Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

With only a few exceptions, the numerical simulation of cosmic and laboratory hydromagnetic dynamos has been carried out in the framework of the differential equation method. However, the integral equation method is known to provide robust and accurate tools for the numerical solution of many problems in other fields of physics. The paper is intended to facilitate the use of integral equation solvers in dynamo theory. In concrete, the integral equation method is employed to solve the eigenvalue problem for a hydromagnetic dynamo model with a spherically symmetric, isotropic helical turbulence parameter alpha. Three examples of the function alpha(r) with steady and oscillatory solutions are considered. A convergence rate proportional to the inverse squared of the number of grid points is achieved. Based on this method, a convergence accelerating strategy is developed and the convergence rate is improved remarkably. Typically, quite accurate results can be obtained with a few tens of grid points.

At present, the GDT facility of the Budker Institute for Nuclear Physics Novosibirsk is being upgraded. The first stage of the upgrade is the Synthesised Hot Ion Plasmoid (SHIP) experiment. It aims, on the one hand, at the investigation of plasmas the parameters of which are expected to appear in the region of high neutron production in a GDT based fusion neutron source as proposed by the Budker Institute and, on the other hand, at the investigation of plasmas the parameters of which have never been achieved before in magnetic mirrors. The expected record values of plasma parameters and several peculiarities of the plasma offer a great field
for interesting investigations. In order to simulate the particle fields inside the GDT device and later in a GDT based neutron source an Integrated Transport Code System (ITCS) is being developed in collaboration between Forschungszentrum Rossendorf and Budker Institute. It consists of modules which allow the calculations of neutral gas, background plasma and of the fast ion component considering their mutual interactions. This contribution explains the concept of the SHIP experiment and presents the
results of first calculations by means of the ITCS modules.

A miniaturised ion selective electrode (ISE) for Cu2+ ions was developed, specially designed for application in a microfluidic system. The electrode was prepared on a silicon wafer substrate coated with a Cu deposit in the thickness range of 50 - 200 nm. The Cu layer was quantitatively converted into CuS by treatment in a sulphidic ambient. The chip electrode has a size of 5x5 mm2 and was mounted on a spacer chip coupled to the fluidic microcell using a chip clip technology. The coupling is liquid proof and reversible, permitting an easy exchange of the chip electrodes. The effective electrode area contacting the liquid of the microsystem flow channel amounts to about 4 mm2.

Sensitivity measurements were performed stationary and in the flow through cell. There was found a good Nernstian response of 29 mV/pCu between pCu 5 and 1 agreeing very well with reference measurements carried out with a commercial ISE.

The rapid response observed even in the dilutest solutions used, is related to the thin, non-porous structure of the CuS layer, minimizing diffusion effects during changing the test solutions. The adhesion of the sensitive CuS layer is different for the substrates Si, SiO2 and Si3N4 and depends on their history, roughness and evaporation conditions.

The first application of a Sonogashira cross-coupling reaction in ¹⁸F chemistry has been developed. The reaction was exemplified by the cross-coupling of terminal alkynes (ethynylcyclopentyl carbinol 6, 17alpha-ethynyl-3,17beta-estradiol 7 and 17alpha-ethynyl-3-methoxy-3,17beta-estradiol 8) with 4-[¹⁸F]fluoroiodobenzene. 4,4'-Diiododiaryliodonium salts were used as precursors for the synthesis of 4-[¹⁸F]fluoroiodobenzene, enabling the convenient access to 4-[¹⁸F]fluoroiodobenzene in 13-70 % yield using conventional heating or microwave activation. The Sonogashira cross-coupling of 4-[¹⁸F]fluoroiodobenzene with terminal alkynes gave the corresponding 4-[¹⁸F]fluorophenylethynyl-substituted compounds [¹⁸F]-9, [¹⁸F]-10 and [¹⁸F]-13 in yields up to 88% within 20 min starting from 4-[¹⁸F]fluoroiodobenzene.

The ¹⁸F-labelled amino acid derivative 3-O-methyl-6-[¹⁸F]fluoro-L-DOPA ([¹⁸F]OMFD) is a potential radiotracer to image tumour tissue using positron emission tomography. The precursor N-formyl-3-O-methyl-4-O-boc-6-trimethyl-stannyl-L-DOPA--ethyl ester enables the direct electrophilic radiofluorination by stereoselective destannylation. After partial hydrolysis, an optimized HPLC purification and sterile filtration the [¹⁸F]OMFD obtained with high radiochemical purity is ready for use. The total synthesis time is about 50 minutes and the radiochemical yield achieved is 20-25% (decay corrected, related to [¹⁸F]F₂). It was demonstrated that [¹⁸F]OMFD can be produced routinely and reliably for clinical use. [¹⁸F]FDOPA - preparation devices can be used with minor modifications.

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

In order to improve the knowledge about the interaction processes between humic acids (HA) and metal ions, e.g., actinide ions, various HA model substances with different functional properties were developed at FZR-IfR. These include synthetic HA with different functional group contents and various structural elements, chemically modified HA with blocked phenolic OH groups as well as 14C-labeled HA. Since start of the project, synthetic HA with distinct redox functionalities are developed.
The report gives an overview about the synthesis, characterization and application of HA with various functional properties. It describes the synthesis and characterization of the melanoidin-based HA type M1 and M42, which are characterized by different carboxyl group contents. In addition, the synthesis and characterization of modified HA with blocked phenolic OH groups as well as of HA with distinct redox functionalities are discussed.

Die Flüchtigkeit von Oxiden der leichten Actiniden Th, Pa, U, Np und Pu im System O₂-H₂O_(g)/SiO_2(s) wurde mittels Thermochromatographie im Temperaturbereich 300 - 1475 K untersucht. Th und Pa bilden unter den experimentellen Bedingungen keine flüchtigen Verbindungen. Bei Temperaturen > 1250 K bilden U, Np und Pu flüchtige Oxidhydroxide, deren Flüchtigkeit in der Reihenfolge Pu<Np<U zunimmt. Die Flüchtigkeit des Plutoniums belegt die Oxidation von Plutoniumdioxid durch Sauerstoff/Wasser zum Trioxid.

A crosslinked polyurethanurea (PUU) coating was synthesised from a solution on metal vascular stents. In the model system the glucocorticoid prednisolone was inserted into the film by the equilibrium swelling method; after this plasma immersion ion implantation (PIII) was applied to modify the coating for improved release kinetics. This treatment causes the formation of oxygencontaining and unsaturated carbon–carbon groups in the PUU and a destruction of the drug in the surface layer. As a consequence, the release rate of prednisolone to water becomes more stable with time than it is at the untreated coating. In this drug release system PIII treatment prevents an initial toxically high release of the drug. By this it allows the incorporation of a higher amount of the drug and an extended action.

High-dose carbon implantation (3x10e17 and 1x10e18 ions/cm2) into cubic SiC on Si was carriedout at elevated temperatures (600 to 1200 °C) and different dose rates (1x10e13 to 1.5x10e14 cm-2 s-1). Transmission electron microscopy revealed the formation of either graphite or diamond precipitates, depending on the implantation parameters. In all cases, the diamond grains were epitaxial to the SiC lattice, while the graphite was textured. The minimum temperature for diamond formation was 900 °C, while graphite formed at 600 °C. The synthesized phase depends as well on the dose rate; graphite was formed at 900 °C with a high dose rate. Obviously, a criticaltemperature for diamond formation exists and increases with increasing dose rate. This behavior is explained by the competition between the accumulation and dynamic annealing of radiation defects in the SiC lattice, which acts as a template for diamond nucleation. Diamond grains with diametersas large as 10 nm have been observed after implantation at 1200 °C.

In the fine chemical industry, complex strongly exothermic reactions are usually carried out in semibatch mode in stirred tank reactors. These reactors are characterised by nonsteady-state conditions due to the discontinuous operation. Thus, it is difficult to estimate the actual conversion and to identify undesired process states during the chemical reaction, particularly, if the reactor is not equipped with expensive measuring systems for chemical on-line analysis. Therefore, an on-line monitoring system was developed that is able to estimate the concentration profiles without the need of chemical on-line analysis.
The on-line estimation of the concentration profiles is based on calculations of the thermal and chemical conversion courses during the chemical process using heat and mass balances. In order to consider factors of influence, such as heat losses, heat bridges and systematic measuring errors, adaptive model components are included. The adaptation of the complex model to the target plant is done by software-supported calculations of the adaptive parameters using process data of at least one normal batch course in the chemical plant.
The monitoring system was developed, optimised and tested by means of experiments in a miniplant at laboratory scale. As a test process, the strongly exothermic catalytic hydrogenation of an aromatic nitro compound was chosen. For industrial testing, the monitoring system was integrated into a batch-information-management system which was implemented into the process control system of a multipurpose reactor installation in the fine chemical factory at Radebeul (Degussa, Inc.). The tests showed good agreements of the estimated concentration profiles with analytical measurements in both, the laboratory and the industrial scale. Furthermore, it was found that deviant reaction courses and undesired process states can be recognised very earlier using the on-line monitoring system than with exclusive knowledge of process variables like temperatures, pressures and volume flows.

The investigation of RPV material from decommissioned NPPs offers the unique opportunity to evaluate the real toughness response. By investigation of material from the decommissioned VVER 440-type Greifswald NPP the evaluation of a standard RPV design and the assessment of the quality of prediction rules and assessment tools will be possible. First results of the investigations are presented in the paper.

Differential production cross sections of K- and K+ mesons have been measured in Ni+Ni and Au+Au collisions at a beam energy of 1.5 A·GeV. The K-/K+ ratio is found to be nearly constant as a function of the collision centrality. The spectral slopes and the polar emission pattern differ for K- and K+ mesons. These observations indicate that K+ mesons decouple earlier from the fireball than K- mesons.

The primary structures of the S-layer proteins of the uranium mining waste pile isolate Bacillus sphaericus JG-A12 and of Bacillus sphaericus NTCC9602 were analysed. The amino acid sequences of the two proteins are almost identical but possess an abrupt homology to some of the other B. sphaericus S-layers studied up to date. This is an indication that a horizontal transfer of genetic information was involved in the evolution of the genes of the mentioned S-layers. An extensive comparative analysis of the S-layer proteins deposited to the GeneBanks demonstrated that several additional S-layers of B. sphaericus and of other Bacillus species were also subjected to late evolutionary events via lateral DNA transfer. The possible mechanism of these events in the case of B. sphaericus will be discussed.
Interestingly, the slight amino acid differences between the S-layer proteins of the strains JG-A12 and NTCC9692 lead to dramatic differences in their ability to interact with metals and also in their stability against proteases. As estimated by using EXAFS spectroscopy phosphorous residues, in addition to the carboxyl groups of the proteins, are involved in the binding of uranium (VI). ICP-MS analysis demonstrated that the two purified and recrystalized S-layer proteins contain phosphorous which indicates that they are phosphorylated. Moreover, the amount of phosphorous found in the S-layer of the strain JG-A12 was six times higher than those found in the S-layer of the reference strain NTCC 9602. This explains the higher ability of the S-layer of the uranium mining waste isolate to complex uranium and other metals. The latter seems to give an advantage to the strain JG-A12 to survive in the heavily polluted with uranium and other toxic metals environment from which it was recovered.

Uranium mining waste pile isolate Bacillus sphaericus JG-A12 and it's closest relative B. sphaericus NTCC 9602 possess S-layer proteins with a similar size of about 135 kDa and with a square lattice symmetry. The two proteins differ significantly in their ability to interact with metals and in their stability against proteases and pH changes. By using ICP-MS, the "Stain-all" dye, and colourimetric method it was demonstrated that both proteins are phosphorylated but the S-layer of the strain JG-A12 contains six times more phosphorous than those of the reference strain NTCC9602. Surprisingly, the two proteins share an extremely high homology of 98 % in the region of the N-terminal S-layer homologous domains and of 91 % in the region of the central domains. It is noticeable that the minor amino acid differences between the S-layers of the studied strains consist of threonine and serine enrichments in the case of JG-A12. Bearing in mind that the majority of the phosphoproteins are usually modified at threonine and serine residues, our observation explains the higher level of phosphorylation of the S-layer of the uranium mining isolate JG-A12. The higher amount of phosphate groups of this protein explains also it's ability to complex more effectively uranium and other metals.
In addition, there are evidences that the two Bacillus sphaericus strains studied possess an additional S-layer or an S-layer-like copy which seems to be located on large indigenous plasmids.

Sol-gel ceramics with high metal binding capacity were prepared via homogeneous dispersion and embedding of vegetative cells, spores and EDC stabilised surface proteins (S-layers) of Bacillus sphaericus JG-A12. The B. sphaericus JG-A12 strain was recovered from a uranium mining waste pile near the town of Johanngeorgen-stadt, Saxony, Germany (1). The whole cells as well as the purified S-layer protein of this strain possess an ability to bind selectively and very effectively uranium and several other metals such as Cu, Pb, Cd, Al, Pt and Pd (1, 2).
In this work the biosorption of U and Cu by the above mentioned three bacteria-based biological ceramics (biocers) was investigated. In addition, the metal binding capacity of the free SiO2 nanomatrix and of the three individual bacterial components (the vegetative cells, the spores and the S-layers) was studied as well.
Our results demonstrate that the high U and Cu binding capability of the three kinds of biocomponents is influenced by the sol-gel process in a different way. The metal binding properties of the vegetative cells and of the S-layers were not negatively influenced by the sol-gel treatments. The metal binding capacity of the embedded spores was, however, significantly lower than those of the non embedded spores. Very limited amounts of U and no Cu were bound by the silicate matrix alone.
The metal binding capacity of the biocers and also the kinetic of the biosorption were positively influenced by adding water soluble compounds such as sorbitol or by freeze drying instead of air drying. These results are connected to the higher porosity achieved by the mentioned treatments.
Both metals can be completely desorbed and washed from the biocers by using 0.5 M solution of citric acid. Afterwards the biocers can be reused for metal biosorption.
Due to their stability, high metal binding capacity and simple and complete removal of the bound metals described biocers are good candidates for construction of intelligent filters for cleaning of heavy metal contaminated liquid wastes.
The geographic origin of the source of the biocomponents, namely the strain B. sphaericus JG-A12, makes the constructed bioceramics promising for in situ bioremediation of the drain waters of the uranium mining waste piles and mill tailings.

References

1. Selenska-Pobell S., Miteva V., Boudakov I., Panak P., Bernhard G., and Nitsche H. (1999) Selective accumulation of heavy metals by three indigenous Bacillus isolates, B. cereus, B. megaterium and B. sphaericus in drain waters from a uranium waste pile.FEMS Microbiol Ecology 29, 59-67.
2. Raff J (2002) Wechselwirkungen der Hüllproteine von Bakterien aus Uran-abfallhalden mit Schwermetallen PhD Thesis, FZR-Report 358

Bacterial communities were studied in several uranium mining waste piles in Germany and in the USA by using 16S rDNA and RISA retrievals. Both approaches revealed extremely high and site-specific bacterial diversity. However, several bacterial groups including also novel lineages seem to be characteristic for the studied heavy-metal-polluted environments.
In parallel with the above mentioned direct molecular approaches, the method of enrichment culturing was applied in order to recover and study particular bacterial strains indigenous for the U wastes. Bacterial isolates belonging to different species representing diverse bacterial groups were recovered and characterized. The resistance and the interactions of these isolates with U and other heavy metals were demonstrated to be species- and even strain-specific. The atomic structures and the cellular location of the complexes formed by the isolates with U(VI) were studied using EXAFS spectroscopy, TEM, and EDX analyses. In all cases phosphate groups were predominantly implicated in the complexation of uranium but the structural parameters and the cellular location of the complexes differed between the studied bacterial groups.
Many of the studied strains possess unusual characteristics as the isolate JG-A12, for instance, which accumulates selectively U, Cu, Pb, Al, and Cd. This strain as well as it's intrinsic S-layer are forming U(VI)-complexes with identical structural parameters in which phosphorous residues in addition to the carboxyl groups are involved. ICP-MS and the "Stain-all" dye methods demonstrated that the S-layer of JG-A12 is phosphorylated. This can explain it's high ability to complex uranium and other metals. The latter seems to give an advantage to the strain to survive in the heavily polluted with uranium and other toxic metals environment from which it was recovered. Pd and Pt metallic nanoclusters were also successfully grown on the sheets of this S-layer. The latter is of interest for the nanotechnology. Interestingly, the S-layer of JG-A12 possesses unusual primary structure which indicates that lateral transfer was involved in the evolution of it's gene.
1848 words.
Keywords: bacterial diversity; S-layer, EXAFS, complexation of uranium

Boron suboxide BOx thin films have been deposited on Si (100) by reactive rf magnetron sputtering of B powders in an Ar/O2 atmosphere. Elastic recoil detection analysis and x-ray diffraction were used to study the influence of the O incorporation on the film composition and structure and relate them to mechanical properties, which were evaluated by nanoindentation. As x in BOx was increased from 0.08 to 0.18, the elastic modulus of the x-ray amorphous films decreased from 273 to 231 GPa, by 15%. This can be understood using classical molecular dynamics (MD) with a Buckingham-like interaction potential: The increase in the O concentration and corresponding formation of B–O bonds, shown to be longer than the B–B bonds, resulted in larger ionic contributions as well as a density reduction. This increased ionicity was responsible for the observed decrease in elastic modulus. As even more O was incorporated (x>0.18), the H concentration increased, exceeding 0.3 at. %. This may cause the formation of boric acid (H3BO3) as a result of the chemical reaction with H2O upon atmosphere exposure. The presence of van der Waals and hydrogen bonding, associated with H3BO3 formation, provides a reasonable explanation for the extensive decrease in elastic modulus from 231 to 15 GPa, by 94%. The parameterization for the Buckingham-like interaction potential, introduced in this study, can be used for MD simulations of amorphous BOx systems without H3BO3.

Structural materials, such as bainitic and austenitic steels and aluminium alloys as
used in the nuclear and aircraft industry are subject to external stresses in different environments. Understanding the growth of an assumed preexisting crack under these conditions is of prime importance to prevent extensive crack propagation and failure of the component. The ongoing research aims to investigate the early stages of ductile fracture, the nucleation, growth and coalescence of microvoids and the evolution of the spatial dislocation distribution. Two commercial Al-alloys, alloys 2024-T351 and 6013-T6 used in the aircraft industry were investigated. Within the above framework, a small region around the crack tip of a 2024-T351 specimen was scanned using a microfocused beam of 5 µm in diameter (Esrf, ID13-Microfocus).
The major improvement lies in the strongly diminsihed influence of grain boundary scattering. Information from fracture toughness tests, from the simulation of the distribution of stresses and strains by means of finite element analysis, from scanning and transmission electron microscopy and positron annihilation microprobe experiments, will support the small angle X-ray scattering investigations.

Der Vortrag gab ein allgemeines Bild von den Kleinwinkelstreuuntersuchungen, die am FZ Rossendorf, Abt.Material-und Komponentensicherheit durchgeführt werden, ein Bild von den Materialien (Al-Legierungen und RDB-Stähle) und Techniken/Anlagen, die dazu erforscht/angewandt werden.

Der Vortrag gab das Ziel des Untersuchungsvorhabens wieder und erteilte allgemeine Informationen über den Stand der Röntgen-Kleinwinkelstreuungsforschung zur Charakterisierung der Rissspitze in Metallen.

Aim of this report is the investigation of suitable operational conditions for the drif{}t chambers MDC III installed in the HADES setup. The simulations performed showed that operating the drif{}t chambers in a mode with nearly constant electron drif{}t velocity in a predominant part of the cell allows a more precise and fast tracking. This is particularly important for electrons and positrons; here the invariant dilepton mass must be reconstructed with high precision to get a resolution of $\Delta M/M\approx 1\%$ for the $\omega$ and $\phi$ mass peaks and thus a chance to verify also small in-medium mass shif{}ts. This helps to realize the physics program at HADES which focuses on the search for such mass shif{}ts to get insight into the in-medium behaviour of hadrons in dense strongly interacting matter.

Das Verhalten einer 3-Punkt-Biegeprobe mit Anriss unter Belastung kann mittels einem Finite-Element-Modell nachgebildet werden. Das Modell ermöglicht die Berücksichtigung von elastisch-plastischem Materialverhalten entsprechend der jeweiligen materialspezifischen nichtlinearen Spannungs-Dehnungs-Kurve, welche mit dem Modell der multilinearen kinematischen Verfestigung (MKIN) umgesetzt wird. Weiterhin gestattet das Modell die Beschreibung der Rollenkinematik beim Biegevorgang. Unter Einbeziehung eines speziellen Damage-Modells für die Beschreibung des Bruchkriteriums ist das Modell in der Lage sowohl den Beginn des Risswachstums als auch den Rissfortschritt wiederzugeben.
Mit diesem Modell lässt sich auch das Teilentlastungs-Compliance-Verfahren nachbilden. Diese Simulation ermöglicht Korrekturansätze zur experimentellen Risslängenbestimmung über die Compliance-Methode.

The A533B Cl.1-type RPV steel, designated JRQ, has been used as IAEA reference steel and shows a high sensitivity against radiation embrittlement. Specimens from this material were irradiated to three different levels of neutron fluences. Thus, the investigation allows to realize the dependence of microstructural changes on the fluence and a comparison with results on VVER-type RPV steels, which differ from the Western RPV steel design.

Durch Bestrahlung mit Neutronen entstehen in Konstruktionswerkstoffen nanoskalige Strukturdefekte, die vielfach mit den hochauflösenden, direkt abbildenden Untersuchungsverfahren nicht oder nicht ausreichend nachweisbar sind. Diese Strukturdefekte führen aber zu einer erhöhten Streuung von Neutronen- und Röntgenstrahlen im Kleinwinkelbereich. Aus der Intensitätsverteilung der Kleinwinkelstreuung lassen sich, wenn vereinfachende Annahmen getroffen werden können oder Vorinformationen vorhanden sind, Größenverteilung und Anzahldichte bestimmen. Darüber hinaus sind Hinweise zum Typ und zur Zusammensetzung der Defekte ableitbar. Das Kleinwinkelstreuverfahren ist effektiv, volumenintegrierend, sensitiv im Größenbereich von ~ 1 nm ... 10 nm und unempfindlich gegenüber Präparationsfehlern. Es ist jedoch eine indirekte Methode der Strukturanalyse und sollte deshalb nicht alternativ, son-dern komplementär angewandt werden. Prozedur und Leistungsfähigkeit des Verfahrens wird am Beispiel von Untersuchungen an bestrahlten Reaktordruckbehälterstäh-len gezeigt.

At present, the Gas Dynamic Trap (GDT) facility of the Budker Institute Novosibirsk is being upgraded. The first stage of the upgrade is the Synthesized Hot Ion Plasmoid (SHIP) experiment. It aims, on the one hand, at the investigation of plasmas which are expected to appear in the region of high neutron production in a GDT based fusion neutron source proposed by the Budker Institute and, on the other hand, at the investigation of plasmas the parameters of which have never been achieved before in magnetic mirrors. In parallel to experimental research at the GDT an Integrated Transport Code System (ITCS) is under development in collaboration with the Forschungszentrum Rossendorf. It is to calculate the relevant physical effects which are connected with neutral gas, background plasma and with the high-energetic ion component inside the central cell of the GDT and later inside the neutron source.
This contribution explains the concept of the SHIP experiment and presents the results of first calculations by means of ITCS modules.

Spin dependent tunnel junctions (Si/Al2O3/Ta/CoFe/AlNx/CoFe/Ta) were studied with grazing angle of incidence Rutherford backscattering spectrometry experiments using a 1.6 MeV He+ beam. While the sensitivity to light elements is too small to detect the N directly, the thickness and composition of the AlNx insulating barrier can be obtained by carefully simulating the signal of the Al and of two CoFe layers, which can be separated. From the observed Al signal the corresponding energy loss can be calculated, and the extra energy loss required to obtain the observed CoFe layer separation is assigned to the N. Eventual oxidation in the AlNx layer during film deposition can be further identified and quantified by analysing a similar tunnel junction, but deposited on a DLC substrate. A depth resolution of 25 Å at the CoFe layers ensures a highly precise measurement of this complex magnetic system.

GaN epitaxial films were grown on silicon substrates by molecular beam epitaxy under different conditions. Some of the films were doped with the rare earths (RE) Er, Eu or Tm during the growth, and were studied regarding its composition and crystalline quality. The Rutherford backscattering/channelling and heavy ion elastic recoil detection techniques were combined in order to get information on the depth distribution of all the elements present in the films. The results show that the single crystalline quality of the films improves with increasing substrate temperature and Ga flux. For these conditions the Ga concentration is the one expected for a stoichiometric film. A decrease of the Ga flux or increase in the RE cell temperature allows an increase of the concentration of the RE incorporated during the growth. The light impurity present in all the films studied, within our detection limits, was hydrogen. The angular scans along the <0 0 0 1> reveal that a fraction of the RE is incorporated into regular lattice sites of the wurtzite structure of GaN. Moreover, the optical properties of the films correlate well with the crystalline quality and the Eu doped samples show an intense red luminescence at room temperature.

Experiments were performed to investigate heating up processes of fluids in storage tanks under the influence of an external heat source. Several tests were carried out both with heating from the bottom and with heating from the side walls. The test tank was equipped with thermocouples for measuring the temperature distribution and with needle probes for measuring of the local void fraction.
Calculations were performed using the CFD-code CFX-4. The simulation comprises two phase flow, subcooled boiling at the heated wall and steam release at the tank surface. The paper presents comparisons of measured and calculated temperatures and void fractions. CFX-4 simulations using the implemented boiling model reproduce and explain the observed physical phenomena. Convergence problems occurred with higher vapour volume fractions. As an application measures were investigated, to reduce the temperature stratification. It could be shown, that the insertion of buffle plates reduces and postpones the steam release.

We report on thin films in the ternary system B–C–N deposited by reactive magnetron sputtering of targets with different B/C ratio in an Ar/N2 gas mixture. First, the proportion of nitrogen in the gas was varied from 0 to 100% with the substrate being at floating potential in order to change the incorporated amount of nitrogen in the films. Secondly, at 50% nitrogen in the gas a negative substrate potential was applied for ion bombardment of the growing film. The film composition was measured by elastic recoil detection analysis. The mechanical properties, Young's modulus and hardness, were determined from nanoindentation measurements. All films were also investigated by Fourier-transformed infrared spectroscopy (FTIR). The mechanical properties show a great variation range in dependence on the film composition (up to a factor of three) and ion bombardment (up to a factor of two), which can be related to the bonding characteristics derived from the FTIR spectra.

Surface coating on austenitic stainless steel 304 (ASS) was generated by plasma immersion ionimmplantation (PIII) of nitrogen. The corrosion resistance was shown to increase by ca. four orders of magnitude. A barrier layer produced by PIII was observed to restrict the underlaying alloy surface exposed to the corrosion environment.

Relativistic heavy-ion collisions lead to a final state which has a higher degree of strangeness saturation than those of elementary collisions. A systematic analysis of this phenomenon, based on the strangeness saturation factor, is made for C+C, Si+Si and Pb+Pb collisions at the CERN SPS collider and for Au+Au collisions at RHIC energies. Strangeness saturation is shown to increase with the number of participants within a colliding system, at both CERN SPS and RHIC energies. The saturation observed in central collisions of lighter nuclei deviates from that seen in peripheral collisions of heavier nuclei with an equivalent participant number, which could be due to the difference in nuclear density.

Structural parameters for the near-neighbor surrounding of Pu(III), Th(IV), Np(IV) and Np(V) in complexes with various natural and synthetic humic and fulvic acids were determined by means of X-ray absorption fine structure (XAFS) spectroscopy. Furthermore, the interaction of the actinides with Bio-Rex70, a cation exchange resin having solely carboxylic groups as metal binding functional groups, was studied to determine structural parameters for the interaction of the respective actinide ions with carboxylic groups. Applying chemically modified humic acids with blocked phenolic/acidic OH groups, the influence of phenolic/acidic OH groups on the complexation of Np(V) by humic acids was studied in the neutral pH range. The structural parameters determined for actinide humate complexes were further compared with structural parameters of aqueous ions of the actinides and of solid actinide carboxylates given in the literature. The results indicate that the interaction between the actinide ions and humic acid is dominated by humic acid carboxylate groups. These carboxylate groups act predominantly as monodentate ligands. A contribution of phenolic/acidic OH groups to the complexation of Np(V) by humic acids at pH 7 cannot completely be excluded by EXAFS analysis.

Boron suboxide thin films have been deposited on Si(100) substrates by reactive RF magnetron sputtering of a sintered B target in an Ar/O2 atmosphere. Elastic recoil detection analysis was applied to determine the film composition and density. Film structure was studied by X-ray diffraction and transmission electron microscopy. The elastic modulus, measured by nanoindentation, was found to decrease as the film density decreased. The relationship was affected by tuning the negative substrate bias potential and the substrate temperature during film growth. A decrease in film density, by a factor of 1.55, caused an elastic modulus reduction by a factor of 4.5, most likely due to formation of nano-pores containing Ar. It appears evident that the large scattering in the published data on elastic properties of films with identical chemical composition can readily be understood by density variations. These results are important for understanding the elastic properties of boron suboxide, but may also be qualitatively relevant for other B-based material systems.

The deposition of homogeneous thin films on porous substrates has been investigated. The thin film deposition of Ta(N) by physical vapor deposition on porous films with different average pore sizes and material compositions has been studied. The continuity of Ta(N) films on top of porous low-k dielectrics is evaluated by means of ellipsometric porosimetry combined with sheet resistance and atomic force microscopy measurements. Interface reactions are analyzed by x-ray photoelectron spectroscopy profiling. It has been observed that the minimal Ta(N) thickness required to obtain a continuous metal layer on top of the porous film depends, on the one hand, on the porosity and pore size and, on the other hand, on the chemical interaction of the thin film with the porous substrate. The sealing of pores is favored by the presence of carbon in the dielectric matrix. This is explained through a mechanism of local enhancement of the degree of crosslinking in the dielectric matrix, catalyzed by Ta.

Der Erfindung liegt die Aufgabe zugrunde, die Lebensdauer einer Sputterionenquelle zu erhöhen, den Wartungsaufwand zu senken und die Zerstäubung der Teile der Ionenquelle, welche sich in der Nähe des für die Erzeugung der negativen Ionen erforderlichen Kathodeneinsatzes befinden, weitgehend zu verhindern.
Die Erfindung geht aus von den Bauteilen Ionisierer (2), Kathode (3), Sputtereinsatz (4), Formierungselektrode (5), Abschirmkappe (6) und Kathodenisolator (7) in einem vakuumdichten Gehäuse.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zu entwickeln, dass Uran(VI) aus stark belasteten bergbaulichen Abwässern, Haldensicker-, und kontaminierten Grundwässern kostengünstig und umweltfreundlich in großen Mengen entfernt, wobei zur Uranfixierung ein Barrierematerial eingesetzt werden soll, das eine Beschaffenheit aufweist, die eine langzeitstabile, sichere Endlagerung oder Wiedergewinnung des angereicherten Urans ermöglicht.
Die technische Lösung geht davon aus, dass das Uran(VI) überwiegend als Karbonat, Sulfat oder Hydroxy-Komplex vorliegt und elementspezifische Filtermaterialien in einer geochemischen Barriere eingesetzt werden.

Die Erfindung betrifft ein Verfahren zur tomographischen Bildrekonstruktion für ein aus zwei asynchron rotierenden Komponenten bestehendes Objekt, wobei an einzelnen Drehwinkelpositionen der Objektkomponenten tomographische Projektionen vorgenommen werden.
Der Erfindung liegt die Aufgabe zugrunde, die beiden mit unterschiedlichen Winkelgeschwindigkeiten gegenüber ihrer Umgebung rotierenden Teilobjekte mit Hilfe eines Tomographen richtig abzubilden.

Die Erfindung betrifft ein bioaktives Material sowie ein Verfahren zu dessen Herstellung. Potentielle Anwendungen sind medizinische Implantologie, Gewebezüchtung und Biotechnologie. Der Erfindung liegt ein von einer Schicht zellausgeschiedener Produkte umgebenes Festkörpermaterial zugrunde.
Der Erfindung liegt die Aufgabe zugrunde, ein Material für Anwendungen in medizinischer Implantologie, Gewebezüchtung und Biotechnologie zu schaffen, bei welchem die Oberfläche für eine breite Klasse von Festkörpermaterialien bei Kontakt mit zellulären Medien zellbiologisch spezifische Wechselwirkungen aktiv vermittelt. Der Erfindung obliegt auch die Aufgabe, ein anwendungswirksames Verfahren zur Herstellung des genannten bioaktiven Materials vorzuschlagen.

Das Biokompositmaterial enthält ein anorganisches Gel und darin homogen verteilte, trocknungsstabile Zellprodukte wie Sporen, Zellwand-Proteine oder abgetötete Zellen. Das Biokompositmaterial ist als Biofilter in der Umwelttechnik zur Entfernung von Schwermetallionen aus wässrigen Lösungen geeignet.

The influence of melt rotation on the microstructure formation of Nd-Fe-B alloys, mainly the volume fraction and grain size of the a-Fe phase, has been investigated using the electromagnetic levitation technique which allows the in-situ measurement of the solidification kinetics containerlessly. Samples were subjected to a strong rotation during levitation and compared to fixed samples without additional sample rotation in the levitation facility. Additionally, experiments have been carried out where specially sealed samples were subjected to a well-defined forced rotation. A distinct reduction of the a-Fe volume fraction in samples with strong rotation was observed by measuring the magnetic moment in a vibrating sample magnetometer (VSM). The influence of cooling rate and undercooling level on microstructure formation and phase distribution has been investigated as well. The melt flow in a levitated droplet is studied numerically under the additional effect of a global sample rotation which may give a strong suppression of internal motions.

The solidification process and the resulting microstructure of Nd-Fe-B alloys in consideration of melt convection has been investigated experimentally with a specially designed floating-zone arrangement. A controlled influence on the melt flow is possible via tailored magnetic fields which enable enhancement or suppression of the melt convection. A specially designed magnetic two-phase stirrer offers a strong influence on the melt flow in the floating-zone facility. As a result, the microstructure pattern, mainly the volume fraction and grain size of the a-Fe phase, vary strongly with the strength of the internal flow motion. The melt flow is studied numerically under the additional effect of the two-phase stirrer taking into account the coupled heat and fluid flow fields. The electromagnetically driven flow during the inductive heating turned out to be of strong influence on the resulting microstructure.

This study was carried out in the frame of the ADS European project aimed to the development of Accelerator Driven System technology for nuclear waste transmutation.
The scope is to verify the possibility to simulate a two phase HLM (Heavy Liquid Metal) bubbly flow using the commercial CFD code CFX4.4.
The first stage consisted of an experimental campaign for the measurement of the phase velocities by means of the ultrasound Doppler velocimetry (UDV) and local volume fractions using resistive probes. The eutectic alloy PbBi is located inside a cylindrical container made of stainless steel which is provided with an electrical heater. The measurements reported here were carried out at a fluid temperature of 180°C. Nitrogen (N2) gas was injected into the stagnant liquid metal by means of a single orifice with an inner diameter of 0.5 mm. The orifice is located in the centre of the cross-sectional area of the fluid container. The gas flow rate chosen for these experiments was restricted to values below 1.2 cm3/s in order to guarantee a single bubble flow regime.
The simulation of the experiment was performed using the two fluid Euler/Euler model of CFX-4.4. The implemented drag laws were tested and compared with other drag laws taken from literature. The influence of the "non-drag forces" like the turbulent dispersion force and the lift force was also tested. Finally an advanced interpolation method based on optimization techniques was adopted in order to get the best fitting of the simulated velocity curves with the experimental ones. The results shows in general a good qualitative agreement of the experiment and the calculations, but a much better agreement can be found using the drag law coefficients derived by the above mentioned optimization technique, especially in the cases where the mass flow rates and the bubble mean diameters are relatively small.

In Argentinien wird das Integralreaktorkonzept CAREM als alternativer Einstieg in die Kerntechnik - speziell für Länder der dritten Welt - entwickelt. Diese sammelten bislang in der Regel ihre ersten Erfahrungen in der Nukleartechnik mit Forschungsreaktoren. Das beim Betrieb der Forschungsreaktoren gesammelte Wissen ist jedoch zu speziell und nicht umfassend genug, um hiermit allein Leistungsreaktoren betreiben zu können. Da das CAREM Konzept sämtliche in großen Leistungsreaktoren vorkommende Systeme beinhaltet, können mit dem CAREM Reaktor bei vergleichsweise ähnlichen - wenn nicht sogar niedrigeren - Kosten wie bei Forschungsreaktoren sämtliche zum Betrieb mittlerer und großer Reaktoren notwendigen Systemkenntnisse erworben werden.

The radiation source ELBE at Dresden-Rossendorf is centered around a superconducting ELectron accelerator of high Brillance and low Emittance (ELBE) which produces electron beams up tu 40 MeV. This new facility delivers secondary radiation of diffrent kinds. Special emphasis will be given to the production of intense THz radiation from its Free-Electron-Lasers (FEL). This radiation will be used for various research activities including the life sciences. Two additional femtosecond Ti:sapphire lase system allow to exploid different methods of THz generation for such investigatin.

In the present work, composite AgSiO2 thin coatings, containing metal nanoparticles, were prepared on glass substrates by the sol–gel route. The coatings were thermally treated in oxidative and reductive conditions up to 500 °C for metal nanoparticle formation. The coating structure and the nanoparticle formation were studied by atomic force microscopy and Rutherford backscattering spectroscopy (RBS) techniques. In the case of RBS, 1.4 MeV 4He+ ions were used for all samples, and low energy 16O and 12C ions in selected ones (heavy ion RBS, HIRBS), in order to improve the depth resolution for the profiling of the metal component. The antibacterial activity against Escherichia coli is examined by antibacterial drop test. The coatings exhibited a high antibacterial activity, which was enhanced with the increase of the metal concentration and was reduced with the increase of the particle size of the metal nanoparticles. The possible correlation between the layer interdiffusion after the thermal treatment and the antibacterial activity is examined and analyzed. Although further studies are required, RBS and HIRBS seem to be excellent tools for the quality control in the production of sol–gel thin coatings.

For the calculation of experiments simulating the behavior of the lower head in a core melt down scenario like FOREVER (performed at the Royal Institute of Technology, Stockholm) it is necessary to model the melt pool convection and the temperature field within the vessel as well as creep and plasticity processes. Therefore a 2D Finite Element Model is developed based on the code ANSYS®. The CFD module is used to calculate the thermodynamics. The resulting temperature field of the vessel wall is applied to the mechanical model. To describe the visco-plastic deformation a numerical creep data base (CDB) is developed where the creep strain rate is evaluated in dependence on the current total strain, temperature and equivalent stress. In this way the use of a single creep law, which employs constants derived from the data for a limited stress and temperature range, is avoided. For an evaluation of the failure times a damage model according to an approach of Lemaitre is applied.
After post-test calculations for the FOREVER-C2 experiment, pre-test calculations for the forthcoming experiments are performed. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios. After analyzing the results of the calculations, it seems to be advantageous to provide a vessel support, which can unburden the vessel from a part of the mechanical load and, therefore, avoid the vessel failure or at least prolong the time to failure. This can be a possible accident mitigation strategy. Additionally, it may be advantageous to install a passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in the event of a core melt down.

CNx thin films have been prepared by IBAD varying the C-atom to N-ion ratio during deposition. The layers were studied by means of TEM and EELS investigation, ERDA and AES depth profiling. The obtained films were amorphous. The incorporation probality of N into the films was found to depend on the C/N arrival ratio. Large amount of N incorporation was found above and small amount below a N/C arrival rate of 0.3. Due to intentional change in the N/C arrival rate, modulated structures have been produced. The N concentration in the individual layers of modulated samples was found to exhibit distinct values of approximately 5 and 20 at.%. The erosion rate of the various CNx layers upon Ar ion bombardment depends on their N content. The relative erosion rate of the samples containing nitrogen of 20 and 5at.% was found to be r(rel)=1.6. It was determined by XTEM and EELS that the origin of the TEM image contrast marking out the individual sublayers is mainly due to density variations in the modulated structure and partly due to thickness differences of the cross sectional TEM samples as a result of Ar ion milling of layers of various compositions

Recent data on the reaction pD -> (pp) n with a fast forward pp pair with very small excitation energy is analyzed within a covariant approach based on the Bethe-Salpeter formalism. It is demonstrated that the minimum non-relativistic amplitude is completely masked by relativistic effects, such as Lorentz boost and the negative-energy P components in the ¹S₀ Bethe-Salpeter amplitude of the pp pair.

Das „Master-Curve“ (MC)-Konzept nach Wallin empfiehlt sich als ein geeignetes Werkzeug zur bruchmechanischen Sprödbruchsicherheitsbewertung von Komponenten und Anlagen. Es hat mit dem ASTM Standard E 1921 bereits Eingang in die Regelwerke gefunden und steht unmittelbar vor einer breiteren internationalen Anwendung. MC-Referenztemperaturen T0 werden an russischern WWER-Druckbehälterstählen im un- und bestrahlten Zustand ermittelt und mit am gleichen Material gemessenen Charpy-V-Übergangstemperaturen TT verglichen. Die unterschiedliche Zähigkeit der verschiedenen Stähle lässt sich ebenso wie der Einfluss der Bestrahlung mit dem MC-Konzept nachweisen. T0 und TT zeigen eine gute Korrelation, wobei die T0 ca. 80 K niedriger liegen. Damit erniedrigen sich auch die Referenztemperaturen für die Reaktordruckbehälter Integritätsbewertung.

The spherical MHD mean-field dynamo is considered from a mathematical viewpoint. It is shown that its 2x2 operator matrix is formally pseudo-Hermitian (J-symmetric), lives in a Krein space and has paired complex eigenvalues. Based on the J-symmetry, an operator intertwining Ansatz with first-order differential intertwining operators is tested for its compatibility with the structure of the alpha²-dynamo operator matrix. An intrinsic structural inconsistency is obtained in the set of associated matrix Riccati equations. This inconsistency is interpreted as a no-go theorem which forbids the construction of isospectral alpha²-dynamo operator classes with the help of first-order differential intertwining operators.

Ziel/Aim: Prospektive Erfassung von Daten zur Charakterisierung des intratumoralen Mikromilieus mittels FDG-PET, interstitieller Messung des Sauerstoffpartialdruckes und MRT-Untersuchung der Tumorperfusion vor radikaler Radio- bzw. Radiochemotherapie und Evaluierung der prognostischen Wertigkeit der Parameter.

Methodik/Methods: 14 Patienten mit inoperablen Kopf-Hals-Tumoren (UICC Stadium IV) wurden untersucht. Der intratumorale p0₂-Gehalt wurde mit einer Eppendorf-Sonde polarographisch gemessen. Die Tumorperfusionsmessung wurde im MRT (1.5 T Siemens Vision mit Kopf-Hals-Spule) durch den gemessenen Signalverlust bei Kontrastmittel-Bolus-Passage ermittelt. Ferner wurden die Tumorvolumina im MRT bestimmt. Als Maß des Glukosestoffwechsels wurde der mittlere Standard uptake value (SUVmean) der Tumorregion im FDG-PET bestimmt (300 MBq ¹⁸F-FDG i.v., ECAT EXACT HR⁺, Siemens/CTI).

Ergebnisse/Results: Die Tumorvolumina reichten von 14 bis 220 cm³ (median 74 cm³). Die SUVmean betrugen im Median 9,7 und waren bis auf in einem Turnor deutlich erhöht (range 2,9 -12,0). Die medianen pO₂-Werte der individuellen Tumoren zeigten eine weite Variabilität (range 0,1 - 33,1 mm Hg), der Median der Gruppe betrug 7,5 mm Hg. Korrelationsanalysen ergaben R²-Werten von 0,25 für Tumorvolumen versus pO₂, 0,15 für SUVmean versus pO₂, 0,13 für Perfusion versus pO₂, 0,06 für SUVmean versus Tumorvolumen und 0,03 für Perfusion versus Tumorvolumen.

Schlussfolgerungen/Consequences: Die nicht vorhandenen bzw. sehr schwachen Korrelationen zwischen den gemessenen Parametern deuten an, dass mit den unterschiedlichen Messmethoden verschiedene Charakteristika des Tumormikromilieus erfasst werden und dass diese sich daher evtl. prognostisch ergänzen könnten. Die nur sehr schwache Korrelation zwischen Glukoseaufnahme und interstitiell gemessenem pO₂ des Tumors weist darauf hin, dass neben anaerober Glykolyse weitere Faktoren die Zuckeraufnahme des Tumors beeinflussen. Derzeit werden weitere Patienten in diese Untersuchung aufgenommen und das Follow-up ergänzt, um die prognostische Relevanz der verschiedenen Messergebnisse, ggf. auch in Kombination, auf die Tumorkontrolle nach Strahlentherapie zu prüfen.

The radiation source ELBE at Dresden Rossendorf is centered around a superconducting ELectron accelerator of high Brilliance and low Emittance (ELBE) which produces electron beams up to 40 MeV. This new facility delivers secondary radiation of different kinds. Special emphasis will be given to the production of intense THz radiation form its Free-Electron Lasers (FEL). This radiation will be used for various research activities including the life sciences. Two additional femtosecond Ti:sapphire laser systems allow to exploit different methods of THz generation for such investigations

Within QCD sum rules at finite baryon density we show the crucial role of four-quark condensates, such as ‹(overline{q} γμλ^aq)²›_n, for the in-medium modification of the ωmeson spectral function. In particular, such a global property as the sign of the in-medium omega meson mass shift is found to be governed by a parameter which describes the strength of the density dependence of the four-quark condensate beyond mean-field approximation.
To study self-consistently the broadening of the omega meson resonance we employ a hadron spectral function based on the omega meson propagator delivered by a effective chiral Lagrangian. Measurements of the ωmeson spectral change in heavy-ion collisions with the HADES detector can reveal the yet unknown density dependence of the four-quark condensate.

Free electron lasers (FELs) allow the generation of electromagnetic radiation (EM) in a wide field of frequencies (respectively wavelengths) throug the proper adjustment of energy of an electron beam and the field configuration of a magnetic undulator passed by this beam. Terahertz (THz) radiation covers the region of the electromagnetic spectrum between approximately 0.3 and 30 THz and thus can be considered a continuation of the optical spectrum beyond the far infrared (IR). The very interesting results obtained from various studies ot the interaction between IR radiation and biomolecules or tissue have stimulated increasing interest in the study of biological systems using THz radiation. This paper points out what role modern FELs can play in this research.

The atomic mechanisms of relaxation processes in carbon films during ion beam deposition and post-deposition annealing are studied using the method of molecular-dynamics with a modified hydrocarbon potential of Brenner. Deposition of films was simulated for ion energies E_ion =10-80 eV and for substrate temperatures T_s =100-900 K. Using a time-resolved analysis of atomic trajectories from the film deposition simulations, a short-term temperature-dependent relaxation stage (t~70-1000 fs), where the film formation is influenced by T_s , was identified. During this stage, depending on T_s , the carbon atoms at metastable four- or fivefold coordinated sites can relax into either three- or fourfold positions, giving rise to graphitic or tetrahedral (ta-C) amorphous carbon films, respectively. In agreement with experiment the simulations predict a sharp transition from ta-C to graphitic carbon as T_s exceeds a critical temperature T_c . Simulating post-deposition annealing, low-temperature structural relaxation of as-deposited ta-C was observed as evidenced by a reduction of potential energy and grown-in stress. The corresponding amorphous network rearrangements consist both in the sp³ -to-sp² conversion and in the
sp² -to-sp³ one. A nearly complete stress relief in ta-C with the sp³ content of ~80% and grown-in compressive stress of 11 GPa was simulated at an annealing temperature of ~1000 K.

Negative and positive charge trapping under constant current regime of high-field electron injection both from Al electrode and Si substrate in high-dose Ge+ ion implanted and then rapid thermal annealed thin-film dioxide has been studied. The negatively charged traps with >10-14 cm2, 1.8x10-15 cm2, 2x10-16 cm2 and 3x10-18 cm2 and generated positive charge with effective capture cross-section (5-7)x10-15 cm2 and 3.3x10-16 cm2 have been shown to be introduced into the oxide layer. A good correlation of the electron trap concentration with with a cross section of >10-14 cm2 and the concentration of the implanted Ge atoms, determined by RBS technique inside the oxide, have been observed. The decrease of Ge concentration within the oxide layer with increasing RTA duration have been associated with Ge atom outdiffision from the oxide at high-temperature annealing. The generated positive charge have been shown to be collected near the SiO2/Si interface during the high field electron injection, both from the Al and Si side. Correlation of the generated positive charge with the Ge atoms embedded in the SiO2/Si interface have been observed. The anode hole injection mechanism is suggested to be responsible for the observed generation of the positive charge.

For realizing futuristic optical communications networks with greater than 100Gb/s transmission capability, highly efficient, ultra-fast all-optical devices are crucial at communication wavelengths (<2 mm). Such devices can be realized by making use of the large and fast intersubband transition (ISBT) non-linearity. However, for achieving ISBTs in the communication wavelength region, one requires a large conduction-band offset material. We reported the possibility of one of the crucial all-optical device, all-optical switch, based on ISBT absorption saturation, operating in the < 2 mm wavelength range using InGaAs-AlAsSb quantum well structures. The efficiency of such a device is defined in terms of the switching response time and the switching energy. While the relaxation time related to the switching response time can be estimated from a direct pump-probe measurement, estimation of the saturation intensity related to the switching energy is not that straightforward. In this work, we carry out a detailed study to estimate the saturation current in Sb-based quantum wells

Nach dem heutigen Stand der Technik wird zur Produktion in Batch-Chemieanlagen der Anlagenstatus im Betrieb vom Anlagenbediener beurteilt. Dies setzt ein hohes Maß an Erfahrungen voraus. Dennoch kommt es zu Fehlproduktionen, die umweltrelevante Entsorgungs- und Nachbearbeitungsaufwände verursachen. Durch eine Zusammenführung aller verfügbaren Informationen und durch deren Verdichtung soll dem Bediener eine Unterstützung bei der Beurteilung des Prozessablaufes gegeben werden, so dass Fehlproduktionen frühzeitig erkannt und vermieden werden können.
Im Teilvorhaben 1 wurden verschiedene Methoden zur Zustandsüberwachung durch neuronale Netze hinsichtlich ihrer Anwendbarkeit anhand von Technikumsversuchen für eine homogene exotherme Veresterungsreaktion geprüft. Hier zeigte sich, dass sowohl die Zustandsbeurteilung als auch die Prognose mit neuronalen Netzen vielversprechende Ansätze liefern. Hierzu ist allerdings ein hohes Maß an Systemwissen in Vorverarbeitungsstufen zu integrieren.
Im Teilvorhaben 2 wurde ein Online-Monitoring-System (MoSys) entwickelt, das auf dimensionslosen Stoff- und Wärmebilanzen mit adaptiven Komponenten basiert. MoSys muss zuerst mit den Prozessdaten von normalen und unerwünschten Batch-Verläufen angelernt werden, die im Miniplant unter den Bedingungen des Industrieprozesses durchgeführt wurden. Die Adaption der Bilanzmodelle an die Zielanlage erfolgt durch zweischichtige Perceptron-Netze. Um eine vollständige Maßstabsübertragung zu gewährleisten, sollte MoSys mit Prozessdaten von mindestens einem normalen Batch-Verlauf in der Chemieanlage angepasst und validiert werden. MoSys wurde sowohl für eine homogene exotherme Veresterungsreaktion als auch für einen komplexen heterogenen exothermen Hydrierprozess konzipiert. Experimentelle Tests wurden für die Veresterung in einer Pilotanlage und für die Hydrierung in einer industriellen Chemieanlage durchgeführt.
Zur Industrieerprobung wurde MoSys in ein Batch-Informations-Management-System (BIMS) integriert, das auch entwickelt und in das Prozessleitsystem (PLS) einer Mehrzweckanlage im Feinchemie-Werk Radebeul (Degussa AG) implementiert wurde. Dadurch konnten die MoSys-Ausgaben simultan mit wichtigen Prozesssignalen auf den Terminals des PLS visualisiert werden. Zum Beispiel werden der Hydrierungsfortschritt, das vorhergesagte Reaktionsende und die Konzentrationsverläufe des Edukts, Zwischenprodukts und Produkts auf den Terminals der Operatorstationen angezeigt. Wenn unerwünschte Betriebszustände auftreten, wird das Bedienungspersonal frühzeitig alarmiert und Empfehlungen für Gegenmaßnahmen, die nur vom Operator ausgeführt werden dürfen, werden auf den Terminals angezeigt. Die Leistungsfähigkeit von MoSys/BIMS konnte während zweier Hydrierungs-Produktionskampagnen nachgewiesen werden.

Traditional dechanneling dopant profiles in the silicon crystal wafers have been achieved by tilting the wafer away the incident beam. As feature sizes of device shrink, the advantages for channeled doping profiles for implants with small
or near zero degree incident angles are being recognized. For example, high-energy CMOS well spacing limitations caused by shadowing and encroachment of the ion beam by photoresist mask can be avoided for near zero degree incident implants. Accurate models of channeled profiles are essential to predict the device performance more important. This paper will discuss the factors important for channeled dopant profiles, such as the acceptance angle, dopant species, energy, incident angle, dose and damage accumulation in the crystal based on SIMS and Crystal-TRIM simulation results. In addition, the control requirements on ion implantation parameters from a channeling perspective will also be discussed.

Im internen Schlussbericht zum BMBF-Projekt 01RV9802/4 wird die Entwicklung des Online-Monitoring-System (MoSys) für homogene und heterogene exotherme chemische Reaktionen beschrieben. Zur Industrieerprobung wurde MoSys in ein neues Batch-Informations-Management-System (BIMS) integriert und in das Prozessleitsystem (PLS) einer Mehrzweckanlage im Feinchemie-Werk Radebeul (Degussa AG) implementiert. Die Betriebserfahrungen von zwei Hydrierungs-Produktionskampagnen werden vorgestellt.
Im Anhang ist eine Beschreibung der BIMS/MoSys-Bedienungsanleitung enthalten. Ferner sind die von BIMS/MoSys genutzten Daten und Informationen sowie ihre Tabellenstruktur in der BIMS-Datenbank zusammengestellt.

Aufgrund ihrer hervorragenden Eigenschaften, wie große Bandlücke, hohe thermische Leitfähigkeit und gesättigte Elektronendriftgeschwindigkeit, sind sowohl Siliziumkarbid als auch Diamant vielversprechende Halbleitermaterialien für elektronische Bauelemente, die unter extremen Bedingungen noch einwandfrei funktionieren sollen. Allerdings ist es bislang noch nicht gelungen, Diamant in zufrieden stellender Weise mit flachen Donatoren zu versehen. Im Gegensatz hierzu ist die p-Dotierung von Siliziumkarbid noch nicht befriedigend gelöst. Da aber sowohl p-leitender Diamant, als auch n-leitendes SiC sehr einfach zu realisieren sind, könnten Heterostrukturen aus diesen so dotierten Materialien erfolgversprechend sein.
Frühere Experimente haben gezeigt, dass eine Hochdosisimplantation von Si in Diamant zur Bildung von ß-SiC führen kann. In dieser Arbeit wurden die Leitfähigkeit und strukturellen Eigenschaften von Diamantproben untersucht, die mit Si-Dosen im Bereich von 3×1017 cm-2 bis 1×1018 cm-2 implantiert worden sind. Die Implantation erfolgte bei 900 °C, um die Schädigung der Diamantmatrix zu reduzieren. Der Einfluß des Implantationsschadens wurde anhand von Vergleichsproben studiert, die mit Argon implantiert wurden. Röntgenbeugung (XRD), IR Absorptionsspectrometrie, hochauflösende cross-sectional Transmissionselektronenmicroscopie (HRTEM) sowie Vierpunktmessungen in van der Pauw Geometrie dienten zur Charakterisierung der implantierten Diamanten.

This communication addresses the production of carbon nitride thin films with fullerene-like structure (f-CNx), i.e. bent and cross-linked graphitic basal planes [1]. Normally, f-CNx thin films are produced by Magnetron Sputtering and a key parameter appears to be the use of low-energy ion bombardment (<100 eV) during the growth process [2]. The aim of the investigations is to obtain f-CNx by means of Ion Beam Assisted Deposition (IBAD), which will provide a better understanding of the growth process since the role of neutrals and ions can be studied separately. In order to reproduce the growth conditions of f-CNx, an IBAD device has been re-constructed, incorporating an End-Hall ion source to operate in the low-energy range (50-150 eV). Preliminary results on the deposition of our films will be shown.
1. H. Sjöstrom, et al. Phys. Rev. Lett. 75 (1995) 1336.
2. L.Hultman, et al. Phys. Lett. 87 (2001) 225503.

Our six years experience in routine operation and maintenance of the Rossendorf CYCLONE 18/9 facility is given here along with improvements for a stable and reliable cyclotron operation.

[no abstract available]

Our quasi-particle model for deconfined matter near T_c is reviewed. The extrapolation of lattice QCD data to finite baryo-chemical is discussed. Determined by the chiral transition temperature T_c, the resulting equation of state of neutral and $\beta$ stable deconfined matter is soft and limits size and mass of pure quark stars.

Microorganisms have a potential to affect mobility and overall environmental behaviour of heavy metals and radionuclides through solubility and speciation changes, biosorption, bioaccumulation or other bio-transformations. In this study we used a combination of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, Infrared (IR) spectroscopy and Time Resolved Laser Induced Fluorescence Spectroscopy (TRLFS) to characterize the uranium complexes formed by different bacterial strains such as Acidithiobacillus ferrooxidans D2, Stenotrophomonas maltophilia JG-2, Bacillus sphaericus JG-A12 which were isolated from uranium mining wastes. In addition several reference strains namely Pseudomonas stutzeri ATCC 17588; 55595 and Pseudomonas migulae CIP 105470 which were demonstrated to be relevant to the bacterial populations in the uranium wastes were studied as well. The EXAFS analysis demonstrated that in the case of B. sphaericus JG-A12, the U(VI) is coordinated to carboxyl groups in a bidentate fashion with an average distance between the U atom and the C atom of 2.91 ± 0.02 Å and to phosphate groups in a monodentate fashion with an average distance between the U atom and the P atom of 3.59 ± 0.02 Å. In the case of the other bacteria, only phosphate groups are implicated in the complexation of uranium in a monodentate mode, with an average distance between the U atom and the P atom of 3.63 ± 0.02 Å. These results are consistent with those found by Infrared measurements. The latter demonstrates the complementary role which EXAFS spectroscopy can play in determining of metal distribution behaviour in the environment. In addition, we applied TRLFS in order to determine the energy and the shape of the emission bands and the fluorescence lifetime of the uranium complexes formed by the different bacterial biomass studied in this work.

Mohamed Merroun1, Johannes Raff1, Christoph Hennig1, Andre Rossberg1, Tobias Reich2 and Sonja Selenska-Pobell1
1Institute of Radiochemistry, Forschungszentrum Rossendorf,D-01314 Dresden, Germany, 2Johannes Gutenberg Universität Mainz, Institut für Kernchemie, Mainz, Germany
Microorganisms have a potential to affect mobility and overall environmental behaviour of heavy metals and radionuclides via bio-transformations such as oxidation and reduction which can change metal's speciation and solubility and also via different biosorption, bioaccumulation, and biomineralisation processes. In this study Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy was used to determine the structural parameters of the uranium complexes formed by vegetative cells of B. sphaericus JG-A12 which was recovered from a uranium mining waste pile and it's genomic analogue, B. sphaericus NTCC 9602. The complexation of uranium (VI) by the purified and recrystalized S-layers of these two strains was studied as well. The EXAFS analysis demonstrated that in all cases studied the U(VI) was coordinated to carboxyl groups in a bidentate fashion with an average distance between the U atom and the C atom of 2.91 ± 0.02 Å and to phosphate groups in a monodentate fashion with an average distance between the U atom and the P atom of 3.59 ± 0.02 Å. By using ICP-MS, "Stain-all" analysis and colourimetric methods it was demonstrated that the S-layers of B. sphaericus NCTC 9602 and B. sphaericus JG-A12 are phosphorylated. The latter explains the atomic structures of the U-complexes formed at the surfaces of the strains.
Interestingly, the uranium complexes formed by both the bacterial cells and the purified S-layer proteins possess the same structural parameters. These results indicate that the S-layers play the main role in the binding of this radionuclide and that they are acting as a protective barrier against it in the polluted environments.

The reaction p d -> d phi p_{sp} is studied within the Bethe-Salpeter formalism. Under special kinematical conditions (slow backward spectator proton p_{sp} and fast forward deuteron) relevant for forthcoming experiments at COSY, the cross section and a set of polarization observables factorize in the contribution of the pure subprocess p n -> d phi and a contribution stemming from deuteron quantities and kinematical factors. This provides a theoretical basis for studying threshold-near processes at quasi-free neutrons.

Design and optimisation of the thermal hydraulics of liquid metal reactor systems is strongly based on numerical simulations of the related fluid flow and heat & mass transfer processes. Whereas these numerical simulations are essentially based on local flow phenomena (small-scale vortices, turbulence or sub-grid scale modeling), experimental results are often limited to integral flow rates or local related data like temperature or pressure. Local velocity measurements would be highly desirable but are mostly lacking due to the very limited possibilities for velocity measurements in liquid metals.

During the last decades the Ultrasound Doppler Velocimetry (UDV) became a very powerful tool to measure the velocity structure of liquid flows. Because of the ability to work in opaque fluids and to deliver complete velocity profiles in real time it becomes very attractive for liquid metal applications. In addition, it can principally operate through the channel wall though a direct contact to the melt reduces ultrasonic losses. However, in case of hot metallic melts the user is confronted with a number of specific problems: First of all, the application of the ultrasonic transducers is usually restricted to maximum temperatures of 150°C. The transmission of a sufficient amount of ultrasonic energy from the transducer to the fluid has to be guaranteed. Here, the acoustic coupling and the wetting conditions have to be considered as important issues. Moreover, the flow has to be seeded with reflecting particles to obtain Doppler signals from the fluid.

The feasibility of velocity profile measurements by UDV has already been demonstrated for low temperature liquid metals like mercury [1] and gallium [2]. We report on first successful measurements in liquid sodium at 150°C [3]. We will present mean profiles of a flow in a rectangular duct exposed to an external, transverse magnetic field. To demonstrate the capability of UDV the transformation of the well-known turbulent, piston-like profile to an M-shaped velocity profile for growing magnetic field strength was observed. The significance of artefacts such as caused by the existence of reflecting interfaces in the measuring domain will be discussed. In the sodium case, the measurements were performed through the channel wall.

An integrated ultrasonic sensor with acoustic wave-guide has been developed to overcome the limitation of ultrasonic transducers to temperatures lower than 200°C. This sensor can presently be applied at maximum temperatures up to 800°C. Stable and robust measurements have been performed in various PbBi flows in our laboratory at FZR as well as at the THESYS loop of the KALLA laboratory of the Forschungszentrum Karlsruhe (FZK). We will present experimental results obtained in a PbBi bubbly flow at 250...300°C. Argon bubbles were injected through a single orifice in a cylindrical container filled with stagnant PbBi. Velocity profiles were measured in the bubble plume. Mean values of the liquid as well as the bubble velocity were extracted from the data and will be presented as function of the gas flow rate. At the THESYS loop of FZK stable velocity profils have been measured in a round tube of diameter 60mm during a period of about 72 hours at temperatures between 180°C and 350°C. Velocity profiles have been obtained at different temperatures for variations of the liquid flow rate. In the PbBi case, the acoustic wave-guide was always in direct contact to the melt. In addition, some results of UDV velocity measurements with a wave-guide in a CuSn alloy of about 620°C and in an Al melt of about 750°C will be presented.

The A(e,e'K⁺)YX reaction has been investigated in Hall C at Jefferson Lab. Data were taken for Q² approx 0.35 and 0.5 GeV² at a beam energy of 3.245 GeV for ³He,⁴He. The missing mass spectra are fitted with Monte Carlo simulations including Lambda, Sigma⁰, Sigma^- hyperon production. Models for quasifree production are compared to the data, excess yields close to threshold are attributed to FSI. Evidence for Lambda-hypernuclear bound states is seen for ^3,4He targets.

Electrical resistance of monotectic melts strongly depends on the state of phase separation. The gravity driven sedimentation leads to an arrangement of the lighter phase above the heavier one,. Because resistance of both phases are different, the state of demixing can be determined by the overall melt resistance using the four-probe-method. Resistance of hypermonotectic Zn-Pb liquid alloys has been measured in a wide temperature range between 820°C and a monotectic line and its dependence on different parameters has been discussed. The results are compared with theoretical predictions. It was shown that the electrical resistance of the demixed melt changed if transport processes (Marangoni convection) took place under microgravity conitions. The measuring arrangement used in the microgravity experiment on Zn-Pb melts during the flight of TEXUS 39 is presented.

The microstructure of Nd-Fe-B alloys changes if the convection in the melt varies. A controlled influence on the melt flow is possible via magnetic fields or sample rotations. The experimental techniques behind are the electromagnetic levitation, mechanical sample rotations and a specially designed float-zone arrangement. We present theoretical/numerical results for the melt convection in those configurations. The melt flow in a levitated droplet is studied under the additional effect of a global sample rotation which may lead to a strong suppression of internal motions. A specially designed two-phase stirrer offers a strong influence on the melt flow in the float-zone facility.

The solidification process and the resulting microstructure of Nd-Fe-B alloys in consideration of melt convection has been investigated using the electromagnetic levitation technique, forced rotation experiments and the application of alternating magnetic fields. The electromagnetic levitation technique, which allows the in-situ measurement of the solidification kinetics containerlessly, has been used in order to investigate the influence of the internal melt motion on the microstructure formation of Nd-Fe-B alloys, mainly with respect to the volume fraction and grain size of the a-Fe phase. Moreover, experiments where specially sealed samples were subjected to a well-defined forced rotation have been carried out. The determination of the a-Fe volume fraction by measuring the magnetic moment in a vibrating sample magnetometer (VSM) resulted in a distinct reduction of the a-Fe volume fraction in samples with strong rotation. The influence of the cooling rate and the undercooling level on the microstructure formation and phase distribution has been investigated as well. Furthermore, a new category of experiment has been started where a tailored magnetic field was applied in order to study the microstructure evolution due to an enhancement or suppression of the melt convection by additional alternating magnetic fields.

The CIRCUS test facility (CIRCUlation during Startup) has been built to study the start-up phase of a natural-circulation BWR. During the start-up so called flashing-induced instabilities can arise. This paper gives an overview about experimental results and the physics of the instabilities. The thermo-hydraulic code ATHLET is used to investigate the dynamic bevavior of the test facility.

We describe the electric characteristics and mass spectra of two liquid metal alloy ion sources;namely Er70Fe22Cr3Ni5 and Er69Ni31.Erbium ions are of great interest for optoelectronic applications.For the first time in the literature the energy spread of triply charged ions (Er 3+ ) is reported.

Radiopharmaceuticals are drugs containing a radionuclide and are used routinely in nuclear medicine for the diagnosis or therapy of various diseases. They are mostly small organic or inorganic compounds, but can also be macromolecules such as monoclonal antibodies or their fragments labeled with a radionuclide. Those agents whose biodistribution is determined by biological interaction, e. g. receptor binding, are termed target-specific radiopharmaceuticals.

For diagnostic imaging agents, technetium-99m is frequently the radionuclide of choice because it has optimal nuclide properties (half-life of 6h and appropriate Gamma-energy of 140 keV). The inconvenience of purchasing a short-lived radionuclide was overcome by the development of the ⁹⁹Mo/^99mTc generator, which is based on transient equilibrium between the parent radionuclide ⁹⁹Mo (66h half-life) and the daughter radionuclide ^99mTc (6h half-life). The generator makes this radionuclide both routinely available and economical. Finally, the ^99mTc-radiopharmaceutical can easily be prepared in the clinic by means of prefabricated kits. So it is no surprise that more than 90% of routine in vivo imaging is performed with technetium-99m [1,2].

Table 1. Metal nuclides for diagnostic or therapeutic application

Beside technetium, many other radiometals have been or are being investigated for their uses in nuclear medicine [3]. This comprises not only radiometal-labeled agents used in gamma scintigraphy and positron emission tomography (PET), but also beta and alpha emitters for radionuclide therapy [4] (Table 1).
The development of effective metalloradiopharmaceuticals is a complex task which is not simply accomplished by attaching a radionuclide to a nonradiolabeled targeting vector (Fig.1).

Fig.1. Schematic representation of the bifunctional approach as a strategy of radiopharmaceutical design

Because of the unphysiological nature of the radiometal, the structure of the biomolecule where the chelate is appended, will be altered and the biodistribution will change drastically. The search for metalloradiopharmaceuticals involves therefore chelate systems that stable bind the radiometal, and, since it will be directly involved in optimizing the biochemical properties of the radiopharmaceutical, it has to be compatible in structure and physicochemical properties. In recent years, new chelate systems have been developed (Fig.2) for binding technetium (as well its congener rhenium) at oxidation states V, III, and I involving metallnitrido cores (1) [5], mixed-ligand complexes (2) [6] and metal-tricarbonyl derived complexes (3) [7,8].

The stability of the complexes of '3+1' type depends not only on the nature of the tridentate ligand but also on the nature of monodentate co-ligand.^[1,2] The recently introduced (tri)bidentate heterofunctionalized phosphines, (H₂PNX; X=O,S), which are quite versatile in terms of charge and denticity towards the [M=O]³⁺ core, form '3+1' mixed-ligand complexes with different thiolated monodentate co-ligands.^[3,4] These complexes show different in vitro stabilities, confirming the importance of the nature of the donor atoms on the stability. Using the H₂PNS ligand and a thiolated arylpiperazine derivative we succeeded on the preparation of the stable '3+1' oxocomplex [M(O)(eta³- PNS)(SCH₂CH₂NHCH₂CH₂CH₂(2-MeOPhpip))] (M = Re, ^99mTc). In spite of its high stability, the complex showed low affinity for the 5HT_1A receptor (120 nM ± ).^[5]
These results prompted us to introduce some chemical modifications in the monodentate co-ligand, in order to increase the affinity and selectivity to the receptor. So, herein we report on the synthesis and characterization of the new thiolated arylpiperazine derivatives and on the preparation of the corresponding '3+1' oxocomplexes at the macroscopic and at the n.c.a. level (80-95% yield). The ^99mTc-complexes obtained were identified by comparing their radioactive HPLC profiles with those of the analogous Re complexes. After purification by semi-preparative HPLC, the radiochemical purity of the complexes is higher than 95%.
The stability of the purified ^99mTc-complexes was studied in saline, 0.01M PBS (pH 7.4) at 37ºC, and all of the complexes revealed stable. No significant exchange with glutathione (1mM and 10mM solutions, 37ºC) was observed.
In order to determine the effect of the chemical modifications introduced in the monodentate ligand, binding affinities and specificities for the 5HT_1A receptor have still to be evaluated.

Acknowledgements: This work is being supported by the COST Action B12.

References
[1] Syhre, R.; Seifert, S.; Spies, H.; Gupta, A.; Johannsen, B.; Eur. J. Nucl. Med. 1998, 25:793.
[2] Seifert S. et al Radioch. Acta, in press.
[3] Correia, J. D. G.; Domingos, A.; Santos, I.; Eur. J. Inorg. Chem. 2000, 7:1523.
[4] Correia, J. D. G.; Domingos, A.; Paulo, A.; Santos, I.; J. Chem. Soc. , Dalton Trans. 2000, 14: 2477.
[5] Fernandes, C.; Correia, J. D. G.; Gano, L.; Santos, I.; Seifert, S.; Syhre, R.; Spies, H.; J. Labelled Cpd. Radiopharm. 2001, 44, Suppl. 1, S518.

Introduction
To expand the scope of ¹¹C-labelled compounds, novel ¹¹C-C bond forming reactions gain more and more attention [1]. The versatile availability of [¹¹C]methyl iodide makes this labelling precursor favourable in several transition-metal mediated cross-coupling reactions. In this contex, technically simple, high-yielding and functional group tolerating reactions are of particular interest. The Sonogashira copper-palladium catalysed coupling of terminal alkynes with aromatic and vinylic halides [2] represents such a reaction. To the best of our knowledge, the Sonogashira-reaction has not yet been employed in ¹¹C-chemistry. Herein, we describe a modified Sonogashira-like reaction [3] for labelling the terminal alkyne group of the potent contraceptive steroid mestranol 1 with [¹¹C]methyl iodide.

Results and Discussion
The classical conditions of the Sonogashira reaction (Pd⁰, CuI and TEA or DIPA as thebase) can not be employed for ¹¹C-labelling with [¹¹C]methyl iodide due to the rapid quaternization the amine base. Therefore, we tested alternative catalyst/base combinations. By using tetrakis(triphenylphosphine)-palladium(0) (TTPP), copper(I) iodide, and 1,8-bis(dimethylamino)naphthalene as a non-nucleophilic base, about 5% of [¹¹C]methyl iodide was converted into [¹¹C]2. Similar results were obtained using the catalyst TTPP and silver oxide as the base. However, in the reaction of 1 with tris-(dibenzylidineacetone)-dipalladium(0), triphenylarsine, and tetrabutylammonium fluoride, 42-53% of [¹¹C]MeI was converted into [¹¹C]2

Scheme 1: ¹¹C-labelling of steroid 1

Conclusion
We developed a new method for a ¹¹C-C bond formation employing the cross-coupling of terminal alkynes with [¹¹C]methyl iodide via a Sonogashira-like reaction in sufficient radiochemical yields.

References
[1] B. Långström et al. Acta Chem. Scand. 53 (1999) 651-669.
[2] K. Sonogashira et al. Tetrahedron Lett. (1974) 4467-4470.

Introduction
Besides the herpes simplex virus type-1 thymidine kinase (HSV-1 TK), cytosine deaminase (CD) presents another system for gene therapy. CD catalyses the hydrolytic deamination of cytosine to form uracil. Its lack in mammalian cells and the ability to convert 5-fluorocytosine to the cell-toxic 5-fluorouracil makes it suitable for use in several gene therapy protocols [1,2]. An appropriate radiolabelled cytosine derivative would make it possible to monitor gene expression with positron emission tomography (PET), providing a sufficient amount of the tracer is trapped in the tumor cells. For this purpose, several cytosine derivatives were tested.

Results
CD was obtained by over-expression and following purification from transformed E. coli bacteria in good yields. The specific activity and K_M were determined using cytosine and 5-fluorocytosine. Some compounds (listed in table 1) were incubated in tris-buffer solution containing the isolated enzyme. Samples were taken and the rate of metabolites formation determined by HPLC.

For cytosine, the specific activity of 38 U/mg enzyme (one unit is the amount of enzyme catalysing the deamination of 1 µmol substrate per minute at 25°C) and a K_M of 0.63 mM falls in the range of further data published [3,4]. For 5-fluorocytosine, the decrease in specific activity (2.1 U/mg protein) and the increase of K_M (5.2 mM) of one dimension is also in good agreement with published data [1]. Additionally, it was shown that the CD tolerates some structural variations of its possible substrates. Beside substances which are varied at the 5-position (5-fluorocytosine, 5-methylcytosine), N-substituted derivatives like N-methylcytosine and N-hydroxycytosine are also accepted. This results offer a number of fluorine-18 labelled compounds as candidates for monitoring gene therapy.

Table 1
-----------------------------------------------------------------------
Turnover to the corresponding product in % after
Compound............10 min.....30 min.....60 min
-----------------------------------------------------------------------
Cytosine...............88.84......100..........100
5-Fluorocytosine......9.39.......22.42........28.61
5-Methylcytosine.....1.07.........5.94........10.25
N-Methylcytosine....1.47..........5.22.........8.53
N-Hydroxycytosine.20.11.......31.23........42.88

References
[1] Rowley, S. et al. J. Surgical Oncology 1996, 61, 42-48.
[2] Haberkorn, U. et. al. J. Nucl. Med. 1996, 37, 87-94.
[3] Ipata, P. L. Methods Enzymol. 1978, 51, 394-401.
[4] Balestreri, E. et al. Biochim Biophys Acta 1973, 315, 443-448.

Introduction
For monitoring gene expression of the herpes simplex virus type-1 thymidine kinase (HSV-1 tk), several reporter probes such as acycloguanosine analogues labelled with fluorine-18 have been described [1]. Studying several methods for radiolabelling eligible precursors with the isotope fluorine-18, we noticed highly varying yields, depending on the precursor used. This is due to the occurrence of competitive reactions that reduce the labelling yields of the tracers.

Results
Conversion of the precursors 5 and 6 into [¹⁸F]FHPG 1 and [¹⁸F]FHBG 2, but also into the non-radioactive fluorine compounds, resulted in a much lower yield compared to the methylated derivatives 7 and 8.

The nucleophilic fluorination with Kryptofix K2.2.2 to prepare the labelled compounds 1-4 was performed according to [2,3]. The unreacted ¹⁸F was removed by purification with a silica gel cartridge eluted with CH₂Cl₂/MeOH 85:15. In splitting off the methoxytrityl protection groups by of aqueous HCl, the precursors behave different. With the acycloguanosines derivatives 1 and 3 bearing an oxygen in their side-chain a by-product was delivered. The carba-analogues 2 and 4 are stable under these conditions.

Non-radioactive fluorination of compounds 5 and 6 delivers a N¹/O (from -OTs) bridged structure (characterized by ¹H NMR, IR, MS and elemental analysis) as by-product in a yield of 20%. This concurrent reaction was also observed in the ¹⁸F-labelling experiments. Since the methyl group in the N¹-position inhibits the cyclisation, 7 and 8 do not form such a by-product.
The splitting off the methoxytrityl protection groups by aqueous HCl is accompanied by decomposition. The two-phase system water-dichloromethane did not allow a satisfying control of the reaction temperature and in consequence, the acyclic side-chain of 1 and 3 was splitted off to result a by-product. These problems were overcome by using methanolic HCl as splitting agent. Its miscibility with CH₂Cl₂ allows a better reaction control, resulting in shorter reaction times and reducing the by-products.

References
[1] Wiebe, L. I. et al. Q. J. Nucl. Med. 1997, 41, 79-89.
[2] Alauddin, M. M. et al. Nucl. Med. Biol. 1998, 25, 175-180.
[3] Alauddin, M. M. et al. Nucl. Med. Biol. 1999, 26, 371-376.
[4] Shiue, G. G. et al. Nucl. Med. Biol. 2001, 28, 875-883.

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