Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32228 Publications
Defects and sintering-induced diffusion processes in yttria-stabilised zirconia nanomaterials studied by positron annihilation spectroscopy
Prochazka, I.; Cizek, J.; Melikhova, O.; Anwand, W.; Konstantinova, T. E.; Danilenko, I. A.;
In the present work, zirconia (ZrO2) nanopowders doped with yttria (Y2O3) and chromia (Cr2O3) were prepared by a co-precipitation technique. The nanopowders were then subjected to a calcination and a successive sintering at elevated temperatures up to 1500 °C. The nanostructures in these nanomaterials were characterized by positron annihilation spectroscopy (positron lifetimes and Doppler broadening measurements) which is a non-destructive technique with a high sensitivity to atomic-scale open-volume defects. It was found that the zirconia-based nanomaterials studied contain vacancy-like defects and nano-scale pores. Diffusion processes induced in these nanomaterials by sintering were investigated also by depth sensitive positron annihilation studies using a variable energy slow positron beam. Sintering was found to cause intensive grain growth and a removal of porosity by a migration of pores from the sample interior toward its surface.
Keywords: Zirconia. Nanopowders. Sintering. Porosity. Positron annihilation

Publ.-Id: 20273 - Permalink


Phase analysis with HRPD and XAFS in the USiO4-ZrSiO4 solid solution system
Hennig, C.;
Invesigation the solid solution USiO4-ZrSiO4 is related with the problem to avoid the formation of the related oxides UO2 and ZrO2. In previous studies we have shown that the formation of UO2 can be relatively easy supressed by using an excess of SiO2 during the hydrothermal synthesis already at relatively low temperature. The formation of ZrO2 is obviously more pronounced in the same temperature range. A part of Zr enters the amorphous phase. The aim of this study is to investigate the Zr containing phases in crystalline and in amorphous state with HRPD and XAFS, respectively.
Keywords: solid solution, USiO4, ZrSiO4, HRPD, XAFS
  • Invited lecture (Conferences)
    TALISMAN Projekt meeting, 06.02.2014, Jülich, Germany

Publ.-Id: 20272 - Permalink


Challenges in Detection, Structural Characterization and Determination of Complex Formation Constants of Uranyl-Arsenate Complexes in Aqueous Solutions
Gezahegne, W.; Hennig, C.; Geipel, G.; Planer-Friedrich, B.; Merkel, B. J.;
Uranium forms analogous minerals with phosphate and arsenate. In aqueous solutions an analogy is expected to govern the complexes that uranium builds with these ligands. Three uranyl arsenate complexes UO2H2AsO4+, UO2HAsO4 0 and UO2(H2AsO4)2 0 were identified and reported previously with TRLFS in the pH range 1 to 3. Using a similar detection system and elevating the pH range a negatively charged fourth uranyl-arsenate complex, UO2AsO4- was found under circum neutral pH. Determining the complex formation constant for this complex was not possible due to the susceptibility of the fluorescence intensity to external influences and the difficulty of resolving the measured spectra into individual fluorescence contributions. By immediate shock-freezing to 15K we succeeded to measure a reproducible EXAFS spectrum of a uranyl-arsenate species in an aqueous solution at pH 2.
Keywords: Arsenate, Uranyl, aqueous solution, EXAFS, TRLFS
  • Book chapter
    Merkel, Broder, Schipek, Mandy: The New Uranium Mining Boom, Challenge and lessons learned, Berlin: Springer Geology, 2012, ISBN 978-3-642-22122-4, 607-616
    DOI: 10.1007/978-3-642-22122-4_70

Publ.-Id: 20271 - Permalink


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

Publ.-Id: 20270 - Permalink


Room-temperature oxidation of hypostoichiometric uranium-plutonium mixed oxides U1-yPuyO2-x – a depth-selective approach
Vauchy, R.; Robisson, A.-C.; Belin, R.; Martin, P.; Scheinost, A.; Hodaj, F.;
The oxygen content of a nonstoichiometric oxide compound is, in numerous cases, decisive regarding the material properties (electrical and/or thermal conductivity, melting point, etc). A phase separation is known to occur in oxygenhypostoichiometric uranium-plutonium mixed oxides beyond 20 mol% Pu. During its fabrication, the (U1-yPuy)O2-x mixed oxide can be subjected to several atmospheres, at room temperature, before being enclosed in the final fuel rods (e.g. storage after reducing sintering). Using a multi-scale approach (from the sample’s bulk to its surface), we reveal the evidence of spontaneous room-temperature oxidation of biphasic (U1-yPuy)O2-x compounds, with y = 0.28 and 0.45, even when exposed to low moisture and oxygen levels. This oxidation is, in both cases, significant within very short timescales. We believe our results are of utmost importance in the prospect of characterizing oxygen-hypostoichiometric uranium-plutonium mixed oxides with high Pu content.
Keywords: hypostoichiometry, multi-scale analysis, uranium-plutonium mixed oxide, XRD, XAS, TGA

Publ.-Id: 20269 - Permalink


Prediction of countercurrent flow limitation in horizontal pipes
Murase, M.; Kinoshita, I.; Lucas, D.; Tomiyama, A.;
To evaluate effects of wall friction coefficients in a one-dimensional model on prediction of countercurrent flow limitation (CCFL), sensitivity computations were done for hot leg models (ratio of length to diameter L/D = 8.6) and a pressurizer surge line model without elbows (L/D = 63) and computed results were compared with measured values. When the interfacial drag coefficient of fi = 0.03 and wall friction coefficients fwG in single-phase gas flows were used, the appropriate amplification for wall friction coefficients fwL in single-phase liquid flows was NwL = 6 to fit the computed CCFL value with the measured CCFL value.
Keywords: Countercurrent gas-liquid flow, CCFL, Horizontal pipe, One-dimensional model
  • Contribution to proceedings
    The 19th National Symposium on Power and Energy Systems (SPES2014), 26.-27.06.2014, Fukui, Japan

Publ.-Id: 20268 - Permalink


Numerical simulation of countercurrent flow in a scaled model of a pressurizer surge line
Murase, M.; Utanohara, Y.; Kusunoki, T.; Lucas, D.; Tomiyama, A.;
Numerical simulation was carried out for air-water countercurrent flows in a 1/10-scale model of the pressurizer surge line in a pressurized water reactor. The model consisted of a vertical pipe, a vertical elbow, and a slightly inclined pipe with elbows. In an actual 1/10-scale experiment, air supplied into the lower tank flowed up to the upper tank through the surge line and water supplied into the upper tank flowed down to the lower tank through the surge line. In the case of water supply into the upper tank in the simulation, the flow pattern in the inclined pipe was not reproduced because of flooding at the upper end of the vertical pipe with a sharp edge. To avoid effects of flooding at the upper end, therefore, water was also supplied from the wall surface of the vertical pipe and then the flow pattern in the inclined pipe was successfully reproduced. The simulated countercurrent flow limitation (CCFL) values agreed well with the experimental CCFL data.
Keywords: pressurizer surge line, countercurrent flow, numerical simulation, CCFL
  • Contribution to proceedings
    The 10th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-10), Paper N10P1020, 14.-18.12.2014, Okinawa, Japan

Publ.-Id: 20267 - Permalink


Prediction of coutercurrent flow limitation in a slightly inclinded pipe with elbows
Murase, M.; Kinoshita, I.; Kusunoki, T.; Lucas, D.; Tomiyama, A.;
Sensitivity computations were carried out for hot leg models (ratio of the horizontal pipe length to the diameter, L/D = 8.6) and pressurizer surge line models with and without elbows (ratio of the inclined pipe length to the diameter, L/D = 63) to evaluate suitable wall friction coefficients and pressure loss coefficients of elbows in a one-dimensional model predicting countercurrent flow limitation (CCFL) in a piping system. Computed results were compared with measured values. When the interfacial drag coefficient of fi = 0.03 and wall friction coefficients fwG of single-phase gas flows (i.e. adjustment factor, NwG = 1) were used, the appropriate adjustment factor for wall friction coefficients fwL of single-phase liquid flows was NwL = 6; this gave good fit of the computed CCFL values with the CCFL values measured in piping systems without elbows (L/D = 8.6 and 63). When fi = 0.03, NwG = 1, and NwL = 6 were used, the appropriate adjustment factor for pressure loss coefficients ζe of elbows in single-phase flows was Nde = 10; this gave good fit of the computed CCFL values with the CCFL values measured in the piping system with elbows (L/D = 63).
Keywords: CCFL, two.phase, modelling
  • Contribution to proceedings
    The 9th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-9), 16.-19.11.2014, Buyeo, Korea

Publ.-Id: 20266 - Permalink


Annual Report 2013 - Institute of Ion Beam Physics and Materials Research
Cordeiro, A. L.; Fassbender, J.ORC; Heera, V.; Helm, M.
The year 2013 was the third year of HZDR as a member of the Helmholtz Association (HGF), and we have made progress of integrating ourselves into this research environment of national Research centers. In particular, we were preparing for the evaluation in the framework of the so-called program oriented funding (POF), which will hopefully provide us with a stable funding for the next five years (2015 – 2019). In particular, last fall we have submitted a large proposal in collaboration with several other research centers. The actual evaluation will take place this spring. Most of our activities are assigned to the program “From Matter to Materials and Life” (within the research area “Matter”). A large fraction of this program is related to the operation of large-scale research infrastructures (or user facilities), one of which is our Ion Beam Center (IBC). The second large part of our research is labelled “in-house research”, reflecting the work driven through our researchers without external users, but still mostly utilizing our large-scale facilities such as the IBC, and, to a lesser extent, the free-electron laser. Our in-house research is performed in three so-called research themes, as depicted in the schematic below. What is missing there for simplicity is a small part of our activities in the program “Nuclear Waste Management and Safety” (within the research area “Energy”).
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-049 2014
    ISSN: 2191-8708

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Publ.-Id: 20265 - Permalink


Annual Report 2013 - Institute of Resource Ecology
Stumpf, T.; Foerstendorf, H.; Bok, F.; Richter, A.; (Editors)
The Institute of Resource Ecology (IRE) ISone of the eight institutes of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The Research activities are mainly integrated into the program “Nuclear Safety Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”.
Additionally, various activities have been started investigating chemical and environmental aspects of processing and recycling of strategic metals, namely rare earth elements. These activities are located in the HGF program “Energy Efficiency, Materials and Resources (EMR)”. Both programs, and therefore all work which is done at IRE, belong to the research sector “Energy” of the HGF.
The research objectives are the protection of humans and the environment from hazards caused by pollutants resulting from technical processes that produce energy and raw materials. Treating technology and ecology as a unity is the major scientific challenge in assuring the safety of technical processes and gaining their public acceptance. Namely, we investigate the ecological risks exerted by radioactive and non-radioactive metals in the context of nuclear waste disposal, the production of energy in nuclear power plants and in processes along the value chain of metalliferous raw materials. A common goal is to generate better understanding about the dominating processes essential for metal mobilization and immobilization on the molecular level. This in turn enables us to assess the macroscopic phenomena, including models, codes and data for predictive calculations, which determine the transport and distribution of contaminants in the environment.
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-048 2014
    ISSN: 2191-8708

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Publ.-Id: 20264 - Permalink


Inter-sublevel transitions in single InAs/GaAs quantum dots
Stephan, D. R.; Bhattacharyya, J.; Helm, M.; Huo, Y.; Rastelli, A.; Schmidt, O.; Schneider, H.;
In the past, inter-band transitions in quantum dots (QDs) have received an appreciable amount of scientific interest. However, inter-sublevel transitions have been studied much less extensively, likely because of their strongly non-radiative nature and because of limited availability of tunable sources for resonant excitation. In this work we explore the dynamics of inter-sublevel transitions in single InAs/GaAs self-assembled QDs. We combine the commonly used micro-photoluminescence (PL) technique with time-resolved detection and additional excitation by a free-electron laser. The experiment is carried out in the following way: the low-density QD sample is illuminated with a picosecond pulsed Ti:sapphire laser. PL from a single QD is coupled into a spectrometer, recording the spectrum with a CCD detector, as well as the time-resolved transient via the time-correlated single photon counting technique. Introducing a free-electron laser pulse tuned to the inter-sublevel transition energy excites carriers to a higher energy level, which decay back to the ground state non-radiatively with a relatively short time constant. These inter-sublevel dynamics causes quenching in the exponential PL decay of the energy of the ground state, which can be observed in timeresolved measurements. Whereas previous studies on inter-sublevel transitions have used QD ensembles[1-3], investigating single dots excludes many-dot effects such as inhomogeneous broadening and inter-dot transfer, which should lead to a better understanding of intersublevel carrier dynamics.
  • Poster
    20th International Conference on Electronic Properties of Two-Dimensional Systems (EP2DS-20) and 16th International Conference on Modulated Semiconductor Structures(MSS-16), 03.07.2013, Wroclaw, Polska

Publ.-Id: 20263 - Permalink


Investigation of the effective mass in GaAsN
Eßer, F.; Drachenko, O.; Schneider, H.; Patanè, A.; Hopkinson, M.; Helm, M.;
As a member of diluted nitrides, GaAsN is a highly interesting material system for many application purposes such as LEDs, lasers, solar cells, and infrared photodetectors because of the tuning possibility of these devices by the variation of the nitrogen content. For an accurate description of this material system, a profound knowledge of the band structure and in particular the effective mass (EM) is crucial. Because of the inconsistency of previous results, which can be traced down to the particular investigation method, we apply several methods on one sample series of GaAsN containing samples with 0.1 - 1 percent of nitrogen. Cyclotron resonance spectroscopy, beeing the most direct method, reveals that the EM is not signicantly affected by the nitrogen doping. Photoluminescence, on the other hand, stems from several transitions, which are not resolved spectrally, but identified in time-resolved measurements. We discuss the different behaviour of the involved transitions in magnetic fields up to 7 T (static) and 41 T (pulsed).
  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 30.03.-04.04.2014, Dresden, Deutschland

Publ.-Id: 20262 - Permalink


Control of the Effective Damping in Heusler/Pt Microstructures via Spin-Transfer Torque
Meyer, T.; Brächer, T.; Sebastian, T.; Pirro, P.; Fischer, T.; Serga, A. A.; Naganuma, H.; Mukaiyama, K.; Oogane, M.; Ando, Y.; Hillebrands, B.;
In this contribution, we present the control of the effective damping by the spin-transfer torque of a pure spin current injected into Heusler compound microstructures. Here, the pure spin current is generated by a DC current in a Pt layer on top of the magnetic layer via the spin-Hall effect. By changing the current density and the direction of the DC current in the Pt layer, the generated pure spin current can be manipulated. Via the spintransfer torque this pure spin current can act on the magnetization in the magnetic layer and, for example, decrease or even compensate the Gilbert damping.
The damping, i.e. the Gilbert damping, is a very crucial parameter for any magnetization dynamics and the possibility to control this parameter, i.e. to further reduce the damping, could give rise to novel nonlinear phenomena. Especially, cobalt-based Heusler compounds as used in this work provide a large spin-wave propagation length and an already very low Gilbert damping. Thus, the threshold for all spin-torque driven phenomena is decreased and only small current densities in the Pt layer are needed. By determining the threshold power for parallel parametric amplification of spin waves, for example, the change of the damping in dependence of the DC current can be determined.
The presented results were obtained using Brillouin light scattering microscopy. Brillouin light scattering is the inelastic scattering of photons on magnons, the quanta of spin waves. By investigating the frequency and the intensity of the inelastically scattered light, the frequency and the intensity of the spin waves can be obtained. Using a microfocussed laser allows for a spatial resolution of about 400 nm.
The results show a strong influence of the pure spin current on the effective damping in the magnetic layer. They show the feasibility of using a DC current in a Platinum layer to control the effective damping an adjacent Heusler layer. Thus, this is very interesting for possible applications using spin waves or for the investigation of nonlinear effects especially in Heusler compounds.
  • Poster
    IEEE International Conference on Microwave Magnetics 2014, 29.06.-02.07.2014, Sendai, Japan

Publ.-Id: 20261 - Permalink


Non-Gilbert-damping Mechanism in a Ferromagnetic Heusler Compound Probed by Nonlinear Spin Dynamics
Pirro, P.; Sebastian, T.; Brächer, T.; Serga, A. A.; Kubota, T.; Naganuma, H.; Oogane, M.; Ando, Y.; Hillebrands, B.;
The nonlinear decay of propagating spin waves in the low-Gilbert-damping Heusler film Co2Mn0.6Fe0.4Si is reported. Here, two initial magnons with frequency f0 scatter into two secondary magnons with frequencies f1 and f2. The most remarkable observation is that f1 stays fixed if f0 is changed. This indicates, that the f1 magnon mode has the lowest instability threshold, which, however, cannot be understood if only Gilbert damping is present. We show that the observed behavior is caused by interaction of the magnon modes f1 and f2 with the thermal magnon bath. This evidences a significant contribution of the intrinsic magnon-magnon scattering mechanisms to the magnetic damping in high-quality Heusler compounds.

Publ.-Id: 20260 - Permalink


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

Publ.-Id: 20259 - Permalink


Fe (II) Uptake on Natural Montmorillonites. I. Macroscopic and Spectroscopic Characterization
Soltermann, D.; Marques Fernandes, M.; Baeyens, B.; Dähn, R.; Joshi, P. A.; Scheinost, A. C.; Gorski, C. A.;
Ferrous iron bound to clay mineral surfaces is an important redox active-phase that is ubiquitous in both engineered and natural environments. In this study, the retention mechanism of Fe(II) on clay minerals was investigated using macroscopic sorption experiments combined with Mössbauer and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopies. Sorption edges and isotherms were measured under anoxic conditions on natural Fe-bearing montmorillonites (i.e. STx, SWy and SWa) having different structural Fe contents ranging from 0.5 to 15.4 wt % and different initial Fe redox states. Batch experiments indicated that, in case of low Fe-bearing (STx) and dithionite-reduced clays, the Fe(II) uptake follows well the sorption behavior of other divalent transition metals, whereas Fe(II) sorption increased by up to two orders of magnitude on the unreduced, Fe(III)-rich montmorillonites (SWy and SWa). Mössbauer spectroscopy analysis revealed that nearly all the sorbed Fe(II) was oxidized to surface-bound Fe(III) and secondary Fe(III) precipitates were formed on the Fe(III)-rich montmorillonite, while sorbed Fe is predominantly present as Fe(II) on Fe-low and dithionite-reduced clays. The results provide compelling evidence that Fe(II) uptake characteristics on clay minerals are strongly correlated to the redox properties of the structural Fe(III). The improved understanding of the interfacial redox interactions between sorbed Fe(II) and clay minerals gained in this study is essential for future studies developing Fe(II) sorption models on natural montmorillonites.
Keywords: Ferrous iron, 2:1 dioctahedral clay minerals, Mössbauer spectroscopy, EXAFS, surface complexation

Publ.-Id: 20258 - Permalink


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

Publ.-Id: 20257 - Permalink


Direct Condensation and Entrainment Experiments with Steam and Water
Seidel, T.;
In a hypothetical Small Break Loss of Coolant Accident in a Pressurized Water Reactor, the Reactor Pressure Vessel wall may be exposed to thermal stress, since Emergency Core Cooling Systems inject cold water into the hot reactor system. The loads on the primary loop and RPV walls are determined by mixing processes with the surrounding hot water and by the condensation of steam on the free surface.
In order to develop Computational Fluid Dynamics Simulations for future safety assessment and design purposes, experiments with stratified steam-water surfaces and with plunging liquid jets have been carried out and are being analyzed. It is shown, that the results may be used to develop and to validate CFD-models for reactor safety applications. Analysis, conditioning and summary of measured data is ongoing and promising.
Keywords: Direct Contact Condensation, steam, water, experiments, high pressure
  • Lecture (Conference)
    45th Annual Meeting on Nuclear Technology, 06.-8.5.2014, Frankfurt Main, Deutschland
  • Contribution to proceedings
    45th Annual Meeting on Nuclear Technology, 06.-8.5.2014, Frankfurt Main, Deutschland
    Proceedings AMNT 2014 (CD)

Publ.-Id: 20256 - Permalink


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

Publ.-Id: 20255 - Permalink


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

Publ.-Id: 20254 - Permalink


Aging of the (2+1)-dimensional Kardar-Parisi-Zhang model
Ódor, G.; Kelling, J.; Gemming, S.;
Extended dynamical simulations have been performed on a (2+1)-dimensional driven dimer lattice-gas model to estimate aging properties. The autocorrelation and the autoresponse functions are determined and the corresponding scaling exponents are tabulated. Since this model can be mapped onto the (2+1)-dimensional Kardar-Parisi-Zhang surface growth model, our results contribute to the understanding of the universality class of that basic system.
Related publications
Efficient Parallel Monte-Carlo Simulations for Large-Scale … (Id 27533) has used this publication of HZDR-primary research data

Publ.-Id: 20253 - Permalink


Elastic Properties of Nickel Carbides
Kelling, J.; Zahn, P.; Gemming, S.;
The nickel -- carbon system has received increased attention over the past years due to the relevance of nickel as a catalyst for carbon nanotube growth and as a substrate for metal-induced crystallization of graphene and graphite.
Nickel carbides as bulk materials are out
of reach for experimental studies because of their meta-stability. Ab-initio studies are rare. We present our ab-initio -- frozen phonon results for the elastic properties of Ni3C, Ni2C and NiC.
  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 30.03.-04.04.2014, Dresden, Germany

Publ.-Id: 20252 - Permalink


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

Publ.-Id: 20251 - Permalink


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

Publ.-Id: 20250 - Permalink


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

[1] Akhmadaliev et al., Nucl. Instr. Meth. B 294 (2013) 5.
[2] Pavetich et al., Nucl. Instr. Meth. B 329 (2014) 22.
[3] Müller et al., Hydrogeology J., in preparation.
[4] Siebert et al., Sci. Total Environ., in preparation.
[5] Smith et al., AMS-13 abstract
Keywords: accelerator mass spectrometry, volatile elements, chlorine, actinides, ion source memory, hydrogeology, cosmic radiation, irradiation ages meteorites, time-of-flight
  • Lecture (Conference)
    Heavy Ion Accelerator Symposium, 30.06.-02.07.2014, Canberra, Australien

Publ.-Id: 20249 - Permalink


Supernova-produced 26Al and 60Fe in deep-sea sediments from the Indian Ocean
Feige, J.; Wallner, A.; Fifield, L. K.; Merchel, S.; Rugel, G.; Steier, P.; Tims, S.; Winkler, S. R.; Golser, R.;
The long-lived radionuclides 26Al (t1/2 = 0.72 Myr) and 60Fe (t1/2 = 2.6 Myr) are generated in massive stars and ejected into space by stellar winds and explosions. If a star ends its life in a supernova (SN) explosion close to the solar system, a fraction of these elements might be deposited in terrestrial archives. Recent analysis of a ferromanganese crust [1,2] evidences an 60Fe concentration enhancement ~2-3 Myr ago. This radionuclide does not have terrestrial sources and is suggested to originate from one or more SNe [1]. Depth profiles with ~100 individual samples from deep-sea sediment cores (Indian Ocean) are studied to obtain a detailed data set of 26Al and 60Fe concentrations within the time period of the 60Fe signal in the crust. The targets were measured using accelerator mass spectrometry [3]. In contrast to our 60Fe data, which shows a clear signal without terrestrial background, a possible 26Al signal from a SN event is hidden within a non-negligible terrestrial background production [4]. The major source of 26Al is spallogenic production by cosmic-rays in the Earth’s atmosphere. This first full history of precise 26Al and 60Fe data over a time period of 2 Myr for two sediment cores is compared to theoretical estimations of a SN-produced radionuclide deposition on Earth considering different nucleosynthesis models and SN signal widths.
[1] Knie et al., Phys. Rev. Lett 93 (2004)
[2] Fitoussi et al., Phys. Rev. Lett 101 (2008)
[3] Wallner er al., this conf.
[4] Feige et al., EPJWC, 63 (2013)
Keywords: accelerator mass spectrometry, supernova, cosmogenic radionuclide
  • Poster
    XIII Nuclei in the Cosmos, 07.-11.07.2014, Debrecen, Ungarn

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Publ.-Id: 20248 - Permalink


Unleashing PFlop/s for Plasma Science with PIConGPU
Huebl, A.; Widera, R.; Burau, H.; Schmitt, F.; Pausch, R.; Schneider, B.; Juckeland, G.; Bussmann, M.;
PIConGPU is a massively parallel open source particle-in-cell (PIC) code written for CUDA capable graphics cards (GPUs). PIC codes are used to model fully relativistic electro-magnetic interactions between particles and discrete mesh points (fields) in a self-consistent manner. That allows for ab-intio simulations ranging from astrophysical scenarios like emerging plasma instabilities to modern laser-driven particle accelerators like the laser-wakefield accelerator (LWFA).

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

Applications will include results of in-situ far field radiation diagnostics for the relativistic Kelvin-Helmholtz-Instability (KHI) by evolving billions of electrons and calculating their individual Liénard-Wiechert potential for arbitrary directions and frequencies on the fly.
Keywords: PIConGPU, CUDA, Plasma, GPU, wakefield, instability, in-situ analysis, HPC
  • Lecture (Conference)
    DPG Spring Meeting 2014 Berlin, 17.-21.03.2014, Berlin, Deutschland

Publ.-Id: 20247 - Permalink


Synthetic Diagnostics of Radiation Phenomena in the Particle-in-Cell Code PIConGPU
Pausch, R.; Bussmann, M.; Burau, H.; Debus, A.; Huebl, A.; Irman, A.; Schramm, U.; Widera, R.;
Synthetic diagnostics in particle-in-cell codes provide physical quantities to the scientist that can be directly compared to experiment. We present simulations of laser-wakefield acceleration of electrons and on the dynamics of the relativistic Kelvin-Helmholtz Instability using the code PIConGPU. With PIConGPU it is possible to compute the radiation of every single electron in the simulation caused by acceleration by computing the Lienard-Wiechert Potentials, including both coherent and incoherent radiation. With GPU-accelerated codes Petaflop performance has become possible.
Keywords: radiation, PIConGPU, synthetic diagnostics, laser-wakefield acceleration, Kelvin-Helmholtz Instability
  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 30.03.-04.04.2014, Dresden, Deutschland

Publ.-Id: 20246 - Permalink


Using XFELs for Probing of Complex Interaction Dynamics of Ultra-Intense Lasers with Solid Matter
Huang, L.; Kluge, T.; Gutt, C.; Zacharias, M.; Bussmann, M.; Schramm, U.; Cowan, T. E.;
We demonstrate the potential of X-ray free-electron lasers (XFEL) to advancethe understanding of complex plasma dynamics by allowing for the first time nanometer and femtosecond resolution at the same time in plasma diagnostics. Plasma phenomena on such short timescales are of high relevance for many fields of physics, in particular in the ultra-intense ultra-short laser interaction with matter. Highly relevant yet only partially understood phenomena may become directly accessible in experiment. These include relativistic laser absorption at solid targets, creation of energetic electrons and electron transport in warm dense matter, including the seeding and development of surface and beam instabilities, ambipolar expansion, shock formation, and dynamics at the surfaces or at buried layers. We demonstrate the potentials of XFEL plasma probing for high power laser matter interactions using exemplary the small angle X-ray scattering, resonant coherent X-ray diffraction imaging and photon correlation spectroscopy, focusing on general considerations for XFEL probing.
Keywords: XFEL,high power laser,instabilities, filamentations, ionization,SAXS
  • Lecture (Conference)
    78. Jahrestagung der DPG und DPG-Frühjahrstagung, 17.-21.03.2014, Berlin, Germany

Publ.-Id: 20245 - Permalink


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

Publ.-Id: 20244 - Permalink


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

Publ.-Id: 20243 - Permalink


Characterization of the spin-½ linear-chain ferromagnet CuAs2O4
Caslin, K.; Kremer, R. K.; Razavi, F. S.; Schulz, A.; Munoz, A.; Pertlik, F.; Liu, J.; Whangbo, M.-H.; Law, J. M.;
The magnetic and lattice properties of the S = 1/2 quantum-spin-chain ferromagnet CuAs2O4, mineral Name trippkeite, were investigated. The crystal structure of CuAs2O4 is characterized by the presence of corrugated CuO2 ribbon chains.Measurements of themagnetic susceptibility, heat capacity, electron paramagnetic resonance, and Raman spectroscopy were performed. Our experiments conclusively show that a ferromagnetic Transition occurs at ∼7.4 K. Ab initio DFT calculations reveal dominant ferromagnetic nearest-neighbor and weaker antiferromagnetic next-nearest-neighbor spin exchange interactions along the ribbon chains. The ratio of Jnn/Jnnn is near −4, placing CuAs2O4 in close proximity to a quantum critical point in the Jnn-Jnnn phase diagram. TMRG simulations used to analyze the magnetic susceptibility confirm this ratio. Single-crystal magnetization measurements indicate that a magnetic anisotropy forces the Cu2+ spins to lie in an easy plane perpendicular to the c axis. An analysis of the field- and temperature-dependent magnetization by modified Arrott plots reveals a 3d-XY critical behavior. Lattice perturbations induced by quasihydrostatic pressure and temperature were mapped via magnetization and Raman spectroscopy

Publ.-Id: 20242 - Permalink


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

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

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

Publ.-Id: 20241 - Permalink


Asphericity of pretherapeutic FDG uptake predicts outcome in NSCLC
Rogasch, J. M.; Steffen, I. G.; Furth, C.; Beyer, M.; Riedel, S.; Schreiber, J.; Buchert, R.; Amthauer, A.; Hofheinz, F.; Apostolova, I.;
Ziel/Aim:
FDG-PET/CT has become the standard for staging of local tumor extent, mediastinal lymph node involvement and distant metastatic disease in patients with non-small-cell lung cancer (NSCLC). However, its role for prognosis is less clear. The aim of the present study was to evaluate the prognostic value of a novel quantitative measure for the spatial heterogeneity of FDG uptake, the asphericity (ASP).

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

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

Schlussfolgerungen/Conclusions:
The novel parameter asphericity of the pretherapeutic FDG-uptake provides more power for the prediction of PFS in NCSLC than conventional quantitative measures including SUVmax, MTV and glycolytic tumor volume.
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, D
  • Abstract in refereed journal
    Nuklearmedizin 53(2014), A13

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Publ.-Id: 20240 - Permalink


Correction of scan time dependence of standard uptake values in oncological PET
van den Hoff, J.; Lougovski, A.; Schramm, G.; Maus, J.; Oehme, L.; Petr, J.; Beuthien-Baumann, B.; Kotzerke, J.; Hofheinz, F.;
Background

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

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

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

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

Publ.-Id: 20239 - Permalink


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

Publ.-Id: 20238 - Permalink


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

Publ.-Id: 20237 - Permalink


Summary talk of AMS-13
Merchel, S.; Steier, P.;
Summary of the important issues presented at the Thirteenth Accelerator Mass Spectrometry Conference (AMS-13)
Keywords: accelerator mass spectrometry
  • Invited lecture (Conferences)
    13th International Conference on Accelerator Mass Spectrometry (AMS-13), 24.-29.08.2014, Aix-en-Provence, France

Publ.-Id: 20236 - Permalink


Novel nitric oxide-releasing selective cyclooxygenase-2 inhibitors as potential radiosensitizers
Bechmann, N.; Mosch, B.; Knieß, T.; Pietzsch, J.;
kein Abstract verfügbar
  • Contribution to proceedings
    23. Symposium Experimentelle Strahlentherapie und Klinische Strahlenbiologie, 27.02.-01.03.2014, Tübingen, Deutschland
    Baumann M, Cordes N, Dikomey E, Krause M, Petersen C, Rodemann HP, Zips D (Hrsg.) Proceedings des 23. Symposiums Experimentelle Strahlentherapie und Klinische Strahlenbiologie, Tübingen,, Rottenburg: Mayer, ISSN 1423-864X, 9-10
  • Poster
    23. Symposium Experimentelle Strahlentherapie und Klinische Strahlenbiologie, 27.02.-01.03.2014, Tübingen, Deutschland

Publ.-Id: 20235 - Permalink


Direct detection of live 60Fe and 244Pu on Earth as a monitor for recent heavy-element nucleaosynthesis
Wallner, A.; Bichler, M.; Faestermann, T.; Feige, J.; Fifield, L. K.; Golser, R.; Korschinek, G.; Kutschera, W.; Merchel, S.; Paul, M.; Rugel, G.; Schumann, D.; Sterba, J.; Tims, S.; Winkler, S. R.;
Observation and detection of freshly produced nuclides provides a direct clue for understanding stellar nucleosynthesis. In particular, radionuclides can act as radioactive clocks for their recent production. Previous measurements in deep-sea manganese crusts and sediments for extraterrestrial 60Fe (t1/2=2.6 Myr) at TU Munich [1] and for 244Pu (t1/2=81 Myr) at Munich [2], Hebrew University [3] and the VERA laboratory, Vienna [4] applied accelerator mass spectrometry (AMS), the most sensitive technique for detecting the expected small traces of interstellar material in terrestrial archives.
Recently, we have started a program at the ANU to follow-up a discovery of a 60Fe excess in an ocean crust sample pointing to a recent close-by supernova (SN) [1]. A substantial beamtime devoted to 60Fe has resulted in an exceptional sensitivity of 60Fe/Fe below 10-16. We have searched for a SN-signal in three deep-sea sediment cores (Indian Ocean). We will present first data for 60Fe allowing high time resolution and will relate it to potential recent SNe.
In addition, we have re-measured with an independent method the 60Fe half-life via 60Fe AMS measurements that allows us addressing the discrepancy of the two existing half-live values [5,6].

[1] K. Knie et al., PRL93 (2004), C. Fitoussi et al., PRL101 (2008).
[2] C. Wallner et al. New Astr. Rev. 48 (2004)
[3] M. Paul et al, ApJL 558 (2001)
[4] A. Wallner et al., submitted
[5] G. Rugel et al., PRL103 (2009)
[6] W. Kutschera et al., NIM B5 (1984)
Keywords: accelerator mass spectrometry, supernova, radionuclide
  • Lecture (Conference)
    XIII Nuclei in the Cosmos, 07.-11.07.2014, Debrecen, Ungarn

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Publ.-Id: 20234 - Permalink


Baseline model for monodispersed bubbly flows: A code comparison
Rzehak, R.; Kriebitzsch, S.; Ziegenhein, T.; Krepper, E.;
CFD simulations of dispersed bubbly flow on the scale of technical equipment are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, accurate numerical predictions depend on suitable closure models. A large body of work using different closure relations of varying degree of sophistication exists, but no complete, reliable, and robust formulation has been achieved so far.
An attempt has been made to collect the best available description for the aspects known to be relevant for adiabatic monodisperse bubbly flows, where closure is required for (i) the exchange of momentum between liquid and gas phases, (ii) the effects of the dispersed bubbles on the turbulence of the liquid carrier phase. Apart from interest in its own right, results obtained for this restricted problem also provide a good starting point for the investigation of more complex situations including bubble coalescence and breakup, heat and mass transport, and possibly phase change or chemical reactions.
The resulting model was previously validated by comparing simulations using ANSYS-CFX with experimental data for a number of test cases comprising vertical upward pipe flows and bubble columns. Here, the exact same model (within the limits of what is known about ANSYS-CFX) has been implemented in OpenFOAM v2.2 based on the twoPhaseEulerFoam solver. In this way a comparison becomes possible also between two different numerical approaches.
Both codes are able to reproduce the experimental data with similar quality but differences between the results of both simulation are not negligible. A discussion of possible reasons is given.
Keywords: Dispersed gas-liquid multiphase flow, two-fluid model, model validation, closure relations, OpenFOAM
  • Lecture (Conference)
    Jahrestreffen der Fachgruppen Computational Fluid Dynamics, Mischvorgänge und Rheologie, 24.-26.02.2014, Würzburg, Deutschland

Publ.-Id: 20233 - Permalink


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

Publ.-Id: 20232 - Permalink


Spin Vortices in Magnetic Multilayers
Wintz, S.;
The focus of this thesis are spin vortices in magnetic multilayers. A spin vortex is a topological spin texture, characterized by a planar magnetization curl that tilts out- of-plane in the nanoscopic core region at the center. There are two different states possible for both the rotation sense of the curl (circulation) and the orientation of the core (polarity), leading to a binary vortex chirality. The spin vortex is typically the ground state of micron sized ferromagnetic thin film disks or square-shaped elements. During the past decades, spin vortices were studied intensively with respect to their magnetostatic and—in particular—their intriguing magneto-dynamic properties. Along with these fundamental studies, proposals were made for the application of vortices for example in data storage and radio-frequency oscillator technology. With respect to density and synchronization in both these application concepts—but also from a fundamental point of view—the interaction between vortices is a crucial issue to address. This holds true especially for the vertical geometry of trilayer vortices (ferromagnet/non-ferromagnet/ferromagnet) in which giant- or tunnel magneto resistance effects as well as spin-transfer torques are exploitable. However, the knowledge on such coupled vortices has been fairly limited. Therefore it was the aim of this work to investigate the magnetic properties of vertically coupled vortex pairs. Investigations were mainly made by means of synchrotron-based transmission x-ray microscopy. This method uniquely allows for a direct and element selective imaging of the magnetic orientation in spin textures with the lateral resolution required. The vortex pair samples were fabricated by electron beam lithography and thin film deposition techniques. Additional magnetometry measurements were employed to address the basic material and coupling properties. Also micromagnetic simulations were carried out in order to complement the experimental results. By this approach, different vortex pair configurations concerning the relative orientation of circulations and polarities, are identified. It is shown that interlayer exchange coupling can be exploited to deterministically set the relative circulation state, and that ion irradiation provides a method to finely tune this coupling after the multilayer has been deposited. In contrast, the polarity states are found not to be controllable by any of the interlayer coupling strengths accessible. Both states are stable in fact, with the parallel configuration representing the ground state. The field response of a vortex pair is evaluated to range from a quasi-independent behavior to a strict coupling between both layers, where the latter can be described by a single layer vortex response with effective magnetic properties. When a relevant non-collinear interlayer coupling is introduced to the vortex pair state, the system is found to exhibit radial magnetization components with opposing sign between both ferromagnetic layers, which in turn results in the formation of a three-dimensional torus vortex accompanied by a symmetry break of the polarity states. The findings achieved in this work mark a significant advance of the state of the art in the field of spin vortices and coupled spin textures, and they may also be of value for future vortex-based applications in technology.
Keywords: magnetism, vortex, multilayer, coupling, x-ray microscopy
  • Doctoral thesis
    TU Dresden, 2014
    Mentor: Prof. Dr. Jürgen Faßbender
    153 Seiten

Publ.-Id: 20230 - Permalink


Experimental investigations on two-phase flows in a vertical pipe using ultrafast electron-beam X-ray tomography
Banowski, M.; Lucas, D.; Beyer, M.; Szalinski, L.; Hampel, U.;
At the Institute of Fluid Dynamics in the Helmholtz-Zentrum Dresden-Rossendorf, two-phase flow experiments at a vertical pipe are performed using ultrafast X-ray tomography. In comprehensive experimental series, upward flows, counter-current flows as well as downward flows were investigated. In this compact, developed processing methods and selected results of these experiments are presented.
Keywords: two-phase flow, bubbles, TOPFLOW, vertical pipe
  • Lecture (Conference)
    45th Annual Meeting on Nuclear Technology - Preserving Competence in Nuclear Technology, 06.-08.05.2014, Frankfurt am Main, Deutschland
  • Contribution to proceedings
    45th Annual Meeting on Nuclear Technology - Preserving Competence in Nuclear Technology, 06.-08.05.2014, Frankfurt am Main, Deutschland

Publ.-Id: 20229 - Permalink


Ga-reiche Schichten in Si – vom Supraleiter zum Isolator
Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Hübner, R.; Schmidt, B.; Skorupa, W.; Helm, M.;
Es hat kein Abstract vorgelegen.
  • Lecture (Conference)
    51. Treffen der Nutzergruppe Ionenimplantation, 03.04.2014, Erlangen, Deutschland

Publ.-Id: 20228 - Permalink


Supraleitende Schichten in Ge und Si – Einfluss der Ausheilbedingungen
Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Hübner, R.; Schmidt, B.; Skorupa, W.; Helm, M.;
Es hat kein Abstract vorgelegen.
  • Lecture (Conference)
    35. Treffen der Nutzergruppe Heißprozesse und RTP, 02.04.2014, Erlangen, Deutschland

Publ.-Id: 20227 - Permalink


On the joint multi point simulation of discrete and continuous geometallurgical parameters
van den Boogaart, K. G.; Tolosana-Delgado, R.; Lehmann, M.; Mueller, U.;
Geometallurgical parameters are descriptions of the mineralogy and microstructure of the ore determining its mineralogical and microstructural characteristics. From a conditional geostatistical simulation of such properties, a processing model could compute recovery, equipment usage, processing costs, and thus the monetary value for mining and processing the block with certain processing parameters. This can be used for optimizing mining sequences or finding optimal processing parameters by solving the corresponding stochastic optimization problem.
The approach requires two properties of the simulation not provided by established geostatistical techniques:
1) Many relevant geometallurgical parameters are from non-Euclidean statistical scales like (mineral) compositions, (grain size) distribution, (grain) geometry, (stratigraphic type) categorical, etc., which might produce impossible values when simulated with standard geostatistical techniques.
2) Due to the nonlinearity of processing, the whole conditional distribution of the geometallurgical parameters is relevant and not only its mean and variance. The geostatistical simulation needs to reproduce the joint conditional distributions of all the geometallurgical parameters.
We have developed a multi-point conditional geostatistical simulation technique, which allows for jointly simulating dependent spatial variables from various sample spaces. The technique combines an MPS-type infill simulation with a new form of distributional regression to estimate conditional distributions of arbitrary scales from different information sources, including training images, training models and observed data. The distributional regression is based on a generalization of logistic regression and has some relation to both BME-type geostatistics and high order cumulants.
The method ensures simulated data to reside within the constrained sample space and honour the characteristics of the joint distribution to be reproduced. The computational effort is substantial, but affordable for a useful application with standard problems: from processing-aware block value prediction and block processing optimization as we show in the test application to a completely defined simulated model situation with a complex processing model.
Keywords: geostatistical simulation, non Euclidean scales, geometallurgy
  • Lecture (Conference)
    SMP 2014, Ore Body modelling and strategic mine planning, 24.-25.11.2014, Perth, Australia
  • Contribution to proceedings
    SMP 2014, Ore Body modelling and strategic mine planning, 24.-25.11.2014, Perth, Australia
    Orebody Modelling and Strategic Mine Planning, SMP 2014, Integrated mineral investment and supply chain optimisation, Charlton Victoria, Australia: Australasian Institute of Mining and Metallurgy, 987-1-925100-19-8, 379-388

Publ.-Id: 20226 - Permalink


Combined PET/MR: Where Are We Now? Summary Report of the Second International Workshop on PET/MR Imaging April 8–12, 2013, Tubingen, Germany
Bailey, D. L.; Barthel, H.; Beuthien-Baumann, B.; Beyer, T.; Bisdas, S.; Boellaard, R.; Czernin, J.; Drzezga, A.; Ernemann, U.; Franzius, C.; Gückel, B.; Handgretinger, R.; Hartenbach, M.; Hellwig, D.; Nadel, H.; Nekolla, S. G.; Pfluger, T.; Pichler, B. J.; Quick, H. H.; Sabri, O.; Sattler, B.; Schäfer, J.; Schick, F.; Siegel, B. A.; Schlemmer, H. P.; Schwenzer, N. F.; van den Hoff, J.; Veit-Haibach, P.; Wehrl, H. F.;
This workshop was held a year after the initial positron emission tomography/magnetic resonance (PET/MR) workshop in Tübingen, which was recently reported in this journal. The discussions at the 2013 workshop, however, differed substantially from those of the initial workshop, attesting to the progress of combined PET/MR as an innovative imaging modality. Discussions were focused on the search for truly novel, unique clinical and research applications as well as technical issues such as reliable and accurate approaches for attenuation and scatter correction of PET emission data. The workshop provided hands-on experience with PET and MR imaging. In addition, structured and moderated open discussion sessions, including six dialogue boards and two roundtable discussions, provided input from current and future PET/MR imaging users. This summary provides a snapshot of the current achievements and challenges for PET/MR.
Keywords: Combined imaging, Molecular imaging, PET/CT, PET/MR, Quantification, MRbased attenuation correction methods, Oncology, Paediatric oncology, Neurology, Cardiology

Publ.-Id: 20225 - Permalink


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

[1] O. Scharf et al., Anal. Chem., Vol. 83, pp. 2532-2538 (2011).
[2] I. Ordavo et al., NIM A, Vol. 654, pp. 250-257 (2011).
Keywords: High-Speed PIXE, SLcam, polycapillary optics, pnCCD, lateral resolution, resource technology, mineralogy, trace elements
  • Invited lecture (Conferences)
    14th International Conference on Nuclear Microprobe Technology and Applications, 06.-11.07.2014, Padova, Italy

Publ.-Id: 20224 - Permalink


A Baseline Model for Monodisperse Bubbly Flows
Rzehak, R.; Krepper, E.; Ziegenhein, T.; Lucas, D.;
For practical applications the Euler-Euler two-fluid model relies on suitable closure relations describing interfacial exchange processes. The quest for models with a broad range of applicability allowing predictive simulations is an ongoing venture. A set of closure relations for adiabatic bubbly flow has been collected that represents the best available knowledge and may serve as a baseline for further improvements and extensions. In order to allow predictive simulations the model must work for a certain range of applications without any adjustments. This is shown here for flows that allow to impose a fixed bubble size distribution which bypasses the need to model coalescence and breakup processes.
Keywords: Dispersed gas-liquid multiphase flow, Euler-Euler two-fluid model, closure relations, CFD simulation, model validation
  • Contribution to proceedings
    CFD2014: 10th International Conference on Computational Fluid Dynamics In the Oil & Gas, Metallurgical and Process Industries, 17.-19.06.2014, Trondheim, Norway
    Proceedings of CFD2014
  • Lecture (Conference)
    CFD2014: 10th International Conference on Computational Fluid Dynamics In the Oil & Gas, Metallurgical and Process Industries, 17.-19.06.2014, Trondheim, Norway

Publ.-Id: 20223 - Permalink


Monodisperse bubbly flows with ANSYS CFX and OpenFOAM: A comparison
Kriebitzsch, S.; Rzehak, R.; Lucas, D.;
Within the framework of two-fluid modelling, the interfacial transfer processes needs to be modelled by suitable closure relations. Based on previous experience with ANSYS CFX (e.g Rzehak and Krepper, 2013) a set of closure relations applicable for adiabatic bubbly flow has been implemented in OpenFOAM. Great effort has been made to match all details of the models so that the same results may be expected and residual differences should be only due to different numerical procedures.
In this work we compare simulation results for dispersed gas-liquid pipe flow with experimental data given by Liu (1998) as well as in-house data obtained with the MTLoop facility described in Lucas et al. (2005). Overall, the experimental data are reasonably well predicted and the predictions are competitive with the results computed with ANSYS CFX. However some differences can be observed, especially in the turbulent quantities in the near wall region
Keywords: Dispersed gas-liquid multiphase flow, two-fluid model, model validation, closure relations.
  • Contribution to proceedings
    CFD2014: 10th International Conference on Computational Fluid Dynamics In the Oil & Gas, Metallurgical and Process Industries, 17.-19.06.2014, Trondheim, Norwegen
    Proceedings of the 10th International Conference on Computational Fluid Dynamics In the Oil & Gas, Metallurgical and Process Industries
  • Lecture (Conference)
    CFD2014: 10th International Conference on Computational Fluid Dynamics In the Oil & Gas, Metallurgical and Process Industries, 17.-19.06.2014, Trondheim, Norwegen

Publ.-Id: 20222 - Permalink


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

[1] Domaschke, K. et al. (2014) Proceedings of ESANN.
Keywords: EXAFS, metal complex, neural networks, self-organizing map
  • Lecture (Conference)
    Actinide XAS 2014, 20.-22.05.2014, Villigen, Switzerland

Publ.-Id: 20221 - Permalink


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

REFERENCES
[1] Casellato, U.; Vigato, P. A.; Vidali, M. Coord. Chem. Rev. 1978, 26, 85-159.
[2] Takao, S.; Takao, K.; Kraus, W.; Emmerling, F.; Scheinost, A.C.; Bernhard, G.; Hennig, C. Eur. J. Inorg. Chem. 2009, 4771-4775.
[3] Takao, K.; Takao, S.; Scheinost, A.C.; Bernhard, G.; Hennig, C. Inorg. Chem. 2012, 51, 1336-1344.
[4] Hennig, C.; Takao, S.; Takao, K.; Weiss, S.; Kraus, W.; Emmerling, F.; Scheinost, A.C. Dalton Trans. 2012, 41, 12818-12823.
[5] Hennig, C.; Ikeda-Ohno, A.; Kraus, W.; Weiss, S.; Pattison, P.; Emerich, H.; Abdala, P.M.; Scheinost, A.C. Inorg. Chem. 2013, 52, 11734-11743.
  • Lecture (Conference)
    Actinide XAS 2014, 20.-22.05.2014, Böttstein, Switzerland

Publ.-Id: 20220 - Permalink


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

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

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

Publ.-Id: 20219 - Permalink


Spin-wave caustic formation by higher-harmonic radiation from a localized spinwave mode in a Heusler waveguide
Sebastian, T.; Pirro, P.; Brächer, T.; Kubota, T.; Serga, A. A.; Naganuma, H.; Oogane, M.; Ando, Y.; Hillebrands, B.;
Cobalt-based full Heusler compounds are very promising candidates for future magnon-spintronic devices as well as for the observation of novel phenomena in magnon transport in magnetic microstructures. The reason for the anticipated advantages is their decreased Gilbert damping in comparison with most conventional metallic 3d-ferromagnets and, in particular, in comparison with the widely used Ni81Fe19.

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

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

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

Subsequently, all three phenomena will be addressed in this talk. The localization of the directly-excited mode is described on the basis of a micromagnetic simulation as well as a dispersion calculation. This localized spin-wave mode can be identified as the source for the generation of the second and third harmonic. Finally, the radiation characteristics of the higher harmonics are described quantitatively by an analytical calculation based on the anisotropic dispersion relation of spin waves in magnetic thin films.
Keywords: spin Dynamics, magnetooptics, Heusler coumpounds, nonlinear
  • Poster
    IEEE International Magnetics Conference - INTERMAG 2014, 04.-08.05.2014, Dresden, Deutschland

Publ.-Id: 20218 - Permalink


Evaluating the Gilbert damping in individual Co2Mn0.6Fe0.4Si microstructures via parametric amplification
Sebastian, T.; Brächer, T.; Pirro, P.; Kawada, Y.; Naganuma, H.; Serga, A. A.; Oogane, M.; Ando, Y.; Hillebrands, B.;
Recent experiments on spin dynamics in microstructures made of the Heusler compound Co2Mn0.6Fe0.4Si (CMFS) yielded promising results in the linear and nonlinear regime. These results were attributed to the low Gilbert damping that was observed with standard ferromagnetic resonance (FMR) technique on homogeneous thin films. However, a quantitative analysis of the damping in CMFS microstructures is still lacking. We present an alternative method to evaluate the damping in individual CMFS microstructures using parametric amplification and show that the low damping is preserved on the microscale.
Keywords: spin dyanmics, magnetooptics, Gilbert damping, Heusler compounds
  • Poster
    DPG Frühjahrstagung 2014, 30.03.-04.04.2014, Dresden, Deutschland

Publ.-Id: 20217 - Permalink


Hydrodynamic modelling of an inclined rotating fixed bed reactor
Vaibhav, V.;
The hydrodynamics of a newly developed reactor concept with rotating fixed-bed were investigated using gamma-ray computed tomography. During these investigations, operational parameters like reactor inclination and rotation as well as flow rates, liquid and fixed-bed properties were varied.
In this work, hydrodynamic models from the literature have to be implemented, extended and parameterized for the new reactor concept.
Keywords: Inclined rotating fixed bed reactor, process intensification, modelling
  • Study thesis
    HZDR, 2014
    Mentor: Hans-Ulrich Härting
    32 Seiten

Publ.-Id: 20216 - Permalink


Experimentelle Untersuchung der Verweilzeitverteilung in einem geneigt rotierenden Festbettreaktor
Donath, T.;
Der geneigt rotierende Festbettreaktor stellt ein neues Reaktorkonzept mit dem Ziel der Prozessintensivierung durch periodische Betriebsweise dar. Aus dessen Betriebsweise ergeben sich zusätzliche Freiheitsgrade zur Strömungsführung in Form von Neigung und Drehzahl und damit zur Beeinflussung der Reaktorleistung.
Im Rahmen der Diplomarbeit ist die Hydrodynamik im geneigt rotierenden Festbettreaktor mit den Schwerpunkten Verweilzeitverteilung und Phasenverteilung zu untersuchen. Die Ergebnisse sind mit denen des etablierten Rieselbettreaktors zu vergleichen.
Durch die im rotierenden Reaktor zusätzlich aufgeprägte transversale Strömungskomponente ist die Eignung des axialen Dispersionsmodells für das neue Reaktorkonzept zu untersuchen und es sind Möglichkeiten zur experimentellen Bestimmung der radialen Dispersion zu präsentieren.
Keywords: Inclined rotating fixed bed reactor, residence time distribution, process intensification
  • Diploma thesis
    Technische Universität Dresden, 2014
    Mentor: Prof. Rüdiger Lange, Hans-Ulrich Härting
    119 Seiten

Publ.-Id: 20215 - Permalink


Reaktionstechnische Untersuchungen an einem geneigt rotierenden Festtbettreaktor
Bischof, C.;
Der geneigt rotierende Festbettreaktor stellt ein neues Reaktorkonzept mit dem Ziel der Prozessintensivierung durch periodische Betriebsweise dar. Aus der neuartigen Betriebsweise ergeben sich in Form von Neigung und Drehzahl zusätzliche Freiheitsgrade zur Strömungsführung und damit zur Beeinflussung der Reaktorleistung.
Im Rahmen der interdisziplinären Projektarbeit ist die Reaktionsführung hinsichtlich der Raum-Zeit-Ausbeute einer Modellreaktion (Hydrierung von α-Methylstyrol zu Cumol) zu untersuchen. Dazu sind abschließende MSR Arbeiten an einer bestehenden Versuchsanlage durchzuführen sowie Lösungen für die einfache Bestimmung von reaktionstechnischen Kenngrößen aus den Versuchsdaten zu präsentieren. Die Ergebnisse des geneigt rotierenden Festbettreaktors sind mit denen des etablierten Rieselbettreaktors zu vergleichen.
Keywords: Inclined rotating fixed bed reactor, process intensification, multiphase reaction, heterogeneous catalysis
  • Study thesis
    Technische Universität Dresden, 2014
    Mentor: Prof. Rüdiger Lange, Hans-Ulrich Härting
    56 Seiten

Publ.-Id: 20214 - Permalink


Live, Interactive, In-Situ, In-GPU Visualization of Plasma Simulations Running on GPU Supercomputers
Pausch, R.; Schneider, B.; Hettmanczyk, D.; Burau, H.; Huebl, A.; Schmitt, F.; Widera, R.; Grottel, S.; Gumhold, S.; Bussmann, M.;
With GPUs large-scale plasma simulations can provide frames-per-second simulation speeds. We present interactive, in-GPU rendering of large-scale particle-in-cell simulations running on GPU clusters. The user can choose which data is visualized and change the direction of view while the simulation is running. A remote visualization client can connect to the running simulation, allowing for live visualization even when bandwidth is limited.
Keywords: PIConGPU remote visualization in-situ live interactive
  • Lecture (Conference)
    GPU Technology Conference, 24.-27.03.2014, San Jose, CA, United States of America

Publ.-Id: 20213 - Permalink


Follow the Light: Plasma Physics on 18,000 GPUs
Pausch, R.; Juckeland, G.; Burau, H.; Bussmann, M.; Cowan, T.; Debus, A.; Huebl, A.; Kluge, T.; Nagel, W.; Schmitt, F.; Schramm, U.; Schuchart, J.; Widera, R.;
We show that with todays largest supercomputers it is possible to follow the trajectories of billions of particles, computing a unique fingerprint of their dynamics. With the use of 18,000 GPUs we could compute a 'sky map' of the radiation emitted by individual electrons in a large-scale, turbulent plasma, providing unique insight into the relation between the plasma dynamics and observable radiation spectra.
Keywords: PIConGPU Kelvin-Helmholtz instability KHI radiation spectra
  • Lecture (Conference)
    GPU Technology Conference, 24.-27.03.2014, San Jose, CA, United States of America

Publ.-Id: 20212 - Permalink


Spectrally resolved sky-map of electromagnetic radiation from the Kelvin-Helmholtz instability
Pausch, R.; Huebl, A.; Schmitt, F.; Burau, H.; Widera, R.; Pugmire, D.; Debus, A.; Juckeland, G.; Nagel, W.; Bussmann, M.;
The Kelvin-Helmholtz instability (KHI) occurs at the interface between two neutral streams of plasma flowing past one another with different velocities. This instability is expected to take place in active galactic nuclei or in the afterglow of gamma-ray bursts, where it is a possible mechanism for non-thermal radiation.
We present results of a KHI scenario with relativistic velocity shear obtained in a petaflop scale run on the TITAN cluster at Oakridge using our relativistic 3D3V particle-in-cell code PIConGPU. From the dynamics of billions of macroparticle, we calculated angularly and temporally resolved radiation spectra based on classical Liénard-Wiechert potentials including the full coherence properties. Thus, in addition to the incoherent synchrotron-type radiation arising from DC magnetic fields in the KHI, we found rich radiation signatures, which we match with the dynamics and electron density structure of the KHI. We present a simple model, which explains these spectral features and connects them to the main quantities of the KHI.
Keywords: PIConGPU Kelvin-Helmholtz instability KHI radiation spectra
  • Lecture (Conference)
    78. DPG-Jahrestagung und Frühjahrstagung der Sektion AMOP, 17.-21.03.2014, Berlin, Deutschland

Publ.-Id: 20211 - Permalink


Radiative particle-in-cell simulations - How synthetic diagnostics help to understand plasma structure and dynamics
Pausch, R.; Debus, A.; Huebl, A.; Steiniger, K.; Burau, H.; Widera, R.; Bussmann, M.;
We present recent results of plasma simulations performed with PIConGPU, a fully relativistic 3D particle-in-cell (PIC) code running on GPU clusters. We extended our code to compute the radiation spectra of all particles in the simulation based on classical Liénard-Wiechert potentials including full coherence and polarization properties. We discuss physics tests, scaling and show simulation results of laser-wakefield accelerator and astrophysical plasmas, for which we calculated angularly resolved spectra ranging from infrared to X-ray wavelengths. Such an extensive treatment of plasma radiation across billions of macro particles makes it possible to explore temporally resolved plasma radiation spectra on linear and logarithmic photon energy scales over large solid angles ("sky-maps").
This ability of obtaining quantitative spectral data in plasma simulations poses a unique tool for determining the phase space distribution of electrons. Since spectral information is readily accessible in experiments, our results can serve as a valuable input to new diagnostics.
Keywords: PIConGPU radiation angularly resolved spectra diagnostics
  • Lecture (Conference)
    78. DPG-Jahrestagung und Frühjahrstagung der Sektion AMOP, 17.-21.03.2014, Berlin, Deutschland

Publ.-Id: 20210 - Permalink


Ferromagnetism and impurity band in a magnetic semiconductor: InMnP
Khalid, M.; Weschke, E.; Skorupa, W.; Helm, M.; Zhou, S.;
We have synthesized ferromagnetic InMnP, a member of the III-Mn-V ferromagnetic semiconductor family, by Mn ion implantation and pulsed laser annealing. Clear ferromagnetic hysteresis loops and a perpendicular magnetic anisotropy are observed up to a Curie temperature of 42 K. Large values of negative magnetoresistance and magnetic circular dichroism as well as an anomalous Hall effect are further evidence of a ferromagnetic order in InMnP. An effort is made to understand the transport mechanism in InMnP using the theoretical models. We find that the valence band of InP does not merge with the impurity band of the heavily doped ferromagnetic InMnP. Our results suggest that impurity band conduction is a characteristic of Mn-doped III-V semiconductors which have deep Mn-acceptor levels.
Keywords: diluted magnetic semiconductor, III-V semiconductor

Publ.-Id: 20209 - Permalink


Analyse von Artefakten in der MR-basierten Schwächungskorrektur am PET-MR
May, C.; Schramm, G.; Platzek, I.; Kotzerke, J.; Beuthien-Baumann, B.;
Ziel/Aim:
Ziel der Arbeit ist die Analyse von Artefakten in MR-basierten Schwächungsbildern (MRMaps) bei Patientenuntersuchungen am Philips Ingenuity TF PET/MR. Die Artefakte wurden auf Art und Häufigkeit untersucht.

Methodik/Methods:
Insgesamt wurden 723 PET/MR Untersuchungen des Körperstamms im Zeitraum 01.10.2012 bis 01.10.2013 ausgewertet. Fehlerhafte MRMaps wurden mit dem zugrundeliegenden Schwächungs-MRT parallel betrachtet. Die Segmentierungsfehler wurden in folgende Kategorien eingeteilt: 1. die Lunge wurde nicht erkannt, 2. die Lunge wies eine falsche Form auf, 3. durch Metallimplantate verursachte Artefakte (z.B. durch Hüft-/Knie-TEP, Sternalcerclagen, Ports oder Zahnfüllungen), 4. sonstige Artefakte.

Ergebnisse/Results:
Es wurden 52 MRMaps mit Segmentierungsfehlern gefunden, die nicht durch eine einfache Nachbearbeitung der MTRA korrigiert werden konnten. In 20 Fällen wurde die Lunge nicht erkannt. In 24 Fällen wurde die Form der Lunge falsch segmentiert, wobei die Form 5 mal zu klein und 19 mal zu groß war. 35 Artefakte fielen in die Kategorie Metallartefakte, 5 in die Kategorie sonstige Artefakte. Einzelne MRMaps wiesen eine Kombination von Segmentierungsfehlern auf. Zusätzliche PET Rekonstruktionen mit korrigierten MRMaps zeigten SUV Abweichungen von bis zu 50% in verschiedenen Körperarealen.

Schlussfolgerungen/Conclusions:
Aufgrund der beobachteten Artefakte und deren Auswirkungen sollten bei allen PET/MRT Untersuchungen die MRMap von der MTRA auf Fehler untersucht werden.Treten gröbere Artefakte in der MRMap auf, müssen diese korrigiert und das PET Bild neu rekonstruiert werden, um eine quantitativ korrekte Auswertung der PET-Daten zu gewährleisten.
  • Open Access LogoAbstract in refereed journal
    Nuklearmedizin 53(2014), A102
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland

Publ.-Id: 20208 - Permalink


Asphericity as a measure of spatial heterogeneity is superior to SUVmax change as a predictor of therapy outcome in FDG-PET of patients with head and neck cancer
Hofheinz, F.; Zöphel, K.; Lougovski, A.; Oehme, L.; Beuthien-Baumann, B.; Maus, J.; Steffen, G.; Buchert, R.; Apostolova, I.; Kotzerke, J.; van den Hoff, J.;
Ziel/Aim:
The prognostic value of SUV is unsatisfactory in head and neck carcinoma. The aim of the present study was to evaluate a new measure of spatial heterogeneity as prognostic factor in FDG PET investigations of this cancer type.

Methodik/Methods:
We define the asphericity of a lesion as ASP=[1/(36*pi)*S^3/V^2]^(1/3)-1 where S is the lesion's surface and V is it's volume. ASP is a dimensionless number having a simple interpretation: ASP represents the fractional increase of the surface of the lesion relative to the surface of a sphere possessing the same volume (i.e. ASP=0 for a spherical lesion). ASP was evaluated retrospectively in 36 FDG PETs of patients with head and neck squamous cell carcinoma prior to chemoradiotherapy. A second FDG PET/CT was performed one to two weeks after start of therapy. The baseline and interim FDG images of the primary tumor were segmented using the ROVER 3D segmentation tool. The change of SUVmax (dSUVmax) of the primary tumor was computed. ASP was computed in the baseline PET. Kaplan-Meier analysis with respect to overall survival (OAS) was performed for dSUVmax and ASP and were compared by log-rank tests.

Ergebnisse/Results:
Mean OAS was 20.7 month. ASP was prognostic for OAS (p=0.0001), as was dSUVmax but with distinctly lower significance (p=0.023). Higher tumor asphericity was associated with reduced survival. Patients with ASP>25% showed a 2-year OAS rate of 12% compared to 74% in patients with ASP < 25%.

Schlussfolgerungen/Conclusions:
ASP of the pretherapeutic FDG uptake pattern in the primary tumor is predictive for survival of patients with head-and-neck carcinoma. It is superior to changes of SUVmax during therapy. This is remarkable since ASP is derived from a single PET scan prior to therapy, while computation of dSUVmax requires at least two PET measurements. Further investigations are necessary to confirm these preliminary results.
  • Poster
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access LogoAbstract in refereed journal
    Nuklearmedizin 53(2014), A85-A86

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Publ.-Id: 20207 - Permalink


Dosimetrische Evaluation des therapeutischen Potentials von Hg-197m
Freudenberg, R.; Walther, M.; Wunderlich, G.; Kotzerke, J.;
Ziel/Aim:
Hg-197m emittiert beim Zerfall Photonen und Elektronen. Damit besitzt es Potential zur nuklearmedizinischen Anwendungen. Während die emittierte Gammastrahlung die Lokalisation ermöglicht, erfolgt durch Elektronen eine lokal begrenzte Dosisdeposition. In Abhängigkeit der Elektronenenergie können damit Läsionen mit Durchmessern bis zu einigen mm therapiert werden. Anhand theoretischer Betrachtungen zur Dosisdeposition erfolgt ein Vergleich mit dem Therapienuklid Lu-177.

Methodik/Methods:
Die Produktion von Hg-197m erfolgt durch Bestrahlung von Gold-Targets am Zyklotron über eine (p,n)-Reaktion. Hg-197m wandelt sich mit einer Halbwertszeit von 23,8 h im Wesentlichen über Hg-197 in stabiles Au-197 um. Die Bildgebungseigenschaften wurden an einer Philips „BrightView“ Gammakamera nachgewiesen, Emissionsspektren mit einem GeLi-Halbleiterdetektor gemessen. Durch Simulationen mit Geant4 wurden Dose-Point-Kernels (DPK) für Hg-197m, Hg-197 und Lu-177 generiert. Weiterhin erfolgten die Schätzung der Dosisdeposition in Läsionen verschiedener Größen sowie ein Vergleich mit MIRD S-Werten.

Ergebnisse/Results:
Die DPK zeigen für Hg-197m und Hg-197 bei einem radialen Abstand < 270 μm eine 10-fach höhere Dosisdeposition im Vergleich zu Lu-177 sowie einen 5-fach höheren Dosiseintrag > 1 mm infolge der intensiveren Photonenemission. Im Bereich dazwischen dominiert die β--Dosisdeposition durch Lu-177. Für eine Läsion mit 10 g resultiert eine 1,9-fach höhere Tumordosis durch Hg-197m bei gleicher Zerfallszahl, bei Komplettzerfall beträgt die zu erwartende Dosis 0,6 Gy/MBq für Hg-197m und 2 Gy/MBq für Lu‑177.

Schlussfolgerungen/Conclusions:
Die Eignung von Hg-197m für nuklearmedizinische Zwecke konnte gezeigt werden, die erreichbaren Dosen liegen in der Größenordnung von Lu-177. Die Synthese neuer Radiopharmaka kann vielversprechende neue Behandlungskonzepte ermöglichen. Zusätzlich ist infolge des hohen linearen Energietransfers der Auger-Elektronen von Hg-197 nach DNA-Bindung eine vermehrte Induktion von Doppelstrangbrüchen zu erwarten.
  • Poster
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access LogoAbstract in refereed journal
    Nuklearmedizin 53(2014), A79

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Publ.-Id: 20206 - Permalink


Radiopharmacology of an Anti-CEA Monoclonal Antibody-l-RNA / l-DNA Duplex Pretargeting System
Bergmann, R.; Schlesinger, J.; Koezle, I.; Förster, C.; Klussmann, S.; Vonhoff, S.; Pietzsch, H.-J.; Pietzsch, J.; Wüst, F.; Behrsin, O.; Micheel, B.; Steinbach, J.;
Ziel/Aim:
This current study is aimed at demonstrating of the applicability of l‑oligonucleotides as a novel recognition system for pretargeting using a radiolabeled 17mer l‑DNA and complementary l‑RNA bound to microspheres and an antibody as targeting vector.

Methodik/Methods:
Small animal PET, biodistribution and metabolite studies of Ga-68 and Y-86-labeled L-DNA were carried out in rats and mice. Hybridization in vivo was demonstrated through cl‑RNA-modified microspheres trapped in the lungs and injection of complementary Ga-68-labeled 17mer l‑DNA. Tumor accumulation and pharmocokinetics in the human colon carcinoma models LS174T (n=10) and LoVo (n=2) tumors on NMRI nu/nu mice were evaluated with a 17mer cl‑RNA modified anti CEACAM5 (CEA) antibody aCEA(IG1)D11-DG2 and Ga-68-L-DNA.

Ergebnisse/Results:
The Ga-68- and Y-86-labeled L-DNAs showed typical biodistributions pattern of hydrophylic compounds with fast renal elimination and displayed high metabolic stability in vivo. cl‑RNA-microspheres trapped in the lungs could be visualized (SUV=0.51), i.e. 1.5%ID of the Ga-68-labeled 17mer l‑DNA were hybridized with the cl‑RNA on the microspheres. The LS174T and LoVo tumors were clearly visible with SUVs (median, 25%; 75% percentile) of 0.20 (0.19; 0.31) and 0.18 (0.16; 0.19), respectively. The averaged tumor/muscle ratio was 5.4±0.4 by administering the DG2 immunoconjugate first and injection of radiolabeled L-DNA after a 24 h delay.

Schlussfolgerungen/Conclusions:
Preliminary results demonstrate that the recognition system has promising properties for pretargeting in vivo to improve molecular imaging and therapy of solid tumors.
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access LogoAbstract in refereed journal
    Nuklearmedizin 53(2014), A49

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Publ.-Id: 20205 - Permalink


Incorporation of position dependent detection probability into a tube-of-response based model for system matrix calculation in 3D PET imagereconstruction
Lougovski, A.; Maus, J.; Hofheinz, F.; Schramm, G.; van den Hoff, J.;
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 by a cylindrical tube of response (TOR) whose diameter matches the size of the detector crystals. We now present a refined model which takes into account solid angle effects and position dependent detection efficiency across the crystal surface by using a TOR with a position-variant density.

Methodik/Methods:
We model the detection efficiency across the crystal surface as a radially symmetric function (superposition of two error functions) which leads to a TOR with a variable radial density. Additionally accounting for the solid angle effects results in a further modification of the TOR density that also varies in the axial direction. Consequently, the density-weighted VOI between TOR and spherical voxel now depends not only on the distance between the center of spherical voxel and line of TOR but also on the axial position along the TOR. The new model was integrated into our Tube-Of-Response High Resolution OSEM Reconstruction (THOR) and evaluated using a cylindrical phantom with spherical inserts. We have investigated several figures of merit (reconstructed spatial resolution, noise level, extend of Gibbs artifacts) and compared them between the original and modified TOR models.

Ergebnisse/Results:
The modified model maintains the high spatial resolution already demonstrated for the original TOR approach while showing an improved noise characteristics and reduction of residual Gibbs artifacts. The improvement of image quality overall is only modest.

Schlussfolgerungen/Conclusions:
The proposed modification of the TOR model for on-the-fly system matrix computation allows more accurate modelling of the scanner geometry and event detection and leads to reduced noise levels and Gibbs artifacts in the reconstructed image. However, it noticeably increases reconstruction times in comparison to the original model.
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access LogoAbstract in refereed journal
    Nuklearmedizin 53(2014), A35-A36

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Publ.-Id: 20204 - Permalink


Detektionraten von Skelettmetastasen neuroendokriner Tumore (NET) im F18-NaF-PET und MRT am PET/MR im Vergleich zur Somatostatin-Rezeptor-Szintigraphie (SSRS)
Beuthien-Baumann, B.; Platzek, I.; Strumpf, A.; Schramm, G.; Zessin, J.; van den Hoff, J.; Kotzerke, J.;
iel/Aim:
NET weisen in fortgeschrittenen Stadien häufig Skelettmetastasen auf. Die Skelettszintigraphie detektiert Metastasen die eine Alteration der Knochenmatrix ausgelöst haben; Knochenmarkmetastasen werden in der MRT frühzeitig erkannt. Erhöht die Kombination von NaF-PET und MRT bei NET die Detektionsrate ossärer Metastasen?

Methodik/Methods:
Untersucht wurden 15 Patienten (5w/ 10m; mittl. Alter 63 Jahre mit NET (n=12), medull. Schilddrüsen-Ca (n=1) und SSR-pos. Foll. Schilddrüsen-Ca (n=2) mittels F18-NaF-PET sowie MRT am sequenziellen PET/MR (Ingenuity PET/MR, Philips) im Vergleich zum „Goldstandard“ SSRS (Ga68 DOTATOC/ DOTATATE) am PET/CT (Biograph 16, Siemens). Die MRT-Sequenzen bestanden neben dem Schwächungs-MRT (T1 TFE) aus einer sag. Wirbelsäulenaufnahe (T1 TSE n=10), einer cor. Ganzkörperaufnahme (T1TFE n=9), einer DWIBS (n=3). Die Kombination mehrerer MR-Sequenzen wurde bei langen Untersuchungszeiten nicht von allen Patienten toleriert.

Ergebnisse/Results:
Ein Patient wies im SSRS und im NaF eine disseminierte Metastasierung auf. Bei 14 Pat. wurden mittels SSRS 200 Metastasen im Skelett detektiert. Im NaF-PET fanden sich 176 Matchbefunde (88%), in den MRT-Untersuchungen zeigten sich 116 Läsionen (58%). Bei der Betrachtung allein der Wirbelsäulenbefunde (n=105 im SSRS), wurden im NaF 87%, im MRT 63% der WS-Läsionen detektiert. Im MRT zeigten sich 10 WS-Läsionen, die im NaF nicht abgrenzbar waren. Die Zusammenschau von NaF-PET und MRT erleichterte die Differenzierung zwischen Metastase oder degenerativem Befund.

Schlussfolgerungen/Conclusions:
Ausgehend vom „Goldstandard SSRS“ zeigte sich eine hohe Detektionsrate der ossären Metastasen im NaF-PET. Die Detektionsrate mit den durchgeführten MRT-Sequenzen fiel geringer aus, hier wird eine Optimierung der MRT-Sequenzen angestrebt. Die Kombination NaF-PET und MRT erleichtert die Differenzierung zwischen Metastase und Degeneration.
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access LogoAbstract in refereed journal
    Nuklearmedizin 53(2014), A30

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Publ.-Id: 20203 - Permalink


Compensation and evaluation of metal-implant-induced artifacts in MR-based attenuation correction
Schramm, G.; Maus, J.; Hofheinz, F.; Petr, J.; Lougovski, A.; Beuthien-Baumann, B.; Platzek, I.; van den Hoff, J.;
Ziel/Aim:
MR-based attenuation correction (MRAC) using tissue type segmentation suffers from metal-implant-induced artifacts (MAs) in the underlying MR scan. We propose an improved MRAC segmentation algorithm compensating MAs in MR-based attenuation maps (MRMaps) and evaluate the quantitative influence of these artifacts on the reconstructed PET images.

Methodik/Methods:
MA-based cavities in MRMaps are filled by the developed algorithm using a delineation of the patient's body contour that is derived from the PET emission image . PET emission data of 11 patients with MAs (endoprotheses, sternal cerlages) examined in a Philips Ingenuity PET/MR were reconstructed with the vendor-provided method for attenuation correction (MRMap1,PET1) and additionally with our MRAC algorithm (MRMap2,PET2). Both types of MRMaps were visually inspected for segmentation errors. The segmentation errors in MRMap1 were classified into four classes (L1 and L2 artifacts inside the lung, and B1 and B2 artifacts inside the remaining body depending on the assigned attenuation coefficients). The average relative SUV differences (eps_relav) between PET1 and PET2 in all regions showing erroneous attenuation coefficients in MRMap1 were calculated.

Ergebnisse/Results:
MRMap1 showed erroneous attenuation coefficients in regions near metal implants and inside the patient's lung in all 11 patients. In MRMap2, all MA regions were filled with the soft tissue attenuation coefficient and the lung was correctly segmented in all cases. MRMap2 showed small residual segmentation errors in 8 patients. eps_relav was (mean+-sd): (-57+-1)% in B1, (-43+-4)% in B2, (19+-19)% in L1 and (128+-50)% in L2 regions.

Schlussfolgerungen/Conclusions:
MAs severely disturb MR-based attenuation correction and SUV quantification in PET/MR. The developed algorithm is able to compensate for these artifacts, improves SUV quantification accuracy distinctly and is suitable for clinical application.
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access LogoAbstract in refereed journal
    Nuklearmedizin 53(2014), A29

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Publ.-Id: 20202 - Permalink


Development of a novel class of spirocyclic σ1 receptor ligands − structure-affinity relationships and fluorine-18 radiolabeling
Xie, F.; Kniess, T.; Deuther-Conrad, W.; Bergmann, R.; Mamat, C.; Brust, P.; Pietzsch, J.; Steinbach, J.; Jia, H.;
Ziel/Aim:
Two subtypes of sigma (σ) receptors were confirmed. While the expression of σ1 is mainly altered in several brain disorders, both of them are expressed in a number of tumor entities. Some radioligands for imaging of σ1 and σ2 have been developed but most of them suffer from lipophilicity too high for tumor targeting. The aim of this study was to synthesize a series of novel spirocyclic σ1 receptor ligands, and to develop by analyzing structure-affinity relationships a suitable hydrophilic radiotracer with high affinity and selectivity for σ1.

Methodik/Methods:
A series of novel spirocyclic σ1 receptor ligands was designed, synthesized, and characterized. The affinity to σ1 and σ2 receptors was assessed and the most superior compound chosen for radiolabeling with fluorine-18. The logD value of the radiotracer, its stability in vitro and in vivo as well the biodistribution in rats were investigated.

Ergebnisse/Results:
Six spirocyclic derivatives have been synthesized; Ki values were determined to be in the range of 3.26 - 11.2 nM for σ1 and 164.4 - 312.4 nM for σ2. Compound 1 (8-[4-(2-fluoroethoxy)benzyl]-1,4-dioxa-8-azaspiro[4.5]decane; Ki σ1=5.38±0.43 nM, Ki σ2=164±20.4 nM, was selected for fluorine-18 radiolabeling. [18F]1 was prepared by fluoroethylation via a two-step automated procedure in 20% yield after column purification. The radiochemical purity was >99% as determined by HPLC analysis, the specific activity was in the range of 25 - 45 GBq/μmol. The logD value of [18F]1 was determined as 0.81±0.13. [18F]1 was stable in saline, ethanol, and human plasma in vitro for up to 2h. In preliminary experiments an uptake in mice brain of 2.6% ID at 5 min p.i. was detected.

Schlussfolgerungen/Conclusions:
We designed a potential spirocyclic σ1 receptor ligand with high affinity, selectivity, and excellent hydrophilicity. The biological evaluation of the corresponding radiotracer in brain and selected tumor models is ongoing.
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Nuklearmedizinischen Gesellschaft (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access LogoAbstract in refereed journal
    Nuklearmedizin 53(2014), A25

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Publ.-Id: 20201 - Permalink


Radiosynthesis of 5-(2-[18F]fluoroethyl)-sunitinib, an inhibitor of VEGFR-2
Knieß, T.; Kuchar, M.; Pietzsch, J.; Steinbach, J.;
Ziel/Aim:
Sunitinib is a multi-tyrosine kinase inhibitor (TKI) targeting VEGFR, PDGFR and FLT-3. Radiolabeled sunitinib might be suitable probe for monitoring angiogenesis with PET and to facilitate the success of corresponding anti-angiogenic
chemotherapy for the individual patient. For this purpose we developed an fluorine-18 radiolabeled PET tracer, 5-(2-[18F]fluoroethyl)-sunitinib basing on the lead structure of sunitinib.
Methodik/Methods:
The reference compound 5-(2-fluoroethyl)-sunitinib was synthesized by Knoevenagel condensation of 5-(2-fluoroethyl)-indoline-2-one with N-[2-(diethylamino)ethyl]-2,4-dimethyl-5-formyl-1H-pyrrole-3-carboxamide. Two suitable precursors for radiolabeling were obtained by reacting 5-(2-bromoethyl)-substituted sunitinib with AgC7H7SO3 and AgCH3SO3, respectively. In a set of experiments for finding the optimal radiolabeling conditions 4 mg of each
precursor was reacted with [18F]fluoride at a scheduled temperature regime for 20 min in acetonitrile, DMF or DMSO.
Ergebnisse/Results:
In a competition binding assay against VEGFR-2 a Kd value of 9 nM for 5-(2-fluoroethyl)-sunitinib was determined. For radiolabeling with [18F]fluoride the methanesulfonyl-substituted precursor in acetonitrile gave radiochemical yields up to 8%. In large scale synthesis using a TracerLAB (GE) synthesiser 8mg of precursor were reacted with 10 GBq of [18F]fluoride in acetonitrile at 110°C for 12 min. After semi-preparative HPLC purification and SPE separation 115-135 MBq of 5-(2-[18F]fluoroethyl)-sunitinib could be obtained in radiochemical purity > 95% and in a specific activity of 38-62 GBq/[mu]mol.
Schlussfolgerungen/Conclusions:
The new VEGFR-2 targeted radiolabeled probe 5-(2-[18F]fluoroethyl)-sunitinib was successfully synthesized by radiofluorination of the corresponding methanesulfonyl-substituted precursor with [18F]fluoride. The radiotracer can be obtained in high chemical and radiochemical purity in 100 MBq scale.
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access LogoAbstract in refereed journal
    Nuklearmedizin 53(2014), A43-A44

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Publ.-Id: 20200 - Permalink


Comparative investigation of the novel radiotracers (R)- and (S)-[18F]fluspidine for imaging of σ1 receptors by PET
Deuther-Conrad, W.; Becker, G.; Patt, M.; Donat, C. K.; Kranz, M.; Stittsworth, S.; Holl, K.; Habermann, B.; Fischer, S.; Wenzel, B.; Mishchenko, L.; Hesse, S.; Steinbach, J.; Wünsch, B.; Lever, S. Z.; Sabri, O.; Brust, P.;
Objectives
Sigma1 receptor (σ1), found in plasma, mitochondrial and endoplasmic reticular membranes and involved in many cellular functions of the endocrine, immune, and nervous systems, is a promising target for novel concepts in diagnostics and therapy of cancer and brain diseases. To support such research by molecular imaging of σ1, we have comparatively evaluated the 18F-labelled (R)- and (S)-enantiomers of the σ1 ligand fluspidine in pigs.

Methods
(R)- and (S)-[18F]fluspidine were synthesized from enantiopure tosylate precursors with high specific activities (650-870 GBq/µmol) and radiochemical purity (>99%). Brain pharmacokinetics were investigated by dynamic PET studies in anaesthetized pigs under baseline (n=3 per enantiomer) and blocking conditions (n=3 per enantiomer) using σ1 selective SA4503. SUVs were calculated for 24 MR-defined brain regions. One- and two-tissue compartment modeling was applied to calculate individual rate constants, total distribution volumes (VT) and binding potentials of (R)- and (S)-[18F]fluspidine. Furthermore, VT was estimated from graphical Logan plot analyses. Organ doses (ODs) and effective doses (ED) of both radiotracers were determined in CD-1 mice and an extended single dose toxicity study of (S)-fluspidine was performed in SPRD rats.

Results
(R)- and (S)-[18F]fluspidine displayed significantly different brain uptake kinetics. Although initial SUVs were similar (R)-[18F]fluspidine showed higher values (60-150%) at 120 min p.i. Brain distribution in pigs correlated with brain distribution in CD-1 mice (Fig. 1). SA4503 reduced SUVs and k3 of both radiotracers by ~65% and 70-95%, respectively, in almost all brain regions (Fig. 1B, C), while effects on k4 differed region-specific. VT values estimated by full nonlinear kinetic and Logan analyses correlated highly and revealed also a significant decrease in all brain regions for both radiotracers by SA4503. The expected EDs of (R)- and (S)-[18F]fluspidine to humans are 31 and 28 µSv/MBq, respectively, and up to 620 µg (S)-fluspidine/kg no test item related effects were observed in the toxicity study.

Conclusion
Both [18F]fluspidine enantiomers appear to be suitable for σ1 imaging in human brain. The different pharmacokinetics of (R)-[18F]fluspidine and (S)-[18F]fluspidine may be translated into diagnostic imaging of different pathological conditions such as degenerative as well as cancerous processes.

Fig. 1: Distribution of [18F]fluspidine binding sites in brain. (A) Ex vivo autoradiography of a sagittal rat brain slice obtained at 45 min after intravenous injection of [18F]fluspidine. (B, C) Sagittal brain PET images acquired as summed data from 0-20 min after intravenous injection of piglet with (S)-[18F]fluspidine under baseline conditions (B) or under blocking with SA4503 (C).
  • Poster
    The 10th International Symposium on Funktional NeuroReceptor Mapping of the Living Brain, 21.-24.05.2014, Amsterdam, The Netherlands

Publ.-Id: 20199 - Permalink


Implementation of a fast running full core pin power reconstruction method in DYN3D
Gomez, A.; Sanchez Espinosa, V. H.; Kliem, S.; Gommlich, A.;
This paper presents a substantial extension of the pin power reconstruction (PPR) method used in the reactor dynamics code DYN3D with the aim to better describe the heterogeneity within the fuel assembly during reactor simulations. The flexibility of the new implemented PPR permits the local spatial refinement of one fuel assembly, of a cluster of fuel assemblies, of a quarter or eight of a core or even of a whole core. The application of PPR in core regions of interest will pave the way for the coupling with sub-channel codes enabling the prediction of local safety parameters. One of the main advantages of considering regions and not only a hot fuel assembly (FA) is the fact that the cross flow within this region can be taken into account by the subchannel code. The implementation of the new PPR method has been tested analysing a rod ejection accident (REA) in a PWR minicore consisting of 3x3 FA. Finally, the new capabilities of DNY3D are demonstrated by the analysing a boron dilution transient in a PWR MOX core and the pin power of a VVER-1000 reactor at stationary conditions.
Keywords: pin power reconstruction; DYN3D; VVER, PWR; whole core pin power predictions, REA, boron dilution

Publ.-Id: 20198 - Permalink


Application of Sub-second Annealing for Diluted Ferromagnetic Semiconductors
Zhou, S.; Bürger, D.; Schmidt, H.;
The dilute ferromagnetic semiconductor GaMnAs provides a great promise for its application in spintronics, which combines two degrees of freedom: charge and spin. Mn ions which substitute Ga sublattice sites provide both local magnetic moments and itinerant holes. The magnetic properties of GaMnAs can be controlled by manipulating free carriers via electrical gating. However, the preparation of ferromagnetic GaMnAs presents a big challenge due to the low solubility of Mn in GaAs. To overcome the low solid solubility limit of transition metal dopants in semiconductors, one needs highly nonequilibrium methods to introduce enough dopants and a short-time annealing to activate them. Both ion implantation and pulsed-laser (or flash-lamp) annealing occur far enough from thermodynamic equilibrium conditions. Ion implantation introduces enough dopants. The subsequent short-time annealing deposits energy in the near-surface region to drive a rapid liquid-phase epitaxial growth. Such a nonequilibrium process maintains the supersaturation induced by ion implantation. In this chapter, we review the application of sub-second annealing in the activation of Mn implanted GaAs as well as GaP.
  • Book chapter
    Wolfgang Skorupa, Heidemarie Schmidt: Subsecond Annealing of Advanced Materials: Annealing by Lasers, Flash Lamps and Swift Heavy Ions (Springer Series in Materials Science), Switzerland: Springer, 2014, 978-3-319-03130-9, 297-314
    DOI: 10.1007/978-3-319-03131-6_15

Publ.-Id: 20196 - Permalink


Sub-nanosecond Thermal Spike Induced Nanostructuring of Thin Solid Films Under Swift Heavy Ion (SHI) Irradiation
Ghosh, S.; Kumar, H.; Singh, S. P.; Srivastava, P.; Kabiraj, D.; Avasthi, D. K.; Bürger, D.; Zhou, S.; Mücklich, A.; Schmidt, H.; Stouquert, J. P.;
The interaction between swift heavy ions (SHI) and a solid has been identified as one of the important physical processes to generate or modify nanostructures in thin solid films. The large part of the energy which is deposited in the electronic subsystem of a material by SHI is known as electronic energy loss and gets coupled to the lattice subsystem in a complex way resulting in a transient (picoseconds to sub-nanosecond) thermal spike within a few nanometer diameter region of the thin solid film along the ion path. The temperature of this narrow zone may raise up to 1000 K or more during this time. This transient heating process is known as lattice thermal spike and can be used as a tool to engineer materials down to the nanoscale. Here we address two important consequences of lattice thermal spike; (i) elongation of metal nanoparticles embedded in dielectric thin films and (ii) generation of a-Si/c-Si nanostructures in a silicon nitride matrix.

(i) Metal nanoparticles embedded in a thin film matrix belong to a class of materials that has potential applications as optical and magnetic sensors, storage, memory devices, field emission display etc. The nanoparticle size and shape, orientation, inter-particle separation and dielectric constant of the surrounding matrix are the crucial parameters which control their properties. Thermal spike generated by SHI in these nanoparticles and surrounding matrix can be used as a unique tool to tailor the shape of the embedded nanoparticles, eventually modifying the physical properties of these materials. Metal nanoparticles, which are mostly spherical in shape in as grown films, get elongated along the direction of SHI due to thermal spike induced melting and stress. After a brief introduction of some fundamental aspects and synthesis of these films, a detailed discussion on elongation of nearly spherical Ni nanoparticles embedded in SiO2 thin film matrix under 120 MeV Au ion irradiation is made. Various physical parameters influencing the shape modification of nanoparticles under the framework of thermal spike model are discussed.

(ii) a-Si/c-Si nanostructures embedded in different Si-based dielectric matrix have attracted researchers because of their potential application in low-cost Si-based optoelectronic devices. We report here the response of in-situ formed Si-nanostructures embedded in a Si-rich hydrogenated amorphous silicon nitride matrix to 100 MeV Ni8+ ions irradiation. Si-rich a-SiN x :H films have been prepared by Hg-sensitized Photo Chemical Vapor Deposition. Presence of elemental Si was confirmed from X-ray photoelectron spectroscopy. Irradiation with a fluence of 5×1012 ions/cm2 under normal incidence at room temperature leads to dissolution of these Si-nanostructures. However, irradiation with a relatively higher fluence of 1×1014 ions/cm2 enhances the nucleation and leads to the formation of amorphous Si-nanostructures in the film. In addition, at the surface a novel effect i.e. partial crystallization of Si-nanostructures along the beam direction is observed. The results are explained on the basis of thermal spike model.
  • Book chapter
    Wolfgang Skorupa, Heidemarie Schmidt: Subsecond Annealing of Advanced Materials: Annealing by Lasers, Flash Lamps and Swift Heavy Ions (Springer Series in Materials Science), Switzerland: Springer, 2014, 978-3-319-03130-9, 107-121
    DOI: 10.1007/978-3-319-03131-6_6

Publ.-Id: 20195 - Permalink


Nanonet Formation by Constitutional Supercooling of Pulsed Laser Annealed, Mn-Implanted Germanium
Bürger, D.; Zhou, S.; Höwler, M.; Ou, X.; Kovacs, G. J.; Reuther, H.; Mücklich, A.; Skorupa, W.; Schmidt, H.;
This subchapter presents interesting aspects of pulsed laser annealing. During this process, a laser pulse incorporates heat in the near surface region of a semiconductor or a metal. If the energy density is high enough, the system may melt near the surface. Because of the large temperature gradient, a very fast recrystallization may lead to novel physical material properties. Here we present interesting aspects of the formation of a Mn-rich nanonet in germanium. Important physical phenomena are explained in detail. The material has been fabricated by pulsed laser annealing of Mn implanted Ge wafers with a pulse duration of 300 ns. Due to a segregation instability during recrystallization, Mn segregates at the liquid-solid interface and an approximately 40 nm thick Ge:Mn surface layer is strongly enriched with Mn. Transmission electron microscopy plan-view images reveal a percolating Mn-rich nanonet after etching the top 10 nm surface layer. Hysteretic anomalous Hall effect has been observed up to 30 K, but it vanishes after etching away the 40 nm thick Mn-rich Ge:Mn layer. The nanonet seems to support the correlation between magnetization and hysteretic Hall resistance. Intrinsic charge carrier scattering in the threads or vertices of the Ge:Mn nanonet may lead to the observed anomalous Hall effect. In the outlook the nanonet formation is revealed for supercooled Mn-implanted Si.
  • Book chapter
    Wolfgang Skorupa, Heidemarie Schmidt: Subsecond Annealing of Advanced Materials: Annealing by Lasers, Flash Lamps and Swift Heavy Ions (Springer Series in Materials Science), Switzerland: Springer, 2014, 978-3-319-03130-9, 15-33
    DOI: 10.1007/978-3-319-03131-6_2

Publ.-Id: 20194 - Permalink


Protein Conformational Rearrangement induced by the modulation of vibrational modes
Lorincz, I. Z.; Schay, G.; Rauscher, A. A.; Kellermayer, M. S. Z.; Gensch, M.; Malnasi-Csizmadia, A.;
We succeeded to induce a specific conformational change in a protein by infrared laser excitation and proved that the reaction was a non-thermal effect. An alpha helical – beta sheet structural rearrangement of an intrinsically fluorescent protein, LSSmOrange was monitored through its fluorescence intensity change upon irradiation with a free electron IR laser. The picosecond timescale IR pulse caused a reversible structural rearrangement of LSSmOrange on the second timescale. We found that the structural rearrangement was induced by a single IR photon with a very low, less than 10-6 photon efficiency and the maximum effect was detected at 1033 cm-1 IR irradiation. The IR induced reaction is not a trivial thermal effect because 1. the IR pulse increases the fluorescence of LSSmOrange whereas temperature jump decreases it, 2. its magnitude depends on the wavelength of the IR pulse. Based on the Arrhenius plots of the IR induced conformational change and its relaxation, we found that the IR excitation increases the free energy of the alpha-helical structure dominated state by 12 kJ/mol. Since this energy shift is exactly equal to the energy of the IR photon, we concluded that there are highly efficient energy flow pathways between the vibrational modes in the protein as it is indicated by recent theoretical calculations. These results may open a new horizon towards the direct investigation of the functional role of vibrational modes in proteins.
  • Lecture (Conference)
    PepCon 2014 - BIT's 7th Annual Protein and Peptide Conference, 25.-28.04.2014, Dalian, China

Publ.-Id: 20193 - Permalink


64Cu-markierte Upconversion-Nanopartikel und ihr Potenzial für die multimodale Bildgebung von Tumoren
Hesse, J.; Barreto, J. A.; Graham, B.; Geipel, G.; Spiccia, L.; Steinbach, J.; Stephan, H.;
Das Interesse an der medizinischen Nutzung von Nanomaterialien ist insbesondere auf deren einzigartigen, strukturbedingten Eigenschaften zurückzuführen. Basierend auf unterschiedlichen Materialien, wie Polymeren, anorganische oder organisch-anorganische Hybridsubstanzen, werden Nanoteilchen auf ihre Anwendbarkeit in komplexen biologischen Systemen untersucht. Upconversion(UC)-Nanopartikel zeigen hierbei ein vielversprechendes Potenzial und besitzen bei einer gut abgestimmten Dotierung des anorganisch, kristallinen Wirtsgitters mit ausgewählten Seltenerd-Metallen eine sehr effiziente Lumineszenz[1]. Damit eröffnet sich speziell deren Nutzung für die optische Bildgebung, welche die Aufklärung von Prozessen auf zellulärer Ebene gestattet. Gleichzeitig erlaubt die Oberflächenstruktur der Partikel eine Mehrfachfunktionalisierung mit Chelatoren für die Bindung von Radiometallnukliden für PET und SPECT und tumoraffinen Einheiten wie beispielsweise Peptiden.
Wir berichten über die Synthese und Fluoreszenz-eigenschaften von ultrakleinen (< 10 nm) UC-Nanopartikeln auf der Basis von NaYF4: Yb3+, Er3+ und deren Umhüllung mit verschiedenen Polymeren zur Erzeugung wasserlöslicher und biokompatibler Materialien. Diese Partikel wurden mit einem Picolyl-Derivat des makrocyclischen Liganden 1,4,7-Triazacyclononan funktionalisiert. Der Chelator dient zur Radiomarkierung der Partikel mit 64Cu2+, was die Anwendung eines zusätzlichen bildgebenden Verfahrens, der Positronen-Emissions-Tomographie (PET), er-möglicht. Es werden weiterhin Synthesestragien zur Einführung von tumoraffinen Einheiten auf der Oberfläche der UC-Nanopartikel vorgestellt, die eine Adressierung des auf vielen Tumoren überexprimierten Epidermal Growth Factor Receptors (EGFR) gestatten.
[1] Mader, H. S., Kele, P., Saleh, S. M., Wolfbeis, O. S., Curr. Opin. Chem. Biol. 2010, 14, 582-596
  • Lecture (Conference)
    GDCh-Wissenschaftsforum Chemie 2013, 01.-04.09.2013, Darmstadt, Deutschland

Publ.-Id: 20192 - Permalink


High-Speed PIXE: A spatially resolved PIXE setup at the 6 MV Tandem accelerator
Buchriegler, J.; von Borany, J.; Hanf, D.; Munnik, F.; Nowak, S. H.; Renno, A. D.; Scharf, O.; Ziegenrücker, R.;
kein Abstract eingereicht
Keywords: High-Speed PIXE, SLcam, Colour X-Ray Camera
  • Invited lecture (Conferences)
    SLcam(R) User Workshop, 16.01.2014, Berlin, Deutschland

Publ.-Id: 20191 - Permalink


Cryo-Fluoreszenzspektroskopie – Eine innovative Technik für die Wissenschaft
Steudtner, R.; Großmann, K.;
Fluoreszenzmikroskopische und fluoreszenzspektroskopische Untersuchungen finden in der Biologie, Medizin, Materialprüfung sowie Geowissenschaften eine breite Anwendung. Dabei spielt die chemische Charakterisierung und die Lokalisierung der verschiedensten Analyte mittels analytischer und bildgebender Verfahren eine wichtige Rolle. Die Analyse von Schwermetallen insbesondere von Radionukliden und seltenen Erden in natürlichen Systemen soll an Hand einer verbesserten Fluoreszenzanalytik bei tiefen Temperaturen erweitert werden. Durch die Weiterentwicklung der Fluoreszenzspektroskopie bei tiefen Temperaturen werden am Helmholz-Zentrum Dresden-Rossendorf nicht nur umweltanalytisch relevante Fragestellung im Bereich der Ressourcenökologie sondern auch verschiedenste Aufgaben aus dem Bereich der medizinischen Forschung bearbeitet.
Durch die Unterstützung der Max-Buchner-Forschungsstiftung konnten wir drei entscheidende Ergebnisse erzielen, welche für zukünftige Projekte die nötige wissenschaftliche Grundlage bieten.
1. Aufbau eines dauerhaften spektroskopischen Tieftemperaturmessplatzes zum schnellen und sensitiven Nachweis von Uran in diversen Umweltproben (Wasser- und Bodenproben)
2. Unterstützung beim Aufbau eines mikroskopischen Tieftemperaturmess-platzes, der mikroskopische Untersuchungen bei -253°C mit bis zu 630 facher Vergrößerung erlaubt.
3. Erste erfolgreiche Messungen mit dem spektroskopischen und mikroskopischen Aufbau im Bereich der Umweltanalytik sowie an verschiedenen medizinisch relevanten Anwendungen.
Langfristig zielen die Arbeiten auf die direkte Visualisierung der Analyten bei tiefen Temperaturen in biologischen und medizinischen Medien in Kombination mit fluoreszenzspektroskopischen Daten, welche zusätzliche molekulare Informationen über die der Mikroumgebung der Chromophore liefern, ab.
  • Open Access LogoCITplus 10(2014), 60-62
  • Lecture (Conference)
    ProcessNet-Jahrestagung, 30.09.-02.10.2014, Aachen, Deutschland

Publ.-Id: 20190 - Permalink


New insight into self-irradiation effects on local and long-range structure of uranium-americium mixed oxides (through XAS and XRD)
Lebreton, F.; Martin, P. M.; Horlait, D.; Bes, R.; Scheinost, A. C.; Rossberg, A.; Delahaye, T.; Blanchart, P.;
Uranium-americium mixed oxides could be used as transmutation targets to lower Am inventory in spent nuclear fuels. Due to 241Am activity, these materials are subjected to α-self-irradiation which provokes structural damages. Previous studies on U-Am mixed oxides gave first insight into α-radiation tolerance of these compounds, but have never been carried out for more than a year, whereas Am-bearing targets might be stored up to a few years between fabrication and irradiation. In this work, we study effects of self-irradiation on the structure of U1-xAmxO2± solid solutions (x = 0.15 and 0.2) aged of 3 to 4 years. Especially, X-ray diffraction and X-ray absorption spectroscopy are combined to observe these effects from both long-range and local perspectives. Obtained results show that the fluorite-type structure of U-Am mixed oxides withstands 241Am α-irradiation without major damage. Even though an increase of interatomic distance and structural disorder was observed during the first year of storage, the present results show that no further evolution occurs. Furthermore, comparison between long-range and local evolution suggests that α-self-irradiation-induced defects are mainly located in low-ordered domains. The major difference between samples was even found to be related to differences in fabrication conditions. Based on these results, no detrimental factors have been identified for several-year storage of U-Am transmutation targets before irradiation.
Keywords: nuclear fuel transmutation uranium americium EXAFS XRD

Publ.-Id: 20189 - Permalink


Sorption data: Ways from a plain collection to recommended values
Bok, F.; Richter, A.; Brendler, V.;
For geochemical modeling of scenarios for the disposal of hazardous radioactive and (chemo)toxic waste, comprehensive and consistent thermodynamic data are required as well as sorption data for the surrounding host rocks. Whereas there are several projects running world-wide to arrive at the comprehensive and consistent thermodynamic data base for the aqueous phase and forming solids, the situation is much worse concerning the reactions on the mineral-water interface. For important processes such as sorption, ion exchange or surface precipitation incompleteness and inconsistencies, restricted ranges of variation (temperature, density, pressure, ionic strength) are abundant leading to hardly comparable results in geochemical modeling.
RES³T – the Rossendorf Expert System for Surface and Sorption Thermodynamics (http://www.hzdr.de/res3t) – is a free-for-use digitized thermodynamic sorption database utilizing surface complexation models (SCM). It is mineral-specific and can therefore also be used for complex real systems such as rocks or soils. Data records comprise of mineral properties, specific surface area values, characteristics of surface binding sites and their protolysis, sorption ligand information, and surface complexation reactions. An extensive bibliography is included, providing links not only to the above listed data items, but also to the primary reference. Currently efforts started to combine RES³T with the thermodynamic database THEREDA (http://www.thereda.de) to provide a comprehensive and consistent database for a holistic geochemical modeling.
Sorption speciation calculations of radionuclides on mineral surfaces will be presented, showing the actual consequences of inconsistent and scattered sorption data that can be found in literature, as well as the possibilities of the RES³T database for calculating radionuclide sorption onto complex geologic formations, e.g. the overburden of a nuclear waste disposal. Generally, RES³T proved to be a powerful tool for identifying data gaps for combinations of minerals and sorbing radionuclide essential for the risk assessment of waste disposals or in accident analysis.
Keywords: RES³T, Rossendorf Expert System for Surface and Sorption Thermodynamics, database, THEREDA
  • Invited lecture (Conferences)
    248th ACS National Meeting, 10.-14.08.2014, San Francisco, USA

Publ.-Id: 20188 - Permalink


Search for a live supernova signature of 60Fe in deep-sea sediments and a new half-life measurements of 60Fe
Wallner, A.; Feige, J.; Fifield, L. K.; Golser, R.; Kutschera, W.; Merchel, S.; Rugel, G.; Schumann, D.; Tims, S.; Winkler, S.; Sterba, J.; Bichler, M.;
60Fe (2.6 My) is one of the most versatile nuclides in astrophysics. Live 60Fe was identified in the Galaxy. Its stellar production requires neutron densities available only in explosive Supernovae (SNe) or SuperAGB stars. 60Fe is also found in meteorites and indirectly via 60Ni anomalies. Fresh nucleosynthetic products may enter the Solar System (SS) trapped in cosmic dust. Hence, nearby SNe might deposit traces on Earth and since it has negligible terrestrial production, 60Fe is an ideal candidate to search for recent SNe. However, detection requires sensitivities of 60Fe/Fe~10-15 and 60Fe-AMS faces interference from stable 60Ni. So far only TU Munich, combining a MP tandem with a gas-filled magnet, measures 60Fe routinely as los as ~10-16. This group discovered live 60Fe in a deep-sea crust indicating that SNe-isotopes found their way to Earth 2-3 My ago [1]. Work is ongoing at TUM to validate this finding in other archives [2,3]. Further, Rugel et al. [4] measured a half-life substantially longer than previously recommended. We have started a similiar program at the ANU using the 14UD accelerator and a split-pole magnetic spectrograph converted into a gas-filled magnet. A substantial beamtime devoted to 60Fe has resulted in an exceptional sensitivity below 10-16. We have searched for a SN-signal in 3 deep-sea sediment cores (indian Ocean) [5]. We will present exciting new data for 60Fe with high time resolution and will relate it to potantial exposure of the SS to recent SNe. In addition, we re-measured in an independent approach the 60Fe half-life via AMS measurements of the 60 Fe/55Fe ratio.
[1] Knie et al. PRL93 (2004)
[2] Ludwig et al. this conf.
[3] Fimiani et al. LPSC 1659 (2012)
[4] Rugel et al. PRL103 (2009)
[5] Feige et al. this conf.
Keywords: accelerator mass spectrometry, supernova, radionuclide
  • Lecture (Conference)
    13th International Conference on Accelerator Mass Spectrometry (AMS-13), 24.-29.08.2014, Aix-en-Provence, France

Downloads:

Publ.-Id: 20187 - Permalink


Paramagnetic Decoration of DNA origami Nanostructures by Eu3+ Coordination
Opherden, L.; Oertel, J.; Barkleit, A.; Fahmy, K.; Keller, K.;
The folding of DNA into arbitrary two- and three-dimensional shapes, called DNA origami, represents a powerful tool for the synthesis of functional nanostructures. Here, we present the first approach toward the paramagnetic functionalization of DNA origami nanostructures by utilizing post-assembly coordination with Eu3+ ions. In contrast to the usual formation of toroidal dsDNA condensates in the presence of trivalent cations, planar as well as rod-like DNA origami maintain their shape and monomeric state even under high loading with the trivalent lanthanide. Europium-coordination was demonstrated by the change in Eu3+ luminescence upon binding to the two DNA origami. Their natural circular dichroism in the Mg2+- and Eu3+-bound state was found to be very similar to that of genomic DNA, evidencing little influence of the DNA origami superstructure on the local chirality of the stacked base pairs. In contrast, the magnetic circular dichroism of the Mg2+-bound DNA origami deviates from that of genomic DNA. Furthermore, the lanthanide affects the magnetic properties of DNA in a superstructure-dependent fashion, indicative of the existence of superstructure-specific geometry of Eu3+ binding sites in the DNA origami that are not formed in genomic DNA. This simple approach lays the foundation for the generation of DNA origami with taylored lanthanide-specificity. Such systems do not require covalent modifications and can be used for the magnetic manipulation of DNA nanostructures or for the paramagnetic alignment of molecules in NMR spectroscopy.
Keywords: magnetic circular dichroism molecular alignment lanthanide NMR spectroscopy

Publ.-Id: 20186 - Permalink


CFD based approach for modeling direct contact condensation heat transfer in two-phase turbulent stratified flows
Apanasevich, P.; Lucas, D.; Beyer, M.; Szalinski, L.;
This paper describes a CFD based strategy for the modeling of stratified two-phase flows with heat and mass transfer across a moving steam-water interface due to direct contact condensation. Such flows have been of major importance for example in connection with the analysis of nuclear reactor safety systems, in particular during two-phase Pressurized Thermal Shock (PTS) scenarios. The approach is based on the two-fluid phase-average model. The interfacial friction was modeled by using an Algebraic Interfacial Area Density (AIAD) framework where the drag coefficient is a function of the local flow characteristics. To show the impact of the modeling of interfacial friction the simulation with the AIAD model was compared with a simulation where a constant drag coefficient of 0.44 was used in the whole domain. For the modeling of interfacial heat and mass transfer two correlations for the water heat transfer coefficient based on the penetration theory were utilized. The CFD simulations were validated against a steady-state TOPFLOW-PTS steam-water experiment. In the experiment, very detailed temperature measurements were conducted using special thermocouple lances and infrared thermography. Total condensation rate was determined indirectly by using three different methods. The simulations have depicted that the results obtained with the AIAD model are considerably closer to the experimental observations than the results obtained with the constant drag coefficient. It was also shown that a correct prediction of condensation rates is very important for prediction of the temperature field. In general, the simulations of the TOPFLOW-PTS steam/water experiment with condensation have revealed that Reynolds Averaged Navier-Stokes method can be applied for the simulation of two-phase stratified flows with rather large free surfaces and interfacial heat transfer. However, the modeling of turbulent interfacial heat transfer should be improved.
Keywords: computational fluid dynamics, stratified two-phase flow, pressurized thermal shock, interfacial heat and mass transfer, direct contact condensation, TOPFLOW-PTS experiments

Publ.-Id: 20185 - Permalink


Investigation of vertical gas-liquid pipe flows using ultrafast X-ray tomography – An overview of methods, measurement series and previous results
Banowski, M.; Lucas, D.; Beyer, M.; Szalinski, L.; Hoppe, D.; Hampel, U.;
In this presentation, methods, measurement series and previous results of upward, counter-current as well as downward gas-liquid flows at the vertical titanium pipe of the TOPFLOW test facility are shown.
  • Lecture (Conference)
    German CFD Network of Competence, Workshop, 19.-20.03.2014, München-Garching, Deutschland

Publ.-Id: 20184 - Permalink


Systematic investigation of terahertz-induced excitonic Rabi splitting
Teich, M.; Wagner, M.; Stehr, D.; Schneider, H.; Helm, M.; Böttge, C. N.; Klettke, A. C.; Chatterjee, S.; Kira, M.; Koch, S. W.; Khitrova, G.; Gibbs, H. M.;
Weak near-infrared and strong terahertz excitation are applied to study excitonic Rabi splitting in (GaIn)As/GaAs quantum wells. Pronounced anticrossing behavior of the split peaks is observed for different terahertz intensities and detunings relative to the intra-excitonic heavy-hole 1s–2p transition. At intermediate to high electric fields the splitting becomes highly asymmetric and exhibits significant broadening. A fully microscopic theory is needed to explain the experimental results. Comparisons with a two-level model reveal the increasing importance of higher excitonic states at elevated excitation levels.
Keywords: QW, FEL, Autler-Townes, THz

Publ.-Id: 20183 - Permalink


One-Group Cross-Section Generation for Monte Carlo Burnup Codes: Multigroup Method Extension and Verification
Kotlyar, D.; Fridman, E.; Shwageraus, E.;
Allowing Monte Carlo (MC) codes to perform fuel cycle calculations requires coupling to a point depletion solver. In order to perform depletion calculations, one-group (1-g) cross sections must be provided in advance. This paper focuses on generating accurate 1-g cross section values using Monte Carlo transport codes.
The proposed method is an alternative to the conventional direct reaction rate tally approach, which requires substantial computational effort. The method presented here is based on the multi-group (MG) approach, in which pre-generated MG sets are collapsed with MC calculated flux. In our previous studies, we showed that generating accurate 1-g cross sections requires their tabulation against the background cross section (σ0) to account for the self-shielding effect in unresolved resonance energy range. However, in previous studies, the model used for calculation of σ0 was simplified by relying on user specified Bell and Dancoff factors.
This work demonstrates that 1-g values calculated under the previous simplified model assumptions may not always agree with the directly tallied values. More specifically, the assumption is not universally applicable to the analysis of wide spectrum of reactor systems and may be inaccurate when the number of energy groups is reduced (i.e. from tens of thousands to hundreds of groups). Therefore, the original background cross section model was extended by implicitly accounting for the Dancoff and Bell factors. The method developed here reconstructs the correct value of σ0 by utilizing statistical data generated within the MC transport calculation by default. The proposed method was implemented in BGCore code system. The 1-g cross section values generated by BGCore were compared with those tallied directly from the MCNP code. Very good agreement in the 1-g cross values was observed. The method does not carry any additional computational burden and it is universally applicable to the analysis of thermal as well as fast reactor systems. Adopting this MG methodology, which accounts for self-shielding, allows generating highly accurate cross sections even for significantly reduced number of energy groups (hundreds vs. tens of thousands). This reduction considerably improves the computational efficiency which makes feasible the analysis of large scale reactor problems.
Keywords: Coupled Monte Carlo codes; BGCore; Multi group; One-group cross sections; Background cross section

Publ.-Id: 20182 - Permalink


Experimente zu vertikalen Dampf-Wasser-Rohrströmungen mit ultraschneller Röntgentomographie
Banowski, M.; Lucas, D.; Beyer, M.; Hampel, U.;
Gas-Flüssigkeits-Zweiphasenströmungen in Rohrleitungen sind für die Entwicklung und Validierung neuer zweiphasiger CFD-Modelle ein geeigneter generischer Untersuchungsgegenstand. Der Grad an strömungsmorphologischer Komplexität ist relativ hoch, was sich insbesondere in der Ausprägung charakteristischer Strömungsregime mit ihren jeweils spezifischen Impulstransferbeziehungen an der Phasengrenze in Abhängigkeit von Leerrohrgeschwindigkeiten und Stoffwerten äußert. An der TOPFLOW-Versuchsanlage des HZDR werden gegenwärtig umfangreiche experimentelle Studien zu Zweiphasenströmungen in senkrechten Testsektionen für Wasser/Luft- und Wasser/Dampf-Strömungen bis 65 bar Druck durchgeführt. Diese Experimente dienen vordergründig der Erhebung von Messdaten für die CFD-Codeentwicklung. Als Messverfahren kommt in aktuellen Versuchen an einer vertikalen DN50 Testsektion die ultraschnelle Röntgentomographie zum Einsatz. Diese ermöglicht es, den Strömungsquerschnitt mit Bildraten von 2500 Bildern/Sekunde und einer räumlichen Auflösung von etwa 1 mm in zwei jeweils 10 mm entfernten Ebenen abzubilden. Verschiedene Strömungsregime werden durch Wahl der Leerohrgeschwindigkeiten für die Gas- und die Flüssigphase am Versuchsstand eingestellt. Neben der Aufklärung des Strömungsregimes und der Erfassung interessanter Detailstrukturen der Strömung können radiale Gasgehaltsprofile ebenso wie Gasphasengeschwindigkeiten durch automatisierte Auswerteroutinen extrahiert werden. Im Beitrag werden Ergebnisse von Dampf-Wasser-Experimenten zu auf- und abwärtsgerichteten Gleichströmungen bei verschiedenen Druckstufen vorgestellt.
Diese Arbeit wird im Rahmen eines aktuellen Forschungsprojekts, welches vom Bundesministerium für Wirtschaft und Technologie unter der Projektnummer 150 1411 gefördert wird, durchgeführt.
  • Poster
    ProcessNet Jahrestreffen der Fachgruppen Mehrphasenströmungen und Wärme- und Stoffübertragung, 24.-25.03.2014, Fulda, Deutschland

Publ.-Id: 20181 - Permalink


Investigation of Scintillation Detectors for Prompt Gamma Imaging
Römer, K.; Petzoldt, J.; Berthel, M.; Dreyer, A.; Enghardt, W.; Golnik, C.; Hueso-González, F.; Kormoll, T.; Müller, A.; Pausch, G.; Rohling, H.; Schöne, S.; Weinberger, D.; Fiedler, F.;
Characterization of Scintillators with respect to their Application in Prompt Gamma Imaging Systems.
Keywords: Prompt Gamma Imaging, Scintillation Detectors
  • Poster
    OncoRay Retreat 2014, 27.-28.03.2014, Dresden, Deutschland

Publ.-Id: 20180 - Permalink


Experimentelle Untersuchung von aufwärtsgerichteten zweiphasigen Rohrströmungen mit ultraschneller Röntgentomographie
Banowski, M.; Lucas, D.; Beyer, M.; Hampel, U.;
Die Entwicklung von CFD-Modellen zur Berechnung von Zweiphasenströmungen für industrielle Anwendungen in der Prozessindustrie stellt eine große Herausforderung dar. Zweiphasenströmungen in Reaktions- oder Trennapparaten sind infolge der auf mehreren Skalen ablaufenden Transportprozesse für Impuls, Stoff und Wärme inhärent hoch komplex. Zur Validierung von CFD-Codes sind daher experimentelle quantitative Daten solcher Strömungen mit hoher zeitlicher und räumlicher Auflösung erforderlich.
An der TOPFLOW-Versuchsanlage des HZDR werden auf diesem Gebiet umfangreiche Versuche an einer vertikalen DN50-Testsektion mit Luft-Wasser und Dampf-Wasser-Strömungen bis zu p = 65 bar und einer weiten Variation der Leerrohrgeschwindigkeiten für Wasser- und Gasphase durchgeführt. Unter Verwendung der am HZDR entwickelten ultraschnellen Röntgentomographie können Strömungsquerschnitte mit Bildraten von bis zu 2500 frames/s und einer räumlichen Auflösung von etwa 1 mm rückwirkungsfrei erfasst und visualisiert werden. Neben der Ermittlung von Strömungsregimen und weiterer charakteristischer Strömunsgkenngrößen dienen diese Untersuchungen dem Erkenntnisgewinn über Strömungsdetails, wie etwa Blasenkoaleszenz und –zerfall, radiale Gasgehaltsprofile, Strömungsverhalten von Kleinblasen in Abhängigkeit benachbarter Blasen sowie Geschwindigkeitsinformationen, in hochturbulenten Zweiphasenströmungen bei industriell relevanten Gasgehalten. Mit Hilfe von speziell entwickelten Bildauswertungsroutinen können diese Daten analysiert und für die Zweiphasen-CFD-Modellvalidierung aufbereitet werden. In diesem Beitrag wird ein Überblick über bisherige Versuche und deren Ergebnisse gegeben.
Diese Arbeit wird im Rahmen eines aktuellen Forschungsprojekts, welches vom Bundesministerium für Wirtschaft und Technologie unter der Projektnummer 150 1411 gefördert wird, durchgeführt.
  • Poster
    ProcessNet Jahrestreffen der Fachgruppen Extraktion und Fluidverfahrenstechnik, 27.-28.03.2014, Fulda, Deutschland

Publ.-Id: 20179 - Permalink


Design, synthesis, characterisation and in vitro studies of hydrophilic, colloidally-stable, 64Cu(II)-labelled, ultra-small iron oxide nanoparticles in a range of human cell lines
Pombo Garcia, K.; Zarschler, K.; Barreto, J. A.; Spiccia, L.; Graham, B.; Stephan, H.;
The application of ultra-small super-paramagnetic iron oxide nanoparticles (USPIONs) as versatile diagnostic probes for multimodal imaging in biomedicine, including via magnetic resonance imaging (MRI) and positron emission tomography (PET), requires hydrophilic and biocompatible surface coatings. Herein, we describe the development of USPIONs stabilised by octylamine-modified polyacrylic acid (OPA) and the subsequent
conjugation of a 64Cu(II) chelator, N-(4-aminophenyl)-2-[4,7-bis(2-pyridylmethyl)-1,4,7-triazacyclononan-1-yl]- acetamide (amino-dmptacn), for radioactivity-based detection. Transmission electron microscopic analysis and dynamic light scattering measurements confirmed the monodispersity and stability of the OPA-USPIONs in aqueous media and revealed a hydrodynamic size of ca. 15 nm. Furthermore, the biocompatibility and cellular uptake efficiency of the functionalised USPIONs was investigated in a range of normal and tumour cell lines. The results clearly show a cell type- as well as time-dependent internalisation of the OPA-USPIONs via active energy-dependent pathways. Biocompatibility of OPA- USPIONs in the concentration range of 10–50 mg mL-1 was demonstrated, while impairment of cellular viability was observed for human umbilical vein endothelial cells at 100 mg mL-1. Upon exposure to human serum, several biomolecules cover the negatively-charged surface of the nanoparticles and a biomolecular corona is formed. Nonetheless, the nanoparticles represent a promising platform for the future development of a bimodal PET-MRI tumour-imaging agent.

References
1. K. Pombo-Garcia, K. Zarschler, J. A. Barreto, J. Hesse, L. Spiccia, B. Graham, H. Stephan, RSC Advances 2013, 3, 22443.
2. M. P. Monopoli, D. Walczyk, A. Campbell, G. Elia, I. Lynch, F. B. Bombelli and K. A. Dawson, J Am Chem Soc, 2011, 133, 2525-2534.

Acknowledgements: Helmholtz Initiative and Networking Fund (Functional nanomaterials for multimodality cancer imaging (NanoTracking), project ID: VH-VI-421). Australian Research Council Discovery Grant and a Discovery Outstanding Researcher Award and a Senior Research Award by the Humboldt Foundation are gratefully acknowledged by L.S.
  • Poster
    e-WISPOC: European-Winter School on Physical Organic Chemistry, 02.-07.02.2014, Bressanone, Italy

Publ.-Id: 20177 - Permalink


Ultrasmall and radiolabelled upconverting nanophosphors – ready for challenge of multimodal cancer imaging
Hesse, J.; Graham, B.; Geipel, G.; Grenzer, J.; Spiccia, L.; Steinbach, J.; Stephan, H.;
The increasing interest in nanomaterials for medical applications is mainly attributed to their unique and structural properties. Based on different materials like polymers, inorganic or organic-inorganic hybrid substances such nanomaterials are investigated for applications in biological systems. Regarding this upconverting nanophosphors exhibit a high potential because of their bright luminescence. With their exceptional characteristic to convert near infrared to visible light (upconversion) these inorganic lanthanide-doped nanoparticles are very attractive as probes for optical imaging with the possibiliy for elucidation of even cellular processes[1]. In addition the surface of the nanoparticles offer the chance for rather multiple functionalisation such as radiometall chelates for PET and SPECT as well as for tumor affine units (peptides, aptamers, antibodies).
We want to present the synthesis and photophysical properties of ultrasmall (<10 nm) upconverting nanophosphors based on a host lattice of NaYF4: (Nd3+),Yb3+, Er3+/Tm3+ which are excited at 800 nm or 980 nm. To generate watersoluble biocompatible nanoparticles the material was coated with different polymers and afterwards functionalized with DMPTACN, a picolyl derivative of the macrocyclic ligand 1,4,7-triazacyclononane. An initial point for further investigations in vitro and in vivo was achieved by radiolabelling with the positron emitter Cu-64.

References
1. Cheng, L. , Wang, C. , Liu, Z. Nanoscale. 2013, 5, 23-37.

Acknowledgements: This work was funded by the Helmholtz Initiative and Networking Fund „Functional nanomaterials for multimodality cancer imaging“ (NanoTracking, project ID: VH-VI-421).
  • Poster
    e-WISPOC: European-Winter School on Physical Organic Chemistry, 02.-07.02.2014, Bressanone, Italy

Publ.-Id: 20176 - Permalink


Emittance minimization at the ELBE superconducting electron gun
Möller, K.; Arnold, A.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.;
The transverse emittance is one of the most important quantities which characterize the quality of an electron source. For high quality experiments low beam emittance is required. By means of theoretical considerations and simulation calculations we have studied how the emittance of the Rossendorf superconducting radio-frequency photoelectron source (SRF gun) can be minimized. It turned out that neither a solenoid magnet nor the effect of space charge forces is needed to create a pronounced emittance minimum. The minimum appears by just adjusting the starting phase of the electron bunch with respect to the RF phase of the gun in a suitable way. Investigation of various correlations between the properties of the beam particles led to an explanation on how the minimum comes about. It is shown that the basic mechanism of minimization is the fact that the longitudinal properties of the particles (energy) are strongly influenced by the starting phase. Due to the coupling of the longitudinal and transverse degrees of freedom by the relativistic equation of motion the transverse degrees of freedom and thereby the emittance can be strongly influenced by the starting phase as well. The results obtained in this study will be applied to minimize the emittance in the commissioning phase of the SRF gun.
Keywords: electron gun, SRF gun, superconducting radio frequency, electron injector, transverse emittance
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-050 2014

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Publ.-Id: 20175 - Permalink


Metastatic potential of B16-F10 melanoma cells is enhanced by extracellular S100A4 derived from RAW264.7 macrophages
Haase-Kohn, C.; Wolf, S.; Herwig, N.; Mosch, B.; Pietzsch, J.;
S100A4, synthesized and secreted from both tumor and stroma cells, modulates an aggressive tumor phenotype in various cancers by intracellular and extracellular interactions which are not completely understood. Because of the high content of tumor-associated macrophages in melanoma, here, a syngeneic model (coculture of mouse B16-F10 melanoma cells (Mel) and RAW264.7 macrophages (Mϕ); administration (i.v.) of Mel and Mϕ/Mel in NMRI nu/nu mice) was used to investigate synthesis and secretion of a) S100A4, b) S100A4-mediated signaling and activation of NFκB, and c) S100A4-mediated modulation of Mel invasiveness in vitro (transwell assay, transwell matrigel assay) and in vivo (metastatic lung colonization), respectively. In this model substantial S100A4 synthesis and secretion is demonstrated in Mϕ. Macrophage-derived S100A4 promotes Mel invasiveness in a paracrine manner in vitro, which is further substantiated in control experiments using recombinant human S100A4 and Mel stably transfected with mouse S100A4. Moreover, the participation of S100A4-mediated signaling, e.g., via the receptor for advanced glycation endproducts (RAGE), resulting in activation of NFκB was demonstrated in all experimental settings. Finally, we demonstrated that interaction of macrophage-derived S100A4 with Mel results in increased metastatic lung colonization in vivo.
Keywords: Melanoma metastasis; Receptor for advanced glycation; endproducts (RAGE); S100 proteins; Tumor-associated macrophages (TAM)

Publ.-Id: 20174 - Permalink


Simultaneous Targeting of Prostate Stem Cell Antigen and Prostate-Specific Membrane Antigen Improves the Killing of Prostate Cancer Cells Using a Novel Modular T Cell-Retargeting System
Arndt, C.; Feldmann, A.; Koristka, S.; Cartellieri, M.; Dimmel, M.; Ehninger, A.; Ehninger, G.; Bachmann, M.;
BACKGROUND
Recently, we described a novel modular platform technology in which T cell-recruitment and tumor-targeting domains of conventional bispecific antibodies are split to independent components, a universal effector module (EM) and replaceable monospecific/monovalent target modules (TMs) that form highly efficient T cell-retargeting complexes. Theoretically, our unique strategy should allow us to simultaneously retarget T cells to different tumor antigens by combining the EM with two or more different monovalent/monospecific TMs or even with bivalent/bispecific TMs, thereby overcoming limitations of a monospecific treatment such as the selection of target-negative tumor escape variants.
METHODS
In order to advance our recently introduced prostate stem cell antigen (PSCA)-specific modular system for a dual-targeting of prostate cancer cells, two additional TMs were constructed: a monovalent/monospecific TM directed against the prostate-specific membrane antigen (PSMA) and a bivalent/bispecific TM (bsTM) with specificity for PSMA and PSCA. The functionality of the novel dual-targeting strategies was analyzed by performing T cell activation and chromium release assays.
RESULTS
Similar to the PSCA-specific modular system, the novel PSMA-specific modular system mediates an efficient target-dependent and -specific tumor cell lysis at low E:T ratios and picomolar Ab concentrations. Moreover, by combination of the EM with either the bispecific TM directed to PSMA and PSCA or both monospecifc TMs directed to either PSCA or PSMA, dual-specific targeting complexes were formed which allowed us to kill potential escape variants expressing only one or the other target antigen.
CONCLUSIONS
Overall, the novel modular system represents a promising tool for multiple tumor targeting.
Keywords: T cell redirection; dual-targeting; recombinant antibody; immunotherapy

Publ.-Id: 20173 - Permalink


A novel ex vivo Isolation and Expansion Procedure for Chimeric Antigen Receptor Engrafted Human T Cells
Cartellieri, M.; Koristka, S.; Arndt, C.; Feldmann, A.; Stamova, S.; von Bonin, M.; Töpfer, K.; Krüger, T.; Geib, M.; Michalk, I.; Temme, A.; Bornhäuser, M.; Lindemann, D.; Ehninger, G.; Bachmann, M. P.;
Genetically engineered T lymphocytes are a promising option for cancer therapy. Prior to adoptive transfer they have to be expanded in vitro to reach therapeutically sufficient numbers. So far, no universal method exists for selective in vitro expansion of engineered T lymphocytes. In order to overcome this problem and for proof of concept we incorporated a novel unique peptide sequence of ten amino acids as epitope (ETag) into the binding domains of two novel chimeric antigen receptors (ECARs) directed against either prostate stem cell antigen (PSCA) for the treatment of prostate cancer (PCa) or CD33 for the treatment of acute myeloide leukemia (AML). The epitope tag then was utilized for expanding ECAR engrafted T cells by triggering the modified T cells via a monoclonal antibody directed against the E-Tag (Emab). Moreover, the E-Tag served as an efficient selection epitope for immunomagnetic isolation of modified T cells to high purity. ECAR engrafted T cells were fully functional and mediated profound anti-tumor effects in the respective models of PCa or AML both in vitro and in vivo. The method can be integrated straightforward into clinical protocols to improve therapeutic efficiency of tumor treatment with CAR modified T lymphocytes.
Keywords: adoptive transfer; genetically engineered T cells; chimeric antigen receptor; in vitro cultivation; tumor immunotherapy; Tumor; cancer; T cell; Genetic engineering

Publ.-Id: 20172 - Permalink


Oxygen depth profiling with subnanometre depth resolution
Kosmata, M.; Munnik, F.; Hanf, D.; Grötzschel, R.; Richter, S.; Möller, W.;
An High-depth Resolution Elastic Recoil Detection (HR-ERD) set-up using a magnetic spectrometer has been taken into operation at the Helmholtz-Zentrum Dresden-Rossendorf for the first time. This instrument allows the investigation of light elements in ultra thin layers and their interfaces with a depth resolution of less than 1 nm near the surface. As the depth resolution is highly influenced by the experimental measurement parameters, sophisticated optimisation procedures have been implemented. Effects of surface roughness and sample damage caused by high fluences need to be quantified for each kind of material. Also corrections are essential for non-equilibrium charge state distributions that exist very close to the surface. Using the example of an high-k multilayer SiO2/Si3N4Ox/SiO2/Si it is demonstrated that oxygen in ultra-thin films of a few nanometres thickness can be investigated by HR-ERD.
Keywords: high resolution depth profiling, ERD, high-k materials

Publ.-Id: 20171 - Permalink


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