Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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28429 Publications
Nanomagnet fabrication by ion beams
Fassbender, J.
Abstract: In recent years the tailoring of magnetic properties by means of ion irradiation and implantation techniques has become fashionable. Early investigations relied on the fact that the perpendicular magnetic anisotropy of Co/Pt multilayers depend sensitively on the interface sharpness [1]. Subsequently also the ion induced modification of exchange bias phenomena as well as interlayer exchange coupling have been investigated [2]. For single magnetic films ion implantation has been used to reduce the Curie temperature and hence the saturation magnetization [3]. Nowadays also the reverse process, i.e. the creation of nanomagnets within special binary alloys is employed [4,5]. In combination with lithography or with focused ion beams a pure magnetic patterning becomes possible [6] leading to hybrid magnetic materials [7] with properties different from both, the ion irradiated as well as the untreated material. Even ion induced chemical reduction can be employed to create a nanomagnetic pattern [8,9].
An overview of the present status in this research field will be given.
[1] C. Chappert et al., Science, 280 (1998) 1919.
[2] J. Fassbender, D. Ravelosona, Y. Samson, J. Phys. D, 37 (2004) R179. [3] J. Fassbender, J. McCord, Appl. Phys. Lett., 88 (2006) 252501.
[4] E. Menendez et al., Small, 5 (2009) 229.
[5] R. Bali et al., Nano Lett., 14 (2014) 435.
[6] J. Fassbender and J. McCord, J. Magn. Magn. Mater., 320 (2008) 579. [7] J. McCord, L. Schultz, J. Fassbender, Adv. Mater., 20 (2008) 2090.
[8] S. Kim et al., Nature Nanotechnology, 7 (2012) 567.
[9] J. Fassbender, Nature Nanotechnology, 7 (2012) 554.
Keywords: magnetism, ion irradiation, magnetic patterning
  • Invited lecture (Conferences)
    Moscow International Symposium on Magnetism, 01.-05.07.2017, Moscow, Russia

Registration No. 26191 - Permalink


Interaction between Double Diffusive Convection and Solidification in Ammonium-Chloride Solutions
Anders, S.; Eckert, S.
Abstract: This paper presents an experimental investigation of thermally and chemically driven
convection with simultaneous crystallisation in a concentrated aqueous ammonium-chloride
solution. Measurements were performed in a transparent Hele-Shaw cell (200·100·10mm3)
between two massive copper blocks equipped with internal water channels controlling the
thermal boundary conditions at the upper and lower horizontal boundaries. The temperatures
were regulated by thermostats in a range between -20°C and +40°C giving Rayleigh
numbers up to around 0.2·10 9 . A double-wall construction with climatisation was implemented
in order to avoid thermal losses through the side walls. Temperatures were monitored by
thermocouples calibrated to an accuracy better than 0.05K.
Various flow regimes were studied by choosing different temperature boundary conditions.
The focus was on configurations with negative vertical temperature gradients where thermal
convection occurs once a critical temperature difference is exceeded. At sufficient
supercooling free crystals nucleate in the upper part of the cell, grow and descend due to
their higher density compared to the ambient fluid.
The flow field in the liquid was measured by PIV using fluorescent tracer-particles and laser
illumination. PTV with LED-background lighting was used to determine the size-evolution and
the trajectories of the free-moving crystals. The application of alternating lighting methods
and advanced digital image filtering allows for simultaneous operation of PIV and PTV. This
approach enables a quantitative study of the interplay of different convection regimes and the
solidification process. For example the relation between drag-coefficient, crystal size and
crystal growth was investigated.
As a reference case a stable stratification resulting from parallel cooling of the top and
bottom walls was investigated. The following solidification phenomena were observed during
the experiments: columnar growth at the walls, nucleation and growth of equiaxed crystals in
the bulk, chimney-formation in the mushy layer as well as the remelting of columnar and
equiaxed dendrites.
Keywords: equiaxed solidification, double diffusive convection, dual phase velocimetry, PTV, PIV
  • Lecture (Conference)
    SP17, Solidification Processing 2017, 25.-28.07.2017, Beaumont Estate, Old Windsor, United Kingdom
  • Contribution to proceedings
    SP17, Solidification Processing 2017, 25.-28.07.2017, Beaumont Estate, Old Windsor, United Kingdom
    Proceddings of the 6th Decennial International Conference on Solidification Processing, London: BCAST, Brunel University London, 978-1-908549-29-7, 350-353

Registration No. 26185 - Permalink


Combined experimental and numerical analysis of a bubbly liquid metal flow
Krull, B.; Strumpf, E.; Keplinger, O.; Shevchenko, N.; Fröhlich, J.; Eckert, S.; Gerbeth, G.
Corresponding author: Krull, B. TU Dresden
Abstract: The paper proposes a combined experimental and numerical procedure for the investigation of bubbly liquid-metal flows. It describes the application to a model configuration consisting of a recirculating GaInSn flow driven by an argon bubble chain. The experimental methods involve X-ray measurements to detect the bubbles and UDV measurements to gain velocity information about the liquid metal. The chosen numerical method is an immersed boundary method extended to deformable bubbles. The model configuration includes typical phenomena occurring in industrial applications and allows insight into the physics of bubbly liquid-metal flows. It constitutes an attractive test case for assessing further experimental and numerical methods.
Keywords: Bubbly liquid-metal flows, Xray radiography, UDV, GaInSn

Registration No. 26184 - Permalink


Decoupling the two roles of Ga droplets in the self-catalyzed growth of GaAs nanowires on SiOx/Si(111) substrates
Tauchnitz, T.ORC; Nurmamytov, T.; Hübner, R.; Engler, M.ORC; Facsko, S.; Schneider, H.; Helm, M.; Dimakis, E.ORC
Corresponding author: Dimakis, Emmanouil
Abstract: Liquid Ga droplets play a double role in the self-catalyzed growth of GaAs nanowires on Si(111) substrates covered with a native SiOx layer: they induce the formation of nano-sized holes in SiOx and then drive the uniaxial nanowire growth directly onto the underlying Si. The independent control of the two mechanisms is a prerequisite for mastering the growth of nanowires, but it is challenging in a conventional growth procedure where they both take place under the same droplets. To that end, we have developed an in situ procedure where the Ga droplets used for the formation of SiOx holes are removed before new Ga droplets drive the growth of GaAs nanowires. In that way, it was made possible to study the interaction between Ga droplets and SiOx, to create holes in SiOx with controlled number density and size and, finally, to grow GaAs nanowires only within those holes. Our results show unprecedented control of the nanowire nucleation with unique possibilities: (1) deliberate control of the number density of nanowires within three orders of magnitude (106-109 cm-2) without patterning the substrate and without changing the growth conditions, (2) highly synchronous nucleation events and, thus, exceptionally narrow nanowire length distributions (standard deviation < 1 % for 3 mm long nanowires), (3) high yield of vertical nanowires up to 80 % (against GaAs islands), (4) highly reproducible results, and (5) independent control of the nanowire diameter from the number density. We anticipate that our methodology could be also exploited for different materials or other types of nanostructures.

Registration No. 26174 - Permalink


Bioflotation with amphiphilic siderophores
Schrader, S.; Kutschke, S.; Pollmann, K.; Rudolph, M.
Abstract: Siderophores are small organic molecules with a high affinity for binding Fe(III) and the ability to form strong complexes. They are produced by microorganisms (aerobic bacteria and fungi) and some plants to equalize the low bioavailability of iron in their environment.
The biotechnological production of siderophores offers the application in very different fields. For example, they are used as medicine against iron or heavy metal poisoning. Other applications are their utilization for the extraction, recovery and treating of iron as well as other elements, that also can be bound by siderophores. In addition, their application in froth flotation processes could be an attractive novel approach. Molecules produced by the chemical industry with functional groups like hydroxamates have been already applied successfully in this processing method. It can be suggested that siderophores carrying the same functional groups should also work well as collectors. Particularly the group of amphiphilic siderophores that have both hydrophilic and hydrophobic areas are very interesting. The natural hydrophobic property of these chelating agents could avoid additional chemicals and further working steps for making the target mineral particles hydrophobic for an efficient flotation process.
The main advantage of using biotechnology for the production of siderophores is the wide natural diversity of the structures. A lot of microorganisms and their produced siderophores have already been identified and analyzed in detail. So there is an enormous variety of different molecules available. The aim of this study is to test for the first time, whether it is possible to use siderophores in flotation processes. In addition optimized processes for both the biotechnological production and the froth flotation have to be developed. This presupposes also the investigation and characterization of the binding properties during these procedures.
  • Lecture (Conference)
    Mineral Engineering Conference 2017, 20.-23.09.2017, Wisła, Poland

Registration No. 26171 - Permalink


Production of amphiphilic hydroxamate siderophore marinobactin by Marinobacter sp. DS40M6 for bioflotation process
Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.
Abstract: Siderophores are small biomolecules (400-1500 Da) with the ability to form strong complexes with Fe(III) and other metals. A wide range of siderophore structures are already well-known.
The biotechnological production of these organic compounds with bacteria enables them to be used for extracting and recycling metals.
The application of siderophores in traditional froth flotation process enables the development of a sustained bioflotation.
Keywords: siderophores; marinobactin; bioflotation
  • Poster
    22. International Biohydrometallurgy Symposium 2017, 24.-27.09.2017, Freiberg, Deutschland

Registration No. 26169 - Permalink


Variability in crystal surface reactivity: A critical constraint for reactive transport modeling
Fischer, C.
Abstract: Reactive transport modeling of fluid-solid interactions relies on (i) contrasts in fluid flow velocity and (ii) variability of surface reactivity. The first point is based on data from, e.g., PET and µCT techniques. The second point, however, is usually addressed by simple kinetic data only. Thus, it neglects information about the intrinsic variability of crystal surface reactivity that often results in a rate range of 2-3 orders of magnitude (1). Such variability is however an important constraint for the evolution of surface roughness and porosity pattern in crystalline matter (2). Here, we highlight important sources of the intrinsic variability of crystal surface reactivity and their impact on surface reaction rates. Rate maps (3) and rate spectra (4) provide critical information about the spatial and temporal variability of surface reactivity that is required to predict the evolution of porosity pattern in crystalline matter (5).

1. Luttge A, Arvidson RS, & Fischer C (2013) A Stochastic Treatment of Crystal Dissolution Kinetics. Elements 9(3):183-188.
2. Fischer C, Kurganskaya I, Schäfer T, & Luttge A (2014) Variability of Crystal Surface Reactivity: What do we know? (Review Article). Applied Geochemistry 43:132-157.
3. Fischer C & Luttge A (2017) Beyond the conventional understanding of water–rock reactivity. Earth and Planetary Science Letters 457:100-105.
4. Fischer C, Arvidson RS, & Luttge A (2012) How predictable are dissolution rates of crystalline material? Geochimica et Cosmochimica Acta 98:177-185.
5. Michaelis M, Fischer C, Colombi Ciacchi L, & Luttge A (2017) Variability of Zinc Oxide Dissolution Rates. Environmental Science & Technology 51(8):4297-4305.
  • Poster
    Reactive Transport in the Earth and Environmental Sciences in the 21st Century, 02.-05.10.2017, Amboise, Frankreich

Registration No. 26168 - Permalink


Manipulation of antiferromagnetic domain distribution in Mn2Au by ultrahigh magnetic fields and by strain
A. A. Sapozhnik, A. A.; Abrudan, R.; Skourski, Y.; Jourdan, M.; Zabel, H.; Kläui, M.; Elmers, H. J.
Corresponding author: A. A. Sapozhnik, A. A. Institute of Physics, Johannes Gutenberg-University Mainz and Graduate School of Excellence, Materials Science in Mainz (MAINZ), Mainz, Germany
Abstract: Evidence for a spin reorientation in antiferromagnetic (AFM) Mn2Au thin films induced by high magnetic fields as well as by the application of in-plane mechanical stress is provided. The AFM domain population in the samples was investigated by resonant X-ray Magnetic Linear Dichroism (XMLD) measurements at the L3 edge of Mn using a variable linear polarization of the incident photon beam. As grown samples show no XMLD signal due to averaging over a random AFM domain distribution. After the exposure to a 70 T in-plane magnetic field a clear XMLD signal indicating the generation of a preferential AFM domain orientation is obtained. The same type of XMLD signal is observed when the thin films are strained, demonstrating the feasibility of AFM Domain manipulation by magnetic fields and stress in Mn2Au.

Registration No. 26167 - Permalink


Magnetic structure in a U(Ru0.92Rh0.08)2Si2 single crystal studied by neutron diffraction in static magnetic fields up to 24 T
Prokes, K.; Bartkowiak, M.; Rivin, O.; Prokhnenko, O.; Förster, T.; Gerischer, S.; Wahle, R.; Huang, Y.-K.; Mydosh, J. A.
Corresponding author: Prokes, K. Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
Abstract: We report a high-field-induced magnetic phase in a single crystal of U(Ru0.92Rh0.08)2Si2. Our neutron study, combined with high-field magnetization, shows that the magnetic phase above the first metamagnetic transition at μ0H = 21.6 T has an uncompensated commensurate antiferromagnetic structure with a propagation vector Q2 = (2/3 0 0) possessing two single-Q domains. U moments of 1.45(9)μB directed along the c axis are arranged in an up-up-down sequence propagating along the a axis, in agreement with bulk measurements. The U magnetic form factor at high fields is consistent with both the U3+ and U4+ types. The low-field short-range order that emerges from pure URu2Si2 due to Rh doping is initially strengthened by the field but disappears in the field-induced phase. The tetragonal symmetry is preserved across the transition, but the a-axis lattice parameter increases already at low fields. Our results are in agreement with an itinerant electron model with 5f states forming bands pinned in the vicinity of the Fermi surface that is significantly reconstructed by the applied magnetic field.

Registration No. 26166 - Permalink


Magnetic field induced tunneling and relaxation between orthogonal configurations in solids and molecular systems
Averkiev, N. S.; Bersuker, I. B.; Gudkov, V. V.; Zhevstovskikh, I. V.; Baryshnikov, K. A.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Korostelin, Y. V.
Corresponding author: Averkiev, N. S. Ioffe Institute, St. Petersburg, Russia
Abstract: We report the effect of magnetic field induced quantum tunneling and relaxation transitions between orthogonal configurations in polyatomic systems where no tunneling is expected. Typical situations of this kind occur in molecular systems and local centers in crystals in ground and excited electronic T states, subject to the T⊗e problem of the Jahn-Teller effect, where the wave functions of the three tetragonally distorted configurations are orthogonal. A detailed microscopic theory of this effect shows how the magnetic field violates the orthogonality between the latter allowing for tunneling and relaxations, which decrease in strong fields due to the induced decoherence. The novel effect is demonstrated experimentally as a big, sharp peak in ultrasound attenuation by Cr2+ centers in ZnSe:Cr2+ in the magnetic field B = 0.15 T at the temperature below 8 K. It may influence a variety of magnetic, electronic, and photonic properties of any system in an electronic T state.

Registration No. 26165 - Permalink


Structural and thermodynamic investigation of AnIVLI(O)HOPO(Article)
Aupiais, J.; Younes, A.; Moisy, P.; Hennig, C.; Rossberg, A.; Brunel, B.; Kerbaa, M.; Vidaud, C.; Den Auwer, C.
Corresponding author: Den Auwer, C. Université Côte d'Azur, CNRS, Institut de Chimie de Nice, France
Abstract: For the first time, capillary electrophoresis coupled with inductively coupled plasma mass spectrometry has been used to determine the stability constants of PuIV with the multidentate hydroxypyridinonate chelating agents 3,4,3-LI(1,2-HOPO) and 5-LIO(Me-3,2-HOPO) in 0.1 M NaNO3 solution, pcH = 1.395 at 25 °C through competition with the NTA ligand. The limiting electrophoretic mobility was found to be zero for AnIV[5-LIO(Me-3,2-HOPO)] and slightly positive for AnIV[3,4,3-LI(1,2-HOPO)] (AnIV = Th, Pu). They were respectively assigned to the formation of the 1:2 neutral species An[5-LIO(Me-3,2-HOPO)]2 and a mixture of the neutral species AnIV[3,4,3-LI(1,2-HOPO)] and its protonated form AnIVH[3,4,3-LI(1,2-HOPO)]+. The corresponding stability constants of ThIV with both chelators were evaluated through the same experiments for the sake of comparison. The stability of both PuIV-HOPOs was about ten orders of magnitude better than that of the equivalent ThIV complexes. To complement these thermodynamic data, structural parameters of Pu[3,4,3-LI(1,2-HOPO)] and Th[3,4,3-LI(1,2-HOPO)] complexes in solution have been derived from EXAFS experiments and compared to previously reported crystallographic structures.

Registration No. 26162 - Permalink


Calibration of scintillation screens for ultrashort electron bunch detection
Kurz, T.; Couperus, J. P.ORC; Krämer, J. M.; Ding, H.; Kuschel, S.; Köhler, A.; Zarini, O.; Hollatz, D.; Schinkel, D.; D‘Arcy, R.; Schwinkendorf, J. P.; Irman, A.; Schramm, U.; Karsch, S.
Abstract: This work reports on the calibration of scintillating screens for diagnoses of high-charge density electron beams origination from laser plasma accelerators (LPA). Our setup at the conventional ELBE accelerator is cross-calibrated with an integrating current transformer (ICT) and allows for calibration over a large charge density range, thus enabling the study both the linear and non-linear scintillating screen response, as well as long-term stability tests of the screens. In contrast to previous works, the calibration presented here is performed under conditions with a close mimic to real experimental LPA conditions.
A linear response of the scintillator to the applied electron charge was found, followed by a saturation process starting in the range of nC/mm^2. Mimicking a 1-Hz LPA, long–term stability tests showed a significant decrease of the scintillation efficiency over time.
Finally, we present a method where a LED-based constant light source provides an easy method for absolute calibration of charge diagnostic systems at LPAs. This method eliminates many potential error sources existing in currently used methods and enables the transfer of absolute charge calibrations between laboratories.
  • Poster
    3rd European Advanced Accelerator Concepts Workshop, 24.-30.09.2017, Isola d'Elba, Italy

Registration No. 26161 - Permalink


Demonstration of a beam loaded nanocoulomb-class laser wakefield accelerator
Couperus, J. P.ORC; Pausch, R.; Köhler, A.; Zarini, O.; Krämer, J. M.; Kurz, T.; Garten, M.; Huebl, A.; Gebhardt, R.; Helbig, U.; Bock, S.; Zeil, K.; Debus, A.; Bussmann, M.; Schramm, U.; Irman, A.
Abstract: Laser-plasma wakefield acceleration is capable of producing quasi-monoenergetic electron beams reaching into the GeV range with few-femtoseconds bunch duration. Scaling the charge to the nanocoulomb range would yield hundreds of kiloamperes peak-current and stimulate the next generation of radiation sources covering high-field THz, high-brightness X-ray and γ-ray sources, compact FELs and laboratory-size beam-driven plasma accelerators. Laser-plasma accelerators generating such high currents operate in the beam loading regime where the accelerating field is strongly modified by the self-fields of the injected bunch, improving the final beam quality if appropriately controlled. Here we experimentally investigate the effects of beam loading at the theoretically predicted limit by loading unprecedented charges of about 0.5 nC within a mono-energetic peak into the first plasma cavity. As the energy balance is reached, the final energy spread is minimized. We show that the beam quality is maintained up to an estimated peak-current of 50 kA, an order of magnitude larger than in state-of-the-art conventional and laser-plasma accelerators.
  • Lecture (Conference)
    3rd European Advanced Accelerator Concepts Workshop, 24.-30.09.2017, Isola d'Elba, Italy

Registration No. 26160 - Permalink


Research on the chemistry of f-elements at HZDR - A general overview of the division Chemistry of the f-Elements
Ikeda-Ohno, A.ORC
Abstract: Established in June 2014, the division Chemistry of the f-Elements at the Institute of Resource Ecology (IRE) is conducting research on the fundamental physics/chemistry of f-elements, i.e. actinides and lanthanides. This presentation intends to provide a general overview of the recent research activities in the division, in order to possible research overlapping between HZDR-IRE and CEA-Marcoule for future collaborations.
Keywords: actinides, f-elements, coordination, chemistry
  • Lecture (others)
    Internal colloquium, 05.10.2017, CEA-Marcoule, France

Registration No. 26159 - Permalink


Ion Beam Induced Surface Modification of ta-C Thin Films
Berova, M.; Sandulov, M.; Tsvetkova, T.; Kitova, S.; Bischoff, L.; Boettger, R.
Corresponding author: Tsvetkova, T. BAS
Abstract: Thin film samples (d ~ 40 nm) of tetrahedral amorphous carbon (ta-C), deposited by filtered cathodic vacuum arc, were implanted with Ga+ at ion energy E = 20 keV and ion fluences D = 3E14 - 3E15 cm-2 and N+ with the same energy and ion fluence D = 3 E14 cm-2. The Ga+ ion beam induced surface structural modification of the implanted material, displayed by formation of new phase at non-equilibrium condition, which could be accompanied by considerable changes in the optical properties of the ta-C films. The N+ implantation also results in modification of the surface structure. The induced structural modification of the implanted material results in a considerable change of its topography and optical properties. Nanoscale topography and structural properties characterisation of the Ga+ and N+ implanted films were performed using atomic spectroscopy analysis. The observed considerable surface structural properties modification in the case of the higher fluence Ga+ implanted samples results from the relatively high concentration of introduced Ga+ atoms, which is of the order of those for the host element.
Keywords: carbon, ion implantation, atomic force microscopy

Registration No. 26157 - Permalink


Visualization of gas-liquid multiphase pseudo-slug flow using Wire-Mesh Sensor
Kesana, N. R.; Parsi, M.; Vieira, R. E.; Azzopardi, B.; Schleicher, E.; Mclaury, B. S.; Shirazi, S. A.; Hampel, U.
Corresponding author: Kesana, N. R. Process and Fluid Flow Technology Department, Institute for Energy Technology, P. O. Box 40, Kjeller, Norway
Abstract: Intermittent two-phase flows are commonly encountered in the petroleum industry. Much attention has been focused by several researchers on intermittent flows existing at low superficial gas velocities (<10 m/s). There is limited work performed on intermittent structures persisting at higher superficial gas velocities (pseudo-slug flows). In the present experimental study, a conductivity-based Wire-Mesh Sensor (WMS) was used to visualize and characterize pseudo-slug flow. Experiments were performed in a 76.2 mm horizontal pipe with air and water as the working fluids at atmospheric conditions. The superficial gas and liquid velocities ranged from 9 m/s to 35 m/s and 0.45 m/s to 0.76 m/s, respectively. A 16 × 16 WMS was placed 17 m away from the pipe inlet to measure spatio-temporal void-fraction distribution. The WMS data acquisition frequency was set to 10 kHz. From the void-fraction time series data, the periodic pseudo-slug structures were visualized. The visualization suggested that unlike slug flow where the liquid structures fill the pipe cross-section, the pseudo-slugs were extremely aerated structures (high gas-liquid mixing) formed due to the gas penetration into the liquid slug body. This paper also presents the measurements of important hydrodynamic characteristics such as cross-sectional averaged void-fraction time series and mean void fraction. The effect of liquid viscosity on the visualized structures is also presented.
Keywords: Flow visualization Intermittent multiphase flows Pseudo-slug flow Slug flow Wire-mesh sensor

Registration No. 26156 - Permalink


Fission and other fast neutron induced reactions investigated at nELBE
Beyer, R.ORC; Junghans, A. R.; Dietz, M.; Kögler, T.; Schwengner, R.; Urlaß, S.; Wagner, A.
Abstract: The nELBE neutron time-of-flight facility provides neutrons in the energy range from about 10 keV up to 10 MeV with an intensity of about 10⁴ n/s/cm². The combination of the superconducting electron accelerator ELBE and a compact liquid lead neutron production target delivers neutron bunches within a time spread of a few picoseconds and a repetition rate of 100 to 400 kHz (cw) enabling high resolution time-of-flight measurement even with flight paths of only 5 to 11 meters. At nELBE different types of fast neutron induced nuclear reactions can be and have been investigated, ranging from total neutron cross section measurement over elastic and inelastic scattering to neutron induced fission. E.g. the neutron induced fission cross section of Pu-242 has been measured in the range from 0.5 to 10 MeV relative to U-235(n,fis) using two fission ionization chambers. A statistical uncertainty down to 1.1 % and systematic uncertainty of about 2.7 % was reached.
Keywords: nELBE, neutron time-of-flight, transmission, inelastic scattering, fission
  • Poster
    LANL FIESTA Fission School & Workshop, 17.-22.09.2017, Santa Fe, New Mexico, USA

Registration No. 26155 - Permalink


Fission measurements at nELBE
Beyer, R.ORC; Dietz, M.; Junghans, A. R.; Kögler, T.; Schwengner, R.; Urlaß, S.
Abstract: The nELBE neutron time-of-flight facility provides neutrons in the energy range from about 10 keV up to 10 MeV with an intensity of about 104 n/s/cm2. The combination of the superconducting electron accelerator ELBE and a compact liquid lead neutron productiontarget delivers neutron bunches within a time spread of a few picoseconds and a repetition rate of 100 to 400 kHz (cw) enabling high resolution time-of-flight measurement even with flight paths of only 5 to 11 meters. At nELBE different types of fast neutron induced nuclear reactions can be and have been investigated, ranging from total neutron cross section measurement over elastic and inelastic scattering to neutron induced fission. E.g. the neutron induced fission cross section of 242Pu has been measured in the range from 0.5 to 10 MeV relative to 235U(n,f) using two fission ionization chambers. A statistical uncertainty down to 1.1% and systematic uncertainty of about 2.7% was reached.
Keywords: nELBE, neutron time-of-flight, fission
  • Invited lecture (Conferences)
    LANL FIESTA Fission School & Workshop, 17.-22.09.2017, Santa Fe, New Mexico, USA

Registration No. 26154 - Permalink


Magnetic field induced strong valley polarization in the three-dimensional topological semimetal LaBi
Kumar, N.; Shekhar, C.; Klotz, J.; Wosnitza, J.; Felser, C.
Corresponding author: Felser, C. Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
Abstract: LaBi is a three-dimensional rocksalt-type material with a surprisingly quasi-two-dimensional electronic structure. It exhibits excellent electronic properties such as the existence of nontrivial Dirac cones, extremely large magnetoresistance, and high charge-carrier mobility. The cigar-shaped electron valleys make the charge transport highly anisotropic when the magnetic field is varied from one crystallographic axis to another. We show that the electrons can be polarized effectively in these electron valleys under a rotating magnetic field. We achieved a polarization of 60% at 2 K despite the coexistence of three-dimensional hole pockets. The valley polarization in LaBi is compared to the sister compound LaSb where it is found to be smaller. The performance of LaBi is comparable to the highly efficient bismuth.

Registration No. 26153 - Permalink


Charge Density Waves in Graphite: Towards the Magnetic Ultraquantum Limit
Arnold, F.; Isidori, A.; Kampert, E.; Yager, B.; Eschrig, M.; Saunders, J.
Corresponding author: Arnold, F. Royal Holloway, University of London, Egham, United Kingdom
Abstract: Graphite is a model system for the study of three-dimensional electrons and holes in the magnetic quantum limit, in which the charges are confined to the lowest Landau levels.We report magneto-transport measurements in pulsed magnetic fields up to 60 T, which resolve the collapse of two charge density wave states in two, electron and hole, Landau levels at 52.3 and 54.2 T, respectively. We report evidence for a commensurate charge density wave at 47.1 T in the electron Landau level, and discuss the likely nature of the density wave instabilities over the full field range. The theoretical modeling of our results predicts that the ultraquantum limit is entered above 73.5 T. This state is an insulator, and we discuss its correspondence to the “metallic” state reported earlier.We propose that this (interaction-induced) insulating phase supports surface states that carry no charge or spin within the planes, but does, however, support charge transport out of plane.

Registration No. 26152 - Permalink


Magnetic field induced phase transitions and phase diagrams of multiferroic Mn0.95Co0.05WO4 with cycloidal spin structure
Urcelay-Olabarria, I.; Ressouche, E.; Wang, Z.; Skourski, Y.; Ivanov, V. Y.; Popov, Y. F.; Vorobev, G. P.; Balbashov, A. M.; Qureshi, N.; Garcia-Munoz, J. L.; Skumryev, V.; Mukhin, A. A.
Corresponding author: Urcelay-Olabarria, I. Departamento de Física Aplicada I, Escuela de Ingeniería de Bilbao, Universidad del País Vasco, Bilbao, Spain
Abstract: Slightly Co-doped MnWO4 at the lowest 5% Co concentration, for which the multiferroic cycloidal phase becomes a ground state, has been studied in magnetic fields up to 60 T by bulk magnetic and electric polarization measurements along different crystallographic directions. The field induced magnetic transitions up to 12 T and the ways they proceed were tracked also by single-crystal neutron diffraction, and the relevant field induced magnetic structures were identified and refined. The complete magnetoelectric phase diagrams for magnetic fields along distinct directions in relation to the cycloidal spin structure have been constructed for magnetic field values exceeding those necessary to induce a spin-flip transition into the paramagnetic state. Their common feature is the existence of nonpolar sinusoidal phases identified by the disappearance of the electric polarization in a field regime slightly below the spin-flip transition. At lower magnetic fields either continuous or abrupt field induced reorientations of the cycloidal magnetic structures were observed, respectively, for a field direction along the crystallographic b axis or along the easy magnetic axis, and the different character of those transitions has been attributed to specific features in the magnetic anisotropy.

Registration No. 26151 - Permalink


Structural and Magnetic Properties of the Trirutile-type 1D-Heisenberg Anti-Ferromagnet CuTa2O6
Golubev, A.; Dinnebier, R. E.; Schulz, A.; Kremer, R. K.; Langbein, H.; Senyshyn, A.; Law, J. M.; Hansen, T. C.; Koo, H.-J.; Whangbo, M.-H.
Corresponding author: Kremer, R. K. Max Planck Institute for Solid State Research, Stuttgart, Germany
Abstract: We prepared trirutile-type polycrystalline samples of CuTa2O6 by low-temperature decomposition of a Cu−Ta−oxalate precursor. Diffraction studies at room temperature identified a slight monoclinic distortion of the hitherto surmised tetragonal trirutile crystal structure. Detailed high-temperature X-ray and neutron powder diffraction investigations as well as Raman scattering spectroscopy revealed a structural phase transition at 503(3) K from the monoclinic structure to the tetragonal trirutile structure. GGA+U density functional calculations of the spin-exchange parameters as well as magnetic susceptibility and isothermal magnetization measurements reveal that CuTa2O6 is a new 1D Heisenberg magnet with predominant anti-ferromagnetic nearest-neighbor intrachain spin-exchange interaction of ∼50 K. Interchain exchange is a factor of ∼5 smaller. Heat capacity and low-temperature high-intensity neutron powder diffraction studies could not detect long-range order down to 0.45 K.

Registration No. 26149 - Permalink


QMOM methods for bubbly flows –potentials for simulation of pumps
Hasse, C.; Salenbauch, S.; Pollack, M.; Oertel, R.; Li, D.; Schlegel, F.; Lucas, D.
Abstract: The temporal and spatial development of a particle size distribution, e.g. in a bubbly flow, can be described with the so-called Population Balance Equation. It represents a continuity statement for the number density of particles in a flow. The presentation contains a comparison of two prominent approaches for solving the population balance equation, i.e. the family of Quadrature-based Moment Methods and the Method of Classes.
Keywords: Population Balance Modeling, Quadrature-based Method of Moments, Class Methods, Pumps
  • Lecture (others)
    VDMA AK-Mehrphasenströmung, 26.09.2017, Frankfurt, Deutschland

Registration No. 26147 - Permalink


Negative Longitudinal Magnetoresistance from the Anomalous N = 0 Landau Level in Topological Materials
Assaf, B. A.; Phuphachong, T.; Kampert, E.; Volobuev, P. S.; Mandal, P. S.; Sanchez-Barriga, J.; Rader, O.; Bauer, G.; Springholz, G.; de Vaulchier, L. A.; Guldner, Y.
Corresponding author: Assaf, B. A. Département de Physique, Ecole Normale Supérieure, PSL Research University, CNRS, Paris, France
Abstract: Negative longitudinal magnetoresistance (NLMR) is shown to occur in topological materials in the extreme quantum limit, when a magnetic field is applied parallel to the excitation current. We perform pulsed and dc field measurements on Pb1−xSnxSe epilayers where the topological state can be chemically tuned. The NLMR is observed in the topological state, but is suppressed and becomes positive when the system becomes trivial. In a topological material, the lowest N = 0 conduction Landau level disperses down in energy as a function of increasing magnetic field, while the N = 0 valence Landau level disperses upwards. This anomalous behavior is shown to be responsible for the observed NLMR. Our work provides an explanation of the outstanding question of NLMR in topological insulators and establishes this effect as a possible hallmark of bulk conduction in topological matter.

Registration No. 26146 - Permalink


Interplay between localization and magnetism in (Ga,Mn)As and (In,Mn)As
Yuan, Y.; Xu, C.; Hübner, R.; Jakiela, R.; Böttger, R.; Helm, M.; Sawicki, M.; Dietl, T.; Zhou, S.
Corresponding author: Yuan, Y.
Abstract: Ion implantation of Mn combined with pulsed laser melting is employed to obtain two representative compounds of dilute ferromagnetic semiconductors (DFSs): Ga1−xMnxAs and In1−xMnxAs. In contrast to films deposited by the widely used molecular beam epitaxy, neither Mn interstitials nor As antisites are present in samples prepared by the method employed here. Under these conditions the influence of localization on the hole-mediated ferromagnetism is examined in two DFSs with a differing strength of p-d coupling. On the insulating side of the transition, ferromagnetic signatures persist to higher temperatures in In1−xMnxAs compared to Ga1−xMnxAs with the same Mn concentration x. This substantiates theoretical suggestions that stronger p-d coupling results in an enhanced contribution to localization, which reduces hole-mediated ferromagnetism. Furthermore, the findings support strongly the heterogeneous model of electronic states at the localization boundary and point to the crucial role of weakly localized holes in mediating efficient spin-spin interactions even on the insulator side of the metal-insulator transition.

Registration No. 26145 - Permalink


Geostatistical simulation of compositional data in the presence of several geological domains
Talebi, H.; Tolosana-Delgado, R.; Lo, J.; Mueller, U.
Abstract: This paper proposes a methodology for geostatistical simulation of compositional data in presence of several geological domains: After applying statistical analysis and compositionally compliant contact analysis on the data set, geological domains with the same compositional characteristics are merged. Plurigaussian simulation (PGS) is utilized to generate multiple numerical models of the remaining domains, with the aim of assessing the uncertainty in the domain boundaries and improving the geological controls in the characterization of compositional attributes. The resulting conditional realisations of geological domains are used to derive the posterior probabilities of occurrence of the domains over the deposit. The compositional data set is classified by geological domain and for each class realisations are generated across the target grid of the resource. The final mineral resource model is obtained by weighting the simulated mineral compositions associated with the different domains by the probabilities of occurrence of each domain. This approach accounts for the uncertainty in the geology of the ore body and spatial variability of mineral composition.

The approach is illustrated through an application to a nickel-cobalt laterite deposit located in Western Australia. A set of 8818 samples is considered in order to provide the conditioning data. Four rock types (Ferruginous, Smectite, Saprolite, and Ultramafic) are considered to define compositionally homogeneous domains. Three major (Fe, Al, and Mg) and two target (Ni and Co) elements are the variables of interest in this study. Since the data are compositional a filler variable is introduced to achieve closure and to retain the intuitive relation between each component and the mass of its associated element.
  • Lecture (Conference)
    Annual Conference of the International Association for Mathematical Geosciences, 04.-07.09.2017, Fremantle, Perth, Australia

Registration No. 26141 - Permalink


Geochemical Interactions of Plutonium with Opalinus Clay Studied by Spatially Resolved Synchrotron Radiation Techniques
Kaplan, U.; Amayri, S.; Drebert, J.; Rossberg, A.; Grolimund, D.; Reich, T.
Corresponding author: Reich, T. Johannes Gutenberg-Universitat Mainz
Abstract: Plutonium plays an important role within nuclear waste materials because of its long half-life and high radiotoxicity. The aim of this study was to investigate with high spatial resolution the reactivity of the more oxidized forms of Pu(V,VI) within Opalinus Clay (OPA) rock, a heterogeneous, natural argillaceous rock considered as a potential repository host. A combination of synchrotron based X-ray microprobe and bulk techniques was used to study the spatial distribution and molecular speciation of Pu within OPA after diffusion and sorption processes. Microscopic chemical images revealed a pronounced impact of geochemical heterogeneities concerning the reactivity of the natural barrier material. Spatially resolved X-ray absorption spectroscopy documented a reduction of the highly soluble Pu(V,VI) to the less mobile Pu(IV) within the argillaceous rock material, while bulk investigations showed second-shell scattering contributions, indicating an inner-sphere sorption of Pu on OPA components. Microdiffraction imaging identified the clay mineral kaolinite to play a key role in the immobilization of the reduced Pu. The findings provide strong evidence that reduction and immobilization do not occur as linked processes on a single reactive phase but as decoupled, subsequent, and spatially separated reactions involving different phases of the OPA.
Keywords: Plutonium opalinus clay sorption XAS ROBL

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Registration No. 26140 - Permalink


Measurements of neutron scattering angular distributions with a new scintillator setup
Pirovano, E.; Beyer, R.; Junghans, A. R.; Nolte, R.; Nyman, M.; Plompen, A.
Abstract: A new experimental setup for the measurement of neutron scattering cross sections and angular distributions is currently being developed at the neutron time-of-flight facility GELINA, at the JRC-Geel. Up to 32 liquid organic scintillators are employed for the detection of neutrons scattered from a sample of the investigated material. The differential cross section is measured at eight different angles, and the angleintegrated cross section is obtained from the differential data by numerical integration. Two experiments for the study of scattering on iron were carried out, one at GELINA and the other at nELBE (HZDR). The first results for the angular distributions of elastic scattering in the neutron energy range from 2 to 6MeV are here presented and compared with evaluations from the major nuclear data libraries.
Keywords: nELBE, GELINA, neutron, angular distribution

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Registration No. 26138 - Permalink


P1513 - Procedure and apparatus for measuring a d.c. magnetic field based on magnetostrictive effect in magnetic wires
Bali, R.; Kolesar, V.; Vazquez, M.
Abstract: The present invention relates to a procedure for measuring a d.c. magnetic field by means of a cylindrical device formed by a magnetostrictive core. A d.c. magnetic field is applied and the mechanical deformation on the device caused by the magnetic field is measured and compared with the obtained measurements from previous calibrations to estimate magnetic field intensity values. The invention also relates to an apparatus for measuring a d.c. magnetic field by means of the indicated procedure. The apparatus comprises:
- a cylindrical sensor element and an abutment/fixing element, such that the cylindrical sensor element experiences mechanical deformation when exposed to the d.c. magnetic field,
- a deformation sensing device configured for detecting the mechanical deformation of the cylindrical sensor element, and
- a processing unit configured for determining the intensity of the d.c. magnetic field based on the detected mechanical deformation of the cylindrical sensor element.
  • Patent
    EP3171189 - Offentlegung: 24.05.2017

Registration No. 26134 - Permalink


P1601 - Verfahren und Vorrichtung
Hoffmann, A.; Speck, O.
Abstract: Gemäß verschiedenen Ausführungsformen kann ein Verfahren (100) Folgendes aufweisen: Erzeugen (101) eines Magnetfeldes in einem Bestrahlungsbereich; Bestrahlen (103) des Bestrahlungsbereichs mittels eines Partikelstrahls, welcher spinpolarisierte Partikel aufweist; Erfassen (105) einer Anregung der spinpolarisierten Partikel, welche durch das Magnetfeld bewirkt wird; und Ermitteln (107) einer räumlichen Charakteristik des Partikelstrahls auf Grundlage der Anregung.
  • Patent
    DE102016100638 - Offenlegung: 20.07.2017, Nachanmeldungen: WO

Registration No. 26132 - Permalink


P1602 - Tomographievorrichtung
Barthel, F.; Hampel, U.; Bieberle, A.
Abstract: Die Erfindung betrifft eine Tomographievorrichtung mit Mitteln zum Erzeugen eines Elektronenstrahls; einer Ablenkvorrichtung zum Ablenken des Elektronenstrahls; einem Target; einer Steuervorrichtung zur Steuerung der Ablenkvorrichtung mittels Steuerungsdaten derart, dass der Elektronenstrahl an einem Auftreffpunkt auf das Target auftrifft und der Auftreffpunkt entlang mehrerer, in unterschiedlichen Ebenen verlaufender Bahnen geführt wird, wobei an dem Auftreffpunkt Röntgenstrahlung entsteht; und mehreren Röntgendetektoren zum Erfassen der Röntgenstrahlung, wobei jeder der Röntgendetektoren ein sich über alle Ebenen hinweg erstreckendes Detektorelement mit Szintillatormaterial und einen Lichtdetektor zum Erfassen von Szintillationslicht und Erzeugen eines Detektorsignals aufweist; wobei jedes der Detektorsignale basierend auf den Steuerungsdaten derjenigen Ebene zugeordnet wird, in der sich der Auftreffpunkt des Elektronenstrahls auf dem Target während der Erzeugung des Detektorsignals befindet.
  • Patent
    DE102016101787 - Offenlegung 03.08.2017, Nachanmeldungen: WO

Registration No. 26131 - Permalink


Two Point Correlation Measurements in Liquid Metal Duct Flows using Ultrasound Phased Arrays
Mäder, K.; Räbiger, D.; Nauber, R.; Büttner, L.; Eckert, S.; Czarske, J.
Abstract: A key to improvements of industrial processes involving liquid metals like continuous steel casting is a good knowledge of the interaction between time-varying magnetic fields and conductive fluids. For investigations in this area, model experiments using low-melting liquid metals are conducted, which require suitable instrumentation for opaque media. Ultrasound Doppler velocimetry allows to measure the flow structures and thus to obtain turbulence statistics. For MHD experiments investigating small-scale and turbulent flows, a spatial resolution in the low millimeter range is required.
However, state of the art systems using arrays of unfocused single transducers are limited in their resolution by the divergence of the far field ultrasound beam. In addition, thus systems allow only one dimensional measurements along the propagation direction of the ultrasound beam. Thus interesting quantities in some experiments like turbulence statistics in the axial direction in duct flows can not be measured.
Using our novel phased array ultrasound Doppler velocimeter (PAUDV), the duct flow of an opaque liquid under the influence of an magnetic field can be studied. The measurement system combines the ultrasound Doppler velocimetry with the phased array technique, which allows to adaptively shape the sound field. Using its possibility to drive phased arrays with up to 256 individual channels simultaneously, the ultrasound beam is dynamically focussed in the measurement area, which increases the spatial resolution. In addition, the cross beam technique is used to enable two component measurements using a single acoustical access. This allows to measure turbulence statistics in the main flow direction of a fluid duct with only one ultrasound array on the duct wall.
Keywords: Ultrasound Phased arrays, flow measurements, liquid metals, duct flows
  • Lecture (Conference)
    16th European Turbulence Conference, 21.-24.08.2017, Stockholm, Sweden

Registration No. 26128 - Permalink


Controlled ion beam hyperdoping of silicon nanowires
Berencén, Y.; Prucnal, S.; Wang, M.; Hübner, R.; Böttger, R.; Glaser, M.; Schönherr, T.; Möller, W.; Georgiev, Y. M.; Rebohle, L.; Erbe, A.; Lugstein, A.; Zhou, S.; Helm, M.; Skorupa, W.
Abstract: The hyperdoping of semiconductors consists of introducing dopant concentrations far above the equilibrium solubility limits. This results in a broadening of dopant energy levels into an impurity or intermediate band. We have recently demonstrated that hyperdoping bulk Si with Se shows promise for Si-based short-wavelength infrared photodetectors [1]. Lately, silicon nanowires (NWs) have gained increasing importance as building blocks for nanodevices like field-effect transistors, light emitting devices and photovoltaic cells [2, 3]. Therefore, the comparison between hyperdoping Si nanowires and bulk Si is a common issue to be examined, which comes along with the transition from a bulk material to semiconductor NWs.
In this work, we report on non-equilibrium processing for controlled hyperdoping of Si/SiO2 core/shell nanowires previously synthesized by the vapor-liquid-solid method. Our approach is based on Se implantation of the upper half of NWs followed by millisecond flash lamp annealing, which allows for a bottom-up template-assisted recrystallization of the amorphized parts of the NWs via explosive solid-phase epitaxy. The Se-hyperdoped Si NWs are successfully recrystallized and accommodate Se concentrations as high as 1021 cm-3. As a proof of device concept, a single Se-hyperdoped NW-based IR photoconductor is shown. In this way, the combination of ion implantation and flash lamp annealing as a promising nanoscale hyperdoping technology is successfully established.
[1] Y. Berencén, S. Prucnal, Fang Liu, I. Skorupa, R. Hübner, L. Rebohle, S. Zhou, H. Schneider, M. Helm, and W. Skorupa, “Room-temperature short-wavelength infrared Si photodetector,” Sci. Rep. 7, 43688 (2017).
[2] B. Tian, T. Cohen-Karni, Q. Qing, X. Duan, P. Xie and C.M. Lieber, “Three-dimensional, flexible nanoscale field-effect transistors as localized bioprobes,” Science 329, 831 (2010).
[3] T. J. Kempa, B. Tian, D.R. Kim, J. Hu, X. Zheng and C.M. Lieber, “Single and tandem axial p-i-n nanowire photovoltaic devices,” Nano Lett. 8, 3456 (2008).
Keywords: Hyperdoping, Si nanowires, ion implantation, flash lamp annealing, impurity band, sub bandgap photoresponse
  • Lecture (Conference)
    E-MRS 2017 Fall Meeting (European-Materials Research Society), Symposium S: Materials- nanoelectronics & nanophotonics, 18.09.2017, Warsaw, Poland

Registration No. 26127 - Permalink


Engineering and modifying two-dimensional materials by electron beams
Zhao, X.; Kotakoski, J.; Meyer, J. C.; Sutter, E.; Sutter, P.; Krasheninnikov, A. V.ORC; Kaiser, U.; Zhou, W.
Corresponding author: Zhao, X. National University of Singapore
Abstract: Electron-beam (e-beam) irradiation damage is often regarded as a severe limitation to atomic-scale study of two-dimensional (2D) materials using electron microscopy techniques. However, energy transferred from the e-beam can also provide a way to modify 2D materials via defect engineering when the interaction of the beam with the sample is precisely controlled. In this article, we discuss the atomic geometry, formation mechanism, and properties of several types of structural defects, ranging from zero-dimensional point defects to extended domains, induced by an e-beam in a few representative 2D materials, including graphene, hexagonal boron nitride, transition-metal dichalcogenides, and phosphorene. We show that atomic as well as line defects and even novel nanostructures can be created and manipulated in 2D materials by an e-beam in a controllable manner. Phase transitions can also be induced. The e-beam in a (scanning) transmission electron microscope not only resolves the intrinsic atomic structure of materials with defects, but also provides new opportunities to modify the structure with subnanometer precision.
Keywords: TEM, graphene

Downloads:

  • Secondary publication expected

Registration No. 26123 - Permalink


Towards diluted magnetism in TaAs
Liu, Yu; Li, Z.; Guo, L.; Chen, X.; Yuan, Y.; Xu, C.; Hübner, R.; Akhmadaliev, S.; Krasheninnikov, A. V.; N'Diaye, A. T.; Arenholz, E.; Helm, M.; Zhou, S.ORC
Corresponding author: Chen, Xiaolong Research & Development Center for Functional Crystals, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Abstract: Magnetism in Weyl semimetals is desired to investigate the interaction between the magnetic moments and Weyl fermions, e.g., to explore anomalous quantum Hall phenomena. Here we demonstrate that proton irradiation is an effective tool to induce ferromagnetism in the Weyl semimetal TaAs. The intrinsic magnetism is observed with a transition temperature above room temperature. The magnetic moments from d states are found to be localized around Ta atoms. Further, the first-principles calculations indicate that the d states localized on the nearest-neighbor Ta atoms of As vacancy sites are responsible for the observed magnetic moments and the long-ranged magnetic order. The results show the feasibility of inducing ferromagnetism in Weyl semimetals so that they may facilitate the applications of this material in spintronics.

Downloads:

  • Secondary publication expected from 25.09.2018

Registration No. 26122 - Permalink


Substitutional carbon doping of free-standing and Ru-supported BN sheets: A first-principles study
Berseneva, N.; Komsa, H.-P.; Vierimaa, V.; Björkman, T.; Fan, Z.; Harju, A.; Todorovic, M.; Krasheninnikov, A. V.ORC; Nieminen, R. M.
Corresponding author: Berseneva, N. Aalto University
Abstract: The development of spatially homogeneous mixed structures with boron (B), nitrogen (N) and carbon (C) atoms arranged in a honeycomb lattice is highly desirable, as they open the possibility of creating stable two-dimensional materials with tunable band gaps. However, at least in the free-standing form, the mixed BCN system is energetically driven towards phase segregation to graphene and hexagonal BN. It is possible to overcome the segregation when BCN material is grown on a particular metal substrate, for example Ru(0 0 0 1), but the stabilization mechanism is still unknown. With the use of density-functional theory we study the energetics of BN/Ru slabs, with different types of con gurations of C substitutional defects introduced to the h-BN overlayer. The results are compared to the energetics of free- standing BCN materials. We found that the substrate facilitates the C substitution process in the h-BN overlayer. Thus, more homogeneous BCN material can be grown, overcoming the segregation into graphene and h-BN. In addition, we investigate the electronic and transport gaps in free-standing BCN structures, and assess their mechanical properties and stability. The band gap in mixed BCN free-standing material depends on the concentration of the constituent elements and ranges from zero in pristine graphene to nearly 5 eV in free-standing h-BN. This makes BCN attractive for application in modern electronics.
Keywords: graphene, doping, first-principles calculations

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  • Secondary publication expected from 04.09.2018

Registration No. 26121 - Permalink


Ionization and reflux dependence of magnetic instability generation and probing inside laser-irradiated solid thin foils
Huang, L. G.; Schlenvoigt, H.-P.; Takabe, H.; Cowan, T. E.
Corresponding author: Huang, L. G. Helmholtz-Zentrum Dresden-Rossendorf
Abstract: When an intense laser accelerated electron beam, with large current density on the order of 10^12 A/cm^2, enters a solid density plasma, it is well-known to be subject to a number of different types of instabilities
that cause it to filament. In this work, we investigate the transport instability of a fast electron beam that is imprinted on the self-generated magnetic filaments inside the solid density plasmas using particle-in-cell simulations. By varying collisional ionization models, our simulations show that the atomic ionization process is crucial to determine the structure of the magnetic filaments. We further attribute the generation of bulk magnetic filaments to Weibel-like instability mechanism caused by counter-propagating hot forward-bulk return current streams and counterpropagating hot forward-reflux current streams. It is found that the magnetic fields in the filament channels near the rear surface are around one order of magnitude higher than those near the front surface of the thin solid target. This asymmetry is likely induced by the very different properties of bulk electron stream and hot reflux electron stream in terms of density and velocity distribution. Finally, we propose to probe the magnetic fields inside the solid density plasmas by X-Ray polarimetry via Faraday rotation using X-Ray free electron lasers (XFELs). The synthetic simulations show that XFELs are capable to detect the magnetic fields from relativistic laser-solid interactions.
Keywords: Laser plasma interactions, Weibel instability,XFEL,Faraday rotation

Registration No. 26120 - Permalink


Ex-situ doping and Ohmic contact formation with low contact resistance on MBE grown GeSn on Si
Prucnal, S.; Augel, L.; Schulze, J.; Fischer, I. A.; Berencén, Y.; Hübner, R.; Böttger, R.; Rebohle, L.; Skorupa, W.; Wang, M.; Voelskow, M.; Helm, M.; Zhou, S.
Abstract: GeSn with quasi-direct band gap is one of the most promising semiconductor materials for light emitters integrated with CMOS technology. The equilibrium solid solubility limit (SSL) of Sn in Ge is in the range of 0.5 % and the predicted theoretical Sn concentration needed for the direct band gap formation is above 5 %. This means that GeSn with direct band gap is metastable and any related material process cannot be thermal equilibrium. Here we propose to utilize strongly non-equilibrium processing i.e. ion implantation followed by millisecond range flash lamp annealing (FLA), for doping and the formation of Ohmic contacts with low contact resistance on Ge0.95Sn0.05. The effective carrier concentration in P+ implanted Ge0.95Sn0.05 layer followed by FLA for 3 ms is above 5×10^19cm-3 with a specific contact resistance rc=4×10^-6Ωcm2. NiGe for Ohmic contact is made by Ni diffusion into GeSn during a single 3 ms long flash pulse. TEM images reveal that NiGe is polycrystalline but with an atomically sharp interface between the metal contact and GeSn. The influence of non-equilibrium processing (ion implantation and FLA) on the optical, electrical and microstructural properties of the GeSn layer grown by MBE on Si will be discussed in details.
Keywords: GeSn, MBE, doping, flash lamp annealing
  • Poster
    EMRS Fall Meeting 2017, 18.-21.09.2017, Warsaw, Poland

Registration No. 26113 - Permalink


Strategies for high doping of Ge
Prucnal, S.
Abstract: One of the main obstacles towards wide application of Ge in nanoelectronics is the lack of an efficient doping method for the fabrication of heavily doped Ge layers with well controlled junction depth. In fact, n-type doping of Ge is a key bottleneck in the realization of advanced negative-channel metal-oxide-semiconductor (NMOS) devices. Here an overview of different doping techniques will be presented. Special attention will be focused on the use of ion implantation followed by flash-lamp (FLA) annealing for the fabrication of heavily doped Ge. In contrast to conventional annealing procedures, rear-side FLA leads to full recrystallization of Ge and dopant activation independently of pre-treatment. The maximum carrier concentration is well above 10^20 cm-3 for n-type and above 10^21 for p-type doping. The recrystallization mechanism and the dopant distribution during rear-side FLA are discussed in detail. In this work, we report on the strong mid-IR plasmon absorption from heavily P-doped Ge thin films and superconductivity in Ga and Al doped Ge obtained by non-equilibrium thermal processing. The mid-IR plasmon spectral response at room temperature from those samples was characterized by means of Fourier transform infrared spectroscopy. It is proven that the position of the plasmonic resonance frequency signal can be tuned as a function of the P concentration.
Keywords: Ge, flash lamp annealing, doping
  • Invited lecture (Conferences)
    EMRS Fall Meeting 2017, 18.-21.09.2017, Warsaw, Poland

Registration No. 26112 - Permalink


An Eulerian-Eulerian Computational Fluid Dynamic Approach to Predict the Boiling Process with New Developed Sub Models
Ding, W.; Krepper, E.; Hampel, U.
Abstract: Time averaged Eulerian multiphase approaches and the heat flux partitioning method is popular to be applied in the computational fluid dynamic simulations of wall boiling especially in the forced convective boiling. In such CFD simulations, many submodels for the bubble dynamics and the implementation of the bubble dynamics into the global models are particularly important. In order to get accurate bubble dynamics, a single bubble model for nucleate boiling based on the known microlayer theory was developed. The single bubble model consideres the dynamic bubble geometry, contact angle and bubble inclination angle in flow boiling at different time periods. The model is able to show the dependency of bubble departure diameter (lift off diameter) and frequency on the different physical quantities such as heat flux, liquid properties, sub-cooling temperature, design of channel (diameter, length), mass flow rate and so on. The implementation of this developed single bubble model requires an update of the conventional nucleation site activation and heat partitioning models in time averaged Eulerian multiphase approaches. The new activation approach considers a distribution of cavity sizes and their influence on the activation temperature. The dynamics of the bubbles generated from different size cavities at the same position differ from each other. The updated heat partitioning model assumes the heat flux at the evaporative area always as constant and equal to the known feed heat flux when the boiling system is in the steady state. With help of the multiple size group (MUSIG) model and a breakup and coalesce model, the time averaged Eulerian approach could simulate the bubble size distribution in a heated pipe. With the necessary calibration of the nucleation site density the comparisons between the calculation results and the Bartolomej’s experiments demonstrate the accuracy of this approach.
Keywords: Forced convective boiling, Eulerian multi-phase approach, microlayer, cavity group activation, heat partitioning
  • Contribution to proceedings
    17th International Topical Meeting on Nuclear Reactor Thermal hydaulics, 04.-08.09.2017, Xi'an, China
    17th International Topical Meeting on Nuclear Reactor Thermal hydaulics

Registration No. 26110 - Permalink


A hypothesis of near critical heat flux (CHF-) based on minimum waiting time
Ding, W.; Krepper, E.; Hampel, U.
Abstract: Boiling is a very efficient heat transfer mechanism with a large heat transfer coefficient and it is widely found in industrial systems. However, boiling heat transfer is limited by the critical heat flux (CHF), also termed as boiling crisis, which may lower efficiency and jeopardize safety of heat transfer systems. The latter is of particular importance for the safe operation of nuclear light water reactors. A clear understanding of the basic mechanisms leading to CHF is still lacking. In this paper a new model for the quantitative prediction of the initiation of critical heat flux is derived from the bubble dynamics and heat fluxes in nucleate boiling. It incorporates effects of mutual bubble interaction and shear stress from bulk flow. The model was successfully validated with available experimental data from literature for both pool boiling and forced convective boiling and with that it can be very widely applied, both as a stand-alone model for heat transfer system design as well as a sub-model in computational fluid dynamics (CFD).
Keywords: Critical heat flux (CHF), boiling heat transfer, pool boiling, forced convective boiling, cavity activation
  • Contribution to proceedings
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, 04.-08.09.2017, Xi'an, China
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics

Registration No. 26109 - Permalink


Photochemical Reduction of Non-fluorescent Tris(carbonato)uranyl(VI) Complex
Takao, K.; Tsushima, S.ORC
Abstract: A uranyl ion usually shows characteristic green emission and photochemical reactions under UV irradiation, while tris(carbonato)uranyl(VI) complex is known to be exceptionally inert because of strong quenching through the bound carbonates. In this study, we report that tris(carbonato)uranyl(VI) was immediately reduced to the corresponding uranyl(V) species under presence of tetrahydroborate and UV irradiation.
  • Lecture (Conference)
    The 67th Conference of Japan Society of Coordination Chemistry, 16.-18.09.2017, Sapporo, Japan

Registration No. 26106 - Permalink


Computational study on the interaction between Eu(III) and calmodulin
Tsushima, S.ORC; Mochizuki, Y.; Komeiji, Y.; Takao, K.
Abstract: there is no abstract
  • Lecture (Conference)
    Atomic Energy Society of Japan 2017 Fall Meeting, 13.-15.09.2017, Sapporo, Japan

Registration No. 26105 - Permalink


Theoretical study on Calmodulin binding with Ca(II) and Eu(III) ions
Tsushima, S.ORC; Mochizuki, Y.; Komeiji, Y.; Okuwaki, K.; Abe, T.; Mori, H.; Tanaka, S.
Abstract: there is no abstract
  • Lecture (Conference)
    The 78th Japan Society of Applied Physics Meeting, 05.-08.09.2017, Fukuoka, Japan

Registration No. 26104 - Permalink


Cloppenburg (H4-5) – first results of a new find
Storz, J.; Bischoff, A.; Degering, D.; Ebert, S.; Heinlein, D.; Jull, T.; Kontul, I.; Li., X.; Merchel, S.; Oberst, J.; Ott, U.; Pack, A.; Peters, S.; Petö, M. K.; Rugel, G.
Abstract: The Cloppenburg meteorite of 141 g was found March 15, 2017 by the facility manager of a school while collecting rocks for the school garden. The rock with a mean density of (3.33 ± 0.03) g/cm3 is a brecciated H-group ordinary chondrite (H4-5) with mean olivine and low-Ca pyroxene of Fa18.5±0.3 and Fs16.4±0.6, respectively. The breccia containing shock veins is weakly shocked (S3) and heavily weathered (W3). The occurrence of vivianite, the oxygen isotopes, and the Ba-enrichment (by INAA) indicate strong weathering in a very wet environment. Radionuclide data evaluation is still ongoing: Accelerator mass spectrometry (AMS) of 14C, will reveal the terrestrial age. An upper limit of the terrestrial age is yet set by low-level gamma-spectrometry in the Felsenkeller underground lab. No 22Na (t1/2=2.6 a) nor 44Ti (t1/2=59 a) could been detected within a counting time of 27 days, whereas 26Al (t1/2=0.7 Ma) was clearly identified. AMS of 10Be (t1/2=1.4 Ma) of ~18 dpm/kg confirms the high cosmic ray exposure age (CRE age) of (7.5 ± 0.4) Ma from noble gas mass spectrometry.
Keywords: AMS, cosmogenic nuclide, mass spectrometry, gamma-spectrometry, INAA
  • Poster
    Paneth-Kolloquium, 11.-13.10.2017, Nördlingen, Deutschland

Registration No. 26103 - Permalink


Investigation of bioreactors by instrumented flow-following sensor particles
Reinecke, S.; Hampel, U.
Abstract: Instrumented flow-following sensor particles have been developed for investigation of hydrodynamic and biochemical processes chemical reactors and bioreactors, where standard measurement techniques are not applicable. The sensor particles allow autonomous long-term measurement of spatially distributed process parameters in the chemically and mechanically harsh environments of agitated industrial vessels. Each sensor particle comprises of an on-board measurement electronics that logs the signals of the embedded sensors. A buoyancy control unit enables automated taring to achieve neutral buoyancy of the sensor particles. Moreover, controlled floating of the sensor particles is possible to expose them for recovery from the fluid surface. The paper presents exemplary results from tests in an air-water column reactor, a pilot biogas digester and a waste water treatment plant.
Keywords: sensor particle, autonomous sensor, flow follower, hydrodynamics, bioreactor
  • Contribution to proceedings
    Sensor 2017, 30.05.-01.06.2017, Nürnberg, Deutschland

Registration No. 26102 - Permalink


The 2017 Magnetism Roadmap
Sander, D.; Valenzuela, S. O.; Makarov, D.; Marrows, C. H.; Fullerton, E. E.; Fischer, P.; Mccord, J.; Vavassori, P.; Mangin, S.; Pirro, P.; Hillebrands, B.; Kent, A. D.; Jungwirth, T.; Gutfleisch, O.; Kim, C. G.; Berger, A.
Corresponding author: Makarov, D. HZDR-FWI
Abstract: Building upon the success and relevance of the 2014 Magnetism Roadmap, this 2017 Magnetism Roadmap edition follows a similar general layout, even if its focus is naturally shifted, and a different group of experts and, thus, viewpoints are being collected and presented. More importantly, key developments have changed the research landscape in very relevant ways, so that a novel view onto some of the most crucial developments is warranted, and thus, this 2017 Magnetism Roadmap article is a timely endeavour. The change in landscape is hereby not exclusively scientific, but also reflects the magnetism related industrial application portfolio. Specifically, Hard Disk Drive technology, which still dominates digital storage and will continue to do so for many years, if not decades, has now limited its footprint in the scientific and research community, whereas significantly growing interest in magnetism and magnetic materials in relation to energy applications is noticeable, and other technological fields are emerging as well. Also, more and more work is occurring in which complex topologies of magnetically ordered states are being explored, hereby aiming at a technological utilization of the very theoretical concepts that were recognised by the 2016 Nobel Prize in Physics. Given this somewhat shifted scenario, it seemed appropriate to select topics for this roadmap article that represent the three core pillars of magnetism, namely magnetic materials, magnetic phenomena and associated characterization techniques, as well as applications of magnetism. While many of the contributions in this Roadmap have clearly overlapping relevance in all three fields, their relative focus is mostly associated to one of the three pillars. In this way, the interconnecting roles of having suitable magnetic materials, understanding (and being able to characterize) the underlying physics of their behaviour and utilizing them for applications and devices is well illustrated, thus giving an accurate snapshot of the world of magnetism in 2017. The article consists of 14 sections, each written by an expert in the field and addressing a specific subject on two pages. Evidently, the depth at which each contribution can describe the subject matter is limited and a full review of their statuses, advances, challenges and perspectives cannot be fully accomplished. Also, magnetism, as a vibrant research field, is too diverse, so a number of areas will not be adequately represented here, leaving space for further roadmap editions in the future. However, this 2017 Magnetism Roadmap article can provide a frame that will enable the reader to judge where each subject and magnetism research field stands overall today and which directions it might take in the foreseeable future. The first material focused pillar of the 2017 Magnetism Roadmap contains five articles, which address the questions of atomic scale confinement, 2D, curved and topological magnetic materials, as well as materials exhibiting unconventional magnetic phase transitions. The second pillar also has five contributions, which are devoted to advances in magnetic characterization, magneto-optics and magneto-plasmonics, ultrafast magnetization dynamics and magnonic transport. The final and application focused pillar has four contributions, which present non-volatile memory technology, antiferromagnetic spintronics, as well as magnet technology for energy and bio-related applications. As a whole, the 2017 Magnetism Roadmap article, just as with its 2014 predecessor, is intended to act as a reference point and guideline for emerging research directions in modern magnetism.
Keywords: magnetism, roadmap, magnetic materials, magneto-optics, spintronics, magnonics, magnetic memory

Registration No. 26101 - Permalink


H-T phase diagram of solid oxygen
Nomura, T.; Matsuda, Y. H.; Kobayashi, T. C.
Corresponding author: Nomura, T. Institute for Solid State Physics, University of Tokyo, Kashiwa, Japan and Hochfeld-Magnetlabor Dresden (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
Abstract: The comprehensive magnetic field–temperature (H-T) phase diagram of solid oxygen including the θ phase is discussed in the context of the ultrahigh-field measurement and the magnetocaloric effect (MCE) measurement. The problems originating from the short duration of the pulse field, nonequilibrium conditions and MCEs, are pointed out and dealt with. The obtained phase diagram manifests the entropy relation between the phases as Sθ ∼ Sα < Sβ << Sγ

Registration No. 26095 - Permalink


Permutation-blocking path-integral Monte Carlo approach to the static density response of the warm dense electron gas
Dornheim, T.; Groth, S.; Vorberger, J.; Bonitz, M.
Abstract: The static density response of the uniform electron gas is of fundamental importance for numerous applications.
Here we employ the recently developed ab initio permutation blocking path integral Monte Carlo (PB-PIMC) technique [T. Dornheim et al., New J. Phys. 17, 073017 (2015)] to carry out extensive simulations of the harmonically perturbed electron gas at warm dense matter conditions. In particular, we investigate in detail the validity of linear response theory and demonstrate that PB-PIMC allows us to obtain highly accurate results for the static density response function and, thus, the static local field correction. A comparison with dielectric approximations to our new ab initio data reveals the need for an exact treatment of correlations. Finally, we consider a superposition of multiple perturbations and discuss the implications for the calculation of the static response function.
Keywords: warm dense matter, quantum monte carlo, response function, electron gas, fermion sign problem, linear response
  • Physical Review E 96(2017), 023203

Registration No. 26091 - Permalink


Optical contrast formation in ta-C films by ion implantation
Berova, M.; Sandulov, M.; Tsvetkova, T.; Szekeres, A.; Terziyska, P.; Kitova, S.; Böttger, R.; Bischoff, L.
Corresponding author: Szekeres, A. BAS
Abstract: Tetrahedral amorphous carbon (ta-C) thin films (d ~ 40 nm), deposited by filtered cathodic vacuum arc (FCVA) method, have been implanted with Ga+ ions with energy 20 keV and ion fluences 3xE14 and 3xE15 cm-2. The implantation induced modification of the films structure is reflected in a considerable change of their optical properties, best manifested by a significant shift of the optical absorption edge to lower photon energies as obtained from optical measurements. This shift is accompanied by a considerable increase of the absorption coefficient in the photon energy range (0.5 ÷ 3.0 eV). The observed effects could be attributed both to additional defect generation and increased graphitization, as well as by gallium colloids formation. The optical contrast thus obtained (between implanted and unimplanted film material) could be of use in the area of high-density optical data storage using focused Ga+ ion beams.
Keywords: ta-C films, Ga implantation, optical properties
  • Revue Roumaine de Chimie 62(2017)10, 761-765

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Registration No. 26090 - Permalink


CFD-simulation of different bubbly flow situations applying the Euler-Euler framework
Krepper, E.; Lucas, D.; Rzehak, R.
Abstract: A widely used approach to model two-phase bubbly flows for industrial applications is the Eulerian two-fluid framework of interpenetrating continua. The loss of details caused by the averaging procedure has to be compensated by consideration of additional closure relations. These concern the momentum exchange between the phases, the effect of the bubbles on liquid turbulence and bubble breakup & coalescence. A set of best available sub models was assembled (Rzehak and Krepper, 2013, 2015). To ensure the predictive capabilities it has to be shown that this model framework is able to describe different flow situations without any changes of model parameters.
The present contribution starts with validation work on upward turbulent bubbly flow in a vertical tube at the MTLoop facility using the wiremesh technique. A second step is the extension to counter-current and co-current downward flow at ROFEX using fast X-Ray tomography (Krepper et al. 2016). Both facilities were operated in Helmholtz - Zentrum Dresden-Rossendorf. Data on the cross sectional distribution of gas volume fraction, of gas and liquid velocity and on bubble size distributions were gained.
The presentation shows the capability of an unified framework of closure relationships to describe different flow situations.
Keywords: CFD, momentum exchange, bubble induced turbulence, fixed polydispersed flow
  • Lecture (Conference)
    The 3rd International Conference on Numerical Methods in Multiphase Flows, ICNMMF-III, 26.-29.06.2017, Tokyo, Japan

Registration No. 26089 - Permalink


CFD analysis on experiments of bubbly flow in a tube with an obstacle
Krepper, E.; Neumann, M.; Lucas, D.
Abstract: Two phase adiabatic air/water flow in a vertical tube with an inner diameter of 54 mm equipped with an inner obstacle was investigated. Experiments are conducted for a wide range of superficial gas and liquid velocities in bubbly flow regime. Flow obstacles, namely a ring shaped diaphragm and a half-moon shaped diaphragm, are used for generation of three-dimensional flow fields. Besides conventional measurement techniques an ultrafast X-ray tomography scanner ROFEX, which was developed by HZDR, are applied. ROFEX determines gas distributions, bubble velocities and bubble sizes (Hampel et al. 2013, 2016).
The experiments were used to analyze the capability of the actual CFD based on the Euler/Eulerian approach. The CFD calculations were performed as pre-test simulations. Measured results for half-moon shaped diaphragm tests were available short before publishing the manuscript and shown with the calculations. Most of the values and at least the tendencies could be predicted with good agreement to measurements. Reasons for deviations are discussed in the paper.
CFD simulation enables the investigation of single components of the model approach. So the distribution of the bubble forces and the strength and location of single breakup&coalescence mechanisms can be analyzed and checked for plausibility.
Keywords: bubbly flow, experiments, CFD, momentum exchange, bubble induced turbulence, bubble breakup & coalescence
  • Contribution to proceedings
    The 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi'an, China
  • Lecture (Conference)
    The 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi'an, China

Registration No. 26088 - Permalink


Concepts of CFD modelling of boiling towards CHF
Krepper, E.; Ding, W.
Abstract: Boiling is an effective heat transfer mechanism which plays an important role in many industrial applications. The heat transfer capability is limited by the critical heat flux (CHF). The conditions for CFX have to be avoided in any cases. The simulation of these not yet fully understood phenomena has not yet reached an acceptable maturity.
The presentation describes actual concepts of simulation of boiling beginning with the heat flux partitioning approach. In recent developments the bubble size distribution was considered. Concepts for describing CHF are presented.
Keywords: Boiling, CFD, Heat flux partitioning, bubble population balance, critical heat flux
  • Lecture (Conference)
    28th Meeting of the German CFD Network of Competence, 07.03.2017, Garching, Deutschland

Registration No. 26087 - Permalink


Radioimmunkonjugate für die theragnostische Anwendung an Prostata-Stammzellantigen-exprimierenden Tumoren
Oertel, F.; Arndt, C.; Feldmann, A.; Bergmann, R.; Steinbach, J.; Pietzsch, H.-J.; Bachmann, M.
Abstract: Ziel: Das Prostata-Stammzellantigen (PSCA) wird auf der Zelloberfläche von über 80% der Prostatatumore (PCa) und deren Knochenmetastasen exprimiert. Aus diesem Grund wird es häufig als Zielstruktur sowohl für die Radioimmuntherapie (RIT) als auch für molekulare Bildgebungstechniken von PCa in der Nuklearmedizin (Positronen-Emissions-Tomographie (PET) und Einzelphotonen-Emissionscomputertomographie (SPECT)) verwendet. Für die jeweiligen Anwendungsgebiete wurden Radioimmunkonjugate basierend auf monoklonalen anti-PSCA-Antikörpern (mAk, 150 kDa) und von diesen abgeleitete Einzelkettenantikörperfragmente („single-chain Fragment variable“ (scFv), 35 kDa) hergestellt. In Kombination sollen diese Radioimmunkonjugaten als therapeutisches und diagnostisches Instrument für PSCA-positive PCa Anwendung finden.
Methoden und Ergebnisse: Zwei unterschiedliche anti-PSCA mAk-Klone, RD1 und RD2 genannt, sowie davon abgeleitete scFvs wurden hergestellt, über Affinitätschromatographie gereinigt und deren Bindungseigenschaften an PSCA-positiven PC3-Zellen mittels Durchflusszytometrie ermittelt. Die unmarkierten mAk-Klone RD1 und RD2 zeigten hohe Affinitäten, mit Dissoziationskonstanten von 10 und 6 nM. Für die scFvs von RD1 und RD2 wurden geringere Affinitäten von 170 und 98 nM bestimmt. Die beiden mAk-Klone wurden anschließend mit dem bifunktionellen Chelator p-SCN-Bn-CHX-A’’-DTPA, die scFv-Antikörper hingegen mit p-SCN-Bn-NOTA konjugiert. Für alle Konstrukte wurde mittels MALDI-TOF-Massenspektrometrie eine durchschnittliche Anzahl von drei Chelator-Einheiten je Antikörpermolekül gemessen. Anschließend wurden die mAk-Konjugate für eine mögliche RIT-Anwendung mit Lutetium-177 und die scFv-Konjugate für eine mögliche PET-Bildgebung mit Kupfer-64 radiomarkiert. Des Weiteren wurden scFv-Antikörper auch direkt mit Technetium-99m mit Hilfe eines Tricarbonyl-Präkursor an ihrem Hexahistidin-Tag für eine mögliche SPECT-Bildgebung markiert. Für alle radiomarkierten Konjugate wurde eine radiochemische Reinheit von über 95% (radio-Dünnschichtchromatographie) erzielt. Nachfolgende In-vitro-Studien an PC3-PSCA-Zellen zeigten, dass die Bindungseigenschaften zum PSCA erhalten bleiben.
Ausblick: An entsprechenden Tumormaus-Modellen wird gegenwärtig geprüft, ob die positiven in-vitro Resultate für die hergestellten Radioimmunkonjugate bestätigt werden können.
  • Poster
    GdCh Wissenschaftsforum Chemie 2017, 10.-14.09.2017, Berlin, Deutschland

Registration No. 26085 - Permalink


Radioimmunoconjugates for theragnostics of Prostate Stem Cell Antigen (PSCA)-expressing tumors
Oertel, Franziska; Arndt, C.; Feldmann, A.; Bergmann, R.; Steinbach, J.; Bachmann, M.; Pietzsch, H.-J.
Abstract: Aim: Advances in molecular engineering have led to the development of a multiplicity of antibody fragments with variations in molecular size. With respect to tumor targeting, the molecular size evidently determines the tumor uptake and pharmacokinetics. Consequently, they are proposed for different applications: small radiolabeled antibody fragments, such as single-chain variable fragments (scFv, 25-35 kDa) for tumor imaging and large full-size monoclonal antibodies (mAbs, 150 kDa) for radioimmunotherapy. Here, mAbs and thereof derived scFvs were produced that are directed against the prostate stem cell antigen (PSCA). Due to its overexpression on the surface of various tumor types, including prostate cancer and its metastases, it is proposed as a promising tumor target structure. Both antibody-based targeting molecules might provide a combinatory tool for theranostics of PSCA-positive prostate cancer.

Methods: In this study, two different anti-PSCA mAb clones, RD1 and RD2, as well as their respective anti-PSCA scFvs were produced and compared with regard to their binding properties towards PSCA, using flow cytometry analysis. The anti-PSCA mAbs were conjugated with the chelating agent p-SCN-CHX-A’’-DTPA, measured by MALDI-TOF, and subsequently radiolabeled with lutetium-177, whereas the scFvs were radiolabeled with technetium-99m on their histidine-tag. Thereafter, all radiolabeled conjugates were characterized by thin-layer chromatography, and regarding binding properties on PC3-PSCA cells in vitro.

Results: The non-radiolabeled anti-PSCA mAbs RD1 and RD2 showed a high affinity, with dissociation constants of 10 and 6 nM, respectively. The corresponding scFvs of RD1 and RD2 exhibit a lower affinity, with Kd-values of 170 and 98 nM. Both full mAbs were conjugated with about three CHX-A’’-DTPA. This conjugation had no influence on binding affinity towards the PSCA. Subsequent radiolabeling of the mAb-conjugates and scFvs could be performed with high radiochemical purity (> 95%) with preserving their binding properties to the PSCA.

Conclusion: Full-size mAbs and scFvs that target the tumor antigen PSCA were successfully produced and radiolabeled. The in vitro characterization showed promising results to proceed with studies on tumor mouse models.
  • Poster
    The 22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), 14.-19.05.2017, Dresden, Deutschland

Registration No. 26084 - Permalink


Investigation of the superconducting gap structure in κ-(BEDT-TTF)2Cu(NCS)2 and κ-(BEDT-TTF)2Cu[N(CN)2]Br by means of thermal-conductivity measurements
Kühlmorgen, S.; Schönemann, R.; Green, E. L.; Müller, J.; Wosnitza, J.
Corresponding author: Green, E. L. Dresden High Magnetic Field Laboratory (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
Abstract: We report temperature-dependent thermal-conductivity, κ, measurements on the layered quasi-two-dimensional organic superconductors κ-(BEDT-TTF)2Cu(NCS)2 and κ-(BEDTTTF)2Cu[N(CN)2]Br down to 160 mK. The results for κ-(BEDT-TTF)2Cu(NCS)2 may be consistent with a nodal superconducting (SC) gap structure as indicated by a nonnegligible remnant linear contribution when κ /T α T2 is extrapolated to T = 0. For κ-(BEDT-TTF)2Cu[N(CN)2]Br, contrary to expectations, higher κ values are observed in the superconducting regime as compared to the normal, high-field state evidencing a dominant phonon contribution to κ in the superconducting state. The strong increase of κ in the normal state below Tc for both samples indicates strong electron–phonon scattering. Our results highlight the need for thermal-conductivity measurements performed down to significantly lower temperatures to determine the symmetry of the SC gap.

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  • Secondary publication expected from 01.09.2018

Registration No. 26080 - Permalink


Quasi-two-dimensional Fermi surfaces with localized f electrons in the layered heavy-fermion compound CePt2In7
Götze, K.; Krupko, Y.; Bruin, J. A. N.; Klotz, J.; Hinlopen, R. D. H.; Ota, S.; Hirose, Y.; Harima, H.; Settai, R.; Mccollam, A.; Sheikin, I.
Corresponding author: Sheikin, I. Laboratoire National des Champs Magnétiques Intenses (LNCMI-EMFL), CNRS, UGA, Grenoble, France
Abstract: We report measurements of the de Haas–van Alphen effect in the layered heavy-fermion compound CePt2In7 in high magnetic fields up to 35 T. Above an angle-dependent threshold field, we observed several de Haas–van Alphen frequencies originating from almost ideally two-dimensional Fermi surfaces. The frequencies are similar to those previously observed to develop only above a much higher field of 45 T, where a clear anomaly was detected and proposed to originate from a change in the electronic structure [M. M. Altarawneh et al., Phys. Rev. B 83, 081103 (2011)]. Our experimental results are compared with band structure calculations performed for both CePt2In7 and LaPt2In7, and the comparison suggests localized f electrons in CePt2In7. This conclusion is further supported by comparing experimentally observed Fermi surfaces in CePt2In7 and PrPt2In7, which are found to be almost identical. The measured effective masses in CePt2In7 are only moderately enhanced above the bare electron mass m0, from 2m0 to 6m0.

Registration No. 26078 - Permalink


Preparation of 18F-labeled building blocks for peptide conjugation using the "minimalist" approach
Omrane, M. A.; Zlatopolskiy, B. D.; Urusova, E.; Mamat, C.; Feni, L.; Neundorf, I.; Neumaier, B.
Corresponding author: Omrane, M. A. Forschungszentrum Jülich + Uniklinik Köln
Abstract: Recently, the “minimalist” protocol for radiofluorination was reported. This method allowed to prepare labeled probes from only [18F]F– and onium salts without base and other additives avoiding time-consuming azeotropic drying. The aim of this work was the implementation of the “minimalist” approach for the preparation of radiofluorinated building blocks via SN2. [18F]Fluoride was eluted from a QMA cartridge with an appropriate azetidinium or onium salt precursor of [18F]AFP, [18F]BFP and 5-[18F]FDR in MeOH. MeOH was evaporated at 55°C (550 mbar) within 2–3 min. MeCN was added and the resulting solutions were heated to give the corresponding 18F-labeled products. Protected 5-[18F]FDR was purified by SPE and thereafter deprotected under acidic conditions. Finally, reaction conditions for the conjugation of 5-[18F]FDR to aminooxy-functionalized peptides via chemoselective oxime ligation were optimized. [18F]F– was eluted from an anion exchange resin almost quantitatively. Under optimized conditions appropriately protected 5-[18F]FDR as well as [18F]AFP and [18F]BFP were prepared from the corresponding 3-N,N,N-trimethylammoniumalkyl(aryl)sulfonyl and azetidinium precursors in RCYs of up to 70%, 90% and 91% (determined by radio-HPLC analysis of the crude product), respectively. After SPE purification 5-[18F]FDR was obtained in 41% RCY (EOB) and excellent RCP >99% after deprotection with 1 m HCl (110 °C, 12 min) . The amount of d-ribose (60–80 μg/batch), a competitor in subsequent oxime ligation, was low enough to allow an efficient conjugation of 5-[18F]FDR with aminooxy-functionalized peptides. The corresponding conjugates were prepared in RCYs of up to 91%. The SN2 radiofluorination under “minimalist” conditions is well suited for the fast production of versatile 18F-labeled building blocks. The positively charged trimethylammonium “tag” of the 5-[18F]FDR precursor enables its simple separation from the labeled product using SPE. The prosthetic group was sufficiently pure for the subsequent labeling of peptides.
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), Dresden, 14.-19.05.2017, Dresden, Deutschland
  • Open Access LogoJournal of Labelled Compounds and Radiopharmaceuticals 60(2017)S1, S261
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3508

Registration No. 26077 - Permalink


Evaluation of Ba/Ra Polyoxopalladates for Radiopharmaceutical Applications
Gott, M.; Yang, P.; Kortz, U.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.
Corresponding author: Gott, M.
Abstract: Alpha particles show great promise for therapeutic applications due to their high rate of linear energy transfer over short path lengths. Radium-223 has excellent decay properties but, a major hurdle for its use is the development of a stable chelator for delivery to the tumor site. Work is underway testing polyoxopalladates, as a novel subclass of polyoxometalates (POMs), to complex barium and radium and establish the feasibility of their radiopharmaceutical use. Nonradioactive BaPd15 POMs were produced by the reported literature method and characterized by NMR, TLC, and HPLC. Radioactive [133Ba, 224Ra]BaPd15 POMs were prepared similarly with either [133Ba]BaCl2 or [224Ra]RaCl2 spiked into the solution prior to heating. Characterization was performed by NMR, RadioTLC, and HPLC. Chromatographic separations were tested using Dowex-50 and Sephadex G-15 to purify the POM product. Dialysis studies were carried out to determine the stability of the [133Ba]BaPd15. Incubation studies with rat serum were performed to explore their biological stability. The POMs were easily prepared in a one-pot reaction and characterized by 1H and 13C NMR. TLC and HPLC were performed to determine the percent of incorporated radionuclide. Cation exchange chromatography with Dowex 50-X8 removed free [133Ba]Ba2+ to non-detectable levels in the product. Size exclusion chromatography with Sephadex G-15 separated the BaPd15 product (eluted first) from the bulk excess of acetate buffer and phenylarsonic acid. Dialysis studies showed measurable quantities of 133Ba in solution after 1 hour and ~ 10% of the radionuclide had escaped after 24 hours. Serum studies indicated the POMs had affinity for serum proteins quickly upon contact with the serum. The results of this study demonstrate the development of radioactive [133Ba, 224Ra]BaPd15 POMs. Stability studies indicated that these POMs quickly began to decompose, significantly so after 24 hours. Additionally, incubation studies with rat serum demonstrated an affinity for serum proteins. For these reasons, these POMs are unsuitable for radiotherapeutic use.
Keywords: Polyoxometalates, Alpha-therapy, Radium
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), Dresden, 14.-19.05.2017, Dresden, Deutschland
  • Open Access LogoJournal of Labelled Compounds and Radiopharmaceuticals 60(2017)S1, S559
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3508

Registration No. 26076 - Permalink


Novel Functionalized Calixarenes as Host Molecules for Complexation with Alkaline Earth Metals
Steinberg, J.; Gott, M.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.
Corresponding author: Mamat, C.
Abstract: Alpha-emitting radionuclides (e.g. radium-223, 224) are of high interest for cancer therapy, but currently, no stable complexing agent for radium is known. Moderate stability constants have been described for complexes of alkaline-earth metal ions with calixarenes, crown and aza crown ethers [2, 3]. By combining calixarenes with crown and aza crown ethers as well as functionalizing the remaining calixarene hydroxyl groups, higher stability constants may be achieved. In this study, we synthesized and evaluated new functionalized calixarenes as host molecules for radium. 1,3 single-bridged crowns were selectively introduced on the lower rim of 4-tert-Butylcalix[4]arene by alkylation with tosylated crown ethers or by acylation and sequential amination with aza crown ethers. The remaining phenolic hydroxyl groups were functionalized by acylation and sequential amination to prepare acetic acid amide and hydroxyl amide derivatives. The complexation was carried out by vortexing the ligand in chloroform with an aqueous BaCl2-solution as surrogate for Ra for 10 min. The barium complex was isolated from the organic layer and characterization was performed by NMR. The barium-133 and radium-224 calixcrowns were prepared similarly and stability studies performed by TLC and HPLC. 1,3-bridged crown and calix(aza)crown ethers were obtained in good yields (53 and 58%, respectively) and acetic acid amide and hydroxyl amide calixcrown derivatives were successfully prepared with yields of 66-82%. Barium was incorporated into the calixarene compounds, isolated by a two-phase extraction and the structure confirmed by NMR. Synthesis and stability of the radioactive complexes will be reported. Future studies will incorporate a targeting moiety on the upper ring. Several novel, functionalized calixarene compounds were prepared and initial complexation studies were performed with nonradioactive barium. The resulting complexes were checked by NMR and the procedure was transferred to radioactive barium-133 and radium-224. Complexation and stability was demonstrated by radiographic imaging of the developed TLC plates. These complexes show great promise for application to cancer therapy.
Keywords: Alpha-therapy, Radium, Calixarenes
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), Dresden, 14.-19.05.2017, Dresden, Deutschland
  • Open Access LogoJournal of Labelled Compounds and Radiopharmaceuticals 60(2017)S1, S488
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3508

Registration No. 26074 - Permalink


Detection of Auger Electron Induced Strand Breaks on Plasmid DNA Caused by Technetium-99m Labeled Pyrene Derivatives
Wunderlich, G.; Reissig, F.; Mamat, C.; Pietzsch, H.-J.; Kotzerke, J.; Steinbach, J.
Corresponding author: Wunderlich, G. UKD / TU Dresden
Abstract: Simultaneously with the known γ-emission, 99mTc causes radical-mediated DNA damage due to Auger electrons, which were also emitted. We have synthesized a series of new 99mTc-labeled pyrene derivatives (common DNA intercalators) with varied distances between the pyrene moiety and the radionuclide (Fig. 1). Plasmids (pUC 19) enable the investigation of the unprotected interactions between the labeled pyrene derivatives (3-15MBq) and DNA that results in single-strand breaks (SSB) or double-strand breaks (DSB) separated by gel electrophoresis in 1.4% agarose gel and quantified by fluorescent staining. We used the 99mTc(CO)3-core for pyrene labeling. 99mTc was tightly bound to the plasmid DNA and its damage is mainly dependent on the chain length between the pyrene residue and the Tc-core. It could not be completely prevented by DMSO, a known free radical scavenger. The effectiveness of the DNA-binding 99mTc-labeled pyrene derivatives was demonstrated by comparison to non-DNA-binding [99mTc]NaTcO4, since nearly all DNA damage caused by [99mTc]NaTcO4 was prevented by DMSO. We prepared a 99mTc-complex with an optimal distance between the [99mTc]Tc(CO)3-core and the pyrene residue to position the 99mTc in close proximity to the plasmid DNA to induce direct SSB and DSB. By increasing the distance between the DNA-intercalating moiety and the bonding moiety for 99mTc, we observed decrease of direct DNA damages. This distance dependence has not been reported for 99mTc until now. Clinical relevant Auger electron therapy is hampered by the prerequisite of DNA binding which is hindered by cell and nucleus membranes.
Keywords: 99mTc, Auger, DNA damage, Therapy
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), Dresden, 14.-19.05.2017, Dresden, Deutschland
  • Open Access LogoJournal of Labelled Compounds and Radiopharmaceuticals 60(2017)S1, S365
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3508

Registration No. 26072 - Permalink


Pharmacokinetic/ pharmacodynamic studies of a copper-64 labelled Kv1.3-blocking peptide targeting autoimmune diseases
Kubeil, M.ORC; Bergmann, R.; Zarschler, K.; Stephan, H.; Norton, R. S.
Abstract: Objectives
The voltage-gated potassium channel Kv1.3 is an attractive therapeutic target to treat autoimmune disorders such as multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus and type-1 diabetes mellitus [1, 2]. This channel is highly expressed in T
effector memory lymphocytes and plays an important role in their activation. A scorpion toxin derived peptide analogue, HsTX1[R14A], blocks Kv1.3 with an affinity in the picomolar range [3].Moreover, this peptide is stabilized by four disulfide bridges, conferring high in vivo stability.
Methods
The peptide was synthesised by SPPS using Fmoc-tBu strategy [3]. The N-terminus of HsTX1[R14A] has been coupled to NOTA (1,4,7-triazacyclononane-triacetic acid) to permit labelling with the positron emitter copper-64. Biodistribution studies and metabolite analysis were carried out in healthy male Wistar rats using Positron Emission Tomography and Radioluminography.
Results
The distribution studies demonstrated a rapid blood clearance after intravenous injection and a fast renal elimination. The highest accumulation was found in the kidney and urine. As a consequence, a long in vivo half-life has been observed. Furthermore, there were no indications of lymphatic cell binding in direct measurements with unfractionated human Tcells.
Conclusion
The promising pharmacological profile of the radiotracer enhances the potential of this peptide to be developed as a therapeutic. Its extraordinary stability and high selectivity for the target channel Kv1.3 make it an attractive candidate for autoimmune disorders.
References
[1] V. Chi, M. W. Pennington, R. S. Norton, E. Tarcha, L. Londono, B. Sims-Fahey, S. K. Upadhyay, J. T. Lakey, S. Iadonato, H. Wulff, C. Beeton, K. G. Chandy, Toxicon 2012, 59, 529-546.
[2] C. Beeton, et al. Proc. Natl. Acad. Sci. U. S. A. 2006, 103, 17414-17419.
[3] M. H. Rashid, R. Huq, M. R. Tanner, S. Chhabra, K. K. Khoo, R. Estrada, V. Dhawan, S. Chauhan, M. W. Pennington, C. Beeton, S. Kuyucak, and R. S. Norton, Sci. Rep. 2014, 4, 1-9.
Keywords: potassium channel, autoimmune disease, PET, peptide
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences, 14.-19.05.2017, Dresden, Deutschland

Registration No. 26068 - Permalink


Neuartige Calix[4]arene zur Komplexierung von Erdalkalimetallen
Mamat, C.ORC; Bauer, D.; Gott, M.; Pietzsch, H.-J.; Steinbach, J.; Steinberg, J.
Abstract: Radium-223 und Radium-224 sind klassische alpha-Emitter, die u.a. zu radiotherapeutischen Zwecken Verwendung finden sollen. Radium-223 ist bereits in der klinischen Anwendung, jedoch lediglich als [223Ra]RaCl2, da geeignete Chelatoren für eine stabile Komplexierung dieses Gruppe-2-Metalls fehlen. Komplexbildner die aus (Aza-)Kronenethern und Calixarenen bestehen stellen vielversprechende Kandidaten dar. Von dieses Derivaten wurden Komplexbildungskonstanten bestimmt mit Ba2+ als nichtradioaktives Surrogat aufgrund der ähnlichen chemischen Eigenschaften. Des Weiteren wurden Komplexierungsstudien mit 133Ba durchgeführt.
Keywords: Calixarene, Radium-223, Radiotherapeutika, alpha-Emitter
  • Lecture (Conference)
    Wissenschaftsforum Berlin - GdCh-Jahrestagung, 10.-13.09.2017, Berlin, Deutschland

Registration No. 26067 - Permalink


New measurement of the 242Pu(n,γ) cross section at n_TOF-EAR1 for MOX fuels: Preliminary results in the RRR
Lerendegui-Marco, J.; Guerrero, C.; Cortés-Giraldo, M. A.; Quesada, J. M.; Mendoza, E.; Cano-Ott, D.; Eberhardt, K.; Junghans, A.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Bacak, M.; Balibrea, J.; Barbagallo, M.; Bečvář, F.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brown, A.; Caamaño, M.; Calviño, F.; Calviani, M.; Cardella, R.; Casanovas, A.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Colonna, N.; Cortés, G.; Cosentino, L.; Damone, L. A.; Diakaki, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Göbel, K.; Gómez-Hornillos, M. B.; García, A. R.; Gawlik, A.; Gilardoni, S.; Glodariu, T.; Gonçalves, I. F.; González, E.; Griesmayer, E.; Gunsing, F.; Harada, H.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Kalamara, A.; Kavrigin, P.; Kimura, A.; Kivel, N.; Kokkoris, M.; Krtička, M.; Kurtulgil, D.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Lo Meo, S.; Lonsdale, S. J.; Macina, D.; Marganiec, J.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Maugeri, E. A.; Mazzone, A.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Musumarra, A.; Negret, A.; Nolte, R.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, I.; Praena, J.; Radeck, D.; Rauscher, T.; Reifarth, R.; Rout, P. C.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Smith, A. G.; Sosnin, N. V.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Warren, S.; Woods, P. J.; Wright, T.; Žugec The N_Tof Collaboration, P.
Abstract: The spent fuel of current nuclear reactors contains fissile plutonium isotopes that can be combined with 238U to make mixed oxide (MOX) fuel. In this way the Pu from spent fuel is used in a new reactor cycle, contributing to the long-term sustainability of nuclear energy. The use of MOX fuels in thermal and fast reactors requires accurate capture and fission cross sections. For the particular case of 242Pu, the previous neutron capture cross section measurements were made in the 70's, providing an uncertainty of about 35% in the keV region. In this context, the Nuclear Energy Agency recommends in its “High Priority Request List” and its report WPEC-26 that the capture cross section of 242Pu should be measured with an accuracy of at least 7–12% in the neutron energy range between 500 eV and 500 keV. This work presents a brief description of the measurement performed at n_TOF-EAR1, the data reduction process and the first ToF capture measurement on this isotope in the last 40 years, providing preliminary individual resonance parameters beyond the current energy limits in the evaluations, as well as a preliminary set of average resonance parameters.
Keywords: 242Pu neutron capture, neutron time-of-flight measurement, CERN nTOF
  • Open Access LogoContribution to proceedings
    International Conference on Nuclear Data for Science and Technology (ND2016), 11.-16.09.16, Bruges, Belgium, 11.-16.09.16, Bruges, Belgium
    European Physical Journal Web of Conferences
    DOI-Link: http://dx.doi.org/10.1051/epjconf/201714611045

Registration No. 26065 - Permalink


Positron Annihilation Studies using a Superconducting Electron LINAC
Wagner, A.; Butterling, M.; Hirschmann, E.; Krause-Rehberg, R.; Liedke, M. O.; Potzger, K.
Abstract: The Helmholtz-Center at Dresden-Rossendorf operates several user beamlines for materials research using positron annihilation energy and lifetime spectroscopy. Two beamlines are being operated at a superconducting electron linear accelerator producing hard X-rays from electron-bremsstrahlung and in turn generating positrons from pair production. Both installations employ bunched continuous-wave (CW) electron beams with energies between 15 MeV and 30 MeV. The CW-operation results in significantly reduced pile-up effects in the detectors in comparison to normal conducting accelerators. Electron bunch lengths below 10 ps FWHM allow positron annihilation lifetime spectroscopy measurements with high timing resolutions. The bunch repetition rate is adjustable to 26 MHz / 2n, n=0, 1, 2 ... 16 matching wide spans in positron or positronium lifetimes. The GiPS (Gamma-induced Positron Source) generates energetic electron-positron pairs inside the sample under investigation from hard x-rays impinging onto the sample [2]. Therefore, the source is especially suited for materials which are not qualified for vacuum conditions or because they are imposing hazardous conditions or intrinsic radioactivity. Exemplary defect studies on the skyrmoin-lattice compound MnSi will be presented. MePS (the Monoenergetic Positron Source) utilizes positrons with fixed energies ranging from 500 eV to 16 keV. A magnetic beam transport system guides positrons to the samples under investigation. A dedicated chopper/buncher system is used to maintain a high timing resolution for depth-dependent annihilation lifetime studies in thin films. The signal-to-noise ratio is beyond 104 while lifetime resolutions of around 280 ps FWHM have been obtained. Applications of porosimetry studies in low-k dielectrics and polymer brushes will be presented.
The MePS facility will be extended by an end-station called AIDA2 (Apparatus for in-situ Defect Analysis) where defect studies can be performed in a wide temperature range during thin film growth and ion irradiation. A similar setup named AIDA-1 is already in operation at a 22Na-based mono-energetic continuous positron beam used for Doppler-broadening spectroscopy experiments.
The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). The initial AIDA system was funded by the Impulse- und Networking fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox). The AIDA facility was funded through the Helmholtz Energy Materials Characterization Platform.
Keywords: positron annihilation superconducting LINAC materials science
  • Invited lecture (Conferences)
    International Workshop on Physics with Positrons at Jefferson Lab, 12.-15.09.2017, Newport News, VA, USA
  • Invited lecture (Conferences)
    International Workshop on Positron Studies of Defects 2017 (PSD-17), 03.-08.09.2017, Dresden, Deutschland

Registration No. 26064 - Permalink


Liquid metal batteries
Weier, T.; Ashour, R.; Herreman, W.; Horstmann, G.; Kelley, D.; Landgraf, S.; Nimtz, M.; Nore, C.; Personnettaz, P.; Salas, A.; Starace, M.; Stefani, F.; Weber, N.
Abstract: Übersicht der Forschungsaktivitäten zu Flüssigmetallbatterien am HZDR
  • Poster
    LIMTECH-Symposium, 19.09.2017, Dresden, Deutschland

Registration No. 26063 - Permalink


High repetition rate, multi-MeV proton source from cryogenic hydrogen jets
Gauthier, M.; Curry, C. B.; Göde, S.; Brack, F.-E.; Kim, J. B.; Macdonald, M. J.; Metzkes, J.; Obst, L.; Rehwald, M.; Rödel, C.; Schlenvoigt, H.-P.; Schumaker, W.; Schramm, U.; Zeil, K.; Glenzer, S. H.
Corresponding author: Gauthier, M. High Energy Density Science Division, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
Abstract: We report on a high repetition rate proton source produced by high-intensity laser irradiation of a continuously flowing, cryogenic hydrogen jet. The proton energy spectra are recorded at 1Hz for Draco laser powers of 6, 20, 40, and 100 TW. The source delivers ca. 10^13 protons/MeV/sr/min. We find that the average proton number over one minute, at energies sufficiently far from the cut-off energy, is robust to laser-target overlap and nearly constant. This work is therefore a first step towards pulsed laser-driven proton sources for time-resolved radiation damage studies and applications which require quasi-continuous doses at MeV energies.

Registration No. 26061 - Permalink


Nitrogen redistribution in annealed LaFeOxNy thin films investigated by FTIR spectroscopy and EELS mapping
Haye, E.; Pierron, V.; Barrat, S.; Capon, F.; Munnik, F.; Bruyère, S.
Corresponding author: Haye, E. Institut Jean Lamour (IJL), CNRS/Université de Lorraine, France
Abstract: LaFeOxNy thin films have been deposited by magnetron sputtering in Ar/O2/N2 gas mixture at 800°C. Such oxynitride perovskites present an uncommon infrared vibration mode position at 2040cm-1, due to presence of nitrogen, which disappears with heating in air. The evolution of this vibration mode with temperature has been studied and permit to determine an activation energy of thermal degradation of LaFeOxNy. The quantification of nitrogen by Elastic Recoil Detection Analysis (ERDA) before and after heating exhibits the same nitrogen content, indicating a redistribution of nitrogen. Such nitrogen redistribution is observed by Electron Energy Loss Spectroscopy (EELS) mapping, showing migration of nitrogen into grain boundaries, in association with film oxidation.
Keywords: Oxynitride perovskite, Thermal stability, EELS mapping, FTIR

Registration No. 26059 - Permalink


The costimulatory domain in chimeric antigen receptor modified T lymphocytes defines their resistance to immunosuppression by regulatory T cells
Kegler, A.; Koristka, S.; Bergmann, R.; Feldmann, A.; Arndt, C.; Aliperta, R.; Albert, S.; Ziller-Walter, P.; Ehninger, G.; Bornhäuser, M.; Schmitz, M.; Bachmann, M.
Keywords: tumor immunotherapy, CAR design, Treg suppression
  • Lecture (Conference)
    47th Annual Meeting of the German Society for Immunology, 12.09.2017, Erlangen, Germany

Registration No. 26058 - Permalink


Using the novel universal CAR platform technology “UniCAR” to target tumors overexpressing disialoganglioside (GD2)
Mitwasi, N.; Feldmann, A.; Bergmann, R.; Rössig, C.; Bachmann, M.
Keywords: CAR Technology, UniCAR T cells, GD2.
  • Lecture (Conference)
    47th Annual Meeting of the German Society for Immunology, 12.09.2017, Erlangen, Germany

Registration No. 26057 - Permalink


Retargeting of human T lymphocytes to EGFR-expressing cancer cells via nanobody-based target modules using the universal chimeric antigen receptor technology
Albert, S.; Bergmann, R.; Koristka, S.; Feldmann, A.; Arndt, C.; Aliperta, R.; Ehninger, A.; Cartellieri, M.; Ehninger, G.; Steinbach, J.; Bachmann, M.
Keywords: CAR T cell therapy, nanobodies, EGFR-targeting
  • Lecture (Conference)
    47th Annual Meeting of the German Society for Immunology, 12.09.2017, Erlangen, Germany

Registration No. 26056 - Permalink


Complex crustal structures: their 3D grav/mag modelling and 3D printing
Götze, H.-J.; Schmidt, S.; Menzel, P.
Abstract: The new techniques are user-friendly because they are highly interactive, ideally real-time and topology conserving and can be used for both flat and spherical models in 3D. These are important requirements for joint inversion for gravity and magnetic modelling of fields and their derivatives, constrained by seismic and structural input from independent data sources. A borehole tool for magnetic and gravity modelling will also be introduced. We are already close to satisfying the demand of treating several geophysical methods in a single model for subsurface evaluation purposes and aim now for fulfilling most of the constraints: consistency of model results and measurements and geological plausibility as well.
For 3D gravmag modelling, polyhedrons built by triangles are used. All elements of the gravity and magnetic tensors can be included. In the modelling interface, after geometry changes the effect on the model is quickly updated because only the changed triangles have to be recalculated. Because of the triangular model structure, our approach can handle complex structures very well and it is flexible (e.g. overhangs of salt domes or plumes). For regional models, the use of spherical geometries and calculations is necessary and available. 3D visualization is performed with a 3D-printer (Ultimaker 2) and gives new insights into even rather complicated Earth subsurface structures.
Inversion can either be run over the whole model, but typically it is used in smaller parts of the model, helping to solve local problems and/or proving/disproving local hypotheses. The basic principles behind this interactive approach are high performance optimized algorithms (CMA-ES: Covariance-matrix-adoption-evolution-strategy). The efficiency of the algorithm is rather high in terms of stable convergence due to topological model validity.
Potential field modelling is always influenced by edge effects. To avoid this, a simple but very robust method has been developed: Derive a density/susceptibility-depth function by taking the mean value of the borders of depth slices through the model. The focus of the presentation is set on two practical study examples: one from the international KTB – Project, Germany´s deep continental borehole, as well as a very complex salt structure in the Northwest German Basin.
Keywords: Potential Field modeling, 3D visualization and printing
  • Poster
    European Geosciences Union General Assembly 2017, 23.-26.04.2017, Wien, Österrreich

Registration No. 26051 - Permalink


Ground-state configuration of neutron-rich 35Al via Coulomb breakup
Chakraborty, S.; Datta Pramanik, U.; Aumann, T.; Beceiro-Novo, S.; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chartier, M.; Cortina-Gil, D.; de Angelis, G.; Diaz Fernandez, P.; Emling, H.; Ershova, O.; Fraile, L. M.; Geissel, H.; Gonzalez-Diaz, D.; Johansson, H.; Jonson, B.; Kalantar-Nayestanaki, N.; Kröll, T.; Krücken, R.; Langer, C.; Le Bleis, T.; Leifels, Y.; Marganiec, J.; Münzenberg, G.; Najafi, M. A.; Nilsson, T.; Nociforo, C.; Panin, V.; Plag, R.; Rahaman, A.; Reifarth, R.; Ricciardi, M. V.; Rigollet, C.; Rossi, D.; Scheidenberger, C.; Scheit, H.; Simon, H.; Taylor, J. T.; Togano, Y.; Typel, S.; Utsuno, Y.; Wagner, A.; Wamers, F.; Weick, H.; Winfield, J. S.
Corresponding author: Datta Pramanik, U. Saha Institute of Nuclear Physics, Kolkata 700064, India
Abstract: The ground-state configuration of 35Al has been studied via Coulomb dissociation (CD) using the LAND-FRS setup (GSI, Darmstadt) at a relativistic energy of ∼403 MeV/nucleon. The measured inclusive differential CD cross section for 35Al, integrated up to 5.0 MeV relative energy between the 34Al core and the neutron using a Pb target, is 78(13) mb. The exclusive measured CD cross section that populates various excited states of 34Al is 29(7) mb. The differential CD cross section of 35Al → 34Al + n has been interpreted in the light of a direct breakup model, and it suggests that the possible ground-state spin and parity of 35Al could be, tentatively, 1/2+ or 3/2+ or 5/2+. The valence neutrons, in the ground state of 35Al, may occupy a combination of either l = 3,0 or l = 1,2 orbitals coupled with the 34Al core in the ground and isomeric state(s), respectively. This hints of a particle-hole configuration of the neutron across the magic shell gaps at N = 20,28 which suggests narrowing the magic shell gap. If the 5/2+ is the ground-state spin-parity of 35Al as suggested in the literature, then the major ground-state configuration of 35Al is a combination of 34Al(g.s.; 4−) ⊗ νp3/2 and 34Al(isomer; 1+) ⊗ νd3/2 states. The result from this experiment has been compared with that from a previous knockout measurement and a calculation using the SDPF-M interaction.
Keywords: Coulomb dissociation electromagnetic strength radioactive beam nuclear astrophysics

Registration No. 26047 - Permalink


Flüssigmetallbatterien als Option für elektrische Großspeicher
Nimtz, M.; Weber, N.; Weier, T.
Abstract: Übersicht über die Forschungsaktivitäten an Flüssigmetallbatterien am HZDR.
  • Poster
    3. Wissenschaftliches SCI-Treffen "Energiesystemintegration", 11.09.2017, Karlsruhe, Deutschland

Registration No. 26042 - Permalink


Selection of Gallium-binding peptides using Phage Display technology
Schönberger, N.; Matys, S.; Lederer, F.; Pollmann, K.
Abstract: Gallium is used essentially in the semiconductor compounds GaAs, GaN or GaP for high-potential future technologies. The resulting rapidly growing demand for gallium shouldn't be exclusively met by the recovery from primary raw material sources.
Biosorptive recycling of gallium from waste waters of the semiconductor industry is a promising and innovative contribution for establishing an economic and clean zero waste technology.
Peptides are excellently suitable ligands for the biosorptive complexation of gallium ions in aqueous solutions due to their variability in their amino acid sequence and their robust properties.
A well-established method for the selection of highly specific peptide ligands in medicine and biotechnology is the phage display technology. Random, short peptide sequences are presented on the surface according to genetically modified bacteriophages. In a biopanning called process, a pool of different bacteriophages is selected against a particular target, thereby enriching specific binding clone variants (figure 1). A very effective method has been established for the selection of different phage display libraries. Gallium ions immobilized on a monolithic ion exchanger are made accessible for biopanning in an FPLC system. This chromatopanning allows the selective enrichment of gallium-binding clone variants under strictly controlled process conditions.
In the present study, we report about the enrichment, identification and characterization of several gallium-binding motifs. Some promising gallium binding bacteriophage clones are chosen for further binding studies. The corresponding peptide sequences can be synthesized and used in subsequent experiments to develop biosorptive materials for selective gallium recovery from industrial waste waters.
Keywords: Phage Surface Display, biopanning, immobilized metal ions, Gallium, metal binding peptides
  • Lecture (Conference)
    6th International Symposium on biosorption and biodegradation/bioremediation, 25.-29.06.2017, Prag, Czech republic

Registration No. 26041 - Permalink


Development of Metal Ion Binding Peptides Using Phage Surface Display Technology.
Schönberger, N.; Matys, S.; Flemming, K.; Lehmann, F.; Lederer, F.; Pollmann, K.
Abstract: Phage surface display technology is a useful tool for the identification of biosorptive peptides. In this work it is used for the identification of cobalt, nickel and gallium binding peptides. We present methods for the enrichment of metal ion binding bacteriophage clones from two commercial phage display libraries. One of them presents cyclic heptamer peptides, in which two cysteins flanke the peptide loop (C7C), and a linear dodecapeptide library (D-12).Metal ion selective peptides are suitable to separate as well as concentrate cobalt and nickel from copper black shale leaching products (EcoMetals project) and gallium from industrial waste waters (EcoGaIn project). In contrast to common capture methods of specific binding phage for solid materials the ionic species have to be immobilized prior to the bio-panning procedure. This was realized by chemical complexation of the metal ions using commercial complexing agents on porous matrices. Moreover, an option to harvest non elutable strong binding phage is proposed.
Keywords: Phage Surface Display, biopanning, immobilized metal ions, nickel, gallium, cobalt, metal binding peptides
  • Contribution to proceedings
    22nd International Biohydrometallurgy Symposium, Solid State Phenomena, 24.-27.09.2017, Freiberg, Deutschland
    22nd International Biohydrometallurgy Symposium, Schweiz: Trans Tech Publications, ISSN: 1662-9779,, 591-595
    DOI-Link: http://dx.doi.org/10.4028/www.scientific.net/SSP.262.591

Registration No. 26040 - Permalink


Overview on Helmholtz Reactor Safety Research
Kliem, S.ORC; Tromm, W.; Reinecke, E.-A.
Abstract: The paper gives an overview on the research conducted within the topic "Reactor Safety" of the Helmholtz NUSAFE programme.
  • Lecture (Conference)
    2nd Sino-German Symposium on Fundamentals of Advanced Nuclear Safety Technology, 12.-15.09.2017, Karlsruhe, Deutschland

Registration No. 26038 - Permalink


Hierarchical thermoplastic rippled nanostructures regulate Schwann Cell adhesion, morphology and spatial organization
Masciullo, C.; Dell'Anna, R.; Tonazzini, I.; Böttger, R.; Pepponi, G.; Cecchini, M.
Corresponding author: Cecchini, Marco NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza San Silvestro 12, 56127 Pisa, Italy;
Abstract: Periodic ripples are a variety of anisotropic nanostructures that can be realized by ion beam irradiation on a wide class of solid surfaces. Only few authors have investigated these surfaces for tuning the response of biological systems, probably because it is challenging to directly produce them in materials that well sustain long-term cellular cultures. Here, hierarchical rippled nanotopographies with lateral periodicity of ∽300 nm are produced from a gold-irradiated germanium mold in polyethylene terephthalate (PET), a biocompatible polymer approved by the US Food and Drug Administration for clinical applications, by a novel three-steps embossing process. The effects of nano-ripples on Schwann Cells (SCs) are studied in view of their possible use for nerve-repair applications. Data demonstrate that nano-ripples can enhance short-term SC adhesion and proliferation (3-24h from seeding), drive their actin cytoskeleton spatial organization and sustain long-term cell growth. Notably, SCs orient perpendicularly with respect to the nanopattern lines. These results provide information about the possible use of hierarchical nano-rippled elements for nerve-regeneration protocols.
Keywords: hierarchical nanostructures, self-organization, ion Irradiation, cell adhesion, nano-ripples

Registration No. 26037 - Permalink


Ultra-dense planar metallic nanowire arrays with extremely large anisotropic optical and magnetic properties
Jia, Q.; Ou, X.; Langer, M.; Schreiber, B.; Grenzer, J.; Siles, P. F.; Rodriguez, R. D.; Huang, K.; Yuan, Y.; Heidarian, A.; Hübner, R.; You, T.; Yu, W.; Lenz, K.; Lindner, J.; Wang, X.; Facsko, S.
Corresponding author: Lenz, Kilian HZDR
Abstract: A nanofabrication method for the production of ultra-dense planar metallic nanowire arrays scalable to wafer-size is presented. The method is based on an efficient template deposition process to grow diverse metallic nanowire arrays with extreme regularity in only two steps. First, III-V semiconductor substrates are irradiated by a low-energy ion beam at an elevated temperature, forming a highly ordered nanogroove pattern by a “reverse epitaxy” process due to self-assembly of surface vacancies. Second, diverse metallic nanowire arrays (Au, Fe, Ni, Co, FeAl alloy) are fabricated on these III-V templates by deposition at a glancing incidence angle. This method allows for the fabrication of metallic nanowire arrays with periodicities down to 45 nm scaled up to wafer-size fabrication. As typical noble and magnetic metals, the Au and Fe nanowire arrays produced here exhibited large anisotropic optical and magnetic properties, respectively. The excitation of localized surface plasmon resonances (LSPRs) of the Au nanowire arrays resulted in a high electric field enhancement, which was used to detect phthalocyanine (CoPc) in surface-enhanced Raman scattering (SERS). Furthermore, the Fe nanowire arrays showed a very high in-plane magnetic anisotropy of approximately 412 mT, which may be the largest in-plane magnetic anisotropy field yet reported that is solely induced via shape anisotropy within the plane of a thin film.
Keywords: self-assembly, metallic nanowire array, reverse epitaxy, magnetic anisotropy, anisotropic dielectric function

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Registration No. 26036 - Permalink


Therapeutic options to overcome tumor hypoxia in radiation oncology
Troost, E.; Koi, L.; Yaromina, A.; Krause, M.
Corresponding author: Troost, Egc HZDR, OncoRay, TUD, DKTK, NCT
Abstract: Purpose
Expert review summarizing the overcome tumor cell hypoxia by treatment modification in radiation oncology.
Methods
An extensive literature search regarding various means of treatment modification was performed and key papers on those modifications were included in this review article.
Results
Based on the identified key papers the means to overcome hypoxia in radiation oncology were summarized in this review article, e.g., increasing levels of oxygen, combining radiotherapy with agents counteracting hypoxia, or modifying radiation treatment itself.
Conclusions
This review summarizes the results of preclinical and clinical studies counteracting hypoxia and highlights the measures that have found their way into clinical practice.
Keywords: Hypoxia, radiotherapy, oxygenation modification, systemic agents, radiation dose-escalation

Registration No. 26034 - Permalink


Spin-transfer driven dynamics in hybrid structures
Fowley, C.; Rode, K.; Gallardo, R.; Thiyagarajah, N.; Lau, Y.-C.; Borisov, K.; Betto, D.; Atcheson, G.; Kampert, E.; Wang, Z.; Lindner, J.; Coey, M.; Stamenov, P.; Deac, A. M.
Abstract: Since the discovery of giant magnetoresistance, metal spintronics has seen unprecedented advances, from the realisation of ultra-high magnetoresistance ratios to substantial output power from both conventional spin transfer torque oscillators as well as spin-torque vortex oscillators [1]. The recently discovered of the fully compensated ferrimagnetic half-metal, manganese ruthenium gallium (MRG), due to its widely tunable magnetic properties [2], could enable spin torque oscillators which work in the range of hundreds of GHz. Being a ferrimagnet, MRG consists of two magnetic sublattices which are coupled antiferromagnetically to each other. It has been shown that in this material the magnetotransport is dominated by one magnetic sublattice whereas the overall magnetisation is determined by both sublattices [3]. This means that MRG behaves magnetically like an antiferromagnet and electrically like a highly spin polarised ferromagnet, implying that spin-transfer torque would act on one sublattice only, enabling efficient current induced excitations. Due to the different temperature dependences of the sublattice magnetisations, MRG displays a compensation temperature at which the total magnetic moment is zero and the magnetic state is impervious to external magnetic fields [4].
Here we conduct high-field magnetotransport measurements [5] on selected films of MRG with differing Ru concentration and, therefore, different compensation temperatures (Tc). Both the transverse Hall resistivity and longitudinal resistivity are recorded in magnetic fields up to 58T. MRG exhibits a large spontaneous Hall angle of ~2%, coercivity exceeding 1T at room temperature (and several Teslas close to Tc) and has very low net magnetisation of 25kA/m. Despite having a no net magnetic moment at the compensation temperature the magnitude of the Hall signal does not become zero, further indicating both the half-metallic nature of the material and that the magnetotransport is dominated by one sublattice only. An additional feature is observed in the transport data, which resembles a spin-flop transition. By comparison to analytical and mean-field calculations of the sublattice magnetisation directions we can estimate the both the sublattice anisotropy (Hk) and interlayer exchange coupling (Hex). The out-of-phase and in-phase magnetic resonance modes, therefore, lie in the range of 0.3THz and 4THz, respectively. This makes MRG a uniquely tuneable material as a free layer in spin-transfer oscillator applications [6].


References:
[1] Baibich M.N. et al., Physical Review B, 61, 2472 (1988), Ikeda S. et al., Applied Physics Letters, 93 082508 (2008), Tsunegi S. et al., Applied Physics Letters, 109, 252402 (2016)
[2] Kurt H. et al., Physical Review Letters, 112, 027201 (2014)
[3] Borisov K. et al., Applied Physics Letters, 108, 192407 (2016)
[4] Betto D. et al., AIP Advances, 6, 055601 (2016)
[5] Fowley C. et al., Journal of Physics D : Applied Physics, 48, 164006 (2015)
[6] Awari N. et al., Applied Physics Letters, 109, 032403 (2016)
Keywords: magnetism, spin-transfer torque, wireless communication
  • Invited lecture (Conferences)
    Moscow International Symposium on Magnetism, 01.-05.07.2017, Moscow, Russia

Registration No. 26032 - Permalink


Wissenschaftliche Software – Anspruch und Realität im Forschungsprozess
Konrad, U.ORC
Abstract: Wissenschaftliche Software ist heute unverzichtbares Werkzeug im Forschungsprozess, sie ist Voraussetzung für die Nachvollziehbarkeit der (publizierten) Ergebnisse und in vielen Fällen auch selbst ein Ergebnis, das publiziert, genutzt und langfristig bewahrt werden muss. Publikationen bestehen künftig häufig aus zitierfähigen Texten, Daten und Software und müssen entsprechend konsistent behandelt werden, dies ist eine Herausforderung auch für die Bibliotheken. Daraus ergeben sich eine Reihe von Fragestellungen und Aufgaben für die gute wissenschaftliche Praxis im Umfeld der „Offenen Wissenschaft“ (Open Science). Diese Fragen werden in dem Vortrag diskutiert.
Ausgangspunkt ist die Frage, welche Kategorien wissenschaftlicher Software es gibt und was für Rollen diese im Forschungsprozess spielen. Mit der voranschreitenden Digitalisierung von Forschung und Lehre steigt die Abhängigkeit von Software-Lösungen. Die grundlegenden Prinzipien der „guten wissenschaftliche Praxis“ wie Nachvollziehbarkeit, Reproduzierbarkeit, Transparenz und Qualitätssicherung müssen auch bei der Entwicklung und Nutzung von wissenschaftlicher Software angewandt werden. Allerdings gibt es eine Reihe von Besonderheiten für den Umgang mit Software, da diese im Vergleich zu Veröffentlichungen und Daten einem meist kontinuierlichen Entwicklungsprozess unterliegt und im Kontext spezifischer Entwicklungs- und Laufzeitumgebungen zu betrachten sind.
Darüber hinaus sind die Publikation, Nachnutzbarkeit und Verwertung von Software zentrale Herausforderungen. Die Zitation von Quellcode, die Open Source Software-Entwicklung, die Bereitstellung forschungsnaher Infrastrukturen für Entwicklung und Test sowie die Lizenzen und rechtliche Aspekte der Softwarenachnutzung sind noch nicht umfassend in der wissenschaftlichen Praxis realisiert. Darüber hinaus fehlen auch Anreizsysteme für eine nachhaltige Softwareentwicklung in der Forschung.
Für viele dieser Fragen gibt es Lösungsansätze und „best practice“ Beispiele, auf die eingegangen wird. Seit einiger Zeit gibt es dazu internationale und nationale Initiativen wie u.a. die Software Carpentry (1998, US), das Software Sustainability Institute (2008, GB) und sciforge (2014, D). Des Weiteren unterstützt die Deutsche Forschungsgemeinschaft (DFG) die Entwicklung dieses Gebietes u.a. mit dem Programm ”Research Software Sustainability”.
Keywords: Wissenschaftliche Software, Softwareentwicklung, Publikation, Repositorien, Infrastruktur, Bibliothek, Scientific software, software development, publication, repository, infrastructure
  • Lecture (Conference)
    Internationale Open Access Tage 2017, 11.-13.09.2017, Dresden, Deutschland

Registration No. 26025 - Permalink


Qualification tests of optical coatings in space environment
Pelizzo, M. G.; Corso, A. J.; Tessarolo, E.; Martucci, A.; Donazzan, A.; Böttger, R.; Hübner, R.; Napolitani, E.
Abstract: Optical components such as mirrors, filters and windows need to be tested and qualified to verify their resistance in space environments. Future space missions, such as ESA JUICE and SOLO, will operate in harsh environments, rich of ions and electrons. Experiments and development of appropriate protocols are needed to develop proper radiation-hard components and to qualify them.
Keywords: Ions, Coatings, Radiation effects, Nonhomogeneous media, Reflectivity, Optical filters, Protons

Registration No. 26017 - Permalink


Structural and optical studies of Pr implanted ZnO films subjected to a long-time or ultra-fast thermal annealing
Ratajczak, R.; Mieszczynski, C.; Prucnal, S.; Guziewicz, E.; Stachowicz, M.; Snigurenko, D.; Gaca, J.; Böttger, R.; Wojcik, M.; Heller, R.; Skorupa, W.; Borany, J. V.; Turos, A.
Abstract: Epitaxial thin ZnO films grown by Atomic Layer Depositionwere implanted with 150 keV Pr ions to a fluence of 1 × 1015 at/cm2. Implanted samples were subjected to two different kinds of annealing: rapid thermal annealing (RTA) and millisecond-range flash lamp annealing (FLA). Structural properties of implanted and annealed ZnO and the optical response were evaluated by the Channeling Rutherford Backscattering Spectrometry (RBS/c), High-resolution X-ray diffraction and Photoluminescence Spectroscopy (PL), respectively. The results shown, that both annealing techniques lead to recrystallization of the ZnO lattice, that was damaged during the ion implantation. Upon RTA performed at 800 °C a return of Zn atoms from interstitial to their regular site positions is accompanied by rejection of primarily substitutional Pr atoms to the interstitial sites. Consequently, it leads to the out-diffusion and precipitation of Pr atoms on the surface. In contrast to RTA, the diffusion of implanted Pr during a millisecond range FLA treatment is completely suppressed. Despite differences in location of Pr inside the ZnO matrix after FLA and RTA, both annealing techniques lead to the optical activation of Pr3+. Interestingly, our RBS/c study for as implanted layers also revealed the anomalous damage peak, called intermediate peak (IP) located between the expected surface and the bulk damage peak. The PL spectra clearly suggest, that the defect which forms the IP, can be assigned to Zn interstitials. The long-time annealing at 800 °C in oxygen atmosphere causes the complete removal of the IP.
Keywords: Zinc oxide Atomic layer deposition Rare-earth Ion implantation Praseodymium Rapid thermal annealing Flash lamp annealing Channeling Rutherford backscattering spectrometry High-resolution X-ray diffraction Photoluminescence

Registration No. 26016 - Permalink


Electrical behaviour of carbon nanotubes under low-energy proton irradiation
Abbe, E.; Schüler, T.; Klosz, S.; Starruß, E.; Pilz, W.; Böttger, R.; Kluge, O.; Schmiel, T.; Tajmar, M.
Corresponding author: Abbe, Elisabeth Institute of Aerospace Engineering, Technische Universität Dresden, Germany
Abstract: Several applications for carbon nanotubes (CNT) have been proposed for space applications in the last years. However, their behaviour in the harsh space environment is mostly unknown. Energetic particles such as protons can influence the material degradation in space. This material damage could result in a system failure of space systems. Therefore it is necessary to investigate the performance of new materials under proton irradiation.

Screen and jet printed disordered single-walled carbon nanotubes (SWNT), multi-walled carbon nanotubes (MWNT) and multi-walled carbon nanotubes/resin composites (ME) were exposed to 1 keV, 15 keV and 100 keV protons. The electrical behaviour of the CNT conductor paths was measured during the experiment. After this exposure, the CNTs were analyzed using Raman scattering and a scanning electron microscope (SEM).

Their is a clear evidence that proton radiation can destroy carbon nanotubes and influence their electrical performance.
Keywords: Mulltiwalled carbon nanotubes; Single walled carbon nanotubes; Irradation; Protons; Enviromental behaviour

Registration No. 26014 - Permalink


Inclusion of Incidental Radiation Dose to the Cardiac Atria and Ventricles Does Not Improve the Prediction of Radiation Pneumonitis in Advanced-Stage Non-Small Cell Lung Cancer Patients Treated With Intensity Modulated Radiation Therapy
Wijsman, R.; Dankers, F. J. W. M.; Troost, E. G. C.; Hoffmann, A. L.; van der Heijden, E. H. F. M.; de Geus-Oei, L.-F.; Bussink, J.
Corresponding author: Wijsman, R. UMCN
Abstract: Purpose: To evaluate if inclusion of incidental radiation dose to the cardiac atria and ventricles improves the prediction of Grade ≥3 radiation pneumonitis (RP) in advanced stage non-small cell lung cancer (AS-NSCLC) patients treated with intensity-modulated radiation therapy or volumetric-modulated arc therapy.
Material and methods: Using a bootstrap modelling approach, clinical parameters and dose-volume histogram (DVH) parameters of lungs and heart (assessing atria and ventricles separately and combined) were evaluated for RP prediction in 188 AS-NSCLC patients.
Results: After a median follow-up of 18.4 months, 26 patients (13.8%) developed RP. Only the median mean lung dose (MLD) differed between groups (15.3 Gy vs 13.7 Gy for the RP and non-RP group, respectively; p=0.004). The MLD showed the highest Spearman correlation coefficient (Rs) for RP (Rs=0.21; p<0.01). Most Rs of the lung DVH parameters exceeded those of the heart DVH parameters. After bootstrap modelling, the heart DVH parameters were seldom included in the model predicting Grade ≥3 RP. The optimal model for RP consisted of the parameters: MLD and cardiac comorbidity (area under the curve: 0.71).
Conclusion: Incidental dose to the cardiac atria and ventricles did not improve RP risk prediction in our cohort of AS-NSCLC patients.
Keywords: Non-small cell lung cancer; Intensity-modulated radiation therapy; Volumetric-modulated arc therapy; radiation pneumonitis; cardiac exposure.

Registration No. 26009 - Permalink


Use of small animal PET/MRI for internal radiation dose assessment
Kranz, M.
Abstract: The thesis is based on three publications investigating newly developed radiotracers in different animal models. The radiation safety and biodistribution has to be proven prior to the application of first-in-man studies. Resultantly, based on the preclinical dosimetry presented herein, a clinical trial was approved by the competent authorities of Germany for (-)-[18F]flubatine, (+)-[18F]flubatine and (S)-(-)-[18F]fluspidine. Although the radiation safety was proven for (R)-(+)-[18F]fluspidine too, so far it is used in preclinical studies only.
  • Doctoral thesis
    Universität Leipzig, 2017
    Mentor: Prof. Brust, Prof. Sattler

Registration No. 26008 - Permalink


Thermally induced magnetic switching in bit-patterned media
Pfau, B.; Günther, C. M.; Hauet, T.; Eisebitt, S.; Hellwig, O.
Corresponding author: Pfau, B. Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin, Germany
Abstract: We have studied the thermal variation of the switching field of magnetic islands at room temperature. A model bit-pattern media composed of an assembly of islands with 80 nm width was fabricated by sputter deposition onto a pre-patterned substrate. Using direct magnetic-contrast imaging of the islands under applied field, we extract the switching probabilities of individual islands. Based on an analytical model for the thermally activated switching of the islands, we are able to determine the intrinsic magnetic anisotropy of each island and, consequentially, a distribution of anisotropies for the island ensemble investigated. In the distribution, we identify a separated group of islands with a particularly small anisotropy. We attribute this group to islands containing misaligned grains triggering the magnetic reversal. At room temperature and slow field sweep rates, the observed thermal broadening of the switching-field distribution is small compared to the intrinsic broadening. However, we illustrate that thermal fluctuations play a crucial role at high sweep rates by extrapolating our results to technological relevant regimes.

Downloads:

  • Secondary publication expected from 31.07.2018

Registration No. 26002 - Permalink


Magnonic band structure in a Co/Pd stripe domain system investigated by Brillouin light scattering and micromagnetic simulations
Banerjee, C.; Gruszecki, P.; Klos, J. W.; Hellwig, O.; Krawczyk, M.; Barman, A.
Corresponding author: Hellwig, O. Institute of Physics, Chemnitz University of Technology, Reichenhainer Straße 70, D-09107 Chemnitz, Germany and Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
Abstract: By combining Brillouin light scattering and micromagnetic simulations, we studied the spin-wave (SW) dynamics of a Co/Pd thin film multilayer, which features a stripe domain structure at remanence. The periodic up and down domains are separated by corkscrew type domain walls. The existence of these domains causes a scattering of the otherwise bulk and surface SW modes, which form mode families, similar to a one-dimensional magnonic crystal. The dispersion relation and mode profiles of SWs are measured for the transferred wave vector parallel and perpendicular to the domain axis.

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Registration No. 26001 - Permalink


Radiative and non-radiative de-excitation of slow highly charged ions transmitted through freestanding single layer graphene
Wilhelm, R. A.; Schwestka, J.; Gruber, E.; Heller, R.; Kozubek, R.; Schleberger, M.; Facsko, S.; Aumayr, F.
Abstract: Slow highly charged ions interacting with a solid surface undergo an ultrafast charge exchange combined with a rapid electronic de-excitation within less than 10 fs. These processes involve capture of some 10 electrons, emission of at least some 10 additional electrons from the surface and radiative as well as non-radiative de-excitation of the ion. To investigate the branching ratio of radiative vs. non-radiative de-excitation we measured x-ray emission of highly charged Ar ions with two, one or no K-shell hole(s) when they are transmitted through a freestanding single layer of graphene.
  • Lecture (Conference)
    Conference on Ion-Surface Interactions 2017 (ISI2017), 20.-25.08.2017, Moskau, Russland

Registration No. 25997 - Permalink


Oncoidal granular iron formation in the Mesoarchaean Pongola Supergroup, southern Africa: Textural and geochemical evidence for biological activity during iron deposition
Smith, A. J. B.; Beukes, N. J.; Gutzmer, J.; Czaja, A. D.; Johnson, C. M.; Nhleko, N.
Corresponding author: Smith, A. J. B. University of Johannesburg
Abstract: We document the discovery of the first granular iron formation (GIF) of Archaean age and present textural and geochemical results that suggest these formed through microbial iron oxidation. The GIF occurs in the Nconga Formation of the ca. 3.0–2.8 GacPongola Supergroup in South Africa and Swaziland. It is interbedded with oxide and silicate facies micritic iron formation (MIF). There is a strong textural control on iron mineralization in the GIF not observed in the associated MIF. The GIF is marked by oncoids with chert cores surrounded by magnetite and calcite rims. These rims show laminated domal textures, similar in appearance to microstromatolites. The GIF is enriched in silica and depleted in Fe relative to the interbedded MIF. Very low Al and trace element contents in the GIF indicate that chemically precipitated chert was reworked above wave base into granules in an environment devoid of siliciclastic input. Microbially mediated iron precipitation resulted in the formation of irregular, domal rims around the chert granules. During storm surges, oncoids were transported and deposited in deeper water environments. Textural features, along with positive δ56Fe values in magnetite, suggest that iron precipitation occurred through incomplete oxidation of hydrothermal Fe2+ by iron-oxidizing bacteria. The initial Fe3+-oxyhydroxide precipitates were then post-depositionally transformed to magnetite. Comparison of the Fe isotope compositions of the oncoidal GIF with those reported for the interbedded deeper water iron formation (IF) illustrates that the Fe2+ pathways and sources for these units were distinct. It is suggested that the deeper water IF was deposited from the evolved margin of a buoyant Fe2+aq-rich hydrothermal plume distal to its source. In contrast, oncolitic magnetite rims of chert granules were sourced from ambient Fe2+aq-depleted shallow ocean water beyond the plume.

Registration No. 25996 - Permalink


Imaging of magnetic skyrmions with the PolLux endstation of the Swiss Light Source
Finizio, S.; Wintz, S.; Watts, B.; Raabe, J.
Keywords: magnetism, x-ray microscopy, skyrmions
  • Poster
    Skymag 2017, 02.-05.05.2017, Paris, Frankreich

Registration No. 25992 - Permalink


Frequency- and Amplitude Modulation of Spin-Wave Signals generated in Topological Spin Textures
Wintz, S.; Finizio, S.; Schultheiss, K.; Liersch, V.; Kilibarda, F.; Warnatz, T.; Suszka, A. K.; Warnicke, P.; Wohlhüter, P.; Erbe, A.; Lindner, J.; Raabe, J.; Fassbender, J.ORC
Keywords: magnetism, spin waves, x-ray microscopy
  • Poster
    IEEE International Magnetics Conference, 24.-28.04.2017, Dublin, Irland

Registration No. 25991 - Permalink


In-situ membrane bending setup for the investigation of magnetostrictive materials with XMCD-STXM imaging
Finizio, S.; Wintz, S.; Kirk, E.; Raabe, J.
Keywords: magnetism, magnetostriction, spin dynamics
  • Poster
    IEEE International Magnetics Conference, 24.-28.04.2017, Dublin, Irland

Registration No. 25990 - Permalink


Spin Wave Emission from Topological Spin Textures
Wintz, S.; Sluka, V.; Schneider, T.; Kakay, A.; Weigand, M.; Schultheiss, K.; Warnatz, T.; Mattheis, R.; Gallardo, R. A.; Roldan-Molina, A.; Landeros, P.; Tiberkevich, V.; Slavin, A.; Erbe, A.; Deac, A.; Lindner, J.; Fassbender, J.ORC; Raabe, J.
Keywords: magnetism, spin waves, x-ray microscopy
  • Invited lecture (Conferences)
    Moscow International Symposium on Magnetism, 01.-05.07.2017, Moskau, Russische Föderation

Registration No. 25988 - Permalink


Control of the magnetic vortex core dynamics in magnetostrictive microstructured elements through the Magneto-Elastic coupling
Finizio, S.; Wintz, S.; Kirk, E.; Suszka, A.; Gliga, S.; Raabe, J.
Keywords: magnetism, vortex, magneto elastic, spin dynamics
  • Lecture (Conference)
    IEEE International Magnetics Conference, 24.-28.04.2017, Dublin, Ireland

Registration No. 25986 - Permalink


Control of the gyration of magnetic vortices by the magneto-elastic effect
Finizio, S.; Wintz, S.; Kirk, E.; Suszka, A.; Gliga, S.; Wohlhüter, P.; Zeissler, K.; Raabe, J.
Corresponding author: Finizio, S. Paul Scherrer Institut
Abstract: The influence of a strain-induced uniaxial magnetoelastic anisotropy on the magnetic vortex core dynamics microstructured magnetostrictive Co40 Fe40 B20 elements was investigated with time-resolved scanning transmission x-ray microscopy. The measurements revealed a monotonically decreasing eigenfrequency of the vortex core gyration with the increasing magnetoelastic anisotropy, which follows closely the predictions from in micromagnetic modeling.
Keywords: magnetism, x-ray microscopy, vortex, spin dynamics

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Registration No. 25984 - Permalink


Investigation of the LET-dependency from BeO using single photon detection for dosimetry in proton beams
Radtke, J.; Kormoll, T.; Grabs, L.; Lutz, B.ORC; Lühr, A.; Ullrich, W.; Sponner, J.; Henniger, J.
Abstract: Optically stimulated luminescence (OSL) is gaining greater importance in the field of personal dosimetry in the last few years. Its principle is based on the release of small amounts of light induced by the prior absorption of ionizing radiation. One suitable luminophore for OSL is beryllium oxide (BeO). Because of its near tissue equivalent effective atomic number of 7, it is excellent for personal dosimetry. Furthermore, the luminescence signal has a wide dose linearity ranging from the µGy region up to few Gy. For this reason, this ceramic can be used for several different areas of application. A new generation of measurement systems based on the OSL of BeO, which has a very low OSL light intensity, was developed by the radiation physics group at TU Dresden. This property allows single photon detection which is superior in contrast to other detection methods. Therefore, a single photon sensor was used as a detector. The single photon mode of the detector in combination with the so called timestamp detection method allows accessing the greatest possible information of the OSL light. This work applies the new system to dosimetry of a proton beam. Because of the LET-dependencies of the luminescence light, this presents a challenge. Common problems of solid state dosimetry are local saturation effects, which were investigated for BeO. Opportunities for correction in terms of the LET-dependency of the luminophore are being discussed. For the empirical determination of the behavior of BeO in proton beams, measurements at the medical proton therapy facility at the University Proton Therapy Dresden (UPTD) were carried out. All collected data were analyzed for LET-dependency on the response signal. For the measurements, BeO ceramics were placed at different depth infront and inside the spread out Bragg peak (SOBP). The dose read from dosimeters was analyzed with respect to the applied dose and the LET. All measurements infront of the SOBP shows no deviation of the estimated dose. The dose determination in the SOBP yielded an underestimation by 15%. This is object of current investigation.
  • Poster
    Jahrestagung der biomedizinischen Technik und Dreiländertagung der medizinischen Physik, 10.-13.09.2017, Dresden, Deutschland

Registration No. 25983 - Permalink


Monte-Carlo simulation of proton treatment fields in patients to support treatment planning
Eulitz, J.; Lutz, B.ORC; Oesten, H.; Wohlfahrt, P.; Enghardt, W.; Lühr, A.
Abstract: Monte-Carlo (MC) simulations may allow for reducing range margins and applying variable relative-biological-effectiveness (RBE) models in proton therapy. Here, an approach is presented to support treatment planning of patients by highlighting regions with increased dose uncertainties originating from dose calculation and the assumption of a constant RBE of 1.1.
A software framework was developed and experimentally validated, which simulates proton plans at the University Proton Therapy Dresden (UPTD) using the MC tool TOPAS. It is based on a commissioned model of the UPTD treatment head in double-scattering mode. Clinical treatment plans and computed tomography datasets were imported in DICOM format. MC-based dose distributions were compared with dose distributions received from the clinically applied treatment planning system (TPS) XIO, Elekta. Obtained dose, linear-energy-transfer (LET), and modelled RBE maps (using experimental in vitro data) were imported into the TPS RayStation, RaySearch for plan evaluation.
TPS doses above the 95% iso dose level are reproduced within gamma pass rates GPR ≥ 98%, when applying 1 mm local and 2 % dose gamma criterion. Dose differences reached values up to 8 Gy for field volumes up to 4 cm 3 , particularly at regions with high-density gradients (e.g. bone and air cavities) and at the field edges. LET and variable RBE hot spots were obtained at (distal) field edges while at the field center RBE values below 1.1 were predicted. Clinical dose values differed by up to 10 Gy using either the assumption of a constant or a variable RBE.
The treatment planning and delivery workflow at UPTD was mapped in a MC simulation. In general, good agreement between TPS and MC clinical dose values was found. However, relevant clinical dose differences were obtained and emphasise the necessity of using MC to enhance the physical and biological dose prediction in patients.
  • Lecture (Conference)
    Jahrestagung der biomedizinischen Technik und Dreiländertagung der medizinischen Physik, 10.-13.09.2017, Dresden, Deutschland

Registration No. 25982 - Permalink


Holographic vector mesons in a dilaton background
Zöllner, R.; Kämpfer, B.
Abstract: Within a holographic framework, we consider vector mesons riding on a gravity-dilaton background. The latter one is determined directly from a Schr\"odinger equivalent potential which delivers a proper ρ meson Regge trajectory. The mapping on the dilaton potential yields a thermodynamic phase structure with a first-order transition.

Registration No. 25974 - Permalink


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