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24033 Publications
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Kelling, J.
  • Invited lecture (Conferences)
    GPU Day 2015 - The Future of Many-Core Computing in Science, 20.05.2015, Budapest, Hungary
Registration No. 21995

Blue shift in absorption edge and widening of band gap of ZnO by Al doping and Al–N co-doping
You, Q.; Cai, H.; Hu, Z.; Liang, P.; Prucnal, S.; Zhou, S.; Sun, J.; Xu, N.; Wu, J.
Abstract: Al doped ZnO (ZnO:Al) and Al–N co-doped ZnO (ZnO:Al–N) films were synthesized based on plasma assisted reactive deposition of ZnO matrix and in-situ doping of Al or co-doping of Al and N. Similar with undoped ZnO, the synthesized ZnO:Al and ZnO:Al–N films are hexagonal wurtzite in structure and exhibit high optical transparency in a wide spectral region. Al doping and Al–N co-doping in ZnO result in a significant variation of the optical properties in the ultraviolet (UV) region and an UV extension of the transparent range. Compared with undoped ZnO, the doped films show blue-shifted absorption edge of 320 nm and widened band gap of 3.69 eV after annealing in H2/N2 mixed gas because of the incorporation of dopants and the improvement in the crystal structure. The ZnO:Al film exhibits declined transparency in the near infrared (IR) region, while the ZnO film co-doped with Al and N preserves high transparency from near UV to medium IR in addition to the UV extension of the transparent range. The annealed ZnO:Al and ZnO:Al–N films show better electrical properties than those of the undoped ZnO film and the as-deposited doped ZnO films.
Keywords: Absorption edge; Band gap; Al doped ZnO; Al–N co-doped ZnO; In-situ doping Registration No. 21991

Mobility Investigations on Strained 30-nm High-k Metal Gate MOSFETs by Geometrical Magnetoresistance Effect
Beister, J.; Wachowiak, A.; Boschke, R.; Herrmann, T.; Uhlarz, M.; Mikolajick, T.
Abstract: In this paper, we present mobility investigations of strained nMOS and pMOS short-channel transistors with dimensions down to 30-nm gate length. Using the geometrical magnetoresistance (MR) effect, carrier mobility of electrons and holes in the inversion channel of a recent state-of-the-art CMOS technology is presented from linear to saturation operation conditions. The MR effect allows for a more direct access to the carrier mobility compared with the conventional current/voltage and capacitance/voltage mobility derivation methods, in which series resistance, inversion charge density, and effective channel length are necessary to extract the mobility values of the short-channel devices. In another way, the MR effect can help to disentangle the performance gain of the strained state-of-the art devices to changes in channel mobility or device connection, e.g., series resistance effects. Registration No. 21987

X-ray observations showing the effect of fluid flow on dendritic solidification in Ga-In alloys
Shevchenko, N.; Roshchupkina, O.; Eckert, S.
Abstract: The directional solidification of Ga–25wt%In alloys within a Hele-Shaw cell has been studied by X-ray radioscopy. The investigations have focused on the influence of melt convection on the dendritic growth. Natural convection occurs during a bottom up solidification because a lighter solute is rejected during crystallization. Forced convection has been produced by a specific electromagnetic pump. The direction of forced melt flow is almost horizontal at the solidification front. Melt flow induces various effects on grain morphology caused primarily by convective transport of solute, such as facilitation of the growth of primary trunks or lateral branches, dendrite remelting, fragmentation or freckle formation depending on the dendrite orientation, the flow direction and intensity. Forced flow eliminates solutal plumes and damps local fluctuations of solute. A preferential growth of the secondary arms occurs at the upstream side of the dendrites, whereas high solute concentration at the downstream side inhibits the formation of secondary branches.
Keywords: Fluid flow, solidification, convection, X-ray radiography, in situ observation
  • Invited lecture (Conferences)
    Advances in the Science and Engineering of Casting Solidification: An MPMD Symposium Honoring Doru Michael Stefanescu; 2015 TMS Annual Meeting & Exhibition, 15.-19.03.2015, Orlando, Florida, USA
  • Contribution to proceedings
    Advances in the Science and Engineering of Casting Solidification: An MPMD Symposium Honoring Doru Michael Stefanescu; 2015 TMS Annual Meeting & Exhibition, 15.-19.03.2015, Orlando, Florida, USA
Registration No. 21980

Modular Ultrasound Array Doppler Velocimeter with FPGA-based Signal Processing for Real-time Flow Mapping in Liquid Metal
Nauber, R.; Thieme, N.; Beyer, H.; Büttner, L.; Räbiger, D.; Eckert, S.; Czarske, J.
Abstract: Investigating the complex interaction of conductive fluids and magnetic fields is relevant for a variety of applications from basic research in magnetohydrodynamics (MHD) to modeling industrial processes involving metal melts, such as the crystal growth process in the photovoltaic industry. This enables targeted optimizations of the melt flow and allows to significantly increase the yield and energy effciency of industrial processes. However, experimental studies in this field are often limited by the performance of flow instrumentation for opaque liquids. We present an ultrasound array Doppler velocimeter (UADV) for flow mapping in opaque liquids at room temperature. It is modular and flexible regarding its measurement configuration, for instance it allows capturing two velocity components in two planes (2d - 2c). It uses up to 9 linear arrays with a total element count of 225, driven in a parallelized time division multiplex (TDM) scheme. A FPGA-based signal pre-processing allows to handle the massive data bandwidth of typ. 1.2 GB/s and enables a continuous and near-realtime operation of the measurement system. The capabilities of the UADV system are demonstrated in a basic MHD research experiment with a metal melt (GaInSn) in a cubic container of (67 mm)³. The flow induced by a rotating magnetic field is captured with a temporal resolution of 250 ms for the horizontal and vertical central cross-section of the cube.
Keywords: Flow-Mapping, Ultrasound Doppler Velocimetry, Liquid Metals, Magnetohydrodynamics, Flow Control, FPGA
  • Lecture (Conference)
    International Congress on Ultrasonic, 10.-14.05.2015, Metz, Frankreich
Registration No. 21979

Realizing Optical Free-Electron Lasers with Traveling-Wave Thomson-Scattering
Steiniger, K.; Bussmann, M.; Debus, A.; Irman, A.; Jochmann, A.; Pausch, R.; Röser, F.; Schramm, U.; Sauerbrey, R.
Abstract: Optical free-electron lasers (OFELs) from the EUV to X-ray range can be realized in Traveling-Wave Thomson-Scattering (TWTS)[1,2] by utilizing pulse-front tilted high-power laser pulses as optical undulators.
The interaction distances required to induce microbunching to the electron beam for coherent radiation emission are realized in TWTS with a combination of side-scattering and a tilt of the laser pulse-front, as depicted in fig. 1. In the side-scattering geometry the electron beam and laser pulse directions of motion enclose the interaction angle. The tilt of the laser pulse-front by half of the interaction angle then ensures continuous overlap of electrons and laser while both are propagating in different directions. In this way, the interaction distances realized in TWTS are only limited by the transverse size of the laser and thus by the available laser power and size of available optics.
Our fully analytic theory of TWTS OFELs provides scaling laws for the electron and laser pulse quality requirements for OFEL operation. We show that TWTS OFELs can be realized with state-of-the-art technology in electron accelerators and laser systems if the presented scheme for dispersion control is applied. Thereby the variability of TWTS with respect to the interaction angle is used to control the electron and laser beam quality requirements. Especially the sub-μm transv. emittance beams from laser wakefield accelerators with energy spreads in the percent level can be used for the realization of all-optical FELs with acceleration and interaction distances in the centimeter range. An outlook on 3D simulations of TWTS OFELs using the particle in cell code PIConGPU is given.

Keywords: Thomson-scattering, X-ray, FEL, PIConGPU
  • Invited lecture (Conferences)
    Laser Plasma Acceleration Workshop 2015, 11.-15.05.2015, Guadeloupe, France
Registration No. 21978

Realizing all optical free-electron lasers with Traveling-Wave Thomson-Scattering
Steiniger, K.; Bussmann, M.; Debus, A.; Irman, A.; Jochmann, A.; Pausch, R.; Roeser, F.; Schramm, U.
Abstract: Optical free-electron lasers (OFELs) from the ultra violet to x-ray range can be realized with Traveling-Wave Thomson-Scattering (TWTS). This becomes possible in TWTS by increasing the photon scattering efficiency of standard Thomson scattering geometries more than one order of magnitude by changing the interaction geometry. In TWTS a side-scattering geometry is used where the laser and electron propagation directions enclose the interaction angle $\phi$. Together with a tilt of the laser pulse front the interaction distance is increased in TWTS beyond the limits of head-on Thomson scattering. TWTS implements dispersion control of the laser pulse to compensate for variations of the optical undulator period originating from the pulse-front tilt. Altogether, the combination of side-scattering, pulse-front tilt and dispersion control in TWTS allows for meter-scale interaction distances in which the electron beam becomes microbunched and OFEL operation is achieved. These TWTS OFELs provide transverse coherence as well as brilliances an order of magnitude enhanced over standard head-on Thomson scattering geometries.
We present the scaling laws of TWTS OFELs derived from a fully analytic theory of the electron laser interaction in TWTS scattering geometries. TWTS OFELs can be realized in an all-optical setup with a meter-scale footprint using laser wakefield accelerated electrons featuring both ultralow transverse emittances and large energy spreads.

Keywords: Traveling-Wave, Thomson scattering, X-ray, FEL
  • Poster
    Novel Light Sources from Laser-Plasma Interactions, 20.-24.04.2015, Dresden, Deutschland
Registration No. 21977

Realizable Optical Free-Electron Lasers with Traveling-Wave Thomson-Scattering
Steiniger, K.; Bussmann, M.; Debus, A.; Irman, A.; Jochmann, A.; Pausch, R.; Röser, F.; Schramm, U.; Sauerbrey, R.
Abstract: In Traveling-Wave Thomson-Scattering (TWTS) a high-power laser pulse is scattered off a relativistic electron pulse to realize optical free-electron lasers (OFELs) with a wavelength range from ultraviolet to Angstrom. TWTS employs a side-scattering geometry where laser and electron beam propagation direction enclose an interaction angle to become independent of the Rayleigh length limit for the maximum interaction distance inherent to standard head-on Thomson scattering geometries. For optimum spatial overlap between electrons and laser pulse in TWTS geometries the laser pulse features a pulse-front tilt. In this way, the electrons interact with all parts of the laser pulse and the brilliance of a TWTS light source become by orders of magnitude larger than in standard head-on geometries where spatial overlap between electrons and laser pulse is lost due to defocusing of the laser pulse. OFELs can be operated with TWTS using multi-hundred to petawatt class laser systems with beam diameters in the centimeter range since the interaction distance in TWTS can be controlled with the laser beam diameter in the interaction plane.
We show that interaction distances achieved in TWTS are long enough for microbunching of the electron beam and coherent amplification of the radiation from our 1.5D FEL theory for the interaction of electrons with laser fields in side-scattering geometries.
We give the scaling laws for the design of TWTS OFELs derived from this 1.5D theory and present possible experimental setups for TWTS OFELs using electrons from conventional and laser wakefield accelerators. We put emphasize on how the ultra-low emittance of a laser wakefield accelerator can be exploited to compensate for the one percent level energy spread and how laser pulse dispersion introduced with the pulse-front tilt in TWTS setups can be compensated with an additional pair of gratings in the laser pulse path before the interaction.

Keywords: Traveling-Wave, Thomson scattering, X-ray, FEL
  • Invited lecture (Conferences)
    SPIE Optics + Optoelectronics 2015, 13.-16.04.2015, Prague, Czech Republic
Registration No. 21976

Experimental design of optical free-electron lasers in the Traveling-Wave Thomson-Scattering geometry
Steiniger, K.; Bussmann, M.; Debus, A.; Irman, A.; Jochmann, A.; Pausch, R.; Röser, F.; Schramm, U.; Sauerbrey, R.
Abstract: Traveling-Wave Thomson-Scattering (TWTS) realizes optical free-electron lasers (OFEL) from the extreme ultraviolet to the X-ray range with existing electron accelerators and high-power laser systems. In TWTS ultrashort laser pulses and relativistic electron bunches are utilized in a side-scattering geometry where laser pulse and electron bunch direction of motion enclose an interaction angle. The laser electric field thereby is the undulator field in which the electrons oscillate and emit radiation during the interaction. When the electrons traverse the laser beam cross-section, TWTS provides continuous overlap of electron bunch and laser pulse by employing a laser pulse-front tilt which compensates the spatial separation of electrons and laser at the beginning and end of the interaction originating from their different propagation directions. The combination of laser pulse-front tilt and side-scattering in TWTS enables interaction lengths long enough to induce microbunching of the electron beam leading to coherent amplification of the emitted radiation and the realization of TWTS OFELs.
We present the scaling laws for the electron beam and laser pulse requirements to operate TWTS OFELs and show with example scenarios that TWTS OFELs can be realized with existing radio-frequency accelerated electrons such as ELBE at HZDR as well as laser-wakefield accelerated electrons. We detail the necessary equipment in a TWTS OFEL experiment and discuss how current experimental limitations affect the design of TWTS OFEL setups.

Keywords: Traveling-wave, Thomson scattering, X-ray, FEL
  • Lecture (Conference)
    DPG Frühjahrstagung Wuppertal 2015, 09.-13.03.2015, Wuppertal, Deutschland
Registration No. 21975

From Optical Undulators to Optical FELs with Traveling-Wave Thomson-Scattering
Steiniger, K.; Bussmann, M.; Debus, A.; Irman, A.; Jochmann, A.; Pausch, R.; Röser, F.; Schramm, U.; Sauerbrey, R.
Abstract: No abstract needed
Keywords: Traveling-Wave, Thomson scattering, X-ray, FEL
  • Invited lecture (Conferences)
    Materie und Technologie Kick-Off Meeting, 24.-26.02.2015, Hamburg, Deutschland
Registration No. 21974

Magnetization and X-ray absorption spectroscopy of Mn implanted Ge after flashlamp annealing
Zhou, S.; Wang, Y.; Prucnal, S.; Jiang, Z.; Zhang, W.; Wu, C.; Weschke, E.; Skorupa, W.; Helm, M.
Abstract: Ge-based diluted magnetic semiconductors have drawn extensive attention over the past decades due to their potential to be applied in spintronic devices and to be integrated with the mainstream Si microelectronics as well. The hole-mediated effect in diluted magnetic semiconductors provides the possibility to realize the control of magnetic properties by the electrical control of free carriers. In this contribution, we will present the magnetic properties and X-ray absorption spectroscopy of Mn implanted Ge annealed by flashlamp.
Keywords: Magnetic thin films and nanostructures
  • Lecture (Conference)
    IEEE International Conference on Magnetics 2015, 11.-15.05.2015, Beijing, China
Registration No. 21972

lll-V nanocrystal formation in ion-implanted Ge and Si via liquid phase epitaxy during short-time flash lamp annealing
Wutzler, R.; Rebohle, L.; Prucnal, S.; Böttger, R.; Hübner, R.; Facsko, S.; Helm, M.; Skorupa, W.
Abstract: The integration of III-V compound semiconductors into existing semiconductor technology is a milestone in future development of micro- and opto-electronics. III-V compound semiconductor nanocrystals (NCs) were fabricated in Ge and Si substrates by high-fluence ion implantation and short-time flash lamp annealing (FLA). The III-V NC formation takes place after amorphization due to implantation, followed by recrystallization via millisecond liquid phase epitaxy. Using this approach, GaAs and InAs NCs were fabricated. Whereas this formation process was recently investigated for Si, the case of Ge has not been reported yet but shows remarkable differences. In order to get III-V/Ge and III-V/Si heterojunctions in the form of free-standing III-V NCs on Ge and Si nanocolumns an additional selective etching of Ge and Si was performed using H2O2 and KOH solution, respectively.
Raman spectroscopy measurements confirmed the formation of III-V NCs within the particular, recrystallized matrices. The microstructural properties of the III-V NCs and the distribution of implanted species were investigated by scanning electron microscopy (SEM), cross-sectional transmission electron microscopy (TEM), and Auger electron spectroscopy (AES). SEM and TEM images show distinct, crystalline NCs. Conductive atomic force microscopy (c-AFM) was performed to investigate the electrical behavior of the fabricated heterojunctions.

Keywords: Ion implantation, Flash lamp annealing, III-V integration, Liquid phase epitaxy, Silicon, Germanium
  • Lecture (Conference)
    E-MRS Spring Meeting 2015, 11.-15.05.2015, Lille, France
Registration No. 21970

Sustainable solutions for restoration & conservation of pipe organs by using Plasma Ion based surface engineering vs. EMA copolymer surface treatment techniques.
Pelic, B.; Skorupa, W.
Abstract: Pipe organs with their unique sound and beautiful housing are important objects of the cultural heritage. The instrument consists of a number of pipes (flute and reed), which are prone to heavy corrosion attack, resulting in a loss of voice. The atmospheric corrosion of reed (CuZn alloys) and flute pipes (PbSn alloys) is strongly enhanced by traces of volatile organic compounds (VOCs) and the alloy’s instability.
Experiments have been undertaken to explore the improvement of an aqueous corrosion with the high acetic acid concentration (2–5 v/v%) of CuZn and PbSn alloys, by deposition of protective films (Al2O3 and Al) in nano scale using Pulsed laser deposition and Magnetron sputtering. Afterwards, the samples were implanted with N+ ions using plasma immersion ion implantation. Such coating is then able to withstand stresses and vibrations due to sound generation in organ pipes, and it produces a barrier to VOCs and water vapor. Furthermore, for the treatments of new or slightly corroded flute pipes, solution of 4% Paraloid B-72 in toluene has been applied as corrosion inhibitor. The complete and overall application of the PB-72 improved significantly the corrosion resistance of flute pipes. The laboratory corrosion tests were combined with field studies at affected church organs.

Keywords: Plasma immersion ion implantation (PI3), Pulsed laser deposition (PLD), Magnetron sputtering (MS), EMA copolymer (Paraloid B-72), corrosion of organ pipes
  • Lecture (Conference)
    E-MRS Spring Meeting 2015, 11.-15.05.2015, Lille, France
Registration No. 21968

SEM-based automated mineralogy: A fast and effective method for in-situ particle analysis
Osbahr, I.; Heinig, T.; Krause, J.
Abstract: Scanning electron microscope-based automated mineralogy such as the Mineral Liberation Analyser (MLA) allows several automated procedures based on backscattered electron (BSE) image acquisition and the collection of energy-dispersive X-ray spectra of particles with a specified contrast in the BSE image. The collected spectra are classified with a standard mineral spectra list which has been collected and specified for the samples. Samples should be solid with a polished surface. Different measurement modes are available on the MLA which can deliver extensive sets of information as modal mineralogy, particle- and grain size/shape distribution, liberation, mineral association or intergrowth. SEM-based automated mineralogy is a well-established tool in applied mineralogy and mineral- and metallurgic processing. The features of this method can also be applied in wide areas of research fields including material sciences, geology or environmental sciences.
Keywords: SEM, MLA, automated mineralogy
  • Lecture (Conference)
    ANAKON 2015, 23.-26.03.2015, Graz, Österreich
Registration No. 21963

Towards safe long-term operation of reactor pressure vessels
Rouden, J.; Hein, H.; May, J.; Planman, T.; Todeschini, P.; Brumovsky, M.; Ballesteros, A.; Gillemot, F.; Chaouadi, R.; Efsing, P.; Altstadt, E.
Abstract: This paper summarizes long-term operation conditions in European nuclear power plants. Recommendations for monitoring the radiation embrittlement of reactor pressure vessels during life extension periods (to 60 or 80 years) are presented. The guidelines were developed in the EURATOM FP7 project LONGLIFE. The work performed responds to the need for guidance to treat long term irradiation effects within the ageing management of NPPs, since the standard RPV surveillance programmes were designed for a time period of 40 years. In particular the following issues are addressed: re-use of tested surveillance speciems, transferability of material test reactor results to reactor operation conditions, extension of reactor pressure vessel surveillance programmes, withdrawal schemes for lon-term operation surveillance programmes.
Keywords: Reactor pressure vessel, irradiation embrittlement
  • atw - International Journal for Nuclear Power 60(2015)5, 287-293
Registration No. 21959

He stripping for AMS of 236U and other actinides using a 3 MV tandem accelerator
Winkler, S. R.; Steier, P.; Buchriegler, J.; Lachner, J.; Pitters, J.; Priller, A.; Golser, R.
Abstract: Interest in the long-lived radioisotope 236U (t1/2 = 23.4 million years) has significantly increased recently, due to the emergence of environmental and earth science applications. Presently, only a few (AMS) accelerator mass spectrometry instruments are suited for this measurement. One major limitation is the relatively low total detection efficiency (on the order of 10^4), which is partly caused by a low stripping yield of the positive ion charge state selected after the tandem accelerator. It has been shown that high yield can be achieved using helium as stripper gas for uranium ion energies below 0.35 MeV. Here we investigate the potential of He stripping of U at the 3-MV tandem accelerator VERA. Phenomenological charge state distributions for U and Th are presented for terminal voltages from 1.0 to 1.7 MV. These terminal voltages provide better background rejection than possible below 1 MeV, and are suited to the widely used 1–3 MV workhorses of many accelerator mass spectrometry laboratories. The methods can be applied to other actinides also.
Keywords: Uranium-236, Accelerator mass spectrometry, Actinides, Gas stripping, Time-of-Flight Registration No. 21958

Efficient Large Scale Simulation of Stochastic Lattice Models on GPUs
Kelling, J.; Ódor, G.; Heinig, K.-H.; Gemming, S.
Abstract: With growing importance of nano-patterned surfaces and nano-composite
materials in many applications from energy technologies to nano-electronics,
a thorough
understanding of the self-organized evolution of nano-structures needs to be
established. Modelling and simulations of such processes can help in this
endeavor and provide predictions for the turnout of manufacturing processes.

In this talk GPGPU-enabled implementations of two stochastic lattice models
will be discussed, shedding light on the complications which arise when
simulations of stochastic processes are to make efficient use of massively
parallel GPU architectures.
A single-GPU implementation of the (2+1)-dimensional
Roof-Top-model allows very precise large-scale studies of surface growth
processes in the Kardar-Parisi-Zhang universality class.[1] Furthermore a
multi-GPU enabled version of the 3d kinetic Metropolis lattice Monte-Carlo
method[2] provides the capability to study the evolution of nano-structures
both towards and out-of-equilibrium at spatio-temporal scales of experiments
using only small to medium-sized GPU clusters.

[1] J. Kelling, G. Ódor Extremely large-scale simulation of a
Kardar-Parisi-Zhang model using graphics cards, Physical Review E 84, 061150
[1] J. Kelling, G. Ódor, F. Nagy, H. Schulz, K. Heinig Comparison of
different parallel implementations of the 2+1-dimensional KPZ model and the
3-dimensional KMC model, The European Physical Journal - Special Topics 210,
175-187 (2012)
  • Lecture (others)
    Seminar Topical Problems, 06.05.2015, Chemnitz, Deutschland
  • Invited lecture (Conferences)
    GPU Day 2015 - The Future of Many-Core Computing in Science, 20.-21.05.2015, Budapest, Hunguary
Registration No. 21951

Lifetime-limited, subnanosecond terahertz germanium photoconductive detectors
Deßmann, N.; Pavlov, S. G.; Pohl, A.; Abrosimov, N. V.; Winnerl, S.; Mittendorff, M.; Zhukavin, R. Kh.; Tsyplenkov, V. V.; Shengurov, D. V.; Shastin, V. N.; Hübers, H.-W.
Abstract: The recombination times of photo-excited free charge carriers in heavily doped and highly
compensated germanium are studied by a time-resolved pump-probe experiment at a frequency of
3THz. The dominant dopant in the germanium samples is either antimony (n-Ge:Ga:Sb) or
gallium (p-Ge:Sb:Ga) with compensating doping levels close to 100%. The recombination time of
the free charge carriers measured by our pump-probe technique varies between 30 and 300 ps. It
decreases with increasing pump pulse energy and increasing compensation due to high concentra-
tions of Coulomb recombination centers. The recombination times at low pump powers are up to
ten times shorter than those previously obtained for low-compensated n-Ge:Sb and p-Ge:Ga. The
photoconductive detector made from this material shows the response time is in the order of its
recombination time.

Keywords: photoconductive detector, THz detector, fast detector Registration No. 21948

Magnetic anisotropy and magnetic Phase transitions in RFe5Al7
Gorbunov, D. I.; Yasin, S.; Andreev, A. V.; Skourski, Y.; Mushnikov, N. V.; Rosenfeld, E. V.; Zherlitsyn, S.; Wosnitza, J.
Abstract: RFe5Al7 (R – Gd, Tb, Dy, Ho, Er and Tm) single crystals have been studied by measurements of magnetization, sound propagation (in static and pulsed magnetic fields up to 60 T) and specific heat. Fundamental magnetic properties have been determined and compared for all these materials. RFe5Al7 are highly anisotropic ferrimagnets. Spontaneous and field-induced magnetic phase transitions of anisotropic and exchange nature have been observed in RFe5Al7. Strong magnetoelastic interactions are manifested by pronounced acoustic anomalies at the phase transformations. The detected magnetization jumps provide important information on the R–Fe inter-sublattice exchange interactions. Registration No. 21942

Pulsed high-magnetic-field experiments: New insights into the magnetocaloric effect in Ni-Mn-In Heusler alloys
Salazar Mejia, C.; Ghorbani Zavareh, M.; Nayak, A. K.; Skourski, Y.; Wosnitza, J.; Felser, C.; Nicklas, M.
Abstract: The present pulsed high-magnetic-field study on Ni50Mn35In15 gives an extra insight into the thermodynamics of the martensitic transformation in Heusler shape-memory alloys. The transformation-entropy change, ΔS, was estimated from field-dependent magnetization experiments in pulsed high magnetic fields and by heat-capacity measurements in static fields. We found a decrease of ΔS with decreasing temperature. This behavior can be understood by considering the different signs of the lattice and magnetic contributions to the total entropy. Our results further imply that the magnetocaloric effect will decrease with decreasing temperature and, furthermore, the martensitic transition is not induced anymore by changing the temperature in high magnetic fields. Registration No. 21941

Upbend and M1 scissors mode in in neutron-rich nuclei - consequences for r-process (n,γ) reaction rates
Larsen, A. C.; Goriely, S.; Bernstein, L. A.; Bleuel, D. L.; Bracco, A.; Brown, B. A.; Camera, F.; Eriksen, T. K.; Frauendorf, S.; Giacoppo, F.; Guttormsen, M.; Görgen, A.; Harissopulos, S.; Leoni, S.; Liddick, S. N.; Naqvi, F.; Nyhus, H. T.; Rose, S. J.; Renstrøm, T.; Schwengner, R.; Siem, S.; Spyrou, A.; Tveten, G. M.; Voinov, A. V.; Wiedeking, M.
Abstract: An enhanced probability for low-energy -emission (upbend, E < 3 MeV) at high excitation energies has been observed for several light and medium-mass nuclei close to the valley of stability. Also the M1 scissors mode seen in deformed nuclei increases the γ-decay probability for low-energy γ-rays (E < 2­ - 3 MeV). These phenomena, if present in neutron-rich nuclei, have the potential to increase radiative neutron-capture rates relevant for the r-process. The experimental and theoretical status of the upbend is discussed, and preliminary calculations of (n,γ) reaction rates for neutron-rich, mid-mass nuclei including the scissors mode are shown.
Keywords: Electromagnetic strength functions, low-energy enhancement, scissors mode, neutron-capture rates, r-process.


Registration No. 21939

Environmental risks induced by elevated thorium contents in the complex rare earth elements deposit Strange Lake, Québec (Canada): Mineralogical investigations
Brombacher, L. C.; Kempe, U.; Möckel, R.; Heide, G.; Gutzmer, J.
Abstract: The Strange Lake pluton is situated on the northern border between Québec and Labrador in northeastern Canada. The ore-body, located within a complex peralkaline granite-hosted system of pegmatites and aplites, contains elevated concentrations of both LREE and the highly coveted HREE, as well as other HFSE (high field strength elements, such as Zr, Nb, Y, Ti, and Th). The REE mineralization, however, is extremely complex and the elements of interest are variably distributed between various “exotic” minerals from different mineral classes that may also contain considerable amounts of unwanted impurities such as thorium, uranium and beryllium. Naturally occurring radioactive materials (NORM) like Th may be concentrated during beneficiation, thus constituting a serious hazard to the workers and the environment. In order to limit transportation and storage of hazardous material during production, it is of the company’s interest to separate these deleterious constituents early in or at best in advance to the extraction process. This study focuses on the characterization of the mineral phases that primarily host thorium for early recognition. Combined chemical and structural analyses indicate that there is one particular mineral phase in which Th is present in highly elevated concentrations. This mineral is best described as a metamict Th-silicate occurring in isolated, rounded grains enclosed in quartz. Further studies are required to indicate if this mineral can be separated early during minerals processing from the ore without considerable loss of valuable REE.
Keywords: rare earth elements, peralkaline complex, exotic minerals, thorium mineralogy
  • Contribution to proceedings
    Problems of use of natural resources - International forum of young scientists, 22.-24.04.2015, St. Petersburg, Russland
    Environmental risks induced by elevated thorium contents in the complex rare earth elements deposit Strange Lake, Québec (Canada): Mineralogical investigations, 978-5-94511-723-8
Registration No. 21937

Improving external beam radiotherapy by combination with internal irradiation.
Dietrich, A.; Koi, L.; Zöphel, K.; Sihver, W.; Kotzerke, J.; Baumann, M.; Krause, M.
Abstract: The efficacy of external beam radiotherapy (EBRT) is dose dependent, but the dose that can be applied to solid tumour lesions is limited by the sensitivity of the surrounding tissue. The combination of EBRT with systemically applied radioimmunotherapy (RIT) is a promising approach to increase efficacy of radiotherapy. Toxicities of both treatment modalities of this combination of internal and external radiotherapy (CIERT) are not additive, as different organs at risk are in target. However, advantages of both single treatments are combined, for example, precise high dose delivery to the bulk tumour via standard EBRT, which can be increased by addition of RIT, and potential targeting of micrometastases by RIT. Eventually, theragnostic radionuclide pairs can be used to predict uptake of the radiotherapeutic drug prior to and during therapy and find individual patients who may benefit from this treatment. This review aims to highlight the outcome of pre-clinical studies on CIERT and resultant questions for translation into the clinic. Few clinical data are available until now and reasons as well as challenges for clinical implementation are discussed. Registration No. 21936

Co-doping GaMnP with Zinc and Carbon
Hentschel, H.; Khalid, M.; Yuan, Y.; Helm, M.; Zhou, S.
Abstract: Spintronics appears to be a new and exciting field of technology, but there is still a lag of suitable materials. In principle magnetic semiconductors (DMS) would be an excellent choice, but even their highest reached Curie temperature (Tc) in GaMnAs is still too low for practical usage. Ferromagnetism in DMS is suggested to be holes according to the Zener-Model. Therefore, it is expected to increase Tc by adding additional holes, e.g. co-doping. But there is a high risk to induce more defects, especially interstitial Mn atoms. Indeed, previous investigation revealed a lower Tc in carbon codoped GaMnAs [1]. Ion Implantation followed by laser annealing might overcome this problem. We choose ferromagnetic GaMnP since it shows insulating behavior [2]. Co-doping with shallow acceptors may lead to a more pronounced change in the conductivity of GaMnP. The samples were investigated with SQUID-VSM and Hall-Effect measurement. First results do not show an increase in Tc. Structural analysis is in progress to check if more defects appear upon carbon codoping.
[1] G. M. Schott, et al., Appl. Phys. Lett. 85, 4678 (2004).
[2] M. A. Scarpulla, et al., Phys. Rev. Lett., 95, 207204 (2005).

Keywords: DMS, Co-Doping, GaMnP
  • Lecture (Conference)
    79. Jahrestagung der DPG und DPG-Frühjahrstagung, 16.03.2015, Berlin, Deutschland
Registration No. 21934

Synthesis and Biodistribution Studies of 3H- and 64Cu-labeled Dendritic Polyglycerol and Dendritic Polyglycerol Sulfate
Pant, K.; Gröger, D.; Bergmann, R.; Pietzsch, J.; Steinbach, J.; Graham, B.; Spiccia, L.; Berthon, F.; Czarny, B.; Devel, L.; Dive, V.; Stephan, H.; Haag, R.
Abstract: Dendritic polyglycerol sulfate (dPGS) is a biocompatible, bioactive polymer which exhibits anti-inflammatory activity in vivo and thus represents a promising candidate for therapeutic and diagnostic applications. To investigate the in vivo pharmacokinetics in detail, dPGS with a molecular weight of ca. 10 kDa was radiolabeled with 3H and 64Cu, and evaluated by performing biodistribution studies and small animal positron emission tomography (PET). 3H-labeling was accomplished by an oxidation-reduction process with sodium periodate and [3H]-borohydride. 64Cu-labeling was achieved by conjugation of isothiocyanate- or maleimide-functionalized copper(II)-chelating ligands based on 1,4-bis(2-pyridinylmethyl)-1,4,7-triazacyclononane (DMPTACN) to an amino functionalized dPGS scaffold, followed by reaction with an aqueous solution containing 64CuCl2. Independent biodistribution by radioimaging and PET imaging studies with healthy mice and rats showed that the neutral dPG was quantitatively renally eliminated, whereas the polysulfated analogs accumulated mainly in the liver and spleen. Small amounts of the dPGS derivatives were slowly excreted via the kidneys. The degree of uptake by the reticuloendothelial system (RES) was similar for dPGS with 40% or 85% sulfation, and surface modification of the scaffold with the DMPTACN chelator did not appear to significantly affect the biodistribution profile. On the basis of our data, the applicability of bioactive dPGS as a therapeutic agent might be limited due to organ accumulation even after 3 weeks. The inert characteristics and clearance of the neutral polymer, however, underlines the potential of dPG as a multifunctional scaffold for various nanomedical applications. Registration No. 21929

Bibliotheksservices für Mitarbeiter des VKTA
Reschke, E.
Abstract: VKTA-MitarbietrInnen sind externe Bibliotheksbenutzer. Im Vortrag werden die für externe Benutzer verfügbaren Bibliotheks- und Informationsservices vorgestellt.
Keywords: Library, Information services, Research Portal, eJournals, eBooks, Data bases
  • Lecture (others)
    VKTA-Leitungskreissitzung, 28.04.2015, Dresden-Rossendorf, Deutschland


Registration No. 21928

photocathodes for high-brightness photoinjectors
Xiang, R.; Teichert, J.
Abstract: The development of the photo-injector has become a significant technology for the future light sources and the electron-ion collider. There are a lot of opportunities to improve the electron source quality, also for the photocathodes. Especially for the high average power gun producing up to mA level of average current, the searching for the better photocathodes is a principal technical challenge. The photocathodes used in the electron gun require four important aspects: high efficiency, long life time, small transverse emittance and prompt time response. The quantum efficiency (QE) needs to be made more reliable, and the cathode material must be more robust. Thus there is a strong motivation to push the cathode R&D: one hand is to modify the present cathodes; the other hand is to search new materials.
In this presentation, we focus on the photocathode research for high brightness gun, DC or RF/SRF guns. There are several types of cathodes, such as the metallic photocathodes, the semiconductor photocathodes, and the recent superconducting (SC) cathodes and the new plasma-enhanced cathodes. The “conventional” normal conducting (NC) metallic photocathodes, such as Cu or Mg, are most robust for RF guns, but their QEs are pitifully very low, mostly on the level of 10-5. The semiconductor photocathodes, alkali antimonides, III-V GaAs(Cs), Cs2Te, have the best QE up to 1~10% but critical working environment is required. Among them, Cs2Te is relative robust and can be used in most of RF/SRF guns. And Cs2KSb achieves the highest current record 65mA in Cornell DC gun. The SC photocathodes consisting of Nb and Pb have been well investigated but the drive laser requirement is more challenging.
  • Lecture (Conference)
    LA³NET: The Laser Applications at Accelerators Conference 2015, 25.-27.03.2015, Mallorca, Spain
Registration No. 21920

Status and running experience of the SRF gun at HZDR
Xiang, R.; Arnold, A.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.
Abstract: In order to achieve a high average current up to 1 mA with a low emittance of 1 mm
mrad at 77 pC, an improved SRF gun has been installed and commissioned at HZDR since 2014. This new gun replaces the first 3.5-cell SRF gun at the superconducting linear accelerator ELBE which had been in operation since 2007. The new gun has been tested first with a Cu photocathode. The RF performance of the niobium cavity has been evaluated, the transverse and longitudinal beam parameters for low charge bunches have been measured, and the first beam has been guided into the ELBE beamline. The photocathode transfer system is also installed for the first high current beam test in 2015. In this contribution the status of the gun and the results of this first measurement period will be presented in detail.
  • Lecture (Conference)
    DPG Frühjahrstagung 2015, 09.-13.03.2015, Wuppertal, Deutschland
Registration No. 21919

Investigations of the interactions of subsurface living microorganisms with uranium
Gerber, U.; Krawczyk-Bärsch, E.; Anrold, T.
Abstract: Actually the former uranium mine Königstein (Saxony, Germany) is in process of controlled flooding. Despite the high uranium concentrations of up to 14 mg/L and the low pH of 3,0 a high biodiversity was detected within this flooding water. Microorganisms are very important for bioremediation of uranium contaminated environments from activities such as uranium mining and extraction or fuel fabrication. Due to their ability to interact with radionuclides and heavy metals microorganisms could help to clean up the contaminated water in Königstein. With a culture dependent method it was possible to isolate different microorganisms from the flooding water. Tolerance tests displayed high resistances to uranium of these natural isolates. Furthermore uranium immobilization experiments show high rates of uranium binding to the cells. Some of the isolates are able to remove nearly 100% of the initial added uranium. TEM analysis showed two different interaction mechanisms, biosorption to the cell membrane and bioaccumulation within the cell.
Keywords: Uranium immobilization, Bioremediation, Königstein
  • Lecture (others)
    3. Workshop – TransAqua, 20.-21.04.2015, Bremen, Deutschland
Registration No. 21915

Investigations of the interactions of subsurface living microorganisms with uranium
Gerber, U.; Krawczyk-Bärsch, E.; Arnold, T.; Kothe, E.
Abstract: Actually the former uranium mine Königstein (Saxony, Germany) is in process of controlled flooding. Despite the high uranium concentrations of up to 14 mg/L and the low pH of 3,0 a high biodiversity was detected within this flooding water. Microorganisms are very important for bioremediation of uranium contaminated environments from activities such as uranium mining and extraction or fuel fabrication. Due to their ability to interact with radionuclides and heavy metals microorganisms could help to clean up the contaminated water in Königstein. With a culture dependent method it was possible to isolate different microorganisms from the flooding water. Tolerance tests displayed high resistances to uranium of these natural isolates. Furthermore uranium immobilization experiments show high rates of uranium binding to the cells. Some of the isolates are able to remove nearly 100% of the initial added uranium. TEM analysis showed two different interaction mechanisms, biosorption to the cell membrane and bioaccumulation within the cell.
Keywords: Uranium immobilization, Bioremediation, Königstein
  • Lecture (Conference)
    2. Projektstatusgespräch zu BMBF-geförderten Forschungs- und Entwicklungsvorhaben auf dem Gebiet der "Nuklearen Sicherheits- und Entsorgungsforschung sowie Strahlenforschung", 25.-26.03.2015, Dresden, Deutschland
Registration No. 21913

Structural and electrical properties of sulfur doped Si by ion implantation
Liu, F.; Prucnal, S.; Gao, K.; Khalid, M.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: Hydoping Si with chalcogens is one of the effective approaches to form an intermediate band (IB). This IB material is a candidate of infrared photodetectors and intermediate band solar cells. However, the chalcogens have relatively low solid solubility limit in Si. We prepared sulfur doped silicon to above the Mott insulator concentration by ion implantation followed by pulsed laser annealing. The degree of crystalline lattice recovery in implanted layers and the lattice location of sulfur in Si were analyzed by Rutherford backscattering spectrometry / Channeling. Our results show that S atoms are occupying substitutional lattice sites in Si. We also observe an insulator-to-metal transition in silicon hyperdoped with sulfur to concentrations well above the maximum solubility limit of about 3×1016 cm-3[1]. Analyzing temperature-dependent conductivity data, we find that a transition from insulating to metallic conduction occurs at a peak sulfur concentration of around 1×1021 cm-3.
Keywords: Hydoping, sulfur, insulator-to-metal transition, lattice location
  • Lecture (Conference)
    DPG 2015 Spring Meeting, 15.-20.03.2015, Berlin, Germany
Registration No. 21912

Low-energy magnetic radiation: Deviations from GOE
Frauendorf, S.; Schwengner, R.; Wimmer, K.
Abstract: A pronounced spike at low energy in the strength function for magnetic radiation (LEMAR) is found by means of Shell Model calculations, which explains the experimentally observed enhancement of the dipole strength. LEMAR originates from statistical low-energy M1-transitions between many excited complex states. Re-coupling of the proton and neutron high-j orbitals generates the strong magnetic radiation. LEMAR is closely related to Magnetic Rotation. LEMAR is predicted for nuclides participating in the r-process of element synthesis and is expected to change the reaction rates. An exponential decrease of the strength function and a power law for the size distribution of the B(M1) values are found, which strongly deviate from the ones of the GOE of random matrices, which is commonly used to represent complex compound states.
Keywords: Magnetic dipole radiation, nuclearstructure, nuclear shell model, Gaussian Orthogonal Ensemble Registration No. 21908

Use of AC magnetic fields for flow control in solidifying metallic alloys
Räbiger, D.; Vogt, T.; Gerbeth, G.; Eckert, S.
Abstract: AC magnetic fields unlock an enormous potential to realize a variety of flow structures in molten metals, which makes the electromagnetic stirring attractive for controlling the melt flow during solidification. We present an experimental study concerning the solidification of AlSi alloys exposed to a pulsed rotating magnetic field. Isothermal flow measurements were carried out in order to understand the flow structures resulting from the application of time-modulated magnetic fields. These investigations revealed transient flow regimes showing distinct inertial oscillations and coherent vortex structures. An intense melt flow with periodic reversals of the flow direction at the solidification front can be created by a suitable choice of the magnetic field parameters. Such resonant states of the flow pattern have been proven to provide beneficial conditions for solidification processes. Optimized flow conditions realized in a solidifying melt result in a significant grain refinement without provoking the formation of harmful segregation freckles.
  • Lecture (Conference)
    TMS 2016 145th ANNUAL MEETING & EXHIBITION, 15.-19.03.2015, Orlando, USA
Registration No. 21905

Melt flow and grain refinement in Al-Si alloys solidified under the influence of applied electric currents
Räbiger, D.; Zhang, Y.; Galindo, V.; Franke, S.; Eckert, S.
Abstract: The application of electric currents during solidification can cause grain refinement in metallic alloys. However, the knowledge about the mechanisms underlying the decrease in grain size remains fragmentary. This study considers the solidification of Al Si alloys under the influence of electric currents for the configuration of two parallel electrodes at the free surface. Solidification experiments were performed under the influence of both direct currents (DC) and rectangular electric current pulses (ECP). The interaction between the applied current and its own induced magnetic field causes a Lorentz force which produces an electro-vortex flow. Numerical simulations were conducted to calculate the Lorentz force, the Joule heating and the induced melt flow. The numerical predictions were confirmed by isothermal flow measurements in eutectic GaInSn. The results demonstrate that the grain refining effect observed in our experiments can be ascribed solely to the forced melt flow driven by the Lorentz force.
Keywords: Grain refinement, Al-Si alloys, External electric field
  • Lecture (Conference)
    TMS 2015 144th ANNUAL MEETING & EXHIBITION, 15.03.-19.04.2015, Orlando, USA
  • Contribution to proceedings
    TMS 2016 145th ANNUAL MEETING & EXHIBITION, 15.-19.03.2015, Orlando, USA
    DOI-Link: http://dx.doi.org/10.1002/9781119093466.ch5
Registration No. 21904

Optical ridge waveguides in Yb:YAG laser crystal produced by combination of swift carbon ion irradiation and femtosecond laser ablation
Cheng, Y.; Lv, J.; Akhmadaliev, Sh.; Hernández-Palmero, I.; Romero, C.; Vázquez De Aldana, J. R.; Zhou, S.; Chen, F.
Abstract: We report on the fabrication of optical ridge waveguides in ytterbium-doped yttrium aluminum garnet (Yb:YAG) single crystal by applying swift C5+ ion irradiation and the followed femtosecond laser ablation. The planar waveguide layer is first produced by C5+ ion irradiation and the laser ablation is used to microstructure the planar waveguide surface to construct ridge structures. The lowest propagation loss of the ridge waveguide has been determined to be ~2.1 dB/cm. From the confocal micro-fluorescence and micro-Raman spectra obtained from the waveguide regions, the intensities, positions and widths of the emission-line peaks had no obvious changes with respect to those from the bulks, which indicate that C5+ ion irradiation does not affect the bulk-related properties of the Yb:YAG crystal significantly in the waveguide regions. The results obtained in this work suggest potential applications of the Yb:YAG ridge waveguides as integrated laser sources.
Keywords: Optical ridge waveguides; Swift ion irradiation; Femtosecond laser ablation Registration No. 21900

Experimentelle Untersuchung zur Strömungsbeeinflussung mittels elektromagnetischer Bremsen beim kontinuierlichen Strangguss von Stahl
Timmel, K.
Abstract: Beim kontinuierlichen Stranggießen von Stahl werden elektromagnetische Felder zur Strömungsbeeinflussung eingesetzt. In dieser Arbeit wird die Wirkung eines statischen Magnetfeldes auf die Kokillenströmung in einem Modellexperiment untersucht. Das statische Magnetfeld strukturiert die Strömung um, kann lokal die Strömungsgeschwindigkeiten erhöhen und verändert die Ausbildung und Anzahl der für Brammenkokillen typischen großskaligen Wirbel. Es zeigt sich weiterhin, dass die elektrische Leitfähigkeit der Kokillenwände einen entscheidenden Einfluss auf die Wirkung einer elektromagnetischen Bremse hat. Unter isolierenden Wänden werden räumliche Oszillationen des Flüssigmetallstrahles initiiert und es bildet sich zwischen den beiden Kokillenhälften eine asymmetrische Strömung aus. Leitfähige Wände verhindern die Oszillationen und die Kokillenströmung ist symmetrisch. Eine eindeutige bremsende Wirkung der elektromagnetischen Bremse auf den Durchfluss konnte jedoch in beiden Fällen nicht festgestellt werden.
Keywords: Continuous Casting of steel, liquid metal model, electro-magnetic brake, Ultrasonic-Doppler-Velocimetry
  • Doctoral thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Prof. Dr.-Ing. Rüdiger Schwarze
    196 Seiten
  • Book (Authorship)
    Freiberg: Verlag der TU Bergakademie Freiberg, 2015
    240 Seiten
  • Book (Authorship)
    Dresden: Qucosa - Sächsischen Landesbibliothek - Staats- und Universitätsbibliothek Dresden, 2015
    196 Seiten


Registration No. 21899

Ferromagnetic and paramagnetic magnetization of implanted GaN:Ho,Tb,Sm,Tm films
Maryško, M.; Hejtmánek, J.; Laguta, V.; Sofer, Z.; Sedmidubský, D.; Šimek, P.; Veselý, M.; Mikulics, M.; Buchal, C.; Macková, A.; Malínský, P.; Wilhelm, R. A.
Abstract: The SQUID magnetic measurements were performed on the GaN films prepared by metal-organic vapour phase epitaxy and implanted by Tb3+, Tm3+, Sm3+, and Ho3+ ions. The sapphire substrate was checked by the electron paramagnetic resonance method which showed a content of Cr3+ and Fe3+ impurities. The samples 5 × 5 mm2 were positioned in the classical straws and within an estimated accuracy of 10−6 emu, no ferromagnetic moment was detected in the temperature region of 2–300 K. The paramagnetic magnetization was studied for parallel and perpendicular orientation. In the case of GaN:Tb sample, at T = 2 K, a pronounced anisotropy with the easy axis perpendicular to the film was observed which can be explained by the lowest quasi-doublet state of the non-Kramers Tb3+ ion. The Weiss temperature deduced from the susceptibility data using the Curie-Weiss (C-W) law was found to depend substantially on the magnetic field. Registration No. 21898

Speciation studies of uranyl(VI) using an advanced combination of theoretical and luminescence spectroscopic methods
Drobot, B.; Tsushima, S.; Steudtner, R.; Raff, J.; Geipel, G.; Brendler, V.
Abstract: Speciation constitutes the basis for actinide complexation studies. These systems can be very complex and challenging especially because of the polynuclear species. An advanced combination of theoretical and experimental methods is proposed here. Continuous wave (CW) and time-resolved laser-induced fluorescence spectroscopy (TRLFS) data of uranyl(VI) hydrolysis were analyzed using parallel factor analysis (PARAFAC). Distribution patterns of five major species were thereby derived under a fixed uranyl concentration (10-5 M) over a wide pH range from 2 to 11. UV (180 nm to 370 nm) excitation spectra were extracted for individual species. Time-dependent density functional theory (TD-DFT) calculations revealed ligand excitation (water, hydroxo, oxo) in this region and ligand-to-metal charge transfer (LMCT) responsible for luminescence. Thus excitation in the UV is extreme ligand sensitive and highly specific. Combining findings from PARAFAC and DFT the aquo complex (1:0) and four hydroxo complexes (1:1, 3:5, 3:7 and 1:3) were identified and characterized.
  • Lecture (Conference)
    Anakon 2015, 23.-26.03.2015, Graz, Östereich
Registration No. 21894

Spin-transfer effects in MgO-based tunnel junctions with an out-of-plane free layer and in-plane polarizer: static states and steady-state precession
Kowalska, Ewa; Sluka, V.; Fowley, C.; Kakay, A.; Aleksandrov, Y.; Lindner, J.; Fassbender, J.; Deac, A. M.
Abstract: 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.
Keywords: spin-torque oscillators, spin-transfer torque, magnetic tunnel junctions, tunnel magnetoresistance
  • Lecture (Conference)
    The IEEE International Magnetics Conference (INTERMAG) 2015, 11.-15.05.2015, Beijing, China
Registration No. 21887

Experimental investigation of interfacial structures within churn flow using a dual wire-mesh sensor
Parsi, M.; Vieira, R. E.; Torres, C. F.; Kesana, N. R.; Mclaury, B. S.; Shirazi, S. A.; Schleicher, E.; Hampel, U.
Abstract: 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.

Keywords: churn flow, huge wave, wire mesh sensor, multiphase flow, interfacial structures Registration No. 21886

Control of intra-excitonic scattering in semiconductor quantum wells by an external magnetic field
Schneider, H.; Bhattacharyya, J.; Zybell, S.; Eßer, F.; Helm, M.; Schneebeli, L.; Böttge, C. N.; Breddermann, B.; Kira, M.; Koch, S. W.
Abstract: 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)

Keywords: intra-exciton transitions, GaAs quantum well, terahertz excitation, free-electron laser
  • Lecture (Conference)
    SPIE Photonics West 2015, 07.-12.02.2015, San Francisco, USA
Registration No. 21885

Spectral history model in DYN3D: Verification against coupled Monte-Carlo thermal-hydraulic code BGCore
Bilodid, Y.; Kotlyar, D.; Margulis, M.; Fridman, E.; Shwageraus, E.
Abstract: 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.
Keywords: History effects; spectral history; coupled Monte Carlo; DYN3D; BGCore Registration No. 21882

Status Report of the ELBE SRF Gun II
Arnold, A.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.; Eremeev, Gr. V.; Kneisel, P.; Stirbet, M.; Turlington, L.
Abstract: 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.
Keywords: SRF gun, superconducting radio frequency electron injector, ELBE linear accelerator
  • Lecture (others)
    HOPE / SINEMP Projekttreffen im Rahmen BMBF Verbundforschungsinitiative, 11.03.2015, Wuppertal, Deutschland
Registration No. 21875

Enhanced photoelectrochemical activity of vertically aligned ZnO-coated TiO2 nanotubes
Cai, H.; Yang, Q.; Hu, Z.; Duan, Z.; You, Q.; Sun, J.; Xu, N.; Wu, J.
Abstract: 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.
Keywords: Titanium dioxide nanotubes; Zinc oxide coating; Photoluminescence; Photoelectrochemical properties.
  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft, 15.-20.03.2015, Berlin, Germany
Registration No. 21873

Quantitative analysis of PET image quality in PET/MR brain examinations
Schramm, G.; Oehme, L.; Maus, J.; Hofheinz, F.; Lougovski, A.; Petr, J.; Beuthien-Baumann, B.; Kotzerke, J.; van den Hoff, J.
Abstract: 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.
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.
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.
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.
[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
  • Abstract in refereed journal
    Nuklearmedizin 54(2015), A127
Registration No. 21870

Comparison of FDG-PET based tumor-to-blood standard uptake ratio and standard uptake value with patient outcome in NSCLC
Steffen, I. G.; Hofheinz, F.; Ego, K.; Furth, C.; van den Hoff, J.; Amthauer, H.; Apostolova, I.
Abstract: 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.
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 (SURmax) was calculated as ratio of tumor SUVmax to blood SUV. The association of SURmax and SUVmax 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).
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). SURmax was significantly correlated with SUVmax (Spearman's rho, 0.92; p<0.001). Cox regression model revealed a significant association of SURmax 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 SUVmax 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).
The maximum tumor-to-blood standard uptake ratio (SURmax) showed a stronger association with patient outcome in comparison to SUVmax. These encouraging results have to be confirmed in further investigations.
  • Abstract in refereed journal
    Nuklearmedizin 54(2015), A121-A122
Registration No. 21869

Synthese und enzymkinetische Charakterisierung von N6-Acryloyllysinpiperaziden als potentielle Radiotracer zur funktionellen Bildgebung der Transglutaminase 2 (TGase 2)
Wodtke, R.; Hauser, C.; Jäckel, E.; Wong, A.; Steinbach, J.; Pietzsch, J.; Pietsch, M.; Löser, R.
Abstract: 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.
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.
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.
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.
(1) Wityak et al. ACS Med. Chem. Lett. 2012, 3, 1024
  • Abstract in refereed journal
    Nuklearmedizin 54(2015), A105
Registration No. 21868

Radioaktive Markierung von NOTA mit Tc-99m -Tricarbonyl - eine Methode zur Markierung von Antikörpern
Naumann, A.; Schubert, M.; Jentschel, C.; Wunderlich, G.; Pietzsch, H.-J.; Kotzerke, J.
Abstract: 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.
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.
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.
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.
  • Abstract in refereed journal
    Nuklearmedizin 54(2015), A102
Registration No. 21867

Radiosynthesis of 18F-cabozantinib, a small molecule angiokinase inhibitor
Schwebe, M.; Steinbach, J.; Pietzsch, J.; Knieß, T.
Abstract: 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.
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.
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.
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.
  • Abstract in refereed journal
    Nuklearmedizin 54(2015), A100-A101
Registration No. 21866

Analyse der Kalibrierung eines TOF-Scanners mit pixelliertem Flächendetektor (Gemini TF 16 BigBore)
Nemer, U.; Maus, J.; Schramm, G.; Meyer, P.; Hennig, J.; Mix, M.
Abstract: 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.
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.
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).
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.
(1) "Phantom-based evaluation of quantification accuracy of combined PET/MRI", Langner et al., DGN Jahrestagung 2013 (P43).
  • Abstract in refereed journal
    Nuklearmedizin 54(2015), A86
Registration No. 21865

On the relation between blob and tube-of-response based approaches to system matrix calculation in PET
Lougovski, A.; Hofheinz, F.; Schramm, G.; Maus, J.; van den Hoff, J.
Abstract: 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.
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.
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.
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.
  • Abstract in refereed journal
    Nuklearmedizin 54(2015), A85
Registration No. 21864

Scan time-normalized tumor to blood standard uptake ratio (SUR) in pretherapeutic FDG PET is superior to SUV as a prognostic factor in patients with esophageal carcinoma
Hofheinz, F.; Bütof, R.; Zöphel, K.; Schütze, C.; Löck, S.; Stadelmann, T.; Schmollack, J.; Kotzerke, J.; Baumann, M.; van den Hoff, J.
Abstract: 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.
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 SUVmax, SURmax and clinically relevant parameters. Additionally, a multivariate Cox regression including clinical parameters, which were univariate significant, as confounding factors was performed.
Both, SUVmax and SURmax, 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 SURmax (HR=2.2, p=0.003) compared to SUVmax (HR=1.8, p=0.01). With respect to DM HR of SURmax was notably larger than HR of SUVmax (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.
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.
[1] van den Hoff et al, EJNMMI Res 2013, 3:77.[2] van den Hoff et al, EJNMMI Res 2014, 4:18.
  • Abstract in refereed journal
    Nuklearmedizin 54(2015), A83-A84
Registration No. 21863

Relationship between asphericity of FDG uptake in the primary tumor and histopathology in NSCLC
Apostolova, I.; Steffen, I. G.; Ego, K.; Kalinski, T.; Schultz, M.; Furth, C.; Genseke, P.; Buchert, R.; Hofheinz, F.; Amthauer, H.
Abstract: 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.
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 SUVmax 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.
Squamous cell carcinomas (SCC) exhibited significantly higher SUVmax 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 SUVmax (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 SUVmax (p=0.07). Grade 3 tumors had a tendency for higher ASP (p=0.07) but not SUVmax (p=0.29). Pathological T and N stage were associated with both SUVmax (Kruskal-Wallis, p=0.004/ p=0.02) and ASP (p<0.001/p=0.06). Only SUVmax was associated with M stage (p=0.02).
Tumor asphericity (ASP) appears to depict different features of tumor biology in NSCLC than SUVmax. This is in line with our previous finding that ASP provides independent information for prognosis in patients with NSCLC.
  • Abstract in refereed journal
    Nuklearmedizin 54(2015), A75
Registration No. 21862

Ga-68-DATATOC: Radiopharmakologie und Bildgebung
Bergmann, R.; Ullrich, M.; Waldron, B. P.; Seemann, J.; Ziegler, C. G.; Pietzsch, J.; Steinbach, J.; Rösch, F.
Abstract: 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.
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 (MPCmCherryt) in NMRI nu/nu Mäusen untersucht. In der Kleintier-PET wurde die Tumordarstellung von Ga-68-DATATOC und Ga-68-DOTATATE verglichen.
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.
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.).
[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.
  • Abstract in refereed journal
    Nuklearmedizin 54(2015), A33-A34
Registration No. 21861

Test-retest variability of quantitative MRI perfusion measurements with ASL underclinical conditions
Petr, J.; Schramm, G.; Platzek, I.; Hofheinz, F.; van den Hoff, J.
Abstract: 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.
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.
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%).
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.
(1) Alsop, et al. Magnetic Resonance in Medicine. 2014.
(2) Heijtel, et al. NeuroImage, 92:182-92(2014).
  • Abstract in refereed journal
    Nuklearmedizin 54(2015), A22
Registration No. 21860

The influence of the phosphor z position on the Fermi surface of SrCo2P2: Experiment and theory
Götze, K.; Klotz, J.; Bergmann, C.; Geibel, C.; Rosner, H.; Kraft, I.; Lorenz, V.; Wosnitza, J.
Abstract: 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.
  • Lecture (Conference)
    Frühjahrstagung der DPG 2015, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21857

Direct measurement of the magnetocaloric effect in Ni50Mn35In15 in pulsed magnetic fields
Ghorbani Zavareh, M.; Salazar Mejia, C.; Nayak, A. K.; Skourski, Y.; Wosnitza, J.; Felser, C.; Nicklas, M.
Abstract: 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.
  • Lecture (Conference)
    Frühjahrstagung der DPG 2015, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21856

Superconductivity and ferromagnetism in nanostructured Bi3Ni
Schönemann, R.; Herrmannsdörfer, T.; Kühne, H.; Zhang, Z.; Naumann, M.; Skrotzki, R.; Kaiser, M.; Heise, M.; Ruck, M.; Kummer, K.; Graf, D.; Wosnitza, J.
Abstract: es hat kein Abstract vorgelegen
  • Poster
    Frühjahrstagung der DPG 2015, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21855

de Haas-van Alphen oscillations in (La,Ce)TiGe3
Grasemann, J.; Uhlarz, M.; Kittler, W.; Fritsch, V.; Stockert, O.; Förster, T.; Wosnitza, J.; von Löhneysen, H.
Abstract: CeTiGe3 is one of the few Kondo-lattice compounds which order ferromagnetically (TC ≈ 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 Ce0.1La0.9TiGe3 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.
  • Poster
    Frühjahrstagung der DPG 2015, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21854

NMR of the Shastry-Sutherland lattice SrCu(BO3)2 in pulsed magnetic fields
Stern, R.; Kohlrautz, J.; Haase, J.; Kühne, H.; Green, E. L.; Wosnitza, J.
Abstract: 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.
  • Poster
    Frühjahrstagung der DPG 2015, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21853

Investigations on vertical gas-liquid downward pipe flows
Banowski, M.
Abstract: 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.
  • Contribution to proceedings
    46th Annual Meeting on Nuclear Technology - Preserving Competence in Nuclear Technology, 05.-07.05.2015, Berlin, Deutschland
Registration No. 21852

Dynamical Schwinger process in a bifrequent electric field of finite duration: survey on amplification
Otto, A.; Seipt, D.; Blaschke, D.; Smolyansky, S. A.; Kämpfer, B.
Abstract: 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. Registration No. 21851

Cross-over versus first-order phase transition in holographic gravity-single-dilaton models of QCD thermodynamics
Yaresko, R.; Knaute, J.; Kämpfer, B.
Abstract: 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). Registration No. 21850

Influence of thyroid hormones on brown adipose tissue activity and browning of white adipose tissues in mice
Krause, K.; Kranz, M.; Weiner, J.; Klöting, N.; Rijntjes, E.; Köhrle, J.; Zeisig, V.; Steinhoff, K.; Deuther-Conrad, W.; Fasshauer, M.; Stumvoll, M.; Sabri, O.; Blüher, M.; Hesse, V.; Brust, P.; Tönjes, A.
Abstract: 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.
  • Abstract in refereed journal
    Experimental and Clinical Endocrinology & Diabetes 2(2015)123
  • Poster
    58th Symposium of the German Society of Endocrinology, 18.-21.03.2015, Lübeck, Deutschland
Registration No. 21836

Feasibility and Importance of the alpha 7 Nicotinic Acetylcholine Receptor (alpha 7nAChR) as Target for PET Imaging
Deuther-Conrad, W.; Teodoro, R.; Scheunemann, M.; Rötering, S.; Patt, M.; Kranz, M.; Donat, C. K.-; Xiong, G.; Fischer, S.; Bucerius, J.; Peters, D.; Cumming, P.; Steinbach, J.; Sabri, O.; Brust, P.
Abstract: 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 (VT) of [18F]NS14490 were calculated. In anticipation of human studies, for [18F]DBT-10 preclinical dose assessment and toxicity studies were performed.
[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 SUVmax:0.54) and 11.5 min p.i. ([18F]DBT-10 SUVmax: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, BPND. NS6740 infusion significantly reduced mean k3’ of [18F]NS14490 by 46% and mean BPND of [18F]DBT-10 by 75%. Reduction of VT on brain blood vessels by NS6740 was clearly visible in parametric maps of [18F]NS14490. SUVmax 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.
[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.
  • Lecture (Conference)
    EANM 2014, 17.-22.10.2014, Göteborg, Sweden
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 41(2014), 209-210
Registration No. 21835

P1403-Kapazitätsdiode, Verfahren zum Herstellen einer Kapazitätsdiode, sowie Speicher und Detektor mit einer solchen Kapazitätsdiode
Schmidt, H.; Selvaraj, L.; Boguzs, A.; Bürger, D.; Prucnal, S.; Skorupa, I.
Abstract: 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.
  • Patent
    DE102014105639 - Erteilung 13.01.2015; Nachanmeldung: WO
Registration No. 21833

P1324-Verfahren und Einrichtung zur Kontrolle der Reichweite von Partikelstrahlung einer Bestrahlungseinrichtung zur Strahlentherapie
Enghardt, W.; Golnik, C.; Pausch, G.
Abstract: 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.
  • Patent
    DE102013218982.6 - Offenlegung - 26.03.2015; Nachanmeldung: WO
Registration No. 21832

SRF Photo Injector for Electron-Laser Interaction
Lu, P.
Abstract: simulation and first results
Keywords: 1 nC simulation
  • Lecture (Conference)
    LA3NET conference: Laser applications at accelerators, 25.-27.03.2015, Mallorca, Spain
Registration No. 21831

Beam Diagnostics of the SRF Photoinjector at HZDR, LA³NET Topical Workshop
Lu, P.
Abstract: Beam Diagnostics of the ELBE SRF Gun II
Keywords: energy spread, emittance, bunch length
  • Lecture (others)
    LA³NET Topical Workshop: Beam Diagnostics, 23.-24.03.2015, Mallorca, Spain
Registration No. 21830

Reduced pulmonary blood flow in regions of injury 2 hours after acid aspiration in rats
Richter, T.; Bergmann, R.; Musch, G.; Pietzsch, G.; Koch, T.
Abstract: 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).

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.

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).

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.

Keywords: Acute lung injury; Respiratory aspiration; Positron emission tomography; Pulmonary circulation; Pulmonary perfusion; Adult respiratory distress syndrome


Registration No. 21823

Sponge-like Si-SiO2 nanocomposite as photovoltaic absorber: Synthesis by solid vs. liquid state decomposition of SiOx
Schumann, E.; Heinig, K.-H.; Hübner, R.; Carcelen, V.; Krause, M.; Gemming, S.
Abstract: 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.
Keywords: sponge-like, nanostructure, nanocomposite, silicon, siliconoxide, photovoltaic
  • Poster
    79. DPG-Jahrestagung und DPG-Frühjahrstagung der Sektion Kondensierte Materie, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21820

Structural and electrical characterization of Ar+ irradiated TiO2 thin films
Blaschke, D.; Agnieszka, B.; Huebner, R.; Munnik, F.; Heller, R.; Scholz, A.; Nierobisch, F.; Rana, V.; Zahn, P.; Gemming, S.
Abstract: 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).

Keywords: TiO2, resistive switching, Ar irradiation
  • Poster
    79. DPG-Jahrestagung und DPG-Frühjahrstagung, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21818

Simultaneous measurement of AMR and observation of magnetic domains with dual Kerr microscopy
Osten, J.; Lenz, K.; Lindner, J.; Fassbender, J.
Abstract: 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.
Keywords: Kerr microscopy, AMR
  • Lecture (Conference)
    79. DPG-Jahrestagung und DPG-Frühjahrstagung, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21817

Partial Volume Correction of Cerebral Perfusion Estimates Obtained by Arterial Spin Labeling
Ambarki, K.; Petr, J.; Wåhlin, A.; Wirestam, R.; Zarrinkoob, L.; Malm, J.; Eklund, A.
Abstract: 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.
Keywords: MRI; cerebral perfusion; gray and white matter; arterial spin labeling and healthy
  • Contribution to proceedings
    16. NBC & 10. MTD 2014 joint conferences, 14.-16.10.2014, Gothenburg, Sweden
    16th Nordic-Baltic Conference on Biomedical Engineering, IFMBE Proceedings: Springer International Publishing, 978-3-319-12966-2, 17-19
    DOI-Link: http://dx.doi.org/10.1007/978-3-319-12967-9_5
  • Lecture (Conference)
    16th Nordic-Baltic Conference on Biomedical Engineering, 14.-16.10.2014, Gothenburg, Sweden
Registration No. 21814

Evidence of U(VI) sorption on Acidovorax facilis by TRLFS and EF-TEM/EELS
Krawczyk-Bärsch, E.; Gerber, U.; Steudtner, R.; Lünsdorf, H.; Arnold, T.
Abstract: 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.
Keywords: Acidovorax facilis, uranium, sorption, TRLFS, EF-TEM
  • Lecture (Conference)
    Goldschmidt Conference, 16.-21.03.2015, Prague, Czech
Registration No. 21813

Estimating the influence of magnetization transfer effects on cerebral blood flow quantification in pseudo-continuous arterial spin labeling
Petr, J.; Schramm, G.; Hofheinz, F.; Maus, J.; van den Hoff, J.
Abstract: 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
  • Contribution to proceedings
    Annual Meeting of the International Society for Magnetic Resonance in Medicine, ISMRM 2014, 10.-16.05.2014, Milano, Italy
    Proceedings of the International Society for Magnetic Resonance in Medicine, 2677
  • Lecture (Conference)
    Annual Meeting of the International Society for Magnetic Resonance in Medicine, ISMRM 2014, 10.-16.05.2014, Milano, Italy
Registration No. 21812

Linear Instability Analysis of 3D Magnetohydrodynamic Flow by Direct Numerical Simulation
Grants, I.; Gerbeth, G.
Abstract: 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).
  • Contribution to proceedings
    ERCOFTAC WORKSHOP Direct and Large-Eddy Simulation 9 (DLES 9), 03.-05.04.2013, Dresden, Deutschland
    ERCOFTAC Series Volume 20: Springer, 978-3-319-14447-4, 561-567
    DOI-Link: http://dx.doi.org/10.1007/978-3-319-14448-1_71
Registration No. 21811

Characterizing the Kelvin-Helmholtz instability in interstellar jets using radiation
Pausch, R.; Debus, A.; Huebl, A.; Steiniger, K.; Widera, R.; Bussmann, M.; Schramm, U.
Abstract: 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.

Keywords: PIConGPU, KHI, radiation
  • Lecture (Conference)
    79. DPG-Jahrestagung und DPG-Frühjahrstagung, 09.-13.03.2015, Wuppertal, Deutschland
Registration No. 21808

Evolution of Spin Wave Modes in Periodically Perturbed Thin Films
Langer, M.; Gallardo, R.; Banholzer, A.; Schneider, T.; Wagner, K.; Landeros, P.; Lenz, K.; Lindner, J.; Fassbender, J.
Abstract: 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.
  • Lecture (Conference)
    79. DPG-Jahrestagung und DPG-Frühjahrstagung, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21807

Radiation as synthetic spectral diagnostics in the particle- in-cell code PIConGPU
Pausch, R.; Debus, A.; Huebl, A.; Steiniger, K.; Widera, R.; Bussmann, M.; Schramm, U.
Abstract: 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).

Keywords: Radiation, Laser Plasma, PIConGPU, GPU, TNSA, KHI, HHG
  • Lecture (Conference)
    DPG-Frühjahrstagung, 09.-13.03.2015, Wuppertal, Deutschland
Registration No. 21806

Plasmonic Superlensing in Doped GaAs
Fehrenbacher, M.; Winnerl, S.; Schneider, H.; Doring, J.; Kehr, S.; Eng, L.; Huo, Y.; Schmidt, O.; Yao, K.; Liu, Y.; Helm, M.
Abstract: 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.
Keywords: Superlens, diffraction limit, surface plasmons, near-field microscopy, semiconductor Registration No. 21805

Determination of the Exchange Stiffness Constant in Ultrathin Magnetic Films by Ferromagnetic Resonance
Langer, M.; Wagner, K.; Sebastian, T.; Schultheiss, H.; Lenz, K.; Lindner, J.; Fassbender, J.
Abstract: 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.
  • Poster
    79. DPG-Jahrestagung und DPG-Frühjahrstagung, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21804

Pulsed magnetic field spectroscopy up to 70 T on the dilute nitride GaAsN
Eßer, F.; Schneider, H.; Winnerl, S.; Drachenko, O.; Patanè, A.; Helm, M.
Abstract: 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)

Keywords: GaAsN, dilute nitride, effective mass, cyclotron-resonance, pulsed magnetic field
  • Lecture (Conference)
    79. DPG-Jahrestagung und DPG-Frühjahrstagung, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21802

THz spectroscopy of solids using a free-electron laser
Helm, M.
Abstract: 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.
Keywords: free electron laser, pump probe, spectroscopy
  • Lecture (others)
    Vortrag am Shanghai Institute for Applied Physics (SINAP), 10.03.2015, Shanghai, China
Registration No. 21801

Topological Spin Textures in Magnetic Multilayers
Wintz, S.
Abstract: 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).

Keywords: vortex multilayer
  • Invited lecture (Conferences)
    DPG Frühjahrstagung der Sektion kondensierte Materie, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21800

Magnetic interactions in BiFe0.5Mn0.5O3 films and BiFeO3/BiMnO3 superlattices
Xu, Q.; Sheng, Y.; Khalid, M.; Cao, Y.; Wang, Y.; Qiu, X.; Zhang, W.; He, M.; Wang, S.; Zhou, S.; Li, Q.; Wu, D.; Zhai, Y.; Liu, W.; Wang, P.; Xu, Y.; Du, J.
Abstract: 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.


Registration No. 21799

Leaching of copper from Kupferschiefer by glutamic acid and heterotrophic bacteria
Kostudis, S.; Bachmann, K.; Kutschke, S.; Pollmann, K.; Gutzmer, J.
Abstract: 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.
Keywords: sulphide ores, bacteria, bioleaching, liberation analysis, ore mineralogy Registration No. 21795

Morphology and Microstructure of Si-SiO2 Nanocomposite Layers
Hübner, R.
  • Invited lecture (Conferences)
    EFDS-Workshop "Morphologie und Mikrostruktur dünner Schichten und deren Beeinflussung", 12.03.2015, Dresden, Deutschland
Registration No. 21790

On the effect of liquid viscosity on interfacial structures within churn flow: experimental study using Wire Mesh Sensor
Parsi, M.; Vieira, R. E.; Torres, C. F.; Kesana, N. R.; Mclaury, B. S.; Shirazi, S. A.; Schleicher, E.; Hampel, U.
Abstract: In the churn flow regime, periodical interfacial structures such as liquid slugs and huge waves can coexist and undoubtedly, a phase property such as liquid viscosity can dominate the behavior of these structures. Regrettably, neither are the characteristics of churn flow widely understood nor have the effects of liquid viscosity on gas-liquid flow received enough attention. A Wire Mesh Sensor (WMS) with a 16×16 spatial resolution was employed to discover the effects of liquid viscosity on the behavior of churn flow in a vertical 76.2 mm pipe. Three liquid viscosities of 1, 10, and 40 cP, and superficial liquid velocities of 0.46, 0.61, and 0.76 m/s were employed; whereas, superficial gas velocity ranged from 10 to 27 m/s. Different techniques such as Probability Density Function (PDF), and 2-D and 3-D image reconstruction methods were applied to study the flow. It was noticed that increasing liquid viscosity not only affected the flow pattern but also the appearance frequencies of interfacial structures.
Keywords: Churn Flow; Huge Wave; Wire Mesh Sensor; Multiphase Flow; Liquid Viscosity Registration No. 21788

Primary and Secondary Beam Stabilization at the ELBE Accelerator Facility
Justus, M.; Jainsch, R.; Kirschke, T.; Lehnert, U.; Michel, P.; Seidel, W.
Abstract: Since 2003, ELBE operates as a user facility for fundamental research and life sciences, providing highly brilliant electromagnetic radiation in a broad spectral range, as well as particle beams. The driving source is a 40 MeV, 1 mA electron LINAC in cw mode, utilizing a 13 MHz pulsed thermionic gun and Tesla acceleration technology. Infrared light from two FELs between 3 and 280μm [1] is the foremost secondary radiation used at ELBE. For its applications, different demands in beam stability are put for successful experiments. Therefore, a feedback system for the electron beam position and energy in combination with IR beam intensity feedback using FPGA technology is under development. It is aimed at suppressing beam instabilities caused by thermal behaviour, microphonics and the 50 Hz mains frequency with upper harmonics. This article depicts hardware and software details of the measurement and feedback system and provides first performance results.
Keywords: ELBE, feedback, FEL, stability
  • Contribution to proceedings
    ICALEPCS 2009, 12.-16.10.2009, Kobe, Japan
    Proceedings of ICALEPCS 2009, Geneva: Jacow, 978-4-9905391-0-8
  • Lecture (others)
    ICALEPCS 2009, 12.-16.10.2009, Kobe, Japan


Registration No. 21787

In-vivo dosimetry for particle beams - Radiation Physics
Helmbrecht, S.; Iltzsche, M.; Jannusch, P.; Lutz, B.; Priegnitz, M.; Rohling, H.; Römer, K.; Schöne, S.; Schumann, A.; Weinberger, D.; Pausch, G.; Enghardt, W.; Fiedler, F.
Abstract: no abstract available
  • Poster
    National Center for Radiation Oncology - 1st Scientific Retreat, 19.-21.03.2015, Heidelberg, Deutschland
Registration No. 21781

Transverse Emittance Compensation
Vennekate, H.; Arnold, A.; Kamps, T.; Kneisel, P.; Lu, P.; Murcek, P.; Teichert, J.; Xiang, R.
Abstract: Superconducting RF injectors are promising candidates for the particle sources of future accelerators. While machines like high power free electron lasers or energy recovery linacs are planned to be operated with large duty factors, or even continuous wave mode, to increase the beam intensity, they also demand high beam quality. As this is already determined at the very start of the generation of each particle bunch, the concept of an SRF gun becomes appealing. Transverse Emittance marks the beam quality which is of tremendous relevance for all beam optics and further more sets the level of angular resolution of any scattering experiment performed with the beam. Several concepts to enhance this quality with the lately comissioned Rossendorf SRF Gun II have been presented in recent year’s conferences. The talk will summarize the expended efforts, discuss some of the reflections on installation and operation of the used tools and present preliminary results of the recent achievements.
Keywords: SRF Gun, Emittance, ELBE
  • Lecture (Conference)
    DPG Frühjahrstagung 2015 Wuppertal, 09.-13.03.2015, Wuppertal, Deutschland
Registration No. 21780

Prompt-Gamma-Imaging for range verification in proton therapy: Towards clinical implementation
Barczyk, S.; Golnik, C.; Priegnitz, M.; Vander Stappen, F.; Janssens, G.; Smeets, J.; Clementel, E.; Hotoiu, L.; de Xivry, J. O.; Baumann, M.; Enghardt, W.; Fiedler, F.; Krause, M.; Prieels, D.; Pausch, G.; Richter, C.
Abstract: No abstract available
  • Poster
    National Center for Radiation Oncology - 1st Scientific Retreat, 19.-21.03.2015, Heidelberg, Deutschland
Registration No. 21778

PGI & PGT Modeling for realistic Patient Treatment Plans
Priegnitz, M.; Rohling, H.; Schumann, A.; Enghardt, W.; Pausch, G.; Fiedler, F.
Abstract: No abstract available.
  • Poster
    National Center for Radiation Oncology - 1st Scientific Retreat, 19.-21.03.2015, Heidelberg, Deutschland
Registration No. 21777

Neutron Dose During Proton Therapy
Lutz, B.; Enghardt, W.; Pausch, G.; Fiedler, F.
Abstract: Work in progress report about the measurement of the neutron field during proton therapy at OncoRay.
  • Poster
    National Center for Radiation Oncology -- 1st Scientific Retreat, 19.-21.03.2015, Heidelberg, Deutschland
Registration No. 21776

Experimental Characterization of Vertical Gas-Liquid Pipe Flow For Annular and Liquid Loading Conditions Using Dual Wire-Mesh Sensor
Vieira, R. E.; Parsi, M.; Torres, C. F.; Mclaury, B. S.; Shirazi, S. A.; Schleicher, E.; Hampel, U.
Abstract: In gas well production, liquid is produced in two forms, droplets entrained in the gas core and liquid film flowing on the tubing wall. For most of the gas well life cycle, the predominant flow pattern is annular flow. As gas wells mature, the produced gas flow rate reduces decreasing the liquid carrying capability initiating the condition where the liquid film is unstable and flow pattern changes from fully cocurrent annular flow to partially cocurrent annular flow. The measurement and visualization of annular flow and liquid loading characteristics is of great importance from a technical point of view for process control or from a theoretical point of view for the improvement and validation of current modeling approaches. In this experimental investigation, a Wire-Mesh technique based on conductance measurements was applied to enhance the understanding of the air-water flow in vertical pipes. The flow test section consisting of a 76 mm ID pipe, 18 m long was employed to generate annular flow and liquid loading at low pressure conditions. A 16×16 wire configuration sensor is used to determine the void fraction within the cross-section of the pipe. Data sets were collected with a sampling frequency of 10,000 Hz. Physical flow parameters were extracted based on processed raw measured data obtained by the sensors using signal processing. In this work, the principle of Wire-Mesh Sensors and the methodology of flow parameter extraction are described. From the obtained raw data, time series of void fraction, mean local void fraction distribution, characteristic frequencies and structure velocities are determined for different superficial liquid and gas velocities that ranged from 0.005 to 0.1 m/s and from 10 to 40 m/s, respectively. In order to investigate dependence of liquid loading phenomenon on viscosity, three different liquid viscosities were used. Results from the Wire-Mesh Sensors are compared with results obtained from previous experimental work using Quick Closing Valves and existing modeling approaches available in the literature.
Keywords: Wire-mesh sensor; gas-liquid flow; void fraction; phase distribution; flow visualization Registration No. 21775

Polymer and cluster chemistry of f-elements in aqueous solutions
Ikeda-Ohno, A.
Abstract: Because of their high charge density, the aqueous chemistry of f-elements with lower valences (i.e. tri- and tetravalent) is predominantly controlled by strong hydrolysis producing a variety of hydroxide species. Interestingly enough, this strong hydrolysis often induces the intrinsic formation of polymer and nano-sized cluster complexes which are stable even in aqueous solutions. This seminar will provide a recent overview of the hydrolysis-induced polymer/cluster formation of tetravalent f-elements particularly from the viewpoint of structural chemistry, as well as the associated characterisation techniques (e.g. X-ray absorption spectroscopy or X-ray scattering).
Keywords: actinides, lanthanides, f-elements, hydrolysis, aqueous solution, polymers, clusters, characterisation
  • Invited lecture (Conferences)
    Internal seminar, Institut für Radioökologie und Strahlenschutz, Leibnitz Universität Hannover, 30.04.2015, Hannover, Germany
Registration No. 21773

The effect of magnetic annealing on crystallographic texture and magnetic properties of Fe-2.6%Si
Salih, M. Z.; Uhlarz, M.; Pyczak, F.; Brokmeier, H.-G.; Weidenfeller, B.; Al-Hamdany, N.; Gan, W. M.; Zhong, Z. Y.; Schell, N.
Abstract: The effect of magnetic annealing on crystallographic texture ,microstructure, defects density and magnetic properties of a Fe-2.6%Si steel has been analyzed. After two stage cold rolling (75% and 60% cold rolled) with intermediate annealing process at (600 °C/1 h) the sample annealed at 600 °C for one hour during which different magnetic field of 0,7 and 14 T were applied has been investigated. The effect of defects density after cold rolling process on the recrystallization texture and magnetic properties was characterized. Heat treatments under a high external field of14 T show a drastic improvement of the magnetic properties such as significantly increased permeability. Neutron diffraction measurements were preferred for measurement of the bulk sample texture so that sufficient grain statistics were obtained. Because of its small wavelength (0.05–0.2 Å) synchrotron diffraction with high photon energy was used to evaluate the defects density by a modified Williamson–Hall plot. Registration No. 21772

Investigating Spinodal Decomposition and Coarsening using Massively Parallel Kinetic Metropolis Lattice Monte-Carlo Simulations
Kelling, J.; Heinig, K. H.; Gemming, S.
Abstract: Nano-structured materials are important for many applications, including energy technologies. The desired structures can be created using bottom-up processes, which utilize self-assembling. By way of spinodal decomposition of a metastable phase, like SiOx into Si and SiO2, sponge-like networks of nanowires can be obtained. Understanding the coarsening kinetics of spinodal structures is crucial not only for bottom-up production, but also helps to increase the life-time of components like porous matrices in fuel cells, where suppression of coarsening has a huge economic impact.

Two theories on coarsening of spinodal structures exist: one assuming diffusion through the bulk [1], the other along interfaces [2]. Since orders of magnitude in both space and time have to be covered by simulations, numerical studies are quite demanding. Nevertheless, simulations are essential in studying systems containing size-inhomogeneities in initial nano-structures, where strongly accelerated coarsening is observed.

Here, a multi-GPU Kinetic Metropolis Lattice Monte-Carlo implementation, capable of atomistic simulations of phase-separation and coarsening at spatio-temporal experimental scales (billions of particles over millions of time-steps) is presented while laying focus on the above-mentioned applications.

[1] A. Chakrabarti, R. Toral, J.D. Gunton, Phys. Rev. B 39(7) 4386 (1989) suggesting a modified Lifschitz-Slyozov law: I.M. Lifshitz, V.V. Slyozov, J. Phys. Chem. Solids 19(1-2), 35-50 (1961)
[2] W.W. Mullins, J. Appl. Phys. 28(3), 333-339 (1957)

Keywords: Nano Structures, GPGPU, Supercomputing, Statistical Physics,
  • Lecture (Conference)
    Conference of the Middle European Cooperation in Statistical Physics, 23.-25.03.2015, Esztergom, Hungary
Registration No. 21768

Simulation of Surface Growth and Lattices Gases Using GPUs
Schulz, H.; Kelling, J.; Ódor, G.; Ódor, G.; Ferenc Nagy, M.
Abstract: Restricted solid on solid surface growth models can be mapped onto binary lattice gases. We show that efficient simulation algorithms can be realized on GPUs either by CUDA or by OpenCL programming. We consider a deposition/evaporation model following Kardar–Parisi–Zhang growth in d+1 dimensions, related to the Asymmetric Simple Exclusion Process. Up to 100 - 400 x speedup can be achieved with respect to the serial code running on a I5 core. This permits studying disorder and aging behavior in these system.
Keywords: Computational Physics, Supercomputing Registration No. 21767
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