Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33407 Publications

Live in-Situ Visualisierung und Steuerung von wissenschaftlichen Simulationen auf Hochleistungsrechnern

Matthes, A.; Widera, R.; Hübl, A.; Zenker, E.; Eckert, C.; Gumhold, S.; Grottel, S.; Bussmann, M.
Hochleistungsrechner sind ein wichtiges Instrument für die Forschung. Hochparallele physikalische Simulationen können in Zusammenarbeit mit Experimenten neue Erkenntnisse erschließen oder bestehende hochkomplexe Modelle überprüfen.
Eine solche Simulation stellt die Plasmasimulation PIConGPU des Helmholtz-Zentrums Dresden – Rossendorf (HDZR) dar, die zusätzlich noch Grafikkarten zur weiteren Rechenbeschleunigung nutzen kann. Dabei entstehen jedoch derart viele Daten, dass ein Speichern und nachträgliches Auswerten der wissenschaftlichen Daten nicht mehr möglich ist, weshalb die Simulationsergebnisse live auf dem Hochleistungsrecher visualisiert werden müssen.
Im Rahmen der vorgestellten Diplomarbeit wurde eine abstrakte Bibliothek für die live in-situ Visualisierung und Steuerung von Simulationen beschrieben und implementiert. Der Projektstand zeigt eine live Visualisierung von PIConGPU auf einer stereoskopischen 3D Leinwand während es auf dem Hochleistungscluster Hypnos des HZDR läuft.
Keywords: in-situ visualization, simulation steering, in-memory visualization, live visualization, heterogeneous architectures, high performance computing
  • Lecture (others)
    OUTPUT.DD, 09.06.2016, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-23724
Publ.-Id: 23724


Ultrafast ion heating above 1 keV temperautres in solid density plasmas driven by ultrashort relativistic laser pulses

Huang, L. G.; Cowan, T.
Bulk ion heating driven by high power laser pulses is a fundamental scientific issue and of great interest to the potential applications such as nuclear excitation by electronic processes, inertial confinement fusion and so on. Yet, most theoretical and experimental investigation focus on several hundred picoseconds to nanosecond time scale evolution of ion heating dynamics, relying on radiation-hydrodynamic simulations and high energy laser facilities with the order of nanosecond pulse durations. Both the theoretical and experimental methodologies have constraints. In one hand, the hydrodynamic simulations may smooth out the kinetic effects in solid density plasmas such as species thermal decoupling, spatial mixing and separation. In the other hand, the experimental access using several hundred to kilo-Joule laser facilities is quite limited at present.

We present our recent results on ultrafast ion heating dynamics in solid buried layer targets driven by relativistic laser pulses with tens to hundreds of femtosecond pulse durations and high repetition rates[1]. The kinetic simulations using Particle-in-Cell methodology showing that the light ions within highly compressed solid density plasmas can be heated above 1 keV temperature in several hundred femtosecond time to picosecond time scales. We also found that significant instabilities and ion species mixture showing up which are originated from the interfaces of the solid buried layer targets. The possible heating mechanisms during the internal expansion and compression passage will be discussed and addressed.

In order to connect the ion heating dynamics seen in simulations with experiments, we will discuss the role of in-situ synthetic diagnostics that mimic experimental diagnostics. As one example, analyzing the energy spectrum and angular distribution of generated neutrons is possible to determine the ion temperature and distinguish the beam fusion and thermonuclear fusion, which is a conventional diagnostic method in experiments currently. The other key example we propose to directly probe the buried layer dynamics with coherent scattering techniques using hard X-Ray Free Electron Lasers, which is in principle and feasible to allow for probing fundamental plasma properties in nanosecond and femtosecond resolutions of plasma processes for the first time in the near future[2].

Reference:

[1] L. G. Huang et al., Phys. Plasmas 20, 093109 (2013)
[2] http://www.hibef.eu/
Keywords: Ion Heating,High power laser,XFEL,solid plasmas
  • Lecture (Conference)
    1st International Conference onMatter and Radiation at Extremes, 08.-12.05.2016, Chengdu, China

Permalink: https://www.hzdr.de/publications/Publ-23723
Publ.-Id: 23723


Overview on recent research activities related to electrochemical processes in magnetic fields

Mutschke, G.; Yang, X.
The talk will first give a brief introduction of the Helmholtz-Center Dresden-Rossendorf and its Institute of Fluid Mechanics.
It will then give an overview on recent research activities related to electrochemical topics, thereby describing the numerical and the experimental techniques applied and the results obtained. Special focus is drawn on the influence of magnetic fields in electrochemical processes, and recent results are presented in the fields of copper deposition, the evolution of hydrogen during water electrolysis and the enrichment of paramagnetic ions in aqueous electrolytes.
Keywords: electrochemistry, metallurgy, hydrogen production, rare-earth metals, electrolysis, magnetohydrodynamics
  • Lecture (others)
    Eingeladener Vortrag an Department of Physical Chemistry and Metallurgy of Non-Ferrous Metalls, AGH University of Science and Technology, 31.05.2016, Krakau, Polen

Permalink: https://www.hzdr.de/publications/Publ-23722
Publ.-Id: 23722


Pulse Flow in Solid Foam Packed Reactors: Analysis of Morphology and Key Characteristics

Zalucky, J.; Claußnitzer, T.; Schubert, M.; Lange, R.; Hampel, U.
In this paper, results of an experimental study on pulsing two-phase flow in SiSiC solid foam packed reactors are presented. Thereby, the pulse characteristics in a wide range of water and air fluxes at different axial positions for foams with pore densities of 20, 30, and 45 ppi were investigated using ultrafast X-ray computed tomography. Morphologically, discs, curtains and bowls were encountered as basic pulse shapes, which occurred randomly. The key characteristics, i.e. frequency, velocity and volume of pulses as well as peak and time-averaged liquid holdup, have been extracted by applying a dynamic threshold criterion to time-variant liquid holdup profiles. The key properties strongly depend on axial position, pore density and fluid fluxes and can be distinguished in a local and global mode of pulsing. In the local mode, which evolves close to the regime transition boundary, pulses with small liquid volumes move slowly but frequently through the solid foam packed reactor. In the global mode, significantly faster pulses with large liquid volumes were encountered, which cover most of the reactor cross-section but occur less frequent. Compared to literature data for conventional random packings, the pulse frequency was in a similar range while both pulse velocity and liquid content largely exceeded their counterparts. Phenomenologically, the pore occlusion model was found to be more applicable than the concepts based on flow stability.
Keywords: pulse flow, solid foam packing, pulse properties, ultrafast X-ray computed tomography, pore occlusion model, liquid holdup

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Permalink: https://www.hzdr.de/publications/Publ-23721
Publ.-Id: 23721


Evaluation of flow dynamics and liquid-solid mass transfer in solid foam packed reactors using the limiting current technique

Zalucky, J.; Schubert, M.; Hampel, U.
In heterogeneous catalytic multiphase reactors, such as trickle-bed reactors, the achieved space time yield depends strongly on the individual mass transfer steps between the individual phases. Being a transfer resistance to all reactants, the liquid-solid mass transfer can be considered as the most crucial mass transfer step.
The limiting current technique (also called electrochemical method) is an established method to study liquid-solid mass transfer at any solid surface. By application of an electric potential to Nickel electrodes having a morphology representative for the solid phase of interest, the limiting electric current can be continuously measured and directly related to the liquid-solid mass transfer. Moreover, the method allows to study dynamic shear stress-related phenomena in the liquid film such as flow regime transition or dynamics of pulses.
In recent years, open-cell solid foams have gained lots of interest as catalyst support in multiphase processes. They consist of a highly tortuous continuous solid network with void fractions of approx. 90% and combine large specific surface area with low flow resistance and high thermal conductivity. Moreover, their hydrodynamic behavior in terms of flow regimes under cocurrent downflow, i.e. trickling flow at high gas and liquid flow rates, may open up new modes of operation.
In the present contribution, the limiting current technique is used to evaluate fast flow dynamics at trickling and pulsing flow and corresponding liquid-solid mass transfer in trickle-bed reactors packed with silicon-infiltrated silicon-carbide (SiSiC) foams.
Keywords: Liquid-solid mass transfer, solid foam packed reactors, limiting current technique
  • Lecture (Conference)
    Jahrestreffen der Fachgruppe Wärme- und Stoffübertragung 2016, 29.02.-02.03.2016, Kassel, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-23720
Publ.-Id: 23720


Alternative FIB Applications using Liquid Metal Alloy Ion Sources

Bischoff, L.; Mazarov, P.; Bruchhaus, L.; Gierak, J.
At this time Focused Ion Beam (FIB) technology is dominated by gallium Liquid Metal Ion Sources (LMIS). But, despite new developments like He/Ne ion microscopes or Xe-FIBs many applications in the µm- or nm range could benefit from ion species other than gallium or noble gases: local ion implantation, ion beam mixing, ion beam synthesis or even Focused Ion Beam Lithography. For this special use cases Liquid Metal Alloy Ion Sources (LMAIS) represent a promising alternative to expand the remarkable application fields for FIB [1]. Switching between the certain species obtained from a chosen alloy using an ExB mass filter in the ion optical column can be applied to change significantly different physical and chemical characteristics of the resulting nanostructures. In other words the electrical, optical, magnetic and/or mechanic properties can be tuned. This offers a large application potential by choosing a well suited LMAIS. Now nearly half of the elements of the Periodic Table are available in FIB technology.
Main properties of a modern LMAIS should be long life-time, high brightness and stable ion current emission. This contribution will involve the physical basics and experimental results of LMAIS, their physical properties and questions of the preparation technology for elementary as well as binary and ternary alloys as source material. Furthermore selected applications of these sources in highly focused beams are given feasible for nano patterning issues as an alternative technology more in research than in industry.

[1] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid metal alloy ion sources—An alternative for focused ion beam, Appl. Phys. Rev. 3 (2016) 021101.
Keywords: Focused Ion Beam; Liquid Metal Alloy Ion Sources; Nanotechnology
  • Lecture (Conference)
    11th DACH FIB workshop, 27.-28.06.2016, Brno, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-23719
Publ.-Id: 23719


Liquid Metal Ion Source driven High Current Ion Beam Injector

Laufer, P.; Bock, D.; Pilz, W.; Bischoff, L.; Tajmar, M.
The capability of Liquid Metal (Alloy) Ion Sources (LMAIS) to emit a broad variety of ions from nearly the half of the periodic table including molecular ions or small clusters, consisting of a few atoms and different charge stages render them unique for special applications. LMAIS are characterized by a high brightness of about 1e6 A/cm² sr, low energy spread of some eV and a compact design which prefer them for focused ion beam (FIB) systems [1] or field emission electric propulsion (FEEP) thrusters in space technology [2].
The main attention is dedicated to the emission of heavy metallic polyatomic ions – a very special of LMAIS. With Bi or Au di- and trimer ions in the energy range of some 10 keV regular self-organized hexagonal dot structures were obtained after room temperature irradiation of Ge at normal incidence using a FIB instrument. The patterning is induced by the enormous energy deposition by the heavy projectiles but due to the low available currents restricted to only small areas [3, 4]. Consequently, an ion injector based on high current LMAIS is the aim of this work to process larger areas adaptable on single-end ion beam systems. Different types of field emitters were tested for a high permanent ion current of much more than 100 µA.
Among classical needle emitters, particularly the application of porous needles from Tungsten and Rhenium and Tantalum capillaries with a 50 µm inner diameter showed an excellent and stable emission behavior. Source materials like Ga for tests, Gold (from Au82Si18 alloy), Lead and Bismuth (Bi or Ga38Bi62 alloy) were investigated. In the developed injector a nearly parallel ion beam of about 2 mm diameter can be obtained by means of an asymmetric ion-optical Einzel lens. Furthermore a mass separation system (Wien filter) selects the desired ions while a quadrupole is used for beam adjustment and astigmatism correction. High cluster ion currents enable the formation of various nanostructures or even smooth surfaces over an area in cm²-range depending on ion species, energy, fluence and angle of incidence. The LMAIS characterization and the performance of the ion beam module for certain experiments will be presented and discussed.

[1] L. Bischoff: “Alloy liquid metal ion sources and their application in mass separated focused ion beams”, Ultramicroscopy 103 (2005), 59. DOI:10.1016/j.ultramic.2004.11.020
[2] M. Tajmar and B. Jang: “New materials and processes for field emission ion and electron emitters”, CEAS Space J. 4 (2013), 47. DOI: 10.1007/s12567-013-0031-z
[3] L. Bischoff, K.-H. Heinig, B. Schmidt, S. Facsko and W. Pilz: “Self-organization of Ge nanopattern under erosion with heavy Bi monomer and cluster ions”, Nucl. Instr. and Meth. B 272 (2012), 198. DOI: 10.1016/j.nimb.2011.01.064
[4] R. Boettger, L. Bischoff, K.-H. Heinig, W. Pilz, and B. Schmidt: “From sponge to dot arrays on (100) Ge by increasing the energy of ion impacts” J. Vac. Sci. Technol. B 30 (2012), 06FFF12. DOI: 10.1116/1.4767269
Keywords: Liquid Metal (Alloy) Ion Sources; polyatomic ions; nanostructures
  • Lecture (Conference)
    1st International Conference on Helium Ion Microscopy and Emerging Focused Ion Beam Technologies (HEFIB 2016), 08.-10.06.2016, Luxembourg City, Luxembourg

Permalink: https://www.hzdr.de/publications/Publ-23718
Publ.-Id: 23718


Focused Ion Beam Applications using Liquid Metal Alloy Ion Sources

Bischoff, L.; Mazarov, P.; Bruchhaus, L.; Gierak, J.
Presently Focused Ion Beam (FIB) processing is dominated by gallium Liquid Metal Ion Sources (LMIS). But, beside new developments in this field like He/Ne ion microscopes or Xe-FIBs many applications in the µm- or nm range could benefit from ion species other than gallium or noble gases: local ion implantation, ion beam mixing, ion beam synthesis or even Focused Ion Beam Lithography. Therefore Liquid Metal Alloy Ion Sources (LMAIS) represent a promising alternative to expand the remarkable application fields for FIB [1,2]. Simple switching between the certain ion species using an ExB mass filter can be applied to change significantly the physical and chemical nature of the resulting nanostructures -in other words the electrical, optical, magnetic and mechanic properties. This offers a large application potential which can be tuned by choosing a well suited LMAIS. Now nearly half of the elements of the Periodic Table are available in FIB technology. Main properties of a modern LMAIS are long life-time, high brightness and stable ion current. This contribution will cover the physical basics and experimental results of LMAIS, their physical properties (I-V characteristics, energy spread) and questions of the preparation technology using elementary as well as binary and ternary alloys as source material. Furthermore selected applications will be presented to underline the impact of these sources in modern nanotechnology by highly focused ion beams. Recent developments could make these sources feasible for nano patterning issues as an alternative technology more in research than in industry.

References
[1] L. Bischoff: “Application of mass-separated focused ion beams in nano-technology”, Nucl. Instr. Meth. B 266 (2008), 1846. DOI:10.1016/j.nimb.2007.12.008
[2] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak: „Liquid Metal Alloy Ion Sources - An Alternative for Focused Ion Beam Technology” , Appl. Phys. Rev. 3 (2016) 021101-1-30
[3] L. Bischoff and Ch. Akhmadaliev: “An alloy liquid metal ion source for lithium”, J. Phys. D: Appl. Phys. 41 (2008) 052001. DOI:10.1088/0022-3727/41/5/052001
Keywords: Focused Ion Beam; Liquid Metal Alloy Ion Sources ; Mass spectra
  • Lecture (Conference)
    1st International Conference on Helium Ion Microscopy and Emerging Focused Ion Beam Technologies (HEFIB 2016), 08.-10.06.2016, Luxembourg City, Luxembourg

Permalink: https://www.hzdr.de/publications/Publ-23717
Publ.-Id: 23717


Incorporation of Eu(III) into Calcite under Recrystallization conditions

Hellebrandt, S. E.; Hofmann, S.; Jordan, N.; Barkleit, A.; Schmidt, M.
The interaction of calcite with trivalent europium under recrystallization conditions was studied on the molecular level using site-selective time-resolved laser fluorescence spectroscopy (TRLFS). We conducted batch studies with a reaction time from seven days up to three years with three calcite powders, which differed in their specific surface area, recrystallization rates and impurities content. With increase of the recrystallization rate incorporation of Eu(III) occurs faster and the speciation comes to be dominated by one species with its excitation maximum at 578.8 nm, so far not identified during previous investigations of this process under growth and phase transformation conditions. A long lifetime of 3750 µs demonstrates complete loss of hydration, consequently Eu must have been incorporated into the bulk crystal. The results show a strong dependence of the incorporation kinetics on the recrystallization rate of the different calcites. Furthermore the investigation of the effect of different background electrolytes (NaCl and KCl) demonstrate that the incorporation process under recrystallization conditions strongly depends on the availability of Na(I). These findings emphasize the different retention potential of calcite as a primary and secondary mineral e.g. in a nuclear waste disposal site.
Keywords: Calcite, recrystallization, incorporation, Europium

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Permalink: https://www.hzdr.de/publications/Publ-23716
Publ.-Id: 23716


Combined use of flow cytometry and microscopy to study the interactions between the gram-negative betaproteobacterium Acidovorax facilis and uranium(VI)

Gerber, U.; Zirnstein, I.; Krawczyk-Bärsch, E.; Lünsdorf, H.; Arnold, T.; Merroun, M. L.
The former uranium mine Königstein (Saxony, Germany) is currently in the process of remediation by means of controlled underground flooding. Nevertheless, the flooding water has to be cleaned up by a conventional wastewater treatment plant. In this study, the uranium(VI) removal and tolerance mechanisms of the gram-negative betaproteobacterium Acidovorax facilis were investigated by a multidisciplinary approach combining wet chemistry, flow cytometry, and microscopy. The kinetics of uranium removal and the corresponding mechanisms were investigated. The results showed a biphasic process of uranium removal characterized by a first phase where 95 % of uranium was removed within the first 8 hours followed by a second phase that reached equilibrium after 24 hours. The bacterial cells displayed a total uranium removal capacity of 130 mg U/g dry biomass. The removal of uranium was also temperature-dependent, indicating that metabolic activity heavily influenced bacterial interactions with uranium. TEM analyses showed biosorption on the cell surface and intracellular accumulation of uranium. Uranium tolerance tests showed that A. facilis was able to withstand concentrations up to 0.1 mM. This work demonstrates that A. facilis is a suitable candidate for in situ bioremediation of flooding water in Königstein as well as for other contaminated waste waters.
Keywords: Acidovorax facilis, AMD, uranium, in situ bioremediation, flow cytometry, metal tolerance

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Permalink: https://www.hzdr.de/publications/Publ-23715
Publ.-Id: 23715


Fundamental investigation of the structure of neodymium-di-(2-ethylhexyl) phosphoric acid combinations using ESI and MALDI spectrometry and NMR spectroscopy

Scharf, C.
Neodymium-DEHPA-species forming in the organic phase during solvent extraction of neodymium with solutions of di-(2-ethylhexyl)phosphoric acid (DEHPA) have been studied. Two samples were prepared, one with a low molar ratio of neodymium to DEHPA which is liquid and clear, and the other with a high molar ratio of neodymium to DEHPA (complete loading) which has the consistency of a gel. Electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometric investigations show numerous compounds in addition to the generally assumed species dimeric DEHPA and Nd(DEHP·DEHPA)3, in the liquid sample. NMR spectroscopic investigation of pure DEHPA and of a completely loaded sample confirm the formula of pure DEHPA and of the organic part of Nd(DEHP)3. Furthermore, chemical analysis of a dried completely loaded sample also proves the existence of the species Nd(DEHP)3. Results of X-ray powder diffraction measurement of this sample agree well with literature data.
Keywords: solvent extraction of neodymium, di-(2-ethylhexyl)phosphoric acid, DEHPA, neodymium-DEHPA gel, neodymium-DEHPA species
  • Contribution to proceedings
    International Chemical Congress of Pacific Basin Societies, 15.-20.12.2015, Honolulu, USA
    Proceedings of the International Chemical Congress of Pacific Basin Societies

Permalink: https://www.hzdr.de/publications/Publ-23714
Publ.-Id: 23714


Ion Beam Injector based on High Current LMIS

Laufer, P.; Bock, D.; Pilz, W.; Bischoff, L.; Tajmar, M.
One of the major advantages of Liquid Metal Alloy Ion Sources (LMAIS) is the capability to emit a broad spectrum of ions from doubly and singly charged ions of nearly the half of the periodic table up to molecular ions or small clusters, consisting of a few atoms and different charge stages. These ion sources, characterized by a high brightness of about 106 A/cm2 sr, low energy spread of some eV and a very compact design are dedicated mostly for focused ion beam (FIB) applications [1] or field emission electric propulsion (FEEP) thrusters in space technology [2]. Normal ions in a wide spectrum of parameters can be provided also by other ion sources. The very special of LM(A)IS are the formation of heavy polyatomic ions from metallic or semiconducting elements, which is of great interest for self-organized surface patterning. So with Bismuth di- and trimer ions regular hexagonal dot structures were obtained after room temperature irradiation of Germanium at normal incidence using a FIB instrument induced by the enormous energy deposition by the heavy projectiles [3, 4]. To employ these heavy ions also for other ion beam systems and especially for larger areas an ion source injector module based on a high current LM(A)IS will be presented. Total emitted ion currents of more than 100 µA can be reached using different types of field emitter in particular porous needles from Tungsten and Rhenium or capillaries, 50 µm inner diameter of Tantalum. Source materials like Ga for tests, Gold (from Au82Si18 alloy), Lead or Bismuth (Bi or Ga38Bi62 alloy) were investigated.
In the injector a nearly parallel ion beam of about 2 mm diameter can be obtained by means of an asymmetric ion-optical Einzel lens. The cluster ion fraction for a certain ion species is in the range of per mil up to a few percent dependent on the emitted elements. A mass separation system (Wien filter) selects the desired ions while a quadrupole is used for beam adjustment and astigmatism correction. High cluster ion currents enable the formation of various nanostructures or even smooth surfaces over an area in cm²-range depending on ion species, energy, fluence and angle of incidence. The LM(A)IS preparation and the performance of the ion beam module at certain experiments will be presented and discussed.

[1] L. Bischoff, Ultramicroscopy 103, 59 (2005).
[2] M. Tajmar and B. Jang, CEAS Space J. 4, 47 (2013).
[3] L. Bischoff, et al., Nucl. Instr. and Meth. B 272,198 (2012).
[4] R. Boettger et al. J. Vac. Sci. Technol. B 30, 06FFF12 (2012).
Keywords: Liquid Metal Alloy Ion Source; Ion Beam Injector; Cluster Ions
  • Lecture (Conference)
    60th International Conference on Electron, Ion, and Photon Beam Technology and Nanofabrication (EIPBN), 31.05.-06.06.2016, Pittsburgh, USA

Permalink: https://www.hzdr.de/publications/Publ-23713
Publ.-Id: 23713


Investigation of thermal spin transfer torque in MgO-based magnetic tunnel junctions using FMR microresonators

Cansever, H.; Kowalska, E.; Fowley, C.; Aleksandrov, Y.; Yildirim, O.; Narkowicz, R.; Lenz, K.; Lindner, J.; Fassbender, J.ORC; Deac, A.
MgO-based magnetic tunnel junctions are commonly used in spintronic device applications, such as recent spin transfer torque random access memory (STT-RAM) because of their non-volatility, fast switching and high storage capacity. Spin transfer torque is defined as a spin polarized current flowing through a ferromagnet exerting a torque on the local magnetization. With thermal spin transfer torque (T-STT), thermally excited electron transport is used instead of spin polarized charge current and provides an interesting way of using thermoelectric effects in magnetic storage applications. Our study focuses on fundamental experimental research aimed at demonstrating that thermal gradients can generate spin-transfer torques in MgO-based magnetic tunnel junctions (MTJs). We use microresonators in order to analyze how the ferromagnetic resonance signal corresponding to the free layer of an in-plane MgO-based tunnel junction device is modified in the presence of a temperature gradient across the barrier.
This work is supported by DFG-SPP1538
  • Poster
    DPG-Frühjahrstagung, 06.-11.03.2016, Regensburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-23712
Publ.-Id: 23712


Ultra-doped n-type germanium thin films for sensing in the mid-infrared

Prucnal, S.; Liu, F.; Voelskow, M.; Vines, L.; Rebohle, L.; Lang, D.; Berencén, Y.; Andric, S.; Boettger, R.; Helm, M.; Zhou, S.; Skorupa, W.
A key milestone for the next generation of high-performance multifunctional microelectronic devices is the monolithic integration of high-mobility materials with Si technology. The use of Ge instead of Si as a basic material in nanoelectronics would need homogeneous p- and n-type doping with high carrier densities. Here we use ion implantation followed by rear side flash-lamp annealing (r-FLA) for the fabrication of heavily doped n-type Ge with high mobility. This approach, in contrast to conventional annealing procedures, leads to the full recrystallization of Ge films and high P activation. In this way single crystalline Ge thin films free of defects with maximum attained carrier concentrations of 2.20±0.11E20 cm-3 and carrier mobilities above 260 cm2/(V·s) were obtained. The obtained ultra-doped Ge films display a room-temperature plasma frequency above 1,850 cm-1, which enables to exploit the plasmonic properties of Ge for sensing in the mid-infrared spectral range.
Keywords: Ge, ion implantation, flash lamp annealing, plasmonics

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Permalink: https://www.hzdr.de/publications/Publ-23711
Publ.-Id: 23711


In-situ, steerable, hardware-independent and data-structure agnostic visualization with ISAAC

Matthes, A.; Widera, R.; Hübl, A.; Zenker, E.; Eckert, C.; Gumhold, S.; Grottel, S.; Bussmann, M.
We showcase the C++ template library ISAAC [1,2] for in-situ visualization of simulations or other high rate data sources running distributed on modern HPC systems. As most in-situ visualization solutions suffer from the problem that the simulation data needs to be converted to visualization specific data structures, ISAAC implements a data structure agnostic raycasting algorithm using C++ templates and C++ meta programming. With this ISAAC is not only able to visualize nearly arbitrary simulation data without the need of deep copying or converting it beforehand, but is also capable to use the very same computation device as the simulation itself.

Using the same computation device as the simulation usually limits the scope of usable hardware as modern many-core devices require programming models optimized for the specific hardware, e.g. CUDA for NVIDIA devices, to achieve optimum performance. In order to circumvent this problem ISAAC is based on the abstract kernel interface library Alpaka [3,4], which defines a redundant parallel hierarchy model for many-core architectures that serves as a front end to underlying models such as CUDA, OpenMP or Thread Building Blocks. With this, the ISAAC software renderer can run in-situ on almost every platform currently available.

Not all simulation data is perfectly suited for direct visualization but sometimes requires transformation. ISAAC thus introduces so called Functor Chains, which are very simple precompiled, but at runtime selectable, functions used for local domain transformations of the original simulation data performed before the data is streamed to the raycasting algorithm.

ISAAC is capable of scaling up to Petascale systems using the IceT library. It is not intended for highly specialized visualization but instead renders the classical representation as glowing gas or as iso surfaces. Aside from the obligatory transfer functions for the classification ISAAC also supports an arbitrary amount of random clipping planes useful for a deeper look into the simulated volumes.

ISAAC includes an interface for simulations to send arbitrary live meta data with the live preview and to receive live steering data. The whole communication layer of ISAAC is intentionally based only on open and widely used standards such as Websockets, RTP Streams and especially the open-standard format JSON.

ISAAC provides a server running on the head or login node of the HPC system, which creates the video streams from the visualization and forwards them together with the meta data to a freely selectable number of clients. The video stream created by the server can be received from arbitrary clients such as VLC or even streaming platforms like Twitch. Furthermore, each client can steer the simulations. ISAAC itself introduces a platform-independent HTML5 client, which can be adjusted to the needs of specific simulations easily.

Since every part of ISAAC is open source and makes use of the openly documented JSON communication protocol, it is easily possible to implement new clients or to extend the visualization core itself for simulation-specific features. ISAAC is designed to be as language-, framework-, data-format- and platform-agnostic as possible.

In order to demonstrate the real time capabilities of ISAA we will showcase a live visualization of the GPU-accelerated plasma simulation PIConGPU [5,6]. We show that we can achieve more than ten frames per seconds using 64 GPUs on the Hypnos cluster at Helmholtz-Zentrum Dresden – Rossendorf running both the simulation and visualization simultaneously.

[1] A. Matthes, In-situ Visualisierung und Streaming von Plasmasimulationsdaten, Technical University Dresden (2016)
[2] https://github.com/ComputationalRadiationPhysics/isaac
[3] E. Zenker et al., Alpaka - An Abstraction Library for Parallel Kernel Acceleration, http://arxiv.org/abs/1602.08477 (2016)
[4] https://github.com/ComputationalRadiationPhysics/alpaka
[5] M. Bussmann et al., Radiative Signatures of the Relativistic Kelvin-Helmholtz Instability, Proceedings of the International Conference on High Performance Computing, Networking, Storage and Analysis, SC'15, 5, 1 (2013)
[6] https://github.com/ComputationalRadiationPhysics/picongpu
Keywords: in-situ visualization, simulation steering, in-memory visualization, live visualization, heterogeneous architectures, high performance computing
  • Lecture (Conference)
    ISC Workshop On In-situ Visualization 2016, 23.06.2016, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-23710
Publ.-Id: 23710


Radiation Dose Measurements for high-intensity laser interactions with solid targets at SLAC

Liang, T.; Bauer, J.; Cimeno, M.; Ferrari, A.; Galtier, E.; Granados, E.; Lee, H. J.; Liu, J.; Nagler, B.; Prinz, A.; Rokni, S.; Woods, H. T. M.
A systematic study of photon and neutron radiation doses generated in high-intensity laser–solid interactions is underway at SLAC National Accelerator Laboratory. These laser–solid experiments are being performed using a 25 TW (up to 1 J in 40 fs) femtosecond pulsed Ti:sapphire laser at the Linac Coherent Light Source’s (LCLS) Matter in Extreme Conditions (MEC) facility. Radiation measurements were performed with passive and active detectors deployed at various locations inside and outside the target chamber. Results from radiation dose measurements for laser–solid experiments at SLAC MEC in 2014 with peak intensity between 10^18 and 7.1 10^19 W cm-2 are presented.
Keywords: radiation measurements, laser-induced ionizing radiation

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Permalink: https://www.hzdr.de/publications/Publ-23707
Publ.-Id: 23707


Ionizing Radiation Measurements from Interaction of MEC Laser (0.7 J, 10^19 W/cm2) with Cu and Ni Targets

Liang, T.; Bauer, J.; Blaha, J.; Cimeno, M.; Ferrari, A.; Liu, J.; Rokni, S.; Woods, M.
Laser system upgrades at SLAC Matter in Extreme Conditions (MEC) have increased the potential dose levels generated from laser-matter interactions at LCLS Hutch 6. In July 2014, the 800 nm Ti:sapphire MEC laser operated at 0.7 J with an intensity of 1.0 10^18 W/cm2, and shots were taken on Cu foils and a Ni nanowire target. In August 2014, MEC scientists utilized a deformable mirror improve the laser spot size to achieve an intensity of 1.0 10^19 W/cm2 with 0.7 J, and laser shots were again taken on Cu foil and Ni nanowire. During both experiments, passive (nanoDot, RADOS, 2 mR PIC) and active (Victoreen 451, BF3) detectors were deployed inside and outside the target chamber to measure ionizing radiation from laser shots on Cu and Ni targets, and measurements from active and passive detectors agree. No local cone shielding was in place at MEC during radiation measurements.
Keywords: laser induced ionizing radiation
  • Other report
    SLAC National Accelerator Laboratory, USA: SLAC RADIATION PHYSICS NOTE RP-14-23, 2014
    23 Seiten

Permalink: https://www.hzdr.de/publications/Publ-23706
Publ.-Id: 23706


Shielding and activation studies for MYRRHA in critical and sub-critical mode

Ferrari, A.; Mueller, S.; Konheiser, J.
This work has been performed in the framework of the FP7 European project MAXSIMA (“Methodology, Analysis and eXperiments for the Safety In MYRRHA Assessment”), which has the goal to support the design of the accelerator-driven system MYRRHA (“Multi-purpose hYbrid Research Reactor for High-Tech Applications”) at SCK-CEN in Mol (Belgium), in view of the licensing of the facility.
The aim of the MAXSIMA Work Package 2 is to provide solid safety analyses for the Belgian safety authorities in view of the licensing process.
The main goal of the Task 2.1 is to support these analyses on one side by providing the needed neutronic parameters as input (see Deliverable D2.1), and on the other side by performing shielding and activation studies using the up-to-date MYRRHA core models.
These studies are the object of the present Deliverable, D2.2.
Keywords: Shielding, accelerator driven systems, MYRRHA, spallation sources
  • Other report
    Report for EU Commission: Deliverable D2.2 of the MAXSIMA EU Project, 2015
    496 Seiten

Permalink: https://www.hzdr.de/publications/Publ-23705
Publ.-Id: 23705


An activation database for materials used at high-intensity laser acceleration facilities

Ferrari, A.; Fasso, A.; Olsovcova, V.; Versaci, R.
The ELI-Beamlines facility, which is expected to start operation in 2017, will be the high-energy, high repetition-rate laser pillar of the Extreme Light Infrastructure (ELI). The goal of the project is to deliver ultra-short, high-energy laser pulses for generation and applications of high-brightness X-ray sources and accelerated particles. Particle beams are expected to operate in an unprecedented energy range for laser-driven accelerators, going from 1 GeV up to 50 GeV for electrons and from 100 MeV up to 3 GeV for protons. The number of particles per laser shot is estimated to be 10^9-10^10 for electron beams and 10^10-10^12 for proton beams. The high energy and the large current per shot of the produced beams, together with the potentiality to operate at 10 Hz laser repetition rate, require an adequate evaluation of activation in structural materials in order to assess several radiation protection problems, such as minimization of residual dose rates close to and inside the experimental chambers and management of active materials (short and long-term storage and eventual decommissioning).
A large database covering all the energies and materials of interest is being developed using FLUKA, a Monte Carlo code successfully benchmarked for the production of radioactive nuclides. Results for electrons and protons at intermediate energies are presented. These results, although focused on the needs of laser-driven accelerators, are likely to be useful also when designing more conventional facilities.
Keywords: activation, laser induced ionizing radiation
  • Lecture (Conference)
    ARIA 2015 - Workshop on Accelerator Radiation Induced Activation, 15.-17.04.2015, Knoxville, Tennessee, United States

Permalink: https://www.hzdr.de/publications/Publ-23704
Publ.-Id: 23704


Activation calculations for the MYRRHA accelerator-driven system design

Ferrari, A.; Castelliti, D.; Konheiser, J.; Mueller, S.; Sarotto, M.; Stankovskiy, A.
The MYRRHA facility at SCK-CEN in Mol (Belgium), which is at present in an advanced phase of the design, aims to demonstrate efficient transmutation of high level waste and associated Accelerator-Driven System (ADS) technology. The system is based on a lead-bismuth eutectic (LBE) cooled reactor, working both in critical and in sub-critical operation modes. Neutrons needed to sustain fission in the sub-critical mode are produced via spallation processes by a 600 MeV, < 4 mA proton beam, which is provided by a linear accelerator and hits a LBE spallation target located inside the reactor core. The use of a high energy/high current proton beam, coupled with a nuclear reactor operating in subcritical mode, presents many challenges for various aspects of the design, being minimization of the induced activation a key point. In order to assess the main activation and shielding problems, a method based on the combined use of the two Monte Carlo codes MCNPX and FLUKA has been developed, with the goal to perform detailed analyses of both the radiation fields due to the system in operation, and the coupled residual radiation due to the activated materials. Activation has been then evaluated for typical irradiation patterns and key structural materials, from the spallation target to the structure above the core, the reactor cover and critical points along the proton beamline.
The results of this simulation work are presented, with some implications on the design solutions.
Keywords: Activation, shielding, accelerator driven systems, spallation sources
  • Lecture (Conference)
    ARIA 2015 - Workshop on Accelerator Radiation Induced Activation, 15.-17.04.2015, Knoxville, Tennessee, United States

Permalink: https://www.hzdr.de/publications/Publ-23703
Publ.-Id: 23703


Source term determination for shielding assessment of high-power laser-plasma experiments

Ferrari, A.; Cowan, T.; Pelka, A.; Nakatsutsumi, M.; Tschentscher, T.; Rokni, S.; Liu, J.; Bauer, J.; Liang, T.; Fasso’, A.; Margarone, D.; Versaci, R.
In an increasing number of experiments, high-power, high-intensity lasers hit targets and create plasma. The laser-plasma interaction will produce hot electrons with a Maxwellian energy spectrum and an electron temperature ranging from about 10 keV to 10 MeV for irradiance between 10^16 and 10^21 W/cm2. The electrons interact in turn with the target, producing bremsstrahlung and possibly photoneutrons, resulting in a radiation field that must be contained by shielding. Since the physics of plasmas is very different from that of the common phases of matter, the shielding design cannot be carried out with only conventional tools.
Different, complementary approaches are possible: to use analytical formulas, to experimentally evaluate source terms to be used as input to established Monte Carlo codes, or to interface those codes with specialized Particle-In-Cell programs, which describe the generation and transport of particles in plasma.
At the Helmholtz-Beamline, which will operate as laser facility at the European XFEL, the shielding design of the High Energy Density (HED) Physics Instrument has been evaluated by using analytical calculations, cross-checked with measurements at the DRACO laser at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). On the other hand an extensive experimental campaign is planned at SLAC, where dedicated radiation measurements will be performed at the Matter in Extreme Conditions (MEC) short-pulse laser facility.
  • Poster
    SATIF-12 Shielding aspects of Accelerators, Targets and Irradiation Facilities, 28.-30.04.2014, Fermilab, Batavia, Illinois, United States

Permalink: https://www.hzdr.de/publications/Publ-23702
Publ.-Id: 23702


Radiation field calculations around the spallation target and the reactor core for the MYRRHA ADS design

Ferrari, A.; Castelliti, D.; Fernandez, R.; Konheiser, J.; Mueller, S.; Sarotto, M.; Stankovskiy, A.
The MYRRHA facility at SCK·CEN in Mol (Belgium), which should enter the construction phase in 2015, aims to demonstrate efficient transmutation of high level waste and associated Accelerator-Driven Systems (ADS) technology. The system is based on a lead-bismuth eutectic (LBE) cooled reactor, working both in critical and in sub-critical operation modes. The neutrons needed to sustain fission in the sub-critical mode are produced via spallation processes by a 600 MeV,  4 mA proton beam, which is provided by a linear accelerator and hits a LBE spallation target located inside the reactor core. In order to assess the main shielding problems, a method based on the combined use of the two Monte Carlo codes MCNPX and FLUKA has been developed, with the goal to perform detailed analyses of both the radiation fields due to the system in operation, and the coupled residual radiation due to the activated materials. The results of this simulation work are presented, with the implications on the design solutions.
Keywords: Accelerator driven systems, spallation targets, shielding
  • Poster
    SATIF-12 Shielding aspects of Accelerators, Targets and Irradiation Facilities, 28.-30.04.2014, Fermilab, Batavia, Illinois, United States

Permalink: https://www.hzdr.de/publications/Publ-23701
Publ.-Id: 23701


Shielding and activation studies for the ELI-Beamlines project

Fasso, A.; Ferrari, A.; Korn, G.; Versaci, R.
ELI-beamlines is one of the four pillars of the Extreme Light Infrastructure, a European ESFRI Project, for the next generation of high-energy and high-intensity lasers. It aims at the development of high-brightness sources of X-rays and the acceleration of proton, electron, and ion beams, to be used both for pure research and practical applications.
Aiming at a proper radiation protection assessment, for both shielding and activation, extensive FLUKA simulations have been performed, taking into account the laser high repetition rates. The present work, which is the continuation of the calculations presented at SATIF-10, is the first one based on the design of the facility being constructed and on the updated experimental set-up.
Keywords: Shielding, Monte Carlo calculations, FLUKA
  • Open Access Logo Contribution to proceedings
    SATIF-12 Shielding aspects of Accelerators, Targets and Irradiation Facilities, 28.-30.04.2014, Fermilab, Batavia, Illinois, United States
    Workshop Proceedings: OECD, Nuclear Science NEA/NSC/R(2015)3, 105-111

Permalink: https://www.hzdr.de/publications/Publ-23700
Publ.-Id: 23700


Measurements of high-intensity laser induced ionising radiation at SLAC

Liang, T.; Bauer, J.; Cimeno, M.; Ferrari, A.; Galtier, E.; Granados, E.; Liu, J.; Nagler, B.; Prinz, A.; Rokni, S.; Tran, H.; Woods, M.
A systematic study of measurements of photon and neutron radiation doses generated in high-intensity laser-target interactions is underway at SLAC National Accelerator Laboratory using a femtosecond pulsed Ti:sapphire laser (800 nm, 40 fs, up to 1 J and 25 TW) at the Linac Coherent Light Source’s (LCLS) Matter in Extreme Conditions (MEC) facility. Preliminary results from recent measurements with the laser-optic-target system (peak intensity 1.8x1018 W/cm2) are presented and compared with results from calculations based on analytical models and FLUKA Monte Carlo simulations.
Keywords: Laser induced ionising radiation, source terms measurements, shielding
  • Open Access Logo Contribution to proceedings
    SATIF-12 Shielding aspects of Accelerators, Targets and Irradiation Facilities, 28.-30.04.2014, Fermilab, Batavia, Illinois, United States
    Workshop Proceedings: OECD, Nuclear Science NEA/NSC/R(2015)3, 40-53

Permalink: https://www.hzdr.de/publications/Publ-23699
Publ.-Id: 23699


Data-driven model for evaluation of cerebrovascular-reserve measurement with hypercapnia BOLD

Vondráčková, L.; Krukowski, P.; Gerber, J.; Linn, J.; Kybic, J.; Petr, J.
Hypercapnia BOLD with the breath-holding task is a technically easier and more clinically available alternative to cerebrovascular reserve (CVR) mapping than administration of CO enriched air using an air-tight mask. The disadvantage is complicated data evaluation in case the subject does not adhere to the breathing protocol completely. Here, a data-driven approach for evaluation is presented that is more robust to protocol deviations and produces a reasonable CVR map in most cases where the standard model-driven approach fails. This is demonstrated on randomized evaluation of CVR maps of a group of 86 subjects with stenosis or vessel occlusion.
  • Contribution to proceedings
    24th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine, 07.05.2016, Singapore, Singapore
    Proceedings of the 24th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine
  • Poster
    24th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine, 07.05.2016, Singapore, Singapore

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Permalink: https://www.hzdr.de/publications/Publ-23698
Publ.-Id: 23698


Deformation and resolution issues in partial volume correction of 2D arterial spin labeling data

Petr, J.; Mutsaerts, H. J.; de Vita, E.; Maus, J.; van den Hoff, J.; Asllani, I.
Partial volume (PV) effects are a well-recognized confounder in arterial spin labeling due to its limited spatial resolution. Several algorithms exist to correct for these errors. Nevertheless, PVcorrection is rarely used, mainly because the PV maps obtained from segmented T1-weighted images are regarded as not being suficiently reliable when transformed into ASL space. Here, we show the impact of spatial deformation and resolution in the PV-maps used for PV-correction in the calculation of mean total gray matter (GM) cerebral blood flow (CBF). We also show how the deformations affect the calculation of PV-uncorrected mean GM CBF.
  • Contribution to proceedings
    24th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine, 07.05.2016, Singapore, Singapore
    Proceedings of the 24th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine
  • Poster
    24th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine, 07.05.2016, Singapore, Singapore

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Permalink: https://www.hzdr.de/publications/Publ-23697
Publ.-Id: 23697


Addressing multi-centre image registration of 3T arterial spin labeling images from the GENetic Frontotemporal dementia Initiative (GENFI)

Mutsaerts, H.; Thomas, D.; Petr, J.; de Vita, E.; Cash, D.; van Osch, M.; Groot, P.; van Swieten, J.; Laforce Jr, R.; Tagliavini, F.; Borroni, B.; Galimberti, D.; Rowe, J.; Graff, C.; Frisoni, G.; Finger, E.; Sorbi, S.; Mendonça, A.; Rossor, M.; Rohrer, J.; Masellis, M.; Macintosh, B.
One obstacle in multi-centre arterial spin labeling (ASL) studies is the variability attributed to differences between vendor- or site-specific ASL implementations. This multi-centre study compares spatial registration methods from ASL to 3D-T1, to reduce the between-subject variability of cerebral blood flow (CBF) maps. Our results demonstrate that choices of image registration have profound effects on ASL data collected using different pulse sequences and/or sites. A rigid-body registration of CBF images to segmented gray matter images produced the most robust similarity outcome as a standard approach across the different ASL implementations.
  • Contribution to proceedings
    24th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine, 07.05.2016, Singapore, Singapore
    Proceedings of the 24th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine
  • Poster
    24th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine, 07.05.2016, Singapore, Singapore

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Permalink: https://www.hzdr.de/publications/Publ-23696
Publ.-Id: 23696


Perfusion decrease in healthy tissue following radiochemotherapy in glioblastoma patients

Petr, J.; Platzek, I.; Seidlitz, A.; Hofheinz, F.; Maus, J.; Beuthien-Baumann, B.; Krause, M.; van den Hoff, J.
Ziel/Aim:
Decrease of perfusion as a side-effect of radio-chemotherapy was observed in several organs (1). However, the relation between the decrease and the radiation dose was not yet extensively studied. Non-invasive measurement of perfusion is now possible with a native MRI sequence called arterial spin labeling (ASL) (2) which offers a semi-quantitative alternative to [O-15]H2O PET measurement. The ASL measurement was used to study the regional perfusion changes in healthy tissue of glioblastoma patients undergoing radiochemotherapy.
Methodik/Methods:
Twenty-five patients (age 55.0±14.2 years) with glioblastoma multiforme were scanned in two (n=25) or three (n=13) sessions with interval 4.8 and 8.1 months from the first session, respectively. The ASL scan was co-registered with the treatment-planning CT and the dose plan. Perfusion changes between sessions were calculated in the hemisphere contralateral to the tumor. The perfusion changes were evaluated also in regions created by categorizing the individual dose maps into 10 Gy steps.
Ergebnisse/Results:
The relative perfusion decrease between the first two sessions was not significant (-2.4% and -7.5%) for the low dose regions 0 and 20 Gy. For the high-dose regions, the change was statistically significant and a decrease of -13.3% (20-30 Gy), -18.0% (30-40 Gy), -16.2% (40-50 Gy), and -16.8% (50-60 Gy) was observed. No further decrease of perfusion was observed on the third session. The mean regional changes were between -1.4% and 3.0% and the results were not statistically significant for any dose.
Schlussfolgerungen/Conclusions:
Global decrease of perfusion was observed in healthy tissue 3 months after the radiochemotherapy. The decrease was correlated with the dose received. No further decrease of perfusion was observed 6 months after the therapy.
  • Contribution to proceedings
    54. Jahrestagung der DGN, 20.04.2016, Dresden, Germany
    Proceedings der 54. Jahrestagung der DGN
  • Poster
    54. Jahrestagung der DGN, 20.04.2016, Dresden, Germany

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Permalink: https://www.hzdr.de/publications/Publ-23695
Publ.-Id: 23695


Bestimmung der zerebrovaskulären Reserve mit BOLDMRT unter Atemanhalten bei Patienten mit Stenosen der hirnversorgenden Gefäße

Krukowski, P.; Petr, J.; Puetz, V.; Abramyuk, A.; Linn, J.; Gerber, J.
Die Autoregulation der zerebralen Perfusion ist wichtiger Mechanismus der Homöostase. Hyperkapnie führt im gesunden Gefäßbett zur Dilatation präkapillärer Gefäße und zur Aktivierung der zerebralen Perfusionsreserve (CVR). BOLD (Blood Oxygen Level Dependent)-MRT unter Atemanhalten stellt die Veränderungen dar. Bei Patienten mit Stenosen hirnversorgender Arterien akquirierten wir prospektiv ein BOLD-MRT unter Atemanhalten, evaluierten die Machbarkeit und korrelierten die Zielstenose mit den BOLD-Veränderungen. Wir werteten das BOLD-MRT modell-basiert (Block-Design gefaltet mit der hämodynamischen Antwortfunktion) aus. Die maximale Kreuzkorrelation des Modells mit der durchschnittlichen Signalantwort des Patienten ergab die individuelle Antwort-Verzögerung des BOLD-Signals zum Stimulus Atemanhalten. Least-square fittings des modellierten Signalverlaufs mit den gemessenen Daten ergaben statistische Parameterkarten, die mit einer T1-gewichteten MRT registriert wurden. Wir werteten keine oder negative BOLDAntworten als pathologisch. Wir beurteilten die Parameterkarten im 3-Leser-Konsensus.
Bei 48 von 58 Patienten (82,8 %) waren die Parameterkarten beurteilbar. 36 Patienten hatten eine symptomatische, 12 hatten eine asymptomatische Stenose. 28 Patienten (58 %) hatten Veränderungen der CVR im Stromgebiet der Zielstenose (bei 21 symptomatischen und 7 asymptomatischen). Die Häufigkeit von BOLD-Veränderungen war bei Patienten mit symptomatischen und asymptomatischen Stenosen gleich (58,3 %).
In der Mehrzahl der Patienten sind BOLD-CVR-Veränderungen im Stromgebiet der stenosierten Arterie nachweisbar. Die Lesbarkeit sollte durch alternative Auswerte-Algorithmen verbessert werden.
  • Contribution to proceedings
    50. Jahrestagung der Deutschen Gesellschaft für Neuroradiologie, 15.10.2015, Gürzenich, Köln, Deutschland
    Clinical Neuroradiology: Springer
    DOI: 10.1007/s00062-015-0445-4
  • Poster
    50. Jahrestagung der Deutschen Gesellschaft für Neuroradiologie, 15.10.2015, Gürzenich, Köln, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-23694
Publ.-Id: 23694


Development of Laser-Driven Proton Beam Therapy

Karsch, L.; Beyreuther, E.; Enghardt, W.; Gotz, M.; Hermannsdörfer, T.; Krause, M.; Masood, U.; Pawelke, J.; Sauerbrey, R.; Schramm, U.; Schürer, M.; Baumann, M.
no abstract available

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Permalink: https://www.hzdr.de/publications/Publ-23692
Publ.-Id: 23692


Design and implementation of a robust and cost-effective double-scattering system at a horizontal proton beamline

Helmbrecht, S.; Baumann, M.; Fiedler, F.; Enghardt, W.; Krause, M.; Lühr, A.
Purpose:
With an increasing number of proton therapy facilities coming into operation, also the interest for research at proton beams increases. Though many centers provide beam at an experimental room, some of these rooms do not feature a device for radiation field shaping, a so called nozzle.
Therefore, a robust, mobile, and cost-effective double-scattering system for horizontal proton beamlines has been designed and implemented.

Materials and methods:
The nozzle is based on the double scattering technique. Two lead scatterers, an aluminum ridge-filter and two brass collimators were optimized in a simulation study to form a laterally homogeneous 10 cm x 10 cm field with a spread-out Bragg-peak (SOBP).
The parts were mainly manufactured using 3D printing techniques and the system was set up at the experimental beamline of the University Proton Therapy Dresden (UPTD).
Measurements of the radiation field were carried out using a water phantom.

Results:
High levels of dose homogeneity were found in lateral (dose variation ΔD < ±2%) as well as in beam direction (ΔD < ±3% in the SOBP). The system has already been used for radiobiology and physical experiments.

Conclusion:
The presented setup allows for creating clinically realistic extended radiation fields at fixed horizontal proton beamlines and is ready to use for internal and external users.
The excellent performance combined with the simplistic design let it appear as a valuable option for proton therapy centers intending to foster their experimental portfolio.
Keywords: radiation field formation; radiobiology; ion beam therapy; proton therapy; cancer

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Permalink: https://www.hzdr.de/publications/Publ-23691
Publ.-Id: 23691


Reducing in-core zinc borate precipitation after LOCA in pressurized water reactors

Kryk, H.; Harm, U.; Hampel, U.
During the sump recirculation phase after loss-of-coolant accidents (LOCAs) in pressurized water reactors (PWRs), coolant spilling from the leak in the primary cooling circuit is collected in the reactor sump and recirculated to the reactor core by residual-heat removal pumps as part of the emergency core cooling system (ECCS).
Lab-scale studies within previous research projects have shown that the long-term contact of the boric acid containing coolant with hot-dip galvanized steel containment internals may cause corrosion of the corresponding materials influencing the cooling water chemistry due to dissolution of the zinc coat. Generic experimental investigations regarding the solubility of Zn corrosion products in boric acid solutions resulted in a decreasing solubility with increasing temperature. Thus, precipitation of solid corrosion products (zinc borates) cannot be ruled out if zinc containing coolant is heated up due to its recirculation into hot zones.
Consequently, generic corrosion experiments were carried out in a lab-scale corrosion test facility aiming at the development and test of water-chemical measures to prevent zinc corrosion and zinc borate precipitation in boric acid containing coolants.
The experimental results showed a decreasing corrosion rate with increasing pH value of the coolant. Thus, the risk of zinc borate precipitation can be reduced by addition of alkalizing media to the coolant after a LOCA. However, by adding of a moderate amount of alkalizing media to enhance the coolant pH into the neutral region, the zinc borate precipitation rate can be reduced only to about one third but not fully prevented. Extensive suppression of zinc corrosion and zinc borate precipitation is only achievable from a coolant pH of 7.5 resulting in a lithium concentration of 125 ppm if LiOH is used as alkalizing additive. Furthermore, foaming of the coolant cannot be ruled out if the coolant pH is increased into the slightly alkaline region.
Keywords: pressurized water reactor, loss-of-coolant accidents, corrosion, zinc, zinc borate, downstream effects
  • Lecture (Conference)
    47th Annual Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Germany
  • Contribution to proceedings
    47th Annual Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Germany
    Proceedings 47th Annual Meeting on Nuclear Technology, Berlin: INFORUM Verlags- und Verwaltungsgesellschaft mbH, 978-3-926956-97-2

Permalink: https://www.hzdr.de/publications/Publ-23690
Publ.-Id: 23690


Bit-Vectorized GPU Implementation of a Stochastic Cellular Automaton Model for Surface Growth

Kelling, J.; Ódor, G.; Gemming, S.
Stochastic surface growth models aid in studying properties of universality classes like the Kardar--Parisi--Zhang class. High precision results obtained from large scale computational studies can be transferred to many physical systems. Many properties, such as roughening and some two-time functions can be studied using stochastic cellular automaton (SCA) variants of stochastic models. Here we present a highly efficient SCA implementation of a surface growth model capable of simulating billions of lattice sites on a single GPU. We also provide insight into cases requiring arbitrary random probabilities which are not accessible through bit-vectorization.
Keywords: Surface Growth, Kardar-Parisi-Zhang, GPU, Monte-Carlo, Stochastic Cellular Automaton
  • Contribution to proceedings
    20th Jubilee IEEE International Conference on Intelligent Engineering Systems 2016, 30.06.-02.07.2016, Budapest, Ungarn
    Proceedings of the 20th Jubilee IEEE International Conference on Intelligent Engineering Systems 2016: IEEE
    DOI: 10.1109/INES.2016.7555127
  • Lecture (Conference)
    20th Jubilee IEEE International Conference on Intelligent Engineering Systems 2016: IEEE, 30.06.-02.07.2016, Budapest, Ungarn
  • Contribution to WWW
    https://arxiv.org/abs/1606.00310

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Permalink: https://www.hzdr.de/publications/Publ-23689
Publ.-Id: 23689


The Sorption Processes of U(VI) onto SiO2 in the Presence of Phosphate: from Binary Surface Species to Precipitation

Comarmond, M. J.; Steudtner, R.; Stockmann, M.; Heim, K.; Müller, K.; Brendler, V.; Payne, T. E.; Foerstendorf, H.
The ternary system containing aqueous U(VI), aqueous phosphate and solid SiO2 was comprehensively investigated using a batch sorption technique, in situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy, time-resolved laser-induced fluorescence spectroscopy (TRLFS), and Surface Complexation Modeling (SCM). The batch sorption studies on silica gel (10 g/L) in the pH range 2.5 to 5 showed no significant increase in U(VI) uptake in the presence of phosphate at equimolar concentration of 20 µM, but significant increase in U(VI) uptake was observed for higher phosphate concentrations. In situ infrared and luminescence spectroscopic studies evidence the formation of two binary U(VI) surface species in the absence of phosphate, whereas after prolonged sorption in the presence of phosphate, the formation of a surface precipitate, most likely an autunite-like phase, is strongly suggested. From SCM, excellent fitting results were obtained exclusively considering two binary uranyl surface species and the formation of a solid uranyl phosphate phase. The results of this study indicate that the sorption of U(VI) on SiO2 in the presence of inorganic phosphate initially involves binary surface-sorption species and evolves towards surface precipitation.

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Permalink: https://www.hzdr.de/publications/Publ-23688
Publ.-Id: 23688


Coordination polymers of tetravalent neptunium with aromatic polycarboxylate ligands

Martin, N.; März, J.; Henry, N.; Volkringer, C.; Ikeda-Ohno, A.; Hennig, C.; Loiseau, T.
Coordination polymers are organic-inorganic complexes built up from the association of metallic centers with O- or N-donor ligands. In the particular case of actinides, previous literatures mainly have reported the synthesis of solid networks bearing U(VI) or Th(IV). Trans-uranium elements have been much less studied due to their high radiotoxicity and limited amount of the material source. Among the possible oxidation states of actinides (An), the tetravalent state has been investigated most actively and large polynuclear oxo-clusters have been isolated for U1,2 or Pu3. In contrast, there is very few data concerning Np(IV) compounds. In 2012, Takao et al.4 reported the presence of a hexanuclear cluster of Np(IV) in an aqueous solution, which is the only polyoxo cluster reported for Np(IV) thus far. The knowledge of the formation of such polynuclear An(IV) species could be of significant importance for the fate of An in contaminated soils containing O-donor ligands, such as humic acids or organic pollutants (e.g. phthalates). In the present work, we studied the crystallization of Np(IV) with various aromatic polycarboxylate ligands in different solvents and analyzed their crystal structures. In water, an infinite chain of Np2O2(H2O)2(1,2-bdc)2 were isolated in the presence of phthalate. This compound crystallizes as aggregates of orange plates, whereas the analogue compound with uranium is obtained as green crystals. With mellitic acid the oxidation of Np(IV) to Np(V) was observed and led to large green plates. Single-crystal XRD analysis revealed layers of {NpO7H2O0-2} units linked to each other via trans-dioxo neptunyl bonds. Similar coordination environments have been observed in the other neptunium(V) compounds5.
The use of other solvents allowed the crystallization of large polynuclear discrete Np(IV) clusters. For example, using DMF, the hexanuclear unit of [Np6O4(OH)4] has been obtained with different dicarboxylic ligands and is the basic building unit to form an open-framework structure. The corresponding structures revealed for the first time the isolation of the hexanuclear cluster An6O8 with Np(IV). These clusters are linked by the ligand creating tetrahedral and octahedral voids in the structure.
Keywords: actinides, neptunium, carboxylates, metal-organic complex, metal-organic framework, polymers, structure characterisation
  • Lecture (Conference)
    Plutonium Futures 2016, 18.-22.09.2016, Baden-Baden, Germany

Permalink: https://www.hzdr.de/publications/Publ-23687
Publ.-Id: 23687


Tunable Picosecond Laser Pulses via the Contrast of Two Reverse Saturable Absorption Phases in a Waveguide Platform

Tan, Y.; Chen, L.; Wang, D.; Chen, Y.; Akhmadaliev, S.; Zhou, S.; Hong, M.; Chen, F.
How to enhance the optical nonlinearity of saturable absorption materials is an important question to improve the functionality of various applications ranging from the high power laser to photonic computational devices. We demonstrate the saturable absorption (SA) of VO2 film attributed to the large difference of optical nonlinearities between the two states of the phase-transition materials (VO2). Such VO2 film demonstrated significantly improved performance with saturation intensity higher than other existing ultrathin saturable absorbers by 3 orders due to its unique nonlinear optical mechanisms in the ultrafast phase change process. Owing to this feature, a Q-switched pulsed laser was fabricated in a waveguide platform, which is the first time to achieve picosecond pulse duration and maintain high peak power. Furthermore, the emission of this VO2 waveguide laser can be flexibly switched between the continuous-wave (CW) and pulsed operation regimes by tuning the temperature of the VO2 film, which enables VO2-based miniature laser devices with unique and versatile functions.

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Permalink: https://www.hzdr.de/publications/Publ-23686
Publ.-Id: 23686


Zwitterionic polymer-coated ultrasmall superparamagnetic iron oxide nanoparticles with low protein interaction and high biocompatibility

Pombo-García, K.; Weiss, S.; Zarschler, K.; Ang, C.-S.; Hübner, R.; Pufe, J.; Meister, S.; Seidel, J.; Pietzsch, J.; Spiccia, L.; Stephan, H.ORC; Graham, B.
We report the synthesis and detailed in vitro evaluation of zwitterionic ultrasmall superparamagnetic iron oxide NPs (USPIONs) comprised of oleic acid/oleyl alcohol-stabilized magnetite particles (5 nm core diameter) coated with an amphiphilic zwitterionic polymer, poly(maleic anhydride-alt-1-decene) substituted with 3-(dimethylamino)propylamine (PMAL). These particles display a near-neutral zeta potential at pH ≥ 7 and possess high colloidal stability, maintaining a hydrodynamic diameter of ca. 15–20 nm over a wide range of pHs (4–10) and ionic strength (up to 1 M NaCl). They exhibit very low levels of nonspecific protein binding upon exposure to serum, and negligible uptake by phagocytic and non-phagocytic hepatocarcinoma cells, which suggests that they may be able to resist rapid accumulation in the liver and spleen, a common in vivo fate for NPs. The PMAL-USPIONs exhibit very low cytotoxicity and do not elicit an inflammatory response or display hemolytic activity in vitro. Minimal nonspecific uptake by either cancerous or non-cancerous cell lines was observed, an important precondition to achieve highly selective targeting upon further functionalization with an active targeting agent (e.g., antibody or peptide). Overall, this study establishes the considerable potential of PMALUSPIONs as a platform for the future development of “stealth” NP-based imaging and/or therapeutic agents.
Keywords: Iron oxide nanoparticles, zwitterionic coatings, protein corona, macrophages, proteomics.

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Permalink: https://www.hzdr.de/publications/Publ-23685
Publ.-Id: 23685


Highlights on metallic photocathodes used in SRF gun

Xiang, R.; Arnold, A.; Michel, P.; Murcek, P.; Teichert, J.; Lu, P.; Vennekate, H.
For the accelerator-based light sources and the electron colliders, the development of photoinjectors has become a key technology. Especially for the superconducting radio frequency cavity based injector (SRF Gun), the searching for better photocathodes is always a principal technical challenge. To use metallic photocathodes for ELBE SRF Gun is the primary choice to prevent cavity contamination. In this contribution, we will report the investigation of Magnesium (Mg) in ELBE SRF gun, including laser cleaning treatment and the measurement on quantum efficiency, Schottky effect, dark current and damage threshold.
Keywords: SRF gun, photocathode, metallic cathode, magnesium
  • Poster
    the Seventh International Particle Accelerator Conference (IPAC’16), 08.-13.05.2016, Busan, Korea
  • Open Access Logo Contribution to proceedings
    the Seventh International Particle Accelerator Conference (IPAC’16), 08.-13.05.2016, Busan, Korea

Permalink: https://www.hzdr.de/publications/Publ-23684
Publ.-Id: 23684


Wire-mesh Sensors: Recent Developments and Applications

Schleicher, E.; Tschofen, M.; Kipping, R.; Hampel, U.
Wire-mesh sensors (WMS) are today well established measurement tools to obtain both temporally and spatially highly resolved structural information as well as averaged phase fraction and phase fraction distribution data in air-water and steam-water two-phase flow experiments. Those data, with a spatial resolution of down to 0.5 mm and frame rates up to 10,000 frames per second are suitable to validate CFD code developments. During the last decade, the technology has widely spread in research laboratories all over the world and has been more and more developed towards a turnkey machine for researchers. In this work we summarize the most recent developments in hardware for high temperature and high pressure applications, new electronics with integrated void fraction calculations and flow pattern identification for industrial applications and latest software developments for data analysis and visualization.

A big issue for the application of wire-mesh sensor technology to high pressure high temperature facilities is the complicated pressure-proven and temperature-resistant insulated support and feedthrough of the measuring electrodes. Our new development facilitates a compact metallic body with flanges on both sides with a slot in sensor unit consisting of ceramic insulators and a stainless steel frame. The feedthrough of the wires is realized by commercially available multiple feedthrough fittings.

The most common and proved codes for WMS data analysis have been capsulated in our wire-mesh sensor data processing FrameWork. The tool has got a new, user friendly graphical interface and allows the implementation of new algorithms by the end user. The resulting data and profiles can be visualized within the software and a batch processing tool allows automated “over the weekend” jobs.

The wire-mesh sensor technology so far is a scientific tool for researchers. The huge amount of data, several gigabytes for one measurement of a couple of seconds, has to be stored and processed offline later on. For industrial applications, the users need online data on liquid/gas holdups and flow pattern in the pipelines. An industrial type of wire-mesh sensor electronics has been developed based on an FPGA (field programmable gate array) microcontroller calculating the frame averaged void fraction instantaneously and moreover identifying the flow pattern based on statistical values of the last 10 seconds from the two-phase flow using Fuzzy clustering algorithm.
Keywords: Industrial Process Tomography, Two-Phase Flow Measurement, Wire-Mesh Sensor
  • Contribution to proceedings
    SWINTH-2016, Specialist Workshop on Advanced Instrumentation and Measurement Techniques for Nuclear Reactor Thermal Hydraulics, 15.-17.06.2016, Livorno, Italy
    Proceedings of SWINTH-2016
  • Lecture (Conference)
    SWINTH-2016, Specialists Workshop on Advanced Instrumentation and Measurement Techniques for Nuclear Reactor Thermal Hydraulics, 15.-17.06.2016, Livorno, Italia

Permalink: https://www.hzdr.de/publications/Publ-23683
Publ.-Id: 23683


X-ray radioscopy as a powerful tool for visualization of liquid metal bubbly flows

Roshchupkina, O.; Shevchenko, N.; Strumpf, E.; Hoppe, D.; Eckert, S.
Many technical applications in metallurgy and the quality of continuous casting rely on liquid metal two-phase flows. Injection of the Argon gas became an integral part of continuous casting since it prevents clogging of the casting nozzle and also separates alumina particles from the melt. On the other hand, injection of gas has many side effects as for example induction of highly turbulent complex two-phase flows. There exist many numerical simulations and water models, but due to large differences in physical properties between water and liquid metals water models and experiments cannot be fully extended to liquid metals. Therefore, direct investigation and understanding of liquid metal two-phase flows became critical. In the present work we demonstrate that X-ray radiography can be used as a powerful tool for the visualization of liquid metal two-phase flows. Here we present an experimental study of ascending bubble chains over a wide range of gas flow rates in GaInSn alloy at room temperature. We report on differences in bubble release frequency, shape, size, velocity etc. and additionally compare with experiments in water. The efficiency of the corresponding measurement technique is primarily validated in water experiments.

* The research is supported by the German Helmholtz Association in form of the Helmholtz-Alliance “LIMTECH”.
Keywords: X-ray radiography, two-phase flows, GaInSn, water
  • Lecture (Conference)
    9th International Conference on Multiphase Flow, 22.-27.05.2016, Firenze, Italy

Permalink: https://www.hzdr.de/publications/Publ-23682
Publ.-Id: 23682


Topologically stable magnetization states on a spherical shell: curvature stabilized skyrmion

Kravchuk, V. P.; Rößler, U. K.; Volkov, O. M.; Sheka, D. D.; van den Brink, J.; Makarov, D.; Fangohr, H.; Gaididei, Y.
Topologically stable structures, e.g. vortices in a wide variety of matter, skyrmions in ferro- and antiferromagnets, hedgehog point defects in liquid crystals and ferromagnets, are characterized by integer valued topological quantum numbers. In this context the closed surfaces are a prominent subject of study, because they realize a link between fundamental mathematical theorems and real physical systems. Here we perform a topological analysis of equilibrium magnetization states for a thin spherical shell with easy-normal anisotropy. Skyrmion solutions are found for a range of parameters. These magnetic skyrmions on a spherical shell have two principal differences compared to the planar case: (i) they become topologically trivial, and (ii) can be stabilized by curvature effects only, also when Dzyaloshinskii-Moriya interactions are absent. Due to its specific topological nature a skyrmion on a spherical shell can be simply induced by an uniform external magnetic field.
Keywords: Dzyaloshinskii-Moriya interaction, skyrmion, curvature induced effects

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Permalink: https://www.hzdr.de/publications/Publ-23681
Publ.-Id: 23681


Purely Antiferromagnetic Magnetoelectric Random Access Memory

Kosub, T.; Kopte, M.; Hühne, R.; Appel, P.; Shields, B.; Maletinsky, P.; Hübner, R.; Liedke, M. O.; Fassbender, J.ORC; Schmidt, O. G.; Makarov, D.
Magnetic random access memory schemes employing magnetoelectric coupling to write binary information promise outstanding energy-efficiency. We propose and realize purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) that offers a remarkable 50 times lower writing threshold compared to ferromagnet-based counterparts, is robust against magnetic disturbances and exhibits no ferromagnetic hysteresis losses. Using the magnetoelectric antiferromagnet Cr2O3, we realize reliable isothermal switching via gate voltage pulses and all-electric read-back at room temperature. As no ferromagnetic component is present in the system, the writing magnetic field does not need to be pulsed and removed for read-out allowing permanent magnets to be used. Based on our prototypes of these novel systems, we construct a comprehensive model of the magnetoelectric selection mechanism in thin films of magnetoelectric antiferromagnets. We identify that growth induced effects lead to emergent ferrimagnetism, which interferes with the linear magnetoelectric effect. After pinpointing lattice misfit as the likely origin, we provide routes to enhance or mitigate this emergent ferrimagnetism as desired. AF-MERAM cells are a general concept for antiferromagnetic spintronics and not limited to memory applications.
Keywords: Magnetoelectric Random Access Memory, Antiferromagnets, anomalous Hall magnetometry, zero-Offset Hall

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Permalink: https://www.hzdr.de/publications/Publ-23680
Publ.-Id: 23680


Synthesis, Morphological, and Electro-optical Characterizations of Metal/Semiconductor Nanowire Heterostructures

Glaser, M.; Kitzler, A.; Johannes, A.; Prucnal, S.; Potts, H.; Conesa-Boj, S.; Filipovic, L.; Kosina, H.; Skorupa, W.; Bertagnolli, E.; Ronning, C.; Fontcuberta I. Morral, A.; Lugstein, A.
In this letter, we demonstrate the formation of unique Ga/GaAs/Si nanowire heterostructures, which were successfully implemented in nanoscale light-emitting devices with visible room temperature electroluminescence. Based on our recent approach for the integration of InAs/Si heterostructures into Si nanowires by ion implantation and flash lamp annealing, we developed a routine that has proven to be suitable for the monolithic integration of GaAs nanocrystallite segments into the core of silicon nanowires. The formation of a Ga segment adjacent to longer GaAs nanocrystallites resulted in Schottky-diode-like I/V characteristics with distinct electroluminescence originating from the GaAs nanocrystallite for the nanowire device operated in the reverse breakdown regime.
The observed electroluminescence was ascribed to radiative band-to-band recombinations resulting in distinct emission peaks and a low contribution due to intraband transition, which were also observed under forward bias. Simulations of the obtained nanowire heterostructure confirmed the proposed impact ionization process responsible for hot carrier luminescence. This approach may enable a new route for on-chip photonic devices used for light emission or detection purposes.
Keywords: Nanowires, flash lamp annealing, ion implantation, GaAs, Si, liquid phase epitaxy

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Permalink: https://www.hzdr.de/publications/Publ-23679
Publ.-Id: 23679


The effect of millisecond flash lamp annealing on electrical and structural properties of ZnO:Al/Si structures

Lindberg, P. F.; Lipp Bregolin, F.; Wiesenhütter, K.; Wiesenhütter, U.; Riise, H. N.; Vines, L.; Prucnal, S.; Skorupa, W.; Svensson, B. G.; Monakhov, E. V.
The effect of millisecond flash lamp annealing (FLA) on aluminum doped ZnO (AZO) films and their interface with Si have been studied. The AZO films were deposited by magnetron sputtering on Si (100) substrates. The electrical and structural properties of the film and AZO/Si structures were characterized by current–voltage, capacitance–voltage, and deep level transient spectroscopy measurements, X-ray diffraction, and secondary ion mass spectrometry. The resistivity of the AZO film is reduced to a close to state-of-the-art value of 2x10-4Ohmcm after FLA for 3ms with an average energy density of 29 J/cm2. In addition, most of the interfacial defects energy levels are simultaneously annealed out, except for one persisting shallow level, tentatively assigned to the vacancy-oxygen complex in Si, which was not affected by FLA. Subsequent to the FLA, the samples were treated in N2 or forming gas (FG) (N2/H2, 90/10%mole) ambient at 200–500 C. The latter samples maintained the low resistivity achieved after the FLA, but not the former ones. The interfacial defect level persisting after the FLA is removed by the FG treatment, concurrently as another level emerges at ~0.18 eV below the conduction band. The electrical data of the AZO films are discussed in term of point defects controlling the resistivity, and it is argued that the FLA promotes formation of electrically neutral clusters of Zink vacancies (VZn’s) rather than passivating/compensating complexes between the Al donors and VZn’s.
Keywords: AZO, flash lamp annealing, magnetron sputtering, doping

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Permalink: https://www.hzdr.de/publications/Publ-23678
Publ.-Id: 23678


Narrow-band tunable terahertz emission from ferrimagnetic Mn3-xGa thin films

Awari, N.; Kovalev, S.; Fowley, C.; Rode, K.; Gallardo, R. A.; Lau, Y.-C.; Betto, D.; Thiyagarajah, N.; Green, B.; Yildrim, O.; Lindner, J.; Fassbender, J.ORC; Coey, J. M. D.; Deac, A. M.; Gensch, M.
Narrow-band terahertz emission from coherently excited spin precession in metallic Mn3-xGa Heusler alloy nanofilms has been observed. The efficiency of the emission, per nanometer film thickness, is comparable or higher than that of classical laser-driven terahertz sources based on optical rectification. The center frequency of the emission from the films can be tuned precisely via the film composition making this type of metallic films a candidate for efficient on-chip terahertz emitters. Terahertz emission spectroscopy is potentially a sensitive probe of magnetic properties of ultra-thin films.
Keywords: THz emission, ferrimagnets, spin excitations

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Permalink: https://www.hzdr.de/publications/Publ-23677
Publ.-Id: 23677


NeptuniumV retention by siderite under anoxic conditions: Precipitation of NpO2–like nanoparticles and of NpIV pentacarbonate

Scheinost, A. C.; Steudtner, R.; Hübner, R.; Weiss, S.; Bok, F.
The NpV retention by siderite, an FeII carbonate mineral with relevance for the near-field of high-level radioactive waste repositories, was investigated under anoxic conditions. Batch sorption experiments show that siderite has a high affinity for aqueous NpVO2+ across pH 7 to 13 as expressed by solid-water distribution coefficients, log Rd, >5, similar to the log Rd determined for the (solely) tetravalent actinide Th on calcite, suggesting reduction of NpV to NpIV by siderite. Np L3-edge X-ray absorption near edge (XANES) spectroscopy conducted in a pH range typical for siderite-containing host rocks (7 - 8), confirmed the tetravalent Np oxidation state. Extended X-ray absorption fine-structure (EXAFS) spectroscopy revealed a local structure in line with NpO2–like nanoparticles with diameter < 1 nm, a result further corroborated by high-resolution transmission electron microscopy (HRTEM). The low solubility of these NpO2–like nanoparticles (10-9 M), along with their negligible surface charge at neutral pH conditions which favors particle aggregation, suggest an efficient retention of Np in the near-field of radioactive waste repositories. When NpV was added to ferrous carbonate solution, the subsequent precipitation of siderite did not lead to a structural incorporation of NpIV by siderite, but caused precipitation of a NpIV pentacarbonate phase.
Keywords: neptunium siderite carbonate radioactive waste respository XAFS XANES

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Publ.-Id: 23676


Speciation of tetravalent uranium with inorganic ligands in aqueous solution investigated by UV/vis and time-resolved laser-fluorescence measurements.

Lehmann, S.; Steudtner, R.; Brendler, V.
This work is focused on uranium as the major component of spent nuclear fuel. For safety assessment of a future repository it is important to predict the environmental behavior of uranium in diluted to highly saline aquifer systems. Currently most reports are related to the hexavalent oxidation state which is stable under oxidizing conditions. However, reducing conditions are expected in the near field of high level nuclear waste repository after sealing the repository. Therefore, the major purpose of this study is to improve the knowledge of the physico-chemical properties of the tetravalent uranium and to provide thermodynamic data to enable a better prediction of speciation and solubility limits under reducing conditions.
The aim of this study is to examine the potential of U(IV) fluorescence for speciation studies. Kirishima et al. described in 2004 for the first time the luminescence spectra of the free U(IV) ion [1, 2]. Since then, only a few studies on U(IV) fluorescence properties have been published [3, 4]. However, spectroscopic data of U(IV) are necessary to provide a basic understanding of the U(IV) speciation under environmental conditions. We used in our study a combination of UV/vis spectroscopy with long path flow cell and time-resolved laser-induced fluorescence spectroscopy (TRLFS).
First, a U(IV) stock solution was produced by reduction in an electrochemical cell and was monitored by UV/vis spectroscopy. The residual content of U(VI) was determined by TRLFS to be lower than 1%. After that, we studied the aqueous speciation in presence of various inorganic ligands (ClO4–, Cl–, SO42–, PO43–, CO32–). To perform TRLFS measurements of U(IV) a laser system employing a Nd/YAG driven OPO system as excitation source with λexc = 245 nm were installed including a cryogenic unit for measurements at liquid nitrogen temperature (77 K). We detected the luminescence of the free U(IV) ion in acidic aqueous solution at room temperature (rt) and in frozen state at 77 K. At rt we observe the typical fluorescence properties of U(IV) with the peak maxima at 321, 410 and 523 nm and a fluorescence decay time of 2.6 ± 0.3 ns in perchloric and chloric acid. The detection limit of 10–5 M at rt was determined. By using cryo-TRLFS at 77 K the detection limit was lowered to 5x10–6 M and the fluorescence lifetime increases up to 148.4 ± 6.5 ns. The spectroscopic results are in good agreement with earlier reports for rt [3] and cryo measurements [2]. In contrast to U(VI), which is often quenched by chloride, a well resolved luminescence spectrum of U(IV) was obtained in 0.1 as well as in 1 M HCl.
The potential of U(IV) fluorescence for speciation analysis was assessed in this study. With our setup we could study aqueous U(IV) systems with concentrations lower than 10–5 M and this corresponds to uranium concentrations occurring in the environment [5, 6].

References
[1] A. Kirishima, Chem. Commun., 2003, (7), 910-911.
[2] A. Kirishima, Radiochim. Acta, 2004, 92, 705-710.
[3] S. Lehmann, J. Radioanal. Nucl. Chem., 2010 283(2), 395-401.
[4] N. Aoyagi, N., J. Radioanal. Nucl. Chem., 2015, 303(2), 1095-1098.
[5] T. Arnold, Geochim. Cosmochim. Acta, 2011, 75(8), 2200-221.
[6] G. Bernhard, J. Alloys Compd., 1998, 271, 201-205.
Keywords: tetravalent uranium, aqueous solution, fluorescence, speciation
  • Lecture (Conference)
    Ninth International Conference on Nuclear and Radiochemistry - NRC9, 29.08.-02.09.2016, Helsinki, Finnland

Permalink: https://www.hzdr.de/publications/Publ-23675
Publ.-Id: 23675


Redox Stability of Uranium in High Ionic Strength Media: An Electrochemical and Spectroscopic Study

Lehmann, S.; Bok, F.; Ikeda-Ohno, A.; Muñoz, A. G.
Knowledge of redox behavior of uranium in concentrated solutions of the hexary oceanic salt system is essential for the transport modeling of radioactive nuclides in repositories for the long-term disposal of radioactive wastes in rock salt formations. Especially critical is the behavior of the couple U(IV)/U(VI) in the surrounding high ionic strength saline milieu, which regulates the release of mobile U(VI) species at given redox conditions defined by the presence of trace oxygen. The redox potential (Eredox) and the solubility in brines in particular implicate the activity of the different ligand- and hydroxo-complexes (ai): Eredox = f(mi, ai, βj), where βj is the complexation constant. Thus, the prediction of transport behavior of uranium at given chemical environments needs appropriate complexation and thermodynamic models assuming the ionic activities beyond the limited Debye-Hückel theory. This latter is supplied by the Pitzer formulation [1], where deviations from the limit Debye-Hückel behavior are given by specific interaction parameters among the constituting ionic species, which have to be determined experimentally.
The kinetics of the electrochemical reduction and oxidation reactions was studied in a three-electrodes type cell using a Au working electrode, Pt wire counter electrode and a Ag/AgCl in3 M KCl reference electrode. Experiments were performed under an oxygen-free atmosphere in a glove-box. Cyclic voltammetry (CV) and normal pulse voltammetry (NPV) were applied to investigate the influence of chloride concentrations in the kinetics parameters, such as reaction rate, k, and the diffusion coefficient in solutions containing U(VI) or U(IV) in HCl solutions from 0.1 to 1.3 M. The solution speciation of uranium was investigated by UV/vis absorption spectroscopy.
Reference: [1] K.S. Pitzer in Activity coefficients in electrolyte solutions, Ch.3, CRC Press, Boca Raton, Florida, 1991.
Keywords: uranium, saline solutions, electrochemistry, redox behaviour, Pitzer
  • Lecture (Conference)
    PRIME 2016 - Pacific rim meeting on electrochemical and solid-state science, 02.-07.10.2016, Honolulu, Hawaii, USA

Permalink: https://www.hzdr.de/publications/Publ-23674
Publ.-Id: 23674


Self-Assembled Magnetite Mesocrystalline Films: Towards Structural Evolution from 2D to 3D Superlattices

Brunner, J.; Baburin, I. A.; Sturm, S.; Kvashnina, K.; Rossberg, A.; Pietsch, T.; Andreev, S.; Sturm, E.; Cölfen, H.
This study describes synthesis and detailed characterization of 2D and 3D mesocrystalline films produced by self-assembly of iron oxide (magnetite) truncated nanocubes. The orientational relations between nanocrystals within the superlattice are examined and atomistic models for a detailed description of the structures of the 2D and 3D mesocrystals are introduced. The most efficient space filling within the 3D superstructure is achieved by changing the orientational order of the nanoparticles and following the “bump-tohollow” packing principle. These data provide a fundamental understanding of a mesocrystal formation mechanism and their structural evolution. Structure, composition and magnetic properties of the synthesised nanoparticles are also characterized.
Keywords: magnetite, nanoparticle, self-assembly, mesocrystal, particle films

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Permalink: https://www.hzdr.de/publications/Publ-23673
Publ.-Id: 23673


Complexation studies of modified calix[4]arenes with uranium in non-aqueous solution

Bauer, A.; Schmeide, K.; März, J.; Jäschke, A.; Glasneck, F.; Kersting, B.
The actinide uranium, well known from nuclear power cycle, plays also a role in rare earth production. The rare earth ores contain, apart from various other components, the actinides uranium and thorium occur as undesired constituents. To facilitate the production of rare earth elements, uranium and thorium have to be removed. Due to their modifiable selectivity and solubility calix[n]arenes are interesting compounds for the extraction of actinides and lanthanides. The chalice-like macrocyclic molecules consist of para-substituted phenolic units. The para-substitution determines the solubility of the molecule and the hydroxyl groups serve either directly as complexation site or can be further functionalized to adjust the selectivity of the calix[n]arene.
Several calix[4]arenes with affinity towards actinides or lanthanides are available. These are to be applied to eliminate uranium (IV)/(VI) and thorium from ore concentrates and subsequently, to separate lanthanides. The separation method based on liquid-liquid extraction utilizing the calix[4]arenes. Thereby metal calix[4]arene complexes are formed in the organic phase. For better process understanding we investigated the mechanisms of uranium interaction with the synthesized calix[4]arenes by UV-Vis spectroscopy, TRLFS, isothermal titration calorimetry, single crystal XRD and extraction experiments. The calix[4]arene modified with 8-hydroxychinolin derivatives called L1 is one of the new calix[4]arenes. It achieves a U(VI) extraction yield between 90 to 100 % in the pH range of 4 to 9. It possesses two potential binding sites for U(VI). Stoichiometry determination by the Job´s Plot from UV-Vis data indicates a ligand to metal ratio of 1:2 (Fig. 1). The calix[4]arene-L1 complex absorbs at 280 nm. During spectrophotometric titration of L1 with U(VI) in acetonitrile the absorption maximum decreases and new peaks at 318, 360 and 525 nm occur. Luminescence signals of L1 and uranyl nitrate in acetonitrile are weakened by complex formation. First microcalorimetric measurements confirm the binding of two metal ions by L1. All measurements in solution were carried out at 25°C. In addition to the UV-Vis spectroscopy and isothermal titration calorimetry, the capillary electrophoresis is to be used for determining stability constants.
Whereas in solution a stoichiometry of 1:2 is obviously preferred, the single crystal XRD analysis reveals a formation of a 1:1 U(VI)-L1 complex (Fig. 2). Thereby the hexavalent uranyl ion is coordinated by the singly deprotonated ligand via a N2O2 donor set. The charge is compensated by an additional coordinated nitrate ion. To complete the structure information of the formed U(VI)-L1 complex in solution mass spectrometric and NMR measurements as well as theoretical studies are currently performed. In addition, for better understanding the complexation properties of L1 the interaction with U(IV) and Th(IV) is studied.
Keywords: SE-FLECX, calix[4]arene, uranium, solvent extraction, complexation studies, rare earth production
  • Poster
    The 9th Conference on Nuclear and Radiochemistry – NRC9, 29.08.-02.09.2016, Helsinki, Finnland

Permalink: https://www.hzdr.de/publications/Publ-23671
Publ.-Id: 23671


Removal of Nickel Impurities from Recycled Mg-Al Alloys by Precipitation of Intermetallic Compounds

Duwe, S.; Scharf, C.; Ditze, A.
The primary production of pure magnesium and its alloys is highly energy intensive and expensive.
Thus, their recycling is necessary considering energy saving and metal content. Magnesium postconsumer scrap often is contaminated with copper, nickel and iron resulting from aluminium alloy adherences, nickel platings and steel. Especially nickel is detrimental to the corrosion properties of magnesium alloys. To produce secondary magnesium alloys nickel impurities have to be removed to obtain appropriate corrosion resistance. In this case no traditional metallurgical refining process is applicable because nickel is nobler than magnesium. It has been found that the refining can be done by a combined addition of aluminium and zirconium to remove nickel by formation of high melting intermetallic compounds and hence their precipitation. The aim of the investigation is to determine and verify the amounts of zirconium and aluminium which are necessary to reach the low nickel content of 10 ppm (high purity quality). However, the mutual solubilities of nickel and zirconium in aluminium containing magnesium alloys are unknown. Therefore, the solubility isotherms of this system at 720 °C were experimentally investigated by adding nickel to magnesium melts with different aluminium contents (5 and 8 mass.-%). Subsequently aluminium and zirconium have been added to remove the nickel. At the near equilibrium state samples have been taken from the melt and analysed for the components. Furthermore, the formed intermetallic aluminium-nickelzirconium compounds have to be determined for identification by chemical analysis and EDX. Besides the solubility isotherms for the system are calculated using a thermodynamic model.
Keywords: Magnesium scrap, recycling, nickel removal, intermetallic compound
  • Open Access Logo Contribution to proceedings
    EMC 2013 - European Metallurgical Conference, 23.-26.06.2013, Weimar, Deutschland: GDMB Verlag GmbH, 978-3-940276-50-6, 597-604

Permalink: https://www.hzdr.de/publications/Publ-23670
Publ.-Id: 23670


Structural modification of Ga+ and N+ ion implanted ta-C films

Berova, M.; Sandulov, M.; Tsvetkova, T.; Karashanova, D.; Boettger, R.; Bischoff, L.
Thin-film samples (d ~ 40 nm) of tetrahedral amorphous carbon (ta-C) deposited by filtered cathodic vacuum arc (FCVA) were implanted with Ga+ at ion energy E = 20 keV and ion fluences D = 3×10^14÷3×10^15 cm-2 and N+ with the same energy and a dose D = 3×1014 cm-2. The Ga+ ion beam induced a structural modification of the implanted material. This resulted in a considerable change of its structural properties, manifested as the formation of a new phase under non-equilibrium conditions, which could be accompanied by considerable changes in the ta-C films optical properties. The N+ implantation also resulted in a modification of the surface structure. These effects were explored using transmission (TEM) and scanning (SEM) electron microscopy.
Keywords: ta-C, ion implantation

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Publ.-Id: 23669


Atomic transport during solid-phase epitaxial recrystallization of amorphous germanium

Radek, M.; Bracht, H.; Johnson, B. C.; Mccallum, J. C.; Posselt, M.; Liedke, B.
We report experimental studies on atomic mixing of matrix atoms during solid-phase epitaxy (SPE). For this purpose isotopically enriched germanium (Ge) multilayer structures were amorphized by Ge ion implantation up to a depth of 1.5 um. Recrystallization of the amorphous structure was performed at temperatures between 350°C and 450°C. By means of secondary-ion-mass-spectrometry (SIMS) the concentration-depth profiles of the Ge isotope before and after the SPE process were determined. Analyses of the experimental depth profiles reveal an upper limit of 0.5 nm for the displacement length of the Ge matrix atoms induced by the SPE process. This small displacement length confirms theoretical models and atomistic simulations of SPE, indicating that the SPE mechanism consists of bond-switching with nearest-neighbours at the amorphous-crystalline (a/c) interface.
Keywords: Solid-phase epitaxial recrystallization, germanium, atom transport
  • Lecture (Conference)
    E-MRS Spring Meeting, Symposium K: Group IV semiconductors materials research - growth, characterization and applications to electronics and spintronics, 02.-06.05.2016, Lille, France

Permalink: https://www.hzdr.de/publications/Publ-23668
Publ.-Id: 23668


Investigation of ion-beam mixing in silicon at temperatures below 500°C and the role of mobile extended defects

Radek, M.; Bracht, H.; Posselt, M.; Liedke, B.
Implantation of germanium (Ge), gallium (Ga), or arsenic (As) ions into crystalline and preamorphized isotopically enriched silicon (Si) multilayer structures at temperatures between 20°C and 500°C was performed to study the mechanisms contributing to atomic mixing. Secondary-ion-mass-spectrometry (SIMS) was applied to determine the concentration-depth profiles of the Si isotopes after ion implantation. In contrast to Ge multilayer structures [1] a radiation enhanced self-diffusion (RESD), as well as a dopant dependence of RESD is observed in Si. The contribution of cascade mixing (thermal spike mixing) to the overall atomic mixing is estimated by means of molecular dynamics simulations leaving the contribution due to RESD. Continuum theoretical calculations reveals that the magnitude of RESD can not be described by the diffusion of isolated native defects in supersaturation. Instead RESD is successfully modelled assuming highly mobile di-interstials that form during annealing of the implantation damage.
[1] M. Radek et al.: Temperature dependence of ion-beam induced atomic mixing in germanium isotope structures, Appl. Phys. Lett. 115, 023506 (2015)
Keywords: Ion-beam mixing, silicon isotope multilayers
  • Lecture (Conference)
    E-MRS Spring Meeting, Symposium K: Group IV semiconductors materials research - growth, characterization and applications to electronics and spintronics, 02.-06.05.2016, Lille, France

Permalink: https://www.hzdr.de/publications/Publ-23667
Publ.-Id: 23667


Self-diffusion in amorphous silicon: An experimental and theoretical study

Kirschbaum, J.; Teuber, T.; Radek, M.; Bracht, H.; Posselt, M.; Bougeard, D.
Amorphous silicon (a-Si) is a widely used material, especially for solar cells and thin-film-transistors. Measuring the self-diffusion coefficient of a-Si is experimentally demanding since recrystallization during diffusion annealing must be suppressed. We used Si on insulator (SOI) structures to stabilize the amorphous state during annealing. Isotopically enriched Si multilayers with a thickness per layer of about 10 nm were grown by means of molecular beam epitaxy on top of SOI wafers. Subsequently the whole top crystalline Si layer was amorphized by means of Si ion implantation. Before and after annealing the distribution of the Si isotopes within the isotope structure was measured with SIMS. The observed broadening suggests a significantly higher self-diffusion in the amorphous compared to the crystalline state. Molecular dynamics simulations are employed to gain information about the mechanism of self-diffusion. We used an adjusted Stillinger-Weber potential, as the original Stillinger-Weber parametrization for Si overestimates the mobility of the matrix atoms. The parameters were chosen to simulate the experimentally observed diffusion in a-Si. The coordination numbers and radial-distribution-function were analyzed to confirm the assumption of bond switching as the dominant mechanism of self-diffusion.
Keywords: amorphous silicon, diffusion
  • Poster
    E-MRS Spring Meeting, Symposium K: Group IV semiconductors materials research - growth, characterization and applications to electronics and spintronics, 02.-06.05.2016, Lille, France

Permalink: https://www.hzdr.de/publications/Publ-23666
Publ.-Id: 23666


Fractional Quantum Hall States in a Ge Quantum Well

Mironov, O. A.; D'Ambrumenil, N.; Dobbie, A.; Leadley, D. R.; Suslov, A. V.; Green, E.
Measurements of the Hall and dissipative conductivity of a strained Ge quantum well on a SiGe/(001)Si substrate in the quantum Hall regime are reported. We analyze the results in terms of thermally activated quantum tunneling of carriers from one internal edge state to another across saddle points in the long-range impurity potential. This shows that the gaps for different filling fractions closely follow the dependence predicted by theory. We also find that the estimates of the separation of the edge states at the saddle are in line with the expectations of an electrostatic model in the lowest spin-polarized Landau level (LL), but not in the spin-reversed LL where the density of quasiparticle states is not high enough to accommodate the carriers required.

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Publ.-Id: 23665


From Describing to Prescribing Parallelism: Translating the SPEC ACCEL OpenACC Suite to OpenMP Target Directives

Juckeland, G.; Hernandez, O.; Jacob, A. C.; Neilson, D.; Vergara Larrea, V. G.; Wienke, S.; Chandrasekaran, S.; Grund, A.; Henschel, R.; Müller, M. S.; Perminov, M.; Shelepugin, P.; Whitney, B.; Joubert, W.; Wang, B.; Kumaran, K.; SPEC High Performance Group (HPG), Email: info@spec.org – Website: http://www.spec.org/hpg; Bobyr, A.
Current and next generation HPC systems will exploit accelerators and self-hosting devices within their compute nodes to accelerate applications. This comes at a time when programmer productivity and the ability to produce portable code has been recognized as a major concern. One of the goals of OpenMP and OpenACC is to allow the user to specify parallelism via directives so that compilers can generate device specific code and optimizations. However, the challenge of porting codes becomes more complex because of the different types of parallelism and memory hierarchies available on different architectures.
In this paper we discuss our experience with porting the SPEC ACCEL benchmarks from OpenACC to OpenMP 4.5 using a performance portable style that lets the compiler make platform-specific decisions to achieve performance. The SPEC ACCEL OpenMP benchmarks were tested on different platforms including Xeon Phi, GPUs and CPU cores. We also discuss some performance-portable best practices that help expose more parallelism in the codes in a portable style. We believe that this expe rience can help the community and compiler vendors understand how users plan to write OpenMP 4.5 applications in a performance portable
style.
Keywords: SPEC, SPEC ACCEL, OpenMP, OpenACC, Offloading
  • Contribution to proceedings
    Workshop on Performance Portable Programming Models for Accelerators (P^3MA), 23.06.2016, Frankfurt (Main), Deutschland
    Lecture Notes on Computer Science (LNCS) - Volume 9934: High Performance Computing ISC High Performance 2016 International Workshops, ExaComm, E-MuCoCoS, HPC-IODC, IXPUG, IWOPH, P^3MA, VHPC, WOPSSS, Frankfurt, Germany, June 19–23, 2016: Springer, 978-3-319-46078-9, 470-488
    DOI: 10.1007/978-3-319-46079-6_33

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Publ.-Id: 23664


Cryogel-Supported Stem Cell Factory for Customized Sustained Release of Bispecific Antibodies for Cancer Immunotherapy

Aliperta, R.; Welzel, P. B.; Bergmann, R.ORC; Freudenberg, R.; Berndt, N.; Feldmann, A.; Arndt, C.; Koristka, S.; Stanzione, M.; Cartellieri, M.; Ehninger, A.; Ehninger, G.; Werner, C.; Pietzsch, J.; Steinbach, J.; Bornhäuser, M.; Bachmann, M.
Combining stem cells with biomaterial scaffolds provides a promising strategy for the development of drug delivery systems. Here we propose an innovative immunotherapeutic organoid by housing human mesenchymal stromal cells (MSCs), gene-modified for the secretion of an anti-CD33-anti-CD3 bispecific antibody (bsAb), in a small biocompatible star-shaped poly(ethylene glycol)-heparin cryogel scaffold as a transplantable and low invasive therapeutic machinery for the treatment of acute myeloid leukemia (AML). The macroporous biohybrid cryogel platform displays effectiveness in supporting proliferation and survival of bsAb-releasing-MSCs overtime in vitro and in vivo, avoiding cell loss and ensuring a constant release of sustained and detectable levels of bsAb capable of triggering T-cell-mediated anti-tumor responses and a rapid regression of CD33+ AML blasts. This therapeutic device results as a promising and safe alternative to the continuous administration of short-lived immunoagents and paves the way for effective bsAb-based therapeutic strategies for future tumor treatments.
Keywords: starPEG-heparin cryogel, Mesenchymal stromal cells, Bispecific antibody, Cancer immunotherapy.

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Publ.-Id: 23663


Tos-Nos-Mos: Synthesis of different aryl sulfonate precursors for the radiosynthesis of the alpha7 nicotinic acetylcholine receptor radioligand [18F]NS14490

Rötering, S.; Scheunemann, M.; Günther, R.; Löser, R.; Hiller, A.; Peters, D.; Brust, P.; Fischer, S.; Steinbach, J.
Radiopharmacological investigations of [18F]NS14490 have proven that this radiotracer could be a potential PETradiotracer for imaging of alpha7 nicotinic acetylcholine receptor particularly with regard to vulnerable plaques of diseased vessels. For further optimisation of the previously automated one-pot radiosynthesis of [18F]NS14490 using a tosylate precursor, precursors with other leaving groups (nosylate and mosylate) were synthesized and compared with the tosylate with respect to their reactivities towards [18F]fluoride. The use of these different precursors resulted in comparable labelling yields of [18F]NS14490. A novel mosylate precursor was synthesized and evaluated, which has revealed a higher stability during a storage period of five months compared to the corresponding tosylate and nosylate.
Keywords: Alpha7 nAChR ligand; PET; Synthesis of precursor; Reactivity of precursor; Tosylate; Nosylate; Mosylate

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Publ.-Id: 23661


Extracellular S100A4 affects endothelial cell integrity and stimulates transmigratory behavior of human A375 melanoma cells

Herwig, N.; Belter, B.; Pietzsch, J.
High extracellular S100A4 level proves a specific characteristic of some cancer cases, including malignant melanoma. Concerning the latter, extracellular S100A4 in an autocrine manner was shown to promote prometastatic activation of A375 cells by interaction with the receptor for advanced glycation endproducts (RAGE). We hypothesized that interaction of extracellular S100A4 with RAGE in a paracrine manner will affect endothelial cell (EC) integrity thus further promoting melanoma metastasis. We investigated the influence of recombinant and cell (A375)-derived S100A4 on RAGE and junction protein expression, and EC (hCMEC/D3) integrity by measuring transendothelial electrical resistance (TEER). RAGE was upregulated by recombinant S100A4. Decrease of TEER and diminished expression of both occludin and VE-cadherin revealed the loss of EC integrity. Transmigration of transgenic A375 cells (A375-hS100A4/A375-hRAGE) through the EC monolayer was significantly higher compared to wild-type A375 cells, and was substantially decreased by sRAGE. An additional pilot study in mice, intracardially injected with A375-hS100A4 or A375-hRAGE cells, showed lower survival rates and a higher incidence of metastases compared to wild-type A375 cells. Tumor development was mostly located in the brain, bones, and ovaries. These findings provide further evidence on extracellular S100A4 as paracrine mediator of prometastatic endothelial dysfunction involving its interaction with RAGE.
Keywords: hCMEC/D3, prometastatic endothelial dysfunction, receptor for advanced glycation endproducts (RAGE), soluble RAGE (sRAGE), S100 proteins, transendothelial electrical resistance (TEER)

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Publ.-Id: 23660


Electrochemical behavior of nanocrystalline Ta/TaN multilayer on 316L stainless steel: Novel bipolar plates for proton exchange membrane fuel-cells

Alishahi, M.; Mahboubi, F.; Mousavi Khoie, S. M.; Aparicio, M.; Hübner, R.; Soldera, F.; Gago, R.
Insufficient corrosion resistance and surface conductivity are two main issues that plague large-scale application of stainless steel (SS) bipolar plates in proton exchange membrane fuel cells (PEMFCs). This study explores the use of nanocrystalline Ta/TaN multilayer coatings to improve the electrical and electrochemical performance of polished 316L SS bipolar plates. The multilayer coatings have been deposited by (reactive) magnetron sputtering and characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. The electrochemical behavior of bare and coated substrates has been evaluated in simulated PEMFC working environments by potentiodynamic and potentiostatic polarization tests at ambient temperature and 80 °C. The results show that the Ta/TaN multilayer coating increases the polarization resistance of 316L SS by about 30 and 104 times at ambient and elevated temperatures, respectively. The interfacial contact resistance (ICR) shows a low value of 12 µOhm cm-2 before the potentiostatic test. This ICR is significantly lower than for the bare substrate and remains mostly unchanged after potentiostatic polarization for 14 h. In addition, the high contact angle (92 °) with water for coated substrates indicates a hydrophobic character, which can improve the water management within the cell in PEMFC stacks.
Keywords: PEMFC, Bipolar plate, Magnetron sputtering, Multilayer coating, Interfacial contact resistance, Corrosion
  • Journal of Power Sources 322(2016), 1-9

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Publ.-Id: 23659


Tailoring the magnetic anisotropy of (Ga,Mn)(As,P) by ion irradiation

Yuan, Y.; Rushforth, A.; Sawicki, M.; Dietl, T.; Helm, M.; Zhou, S.
The rich phenomena in the magnetic anisotropy of diluted ferromagnetic semiconductors (DFS) have opened new concepts for spintronics beyond conventional electronic logic devices [1]. As an example, the magnetic anisotropy of (Ga,Mn)(As,P) can be changed from in-plane to out-of-plane by low temperature annealing [2, 3]. In this work, we demonstrate another flexible approach to tune the magnetic anisotropy by He+ ion irradiation, which is a well-developed chip-technology. For the as-prepared (Ga,Mn)(As,P), the low-temperature long-time annealing suppresses the compensation from Mn interstitials, resulting in a higher carrier concentration and the switching of the magnetic easy axis from the in-plane [100] to the out-of-plane [001] direction [3]. By He+ irradiation, we can turn the magnetic easy axis gradually back to the out-of-plane direction. Therefore, ion irradiation combined with low-temperature long-time annealing boosts the prospects of flexible tailoring of the magnetic anisotropy of DFS material, allowing for the development of new concepts for spintronic devices.

[1] T. Dietl et al., Rev. Mod. Phys. 86, 187-251 (2014).
[2] M. Sawicki et al., Phys. Rev. B 70, 245325 (2004).
[3] A. Casiraghi et al., Appl. Phys. Lett. 97, 122504 (2010).
  • Poster
    EMRS 2016 Spring, 02.-06.05.2016, Lille, France

Permalink: https://www.hzdr.de/publications/Publ-23658
Publ.-Id: 23658


Pulsed laser melting: A versatile approach for the preparation of dilute ferromagnetic semiconductors

Yuan, Y.; Helm, M.; Zhou, S.
Mn doped III-V dilute ferromagnetic semiconductors (DFS) are of great interest in recent decades due to their potential for spintronics [1]. However, the low solid solubility of Mn in III-V semiconductors prohibits the common equilibrium preparation process. For long time, the low-temperature molecule beam epitaxy (LT-MBE) has been the only method to obtain DFS. The technical challenges in LT-MBE result in the fact that GaMnAs (and its alloys with low concentration of phosphorus or indium) is the only available DFS.
In our work, making the full use of ion implantation combined with pulsed laser melting, we have extended the family of Mn doped III-V DFSs. All specimens exhibit the epitaxial structure and pronounced uniaxial magnetic anisotropy. Particularly, we have prepared InMnAs with both high Curie temperature and perpendicular magnetic anisotropy, which is difficult to prepare by LT-MBE due to many n-type defects [3], as well as GaMnP [4] and InMnP [5] which have only been prepared by ion implantation up to now. When compared with LT-MBE, this approach combining ion implantation and pulsed laser melting brightens the future of III-Mn-V DFS by two aspects: (1) Its efficiency and reproducibility make the possibility of the large-scale production in industry; (2) The introduction of new materials (GaMnP and InMnP) provides a more complete platform for understanding the DFS family.

[1]. T. Dietl et al., Rev. Mod. Phys., 86, 187-251 (2014)
[2]. D. Bürger et al., Phys. Rev. B, 81, 115202 (2010)
[3]. Y. Yuan et al., J. Phys. D: Appl. Phys. 48, 235002 (2015)
[4].Y. Yuan et al., IEEE Trans. Mag. 50, 2401304 (2014)
[5]. M. Khalid et al., Phys. Rev. B, 89, 121301(R) (2014)
  • Lecture (Conference)
    EMRS 2016 Spring Meeting, 02.-06.05.2016, Lille, France

Permalink: https://www.hzdr.de/publications/Publ-23657
Publ.-Id: 23657


Numerical simulation of mass transfer and convection near a hydrogen bubble during water electrolysis in a magnetic field

Mutschke, G.; Fröhlich, J.; Yang, X.; Eckert, K.; Karnbach, F.; Uhlemann, M.; Baczyzmalski, D.; Cierpka, C.
Hydrogen produced from wind or solar power could be used easily for storing energy also at large scale, thus allowing to bridge the gap between supply and demand of renewable energy with respect to time and place. When splitting water by electrolysis, a deeper look at local phenomena near single bubbles at the electrode might be helpful to improve our understanding of the process. In the recent literature, magnetic fields are discussed with respect to the bubble departure, thereby possibly influencing the efficiency of the process [1-6].
The contribution will present numerical simulations resolving in detail local phenomena near a single hydrogen bubble at the cathode during the electrolysis of water. The modeling is supported by data of recent experiments on hydrogen single bubbles evolving at a platinum micro-electrode. The results will provide insight into the local and temporal behavior of electrolyte convection, species concentration and mass transfer during electrolysis. Furthermore, the influence of the Lorentz force caused by vertical magnetic fields will be discussed in detail.
[1] X. Yang et al., Langmuir 31 (2015) 8184-8193.
[2] D. Fernandez et al., Langmuir 30 (2014) 13065-13074.
[3] H. Liu et al., J. Electroanal. Chem. 754 (2015) 22-29.
[4] H. Liu et al., Can. J. Chem. Eng. 94 (2016) 192-199.
[5] D. Baczyzmalski et al., Exp. Fluids 56 (2015) 162ff.
[6] J. Koza et al., Electrochem. Comm. 10 (2009) 425-429.
Keywords: electrolysis, hydrogen evolution, magnetic field, Lorentz force, convection, mass transfer
  • Poster
    67th Annual Meeting of the International Society of ELectrochemistry, 21.-26.08.2016, Den Haag, Niederlande
  • Lecture (Conference)
    10th PAMIR International Conference on Fundamental and Applied MHD, 20.-24.06.2016, Cagliari (Sardinia), Italia
  • Contribution to proceedings
    10th PAMIR International Conference on Fundamental and Applied MHD, 20.-24.06.2016, Cagliari (Sardinia), Italia
    Proceedings of the 10th PAMIR International Conference on FUndamental and Applied MHD, 978-88-90551-93-2, 97-101
  • Open Access Logo Magnetohydrodynamics 53(2017)1, 193-199

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Publ.-Id: 23656


PET/CT during degradation processes at the cement-clay interface and derivation of process parameters

Kulenkampff, J.; Mäder, U.; Gründig, M.; Eichelbaum, S.; Lippmann-Pipke, J.
Observation of degradation processes is complicated by the heterogeneous nature of the process. Better process understanding requires methods for both monitoring the fate of chemical species (mobile phase) and structural alterations (stationary phase). In the past decade, we empowered positron emission tomography (PET) for quantitative transport visualization in geological media – GeoPET. It has an unrivalled sensitivity and robustness for quantitative, non-destructive, spatio-temporal concentration measurements cPET(x,y,z,t). CT adds structural information.
  • Poster
    1st Annual Workshop of the CEBAMA project, 11.-13.05.2016, Barcelona, Spanien
  • Open Access Logo Contribution to proceedings
    1st Annual Workshop of the CEBAMA project, 11.-13.05.2016, Barcelona, Spanien
    Proceedings of the First Annual Workshop of the HORIZON 2020 CEBAMA Project KIT scientific reports 7734, Karlsruhe: KIT Scientific Publishing, 978-3-7315-0660-7, 113-119
    DOI: 10.5445/KSP/1000068889

Permalink: https://www.hzdr.de/publications/Publ-23655
Publ.-Id: 23655


Multiscale Self-Assembly of Silicon Quantum Dots into an Anisotropic Three-Dimensional Random Network

Ilday, S.; Ilday, F. O.; Hübner, R.; Prosa, T. J.; Martin, I.; Nogay, G.; Kabacelik, I.; Mics, Z.; Bonn, M.; Turchinovich, D.; Toffoli, H.; Toffoli, D.; Friedrich, D.; Schmidt, B.; Heinig, K.-H.; Turan, R.
Multiscale self-assembly is ubiquitous in nature but its deliberate use to synthesize multifunctional three-dimensional materials remains rare, partly due to the notoriously difficult problem of controlling topology from atomic to macroscopic scales to obtain intended material properties. Here, we propose a simple, modular, noncolloidal methodology that is based on exploiting universality in stochastic growth dynamics and driving the growth process under far-from-equilibrium conditions toward a preplanned structure. As proof of principle, we demonstrate a confined-butconnected solid structure, comprising an anisotropic random network of silicon quantum-dots that hierarchically self-assembles from the atomic to the microscopic scales. First, quantum-dots form to subsequently interconnect without inflating their diameters to form a random network, and this network then grows in a preferential direction to form undulated and branching nanowire-like structures. This specific topology simultaneously achieves two scale-dependent features, which were previously thought to be mutually exclusive: good electrical conduction on the microscale and a bandgap tunable over a range of energies on the nanoscale.
Keywords: Si, random network, hierarchical, multiscale, self-assembly, stochastic deposition
  • Nano Letters 16(2016), 1942-1948

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Publ.-Id: 23654


Investigation of single bubbles and bubble chains in liquid metal under the influence of magnetic fields

Strumpf, E.; Eckert, S.
Two-phase flows play an important role in industrial applications, such as the continuous casting of steel. Here, inert gas is injected into the beginning of the submerged entry nozzle to avoid nozzle clogging as well as to catch impurities within the melt and to transport them to the free surface, away from the solidification front. Furthermore electromagnetic brakes are used with the aim to dampen the highly turbulent flow and to reduce high velocities in the liquid metal. Although a vast number of simulations and experiments of bubbly flows in water exist, such investigations in liquid metal still lack quantity. However, liquid metal experiments are unavoidable for a correct modelling of such special cases, like the influence of magnetic fields on the flow or the two-phase flow behavior. In the present study the ascents of single bubbles and of bubble chains in a liquid metal are investigated. For this purpose a benchmark experiment is set up, a cuboid vessel of the dimensions 144 x 144 x 12 mm³, which is filled with eutectic alloy GaInSn. A transversal magnetic field up to 1.1 T is imposed to this vessel. Ultrasound Doppler Velocimetry (UDV) is used to map the flow in the continuous phase of bubble chain regimes as well as the ascent velocity of single bubbles.
Keywords: liquid metal, single bubble, bubble chain, magnetic field, ultrasound
  • Lecture (Conference)
    International Conference on Multiphase Flow (ICMF 2016), 22.-27.05.2016, Firenze, Italia

Permalink: https://www.hzdr.de/publications/Publ-23653
Publ.-Id: 23653


Magnetic vortex cores as tunable spin wave emitters

Wintz, S.; Tyberkevych, V.; Weigand, M.; Raabe, J.; Lindner, J.; Erbe, A.; Slavin, A.; Fassbender, J.ORC
The use of spin waves as information carriers in spintronic devices can substantially reduce energy losses by eliminating the ohmic heating associated with electron transport. Yet, the excitation of short-wavelength spin waves in nanoscale magnetic systems remains a significant challenge. Here, we propose a method for their coherent generation in a heterostructure composed of antiferromagnetically coupled magnetic layers. The driven dynamics of naturally formed nanosized stacked pairs of magnetic vortex cores is used to achieve this aim. The resulting spin-wave propagation is directly imaged by time-resolved scanning transmission X-ray microscopy. We show that the dipole-exchange spin waves excited in this system have a linear, non-reciprocal dispersion and that their wavelength can be tuned by changing the driving frequency.
Keywords: magnetism spinwaves magnonics vortex

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Publ.-Id: 23652


Defect studies of Mg films deposited on various substrates

Hruška, P.; Čížek, J.; Anwand, W.; Bulíř, J.; Drahokoupil, J.; Stráská, J.; Melikhova, O.; Procházka, I.; Lančok, J.
In the present work the structure of Mg films deposited by RF magnetron sputtering was characterized using variable energy positron annihilation spectroscopy combined with scanning electron microscopy and X-ray diffraction. The effect of deposition parameters, namely temperature, type of substrate and deposition rate, on the microstructure was examined. All Mg films studied grow with the basal (0001) plane parallel with the substrate and exhibit only negligible in-plane stress. Films deposited at room temperature are characterized by nanocrystalline structure with high volume fraction of grain boundaries. and positrons are preferentially trapped in open volume defects present at grain boundaries. In these films positrons are trapped predominantly in open-volume defects present at grain boundaries. With increasing deposition temperature the mean grain size increases and the volume fraction of grain boundaries decreases. Hence, in Mg films prepared at elevated temperatures positrons are trapped mainly at misfit dislocations compensating different atomic spacing in the films and the substrate. Moreover, it was found that slow deposition rate leads to higher density of defects compared to fast deposition rate. By annealing of Mg film with thin 20 nm Pd over-layer at 300°C for 1 hour Pd layer is mixed with Mg film forming a Mg-Pd compound. The Mg-Pd phase likely contains structural open-volume defects which trap positrons.
Keywords: defect studies, Mg films, positron annihilation

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Publ.-Id: 23651


Ferromagnetism in 5f-band metamagnet UCoAl induced by Os doping

Andreev, A. V.; Shirasaki, K.; Sebek, J.; Vejprovova, J.; Gorbunov, D. I.; Havela, L.; Danis, S.; Yamamura, T.
UCoAl is a 5f-band metamagnet with a uniquely low paramagnetic-to-ferromagnetic transition field, 0.7 T, extremely sensitive to any perturbation such as elemental substitution. Here, we study variations of magnetic properties in the UCoAl-UOsAl system on single- and polycrystalline samples with different concentration of Os. We found that osmium can substitute Co in UCoAl up to 20%, while preserving the ZrNiAl structure type. Pure UOsAl was identified as a hexagonal Laves phase, MgZn2 type. It is a weak Pauli paramagnet. Even a 2%-substitution of Os for Co in the 5f band metamagnet stabilizes ferromagnetism with the Curie temperature TC = 26 K and uranium magnetic moment µ = 0.4 µB and shifts the critical metamagnetic field to zero. Higher Os concentrations enhance both TC and µ. All magnetic response is concentrated into the c-axis; the susceptibility for magnetic field perpendicular to c is low and practically temperature-independent. Our study reflects the decisive role of the 5f-5d hybridization in the magnetism of the UCoAl-UOsAl system. This work completes the study of the alloying of UCoAl with late transition metals and indicates that the non-magnetic phase exhibiting band metamagnetism is very limited in the concentration range.

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Evaluation of covalence in An(III)- and Ln(III)-complexes by NMR Spectroscopy

Adam, C.; Kaden, P.; Beele, B. B.; Geist, A.; Müllich, U.; Panak, P. J.
Partitioning and transmutation (P&T) facilitates a reduction of the long-term radiotoxicity and heat load of spent nuclear fuel by separation of the actinides and subsequent conversion into shorter-lived or stable nuclides. A chemically demanding key step in this process is the separation of the trivalent actinides from fission lanthanides. This can be achieved by liquid-liquid extraction using highly selective extraction agents, such as nPrBTP (1) or C5-BPP (2). These have high separation factors (>100) for trivalent americium over europium. However, the molecular origin of their selectivity is largely unclear.
NMR spectroscopy on paramagnetic samples allows a separation of the observed paramagnetic shift into a part due to transferred electron spin density (Fermi contact shift, FCS) and a part due to dipolar coupling of electron and nuclear spin (Pseudo contact shift, PCS). Evaluation of the FCS thus allows an assessment of the share of covalence in the metal-ligand bond of the N-donor complexes. Several methods that enable the separation of the shift contributions have been proposed in literature. So-called “model free methods” that do not require structural models of the complexes appear most promising.
We will present and compare the results of different temperature-dependent and temperature-independent model-free methods for complexes of both ligands. The merits, but also the limitations of currently available methods will be discussed in detail. Furthermore, we will evaluate the applicability of temperature-dependent methods for shift separation of Am(III) complexes and give a qualitative assessment on covalence in the bonding of these complexes.
Keywords: NMR Spectroscopy, Separation, Partitioning Ligands, Bonding
  • Poster
    ATALANTE 2016 – Nuclear Chemistry for Sustainable Fuel Cycles, 05.-10.06.2016, Montpellier, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-23649
Publ.-Id: 23649


Comparative NMR Study of nPrBTP and iPrBTP Complexes

Adam, C.; Rohde, V.; Müllich, U.; Kaden, P.; Geist, A.; Panak, P. J.
Partitioning and transmutation (P&T) is a strategy for reducing the long-term radiotoxicity and heat load of spent nuclear fuel by separating actinides from the used fuel and converting them into shorterlived or stable products. A key step in this process is the separation of the trivalent actinides from lanthanides, which can be achieved by liquid-liquid extraction using selective N-donor extracting ligands, such as alkylated bis-triazinyl pyridines (BTP). These have high separation factors (>100) for trivalent americium over europium. However, little is known about the molecular origin of their selectivity.
The aliphatic side chains of BTP ligands influence the stability against radiation and hydrolysis, the solubility, but also the selectivity and extraction behaviour. While nPrBTP (1) has been thoroughly studied over the past years, only few data are available for its isomer iPrBTP (2). TRLFS studies showed that the stability constants for the Eu(III) complex are almost three orders of magnitude higher than for nPrBTP, while the increase for Cm(III) complexes is less pronounced.
This result prompted us to investigate Ln(III) and the Am(III) complexes by NMR spectroscopy, which offers insight into the metal-ligand bond properties. For the NMR studies, iPrBTP with 15N isotope labelling of the nitrogen atoms in the pyrazole moiety was synthesized. We will show a comparison of the bonding properties in complexes of (1) and (2) and discuss the share of covalence in the bonding. Furthermore, the implications for the mechanism of complex formation with ligand (2) will be evaluated.
Keywords: NMR Spectroscopy, Separation, Partitioning Ligands, Bonding
  • Lecture (Conference)
    ATALANTE 2016 – Nuclear Chemistry for Sustainable Fuel Cycles, 05.-10.06.2016, Montpellier, Frankreich

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Publ.-Id: 23648


Comparative NMR study of nPrBTP and iPrBTP

Adam, C.; Rohde, V.; Müllich, U.; Kaden, P.; Geist, A.; Panak, P. J.; Geckeis, H.
Bistriazinyl-pyridine type ligands are important extracting agents for separating trivalent actinide ions from trivalent lanthanides. The alkyl substituents on the lateral triazine rings have a significant effect on the stability of the ligand against hydrolysis and radiolysis. Furthermore they influence solubility, extraction behaviour and selectivity. TRLFS and extraction studies suggest differences in complexation and extraction behaviour of BTP ligands bearing iso-propyl or n-propyl substituents, respectively. As NMR studies allow insight into the metal-ligand bonding, we conducted NMR studies on a range of 15N-labelled nPrBTP and iPrBTP complexes. Our results show that no strong change in the metal-ligand bonding occurs, thus excluding electronic reasons for differences in complexation behaviour, extraction kinetics and selectivity. This supports mechanistic reasons for the observed differences.
Keywords: NMR Spectroscopy, Bonding, Extraction, BTP, An(III)/Ln(III) separation
  • Open Access Logo Contribution to proceedings
    Comparative NMR study of nPrBTP and iPrBTP, 05.-10.06.2016, Montpellier, Frankreich
    Procedia Chemistry
    DOI: 10.1016/j.proche.2016.10.006

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Guided-wave second harmonics in Nd:YCOB ridge waveguides produced by combination of carbon ion irradiation and precise diamond blade dicing

Li, R.; Nie, W.; Shang, Z.; Cheng, C.; Akhmadaliev, S.; Zhou, S.; Lu, Q.; Chen, F.
We report on the fabrication of Nd:YCa4O(BO3)3 (Nd:YCOB) ridge waveguides by combining carbon ion irradiation and precise diamond blade dicing. The guiding and spectroscopic properties of the planar as well as ridge waveguides are investigated. The second harmonic generation (SHG) at 532 nm has been realized through the waveguide structures. With nearly the same input power, the maximum average output powers are 0.56 mW and 0.62 mW, and the maximum conversion efficiencies reach 0.3%W−1 and 0.5%W−1, for planar and ridge waveguides, respectively.
Keywords: Optical waveguides; Nd:YCOB crystal; Second harmonic generation

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Universality of (2+1)-dimensional restricted solid-on-solid models

Kelling, J.; Ódor, G.; Gemming, S.
Extensive dynamical simulations of Restricted Solid on Solid models in D=2+1 dimensions have been done using parallel multisurface algorithms implemented on graphics cards. Numerical evidence is presented that these models exhibit KPZ surface growth scaling, irrespective of the step heights N. We show that by increasing N the corrections to scaling increase, thus smaller step sized models describe better the asymptotic, long wave scaling behavior.
Related publications
Efficient Parallel Monte-Carlo Simulations for Large-Scale … (Id 27533) has used this publication of HZDR-primary research data

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A possible new origin of long absorption tail in Nd-doped yttrium aluminum garnet induced by 15 MeV gold-ion irradiation and heat treatment

Amekura, H.; Akhmadaliev, S.; Zhou, S.; Chen, F.
When ion irradiation introduces point-defects in semiconductors/insulators, discrete energy levels can be introduced in the bandgap, and then optical transitions whose energies are lower than the bandgap become possible. The electronic transitions between the discrete level and the continuous host band are observed as a continuous tail starting from the fundamental edge. This is the well-known mechanism of the absorption tail close to the band-edge observed in many semiconductors/insulators. In this paper, we propose another mechanism for the absorption tail, which is probably active in Nd-doped yttrium aluminum garnet (Nd:YAG) after ion irradiation and annealing. A Nd:YAG bulk crystal was irradiated with 15 MeV Au5+ ions to a fluence of 8 × 1014 ions/cm2. The irradiation generates an amorphous layer of ∼3 μm thick with refractive index reduction of Δn = −0.03. Thermal annealing at 1000 °C induces recrystallization to randomly aligned small crystalline grains. Simultaneously, an extraordinarily long absorption tail appeared in the optical spectrum covering from 0.24 to ∼2 μm without fringes. The origin of the tail is discussed based on two models: (i) conventional electronic transitions between defect levels and YAG host band and (ii) enhanced light scattering by randomly aligned small grains.

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Structure and X-ray diagnostics in non-equilibrium warm dense matter

Vorberger, J.; Chapman, D. A.
We present a quantum theory for the dynamic structure factors in non-equilibrium, non-ideal, two-component warm dense matter. This general framework allows the derivation of expressions for the local field corrections in non-equilibrium. Based on a perturbation expansion of the non-equilibrium polarization function in terms of the interaction strength and taking the Wigner function as input quantity, we calculate the dynamic structure for a variety of typical scenarios and demonstrate typical effects. Example situations include laser heated matter or shock produced warm dense matter.
We provide a generalized Chihara decomposition of the total dynamic electron structure factor. The formula features the free electrons, the non-equilibrium ion structure, the generalized non-equilibrium screening cloud and an additional term arising due to not invoking the Born-Oppenheimer approximation. This puts the theory of x-ray scattering in non-equilibrium on a sound theoretical basis and makes x-ray scattering a possible diagnostics for non-equilibrium warm dense matter on all time scales, in particular on femtosecond electronic time scales.
We give examples for the expected x-ray scattering signals in laser heated systems and in two-temperature systems. We discuss the possibility to resolve temperature relaxation using x-ray scattering and point out possible problems in the current models used for the description of such relaxation processes.
Keywords: x-ray scattering, warm dense matter, dynamic structure factor, exchange, correlations
  • Poster
    HEDLA 2016, 16.-20.05.2016, Menlo Park, USA

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Time structure influence on the radiobiological response to MeV electron beams

Beyreuther, E.; Gotz, M.; Karsch, L.; Lessmann, E.; Schürer, M.; Pawelke, J.
No abstract available

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Status of the Development of a Novel Compact Proton Therapy Gantry System Based on Pulsed Magnets for Laser-driven Beams

Masood, U.; Baumann, M.; Cowan, T. E.; Enghardt, W.; Herrmannsdörfer, T.; Karsch, L.; Kroll, F.; Schramm, U.; Schürer, M.; Pawelke, J.
Purpose/Objective(s):
Proton acceleration on m scale via high intensity laser has become a compelling alternative to conventional accelerators and gained interests for its potential to reduce size and costs for proton therapy (PT) facilities. Next generation petawatt lasers promise laser-driven protons (LDP) with therapeutic energies. But, in contrast to conventionally accelerated quasi-continuous mono-energetic pencil beams with about 30 Gy/sec dose rate, LDP beams have diverse properties, i.e. ultra-intense pico-sec bunches with up to 1010 Gy/sec dose rate, large energy spread and divergence, and with only up to 10 Hz repetition rate. These properties make it challenging to adapt LDP beams directly for medical applications. The presented work is an ongoing joint translational research project of several institutions aiming to establish laser-driven PT. We will present the recent progress in design concepts and the status of the development.

Materials/Methods:
In addition to laser accelerator development, LDP beams demand radiobiological characterization and new solutions for beam transport and dose delivery. Laser-based technology for low energy LDP beams has been established for cell and small animal irradiation using a fixed beamline and is being utilized for systematic extreme dose rate radiobiological studies. For translation towards patient irradiation a highly compact 360° isocentric proton gantry system was designed based on light-weight iron-less high-field pulsed magnets. The gantry is integrated with beam control, energy selection and a novel dose delivery system, capable to magnetically control the beam spot size and to scan the beam for advanced irradiation schemes. A 3D TPS has been adapted and used to demonstrate clinical functionality of our system. For its realization, key high-field pulsed magnets are being developed.

Results:
Radiobiologically, so far no overall difference is observed for laser-driven ultra-high dose rates compared to conventional PT beams. Our double achromatic gantry system is about 3 times smaller than conventional PT gantries. The new dose delivery system can simultaneously widens the beam size (Ø 1-20 cm) and scan 10x20 cm2 field size, for the most efficient dose delivery. High quality clinical treatment plans can be provided with such beams. For the gantry realization a pulsed 40 T solenoid for particle capture and a 10 T compact iron-less 50° sector magnet were successfully tested. A pulsed 120 T/m gradient quadrupole is being manufactured.
Conclusions:
Our compact, light-weight gantry could provide an optimized solution for the laser-driven PT. The tests of pulsed gantry magnets are being continued. Our new conventional PT facility is additionally equipped with a petawatt laser laboratory and an experimental bunker. This will allow testing for clinical applicability of LDP systems side-by-side with conventional therapeutic proton beams as reference.

Acknowledgment:
This project was supported by German BMBF grant (03Z1N511 and 03Z1O511).
Keywords: Proton Therapy, Gantry, Pulsed Magnets, Laser acceleration
  • Poster
    ASTRO 2016 Annual Meeting, 25.-28.09.2016, Boston, USA
  • Abstract in refereed journal
    International Journal of Radiation Oncology Biology Physics 96(2016)2, E612
    DOI: 10.1016/j.ijrobp.2016.06.2162

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Publ.-Id: 23641


Systematic investigation of projectile fragmentation using beams of unstable B and C isotopes

Thies, R.; Heinz, A.; Adachi, T.; Aksyutina, Y.; Alcantara-Núñes, J.; Altstadt, S.; Alvarez-Pol, H.; Ashwood, N.; Aumann, T.; Avdeichikov, V.; Barr, M.; Beceiro-Novo, S.; Bemmerer, D.; Benlliure, J.; Bertulani, C. A.; Boretzky, K.; Borge, M. J. G.; Burgunder, G.; Camaño, M.; Caesar, C.; Casarejos, E.; Catford, W.; Cederkäll, J.; Chakraborty, S.; Chartier, M.; Chulkov, L. V.; Cortina-Gil, D.; Crespo, R.; Datta, U.; Díaz Fernández, P.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estradé, A.; Farinon, F.; Fraile, L. M.; Freer, M.; Freudenberger, M.; Fynbo, H. O. U.; Galaviz, D.; Geissel, H.; Gernhäuser, R.; Göbel, K.; Golubev, P.; Gonzalez Diaz, D.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Henriques, A.; Holl, M.; Ickert, G.; Ignatov, A.; Jakobsson, B.; Johansson, H. T.; Jonson, B.; Kalantar-Nayestanaki, N.; Kanungo, R.; Knöbel, R.; Kröll, T.; Krücken, R.; Kurcewicz, J.; Kurz, N.; Labiche, M.; Langer, C.; Le Bleis, T.; Lemmon, R.; Lepyoshkina, O.; Lindberg, S.; Machado, J.; Marganiec, J.; Maroussov, V.; Mostazo, M.; Movsesyan, A.; Najafi, A.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Perea, A.; Petri, M.; Pietri, S.; Plag, R.; Prochazka, A.; Rahaman, A.; Rastrepina, G.; Reifarth, R.; Ribeiro, G.; Ricciardi, M. V.; Rigollet, C.; Riisager, K.; Röder, M.; Rossi, D.; Sanchez Del Rio, J.; Savran, D.; Scheit, H.; Simon, H.; Sorlin, O.; Stoica, V.; Streicher, B.; Taylor, J. T.; Tengblad, O.; Terashima, S.; Togano, Y.; Uberseder, E.; van de Walle, J.; Velho, P.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Weigand, M.; Wheldon, C.; Wilson, G.; Wimmer, C.; Winfield, J. S.; Woods, P.; Yakorev, D.; Zhukov, M. V.; Zilges, A.; Zuber, K.
Background: Models describing nuclear fragmentation and fragmentation fission deliver important input for planning nuclear physics experiments and future radioactive ion beam facilities. These models are usually benchmarked against data from stable beam experiments. In the future, two-step fragmentation reactions with exotic nuclei as stepping stones are a promising tool for reaching the most neutron-rich nuclei, creating a need for models to describe also these reactions.
Purpose: We want to extend the presently available data on fragmentation reactions towards the light exotic region on the nuclear chart. Furthermore, we want to improve the understanding of projectile fragmentation especially for unstable isotopes.
Method: We have measured projectile fragments from C10,12−18 and B10−15 isotopes colliding with a carbon target. These measurements were all performed within one experiment, which gives rise to a very consistent data set. We compare our data to model calculations.
Results: One-proton removal cross sections with different final neutron numbers (1pxn) for relativistic C10,12−18 and B10−15 isotopes impinging on a carbon target. Comparing model calculations to the data, we find that the epax code is not able to describe the data satisfactorily. Using abrabla07 on the other hand, we find that the average excitation energy per abraded nucleon needs to be decreased from 27 MeV to 8.1 MeV. With that decrease abrabla07 describes the data surprisingly well.
Conclusions: Extending the available data towards light unstable nuclei with a consistent set of new data has allowed a systematic investigation of the role of the excitation energy induced in projectile fragmentation. Most striking is the apparent mass dependence of the average excitation energy per abraded nucleon. Nevertheless, this parameter, which has been related to final-state interactions, requires further study.
Keywords: nuclear fragmentation fission radioactive ion beam facilities C10 C12−18 B10−15 isotope

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Publ.-Id: 23640


Remote Sensing-Based Exploration of Structurally-Related Mineralizations around Mount Isa, Queensland, Australia

Jakob, S.; Gloaguen, R.; Laukamp, C.
Hyperspectral imaging is a powerful tool for mineral mapping and increasingly used in poorly-accessible areas. It only requires a limited amount of validation sample points, but can fail to discriminate spectrally-similar features. In this manuscript, we show that we improve the identification of interesting targets by including geomorphological data in the spectral mapping scheme. We jointly use geomorphic and spectral features to locate gossanous ironstone ridges as an indicator for possible Pb-Zn-Ag-mineralization and provide an application around Mount Isa and George Fisher/Hilton mine, Queensland, Australia. We combine hyperspectral HyMap data using mixture tuned matched filtering with topographical indices, such as maximum curvature and the topographical position index. As it is often the case with structurally-controlled mineralization, the amount of training sites is limited, and supervised classification methods cannot be implemented. Therefore, we implement expert knowledge in a decision tree to take advantage of the relationship between mineralization, alteration and structure. Optimized rock sampling and spectral measurements provided data for validation. We are able to map sets of gossanous ridges with a minimum of validation points, not only within the Mount Isa mining area itself, but also outside the commonly-accepted host rocks. The ridges are parallel to north-south trending geomorphological features and probably associated with the Paroo fault zone. Similarities between the ridges were confirmed by field observations, spectral measurements and a qualitative rock sample analysis. We identified new mineralized ridges that we could subsequently attribute to a poorly-known and sub-economic deposit known as the Mount Novit Pb-Zn-deposit.
Keywords: HyMap, hyperspectral, mineral mapping, geomorphological features, alteration mapping

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Publ.-Id: 23639


JRQ and JPA irradiated and annealed reactor pressure vessel steels studied by positron annihilation

Slugen, V.; Gokhman, O.; Pecko, S.; Sojak, S.; Bergner, F.
The paper is focused on a comprehensive study of JRQ and JPA reactor pressure vessel steels from the positron annihilation lifetime spectroscopy (PALS) point of view. Based on our more than 20 years’ experience with characterization of irradiated reactor steels, we confirmed that defects after irradiation start to grow and/or merge into bigger clusters. Experimental results shown that JPA steel is more sensitive to the creation of irradiation-induced defects than JRQ steel. It is most probably due to high copper content (0.29 wt.% in JPA) and copper precipitation has a major impact on neutron-induced defect creation at the beginning of the irradiation. Based on current PALS results, no large vacancy clusters were formed during irradiation, which could cause dangerous embrittlement concerning operation safety of nuclear power plant. The combined PALS, small angle neutron scattering and atomic probe tomography studies support the model for JRQ and JPA steels describing the structure of irradiationinduced clusters as agglomerations of vacancy clusters (consisting of 2–6 vacancies each) and are separated from each other by a distribution of atoms.
Keywords: Nuclear materials; positron annihilation spectroscopy; RPV steel; irradiation; ion beam implantation

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Publ.-Id: 23638


Interaction of radio-metals with microorganisms

Raff, J.; Vogel, M.; Günther, A.; Drobot, B.; Schmoock, C.; Moll, H.; Börnick, H.; Worch, E.; Stumpf, T.
Metals interact in various ways with living organisms. This affects first of all the behavior of the metals in the environment as different metal species differ in their mobility in the geo- and the biosphere as well as in their bioavailability. Conversely, metals are essential for the vitality of cells. Many metals are an integral part of one or more enzymes involved in metabolic and biochemical processes. Beside essential metals there are also toxic and radioactive metals that can seriously damage an organism at least at higher concentrations. Figure 1 shows possible interaction mechanisms between microorganisms and radio-metals.
Furthermore, radio-metals may damage or even destroy cells by radiation. The latter excites or ionizes atoms or molecules causing the formation of radicals, changes of biomolecules or even the breakage of chemical bonds. But also for this kind of damage microorganisms have successfully developed effective strategies. Different spectroscopic methods and electron microscopy reveal that different groups of organisms such as bacteria, algae and fungi, differ in their interaction with radio-metals.
In case of bacterial uranium mining waste pile isolates belonging to the genera Lysinibacillus and Bacillus it was demonstrated that so-called S-layer proteins, forming a latticed protein envelope on many bacteria and almost all archaea, are able to effectively scavenge reactive oxygen species (ROS). The latter can be formed by either radiolysis of water or the Fenton reaction. These ROS react with tyrosine side chains of the proteins forming bityrosines and thereby causing an intramolecular crosslinking. Furthermore, these S-layers possess different functional groups on their surface such as carboxyl, hydroxyl, amino, phosphate, sulfoxide and sulfate groups. These groups mediate selective binding of different metals including uranyl(VI) [2]. As most S-layer proteins are also calcium binding proteins, these S-layers additionally possess at least two different Ca binding sites binding trivalent actinides such as Cm(III) with high affinity [3]. In case of the alga Chlorella vulgaris U(VI) concentrations up to 5 µM are bound via carboxyl and phosphate groups being located on the cell surface. This process is followed by desorption in which probably the secretion of complexing bio-ligands is involved [4]. At higher uranium concentrations of 100 µM the alga will die and no desorption can be observed. In comparison to this alga, the fungus Schizophyllum commune interacts with moderate concentrations of uranium (4.2 µM) via organic phosphates. At higher U(VI) concentrations (420 µM) the fungus stays alive and accumulates uranium additionally inside the cell by forming inorganic uranyl phosphates [5]. Due to their high uranium resistance and high accumulation rates different fungi were selected to be further investigated regarding their application potential for a fungal-based concept for the reliable immobilization of released radionuclides within the so called BioVeStRa project.

References
[1] Lloyd J.R. and Macaskie L. E. (2002), In Interactions of Microorganisms with Radionuclides, Ed. Keith-Roach & Livens, Elsevier, 313-342,
[2] Merroun M.L. et al. (2005), Appl. Environ. Microbiol. 71(9), 5532-5543.
[3] Moll H. et al. (2011), Curium(III) complexation with surface-layer (S-layer) proteins from a uranium mining waste pile isolate. Poster at Migration 2011, 18.-23.09.2011, Beijing, PR China.
[4] Vogel M. et al. (2010), Sci. Total Environ. 409, 384-395.
[5] Günther A. et al. (2014), Biometals 27,775-785.
Keywords: radionuclides, microorganism, interaction
  • Poster
    Ninth International Conference on Nuclear and Radiochemistry – NRC9, 29.08.-02.09.2016, Helsinki, Finnland

Permalink: https://www.hzdr.de/publications/Publ-23637
Publ.-Id: 23637


Pulsed-power high-field magnets for laser-driven proton therapy gantry systems

Karsch, L.; Cowan, T. E.; Enghardt, W.; Herrmannsdörfer, T.; Kroll, F.; Masood, U.; Schramm, U.; Schürer, M.; Pawelke, J.
please ask the authors
  • Lecture (Conference)
    EAPPC with BEAMS and MEGAGAUSS 2016, 18.-22.09.2016, Estoril, Portugal

Permalink: https://www.hzdr.de/publications/Publ-23636
Publ.-Id: 23636


Ionization chamber collection efficiency in pulsed radiation fields of high pulse dose

Gotz, M.; Karsch, L.; Pawelke, J.
please ask the authors
  • Poster
    AAPM 58th Annual Meeting, 31.07.-04.08.2016, Washington, DC, USA
  • Abstract in refereed journal
    Medical Physics 43(2016)6, 3316
    DOI: 10.1118/1.4955543

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Publ.-Id: 23635


Entwicklung kompakter, gepulster Elektro-Dipolmagnete für die laserbasierte Protonentherapie

Schürer, M.; Herrmannsdörfer, T.; Karsch, L.; Kroll, F.; Masood, U.; Pawelke, J.
no abstract is available
  • Lecture (Conference)
    Entwerfen Entwickeln Erleben – EEE2016, 30.06.-01.07.2016, Dresden, Deutschland
  • Contribution to proceedings
    Entwerfen Entwickeln Erleben – EEE2016, 30.06.-01.07.2016, Dresden, Deutschland
    Entwickeln - Entwerfen - Erleben 2016: Beiträge zur virtuellen Produktentwicklung und Konstruktionstechnik, Dresden: Verlag der Wissenschaften GmbH, TUDpress, 978-3-95908-062-0, 91-96

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Publ.-Id: 23634


Preparation of in vivo radiobiological characterization of laser-driven proton beams

Karsch, L.; Baumann, M.; Beyreuther, E.; Brüchner, K.; Gotz, M.; Krause, M.; Leßmann, E.; Schmidt, M.; Schramm, U.; Schürer, M.; Pawelke, J.
please ask the authors
  • Poster
    Annual ARR Meeting, 27.-29.06.2016, Leicester, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-23633
Publ.-Id: 23633


A compact proton therapy facility concept for pulsed beams from high power laser accelerators

Masood, U.; Baumann, M.; Enghardt, W.; Hofmann, K. M.; Karsch, L.; Kroll, F.; Schramm, U.; Schürer, M.; Wilkens, J. J.; Pawelke, J.
please ask the authors
  • Poster
    55th Annual Conference of the PTCOG, 22.-28.05.2016, Prague, Czech Republic
  • Open Access Logo Abstract in refereed journal
    International Journal of Particle Therapy 3(2016)1, 160
    DOI: 10.14338/IJPT.16-PTCOG-1.1

Permalink: https://www.hzdr.de/publications/Publ-23632
Publ.-Id: 23632


Novel Approach to utilize Proton Beams from High Power Laser Accelerators for Therapy

Masood, U.; Baumann, M.; Cowan, T. E.; Enghardt, W.; Herrmannsdörfer, T.; Hofmann, K. M.; Karsch, L.; Kroll, F.; Schramm, U.; Schürer, M.; Wilkens, J. J.; Pawelke, J.
please ask the authors
  • Poster
    7th International Particle Accelerator Conference (IPAC), 08.-13.05.2016, Busan, South Korea
  • Contribution to proceedings
    7th International Particle Accelerator Conference (IPAC), 08.-13.05.2016, Busan, South Korea
    Proceedings of IPAC2016, 978-3-95450-147-2, 1-3

Permalink: https://www.hzdr.de/publications/Publ-23631
Publ.-Id: 23631


In-vivo Simulation of the Relative Biological Effectiveness in Proton Therapy Using a Monte Carlo Method

Oesten, H.; Loeck, S.; Helmbrecht, S.; Tillner, F.; Wohlfahrt, P.; Schuemann, J.; Luehr, A.
urpose: In proton therapy, the relative biological effectiveness (RBE) – compared with conventional photon therapy – is routinely set to 1.1. However, experimental in vitro studies indicate evidence for the variability of the RBE. To clarify the impact on patient treatment, investigation of the RBE in a preclinical case study should be performed.
Methods: The Monte Carlo software TOPAS was used to simulate the radiation field of an irradiation setup at the experimental beamline of the proton therapy facility (OncoRay) in Dresden, Germany. Simulations were performed on cone beam CT-data of a xenogeneous mouse with an orthotopic lung carcinoma obtained by an in-house developed small animal image-guided radiotherapy device. A homogeneous physical fraction dose of 1.8Gy was prescribed for the contoured tumor volume. Simulated dose and linear energy transfer distributions were used to estimate RBE values in the mouse based on an RBE model by Wedenberg et al. To characterize radiation sensitivity of normal and tumor tissue, α/β-ratios were taken from the literature for NB1RGB (10.1Gy) and human squamous lung cancer (6.2Gy) cell lines, respectively.
Results: Good dose coverage of the target volume was achieved with a spread-out Bragg peak (SOBP). The contra-lateral lung was completely spared from receiving radiation. An increase in RBE towards the distal end of the SOBP from 1.07 to 1.35 and from 1.05 to 1.3 was observed when considering normal tissue and tumor, respectively, with the highest RBE values located distal to the target volume.
Conclusion: Modeled RBE values simulated on cone beam CT-data for experimental preclinical proton therapy varied with tissue type and depth in a mouse and differed therefore from a constant value of 1.1. Further translational work will include, first, conducting preclinical experiments and, second, analogous RBE studies in patients using experimentally verified simulation settings for our clinically used patient-specific beam conforming technique.
Keywords: proton therapy, cancer, hadron therapy, RBE, radiobiology, lung cancer, orthotopic tumor model, Monte Carlo, TOPAS
  • Contribution to proceedings
    AAPM Annual Meeting, 31.07.-04.08.2016, Washington, DC, USA
    Medical Physics 43, 3621
    DOI: 10.1118/1.4956868

Permalink: https://www.hzdr.de/publications/Publ-23630
Publ.-Id: 23630


The specific sorption of Np(V) on the corundum (α-Al2O3) surface in the presence of trivalent lanthanides Eu(III) and Gd(III): a batch sorption and XAS study

Virtanen, S.; Bok, F.; Ikeda-Ohno, A.; Rossberg, A.; Lützenkirchen, J.; Rabung, T.; Lehto, J.; Huittinen, N.
The sorption of pentavalent neptunium, Np(V), on corundum (α-Al2O3) was investigated in the absence and presence of trivalent europium or gadolinium as competing element under CO2-free conditions. The objective of this study was to investigate how a trivalent metal ion with a higher charge than that of the neptunyl ion would affect the sorption of Np(V) when allowed to adsorb on the mineral surface before the addition of Np(V). Batch sorption experiments conducted as a function of pH (pH-edges) and as a function of Np(V) concentration (isotherms) in the absence and presence of 1×10-5 M Eu(III) showed no sign of Eu being able to block Np sorption sites. Surface complexation modelling using the diffuse double layer model was employed to the batch data to obtain surface complexation constants for the formed Np(V) complexes on corundum. To account for potential changes occurring in the coordination environment of the neptunium ion in the presence of a trivalent lanthanide, X-ray absorption spectroscopic (XAS) studies of samples containing only Np(V) or Np(V) and Gd(III) were conducted. The XAS-measurements reveal the presence of a bidentate Np(V) edgesharing complex on the corundum surface in the absence of Gd(III). In the presence of Gd(III) our Np(V) EXAFS data show a contraction of the Np-Al distance together with the formation of an additional peak that is not resolved in the absence of the competing metal. These differences might point toward a change in the Np(V) surface configuration on corundum when Gd(III) is added to the sample before Np(V).
Keywords: Np(V), Eu(III), Gd(III), sorption competition, batch sorption, EXAFS

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Permalink: https://www.hzdr.de/publications/Publ-23628
Publ.-Id: 23628


Completing the nuclear reaction puzzle of the nucleosynthesis of 92Mo

Tveten, G. M.; Spyrou, A.; Schwengner, R.; Naqvi, F.; Larsen, A. C.; Eriksen, T. K.; Bellogarrote, F. L.; Bernstein, L. A.; Bleuel, D. L.; Crespo-Campo, L.; Guttormsen, M.; Giacoppo, F.; Görgen, A.; Hagen, T. W.; Hadynska-Klek, K.; Klintefjord, M.; Meyer, B. S.; Nyhus, H. T.; Renstrom, T.; Rose, S. J.; Sahin, E.; Siem, S.; Tornyi, T. G.
One of the greatest questions for modern physics to address is how elements heavier than iron are created in extreme, astrophysical environments. A particularly challenging part of that question is the description of the so-called p-nuclei, which are believed to be mainly produced in some types of supernovae.
In this work, we present for the first time measurements on the nuclear level density and average strength function of 92 Mo. State-of-the-art p-process calculations systematically underestimate the observed solar abundance. Our data provide stringent constraints on the 91 Nb(p,gamma92 Mo reaction rate, which is the last unmeasured reaction in the nucleosynthesis puzzle of 92 Mo. Based on our results, we conclude that the 92 Mo abundance anomaly is not due to the nuclear physics input.
Keywords: P-nuclei, p-process, nucleosynthesis, solar abundance, strength function, reaction rate

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Permalink: https://www.hzdr.de/publications/Publ-23627
Publ.-Id: 23627


Comprehensive UV/vis and Infrared Studies of Light-induced Carbon Monoxide Release From Ruthenium(II) Complexes

Kubeil, M.; Vernooij, R. R.; Wood, B. R.; Stephan, H.ORC; Graham, B.; Spiccia, L.
The use of carbon monoxide as a therapeutic agent has been demonstrated in pre-clinical trials, with CO-releasing molecules (CORMs) exhibiting anti-inflammatory, anti-proliferative, anti-apoptotic, anti-oxidative and vasodilatory effects. Organometallic compounds that can release CO in a highly controlled fashion under physiological conditions have therefore become a major field of scientific and medical research. Light-induced activation of CORMs is a controlled CO release approach that has received considerable attention. However, despite the number of photo-CORMs reported in the literature, their utility has been limited because excitation into the UV region results in low tissue penetrability and direct damage to healthy tissue. The challenge to extend the excitation wavelength further into the visible region of the electromagnetic spectrum has led us to explore the application of ruthenium(II) -carbonyl complexes as photo-CORMs.
Herein, we report the synthesis of ruthenium(II)-carbonyl complexes (Figure 1) functionalized with bidentate polypyridyl ligands and investigate the mechanism of CO release (before and after light-activation) using a combination of spectral techniques (UV/Vis, FTIR and Raman spectroscopy). The photo-induced CO-release kinetics of the Ru(II)-photo-CORMs, as well as the identity of the intermediates and photo-activated products, will be presented. These results have important implications in guiding the design of new photo-CORMs activated by visible light.
  • Lecture (Conference)
    27th International Conference on Organometallic Chemistry (ICOMC), 17.-22.07.2016, Melbourne, Australia

Permalink: https://www.hzdr.de/publications/Publ-23626
Publ.-Id: 23626


Experimental investigations on a common centrifugal pump operating under gas entrainment conditions

Schäfer, T.; Neumann, M.; Bieberle, A.; Hampel, U.
This paper presents an experimental study on the effects of additional gas entrainment in centrifugal pumps designed for conveying liquid phases only. The pump performance has been evaluated for several gas entrainment conditions, and for various operational settings of the pump, such as its alignment and the rotational speed of the impeller. As a main performance indicator the impact of entrained gas on the hydraulic power of the pump has been analyzed using experimental data. Additionally, high-resolution gamma-ray computed tomography (HireCT) operated in time-averaged rotation-synchronized scanning mode has been applied to quantify local phase fraction distributions inside the rapidly rotating pump impeller. Based on these quantitative tomographic measurements, gas holdup profiles along selected streamlines have been calculated and gas accumulation areas inside the impeller chambers have been visualized. Thus, various internally accumulated gas holdup patterns have been identified and, eventually, associated with characteristic pump performance behaviors. Moreover, the tomographic measuring method allowed an enhanced gas holdup analysis in specified pump compartments. As a result, the related specific gas and liquid phase holdup profiles have been evaluated.
Keywords: centrifugal pump, gas entrainment, two-phase flow, gas holdup, gamma-ray computed tomography

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Permalink: https://www.hzdr.de/publications/Publ-23625
Publ.-Id: 23625


Commissioning of a Compton Camera for particle beam range monitoring

Thirolf, P. G.; Aldawood, S.; Böhmer, M.; Bortfeldt, J.; Castelhano, I.; Dedes, G.; Enghardt, W.; Fiedler, F.; Gernhäuser, R.; Golnik, C.; Helmbrecht, S.; Hueso-González, F.; Kolff, H. V. D.; Kormoll, T.; Lang, C.; Liprandi, S.; Maier, L.; Marinšek, T.; Miani, A.; Pausch, G.; Petzoldt, J.; Pocevicius, M.; Römer, K.; Schaart, D. R.; Valencia-Lozano, I.; Parodi, K.
A Compton camera prototype for the position-sensitive detection of prompt γ rays from nuclear reactions between proton (or ion) beams and organic targets is being commissioned in Garching. The detector system is designed to allow for reconstructing the γ-source position from the Compton scattering kinematics of the primary photon as well as from tracking the Compton-scattered electron trajectory. The camera consists of a monolithic LaBr3(Ce) scintillation absorber crystal, read out by a 256-fold segmented multi-anode PMT and preceded by a stacked array of 6 double-sided silicon strip detectors acting as scatterers. The detector system has been calibrated and characterized in the laboratory as well as at different accelerator facilities, including clinical proton beams. Results from online commissioning runs will be presented, demonstrating excellent agreement between experimental prompt-γ spectra and Monte-Carlo simulations. Particular effort was dedicated to characterize the spatial resolution achievable with the monolithic LaBr 3 (Ce) scintillator when targeting the primary photon interaction position. Intense, tightly collimated 137Cs and 60Co sources were used for 2D irradiation scans as prerequisite for studying the performance of the “k-Nearest Neighbour”-algorithm developed in Delft and extending its applicability into the energy range beyond 511 keV. Systematic results of the monolithic scintillator’s spatial resolution will be presented as a function of the k-NN parameters (e.g. events per irradiation position) and the PMT segmentation, resulting in the realization of the presently optimum spatial resolution (3.8(2) mm @1.3 MeV) already for a reduced PMT segmentation (8x8). An outline of ongoing and planned further experimental activities and upgrade plans will be presented.
This work is supported by the DFG Cluster of Excellence MAP (Munich-Centre for Advanced Photonics).
Keywords: in-vivo dosimetry, prompt gamma, proton therapy, ion beam therapy, compton camera, cancer, radiooncology, imaging
  • Contribution to proceedings
    2016 IEEE Nuclear Science Symposium and Medical Imaging Conference (IEEE NSS/MIC), 29.10.-06.11.2016, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-23623
Publ.-Id: 23623


The inhibitory potency of polyoxometalates at P2X receptors

Spanier, C.; Abdelrahman, A.; Tang, J.; Hausmann, R.; Kortz, U.; Schmalzin, G.; Stephan, H.ORC; Wang, W.; Müller, C. E.
P2X receptors are trimeric ligand-gated ion channels activated by ATP and permeable for cations such as Na+, K+ and Ca2+. Seven different subunits exist, assembled as homo- or heterotrimers of various stoichiometry.1 Polyoxometalates (POMs) are polynuclear metal-oxo anions of early transition metals in high oxidation states (e. g. W6+, Mo6+, V5+). This class of inorganic metal cluster compounds exhibits great variability with respect to shape, size, charge and composition.2 POMs bear several negative charges and in this respect resemble ATP, which binds to P2X receptors in its negatively charged state. We previously found that certain POMs can inhibit ATP-hydrolyzing ectonucleotidases.2-4 In the present study we investigated whether tungsten-containing POMs can interact with P2X receptors. A series of POMs was investigated for their ability to inhibit ATP-induced calcium influx in recombinant 1321N1 astrocytoma cells stably transfected with P2X receptor subtypes. Several POMs were found to be highly potent inhibitors of P2X receptors exhibiting low nanomolar potency. PEGylation of POMs to increase their metabolic stability was tolerated by the receptors. Structure-activity relationships at P2X receptor subtypes differed from those observed for ecto¬nucleotidases. The majority of POMs were found to be non-cytotoxic at pharmacologically active concentrations.
  • Poster
    Frontiers in Medicinal Chemistry (FiMC) Meeting 2016, 13.-16.03.2016, Bonn, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-23622
Publ.-Id: 23622


Experimental and Theoretical Investigation of the Collection Efficiency of Air-Filled Ionization Chambers in Pulsed Radiation Fields of High Pulse Dose

Gotz, M.; Karsch, L.; Pawelke, J.
Ionization chambers are used in physical radiation research and are the most important dosimeters in radiation therapy. In this contribution an investigation of the collection efficiency by experiments and theoretical description is presented. The collection efficiency was measured for a plane-parallel advanced Markus ionization chamber (PTW 34045, 1 mm electrode spacing, 300 V nominal voltage), a chamber often used in clinical practice. The measurements were performed for collection voltages of 100 V and 300 V by irradiation with a pulsed electron beam of varied pulse dose up to approximately 600 mGy (0.8 nC liberated charge). These results are compared to existing descriptions of the collection efficiency and our own model based on a numeric solution by Euler method of a differential equation system modelling the processes within the chamber.
While the existing models accurately describe the collection efficiency at the lower collection voltage (100 V) they fail to reproduce the experimentally observed behavior at the higher collection voltage (300 V) particularly at high pulse doses. In contrast, our own numeric solution reproduces the collection efficiency at all tested voltages and pulse doses. This illustrates the importance of considering additional effects such as electric shielding by the liberated charges and field strength dependent attachment of electrons which are not considered in the existing models. Subsequently, the developed more accurate numeric solution might provide a valuable tool for future investigations.
  • Poster
    Nuclear Science Symposium & Medical Imaging Conference, 29.10.-06.11.2016, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-23621
Publ.-Id: 23621


Small, but hitting the target – towards novel nanoparticle platforms for diagnostic cancer imaging

Zarschler, K.
For effective localization of functionalized nanoparticles at diseased tissues such as solid tumours or metastases through biorecognition, appropriate targeting vectors directed against selected tumour biomarkers are a key prerequisite. The diversity of such vector molecules ranges from proteins, including antibodies and fragments thereof, through aptamers and glycans to short peptides and small molecules.
The presented work focusses on the epidermal growth factor receptor (EGFR) acting as a model receptor, since it is overexpressed and/or deregulated in a variety of solid tumours. Thus, bioconjugation of EGFR-specific single-domain antibodies (sdAbs) to different nanomaterials and characterization of sdAb-conjugates covering in vitro cancer cell imaging, cell proliferation as well as EGFR phosphorylation and signalling are described. The specificity of the sdAb-conjugates is investigated by way of receptor RNA silencing techniques with increasing complexity in vitro by introducing increasing concentrations of human or bovine serum. The results show that sdAb-functionalised nanomaterials can effectively target the EGFR, even in more complex bovine and human serum conditions where targeting specificity is largely conserved for increasing serum concentration. For highly affine targeting ligands such as sdAbs, targeting a receptor such as EGFR with low serum competitor abundance, receptor recognition function can still be partially realised in complex conditions. Moreover, sdAb-mediated biorecognition of EGFR is not restricted to particular nanomaterials, but was observed to work efficiently in combination with a variety of materials.
  • Lecture (others)
    Eingeladener Vortrag am Institut für Chemie der Universität Zürich, Schweiz, 29.01.2015, Zürich, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-23620
Publ.-Id: 23620


Small, but hitting the target – towards novel nanoparticle platforms for diagnostic cancer imaging

Zarschler, K.
For effective localization of functionalized nanoparticles at diseased tissues such as solid tumours or metastases through biorecognition, appropriate targeting vectors directed against selected tumour biomarkers are a key prerequisite. The diversity of such vector molecules ranges from proteins, including antibodies and fragments thereof, through aptamers and glycans to short peptides and small molecules.
The presented work focusses on the epidermal growth factor receptor (EGFR) acting as a model receptor, since it is overexpressed and/or deregulated in a variety of solid tumours. Thus, bioconjugation of EGFR-specific single-domain antibodies (sdAbs) to different nanomaterials and characterization of sdAb-conjugates covering in vitro cancer cell imaging, cell proliferation as well as EGFR phosphorylation and signalling are described. The specificity of the sdAb-conjugates is investigated by way of receptor RNA silencing techniques with increasing complexity in vitro by introducing increasing concentrations of human or bovine serum. The results show that sdAb-functionalised nanomaterials can effectively target the EGFR, even in more complex bovine and human serum conditions where targeting specificity is largely conserved for increasing serum concentration. For highly affine targeting ligands such as sdAbs, targeting a receptor such as EGFR with low serum competitor abundance, receptor recognition function can still be partially realised in complex conditions. Moreover, sdAb-mediated biorecognition of EGFR is not restricted to particular nanomaterials, but was observed to work efficiently in combination with a variety of materials.
  • Lecture (others)
    Eingeladener Vortrag am Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Australia, 27.11.2014, Melbourne, Australien

Permalink: https://www.hzdr.de/publications/Publ-23619
Publ.-Id: 23619


Specific nanoparticle targeting of the EGF-receptor using single-domain antibodies

Zarschler, K.; Rocks, L.; Mahon, E.; Prapainop, K.; Stephan, H.; Dawson, K. A.
Introduction
For effective localization of functionalized nanoparticles at diseased tissues such as solid tumors or metastases through biorecognition, appropriate targeting vectors directed against selected tumor biomarkers are a key prerequisite. The diversity of such vector molecules ranges from proteins, including antibodies and fragments thereof, through aptamers and glycans to short peptides and small molecules.
In the presented work we analyze the specific nanoparticle targeting capabilities of a small camelid single-domain antibody (sdAb), representing a potential recognition agent for the epidermal growth factor receptor (EGFR).

Methods
Bioconjugation of EGFR-specific sdAbs to different nanomaterials and characterization of sdAb-conjugates covering in vitro cancer cell imaging, cell proliferation as well as EGFR phosphorylation and signaling are described. The specificity of the sdAb-conjugates is investigated by way of receptor RNA silencing techniques with increasing complexity in vitro by introducing increasing concentrations of human or bovine serum.

Results and Discussion
The results show that sdAb-functionalized nanomaterials can effectively target the EGFR, even in more complex bovine and human serum conditions where targeting specificity is largely conserved for increasing serum concentrations. For highly affine targeting ligands such as sdAbs, targeting a receptor such as EGFR with low serum competitor abundance, receptor recognition function can still be partially realized in complex conditions. Moreover, sdAb-mediated biorecognition of EGFR is not restricted to particular nanomaterials, but was observed to work efficiently in combination with a variety of materials.
  • Lecture (Conference)
    ICONAN 2016 - International Conference on Nanomedicine and Nanobiotechnology 2016, 28.-30.09.2016, Paris, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-23618
Publ.-Id: 23618


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