Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34118 Publications

Substitution of the Klystrons by Solid State Power Amplifiers (SSPA) at ELBE

Büttig, H.

In January 2012 the 10 kW CW klystrons (CPI VKL7811St) used to operate the superconducting cavities of ELBE since 2001 have been replaced by pairs of 10 kW solid state amplifiers (SSPA) providing 20 kW RF power per cavity. The paper gives an overview on the activities and the problems during high power CW operation.

Keywords: ELBE RF-system; 1.3GHz SSPA; SC-LINAC RF Power Generation

  • Lecture (Conference)
    ARD Workshop “Pushing the ELBE CW RF-system to high average beam current”, 14.-15.03.2013, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18718
Publ.-Id: 18718


Design and Performance of the Upgraded ELBE RF-System Based on Solid State Amplifiers

Büttig, H.; Arnold, A.; Büchner, A.; Justus, M.; Kuntzsch, M.; Lehnert, U.; Michel, P.; Schurig, R.; Staats, G.; Teichert, J.

With the expansion of the radiation source ELBE, a centre for high power radiation sources is being built until 2014 at the Helmholtz Zentrum Dresden Rossendorf. One part of this program is to double the beam current of the ELBE LINAC. In January 2012 the 10 kW CW klystrons, used to operate the superconducting cavities of ELBE since 2001, had been replaced by a pair of 10 kW solid state amplifiers. The paper gives an overview on the activities around this project and the first experience with the new RF-system.

Keywords: ELBE RF system; Superconducting LINAC RF; 1.3 GHz Solid State Power Amplifiers; Solid State Poer Amplifiers for Particle Accelerators

  • Invited lecture (Conferences)
    TIARA Workshop on RF Power Generation for Accelerators, 17.-19.06.2013, Uppsala, Schweden

Permalink: https://www.hzdr.de/publications/Publ-18717
Publ.-Id: 18717


Effective Spin Meron Pairs In Ferromagnetic Multilayers

Wintz, S.; Bunce, C.; Neudert, A.; Körner, M.; Strache, T.; Buhl, M.; Erbe, A.; Gemming, S.; Raabe, J.; Quitmann, C.; Fassbender, J.

We report on pairs of diverging/converging spin vortices in Co/Rh/Ni81Fe19 trilayer disks. The lateral magnetization distribution of these effective spin merons is imaged directly by means of element-selective x-ray microscopy. By this method, both the divergence and circulation states of the individual layers are identified as antisymmetric. Reversal measurements on corresponding continuous films reveal that biquadratic interlayer exchange coupling is the origin for the formation of effective meron pairs. Furthermore, their three-dimensional magnetization structure is determined by micromagnetic simulations. Interestingly, the magnetic induction follows a kind of flux-closing torus. This toroidal topology enforces a symmetry break, which ties the core polarities to the divergence configuration.

Keywords: spin; texture; vortex; meron; topology

  • Lecture (Conference)
    Joint European Magnetic Symposia 2013, 25.-30.08.2013, Rhodos, Griechenland

Permalink: https://www.hzdr.de/publications/Publ-18716
Publ.-Id: 18716


Commisioning of the upgraded superconducting linac ELBE

Büttig, H.; Arnold, A.; Büchner, A.; Justus, M.; Kuntzsch, M.; Lehnert, U.; Michel, P.; Schurig, R.; Staats, G.; Teichert, J.

In January 2012 the 10 kW CW klystrons (CPI VKL7811St) used to operate the superconducting cavities of ELBE since 2001 have been replaced by pairs of 10 kW solid state amplifiers (SSPA) providing 20 kW RF power per cavity. The paper gives an overview on the activities and the problems during high power CW operation.

Keywords: Linac-RF; SSPA; High power solid state RF amplifiers; Accelerator RF systems; Superconducting Linac RF; CW Linac RF

  • Open Access Logo Contribution to proceedings
    4th International Particle Accelerator Conference, IPAC13, 12.-17.05.2013, Shanghai, China
    IPAC2013-Proceedings , Paper WEPME007, page 2935, Geneva: JACoW, 2935
  • Poster
    4th International Particle Accelerator Conference, IPAC13, 12.-17.05.2013, Shanghai, China

Permalink: https://www.hzdr.de/publications/Publ-18715
Publ.-Id: 18715


X-ray diffraction studies during magnetron co-sputtering of Ni-Ti shape memory alloy films

Martins, R. M. S.; Schell, N.; Mahesh, K. K.; Silva, R. J. C.; Braz Fernandes, F. M.

The study of Ni-Ti shape memory alloy films is of great technological interest for applications in the field of microengineering. They can work as sensors and actuators at the same time. However, there are still important issues unresolved like formation of film crystallographic orientation and its control. Films exhibiting the two-way shape memory effect are also required.
A two-magnetron sputter deposition chamber mounted into the six-circle diffractometer of the Rossendorf Beamline at the European Synchrotron Radiation Facility was used for the processing of Ni-Ti films. The in-situ x-ray diffraction studies enabled to identify the different steps of the structural evolution during film growth.
Deposition conditions leading to Ni-Ti films mainly containing grains with (100) or (110) planes of the B2 phase parallel to the film surface were successfully defined. This is an important achievement since texture has a strong influence on the extent of the strain recovery. The deposition of films with a “two-way” actuation (films with a combination of superelasticity and shape memory characteristics) was also achieved. It will allow the development of smaller devices since no consideration has to be paid to a resetting spring.

Keywords: Shape Memory Alloy; Ni-Ti; Deposition by sputtering; In-situ X-ray diffraction; Texture development

  • Open Access Logo Ciência & Tecnologia dos Materiais 24(2012)3/4, 161-169

Permalink: https://www.hzdr.de/publications/Publ-18714
Publ.-Id: 18714


Ein neuartiges Konzept zur Berechnung der Positronenemitter-Ausbeuten für die Reichweiteverifikation bei der Partikeltherapie mittels PET

Priegnitz, M.; Enghardt, W.; Laube, K.; Fiedler, F.

no abstract available

  • Lecture (Conference)
    44. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik, 18.-21.09.2013, Köln, Deutschland
  • Open Access Logo Contribution to proceedings
    44. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik, 18.-21.09.2013, Köln, Deutschland
    Medizinische Physik - Abstractband, 978-3-9816002-1-6, 119-121

Permalink: https://www.hzdr.de/publications/Publ-18713
Publ.-Id: 18713


Flashing evaporation under different pressure levels

Liao, Y.; Lucas, D.; Krepper, E.; Rzehak, R.

Flashing evaporation of water inside a vertical pipe under four different system pressures is investigated by mono-dispersed CFD simulations. Phase change is assumed to be caused only by thermal heat transfer. The available thermal energy decreases rapidly with the increase of pressure level. Under low-pressure conditions, the maximum steam volume fraction is over-predicted, while an overestimation is observed in high-pressure cases. The possible explanation for the deviation is that bubble growth during the evaporation is especially significant in low-pressure cases, which reduces the evaporation rate but is not considered in the simulation. Furthermore, as the system pressure increases the contribution of nucleation to the total steam generation rate becomes large, which is confirmed by the experimental data. In addition, the effect of pressure on the critical bubble diameter that succeeds in starting flashing as well as the nucleation mechanism is discussed.

Keywords: Flashing; Nucleation; Thermal Energy; Vertical Pipe Flow; Pressure Effect

Permalink: https://www.hzdr.de/publications/Publ-18712
Publ.-Id: 18712


Time-resolved spectroscopy on intraband Landau-level transitions in graphene

Mittendorff, M.; Winnerl, S.; Orlita, M.; Potemski, M.; Berger, C.; de Heer, W. A.; Schneider, H.; Helm, M.

The linear dispersion for electrons in graphene leads to a non-equidistant Landau-level (LL) spectrum. This enables one to investigate single Landau-level transitions by resonant pump-probe experiments. So far, however, only the quasi-continuum of high-index LL states has been studied in near-infrared pump-probe experiments. Here we report on terahertz pump-probe measurements at a fixed photon energy of 14 meV, where the free-electron laser FELBE at Dresden-Rossendorf served as radiation source. The magnetic field was varied between 0 T and 7 T. For these measurements we used a sample with 50 layers of graphene, which were epitaxially grown on the C-face of silicon carbide. While the interface layers are highly doped, the major part of the layers is quasi neutral with a Fermi energy in the range of ~10 meV.
At a magnetic field of 0.165 T the photon energy of 14 meV becomes resonant with the inter-LL transition LL-1(0) -> LL0(1). The amplitude of the pump-probe signal is increased by roughly a factor of 4 compared to zero field. Only the quasi neutral layers contribute to this signal, since the first LL is fully occupied for the interface layers with a higher doping. Surprisingly a decreased relaxation time is observed on resonance. We will discuss how the contribution of the LL-1 -> LL0 and LL0 -> LL1 and Auger-type processes lead to a unique relaxation scenario. At higher magnetic fields higher intraband LL transitions can be tuned into resonance (LLn -> LLn+1, n=1,2,3,…). The observed pump-probe signals then stem from these transitions in the interface layers, where the elevated Fermi energy ensures that the ground state LL is populated. With increasing magnetic field both amplitude and decay time constants vary non-monotonically. In the magnetic field region around 3 T negative pump-probe signals occur. The main features observed in the experiments are explained by a model for the electron temperature after optical excitation, which describes the absorption in the layers via the Kubo formalism and takes into account the doping level of the interface layers. The doping levels agree well with values previously obtained from pump-probe experiments without magnetic field.

Keywords: Landau quantization; relaxation dynamics; pump-probe spectroscopy; magnetic field

  • Lecture (Conference)
    Graphene Week 2013, 02.-07.06.2013, Chemnitz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18711
Publ.-Id: 18711


THz spectroscopy of optically excited InGaAs quantum wells in the high charge-carrier density regime

Schmidt, J.; Teich, M.; Wagner, M.; Winnerl, S.; Stehr, D.; Schneider, H.; Helm, M.

In this work we study the THz transmission of a 40 nm wide undoped In0.1Ga0.9As quantum well (QW) under optical excitation. Carriers are photoexcited by a near-infrared (NIR) fs pulse and probed in the frequency range from 0.1 to 3 THz by electro-optic sampling using the modified setup of Ref. [1]. The THz pulse is focused on a side facet of the QW sample such that the THz electric field is mostly polarized perpendicular to the QW layer. Fig. 1a depicts the THz field transients for modulated (signal) and un-modulated (reference) NIR excitation. The presence of the carriers which were photoinjected several ps prior to the THz pulse creates a large amount of THz signatures in the QW. Our present goal is to disentangle the various possible contributions to the THz signal: electron intersubband, heavy-hole intersubband, 1s-2p intraexciton and free-carrier absorption. In addition we search for a Fano-like behavior, similar as has been observed in narrower QWs in the mid infrared [2], which is supposed to arise from the interplay between the intersubband absorption and the purely reactive ponderomotive contribution. The different phase of the associated dielectric functions results in a (non-quantum like) interference between these two polarizations, which is only visible in the differential transmission but not in the absorption. We will also report experiments where we use wavelength tuning of the near-infrared pulse using an optical parametric amplifier in order to selectively pump optically either into the barrier or into the QW. Polarization resolved measurements are underway which should help us to reveal the various contributions.
[1] M. Wagner et. al. , Appl. Phys. Lett. 99, 131109 (2011).
[2] D. Golde, M. Wagner et. al., PRL 102, 127403 (2009).

Keywords: quantum well; THz time domain; photoexcitation

  • Poster
    OTST 2013: International Workshop on Optical Terahertz Science and Technology 2013, 01.-05.04.2013, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-18710
Publ.-Id: 18710


Terahertz nonlinear optics of excitons in quantum wells: the Autler-Townes effect and beyond

Helm, M.; Teich, M.; Wagner, M.; Winnerl, S.; Schneider, H.; Klettke, A. C.; Chatterjee, S.; Kira, M.; Koch, S. W.

Keywords: terahertz; nonlinear optics; Autler-Townes effect; excitons

  • Invited lecture (Conferences)
    International Workshop on Optical Terahertz Science and Technology (OTST 2013), 01.-05.04.2013, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-18709
Publ.-Id: 18709


How does a free-electron laser work and why is it useful in the THz range ?

Helm, M.

Keywords: free-electron laser; terahertz

  • Lecture (others)
    Terahertz Seminar (invited talk), 30.03.2013, Osaka, Japan

Permalink: https://www.hzdr.de/publications/Publ-18708
Publ.-Id: 18708


THz spectroscopy of semiconductor nanostructures with the free electron laser

Helm, M.

Keywords: terahertz; free electron laser; semiconductor nanostructures

  • Lecture (others)
    TeraNano Student Seminar (invited talk), 02.-03.03.2013, Würzburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18707
Publ.-Id: 18707


PIC and GPUs - About my Work at HZDR

Hübl, A.

Presentation of my scientific CV, laser-electron theory at HZDR and the work on PIConGPU.

Keywords: picongpu; epp; ist; lisboa; GPGPU

  • Invited lecture (Conferences)
    Meeting of the extreme plasma physics team of the Group for Lasers and Plasmas of the Instituto de Plasmas e Fusão Nuclear at Instituto Superior Técnico., 12.10.2012, Lisboa, Portugal

Permalink: https://www.hzdr.de/publications/Publ-18706
Publ.-Id: 18706


PIConGPU - Validations, Enhancements and Recent Draco Sims

Hübl, A.; Bussmann, M.; Burau, H.; Widera, R.; Steiniger, K.; Berninger, F.; Pausch, R.; Buikstra, L.; Debus, A.; Kluge, T.; Irman, A.; Jochmann, A.; Couperus, J. P.; Schmitt, F.; Höhnig, W.; Juckeland, G.

Presentation of recent feature enhancements and physical Validations of PIConGPU. We presented laser dispersion test, radiation tests and thermal plasma tests, added new numerical shemes for the PIC cycle and performed HPC simulations for the recent laser-electron experiment at draco, performed by A. Irman et al.

Keywords: PIConGPU; GPGPU; CUDA; numerics; draco; simulation

  • Lecture (others)
    Meeting of Laser Particle Acceleration Division at the Institute for Radiation Physics, 01.08.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18705
Publ.-Id: 18705


EPP/IPFN Annual Report 2012 (Contribution)

Hübl, A.; EPP team of GoLP at IST (Lisboa)

Contribution to the Annual Report 2012 of EPP/IPFN at Instituto Superior Técnico (Lisboa).

Keywords: annual report 2012; ist; epp; lisboa

  • Open Access Logo Contribution to external collection
    in: Annual Report 2012 of EPP/IPFN, Lisboa: Instituto Superior Técnico, 2015

Permalink: https://www.hzdr.de/publications/Publ-18704
Publ.-Id: 18704


Measurement of spin observables in the quasi-free np -> {pp}sπ reaction at 353 MeV

Dymov, S.; Shmakova, V.; Azaryan, T.; Barsov, S.; Baru, V.; Benati, P.; Chiladze, D.; Dzyuba, A.; Engels, R.; Gaisser, M.; Gebel, R.; Grigoryev, K.; Goslawski, P.; Guidoboni, G.; Hartmann, M.; Kacharava, A.; Kamerdzhiev, V.; Khoukaz, A.; Komarov, V.; Kulessa, P.; Kulikov, A.; Kurbatov, V.; Lehrach, A.; Lenisa, P.; Lensky, V.; Lomidze, N.; Lorentz, B.; Macharashvili, G.; Maier, R.; Mchedlishvili, D.; Merzliakov, S.; Mielke, M.; Mikirtychyants, M.; Mikirtytchiants, S.; Nioradze, M.; Oellers, D.; Ohm, H.; Polyanskiy, A.; Papenbrock, M.; Prasuhn, D.; Rathmann, F.; Serdyuk, V.; Seyfarth, H.; Steffens, E.; Stein, H. J.; Stockhorst, H.; Ströher, H.; Tabidze, M.; Trusov, S.; Tsirkov, D.; Uzikov, Y.; Valdau, Y.; Weidemann, C.; Wilkin, C.; Wüstner, P.; Ye, Q. J.; Zhabitsky, M.

The transverse spin correlations Ax,x and Ay,y have been measured in the ~d~p ! pspec{pp}sπ−reaction at COSY-ANKE at 353 MeV per nucleon. Here {pp}s denotes a proton-proton pair with low excitation energy, which is dominantly in the 1S0 state. By measuring three protons in the final state it was possible to extract events where there was a spectator proton pspec so that the reaction could be interpreted in terms of quasi-free ~n ~p ! {pp}sπ−. The proton analyzing power in this reaction was also deduced from this data set by averaging over the polarization of the deuteron beam. The values of Apy were shown to be consistent with a refined analysis of our earlier results obtained with a polarized proton incident on a deuterium target. Taking these data in combination with our earlier measurements of the differential cross sections and analyzing powers in the ~pp ! {pp}s π0 reaction, a more robust partial wave decomposition was achieved. Three different acceptable solutions were found and the only way of resolving this ambiguity without further theoretical input would be through a measurement of the mixed spin-correlation parameter Ax,z.

Permalink: https://www.hzdr.de/publications/Publ-18703
Publ.-Id: 18703


Accelerated Codes and Charges

Hübl, A.

Final talk about the results of the cooperation/internship at Instituto Superior Técnico (IST) in 2012/13.
A new method for charged beam loading in particle-in-cell simulations was presented. Furthermore, side-topics like the creation of a Raspberry Pi (ARM) cluster, the development of a dependency analyser for fortran modules for parallel builds, a GPU vs CPU benchmark, the development of a transversal resolution criteria for gaussian laser beams and a Thrust-Fortran binding were presented.

Keywords: beam loading; cooperation; internship; fortran parallel make; raspberry pi; arm; cluster; thrust; transversal resolution gaussian laser beam

  • Lecture (others)
    Final talk with results of the cooperation, 20.02.2013, Lisboa, Portugal

Permalink: https://www.hzdr.de/publications/Publ-18702
Publ.-Id: 18702


PIConGPU - Physics Validation for Laser Plasma and Astrophysics Plasma Simulations

Hübl, A.; Burau, H.; Helm, A.; Widera, R.; Debus, A.; Kluge, T.; Couperus, J. P.; Irman, A.; Bussmann, M.; Schramm, U.; Cowan, T.; Schmitt, F.; Juckeland, G.; Nagel, W.

PIConGPU is a highly-scalable implementation of the fully relativistic electromagnetic particle-in-cell algorithm for GPGPUs. It allows for fast simulations of laser plasma interaction and astrophysical plasmas.
We present several physics validation results, allowing reliable checks during development stages of the code. Furthermore, we show applications in astrophysical scenarios and in laser wakefield acceleration experiments for next generation electron accelerators.

Keywords: particle-in-cell; PIConGPU; CUDA; GPGPU; laser-electron acceleration; laser-plasma interaction; underdense plasma; numerics; HPC; cluster; instabilities; astro physics

  • Poster
    77. Jahrestagung der DPG und DPG-Frühjahrstagung, 04.-08.03.2013, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18701
Publ.-Id: 18701


Spin Torque Generated Magnetic Droplet Solitons

Mohseni, S. M.; Sani, S. R.; Persson, J.; Anh Nguyen, T. N.; Chung, S.; Pogoryelov, Y.; Muduli, P. K.; Iacocca, E.; Eklund, A.; Dumas, R. K.; Bonetti, S.; Deac, A.; Hoefer, M. A.; Åkerman, J.

Dissipative solitons have been reported in a wide range of nonlinear systems, but the observation of their magnetic analog has been experimentally challenging. Using spin transfer torque underneath a nanocontact on a magnetic thin film with perpendicular magnetic anisotropy (PMA), we have observed the generation of dissipative magnetic droplet solitons and report on their rich dynamical properties. Micromagnetic simulations identify a wide range of automodulation frequencies, including droplet oscillatory motion, droplet "spinning," and droplet "breather" states. The droplet can be controlled by using both current and magnetic fields and is expected to have applications in spintronics, magnonics, and PMA-based domain-wall devices.

Keywords: spin-transfer torque; droplet soliton; magnetic nanostructure

Permalink: https://www.hzdr.de/publications/Publ-18700
Publ.-Id: 18700


Weighted Poisson cells as models for random convex polytopes

Ballani, F.; van den Boogaart, K. G.

We introduce a parametric family for random convex polytopes in Rd which allows for an easy generation of samples for further use, e. g., as random particles in materials modelling and simulation. The basic idea consists in weighting the Poisson cell, which is the typical cell of the stationary and isotropic Poisson hyperplane tessellation, by suitable geometric characteristics. Since this approach results in an exponential family, parameters can be efficiently estimated by maximum likelihood. This work has been motivated by the desire for a flexible model for random convex particles as can be found in many composite materials such as concrete or refractory castables.

Keywords: Random polygon; Random polyhedron; Poisson cell; Crofton cell; Exponential family; Gibbs distribution

Permalink: https://www.hzdr.de/publications/Publ-18699
Publ.-Id: 18699


Superconducting layers in Si – a new approach for Quantum-bits?

Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Hübner, R.; Philipp, P.; Schmidt, B.; Skorupa, W.; Gobsch, G.; Helm, M.

With the observation of superconductivity at ambient pressure conditions in B doped Si in 2006 [1] and Ga doped Ge [2] the group-IV semiconductors become of interest for future information processing technologies like quantum computing.
To achieve the high doping levels needed for superconductivity non-equilibrium doping techniques like gas immersion laser doping or ion implantation and short term annealing are needed. Only the latter one is fully compatible to standard microelectronic technology. In a new approach we implanted a Ga concentration up to 11 at.% through a 30 nm SiO2 cover layer into commercial Si and Ge wafers [3-6]. During annealing a thin superconducting Ga-rich nanolayer is formed at the SiO2/semiconductor interface. These layers show promising superconducting properties (TC = 7 K, BC < 8 T, jC < 50 kA/cm2).
Detailed microstructural investigations by means of XTEM and RBS/C will be discussed. Recent results show the adjustability of the superconducting properties. We are able to produce superconducting microstructures having a width of 3 µm and used the FIB to implement a Josephson junction as key element for a prospective SQUID.
[1] E. Bustarret et al., Nature 444 (2006) 465
[2] T. Herrmannsdörfer et al., Phys, Rev. Lett. 102 (2009) 217003
[3] R. Skrotzki et al., Appl. Phys. Lett. 97 (2010) 192505
[4] J. Fiedler et al., Phys. Rev. B 83 (2011) 214504
[5] J. Fiedler et al., Phys. Rev. B 85 (2012) 134530
[6] V. Heera et al., Appl. Phys. Lett. 100 (2012) 262602

  • Lecture (Conference)
    E-MRS 2013 Spring Meeting (Ausgezeichnet mit dem "Young Scientist Award" - Symposium J), 27.-31.05.2013, Strasbourg, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-18698
Publ.-Id: 18698


Insights into the Biodiversity of salt sumps in the Asse II salt mine, Germany

Zirnstein, I.; Arnold, T.

The former salt mine (1908-1964) Asse II, Germany is a final disposal site of radioactive waste. It is composed of salt rocks, which are approximately 250 million years old. A number of salt sumps exist in the Asse II, which were so far not microbiologically characterized. In this study, cultivation-independent methods, e.g. pyrosequencing, were applied to identify the microbial diversity in these unique salt sump habitats.
In this study, a total of 3.168 sequences, divided in 314 operational taxonomic units (OTUs), representing bacterial and archaeal groups from the underground Asse II salt mine. The class halobacteria (Euryarchaeota) predominates the archaeal community, representing 99.5% of all sequences. The least abundant sequences were represented by Thermoprotei (Crenarchaeota) and Methanobacteria (Euryarchaeota).
In addition, halophilic bacteria have been detected in the salt sumps of the underground Asse II mine. A total of 8 phyla of bacteria were identified by 16S rRNA sequence analyzes. The dominating phylum are Firmicutes (e.g. Bacilli, Halocella, Filifactor, Veillonella) with ~51% of all detected bacterial sequences, followed by Proteobacteria (Marinobacter, Hyphomicrobium, Methylophilus, Pseudomonas, Sphingomonas) with ~19%.
This study identified for the first time extreme halophilic bacteria and archaea in the underground salt sumps of the Asse II environment. For generating a final disposal site, not only geological, chemical or physical, but also microbiological aspects are important to consider.

Keywords: extreme environment; halophilic microorganisms; 16S rDNA; pyrosequencing; salt rock; Asse

  • Lecture (Conference)
    Actinide and Brine Chemistry in a Salt Repository Workshop (III), 15.-17.04.2013, Santa Fe (NM), USA

Permalink: https://www.hzdr.de/publications/Publ-18697
Publ.-Id: 18697


Thermally assisted all-optical helicity dependent magnetic switching in amorphous Fe100-xTbx alloy films.

Hassdenteufel, A.; Hebler, B.; Schubert, C.; Liebig, A.; Teich, M.; Helm, M.; Aeschlimann, M.; Albrecht, M.; Bratschitsch, R.

All-optical switching (AOS) in ferrimagnetic Fe100−x Tbx alloys is presented. AOS is witnessed below, above, and in samples without a magnetic compensation point. It is found that AOS is associated with laser heating up to the Curie temperature and intimately linked to a low remanent sample magnetization. Above a threshold magnetization of 220 emu cm−3 helicity dependent AOS is replaced by pure thermal demagnetization.

Keywords: all optical switching; magnetic switching; ferrimagnetism

Permalink: https://www.hzdr.de/publications/Publ-18696
Publ.-Id: 18696


Particle-Mesh-Methods on Next Generation Supercomputers

Bussmann, M.

In the coming years supercomputers will have millions of compute cores.
It is estimated that the computing power will grow by a factor of 1000 in the coming years while the memory will only grow by a factor of 10.
This means that at optimum codes can be 100 times faster than before.
I will show that such codes exist today and both allow and require online visualization and interaction with the user.
Based on the example of particle-mesh methods I will present the most important techniques on how to write optimum codes.

Keywords: particlemesh; gpu; exaflop

  • Invited lecture (Conferences)
    Seminar, Center of Excellence for Computational Fluid Dynamics, 12.04.2013, Warszawa, Polska

Permalink: https://www.hzdr.de/publications/Publ-18695
Publ.-Id: 18695


Free-electron laser spectroscopy of exciton dynamics in GaAs quantum wells

Zybell, S.; Bhattacharyya, J.; Winnerl, S.; Helm, M.; Schneider, H.

Intraband excitation of optically injected carriers using strong mid-infrared or THz pulses provides interesting opportunities to study carrier and exciton dynamics in semiconductor quantum wells (QW). In particular, owing to the odd parity of the dipole operator, such intraband excitation transfers excitons located in radiative states into dark (or interband-forbidden) states as long as the symmetry of the QW ensures parity conservation. This property yields spectroscopic access to specific dark states, giving rise to resonant enhancement of intraband absorption as well as suppression of the photoluminescence (PL), and allows us to investigate associated dynamical processes.
We will report on time-resolved PL studies, where we investigate the dynamics of excitons and electron-hole plasma subsequent to pulsed irradiation using the free-electron laser (FEL) at the Helmholtz-Zentrum Dresden-Rossendorf. The FEL is tuned into resonance with, respectively, intraexcitonic and intersubband transitions. Specifically, Figs. 1(a)-(b) demonstrate the effect of FEL excitation of radiative excitons in resonance with the 1s-2p transition, located at 9 meV for 8.2 nm wide high-quality QWs (sample 1). Besides quenching and recovery of the 1s PL, the salient feature in Fig. 1(b) is the appearance of PL originating from the 2s exciton. As direct excitation from 1s into 2s is dipole forbidden, the latter has to be the consequence of rapid scattering from the 2p into the 2s state, which nicely confirms earlier theoretical predictions. This 2s PL is specific for resonant 1s-2p excitation and just seen in high-quality quantum wells. Figs. 1(c) and (d) show PL transients for FEL excitation at 173 meV, in resonance with the electron intersubband transition for 6 nm wide GaAs QWs (sample 2). Typically, the PL recovery after the FEL pulse obeys the same time constant as the initial PL formation after NIR excitation, and its value after recovery exceeds the reference value since the population transferred into nonradiative states eventually returns into the radiative ones, such that the time-integrated PL emission is conserved.

Keywords: Exciton dynamics; semiconductor quantum wells; time-resolved photoluminescence; free-electron laser

  • Poster
    OTST 2013 - International Workshop on Optical Terahertz Science and Technology 2013, 01.-05.04.2013, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-18692
Publ.-Id: 18692


Microorganisms in flooded underground uranium mines of East Germany

Gagell, C.; Arnold, T.

After the German reunification the Wismut GmbH, formerly the 3rd largest U producer of the world, started to remediate the legacies of their U mining activities. As part of the remediation strategy the pit body was flooded to induce reductive processes. Although flooding of the mines Pöhla and Schlema-Alberoda was already finished about ten years ago, the mine water still contains elevated concentrations of toxic metals such as U, As and Ra. Thus, expensive and long-lasting monitoring and waste water treatment is required. Since microorganisms can influence the toxicity of metals directly or indirectly, one alternative approach is to use them for bioremediation. Here, the diversity of the indigenous microbial community of the mine water from Pöhla and Schlema-Alberoda is reported. Bacteria as well as Archaea were analyzed by state-of-the-art pyrosequencing of the 16S rRNA gene. Mine water samples were either filtrated or harvested from a flow cell. For the filtrated Pöhla mine water, the Pöhla flow cell, the filtrated Schlema mine water, and the Schlema flow cell 485, 697, 325 and 527 sequences, respectively, were divided into 98, 189, 188 and 89 operational taxonomical units (OTUs), respectively, belonging mainly to Bacteria. The bacterial sequences from the Pöhla mine were classified into Proteobacteria, Verrumicrobia, Bacteriodetes, WS3, Chloroflexi, Firmicutes, Acidobacteria, SR1, Actinobacteria, Spirochaetes and OD1. For the Schlema mine Proteobacteria, Acidobacteria, WS3, Bacteriodetes, Chloroflexi, SR1, Chlorobi, TM7 and Acinobacteria were found. The dominant bacterial phylum in all samples are the Proteobacteria. Higher bacterial diversities were observed in flow cells in comparison with filtrated waters. A dataset of 15786, 17872, 11404, 7780 sequences revealed 639, 643, 769 and 455 OTUs, respectively, mainly for Archaea of the filtrated Pöhla mine water, the Pöhla flow cell, the filtrated Schlema mine water and the Schlema flow cell, respectively. The archaeal sequences of the Pöhla as well as the Schlema mine water belong to the class of Methanobacteria, Thermoprotei, Methanomicrobia, Thermoplasmata and Halobacteria.

  • Contribution to proceedings
    Goldschmidt 2013, 25.-30.08.2013, Florenz, Italien

Permalink: https://www.hzdr.de/publications/Publ-18691
Publ.-Id: 18691


Observation of Forbidden Exciton Transitions Mediated by Coulomb Interactions in Photoexcited Semiconductor Quantum Wells

Rice, W. D.; Kono, J.; Zybell, S.; Winnerl, S.; Bhattacharyya, J.; Schneider, H.; Helm, M.; Ewers, B.; Chernikov, A.; Chatterjee, S.; Khitrova, G.; Gibbs, H. M.; Schneebeli, L.; Breddermann, B.; Kira, M.; Koch, S.

We use terahertz pulses to induce resonant transitions between the eigenstates of optically generated exciton populations in a high-quality semiconductor quantum well sample. Monitoring the excitonic photoluminescence, we observe transient quenching of the 1s exciton emission, which we attribute to the terahertz-induced 1s-to-2p excitation. Simultaneously, a pronounced enhancement of the 2s exciton emission is observed, despite the 1s-to-2s transition being dipole forbidden. A microscopic many-body theory explains the experimental observations as a Coulomb-scattering mixing of the 2s and 2p states, yielding an effective terahertz transition between the 1s and 2s populations.

Keywords: THz spectroscopy; time-resolved photoluminescence; interexcitonic transitions; semiconductor quantum wells; microscopic many-body theory; Coulomb-scattering mixing

Permalink: https://www.hzdr.de/publications/Publ-18690
Publ.-Id: 18690


Sorption and desorption processes of U(VI) on iron (hydr)oxide phases

Foerstendorf, H.; Heim, K.; Jordan, N.

In this comparative study, the surface speciation of uranium(VI) on ferrihydrite (Fh) and maghemite (Mh) were investigated by vibrational spectroscopy. The experimental setup allows the monitoring of the surface processes at the water-solid interface in real time with a time resolution in the subminute time range. The performance of the experiments under inert gas atmosphere and under ambient conditions provides further insight into the molecular events of the binary and ternary sorption systems, respectively.
The spectra clearly demonstrate a characteristic surface speciation in dependence of the solid phase. On Fh, the formation of ternary inner sphere complexes are observed as it was derived earlier [1]. In addtion, the time-resolved spectra reveal the change of the surface speciation of atmospherically derived carbonate upon U(VI) sorption [2].
From the sorption experiments on Mh, outer sphere complexation of the uranyl ion can be derived. In ambient atmosphere, contributions of carbonate ions to the U(VI) surface speciation on Mh can not be ruled out.

[1] Ulrich et al. (2006) Geochim. Cosmochim. Acta 70, 5469-5487. [2] Foerstendorf et al. (2012) J. Colloid Interface Sci. 377, 299-306.

  • Lecture (Conference)
    Goldschmidt 2013, 25.-30.08.2013, Florence, Italy
  • Open Access Logo Abstract in refereed journal
    Mineralogical Magazine 77(2013)5, 1098-1098
    DOI: 10.1180/minmag.2013.077.5.6

Permalink: https://www.hzdr.de/publications/Publ-18689
Publ.-Id: 18689


Formation of Se(0) nanoparticles by Azospirillum brasilense

Steudtner, R.; Maffert, A.; Vogel, M.; Franzen, C.; Scheinost, A. C.

In the present study we investigated the reduction of SeO32− by Azospirillum brasilense. The formation of fairly soluble Se(0) nano-particles during this process might be of interest for both bioremediation of Se-contaminated sites and for nanobiotechnology. After A.brasilense being exposed to Se(IV), the bacterial growth continued subsequent to a prolonged lag-phase. After a cultivation time of 3 days, a clearly reddish staining of the sample was observed and a bright red precipitate occurred, indicating the formation of Se(0) nano-particles. The SEM-EDX spectra derived from the nano-spheres indicated that they mainly consist of selenium. In addition, only 10 % of the initial Se(IV) concentrations was recoverd in culture media by means of HG-AAS, indicating a Se(IV) removal from the media. The isolated and resuspended Se(0) nanoparticles showed a long time stability of some hours, which is sufficient for the PCS and the zeta potential measurements. In contrast, Se(0) chemically formed by reduction with hydroxylamine solution produced amorphous aggregates with a rapid sedimentation behavior. The PCS measurement and the SEM imaging of the Se(0) particles showed a particle size distribution between 100 and 300 nm with an averaged particle diameter of 200 nm. The isoelectric point of Se(0) particles was found at pH 2.8 ± 0.2. The preference of forming Se(0) particles with a negative charge agree very well with the literature [1].

[1] Dhanjal & Cameotra (2010) Microb. Cell Fact. 9,1-11.

Keywords: Selen; Redox reaction; HG-AAS; SEM-EDX; PCS; Zeta potential

  • Contribution to proceedings
    Goldschmidt 2013, 25.-30.08.2013, Florence, Italy

Permalink: https://www.hzdr.de/publications/Publ-18688
Publ.-Id: 18688


Retention of selenate at the water-mineral interface in the context of salt dome repositories

Franzen, C.; Hering, D.; Jordan, N.

One major process controlling the mobility and bioavailability of selenium, a long-lived fission product found in nuclear waste, is the adsorption onto mineral surfaces of both the engineered and geological barrier. In this context, it is important to understand to what extent this sorption is influenced particularly by characteristic parameters as expected in deep underground repositories for high level and long-lived radioactive waste. These parameters include inter alia the presence of different background salts which are important with regard to salt domes as potential repositories.
In the present study, a combination of macroscopic sorption experiments, electrophoretic mobility and in-situ ATR FT-IR spectroscopy measurements was used to study the interaction of selenate with aged γ-Al2O3 in the presence of NaCl and MgCl2. From in-situ ATR FT-IR spectra, a change in the symmetry of the aqueous tetrahedral selenate anion can be derived evidencing the formation of a surface complex on γ-Al2O3. From batch experiments, we observe a dependence of selenate sorption on the ionic strength and composition of the electrolyte. Additionally, the sorption generally decreases with increasing pH. However, in the presence of 0.1 M MgCl2, the sorption increased again at a pH above 9.5.
The isoelectric point (pHIEP) of γ-Al2O3 is located at pH 9.6 for low NaCl background electrolyte concentration (I = 0.1 M). The increase of ionic strength (up to I = 1 M) results in a decrease of the zeta potential for both the acidic and alkaline pH range. However, in the alkaline range the decrease of the zeta potential is more pronounced. Additionally, we observe that the pHIEP is shifted to more alkaline values and finally no charge reversal is observed. In the presence 0.1 M MgCl2, the surface charge of γ-Al2O3 is positive throughout the studied pH range (3-11). Above pH 10, a sharp potential decrease occurs due to Mg(OH)2 precipitation. The impact of the varied parameters on the sorption of selenate in the alkaline pH range will be verified in detail.

Keywords: sorption; selenate; gamma-al2O3

  • Poster
    Goldschmidt 2013, 25.-30.08.2013, Florence, Italy
  • Mineralogical Magazine 77(2013)5, 1107-1107
    DOI: 10.1180/minmag.2013.077.5.6

Permalink: https://www.hzdr.de/publications/Publ-18687
Publ.-Id: 18687


Sorption of uranium and neptunium onto diorite from Äspö HRL

Schmeide, K.; Gürtler, S.; Müller, K.; Steudtner, R.; Joseph, C.; Bok, F.; Brendler, V.

The retention behavior of the crystalline rock diorite from the Äspö Hard Rock Laboratory (HRL, Sweden) towards the redox-sensitive actinides U and Np was studied by means of batch sorption experiments. The influence of various parameters, such as grain size (0.063 – 0.2 mm, 0.5 – 1 mm, 1 – 2 mm), temperature (25 and 10°C), atmosphere and sorption time (5 to 108 days) was studied using a synthetic Äspö groundwater (pH 7.8, I = 0.178 M) as background electrolyte. For U(VI), sorption isotherms were recorded (5x10−9 M to 7x10−5 M). Distribution coefficients, Kd values, were determined.

Keywords: uranium; neptunium; sorption; reduction; diorite

  • Lecture (Conference)
    Goldschmidt 2013, 25.-30.08.2013, Florence, Italy
  • Open Access Logo Abstract in refereed journal
    Mineralogical Magazine 77(2013)5, 2155-2155
    DOI: 10.1180/minmag.2013.077.5.19

Permalink: https://www.hzdr.de/publications/Publ-18686
Publ.-Id: 18686


THz free-electron laser spectroscopy of zero- and two-dimensional semiconductors

Schneider, H.

There is no abstract.

  • Invited lecture (Conferences)
    6th Annual Meeting, Deutsches THz-Zentrum e.V., ISL Saint-Louis, 25.-26.02.2013, Saint-Louis, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-18685
Publ.-Id: 18685


Mid-infrared and terahertz free-electron laser spectroscopy of zero- and two-dimensional semiconductors

Schneider, H.; Winnerl, S.; Helm, M.

The free-electron laser (FEL) facility FELBE in Dresden provides unique opportunities to advance our knowledge on the interaction of intense mid-infrared and terahertz fields with materials and devices. Its nearly transform-limited ps pulses, which can also be combined with synchronous ps or fs pulses from near-infared tabletop lasers, represent a versatile radiation source for novel experiments, which is also available to external users. This talk reviews some of our recent experimental studies, which are also representative for advanced measurement techniques at FELBE.
In high-quality semiconductor quantum wells, time-resolved photoluminescence allows us to investigate the dynamics of excitons, i.e. two-dimensional, hydrogen-like electron-hole quasiatoms. In particular, applying time-delayed FEL pulses tuned to the intra-excitonic 1s-2p transition (at 9 meV for an 8 nm wide GaAs/AlGaAs quantum well), we have studied the population transfer between the 2p and 2s exciton states. Moreover, strong terahertz pumping in resonance with the 1s-2p transition results in a characteristic splitting (Rabi splitting) of the 1s exciton state, which is a manifestation of the intra-excitonic Autler-Townes effect [1].
In semiconductor quantum dots, resonant excitation between s, p and d sublevels in these zero-dimensional atom-like nanostructures is shown to produce an absorption contrast in aperture-less scattering scanning near-field optical microscopy (s-SNOM). This effect allows us to obtain functional s-SNOM images with deep sub-wavelength resolution, where far-infrared absorption by single electrons produces sufficient contrast to map individual quantum dots [2].
In graphene, FEL-based pump-probe spectroscopy has shown evidence of different relaxation times for excitation energies above and below those of the optical phonons, as well as a transition from induced transmission (bleaching) to induced absorption if the photon energy becomes smaller than twice the Fermi energy [3]. In particular, the latter observation is indicative for interesting potential applications of this two-dimensional semiconductor material, e.g. as an electro-optical modulator.
[1] J. Wagner et al., Phys. Rev. Lett. 105, 167401 (2010)
[2] R. Jacob et al., Nano Lett. 12, 4336–4340 (2012))
[3] S. Winnerl et al., Phys. Rev. Lett. 107, 237401 (2011)

  • Lecture (Conference)
    41st Freiburg Infrared Colloquium, 26.-27.02.2013, Freiburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18684
Publ.-Id: 18684


Terahertz spectroscopy of zero- and two-dimensional semiconductors

Schneider, H.

There is no abstract.

  • Lecture (others)
    Seminarvortrag, Okinawa Institute of Science and Technology Graduate University, 28.03.2013, Onna, Okinawa, Japan

Permalink: https://www.hzdr.de/publications/Publ-18683
Publ.-Id: 18683


Axial discontinuity factors for the nodal diffusion analysis of high conversion BWR cores

Fridman, E.; Duerigen, S.; Bilodid, Y.; Kotlyar, D.; Shwageraus, E.

High conversion Light Water Reactor concepts typically rely on heterogeneous core configuration, where fissile zones are interspersed with fertile blanket zones in order to achieve high conversion ratio. Such a heterogeneous structure renders the modeling of these cores impossible using conventional reactor analysis methods. It was recently suggested to overcome such difficulties, in particular, for the case of axially heterogeneous reduced moderation BWRs, by introducing additional set of discontinuity factors in the axial direction at the interfaces between fissile and fertile fuel assembly zones. However, none of the existing nodal diffusion core simulators have the capability of accounting for discontinuity of homogeneous nodal fluxes in the axial direction since the fuel composition of conventional LWRs is much more axially uniform. In this work, we modified nodal diffusion code DYN3D by introducing such capability. The new version of the code was tested on a series of reduced moderation BWR cases with Th-U233 and U-Pu-TRU fuel. The library of few-group homogenized cross sections and the data required for calculation of discontinuity factors were generated using Monte Carlo transport code Serpent. The results obtained with the modified version of DYN3D were compared with the reference Monte Carlo solutions and were found to be in a good agreement. The current analysis demonstrated that high conversion LWRs can in principle be modeled using existing nodal diffusion core simulators.

Keywords: Serpent; Monte Carlo; DYN3D; few-group cross-section generation; axial discontinuity factors

Permalink: https://www.hzdr.de/publications/Publ-18682
Publ.-Id: 18682


Design and analysis of an innovative pressure tubes light water reactor with variable moderator control

Rachamin, R.; Fridman, E.; Galperin, A.

An innovative light water reactor constructed as a multitude of modular, horizontal fuel channels has been proposed. The basic novelty of the proposed design is an implementation of the “breed & burn” mode of operation by a dynamic variation of the moderator content in the core. This paper describes the novel reactor core design and explores the physical principles underlying its operation. Initially, a single fuel channel assembly was analyzed in order to evaluate the impact of the moderator variation on the reactivity and “breed & burn” processes. At the second stage, a full core model was analyzed, demonstrating a possibility of a realistic fuel management scheme with on-power moderator addition. The BGCore Monte-Carlo based depletion code was used for the analyses. It has been shown that the proposed design has a potential to increase the fuel utilization, attain negative reactivity coefficients and reduce the excess core reactivity during the power operation. The physical observations, presented and discussed in this paper, provide an interesting research lines for future investigation and continuous design developments.

Keywords: pressure tube reactor; “breed & burn”; moderator variation; H/HM ratio; reactivity control

Permalink: https://www.hzdr.de/publications/Publ-18681
Publ.-Id: 18681


The nELBE Neutron Time-of-Flight Facility

Junghans, A. R.; Wagner, A.; Bemmerer, D.; Beyer, R.; Birgersson, E.; Ferrari, A.; Grosse, E.; Hannaske, R.; Kempe, M.; Kögler, T.; Massarczyk, R.; Matic, A.; Nolte, R.; Schwengner, R.

The compact neutron-time-of-flight facility nELBE at the superconducting electron accelerator ELBE of Helmholtz-Zentrum Dresden-Rossendorf is currently being rebuilt. As the neutron radiator consists of a liquid-lead circuit no moderated neutrons are produced and also the background from capture gamma-rays is very small. The useful neutron spectrum extends from some tens of keV to about 10 MeV. nELBE is intended to deliver cross section data of fast neutron nuclear interactions e.g. for the transmutation of nuclear waste and an improvement of neutron physical simulations of innovative nuclear systems. The new experimental hall will allow measurements of angular distributions in neutron scattering. Inelastic neutron scattering, e.g. on 56Fe, has been studied with a double time-of-flight setup and with photon detectors to measure the gamma-rays produced in the process. The neutron total cross sections of Au and Ta were determined in a transmission experiment.

Keywords: neutron fission transmutation inelastic scattering time-o-flight

  • Contribution to external collection
    D. Ridikas, IAEA: IAEA-TECDOC-1743: Compendium of Neutron Beam Facilities for High Precision Nuclear Data Measurements, Vienna: IAEA, 2014

Permalink: https://www.hzdr.de/publications/Publ-18680
Publ.-Id: 18680


Microbial mediated immobilization of radionuclide in a future crystalline nuclear-waste repository

Krawczyk-Bärsch, E.; Pedersen, K.; Arnold, T.; Bok, F.; Lehtinen, A.

The world’s first permanent nuclear-waste repository for high-level waste (HLW) will be the underground rock characterization facility tunnel ONKALO, situated near the nuclear power plants of Olkiluoto, approximately 300 km northwest of Helsinki (Finland). Geological mapping showed that the bedrock of the tunnel is mainly composed of veined gneisses with a migmatic appearance, which are interspersed by numerous fractures. Massive 5–10-mm thick biofilms (microbial communities) are observed attached to the tunnel walls where groundwater is seeping from bedrock fractures feeding the biofilm. Groundwater and biofilm samples were taken during the EURATOM collaborative project ReCosy for laboratory experiments in flow cells, where uranium(VI) was added to the circulating groundwater with a final uranium concentration (4.25×10–5 M), which was expected from a damaged and leaking waste canister in the far-field of a nuclear-waste repository. The aim of our studies was to simulate the fate and behaviour of uranium(VI) in the presence of microorganisms using different methods to find evidence of the possibility of uranium retention.

In our experiments, aqueous uranium percolated the biofilm and induced interaction between biofilm microorganisms and uranium(VI), forming an intracellular U-phosphate mineral similar to autunite (Ca[UO2]2[PO4]2 • 2-6H2O or meta-autunite Ca[UO2]2[PO4]2 • 10-12H2O) as determined by means of EF-TEM/EELS. The potential toxicity of uranyl was consequently avoided by the uranium forming these strong complexes with phosphate in the cytoplasm of these microorganisms. Inorganic phosphate (H2PO4–) was released from the cellular polyphosphate as a cells’ response to the heavy metal stress. In contrast, aqueous uranium carbonate species, likely calcium uranyl carbonates species (Ca2UO2[CO3]3), were formed using the large available amount of carbonate in the uranium-contaminated circulating groundwater. The results of the laser-induced fluorescence spectroscopy studies performed at 283 K are in excellent agreement with the thermodynamic calculations of the theoretical predominance fields of the uranium species formed in the uranium-contaminated circulating groundwater. These complexes consequently influence the speciation of uranium, contributing to the transport and migration of uranium(VI).

Our studies aimed to improve our understanding of the mechanisms by which biofilms respond to the exposure to radionuclide with respect to safety assessments in the far-field of nuclear-waste repositories. In this environment, microorganisms must be considered, along with minerals, as an important factor influencing radionuclide transport.

Keywords: uranium; biofilm; nuclear-waste repository

  • Poster
    EURADWASTE´13, 8th EC Conference on the Management of Radioactive Waste, 14.-16.10.2013, Vilnius, Lithuania
  • Contribution to proceedings
    EURADWASTE `13, 8th EC Conference on the Management of Radioactive Waste, 14.-16.10.2013, Vilnius, Lithuania

Permalink: https://www.hzdr.de/publications/Publ-18679
Publ.-Id: 18679


Pushing Plasma Simulations Towards Exascale Performance with PIConGPU

Bussmann, M.; Juckeland, G.

With PIConGPU, new physics phenomena previously not accessible within laser plasma simulations can be studied, which will help us optimize laser-driven radiation sources. Presents results on laser wakefield acceleration of electrons simulated on the Oakridge TITAN system and discuss in detail which techniques help us to get the most out of these clusters. Finally showing how to add fault-tolerance and load-balancing to a large hybridh CPU-GPU code such as PIConGPU to achieve optimum performance.

Keywords: gpu; particle-in-cell; pic; cuda; simulation

  • Lecture (Conference)
    GPU Technology Conference (GTC), 18.-21.03.2013, San Jose, United States of America

Permalink: https://www.hzdr.de/publications/Publ-18678
Publ.-Id: 18678


PIConGPU - How to built one of the fastest GPU particle-in-cell codes in the world

Burau, H.; Debus, A.; Helm, A.; Hübl, A.; Kluge, T.; Widera, R.; Bussmann, M.; Schramm, U.; Cowan, T. E.; Juckeland, G.; Schmitt, F.; Nagel, W.

We present the algorithmic building blocks of PIConGPU, one of the fastest implementations of the particle-in-cell algortihm on GPU clusters. PIConGPU is a highly-scalable, 3D3V electromagnetic PIC code that is used in laser plasma and astrophysical plasma simulations.

Keywords: picongpu; particle-in-cell; pic; simulation; plasma; parallel; cuda

  • Poster
    77. Jahrestagung der DPG und DPG-Frühjahrstagung, 04.-08.03.2013, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18677
Publ.-Id: 18677


Relativistic LTE fluid plasma simulation

Buikstra, L.; Bussmann, M.; van Goor, F.; Irman, A.; Schramm, U.; Cowan, T. E.

To allow simulation of nanosecond scale plasma processes, we are developing a 3D fully relativistic fluid code with LTE (local thermal equilibrium) closure. This code is intended to be able to take output from PIC simulations as its initial state, to allow self-consistent simulation of processes acting over multiple time and density scales. In this code, both electrons and ions are treated as inertial fluids. Local fluid pressure is tied to the energy density using the Maxwell-Jüttner distribution, allowing investigation of the effect of local temperatures on, for example, the expanding sheath in TNSA (target normal sheath acceleration) experiments.

Keywords: lte; plasma; fluid; simulation; tnsa

  • Poster
    77. Jahrestagung der DPG und DPG-Frühjahrstagung, 04.-08.03.2013, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18676
Publ.-Id: 18676


Dynamics of ion heating and ionization in high power ultra-short laser pulses interacting with solid density plasmas

Huang, L.; Kluge, T.; Gutt, C.; Bussmann, M.; Cowan, T. E.

Plasma heating and ionization are important processes during the interaction of high power ultra-short laser pulses with solid density targets. In order to understand the relevant physics, particle-in-cell simulations including collisions and ionization were run to study ion heating dynamics in buried layer targets illuminated by high-intensity, ultra-short laser pulses. Our results show that bulk ions can be heated to above 1keV temperature. When studying the ionization dynamics strong filaments have been observed which depend on preplasma on the target front side, laser pulse duration and intensity. In order to study the evolution of ionization and ion bulk heating in experiment, ultra-bright X-ray free electron lasers - such as the European XFEL - are a very promising and strong tool to resolve the spatial and temporal scales of these processes inside the solid target.

Keywords: plasma; solid density; heating; buried layer; laser; simulation; xfel

  • Lecture (Conference)
    77. Jahrestagung der DPG und DPG-Frühjahrstagung, 04.-08.03.2013, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18675
Publ.-Id: 18675


Hyperfine splitting in lithium-like bismuth

Lochmann, M.; Andelkovic, Z.; Botermann, B.; Bussmann, M.; Dax, A.; Frömmgen, N.; Hammen, M.; Hannen, V.; Jöhren, R.; Geppert, C.; Kühl, T.; Litvinov, Y.; Vollbrecht, J.; Nörtershäuser, W.; Stöhlker, T.; Thompson, R.; Volotka, A.; Weinheimer, C.; Wen, W.; Will, E.; Winters, D.; Sánchez, R.

High-precision measurements of the hyperfine splitting values on Li- and H-like bismuth ions, combined with precise atomic structure calculations allow us to test QED-effects in the regime of the strongest magnetic fields that are available in the laboratory. Performing laser spectroscopy at the experimental storage ring (ESR) at GSI Darmstadt, we have now succeeded in measuring the hyperfine splitting in Li-like bismuth. Probing this transition has not been easy because of its extremely low fluorescence rate. Details about this challenging experiment will be given and the achieved experimental accuracy will be presented.

Keywords: bismuth; li-like; spectroscopy; qed

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion AMOP (SAMOP), 18.-22.03.2013, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18674
Publ.-Id: 18674


Broadband lasercooling of relativistic ions at the ESR

Winters, D.; Clark, C.; Dimopoulou, C.; Giacomini, T.; Kozhuharov, C.; Kühl, T.; Lochmann, M.; Nörtershäuser, W.; Nolden, F.; Sanchez, R.; Sanjari, S.; Steck, M.; Stöhlker, T.; Ullmann, J.; Beck, T.; Birkl, G.; Rein, B.; Tichelmann, S.; Walther, T.; Ma, X.; Wen, W.; Yang, J.; Zhang, D.; Schramm, U.; Seltmann, M.; Siebold, M.; Bussmann, M.

We present new results on broadband laser cooling of stored relativistic C3+ ion beams at the ESR in Darmstadt. For the first time we could show laser cooling of bunched relativistic ion beams using a UV-laser which could scan over a very large range and thus cool all the ions in the ‘bucket’. This scheme is much more versatile than a previous scheme, where the bunching frequency was scanned relative to a fixed laser frequency. We have also demonstrated that this cooling scheme works without pre-electron cooling, which is a prerequisite for its general application to future storage rings and synchrotrons, such as the HESR and the SIS100 at FAIR. We also present results from in vacuo VUV-fluorescence detectors, which have proven to be very effective.

Keywords: laser cooling; ion beam; fair; esr

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion AMOP (SAMOP), 18.-22.03.2013, Hannover, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18673
Publ.-Id: 18673


Broadband Lasercooling of Relativistic Ion Beams at ESR

Bussmann, M.; Seltmann, M.; Siebold, M.; Schramm, U.; Wen, W.; Winters, D.; Beck, T.; Rein, B.; Walther, T.; Tichelmann, S.; Birkl, G.; Sanchez-Alarcon, R.; Ullmann, J.; Lochmann, M.; Nörtershäuser, W.; Clark, C.; Kozhuharov, C.; Steck, M.; Dimopoulou, C.; Nolden, F.; Zhang, D.; Ma, X.; Stöhlker, T.; Sanjari, S.; Giacomini, T.; Yang, J.

We present new results on laser cooling of relativistic C3+ ion beams at the Experimental Storage Ring at GSI. For the first time we could show laser cooling of bunched relativistic ion beams using fast scanning of the frequency of the cooling laser over a range larger than the momentum acceptance of the bucket. Unlike previously employed cooling schemes where the bucket frequency was scanned relatively to a fixed laser frequency, scanning of the laser frequency can be readily applied to future high energy storage rings such as HESR or SIS 100 at FAIR.

Keywords: laser cooling; ion beam; esr

  • Lecture (Conference)
    77. Jahrestagung der DPG und DPG-Frühjahrstagung, 04.-08.03.2013, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18672
Publ.-Id: 18672


PIConGPU - A Highly-Scalable Particle-in-Cell Implementation for GPU Clusters

Bussmann, M.; Burau, H.; Debus, A.; Hübl, A.; Kluge, T.; Pausch, R.; Schmeisser, N.; Schneider, B.; Steiniger, K.; Widera, R.; Wyderka, N.; Schramm, U.; Cowan, T. E.; Schmitt, F.; Grottel, S.; Gumhold, S.; Juckeland, G.; Nagel, W.

PIConGPU can handle large-scale simulations of laser plasma and astrophysical plasma dynamics on GPU clusters with thousands of GPUs. High data throughput allows to conduct large parameter surveys but makes it necessary to rethink data analysis and look for new ways of analyzing large simulation data sets. The speedup seen on GPUs enables scientists to add physical effects to their code that up until recently have been too computationally demanding. We present recent results obtained with PIConGPU, discuss scaling behaviour, the most important building blocks of the code and new physics modules recently added. In addition we give an outlook on data analysis, resiliance and load balancing with PIConGPU.

Keywords: gpu; particle-in-cell; pic; simulation

  • Lecture (Conference)
    77. Jahrestagung der DPG und DPG-Frühjahrstagung, 04.-08.03.2013, Dresden, Deutschland
  • Lecture (Conference)
    DPG-Frühjahrstagung, 25.02.-01.03.2013, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18671
Publ.-Id: 18671


Comparision of (-)-[18F]-Flubatine and 2-[18F]FA-85380 Binding to Nicotinic α4β2* Acetylcholine Receptors in Human Brains

Becker, G. A.; Wilke, S.; Schönknecht, P.; Patt, M.; Luthardt, J.; Hesse, S.; Meyer, P. M.; Barthel, H.; Sorger, D.; Seese, A.; Wagenknecht, G.; Hoepping, A.; Fischer, S.; Brust, P.; Sabri, O.

Aim:
Nicotinic α4β2* acetylcholine receptors (nAChR) are an important target for diagnostic neuroimaging because of their involvement in Alzheimer's disease, Parkinson's disease, tobacco and alcohol addiction. 2-[18F]FA-85380 (2-FA) has been used extensively for PET imaging of α4β2* receptors but is limited as biomarker by its unfavourable slow kinetic. The newly developed radiotracer (-)-[18F]-Flubatine (Flubatine) shows a significantly improved brain uptake, receptor affinity and selectivity (1). Here we estimated the compartmental parameters of both tracers by full kinetic modeling and compared them.

Materials and methods:
After intravenous administration of ~370 MBq radiotracer PET brain imaging was performed in 20 healthy controls with Flubatine (age 70.6±4.6, scan duration 90 min) and in 7 healthy controls with 2-FA (age 60.7±9.0, scan duration 420 min) using an ECAT EXACT HR+ system. PET frames were motion corrected with SPM2 and kinetic modeling using a 1-tissue compartment model (1TCM) with arterial input-function was applied to the volume of interest (VOI) based tissue time-activity curves (TACs) generated for 29 brain regions (anatomically defined via MRI co-registration). The model-based receptor parameter used was the total distribution volume VT (ml/cm3), tracer uptake was measured by K1 (ml/cm3/min) and tracer tissue clearance by k2 (1/min).

Results:
For both tracers TACs of all 29 brain regions could be described appropriately with the 1TCM and all kinetic parameters could be reliably estimated from the PET data. Regional VT increased as expected with regional nAChR density. Parameters of Flubatine in characteristic regions with very low, medium and high receptor density were: Corpus callosum (K1= 0.18±0.04, k2= 0.032±0.004, VT= 5.68±1.01), Frontal cortex (K1= 0.37±0.04, k2= 0.040±0.003, VT= 9.18±0.59), Thalamus (K1= 0.48±0.06, k2= 0.020±0.003, VT= 25.03±3.33). The respective parameters of 2-FA were: Corpus callosum (K1= 0.063±0.009, k2= 0.014±0.003, VT= 4.45±0.65), Frontal cortex (K1= 0.099±0.013, k2= 0.018±0.001, VT= 5.42±0.56), Thalamus (K1= 0.13±0.019, k2= 0.010±0.001, VT= 13.06±2.62).

Conclusions:
Flubatine is superior to 2-FA in tracer uptake velocity (characterized by K1), velocity of washout (characterized by k2) and in the amount of measured specific binding (characterized by VT-target - VT-reference). It shows a threefold higher uptake rate constant K1 and a twofold higher washout rate constant k2, providing the rational for much shorter scan durations in case of Flubatine. These results are in good agreement with our former findings in an animal (pig) model (1).

Reference:
1. P. Brust, ..O. Sabri: In vivo measurement of nicotinic acetylcholine receptors with [18F]Norchloro-Fluoro-Homoepibatidine (Flubatine). Synapse 2008;62:205-218.

  • Poster
    EANM 2013 - Annual Congress of the European Association of Nuclear Medicine, 19.-23.10.2013, Lyon, France, 19.-23.10.2013, Lyon, Frankreich
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 40(2013)2, S271-S271

Permalink: https://www.hzdr.de/publications/Publ-18670
Publ.-Id: 18670


Laser-driven Sources of Radiation Fundamentals, Simulations and Applications

Bussmann, M.

We present recent results on TNSA, simulations and laser cooling of ion beams

Keywords: tnsa; pic; gpu; picongpu; laser; cooling; ion; beam; acceleration

  • Invited lecture (Conferences)
    XLIV. Arbeitstreffen "Kernphysik", 21.-28.02.2013, Schleching/obb., Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18669
Publ.-Id: 18669


Scanner independent implementation of 3D list-mode reconstruction: proof of concep

Lougovski, A.; Domula, S.; Langner, J.; Hofheinz, F.; Schramm, G.; Steinbach, J.; van den Hoff, J.

Ziel/Aim:
Our aim was to port our previously developed high resolution 3D list-mode image reconstruction for the HR+ PET to the Philips Ingenuity TF PET/MR system. Porting to a different scanner usually requires a major rewrite to account for system specific aspects. Instead, a general interface was designed and implemented in our reconstruction to allow simultaneous support of multiple scanners and to facilitate future adoption to further scanner types. We report on application of this strategy for implementing our reconstruction on the Philips PET/MR.

Methodik/Methods:
We implemented a generalized interface using abstract classes which completely removes scanner dependency from the reconstruction algorithm and allows runtime switching between scanners. The reconstruction obtains system specific information
such as geometry parameters and data formats directly via an abstract interface using internal formats. The port to the Philips PET/MR was performed accordingly and evaluated: i) quantitative accuracy and spatial resolution in phantoms, ii) visual evaluation of patient studies, iii) runtime performance evaluation.

Ergebnisse/Results:
The use of an abstract interface influences the runtime performance of the reconstruction only minimal. The ported reconstruction shows substantial improvements in comparison to the vendor provided software. In phantoms we obtain improved resolution and a high level of quantitative accuracy. Visual inspection of phantom and patient data reveals an improved level of detail rendering.

Schlussfolgerungen/Conclusions:
The implementation of an abstract interface simplifies porting of the software to other scanners. For the Philips PET/MR we observed improved resolution and overall image quality compared to the vendor provided software. Support of Time-of-Flight information is currently implemented and already shows further improvements of image quality at reduced reconstruction times.

  • Poster
    51. Jahrestagung der Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A81-A82

Permalink: https://www.hzdr.de/publications/Publ-18668
Publ.-Id: 18668


Development and preparation of a novel carbon-11 containing radiotracer for non-invasive PET-Imaging of EphB4

Mamat, C.; Ebert, K.; Knieß, T.; Steinbach, J.

Ziel/Aim:
Members of the Eph receptor tyrosine kinase family play an essential role in the pathogenesis of cancer and, therefore, are promising candidates for molecular imaging purposes, e.g. by PET. In this regard, radiochemical access to 11C-radiotracers derived from potent inhibitors (IC50 = 1.3 nM, calcd. logP = 3.42) targeting EphB4 kinase domain and bearing the indazolylpyrazole structural motif was developed.

Methodik/Methods:
The evaluation of a protecting group strategy based on the ethoxyethyl moiety (EOE) was necessary for the regioselective labeling with [11C]CH3I due to three secondary amino groups of the precursor. The labeling was accomplished in a remotely controlled synthesis module in three steps. The first step involved the preparation of [11C]CH3I from [11C]CH4, the second step comprehended the radiolabeling of the protected precursor and the final step included the cleavage of the protecting group.

Ergebnisse/Results:
The synthesis of the reference as well as the precursor was done starting from EOE protected indazole. Subsequent reaction with 2,4-diochloropyrimidine give the first substructure. For the preparation of the precursor, the first substructure was treated with 3,5-di(morpholino)aniline under Buchwald-Hartwig conditions. For the preparation of the reference, the first substructure was first methylated and then treated with 3,5-di(morpholino)aniline. The radiolabeling was done starting with ~ 1-1.5 GBq [11C]CH3I under basic conditions. After 2 min reaction time 1 M HCl was added and the mixture was maintained for 2 min. Approx. 200 MBq of the desired radiotracer could be obtained within 20 min after EOB (30-35% d.c. yield based on [11C]CH4).

Schlussfolgerungen/Conclusions:
The two-step radiolabeling of a novel indazolylpyrazole derivative with [11C]CH3I was successfully demonstrated. First stability tests showed beneficial behaviour ex vivo. Further biological studies for an application as radiotracer for functional tumor imaging are ongoing.

Literatur/References:
Mamat C, Mosch B et al. (2012) ChemMedChem 7:1991-2003.

  • Poster
    51. Jahrestagung der Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A72

Permalink: https://www.hzdr.de/publications/Publ-18667
Publ.-Id: 18667


Application of the Huisgen reaction for the radiofluorination of SNEW peptides as probes for the Eph receptor monitoring

Mamat, C.; Pretze, M.; Bergmann, R.; Pietzsch, J.; Steinbach, J.

Ziel/Aim:
The synthesis of fluorine-18 labeled peptides with high affinity towards the EphB2 receptor and the evaluation as radiotracers for PET was described. This receptor is known to be overexpressed in various types of cancer. Thus, a peptide was applied with high affinity to the EphB2 receptor which is strongly constrained of the amino acid key sequence SNEW. Two novel bifunctional and bioorthogonal building blocks were evaluated. The labeling of the peptides was done using the Huisgen click approach.

Methodik/Methods:
Two labeling building blocks based on the piperazine skeleton with either alkyne or azide function were used and an automated module synthesis was evaluated. Further, it was found that the peptide SNEWILPRLPQH show a high affinity to EphB2. Thus, the C-terminus of the peptide was functionalized with alkyne or azide, to retain the high affinity which is constrained of the key sequence SNEW at the N-terminus.

Ergebnisse/Results:
The automated one-step radiosynthesis of two novel building blocks gave the desired piperazine derivatives [18F]AFP and [18F]BFP in radiochemical yields of 25-45% (d.c.) within 50 min and a high purity after convenient separation from [18F]F- and precursor using silica gel cardridges. Radiolabeling of several functionalized SNEW peptides under Click conditions pointed out that [18F]AFP is only suitable and yielded the radiofluorinated peptide in 10-15 % RCY (d.c.). A by-product was observed when the alkyne building block [18F]BFP was used due to the competing Glaser coupling. Finally, the peptide was prepared, radiolabeled and purified from the Cu with bispidine on SPPS. This is urgent, otherwise, aggreagtion of the peptide with Cu occur. Finally, the stability of the labeled SNEW peptide was investigated ex vivo showing >80% intact peptide after 1 h. Three more hydrophilic metabolites were observed not determined as [18F]F-.

Schlussfolgerungen/Conclusions:
With the SNEW peptides highly potent 18F-containing EphB2 inhibitors were found and the labeling on SPPS with [18F]AFP was successfully established.

  • Poster
    51. Jahrestagung der Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A72

Permalink: https://www.hzdr.de/publications/Publ-18666
Publ.-Id: 18666


Realistic simulations of laser-driven radiation sources. What we need and what is there.

Bussmann, M.

With upcoming supercomputer technology, the simulation of laser-driven radiation sources enters the realm of large-scale parameter surveys, interactive simulation and the possibility to add physical effects hitherto impossible to account for.
We present new ideas and techniques to deliver simulations that are closer to experiment and can be better connected to new experimental diagnostics.
We finally show how an integrated experimental and theoretical program is needed to increase the predictive capability of codes and why code validation will be the focus of laser plasma simulations.

Keywords: gpu; particle-in-cell; laser; acceleration; simulation; pic

  • Invited lecture (Conferences)
    Institute Seminar MTA-PTE High-Field Terahertz Research Group, 07.02.2013, Pécs, Hungary

Permalink: https://www.hzdr.de/publications/Publ-18665
Publ.-Id: 18665


Festphasensynthese von selektiv mono-fluorbenzoylierten Polyaminen zur In-vivo-Adressierung von Transglutaminasen und Polyamin-Transportern

Wodtke, R.; Steinbach, J.; Pietzsch, J.; Löser, R.

Ziel/Aim:
Transglutaminasen und Polyamin-Transporter sind interessante Targets für die funktionelle Bildgebung von Tumoren mittels PET. Zur Adressierung dieser Targets sollen Polyamin-basierte Fluor-18-Tracer Anwendung finden, in denen das Radionuklid über die 4-Fluorbenzoylgruppe (FBz) eingeführt wird. Um die dafür erforderlichen Fluor-19-Analoga zugänglich zu machen, wurde eine Festphasensynthese entwickelt, die die selektive Fluorbenzoylierung an einer Aminogruppe in verschiedenen Polyaminen (u. a. Putrescin, Spermidin, Spermin) ermöglicht. Der etablierte Syntheseweg soll auf die entsprechenden F-18-markierten Analoga übertragen werden.

Methodik/Methods:
Zur selektiven mono-Fluorbenzoylierung wurde das von Wang et al. beschriebene Synthesekonzept angewendet (1). Es beinhaltet den Aufbau des Polyamin-Gerüstes durch Festphasensynthese der entsprechenden Oxopolyamine und deren anschließende Reduktion durch BH3/THF. Durch Einsatz von Dde und Boc als orthogonale Schutzgruppen und der Möglichkeit, mit 2-Acetyldimedon selektiv primäre Aminogruppen zu schützen, wird die selektive Fluorbenzoylierung verschiedener Aminogruppen ermöglicht.

Ergebnisse/Results:
Durch gezielte Anwendung des genannten Synthesekonzeptes konnten folgende neue Verbindungen in guten bis sehr guten Ausbeuten erhalten werden: N-FBz-Putrescin, N-FBz-Cadaverin, N1-FBz-3-Oxospermidin, N8-FBz-5-Oxospermidin, N1-FBz-3,8-Dioxospermin, N1-FBz-Spermidin, N4-FBz-Spermidin, N8-FBz-Spermidin und N1-FBz-Spermin. Die Identitäten der Verbindungen wurden NMR-spektroskopisch bestätigt.

Schlussfolgerungen/Conclusions:
Die Festphasensynthese mono-fluorbenzoylierter Polyamine und Oxopolyamine konnte erfolgreich etabliert werden. Durch das Vorliegen der Referenzverbindungen kann nun die Radiosynthese der Fluor-18-Analoga erfolgen, bei denen die 4-Fluorbenzoylgruppe [F-18]SFB-vermittelt angeknüpft wird. Dabei kann vermutlich analog zur Synthese der nichtradioaktiven Verbindungen vorgegangen werden.

Literatur/References:
(1) F. Wang, S. Manku, D. G. Hall, Org. Lett. 2000, 2, 1581-1583

  • Poster
    51. Jahrestagung der Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A71

Permalink: https://www.hzdr.de/publications/Publ-18664
Publ.-Id: 18664


Identification of Np(V) sorption complexes at the hematite-water interface studied by in-situ ATR FT-IR spectroscopy

Müller, K.; Gröschel, A.

Neptunium (Np) is one of the most important components of nuclear waste to consider for the long-term safety assessment of nuclear waste repositories, due to the increasing en-richment, the long half-life and the high toxicity of Np-237. Hence, great attention is attract-ed to its geochemistry [1]. Among the various geochemical reactions, the molecular pro-cesses occurring at the solid-water interface, e.g. sorption onto mineral phases, surface precipitation, and colloid formation strongly affect the migration behavior of the radioactive contaminant in the environment [2]. Thus, various components of geological materials, such as iron oxides and hydroxides play an important role in regulating the mobility of actinides in aquifers, due to their widespread environmental presence, high sorption capacity and tendency to form coatings on mineral surfaces [3]. In recent years, the sorption behavior of Np(V), the most relevant oxidation state under ambient conditions, onto iron oxides was mainly studied by macroscopic experiments [4]. For a better understanding of the molecular events occurring at the mineral’s surfaces, ATR FT-IR spectroscopy is a useful tool for the in-situ identification of surface species [5]. In addition, time-resolved measurements provide kinetic information on the surface reactions.
In this work, Np(V) sorption on hematite is studied under a variety of environmentally rele-vant sorption conditions by in-situ ATR FT-IR spectroscopy [5]. The IR spectra obtained from the subsequent steps of the experiment, that is (1) conditioning, (2) sorption, and (3) flushing, are shown in Fig. 1.
The absence of significant bands below 1000 cm−1 in the conditioning spectrum demon-strates the stability of the stationary hematite film directly prepared on the ATR crystal’s surface. The bands at 1491 and 1356 cm−1 represent the removal of carbonate by rinsing the hematite film, prepared in air with the CO2 free solution. Upon Np(V) sorption, the band observed at 790 cm−1 is assigned to the antisymmetric stretching vibrational mode (ν3) of the neptunyl ion. The IR spectrum obtained from an aqueous solution at 50 µM Np(V), 0.1 M, pH 6 shows the absorption of ν3(NpVO2) at 818 cm−1. The red shift of ν3 to 790 cm−1 upon sorption can be assigned to an inner-sphere monomeric sorption complex, as previ-ously reported for TiO2, SiO2 and ZnO [5]. The band at 1042 cm−1 is most probably due to surface modes of the mineral oxide provoked by the sorption processes and were already observed for interactions with U(VI), Cs(I) and CO32 [5]. In the flushing stage, a weakly bound species is released from the stationary phase, reflected by a negative band at 795 cm−1 in the respective spectra.
Additional experiments were performed at varied values of pH (5.6 – 12) and ionic strength (0.001 – 0.1) (Fig. 2). Upon increasing the pH from 5.6 to 8.6, no shifts of the bands at 1041 and 790 cm−1 are observed. But the intensities of these spectral features are consid-erably increased at higher pH values indicating an enhanced sorption capacity close to the IEP at pH 9.2. At pH > 10, the aqueous Np(V) speciation changes and NpO2OHaq is formed and distinctly changes the sorption behavior. The band of ν3(NpVO2) is shifted to 773 cm−1. The variation of ionic strength between 0.1 and 0.01 does not change the spectral characteristics. The higher intensities observed at 0.0001 M NaCl can be attributed to contributions of an outer-sphere complex which has to be verified by future experiments.
In summary, the IR spectra evidence the formation of Np surface complexes on hematite which can be easily removed to a considerable extent by flushing with blank solution. From this behavior, the simultaneous formation of an inner-sphere species with con-tributions of an outer-sphere complex is suggested.

[1] Kaszuba, J. P. et al. (1999) Environ. Sci. Technol. 33, 4427-4433.
[2] O'Day, P. A. (1999) Reviews of Geophysics 37, 249-274.
[3] Tochiyama, O. et al. (1996) Radiochim. Acta 73, 191-198.
[4] Brendler, V. et al. (2003) Journal of Contaminant Hydrology 61, 281-291.
[5] Müller, K. et al. (2009) Environ. Sci. Technol. 43, 7665-7670.

  • Contribution to proceedings
    Actinides 2013 - 9th International Conference on the Chemistry and Physics of the Actinide Elements, 21.-26.07.2013, Karlsruhe, Deutschland
    Proceedings of Actinides 2013
  • Lecture (Conference)
    Actinides 2013 - 9th International Conference on the Chemistry and Physics of the Actinide Elements, 21.-26.07.2013, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18663
Publ.-Id: 18663


Verlaufsuntersuchung des periacetabulären Knochenstoffwechsel nach Hüft-Pfannenwechsel mittels Positronen-Emissions-Tomographie und F18-NaF (NaF-PET)

Beuthien-Baumann, B.; Bernstein, P.; Hofheinz, F.; Zessin, J.; Kotzerke, J.; Günther, K. P.

Ziel/Aim:
Die Revision von gelockerten Hüft-Pfannen kann den Einsatz von impaktierten Knochen-Allografts (CBA) zur Stabilisierung der Pfanne und zum Auffüllen von Knochendefekten erfordern. Können mittels NaF-PET osteometabolische Veränderungen des CBA zu einem frühen Zeitpunkt nach Revision dokumentiert werden?

Methodik/Methods:
18F-NaF-PETs wurde 1 und 6 Wochen nach Revision durchgeführt. 12 Patienten wurden in die Studie (BfS- und Ethik-Votum) eingeschlossen, 9 Patienten absolvierten PET1+2. Die PET wurden an einem ECAT EXACT HR+ (Siemens/ CTI, USA) durchgeführt. Nach einer 4-min. Transmissionsmessung (Ger-68-Stabquellen) begann mit i.v.-Injektion von 240– 300 MBq F18-NaF eine dynamische Emission über 30 min über den Hüften. Auf einem post-op CT wurden Volumes of interest (VOIs) abgegrenzt (CBA, supracetabulär, os pubis) und nach Fusion von CT- und PET-Datensätze auf das PET übertragen. Die quantitative NaF-Aufnahme der VOIs wurde mit einem irreversiblen 2-Kompartment-Modell berechnet. Die Inputfunktion wurde aus der A. iliaca communis der dynamischen PET bestimmt. Der Parameter km (min-1) repräsentiert den Fluorid-influx in den Knochen.

Ergebnisse/Results:
km des supracetabulären Knochen zeigte auf der operierten Seite von PET1 zu PET2 eine nicht signifikante Zunahme (mean (±SD)) von 0,0491 (±0,0249) auf 0,0678 (±0,0367). Das CBA zeigte eine nicht signifikante Zunahme von 0,0384 (±0,0307) auf 0,0549 (±0,0319). In Zusammenschau mit dem CT war diese Zunahme im Randbereich des CBA lokalisiert und konnte nicht sicher von angrenzendem genuinem Knochengewebe, das visuell bei PET2 eine höhere Stoffwechselaktivität aufwies, getrennt werden.

Schlussfolgerungen/Conclusions:
Die NaF-PET 1 und 6 Wochen nach Revision zeigt eine nicht signifikante Zunahme des Knochenstoffwechsels ipsilateral supracetabulär. In dem CBA können beginnende osteometabolische Veränderungen im Randbereich zum genuinen Knochen nicht ausgeschlossen werden, zur sicheren Dokumentation einer stabilen Durchbauung des CBA wäre eine NaF-PET zu einem späteren Zeitpunkt erforderlich.

  • Lecture (Conference)
    51. Jahrestagung der Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A64

Permalink: https://www.hzdr.de/publications/Publ-18662
Publ.-Id: 18662


Combined measurement of perfusion and glucose metabolism by PET/CT using O-15-water and F-18-fluorodeoxyglucose for improved tumor characterization in advanced cervical carcinoma

Apostolova, I.; Buchert, R.; Steffen, I. G.; Hofheinz, F.; Köhler, C.; Marnitz, S.; Brenner, W.

Ziel/Aim:
Therapy response varies considerably in advanced cervical carcinoma(ACC). Glucose metabolism and microvascular characteristics of the tumor have been evaluated as biomarkers for identification of patients with poor response before or early during treatment. The combination of both biomarkers for detection of tumor regions with a ‘malignant mismatch’(MM), i.e. strongly increased glycolysis at low blood flow levels, might indicate resistance to therapy. The aim of the present study was to test whether ACC show MM that can be detected by the combination of FDG- and O-15-water-PET.

Methodik/Methods:
Twelve women (27-69y) with locally ACC (FIGO IIB-IIIB; grade G2 n=7, G3 n=5) were included prior to chemo-radiation. Regional blood flow was computed voxel-by-voxel from the O-15-water PET using a weighted integral approach and an image-derived arterial input function. FDG uptake was characterized by SUV. The primary tumor was segmented manually in the CT. A tumor voxel was considered to present MM if the perfusion was lower than the median perfusion in the tumor and the SUV was higher than the median SUV. The absolute total MM volume (aMMV) was obtained by multiplying the number of MM voxels with the voxel volume. The relative MM volume (rMMV) was obtained by dividing the aMMV by the tumor volume.

Ergebnisse/Results:
The volumes of the primary tumors ranged from 54 to 225ml. The tumors were quite heterogeneous with respect to both FDG uptake and perfusion. The aMMV ranged from 7.7 to 35.5ml, the rMMV from 7.9 to 26.6%. There was no correlation between rMMV and tumor volume (p=0.517). T-testing revealed a tendency (p=0.083) for an association between aMMV and histological grading, aMMV being higher in the G3 than in the G2 tumors. There was no association between grading and rMMV (p=0.888).

Schlussfolgerungen/Conclusions:
ACC show a metabolism/perfusion MM to a strongly variable extent. The mismatch volume seems to be associated with the tumor grade. Evaluation of the prognostic value requires follow-up data in a larger cohort.

  • Lecture (Conference)
    51. Jahrestagung der Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A54

Permalink: https://www.hzdr.de/publications/Publ-18661
Publ.-Id: 18661


Fluor-18-Misonidazol-PET/CT unter kurativ intendierter Radiochemotherapie bei Patienten mit lokal fortgeschrittenen Kopf-Hals-Tumoren (KHT) – eine prospektive Explorationsstudie

Zöphel, K.; Zips, D.; Abolmaali, N.; Perrin, R.; Abramyuk, A.; Haase, R.; Appold, S.; Steinbach, J.; Baumann, M.; Kotzerke, J.

Ziel/Aim:
Hypoxie ist charakteristisch für solide Tumoren und trägt maßgeblich zu einem potenziellen Versagen einer Radiochemotherapie (RCT) bei. Ziel dieser prospektiven Studie war es deshalb, den prognostischen Wert der Hypoxie-Bildgebung vor und unter RCT bei Patienten mit lokal fortgeschrittenen Kopf-Hals-Tumoren (KHT) zu explorieren.

Methodik/Methods:
Fünfundzwanzig Patienten mit histologisch gesicherten, unbehandelten KHT im klinischen Stadium III / IV wurden mit der F-18-Misonidazol- (F-MISO-) PET/CT zu 4 Zeitpunkten der kurativ intendierten RCT (initial, 8-10 Gy, 18-20 Gy und 50-60 Gy) untersucht. Parameter wie die maximale Ziel-Hintergrund-Ratio und das Schwellwert-basierte Tumorvolumen bei verschiedenen Ziel-Hintergrund-Rationes, das Tumorvolumen aus der CT sowie typische Basisparameter der initial und bei 40 Gy durchgeführten FDG-PET/CT wurden zu allen Untersuchungszeitpunkten auf ihren prognostischen Wert hin untersucht. Als Endpunkt diente das lokal Progressions-freie Überleben (LPFS). In einer multivariaten Cox-Analyse (einschließlich klinischer Parameter) und mehreren Log-Rank-Tests erfolgte die Prüfung auf signifikante Unterschiede.

Ergebnisse/Results:
Die Parameter aus der F-MISO-PET zeigten eine Assoziation mit dem LPFS-Endpunkt, am strengsten assoziiert waren die Zeitpunkte bei 10 Gy und 20 Gy unter der RCT (p = 0,023-0,048 und 0,042-0,061 in der multivariaten Cox-Analyse). Parameter aus der initialen F-MISO-PET/CT waren nur in der univariaten Analyse signifikant. Weder klinische Parameter, noch CT- oder FDG-PET-basierte Tumorvolumina zeigten eine signifikante Assoziation mit dem LPFS.

Schlussfolgerungen/Conclusions:
Diese prospektive Explorationsstudie demonstriert die prognostische Bedeutung der F-MISO-PET/CT in der frühen Phase der kurativen RCT. F-MISO-Bilder nach 1 oder 2 Wochen RCT (bei 10 bzw. 20 Gy) sind vielversprechend, wenn es um die Selektion der Patienten geht, die von einer Modifikation der Hypoxie oder von einer Dosis-eskalierten Radiatio profitieren könnten. Eine prospektive Validierungsstudie läuft bereits.

  • Lecture (Conference)
    51. Jahrestagung der Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A52-A53

Permalink: https://www.hzdr.de/publications/Publ-18660
Publ.-Id: 18660


Investigating dust behaviour for safety

Barth, T.; Hampel, U.

The main purpose of Subproject 2 is to further investigate the Key Safety Aspects identified by the Safety Advisory Group of the RAPHAEL project and to contribute to their resolution. Work package 23 targets to fill the knowledge gaps in dust production, deposition and remobilisation. Experimental and (advanced) analytical methods have been adopted to investigate all aspects of dust behaviour.

Keywords: graphite dust; high temperature reactor; pebble bed; positron emission tomography

Permalink: https://www.hzdr.de/publications/Publ-18659
Publ.-Id: 18659


Imaging of α7 nicotinic acetylcholinereceptors (nAChRs): Automated synthesis and biological evaluation of [18F]NS14490 in mice and pig

Rötering, S.; Fischer, S.; Hiller, A.; Donat, C.; Scheunemann, M.; Peters, D.; Bergmann, R.; Ullrich, M.; Sabri, O.; Steinbach, J.; Deuther-Conrad, W.; Brust, P.

Aim
There is evidence that α7nAChRs play an important role in cancer and neurodegenerative diseases. Therefore, quantitative imaging of α7nAChRs using PET represents a new approach for investigation of those diseases.
Due to its high target affinity and selectivity [18F]NS14490, an oxadiazolyl-diazabicyclononane derivative, is a promising radiotracer for α7nAChRs imaging. Manual radiosynthesis of [18F]NS14490 and its in vivo evaluation in mice were already reported [1]. The subsequent assessment of its imaging potential by dynamic PET studies in piglets and PET/CT studies in tumor-bearing mice required the transfer of the manual synthesis to an automated synthesis module.

Materials and Methods
For dynamic PET studies, the manual radiosynthesis of [18F]NS14490 [1] was transferred to an automatic synthesis module (Tracerlab FX-N) including azeotropic drying of [18F]F- with Kryptofix K222/K2CO3 in acetonitrile, direct nucleophilic substitution at the precursor, semipreparative HPLC and solid phase extraction. After evaporation the radiotracer was formulated in phosphate buffered saline containing 5% ethanol.
Dynamic PET studies in piglets (female, 15-18 kg) were performed under control and blocking conditions (n=2 each) with a highly selective α7nAChRs ligand (NS6740; bolus: 3 mg kg-1 h-1; infusion: 1 mg kg-1 h-1) for 4 hours. The metabolism of [18F]NS14490 in piglets was analyzed by chromatography of plasma samples.
PET/CT studies were performed in tumor-bearing nude mice under control and blocking conditions with NS6740.

Results and Conclusion
During transfer of radiosynthesis into an automated synthesis module, solid phase extraction was challenging. For desorption of the radiotracer from divinyl/polystyrene cartridge, the elution solvent ethanol/acetic acid used in manual synthesis was replaced by acetonitrile/formic acid resulting in more efficient elution, formerly not accomplished. The radiotracer was achieved within 1.25 hours and radiochemical yields (32%), radiochemical purity (> 90%) and specific activity (> 150 GBq μmol-1) were comparable to the manual synthesis [1]. Brain uptake of [18F]NS14490 peaked in piglets at 3 min p.i. and is with a value of SUVmax = 0.504 about tenfold higher than in mice. Blocking by NS6740 decreased the specific uptake in brain by 28% (SUV 240 min p.i. 0.174 vs. 0.125 under baseline and blocking conditions, respectively).The metabolic stability of [18F]NS14490 in piglets is lower than in mice. At 60 min p.i. intact radiotracer represented 30% of plasma activity in piglets compared to 55% in mice.
Preliminary animal PET/CT studies in tumor-bearing mice provide evidence that [18F]NS14490 may also be suitable for tumor imaging.
[1] Rötering, S. et al. Bioorg. Med. Chem. 2013

  • Poster
    EANM 2013 - Annual Congress of the European Association of Nuclear Medicine, 19.-23.10.2013, Lyon, Frankreich
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 40(2013)2, S317-S317
    DOI: 10.1007/s00259-013-2535-3

Permalink: https://www.hzdr.de/publications/Publ-18658
Publ.-Id: 18658


Oxygen-18 water: Recycle?

Rötering, S.; Franke, K.; Brust, P.; Fischer, S.; Steinbach, J.

Aim
The standard method for fluorine-18 production relies on proton irradiation of oxygen-18 water. Increased demand and costs of O-18 water forced us to consider its re-use for research purposes. After irradiation and F-18 separation the target water is contaminated with radioactive metal ions and organic solvents disturbing its re-use. Therefore, thorough purification is needed before further irradiation is possible. Here, we present two methods for the removal of organic contaminants from used target water.

Materials and Methods
Two different methods were accomplished to oxidize the organic contaminants ethanol and acetone in O-18 water using photo-oxidation (Pen-Ray 254 nm, 5.4 W) [1] and a wet chemical method with KMnO4 and NaOH. Thereafter vacuum distillation was performed and the target water was validated by gas chromatography, ICP-OES, pH value, conductivity and pycnometry. In addition artificially contaminated O-16 water was used to evaluate the potential of both methods concerning the oxidation of other potential contaminants such as methanol and acetonitrile.
Target irradiations were performed at equal parameters of bombarding (beam current on target 35 μA, 11.7 μAh) at a CYCLONE 18/9 (IBA Molecular, Nirtra® Fluor L-target (99.9% niobium): 2 mL, target window: Havar alloy, 50 μm).
Radionuclide purity and yields were determined by gamma spectrometry (ORTEC) and an ionization chamber (MED Nuklear-Medizintechnik Dresden GmbH). Produced F-18 was used in nucleophilic substitution reactions in various radiosyntheses of ongoing projects.

Results and Conclusion
Using both purification methods a comparable decrease of organic contaminants from 400 μg mL-1 ethanol and 44 μg mL-1 acetone to 10 μg mL-1 – 50 μg mL-1 ethanol was achieved. Photo-oxidation was approximately 1.5times faster. Important parameters (amount of oxidation agent, temperature, treatment time) for both methods were defined to ensure reproducibility of the radiosyntheses after comparable proton irradiation as done for the purchased target water. We observed a loss of production yield (19%) compared to purchased water due to a lower O-18 concentration. No influence on radionuclide purity or radiochemical yields was observed. Both methods enable a multiple re-cycling of target water for successful F-18 production and application for research purposes. The re-cycling process is limited by the amount of F-18 required for radiosyntheses. Starting from 87% enrichment of O-18 in target water we found 83% enrichement after one cycle allowing reasonable production yields and efficient economical usage of the purchased target water including efforts to minimize the contamination of target water.
[1] DE 29504388 U1, 1995
:

  • Poster
    EANM 2013 - Annual Congress of the European Association of Nuclear Medicine, 19.-23.10.2013, Lyon, France
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 40(2013)2, S318

Permalink: https://www.hzdr.de/publications/Publ-18657
Publ.-Id: 18657


Synthesis and Evaluation of Novel 18F-Labeled Spirocyclic Piperidine Derivatives as σ1 Receptor Ligands for Positron Emission Tomography Imaging

Li, Y.; Wang, X.; Zhang, J.; Deuther-Conrad, W.; Xie, F.; Zhang, X.; Liu, J.; Qiao, J.; Cui, M.; Steinbach, J.; Brust, P.; Liu, B.; Jia, H.

A series of spirocyclic piperidine derivatives were designed and synthesized as σ1 receptor ligands. In vitro competition binding assays showed that 1'-(4-(2-fluoroethoxy)benzyl)-3H-spiro[2-benzofuran-1,4'-piperidine] (19) possessed high σ1 receptor affinity (Ki= 0.79 nM) and excellent σ12 subtype selectivity (350-fold) as well as high σ1/VAChT selectivity (799-fold). The radiolabeled compound [18F]19 was synthesized by substitution of the tosylate precursor 24 with [18F]fluoride, with isolated radiochemical yield of 35–60%, radiochemical purity of >99%, and specific activity of 30–55 GBq/Qmol. Biodistribution studies in ICR mice indicated that [18F]19 displayed excellent initial brain uptake and slow washout. Ex vivo autoradiography in Sprague-Dawley rat demonstrated high accumulation of the radiotracer in brain areas known to express high levels of σ1 receptors. MicroPET imaging and blocking studies confirmed the specific binding of [18F]19 to σ1 receptors in vivo.

Keywords: σ1 receptor; brain; spirocyclic piperidine derivatives; 18F; PET imaging

Permalink: https://www.hzdr.de/publications/Publ-18655
Publ.-Id: 18655


Phantom-based evaluation of quantification accuracy of combined PET/MRI

Langner, J.; Schramm, G.; Hofheinz, F.; Lougovski, A.; Steinbach, J.; van den Hoff, J.

Ziel/Aim:
A widely discussed question in PET is the quantitative accuracy (QA) of combined PET/MRI systems. To evaluate QA of the Philips Ingenuity TF PET/MR system we have performed phantom-based evaluations and compared them to measurements on traditional PET systems.

Methodik/Methods:
With the Philips PET/MR a SUV calibration is the standard procedure to calibrate the PET against a dose calibrator (DC). A dynamic scan is started at high activity (≈500 MBq) and run for 7 half-life times. Than a SUV validation with lower activity (≈70 MBq) is run as a static scan for 3 min. We augmented the validation protocol to start at higher activity and to run as a dynamic protocol. To evaluate the clinical relevant QA we have determined typical singles rates (SR) for whole-body (WB) scans. To analyse the influence of the MR-based attenuation (MRAC) we have created an attenuation template (AT) of the phantom and applied it.

Ergebnisse/Results:
The PET-derived activity concentrations and SUVs are significantly lower than calculated from the DC. Using the standard procedure the PET vs. DC ratio is 0.895=10.5% deviation at a level of 73.7 MBq (SR: 14.7 Mcps). For activity increasing from 8.6 to 89.7 MBq the PET/DC ratio decreases from 0.943 to 0.877, corresponding to deviations of 6–12% (SR: 3.8–17.0 Mcps). The use of an AT changes the deviation < 1%. For typical WB scans the SR were found to range from 8.0–16.6 Mcps, corresponding to a underestimates of true activity by 6.8–9.9%.

Schlussfolgerungen/Conclusions:
Our preliminary results show, that QA of the Philips PET/MR in phantoms is off by 6–12%. The effect shows a notable dead-time dependency and cannot be explained by inaccurate MRAC. In addition to the dead-time related variance of ≈3% there remains a systematic error in the calibration, which biases QA of clinical scans by ≈6%. Philips has been informed about the inconsistencies and has acknowledged to provide a fix.

  • Poster
    51. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A77

Permalink: https://www.hzdr.de/publications/Publ-18654
Publ.-Id: 18654


In-vivo evaluation of quantification accuracy of combined PET/MRI

Langner, J.; Schramm, G.; Hofheinz, F.; Lougovski, A.; Beuthien-Baumann, B.; Platzek, I.; Kotzerke, J.; Steinbach, J.; van den Hoff, J.

Ziel/Aim:
Quantitative accuracy (QA) of PET parameters like standardised uptake values (SUV) and tracer kinetic rate constants strongly depends on applicability of the (phantom-based) scanner calibration in-vivo. In a previous study we introduced a method for direct in-vivo QA evaluation: for 3 PET(/CT) systems the activity concentrations (Cs) of urine samples measured in a well-counter were compared to the Cs of PET images of the bladder in 56 patients. That study showed a small (7-12%) but systematic underestimation of the true Cs by PET. To address the widely discussed question of QA of combined PET/MRI we have applied this method to our Philips PET/MR.

Methodik/Methods:
Up to now 10 clinical F18-FDG scans have been evaluated. The bladder region was imaged as the last bed position and urine samples collected afterwards. Using the ROVER software, 3D region-of-interests (ROI) of the bladder were delineated by 3 observers. To exclude partial volume effects ROIs were concentrically shrunk by 8–10 mm. Then, Cs were determined in the PET images of the bladder as well as in the urine samples using a cross-calibrated well-counter.

Ergebnisse/Results:
The measured Cs and SUVs are significantly lower in PET/MR than in the well-counter: ratio=0.773±0.035 (mean±SEM) [0.617–0.942] (p=0.00011). After correcting for known (but not yet fixed) inconsistencies in the manufacturer’s scanner calibration of the Philips PET/MR, the ratio is 0.827±0.035 [0.664–1.004] (p=0.0011).

Schlussfolgerungen/Conclusions:
Our preliminary results indicate that the Philips PET/MR underestimates true Cs by ≈17% in-vivo which is ≈7% larger than we observed for PET(/CT). The requirement to apply a correction factor due to inconsistencies in the manufacturer’s provided calibration and similar deviations reported on other PET/MR systems show that vendors of PET/MR systems need to pay special attention regarding QA. In this context, our method might serve as a convenient method to evaluate the actual QA in-vivo.

  • Lecture (Conference)
    51. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A50

Permalink: https://www.hzdr.de/publications/Publ-18653
Publ.-Id: 18653


Preclinical radiopharmacological characterization of a Cu-64-labeled bis(2-pyridylmethyl) )-1,4,7-triazacyclononane bombesin analogue

Bergmann, R.; Ruffani, A.; Graham, B.; Spiccia, L.; Steinbach, J.; Pietzsch, J.; Stephan, H.

Ziel/Aim:
The bifunctional chelating agent 2-[4,7-bis(2-pyridylmethyl)-1,4,7-triazacyclononan-1-yl]acetic acid (DMPTACN-COOH) has been coupled to the stabilized bombesin (BBN) derivative [Cha13,Nle14]-BBN(7–14) using the spacer homo-Glu-Ala-Ala, was radiolabeled with the positron emitter copper-64, and the new radiotracer was preclinically characterized.

Methodik/Methods:
The in vitro and in vivo binding characteristics of the Cu-64-labeled bombesin conjugate in gastrin-releasing peptide receptor (GRPR) over-expressing prostate cancer (PC-3) cells/tumors have been evaluated. Biodistribution and metabolism studies were performed in Wistar rats. Small animal PET imaging was carried out to evaluate the biokinetics and tumor accumulation in tumor bearing NMRI nu/nu mice.

Ergebnisse/Results:
The pendant carboxylic group enables this derivative to be conjugated to the N-terminal amino acid residues of the peptide. The resulting radiocopper(II)-ligand complex exhibits high stability. The IC50 value on PC3 cells was 15 nM, the specific binding was confirmed by high uptake in the GRPR-rich pancreas used as reference organ. The peptide showed a good metabolic stability, however, it was fast eliminated by the kidneys. The PC3 tumors in the mice could be clearly imaged with tumor-to-muscle ratios steadily increasing over the time up to 30. The tumor uptake could be blocked by GRP.

Schlussfolgerungen/Conclusions:
Preclinical characterization of the Cu-64-labeled DMPTACN-COOH with incorporation of a single glutamic acid residue within the spacer between bombesin and the radiolabeled complex showed that the probe represents a promising GRPR radiotracer.

  • Lecture (Conference)
    51. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A36-A37

Permalink: https://www.hzdr.de/publications/Publ-18652
Publ.-Id: 18652


Comparison of current reconstruction algorithms for F18-FDG-PET based volume definition – phantom measurements

Rogasch, J.; Hofheinz, F.; Furth, C.; Ruf, J.; Grosser, O.; Mohnike, K.; Hass, P.; Amthauer, H.; Steffen, I. G.

Ziel/Aim:
Oncological microtherapy planning, e.g. brachytherapy, based on PET-datasets requires exact quantification and volume definition. The aim of this study was to analyze the influence of current reconstruction algorithms on SUVmax, metabolic volumes and spatial resolution using phantom measurements.

Methodik/Methods:
Measurements were performed on a SIEMENS Biograph mCT 64 using a cylindrical phantom (volume, 6595 ml) containing 4 spheres (14-177 ml) filled with F18-FDG (50 kBq/ml) resulting in 3 background fractions (BGF). Images were reconstructed applying 5 algorithms (3D-OSEM, FBP, FBP-TOF, HD-PET, ultraHD-PET) and two slice thicknesses (3 mm, 5 mm). Segmentation of sphere volumes was performed using semiautomatic tumor-to-background algorithm (ROVER). Spatial resolution was determined using point spread function and fitting of radial activity profiles.

Ergebnisse/Results:
The highest SUVmax deviations were found between ultraHD-PET and FBP-TOF with a mean absolute difference of 1.3 (range, 0.7–2.1) and a corresponding mean relative difference of 13.2% (range, 8.2–20.9%). Metabolic volume difference to reference volume was significantly associated to reconstruction algorithm (p<0.05), background fraction (BGF3 vs BGF1, p<0.001; BGF2 vs BGF1, p=0.1), sphere diameter (p<0.001) but not to slice thickness (p=0.3). Best spatial resolution for BGF1 and BGF2 was detected for ultraHD-PET (5.3/4.5 mm) compared to FBP (6.8/6.6 mm) and 3D-OSEM (5.9/5.4). In contrast, similar spatial resolutions were detected for BGF3 ranging from 5.9 mm (3D-OSEM/FBP) to 6.5 mm (HD-PET). However, TrueX-algorithms (HD-PET, ultraHD-PET) showed substantial edge elevations in radial activity profiles (Gibbs artifacts).

Schlussfolgerungen/Conclusions:
Reconstruction algorithms showed substantial effect on SUVmax. This might be of clinical importance if PET quantification is used in oncological microtherapy planning. The clinical impact of high spatial resolution combined with Gibbs artifacts in TrueX reconstructions has to be analyzed in further trials.

  • Lecture (Conference)
    51. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A26

Permalink: https://www.hzdr.de/publications/Publ-18651
Publ.-Id: 18651


Population averaged image derived arterial input function in 15-O Water PET

Hofheinz, F.; Langner, J.; Beuthien-Baumann, B.; Steffen, I. G.; Apostolova, I.; Burchert, R.; Steinbach, J.; Kotzerke, J.; van den Hoff, J.

Ziel/Aim:
Arterial input function (IF) determination is traditionally based on arterial blood sampling which is invasive and ill-suited for clinical routine. Alternatively, one can use a population averaged IF determined via blood samples (BSIF) in a separate study. We present a strategy for generation of a population averaged image derived IF (IDIF) in brain investigations.

Methodik/Methods:
An image subvolume enclosing the carotid arteries is manually defined. Further processing is fully automated: 1: peak phase detection of the IF, 2: threshold based, background aware delineation using peak phase optimized for small structure size (~ 5 mm), 3: time activity curve generation, 4: model free recovery coefficient (R) determination 5: recovery and spillover correction according to Cm = R x Ct + (1 - R) x B, Cm/Ct: measured/true signal/IF, B: local background. This method was applied to 48 15-O Water brain studies (acquired with an ECAT HR+ PET). The resulting IFs were averaged, leading to a population averaged image derived IF (IDIF). Gray matter perfusion was computed from the Kety-Schmidt model assuming a partition coefficient in gray matter of 0.9 (f1). Perfusion was also computed using a BSIF from a different institution (f2). f1 and f2 were compared.

Ergebnisse/Results:
f1 and f2 are strongly correlated (Pearson 0.999) and differences are small: (f2-f1)/f2 = (9.7 +/- 0.9)% (mean +/- sd), range 6.7% - 12.7%.

Schlussfolgerungen/Conclusions:
The presented method allows to generate an IDIF which reproduces the results achieved with BSIF with good accuracy. One significant advantage of the new approach is the ease of regeneration of the IDIF for each study group (e.g. after injection and acquisition protocol changes). Due to statistical fluctuations of vessel delineation individual IF determination is not yet possible with this method due to the modest reconstructed resolution of the HR+ data. This might become possible when using state-of-the-art scanners and reconstruction algorithms.

  • Lecture (Conference)
    51. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A21
  • Poster
    Annual Congress of the European Association of Nuclear Medicine, 19.-23.10.2013, Lyon, France
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 40(2013), S302-S303

Permalink: https://www.hzdr.de/publications/Publ-18650
Publ.-Id: 18650


Relative cerebrovascular reserve capacity in Moyamoya disease assessed by brain perfusion imaging: PET versus SPECT in the same patients

Steffen, I. G.; Apostolova, I.; Michel, R.; Schulze, O.; Rosner, C.; Hofheinz, F.; Prasad, V.; Brenner, W.; Vajkoczy, P.; Buchert, R.

Ziel/Aim:
Moyamoya disease (MMD) is characterized by progressive stenosis or occlusion of the terminal internal carotid arteries with varying development of collaterals requiring the exact characterization of hemodynamics for adequate therapy. The aim of the present study was to compare perfusion SPECT and PET with O-15-water in the same patients.

Methodik/Methods:
Static SPECT and dynamic PET were performed within 1-5 d in 9 MMD patients (18-67 y), both in resting state and after vasodilatory challenge with acetazolamide. The PET data were analyzed with the Watabe reference tissue method for the voxelwise computation of the regional cerebral blood flow. Vasodilatation and resting images were coregistered, stereotactically normalized (SPM8) and smoothed (3d isotropic Gaussian kernel, 20 mm FWHM). The relative cerebrovascular reserve (rCVR) was computed voxel-by-voxel according to the formula rCVR = 100*(s*vasodilatation – resting)/resting. The scale factor (s) was determined to a mean rCVR of 50%. The resulting rCVR maps were assessed visually and using standard ROIS for ACA, MCA and PCA territory (left/ right). A general linear model was used to analyze the effect of modality (SPECT, PET) and territory (ACA, MCA, PCA) on rCVR.

Ergebnisse/Results:
The pattern of rCVR differed significantly between SPECT and PET in 5/9 patients according to visual inspection. PET showed additional or more extended regions with reduced rCVR in these cases. The ROI analysis revealed a significant effect of the modality (p=0.015) and a highly significant modality*territory interaction (p=0.000). PET-rCVR was lower than SPECT-rCVR in the ACA and MCA territory, whereas it was higher in the PCA territory.

Schlussfolgerungen/Conclusions:
There was a substantial difference in the cerebrovascular reserve capacity as measured by SPECT versus PET, both visually and quantitatively. The modality*territory interaction suggests that PET is more accurate than SPECT, as MMD often spares the posterior circulation. However, this has to be confirmed in further studies.

  • Lecture (Conference)
    51. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A14

Permalink: https://www.hzdr.de/publications/Publ-18649
Publ.-Id: 18649


Kupfer-64 markierte Peptid-Konjugate an epidermalen Wachstumsfaktor-Rezeptor (EGFR)-exprimierenden Zellen

Sihver, W.; Starke, F.; Heldt, J.-M.; Sachse, S.; Naumann, S.; Pietzsch, H.-J.; Steinbach, J.

Ziel/Aim:
Der EGFR wird oft überexprimiert in verschiedenen Tumorarten. Daher werden geeignete radionuklidmarkierte EGFR-Liganden für eine gezielte Tumordiagnostik mittels bildgebender Verfahren, z.B. PET, entwickelt. Zwei kürzlich beschriebene EGFR-spezifische Peptide GE11 (1) und D4 (2) sollten mit Chelatoren sowie Spacern so konjugiert werden, dass sie mit dem PET-Nuklid Kupfer-64 markiert werden können. Mit einem der markierten Peptid-Konjugate sollte das Bindungsverhalten (Zeitabhängigkeit und Affinität) an Zellmembranen charakterisiert werden.

Methodik/Methods:
Die Peptide wurden am N-Terminus jeweils mit verschiedenen Spacern sowie mit dem Chelator NOTA verknüpft und anschließend mit Kupfer-64 radiomarkiert. Für Bindunggsassays wurden Membranen der EGFR-exprimierenden A431-Zellen (epidermoides Karzinom) und FaDu-Zellen (Plattenepithelkarzinom) untersucht. Kinetik- und Sättigungs-Assays wurden mit einem Kupfer-64 markierten NOTA-D4-Konjugat ([64Cu]Cu-D4-JM) durchgeführt.

Ergebnisse/Results:
Die Peptidkonjugate konnten mit einer Ausbeute von 75-91% hergestellt werden. Bei der Radiomarkierung mit Kupfer-64 konnten spezifische Aktivitäten von bis zu 1000 GBq/µmol erreicht werden, jedoch wurden diese für Bindungsassays auf etwa 30 GBq/µmol eingestellt. Für die Bindung mit [64Cu]Cu-D4-JM an A431-Membranen war nach 1 Stunde Assoziation das Bindungsgleichgewicht erreicht, an FaDu-Membranen nach 2 Stunden nicht vollständig. TDiss½ lag unter 5 min. Die Affinität mittels Sättigung ergab für A431- und für FaDu-Membranen Kd-Werte von 19 bzw. 42 nM.

Schlussfolgerungen/Conclusions:
Mit GE11 und D4 konnten verschiedene EGFR-spezifische Peptid-Konjugate erfolgreich hergestellt werden. Nachdem [64Cu]Cu-D4-JM an Zellmembranen untersucht wurde, sind weiterführende Assays an intakten Zellen sowie Tumoraufnahme an Xenograft tragenden Mäusen geplant.

Literatur/References:
(1) Li Z, Zhao R, Wu X et al. FASEB J. 2005, 19(14), 1978-85
(2) Song S, Liu D, Peng JL, et al. Intl. Conf. on Biomedical and Pharmaceutical Engineering 2006, 290-3

  • Lecture (Conference)
    51. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A12

Permalink: https://www.hzdr.de/publications/Publ-18648
Publ.-Id: 18648


Fluor-18-markierte Telopeptidderivate als Substrat-basierte Radiotracer zur Bildgebung der Lysyloxidase in vivo

Kuchar, M.; Wodtke, R.; Bergmann, R.; Lenk, J.; Mosch, B.; Pietzsch, J.; Löser, R.

Ziel/Aim:
Dem Enzym Lysyloxidase (LOX, EC 1.4.3.13), wird eine Schlüsselfunktion für die Hypoxie-induzierte Tumormetastasierung zugeschrieben (1). Ziel unserer Untersuchungen war die Entwicklung Fluor-18-basierter Radiotracer, die eine In-vivo-Bildgebung dieses Enzyms ermöglichen.

Methodik/Methods:
Das N-terminale Telopeptid der α1-Kette des Typ-I-Kollagens und davon abgeleitete Peptide, die potentielle LOX-Substrate sind, wurden an von den funktionellen Lysinresten verschiedenen Aminogruppen Fluor-18-markiert. Dazu wurde eine Methode entwickelt, die die selektive F-18-Fluorobenzoylierung von Peptiden mit [F-18]SFB ermöglicht (2). Die metabolische Stabilität und Bioverteilung der Radiotracer wurde in normalen männlichen Wistarratten untersucht. Über die Wechselwirkung der verschiedenen Lysin-enthaltenden Peptide mit Atelokollagen wurde durch Oberflächenplasmonenresonanz (SPR) Aufschluss erhalten. Verschiedene Tumorzelllinien wurden in vitro auf die Expression der Lysyloxidase hin untersucht. Die Charakterisierung der Verbindungen erfolgte an A375-Tumormäusen durch dynamisches Kleintier-PET-Imaging und Ex-vivo-Autoradiographie.

Ergebnisse/Results:
Die F-18-fluorbenzoylierten Telopeptidderivate wurden in hohen radiochemischen Ausbeuten und Reinheiten synthetisiert. Alle Peptide zeigten eine gute In-vivo-Stabilität, insbesondere ein cyclisches Derivat des N-Telopeptids. In den Bioverteilungsstudien konnten keine Organanreicherung und eine schnelle renale Eliminierung beobachtet werden. Die Telopeptid-Kollagen-Interaktion konnte erstmals quantitativ untersucht werden.

Schlussfolgerungen/Conclusions:
Geeignete LOX-Substrate wurden Fluor-18-markiert und in vivo eingehend charakterisiert. Trotz ungünstiger Pharmakokinetik infolge schneller renaler Eliminierung zeigen die Tracer das Potential, die LOX-Aktivität in vivo abzubilden.

Literatur/References:
(1) J. T. Erler, K. L. Bennewith, M. Nicolau et al. Nature 2006, 440, 1222-1226
(2) M. Kuchar, M. Pretze, T. Kniess et al. Amino Acids 2012, 43, 1431-1443

  • Lecture (Conference)
    51. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A11

Permalink: https://www.hzdr.de/publications/Publ-18647
Publ.-Id: 18647


Automatisierte F-18-Fluorethylierung als Markierungsmethode neuer potentieller COX-2 Inhibitoren

Laube, M.; Kniess, T.; Pietzsch, J.; Steinbach, J.

Ziel/Aim:
Das Enzym Cyclooxygenase-2 reguliert entzündungsassoziierte Prozesse und wird in vielen Tumoren exprimiert. Die Visualisierung der COX-2 Expression in vivo durch PET könnte daher neue Ansatzpunkte zur Charakterisierung von Tumoren liefern. Um erstmals zu F-18-Fluorethoxy-substituierten COX-2 Inhibitoren zu gelangen und um unterschiedliche COX-2 Inhibitoren mit mono- und bizyklischer Kernstruktur als PET-Tracer zur Verfügung zu stellen, entwickelten wir eine universelle, automatisierte Markierungsmethode.

Methodik/Methods:
Die Entwicklung zweier neuer Fluorethoxy-substituierter Derivate 2-(4-(2-Fluorethoxy)phenyl)-3-(4-(methansulfonyl)phenyl)pyrazolo[1,5-b]pyridazine (A) und 1-(2-Fluorethoxy)-4-(2-(4-(methansulfonyl)phenyl)cyclopent-1-enyl)benzen (B) erfolgte ausgehend von den Ethoxy- bzw. Methoxy-substituierten Derivaten A* und B* (IC50 COX-2: 3 bzw. 5 nM) (1,2). F-18-A und F-18-B wurden in einer automatisierten Syntheseapparatur (TracerlabFX-N) unter optimierten Parametern durch indirekte Markierung der entsprechenden Hydroxyl-Präkursoren mit 1,2-[F-18]Fluorethyltosylat (F-18-C) hergestellt.

Ergebnisse/Results:
Durch enzymatischen Assay wurde für A und B bestätigt, daß die Fluorethylgruppe die COX-2 Inhibitoraktivität nur wenig beeinflusst. Mittels zwei-Stufen/ein-Topf-Synthese inklusive HPLC Reinigung konnte F-18-A ausgehend von [F-18]Fluorid in 70 min mit 7,5% RCA (n=5; zerf.korr.) hergestellt werden (RCR >95%; spezif. Aktivität 27-71 GBq/µmol). In analoger Weise wurde F-18-B in 80 min mit 7,8% RCA (n=7; zerf.korr.) erhalten (RCR 98%; spezif. Aktivität 19-43 GBq/µmol).

Schlussfolgerungen/Conclusions:
Durch die entwickelte automatisierte F-18-Fluorethylierung konnten die COX-2 Inhibitoren F-18-A und F-18-B erfolgreich hergestellt werden, ihre radiopharmakologische Evaluierung findet zur Zeit statt. Die Methode bietet einen effektiven Zugang zur Radiomarkierung von COX-2 Inhibitoren mit Methoxy- bzw. Ethoxy-Funktionen.

Literatur/References:
(1) Beswick et al., Bioorg. Med. Chem. Lett. 2004, 14, 5445.
(2) Wüst et al., Bioorg. Med. Chem. 2008, 16, 7662.

  • Lecture (Conference)
    51. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A11

Permalink: https://www.hzdr.de/publications/Publ-18646
Publ.-Id: 18646


Truncation artifacts in hybrid PET/MR - evaluation and compensation

Schramm, G.; Langner, J.; Hofheinz, F.; Petr, J.; Beuthien-Baumann, B.; Platzek, I.; Kotzerke, J.; Steinbach, J.; van den Hoff, J.

Ziel/Aim:
MR-based attenuation correction in hybrid PET/MR imaging is affected by the reduced transaxial FOV of the MR (40cm) in comparison to that of the PET scanner (60cm) which leads to truncation artifacts in the MR-based attenuation map
(MRMap). In this study we investigate the quantitative influence of truncation artifacts on the reconstructed whole-body PET image volumes and present a new method for truncation compensation (TC).

Methodik/Methods:
Data sets of 17 whole-body FDG patients (BMI 16-38) examined with an Philips Ingenuity PET/MR with arms down were reconstructed using different techniques for TC: (1) no TC (PET-noTC), (2) vendor-provided TC (PET-TC1), (3) newly
developed TC (PET-TC2) based on automatic 3D segmentation of PET-noTC. In all PET volumes, the resulting SUVmax/mean of ROIs in different body regions (e.g. heart, bladder, mediastinum, kidneys, arms etc.) were compared.
Furthermore, a correlation analysis between all voxels in the trunk and truncated arms was performed.

Ergebnisse/Results:
Residual artifacts in the truncation compensated MRMaps were found in 11 (TC1)and 3 (TC2) out of 17 cases. Average SUVmax differences between PET-noTC and PET-TC1/PET-TC2 were: -2.5%/-3.2% (bladder), -4%/-3.4% (kidney),
-3.2%/-3.5% (heart), -2.8/-3.3% (abdomen), -29%/-37% (arms). The correlation analysis showed average SUV deviations of -5% to -1% and -60% to -30% depending on patients' BMI for all voxels in the trunk and truncated arms, respectively.

Schlussfolgerungen/Conclusions:
In whole-body PET imaging, truncation of the arms in the MRMap leads to an average SUV underestimation of ca. 3% in the trunk. In the truncated areas SUV underestimations in the range of 30-60% can be expected. Truncation
compensation based on PET-noTC is straightforward and improves quantification accuracy distinctly. According to our experience the procedure is also well suited for clinical routine.

  • Lecture (Conference)
    51. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 17.-20.04.2013, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 52(2013), A6

Permalink: https://www.hzdr.de/publications/Publ-18645
Publ.-Id: 18645


Environmental parameters that determine distribution coefficients of radionuclides for repositories

Stockmann, M.; Brendler, V.; Richter, C.; Flügge, J.; Britz, S.; Noseck, U.

In order to treat radionuclide sorption processes in natural systems more realistically, temporally and spatially variable distribution coefficients (smart Kd values) are calculated as a function of important environmental parameters such as pH, ionic strength (IS), concentration of dissolved inorganic carbon [DIC], calcium [Ca] and radionuclides [RN]. This smart Kd concept is implemented into the transport code r³t [1].
As a test of the modified code r³t and sensitivity analysis of radionuclide sorption regarding the mentioned environmental parameters, a possible future climate transition (seawater transgression) at Gorleben site / Germany was modelled [2]. Seawater inundation drastically influences the distribution and values of all environmental parameters. Chemical changes cause dissolution or precipitation of calcite and these in turn affect the pH, DIC and Ca concentration. In consequence the Kd values and therewith the transport of radionuclides is impacted.
The results of the calculations are plausible: environ-mental parameters follow expected trends and major dependencies. As a consequence of the low Ca and DIC concentration in seawater, calcite dissolves in the aquifer and causes an increase of the pH. The Kd values change according to the changes in environmental parameters. The pH has the most dominant impact on the smart Kd values for most of the considered RNs, except for Pu and Th, for which the DIC concentration has the strongest impact. Under the assessed conditions for seawater transgressions the smart Kd values of Cs, Ni, Am and Np(V) increase, those of Se(VI) and U(VI) decrease with increasing pH. The smart Kd value particularly of Pu and Th decreases with increasing DIC concentration.

  • Poster
    Goldschmidt 2013, 25.-30.08.2013, Florence, Italy

Permalink: https://www.hzdr.de/publications/Publ-18644
Publ.-Id: 18644


Microorganisms in saline environments

Geissler, A.; Bachvarova, V.; Flemming, K.; Selenska-Pobell, S.

The long-term safety of nuclear waste in deep geological repositories is an important issue in the German society. The migration of actinides and long-lived fission products within the respective host rock and the transport behaviour after a possible release from the repository should be well known. Presence of microorganisms was shown in the subsurface geologic layers, including salt formations, which are considered as potential host rocks /1/. This is of interest because microbes can affect physical and geochemical conditions (e.g. pH, Eh, release of gases) on site and they can also interact with actinides. Important interaction processes are biosorption, bioaccumulation, biotransformation, biomineralization and microbial enhanced chemisorption /2/.
In this work microbial communities were investigated in two different saline environments - the Arava desert in Israel and the salt formation near Gorleben village in Germany.

DESCRIPTION OF THE WORK

Total DNA was recovered from the salt crust (7EY) and from 0 to 3cm depth (10EY) samples of the Arava desert and from one hydrocarbon rich sample C1 from the Gorleben site. Direct molecular analyses of prokaryotic communities were performed by using bacteria specific 16S rRNA gene primers 27F and 1513R /3/ and archaea specific 16S rRNA gene primers 21F and 968R /4/.
Modified R2A medium was used for cultivation of halophilic microbial isolates as described in /5/.

RESULTS

It was demonstrated that the archaeal communities in both 7EY and 10EY samples were predominated by Halobacteriaceae /4/. The recently actualized affiliation of the 16S rRNA gene sequences demonstrated presence of representatives of the genera Haloplanus, Natronomonas, Halobacterium and Halolamina. Several haloarchaeal isolates were cultivated from the salt crust sample 7EY and one of them was characterized as Halobacterium sp. UJ-EY-1 /5/.
On the bacterial phylum level, the samples 7EY and 10EY were predominated by Bacteroidetes, which were accompanied by Firmicutes, Gamma-, Alpha-, and Delta-proteobacteria occurring in a sample-specific way. In addition, differences were found on the species level.
Preliminary results demonstrate that Bacteroidetes are rather abundant in the Gorleben sample C1 where, in addition, Firmicutes are also predominant. Different Proteobacteria are identified in this sample as well. Further investigations of microbial diversity in this and other samples from the Gorleben site are in progress.

At this step of investigation characterization of microbial communities in salt formations representative for potential nuclear waste disposals is ongoing. The next step will be to understand the microbe-actinide interactions of the salt-specific microorganisms. This knowledge will be used to take the microbial activity into account in evaluating the long-term safety of the repositories hosted in salt formations.

REFERENCES

1. Vreeland, R.H., Pisseli A.F., McDonnough, S., Meyers, S. Distribution of halophilic bacteria in a subsurface salt formations. Extremophiles 2, 321-331 (1998).
2. Lloyd, J. R., Macaskie, L. E.: Biochemical basis of microbe-radionuclide interactions. Interactions of Microorganisms with Radionuclides, eds Keith-Roach, M. J., Livens, F. R. Elsevier Science Ltd., 313-342 (2002).
3. Geissler, A., Selenska-Pobell, S.: Addition of U(VI) to a uranium mining waste sample and resulting changes in the indigenous bacterial community. Geobiology 3, 275-285 (2005).
4. Buchvarova, V., Jankowski, U., Flemming, K., Selenska-Pobell S. Halophilic archaeal populations in Arava Desert (Israel) as examined by using direct molecular and cultivation methods FZR-Report 511, p. 34 (2009).
5. Jankowski, U., Flemming, K., Selenska-Pobell, S. Characterization of a Halobacterium sp. isolate cultivated from samples collected from Arava Desert. FZR-Report 511, p. 35 (2009).

Keywords: Microbial diversity; salt formations; radioactive waste depositories

  • Lecture (Conference)
    ABC-Salt Workshop III, 15.-17.04.2013, Santa Fe, New Mexico, USA

Permalink: https://www.hzdr.de/publications/Publ-18643
Publ.-Id: 18643


Vibrational spectroscopic study of Np(V) sorption on mineral oxides

Müller, K.; Berger, J.; Cordiez, M.; Gröschel, A.; Foerstendorf, H.

Mineral oxides play a decisive role in regulating the mobility of contaminants in the environment because of their widespread occurrence in rocks and soils, their tendency to form coatings on mineral surfaces and their wide-ranging technical applications [1].
Due to its long half-life and its toxicity, Np-237 is considered as a major contaminant of the ecosystem in the long-term safety assesment of nuclear waste repositories. The pentavalent state is environmentally most relevant [2].
For the first time, in-situ Np(V) sorption is comparatively studied on the oxyhydroxides of Fe, Mn, Si and Ti by ATR FT-IR spectroscopy under a variety of environmentally relevant sorption conditions. From the results, the formation of binary inner-sphere complexes on oxides of Si, Mn, Fe and Ti can be derived [3]. In case of ferrihydrite, the formation of an additional ternary Np-carbonato surface species is assumed. In addition, time resolved spectra provide kinetic information on the surface reactions.
[1] Dixon J. B. et al.(1989) Minerals in soil environments. Madison, Wisc.: Soil Science Soc. of America. 1244. [2] Kaszuba J. P. et al. (1999) Env. Sci. & Techn. 33(24), 4427-4433. [3] Müller K. et al. (2009) Env. Sci. & Techn. 43(20): p. 7665-7670

  • Lecture (Conference)
    Goldschmidt 2013, 25.-30.08.2013, Florence, Italy
  • Abstract in refereed journal
    Mineralogical Magazine 77(2013)5, 1806

Permalink: https://www.hzdr.de/publications/Publ-18642
Publ.-Id: 18642


Raman imaging of copper ores

Kostudis, S.; Hof, M.; Kutschke, S.; Pollmann, K.

In Middle Europe large deposits of Kupferschiefer involve the Upper Lusatia, the northeastern part of Saxony. The regional Kupferschiefer raised again interest of both industry and science because in this region its copper content constitutes the most important natural copper resource. There is no efficient biotechnological approach applied yet due to the fact that Kupferschiefer is complexly composed comprising different sulfidic minerals, carbonates and organic compounds. Bioleaching, which means the use of microorganisms and their metabolites to extract metals from their ores, reduces costs of high energy input and avoids the usage of toxic chemicals thus benefitting environment (Narayan 2009) and employees.
Raman spectroscopy enables a fast and specific chemical identification of minerals and ores (Hope 2001) as well as the detection of changes e.g. that are caused by oxidation (García-Meza 2012). Also Raman spectroscopic imaging of biotic components such as biofilms has already been performed (Virdis 2012).
We aim to use Raman spectroscopy to investigate the interactions of microorganisms and ore surface: Different polished sections of bornite, chalcopyrite (both from Henderson Mine, Namagualand, South Africa), chalcosite (Ashio, Japan) and copper shale (Polkovice, Poland) were analysed by polarising microscopy to ensure correct spectra assignment. Subsequently identical areas were analysed by Raman imaging using 2D scanning function. After incubation with microorganisms the sections will be investigated again in order to evaluate chemical changes of the ore surfaces, biofilm formation and to monitor bioleaching processes.

  • Poster
    RamanFest 2013 Symposium, 23.-24.05.2013, Lille (Nord), Frankreich

Permalink: https://www.hzdr.de/publications/Publ-18641
Publ.-Id: 18641


Identification of multiple S-layer genes that are expressed by Lysinibacillus sphaericus JG-B53 – a bacterial survival strategy in metalliferous environments?

Lederer, F.; Weinert, U.; Günther, T.; Raff, J.; Pollmann, K.

Generally, heavy metal contamination of the environment is a result of either natural events like volcanic emissions or human activities such as mining processes. High concentrations of heavy metals are toxic to the majority of organisms. However, several bacteria exhibit surprising strategies to survive in metalliferous environments. These strategies are attractive for novel bio-based resource technologies. Their understanding is the purpose of our research.
Aim of this study was the identification of bacterial methods to accept heavy metals in their environment. Genes that are related to the bacterial heavy metal tolerance strategy were analysed.
Lysinibacillus sphaericus JG-B53, an isolate from the uranium mining waste pile Haberland, was studied using genome sequencing analyses in order to identify strain intrinsic survival strategies like surface (S) layer proteins with metal specific binding affinities and metal specific transporter proteins. The genome of Lysinibacillus sphaericus JG-B53 was sequenced using the Next Generation Sequencing Technology. Bioinformatic analyses of generated data were performed with the Genomics Workbench (CLCbio). The expression of selected genes was studied using mRNA methods. Genes and encoded proteins were characterised with special analysing tools.
The genome of Lysinibacillus sphaericus JG-B53 encodes at least 13 S-layer like proteins and 3 metal ion exporter protein genes for metals that occur in the natural habitat. Their characteristics were analysed with multiple gene and protein analysing programs. Using cDNA analyses the expression of 6 putative S-layer proteins was detected.
Future studies will analyse recombinant S-layer proteins regarding their lattice symmetry and metal binding affinities.

  • Lecture (Conference)
    5th Congress of European Microbiologists - FEMS 2013, 21.-25.07.2013, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18640
Publ.-Id: 18640


Milling Result Prediction

Matos Camacho, S.; Leißner, T.; Atanasova, P.; Kamptner, A.; Rudolph, M.; Peuker, U. A.; van den Boogaart, K. G.

Fine grained ore can only be exploited with finer milling, which results in additional milling costs. The ability to infer the optimal milling parameters and corresponding grades of recovery from microstructural information allows optimal extraction and predicting processing costs and final recovery. The MLA (Mineral Liberation Analyzer) allows quantifying the 2D size of grains in the ore. We have developed a method to predict the effect of milling from milling experiments and MLA-images to the 3D liberation of the value mineral in the ore.

Keywords: grinding; geometallurgy; MLA; milling

  • Lecture (Conference)
    15th Annual Conference of the International Association for Mathematical Geosciences - IAMG 2013, 02.-06.09.2013, Madrid, Espana
  • Contribution to proceedings
    15th Annual Conference of the International Association for Mathematical Geosciences - IAMG 2013, 02.-06.09.2013, Madrid, Espana
    Mathematics of Planet Earth - Proceedings of the 15th Annual Conference of the International Association for Mathematical Geosciences, Berlin, Heidelberg: Springer, 978-3-642-32407-9, 717-721
    DOI: 10.1007/978-3-642-32408-6

Permalink: https://www.hzdr.de/publications/Publ-18639
Publ.-Id: 18639


Dendrimers as Nb3+ ligands: effect of generation on the efficiency of the sensitized lanthanide emission

Pillai, Z. S.; Ceroni, P.; Kubeil, M.; Heldt, J.-M.; Stephan, H.; Bergamini, G.

We have designed two novel dendrimers with cyclam cores with appended poly(amido amine) (PAMAM) dendrons, decorated at the periphery with four and eight dansyl chromophores, respectively. The photophysical properties of the dendrimers and their Nd3+ complexes have been investigated. The energy-transfer efficiency to the lanthanide ions from these dendrimers has been studied as a function of the generation. It has been observed that an increase in the dendrimer generation as well as the number of amide units enhances the energy transfer to the lanthanide ion.

Permalink: https://www.hzdr.de/publications/Publ-18638
Publ.-Id: 18638


Herstellung und Reinigung von 64Cu am Leipziger Zyklotron Cyclone® 18/9

Mansel, A.; Franke, K.; Fischer, S.; Steinbach, J.

Die Abteilung „Reaktiver Transport“ der Forschungsstelle Leipzig beschäftigt sich mit dem Migrations-/Sorptionsverhalten von (Schad)stoffen in geologischen Formationen. In aktuellen Projekten werden partikuläre, kolloidale, gelöste und komplexierte, toxische und radiotoxische Stoffe in Batch- und Säulenstudien untersucht. Bei der eingesetzten Radiotracertechnik kommen kurzlebige Radionuklide zum Einsatz. Am Leipziger Zyklotron Cyclone® 18/9 neu implementiert ist die 64Cu-Herstellung durch Protonenbeschuss von isotopenangereichertem 64Ni via (64Ni(p,n)64Cu)[1]. Das Target wird durch elektrolytische Abscheidung von ca. 5 mg 64Ni auf Goldfolien hergestellt. Die Bestrahlung erfolgt bei einem Protonenstrom von 20 µA bei Strahlzeiten von bis zu 7 Stunden und einer Projektilenergie von ca. 12 MeV. Die chemische Aufarbeitung des bestrahlten Nickels erfolgt durch Ionenchromatographie mit AG1-X8 aus salzsaurer Lösung[2,3]. 64Cu wird mit einer radiochemischen Ausbeute von ca. 95 % erhalten. Das wertvolle Targetmaterial (isotopenangereichert auf 95 %) wird mit ~ 90 % Ausbeute wiedergewonnen. Das produzierte Radionuklid wurde erfolgreich zur Visualisierung von Fluidtransport in Geomaterialien mittels PET[4] sowie in der Calixarenkomplexierung[5] eingesetzt.

Literatur:
[1] F. Szelecsényi, G. Blessing, S. M. Qaim, 1993, Appl. Radiat. Isot. 44(3) 575-580.
[2] M. A. Avila-Rodriguez, J. A. Nye, R. J. Nickles, 2007, Appl. Radiat. Isot. 65(10) 1115-1120.
[3] S. Thieme, M. Walther, H.-J. Pietzsch, J. Henninger, S. Preusche, P. Mäding, J. Steinbach, 2012, Appl. Radiat. Isot. 70(4) 602-608.
[4] M. Stoll, Diplomarbeit, in Bearbeitung, Universität Mainz.
[5] M. Poetsch, Masterarbeit, 2012, Universität Leipzig.

  • Lecture (Conference)
    Wissenschaftsforum Chemie 2013 - Fachgruppe Nuklearchemie, 01.-04.09.2013, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18635
Publ.-Id: 18635


Generation of electron beams with superconducting photoinjectors

Teichert, J.; Arnold, A.; Büttig, H.; Justus, M.; Lehnert, U.; Lu, P.; Michel, P.; Murcek, P.; Schurig, R.; Vennekate, H.; Xiang, R.; Kamps, T.; Rudolph, J.; Kneisel, P.; Will, I.

The production of beams with low emittance as well as high average current is one of the key techniques for future electron accelerators and next generation light sources. The superconducting radio-frequency photo electron source (SRF gun) has the potential to fulfill the requirements for these new accelerators. The presentation will give an introduction and overview of this type of modern electron injector. The main issues such as niobium cavity design and fabrication, cryomodule, radio-frequency system, photocathodes, drive laser will be discussed. The status of the various R&D project for SRF guns will be presented, and a comparison to alternative high-current injector concepts like DC photo guns and low-frequency, normal-conducting RF guns will be given.

Keywords: superconducting RF; electron source accellerator; photoelectron injector; niobium cavity; photo cathode

  • Invited lecture (Conferences)
    LA3NET 1st Topical Workshop on Laser Based Particle Sources, 20.-22.02.2013, Geneva, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-18634
Publ.-Id: 18634


Evidences for a more restricted Icelandic Ice cap re-advance after the Bølling warming period

Meriaux, A.-S.; Delunel, R.; Merchel, S.; Finkel, R.

Moraines dated north of Vatnajökull by cosmogenic surface exposure dating show that the Icelandic Ice cap (IIS) was less extended during the Younger Dryas than previously suggested. The data imply that this glacial advance was more complex and restricted in some glacial valleys in NE Iceland. While the IIS margins are relatively well constrained offshore by marine or coastal evidences, little is known about their onshore characteristics and rates of recession during the warmer Holocene periods. This is especially the case in the NE of Iceland where volcanic activity and major outburst floods (jökulhlaups) have removed a large amount of morphological evidences of past ice margins. Our study aimed at filling this chronological gap of the IIS inland during the late Quaternary deglaciation by dating past preserved ice margins using 36Cl and 3He cosmogenic nuclides.
We studied moraines and outwash located 44 km, 48 km and 60 km north of Vatnajökull, between the Jökulsà à Fjöllum and Jökulsà à Brú, the main northern glacial river systems draining the icecap. Preliminary 36Cl ages of the northernmost moraine at Skessugarður, 60 km north of present-day IIS and 65 km away from the coastline, indicate that the minimum exposure ages derived from Ca-rich plagioclases range from 11.0 + 1.2 ka to 13.4 + 1.4 ka with an average at 12.2 + 1.0 ka (+1 sigma, n=6), using the local Icelandic production rates for Ca spallation of Licciardi et al. (2008). These ages are close to the Younger Dryas at a time when the Icelandic Ice Sheet is thought to have re-advanced further north toward the coastline. Overall, our results call for a Revision of our understanding of the IIS deglaciation history and provide new tie-points for the calibration of the IIS models.
References: Licciardi et al., EPSL 267 (2008) 365–377.

Keywords: cosmogenic nuclide; AMS; deglaciation; iceland

  • Poster
    EGU General Assembly 2013, 07.-12.04.2013, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-18633
Publ.-Id: 18633


Selenium(IV) Uptake by Maghemite (gamma-Fe2O3)

Jordan, N.; Ritter, A.; Scheinost, A. C.; Weiß, S.; Schild, D.; Hübner, R.

The mechanism of selenium(IV) uptake by maghemite was investigated on both the macroscopic and the molecular level. Maghemite nanoparticles exhibited fast adsorption kinetics toward selenium(IV). Batch experiments showed a decreased sorption with increasing pH (3.5-11).
Ionic strength variations (0.01 to 0.1 M NaCl) had no significant influence on selenium(IV) uptake. Electrophoretic mobility measurements revealed a significant shift toward lower values of the isoelectric point of maghemite upon selenium(IV) uptake, suggesting the formation of inner-sphere surface complexes. At the molecular level, using X-ray Absorption Fine-Structure Spectroscopy (EXAFS), the formation of both bidentate binuclear corner-sharing (C-2) and bidentate mononuclear edge-sharing (E-1) inner-sphere surface complexes was observed, with a trend toward solely E-1 complexes at high pH. The absence of a tridentate surface complex as observed for arsenic(III) and antimonite(III) might be due to the relatively small size of the (SeO3)-O-IV unit. These new spectroscopic results can be implemented in reactive transport models to improve the prediction of selenium migration behavior in the environment as well as its monitoring through its interaction with maghemite or maghemite layers at the surface of magnetite. Due to its chemical stability even at low pH and its magnetization properties allowing magnetic separation, maghemite is a promising sorbing phase for the treatment of Se polluted waters.

Keywords: selenium(IV); uptake; maghemite; EXAFS

Permalink: https://www.hzdr.de/publications/Publ-18632
Publ.-Id: 18632


Efficient laser-driven proton acceleration in the ultra-short pulse regime

Zeil, K.; Bock, S.; Burris-Mog, T.; Bussmann, M.; Helbig, U.; Kluge, T.; Kraft, S. D.; Metzkes, J.; Debus, A.; Roeser, F.; Cowan, T. E.; Sauerbrey, R.; Schramm, U.; Beyreuther, E.; Karsch, L.; Laschinsky, L.; Naumburger, D.; Oppelt, M.; Richter, C.; Schürer, M.; Baumann, M.; Enghardt, W.; Pawelke, J.

Erläuterung des Prinzips der Laserprotonenbeschleunigung und Präsentation der Experimente des TNSA Beschleunigungsmechanismus unter Verwendung ultrakurzer Laserpusle. Weiterhin wird die Anwendung der erzeugten Protonenpulse für strahlenbioloigsche Untersuchnungen vorgestellt.

  • Invited lecture (Conferences)
    Arbeitstreffen „Kernphysik“ Schleching 2013, 27.2.2013, Schleching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18631
Publ.-Id: 18631


Observation of prompt pre-thermal laser ion sheath acceleration and implication on scaling

Zeil, K.; Metzkes, J.; Kluge, T.; Bussmann, M.; Cowan, T.; Kraft, S.; Sauerbrey, R.; Schramm, U.

High-intensity laser-plasma ion generation is promising as a compact, low-cost proton source for applications like ion beam therapy. Using a femtosecond table-top laser system, we studied the intra-pulse phase of the laser driven proton acceleration and show that protons efficiently gain energy in these early times.

  • Lecture (Conference)
    DPG-Frühjahrstagung Dresden, 4.3.2013, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18630
Publ.-Id: 18630


Breit-Wheeler process in very short electromagnetic pulses

Titov, A.; Kämpfer, B.; Takabe, H.; Hosaka, A.

he generalized Breit-Wheeler process, i.e. the emission of $e^+e^-$ pairs off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g.\ laser) wave field, is analyzed. We show that the production probability is determined by the interplay of two dynamical effects. The first one is related to the shape and duration of the pulse and the second one is the non-linear dynamics of the interaction of $e^\pm$ with the strong electromagnetic field. The first effect manifests itself most clearly in the weak-field regime, where the small field intensity is compensated by the rapid variation of the electromagnetic field in a limited space-time region, which intensifies the few-photon events and can enhance the production probability by orders of magnitude compared to an infinitely long pulse. Therefore, short pulses may be considered as a powerful amplifier. The non-linear dynamics in the multi-photon Breit-Wheeler regime plays a decisive role at large field intensities, where effects of the pulse shape and duration are less important. In the transition regime, both effects must be taken into account simultaneously. We provide suitable expressions for the $e^+e^-$ production probability for kinematic regions which can be used in transport codes.

Permalink: https://www.hzdr.de/publications/Publ-18629
Publ.-Id: 18629


Properties of the electron-positron plasma created from vacuum in a strong Laser Field I. Quasiparticle excitations

Blaschke, D.; Kämpfer, B.; Schmidt, S. M.; Panferov, A. D.; Prozorkevich, A. V.; Smolyansky, S. A.

Solutions of a kinetic equation are investigated which describe, on a nonperturbative basis, the vacuum creation of quasiparticle electron-positron pairs due to a strong laser field. The dependence of the quasiparticle electron (positron) distribution function and the particle number density is explored in a wide range of the laser radiation parameters, i.e., the wavelength \lambda and amplitude of electric field strength E_0. Three domains are found: the domain of vacuum polarization effects where the density of the e-e+ pairs is small (the "calm valley"), and two accumulation domains in which the production rate of the e-e+ pairs is strongly increased and the e-e+ pair density can reach a significant value (the short wave length domain and the strong field one). In particular, the obtained results point to a complicated short-distance electromagnetic structure of the physical vacuum in the domain of short wavelengths \lambda \lessim \lambda_{acc} = \pi/m. For moderately strong fields E_0 \lesssim E_c=m^2/e, the accumulation regime can be realized where a plasma with a high density of e-e+ quasiparticles can be achieved. In this domain of the field strengths and in the whole investigated range of wavelengths, an observation of the dynamical Schwinger effect can be facilitated.

Permalink: https://www.hzdr.de/publications/Publ-18628
Publ.-Id: 18628


Investigation on magnetoacoustic properties of spin-ice materials Dy2Ti2O7 and Ho2Ti2O7

Erfanifam, S.; Zherlitsyn, S.; Wosnitza, J.; Moessner, R.; Zvyagin, A. A.; Mcclarty, P.; Petrenko, O.; Balakrishnan, G.

We have investigated elastic properties of the spin-ice materials Dy2Ti2O7 (DTO) and Ho2Ti2O7 (HTO) for a wide range of temperature and magnetic field. Our studies of the sound characteristics for several acoustic modes evidence a renormalization of the sound velocity and the sound attenuation due to phase transformations at applied magnetic field as well as an interaction with low-energy magnetic excitations (topological defects). The most prominent anomalies are quasi-periodic peaks in the sound velocity and in the sound attenuation observed in DTO due to non-equilibrium processes arising in the external magnetic field. These results were analyzed theoretically using exchange-striction coupling, which shows a good agreement between theory and experiment. The obtained results at high magnetic fields exhibit some pronounced anomalies around 50 T for both compounds. Our calculations including crystal-electric field effects show satisfactory agreement with experiment.

  • Lecture (Conference)
    Frühjahrstagung der DPG, 10.-15.03.2013, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18627
Publ.-Id: 18627


Similarities between the phase diagrams of the S=3/2 Heisenberg spin chains CrXO4 [X=V,P]

Law, J.; Foerster, T.; Glaum, R.; Kremer, R.

CrVO4 and CrPO4 both adopt the same structure type. They can be well described as S=3/2 Heisenberg spin chains with predominant nearest-neighbour only spin exchange interaction. We show here an in-depth investigation into the magnetic structures of both compounds which is complimented by magnetic property measurements. Wherein, we’ve shown that both compounds exhibit a high field phase transition into an unknown state.

  • Lecture (Conference)
    Frühjahrstagung der DPG, 10.-15.03.2013, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18626
Publ.-Id: 18626


Padé approximations for the magnetic susceptibilities of Heisenberg antiferromagnetic spin chains for various spin values

Law, J.; Kremer, R.

The temperature dependence of the spin susceptibilities of S=1, 3/2, 2, 5/2 and 7/2 Heisenberg nearest-neighbor antiferromagnetic 1D spin chains was simulated via Quantum Monte Carlo calculations, within the temperature range of 0.005 ≤ T⋆ ≤ 100 and fitted to Padé approximations with deviations between the simulated and fitted data of the same order of magnitude or smaller than the Quantum Monte Carlo error. To demonstrate the practicality of our theoretical findings, we successfully compared them with the well known 1D chain compound TMMC (d5, S=5/2) and the new S=1 Heisenberg spin chain NiTa2O6.

  • Lecture (Conference)
    Frühjahrstagung der DPG, 10.-15.03.2013, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18625
Publ.-Id: 18625


High-Field Magnetotransport in the Electron-Doped Cuprate Superconductor Nd2−xCexCuO4

Helm, T.; Kartsovnik, M. V.; Kampert, E.; Putzke, C.; Biberacher, W.; Grigoriev, P. D.; Baddoux, S.; Proust, C.; Sheikin, I.; Kiswandhi, A.; Brooks, J. S.; Choi, E. S.; Wosnitza, J.; Erb, A.; Gross, R.

es hat kein Abstract vorgelegen

  • Poster
    Frühjahrstagung der DPG, 10.-15.03.2013, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18624
Publ.-Id: 18624


Investigation of the magnetocaloric effect in La(Fe,Si,Co)13 compound in pulsed magnetic fields

Ghorbani Zavareh, M.; Scurschii, I.; Skokov, K.; Gutfleisch, O.; Wosnitza, J.

es hat kein Abstract vorgelegen

  • Poster
    Frühjahrstagung der DPG, 10.-15.03.2013, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18623
Publ.-Id: 18623


Spin dynamics in Azurite: high-field ESR studies

Ozerov, M.; Kamenskyi, D.; Wosnitza, J.; Engelkamp, H.; Wolff-Fabris, F.; Francoual, S.; Jaime, M.; Zvyagin, S.

es hat kein Abstract vorgelegen

  • Poster
    Frühjahrstagung der DPG, 10.-15.03.2013, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18622
Publ.-Id: 18622


AMS measurements of cosmogenic and supernova–ejected radionuclides in deep–sea sediment cores

Feige, J.; Wallner, A.; Fifield, L. K.; Golser, R.; Korschinek, G.; Merchel, S.; Rugel, G.; Winkler, S. R.

Accelerator Mass Spectrometry (AMS) provides the highest sensitivity for measurements of long-lived radionuclides with half-lives in the order of million years. We apply this method to search for live supernova (SN)-produced radionuclides on Earth.

The first indication of a SN close-by to the solar system was published by Knie et al. in 2004. AMS measurements of a ferromanganese crust from the Pacific Ocean showed an excess of 60Fe corresponding to a time some 2 Myr ago. We have obtained two deep-sea sediment cores from the Indian Ocean, which provide a better time resolution due to higher accumulation rates. We use AMS for measuring concentrations of the long-lived radionuclides 26Al, 53Mn and 60Fe in these sediment cores with high time resolution. All three radionuclides, with half-lives between 0.7 and 3.7 Myr, are produced in the late burning phases and during a supernova explosion of a massive star and are ejected into the interstellar medium in the explosion. In contrast to 60Fe, which is not produced in-situ on Earth, cosmogenic production of 26Al and 53Mn in the atmosphere and in-situ adds to a potential extraterrestrial signal. Therefore, accurate data are required for these radionuclides. The cosmogenic isotope 10Be, produced from cosmic rays in the Earth’s atmosphere, is analysed for dating purposes.

We will present our first AMS measurement results for 10Be (DREAMS facility, Germany) and 26Al (VERA, Austria) and will show that, in addition to 10Be, 26Al might be a valuable isotope for dating of deep-sea sediment cores for the past few million years.

Keywords: SN; supernova; AMS; radionuclides

  • Lecture (Conference)
    Heavy Ion Accelerator Symposia on Fundamental and Applied Science (HIAS), 08.-12.04.2013, Canberra, Australia

Permalink: https://www.hzdr.de/publications/Publ-18621
Publ.-Id: 18621


Eu valence and Fermi-surface development in EuX2Si2 (X = Co, Rh, Ir) systems

Götze, K.; Seiro, S.; Geibel, C.; Rosner, H.; Petzold, V.; Polyakov, A.; Wosnitza, J.; Sheikin, I.; Suslov, A.

The valence-fluctuating Eu systems EuX2Si2, with X being the transition metal Co, Ir, or Rh, show different types of ground states, strongly depending on X. The instability of the Eu 4f shell underlies this phenomenon and leads among other effects to different valence states ranging from Eu2+ over mixed valence and intermediate valence behavior to Eu3+ [1]. Investigations on the structure and the magnetic behavior of EuCo2Si2, EuIr2Si2, and EuRh2Si2 have revealed their Eu valence. Further experiments on specific heat and resistivity gave insights to magnetic ordering, electronic correlations, and possible valence fluctuations. We report about a systematic de Haas-van Alphen study on the Fermi-surface development of the EuX2Si2 compounds in magnetic fields up to 35 T. High-quality single crystals were available for the first time. We will focus on the Fermi-surface topology obtained by angle dependent measurements and discuss a comparison to band-structure calculations .

  • Lecture (Conference)
    Frühjahrstagung der DPG, 10.-15.03.2013, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18620
Publ.-Id: 18620


de Haas-van Alphen investigations on the filled skutterudite LaRu4As12 superconductor

Klotz, J.; Götze, K.; Cichorek, T.; Henkie, Z.; Wosnitza, J.

es hat kein Abstract vorgelegen

  • Poster
    Frühjahrstagung der DPG, 10.-15.03.2013, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18619
Publ.-Id: 18619


Terahertz spectroscopy of superconducting Fe(Se,Te)

Chanda, G.; Pronin, A. V.; Wosnitza, J.; Molatta, S.; Hühne, R.; Holzapfel, B.; Iida, K.

es hat kein Abstract vorgelegen

  • Lecture (Conference)
    Frühjahrstagung der DPG, 10.-15.03.2013, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18618
Publ.-Id: 18618


Low-Spin Hexacoordinate Mn(III): Synthesis and Spectroscopic Investigation of Homoleptic Tris(pyrazolyl)borate and Tris(carbene)borate Complexes

Forshaw, A.; Smith, J.; Ozarowski, A.; Krzystek, J.; Smirnov, D.; Zvyagin, S.; Harris, T.; Karunadasa, H.; Zadrozny, J.; Schnegg, A.; Holldack, K.; Jackson, T.; Alamiri, A.; Barnes, D.; Telser, J.

Three complexes of Mn(III) with "scorpionate" type ligands have been investigated by a variety of physical techniques. The complexes are [Tp2Mn]SbF6 (1), [Tp2*Mn]-SbF6 (2), and [{PhB(MeIm)3}2Mn](CF3SO3) (3a), where Tp- = hydrotris(pyrazolyl)borate anion, Tp*- = hydrotris(3,5-dimethylpyrazolyl)borate anion, and PhB(Melm)3- = phenyltris(3-methylimidazol-2-yl)borate anion. The crystal structure of 3a is reported; the structures of 1 and 2 have been previously reported, but were reconfirmed in this work. The synthesis and characterization of [{PhB(MeIm)3}2Mn]Cl (3b) are also described. These complexes are of interest in that, in contrast to many hexacoordinate (pseudo-octahedral) complexes of Mn(III), they exhibit a low-spin (triplet) ground state, rather than the high-spin (quintet) ground state. Solid-state electronic absorption spectroscopy, SQUID magnetometry, and high-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy were applied. HFEPR, in particular, was useful in characterizing the S = 1 spin Hamiltonian parameters for complex 1, D = +19.97(1), E = 0.42(2) cm-1, and for 2, D = +15.89(2), E = 0.04(1) cm-1. In addition, frequency domain Fourier-transform THz-EPR spectroscopy, using coherent synchrotron radiation, was applied to 1 only and gave results in good agreement with HFEPR. Variable-temperature dc magnetic susceptibility measurements of 1 and 2 were also in good agreement with the HFEPR results. This magnitude of zero-field splitting (zfs) is over 4 times larger than that in comparable hexacoordinate Mn(III) systems with S = 2 ground states. Complexes 3a and 3b (i.e., regardless of counteranion) have a yet much larger magnitude zfs, which may be the result of unquenched orbital angular momentum so that the spin Hamiltonian model is not appropriate. The triplet ground state is rationalized in each complex by ligand-field theory (LFT) and by quantum chemistry theory, both density functional theory and unrestricted Hartree-Fock methods. This analysis also shows that spin-crossover behavior is not thermally accessible for these complexes as solids. The donor properties of the three different scorpionate ligands were further characterized using the LFT model that suggests that the tris(carbene)borate is a strong sigma-donor with little or no pi-bonding.

Permalink: https://www.hzdr.de/publications/Publ-18617
Publ.-Id: 18617


Magnetic poly(epsilon-caprolactone)/iron-doped hydroxyapatite nanocomposite substrates for advanced bone tissue engineering

Gloria, A.; Russo, T.; D'Amora, U.; Zeppetelli, S.; D'Alessandro, T.; Sandri, M.; Banobre-Lopez, M.; Pineiro-Redondo, Y.; Uhlarz, M.; Tampieri, A.; Rivas, J.; Herrmannsdoerfer, T.; Dediu, V. A.; Ambrosio, L.; de Santis, R.

In biomedicine, magnetic nanoparticles provide some attractive possibilities because they possess peculiar physical properties that permit their use in a wide range of applications. The concept of magnetic guidance basically spans from drug delivery and hyperthermia treatment of tumours, to tissue engineering, such as magneto-mechanical stimulation/activation of cell constructs and mechanosensitive ion channels, magnetic cell-seeding procedures, and controlled cell proliferation and differentiation. Accordingly, the aim of this study was to develop fully biodegradable and magnetic nanocomposite substrates for bone tissue engineering by embedding iron-doped hydroxyapatite (FeHA) nanoparticles in a poly(epsilon-caprolactone) (PCL) matrix. X-ray diffraction analyses enabled the demonstration that the phase composition and crystallinity of the magnetic FeHA were not affected by the process used to develop the nanocomposite substrates. The mechanical characterization performed through small punch tests has evidenced that inclusion of 10 per cent by weight of FeHA would represent an effective reinforcement. The inclusion of nanoparticles also improves the hydrophilicity of the substrates as evidenced by the lower values of water contact angle in comparison with those of neat PCL. The results from magnetic measurements confirmed the superparamagnetic character of the nanocomposite substrates, indicated by a very low coercive field, a saturation magnetization strictly proportional to the FeHA content and a strong history dependence in temperature sweeps. Regarding the biological performances, confocal laser scanning microscopy and AlamarBlue assay have provided qualitative and quantitative information on human mesenchymal stem cell adhesion and viability/proliferation, respectively, whereas the obtained ALP/DNA values have shown the ability of the nanocomposite substrates to support osteogenic differentiation.

Permalink: https://www.hzdr.de/publications/Publ-18616
Publ.-Id: 18616


Superconductivity in Ge and Si via Ga-ion implantation

Skrotzki, R.; Herrmannsdörfer, T.; Schönemann, R.; Heera, V.; Fiedler, J.; Kampert, E.; Wolff-Fabris, F.; Philipp, P.; Bischoff, L.; Voelskow, M.; Mücklich, A.; Schmidt, B.; Skorupa, W.; Helm, M.; Wosnitza, J.

es hat kein Abstract vorgelegen

  • Poster
    Frühjahrstagung der DPG, 10.-15.03.2013, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18615
Publ.-Id: 18615


Accuracy of 9Be-data and its influence on 10Be cosmogenic nuclide data

Merchel, S.; Bremser, W.; Bourlès, D. L.; Czeslik, U.; Erzinger, J.; Kummer, N.-A.; Leanni, L.; Merkel, B.; Recknagel, S.; Schaefer, U.

A 9Be-solution has been chemically prepared from phenakite (Be2SiO4) mineral grains as commercial 9Be-solutions are too high in long-lived 10Be. The solution is intended to be used as a carrier for radiochemical separation of 10Be to be measured by accelerator mass spectrometry (AMS). Thus, accurate data of the 9Be-concentration of this solution is essential to guarantee for high-accuracy 10Be data in the future. After devastating preliminary results (~8% standard deviation), eight laboratories finally produced twelve individual results by four different analytical methods. A certain lab and method bias might be identified by sophisticated statistical evaluation. Some laboratories also (grossly) underestimate their uncertainties. Thus, the simple weighted mean of this round-robin exercise needed to be corrected by introducing additional allowances (Paule-Mandel-approach). The final result has been calculated to (2246 ± 11) µg 9Be/(g solution) with a reasonably low weighted standard deviation of 0.49%. The maximum deviation of a single lab value from the weighted mean is 2.4% when removing one Grubbs outlier (11% off from the mean) from the data set. As 10Be-data, which is usually calculated from measured 10Be/9Be by AMS and stable 9Be, cannot be more accurate than the determined 9Be-concentration, it seems highly advisable to establish or improve quality assurance by having self-made carrier-solutions analysed at more than a single lab and regularly taking part in round-robin exercises.

Keywords: cosmogenic nuclide; ICP-MS; ICP-OES; AAS; round-robin; accelerator mass spectrometry; AMS

Permalink: https://www.hzdr.de/publications/Publ-18614
Publ.-Id: 18614


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