Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Presentation of the complexation of Uranium(VI) with selected Schiff bases in methanol investigated by UV/Vis spectroscopy and ATR FT-IR spectroscopy.

Presently, argillaceous rock formations are under investigation as potential host rocks for nuclear waste repositories. The sorption of radionuclides on mineral phases is an important physicochemical process in a nuclear waste repository in the case of a water inleakage. Concerning the required long-term safety and risk assessment of the storage of high-level radioactive waste the understanding of this process is essential. Opalinus Clay (OPA) is a complex composed argillaceous rock. This natural occurring clay rock is discussed as host rock formation for nuclear waste repositories. In a repository based on argillaceous rock an initial temperature of around 100°C is expected. But although elevated temperatures are able to influence the sorption behaviour of radionuclides on mineral phases the temperature effect is still investigated insufficiently. Due to the fact that natural organic matter was found in the OPA the influence of organic matter on the radionuclide sorption hast to be investigated. The investigations concentrated on the sorption of Eu(III) and U(VI) on OPA under realistic OPA pore water conditions (OPA pore water medium, pH 7.6, I = 0.4 mol•L-1) up to 50°C. In addition to the temperature dependent investigations the influence of small organic molecules (e.g. lactate, acetate, propionate, tartrate, citrate) on the Eu(III) and U(VI) sorption on OPA was studied up to 50°C.
The Eu(III) sorption is characterized by a strong binding of Eu(III) and the U(VI) sorption is characterized by a weak binding of U(VI) to the clay surface. A significant temperature dependency for the Eu(III) and U(VI) sorption was observed. In the presence of the organic matter the Eu(III) and U(VI) sorption decreases with rising ligand concentration due to a complexation of the metal ions by the ligands in solution. The mobilization of Eu(III) and U(VI) correlates with the complex formation strength of the organic ligands.

Most information about the micro-world has been obtained by light microscopy, i.e. observations with photons and our knowledge about the structure of atoms and molecules mainly originates from electromagnetic spectroscopy.

In conformity to new findings about the widespread occurrence of triaxiality arguments are given in favor of a description of the giant dipole resonance in heavy nuclei by the sum of three Lorentzians. This TLO parameterization allows a strict use of resonance widths {\Gamma} in accordance to the theoretically founded power law relation to the resonance energy. No additional variation of {\Gamma} with the photon energy and no violation of the sum rule are necessary to obtain a good agreement to nuclear photo-effect, photon scattering and radiative capture data. Photon strength other than E1 has a small effect, but the influence of the level density on photon emission probabilities needs further investigation.

We have demonstrated a laser-produced plasma extreme ultraviolet source operating in the 6.5-6.7 nm region based on rare-earth targets of Gd and Tb coupled with a Mo/B4C multilayer mirror. Multiply charged ions produce strong resonance emission lines, which combine to yield an intense unresolved transition array. The spectra of these resonant lines around 6.7 nm (in-band: 6.7 nm +/-1%) suggest that the in-band emission increases with increased plasma volume by suppressing the plasma hydrodynamic expansion loss at an electron temperature of about 50 eV, resulting in maximized emission.

Employing QCD sum rules the in-medium modifications of scalar charm mesons in a cold nuclear matter environment are estimated. The mass splitting of D* - (D) over bar* is quantified.

The isotope ⁴¹Ca is produced by neutron capture of the stable and most abundant calcium nuclide ⁴⁰Ca in concrete of the bioshield around nuclear reactors. Because of its long half-life (1.04*10⁵ a) the declaration of ⁴¹Ca in concrete is often requested for radioactive waste disposal.
The radioanalytical ⁴¹Ca determination by liquid scintillation counting (LSC) is still a reasonable option for laboratories involved in decommissioning of nuclear installations despite the emission of only low-energy Auger electrons (ca. 3.6 keV) and the difficulty of obtaining a certificated standard. Besides accelerator mass spectrometry (AMS), being the most sensitive analytical technique not only for ⁴¹Ca, is increasingly gaining broader accessibility and applicability. Herein, we present a radiochemical separation procedure developed for ⁴¹Ca determination with LSC and AMS in varying materials. The radioanalytical isolation consists of anion exchange and extraction chromatography as well as carbonate precipitation and recrystallization from organic solvents. Thereby, disturbing radionuclides as ⁵⁵Fe, ⁶⁰Co, ⁹⁰Sr, ¹³⁷Cs, ¹⁵²Eu or ²⁴¹Pu are removed with decontamination factors of 10²-10⁴. Quench curves for determining the measurement efficiency are generated with a ⁴¹Ca solution gained from the ⁴¹Ca/⁴⁰Ca certified reference material ERM-AE701. In routine application the procedure is characterized by chemical yields of 25-80%, measurement efficiencies of 1-10% and detection limits of 0.05 Bq*g^-1 ash and 0.3 Bq*l^.1. Aliquot solutions of LSC can be easily converted into CaF₂-AMS-targets by successive oxalate and fluoride precipitation. Pros and cons for both measurement techniques are addressed based on ⁴¹Ca results from LSC and AMS for the same material.

Designing laser-driven radiation sources requires realistic simulations, new ideas and good modeling. For inventing a design, a thorough analysis of existing designs is of great help. For planing designs, the fundamentals of the radiation generation process must be well understood. For testing designs, a fast return of results and the possibility to perform surveys of a large landscape of parameters is essential. In my talk I will address all steps in the source design using three examples from our recent research
* Scaling of hot electron energies with laser intensity in laser-solid interaction
* Laser-driven x-ray sources with tunable energy and bandwidth
* Fast computation of laser-plasma interaction with new computation hardware

We present PIConGPU, a performant implementation of the particle-in-cell algorithm for GPUs that is scalable on GPU clusters. PIConGPU is used for fast-response simulations of laser-plasma interaction, including laser wakefield acceleration using the sliding-window technique. We discuss lessons learned from going from the initial two-dimensional PICimplementation to a full 3D implementation, focusing on data storage on the GPU and data communication between GPU nodes in a cluster. We show how communication and data storage can be efficiently hidden from users who want to extend the code by adding new physics so that users can assume to be working in a singledata single-instruction environment without deeper knowledge of GPU programming. As an example we show how the far field of relativistic electrons performing betatron oscillations in a laser-driven wakefield can be calculated from macro-particle trajectories on the GPU and subsequently stored in CPU. First simulation results obtained with PIConGPU are shown to illustrate the advantage of fast response simulations for large parameter scans.

A scalable, performant, highly-parallel Particle-in-Cell code for fast simulations of large Laser-Plasma experiments. Investigating parameters for optimizing laser particle acceleration is a timeconsuming task since realistic simulations of laser plasma interactions using the particle-in-cell technique can require the computation of several hundred million particle trajectories on a grid of several ten million cells. The computational effort needed to investigate the dependence of the performance of new acceleration scenarios on only a few parameters thus normally requires the use of large-scale high-performance computing systems only available at central super computing centres. Thus, parameter scans are usually performed by reducing the system size, the particle density, the computation time and the dimensionality of the problem. Such a scan is then at best complimented by a small number of more realistic large-scale simulations with parameters closer to the experimental parameters. Recently, general purpose graphical processing units (GPGPUs) have entered the stage of high performance computing. This new hardware offers a computational power exceeding that of standard CPU-based computers by several orders of magnitude at much lower investment and maintenance costs. Making good use of this computational power is only possible if the algorithm can run on a massively parallel system consisting of a huge number of independently working processors. However, the memory on a single GPGPU and thus the system size that can be computed on it is limited We present PIConGPU [1], a particle-in-cell algorithm that can run efficiently on a cluster of GPGPU nodes. PIConGPU can run largescale, realistic simulations by mapping the physical system onto many GPGPUs. Thus, the time needed to calculate the evolution of the large system is comparable to the time it takes to compute the small sub-region that can fit on a single GPU and therefore can lead to turnaround times of only a few hours for a hundred thousand time steps and single time steps of under a nanosecond per macro-particle [2].
If computational stability and dispersion is treated appropriately, using GPGPUs to simulate for example laser wakefield acceleration of electrons can greatly enhance the study of large parameter spaces while at the same time using simulation parameters resembling those of the experimental system studied. We focus on real-world examples of using PIConGPU for the simulation of laser electron acceleration scenarios investigated with the DRACO laser system at the Forschungszentrum Dresden-Rossendorf and show how the fast response time of GPGPU-based simulations can open up the path for optimizing experimental parameters.

In 2006, Arias et al.[1] chemically characterized a new obsidian source on the island of Melos. This third obsidian source, obsidian blocks inside the volcanoclastic deposits at Agios Ioannes, was claimed to be well distinguishable from the two well-known sources Agia Nychia and Demenegakion.
Following a sampling campaign in 2010, investigations of samples collected from all three Melos obsidian finding spots (Agia Nychia, Demenegakion, Agios Ioannes) were performed by three complementary analytical techniques (Neutron Activation Analysis, Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry, Ion Beam Analysis). Unfortunately, investigations had to be conducted on rubblestones, since the obsidian blocks described by Arias et al. could not be located. The “chemical fingerprint” composed of 43 elements clearly separates the rubblestones into the two known groups of Agia Nychia and Demenegakion. Elevated Sb concentrations already mentioned in Arias et al. could be confirmed but are probably attributed to a local contamination.

References: [1] Arias et al., J. Radioanal. Nucl. Chem. 268 (2006) 371–386.

In order to investigate the two-phase flow behaviour during counter-current flow limitation in the hot leg of a pressurised water reactor, dedicated experiments were performed in a scaled down model of the Kobe University. The structure of the interface was observed from the side of the channel test section using a high-speed video camera. An algorithm was developed to recognise the stratified interface in the camera frames after background subtraction. The evolution of the water level along the hot leg is analysed in function of the liquid and gas flow rates.

Die geplante Elektronik für einen neuen Strahllagemonitor (BPM) an ELBE wird vorgestellt. Der neue Strahllagemonitor soll einen wesentlich höheren Dynamikbereich haben und gleichzeitig die alten Differenzstrommonitore (DCM) ablösen. Dazu werden die einzelnen Signale vom Stripline-Monitor aufbereitet, digitalisiert und in einem FPGA verarbeitet. Die Strahllage und der Strahlstrom werden bestimmt und sowohl analog wie auch digital ausgegeben. Die Differenz des Strahlstromes zweier Strahllagemonitore wird gebildet und für das Maschinenschutzsystem überwacht.

The phosphodiesterase (PDE) 10A plays an important role in neurotransmission by regulating intracellular levels of the cyclic nucleotides cAMP and cGMP in dopaminergic neurons. In consequence, PDE10A is associated with dopamine-related central nervous diseases such as Huntington’s disease and schizophrenia. Thus, PDE10A is a promising candidate for drug development with a variety of selective PDE10A inhibitors published during the last decade [1, 2]. The aim of the presented work is the development of a positron emission tomography (PET)
radiotracer for imaging of PDE10A in vivo.
Based on a lead structure (IC50PDE10A = 8 nM), published for therapeutic applications [3], three nonradioactive fluoroalkoxy derivatives (1, 2, 3) were enantioselectively synthesized over 11-14 steps and characterized regarding their potency and selectivity to inhibit PDE10A in a cAMP competition assay. Prolongation of the alkyl chain from 1 to 3 by one methylene group each resulted in decreased inhibitory potency from IC50 = 24 nM over 106 nM to 144 nM. Metabolic stability of 2 was determined in comparison to the lead compound in an in-vitro metabolism assay using rat liver S9-fractions. Metabolites were structurally characterized using ESI-MS-MS coupling techniques.
With regard to radiochemical accessibility, derivative 2 appeared as the most promising candidate for radioligand investigation. Initially, a two-step synthesis of [18F]2, consisting of 18F-labelling of 1,3-bistosyloxyethane and following coupling with phenolic precursor 4, was carried out. For the 18F-fluoroalkylation step labeling yields (LY) of 30-45% were achieved. Consequently, in a one-step procedure the tosylethoxy precursor 5 was used for 18Flabelling, improving LY up to 42-72%. Biodistribution studies in female CD-1 mice revealed high initial brain uptake of [18F]2. However, it was not significantly inhibited by competition with 2 or by pre-treatment with MP-10, a high PDE10A specific inhibitor, indicating lack of specificity in vivo. In conclusion, these results motivate for further structural variation of the lead compound to make it suitable for neuroimaging of PDE10A with PET.
Acknowledgements: We would like to thank J. Ortwein (Institute of Pharmacy, University of Leipzig) and the team of L. Hennig (Institute for Analytical Chemistry, University of Leipzig) for their analytical support. This project was financed by resources of the European Fond for Regional Development (EFRE) and the Free State of Saxony.
References:
1. Chappie et al., Current Opinion in Drug Discovery & Development 2009, 12, 458–467.
2. Kehler and J. P. Kilburn, Expert Opinion on Therapeutic Patents 2009, 19, 1715–1725.
3. Chappie et al., J. Med. Chem. 2006, 50, 182–185.

The phosphodiesterase 10A (PDE10A) has an important role in neurotransmission regulating the intracellular cyclic nucleotides especially in dopaminergic neurons. The PDE10A is a promising candidate for drug development and inhibiton of the PDE10A could be an interesting therapeutic stategy for treatment of brain dysfunctions, such as schizophrenia. The present study was designed to examine pharmacological and toxicological properties of a potent and selective brain permeable inhibitor of PDE10A (Ki = 31.9 nM) as nonradioactive derivative for the development of a radiotracer for positron emission tomography (PET).
The lead compound (3006) and the fluoric substituted derivative with prolonged alkyl chain by one methylen group (3039) had no effect on basal intracellular calcium concentration [Ca+]i in human neuroblastoma cells (SH-SY5Y). High concentrations (100 μM) of 3039 but not 3006 increased potassium-induced calcium mobilisation. Electrophysiological investigations on rat brain slices indicated no effect of 3039 or 3006 on postsynaptic membrane parameters and synaptic transmission up to 100 μM. After long-term incubation (48 h) 3039 and 3006 enhanced metabolic activity and reduced LDH-release of SH-SY5Y cells up to 1 μM whereas at high concentration (100 μM) metabolic activity was decreased due to slightly increased cell damage. Using the zebrafish embryo toxicity test mortality was observed at concentration of 100 μM for 3039 and ≥ 1μM for 3006 after incubation of 48 h.
The results suggest a different pharmacological profile of 3039 in comparison to its lead compound 3006 possibly by distinct binding characteristics to the PDE10A enzyme. Both compounds had no toxic effects in concentrations relevant for PET ligands. 3039 seems to be an appropriate candidate for developing a PET probe for studying distribution of PDE10A in vivo.

Vortrag im Rahmen eines Workshops, kein Abstract vorhanden

Vortrag für das Kompetenzzentrum OST 2011 in Zittau. Inhalt ist die realitätsnahe Integration von Sorptionsprozessen in Langzeitsicherheitsanalysen. Nach einer kurzen Erläuterung zur Motivation und der Vorstellung des Projektes ESTRAL wird die konzeptionelle Vorgehensweise zur realitätsnahen Integration von Sorptionsprozessen exemplarisch am Standort Gorleben vorgestellt. Für die verwendeten smart-Kd Matrizen werden am Beispiel des oberen Grundwasserleiters anschließend Sensitivitäts- und Unsicherheitsanalysen vorgestellt. Ein Ergebnis dieser Analysen ist die Identifikation von wichtigen Einflussfaktoren. Für den Kd-Wert von U(VI) sind dies zum Beispiel der DIC-Gehalt und die Konzentration an Calciumionen.

An enhanced concentration of ⁶⁰Fe was found in a deep ocean's crust in 2004 in a layer corresponding to an age of ~2 Myr. The conrmation of this signal in terrestrial archives as supernovainduced and detection of other supernova-produced radionuclides is of great interest. We will investigate a marine sediment from the South Australian Basin to search for live ²⁶Al, ⁶⁰Fe, ⁵³Mn, ⁶⁰Be and the pure r-process element ²⁴⁴Pu. A possible nding of these radionuclides in a sediment core might allow us to improve the time resolution of the signal and thus to link the signal to a supernova event in the solar vicinity ~2 Myr ago. Furthermore, we might get an insight on nucleosynthesis scenarios in massive stars, the condensation into dust grains and transport mechanisms from the supernova-shell into the solar system.

The crystal and molecular structure of 1,2:5,6-Di-O-isopropylidene-3-O-toluenesulfonyl-a-D-glucofuranose is reported. This compound crystallizes from a petroleum ether/ethyl acetate mixture with the chiral orthorhombic space group P212121 with four molecules in the unit cell. The unit cell parameters are: a = 9.7945(7), b = 10.1945(7), and c = 21.306(1), and V = 2127.4(2) Å3. Bond lengths and angles of this tosyl-protected glucofuranose are typical

1D-confinement of polyiodides inside single-wall carbon nanotubes (SWCNT) is investigated. Structural arrangement of iodine species as a function of the SWCNT diameters is studied. Evidence for long range one dimensional ordering of the iodine species is shown by x-ray and electron diffraction experiments independently of the tube diameter. The structure of the confined polyiodides is investigated by x-ray absorption spectroscopy. The confinement influences the local arrangement of the chains. Below a critical diameter Φc of 1 nm, long linear polyiodides are evidenced leading to a weaker charge transfer than for nanotube diameter above Φc. A shortening of the polyiodides is exhibited with the increase of the nanotube diameter leading to a more efficient charge transfer. This point reflects the 1D-confinement of the polyiodides inside the nanotubes.

Ziel/Aim:

Das Isotop I-124 besitzt zusätzlich zum β+-Zerfall γ−Linien, die in sogenannten „falschen“ Koinzidenzen resultieren und eine bildverschlechternde Hintergrundaktivität verursachen. Wegen der maximalen Positronenzerfallsenergie von 2,1MeV besitzt I-124 eine hohe Reichweite, die die Ortsauflösung reduziert. Ziel dieser Arbeit war die Implementation einer Korrektur, die beide Effekte korrigiert.
Methodik/ Methods:
Ausgehend von optimalen Akquisitionseinstellungen wurde eine sinogrammbasierte Hintergrundsubtraktion sowie ein Rekonstruktionsalgorithmus mit Auflösungsrückgewinnung implementiert. Messungen wurden am MicroPET Focus 120 durchgeführt und mit GATE [1] Monte-Carlo (MC) Simulationen für verschiedene Phantome verglichen (Mausvoxelphantom, NEMA Image Quality Phantom (IQ) und ein selbstgebautes Mini-NEMA Schwächungsphantom). Die Bildrekonstruktion erfolgte mit Hilfe eines modifizierten OSEM-Algorithmus aus der STIR Library [2]. Über die MC-Simulationen lassen sich die Anteile der falschen zu wahren Koinzidenzen separieren und bei der Korrektur berücksichtigen. Für die Auflösungsrückgewinnung wurden Punktquellen in verschiedenen Schwächungsmaterialien simuliert und über die Reichweitenhistogramme materialabhängige Faltungskerne berechnet. Diese sind über den Vorwärtsprojektor in den Algorithmus integriert.
Ergebnisse/ Results:
Simulationen und vergleichende Messungen zeigen, dass am MicroPET durch Verkleinerung des Energiefensters von 350-650keV auf 400-550keV eine deutliche Reduktion der störenden Hintergrundaktivität und eine Verbesserung der Bildqualität erzielt werden kann. Die Anteile falscher zu wahrer Koinzidenzen sind außerhalb des Objektes homogen und nicht aktivitätsabhängig: 0,76 (MC: IQ, 90MBq, 50s) bzw. 0,77 (MC: IQ, 9MBq, 70s). Innerhalb existiert ein aktivitätsabhängiger Anteil von 0,29 bzw. 0,18, der über Gauß-Fits in der sinogrammbasierten Hintergrundsubtraktion berücksichtigt wird. Als Resultat ergeben sich quantitativ genauere und kontrastreichere Bilder. Simulationen eines realistischen Mausphantoms mit I-124, Ga-68 und F-18 zeigen, dass der dominante Effekt für die Bildverschlechterung in der Kleintierbildgebung der Auflösungsverlust durch die hohe Positronenzerfallsenergie ist. Die Anwendung der o.g. Entfaltungsmethode verbessert bei I-124 die Ortsauflösung von 4,9mm FWHM vor der Korrektur auf 2,5mm nach der Korrektur (IQ, Insert mit d=5mm, nach 20 Iterationen). Kritisch bei dieser Korrektur ist die genaue Definition des Abbruchkriteriums, da für höhere Iterationen eine Überkorrektur mit Artefakten entsteht.

Schlussfolgerungen/ Conclusions:

Unter Berücksichtigung von MC-Simulationen wurden Korrekturen für die Bildrekonstruktion von nichtreinen, hochenergetischen Positronenstrahlern erarbeitet. Die Ergebnisse der Simulationen konnten verifiziert und erfolgreich auf reale Daten übertragen werden.

Literatur:

[1]Jan et al. Med. Biol. (56) (2011) 881-901
[2]Thielemans et. al. IEEE NSS & MIC Record 2006

AIM
In the course of treating liver cancer, frequently SIRT (selective internal radiation therapy) with Yttrium-90 is applied. In order to study the bio-distribution, often SPECT or SPECT/CT imaging is used, based on the detection of low-energy bremstrahlung photons. However, there is also another imaging option, namely through observation of the very rare internal pair production of Y-90, leading to an experimental situation well suited for PET (2). The aim of this study is to study the influence of the low-energy bremsstrahlung photons, which come at relatively high count-rate, but at the same time preserving the PET signal, i.e. the two gammas originating from the e+-e- annihilation, since only 32 out of one million decays of Yttrium-90 happen via internal pair production.

METHODS
The normal decay channel, the emission of therapeutically used electrons with high energy, comes with the production of low energy bremsstrahlung photons. Despite their relatively low energy (only a fraction of 16,6% of such photons exceeds more than 300 keV), the high-count rate could lead to saturation effects (via pulse pile-up) of the PET detector electronics. To absorb these low-energy photons, it was suggested to insert a copper ring into the gantry (1). To analyze a) where or not such a ring is required and b) which material might be best suited, we simulated a Siemens MicroPET Focus 120 and the PET part of a Philips Gemini TOF PET-CT with GATE (2) with different ring materials and a contrast medium filled phantom. Results from simulations were compared with experimental data obtained from measurements under condition comparable to the simulation.

RESULTS
First preliminary results from the simulation showed, that a 0.5 cm thick copper ring absorbs the low-energy bremsstrahlung, while preserving those at higher energy around 511 keV. In contrast, a ring of 0.5 cm of lead also absorbs many of the gammas around 511 keV. However, so far it is not certain, whether such a ring made of copper or lead would be required at all. Further studies are needed, especially with taking into account the signal processing chain as offered by GATE to differentiate further options in improving the detection of very rare signals for PET. Additional measurements might also provide more details of what exactly the PET-images show, because a superposition of the bremsstrahlung photons from interacting electrons with the true coincidence signals cannot be ruled out.
CONCLUSION
Our first results of distributions of simulated and measured events from Y-90 internal pair production look promising. The PET-images show very clear distributions of Y-90, yet need further confirmation, especially studying the influence of pile-up, dead-time effects on the rare coincidence signal.

(1) R Lhommel et al: Eur J Nucl Med Mol Imaging (2009) 36:1696.
(2) S Jan et al: GATE V6. Phys. Med. Biol. (2011) 56 881-901.

The paper presents an experimental investigation regarding the phenomenon of air entrainment as a result of a jet impinging into a tank filled with water. The main objective of the work consists of gathering information about the concentration of the entrained void fraction, bubble velocities and the entrainment rate. For this purpose, a measuring technique based on wire-mesh sensors was used. For distinct combinations of nozzle exit velocity, jet length and immersion depth, the concentration and distribution of the entrained void fraction, as well as bubble size distributions and velocities were acquired. The corresponding calculated entrainment rate was found to increase linearly with both jet exit velocity and length, and to be smaller than predicted by literature. The experiments aim to provide an extensive database for air entrainment under plunging jets, needed for validation of Computational Fluid Dynamics (CFD) codes.

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. The influence of the annealing types (furnace annealing - FA, rapid thermal annealing – RTA and Flash-lamp-annealing – FLA) on the optical and electrical properties of mc-Si solar cell was investigated. 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, a 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.

Cost reduction is the overall goal in the further development of solar cell technologies. Multicrystalline silicon has attracted considerable attention because of its high stability against light soaking. In case of Solar Grade (SoG) mc-Si the rigorous control of metal impurities is desirable for solar cell fabrication. The main source of degradation of the photovoltaic effect in p-type mc-Si is iron present as interstitials (Fei) and Fe-B pairs. Processing solar cells at lower temperatures helps reducing the energy cost and in thin film technologies may also facilitate the use of less temperature stable substrates such as normal glass or polymers foils. In the present work a new technique will be presented and explored, which allows the implantation of the doping element by a plasma process and the subsequent annealing by a short time light pulse (Flash Lamp Annealing). Plasma Immersion Ion Implantation (PIII) technique can be used for the emitter formation of solar cells. It is much easier to handle and has the potential for mass production. A dedicated PIII - machine has been built suitable for the implantation of doping impurities into silicon.
The phosphorous implanted and annealed SoG mc-Si wafers were characterised by means of μ-Raman spectroscopy, temperature dependent photoluminescence (PL), surface photo-voltage method (SPV) and four-point probe resistor measurements. It could be demonstrated that FLA at 1000°C for 3 ms even without preheating is sufficient to recrystallize implanted silicon and to electrically activate the phosphorous. The sheet resistance (SR) of FLA samples shows values of about 40 μ/sq. Moreover, the minority carrier diffusion length for the FLA samples is in the range of 80 m. This is up to one order of magnitude higher than that observed from RTA or FA samples.

Integration of III-V semiconductors with a silicon technology is crucial for the devices performance. In this paper we present investigations of the microstructural, optical and electrical properties of III-V quantum dots (InAs, GaAs, InP and GaP) formed in silicon. The III-V QDs were obtained by means of sequential ion implantation and flash lamp annealing (FLA). Conventional selective etching was used to form the n-III-V/p-Si heterojunction. In case of InAs/Si heterostructures, the current-voltage measurement confirms the heterojunction diode formation with the ideality factor of n=4.6. Kelvin Probe Force Microscopy measurements indicate a type-II band alignment of n-type InAs NPs on p-type silicon. The main advantage of our method is its integration with large-scale silicon technology, which also allows applying it for Si-based electronic devices.

Cost reduction is the overall goal in the further development of solar cell technologies. Multicrystalline silicon has attracted considerable attention because of its high stability against light soaking. In case of Solar Grade (SoG) mc-Si the rigorous control of metal impurities is desirable for solar cell fabrication. Although ion implantation doping got very recently distinct consideration for doping of monocrystalline solar material, efficient doping of multicrystalline solar material remains the main challenge to reduce costs. The influence of different annealing techniques on the optical and electrical properties of mc-Si solar cells was investigated. Flash Lamp Annealing in the ms-range is demonstrated here as a very promising technique for the emitter formation at an overally low thermal budget. It could be presented that FLA at 1000oC for 3 ms even without preheating is sufficient to recrystallize implanted silicon. The sheet resistance (SR) of FLA samples shows values of about 50 Ohm/sq. A specially, the minority carrier diffusion length for the FLA samples is in the range of 80 um without surface passivation. This is up to one order of magnitude higher than that observed from RTA or FA samples. This technology shows great promise to replace the conventional POCl3 –doping.

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. The influence of the annealing types (furnace annealing - FA, rapid thermal annealing – RTA and Flash-lamp-annealing – FLA) on the optical and electrical properties of mc-Si solar cell was investigated. 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, a 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 phosphorous implanted and annealed silicon wafers were characterised by means of u-Raman spectroscopy, temperature dependent photoluminescence (PL), surface photo-voltage method (SPV) and four-point probe resistor measurements. The μ-Raman spectroscopy showed that the silicon surface is amorphous after ion implantation. It could be demonstrated that FLA at 1000oC for 3 ms even without preheating is sufficient to recrystallize implanted silicon. The maximum PL intensity (band-to-band transition in silicon) was obtained from samples annealed for 3 ms, at the same time the sheet resistance (SR) of FLA samples shows the value of about 50 Ohm/sq. Moreover, the minority carrier diffusion length for the FLA samples is in the range of 100 um, what is fivefold longer than that observed from RTA or FA samples.

Crystalline InAs quantum dots (QDs) were successfully synthesized in silicon by hot ion implantation and millisecond flash lamp annealing (FLA). The crystallinity and shape of the InAs quantum dots were proven by high resolution transmission electron microscopy, -Raman spectroscopy and X-ray diffraction (XRD). Selective etching was used to form InAs/Si heterowires. The Kelvin Probe Force Microscope (KPFM) measurements prove the type-II band alignment of n-type InAs QD on p-type silicon nanowires. The Fermi level at the position of the InAs QD lies deep inside the conduction band region of InAs. The measured lateral KPFM bias variation ranges between 0 mV at the edge of the InAs QD and 100 mV at the center of the QD. The lattice parameter and the size of the QDs increases from 6.051 to 6.055 Ǻ and from 40 up to 50 nm with annealing temperature increasing from 1100 up to 1200 oC, respectively. By the proper choice of the preparation conditions such as ion fluence, annealing time and temperature we can synthesize and fully control the size and shape of InAs quantum structures in silicon. The main advantage of this method is its integration with large-scale silicon technology, which allows applying it for Si-based optoelectronic devices.

We present a novel method to preselect the direction of an induced in-plane uniaxial magnetic anisotropy (UMA) in thin Fe films on MgO(001). Ion beam sculpturing is used to modulate the MgO(001) surface with quasi-sinusoidal ripples on the nanoscale. The ripple direction determines the orientation of the uniaxial magnetic anisotropy, whereas the intrinsic cubic anisotropy of the Fe film is not affected. Thus, it is possible with a precision of a few degrees to superimpose an in-plane UMA---a level of control not reported so far that can be relevant for example in spintronic applications.

Remarkable thermomechanical and electrical properties of silicon carbide (SiC) make this material very
attractive for high-temperature, high-power, and high-frequency applications. Because of very low values of
diffusion coefficient of most impurities in SiC, ion implantation is the best method to selectively introduce
dopants over well-defined depths in SiC. Aluminium is commonly used for creating p-type regions in SiC.
However, post-implantation radiation damage, which strongly deteriorates required electric properties of the
implanted layers, is difficult to anneal even at high temperatures because of remaining residual damage. Therefore
implantation at elevated target temperatures (hot implantation) is nowadays an accepted method to decrease the
level of the residual radiation damage by avoiding ion beam-induced amorphization. The main objective of this
study is to compare the results of the Rutherford backscattering spectroscopy with channeling and micro-Raman
spectroscopy investigations of room temperature and 500 ±C Al+ ion implantation-induced damage in 6H-SiC and
its removal by high temperature (up to 1600 ±C) thermal annealing.

We present the inclusive invariant-mass, transverse momentum and rapidity distributions of dielectrons (e+e^- pairs) in p+p interactions at 3.5 GeV beam kinetic energy. In the vector-meson mass region, a distinct peak corresponding to direct ω decays is reconstructed with 2% mass resolution. The data is compared to predictions from three model calculations. Due to the large acceptance of the HADES apparatus for e+e^- invariant masses above 0.2 GeV/c² and for transverse momenta p_t < 1 GeV/c, acceptance corrections are to a large extent model independent. This allows us to extract from dielectron data for the first time at this energy the inclusive production cross sections for light vector mesons. Inclusive production cross sections for π⁰ and η mesons are also reported. The obtained results will serve as an important reference for the study of vector mesons production in proton-nucleus and heavy-ion collisions. Furthermore, using this data, an improved value for the upper bound of the branching ratio for direct η decays into the electron-positron channel is obtained.

The Autler-Townes effect (Rabi splitting) is observed in semiconductor quantum wells, when pumping the intra-excitonic 1s-2p transition with a THz free-electron laser. In a second experiment using time-domain spectroscopy, it is shown that the THz intersubband polarization in a quantum well can be coherently manipulated using a second, phase-locked THz pulse.

THz science in semiconductor quantum structures

Spin structures have been a relevant topic of magnetism research for many years. In particular, magnetic vortices have attracted much at- tention, due to their non-trivial topology and the various dynamic modes they exhibit. A magnetic vortex consists of a planar, flux- closing magnetization curl that turns out of the plane in the central nanoscopic core. For a single layer structure, the curl’s radial components typically cancel each other out. Recent investigations show that this holds also true for multilayer vortex systems comprising bilinear interlayer exchange coupling (IEC). In this contribution we report on pairs of diverging-converging spin vortices occurring in biquadratically coupled systems. Using magnetic x-ray microscopy we directly observe that the individual vortices of such pairs possess a residual radial magnetization component. From this ∇M𝑥𝑦 ̸= 0, an additional perpendicular magnetization divergence ∇M𝑧 is analytically deduced. We compare our continuous model with discrete micromagnetic simulations.

Purpose [1134 C]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. Labelling with fluorine-18 allows in principle for longer acquisition times for kinetic analysis in brain tissue and may provide higher sensitivity. The aim of our study was to firstly apply in human the new highly SERT-selective fluorine-18 labelled fluoromethyl analogue of (+)-McN5652 ((+)-[1840 F]FMe-McN5652) and to evaluate its potential for SERT quantification.
Methods
The PET data of five healthy volunteers (3 male, 2 female, age 39 ± 10 years) coregistered with individual MRI were semi-quantitatively assessed by volume-of-interest analysis using the software package PMOD. Rate constants and distribution volume ratios (DVR) were calculated using a 2-tissue compartment model and arterial input function measurement were corrected for metabolites/plasma data. Standardized uptake region-to-cerebellum ratios as measure of specific radiotracer accumulation were compared with those of a [1146 C]DASB-PET data set of healthy subjects (10 male, 11 female, 38 ± 8 years).
Results
The 2-tissue compartment model provided adequate fits to the data. Estimates of total distribution volume (VT) demonstrated good identifiability based on coefficient of variation (COV) for the volumes of interest (VOIs) in SERT-rich and also for cortical areas (COV VT < 10%).
Compared with [11C]DASB-PET, there was a tendency to lower mean values in (+)-[1851 F]FMe-McN5652 PET, however, the standard deviation was also somewhat lower. Altogether, cerebral (+)-[1853 F]FMe-McN5652 uptake corresponds well with the known SERT distribution also in humans.
Conclusion
The results showed also that (+)-[1855 F]FMe-McN5652 is suitable for in vivo quantification of SERT with PET. Because of the long half-life of fluorine-18, a widespread application within a satellite concept seems feasible.

Molecular imaging of brain structures by highly sensitive non-invasive techniques offers unique possibilities in the understanding of physiological and pathological processes in the central nervous system. In particular, the quantitative analysis by positron emission tomography (PET) of α7 nicotinic acetylcholine receptors ( α7 nAChR), which are involved in different signalling pathways in the brain, is assumed to provide important information on the relation between receptor dysfunction and the pathogeneses of neuropsychiatric brain diseases, but the applicability of this imaging approach is still hampered due to insufficient imaging agents. This paper presents the recent efforts made to develop PET radiotracers targeting α7 nAChR as well as the current state of the evaluation of the most promising radiolabelled compounds in animal models and humans.

The spirocyclic s1 receptor ligand 1 (1’-benzyl-3-(fluoromethyl)-3H-spiro[[2]benzofuran-1,4’-piperidine]) was prepared in four steps starting from methoxy derivative 5. Due to its high s1 affinity (Ki = 0.74 nM) and selectivity against several other relevant targets, 1 was investigated as ¹⁸F-labeled PET tracer and its biological properties were compared with those of homologous fluoroalkyl derivatives 2-4. The fluoromethyl derivative 1 was faster metabolized in vitro than homologues 2-4. In contrast to the radiosynthesis of [¹⁸F]2-4, the nucleophilic substitution of the tosylate 15 using the K[¹⁸F]F-K222-carbonate complex required heating to 150 °C in DMSO to achieve high labeling efficiencies. Whereas radiometabolites of [¹⁸F]2-4 were not detected in vivo in the brain of mice, two radiometabolites of [¹⁸F]1 were found. Analysis of ex vivo autoradiography images provided rather low target-to-nontarget ratio for [¹⁸F]1 compared with [¹⁸F]2-4. [¹⁸F]1 showed a fast uptake in the brain, which decreased continuously over time. The brain-to-plasma ratio of the radiotracer [¹⁸F]1 was only exceeded by the fluoroethyl tracer [¹⁸F]2.

The migration behavior of actinides and other radioactive contaminants in the environment is controlled by prominent molecular phenomena such as hydrolysis and complexation reactions in aqueous solutions as well as the diffusion and sorption onto minerals present along groundwater flow paths. These reactions significantly influence the mobility and bioavailability of the metal ions in the environment, in particular at liquid-solid interfaces.
Hence, for the assessment of migration processes the knowledge of the mechanisms occurring at interfaces is crucial. The required structural information can be obtained using various spectroscopic techniques.
In the present study, the speciation of uranium(VI) and neptunium(V) at environmentally relevant mineral - water interfaces of oxides of titania, alumina, silica, zinc, and alumosilicates has been investigated by the application of attenuated total reflection Fouriertransform infrared (ATR FT-IR) spectroscopy. Moreover, the distribution of the hydrolysis products in micromolar aqueous solutions of U(VI) and Np(V/VI) at ambient atmosphere has been characterized for the first time, by a combination of ATR FT-IR spectroscopy, near infrared (NIR) absorption spectroscopy, and speciation modeling applying updated thermodynamic databases.
From the infrared spectra, a significant change of the U(VI) speciation is derived upon lowering the U(VI) concentration from the milli- to the micromolar range, strongly suggesting the dominance of monomeric U(VI) hydrolysis products in the micromolar solutions. In contradiction to the predicted speciation, monomeric hydroxo species are already present at pH ≥ 2.5 and become dominant at pH 3. At higher pH levels (> 6), a complex speciation is evidenced including carbonate containing complexes.
For the first time, spectroscopic results of Np(VI) hydrolysis reactions are provided in the submillimolar concentration range and at pH values up to 5.3, and they are comparatively discussed with U(VI). For both actinides, the formation of similar species is suggested at pH ≤ 4, whereas at higher pH, the infrared spectra evidence structurally different species. At pH 5, the formation of a carbonate-containing dimeric complex, that is (NpO2)2CO3(OH)3^-, is strongly suggested, whereas carbonate complexation occurs only under more alkaline conditions in the U(VI) system.
The results from the experiments of the sorption processes clearly demonstrate the formation of stable U(VI) surface complexes at all investigated mineral phases. This includes several metal oxides, namely TiO2, Al2O3, and SiO2, serving as model systems for the elucidation of more complex mineral systems, and several alumosilicates, such as kaolinite, muscovite and biotite. From a multiplicity of in situ experiments, the impact of sorbent characteristics and variations in the aqueous U(VI) system on the sorption processes was considered.
A preferential formation of an inner-sphere complex is derived from the spectra of the TiO2 and SiO2 phases. In addition, since the in situ FT-IR experiments provide an online monitoring of the absorption changes of the sorption processes, the course of the formation of the U(VI) surface complexes can be observed spectroscopically. It is shown that after prolonged sorption time on TiO2, resulting in a highly covered surface, outer-sphere complexation predominates the sorption processes. The prevailing crystallographic modification, namely anatase and rutile, does not significantly contribute to the spectra, whereas surface specific parameters, e.g. surface area or porosity are important.
A significant different surface complexation is observed for Al2O3. The formation of innerspheric species is assumed at low U(VI) surface coverage which is fostered at low pH, high ionic strength and short contact times. At proceeded sorption the surface complexation changes. From the spectra, an outer-spheric coordination followed by surface precipitation or polymerization is deduced. Moreover, in contrast to TiO2, the appearance of ternary U(VI) carbonate complexes on the γ-Al2O3 surface is suggested.
The first results of the surface reactions on more complex, naturally occurring minerals (kaolinite, muscovite and biotite) show the formation of U(VI) inner-sphere sorption complexes. These findings are supported by the spectral information of the metal oxide surfaces.
In this work, first spectroscopic results from sorption of aqueous Np(V) on solid mineral phases are provided. It is shown that stable inner-sphere surface species of NpO2 ^+ are formed on TiO2. Outer-sphere complexation is found to play a minor role due to the pH independence of the sorption species throughout the pH range 4 - 7.6. The comparative spectroscopic experiments of Np(V) sorption onto TiO2, SiO2, and ZnO indicate structurally similar bidentate surface complexes.
The multiplicity of IR spectroscopic experiments carried out within this study yields a profound collection of spectroscopic data which will be used as references for future investigations of more complex sorption systems in aqueous solution. Furthermore, from a methodological point of view, this study comprehensively extends the application of ATR FT-IR spectroscopic experiments to a wide range in the field of radioecology.
The results obtained in this work contribute to a better understanding of the geochemical interactions of actinides, in particular U(VI) and Np(V/VI), in the environment. Consequently, more reliable predictions of actinides migration which are essential for the safety assessment of nuclear waste repositories can be performed.

Einleitung
In Alzheimer’s disease (AD), there is growing evidence for the brain nicotinic acetylcholine receptors (nAChRs) being reduced at very early disease stages (in transgenic Tg2576 mice even earlier than beta-amyloid plaque deposition [Int J Devl Neurosci 2003]) and for this reduction being strongly associated with cognitive decline. Our group aims at developing and testing new nAChR positron emission tomography (PET) tracers with the goal to improve early dementia diagnosis.
Methode
We tested A85380, an ¹⁸F-labeled PET tracer which binds to the α4β2-subunit of the nAChR, and could show that nAChRs are highly significantly reduced in brain areas affected by AD-pathology in patients with early AD (correlating significantly with impaired cognition), and even in subjects with MCI who later progressed to AD [Eur J Nucl Med Mol Imaging 2011]. Using A85380, however, PET imaging of up to seven hours is required. This limitation encouraged to search for better suited tracers to be used as biomarkers in clinical routine. As a result we developed the 18F-labeled epibatidine derivative NCFHEB [Synapse 2008]. The first-in-man study testing this tracer in AD-patients and healthy controls (HCs) is ongoing. First results show that this tracer might allow imaging of nAChRs in a 20 minutes scan within 90 minutes and a significantly lower tracer binding in AD-patients compared to HCs.
Diskussion/Ergebnisse
Taken together, we were successful in the implementation of PET to image nAChRs in dementia. Our PET results support the concept of the nicotinic system being involved at early AD stages, providing motivation to further develop PET imaging for early AD diagnosis, prognosis, and therapy control.

The radiosynthesis of N-(5-(((5-(tert-butyl)oxazol-2-yl)methyl)thio)thiazol-2-yl)-4-[¹⁸F]fluoro-benzamide [¹⁸F]2 as a potential radiotracer for molecular imaging of cyclin-dependent kinase-2 (CDK-2) expression in vivo by positron emission tomography is described. Two different synthesis routes were envisaged. The first approach followed direct radiofluorination of respective nitro- and trimethylammonium substituted benzamides as labeling precursors with no-carrier-added (n.c.a.) [¹⁸F]fluoride. A second synthesis route was based on the acylation reaction of 2-aminothiazole derivative with labeling agent [¹⁸F] SFB. Direct radiofluorination afforded ¹⁸F-labeled CDK-2 inhibitor in very low yields of 1%–3%, whereas acylation reaction with [¹⁸F]SFB gave ¹⁸ F-labeled CDK-2 inhibitor [¹⁸ F]2 in high yields of up to 85% based upon [¹⁸ F]SFB during the optimization experiments. Large scale preparation afforded radiotracer [¹⁸ F]2 in isolated radiochemical yields of 37%–44% (n=3, decay-corrected) after HPLC purification within 75 min based upon [¹⁸ F]SFB. This corresponds to a decay-corrected radiochemical yield of 13%–16% based upon [¹⁸F]fluoride. The radiochemical purity exceeded 95% and the specific activity was determined to be 20 GBq/mmol.

kein Abstract verfügbar

The effects of a microbial habitat (biofilm) on the transport behavior of uranium in a simulated incident in an underground repository were studied by pH and Eh microelectrodes and energy-filtered transmission electron microscopy (EF-TEM), and electron energy-loss spectroscopy (EELS). Biofilm samples were collected in the underground rock characterization facility tunnel ONKALO (Finland) and positioned in a rectangular flow cell for immobilization experiments by adding uranium to the bulk solution to a final uranium concentration of 4.25 × 10–5 M. The bulk solution was pumped through the flow cell in a closed circuit, simulating in situ conditions on the tunnel wall. The use of microelectrode with a tip diameter of 10 µm to measure pH and Eh in the biofilm proved to be essential to indicate that the biofilm has formed its own microenvironment. EF-TEM and EELS studies indicated that uranium in the biofilm was immobilized intracellularly in microorganisms by the formation of metabolically mediated uranyl phosphate, similar to Autunite. In contrast, time resolved laser fluorescence spectroscopy (TRLFS) in the bulk solution identified aqueous uranium carbonate species, likely (Ca2UO2[CO3]3), formed due to the high concentration of carbonate. The results were further confirmed by thermodynamic calculations of the predominant field of uranium species, formed in the bulk solution.
Our combined approach clearly showed that uranium was removed from solution and immobilized exclusively in biofilm microorganisms. In contrast, the aqueous uranyl carbonates species, formed in the bulk solution, may contribute to the migration of U(VI) and consequently to environmental hazard.

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

The fabrication of ferromagnetic semiconductors is one big step to realize spintronic devices. Beside GaAs:Mn also Ge:Mn is a very interesting material system [1-2].
Moreover, the lattice inversion symmetry of Ge leads to weak spin-orbit interaction and enhanced spin-lifetime and spin-diffusion lengths of more than 100 μ m. This is shown in Ge nanowires at 4.2 K [3].
Also a spin diffusion up to 225 K could be shown in weakly n-doped Ge [4].
In a previous work we investigated ferromagnetism in Ge:Mn thin films. Hysteretic Hall resistance after Mn implantation and short-time pulsed laser annealing (PLA) has been observed [5].
Similar to low temperature molecular beam epitaxy [1], the clustering of Mn inside the material has to be prevented. Especially after PLA, the Mn segregation leads to the formation of a Mn enriched surface layer. In our work, we performed layer by layer magneto-transport measurements after different etching steps. The hysteretic properties are vanishing after removing the segregated Mn-rich phases. In conclusion, we think that the observed hysteretic Hall resistance may have its origin in the scattering of spin-polarized holes on these Mn-rich phases. Such hysteretic transport properties have not yet been reported for Ge with embedded Mn-rich clusters. The vanishing hysteresis at 30 K and above can be interpreted by the increasing decoherence between the individual Mn rich clusters or/and the reduced magnetization of the clusters itself.
[1] M. Jamet et al., Nature Materials 5, 653 (2006) [2] Y.D. Park et al., Science 295, 651 (2002) [3] E. S. Liu et al., Nano Letters 10, 3297 (2010) [4] Y. Zhou et al. arXiv:1103.5095v1 (2011) [5] S. Zhou et al., Phys. Rev. B 81, 165204 (2010)

The fabrication of ferromagnetic semiconductors is one big step to realize spintronic devices. Beside GaAs:Mn also Ge:Mn is a very interesting material system [1-2]. Moreover, the lattice inversion symmetry of Ge leads to weak spin-orbit interaction and enhanced spin-lifetime and spin-diffusion lengths of more than 100 µm. This is shown in Ge nanowires at 4.2 K [3]. Also a spin diffusion up to 225 K could be shown in weakly n-doped Ge [4]. We investigated ferromagnetism in Ge:Mn thin films [5]. Hysteretic Hall resistance after Mn implantation and short-time pulsed laser annealing (PLA) has been observed. Similar to low temperature molecular beam epitaxy [1], the inhomogenous distribution of Mn inside the material has to be prevented. Especially after PLA, the Mn segregation leads to the formation of a Mn enriched surface layer. In our work, we performed layer-by-layer etching of ferromagnetic Ge:Mn and subsequent depth-resolved magnetotransport measurements. The hysteretic properties are vanishing after removing the segregated Mn-rich phases. In conclusion, we think that the hysteretic Hall resistance may have its origin in the scattering of spin-polarized holes on these Mn-rich phases. The vanishing hysteresis at 30 K can be interpreted by the increasing spin decoherence between the individual Mn rich clusters or/and the reduced magnetization of the clusters itself at increased temperature.

Cuprous oxide is a highly interesting material for the emerging field of transparent oxide electronics. In this work the energy dispersion of the dielectric function of Cu₂O bulk material is revised by spectroscopic ellipsometry measurements in an extended spectral range from 0.73 to 10 eV. For the first time, the magneto-optical Kerr effect was measured in the spectral range from 1.7 to 5.5 eV and the magneto-optical Voigt constant of Cu₂O was obtained by numerical calculations from the magneto-optical Kerr effect spectra and the dielectric function.

Phosphodiesterase 10A (PDE10A) is a key enzyme of intracellular signal transduction which is involved in the regulation of neurotransmission. The molecular imaging of PDE10A by PET is expected to allow a better understanding of physiological and pathological processes related to PDE10A expression and function in brain. The aim of this study was to develop a new 18F-labeled PDE10A ligand based on a 6,7-dimethoxy-4-pyrrolidinylquinazoline and to evaluate its properties in biodistribution studies. Nucleophilic substitution of the 7-tosyloxy-analogue led to the 7-[18F]fluoroethoxy-derivative [18F]IV with high PDE10A affinity (KD,PDE10A=14 nM), radiochemical yields of 25±9% (n=9), high radiochemical purity of ≥99% and specific activities of 110-1100 GBq/mol. [18F]IV entered rapidly into the brain of female CD-1 mice with a peak uptake of 2.3%ID/g in striatum at 5 min p.i.. High metabolic stability in brain was observed. However, blocking studies revealed no target specific accumulation of [18F]IV. Therefore, successful imaging of PDE10A using 18F-labeled 6,7-dialkoxyquinazoline derivatives requires further structural optimization.

Molecular imaging of brain structures by non-invasive techniques offers unique possibilities in the understanding of physiological and pathological processes in the central nervous system. In particular, the quantitative analysis by positron emission tomography (PET) of alpha7 nicotinic acetylcholine receptors (α7nAChR) could provide important information on the relation between receptor dysfunction and the pathogeneses of neurodegenerative brain diseases. However, the applicability of PET for α7nAChR imaging is still hampered by a lack of validated radiotracer for human use.
As radiotracers for imaging α7nAChR, 18F- and 11C-labelled 1,4-diazabicyclo-[3.2.2]nonane derivatives (NS10743 and NS14492) were developed and investigated for in vivo imaging characteristics. Brain autoradiography and organ distribution in mice showed specific accumulation of [18F]NS10743 in α7nAChR expressing brain substructures and peripheral organs. In pigs [18F]NS10743 readily entered the brain (peak SUV ~2.5), with the highest uptake in α7nAChR expressing brain regions such as the colliculi, thalamus, temporal lobe, and hippocampus. Pretreatment followed by constant infusion of NS6740, a selective α7nAChR antagonist, significantly reduced the specific binding of [18F]NS10743 in receptor-dense regions of pigs.
[11C]NS14492, a radioligand of similar high affinity and selectivity in vitro, also showed high uptake in the pig brain (peak SUV ~2.2) with a distribution pattern in accordance with α7nAChR expression. Homologous blocking or pretreatment with the α7nAChR partial agonist SSR180711 both reduced distribution volumes of [11C]NS14492 in all examined regions in a dose-dependent manner.
In conclusion, because of their high brain uptake and regional distribution in accordance with α7nAChR expression pattern in the pig brain, 1,4-diazabicyclo-[3.2.2]nonane derivatives are promising PET radioligands for in vivo mapping and quantitative imaging of α7nAChR. Furthermore, in vivo in pigs the PET radioligand brain binding can be dose-dependently blocked by α7nAChR antagonists.

The effect of the substrate temperature on the sublattice ordering in ZnO layers grown by reactive pulsed magnetron sputtering on sapphire has been investigated by different techniques. The improvement of the crystal quality and heteroepitaxial growth at relatively low temperatures (550 °C) is verified by X-ray diffraction, high-resolution transmission electron microscopy, Rutherford backscattering spectrometry in channeling mode (RBS/C), and Raman spectroscopy. Sublattice-resolved analysis by resonant RBS/C and Raman spectroscopy reveals that the progressive transition to the single crystal phase is accomplished in a faster way for Zn- than for O-sublattice. This behavior is attributed to the preferential annealing of defects in the Zn sublattice at low temperatures when compared to those of the O sublattice.

Im Fall eines Frischdampfleitungsbruchs wird Dampf über die Kondensationsrohre in die Kondensationskammer gepresst. Dabei ergeben sich an den in die Wasservorlage eintauchenden Rohrenden Dampfblasen, die sich zyklisch erweitern und wieder kollabieren. Bei geringem Anteil nicht kondensierbaren Gases führt der Kollaps der Blasen zu starken Druckstößen, welche die Wände der Kondensationskammer belasten. Die physikalischen Zusammenhänge des intermittierenden Blasenkollapses sowie die den Vorgang beeinflussenden Parameter sind in umfangreichen Experimenten untersucht. Die auftretenden Drücke auf der Behälterwand wurden in Testbehältern experimentell ermittelt, statistisch ausgewertet und in konservativer Weise für die Spezifikation der entsprechenden Lasten am Sicherheitsbehälter des KKK verwendet. Dazu erfolgte eine potentialtheoretische Skalierung des Druckes aufgrund der berechneten Lösung der Potentialgleichung auf Basis einer vereinfachten abgewickelten, rechteckigen Geometrie der Wasservorlage.
Der vorliegende Bericht bewertet diese mit vereinfachter Geometrie erzeugte Lösung der Potentialgleichung anhand einer genaueren Berechnung des Behälterpotentials für die tatsächliche 3-dimensionale Geometrie. Die Potentialgleichung wird hier mit einer Randelemente-Methode gelöst. Anschließend werden mit Hilfe von Monte-Carlo-Rechnungen die Einflüsse der unterschiedlich stark auftretenden Druckamplituden sowie der Asynchronität der Kondensationsereignisse auf die zu erwartenden Lasten ermittelt.

Second harmonic generation (SHG) and X-ray diffraction rocking curves of high-quality ZnO single crystals implanted by different ions (He, Cu, and Zn) were investigated. Interestingly, it was found that both He-and Zn-implanted samples show a convinced increment in SHG efficiency while the Cu-implanted one does not. X-ray diffraction rocking curves of the samples show satellite structures, and the simulations firmly reveal the formation of quasi-interfaces inside He-and Zn-implanted crystals. These quasi-interfaces lead to SHG improvement in the two samples. Polarization dependence of SHG of the samples on the excitation light also evidences this conclusion.

We investigate the effect of mid-infrared (MIR) pumping on the transport properties of GaAs/(Al,Ga)As terahertz (THz) quantum lasers (TQLs), which rely on quantum coherence effects of intersubband transitions. Aiming at THz lasing at elevated temperatures, we extend the concept of THz gain with and without population inversion of a single, MIR-pumped, electrically driven THz stage proposed by Waldmueller et al. [Phys. Rev. Lett. 99, 117401 (2007)] to an entire TQL. However, experiments using a CO2 as well as a free-electron laser and numerical simulations show that this resonant MIR pumping causes a negative differential conductivity (NDC) in addition to the NDC caused by sequential tunneling. Lasing of these TQLs is prevented by the formation of electric-field domains below the resonance field strength for gain of each single THz stage.

This seminar reviews our recent experimental studies involving terahertz (THz) and mid-infrared radiation from the free-electron laser facility FELBE in Dresden, Germany. As examples for linear measurements, cyclotron resonance spectroscopy and aperture-less near-field microscopy will be addressed. Applications of nonlinear THz spectroscopy include pump-probe experiments in graphene, and nonlinear THz two-photon intersubband excitation in semiconductor quantum wells. The final part of my talk will concentrate on two-color THz spectroscopy, in particular THz sideband generation and coherent dynamics of excitons dressed by strong THz beams.

By methods of modern spectral analysis, we rigorously find distributions of eigenvalues of linearized operators associated with an ideal hydromagnetic Couette-Taylor flow. Transition to instability in the limit of vanishing magnetic field has a discontinuous change compared to the Rayleigh stability criterion for hydrodynamical flows, which is known as the Velikhov-Chandrasekhar paradox.

Recently, we developed a transportable high-resolution gamma-ray computed tomography (GCT) measurement system for the investigation of phase distributions in multi-phase flows in technical apparatus. The GCT measurement system contains a collimated isotopic source (137Cs), a radiation detector arc and an external signal processing as well as thermal stabilisation unit. For tomographic scans radiographic projections are obtained from different angular positions by rotating either the measuring ensemble or the object of interest. To improve the mechanical and thermal handling of the existing radiation measurement electronics, in a first step a new modular signal processing board was developed. It implements variable gain amplifier stages, gamma photon counters as well as data transfer and communication to a standard PC into the detector arc. Furthermore, the new developed electronics allows various arrangements of multiple detector modules. In a second step the thermal stabilisation system was integrated into the detector arc. Two 30 W (thermal power) Peltier elements directly placed onto the top side of the detector base plate undertake the task of thermal stabilisation. Into the back side of the base plate, a spatially optimised channel is milled in which a fluid, driven by an integrated centrifugal pump, realises a homogeneous temperature distribution. Thus, the heat losses of the active electronics that are connected to the base plate can be efficiently dissipated, which is the key for a good measuring repeat accuracy. The functionality of the thermal stabilisation design was proven by an IR camera.

This study investigated the green and orangy brown spots that commonly occur on the surface of rough diamonds and which are caused by external irradiation by helium ions in the form of alpha particles. These ions are believed to be generated by the decay of radionudides in radioactive minerals that were located close to a diamond in irs geologic past. Helium ions generated in the U- and Th-decay chains have energies in the 4.0-8.8 MeV range; their travel distances in diamond arc up tO 29 1-1m. Depending on rhe sizes (mostly unknown) of rhe radiation sources and their proximity to the diamond's surface, helium irradiation typically results in blurred round spots with green color. These spots are usually deformed semi-spheres with fuzzy boundaries. With moderate-temperature heating, the green radio-coloration turns orange-brown. Raman measurements revealed that these richly colored green and brown spots represent elevated levels of radiation dan1age. The same observation was made on spots produced by the irradiarion of diamond plates with 8.8 MeV He ions in a tandem accelerator, foUowed by annealing experiments. The transformation from green to brown was accompanied by relatively low degrees of structural reconstitution.
Our experiments showed that irradiation with about l x l 0¹⁶ He ions per cm₂ is needed to produce strong radio-coloration. This in rum leads us to conclude that radio-coloration on the surface of natural stones must be a long-tenn process: A typical spot has a size on the order of 1,000 fU112, requiring about 1 x 10¹¹ helium ions. If the helium irradiation emanated, for instance, from a 5 fUll uraninirecrysral {>80wr.% U), it would rake more than 10 million years to accumulate l x 10¹¹ helium ions in the neighboring diamond In the case of a lO fUll zircon crysra1 containing 1,000 ppm of uraniurn, that same alpha dose would require more than 2 billion years, which seems implausible. Therefore, radio-coloration is likely due to the action of small grains of strongly radioactive phases that lay adjacent to the diamond for at least several million years.

German-Turkish Workshop on Superconducting Accelerators for FEL and Bremsstrahlung Applications

The Radiation Source ELBE at Helmholtz-Zentrum Dresden-Rossendorf is undergoing an extension to offer capacity for various applications. The extension includes the setup of a THz-beamline with a dedicated laboratory and a beamline for electron-beam - high-power laser interaction. The current synchronization scheme offers stability on the picoseconds level. For pump-probe experiments using optical lasers, the desired synchronization between the pump and the probe pulse should be on the femtosecond scale. In the future there will be an optical synchronization system with a pulsed fiber laser as an optical reference. The laser pulses will be distributed over stabilized fiber links to the remote stations. It is planned to install EOM-based beam arrival time monitors (BAMs) in order to monitor the bunch jitter and to establish a beam-based feedback to reduce the jitter. Besides that, the timing system has to be revised to generate triggers for experiments with low repetition rate, two electron guns (thermionic DC, superconducting RF) and several lasers. The Poster will show the possible layout of the future Timing and Synchronization System at ELBE.

Recently, the fibre link stabilisation unit of the optical synchronisation system at FLASH has been subject to several design changes involving some major issues. Enhancements of the optical design have led to improvements in the efficiency of the free space optics and a new optical delay line allows for a more than two times longer adjustment range. The amplitude noise, encountered previously at the remote station of the links, was drastically decreased by a new beam splitting configuration. In future, this new link design will not only be used for the planned additional fibre links at FLASH, but it will also replace the already installed ones. In this paper we report on the changes of opto-mechanical design and we present first results from the recently commissioned links.

The Radiation Source ELBE at Helmholtz-Zentrum Dresden-Rossendorf is currently extended to oer capacity for new experiments. The reconstruction includes the setup of a THz-beamline with a dedicated user laboratory and a beamline for electron-beam - high-power laser experiments. The current synchronization scheme oers stability to the picoseconds level. The newexperiments require a femtosecond synchronization in order to get field-strength resolved THz-probes and to have a stable overlap between the electron-bunches with the laser pulses. In the future there will be a MIT/Desy-like System with a pulsed fiber laser as an optical reference oscillator. The laser pulses will be distributed over stabilized fiber links to the remote stations. Later on it is planned to install EOM-based beamarrival timemonitors (BAMs) in order tomonitor the bunch jitter and to establish a feedback system to reduce the jitter. Besides that, the timing system has to be revised to trigger experiments with lowrepetition rate, two guns (thermionic DC, superconducting RF) and lasers. The Posterwill showthe Layout of the possible future Timing and Synchronization System at ELBE.

Im Zuge der immer genaueren Kontrollen von Arzneimittelresten in z. B. Lebensmitteln, steigt die Nachfrage nach sensitiveren und spezifischeren Sensoren. Auch in der Trinkwassserqualität steigt die Nachfrage nach Kontrollen von Pharmaka-Reststoffen. Dem entgegen steht, dass die Detektion von derartigen Substanzen häufig mit viel analytischen Aufwand verbunden ist und meist nur offline erfolgen kann.
In dieser Arbeit soll daher ein Biosensor entwickelt werden, der bestehend aus bakteriellen Hüllproteinen, Aptameren und Fluorophoren, in der Lage ist kleinste Mengen an bestimmten Arzneimitteln in wässrigen Systemen zu detektieren.

Titanium and its alloys can not be used at elevated temperatures in oxidizing environment because the rutile layer gets deteriorated. With increasing temperature the passivation vanishes which protects the alloys at low temperatures. Furthermore the enhanced oxygen inward diffusion at elevated temperatures worsens the mechanical properties by -case formation. To overcome this problem a combined Al- plus F-treatment was developed. The combination of Al-enrichment at the surface zone so that intermetallic TiyAlx-layers are formed plus stabilisation of the alumina formation by the fluorine effect led to good results in high temperature exposure tests of several Ti-alloys. In this paper the achieved improvements are described and the results will be discussed for a use of Ti-alloys in several high temperature applications.

The fluorine effect improves the oxidation resistance of TiAl-alloys drastically. The formation of a non protective fast growing mixed oxide scale is suppressed and instead a protective alumina layer is formed after fluorine treatment. Fluorine can be applied by several methods which, however, have to be optimised. An overdoping can lead to enhanced oxidation and worsen the situation. The parameters for an optimised process will be described. An improvement of the already good performance of specimens treated only with fluorine can be achieved e.g. by dipping in inorganic acids containing additional elements to fluorine. The results of high temperature oxidation tests of differently treated TiAl-samples will be presented. Post experimental metallographic investigations reveal the oxide scales formed so that the effect can be rated. Finally the results will be discussed in the view of the models for the fluorine effect.

Titanium aluminides exhibit quite good mechanical properties even at elevated temperatures for aeronautic and automobile applications. Their low specific density (half of classical nickel based super alloys) makes them attractive for applications where the mass is a critical parameter, i.e. rotating pieces. At elevated temperatures they suffer of environmental embrittlement by hot gases, which deteriorates drastically their mechanical properties and still hampers their use to temperatures above 500°C in industrial applications. In this work, coatings involving reactive elements such Cr, Y combined with the halogen effect (fluorine surface treatment) have been developed using MO-CVD, CVD, PVD and HVOF techniques. The coatings were characterized as produced and after annealing by means of glancing XRD, GDEOS to analyze their structure, homogeneity and composition, respectively. The adhesion properties of the coatings were measured by using impact tests before and after oxidation. The oxidation behavior of the produced coatings was evaluated in the temperature range of the industrial use, e.g. 600-850°C whereas corrosion tests were conducted using Na2SO4-NaCl mixtures in dry and wet environments. After oxidation/corrosion test post-mortem analysis was carried out using SEM-EDX, EPMA analysis to investigate the oxide layer composition, structure and the corrosion products, respectively. Mechanical properties losses of coated specimens after oxidation/corrosion due to embrittlement were evaluated using 4 point bending test combined with acoustic emission. It was shown that some of the developed coatings reduce the embrittlement sensibility of these alloys.

An oxygen barrier coating has been developed, which is effective in preventing oxidation and oxygen embrittlement of Ti and several low-Al content Ti-base alloys during exposure to oxidizing environments at elevated temperatures. The fabrication process has involved magnetron co-sputtering of titanium and aluminum followed by vacuum annealing and plasma immersion ion implantation of fluorine. The resulting coating consists primarily of γ-TiAl while containing a minor portion of Ti3Al present in the coating/substrate interfacial region. The implantation of fluorine provides the necessary conditions for triggering the halogen effect upon subsequent high-temperature exposure in air. Systematic characterization of the coating material in terms of microstructure, phase formation and element depth distribution has been performed using cross-sectional transmission electron microscopy (XTEM) in conjunction with electron energy loss spectroscopy (EELS), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and elastic recoil detection (ERD). Overall, the coating fabrication process has been found to be independent of the substrate material making the technique universally applicable at least to the alloys studied. Following oxidation in air at 600°C for 100 h, specimens have been prepared for metallographic analysis, and their cross sections have been characterized by scanning electron microscopy (SEM) in combination with EDX, and electron probe microanalysis (EPMA). The results obtained show that during oxidation exposure the γ-TiAl coating is capable of forming a protective alumina-containing scale, which serves as an oxygen barrier, thereby preventing oxygen embrittlement in the substrate material. In addition, since the only constituents of the coating are Ti and Al, it exhibits excellent chemical substrate compatibility.

Large-angle magnetization precession induced by a short pulsed magnetic field in a 15-nm thick Ni₈₁Fe₁₉ film is observed by use of a time-resolved magneto-optical Kerr effect technique with sensitivity to all three components of the magnetization vector. A reduction of the magnitude of the magnetization vector |M| during large-angle precession is inferred and indicates incoherent dynamics due to excitation of traveling spinwaves with wavelengths smaller than the diameter of the sampling area, that is, the laser spot size for the magneto-optical measurements. The reduction in |M| depends on the magnetic bias field Hbias, which can be qualitatively understood by comparison to the theoretical threshold for observing four-magnon scattering in a small time interval t. We estimate that two-magnon scattering cannot explain the experimental results.

Vortrag im Rahmen eines Workshops, kein gesonderter Abstract vorhanden.
Dieser Workshop beschäftigt sich speziell mit der Radiomarkierung von Nanopartikeln. Eigene Ergebnisse sollen mit Fachkollegen aus ganz Europa diskutiert werden. Ziel ist es auch, ggf. neue Kooperationen anzubahnen.

This article is aimed on the calibration and registration of electromagnetic tracking system for the purpose of immersive virtual reality application. The first part of the article provides a basic introduction into position and orientation tracking subsystems and denotes problems which are occurring while electromagnetic approach is used for tracking purposes. After that two methods for tracking system calibration are presented and also a solution for position registration of tracking systems with projection space is provided. Second part is focused on interactive calibration application, where the process of development and a resulting application structure is described. Finally results obtained by usage of interactive calibration application are compared. The main goal of this article is to present a way of dealing with static errors in virtual reality application in order to obtain proper alignment of the virtual and real world.

This article is aimed on the specific task of interaction with an immerse visualisation application. The first part of the article provides basic introduction into interaction paradigms in 3D space. After that classification and description of standard interaction tasks are presented. We introduce our view of matter on relations between the 3D interaction and standard interaction techniques. The second part describes hardware and software components of our VR system. Furthermore an overview of the architecture and implementation details of system for interactive visualisation configuration is discussed. We describe design specifications of a 3D UI, which helps to make interaction less error prone for inexperienced users. A specific solution for performing numerical input is also provided. The main goal of the article is to describe how 3D user interface paradigms can be implemented in the VR system.

Das Ziel des Vorhabens bestand in der Ertüchtigung von CFD-Codes für Wasser-Dampf-Strömungen mit Phasenübergang. Während CFD-Verfahren für einphasige Strömungen bereits breite Anwendung in der Industrie finden, steht ein entsprechender Einsatz für Zweiphasenströmungen auf Grund der komplexen Phasengrenzfläche und den davon beeinflussten Wechselwirkungen erst am Anfang. Für die Weiterentwicklung und Validierung geeigneter Schließungsmodelle werden experimentelle Daten mit hoher Orts- und Zeitauflösung benötigt. Solche Daten wurden an der TOPFLOW-Versuchsanlage des HZDR durch Kombination von Experimenten bei praxisnahen Parametern für die Reaktorsicherheit (große Skalen, hohe Drücke und Temperaturen) und innovativer Messtechnik gewonnen. Die Gittersensortechnik, mit der detaillierte Informationen über die Phasengrenzfläche gewonnen werden können, wurde in adiabaten Wasser-Luft-Experimenten sowie Kondensations- und Druckentlastungsexperimenten in einem großen DN200-Rohr eingesetzt. Umfangreiche Datenbasen mit hoher Qualität stehen im Ergebnis des Vorhabens zur Verfügung. Die Technologie für die schnelle Röntgentomographie, die Messungen ohne Strömungsbeeinflussung ermöglicht, wurde weiter entwickelt und in einer ersten Messserie erfolgreich eingesetzt. Hochaufgelöste Daten wurden auch in Experimenten zu verschiedenen Strömungssituationen (z. B. Gegenstrombegrenzung) in einem Modell des heißen Strangs eines Druckwasserreaktors gewonnen. Für die Wasser-Dampf-Experimente bei Drücken von bis zu 5 MPa wurde dabei erstmals die neu entwickelte innovative Drucktanktechnologie eingesetzt. Zur Ertüchtigung von CFD-Codes für Zweiphasenströmungen wurde das Inhomogene MUSIG-Modell für Phasenübergänge in Kooperation mit ANSYS erweitert und anhand der o.g. TOPFLOW-Experimente validiert. Außerdem erfolgten Verbesserungen u. a. für die Turbulenzmodellierung in Blasenströmungen sowie Simulationen zur Validierung der Modelle für Blasenkräfte und Blasenkoaleszenz und -zerfall. Ein wesentlicher Fortschritt wurde bei der Modellierung freier Oberflächen durch die Verallgemeinerung des AIAD-Modells erreicht. Die am Heißstrangmodell ermittelten Flut¬kurven können unter Nutzung dieses Modells in guter Übereinstimmung berechnet werden.

Cyclotron resonance spectra of 2D electrons in HgTe/Cd_xHg_1−xTe (0 1 3) quantum well (QW) heterostructures with inverted band structure have been thoroughly studied in quasiclassical magnetic fields versus the electron concentration varied using the persistent photoconductivity effect. The cyclotron mass is shown to increase with QW width in contrast to QWs with normal band structure. The measured values of cyclotron mass are shown to be systematically less than those calculated using the 8 × 8 Kane model with conventional set of HgTe and CdTe material parameters. In quantizing pulsed magnetic fields (Landau level filling factor less than unity) up to 45 T, both intraband (CR) and interband magnetoabsorption have been studied at radiation wavelengths 14.8 and 11.4 µm for the first time. The results obtained are compared with the allowed transition energies between Landau levels in the valence and conduction bands calculated within the same model, the calculated energies being again systematically less (by 3–14%) than the observed optical transition energies.

Experiments have been undertaken to explore the possibility of rapidly melting and alloying thin metal films by flashlamp annealing (FLA). Aluminum layers of a thickness of 100 to 500 nm have been deposited on α-titanium substrates by magnetron sputtering. The structures have then been heat-treated by FLA in air using flash duration of 20 msec, energy density of 60 to 100 J/cm², and maximal temperature of 800 to 1660°C. X-ray diffraction (XRD) and elastic recoil detection analysis (ERDA) have been used for sample characterization. The as-deposited Al films are amorphous/nanocrystalline (grain size ~ 5 nm) in nature. Heat treatment by FLA has been found to produce an intermetallic TiAl₃ phase. For comparison, under conditions of standard furnace annealing, the formation of this compound in the thin film reaction of Al and Ti necessitates anneal temperatures and times typically in excess of 400°C and 1 h, respectively. Furthermore, the intermetallic TiAl₃ phase formed by FLA appears to be present in a region extending from the surface to a depth of a few hundred nm. Importantly, no pure Al phase has been detected either at the surface or in the substrate bulk. XRD measurements have also identified negligibly small amounts of Al and Ti oxide phases. It is expected that one may obtain TiAl phases other than TiAl₃ by varying both the film composition (i.e. by co-depositing Al and Ti instead of Al only) and the FLA parameters. The results of this study indicate that FLA of thin metal films is a promising technique for rapid surface alloying and compound formation. For the particular case of the Ti/Al system, t he i ntermetal lc if il ms s o f abricated m ay h ave r el evance t o h igh-temperature m icroel ectronics applications (diffusion barriers, conduction lines etc) as well as to the oxidation protection of titanium and titaniumaluminum alloy surfaces by forming suitable intermetallic TiAl phases.

The adsorption qualities of GaO₄Al₁₂(OH)₂₄(H₂O)127+, a polycation with ε-Keggin structure, and its stability in contact with anionic cellulosic materials, was investigated under different concentration and ionic strength conditions. The cellulosic materials employed were two different fully bleached fibre materials, carboxyl methyl cellulose (CMC), and a spin coated cellulose model surface. As analytical techniques, pH-measurements, potentiometric titrations, ICP-OES, QCM-D, equilibrium calculations and Extended X-ray Absorption Fine Structure (EXAFS) were used. The adsorption is very strong and the addition of GaO₄Al₁₂(OH)₂₄(H₂O)127+ to a fibre suspension results in a rapid decrease in pH, followed by a small and slow increase in pH. This behaviour can be explained as due to a rapid and strong adsorption of intact GaO₄Al₁₂(OH)₂₄(H₂O)127+ ions, followed by a slow, and minor, 3-8 %, decomposition into different monomers. Alternative layer by layer adsorption of this ion, and CMC, on a spin coated cellulose model surface, constitutes further evidence for the strong interactions between the anionic cellulose materials and GaO₄Al₁₂(OH)₂₄(H₂O)127+. It is shown that the strong adsorption observed could not be described as due to an unspecific Donnan adsorption behaviour, neither of GaO₄Al₁₂(OH)₂₄(H₂O)127+ nor Ga and Al monomers, and specific surface complex formation is therefore discussed and applied.

no abstract available

The sorption reactions of uranium(VI) at the ferrihydrite(Fh)-water interface were investigated in the absence and presence of atmospherically derived CO2 by time-resolved in situ vibrational spectroscopy. The spectra clearly show that a single uranyl surface species, most probably a mononuclear bidentate surface complex, is formed irrespective of the presence of atmospherically derived CO2. The character of the carbonate surface species correlates with the presence of the actinyl ions and changes from a monodentate to a bidentate binding upon sorption of U(VI). From the in situ sorption experiments under mildly acid conditions, the formation of a ternary surface complex is derived where the carbonate ligands coordinate bidentately to the uranyl moiety (≡UO2(O2CO)x). Furthermore, the release reaction of the carbonate ligands from the ternary surface complex is found to be considerably retarded compared to those from the pristine surface suggesting a tighter bonding of the carbonate ions in the ternary complex. Simultaneous sorption of U(VI) and atmospherically derived carbonate onto pristine Fh shows formation of binary monodentate carbonate surface complexes prior to the formation of the ternary complexes.

This paper presents a preliminary design of a high conversion Th-U233 fuel assembly applicable for current generation of Pressurized Water Reactor (PWRs). The considered fuel assembly has a typical 17×17 PWR lattice. However in order to increase the conversion of Th232 to U233, the assembly was subdivided into the two regions called seed and blanket. The central seed region has a higher than blanket U233 content and acts as a neutron source for the peripheral blanket region. The latest acts as a U233 breeder. While the seed fuel pins have a standard dimensions the blanket fuel radius was increased in order to reduce the moderation and to facilitate the resonance neutron absorption in blanket Th232. The U233 content in the seed and blanket regions was optimized to achieve maximal initial to discharged fissile inventory ratio (FIR) taking into account the following constrains: 1) target fuel cycle length of 18 months assuming 3-batch reloading scheme, 2) during the fuel cycle the core k-eff should be higher or equal to 1. In this study the neutronic calculations were performed on the fuel assembly level using the Helios deterministic lattice transport code. The fuel cycle length and the core k-eff were estimated with the help of Non Linear Reactivity Model. The applicability of the Helios code for the analysis of the Th-based high conversion designs was confirmed with the help of continuous-energy Monte-Carlo code Serpent. The results of optimization studies show that for the heterogeneous seed and blanket (SB) fuel assembly the FIR of about 0.94 can be achieved.

The qualitative and quantitative risk assessment of radiotoxicity in contaminated sites plays a key role in radioecological monitoring and for environmental protection. High doses of radioactivity are physically measurable in the near field of nuclear waste disposals. However, it is a major challenge to develop methods for low dose risk assessments typical for the far field, where transmission of radionuclides into the food chain may lead to health risks that are not detectable by conventional methods. To address this problem, a novel approach using metabolic monitoring of bacterial cell growth was established using the Thermal Activity Monitor (TAMIII; TA intruments, USA) as a multichannel microcalorimeter to identify the minimal dose of radionuclides that generates a measurable change in metabolic heat release. In this approach, the toxicity of a radionuclide was defined as a measurable effect on the metabolic activity of Peanibacillus sp. JG-TB8, a gram-positive bacterium isolated from a soil sample of the uranium mining waste pile “Haberland” (Johanngeorgenstadt, Saxony, Germany). Liquid cultures of this strain were exposed to micromolar concentrations of uranium (VI) salts and the metabolic heat release measured as a function of time and temperature. The non-radioactive "heavy metal stress" exerted by europium (Eu(III)) served as reference under the same conditions. Preliminary results show distinct and reproducible effects of uranium and europium on the time-dependent heat release already at 10 µM concentration. The toxicity of uranium and europium caused a decrease of maximal heat flow compared to control samples. In contrast to europium, for which the inhibitory action scales with concentration, uranium influences bacterial growth in a more complicated manner which strongly depends on temperature and pH, probably as a consequence of its different speciations. The results demonstrate that microcalorimetric monitoring is an extremely sensitive tool to investigate the influence of low heavy metal and radionuclide concentrations on the metabolic activity of microorganisms as shown here for Peanibacillus sp. JG-TB8.

We measured the non-radiative intersubband relaxation time in n-type modulation-doped Ge/SiGe multi-quantum wells of different thickness by means of degenerate pump-probe experiments. The photon energy was tuned to be resonant with the lowest conduction band intersubband transitionenergy (14-29 meV), as measured by terahertz absorption spectroscopy and in agreement with bandstructure calculations. Temperature-independent lifetimes in excess of 30 ps were observed.

This paper presents new calculation methods, recently implemented in the Serpent Monte Carlo code, and related to the production of homogenized few-group constants for deterministic 3D core analysis. The new methods fall under three topics: 1) Improved treatment of neutron-multiplying scattering reactions, 2) Group constant generation in reflectors and other non-fissile regions and 3) Homogenization in leakage-corrected criticality spectrum. The methodology is demonstrated by a numerical example, comparing a deterministic nodal diffusion calculation using Serpent-generated cross sections to a reference full-core Monte Carlo simulation. It is concluded that the new methodology improves the results of the deterministic calculation, and paves the way for Monte Carlo based group constant generation.

Objectives:

Radio (⁶⁴Cu⁺⁺) and fluorescence (Alexa Fluor 488) labelled Cetuximab (C225) offers the possibility of multimodal imaging of epidermal growth factor receptor (EGFR). ([⁶⁴Cu]Cu-NOTA)₇-C225-(Alexa Fluor 488)⁷ was synthesized and the imaging and biodistribution has been proved by small animal PET and ex vivo studies of cryo-sections of xenotransplanted mice.
Methods:
1) Synthesis of (NOTA)_x-C225-(Alexa Fluor 488)_y (C225-Conjugate). The C225 solution (Erbitux, Merck KGaA, Germany) was buffer-exchanged with a NaHCO3 solution (50 mM, pH 6.0) containing NaCl (150 mM) using a Jumbosep 30 k molecular weight cut-off concentrator (Pall Life Sciences, Germany). NOTA (2-(pisothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid, p-SCN-Bn-NOTA, Macrocyclics, USA) and Alexa Fluor 488 (Alexa Fluor 488 carboxylic acid 2,3,5,6-tetrafluorophenyl ester, Invitrogen, United Kingdom) has been conjugated to C225 lysine amino residues in a single step. Just prior to protein conjugation, NOTA and Alexa Fluor 488 were dissolved in HEPES-buffer (400 μL, 500 mM, pH 7.2) and added to the C225 solution to achieve a molar reaction ratio of 10:1 (NOTA:C225) and gently manually agitated. The reaction mixture was allowed to incubate in the dark at 25°C for 24 h without further stirring. Excess NOTA chelator and dye were removed by passage of the reaction solution through a Jumbosep. The buffer-exchange was performed with an NH4OAc solution (50 mM, pH 6.0) containing NaCl (150 mM). Protein concentration and the number of conjugated dye molecules per mAb were determined by UV/VIS absorption at 280 nm and 495 nm (excitation maxima of Alexa Fluor 488), respectively. The number of NOTA introduced was determined using MALDI-TOFMS. 2) Radiolabeling with ⁶⁴Cu. A solution of [⁶⁴Cu]CuCl₂ in HCl (0.04 M, 50 MBq) was added to the C225-conjugate (100 μg) plus MES buffer (100 μL, 200 mM, pH 6.1) in 2 mL protein low-binding tubes (Eppendorf, Germany), vortexed immediately and incubated at 30°C for 30 min. Radiochemical yield (RCY) was determined by radio-ITLC. Before ITLC-analyses, free TETA chelator (32 μL; 0.1 μg/μL) was added to the reaction mixture for quenching the labelling reaction and fixing unreacted radionuclide. Therefore a second incubation at 30°C for 30 min was necessary. As stationary ITLC-phase, a 10 cm ITLC-SA strip (Varian GmbH, Germany) and as mobile phase a 0.9% NaCl solution has been used. The radio labelled antibody was purified by spin filtration using Microcon 30 k (Millipore). 3) Biodistribution. Squamous cell carcinoma (FaDu) tumour bearing NMRI nu/nu mice were studied with PET at 24 h p.i. The fine distribution of the probe was then characterized using whole body cryosectioning. The ⁶⁴Cu-activity was compared with the fluorescence distribution.
Results:
The BFC NOTA and Alexa Fluor 488 were successfully simultaneously conjugated to C225. The resulting conjugate is (NOTA)₁-C225-(Alexa Fluor 488)₇. Radionuclide labelling was achieved within 30 min with optimization of the molar ratio of NOTA:C225: Alexa Fluor 488 during the conjugation. The radioimmunoconjugate exhibited high accumulation in xenotransplanted FaDu tumours in mice after 24 hours. The ⁶⁴ Cu-activity concentration correlated well with the fluorescence in most tissues except the liver.
Conclusions:
Dual-labelled immunoconjugates represent a potential probe for translational application in tumour detection, evaluation of long-term distribution and stability studies of the labelled antibody.
Research support: This project was partially supported by “Kompetenzverbund Strahlenforschung” (grant 02NUK006A-E).

A precise knowledge of the temperature and number of hot electrons generated in the interaction of shortpulse high-intensity lasers with solids is crucial for harnessing the energy of a laser pulse in applications such as laser-driven ion acceleration or fast ignition. Nevertheless, present scaling laws tend to overestimate the hot electron temperature when compared to experiment and simulations. We present a novel approach that is based on a weighted average of the kinetic energy of an ensemble of electrons. We find that the scaling of electron energy with laser intensity can be derived from a general Lorentz invariant electron distribution ansatz that does not rely on a specific model of energy absorption. The scaling derived is in perfect agreement with simulation results and clearly follows the trend seen in recent experiments, especially at high laser intensities where other scalings fail to describe the simulations accurately.

Objectives:

Thiol-dependent cathepsins are a class of cysteine proteases that have been shown to be linked to the progression of cancer in multiple ways. Particularly crucial is their involvement in proteolytic pathways that are related to tumour invasion and metastasis [1]. The aim of this study was the design of cathepsin inhibitors based on the structure of the azadipeptide nitrile chemotype [2] that permit the labelling with the positron emitters fluorine-18 and carbon-11 and to evaluate the
potential of this inhibitor class for functional tumour imaging by PET. Additionally, a first insight into the pharmacokinetic behaviour of these inhibitors should be gained.
Methods:
The fluorine atom was linked by an ethylene bridge to the inhibitor core structure. Labelling with fluorine-18 was achieved by fluoroethylation of 1 with different substituted [¹⁸F]2-fluoroethyl benzenesulfonates [3]. In addition, the introduction of radiofluorine into 2 was attempted by direct fluorination of the corresponding tosyl and nosyl precursors. The stability of the tracer against chemical and enzymatic degradation as well as its metabolic fate in rat blood was investigated and its biodistribution was studied in vivo by small animal PET. To obtain an ¹¹C-based tracer, the fluoroethyl group of 2 was replaced by methyl. Introduction of carbon-11 was done by conversion of the phenolic precursor 1 with [¹¹C]methyl iodide generated by the gas-phase method. The affinities of the compounds 1-3 to their targets were determined in kinetic enzyme assays.
Results:
The azadipeptide nitriles 1-3 exhibited inhibition constants in the single-digit to subnanomolar range against the oncologically relevant cathepsins L, S, and B. Among the various ¹⁸F-fluoroethylating agents tested, [¹⁸F]2-fluoroethyl nosylate revealed as the most efficient one. This enabled the two-step radiosynthesis of [¹⁸F]2 in an average RCY (d.c.) of 27±5% (n = 13). The direct radiofluorination of the corresponding sulfonate precursors could provide [¹⁸F]2 in only low labelling yields. PET studies in rats together with in vitro investigations indicated the trapping of the tracer in erythrocytes, which could be attributed to its inherent thiol reactivity. The tracer [¹¹C]3 could be obtained in labelling yields of 35-42% depending on the employed base. Its radiopharmacological behaviour is under current investigation.
Conclusions:
With the azadipeptide nitriles 2 and 3 highly potent cathepsin inhibitors were found and their labelling with fluorine-18 and carbon-11 could be successfully established. The compounds’ suitability as PET tracers for functional tumour imaging seems to be limited due to their thiol reactivity. The radiolabelling of further cathepsin inhibitors is underway.
References:
[1] Mohamed & Sloane (2006) Nat. Rev. Cancer 6, 764-775, [2] Löser et al. (2008) Angew. Chem.
Int. Ed. 47, 4331-4334, [3] Musachio et al. (2005) J. Label. Compd. Radiopharm. 48, 735-747

Objectives: Ephrins and Eph receptors were found to be disregulated in several human tumor entities like breast, colon, liver, prostate or melanoma [1]. Concerning Eph/ephrin signalling, the EphB4/ephrinB2 system seems to play a major role in tumor angiogenesis [2]. Several inhibitors were reported based either on peptides which block the extracellular ephrin binding domain [3] or small organic molecules which block the intracellular kinase domain of Eph receptors. For this purpose, promising EphB4 kinase inhibitors based on the dioxolylpyrimidine scaffold were used for the development of a novel radiofluorinated PET tracer candidate [4].
Methods:
Compound 1 (figure 1) represents an advantageous molecule for the development of a fluorine-18 containing radiotracer. It shows an adequate affinity to EphB4 (90 nM) and consists of two structural parts. For the synthesis of the new radiotracer [¹⁸F]2, the methylsulfonylphenyl residue in 1 was replaced by a 3-fluoropropylsulfonylphenyl moiety (part B). This part of the molecule was prepared starting from sodium benzenesulfinate and 1-bromopropanol in 5 synthesis steps. Part A of the radiotracer as well as the lead compound containing the benzodioxole moiety was synthesized as described previously [4]. Finally, the non-radioactive reference 2 was obtained after 6 steps, whereas the respective tosylate precursor was prepared within 7 steps. Cellular binding and internalization of [¹⁸F]2 was investigated in human A375 melanoma cells as well as A375 cells stably transfected with human EphB4 receptor or mock vector. Furthermore, specific binding and potential transport mechanisms were analyzed by application of different specific inhibitors.
Results:
Starting from a 2 GBq [¹⁸F]fluoride batch, 65±5 MBq of [¹⁸F]2 were obtained with >95% radiochemical purity within 60 min synthesis time (including HPLC purification tR = 3.9 min, acetonitrile:water, 1:1 + 0.1% TFA). The best conditions for radiolabeling of the tosylate precursor were found to be acetonitrile as solvent at 90 °C for 15 min. Afterwards, water was added and the mixture was filtered prior to the HPLC purification. Cell association studies in melanoma cells showed time dependent increase in binding and internalization of [¹⁸F]2. Both inhibition with lead compound 1 and [¹⁹F]2 significantly decreased binding and internalization of [¹⁸F]2
indicating specific EphB4 binding. However, involvement of other kinases for binding can not be excluded. Moreover, participation of ATP-binding cassette transporters for cellular uptake is indicated.
Conclusions:
A novel potential EphB4 inhibitor based on the dibenzodioxolylpyrimidine scaffold has been synthesized and successfully radiolabeled with fluorine-18. Further biological studies including dynamic small animal PET are currently in progress.
References:
[1] B. Mosch, B. Reissenweber, C. Neuber, J. Pietzsch (2010), J. Oncol., DOI: 10.1155/2010/135285,
[2] E. Pasquale (2010), Nature Rev. Cancer, 10, 165, [3] J. E. Chrencik, A. Brooun, M. I. Recht, G. Nicola, L. K.
Davis, R. Abagyan, H. Widmer, E. B. Pasquale, P. Kuhn, (2007), J. Chem. Biol. 282, 36505, [4] C. Bardelle, T.
Coleman, D. Cross, S. Davenport, J. G. Kettle, E. J. Ko, A. G. Leach, A. Mortlock, J. Read, N. J. Roberts, P.
Robins, E. J. Williams, (2008) Bioorg. Med. Chem. Lett., 18, 2776.

Objectives:

Cyclooxygenase-2 (COX-2) is an inducible enzyme overexpressed under inflammatory conditions and is assumed to play a key role in cancerogenesis. Functional imaging of COX-2 expression in vivo by means of COX-2 inhibitors radiolabeled with positron emitters is a challenging approach, e.g., for differentiation of inflammatory processes and cancer¹. Despite of different attempts, up to now a suitable radiotracer for COX-2 expression is unavailable. We developed an ¹⁸F-labeled COX-2 inhibitor [¹⁸F]3 from the type of a 2,3-diarylsubstituted indole via the McMurry cyclization. Thereby, with this labeling approach we got access with [¹⁸F]fluoride to the indole system which is, in principle, poorly activated for a nucleophilic substitution.
Methods:
The potent COX-2 inhibitor 3 (IC₅₀=0.02 μmol) was synthesized as reference compound2. The labeling precursor 1 bearing a trimethylammonium leaving group was obtained in a six-step synthesis sequence. The radiolabeling reaction was performed as an one pot-two step procedure starting first by introduction of [¹⁸F]fluoride by a nucleophilic substitution at 1 followed by McMurry cyclization to form the indole core structure (Figure 1). The radiosynthesis was carried out with an automated nucleophilic synthesizer TracerLAB_FXN (GE) and has been optimized with respect of the base, solvent, and temperature. Purification of [¹⁸F]3 was performed by semi-preparative HPLC and SPE with C18 cartridges.
Results:
Considering a set of optimization experiments it turned out that for the McMurry cyclization the use of THF is inevitable. Hence, the radiolabeling was performed in acetonitrile at 110-120°C, the solvent was removed under vacuum, and the McMurry reaction was run in pure THF at 90-100°C. Under these conditions the intermediate [¹⁸F]2 was formed in 10-15% yield and the cyclization step provided the desired McMurry product [¹⁸F]3 in 50-82% yield. A typical module assisted radiosynthesis of [¹⁸F]3 starting with 8 GBq of [¹⁸F]fluoride and 15 mg precursor 1 yielded 490 MBq of [18F]3 (10% overall yield d.c.) within 80 min synthesis time. The radiochemical purity of [¹⁸F]3 after HPLC purification was > 98% and the specific activity was determined to be 74-91 GBq/μmol at end of synthesis.
Conclusions:
A highly potent and selective COX-2 inhibitor from type of a 2,3-diarylsubstituted indole was labeled with fluorine-18 in a two step fully automated radiosynthesis giving a potential PET tracer for functional imaging of COX-2 in vivo. In best to our knowledge, this is the first time that McMurry cyclization was utilized in PET-chemistry as labeling approach to get access to poorly activated compounds by nucleophilic substitutions with [¹⁸F]fluoride. In vitro stability studies in rat plasma and blood and in vivo studies in rats showed high stability of [¹⁸F]3 over two hours. Cell uptake studies with [¹⁸F]3 in THP-1, FaDu, HT29, A2058 and A375 cell lines are under the way as well as small animal PET investigations in HT29 mouse xenograft models.
References:
[1] Kuge et al., (2009), Nucl. Med. Biol., 36, 869-876,
[2] Hu et al., (2003), Bioorg. & Med. Chem.,11, 1153-1160

Objectives:

The favorable properties of non-natural, L-configured oligonucleotides (L ON) such as rapid hybridization, the lack of natural hybridization targets in vivo as well as their high metabolic stability [1] award L-ONs as a promising tool for tumor pretargeting technologies. As a result of their oligoanionic nature, 17mer-L-ONs are correlated with very fast blood clearance and high kidney retention [1]. Therefore, improvement of these two parameters was indispensable. To minimize the kidney accumulation and to increase the bioavailability by increasing of the area under the blood curve (AUC), polyethylene glycol (PEG) units of increasing size 2000-20000 Da were conjugated to the 17mer lead structure. Beside effect of PEGylation, the influences of different chelators and labeling ions on the biodistribution behavior of ⁶⁴Cu- and ⁶⁸Ga-labeled 17mer-L-ON-PEGs were investigated.
Methods:
17mer-L-DNA (HO-C₆H₁₂-S-S-C₆H₁₂-^5’GCGGCTGTG-CGGTGCGG^3’-amino modifier) was 3’-modified with different PEG substituents. By using the mercaptohexyl spacer at 5’-position, new developed NOTA-maleimide derivatives as well as a commercially available DOTA-maleimide were conjugated. After radiolabeling with ⁶⁴Cu and ⁶⁸Ga and intravenously administration in healthy Wistar rats, biodistribution data by organ and tissue sampling were determined 5 min p.i. as well as 60 min p.i. Blood clearance half lifes were calculated using of dynamic PET studies. The influence of PEGylation on hybridization was investigated in vitro by gel-electrophoresis.
Results:
The increasing molecular mass of the conjugated PEG units led to significantly decreased kidney retention at 60 min from 56.3±4.1%ID (⁶⁴Cu; 2 kDa PEG) and 52.4±6.1%ID (⁶⁸Ga; 2 kDa PEG) to 6.5±0.4%ID (⁶⁴Cu; 20 kDa PEG) and 6.9±0.6% (⁶⁸Ga; 20 kDa PEG), respectively. However, the liver uptake was slightly increased at 60 min p.i. from 4.8±0.2%ID (⁶⁴Cu; 2 kDa PEG) and 2.6±0.4%ID (⁶⁸Ga; 2 kDa PEG) to 13.3±2.1%ID (⁶⁴Cu; 20 kDa PEG) and 10.7±2.7%ID (⁶⁸Ga; 20 kDa PEG). The activity concentrations in all other measured organs, except the blood, were at 60 min p.i. negligible (< 0.5%ID/g or <1 SUV). The biological half-lives in the blood were 10.8 min (2 kDa PEG), 9.6 min (5 kDa PEG), 27.7 min (10 kDa PEG), and 39.4 min (20 kDa PEG) for ⁶⁸Ga-labeled compounds. Based on gel-electrophoresis investigations, no PEG-induced inhibition of hybridization was found. In vitro hybridization was completed in less than 30 s, whereas the optimal ratio of complementary L DNA single strands was between 1:1 (2-5 kDa) to 1:1,25 (10-20 kDa).
Conclusions:
PEGylation of our 17mer-L-ON resulted in significantly reduced kidney retention, favorable blood circulation half-life, and very low unspecific tissue accumulations. Low kidney and liver accumulations were found for 5 kDa and 10 kDa PEG derivatives. Increasing size of PEG units shifted the hybridization equilibrium to slightly higher DNA ratios without clear hybridization inhibition. The introduction of NOTA or DOTA as chelating moiety enables radiolabeling with various metallic radionuclides for diagnostics and therapy. These results emphasize the high-grade potential of L-ON as a complementary tool for tumor pretargeting technologies.
Reference:
Schlesinger, J. et al., (2008), Lett. Drug Des. Discovery, 3, 330-335

The combination of low-temperature deposition with very rapid thermal processing (vRTP) at air is a promising approach of synthesis of high-quality thin films of transparent conductive oxides (TCOs) at large areas. However, microscopic mechanisms of TCO film properties modification during such treatment are not understood properly which hampers application of the post-deposition vRTP. In order to resolve this problem, Al-doped ZnO (AZO) films grown onto unheated fused silica substrates by reactive pulsed magnetron sputtering were vRTP processed using a laser source with ~1 ms dwell time. The morphology, bonding structure, electrical and optical properties of as-deposited films were systematically compared with those of the vRTP processed ones. The electrical resistivity of the films drops from 1.4x10^-3 to 4.6x10^-4 Ohm cm with simultaneous substantial decrease of the film optical extinction in the visible at optimum processing conditions. The resistivity decrease is due to simultaneous increase of the free electron density (from 3.8x10²⁰ to 6.2x10²⁰ cm^-3) and mobility (from 12 to 22 cm²V^-1s^-1). It is also observed that vRTP leads to a substantial decrease of the A1(LO) and E1(LO) disorder-enhanced lines in Raman spectra. This is interpreted in terms of decreasing concentration of point defects because both x-ray diffraction and high-resolution TEM show no improvement of the film crystal quality which might have a similar effect on the Raman spectra. Substantial modification of the O K-edge x-ray absorption near edge structures (XANES) spectra of the vRTP processed AZO films (which are dense and void free already in as deposited state) suggests that these might be oxygen-related point defects or defect complexes. Decrease of concentration of these defects may explain increase of the free electron mobility and decrease of the optical extinction in the visible.
The authors gratefully acknowledge financial support of BMBF under the RainbowEnergy Project.

Owing to the exceptional intracellular distribution and the heterogeneous expression pattern during transformation and metastasis in various tumors, the EF-hand calcium-binding protein S100A2 attracts increasing attention. Unlike the majority of S100 proteins, S100A2 expression is downregulated in many cancers and the loss in nuclear expression has been associated with poor prognosis. On the other hand, S100A2 is upregulated in some cancers. This mini review highlights the general characteristics of S100A2 and discusses recent findings on its putative functional implication as a suppressor or promoter in cancerogenesis.

Background: The development of the new technology of proton and ion acceleration by ultra-high intensity lasers for cancer therapy is the goal of the German joint research project “onCOOPtics”. The laser based acceleration promises compact and economic therapy facilities that are suitable for already existing clinics. In contrast to conventional particle acceleration the laser based method results in beams of very short pulses with ultra-high pulse dose and correspondingly peak dose rate. Within the project multidisciplinary issues like development and optimization of high-intensity laser systems, efficient proton acceleration schemes and proton beam transport are handled. Moreover, the physical and real-time dosimetric characterization as well as the investigation of radiobiological consequences of laser accelerated beams are essential. These imply translational investigations starting from in vitro cell irradiation.

Material and Methods: Systematic in vitro cell experiments were performed at the 150 terawatt laser facility DRACO at HZDR. Proton pulses up to 20MeV were accelerated, whereas the broad proton spectrum was downward limited to 6MeV using an energy-filter-system. An in-house developed integrated dosimetry and cell irradiation system (IDOCIS) was tested and calibrated allowing precise dosimetry as well as the exact positioning of each cell sample. Cell survival and residual DNA double strand breaks were determined after irradiation of the tumour cell line SKX in a dose range from 0.5Gy to 4.3Gy. Additionally, reference irradiation were performed with continuous proton beam at a conventional Tandem accelerator and with a 200 kVp X-ray tube.

Results: A stable and reproducible laser driven proton beam was achieved for experiments over weeks including real-time dose and energy spectrum monitoring as well as precise absolute dosimetry. The comparison of the radiobiological effectiveness of conventional and laser accelerated proton beams show no significant difference for in vitro cell irradiation.

Conclusions: These first systematic in vitro cell response studies with precise dosimetry of laser driven protons represent an important step toward the development of laser accelerated particles for radiotherapeutic application. Further experiments with other human cell lines and in vivo studies are under way.

The work was supported by the BMBF, grant no. 03ZIK445.

kein Abstract verfügbar

Gas-solid fluidized beds find various applications in chemical and process engineering, for instance in fluid catalytic cracking, drying of particulate solids or polyolefin production. The gas-particle flow in fluidized beds is generally complex and difficult to observe, but exact information on voidage distribution and solid transport is urgently needed for assessment, monitoring, modelling and optimization of fluidized bed operation.
Only few of the currently available flow measurement techniques are applicable to dense fluidized beds. Optical imaging and laser-based methods are at the most merely able to capture the peripheral structure of the solids phase or to provide local information by using probes. For tomographic techniques, such as electrical capacitance tomography (ECT), positron emission tomography (PET) or common X-ray CT, it is in general difficult to provide high spatial and high temporal resolution at the same time.
We here introduce a much faster X-ray tomography approach which is based on electron beam scanning. There, an electron beam is rapidly swept along a circular target to produce a moving X-ray source. A static detector ring with 240 detector elements synchronously captures the radiation intensity. From the resulting radiographic projections of the object of interest non-superimposed cross-sectional density distributions are reconstructed. Beside its really fast scanning capability other advantages of this approach are the use of a single electron beam generator and the high versatility of the electron beam with respect to scan patterns and scanning speed. With our approach we have already demonstrated multiphase flow imaging with frame rates of up to 10.000 fps and a spatial resolution in the range of better than 1 mm.
The results presented here include studies at a bubbly fluidized bed with monodisperse spherical particles, in which the capability of the method to visualize the particle dynamics and the internal structure of the fluidized bed in very detail are demonstrated.

Gas-particle flow in fluidized beds is generally complex and difficult to observe. But exact information on voidage distribution and solid transport is urgently needed for assessment, monitoring, modelling, and optimization of fluidized bed operation. So far, there was a lack of suitable measurement and imaging techniques to disclose the complex flow structures in fluidized beds with high spatial and temporal resolution. The recently developed ultrafast X-ray computed tomography technique is superior for such types of multiphase flows and its performance has been demonstrated in this study. Spatial resolution in the range of one millimetre and temporal resolution of several thousand cross-sectional images per second allows at the same time imaging and analysis of voidage structures as well as single particle movement. In this study, the capability of imaging fluidized bed behaviour at different column diameters and gas flow rates has been analysed.

Nanoparticle (NP) tracking in complex media is still a challenge since NP concentrations are expected to be low compared to elemental background levels as it can be found in environmental matrices. This study presents a new method for radiolabeling of commercial silver nanopowder (Ag0-NPs, dp < 100 nm) with 110mAg radionuclides (t1/2 = 250 d) that provide an adequate time frame for particle detection, localization and tracking under various experimental conditions. The radiolabeling procedure ensures high efficiency, stability and consistency of particle properties. Detection of Ag0-NP in concentrations as low as 125 ng kg-1 could be reached. For the first time, an appropriate tool for life-cycle studies of commercial Ag0-NPs is provided without changing chemical composition of the material. This is of great importance e.g. for research in the field of nanotoxicology.

A series of experiments have been performed with the aim to improve the electrical and structural properties of CVD – deposited thin polycrystalline silicon films. Using an advanced ion implantation technique like Plasma-Immersion-Ion- Implantation (PIII) in combination with short time Flash-Lamp-Annealing (FLA) it has been shown that in comparison to the as deposited state a significant enlargement of the mean grain size occurs, accompanied by a more pronounced texturizing. Furthermore, the main crystallographic axes of the grains have been found to be mostly parallel to the direction of the particle stream. Whereas the enlargement of the mean grain size due to ion channelling was already reported by Reif et al. in the 80s, in the present work the SSIC technique (Seed Selection though Ion Channelling) was applied for the first time using the PIII process. This technique ensures a high throughput; additionally the costs for the implantation step can be reduced in comparison to conventional ion implantation. Furthermore, in contrast to the well known existing recrystallization techniques like cw-laser annealing or lateral zone melting recrystallization (ZMR), the proposed method circumvents problems arising from several mass transports characteristics of techniques based on melt processes.

Many fundamental processes in nature like chemical reactions or phase transitions occur on the few femtosecond time and few nanometres to few angstroms length scale. On a way to their understanding, great hope lies on investigations of their dynamic using the bright, coherent X-ray pulses from free electron lasers (FELs) that have a duration and wavelength commensurate with that of these processes.
We developed a method to measure the arrival time of the X-ray pulses at FLASH with respect to the pump-probe laser in the experimental hall on a few femtosecond timescale, making use of the THz beamline [1]. Method is easily transferable to other advanced light source working with ultrashort electron bunches and therefore of high general interest.

The Rossendorf Beamlines at ESRF is operated since 1997 by the Helmholtz Center Dresden-Rossendorf. As a multipurpose synchrotron x-ray beamline, it serves both inhouse and collaborative research in Environmental and Materials Science. Its optics provide tunable monochromatic x-rays to two experimental stations, the first specialized in bulk x-ray absorption spectroscopy for environmental radionuclide research, and the second specialized in a variety of scattering techniques to elucidate the structure of thin films and other materials. The first focus of my talk will be on the performance of the optics, which are donated to SESAME. I will then show some research examples, and give an overview on the organization, funding and personnel input, and productivity parameters (publications, projects, and outreach).

Due to its element specificity, low detection limit, and independence on long-range and crystalline order, X-ray absorption spectroscopy (XAS) is one of the most versatile tools to elucidate the electronic and molecular structure of almost any element in environmental samples. It is fundamental to study the speciation and structure of dissolved (aqueous) complexes, from the most simple solvated ion to polyatomic complexes, to colloids, amorphous and crystalline solids. Furthermore, it is extremely useful to study sorption and redox reactions at the water/solid interface. I will demonstrate its application in environmental chemistry to study the fate of metal contaminants in soils, sediments and water bodies.

We report on the discovery of a new shergottite from Tunisia, Ksar Ghilane (KG) 002, which is the 100^th Martian meteorite fragment registered in the Meteoritical Bulletin. This single stone, weighing 538 g, is a coarse-grained basaltic shergottite, mainly composed of maskelynitized plagioclase (~52 vol.%) and pyroxene (~37 vol.%). It also contains Fe-rich olivine (~4.5 vol.%), large Ca-phosphates, including both merrillites and Cl-apatites (~3.4 vol.%), minor amounts of silica or SiO₂2-normative K-rich glass, pyrrhotite, Ti-magnetite, ilmenite, and accessory baddeleyite. The largest crystals of pyroxene and plagioclase reach sizes of ~4 mm and ~5 mm. Regarding texture, KG 002 shares some similarities with the evolved NWA 2800 Martian sample. Pyroxene compositions in KG 002 are Fs_26-96En_5-50Wo_2-41 (n=82). They typically range from cores of about Fs₂₉En₄₁Wo₃₀ to rims of about Fs₆₈En₁₄Wo₁₇. Most plagioclases (maskelynites) are Ab_41-49An_39-58Or_1-7 in composition, but some can be as anorthitic as An₉₄. Olivine occurs mainly within symplectitic intergrowths, in paragenesis with ilmenite, or at neighboring areas of symplectites. These minerals are Fa_91-96 in composition. Ksar Ghilane 002 is heavily shocked (S5) as indicated by mosaic extinction of pyroxenes, maskelynitized plagioclase, the occurrence of localized shock melt glass pockets and low radiogenic He concentration. Two analyses of oxygen isotopes (delta18O=+5.09 and 5.26‰, delta17O=+3.0 and +3.2‰, and Δ17O=+0.28 and +0.43‰) confirm that this rock is a normal member of the SNC suite of meteorites. Bulk chemical analyses indicate that KG 002 belongs to the main group of basaltic shergottites and it is strikingly similar to the highly-evolved Los Angeles meteorite. According to the K, U, Ba and Sr abundances and fresh appearance of sulfides, KG 002 is not significantly weathered, although a positive Ce anomaly is recognized in the REE pattern. Ksar Ghilane 002 is slightly depleted in LREE and shows a positive Eu anomaly providing evidence for complex magma genesis and mantle processes on Mars. Noble gases with a composition thought to be characteristic for Martian interior may be a dominant component in KG 002. ¹⁰Be, ²⁶Al, and ⁵³Mn measurements and comparison with theoretical Monte-Carlo calculations of production rates indicate that KG 002 has been exposed most likely as a single meteoroid body of 35-65 cm radius between 2.8 and 3.7 Ma. Ksar Ghilane 002 strongly resembles Los Angeles and NWA 2800 basaltic shergottites in element composition, petrography and mineral chemistry, suggesting a possible launch-pairing. The CRE ages of KG 002 and Los Angeles may suggest an ejection event at ~3.0 Ma.

The breeding of male layer chickens is currently considered to be highly uneconomical. In Germany alone, 40 to 50 million newly hatched male chickens were killed annually immediately after hatching. Therefore, it is necessary to find a method for sexing chickens early in the embryonic development, preferably before incubation. The genotypic sex of an egg can be determined using information found in the germinal disc, so knowledge of the exact position of the germinal disc is essential for further sexing, or for other actions such as the in ovo injection of agents. Previous studies have shown that the germinal disc is located somewhere on top of the yolk. However, no studies have yet been performed that investigate the influence of time spent in horizontal storage on the position of the germinal disc. Magnetic resonance imaging was chosen to determine this influence on the position of the germinal disc. It was found that eggs placed horizontally for long periods of time befor!
e scanning had significant changes in the positions of their germinal discs compared with those of eggs scanned minutes after positioning. The position of the germinal disc in eggs, minutes after horizontal positioning, deviated 14.7 +/- 0.6 mm from the maximum vertical plane of the egg (zero position) in the z-direction; eggs scanned after 96 h of horizontal positioning showed a deviation of only 4.9 +/- 1.6 mm. The x-axis also exhibited changes in the position of the germinal disc over time. Immediately after horizontal positioning, the eggs showed a deviation of 0.4 +/- 0.4 mm in the x-direction, whereas the deviation after 96 h was 2.9 +/- 0.5 mm. These results show that horizontal positioning of the egg hours before the measurement is necessary.

The structure for the development of a fuel assembly design with reduced sodium void achieved by the use of the moderating material ZrH is investigated. In the study the sodium void effect, as well as the major feedback coefficients are analyzed. Besides the feedback coefficients, the influence on the operational parameters like neutron flux distribution, power distribution, and burnup distribution is investigated for the different possibilities of arranging the moderating material in the fuel assembly. Additionally, the fuel cycle parameters – breeding and minor actinide production – are analyzed. For a first evaluation of the behavior during transients the influence of temperature changes in the ZrH is studied.