scan only little tracer uptake was observed in the muscles, thorax and abdomen.

CONCLUSION: In vitro and in vivo experiments showed increased [18F]OMFD uptake in tumor tissue. The results of preliminary diagnostic studies with [18F]OMFD in patients with glioblastoma multiforme indicate its potential for tumor imaging.

  • Lecture (Conference)
    47th Annual Meeting of the Society of Nuclear Medicine, St. Louis, USA, 03.-07.06.2000
  • Abstract in refereed journal
    J. Nucl. Med. 41 (Suppl. 5) (2000), 43P

Publ.-Id: 3384

Structural diagnostics of near surface regions with synchrotron radiation at ROBL

Matz, W.; Eichhorn, F.; Prokert, F.; Schell, N.; Berberich, F.

The ROssendorf BeamLine (ROBL) at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, was built and is operated since 1999 by the Forschungszentrum Rossendorf. Two different experimental stations, a radiochemistry hutch and a materials research hutch, are available alternatively.
An overview of the experimental equipment of the materials research hutch (MRH) is given. This end-station is dedicated to diffraction and reflectometry with synchrotron radiation. Its basic instrument is a high precision six-circle goniometer for heavy duty. Various detector systems and special sample environments are available.
The contribution presents results from the Institute of Ion Beam Physics and Materials Research of the FZR so far obtained at ROBL-MRH. They demonstrate the capability of synchrotron radiation for the analysis of surface near structures produced by ion implantation or of thin surface films.
 Depth distribution of phases produced by ion implantation.
 Formation of SiC crystals by ion implantation of C in Si and the orientation correlation to the host lattice.
 Modification of interface roughness in Co/Cu-multilayers by ion beam mixing.

Keywords: synchrotron radiation; surfaces layer analysis; X-ray diffraction; ROBL

  • Lecture (Conference)
    11. Arbeitstagung Angewandte Oberflächenanalytik (AOFA11) Leipzig, 24.-28.9.2000

Publ.-Id: 3382

Trans-projected-range effect in proximity gettering of impurities in silicon

Gueorguiev, Y. M.; Kögler, R.; Peeva, A.; Panknin, D.; Mücklich, A.; Yankov, R. A.; Skorupa, W.

Deep gettering layers have been formed in n-type Si wafers by high-energy ion implantation of Si+, P+, Ge+ and As+ and subsequent annealing. The samples have been then contaminated with Cu by implanting the impurity into the backface and an additional thermal treatment. The resulting copper depth profiles measured by secondary ion mass spectrometry show strong gettering of Cu well behind the projected ion range Rp and formation of a separate gettering band therein. We call this phenomenon the "trans-Rp effect". It has been observed for P and As implants, whereas for Si and Ge implants it was missing. This effect indicates the presence of a significant amount of defects much deeper than Rp. The size of these defects is below the resolution limit of our transmission electron microscopy analysis and we suggest that they are small interstitial clusters. Their gettering ability should be higher than that of the extended defects at Rp since the amount of Cu atoms gettered beyond Rp is much greater than that in the implanted gettering layer. A mechanism of the defect formation and clustering in the trans-Rp region is proposed, and an explanation is given of the differences in the results for the P and As implants.

Keywords: Ion implantation (61.72.Q); Defect formation and annealing (61.72.C); Indirect evidence of defects (61.72.H); Defects diffusion (66.30.L); Gettering (61.72.T)

  • Contribution to proceedings

Publ.-Id: 3381

A novel approach to robust Tc(III) mixed-ligand chelates as tools for conjugating biologically active molecules

Pietzsch, H.-J.; Spies, H.

To meet the need for small and "robust" chelates we focussed our recent investigations on new types of technetium(III) chelates, their synthesis and evaluation of molecular properties. Here we report on five-coordinated compounds with "3+1+1", "3+2", and "4+1" donor arrangements.
Such species, all belonging to the family of "n+1"mixed-ligand technetium complexes, were developed and characterized towards versatility, lipophilicity and stability.
The "3+2" approach make use of the combination of a tridentate HS-E-SH ligands with a PR2-SH chelator, common action of the tripodal nitrilotris(ethanethiol) with isocyanide co-ligands leads to
trigonal-bipyramidal "4+1" Tc(III) complexes.
Both types enables easy functionalization and thus a fine-tuning of physicochemical properties of the complexes or to link the chelate unit to biomolecules.
The sterically well shielded oxo-free species are non-polar, showing higher logP values as the "3+1" oxotechnetium(V) compounds. The "3+2" and "4+1" complexes are stable towards re-oxidation and transchelation in challenge experiments with glutathione. The "3+2" type is the most versatile one while the compact "4+1" seems to be the most stable arrangement.
The presented "3+2" and "4+1" complex types are useful tools in designing of 99mTc or 186/188Re radiopharmaceuticals.

  • Lecture (Conference)
    Meeting der COST B12 Action, WG 5, Rom, 29.05.2000

Publ.-Id: 3380

Effects of Neutron Irradiation and Thermal Annealing on Model Alloys using Positron Annihilation Techniques

Cumblidge, S. E.; Catchen, G. L.; Motta, A. T.; Brauer, G.; Böhmert, J.

We present the results of a systematic investigation of neutron-irradiated and thermally-annealed model alloys using positron annihilation spectroscopy (PAS), including both lifetime and Doppler broadening techniques. The objective of this work is to use PAS to provide information on the irradiation-induced microstructural features that are thought to cause embrittlement in pressure-vessel steels. Such information could complement the results obtained by other techniques, especially small-angle neutron scattering (SANS) and atomic probe field ion microscopy (APFIM). We examined a series of model Fe-based alloys, in which the Cu, P and Ni concentration were systematically varied. These alloys were examined in the as-fabricated state, after irradiation to 1 x 10 19 nxcm-2, and to 8 x 10 19 nxcm-2, and after successive post-irradiation 30-minute isochronal anneals at temperatures ranging from 200 to 600 °C. In each case, we measured the positron annihilation lifetime distribution, the Doppler broadening (S-parameter), and the 15 N Rockwell hardness for the samples.

  • Lecture (Conference)
    Effects of Radiation on Materials: 20th International Symposium, ASTM STP 1405, S. T. Rosinski, M. L. Grossbeck, T. R. Allen and A. S. Kumar (Eds.), American Society for Testing and Materials, West Conshohocken, PA, 2001, pp. 247-261
  • Contribution to proceedings
    Effects of Radiation on Materials: 20th International Symposium, ASTM STP 1405, S. T. Rosinski, M. L. Grossbeck, T. R. Allen and A. S. Kumar (Eds.), American Society for Testing and Materials, West Conshohocken, PA, 2001, pp. 247-261

Publ.-Id: 3379

Sideward Flow of K+ mesons in Ru+Ru and Ni+Ni Reactions near threshold

Crochet, P.; Herrmann, N.; Wisniewski, K.; Leifels, Y.; Andronic, A.; Averbeck, R.; Devismes, A.; Finck, C.; Gobbi, A.; Hartmann, O.; Hildenbrand, K. D.; Koczon, P.; Kress, T.; Kutsche, R.; Reisdorf, W.; Schüll, D.; Alard, J. P.; Barret, V.; Basrak, Z.; Bastid, N.; Belyaev, I.; Bendarag, A.; Berek, G.; Caplar, R.; Cindro, N.; Dupieux, P.; Dzelalija, M.; Eskef, M.; Fodor, Z.; Grishkin, Y.; Hong, B.; Kecskemeti, J.; Kim, Y. J.; Kirejczyk, M.; Korolija, M.; Kotte, R.; Kowalczyk, M.; Lebedev, A.; Lee, K. S.; Manko, V.; Merlitz, H.; Mohren, S.; Moisa, D.; Neubert, W.; Nianine, A.; Pelte, D.; Petrovici, M.; Plettner, C.; Rami, F.; de Schauenburg, B.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczynska, K.; Smolyankin, V.; Somov, A.; Stockmeier, M.; Stoicea, G.; Vasiliev, M.; Wagner, P.; Wohlfarth, D.; Yang, J. T.; Yushmanov, I.; Zhilin, A.

Experimental data on K+ meson and proton sideward flow measured with the FOPI detector at SIS/GSI in the reactions Ru+Ru at 1.69 AGeV and Ni+Ni at 1.93 AGeV are presented. The K+ sideward flow is found to be anti-correlated (correlated) with the one of protons at low (high) transverse momenta. When compared to the predictions of a transport model, the data favour the existence of an in-medium repulsive K+ nucleon potential.

Keywords: strangeness; collective motion; directed flow; sideward flow; in-medium potential

  • Physics Letters B 486 (2000) 6

Publ.-Id: 3378

Dose rate and temperature dependence of Ge range profiles in Si obtained by channeling implantation

Posselt, M.; Teichert, J.; Bischoff, L.; Hausmann, S.

The strong influence of dose rate and implantation temperature on the dose dependence of the shape of Ge channeling implantation profiles is demonstrated for the first time. Applying a focused ion beam (FIB) system allows the use of a very high (1018 cm-2s-1) and a very low (1010-1011 cm-2s-1) dose rate. Implantations are performed at R.T. and at 250°C. At the high dose rate and R.T. the dose rate dependence of the profile shape is found to be most pronounced. Atomistic computer simulations using a relatively simple damage buildup model can explain the effects observed. It is shown that at R.T. defect relaxation processes can last up to 1 s, which is longer than assumed so far. The lifetime of implantation defects at 250°C is estimated to be in the order of 10s.

Keywords: Ion implantation; focused ion beam; computer simulation; defects; channeling

  • Lecture (Conference)
    Symposium R, E-MRS Spring Meeting, May 30- June 2, 2000, Strasbourg
  • Nuclear Instruments and Methods in Physics Research B 178 (2001) 170-175

Publ.-Id: 3377

The role of three-body collisions in phi-meson production processes near threshold

Barz, H. W.; Kämpfer, B.

The amplitude of subthreshold phi-meson production is calculated using dominant tree-level diagrams for three-body collisions. It is shown that the production can overwhelmingly be described by two-step processes. The effect of the genuine three-body contribution (i.e. the contribution which cannot be factorized) is discussed. The production rate of phi-mesons is presented for proton induced reactions on carbon.

Keywords: nuclear reactions; three-body collisions; meson production

  • Nuclear Physics A 683 (2001) 594-604

Publ.-Id: 3376

Formation of the phases Ti3Al and TiAl by high-dose implantation of aluminium into titanium

Tsyganov, I.; Wieser, E.; Matz, W.; Mücklich, A.; Reuther, H.

Surface modification of titanium is of interest considering the necessary improvement of mechanical properties of this material for
applications as e.g. artificial joints. This work is devoted to the formation of a layer with a high content of the titanium aluminides Ti3Al
and TiAl below the surface by high-dose aluminium implantation. If the maximum aluminium concentration exceeds 20 at.%,
precipitation of Ti3Al is detected by XRD already in the as-implanted state. For maximum aluminium concentrations between 50 and 55
at.%, the phase TiAl is found beside Ti3Al after annealing at 700°C. For a double implantation resulting in an aluminium concentration of
about 60 at.% in the depth range between 100 and 200 nm, a disordered fcc TiAl phase is observed after implantation as precursor for
the ordered tetragonal TiAl formed by subsequent annealing at 600°C.

Keywords: Titanium; Ion implantation; Aluminium; Intermetallic phases; Microstructure

  • Nuclear Instruments and Methods in Physics Research B 161-163 (2000) 1069-1074


Publ.-Id: 3375

Anordnung zur Messung der lokalen elektrischen Leitfähigkeit und Temperatur in Fluiden

Baldauf, D.; Prasser, H.-M.; Zschau, J.

Aufgabe der vorliegenden Erfindung ist es, die Messsysteme für Leitfähigkeits- und Temperaturmessung so zu verkleinern und aufeinander abzustimmen, dass beide Messungen weitestgehend am gleiche geometrischen Ort erfolgen können und somit eine höchstmögliche Messgenauigkeit für die um den Temperatureinfluss korrigierte Leitfähigkeit erzielt wird.

  • Patent
    DE 100 12 938 A1
  • Patent
    DE 100 12 938 C2
  • Patent
    WO 01/69224 A1

Publ.-Id: 3374

Verfahren zur Herstellung von Aerosolen im Nanometerbereich

Rettig, D.; Merker, P.; Rudolph, A.; Adam, R.

Aufgabe der Erfindung ist es, einen photochemischen Nanopartikelgenerator anzugeben, der mit toxisch unbedenklichen, chemisch stabieln und einfach zu handhabenden Ausgangssubstanzen betrieben werden kann, wobei die Bildung toxisch bedenklicher Reaktionsprodukte weitestgehend vermieden werden soll.

  • Patent
    Patentanmeldung 199 42 210.9
  • Patent
    DE 199 42 210 A1
  • Patent
    DE 199 42 210 C2

Publ.-Id: 3373

Integrierter Optokoppler und Verfahren zu seiner Herstellung

Gebel, T.; Skorupa, W.; von Ny, J.; Rebohle, L.; Borchert, D.; Fajrner, W.

Der Erfindung liegt die Aufgabe zugrunde, einen integrierten Optokoppler und ein Verfahren zu seiner Herstellung vorzuschlagen, bei denen eine direkte monolithische Integration des gesamten Optokopplers in Silizium-Technologie mit geringem Aufwand erfolgen kann, wobei Einschränkungen bei der Herstellung des Optokopplers weitgehend vermieden werden sollen.

Die Erfindung geht von einem Optokoppler aus, bei dem Empfangs- und Sendeelement benachbart angeordnet und durch ein optisch transparentes und elektrisch isolierendes Material galvanisch getrennt sind.

  • Patent
    DE 100 11 258 A1
  • Patent
    EP 1 132 975 A1

Publ.-Id: 3371

Verfahren zur Herstellung Ohmscher Kontakte auf Siliziumkarbid-Halbleiterbereichen

Heera, V.; Höfgen, A.

Der Erfindung liegt die Aufgabe zugrunde, Ohmsche Kontakte mit geringem Kontaktwiderstand auf p-leitenden SiC-Halbleiterbereichen zu erzeugen, wobei die Maximaltemperatur bei der Prozessführung 1000oC nicht überschreiten soll.

  • Patent
    DE 100 06 378 A1
  • Patent
    DE 100 06 378 C 2

Publ.-Id: 3370

Verfahren zur Herstellung von 16 a-[18F]Fluorestradiolsulfamaten

Roemer, J.; Fuechtner, F.; Steinbach, J.; Kasch, H.; Johannsen, B.

Der Erfindung liegt die Aufgabe zugrunde, diese Nachteile zu überwinden und ein schnelles, reproduzierbares Herstellungsverfahren für chemisch und radiochemisch reine 16a- [18F]Fluorestradiolsulfamate, die wahlweise in 3-oder 17-Stellung monosulfamoyliert bzw. in 3, 17-Stellung disulfamoyliert worden sind, vorzustellen. Die Synthese kann, ausgehend von den 16,17-O-Sulfuryl-16-epiestriolderivaten, ohne Zwischenisolierung der intermediär anfallenden 16a-[18F]Fluorestradiolderivate in eigens für die Markierung vorgesehenen käuflichen Modulen mittels computergestützter Programme durchgeführt werden. Dadurch wird die Kontaminierungsgefahr mit radioaktivem Material auf ein Mindestmaß reduziert.

  • Patent
    DE 100 06 155 A1
  • Patent
    DE 100 06 155 B4

Publ.-Id: 3369

Verfahren und Vorrrichtung zur Metallfaserherstellung nach dem Schmelzextraktionsverfahren

Cramer, A.; Gerbeth, G.; Gelfgat, J.; Bojarevichs, A.; Stephani, G.; Kostmann, C.

Aufgabe der Erfindung ist es, eine Beruhigung des Schmelzbades und des sich an der Walzenschneide ausbildenden Meniskus zu erreichen, um auf diese Weise den Schmelzextraktionsprozeß zu stabilisieren und die reproduzierbare Herstellung speziell von dünnen Fasern mit Durchmessern unterhalb 100 mm zu ermöglichen. Die statistische Verteilung des Durchmessers der produzierten Fasern um den durch die Prozeßparameter vorgegebenen mittleren Faserdurchmesser soll möglichst schmal sein.

  • Patent
    Patentanmeldung Az 100 00 097.5
  • Patent
    DE 100 00 097 A1 DE 100 00 097 C2

Publ.-Id: 3368

Re-188 markierte HSA-Mikrosphären für die intraarterielle Tumorembolisation

Pinkert, J.; Wunderlich, G.; Bergmann, R.; Hliscs, J.; Kropp, J.; Franke, W. G.

Ziel: Zahlreiche Studien in den letzten Jahren belegen den Stellenwert der intraarteriellen Radioembolisation maligner Tumoren. Bisher sind aber in Europa keine mit einem Betastrahler kurzer Halbwertszeit markierte Mikrosphären kommerziell verfügbar. Nach erfolgreicher Markierung verschiedener, metabolisierbarer und nicht metabolisierbarer Partikel mit 188Re (T1/2=17h) in hoher Ausbeute wurde die Biokinetik von Humanserumalbuminmikrosphären (HSAM) mit einem Durchmesser von 25 µm hinsichtlich Belastung der Normalgewebe untersucht.

Methodik: Für die Markierung wurden ca. 370 MBq 188Re Generatoreluat (2 ml) mit 6 mg Gentisinsäure, 7,5 mg SnCl2 2H2O und 0,5-5 mg der HSAM gemischt und für 1 h bei 100 °C in einer Glasampulle erwärmt. Nach Entfernung des Überstandes durch Zentrifugation und zweimaliges Waschen erfolgte die Resuspension in NaCl-Lösung und Röntgenkontrastmittel. Zur Untersuchung der Biokinetik wurden nachi.v. Injektion Wistarratten nach 20 min, 4 h, 24 h, 48 h und 96 h getötet. Proben verschiedener Organe sowie von Blut, Urin und Faeces entnommen und der Radioaktivitätsgehalt gemessen (vgl. Tab.). Die Lunge diente dabei als Modell eines gut perfundierten Tumors.

Ergebnisse: Obwohl es sich bei den 188Re-HSAM um biologisch abbaubare Partikel handelt, belegen unsere Ergebnisse die gute in-vivo-Stabilität mit geringer Anreicherung in den Normalgeweben bis 96 h p.i. Die Dosisberechnung nach MIRD-Modell mit dem PC-Programm Mirdose 3.1 zeigen, ausgehend von den experimentellen Daten, die Niere als kritisches Organ mit einer Belastung von 0,26 mGy/MBq.

Schlussfolgerungen: Da mehr als 100 GBq der 188Re-HSAM appliziert werden müssten, um die TD5/5 der Niere zu erreichen, erscheinen die bereits für die Lungenperfusionsszintigraphie zugelassenen Mikrosphären hinsichtlich der Anwendung am Menschen als sicher.

Biokinetik von 188Re-HSAM (%/inj. Aktivität/Organ)

Zeit [h]........Lunge........Leber........Milz..........Nieren........Magen........Darm
4.................97.9...........2.3...........0.30...........0.35...........0.37........... 0.23

  • Lecture (Conference)
    Nuklearmedizin 2000, 38. Intern. Jahrestagung DGN, München, 30.03.-01.04.2000
  • Abstract in refereed journal
    Nuklearmedizin 2000, 39, A44

Publ.-Id: 3367

3-O-Methyl-6-[18F]Fluor-DOPA ([18F]OMFD) zur Tumordiagnostik: Entwicklung eines neuen Tracers und erste Anwendung am Patienten

Ahlheit, H.; Bergmann, R.; Beuthien-Baumann, B.; Burchert, W.; Franke, W. G.; Füchtner, F.; Steinbach, J.; Syhre, R.; Zips, D.

Ziel: Entwicklung einer synthetischen Aminosäure als Tracer zur Tumordiagnostik. Synthese, biologische Evaluierung und erste Anwendung am Menschen von 18F-markierten OMFD.

Methode: Für die Synthese des [18F]OMFD wurde ein neuer Precursor entwickelt (n-Formyl-3-O-Methyl-4-O-Boc-6-trimethylstannyl-L-DOPA-ethyl-ester), der eine hohe Ausbeute bei relativ kurzer Synthesedauer ermöglicht. Die biologische Evaluierung erfolgte an Zellkulturen (HT-29;RBE-4) und tumortragenden Nacktmäusen (PE-Ca). Erste klinische Ergebnisse wurden bei 3 Patienten mit Glioblastoma multiforme erhoben, die bereits z.T. mehrfach voroperiert und bestrahlt worden waren. Zur Planung einer stereotaktischen Hirnbestrahlung bei klinischem V.a. Rezidiv und inkonklusiven Ergebnissen in der übrigen bildgebenden Diagnostik wurde ein Aminosäure-PET zur weiteren Abklärung durchgeführt. Nach Injektion von 330 MBq [18F]OMFD wurde eine dynamische Sequenz über 90 min und eine Aufnahme des Körperstammes durchgeführt.

Ergebnisse: Synthese: Die Ausbeute mit dem neuen Precursor beträgt 20-25% in 50 min Synthesezeit.
Zellkultur: In vitro zeigte sich eine hohe Traceraufnahme in die Tumorzellen über den L-Transporter ohne Nachweis einer Metabolisierung oder Proteininkorporation.
Tiermodell: Biodistributionsdaten zeigten eine hohe Tumoraufnahme (12,4±1,8%ID/g) mit hohem Tumor/Blut-Verhältnis (45 min p.i.: 9,2±0,8).
Patienten: Bei allen Patienten ließ sich im Gebiet des vermuteten Tumorrezidivs mit [18F]OMFD eine fokal erhöhte Traceraufnahme darstellen. Das Verhältnis von Tumor zu Nicht-Tumor betrug 2,2±0,5. Die maximale Traceraufnahme wurde zw. 12 min und 25 min p.i. beobachtet. Im Körperstamm zeigte sich nur eine sehr geringe Traceraufnahme in der Muskulatur, im Thorax und dem Abdomen.

Schlussfolgerung: Die in vivo- und in vitro-Experimente haben gezeigt, dass [18F]OMFD als synthetische Aminosäure in Tumoren angereichert wird. Die ersten diagnostischen Anwendungen an Patienten zeigten ermutigende Ergebnisse in der Lokalisation von Rezidivtumoren beim Glioblastom.

  • Lecture (Conference)
    Nuklearmedizin 2000, 38. Intern. Jahrestagung DGN, München, 30.03.-01.04.2000
  • Abstract in refereed journal
    Nuklearmedizin 2000, 39, A43

Publ.-Id: 3366

Synthesis, characterization and solubility of Bayleyite Mg2[UO2(CO3)3].18H2O

Amayri, S.; Geipel, G.; Reich, T.; Bernhard, G.; Matz, W.

The intensive uranium mining and milling activities in the southeast of Germany (Saxony and Thuringia) have caused severe environmental pollution in this region. The uranium intrusion into the biosphere occurs most likely through aqueous transport. The prediction of the uranium transport behavior is essential for safety assessment studies and for the development of efficient remediation methods.
The seepage water of the rock piles and the flooding water of the mines contain relatively high amounts of magnesium, calcium, hydrogen carbonate/carbonate and sulfate ions. In these waters the pH values range from 7.0 to 8.0 and the uranium content is about 0.02 mmol/L /1/. In a former study /2/ we have found that Ca2[UO2(CO3)3]aq. is the dominating uranium species in mining related waters. Under these conditions the precipitation of the secondary uranium mineral - liebigite, Ca2[UO2(CO3)3] x 10H2O - is possible. In oxidizing water which contains uranyl, magnesium and hydrogen carbonate/carbonate ions, the formation of magnesium uranyl carbonate as solid or dissolved species could be expected. In nature the mineral bayleyite - Mg2[UO2(CO3)3] x 18H2O - is a comparatively common secondary mineral in uranium ore deposits set within an alkaline environment and associated with gypsum, carnotite and metaautunite.

The aim of this work was to synthesize and to characterize the bayleyite using several analytical methods. This well characterized substance was used for the determination of its solubility and for speciation experiments.

Synthesis and characterization of Mg2[UO2(CO3)3] x 18H2O:
Several methods for preparation of bayleyite are described in the literature /3,4/. By variation of the preparation conditions, we could increase the reproducibility and the yield (95±3%) of the product. Bayleyite was prepared by mixing stoichiometric amounts of dissolved uranyl nitrate (Merck p.a.), mag-nesium carbonate (-Merck p.a.) and sodium carbonate (-Merck p.a.) at ambient temperature. During this process, carbon dioxide was passed through the solution until dissolution of all reactants. Then bayleyite was p--recipitated by s-low evaporation of the solution at room temperature. The product was purified by recrystallization. The obtained transparent green-ish yellow p-risms were dried on air.
The results of the chemical analysis are represented in Tab. 1. The determined chemical composition was in good agree-ment with the calculated values.

Tab. 1: Chemical analysis of Mg2[UO2(CO3)3] x18H2O

Element U Mg C H
Found (%) 28.92 ± 0.60 5.90 ± 0.70 4.34 ± 0.01 3.98 ± 0.28
Calculated (%) 28.92 5.91 4.38 4.41

The thermoanalytical measurements showed that the water is released in a temperature range from 22 to 338oC. The CO2 release occurred from 338 to 800oC. As a result from these measurements, the content of water and CO2 was determined to be 17.36±0.52 and 3.17±0.10 moles, respectively.

The synthesized bayleyite was identified and characterized by X-ray Powder Diffraction (XRD), Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS), and Time-resolved Laser-induced Fluorescence Spectroscopy (TRLFS).
The indexing of the diffraction pattern peaks observed in the X-ray diffraction diagram showed that the synthesized substance has monoclinic structure as described in the literature /3,5/. The lattice parameters (Tab. 2), which were calculated from all clearly identifiable reflections, are in good agree-ment with those found by Mayer et al. /5/ and described in PDF /6/.

Tab. 2: Lattice constants of Mg2[UO2(CO3)3] x18H2O

This work H. Mayer /5/ PDF /6/
a (Å ) 26.593 ± 0.101 26.560 (3) 26.65 (5)
b (Å) 15.263 ± 0.052 15.256 (2) 15.31 (5)
c (Å) 6.503 ± 0.026 6.505 (1) 6.53 (2)

We performed EXAFS measurements of the solid bayleyite and its solution (pH 8.0, Uconc. 0.182 mol/L) in order to compare the obtained structural parameters with the XRD data and to detect agreements or dif...

  • Lecture (Conference)
    NRC5 5. Internationale Conference on Nuclear and Radiochemistry, Pontresina, Sept. 2000

Publ.-Id: 3365

Dwell-time dependence of irradiation damage in silicon

Bischoff, L.; Teichert, J.; Hausmann, S.

The influence of the dose rate on the damage creation in silicon has been investigated by means of high current density focused ion beam (FIB) implantation. 70 keV Co and Ge ions with a current density of about 1 A/cm2 have been implanted into silicon at target temperatures in the range from room temperature to 420°C. The effective dose rate was varied between 1013 ions/cm2s and about 1019 ions/cm2s applying different pixel dwell times from 1 µs to 250 µs. The samples have been investigated using Rutherford backscattering / channeling combined with a special preparation technique, scanning electron microscopy, micro-Raman spectroscopy and reflectivity measurements. It have been found that at short dwell times at implantation temperatures of about 400°C the silicon remains crystalline after Co as well as Ge ion bombardment also in the limit of high doses while at long dwell times the crystal becomes amorphous. These studies of damage accumulation and dynamic annealing reveal that the characteristic time of defect annealing lies in the µs-range.

Keywords: Focused ion beam; dwell-time; current density; damage; annealing

  • Nuclear Instruments and Methods in Physics Research B 178 (2001) 165-169
  • Lecture (Conference)
    E-MRS Spring Meeting, Strasbourg, France, May 30 - June 2, 2000

Publ.-Id: 3364

Temperature dependence of emission spectra of liquid metal alloy ion sources

Bischoff, L.; Ganetsos, T.; Teichert, J.; Mair, G. L. R.

The variation with temperature of the ion mass spectra of a liquid metal alloy ion source (LMAIS) (Au77Ge14Si9) is reported. Analysis of our results suggests the co-existence of two diffrent ion creation mechanisms for the doubly charged atomic ions. Whereas some doubly charged ions are post-ionised from the singly charged state, others are directly field-evaporated. The temperature dependence of the abundance of the ionic clusters emitted by the source has also been investigated.

Keywords: Liquid metal alloy ion source; temperature dependence; surface tension; emission spectra; cluster

  • Nuclear Instruments and Methods in Physics Research B 164-165 (2000) 999 - 1003

Publ.-Id: 3363

Complex formation between uranium(VI) and adenosine triphosph

Geipel, G.; Bernhard, G.; Brendler, V.; Reich, T.

Adenosine triphosphate is an important enzymatic compound, which is able to transfer the phosphate and diphosphate group between molecules. Heavy metal ions bound to the adenosine phosphates can be transported into living cells and than deposited.
In addition to studies of the soil-to-plant transfer factors /1/ and the interaction of the uranyl ion with microorganisms /2/ we studied the complex formation of the uranyl ion with adenosine triphosphate (ATP).
We found that adenosine phosphates are very strong quenchers of the fluorescence of the uranyl ion and also of the formed complexes. In the uranyl - adenosine monophosphate (AMP) system UV-vis measurements were carried out in the wavelength range from 180 nm to about 300 nm using a CARY5G spectrometer (VARIAN, Canberra). The adenosine monophosphate shows a strong absorption in this range and no fluorescence could be observed at all.
In the uranyl - adenosine triphosphate system fluorescence emission was observed only in a small range of the adenosine concentration. The deconvoluted fluorescence spectra show different emission maxima compared both to the uranyl ion and to phosphate complexes. This leads to the conclusion that a complex between uranyl and adenosine triphosphate is formed.

  • Lecture (Conference)
    5th Internationale Conference on Nuclear and Radiochemistry, Pontresina, Sep. 3.-8. 2000, extended Abstract, Volume 2. P. 473

Publ.-Id: 3361

Potential application of PET in quality assurance of proton therapy

Parodi, K.; Enghardt, W.

Our investigation supporting the feasibility of the in-situ
PET monitoring in proton therapy is presented. We simulated by means of the FLUKA code the amount and the spatial distribution of the main ß+ emitters created in PMMA targets by protons at typical therapeutic energies. The quantitative comparison with the activation induced by 12C ions of energies corresponding to the same range shows that the available signal at the same physical dose level should be up to two times more intense for protons than that actually successfully used for the control of carbon ion therapy at GSI Darmstadt. The spatial correlation between the activity and the dose profile for protons is poorer than for 12C nuclei. However, an important check of the particle range, dose localization and stability of the treatment during all the fractions seems to be possible.

  • Physics in Medicine and Biology 45 (2000) N151-6

Publ.-Id: 3360

Bacterial diversity in soil samples from two uranium waste piles as determined by rep-APD, RISA and 16S rDNA retrieval

Selenska-Pobell, S.; Kampf, G.; Flemming, K.; Radeva, G.; Satchanska, G.

Bacterial diversity in two uranium waste piles in Germany was studied. For this study, total DNA was recovered by two alternative procedures for direct lysis from a large number of soil samples drawn from different sites and depths of the piles. Significant differences in the bacterial composition of the samples investigated were revealed by the use of rep-APD, RISA, and 16S ARDREA. The 16S rDNA retrieval allowed also to demonstrate that both uranium wastes were dominated by Thiobacillus ferrooxidans and by several Pseudomonas species of g-subdivision of the Proteobacteria. Three kinds of T. ferrooxidans 16S and IGS rDNA specific fragments corresponding to the recently described three phylogenetic groups of this species (Flemming at al., 1999) were amplified in different ratios from distinct soil samples which were polluted with heavy metals to different extent. This microdiversity probably reflects the genetic adaptation of the uranium waste strains to the different heavy metal concentrations in their natural surrounding.

Keywords: Keywords: Bacterial diversity; microdiversity; rep-APD; RISA; 16S ARDREA; uranium wastes

  • Antonie van Leewenhuek Journal of Microbiology 79 (2001), 149-161

Publ.-Id: 3359

Votrag KTG-Seminar am 11.05.2000: Was wird mit dem Plutonium?

Weiß, F.-P.

Nuklidvektor in verbrauchtem Kernbrennstoff;
Globale Plutoniumbilanz;
Recycling oder Endlagerung von Plutonium;
Accelerator-Driven-Systems (ADS) zur Aktiniden- und Spaltprodukttransformation

  • Lecture (others)
    KTG-VDI-Seminar am 11.05.2000 in Dresden

Publ.-Id: 3356

Intrauterine growth restriction induces up-regulation of cerebral aromatic amino acid decarboxylase activity in newborn piglets: [18F]fluorodopa positron-emission-tomographic study

Bauer, R.; Walter, B.; Vorwieger, G.; Bergmann, R.; Füchtner, F.; Brust, P.

There is evidence that intrauterine growth restriction (IUGR) is associated with altered dopaminergic function in the immature brain. However, the relevant enzyme activities have not been measured in the living neonatal brain together with brain oxidative metabolism. Therefore 18F-labelled 6-fluoro-L-3,4-dihydroxyphenylalanine (FDOPA) was used together with positron-emission-tomography to estimate the activity of the aromatic amino acid decarboxylase in the brain of 10 newborn IUGR piglets (2 to 5 days old; body weight 908±109g) and in 10 normal-weight (3 to 5 d old; body weight 2142±373g) newborn piglets. The regional transport of FDOPA to the brain and the clearance rate of labeled metabolites from brain tissue were broadly similar in the two groups. However, the regional rate constant for back flux from the brain was markedly increased in IUGR piglets for striatum (72%) and frontal cortex (83%) (p < 0.05). Furthermore, the rate constant for conversion of FDOPA to fluordopamine was markedly increased (between 48 % in cerebellum and 91 % in mesencephalon, p < 0.05) in all brain regions of IUGR piglets studied.
Thus, it is suggested that IUGR induces an up-regulation of amino acid decarboxylase activity that is not related to alterations in brain oxidative metabolism.

  • Pediatric Research 49 (2001) 474-480

Publ.-Id: 3354

Metal nanoclusters on a bacterial surface layer

Raff, J.; Wahl, R.; Mertig, M.; Pompe, W.; Reich, T.; Selenska-Pobell, S.

A novel surface layer (S-layer) protein was found on Bacillus sphaericus isolate recovered from a uranium mining waste pile. Formation of highly ordered platinum and palladium nanoclusters on this crystalline protein template was studied. The average diameter of the metal clusters is 1.9±0.6 nm. They are located in the nano-sized pores and gaps of the crystalline S-layer. The atomic structure of the S-layer-metal nano-clusters was analysed by the use of EXAFS spectroscopy.
In addition, it was demonstrated that the B. sphaericus isolate is able to accumulate selectively large amounts of U, Pb, Cd, and Al from drain waters of the uranium mining waste pile. For this reason, this strain was chosen for construction of so called bio-ceramic "Biocere" which may be used for bioremediation of heavy metal contaminated liquid wastes. Our first analyses of the properties of this nano-scalic bio-ceramic will be presented.

  • Lecture (Conference)
    4. General Conference of the Balkan Physical Union - Bulgarien

Publ.-Id: 3353

Tritium depth profiling by AMS in carbon samples from fusion experiments

Friedrich, M.; Pilz, W.; Sun, G.; Penzhorn, R.-D.; Bekris, N.; Behrisch, R.; Garcia-Rosales, C.

Tritium depth profiling measurements by accelerator mass spectrometry have been performed at the facility installed at the Rossendorf 3 MV Tandetron. In order to achieve an uniform erosion at the target surface inside of a commercial Cs ion sputtering source and to avoid edge effects, the samples were mechanically scanned inside of a commercial Cs sputter ion source. The sputtered negative ions were mass analysed by the injection magnet of the Tandetron. Interesting ions except tritium are measured with the Faraday cup between the injection magnet and the accelerator, while the tritium is counted after the accelerator with semiconductor detectors. Depth profiles have been measured for carbon samples which had been exposed to the plasma at the first wall of the Garching fusion experiment ASDEX-Upgrade and from the European fusion experiment JET, Culham/UK. Tritium contents in the JET samples were up to six orders higher than in samples from ASDEX-Upgrade. Tritium beam currents from samples with high tritium content can be measured partly in the Faraday cup before the accelerator. A dedicated tritium AMS facility with an air-insulated 100 kV tandem accelerator is under construction. First results of test operation are presented.

Keywords: Mass Spectrometry; Tritium; Fusion

  • Contribution to proceedings
    5th Int. Workshop on Hydrogen in Solids, May 17-19, 2000, Stockholm
  • Lecture (Conference)
    Physica Scripta T94 (2001) 98-101
  • Contribution to external collection
    Physica Scripta T94 (2001) 98-101

Publ.-Id: 3352

Liquid Metal Ion Source Working with an Er70Fe22Cr3Ni5 Alloy

Bischoff, L.; Teichert, J.

For focused ion beam applications of Erbium as well as of several metal ions which are of interest for optical and semiconductor investigations a liquid metal ion source operating with an Er-stainless steel alloy was developed and investigated. This alloy consists of a mixture of Er70Fe22Cr5Ni3 and has a melting point of about 860°C. The wetted needle type tungsten emitter showed a stable emission behaviour down to 1µA emission current. The I-V characteristics, the temperature dependence of the extraction voltage, the mass spectrum, and the energy spread of the main beam components depending on the emission current were investigated. While in the case of singly charged metal ions the beam is not defined due to isotope interference in the case of doubly charged ions the species well separated for focused ion beam applications are available.

Keywords: alloy liquid metal ion source; erbium; temperature dependence; I-V- characteristics; energy spread

  • Journal of Physics D: Applied Physics 33 (2000) L69 - L72

Publ.-Id: 3351

Automated Synthesis of 16alpha-[18F]fluoroestradiol-3,17beta-disulphamate

Römer, J.; Füchtner, F.; Steinbach, J.; Kasch, H.

After 16alpha-[18F]fluoroestradiol ([18F]FES) has been successfully prepared in an automated module, the synthesis of 16alpha-[18F]fluoroestradiol-3,17beta-disulphamate ([18F]FESDS) is described as a module-assisted one-pot procedure which can provide 10 GBq [18F]FESDS with a radiochemical purity better than 99 %. The procedure is reliable and reproducible and requires a time of about 90 min. Because of its high sulphatase-inhibitory effect [18F]FESDS is thought to be a new PET tracer to image sites of high sulphatase activity.

Keywords: Fluorine-18; Nucleophilic fluorination; Sulphamoylation; Steroidal sulphatase inhibitors; Automated synthesis; PET tracer

  • Applied Radiation and Isotopes 55 (2001) 631-639.

Publ.-Id: 3349

Synthesis of 16alpha-[18F]fluorestradiol-3,17beta-disulphamate

Römer, J.; Füchtner, F.; Steinbach, J.

The synthesis of 16alpha-[18F]fluorestradiol-3,17beta-disulphamate ([18F]FESDS) is described. 16alpha-[18F]fluorestradiol ([18F]FES) is converted using excess sulphamoyl chloride in absolute acetonitrile in the presence of Kryptofix 2.2.2 and potassium carbonate using an automatically operating module. The required time for the synthesis related to end of bombardment is 3h, the maximum yield is 6%, and the maximum decay-corrected yield is 20%. The radiochemical purity of [18F]FESDS is > 99%. The specific radioactivity of [18F]FESDS is found to be between 150 and 200 GBq/µmol.

Keywords: 16alpha-[18F]fluorestradiol-3; 17beta-disulphamate; 18F-labelled tracer; positron emission tomography; sulphamoylation; HPLC purification

  • J. Labelled Cpd. Radiopharm. 43 (2000) 425-436

Publ.-Id: 3347

Design and Biological Evaluation of Technetium(V) Complexes for Serotonin-5-HT2A Receptor Binding

Pietzsch, H.-J.; Scheunemann, M.; Kretzschmar, M.; Seifert, S.; Syhre, R.; Johannsen, B.

Starting from the lead structure of ketanserin, a prototypic serotonin (5-HT) antagonist, a series of oxotechnetium(V) complexes were synthesized which are able to compete with [3H]ketanserin in receptor binding assays.
In order to imitate organic 5-HT2 receptor ligands, fragments of ketanserin were combined with chelate moieties. Lipophilic complexes, consisting of a small S4 or S3N thiolate/thioether chelate unit, protonable nitrogen containing spacer and benzyl moiety significantly inhibited the specific binding of [3H]ketanserin with IC50 values between 10 and 50 nM.
Low brain uptake is a generally accepted problem in developing 99mTc brain receptor imaging agents. For some representatives of 5-HT2A receptor binding agents it was tried to improve the original low brain uptake of 0.4 % ID in rats 5 min p.i. by modifying the lipophilic properties of the molecules. Because of the presence of a protonable nitrogen, which according to the pK value leads to ionization of the molecule at blood pH, the pK value was considered to be the parameter most suitable for adjustment of lipophilicity. Insertion of ether-oxygen in the molecule of 5 candidates lowers the apparent pK value from 10.0 to 8.3 and dramatically increases the brain uptake up to 1.3 % ID at 5 min.
Finally, the synthesis and in vitro autoradiography of a novel Tc-99m ligand with subnanomolar affinity to the 5-HT2A receptor is reported. The complex combines the 4-(4-fluoro)-benzoyl piperidine portion derived from ketanserin with a neutral oxotechnetium(V) chelate in form of a mixed ligand "3+1" unit containing the SNS/S donor set. The analogous 99Tc compound has been synthesized as a surrogate for the Tc-99m complex for use in receptor binding assays and for complete structural characterization.
In competition experiments the Tc-99 complex as well as its Re analogue display subnanomolar affinity towards the 5-HT2A receptor (Ki 0.44 nM for Tc, 0.25 nM for Re).
In vitro autoradiographic studies clearly indicate the accumulation of the Tc-99m compound in 5-HT2A receptor rich areas of the brain. This enrichment can be blocked by 5-HT2A receptor antagonists such as mianserin and ketanserin and is therefore specific.

  • Contribution to external collection
    IAEA Technical Document (IAEA TECDOC)
  • Lecture (Conference)
    IAEA Research Coordination Meeting on CNS Receptors, Montevideo/Uruguay, 24.-28.04.2000

Publ.-Id: 3346

Composition Effects on the Radiation Embrittlement of Iron Alloys

Böhmert, J.; Ulbricht, A.; Kruykov, A.; Nikolaev, Y.; Dmitry, E.

The effect of copper, phosphorus and nickel on the radiation embrittlement was investigated by using an irradiation experiment at surveillance positions in two Russian VVER-type reactors with 8 iron-base testing alloys. Their chemical composition varied between 0.015 to 0.42 % Cu, 0.002 to 0.039 % P, 0.01 to 1.98 % Ni, 0.09 to 0.37 % Si, and 0.35 to 0.49 % Mn. Charpy-V impact tests and tensile tests were performed with specimens machined from these alloys. The specimen were tested in the as-received state, in the irradiated state (fluence: 1×10 19 and 8×10 19 cm -2 [En > 0.5 MeV]) and in the post-irradiation annealed state.
Irradiation produces strong hardening and embrittlement. The effect increases with the Cu and P content. Ni causes an additional embrittlement. It does not depend on the Ni content within the range of 1.1 to 2 % Ni. The irradiation effect can be eliminated by annealing at 475 °C / 100 h but not absolutely in the case of high Cu or P content.
Small angle neutron scattering experiment at these alloys show that not only the volume fraction but also the type of the radiation defects vary in dependence on the composition of the alloys.

Keywords: radiation embrittlement; iron alloy; neutron scattering; Charpy impact testing; phosphorus; nickel; copper

  • Lecture (Conference)
    Effects of Radiation on Materials: 20th International Symposium, ASTM STP 1405, S.T. Rosinski, M. L. Grossbeck, T. R. Allen and A. S. Kumar, Eds., American Society for Testing and Materials, West Conshohocken, PA, 2001, pp. 383-398
  • Contribution to proceedings
    Effects of Radiation on Materials: 20th International Symposium, ASTM STP 1405, S.T. Rosinski, M. L. Grossbeck, T. R. Allen and A. S. Kumar, Eds., American Society for Testing and Materials, West Conshohocken, PA, 2001, pp. 383-398

Publ.-Id: 3343

Tc complexes as ligands for CNS receptors: state of the art (1993-1999)

Pietzsch, H.-J.

  • Lecture (Conference)
    3rd Research Co-ordination Meeting on"Development of Agents for Imaging CNS Receptors Based on 99mTc", Montevideo, Uruguay, April 24-28, 2000

Publ.-Id: 3341

Development of 99mTc complexes for imaging the serotonin-5HT2A receptor in the Central Nervous System

Pietzsch, H.-J.

  • Lecture (Conference)
    3rd Research Co-ordination Meeting on"Development of Agents for Imaging CNS Receptors Based on 99mTc", Montevideo, Uruguay, April 24-28, 2000

Publ.-Id: 3340

Functionalized dendrimers: Emerging opportunities for the application in medicine

Stephan, H.

Dendrimer chemistry is a rapidly espanding field for both fundamental studies and applications. Their unique structural features and properties make them ideally suited for use in diagnostic imaging and therapy, transfection, and drug delivery. A short overview about some fields of application in medicine was given. It was reported the binding and transport behaviour of dendrimers having urea, azobenzene, methyl orange and diamidopyridine moieties at the periphery towards pertechnetate, and the nucleotides AMP, ADP and ATP.

  • Lecture (others)
    4-Center Meeting Amsterdam-Bologna-Bonn-Fribourg, Oegstgeest/Leiden (Netherlands), 24-26 March 2000

Publ.-Id: 3339

Microdiverse types of Thiobacillus ferrooxidans and their interactions with uranium

Merroun, M.; Flemming, K.; Selenska-Pobell, S.

Sequence analysis of the 16S rRNA genes of several reference strains and uranium mining waste pile isolates of Thiobacillus ferrooxidans revealed specific signatures which distinguish three types within the species. This allowed to develop a technique for analysis of the distribution of the T. ferrooxidans eco-types in the soil samples of a uranium mining waste pile.
The technique is based on amplification of 16S rDNA fragments in total soil DNA by the use of two T. ferrooxidans species specific primers 16S458F and 16S1473R (De Wulf-Durand et al., 1997). The resulting amplicons were then digested with a frequently cutting enzyme RsaI which produced three different type-specific profiles (Selenska-Pobell et al., 2000). Using this direct approach we have demonstrated that one of the T. ferrooxidans types (type I) was predominant in the soil samples studied and was found in more polluted sites, whereas the type II was found in less contaminated samples. The type III was found mostly to coexist with the type II.
The complexation of uranium by the three eco-types of T. ferrooxidans was investigated. The uranium sorption studies showed that the strains from the three different types possess different capability to accumulate uranium. The process of uranium accumulation is affected by the initial uranium concentration and pH. Using sodium carbonate as a desorbing agent, 97% of the biosorbed uranium was recovered from the cells of T. ferrooxidans type III, and 88.33 and 88.50% from the cells of the type I and II, respectivley. Extended x-ray absorption fine structure (EXAFS) and infrared (IR) spectroscopy were performed to obtain information about the exact chemical structure of the uranium complexes formed on the surfaces of the three eco-types of T. ferrooxidans.

  • Poster
    IBS-2 International Biometals Symposium Tübingen

Publ.-Id: 3333

Bacteria from uranium waste piles and their interactions with uranium (VI)

Selenska-Pobell, S.; Merroun, M.; Panak, P.; Hennig, C.; Reich, T.; Tzvetkova, T.

Gram-positive spore-forming bacterial isolates belonging to the species Bacillus cereus, B. sphaericus and B. megaterium and also Gram-negative chemolithoautotrophic isolates of the species Thiobacillus ferrooxidans and Leptospirillum ferrooxidans were cultured from soil and sediment samples of several uranium polluted waste piles in Saxony, Germany. The interactions of these natural bacterial isolates with uranium (in particular, sorption - desorption, accumulation, reduction, and tolerance) were studied.
We have demonstrated that the natural Bacillus isolates are able to accumulate selectively and reversible a variety of toxic metals from drain waters of a uranium mining waste pile (Selenska-Pobell et al., 1999). By the use of extended X-ray absorption fine structure (EXAFS) analysis and time resolved laser fluorescence spectroscopy (TRLFS) it was demonstrated that the main chemical group involved in the interaction of the mentioned Bacillus strains with U(VI) is the phosphate group (Hennig et al., 1999; Panak et al., 2000).
Our studies on the interactions of the recently described in our laboratory three ecological types (eco-types) of T. ferrooxidans (Selenska-Pobell et al., 1999) and two eco-types of L. ferrooxidans (Tzvetkova et al., 1999) with uranium (VI) by the use of EXAFS, TRLFS, and infrared spectroscopy (IRS) indicate that the nature and the strength of the uranium complexes built by these Gram-negative acidophilic chemolithoauthotrops differ significantly from those built on the cell surfaces of the Gram-positive Bacilli. The tolerance and the interactions of the natural T. ferrooxidans isolates with U were type-specific.

  • Poster
    IBS-2 International Biometlas Symposium Tübingen

Publ.-Id: 3332

Complexation of uranium by three eco-types of Thiobacillus ferrooxidans

Merroun, M.; Selenska-Pobell, S.

The complexation of uranium by the cells of the three recently described eco-types of T. ferrooxidans (Flemming et al., 1999; Selenska-Pobell et al., 1999) was studied. The uranium sorption studies showed that the strains from the three different types possess different capability to accumulate uranium. We have found that the representatives of type II accumulate significantly higher amounts of uranium in comparison to the other T. ferrooxidans strains studied. The amount of accumulated uranium gradually increased with increasing metal concentration at pH 1.5 and 4. The uranium tolerance investigations demonstrated that the types I and III are resistant to 8 and 9 mM of uranium respectively, whereas the type II does not tolerate more than 2 mM of uranium. Sodium carbonate was the most efficient desorbing agent tested, removing 97% of the uranium sorbed from the cells of T. ferrooxidans type III, and 88.33 and 88.50% from the cells of the types I and II, respectivley. Sodium citrate was the second best metal desorbing agent, whereas EDTA could remove only between 10 and 30% of the accumulated uranium. By the use of extended x-ray absorption fine structure (EXAFS) and infrared (IR) information was obtained about the exact chemical structure of the uranium complexes formed on the surface by the three eco-types of T. ferrooxidans.

  • Lecture (Conference)
    IBS-2 2nd International Biometal Symposium Tübingen

Publ.-Id: 3331

Pairing correlations in high-K bands

Almehed, D.; Frauendorf, S.; Dönau, F.

The tilted axis cranking model is used in combination with the random phase approximation and particle number projection to analyze the influence of dynamical pairing correlations in the high-K bands of 178-W and their effect on relative energy and angular momentum. The calculations show the importance of dynamical pairing correlations to describe the experiment as well as advantages and problems with the different models in the superfluid and normal state regions.

Keywords: Hatree-Fock-Bogoliubov states; Tilted Axis Cranking model; High-K bands; Particle Number Projection; Random Phase Approximation

  • Physical Review C 63 (2001) 044311

Publ.-Id: 3330

The Modeling of Fuel Rod Behaviour under RIA Conditions in the Code DYN3D

Rohde, U.

A description of the fuel rod behaviour and heat transfer model used in the code DYN3D for nuclear reactor core dynamic simulations is given. Besides the solution of heat conduction equations in fuel and cladding, the model comprises detailed description of heat transfer in the gas gap by conduction, radiation and fuel-cladding contact. The gas gap behaviour is modeled in a mechanistic way taking into account transient changes of the gas gap parameters based on given conditions for the initial state. Thermal, elastic and plastic deformations of fuel and cladding are taken into account within 1D approximation. A creeping law for time-dependent estimation of plastic deformations is implemented. Metal-water reaction of the cladding material in the high temperature region is considered. The cladding - coolant heat transfer regime map covers the region from one-phase liquid convection to dispersed flow with superheated steam. Special emphasis is put on taking into account the impact of thermodynamic non-equlibrium conditions on heat transfer.

For the validation of the model, experiments on fuel rod behaviour during RIAs carried out in Russian and Japanese pulsed research reactors with shortened probes of fresh fuel rods are calculated. Comparisons between calculated and measured results are shown and discussed. It is shown, that the fuel rod behaviour is significantly influenced by plastic deformation of the cladding, post crisis heat transfer with subcooled liquid conditions and heat release from metal water reaction.

Numerical studies concerning the fuel rod behaviour under RIA conditions in power reactors are reported about. It is demonstrated, that fuel rod behaviour at high pressures and flow rates in power reactors is different from the behaviour under atmospheric pressure and stagnant flow conditions in the experiments. The mechanisms of fuel rod failure for fresh and burned fuel reported from the literature can be qualitatively reproduced by the DYN3D model. However, the model must be extended and improved for proper description of burned fuel behaviour.

The realistic simulation of the fuel rod behaviour is important not only under RIA conditions, but also for the analysis of operational transients. This has been shown in a calculation of an operational transient with power decrease after switching-off one from the two working feed water pumps in the NPP Balakovo (VVER-1000).

Keywords: nuclear reactors; reactivity initiated accidents; fuel rod; gas gap; heat transfer; creeping; metal water reaction

  • Annals of Nuclear Energy 28 (2001), Vol. 13, pp. 1343-1363

Publ.-Id: 3329

Ligand-Exchange Reaction of Labile "3+1" 99mTc(V) Complexes with SH Group-Containing Proteins

Seifert, S.; Gupta, A.; Syhre, R.; Spies, H.; Johannsen, B.

The reactivity of labile 3+1 mixed-ligand 99mTc complexes of the type [99mTcO(SES)(RS)] with SES being a tridentate dithiol ligand and glutathione or dimethylcysteamine as monodentate ligands RSH towards proteins was investigated in vitro and in vivo. It was found that the complexes undergo reversible transchelation reactions with SH group-containing components of blood such as albumin or hemoglobin. High labelling yields were obtained when 3+1 complexes with the tridentate SSS ligand were used. The biodistribution of blood proteins labelled by ligand-exchange reaction with the [99mTcO(SSS)] or [99mTcO(SNMeS)] core was studied and compared with the in vivo distribution of the labile 3+1 complexes containing glutathione as monodentate ligand.

Keywords: labile 3+1 Tc complexes; reaction with proteins

  • Appl. Radiat. Isot. 54 (2001) 637-644

Publ.-Id: 3328

Helium implantation induced metal gettering in silicon at half of the projected ion range

Peeva, A.; Koegler, R.; Skorupa, W.; Fichtner, P.; Behar, M.

He+ ions were implanted at 40 keV into Si <100> random direction at room temperature to fluences between 5×1015 He+/cm2 and 3.5×1016 He+/cm2. The samples were than contaminated with Cu in order to study the gettering of Cu atoms at the defective layer. A subsequent annealing at 800ºC was performed in order to recover the implantation damage and redistribute the Cu into the wafer. The samples were analyzed by Rutherford backscattering/channeling (RBS/C) and transmission electron microscopy (TEM) techniques. The Cu distribution was measured by secondary ion mass spectrometry (SIMS). The SIMS results show that the 5×1015 He+/cm2 implant induces gettering at the He+ projected range (Rp) region, while the 8×1015 He+/cm2 and 3.5×1016 He+/cm2 implants have resulted in gettering at both the Rp and Rp/2 depths. The TEM micrographs show no visible defects at Rp/2 region. This corresponds to the so called Rp/2 gettering effect. It is important to note that in this study the Rp/2 related effect is observed after an implantation of a light ion at low energy.

Keywords: Gettering; Silicon; Helium; bubbles; ion implantation; defect formation and annealing

  • Contribution to proceedings
    2nd ENDEAST Workshop, Stockholm, Sweden, Junie 27-29, 2000

Publ.-Id: 3327

The study of Ti doped ZSM-5 particles and cavities inside them

Klimenkov, M.; Nepijko, S. A.; Matz, W.; Bao, X.

The TEM study of titanium contained ZSM-5 zeolite before and after hydrothermal treatment was performed. The use of different TEM techniques - such as conventional TEM, HRTEM and EDX line scans provides important information about the zeolite catalyst consisting from several phases. The hydrothermal treatment of zeolite powder leads to strong changes in the morphology of the constituting particles. They are characterised by a homogeneous structure before hydrothermal treatment while the occurrence of holes after thermal treatment was observed. These changes lead to the enrichment of zeolite with titanium that enhance its catalytic activity. Some of the titanium surplus precipitates as TiO2 anatase nanoparticles within the holes.

Keywords: zeolites; TEM; nanoparticles

  • Journal of Crystal Growth 231 (2001) 577-588

Publ.-Id: 3325

Trans-projected-range gettering of copper in high-energy ion-implanted silicon

Gueorguiev, Y. M.; Kögler, R.; Peeva, A.; Mücklich, A.; Panknin, D.; Yankov, R. A.; Skorupa, W.

Strong gettering of Cu atoms beyond the projected ion range RP has been found in single-crystal Si implanted with P+ and As+ ions at MeV energies. We call this phenomenon the "trans-RP effect". The formation of a separate Cu gettering band below RP, as detected by secondary ion mass spectrometry, indicates the presence of a significant amount of defects therein. These defects are not detectable by transmission electron microscopy and we suggest that they are small interstitial clusters. The amount of Cu atoms gettered beyond RP is, particularly for the P implants, much greater than that in the implanted gettering layer, indicating that the gettering ability of the defects beyond RP is higher than that of the extended defects at RP. A mechanism responsible for their formation and clustering in the trans-RP region is proposed, and an explanation is given of the differences in the results for the P and As implants.

Keywords: Ion implantation (61.72.Q); Defect formation and annealing (61.72.C); Indirect evidence of defects (61.72.H); Defects diffusion (66.30.L); Gettering (61.72.T)

  • Journal of Applied Physics 88 (200) 6934

Publ.-Id: 3324

High dose implantation in 6H-SiC

Heera, V.; Skorupa, W.; Stoemenos, J.; Pécz, B.

There are two major reasons to study the effects of high dose implantation in SiC. First, the production of low-resistivity, p-type layers requires high acceptor concentrations which are far above the equilibrium solubility. It is essential to know the critical acceptor concentration for thermally stable, homogeneously doped SiC. On the other hand, there is a lack of information about the precipitation of new phases in SiC, their properties and influence on the SiC matrix. Such information is needed for the assessment whether insulating or conductive layers with device quality can be formed in SiC by ion beam synthesis. Two examples of high dose implantation in 6H-SiC are presented.

In the first example high doses of 350 keV Al+ ions were implanted in 6H-SiC single crystals at temperatures between 400oC and 800oC in order to preserve the crystallinity of the SiC matrix. The phase formation was studied by TEM, SIMS and AES. A critical Al concentration of about 10 at% was found below that the 6H-SiC structure remains stable during implantation at 500°C. The Al atoms occupy preferentially Si sites in the SiC lattice. At higher Al concentrations the SiC matrix is decomposed and precipitates of Si and Al4C3 are formed. It was found that the Al4C3 precipitates have a perfect epitaxial orientation to the SiC matrix. The phase transformation is accompanied by atomic redistribution and strong volume swelling. The observed atomic depth profiles can be accounted for by a a simple chemical reaction model. Implantation at 800°C leads to the formation of Si and Al precipitates accompanied by a dramatic volume swelling which results in surface cracking and material outflow. Post-implantation annealing above 1500°C severely deteriorate the SiC matrix by local melting of Al and Si precipitates.

In the second example the evolution of the binary system C -> SiC was studied as function of implantation temperature. 1 1018 cm-2, 60 keV carbon ions were implanted into single crystalline 6H silicon carbide (SiC) at elevated temperatures. The formation of carbon phases in the crystalline SiC lattice was investigated by cross sectional transmission electron microscopy. An amorphous, carbon rich phase was produced at 300oC. Precipitates of graphite were obtained at 600oC, whereas at 900oC small diamond grains were produced. These grains are in perfect epitaxial relation with the surrounding SiC lattice. The mechanism of the diamond formation by IBS in SiC is not quite clear. It can be assumed that the tetrahedrally coordinated SiC lattice, which is preserved during the high temperature implantation, acts as a template for the growth of diamond. In addition, local nonequilibrium conditions in the ion cascades (thermal spikes, shock waves) or temporary stress on interstitially incorporated carbon atoms by the surrounding SiC lattice could contribute to the diamond nucleation.

Keywords: high dose implantation; silicon carbide; 6H-SiC; ion beam synthesis

  • Lecture (Conference)
    ECSCRM2000, Kloster Banz, Germany, Sep. 3-7, 2000 Mater.Sci. Forum Vols. 353-356 (2001) 579-582

Publ.-Id: 3323

Master Curve Evaluation of Irradiated Russian VVER Type Reactor Pressure Vessel Steels

Viehrig, H.-W.; Böhmert, J.; Dzugan, J.; Richter, H.

Results of a joint German/Russian irradiation programme performed on the prototype pressurized water reactor VVER-2 of the Rheinsberg nuclear power plant Germany) are summarized. The experiment comprises Charpy V-notch (CVN), precracked Charpy size (SENB) and compact tension (CT) specimens made of different heats of Russian VVER type reactor pressure vessel (RPV) base and weld metals. Reference temperatures, T0, were evaluated according to the Master Curve (MC) concept using the
multi temperature method. Neutron irradiation induced ductile-to-brittle transition temper ature (DBTT) shifts determined on the basis of CVN and SENB tests are compared. On the base of the DBTT the neutron embrittlement sensitivity and the annealing behaviour of tested RPV steels are evaluated. Different heats of the same VVER-RPV steel exhibit different neutron induced embrittlement and annealing behaviour. The determined CVN transition temperatures correlates to the T0 temperatures evaluated by the MC concept.

Keywords: reactor pressure vessel steel; integrity assessment; Charpy V test; transition temperature; fracture toughness; reference temperature; predicting formulas; radiation embrittlement

  • Lecture (Conference)
    Effects of Radiation on Materials: 20th International Symposium, June 2000, ASTM STP 1405, S.T. Rosinski, M.L. Grossbeck, T.R. Allen, and A.S. Kumar, Eds., American Society for Testing and Materials, West Conshohocken, pp. 109-124
  • Contribution to proceedings
    Effects of Radiation on Materials: 20th International Symposium, June 2000, ASTM STP 1405, S.T. Rosinski, M.L. Grossbeck, T.R. Allen, and A.S. Kumar, Eds., American Society for Testing and Materials, West Conshohocken, pp. 109-124

Publ.-Id: 3322

Cosmic Phase Transitions

Kämpfer, B.

The sequence of phase transitions during the hot history of the universe is followed within a phenomenological framework.
Particular emphasis is put on the QCD confinement transition, which is at reach under earth laboratory conditions.
A tepid inflationary scenario on the GUT scale with bubble grow at moderate supercooling is discussed.

Keywords: cosmic phase transitions; deconfinement; inflation

  • Annalen der Physik (Leipzig) 9 (2000) 8, 605-635
  • Contribution to WWW
    Astro-ph Server LANL

Publ.-Id: 3321

Determination of uranium speciation in plants

Bernhard, G.; Günther, A.; Geipel, G.; Rossberg, A.; Reich, T.; Nitsche, H.

The overall process of uptake of heavy elements (actinides) into plant tissues from contaminated soils has been quantified using the soil-to-plant transfer factor (TF). Considering the radionuclide transfer, it is quantified as TF(RN) = plant specific activity (Bq/kg-1) /soil specific activity (Bq/kg-1). In practice the predominant pathway of plant contamination is direct contamination by deposition and resuspension. The comparable uptake via soil-plant transfer is about 10%. But this ratio strongly depends on the real accident scenario (distribution of contaminants via aerosol in air, as soluble or colloidal species in aquifer or surface water).Up to now, the chemistry of the various actinides has not been considered along the pathway soil-plant-animal-humans. The transfer factor has to be unfolded into the basic parameters like changes in oxidation state and complexation, differences in bonding of the elements like adsorption and ion exchange processes, formation of colloids e.g.
It was our goal to obtain first results on the change of uranium speciation during the soil-to-plant transfer. X- ray absorption spectroscopy (XAS) with synchrotron radiation and the time-resolved laser-induced fluorescence spectroscopy (TRLFS) were used as tools for the determination of uranium speciation in soil, water, and different parts of the plants. The reported investigations about the distribution and speciation of uranium were focused on lupins.

  • Lecture (Conference)
    Vortrag zur 5.Tagung "NRC" 3.-8.9.2000

Publ.-Id: 3320

Untersuchungen zur chemischen Speziation von Uran(VI) in Pflanzen

Günther, A.; Bernhard, G.; Geipel, G.; Roßberg, A.; Reich, T.

Radionuklidkontaminationen können über den Belastungspfad Boden-Pflanze-Nahrungkette deutlich zur Strahlenbelastung des Menschen beitragen. Die Bestimmung des Transfers von Radionukliden aus kontaminierten Böden ist daher für Risikoabschätzungen unbedingt erforderlich. Bisher stand die Bestimmung von Transferfaktoren im Mittelpunkt der Untersuchungen. Um zuverlässigere Abschätzungen über eine Radionuklidmigration im System Boden-Pflanze machen zu können, ist die Charakterisierung des chemischen Zustands der einzelnen Radionuklide notwendig. Bislang ist eine direkte Bestimmung der chemischen Speziation von Uran und anderen Actiniden in Pflanzen aus der Literatur nicht bekannt. Für die Bestimmung der chemischen Speziation von Uran in Pflanzen wurden insbesondere die Lupine und der Löwenzahn auf natürlich und künstlich mit Uran kontaminierten Böden und als Hydrokulturen in uranhaltiger Lösung gezüchtet. Frische und trockene Pflanzenproben wurden vorrangig mit Hilfe der zeitaufgelösten Laserfluoreszenzspektroskopie und der Röntgenabsorptionsspektroskopie als äußerst leistungsstarke und empfindliche Speziationsmethoden untersucht. Über die bisherigen Ergebnisse soll hier berichtet werden

  • Poster
    Botanikertagung - 2000, Jena

Publ.-Id: 3319

Radial Gas Profiles in Vertical Pipe Flow in Dependence on the Bubble Size Distribution

Lucas, D.; Krepper, E.; Prasser, H.-M.

The paper presents a method for the prediction of the radial gas profile in vertical pipe flow for a given bubble size distribution. The method assumes equilibrium of the forces acting on a bubble perpendicular to the flow direction. On basis of the radial profile of the liquid velocity, radial distributions of the volume fraction are calculated separately for all bubble classes according to a given bubble size distribution. The sum of these distributions is the radial profile of the gas fraction. The model is the basis of a fast running one-dimensional steady state computer code. The results of the model are compared with experimental data for a number of gas and liquid volume flow rates.

  • Lecture (Conference)
    38th European Two-Phase Flow Group Meeting, May, 29-31 2000, Karlsruhe, Germany, Paper G4
  • Contribution to proceedings
    38th European Two-Phase Flow Group Meeting, May, 29-31 2000, Karlsruhe, Germany, Paper G4

Publ.-Id: 3318

XANES and EXAFS Measurements of Pu(III) and Pu(VI) Hydrates

Reich, T.; Geipel, G.; Funke, H.; Hennig, C.; Bernhard, G.

The hydrate is the simplest chemical form of plutonium in aqueous solution. The knowledge of the structural parameters of the hydration sphere is important for the interpretation of EXAFS results on complicated aqueous plutonium complexes where the water molecules are partly or fully replaced by other ligands. Plutonium(VI) hydrate was prepared by dissolution of PuO2 (Pu-242, AEA Technology, QSA GmbH) and electrochemical oxidation. Part of this solution was reduced to Pu(III) in an electrochemical cell. The Pu(III) and Pu(VI) hydrates were in perchloric and nitric media (1 M acidic solution), respectively. The final Pu concentration was 50 mol/L. The Pu oxidation states were confirmed by UV/Vis spectroscopy. For the measurements 4.7 mL of solution (7.5 MBq)
was filled and sealed in polyethylene cuvettes. The samples were measured at the Rossendorf Beamline ROBL at the European Synchrotron Radiation Facility (ESRF), Grenoble, France within 48 hours after their preparation.

Multiple scans of the Pu LIII-edge EXAFS were collected in transmission mode at room temperature using the Si(111) double-crystal monochromator in fixed-exit mode /1/. The energy scale was calibrated using the first inflection point of the absorption spectrum of a Zr foil (17998 eV). The scattering phases and amplitudes where calculated for hypothetical clusters of PuO8, and PuO2O5 using FEFF6.

As one can see from the XANES spectra given in Fig. 1, the LIII absorption edge of Pu(VI) is shifted by 4 eV toward higher energy as compared to that of Pu(III). The energy shift and the distinct XANES features of these two Pu hydrates can be used for the determination of the Pu oxidation states /2/.

The different electronic and molecular structures of Pu(III) and Pu(VI) hydrates are also reflected in the EXAFS shown in Fig. 2. The coordination sphere of Pu(III) hydrate can be written as Pu(H2O)83+ with an average Pu-O bond distance of 2.48 Å. The Fourier transform corresponding to the EXAFS of Pu(VI) hydrate shows two coordination shells. The Pu(VI) forms a plutonyl ion PuO2(H2O)4-52+. The axial and equatorial Pu-O bond distances are 1.74 and 2.42 Å, respectively. The structural parameters of Pu(VI) hydrate are nearly identical to those of U(VI) and Np(VI) hydrates (see Tab. 1), which were measured recently at ROBL /3/.

Fig. 2: Raw Pu LIII-edge k3-weighted EXAFS spectra (left) and corresponding Fourier transforms (right) of 50 mMol/L Pu hydrates. Solid line - theoretical fit; dots - experiment.

Tab. 1: EXAFS structural parameters for 50 mMol/L Pu hydrates and comparison with 50 mMol/L Np(VI) and U(VI) hydrates.
Sample Shell R(Å) N s2 a)
Pu(III) Pu-O 2.48 7.6(2) 1.02
Pu(VI) Pu -Oax 1.74 1.9 0.12
Pu -Oeq 2.42 4.4(2) 0.50
Np(VI) Np-Oax 1.75 2.0 0.15
Np-Oeq 2.42 4.6(2) 0.56
U(VI) U-Oax 1.76 1.9 0.12
U-Oeq 2.41 4.9(2) 0.61
a) s2 in units of 10-2 Å2

  • Lecture (Conference)
    Journees des Actinides, 4.-6.5.2000 Dresden

Publ.-Id: 3317

Problems and Possibilities of Neutron Spectrum Adjustments

Böhmer, B.

Two principal methods of neutron spectrum adjustment have been compared. Their advantages and problems were discussed. Thereby, the possible use of spectrum adjustment at the LR-0 facility Rez was considered. Recent improvements of the Rossendorf adjustment procedure COSA3 were described. A wider use of spectrum adjustment has been justified by its close relation to uncertainty analysis always required in serious investigations.

Keywords: neutron spectrum adjustment; reactor dosimetry

  • Lecture (Conference)
    IAEA RER 4/017 Technical Meeting "Fine Group Spectrum Calculations and Comparison with Experimental Results held in FZ Rossendorf, October 25 - 30, 1999

Publ.-Id: 3316

Ion flux, ion energy distribution and neutral density in an inductively coupled argon discharge

Chevolleau, T.; Fukarek, W.

The dependence of ion flux, ion energy distribution, and neutral density of a planar radio frequency (RF) driven inductively coupled plasma source on pressure and power is analyzed using an energy selective mass spectrometer and a retarding field analyzer. The ion flux is about 7 mA/cm^2 at 5 Pa and 300 W and increases as RF power and argon pressure increase. The ion energy distribution consists of a single peak with a full width at half maximum of 3 eV for a discharge power in the range from 50 to 300 W and for a pressure in the range from 0.5 to 5 Pa. This indicates that inductive coupling mainly drives the discharge while capacitive coupling between coil and plasma is weak. A significant decrease in Ar neutral density is observed when the plasma is ignited. The Ar depletion increases with increasing RF power and increasing Ar base pressure and reaches 30 % at 5 Pa and 300 W. The decrease in neutral density cannot be explained by the ionization of Ar atoms only but is also attributed to heating of Ar atoms by collisions with energetic particles. A simple model is proposed to understand and to estimate the effect of these collisions on the neutral temperature.

Keywords: ICP; plasma; ion energy distribution; ion flux; neutral density

  • Plasma Sources Science and Technology 9(2000) 568

Publ.-Id: 3315

Thickness dependent phase transformations in implanted iron

Kopcewicz, M.; Jagielski, J.; Matz, W.

The dependence of the iron nitride formation and the phase transformations in the nitrogen implanted layer on the thickness of the implanted material is investigated by Conversion Electron Mössbauer Spectroscopy (CEMS). Phase transformations in nitrogen-implanted iron layers of various thickness ranging from 60 nm to 870 nm deposited on SiO2 substrate by rf sputtering technique have been studied. Such prepared samples were implanted at room temperature with nitrogen ions with the energy of 50 keV with ion doses ranging from 1x1017 at. N/cm2 to 5x1017 at. N/cm2. After each implantation step the samples were characterized by CEMS using the gas flow electron counter with He-6%CH4 gas. The implanted samples were also investigated by the Grazing Angle X-ray Diffraction (GXRD). The results revealed that the nitride formation is strongly enhanced in thin films as compared to thicker layers or bulk iron samples. In thin iron films a given nitride phases (‘/”, -Fe3N, -Fe2N) are formed at lower nitrogen doses and the transformation of the original iron layer into iron nitrides is more complete than in the bulk -Fe. In bulk iron samples about 20 % of Fe atoms remain in the -Fe phase even for the highest implantation doses (5x1017 at. N/cm2) whereas the complete transformation of thin 60 - 230 nm iron layer into Fe nitrides has been observed.
The observed effects are not fully understood yet. The GXRD experiments performed for the same samples revealed that the stress in the interfacial region of Fe layer and the substrate is significantly larger than in the top (free) surface of the layer. The higher stress may favor the formation of iron nitrides. On the other hand the presence of the interface between Fe film and the substrate may block the in-bulk diffusion of N atoms leading to the higher nitrogen concentration in thin films as compared to the bulk.
The strong dependence of the nitride formation due to N-implantation on the thickness of the implanted material is important for implantation metallurgy, especially for implantation of thin coatings often used for the extension of lifetime of precise tools and details. The phase transformations in thin films may occur in significantly different way as compared to the bulk materials leading to the formation of new phases characterized by extremely high impurity concentration.

Keywords: iron thin layers; ion implantation; Mössbauer effect; X-ray diffraction

  • Lecture (Conference)
    ISIAME-2000 International Symposium on the Industrial Applications of the Mössbauer Effect, 13-18 August, 2000. Virginia Beach, Virginia USA
  • Hyperfine Interactions 139-140 (2002) 369-377

Publ.-Id: 3313

Coupled Thermal Structural Analysis of LWR Vessel Creep Failure Experiments

Willschütz, H.-G.; Altstadt, E.; Sehgal, B. R.; Weiß, F.-P.

Considering the hypothetical core melt down scenario for a Light Water Reactor the behaviour of the Reactor Pressure Vessel during the late phase of the accident has to be investigated. The FOREVER-experiments, currently underway, are simulating the lower head under the load of a melt pool with internal heat sources. Due to the multi-axial creep deformation of the vessel with a non-uniform temperature field these experiments are an excellent possibility to validate numerical creep models. Therefore a Finite Element model is developed on the basis of a commercial multi-purpose code. Using the CFD module the temperature field within the vessel wall is evaluated. The transient structural mechanical calculations are performed using a new numerical approach which avoids the use of a single creep law with constants evaluated for a limited stress and temperature range. Instead of this a three-dimensional array is developed where the creep strain rate is evaluated according to the actual total strain, temperature and equivalent stress. Performing post-test calculations it was found that the assessment of the experimental data and of the numerical results has to be done very carefully. Considering the experiment FOREVER-C2, for example, the recorded creep process appears to be tertiary, if a constant temperature field is assumed. But slight temperature changes during the creep deformation stage could explain the observed creep behaviour, too. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios.

Keywords: Finite Element Calculations; FOREVER-Experiment; Coupling of Thermo-Fluid dynamic and Structural Mechanical Model; Advanced Creep Modelling

  • Nuclear Engineering and Design, Elsevier, 208 (2001)265-282

Publ.-Id: 3312

Beitrag zur Bewertung des Bestrahlungsverhaltens russischer WWER Reaktordruckbehälterstähle

Viehrig, H.-W.; Böhmert, J.; Dzugan, J.

In dem Vortrag werden Ergebnisse von Bestrahlungsexperimenten vorgestellt, die im Druckwasserreaktor WWER-2 des KKW Rheinsberg durchgeführt worden sind. Im WWER-2 wurden ISO-V und Bruchmechanikproben aus unterschiedlichen Chargen
von WWER-Grundwerkstoff und Schweißgut bestrahlt. Der Schwerpunkt liegt auf Ergebnissen eines Bestrahlungsprogrammes (WTZBRh), das im Rahmen der wissenschaftlich-technischen Zusammenarbeit zwischen Deutschland und Russland mit den Zielstellungen:der Untersuchung des Einflusses von Begleit- (P, Cu) und Legierungselementen (Ni) auf die bestrahlungsinduzierte Versprödung, der Bewertung der Gültigkeit der Vorhersageformeln des russischen Regelwerkes und der Untersuchung des Ausheilverhaltens durchgeführt worden ist. Die Prüfung der Proben des WTZBRh erfolgte im Rahmen von Förderprojekten des BMBF/BMWi durch das Forschungszentrum Jülich GmbH, die Staatliche Materialprüfungsanstalt Universität Stuttgart und das Forschungszentrum Rossendorf e.V.
Das Bestrahlungs- und Ausheilverhalten der WWER-RDB-Stähle wird auf der Basis der im ISO-V- und Bruchmechaniktests ermittelten Parameter bewertet. Als bruchmechanische Parameter wurden im unteren Spröd-Duktil Übergangsbereich
Referenztemperaturen T0 nach dem Master-Curve Konzept und im duktilen Bereich Risswiderstandskurven und Risseinleitungszähigkeiten ermittelt.

Keywords: Reaktordruckbehälterstahl; Bruchzähigkeit; Neutronenbestrahlung; Versprödung

  • Lecture (Conference)
    26. MPA-Seminar "Sicherheit und Verfügbarkeit in der Energietechnik", Staatliche Materialprüfanstalt Stuttgart, Universität Stuttgart, 5.-6. Oktober 2000, Sammelband, S. 20.1-20.20
  • Contribution to proceedings
    26. MPA-Seminar "Sicherheit und Verfügbarkeit in der Energietechnik", Staatliche Materialprüfanstalt Stuttgart, Universität Stuttgart, 5.-6. Oktober 2000, Sammelband, S. 20.1-20.20

Publ.-Id: 3311

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