Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The β decay of ⁹⁶Ag (Z=47,N=49) was investigated by measuring positrons, X rays as well as β-delayed protons and γ rays. The γ radiation was studied by means of germanium detectors and a NaI total-absorption spectrometer. Two β-decaying isomers in ⁹⁶Ag were established with half-lives of 4.40(6) and 6.9(6) s and tentative spin–parity assignments of (8⁺) and (2⁺), respectively. For both isomers, the intensities of β transitions to low-lying levels of ⁹⁶Pd (Z=46,N=50) and β-delayed proton decays to levels in ⁹⁵Rh (Z=45,N=50) were measured. Several new ⁹⁶Pd levels were firmly established. The level energies, their γ decays and the Gamow–Teller decay of ⁹⁶Ag are compared to shell-model predictions. A new low-lying level in ⁹⁵Rh was found at 680 keV excitation energy. Through a comparison with low-lying states of N=50 isotones, this level is interpreted as the first excited 7/2⁺ state built on the proton 9/2⁺ ground state. The assignments of further excited states in ⁹⁵Rh are discussed.

kein Abstract

Microorganisms and their biocomponents affect the mobility and toxicity of radionuclides through solubility and speciation changes, biosorption, bioaccumulation or other bio-transformations. In this paper we report structural information on the uranium complexes formed by different bacterial isolates from uranium mining waste piles and by their purified biocomponents. EXAFS fits indicate that for B. sphaericus JG-A12 U(VI) is coordinated to carboxyl groups in a bidentate arrangement (RU-C= 2.91 ± 0.02 Å), and to phosphates in a mondentate fashion (RU-P = 3.59 ± 0.02 Å). For the other bacteria strains belonging to A. ferrooxidans, S. maltophilia, P. stutzeri, and P. migulae species U (VI) was bound only to phosphate (RU-P = 3.63 ± 0.02 Å). Because of the ability of the strain B. sphaericus JG A12 to bind selectively and reversibly U and other heavy metals, it was chosen for construction of so called biological ceramics (biorers) for bioremediation of metal-polluted waters. The sorption of U(VI) by the biocers occurs mainly via silicate and phosphate groups. The SiO2-matrix alone binds U (VI) via hydroxyl (water molecules) and silicate groups.

Uranium mining waste pile environments are rich in uranium and heavy metals. In addition, they are a reservoir of a large variety of metal-resistant microorganisms. These natural microbial populations are able to influence dissolution and/or precipitation of actinides. The overall goals of this work are to identify the key interactions between uranium and the strains JG-2 and JG-7B isolated from a uranium mining waste pile situated near the town of Johanngeorgenstadt in the Southeast of Germany. Phylogenetic analysis of these strains revealed that they are related to Stenotrophomonas maltophilia and Bacillus sphaericus. As estimated by using ICP-MS these natural isolates possess high ability to accumulate uranium and other heavy metals such as Cd, Pb, Ni and Ag. The Extended X-ray Absorption Fine Structure (EXAFS) analysis of the uranium complexes formed by these isolates demonstrated that the U(VI) is coordinated 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. Transmission Electron Microscope (TEM) and Enery-Dispersive X-ray (EDX) analysis demonstrated that the uranium accumulated by S. maltophilia JG-2 is located at the cell wall and in the cytoplasm. In the case of B. sphaericus JG-7B the uranium was located only in the cell wall. 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 two different bacterial strains studied in this work. The results may ultimately help to develop effective methods for remediation of heavy-metal-polluted environments.
This work was supported by grant No.03I4004B from the Bundesministerium für Bildung und Forschung, Germany.

An important factor to influence the microstructure of a metallic alloy is the convection in the melt during the solidification process. The application of time varying magnetic fields can be considered as an effective tool to organise a well-defined flow structure in the liquid phase affecting the nucleation and growth process. The aim of our work is to improve the understanding of the basic mechanisms allowing us to find a strategy to refine the microstructure of castings by an optimal combination of magnetic field intensity, field frequency and cooling rate.
Directional solidification experiments were carried out with a Pb85wt%Sn alloy contained inside a cylindrical crucible with a diameter of 50 mm. A melt height of 60 mm was chosen. The container bottom is positioned on a water cooled copper chill allowing a directed solidification by a vertical heat flux. A rotating magnetic field was generated by an inductor system with 6 coils. A maximum field amplitude up to 25 mT can be applied. The frequency of the field can be varied between 10 and 400 Hz.
Local temperatures were determined during the solidification process using a set of thermocouples. Cooling curves measured at different locations inside the sample reveal the significant influence of the electromagnetic convection on the local heat transfer. Profiles of the melt velocity were obtained applying the ultrasonic Doppler method..
The Pb-85wt%Sn alloy shows a microstructure with primary tin-crystallites and eutectic. Specimens solidified without a rotating magnetic field showed a columnar dendritic microstructure which is orientated in heat flux direction. The tin crystallites and the eutectic are homogeneously distributed over the whole sample. If the alloy solidifies in a rotating magnetic field the microstructure changes. The shape of the dendrites changes from columnar to equiaxed in direction from the bottom to the top of the specimen and in the same direction the volume content of the eutectic increases.
Numerical calculations were performed using a continuum two-phase model for the directional solidification of a binary alloy. The model includes mass, momentum, energy and species mass conservation equations written in compressible form in order to be able to model shrinkage flow. The Lorentz force term has been included into the momentum conservation equation in order to take into account the effect of the applied magnetic field. The temperature-solute coupling has been described by conduction dominated solidification rule. The two-phase mushy zone has been treated by means of a porous medium approach.
The system of equations has been solved by means of a Finite Volume method. SIMPLE algorithm was used. The results are compared with numerical solutions for diffusion dominated solidification of PbSn and with the data obtained from the experiment.
It was demonstrated by the numerical simulations that a rotating liquid phase forms a mushy zone front showing a convex shape with the maximum on the axis of rotation. This phenomena is confirmed by the experiment.

Various types of AC magnetic fields are already used as stirrers in liquid metal processing. We distinguish between rotating, travelling and pulsating magnetic fields depending on the coil arrangement and the number of phases of the coil currents. Considering the melt motion driven by each of these AC fields in a cylindrical cavity, the basic flow structures are well-known. As a common feature, they typically consist of a rather rigid flow configuration providing only a limited mixing of the melt. Instead a three-dimensional mixing is often needed in metallurgical applications, for instance, in order to dissolve alloying agents or to submerge lighter parts into the melt.

We report on model experiments for the electromagnetic stirring of liquid metals in a cylindrical cavity using a rotating and a travelling magnetic field. The eutectic melt InGaSn in a cylindrical cavity of aspect ratio 1.5 has been used. Velocity measurements are performed using both the ultrasonic Doppler velocimetry (UDV) as well as local potential probes. UDV delivers profiles of the vertical velocity component. In the case of the rotating magnetic field this component represents only a weak secondary flow compared to the primary azimuthal rotation. In case of a separate action of the two field types, the expected flow fields have been found. An efficient mixing can be obtained by a combination of the two field types. Velocity measurements will be presented demonstrating this behaviour.

During last decades magnetohydrodynamic (MHD) effects have attracted growing interest because of its potential impact on numerous industrial technologies. In processes involving electrically conducting liquids, the application of an external magnetic field offers efficient opportunities for a contactless flow control and fluid handling. However, for a well-aimed optimisation of the flow structure local information about flow quantities like velocity, pressure, temperature, concentration or void fraction is necessary. In case of liquid metals the choice of a suitable measuring technique is a crucial problem, because the user is confronted with the problems of opaque fluids, high temperatures as well as a strong chemical reactivity of the fluid against many materials. Therefore, measuring techniques well-known from ordinary hydrodynamics generally fail for liquid metal applications. As a consequence, no commercial measuring systems are available for liquid metal applications.
We present a summary of our R&D activities on velocity measuring techniques for liquid metal flows. Various model experiments with various liquid melts at different temperatures have been performed to test and evaluate local sensors as well as integral methods.
A mechano-optical probe was developed which has to be positioned directly inside the liquid metal flow. The measuring principle is based on the separation of a direct mechanical interaction between flow and sensor tip and the optical acquisition and processing of the signal. The insensitivity of the system to electrical noise and external magnetic fields can be considered as an important advantage. Until now, the sensor has been tested in metallic melts up to temperatures of about 450 °C, but an extension up to 800°C should be straightforward.
The ultrasound Doppler velocimetry (UDV) represents a powerful tool since it delivers a full velocity profile along the ultrasonic beam. It can operate with a direct contact to the melt, but also through a channel wall. To overcome the thermal restriction of the ultrasonic transducers an acoustic wave guide has been used. The acoustic wave guide and the piezoelectric element are combined in form of an integrated sensor. This approach allowed the first successful application of the ultrasound Doppler technique in liquid metals at temperatures above 200°C. The feasibility of this integrated sensor concept was demonstrated in experiments in metallic melts as sodium, PbBi, CuSn or aluminium.
In some applications even a coarse knowledge of the flow topology and the direction of the main eddies would be of high value. We study the possibility of velocity reconstruction in electrically conducting fluids from external measurements of induced magnetic fields. The method is based on the fact that an external magnetic field is deformed by the motion of the fluid. Applying the primary magnetic field in two different directions and measuring the related induced magnetic fields at an array of Hall probes, the three-dimensional velocity field can be reconstructed. Besides some theoretical basics, we present experimental results of a demonstration experiment.

Induction heating is widely used in metals processing. In many cases, additional wishes exist for the flow structure in the melt and the heat and mass transport processes connected with it. The induction heating itself causes a flow in the melt which in a cylindrical configuration typically consists of a double vortex driving the flow on the melt surface radially outwards.
We present the solution of a two-phase stirrer which allows a flexible control of the melt motion in addition to the induction heater. In order to demonstrate this approach, we consider the case of a float-zone arrangement working with an RF induction heater. The two-phase stirrer basically consists in an additional coil superimposed to the primary induction coil. The additional coil is not connected to any power supply, but it is part of a secondary circuit with adjustable capacitor and resistance. The current in the secondary coil is solely induced by the primary coil. In that way, an electromagnetic pump is created. Its intensity and resulting flow direction can easily be adjusted to the process needs. The flexible system parameter are the location and distance of the secondary coil with respect to the primary one, and the capacitor and resistance of the secondary circuit.
We present numerical and experimental results for two applications: the float-zone crystal growth of Ni-based single crystals, and the solidification of the magnetic material NdFeB under varying flow conditions at the solidification front. In the first case, the main interest is directed to a change of the phase boundary geometry in order to obtain a single crystal at all. In the second case, the interest is focused on the microstructure of the solidified material resulting from strongly differing flow conditions in the molten phase. Compared to the usual induction heater, the two-phase stirrer allows to provide a much stronger flow in both directions, i.e. radially inwards or outwards at the solidification front, or an almost stagnant melt. The theoretical part contains the solutions of the electromagnetic problem and the heat & fluid flow equations with a free form of the solid-liquid interface. Experimental results will be given for the resulting phase boundary in single crystals of Ni97Si3, and the convection influenced microstructure of NdFeB alloys.

We present results on the design and application of a DC magnetic field in order to control the filling process of the investment casting of aluminium alloys. The configuration basically consists in a U-bend, and the main request is to reduce the high flow velocities during the starting phase of the filling process. They are considered as the main source of problems like bubble or inclusion entrapment.
At first, the process was simulated using a plexiglas model and the eutectic melt InGaSn which is liquid at room-temperature. Local velocity measurements have been performed using the ultrasonic Doppler velocimetry, whereas flow rates have been determined independently using the contact-less transmitter technique. Measurements and video visualizations clearly show effects like flow rate oscillations or gas bubble entrapment. Depending on geometric and process parameters, the time-scale to get rid of these entrapments may become longer than the process itself. In order to decrease the maximum values of the velocity at the beginning of the process, an external steady magnetic field has been applied. The measurements show that it is capable of reducing the velocity peaks significantly.
Numerical simulations have been performed for the filling process with DC magnetic field control. The free surface problem which occurs in the riser of the casting process is taken into account by a Volume of Fluids Method. The simulations have been compared to the model experiments, and afterwards scaled up to the realistic aluminium casting process. For the influence of the DC magnetic field, a good agreement is obtained between numerics and measurements.
Real tests have been performed with molten aluminium at an industrial investment caster. They clearly show the primary action of the magnetic field, i.e. to reduce the velocity peaks at the beginning of the process. In a second set of experiments the amplitude of the DC field has been adapted in such a way that at the beginning of the process the full breaking action takes place, whereas the field strength has been reduced during the course of the filling process. In this regime, a clear reduction of the peak velocities is obtained with an only slight increase of the overall filling period.
For the flow rate measurement in a pipe, a contact-less solution based on a pair of alternating magnetic field transmitter and receiver has been developed. Test results from a laboratory model and the industrial Al casting process will be presented.

The influence of melt convection on the microstructure formation of Nd-Fe-B alloys, mainly the volume fraction and grain size of the a-Fe phase, has been investigated experimentally using the electromagnetic levitation technique and a specially designed floating-zone arrangement. Samples were subjected to a strong rotation during levitation and compared to fixed samples without additional sample rotation in the levitation facility. A controlled influence on the melt flow is possible via tailored magnetic fields which enable enhancement or suppression of the melt convection using the floating-zone arrangement. A specially designed magnetic two-phase stirrer offers a strong influence on the melt flow in the floating-zone facility. 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 in both types of experiments. The melt flow in a levitated droplet was studied numerically under the additional effect of a global sample rotation giving rise to the assumption of strong suppression of internal motions. The electromagnetically driven flow in the inductively heated melt zone of the floating-zone arrangement turned out to be of strong influence on the resulting microstructure. Numerical simulations are essential in order to understand and design the various flow structures.

The performance and in-beam imaging capabilities of two Hamamatsu avalanche photodiode arrays (S8550) individually coupled to crystals of cerium-doped lutetium oxyorthosilicate (LSO) are presented. The two detectors were operated in coincidence at the GSI medical beam line of the Gesellschaft für Schwerionenforschung, in Darmstadt, Germany. In a first set of experiments their imaging performance was tested before, during and after the irradiation of phantoms of polymethylmethacrylate with carbon ion beams with fluences equivalent to 1000 typical daily therapeutic fractions. Only minor energy, time and spatial resolution deterioration was observed, with the initial values being recovered after stopping the irradiation. A second set of experiments successfully imaged the depth distribution of positron emitter radionuclides created in a phantom that stopped the high energy carbon ion beam. The particular details for the in-beam PET acquisition are shortly outlined. The obtained results show that LSO is a suitable material for in-beam PET and that its coupling with avalanche photodiode arrays is feasible for a PET system dedicated to in-beam monitoring of ion therapy.

The response of pig lungs to irradiation with ¹²C-ions was assessed in two experiments to validate the procedures for heavy ion therapy planning at the Gesellschaft für Schwerionenforschung (GSI) and to explore their range of applicability. In both experiments, the target volume (spread-out Bragg peak, SOBP) was planned to be a 4 cm long cylinder with a diameter of 4 cm. Doses in the SOBP were prescribed to be equivalent to 5x4 Gy, 5x5.5 Gy and 5x7 Gy of x-rays in the first experiment, and to 5 fractions of 7 Gy and 9 Gy in the second experiment. The lung response in the first experiment was less than exepted on the basis of earlier experiments with photons. Pneumonitis reaction and chronic fibrotic changes were observed outside the prescribed high-dose region. In the second experiment, the effects were more pronounced than had been expected on the basis of the first experiment. Changes were most intense in the high-dose region, but were also seen troughout the lung along the beam channel. Moreover, significant skin reactions were observed at the beam entrance site in all animals and - less pronounced - at the beam exit site in 3 of the 6 animals. In conclusion, the complex irradiation geometry of the pig lung, the changes of body weight between the two experiments, and in sufficient accounting for a change in the relative biological effectivness (RBE) computation led to substantial deviations of the observed reactions from expectations, the reasons for which could be identified in a subsequent analysis. The less pronounced lung reaction in the first experiment was due to an overestimation of RBE in a preliminary version of the algorithm for its determination. The extension of the fibrotic reaction resulted from the smear-out of the high-dose region due to density variations in tissue structures, respiratory movement, and limited positioning accuracy. The skin reactions at the entrance port reflect the different treatment geometry in the two experiments. The one unexplained observation is the mild skin reaction that was observed in the second experiment at the beam exit site.

Purpose: Compared to photon irradiation, carbon ions provide physical and biologic advantages that may be exploited in chordomas and chondrosarcomas.
Methods and Materials: Between August 1998 and December 2000, 37 patients with chordomas (n = 24) and chondrosarcomas (n = 13) were treated with carbon ion radiotherapy within a Phase I/II trial. Tumor conformal application of carbon ion beams was realized by intensity-controlled raster scanning with pulse-to-pulse energy variation. Three-dimensional treatment planning included biologic plan optimization. The median tumor dose was 60 GyE (GyE =Gy x relative biologic effectiveness).
Results: The mean follow-up was 13 months. The local control rate after 1 and 2 years was 96% and 90%, respectively. We observed 2 recurrences outside the gross tumor volume in patients with chordomas. Progression-free survival was 100% for chondrosarcomas and 83% for chordomas at 2 years. Partial remission after carbon ion radiotherapy was observed in 6 patients. Treatment toxicity was mild.
Conclusion: These are the first data demonstrating the clinical feasibility, safety, and effectiveness of scanning beam delivery of ion beams in patients with skull base tumors. The preliminary results in patients with skull base chordomas and low-grade chondrosarcomas are encouraging, although the follow-up was too short to draw definite conclusions concerning outcome. In the absence of major toxicity, dose escalation might be considered.

Für eine genauere Einordnung der Sicherheitsreserven des Reaktordruckbehälters im Falle einer Kernschmelze ist es notwendig, mögliche Versagensformen des Reaktordruckbehälters sowie Versagenszeiträume zu untersuchen. Dazu wurden und werden derzeit weltweit Versuche zum Versagen der Bodenkalotte durchgeführt, wie die amerikanischen OLHF- (OECD Lower Head Failure) oder die schwedischen FOREVER-Experimente (Failure of Reactor Vessel Retention). Am Institut für Sicherheitsforschung des Forschungszentrums Rossendorf bei Dresden wurde ein Finite-Elemente-Modell entwickelt, das sowohl die Thermofluiddynamik der Schmelze als auch die elastoplastische Mechanik des Reaktordruckbehälters modelliert. Nach der Validierung und der Anwendung dieses numerischen Modells bei der Simulation der FOREVER-Experimente führte die Analyse der Ergebnisse zur Einführung einer "Kriechstütze" und einer passiven Steuereinrichtung zur Flutung der Reaktorgrube im Falle einer Kernschmelze. Die Funktion der Kriechstütze besteht darin, die am schwersten beanspruchten Bereiche des Reaktordruckbehälters im Falle einer Kernschmelze zu entlasten und somit ein Versagen zu verhindern oder zumindest deutlich zu verzögern. Dazu werden unterhalb der Bodenkalotte des Reaktordruckbehälters sehr tragfähige Stützen in geeigneter Form angeordnet. Beide Ideen wurden erfolgreich als Patent angemeldet (vgl. "Abstützvorrichtung für Stahlbehälter" Patent DE 100 41 778 C2"Steuereinrichtung für einen Kühlkreislauf" Patent DE 100 41 779 C1). In ersten Rechnungen zur FOREVER-Anordnung wurde gezeigt, dass selbst bei einem Szenario ohne Flutung der Bodenkalotte von außen die Zeit bis zum Versagen durch die Wirkung der Kriechstütze bei gleichbleibenden Randbedingungen verdoppelt werden kann. Eine weitere Verfolgung dieses Konzepts bei bestehenden und zukünftigen Kernkraftwerken erscheint daher vielversprechend.

In vivo dose localization in light ion tumour therapy can be performed by measuring the range distributions of beta⁺ active ions in tissue employing positron emission tomographic techniques. For this purpose a multiplicative iteration scheme for reconstructing three-dimensional images from shift-variant, limited-angle data is presented. In the iterative correction steps the algorithm uses the geometric means of quotients calculated from the three-dimensional Radon transforms of the backprojected measured and approximated source distributions. When sources measured with poor statistics are reconstructed, an effective noise suppression is achieved.

A multiplicative iteration scheme for reconstructing three-dimensional images from shift variant, limited angle data taken by a large area positron camera is proposed. Using simulated data sets the algorithm has been proven to be capable of reconstructing source distributions from a very small number of annihilation events. This suggests the applicability of the technique to the measurement of range distributions of beta⁺-active ions implanted into thick targets and especially to in-vivo dose localization in light ion tumor therapy by means of positron emission tomography.

Kein Abstract.

In-line nitrogen PIII/ion nitriding processing of metallic materials

Improvements of tribological properties of Ti6Al4V by nitrogen plasma
immersion ion implantation

Dynamic in situ analysis of stress and film thickness provide fast and more physical information on growth and stress evolution in cBN layers than integrating (ex situ) methods. Especially features of the layered structure of boron nitride films, like the evolution of instantaneous stress and growth rates during deposition can be resolved by in situ methods. This work is concerned with dynamic in-situ stress measurement by means of cantilever bending during magnetron sputter deposition of cBN thin films. Laser deflection in combination with in situ ellipsometry is used to determine the instantaneous stress of the films. The results show, in agreement with results that were obtained previously from ion beam assisted deposition (IBAD), that the hBN and cBN layers exhibit different levels of stress under constant deposition conditions. The stress increases from less than -4 GPa to very high values (-10 GPa) after the coalescence of the cBN nuclei. It is therefore possible to establish the point of cBN nucleation instantly. A simultaneous medium energy ion bombardment is used for stress relaxation during film deposition. A modified substrate bias voltage, combining negative high and low voltage pulses, is used to enable an ion bombardment of the growing film with energies up to 8 keV. In this way, cBN films with a stress as low as –1.7 GPa could be produced without destroying the sp3-bonds significantly.

Backround: Radiobiological and physical examinations suggest clinical advantages of heavy ion irradiation. We report the results of 23 women and 22 men (median age 48 years) with skull base tumors irradiated with carbon ion beams at the Gesellschaft für Schwerionenforschung (GSI), Darmstadt, from December 1997 until September 1999.
Patients and Methods: The study included patients with chordomas (17), chondrosarcomas (10) and other skull base tumors. It is the first time that the intensity-controlled rasterscan-technique and the application of positron emission tomography (PET) for quality assurance was used. All patients had computed tomography for three-dimensional treatment planning. Patients with chordomas and chondrosarcomas underwent fractionated carbon ion irradiation in 20 consecutive days (median total dose 60 GyE). Other histologies were treated with a carbon ion boost of 15 to 18 GyE delivered to the macroscopic tumor after fractionated stereotactic radiotherapy (median total dose 63 GyE).
Results: Mean follow-up was 9 months. Irradiation was well tolerated by all patients. Partial tumor remission was seen in 7 patients (15.5%). One-year local control rate was 94%. One patient (2.2%) deceased. No severe toxicity and no local recurrence within the treated volume were observed.
Conclusion: Clinical effectiveness and technical feasibility of this therapy modality could clearly be demostrated in our study. To evaluate the clinical relevance of the different beam modalities studies with larger patient numbers are necessary. To continue our project a new heavy ion accelator exclusively for clinical use is planned to be constructed in Heidelberg.

Beams of heavy charged particles like protons or carbon ions represent the optimum tool for the treatment of deep seated, inoperable and radioresistant tumors growing in close vicinity to organs at risk. In contrast to photon therapy, the dose deposited by heavy charged particles increases with the penetration depth, culminating in a sharp maximum at the end of the particle range - the Bragg peak. This peak can be shifted in depth by energy variation and distributed laterally through magnetic deflection of the particle beam, thus allowing a precise and conform irradiation of the selected target volume. Furthermore, carbon ions offer the most conform irradiation due to their lower lateral scattering when compared to protons. In addition to this excellent physical selectivity, the biological efficiency concerning cell killing increases towards the end of carbon ion range. Therefore, the high dose at the Bragg peak is further enhanced by an increase in biological efficiency. Finally, by applying PET techniques, an in-situ dose localization control can be performed by tracing the small amount of beta⁺ emitters (¹¹C, ¹⁵O, ¹⁰C) which are produced in nuclear fragmentation reactions between the ¹²C projectiles and atomic nuclei in the target volume. A pilot tumor therapy unit that fully exploits the advantages of carbon ions is under operation at GSI since December 1997 and has now treadet more than 70 patients. Its mayor goal is to demonstrate the safe and routine application of charged particle beams for radiotherapy.

The performance of Hamamatsu S8550 avalanche photodiode (APD) arrays for scintillator matrices readout has been evaluated. The S8550 device is a monolithic 8 X 4 pixels structure with an active area of 2.56 mm² for each pixel. The device allows stable operation at gains up to 74, with a detection efficiency of about 60% for photons of 420 nm wavelength. It is characterized by a low noise equal to 27 electrons equivalent noise charge at room temperature. The energy resolution of 14.6%, for the 511 keV peak from ²2;Na source has been recorded with a 2 x 2 x 10 mm³ LSO crystal coupled to one pixel. The number of electron-hole pairs produced by the 511 keV photopeak absorbed in LSO is equal to 4830 ± 240 e-h/MeV. Coupling LSO scintillator crystals to individual pixels of the APD array a coincidence timing resolution of 3.0 ± 0.2ns FWHM has been measured for the 511 keV b3;-rays from a ²2;Na source. Finally, we compared the characteristics and readout performance of the Hamamatsu array with the results measured earlier under the same conditions for the quadrant large area avalanche photodiodes of Advanced Photonics Inc.

In this paper, we evaluate the performance of recently released avalanche photodiode arrays from Advanced Photonix, Inc. (API) for scintillator matrices readout. The Large Area Avalanche Photodiode (LAAPD) quadrant device is a monolithic 2x2 pixels structure with an active area of 5.3 mm² per pixel. The device allows stable operation with high gains up to 200, and detection efficiency of 73+-10 % for 420 nm photons. It is furthermore characterized by a high linear fill factor of 90 % and low noise equal to16 electrons ENC measured at room temperature. We have measured pixel-to-pixel gain non-uniformity smaller than 1.5 % and inter-pixel crosstalk of 1.7 % in the pulse mode operation with the device gain of 50. The energy resolution of 12.3+-0.5 % was achieved for the 511 keV photopeak from a ²²Na source placed on top of a 2x2x10 mm³ LSO crystal coupled to one pixel of quadrant LAAPD. An array of LSO crystals was later coupled to the device allowing individual crystal identification. Coincidence timing resolution of 1.9+-0.1 ns FWHM has been obtained for quadrant pixel with LSO scintillator for the 511 keV peak from ²²Na source. Finally, we compared the characteristics and readout performance of LAAPD array with published results of some commerciallly available APD arrays.

The Master Curve (MC) approach and the associated reference temperature, T0, as defined in the test standard ASTM E1921, is rapidly moving from the research laboratory to application in integrity assessment of components and structures. T0 is the index temperature for the universal MC, which considers the behaviour of a specific material. “The Structural Integrity Assessment Procedures for European Industry” (SINTAP) contain a MC extension for analysing the fracture behaviour shown by inhomogeneous ferritic steels statistically. This paper presents the application of the MC approach to the T0 determination of different types of Russian WWER-type reactor pressure vessel (RPV) steels. In addition the SINTAP-MC approach was applied to determine an alternative reference temperature, TR.
The influence of different microstructures and compositions within one type of RPV steel and the effect of irradiation with fast neutrons on T0 are experimentally evaluated. In general the MC based T0 is about 72 K below the Charpy V-notch transition temperature related to an impact energy of 48J. The paper demonstrates the application of MC based T0 and TR as an alternative reference temperature for neutron embrittled RPV steels used in the RPV integrity assessment.

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The in-beam dual head positron camera BASTEI (Beta+ Activity meaSurements at the Therapy with Energetic Ions) is used to monitor and control the applied dose distributions simultaneously to tumor irradiations with carbon ion beams at the experimental heavy ion therapy facility at GSI Darmstadt. Therefore, the PET system has been mounted directly at the treatment site. A fully 3D reconstruction algorithm based on the Maximum Likelihood Expectation Maximization algorithm has been developed and adapted to a spatially varying imaging situation. The scatter and attenuation correction is applied to the measured list mode data before each iterative step. This requires an attenuation map containing the information on the tissue composition and densities. This information is derived from the X-ray computed tomograms (CT) of the patient and the patient fixation system including the head rest. The scatter correction is included into the forward projection step of the Maximum Likelihood image reconstruction. The normalization of scattered events relative to the unscattered events is done by a global scatter fraction factor. The results are presented.

The in beam dual head positron camera BASTEI (Beta+ Activity meaSurements at the Therapy with Energetic Ions) is used to monitor and control the applied dose distributions simultaneously to the irradiation of the therapeutic carbon ion beam at the experimental heavy ion therapy facility at GSI Darmstadt. Therefore, the PET system is mounted directly at the treatment site. A fully 3D reconstruction algorithm based on the Maximum Likelihood Estimator algorithm has been developed and adapted to a strongly spatially-varying imaging situation. A scatter and attenuation correction is applied to the measured listmode data prior to the image reconstruction. The scatter correction method uses the subtraction of scattered data from measured data.
In this particular PET-application the fluence of registered events at the detector surface is in the order of 10 to 102 cm-2 compared with about 102 to 103 cm-2 in conventional PET in nuclear medicine. The emission data are acquired in a 3D list mode. Since less than 100,000 out of approximately 4 millions coincidence channels typically contribute to the reconstruction all detected events have to be utilized. In addition, they cannot be sorted into sinograms because the necessary interpolation procedures would generate additional noise. Therefore the reconstruction algorithm takes the original emission data as input. The non-zero elements of the 3D transition matrix are calculated at run-time using a Monte-Carlo code that models the individual crystal responses along each coincidence channel. Results of the performance studies as well as examples of use are presented.

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Bei der Gesellschaft für Schwerionenforschung in Darmstadt ist in den vergangenen Jahren eine experimentelle Anlage für die Krebstherapie mit Strahlen schwerer Ionen errichtet worden. Im Herbst 1997 sollen dort die ersten Tumorpatienten mit ¹²C Strahlen behandelt werden. Bei der Installation der Anlage und ihrem künftigen Betrieb kooperieren die Gesellschaft für Schwerionenforschung Darmstadt (GSI), das Deutsche Krebsforschungszentrum in Heidelberg (DKFZ), die Radiologischen Kliniken der Universitäten Heidelberg und Magdeburg sowie das Forschungszentrum Rossendorf. Der Rossendorfer Beitrag zur Therapieanlage besteht in der Entwicklung und Realisierung von Verfahren, welche die Positronen-Emissions-Tomographie (PET) für die Kontrolle der Schwerionen-Tumortherapie anwenden. Mit der Installation des in Rossendorf gebauten Positronen-Emissions-Tomographen am Therapieplatz in Darmstadt im Januar 1996 konnten die methodischen Vorarbeiten zum Einsatz von PET für die Tumortherapie mit schweren Ionen beginnen.

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Abstract wir von Dr. Geipel nachgereicht

Outline
Actinides are the fourteen elements, which follow the element actinium in the periodic table of elements. The first three actinides uranium, protactinium and thorium can be found in the nature, the other elements are artificial elements. Most speciation studies are carried with actinides from thorium to curium. The elements uranium, neptunium and plutonium show a wide variety of oxidation states. In tetravalent oxidation state the solubility is very low. In this oxidation state the hydrolysis is the most important reaction.

All these elements are radioactive. Therefore special laboratories to handle these elements are necessary. The concentration range for speciation studies with actinides is below 1 x 10-5 M. Therefore several speciation techniques, mostly basing on laser induced methods, are developed. A short overview in these methods will be given.

For thorium and protactinium only few data are available. Thorium does only exist in tetravalent oxidation state. Hydrolysis and phosphate speciation will be described. Protactinium exists in the pentavalent oxidation state and forms a dioxy-cation.

Most data are available for uranium speciation. Uranium exists in four oxidation states. Uranium-(III) is only stable in non-aqueous environments and plays therefore no role in speciation studies. Under reducing conditions uranium-(IV) is formed. Speciation examples for hydrolysis, sulfate, phosphate and arsenate will be given. In aqueous solutions uranium?(V) disproportionates into uranium-(IV) and uranium-(VI). Hexavalent uranium exists only as dioxy-cation.
In a next section environmental aspects of the uranium-(VI) speciation will be described. Uranium is found in more or less high concentrations in anywhere in the environment. Speciation examples from mining and milling will be described.
Uranium speciation in plants (as example for the food chain) will be described.
Neptunium forms oxidation states from +3 to + 7. Np(III) is slightly oxidized to Np(IV). The most stable oxidation states are Np(IV) and Np(V), the latter also forms a dioxy-cation. As example for environmental speciation the speciation of Np(V) with humic substances will be quoted.
Plutonium has oxidation states from + 3 to + 6. The redox potentials between these oxidation states are close together, so one can often find several oxidation states existing together. Examples for speciation in environment (here as specials case the Oklo mine in Gabun and results of bomb tests will be included) are shown, clinical and health aspects should be discussed (Pu is one of the most toxic elements).
Americium and Curium form trivalent ions in solution. These elements are important in waste repositories. Speciation in concentrated salt solutions and in mineral (calcite) phases are important examples for speciation in natural environments.
Actinides higher than Curium show at least short half-life. The long living isotopes are Berkelium 247 (1400 y), Californium 251 (900 y) and Einsteinium 252 (1.24 y). Fermium, Mendelevium, Nobelium and Lawrencium as well as the transactinide elements have half-life less than 1 y. Due to the very low production rates most of these elements are less relevant in speciation chemistry. Berkelium is found to have two oxidation states (III and V). Only few data on chloride and sulfate speciation are available.

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A secondary beam facility had been built at the end of last fiscal year and commenced the operation since the second term of HIMAC machine time. Optimum momentum spread was sought so as to compromise two contradictory factors, the blurring of sharp Bragg peak and broadening of the ¹¹C end-point distribution. Three types of irradiation, namely, focused beam irradiation, line irradiation and curved surface irradiation, were tested to see the uniformity of the irradiation field. The field uniformity turned out competent with the assessment of beam end-point in all cases, since it only affects the statistical noise in PET images that degrades indirectly the assessment of end-point. Preliminary irradiation tests were performed on rabbits to see biological half-life of ¹¹C in the thigh muscle of the rear leg.

In the application of positron emitting secondary beams to the verification of heavy ion treatment planning, the implanted radioactive isotopes undergo metabolism. Experiments on rabbit thigh muscle were performed using ¹¹C secondary beams from HIMAC. PET allows us three-dimensional imaging of the implanted ¹¹C, however, the early phase cannot be measured. The positron camera allows us in-situ measurement. By focusing the beam to narrow region, time-activity analysis of the volume of interest revealed the existence of faster metabolic component.

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Thin films NiTi (< 100 nm) having surface Ni content below 5 at. % were prepared by ion implanting Ni into Ti surfaces. The Ni containing phase exposed or buried within the Ti matrix was amorphous. Following an anodic oxidation in NaOH the material was shown to be redox active and promote the electrocatalytic oxidation of glucose depending on the surface NiTi composition. Compared to the NiTi bulk alloy (55.9:44.08) the Ni implanted Ti displayed a more efficient catalytic activity and improved corrosion resistance.

Bubbly flow is encountered in a wide variety of industrial applications ranging from flows in nuclear reactors to process flows in chemical reactors. The presence of a second phase, re-circulating flow, instabilities of the gas plume and turbulence, complicate the hydrodynamics of bubble column reactors. This paper describes preliminary experimental and numerical results obtained in a rectangular bubble column with a cross-sectional area of 20 cm2. Images obtained from a high speed camera have been processed to calculate bubble velocities, bubble turbulence parameters and bubble size distributions. Gas disengagement technique was used to obtain the volume averaged gas fraction over a range of superficial gas velocities. Numerical calculations were performed with an Eulerian-Eulerian two–fluid model approach using the commercial code CFX-4.4. In this paper, the image processing algorithms and numerical modeling are discussed and an analysis of the preliminary results presented.

Proton-proton correlations of protons, deuterons and tritons with alpha particles from spectator decays following 197Au+197Au collisions at 1000 MeV per nucleon have been measured with two highly efficient detector sodoscopes. The constructed correlation functions, interpreted within the approximation of a simultaneous volume decay, dedicate a moderate expansion and low breakup densities, similar to assumptions made in statistical multifragmentation models.

Beams of heavy-charged particles of high energy like carbon ions are superior to any other type of radiation conventionally used in external radiotherapy. In contrast to photons and neutrons, the dose for the ions increases with penetration depth and culminates in a sharp maximum at the end of range. Due to the microscopic track structure this region of high energy deposition has an increased biological efficiency. In addition, a small amount of positron emitting isotopes is produced by the projectile and makes it possible to trace the beam inside the patient's body by PET techniques. At GSI an experimental heavy-ion therapy started with patient treatment. It is based on a totally active beam delivery and a biology-oriented treatment planning system in order to exploit the favourable particle properties to a maximum extent.

Kinetic energies of light fragments (A ? 10) from the decay of target spectators in 197Au + 197Au collisions at 1000 MeV per nucleon have been measured with high-resolution telescopes at backward angles. Except for protons and apart from the observed evaporation components, the kinetic-energy spectra exhibit slope temperatures of about 17 MeV, independent of the particle species, but not corresponding to the thermal or chemical degrees of freedom at breakup. It is suggested that these slope temperatures may reflect the intrinsic Fermi motion and thus the buld density of the spectator system at the instant of becoming unstable.

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Numerical investigations of the heat transfer from hot wires in near-wall measurements were carried out. Special attention was paid to the effect of the wall thickness, the flow conditions below the wall and the shear velocity connected to different wall
materials. Compared with previous studies, an improved physical model taking into account the flow region below the wall
in the computational domain was applied. The results obtained agree well with experimental data in the literature for walls consisting of both highly and poorly conducting materials. The investigation showed that the shear velocity $U_\tau$ has a significant influence on hot-wire measurements in the vicinity of a wall. Nevertheless, discernible effects of the wall thickness and the flow condition below the wall were found only in the case of a poorly conducting wall. In addition, the results also suggest a weak effect of the overheat ratio for a wire with an infinitely large aspect ratio.

Susceptibilitys contrast based MR perfusion measurement in contrast uptaking tissues are complicated by the contribution of the interstitially deposited contrast medium (CM) to the shortening of both T1 and T2. Applying double echo sequences, both contributions can be corrected for. In this paper, the consequences of different degrees of correction on perfusion parameters are investigated.

Positron emission tomography (PET) offers the possibility of in-situ monitoring the tumour treatment with light ion beams by means of imaging the spatial distribution of positron-activity that is produced as a byproduct of the therapeutic irradiation via nuclear fragmentation reactions between the projectiles and the atomic nuclei of the tissue within the target volume. The implementation of this PET technique at the experimental tumour therapy facility at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt and first results of its clinical application are presented.

Two-dimensional numerical investigations of the forced heat convection from a microcylinder in laminar cross-flow, both in free stream and in near-wall flow, were carried out aiming at a better understanding of the physics behind the wall effects on hot-wire near-wall measurements. In the physical model, an infinitely thin plate with the same properties as the fluid (air) was used as an
artificial wall. The conjugate heat transfer between the flow regions on both sides of the plate was taken into account. The effect of the conjugate thermal conditions (temperature distribution and diffusive heat flux) at the interface of the two flow regions on the heat transfer from the wire was investigated by varying the flow conditions on the side opposite to the wire location. Careful energy balance analysis was performed for both the free-stream case and the near-wall case. This enabled the authors to verify their own understanding of the physical mechanism responsible for the wall effect on hot-wire measurements and to examine other mechanisms proposed in the literature. The numerical results showed that the heat diffusion from the wire is significantly enhanced in the case of small wire-to-wall distances (Y+ < 3). This is mainly caused by modifications of the thermal boundary condition (diffusive effect) at the fluid-wall interface. In contrast, the flow distortion (enhanced convection) was shown not to be the most important influencing factor for the heat transfer of a hot wire. Although the present model study was performed for a laminar
flow, the results obtained are applicable to hot-wire measurements in turbulent flows, as stated in the literature.

A combined analytical-numerical method based on a matching asymptotic algorithm is proposed for treating angular (sharp corner or wedge) singularities in the numerical solution of the Navier-Stokes equations. We adopt an asymptotic solution for the local flow around the angular points based on the Stokes flow approximation and a numerical solution for the global flow outside the singular regions using a finite-volume method. The coefficients involved in the analytical solution are iteratively updated by matching both solutions in a small region where the Stokes flow approximation holds. Moreover, an error analysis is derived for this method, which serves as a guideline for the practical implementation. The present method is applied to treat the leading-edge singularity of a semi-infinite plate. The effect of various influencing factors related to the implementation are evaluated with the help of numerical experiments. The investigation showed that the accuracy of the numerical solution for the flow around the leading edge can be significantly improved with the present method. The results of the numerical experiments support the error analysis and show the desired properties of the new algorithm, i.e., accuracy, robustness and efficiency. Based on the numerical results for the leading-edge singularity, the validity of various classical approximate models for the flow, such as the Stokes approximation, the inviscid flow model and the boundary layer theory of varying orders are examined.

G protein-coupled receptors (GPCRs) are heptahelical transmembrane proteins. They transduce a large variety of extracellular signals, allowing perception of taste, odor, hormones, and light. Binding of an extracellular ligand induces structural changes in the cytosolic domain of a GPCR which, thereby, catalyzes nucleotide exchange in a G protein. Rhodopsins, the visual pigments, are prototypical GPCRs that are activated by photoisomerization of covalently bound 11-cis retinal. Unlike other GPCRs, bovine rhodopsin and transducin, its cognate G protein, can be prepared from cow eyes in large quantities for spectroscopic and biochemical investigations. Rhodopsin is the best studied GPCR and the only one for which an X-ray structure has been solved. Structural information together with the wealth of biophysical data on native and recombinant rhodopsins allows to determine structure function relationships that are relevant to GPCR-dependent signaling in general. Here, results from Fourier-transform-infrared (FTIR) spectrocopic studies of rhodopsin and measurements of nucleotide-dependent transducin fluorescence are reviewed. Intra- and intermolecular processes during signaling by the photoreceptor have thus been identified and analyzed kinetically. Recent applications of these techniques concern rhodopsin transducin coupling in synthetic lipidic matrices and analysis of drug action at the receptor G protein interface.The data are discussed in the context of the crystal structure of rhodopsin and additional biochemical information if required for the understanding of the spectroscopic results.

Si (100) and (111) crystals were irradiated in the random as well as in the channeling direction, using 5 MeV 19F+ ions, to a maximum dose of approximately 1×1017 particles/cm2. The occurring deep implanted profiles were subsequently investigated using the Resonant Nuclear Reaction Analysis technique in the energy range Ep=950-1200 keV. The reaction 19F(p, αγ)16O reaction exhibits a strong resonant behavior in the above mentioned energy range, thus providing an excellent tool for the depth profiling of fluorine, yielding minimum detection limits of the order of a few ppm. The occurring profiles are analyzed with SRIM and c-TRIM and an attempt is made to explain the peculiarities of the experimental spectra, as well as to compare with results already existing in literature

We have measured the nuclear transparency of the fundamental process gamma n to pi- p in 4He. These measurements were performed at Jefferson Lab in the photon energy range of 1.6 to 4.5 GeV and at theta_cmSUP>pi = 70 and 90 . These measurements are the first of their kind in the study of nuclear transparency in photoreactions. They also provide a benchmark test of Glauber calculations based on traditional models of nuclear physics. the transparency results suggest deviations from the traditional nuclear physics picture. The momentum transfer dependence of the measured nuclear transparency is consistent with Glauber calculations which include the quantum chromodynamics phenomenon of color transparency.

Double differential cross sections d2?/dpd? have been measured for ?+ and K+ emitted around midrapidity in d+A and ?+A collisions at a beam kinetic energy of 1.15 GeV/nucleon. The total ?+ yield increases by a factor of about 2 when using an alpha projectile instead of of a deuteron whereas the K+ yield increases by a factor of about 4. According to transport calculations, the K+ enhancement depends both on the number of hadron-hadron collisions: their center-of-mass energy increases with increasing number of projectile nucleons.

During the last decades, the focused ion beam (FIB) became a very useful and versatile tool in the microelectronics industry, as well as in the field of research and development. For special purposes like writing ion implantation or ion mixing in the µm- or sub-µm range ion species other than gallium are needed. Therefore alloy liquid metal ion sources (LMIS) were developed. The energy distribution of the ions from an alloy LMIS is one of the determining factors for the performance of an FIB column. Different source materials like Au73Ge27, Au82Si18, Au77Ge14Si9, Co36Nd64, Er69Ni31, and Er70Fe22Ni5Cr3 were investigated with respect to the energy spread of the different ion species as a function of emission current I, ion mass m and emitter temperature T. For singly charged ions a predicted dependence of the energy spread, DE µ I2/3 m1/3 T1/2 found for Ga could be reasonable confirmed. The alloy LMIS`s discussed above have been used in the Rossendorf FIB system IMSA-100 especially for writing implantation to fabricate sub-µm pattern without any lithographic steps. A Co-FIB obtained from a Co36Nd64 alloy LMIS was applied for the ion beam synthesis of CoSi2 micro-structures down to 60 nm. Additionally, the possibility of varying the current density of the FIB by changing the pixel dwell-time was used for investigations of radiation induced damage and its dynamic annealing in Si and SiC at elevated implantation temperatures. Furthermore, a broad spectrum of ions was employed to study the sputtering process depending on temperature, angle of incidence and ion mass on a couple of target materials using the volume loss method. Especially this direct patterning 3D technique was used for the fabrication of various kinds of micro-tools.
All these examples underline the importance of FIBs in modern research and the new possibilities opened up by a mass separated system applying a broad spectrum of ion species.

Sophisticated microstructural analysis methods like small angle neutron scattering and atom probe field ion microscopy have proven the presence of so-called multicomponent clusters due to neutron irradiation in ferritic reactor pressure vessel steels. The formation of such clusters is surprising from the thermodynamic point of view. The cluster formation from the solid solution was modelled as phase transformation of the first kind that corresponds to the negative minimum of the so-called thermodynamic force under consideration of six components. The essential parameter is the sum of interaction energy between all pairs of atoms in the system. The approach result in stable multicomponent cluster if the clusters exhibit a high content of vacancies and a core-shell structure with very high vacancy content within the shell. The kinetics background of the suggested model was investigated using the cluster dynamic approach generalized for multiple components. The computed results are consistent with the experimental findings.

Aim. To investigate the mechanisms and dynamics of cholesteryl ester (neutral lipid) transfer protein activity in subjects with impaired glucose tolerance. Methods. Eighty six Caucasian subjects were recruited by advertisement from the local population between January 1998 and December 1999. The activity of cholesteryl ester transfer protein in 44 non-obese subjects with impaired glucose tolerance (plasma triglycerides 1.56-/+0.64 mmol/L; high density lipoprotein (HDL) cholesterol 0.96-/+0.25 mmol/L; and plasma insulin 78-/+8 pmol/L) and in 42 normoglycemic controls (plasma triglycerides 0.88-/+0.41 mmol/L; HDL cholesterol 1.48-/+0.29 mmol/L; and plasma insulin 38-/+14 pmol/L) was measured with a new fluorometric assay. Results. Cholesteryl ester transfer protein activity was increased in subjects with impaired glucose tolerance by 47% (39.5-/+7.8 vs 26.8-/+6.8 nmol/mL x h-1; t-test, p<0.05). Linear regression analysis showed that cholesteryl ester transfer protein activity in subjects with impaired glucose tolerance significantly correlated with the following parameters: plasma triglycerides (r=0.614, p<0.05), HDL-triglycerides (r=0.595, p<0.05), percentage of HDL-triglyceride (r=0.667, p<0.05), percentage of HDL cholesterol ester (r=-0.751, p<0.01), percentage of HDL phospholipid (r=0.648, p<0.05), 2-h-insulin (r=0.668, p<0.05), and 2-h-proinsulin (r=0.658, p<0.01). In a subgroup of 13 subjects with impaired glucose tolerance, cholesteryl ester transfer protein activity correlated with HDL apoA-I fractional catabolic rate (r=0.701, p<0.01). In normoglycemic subjects, significant correlations were found only between cholesteryl ester transfer protein activity and percentage of HDL-triglycerides (r=0.541, p<0.05), percentage of HDL cholesteryl ester (r=-0.639, p<0.01), 2-h-proinsulin (r=0.642, p<0.05), and HDL apoA-I fractional catabolic rate (n=10, r=0.587, p<0.05). Conclusion. Cholesteryl ester transfer is important for HDL composition and HDL catabolism both in normoglycemic subjects and subjects with impaired glucose tolerance. Under insulin resistant conditions, increased cholesteryl ester transfer protein activity modulates HDL metabolism more drastically than in normoglycemic conditions. This modulation may be explained by increased availability of triglyceride-rich lipoproteins for neutral lipid exchange in subjects with impaired glucose tolerance.

Several in vitro investigations showed that serum paraoxonase 1 (PON1) that is located on high-density lipoprotein reduces or prevents low-density lipoprotein (LDL) oxidation and therefore retards atherosclerosis. Accordingly, the well documented loss of PON1 activity in patients with overt diabetes mellitus was causally related to the development of micro- and macroangiopathy in the disease course. Because vascular complications start already in prediabetic states, e.g. impaired glucose tolerance (IGT), we investigated serum PON1 activities and circulating levels of oxidized LDL (oxLDL) in 125 IGT subjects, 75 patients with newly diagnosed diabetes mellitus type 2, and 403 individuals with normal glucose tolerance. Using three different substrates (paraoxon, phenylacetate, p-nitrophenylacetate) we found that PON1 activity is not significantly altered in IGT and diabetes mellitus subjects, respectively, when compared with normoglycemic controls. Both IGT subjects and diabetes mellitus patients had significantly increased levels of oxLDL in the circulation. However, serum PON1 activity variations and glutamine/arginine phenotype were not related to the levels of oxLDL. The data suggest that 1) PON1 activity loss is an event occurring later in the course of diabetes mellitus; and 2) PON1 does not affect oxidation of circulating LDL, at least in early diabetes mellitus.

N(O,S)-Ethoxycarbonyltrifluoroethyl amino acid esters are formed by the reaction of amino acids with ethylchloroformate plus trifluoroethanol plus pyridine. The use of these derivatives for a rapid and sensitive determination of 3-chlorotyrosine, a highly specific marker of myeloperoxidase-catalyzed protein oxidation, by using standard gas chromatography/electron impact mass spectrometry, is discussed.

Low density lipoprotein (LDL) apheresis is an effective treatment option for patients with severe hypercholesterolemia not adequately responding to diet and drug therapy. Membrane differential filtration (MDF), synonymous with double filtration plasmapheresis (DFPP), here named Lipidfiltration, and heparin-induced extracorporeal LDL-precipitation (HELP) are two of the five methods available for extracorporeal LDL apheresis. In this prospective investigation 6 patients with severe LDL-hypercholesterolemia and CAD were treated in a cross-over design with Lipidfiltration at two stages of technical development and HELP to compare the efficacy of these two LDL apheresis methods with respect to lowering and modifying plasma lipids and rheologically relevant plasma proteins, especially fibrinogen. In total, 44 LDL apheresis sessions were investigated. In weekly intervals, patients were treated with consecutive LDL apheresis sessions with either Lipidfiltration and HELP, treating identical plasma volumes. In one part of the investigation Lipidfiltration was performed with the novel Lipidfilter EC-50, combined with a newly developed blood and plasma therapy machine allowing optimized plasma heating. The results showed that the reduction rates of LDL-cholesterol, lipoprotein(a) and triglycerides were essentially identical for both methods. Also pretreatment levels of total cholesterol, triglycerides, LDL-cholesterol and HDL-cholesterol were not significantly different in both treatment groups. Both methods lead to a significant reduction of serum lipoproteins, especially for LDL-cholesterol, which was decreased by 61.4% with Lipidfiltration (treated plasma volume: 2998 ml) and 61.3% with HELP (treated plasma volume: 3013 ml). With respect to Lipidfiltration LDL-cholesterol reduction was more efficient with the novel Lipidfilter EC-50. Mean pretreatment HDL cholesterol concentrations remained unchanged. Comparing Cascadeflo AC-1770 with the novel Lipidfilter EC-50 reduction rates of HDL-cholesterol (17.4% versus 6.4%) and total protein (17.9% versus 7.8%) were significantly reduced. Lipidfiltration and HELP both resulted in a reduction of plasma viscosity and hemorheologically relevant plasma proteins, like fibrinogen.

Over the last 3 years in-beam PET has proven its capability of quality assurance in carbon ion tumour therapy at the pilot project of cancer therapy at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany. In this paper we investigate the possibility of using LSO as the scintillation material for the next generation of in-beam PET cameras. We address the issue of background coincidences arising from the natural radioactivity of LSO. Because the true count rate measured with a BGO-based dual-head positron camera (total sensitive area of each head 21 x 42 cm²) during the cancer treatment averages at only 100 coincidences/s we studied the influence of the LSO backround on realistic in-beam PET-images.

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The new TOPFLOW facility of the Forschungszentrum Rossendorf allows investigations of two-phase flow phenomena in vertical pipes with an inner diameter up to 194 mm (DN200) and a length up to 8.5 m. The maximum water mass flow of 50 kg/s equals to a superficial velocity of 1.7 m/s in such a pipe, while the maximum air flow rate of 900 m3/h corresponds to a superficial velocity of 8 m/s. For the measurements presented here, a wire-mesh sensor with 64*64 measuring points was installed. It corresponds to a lateral resolution of 3 mm. The senor delivers instantaneous void fraction distributions over the entire cross section with a time resolution of 2500 frames per second, which can be used for fast flow visualisation as well as to obtain averaged void fraction profiles and bubble size distributions. Earlier, similar experiments were carried out at a 51.2 mm pipe. In this case, sensors with 16x16 and 24x24 points were applied. A comparison of the data obtained for the two diameters allows to identify the effects of scaling on void fraction profiles, bubbles size distributions and the flow patterns. In the small pipe, the increase of the air flow rate leads to a transition from bubbly to slug flow. In the bubble size distributions a second peak corresponding to the class of large Taylor bubbles respectively gas plugs was found in the slug flow region. In the large pipe at identical superficial velocities a similar behaviour was found, though the large bubble fraction has a significantly bigger mean diameter, the peak is less high but wider. This reflects the fact that large bubbles move more freely than in the small pipe. The transition from a mono-modal to a bimodal bubble size distribution starts in both pipes, if bubbles with an equivalent diameter larger 1/3 of the pipe diameter occur. Due to the less pronounced confining action of the pipe walls, the bubbles show much more deformations. Their shape can be complicated and far from an ideal Taylor bubble. The small bubble fraction can also develop more freely in the large pipe. This is reflected by a wider bubble size distribution in the small bubble region. Small bubbles that surround the large bubbles obstruct the view and lead to the empirical impression of a direct transition from bubbly to churn turbulent flow.

Heavy-ion radiotherapy gives a good localized dose distribution just on a cancer tumor. In order to emphasize this advantage, the verification system of a particle range and an irradiated area in a human body has been developed for the Heavy Ion Medical Accelerator in Chiba (HIMAC) at National Institute of Radiological Sciences (NIRS). The idea comes from the fact that the stopping position of a short-lived positron emitting nuclei, such as ¹¹C, ¹⁵O or ¹⁹Ne, can be precisely detected by measuring annihilation gamma-rays.

In this seminar the production of nanopatterning by ion beam sputtering (IBS) is presented, namely ripple and dot morphologies. The work is focused on the irradiation of Si surfaces but a general view of this research field is also discussed. Finally, the search of potential applications for these nanostructures is addresed.

Middle frequency dual reactive magnetron sputter deposition was used in order to prepare the Indium tin oxide (ITO) films with an optimum of resistance and transmittance. The films were deposited on Si covered with 500 nm SiO2 and soda lime glass substrates. The plasma ions and neutrals flow parameters have been studied during the deposition process by the Langmuir probe, HIDEN analyzer, and optical emission spectroscopy. Complex characterization of the ITO films have been carried out in order to relate their properties with pulsed magnetron operation parameters. The optical constants and the thickness of these films were determined by means of spectroscopic ellipsometry (SE) operating within the wavelength range l=300-1700 nm. The optical transmittance was measured for l=350-2000 nm. Four probe technique was used to determine the film specific resistance. The dependence of the ITO film properties on the O2/Ar partial pressure relation was obtained similarly to known researches. The influence of the pulse duration and base pressure level on the film characteristics was detected. The decrease of the magnetron pulse on-time to the values of about 50 micro seconds, leads to strong increase of the films resistance at their high transmittance. The AFM data for these samples demonstrated five-times increase of the film grain sizes compared to those obtained at the on-time values 100 micro seconds. The observed decrease of optical transmittance in the near IR spectral range corresponds to the decrease of the film resistance. High optical transmittance at low resistance is found only at certain relation between the free electron plasma and relaxation frequency. The grading of optical constants was revealed by SE while the other techniques did not show depth grading of the film properties. Annealing of the ITO films in air atmosphere reduces the film resistance.