Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Local gallium (Ga) ion implantation in silicon (Si) by focused ion beam (FIB) and subsequent anisotropic and selective wet etching has been used to fabricate freely suspended nanowires (NWs) with reproducible widths between 20 and 200 nm. The dependence of the resulting NW width on the implanted fluence has been investigated and is supported by a numerical model reproducing the experimental data and enabling an a priori estimation of the NW width as a function of the implanted fluence. Furthermore, the resistance of the NWs, its temperature response and the activation energy for electrical current flow were investigated before and after direct current (DC) annealing in air and in vacuum. Annealed NWs showed a decrease of their resistivity up to two orders of magnitude, indicating a partial re-crystallization of the NWs through self-heating and a change in the conduction. The assumption of recrystallization is supported by scanning electron microscopy (SEM) and Raman spectroscopy.

We present a simple method to derive a planar, instantaneous body force distribution from a given 2-D velocity field without knowledge of the pressure field. If the body force consists of one component only, spatial integration completely recovers this component.
Particle Image Velocimetry and Direct Numerical Simulations of a wall jet induced by a known body force were conducted to validate the method, demonstrating a good agreement of the original and reconstructed force fields.

Die für die primordiale Nukleosynthese wichtige Reaktion d(γ,n)p wurde am supraleitenden Elektronen-Linearbeschleuniger ELBE mit Bremsstrahlung bei einer Endpunktenergie von 5,0 MeV untersucht.
Der Photonenfluss wurde mit Hilfe der resonanten Streuung an Aluminiumkernen bei Energien von 2,2 und 3,0 MeV bestimmt. Die Effektivität der verwendeten Germanium-Detektoren wurde mit Hilfe von Referenzstrahlern und Simulationsrechnungen ermittelt. Mit beidseitig ausgelesenen Szintillationsdetektoren wurden Flugzeit und -strecke der Neutronen bestimmt. Wegen der niedrigen Nachweisschwelle der Detektoren kann der Wirkungsquerschnitt für Neutronenenergien von 50 keV bis 1,4 MeV bestimmt werden. Die erreichte statistische Unsicherheit beträgt 5 %, die Energieauflösung 4 %. Bisher untersuchte systematische Unsicherheiten werden diskutiert.

The investigation of reactor pressure vessel (RPV) materials from decommissioned nuclear power plants (NPPs) offers the unique opportunity to scrutinize the irradiation behavior under real conditions. Material samples taken from the RPV wall enable a comprehensive material characterization. The paper describes the investigation of trepans taken from the decommissioned WWER-440 first generation RPVs of the Greifswald NPP. Those RPVs represent different material conditions such as irradiated (I); irradiated and recovery annealed (IA); and irradiated, recovery annealed, and reirradiated (IAI). The working program is focused on the characterization of the RPV steels (base and weld metal) through the RPV wall. The key part of the testing is aimed at the determination of the reference temperature T0 following the American Society for Testing of Materials (ASTM) Test Standard E1921–08 to determine the fracture toughness of the RPV steel in different thickness locations. In a first step, the trepans taken from the RPV Greifswald unit 1 containing the X-butt multilayer submerged welding seam and from base metal ring 0.3.1 both located in the beltline region were investigated. Unit 1 represents the IAI condition. It is shown that the master curve (MC) approach as adopted in ASTM E1921 is applicable to the investigated original WWER-440 weld metal. The evaluated T0 varies through the thickness of the welding seam. The lowest T0 value was measured in the root region of the welding seam representing a uniform fine grain ferritic structure. Beyond the welding root T0 shows a wavelike behavior. The highest T0 of the weld seam was not measured at the inner wall surface. This is important for the assessment of ductile-to-brittle temperatures measured on subsize Charpy specimens made of weld metal compact samples removed from the inner RPV wall. Our findings imply that these samples do not represent the most conservative condition. Nevertheless, the Charpy-V transition temperature TT41J estimated with results of subsize specimens after the recovery annealing was confirmed by the testing of standard Charpy-V-notch specimens. The evaluated TT41J shows a better accordance with the irradiation fluence along the wall thickness than the master curve reference temperature T0. The evaluated T0 from the trepan of base metal ring 0.3.1 varies through the thickness of the RPV wall. The KJc values generally follow the course of the MC, although the scatter is large. The reembrittlement during two campaign operations can be assumed to be low for the weld and base metal.

This paper is concerned with numerical and experimental investigations focusing on the fluid flow in the continuous casting process under the influence of an external DC magnetic field. Systematic measurements of the mould flow were carried out using the eutectic alloy GaInSn inside a plexiglass model at room temperature. The jet flow discharging from the submerged entry nozzle was exposed to a level magnetic field spanning across the entire wide side of the mould. The ultrasound Doppler velocimetry (UDV) was applied to obtain a detailed experimental data base with respect to the mean values and transient properties of the velocity fields occurring in the mould. Numerical calculations were performed by means of the software package CFX with an implemented RANS-SST turbulence model. The comparison between our numerical calculations and the experimental results displays a very well agreement. An important outcome of this study is the feature that the magnetic field does not provide a smooth reduction of the velocity fluctuations at the nozzle outlet.

An experimental facility is described which has been designed to perform ultrafast two- and three-dimensional electron beam computed tomography. As a novelty a specially designed transparent target enables tomography with no axial offset for 2D imaging and high axial resolution three-dimensional im-aging employing the cone-beam tomography principles. The imaging speed is 10,000 frames per second for planar scanning and more than 1000 frames per second for 3D imaging. The facility serves a broad spectrum of potential applications primarily the study of multiphase flows, but also in principle non-destructive testing or small animal imaging. In order to demonstrate the aptitude for these applications static phantom experiments at a frame rate of 2000 fps were performed. Resulting spatial resolution was found to be 1.2 mm and better for a reduced temporal resolution.

Imaging systems and techniques have found widespread application in medical and biological imaging, security and surveillance systems, remote sensing, biometrics, non-destructive testing, computer sciences, materials research, and most recently also in various types of customer products. Imaging systems may be based on different physical measuring principles, such as optical, infrared, acoustic, microwave, terahertz, electrical, X-ray and gamma ray sensing techniques, for example. But behind the imaging sensor there is strong common ground in electronics concepts and circuits for signal conversion, processing, acquisition, and storage as well as algorithms for image enhancement, image reconstruction and image analysis. Imaging systems are increasingly complex and therefore challenge electronic engineers and computer scientists. Concurrently to an ongoing trend of increasing the spatial and temporal resolution of such systems, there is a growing demand for hardware-supported image processing, multi-modality imaging, data reduction as well as improved sensitivity, specificity and robustness.

In einem Überblicksvortrag werden aktuelle Fakten und Entwicklungen zur Kernenergienutzung in Deutschland und der Welt vorgestellt und diskutiert. Das schließt auch die Darstellung aktueller Forschungsschwerpunkte für gegenwärtige und zukünftige Reaktoren ein.

The nature of the sodium void effect in an infinite lattice is discussed with all different contributions. In a next step, the insertion of a layer consisting of moderating material for a reduction of the effect is proposed. The effect of three different moderating layers on the sodium void defect, the neutron spectrum, and the kinf over burnup is investigated. Special emphasis is given to the influence of the moderation layer on the feedback effects. Especially the uranium-zirconium hydride UzrH layer causes a strong reduction of the sodium void effect. Additionally this layer improves the fuel temperature effect and the coolant effect of the system significantly. All changes cause by the insertion of the UZrH layer lead to a significant increase in stability of the fast reactor system against transients. The moderating layers have only a small influence on the breeding effect and on the production of minor actinides. The insertion of the moderating layer does not imply any constraints on the core design and the power distribution in the fuel element an. Thus the use of a moderation layer gives the opportunity of designable feedback effects in a fast reactor core.

The SC3A experiment in the YALINA-Booster facility in Belarus is described and investigated. For this investigation the very special configuration of YALINA-Booster core, consisting of a fast and a thermal zone, decoupled with a neutron ‘valve’is analyzed based on a full HELIOS model for the calculations. The effect of the two region design on the experimental results at different detector positions is leading to unexpected results and the special problems for the analysis of the experiments have been shown. For a more detailed representation, a recently developed two group analytical solution for the time dependent diffusion equation obtained by Green’s function method without separation of space and time was used. To model the above mentioned streaming of neutrons from the thermal area into the fast area an analytical solution for the time dependent neutron flux with two sources has been developed from the available Green’s functions for two groups. In addition to the central source pulse of the external source a source at the boundary of the system has been introduced. The new analytical solution shows very good agreement with the experimental results, even for the unexpected behavior of the outermost deterctor. Thus analytical solution without separation of space and time are a very promising tool to develop a new method for the analysis of ADS experiments.

This paper presents arrangement of the problem, methodology of experiment performance and results of experimental investigation of coolant mixing in downcomer and lower plenum of VVER-1000. Three groups of experiments simulating coolant mixing were executed: in conditions of RCP start-up, during natural circulation recovery in the course of SB LOCA and in conditions of stable operation of different amount of RCPs. Results of experiments are used for validation of codes.

In-vessel turbulent mixing phenomena affect the time and space distribution of coolant properties (e.g. boron concentration and temperature) at the core inlet which impacts consequently the neutron kinetics response. For reactor safety evaluation purposes and to characterize these phenomena it is necessary to set and validate appropriate numerical modelling tools to improve the current conservative predictions. With such purpose, an experimental campaign was carried out by OKB Gidropress, in the framework of the European Commission Project “TACIS R2.02/02 - Development of safety analysis capabilities for VVER-1000 transients involving spatial variations of coolant properties (temperature or boron concentration) at core inlet”. The experiments were conducted on a scaled facility representing the primary system of a VVER-1000 including a detailed model of the Reactor Pressure Vessel with its internals. The simulated transients involved perturbations of coolant properties distribution providing a wide validation matrix. The main achievements of the set of experiments featuring transient asymmetric pump behaviour are presented in this paper. The potential of the obtained experimental database for the validation of thermal fluid dynamics numerical simulation tools is also discussed and the role of computational fluid dynamics in supporting the experimental data analysis is highlighted.

Variable-angle and Mueller matrix spectroscopic ellipsometry measurements of highly anisotropic plasmonic materials composed of random and aligned silver nanoparticles and nanorods are presented. We show that the effective dielectric tensors of randomly dispersed particles are uniaxially anisotropic and those of aligned particles are biaxially anisotropic, with the anisotropy predominantly at the plasmonic resonances. The strong resonances in nanorod arrays result in the real part of the effective in-plane permittivities being opposite in sign over a significant range in the visible, suggesting the potential to design materials that display tunable negative-refraction.

A concentration of dipole strength at energies below the giant dipole resonance was observed in neutron-rich nuclei around 132Sn in an experiment using the FRS-LAND setup. This so-called “pygmy” dipole strength can be related to the parameters of the symmetry energy and to the neutron skin thickness on the grounds of a relativistic quasiparticle random-phase approximation. Using this ansatz and the experimental findings for 130Sn and 132Sn, we derive a value of the symmetry energy pressure of p-bar0 = 2.2±0.5 MeV/fm3. Neutron skin thicknesses of Rn−Rp = 0.23±0.03 fm and 0.24±0.03 fm for 130Sn and 132Sn, respectively, have been determined. Preliminary results on 68Ni from a similar experiment using an improved setup indicate an enhanced cross section at low energies, while the results for 58Ni are in accordance with results from photoabsorption measurements.

The influence of the annealing atmosphere on the temperature induced phase separation of Ge oxide in GeOx/SiO2 multilayers (x ~ 1) leading to size controlled growth of Ge nanocrystals is explored by means of x-ray absorption spectroscopy at the Ge K-edge. Ge sub-oxides contained in the as-deposited multilayers diminish with increasing annealing temperature, showing a complete phase separation at approximately 450 °C using inert N2 ambient. The use of reducing H2 in the annealing atmosphere influences the phase separation even in an early stage of the disproportionation. In particular, the temperature regime where the phase separation occurs is lowered by at least 50 °C. At temperatures above 400 °C the sublayer composition and thus the density of the Ge nanocrystals can be altered by making use of the reduction of GeO2 by H2.

Präsentation von PIConGPU

Results on pp, π⁺π⁺, and π^-π^- intensity interferometry are reported for collisions of Ar+KCl at 1.76$A$~GeV beam energy, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18/GSI. The experimental correlation functions as a function of the relative momentum are compared to model calculations allowing the determination of the space-time extent of the corresponding emission sources. The π π source radii are found significantly larger than the pp emission radius. The present radii do well complement the source-size excitation functions of the collision system of size $A+A \simeq 40+40$. The pp source radius at fixed beam energy is found to increase linearly with the cube root of the number of participants. From this trend, a lower limit of the pp correlation radius is deduced.

Base and weld metal and cladding of the not commissioned SKODA reactor pressure vessel of Greifswald Unit 8 was investigated. Tensile, Charpy size SE(B) and 0.5T-C(T) specimens were irradiated at the LYRA and BAGIRA irradiation rigs with different neutron fluxes. The main focus was on fracture toughness testing according to the Mater Curve approach and crack extension curves. With these tests the reference temperature T0 and fracture toughness values for ductile tearing according to the ASTM test standards ASTM E1921 and ASTM E1820, respectively, were determined.
The irradiation in the LYRA rig with a neutron flux of about 1.57•1012 n/cm² results in shifts of the reference temperature ΔT0 which correspond with the prediction according to the Russian WWER-440 code. In contrast the BAGIRA irradiation with a neutron flux of about 68.6•1012 n/cm2 results in remarkable higher ΔT0 values then predicted. For weld metal from multilayer welding seams the orientation of the specimens is crucial for the direct measurement of the fracture toughness by using the MC concept. The evaluation of J-R curves measured on Charpy size SE(B) specimens is demanding because of the unsteady developing through the different structures of the cladding.

The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald NPP representing the first generation of Russian type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The Greifswald RPVs represent different material conditions viz. irradiated, irradiated and annealed and irradiated, annealed and re-irradiated.
The paper presents test results measured on the trepan taken from the beltline welding seam located in the reactor core region of the Unit 4 RPV. This unit was shut down after 11 years of operation and represents the irradiated condition. The working program comprises chemical analysis, microstructure investigations (by means of metallography and SEM), mechanical testing (hardness and tensile), and fracture mechanics testing. The key part of the testing is focused on the determination of the reference temperature T0 following the ASTM test standard E1921-10. The KJc values measured on TS oriented pre-cracked and side-grooved Charpy size SE(B) specimens from defined thickness locations of the welding seam approximately follow the course of the Master Curve but with a large scatter. Reference temperatures T0 through the thickness of the RPV beltline welding seam runs almost opposite to the trend predicted by the Russian code for the decrease of the neutron fluence from 5.1•E19 n/cm² to 1.1•E19 n/cm2 (E>0.5MeV). T0 varies between 6°C from near the welding root at ¼ wall thickness to 117°C at ¾ wall thickness. The scatter of T0 beyond the welding root is about 40 K and depends strongly on the structure at the crack tip. The results are also evaluated according to integrity assessment procedures based on the Master Curve concept.

Processing of small structures on µm- or nm-scales using swift heavy ions of some MeV/u energy (SHI) has become an important research topic because of the unique features of the ion irradiation technique. Each single ion impact in the solid results in a highly excited (some eV per atom), almost one-dimensional excitation, which because of its cold surrounding lasts for only a few tens of picoseconds. In many crystalline materials (especially insulators) this rapidly quenched local excitation manifests itself in a highly disordered or even amorphous cylinder of the above mentioned dimensions. The irradiation was carried out in our new in-situ high resolution scanning electron microscope (HRSEM), which we have recently installed at the new UNILAC accelerator of the Helmholtz Gesellschaft für Schwerionenforschung (GSI) in Darmstadt. This setup enables us to perform sequences of combined ion irradiation and HRSEM analysis steps at one and the same spot on target surface throughout the whole experiment and allows us to investigate the evolution of individual objects during ion irradiation with a lateral resolution of a few nm. The specimen consisted of a 100 nm thick NiO film, which has been deposited onto an oxidized Si substrate by of reactive magnetron sputtering. The film was prestructured with a grid of 50 x 50 right-angled trenches by means of a focused ion beam (FIB) at the Forschungszentrum Dresden-Rossendorf. The trenches extended from the surface down to the NiO/SiO2 interface and had a width of about 100 nm. The distances were varied from 0.2 µm to 5 µm, with always 5 trenches having the same distance. This way NiO-blocks of 100 nm height were created, having quadratic (along the diagonal of the grid) respectively rectangular cross sections (off-grid elements). The specimen was then irradiated with 5.9 MeV/u U-ions under grazing incidence (tilt angle 80) and continuous azimuthal rotation (angular velocity 1.45_/s). We have investigated the reshaping of µm- to nm-sized rectangular NiO-blocks by SHI irradiation under grazing incidence and continuous azimuthal rotation. While initially small blocks form single pillar-like structures, blocks of larger dimensions rearrange into tooth-like objects. Below a certain size (~100 nm in diameter) the structures become instable and start to move and coalesce. The plastic deformation and the formation of the pillars can be understood in terms of the hammering effect (or better: in terms of isotropic tensile in-plane stresses due to the irradiation). The observed saturation effect and the instability until now remain unexplained and need further experiments for their clarification.

Compton camera imaging is a promising technique for the measuring of high energetic gamma rays. Potential applications of Compton cameras are homeland security and medical imaging.
Up to now the only method for the monitoring of ion radiation therapy is positron emission tomography (PET). The main disadvantage of the PET technique is the distortion of the measured β+-activity by metabolism and blood flow due to a half-live of up to 20 min for the therapy relevant positron emitters. This problem can be overcome by measuring the prompt photons of wide energies using Compton cameras. Compton cameras can also be used in homeland security for location and nuclide identification of remote radiation sources.
We developed an application independent method for representation and calculation of the system matrix (SM) for Compton cameras. The method provides a structured approach for the SM creation which simplifies the software development process and the optimization of the computational performance. Additionally, the SM calculation is completely independent of the reconstruction algorithm itself.
The first reconstruction results based on this unified SM calculation approach for medical imaging and homeland security applications are presented.

no abstract available

Thermodynamic parameters for the complexation of Eu³⁺ with pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid, BTC) as a model system for polymerisable metal-complexing humic acids were determined using temperature-dependent time-resolved laser-induced fluorescence spectroscopy (TRLFS) and isothermal titration calorimetry (ITC). At low metal and ligand concentrations (<50 µM Eu³⁺, <1 mM BTC), a 1:1 monomeric Eu-BTC complex was identified in the range of 25-60°C. At elevated concentrations (>500 µM Eu³⁺ and BTC) a temperature-dependent polymerization was observed. The two methods lead to consistent thermodynamic data (ΔH = 18.5 ± 1.5/16.5 ± 0.1 kJ mol^-1; ΔS = 152 ± 5/130 J mol^-1 K-1; TRLFS/ITC) in the absence of polymerisation. With the onset of polymeristaion, TRLFS reveals the water coordination number of the lanthanide, whereas calorimetry is superior in determining the thermodynamic data in this regime. Evaluating the heat uptake kinetics, the monomer and polymer formation steps could be separated by "time-resolved" ITC, revealing almost identical binding enthalpies for the sequential reactions. Structural features of the complexes were studied by Fourier-transform infrared (FTIR) spectroscopy in combination with density functional theory (DFT) calculations showing predominantly monodentate binding of a single carboxylate group in both the monomeric and the polymeric complexes of the polycarboxylate with Eu3+. The data show that pyromellitic acid is a suitable model for the study of metal-mediated polymerisation as a crucial factor in determining the effect of humic acids on the mobility of radionuclides in soils.

Two humic acids (HAs) were isolated from contaminated river sediments present under comparative conditions in the Pearl River Basin, China. YFHA (the HA extracted at an open pyrite mining area in Yunfu) exhibits a lower absorption intensity for certain bands in the Fourier Transform Infrared spectra, a lower E4/E6 value (the UV absorbances at 465 nm (E4) and 665 nm (E6)), a lower apparent molecular weight, a lower polarity index and a lower oxygen functionality in comparison with GZHA (the HA isolated at an urban living area in Guangzhou). All these differences generally indicate a higher degree of humification of YFHA than GZHA. Overall, the enrichment patterns of permanent heavy metals in the studied HAs are similar to those in the corresponding sediments. In particular, YFHA exhibits high enrichment of trace element Tl, a characteristic concomitant from the mining of the pyrite minerals. The adsorption isotherms of two HAs for goethite and pyrolusite--two representative geological materials generally conform to the Langmuir equation. Based on the qualitative relationships between the Langmuir constants of the adsorption isotherms and the chemical characteristics of HAs, the main mechanism of HA adsorption on these materials is suggested to be hydrophobic interaction. This study highlights the promising use of HA as a peculiar bio-indicator of uncommon trace metal contaminations. The HA adsorption mechanism on representative geological materials further provides a theoretical basis for the study on the unusual metal behavior in complex environmental settings.

For the long-term development of nuclear power, innovative nuclear systems such as Gen-IV reactors and transmutation systems need to be developed for meeting future energy challenges. Thermal-hydraulics is recognized as a key scientific subject in the development of innovative reactor systems. In Europe, a consortium is established consisting of more than 20 institutions of research centers, universities and nuclear industries with the main objectives to identify and to organize research activities on important crosscutting thermal-hydraulic issues encountered in various innovative nuclear systems. A large-scale integrated research project is proposed to FP7 of European Commission and expected to start in the near future.
The main topics considered in the THINS (Thermal-Hydraulics of Innovative Nuclear Systems) project are (a) Advanced reactor core thermal-hydraulics; (b) Single phase mixed convection; (c) Single phase turbulence; (d) Multiphase flow; (e) Numerical code coupling and qualification. The main objectives of the project are:

• Generation of a data base for the development and validation of new models and codes describing the selected crosscutting thermal-hydraulic phenomena. This data base contains both experimental data and data from direct numerical simulations (DNS).
• Development of new physical models and modelling approaches for more accurate description of the crosscutting thermal-hydraulic phenomena such as heat transfer and flow mixing, turbulent flow modelling for a wide range of Prandtl numbers, and modelling of flows under strong influence of buoyancy.
• Improvement of the numerical engineering tools and establishment of a numerical platform for the design analysis of the innovative nuclear systems. This platform contains numerical codes of various classes of spatial scales, i.e. system analysis, sub-channel analysis and CFD codes, their coupling and the guidelines for their applications.

Ziel: It is accepted that at least two σ receptor subtypes exist, termed σ1 and σ2 [1, 2]. Of these, σ1 receptor, the best characterized up to now [3], is assumed to be involved in several neurological diseases. PET imaging using specific σ1 receptor radioligands could be very helpful to obtain a target validation during drug development, a quantitative in vivo mapping of σ1 receptors as well as an improvement of our understanding of all the processes in which σ1 receptors are involved. Recently, a new class of spirocyclic piperidines with high affinity and selectivity for σ1 receptor binding site has been developed. Within this series, [18F]WMS1813 ([18F]1’-benzyl-3-(3-fluoropropyl)-3H-spiro[[2]benzofuran-1,4’-piperidine]) has been successfully developed and used for detection of central σ1 receptors in mice [4]. Further structure-activity relationship studies on the linear ω-fluoroalkyl chain provided three other promising analogues, bearing either fluoromethyl- (WMS1850), fluoroethyl- (WMS1828) or fluorobutyl- (WMS1847) moieties. Herein, we report on the radiosynthesis and preliminary biological evaluation of these new candidates for PET imaging of σ1 receptors.
Methoden: [18F]WMS1850, [18F]WMS1828, and [18F]WMS1847 were synthesized by direct aliphatic nucleophilic substitution of the corresponding tosylate precursors by using the K[18F]F-K222-carbonate complex. For each radiotracer studied, solvent, temperature, reaction time and precursor concentration were optimized. Preliminary experiments on lipophilicity, chemical stability, organ distribution and metabolic stability in CD-1 mice were performed.
Ergebnisse: Optimisation of radiofluorination parameters provided high labelling efficiencies of 61-88% using acetonitrile or DMSO as solvent, at 83 °C or 150°C respectively, with precursor concentrations between 2.0 and 3.0 mg/mL. [18F]WMS1850, [18F]WMS1828, and [18F]WMS1847 were obtained with radiochemical yields of 43-50%, 35-45%, and 45-53%, respectively, radiochemical purities of >98.5%, and high specific activities, generally ≥150 GBq/µmol. Distribution coefficients determined experimentally (Log D = 2.39-3.16, pH = 7.2), underline the moderate lipophilic character of the three radiotracers. The radiolabeled compounds also show appropriate chemical stabilities in acetonitrile, PBS, TRIS-HCl, and Dulbecco buffer.
No radiometabolites permeated into the brain of mice up to 60 min p.i. Metabolic profiles in liver, plasma, and urine were also investigated. By ex vivo autoradiography, the highest target (facial nucleus)-to-nontarget (olfactory bulb) tissue ratio has been determined for [18F]WMS1828 with a value of 4.69 at 45 min p.i. [18F]WMS1828 was superior also in organ distribution studies with a value of brain uptake of 4.71 ± 1.39 %ID/g in comparison to [18F]WMS1813 (3.18 ± 0.68 %ID/g), and [18F]WMS1847 (1.78 ± 0.16 %ID/g), and [18F]WMS1850 (2.65 ± 0.68 %ID/g) at 30 min p.i.
Schlussfolgerungen: For the three radiotracers studied, optimised protocols led to very efficient radiosyntheses. With respect to first biological data, [18F]WMS1828 appears to be the most promising candidate for PET imaging of σ1 receptors, with even better pharmacological profile than the lead compound. Hence, [18F]WMS1828 radiosynthesis is selected for transfer onto an automated radiosynthesis module with a view to further clinical development.
Referenzen:
[1] Quirion, R.; Bowen, W. D.; Itzhak, Y.; Junien, J. L.; Musacchio, J. M.; Rothman, R. B.; Su, T. S.; Tam, S. W.; Taylor, D. P. Trends Pharmacol Sci. 1992; 13: 85-86.
[2] Hayashi, T. ; Su, T. P. Current Neuropharmacology. 2005; 3: 267-280.
[3] van Waarde, A.; Ramakrishnan, N. K.; Rybczynska, A. A.; Elsinga, P. H.; Ishiwata, K.; Nijholt, I. M.; Luiten, P. G. M.; Dierckx, R. A. Behavioural Brain Research. 2010; doi:10.1016/j.bbr.2009.12.043.
[4] Maestrup, E. G.; Fischer, S.; Wiese, C.; Schepmann, D.; Hiller, A.; Deuther-Conrad, W.; Steinbach, J.; Wünsch, B.; Brust, P. J. Med. Chem. 2009; 52: 6062-6072.

In order to develop a fluorinated radiotracer for imaging of σ1 receptors in the central nervous system a series of (2-fluoroethyl) substituted spirocyclic piperidines 3 has been prepared. In the key step of the synthesis 2-bromocinnamaldehyde acetal 5 was added to piperidones 6 with various substituents at the N-atom. Unexpectedly, this reaction led to 2-benzoxepines 8, which were contracted with acid to afford the spirocyclic 2-benzofuranacetaldehydes 9. The best yields were obtained, when the transformations up to the alcohols 10 were performed without isolation of intermediates. Generally the (2-fluoroethyl) derivatives 3 have higher σ1 affinity and σ1/σ2 selectivity than the corresponding (3-fluoropropyl) derivatives 2. The most promising candidate for the development as radiotracer is the (2-fluoroethyl) derivative 3a (WMS-1828, fluspidine, 1’-benzyl-3-(2-fluoroethyl)-3H-spiro[[2]benzofuran-1,4’-piperidine]), which shows subnanomolar σ1 affinity (Ki = 0.59 nM) and excellent selectivity over the σ2 subtype (1331-fold) as well as some other receptor systems. The novel synthetic strategy also allows the systematic pharmacological evaluation of intermediate alcohols 10. Despite their high σ1 affinity (Ki = 6-32 nM) and selectivity the alcohols 10 are 10-30-fold less potent than the bioisosteric fluoro derivatives 3.

The pathogenetic role of the central serotonin transporters (SERT) in obsessive-compulsive disorder (OCD) has been investigated in vivo by positron emission tomography (PET) or single-photon emission computed tomography (SPECT) studies with inconsistent results. This might reflect methodological differences but possibly also the pathophysiological heterogeneity of the disorder, i.e. the age at onset of OCD. The aim of our study was to compare the SERT availability in patients with OCD to healthy controls (HC) taking into account the onset type, other factors and covariates (e.g. SERT genotype, age, depression level, gender). We studied 19 drug-naïve OCD patients (36±13 years, 8 females) with early onset (EO-OCD, n=6) or with late onset (LO-OCD, n=13), and 21 HC (38±8 years, 9 females) with PET and the SERT-selective radiotracer [11C]DASB. Statistical models indicated that a variety of covariates and their interaction influences SERT availability as measured by distribution volume ratios (DVR). These models revealed significant effects of onset type on DVR with lower values in the LO-OCD (starting at an age of 18 years) compared with EO-OCD and HC in limbic (e.g., the amygdala), paralimbic brain areas (the anterior cingulate cortex), the nucleus accumbens and striatal regions, as well as borderline significance in the thalamus and the hypothalamus. The putamen, the nucleus accumbens and the hypothalamus were found with significant interaction between two SERT gene polymorphisms (SERT-LPR and VNTR). These findings suggest that late but not early onset of OCD is associated with abnormally low SERT availability. In part, functional polymorphisms of the SERT gene might determine the differences.

Artificial antiferromagnets made from magnetically coupled trilayer structures are the basis for all types of spintronic devices like MRAM, GMR sensors etc. For years major effort lay on adjusting the coupling strength by changing the spacer thickness or material. Today, nanostructures offer a different approach as they add additional coupling mechanisms like proximity effects or Néel orange-peel coupling to the common interlayer exchange coupling (IEC). By means of ion beam erosion techniques it is possible to create well ordered substrate ripples with nanometer periodicity. They are transferred into the films grown on these rippled substrates. Hence, such ripples are a convenient way to induce Néel orange-peel coupling [1] and thus allow for tailoring the magnetic properties [2] as well as the coupling strength by varying the ripple periodicity without adjusting the spacer thickness. We have investigated the influence of rippled vs. flat Si substrates on the interlayer exchange coupling contributions in polycrystalline Fe (4nm)/Cr (x nm)/Fe (4nm) thin film trilayers (x=0–5 nm). The substrate surface was periodically modulated (periods of 23 nm and 37 nm) by Ar+ ion beam erosion. The influence of the resulting surface and interface structure on the magnetic properties has been investigated by longitudinal magneto-optical Kerr effect (MOKE) applying a Stoner-Wohlfarth model on the magnetization reversal loops. Using 23 nm period ripples, we find an orange peel type coupling, predicted by Néel's theory superimposed on the IEC. In addition due to the morphology of the magnetic layers, a strong uniaxial magnetic anisotropy is induced.
This work is supported by DFG grant FA 314/6-1.
REFERENCES
1. Körner M. et al., Physical Review B 80, 214401, 2009.
2. Fassbender J. et al., New Journal of Physics 11, 125002, 2009

no abstract available

no abstract available

Thema zur Einreichung im DFG-Schwerpunktprogramm

Bio-inorganic materials are very attractive for a variety of technical applications. The use of self-assembling proteins as part of such a hybrid material is an attractive approach for the development of such materials. Especially the proteinaceous paracrystalline bacterial surface layers (S-layers) that envelop bacterial cells are attractive for fabricating and patterning of nanostructures. These proteins are mostly composed of protein monomers with the ability to self-assemble into two-dimensional arrays on interfaces and surfaces. The regular distributed pores of these paracrystalline arrays work as binding sites for various metals and offer ideal structures for the formation of regular distributed metallic nanoclusters of a defined size [1]. Such arrays are very attractive for technical applications ranging from the development of novel catalysts to biomedical applications, the programmed assembly of nanometre scale electronic devices, and optical industry [2]. Another approach is the embedding of S-layer proteins into ceramics thus producing metal binding functionalized nanocomposites [3].
In a current project we use monolayers of the S-layer protein of Lysinibacillus sphaericus for the construction of sensory layers. These S-layers are functionalized by aptamers (oligonucleotides) that work as receptor and two different fluorophores working as donor/acceptor for detection. Appropriate excitation/emission spectra and closest proximity of the fluorophores permit FRET. The binding of the analyte to the aptamer should influence the fluorescence, ideally causing the interruption of the FRET.
In other projects we used the S-layers for the formation of (photo)catalytic layers. In this approach S-layers work as template for the bioinspired formation of (photo)catalytic particles such as Pd or ZnO. Size, crystallinity, distribution and morphology of the particles are influenced by the proteinaceous template.
These examples demonstrate the high potential of the S-layers for various applications.

[1] Wahl, R. et al. (2001). Adv. Materials 13, 736-740
[2] Pollmann, K. et al. (2006). Biotechnol. Adv. 24, 58-68
[3] Raff, J. et al. (2003). Chem. Mater. 15, 240-244

In a forest close to the city of Dresden, Germany, lies the ELBE radiation source - the largest facility of the Research Centre Dresden-Rossendorf (FZD). After years of research, February saw the first SRF gun beam injected and accelerated in ELBE. Jochen Teichert tells more about the facility, the research and the gun.

The driving forces of nanomaterials processing by swift heavy ions as identified by our studies are (i) the mate-rials dependent electronic stopping power, (ii) the vol-ume change upon melting, (iii) the asymmetric hydro-dynamic flow due to stress field hysteresis, as well as (iv) far-from-equilibrium steady-state solubilities and strongly anisotropic diffusion coefficients. Size distributions, shapes and anisotropies of nanoparticles can be tailored by appropriate tuning of these driving forces. The evolution of Au and Ge nanospheres under swift heavy ion irradiation was studied experimentally and by atomistic computer simulations. Ge nanospheres of different sizes embedded in SiO2 show different response to I7+ ion irradiation at 38 MeV. Spheres below a critical size become discus-shaped, very small ones show Ge loss at their equator. Computer simula-tions based on a model which includes the driving forces listed above describe the Ge shaping and the Au shaping, where Au nanospheres of 15 nm diame-ter elongate to rods. Our model describes the ion-induced shape evolution of different elements for different ion species, energies and fluences quantitatively, where only one fit parameter describes all experiments. This is a strong evidence that our model based on classical thermodynamics and hydrodynamics describes the shaping mechanism appropriate. Using critical-size nanospheres with an unimodal size distributions and changing the ion impact angle during irradiation, tailoring of very exotic nanoparticle shapes become feasible.

In 2004 Ketek has established a long term co-operation with the Reasearch Centre Dresden (FZD) and the Universität der Bundeswehr München (UBW) targeted on the development of new silicon radiation detectors as well as on their commerz-ialization.
Silicon Drift Detectors (SDDs) are widely used in XRF, TXRF, electron micro-probe analysis systems and synchrotron applications. The big benefit of SDDs compared to other x-ray de-tectors as Si(Li)s or pin-diodes is the spectroscopic performance principally being independent of the sen-sitive area. KETEK offers silicon drift detectors with sizes varying from 10 to 100 mm² whereby the large area devices become more and more attractive for most of the applications. Energy resolution below 130 eV for the Manganese Ka line and peak to background values of more than 10.000 can be achieved for devices with active areas of 100 mm² when cooled down to -60°C. This temperature can be already realized by a Peltier element integrated into the detector module, since the thermal budget of this evacuated device is well optimized. Count rate dependency of the energy resolution and the peak position is negligible up to count rates of 100.000 counts per second.
Silicon Photomultiplier (SiPMs) are single photon sensitive devices built from an avalanche photodiode (APD) array on common Si substrate, whereby the APDs are operated in Geiger modus (above break down voltage). All applications for this sensor are connected with fast low level light sensing like e.g. the indirect gamma radiation detection by a scintillator. The first SiPM prototypes which have been realized by Ketek in co-operation with FZD show promising val-ues for photon detection efficiency, dark rate and opti-cal cross talk. Now this detector shall be further opti-mized for PET application.

The properties of magnetic metals such as saturation magnetization and magnetic anisotropy can be modified in a controllable manner by energetic ions [1]. GaMnAs is a well known magnetic semiconductor. The ability to tune the magnetic properties of magnetic semiconductors is an important issue in future semiconductor devices. Here we tailored the magnetism of GaMnAs films by He+ ion irradiation. The GaxMn1-xAs films with a Mn concentration of 5% and the easy axis of magnetization lying in-plane have been grown on GaAs substrates by LT-MBE. He+ ions of 650 keV were used to place the peak of damage into the GaAs substrate, so that the GaMnAs epilayer lies in the relatively uniform part of the damage profile. We show that the coercivity can be increased (Fig.1) from 50 Oe to 165 Oe when the dose reaches 3×10¹⁴/cm² ~ 6×10¹⁴/cm². Meanwhile, the saturation magnetization at 5 K is only reduced slightly to 22 emu/cm3 compared to non-irradiated GaMnAs films with a saturation magnetization amounting to 27 emu/cm3. Magneto-transport results indicate that the sheet resistance is increased by about 4 times compared to the non-irradiated GaMnAs film with a sheet resistance of 103 Ω. The irradiated GaMnAs still has an in-plane easy axis of magnetization at 5 K, but the anisotropy energy is much decreased. When the dose increases to 1×10¹⁵/cm², no M-H hysteresis has been probed. Our study demonstrates the tailoring of magnetism and magnetoresistance in GaMnAs films by He+ ion irradiation.
[1] J. Fassbender and J. McCord, J. Magn. Magn. Mater. 320 (2008) 579–596

The success of GaMnAs ferromagnetic semiconductors stands on two facts: (1) the efficient suppression of Mn-rich precipitates and (2) the large hole concentration created by substitutional Mn ions. If GaMnAs can be a guide, these two prerequisites should be considered when fabricating Si based ferromagnetic semiconductors. In this paper, nearly intrinsic Si wafers were implanted with Mn ions. The implanted Si films were annealed by pulsed laser annealing (PLA) or rapid thermal annealing (RTA). Activation of acceptors was only realized in the PLA films with a free hole concentration of 4×10¹⁷ cm^-3, compared to the activation of donors in RTA films with a free electron concentration of 6×10¹⁵ cm^-3. The PLA films reveal negative magnetoresistance with MR= 0.5% at 20 K and 30 K and at 7 T, hinting towards spin polarization of holes. Ferromagnetism was probed for both RTA and PLA films by a SQUID magnetometer at low temperatures. The formation of ferromagnetic MnSi1.7 nanoparticles has been proven in RTA films by synchrotron radiation X-ray (SR-XRD) measurements [1] and could be excluded in Mn implanted Si annealed by PLA.
[1] S. Zhou et al., Phys. Rev. B 75, 085203 (2007).

Low energy ion implantation has been applied to fabrication of shallow piezoresistive elements for AFM deflection sensing. The corresponding process parameters have been optimized to meet the demands of the electronics (power supply, resistance) connected to the piezoresistors. For the dimension (length x width = 5x20 µm2) of the piezoresistors designed by the University of Ilmenau, the resistance of them is 2.3-2.5 kOhm. The full processing of PRONANO AFM arrays consists additional three ion implantation steps for integrated heater and interconnect fabrication as well as for substrate reverse-biasing.

During molecular dynamics (MD) simulation of Xe+, 500eV ion bombardment with the incidence angle 67° on Si (001), some dislocation patterns of near surface Si atoms were observed. We focused on the distribution of adatom generation points on Si (001) surface.
After 500 single ion bombardment MD simulations, the observed distribution shapes Gaussian distribution with different aspect ratio. The center of distribution is around 1.8 nm forward from the impact point. We performed 3 dimensional lattice kinetic Monte-Carlo simulations with this adatom generation distribution and surface diffusion process. In early stage, the surface was simply roughened homogeneously and after around 3 x 10¹⁵ ion/cm² dose, the surface started to form ripple structure perpendicular to the azimuthal incidence angle with wavelength ~15 nm. The ripple moves forward to the incident angle. These processes agree nicely with experimental observation. The mechanism of ripple formation related to surface atomic flows induced by ions, surface damage distribution and Mullin’s diffusion is discussed.

Energy-filtered transmission electron microscopy (EFTEM) in combination with electron energy loss spectroscopy (EELS) and cathodoluminescence (CL) have been used to investigate Si+-implanted amorphous silicon dioxide layers and the formation of Si nanoclusters. Therefore, amorphous, thermally grown SiO2 layers on Si substrate were implanted by Siþ ions with an energy of 150 keV and a dose of 5x1016 ions/cm2 leading to an atomic dopant fraction of about 4 at%. Afterwards a post-implantation thermal annealing has been performed at temperatures Ta=700–1300 °C, for 60 min in vacuum. This thermal annealing leads to Si cluster formation and a change of the SiOx matrix from about x=1.923 to 1.929 connected with additional visible luminescence bands in the green-yellow region. CL spectra in the near infrared (NIR) region indicate such Si aggregation by appearance of an additional band in extension of the common NBOHC band at 1.9 eV towards the NIR region. This band shifts with increasing annealing temperatures of the implanted sample to lower energies, probably, due to cluster growth and quantum confinement effects.

A self-alignment of metal nanoclusters has been observed on ripple like pre-patterned oxidized Si surfaces by oblique angle electron-beam evaporation. During the metal deposition perpendicular to ripples the metal nanoclusters are grown on the slopes which point towards the evaporation source.The self-ordering of metal nanoclusters has not been observed for normal deposition and for low-angle deposition parallel to the ripple direction. This indicates that the features of the metal nanostructure depend strongly on the local deposition angle. With the 3D lattice kinetic Monte Carlo simulations we studied the process of silver deposition on pre-patterned surfaces. The experimentally observed Ag nanostructures could be reproduced by using the many-body potential to estimate the atomistic migration barriers. It was shown that the extremely short range of surface adatom migration causing low sticking probability together with a slope-dependent deposition rate promotes the localization of the Ag nanocluster nucleation distribution. Consequently, the observed selective Ag nano structure formation can be understood by the separation of the Volmer-Weber growth mode and the layer-by-layer growth mode due to the localized coalescence of clusters.

Atomistic understanding of surface morphology evolution induced by ion beam sputtering is still strongly limited. Available continuum models cannot explain microscopic processes during ion beam irra-diation. On the other hand, so far atomistic simula-tions could not describe pattern dynamics in the spa-tiotemporal scales of experiments.
However, combined atomistic single ion impacts with continuum equations [1] gives a better under-standing of additional smoothing mechanisms, like an effective mass ‘downhill’ current induced by ballistic atomic drift [2][3].
We developed a novel program package which unifies the collision cascade with kinetic Monte-Carlo simulations. The 3D atom relocations were calculated in the Binary Collision Approximation (BCA), whereas the thermally activated relaxation of ener-getic atomic configurations as well as diffusive proc-esses were simulated by a very efficient bit-coded kinetic 3D Monte Carlo code.
Effects like ballistic mass drift or dependence of local morphology on sputtering yield are automati-cally included in the BCA approach. Distributions presented in Figure 1 show the mean preferential lo-cation of ad-atoms creation and the sputtering re-gions.
Low energy (up to 5 keV) ion a sputtering simula-tions have been performed on the simulation cell of about 17 million atoms, where irradiation fluence goes up to few 10¹⁸ cm^-2. The pattern topography has been study by means of various intensive parameters like incidence angle (Fig. 2), ion beam energy, ion fluence, and migration energy of defects. Moreover, the scaling behaviour of surface roughness and pat-tern periodicity has been analysed.
Finally, we compare our results with experiments as well as with continuum theory.
[1] S. A. Norris and M. P. Brenner and M. J. Aziz J. Phys. Condens. Matter 21 (2009) 224017.
[2] G. Carter and V. Vishnyakov PRB 54 (1996) 17647.
[3] M. Moseler and P. Gumbsch and C. Casiraghi and A. C. Ferrari and J. Robertson Science 309 (2005) 1545.

Recent developments in computational materials modelling methods have to provide a qualitatively new level of predictive power and insight into materials design. In nature, different physical processes govern simultaneously the evolution of systems. Due to the complexity of the individual processes, so far their simulations are performed separately. One key to computational progress is the multiphysical treatment in a single computer program package.
Here, we consider the evolution of interfaces under energetic ion irradiation. There, the physical process of collisional mixing is in competition with thermally activated diffusion and phase separation. We developed a novel program which treats both physical processes simultaneously. The 3D atom relocations were calculated in the Binary Collision Approximation (BCA), whereas the thermally activated relaxation of energetic, atomic configurations as well as diffusive processes, were simulated by a very efficient bit-coded kinetic 3D Monte Carlo code. Contrary to molecular dynamics simulations, our approach allows studies on experimental spatiotemporal scales.
As applications we present two extremes of interface mixing: (i) Irradiation of interfaces made by immiscible elements, here Al and Pb, with He ions causes ballistic interface mixing accompanied by phase separation. Al and Pb clusters, which form in the interface region, show self-ordering. (ii) Irradiation of interfaces made by metals which form intermetallics, here Pt and Co, with He ions causes the formation of nanometric intermetallic layers with the sequence Pt/Pt3Co/PtCo/PtCo3/Co across the former interface. In the element mapping perpendicular to the interface (e.g. by RBS measurements), this results in step-wise changes of Pt/Co concentrations. Novel magnetic properties of such sandwiched phases are expected. In particular, a very interesting magnetic behaviour of irradiated Pt/Co/Pt multilayers has been observed. It can be shown that the transition between out of plane and in-plane magnetic anisotropy can be triggered by ion beam irradiation, whereas computer experiment can be useful for understanding the physical mechanism.

By utilizing electron-beam evaporation, metal nanoclusters have been produced on pre-patterned oxidized Si surfaces. During the oblique deposition perpendicular to ripples the metal nanoclusters are grown on the slopes which point towards the evaporation source.The self-ordering of metal nanoclusters has not been observed for normal deposition and for low-angle deposition parallel to the ripple direction. This indicates that the features of the metal nanostructure depend strongly on the local deposition angle. Here, by means of 3D lattice kinetic Monte Carlo simulations, we studied the process of silver deposition on pre-patterned surfaces. The experimentally observed Ag nanostructures could be reproduced by using the many-body potential to estimate the atomistic migration barriers. It was shown that the extremely low sticking probability of deposited Ag together with a slope-dependent local deposition rate leads to a strongly localized Ag nanocluster nucleation distribution on the surface because the nucleation rate depends approximately on the dimer adatom concentration.

Corrosion of hot-dip galvanized grating treads, installed in the containment, may exacerbate ECCS strainer clogging problems during LOCA incidents in LWR. In order to identify the corrosion mechanisms as well as the nature of particulate corrosion products formed, corrosion investigations were carried out in boric acid solutions as well as in demineralized water using hot-dip galvanized steel samples. For the related experiments, tailored bench-scale facilities have been constructed. The results of batch experiments as well as of long-time corrosion investigations in the KorrVA test facility at FZD suggest that there is a multi-stage corrosion process. The first stage comprises the dissolution of the Zn layer in the acidic coolant forming zinc ions, which can generate crystalline zinc borate in boric acid solutions, if the ion concentration exceeds the saturation concentration. The base material (steel) is cathodically protected as long as the zinc layer is present. During the second stage, a slight head loss rise may occur due to the release of hard zinc (Zn/Fe) particles. After the complete removal of the hard zinc layer, the base material dissolves forming insoluble corrosion particles similarly to a flow accelerated corrosion process, which can subsequently lead to acceleration of the strainer clogging. The main influences on corrosion were identified as jet impact, water chemistry and Zn surface / coolant volume ratio.

Zur Aufklärung von Korrosionsprozessen und deren Auswirkungen auf die Verstopfung von mit Isoliermaterialfasern belegten Sumpfansaugsieben bei Kühlmittelverluststörfällen in Leichtwasserreaktoren wurden Korrosionsuntersuchungen in speziellen Laboranlagen unter Nutzung von feuerverzinkten Stahlproben durchgeführt. Die Ergebnisse der Batch- sowie der Langzeit-Korrosionsexperimente mit borsäurehaltigen Lösungen lassen auf einen mehrstufigen Korrosionsmechanismus schließen, wobei im ersten Schritt die Auflösung der Reinzinkschicht erfolgt. Die dabei entstehenden Zink-Ionen gehen in Lösung und tragen somit nicht signifikant zur Verstopfung der Sumpfansaugsiebe bei. Im weiteren Verlauf kann es zu einer leichten Differenzdruckerhöhung an den Sumpfsieben durch Ablösung von Partikeln aus der herstellungsbedingten darunterliegenden Hartzinkschicht (Zn/Fe-Legierung) kommen. Nach der kompletten Entfernung der Hartzinkschicht erfolgt eine strömungsinduzierte Korrosion des Basismaterials (Stahl), die zur Bildung unlöslicher Korrosionsprodukte des Eisens in Form kleiner Partikel führt. Diese Partikel lagern sich in die Isoliermaterialfasern an den Sumpfansaugsieben ein, was zu einer starken Erhöhung des Strömungswiderstandes führt. Der Differenzdruckanstieg beginnt, abhängig von den hydrodynamischen Bedingungen, 6 bis 15 Stunden nach Beginn der Beaufschlagung der Proben mit dem Leckwasserstrahl. Eine zweite (theoretische) Quelle für die Bildung partikelförmiger Produkte stellt die Kristallisation von Zinkborat aus einer übersättigten Lösung bei Temperaturerhöhung und/oder Verdampfung des Kühlmittels dar. Haupteinflussfaktoren des Gesamtprozesses sind die Aufprallkraft des Leckstrahls auf die Materialoberfläche, die Wasserchemie (Borsäurekonzentration, pH-Wert) sowie das Verhältnis der Korrosions-Oberfläche zum Kühlmittel-Volumen.

Demands on modern silicon detector technology and the detector development for improving analysis in the frame of the EU-Project SPIRIT will be described. For high energy resolution RBS and ERDA experiments large area silicon strip detector with increased sensitivity and energy resolution down to 10 keV FWHM (He+ at max. 2MeV) are required. By applying such strip detectors with certain position resolution kinematic correction procedures will be possible.

Starting from a random or ordered distribution of 0.8, 1.6, 3.7 and 12.5 % dopants over the lattice sites of a simple cubic host lattice, we estimate the fraction of unclustered dopants after pulsed laser quenching of different host:dopant systems. Initial clustering events are simulated with a greedy algorithm implemented in a Monte-Carlo study. The greedy algorithm gives adequate results for dopants with low diffusity and low solubility.
The absolute initial dopant concentration and declustering strongly in influence the kinetics of clustering. Particularly, we consider transition metal doped Si and GaAs after pulsed laser annealing, which are of interest for spintronics applications. An uncritical integral diffusion of Mn in GaAs:Mn and a tendency of Mn to form silicides in Si:Mn are simulated. These results are in good agreement with experimental observations.

Rutherford Backscattering Spectrometry (RBS) is an analysis technique that uses fast ions like He+ to obtain information about the chemical composition in the surface region. In case of crystalline samples, the ion beam can be aligned with the crystal orientation thereby allowing the ions to penetrate the sample much deeper than in a random direction. This results in a large reduction of the yield of backscattered ions, the so-called channeling dip. Information about crystal quality can be obtained from the width and the depth of the channeling dip. The position of atoms of a certain species in the crystal can de deduced from the yield reduction in various crystal orientations.

In this presentation, the basic principles of channeling are explained. Channeling can be used to obtain information about the position of impurities in a crystal and to assess damage caused by implantation and the quality of the crystal after subsequent annealing. Examples of these types of analysis are presented. Complementary PIXE (Particle Induced X-ray Emission) channeling can be applied to obtain information about elements that have a mass similar to the main elements, which cannot be measured with RBS. An example of PIXE channeling is also presented.

The III-V compound GaMnAs is considered as being the prototype diluted ferromagnetic semiconductor (FMS), exhibiting negative magneto-resistance (MR) and anomalous Hall-effect (AHE) related to carrier-mediated ferromagnetism. However, it would be very desirable to have a group-IV FMS, being compatible with silicon technology. In particular manganese-doped germanium prepared using low-temperature molecular beam epitaxy (LT-MBE) has been proven to be a very promising material [1]. Still, no direct correspondence between transport and magnetization data has been reported yet to date. We believe that the origin of these observations lies in the less effective substitution of Mn at Ge sites, which results in too low a hole concentration, making carrier-mediated ferromagnetism impossible. The hole concentrations realized in Ge:Mn grown by LT-MBE are mostly well below 10¹⁹ cm^-3, which indicates the possible unsuitability of LT-MBE to achieve a large hole concentration in Ge:Mn.
In this contribution, we show that the hole concentration can be increased by two orders of magnitude, from 10¹⁸ to 10²⁰ cm^-3, through Mn-ion implantation into Ge followed by pulsed laser annealing [2]. This non-equilibrium technique allows the preparation of metastable materials with interesting material properties, e.g. diluted ferromagnetic GaMnAs [3]. In Mn-doped Ge with a hole-concentration of around 2.1×10²⁰ cm^-3, we observe that the longitudinal and the Hall resistance exhibit the same hysteresis as the magnetization at temperatures below 10 K. This hysteresis in magneto-transport is usually considered as a direct evidence of carrier-mediated ferromagnetism. We will present a comprehensive correlation between the magnetic, transport and structural properties of Ge:Mn samples with different hole concentrations, as well as a comparison with literature. Note that ion implantation followed by pulsed laser annealing is an established scalable chip technology and may have a significant industry impact.

[1] Y. D. Park et al., Science 295, 651 (2002); M. Jamet et al., Nature Mater. 5, 653 (2006).
[2] S. Zhou et al., Phys. Rev. B 81, 165204 (2010).
[3] D. Bürger et al., Phys. Rev. B 81, 115202 (2010).

In Material Science (powder) diffraction methods are a common sample characterisation tool. Beside the laboratory sources synchrotron radiation offers the advantages of high brilliance and tuneable wavelength. As an example for high resolution diffraction the localisation of incorporated guest molecule in zeolites faujasite by crystal structure refinement will be presented.
Heavy load goniometer allows also experiments with high sophisticated sample environments to perform in-situ investigations. Hereby solid state reactions can be monitored or catalyst characterized. Carbon nano tubes (CNT) are synthesized by chemical vapour deposition and the use of iron nano particles. The catalyst processing and CNT synthesis was observed by XRD and the catalytic active species determinated.
By the use of hard X-rays absorption effects are minimized and more complex system like a secondary lithium ion battery can be investigated. Hereby the diffraction pattern of the system in operation can be collected. The charge-discharge behaviour of lithium manganese oxide will be discussed.
In general in-situ investigations have the advantage to monitor different processes directly and being more time efficient. Misleading results of ex-situ measurements by metastable phases, subsequent reactions or aging of the material are avoided.

The last few years have seen an increasing interest in in-situ investigations using different diffraction methods. This is one of the main applications of the Material Research Station of the Rossendorf Beamline (ROBL) at the ESRF. The beamline operates with a monochromatic beam in the energy range of 6 to 36 keV and an energy resolution of ΔE/E of 5*10-4. Equipped with a six circle goniometer, different high temperature chambers can be mounted and various diffraction experiments can be performed, e.g. under controlled reaction conditions. A detector bank behind the goniometer allows the use of additional heavy weight detectors. One field of interest is the synthesis of carbon nanotubes (CNT) by chemical vapor deposition. Here, CNTs were grown from iron nanoparticles acting as the catalyst. The particles were formed by annealing Fe thin films with thicknesses ranging from 1-10 nm. The Fe films were evaporated on Si substrates covered with a SiO2 or Al2O3 buffer layer respectively. The splitting was initiated by annealing the initial Fe films at a temperature of up to 760°C in an Argon/Hydrogen atmosphere at ~200 mbar. The reducing atmosphere also removed initially amorphous iron oxide layers. The splitting temperature depends on the buffer layer, and the particle size of the formed nanocrystals depends on the initial film thickness of the pristine material. Adding acetylene (C2H2) to the gas stream initiated CNT-growth. Two different reaction pathways were observed. A very high α/γ iron ratio at high temperature under reducing atmosphere led to the formation of iron carbide when acetylene is added. If the ratio is around 1, no carbide was observed during CNT synthesis. SEM images show a comparable yield of CNTs in both scenarios. Therefore, the catalytic activity of iron carbide in this process is doubtful [1]. The influence of the buffer layer will be discussed. Thick Ni films (>170 nm) can be used to synthesize graphene also by chemical vapour deposition [2]. Compared with the usual increase of the lattice parameter with temperature due thermal expansion (measured at 5*10-6 mbar), an unusual increase of the the lattice parameter is observed when acetylene is introduced (at 2*10-3 mbar). Also, Rietveld refinement does not reveal any structural changes. This effect can only be explained by cracking of the acetylene molecules on the surface and subsequent carbon storage on interstitials. Upon cooling to room temperature, the differences in lattice parameter are negligible. These examples show that in-situ investigations are a powerful and versatile tool to monitor the deposition of nanosized materials from chemical processes.

The nature of the S phase in austenitic stainless steel (ASS) produced by incorporation of large amounts of nitrogen is investigated. The S phase has been produced by plasma nitriding of AISI 304L ASS at 400 °C for 30 h. The S phase structure was studied using a combination of global (X-ray diffraction (XRD), nuclear reaction analysis, glow discharge optical emission spectroscopy) and local (Conversion Electron Mössbauer, X-ray absorption near edge structure, extended X-ray absorption fine structure (EXAFS) spectroscopies) probe techniques. This combination of analytical methods allows direct comparison of the data obtained from atomic up to macroscopic levels. The results show that Fe, Cr and Ni have different local chemical environments: Cr is very similar to CrN, Fe is in a phase similar to Fe4N, while Ni stays metallic. The N coordination is by a factor of 3 higher around than around Fe while negligible around Ni. Three lattice parameters for Fe, Cr and Ni, and a large disorder have been detected by EXAFS analysis. None of these phases could be identified by XRD, except a set of broad peaks which are commonly attributed to the supersaturated nitrogen solid solution in the literature. It is suggested that the incorporation of interstitial nitrogen destabilizes homogeneous distribution of ASS constituents and leads to the segregation of elements with the zones rich in Cr and Ni being small and coherent with the Fe-rich matrix. The data provide strong evidence that the decomposition of the nitrogen saturated ASS is of spinodal nature. The findings of this work on S phase microstructure are correlated to mechanical, magnetic and electrochemical properties.

The last few years have seen an increasing interest in in-situ investigations on thin filmor nano structured systems. The advantages of these methods are clear: The (x-ray)investigations are done at the time of the phase or structure formation. Misleading results of ex-situ investigation due to altering or decomposition of the sample were avoided, metastable intermediate states were observed and additionally these experiments are less time consuming.The presented experiments were carried out at Material Research Station of the instrument BM20 at ESRF that is operated by the Forschungszentrum Dresden- Rossendorf. Our experimental station focuses on in-situ studies using different X-Ray diffraction and scattering methods in the energy range of 6 to 30 keV. The experiments can be combined with XRF and electrical resistivity measurements on demand. Two different topics of synthesis and processing are given. First, results on the formation of isolated Ge nano particles with well defined size by disproportion of germanium oxides in a silicondioxid matrix at higher temperatures of corresponding multilayer system were presented. Such materials are potential candidates for solar cells, extending the working spectral range for energy conversion. The size and ordering of the Ge nano crystallite can be controlled by the layer thicknesses as well as growth and annealing temperatures. Different in-situ growth techniques like reactive DC magentron sputtering of Si and RF- sputtering of SiO2 are compared. Secondly, the phase behavior of different metal catalyst onto different buffer layers for the carbon nanotube and graphene synthesis will be shown and discussed. Hereby diffraction experiments under controlled and reactive atmosphere were performed. As shown by in-situ investigations process were characterized on-line and structural as well as functional properties are correlated directly with each other. This increases the comprehension of synthesis and processing of functional materials.

Thin solid films of metastable rocksalt structure (c-) Sc1−xAlxN and Ti1−xAlxN were employed as model systems to investigate the relative influence of volume mismatch and electronic structure driving forces for phase separation. Reactive dual magnetron sputtering was used to deposit stoichiometric Sc0.57Al0.43N (111) and Ti0.51Al0.49N (111) thin films, at 675 °C and 600 °C, respectively, followed by stepwise annealing to a maximum temperature of 1100 °C. Phase transformations during growth and annealing were followed in situ using x-ray scattering. The results show that the as-deposited Sc0.57Al0.43N films phase separate at 1000–1100 °C into nonisostructural c-ScN and wurtzite structure (w-) AlN, via nucleation and growth at domain boundaries. Ti0.51Al0.49N, however, exhibits spinodal decomposition into isostructural coherent c-TiN and c-AlN, in the temperature interval of 800–1000 °C. X-ray pole figures show the coherency between c-ScN and w-AlN, with AlN(0001)|| ScN(001) and AlN(01-10)|| ScN(1-10). First-principles calculations of mixing energy-lattice spacing curves explain the results on a fundamental physics level and open a route for design of novel metastable pseudobinary phases for hard coatings and electronic materials.

The effect of microstructure on the thermal stability and hardness of the cathodic arc evaporated Ti0.5Al0.5N coatings was investigated with the aid of the in-situ high-temperature X-ray diffraction experiments, which were accompanied by high-resolution transmission electron microscopy (HRTEM) and nanoindentation measurements. The microstructure of the coatings was modified through the choice of the bias voltage in the deposition process. It was found that the bias voltage affects strongly the uniformity of the local distribution of titanium and aluminum in the coatings. The nonuniform distribution of the elements contributes to the formation of lattice strains at the crystallite and phase boundaries. The lattice strains at the crystallite boundaries increase the hardness of the coatings; the lattice strains at the phase boundaries improve their thermal stability. A certain nonuniformity of the distribution of the metallic species in the coatings is regarded as advantageous. However, a great nonuniformity in the distribution of the metallic species accelerates the degradation of the coatings at high temperatures. As a measure for the nonuniformity of the distribution of the atomic species in the as-deposited (Ti, Al) N samples, the stress-free lattice parameter of fcc-(Ti, Al) N is suggested.

The synthesis of fiber-textured Ti2AlN(0001) films on SiO2 was characterized by in-situ and ex-situ X-ray scattering and Rutherford backscattering spectrometry. Ti2AlN was formed by solid-state reaction between sequentially deposited Ti and AlN layers. A deposition at 275 °C yields a Ti(0001) outof-plane orientation which is maintained for the following AlN(0001)/Ti(0001) layers. Annealing to 600 °C yields AlN decomposition and diffusion of Al and N into Ti, with consecutive transformation into Ti3AlN(111) and Ti2AlN(0001) plus AlN residuals. Despite preferred Ti2AlN(0001) out-ofplane orientation, the in-plane distribution is random, as expected from the self-organized pseudo-epitaxial growth.

THz spectroscopy on semiconductor heterostructures has revealed new insight in low-energy excitations such as intersubband transitions (ISTs). A microscopic analysis has to consider the true THz transitions, but also the so-called ponderomotive response as a charge current of carriers generated by the alternating classical electric field. In former experiments the ponderomotive contribution could only be seen rather indirectly [1].
Here, we directly study the interplay between ponderomotive contribution and true IST [2]. In our experiment we create electrons in the conduction band of an undoped GaAs/Al0.34Ga0.66As multiple quantum well by resonant interband excitation at the 1s heavy-hole exciton, using either a broad- or narrowband laser. Broadband THz pulses probe the IST and are detected by electro-optic sampling. The observed differential THz transmission transient as the pump-induced change in the transmitted THz field shows a strong beating. In the frequency domain this results in an intersubband resonance with a broad additional low-frequency peak. The line shape of this intersubband resonance strongly resembles a Fano-resonance with an undershoot at the low-frequency side and an asymmetric peak to higher frequencies. However, since we are able to measure differential transmission and total THz absorption separately, we find that the absorption does not show such a Fano-asymmetry, but reveals the expected Lorentzian-like line shape of the intersubband resonance. Especially, it is a single peak and therefore the beating in the time domain cannot originate from an adjacent second absorptive resonance next to the true intersubband resonance.
In our microscopic theory these features can be explained unambiguously by a phase-sensitive superposition of the true THz intersubband current and the ponderomotive current.
[1] J. R. Danielson et al. ,”Interaction of Strong Single-Cycle Terahertz Pulses with Semiconductor Quantum Wells“, Phys. Rev. Lett. 99, 237401 (2007).
[2] D. Golde et al., “Fano Signatures in the Intersubband Terahertz Response of Optically Excited Semiconductor Quantum Wells”, Phys. Rev. Lett. 102, 127403 (2009)

Thallium (Tl) is a rare element of high toxicity. Sediments sampled in three representative locations near industries utilizing Tl-containing raw materials from the Pearl River Basin, China, were analyzed for their total Tl contents and the Tl contents in four sequentially extracted fractions (i.e., weak acid exchangeable, reducible, oxidizable, and residual fraction). The results reveal that the total Tl contents (1.25–19.1 µg/g) in the studied sediments were slightly high to quite high compared with those in the Chinese background sediments. This indicates the apparent Tl contamination of the investigated sediments. However, with respect to the chemical fractions, Tl is mainly associated with the residual fraction (>60%) of the sediments, especially of those from the mining area of Tl-bearing pyrite minerals, indicating the relatively low mobility, and low bioavailability of Tl in these sediments. This obviously contrasts with the previous findings that Tl is mainly entrapped in the first three labile fractions of the contaminated samples. Possible reasons were given for the dominating association of Tl with the residual fraction (>95%) of the mining area sediments. The significant role of certain K-containing silicates or minerals of these sediments on retaining Tl in the residual fraction, discovered by this study, provides a special field of research opportunity for the Tl-containing wastewater treatment.

In dieser Arbeit wurde ein Sensorkonzept mit Hilfe der Si-basierten Lichtemitter (MOSLED) zum Östrogennachweis in wässrigen Lösungen entwickelt. Das Sensorkonzept basiert auf einer direkten Fluoreszenzanalyse und besteht aus der Anordnung der Bio-Komponenten und dem Verfahren zu ihrer Herstellung sowie dem eigentlichen Meßverfahren. Die Anordnung besteht aus drei Teilen: die Funktionalisierung der MOSLED-Oberfläche, die Immobilisierung des hER-Rezeptors und die Herstellung der Referenzlösung. Den Schwerpunkt dieser Arbeit bildet die Ausführung dieser drei Teile.
Die Funktionalisierung der SiO2-Oberfläche der MOSLED wurde mit Hilfe eines im Rahmen dieser Arbeit entwickelten SSC (Spraying Spin Coating)- Verfahrens realisiert. Die Ausgangsmaterialien dieses Verfahrens sind organofunktionelle Silangruppen mit drei unterschiedlichen funktionellen Gruppen, nämlich die Amino-, Carboxyl- und die Thiolgruppen. Die Optimierung dieser Methode erfolgte mittels der zwei Silangruppen APMS ((3- Aminopropyl)trimethoxysilane und Triamino-APMS (N-[3-(Trimethoxysilyl)propyl]ethylenediamine mit der gleichen Molekülstruktur, aber mit einer unterschiedlichen Anzahl an funktionellen Gruppen. Diese Resultate wurden mit in der Literatur beschriebenen Verfahren verglichen. Die Optimierung der SSC-Methode wurde zuerst auf einfache SiO2-Oberflächen und dann auf der Oberfläche der MOSLED angewendet. Die Proben wurden mit Hilfe üblicher Methoden der Oberflächenphysik- wie FTIR-, Raman- und XPS-Spektroskopie untersucht.Die Oberflächenrauhigkeit wurde mittels AFM-Spektroskopie ermittelt, deren Aufnahmen eine glatte Oberfläche bei den mit der SSC-Methode silanisierten Proben zeigen. Während die Hydrophobizität der funktionalisierten SiO2-Oberflächen zunimmt, sinkt dabei die Oberflächenenergie, welche die Anbindung eines hER-Rezeptors mit großer Bindungsenergie begünstigt. Zur Immobilisierung des hER-Rezeptors wurde dieser erst an das Hüllenmolekül des QDots R-655-Farbstoffs gebunden und anschließend an der SSC-silanisierten SiO2-Oberflächen adsorbiert. Der Anteil der immobilisierten Rezeptoren wurde mittels PL-Messung kontrolliert.
Eine andere Immobilisierungstrategie des hER-Rezeptors an die SiO2-Oberfläche kann mit Hilfe eines Aminosäure-Derivates um den Rezeptor realisiert werden. Eine Adsorption der Lysinaminosäure an die SSC-APMS silanisierten SiO2- Oberflächen als Funktion des pH-Wertes wurde durchgeführt, und der Adsorbatsanteil des Lysins mittels XPS-Messung durch die Bindungsenergien der Energieniveaus C1s und N1s berechnet. Eine Referenzlösung mit QDots R 800-Farbstoff markierten Östrogenmolekülen kommt zum Einsatz. Dabei wird die Position 17 des β-Estradiolmoleküls, welches mit einem N-Hydroxysuccinimide Derivat versehen ist, an das Hüllenmolekül des QDots R 800-Farbstoff gebunden,sodass der Phenolring des β-Estradiols frei bleibt. Insbesondere ist bei den FTIR-Spektren
eine nichtgebunden OH-Gruppe des β-Estradiolmoleküls gut erkennbar. Das gesamte Sensorkonzept wurde an zwei mit Östrogen mit einer Konzentration von 1mM und 1μM versetzten Wasserproben getestet. Die Anordnung der Bio-Komponenten wurde mittels PL nachgewiesen. Der Östrogennachweis wurde mit Hilfe des Ge- und Tb-basierten Lichtemitters demonstriert.

This seminar gives an overview on our recent experimental studies involving terahertz (THz) radiation from photoconducting antennae and from the free-electron laser in Dresden, Germany. In particular, microstructured scalable antennae for photoconductive THz emitters and semiconductor quantum well detectors for quadratic autocorrelation of pulsed THz radiation will be discussed. The final part of my talk will concentrate on nonlinear THz spectroscopy, in particular THz sideband generation and coherent dynamics of excitons dressed by strong THz beams.

Two-photon quantum well infrared photodetectors (QWIPs) are based on quantum wells comprising three energetically equidistant states, namely two bound subbands and one resonant state in the continuum. This configuration is extremely efficient for two-photon transitions, giving rise to strong resonant enhancement and to optical nonlinearities which are six orders of magnitude stronger than in bulk crystals. Using this approach, extremely sensitive quadratic detectors for mid-infrared and THz radiation can thus be realized. These devices are very useful for quadratic autocorrelation measurements of THz radiation from free-electron lasers, nonlinear optical converters, and modelocked quantum cascade lasers.
Exploiting the two-photon QWIP approach, we have investigated various detectors based on different epitaxial structures, covering operation wavelengths from the mid-wavelength infrared to the THz regime. In particular, we have demonstrated a two-photon QWIP which operates below the Reststrahlen band at 42 μm (7.1 THz) [1]. At shorter wavelengths, quadratic detection also works at higher temperatures, which is crucial for applications in practical systems. In particular, room temperature operation has been achieved at 5.5 μm (54.5 THz) [2].
In this talk, we will concentrate on the detection properties of two-photon QWIPs. We confirm their quadratic intensity dependence and demonstrate autocorrelation measurements and pulse monitoring of far-infrared picosecond pulses from the free-electron laser at the Forschungszentrum Dresden Rossendorf. Huge optical nonlinearities allow for quadratic detection at THz pulse energies as low as a few pJ. The time resolution of this detector is limited by the intersubband dynamics associated with the intermediate state. Besides applications in THz pulse diagnostics, the two-photon QWIP thus also provides interesting opportunities for studies of the associated intersubband population and polarization lifetimes.
[1] H. Schneider, H. C. Liu, S. Winnerl, C. Y. Song, M. Walther, M. Helm, Opt. Express 17, 12279 (2009)
[2] H. Schneider, H. C. Liu, S. Winnerl, O. Drachenko, M. Helm, J. Faist, Appl. Phys. Lett. 93, 101114 (2008)

Two nanocrystalline magnesium-rich alloys, Mg90Ni10 and Mg80Ni10Y10, were produced by meltspinning. After hydrogenation they consist of a MgH2 matrix with finely dispersed Mg2NiH4 grains of about 2m in size. In the case of Mg80Ni10Y10, nanocrystalline YH3 grains are found, additionally. The desorption kinetics of hydrogenated Mg90Ni10 and Mg80Ni10Y10 was investigated by thermogravimetry at different temperatures in the range from 150°C to 250°C. It was observed that Mg80Ni10Y10 exhibits a much faster desorption kinetics in comparison toMg90Ni10 of up to 1.3 wt.%H2/min. Differential scanning calorimetry indicates that these alloys undergo a two-step desorption process. The corresponding phase transformations were investigated in detail by in situ synchrotron X-ray diffraction, thus, the different hydrogen desorption kinetics can be explained.

While typical pulsed terahertz (THz) systems operate with freely propagating THz waves of linear polarization and Gaussian beam profile, modes of different polarization can also be attractive. In particular, radially polarized beams exhibit longitudinal fields at the focus and smaller spot sizes as compared to linearly polarized beams. These key properties of radially polarized beams have been demonstrated indirectly for visible light [1]. Recently radially polarized single cycle THz beams have been generated by velocity-mismatched optical rectification [2] and photoconductive antennas [3,4]. However, longitudinal THz fields have been observed so far only in the near field of plasmon-polariton excitations in a metal tip [5].

We report on longitudinal THz fields in the focus of freely propagating waves. Single cycle THz pulses with radial polarization are generated by photoexcitation of emitters with an electrode structure consisting of concentric rings [4]. By means of electro-optic detection we determine the phase relation between transverse and longitudinal field components. The radiation is focused onto ZnTe sensing crystals oriented along the (110) and (100) axis, respectively, in order to detect transverse and longitudinal THz fields. While the THz beam is kept fixed, the electro-optic detection system is scanned along the x-axis, which denotes the horizontal direction perpendicular to the axis of propagation. For comparison, emitters for linearly polarized beams are operated under the same conditions.

The transverse field changes sign, as the detector is moved across the propagation axis located at x = 0, as expected for a radially polarized wave. The longitudinal field, however, is located around the propagation axis and does not change sign as x changes from negative to positive. At t = 0 where the transverse fields exhibits extrema (dashed line), the longitudinal field is zero. This phase difference of pi/2 has been predicted theoretically as a consequence of Maxwell’s equation div E = 0. To our knowledge, this phase relation has not been measured previously in the entire range of the electromagnetic spectrum. Furthermore we show that the spot size of the longitudinal component is smaller than the diffraction limited spot of a linearly polarized THz beam. The results are analyzed by calculations based on the vector Helmholtz equation beyond the paraxial approximation.

[1] R. Dorn, S. Quabis, G. Leuchs, Sharper focus for a radially polarized light beam, Phys. Rev. Lett. 91, 233901 (2003).
[2] G. Chang, Ch.J. Divin, C.-H. Liu, S.L. Williamson, A. Galvanauskas, T.B. Norris, Generation of radially polarized terahertz pulses via velocity-mismatched optical rectification, Opt. Lett. 32, 433 (2006).
[3] J.A. Deibel, K. Wang, M.D. Escarra, D. Mittleman, Enhanced coupling of terahertz radiation to cylindrical wire waveguides, Opt. Express. 14, 279 (2006).
[4] S. Winnerl, B. Zimmermann, F. Peter, H. Schneider, M. Helm, Thz Bessel-Gauss beams of radial and azimuthal polarization from microstructured photoconductive antennas, Opt. Express 17, 1571 (2009).
[5] N.C.J. van der Valk and P.C.M. Planken, Electro-optic detection of subwavelength terahertz spot sizes in the near field of a metal tip, Appl. Phys. Lett. 81, 1558 (2002).

In this study UV-vis spectroscopy as well as RT and cryo time-resolved laser-induced fluorescence spectroscopy (TRLFS) were applied to reinvestigate the complexation of uranium(VI) by benzoic acid (BA). For the first time in the liquid phase the existence of a U(VI)-BA complex with a 1:2 stoichiometry could be proven.
RT TRLFS measurements revealed a static as well as a dynamic ligand-initiated quench process in the U(VI)-BA system. At these conditions no luminescence emission resulting from complex formation was found. Consequently cryo TRLFS was applied to increase the maximum detect-able BA:U(VI) ratio. By this for the first time a lumines-cence spectrum of the 1:2 U(VI)-BA complex could be determined. This species is characterized by emission bands at 467, 485, 505, 526, and 550 nm which are blue-shifted compared to the ones of the uranyl ion. The luminescence lifetime of the 1:2 complex amounts to 9.21 ± 0.01 µs at -18°C compared to 150.4 ± 0.5 µs for uranyl.
Stability constants of both, the 1:1 and the 1:2 species, have been calculated to be log β110 = 2.66 ± 0.18 and log β120 = 4.48 ± 0.24, respectively. UV-vis spectroscopy combined with factor analysis yielded the molar absorption spectrum of the 1:2 U(VI)-BA species which is characterized by absorption bands at 406, 418, 432.5, 447, and 461 nm and a molar absorption coefficient of 22 L•mol-1•cm-1.

In the continuous casting process, an adequate control of liquid steel flow through the submerged entry nozzle is essential for maintaining steel cleanliness and ensuring good surface quality in downstream processing. Monitoring the flow in the nozzle presents a challenge for the instrumentation system because of the high temperature environment and the limited access to the nozzle in between the tundish and the mould.
In this paper, the distribution of a two-phase liquid metal/gas flow is studied by using a liquid metal laboratory model of an industrial steel caster and an inductive sensor array. The experiments were performed with the liquid eutectic alloy GaInSn as an analogue for liquid steel, which has similar conductive properties as molten steel and allows the measurements at room temperature. A scaled (approx. 1:10) experimental rig consisting of a tundish, a stopper rod, a nozzle and a mould was used. Argon gas was injected through the centre of the stopper rod and the behavior of two phase GaInSn/Argon flows was studied.
The electromagnetic system used in the experiments to monitor the behavior of two phase GaInSn/Argon flows consists of an array of 8 equally spaced inductive coils arranged around the object, a data acquisition system and a host computer. The present system operates at 10 kHz and has a capture rate of 10 frames per second.
The results show clearly that the injection of the Argon gas is distinguishable from the single phase flow by observing the appearance of oscillation patterns. These oscillations become more dominant with the increase of the Argon flow. In some cases two main oscillation patterns were present in the raw signals. In general, the signals and the reconstructed void fractions in the nozzles are highly correlated with the observed oscillations of the level height in the mould and the pressure in the nozzle.

The complex formation of U(VI) with humic acid (HA) in the presence of carbonate was studied by time-resolved laser-induced fluorescence spectroscopy at low temperature (cryo-TRLFS) at pH 8.5. In the prescence of HA, a decrease of the luminescence intensity of U(VI) and no shift of the emission band maxima in compari-son to the luminescence spectrum of the UO₂(CO₃)₃ ^4- complex, the dominating U(VI) species under the applied experimental conditions in the absence of HA, was observed. The formation of a ternary U(VI) carbonato hu-mate complex of the type UO₂(CO₃)₂HA(II)⁴⁻ starting from UO₂(CO₃)₃ ^4- was calculated from the luminescence data. A complex stability constant of log K = 2.83 ± 0.17 was determined and the result of the slope analysis with a slope of 1.12 ± 0.11 verifies the postulated complex reaction. These results agrees very well with literature data. Speciation calculations show, that the formation of the ternary U(VI) carbonato humate complex can significantly influence the U(VI) speciation under environmental conditions.

Aufgabe der vorliegenden Erfindung ist es, eine Anordnung zur Elektronenstrahltomographie anzugeben, die eine kontinuierliche und gleichzeitige Aufnahme zweidimensionaler Schnittbilder eines Objektes in verschiedenen Durchstrahlungsebenen mit hoher zeitlicher und räumlicher Auflösung gestattet.
Die Erfindung beinhaltet, dass die Targets (5) von Öffnungen (14) gegebener Breite und regelmäßiger Anordnung in Umfangsrichtung durchbrochen sind, wobei die Öffnungen (14) in den Targets (5) jeweils auf einer Bahnkurve liegen, die den Schnitt der Mantelfläche des Elektronenstrahlkegels (11) mit dem jeweiligen Target (5) bilden; die in Strahlrichtung aufeinanderfolgenden Targets (5) mit jeweils einem kleinen Winkelversatz zum davorliegenden Target (5) bezüglich der optischen Achse (10) angeordnet sind, so dass ein entlang der Mantelfläche des Elektronenstrahlkegels (11) zirkulierender Elektronenstrahl (4) mit mindestens einem Teil seines Querschnitts nacheinander die Materialstege (15) zwischen den Öffnungen (14) aller Targets (5) bestrahlt und zu jedem Target (5) ein Röntgendetektorbogen (6) koplanar radial vor oder hinter dem jeweiligen Target (5) angeordnet ist.

In Deutschland ist die Grenze zwischen großen und kleinen Wasserkraftanlagen (WKA) bei einer Generator-Leistung von 1 MW festgelegt. Die vorliegende Untersuchung stellt den aktuellen Stand der großen WKA im deutschen Elbe-Einzugsgebiet dar. An der Elbe selbst bestehen heute keine Voraussetzungen (Staustufen) für die Nutzung der erheblichen Wasserkräfte (etwa 1 TWh/a). Die 31 an den Nebenflüssen der Elbe bestehenden WKA haben eine Leistung von insgesamt etwa 59 MW, wovon 50 MW etwa zu gleichen Teilen auf die Flussgebiete der Saale und der Mulde entfallen. Neubaumöglichkeiten für weitere WKA an bestehenden Stauanlagen mit einer Leistung von 6 bis 8 MW werden derzeit untersucht.

The strength of selected resonances in the 40Ca(alpha,gamma)44Ti reaction is studied by activation, using the Felsenkeller low-level gamma-counting facility. In addition, the background conditions for possible accelerator experiments inside Felsenkeller are reviewed.

Magneto-optical generalized ellipsometry is the most general approach to characterize the magneto-optical response of materials. We extended this experimental approach to Vector-Magneto-Optical Generalized Ellipsometry (VMOGE) in the IR-UV spectral range, by constructing a generalized spectroscopic ellipsometer combined with a 3D vector magnet. VMOGE measures the upper 3 x 4 submatrix of the 4 x 4 Mueller matrix in a magnetic field of arbitrary orientation and magnitude up to 0.4 T at room temperature. Searching the best match model between experimental and calculated VMOGE data, the complex-valued magneto-optical dielectric tensor ε _MO is determined. Comparison with vector magnetometry measurements can provide the complex and anisotropic magneto-optical coupling constant Q_x, Q_y, Q_z. We have determined the wavelength dependence of the isotropic Q_x and Q_y of ferromagnetic Co, Fe, and Ni films. Besides, VMOGE is also employed to study Co nanowires with very strong anisotropic optical response. Having knowledge of the magneto-optical coupling constant Q(λ), one can design magneto-optical devices, e.g., ferromagnetic thin film and nanowire structures, with a strong magneto-optical response for a selected wavelength.

Zur Herstellung von Mitteldichten Faserplatten (MDF) werden Holzfasern definierter Qualität benötigt. Für die Prozess- und Energieoptimierung soll die Holzfaserverteilung im Laborrefiner des Institut für Holztechnologie Dresden gGmbH (IHD) erfasst werden.

A small prototype detector based on high pressure thin-walled tubes (straws) has been developed and its parameters have been studied on a bench at JINR, Dubna, and SPS at CERN. The inner diameter of the straws is 9.53 mm. The pressure of the active gas mixture Ar/CO₂ (80/20) has been varied from 1 to 5 bar. The best spatial resolution achieved in this pressure range is ~40 μm. Both the high efficiency and high rate capability are retained.

The sorption of americium(III), (Am(III)), onto kaolinite was studied in batch experiments in the absence and presence of humic acid (HA) ([Am(III)]0 = 1x10-6 M, [HA]0 = 0 or 10 mg/L, I = 0.01 M NaClO4, pH = 3–10, pCO2 = 10-3.5 atm, solid-to-liquid ratio (S/L) = 1 or 4 g/L). The results show that the Am(III) sorption onto kaolinite is influenced by S/L, the presence of HA and the pH value. In the absence of HA, Am(III) exhibits a very strong and almost pH independent sorption onto kaolinite at the S/L ratio of 4 g/L. In the presence of HA, there are small differences in the Am(III) sorption compared to the HA free system. At pH values < 5, HA very slightly enhances the sorption of Am(III). Conversely, at pH values ≥ 5.5, the presence of HA decreases the sorption of Am(III) due to the formation of dissolved Am(III) humate complexes. The decrease of S/L from 4 to 1 g/L has a significant effect on the Am(III) sorption onto kaolinite. A sorption edge occurs at pH 6 and the influence of carbonate on the Am(III) sorption at higher pH values becomes evident. Furthermore, the influence of HA on the Am(III) sorption onto kaolinite is more pronounced. The Am(III) sorption results are compared to literature and to those of U(VI) sorption onto kaolinite obtained under the same experimental conditions.

Ion beam irradiation enables to modify magnetic properties of magnetic ultrathin films and multilayers [1, 2]. Such a method is a very promising technique for magnetic patterning [3]. In films with initial perpendicular magnetization the decrease of perpendicular magnetic anisotropy, followed by the magnetization rotation to the in-plane orientation and finally a transition to superparamagnetic state has been observed with increasing irradiation dose D [1-3]. Recently a double magnetisation reorientation from in-plane to out-of-plane direction and back to in-plane alignment, driven by Ga+ ion 30 keV irradiation, has been observed in sputtered Pt/(Co 2.6 nm)/Pt films [4].
In this work we report the influence of focused ion beam (FIB) irradiation on magnetic properties of MBE grown Mo/Pt/(Co 3.3nm)/Pt sandwiches. In the as deposited sample magnetization was aligned in the film plane. The numerous areas of the sample (squares 100x100μm² or 50x50μm²) have been irradiated by Ga+ ions with doses D ranging between 2x10¹² and 1x10¹⁶ ions/cm². A development of perpendicular magnetic anisotropy in irradiated regions has been correlated with modifications of a surface morphology using polar Kerr effect magnetometry (sensitive to perpendicular magnetization component), as well as atomic/magnetic force microscopy techniques.

[1] C. Chappert, H. Bernas, et al., Science 280, 1919 (1998).
[2] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320, 579 (2008).
[3] J. Ferré, J.-P. Jamet, in Handbook of Magnetism and Advanced Magnetic Materials, Vol. 3, p.1710 H. Kronmüller, S. Parkin Ed. (John Wiley & Sons, Ltd, 2007).
[4] J.Jaworowicz et al., APL 95, 022502 (2009).

Cetuximab (C225) as a chimeric monoclonal antibody specifically targets the epidermal growth factor receptor (EGFR) that is often overexpressed in human malignancies. This phenotype is associated with tumor aggressiveness, treatment
resistance and biological heterogeneity with potential to bypass the blockade of the EGFR signaling pathways.
The aim of this work was to modify the C225 for radiolabeling with therapeutic radionuclides like ⁹⁰Y and ¹⁷⁷Lu as a prerequisite for combination of endoradionuclide therapy with antibody-, chemo- or external radiation therapy for routine application.
C225 was conjugated with the bifunctional chelator CHX-A″-DTPA up to a molar DTPA to C225 ratio of 5. The EGFR-affinity of the immunoconjugate resulted in 94% versus 100% of the unmodified C225 measured with enzyme-linked immunosorbent assay on EGFR-positive tumor cell line A431. DTPA-C225 was labeled with ⁹⁰YCl₃ or ¹⁷⁷LuCl₃ within 30 min with a radiolabeling yield of N95%. The radio-immunoconjugates exhibited high accumulation in squamous cell carcinoma xenotransplanted tumors shown by single photon emission computed tomography and autoradiography. The radiolabeled C225 can be produced in routine with high avidity and specific activity as prerequisite for long term preclinical therapeutic studies.

Cu-61 (T_1/2=3.32 h, E_β+=1.22 MeV 60%) is a positron emitter from the set of medically useful copper radioisotopes. Its nuclear properties and ease of production make it suitable for positron emission tomography imaging. The ⁶⁴Zn (p,α)⁶¹Cu reaction with enriched Zn-64 as target material seems to be more convenient for the routine production of Cu-61 than the ⁶¹Ni(p,n)⁶¹Cu route, due to the higher costs of enriched Ni-61. As reported, the ⁶⁴Zn(p,α)⁶¹Cu reaction delivers adequate yields of Cu-61 in an energy window of 19à10MeV with low contaminants like Cu-60/62 which occur at higher proton energies.
Cu-61 was generated using the ⁶⁴Zn(p,α)⁶¹Cu reaction utilizing 16 MeV. For the purification of Cu-61, a system of cation- and anion-exchange columns was applied which allows recycling of the target material for uncomplicated electro deposition for the next irradiation cycle. The abandonment of heating and drying steps, applying pumps or any pressure to the columns makes this process suitable for remote handling in hot cells and causing fewer sources of contaminants and enables good/reasonable yields. An overview of the key data (yield at EOB and after processing, specific activity and radiochemical purity) will be presented.

An efficient procedure for the preparation of [¹⁸⁸Re(N)(PNP)]-based complexes is reported. The radiochemical yield (RCY) of the compounds was optimized considering reaction parameters such as: nature of nitrido nitrogen donors, reaction times and pH.
The chemical identity of ¹⁸⁸Re-agents was determined by high-performance liquid chromatography comparison with the corresponding well characterized cold Re-compounds. The stability of the [¹⁸⁸Re(N)(PNP)] complexes toward transchelation with glutathione and degradation by serum enzymes was assessed. The clearance of selected radiolabeled agents from normal tissues was evaluated in rats.
[¹⁸⁸Re(N)(cys∼)(PNP)]^+/0 asymmetrical compounds were prepared in aqueous solution from perrhenate using a multistep procedure based on the preliminary formation of the labile ¹⁸⁸Re^IIIEDTA species which easily undergo to oxidation/ligand exchange reaction to afford in presence of DTCZ the [¹⁸⁸Re^V≡N]²⁺core. The final compounds were obtained by adding to the [¹⁸⁸Re^V≡N]_int ²⁺ the two bidentate ligands. However, a relative high amount of cys∼ ligand was required to obtain a quantitative RCY. The complexes were stable toward reoxidation to perrhenate and ligand exchange reactions. In vivo studies showed a rapid distribution and elimination of the complexes from the body. No specific uptakes in radiation sensitive tissues/organs were detected.
A positive correlation of the distribution of the complexes estimated with biodistribution studies (% injected dose) andwithmicro-single photon emission computed tomography semiquantification imaging analysis was observed. The low labeling efficiency limits but not excludes the possibility to apply [¹⁸⁸Re(N)(PNP)]-technology to the preparation of target specific radiotherapeutical agents.

Complementary mirror-image L-oligonucleotides (L-ON) and tumorspecific antibodies appear as a suitable system for pretargeting technologies. However, optimization of the radiopharmacological characteristics of the LON is a prerequisite for high accumulation in the target. The objective was to decrease the kidney uptake, to increase the area under the blood curve (AUC), and to minimize the nonspecific accumulation in the body. Therefore the L-ON were conjugated with PEG units of increasing size (2, 5, 10, 20 kDa) and subsequently derivatized with NOTA and DOTA for radiolabeling with Ga-68, Cu-64, Y-86, Y-90, Lu-177.
We investigated the impact of size and structure of the radiolabeled (Ga-68, Cu-64) L-ON on biodistribution and positron emission tomography kinetics. The increasing PEG units, up to 20 kDa PEG, decreased the kidney uptake, increased the activity concentration in the blood, e.g., the AUC, but also increased the liver uptake. We can decisively influence the pharmacokinetics resulting in optimal L-ON kinetics and distribution. These results, combined with the option of different radionuclides and high specific activities of the radiolabeled L-ON, emphasizes the attractiveness of this complementary system for pretargeting approaches.

The aim of the paper was to synthesize and investigate the conjugate of the “4+1” mixed-ligand technetium(III) complex with the vasopressin peptide-^99mTc(NS₃)(CN-AVP). The overexpression of vasopressin receptor V2 has been found in the case of small-cell lung cancer.
The “4+1” mixed-ligand technetium complex consists of central metal ion Tc(III) coordinated simultaneously by a tetradentate NS₃ tripodal chelator tris(2-mercaptoethyl)-amine and a monodentate isocyanide ligand, previously coupled with the selected biomolecule. The identity of the ^99mTclabelled vasopressin peptide was corroborated by investigation of the analogous rhenium compound. The ^99mTc-labelling vasopressin conjugate was formed in two-step synthesis, via the ^99mTc-EDTA intermediate complex, with the final yield of 95%. After 24 h of incubation of the conjugate in the 10 mM solution of histidine or cysteine, the obtained highperformance liquid chromatography chromatograms have shown the existence of one radioactive species, with the retention time characteristic for the complex studied. The log D value of −0.48±0.02 for the 99mTclabelled vasopressin peptide was found. This value (higher than the lipophilicity of the free vasopressin peptide equal to −2.15) can be corrected by introducing a hydrophilic group, R, at the periphery of the NS₃ ligand.

This study was focused on evaluating the applicability of a new labelling procedure to the preparation of ^99mTc(N)-based target specific compounds. The chemistry is based on the use of the [Tc(N)Cl(PS)(PPh₃)] species (PS=alkyl-phosphino-thiolate ligand), which selectively reacts with an appropriate mono-negative chelate, such as a dithiocarbamate (DTC), to give neutral [Tc(N)(PS)(DTC)] compounds. The 2-methoxyphenylpiperazine (L) pharmacophore, which displays a potent and specific affinity for 5HT_1A receptors, was selected as functional group and conjugated to the dithiocarbamate unit through different spacers.
The synthesis of [^99m/99gTc(N)(PS)(Ln)] complexes, and their stability as well as their biological in vitro and in vivo assays were investigated. [^99mTc(N)(PS)(Ln)] compounds were prepared in high yield (N90%) using a multi-step procedure and their chemical identity was determined by highperformance liquid chromatrography comparison with the ^99gTc-analogues. All complexes were found to be inert toward transchelation with glutathione and sufficiently stable to the in-vitro action of serum and liver enzymes. Nanomolar affinities for the 5-HT_1A receptor were obtained for [^99mTc(N) (PSiso)L³] (IC₅₀=1.5 nM). However, a negligible brain uptake was observed after in-vivo administration of the complex.
This work describes the application of a new labelling procedure for incorporating a bioactive molecule into a stable dissymmetric ^99mTc(N)-complex. Despite the lack of BBB penetration of [^99mTc(N)(PSiso)L³] the favourable binding properties of this compound strongly support the possibility to apply [Tc(N)(PS)]-technology to the preparation of target specific agents useful in peripheral applications.

Induction heating for pendent-drop melt extraction (PDME) from a metallic sheet is simulated and optimized. This numerical study aims at concentrating dissipated powers on the lower edge of the metallic sheet so that multi-extraction of fine fibers from the wide metallic drop is realized. The solutions on the electromagnetic field are obtained numerically by three-dimensional (3D) modeling based on Finite Element Method (FEM) using ANSOFT Maxwell software, then verified experimentally by lab-scale tests. Subjects to variation are (1) the extension of the substrate (extraction wheel) in both directions parallel and perpendicular to the inductor, (2) the protrusion depth of the edge below the lower face of the inductor and (3) the shape of the inductor. The numerical simulations suggest that the vertical position of the inductor has to be significantly higher than that in Reference 1 in order to increase the efficiency of the process.

Trapped carrier dynamics in semiconductor quantum dots (QDs) have been studied using terahertz activated luminescence. This technique enabled us to isolate the luminescence emitted by the trapped carriers from the photoluminescence due to interband excitation. Trapped carriers having long lifetimes ~ 250 ns at 8 K were observed. Temperature dependence of the trapped carrier lifetime was measured. Activation energy for the trapped carrier decay rate was found to be close to the intersublevel transition energy of the QDs.

Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications. We present the new experimental facility LIMMCAST for modelling the continuous casting process of steel using the alloy SnBi at temperatures of 200-400°C. The possibilities for flow investigations in tundish, submerged entry nozzle and mould will be discussed. In addition, experimental results will be presented on the impact of a steady magnetic field on the outlet flow from the nozzle, obtained at a smaller-scale set-up working with the room-temperature alloy GaInSn. Local velocities are measured by Ultrasound Doppler Velocimetry and contactless inductive flow tomography. The magnetic field significantly changes the jet-type flow in the mould. Surprisingly, in some parameter ranges the DC field creates low-frequency oscillations of the flow structure which resulted in increased velocity fluctuations. Numerical simulations using the CFX code confirm this magnetic field action.

In order to improve the efficiency of radioimmunotherapy by augmenting the specific activity of the radiolabeled bioconjugates while preserving their immunoreactivity, we prepared a water-soluble dendron bearing four 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid moieties by solidphase peptide synthesis. An N-hydoxysuccinimide ester of the dendron was synthesized and the dendron conjugated to lysine amino groups of the therapeutic monoclonal antibody Cetuximab which is specific for the epidermal growth factor receptor and overexpressed by various tumours. Dendron-bearing Cetuximab is thus used for treatment of colon, head, and neck cancer, so as to combine high specific activities brought by multilabeling to achieve a more effective targeted radionuclide therapy as it has been shown for Zevalin and Rituximab. The dendron to antibody ratio was determined by MALDI-TOF MS. These new conjugates have been radiolabeled by ⁶⁴Cu and ⁹⁰Y and higher specific activities have been obtained compared to monochelator- labeled antibody. positron emission tomography imaging in mice showed a significant tumour accumulation. Here we discuss the relationships between dendron to antibody ratio, antigen affinity and specific activity of monochelator and dendron-labeled Cetuximab conjugates.

To handle the present shortage of Mo-99 in the nuclear medicine community, we offer alternative preparations for lung scintigraphy, Ga-68-labelled DOTA microspheres (DOTA MS) and labelled aerosol, analogously to well-known Technegas.
Over the last three decades, several trials have been made to label HSA microspheres with Ga-68 in an efficient manner and with stability. Biodegradable albumin microspheres (HSAM) have been widely applied for lung perfusion scintigraphy (Tc-99m HSAM) or labelled with Re-188 for internal radiation therapy. We present in vitro and in vivo stability data of Ga-68 DOTA HSAM in Wistar rats.
DOTA-Bz-NCS was reacted with HSAM and labelled with Ga-68 from a Ge-68/Ga-68 generator by a simple and reproducible method in high yields. The in vitro stability of Ga-68-labelled DOTA-HSAM was checked by incubation in human plasma and by challenging with DTPA.
After intravenous injection into a tail vain, the Ga-68 DOTA MS was rapidly filtered from venous blood and accumulated almost quantitatively in the lungs. Radioactivity level then remains constant for at least 30 min (PET studies with microPET P4). Ga-68-labelled particles showed high in vitro stability and almost quantitative accumulation in the lungs after intravenous application. We consider that Ga-68 DOTA HSAM is a potential radiotracer for lung and other organ perfusion studies.
On the other hand, for ventilation, Ga-68 Galligas aerosol for PET imaging is simple to produce in a Technegas apparatus which can produce Ga-68 eluate concentrated in acetone/HCl. It was stable in vivo (tested over 3.5 h) and allows PET imaging in man with 5–10 MBq Ga-68 only.

Semiconductor quantum dots (QDs) are found to have relatively long spin depolarization times, which makes them promising candidates for practical realization of qubits for spintronics based computation. For doped QDs the presence of the excess carriers in the dots modifies the electron-hole interaction leading to unusual spin polarization properties like negative spin polarization. From our experiments we found that the sign and magnitude of the spin polarization depended on the excitation energy and the QD transition involved. Therefore, to understand the spin dynamics in doped QDs and the role of excited states, we performed photoluminescence quenching measurements using circularly polarized interband excitation and temporally synchronized terahertz pulses to induce intersublevel transitions.

The sample studied was an ensemble of n-doped InGaAs/GaAs QDs with an average doping of one electron per dot. The s-p intersublevel energy was tuned to about 20 meV (5 THz) by thermal annealing. A circularly polarized Ti:sapphire laser was used for interband excitation, where the wavelength was adjusted to enable excitation in the barrier, the wetting layer (WL) or the QDs. Terahertz pulses from a free-electron laser (FEL), synchronized to the Ti:sapphire laser, were used to excite intersublevel transitions (~ 20 meV, i.e. 5 THz) in the QDs. A streak-camera coupled to a CCD enabled time and wavelength resolved PL detection.

Time-resolved photoluminescence measurements at ~10 K, for cross-circular (s+s+), i.e. excitation s+ and detection s+, and cross-circular (s+s-) polarizations showed weak negative spin polarization for the QD ground state transition (Figure 1(a)). When excited by long wavelengths, the PL spectrum showed multiple peaks due to selective excitation of the QD ensemble. Some of these features were associated with phonon mediated transitions and exhibited strong positive circular polarization anisotropy (Figure 1(b)). The effect of the FEL pulses on the spin polarization was found to depend on the excitation wavelength. While the strong positive spin polarization for excitation below the wetting layer was drastically reduced by the FEL pulse (as shown by the solid lines in Figure 1 (b)), the weak negative polarization was found to persist. This suggests different mechanisms involved in the generation of spin polarization for different excitation energies. We will discuss the origins of these spin polarizations associated with different transitions in the QD ensemble and their dynamical behaviour. By varying the time-delay of the FEL pulses with respect to the Ti:sapphire laser pulses for interband excitation in the barrier or the WL, we confirmed the existence of trapped carriers. Trapped carriers have been reported to have considerable effect on the PL response of QDs. The FEL pulses induced two competitive phenomena that affect the spin polarization, i.e. (i) diffusion of trapped carriers resulting in increased PL and (ii) intersublevel transitions resulting in a quenching of the PL signal. To summarize, this work investigates the influence of the intradot transitions and interdot diffusion of the trapped carriers on the spin polarization of the QD ensemble.

Different RP-HPLC columns (phenyl, conventional ODS, cross-linked C18 and special end-capped C8 and C18 phases) were used to investigate the separation of four basic ionizable isomers. Using ACN/20 mM NH4OAc aq., a separation was observed exclusively on RP columns with higher silanol activity at unusual high ACN concentration, indicating cation-exchange as main retention mechanism. Using MeOH/20 mM NH4OAc aq., another separation at low MeOH concentrations was observed on both, RP columns with higher as well as RP columns with lower silanol activity, which is mainly based on hydrophobic interactions. The isomers were also separated on a bare silica column at higher MeOH content using NH4OAc as buffer. Since cation-exchange governs this retention, the elution order was different compared to the RP phases. A strong retention on the silica column was observed in ACN, which could be attributed to partition processes as additional retention mechanism.

Purpose Neuroimaging of σ1 receptors in the human brain has been proposed for the investigation of the pathophysiology of neurodegenerative and psychiatric diseases. However, there is a lack of suitable ¹⁸F-labelled PET radioligands for that purpose.

Methods The selective σ1 receptor ligand [¹⁸F]fluspidine (1'-Benzyl-3-(2-[¹⁸F]fluoroethyl)-3Hspiro[[2]benzofuran-1,4'-piperidine]) was synthesised by nucleophilic ¹⁸F- substitution of the tosyl precursor. In vitro receptor binding affinity and selectivity were assessed by radioligand competition in tissue homogenate and autoradiographic approaches. In female CD-1 mice, in vivo properties of [¹⁸F]fluspidine were evaluated by ex vivo brain section imaging and organ distribution of intravenously administered radiotracer. Target specificity was validated by organ distribution of [¹⁸F]fluspidine after treatment with 1 mg/kg, i.p. of the σ receptor antagonist haloperidol or the emopamil binding protein (EBP) inhibitor tamoxifen. In vitro metabolic stability and in vivo
metabolism were investigated by LC-MSn and radio-HPLC analysis.

Results [¹⁸F]Fluspidine was obtained with a radiochemical yield of 35-45%, a radiochemical purity of ≥99.6%, and a specific activity of 150-350 GBq/μmol (n=6) within a total synthesis time of 90-120 min. In vitro, fluspidine bound specifically and with high affinity to σ1 receptors (Ki = 0.59 nM). In mice, [¹⁸F]fluspidine rapidly accumulated in brain with uptake values of 3.9 and 4.7 %ID/g and brain to blood ratios of 7 and 13 at 5 and 30 min after intravenous application of the radiotracer, respectively. By ex vivo autoradiography of brain slices, resemblance between binding site occupancy of [¹⁸F]fluspidine and the expression of σ1 receptors was shown. The radiotracer uptake in the brain as well as in peripheral σ1 receptor expressing organs was significantly inhibited by haloperidol but not by tamoxifen. Incubation with rat liver microsomes led to a fast biotransformation of fluspidine. After an incubation period of 30 min only 13 % of the parent compound was left. Seven metabolites were identified by HPLC-UV and LC-MSn techniques. However, [¹⁸F]fluspidine showed a higher metabolic stability in vivo. In plasma samples ~94% of parent compound remained at 30 min and ~ 67% at 60min p.i. Only one major radiometabolite was detected. None of the radiometabolites did cross the blood-brain-barrier.
Conclusion [¹⁸F]Fluspidine demonstrated favourable target affinity and specificity as well as metabolic stability both in vitro and in animal experiments. The in vivo properties of [¹⁸F]fluspidine offer a high potential of this radiotracer for neuroimaging and quantitation of σ1 receptors in vivo.

We present a high-resolution X-ray diffraction pattern of periodic GaAs nanorod (NR) ensembles and individual GaAs NRs grown catalyst-free throughout a prepatterned amorphous SiN x mask onto GaAs[111]B surfaces. The experiments were performed at a home laboratory using synchrotron radiation in combination with a micron-sized beam prepared by compound refractive lenses. The structural properties were probed by measuring RSMs (q x , q z ) in the vicinity of GaAs(111) and (222) reflections. Besides the GaAs substrate peak, we found a second peak referring to NRs with lattice mismatch of 0.23 pct with respect to the substrate, probably caused by structural defects. The lateral periodicity of NRs was probed by q x scans, and the NR height obtained from the width of the diffraction curve along q z . Grazing-incidence in-plane diffraction revealed the appearance of small crystallites of cubic γ-Si3N4 caused by recrystallization of SiN x during NR growth. Whereas measurements at the home diffractometer provided average structure parameters, the micron-sized X-ray beam experiment was used to probe the parameters at individual NRs.

Aim: DASB is currently the most frequently applied highly selective radiotracer for visualisation and quantification of central SERT. Its use, however, is hampered by the short half‐life of carbon‐11, the moderate cortical test retest reliability, and the lack for quantifying endogenous serotonin. The aim of our study was to first apply in human the new highly SERT‐selective fluorine‐18 labelled fluoromethyl analogue of (+)‐McN5652 ([18F]FMe‐McN).
Methods: The synthesis of [18F]FMe‐McN was performed according to Zessin et al. with some modifications. Briefly, the demethylated (+)‐McN5652 was reacted with bromo‐[18F]fluoromethane to yield [18F]FMe‐McN, which was purified by reversed‐phase HPLC. For in vivo human studies, five healthy volunteers (2 female, age 39±10 years) underwent dynamic PET over 120 minutes after intravenuous injection of a 90 s bolus of 298±57 MBq [18F]FMe‐McN and a static acquisition over 30 minutes 3 h p.i.. PET data were coregistered with individual MRI data set using PMOD and VOI analysis was performed. Target‐to‐background‐ratios (TB‐R, cerebellum as background structure) were compared with those of a reference data set assessed by [11C]DASB‐PET in 21 healthy subjects (11 female, 38±8 years).
Results: TB‐R ([18F]FMe‐McN) displays no hemispheric differences. The values are for the frontal cortex (FC) 1.02±0.04 (right‐hand side) and 1.01±0.03 (left), for the head of caudate region (caud) 1.46±0.16 (right) and 1.50±0.15 (left) and for the raphé region 2.04±0.11. Corresponding TB‐R ([11C]DASB) are 1.10±0.07 (FC right, ANOVA p=0.05), 1.08±0.78 (FC left, 0.06), 2.14±0.21 (caud right, 0.02), 2.06±0.19 (caud left, 0.04) und 2.23±0.39 (raphé, 0.04). Visually, image quality of [11C]DASB‐PET is superior to [18F]FMe‐McN .
Conclusion: Cerebral radiotracer uptake fits well with the known SERT distribution also in humans. Hence, [18F]FMe‐McN might be suitable for in vivo quantification of SERT. Despite a tendency to lower TB‐R compared to [11C]DASB, the lower standard deviation of [18F]FMe‐McN TB‐R can be advantageous with regard to test‐retest estimations in larger study cohorts. Also, labelling with fluorine‐18 allows (1) later data acquisition times, which is useful for the investigation of the
tracer kinetics in brain tissue (modelling), and (2) a widespread application within a satellite concept e.g. in multicenter trials.
References Zessin J, Eskola O, Brust P et al. Nucl Med Biol 2001; 28: 857‐863.

So far, the growth of spatially ordered nanoclusters by multilayer deposition has been reported and explained satisfactorily only in crystalline materials. Here we demonstrate a method for the growth of spatially ordered nanoclusters in amorphous matrices, where the ordering is achieved in the single large domain. The regular ordering is induced by the deposition of a multilayer on a periodically rippled substrate at an elevated substrate temperature. During the deposition, the nanoclusters self-arrange, following the morphology of the substrate.

Aim: Due to the fact that receptor tyrosine kinases (RTKs) are overexpressed in some tumour entities, they might be a suitable target for PET or SPECT imaging. Then, tyrosine kinase inhibitors labeled with a radioisotope could represent a useful tool for monitoring levels of RTKs in tumour tissue giving valuable information for anti‐angiogenic therapy. SU11248 (Sunitinib®) is a novel highly potent RTK inhibitor targeting vascular endothelial growth factor receptor (VEGFR)
(IC50=0.08μM) [1]. We report here the synthesis of a 125I‐labeled derivative of SU11248 and its first radiopharmaceutical characterization.
Materials and methods: 5‐[125I]lodo‐SU11248 was obtained via destannylation of the corresponding tributylstannyl precursor with [125I]NaI in the presence of H2O2. The radioiodinated compound has been purified by RP‐HPLC with UV and radioactivity detection using methanol/0.1% TFA (85:15) as eluent. Determination of human plasma protein binding at time intervals of 0; 1; 2; 4 and 24h was accomplished by incubation of the radiotracer in fresh human serum at 37°C. Preliminary biodistribution studies were carried out in healthy CD‐1 mice and in vivo stability was assessed by HPLC analysis of urine samples collected at sacrifice time.
Results: 5‐[125I]Iodo‐SU11248 could be obtained in high radiochemical yield (>95%). After HPLC purification the radiochemical purity exceeded 98%. The identity of the radiotracer was confirmed by co‐elution with 5‐Iodo‐SU11248 as reference compound [2]. Lipophilicity of 5‐[125I]Iodo‐SU11248 has been assessed using the octanol/PBS partition coefficients (logPo/w) and was found to be 2.25. Determination of human plasma protein binding suggested a low non‐specific binding of 5‐10%. Biodistribution studies showed a relatively high uptake in VEGFR‐2 rich tissues like kidney and lung, followed by rapid washout (9.6 and 9.7; 4.5 and 3.8% ID/g kidney and lung at 1 and 4 h, respectively).
Conclusion: The new 5‐[125I]Iodo‐SU11248 was synthesized in high radiochemical yield and purity. The high stability in human serum and urine samples, suggests that the tracer is not significantly metabolized. The ability of 5‐Iodo‐SU11248 to inhibit tyrosine kinase activity, a mandatory prerequisite for further studies on RTK expressing cells, is underway, to disclose whether this radiotracer would be a useful tool for monitoring VEGFR expression. Ultimately, the radiochemical profile of 5‐[125I]Iodo‐SU11248 associated to a low non‐specific binding and rapid clearance from most tissues encourages further radiolabeling with other radioisotopes, such as 123I for SPECT or 124I for PET.
[1] Sun L., Liang C. et al., J. Med. Chem., 46, (2003), 1116 [2] Kniess T., Oliveira C. et al., unpublished results

We studied the generation of an ordered Ge quantum dot array in an amorphous silica matrix by ion beam irradiation. In particular we investigated the influence of the irradiation process on the nucleation of Ge clusters, on the correlations in their positions and on the crystalline quality of Ge quantum dots formed after subsequent annealing. We have developed a method for the description of the intensity of grazing-incidence x-ray small-angle scattering from irradiated multilayers, which enables a precise determination of the arrangement of quantum dots as well as their position correlation and size distribution. The analysis shows that the irradiation causes an ordering of Ge clusters along the irradiation direction, which substantially improves the correlations of the Ge dot locations in their three-dimensional array. The observed phenomena are explained and simulated by a Monte Carlo model based on the modification of local Ge density induced by ion tracks in the irradia!
ted multilayers.

Aim: An promising therapeutic approach to treat cancer focus on the inhibition of tumourinduced angiogenesis. One target structure involved is integrin alpha(v)beta3. Imaging modalities allowing monitoring of alpha(v)beta3 may provide insights into corresponding molecular process. Labelling techniques becoming more and more interesting for molecular imaging with PET are based on Ga‐68. Especially, due to the straightforward labelling protocols this is an interesting alternative to F‐18 labelling of peptides. Here the imaging properties of c(RGDfK) conjugated to different chelating systems are compared.
Methods: Peptide synthesis follows standard SPPS protocols. The cyclised and selectively deprotected peptides were conjugated with the chelating moieties via the side chain amino function of the lysine. The chelating systems include 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐acetic acid (DOTA), 1,4,7‐triaazacyclononane‐4,7‐acetic acid‐1‐2‐glutaric acid (NODAGA), and a tris(2‐mercaptoethyl)amine derivative (NS3). Labelling was carried out using the fractionated elution method in sodium acetate (DOTA; NODAGA) or phosphate buffer (NS3). In vitro evaluation included log D determination, protein binding assays, plasma stability studies, isolated receptor binding assays, and cell uptake studies. In vivo evaluation was carried out using M21 (alpha(v)beta3 positive) and M21L (alpha(v)beta3 negative) bearing nude mice. For all tracer biodistribution data were collected. For DOTA‐RGD and NODAGA‐RGD also small animal PET imaging was carried out. Results: NODAGA‐RGD and NS3‐RGD could be labelled at room temperature, whereas labelling of DOTA‐RGD has to be carried out at elevated temperature. NODAGA‐RGD and DOTA‐RGD could be labelled in high radiochemical purity without further purification. For NS3‐RGD a subsequent Seppak separation was necessary to obtain the product in high radiochemical purity. The compounds showed comparable log D (‐2.9 ‐ ‐3.9) and IC(50) values (~5 nM) as well as receptor specific uptake. In contrast, great differences were found in the protein binding properties. The found protein bound activity after 1 h incubation was 18.6% (DOTA‐RGD), 42,4% (NS3‐RGD), and 1.4% (NODAGA‐RGD). This performance is reflected in the biodistribution data. Lowest activity concentration in blood (%ID/g 1h p.i.: NODAGA‐RGD=0.12±0.06 ; DOTA‐RGD=0.72±0.07; NS3‐RGD=3.33±1.9) and best tumour/background ratios were found for NODAGA‐RGD. Small animal imaging confirmed these findings and indicated that NODAGA‐RGD might have similar imaging properties as found for F‐18‐Galacto‐RGD. Conclusions: In this series NODAGA‐RGD revealed most promising properties for imaging alpha(v)beta3 expression. Easy radiolabelling at room temperature, low amount of protein bound activity and the resulting lower activity concentration found in blood compared to the other compounds makes it to an attractive alternative to F‐18‐Galacto‐RGD, worth to be tested in clinical studies.

Aim: The lipophilic cationic Ga‐68‐complex (Tsang B.W. et al. J Nucl Med 1993; 34; 1127) of Tris(4,6‐dimethoxysalicylaldimine)‐N,N′‐bis(3‐aminopropyl)‐N,N′‐ethylenediamine (BAPEN), showed high accumulation in mice hearts (Nucl Med Biol 2010; 37; 149). To reevaluate the radiopharmacological profile in rats the Ga‐68‐BAPEN was produced by a kit formulation and the biodistribution, kinetics and metabolism were studied with small animal PET.
Materials & methods: The BAPEN was labeled with 0.1 M HCl Ga‐68‐Cl3 (generator eluate 1 M HCl) in a one step procedure. Before application human serum albumin was added to a final concentration of 1%, and the solution filtrated (22 μm pore size). The biodistribution at 5 and 60 min p.i. (each time point 8 rats) after single intravenous injection, arterial blood clearance over 1 h (n=2), and the in vivo metabolism in Wistar rats were investigated in combination with small animal PET, and the main biokinetic parameters of Ga‐68‐BAPEN were estimated.
Results: Ga‐68‐BAPEN was prepared with purity >91% within 20 min. The activity was fast accumulated in the rat heart (values in SUV; 5 min p.i., 1.56 ± 0.19; 60 min, 1.42 ± 0.35) with the following heart‐to‐tissue ratios at 5 min p.i.: blood 4.2, lung 2.2, liver 0.4, kidneys 0.3, and brain 109.6. No clearance of Ga‐68‐activity from the heart was observed over 1 hour. The arterial blood clearance of the original compound was biphasic with half lifes of 2 min and 23 min respectively; it was metabolized with a half‐life of 1.6 min. The Ga‐68‐activity was rapidly excreted into the intestine (5 min p.i. 34.9 ± 4.0%ID; 60 min p.i. 56.7 ± 7.0%ID).
Conclusion: Ga‐68‐BAPEN showed a typical perfusion dependent biodistribution pattern in rats, with high accumulation in heart, kidneys, liver, adrenals, and pancreas. The heart was clearly delineated with low background. The increasing liver uptake could complicate the quantitative imaging of the heart apex at late time points. Ga‐68‐BAPEN was fast distributed followed by a slow blood clearance on a low activity level. The fast in vivo metabolism of the Ga‐68‐BAPEN in rats prevented a more distinct perfusion dependent biodistribution pattern. No transport through the blood‐brain‐barrier into the brain was observed. The Ga‐68‐BAPEN may be useful as radiopharmaceutical for perfusion imaging, particularly, for the heart.

Aim: (‐)‐[F‐18] Norchloro‐fluoro‐homoepibatidine ((‐)‐NCFHEB) is a new and promising tracer for neuroimaging of alpha4beta2 nicotinic acetylcholine receptors with PET. To assess the radiation risk to humans caused by systemic application of the tracer, CD1 mice were injected with (‐)‐NCFHEB. The biodistribution of the tracer and, thereby, resulting organ doses (OD) and the effective dose (ED) were calculated.
Methods: 27 female CD1 mice (weight: 28.2 ± 2.1g) were injected i.v. with 0.75± 0.334MBq of (‐)‐[F18]NCFHEB (specific activity >100GBq/μmol) through the V. caudata lateralis. At 5, 15, 30, 45, 60, 90, 120, 180 and 240 min. p.i. the animals were sacrificed (n=3 per time). The organs (brain, heart, lung, stomach, small intestine, large intestine, liver, kidneys, urinary bladder, spleen, thymus, pancreas, adrenals, ovaries, blood, skin, muscle, skeleton) were isolated, weighed and counted in a γ‐counter to determine mass and radioactivity. The masses of the skeleton and the muscle were extrapolated from tissue samples [1]. Time and mass scales were adapted to the respective human scales [2]. The fractions of activity in source organs were displayed as %ID/g, and %ID/organ for both scales. Time‐activity curves were derived by trapezoidal and exponential fits. The numbers of disintegrations in the source organs were calculated and ODs and the ED was calculatedusing OLINDA.
Results: The urinary bladder receives the highest OD of 104.0 μSv/MBq, followed by the kidneys (24.2 μSv/MBq), uterus (14.1 μSv/MBq), liver (14.0 μSv/MBq), pancreas (14.0 μSv/MBq) and small intestine (14.0 μSv/MBq) The highest contribution to the ED was by urinary bladder (5.2μSv/MBq) followed by the ovaries (2.1μSv/MBq), lower large intestine (1.5μSv/MBq) and red marrow (1.3 μSv/MBq). According to these data, the ED by i.v. application of (‐)‐[F18]NCFHEB
results in an ED of 14.2 μSv/MBq.
Conclusion: The ED as a measure of the overall radiation risk upon i.v. application of about 370 MBq (‐)‐[F‐18] NCFHEB to humans would be 5.3 mSv. This is well within the range of the application of other [F18]‐labeled compounds to humans. This risk assessment encourages to transfer (‐)‐[F‐18]NCFHEB from preclinical to clinical study phases and to further develop as a clinical tool for PET brain imaging.
References: [1] Lindstedt SL, Schaeffer PJ.: Use of allometry in predicting anatomical and physiological parameters of mammals Laboratory Animals (2002) 36, 1‐19 [2] Stabin MJ: Fundamentals of Nuclear Medicine Dosimetry, Springer 2008, ISBN 978‐0‐387‐74578‐7, 237P The trial is granted by the German Federal Ministry of Education and Research (Nr. 01EZ0820)

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The near-infrared transmission of a semiconductor multiple quantum well is probed under intense terahertz illumination. We observe clear evidence of the intraexcitonic Autler-Townes effect when the terahertz beam is tuned near the 1s-2p transition of the heavy-hole exciton. The strongly coupled effective two-level system has been driven with terahertz field strengths of up to 10  kV/cm resulting in a Rabi energy of ≈0.6 times the transition energy. The induced near-infrared spectral changes at low intensities are qualitatively explained using a basic two-level model.