Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

MOSFET´s with gateoxides containing nanoclusters (Si, Ge, Sn, Sb) fabricated with different techniques (implantation, LPCVD, sputtering) are a very promising approach for future memories. This contribution reports on results obtained on Ge-implanted MOS capacitors. By varying the implantation and annealing parameters the Ge depth profile and the cluster size and distribution can be controlled. The experimental results are explained by a theoretical model, which is based on TRIM calculations, rate-equation studies and 3D kinetic Monte Carlo simulations. The electrical properties of gate-SiO\sub{2} containing Ge-nanoclusters are investigated in detail with emphasis on its feasibility for memory applications.

Aufgabe der Erfindung ist es, eine Substanz vorzuschlagen, die bei der Verwendung zum Monitoring der Expression von Cytosin-Deaminase mit 18F-Tracer genügend lange Zeit in der Zelle verbleibt sowie ein Verfahren zur Herstellung der Substanz anzugeben.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren und eine Anordnung vorzuschlagen, mit der die Steuerung der Blasengröße ermöglicht wird. Eine spezielle Aufgabenstellung besteht in der Generierung möglichst kleiner Gasblasen.

Der Erfindung liegt die Aufgabe zugrunde, eine Spindelmutterhalterung für ein Hebel antreibendes Spindelgetriebe vorzuschlagen, das auch unter extremen Bedingungen
wie im Vakuum, unter Strahlenbelastung und bei einer Temperatur nahe dem absoluten Nullpunkt sicher funktioniert und dauerhaft eine exakte Wegauflösung im Nanometer-Bereich realisiert.

Der Erfindung liegt die Aufgabe zugrunde, Kontakte und Leitbahnen in oder auf kristallinen SiC-Halbleitersubstraten mit geringerem Kosten- und Herstellungsaufwand sowie gutem Grenzflächenverhalten herzustellen, wenn eine Schicht über den Kontakten bzw. Leitbahnen aus SiC erforderlich ist.

Aufgabe der Erfindung ist es, eine Anordnung vorzuschlagen, mit der beim Absperren oder beim Drosseln der Flüssigkeitsförderung mit einer Armatur das Auftreten von unerwünschten Drücken in der Rohrleitung sicher verhindert wird, ohne eine Einspeisung von Luft oder anderen Gasen in die Rohrleitung vorzunehmen sowie ohne einen Windkessel oder eine Hilfsarmatur oder zusätzliche Regler einzusetzen bzw. ohne fest eingestellte Schließ- und Drosselgeschwindigkeiten vorzugeben. Die Ausführung der Erfindung soll sowohl die unzulässigen Drücke stromaufwärts als auch stromabwärts der Absperrarmatur verhindern.

Der Erfindung liegt die Aufgabe zugrunde, ein mechanisches Getriebe für ein Abstimmgerät für Hohlraumresonatoren vorzuschlagen, das in weniger aufwendiger Ausführung vergegenständlicht und betreibbar ist und dessen hohe Lebensdauer und geringe Spielfreiheit auch bei sehr niedrigen Temperaturen gewährleistet sind.
Dabei soll auf piezoelektrische oder magnetostriktive Antriebe oder deren Kombination mit mechanischen Grobantrieben verzichtet werden.

Aufgabe der Erfindung ist es, ein Verfahren zu schaffen, das die Erzeugung von Nanoclustern zur Ladungsträgerspeicherung im Siliziumdioxid in konkretem Abstand von der Siliziumdioxid/Silizium-Grenzfläche mit idealerweise unimodaler Größenvertei-lung, und in einer Monolage angeordnet, erlaubt, ohne daß von außen zusätzliche Stoffe in die Siliziumdioxid-Schicht eingebracht werden müssen.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zur Herstellung von 3-0-Methyl-6-[18F]Fluor-DOPA, (3-0-Methyl-6-[ 18F]Fluor-L-4-hydroxyphenylalanin, 3-(2-[ 18F]Fluor-4-hydroxy-5-methoxy-phenyl)-2-amino-propansäure) vorzuschlagen, das eine höhere radioaktive Ausbeute bei einer kürzeren Verfahrensdauer ermöglicht.

Der Erfindung liegt die Aufgabe zugrunde, eine einfach bedienbare, während des bestimmungsgemäßen Gebrauchs dichte Einrichtung vorzuschlagen, bei der die Anhaftung der dünnen Scheibe an dem elastischen Dichtmaterial vermieden wird.

Die Erfindung betrifft eine Einrichtung zur lokalen Messung von Strömungsgeschwindigkeiten in Gasen und Flüssigkeiten. Die Erfindung ist auch zur Bestimmung der Strömungsgeschwindigkeit in nichttransparenten Fluiden und bei hohen Temperaturen, zum Beispiel in Metallschmelzen, geeignet.
Der Erfindung liegt die Aufgabe zugrunde, eine Einrichtung zur lokalen Messung von Strömungsgeschwindigkeiten in Gasen und Flüssigkeiten vorzuschlagen, mit der ein gut reproduzierbares Arbeiten auch bei hohen Temperaturen und größerer Einsatztiefe ermöglicht wird. Insbesondere soll die Erfindung in Metallschmelzen anwendbar sein.

Die vorliegende Erfindung dient der Bestimmung von räumlichen Geschwindigkeitsverteilungen in elektrisch leitfähigen Flüssigkeiten.

Der Erfindung liegt die Aufgabe zugrunde, eine Einrichtung vorzuschlagen, mit der ein Ionenstrahl mittlerer Energie für eine Niederenergie-Ionenimplantation einsetzbar ist. Dabei soll der Ionenstrahl so abgebremst werden, daß er mit Niederenergie auf das Target trifft und dort über die Targetfläche eine weitgehend konstante Ionendosis einbringt.

Die Erfindung betrifft ein Kompositmaterial zur Resonanzverstärkung optischer Signale an strukturell inhomogenen, mit metallischen Partikeln ausgestatteten Oberflächen sowie ein Verfahren zur Herstellung dieses Kompositmaterials.

Erfindungsgemäß ist das Kompositmaterial gekennzeichnet durch eine Oberflächenmorphologie mit metallischen Partikeln einheitlicher Teilchenform, welche lateral zu matrix-fixierten quasi-zweidimensionalen Arrays von Oberflächenheterogenitäten angeordnet sind und vertikal in der planar ausgebildete Dünnfilmmatrixphase verankert sind. Ein solches Kompositmaterial wird erfindungsgemäß durch ein Verfahren hergestellt, bei welchem die Matrixoberfläche mit einem Ionenstrahl der Zielmetallkomponente beschossen wird, wodurch es zu einer spontanen Bildung, Anordnung und Verankerung der metallischen Partikel kommt
Das Kompositmaterial zeichnet sich in besonderer Weise durch die hohe Stabilität, Reproduzierbarkeit, Fähigkeit der Wiederverwenbarkeit und Verkopplungsfähigkeit mit verschiedenen Strukturen aus. Das Verfahren zur Herstellung ist einfach und flexibel, gestattet die Gewinnung großflächiger Objekte, wie auch die Mikrostrukturierung und Integration, und zeichnet sich durch eine hohe Variabilität in Auswahl und Kombination von Metall- und Matrixmaterial aus.

...wird nachgereicht.

A model for the transport of nitrogen in austenitic stainless steel at temperatures around 400°C is presented and discussed. The model considers the diffusion of nitrogen under the influence of trapping and detrapping at trap sites formed by local chromium. Nitrogen depth profiles simulated on the basis of the model with diffusion and trapping activation energies of 1.1 eV and 1.45 eV, respectively, are in good agreement with experimental nitrogen profiles.

The influence of the high current density of a focused ion beam on the ion beam synthesis of CoSi2 layers has been investigated. After 35 keV Co+ or 70 keV Co2+ implantation into a heated Si(111) substrate and subsequent annealing, the layers have been investigated by scanning electron microscopy and Rutherford backscattering spectroscopy. It is shown that the mode of beam scanning influences the CoSi2 layer formation significantly. At a given substrate temperature, a sufficient low dwell-time is required to obtain a continuous layer rather than a laterally disrupted structure. With increasing target temperature, the dwell-time window becomes less restricted. The results are discussed in terms of damaging and dynamic annealing of the silicon crystal. RBS/channeling investigations demonstrate that continuous or disrupted CoSi2 layers are formed when the substrate remains crystalline or becomes amorphous, respectively.

The International Workshop on "Measuring Techniques in Liquid Metal Flows" (MTLM Workshop) was organised in frame of the Dresden "Innovationskolleg Magnetofluiddynamik". The subject of the MTLM Workshop was limited to methods to determine physical flow quantities such as velocity, pressure, void fraction, inclusion properties, crystallisation fronts etc. The present proceedings contain abstracts and viewgraphs of the oral presentations.
During the last decades numerical simulations have become an important tool in industry and research to study the structure of flows and the properties of heat and mass transfer. However, in case of liquid metal flows there exists a significant problem to validate the codes with experimental data due to the lack of available measuring techniques. Due to the material properties (opaque, hot, chemical aggressive) the measurement of flow quantities is much more delicate in liquid metals compared to ordinary water flows. The generalisation of results obtained by means of water models to real liquid metal flows has often to be considered as difficult due to the problems to meet the actual values of non-dimensional flow parameters (Re, Pr, Gr, Ha, etc.). Moreover, a strong need has to be noted to make measuring techniques available to monitor and to control flow processes in real industrial facilities.

see abstract of the above mentioned publication in APL 75, 9, 1279 (1999)

Uranium LIII-edge EXAFS analysis was carried out on aqueous uranium(VI) complexes with monomeric intermediates of the natural wood-degradation process such as protocatechuic acid (3,4-dihydroxy-benzoic acid), catechol (2-hydroxyphenol), pyrogallol (1,2,3-trihydroxybenzol), and vanillic acid (4-hydroxy-3-methoxybenzoic acid). The structural parameters of the 1:1 complexes with protocatechuic acid and vanillic acid indicate that the carboxylic group coordinates the uranyl cation in a bidentate mode in the equatorial plane. Based on the identical structural parameters observed for all complexes in alkaline media, except for vanillic acid, we conclude that the coordination occurs via the neighboring OH groups of the phenols under formation of a five-membered ring.

X-ray absorption fine structure (XAFS) spectroscopy is a powerful tool for obtaining basic molecular-level information, which is required for a better understanding of the mechanisms responsible for radionuclide transport in the environment. A unique experimental station dedicated to the study of actinides by XAFS spectroscopy has become operational at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. The main characteristics of the Rossendorf Beamline, ROBL, and its radiochemistry end station and selected results obtained on Tc and Np solutions are presented.

Graphical contents entry
Thiosemicarbazones react with [Au(damp-C1,N)Cl2] under cleavage of the Au-N bond and protonation of the dimethylamino group to give cationic or neutral Au(III) complexes. The products have remarkable biological properties.
Summary: Dichloro[2-(N,N-dimethylaminomethyl)phenyl-C1,N]gold(III), [Au(damp-C1,N)Cl2], reacts with salicylaldehyde thiosemicarbazone (H2saltsc), vanilline thiosemicarba-zone (Hvantsc), N-methylpyrrole aldehyde thiosemicarbazone (Hmepyrtsc), pyridoxal meth-ylthiosemicarbazone (H2pydoxmetsc), 2-diphenylphosphinobenzaldehyde thiosemicarbazone (HPtsc) or variously substituted acetylpyridine thiosemicarbazones (HapRtsc; R = H, me, ph) under cleavage of the Au-N bond and protonation of the dimethylamino group. Compounds of the general formulae [Au(Hdamp-C1)Cl(L)]+ (L = Hsaltsc-, vantsc-, mepyrtsc-), [Au(Hdamp-C1)Cl(L)]2+ (L = H2pydoxmetsc) or [Au(Hdamp-C1)(L)]2+ (L = Ptsc-, apRtsc-, R = H, me, ph) have been isolated and characterized. The presence of the s-bonded 2-(dimethylaminomethyl)phenyl ligand is mandatory to prevent reduction of the gold(III) cen-tre. The crystal structures of [Au(Hdamp-C1)Cl(Hsaltsc)]-(PF6), [Au(Hdamp-C1)Cl(H2pydox-metsc)]Cl2 · MeOH, [Au(Hdamp-C1)Cl(mepyrtsc)]Cl, [Au(Hdamp-C1)(apphtsc)]-Cl2 · 2 Me-OH and [Au(Hdamp-C1)(Ptsc)]Cl2 · MeOH · 0.5 Et2O have been elucidated showing the gold atoms in distorted square co-ordination environments.
The potentially O,N,S tridentate ligands H2saltsc and H2pydoxmetsc co-ordinate bidentate and do not incorporate the OH groups in the chelating framework, whereas the HapRtsc's or Ptsc co-ordinate tridentate. Generally, one or more hydrogen atoms of the heterocyclic ligands and/or the NMe2H+ group form hydrogen bridges in the solid state structures.
First results of antiproliferation tests on tumor cells prove considerable cytotoxicity of the new gold complexes.

The organometallic precursor (NEt₄)₂[ReBr₃(CO)₃] was reacted with bidendate dithioethers (L) of the general formula H₃C-S-CH₂CH₂-S-R (R = -CH₂CH₂COOH, CH₂-C=CH) and R'-S-CH₂CH₂-S-R' (R' = CH₃CH₂-, CH₃CH₂-OH, CH₂COOH) in methanol to form stable rhenium(I) tricarbonyl complexes of the general composition [ReBr(CO)₃L]. Under these conditions the functional groups do not participate in the coordination. As a prototypic representative of this type of Re compounds the propargylic-group-bearing complex [ReBr(CO₃)(H₃C-S-CH₂CH₂-S-CH₂C=CH)] Re₂ was studied by X-ray diffraction analysis. Its molecular structure exhibits a slightly distorted octahedron with facial coordination of the carbonyl ligands.
The potentially tetradentate ligand HO-CH₂CH₂-S-CH₂CH₂-S-CH₂CH₂-OH was reacted with the trinitrato precursor [Re(NO₃)₃(CO)₃]^2- to yield a cationic complex [Re(CO)₃(HO-CH₂CH₂-S-CH₂CH₂-S-CH₂CH₂-OH)]NO₃ Re8 which shows the coordination of one hydroxy group. Re8 has been characterized by correct elemental analysis, infrared spectroscopy, capillary electrophoresis and X-ray diffraction analysis.
Ligand exchange reaction of the carboxylic group bearing ligands H₃C-S-CH₂CH₂-S-CH₂CH₂-COOH and HOOC-CH₂-S-CH₂CH₂-S-CH₂-COOH with (NEt₄)₂[ReBr₃(CO)₃] in water and with equimolar amounts of NaOH led to complexes in which the bromide is replaced by the carboxylic group. The X-ray structure analysis of the complex [Re(CO)₃(OOC-CH₂-S-CH₂CH₂-S-CH₂-COOH)] Re6 shows the second carboxylic group non-coordinated offering an ideal site for functionalization or coupling a biomolecule.
The no-carrier-added preparation of the analogue ^99mTc(I) carbonyl thioether complexes could be performed using the precursor fac-[99mTc(H₂O)₃(CO)₃]⁺
with yields up to 90 %. The behaviour of the chlorine containing ^99mTc complex ^[99mTcCl(CO)₃(CH₃CH₂-S-CH₂CH₂-S-CH₂CH₃)] Tc1 in aqueous solution at physiological pH value was investigated. In saline, the chromatographically separated compound was stable for at least 120 min. However, in chloride free aqueous solution a water-coordinated cationic species Tc1a of the proposed composition [^99mTc(H₂O)(CO)₃(CH₃CH₂-S-CH₂CH₂-S-CH₂CH₃)]⁺ occured. The cationic charge of the conversion product was confirmed by capillary electrophoresis. By the introduction of a carboxylic group into the thioether ligand as a third donor group the conversion could be suppressed and thus the neutrality of the complex preserved.
Biodistribution studies in the rat demonstrated for the neutral complexes [^99mTcCl(CO)₃(CH₃CH₂-S-CH₂CH₂-S-CH₂CH₃)] Tc1 and [^99mTcCl(CO)₃(CH₂-S-CH₂CH₂-S-CH₂-C=CH)] Tc2 a significant initial brain uptake (1,03 ± 0.25 % and 0.78 ± 0.08 % ID/organ at 5 min. p.i.). Challenge experiments with glutathione clearly indicated that no transchelation reaction occurs in vivo.

Two novel oxorhenium complexes containing the 2,6-dithiomethylpyridine ligand were synthesized according to the '3 + 1' and the '3 + 2' approaches, respectively, and characterized by classical methods of analysis. The [2,6-dithiomethylpyridinato][p-methoxybenzenethiolato]oxorhenium complex, 1, was produced by simultaneous action of equimolar quantities of 2,6-dithiomethylpyridine and p-methoxybenzenethiol on the precursor [(n-C₄H₉)₄N][ReOCl₄] in EtOH. As revealed by spectroscopic data as well as X-ray structure analysis, complex 1 adopts a distorted square pyramidal geometry around the metal with the SNS/S donors forming the basal plane and the oxygen occupying the apex of the pyramid. When the same tridentate ligand reacts with [(n-C₄H₉)₄N][ReOCl₃(PO)] (PO = o-diphenylphosphinophenolato) as a precursor, complex 2a, [2,6-dithiomethylpyridinato][o-diphenylphosphinophenolato]oxorhenium, is obtained. The latter is a six-coordinate rhenium species to which the distorted octahedral geometry is assigned, according to the analytical findings. In this case, the SNS/P donors occupy the equatorial plane and the two oxygen atoms the apices of the distorted octahedron positioned trans to each other.

Supramolekulare Systeme mit spezifischen, wohldefinierten Funktionen ermöglichen eine hochselektive Erkennung und Bindung unterschiedlicher Spezies und erschließen damit neue Anwendungsfelder in der Medizin, Analytik, Informations- und Energietechnik sowie in der chemischen Technik.
Möglichkeiten der selektiven Bindung und gezielten Freisetzung von medizinisch und biologisch relevanten Anionen wie Pertechnetat, Perrhenat und ATP werden am Beispiel photo- und pH-schaltbarer Dendrimere diskutiert. Über die Bildung von Einschlussverbindungen natürlicher helicaler Amyloseeinheiten mit anionischen, kationischen und nichtionischen Tensiden wird berichtet. Die eingesetzten Methoden wie Flüssig-Flüssig-Extraktion, Lipophiliebestimmung und Kalorimetrie gestatten die Charakterisierung kleinster Substanzmengen.

We have measured the Coulomb dissociation of 8B into 7Be and a proton at 254 MeV/nucleon using a large-acceptance focusing spectrometer.
The astrophysical S17-factor for the 7Be(p, gamma)8B reaction at Ec.m. = 0.25-2.78 MeV is deduced yielding S17(0) = 20.6±1.2 (expt)
±1.0(theor) eV b. This result agrees with the presently adopted zero-energy S17-factor obtained in direct-reaction measurements and with the
results of other Coulomb-dissociation studies performed at 46.5 and 51.2 MeV/nucleon.

Technetium and rhenium in the form of special complexes are important metals for the use in nuclear medicine. In order to design such complexes, detailed knowledge about the complexation behaviour of ligands and complex structures is required. EXAFS spectroscopy using synchrotron radiation provides the possibility to investigate complex structures in solid and soluted state. In the present study, EXAFS spectroscopy was applied to study the co-ordination spheres of technetium-99 and rhenium-187 complexes of different kinds of complexes. Rhenium complexes of model peptides were investigated and the extent to which the co-ordination mode depends on the peptide sequences was shown. EXAFS measurements at different pH values revealed changes in the metal co-ordination spheres. In case of the dipeptide Cys-Gly, a 1:2 complex with a Re(V) oxo core and a formal S2N2 co-ordination sphere is formed. By increasing the pH, a Re(V) dioxo core is generated. The tripeptide Gly-Gly-Cys was shown to exhibit a formal SN3 co-ordination with the Re(V) oxo metal centre. Using multiple scattering analysis, the involvement of the peptide backbone in the metal co-ordination was found. Under alkine conditions, the co-ordination of a hydroxyl group at the metal core takes place. EXAFS spectroscopy was further applied to study the technetium binding sites in large, biologically relevant peptides. The technetium complex of an endothelin derivative was shown to be a 1:2 Tc(V) oxo complex with a formal S4 co-ordination as realised by the peptide cysteine residues. A LHRH derivative bearing a cysteine residue at the side chain of a lysine residue was analysed to represent a 1:2 Tc(V) oxo complex with a formal S2N2 co-ordination sphere. Thereby, the metal co-ordination is ensured by the free cysteine residue of the peptides. The investigation of mixed ligand complexes of technetium and rhenium using the "3+1"-concept showed characteristic EXAFS features of this class of complexes. The co-ordination spheres as known from XRD analyses could be confirmed for solution. Reaction pathways leading to different products during the formation of "3+1" complexes were monitored and helped to understand reaction mechanisms. Furthermore, stability studies of the mixed-ligand complexes under biological conditions were performed and showed the possibility to record EXAFS data in situ. As a further complex category, mixed ligand Tc and Re carbonyl compounds were studied. The metal co-ordination spheres gave typical EXAFS patterns with the carbonyl co-ordination detectable by single and multiple scattering effects with excellent correlation between EXAFS and known XRD data found. By measurements in solution, significant changes in the metal environment of the metal carbonyl precursor molecules were observed. In conclusion, EXAFS spectroscopy is an excellent tool for structural analysis of technetium and rhenium complexes relevant to nuclear medicine.

Double differential production cross sections of pi- and pi+ mesons and the number of participating protons have been measured
in central Au+Au collisions at 1 GeV/nucleon.
At low pion energies the pi- yield is strongly enhanced over the pi+ yield.
The energy dependence of the pi-/pi+ ratio is assigned to the Coulomb interaction of the charged pions with the protons in the reaction zone.
The deduced Coulomb potential increases with increasing pion c.m. energy.
This behavior indicates different freeze-out radii for different pion energies in the c.m. frame.

A nuclear resonance fluorescence experiment on 88Sr has been performed with bremsstrahlung of 6.7 MeV endpoint energy. The gamma-ray linear polarisation has been measured with a EUROBALL CLUSTER detector as a Compton polarimeter. ...(wird komplettiert)

For the analysis of boron dilution transients and main steam line break scenarios the modeling of the coolant mixing inside the reactor vessel is important. The reactivity insertion due to overcooling or deboration depends strongly on the coolant temperature and boron concentra-tion.

The coolant mixing in the downcomer and lower plenum depends significantly on the con-struction of the reactor vessel and flow conditions are different in each reactor type. In the German Konvoi type reactors a complicated flow picture with large vortexes was obtained which is typical probably also for the European Pressurized Water Reactor (EPR). The models and assumptions for the coolant mixing description used in the coupled neutron kinet-ics/thermohydraulic system codes have to be validated on experimental data from the Rossendorf coolant mixing model and detailed computational fluid dynamics (CFD) calcula-tions.

The requirements concerning quality of the experimental results need a non-pressurized test facility operating with water (room temperature). The reactor vessel is made of Plexiglas for flow visualization and LDA measurements. It has to dispose of separately controllable main coolant pumps in each loop. The measurement instrumentation has to be designed for the nec-essary spartial and time resolution.

First experiments at the test facility ROCOM show that the mixing in the downcomer and the lower plenum is incomplete (sector formation) at nominal conditions (all loops are operating). At the moment when the plug is entering the downcomer and also the core inlet, two maxima are clearly to be seen. This phenomenon is caused by a re-circulation area below the inlet noz-zle.

To simulate real accident scenarios and for code validation an extensive test programme is planned. The experimental results will be compared against CFD calculations for analysing the dependencies of the power output of the reactor on the temperature and/or boron distribution.

For the analysis of boron dilution transients and main steam line break scenarios the modeling of the coolant mixing inside the reactor vessel is important, because the reactivity insertion strongly depends on boron acid concentration or the coolant temperature distribution.

Calculations for steady state flow conditions for the VVER-440 were performed with a CFD code (CFX-4). For this calculation the RPV from the cold legs inlet through the downcomer, the lower plenum and the lower core support plate was nodalized in detail. The comparison with experimental data and an analytical mixing model which is implemented in the neutron-kinetic code DYN3D showed a good agreement for near-nominal condi-tions (all MCPs are running). The comparison between the CFD-results and the analytical model revealed differences for MSLB conditions [1].

After investigating coolant mixing under steady-state nominal flow conditions, first experiments at the Rossendorf Mixing Test Facility ROCOM were performed simulating the start-up of the first main coolant pump. The reference reactor for the geo-metrically 1:5 scaled Plexiglas model is the German Konvoi type PWR. This transient is impor-tant in the case of the existence of plugs of lower borated water in one of the loops. The travelling of plugs of different size from the inlet nozzle of the started loop to the core inlet and the resulting parameter distribution at the core inlet were investigated. CFD calculations for these experiments show the same qualitative parameter distribution picture with typical maxima, which are located at the opposite of the reactor from the started loop, as it was observed in the experiments. After demonstrating the capability of the CFD code to simulate these complicated flow transients, calculations were performed for the start-up of the first pump in a VVER-440 type reactor. However, no data from transient experiments are available at the moment for this reactor type. Therefore the calculations are a first step of understanding the coolant mixing in the RPV of a VVER-440 type reactor under transient conditions.

The results of the calculation show a very complex flow in the downcomer. The injection is distributed into two main jets, the so called butterfly distribution. In addition several secondary flows are seen in various parts of the downcomer. Especially strong vortices occur in the areas below the non operating loop nozzles and also below the injection loop. The results show that a high downcomer of VVER-440 and the existence of the lower control rod chamber support coolant mixing.

Ion-beam-induced crystallization (IBIC) was used to produce nanocrystals in the preamorphized region of a 6H-SiC bulk crystal. The precipitation was stimulated by high dose implantation with Al and Si at temperatures between 300 °C and 700 °C. The morphology of the nanocrystalline phase and its dependence on the implantation parameters were investigated by cross-sectional transmission electron microscopy (XTEM). Above a certain threshold dose, randomly oriented grains of 3C-SiC with almost spherical shape and mean diameters ranging from 4 to 25 nm are formed. The recrystallization is completed within a very narrow time window. Therefore, in our experiments the nucleation and growth process could not be observed directly. From the extrapolation of the kinetics of the secondary grain growth to zero time the window of suitable parameters for the observation of nucleation and primary grain growth was estimated. A critical temperature (TC 300 °C) as well as an incubation time (tI 300 s below 700°C) for the beginning of the recrystallization were found.

The change of the depth profile and chemical bond character of Ge in Ge+ ion implanted SiO2 layers during annealing in O2 atmophere has been studied by x-ray photoelectron spectroscopy (XPS). The Ge depth profiles in as-implanted and annealed samples as measured by XPS are in agreement with profiles measured by Rutherford backscattering spectroscopy (RBS). At interfaces XPS gives more information about the Ge depth distribution than RBS. Thus, other than RBS, XPS could proof that the fraction of implanted Ge, with moves during annealing to the SiO2/Si interface region, resides on the Si side of this interface. Additionally, the high and low contrast nanoclusters in Ge implanted samples, which have been found recently in cross-section transmission electron microscopy (XTEM) images, could be identified by XPS, in combination with data analysis by factor analysis, to consist mainly of elemental Ge and GeO2, respectively.

The report gives an overview on the scientific work of the Institute of Safety Research between January 1998 and June 1999.

The electrical properties of high concentration aluminum and nitrogen implanted layers have been investigated after furnace as well as flash lamp annealing. For Al doped layers the electrical efficiency is enhanced using flash lamp annealing. For highest Al concentrations the doped layer shows metal like conductivity. For N doped layers the flash lamp annealing effects no increase of the carrier concentration. Due to the short annealing time only the nitrogen on hexagonal sites is electrically active. Flash lamp annealing produced no extra damage of the vacancy type as proved by Positron Annihilation Spectroscopy.

A Q-band single-crystal EPR study of tetraphenylarsoniumtetrachloro-nitridorhenate(VI), [(C6H5)4As][ReVINCl4], diamagnetically diluted by the isoelectronic oxorhenate(V) complex is reported. The EPR spectra are typical of an ion with 5d1 (S = 1/2) configuration and are influenced by large rhenium hyperfine coupling constants and nuclear quadrupole interactions. They are characterized by well-resolved 185,187Re hyperfine patterns with almost equal spacings and the occurrence of "forbidden" transitions (DmI = ± 1, DmI = ± 2).
The 185,187Re hyperfine parameters as well as the data obtained from density functional theory (DFT) and extended Hückel theory (EHT) molecular orbital calculations are used to analyze the spin-density distribution in the system under study. Thereby, the negative sign found for the spin-density at the nitrogen from DFT is mainly determined by spin polarization. In addition, both MO methods are used to calculate the electric field gradient being responsible for the 185,187Re nuclear quadrupole coupling.

This paper presents a neural-network approach to operator-independent assessing the operational states of chemical semibatch reactors. The suitability of neural networks for process monitoring was investigated in a miniplant in which strongly exothermic chemical reference processes were carried out. Before being applied to state classification, the neural network classifiers first have be trained using process data of normal and abnormal sequences of reaction to establish a nonlinear decision model between process parameters and state classification. Afterwards, the trained classifiers can be used for process monitoring. Best results were reached with three-layer perceptron networks. For assessing the danger potential of fault states, separate perceptron networks for danger classification and for fault isolation were used.

A new one-dimensional model suitable for practically orientated simulations of transient multiphase flows within vessels was developed. The model bases on a new developed specific Particle-In-Cell method. The equations of transport are solved free of numerical diffusion. This property and the distinction between continuous and dispersed phases make an implicit reflection of discontinuities as e.g. the top level of the mixture possible. Flexible interfaces allow a convenient coupling of this model with constitutive correlations and models for special phenomena. There is also an interface, which enables the implementation of foam models. By such a model the generation decay of foam at the top level of the mixture may be simulated. A special goal of the code is the transient simulation of emergency relief from chemical reactors. For this reason the code was equipped with models for pressure calculation, conservation of energy, phase transfer, bubble generation, bubble growth, coalescence, drift of the phases, heat release from the vessel wall, discharge and homogeneous chemical reactions.

Following an overview on kinetics of carbon/gas-reactions, status and further needs in selected safety relevant fields of graphite oxidation in HTR and fusion reactors are outlined: Considering severe air ingress, lack of experimental data on Boudouard reaction and in the field of advanced oxidation kinetics was detected. Development of coatings, protecting against oxidation, has to focus on stability under neutron irradiation and on general feasability of coatings on HTR pebble fuel graphite. Oxidation in normal operation of direct-cycle HTR requires examinations on gas atmospheres and on catalytic effects. Advanced carbon materials like CFCs and mixed materials should be developed and tested with respect to their oxidation resistance in a common HTR/fusion task. In an interim HTR fuel storage radiolytic oxidation in normal operation and thermal oxidation in accidents have to be considered. Plans for future work in these fields are described.

Die Entwicklung von supramolekularen Komplexbildnern für Pertechnetat und Perrhenat eröffnet den Zugang zu bisher nicht bekannten Tc(VII)- bzw. Re(VII)-Spezies und bietet damit eine realistische Alternative zu den gegenwärtig in der Diagnostik angewendeten Tc(V)-, Tc(III)- und Tc(I)-Koordinationsverbindungen.
Möglichkeiten der selektiven Bindung und des Phasentransfers für die tetraedrischen Oxoanionen Pertechnetat und Perrhenat werden am Beispiel von bicyclischen Guanidiniumverbindungen sowie photo- und pH-schaltbarer Dendrimere diskutiert.

To study the role of carboxylic and phenolic hydroxyl groups in the complexation of uranium(VI) with phenolic wood degradation products in aqueous solution, we prepared 1 mMol/L U(VI) complexes with the following simple model compounds in two pH ranges, i.e., 4-5 and 8-10: protocatechuic acid (3,4-dihydroxybenzenecarboxylic acid), catechol (1,2-dihydroxybenzene), pyrogallol (1,2,3-trihydroxybenzene), and vanillic acid (4-hydroxy-3-methoxybenzenecarboxylic acid). The structural parameters of these complexes were measured by uranium LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy.
In acid solutions containing 1:1 complexes with ligands having both carboxylic and hydroxyl groups, the uranium is surrounded by 5 equatorial oxygen (Oeq) at a distance of 2.44 Å and 2.46 Å for vanillic acid and protocatechuic acid, respectively. This relatively long U-Oeq bond distance is characteristic for bidentate coordination of the carboxylic group to the uranyl cation [Denecke et al., J. Phys. IV France 7, C2-637 (1997)]. If the ligands have only neighbouring hydroxyl groups as in case of catechol and pyrogallol the uranium is surrounded by 5-6 oxygen atoms at a shorter U-Oeq distance (2.39 Å). This shows that in the pH range of 4-5, the coordination behaviour of the acids is dominated by the carboxylic groups and not the hydroxyl groups. In the pH range of 8-10, the neighbouring phenolic hydroxyl groups dominate the com-plexation. This is in agreement with the observed similarities in the EXAFS structural parameters of the corresponding 1:2 and 1:3 complexes. In all these complexes the measured U-Oeq bond distance is 2.38 Å. It can be concluded that this relatively short U-Oeq bond distance is characteristic for the complexation of the uranyl ion with two or three ligands having neighbouring phenolic hydroxyl groups.

Large underground mines are beiing flooded by surface and groundwater during the restoration of the East German uranium mining sites. The mine shafts and galleries are heavily reinforced with wood, and the flooding process isolates the wood from exposure to air. In conjunction with the wood degradation, this may cause potentially reducing conditions.

To study this effect, redox potential measurements and redox titrations with potassium hexacyanoferrate(III) were carried out on hydrothermal wood leachates, lignin and humic acid using a platinum electrode in combination with a silver-silver chloride electrode in a cell with liquid junction. The redox potentials of spruce lignin and humic acid, extrapolated to pH 0 and infinite dilution, were determined to be 570"5 mV for both with a negative pH gradient of 54.0"1 mV/pH. The potential indicates that the organic matter produced by the wood degradation can reduce U(VI) to U(IV). We identified U(IV) as the reduction product by spectrophotometry of the U(IV)-arsenazo(III) complex . The capacity for lignin to reduce U(VI) in-creases from pH 5 to 8 from 1.3@10-2 to 0.5 µeq/g, respectively. For comparison, iron(III) was reduced at pH 4.5 with a capacity of 0.15 meq/g.

We also studied how reducing conditions were generated by the decay of wood in a highland bog . We measured the redox potential in the field as a function of depth, and found that the redox potential de-creased by more than 800 mV from the surface to the depth of one meter. In comparison, the redox potential in deeper layers of the flooded mines was diminished by about 700 mV. This is ascribed to the oxidation of sulfidic and arsenic min-erals, especially of pyrite, markasite and arsenopyrite. This lowering of the redox potential causes the UO22+ to be immobilized as UO2. Our results show that the degradation of the large quantities of wood in the mines also contribute to establish, maintain and enhance reducing conditions and, hence, to immobilize significant parts of the 100 tons of urani-um and 50 tons of arsenic that are dissolved in Saxony=s largest underground mine at Schlema.

In a transport model calculation we study some of the basic assumptions of thermal models. We find at SIS energies the particles are mainly produced in a highly non-equilibrium situation. At freeze-out only nucleons are thermalized.

We analyze for the first time the full γγ directional correlations from oriented states (DCO) in an experiment performed with the GASP detector array. Our analysis based on a transformation of the directional information into expansion coefficients of an orthogonal basis. With this method, which we call SpeeDCO (spectral expansion of DCO), the complete DCO information is concentrated in 12 γγ coincidence spectra. The analysis is applicable to all detector arrays which uniformly cover the solid angle. We show that the complete DCO information can be used for a reliable and unique determination of spins and multipolarity mixing ratios in weakly populated bands. We were able to establish the spins and the positive parity of the Δ I=1 ''M1 band'' in ¹²⁸Ba and multipolarity mixing ratios of M1/E2 in-band transitions were derived as well. The measured values are in good agreement with those expected for a high-K rotational band.

The four-quasiparticle magnetic dipole band in ¹²⁸Ba has been investigated with the ⁹⁶Zr(³⁶S,4n)¹²⁸Ba reaction at the GASP spectrometer of the Laboratori Nazionali di Legnaro. Linking transitions to the previously known positive parity states have been observed for the first time in this mass region and new transitions on top of the band have been found. The experimental results are compared to previously made tilted axis cranking calculations.

The sensitivity of polarization observables in the reaction NN NN slightly above the threshold is studied with respect to the details of the one-boson exchange model and a possible admixture of hidden strangeness in the nucleon. It is shown that the finite-energy predictions differ strongly from the threshold predictions. A measurement of the beam-target asymmetry and the decay anisotropy can help to disentangle the role of various reaction mechanisms.

Breakup temperatures in central collisions of ¹⁹⁷ Au + ¹⁹⁷Au at bombarding energies E/A = 50 to 200 MeV were determined with two methods. Isotope temperatures, deduced from double ratios of hydrogen, helium, and lithium isotopic yields, increase monotonically with bombarding energy from 5 to 12 MeV, in qualitative agreement with a scenario of chemical freeze-out after adiabatic expansion. Excited-state temperatures, derived from yield ratios of states in ⁴He, ^5,6Li, and ⁸Be, are about 5 MeV, independent of projectile energy, and seem to reflect the internal temperature of fragments at their final separation from system.

The production and propagation of kaons and antikaons has been studied in symmetric nucleus-nucleus collisions in the SIS energy range. The ratio of the excitation function of K⁺ production in Au+Au and C+C collisions increases with decreasing beam energy. This effect was predicated for a soft nuclear equation-of-state. In noncentral Au+Au collisions, the K⁺ mesons are preferentially emitted perpendicular to the reaction plane. The K^-/K⁺ ratio from A+A collisions at beam energies which are equivalent with respect to the threshold is found to be about two orders of magnitude larger than the corresponding ratio from proton-proton collisions. Both effects are considered to be experimental signatures for a modification of kaon properties in the dense nuclear medium.

Directed sideward flow of light charged particles and intermediate mass fragments was measured in different symmetric reactions at bombarding energies from 90 to 800 AMeV. The flow parameter is found to increase with the charge of the detected fragment up to Z=3-4 and turns into saturation for heavier fragments. Guided by simple simulations of an anisotropic expanding thermal source, we show that the value at saturation can provide a good estimate of the flow angle, Θ_flow, in the participant region. It is found that Θ_flow, depends strongly on the impact parameter. The excitation function of Θ_flow, reveals striking deviations from the ideal hydrodynamical scaling. The data exhibit a steep rise of Θ_flow, to a maximum at around 250-400 AMeV, followed by a moderate decrease as the bombarding energy increases further.

High spin states have been populated in ¹¹⁷  ₅₃I via the ⁹⁰Zr(³¹P,2p2n) reaction at 150 MeV, using the EUROGAM II γ-ray spectrometer to record high-fold γ-ray coincidences. A quadruples γ-ray analysis (γ⁴) has been used to extend the known level scheme. In addition to several aligned noncollective states, a new high-spin band showing characteristics of smooth termination has been established at and linked into the low-spin level scheme. Its structure has been inferred through comparison with cranked Nilsson-Strutinsky calculations.

A possibility for the determination of velocity fields in electrically conducting fluids is presented. Applying an external magnetic field, electric and magnetic fields are induced by the fluid motion. The electric potential can be measured at the walls and the magnetic field outside the fluid volume. The inverse problem of reconstructing the velocity from the measured quantities is solved using Tikhonov regularization. Several examples will be given to illustrate the potential of such type of velocity reconstruction. The problem of uniqueness is treated in detail for the spherical geometry. Our ultimate aim is to develop a fully contactless velocity measurement technique whereby measuring the electric potential at the wall can be avoided.

In einigen Wochen wird der Grundstein für die Strahlungsquelle ELBE am Forschungszentrum Rossendorf (FZR) bei Dresden gelegt. Das Kernstück dieser neuen Anlage wird ein supraleitender Elektronen-Linearbeschleuniger hoher Brillanz sein, der in seiner kombination von hoher Strahlintensität und guter Strahlqualität (d. h. niedriger Emittanz) alle in Europa existierenden Anlagen übertreffen soll (das Akronym ELBE wurde aber nicht nur deshalb gewählt).

The production of pions in pp collisions at beam energies of ≤ 300 MeV has been studied with the COSY-TOF spectrometer, which was recently extended to flight paths of ~ 3 m for charged particles through the addition of a barrel section. Together with the bremsstrahlung channel, which was investigated in an earlier
experiment, pion production exhausts the inelastic pp cross section at these energies. TOF allows the simultaneous study of
all channels, the measurement of pnπ⁺ being facilitated by the neutron detector COSYnus. In this contribution, preliminary results on the pionic three-body final states are discussed.

If a moving electrically conducting fluid is exposed to an external magnetic field electrical currents are induced. These currents give rise
to an additional magnetic field which can be measured outside the fluid volume and to an electric potential measurable at the fluid
boundary. From the viewpoint of inverse problems, we consider the possibility of velocity reconstruction from the measured
electromagnetic fields. Possible applications for a contactless measuring technique are delineated.

The reaction pp → K⁺ λ,p was measured exclusively at the cooler synchrotron COSY at beam momenta of p_Beam = 2.50 GeV/c and p_Beam = 2.75 GeV/c using the TOF detector. Angular and momentum distributions were obtained for the full phase space of the reaction products. Total cross sections were extracted to be (2.7 ± 0.3)μ b and (12.0 ± 0.4) μ b,
respectively. The polarization of the λ-hyperon was determined as a function of its transversal momentum and was found to be negative for transverse momentum transfers of p_T ≥ 0.3 GeV/c. The results together with existing data are compared with phenomenological parameterizations and model calculations on the basis of meson exchange.

At COSY pp-bremsstrahlung was measured at a beam momentum of 797 MeV/c using an external proton beam. Data were taken with a wide angle spectrometer covering a solid angle of approximately 1 sr. The complete data set is presented in a series of c.m. angular distributions as well as a single Dalitz plot. The absence of final state interaction effects is understood as being due to a general insensitivity of the pp γ reaction to the spin-singlet component of the NN interaction. Coplanar angular distributions (in the laboratory system) are well reproduced by recent model calculations; also good agreement is found with the original TRIUMF data [K. Michaelian et al., Phys. Rev. D 41 (1990) 286] when omitting the rescaling factor of 2/3.

Coulomb effects on π^± and K^± spectra in relativistic nuclear collisions are investigated. At collision energies around 1 GeV the ratio of π^- to π⁺ is enhanced several times at low transverse momenta but less at ultrarelativistic energies. We describe the ratios at SIS, AGS, and SPS energies with simple analytic models as well as more elaborate numerical models incorporating the expansion dynamics. The Coulomb effect
depends on the properties of the source after the violent collision phase and provides information on source sizes, freeze-out times, and expansion velocities. Comparison with results from HBT analyses are made. Predictions for π^± and K^± at RHIC and LHC energies are given.

A magnetic spectrometer system has been constructed for the study of reactions with multiple charged particles in the final state, induced by polarized proton beams of few GeV energy. The system is based on a large-gap dipole magnet, with a liquid hydrogen target and scintillating fiber tracking detectors embedded inside the magnet. Multiwire proportional chambers, plastic scintillator hodoscopes, and threshold Cerenkov detectors placed outside the magnet provide additional tracking, triggering and particle identification capabilities. The system has been applied to study exclusive hyperon as well as pseudoscalar and vector meson production reactions at bombarding energies below 3 GeV. Additionally, it has been used to monitor the proton beam polarization at Laboratoire National Saturne. The components and performance of the system are reported.

Übersicht über Routinebetrieb, Verbesserungen am PET-Zyklotron, Erfahrungen beim Betrieb und bei der Wartung des PET-Zyklotrons, Vorstellung der "CYCLONE 18/9 & 10/5 USER COMMUNITY"

Bei vielen neurologischen und psychiatrischen Erkrankungen wie Alzheimer-Krankheit, Depression, Schizophrenie, Migräne usw. sind postmortem veränderte Serotonin Rezeptor-dichten im Gehirn nachweisbar. Die Entwicklung von spezifischen SUP>99mTc-Tracern für SPECT (Single- Photonen- Emissions- Tomo-graphie), mit denen derartige Veränderungen bereits im lebenden Organismus erkennbar wären, stellt daher einen wesentlichen Beitrag zur Diagnose dieser pathophysiologischen Veränderungen des serotoninergen Systems dar.

Ketanserin ist eine Leitsubstanz mit hoher Affinität zum Serotonin-(5-HT_2A) Rezeptor. In struktureller Analogie zu dieser Leitsubstanz wurde in den letzten Jahren eine Reihe von Tc-Koordinationsverbindungen synthetisiert, welche in Hemmexperimenten an Homogenaten des Rattenhirns Affinitäten mit K_i-Werten ( = Hemmkonstanten) unter 10 nM aufwiesen.

In dieser Arbeit wird die spezifische Bindung eines neuen hochaffinen ^99mTc Komplexes, der in Hirnregionen mit bekanntermaßen hoher 5-HT_2A Rezeptordichte eine subnanomolare Affinität (K_i = 0,5 nM) zum Rezeptor aufweist, autoradiografisch in verschiedenen Tierarten dargestellt. Als Methode wurde die Radioluminografie eingesetzt. Als Referenz für die autoradiografische Darstellung der 5-HT_2A-Rezeptordichte diente die In-vitro-Verteilung von [³H]Ketanserin und [¹⁸F]Altanserin in Hirnschnitten von Ratte und Schwein. Zur Bestimmung der Spezifität und Selektivität der Rezeptorbindung des untersuchten Tc-Komplexes wurden In-vitro-Hemmversuche mit den spezifischen 5-HT_2A Antagonisten Mianserin und Ketanserin, dem D₂ Antagonisten Haloperidol, dem 5-HT_1A Agonisten 8-OH-DPAT sowie dem alpha- und beta₁- adrenergen Rezeptoragonisten (±) Norepinephrin durchgeführt.

Die an Hirnhomogenaten bestimmte hohe Affinität und Spezifität für den 5-HT_2A Rezeptor wurde auch im Autoradiogramm bestätigt. Es zeigte sich die Anreicherung in 5-HT_2A rezeptorreichen Regionen wie Cortex frontalis, Nucleus olfactorius anterior und Nucleus caudatus-Putamen sowie eine Verdrängung der totalen Bindung durch Mianserin zwischen 38 und 42 % im Gesamtschnitt, 48 und 51 % im frontalen Cortex und 31 und 42 % im Striatum. Diese Werte entsprechen der mit [³H]Ketanserin erfaßbaren spezifischen Bindung an den 5-HT_2A Rezeptor. Eine hohe Selektivität des ^99mTc Komplexes besteht gegenüber dem 5-HT_1A Rezeptor, dem 5-HT- und dem Dopamin Transporter. Durch Verdrängungsexperimente mit Haloperidol wurde allerdings festgestellt,daß der Komplex auch eine Affinität für den D₂ Rezeptor aufweist.

Mit diesen Arbeiten gelang erstmals überhaupt,wenn auch In vitro, mit einem Tc-Komplex eine Bildgebung des 5-HT_2A -Rezeptors zu erreichen. Die Hirnaufnahme in der Ratte erwies sich allerdings noch als zu gering, um eine In-vivo-Darstellung erwarten zu lassen. Durch geeignete Modifikation der Verbindung wird ein besseres In-vivo-Verhalten angestrebt.

In ion beam analysis the decrease of the measuring signal with a number of incident ions, due to a destruction of the surface layer being analysed, depends critically
on the lateral intensity distribution in the analysing ion beam. For the assumption of destruction in one step, the decrease was calculated and the obtained analytical
formulae was fitted to the decrease as measured in ERDA and PIXE analyses. This allows to obtain values for the destruction cross sections for the ions and the
samples in the analysis, as well as information about the lateral intensity distribution in the analysing ion beam.

Molecular-dynamics calculations were performed to simulate ion beam deposition of diamond-like carbon films. Using the computationally efficient analytical potentials of Tersoff and Brenner we are able to simulate more than 10³ carbon atom impacts on {111} diamond, so that steady-state film properties can be computed and analyzed. For the Tersoff potential, we achieve sp³ fractions of approximately half of the experimentally observed values. For the more refined hydrocarbon potentials of Brenner the fraction of tetrahedrally coordinated atoms is much too low, even if structures with densities close to diamond are obtained. We show, that the sp³ contents calculated with Tersoff's potential are an artifact related to the overbinding of specific bonding configurations between three- and fourfold coordinated sites. On the other hand we can prove, that the range for the binding orbitals represented by the cutoff-function is too short in Brenner's parametrization. If an increased C-C interaction cutoff value is chosen, we achieve a distinct improvement in modeling the sp³ content of deposited ta-C films. As a result, we compute sp³ fractions which lie between 52 and 95% for the C⁺ ion energies E = 30-80eV and are in reasonable agreement to recent experimental studies.

Bei der Freimessung von Bauschutt aus dem Abriß von Nuklearanlagen sind für die Bestimmung der (gamma-und beta-Aktivivtät in-situ Messungen verfügbar. Eine direkte Messung der alpha-aktiven Nuklide im stehenden Gebäude ist auf Grund der geringen Reichweite der alpha-Strahlung und ihrer Absorption im Beton nicht möglich. Die im Rahmen dieses und der vorhergehenden Projekte entwickelten Methode der direkten alpha-Spektrometrie nach nur mechanischer Präparation des Betons ermöglicht eine Bestimmung der Actinide bis zu 0,02Bq/g in Multielementspektren. In einem aus zwei Schritten bestehendem Zerkleinerungsprozeß wurden mittlere Partikeldurchmesser von 0,5µm erreicht. Die Meßproben mit einem Durchmesser von 20cm und Schichtdicken zwischen 0,6 und 5µm wurden durch Sprühen aus der Betonsuspension auf Probenträger und anschließendes Trocknen hergestellt. Die Suspensionsstabilität (nachgewiesen durch Zeta-Potentialmessungen) wurde durch verschiedene Dispergatoren erreicht. Die Spektren der Meßproben wurden in einer Gitterionisationskammer aufgenommen. Durch die Verwendung von Standardbeton mit zugefügten Actiniden konnten die Selbstabsorption der alpha-Strahlung und die Peakform in Abhängigkeit der Probendicke ermittelt werden. Somit konnten die Spektren unbekannter Betonproben gleicher Geometrie entfaltet werden. Das für diese Arbeit entwickelte Programm WINKRUM basiert auf einem geometrischen Modell für Partikelgröße, Partikelverteilung und Packungsdichte. Mit Strahlungstransportberechnungen können Spektren simuliert werden, die ebenfalls eine Peakentfaltung von Multielementspektren ermöglichen.

A two-beam laser deflection system has been setup for real-time measurement of the stress in thin films during processing. The curvature of a Si-cantilever, laser reflectivity and real time spectroscopic ellipsometry data are recorded simultaneously. Reliable real time film thickness data are essential for the calculation of the instantaneous stress from the bending force per unit width measured. Instantaneous stress data with a depth resolution in the nanometer range provide detailed information on growth processes. It is demonstrated that force per unit width or global stress data, as calculated by applying the simple form of Stoney's equation, are not appropriate for the analysis of the stress in layered structures like boron nitride films.
The depth distribution of the instantaneous stress in boron nitride films recorded during growth by ion beam assisted deposition has been analyzed. The layer sequence of interfacial turbostratic BN layer / mixed (t-BN+c-BN) transition layer / cubic BN can be clearly identified in the instantaneous stress data. The instantaneous stress has been found to depend sensitively upon fluctuations in the boron deposition rate which in turn cause variations in the ion/atom arrival ratio. Real time global stress data recorded during ion implantation into c-BN films have revealed for the first time two mechanisms being involved.

Trinuclear complexes with bridging nitrido ligands between the rhenium atoms are formed when [ReN(Et2dtc)2(Me2PhP)] (Et2dtc- = N,N-diethyldithio-carbamate) reacts with TlCl or Pr(O3SCF3)3. [Cl(Me2PhP)2(Et2dtc)ReºN-Re(N)Cl2(Me2PhP)-NºRe(Et2dtc)(Me2PhP)2Cl] and [(Et2dtc)2(Me2PhP)ReºN-Re(N)-(Et2dtc)(Me2PhP)-NºRe(Me2PhP)(Et2dtc)2]+ contain two almost linear, asymmetric nitrido bridges. Additional, terminal nitrido ligands are located at the middle rhenium atoms.

The reaction of dibenzenediselenide, (SePh)2, with mercury in refluxing xylene gives bis(benzeneselenolato)mercury(II), [Hg(SePh)2], in a good yield. (nBu4N)[Hg(SePh)3] is obtained by the reaction of [Hg(SePh)2] with a solution of [SePh]- and (nBu4N)Br in ethanol. The solid state structures of both compounds have been determined by X-ray diffraction.
The mercury atom in [Hg(SePh)2] (space group C2, a = 7.428(2), b = 5.670(1), c = 14.796(4) Å, b = 103.61(1)°) is linearly co-ordinated by two selenium atoms (Hg-Se = 2.471(2) Å, Se-Hg-Se = 178.0(3)°). Additional weak interactions between the metal and selenium atoms of neighbouring molecules (Hg···Se = 3.4 - 3.6 Å) associate the [Hg(SePh)2] units to layers.
The crystal structure of (nBu4N)[Hg(SePh)3] (space group P21/c, a = 9.741(1), b = 17.334(1), c = 21.785(11) Å, b = 95.27(5)°) consists of discrete complex anions and (nBu4N)+ counter ions. The coordination geometry of mercury is distorted trigonal-planar with Hg-Se distances ranging between 2.5 and 2.6 Å.

The synthesis of hitherto unknown 1-benzoyl-1´,3´,3´-trimethyl-4,6-diphenylspiro[1,2-dihydropyridine-2,2´-indolines] 5 from 2,4,6-triphenyl-1,3-oxazinium tetrafluoroborate (1b) and 1,3,3-trimethyl-2-methylene-indolines 2 (used as such or generated in situ from the corresponding 3H-indolium salts 4) in the presence of triethylamine in anhydrous acetonitrile by a 3,6-[C3N+C2] 1,3-oxazinium ring transformation is reported. Structure elucidation is performed by an X-ray structure determination of the spiro[dihydropyridine-indoline] 5a. Spectroscopic data of the transformation products and their mode of formation are discussed.

Double differential cross sections of fragment production in 1 GeV proton interactions with carbon were measured with a two-arm spectrometer installed at 30° and 126° with respect to the proton beam line of the PNIP synchrocyclotron. Mass and charge identifications of the fragments were performed by time-of-flight and Bragg spectroscopy methods for both registration angles. The obtained kinetic energy spectra were reproduced by moving source fits with a Maxelllian-like emission pattern.

The suitability of pattern recognition for safety diagnosis of chemical plants is discussed. Experiments in a miniplant and with a process simulator are carried out. The process characteristics are treated with different recognition methods and classified with the aid of expert know how. Afterwards, the trained system can be used for process diagnosis. The capability of neural networks for this problem can be shown.

Huminsäuren (HS) spielen aufgrund ihrer guten Löslichkeit im pH-Bereich natürlicher Wässer sowie aufgrund ihres hohen Komplexierungsvermögens eine entscheidende Rolle innerhalb von natürlichen Wechselwirkungsvorgängen. Dazu gehören Wechselwirkungs-prozesse von HS mit Metallionen, z. B. Actinidionen, welche die Speziation der Actinidionen und daraus folgend das Migrations- bzw. Retardationsverhalten dieser Schadstoffe beeinflussen. Die Untersuchung der Wechselwirkung von HS und Actinidionen ist unbedingt erforderlich, z. B. für die Erstellung von Langzeitsicherheitsabschätzungen potentieller Endlager für nuklearen Abfall sowie für unter- und obertägige Einrichtungen des früheren Uranerzbergbaus in Sachsen und Thüringen. Aufgrund der heterogenen Natur der HS ist jedoch die genaue Beschreibung ihres Komplexbildungsverhaltens mit Metallionen schwierig.
In Fortsetzung unserer früheren Untersuchungen1,2 wollen wir die Kenntnisse zur Wechselwirkung von HS mit Metallionen erweitern. Dazu untersuchten wir den Einfluß phenolischer OH-Gruppen auf das Komplexbildungsverhalten von HS mit Uran(VI). Ausgehend von einer synthetischen HS (Typ M11) und zwei natürlichen HS (Aldrich, Kranichsee3) synthetisierten wir modifizierte HS mit blockierten phenolischen OH-Gruppen. Die partielle Blockierung der phenolischen OH-Gruppen wurde mit einer radiometrischen Methode zur Bestimmung der Huminsäurefunktionalität sowie FTIR-spektroskopisch nachgewiesen. Mittels zeitaufgelöster laserinduzierter Fluoreszenzspektroskopie untersuchten wir in Lösung das Komplexbildungsverhalten der modifizierten HS mit blockierten phenolischen OH-Gruppen mit UO22+-Ionen im Vergleich zu den nicht modifizierten HS. Für die modifizierten HS vom Typ M1 und Aldrich bestimmten wir signifikant kleinere Beladungskapazitäten mit UO22+-Ionen als für die entsprechenden originalen HS. Dieses Ergebnis weist daraufhin, daß die Blockierung der phenolischen OH-Gruppen das Komplexbildungsverhalten der HS in Lösung verändert.
Weiterhin führten wir mittels FTIR- und EXAFS-Spektroskopie Strukturuntersuchungen an festen Uranyl-Humat-Komplexen der modifizierten und nicht modifizierten HS durch. Mit der FTIR-Spektroskopie erbrachten wir den Nachweis für die Komplexierung von UO22+-Ionen durch die HS. Als Ergebnis der EXAFS-Untersuchungen bestimmten wir für die festen Uranyl-Humat-Komplexe Strukturparameter, d.h. axiale und äquatoriale Bindungsabstände zwischen Uran und Sauerstoff.

Theoretically, the reaction of the tridentate aminedithiol ligand EtN(CH₂CH₂SH)₂, L1H₂, and the monodentate thiol 4-ClC₆H₄SH, L2H, with the Re^VOCl₃(PPh₃)₂ may lead to the formation of the following complexes: (i) neutral mixed ligand complexes ReOL1L2 (the syn isomer, complex 1 and the anti isomer, complex 2, (ii) binuclear complex of the tridentate ligand, (MO)₂(L1)₃, complex 3, and (iii) anionic complex of the monothiol [MO(L2)₄]^-, complex 4. When a mixture of L1H₂/L2H, 1/1 ratio, is applied, the major product of the reaction is the syn isomer 1. A small amount of the anti isomer 2 is also isolated (yield < 2 %) while none of the complexes 3 and 4 form during the reaction under the above conditions. The oxorhenium complexes 3 and 4 have been synthesized by the reaction of L1H₂ or L2H with the precursor ReOCl₃(PPh₃)₂. The crystal structure of 1, 3, and 4 is determined by X-ray crystallography. The corresponding Tc-99m complexes have been prepared by exchange reaction using Tc-99m glucoheptonate as precursor. Similarly the major reaction product is the syn isomer, complex 1´, while none of the other complexes form during the reaction at tracer level. The above studies demonstrate that simultaneous action of a tridentate SNS ligand and a monodentate thiol in equimolar quantities on Re^VOCl₃(PPh₃)₂ or Tc-99m glucoheptonate leads to a single rhenium or technetium-99m species, the syn MOL1L2.

Thermoanalytische Untersuchungen (TG, DTA, DSC) haben sich als Methoden zur qualitativen Identifizierung und strukturellen Charakterisierung der Huminstoffe bewährt. In der vorliegenden Arbeit werden der exotherme, oxiadative Abbau unter Sauerstoff und die endotherme, thermische Zersetzung unter Stickstoff untersucht.
Die auf die Änderungen des thermischen Verhaltens empfindlich reagierenden DTA Diagramme zeigen für die Huminsäuren (HS) und ihre Metallkomplexe den ähnlichen strukturellen Aufbau eines endothermen Peaks bis 150°C und von zwei bzw. drei exothermen Peaks bis 500°C mit individuellen Unterschieden der Temperaturlagen und der Umsatzraten der einzelnen Teilreaktionen. Auf diese Weise wurden z. B. HS von Aldrich®, HS aus Gartentorf und HS aus dem Wasser des Hochmoors "Kleiner Kranichsee" bei Johann-georgenstadt deutlich differenziert. Mit Hilfe der ermittelten H : C und O : C Verhältnisse der gasförmigen Thermolyseprodukte konnten die in den Teilreaktionen abgebauten Gruppen hinsichtlich ihrer atomaren Zusammensetzung näher spezifiziert werden. So sind z. B. die Fulvinsäuren gegenüber den HS gleicher Herkunft durch einen höheren Gehalt an wasserstoff- und sauerstoffreichen Gruppen gekennzeichnet.
Die von uns präparierten synthetischen HS vom Melanoidintyp wurden thermoanalytisch mit natürlichen HS verglichen und als geeignete Funktionsmodelle für die natürlichen HS bestätigt. Die DTA Diagramme sind bei beiden ähnlich strukturiert. Auffällige Analogien wurden dabei zwischen der HS aus Torf und den synthetischen HS festgestellt, während die HS aus dem Wasser des Hochmoors "Kleiner Kranichsee" mehr der Aldrich HS ähnlich ist.
Chemische Eingriffe in das Makromolekül verändern das thermische Verhalten in charakteristischer Weise. Bereits das übliche Abtrennungs- und Reinigungsverfahren für HS durch Lösen in Natronlauge und Fällung mit HCI erhöht ganz entscheidend deren Reaktionsfähigkeit und setzt die thermische Stabilität stark herab. Die Methylierung der phenolischen OH Gruppen und der Carboxylgruppen der HS dokumentiert sich in einer signifikanten Verstärkung des ersten exothermen Peaks bis 350°C, der für den Abbau der wasserstoffreichen, aliphatischen Gruppen charakteristisch ist. Zugleich wird die thermische Stabilität dieser Huminstoffe durch den Eingriff geringfügig erhöht.
Deutliche Veränderungen der DTA Diagramme werden durch die Bindung von Metallionen über die Carboxylgruppen der HS bewirkt. Dabei wird die thermische Stabilität des Makromoleküls stark herabgesetzt. Dieser Effekt ist für den Fe(III)-HS-Komplex deutlich stärker als für den UO22+-HS-Komplex. In beiden Fällen ist er konzentrationsabhängig und wächst mit steigender Menge des gebundenen Metalls, die ebenfalls thermoanalytisch bestimmt wurde. Da dieser Effekt den Komplexbildungskonstanten direkt proportional ist, ist anzunehmen, daß intramolekulare Spannungen für die thermische Destabilisierung verantwortlich sind, die durch die Bindung der Metallionen in das Makromolekül eingebracht werden. Sie sind um so stärker, je fester das Metall gebunden ist.

Durch Reaktion fester, vorwiegend ungelöster natürlicher und synthetischer Huminsäuren mit wässerigen Metallsalzlösungen wurden in heterogener Phase feste Huminsäurekomplexe synthetisiert. Hierfür wurden als natürliche Huminsäuren die aufgereinigte Huminsäure der Fa. Aldrich und die aus dem "Kleinen Kranichsee" (Johanngeorgenstadt, Erzgebirge) gewonnene, aquatische Huminsäure eingesetzt. Als synthetische Huminsäure wurde eine Melanoidinfraktion mit huminsäureartigen Eigenschaften (M1) verwendet /1/. Die Komplexierungen erfolgten mit den umweltrelevanten Metallionen UO22+, Fe3+, Ca+ und Mg2+ sowie mit natürlich vorkommenden Mineralen, in denen Uran(VI), Calcium und Magnesium als Carbonatokomplex vorliegt.
Es wurden Humate mit unterschiedlicher Metallbeladung gewonnen, indem der pH-Wert des Reaktionsgemisches und die stöchiometrischen Verhältnisse der Reaktionspartner variiert wurden. Die Konzentration der Huminsäure wurde dabei auf die COOH-Äquivalente bezogen. Durch Konkurrenzreaktionen mit Gemischen unterschiedlicher Metallkationen und Kationenaustausch-reaktionen an definierten Metallhumaten mit "freien" Kationen konnte die unterschiedliche Affinität von Eisen gegenüber natürlichen und synthetischen Huminsäuren nachgewiesen werden.
Am Beispiel der Umsetzung freier Huminsäuren mit den gemischten Carbonatokomplexen von Uran(VI) und Calcium (Liebigit) bzw. Uran(VI) und Magnesium (Bayleyit) wurden natürliche Komplexierungsvorgänge simuliert.
An den synthetisierten Metall-Humat-Komplexen wurden Strukturuntersuchungen mit Hilfe von FTIR /2/ sowie EXAFS /3/ und ESCA /4/ durchgeführt und die thermische Stabilität durch Thermische Analyse /5/ bestimmt.

Im Vortrag werden Versuche zum reaktiven Stoffübergang über die Phasengrenze zweier nicht mischbarer Lösungsmittel und die dabei auftretenden hydrodynamischen Instabilitäten sowie die numerische Simulation dieser Vorgänge in einer vertikalen Spaltgeometrie vorgestellt.

Spontane Grenzflächenkonvektionen an fluiden Phasengrenzen führen beim Stoffübergang zu einer signifikanten Erhöhung der pro Zeiteinheit übertragenen Stoffmenge. Zwei Mechanismen, die Rayleigh-Bénard- und die Marangoniinstabilität, sind für die Entstehung dieser Konvektionen verantwortlich. Gegenstand der Arbeit sind Stoffaustauschvorgänge, die von exothermen chemischen Reaktion begleitet werden. Diese führen zur Ausbildung von Konzentrations- und Temperaturgradienten im Bereich der fluiden Phasengrenze. Grenzflächenkonvektionen treten als Folge der Kopplung von Stoff-, Energie- und Impulstransport auf. Bei einfachen Neutralisationsreaktionen an der Phasengrenze konnte eine Vielzahl unterschiedlicher Konvektionsstrukturen festgestellt werden.

In einem vertikalen Spalt (Breite=1mm) wurden zwei miteinander begrenzt mischbare Lösungsmittel (Wasser und Isobutanol bzw. Cyclohexan) übereinandergeschichtet. In der leichteren organischen Phase liegt eine Fettsäure (Ameisen-, Essig- oder Propionsäure), in der schwereren wässrigen Phase Natronlauge vor. Der Stoffübergang der Fettsäure erfolgt von der organischen an die wässrige Phase. Daran schließt sich unter Wärmefreisetzung die Neutralisationsreaktion in unmittelbarer Nachbarschaft der Phasengrenze an.

Im Verlauf des reaktiven Stoffübergangs durchläuft das System 3 Stadien. Das Anfangsstadium ist von aufsteigenden Plumes (pilzförmige Bereiche von Fluid geringerer Dichte) in der organischen Phase gekennzeichnet. Das Zwischenstadium wird von Plumes in der oberen Phase und der unregelmäßigen Bildung von Fingern in der unteren Phase bestimmt. Das Plume-Regime der oberen Phase wird zunehmend ungeordneter und löst sich im weiteren Verlauf auf. Im Endstadium hat sich in der unteren Phase ein regelmäßiges Fingerregime ausgebildet. Dieses Regime ist charakteristisch für die doppelt-diffusive Instabilität, die hier durch die unterschiedlichen Diffusivitäten von Wärme und Stoff sowie die Überlagerung zweier die Stabilität gegensätzlich beeinflussender Gradienten verursacht wird. Die Fingerinstabilität ist von der thermohalinen Konvektion, dem Transport von Salz und Wärme in Ozeanen her bekannt und stellt einen sehr effizienten Mischungsvorgang dar. Sowohl Plume- als auch Fingerinstabilität sind verantwortlich für die sich selbst erhaltende Dynamik des Systems, die im Experiment über 2 Stunden lang beobachtet werden konnte.

Numerische Untersuchungen werden mit dem Ziel durchgeführt, die beobachteten Transportvorgänge durch ein 2D-Modell, das die Bilanzgleichungen für Stoff, Energie und Impuls berücksichtigt, nachzubilden. Die Abbildung zeigt die zeitliche Entwicklung des Stoffstroms durch die Phasengrenze für den reaktiven und den reaktionsfreien Stoffübergang von Essigsäure. Nach anfänglich diffusivem Stoffübergang werden die Konzentrationsgrenzschichten instabil und es setzen Konvektionsbewegungen ein. Diese führen zum sprunghaften Ansteigen des Stoffstroms. Durch die Kombination solutaler und thermischer Effekte fällt dieser Anstieg beim reaktiven Stoffübergang wesentlich stärker als beim nichtreaktiven aus. Die Fluktuationen der dargestellten Größe resultieren aus dem instationären Charakter des konvektiven Stoffübergangs.

The water of a mine drainage gallery was investigated for its contents of colloid-borne heavy metals with empha-sis on uranium. About 1 mg/L of colloid particles of 100 to 300 nm in size were found. They consist of a matrix of Fe and Al oxyhydroxides and are formed when anoxic slightly acidic shaft waters mix with oxic near-neutral gal-lery water. The colloid matrix bears toxic trace elements metals such as As, Pb, and Cu. Carbonato and aquo complexes prevent the uranyl from being adsorbed to the colloids in the unaltered gallery water. Acidification destroys these complexes: up to 50 mass percent of the uranium is attached to the colloids in the slightly acidic pH region. Further acidification converts the uranyl again to a "non-colloidal" form. The heavy metals are most likely bound to the Fe and Al colloids as inner sphere surface complexes.

Boron nitride films have been grown by ion beam assisted deposition (IBAD) using a Kaufman ion source and an electron beam evaporator. Cantilevers made from <100> Si have been used as substrates. Instantaneous stress data are derived from dynamic simultaneous measurement of cantilever bending and film thickness during growth. The instantaneous stress in t-BN layers is found to increase with film thickness and to be in the range between 1.6 and 4.2 GPa. At the nucleation of c-BN the stress increases up to about 10 GPa and remains constant during c-BN growth. Correlations between the ion to atom arrival ratio and the Ar/N2 ratio and the instantaneous stress are discussed. The stress relaxation during Ar+-ion post implantation has been measured.

An improved stress-measuring technique based on the cantilever bending principle is presented. Thermal shift of the sample holder position that results in errors in the stress data is minimised by evaluating the difference in the deflection of two laser beams. The film thickness is calculated from the reflected laser intensity or from ellipsometry data recorded simultaneously during film growth. Without using a lock-in technique or image processing, the resolution in bending force-per-unit-width is 0.02 N/m for a 50 µm thick cantilever. The system represents an easy, versatile and cheap technique to measure intrinsic and thermal stresses in thin films. The system has been employed to record the instantaneous stress during ion beam assisted deposition of BN films and the global stress during ion induced amorphisation of silicon.

Hard CNx films were prepared by nitrogen ion beam assisted deposition (IBAD) of evaporated carbon on silicon wafers with a nitrogen ion energy of 100 to 1200eV, ion/neutral transport ratios from 0.7 to 1.7, and deposition temperatures from RT to 1000°C. The films were characterised by ERDA, XPS, TEM, ED, EELS, and nanoindentation.
By varying the deposition parameters a maximum nitrogen content of < 33 at.% was found at N/C transport ratios of about 1.2. Further increase of this ratio did not result in a higher nitrogen content in the films. XPS measurement reflects a shift of the main chemical state of the nitrogen bonds with changing nitrogen content of the films and with increasing deposition temperature. The nitrogen content of the films was drastic decreased with increasing temperatures > 600°C.
EELS investigations have shown weak changes of the plasmon peak position and the sp2/sp3 ratio with increasing deposition temperature in correlation to the nitrogen content of the carbon films.
Nanoindentation techniques have been used to investigate the mechanical properties such as hardness and elastic modulus of the films. High hardness and elastic modulus values for those composites have been found. All measured structural and mechanical properties correlate with the analysed nitrogen content.

Titanium aluminide alloys based on gamma-TiAl have a substantial potential for high temperature application. However, there are still problems concerning the high temperature oxidation behavior. Ion implantation is a promising tool to improve the oxidation resistance without disturbing the mechanical properties. A systematic investigation of the microstructure and phase development of silicon and molybdenum implanted gamma-TiAl is presented. For Si, the fluence is varied from 2.5·10¹⁶ cm^-2 to 8·10¹⁷ cm^-2 at an implantation energy of 1 MeV resulting in a local con-centration of Si between 1 at% and 35 at% at a projected range of 1 µm measured by AES depth profiling. Grazing incidence XRD and transmission electron microscopy show the formation of a buried Ti_5Si3 enriched layer at 650 °C, which acts as a diffusion barrier for oxygen. Long term TGA oxidation tests at 900 °C in air show a positive effect in the beginning of oxi-dation for the fluence of 8·10¹⁷ cm^-2. After a few hours the oxidation kinetic is similar to unimplanted Ti50Al, but the mass gain after 100 h is still 30 % smaller. The influence of the local Si concentration on the oxidation behavior is discussed. Implantation of Mo at 180 keV (2·10¹⁶ cm^-2 and 1·10¹⁷ cm^-2) has only minor influence on the oxidation at 900 °C. After implantation, Mo precipitates are found for the high fluence.

Zur Bewertung der strukturellen Integrität von Bauteilen werden auch Festigkeitskennwerte unter schlagartigen Belastungsbedingungen benötigt.
Eine Möglichkeit dynamische Festigkeitskennwerte abzuschätzen, bietet die Berechnung der dynamischen Fließ- und Biegebruchspannungen aus den nach ISO/CD 14 556 im instrumentierten Kerbschlagbiegeversuch bestimmten charakteristischen Kräften. Üblicherweise werden die Festigkeitswerte unter Schlagbiegebelastung nach einem Vorschlag von SERVER (1978) berechnet. Dieser Vorschlag wurde aus einer Lösung der Fließlinientheorie nach EWING (1968) abgeleitet.
SERVERs Formalismus gilt für ISO-V-Proben, die mit einer ASTM-Finne belastet werden, da die Zusammenhänge durch EWING (1968) für diese Belastung hergeleitet wurden. Bei Anwendung einer DIN/ISO-Hammerfinne (r=2 mm) ist aber davon auszugehen, dass sich für gekerbte Proben ungefähr 5 % und bei zusätzlicher Berücksichtigung einer größeren Stützweite 9 % höhere Festigkeitswerte ergeben können.