Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The cooperative project THEREDA establishes a consistent and quality assured database for elements, temperature and pressure ranges relevant for (nuclear) waste disposal. Its focus is on repositories in salt host rocks, thus utilizing the Pitzer model for ion-ion-interactions. Data access is possible via http://www.thereda.de including ready-to-use databases for four common geochemical codes (ChemApp, EQ3/6, Geochemist’s Workbench, PHREEQC). A first data release was issued in 2011; the newest release covers tetra- and hexavalent uranium data for the system of oceanic salts containing Na, K, Mg, Ca, Cl, S, C, and Si.
The NEA Thermodynamic Database (TDB) [1,2] is the major source for thermodynamic data of the aqueous and solid uranium species. Additionally, recently published papers and partially unpublished works from KIT-INE are considered, also addressing Pitzer parameters [3]. Moreover, the THEREDA data release included thermodynamic data of secondary mineral phases formed in the waste material, which were excluded by [1,2] as a result of very stringent quality demands.
The main focus of the THEREDA database is the provision of data for the correct calculation of the solubility of radiotoxic elements in highly saline solutions. Thus, predictive test calculations for the solubility of uranium minerals for both main redox states of uranium (+IV and +VI) were carried out including other Pitzer databases. Modeling results were compared to experimental solubility data from literature references [4–6] and indicate the high quality of the THEREDA data base itself.

Das Helmholtz-Institut Freiberg für Ressourcentechnologie entwickelt innovative Analysemethoden, um Technologien zur Erkundung, Gewinnung, Nutzung und Recycling von Rohstoffen entlang der Wertschöpfungskette zu bewerten und zu verbessern. Eines dieser neuen Verfahren ist die unikale High-Speed PIXE, eine schnelle ortsaufgelöste teilchen-induzierte Röntgenemission (PIXE = Particle-Induced X-ray Emission). Via High-Speed PIXE wird die chemische Zusammensetzung großflächiger Proben in kurzer Zeit (min-h) bestimmt.

Die elementspezifische Röntgenstrahlung wird mit 3 MeV Protonen aus einem Tandembeschleuniger [1] angeregt. Der ca. 3 mm große Strahl wird mittels eines elektrostatischen Scanningsystems aufgeweitet und regt simultan alle Atome über einer Probenfläche von bis zu 12 x 12 mm² an. Für die ortsaufgelöste Detektion wird eine sog. Röntgenfarbkamera SLcam® [2] verwendet, bestehend aus einer speziellen Röntgenkapillaroptik in Verbindung mit einer pnCCD. Der Detektorchip dieser Kamera ist aus 69696 48x48 µm² großen Pixeln aufgebaut, die alle ein energieaufgelöstes, elementspezifisches und quantifizierbares Röntgenspektrum messen. Es sind somit Elementverteilungsbilder mit einer lateralen Auflösung von 50 µm (in Zukunft mit 6:1-Optik ~10 µm) möglich. Derzeit können alle Elemente von Magnesium bis Uran und zukünftig ab Bor mit Nachweisgrenzen bis in den µg/g-Bereich detektiert werden.

Ref.: [1] Akhmadaliev et al., NIMB 294 (2013) 5. [2] Scharf et al., Anal. Chem. 83 (2011) 2532.

A sound understanding of the major reaction mechanisms is crucial to handle uranium containing waste appropriately. This means both the synthesis of unique compounds and the treatment of uranium occurring in or released into the environment. In an environmental context, uranium occurs in two main redox states: mobile U(VI) and immobile U(IV).
Due to both its model character in U(VI) complexation by chelating polycarboxylates and the citrate being a ubiquitous occurring ligand, particularly being important in the citric acid cycle in vivo, the uranyl citrate system itself [1–4] and also its photoreaction [5, 6 and refs. cited therein] is already repeatedly investigated, but still not fully understood.
This investigation provides not only further insight into the U(VI)-citrate complexation, but also a better understanding of the (photo-)redox chemistry of uranium in general.
Here we want to present the reaction pathway of the U(VI) citrate complex photooxidation to its degradation products ketoglutaric acid, acetoacetic acid and acetone with concomitant CO₂ formation by several decarboxylation steps and the formation of U(IV). The oxidation state of the latter is indicated by NMR showing ¹H chemical shifts > 50 ppm and proven by UV-vis. Moreover, the yielded U(IV) appears as soluble complexes of citrate and its degradation products. The identity of the formed compounds was experimentally proven by one- and twodimensional NMR methods and confirmed by DFT calculations.
The photoreaction starts by irradiating the sample with light from a simple light source such as the sun or a commercial mercury lamp. Interestingly, the initial chemical alteration starts by a single electron transfer from a citrate molecule, being hydrogen bonded to the fifth remaining coordination site not occupied by U(VI)–coordinating citrate. Most likely the intermediate, i.e., not observable U(V) disproportionates fast to U(VI) and the aforementioned U(IV).

[1] R. Bramley, W. F. Reynolds, I. Feldman, J. Am. Chem. Soc. 1965, 87, 3329–3332.
[2] E. Ohyoshi, J. Oda, A. Ohyoshi, Bull. Chem. Soc. Jap. 1975, 48, 227–229.
[3] S. P. Pasilis and J. E. Pemberton, Inorg. Chem. 2003, 42, 6793–6800.
[4] A. Günther, R. Steudtner, K. Schmeide, G. Bernhard, Radiochim. Acta 2011, 99, 535–541.
[5] H. D. Burrows and T. J. Kemp, Chem. Soc. Rev. 1974, 3, 139–165.
[6] A. J. Francis and C. J. Dodge, DAE-BRNS Biennial Symposium on Emerging Trends in Separation Science and Technology (SESTEC) 2008 (BNL-80322-2008-CP).

Lanthanide complexes have become a useful tool in nuclear magnetic resonance (NMR) spectroscopy within the last 40 years as lanthanide shift reagents (LSR) [1,2]. Since signal separation by LSR has been overcome by elaborate pulse sequences and high-field spectrometers, lanthanides have advanced from auxiliaries to real objects of interest, also as inactive analogues for trivalent actinides in consequence of their similar chemistry.
Here we want to report on interactions and structures of the Ln(III) (La³⁺, Eu³⁺ and, where applicable, Y³⁺) with selected systems, i.e., O-phospho-L-serine, L-lactate [3] and (poly)borates [4]. Both organics are important as model molecules and potential complexing agents found throughout the biosphere and in vivo. Borates occur in remarkable amounts in geological (salt) formations for nuclear waste repositories, but also in boron containing cooling water or borosilicate glass coquilles for spent nuclear fuel.
Among several possible structures, infrared (IR) and NMR measurements, supported by density functional theory (DFT) calculation, revealed that lactate forms Ln(III) (and Am³⁺) complexes with both the carboxyl and hydroxyl group involved. The phosphorylated amino acid phosphoserine, able to act as a bifunctional ligand, shows Ln(III) complexation by both the phosphate and the carboxylate group as studied by solution and solid state NMR methods. Upon complexation, even at low pH, the respective protons are abstracted, followed by aggregation and precipitation, possibly forming coordination polyhedra rather than 1:1 (chelate) complexes. Polyborates, i.e., triborate and pentaborate form soluble weak aqueous Ln(III) complexes prior to precipitation as white solids, whereas condensation to higher polyborates can be excluded. Two signals in both the ⁸⁹Y and the ¹¹B NMR spectra probably arise from two coordination sites, which may reflect the polyborate species found in the supernatant solution.

[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] A. Barkleit, J. Kretzschmar, S. Tsushima, M. Acker, Dalton Trans. 2014, submitted.
[4] J. Schott, J. Kretzschmar, M. Acker, S. Eidner, M. U. Kumke, B. Drobot, A. Barkleit, S. Taut, V. Brendler, T. Stumpf, Dalton Trans. 2014, accepted.

The influence of SiO₂ and SiN_x cover layers on the dopant distribution as well as microstructure of high fluence Ga implanted Si after thermal processing is investigated. Rapid thermal annealing at temperatures up to 750°C leads to a polycrystalline layer structure containing amorphous Ga-rich precipitates. Already after a short 20 ms flash lamp annealing a Ga-rich interface layer is observed for implantation through the cover layers. This effect can partly be suppressed by annealing temperatures of at least 900°C. However, in this case Ga accumulates in larger, cone-like precipitates without disturbing the surrounding Si lattice parameters. Such a Ga-rich crystalline Si phase does not exist in the equilibrium phase diagram according to which the Ga solubility in Si is less than 0.1 at%. The Ga-rich areas are capped with SiO_x grown during annealing which only can be avoided by the usage of SiN_x cover layers.

The last decades have seen a number of liquid metal experiments on the interaction of magnetic fields and the flow of electrically conducting fluids. The opaqueness of liquid metals requires non-optical methods for inferring the velocity structure of the flow. Quite often, such experiments are carried out with very high electrical currents to generate the necessary magnetic fields. Depending on the specific purpose, these currents can reach several kA. The utilized switching mode power supply can then influence seriously the UDV measurements by electromagnetic interference. As an example, a recent experiment on the azimuthal magnetorotational instability (AMRI) has shown that a hydrodynamically stable Taylor-Couette flow becomes unstable under the influence of a high azimuthal magnetic field. An electrical current on the axis of the experiment with up to 20 kA generates the necessary field to destabilize the flow. We will present experimental results on this AMRI experiment carried out at the PROMISE facility with an enhanced power supply. For this system, we discuss the elaborate measures that were needed to obtain a reasonable signal-to-noise ratio of the ultrasonic measurement system. In dependence on various parameter variations, some typical features of the observed instability, such as the energy content, the wavelength, and the frequency are analyzed and compared with theoretical predictions.

Purpose: Epidermal growth factor receptor (EGFR) is critically involved in progression and therapy resistance of squamous cell carcinoma (SCC). Albeit EGFR targeting could improve the effect of radiotherapy on patients' outcome, the clinical results failed to meet expectations from preclinical studies. In this work, we evaluated the potential of the radionuclide Yttrium-90 (90Y) bound to Cetuximab (90Y-Cetuximab) as novel targeting approach for SCC cells in vitro. Materials and methods: FaDu and A431 cell lines were used. EGFR subcellular localization, clonogenic survival, radiation-induced γH2AX foci and EGFR signaling were examined. Cells were treated with DTPA, DTPA-Cetuximab, 90Y and 90Y-Cetuximab alone or in combination with external X-ray irradiation. Results: Dose- and cell line-dependently, 90Y-Cetuximab mediated a significant reduction in clonogenicity relative to unbound 90Y. Combined 2-Gy external radiation plus 2-Gy equivalent dose of 90Y-Cetuximab was more effective than equivalent doses of 90Y and X-ray radiation. Analogous effects were observed in the number of residual radiation-induced foci. Additionally, EGFR, ERK1/2 and AKT phosphorylation showed alterations upon different treatments. Conclusions: Our findings show that Cetuximab-conjugated 90Y has a significant potential to eradicate human SCC cells. A combination of radioimmunotherapeutic compounds and external radiotherapy might be a promising treatment strategy for clinical application.

We report on a systematic study of the synthesis and magnetism of hybrid ferromagnetic semiconductors comprised of MnAs and MnP nanoclusters embedded in GaAs and InP matrices, respectively. Samples were prepared by Mn-ion implantation followed by millisecond-range flash lamp annealing. X-ray diffraction and Auger electron spectroscopy results confirm the formation of MnAs nanoclusters of sizes 150 ± 50 nm. Ferromagnetic properties of MnAs: GaAs (MnP:InP) hybrid systems are studied by magnetic force microscopy and superconducting quantum interference device magnetometry. We show that the magnetization at saturation and the ferromagnetic transition temperature Tc, of MnAs:GaAs depend on the Mn-concentration and on the annealing energy density. While in the case of MnP:InP they are independent of the annealing energy density used. Ferromagnetism in such hybrid systems (ferromagnet–semiconductor) above 300 K makes them very attractive for applications in spintronic devices.

SLcam® – a full-field energy dispersive portable X-ray camera [1,2], is a combination of a single photon counting CCD with a poly capillary optics objective. The standard CCD matrix consist of 48×48 μm² pixels sensitive for photons from 3 to 18 keV and has an energy resolution of 156 eV (@Mn Kα). The polycapillary optics is used to achieve the spatial resolution guiding the fluorescence photons from the point of origin to the detection pixel. The device allows fast overview over a large detection area with first results visible almost immediately. A dedicated software enables steering the camera and online visualization of the hyper spectral data cube (x,y,E) by displaying regional spectra, element/line maps and overlay images.
With the use of a sub-pixel resolution algorithm the SLcam® spatial resolution becomes limited by the end diameter of a single capillary channel. A one to one optics, with a field of view of 12 × 12 mm², can reach a resolution of 20 μm. This optics has an unlimited depth of sharpness and is ideal to visualize uneven objects. With the use of a conical shaped optics allowing 8 times magnification and a field of view of 1.5 × 1.5 mm² a resolution approaching 1 μm is possible also with laboratory X-ray sources.
We will present recent developments for the SLcam® concerning the sub-pixel resolution, optics aperture, image processing software, and connection to new High-Speed PIXE beamline at Helmholtz-Zentrum Dresden-Rossendorf (HZDR).

[1] O. Scharf, et al., Analytical Chemistry, 83 (7), 2011, 2532-2538.
[2] I. Ordavo, et al., NIM A, 654 (1), 2012, 250-257.

In a Taylor-Couette experiment on the non-axisymmetric version of the magnetorotational instability, performed by Seilmayer et al. [1], a dominantly azimuthal magnetic field was created by a central vertical copper rod connected to the power source by two horizontal rods at a height of approximately 0.8 m below and above the cylindrical volume. The liquid metal flow in the cylindrical gap between the cylinders was simulated using the OpenFoam library including a Poisson equation for the determination of the induced electric potential. The slight deviation from a purely axisymmetric azimuthal imposed magnetic field turns out to have a surprisingly strong effect on both the critical Hartmann number and the flow structure of the instability.

We present preliminary results of flow measurements for two different models of continuous casters using the contactless inductive flow tomography. In the first experiment we used a rectangular slab caster with a dominating two-dimensional flow structure under the influence of an electromagnetic brake. For the second experiment a round caster was used in which a magnetic stirrer around the submerged entry nozzle should create an unstable three-dimensional swirling flow.

A non-conventional positron source using the channeling radiation of relativistic electrons on different planes and axes of Si, C, Ge and W crystals which materialize into e+e- pairs in a tungsten amorphous converter is described. In this work we have calculated channeling radiation spectra from different planes and axes of Si, C, Ge and W crystals using the Doyle-Turner approximation for the continuum potentials of crystallographic planes and axes. The dependence of channeling radiation on the incidence angle of electrons are also investigated. The channeling radiation is then impinging on an amorphous tungsten target producing positrons by e+e- pair creation. The simulations are made with our developed Mathematica codes which realy calculate the photon energy spectrum of channeled electrons in the crystal target and Geant4 Monte Carlo code which calculates the the materialization of photons into e+e- pairs in an amorphous W target.

Industrial system that comprises flow of suspended particles in fluid generally requires an understanding of the multiscale physics occurring from micro/nanoscale to mesoscale and eventually to the macroscale phenomena. Because of the inherent complexities that are prevalent in such flow, investigations are certainly at the crossroads of intense research and development in the environment of significant advancements in experimentation as well as in computing power and performance. Much concerted development is nonetheless still needed to gain a better understanding of the complicated physics through the advancement of experimental techniques and computational methodologies and models and to specifically meet the increasing demand of improving efficiency of industrial multiphase flow system. The advances of experimental and modelling investigation of multiphase flow system are presented in this special issue.

Double barrier magnetic tunnel junctions (DB-MTJs) allow for operation at higher bias voltages than their single barrier counterparts, but their total tunnelling magnetoresistance (TMR) ratio is still less than in the single barrier case.[1] Here, we prepare CoFeB/MgO-based DB-MTJs with differing free layer deposition conditions. The deposition conditions for the outer CoFeB electrodes and the MgO barriers were kept the same. The middle CoFeB layer was deposited at differing sputtering power densities (from 1.3 to 4.4 W/cm2) to vary the B concentration.[2] Contributions of the upper and lower junction to the total TMR were compared as a function of sputtering power density and annealing temperature. As the sputtering power density of the free layer is increased the TMR response of the upper and lower junctions is opposite, indicating that the growth of both MgO on CoFeB as well as CoFeB on MgO is sensitive to B content. This is attributed to the suppression of B diffusion which is confirmed by transmission electron microscopy analysis. [1] T. Nozaki et al., Appl. Phys. Lett., 86, 082501 (2005). [2] H.D. Gan et al., IEEE Trans. Magn. 47, 1567 (2011).

Annular flow occurs in many industrial processes, and is characterized by high gas flow at the center of the pipe and liquid film flow around the pipe wall. Due to the high gas velocity, large shear velocities are induced that result in high interfacial shear stress causing continuous entrainment of liquid droplets into the gas core from the liquid film. When the liquid fraction is small in horizontal annular flow, it is possible to cause an extremely important problem that relates to the damage of heat exchanger tubes, because the drainage of liquid due to gravity, as well as the evaporation, leads to the dry-out of thin liquid film near the top of the tube. Therefore, it is important to accurately predict the circumferential distribution of film thickness in horizontal annular flow. Furthermore the thin water film at the cold wall plays a major role for the heat transfer resistance of the condensation process. For better understanding of condensation heat transfer the film formation mechanism and the film distribution need to be known.
One limitation in current simulating horizontal annular flows is the lack of treatment of droplet formation mechanisms. For self-generating annular flows in horizontal pipes, the interfacial momentum exchange and the turbulence parameters have to be modelled correctly. Furthermore the understanding of the mechanism of droplet entrainment in annular flow regimes for heat and mass transfer processes is of great importance in the chemical and nuclear industry.
The development of general computational fluid dynamics (CFD) models closer to physics and including less empiricism is a long-term objective of the activities of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) research programs. Such models are an essential precondition for the application of CFD codes to the modelling of flow related phenomena in industrial scales. The algebraic interfacial area density model (AIAD), which is one result of these HZDR activities, allows the use of different physical models depending on the local morphology inside a macro-scale multi-fluid framework.
A further step of improvement of modelling interfaces is the consideration of droplet entrainment mechanisms. The proposed entrainment model assumes that due to liquid turbulence the interface gets rough and wavy and forms droplets. The new approach is validated with HZDR annular flow experiments. Important phenomena like the pressure drop, the wave pumping effect, the droplet entrainment rate, the liquid film formation and the transient flow behavior could be calculated, analyzed and compared with the measurement. Verification and Validation is going on – more experimental data are required for the validation.

To elucidate the potential risk of 126Sn migration from nuclear waste repositories, we investigated the surface reactions of SnII on goethite as a function of pH and SnII loading under anoxic condition with O2 level < 2 ppmv. Tin redox state and surface structure were investigated by Sn-K edge X-ray absorption spectroscopy (XAS), goethite phase transformations were investigated by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The results demonstrate the rapid and complete oxidation of SnII by goethite and formation of SnIV 1E and 2C surface complexes. The contribution of 2C complexes increasesd with Sn loading. The SnII oxidation leads to a quantitative release of FeII from goethite at low pH, and to the precipitation of magnetite at higher pH. Based on the XAS data, we developed a surface complexation model using the CD-MUSIC approach, with log K values of 15.5 ±1.4 for the 1E complex and 19.2 ±0.6 for the 2C complex. This model predicts Sn sorption across pH 2 to 12 and at two different Sn loadings (12.5 and 62.5 μmol/g).

One of the key questions in biology is how the metabolism of a cell responds to changes in the environment. In budding yeast, starvation causes a drop in intracellular pH, but the functional role of this pH change is not well understood. Here, we show that the enzyme glutamine synthetase (Gln1) forms filaments at low pH and that filament formation leads to enzyme inactivation. Filament formation by Gln1 is a highly cooperative process, strongly dependent on macromolecular crowding, and involves back-to-back stacking of cylindrical homo-decamers into filaments that associate laterally to form higher order fibrils. Other metabolic enzymes also assemble into filaments at low pH. Hence, we propose that filament formation is a general mechanism to inactivate and store key metabolic enzymes during a state of advanced cellular starvation. These findings have broad implications for understanding the interplay between nutritional stress, the metabolism and the physical organization of a cell.

For the redox-reactive fission products and actinides Se, Tc, U, and Np, it is assumed that the strongly reducing conditions in deep underground, anoxic nuclear waste repositories will reduce their mobility, since their lower-oxidation states commonly form solids of very low solubility. This is not necessarily the case for Pu, where the hexa- and pentavalent aquo-complexes prevalent at higher pe are replaced at lower pe by a tetravalent solid of low solubility, PuO2, but also by a trivalent aquocomplex at lower pH. FeII-bearing mineral phases, especially those with low bandgap, play an important role in this process, since they are able to catalyse redox reactions at their surface. Magnetite, FeIII2FeIIO4, is an important mineral in this context, since it forms by steel corrosion under anoxic conditions and is also prevalent as geogenic mineral. Therefore, we investigated the reaction of PuV, and in comparison also of NpV, with magnetite in sorption and coprecipiation experiments with X-ray absorption spectroscopy. We found that PuV is indeed reduced to the trivalent oxidation state in the presence of magnetite. The PuIII aquo-complexes are, however, strongly sorbed by forming tridentate surface complexes [1]. PuIII can also be partly incorporated by the structure of magnetite by rapid coprecipitation. During aging, however, it is expelled from the structure and readsorbed at the magnetite surface. This behaviour of Pu is then compared to that of Np.
[1] Kirsch, R., Fellhauer, D., Altmaier, M., Neck, V., Rossberg, A., Fanghänel, T., Charlet, L., and Scheinost, A. C. (2011). Oxidation state and local structure of plutonium reacted with magnetite, mackinawite and chukanovite. Environmental Science & Technology 45, 7267–7274.

Objective
To assess the diagnostic value of PET/MR (positron emission tomography/magnetic resonance imaging) with FDG (18F-fluorodeoxyglucose) for lymph node staging in head and neck cancer.

Materials and Methods
This prospective study was approved by the local ethics committee; all patients signed informed consent. Thirty-eight patients with squamous cell carcinoma of the head and neck region underwent a PET scan on a conventional scanner and a subsequent PET/MR on a whole-body hybrid system after a single intravenous injection of FDG. The accuracy of PET, MR and PET/MR for lymph node metastases were compared using receiver operating characteristic (ROC) analysis. Histology served as the reference standard.

Results
Metastatic disease was confirmed in 16 (42.1%) of 38 patients and 38 (9.7%) of 391 dissected lymph node levels. There were no significant differences between PET/MR, MR and PET and MR (p > 0.05) regarding accuracy for cervical metastatic disease. Based on lymph node levels, sensitivity and specificity for metastatic involvement were 65.8% and 97.2% for MR, 86.8% and 97.0% for PET and 89.5% and 95.2% for PET/MR.

Conclusions
In head and neck cancer, FDG PET/MR does not significantly improve accuracy for cervical lymph node metastases in comparison to MR or PET.

We present the formation of an ordered three-dimensional lattice of Ni nanocrystals in an amorphous alumina matrix by a self-assembly process. The self-assembled growth achieved by single-step magnetron sputtering deposition of a Ni/Al2O3 multilayer is driven by surface morphology effects. The influence of the Ni layer thickness on the Ni particle size, separation, and quality of ordering is examined. The quality of Ni nanoparticles ordering in alumina is compared to their ordering in a silica matrix. The obtained results are important for the understanding of the self-assembly process of metallic particles in amorphous matrices and the applications of such materials.

A general common statistical task in geosciences is to relate a compositional data set with a set of covariables, a task often dealt with a linear model. Within the Euclidean framework of the Aitchison geometry on the simplex, the sample space of compositional data, such models are easy to construct, fit, visualize, test and use for prediction. This contribution presents in a systematic way the three cases of compositional regression, namely: (1) regression and analysis of the variance with compositional response (composition as Y); (2) regression with compositional explanatory variables (composition as X); and (3) composition-to-composition regression (compositions as both X and Y). The construction of these models is based on common tools of linear algebra: (1) the linear vector operations of the simplex, perturbation and powering; (2) the Aitchison scalar product; and (3) the concept of a linear operator between vector spaces. Fitting and usage for prediction is straightforward to obtain in logratio coordinates of the compositional objects, using classical multivariate regression (cases 1,2 and 3). Visualization of the output is based on matrices of scatterplots or boxplots, the principle of parallel plotting and the usage of all possible pairwise logratios (1 and 2). Visualization of case 3 models is possible through biplots, based on ideas from correspondence analysis. Finally, testing should target hypotheses of subcompositional independence (i.e. that the linear dependence is limited to a given subcomposition), which requires joint testing techniques. Existing multivariate tests can be adapted to the cases 1 and 2, but case 3 is only possible with asymptotic likelihood ratio tests. These concepts are illustrated with data from GEMAS, a soil survey campaign covering whole Europe.

Contact analysis provides an assessment of the evolution of the average value along boreholes of a given variable at increasing distances from the contact between two facies or domains. The concept is long established in the geostatistical literature and software, albeit for studying the behavior of a single variable. This contribution explores practical ways for studying this transient behavior of a set of variables forming a composition, in such a way that spurious correlation effects are avoided. The main idea is to complement a classical contact analysis of raw percentages with similar diagrams for each possible pairwise logratio of two components, as well as with a contact analysis of the centered-logratio transformed components. This approach is particularly promising when the set of components considered account for a considerable amount of the total mass, or dilution effects are suspected to have affected only a subset of the components. In these scenarios, the classical approach would show an apparent parallel absolute enrichment of the unaffected components, although in reality, the relations between them would have not changed. Thus, a classical assessment would lead the analyst to consider all contacts as “hard”, while in nature a subset of parts would actually be virtually unchanged near the contact. This might be unimportant for simple tonnage or grade calculations (where the raw percentage of value metal present is relevant), but it becomes critical where the relations between several value and/or deleterious elements are necessary, like in complex polymetallic deposits and in geometallurgical studies. These concepts are illustrated with toy examples and data from Murrin Murrin, WA, a Ni-Co laterite deposit where intensive remobilitzation of both value and deleterious components is known to have occurred.

Various geostatistical techniques have been developed for several data scales, like: sequential Gaussian simulation or cumulants for continuous variables, SNESIM and extensions for binary and categorical variables, or lognormal geostatistics for positive variables. However, the same material can often be described at the same time by multiple aspects, like its facies, its composition or its grade in a certain value element. Typically, these different regionalized variables are stochastically mutually dependent, and often observed at different locations. It would thus be interesting to have a joint conditional simulation methodology of all random fields integrating all observations regardless of its scale. We have developed a multipoint-based conditional simulation technique, which allows to simulate dependent random fields of more than one scale. It fits generalized linear models to training images in order to predict the conditional distribution of prediction points to the observed or already simulated data. It then follows an iterative scheme to fill in more points until a complete simulation is obtained. For well-chosen combinations of generalized linear models for all scales we get a simulation system preserving the observations and various properties of the joint distribution in the training image. Training images need to have a separate layer for each of the regionalized variables and typically must be quite large to ensure enough variation of conditioning variables. Training images are sampled with space-filling sequences rather than systematically in order to get reasonable performance. The generalized linear modes are stabilized to avoid specific artifacts generated by complex dependence.

Molecular electronics has been a eld of big interest for the last years. Using the technique of mechanically controllable break junctions we characterize the Switchable Molecular Wire Oligo(phenylene ethynylene)-embedded Difurylperuorocyclopentenes (SMW) in liquid environment. Via light irradiation the SMW can be switched between two well-defined conductance states. Conductance and hysteresis measurements allow us to identify the two states providing the basis for a comprehensive study of the in situ switching process. Based on the analysis with the transport model assuming transport through a single molecular level, we confirm that a reliable contact of the molecules to the gold contacts is formed and extract the energy of the molecular levels and the coupling constants between molecule and electrodes.

We study the nonlinear multi-magnon processes in a micro-structured magnonic crystal consisting of a Ni81Fe19 waveguide, which has been periodically modulated in its saturation magnetization by localized ion implantation. A significant modification of the nonlinear magnon spectrum compared to a reference waveguide is determined, exhibiting a predominant scattering into modes with a frequency at the magnonic band gaps and an enhancement of the nonlinearities for some excitation frequencies. The results prove the feasibility to utilize nonlinear multi-magnon scattering for magnon spintronic applications on the micrometer scale.

The relaxation of free holes and electrons in highly compensated germanium doped with gallium (p-Ge:Ga:Sb) and antimony (n-Ge:Sb:Ga) has been studied by a pump-probe experiment with the free-electron laser FELBE at the Helmholtz-Zentrum Dresden-Rossendorf. The relaxation times vary between 20 ps and 300 ps and depend on the incident THz intensity and compensation level. The relaxation times are about five times shorter than previously obtained for uncompensated n-Ge:Sb and p-Ge:Ga. The results support the development of fast photoconductive detectors in the THz frequency range.

We present near-infrared pump-probe measurements to investigate the polarization dependence of optical carrier excitation in graphene. Excitation with linearly polarized radiation leads to an anisotropic distribution of the nonequilibrium carriers in momentum space. This anisotropy can be revealed by the comparison of pump-probe signals for different polarization configurations. In parallel configuration the probe beam has the same polarization with respect to the pump beam, for the perpendicular configuration the polarization of the probe beam is rotated by 90°. The signal amplitude of the parallel configuration is about twice as large as compared to the perpendicular configuration. The initial relaxation process is faster for the parallel polarized probe beam, which leads to identical signals about 150 fs after excitation. At this time delay an isotropic carrier distribution is reached by electron-phonon scattering. These findings are confirmed by microscopic calculations.

We investigate the ultrafast dynamics of low-energetic Dirac electrons in graphene under Landau quantization [1]. In a joint experiment-theory study, we provide calculations based on the density matrix formalism [2] as well as measurements of the relaxation dynamics via differential transmission spectroscopy.

As a consequence of the linear dispersion at the Dirac points, graphene exhibits a non-equidistant Landau level spectrum which allows to address specific transitions by optical pumping. Exploiting this to selectively excite the energetically lowest Landau levels, we employ pump-probe spectroscopy to explore the carrier dynamics in this regime. A surprising sign reversal in differential transmission spectra is observed both in experiment and theory and provides evidence for strong Auger scattering on a picosecond timescale. Our calculations even predict the occurrence of a substantial carrier multiplication in Landau quantized graphene [3].

[1] M. Mittendorff et al., (in preparation).

[2] E. Malic, A. Knorr, Graphene and Carbon Nanotubes: Ultrafast Optics and Relaxation Dynamics, (Wiley-VCH, Berlin, 2013).

[3] F. Wendler, A. Knorr, and E. Malic, (submitted).

CFD-simulations for two-phase flows applying the multi-fluid approach are not yet qualified to provide reliable predictions for unknown flows. Among others, one important reason is the missing agreement within the community on closure models to be used. Considering specific phenomena or not, using different models and adjustable constants, most papers presenting a model validation end up with a good agreement with experimental data. However a case by case selection of models and constants does not help to improve the predictive capabilities of such models. For this reason the definition of baseline models considering all known phenomena that could be important is proposed. In such baseline models all parameter have to be defined, i.e. there are no tuning parameters by definition. Such baseline models have to be applied to many experiments with different complexity. Shortcomings of the models and our physical understanding of the complex flow phenomena have to be identified by detailed analyses on the deviations between experimental data and simulation results. A modification of the baseline model will only be done if it bases on physical considerations and improves the overall performance of the model. This requires a huge effort, but seems to be the only way to improve the situation. More complete experimental data are required. Joint activities on the development of such baseline models are desirable. The paper illustrates this strategy by a baseline model for polydisperse bubbly flows which is presently developed at HZDR.

Numerical simulation was carried out for air-water countercurrent flows in a 1/10-scale model of the pressurizer surge line and
the simulated countercurrent flow limitation (CCFL) values agreed well with the experimental CCFL data.

Stimulated emission in the terahertz frequency range has been realized from boron acceptor centers in silicon. Population inversion is achieved at resonant optical excitation on the 1Γ+8 → 1Γ−7, 1Γ−6, 4Γ−8 intracenter transitions with a midinfrared free-electron laser. Lasing occurs on two intracenter transitions around 1.75 THz. The upper laser levels are the 1Γ−7, 1Γ−6, and 4Γ−8 states, and the lower laser level for both emission lines is the 2Γ+8 state. In contrast to n-type intracenter silicon lasers, boron-doped silicon lasers do not involve the excited states with the longest lifetimes. Instead, the absorption cross section for the pump radiation is the dominating factor. The four-level lasing scheme implies that the deepest even-parity boron state is the 2Γ+8 state and not the 1Γ+7 split-off ground state, as indicated by other experiments. This is confirmed by infrared absorption spectroscopy of Si:B.

Because of their involvement in growth and survival signaling cascades, the sigma₁ receptors (σ₁Rs) represent a novel target for the treatment of cancer and several brain diseases such as depression and neurodegeneration. From a series of σ₁R-specific ¹⁸F-fluoroalkylated spirocyclic piperidines, we have chosen ¹⁸F-fluspidine for detailed investigation of the in vivo kinetics of the (R)-(+)- and (S)-(-)-enantiomers to identify their potential for imaging in humans.
Methods:
Enantiopure tosylate precursors for radiolabeling were obtained using chiral preparative high-performance liquid chromatography and used for radiosynthesis of both ¹⁸F-fluspidine enantiomers by nucleophilic substitution with K-¹⁸F-F-Kryptofix 222-carbonate complex in a synthesis module. Brain pharmacokinetics were investigated by dynamic PET studies in piglets under baseline and blocking conditions using the highly selective σ₁R agonist SA4503. Standardized uptake values (SUVs) were calculated for 24 MR-defined brain regions. Total distribution volume (V_T) and binding potentials (k₃'/k_4T Results:
The (S)- and (R)-tosylates were obtained in excellent enantiomeric purities (>98% and >96% enantiomeric excess, respectively). (S)-(-)- and (R)-(+)-¹⁸F-fluspidine were synthesized within approximately 70 min (radiochemical yield, 35%-45%; specific activity, 650-870 GBq/µmol; radiochemical purity, >99%). Both radiotracers displayed different brain uptake kinetics. Although the initial brain uptake was similar, the SUV at the end of the study differed significantly (P<0.05), with (R)-(+)-¹⁸F-fluspidine showing about 60%-150% higher values. Administration of SA4503 reduced SUV almost equally for both radiotracers by approximately 65%. Furthermore, k₃' was significantly decreased under blocking conditions in almost all regions ((S)-(-)-¹⁸F-fluspidine, -90%-95%; (R)-(+)-¹⁸F-fluspidine, -70%-90%) wereas effects on k₄ differd according to the particular brain region. V_T estimated by both graphical analysis using Logan plots and full nonlinear kinetic analysis revealed significant inhibition for both radiotracers under blocking conditions.
Conclusion:
Both (S)-(-)-¹⁸F-fluspidine and (R)-(+)-¹⁸F-fluspidine appear to be suitable for σ₁R imaging in humans. The different pharmacokinetics of (S)-(-)-¹⁸F-fluspidine and (R)-(+)-¹⁸F-fluspidine may have the potential for application in the diagnostics of different pathologic conditions.

This article presents the implementation of a coupling between the 3D neutron kinetic core model DYN3D and the commercial, general purpose computational fluid dynamics (CFD) software ANSYS-CFX. In the coupling approach, parts of the thermal hydraulic calculation are transferred to CFX for its better ability to simulate the three-dimensional coolant redistribution in the reactor core region. The calculation of the heat transfer from the fuel into the coolant remains with DYN3D, which incorporates well tested and validated heat transfer models for rod-type fuel elements. On the CFX side, the core region is modelled based on the porous body approach. The implementation of the code coupling is verified by comparing test case results with reference solutions of the DYN3D standalone version. Test cases cover mini and full core geometries, control rod movement and partial overcooling transients.

Durchflussexperimente mit Bohrkernsäulen in Kombination mit der Positronen-Emissions-Tomographie (PET) erlauben die Charakterisierung und Beobachtung von Transporteigenschaften radioaktiv markierter Substanzen innerhalb der Säule. Unter Verwendung der Methode der PET wird das Fließverhalten zweier radioaktiv markierter Lösungen, Natron-Wasserglas (NWG) und gesättigte NaCl-Lösung (NaClges), in einem Kalisalzbohrkern (KSB) visualisiert. Ziel der Injektion von NWG ist es, die innere Struktur des KSB abzudichten bzw. zu vergüten. Über eine im Anschluss an die NWG-Injektion durchgeführte Injektion von NaClges wird die Güte der Abdichtung überprüft. Der Reaktionsmechanismus von NWG im salinarem Milieu wurde mittels Voruntersuchungen in Form von Batch- und Säulenexperimenten untersucht. Das Ergebnis dieser Voruntersuchung zeigte, dass die Reaktion von NWG in NaClges, Salzgrus- und Kochsalzschüttung schnell und nahezu instantan verläuft. Die Hauptuntersuchung, d.h. die Einspritz- und Durchflussexperimente der beiden mit 18F[KF] radioaktiv markierten Injektionslösungen durch den KSB, wurde in den PET-Aufnahmen, in Form von Zeitserien visualisiert. Die Hauptuntersuchung wurde in 5 Teilschritte untergliedert, wobei NaClges im ersten, dritten und fünften Teilschritt injiziert wurde. Injektion von NWG erfolgte im zweiten und im vierten Teilschritt. Eine hochauflösende Computertomographie (µCT) des KSB wurde den PET-Experimenten vorangestellt. Die Aufnahmen der µCT wurden dann mit den Aufnahmen der PET-Experimente verglichen. Die PET-Aufnahmen zeigen im Vergleich mit denen der µCT, bei der ersten Injektion von NaClges des Hauptexperiments einen signifikanten Strömungskanal am Rand des KSB sowie kleinere Strömungswege im zentralen Bereich der Kernstruktur. Nach erfolgten Injektionen von NWG und erneuten Injektionen von NaClges zeigte sich ein stark rückläufiger Randeinstrom und ein stark ausgeprägter zentraler Fluss im Zentralbereich des KSB. Das NWG drang während der Injektionen nur wenige Millimeter in den KSB ein, führt jedoch zu einer signifikanten Permeabilitätsreduktion. Das Verfahren der PET war für die Studie zur Bewertung von Vergütungsmaßnahmen mittels NWG sehr gut anwendbar und konnte das Fließverhalten beider Injektionslösungen im KSB in geeigneter Weise darstellen.

Flowthrough experiments with core columns in combination with positron emission tomography (PET) allow the characterization and monitoring of transport properties of radioactively labeled substances within these columns. By using the method of PET, the flow behavior of two radiolabelled solutions, sodium waterglass (NWG) and saturated sodium chloride solution (NaClges), is visualized in a potash salt drill core (KSB). The aim of the injection of NWG is to seal the interior structure of the KSB. After the injection of NWG an injection of NaClges is performed to verify the seal. The reaction mechanism of the NWG in salty milieu was examined by preliminary tests in the form of batch and column experiments. The reaction mechanism of the NWG in salty milieu was examined by preliminary tests in the form of batch and column experiments. The results of this preliminary study showed that the reaction of NWG in NaClges, in crushed salt rock and crystalline NaCl is rapid and almost instantaneous. The main experiment, the injection and flow experiments of the two 18F[KF] radiolabeled injection solutions in the KSB was visualized in PET images, in the form of time series. The main study was divided into 5 steps, NaClges was injected in the first, the third and the fifth sub-step. The injection of NWG was in the second and the fourth sub-step. Before the PET experiments, a high-resolution computed tomography (μCT) of KSB was carried out. The images of the μCT were compared with the recordings of the PET experiment. In the first injection of NaClges the μCT images in comparison with the PET images of the main experiment showed a significant flow channel at the superficial area of the KSB and smaller flow paths in the central region of the core structure. After the injections of NWG and renewed performed injections of NaClges the PET-images showed a sharp decline of the fluid flow in the superficial area and a very pronounced central flow in the central region of the KSB. The penetration depth of the NWG during the injections was only a few millimeters into the KSB, however it leads to a significant permeability reduction. The process of the PET was very well applicable for the study to evaluate the sealing methods with NWG and could represent the flow behavior of both injection solutions in the KSB appropriately.

While meteorites travel through space, they are exposed to cosmic rays, which induce nuclear reactions producing so-called cosmogenic nuclides (CNs). If meteorites land on Earth, production stops and radioactive nuclides start to decay. Thus, CNs, stable and radioactive, are archives of the exposure and terrestrial history of individual meteorites. Moreover, when looking at a larger number of meteorites, this may also give hints about the constancy of the cosmic radiation itself [1].
Data for the lighter cosmogenic radionuclides ¹⁰Be, ²⁶Al, ³⁶Cl, and ⁴¹Ca (t_1/2=0.1-1.4 Ma) are now attainable at the accelerator mass spectrometry facility DREAMS [2]. Accompanied by data for the heavier radionuclides ⁵³Mn (t_1/2=3.7 Ma) and ⁶⁰Fe (t_1/2=2.6 Ma), which are measured at the large tandems at Canberra and Munich, and stable noble gas nuclides from Mainz and Bern, complete exposure histories of extraterrestrial material can be reconstructed.
One of the first meteorites investigated by this team is Gebel Kamil, an ungrouped Ni-rich iron meteorite that produced an impact crater (Ø: 45 m) in southern Egypt. Two neighboured shrapnel (S) samples and two from the only individual (I) fragment (~83 kg) have been analysed. Concentrations of all CNs – stable and radioactive – are a factor ~4 x lower in S-samples than in I-samples. Comparison with Monte-Carlo calculations of production rates indicate that Gebel Kamil was exposed as a meteoroid body of 115-120 cm radius (50-60 tons). Samples I originate from a moderate shielding of ~20 cm, whereas samples S are from a deeper position of 50-80 cm. Most reliable ³⁶Cl-³⁶Ar ages of I and S are (366 ± 18) Ma [3].
Chemically and analytically more challenging are the analyses of corresponding pairs of chondrule and matrix to decipher the ancient and recent exposure history from two highly primitive meteorites [4]. Chondrules may have been irradiated for millions of years as free-floating particles in the solar nebula by the cosmic rays at that time. Despite sample masses of only 1.6-1.8 mg for single chondrules, radioactive CN results for two highly primitive Renazzo-type (CR3) chondrites from Antarctica (MET00426 & QUE99177) are clearly dis-tinguishable from processing blank and can, thus, be used in combination with noble gas data.
Chemically and analytically demanding for both noble gases and ³⁶Cl are also the analyses of pairs of troilite (FeS) inclusions and metal fractions from the iron meteorite Mundrabilla. This work is struggling with mg-amounts of sulphur, where ³⁶S is a troublesome isobar of ³⁶Cl and also causes severe problems in noble gas spectrometry. It is aimed at improving determination of production rates for lighter nuclides such as ^3,4He, ¹⁰Be, ²¹Ne, ²⁶Al and ³⁶Cl.
Ackn.: L. Folco, J. Zipfel (meteorites) & accelerator crews and colleagues (support AMS).

[1] Smith et al. contribution to 13th Int. Conf. on Accelerator Mass Spectrometry (AMS-13).
[2] Akhmadaliev et al., Nucl. Instr. Meth. B 294, 5 (2013) & Pavetich et al., this meeting.
[3] Ott et al., submitted to Meteorit. Planet. Sci.
[4] Ott et al., contribution to 13th Int. Conf. on Accelerator Mass Spectrometry (AMS-13).

not available, please contact the authors

Vacancy-type defects created by helium implantation in tungsten and their impact on the
nano-hardness characteristics were investigated by correlating the results from the positron annihilation spectroscopy and the nano-indentation technique. Helium implantation was performed at room temperature (RT) and at an elevated temperate of 600 C. Also, the effect of post-annealing of the RT implanted sample was studied. The S parameter characterizing the open volume in the material was found to increase after helium irradiation and is significantly enhanced for the samples thermally treated at 600 C either by irradiation at high temperature or by post-annealing. Two types of helium-vacancy defects were detected after helium irradiation; small defects with high helium-to-vacancy ratio (low S parameter) for RT irradiation and large defects with low helium-to-vacancy ratio (high S parameter) for thermally treated tungsten. The hardness of the heat treated tungsten coincides with the S parameter, and hence is controlled by the large helium-vacancy defects. The hardness of tungsten irradiated at RT without thermal treatment is dominated by manufacturing related defects such as dislocation loops and impurity clusters and additionally by trapped He atoms from irradiation effects, which enhance hardness. He-stabilized dislocation loops mainly cause the very high hardness values in RT irradiated samples without post-annealing.

In the present work, zirconia (ZrO2) nanopowders doped with yttria (Y2O3) and chromia (Cr2O3) were prepared by a co-precipitation technique. The nanopowders were then subjected to a calcination and a successive sintering at elevated temperatures up to 1500 °C. The nanostructures in these nanomaterials were characterized by positron annihilation spectroscopy (positron lifetimes and Doppler broadening measurements) which is a non-destructive technique with a high sensitivity to atomic-scale open-volume defects. It was found that the zirconia-based nanomaterials studied contain vacancy-like defects and nano-scale pores. Diffusion processes induced in these nanomaterials by sintering were investigated also by depth sensitive positron annihilation studies using a variable energy slow positron beam. Sintering was found to cause intensive grain growth and a removal of porosity by a migration of pores from the sample interior toward its surface.

Invesigation the solid solution USiO4-ZrSiO4 is related with the problem to avoid the formation of the related oxides UO2 and ZrO2. In previous studies we have shown that the formation of UO2 can be relatively easy supressed by using an excess of SiO2 during the hydrothermal synthesis already at relatively low temperature. The formation of ZrO2 is obviously more pronounced in the same temperature range. A part of Zr enters the amorphous phase. The aim of this study is to investigate the Zr containing phases in crystalline and in amorphous state with HRPD and XAFS, respectively.

Uranium forms analogous minerals with phosphate and arsenate. In aqueous solutions an analogy is expected to govern the complexes that uranium builds with these ligands. Three uranyl arsenate complexes UO2H2AsO4+, UO2HAsO4 0 and UO2(H2AsO4)2 0 were identified and reported previously with TRLFS in the pH range 1 to 3. Using a similar detection system and elevating the pH range a negatively charged fourth uranyl-arsenate complex, UO2AsO4- was found under circum neutral pH. Determining the complex formation constant for this complex was not possible due to the susceptibility of the fluorescence intensity to external influences and the difficulty of resolving the measured spectra into individual fluorescence contributions. By immediate shock-freezing to 15K we succeeded to measure a reproducible EXAFS spectrum of a uranyl-arsenate species in an aqueous solution at pH 2.

CFD simulations of dispersed bubbly flow on the scale of technical equipment become feasible within the Eulerian two-fluid framework of interpenetrating continua. For practical applications suitable closure relations are required which describe the interfacial exchange processes. Implementations of such closures have been provided in major commercial codes for years, but more recently there is a growing interest also in open source packages among which in particular OpenFOAM has become widely known.
In the present work a set of closure relations suitable for adiabatic bubbly flow has been implemented in OpenFOAM. Selection of closure models has been based on previous experience with ANSYS-CFX. Great effort has been made to match all details of the models so that the same results may be expected and residual differences are only due to different numerical procedures. In this way the new open source implementation is validated and shown to be competitive with commercial codes.

The oxygen content of a nonstoichiometric oxide compound is, in numerous cases, decisive regarding the material properties (electrical and/or thermal conductivity, melting point, etc). A phase separation is known to occur in oxygenhypostoichiometric uranium-plutonium mixed oxides beyond 20 mol% Pu. During its fabrication, the (U1-yPuy)O2-x mixed oxide can be subjected to several atmospheres, at room temperature, before being enclosed in the final fuel rods (e.g. storage after reducing sintering). Using a multi-scale approach (from the sample’s bulk to its surface), we reveal the evidence of spontaneous room-temperature oxidation of biphasic (U1-yPuy)O2-x compounds, with y = 0.28 and 0.45, even when exposed to low moisture and oxygen levels. This oxidation is, in both cases, significant within very short timescales. We believe our results are of utmost importance in the prospect of characterizing oxygen-hypostoichiometric uranium-plutonium mixed oxides with high Pu content.

To evaluate effects of wall friction coefficients in a one-dimensional model on prediction of countercurrent flow limitation (CCFL), sensitivity computations were done for hot leg models (ratio of length to diameter L/D = 8.6) and a pressurizer surge line model without elbows (L/D = 63) and computed results were compared with measured values. When the interfacial drag coefficient of fi = 0.03 and wall friction coefficients fwG in single-phase gas flows were used, the appropriate amplification for wall friction coefficients fwL in single-phase liquid flows was NwL = 6 to fit the computed CCFL value with the measured CCFL value.

Numerical simulation was carried out for air-water countercurrent flows in a 1/10-scale model of the pressurizer surge line in a pressurized water reactor. The model consisted of a vertical pipe, a vertical elbow, and a slightly inclined pipe with elbows. In an actual 1/10-scale experiment, air supplied into the lower tank flowed up to the upper tank through the surge line and water supplied into the upper tank flowed down to the lower tank through the surge line. In the case of water supply into the upper tank in the simulation, the flow pattern in the inclined pipe was not reproduced because of flooding at the upper end of the vertical pipe with a sharp edge. To avoid effects of flooding at the upper end, therefore, water was also supplied from the wall surface of the vertical pipe and then the flow pattern in the inclined pipe was successfully reproduced. The simulated countercurrent flow limitation (CCFL) values agreed well with the experimental CCFL data.

Sensitivity computations were carried out for hot leg models (ratio of the horizontal pipe length to the diameter, L/D = 8.6) and pressurizer surge line models with and without elbows (ratio of the inclined pipe length to the diameter, L/D = 63) to evaluate suitable wall friction coefficients and pressure loss coefficients of elbows in a one-dimensional model predicting countercurrent flow limitation (CCFL) in a piping system. Computed results were compared with measured values. When the interfacial drag coefficient of fi = 0.03 and wall friction coefficients fwG of single-phase gas flows (i.e. adjustment factor, NwG = 1) were used, the appropriate adjustment factor for wall friction coefficients fwL of single-phase liquid flows was NwL = 6; this gave good fit of the computed CCFL values with the CCFL values measured in piping systems without elbows (L/D = 8.6 and 63). When fi = 0.03, NwG = 1, and NwL = 6 were used, the appropriate adjustment factor for pressure loss coefficients ζe of elbows in single-phase flows was Nde = 10; this gave good fit of the computed CCFL values with the CCFL values measured in the piping system with elbows (L/D = 63).

The year 2013 was the third year of HZDR as a member of the Helmholtz Association (HGF), and we have made progress of integrating ourselves into this research environment of national Research centers. In particular, we were preparing for the evaluation in the framework of the so-called program oriented funding (POF), which will hopefully provide us with a stable funding for the next five years (2015 – 2019). In particular, last fall we have submitted a large proposal in collaboration with several other research centers. The actual evaluation will take place this spring. Most of our activities are assigned to the program “From Matter to Materials and Life” (within the research area “Matter”). A large fraction of this program is related to the operation of large-scale research infrastructures (or user facilities), one of which is our Ion Beam Center (IBC). The second large part of our research is labelled “in-house research”, reflecting the work driven through our researchers without external users, but still mostly utilizing our large-scale facilities such as the IBC, and, to a lesser extent, the free-electron laser. Our in-house research is performed in three so-called research themes, as depicted in the schematic below. What is missing there for simplicity is a small part of our activities in the program “Nuclear Waste Management and Safety” (within the research area “Energy”).

The Institute of Resource Ecology (IRE) ISone of the eight institutes of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The Research activities are mainly integrated into the program “Nuclear Safety Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”.
Additionally, various activities have been started investigating chemical and environmental aspects of processing and recycling of strategic metals, namely rare earth elements. These activities are located in the HGF program “Energy Efficiency, Materials and Resources (EMR)”. Both programs, and therefore all work which is done at IRE, belong to the research sector “Energy” of the HGF.
The research objectives are the protection of humans and the environment from hazards caused by pollutants resulting from technical processes that produce energy and raw materials. Treating technology and ecology as a unity is the major scientific challenge in assuring the safety of technical processes and gaining their public acceptance. Namely, we investigate the ecological risks exerted by radioactive and non-radioactive metals in the context of nuclear waste disposal, the production of energy in nuclear power plants and in processes along the value chain of metalliferous raw materials. A common goal is to generate better understanding about the dominating processes essential for metal mobilization and immobilization on the molecular level. This in turn enables us to assess the macroscopic phenomena, including models, codes and data for predictive calculations, which determine the transport and distribution of contaminants in the environment.

In the past, inter-band transitions in quantum dots (QDs) have received an appreciable amount of scientific interest. However, inter-sublevel transitions have been studied much less extensively, likely because of their strongly non-radiative nature and because of limited availability of tunable sources for resonant excitation. In this work we explore the dynamics of inter-sublevel transitions in single InAs/GaAs self-assembled QDs. We combine the commonly used micro-photoluminescence (PL) technique with time-resolved detection and additional excitation by a free-electron laser. The experiment is carried out in the following way: the low-density QD sample is illuminated with a picosecond pulsed Ti:sapphire laser. PL from a single QD is coupled into a spectrometer, recording the spectrum with a CCD detector, as well as the time-resolved transient via the time-correlated single photon counting technique. Introducing a free-electron laser pulse tuned to the inter-sublevel transition energy excites carriers to a higher energy level, which decay back to the ground state non-radiatively with a relatively short time constant. These inter-sublevel dynamics causes quenching in the exponential PL decay of the energy of the ground state, which can be observed in timeresolved measurements. Whereas previous studies on inter-sublevel transitions have used QD ensembles[1-3], investigating single dots excludes many-dot effects such as inhomogeneous broadening and inter-dot transfer, which should lead to a better understanding of intersublevel carrier dynamics.

As a member of diluted nitrides, GaAsN is a highly interesting material system for many application purposes such as LEDs, lasers, solar cells, and infrared photodetectors because of the tuning possibility of these devices by the variation of the nitrogen content. For an accurate description of this material system, a profound knowledge of the band structure and in particular the effective mass (EM) is crucial. Because of the inconsistency of previous results, which can be traced down to the particular investigation method, we apply several methods on one sample series of GaAsN containing samples with 0.1 - 1 percent of nitrogen. Cyclotron resonance spectroscopy, beeing the most direct method, reveals that the EM is not signicantly affected by the nitrogen doping. Photoluminescence, on the other hand, stems from several transitions, which are not resolved spectrally, but identified in time-resolved measurements. We discuss the different behaviour of the involved transitions in magnetic fields up to 7 T (static) and 41 T (pulsed).

In this contribution, we present the control of the effective damping by the spin-transfer torque of a pure spin current injected into Heusler compound microstructures. Here, the pure spin current is generated by a DC current in a Pt layer on top of the magnetic layer via the spin-Hall effect. By changing the current density and the direction of the DC current in the Pt layer, the generated pure spin current can be manipulated. Via the spintransfer torque this pure spin current can act on the magnetization in the magnetic layer and, for example, decrease or even compensate the Gilbert damping.
The damping, i.e. the Gilbert damping, is a very crucial parameter for any magnetization dynamics and the possibility to control this parameter, i.e. to further reduce the damping, could give rise to novel nonlinear phenomena. Especially, cobalt-based Heusler compounds as used in this work provide a large spin-wave propagation length and an already very low Gilbert damping. Thus, the threshold for all spin-torque driven phenomena is decreased and only small current densities in the Pt layer are needed. By determining the threshold power for parallel parametric amplification of spin waves, for example, the change of the damping in dependence of the DC current can be determined.
The presented results were obtained using Brillouin light scattering microscopy. Brillouin light scattering is the inelastic scattering of photons on magnons, the quanta of spin waves. By investigating the frequency and the intensity of the inelastically scattered light, the frequency and the intensity of the spin waves can be obtained. Using a microfocussed laser allows for a spatial resolution of about 400 nm.
The results show a strong influence of the pure spin current on the effective damping in the magnetic layer. They show the feasibility of using a DC current in a Platinum layer to control the effective damping an adjacent Heusler layer. Thus, this is very interesting for possible applications using spin waves or for the investigation of nonlinear effects especially in Heusler compounds.

The nonlinear decay of propagating spin waves in the low-Gilbert-damping Heusler film Co2Mn0.6Fe0.4Si is reported. Here, two initial magnons with frequency f0 scatter into two secondary magnons with frequencies f1 and f2. The most remarkable observation is that f1 stays fixed if f0 is changed. This indicates, that the f1 magnon mode has the lowest instability threshold, which, however, cannot be understood if only Gilbert damping is present. We show that the observed behavior is caused by interaction of the magnon modes f1 and f2 with the thermal magnon bath. This evidences a significant contribution of the intrinsic magnon-magnon scattering mechanisms to the magnetic damping in high-quality Heusler compounds.

We report on the Q-switched laser operation by the evanescent-field interaction with the graphene layers deposited on a Nd:YAG surface planar waveguide, which was fabricated by the 15 MeV carbon ion irradiation. Based on the simple and compact design of the cavity with saturable-absorber features, the Q-switched pulsed waveguide laser operation was achieved at the wavelength of 1064 nm through the interaction between the graphene layer and the evanescent-field of the waveguide mode. The maximum output pulse repetition rate was ~29 kHz with the pulse duration of ~9.8 µs.

Ferrous iron bound to clay mineral surfaces is an important redox active-phase that is ubiquitous in both engineered and natural environments. In this study, the retention mechanism of Fe(II) on clay minerals was investigated using macroscopic sorption experiments combined with Mössbauer and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopies. Sorption edges and isotherms were measured under anoxic conditions on natural Fe-bearing montmorillonites (i.e. STx, SWy and SWa) having different structural Fe contents ranging from 0.5 to 15.4 wt % and different initial Fe redox states. Batch experiments indicated that, in case of low Fe-bearing (STx) and dithionite-reduced clays, the Fe(II) uptake follows well the sorption behavior of other divalent transition metals, whereas Fe(II) sorption increased by up to two orders of magnitude on the unreduced, Fe(III)-rich montmorillonites (SWy and SWa). Mössbauer spectroscopy analysis revealed that nearly all the sorbed Fe(II) was oxidized to surface-bound Fe(III) and secondary Fe(III) precipitates were formed on the Fe(III)-rich montmorillonite, while sorbed Fe is predominantly present as Fe(II) on Fe-low and dithionite-reduced clays. The results provide compelling evidence that Fe(II) uptake characteristics on clay minerals are strongly correlated to the redox properties of the structural Fe(III). The improved understanding of the interfacial redox interactions between sorbed Fe(II) and clay minerals gained in this study is essential for future studies developing Fe(II) sorption models on natural montmorillonites.

The mechanism of tailored magnetic anisotropy in amorphous Co68Fe24Zr8 thin films was investigated by ferromagnetic resonance (FMR) on samples deposited without an applied magnetic field, with an out-of-plane field and an in-plane field. Analysis of FMR spectra profiles, high frequency susceptibility calculations, and statistical simulations using a distribution of local uniaxial magnetic anisotropy reveal the presence of atomic configurations with local uniaxial anisotropy, of which the direction can be tailored while the magnitude remains at an intrinsically constant value of 3.0(2) kJ/m(3). The in-plane growth field remarkably sharpens the anisotropy distribution and increases the sample homogeneity. The results benefit designing multilayer spintronic devices based on highly homogeneous amorphous layers with tailored magnetic anisotropy.

In a hypothetical Small Break Loss of Coolant Accident in a Pressurized Water Reactor, the Reactor Pressure Vessel wall may be exposed to thermal stress, since Emergency Core Cooling Systems inject cold water into the hot reactor system. The loads on the primary loop and RPV walls are determined by mixing processes with the surrounding hot water and by the condensation of steam on the free surface.
In order to develop Computational Fluid Dynamics Simulations for future safety assessment and design purposes, experiments with stratified steam-water surfaces and with plunging liquid jets have been carried out and are being analyzed. It is shown, that the results may be used to develop and to validate CFD-models for reactor safety applications. Analysis, conditioning and summary of measured data is ongoing and promising.

Abstract:

The aim of this analysis was to investigate the impact of tumour-,
treatment- and patient-related cofactors on local control and survival after postoperative adjuvant radiotherapy in patients with non-small cell lung cancer (NSCLC), with special focus on waiting and overall treatment times.
For 100 NSCLC patients who had received postoperative radiotherapy, overall, relapse-free and metastases-free survival was retrospectively analysed using Kaplan-Meier methods. The impact of tumour-, treatment- and patient-related cofactors on treatment outcome was evaluated in uni- and multivariate Cox regression analysis.
No statistically significant difference between the survival curves of the groups with a short versus a long time interval between surgery and radiotherapy could be shown in uni- or multivariate analysis.
Multivariate analysis revealed a significant decrease in overall survival times for patients with prolonged overall radiotherapy treatment times exceeding 42 days (16 vs. 36 months) and for patients with radiation-induced pneumonitis (8 vs. 29 months).
Radiation-induced pneumonitis and prolonged radiation treatment times significantly reduced overall survival after adjuvant radiotherapy in NSCLC patients. The negative impact of a longer radiotherapy treatment time could be shown for the first time in an adjuvant setting. The hypothesis of a negative impact of longer waiting times prior to commencement of adjuvant radiotherapy could not be confirmed.

We report a unipolar, nonvolatile resistive switching in polycrystalline YMnO₃ thin films grown by pulsed laser deposition and sandwiched between Au top and Ti/Pt bottom electrodes. The ratio of the resistance in the OFF and ON state is higher than 10³. The observed phenomena can be attributed to the formation and rupture of the conductive filaments within the YMnO₃ film. The generation of conductive paths under applied electric field is discussed in terms of the presence of grain boundaries and charged domain walls inherently formed in hexagonal YMnO₃. Our findings suggest that engineering of the ferroelectric domains might be a promising route for designing and fabrication of novel resistive switching devices.

Extended dynamical simulations have been performed on a (2+1)-dimensional driven dimer lattice-gas model to estimate aging properties. The autocorrelation and the autoresponse functions are determined and the corresponding scaling exponents are tabulated. Since this model can be mapped onto the (2+1)-dimensional Kardar-Parisi-Zhang surface growth model, our results contribute to the understanding of the universality class of that basic system.

The nickel -- carbon system has received increased attention over the past years due to the relevance of nickel as a catalyst for carbon nanotube growth and as a substrate for metal-induced crystallization of graphene and graphite.
Nickel carbides as bulk materials are out
of reach for experimental studies because of their meta-stability. Ab-initio studies are rare. We present our ab-initio -- frozen phonon results for the elastic properties of Ni₃C, Ni₂C and NiC.

The Kinetic Metropolis Lattice Monte-Carlo (KMC) method is a means of performing atomistic simulations of self-organization processes in solids at by far larger scales than those accessible via Molecular Dynamics. Employing a cellular automaton approach allows incorporation of many body interactions and external driving forces. Here, we present an efficient KMC implementation on single and multiple GPUs, which allows us to study phase separation and nanostructure-evolution at spatio-temporal experimental scales. The KMC implementation has been used to develop with industrial partners a new Si-based nanocomposite for next-generation thin-film solar cells.

A gravity-scalar model in 5-dimensional Riemann space is adjusted to the thermodynamics of SU(3) gauge field theory in the temperature range of 1–10 T/Tc to calculate holographically the bulk viscosity in 4-dimensional Minkowski space. Various settings are compared, and it is argued that, upon an adjustment of the scalar potential to reproduce exactly the lattice data within a restricted temperature interval above Tc, rather robust values of the bulk viscosity to entropy density ratio are obtained.

The DREAMS (DREsden Accelerator Mass Spectrometry) facility [1] is designed for routine measurements of the radionuclides ¹⁰Be, ²⁶Al, ³⁶Cl, ⁴¹Ca and ¹²⁹I. By upgrading the facility the measurement conditions for volatile elements could be improved, e.g. minimisation of the ion source memory effect. Additionally the detection of heavy nuclides has been achieved.
For the measurement of volatile elements e.g. Cl and I, a low-memory-effect ion source, based on the original High Voltage Engineering design was developed and successfully compared to other up-to-date ion sources [2]. Recently, first analyses of unknown ³⁶Cl-AMS samples were performed with this modified ion source. Parameters like current output, ion source fractionation effects, normalization factors, blank values and sulphur suppression factors have been investigated to enhance the accuracy of 36Cl data. Applications cover a wide spectrum from groundwater dating [3] and the characterisation of water/rock interactions including brine admixture [4] in arid regions, respectively the investigation of the constancy of the galactic cosmic radiation [5] and the reconstruction of exposure histories of individual meteorites. This broad range of applications also implies highly variable ³⁶Cl/³⁵⁺³⁷Cl-ratios ranging from nearly background level of ~10^-15 up to 10^-10.
To extend the measurement capabilities to actinides a time-of-flight system based on thin carbon foils and Micro Channel Plates was designed and is under construction at DREAMS. Special beam diagnostic elements were manufactured for an optimal tuning of the system with low currents. In cooperation with the Australian National University first actinide samples were measured at DREAMS.

[1] Akhmadaliev et al., Nucl. Instr. Meth. B 294 (2013) 5.
[2] Pavetich et al., Nucl. Instr. Meth. B 329 (2014) 22.
[3] Müller et al., Hydrogeology J., in preparation.
[4] Siebert et al., Sci. Total Environ., in preparation.
[5] Smith et al., AMS-13 abstract

The long-lived radionuclides ²⁶Al (t_1/2 = 0.72 Myr) and ⁶⁰Fe (t_1/2 = 2.6 Myr) are generated in massive stars and ejected into space by stellar winds and explosions. If a star ends its life in a supernova (SN) explosion close to the solar system, a fraction of these elements might be deposited in terrestrial archives. Recent analysis of a ferromanganese crust [1,2] evidences an ⁶⁰Fe concentration enhancement ~2-3 Myr ago. This radionuclide does not have terrestrial sources and is suggested to originate from one or more SNe [1]. Depth profiles with ~100 individual samples from deep-sea sediment cores (Indian Ocean) are studied to obtain a detailed data set of ²⁶Al and ⁶⁰Fe concentrations within the time period of the ⁶⁰Fe signal in the crust. The targets were measured using accelerator mass spectrometry [3]. In contrast to our ⁶⁰Fe data, which shows a clear signal without terrestrial background, a possible ²⁶Al signal from a SN event is hidden within a non-negligible terrestrial background production [4]. The major source of ²⁶Al is spallogenic production by cosmic-rays in the Earth’s atmosphere. This first full history of precise ²⁶Al and ⁶⁰Fe data over a time period of 2 Myr for two sediment cores is compared to theoretical estimations of a SN-produced radionuclide deposition on Earth considering different nucleosynthesis models and SN signal widths.
[1] Knie et al., Phys. Rev. Lett 93 (2004)
[2] Fitoussi et al., Phys. Rev. Lett 101 (2008)
[3] Wallner er al., this conf.
[4] Feige et al., EPJWC, 63 (2013)

PIConGPU is a massively parallel open source particle-in-cell (PIC) code written for CUDA capable graphics cards (GPUs). PIC codes are used to model fully relativistic electro-magnetic interactions between particles and discrete mesh points (fields) in a self-consistent manner. That allows for ab-intio simulations ranging from astrophysical scenarios like emerging plasma instabilities to modern laser-driven particle accelerators like the laser-wakefield accelerator (LWFA).

In this talk, we will present the strategy to port a non-trivial algorithm to a modern, massively parallel hardware architecture like GPUs. We give a short introduction in our free multi-GPU Framework libPMacc for general mesh and particle based simulations. Based on that, scalings up to 18,000 GPUs on the Titan supercomputer (Oak Ridge National Lab) will be discussed.

Applications will include results of in-situ far field radiation diagnostics for the relativistic Kelvin-Helmholtz-Instability (KHI) by evolving billions of electrons and calculating their individual Liénard-Wiechert potential for arbitrary directions and frequencies on the fly.

Synthetic diagnostics in particle-in-cell codes provide physical quantities to the scientist that can be directly compared to experiment. We present simulations of laser-wakefield acceleration of electrons and on the dynamics of the relativistic Kelvin-Helmholtz Instability using the code PIConGPU. With PIConGPU it is possible to compute the radiation of every single electron in the simulation caused by acceleration by computing the Lienard-Wiechert Potentials, including both coherent and incoherent radiation. With GPU-accelerated codes Petaflop performance has become possible.

We demonstrate the potential of X-ray free-electron lasers (XFEL) to advancethe understanding of complex plasma dynamics by allowing for the first time nanometer and femtosecond resolution at the same time in plasma diagnostics. Plasma phenomena on such short timescales are of high relevance for many fields of physics, in particular in the ultra-intense ultra-short laser interaction with matter. Highly relevant yet only partially understood phenomena may become directly accessible in experiment. These include relativistic laser absorption at solid targets, creation of energetic electrons and electron transport in warm dense matter, including the seeding and development of surface and beam instabilities, ambipolar expansion, shock formation, and dynamics at the surfaces or at buried layers. We demonstrate the potentials of XFEL plasma probing for high power laser matter interactions using exemplary the small angle X-ray scattering, resonant coherent X-ray diffraction imaging and photon correlation spectroscopy, focusing on general considerations for XFEL probing.

Ground-state properties of Nd³⁺ ion in the magnetically concentrated CsNd(MoO₄)₂ lattice of orthorhombic symmetry have been investigated at low temperatures. Magnetic-field dependence of magnetization measured at 5 K in the magnetic field applied along the a, b, c crystallographic axes reflects slight deviations from the tetragonal symmetry of a local surrounding of Nd³⁺ ion. The analysis of the data performed within a model of an ideal paramagnet provided g-factor values, g_a = 3.08, g_b = 1.90, and g_c = 1.95. Angular dependence of the electron paramagnetic resonance spectra studied at temperature 2.5 K was investigated in the ab, ac and bc planes. The spectra are dominated by a broad asymmetric line which is strongly deformed due to the formation of a fine structure ascribed to the presence of nonequivalent Nd³⁺ sites. The analysis of the spectra confirmed the easy-axis character of a magnetic anisotropy. In addition, nontrivial tilting of the local anisotropy axes from the crystallographic axes was revealed, indicating lowering of crystal symmetry at low temperatures.

The temperature dependence of the spin susceptibilities of S = 1, 3/2 , 2, 5/2 and 7/2 Heisenberg antiferromagnetic 1D spins chains with nearest-neighbor coupling was simulated via Quantum Monte Carlo calculations, within the reduced temperature range of 0,005 ≤ T* ≤ 100, and fitted to a Padé approximation with deviations between the simulated and fitted data of the same order of magnitude as or smaller than the quantum Monte Carlo simulation error. To demonstrate the practicality of our theoretical findings, we compare these results with the susceptibility of the well known 1D chain compound TMMC ([(CH₃)₄N[MnCl₃]], d⁵, S = 5/2) and find that different intra-chain spin–exchange parameters result if we consider the data above and below the structural phase transition reported for TMMC at ~126 K. The structural phase transition, which gives rise to an anomaly in the magnetic susceptibility, is independent of the magnetic field up to magnetic fields of 7 T. Additionally, we show that the S = 1 system NiTa₂O₆ with tri-rutile crystal structure can be very well described as a Heisenberg S = 1 spin chain.

The magnetic and lattice properties of the S = 1/2 quantum-spin-chain ferromagnet CuAs₂O₄, mineral Name trippkeite, were investigated. The crystal structure of CuAs₂O₄ is characterized by the presence of corrugated CuO₂ ribbon chains.Measurements of themagnetic susceptibility, heat capacity, electron paramagnetic resonance, and Raman spectroscopy were performed. Our experiments conclusively show that a ferromagnetic Transition occurs at ∼7.4 K. Ab initio DFT calculations reveal dominant ferromagnetic nearest-neighbor and weaker antiferromagnetic next-nearest-neighbor spin exchange interactions along the ribbon chains. The ratio of J_nn/J_nnn is near −4, placing CuAs₂O₄ in close proximity to a quantum critical point in the Jnn-Jnnn phase diagram. TMRG simulations used to analyze the magnetic susceptibility confirm this ratio. Single-crystal magnetization measurements indicate that a magnetic anisotropy forces the Cu²⁺ spins to lie in an easy plane perpendicular to the c axis. An analysis of the field- and temperature-dependent magnetization by modified Arrott plots reveals a 3d-XY critical behavior. Lattice perturbations induced by quasihydrostatic pressure and temperature were mapped via magnetization and Raman spectroscopy

We perform kinematic simulations of dynamo action driven by a helical small scale flow of a conducting fluid in order to deduce mean-field properties of the combined induction action of small scale eddies. We examine two different flow patterns in the style of the G.O. Roberts flow but with a mean vertical component and with internal fixtures that are modelled by regions with vanishing flow. These fixtures represent either rods that lie in the center of individual eddies, or internal dividing walls that provide a separation of the eddies from each other. The fixtures can be made of magnetic material with a relative permeability larger than one which can alter the dynamo behavior. The investigations are motivated by the widely unknown induction effects of the forced helical flow that is used in the core of liquid sodium cooled fast reactors, and from the key role of soft iron impellers in the von-Kármán-Sodium (VKS) dynamo.

For both examined flow configurations the consideration of magnetic material within the fluid flow causes a reduction of the critical magnetic Reynolds number of up to 25%. The development of the growth-rate in the limit of the largest achievable permeabilities suggests no further significant reduction for even larger values of the permeability.

In order to study the dynamo behavior of systems that consist of tens of thousands of helical cells we resort to the mean-field dynamo theory (Krause & Rädler 1980) in which the action of the small scale flow is parameterized in terms of an α- and β-effect. We compute the relevant elements of the α- and the β-tensor using the so called testfield method. We find a reasonable agreement between the fully resolved models and the corresponding mean-field models for wall or rod materials in the considered range 1 ≤ μ ≤ 20. Our results may be used for the development of global large scale models with recirculation flow and realistic boundary conditions.

Ziel/Aim:

FDG-PET/CT has become the standard for staging of local tumor extent, mediastinal lymph node involvement and distant metastatic disease in patients with non-small-cell lung cancer (NSCLC). However, its role for prognosis is less clear. The aim of the present study was to evaluate the prognostic value of a novel quantitative measure for the spatial heterogeneity of FDG uptake, the asphericity (ASP).

Methodik/Methods:

FDG-PET/CT had been performed in 47 patients (65.1±8.8y, 38 males) with newly diagnosed NSCLC prior to treatment. PET images of the primary tumor were segmented using the ROVER 3D segmentation tool based on thresholding at the volume-reproducible intensity threshold after subtraction of local background. The ASP defined as the deviation of the tumor's shape from sphere symmetry was implemented in ROVER. Kaplan-Meier analysis with respect to overall (OS) and progression-free survival (PFS) was performed for localization (central vs. peripheral), SUVmax, metabolically active tumor volume (MTV), total lesion glycolysis (MTV*SUVmean) and ASP. OS and PFS curves were separated by the median value and compared by log-rank tests.

Ergebnisse/Results:

32 patients experienced tumor progression or recurrence after a median interval of 6.2 (range, 0.4-26.7) months. 19 of these patients died during a median follow-up of 8.7 (0.4-26.7) months. ASP was the only prognostic factor for PFS (p=0.01): the probability of 1-year PFS decreased from 69 % in the patients with low ASP to 37 % in the patients with high ASP. Furthermore, there was a tendency towards longer OS in case of small vs large ASP (p=0.06, 1-year-OS 81% vs 51%). The localization of the tumor was a strong predictor for OS (p=0.004, 1-year OS 78% vs 25% for peripheral vs central localization), but not for PFS (p=0.12).

Schlussfolgerungen/Conclusions:

The novel parameter asphericity of the pretherapeutic FDG-uptake provides more power for the prediction of PFS in NCSLC than conventional quantitative measures including SUVmax, MTV and glycolytic tumor volume.

Background

Standard uptake values (SUV) as well as tumor-to-blood standard uptake ratios (SUR) measured with [18F-]fluorodeoxyglucose (FDG) PET are time dependent. This poses a serious problem for reliable quantification since variability of scan start time relative to the time of injection is a persistent issue in clinical oncological Positron emission tomography (PET). In this work, we present a method for scan time correction of, both, SUR and SUV.
Methods

Assuming irreversible FDG kinetics, SUR is linearly correlated to Km (the metabolic rate of FDG), where the slope only depends on the shape of the arterial input function (AIF) and on scan time. Considering the approximately invariant shape of the AIF, this slope (the `Patlak time?) is an investigation independent function of scan time. This fact can be used to map SUR and SUV values from different investigations to a common time point for quantitative comparison. Additionally, it turns out that modelling the invariant AIF shape by an inverse power law is possible which further simplifies the correction procedure. The procedure was evaluated in 15 fully dynamic investigations of liver metastases from colorectal cancer and 10 dual time point (DTP) measurements. From each dynamic study, three `static scans? at T = 20, 35, and 55 min post injection (p.i.) were created, where the last scan defined the reference time point to which the uptake values measured in the other two were corrected. The corrected uptake values were then compared to those actually measured at the reference time. For the DTP studies, the first scan (acquired at 78.1 ? 15.9 min p.i.) served as the reference, and the uptake values from the second scan (acquired 39.2 ? 9.9 min later) were corrected accordingly and compared to the reference.
Results

For the dynamic data, the observed difference between uncorrected values and values at reference time was (?52 ? 4.5)% at T = 20 min and (?31 ? 3.7)% at T = 35 min for SUR and (?30 ? 6.6)% at T = 20 min and (?16 ? 4)% at T = 35 min for SUV. After correction, the difference was reduced to (?2.9 ? 6.6)% at T = 20 min and (?2.7 ? 5)% at T = 35 min for SUR and (1.9% ? 6.2)% at T = 20 min and (1.7 ? 3.3)% at T = 35 min for SUV. For the DTP studies, the observed differences of SUR and SUV between late and early scans were (48 ? 11)% and (24 ? 8.4)%, respectively. After correction, these differences were reduced to (2.6 ? 6.9)% and (?2.4 ? 7.3)%, respectively.
Conclusion

If FDG kinetics is irreversible in the targeted tissue, correction of SUV and SUR for scan time variability is possible with good accuracy. The correction distinctly improves comparability of lesion uptake values measured at different times post injection.

The redox behaviour of Tc(VII)/Tc(IV) was investigated within the pHc range 2–14.6 in (0.5 M and 5.0 M) NaCl and (0.25 M, 2.0 M and 4.5 M) MgCl2 solutions in the presence of different reducing agents (Na2S2O4, Sn(II), Fe(II)/Fe(III), Fe powder) and macroscopic amounts of Fe minerals (magnetite, mackinawite, siderite: S/L = 20–30 g×L–1). In the first group of samples, the decrease of the initial Tc concentration (1´10–5 M, as Tc(VII)) indicated the reduction to Tc(IV) according to the chemical reaction TcO4– + 4 H+ +3e– Û TcO2·1.6H2O(s) + 0.4 H2O. Redox speciation of Tc in the aqueous phase was further confirmed by solvent extraction. A good agreement is obtained between the experimentally determined Tc redox distribution and thermodynamic calculations based on NEA–TDB and ionic strength corrections by SIT or Pitzer approaches. These observations indicate that experimental pHc and Eh values in buffered systems can be considered as reliable parameters to predict the redox behaviour of Tc in dilute to highly concentrated NaCl and MgCl2 solutions. Eh of the system and aqueous concentration of Tc(IV) in equilibrium with TcO2·1.6H2O(s) are strongly affected by elevated ionic strength, especially in the case of 4.5 M MgCl2 solutions. In such concentrated brines and under alkaline conditions (pHc = pHmax ~9), kinetics play a relevant role and thermodynamic equilibrium for the system Tc(IV)(aq) Û Tc(IV)(s) was not attained from oversaturation conditions within the timeframe of this study (395 days). Tc(VII) is reduced to Tc(IV) by magnetite, mackinawite and Siderite suspensions at pHc = 8–9 in concentrated NaCl and MgCl2 solutions. Sorption is very high in all cases (Rd ³ 103 L×kg–1), although Rd values are significantly lower in 4.5 M MgCl2 solutions. XANES evaluation of these samples confirms that Tc(VII) is reduced to Tc(IV) by Fe(II) minerals also in concentrated NaCl and MgCl2 brines.

The decompression experiments performed at TOPFLOW facility in 2010 have been reproduced using the latest best-estimate thermohydraulic system code TRACE (V 5.0 Patch 3). The main component of TOPFLOW facility was about 8 m long vertical tube with an inner diameter of 195.3 mm. The evaporation of liquid water to steam caused by depressurization was simulated using two dierent procedures: from stagnant water and during circulating of water in tubes. The liquid water was almost saturated at initial pressure values of 1:0, 2:0, 4:0 and 6:5 MPa. Our approach applies one-dimensional code to simulate all the important parts of the facility not just the vertical test section, where the measurements were taken. The obtained simulated pressure, temperature and void fractions are compared with measured values. The simulations of the first procedure (stagnant water at beginning) are in a good agreement with measurements, especially for the cases with longer transients and higher initial pressure, however, choked flow model through the blow-of valve had to be adjusted. There is a short transient (about 2 s) after the fast opening valve opens, which was not reproduced correctly with TRACE. The simulations of the second procedure (circulating water in a loop) correctly predict pressure and temperature decrease, but underpredict void fraction. No modication of the default TRACE choked flow model was needed for procedure B.

Summary of the important issues presented at the Thirteenth Accelerator Mass Spectrometry Conference (AMS-13)

kein Abstract verfügbar

Observation and detection of freshly produced nuclides provides a direct clue for understanding stellar nucleosynthesis. In particular, radionuclides can act as radioactive clocks for their recent production. Previous measurements in deep-sea manganese crusts and sediments for extraterrestrial ⁶⁰Fe (t_1/2=2.6 Myr) at TU Munich [1] and for ²⁴⁴Pu (t_1/2=81 Myr) at Munich [2], Hebrew University [3] and the VERA laboratory, Vienna [4] applied accelerator mass spectrometry (AMS), the most sensitive technique for detecting the expected small traces of interstellar material in terrestrial archives.
Recently, we have started a program at the ANU to follow-up a discovery of a ⁶⁰Fe excess in an ocean crust sample pointing to a recent close-by supernova (SN) [1]. A substantial beamtime devoted to ⁶⁰Fe has resulted in an exceptional sensitivity of ⁶⁰Fe/Fe below 10^-16. We have searched for a SN-signal in three deep-sea sediment cores (Indian Ocean). We will present first data for ⁶⁰Fe allowing high time resolution and will relate it to potential recent SNe.
In addition, we have re-measured with an independent method the ⁶⁰Fe half-life via ⁶⁰Fe AMS measurements that allows us addressing the discrepancy of the two existing half-live values [5,6].

[1] K. Knie et al., PRL93 (2004), C. Fitoussi et al., PRL101 (2008).
[2] C. Wallner et al. New Astr. Rev. 48 (2004)
[3] M. Paul et al, ApJL 558 (2001)
[4] A. Wallner et al., submitted
[5] G. Rugel et al., PRL103 (2009)
[6] W. Kutschera et al., NIM B5 (1984)

CFD simulations of dispersed bubbly flow on the scale of technical equipment are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, accurate numerical predictions depend on suitable closure models. A large body of work using different closure relations of varying degree of sophistication exists, but no complete, reliable, and robust formulation has been achieved so far.
An attempt has been made to collect the best available description for the aspects known to be relevant for adiabatic monodisperse bubbly flows, where closure is required for (i) the exchange of momentum between liquid and gas phases, (ii) the effects of the dispersed bubbles on the turbulence of the liquid carrier phase. Apart from interest in its own right, results obtained for this restricted problem also provide a good starting point for the investigation of more complex situations including bubble coalescence and breakup, heat and mass transport, and possibly phase change or chemical reactions.
The resulting model was previously validated by comparing simulations using ANSYS-CFX with experimental data for a number of test cases comprising vertical upward pipe flows and bubble columns. Here, the exact same model (within the limits of what is known about ANSYS-CFX) has been implemented in OpenFOAM v2.2 based on the twoPhaseEulerFoam solver. In this way a comparison becomes possible also between two different numerical approaches.
Both codes are able to reproduce the experimental data with similar quality but differences between the results of both simulation are not negligible. A discussion of possible reasons is given.

In this paper a new preparation method is described that allows the in-vivo AFM imaging of wide range of different microorganisms. The work was mainly focused on the immobilization of fixed and living cells of various microorganisms of our interest on substrates. Tested organisms are Gram-negative and Gram-positive bacteria, yeast and algae. For AFM of biological samples their reliable immobilization on a sample holder is crucial. Lateral forces of the probe tip can alter or remove sample material during scanning. This effect occurs especially on soft biological samples, causing artifacts in imaging and leads to a loss in quality and structural information. For the immobilization, organisms were deposited on polyelectrolyte coated surfaces by centrifugation. Microorganisms were imaged without drying steps either living or with glutaraldehyde fixation. Glutaraldehyde fixation enables long time scans that cover wide areas or the investigation of organisms in special growth stages such as cell division or budding. Skipping fixation steps allows in vivo imaging to investigate living organisms and cellular processes under physiological conditions. The reliable immobilization is demonstrated by imaging the proteinaceous surface layer (S-layer) of living Lysinibacillus sphaericus and Viridibacilli arvi cells. In additional experiments, cell division of E. coli was successfully imaged. During repeated scans of wide areas fixed sample material was not removed by the AFM tip, proving the suitability of the methods for AFM analyses. In conclusion, the method can be easily applied for a wide range of microorganisms and enables the in vivo imaging of whole cells and cell ultrastructure.

The focus of this thesis are spin vortices in magnetic multilayers. A spin vortex is a topological spin texture, characterized by a planar magnetization curl that tilts out- of-plane in the nanoscopic core region at the center. There are two different states possible for both the rotation sense of the curl (circulation) and the orientation of the core (polarity), leading to a binary vortex chirality. The spin vortex is typically the ground state of micron sized ferromagnetic thin film disks or square-shaped elements. During the past decades, spin vortices were studied intensively with respect to their magnetostatic and—in particular—their intriguing magneto-dynamic properties. Along with these fundamental studies, proposals were made for the application of vortices for example in data storage and radio-frequency oscillator technology. With respect to density and synchronization in both these application concepts—but also from a fundamental point of view—the interaction between vortices is a crucial issue to address. This holds true especially for the vertical geometry of trilayer vortices (ferromagnet/non-ferromagnet/ferromagnet) in which giant- or tunnel magneto resistance effects as well as spin-transfer torques are exploitable. However, the knowledge on such coupled vortices has been fairly limited. Therefore it was the aim of this work to investigate the magnetic properties of vertically coupled vortex pairs. Investigations were mainly made by means of synchrotron-based transmission x-ray microscopy. This method uniquely allows for a direct and element selective imaging of the magnetic orientation in spin textures with the lateral resolution required. The vortex pair samples were fabricated by electron beam lithography and thin film deposition techniques. Additional magnetometry measurements were employed to address the basic material and coupling properties. Also micromagnetic simulations were carried out in order to complement the experimental results. By this approach, different vortex pair configurations concerning the relative orientation of circulations and polarities, are identified. It is shown that interlayer exchange coupling can be exploited to deterministically set the relative circulation state, and that ion irradiation provides a method to finely tune this coupling after the multilayer has been deposited. In contrast, the polarity states are found not to be controllable by any of the interlayer coupling strengths accessible. Both states are stable in fact, with the parallel configuration representing the ground state. The field response of a vortex pair is evaluated to range from a quasi-independent behavior to a strict coupling between both layers, where the latter can be described by a single layer vortex response with effective magnetic properties. When a relevant non-collinear interlayer coupling is introduced to the vortex pair state, the system is found to exhibit radial magnetization components with opposing sign between both ferromagnetic layers, which in turn results in the formation of a three-dimensional torus vortex accompanied by a symmetry break of the polarity states. The findings achieved in this work mark a significant advance of the state of the art in the field of spin vortices and coupled spin textures, and they may also be of value for future vortex-based applications in technology.

At the Institute of Fluid Dynamics in the Helmholtz-Zentrum Dresden-Rossendorf, two-phase flow experiments at a vertical pipe are performed using ultrafast X-ray tomography. In comprehensive experimental series, upward flows, counter-current flows as well as downward flows were investigated. In this compact, developed processing methods and selected results of these experiments are presented.

Es hat kein Abstract vorgelegen.

Es hat kein Abstract vorgelegen.

Geometallurgical parameters are descriptions of the mineralogy and microstructure of the ore determining its mineralogical and microstructural characteristics. From a conditional geostatistical simulation of such properties, a processing model could compute recovery, equipment usage, processing costs, and thus the monetary value for mining and processing the block with certain processing parameters. This can be used for optimizing mining sequences or finding optimal processing parameters by solving the corresponding stochastic optimization problem.
The approach requires two properties of the simulation not provided by established geostatistical techniques:
1) Many relevant geometallurgical parameters are from non-Euclidean statistical scales like (mineral) compositions, (grain size) distribution, (grain) geometry, (stratigraphic type) categorical, etc., which might produce impossible values when simulated with standard geostatistical techniques.
2) Due to the nonlinearity of processing, the whole conditional distribution of the geometallurgical parameters is relevant and not only its mean and variance. The geostatistical simulation needs to reproduce the joint conditional distributions of all the geometallurgical parameters.
We have developed a multi-point conditional geostatistical simulation technique, which allows for jointly simulating dependent spatial variables from various sample spaces. The technique combines an MPS-type infill simulation with a new form of distributional regression to estimate conditional distributions of arbitrary scales from different information sources, including training images, training models and observed data. The distributional regression is based on a generalization of logistic regression and has some relation to both BME-type geostatistics and high order cumulants.
The method ensures simulated data to reside within the constrained sample space and honour the characteristics of the joint distribution to be reproduced. The computational effort is substantial, but affordable for a useful application with standard problems: from processing-aware block value prediction and block processing optimization as we show in the test application to a completely defined simulated model situation with a complex processing model.

This workshop was held a year after the initial positron emission tomography/magnetic resonance (PET/MR) workshop in Tübingen, which was recently reported in this journal. The discussions at the 2013 workshop, however, differed substantially from those of the initial workshop, attesting to the progress of combined PET/MR as an innovative imaging modality. Discussions were focused on the search for truly novel, unique clinical and research applications as well as technical issues such as reliable and accurate approaches for attenuation and scatter correction of PET emission data. The workshop provided hands-on experience with PET and MR imaging. In addition, structured and moderated open discussion sessions, including six dialogue boards and two roundtable discussions, provided input from current and future PET/MR imaging users. This summary provides a snapshot of the current achievements and challenges for PET/MR.

A new PIXE-beamline equipped with a full-field energy dispersive X-ray camera [1,2] has recently been put into operation at HZDR. This so-called SLcam® comprises poly-capillary optics guiding the proton-induced X-ray fluorescence radiation towards a 264×264 pixel pnCCD-chip, each with an energy resolution of 156 eV (@Mn Kα). Two X-ray optics are available, with a magnification of one and six, allowing a field of view of 12×12 mm² and 2×2 mm², respectively. Attached to a large sample analysis vacuum chamber containing a precision sample manipulator, high throughput of even large samples is feasible. Additionally, a beam broadening system ensures a homogeneous illumination of the detection area and an optical microscope allows correlative superimposition of the PIXE maps with optical images. The single CCD pixel size is 48×48 µm² leading to a lateral resolution better than 100 µm for the 1:1 optics. By using sub-pixel resolution algorithms imaging of single capillary channels (25 µm) is expected.
The new setup is mainly developed for the investigation of geological samples for resource technology research which comprises the analysis of grain composition and intergrowths as well as the determination of rare earth element distributions. The simultaneous measurement of a huge array of pixel enables a fast overview over a large region of the sample with first results becoming visible almost immediately. Together with the PIGE implementation at the classical micro-beamline at HZDR this new approach allows analysis of most of the elements of interest in mineralogy.
First results concerning lateral resolution and detection limits on geological samples are encouraging. Due to the low background in the PIXE spectra investigation of trace elements with concentrations below 0.1 at.% is achievable.

[1] O. Scharf et al., Anal. Chem., Vol. 83, pp. 2532-2538 (2011).
[2] I. Ordavo et al., NIM A, Vol. 654, pp. 250-257 (2011).

For practical applications the Euler-Euler two-fluid model relies on suitable closure relations describing interfacial exchange processes. The quest for models with a broad range of applicability allowing predictive simulations is an ongoing venture. A set of closure relations for adiabatic bubbly flow has been collected that represents the best available knowledge and may serve as a baseline for further improvements and extensions. In order to allow predictive simulations the model must work for a certain range of applications without any adjustments. This is shown here for flows that allow to impose a fixed bubble size distribution which bypasses the need to model coalescence and breakup processes.

Within the framework of two-fluid modelling, the interfacial transfer processes needs to be modelled by suitable closure relations. Based on previous experience with ANSYS CFX (e.g Rzehak and Krepper, 2013) a set of closure relations applicable for adiabatic bubbly flow has been implemented in OpenFOAM. Great effort has been made to match all details of the models so that the same results may be expected and residual differences should be only due to different numerical procedures.
In this work we compare simulation results for dispersed gas-liquid pipe flow with experimental data given by Liu (1998) as well as in-house data obtained with the MTLoop facility described in Lucas et al. (2005). Overall, the experimental data are reasonably well predicted and the predictions are competitive with the results computed with ANSYS CFX. However some differences can be observed, especially in the turbulent quantities in the near wall region

Sixty U LIII-edge EXAFS spectra from 13 structurally different aliphatic ((di-)hydroxy-) carboxylic acids (acetic, succinic, tartaric, lactic, 3-hydroxybutyric, citric, formic, malic, maleic, malonic, oxalic, propionic, and tricarballylic acid) were measured at different pH, uranium and ligand concentrations. Each of the ligands can form several metal complexes, which may coexist as mixtures depending on the physicochemical parameters (pH, concentration).. The ligands were chosen in such a way that they would allow a structural analysis of the complexes solely by using the exclusion principle, i.e. by comparing the spectra with respect to pH, concentration, presence/absence, number, position and the type of the functional group/s. Due to the high number of different constellations in this highly correlated system, simple inspection by eye and other conventional tools will possibly lead to different solutions and is therefore prone to misinterpretation. Artificial neural networks, such as self-organizing maps (SOM), are expected to be better adapted and more specialized for dealing with such highly complex systems. We show that the inclusion of the Beer-Lambert law, in the training period of SOM, leads to a new kind of supervised learning algorithm [1] which enables the determination of the spectra and fractions of the different U(VI) complexes. Moreover, we show that the new SOM algorithm allows the inclusion of available information such as the ligand structures and the physicochemical parameters so that latent relationships between them and the spectra of the complexes are revealed.

[1] Domaschke, K. et al. (2014) Proceedings of ESANN.

Tetravalent actinides and lanthanides form strong complexes with carboxyl containing ligands. Such complexes play an important role in technological processes as well as in biological and environmental systems. So far, most of the thermodynamic data of actinide(IV) and lanthanide(IV) carboxylates are estimated by assuming mononuclear solution species [1]. We applied comprehensive studies with EXAFS, UV-Vis-NIR spectroscopy and X-ray diffraction on Th4+, U4+, Np4+ and Ce4+ carboxylates (RCOO–; R = H, CH3, CHR’NH2; R’ = H, CH3, CH2SH) in aqueous solution and solid state [2-5]. Our studies reveal that in all of the investigated systems hexanuclear complexes appear, which become predominant with increasing metal and ligand concentration and increasing pH, and dominate finally the species distribution. We present here their structure, stability constants, and the mechanisms of complex formation. The appearance of hexanuclear complexes in aqueous solution coincides with the onset of the An(IV) hydrolysis on the one hand, and the deprotonation of the carboxylic function on the other hand. This results in a competing reaction between hydrolysis and ligation. The hydrolysis induces a polymerization of the metal ions via oxo and hydroxo bonds, whereas 12 carboxylic ligands provide charge neutrality of the hexanuclear core and prevent further polymerization. Our studies indicate that future work on tetravalent actinide carboxylates in aqueous solution requires consideration of these hexanuclear species.

REFERENCES
[1] Casellato, U.; Vigato, P. A.; Vidali, M. Coord. Chem. Rev. 1978, 26, 85-159.
[2] Takao, S.; Takao, K.; Kraus, W.; Emmerling, F.; Scheinost, A.C.; Bernhard, G.; Hennig, C. Eur. J. Inorg. Chem. 2009, 4771-4775.
[3] Takao, K.; Takao, S.; Scheinost, A.C.; Bernhard, G.; Hennig, C. Inorg. Chem. 2012, 51, 1336-1344.
[4] Hennig, C.; Takao, S.; Takao, K.; Weiss, S.; Kraus, W.; Emmerling, F.; Scheinost, A.C. Dalton Trans. 2012, 41, 12818-12823.
[5] Hennig, C.; Ikeda-Ohno, A.; Kraus, W.; Weiss, S.; Pattison, P.; Emerich, H.; Abdala, P.M.; Scheinost, A.C. Inorg. Chem. 2013, 52, 11734-11743.

External or internal hazards, combined with multiple failures of components and safety systems or human errors can lead to a reactor core melt. In that case the reactor pressure vessel is the last barrier to keep the molten materials inside the reactor and to prevent further challenges to the nuclear power plant structures and consequently to the environment. In-vessel melt retention by external vessel cooling is a possible mitigative severe accident measure. Up to the moment it is not considered as a severe accident management strategy for VVER-1000 reactors. In this paper we analyse the possibility of in-vessel melt retention for a generic pressurized water VVER-1000 reactor during the late phase of a postulated station blackout scenario.

We developed a numerical model describing the thermal behaviour of a segregated molten pool situated in the lower plenum of the reactor pressure vessel and the thermo-mechanic behaviour of the vessel wall. The finite element code ANSYS® was used for the simulations.

The results show that the highest thermo-mechanical loads are observed in the vertical part of the vessel wall, which is in contact with the molten metal. Parameter studies on the thickness of the metal layer have also been performed. Without flooding, the vessel wall will fail, as the necessary temperature for a balanced heat release from the external surface via radiation is near to or above the melting point of the steel. However, the external flooding could help the retention of the corium within the reactor pressure vessel.

Cobalt-based full Heusler compounds are very promising candidates for future magnon-spintronic devices as well as for the observation of novel phenomena in magnon transport in magnetic microstructures. The reason for the anticipated advantages is their decreased Gilbert damping in comparison with most conventional metallic 3d-ferromagnets and, in particular, in comparison with the widely used Ni81Fe19.

As shown recently, the decay length of propagating spin waves in spin-wave waveguides made of the Heusler compound Co2Mn0.6Fe0.4Si (CMFS) shows a significant increase in comparison with wave propagation Ni81Fe19. This observation reflects the decreased Gilbert damping of α=0.003 in CMFS with respect to the damping constant of α=0.008 in Ni81Fe19.

The decreased losses in CMFS not only lead to an increase of the decay length but also to the pronounced occurrence of nonlinear effects in the spin system. In this talk, we report the nonlinear emission of spin-wave beams with a well-defined propagation direction from the directly-excited spin-wave mode.

The overall process that led to our observation comprises three interesting phenomena of spin dynamics: the localization of a spin-wave mode due to a field gradient, higher harmonic generation, and the formation of spin-wave caustic beams. Even though, each of the constituent phenomena stimulated serious research efforts in the field of magnon spintronics on its own, their complex interplay was observed for the first time in a CMFS spin-wave waveguide just recently. This highlights the advantage of the Heusler material compared to the commonly used 3d-ferromagnets.

Subsequently, all three phenomena will be addressed in this talk. The localization of the directly-excited mode is described on the basis of a micromagnetic simulation as well as a dispersion calculation. This localized spin-wave mode can be identified as the source for the generation of the second and third harmonic. Finally, the radiation characteristics of the higher harmonics are described quantitatively by an analytical calculation based on the anisotropic dispersion relation of spin waves in magnetic thin films.

Recent experiments on spin dynamics in microstructures made of the Heusler compound Co2Mn0.6Fe0.4Si (CMFS) yielded promising results in the linear and nonlinear regime. These results were attributed to the low Gilbert damping that was observed with standard ferromagnetic resonance (FMR) technique on homogeneous thin films. However, a quantitative analysis of the damping in CMFS microstructures is still lacking. We present an alternative method to evaluate the damping in individual CMFS microstructures using parametric amplification and show that the low damping is preserved on the microscale.

The hydrodynamics of a newly developed reactor concept with rotating fixed-bed were investigated using gamma-ray computed tomography. During these investigations, operational parameters like reactor inclination and rotation as well as flow rates, liquid and fixed-bed properties were varied.
In this work, hydrodynamic models from the literature have to be implemented, extended and parameterized for the new reactor concept.

Der geneigt rotierende Festbettreaktor stellt ein neues Reaktorkonzept mit dem Ziel der Prozessintensivierung durch periodische Betriebsweise dar. Aus dessen Betriebsweise ergeben sich zusätzliche Freiheitsgrade zur Strömungsführung in Form von Neigung und Drehzahl und damit zur Beeinflussung der Reaktorleistung.
Im Rahmen der Diplomarbeit ist die Hydrodynamik im geneigt rotierenden Festbettreaktor mit den Schwerpunkten Verweilzeitverteilung und Phasenverteilung zu untersuchen. Die Ergebnisse sind mit denen des etablierten Rieselbettreaktors zu vergleichen.
Durch die im rotierenden Reaktor zusätzlich aufgeprägte transversale Strömungskomponente ist die Eignung des axialen Dispersionsmodells für das neue Reaktorkonzept zu untersuchen und es sind Möglichkeiten zur experimentellen Bestimmung der radialen Dispersion zu präsentieren.

Der geneigt rotierende Festbettreaktor stellt ein neues Reaktorkonzept mit dem Ziel der Prozessintensivierung durch periodische Betriebsweise dar. Aus der neuartigen Betriebsweise ergeben sich in Form von Neigung und Drehzahl zusätzliche Freiheitsgrade zur Strömungsführung und damit zur Beeinflussung der Reaktorleistung.
Im Rahmen der interdisziplinären Projektarbeit ist die Reaktionsführung hinsichtlich der Raum-Zeit-Ausbeute einer Modellreaktion (Hydrierung von α-Methylstyrol zu Cumol) zu untersuchen. Dazu sind abschließende MSR Arbeiten an einer bestehenden Versuchsanlage durchzuführen sowie Lösungen für die einfache Bestimmung von reaktionstechnischen Kenngrößen aus den Versuchsdaten zu präsentieren. Die Ergebnisse des geneigt rotierenden Festbettreaktors sind mit denen des etablierten Rieselbettreaktors zu vergleichen.

With GPUs large-scale plasma simulations can provide frames-per-second simulation speeds. We present interactive, in-GPU rendering of large-scale particle-in-cell simulations running on GPU clusters. The user can choose which data is visualized and change the direction of view while the simulation is running. A remote visualization client can connect to the running simulation, allowing for live visualization even when bandwidth is limited.

We show that with todays largest supercomputers it is possible to follow the trajectories of billions of particles, computing a unique fingerprint of their dynamics. With the use of 18,000 GPUs we could compute a 'sky map' of the radiation emitted by individual electrons in a large-scale, turbulent plasma, providing unique insight into the relation between the plasma dynamics and observable radiation spectra.

The Kelvin-Helmholtz instability (KHI) occurs at the interface between two neutral streams of plasma flowing past one another with different velocities. This instability is expected to take place in active galactic nuclei or in the afterglow of gamma-ray bursts, where it is a possible mechanism for non-thermal radiation.
We present results of a KHI scenario with relativistic velocity shear obtained in a petaflop scale run on the TITAN cluster at Oakridge using our relativistic 3D3V particle-in-cell code PIConGPU. From the dynamics of billions of macroparticle, we calculated angularly and temporally resolved radiation spectra based on classical Liénard-Wiechert potentials including the full coherence properties. Thus, in addition to the incoherent synchrotron-type radiation arising from DC magnetic fields in the KHI, we found rich radiation signatures, which we match with the dynamics and electron density structure of the KHI. We present a simple model, which explains these spectral features and connects them to the main quantities of the KHI.

We present recent results of plasma simulations performed with PIConGPU, a fully relativistic 3D particle-in-cell (PIC) code running on GPU clusters. We extended our code to compute the radiation spectra of all particles in the simulation based on classical Liénard-Wiechert potentials including full coherence and polarization properties. We discuss physics tests, scaling and show simulation results of laser-wakefield accelerator and astrophysical plasmas, for which we calculated angularly resolved spectra ranging from infrared to X-ray wavelengths. Such an extensive treatment of plasma radiation across billions of macro particles makes it possible to explore temporally resolved plasma radiation spectra on linear and logarithmic photon energy scales over large solid angles ("sky-maps").
This ability of obtaining quantitative spectral data in plasma simulations poses a unique tool for determining the phase space distribution of electrons. Since spectral information is readily accessible in experiments, our results can serve as a valuable input to new diagnostics.