Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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.

We present a terawatt diode-pumped laser employing single-crystalline Yb:CaF2 as the amplifying medium. A pulse energy of 197 mJ and a duration of 192 fs were obtained, corresponding to a peak power of 1 TW.

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Si and Ge nanocrystals are supposed to be a promising material for high efficient 3rd generation multiple bandgap thin film solar cells. Photoluminescence studies of the quantum confinement effect in Si and Ge nanocrystals showed the feasibility of this approach [1, 2]. We propose the design sketched in Fig. 1 using a stack of well separated, mono-dispersed Ge nanoclusters of different size which allows bandgap tuning for light absorption from the blue to the infrared region.
In this contribution investigations on Ge nanocrystals formation in GeOx-SiO2 multilayer structures will be presented. The nanocrystals growth during annealing is vertically limited by the SiO2 separation layer while the phase separation of the GeOx layer during annealing leads to laterally GeO2 separated Ge nanocrystals. The goal is to achieve well confined, graded, equally sized and dense nano¬crystal superlattices only by the variation of the layer thicknesses and the GeOx composition. The GeOx-SiO2 stacks were deposited via reactive DC magnetron sputtering. A process window for the oxygen partial pressure in the O2/Ar sputtering gas mixture allows both, SiO2 formation for the separation layers as well as GeOx films with tuneable stoichiometry in the range of x = 0.2 - 2 [4].
Very smooth interfaces of the multilayers with roughness’s below 1 nm and a SiO2 separation layer thickness < 2 nm could be revealed with XRR and TEM – fig. 2 shows an annealed sample with Ge nanocrystals with a size of 2 nm. XANES synchrotron measurements (fig. 3) show that the phase separation of GeOx~1 is already finished at 400°C. The crystallisation occurs at 550°C which was monitored by GIXRD and Raman scattering. The Ge nanocrystal size was determined to be 2, 3 or 6 nm for different samples by GIXRD, TEM and Raman. Ellipsometry and absorbance measurements showed additional information’s about the structural and optical parameters of the multilayers. The stochiometry of the stack was always controlled with RBS.
Ge nanoclusters of 2 … 6 nm in size could be formed by phase separation at a temperature of about 400°C and crystallised at 550°C into nanocrystals which allows a broad variety of substrate materials. The very thin and smooth SiO2 separation layer enable interesting possibilities for charge transport via tunnelling.
[1] G. Conibeer et al. TSF 511-512, 654 (2006)
[2] Y. M. Niquet et al. APL 77, 1182 (2000)
[3] F. Dimroth et al. MRS Bulletin 32,230 (2007)
[4] M. Zschintzsch et al. JAP, in print (2010)

Si and Ge nanocrystals are believed to be a promising material for high efficient 3rd generation multiple bandgap thin film solar cells. Photoluminescence studies of the quantum confinement effect in Si and Ge nanocrystals showed the feasibility of this approach [1, 2].
Our design is sketched in Fig. 1 which uses a stack of well separated, mono-dispersed Ge nanoclusters of different size on an absorbing Ge layer which allows bandgap tuning for light absorption from the blue to the infrared region. In this conference contribution investigations on Ge nanocrystals formation in GeOx-SiO2 multilayer structures will be reported. The goal is to achieve well separated, equally sized and dense nanocrystal superlattices only by the variation of the layer thicknesses and the GeOx composition. The GeOx-SiO2 multilayers were deposited via reactive DC magnetron sputtering. A process window for the oxygen partial pressure in the O2/Ar sputtering gas mixture allows both, SiO2 formation for the separation layers as well as GeOx films with tuneable stoichiometry in the range of x = 0.2 - 2 [4]. The films stoichiometry were always controlled with RBS. The nanocrystals growth during annealing is vertically limited by the SiO2 separation layer while the phase separation of the GeOx layer during annealing leads to laterally GeO2 separated Ge nanocrystals.
Very smooth interfaces of the multilayers with roughness’s below 1 nm and a SiO2 separation layer thickness < 2 nm could be revealed with XRR and TEM – fig. 2 shows an annealed sample with Ge nanocrystals of 3 nm size. XANES synchrotron measurements (fig. 3) show that the phase separation of GeOx~1 -> Ge + GeO2 is already completed at 400°C. GIXRD and Raman scattering confirme a crystallisation temperature of about 550°C. Ge nanocrystals with well defined sizes between 2 and 10 nm have be fabricated by the variation of the GeOx sublayer thickness. As derived from RAMAN measure¬ments, the degree of crystallinity decreases with reduced layer thickness. The energy dependent optical parameters were determined by means of photoluminescence, ellipsometry and absorbance mea¬surements. The very thin and smooth SiO2 separation layer enables interesting possibilities for charge transport via direct tunnelling.
References:
[1] G. Conibeer et al. Thin Solid Films 511-512, 654 (2006)
[2] Y. M. Niquet et al. Applied Physics Letters 77, 1182 (2000)
[3] F. Dimroth et al. Materials Research Society Bulletin 32, 230 (2007)
[4] M. Zschintzsch et al. Journal Applied Physics 107, 0343061-8 (2010

Bandgap engineered Si and Ge nanocrystal solar cells are supposed to be a candidate for high effective 3rd generation thin film solar cells. Photoluminescence studies of the quantum confinement effect in Si and Ge nanocrystals showed the feasibility of this approach [1,2]. However the design and the fabrication of a high density of well separated, monodispersed nanoclusters remains a great challenge.
We want to present our investigations [3] on Ge nanocrystals formation in GeOx-SiO2 multilayer structures based on the phase separation of GeOx during annealing. The size of the laterally self-ordered Ge nanocrystals is vertically limited by the SiO2 separation layer. The final goal is to achieve well confined, graded, equally sized and dense nanocrystal superlattices only by the variation of the layer thicknesses and the oxygen content in the GeOx layer.
The GeOx-SiO2 stacks were deposited via reactive DC magnetron sputtering. A process window for the oxygen partial pressure in the O2/Ar sputtering gas mixture can be defined which allows both, SiO2 formation for the separation layers as well as GeOx films with tunable stoichiometry in the range of x = 0.2 … 2.
In-situ X-ray studies at synchrotron beamlines were performed to monitor the phase separation (XANES) of GeOx and the Ge nanocrystal formation (GIXRD, XRR, GISAXS) which was proofed in addition via TEM, Raman scattering and Absorbance.
Separated Ge nanocrystals of 2 … 6 nm in size can be formed at temperatures < 600°C. Very smooth interfaces with roughnesses below 1 nm allowed the separation of the Ge nanocrystal layers by SiO2 films < 2 nm which enables interesting possibilities for charge transport via tunnelling.
[1] G. Conibeer et al. TSF 511-512, 654 (2006)
[2] Y. M. Niquet et al. APL 77, 1182 (2000)
[3] M. Zschintzsch et al. JAP, 107, 0343061 - 8 (2010)

We use a combination of a scattering-type near-field infrared microscope with a free-electron laser as an intense, tunable radiation source to spatially and spectrally resolve buried doped layers in silicon. To this end, boron implanted stripes in silicon are raster scanned at different wavelengths in the range from 10 to 14 μm. An analysis based on a simple Drude model for the dielectric function of the sample yields quantitatively correct values for the concentration of the activated carriers. In a control experiment at the fixed wavelength of 10.6 μm, interferometric near-field signals are recorded. The phase information gained in this experiment is fully consistent with the carrier concentration obtained in the spectrally resolved experiments.

The key element providing hadron identification in the future Compressed Baryonic Matter spectrometer at FAIR is a time-of-flight wall placed at 10 m distance from the target. The most promising technological option for such a task consists on a 150 m² carpet based on Resistive Plate Chambers. Due to the fixed-target geometry, the conceptual design foresees two extreme regions: an outermost region (low rate/low multiplicity) covered by float glass RPCs in multi-strip fashion, and a central region (high rate/high multiplicity) consisting of densely packed read-out cells made with low resistive electrodes. The status of the ongoing R&D efforts in both regions is presented.

5 at.% Mn-doped and undoped, 200 nm thick BaTiO3 thin films have been grown under different oxygen partial pressures by pulsed laser deposition on Pt/sapphire substrates. X-ray diffraction (XRD) measurements reveal the same polycrystalline single-phase perovskite structure for all the thin films despite the different oxygen partial pressure, while their preferred orientation strongly depends on the oxygen partial pressure. The 5 at. % Mn-doping decreases the dielectric loss of the Mn-doped BaTiO3 thin films, however, their relative permittivity is also decreased. Ferroelectricity has been probed on the Mn-doped and undoped BaTiO3 thin films grown under relatively high oxygen partial pressure. A ferromagnetic coupling of the Mn dopant ions has been probed at room tempetature on the Mn-doped BaTiO3 thin films prepared under low oxygen partial pressure and is understood in terms of the bound magnetic polaron model.

The investigation of insulation debris generation, transport and sedimentation becomes important with regard to reactor safety research for PWR and BWR, when considering the long-term behaviour of emergency core cooling systems during all types of loss of coolant accidents. A joint research project on such questions is being performed in cooperation between the University of Applied Sciences Zittau/Görlitz and the Forschungszentrum Dresden-Rossendorf. The project deals with the experimental investigation of particle transport phenomena in coolant flow and the development of CFD models for its description. While the experiments are performed at the University at Zittau/Görlitz, the theoretical modelling efforts are concentrated at Forschungszentrum Dresden-Rossendorf. In the current presentation the basic concepts for CFD modelling are described and feasibility studies are presented. On the example of a complex flow situation at plunging jet conditions the model capabilities are demonstrated.

In the presentation the recent developments of the coupling of the reactor dynamics code DYN3D with the coarse-mesh CFD code FLICA-4 and the CFD code ANSYS CFX are presented. First results of verification calculations for small-size test problems confirm the correctness of the implementation of the coupling.

Polynuclear metal compounds may have considerable potential as metallic drugs. The most prominent representatives are polyoxometalates which have been investigated since the last third of the 19^th century. In addition to applications in catalysis, separation, analysis, and as electron-dense imaging agents, some of these substances have been shown to exhibit biological activity in vitro as well as in vivo ranging from anti-cancer, antibiotic, and antiviral to anti-diabetic effects.¹
Polymetalates represent a diverse ensemble of nanostructures with an almost infinite variability of chemical, physical and biological properties. The size of typical covalent bridged cluster compounds is in the range from 1 to 3 nm. The attachment of special surface groups on the periphery of cluster compounds may result in self-assembled non-covalent organized structures larger than 5 nm which are characteristic for bio-molecules, such as enzymes. Cells of mammalian organisms are typically 10 to 30 µm. However, sub-cellular organelle dimensions are smaller and range in sub-µm sizes. This comparison of size dimension illustrates that polymetalates are small enough to allow the cell membrane to be penetrated without too much interference. Evidently, some types of polymetalates are able to be transported into cells, particularly into mitochondria. Our aim is focused on the development of novel cluster compounds with improved chemical and metabolic stability. Furthermore, increased recognition of target biomolecules - such as enzymes - shall be achieved.
On the way to explore the biological activity of polynuclear cluster compounds, we recently recognised polyoxometalates as a new class of potent enzyme inhibitors.² Certain polymetalates are able to inhibit E-NTPDases (ecto-nucleoside triphosphate diphosphohydrolases) that are surface-located nucleotide-hydrolyzing enzymes involved in the regulation of signaling cascades by activating P2 (nucleotide) receptors. The most potent compound - described to date – is K₆H₂[TiW₁₁CoO₄₀] I exhibiting IC₅₀ values which are significantly lower than those of known standard inhibitors. Some compounds are also able to directly interact with P2 receptors. A further promising new class of cluster compounds to permit selective inhibition of E-NTPDases are hexanuclear rhenium complexes with bridging sulfur, selenium and/or tellurium atoms. In this perspective, a broad ensemble of water-soluble octahedral rhenium cluster compounds II becomes available by ligand exchange reactions.³
The paper will give a brief overview about the potential of inorganic cluster compounds in medicine as well as a survey of recent progress that was achieved on E-NTPDase inhibition and P2 receptor antagonism with polymetalates.

[1] J. T. Rhule, C. L. Hill, D. A. Judd, R. F. Schinazi, Chem. Rev.1998, 98, 327-357.
[2] C. E. Müller, J. Iqbal, Y. Baqi, H. Zimmermann, A. Röllich, H. Stephan, Bioorg. Med. Chem. Lett. 2006, 16, 5943-5947.
[3] K. A. Brylev, Y. V. Mironov, S. Kozlova, V. E. Fedorov, S.-J. Kim, H.-J. Pietzsch,
H. Stephan, A. Ito, S. Ishizaka, N. Kitamura, Inorg. Chem. 2009, 48, 2309-2315.

A novel carboxylic acid substituted dibenzoazacyclooctyne precursor has been synthesized using a fast and innovative three-step synthesis. It can be easily converted into the corresponding alkyne through UV-irradiation. Due to its fast and regioselective reaction with azides, the alkyne is a promising agent for copper-free "click chemistry". The second order reaction rate constant was determined by ¹H-NMR.

Nanocoatings have the potential to improve the surface properties of various materials. They are of extreme importance for surfaces in sliding lubricated contact such as highly stressed automotive engine parts. Here, nanocoatings have to be optimized with respect to low friction properties and a high wear resistance to enhance the energetic and environmental efficiency. An additional variation of the tribological characteristics arises due to the presence of the fuel as the lubricant.
The present study employs atomic-scale simulations in order to assist the manufacturing and optimization of functional nanocoatings. Our investigations focus on two basic functional film species - tetrahedral amorphous carbon (ta-C) and transition metal enriched carbon (TM:C) coatings. These films are modeled and studied with the help of bond-order potentials such as the reactive empirical bond-order (REBO) potential [1] for carbon-carbon interaction and the Shibuta potential [2] for TM-carbon interaction. Our simulations also incorporate an adaptive cutoff scheme, which is able to enhance the REBO potential characteristics [3]. Since the tribological properties of lubricated engine parts depend not only on the properties of the nanocoatings but also on the lubricant, the hydrocarbon dodecan is selected as a representative of the fuel in the automotive engines. Preliminary results on the ta-C film morphology and its tribological properties such as friction coefficients with and without lubrication are presented.

[1] D. W. Brenner et al., J. Phys.: Condens. Matter 14 (2002) 783
[2] Y. Shibuta et al., Chem. Phys. Lett. 472 (2009) 200
[3] L. Pastewka et al., Phys. Rev. B 78 (2008) 161402

In semiconductor technology amorphous Si layers are formed by ion implantation, and during subsequent annealing the solid phase epitaxial recrystallization (SPER) of the amorphous material takes place. In order to simulate the SPER process and to understand its atomic-level mechanisms, classical molecular dynamics calculations are employed since they allow the consideration of several thousand atoms and a time scale up to some hundreds of nanoseconds. In the last decade different authors investigated SPER in Si by this type of simulations, but the critical review shows that their results are not consistent with the experimental data. In most cases the SPER rate was strongly overestimated. Moreover, the results obtained by different groups under virtually equal conditions do not agree. This may be due to the different approaches used to prepare the initial state consisting of an atomic system with a nearly planar amorphous-crystalline interface. The main cause for the disagreement with experimental data is the inaccuracy of the interatomic potentials used in the different studies. The improvements considered in the present work are based on a better description of the amorphous phase using a modified potential without changing the established potential for the single-crystalline material. It is found that amorphous Si with realistic structural and thermodynamic properties can be obtained by certain modifications of known interatomic potentials, but these modifications do not yield the correct SPER rate. However, it is shown that the value of the SPER rate is strongly correlated with the melting temperature of amorphous silicon obtained by the corresponding modified potential. Obviously, this dependence can be explained by the fact that both melting and SPER are essentially determined by the flexibility of atomic bonds. The atomic mechanism of SPER consists in sequential local arrangements of atomic bonds and positions, preferentially along {111} facets or terraces.

first steps to laser driven radiation oncology
and the future of the Dresden laser lab

Vorstellung des BMBF-geförderten "NanoPharm"-Projekts

Protecting the environment and saving resources are two of the society’s challenges of the 21th century. Therefore interesting insights coming also from nature. As many bacteria and archaea live in extreme habitats, they developed early in evolution so called surface layers (S-layers), which function as intelligent interface between cells and their environment. One function of such S-layers is the binding of toxic metals and metalloids and thusly the protection of the cells from being damaged by these elements and their compounds. This makes, together with their self-assembling properties, S-layer very interesting building blocks for the construction of new bioinspired nanomaterials for different technical applications. Currently under development are materials for the selective metal-binding for the removal of toxic metals and metalloids or the recovery of precious metals, highly efficient (photo)catalysts for the elimination of organic pollutants or organic synthesis and new biosensors for chemicals or pharmaceuticals.

Magnetic domains in the shape memory alloy NiMnGa are investigated using magneto-optical indicator film technique. Depending on whether the twin boundary is moved by applying mechanical stress or magnetic fields a different domain state is found after twin boundary motion.

The control of the effective magnetic anisotropy, saturation magnetization as well as the dynamic magnetic properties in ferromagnetic thin films is of significant importance for most applications in spin electronics. The two materials’ parameters which control the dynamic response of soft magnetic thin films are the precessional frequency f_res and the effective damping parameter alpha. Whereas anisotropy and saturation magnetization together determine the precessional frequency of the films, the magnetic damping parameter cannot be varied easily. However it was shown that exchange coupled ferromagnetic/antiferromagnetic (F/AF) systems exhibit strong changes in f_res and alpha independent of the occurrence of exchange bias [1, 2]. On the other hand, ion irradiation of magnetic thin films [3] has been shown to provide an alternative method to alter soft magnetic properties of magnetic multilayer films due to ion induced changes in the interfacial structure. Here we use Ni-ion irradiation to control the dynamic magnetic properties in Ni81Fe19/IrMn/Ni81Fe19 structures in a controlled way. We show that for very thin AF layers alpha can be increased significantly [4]. Selecting an IrMn thickness below the onset of exchange bias, it is possible to solely alter alpha. This effect is reversible by low fluence Ni ion irradiation without changing the composition of the ferromagnetic alloy and thus can be used to adjust alpha over a wide range. As a consequence, the method can be used to laterally pattern samples only by the damping parameter. As shown in Fig. 1 the overall integral damping parameter then is determined by the relative fraction of materials with high and low damping parameter. alpha is thereby varied linearly without any significant change in f_res. The demonstrated paths of film alteration by ion irradiation provide an additional degree of freedom for the tailoring of dynamic magnetic properties of softmagnetic thin films. The method not only allows for general adjustment of magnetic properties, but also for a local setting of dynamic magnetic properties.
This work was supported by the German Science Foundation DFG under grant no. MC9-8/2.

[1] J. McCord et al., Phys. Rev. B 70, 094420 (2004)
[2] J. McCord et al., Phys. Rev. B 75, 134418 (2007).
[3] J. Fassbender and J. McCord, J. Magn. Magn. Mater. 320, 579 (2008).
[4] J. McCord, et al., Appl. Phys. Lett. 92 162506 (2008).

Understanding the role of the magnetic domain structure on the magneto-dynamic properties of patterned magnetic thin film structures is crucial for the optimization of devices, e.g. recording heads and integrated inductors. Arrays of rectangular amorphous Co40Fe40B20 elements of micron size, a separation to width ratio of 1.5 and a thickness of 60 nm have been fabricated. Magneto-optical Kerr microscopy was used to study the domain structure. At zero field closure domain patterns are present whereas the domain width was systematically altered by varying the magnetic field history. The magneto dynamic response of different domain patterns with adjusted domain width was measured using pulsed inductive microwave magnetometry. We show that the resonance frequency is the lowest for broad closure domain structures and increases when the domain width is decreased.

The control of dynamic magnetic properties in ferromagnetic thin films is of significant importance for applications in spin electronics. We demonstrate the use of low fluence Ni-ion irradiation to locally and solely tailor the magnetic damping parameter e in ferromagnetic-antiferromagnetic Ni81Fe19/IrMn/Ni81Fe19 sandwich structures. The overall relaxation time then depends on the relative fraction of the phases with different e , which thereby can be controlled without changing the precessional frequency. The superposition of alpha is confirmed by modeling of the dynamic response. The demonstrated path of film engineering by local ion irradiation [J. Fassbender, J. McCord, JMMM 320 (2008) 579] provides an additional degree of freedom for the local tailoring of dynamic magnetic properties of soft-magnetic thin films.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zum schnellen Nachweis von Östrogen in wässrigen Lösungen vor Ort zu realisieren. Der Nachweis basiert auf einer Fluoreszenzanalyse, wobei eine integrierte Lichtquelle mit einer bioaktiven Schicht auf deren Oberfläche verwendet wird. Die bioaktive Schicht wird durch ein spezielles Hybridisierungs- und Silanisierungsverfahren erzeugt. Die Messung erfolgt durch die optische Detektion farbstoffmarkierter Hormonmoleküle, die nach einem bestimmten Messprotokoll die Rezeptoren belegen, die noch nicht durch Hormone aus der Messprobe gesättigt worden sind.

The InAs quantum structures were formed in silicon by sequential ion implantation and subsequent thermal annealing. Samples were characterized by micro-Raman spectroscopy, Rutherford backscattering spectrometry (RBS), low temperature photoluminescence (PL), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Two kinds of crystalline InAs nanostructures were successfully synthesized:quantum dots (QDs) and nanopyramides (NPs). The Raman spectrum shows two peaks at 215 and 235 cm-1 corresponding to the transverse optic (TO) and longitudinal optic (LO) InAs single-phonon modes, respectively. The narrow PL band at around 1.3 mm due to the excitation of InAs QDs with an average diameter 7.5 ± 0.5 nm was observed. The InAs NPs were found only in samples annealed for 20 ms at temperatures ranging from 1000 up to 1200 oC. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by HRTEM and XRD techniques. The average size of the NPs is 50 nm base and 50 nm high and they are oriented parallel to the Si (001) planes. The lattice constant of the NPs increases from 6.051 to 6.055 Ǻ with the annealing temperature increasing from 1100 to 1200 oC due to network relaxation. Energy dispersive spectroscopy (EDS) shows almost stoichiometric composition of the InAs NPs.

Both mono- and multicrystalline p-type silicon wafers were used for the phosphorous ion implantation. After ion implantation the silicon is strongly disordered or amorphous within the ion range. Therefore subsequent annealing is required to remove the implantation damage and to activate the doping element. During FLA, only the wafer surface is heated homogeneously to very high temperatures at ms time scales, resulting in the annealing of the implantation damage and an electrical activation of the phosphorous. It is demonstrated that FLA at 800 oC for 20 ms even without preheating is sufficient to recrystallized implanted silicon. The highest recrystallization and the lowest resistivity were obtained after annealing at 1200 oC for 20 ms both for mono- and multicrystalline silicon wafers. Photoluminescence results point towards P - cluster formation at high annealing temperatures which effects on metal impurity gettering within the emitter.

Aufgabe der vorliegenden Erfindung ist es, eine Anordnung zur Röntgen-Computertomographie anzugeben, die eine kontinuierliche dreidimensionale Abbildung des Untersuchungsobjektes bzw. eines Teilvolumens des Untersuchungsobjektes bei hoher zeitlicher und räumlicher Auflösung gestattet, wobei mit hoher räumlicher Auflösung sowohl eine hohe Auflösung innerhalb der Schnittebene als auch in axialer Richtung definiert ist.

Phosphorous ion implantation was used for the emitter formation in mono- and multicrystalline silicon solar cells. After ion implantation the silicon is strongly disordered or amorphous within the ion range. Therefore subsequent annealing is required to remove the implantation damage and to activate the doping element. Flash-lamp-annealing (FLA) offers here an alternative route for the emitter formation at an overall low thermal budget. During FLA, only the wafer surface is heated homogeneously to very high temperatures at ms time scales, resulting in the annealing of the implantation damage and an electrical activation of the phosphorous. However, variation of the pulse time also allows to modify the degree of annealing of the bulk region to some extent as well, which can have an influence on the gettering behaviour of metallic bulk impurities.
The μ-Raman spectroscopy showed that the silicon surface is amorphous after ion implantation. It could be demonstrated that FLA at 800°C for 20 ms even without preheating is sufficient to recrystallize implanted silicon. The highest carrier concentration and efficiency and the lowest resistivity were obtained after annealing at 1200°C for 20 ms both for mono- and multicrystalline silicon wafers. Photoluminescence results point towards P-cluster formation at high annealing temperatures which effects on metal impurity gettering within the emitter.

The In(As, N) quantum structures were formed in silicon, SiO2 and Si3N4 films by sequential ion implantation and subsequent thermal annealing. Samples were characterized by -Raman spectroscopy, Rutherford backscattering spectrometry (RBS), low temperature photoluminescence (PL), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Two kinds of crystalline InAs nanostructures were successfully synthesized: quantum dots (QDs) and nanopyramides (NPs). The Raman spectrum shows two peaks at 215 and 235 cm-1 corresponding to the transverse optical (TO) and longitudinal optical (LO) InAs phonon modes, respectively. The narrow PL band at around 1.3 m from the InAs QDs with an average diameter 7.5 ± 0.5 nm was observed.
The InAs NPs were found only in samples annealed for 20 ms at temperature range from 1000 up to 1200 oC. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by high resolution transmission electron microscopy (HRTEM) (see Fig. 1) and X-ray diffraction (XRD). The average size of the NPs is 50 nm base and 50 nm high and they are oriented parallel to the Si (001) planes. The InAs nanopyramids grow in silicon due to liquid phase epitaxy. The InN crystals are formed on the top of silicon nitride layer due to outdiffusion of indium and in Si3N4 film. The PL measurements shows narrow band at around 1.35 m originated from hexagonal InN nanocrystals due to quantum confinement size effect. -Raman scattering study shows two peaks at 495 and 588 cm-1, which correspond to (TO) of E2h and (LO) of A1 phonon modes, respectively.

Die Erfindung betrifft die Herstellung von Radiopharmaka, insbesondere in Verfahren, und eine Anordnung zur Reinigung des Reaktionsgemisches bei der Herstellung von Radiopharmaka, insbesondereF-markierte Radiopharmaka, wie z. B. [F]FDOPA und [F]OMFD sowie [F]FMeMcN. Erfindungsgemäß wird zur Reinigung des Raktionsgemisches eine Vorsäule als Vorreinigungssäule, gefüllt mit RP-Material (Reversed Phase Material), zur Abtrennung des bei der Reaktion verwendeten Lösungsmittels (Matrix) bzw. unerwünschter Nebenprodukte verwendet, während die eigentliche chromatographische Trennung des Reaktionsgemisches auf einer HPLC-Säule, bevorzugt einer RP-HPLC-Säule, durchgeführt wird.

Ion beam erosion techniques allow for the creation of well-ordered substrate ripples with nanometer periodicity. Moreover, the periodicity can be tuned by changing the ion beam energy over a wide range [1]. The ripple pattern is directly transferred into films grown on these substrates. This offers the possibility of tailoring the magnetic properties by inducing additional magnetic anisotropy due to the structural modifications.
We study the influence of rippled vs. flat Si substrates for 10 nm thin Fe and Co films, as well as technologically relevant Heusler alloys (Fe₃Si and Co₂Fe_xMn_1-xSi). The magnetic anisotropy is measured by frequency and angle dependent vector network analyzer ferromagnetic resonance. The ripple morphology of the magnetic layers induces a strong uniaxial magnetic anisotropy.

Die vorliegende Erfindung betrifft eine hochgeordnete Nanostruktur und Sensor, in der bzw. dem organische Molekülgruppen, die spezifische Bindungseigenschaften für ein Zielmolekül haben, geordnet gebunden sind, und deren Verwendung. Anwendungsgebiet dafür finden sich in der Biotechnologie, Verfahrenstechnik, Umwelttechnik und Pharmazie, insbesondere bei der Herstellung von Biosensoren, in der biomedizinischen Analytik, bei der Beseitigung von Schadstoffen und Pathogenen, in der DNA-Analytik, für die Herstellung von Filtermaterialien, für Separationsverfahren, für Katalysatoren und in der medizinischen Therapie. Die Aufgabe der Erfindung ist es, eine Struktur zur Verfügung zu stellen, in der organische Molekülgruppen, insbesondere Molekülgruppen, die spezifische Bindungseigenschaften haben, geordnet gebunden sind, und dadurch die von den organischen Molekülgruppen gebundenen Substanzen in die Nähe funktioneller Bestandteile zu bringen. Dies wird gelöst durch eine Nanostruktur, die selbstorganisierende Proteine, an die Aptamere oder andere organische Molekülgruppen, die spezifische Bindungseigenschaften für ein Zielmolekül aufweisen, gebunden sind, und an die selbstorganisierenden Proteine gebundene anorganische Nanopartikel enthält.

Both mono- and multicrystalline p-type silicon wafers were used for the implantation of phosphorous. After ion implantation the silicon is strongly disordered or amorphous within the ion range. Therefore subsequent annealing is required to remove the implantation damage and to activate the doping element. Flash-lamp-annealing (FLA) offers here an alternative route for the emitter formation at an overall low thermal budget. During FLA, only the wafer surface is heated homogeneously to very high temperatures at ms time scales, resulting in the annealing of the implantation damage and an electrical activation of the phosphorous. However, variation of the pulse time also allows to modify the degree of annealing of the bulk region to some extent as well, which can have an influence on the gettering behaviour of metallic bulk impurities.
The μ-Raman spectroscopy showed that the silicon surface is amorphous after ion implantation. It could be demonstrated that FLA at 800oC for 20 ms even without preheating is sufficient to recrystallize implanted silicon. The highest carrier concentration and efficiency and the lowest resistivity were obtained after annealing at 1200oC for 20 ms both for mono- and multicrystalline silicon wafers. Photoluminescence results point towards P-cluster formation at high annealing temperatures which effects on metal impurity gettering within the emitter.

InAs quantum dots (QDs) were successfully formed in single-crystalline Si by sequential ion implantation and subsequent milliseconds range flash lamp annealing (FLA). Samples were characterized by μ-Raman spectroscopy, Rutherford Backscattering Spectrometry (RBS) high-resolution transmission electronmicroscopy (HRTEM) and low temperature photoluminescence (PL). The Raman spectrum shows two peaks at 215 and 235 cm−1 corresponding to the transverse optical (TO) and longitudinal optical (LO) InAs phonon modes, respectively. The PL band at around 1.3 μm originates from the InAs QDs with an average diameter 7.5±0.5 nm and corresponds to the increased band gap energy due to the strong quantum confinement size effect. The FLA of 20 ms is sufficient for InAs QDs formation. It also prevents the out-diffusion of implanted elements.
Moreover, the silicon layer amorphized during ion implantation is recrystallized by solid-phase epitaxial regrowth during FLA.

The furnace and flash-lamp annealing (FLA) temperature dependent variation in the room temperature 1.53 μm Er photoluminescence (PL) from Er-doped Ge-rich SiO2 layers is investigated. The appearance of the 1.53 μm Er PL is discussed in the framework of the phonon-assisted fluorescent resonant energy transfer from Ge-related luminescence-centers (LCs) to the Er3+. Detailed analyses suggest that in case of FLA the decrease in the 1.53 μm Er PL intensity is governed by the temperature dependent recrystallization of Ge nanoclusters, while for furnace-annealing it is associated with the reduction in the LC-Er3+ coupling due to Ge out-diffusion and the formation of Er-rich clusters with increasing temperature.

We present a magneto-transmission experimental set up covering spectral region from 5 to 120 µm. Interchangable quintum cascade lasers are used as an excitation sources. Performance of the setup is illustrated via cyclotron resonance studies of InGaAs/GaAs QWs under magnetic fields up to 60T

Copper-rich precipitates are assumed to be the main cause of hardening and embrittlement of Cu-bearing reactor pressure vessel steels since they act as obstacles to dislocation motion within the grains of the polycrystalline bcc-Fe. Multiscale modeling contributes to a better understanding of point-defect-enhanced formation of these clusters during reactor operation. Rate theory is an efficient tool to simulate the cluster evolution on realistic time and length scales. However, many parameters used in rate theory, such as the diffusion coefficients of mobile species and the free binding energies of clusters, are not very well known from experimental investigations. Atomic-level computer simulations can provide these data. In the present work the nucleation free energy is determined for pure copper and pure vacancy clusters as well as for mixed clusters up to a maximum cluster size of 200. The energetics of the coherent CunVm clusters in bcc-Fe is obtained using a combination of on-lattice Monte Carlo simulations and off-lattice molecular dynamics. The most recent Fe-Cu interatomic potential by Pasianot and Malerba [1] is employed in the calculations.
[1] R. C. Pasianot and L. Malerba, J. Nucl. Mater. 360, 118 (2007).

Traumatic brain injury (TBI) is a major cause of death and disability worldwide, especially in children and young adults. Previous studies have shown alterations in the central cholinergic neurotransmission after TBI. We therefore determined α7 nicotinic acetylcholine receptor (nAChR) densities in newborn piglets and adult rats after experimental TBI. Thirteen newborn piglets (post-TBI survival time: 6 h) underwent fluid percussion (FP) injury
(n = 7) or sham operation (n = 6). Furthermore, adult rats randomized into three groups of post-TBI survival times (2, 24, 72 h) received controlled cortical impact injury (CCI, n = 8) or sham operation (n = 8). Brains were frozen, sagittally cut and incubated with the α7-specific radioligand [125I]a-bungarotoxin for autoradiography. In injured newborn piglets, decreased α7 receptor densities were observed in the hippocampus (-38%), the hippocampus CA1 (-40%), thalamus (-30%) and colliculus superior (-30%). In adult rats, CCI decreased the receptor densities (between -16 and -47%) in almost any brain region within 2 and 24 h. In conclusion, widespread and significantly lowered α7 nAChR densities were demonstrated in
both TBI models. Our results suggest that a nearly similar TBI-induced decrease in the α7 density in the brain of immature and adult animals is found, even with the differences in species, age and experimental procedures. The alterations make the α7 nAChR a suitable target for drug development and neuroimaging after TBI.

Near equiatomic Ni–Ti films have been deposited by magnetron co-sputtering on TiN films with a topmost layer formed by b111N oriented grains (TiN/SiO2/Si(100) substrate) in a chamber installed at a synchrotron radiation beamline. In-situ X-ray diffraction during Ni–Ti film growth and their complementary ex-situ characterization by Auger electron spectroscopy, scanning electron microscopy and electrical resistivity measurements during temperature cycling have allowed us to establish a relationship between the structure and processing parameters. A preferential development of b110N oriented grains of the B2 phase since the beginning of the deposition has been observed (without and with the application of a substrate bias voltage of −45 and −90 V). The biaxial stress state is considerably influenced by the energy of the bombarding ions, which is dependent on the substrate bias voltage value applied during the growth of the Ni–Ti film. Furthermore, the present work reveals that the control of the energy of the bombarding ions is a promising tool to vary the transformation characteristics of Ni–Ti films, as shown by electrical resistivity measurements during temperature cycling. The in-situ study of the structural evolution of the growing Ni–Ti film as a consequence of changing the Ti:Ni ratio during deposition (on a TiNb111N layer) has also been performed. The preferential growth of b110N oriented grains of the Ni–Ti B2 phase has been as well observed despite the precipitation of Ti2Ni during the deposition of a Ti-rich Ni–Ti film fraction. Functionally graded Ni–Ti films should lead to an intrinsic “twoway” shape memory effect which is a plus for the miniaturization of Ni–Ti films based devices in the field of micro-electro-mechanical systems.

It was shown that racemic (±)-2 [1’-benzyl-3-(3-fluoropropyl)-3H-spiro[[2]benzofuran-1,4’-piperidine], WMS-1813] represents a promising positron emission tomography (PET) tracer for the investigation of centrally located σ1 receptors. To study the pharmacological activity of the enantiomers of 2, a preparative HPLC separation of (R)-2 and (S)-2 was performed. The absolute configuration of the enantiomers was determined by CD-spectroscopy together with theoretical calculations of the CD-spectrum of a model compound. In receptor binding studies with the radioligand [3H]-(+)-pentazocine, (S)-2 was thrice more potent than its (R)-configured enantiomer (R)-2. The metabolic degradation of the more potent (S)-enantiomer was considerably slower than the metabolism of (R)-2. The structures of the main metabolites of both enantiomers were elucidated by determination of the exact mass using an Orbitrap-LC-MS system. These experiments showed a stereoselective biotransformation of the enantiomers of 2.

We present transverse momentum spectra, rapidity distribution and multiplicity of Lambda-hyperons measured with the HADES spectrometer in the reaction Ar(1.76A GeV)+KCl. The yield of Xi- is calculated from our previously reported Xi-/(Lambda+Sigma0) ratio and compared to other strange particle multiplicities. Employing a strangeness balance equation the multiplicities of the yet unmeasured charged Sigma hyperons can be estimated. Finally a statistical hadronization model is used to fit the yields of pi-, K+, K0s, K-, phi, Lambda and Xi-. The resulting chemical freeze-out temperature of T=(76+-2) MeV is compared to the measured slope parameters obtained from fits to the transverse mass distributions of the particles.

Computer simulations using classical interatomic potentials are an efficient and promising tool to investigate and understand atomic-level properties and processes in advanced materials. They allow the consideration of length and time scales which are often hardly accessible by experiments. However, the accuracy of the interatomic potentials employed in such type of simulations determines decisively the quality of the obtained results. Therefore, these potentials must be continuously improved and evaluated.
In the present contribution three applications of atomistic computer simulations are illustrated. The focus is on energetics and kinetics of defects, impurities, nanostructures and interfaces in materials for micro- and nanoelectronics and in structural materials for fission reactors. Implications of the simulation results for the explanation of experimental findings are discussed.

The first example deals with molecular dynamics simulations on basic migration mechanisms of mono- and di-(self-)interstitials in Si. Both the atomic mobility due to the presence of the defect and the defect mobility itself are determined. The mechanism of di-interstitial migration depends on temperature, in contrast to that of the mono-interstitial.

In the second example amorphous Si and Ge as well as their solid-phase epitaxial recrystallization (SPER) are considered. Results obtained by different interatomic potentials are compared. The molecular dynamics simulations yield amorphous material with realistic structural and thermodynamic properties, but the SPER rate is strongly overestimated. It is shown that a more realistic SPER rate can be obtained using a modified interatomic potential which yields a higher melting temperature of the amorphous phase. This is explained by the fact that both melting and SPER are essentially determined by the flexibility of atomic bonds.

The subject of the third example is the formation of coherent Cu-rich precipitates in bcc-Fe, i.e. nanostructures containing Cu and vacancies. For pure vacancy and pure Cu clusters as well as for mixed clusters up to a maximum size of 200 the free binding energy and nucleation free energy are determined, using a combination of on-lattice Metropolis Monte Carlo simulations and off-lattice molecular dynamics calculations. The data which are obtained for the binding energy of a single Cu atom and a single vacancy to a cluster are important input parameters of the rate theory. This type of simulation is an efficient multi-scale modeling tool to simulate the cluster evolution on realistic length and time scales.

Experimental investigations revealed that both the impurity Cu and the alloying element Ni may contribute to hardening and embrittlement of reactor pressure vessel (RPV) steels during the irradiation by fast neutrons. The irradiation-induced supersaturation of vacancies and self-interstitials amplifies the diffusion of the foreign atoms in bcc-Fe and causes the formation of nanosized Cu- or Ni-rich clusters which act as obstacles to dislocation motion within the grains of the polycrystalline matrix. The concentration of Cu in RPV steels is typically higher than its solid solubility and, therefore, irradiation-enhanced formation of Cu-rich precipitates is observed. Measurements showed that these clusters may not only consist of pure Cu but also include vacancies [1]. On the other hand, the Ni concentration is typically below its solubility limit. That means, any formation of Ni-rich clusters as found in [2] for neutron-irradiated binary Fe-Ni alloys is essentially irradiation-induced. Obviously, these clusters must contain additional species in order to be stable. Small-angle neutron scattering analysis [2] indicated that vacancies could be the other constituent.
In the present work atomistic computer simulations using the ternary Fe-Cu-Ni interatomic potential by Bonny et al. [3] are employed to investigate the thermodynamics of Cu-vacancy and Ni-vacancy precipitates in bcc-Fe. The nucleation free energy of the clusters is determined by the energy and the entropy change due to precipitation using isolated (diluted) Cu and Ni atoms as well as vacancies as the reference. In agreement with indications from measurements the nanoclusters are assumed to have the bcc structure of the iron matrix. The binding energy of the most stable cluster configurations is calculated by simulated annealing within the framework of on-lattice Metropolis Monte Carlo simulations and by subsequent relaxation using off-lattice molecular dynamics calculations.
[1] Q. Xu, T. Yoshiie, K. Sato, Phys. Rev, B 73 (2006) 134115.
[2] F. Bergner, A. Ulbricht, M. Hernandez-Mayoral, P. K. Pranzas, J. Nucl. Mater. 374 (2008) 334.
[3] G. Bonny, R. C. Pasianot, N. Castin, L. Malerba, Phil. Mag. 89 (2009) 3531.

Reactor pressure vessel (RPV) steels consist of polycrystalline bcc-Fe with different alloying elements, e.g. Ni, and different impurities, e.g. Cu. The continuous irradiation by fast neutrons leads to a supersaturation of vacancies and self-interstitials which enhances the diffusion of the foreign atoms and causes the formation of nanosized clusters. The interaction of dislocations with these precipitates is considered to be the main cause of hardening and embrittlement of RPV steels. In order to model the evolution of the nanoclusters under irradiation at typical temperatures by rate theory the dependence of their nucleation free energy on cluster size and composition must be known. In the present work atomic-level computer simulations are employed to determine these data since they are hardly obtainable by experimental investigations. The ternary Fe-Cu-Ni interatomic potential by Bonny et al. [1] is used in order to consider the thermodynamics of nanoclusters which may consist of the two foreign species and vacancies. In particular the influence of Ni on the formation of clusters containing Cu and vacancies is investigated since previous theoretical [1] and experimental [2,3] studies indicated synergistic effects. The nucleation free energy of the clusters is determined by the energy and the entropy change due to precipitation using isolated (diluted) Cu and Ni atoms as well as vacancies as the reference. In agreement with experimental observations the nanoclusters are assumed to have the bcc structure of the iron matrix. The energy and entropy contributions are calculated using combinations of on-lattice Monte Carlo simulations and off-lattice molecular dynamics calculations.
[1] G. Bonny et al., Phil. Mag. 89 (2009) 3531.
[2] J. T. Buswell et al., Effects of Radiation on Materials: 14th Int. Symp. (Vol. II), ASTM STP 1046, Philadelphia, 1990, p.127.
[3] F. Bergner et al., J. Nucl. Mater. (2009) in press

Der ehemalige Kali- und Steinsalzbergbau im Raum Staßfurt (Sachsen-Anhalt) führt seit dem 19. Jahrhundert zu stellenweise erheblichen Bergschäden im Stadtgebiet, die auf Subrosion und Konvergenz untertägiger Hohlräume zurück gehen. Gebäude und Infrastruktur sind von großflächigen Absenkungen, Vernässungen und lokalen Tagesbrüchen in Mitleidenschaft gezogen worden.

Da man ähnliche Bergbaufolgeschäden in vielen Regionen des Salzbergbaus antrifft, hat sich das aus mehreren Forschungseinrichtungen, Universitäten und Unternehmen bestehende Forschungsverbundvorhaben Dynamik abgesoffener oder gefluteter Salzbergwerke und ihres Deckgebirgsstockwerks unter Federführung der Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) zum Ziel gesetzt, Ursachen, Prozesse und Auswirkungen der Bergschäden exemplarisch und allumfassend zu untersuchen.

Um ein möglichst umfassendes Bild der im Untergrund ablaufenden Prozesse und deren Ursachen und Folgen zu erhalten, sind Untersuchung der kleinräumigen Strukturen und Prozesse im Labormaßstab erforderlich. Die großräumige Abschätzung der Grundwasserdynamik im Salinar und im Deckgebirge, also der Ursachen und Folgen der Subrosion, bedarf der Charakterisierung von Wegsamkeiten und der Fluiddynamik bis in den Milli- und Mikrometerbereich, da sich die grundlegenden Prozesse auf der molekularen Ebene in der Mikroskala abspielen und somit die Dynamik in der regionalen Größenordnung bestimmen.

Wie auf der Feldskala, so wird auch auf der Laborskala die Verteilung von hydrologischen Parametern, wie z. B. Permeabilitäten, Abstandsgeschwindigkeiten und Dispersionsraten von der heterogenen Struktur des Gesteins kontrolliert, weswegen diese Parameter nicht nur im regionalen sondern auch im Labormaßstab strukturbezogen, also räumlich differenziert, erhoben werden sollten.

Daher wurde in enger Zusammenarbeit mit dem Geologischen Institut der JGU Mainz eine Methode zur direkten räumlich aufgelösten und quantitativen Prozessbeobachtung entwickelt und angewendet. Hierfür wurde die Methode der Positronen-Emissions-Tomographie (PET) eingesetzt, ein ursprünglich medizinisches, bildgebendes Verfahren. Dieses Verfahren erlaubt es, zerstörungsfrei, mit höchstmöglicher Empfindlichkeit und geeignetem Auflösungsvermögen, die Bewegung einer mit einem radioaktiven Tracerisotop (hier F-18 und I-124) markierten Wassermenge in Raum und Zeit zu beobachten, wobei die Menge des eingesetzten Radiotracers im Bereich weniger Nanogramm gehalten werden kann. Das System wird somit durch den Tracer auf geringst mögliche Weise beeinflusst und es wird ein sehr realistisches Bild des Fließverhaltens mit einer räumlichen Auflösung von 1 mm und einer zeitlichen Auflösung von 60 s erzeugt.

Bislang wird in der Literatur nur von wenigen Ansätzen berichtet, die das Ziel verfolgen, die realistischen Verhältnisse strömender Fluide in heterogen strukturierten Gesteinen dreidimensional abzubilden. Solche Strömungsmuster werden in der Regel mittels stochastischer Modelle durch Computersimulationen erzeugt. Erst ein Abgleich mit gemessenen Strömungsmustern kann zur Validierung dieser Simulationen führen, was auch erst ein valides Upscaling in die Feldskala ermöglicht.

In Kooperation mit der Bundesanstalt für Materialforschung- und prüfung Berlin (BAM) und dem Geologischen Institut der Johannes-Gutenberg Universität Mainz (JGU) werden daher die PET-Messungen zur Fluiddynamik mit Lattice-Boltzmann-Simulationen der Fließprozesse verglichen, die auf hochauflösenden computertomographischen µXCT Messungen der internen Struktur der identischen Bohrkerne beruhen.

Der Vergleich von PET-Messdaten mit Lattice-Boltzmann - Simulationsdaten bedeutet eine Skalenübertragung um etwa drei Größenordnungen (µm - mm). Daher erfolgt der Abgleich zwischen gemessenen und simulierten Daten auf statistischem Wege. Gemessene und simulierte Strömungsmuster werden mittels Variographie mit einander abgeglichen, da diese Methode skalenübergreifend die Korrelationen zwischen den Fließmustern wider gibt. Ebenso werden räumlich differenzierte Durchbruchkurven und Histogramme für den Vergleich von Messung und Simulation heran gezogen.

Diesem Ansatz liegt das Bestreben zugrunde, zu einer Erweiterung des generellen Prozessverständnisses und der Vorhersagbarkeit über das Verhalten von Fluiden in porösen und klüftigen Gesteinen beizutragen und die beobachteten Phänomene und Prozesse von der Labor- auf die Feldskala zu übertragen.

Nicht in jedem Fall war dieser Abgleich zwischen Simulation und Experiment jedoch möglich: während in klüftig-porösen Materialien gewöhnlich mit beiden Methoden räumlich stark differenzierte präferentielle Fließwege im Kluftsystem gefunden wurden, konnte in eher mikrostrukturell ausgeprägten Materialien trotz messbarer Permeabilität gelegentlich kein verbundener Porenraum aus den CT-Bildern segmentiert und somit keine Lattice-Boltzmann-Simulation durchgeführt werden. In diesem Fall zeigte die PET-Untersuchung ein diffuses Ausbreitungsverhalten des Tracers.

This thesis is located at the Institute of Radiochemistry, FZD Research Site Leipzig for Interdisciplinary Isotope Research, Reactive Transport Division (FWRT). The main focus of this division is the investigation of transport processes in geosystems by means of radiotracer applications. The main topic of the thesis is the visualization of transport processes in geologic material by means of the in-house development of the GeoPET-method. This work is conducted as part of the scientific joint venture: „Dynamik abgesoffener oder gefluteter Salzbergwerke und ihres Deckgebirgsstockwerks“ („Dynamic of drowned or flooded salt mines and their overburden“), coordinated by the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR).

Since the late 19. century drowned salt mines cause severe mining damages in the city of Stassfurt (Saxony-Anhalt). Sink hole depressions and subsidence of the surface below the groundwater table destroyed large parts of the down town. The general causation was lack of experience with salt mines and mining in gypsum karst in the 19. century. The causation in detail why and how exactly salt rock has washed out is more complicated to identify, as streaming mechanisms at the small scale level are partly still unclear; the general fluid dynamics at small scales is partly unknown.

To reveal these processes and mechanisms the behaviour of salt brines at the millimetre scale in drilling cores of the different geological units of the salt rock and its surrounding is examined by three-dimensional visualization of the distribution of radioactive labelled water measured with PET. Mechanisms at millimetre scale control mechanisms at the kilometre scale and are of utmost importance for the principal understanding of fluid dynamics. In the laboratory you can have „a look into the rock“. In the field this is not possible this way.

Combining PET data with high resolution CT-scans of the samples (conducted by the cooperation partners JGU Mainz and BAM Berlin) allows an alignment of processes of the fluid flow and its associated hydraulic pathway structures. This matching is important for understanding and for generalized conclusion about ongoing processes and is a necessary preparatory work for computer modelling.

Lattice-Boltzmann-simulations of velocity fields and streaming patterns based on CT-data are compared with PET-data derived from the same samples. This comparison of the flow patterns is done by means of geostatistic methods that allows scale independant spatial correlation of the patterns and therefore provide scale indpendant parameters like correlation lengths that are a necessity for upscaling.

Short term objective is the improvement and validation of parameters and fluid flow concepts derived from small scale simulations. Long term objective is the improvement of upscaling of parameters and concepts to the field scale and a better understanding and prediction of mining damages and groundwater behaviour.

3,7-Diazabicyclo[3.3.1]nonane derivatives (bispidines) represent a versatile platform for the development of new copper radiopharmaceuticals.^[1] An extensive research effort has shown that bispidines with additional donor substituents form very stable complexes with copper(II) (L1, logK = 16.3). The CuII complexes of these so-called 1st generation hexadentate bispidine ligands (L1-Cu) enforce a distorted octahedral geometry which is well preorganized for Cu^II.

Recently, the 2^nd generation of bispidine derivatives has been reported (L2 – L3).^{[2, 3]} These ligands yield very high complex stabilities with Cu^II (logK from 19.5 to 26.4) similar to [Cu^II(cyclam)]²⁺ (logK = 27.2). In contrast to the 1^st generation bispidines they provide exclusively aliphatic nitrogen atoms in the backbone, combined with one (L2) or two (L3) rigid diazacycloheptane rings for tetra- or hexadentate coordination, leading to distorted trigonal bipyramidal or distorted trigonal prismatic coordination geometries.

Ligands L1 – L3 have been labeled with ⁶⁴Cu, and their radiopharmacological data, e.g. labeling efficiency and kinetics, lipophilicity and in vitro stability will be discussed.

Literature:

[1] S. Juran, M. Walther, H. Stephan, R. Bergmann, L. Steinbach, W. Kraus, F. Emmerling, P.Comba; Bioconjugate Chem. 2009, 20, 347-59.
[2] P. Comba, C. Haaf, H. Wadephol; Inorg. Chem. 2009, 48, 6604-6614.
[3] P. Comba, C. Haaf, A. Lienke, A. Muruganantham, H. Wadepohl: Chem.-Eur. J., 2009, 41, 10880-10887.

In recent years polynuclear metal complexes have become increasingly important due to their antitumoral as well as antiviral properties. _[1] Their wide variety of biochemical, chemical and physical properties gives the opportunity to create tailor-made drugs. In this perspective, the enhancement of the hydrolytic stability and in particular the improvement of the in vivo selectivity of inorganic cluster compounds represents the major burden to circumvent.

Appropriate nanocontainers may be utilized to enable the cluster compounds to be transported and released within target tissues. Of great interest is the encapsulation of potential drug molecules by non-covalent binding at the interior of dendritic structures which provide well-defined cavities. In this context, dendritic nanocontainer with maltose-modified shell _[2] appears appealing to act as a host for nanometer sized anionic rhenium cluster compounds.

The inclusion and release phenomena of an octahedral rhenium cluster with six terminal hydroxo ligands [Re⁶S⁸(OH)⁶]_{4- [3]} into poly(propylene amine) dendrimers (POPAM, generation 4 and 5) with dense maltose shell have been studied in detail applying different physico-chemical methods, e.g. UV/vis, time-resolved laser-induced fluorescence spectroscopy (TRLFS) and laser induced liquid bead ion desorption (LILBID) mass spectrometry.

On average, 4 – 5 cluster anions can be captured in the interior of the investigated sugar-coated dendrimers, and a slow release of cluster complexes was observed under physiological conditions.

Altogether, the studied system shows the possibility for the development of dendritic nanocarriers with specific targeting and paves the way for therapeutic applications.

[1] J. T. Rhule, C. L. Hill, D. A. Judd, R. F. Schinazi, Chem. Rev.1998, 98, 327-357.
[2] B. Klajnert, D. Appelhans, H. Komber, N. Morgner, S. Schwarz, S. Richter, B. Brutschy, M. Ionov, A. K. Tonkikh, M. Bryszewska, B. Voit, Chem. Eur. J. 2008, 14, 7030.
[3] K. A. Brylev, Y. V. Mironov, S. S. Yarovoi, N. G. Naumov, V. E. Fedorov, S.-J. Kim, N. Kitamura, Y. Kuwahara, K. Yamada, S. Ishizaka, Y. Sasaki, Inorg. Chem. 2007, 46, 7414-7422.

Titanium is widely used as a structural material because of its low specific weight, good mechanical properties and excellent corrosion resistance at low temperatures due to the formation of a passive TiO2layer. The melting point (1677°C) is very high. Usually the maximum tolerable operating temperature is lower than 600°C. Because of increased oxidation and environmental embrittlement Ti-Alloys can not be used at higher temperatures in oxidizing environments. An enrichment of Al in the surface zone of Ti-alloys leads to an improvement of the oxidation resistance by the formation of intermetallic TixAly-phases but this is not sufficient. A fluorine treatment on TiAl-alloys results in the formation of a protective alumina scale by the so called fluorine effect. Therefore, the combination of Al-enrichment in the surface zone so that a TiAl-layer is formed and an additional F-treatment gives good results. The alumina scale is very protective against environmental attack and also prevents oxygen inward diffusion which causes embrittlement. In this paper the results of isothermal and thermocyclic oxidation tests at 600°C of several Ti-alloys (-Ti, Ti3Al, etc.) are presented without any treatment, with single Al-treatment, pure F-treatment and the combination of both. Aluminium was either enriched by a powder pack process or by magnetron sputtering. Fluorine was applied by several ways e.g. by a liquid phase process. Post experimental investigations like SEM revealed the formation of thin oxide layers on samples with the combined Al + F-treatment. Hardness measurements showed that no embrittlement was observed on the treated samples while untreated specimens showed increased hardness values in the oxygen enriched zone.

Titanium aluminides are very promising light weight materials for several high temperature applications e.g. in aero or automotive engines but due to their insufficient oxidation resistance at temperatures above roughly 800°C they can not be used for longer times. The oxidation behaviour of TiAl-alloys can be improved significantly by microalloying of small amounts of fluorine into the subsurface zone. The use of TiAl-components after fluorine treatment is possible up to temperatures above 1000°C in oxidizing atmospheres due to the formation of a thin protective alumina layer. One possibility to apply fluorine to the surface of complex TiAl-components is the PI³-technique (plasma immersion ion implantation). The use of an Ar/CH2F2-plasma for the F-PI³ into small coupons leads to a positive effect which is as good as the beamline implantation of elemental fluorine gas into samples of the same size. Other treatments are using liquid or gaseous fluorine containing compounds which react with the surface of the specimens. The oxidation kinetics of F-treated TiAl-alloys will be discussed in the paper. Several more complex TiAl-samples and turbine blades as examples for real TiAl-components have been treated. Their oxidation behaviour will be shown. Post exposure investigations like SEM reveal a thin protective alumina scale on the surface of the implanted samples in contrast to a thick mixed scale (TiN/TiO2/Al2O3) growing on untreated samples during high temperature exposure in air.

Titanium has a large strength-to-weight ratio and good corrosion resistance at moderate temperatures, which make it an important structural material in a number of advanced technical applications. A major problem with the use of Ti is its high affinity to oxygen giving rise to massive oxygen in-diffusion at temperatures of about 550° to 600°C. The presence of large amounts of oxygen renders the material brittle and deteriorates its mechanical properties. In this work, we describe an effective way of overcoming the oxygen-induced embrittlement problem by forming a surface barrier to the diffusion of oxygen. Surface processing has involved two steps, namely enrichment of the Ti near-surface region with Al, and introduction of fluorine. For the Al enrichment, a novel hybrid system has been developed to implant Al into Ti. The apparatus consists basically of a PIII chamber configured with two magnetrons having an Al target each, and facing the RF antenna. The magnetrons are synchronized with the bias applied to the sample holder in such a way that the accelerating high-voltage pulse is triggered with a certain delay, i.e. during the time when the Al plasma generated by the magnetrons is most dense, thereby minimizing deposition. Alternative aluminization techniques have involved either magnetron sputtering of Al onto Ti followed by a thermal drive-in step or pack processes. Fluorine has been subsequently introduced by PIII employing a mixture of CH2F2 and Ar as the precursor gas. A variety of analytical techniques such as elastic recoil detection analysis (ERDA), Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and x-ray diffraction (XRD) have been used for characterization. Optimized PIII-based processing has been found to produce a continuous, adherent alumina scale on the Ti surface. Thus, the resulting material is inherently resistant to oxygen absorption and is not embritteled upon extended exposure to oxygen-containing environments at elevated temperatures up to about 600° C.

Titanium aluminides are of great interest for several structural high temperature applications because of their low specific weight (about 4 g/cm3) and their excellent high temperature strength. They could replace the much heavier high temperature steels or Ni-based superalloys (up to 9 g/cm3) which are usually in service. The implementation of this new group of intermetallic alloys in e.g. the aerospace or automotive industry is therefore due to economic and ecologic reasons. The use of TiAl-based alloys is still limited to a temperature of about 750 °C because of their poor oxidation resistance despite of their good mechanical properties which would allow the use at higher temperatures. The oxidation resistance can be improved significantly by small amounts of halogens such as fluorine, chlorine, bromine and iodine (so called halogen effect).
A defined dose of these halogens has to be provided at the metal/oxide interface of the component. The halogens promote the selective formation of gaseous Al-halides at temperatures above 700 °C which are oxidised to Al2O3 during their outward diffusion through the naturally grown oxide scale. So finally a protective alumina scale is formed which is stable for long times even under thermocyclic exposure and wet atmospheres. In this presentation the results of isothermal and thermocyclic high temperature oxidation tests of technical TiAl-alloys with and without fluorine ion implantation are shown.

Ti and TiAl alloys are lightweight materials that hold great promise for advanced aerospace, automotive and power generation applications. They are, however, limited in applicability by their poor oxidation resistance above 600°C. We have developed a process for enhancing the high-temperature oxidation resistance of these materials. For TiAl, the process involves a single step, i.e. plasma immersion implantation (PIII) of fluorine relying on the so-called "halogen effect". Optimum conditions have been established under which the alloys acquire a stable, adherent and highly protective alumina scale upon subsequent high-temperature oxidation in air. The extent of oxidation protection has been evaluated by testing F-implanted TiAl samples at temperatures up to 1050°C. Results from characterization by elastic recoil detection, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analysis have proven the possibility of forming a protective alumina scale on both laboratory coupons and components such as turbine blades and turbochargers. In the case of Ti, surface processing involves two steps, i.e. Al enrichment of the Ti near-surface, and introduction of F by PIII. The Ti samples so modified have shown marked environmental stability at temperatures up to 700°C.

Titanium alloys cannot be used at elevated temperatures above approximately 500°C because of their limited environmental stability. Several ways have been investigated so far to improve the environmental stability of Ti-alloys e.g. coatings but these attempts in a majority of cases have not been really successful. A new way to improve the performance of these alloys is the combination of Al-enrichment in the surface zone plus additional fluorine treatment. The Al-enrichment leads to the formation of intermetallic phases. These phases improve the oxidation resistance of Ti-alloys but not to a sufficient extent. An additional fluorine treatment on top of the Al-enriched surface leads to the formation of a stable alumina scale due to the fluorine effect. In this paper results from oxidation and other tests performed on Ti-samples without any treatment, with single Al- or F-treatment and with a combination of both are presented and the results are discussed.

Surfaces of titanium aluminides were treated with fluorine either physically by plasma immersion ion implantation (PIII) or chemically using a F-based polymer. Under optimum conditions of fluorination, both treatments were shown to improve the oxidation resistance of the alloys even in aggressive environments containing sulfur dioxide (0.1 vol. %). No sulfur was detected in the oxide scale although thermodynamic calculations predict the formation of sulfides. The inward diffusion of oxygen and nitrogen was found to be reduced in the presence of SiO2.

Titaniumdioxide filmswere grown on unheated substrates bymid-frequency (100 kHz) reactive pulsed magnetron sputtering at different O2 partial pressures in an Ar/O2 atmosphere. X-ray diffraction and absorption measurements reveal a transition from amorphous anatase to nanocrystalline rutile with [O2], with a mixture of both phases at intermediate values. Atomic forcemicroscopy shows that the promotion of rutile is accompanied by surface roughening due to the apparition of hollow structures (holes) on the surface, in contrast with the extremely smooth morphology of amorphous anatase films. The number and size of holes increase with [O2] and growth time in such a way that they eventually coalesce and percolate to lead to a rough surface for those growth conditions for which a rutile rich filmis obtained. Transmission electron microscopy analysis shows the growth evolution of a heterogeneous phase mixture and provides unambiguous correlation between the hole (smooth) morphology and the underlying rutile (anatase) phase. Therefore, the surface morphology results fromthe slower local growth rate of nanocrystalline rutile compared to that of the surrounding amorphous anatase flat regions as well as from the fast (slow) lateral (vertical) growth rate of the rutile domains.

Studies that investigate the radiation of human tumour xenografts require an appropriate radiation source and highly standardized conditions during radiation. This work reports on the design of a standardized irradiation device using a commercially available X-ray tube with a custom constructed lead collimator with two circular apertures and an animal bed plate, permitting synchronous irradiation of two animals. Dosimetry and the corresponding methodology for radiotherapy of human non-small cell lung cancer xenograft tumours transplanted to and growing subcutaneously on the right lower limb in a nude rat model were investigated. Procedures and results described herein prove the feasibility of use of the device, which is applicable for any investigation involving irradiation of non-tumorous and tumorous lesions in small animals.

Human tumour xenografts in a nude rat model have consistently been used as an essential part of preclinical studies for anticancer drugs activity in human. Commonly, these animals receive whole body irradiation to assure immunosuppression. But whole body dose delivery might be inhomogeneous and the resulting incomplete bone marrow depletion may modify tumour behaviour. To improve irradiation-mediated immunosuppression of human non-small cell lung cancer (NSCLC) xenografts in a nude rat model irradiation (2 + 2 Gy) from opposite sides of animals has been performed using a conventional X-ray tube. The described modification of whole body irradiation improves growth properties of human NSCLC xenografts in a nude rat model. The design of the whole body irradiation mediated immunosuppression described here for NSCLC xenografts may be useful for research applications involving other types of human tumours.

Bacteria developed during evolution highly effective mechanisms and structures to survive at the most forbidding, uninviting places on Earth. One example is the binding of metalloids, heavy metals and actinides by cell surface proteins of uranium mining waste pile isolates. The so called surface layer (S-layer) proteins avoid the uptake and any sustainable damage of the cell by toxic and/or radioactive elements. The proteins possess additionally self-assembling properties and form symmetric lattices. These properties altogether qualifies the protein for nano-technological purposes and allow the production of advanced bio-composite materials such as metal filters, (photo)catalysts, functionalized membranes or biosensors for the treatment of water.

Die U(VI)-Komplexierung durch Milchsäure in Abhängigkeit von der Temperatur (7-65°C) wurde mittels UV/VIS-Spektroskopie und TRLFS untersucht. Dabei konnten zwei U(VI)-Lactat-Komplexe, UO2Lac+ und UO2Lac2, identifiziert werden. Die entsprechende Enthalpie und Entropie der U(VI)-Komplexierung wurde bestimmt.
Die U(VI)-Sorption an Opalinuston (OPA) in Abhängigkeit von Modellliganden und der Temperatur (25-60°C) wurde untersucht. Dabei beeinflussten die Modellliganden die U(VI)-Sorption an OPA in folgender Reihenfolge: Citronensäure > Weinsäure > Milchsäure ≈ Essigsäure > Ameisensäure. Die U(VI)-Sorption nahm mit steigender Ligandenkonzentration ab, nahm aber mit steigender Temperatur zu. Bei 60°C wurde ein Sprung im Kd-Wert des Urans verzeichnet. Milchsäure hatte dabei keinen signifikanten Einfluss auf die Enthalpie und Entropie der U(VI)-Sorption an OPA in Abhängigkeit von der Temperatur.
HTO-Diffusionsversuche mit OPA bei 25°C und 60°C wurden durchgeführt um die Diffusionsparameter (effektiver Diffusionskoeffizient, Porosität) der Tonproben zu bestimmen. Die experimentellen Werte bestätigten die Literaturdaten.

A series of 2-{4-[4-(2,5-disubstituted thiazolyl)phenylethyl] piperazin-1-yl}-1,8-naphthyridine-3-carbonitriles were synthesized in an effort to prepare novel atypical antipsychotic agents. The compounds were synthesized by either microwave irradiation technique or by conventional synthesis and were characterized by spectral data (IR, 1H NMR, and MS) and the purity was ascertained by microanalysis. The D2 and 5-HT2A affinity of the synthesized compounds was screened in vitro by radioligand displacement assays on membrane homogenates isolated from rat striatum and rat cortex, respectively. Furthermore, all the synthesized compounds were screened for their in vivo pharmacological activity in Swiss albino mice. The D2 antagonism studies were performed using climbing mouse assay model and 5-HT2A antagonism studies were performed using quipazine induced head twitches in mice. It was observed that none of the new chemical entities exhibited catalepsy and 10f is the most active among the synthesized compounds with 5-HT2A/D2 ratio of 1.1286 while the standard drug risperidone exhibited 5-HT2A/ D2 ratio of 1.0989

A prototype detector based on thin-walled segmented tubes has been developed and its parameters have been studied. The detector contains 360 registration channels with a straw diameter of 4mm. The prototype granularity is 4 cm² and the length of insensitive region due to straw internal elements is less than 5% of its full sensitive area. Deterioration of the spatial resolution near these elements is observed for 1.0% of the detector sensitive area. The time and spatial parameters of the detector do not differ from those of conventional tracking detectors based on drift tubes.

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The plasma immersion ion implantation (PIII) technique was used to modify and improve the surface of a Ni-Ti alloy (» 50.2 at.% Ni) for biomedical applications. The main goal has been the formation of a Ni-depleted surface, which should serve as a barrier to out-diffusion of Ni ions from the bulk material. Ion implantation of oxygen was carried out. The depth profiles of the elemental distribution in the alloy surface region, obtained by Auger electron spectroscopy (AES), confirm the formation of a Ti-rich oxide layer. The working plan also comprised ion implantation of nitrogen. In this case, the formation of titanium oxynitride (TiNxOy) was observed. The AES depth profiles clearly show a Ni-depleted fraction for experiments performed with 40 keV.

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The superconducting linear accelerator ELBE at the Forschungszentrum Dresden/Rossendorf has two superconducting accelerator modules and a superconducting photo injector (SRF-Gun). They are operated by a cryogenic Helium plant with a cooling power of 200 W at 1.8 K. Since the commissioning of the plant in 1999 minor and major impurity problems have influenced the operation stability of the plant. The presentation will give an overview of the ELBE cryogenic system and will focus on the different sources of plant contamination and their effects on the plant operation, which have been found during the nearly 10 years of plant lifetime. Especially the contamination with oil brake up components as well as air and water from different sources have limited the run periods of the plant and effected special service and maintenance procedures.

Die ultraschnelle Röntgentomographie wird am FZD vorrangig für die Untersuchung von Zweiphasenströmungen eingesetzt. Potentielle Anwendungsgebiete sind aber auch auf dem medizinischen Sektor zu erwarten. Daher soll die Möglichkeit des Einsatzes der ultraschnellen Röntgentomographie für die Kleintierbildgebung untersucht werden. In dieser Diplomarbeit wurden statische und dynamische Labormodelle entwickelt, mit deren Hilfe die Abbildungseigenschaften für die Kleintierdiagnostik evaluiert werden können.

Detoxification strategy of bacteria, living in uranium mining waste piles, is one part of radio-ecological investigation at the Institute of Radiochemistry of the Forschungszentrum Dresden-Rossendorf. On that account several isolates were subsequently analyzed regarding their growth in presence of different heavy metals and their heavy metal binding properties, particularly using uranium. Some isolates show a high and selective binding for uranium, cadmium, lead, and a few other heavy metals. Interestingly, the heavy metals were immobilized on the cell surface, preventing any sustainable damage of the cell. Responsible for the binding of heavy metals outside the cell is a proteinaceous cell envelope, a so-called surface layer (S-layer).
Using these heavy metal binding properties of bacterial cells and S-layer different filter materials were developed. These include the production of biofilm based materials and the protein immobilization on conventional carriers. Thereby, a different binding behaviour between whole cells and their corresponding S-Layers could be observed. Moreover the S-layer based filter materials bind also some precious metals. So a metal selective filter material for the removal of heavy metals and precious metals from aqueous solutions is developing.

The sorption behaviour of the severely toxic heavy metal thallium (Tl) as a monovalent cation onto three representative materials (goethite, pyrolusite and a natural sediment sampled from a field site) was examined as a function of pH in the absence and presence of two natural humic acids (HAs), using 204Tl(I) as a radiotracer. In order to obtain a basic understanding of trends in the pH dependence of Tl(I) sorption with and without HA, sorption of HAs and humate complexation of Tl(I) as a function of pH were investigated as well. In spite of the low complexation between Tl(I) and HAs, the presence of HAs results in obvious alterations of Tl(I) sorption onto pyrolusite and sediment. An influence on Tl(I) sorption onto goethite was not observed. Predictions of Kd (distribution coefficient) for Tl(I) on goethite in the presence of HAs, based on a linear additive model, agree well with the experimental data, while a notable disagreement occurs for the pyrolusite and sediment systems. Accordingly, it is suggested that HAs and goethite may act as a non-interacting sorbent mixture under the given conditions, but more complex interactions may take place between the HAs and the mineral phases of pyrolusite or sediment.

Based on a quasiparticle model for \beta stable and electrically neutral deconfined matter we address the possibility of pure quark stars. The model is adjusted to recent hot lattice QCD results for 2+1 flavors with almost physical quark masses. Using stability and binding arguments general statements can be made concerning the existence of such compact stellar objects.

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The magnetoresistance of n-type conducting, paramagnetic Co-doped ZnO films prepared by pulsed laser deposition on sapphire substrates has been studied experimentally and theoretically. Positive magnetoresistance (MR) of 124% has been observed in the film with the lowest electron concentration, while only a negative MR of −1.9% was observed in the film with a large electron concentration at 5 K. The positive MR is attributed to the quantum correction on the conductivity due to the s-d exchange interaction induced spin splitting of the conduction band. The negative MR is attributed to the magnetic field suppressed weak localization. Voltage control of the electron concentration in Schottky diodes revealed a drastic change of the magnetoresistance and demonstrated the electrically controllable magnetotransport behavior in Co-doped ZnO. The magnetically controllable spin polarization in Co-doped ZnO has been demonstrated at 5 K in magnetic tunnel junctions with Co-doped ZnO as a bottom electrode and Co as a top electrode. There spin-polarized electrons were injected from Co-doped ZnO to a crystallized Al2O3 layer and tunnelled through an amorphous Al2O3 barrier. Our studies demonstrate the spin polarization and manipulation in Co-doped ZnO.

During the session titled "The use of PET-CT for lung cancer" several topics will be addressed, such as the technical background of PET-CT and an overview of the possibilities offered by PET imaging in lung cancer. The aim of all PET imaging in treatment planning for tumours is an improved delineation of the Gross Tumour Volume (GTV). Knowing exactly the position and extent of the vital tumour should increase local control and lead to longer survival of patients. As long as the target is immobile as is the case in the brain fusion of the PET information into the planning CT seems to be effortless. But problems arise when PET imaging is to be used for moving targets such as in lung. Therefore, the issue to be discussed in this presentation is "Should we match on bone or on tumour?". Necessity of motion comprehension during PET-CT imaging: In PET-CT imaging two different motion-related effects have to be considered:

(1) the direct effect of motion on the CT and PET modalities separately, and
(2) the effect of improper attenuation correction caused by a mismatch in the temporal resolutions of the two data sets.Examples of direct effects are artefacts in the region between the lung and liver in 3D-CT data and motion-induced smearing of the activity concentration in 3D-PET data. These artefacts are unavoidable in 3D imaging but can be overcome with the introduction of 4D imaging (4D-CT and 4D-PET). The second effect (i.e. smearing) has to be considered in both 3D- and 4D-imaging. In 3D-imaging the 3D-CT artefacts described above can propagate into the PET data set due to attenuation correction. One example given by Beyer et al. shows 3D PET-CT data that appears to show soft tissue in the lung, but which in fact is part of the moving liver (Eur J Nucl Med Mol Imaging 2003). Additionally, the different temporal resolution of 3D-PET and 3D-CT can generate artefacts in attenuation corrected data sets although both 3D-CT and uncorrected 3D-PET are free of artefacts. One impressive example of this phenomenon was shown by Osman et al. (J Nucl Med 2003), where liver metastases appeared in the lung region. In 4D-imaging, artefacts due to improper attenuation correction can be avoided if the different datasets of the 4D-PET are corrected with corresponding datasets of the 4D-CT, as has been demonstrated by Pnisch et al. (Med Phys 2008).
Possibilities for motion compensation during treatment: Several technical approaches have been introduced into clinical practice to compensate for motion during radiotherapy.
Two questions have to be addressed: a) How can the motion be turned into a signal and b) how can this signal be used to compensate the motion? Answering question a), helpful techniques which can be mentioned include spirometry, pressure based systems or optical systems detecting the motion of points on the thorax or of the whole body surface. In all these techniques, the motion leads to a signal that represents more or less precisely the motion of the patient. However, it is not proven that any signal also exactly follows the motion of the tumour. Answering question b), two approaches can be mentioned: "Gating" and "Tracking". Gating uses the motion signal to trigger the linear accelerator according to a defined "gate", i.e. to turn the beam on and off in synchronization with the breathing motion. Tracking is a method in which the motion of the target is followed (tracked) either by motion of the leaves in the MLC or by motion of the table. Verification of motion in the chain from planning to treatment: 4D treatment planning including 4D-PET/4D-CT and breathing-synchronized radiotherapy for lung cancer patients need a carefully considered concept of verification.
In contrast to conventional verification procedures at the linear accelerator, where the position of the patient is verified only by bony anatomy (brain), target motion adapted methods require appropriate additional imaging in the treatment room. Either radioopaque markers or kV-CT images are necessary. For organs with mainly interfractional motion such as the prostate, correct positioning of the target before the start of the fraction is essential. The treatment of intrafractional moving targets imposes more complexity. Besides verification of the baseline, the amplitude of the motion is a second point to be considered. The most important in the verification of a breathing synchronized radiotherapy is the comparison with the 4D treatment planning dataset. The basic principle is the use of the identical motion signal both for 4D imaging and for the 4D treatment. Only then a possible shift between real tumour motion and visualized tumour motion can be neglected.
Conclusions: Should we match on bone or on tumour? The short answer should be ON TUMOUR. But the longer answer is, BUT NOT FOR EVERY PATIENT. The challenge is the finding of clinical values used as guidance as to which patients will benefit from the high workload of 4D treatment planning and delivery.

Temperature fluctuations are observed experimentally in a cylinder of liquid mercury heated from below and cooled from above under action of a rotating magnetic field (RMF). The Grashof number (Gr) exceeds that of earlier studies by a factor of 10 at least. The setup models a proposed modification of the Czochralski crystal growth process where crucible rotation is replaced by RMF. It is known that the RMF characterized by the magnetic Taylor number Ta=15Gr^0.8 suppresses buoyant temperature fluctuations in a cylinder cooled from above [1]. To achieve a comparable effect by a mechanical rotation of the crucible, a considerably higher rotation rate is required and the difference grows with Gr. The effect has been demonstrated up to Gr~5x10⁷ that corresponds to a medium size gallium arsenide liquid encapsulated Czochralski process. Does the “0.8” scaling keep as Gr is increased? This is the central question of the study. One of the possible explanations of the phenomenon is a hypothetical stabilizing action of the core meridional flow. It is known that the angular velocity scaling Omega~Ta^2/3 experiences a change at Ta~2x10⁷ (that is able to stabilize the Gr~5x10⁷ configuration). Besides, it is known that the product of mean radial velocity Vr and mean angular velocity Omega equals the magnetic force (Ta~V, Omega). Thus, if the meridional flow indeed plays a major role, then there should be a change of the Tacr(Gr) scaling above Gr~5x10⁷. The experiment will allow Gr in the range [5x10⁷ : 5x10⁸]. It is prepared and scheduled for April 2010

The DEMETRA domain of the EUROTRANS project provides a wealth of experimental and theoretical results within key technological areas related to the Heavy Liquid Metal (HLM) Technology. HLMs as Pb and Lead-Bismuth Eutectic (LBE) are the reference coolant and spallation materials choices for the ADS facilities studied within the EUROTRANS project.
For these coolants the key items that have been addressed within DEMETRA are:
Coolant quality control in terms of oxygen and impurities control;
Materials compatibility in terms of corrosion, mechanical and irradiation resistance;
Thermal-hydraulics studies related to heat transfer in turbulent conditions through dedicated experiments on a single pin, a fuel bundle and integrated component tests;
Safety related studies through experimental and simulation studies on HLM/water interaction;
Support to component design and testing, where in particular substantial support has been given to the development of the windowless-neutron spallation target and the assessment of the window spallation target behaviour through the post test analysis of MEGAPIE;
Measurement and operational techniques development;

The technical work programme of DEMETRA is herein summarised and some major experimental results are discussed.

no abstract available

Es wird eine übersicht gegeben zu Strömungen und deren Stabilität in magnetischen Wanderfeldern. Die Sensitivität der TMF-Strömung gegenüber geringen Achsenverschiebungen zwischen TMF und Schmelztiegel ist sehr hoch und sollte in der Praxis großen Einfluss auf die tatsächlichen Strömungen in Kristallzüchtungsprozessen haben.

Die Gestalt der Kristallisationsfront und das damit verbundene monokristalline Wachstum im Czochralski-Kristallzuchtprozess hängt stark vom Verhältnis zwischen horizontalem und vertikalem Temperaturgradienten r*=deltaT_h/deltaT_v an der Schnittstelle zwischen Schmelze, Kristall und Atmosphäre ab. Der Wert von r* liegt dabei idealerweise in der Nähe von 1. Deshalb wurde ein Flüssigmetall-Modellexperiment aufgebaut, das die Untersuchung von r* unter dem Einfluss von Magnetfel-dern ermöglicht. Das zylindrische Flüssigmetallvolumen wird dabei homogen von unten geheizt, und um den wachsenden Kristall zu simulieren wird die Wärme oben konzentrisch mit einem Kühler entzogen, der die Oberfläche nur bis zu einem Drittel des Radius bedeckt. Ohne Strömungskontrolle findet sich ein von der Zielfunktion weit entfernter Wert von r*=3. Das Ziel r*=1 kann durch elektromagnetische Strömungsbeeinflussung erreicht werden.

The shape of the solidification front and the related mono-crystalline growth in the Czochralski crystal growth process is thought of being strongly influenced by the ratio of the horizontal and the vertical temperature gradient r* = deltaT_h / deltaT_v at the triple point liquid-solid-atmosphere, which ratio desirably should be in the order of unity. A liquid metal model experiment was therefore built that allows studying r* under the influence of magnetic fields. The cylindrical liquid metal column was homogeneously heated from below, whereas on top the heat was extracted in a centrical region covering only one third of the surface in order to simulate the growing crystal. Without flow control, r* ≈ 3 is far removed from unity. It was then possible to reach the target value r* = 1 for any temperature difference between the bottom and the top at a moderate field strength while applying a rotating magnetic field.

The aim of the work is the growth and characterisation of Ti55Nb45 (wt %) single crystals with the floating-zone single crystal growth of intermetallic compounds using two-phase radio-frequency (RF) electromagnetic heating. Thereby, the process and, in particular, the flow field in the molten zone is influenced via additional magnetic fields. The growth of massive intermetallic single crystals is very often unsuccessful due to an unfavourable solid-liquid interface geometry enclosing concave fringes. It is generally known that the crystallization process stability is enhanced if the crystallization interface is convex. As a result, a tailored magnetic two-phase stirrer system has been developed which enables the controlled influence on the melt ranging from intensive inwards to outwards flows. Due to their attractive properties such as light, strong and totally biocompatible, titanium is one of few materials that naturally match the requirements for implantation in the human body. Therefore, the magnetic system was applied to crystal growth of Ti alloys. The grown crystals were oriented and cut to cubes with the desired crystallographic orientations (-1,0,0) and (1,0,1) normally on a plane. The electron backscatter diffraction (EBSD) technique was applied to clearly define crystal orientation and orientation changes in the crystallographic textures. The elastic modulus, the shear modulus and the bulk modulus were determined in dependence on the crystal orientation using ultrasonic measurements. Moreover, the oxide formation behavior on Ti surfaces in dependence on the grain orientation was investigated, performed anodically from fluoride containing electrolyte.

TiAl intermetallic alloys were developed as potential materials for high temperature applications because of their excellent chemical and physical properties such as low density, high modulus and corrosion resistance. These characteristics are attractive for applications in aerospace and automotive industries but also for chemical and biomedical application. However, their low ductility at room temperature limits their application. Also microscopic factors like volume fraction of the apparent phases, the distribution of orientation variants, fineness of the microscopic structure strongly affect the mechanical properties.

Investigation of thermophysical and structure-sensitive properties of liquid low-temperature ternary metal eutectic alloys are stimulated both by pure academic as well as by applied science. In particular, there exist few reliable experimental data on the electrophysical, transport and surface properties of multicomponent alloys and, therefore, they are often estimated with analytical approaches. In order to prove any theory, experimental results are needed.
The favorable combination of the technical characteristics of Ga-based melts brought about their extensive application as sliding contacts, the working medium of magnetohydrodynamic devices, heat-sensitive elements of liquid-metal thermometers and thermocouples, and the base for conducting magnetic fluids. The GaInSn eutectic alloy is a suitable alternative to mercury since it exhibits an equilibrium melting point of 284 K. Bi-Pb-Sn liquid eutectics are chosen as model substances for experimental

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no abstract available

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 CONCAST 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 in both facilities are measured by Ultrasound Doppler Velocimetry and contactless inductive flow tomography. The latter is attractive also for real-scale steel casting.