Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Durch den Einsatz neuer bildgebender Messverfahren werden strukturierter Mehrphasenreaktoren hydrodynamisch charakterisiert und Strömungsdaten aus sonst optisch unzugänglichen Strukturen, wie keramischen Monolithen und Schäumen sowie metallischen zellularen Packungen vor allem unter prozessnahen Betriebsbedingungen gewonnen.

Visionäres Ziel der Forschung ist es, neue Reaktorkonzepte für energie- und ressourceneffiziente chemische Prozesse auf Basis prozess- und reaktionsangepasster strukturierter Mehrphasenapparate zu entwickeln. Im Rahmen der HGF-Energie-Allianz werden dazu umfassende Grundlagenarbeiten im Bereich der Reaktionsaufklärung, zur Herstellung neuer funktionalisierter Strukturelemente, auf den Gebieten Mehrphasenströmungsmechanik und Mehrphasenthermodynamik, sowie in der numerischen Simulation und der Prozessmesstechnik durchgeführt.

The time evolution of vector meson spectral functions is studied within a BUU-type transport model. Applications focus on ρ and ω mesons being important pieces for the interpretation of the dielectron invariant mass spectrum. Since the evolution of the spectral functions is driven by the local density, the inmedium modifications turn out to compete, in this approach, with the known vacuum contributions.

Uranium can be released into the natural environment especially from mining areas by weathering, erosion and anthropogenic activities as well as by nuclear incidents and thus represents a hazard potential for humans. New supramolecular complexing agents with N, O, S donor function are developed for the use in nuclear field and environmental protection to separate the metals of the d- and f-block and thus to clean contaminated areas. An essential basic component of these new organic ligands are Schiff bases.
In this study the complexation of uranium(VI) with Schiff bases N-benzylideneaniline (NBA), 2-(2-hydroxybenzylidenamino)phenol (HBAP) and alpha-(4-hydroxyphenylimino)-p-cresol (HPIC) was investigated in alcoholic solution using the UV-vis spectroscopy and time-resolved laser fluorescence spectroscopy with ultrashort laser pulses (fs-TRLFS). Through the change of the absorption or emission properties of organic ligands can be observed the complexation with uranium(VI).
The complexation of uranium(VI) with NBA was observed by a hypsochromic shift in the NBA band to 237 nm with the UV-vis spectroscopy. Investigations with the ligand HBAP show a bathochromic shift to 281 nm. The UV-vis absorption spectra of HPIC with uranium(VI) show no spectral shift, but a decrease in intensity of the double band at 283nm and 332 nm in comparison to the free ligand. All three ligands form complexes MLx with more ligand molecules (x=2,3).
The fs-TRLFS as a sensitive speciation technique was used to determine the luminescence properties of formed complexes in the uranium(VI)-NBA, uranium(VI)-HBAP and uranium(VI)-HPIC systems. The emission signals had a hypsochromic, bathochromic and hypsochromic shift in comparison to the emission maxima of the uncomplexed ligand. This fs-TRLFS investigation opens up the possibilities for the determination of very short-lived complex species via the fluorescence of the organic compounds by delocalized -electron systems. The calculation of corresponding complex formation constants is shown and discussed.

Fission gas retention or release has a critical impact on the function of advanced nuclear materials. Helium trapping in, and release from, radiation defects induced by neutrons and by α decay in YSZ (yttria-stabilized zirconia) is experimentally simulated using synchronized Zr+ and He+ dual ion beam irradiation. The measured damage profiles consist of two peaks which agree well with the calculated profiles of implantation induced excess point defects. This special implantation related effect has to be carefully considered in the evaluation of experimental investigations which simulate isotropic irradiation effects such as α decay. First-principles calculations show that helium is energetically favorable to be trapped by Zr vacancies in YSZ. Implanted helium alone in YSZ is accumulated in undesirable helium bubbles and results in local surface swelling and lift-off. However, under dual beam irradiation helium is released from vacancy defects and is out-diffused at room temperature. Helium is mobilized by a vacancy-assisted trapping/detrapping mechanism induced by the simultaneous Zr+ ion implantation. This behavior avoids the deleterious helium bubble formation and contributes to the suitable application characteristics of YSZ which result in its excellent radiation hardness.

Four basic two-dimensional (2D) plaquette configurations are introduced with onsite cubic nonlinearities, which may be used as building blocks for 2D PT-symmetric lattices. For each configuration, a dynamical model is developed and its PT symmetry is examined. The corresponding nonlinear modes are analyzed starting from the Hamiltonian limit, with zero value of the gain-loss coefficient. Once the relevant waveforms have been identified (chiefly, in an analytical form), their stability is examined by means of linearization in the vicinity of stationary points. This reveals diverse and, occasionally, fairly complex bifurcations. The evolution of unstable modes is explored by means of direct simulations. In particular, stable localized modes are found in these systems, although the majority of identified solutions is unstable.

This is a call for contributions to a special issue of Journal of Physics A: Mathematical and Theoretical dedicated to quantum physics with non-Hermitian operators. The main motivation behind this special issue is to gather together recent results, developments and open problems in this rapidly evolving field of research in a single comprehensive volume. We expect that such a special issue will become a valuable reference for the broad scientific community working in mathematical and theoretical physics. The issue will be open to all contributions containing new results on non-Hermitian theories which are explicitly PTsymmetric and/or pseudo-Hermitian or quasi-Hermitian. The main novelties in the past years in this area have been many experimental observations, realizations, and applications of PT symmetric Hamiltonians in optics and microwave cavities. We especially invite contributions on the theoretical interpretations of these recent PT-symmetric experiments and on theoretical proposals for new experiments.

The beat time associated with the energy transfer between two coupled oscillators is dictated by the bandwidth theorem which sets a lower bound. We show, both experimentally and theoretically, that two coupled active LRC electrical oscillators with parity-time (PT) symmetry bypass the lower bound imposed by the bandwidth theorem, reducing the beat time to zero while retaining a real valued spectrum and fixed eigenfrequency difference. Our results foster design strategies which lead to (stable) pseudo-unitary wave evolution, and may allow for ultrafast computation, telecommunication, and signal processing.

New results are reported on two PT-symmetry topics. In the first part of the talk, an entanglement related quantum state discrimination scheme is described which is based on the fine-tuned Naimark-dilation of a PT-symmetric subsystem in 2D Hilbert space. (Work together with Carl M. Bender, Dorje C. Brody and Boris F. Samsonov). In the second part of the talk, the stability properties of nonlinear PT-symmetric 2D
plaquettes are discussed. Specific emphasis is laid on the role of the nonlinear terms in shifting the PT-threshold of associated linear systems. This part of the talk is based on common work with Panayotis Kevrekidis, Kai Li and Boris Malomed (arXiv:1204.5530[quant-ph]) as well as on newer results going beyond the findings in this e-print.

Four basic two-dimensional (2D) plaquette configurations are introduced with onsite cubic nonlinearities, which may be used as building blocks for 2D PT-symmetric lattices. For each configuration, a dynamical model is developed and its PT symmetry is examined. The corresponding nonlinear modes are analyzed starting from the Hamiltonian limit, with zero value of the gain-loss coefficient. Once the relevant waveforms have been identified (chiefly, in an analytical form), their stability is examined by means of linearization in the vicinity of stationary points. This reveals diverse and, occasionally, fairly complex bifurcations. The evolution of unstable modes is explored by means of direct simulations. In particular, stable localized modes are found in these systems, although the majority of identified solutions is unstable. Based on arXiv:1204.5530.

The presentation consists of two parts. In the first part, recent results on PT-symmetric LRC circuits are reported, including the hidden special representations of the linear parity involution P and the antilinear time reversal operation T. Analytical formulae for the evolution time contraction (so called tachistochrone solutions) and dilation are presented. The simple underlying phase-shift-versus-amplitude-enhancement mechanism is explained. (Partially based on common work with Hamid Ramezani, Joseph Schindler, Fred Ellis, and Tsampikos Kottos published in Phys. Rev. A 85, (2012), 062122.)

In the second part of the talk, it is shown that the mathematical investigation of the symmetry structures hidden in gauged PT-symmetric systems indicates on possible realizations of such setups as Jaynes-Cummings type models. The latter ones are used e.g. to describe multilevel artificial atoms in cavity QED. A question that naturally arises is whether PT-symmetric extensions of cavity QED might become feasible experimentally and how to possibly realize them. (Partially based on common work with Sergii Kuzhel published in J. Phys. A 43, (2010), 392002.)

In 1998, 1999 it was shown by Bender and collaborators that there are certain classes of Hamiltonians which at a first glance seem not selfadjoint in Hilbert spaces, but which nevertheless are having real spectra. Examples are Hamiltonians of the type H=p2+x2(ix)μ. For parameters μ ∈ [0,1] these Hamiltonians have positive real eigenvalues with square integrable eigenfunctions defined over the real line. It was found that the reality of the eigenvalues was connected with an underlying PT-symmetry of the Hamiltonians and their eigenfunctions, i.e. the systems are in a sector of unbroken PT-symmetry. There exist other sectors like μ ∈ (-1,0) where this PT-symmetry is spontaneously broken: although the Hamiltonian remains PT-symmetric, part of its eigenfunctions loose PT-symmetry and the corresponding eigenvalues are coming in complex conjugate pairs. A PT phase transition occurs at μ=-0.
It turns out that the PT-symmetry of the Hamiltonian H induces a natural indefinite metric structure in Hilbert space and that H, instead of being selfadjoint in a usual Hilbert space (with positive definite metric), is selfadjoint in a generalized Hilbert space with an indefinite metric --- a so called Krein space. Similar to time-like, space-like and light-like vectors in Minkowski space a Krein space has elements of positive and negative type as well as neutral (isotropic) elements. Moreover in analogy to passing via Wick-rotation from Minkowski space to Euclidian space, in the sector of exact PT-symmetry there exists an operator which allows to pass from a Krein space description of the system to a description in a Hilbert space with a highly nontrivial metric operator. At the PT phase transition point this operator becomes singular and the corresponding mapping breaks down.
In the talk, on an introductory level, some of the basic structures of PT-symmetric quantum mechanics and their relation to corresponding Krein-space setups are sketched. For gaining some rough intuition, the facts are illustrated by simple matrix models. The richness of the systems is demonstrated on the simple example of a PT-symmetric two-mode Bose-Hubbard model, PT-symmetric brachistochrone setups and gain-loss-balanced PT-symmetric optical waveguide systems.

In recent work by Bender, Brody, Caldeira and Meister it was shown that the brachistochrone solution of PT Quantum Mechanics (PTQM) can be used to orthogonalize a set of two originally non-orthogonal quantum states. The still remaining draw-back of the proposed technique is in its use of a non-Hermitian PT-symmetric Hamiltonian to achieve the PTQM brachistochrone evolution --- a Hamiltonian which up to now for quantum systems is beyond experimental reach.

We demonstrate that the Bender-Brody-Caldeira-Meister approach can be naturally extended into a higher-dimensional Hilbert space. This allows to interpret the PTQM setup as a very special subsystem of a larger Hermitian system. Moreover we show that this extension can be connected with the standard text-book scheme of unambiguous quantum state discrimination. Technical details of the extension procedure are discussed and ways toward a time-optimal unambiguous state discrimination scheme are indicated.

The identification of the molecular interactions occurring at solid-liquid interfaces is of great signifi-cance to the assessment of the migration behavior of heavy metal ions in the environment. In particu-lar, the dissemination of radioactive metals, such as uranium (U), in soils and aquifers is determined by sorption and desorption processes at mineral surfaces.
Information of the molecular structures of the sorption complexes can be obtained by vibrational spec-troscopy. The application of the Attenuated Total Reflection (ATR) technique in combination with a flow cell experiment potentially provides insights into the dynamic processes occurring during com-plex formation at the solid-liquid interface [1]. This technique allows an on line monitoring of the sorption processes with a time resolution in the sub minute range and under selective conditions ap-proaching near environmental relevant conditions [2,3]. In particular, the variation of selective ex-perimental parameter, e.g. pH, c(UO22+) or pCO2, and the selection of modified solid phases are ex-pected to generate selective spectral changes which potentially facilitate the identification of molecular features.
In this work, we provide vibrational spectroscopic data from binary and ternary U(VI) surface species on iron oxide mineral phases in the absence and presence of atmospherically derived CO2¸ respec-tively. In a comparative study of two iron oxide phases, namely ferrihydrite and maghemite, the dif-ferent character of sorption complexes can be spectroscopically identified. From the frequency of the ν3(UO2) mode, the formation of different types of surface species, that is inner- and outer-sphere com-plexes, can be derived. This is corroborated by time-resolved spectra of the sorption step and of the subsequently induced desorption process. From the time courses of these reactions, a first assignment to the different types of surface species predominantly formed at the different mineral surfaces can be given.
Results from the ternary sorption systems (U(VI)/atm. CO2/iron oxide phase) demonstrate signifi-cantly different affinities of the carbonate ions to the different mineral phases. While atm. CO2 forms binary and ternary sorption species on ferrihydrite in the absence and presence of U(VI), respectively, only ternary uranyl carbonato species were observed at the maghemite-water interface.

[1] Voegelin, A. et al. (2003) Environ. Sci. Technol. 37, 972-978.
[2] Müller, K. et al. (2012) Geochim. Cosmochim. Acta 76, 191-205.
[3] Foerstendorf, H. et al. (2012) Journal of Colloid and Interface Science 377, 299-306.

Since providing optical resolution on the nanometer length scale, scanning near-field optical microscopy (SNOM) has turned out to be a powerful technique to investigate the optical properties of perovskites and nanostructured semiconductors, e.g. having a buried doping profile. Using a scattering-type-SNOM (s-SNOM) combined with a tunable free-electron laser (FEL) light source operating in the mid- and far-infrared regime we investigated the electronic structure of single InAs quantum dots (Q-dots) that were capped with a 70 nm thick GaAs layer. Spectroscopic near-field scans on individual Q-dots clearly identified two inter-sublevel transitions at 85 meV and 120 meV, providing optical contrast to the surrounding GaAs substrate. As a consequence the room temperature linewidth of these transitions measure 5 - 8 meV only, hence being significantly smaller as compared to the inhomogeneously broadened peaks resulting from integral spectroscopic analysis. Moreover, spatially scanning the s-SNOM tip at fixed excitation energies allowed mapping the spatial distribution of such buried quantum dots.

Providing an optical resolution on the nanometer length scale, scanning near-field optical microscopy (SNOM) turned out to be a capable technique to investigate the optical properties of perovskites, buried semiconductors and single quantum dots. Thereby, the line-width of the observed resonances (5 - 8 meV) is significantly smaller than the inhomogeneously broadened line-width of other spectroscopic measurements.
Using a scattering-type-SNOM (s-SNOM) combined with a tunable free-electron laser (FEL) light source we investigated the electronic structure of single InAs quantum dots, capped under a 70 nm thick GaAs layer. Spectroscopic near-field scans clearly identified two inter-sublevel transitions within the quantum dots at 85 meV and 120 meV, contrasting from the surrounding medium. Moreover, spatially scanning the s-SNOM tip at fixed excitation energies allowed mapping the 3D distribution of such buried quantum dots.

PIConGPU ist ein Particle-in-Cell (PIC) Code fur Grakprozessoren (GPUs). Der Particle-in-Cell Algorithmus ist ein zentraler Algorithmus in der Plasmaphysik. Er erlaubt die Dynamik eines Plasmas, die Bewegung der Elektronen und Ionen, auf Basis der Maxwell-Gleichungen voll relativistisch zu beschreiben.
Das PIConGPU Projekt integriert die 3D-Physiksimulation, eine Online-Visualisierung zur interaktiven Auswertung sowie eine einfache Parametrisierung der Simulationsläufe. Die Umsetzung erfolgte so generisch, dass PIConGPU auch als Grundlage fur weitere GPU-Simulationen dienen kann. Um komplexe physikalische Probleme simulieren zu können ist die Skalierbarkeit auf massiv-parallele GPU-Cluster ausgelegt.

We present the validation of the key physics features of PIConGPU according to known physical scenarios. For this, we evaluate the evolution of position and energy errors for analytically known particle trajectories and the numerical dispersion of a Gaussian wavepacket over time.
Furthermore, we present a new approximation within the particle push step.
This allows for a comparison of the established CPU/FORTRAN code ILLUMINATION with the GPU/C++ code PIConGPU for selected physical test cases in laser-electron acceleration.

With decreasing layer thicknesses e.g. in semi-conductor devices, there is a strong need for increasing depth resolution in analytical methods used for the determination of elemental depth profiles. Standard RBS using Si detectors has a depth resolution of about 5 – 15 nm mainly depending on incidence angle and energy resolution. The traditional and high-tech solution is to use a magnetic spectrometer or a time-of-flight system to improve the energy resolution of the detector and thus the depth resolution.
At HZDR, a Browne-Buechner type magnetic spectrometer is available for high depth resolution measu¬rements with sub-nm depth resolution in a near-surface region  5 nm. However, such a system is expensive and requires complicated operation. In addi¬tion, the small energy window of the magnetic spectrometer limits the measurement to one element and about 10 nm depth range. Currently we are implementing a low-tech detection system that uses improvements in amplifiers and cooling to improve the energy resolution of standard semiconductor detectors to sub-10 keV values. The capabilities of such a system are described and compared to the magnetic spectrometer.

Swift heavy ions (SHI) of MeV–GeV energy lead to the creation of nanometric surface structures as well as modifications in the bulk along the ion penetration depth. Recently, similar surface modifications have been observed for the impact of individual slow highly charged ions (HCI). Non-amorphizable ionic-halide single crystals, like KBr, CaF2 and BaF2, are considered as the most intensively studied materials after irradiation with HCI.
In this contribution we study the creation of surface nanostructures in an amorphizable material, namely SiO2 quartz after irradiation with slow highly charged Xe ions from the Electron Beam Ion Trap at Helmholtz Zentrum Dresden-Rossendorf and swift xenon ions from Universal Linear Accelerator at GSI in Darmstadt. After irradiation at room temperature, the crystals were investigated by scanning force microscopy. For both SHI and HCI, the created nanostructures exhibit the shape of hillocks. Moreover UV–VIS spectroscopy was performed to identify the defects created by ion irradiation at high fluence. The results are discussed in terms of the creation mechanisms driven by the dependence on both potential and kinetic energies of the ions.

Some personal remarks on scientific poetry in general are presented together with a little poetry collection, in particular about the positron and its fate.

In the last decade focused ion beams (FIB) became an irrecoverable instrument in research and industry. Sample preparation, local ion implantation and ion analysis are the main application topics. Most of the systems are equipped with a gallium liquid metal ion source (LMIS). But, modern trends in nanotechnology require more extended properties like variable ion species, non-contaminating milling at higher rates or higher lateral resolution in the field of ion microscopy.
In this contribution the status and application of new source concepts including prototypes will be reviewed in particular high current gas sources (ECR, ICP) for effective high rate milling, ion trap sources providing highly charged ions or used for SIMS applications as well as gas field ion sources for high resolution ion microscopy in the sub-nm range. Furthermore the use of alloy liquid metal ion sources and its characterization for mass separated FIB systems and ToF-SIMS applications will be presented.
New trends and prospective developments in FIB instrumentation will be discussed.

Der Mangel an kommerziell verfügbarer Messtechnik zum Einsatz in heißen, nichtransparenten Fluiden erschwert Strömungsmessungen in einer Reihe von technologischen Prozessen, in denen Flüssigmetalle oder Halbleiterschmelzen eine wichtige Rolle spielen. Ultraschall-methoden erscheinen für derartige Anwendungen äußerst attraktiv, da sie in der Lage sind, quantitative Messdaten aus opaken Schmelzen zu liefern. Dieser Artikel gibt einen Überblick über internationale Forschungsaktivitäten der letzten 3 Jahrzehnte, die auf eine Nutzung dieser Methode für Strömungsmessungen in Metallschmelzen abzielen.

The detection of pharmaceuticals in drinking water and food becomes of increasing relevance. Currently there are only few methods available allowing their reliable detection. These methods are mostly highly complicated and time consuming. Therefore, new techniques are required which enable a fast and easy detection of traces of pharmaceuticals. Biosensors based on natural self-organising biomolecules may provide new approaches for a highly specific detection of pharmaceuticals.

Aim of the presented project is the development of such a sensory layer. Our sensory device consists of S layer proteins, aptamers and fluorescence dyes. The S layer proteins serve as binding matrix, aptamers are used as receptors and fluorescence dyes represent our transducer system.
S layer proteins are structural proteins found in numerous bacteria and almost all archaea. They are able to self-assemble in aqueous solutions and on surfaces forming highly ordered crystalline structure with different symmetries. The proteins expose many COOH and NH2-groups that can be modified and functionalized. Aptamers are short DNA or RNA oligonucleotides which are able to reversibly bind specific analytes due to their 3D-structure. For the optical signal of our sensory layer we use two fluorescence dyes which are able to perform a fluorescence resonance energy transfer (FRET).
This effect is very sensitive and is affected by its environment. In our assembly, fluorescence dyes and aptamers are very close to each other. It is expected that a binding of an analyte to the aptamer will also affect FRET.

Our experiments prove a FRET between two fluorescence dyes linked to S layer proteins in solution and on a surface. In addition, the Anti-Thrombin-aptamer, used as model aptamer, was successfully coupled to S-layer proteins without losing its function. These results provide the basis for the intended sensor concept.

Sr-90 is a long-lived radionuclide (T(1/2) = 28.6 a), produced as a by-product in nuclear power plants. Due to its chemically similarity to calcium, it follows the food chain from environment (e.g. aquatic systems and soil) to fauna and human in case of release in the biosphere. Strontium can be, as well as calcium, incorporated in bones. Stable isotopes of strontium might not be harmful, but radioactive strontium can lead to bone disorders and diseases, including leukaemia[1].
Calixarenes and their functionalised derivatives are research subjects in the development of extracting agents, transporters, stationary phases[2] or biosensors. We used modified calixarenes, including derivatives having carbonyl binding sites, for the extraction of strontium[3] by means of a liquid-liquid extraction in a chloroform / water system. As a simulated contamination solution with Sr-90, the aqueous strontium phase was traced using the short-lived radionuclide Sr-85 (T(1/2) = 64.9 d), which was produced and purified at the in-house 18 MeV-cyclotron[4].
Under alkaline conditions, strontium extraction yields of >(90±4)% were obtained. Furthermore, the impact of inorganic and organic impurities, competing ions like sodium, calcium, acetate or tartaric acid, to the extraction performance was studied. The used carboxy-modified calixarenes are highly potent and selective extracting agents towards strontium, under conditions near to nature (e.g. synthetic groundwater).

The authors gratefully thank the German Federal Ministry of Education and Research (BMBF) for financial support of this study (project no. 02NUK014).

[1] Wallova, G., N. Kandler, and G. Wallner, Monitoring of radionuclides in soil and bone samples from Austria. Journal of Environmental Radioactivity, 2012. 107(0): p. 44-50.
[2] Wendel, V., Neuartige Wirt-Gast-Komplexe basierend auf Cycloheptatrienbausteinen, Mathematisch-Naturwissenschaftliche Fakultät I 1998, Humboldt-Universität zu Berlin: Berlin.
[3] Casnati, A., et al., New Efficient Calixarene Amide Ionophores for the Selective Removal of Strontium Ion from Nuclear Waste: Synthesis, Complexation, and Extraction Properties. J. Am. Chem. Soc., 2001. 123: p. 12182-12190.
[4] Mansel, A., et al., Production of Sr-85 at a 18 MeV-cyclotron and purification for geochemical investigations, 2012. (submitted)

In recent years detection of pharmaceuticals in drinking water and food becomes increasing relevance. Nevertheless, most recently used methods are complex and time consuming. Thus, new solutions are required allowing a fast and their reliable detection of pharmaceuticals.

Therefore we are developing sensory layers which are able to specifically detect small amounts of pharmaceuticals. This sensory device will consist of surface(S)-layer proteins, aptamers and fluorescence dyes.
S-layer proteins are structural proteins found in numerous bacteria and archaea. They have the ability to self assembly in aqueous solutions and on surfaces building highly ordered paracrystalline structures. On the surface of such a layer different functional groups are available which can be modified without the loss of its paracrystalline structure. Hence S-layer proteins are useful binding blocks for the defined arrangement of aptamers and fluorescence on an area of a few nanometers. Thereby aptamers serve as receptor for specific analytes and two fluorescence dyes allowing a FRET a signal transducer system.

In first experiments we coupled the model aptamer, Anti-thrombin-aptamer, on S-layer proteins and proved its functionality after being linked to the protein. Furthermore we modified S-layer proteins with a FRET pair containing a green and red fluorescence dye and succeed to detect a FRET between those S-layer linked fluorescence dyes.

In subsequent work we will assemble the components, aptamers and fluorescence dyes, on the S layer proteins. The aptamer will bind the specific analyte. It is supposed that the binding will affect the fluorescence dyes and disturb FRET due to their close proximity to each other. As a result a sensory layer is created which uses the high specifity of aptamers in combination with the sensitivity of fluorescence dyes, thus enabling the easy and reliable detection of analytes by an optical signal.

Self-atom mixing induced by Gallium (Ga) implantation in crystalline and amorphous germanium (Ge) is investigated using an isotopic multilayer structure of alternating 73Ge and natGe layers grown by molecular beam epitaxy. The distribution of the implanted Ga atoms and ion-beam induced depth-dependent mixing was determined by means of the secondary ion mass spectroscopy (SIMS). The position and form of the implanted Ga peak is very similar in the amorphous and crystalline Ge and can be reproduced accurately by computer simulations based on binary collision approximation (BCA), whereas the ion-beam induced self-atom mixing strongly depends on the state of the Ge structure. The data from SIMS-measurements reveal a stronger mixing in the crystalline than in the amorphous Ge. Atomistic simulation based on BCA can reproduce the experimental data only if unphysically low displacement energies are assumed. The low displacement energies deduced within the BCA approach are confirmed by experiments with mixing induced by silicon implantation. The disparity observed in the ion-beam mixing efficiency of crystalline and amophous Ge indicates different dominant mixing mechanisms. We propose that self-atom mixing in crystalline Ge is mainly controlled by radiation enhanced diffusion during the early stage of mixing before the crystalline structure turns into an amorpous state, whereas in an already amoprhous state self-atom mixing is mediated by cooperative diffusion events.

Molecular dynamics simulations using Stillinger-Weber-type interatomic potentials were performed in order to investigate ion-beam mixing by 400 eV self-ion implantation at different fluences and temperatures. In general the magnitude of mixing in an amorphous structure was found to be higher than in its crystalline counterpart. This supports the results of earlier calculations (K. Nordlund et al., J. Appl. Phys. 83 (1998) 1238). The trends observed in our simulations are compared to our experimental results on ion beam mixing in crystalline and amorphous isotopically modulated Si and Ge multilayer structures.

The hydrodynamic flow behaviour of the gas phase in a slurry bubble column was investigated using ultra-fast electron beam X-ray tomography, which provides images at temporal resolution of 7000fps and spatial resolution of 1 mm. Bubble coalesces and breakup regime was observed with the addition of wettable solids particles. The effect of solid volumetric concentration (0 ≤ Cs ≤ 0.36) on the radial distribution of gas holdup in a slurry bubble column was established at different scanning heights (30, 60, 95 cm) and at different superficial gas velocity (0.02 ≤ UG ≤ 0.05 m/s).

Nanostructure evolution is a common phenomenon occurring during ion and neutron irradiation as well as during thermal treatment. It is characterized by diffusion and reaction processes that can cause the formation of embedded nanoclusters which often leads to a modification of the materials properties. Multiscale modeling can substantially contribute to a better understanding of nanostructure evolution. Atomic-scale molecular dynamics and kinetic Monte Carlo simulations are applicable on relatively small length and time scales whereas coarse-grained methods such as object kinetic Monte Carlo simulations and rate theory can be used on scales more easily accessible by experiments. The latter methods need a number of input parameters. One of the most important is the free binding energy of a monomer to a cluster which can be hardly obtained by experimental investigations but can be provided by atomistic simulations. The fundamental quantity that must be determined is the free formation energy of the clusters which consists not only of the formation energy but also of vibrational and configurational contributions. The focus of the present work is on the evaluation of the configurational part of the free formation energy. The simple example of coherent Cu nanoclusters in bcc-Fe is considered. First, at T=0 the most stable cluster configurations are determined by Metropolis Monte Carlo simulations and their formation and binding energies are calculated. Second, a modified Wang-Landau Monte Carlo method is employed in order to determine the contribution of all possible geometrical configurations of nanoclusters to the free formation energy. Finally, the total and monomer free binding energies are calculated. It is shown that even at moderate temperatures such as 600 K the configurational contributions to the free formation energy cannot be neglected. The calculation scheme applied in this work can be extended to other types of embedded nanoclusters in solids. The presented method should be especially important for nanoclusters with relatively low formation energies. Further investigations are required in order to estimate the vibrational contribution to the free formation energy and to perform a comparison with the configurational part.

The Emergency Core Coolant System has to remove the decay heat in case of a Loss of Coolant Accident (LOCA). Sump strainers are mounted at the pump inlets to retain particles and fibrous insulation material during recirculation. However, fiber fragments, debris or corrosion products could initiate a critical head loss on strainers. Problems of insulation materials NUKON® (fiberglas) or CalSil and aluminum may appear if containment spray systems using alkaline additives are installed. In such cases, dissolution / precipitation reactions resulting from insulation materials were observed, which increase the risk of sump screen blockage. In German NPPs, there are no containments spray systems, and insulation consists of more resistant materials like mineral wool (rock wool) and stainless steel. However, large scale experiments from AREVA have shown that sump screen clogging may be initiated by boric acid containing leakage jets directed towards galvanized containment internals.
The down-scaled test facility KorrVA was designed for generic corrosion investigations of galvanized steel under post-LOCA conditions. About 90 experiments were carried out with galvanized steel gratings and galvanized steel coupons in boric acid media in order to determine corrosion mechanisms depending on different experimental conditions like temperature, water chemistry and hydrodynamic conditions (flow impact, simulated by different nozzles). Changes of the chemical composition of the circulating media were determined by chemical analysis and general parameters such as conductivity and pH were measured. Galvanized samples and fiber beds were examined after each experiment by means of photographic methods, light-microscopy and different kinds of chemical analysis.
The chemical analyses of the deposits on fiber beds showed that the clogging is predominantly caused by the corrosion products of iron and lower amounts of zinc compounds. Thus, the corrosion of galvanized steel in boric acid is explained by a mechanism starting at the surface with fast Zn dissolution but without formation of solid corrosion products. The Zn corrosion is mainly influenced by pH and concentration of zinc ions in the coolant. Since boric acid/borate acts as a buffer system, the pH value increases faster at the beginning and reaches up to 6.8 in case of sufficient solved Zn, generated by corrosion. A local (flow induced) corrosion occurs if a fast liquid flow strikes the top face of a horizontal galvanized coupon. Precondition for this process is a sufficiently low pH of solution in connection with a high hydrodynamic impact of the liquid flow on the corroding surface.
For a limited period, the risk of strainer clogging due to formation of corrosion products of galvanized steel may be reduced by an additional amount of submerged Zn or changing the coolant chemistry by alkaline additions. These two possibilities were investigated by test series using galvanized steel coupons. The addition of borax seems to be the most effective method to reduce the corrosion rate and the risk of sump screen clogging.
The results were validated with galvanized gratings in a further test series since the flow conditions of a liquid jet on flat coupons significantly differ from those on gratings. Three different regions of corrosion attack were noticed on these real samples contributing to the increase of solved Zn. But the Zn dissolution should be limited since it may lead to undesired secondary effects by deposition of sparingly soluble borate salts depending on coolant temperature.

Die Aufgaben des Arbeitspaketes 2.5 des Projektes „Energieeffiziente chemische Mehrphasenprozesse“ werden kurz vorgestellt. Das Potential der Energieeffizienzverbesserung der Oxidation von Iso-butan mit Sauerstoff zu tert.-Butylhydroperoxid wird angesichts der Technologie mikrostrukturierter Reaktoren evaluiert. Ein vereinfachter Mechanismus der Reaktion wird angegeben. Darauf aufbauend wird das weitere Vorgehen zur Reaktionsaufklärung im Rahmen des Projekts skizziert, sowie die Verknüpfungen des Arbeitspaketes 2.5 mit anderen Arbeitspaketen aufgezeigt.

In a high temperature pebble-bed reactor, carbonaceous dust is conveyed by the cooling carrier phase and eventually deposits in the primary circuit of the reactor. The numerical dispersion and deposition of Lagrangian aerosol particles in a turbulent flow is here investigated. The flow field is simulated using a Reynolds-averaged Navier-Stokes method. A Langevin equation is implemented to reproduce the turbulent dispersion of particles. Results of the deposition experiments in a vertical and horizontal square duct flow show good agreement with recently published experimental data.

Depth resolved positron Doppler broadening spectroscopy was used to investigate the effect of neutron irradiation (simulated by self-implantation with Fe ions) on the defect structure of Fe-Cr alloys with different Cr content (2.5at% - 12at%). Different defect situations depending on the Cr content were found for the alloys.

In this presentation the state of the ongoing gas/graphite transport experiments is presented. In the frame of the EU projects THINS and ARCHER two small-scale test facilities were designed to study the particle transport in complex geometries. Background motivation is the carbonaceous dust issue in the primary circuit of the High Temperature Reactor. It is a safety issue to explore the deposition and resuspension behaviour of such graphite particles to assess the transport behaviour during loss of coolant accidents. The first facility is called Gas Particle Loop and it is used to study the particle deposition and resuspension behaviour in a turbulent square duct flow field. The turbulent flow field was recorded using a Particle Image Velocimetry system. Furthermore, single particle as well as multilayer particle deposition and resuspension experiments were conducted to generate a data basis for the understanding of the particle transport behaviour. The second facility is called Pebble Bed Loop was specially design to generate a particle laden turbulent flow through a pebble bed. The test section is designed to fit into a Positron Emission Tomography (PET) scanner situated at the Reactive Transport Division in Leipzig. The time and space resolved formation of the particles was recorded by means of this PET scanner. The data presented can be used for CFD code development.

The presentation is a short-course lecture that introduced the current state of the art in multiphase flow measurement techniques. Sensors and measurement techniques, which are intoduced are: electrical and optical needle probes, wire-mesh sensors and tomography techniques. Beside the physical measuring and sensor construction principles the presentation addresses the topic of data processing for multiphase flow measurements.

ZnO thin films were grown by pulsed laser deposition on three different substrates: sapphire (0 0 0 1), MgO (1 0 0) and fused silica (FS). The structure and morphology of the films were characterized by x-ray diffraction and scanning electron microscopy and defect studies were carried out using slow positron implantation spectroscopy (SPIS). Films deposited on all substrates studied in this work exhibit the wurtzite ZnO structure and are characterized by an average crystallite size of 20-100 nm. However, strong differences in the microstructure of films deposited on various substrates were found. The ZnO films deposited on MgO and sapphire single-crystalline substrates exhibit local epitaxy, i.e. a well-defined relation between film crystallites and the substrate. Domains with different orientation relationships with the substrate were found in both films. On the other hand, the film deposited on the FS substrate exhibits fibre texture with random lateral orientation of crystallites. Extremely high compressive in-plane stress of sigma similar to 14 GPa was determined in the film deposited on the MgO substrate, while the film deposited on sapphire is virtually stress-free, and the film deposited on the FS substrate exhibits a tensile in-plane stress of sigma similar to 0.9 GPa. SPIS investigations revealed that the concentration of open-volume defects in the ZnO films is substantially higher than that in a bulk ZnO single crystal. Moreover, the ZnO films deposited on MgO and sapphire single-crystalline substrates exhibit a significantly higher density of defects than the film deposited on the amorphous FS substrate.

In this presentation the state of the ongoing gas/graphite transport experiments is presented. In the frame of the EU THINS project a small-scale test facility was designed to study the particle transport in turbulent duct flows. Background motivation is the carbonaceous dust issue in the primary circuit of the High Temperature Reactor. It is a safety issue to explore the deposition and resuspension behaviour of such graphite particles to assess the transport behaviour during loss of coolant accidents. The turbulent flow field was recorded using a Particle IImage Velocimetry system. Furthermore, single particle as well as multilayer particle deposition and resuspension experiments were conducted to generate a data basis for the understanding of the particle transport behaviour. This data basis can be used for CFD code development.

Gas hold-up and bubble size distribution in a slurry bubble column (SBC) were measured using the advanced non-invasive ultrafast electron beam X-ray tomography technique. Experiments have been performed in a cylindrical column (DT = 0.07 m) with air and water as the gas and liquid phase and spherical glass particles (dP = 100 µm) as solids. The effects of solids concentration (0 ≤ Cs ≤ 0.36) and superficial gas velocity (0.02 ≤ UG ≤ 0.05 m/s) on the flow structure, radial gas hold-up profile and approximate bubble size distribution at different column heights in a SBC were studied. Bubble coalescence regime was observed with addition of solid particles, however, at higher solids concentrations, larger bubble slugs were found to break-up. The approximate bubble size distribution and radial gas hold-up was found to be dependent on UG and Cs. The average bubble diameter calculated from the approximate bubble size distribution was increasing with increase of UG. The average gas hold-up was calculated as a function of UG and agrees satisfactorily with previously published findings. The average gas hold-up was also predicted as a function of Cs and agrees well for low Cs and disagrees for high Cs with findings of previous literature.

Der Vortrag stellt die neue Helmholtz-Energie-Allianz Energieeffiziente Chemische Mehrphasenprozesse vor.

Bei Kühlmittelverluststörfällen in Kernreaktoren wird die Kernkühlung unter anderem durch Notkühleinspeisung (emergency core cooling, ECC) in den kalten oder heißen Strang des Primärkreislaufs unterstützt. Hierbei wird zusätzliches Kühlmittel aus Notkühlreservoirs in die mit dem Reaktordruckbehälter (RDB) verbundenen Hauptkühlmittelleitungen eingespeist. Ein sicherheitsrelevantes Problem dieser Maßnahme sind thermomechanische Belastungen der Reaktordruckbehälterwand durch plötzliche Abkühlung. Das stark unterkühlte Notkühlwasser vermischt sich in der Hauptkühlmittelleitung mit dem dort stehenden Sattwasser, dessen Höhe in der Leitung durch den aktuellen RDB-Füllstand und dessen Sättigungstemperatur durch den aktuellen Systemdruck gegeben sind. Das in den Ringraum des RDB einströmende Wasser kann bei unzureichender Vermischung eine plötzliche Abkühlung der Reaktordruckbehälterwand (Thermoschock) unterhalb des Leitungsstutzens mit dem Risiko einer Rissbildung bewirken. Das Risiko eines Behälterversages hängt damit einerseits vom aktuellen strukturmechanischen Zustand der Behälterwand ab, andererseits von den die Vermischung bestimmen thermohydraulischen Phänomenen in der Hauptkühlmittelleitung. Letztere umfassen die durch die Strömungsdynamik bestimmte thermische Vermischung (Jet-Form, Turbulenz, Dampfblasenmitriss) sowie den Wärmetransport durch Kondensation am ECC-Strahl und an der Wasseroberfläche und hängen von einer Vielzahl von Parametern, wie dem ECC-Massenstrom, der ECC-Unterkühlung, dem aktuellen Systemdruck (Sättigungstemperatur) und der Höhe der Wasservorlage in der Hauptkühlmittelleitung ab.
Im Rahmen eines seit 2006 laufenden Konsortialprojektes der Partner HZDR, EDF France, AREVA NP France, IRSN, CEA, PSI Switzerland und ETH Zürich werden an der TOPFLOW-Anlage parametrische experimentelle Untersuchungen zu dem oben beschriebenen Thema durchgeführt. Ziel ist die Bereitstellung hochaufgelöster Experimentaldaten für die Ertüchtigung von CFD-Codes, die unter anderem in den europäischen Projekten NURESIM, NURISP und NURESAFE entwickelt werden. Der Vortrag gibt einen Überblick über das Projekt und seine Zielsetzungen, über den Versuchsstand und seine Instrumentierung sowie über das bisherige Experimentalprogramm, ausgewählte experimentelle Ergebnisse sowie CFD-Simulationsrechnungen.

The presentation gives an overview over the ongoing project activities of HZDR in the ARCHER EU project. An air-particle test loop GPLoop has been setup in the HDZR laboratory and was equipped with various measurement systems. The purpose is the study of graphite dust deposition and remobilization in a pebble bed heap. Studies will be done with positron emission tomography.

The presentation describes the actual status of the TOPFLOW-PTS consortial project on thermal hydraulics of pressurized thermal shock.

Many innovative reactor concepts for Generation III nuclear power plants use passive safety equipment for residual heat removal. These systems use two phase natural circulation. Heat transfer to the coolant results in a density difference providing the driving head for the required mass flow. By balancing the pressure drop the system finds its operational mode. Therefore the systems depend on a strong link between heat transfer and pressure drop determining the mass flow through the system. In order to be able to analyze these kind of systems with the help of state of the art computer codes the implemented numerical models for heat transfer, pressure drop or two phase flow structure must be able to predict the system performance in a wide parameter range. Goal of the program is to optimize the numerical models and therefore the performance of computer codes analyzing passive systems. Within the project the heat transfer capacity of a heat exchanger tube will be investigated. Therefore the tube will be equipped with detectors, both temperature and pressure, in several directions perpendicular to the tube axis to be able to resolve the angular heat transfer. In parallel the flow structure of a two phase flow inside and along the tube will be detected with the help of x-ray tomography. The water cooling outside of the tube will be realized by forced convection. It will be possible to combine the flow structure measurement with an angular resolved heat transfer for a wide parameter range. The test rig is set up at the TOPLFOW facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), so that it will be possible to vary the pressure between 5 and 70 bar. The steam mass content will be varied between 0 and 100 percent. The results will be compared to the large scaled Emergency Condenser Tests performed at the INKA test facility in Karlstein (Germany). The paper will explain the test setup and the status of the project will be presented.

The presentation introduces to activities at HZDR, which are related to thermal hydraulics safety concerns of Gen II and GEN-III nuclear reactors. We show examples of thermal hydraulic studies conducted at the TOPFLOW facility, which comprises two-phase pipe flow experiments, condensation experiments, pressurized thermal shock experiments, counter-current flow experiments, and boiling experiments. The ROCOM facility was created to study mixing and boron dilution in a 1:5 scaled-down PWR model. Both facilities, though serving different purposes and working in different parameter ranges, are equipped with most sophisticated measurement techniques and contribute to the answers on many thermal hydraulic phenomena occurring in today’s light water reactor systems.

Multiphase flows are widely found in many fields of science, engineering, and industry. Examples are mineral oil processing, chemical reaction engineering, and nuclear thermal hydraulics. Measurement and visualisation of multiphase flows is therefore of high scientific and engineering relevance. In particular the development and validation of multiphase CFD models requires measurement data from flow scenarios with high spatial and temporal resolution.
Since multiphase flows are complex in space and time, high-resolution imaging modalities are needed as measurement tools. Unfortunately, multiphase flow research made only partial benefit from the recent tremendous progress in optical, laser and ultrasound based measurement techniques, because of the opaqueness of such flows for light and sound. Especially radiation based tomographic methods are therefore being considered as the key technology for multiphase flow visualisation. However, to date only few methods are suited because of the stringent requirements for high spatial and temporal resolution. In particular, methods are sought, which can visualize multiphase flow in complex geometries, within vessels with opaque walls and inserts, such as chemical reactors, heat exchangers or fuel rod assemblies, but also porous media of fixed bed reactors or rock samples. The presentation now will give an introduction to the recent progress in radiation based tomographic imaging techniques for multiphase flow measurement and discuss their particular role with respect to CFD code development.

The presentation gives an overview over state-of-the art ultrafast and high resolution tomographic imaging methods for multiphase flows. In particular the presentation elucidates recent developments in wire mesh sensor imaging, high resolution gamma ray tomography for process vessels and ultrafast X-ray tomography for real time flow studies. Sensor and hardware issues will be addressed along with problems and solutions for massive 3D image data processing and flow parameter extraction.

Multiphase flows are widely found in different fields of science, engineering, and industry. Examples are mineral oil processing, chemical reaction engineering, and nuclear thermal hydraulics. Measurement and visualisation of multiphase flows is therefore of high scientific and engineering relevance. In particular the development of multiphase CFD codes requires measurement data from flow scenarios with high spatial and temporal resolution, in order to develop and validate physics based models for momentum, heat and mass transfer. If information about phase distributions, interfacial area structure, velocity and species concentration fields in flows are required, high-resolution imaging modalities are needed as measurement tools. However, yet there is no universal measurement or imaging modality for multiphase flow. Traditional visualisation tools, such as high-speed camera imaging and ultrasound measurements fail in multiphase systems due to the nonlinear propagation and attenuation of the signal carriers, e.g. light and sound waves. Especially radiation based tomographic methods are therefore being considered as the key technology for multiphase flow visualisation. However, to date only few methods are suited because of the stringent requirements for high spatial and temporal resolution. In particular, methods are sought, which can visualize multiphase flow in complex geometries, often with opaque walls and inserts, such as chemical reactor vessels, heat exchangers or nuclear fuel rod assemblies, but also porous media of fixed bed reactors or rock samples. The presentation introduces two novel imaging modalities, namely wire mesh sensors and ultrafast X-ray tomography and their use in two-phase flow measurement in complex flow domain geometries. It will be shown how gas-liquid and gas-solid flows can be visualized in in pipes, columns, fixed bed packings and flow channels with inserts. The presentation shows results of dedicated flow studies and introduces data analysis methods for extraction of quantitative flow parameters.

Magnetic properties of Au nanoparticles deposited on an archaeal S-layer are reported. XMCD and SQUID magnetometries demonstrate that the particles are strongly paramagnetic, without any indication of magnetic blocking down to 16 mK. The average magnetic moment per particle is 2.36(7) mkB. This contribution originates at the particles Au 5d band, in which an increased number of holes with respect to the bulk value is observed. The magnetic moment per Au atom is 25 times larger than any measured in other Au nanoparticles or any other configurations up to date.

Electron beam tomography is a promising imaging modality for the study of fast technical processes. But for many technical objects of interest X-rays of several hundreds of keV energy are required to achieve sufficient material penetration. In this article we report on a feasibility study for fast electron beam computed tomography with a 1 MeV electron beam. The experimental setup comprises an electrostatic accelerator with beam optics, transmission target, and a single X-ray detector. We employed an inverse fan-beam tomography approach with radiographic projections being generated from the linearly moving X-ray source. Angular projections were obtained by rotating the object.

This short communication describes the application of a capacitance wire-mesh sensor for the investigation of a simulated gas-liquid-liquid three-phase flow in a laboratory setup. Experiments with air, silicone oil and water are performed first in static and second in dynamic conditions. The capacitance mesh sensor is capable of generatinge images of the cross-sectional distribution of relative permittivity values, which in turn is an indication to the phases present in the multiphase mixture. Initial tests show that the sensor is a valuable tool to investigate such three-phase flows, which are very common in the oil industry.

We show how the high charged-particle fluxes (1-20 kHz/cm²) expected over the 150 m² large time-of-flight wall of the future Compressed Baryonic Matter experiment (CBM) at FAIR can be realistically handled with Multi-gap Resistive Plate Chambers (MRPCs). This crucial 100-fold increase of the chamber rate capability, as compared to that of standard MRPCs presently employed in experiments resorting to sub-100 ps timing, has been achieved thanks to the development of a new type of low-resistive doped glass. Following the encouraging results previously obtained with small counters, two types of modules (active area: ~150 cm²) have been built at Tsinghua University with the new material. The measurements conveyed in this work, obtained with a quasi-minimum ionizing electron beam, prove their suitability as the building blocks of the present hadron-identification concept of the CBM experiment. Namely, they provide a time resolution better than 80 ps and an efficiency above 90% at particle fluxes of 50 kHz/cm², being at the core of a modular concept that is easily scalable. Recent measurements of the electrical and mechanical properties of this new material, together with its long-term behavior, are shortly summarized.

⁶⁰Co (T_1/2 = 5.27 a) is one of the most used radionuclide for sterilization of medical equipment, as a radiation source for medical radiotherapy, industrial radiography and food irradiation due to the high gamma-energy of 1.33 MeV. In case of release in the geosphere, e.g. soil and aquatic systems, the migration behaviour of cobalt is not well understood. For geochemical investigations, e.g. migration and adsorption studies in soil and rock formations, the short-lived isotope ⁵⁶Co (T_1/2 = 77 d) can be used.
We produced ⁵⁶Co at a recently installed 18 MeV-cyclotron by using the nuclear reaction ⁵⁶Fe(p,n)⁵⁶Co.^[1] The target was prepared by pressing metallic iron powder into an aluminium plate and cover it with an aluminium foil. After the irradiation with 11 MeV protons for 1 h at a current of 25 µA, the iron was dissolved with a mixture of concentrated HCl and concentrated H₂O₂.^[2] The separation of ⁵⁶Co from the target material was done by liquid-liquid extraction with methyl-tert-butylether (MTBE) from 5.2 M HCl.^[3] Alternatively, an anionic exchange with DOWEX 1x8 as a column material can be used.^[4] Due to the shorter separation time the liquid-liquid extraction is preferred. The radiochemical yield was 82% ± 6%. The activity concentration in the ⁵⁶Co stock solution was ~4.5 MBq / ml.

[1] Jenkins, I. L., Wain, A. G., (1970) J. Inorg. Nucl. Chem. 32(5) 1419-1425.
[2] Lagunas-Solar, M. C., Jungerman, J. A., (1979) Int. J. Appl. Radiat. Isot. 30(1) 25-32.
[3] V. Wiskamp, S. Zenker, (1997), Eisenextraktion mit tertiärem Butylmethylether. CLB 48 (Beilage Memory) 22.
[4] Kraus, K. A., Moore, G. E., (1953) J. Am. Chem. Soc. 75(6) 1460-1462.

As described in Chapter, peptide nucleic acids (PNAs) have very attractive properties, which include, among them, high selectivity towards DNA/RNA recognition. It is therefore not surprising that their potential in nuclear medicine and biology to explore in vitro and in vivo processes has also been investigated. The high thermal and radiolytic stability as well as resistance toward nuclease/protease degradation of these bioconjugates offers new opportunities in this field of research, which could, potentially, lead to a transformation of the whole scope of diagnostically and therapeutically relevant radionuclides. Importantly, as demonstrated in Chapter with metal complexes, PNAs can be synthetically modified allowing their intrinsic physico-chemical properties to be significantly modulated. For example, the attachment of appropriate spacer elements and specific building blocks, such as targeting units, to both the C- and N-terminus of PNAs allows a broad variation of the pharmacologic properties of PNA bioconjugates, hence enabling the development of application-orientated probes for imaging of gene expression. Furthermore, the high metabolic resistance of these non-natural oligonucleotides makes them interesting for therapeutic applications. In this book chapter, we report on the current developments towards the preparation of radiometal-containing PNA constructs and summarize the protocols for labeling these oligonucleotides with ^99mTc, ¹¹¹In, ⁶⁴Cu, ⁹⁰Y and ¹⁷⁷Lu.

Polynuclear metal compounds may have considerable potential as metallic drugs. The most prominent representatives are polyoxometalates (POMs) which have been investigated since the last third of the 19th century. In addition to applications in catalysis, separation, analysis, and as electron-dense imaging agents, some of these substances have been shown to exhibit biological activity in vitro as well as in vivo ranging from anti-cancer, antibiotic, and antiviral to anti-diabetic effects.
Polyoxometalates represent a diverse ensemble of nanostructures with an almost infinite variability of chemical, physical and biological properties. The size of typical covalent bridged cluster compounds is in the range from 1 to 3 nm. The attachment of special surface groups on the periphery of cluster compounds may result in self-assembled non-covalent organized structures larger than 5 nm which are characteristic for bio-molecules, such as enzymes. Cells of mammalian organisms are typically 10 to 30 µm. However, sub-cellular organelle dimensions are smaller and range in sub-µm sizes. This comparison of size dimension illustrates that polymetalates are small enough to allow the cell membrane to be penetrated without too much interference. Evidently, some types of polyoxometalates are able to be transported into cells, particularly into mitochondria. However, many of such polyanions are only slightly taken up by cells, obviously caused by negatively charged membranes.
On the way to explore the biological activity of polynuclear cluster compounds, we recently recognised POMs as a new class of potent enzyme inhibitors. Certain polyanionic complexes are able to inhibit extracellular E-NTPDases (ecto-nucleoside triphosphate diphosphohydrolases) that are surface-located nucleotide-hydrolyzing enzymes involved in the regulation of signaling cascades by activating P2 (nucleotide) receptors.
We want to present a brief overview about the potential of POMs as E-NTPDase inhibitors and P2 receptor antagonists.

Due to the relatively low spatial resolution, arterial spin labeling (ASL) images are strongly affected by partial volume effects (PVE). This can make the qualitative analysis of ASL images difficult and it also significantly decreases the accuracy of cerebral blood flow (CBF) quantification. The PVE can be corrected for by using gray matter (GM) and white matter (WM) tissue segmentation of high-resolution T1-weighted images as proposed by Asllani et al1. The main drawback of this method is the need for precise knowledge of the partial volume ratios. However, the segmentation of T1-weighted images is very difficult at the border of GM and WM. Moreover, ASL images contain susceptibility induced deformations typical for EPI images and thus a correct registration with T1-weighted images is not always possible. Hence, the PVE correction using segmented T1-weighted images can introduce artifacts. In this study, we analyze an alternative method to obtain the partial volume ratios through the longitudinal magnetization relaxation times obtained from a Look-Locker sampling acquired in a multiple inversion time (TI) ASL sequence.

Das Institut für Fluiddynamik im Helmholtz-Zentrum Dresden-Rossendorf (HZDR) beschäftigt sich unter anderem mit der Untersuchung mehrphasiger verfahrenstechnischer Prozesse sowie der Entwicklung und Charakterisierung neuer effizienter Mehrphasenkontaktapparate und -reaktoren.
Ein solches neuartiges Konzept stellt der geneigt rotierende Festbettreaktor dar. Im Gegensatz zum zeitlich-periodischen Reaktorbetrieb erfolgt die Prozessintensivierung hier durch Aufprägung einer örtlichen Periodizität unter ansonsten stationären Betriebsbedingungen. Aus dieser veränderten Betriebsweise ergeben sich durch die Wahl von Reaktorneigung und Reaktordrehzahl zusätzliche Freiheitsgrade bei der Strömungsführung und damit zur Beeinflussung der Reaktorleistung.
Im Rahmen der Diplomarbeit ist ein tomographisches Messsystem für die Ermittlung von Phasenanteilen zu validieren. Weiterhin ist der Einfluss von Reaktorneigung und –drehzahl auf die Verteilung der Phasenanteile und den Druckverlust bei ausgewählten Gas- und Flüssigkeitsdurchsätzen zu untersuchen und mit dem etablierten Rieselbettreaktor zu vergleichen.

The PET radionuclide ⁶¹Cu is accessible through several nuclear reactions. Besides the common production route via ⁶¹Ni(p,n)⁶¹Cu the ⁶⁴Zn(p,α)⁶¹Cu reaction offers some advantages. Especially the comparatively cheap enriched ⁶⁴Zn makes this process economical. For fast product purification and recycling of target material an ion exchanger cascade was developed. In addition a separation technique with a copper selective resin was tested. ⁶¹Cu with specific activities up to 1000 GBq/µmol was produced with these methods.

We investigate the saturation of the optical absorption in graphene induced by ultrafast optical pulses. Within a microscopic theory, we study the momentum-, angle-, and time-resolved interplay of anisotropic excitation, carrier-carrier and carrier-phonon scattering and its influence on the saturation of absorption and transmission as a function of the input intensity. In agreement with recent experiments, we observe a linear regime for the intensity-dependence of the transmission at low pump fluences and a nonlinear saturation in the high excitation regime. Applying 10 fs-pulses we obtain a saturation fluence of approximately 6.5mJ/cm2. We demonstrate how the interplay of Pauli-blocking and intensity-dependent relaxation determines the saturation behavior.

We report on high power Terahertz emission from ErAs-enhanced InAlAs-InGaAs superlattices for operation at 1550 nm. ErAs clusters act as ecient recombination centers. The optical power is distributed among a large, microstructured area in order to reduce the local optical intensity. A THz field strength of 0.7 V/cm (1 V/cm peak-to-peak) at 100 mW average optical power has been obtained, with emission up to about 4 THz in air, limited by the detection crystal used in the system.

As a gapless material with linear dispersion graphene is of great interest for the infrared spectral range. In this study we investigate the carrier relaxation dynamics of graphene in a wide spectral range from the near to the far-infrared, covering more than two orders of magnitude in photon energy.
The samples for this study are epitaxially grown graphene layers on the carbon-terminated face of SiC, which behave essentially like a stack of electronically uncoupled layers. In the near infrared (NIR) spectral range (photon energy 0.41 eV – 1.5 eV) degenerate and two-color experiments were performed. In the mid (MIR) and far infrared (FIR) range (photon energy 10 meV – 250 meV) degenerate pump-experiments were carried out employing the free-electron laser FELBE as a source.
In the NIR range pump-induced transmission was observed in two-color experiments with both red and blue shifted probe radiation. The signals in case of the blue shifted probe are evidence for a hot carrier distribution. The thermalization process is beyond the temporal resolution of our experiment (~ 100 fs in the near infrared). The observed decay times are in the range of 2 – 4 ps. In the MIR range we observe a significant increase of the relaxation time as the photon energy is decreased to values below the optical phonon energy (~200 meV). These experiments are complemented by microscopic theory based on the density matrix formalism [1]. The theory reflects the trends seen in the experiment well. It reveals the contribution of Coulomb scattering as well as the role of both optical and acoustic phonons in the observed dynamics.
In the FIR range an unexpected change from enhanced transmission to enhanced absorption is found (cf. Fig. 1). It is caused by an interplay of interband and intraband processes. For photon energies above twice the value of the Fermi energy, bleaching of interband transitions results in pump-induced transmission. For smaller photon energies, however, interband transitions are not possible. Here intraband transitions cause a heating of the carrier distribution, which is responsible for the intraband absorption.

Detailed knowledge of the ultrafast carrier dynamics is of crucial importance for the development of novel electronic and optoelectronic devices. Graphene, a gapless semiconductor, is very attractive for broadband photonic and optoelectronic applications. We performed pump-probe experiments on graphene samples in a wide spectral range from the near-infrared to the terahertz region (wavelength 0.8 µm – 120 µm). We show results on the relaxation dynamics and identify the main relaxation channels, namely optical phonons, intraband carrier-carrier scattering, and Auger-type processes [1]. Furthermore the saturation behaviour of the signals is investigated. This is important with respect to graphene-based saturable absorbers. Here we find that the intensity required for full beaching of graphene decreases by three orders of magnitude, when the pump wavelength is increased from 5 µm to 40 µm. Finally we present a fast graphene-based terahertz detector, which can be operated at room temperature.
This work was carried out in collaboration with M. Mittendorff, F. Göttfert, H. Schneider, and M. Helm from the Helmholtz-Zentrum Dresden Rossendorf, M. Orlita and M. Potemski from LNCMI-CNRS Grenoble. Modelling based on microscopic theory was performed by T. Winzer, E. Malic, and A. Knorr at the TU Berlin, sample growth by M. Sprinkle, C. Berger, and W.A. de Heer from the Georgia Institute of Technology, Atlanta. We acknowledge support by the German Science Foundation (DFG) in the framework of the priority program “Graphene”.
[1] S. Winnerl, M. Orlita, P. Plochocka, P. Kossacki, M. Potemski, T. Winzer, E. Malic, A. Knorr, M. Sprinkle, C. Berger, W. A. de Heer, H. Schneider, and M. Helm, Phys. Rev. Lett. 107, 237401 (2011).

Using scattering-type near-field infrared microscopy in combination with a free-electron laser, intersublevel transitions in buried single InAs quantum dots are investigated. The experiments are performed at room temperature on doped self-assembled quantum dots capped with a 70 nm GaAs layer. Clear near-field contrast of single dots is observed when the photon energy of the incident beam matches intersublevel transition energies, namely the p-d and s-d transition of conduction band electrons confined in the dots. The observed room-temperature linewidth of 5 – 8 meV of these resonances in the mid-infrared range is significantly below the inhomogeneously broadened spectral lines of quantum dot ensembles. The experiment highlights the strength of near-field micro-spectroscopy by demonstrating signals from bound-to-bound transitions of single electrons in a probe volume of the order of (100 nm)^3.

A wide variety of radiometal-chelating bioconjugates have been studied intensively to design effective radiopharmaceuticals for diagnostic and therapeutic purposes. Azamacrocycles offer an enormous potential to achieve highly stable radiometal complexes and allow the covalent attachment of targeting and/or fluorescence units at the ligand skeleton. In this context, 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid (TETA) is quite often used for the development of copper-based target-specific radiopharmaceuticals, although demetallation and transchelation occur in biological systems. In contrast, radiolabeling of propionic acid analogues has not been reported so far.
An appropriate building block to form very stable complexes with copper(II) is N-mono-(2-(carboxy)ethyl)-1,4,8,11-tetraazacyclotetradecane (Cyclammonopropionic acid, CMPA) which permits the formation of stable radiocopper complexes as well as a facile approach to obtain peptide multimers. An improved pharmaceutical targeting might be utilized due to the multimeric peptide functionalization of the chelating agent. The Epidermal-Growth-Factor-Receptor (EGFR), which is overexpressed on a multitude of tumors, has been chosen as target system to be studied.
Herein, we want to report about coupling reactions of the model dipeptide H-(L)-Leu-(L)-Ala-OH, which is a part of an EGFR-specific peptide, with the cyclammonopropionic acid skeleton. Radiolabeling of CMPA-peptide conjugates with copper-64 indicate high in vitro stability of the complexes formed. So far, this promising behavior may pave the way to develop attractive candidates for radiopharmaceutical applications.

The peculiar properties of graphene, most importantly its gapless, linear band structure, give rise to exciting phenomena such as constant optical absorption over a wide range of photon energies and an unusual quantum Hall effect. Furthermore graphene is considered as an interesting material for electronic and optoelectronic applications. A good understanding of the relaxation dynamics is essential both for fundamental research and applications.
After an introduction into graphene research, I will present our results of pump-probe experiments in the mid- and far-infrared spectral range (photon energy 245 meV – 10 meV). We identify the role of optical phonons in the relaxation dynamics and discuss contributions from Auger-type processes and acoustic phonons. Furthermore an interesting change in sign of the pump-probe signal is observed at low photon energies (20 – 30 meV), which can be explained by an interplay of intraband and interband absorption processes [1]. In the second part of the talk I will focus on the relaxation dynamics in Landau-quantized graphene. Since the Landau levels (LLs) in graphene are not equidistant but scale with both the square root of the LL index and the square root of the magnetic field, optical pumping of individual LL-transitions is possible. Here we focus on the LL-1 → LL0 and LL0 → LL1 transitions, which exhibit equal transition energies but can be distinguished by applying either right-handed or left-handed circularly polarized light. Employing all four combinations of pumping and probing with right-handed and left-handed circularly polarized light, respectively, results in complex pump-probe signals: They involve fast and slow components, which exhibit either positive or negative signs. The relaxation dynamics in this regime can be understood by attributing the fast components to Auger-type processes and the slower components to phonon-mediated energy relaxation.
[1] S. Winnerl, M. Orlita, P. Plochocka, P. Kossacki, M. Potemski, T. Winzer, E. Malic, A. Knorr, M. Sprinkle, C. Berger, W. A. de Heer, H. Schneider, and M. Helm, Phys. Rev. Lett. 107, 237401 (2011).

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The FELBE user facility located at the Helmholtz-Zentrum Dresden-Rossendorf operates two free-electron lasers (FELs). Here we discuss the basic parameters of the FELs and the experimental opportunities at the facility. The FELs are based on the superconducting electron linear accelerator ELBE, which provides short (picosecond) electron bunches with energies up to 35 MeV at a 13 MHz repetition rate. The two FELs of FELBE (FELBE stands for FEL@ELBE) are equipped with two undulators, one for the mid-infrared spectral range (wavelengths 4 – 22 μm) and one for the far-infrared or THz range (wavelengths 20 – 250 μm). The key feature which distinguishes FELBE from other FEL user facilities is the possibility of “quasi cw” operation (meaning a continuous train of pulses, also called micropulses), made possible by the superconducting accelerator cavities. The FEL thus provides picosecond optical pulses at a repetition rate of 13 MHz. In this mode, the average power can reach up to 30 W (depending on the wavelength) corresponding to more than 1 μJ pulse energy. Additionally FELBE can be operated in a macrobunch mode and, via pulse-picking, a 1 kHz mode. The two FELs can be synchronized to a number of tabletop femtosecond and picosecond lasers, enabling two-color experiments from the near-infrared to the THz frequency range. The main techniques at FELBE are pump-probe spectroscopy [1-3] and time-resolved photoluminescence [4]. Furthermore there is a lab devoted to near-field microscopy [5,6]. Spectroscopy with FELBE radiation is also possible in pulsed high magnetic fields up to 70 T (150 ms magnetic pulse duration) [7,8]. FELBE is operated as a user facility, i.e., scientists from other institutions are invited to submit short research proposals and apply for beamtime.
References
[1] D. Stehr et al., Appl. Phys. Lett. 92, 051104 (2008).
[2] E.A. Zibik, et al., Nature Mat. 8, 803 (2009).
[3] S. Winnerl et al., Phys. Rev. Lett. 107, 237401 (2011).
[4] J. Bhattacharyya et al., Rev. Sci. Instr. 82, 103107 (2011).
[5] S.C. Kehr et al., Phys. Rev. Lett. 100, 256403 (2008).
[6] S.C. Kehr et al., Nature Comm. 2, 249 (2011).
[7] S. A. Zvyagin, et al, Rev. Sci. Instr. 80, 073102 (2009).
[8] O. Drachenko et al., Phys. Rev. B 79, 245207 (2011).

The application of radiolabeled peptides in biomedicine is increasing rapidly and offers excellent prospects for the development of target-specific tumor imaging agents. In this perspective, the incorporation of the positron-emitting radionuclide ⁶⁴Cu^II into ligand-peptide conjugates would permit the use of positron emitting tomography (PET) for tumor identification. An important requirement is that the resulting radiocopper-ligand complex is both kinetically and thermodynamically stable in vivo. We have developed a ligand scaffold based on bis(2-pyridylmethyl)triazacyclononane (DMPTACN) that forms very stable CuII complexes [1]. This structure allows for the introduction of linker groups, such as carboxylic acids, maleimide or isothiocyanate, thereby facilitating coupling of targeting molecules.
Among many characteristic targets of cancer tissue, the epidermal growth factor receptor (EGFR) is one of the most important mediators involved in the development of highly malignant tumors. This surface receptor is overexpressed in several tumor entities. The altered expression of EGFR during tumor growth, invasion, and metastasis present an interesting molecular target for tumor diagnosis and therapy.
Meanwhile, some specific peptides are identified capable of recognition EGFR-rich cancer tissue. Among these, the hexapeptide D4 (Leu-Ala-Arg-Leu-Leu-Thr) has been described [2]. We want to present the synthesis of a DMPTACN-peptide conjugate, applying thiourea coupling of the hexapeptide D4 by a DMPTACN isothiocyanate derivative. Radiochemical and radiopharmacological properties will be reported. In vitro binding characteristics of the [⁶⁴Cu]Cu^II-labeled DMPTACN-peptide conjugate in EGFR overexpressing cancer cells ( FaDu, A431) using an immunoprecipitation protocol point to specific interactions.

[1] G. Gasser, L. Tjioe, B. Graham, M. J. Belousoff, S. Juran, M. Walther, J.-U. Künstler, R. Bergmann, H. Stephan, L. Spiccia, Bioconjugate Chem. 2008, 9, 719-730.
[2] S. Song, D. Liu, J. Peng, H. Deng, Y. Guo, L. X. Xu, A. D. Miller, Y. Xu, FASEB J. 2009, 23, 1396–1404.

Electronic resonances in semiconductor quantum structures such as quantum wells and quantum dots are often accompanied by nonlinear phenomena. The intense, spectrally narrow radiation of a free-electron laser (FEL) is ideally suited for studying these nonlinear effects. We briefly discuss effects that can be treated in a perturbative way, such as the appearance of THz-sidebands around near-infrared absorption lines of quantum wells and quantum dots. Mainly we focus on an effect, which is beyond the perturbative description, namely the Autler-Townes splitting of excitonic absorption lines. Photogenerated electrons and holes in semiconductors form excitons, which exhibit a hydrogen-like energy spectrum. Due to the presence of the crystal lattice, however, the energy is scaled to the meV range. Excitation with intense THz pulses from an FEL "dresses" the excitonic states and leads to a splitting of energy levels. This splitting can be observed by probing the samples's transmission with broadband near-infrared radiation. While the main features, such as the dependence of the peak position on the THZ intensity, can be explained by a simple two-level model, other observations such as the relative strength of the peaks require more complex modelling. The mauin results presented here were obtained by M. Wagner, D. Stehr, H. Schneider and M. Helm on a sample grown by A. M. Andrews, S. Schartner, and G. Strasser.

Proton beams are a promising tool for the improvement of radiotherapy of cancer, and compact laserdriven proton radiation (LDPR) is discussed as an alternative to established large-scale technology acilitating wider clinical use. Yet, clinical use of LDPR requires substantial development in reliable beam generation and transport, but also in dosimetric protocols as well as validation in radiobiological studies. Here, we present the first dose-controlled direct comparison of the radiobiological effectiveness of intense proton pulses from a laser-driven accelerator with conventionally generated continuous proton beams, demonstrating a first milestone in translational research. Controlled dose delivery, precisely online and offline monitored for each out of *4,000 pulses, resulted in an unprecedented relative dose uncertainty of below 10 %, using approaches scalable to the next translational step toward radiotherapy application.

New oxorhenium complexes with tridentate 3-thia- and 3-methylazapentane-1,5-dithiolate and monodentate pyridine and quinoline derivatives have been synthesized. As a result of investigation of biological activity a high cytotoxicity was found for the synthesized complexes in relation to tumor cells. The specificity of the 2-pyridylthiolato[3-(N-methyl)azapentane-1,5-dithiolato]oxorhenium(V) cytotoxic action towards cells of mouse hepatoma MG-22A on a background of low acute toxicity was established.

The relaxation dynmics in graphene is studied in the mid- and far-infrared spectral range.

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Advantages of a stacked assembly of target support components for ⁶⁴Cu production via ⁶⁴Ni(p,n)⁶⁴Cu reaction were reported recently.1 The present work shows the applicability of these composit targets for beam currents up to 22 µA. Gold and platinum foils were evaluated as ⁶⁴Ni backing. The effective specific activity (ESA) and specific activity (SA) were determined by TETA titration at room temperature and at 80 °C and compared with additional copper quantification results via stripping voltammetric trace analysis (VA).

The relaxation dynamics at low photon energies (10 meV - 300 meV) is studied experimentally. Comparison with mcroscopic theory allows us to identify teh role of carrier-carrier scattering and scattering by optical and acoustic phonons.

Experience in operation of the [¹⁸F]F₂-p target to achieve stable and sufficient activity yields and reaction yields for [¹⁸F]FDOPA preparations are summarized. Hints for maintenance are given.

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Einführung in den Transport von Kohlenstoffnanoröhrchen in Umweltsystemen

An increasing demand of radiopharmaceuticals based on electrophilic reaction with [¹⁸F]F₂ gas (for instance [¹⁸F]FDOPA) led to an upgrade of the IBA [¹⁸F]F₂ gas target system in summer 2007. The more than 10 years operated [¹⁸F]F₂ deuteron target [²⁰Ne(p,α)¹⁸F] was not able to meet the increasing requirements in terms of activity anymore and was thus replaced by an IBA [¹⁸F]F₂ proton gas target [¹⁸O(p,n)¹⁸F] based on the so-called “double-shot” ‘irradiation method by R.J. Nickles [1]. The upgrade itself was done by IBA.
We run the Cyclone® 18/9 cyclotron in routine operation for more than 14 years. One of the specific features of the Rossendorf PET Center is the Radionuclide transport system (RATS) [2], 500 m in length that bridges the distance from the cyclotron to the radiopharmaceutical laboratories. The activity at the end of bombardment (EOB) is calculated taking in account the transfer time and experimental data of activity losses (about 30%) in the transfer tube [2].

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To achieve above keV ion temperatures, we propose a method to deposit enough energy of an ultra-short intense laser pulse into a multilayer solid target by creating an ion shock wave. In the scenario studied the bulk ions are heated efficiently when the shock wave is created inside the target and propagates through the target. To study the feasibility of this scheme a heterogeneous solid target with of CD-Al-CD multi-layer structure is studied using Particle-in-Cell (PIC) simulations. These simulations give insight into the dynamics of the shock generation by an ultra-short intense laser pulse (~100fs, 10^20W/cm2). The simulations show that shock waves are created in the interfaces of the CD-Al layer. Deuteron temperatures in the keV range are observed after the shock. Such high ion temperatures may be benefitial for neutron production via D-D fusion reactions.

Material behavior and properties at different scales, from nanometers to millimeters, are the input data needed for a model-based design-for-manufacturing approach of 3-D through-silicon-via (TSV) stacked ICs. In particular, mechanical and thermomechanical material data have to be used as input for physics-based modeling and simulation of stress-induced phenomena in 3-D stacks. Both package-and wafer-level properties, including their interaction, have to be considered. This paper reviews the thermomechanical and mechanical properties of several structures: time-dependent properties of solder materials (millimeter and micrometer scales), microstructure-dependent properties of Cu TSVs (micrometer scale), and process-dependent properties of ultralow-k materials in on-chip interconnect stacks (10-nm scale). To minimize the keep-out zone for active devices in the stress-affected surrounding of TSVs, while maintaining the device performance during 3-D TSV stacking of ICs, highly accurate material data are needed as input for the thermomechanical stress simulation. A similar strategy is supposed to be developed for a model-based design-for-reliability approach of 3-D TSV stacked ICs.

Radiolabelling of engineered nanoparticles for environmental particle tracing --> Presentation of the radionuclide production at the HZDR - cyclotron facility in Leipzig together with yields and stability of different radiolabelling strategies for nanoparticles

Untersuchung des Lebenszyklus von TiO₂ - und Ag⁰ - Nanopartikeln mithilfe Radiotracern. Radionuklidherstellung, Markierungsausbeuten, Markierungsstabilität und erste Ergebnisse zur Partikelfreisetzung aus Lacksystemen werden vorgestellt.

Presentation of results on microwave-assisted carbon nanotube modification and iodine radiolabelling

Presentation of results on carbon nanotube modification via microwave-assisted oxidation and iodine radiolabelling of carbon nanotubes for particle tracing applications

Lanthanides have become a useful tool in NMR spectroscopy within the last 40 years. Due to their paramagnetic properties they can be utilized as probes to determine the binding sites of biologically or environmentally relevant organic molecules as they cause significant line broadenings and / or paramagnetic induced shifts [1-3].
Actual research deals with the interactions, thermodynamic and kinetic behaviour of actinides and biomolecules. Lanthanides can easily be used as inactive analogues for trivalent actinides in consequence of their similar chemistry.
Glutathione is a high concentrated intracellular reducing agent, playing a major role in detoxification processes. Important targets are electrophiles such as heavy metal ions. With its high natural abundance, different functional groups and reducing ability, this tripeptide provides outstanding characteristics for actinide complexation research and, furthermore by its small size it is well suited as a model molecule in NMR spectroscopy.
1H-NMR signals are shifted and broadened by the paramagnetic induced shift of the Eu3+ with their 4f6 electron configuration. These interactions between nuclear spins and electron unpaired spins exhibit a strong distance dependency. The closer the binding site, the bigger the shift of the signals.
From these findings, it can be derived that the carboxylate group of the glutamate residue is the most potential binding site at pH 2.9. According to the aqueous speciation, the glycine carboxylic acid group is only partially deprotonated and therefore less involved in complexation. The thiol group does not interact with the metal ion.

Acknowledgement: We thank Dr. Erica Brendler, Technische Universität Bergakademie Freiberg, for providing the possibility to acquire 2D-NMR spectra.

[1] C. C. Hinckley, J. Am. Chem. Soc. 1969, 91, 5160-5162.
[2] O. A. Gansow, M. R. Willcott, R. E. Lenkinski, J. Am. Chem. Soc. 1971, 93, 4295-4297.
[3] I. Bertini, C. Luchinat, G. Parigi, Solution NMR of paramagnetic molecules, Vol. 2, in: Current methods in inorganic chemistry, Elsevier, Amsterdam, 2001.

The Traveling-wave Thomson scattering (TWTS) scheme is a novel high-yield Thomson scattering geometry using ultrashort laser pulses with tilted pulse fronts. Combined with relativistic electron bunches this can be utilized as an optical undulator or as an optically driven free electron laser for generation of high-brightness, narrow bandwidth X-Ray pulses. In order to examine the wave-optical propagation of these TWTS pulses we developed an analytical formalism to calculate the electrical field of a spatio-temporal distorted laser pulse which has been diffracted at a grating of arbitrary periodicity function. This allows for numerical analysis of a TWTS laser pulse in terms of its envelope and dispersion properties. We use this to investigate the applicability of the scheme as an optical undulator and free electron laser.

Objective: Evaluation of the quantitative accuracy of MR-based atten- uation correction (MRAC) in the Philips Ingenuity TF whole-body PET/MR.

Materials and methods: In 13 patients, PET emission data from the PET/MR were reconstructed using two different methods for attenuation correction. In the first reconstruction the vendor-provided standard MRAC was used. In the second reconstruction, a coregistered transmission-based attenuation map from a second immediately preceding investigation with a stand-alone Siemens ECAT EXACT HR+ PET scanner was used (TRAC). The two attenuation maps were compared regarding occurrence of segmentation artifacts in the MRAC procedure.
Standard uptake values (SUVs) of multiple VOIs (liver, cerebellum, hot focal structures at various locations in the trunk) were compared between both reconstructed data sets. Furthermore, a voxel-wise intensity correlation analysis of both data sets in the lung and trunk was performed.

Results: VOI averaged SUV differences between MRAC and TRAC were as follows (relative differences, mean ± standard deviation): (+12 ± 6)% cerebellum, (−4 ± 9% liver, (−2 ± 11)% hot focal structures. The fitted slopes of the voxel-wise correlations in the lung and trunk were 0.87 ± 0.17 and 0.95 ± 0.10 with averaged adjusted R2 -values of 0.96 and 0.98, respectively. These figures include two instances with partially erroneous lung segmentation due to artifacts in the underlying MR images.

Conclusion: The MR-based attenuation correction implemented on the Philips Ingenuity PET/MR provides reasonable quantitative accuracy. On average, deviations from TRAC-based results are small (on the order of 10% or below) across the trunk, but due to interindividual variability of the segmentation quality, deviations of more than 20% can occur.
Future improvement of the segmentation quality would help to increase the quantitation accuracy further and to reduce the inter-subject variability.

Modern laser-plasma simulations are able to model complex plasma processes. However, since particle dynamics within a plasma are usually not directly accessible to experiments, there is interest to compare experimental results with Particle-In-Cell (PIC) simulations.
One way to accomplish this task is to simulate the electro-magnetic emissions from both relativistic and sub-relativistic plasma electrons.
Here we present a newly developed software for spectral analysis of laser-plasma phenomena and for simulating novel light sources. Moreover, a GPU based code was developed to work directly within PIConGPU.

Diagnosis of Alzheimer’s disease (AD) with positron emission tomography (PET) using ¹⁸F-fluorodeoxyglucose (FDG) relies on typical alterations of brain glucose metabolism which are, however, not disease specific. Amyloid-β imaging has not entered clinical routine yet. Post mortem histological specimen of brain tissue from AD patients revealed enhanced expression of the chemotactic cytocine receptor 1 (CCR1). Participants, methods: CCR1-antagonist ZK811460 was labeled with fluorine-18 to explore its possible use as specific diagnostic tool in AD. Tracer characterization comprising PET imaging of brain and metabolite analysis was performed in AD patients and controls.
Results: Neither qualitative evaluation nor quantitative compartment analysis of PET data did show any enhanced binding of the ¹⁸F-labeled CCR1-antagonist in the brain of AD patients or controls.
Conclusion: ¹⁸F-ZK811460 did not fulfill the expectation as diagnostic tracer in PET imaging of AD.

At this project the effects of low doses of radionuclides and heavy metals on the metabolic activity of microorganisms was assessed, using the state of the art Thermal Activity monitor microcalorimeter, TAM(III), as a novel monitoring tool in this study. Therefore, the toxicity was measured as the metabolic response for these low doses reflected by bacterial growth thermograms. The bacterial strain used in this project, Paenibacillus sp. JG-TB8, was isolated from a soil sample of the uranium mining waste pile “Haberland” (Johanngeorgenstadt, Saxony, Germany) by Thomas Reitz [4]. This bacterial strain was exposed to different concentrations in the range of micromolar of Eu(III) and U(VI) salts. Thetoxicity of europium chloride (Eu(III)Cl3) as a heavy metal was reflected by the thermogram as a decrement of its maximal heat flow. In contrast, the effect of the uranium salts was more complicated. It showed a strong dependence on temperature and pH. Correlation of the degree of toxicity with concentration of the uranium salt was observed strongly at 30 °C in R2A medium, while it showed more constructive effect related to the usage of uranium as energetic source for the metabolic activity of the PB at 20°C. The mentioned thermograms showed that the general toxic effect of uranium is present but does not scale systematically with the applied concentrations. The data reveal that the thermal signature of a contaminant is unique for each concentration.

Letter to the editor - kein Abstract verfügbar

The aim of this study is to investigate the structure and function of P-type-ATPases. Enterococcus hirae is a gram-positive lactic acid bacterium with two copper ATPases CopA and CopB. They show sequence similarity to known P-type-ATPases. The monovalent copper exporting ATPase CopB is a central regulator for copper homeostasis in E. hirae which shows 39 % sequence similarity to the sarcoplamic reticulum calcium ATPase SERCA1a of rabbit hind leg muscle (Oryctolagus cuniculus). SERCA1a undergoes large conformational changes of cytoplasmatic and transmembrane domains to translocate ions. Despite some former work, the transport of copper and the biochemical properties of the ATPase, however, has to be analyzed and the observation of hydrolytic activities has to be pursued. During thesis work the functional status of conformational states was studied by spectroscopy work on metal and nucleotide binding. The ability of nonionic detergents to stabilize the membrane-bound enzymes was used to work in lipid analogue environment, whereby the effect of light scattering of lipid systems is prevented. I have investigated the secondary structure of purified CopB in the absence and presence of the non-hydrolyzable ATP analogs ATPgS, mantATP and silver (a redox inert Cu+ analog) using circular dichroism spectroscopy. Binding of metals unfolds the protein, whereas ATP analogs partially elliminate this effect. ATPgS and silver form an optically active complex. Negative and positive CD peaks appear, at 257 nm and 277 nm, respectively, at a ratio of 1:3 of Ag:ATPgS corresponding to the predominant species ATPgS3Ag4. CopB competes with complex formation by binding both ATPgS and silver. To my knowledge this is the first description of such a complex. It is used in this work as a possible high sensitive realtime ATPase monitor. This assay could ultimately be exploited to determine binding affinities of nucleotide, silver and CopB in enzyme assays in real time. In the present work it is used to determine binding affinitiy of CopB to ATPgS. In addition to check the influence of the binding of ATP analogs and silver on stability of CopB, the protein was denaturated in the absence and presence of ATPgS, mantATP, ADP and silver. Whereas ATPgS and mantATP stabilize CopB, the same nucleotide-CopB complex is destabilized by silver. This evidences a strong negative coupling between the nucleotide and metal binding site as an important output of my work.

The diagnostic evaluation and treatment of complex diseases, like cancer, is very difficult using only standing alone methods with their individual limitations. To overcome these restrictions, a combination of different imaging modalities will be conceivable. The radionuclide based positron emission tomography (PET) and single photon emission computed tomography (SPECT) are useful for functional imaging. To obtain anatomical information, computer tomography (CT) and magnetic resonance imaging (MRI) can be used, whereas fluorescence-based optical imaging finds application in surgery guidance. [1]

Extensive research effort has shown, that 3,7-diazabicyclo[3.3.1]nonane-derivatives (bispidines) built up thermodynamic and kinetic very stable complexes with copper(II) ions (logK = 16.28) [2]. Different functional groups of the backbone (hydroxyl and carboxyl groups) provide the opportunity for simultaneous attachment of dyes and biomolecules (e. g. peptides, proteins, antibodies) as vector molecules. After that functionalization, the complexation of radioactive copper isotopes (⁶¹Cu, ⁶⁴Cu, ⁶⁷Cu) allows visualization of cancer tissue with PET and radiotherapy.

The hydroxyl group at C9 was functionalized using nitrophenyl chloroformate for active ester generation. Therefore, a fluorescence label could be coupled to the bispidine by urethane bond formation.

We will report about the versatility of bispidines as compounds to realize different functionalities in one molecule. The synthesis and characterization of such derivatives, and radiolabeling experiments with the PET-radionuclide 64Cu will be discussed.

[1] Kuil, J., Velders, A. H., van Leeuwen, F. W. B.; Bioconjugate Chem. 2010, 21, 1709-1719.
[2] Juran, S., Walther, M., Stephan, H., Bergmann, R., Steinbach, J., Kraus, W., Emmerling, F., Comba, P.; Bioconjugate Chem. 2009, 20, 347-359.

Rigid bispidine (3,7-diazabicyclo[3.3.1]nonane) derivatives have been shown to form stable complexes, particularly with first row transition metal ions [1]. The variable number, type and position of donor groups provide a variety of tailor-made coordination sites for specific metal ions. Furthermore, the bispidine skeleton opens suitable pathways to introduce biomolecules, which are important in view of the pharmaceutical targeting of such complexes. Due to these interesting features, bispidines are predestined as attractive bifunctional chelating agents for the development of target-specific copper-based radiopharmaceuticals. In this perspective, a hexadentate bispidine ligand consisting of pyridine units in the positions C-2, C-4, N-3, and N-7 was conjugated to the tumour-seeking peptide bombesin. The ⁶⁴Cu-labeled bioconjugate is accumulated in human prostate tumors to allow clear visualization of the tumor tissue [2].
In order to optimize the radiopharmaceutical behavior, further bispidine ligands have been developed with different denticity (tetra-, penta, hexadentate) with pyridine and/or methoxypyridine donor groups and with the possibility to introduce functionalities, such as targeting units and fluorescence labels in view of pharmaceutical targeting as well as dual labeling (PET and optical imaging).
These ligands and the important properties of their Cu^II complexes, e. g. stabilities, exchange kinetics and partition coefficients (⁶⁴Cu: octanol/water) will be reported.

[1] P. Comba, M. Kerscher, W. Schiek, Progr. Inorg. Chem. 2008, 55, 613-704.
[2] S. Juran, M. Walther, H. Stephan, R. Bergmann, J. Steinbach, W. Kraus, F. Emmerling, P. Comba, Bioconjugate Chem. 2009, 20, 347-359.

The diffusion of U(VI) (c0 = 1×10-6 M) in compacted Opalinus Clay from the Mont Terri underground laboratory, Switzerland, was studied in the absence and presence of humic acid (10 mg/L) at two different temperatures (25 °C, 60 °C) under anaerobic conditions. As background electrolyte a synthetic Opalinus Clay pore water (pH 7.6, I = 0.36 M) was used. The diffusion-accessible porosity, ε, was determined for each Opalinus Clay bore core sample by through-diffusion experiments with tritiated water (HTO) before the U(VI) diffusion experiments were carried out. The values for the effective diffusion and distribution coefficients De and Kd obtained for U(VI) and humic acid at 25 °C as well as at 60 °C showed that humic acid has no significant influence on the U(VI) diffusion. The diffusion profiles of humic acid in Opalinus Clay at 25 and 60 °C indicate the contributions of two different humic acid particle size fractions (< 1 kD and 10-100 kD). The small-sized humic acid fraction diffused through the whole Opalinus Clay samples at both temperatures within the three months duration of the U(VI) diffusion experiments. At 60 °C, diffusion profiles of two different U(VI) species were observed. In a separate experiment the U(VI) speciation in the source reservoir solution at 60 °C was analyzed by laser-induced fluorescence spectroscopy, photon correlation spectroscopy and scanning electron microscopy with an energy dispersive X-ray detector. The two diffusion profiles could be attributed to an unknown colloidal and a known aquatic U(VI) species (Ca2UO2(CO3)3(aq)). The diffusion results showed that the interaction of U(VI) and of the large-sized humic acid colloid fraction with the clay is stronger at 60 °C. An increase of Kd from 0.025 ± 0.003 m3/kg at 25 °C to 0.25 ± 0.05 m3/kg for U(VI)colloidal at 60 °C was determined. In addition, the value for De of U(VI) increased with increasing temperature. Using the De values at 25 and 60 °C, a preliminary activation energy for the diffusion of U(VI) through Opalinus Clay of 10 kJ/mol was calculated. The observed increased Kd and De values for U(VI)aqueous at 60 °C compensated each other to almost equal values of the apparent diffusion coefficient Da at 25 and 60 °C. Hence, the migration of U(VI) through OPA was not significantly influenced by the investigated higher temperature of 60 °C.

Presentation of current activities and results from the NanoTrack project, especially results from radiolabelling of Ag(0) and TiO2 nanoparticles