Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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Motivation
Kompakte Protonen- und Ionenbeschleuniger
Physik der Laserbeschleunigung
Stand von Forschung und Entwicklung

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The structures of the complex of 2,2'-(methylimino)bis(N,N-dioctylacetamide) (MIDOA) with M-(VII)O-4(-) (M = Re and Tc), which were prepared by liquid-liquid solvent extraction, were investigated by using H-1 nuclear magnetic resonance (NMR), extended X-ray absorption fine structure (EXAFS), and infrared (IR) spectroscopy. The H-1 NMR spectra of the complex of MIDOA with Re(VII)O-4(-) prepared in the organic solution suggest the transfer of a proton from aqueous to organic solution and the formation of the H(+)MIDOA ion. The EXAFS spectra of the complexes of H(+)MIDOA with Re(VII)O-4(-) and Tc(VII)O-4(-) show only the M-O coordination of the aquo complexes, suggesting that the chemical state of M(VII)O-4(-) was unchanged during the extraction process. The results from H-1 NMR and EXAFS, therefore, provide evidence of M(VII)O-4(-)center dot center dot center dot H(+)MIDOA complex formation in the organic solution. The IR spectra of Re(VII)O-4(-)center dot center dot center do!
t H(+)MIDOA and Tc(VII)O-4(-)center dot center dot center dot H(+)MIDOA were analyzed based on the structures and the IR spectra that were calculated at the B3LYP/cc-pVDZ level. Comparison of the observed and calculated IR spectra demonstrates that an intramolecular hydrogen bond is formed in H(+)MIDOA, and the M(VII)O-4(-) ion interacts with H(+)MIDOA through multiple C-H-n center dot center dot center dot O hydrogen bonds.

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1. Physikalische Eigenschaften von Ionenstrahlen
2. Bestrahlungsfeld-Formierung für Ionenstrahlen
3. Kernreaktionen
4. Exotische Strahlen

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1.Die Wechselwirkung ionisierender Strahlung mit (belebter) Materie
2.Die Formen der Strahlentherapie
3.Exkurs in die Radionuklid- und Brachytherapie
4.Teletherapie
4.1. Die Erzeugung von Photonen- und Elektronenstrahlen für
die Strahlentherapie (Elektronen-Linearbeschleuniger)
4.2. Ionenstrahl-Therapie
4.3. Adaptive Strahlentherapie

1. Die Wechselwirkung ionisierender Strahlung mit (belebter) Materie
2. Moderne strahlentherapeutische Techniken
3. Photonen- und Elektronenstrahlen für die Therapie
4. Ionenstrahl-Therapie
5. Adaptive Strahlentherapie

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The NURESIM and NURISP successive projects of the 6th and 7th European Framework Programs joined the efforts of 21 partners for developing and validating a reference multi-physics and multi-scale platform for reactor simulation. The platform includes system codes, component codes, and also CFD or CMFD simulation tools. Fine scale CFD simulations are useful for a better understanding of physical processes, for the prediction of small scale geometrical effects and for solving problems that require a fine space and/or time resolution. Many important safety issues usually treated at the system scale may now benefit from investigations at a CFD scale. The Pressurized Thermal Shock is investigated using several simulation scales including Direct Numerical Simulation, Large Eddy Simulation, Very Large Eddy Simulation and RANS approaches. At the end a coupling of system code and CFD is applied. Condensation Induced Water-Hammer was also investigated at both CFD and 1-D scale. Boiling flow in a reactor core up to Departure from Nucleate Boiling or Dry-Out is investigated at scales much smaller than the classical sub-channel analysis codes. DNS was used to investigate very local processes whereas CFD in both RANS and LES was used to simulate bubbly flow and Euler-Lagrange simulations were used for annular mist flow investigations. Loss of Coolant Accidents are usually treated by system codes. Some related issues are now revisited at the CFD scale. In each case the progress of the analysis is summarized and the benefit of the multi-scale approach is shown.

We propose and demonstrate a method for shaping the focus of high intensity lasers into an annular or “donut” mode. The method, based on helical phase plates, has been implemented at the PHELIX laser facility.

Reactor pressure vessel (RPV) steel, when exposed to neutron irradiation, induces the formation of nano-sized features. Using small angle neutron scattering (SANS) we have studied the neutron fluence dependence of the precipitate volume fraction for high-Cu and low-Cu materials separately. Cu-rich precipitates have long been recognized to play the dominant role in embrittlement of Cu-bearing RPV steels. In contrast, Mn-Ni-rich precipitates seem to govern embrittlement in the case of low levels of impurity Cu. The objective is to work out the resulting differences from the microstructural point of view. For low-Cu materials, the volume fraction was found to be within the detection limit of SANS at fluences below an apparent threshold fluence, whereas the slope increases considerably beyond. The relationship between irradiation-induced yield stress increase and precipitate volume fraction was also considered. We have derived estimates of the obstacle strength for Cu-rich precipitates and for Mn-Ni-rich precipitates.

Nitrogen sputtering yields as high as 2×10³ N / ion are obtained by irradiating N-rich-Cu₃N films (N concentration (33±2) at.%) with Cu ions at energies in the range 10-42 MeV. The kinetics of N sputtering as a function of ion fluence is determined at several energies (stopping powers) for films deposited on both, glass and silicon substrates. The kinetic curves show a three stage-behaviour: an initial inhibition stage I of low sputtering yield, followed by a more extended linear region II that finally reaches a saturation stage III at a low remaining nitrogen fraction (5-10 %). For the case of silicon substrates the contribution of the initial stage is not significant. The sputtering rate of stage II is found to be independent of the substrate and to linearly increase with electronic stopping power (S_e). A S_e threshold for nitrogen depletion of ~3.4 keV/nm is estimated. Experimental kinetic data are successfully analysed within the bulk molecular recombination model. All features are in accordance with electronic excitation mechanisms, showing for the first time evidence of the excitonic model.

The atomic layer deposition (ALD) of phosphate containing thin films using reactions between metal halide and phosphorus source without any additional oxygen sources was examined. Two very common metal halides, AlCl₃ and TiCl₄, were used in conjunction with trimethyl phosphate (TMPO) to grow corresponding metal phosphate films. Aluminum phosphate thin films were deposited at temperatures between 150 and 400 °C while titanium phosphate films grew between 275 and 450 °C. Amorphous films of Al_2.6PO_7.0 and Al_1.6PO_5.6 were deposited at 200 and 300 °C, respectively, while the amorphous titanium phosphate films deposited at 300 and 400 °C consisted of Ti_0.8PO_3.9 and Ti_0.6PO_3.5 (Ti_1.2P₂O₇). The films were analyzed using high temperature XRD to study the crystallization and stability of the deposited films. Also the surface morphology of the annealed films was examined by FESEM.

Lithiumphosphate, Li₃PO₄, has been considered a potential electrolytematerial for lithiumion batteries and CO₂ sensors in particular if the films can be made dense and of high quality already at low thickness. In this work, Li3PO4 thin films were deposited by atomic layer deposition (ALD) between 225 and 350°C using trimethyl phosphate and either of the two lithium sources, namely lithium hexamethyldisilazide or lithium tert-butoxide. The deposited films showed slightly crystalline Li₃PO₄ structure in X-ray diffraction and the elastic recoil detection analysis confirmed this stoichiometry with some carbon and hydrogen impurities. The crystallinity and thermal stability of the films at elevated temperatures in N₂ were also examined. The long term stability of the deposited Li₃PO₄ films under ambient air may be an issue for the applicability of these processes.

The ELI (Extreme Light Infrastructure) Beamlines Facility in the Czech Republic, which is planned to complete the installation in 2015, is one of the four pillars of the ELI european project. Several laser beamlines with ultrahigh intensities and ultrashort pulses are foreseen, offering versatile radiation sources in an unprecedented energy range: laser-driven particle beams are expected to range between 1 GeV and 50 GeV for electrons and from 100 MeV up to 3 GeV for protons. The number of particles delivered per laser shot is estimated to be 109-1010 for the electron beams and 1010-1012 for the proton beams.
The high energy and current values of the produced particles, together with the potentiality to operate at 10 Hz laser repetition rate, require an accurate study of the primary and secondary radiation fields to optimize appropriate shielding solutions: this is a key issue to minimize prompt and residual doses in order to protect the personnel, reduce the radiation damage of electronic devices and avoid strong limitations in the operational time.
A general shielding study for the 10 PW (0.016 Hz) and 2 PW (10 Hz) laser beamlines is presented here. Starting from analytical calculations, as well as from dedicated simulations, the main electron and proton fields produced in the laser-matter interaction have been described and used to characterize the "source terms" in full simulations with the Monte Carlo code FLUKA. The secondary radiation fields have been then analyzed to assess a proper shielding. The results of this study and the proposed solutions for the beam dumps of the high energy beamlines are presented, together with a cross-check analysis performed with the Monte Carlo code GEANT4.

In a previous work [1], we fabricated ferromagnetic Ge:Mn by Mn ion implantation and pulsed laser annealing (PLA) and observed hysteretic Hall resistance below 10 K. By applying different PLA conditions we fabricated a percolating, Mn-rich, amorphous Ge:Mn nano-network with hysteretic Hall resistance up to 30K. This nano-network is embedded in crystalline Ge:Mn between 5 nm and 40 nm under the sample surface.
We applied chemical and physical etching to confirm the contribution of the nano-network to the magnetic properties. The nano-network has a significant influence on the correlation between magnetism and anomalous Hall resistance. In the future such nano-networks may be used to spin-polarize free charge carriers in semiconductors at room temperature.
[1] S. Zhou et al., Phys. Rev. B 81, 165204 (2010)

A systematic geometallurgical assessment was carried out to follow changes of mineralogical composition and microfabric following the ore extracted from a single mined block extracted at the Cavanacaw Au Mine from the open pit (in situ ore) through the entire beneficiation process. SEM-based image analyses was used as major analytical tool to carry out the investigation on the finely disseminated Au ores. First of all no Au was found in the tailings, the beneficiation plant recovers the bulk of the sulfides and electrum to the concentrate, and finally Au liberation is good. Despite of these positive assesment results illustrate, there are still some losses that appear to be systemic. In particular, large electrum grains (>60 µm) that are abundant in the original uncrushed material only make a minor contribution to the final concentrate. Due to the ductile behaviour of electrum, fracturing of larger electrum grains into smaller grain sizes appears unlikely – it is thus suspected that these larger particles may be lost during processing.
Furthermore, our results clearly reveal that narrow high grade and sulphide-rich veins are higher in gold grade than the final flotation concentrate. This results from processing a mixture of high grade ore and partly mineralised wall rock. To reduce processing costs it should thus be considered to introduce optical sorting to separate the high-grade vein from lower grade mineralised wall rock. Such pre-selection may further improve recovery

A benchmark exercise for thorium-plutionium fuel, based on experimental data, has been carried out. A thoriumplutonium oxide fuel rodlet was irradiated in a PWR for four consecutive cycles, to a burnup of about 37MWd/kgHM.
During the irradiation, the rodlet was inserted into a guide tube of a standardMOX fuel assembly. After the irradiation, the rod was subjected to several PIE measurements, including radiochemical analysis. Element concentrations and radial distributions in the rodlet, multiplication factors and distributions within the carrier assembly of burnup and power were calculated. Four participants in the study simulated the irradiation of the MOX fuel assemblies including the thorium-plutonium rodlet using their respective code systems; MCBurn, HELIOS, CASMO-5 and ECCO/ERANOS combined with TRAIN. The results of the simulations and the measured results of the radiochemical analysis were compared and found to be in fairly good agreement when the calculated results were calibrated to give the same burnup of the thorium-plutonium rodlet as that experimentally measured. Average concentrations of several minor actinides and fission products were well reproduced by all codes, to the extent that can be expected based on known uncertainties in the experimental setup and the cross section libraries. Calculated results which could not be confirmed by experimental measurement were compared and only two significant anomalies were found, which can probably be addressed by limited modifications of the codes.

1. Introduction
The F-18-benzoyl group is a useful functionality for the development of PET-radiotracers in order to introduce F-18 in a simple one step radiosynthesis. Since nitro leaving groups are common for the nucleophilic F-18-substitution, we utilized a nitro precursor for F-18-labeling of a vesamicol analog to evaluate it as new radioligand for the vesicular acetylcholine transporter (VAChT), which is an interesting target for imaging of presynaptic cholinergic deficiencies using PET.
The separation of a F-18-labeled compound from its nitro precursor in the radiosynthesis is often challenging, accordingly we firstly used the approach of reduction of the remaining nitro precursor to its amine, because this amine is normally easier to isolate from the radiotracer by semi-preparative HPLC than the nitro precursor itself. However, in order to avoid this additional step during the radiosynthetic procedure, we were interested to develop a suitable HPLC method to separate directly the radiotracer from its nitro precursor. Several analytical HPLC columns and eluent systems were investigated.

2. Materials & Methods
Because of the basic character of the analytes (tertiary amines) several columns were selected which are specially designated for the separation of basic analytes due to their potential to reduce peak tailing (LiChrospher Select B, Nucleosil AB, Reprosil Gold, Reprosil-Pur Basic HD). To study the influence of possible pi-pi-interactions, especially of the nitro precursor, we also used different phenyl and cyano columns (Nucleodur Sphinx, Fortis Phenyl, Reprosil Phenyl, LiChrospher CN). For comparison also a bare silica phase and commonly used AQ phases were investigated.
Aqueous acetonitrile and methanol mixtures with ammonium acetate, triethylamine/acetic acid, and trifluoroacetic acid were used as typical eluent systems.

3. Results
The aims of this HPLC study were: (i) to find a suitable separation method in which the fluoro compound clearly elutes in front of the nitro precursor, and (ii) to get more information about the suitability of different column types regarding separation data such as retention, peak tailing and resolution.
In general, with almost all columns the two compounds could be separated, however, the quality of separations was different and surprisingly, changes in elution order were observed. For example, using aqueous acetonitrile/ammonium acetate as eluent system, the fluoro compound elutes in front of the nitro precursor at low content of organic modifier. In contrast, a reversed retention behavior was observed at high content of acetonitrile which was also found by using methanol as organic modifier. Additionally, we observed that not all columns, designated to be especially appropriate for basic analytes, showed satisfying separation properties. Finally, a phenyl column was selected for the semi-preparative separation of the 18-F-labeled radiotracer from its nitro precursor and a reduction of the total radiosynthesis time by one hour could be achieved .

4. Conclusion
Due to this intensive analytical HPLC study, we were able to select a suitable column for an improved purification of a radiotracer from its remaining nitro precursor, which resulted in a considerable shortening of the radiosynthetic procedure.

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Radioactive carbonaceous aerosol particles deposit within the primary circuit of a high temperature reactor (HTR). These particles can pose a considerable threat if resuspended by a shock wave in the case of an unlikely loss-of-coolant accident and partially released into the environment (Kissane, 2009).
Stempniewicz et al. (2010) carried out simulations of the spatial and temporal development of carbonaceous dust deposits in the primary circuit of a HTR. Maximum dust layer thickness after full operation time of 60 years was well above 10 mm. However, the underlying multilayer models require additional experimental verification.
Therefore, particle deposition and resuspension experiments of multilayer graphite deposits have been conducted in a small-scale test facility. The results for particle layer thickness have been correlated to corresponding flow data as measured by means of a 2C2D Particle Image Velocimetry (PIV) system.
The experimental facility consists of a ventilated square duct (d = 100 mm), which is operated with air at ambient conditions. The average air velocity can be regulated over the range u = 1..7 m/s, corresponding to Reynolds numbers between Red = 8.9k..42k. As flow obstacles, periodic steps have been chosen (Fig. 1) allowing the comparison of results with previous studies on monolayer deposition (e.g. Lai et al., 1999).
Graphite aerosol particles (Thielmann Graphite, 23061) have been injected into the duct 15 diameters upstream of the test section by means of a dust disperser TOPAS - SAG 410. Setting the mass flux to 80 g/h an average mass concentration of airborne particles of up to 2 g/m³ is established. The aerodynamic particle size distribution of the graphite particles was determined by means of a TSI – APS 3321confirming that the particles cover well the range of interest for HTR conditions (quantiles:
dP,10 = 1.83 µm, dP,50 = 4.40 µm and dP,90 = 10.64 µm).
The deposition experiments have been conducted under different flow conditions and the development of graphite particle deposits in the vicinity of the steps have been observed by hourly laser triangulation measurements. Subsequently, the generated multilayer has been resuspended at a higher flow velocity and the thickness of the remaining structure has been measured using the same techniques.
Results show that for a relatively low Reynolds number of Red = 8.9k (Fig.2), deposition is mainly governed by gravitational settling and the deposition rate is almost independent of position and time. On the other hand, subsequent resuspension at higher flow velocities (Red =27.2k) reveals a strong relation between flow field and remaining layer (Fig.3), which is further being investigated.

Isokinetic sampling from stacks and ducts is a widely used method for air pollution control in many industrial and environmental applications.
During the last 40 years, U.S. EPA developed reference methods for air pollutant emission sampling of stationary sources, which included a compendium of technical guidelines for the monitoring of aerosol particles. One of the main parts of the sampling system is the sampling probe nozzle for which it was suggested in the reference methods that the lower bound diameter should be greater than di = 6 mm (Cohen, 2001). The influences of sampling nozzle tube diameter, the velocity ratio between free stream and the sampling tube as well as the tube inclination have been considered widely (Vincent, 2007). On the other hand, the influence of tube diameter has not been quantified by means of aerosol particle size spectrometry yet.
McFarland et al. (1997) as well as Peters and Leith (2004) experimentally investigated the deposition losses of aerosol particles in pipe bends. Both found a strong increase of deposition losses in the sampling tube for particle Stokes number of Stk > 0.3.
In this work, the influence of the nozzle diameter of the sampling probe on the aerosol particle size distribution was investigated by means of TSI APS 3321 and TOPAS LAP 321 measurements.
The considered gas/aerosol test facility is a small scale wind tunnel, which consists of a HEPA at the inlet and a square duct section in diameter of dhyd = 10 cm and length of l = 20dhyd = 2 m. The test section, where sampling takes place, is followed by a diffuser stage, an electrical precipitator and a radial fan in order to generate the desired pressure head. The average air velocity can be regulated over the range u = 1..7 m/s, corresponding to Reynolds numbers between Red = 8.9k..42k. In order to achieve isokinetic sampling, the flow rate of the sampling device has been accurately adjusted using Particle Image Velocimetry data.
AC Fine Test Dust (ISO 12103-1, dnom = 0.1..80 µm, bimodal distribution) was injected 17 diameter lengths upstream of the sampling point by means of a dust disperser TOPAS SAG 410. Four probe nozzle diameters di = [3,5,7,9] mm were chosen.
Figure 1 displays the volume weighted aerodynamic particle size distribution of AC Fine under variation of nozzle tube diameter as measured by the APS 3321. The modal dP,aero = 5 µm is roughly independent of nozzle size, whereas the values of the distribution for particle diameters above dP,aero > 12 µm increase continuously with increasing nozzle diameter.
A similar upward tendency in size distribution with increasing nozzle diameter is observed in the LAP measurement results (not shown here). This leads to the conclusion that deposition losses due to inertia, which consequently affect the larger particles, can be considerably reduced by accordingly increasing tube nozzle diameter. In addition, a comparison of aerodynamic particle size (APS 3321) and scattering particle size (LAP 321) will be presented.

This paper presents numerical and experimental investigations with respect to the fluid flow in the continuous casting process under the influence of an external DC magnetic field. Numerical calculations were performed by means of the software package CFX with an implemented RANS-SST turbulence model. The non-isotropic nature of the MHD turbulence was taken into account by specific modifications of the turbulence model. The numerical results were validated by flow measurements carried out in a small-scale mockup using the eutectic alloy GaInSn. The jet flow discharging from the submerged entry nozzle was exposed to a level magnetic field spanning across the entire wide side of the mold. The comparison between our numerical calculations and the experimental results displays a very well agreement, in particular, we were able to reconstruct the peculiar phenomenon of an excitation of non-steady, non-isotropic large-scale flow perturbations due to the application of the DC magnetic field. Another important result of our study is the feature that the electrical boundary conditions, namely the wall conductivity ratio, have a serious influence on the mold flow just as it is exposed to an external magnetic field.

Until 2014 ELBE will be upgraded to a Centre for High Power Radiation Sources. The concept contains additional broad and narrow band coherent THz sources and the development of a 500 TW Ti:Sa Laser and even a 2 PW diode pumped Laser system. Laser plasma electron acceleration and proton acceleration experiments for medical applications are planed. Additionally coupled electron laser beam experiments like Thomson scattering or injection of ELBE electron into the laser plasma will be done.

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A superconducting Electron Linac with high Brilliance and low Emittance (ELBE) which provides an average beam current of 1 mA with maximum beam energy of 36 MeV was constructed in the Forschungszentrum Dresden-Rossendorf, Germany. The electron beam is used to generate infrared light (Free Electron Lasers), MeV-Bremsstrahlung, X-rays (electron channelling), fast neutrons and positrons. The ELBE secondary beams are used for a wide range of basic research like semiconductor physics, nuclear astrophysics and radio biological investigations. Furthermore a 150 TW Ti:Sa Laser delivers high intense and very short laser pulses used for laser plasma acceleration of electrons and protons.
ELBE was built by an internal project group of the Rossendorf research center. The professional structure of this project group, the project management tools and the available budget and the schedules will be discussed, as well.

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Aim: Cyclooxygenase-2 (COX-2) is an enzyme induced during inflammation, but overexpression of COX-2 also has been observed in carcinogenic processes. Noninvasive monitoring and quantitative characterization of functional expression of
COX-2 by means of PET would substantially improve understanding of the role of this enzyme during manifestation and progression of inflammatory diseases and cancer. Herein we report first radiosynthesis and cellular uptake studies of two
highly affine COX-2 inhibitors having a 1,2-diaryl substituted indole scaffold.
Materials and methods: The highly affine COX-2 inhibitors 3-(4-fluorophenyl)-2-(4-methylsulfonylphenyl)-1H-indole 1 and 3-(4-methoxyphenyl)-2-(4-methylsulfonylphenyl)-1H-indole 2 (both IC50 COX-2 ~ 20 nM) [1] served as nonradioactive references. The 18F-radiolabeled tracer [18F]1 was synthesized by nucleophilic substitution of an appropriate trimethylammonium-substituted aromatic precursor with [18F]fluoride and subsequent McMurry cyclization. The 11C-radiolabeled probe [11C]2 was formed via a methylation reaction of the corresponding desmethyl precursor with [11C]CH3I. Different human tumor cell lines showing selectively high COX-2 (FaDu, HT-29, A2058) or COX-1 expression (A375) were used to study the overall uptake or cellular association of [18F]1 and [11C]2 in vitro. To further differentiate the specific contribution of COX-1 and COX-2 to overall tracer uptake, unstimulated human monocytic leukemia cells (THP-1) and phorbol ester stimulated THP-1 macrophages (THP-1M) were used as models. The cell tracer uptake experiments using compounds [18F]1 and [11C]2 (0.4 MBq/mL) were performed in quadruplicate at 37°C for 30, 60, and 120 min.Results:[18F]1 was synthesized from [18F]fluoride in 10% yield (d.c.) in 98% radiochemical purity with a specific activity of 74-91 GBq/μmol. The 11Cradiolabeled compound [11C]2 was obtained in 23% yield (d.c.) in 99% radiochemical purity with a specific activity of 79-89 GBq/μmol. The radiotracer cellular uptake in each model used correlated well with the observed COX protein synthesis. Cell models with prominent COX-2 overexpression showed a substantially higher uptake of both [18F]1 and [11C]2 in the order FaDu>HT29>THP-1M>A2058 when compared to COX-1 overexpressing A375 cells. The lowest cellular uptake was observed in THP-1 showing no or very low baseline expression of both COX-1 and COX-2.
Conclusion:The new radiolabeled COX-2 inhibitors were synthesized in good radiochemical yield and high purity. Cellular studies demonstrated well correlation of the overall radiotracer uptake with COX expression/protein synthesis rate. Further exploration of the new COX-2 inhibitors [18F]1 and [11C]2 regarding in vivo metabolic stability and biodistribution, including dynamic small animal PET investigations in tumor bearing mice, is currently under the way.[1] Hu W., Bioorg. Med. Chem. 11, (2003), 1153

Vorstellung von geplanten Arbeiten am HIF

The recently introduced whole-body PET/MRI systems combine the unique metabolic imaging capabilities of positron emission tomography (PET) and the excellent soft tissue contrast of magnetic resonance imaging (MRI). The aim of this pilot study was to evaluate the feasibility of PET/MRI for initial staging of head and neck cancer.
Materials and Methods:Ten male patients aged (age 52 to 78 years, median age 62.8 y) with histologically proven squamous cell carcinoma of the head and neck region were examined using both a stand-alone PET scanner and a wholebody
PET/MRI scanner. Scanning started 60 minutes after intravenous administration of 350 MBq [18-F]-2-fluoro-2-deoxy-D-glucose (FDG) for the body trunk to exclude distant metastases. PET/MRI of the head and neck region followed immediately the first scan. The study was approved by the local ethics committee. A four-point-scale was used for qualitative evaluation of PET image quality. Furthermore, the signal-to-noise ratio (SNR) of the tumor and of both cerebellar hemispheres were determined for both PET data sets and used for semiquantitative comparison of image quality. Results were compared using the Wilcoxon matched-pair test.Results:The primary tumor was detected by PET/MRI in all 10 patients, by PET in 9 out of 10 cases, and by MRI in 9 out of 10 cases. Seven patients had lymph nodes suspect for metastatic disease. In two patients, lymph nodes considered suspect using MRI showed no pathological FDG uptake. In contrast, a single patient had lymph nodes considered suspect by PET but not by MRI. Visual evaluation of PET images showed consistent results (including regional contrast) for both scanners. There were no statistically significant differences regarding SNR between conventional PET and PET/MRI for the tumor and for both cerebellar hemispheres (p > 0.05).
Conclusion: PET/MRI of head and neck cancer is feasible with a whole-body PET/MRI scanner with excellent image quality and - fusion. While previously available PET/MRI systems were largely restricted to brain examinations, whole-body PET/MRI scanners allow comprehensive tumor staging. Further patients will be examined to evaluate the clinical role of PET/MRI in head and neck cancer.

This work shows the application of ion beam techiques to the structural characterization of different ZnO compounds. Taking advantage of ion channelling phenomena in combination with some specific nuclear resonances, the individual evaluation of defects in the IIb-metal and O sublattices is achieved.

The relative influence of the Lorentz force and the magnetic gradient force on micro-structured copper deposition is studied with simple magnetic elements consisting of cylindrical permanent magnets are placed closely behind the surface of the cathode. Analytical findings and numerical simulations reveal that for magnets of small diameter the magnetic gradient force dominates. Experimental investigations find that the thickness of the deposited copper layer increases in the vicinity of the magnets. The combined analysis of simulations and experiments shows that this enhancement of mass transfer results from a local convection towards the electrode which is forced by the magnetic gradient force.

Vorstellung der aktuellen und geplanten Forschungsarbeiten zum Thema (Rück)Gewinnung seltener Industriemetalle mittels biotechnologischer Verfahren am Helmholtz-Institut Freiberg für Ressourcentechnologie (HIF) und am Institut für Ressourcenökologie.

The adsorption of formic acid on clean TiO(2) anatase (101) and rutile (110) surfaces is studied by density-functional-based methods and compared with the results for coupling related phosphonic acids to titania surfaces. The preferred adsorption mode of the formic acid on both surfaces is a dissociative bridging bidentate complex, which is similar to the adsorption geometry of phosphonic acid. Higher adsorption energies and shorter Ti-O bond lengths indicate that phosphonic acid binds more strongly to TiO(2) than formic acid. The preference for the bidentate adsorption mode is supported by a detailed analysis of the charge distribution in the adsorption complexes. The strong interfacial electronic coupling between the adsorbate orbitals and the electronic states of the anatase (101) surface slab leads to additional states in the band gap of the clean surface. For rutile (110) no or only weak coupling of the adsorbate orbitals and the surface states occurs at the band edges, which leads to an increase of the band gap.

Overview presentation on the dependence of dimensionality, structure, size, composition, electronic properties and preparation conditions of molybdenum sulfide nanostructures at the Seifert group seminar.

Overview presentation of FWIO activities.

DFTEM 2011 Tutorial on nanoscale electronic transport

Workshop DFTEM 2011 - Introductory Lecture to DFT

In the central nervous system (CNS) ATP and adenosine act as transmitters and neuromodulators on their own receptors but it is still unknown which part of extracellular adenosine derives per se from cells and which part is formed from the hydrolysis of released ATP. In this study extracellular concentrations of adenosine and ATP from the rat striatum were estimated by the microdialysis technique under in vivo physiological conditions and after focal ischemia induced by medial cerebral artery occlusion. Under physiological conditions, adenosine and ATP concentrations were in the range of 130 nmol/L and 40 nmol/L, respectively. In the presence of the novel ecto-ATPase inhibitor, PV4 (100 nmol/L), the extracellular concentration of ATP increased 12-fold to ~360 nmol/L but the adenosine concentration was not altered. This demonstrates that, under physiological conditions, adenosine is not a product of extracellular ATP. In the first 4 h after ischemia,
adenosine increased to ~690 nmol/L and ATP to ~50 nmol/L. In the presence of PV4 the extracellular concentration of ATP was in the range of 450 nmol/L and a significant decrease in extracellular adenosine (to ~270 nmol/L) was measured. The contribution of extracellular ATP to extracellular adenosine was maximal in the first 20 min after ischemia onset. Furthermore we demonstrated, by immunoelectron microscopy, the presence of the concentrative nucleoside transporter CNT2 on plasma and vesicle membranes isolated from the rat striatum. These results are in favor that adenosine is transported in vesicles and is released in an excitation–secretion manner under in vivo physiological conditions. Early after ischemia, extracellular ATP is hydrolyzed by ecto-nucleotidases which significantly contribute to the increase in extracellular adenosine. To establish the contribution of extracellular ATP to adenosine might constitute the basis for devising a correct putative purinergic strategy aimed at protection from ischemic damage.

Semaxanib (SU5416) and 3-[4'-fluorobenzylidene]indolin-2-one (SU5205) are structurally similar drugs that are able to inhibit vascular endothelial growth factor receptor-2 (VEGFR2), but the former is 87 times more effective than the latter. Previously, SU5205 was used as a radiolabelled inhibitor (as surrogate for SU5416) and a radiotracer for positron emission tomography (PET) imaging, but the compound exhibited poor stability and only a moderate IC50 toward VEGFR2. In the current work, the relationship between the structure and activity of these drugs as VEGFR2 inhibitors was studied using 3D-QSAR, docking and molecular dynamics (MD) simulations. First, comparative molecular field analysis (CoMFA) was performed using 48 2-indolinone derivatives and their VEGFR2 inhibitory activities. The best CoMFA model was carried out over a training set including 40 compounds, and it included steric and electrostatic fields. In addition, this model gave satisfactory cross-validation results and adequately predicted 8 compounds contained in the test set. The plots of the CoMFA fields could explain the structural differences between semaxanib and SU5205. Docking and molecular dynamics simulations showed that both molecules have the same orientation and dynamics inside the VEGFR2 active site. However, the hydrophobic pocket of VEGFR2 was more exposed to the solvent media when it was complexed with SU5205. An energetic analysis, including Embrace and MM-GBSA calculations, revealed that the potency of ligand binding is governed by van der Waals contacts

The vascular endothelial growth factor (VEGF) is a key regulator of neovascularization and an elevated level of VEGF is known to correlate with increased metastatic invasion. Anti-angiogenic therapies focus on targeted inhibition of overexpressed growth factors with the aim of suppressing tumor proliferation, one approach is the attempt to block the intracellular tyrosine kinase at the adenosine triphosphate (ATP) binding site with small molecule inhibitors. For most effective treatment these targeted tumor therapies are accompanied with a more sensitive need for dose optimization and monitoring the therapeutic response. Direct non-invasive molecular imaging of tumor vascularization and of the angiogenic process in vivo would facilitate the selection of patients and help to evaluate the efficacy of an anti-angiogenic therapy. Radionuclide-based imaging technologies like PET and SPECT are progressively affecting the clinical diagnosis and treatment of cancer. A non-invasive and a reliable quantitative method to determine in vivo the levels of VEGFR expression using radiolabeled small molecules would help to develop a customized VEGFR-targeted chemotherapy. This review will give an overview on radiolabeled derivatives of small molecule VEGFR inhibitors basing on lead structures that have been approved or have reached clinical trials. It is covering aspects of the radiosynthesis as well the results of radiopharmacological and biological evaluation.

In this work the production of ⁶⁴Cu via the ⁶⁴Ni(p,n)⁶⁴Cu reaction with optimized conditions for low current irradiation is presented. Different target setups and cleaning steps for lowering metal contaminations in the product were applied. ⁶⁴Cu with high specific activities up to 1685 GBq/µmol were produced despite low overall activity ( ~ 4.2 GBq per run). The module processing leads to a highly reproducible, reliable product quality (< 1 µg Cu and < 7 µg Ni). Beside its diagnostic value ⁶⁴Cu may be of interest even for therapeutic purposes due to its decay characteristics.

Aim: Regional blood flow represents an important physiological parameter in experimental animals of various disease models. The ‘gold standard’ in large animals is to inject microspheres into the left ventricle using heart catheters; the number of microspheres trapped in the tissue capillaries is directly proportional to blood flow. Injection of radioactive microspheres directly into the left ventricle allows easy assessment of relative blood flow using imaging technologies. Absolute blood flow quantification will be also possible after additional arterial catheterization (required for reference blood sampling). However, up to now this technique has been rarely used in small rodents. In this pilot study we evaluated the technique in small rodents (mouse, rats) using radioactive microspheres.

Methods: Human serum albumin microspheres (20 µm diameter) were modified with NOTA. NOTA-microspheres were radiolabeled with Ga-68, Cu-64 or with F-18-fluoro-benzyol-succinimide using non modified microspheres. The number of injected microspheres was varied between 50,000 and 500,000. The microspheres were directly injected into the left ventricle over a time period of 30 s in desflurane-anesthetized animals on a heating pad. The animals were sacrificed 60 s after the end of injection. Total body activity was measured using a dose calibrator followed by small animal PET scan. The PET images were coregistered with MRI or CT images for identification of the tissues of interest. Standard uptake values were calculated and used for determination of relative blood flow.

Results: Radiolabeling resulted in high radiochemical yields and purity. The microsphere distribution was derived from the radioactivity distribution in the organs. The microspheres were virtually completely trapped (>99%) in the capillary bed. The injection is the most critical step of the experimental procedure. The number of applied microspheres was the limiting factor for measurements in low flow areas, where the number of measured microspheres was below 400. The heart was not included because of potential injury of the coronary arteries. The highest perfusion was found in the kidneys and the cerebellum while the blood flow in the anesthetized animals was low in the cerebral cortex. In rats it was also possible to assess the high flow in the thyroid gland.

Conclusion: This pilot study shows that the microsphere technique allows imaging and assessment of relative organ blood flow. This work will be continued to enable absolute blood flow measurements as well.

First results obtained from electron beam annealed sequentially implanted Pb⁺ (29 keV) and Se ⁺ (25 keV) ions into a SiO₂ matrix are presented. Key results from Rutherford backscattering spectrometry and transmission electron microscopy investigations are: (1) Pb and Se atoms are found to bond in the SiO₂ matrix during implantation, forming into nanoclusters even prior to the annealing step, (2) Pb and Se atoms are both present in the sample after annealing at high temperature (T = 760 °C, t = 45 min) and form into PbSe nanoclusters of varying sizes within the implanted region, and (3) the broader concentration profile of implanted Se creates a number of secondary features throughout the SiO₂ film, including voids and hollow shell Se nanoclusters. A sequential ion implantation approach has several advantages: selected areas of nanocrystals can be formed for integrated circuits, the technique is compatible with present silicon processing technology, and the nanocrystals are embedded in an inert matrix - making them highly durable. In addition, a higher concentration of nanocrystals is possible than with conventional glass melt techniques.

RATIONALE: Acid-aspiration is recognized as a risk factor for subsequent development of acute lung injury or ARDS. Areas of aspiration induced injury matches regions of high pulmonary blood flow (PBF) in the early stage of acute lung injury, as we shown recently. The aim this project was to characterize the changes of spatial PBF distribution as a function of time after injury.
METHODS: The protocol was approved by the Animal Studies Committee of the Landesdirektion Dresden. Eleven anesthetized, spontaneous breathing male Wistar rats were scanned with a small animal CT scanner before and after injury. Positron emission tomography (PET) was carried out after aspiration-induced lung injury. Aspiration was achieved by installation of 0.1 HCl (0.4 ml/kg body weight) through a tracheostomy tube. Pulmonary blood flow (PBF) was calculated from the radioactivity distribution in the lungs of infused 68Ga-DOTA-human serum albumin microspheres ten minutes after injury in group 1 (n=6) and two hours after injury in group 2 (n=5). CT- and PET images were co-registered. Areas of injury, as identified from CT derived changes in density, were labeled with a spherical mask. Regions of interest were derived using a threshold (80% of maximum) within the masks. Identical masks were used for the contralateral lung as reference. PBF was calculated and compared as a fraction of injured and reference side with Wilcoxon matched-pairs signed rank test. The PBF-fraction after the different time points was compared between the groups by unpaired t test with Welch's correction. RESULTS: Data presented are median (interquartile range). CT images after injury showed areas of lung injury different in size and location within the groups. Fraction of PBF was higher in group 1 (1.34 (1.15-1.45)) compared to group 2 (0.9 (0.85-1.06); P=0.0014) shown in Figure 1. The difference between both groups was determined by a high PBF in injured lung regions compared to the contralateral reference side at 10 min after injury (P = 0.03), whereas at 120 min after aspiration, injured regions have shown similar PBF compared to the contralateral reference side (0.81).
CONCLUSION: Regional PBF is increased 10 minutes after acid aspiration in regions of lung injury. This effect disappears within two hours after injury in anesthetized rats. These PBF-changes may be important for early treatment strategies after acid aspiration.

Background: To evaluate the influence of different SUV-measurements and patient-specific corrections thereof on the positive predictive value (PPV) of FDG-PET in pediatric Hodgkin lymphoma (pHL) using SUV-based response assessment.
Methods: PET-datasets of 33 children [female, n = 13, male, n = 20; range of age, 8.0–17.8 (mean, 15.0) years; follow-up, 44.5–83.3 (mean 63.0) months] with HL were analyzed retrospectively. PET-scans were obtained baseline (PET1) and after two cycles of chemotherapy (PET2). Within the leading lesion maximal SUV (SUVmax) and mean SUVs were generated by using isocontur-thresholds for different volumes of interest: Absolute, SUV2.5; relative to SUVmax, SUVmean40% to SUVmean70%. Generated SUVs were adjusted to body weight (SUV) and corrected for body surface area (SUV_BSA), patient's blood glucose and a combination thereof. The decrease in SUV or respective derivates thereof between PET1 and PET2 (ΔSUV) was assessed for response prediction using receiver operating characteristics (ROC)-analysis.
Results: Three patients had recurrence of disease. ROC-analysis showed the most accurate differentiation of responders and non-responders for ΔSUVmax_BSA [AUC, 0.97; P = 0.0026; sensitivity, 100%; specificity, 93.3%; PPV, 60.0%; negative predictive value (NPV), 100%; accuracy, 93.3%]. However, comparable results were obtained for conventional ΔSUVmax-determination (AUC, 0.96; P = 0.0112; sensitivity, 100%; specificity, 90.0%; PPV, 50.0%; NPV, 100%; accuracy, 90.9%). Threshold-based approaches were less effective or technically not performable in all patients.
Conclusions: At early response assessment by FDG-PET, patient-specific correction of ΔSUVmax by BSA improves PPV without impairment of excellent NPV in pHL. However, it is not statistically superior to simple ΔSUVmax-analyses. Larger cohorts are needed to investigate this observation.

Background: To achieve an acceptable signal-to-noise ratio (SNR) in PET images, smoothing filters (SF) are usually employed during or after image reconstruction preventing utilisation of the full intrinsic resolution of the respective scanner. Quite generally Gaussian-shaped moving average filters (MAF) are used for this purpose. A potential alternative to MAF is the group of so-called bilateral filters (BF) which provide a combination of noise reduction and edge preservation thus minimising resolution deterioration of the images. We have investigated the performance of this filter type with respect to improvement of SNR, influence on spatial resolution and for derivation of SUV_max values in target structures of varying size.
Methods: Data of ten patients with head and neck cancer were evaluated. The patients had been investigated by routine whole body scans (ECAT EXACT HR⁺, Siemens, Erlangen). Tomographic images were reconstructed (OSEM 6i/16s) using a Gaussian filter (full width half maximum (FWHM): Γ₀ = 4 mm). Image data were then postprocessed with a Gaussian MAF (FWHM: Γ_M = 7 mm) and a Gaussian BF (spatial domain: Γ_S = 9 mm, intensity domain: Γ_I = 2.5 SUV), respectively. Images were assessed regarding SNR as well as spatial resolution. Thirty-four lesions (volumes of about 1-100 mL) were analysed with respect to their SUV_max values in the original as well as in the MAF and BF filtered images.
Results: With the chosen filter parameters both filters improved SNR approximately by a factor of two in comparison to the original data. Spatial resolution was significantly better in the BF-filtered images in comparison to MAF (MAF: 9.5 mm, BF: 6.8 mm). In MAF-filtered data, the SUV_max was lower by 24.1 ± 9.9% compared to the original data and showed a strong size dependency. In the BF-filtered data, the SUV_max was lower by 4.6 ± 3.7% and no size effects were observed.
Conclusion: Bilateral filtering allows to increase the SNR of PET image data while preserving spatial resolution and preventing smoothing-induced underestimation of SUV_max values in small lesions. Bilateral filtering seems a
promising and superior alternative to standard smoothing filters.

Aim: Evaluation of a dedicated software tool for automatic delineation of 3D regions of interest in oncological PET. Patients, methods: The applied procedure encompasses segmentation of user-specified subvolumes within the tomographic data set into separate 3D ROIs, automatic background determination, and local adaptive thresholding of the background corrected data. Background correction and adaptive thresholding are combined in an iterative algorithm. Nine experienced observers used this algorithm for automatic delineation of a total of 37 ROIs in 14 patients. Additionally, the observers delineated the same ROIs also manually (using a freely chosen threshold for each ROI) and the results of automatic and manual ROI delineation were compared.
Results: For the investigated 37 ROIs the manual delineation shows a strong interobserver variability of (26.8±6.3)% (range: 15% to 45%) while the corresponding value for automatic delineation is (1.1±1.0)% (range: <0.1% to 3.6%). The fractional deviation of the automatic volumes from the observer-averaged manual ones is (3.7±12.7)%. Conclusion: The evaluated software provides results in very good agreement with observer-averaged manual evaluations, facilitates and accelerates the volumetric evaluation, eliminates the problem of interobserver variability and appears to be a useful tool for volumetric evaluation of oncological PET in clinical routine.

Aim: Image fusion of anatomical and functional data is an established procedure in nuclear medicine. Whereas elastic image fusion is expected to alter the information of the transformed data, we assessed whether rigid transformations also change the information contained in the PET-data.
Methods: F-18-FDG-PET/CT (Biograph 16, Siemens Medical, Erlangen, Germany) data of 14 tumor patients with a total of 18 solid pulmonary lesions were included in this retrospective analysis. For coregistration, rigid fast (RF) and rigid slow (RS) transformation algorithms of the Fusion7d-software were employed (Fusion7d, Mirada Solutions Ltd./Siemens Medical, Erlangen, Germany). Original PET-images (voxel size: 0.417cm x 0.417cm x 0.5cm) were fused with the attenuation-corrected CT (LR, voxel size: 0.417cm x 0.417cm x 0.5cm) and diagnostic CT (HR, voxel size: 0.098cm x 0.098cm x 0.1cm).PET data were saved in the respective CT-geometry and CT-resolution. Segmentation of lesions was performed using a 3D ROI volume determination software with automatic background detection (Rover, ABX GmbH, Radeberg, Germany). SUVmax, SUVmean, volume and metabolic volumes (volume*SUVmax and volume*SUVmean) of the lesions were determined in the original and in the coregistered PET data and compared. SUVmax in original PET ranged from to 1.6-30.9 (mean±SD, 8.8±7.0). CT-segmented volumes ranged from 1-58 ml (mean±SD, 9.9±15 ml).
Results: The relative differences of volume between original data and rigid fast fused-data ranged from 2-45% (mean±SD, 19%±13%) for LR-coregistration and from 0-12% (mean±SD, 3%±3%) for HR-coregistration. Fusing data with the rigid slow algorithm resulted in relative volume differences ranging from 1-48% (mean±SD, 20%±18%) for LR-coregistration and from 0-14% (mean±SD, 4%±4%) for HR-coregistration. Analyzing relative differences of metabolic volume products (volume*SUVmax) between original data and rigid fast fused-data ranged from 0-33% (mean±SD, 12%±9%) for LR-coregistration and from 0-11% (mean±SD, 3%±3%) for HR-coregistration. After fusion with the rigid slow method differences of volume*SUVmax ranged from 0-41% (mean±SD, 13%±13%) for LR-coregistration and from 0-16% (mean±SD, 4%±5%).Conclusions:Transformation of PET data by rigid coregistration algorithms results in a redistribution of the respective voxel information in the new coordinate system. Volumetric analysis based on a source-to-background algorithm showed substantial differences between original and coregistered data, which may have a potential impact on e.g. PET-based planning of radiotherapy or the assessment of treatment response by measurement of metabolic burden in follow-up studies. This effect is dependent on the source data (CT) resolution. The extent of the observed effect on the data of modern high resolution PET-systems remains to be evaluated.

Objectives : As is well known, limited spatial resolution leads to partial volume effects and consequently to limited signal recovery. Determination of the true activity concentration of a target structure is thus compromised even at target sizes much larger than the reconstructed spatial resolution. This leads to serioussize-dependent underestimates of true signal intensity in hot spotimaging. For quantitative PET in general and in the context of therapy assessment in particular it is therefore mandatory to perform an adequate recovery correction (RC). The goal of our work was to
developand to validate a model-free RC for hot spot imaging.
Methods : The algorithm proceeds in two steps. Step 1: automatic estimation of the true object volume V with an automatic thresholdbased method and the corresponding total activity A within V. Step 2:automatic determination of the background corrected activity fractionB, which is measured outside the object due to the partial volume effect. The recovery coefficient is then given by R = A/(A+B). For validation, we used a cylindrical phantom with six sphere inserts(volume: 2.5 - 27
ml) and performed measurements at three different target/background levels. RC was computed using the analytical convolution of the object function with the best fitting Gaussianpoint spread function and then compared to the results of the model-free approach.
Results : For the investigated target/background contrasts the model-free approach yields RC values which agree very well with the known (computable) RC values for the spheres (mean deviation +/-5%). The model-free nature of the approach allows, however, direct application to real patient data where the exact target shape is not known and model-based RC would fail.
Conclusions : The described method provides an easy and essentially automated way of doing quantitative RC in oncological hot spotimaging. It works well for sufficiently high contrast (>5) and a homogeneous background. The limits of the method have to be investigated further.

The crystal and molecular structure of tert-butyl 4-(2-tert-butoxy-2-oxoethyl)-piperazine-1-carboxylate is reported. The title compound crystallizes from a petroleum ether/ethyl acetate mixture in the monoclinic space group P 21/c with four molecules in the unit cell. The unit cell parameters are: a = 8.4007(2) Å, b = 16.4716(4) Å, c = 12.4876(3) Å; β = 90.948(1)° and V = 1727.71(7) Å3. Bond lengths and angles of this piperazine-carboxylate are typical.

Two novel indazole derivatives protected with p-methoxybenzyl group were synthesized and characterized. The crystal and molecular structure of 2-(4-methoxybenzyl)-4-nitro-2H-indazole as one out of the two regioisomers is reported. The compound was obtained from a saturated petroleum ether/ethyl acetate mixture and crystallizes in the triclinic space group P`1. The unit cell parameters are: a = 6.8994(1) Å, b = 9.8052(2) Å, c = 11.1525(2) Å; α = 71.729(1)°, β = 79.436(1)°, γ = 74.349(1)° and V = 685.83(2) Å3. There are two independent molecules found in the asymmetric unit.

Germanium nanocrystals in silicondioxide were studied by atomic force microscopy (AFM) in order to reveal their size, density and distribution. The generation of the nanocrystals was accomplished by Ge+ ion implantation into a 100 nm silicondioxide layer and subsequent annealing at high temperatures in an inert atmosphere. Rutherford backscattering spectroscopy was applied in order to reveal the Ge distribution after implantation and annealing, and the formation of the nanocrystals was proven by transmission electron microscopy. The oxide layer was gradually etched in order to uncover the nanocrystals located at different depth positions within the SiO2 layer. Subsequently, the unveiled surfaces were examined by AFM in order to determine the size and density of the exposed nanocrystals. A correlation between the nanocrystal properties and the Ge implantation dose was corroborated.

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SPIRIT (Support of Public and Industrial Research using Ion beam Technology) is an Integrating Activities project integrating 11 leading European ion beam facilities. Transnational access is provided by supplying ions in an energy range from ~10 keV to 100 MeV for modification and analysis of solid surfaces, interfaces, thin films and nanostructured systems. The techniques cover materials, biomedical and environmental research and technology. Related R&D activities aim at the improvement of the experimental procedures and the installation of novel equipment. Numerous networking activities address both the interaction between the project partners and information and dissemination towards new users. The present contribution gives a short overview of the project structure and its activities, as well as its performance during the first two years.

For geochemical modeling of scenarios for the disposal of radioactive and (chemo)toxic waste, comprehensive and internally consistent thermodynamic data are required as well as sorption data for the surrounding host rocks. The use of different databases renders it difficult to compare results of geochemical modeling, due to incompleteness, inconsistencies, resticted ranges of variation (temperature, density, pressure), limitations in solution composition (ionic strength) and last but not least missing sorption data.
THEREDA (THErmodynamic REference DAtabase, www.thereda.de) – a cooperative project of leading research institutes in Germany – adresses these issues, providing full documentation, transparency of all data and a detailed quality assurance scheme [1,2].
THEREDA contains data for the three ion-ion interaction models: extendend Debye-Hückel, Specific Ion Interaction Theory, and Pitzer model. At present, two datasets has been released: the oceanic salt system (Na+, K+, Mg2+, Ca2+, Cl−, SO42−, H+, and H2O(l) within a temperature range of 273.15–523.15 K) and Am/Nd/Cm (Am(III), Nd(III), Cm(III), Na+, Mg2+, Ca2+, Cl−, H+, H2O(l) at 273.15 K). Tailored parameter files for various geochemical modeling codes are provided (PhreeqC, ChemApp, EQ3/6, Geochemist‘s Workbench). Documented benchmark calculations allow comparisons with other databases as well as between the different geochemical codes. All data, documentation and references are freely accessible via the projects homepage. Additionally, a user forum allows direct contact with the THEREDA members.
A holistic view of geochemical processes in the context of a safety analysis requires the inclusion of sorption calculations. A thermodynamically consistent treatment of these processes is only possible with surface complexation modeling (SCM). Respective data are already compiled in the RES³T database [3] (www.hzdr.de/res3t), providing competing entries for many systems. An integration into THEREDA thus not only requires a synchronisation of data structures but also a rigorous review process, leading to uniform recommended data sets for each sorbent-sorptive system. This data review process is already in progress.

[1] Altmaier et al. (2011), Report GRS-265, 63 p.
[2] Altmaier et al. (2008) ATW 53, 249–253.
[3] Brendler et al. (2003) J. Contam. Hydrol. 61, 281–291.

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The pump-induced transmission of graphene grown epitaxially on hexagonal SiC was studied in degenerate pump-probe experiments with photon energies in the range from 10 to 250 meV. Different relaxation times ranging from 0.5 ps to 300 ps were found. A strong increase of the relaxation time was observed when the photon energy was below the optical phonon energy (~200 meV). The experiments were complemented by microscopic modelling based on the graphene Bloch equations. This allowed us to identify the physical processes which are responsible for the carrier relaxation channels. We discuss the role of Auger-type processes, optical and acoustic phonons. The modelling, which is in good agreement with the experimental results, reveals that optical phonon scattering becomes significantly less efficient when the energy of the excitation photons is below the optical phonon energy. Surprisingly, however, scattering via optical phonons is still the predominant relaxation channel, even at lower energies. This is attributed to the presence of hot carriers, which can still fulfil energy conservation requirements [1].
For photon energies about twice the value of the Fermi energy Ef, which is about 10 meV for the quasi-intrinsic layers of the epitaxial graphene, an interesting effect is observed. As the photon energy is reduced below 2Ef, a transition from pump-induced transmission to pump-induced absorption occurs. While the induced transmission is associated with Pauli blocking of carriers which underwent interband transition, the induced absorption is caused by a change of the electron temperature due to intraband absorption.

In contrast to usual semiconductors in graphene the Landau levels (LL) are not equidistant. This provides the unique feature to investigate a single LL transition selectively. By applying magnetic fields of up to 7 T we could investigate three different transitions at a fixed wavelength of 16.5 µm via pump-probe measurements. By varying the magnetic field the photon energies got resonant to the different transitions. For the transition LL0(-1)->LL1(0) we could not only observe an increase of the pump-probe signal by a factor of 2.5 but also a decrease of the relaxation time from 20 ps to 5 ps. Interestingly, the reduced relaxation time is observed in a wider range of magnetic fields then the increase of the signal amplitude. Additionally the minimum of the relaxation time is shifted in respect to the maximum signal. For the transitions LL-1(-2)->LL2(1) and LL-2(-3)->LL3(2) we could only observe an slight increase of the pump-probe signal.

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We report on pump-probe measurements on quasi-neutral sheets of multilayer epitaxial graphene in magnetic fields. Using THz radiation, generated by the free electron laser, we directly probe the relaxation of Dirac fermions among well-resolved Landau levels (LLs). In contrast to conventional semiconductors, the Landau level spacing in graphene is not equidistant. Hence it is possible to investigate a single LL transition selectively. To this end we performed pump-probe measurements at a wavelength of 16.5 µm and applied a magnetic field of up to 7T. We varied the magnetic field for resonant measurements at different LL transitions. For the transitions LL-1(-2) -> LL2(1) and LL-2(-3) -> LL3(2) we could observe a slight increase of the pump-probe signal but no change in the relaxation time. For the transition LL-1(0) -> LL0(1) the pump-probe signal increased by a factor of 2.5 while the relaxation time decreased from 20 ps to 5 ps. These measurements were done with linear polarized radiation. To understand the decrease in the relaxation time additional measurements were carried out with circularly polarized radiation. The circularly polarized radiation enables to distinguish between the transition LL-1->LL0 and LL0->LL1. We performed the experiment in all combinations of left and right polarized radiation for the pump and probe beam. This revealed complex dynamics involving positive and negative signals. We suggest this to result from different relaxation channels including Auger processes.

wird nachgereicht

Armenian Precambrian basement rocks metamorphism P and T conditions are defined applying amphibole thermobarometer by means of 104 amphibole microprobe chemical analyses. Measurements have been done on 2 samples of ophiolitic metabasalte amphibolites of the Precambian Kasakh suite. The general trend of metamorphism has been defined in the average amphibolite and green-schist facies in ranges T=420-640°C and P=1,6-5,7 kbar of low geothermal gradient of 12°C/km. Prograde megnesiohornblende-tschermakite and retrograde megnesiohornblende-actinolite zonation has been revealed, and also relics of kaersutite have been found. Relics of kaersutite are preserved from primary magmatic hornblende of the initial basalts

Radiation pulse from a Self-Amplified Spontaneous Emission Free Electron Laser (SASE FEL) consists out of spikes (wavepackets). Energy loss in the electron beam (averaged over radiation wavelength) also exhibit spiky behavior on a typical scale of coherence length, and follows the radiation pulse envelope. These modulations of the electron beam energy are converted into large density (current) modulations on the same temporal scale with the help of a dispersion section, installed behind the x-ray undulator.
Powerful optical radiation is then generated with the help of a dedicated radiator (afterburner). We have recently demonstrated this principle at the Free Electron Laser in Hamburg (FLASH), and this paper present the first experimental results.

We report on both the global and micromagnetic properties of interlayer exchange coupled spin systems. Irradiation with Ne ions is employed to achieve a phase transition from antiferromagnetic to ferromagnetic coupling. For extended trilayer films a full quantitative analysis of the bilinear and biquadratic coupling constants is performed. With increasing ion fluence we observe a steady increase of the bilinear coupling constant at an almost negligible decrease in saturation magnetization. The mixing of atoms at the layer interfaces is identified as the origin for this. The effects of ion modification on the magnetic microstructure are studied for the model system of layered vortex pairs. X-ray microscopy is used to directly image the individual magnetization circulations in trilayer disks. The circulation configuration is found to be determined by the film coupling for both coupling orientations with a homogenous coupling angle throughout the structure. For the vortex cores however, micromagnetic simulations indicate that due to the significant local demagnetization fields the parallel states are always energetically preferred. Nevertheless antiparallel configurations are metastable, having their signature in reduced core diameters. Our study provides new results on spin structures in interlayer exchange coupled trilayers and it demonstrates a promising way to control the local interlayer coupling post-deposition.

Ion beam are used largely in industry for surface treatment and deposition. In the last years low energy ion beam irradiation have shown potential for surface nanostructuring, either by direct writing with a focused ion beam, or by self-organized pattern formation during broad beam irradiations. I will present current activities of the HZDR of surface nanostructuring with oin beams and the application of such patterns in magnetism and plasmonics.

Erosion of surfaces by ion beam sputtering leads frequently to the formation of periodic patterns, which show up as a ripple pattern under off-normal incidence and as hexagonally ordered dot patterns under normal or close to normal ion incidence.1 A first successful attempt to describe the formation of these patterns theoretically has been given by Bradley and Harper.2 In their model they assumed that ion sputtering is introducing a surface instability which is proportional to the surface curvature and will increase surface roughness. In addition, thermally activated surface self-diffusion has been considered as a smoothing mechanism. Finally, the interplay between these two competing mechanisms leads to a selection of a narrow range of surface modes which grow fastest under ion irradiation. This model has been translated into a linear continuum equation, now well known as the Bradley-Harper equation. The simplified partial differential equation already predicts successfully main experimental observations, like the change in ripple orientation when going to grazing incidence and isotropic patterns under normal incidence. However, it fails to explain the long time behaviour and the detailed dynamics of the pattern evolution.
Based on the Bradley-Harper model many extensions have been proposed since then. Some of them like the damped or undamped Kuramoto-Sivashinsky (KS) equation3 show a good qualitative agreement, however they still fail to predict several important experimental observations. In addition main improvements have been achieved by including the mass rearrangement on the surface induced by the ion impact.4
Recently, new models have been proposed for the description of pattern formation, which go beyond the KS equation. They introduce coupled fields, e.g. for the mobile species or the concentrations of the elements in compound materials.5 However, there is still a gap to be closed between the continuum equations and the microscopic model describing the collision cascade, the energy deposition into the surface, or the crater function induced by the ion impact. Here, theoretical approaches combining binary collision approximation for the ion irradiation and kinetic Monte Carlo simulations for the subsequent relaxation promise a detailed description of the mechanisms involved in the pattern formation process.
In this presentation the strengths and limitations of the existing continuum equations and extended models will be discussed and will be compared to experiments and kMC simulations.