Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Phosphodiesterase 2A (PDE2A) is highly and specifically expressed in particular brain regions affected by neurological disorders and in certain tumors. Development of a specific PDE2A radioligand enables molecular imaging of the PDE2A protein via positron emission tomography (PET). Herein we report on the syntheses of three novel fluoroalkylated triazine derivatives (TA2-4) and on the evaluation of their effect on the enzymatic activity of human PDE2A. The most potent PDE2A inhibitors were ¹⁸F-radiolabelled ([¹⁸¹⁸F]TA4) and investigated regarding their potential as PET radioligands for imaging of PDE2A in mouse brain. In vitro autoradiography on rat brain showed region-specific distribution of [¹⁸F]TA3 and [¹⁸F]TA4, which is consistent with the expression pattern of PDE2A protein. Metabolism studies of both [¹⁸/F]TA3 and [¹⁸F]TA4 in mice discovered a significant accumulation of two major radiometabolites of each radioligand in brain as investigated by micellar radio-chromatography. Small-animal PET/MR studies in mice using [¹⁸F]TA3 revealed a constantly increasing uptake of activity in the non-target region cerebellum, which may be caused by the accumulation of brain penetrating radiometabolites. Hence, [¹⁸F]TA3 and [¹⁸F]TA4 are exclusively suitable for in vitro investigation of PDE2A. Nevertheless, further structural modification of these promising radioligands might result in metabolically stable derivatives.

Flow and transport simulations in geomaterials are commonly conducted on high-resolution tomograms (µCT) of the pore structure or stochastical models that are calibrated with measured integral quantities, like break through curves (BTC). Yet, there existed virtually no method for experimental verification of the simulated velocity distribution results.
Positron emission tomography (PET) has unrivaled sensitivity and robustness for non-destructive quantitative spatio-temporal measurement of tracer concentrations in body tissue. We empowered PET for its applicability in opaque/geological media (GeoPET). Thus it is the appropriate method for experimental verification and calibration of computer simulations of pore-scale transport by means of the observed propagation of a tracer pulse, c_PET(x,y,z,t).
As a principal concept, velocity and residence time distributions, as well as the tortuous pathway topology, principally can be derived directly from c_PET(x,y,z,t). However, the fundamental experimental limit of finite signal to noise ratios is manifested in apparently intermittent propagation pathways, with gaps in zones where the concentration cPET falls below the significance threshold. This hampers the direct parameter estimation of velocity, v(x,y,z), and porosity distribution n(x,y,z) from c_PET(x,y,z,t).

This issue is overcome to some extent by introduction of causality (continuity) into the here presented evaluation algorithm.

Likely Topics in math & comp. sciences
1) Space-Time Processes
2) Image Analysis
3) Numerical Modelling and Numerical Simulation
4) Inverse Problem solving
5) other computer sciences methods

Likely Geoscience topics:

1) Water: sea, surface and subsurface

the publication has no abstract

Due to chemochromism, Mg2Me (Me=Fe, Co, Ni) based alloys are low-cost and rare-earth-free candidates for switchable mirrors upon hydrogen loading. In order to understand the basic physical properties of Mg2Fe based thin films and its hydride, as-sputtered as well as hydrogen loaded films have been investigated using magnetometry, X-ray diffraction, 4-point probe sheet resistance technique and positron annihilation spectroscopy (PAS). The interplay of hydrogen loading, the magnetic moment, and structural properties like the sizes and chemical decoration of open volume defects in thin films detected by PAS will be presented.

Our aim is to infer the mineral composition from the chemical composition of a material. Several difficulties occur: Different mineral compositions can lead to the same chemical composition. Not all chemical compositions can be reached by compositions of certain minerals, while e.g. due to measurement errors impossible chemical compositions will typically be observed. In principle the dependency between mineral composition and chemical composition is linear. Inversion of the linear system however often leads to negative portions for some mineral components. Only the first problem is properly solved by state of the art linear end member calculation methods (see e.g. Tolosana et al. 2011).
Our algorithm computes the set of all mineral compositions leading to the chemical composition maximizing the likelihood of the observed concentrations. The measurement error for the chemical components are modelled as independent normal distributions with mean zero and standard deviation given by the measurement error reported by the lab. For any given mineral composition, the chemical composition can thus be computed by stoichiometric calculations and Maximum log-likelihood is than a weighted least squares problem. The parameter space is however constraint to the possible mineral compositions. The problem is transformed into a quadratic programming problem with linear equality and inequality constraints with a unique solution for the chemical composition. From this unique solution we can than compute all possible mineral compositions leading to the corresponding chemical composition by enumerating the corners of the simplex of equally fitting solutions.
As an example we will discuss a sample of waste material consisting of Rare Earth Elements (REE), since recycling of waste materials is getting more and more important. Rare Earth Elements (REE) are used in mostly all new technologies and until now, there is no environmentally friendly recycling-process for fluorescent phosphor. For the development of a suitable recycling method, it is important to know the composition of the materials. Due to company secrecy, in some cases only rough informations about the composition of the material can be found. In the case of fluorescent phosphor, which is collected during the recycling-process of energy saving bulbs, only the type of the dye but not the precise composition is known. Because of different restrictions in the analytical methods and the complex composition, only the elemental concentrations with relatively high measurement errors can be measured.

The only method for in-vivo dose delivery verification in proton beam radiotherapy in clinical use today is positron emission tomography (PET) of the positron emitters produced in the patient during irradiation. PET imaging during irradiation maximizes the number of detected counts and minimizes biological washout. In such a scenario, also short-lived positron emitters will be observed. We determined which short-lived positron emitters are relevant by measuring their production in the stopping of 55 MeV protons in water, carbon, phosphorus and calcium. The most copiously produced short-lived nuclides and their production rates relative to the relevant long-lived nuclides are: 12N (T1/2 = 11 ms) on carbon (9% of 11C), 29P (T1/2 = 4.1 s) on phosphorus (20% of 30P) and 38mK (T1/2 = 0.92 s) on calcium (113% of 38gK). No short-lived nuclides are produced on water. The production on PMMA and 4 tissue materials is calculated from the experimental results. The number of decays, integrated over an irradiation, is calculated as function of the duration of the irradiation. For an irradiation in (carbon-rich) adipose tissue, 12N dominates the PET image up to an irradiation duration of 70 s. On bone tissue, 12N dominates over 15O during the first 8-15 s (depending on the carbon-to-oxygen ratio). The short-lived nuclides created on phosphorus and calcium provide 2.5 times more decays than the long-lived ones during a 70 s irradiation. Bone tissue will thus be better visible in in-beam PET compared to PET imaging after an irradiation. 12N needs to be considered in PET imaging during proton beam irradiations as its large positron range blurring may noticeably degrade image quality. Investigations into the energy-dependent production of 12N, 29P and 38mK and their effect on the quality of in-vivo treatment verification in proton therapy with PET imaging are urgently needed.

Spin-torque nano-oscillators (STNOs) are novel devices which may be exploited for wireless communication applications. In particular, it has recently been demonstrated that STNOs utilizing an in-plane (IP) magnetized polarizer and out-of-plane (OOP) magnetized free layer allow for the full parallel (P)-to-antiparallel (AP) resistance variation to be exploited in the limit of 90° precession angle, thereby maximizing the output power. However, for this specific geometry, steady-state precession can only be sustained if the spin-transfer torque exhibits an asymmetric dependence on the angle between the free and the polarizing layer, such as in the case of fully metallic devices. Nevertheless, it has recently been reported that dynamics have been experimentally observed in similarly designed MgO-based MTJs under constant applied electrical current, in spite of the fact that such devices do not exhibit any asymmetry in the spin-torque angular dependence. These results have so far been interpreted based on the formalism for metallic devices, including the spin-torque angular dependence. Here, we explore potential mechanisms for sustaining steady-state precession in MgO-based MTJs with an IP polarizer and an OOP free layer. To this end, we analytically and numerically solve the Landau-Lifshitz-Gilbert-Slonczewski equation for a nano-pillar MTJ with circular cross-section, under a constant perpendicular applied current and field. Since for realistic current range, the field-like torque is negligible compared to effective field acting along z axis, we take into account only the in-plane spin-torque term. To sustain steady-state precession, the energy supplied by the in-plane spin-torque term and energy dissipated through damping must compensate over a full precession period. In an MgO-MTJ, the magnitude of the STT is determined not by the current, but by the corresponding voltage across the barrier. As the magnetization of the free layer precesses around the z axis, the angle between the magnetic moments of the two layers changes and through the magnetoresistance effect the voltage changes if the Experiment is conducted at constant applied current. This cosine-like angular dependence of the MTJ resistance effectively introduces a spin-torque angle dependence asymmetry. In addition, even for a given angle, the resistance exhibits a specific bias dependence, with the resistance of the AP state decreasing approximately linearly with the bias, while remaining mostly constant in the P configuration. In this work, we demonstrate that the spin-torque angular asymmetry exhibited in such systems is sufficient to sustain STT-driven dynamics.

A challenging area in the field of multiphase flow is the study of churn flow. According to the multiphase flow community, churn flow has not been widely investigated in intermediate and large diameter pipes at high gas and liquid flow rates. The present work deals with an experimental study of upward vertical air–water flow in a 76.2 mm I.D. pipe. Superficial gas velocities ranging from 10 to 38 m/s and four superficial liquid velocities (0.30, 0.46, 0.61 and 0.76 m/s) were employed. The experimental data points are mostly located in churn flow and at the transition between churn and annular flow. A dual 16x16 Wire Mesh Sensor (WMS) was used to obtain the temporal/spatial variations of phase distributions over the pipe cross-section at one specific axial location (L/D = 236).
Sequences of phase distributions, axially sliced images, virtual 3-D images as well as void fraction timeseries were used to distinguish between different interfacial structures such as slugs and huge waves.
Results showed that huge waves occur with either a continuous gas core with a distinct boundary between two phases or a core with a gas–liquid mixture. Furthermore, velocities and frequencies of interfacial structures were obtained. Results are qualitatively and quantitatively consistent with the previous findings available in literature.

We report on the internal dynamics of excitons in high-quality GaAs quantum wells and on the control of intra-excitonic transitions by an external magnetic field. The free-electron laser FELBE in Dresden is ideally suited for selective excitation of intra-excitonic transitions, since it provides intense, spectrally narrow transform-limited terahertz pulses in a unique continuous pulse train, which also allows us to use a synchroscan streak camera system [1]. Subsequent to the production of excitons by pulsed interband excitation, we resonantly pump the 1s-2p intra-excitonic transition which is located at around 2 THz. Coulomb-mediated transfer from the optically "dark" 2p to the radiative 2s state and relaxation into the fundamental 1s state is investigated by time-resolved photoluminescence involving the 1s and 2s excitonic levels [2]. In particular, applying an external magnetic field strongly affects the observed behavior. Detailed analysis of the experimental behavior based on a newly developed microscopic theory allows us to demonstrate the remarkable impact of magnetic fields on the Coulomb and terahertz interactions in the excitonic system, which occurs as a consequence of magnetically induced changes of excitonic orbitals and energetic detuning of excitonic levels [3]. As an interesting application, we also discuss the possibility of observing terahertz gain induced by intra-excitonic transitions.
[1] J. Bhattacharyya et al., Rev. Sci. Instrum. 82, 103107 (2011)
[2] W. D. Rice et al., Phys. Rev. Lett. 110, 137404 (2013)
[3] J. Bhattacharyya et al., Phys. Rev. B 89, 125313 (2014)

We report effect of the annealing temperature on the dynamic and static magnetic properties of MgO/CoFeB/Ta/Ru multilayers. The angular resolved ferromagnetic resonance measurements results show that the as-deposited film exhibits in-plane magnetic anisotropy, whereas in the annealed films the magnetic easy-axis is almost along the direction perpendicular to the plane of the layers. The extracted interfacial anisotropy energy, Ki, is maximized at an annealing temperature 225 °C, in agreement with the vibrating sample magnetometry results. Although the magnetization is not fully out-of-plane, controlling the degree of the magnetization obliquity may be advantageous for specific applications such as spin-transfer oscillators.

A number of recent studies successfully demonstrated the feasibility of using Monte Carlo code Serpent to generate few-group cross sections (XS) for full core nodal diffusion analyses of SFR cores. The current study investigated the potential of the SPH method, applied to correct the few-group XS produced by Serpent, to further improve the accuracy of the nodal diffusion solutions. The procedure for the generation of SPH-corrected few-group XS is presented in the paper. The performance of the SPH method was tested on a large oxide SFR core from the OECD/NEA SFR benchmark. The reference SFR core was modeled with the DYN3D and PARCS nodal diffusion codes using the SPH-corrected few-group XS generated by Serpent. The nodal diffusion results obtained with and without SPH correction were compared to the reference full-core Serpent MC solution. It was demonstrated that the application of the SPH method improves the accuracy of the nodal diffusion solutions, particularly for the rodded core state.

This research focuses on the verification of a recently developed methodology accounting for spectral history effects in 3D full core nodal simulations. The traditional deterministic core simulation procedure includes two stages: (1) generation of homogenized macroscopic cross section sets and (2) application of these sets to obtain a full 3D core solution with nodal codes. The standard approach adopts the branch methodology in which the branches represent all expected combinations of operational conditions as a function of burnup (main branch). The main branch is produced for constant, usually averaged, operating conditions (e.g. coolant density). As a result, the spectral history effects that associated with coolant density variation are not taken into account properly. Number of methods to solve this problem (such as micro-depletion and spectral indexes) were developed and implemented in modern nodal codes. Recently, we proposed a new and robust method to account for history effects. The methodology was implemented in DYN3D and involves modification of the few-group cross section sets. The method utilizes the local Pu-239 concentration as an indicator of spectral history. The method was verified for PWR and VVER applications. However, the spectrum variation in BWR core is more pronounced due to the stronger coolant density change. The purpose of the current work is investigating the applicability of the method to BWR analysis. The proposed methodology was verified against recently developed BGCore system, which couples Monte Carlo neutron transport with depletion and thermal-hydraulic solvers and thus capable of providing a reference solution for 3D simulations. The results clearly show that neglecting the spectral history effects leads to a very large deviation (e.g. 1700 pcm in multiplication factor) from the reference solution. Application of the Pu-correction method results in a very good agreement between DYN3D and BGCore on the order of 200 pcm in kinf.

Due to their essential role in the pathogenesis of cancer, members of the Eph (erythropoietin-producing hepatoma cell line-A2) receptor tyrosine kinase family represent promising candidates for molecular imaging. Thus, the development and preparation of novel radiotracers for the noninvasive imaging of the EphB4 receptor via positron emission tomography (PET) is described. First in silico investigations with the indazolylpyrimidine lead compound which is known to be highly affine to EphB4 were executed to identify favorable labeling positions for an introduction of fluorine-18 to retain the affinity. Based on this, reference compounds as well as precursors were developed and labeled with carbon-11 and fluorine-18, respectively. For this purpose, a protecting group strategy was essential to generate for the prevention of unwanted methylation and to enable the introduction of fluorine-18. Further, a convenient radiolabeling strategy using [¹¹C]methyl iodide was established which afforded the isotopically labeled radiotracer in 30-35% RCY (d.c.) which is identical with the original inhibitor molecule. A spiro ammonium precursor was prepared for radiolabeling with fluorine-18. Unfortunately, the labeling did not lead to the desired ¹⁸F-radiotracer under the chosen conditions.

Recent progress in material science has enabled the first experimental studies concerning the static magnetization characterization of samples with tubular geometry to be carried out. Although investigating spin-wave and domain-wall dynamics remains a challenge from an experimental point of view, theory predicts that it is fundamentally different than in previously investigated flat geometries. This is a direct consequence of the specific boundary conditions in such structures. Here, we discuss the effect of the curvature on the dynamics of domain walls and spin waves. Using extensive finite element micromagnetic simulations, we demonstrate that a typical vortex-type domain wall formed in a ferromagnetic tube exhibits advantageous properties regarding the domain wall speed and stability. For topological reasons, these robust domain walls do not encounter the Walker breakdown in certain nanotubes and can propagate with velocities faster than the spin wave phase velocity. Above a critical velocity, the domain wall triggers a Cherenkov-type spin wave radiation. Note that the Spin-Cherenkov Effect is general and not specific to nanotubes. We show that this effect is present in any magnetic medium where a perturbation travels with a velocity faster than the magnonic limit. A characteristic of ferromagnetic nanotubes is that the chiral symmetry of the domain wall propagation is broken. This is attributed to the lack of local inversion symmetry due to the curved surface of the nanotube. Micromagnetic studies show that this lack of inversion symmetry leads to a non-reciprocal dispersion relation for the spin waves with regards to the sign of the propagation vector k. The split in the frequencies for spin waves traveling in opposite directions is of the order of several GHz. This effect is the largest when the nanotube radius is comparable with the wavelength of the traveling spin waves and is already present for bended thin films that form a half or even less than a half nanotube only. Moreover, we demonstrate that even in flat geometries, a similar lift of the degeneracy of the dispersion relation can be achieved if the magnetization distribution shows a non-divergence free curved pattern. This indicates that, in the presence of an external field, a set of curved surfaces of opposite bending behaves as a directional filter device in which the spin waves can propagate to a specific direction only.

The gyrotropic rotation around the equilibrium position constitutes the fundamental excitation of magnetic vortices in nanostructures. The frequency of this mode varies with material and sample geometry, but is independent of the vortex handedness and its core direction. Here, we demonstrate that this degeneracy is lifted in a spin-torque oscillator containing two vortices stacked on top of each other. When driven by spin-polarized currents, such devices exhibit a set of dynamic modes with discretely split frequencies, each corresponding to a specific combination of vorticities and relative core polarities. The fine splitting occurs even in the absence of external fields, demonstrating that such devices can function as zero-field, multi-channel, nano-oscillators for communication technologies. It also facilitates the detection of the relative core polarization and allows for the eight non-degenerate configurations to be distinguished electrically, which may enable the design of multi-state memory devices based on double-vortex nanopillars.

To obtain basic information on the sorption and recycling of gold from aqueous systems the interaction of Au(III) and Au(0) nanoparticles on S-layer proteins were investigated. The sorption of protein polymers was investigated by ICP-MS and that of proteinaceous monolayers by QCM-D. Subsequent AFM enable the imaging of the nanostructures.

Modeling of nanostructure evolution in solids requires comprehensive data on the properties of defects such as the vacancy and foreign atoms. Since most processes occur at elevated temperatures not only the energetics of defects in the ground state but also their temperature-dependent free energies must be known. The first-principles calculation of contributions of phonon and electron excitations to free formation, binding, and migration energies of defects is illustrated in the case of bcc-Fe. First of all, the ground state properties of the vacancy, the foreign atoms Cu, Y, Ti, Cr, Mn, Ni, V, Mo, Si, Al, Co, O, and the O-vacancy pair are determined under constant volume (CV) as well as zero pressure (ZP) conditions, and relations between the results of both kinds of calculations are discussed. Second, the phonon contribution to defect free energies is calculated within the harmonic approximation using the equilibrium atomic positions determined in the ground state under CV and ZP conditions. In most cases the ZP-based free formation energy decreases monotonously with temperature, whereas for CV-based data both an increase and a decrease were found. The application of a quasi-harmonic correction to the ZP-based data does not modify this picture significantly. However, the corrected data are valid under zero-pressure conditions at higher temperatures than in the framework of the purely harmonic approach. The difference between CV- and ZP-based data is mainly due to the volume change of the supercell since the relative arrangement of atoms in the environment of the defects is nearly identical in the two cases. A simple transformation similar to the quasi-harmonic approach is found between the CV- and ZP-based frequencies. Therefore, it is not necessary to calculate these quantities and the corresponding defect free energies separately. In contrast to ground state energetics the CV- and ZP-based defect free energies do not become equal with increasing supercell size. Third, it was found that the contribution of electron excitations to the defect free energy can lead to an additional deviation of the total free energy from the ground state value or can compensate the deviation caused by the phonon contribution. Finally, self-diffusion via the vacancy mechanism is investigated. The ratio of the respective CV- and ZP-based results for the vacancy diffusivity is nearly equal to the reciprocal of that for the equilibrium concentration. This behavior leads to almost identical CV- and ZP-based values for the self-diffusion coefficient. Obviously, this agreement is accidental. The consideration of the temperature dependence of the magnetization yields self-diffusion data in very good agreement with experiments.

A systematic geometallurgical study of the rare earth mineralogy and beneficiation potential as by-product was carried out at the Vergenoeg Fluorite Mine, South Africa. For this purpose, a representative suite of samples was collected from a mining block prior to blasting. After mining, this material was tracked through the beneficiation plant by sampling all crucial steps. Whole rock geochemical analyses, quantitative mineralogical and microstructural analyses (by MLA), complemented by mineral chemistry data for relevant REE minerals, were obtained for undisturbed and processed samples. These data were used to assess the deportment of REE and to track the route of REE minerals within the beneficiation process.
Microcrystalline xenotime and monazite were found to be the two most abundant REE minerals, with all other REE minerals of only very minor quantitative importance. Process samples from the flotation circuit illustrate that the material from the cleaner circuit (B) tailing, being usually considered as waste, is strongly enriched in both monazite and xenotime. The REE minerals are well liberated, thus leading to the conclusion that it may be feasible to produce REE minerals as a future by-product by only slight modification of the current flow sheet.

As in 2007 the first 3.5 cell superconducting radio frequency (SRF) gun was taken into operation, it turned out that the specified performance has not been achieved. However, to demonstrate the full potential of this new type of electron source, a second and slightly modified SRF gun II was built in collaboration with Thomas Jefferson National Accelerator Facility (TJNAF). We will report on commissioning and recent results of the new gun, which includes in particular the characterization of the most important RF properties as well as investigations on photo cathode preparation.

Bei der Explosion massereicher Sterne werden langlebige Radionuklide erzeugt und in den Weltraum hinausgeschleudert. Relikte naher Supernovae lassen sich nicht nur im All, sondern auch auf der Erde selbst entdecken [1]. Um Supernova-Spuren in Tiefseearchiven nachzuweisen, wurden 100 Proben aus 4 Sedimenten untersucht. Die Bohrkerne stammen aus einer Tiefe von 4 200 m des Indischen Ozeans. Sie umfassen ein Altersprofil von 1,7-3,2 Millionen Jahren, in dem sich Supernova-Radionuklide abgelagert haben.
Die Proben wurden chemisch aufbereitet, einzelne Elementfraktionen voneinander getrennt und analysiert. Mit der Beschleunigermassenspektrometrie (AMS), einer sehr sensitiven Methode zur Bestimmung extrem niedriger Konzentrationen langlebiger Radionuklide, wurden ¹⁰Be, ²⁶Al, und ⁶⁰Fe gemessen. Isotopenverhältnisse im Bereich von 10^-9 (¹⁰Be/⁹Be) bis zu 10^-16 (⁶⁰Fe/Fe) konnten so quantifiziert werden.
Die Nuklide ¹⁰Be und ²⁶Al werden kontinuierlich in der Erdatmosphäre durch hochenergetische Kernreaktionen hauptsächlich an Stickstoff, Sauerstoff und Argon gebildet und können zur Datierung der Sedimente verwendet werden. ⁶⁰Fe hat keine terrestrischen Quellen, wird jedoch kurz vor und während einer Sternexplosion produziert. Da in dem gemessenen Zeitbereich eine Erhöhung dieses Eisen-Isotops festgestellt wurde, kann davon ausgegangen werden, dass es aus dem Weltall in die Tiefseesedimente eingetragen wurde.

[1] K. Knie, Phys. Rev. Lett., 2004, 93, id. 171103

Vertically aligned ZnO-TiO2 hetero-nanostructures constructed of anatase TiO2 nanotubes (NTs) and wurtzite ZnO coatings are fabricated by atomic layer deposition of ZnO coatings on electrochemical anodization formed TiO2 NTs, and their photoelectrochemical activities are studied through photoelectrochemical and electrochemical characterization. Compared with bare TiO2 NTs, the transient photocurrent increases to over 1.5-fold for the annealed ZnO-coated TiO2 NTs under visible illumination. The ZnO-coated TiO2 NTs also show a longer electron lifetime, a lower charge-transfer resistance and a more negative flat-band potential than the bare TiO2 NTs, confirming the improved photoelectrochemical activity due to the enhanced Charge separation.

Vertically aligned ZnO/TiO2 hetero-nanostructures are successfully fabricated by atomic layer deposition of ZnO shells on electrochemical anodization formed TiO2 nanotube (NT) arrays. The ultrathin and highly conformal ZnO shells (as thin as ~ 2.0 nm) were deposited on TiO2 NTs with precise thickness-control at atomic scale. Its thickness dependent changes in crystallographic, optical and photoelectrochemical properties of ZnO/TiO2 NTs are investigated. The photoelectrochemical activities are studied through electrochemical impendence spectroscopy, flat-band potential and transient photocurrent density measurements. The ZnO/TiO2 NTs with 10-cyle ZnO layers show a longer electron lifetime, a lower charge-transfer resistance and a more negative flat-band potential than the bare TiO2 NTs and the sample with 25-cyle ZnO layers. Consequently, the transient photocurrent of ZnO/TiO2 improves under visible illumination. The improved photoelectrochemical activity in ZnO/TiO2 hetero-nanostructures is attributed to the enhanced charge separation due to the ZnO layer covering out of TiO2 NTs. Our results also indicate that a thinner ZnO layer leads to a larger and more stable photocurrent.

Ziel/Aim:

According to [1] and [2] the Philips Ingenuity PET/MR (PETMR) has the same NEMA sensitivity as the Siemens ECAT HR+ standalone PET (PET). However, the NEMA sensitivity is measured without taking into account any attenuating materials such as the patient bed or MRI head coil which are present in every PET/MR brain examination. The aim of this work is to measure and compare the effective PET sensitivity and signal to noise ratios of reconstructed images (SNR) of PETMR for brain examinations under clinical conditions.
Methodik/Methods:
A solid 68-Ge phantom (33 MBq) was measured in PETMR and PET on the same day. The total acquisition time was 5min. The phantom was positioned in the MRI head coil in the PETMR and on a dedicated carbon head support in PET as used in clinical examinations. The ratio of prompt coincidences (PR) from the listmode files was calculated. Images were reconstructed employing parameters used in clinical routine. The SNR was calculated as mean over a 3D ROI with a diameter of 10cm divided by standard deviation.
Ergebnisse/Results:
PR was 0.52 (PETMR / PET). SNR was (8.6, 5.2, 3.7, 1.6) (PETMR) and (6.2, 3.9, 2.9,1.6) (PET) for frame durations of 300s, 100s, 50s and 10s, respectively.
Schlussfolgerungen/Conclusions:
Although the effective sensitivity of PETMR for brain examinations is lower than the one of PET, the resulting SNR in the reconstructed images is superior except for short frame durations. The influence on clinical quantification is currently investigated and will be reported.
Literatur/References:
[1] Zaidi et al. Design and performance evaluation of a whole-body Ingenuity TF PET-MRI system. Phys Med Biol 2011
[2] Herzog et al. NEMA NU2-2001 guided performance evaluation of four Siemens ECAT PET scanners, IEEE TMI
2004

Ziel/Aim:

It has been demonstrated that the tumor-to-blood standard uptake ratio (SUR) shows a higher linear correlation with the metabolic trapping rate of ¹⁸F-fluorodeoxyglucose (FDG) in comparison to the tumor standard uptake value (SUV). The aim of this study was to compare the association of SUR and SUV with patient outcome in NSCLC.
Methodik/Methods:
In total 72 patients (66.3±9.4 years) with newly diagnosed, untreated NSCLC were retrospectively included. All patients underwent FDG-PET/CT with dosages ranging from 179 to 254 MBq. Primary tumors were segmented using an
adaptive tumor-to-background thresholding algorithm (ROVER, ABX, Radeberg, Germany). The blood SUV was determined from a cylindrical three-dimensional region of interest placed in the aorta and the maximum SUR (SUR_max) was calculated as ratio of tumor SUV_max to blood SUV. The association of SUR_max and SUV_max with progression free survival (PFS) and overall survival (OS) was analyzed using the cox proportional hazard model. 95%-confidence intervals are given for hazard ratios (HR).
Ergebnisse/Results:
Progression was observed in 47 patients (65.3%) with a median time of PFS of 10.8 months (range, 0.7-31.4 months). 33 patients died (median OS, 15.4 months [range, 0.7-32.5 months]). The median follow-up time was 20.9 months
(range, 5.2-32.5 months). SUR_max was significantly correlated with SUV_max (Spearman's rho, 0.92; p<0.001). Cox regression model revealed a significant association of SUR_max with PFS (HR, 1.08 [1.01-1.15]; p=0.029) and a tendency for significance with OS (HR, 1.07 [0.99-1.16]; p=0.071) whereas no significant association was observed for SUV_max neither for PFS (HR, 1.01 [0.98-1.03]; p=0.548) nor for OS (HR, 1.01 [0.98-1.04]; p=0.558).
Schlussfolgerungen/Conclusions:
The maximum tumor-to-blood standard uptake ratio (SUR_max) showed a stronger association with patient outcome in comparison to SUV_max. These encouraging results have to be confirmed in further investigations.

Ziel/Aim:

Eine erhöhte Aktivität der TGase 2 in Tumoren geht einher mit erhöhtem invasivem Potential sowie gesteigerter Chemo- und Strahlenresistenz. Daher stellt dieses Enzym ein interessantes Target für die Entwicklung von PET-Tracern zur funktionellen Bildgebung von Tumoren dar. Unter den in der Literatur beschriebenen Inhibitoren der TGase 2 erscheinen die N⁶-Acryloyllysin-4-arylpiperazide für die Entwicklung von Radiotracern als besonders geeignet, da sie über eine hohe inhibitorische Potenz und Selektivität sowie günstige pharmakokinetische Eigenschaften verfügen (1). Daher sollten ausgehend von dieser Verbindungsklasse Derivate dargestellt werden, die eine Funktionalisierung mit Radionukliden wie F-18 oder I-124 ermöglichen, sowie deren inhibitorisches Potential gegenüber der TGase 2 ermittelt werden.
Methodik/Methods:
Ausgehend von N²-Boc-Lysin wurden in einer Sequenz bestehend aus N⁶-Acrylierung, Amidknüpfung, Boc-Entschützung und N²-Acylierung verschiedene N²_Acyl-N⁶-acryloyllysin-4-pyridylpiperazide synthetisiert. Die benötigten Pyridylpiperazine wurden entweder kommerziell bezogen oder in wenigen Syntheseschritten hergestellt. Alle Zielverbindungen wurden in zwei unabhängigen enzymkinetischen Assays, welche die Transamidase- bzw. Hydrolaseaktivität der TGase 2 erfassen, evaluiert. Dabei diente N²_Phenylacetyl-N⁶-acryloyllysin-4-(6-methylpyridin-2-yl)piperazid als literaturbekannter Referenzinhibitor.
Ergebnisse/Results:
Mit Hilfe der umrissenen Syntheseroute konnte eine Serie von 21 N²_Acyl-N⁶-acryloyllysin-4-pyridylpiperaziden hergestellt werden. Die verschiedenen Substituenten wurden dabei unter Gesichtspunkten ausgewählt, die auf die Ermöglichung von Synthesen F-18- und Radioiod-basierter Tracerverbindungen abzielen. Die enzymkinetische Charakterisierung der Verbindungen deckte interessante Struktur-Wirkungsbeziehungen auf, wobei unter anderem der Ersatz der Methylgruppe im Referenzinhibitor gegen Fluor zu höherer inhibitorischer Potenz gegenüber der TGase 2 führte.
Schlussfolgerungen/Conclusions:
Fluorierte und iodierte N²_Acyl-N⁶-acryloyllysin-4-pyridylpiperazide wurden zugänglich gemacht und bezüglich ihrer Hemmwirkung an TGase 2 untersucht, wodurch die Entwicklung von Inhibitor-basierten Radiotracern zur molekularen Bildgebung dieses Enzyms ermöglicht wird. Untersuchungen zur F-18-Markierung geeigneter Kandidaten sind in Planung.
Literatur/References:
(1) Wityak et al. ACS Med. Chem. Lett. 2012, 3, 1024

Ziel/Aim:

Cetuximab ist ein EGFR affiner Antikörper. Bei Markierungen mit Tc-99m werden hohe Temperaturen und Reduktionsmittel benötigt, um Kopplungen an Biomolekülen zu erzielen. Mit dem Komplexbildner 2,2',2''-(1,4,7-triazonane-1,4,7-triyl)triacetic acid (NOTA) ist eine schonende Komplexierung mit Tc-99m-Tricarbonyl möglich. Mit einem doppelt funktionalisierten Alexa488-Cetuximab-NOTA-Konjugat wurden Markierungsparameter angepasst und erste Zellstudien durchgeführt. Radioaktivität und Fluoreszenz konnten mit dem gleichen Antikörper parallel in der Zelle detektiert werden.
Methodik/Methods:
Die Markierung des Antikörpers mit Tc-99m[(CO)₃(H₂O)₃]⁺ wurde durch Anpassung der Reaktionsparameter und Reinigungsverfahren optimiert. Aussagen über Ausbeute, Qualität und Stabilität wurden mit Radio-HPLC und Radio-DC getroffen. Die Integrität des Antikörpers nach der Markierung wurde über SDS-Page untersucht. Zelluläre Studien mit EGFR-positiven A431- und EGFR-negativen MDA-Zellen beinhalteten Uptake und Bindungsstudien (Gamma-Counter) bei 4°C/37°C. Die Detektion der Fluoreszenz fand über ein invers messendes Fluoreszenzmikroskop (Zeiss) statt.
Ergebnisse/Results:
Eine Komplexierung Tc-99m[(CO)₃(H₂O)₃]⁺ mit NOTA konnte erzielt werden. Die Markierung des modifizierten Antikörpers zeigte eine radiochemische Reinheit von > 95%. Nach 24h konnten noch 75% des markierten Antikörpers nachgewiesen werden. Zelluläre Untersuchungen ergaben max. spezifische Aufnahmen bei A431-Zellen nach 1h (48%/0,5Mio.Zellen/2MBq) mit ca. 30% Membran gebundenem Anteil, welcher nach 24h abnimmt (1,5%/0,5Mio.Zellen/2MBq). Ein fluoreszenzmikroskopischer Bindungsnachweis konnte erbracht werden.
Schlussfolgerungen/Conclusions:
Eine Markierung des modifizierten Cetuximabs mit Tc-99m[(CO)₃(H₂O)₃]⁺ konnte entwickelt werden. Geeignete Parameter und Reinigungsverfahren wurden etabliert. Bindungsstudien zeigten eine spezifische Anreicherung an A431-Zellen mit maximaler Aufnahme nach 1h. Die Anreicherung des modifizierten Antikörpers konnte über Fluoreszenzmikroskopie visualisiert werden.

Ziel/Aim:

Cabozantinib is a highly affine receptor tyrosine kinase (angiokinase) inhibitor (TKI) selectively targeting VEGFR-2 and c-Met. Radiolabeled cabozantinib might be a valuable probe to monitor induction of angiogenesis and the success of anti-angiogenic therapy in vivo. For this purpose, we developed ¹⁸F-cabozantinib, a potential PET tracer where the already existing fluorine atom is replaced by fluorine-18.
Methodik/Methods:
The radiotracer ¹⁸F-cabozantinib is obtained via a condensation of an acyl chloride precursor with 4-[¹⁸F]fluoroaniline. Briefly, 1,4-dinitrobenzene reacts with [¹⁸F]fluoride in DMSO for 5 min at 140°C to build 4-[¹⁸F]fluoronitrobenzene which subsequently is separated by SPE and eluted with methanol. Reduction with Pd/C and NaBH₄ then delivered 4-[¹⁸F]fluoroaniline which is trapped on a second SPE cartridge and eluted with THF to the precursor to form ¹⁸F-cabozantinib.
Ergebnisse/Results:
1-[4-(6,7-dimethoxy-quinoline-4-yloxy)-phenylcarbamoyl]-cyclopropanecarbonyl chloride as precursor was synthesized via three steps in 48% overall yield. 4-[¹⁸F]fluoroaniline was obtained in > 50 radiochemical yield (dc) after cartridge purification. By large scale synthesis via a TracerLAB (GE) synthesizer comprising ¹⁸F-fluorination and reduction, 4-[¹⁸F]fluoroaniline was produced in a 2 GBq scale. 10 mg of the acyl chloride precursor was reacted with 2 GBq of 4-[¹⁸F]fluoroaniline in THF at ambient temperature for 15 min to build ¹⁸F-cabozantinib with > 90% radiochemical yield. Final semi-preparative HPLC purification delivered ¹⁸F-cabozantinib in radiochemical purity > 95% and a specific activity > 20 GBq/µmol.
Schlussfolgerungen/Conclusions:
In a multitude of experiments the optimal conditions for radiosynthesis and purification of -[¹⁸F]fluoroaniline and ¹⁸F-cabozantinib could be established. By a partly automated procedure the small molecule angiokinase inhibitor ¹⁸F-cabozantinib was successfully synthesized in high chemical and radiochemical purity in a 200 MBq scale.

Ziel/Aim:

An den Philips Gemini TF PET/CT-Scannern wird die SUV-Kalibrierung für die korrekte Quantifizierung über eine Zerfallsreihe mit Akquisition im Sinogramm (SM)-Format durchgeführt. Die klinische Akquisition erfolgt jedoch im
Listmode (LM)-Format. Durch eine zusätzliche SUV-Validierung (SUV-Val) soll der Unterschied zwischen beiden Formaten korrigiert werden, unter der Annahme, dass dieser über die gesamte Breite der Singles-Zählraten prozentual
konstant bleibt. In wie weit dies korrekt ist und welche quantitativen Auswirkungen dies hat, wurde untersucht.
Methodik/Methods:
Für die Messung wurde ein zylindrisches Phantom (V=9,3l) mittig im Scanner positioniert und über 12h gemessen. Neben der Kalibrierung im SM-Format (SM-Kalib) und der dazugehörenden SUV-Val, wurde die Zerfallsreihe wiederholt, allerdings im LM-Format (LM-Kalib). Die Rekonstruktion der TOF-Messung erfolgte im klinischen WB-Protokoll. Auf Grundlage dieser Messungen wurden Kalibrierungstabellen erstellt und an Messungen des NEMA Image Quality Phantoms und eines ebenfalls über 12h gemessenen 5,6l-Phantoms, überprüft.
Ergebnisse/Results:
Im Vergleich zur LM-Kalib verhalten sich die Kalibrierungsfaktoren bis 10 Mcps äquivalent, bei größeren Zählraten ergibt sich jedoch ein Unterschied von bis zu 15%. Die unterschiedlichen Kalibrierungstabellen resultierten beim
NEMA-Phantom in einer Abweichung von 1% im SUV-Wert des Hintergrundes und im Mittel um 2% bei den Recovery-Koeffizienten. Bei der dynamischen Messung des Brain-Phantoms ergibt sich für die SUV-Werte eine
Verteilung von [0,94-1,02] SUV (LM-Kalib) zu [0,83-1,01] SUV (SM-Kalib).
Schlussfolgerungen/Conclusions:
Es konnte gezeigt werden, dass im klinisch relevanten Zählratenbereich nur ein geringer Unterschied zwischen beiden Verfahren besteht. Bei höheren Zählraten kann jedoch eine größere Abweichung entstehen,die bei dynamischen
Untersuchungen mit Bolusinjektion oder kurzlebigeren Isotopen von Relevanz sein kann. In (1) wurde ebenfalls auf eine ähnliche Problematik bei den Philips PET/MR-Geräten hingewiesen, es scheint sich daher um einen systemweiten Effekt bei Philips-Geräten zu handeln.
Literatur/References:
(1) "Phantom-based evaluation of quantification accuracy of combined PET/MRI", Langner et al., DGN Jahrestagung 2013 (P43).

Ziel/Aim:

We have presented previously a model for fast on-the-fly volume-of-intersection (VOI) system matrix calculation for PET image reconstruction. The model replaces cubic voxels by spheres and the usual line of response (LOR) by a cylindrical tube of response (TOR). The use of spherically symmetric voxel makes it superficially similar to the blob model, where tracer distribution is discretized using modified Kaiser-Bessel window functions (KBWF) rather than cubic voxels. We now present an extended TOR model with radially varying tube density (eTOR) and investigate the relation between eTOR and the blob model. We also analyse under which conditions they can be mapped to each other and which density function leads to the best mapping.
Methodik/Methods:
We start with an analyses of circumstances under which both models generate equivalent system matrices. For that we investigate weighting functions of both models (Length of Intersection between LOR and blob and VOI between
TOR and sphere as functions of the impact parameter, respectively). We tried several candidate TOR density functions (Gaussian, difference of error functions and modified KBWF) and determined optimal parameters for the density
functions by least squares fitting of the respective TOR weighting function to the targeted weighting function of the blob model. Both, eTOR and blob models, were evaluated (using phantom data acquired on the Philips Ingenuity TF PET/MR system) regarding reconstructed resolution and noise level.
Ergebnisse/Results:
A good concordance between eTOR and blob model weighting functions can be achieved with all candidate functions. The best fit (residuals <5e-4) was obtained for KBWF. As expected, the close equivalence between the
weighting functions resulted in almost identical reconstructed resolution and noise level for all investigated voxel sizes and contrast ratios.
Schlussfolgerungen/Conclusions:
We analysed different density function for eTOR models and showed that all of them can be used to mimic (with high accuracy) the conventional blob model, proving a generic nature of the eTOR approach. The achieved equivalence of the weighting functions between eTOR and blob models also indicates that the conventional resampling step of the blob model might be unnecessary.

Ziel/Aim:

Tumor SUV is widely used for quantitative assessment of tumor metabolism in FDG PET and its potential for therapy outcome prediction in various cancer diseases has been investigated in many publications. However, the SUV approach has well known limitations compromising its ability to act as a surrogate parameter of glucose consumption. Recently, we have shown that SUR overcomes most of these limitations as long as FDG kinetics in the target structure can be considered irreversible [1,2]. The aim of this work was to compare the prognostic value of SUR and SUV in patients with esophageal carcinoma.
Methodik/Methods:
FDG-PET/CT was performed in 103 consecutive patients ((63+/-11)y, 89 males) with newly diagnosed esophageal cancer prior to definitive radiochemotherapy. In the PET images the metabolic active volume (MTV) of the primary tumor was delineated with an adaptive threshold method. The blood SUV was determined by manually delineating the aorta in the low dose CT. SUR values were computed as ratio of tumor SUV and blood SUV. SUR values were
scan-time-normalized to 60 min p.i. as described in [2]. Kaplan-Meier analysis and univariate Cox regression with respect to overall survival (OS), locoregional control (LRC), and distant-metastases-free survival (DM) was performed
for SUV_max, SUR_max and clinically relevant parameters. Additionally, a multivariate Cox regression including clinical parameters, which were univariate significant, as confounding factors was performed.
Ergebnisse/Results:
Both, SUV_max and SUR_max, were prognostic factors for OS and DM, but not for LRC. With respect to OS a univariate Cox regression showed a slightly increased hazard ratio (HR) for SUR_max (HR=2.2, p=0.003) compared to SUV_max (HR=1.8, p=0.01). With respect to DM HR of SUR_max was notably larger than HR of SUV_max (HR=6.5, p=0.01 compared to 2.8, p=0.044). Moreover, in multivariate Cox regression only SUR was an independent prognostic factor for OS and for DM the prognostic value of SUR was notably higher than of SUV.
Schlussfolgerungen/Conclusions:
Our results indicate that blood- and time-normalization increases the prognostic value of lesion uptake in pretherapeutic FDG PET of patients with esophageal carcinoma. More comprehensive investigations are necessary to confirm these results.
Literatur/References:
[1] van den Hoff et al, EJNMMI Res 2013, 3:77.[2] van den Hoff et al, EJNMMI Res 2014, 4:18.

Ziel/Aim:

Asphericity (ASP) is a novel FDG-PET-based in vivo measure of tumor heterogeneity which quantitatively characterizes the tumor's deviation from sphere shape. To better understand its biological and histopathological correlates we
investigated the relationship with histopathological features in NSCLC.
Methodik/Methods:
FDG-PET/CT had been performed in 76 unselected patients (66.4±9.3 years) with newly diagnosed NSCLC prior to therapy. Primary tumor resection specimens and core biopsies were used to assess histologic subtype, degree of
differentiation, and Ki-67 proliferation index. The FDG PET image of the primary tumor was delineated by an automatic algorithm based on adaptive thresholding taking local background into account. ASP and SUV_max were considered as quantitative PET measures. Their correlation with clinicopathological features was analyzed using Spearman's correlation; differences between groups were analyzed using Kruskal-Wallis and Mann-Whitney tests.
Ergebnisse/Results:
Squamous cell carcinomas (SCC) exhibited significantly higher SUV_max than adenocarcinomas (ADC, Mann-Whitney, p=0.04), whereas there was no significant effect of histological type on ASP. There was a moderate but significant correlation with Ki-67 for ASP (r=0.39, p=0.001), a weak correlation for SUV_max (r=0.28, p=0.02). Both correlations were stronger in the ADC than in the SCC subgroup. Ki-.67 > 50% was associated with higher ASP (Mann-Whitney, p=0.04) and higher SUV_max (p=0.07). Grade 3 tumors had a tendency for higher ASP (p=0.07) but not SUV_max (p=0.29). Pathological T and N stage were associated with both SUV_max (Kruskal-Wallis, p=0.004/ p=0.02) and ASP (p<0.001/p=0.06). Only SUV_max was associated with M stage (p=0.02).
Schlussfolgerungen/Conclusions:
Tumor asphericity (ASP) appears to depict different features of tumor biology in NSCLC than SUV_max. This is in line with our previous finding that ASP provides independent information for prognosis in patients with NSCLC.

Ziel/Aim:

Ga-68-DOTATOC und Ga-68-DOTATATE werden intensiv in der Routinediagnostik von neuroendokrinen Tumoren und deren Metastasen eingesetzt. Der neue Radiotracer Ga-68-DATATOC (Chelator DATA (6-Amino-1,4-diazepin-triessigsäure) verknüpft mit [Tyr³]-Octreotid) kann aber im Unterschied zu den Ga-68-DOTA-Peptiden bereits bei Raumtemperatur quantitativ radiomarkiert werden. In ersten präklinischen Untersuchungen des Ga-68-DATATOC sollte dessen radiopharmakologisches Profil und Potential zur Bildgebung von neuroendokrinen Tumoren ermittelt werden.
Methodik/Methods:
Nach manueller Radiomarkierung mit Ga-68 und einmaliger, intravenöser Injektion des Ga-68-DATATOC, wurden dessen Bioverteilung (Ratte und Maus), -Kinetik, metabolische Stabilität und die spezifische Akkumulation (Blockierung mit Octreotide (OC)) im Somotostatin-Rezeptor-exprimierenden Maus-Phäochromozytom-Modell (MPCmCherry^t) in NMRI nu/nu Mäusen untersucht. In der Kleintier-PET wurde die Tumordarstellung von Ga-68-DATATOC und Ga-68-DOTATATE verglichen.
Ergebnisse/Results:
In der PET wurden die Tumoren mit Ga-68-DATATOC bereits nach 10 min klar und kontrastreich dargestellt. Die Bioverteilung ergab eine spezifische Anreicherung im Tumor (3.73 ± 1.49 SUV) und Pankreas (0.57 ± 0.17 SUV) als
SSTR exprimierenden Organen, die durch OC blockiert (0.45 ± 0.15;0.12 ± 0.06; entsprechend) werden konnte. Über 70%ID wurden renal ausgeschieden und nur maximal 5%ID in den Nieren zurückgehalten. Der Blutspiegel von
Ga-68-DATATOC war nach einer Stunde niedriger als der von Ga-68-DOTATATE. 93,7% (Maus, 1 h) bzw. 72% (Ratte, 2 h) der Blutplasmaaktivität lagen dabei als Ga-68-DATATOC vor.
Schlussfolgerungen/Conclusions:
Im Unterschied zu DOTA, konnte DATA in Verbindung mit [Tyr³]-Octreotid bereits bei Raumtemperatur quantitativ mit Ga-68 radiomarkiert werden. Die Bioverteilung, Blockierungsexperimente und dynamischen PET-Untersuchungen an MPCmCherry-tumortragenden Mäusen ergaben für Ga-68-DATATOC das typische Profil eines an SSTR bindenden Radiotracers. Das schnelle Erreichen eines hohen Kontrastes zeigt auf das beachtliche Potential als diagnostisches Radiopharmakon.
(Die Arbeiten wurden von der DFG-in dem Projekt BE-2607/1-1 und ZI-1362/2-1 gefördert.).
Literatur/References:
[1] In vivo fluorescence imaging and urinary monoamines as surrogate biomarkers of disease progression in a mouse
model of pheochromocytoma. Ullrich M, Bergmann R et al. Endocrinology. 2014 Nov;155(11):4149-56.

Ziel/Aim:

While [O-15]H₂O PET is still considered the gold-standard for brain perfusion measurement, a native MRI sequence called arterial spin labeling (ASL) which offers a semi-quantitative alternative becomes increasingly relevant in the clinical setting and might be especially relevant for applications in combined PET/MR systems. For ASL, an accuracy and repeatability comparable to that of PET has been reported. A serious limitation of the respective studies is the fact that mainly young healthy subjects were used. Also, time and subject comfort were sacrificed to reach high repeatability. Our aim was to test the repeatability of ASL under realistic clinical conditions on elderly cancer patients.
Methodik/Methods:
Fifteen patients (age 55.5±12.8 years) with glioblastoma were scanned in two or more sessions (in total 21 sessions, 125±37 days apart). We used a pseudo-continuous ASL sequence with background suppression and 2D multi-slice
readout, labeling time/delay 1525/1650 ms, voxel size 2.75x2.75x6.6mm³, and standard CBF quantification (1). Mean CBF was assessed for regions corresponding to anterior cerebral artery (ACA), posterior CA, middle CA, and vertebral artery, respectively, on the contralateral side from the tumor. Repeatability index and mean relative CBF difference was assed for the two sessions for all regions.
Ergebnisse/Results:
The whole-brain mean CBF was 33.0±4.9 mL/min/100 g (45.5±6.1 mL/min/100 g in gray matter). The repeatability index was 30.4%, 34.3%, 29.7%, 31.5% and 36.8% in whole brain, ACA, MCA, PCA and VA regions, respectively. The mean relative difference between sessions for whole brain was 18.9% (range 0.4-63.0%, median 17.1%).
Schlussfolgerungen/Conclusions:
The repeatability index is close to the values measured by Heijtel (2) in healthy volunteers (27.6% for PET, 25.1% for ASL). A slight decrease in repeatability in elderly patients is to be expected. The mean gray matter perfusion is slightly lower than in (2) (48.5±5.6 in PET, 50.8±6.5 mL/min/100 g for ASL) which might be attributed to the known decline of CBF in elderly subjects. Our results thus show that pCASL measurements yield stable CBF values even under clinical conditions.
Literatur/References:
(1) Alsop, et al. Magnetic Resonance in Medicine. 2014.
(2) Heijtel, et al. NeuroImage, 92:182-92(2014).

Introduction:

The α₇ subtype of nicotinic acetylcholine receptors (nAChRs) is involved in neuropsychiatric disorders including Alzheimer’s disease, substance abuse, and schizophrenia. Recently, ¹⁸F-ASEM and ¹⁸F-DBT-10 were developed to image α₇ nAChRs in vivo. We performed PET studies in nonhuman primates to directly compare the pharmacokinetic properties of these tracers.
Methods:
¹⁸F-ASEM and ¹⁸F-DBT-10 were produced via nucleophilic substitution of their respective nitro-precursors. PET data were acquired with a Focus-220 scanner in two rhesus monkeys. Bolus injection of tracer was followed by 240 min of PET acquisition, including arterial plasma assay and metabolite analysis to determine the input function. Blocking studies with cold ASEM were conducted to assess the extent of specific binding. Data were analyzed with the one- and two- tissue compartment models (1TCM & 2TCM) and multilinear analysis to measure distribution volumes (V_T).
Results:
Both ¹⁸F-ASEM and ¹⁸F-DBT-10 were prepared in high specific activity and >99% radiochemical purity. Higher parent fractions of ¹⁸F-DBT-10 were found, as well as higher plasma free fraction (¹⁸F-ASEM:13±3%; ¹⁸F-DBT-10:18±2%). Tissue kinetics were faster for ¹⁸F-ASEM. The 2TCM best modeled the PET data for both radiotracers. Regional V_T values were slightly higher for ¹⁸F-DBT-10, ranging from 32-53 mL/cm³ (¹⁸F-ASEM) and 35-58 mL/cm³ (¹⁸F-DBT-10) with the rank order of thalamus>frontal cortex>striatum=temporal cortex>hippocampus>occipital cortex>cerebellum. Blocking studies decreased V_T values from baseline levels throughout the brain.
Conclusion:
¹⁸F-ASEM and ¹⁸F-DBT-10 both exhibit suitable properties for PET imaging of α₇ nAChRs in nonhuman primates. ¹⁸F-ASEM exhibits faster kinetics and has been extended to human use (Wong et al., 2014).

Ice cores are established as archives for environmental changes since many years. On Severnaya Zemlya, the easternmost archipelago with considerable glaciation in the Eurasian Arctic, a 724 m long ice core has been drilled on Akademii Nauk the largest ice cap there. Stable water isotope and major ions concentrations in this ice core are presented (e.g. Fritzsche et al., 2005, Opel et al., 2013). They represent more than 3000 years of regional climate and environmental history. A well‐known depth‐age relationship is necessary for a paleoclimate interpretation of the data. In a first approach the dating was performed by counting of annual cycles of stable isotopes well‐preserved in the core even though overprinted by the effect of percolating melt water from summer surface melting. The depth‐age scale produced by counting has been matched to volcanic eruption events with well‐known ages detectable in the sulphate record of the core. This approach has some disadvantages due to the fact that the pattern of stratospheric volcanic events recorded in well‐dated ice cores from Greenland and Antarctica is influenced by rather regional tropospheric eruptions as in our case probably in Iceland and Kamchatka, partly less precisely dated. The depth‐age relationship has therefore to be proofed by an independent method.
The isotope ¹⁰Be is produced by cosmic radiation in the Earth’s atmosphere. Its residence time there is about one year, shorter than it is for ¹⁴C, for which reason variability of ¹⁰Be in archives like glaciers is much higher compared to ¹⁴C. The production rate of both radionuclides is depending on the solar activity. Their concentrations were used for the reconstruction of heliomagnetic variations in the past and can be vice versa used for dating of ice cores.
Today, accelerator mass spectrometry (AMS) allows measurements of ¹⁰Be in ice cores. Its concentration is depending on the geomagnetic coordinates of the location of its production, transport and deposition mechanisms, accumulation rates etc. Therefore, local differences in ¹⁰Be concentrations are observed (Berggren et al., 2009). Here, we present ¹⁰Be concentrations measured by the team of DREsden AMS (DREAMS) (Akhmadaliev et al., 2013) in discrete Akademii Nauk ice core samples of about 300 g. Our ¹⁰Be record shows its general potential to validate our depth‐age model matching the ¹⁰Be concentration pattern to that of Greenlandic ice cores as well as ¹⁴C production reconstruction.
References
Akhmadaliev, S., Heller, R., Hanf, D., Rugel, G., and S. Merchel (2013): The new 6 MV AMS‐facility DREAMS at Dresden, Nucl. Instr. and Meth. in Phys. Res. B., 294, pp .5‐10.
doi:10.1016/j.nimb.2012.01.053.
Berggren, A.‐M., J. Beer, G. Possnert, A. Aldahan, P. Kubik, M. Christl, S. J. Johnsen, J. Abreu and B. M. Vinther (2009): A 600‐year annual ¹⁰Be record from the NGRIP ice core, Greenland, Geophys. Res. Lett., 36, L11801, doi:10.1029/2009GL038004.
Fritzsche, D., Schütt, R., Meyer, H., Miller, H., Wilhelms, F., Opel, T. and Savatyugin, L. M. (2005): A 275 year ice core record from Akademii Nauk ice cap, Severnaya Zemlya, Russian Arctic, Annals of Glaciology, 42, pp. 361‐366. doi:10.3189/172756405781812862.
Opel, T., Fritzsche, D. and Meyer, H. (2013): Eurasian Arctic climate over the past millennium as recorded in the Akademii Nauk ice core (Severnaya Zemlya) , Climate of the Past, 9 (5), pp. 2379‐2389. doi:10.5194/cp‐9‐2379‐2013.

The exact crystallographic and electronic structure plays an important role for the occurrence of quantum criticality, magnetic order, and superconductivity in the family of transition-metal pnictides AT₂Pn₂. The pnictide-distance z is a crucial parameter for the electronic structure because the distance between the T₂Pn₂ layers determines whether the tetragonal crystal structure is collapsed or uncollapsed and, thereby, whether pnictide bonds are formed or not. We have investigated the influence of the P z position on the band structure of the strongly enhanced Pauli paramagnet SrCo₂P₂, a close relative to the superconducting iron arsenides, that is on the verge of magnetic order. The pronounced temperature dependence of the P z position influences the density of states (DOS) at the Fermi energy strongly. Therefore, we have investigated the Fermi surface of SrCo₂P₂ in the paramagnetic ground state with the de Haas-van Alphen effect. We compare our experimental results to band-structure calculations in order to determine the exact contribution of individual orbits to the DOS. We will also address the renormalization of the effective masses and the dimensionality of the Fermi surface.

Ferromagnetic shape-memory Heusler alloys undergo a martensitic transformation, i.e., a first-order structural transition from a cubic high-temperature phase to a low-temperature monoclinic phase. Due to a pronounced magneto-structural interaction in these compounds, a strong magnetic field can induce a metamagnetic transition and drive the system from a martensite to an austenite phase. In this case, both lattice and magnetic entropy contribute to the net magnetocaloric effect (MCE). We have measured the MCE of the shape memory Heusler alloy Ni₅₀Mn₃₅In₁₅ using a set-up for direct magnetocaloric measurements in pulsed magnetic fields. The martensitic transition occurs at about 246 K in zero field and the material has a Curie temperature of 315 K. We find a saturation of the inverse MCE, related to the first-order martensitic transition, with a maximum value of -7 K. The MCE associated with the Curie temperature evolves as typical for a second-order magnetic transition. The effect is positive, nearly temperature independent and yields a value of 11 K.

es hat kein Abstract vorgelegen

CeTiGe₃ is one of the few Kondo-lattice compounds which order ferromagnetically (T_C ≈ 14 K); LaTiGe₃ may be used as its nonmagnetic reference, since both compounds crystallize in the same hexagonal perovskite structure [1, 2]. We report on angular-resolved de Haas-van Alphen oscillations in single crystals of CeTiGe₃, LaTiGe₃, and Ce_0.1La_0.9TiGe₃ grown from Ge flux, measured in magnetic fields up to 13 T in a cantilever-type torque magnetometer. We found several dHvA frequencies, ranging in CeTiGe₃ from 100 to 530 T and with effective masses around 0.7 m₀, featuring a comparably weak angular dependence. Further, we give an interpretation of our results on the basis of DFT calculations of the electronic band structure of CeTiGe₃ and LaTiGe₃.

SrCu₂(BO₃)₂ is a quasi-two-dimensional spin system consisting of Cu²⁺ ions which form orthogonal spin-singlet dimers, also known as the Shastry-Sutherland lattice. This system has been studied extensively using a variety of techniques to probe the spin-triplet excitations, including recent magnetization measurements over 100 T. Spectroscopic techniques, such as nuclear magnetic resonance (NMR), can provide further insight into the spin-coupling mechanisms and excitations. We present ¹¹B NMR spectra measured in pulsed magnetic fields up to 54 T, and compare those with prior results obtained in static magnetic fields at 41 T. Herewith, we prove the feasibility and efficacy of this technique, yielding the capability for extended studies at highest magnetic fields up to the 100 T regime that determine the spin structure in the 1/3 magnetization plateau and beyond.

At the Institute of Fluid Dynamics in the Helmholtz-Zentrum Dresden-Rossendorf, two-phase downward flow experiments at a vertical pipe are performed using ultrafast X-ray tomography. For processing segmented data of co-current downward and counter-current flows, two methods for velocity estimation were developed: A morphological method and a bubble pairing one. The results agree well with expectations.

The electron-positron pair production due to the dynamical Schwinger process in a slowly oscillating strong electric field is enhanced by the superposition of a rapidly oscillating weaker electric field. A systematic account of the enhancement by the resulting bifrequent field is provided for the residual phase space distribution. The enhancement is explained by a severe reduction of the suppression in both the tunneling and multiphoton regimes.

A dilaton potential is adjusted to recently confirmed lattice QCD thermodynamics data in the temperature range (0.7…3.5)Tc where Tc=155MeV is the pseudo-critical temperature. The employed holographic model is based on a gravity--single-field dilaton dual. We discuss conditions for enforcing (for the pure gluon plasma) or avoiding (for the QCD quark-gluon plasma) a first-order phase transition, but still keeping a softest point (minimum of sound velocity).

Advanced monitoring of the spatio-temporal distribution of process parameters in large-scale vessels and containers such as stirred chemical or bioreactors offers a high potential for the investigation and further optimization of plants and embedded processes. This applies especially to large-scale plants, such as industrial fermenters, biogas reactors and activated sludge basins, where the process performance including the biological processes highly depend on mixing parameters of the complex bio-substrates. Sufficient mixing is a basic requirement for a stable operation of the process and adequate process performance. However, this condition is rarely met and the process efficiency is often reduced dramatically by inhomogeneities in the agitated vessels. Without a doupt, investigation and monitoring of biochemical parameters, such as the fermentation rate, pH distribution as well as O2 and CO2 concentration is of great importance. Nevertheless, also understanding of non-biological parameters, such as fluid dynamics (flow velocity profiles, circulation times), suspension mixing (homogeneity, location of dead zones and short-circuits) and heat transfer (temperature profiles), is necessary to analyze the impact of mixing on the biological system and also to improve the process efficiency.
However, in most industrial scale applications the acquisition of these parameters and their spatial distributions in the large-scale vessels is hampered by the limited access to the process itself, because sensor mounting or cable connections are not feasible or desired. Therefore, state of the art instrumentation of such reactors is commonly limited to few spatial positions where it is doubtfully assumed that the measured parameters are representative for the whole reaction mixture.
In this work, a concept of flow following sensor particles was developed. The sensor particles allow long-term measurement of spatially distributed process parameters in the chemically and mechanically harsh environments of agitated industrial vessels. Each sensor particle comprises of an onboard measurement electronics that logs the signals of measurement devices, namely temperature, absolute pressure (immersion depth, axial position) and 3D acceleration. The whole electronics is enclosed in a robust neutrally buoyant capsule (equivalent diameter 58.2 mm; sphericity 0.91), to allow free movement with the flow.
The sensor particles were tested in pilot fermenters under comparable flow conditions of biogas fermenters. The experiments proved the applicability of the sensor particles and the robustness to resist the harsh environments of mixing processes. Moreover, the results show the capabilities of the sensor particles to monitor the internal conditions of the vessel correctly and thus deliver significant information about the flow regime. Therefore effects of liquid rheology, vessel geometry, impeller speed and axial impeller position on the macro-mixing process were properly detected. Evaluation of the impeller efficiency and the mixing processes was done based on mixing homogeneity, location of dead zones, axial velocity profiles, circulation time distributions as well as average circulation times, acceleration spectra and temperature profiles that were extracted from the measured data. Furthermore, it is shown, that parameters of mixing models such as circulation number, impeller head, PECLÉT-number and variance of suspended solid particles can be estimated from the measured data.
The main achievement of this work is therefore the development and validation of instrumented flow followers for the investigation of macro-mixing effects in agitated vessels. The sensor particles show potential for employment to real applications such as biogas fermenters or large bioreactors and to monitor and improve the mixing and heating regimes.

For the long-term storage of radioactive waste in host rock formations with highly saline environments it is important to know how indigenous halophilic microorganisms can affect the performance of a repository. An important interaction mechanism is the soprtion of radionuclides like uranium on cell surface of microorganisms, which has an influence on U migration behaviour. Biosorption studies at highly saline conditions are also of interest for saline wastewater treatment.
The sorption of U(VI) on cells of the halophilic archaeum Halobacterium noricense DSM 15987 was studied at pH 6.0 and a NaCl concentration of 3.0 M in dependence on uranium concentration, time and temperature. Independent on the added uranium concentration (10 – 120 µM) around 90 % of the added uranium was sorbed by the cells at room temperature. Time-dependent sorption studies indicated a two-step binding process with a fast step within the first hours and a second slower one. A slightly faster sorption of added uranium could be demonstrated at higher temperatures of 50°C.
Interestingly, with increasing time, uranium concentration and temperature the cells began to form agglomerates. Live/Dead staining (LIVE/DEAD® Bac LightTM Bacterial Viabilit Kit, Molecular Probes) of cells after biosorption with uranium showed that nearly all single cells were dead whereas agglomerated cells were alive. The cell agglomeration is a stress response to protect the cells themselves from environmental challenges.
The characterization of the formed cell-uranium-complexes was even at 3M NaCl with Time-resolved Laser-induced Fluorescence Spectroscopy possible and indicated that uranium was bound to cellular carboxylic groups. The bounding of uranium not only to carboxylic groups but also to phosphate groups of the cell could be verified with Infrared Spectroscopy.
This knowledge is important in understanding microbe-radionuclide interactions at highly saline conditions in respect of geological disposal of nuclear waste and is useful for saline wastewater treatment.

The Central European Kupferschiefer constitutes one of the most important natural copper sources in Europe (Borg et al. 2012). The Kupferschiefer sensu strictu challenges conventional exploitation due to its organic load, complex mineralogy and fine dispersion of ores. Thus alternative beneficiation strategies are investigated. Bioleaching – the use of microorganisms or microbial metabolites for metal solubilisation from ore material – may serve as an efficient and environmentally benign approach. Among others leaching with microbially produced organic acids provided good results (Anjum et al 2010). In previous studies (Kostudis et al. 2015) leaching of copper from Kupferschiefer sensu strictu (Polkowice Mine, Lubin, Poland) using glutamic acid was examined. It was shown that copper is primarily released from chalcocite (Cu2S) being the main copper mineral in the shale sample. However, decrease in chalcopyrite (CuFeS2) and bornite (Cu5FeS4) content by 40 % and 37 %, respectively, has also been reported as well as formation of secondary minerals such as covellite (CuS). As the Kupferschiefer sensu strictu is constituted very complexly investigation of the single main copper minerals without the matrix is worthwhile. Thus the current study addresses the influence of organic acids on chalcocite, bornite and chalcopyrite. Experiments were performed using strewn slides prepared as thick sections. Ore samples of chalcopyrite, bornite and chalcocite were provided from Ashio/Japan; Butte/Montana/USA and Henderson Mine/Namaqualand/South Africa, respectively. The samples (fig. A) were analysed prior to and after leaching with citric and glutamic acid using mineral liberation analysis (MLA) consisting of combined SEM and ED X-ray spectrometry and a specific software for automated data acquisition (fig. B), micro-Raman spectroscopy (fig. C), and atomic force microscopy (fig. D). The presentation shows results of comprehensive mineralogical analysis of both pristine and processed copper ores.

Objectives :

(-)-[¹⁸F]flubatine is successfully used for neuroimaging of alpha4beta2 nicotinic acetylcholine receptors in human. In this study the biokinetic of the (+) enantiomer was studied first time into humans. To assess the radiation risk by this new radioligand the biodistribution, organ doses (OD) and the effective dose (ED) were determined in 3 healthy volunteers. The results will be compared to the preclinical (mice: PET/MR piglets: PET/CT) and clinical (PET/CT) data and to the (-) enantiomer of flubatine [1].
Methods :
Whole body dosimetry was performed in 3 healthy volunteers (2 m, 1 f ; age: 58.3±5.8 y weight: 80.7±5.5 kg). The volunteers were sequentially PET-imaged up to 7h post i.v. injection of 285±13 MBq on a SIEMENS Biograph16 PET/CT-system on 9 bed positions (BP) per frame, 1.5 to 6 min/BP, CT-attenuation correction and iterative reconstruction. All relevant organs were defined by volumes of interest. Exponential curves were fitted to the time-activity-data (%ID/g, and %ID/organ). The ODs were calculated using the adult male model with OLINDA. The ED was calculated using tissue weighting factors as published in the ICRP103.
Results :
The highest OD [µSv/MBq] was received by urinary bladder (102.0 ± 29.6) and liver (53.1±29.8). The highest contribution to the ED [µSv/MBq] was by urinary bladder (4.1±1.2) and lungs (3.2±0.3). The estimated ED in humans is 23.0±1.9.
Conclusions :
The overall radiation risk was calculated to be 6.9 mSv/300MBq which is almost identically with the results of the (-)-enantiomer in humans (7.02 mSv/MBq). This is in the same magnitude as for other ¹⁸F labeled compounds too. Furthermore, the underestimation of the ED to humans based on preclinical data as mentioned in [1] could be verified for mice (12.1 µSv/MBq) and piglets (14.3 µSv/MBq) with this tracer too. This supports the use of animal image derived data for preclinical dose assessment to humans taking into account an underestimation of about 40%.
However, the risk assessment shown in this study encourages to transfer (+)-[18F]flubatine into further clinical study phases and further develop it as a clinical tool for PET brain imaging.

Objectives:

[¹⁸F]fluspidine is a PET radioligand for neuroimaging of σ1 receptors. The two enantiomers have different kinetics and affinities [1]. Biodistribution, organ doses (OD) and the effective dose (ED) of (S)-(—)-fluspidine (S) and (R)-(+)-fluspidine (R) were determined in mice using PET/MRI to assess the radiation risk to humans.
Methods:
Six female CD1 mice (weight: 30.9±1.3 g) were injected i.v. with 13.2±3.0 MBq (S, n=3) or 12.6±1.4 MBq (R, n=3), respectively. A dynamic 2 h animal PET/MR study was performed. All relevant organs were defined by volumes of interest. Time- and mass-scales were adapted to the human anatomy; exponential curves were fitted to the time-activity-data (%ID/organ). The ODs were computed using the adult male model with OLINDA and the ED using tissue weighting factors (ICRP103).
Results:
For S the highest OD [µSv/MBq] was received by urinary bladder (UB) (58.0), followed by kidneys (37.6). The highest contribution to ED [µSv/MBq] was by UB (2.32) and red marrow (1.30).For R the UB received the highest OD (55.7), followed by small intestine (22.6). The highest contribution to ED was by UB (2.23) and upper large intestine (1.54). The estimated EDs (S: 12.9±0.4; R: 14.0±0.5) differ significantly (p<0.05, student's t-test).
Conclusion:
The estimated ED is well within the range of other ¹⁸F-labeled radiotracer and supports further translational research. Furthermore, we have demonstrated that the enantiomer with higher affinity and slower kinetics (R) causes a higher dosimetric burden than its counterpart (S).
References:
[1] Brust, P. et al. "Distinctive In Vivo Kinetics of the New σ1 Receptor Ligands (R)-(+)-and (S)-(–)-¹⁸F-Fluspidine in Porcine Brain." Journal of Nuclear Medicine 55.10 (2014): 1730-1736.

The last decade has seen an increasing use of three-dimensional CFD codes to predict steady state and transient flows in nuclear reactors because a number of important phenomena such as pressurized thermal shocks, coolant mixing, and thermal striping cannot be predicted by traditional one-dimensional system codes with the required accuracy and spatial resolution. CFD codes contain models for simulating turbulence, heat transfer, multi-phase flows, and chemical reactions. For this reason the long-term objective of the activities of the Helmholtz-Zentrum Dresden-Rossendorf Germany (HZDR) R&D program lies in the development of theoretical models for basic phenomena of transient, three-dimensional single and multiphase systems. Such models must be validated before they can be used with sufficient confidence in nuclear reactor safety (NRS) applications. The necessary validation is performed by comparing model results against measured data. However, in order to obtain a reliable model assessment, CFD simulations for validation purposes must satisfy strict quality criteria given in the Best Practice Guidelines (BPG). The following topical issues which are related to PWR, where CFD calculations have been performed, will be briefly discussed: Coolant mixing of the primary circuit, horizontal stratified flow phenomena in the hot leg and fibre material transport in a core under loss of coolant conditions.

This paper presents a combined experimental and numerical study of the properties of a liquid metal flow inside a cylinder driven by the application of a strong electrical current. The interaction between the electric current running through the melt and the corresponding induced magnetic field produces so-called electro-vortex flows. We consider here a configuration of two parallel pencil electrodes immersed at the free surface. Velocity measurements were performed by means of the Ultrasound Doppler method. A linear array of 25 singular transducers was used to determine the two-dimensional pattern of the vertical flow component. Numerical simulations of the magnetohydrodynamic (MHD) problem were conducted to calculate the Lorentz force, the Joule heating and the induced melt flow. Experimental and numerical results reveal a complex three-dimensional flow structure of the liquid metal flow. In particular, two pronounced downward jets are formed below both electrodes. The flow structure appears to be symmetrical with respect to two vertical cross sections being perpendicular to each other and one of the two planes contains the electrodes. The comparison between the experimental data and the numerical results shows a very good agreement.

In the two-fluid transport model, the coupling of mass, momentum and energy transfer between phases is highly dependent on interfacial area transfer terms. Several research efforts in the past have been focused on the development of an interfacial area transport equation model (IATE), in an attempt to eliminate the drawbacks of static flow regime maps currently used in best-estimate thermal-hydraulic system codes. The IATE attempts to model the dynamics that are involved in two phase flows by accounting for the different interaction mechanisms affecting bubble transport in the flow.
The further development and validation of IATE models has been hindered by the lack of adequate experimental data, especially in regions beyond the bubbly flow regime for large diameter pipes. At the Helmoltz Zentrum Dresden Rossendorf (HZDR) experiments utilizing wire mesh sensors have been performed over all flow regimes, establishing a database of high-resolution (in space and time) data [1]. A 195 mm diameter pipe with a 64 by 64 wire mesh sensor is utilized in the air-water experimental database used in this work. Analysis of flow conditions in the bubbly flow and churn turbulent flow regimes is presented.
The performance of the current two-group IATE model is evaluated. While the qualitative propagation of interfacial area is predicted sufficiently well, there is a discrepancy in magnitude between the model’s prediction and the experimental results. Overall, the study suggests that differences exist in the incidence of interaction mechanisms between small and large diameter pipes and further efforts are needed in order to extend the range of validity of current IATE models.

The Fe(II)-bearing secondary mineral phases siderite and magnetite form under anoxic nuclear respository conditions at the surface of corroding steel containers. Due to their redox reactivity, they control the retention of critical, long-lived radionuclides like Se, Tc and Pu (1-3). Here we show their interaction with another radionuclide of high safety concern, Np, which is more soluble and hence mobile at its oxic, pentavalent redox state in comparison to its reduced, tetravalent oxidation state. The Np(V) reactions at the mineral/water interface were investigated by macroscopic batch experiments and at the molecular level by in situ vibrational (ATR FT IR) and X-ray absorption spectroscopies (XAS). For magnetite, we could distinguish four different processes, the fast formation of a Np(V) inner-sphere sorption complex, followed by the surface reduction of Np(V) to Np(IV), which forms a tridentate Np(IV) inner-sphere sorption complex, and the precipitation of poorly ordered and/or nano-sized NpO2-like particles. The Np(IV) inner-sphere sorption complex prevails at lower pH (<6) and at shorter reaction time, while the precipitate prevails at higher pH (>7) and longer reaction time. In the siderite system, we observed neither the formation of Np(V) nor of Np(IV) sorption complexes at the mineral surface, but only the formation of NpO2 nanoparticles, pointing towards a redox reaction already in solution. Independent of the mechanism, retention of Np(V) by the two minerals was strong; even at high pH and in presence of carbonate – conditions where the retention of Np by the clay barrier becomes weak – the log Rd values remain above 3.5.

1. A. C. Scheinost et al., J. Contam. Hydrol. 102, 228-245 (2008).
2. R. Kirsch et al., Environ. Sci. Technol. 45, 7267–7274 (2011).
3. T. Kobayashi, A. C. Scheinost, D. Fellhauer, X. Gaona, M. Altmaier, Radiochim. Acta 101, 323-332 (2013).

Wire mesh sensors (WMS) are state of the art devices that allow high resolution (in space and time) measurement of 2D void fraction distribution in any two-phase flow regime. Data using WMS have been recorded at the Helmholtz Zentrum Dresden Rossendorf (HZDR) [1] for a wide combination of superficial gas and liquid velocities, providing an excellent database for advances in two-phase flow modeling. In two-phase flow, the interfacial area plays an integral role in coupling the mass, momentum and energy transport equations of the liquid and gas phase. While current models used in best-estimate thermal-hydraulic codes (e.g. RELAP5, TRACE, TRACG, etc.) are still based on algebraic correlations for the estimation of the interfacial area in different flow regimes, interfacial area transport equations (IATE) have been proposed to predict the dynamic propagation in space and time of interfacial area [2]. IATE models are still under development and the HZDR WMS experiments would provide an excellent basis for the validation and further advance of these models. The current paper is focused on the algorithms used to reconstruct interfacial area densities from the void-fraction voxel data measured using WMS.

In a hypothetical Small Break Loss of Coolant Accident (SB-LOCA) in a Pressurized Water Reactor (PWR), the Reactor Pressure Vessel wall (RPV) may be exposed to thermal stress, since the Emergency Core Cooling System (ECCS) injects cold water. 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 surface.
Computational Fluid Dynamics models are not reliable enough to contribute to reliable safety analysis. For the development and validation of CFD-models, experiments have to meet a high standard of reproducibility, measurement certainty and temporal and local resolution. The pressure tank technology of the TOPFLOW facility allows conducting such experiments at reasonable effort.
The Direct Condensation and Entrainment Installation for Steam Experiments (DENISE) is made for CFD-grade condensation experiments at up to 50 bars pressure. Subcooled water is injected into the DENISE-basin in three different configurations to generate stratified flow, jet and plunging jet (steam entrainment with a jet) experiments with condensation.
The experimental facility is presented along with the high degree of instrumentation. High speed camera, micro thermocouples, coriolis flow meters and movable thermal lances were used.

Chemical energy storage systems, e.g. in the form of hydrogen or methanol, have a great potential for the establishment of volatile renewable energy sources due to the large energy density. The efficiency of hydrogen production through water electrolysis is, however, limited by gas bubbles evolving at the electrode’s surface and can be enhanced by an accelerated bubble detachment. In order to characterize the complex multi-phase flow near the electrode, simultaneous measurements of the fluid velocities and the size and trajectories of hydrogen bubbles were performed in a water electrolyzer. The liquid phase velocity was measured by PIV/PTV, while shadowgraphy was used to determine the bubble trajectories. Special measurement and evaluation techniques had to be applied as the measurement uncertainty is strongly effected by the high void fraction close to the wall. In particular, the application of an advanced PTV scheme allowed for more precise fluid velocity measurements closer to electrode. This way, the effect of Lorentz forces on the near-wall fluid velocities was investigated. The results show a significantly increased wall parallel liquid phase velocity with increasing Lorentz forces. It is presumed that this enhances the detachment of hydrogen bubbles from the electrode surface and, consequently, decreases the fractional bubble coverage and improves the efficiency. In addition, the effect of large rising bubbles with path oscillations on the near-wall flow was investigated. These bubbles can have a strong impact on the mass transfer near the electrode and thus affect the performance of the process.

Objectives:

CB2R represents a target with increasing importance for neuroimaging due to its upregulation in various pathological conditions. Encouraged by preliminary results obtained with ¹¹C-A-836339 (Ki = 1.2 nM) in a mouse model of acute neuroinflammation (induced by lipopolysaccharide, LPS), we designed a library of fluorinated analogs to develop a radioligand with improved CB2R binding affinity and selectivity.
Methods:
A series of fifteen analogs of A836339 was synthesized and JHU94620, selected as ligand with the highest CB2R affinity (Ki = 0.38 nM) and selectivity over CB1R (factor 1000). It was labelled from the bromo precursor by standard nucleophilic radiofluorination. For in vivo experiments, control and LPS-treated CD1 mice have been used. Metabolic stability was investigated in plasma samples (30 min p.i) by radio-HPLC. In vitro autoradiography was performed on rat spleen and pig brain using CB1, CB2, and CB1/CB2 specific ligands as competitors.
Results:
¹⁸F-JHU94620 was prepared in ~10% radiochemical yield, >98% radiochemical purity and specific activity of >150 GBq/μmol. Animal PET revealed a brain uptake comparable to 11C-A-836339. 20-30% higher uptake in LPS-treated mice was found (n=3, p<0.05). In plasma, ~10% of total radioactivity accounted for intact tracer at 30 min p.i. Binding of ¹⁸F-JHU94620 on spleen could be displaced by CB2- and CB1/CB2-specific but not by CB1-specific compounds (61%, 44%, and 107% of total binding, respectively, at 1 μM). As expected, in brain slices from healthy pig no specific binding was observed.
Conclusion:
¹⁸F-JHU94620 is a potential candidate for further studies with PET in neuroinflamation and related disorders.

Administration of thyroid hormones (TH) to mammals leads to an increase in basal metabolic rate and thermogenesis. These effects have been attributed to direct actions of TH on metabolically active tissues, such as brown adipose tissue (BAT). Furthermore, TH might stimulate “browning”, i.e. conversion of existing white fat cells to ''brite'' or ''beige'' adipocytes with features of brown adipocytes. However, the impact of TH on BAT activity and “browning” of white adipocytes has not been analyzed under well-controlled conditions in the same experimental setting.
Therefore, it was assessed how thyroid dysfunction, i.e. hyper- and hypothyroidism, affects 1) activity of BAT by ¹⁸F-FDG PET/MRI, and 2) affects gene expression of brown and beige adipose tissue differentiation markers in white adipose tissues (inguinal and epididymal, iWAT and eWAT, respectively) and interscapular BAT (iBAT) in mice. We randomized female C57BL/6NTac mice and rendered them hyper- or hyperthyroid (n = 20 per group) according to ATA guidelines (Bianco et al. Thyroid 2014). After 4 weeks of treatment, small animal PET/MR analysis revealed that hypothyroid mice had significantly decreased and hyperthyroid mice had significantly increased interscapular BAT (iBAT) ¹⁸F-FDG uptake as compared to euthyroid controls (SUV 3.5 ± 0.7 vs. 6.2 ± 0.6 and SUV 78.0 ± 2.1 vs. 6.16 ± 0.6, respectively). In addition to the findings in iBAT, hypothyroid mice also had significantly diminished glucose disposal in skeletal muscle as compared to both other groups. However, despite the iBAT of hypothyroid mice showing low metabolic activity, significantly higher levels of Ucp1 mRNA was found in iBAT when compared with hyper- and euthyroid animals (p < 0.05 for both). In accordance with these findings, other thermogenic markers including Prdm16, Fgf21, Cidea, Elovl3 and Cox7a1 were all overexpressed in the hypothyroid iBAT. In contrast, the thermogenic genes Ucp1, Prdm16, Fgf21, Cidea, Pgc1α were upregulated in eWAT in hyperthyroid mice as compared to hypothyroid and euthyroid mice. In addition, also markers for beige adipocytes (Cd137, Tmem26), and adipocyte recruitment (Zfp423) were significantly increased in the eWAT of hyperthyroid mice as compared hypo-and euthyroid mice.
In conclusion, these data suggest that TH induce both BAT activity and the thermogenic program in white adipose tissues possibly leading to the browning of white fat depots.

Aim:

The α7nAChR is regarded of importance for neurodegeneration, inflammatory processes, certain types of cancer, and in the pathophysiology of atherosclerosis. Our recently developed PET radioligands [¹⁸F]NS14490 and [¹⁸F]DBT-10 showed high in vitro affinity and selectivity towards α7nAChR. We present the automated syntheses and the preclinical evaluation of both radiotracers by PET in pigs and provide evidence on their suitability for imaging of α7nAChRs in the mentioned diseases.
Materials and Methods:
[¹⁸F]NS14490 and [¹⁸F]DBT-10 were synthesized using a Tracerlab FX F-N module by direct radiofluorination using the corresponding tosylate and nitro precursors. Dynamic PET studies (~300-400 MBq) were performed in anaesthetized female piglets under control (n=3 each) and blocking conditions (n=3 each; continuous infusion of the highly selective antagonist ligand NS6740). By compartmental modeling using metabolite-corrected plasma input functions the binding parameters in 24 brain regions and on brain blood vessels were estimated. Parametric maps of the distribution volumes (V_T) of [¹⁸F]NS14490 were calculated. In anticipation of human studies, for [¹⁸F]DBT-10 preclinical dose assessment and toxicity studies were performed.
Results:
[¹⁸F]NS14490 and [¹⁸F]DBT-10 were obtained with comparably high RCY (~30-40%), radiochemical purities (~92-95%) and specific activities (>150 GBq/µmol). Maximum brain uptake was reached at 3 min ([¹⁸F]NS14490 SUV_max:0.54) and 11.5 min p.i. ([¹⁸F]DBT-10 SUV_max:1.89). Comparable metabolism was observed, with 25-30% of both parent compounds in plasma at 60 min p.i. Compartmental modeling allowed reliable estimates of k₃’ and binding potential, BP_ND. NS6740 infusion significantly reduced mean k₃’ of [¹⁸F]NS14490 by 46% and mean BP_ND of [¹⁸F]DBT-10 by 75%. Reduction of V_T on brain blood vessels by NS6740 was clearly visible in parametric maps of [¹⁸F]NS14490. SUV_max in blood vessels of 1.3-1.4 was reached at 2-4 min p.i. NS6740 reduced the SUV by 25-35% at 4 h p.i. The estimated effective dose of [¹⁸F]DBT-10 administration to humans is 12-14 μSv/MBq. DBT-10 toxicity tests did not predict harmfulness for human tracer studies.
Conclusion:
[¹⁸F]NS14490 and [¹⁸F]DBT-10 are promising PET tracers for imaging of α7nAChR. Our preclinical studies provide evidence for the detection of α7nAChRs by PET in the parenchyma and vasculature of pig brain. This further elucidates the feasibility of PET to visualize vascular α7nAChRs, which may present a tool for investigating involvement of α7nAChRs in the pathophysiology of atherosclerosis. [¹⁸F]DBT-10 is selected for further evaluation to obtain approval for translational clinical validation in humans due to its higher affinity, brain uptake, and specific binding.

The Central European Kupferschiefer deposit bearing copper up to five percent is the most important natural copper resource in Europe, and thus raised again interest of both industry and science. Due to the complex composition of the shale including copper and sulfide rich ores, carbonates and organic compounds there is no efficient biotechnological approach applied yet. Although promising approaches using acidophilic micoorganisms were presented [1] issues such as acid pretreatment and resulting gypsum waste remain. Thus leaching at neutral and alkalic pH ranges has been investigated using both foreign and indigenous species including yeasts [2-4]. Especially usage of microbially produced organic acids [5] has shown good results regarding copper recovery. In previous studies [4] the impact of glutamic (see figure) and citric acid on copper minerals in Kupferschiefer ore has been examined using bulk chemicals. The presentation compares those results to copper leaching with citric acid as biotechnologically produced product in fermentation broth produced by the yeast Yarrowia lipolytica.

Die Erfindung betrifft eine Kapazitätsdiode, ein Verfahren zum Herstellen derselben, sowie einen Speicher und Detektor mit einer solchen Kapazitätsdiode, wobei die Kapazitätsdiode eine erste und eine zweite Elektrode sowie eine kontaktierend zwischen den beiden Elektroden angeordnete Schichtanordnung aufweist, und wobei die Schichtanordnung in Richtung von der ersten zu der zweiten Elektrode hin nacheinander eine Schicht aus einem ferroelektrischen Material und eine Schicht aus einem dielektrischen Material mit elektrisch geladenen Störstellen aufweist.

Die Erfindung betrifft Verfahren und Einrichtungen zur Kontrolle der Reichweite einer Partikelstrahlung in der Strahlentherapie über die Messung prompter Gammastrahlung mit wenigstens einem einzelne Gammaquanten nachweisenden Detektor und mindestens einem Analysator, die sich insbesondere durch ihre einfache und robuste Realisierung sowie eine durch stark reduzierte Messzeit auszeichnen, die eine Reichweitekontrolle in Echtzeit erlaubt. Dazu werden mit Hilfe des Detektors und des Analysators unter Verwendung eines Referenzsignals der Bestrahlungseinrichtung oder eines separaten Partikeldetektors Zeitverteilungen gemessen, die statistische Verteilungen der Flugzeiten von Therapiepartikeln bis zur Emission eines prompten Gammaquants, ergänzt um die Flugzeit des entsprechenden Gammaquants zum Detektor, widerspiegeln. Informationen über die Reichweite der Therapiepartikel werden im Wesentlichen aus diesen Zeitverteilungen abgeleitet.

simulation and first results

Beam Diagnostics of the ELBE SRF Gun II

99Tc is a long-lived (T1/2=2.13·105 y) fission product (FP) of the nuclear fuel cycle (NFC). As a component of nuclear wastes it remains a FP of concern for the safety assessment of a final disposal site. In the heptavalent form Tc(VII)O4-, it is well soluble, poorly sorbed and hence, a highly mobile anion in the environment. A number of strategies have been proposed to reduce 99Tc mobility by irreversible incorporation into the structure of ubiquitous mineral phases . We have recently demonstrated the incorporation of TcO4- in layered double hydroxides (LDH) that were earlier proposed for 79Se and 129I remediation in water treatment technology.
This work is focused on the interaction of 99Tc(VII) with Pyroaurite (PyA) and Hydrotalcite (HTC) - Mg-Fe and Mg-Al LDHs respectively, on simplified CO2- and O2-free conditions. Earlier experiments with Re(VII), considered to be a chemical analogue for 99Tc(VII), have demonstrated little to no uptake of Re(VII). Similar experiments with 99Tc(VII) however have shown a significant increase in 99Tc uptake on LDHs even in the concurrency with CO32- ions. Subsequent leaching experiments have revealed the irreversible character of the 99Tc(VII)-LDH compound. Modern spectroscopic methods are applied in order to understand how 99Tc is accommodated in between the brucite layers of LDHs and whether 99Tc(VII) is reduced to Tc(IV). This information will help to verify, whether LDHs can be used as a host phase for 99Tc long-term and safe storage. Additionally, these data aquired on controlled conditions can be used for modelling of 99Tc geochemical behavior in more complex repository relevant systems.

⁷⁹Se and ⁹⁹Tc are fission products of the nuclear fuel cycle and, thus, are of concern during the safety assessment of a nuclear waste disposal site. For a comprehensive description of their mobility in the near and far field of a deep geological repository, the interactions of respective dissolved species with mineral surfaces are of special interest. In particular, the oxoanions Se(VI)O₄ ²⁻ and Tc(VII)O₄ ⁻ are considered as mobile species in aquifer due to their high solubility and negative charge.
In this study, the surface reactions of these anions were studied by in situ vibrational spectroscopy which is a dedicated technique for the real time monitoring of the surface processes at the water-mineral interface [1, 2]. For the selenate anion, the formation of two different types of outer-sphere complexes was observed depending on the mineral’s surface. Although both types of sorption complexes behave like typical outer-sphere complexes in terms of macroscopic properties, the different spectral signatures clearly reflect two different molecule symmetries. From the spectra, a slightly distorted tetrahedral geometry, which is close to the aqueous species, and a bidendately coordinated species showing a C_2v symmetry were derived. These surface species are denoted as “extended” and “classical” outer sphere complexes, respectively [3, 4].
In homology, spectroscopic sorption experiments with Tc(VII) were performed. The aqueous species should share the same symmetry as for Se(VI), that is a tetrahedral TcO₄ ⁻ ion. From preliminary results of the vibrational spectroscopic sorption experiments, mainly outer-sphere complexes were found which are obviously less specific as it was found for Se(VI).

[1] Foerstendorf, H. et al. (2012) J. Colloid Interface Sci. 377, 299–306. [2] Müller, K. et al. (2015) Environ. Sci. Technol. 49, 2560–2567. [3] Jordan, N. et al. (2011) Geochim. Cosmochim. Acta 75, 1519–1530. [4] Jordan, N. et al. (2013) Geochim. Cosmochim. Acta 103, 63–75.

Für die Bestimmung von Geschwindigkeiten am schnellen Röntgentomographen Rofex eignet sich die Methode der Kreuzkorrelation. Weil dabei manchmal relativ große Integrationsintervalle notwendig sind, kann es zur entsprechend schlechten zeitlichen Auflösung der Geschwindigkeiten kommen. Gezeigt wird, dass mit geeignetem Vorwissen über das sich bewegende Medium oder Objekt trotzdem zumindest regional relativ hohe zeitliche Auflösungen erreichbar sind.

Durch schnelle Röntgentomographie auf der Grundlage eines magnetisch abgelenkten Elektronenstrahls ist es möglich, 2D-Abbildungen von fluiden Medien zu erzeugen. 3D-Abbildungen wären zwar wünschenswert, sind aber vorerst noch nicht mit vertretbarem Aufwand realisierbar. Trotzdem soll bereits jetzt versucht werden, methodische Studien zur Bestimmung von Geschwindigkeiten in röntgentomographischen 3D-Abbildungen durchzuführen. Speziell werden dynamische Vorgänge in flüssigem Schaum betrachtet.

Der effiziente und sorgsame Umgang mit natürlichen Ressourcen bleibt ein Thema von globaler Tragweite. Unabhängig vom Tagespreis steigt der Rohstoffhunger der Welt ungebremst; die Qualität, der für eine Nutzung verfügbaren, primären und sekundären Rohstoffe nimmt dagegen stetig ab. Deshalb ist es wichtig, die Gesellschaft nicht nur für eine Energie-, sondern auch für eine Rohstoffwende mit allen daraus resultierenden Folgen zu sensibilisieren. Vier Jahre nach der Gründung der ersten Knowledge & Innovation Communities (KICs) in den Bereichen Klimaschutz, erneuerbare Energien sowie Informations- und Kommunikationstechnologien rief das Europäische Institut für Innovation und Technologie (EIT) nun ein neues KIC für die mineralischen und metallischen Rohstoffe ins Leben. „EIT Raw Materials“, das weltweit größte Ressourcenkonsortium umfasst mehr als 100 führende Unternehmen, Universitäten und Forschungsinstitute aus 22 europäischen Ländern. Sein Ziel wird es in den kommenden Jahren sein, ein pan-europäisches Netzwerk für die langfristige Zusammenarbeit von Bildung, Forschung und Wirtschaft entlang der gesamten Rohstoff-Wertschöpfungskette zu erschaffen.

Das Helmholtz-Institut Freiberg für Ressourcentechnologie (HIF) wurde als nationales Rohstoff-Institut im Jahr 2011 durch das Bundesministerium für Bildung und Forschung (BMBF) gegründet. Es erforscht und entwickelt Technologien für die nachhaltige Versorgung der deutschen Volkswirtschaft mit dringend benötigten mineralischen, insbesondere metallhaltigen Rohstoffen. Das HIF war von Anfang an als ein an das Helmholtz-Zentrum Dresden-Rossendorf (HZDR) angegliedertes Helmholtz-Institut mit Standort Freiberg geplant. Denn so profitiert das HIF sowohl von den Ressourcenkompetenzen der TU Bergakademie Freiberg als auch von der strukturellen Kompetenz des HZDR. Im Folgenden wird die Einbindung des HIF in die Helmholtz-Gemeinschaft Deutscher Forschungszentren und in die Bergakademie dargestellt sowie einige Beispiele aus der gemeinsame Zusammenarbeit beschrieben.

Background
Aspiration-induced lung injury can decrease gas exchange and increase mortality. Acute lung injury following acid aspiration is characterized by elevated pulmonary blood flow (PBF) in damaged lung areas in the early inflammation stage. Knowledge of PBF patterns after acid aspiration is important for targeting intravenous treatments. We examined PBF in an experimental model at a later stage (2 hours after injury).

Methods
Anesthetized Wistar-Unilever rats (n = 5) underwent unilateral endobronchial instillation of hydrochloric acid. The PBF distribution was compared between injured and uninjured sides and with that of untreated control animals (n = 6). Changes in lung density after injury were measured using computed tomography (CT). Regional PBF distribution was determined quantitatively in vivo 2 hours after acid instillation by measuring the concentration of [⁶⁸Ga]-radiolabeled microspheres using positron emission tomography.

Results
CT scans revealed increased lung density in areas of acid aspiration. Lung injury was accompanied by impaired gas exchange. Acid aspiration decreased the arterial pressure of oxygen from 157 mmHg [139;165] to 74 mmHg [67;86] at 20 minutes and tended toward restoration to 109 mmHg [69;114] at 110 minutes (P < 0.001). The PBF ratio of the middle region of the injured versus uninjured lungs of the aspiration group (0.86 [0.7;0.9], median [25%;75%]) was significantly lower than the PBF ratio in the left versus right lung of the control group (1.02 [1.0;1.05]; P = 0.016).

Conclusions
The PBF pattern 2 hours after aspiration-induced lung injury showed a redistribution of PBF away from injured regions that was likely responsible for the partial recovery from hypoxemia over time. Treatments given intravenously 2 hours after acid-induced lung injury may not preferentially reach the injured lung regions, contrary to what occurs during the first hour of inflammation.

Background: The stable nucleus 15N is the mirror of 15O, the bottleneck in the hydrogen burning CNO cycle. Most of the 15N level widths below the proton emission threshold are known from just one nuclear resonance fluorescence (NRF) measurement, with limited precision in some cases. A recent experiment with the AGATA demonstrator array determined level lifetimes using the Doppler Shift Attenuation Method (DSAM) in 15O. As a reference and for testing the method, level lifetimes in 15N have also been determined in the same experiment.
Purpose: The latest compilation of 15N level properties dates back to 1991. The limited precision in some cases in the compilation calls for a new measurement in order to enable a comparison to the AGATA demonstrator data. The widths of several 15N levels have been studied with the NRF method.
Method: The solid nitrogen compounds enriched in 15N have been irradiated with bremsstrahlung. The g-rays following the deexcitation of the excited nuclear levels were detected with four HPGe detectors.
Results: Integrated photon-scattering cross sections of ten levels below the proton emission threshold have been measured. Partial gamma-ray widths of ground-state transitions were deduced and compared to the literature. The photon scattering cross sections of two levels above the proton emission threshold, but still below other particle emission energies have also been measured, and proton resonance strengths and proton widths were deduced.
Conclusions: Gamma and proton widths consistent with the literature values were obtained, but with greatly improved precision.

Introduction: Long-lived radionuclides with half-lives of 0.1-16 Ma (Tab. 1) have nowadays thousands of exciting applications, especially within environmental and geosciences. In nature, the so-called cosmogenic nuclides (CNs) are products of nuclear reactions induced by primary and secondary cosmic rays. Hence, they can be found in extraterrestrial material such as meteorites - originating from the asteroid belt, the Moon or Mars - and lunar samples in higher concentrations (e.g. ~10^{10 10}Be atoms/g or < 0.5 mBq/g). A combination of several CNs is used to reconstruct the exposure history of this unique material while in space (irradiation age) and on Earth (terrestrial age).
Though, in terrestrial material the concentrations are typically only on the order of 10⁴-10⁹ atoms/g (i.e. μBq/g - nBq/g) for ¹⁰Be produced in the Earth’s atmosphere, so-called atmospheric or meteoric ¹⁰Be, transported to the surface and further absorbed and incorporated at and in, e.g. sediments or ice. Some of the lowest ¹⁰Be concentrations (~10³ atoms/g), produced in-situ by neutron- and muon-induced nuclear reactions from e.g. oxygen and silicon in quartz, can be found in samples taken from the Earth’s surface. The concentrations of atmospheric or in-situ produced CNs record information to reconstruct sudden geomorphological events such as volcanic eruptions, rock avalanches, tsunamis, meteor impacts, earthquakes and glacier movements. Additionally, glacier movements and data from ice cores give hints for the reconstruction of historic climate changes and providing information for the validation of climate model predicting future changes. Slower processes such as sedimentation, river incision and erosion rates can also be investigated and last but not least, indirect dating of bones as old as several Ma’s is possible.
Anthropogenic production by release from nuclear reprocessing, accidents and weapons testing led to increased levels of CNs in surface water and soil (¹²⁹I,…), ice (³⁶Cl,…) and of course, material from nuclear installations themselves (⁴¹Ca,…).
Some of the CNs can be further used as natural or artificial tracers to follow pathways in oceanography, to date and identify sources of groundwater, to perform retrospective dosimetry and to study aspects in radioecology, phytology, nutrition, toxicology and pharmacology.
Method: Today, the analytical method of choice for long-lived cosmogenic radionuclides – especially non-gamma-active ones - is accelerator mass spectrometry (AMS). In contrast to decay counting, AMS scientists do not wait for the disintegration of the radioactive nucleus. In fact, the not-yet-decayed radionuclides are identified more efficiently by mass spectrometry. The main advantage of using a high-energy accelerator for mass spectrometry is the nearly complete elimination of background and interfering signals, resulting from molecular ions and ions with similar masses e.g. isobars. Thus, AMS generally provides much lower detection limits in comparison to conventional mass spectrometry. Our DREAMS (DREsden AMS) system (Akhmadaliev et al., 2013) offers excellent measurement capabilities also for external users.

Table 1. Radionuclides measured by AMS at DREAMS.
Nuclide t1/2 [Ma] Nuclide ratios of samples [10^-12]
(machine blank level)
¹⁰Be 1.387 0.01-300 (5x10^-16) ¹⁰Be/⁹Be
²⁶Al 0.705 0.001-60 (8x10^-16) ²⁶Al/²⁷Al
³⁶Cl 0.301 0.007-700 (2x10^-16) ³⁶Cl/³⁵Cl
⁴¹Ca 0.104 0.02-9000 (8x10^-15) ⁴¹Ca/⁴⁰Ca
¹²⁹I 15.7 artificial samples (3x10^-14) ¹²⁹I/¹²⁷I
actinides under development

The benefits from using AMS are obvious and manifold: Smaller sample sizes, easier and faster sample preparation, higher sample throughput and the redundancy for radiochemistry laboratories are largely reducing costs. Lower detection limits widen applications to shorter and longer time-scales and to sample types that could never be investigated before. Nevertheless, basic but accurate radiochemical sample separation is an essential prerequisite for AMS measurements.
Model applications: Some of the first successful CN-projects performed at DREAMS had been:

• Dating of marine sediments (with ANU, ETH, TANDAR, TUM & VERA) by ¹⁰Be & ²⁶Al and search for supernova-origin ⁶⁰Fe (by AMS at ANU & TUM)
• Growth rates of deep-sea manganese nodules by ¹⁰Be and ²⁶Al (with Senckenberg)
• ⁴¹Ca-determination in water and concrete from a nuclear power plant by LSC and AMS (with VKTA)
• Reconstruction of meteorites’ history by ¹⁰Be, ²⁶Al, ³⁶Cl, ⁴¹Ca (with U Poznan & Bern, MPI Mainz,…).

Acknowledgments
Thanks to all brave DREAMS-users working with a newly installed AMS-facility and for help from colleagues at other AMS-facilities (ANSTO, ANU, ASTER, ETH, VERA…) with cross-measurements and setting-up the time-of-flight-system for future actinide measurements.

References
Akhmadaliev et al. (2013) Nucl. Instr. Meth. Phys. Res. B 294, 5-10.

Absorber layers consisting of nanostructured Si are candidates to improve the efficiency of thin film Si solar cells. Si-SiO2 nanocomposites with sponge-like Si embedded in SiO2 are promising materials due to a widened band gap and a maintained electrical interconnectivity. These structures can be formed upon isothermal or rapid thermal annealing of SiOx films (x<1), which leads to phase separation into a percolated network of Si nanowires embedded in SiO2, tentatively accompanied by crystallization of the Si. SiOx layers have been grown by ion beam sputter deposition as well as by reactive magnetron sputtering. Phase separation into Si-SiO2 nanocomposites has been achieved by classical thermal oven treatment, which has been compared to a very rapid thermal processing by scanning a diode laser line source. Compositional and structural characterization has been performed by Rutherford backscattering spectroscopy, energy filtered transmission electron microscopy, and Raman spectroscopy. The two sputter techniques of SiOx lead to distinct nanostructures during the classical thermal treatment throughout a phase separation in the solid state. In contrast, the decomposition with laser treatment occurs in the liquid state.

Reactively sputtered TiO2 thin films on Pt/Ti/SiO2/Si substrates were irradiated with low energy Ar+ ions of different energies to create surface or bulk modifications in the material. Furthermore, the fluence was varied to optimize the level of the modifications, which are e.g. amorphization, surface smoothing, and preferential sputtering of oxygen. These effects were detected by TEM, AFM and supported by TRIDYN simulations, respectively.
The impact of these changes on the electrical properties of the TiO2 layers was monitored by I-V and C-V measurements in top-bottom geometry with Pt, as well as Ti/Pt top contacts. The results indicate a transition from a Schottky-like behavior of the Pt/TiO2 interface to an ohmic one with increasing fluence, which is very similar to the behavior of a Ti/TiO2 interface. Furthermore, the capacity of the complete MIM stack increases with fluence, which points to a reduced effective thickness of the dielectric TiO2 layer after irradiation.

The project is funded by the Initiative and Networking Fund of the Helmholtz Association (Virtual Institute Memriox, VH-VI-422).

Transition metal oxide thin films, like TiO2, which show a redox-based switching process between two or more resistance levels, are promising candidates for future memory storage devices.
They are extensively studied to get a better understanding of the role of mobile oxygen ions and/or oxygen vacancies for structural changes and electronic transport inside the films.
A defective, nonstoichiometric TiO2-x layer can act as a reservoir for oxygen vacancies and improves the switching characteristics. Such a layer was introduced into the virgin TiO2 film by low energy Ar+ irradiation with different energies and fluencies to modulate the depths and level of the defective region. The impact of the irradiation to the surface morphology and crystal structure was monitored by AFM and TEM measurements and was found to be surface smoothing and amorphization. The role of the preferential sputtering of oxygen to the stoichiometry of the film was investigated with TRIDYN simulations. Electrical properties of the irradiated films were characterized by I-V and C-V measurements and are related to the structural changes caused by the Ar+ irradiation.

The project is funded by the Initiative and Networking Fund of the Helmholtz Association (Virtual Institute Memriox, VH-VI-422).

Anisotropic magneto resistance (AMR) sensors are widely used in daily life. But the influence of magnetic domains on the AMR is still not fully understood. AMR depends on the direction of the magnetization. For the understanding of the AMR it is therefore important to know about the domain structure. Dual Kerr microscopy is used for the observation of the magnetic domains while at the same time the AMR is measured. Dual Kerr microscopy means that it is possible to measure two magnetization directions at the same time. These two sensitivity directions make it possible to calculate quantitative Kerr images for a complete loop. The investigated samples were magnetic stripe patterned permalloy. The patterning was archived with Cr-Implantation. In addition to the measured resistance the AMR is calculated from the quantitative Kerr images. We also compare the field dependence of the AMR by variation of the magnetic field angle.Our measurements show a clear dependence of the AMR on the magnetic domain types. This work is supported by DFG grant FA316/3-2.

Magnetic MAX phase (Cr0.5Mn0.5)2GaC thin films grown epitaxially on a MgO(111) substrates were studied by ferromagnetic resonance (FMR) at temperatures between 110 K and 300 K. The spectroscopic splitting factor g = 2.00 ± 0.01 measured at all temperatures indicates pure spin magnetism in the sample. At all temperatures we find the magnetocrystalline anisotropy energy to be negligible which is in agreement with the identified pure spin magnetism.

Background and Purpose: Arterial spin-labeling method for CBF assessment is widely available but its accuracy is not fully established. We investigated the accuracy of a whole brain arterial spin-labeling technique for assessment of the mean parenchymal CBF (pCBF) and the effect of ageing in healthy volunteers. Phase-contrast MRI was used as the reference method.
Materials and Methods: Ninety-two healthy volunteers were included: 49 young (age range 20-30y) and 43 elderly (65-80y). Arterial spin-labeling pCBF values were averaged over the whole brain to quantify mean pCBFASL.
Total CBF was assessed with phase-contrast MRI as the sum of flow in the internal carotids and vertebral arteries, and subsequent division by brain volume returned the pCBFPCMRI. Accuracy was considered as good if there was less than 5 mL/min/100g in systematic difference against the reference method and if the 95% limits of agreement interval are equal or better than ±10 mL/min/100g
Results: pCBFASL was correlated with pCBFPCMRI (r=0.73, P<0.001).
Significant differences were observed between pCBFASL and pCBFPCMRI in young (P=0.001) as well as in elderly (P<0.001), and the systematic differences were -4±14 mL/min/100g (mean ± 2SD) in young and +6±12 mL/min/100g in elderly. Young subjects showed higher pCBF than elderly for both pCBFPCMRI (Young:57±8, Elderly:54±7 mL/min/100g, P=0.05) and pCBFASL (Young:60±10, Elderly:48±10 mL/min/100g, P<0.001).
Conclusion: Regarding accuracy of the arterial spin-labeling, limits of agreements were too wide while the systematic overestimation in young and underestimation in elderly was close to acceptable. Age-related decrease in pCBF was augmented in arterial spin-labeling compared to phase contrast MRI.

Arterial Spin labeling (ASL) is a fully noninvasive MRI method capable to quantify cerebral perfusion. However, gray (GM) and white matter (WM) ASL perfusions are difficult to assess separately due to limited spatial resolution increasing the partial volume effects (PVE). In the present study, ASL PVE correction was implemented based on a regression algorithm in 22 healthy young men. PVE corrected perfusion of GM and WM were compared to previous studies. PVE-corrected GM perfusion was in agreement with literature values. In general, WM perfusion was higher despite the use of PVE correction.

Acidovorax facilis, an aerobic Gram-negative Betaproteobacteria which is commonly found in soil, was used for U(VI) sorption experiments. Experiments were performed in batch cultures under aerobic conditions at 25 °C using nutrient broth. For U(VI) sorption experiments UO2(NO3)2 was added to the culture to achieve an initial U concentration of 0.05 and 0.1 M, respectively, at a neutral pH range. The duration of the sorption experiments were limited to 8 h and 48 h, respectively. By time-resolved laser fluorescence spectroscopy (TRLFS) the measured emission spectrum of the cells is characterized by four emission bands with peak maxima at 497.8, 519.5, 544.1 and 568.6 nm ± 0.5 nm. In addition, the spectra of the Uranyl-lipopolysaccharide-complexes R-O-PO3-UO2 and [R-O-PO3]2-UO22-, reported by Barkleit et al. (2008), were used for comparison. They show only a small deviation from those observed in our studies. Hence, it can be concluded that phosphoryl groups are the main binding sites for uranyl, located in the lipopolysaccharide (LPS) unit in the outer membrane by Gram-negative Acidovorax facilis cells. After the U(VI) biosorption experiments, Acidovorax facilis cells were prepared for Energy-filtered transmission electron microscopy (EF-TEM) and electron energy-loss spectroscopy (EELS). The results provide microscopically and spectroscopically evidence of U(VI) sorbed at the outer membrane of Acidovorax facilis cells by showing high electron density and U ionization intensity peaks.

The magnetization transfer (MT) effects were studied in pseudo-continuous ASL (pCASL). The MT exchange rate was obtained from two pCASL sequences with and without labeling acquired at multiple delays. A mean white-matter MT exchange rate was obtained and the exchange rate in blood was derived from it. Effect on CBF quantification was then calculated using the standard pCASL quantification model for different distances from the labeling plane and different blood velocities in the arteries. CBF underestimation of up to 6% was shown in the slices closest to the labeling plane if the MT effects were ignored

Direct numerical simulation (DNS) is normally used to study turbulent flows. Though, it may be also very useful for linear instability analysis of complex laminar flows. given an essentially three-dimensional basic flow the number of coupled active degrees of freedom may easily exceed 10⁵. Calculation of the full spectrum is hardly possible if meaningful in such cases. Only a few leading modes are needed for the linear instability anaxix. Iteration techniques such as Arnold iteration may be used to find an isolated eigenvalue. A separate effort, however, is then needed to verify that this eigenvalue really has the maximum real part.
Our study demonstrates that the linear instabiolity problem can be effectively solved by means of DNS. The most straight-forward approach would be to calculate the transient equations long enough to ensure that only the leading eigenmode survives. There is, however, a more efficient way to find few leading eigenvalues and eigenmodes. this method approximates n+1 equidistant flow "snapshot" by n modes that vary exponentially in thime. We describe the numberical implementation of this method coupled with DNS and demonstrate it on an example of three-dimensional magnetohydrodynamic flow. This flow models meld motion in the Cxochralski crystal growth process with a horizontal magnetic field (HMF).

In the present contribution we will show that in a stacked vortex pair system with uniaxial magnetic anisotropy, spin waves of different symmetries and dimensionalities can be excited.

We present PIConGPU a fully-relativistic, 3D3V particle-in-cell code running on multiple GPGPUs. Its parallelization and its application in predicting far field radiation during laser-plasma interactions are discussed during the talk.

We present a new diagnostic method to determine the presence of the Kelvin-Helmholtz instability (KHI) in interstellar jets and measuring its main property, the exponential growth rate, using radiation observable on Earth.

Our findings are based on simulations of the relativistic KHI using the 3D3V particle-in-cell code PIConGPU. With its in-situ computation of the emitted far field radiation, we determined angularly resolved radiation spectra for all billions of particles simulated.

We will explain how measuring the electromagnetic radiation from particle jet allows for identifying the stages of the instability and provides a method to settle the question whether the KHI occurs in astro-physical particle jets or not. By identifying these stages, determining the characteristic growth rate of the KHI becomes possible thus providing quantitative insides to the jet dynamics using only the radiation observed on Earth.

The transition from a continuous thin film to a magnonic crystal is studied by ferromagnetic resonance (FMR). Ion irradiation as well as reactive ion beam etching were used to realize a periodic modulation of the sample surface after patterning by electron beam lithography. Mode-splitting in the FMR spectra has been investigated dependent on the size of the perturbations and compared to available analytical perturbation theory. Numerical simulations have been carried out to identify the spin waves corresponding to the mode spectra as well as to understand deviations between measurement and analytical theory for large perturbations. This work is supported by DFG grant LE2443/5-1.

We present in-situ computation of relativistic radiation in the particle- in-cell code PIConGPU that can give both qualitative and quantitative agreement with analytical models and thus has predictive capabilities. This new kind of synthetic spectral diagnostics can be used to infer plasma dynamics with high spatial and temporal resolution.

Our method is based on the far field approximation of Liénard-Wiechert potential. Its direct integration with the highly-scalable GPU framework of PIConGPU allows computing the spectrally and angu- larly resolved radiation for thousands of frequencies, ranging from infrared to x-rays, hundreds of detector positions and billions of particles efficiently. Recent updates allow studying polarization and improve time resolution thus extending the range of applications.

These capabilities are demonstrated using recent simulations of laser wakefield acceleration (LWFA), high harmonics generation during target normal sheath acceleration (TNSA) and the Kelvin-Helmholtz in- stability (KHI).

We demonstrate a semiconductor based broadband near-field superlens in the mid-infrared regime. Here, the Drude response of a highly doped n-GaAs layer induces a resonant enhancement of evanescent waves accompanied by a significantly improved spatial resolution at radiation wavelengths around lambda = 20 mu m, adjustable by changing the doping concentration. In our experiments, gold stripes below the GaAs superlens are imaged with a lambda/6 subwavelength resolution by an apertureless near-field optical microscope utilizing infrared radiation from a free-electron laser. The resonant behavior of the observed superlensing effect is in excellent agreement with simulations based on the Drude-Lorentz model. Our results demonstrate a rather simple superlens implementation for infrared nanospectroscopy.

In ultrathin magnetic films of 10 — 20 nm thickness, it is hardly possible to determine the exchange constant A using conventional techniques, such as Brillouin light scattering. In this work, a method is presented allowing for analytical determination of the exchange constant A in ultrathin magnetic films. Periodical surface modulations are introduced by electron beam lithography with subsequent sub-nanometer etching. The periodical stray field induces two-magnon scattering leading to a coupling of the uniform excitation with higher in-plane spin waves. An analytical model is presented, that can be used to precisely calculate the exchange constant A under usage of the measured ferromagnetic
resonance spectra (frequency versus field dependence). This work is supported by DFG grant LE2443/5-1.

The tagged quasi-free np→npπ+π− reaction has been studied experimentally with the High Acceptance Di-Electron Spectrometer (HADES) at GSI at a deuteron incident beam energy of 1.25 GeV/nucleon (s√∼ 2.42 GeV/c for the quasi-free collision). For the first time, differential distributions for π+π− production in np collisions have been collected in the region corresponding to the large transverse momenta of the secondary particles. The invariant mass and angular distributions for the np→npπ+π− reaction are compared with different models. This comparison confirms the dominance of the t-channel with ΔΔ contribution. It also validates the changes previously introduced in the Valencia model to describe two-pion production data in other isospin channels, although some deviations are observed, especially for the π+π− invariant mass spectrum. The extracted total cross section is also in much better agreement with this model. Our new measurement puts useful constraints for the existence of the conjectured dibaryon resonance at mass M∼ 2.38 GeV and with width Γ∼ 70 MeV.

Magnetic fields above 45 T offer great opportunities as a tool for materials research but can only be realized in the pulsed regime. We use pulsed magnetic fields up to 70 T for spectroscopic investigations of the dilute nitride GaAsN. This material is a promising candidate for optical applications because of the possibility for tuning its band gap by the nitrogen content. Our studies focus on the exploration of the band structure and in particular on the determination of the effective mass. Cyclotron-resonance spectroscopy indicates that the effective mass is not strongly affected by nitrogen in comparison to previous publications. Our magneto-photoluminescence investigations reveal the formation of localized and delocalized states as a result of the nitrogen incorporation. Delocalized states undergo transitions to localized ones in very high magnetic fields. This result is in good agreement with a pressure dependent study [1].

[1] J. Endicott, A. Patanè, D. Maude, L. Eaves, M. Hopkinson, and G. Hill, Phys. Rev. B 72, 041306(R) (2005)

I will start describing the Dresden free-electron laser FELBE as an intense, tunable, pulsed and narrowband source of infrared and THz radiation and the unique opportunities it offers for the spectroscopy of low-energy excitations in solids. In particular, the FEL can be used for nonlinear optical experiments, for time-resolved pump-probe studies, and also for near-field microscopy. I will present some recent results and will conclude with an outlook on further developments, including the superradiant THz radiation source TELBE.

Topological spin textures, such as vortices or skyrmions, are attracting significant attention because of their intriguing fundamental properties as well as their promising applicability in memory devices or spin torque oscillators. A particular topological texture that was theoretically predicted is the two-dimensional hedgehog state, also known as ’spin meron’. It had been unclear, however, whether this kind of highly divergent magnetization structure may occur in real systems. Only recently, evidence for the existence of meron-like pair states was reported for the case of trilayer elements consisting of two ferromagnetic layers and a non-ferromagnetic interlayer [1]. On this background, a direct proof for the existence of meron-like states in trilayer elements via direct magnetic imaging will be presented. It will also be shown that in the presence of biquadratic interlayer exchange coupling, such meron-like pair states may even represent the magnetic ground state of the system. Interestingly, the highly divergent magnetization distribution induces an additional, three-dimensional torus vortex that in-turn causes a symmetry break for the possible topological pair configurations [2]. In addition the dynamic properties of vertically coupled topological spin textures will be addressed, where the focus will be set on spin wave emission processes in such systems.
References: [1] C. Phatak et al., Phys. Rev. Lett. 108, 067205 (2012). [2] S. Wintz et al., Phys. Rev. Lett. 110, 177201 (2013).

The clear understanding of exchange interactions between magnetic ions in substituted BiFeO3 is the prerequisite for the comprehensive studies on magnetic properties. BiFe0.5Mn0.5O3 films and BiFeO3/BiMnO3 superlattices have been fabricated by pulsed laser deposition on (001) SrTiO3 substrates. Using piezoresponse force microscopy (PFM), the ferroelectricity at room temperature has been inferred from the observation of PFM hysteresis loops and electrical writing of ferroelectric domains for both samples. Spin glass behavior has been observed in both samples by temperature dependent magnetization curves and decay of thermo-remnant magnetization with time. The magnetic ordering has been studied by X-ray magnetic circular dichroism measurements, and Fe-O-Mn interaction has been confirmed to be antiferromagnetic (AF). The observed spin glass in BiFe0.5Mn0.5O3 films has been attributed to cluster spin glass due to Mn-rich ferromagnetic (FM) clusters in AF matrix, while spin glass in BiFeO3/BiMnO3 superlattices is due to competition between AF Fe-O-Fe, AF Fe-O-Mn and FM Mn-O-Mn interactions in the well ordered square lattice with two Fe ions in BiFeO3 layer and two Mn ions in BiMnO3 layer at interfaces.

Particle therapy is a highly conformal radiotherapy technique which reduces the dose deposited to the surrounding normal tissues. In order to fully exploit its advantages, treatment monitoring is necessary to minimize uncertainties related to the dose delivery. Up to now, the only clinically feasible technique for the monitoring of therapeutic irradiation with particle beams is Positron Emission Tomography (PET).
In this work we have compared a Resistive Plate Chamber (RPC)-based PET scanner with a scintillation-crystal-based PET scanner for this application. In general, the main advantages of the RPC-PET system are its excellent timing resolution, low cost, and the possibility of building large area systems. We simulated a partial-ring scanner based on an RPC prototype under construction within the Fondazione per Adroterapia Oncologica (TERA). For comparison with the crystal-based PET scanner we have chosen the geometry of a commercially available PET scanner, the Philips Gemini TF.
The coincidence time resolution used in the simulations takes into account the current achievable values as well as expected improvements of both technologies. Several scenarios (including patient data) have been simulated to evaluate the performance of different scanners. Initial results have shown that the low sensitivity of the RPC hampers its application to hadron-beam monitoring, which has an intrinsically low positron yield compared to diagnostic PET. In addition, for in-beam PET there is a further data loss due to the partial ring configuration. In order to improve the performance of the RPC-based scanner, an improved version of the RPC detector (modifying the thickness of the gas and glass layers), providing a larger sensitivity, has been simulated and compared with an axially extended version of the crystalbased device. The improved version of the RPC shows better performance than the prototype, but the extended version of the crystal-based PET outperforms all other options.

The talk summarises PhD research activities and results with respect to (bio)leaching of copper from copper shale.

Safety analysis of a cement-based repository for low- and intermediate level nuclear waste (L/ILW) has shown that 79Se is an important redox-sensitive, dose-determining radio-nuclide due to its long half-life and weak retardation by common near- and far field minerals. In the sorption data bases currently used for safety analysis it is considered that 79Se is predominantly present as SeO32- in the cementitious near field because oxidizing conditions prevail during waste conditioning. With time, however, reducing conditions will establish in the near field caused by oxygen consumption in the course of metal corrosion. In these conditions Se(-II) is expected to be the dominant redox state of Se. Hence, investigations into the interaction of Se(IV) and Se(-II) with cementitious materials and the reduction of Se(IV) to Se(-II) enable us to assess the long-term fate of Se in conditions relevant to a cement-based repository.
Sorption studies with Se on cementitious materials indicate that Se(IV) and Se(-II) uptake by hydrated calcium aluminates (AFm) and calcium silicate hydrates (C-S-H) phases, the principal host phases for radionuclides in cement paste, is significant and comparable to the uptake by cement paste. The uptake mechanisms of the Se species, however, are only poorly understood. EXAFS studies on Se(IV)-loaded cement phase and wet chemistry experiments suggest that Se(IV) could be taken up into the structure of the cement phases. In the case of AFm phases, for example, anions bound in the interlayer can be replaced, at least partially, by Se(IV) and Se(-II). This explains why AFm phases are more effective in removing Se(IV) and Se(-II) from solution than C-S-H phases.
Investigations into redox transformation are ongoing and the first results already suggest that the uptake mechanism of the Se species plays an important role in the reduction of Se(IV) to Se(-II) in cementitious materials.

Polymetallic Cu–Ag ores of the Central European Kupferschiefer deposits are one of the most important sources of copper in Europe. Because the ores are typically complex and often exceptionally fine-grained the development of efficient alternatives to conventional beneficiation strategies are an important target of current research. Biomining – the use of biological components for metal extraction – may offer solutions that are both efficient and environmentally benign. As conventional bioleaching with acidophilic microorganisms is impeded by the high carbonate content of the Kupferschiefer ores, heterotrophic microorganisms and glutamic acid are investigated as a possible alternative in the present study. The focus of this investigation is solely on the recovery of copper from the Kupferschiefer sensu strictu. Bioleaching experiments were carried out using such material from the Polkowice Mine in Poland. This material is marked by high grade (3.8 wt.% Cu), complex ore mineralogy (chalcocite, bornite, chalcopyrite and covellite in significant quantity) and a gangue mineralogy that is rich in carbonate, organic carbon and clay minerals that together form a very fine-grained matrix. (Bio)leaching experiments yield best results when glutamic acid alone is used – reaching copper recoveries up to 44%. Recoveries are consistently lower in experiments in which glutamic acid and microbiological metabolites are both present. The leaching of chalcocite renders the greatest contribution to the copper recovered to the leach solution in all experiments. It can be concluded that glutamic acid solubilises copper efficiently from Kupferschiefer, mainly from chalcocite.

Der Vortrag stellt das Helmholtz-Zentrum Dresden-Rossendorf sowie das Helmholtz-Institut Freiberg für Ressourcentechnologie vor und liefert allgemeine Informationen zu biotechnologischen Prozessen in der Kupfergewinnung sowie Einlick in Arbeiten der Arbeitsgruppe Biotechnologie.

Vancomycin is an important glycopeptide antibiotic which is used to treat serious infections caused by Gram positive bacteria. However, during the last years a tremendous rise in vancomycin resistances, especially among enterococci, was reported, making fast diagnostic methods inevitable.
In this contribution, we apply Raman spectroscopy to systematically characterize vancomycin-enterococci interactions over a time span of 90 minutes using a sensitive E. faecalis strain and two different vancomycin concentrations above the minimal inhibitory concentration (MIC). Successful action of the drug on the pathogen could be observed already after 30 minutes of interaction time. Characteristic spectral changes are visualized with the help of multivariate statistical analysis (linear discriminant analysis and partial least squares regressions). Those changes were employed to train a statistical model to predict vancomycin treatment based on the Raman spectra. The robustness of the model was tested using data recorded by an independent operator. Classification accuracies of >90% were obtained for vancomycin concentrations in the lower range of a typical trough serum concentration recommended for most patients during appropriate vancomycin therapy.
Characterization of drug-pathogen interactions by means of label-free spectroscopic methods, such as Raman spectroscopy, can provide the knowledge base for innovative and fast susceptibility assays which could speed up microbiological analysis as well as could find applications in novel antibiotic screenings assays.