Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31629 Publications
Euler-Euler Simulation und Modellvalidierung für Blasenströmungen
Guo, J.;
Die Anwendung von Methoden der CFD („Computational fluid dynamics“) für Scale-up und Intensivierung verfahrenstechnischer Prozesse bietet die Möglichkeit, energie- und ressourceneffiziente Lösungen zu identifizieren, deren Untersuchung mit konventionellen halb-empirischen Methoden kostspielig und langwierig wäre.
Eine solche Simulation im großtechnischen Maßstab ist im Rahmen der Euler-Euler Beschreibung möglich, in der Prozesse auf der Skala einzelner Blasen modelliert werden. Ein solches Schließungsmodell für Hydrodynamik und Stofftransport in Blasenströmungen wird am HZDR entwickelt. Ziel dieser Entwicklung ist, ein vorhersagetaugliches Modell zu etablieren, das für einen breiten Bereich von Anwendungsbedingungen validiert ist.
Zu diesem Zweck werden Simulationsrechnungen mit experimentellen Daten verglichen, die zunehmend komplexere Geometrien und Effekte einbeziehen. Auf Basis der jeweils erzielten Übereinstimmung werden Modellerweiterungen und -verbesserungen vorgenommen. Im Rahmen der Diplomarbeit sollen hierzu Strömungen in Blasensäulen und Blasenströmungen in Rohren untersucht werden.
Keywords: Blasenströmung, Euler-Euler zwei-Fluid-Modell, CFD-Simulation
  • Diploma thesis
    TU Dresden, 2016
    Mentor: Dr. Roland Rzehak (HZDR), Prof. Rüdiger Lange (TU-Dresden)
    57 Seiten

Publ.-Id: 24313 - Permalink


Analysis of SAM Coatings for Dropwise Condensation in Passive Safety Systems
Unger, S.; Sarker, D.; Harm, U.; Hampel, U.;
Passive safety systems of spent fuel pools are one key technology for further improvement of the reliability of nuclear power plants. These systems transfer high amount of heat, while using air as a heat sink. For that reason the overall temperature differences are small. Since the heat transfer is based on natural convection and gravitational force, the heat transfer resistance of the heat exchangers are high compare to active systems. A Self-Assembled Monolayer (SAM) coating can address both challenges by enable a high compact condensation heat exchanger and by reducing the heat transfer resistance during condensation. Therefore different coating chemicals and surface roughness were analysed, to create the most beneficial heat transfer surface.
Keywords: Passive safety, dropwise condensation, condensation, heat transfer
  • Lecture (Conference)
    47th Annual Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Deutschland
  • Contribution to proceedings
    47th Annual Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Deutschland
    Proceedings of the 47th Annual Meeting on Nuclear Technology

Publ.-Id: 24312 - Permalink


Surprising effects of electron-electron scattering in graphene
Helm, M.; König-Otto, J.; Mittendorff, M.; Pashkin, A.; Schneider, H.; Wendler, F.; Winzer, T.; Malic, E.; Knorr, A.; Winnerl, S.;
Two surprising effects related to electron-electron scattering in graphene are demonstrated: One is a long-lived anisotropic carrier distribution after THz excitation, and the other one is an unexpected sign reversal of the pump-probe signal in a magnetic field. The latter reflects an Auger scattering so strong that it overcomes the effect of optical pumping.
Keywords: graphene, pump-probe, terahertz, free-electron laser
  • Invited lecture (Conferences)
    5th Russia-Japan-USA-Europe Symposium on Fundamental & Applied Problems of Terahertz Devices & Technologies (RJUSE TeraTech-2016), 31.10.-04.11.2016, Sendai, Japan

Publ.-Id: 24311 - Permalink


Glacial chronology and production rate cross-calibration of five cosmogenic nuclide and mineral systems from the southern Central Andean Plateau
Luna, L. V.; Bookhagen, B.; Niedermann, S.; Rugel, G.; Scharf, A.; Merchel, S.;
Glacial deposits on the high-altitude, arid southern Central Andean Plateau (CAP), the Puna in northwestern Argentina, document past changes in climate, but the associated geomorphic features have rarely been directly dated. This study provides direct age control of glacial moraine deposits from the central Puna (24°S) at elevations of 3900–5000 m through surface exposure dating with cosmogenic nuclides.
Our results show that the most extensive glaciations occurred before 95 ka and an additional major advance occurred between 46 and 39 ka. The latter period is synchronous with the highest lake levels in the nearby Pozuelos basin and the Minchin (Inca Huasi) wet phase on the Altiplano in the northern CAP. None of the dated moraines produced boulder ages corresponding to the Tauca wet phase (24–15ka).
Additionally, the volcanic lithologies of the deposits allow us to establish production ratios at low latitude and high elevation for five different nuclide and mineral systems: 10Be, 21Ne, and 26Al from quartz (11 or 12 samples) and 3He and 21Ne from pyroxene (10 samples). We present production ratios for all combinations of the measured nuclides and cross-calibrated production rates for 21Ne in pyroxene and quartz for the high, (sub-)tropical Andes. The production rates are based on our 10Be-normalized production ratios and a weighted mean of reference 10Be production rates calibrated in the high, tropical Andes (4.02 ±0.12 at g-1yr-1). These are, 21Neqtz: 18.1 ±1.2 and 21Nepx: 36.6 ±1.8 (En88–94) scaled to sea level and high latitude using the Lal/Stone scheme, with 1σuncertainties. As 3He and 26Al have been directly calibrated in the tropical Andes, we recommend using those rates.
Finally, we compare exposure ages calculated using all measured cosmogenic nuclides from each sample, including 11 feldspar samples measured for 36Cl, and a suite of previously published production rates.
Keywords: cosmogenic nuclides, production rate, cross-calibration, South American Monsoon, Quaternary climate change, moraine

Publ.-Id: 24310 - Permalink


10Be surface exposure dating of the last deglaciation in the Aare Valley, Switzerland
Wüthrich, L.; Garcia Morabito, E.; Zech, J.; Trauerstein, M.; Veit, H.; Gnägi, C.; Merchel, S.; Scharf, A.; Rugel, G.; Christl, M.; Zech, R.;
The combined Rhone and Aare Glaciers presumably reached their last glacial maximum (LGM) extent on the Swiss Plateau prior to 24 ka. Two well-preserved, less extensive moraine stades, the Gurten and Bern Stade, document the last deglaciation of the Aare Valley, yet age constraints are very scarce. In order to establish a more robust chronology for the glacial/deglacial history of the Aare Valley, we applied 10Be surface exposure dating on eleven boulders from the Gurten and Bern Stade. Several exposure ages are of Holocene age and likely document post-depositional processes, including boulder toppling and quarrying. The remaining exposure ages, however yield oldest ages of 20.7 ± 2.2 ka for the Gurten Stade and 19.0 ± 2.0 ka for the Bern Stade. Our results are in good agreement with published chronologies from other sites in the Alps.
Keywords: Pleistocene, Cosmogenic nuclides, Exposure Dating, Alpine foreland, accelerator mass spectrometry

Publ.-Id: 24309 - Permalink


Simulation of Liquid Metal Batteries by Continuum Mechanics
Weber, N.; Beckstein, P.; Galindo, V.; Landgraf, S.; Stefani, F.; Weier, T.;
Liquid metal batteries (LMB) are built as a stable density stratification of two liquid metals, separated by a likewise liquid salt. If the materials are correctly chosen, all three phases self-assemble (figure 1). During discharge, the anode metal will donate electrons, the ion will diffuse through the electrolyte layer and alloy there with the cathode metal.
The main advantage of LMBs is the very low price: low-cost raw materials together with a simple set-up and scalability make such cells an ideal stationary storage, which is highly needed for buffering fluctuating renewable energies. The liquid-liquid interfaces allow for optimal kinetics, i.e. for a fast response time and current densities up to 10 A/cm2. Furthermore, they avoid micro-degradation - as known from solid cells - and allow for potentially very high life-times.
Safety will play a major role in the construction of such cells – especially due to the high amount of liquid and reactive metals. In that context, a short circuit of the thin electrolyte layer should be avoided. In large liquid metal batteries with diameters in the order of several decimetres, even the discharging current itself may lead to a fluid flow, able to short-circuit the battery.

We will present numerical simulations of the fluid flow in LMBs and estimate their relevance for real cells. The numerical solvers combining heat transfer, fluid- and electrodynamics with the volume of fluid method are implemented in the open source library OpenFOAM. Reviewed phenomena include thermal convection, electro-vortex flow, the Tayler-instability as well as metal pad rolling, which is well known from aluminium reduction cells.
Keywords: OpenFOAM, liquid metal battery
  • Lecture (Conference)
    Helmholtz-Workshop "Multiscale Modeling of Energy Storage Materials", 10.-11.11.2016, Berlin, Deutschland

Publ.-Id: 24308 - Permalink


Particles as concentrated sources related to uptake and radiological dose in mammals
Johansen, M. P.; Caffrey, E.; Child, D. P.; Collins, R.; Hotchkis, M. A. C.; Howell, N. A.; Payne, T. E.; Mokhber-Shahin, L.; Ikeda-Ohno, A.;
The radiological residues at the former weapons testing sites at Maralinga, Emu and the Monte Bello Islands often occur in particulate form (so called hot particles). Large numbers of these particles were emitted from nuclear and non-nuclear tests. For example each square meter in a plume which extends for tens of kilometres at the Taranaki site (Maralinga) can contain more than 3000 readily identifiable particles. The physical and chemical characteristics of these particles affect their mobility and availability for uptake into living organisms. When they contain long-lived radionuclides (e.g. 239Pu) these particles may slowly weather, and thus provide a persistent source of ionic forms, or smaller particles, for many thousands of years.
From these Australian sites, we have gathered a series of particles that have weathered and interacted with the environment for 50+ years since their initial formation and release events. The particles are being evaluated using a range of methods including gamma spectrometry, autoradiography, high sensitivity Accelerator Mass Spectrometry analysis (AMS), leaching studies, and synchrotron X-ray fluorescence microscopy.
Significant findings include the clustering of Cs on the exterior of a glassy fission fragment, with Sr occurring in the nearby interior, suggesting the 137Cs may be more available for weathering processes, and the beta emissions from the 90Sr may be largely self-shielded within the particle. In contrast, a different particle from a nearby site lacked any fission products, but contained Pu(IV) oxyhydroxides consistent with weathering in a semi-arid environment. Although the 239Pu is very active, detailed dose modelling suggests most of the alpha emissions from particles > 5µm are shelf-shielded within the particles themselves, and therefore impart lower dose than the equivalent Pu dissolved and distributed throughout an organ. However, when Pu exists on exterior surfaces, a hot particle that has been internalised (e.g. lodged in a mammalian lung) may produce relatively highly concentrated dose rates to adjacent tissues.
Keywords: Plutonium, actinides, particulates, update, nuclear tests, dose, mammals, radio ecology
  • Lecture (Conference)
    2nd International Conference on Radioecological concentration processes (50 years later), 09.11.2016, Seville, Spain

Publ.-Id: 24307 - Permalink


The cosmic-ray exposure history of the Twannberg iron meteorite (IIG)
Smith, T.; Hofmann, B. A.; Leya, I.; Merchel, S.; Pavetich, S.; Rugel, G.; Scharf, A.;
The Twannberg iron meteorite is one out of only six members of the group IIG. The numerous finds of Twannberg meteorites in recent years have challenged our knowledge about its cosmic-ray exposure history and especially on the time of fall with respect to glacial events. The combined noble gas and radionuclide data obtained in this new systematic study indicate that Twannberg was a large object with a pre-atmospheric radius in the range of 2-4 meters, which corresponds to ~1000 tons. The cosmic-ray exposure age for Twannberg is 66.0±7.8 Ma. The most surprising result is the long terrestrial age of Tterr = 202 +19 -20 ka, which is unexpected considering the humid conditions in Switzerland. However, this age is in accord with glaciation events, indicating that the less shielded samples from Mt. Sujet still represent the original strewnfield but that the samples from Gruebmatt and Twannbach, which are from more shielded positions, have been glacially transported during the second last ice age from an original position west of Mt. Sujet towards east-north-east.
Keywords: AMS, cosmic rays, accelerator mass spectrometry, exposure age, terrestrial age, meteorite

Publ.-Id: 24306 - Permalink


Scaling EUV and X-ray Thomson Sources to Optical Free-Electron Laser Operation with Traveling-Wave Thomson-Scattering
Steiniger, K.; Albach, D.; Debus, A.; Loeser, M.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.;
Traveling-Wave Thomson-Scattering (TWTS) allows for the realization of ultra-compact, inherently synchronized and highly brilliant light sources by providing optical undulators with hundreds to thousands of undulator periods from high-power, pulse-front tilted lasers pulses.

With TWTS the realization of optical free-electron lasers (OFELs) as well as incoherent radiation sources with orders of magnitude higher photon yields than classic head-on Thomson sources becomes possible with state-of-the-art technology in electron accelerators and laser systems.

TWTS employs a side-scattering geometry where laser and electron propagation direction of motion enclose an angle. Tilting the laser pulse front with respect to the wave front by half of this interaction angle optimizes electron and laser pulse overlap by compensating the spatial offset between electrons and the laser pulse-front at the beginning of the interaction when the electrons are far from the laser pulse axis. The laser pulse-front tilt ensures continuous overlap between electrons and laser pulse while the electrons cross the laser pulse cross-sectional area. Thus the interaction distance can be controlled in TWTS by the laser pulse width rather than laser pulse duration. Utilizing wide, petawatt class laser pulses allows to realize thousands of optical undulator periods.

The talk will show that TWTS OFELs emitting ultraviolet radiation are realizable today with existing technology for electron accelerators and laser systems. Especially the ultra-low emittance of laser wakefield accelerated electron beams can be exploited to compensate for their one percent level energy spreads. We discuss an experimental setup to generate the tilted TWTS laser pulses. The method presented provides dispersion compensation, required due to angular dispersion, and is especially relevant when building compact, high-yield hard X-ray TWTS sources in large interaction angle setups.
Keywords: Traveling-Wave, Thomson scattering, FEL, X-ray, Laser dispersion compensation
  • Lecture (others)
    Invited Seminar talk at Helmholtz Institut Jena, 30.09.2016, Jena, Deutschland

Publ.-Id: 24305 - Permalink


Scaling EUV and X-ray Thomson Sources to Optical Free-Electron Laser Operation with Traveling-Wave Thomson-Scattering
Steiniger, K.; Albach, D.; Debus, A.; Loeser, M.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.;
Traveling-Wave Thomson-Scattering (TWTS) is a novel Thomson scattering geometry which allows for orders of magnitude higher photon yields than classic head-on Thomson sources. TWTS thereby remains compact and provides narrowband and ultra-short ultraviolet to γ-ray radiation pulses just as classic Thomson sources. Even the realization of optical free-electron lasers is possible with the TWTS geometry since it provides both optical undulators with thousands of periods needed to microbunch the electron beam and a reduction of electron beam quality requirements compared to classic Thomson scattering to a level technically feasible today.
TWTS employs a side-scattering geometry depicted in fig. 1. Laser and electron propagation direction of motion enclose the interaction angle ϕ. Tilting the laser pulse front with respect to the wave front by half the interaction angle ensures continuous overlap of electrons and laser pulse over the whole laser pulse width while the laser pulse crosses the electron beam trajectory. In this way the interaction length becomes controllable by the laser pulse width and independent of the laser pulse duration. Utilizing wide, petawatt class laser pulses for TWTS allows to realize thousands of optical undulator periods.
The variability of TWTS with respect to the interaction angle can be used to control the radiation wavelength even for electron sources with fixed energy. For a fixed target wavelength on the other hand, the free choice of interaction angle enables control over electron beam quality requirements. Small interaction angle scenarios (ϕ∼10°) typically yield the best trade-off between requirements on electron beam quality, laser power and laser intensity stability.
In the talk we will show that TWTS OFELs emitting extreme ultraviolet radiation are realizable today with existing technology for electron accelerators and laser systems. We detail an experimental setup to generate the tilted TWTS laser pulses which aims at compactness and provides focusing of these high-power pulses and compensation of dispersion accompanying pulse-front tilts. The method presented for dispersion compensation is especially relevant when building high yield X- and γ-ray sources in large interaction angle setups of TWTS.
Keywords: Traveling-Wave, Thomson scattering, FEL, X-ray, Laser dispersion compensation
  • Poster
    The 15th International Conference on X-Ray Lasers, 22.-27.05.2016, Nara, Japan

Publ.-Id: 24304 - Permalink


Inclusive Λ production in proton-proton collisions at 3.5 GeV
Adamczewski-Musch, J.; Agakishiev, G.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Kuc, H.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Maurus, S.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataroe, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.;
The inclusive production of {\Lambda} hyperons in proton-proton collisions at s√ = 3.18 GeV was measured with HADES at the GSI Helmholtzzentrum f\"ur Schwerionenforschung in Darmstadt. The experimental data are compared to a data-based model for individual exclusive {\Lambda} production channels in the same reaction. The contributions of intermediate resonances such as {\Sigma}(1385), {\Delta}++ or N* are considered in detail. In particular, the result of a partial wave analysis is accounted for the abundant pK+{\Lambda} final state. Model and data show a reasonable agreement at mid rapidities, while a difference is found for larger rapidities. A total {\Lambda} production cross section in p+p collisions at s√ = 3.18 GeV of {\sigma}(pp → {\Lambda} + X) = 207.3 ± 1.3 +6.0 -7.3 (stat.) ± 8.4 (syst.) +0.4 -0.5 (model) {\mu}b is found.

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Publ.-Id: 24303 - Permalink


MMM2016: Magnetic functionalities for flexible interactive electronics
Makarov, D.;
The flourishing and eagerness of portable consumer electronics necessitates functional elements to be lightweight, flexible, and even wearable [1,2]. Next generation flexible appliances aim to become fully autonomous and will require ultra-thin and flexible navigation modules, body tracking and relative position monitoring systems. Such devices fulfill the needs of soft robotics [3], functional medical implants [4] as well as epidermal [5], imperceptible [6] and transient [7] electronics. Key building blocks of navigation and position tracking devices are the magnetic field sensors.
We developed shapeable magnetoelectronics [8] – namely, flexible [9-11], printable [12-14], stretchable [15,16] and even imperceptible [17] magnetosensitive large area elements, which were completely missing in the family of flexible electronics. The unique mechanical properties open up new application potentials for smart skins, allowing to equip the recipient with a “sixth sense” providing new experiences in sensing and manipulating the objects of the surrounding us physical as well as digital world [15,17].
Combining large-area printable and flexible electronics paves the way towards commercializing the active intelligent packaging, post cards, books or promotional materials that communicate with the environment and provide the respond to the customer [14]. Realization of this vision requires fabrication of printable electronic components that are flexible and can change their properties in the field of a permanent magnet [13]. For this concept, we fabricated high performance magnetic field sensors relying on the giant magnetoresistive (GMR) effect, which are printed at pre-defined locations on flexible circuitry and remain fully operational over a temperature range from -10°C up to +95°C, well beyond the requirements for consumer electronics [12]. Our work potentially enables commercial use of high performance magneto-sensitive elements in conventional printable electronic industry, which, although highly demanded, had not yet been possible.
This work is supported in part via the EU FP7 (ERC Grant No. 306277) and the EU FET Programme (Grant No. 618083).
  • Invited lecture (Conferences)
    61st Annual Conference on Magnetism and Magnetic Materials, 31.10.-04.11.2016, New Orleans, USA

Publ.-Id: 24302 - Permalink


Forschung und Lehre innerhalb des Kompetenzzentrums Ost für Kerntechnik auf den Gebieten Endlagerung, Reaktorsicherheit und Strahlenschutz
Kliem, S.ORC; Hampel, U.; Hurtado, A.; Kästner, W.; Kratzsch, A.; Sahre, P.; Jansen, S.
Das Kompetenzzentrum Ost für Kerntechnik ist ein regionaler Zusammenschluss der kerntechnischen Einrichtungen mit dem Ziel, die kerntechnische, strahlentechnische und radiochemische Ausbildung an den sächsischen Ausbildungseinrichtungen wie bspw. der TU Dresden und der Hochschule Zittau/Görlitz zu erhalten und möglichst weiter zu entwickeln. Damit einhergehend werden für Lehre und Forschung Versuchseinrichtungen und andere Forschungsinfrastrukturen der Partner gemeinsam genutzt.
Das Kompetenzzentrum Ost für Kerntechnik hat sich die Sicherung des akademisch gebildeten Fachkräftenachwuchses in Universitäten, Hochschulen, Instituten, bei Kernkraftwerksbetreibern und -herstellern sowie in Behörden und Gutachtern zum obersten Ziel gemacht. Dazu werden die einschlägigen Anstrengungen der Mitgliedsorganisationen durch die Vertreter der einzelnen Unternehmen des Kompetenzzentrums koordiniert, um für effizienten Wissenstransfer und Kompetenzerhalt Sorge zu tragen.
Durch den politischen Beschluss bezüglich des Umbaus des Energieversorgungssystems in Deutschland und den damit verbundenen Entscheidungen zur Beendigung der Stromerzeugung aus Kernenergie bis Ende 2022 hat auch für die Mitglieder des Kompetenzzentrums Ost eine Zäsur im Bereich Lehre und Forschung zur Folge. Neben einer deutlichen Reduzierung der Forschungsförderung seitens der Industrie schlägt sich das auch in sinkenden Studenten- und Doktorandenzahlen nieder.
Im Vortrag werden die aktuellen Lehr- und Forschungsaktivitäten der Mitglieder des Kompetenzzentrums Ost mit besonderem Augenmerk auf die gemeinsam bearbeiteten Projekte vorgestellt und Perspektiven zukünftigen Wirkens aufgezeigt.
  • Lecture (Conference)
    48. Kraftwerkstechnisches Kolloquium, 18.-19.10.2016, Dresden, Deutschland
  • Contribution to proceedings
    48. Kraftwerkstechnisches Kolloquium, 18.-19.10.2016, Dresden, Deutschland
    Kraftwerkstechnik 2016, Freiberg: SAXONIA, 9783934409699, 725-733

Publ.-Id: 24301 - Permalink


The X2 Benchmark for VVER-1000 reactor calculations - overview and current status
Lötsch, T.; Kliem, S.ORC; Bilodid, E.; Khalimonchuk, V.; Kuchin, A.; Ovdiienko, Y.; Ieremenko, M.; Blank, R.; Schultz, G.
The paper gives an overview about the tasks defined in the framework of the X2 benchmark, firstly proposed at the 19th symposium of the AER in 2009. The X2 benchmark was proposed for further validation and verification of the reactor physics code systems for VVER-1000 reactors with TVSA fuel assemblies. The X2 benchmark comprises all stages of reactor core calculations starting with the fuel assembly data preparation. Therefore X2 benchmark specifies the FA and core characteristics as well as the core loading patterns of four consecutive cycles for a Ukraine VVER-1000 reactor core. A set of operational data for comparisons with steady state reactor core calculations and transient neutron kinetics calculations were provided. The benchmark is useful for validating and verifying the whole system of codes and data libraries for reactor physics calculations including fuel assembly modelling, fuel assembly data preparation and reactor core modelling. Reviewed results of the tasks 1 and 2 for X2 benchmark steady state calculations were presented at the AER symposia. In the framework of several projects supported by the German BMU5) the 3D neutron kinetic code DYN3D and the coupling of DYN3d with thermo-hydraulics system codes were validated and verified on the basis of the data provided in the framework of the X2 benchmark. In preparing results for the X2 benchmark several organisations have been participated: IBBS, HZDR, SSTC, TÜV SÜD. On that basis TÜV SÜD has been provided the analysis and formulation of the specific X2 benchmark tasks. As continuation of the work on the X2 benchmark the tasks were extended with task 3 including data of the 3D calculations results and pin-by-pin distributions for selected fuel assemblies as well as task 4 providing data for 3D neutron kinetic calculations of reactor transients. The paper presents the current state of the X2 benchmark and discusses new results as continuation of the work started with the X2 benchmark proposal in 2009.
  • Contribution to proceedings
    26th Symposium of AER on VVER Reactor Physics and Reactor Safety, 10.-14.10.2016, Helsinki, Finland
    Proceedings of the 26th Symposium of AER on VVER Reactor Physics and Reactor Safety, Budapest: MTA EK

Publ.-Id: 24300 - Permalink


AER Working Group D on VVER Safety Analysis – Report of the 2016 Meeting
Kliem, S.ORC
The AER Working Group D on VVER reactor safety analysis held its 25th meeting in Villigen, Switzerland, during the period 30-31 May, 2016. The meeting was hosted by PSI Villigen and was held in conjunction with the 10th workshop on the OECD Benchmark for Uncertainty Analysis in Best-Estimate Modelling (UAM) for Design, Operation and Safety Analysis of LWRs. Altogether 19 participants attended the meeting of the working group D, 9 from AER member organizations and 5 guests from non-member organization. The co-ordinator of the working group, Mr. S. Kliem, served as chairman of the meeting.

The meeting started with a general information exchange about the recent activities in the participating organizations.

The given presentations and the discussions can be attributed to the following topics:

• Safety analyses methods and results
• Code development and benchmarking
• Thermal hydraulic analyses of passive safety systems
• Future activities

A list of the participants and a list of the handouts distributed at the meeting are attached to the report. The corresponding PDF-files of the handouts can be obtained from the chairman.
  • Contribution to proceedings
    26th Symposium of AER on VVER Reactor Physics and Reactor Safety, 10.-14.10.2016, Helsinki, Finland
    Proceedings of the 26th Symposium of AER on VVER Reactor Physics and Reactor Safety, Budapest: MTA EK
  • Lecture (Conference)
    26th Symposium of AER on VVER Reactor Physics and Reactor Safety, 10.-14.10.2016, Helsinki, Finland

Publ.-Id: 24299 - Permalink


Self-organized Ge & Si nanostructures by heavy-ion irradiation
Böttger, R.; Heinig, K.-H.; Bischoff, L.; Huebner, R.;
Heavy ions like Bi or Au of a few tens of keV deposit a high energy density into the collision cascade volume of due to (i) their high mass and (ii) their low projected range. At higher energies, this density becomes diluted as the cascade volume increases super-linearly with ion energy. Compared to monatomic ions, heavy polyatomic ions deposit an even higher energy density. This is sufficient to form a pool of a localized, almost classical melt in a semiconductor surface lasting up to half of a nanosecond.
Local melting and re-solidification by single polyatomic ion impacts is proven by molecular dynamics calculations. Well-ordered, self-organized dot patterns on Si and Ge surfaces have been found after heavy polyatomic ion irradiation, which can be attributed to impact-induced local transient melting. Similar patterns were found with monoatomic ions at elevated substrate temperatures, where the energy per substrate atom exceeds a critical value within a larger volume.
The kinetics of localized melt pools leads to a generic, Kuramoto-Sivashinsky-type (KS) partial differential equation for the surface evolution. Whereas so far the mechanisms of ion-induced surface pattern evolution are assumed to be surface-curvature-dependent ion erosion or ion-momentum-induced mass drift of surface atoms, for heavy polyatomic ions we have identified a completely different mechanism.
The local melting and quenching process is so far from equilibrium that particularities of phase diagrams like the Bi state in Si or Ge are frozen into the nanostructure of the re-solidified volume. This opens the possibility to study extremely fast solid-liquid phase transitions.
The authors thank the German Research Foundation for financial support.
Keywords: Silicon, Germanium, nanostructures, self-organization, ion irradiation
  • Invited lecture (Conferences)
    24th International Conference on the Application of Accelerators in Research and Industry, 30.10.-04.11.2016, Texas, USA

Publ.-Id: 24298 - Permalink


Fluid dynamics of bubbly flows
Ziegenhein, T.ORC
Bubbly flows can be found in many applications in chemical, biological and power engineering. Reliable simulation tools of such flows that allow the design of new processes and optimization of existing one are therefore highly desirable. CFD-simulations applying the multi-fluid approach are very promising to provide such a design tool for complete facilities. In the multi-fluid approach, however, closure models have to be formulated to model the interaction between the continuous and dispersed phase. Due to the complex nature of bubbly flows, different phenomena have to be taken into account and for every phenomenon different closure models exist. Therefore, reliable predictions of unknown bubbly flows are not yet possible with the multi-fluid approach.
A strategy to overcome this problem is to define a baseline model in which the closure models including the model constants are fixed so that the limitations of the modeling can be evaluated by validating it on different experiments. Afterwards, the shortcomings are identified so that the baseline model can be stepwise improved without losing the validity for the already validated cases. This development of a baseline model is done in the present work by validating the baseline model developed at the Helmholtz-Zentrum Dresden-Rossendorf mainly basing on experimental data for bubbly pipe flows to bubble columns, bubble plumes and airlift reactors that are relevant in chemical and biological engineering applications.
In the present work, a large variety of such setups is used for validation. The buoyancy driven bubbly flows showed thereby a transient behavior on the scale of the facility. Since such large scales are characterized by the geometry of the facility, turbulence models cannot describe them. Therefore, the transient simulation of bubbly flows with two equation models based on the unsteady Reynolds-averaged Navier–Stokes equations is investigated. In combination with the before mentioned baseline model these transient simulations can reproduce many experimental setups without fitting any model. Nevertheless, shortcomings are identified that need to be further investigated to improve the baseline model.
For a validation of models, experiments that describe as far as possible all relevant phenomena of bubbly flows are needed. Since such data are rare in the literature, CFD-grade experiments in an airlift reactor were conducted in the present work. Concepts to measure the bubble size distribution and liquid velocities are developed for this purpose. In particular, the liquid velocity measurements are difficult; a sampling bias that was not yet described in the literature is identified. To overcome this error, a hold processor is developed.
The closure models are usually formulated based on single bubble experiments in simplified conditions. In particular, the lift force was not yet measured in low Morton number systems under turbulent conditions. A new experimental method is developed in the present work to determine the lift force coefficient in such flow conditions without the aid of moving parts so that the lift force can be measured in any chemical system easily.
Keywords: Bubbly flows, Fluid Dynamics, CFD, PTV, PIV, Lift-force, Bubble column
  • Doctoral thesis
    TU Berlin, 2016
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-074 2016

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Publ.-Id: 24297 - Permalink


Fundamentals of Ion-Solid Interaction - A Compact Introduction
Möller, W.ORC Keywords: Ion-Solid Interaction, Computer Simulation, Ion Stopping and Ranges, Ion Damage, Sputtering, Ion Mixing
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-073 2017

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Publ.-Id: 24296 - Permalink


Image-guided high precision proton irradiation of pancreatic adenocarcinoma using a gold fiducial marker
Stefanowicz, S.; Thiele, J.; Hoffmann, A.; Troost, E.;
Introduction
The inter- and intra-fractional position variability of the target volume and the abdominal organs and their poor visibility on currently used imaging modalities for proton beam irradiation, make high-precision radiation therapy of pancreatic cancer challenging. Moreover, due to the specific physical properties of protons, an accurate patient positioning is mandatory. This can be accomplished by image-guided setup, possibly aided by implanted fiducial markers. Here we present our first experience treating a pancreatic adenocarcinoma patient using gold fiducial markers and passive scattered proton therapy (PSPT).

Material and Methods
A patient with a primary irresectable adenocarcinoma of the pancreatic head (cT4N1M0) underwent neoadjuvant radiochemotherapy (50.4 Gy(RBE) in 28 fractions, weekly gemcitabine). Prior to treatment planning, three radiopaque fiducial markers (Gold AnchorTM, Naslund Medical AB, Sweden) were endoscopically implanted in the proximity of the tumour. The radiation treatment plan was generated in XiO (Elekta, Sweden) using two ventro-dorsally opposing double-scattered proton beams such that 95% of the prescribed dose covered the clinical target volume (CTV). Orthogonal X-rays were acquired for daily positioning, and on a weekly basis, target volume coverage and potential anatomical changes were assessed using an in-room dual-energy/4D-CT (Somatom Definition AS, Siemens Healthineers, Germany). In order to estimate the inter- and intra-fractional motion of the markers and to recalculate the delivered dose, the per-treatment CTs were rigidly fused to the planning CT using Raystation 4.7 (RaySearch Laboratories AB, Sweden), and the CTV and the organs at risk were copied and if necessary adapted.

Results
The patient completed radiochemotherapy with grade 1 nausea only. The markers did not migrate into surrounding tissues and inter- as well as intra-fractional baseline shifts of < 1 cm in all spatial directions (LR, AP, CC) were measured. In all recalculated plans the dose specification for the CTV and the organ at risks were achieved. However, the mean value of all average doses to the kidneys was increased by 25% (right, range of 17% - 37%) and 33% (left, range of -0.6% - 51%) in comparison to the initial treatment plan, but was within the dose constraints (< 15 Gy).

Conclusion
There was no significant difference between the prescribed and the delivered dose based on the recalculation. The gold fiducial markers remained stable and baseline shifts were limited [1]. Fiducial markers enable accurate positioning of the pancreas, however, markers with minor perturbation behaviour for proton therapy may be preferred.

References
[1] Wysocka, B. et al.: Interfraction and Respiratory Organ Motion During Conformal Radiotherapy in Gastric Cancer, Int. J. Radiation Oncology Biol. Phys., 2010, 77 (1), pp. 53 – 59.
  • Lecture (Conference)
    4D Workshop 2016, 08.-09.12.2016, Groningen, Niederlande

Publ.-Id: 24295 - Permalink


Effect of baffles on bubble rising behavior
Sommer, A.-E.;
Up to 80 % of the total energy budget of waste water treatment plants is consumed by the activated sludge process. One idea to improve the efficiency of an aeration tank is to increase the residence time of bubbles within the tank through baffles in the form of plates. Therefore, a detailed study was carried out to obtain an improved understanding of the hydrodynamics and mass transfer process of air bubbles along an inclined plate. For this small-scale investigation, the effects on the bubbly flow in deionized water were observed in a rectangular channel with the help of a high-speed camera and a dissolved oxygen sensor. The target parameters were bubble size distribution, equivalent Sauter mean diameter of the bubbles, bubble rise velocity, residence time, local and global mass transfer coefficient under the variation of wetting behavior of the material (hydrophilic, hydrophobic), roughness profile of the material, inclination angle and length of a plate. The wetting characteristics of these plates were also tested within activated sludge to analyze the influence of a developed biofilm to the surface characteristics of the plates. All plate configuration achieved a clear extension of the residence time whereas only a hydrophilic plate with a low inclination angle and a small length rose the local mass transfer coefficient after the plate contact. Eventually, all results were combined to develop ideas for the application of plates within the activated sludge process.
Keywords: Activated sludge process, baffles, oxygen mass transfer, residence time
  • Diploma thesis
    TU Dresden, 2016
    Mentor: Herrmann-Heber, Robert; Reinecke, Sebastian
    94 Seiten

Publ.-Id: 24292 - Permalink


Enhanced proton acceleration in an applied longitudinal magnetic field
Arefiev A.; Toncian T.; Fiskal G.;
Using two-dimensional particle-in-cell simulations, we examine how an externally applied strong magnetic field impacts proton acceleration in laser-irradiated solid-density targets. We find that a kT- level external magnetic field can sufficiently inhibit transverse transport of hot electrons in a flat laser- irradiated target. While the electron heating by the laser remains mostly unaffected, the reduced electron transport during proton acceleration leads to an enhancement of maximum proton energies and the overall number of energetic protons. The resulting proton beam is much better collimated compared to a beam generated without applying a kT-level magnetic field. A factor of three enhancement of the laser energy conversion efficiency into multi-MeV protons is another effect of the magnetic field. The required kT-level magnetic fields are becoming feasible due to a significant progress that has been made in generating magnetic fields with laser-driven coils using ns-long laser pulses. The possibility of improving characteristics of laser-driven proton beams using such fields is a strong motivation for further development of laser-driven magnetic field capabilities.
Keywords: proton acceleration, magnetic field, laser

Publ.-Id: 24291 - Permalink


Entwicklung und Umsetzung eines echtzeitfähigen Datenverarbeitungs- und Rekonstruktionsalgorithmus für die ultraschnelle Elektronenstrahl-Röntgen-CT
Frust, T.;
This thesis demonstrates the development and the implementation of a real-time capable data processing and reconstruction algorithm for the ulftrafast X-ray scanner ROssendorf Fast Electron beam X-ray tomograph (ROFEX). This measuring system is built for non-invasive imaging of multiphase fluids. Thus, it requires a high scan rate of more than 1 kHz. This is achieved by an arrangement without mechanically rotating parts providing scan rates of up to 8 kHz. Current data processing is not suited to reconstruct a data stream of around 1,3 GB/s. Hence, visual inspection or active process feedback control is not possible yet. This work presents the design and implementation of real-time capable data processing providing a better usability and new fields of application for ROFEX. Therefore, the adjustment of data transfer from the measuring system to the reconstruction workstation as well as the implementation of a new software is essential. The application is implemented using a generic software pipeline consisting of distinct processing units exploiting data parallelism of NVIDIA GPUs with CUDA. Measurements on a NVIDIA GeForce GTX 1080 and NVIDIA Tesla K20c yield a reconstruction rate of more than 1 kHz, which is well-suited for an online application of ROFEX. Furthermore, a test system is introduced simulating an online capable detector. It shows the online visualization of reconstructed images as a first new application.
Keywords: cuda, parallel data processing, in-situ, ROFEX
  • Diploma thesis
    TU Dresden, 2016
    Mentor: Prof. Uwe Hampel
    81 Seiten
  • Lecture (others)
    Verteidigung der Diplomarbeit, 03.11.2016, Dresden, Deutschland

Publ.-Id: 24290 - Permalink


Advanced Gamma and X-ray Computed Tomography for Multiphase Flow Analysis
Bieberle, A.;
Investigation of two- and multiphase flow phenomena inside technical apparatuses and hydraulic components are of highest interest for equipment designers and operators since the knowledge helps to assess and understand complex flows, e.g. in chemical and process engineering. This in turn expedites the development of safer and more efficiently operated industrial facilities. Furthermore, measured data are used to validate new models developed for multiphase computational fluid dynamics (CFD). For non-intrusive two-phase flow investigations, two radiation-based computed tomography (CT) scanners were developed and are operated at the Helmholtz-Zentrum Dresden - Rossendorf (HZDR), Institute of Fluid Dynamics: a high-resolution gamma-ray computed tomography scanner (HireCT) first presented by Hampel et al. (2007) and an ultrafast electron beam X-ray CT scanner (ROFEX) first presented by Fischer et al. (2010). Both CT scanners are able to recover cross-sectional phase distribution images of a scanned plane or volume section within the flow as time averaged images or time resolved image sequences. The capabilities of both CT systems are introduced exemplarily with reference to experiments on an industrial scale bubble column, a fluidized bed and a static mixer.
Keywords: computed tomography, multi-phase flow, CFD
  • Contribution to proceedings
    International Workshop on Process and Biomedical Tomography, 07.-09.11.2016, Warschau, Polen
  • Invited lecture (Conferences)
    International Workshop on Process and Biomedical Tomography, 07.-09.11.2016, Warschau, Polen

Publ.-Id: 24289 - Permalink


Simulation of a Main Steamline Break scenario using the 3D neutron kinetic core model Dyn3D coupled with the CFD software Trio U
Grahn, A.; Gommlich, A.; Kliem, S.;
In the framework of the European project Nuresafe, the reactor dynamics code Dyn3D, developed at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), was coupled with the Computational Fluid Dynamics (CFD) solver Trio U, developed at CEA France, in order to replace Dyn3D’s one-dimensional hydraulic part with a full three-dimensional description of the coolant flow in the reactor core at higher spatial resolution. The present document gives an introduction into the coupling method and shows results of its application to the simulation of an Main Steamline Break (MSLB) accident of a Pressurised Water Reactor (PWR).
Keywords: reactor safety, code coupling, thermal hydraulics, computational fluid dynamics, reactor dynamics
  • Lecture (Conference)
    International Conference on Mathematics & Computational Methods Applied to Nuclear Science & Engineering (M&C 2017), 16.-20.04.2017, Jeju, Korea
  • Contribution to proceedings
    International Conference on Mathematics & Computational Methods Applied to Nuclear Science & Engineering (M&C 2017), 16.-20.04.2017, Jeju, Korea

Publ.-Id: 24287 - Permalink


Hindrance in MWCNT nanofluid flow through porous media observed by PET
Schymura, S.; Kulenkampff, J.; Franke, K.; Lippmann-Pipke, J.;
We studied the behaviour of a concentrated multi-wall carbon nanotube (MWCNT) nanofluid injected into a synthetic porous media. The experimental conditions were chosen for optimal particle mobility: strongly repulsive interactions between particles and between particles and the glass matrix, inhibiting aggregation and adsorption. Furthermore, a large glass bead size rendered filtration unlikely. However, hindrance effects in the concentrated, though stable against sedimentation, nanofluid due to particle- particle interactions showed to have a decisive influence on the fluid flow characteristics, in particlular, the particle transport.
Using positron emission tomography (PET) as imaging modality we could observe the transport of the MWCNT nanofluid through the glass bead packing in situ. During pulse injection of the suspension into the porous media the suspension spread out as a horizontal plume at the bottom of the column by “flooding” the respective pore volume. After this pulse injection the subsequently injected water seemed to penetrate the suspension only mobilizing MWCNTs from the top of the suspension plume rather than displacing the bulk of injected nanofluid. This mobilization from the top of the plume is most effective in the central parts of the column where the flow velocity is highest while most of the nanofluid is trapped in more stagnant zones of the pore space at the bottom edges of the column with minimal MWCNT displacement. The mobilized MWCNTs are higly diluted and mainly visible via the continuous diminishing of the plume from its central top boundry.
These observations can be explained by a pronounced hindrance of the particle transport due to particle-particle interactions in the concentrated suspension which is only overcome at the edges of the nanofluid plume, primarily in the central zones of highest flow velocity.
In order to achieve the PET measurements the MWCNTs used in this experiment were oxidzed by oxidative acid treatment (Wang et al. 2006) and radiolabeled with the positron emitter I-125. In an uncomplicated one-pot synthesis the CNTs were labeled by an electrophilic attack of I+ on the electron-rich CNT side-wall catalyzed by the so-called iodogen 1,3,4,6-Tetrachloro-3α-6α- diphenylglucoluril.
Keywords: Kohlenstoffnanoröhrchen, carbon nanotubes Positronenemissionstomografie, Positron Emission Tomography Transport Experiment, transport experiment
  • Lecture (Conference)
    Interpore - First German National Chapter Meeting, 05.-06.12.2016, Leipzig, Deutschland

Publ.-Id: 24286 - Permalink


Environmental transformation of CeO2 Nanoparticles - Elucidating the role of dissolution by smart radiolabeling
Schymura, S.; Fricke, T.; Hildebrand, H.; Franke, K.;
Environmental transformations of nanoparticles (NPs) play a major role in determining their likely fate in the environment and the implications for toxicity, mobility and general risk assessment. A main question in this context is the dissolution of nanoparticles. If a Nanoparticle dissolves quickly it may be treated as ionic species in terms of risk assessment, while particulate species can show different tendencies of transport, uptake by organisms and consequently toxicity. Slowly dissolving NPs can exhibit a so-called Trojan-horse effect, transporting and releasing ions at places where said ions would not have been transported – at least not at the same concentrations - without traveling on horseback, i.e. in particulate forms.
Using different radiolabeling techniques we have investigated the dissolution of CeO2 NPs. Through activation by proton bombardment using a cyclotron we have radiolabeled CeO2 NP with radioactive 139Ce via a (p,2n) nuclear reaction from 140Ce to 139Pr followed by the decay of 139Pr to 139Ce. Here the radiolabel can be assumed to be uniformly distributed in the resulting [139Ce]CeO2 NP. In contrast to this we also have produced [139Ce]CeO2 NP using an in-diffusion technique where ionic radioactive 139Ce diffuses into the NPs at elevated temperatures. Here the radiolabel is located close to the surface of the NPs. This results in different leaching kinetics of 139Ce for the two batches of [139Ce]CeO2 NP (Fig. 1). The comparison of the different rates allows us to calculate that about 47 % of the 139Ce introduced by in-diffusion is located in the first atomic layer of the CeO2 NP. We can show that dissolution plays an insignificant role under environmentally relevant conditions with leaching rates well below 1 % of Ce. However, this still reflects significant changes of the surface of the CeO2, as a dissolution of only 1.5 % corresponds to a complete removal of the first atomic layer.
Furthermore, using the differently labeled [139Ce]CeO2 NP we can show that the uptake of Ce into plants when exposed to CeO2 NP is mainly an uptake of particulate CeO2 rather than dissolved ionic Ce.
Keywords: Radiomarkierung, radiolabeling Nanopartikel, nanoparticle Cerdioxid, cerium dioxide Planzenaufnahme, plan tuptake
  • Lecture (Conference)
    Nanosafe 2016, 07.-10.11.2016, Grenoble, Frankreich

Publ.-Id: 24285 - Permalink


Measuring at relevant concentrations - radiolabeling as a versatile tool in nanosafety research
Schymura, S.; Hildebrand, H.; Fricke, T.; Bellido, E.; Ojea-Jimenez, I.; Cydzik, I.; Kozempel, J.; Dalmiglio, M.; Bulgheroni, A.; Freyer, A.; Cotogno, G.; Simonelli, F.; Mansel, A.; Kulenkampff, J.; Holzwarth, U.; Gibson, N.; Franke, K.;
The employment of radiotracers is a versatile tool for the detection of nano-particulate materials in complex systems such as environmental samples or organisms. With the increasing usage of nanoparticles in applications outside of research laboratories, a careful risk assessment of their release into the environment becomes mandatory. However, the monitoring of nanoparticles in such complex natural systems as soil, natural waters, plants, sewage sludge, etc. is nearly impossible using conventional methods, especially at environmentally relevant concentrations. This obstacle can be overcome by radiolabeling, which may be of crucial value in enabling such research.
We have developed various methods of introducing radiotracers into some of the most common nanoparticles, such as Ag, carbon, SiO2, CeO2 and TiO2 nanoparticles. The labeling techniques are the synthesis of the nanoparticles using radioactive starting materials, the binding of the radiotracer to the nanoparticles, the activation of the nanoparticles using proton irradiation, the recoil labeling utilizing the recoil of a nuclear reaction to implant a radiotracer into the nanoparticle, and the in-diffusion of radiotracers into the nanoparticles at elevated temperatures. Using these methods we have produced [105/110mAg]Ag, [124/125/131I]CNTs, [48V]TiO2, [139Ce]CeO2, [7Be]MWCNT, [7Be]SiO2, [44/45Ti]TiO2, etc.. The methods are adaptable for a wide range of other nanoparticles. The so-labelled nanoparticles can be detected at minimal concentrations well in the ng/L range even with a background of the same element and without complicated sample preparations necessary.
Using our methods one can radiolabel commercial nanoparticle samples for sensitive detection in environmentally relevant trace concentrations. The labeled particles have been successfully used in release studies, environmental mobility studies, fate studies in waste water treatment and plant uptake studies.
Keywords: Radiomarkierung, radiolabeling Nanopartikel, nanoparticles cyclotron, Zyklotron
  • Poster
    Nanosafe 2016, 07.-10.11.2016, Grenoble, Frankreich

Publ.-Id: 24284 - Permalink


Shielding and activation studies for the MYRRHA research reactor
Müller, S. E.ORC; Ferrari, A.; Konheiser, J.
The planned MYRRHA research reactor in Mol (Belgium) aims to demonstrate efficient transmutation of high level waste and associated Accelerator-Driven Systems (ADS) technology. The system is based on a lead-bismuth eutectic (LBE) cooled reactor, working both in critical and in sub-critical operation modes. The neutrons needed to sustain fission in the sub-critical mode are produced via spallation processes by a 600 MeV, 4 mA proton beam, which is provided by a linear accelerator and hits a LBE spallation target located inside the reactor core. In order to assess the main shielding problems, a method based on the combined use of the two Monte Carlo codes MCNPX and FLUKA has been developed, with the goal to perform detailed analyses of both the radiation fields due to the system in operation, and the coupled residual radiation due to the activated materials. As a result, neutron and photon fluences as well as prompt and residual ambient dose equivalent rates have been evaluated. In addition, an activation database for many of the structural materials has been built.
  • Lecture (Conference)
    16th International Symposium on Reactor Dosimetry, 07.-12.05.2017, Santa Fe, New Mexico, USA
  • Contribution to proceedings
    16th International Symposium on Reactor Dosimetry, 08.-12.05.2017, Santa Fe, New Mexico, USA
    Proceedings of the 16th International Symposium on Reactor Dosimetry, West Conshohocken, PA (USA): ASTM International, West Conshohocken, PA,, 978-0-8031-7661-4, 15-22
    DOI: 10.1520/STP160820170088

Publ.-Id: 24283 - Permalink


Free-surface dynamics in Induction Processing Applications
Beckstein, P.; Galindo, V.ORC; Gerbeth, G.
Induction processing technology is widely applied in metallurgical and crystal growth industry where conducting or semi-conducting material is involved. In many applications, alternating magnetic fields which are used to generate heat and force occur together with a free-surface flow. The numerical analysis of such three-dimensional, multi-physical phenomena on industrial scale is still a big challenge.
We present an overview of a novel multi-mesh model to address these kind of coupled problems by means of computational simulations. It is based on the Finite Volume Method (FVM) of the software foam-extend (http://www.foam-extend.org) - an extended version of OpenFOAM (Weller et al, 1998). Our development is motivated by the desire to investigate the so called Ribbon Growth on Substrate
(RGS) process. RGS is a crystallisation technique that allows the production of silicon wafers and advanced metal-silicide alloys (Schönecker et al, 2004) with high volume manufacturing and outstanding material yield.
Keywords: Numerical simulation, coupled multi-physics, free-surface flow, eddy-currents, Ribbon Growth on Substrate process
  • Book chapter
    J. Miguel Nóbrega and Hrvoje Jasak: OpenFOAM® - Selected papers of the 11th Workshop, Cham (ZG) Switzerland: Springer International Publishing AG, 2019, 978-3-319-60845-7, 197-210
    DOI: 10.1007/978-3-319-60846-4
  • Lecture (Conference)
    11th OpenFOAM® Workshop, 26.-30.06.2016, Guimarães, Portugal

Publ.-Id: 24282 - Permalink


Biotransformation and detoxification of selenite by microbial biogenesis of selenium-sulfur nanoparticles
Vogel, M.; Fischer, S.; Maffert, A.; Hübner, R.; Scheinost, A.; Franzen, C.; Steudtner, R.;
This study combines the interaction between the toxic oxyanions selenite and selenate and the plant growth promoting bacterium Azospirillum brasilense with a comprehensive characterization of the formed selenium particles. As selenium is an essential trace element, but also toxic in high concentrations, its state of occurrence in nature is of major concern. Growth of the bacterium was affected by selenite (1–5 mM) only, observable as a prolonged growth lag-phase of 3 days. Subsequently, selenite reduction occurred under aerobic conditions resulting in extracellularly formed insoluble Se0 particles. Complementary studies by microscopic and spectroscopic techniques revealed the particles to be homogeneous and stable Se8-nSn structured spheres with an average size of 400 nm and highly negative surface charge of −18 mV in the neutral pH range. As this is the first study showing Azospirillum brasilense being able to biotransform selenite to selenium particles containing a certain amount of sulfur, even if environmental waters supplemented with selenite were used, they may significantly contribute to the biogeochemical cycling of both elements in soil as well as to their soil-plant transfer. Therefore, microbial biotransformation of selenite under certain circumstances may be used for various bio-remediation and bio-technological applications.
Keywords: selenium, Azospirillum brasilense, nanoparticle, reduction, selenite

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  • Secondary publication expected

Publ.-Id: 24281 - Permalink


Free-surface dynamics in the Ribbon Growth on Substrate (RGS) Process
Beckstein, P.; Galindo, V.ORC; Gerbeth, G.
With the Ribbon Growth on Substrate (RGS) technology, a new crystallization technique is available that allows controlled high crystallization rate production of silicon wafers and advanced metal-silicide alloys. Compared to other casting methods, such as e.g. directional solidification, the RGS process allows better crystallization control, high volume manufacturing and high material yield due to its continuous, substrate-driven design. Insights from modelling the characteristic melt flow in the casting frame are very desirable. To address this demand, we are developing a new numerical tool based on OpenFOAM which can be utilized to simulate the free-surface dynamics of the melt flow under the influence of alternating electromagnetic fields. The underlying multi-physical model involves three-dimensional hydrodynamic and magnetodynamic effects and their interaction.
Keywords: Ribbon Growth on Substrate, numerical simulation, coupled multi-physics, free-surface flow, eddy-currents
  • Open Access LogoInternational Journal of Applied Electromagnetics and Mechanics 53(2017)51, 543-551
    DOI: 10.3233/JAE-162237
  • Poster
    International Conference on Heating by Electromagnetic Sources, 25.-27.05.2016, Padua, Italy
  • Contribution to proceedings
    International Conference on Heating by Electromagnetic Sources, 24.-27.05.2016, Padua, Italy
    Proceedings of the International Conference on Heating by Electromagnetic Sources, Padova: SGEditoriali Padova, 127-134

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Publ.-Id: 24280 - Permalink


Experimental measurements in melting ingots in the melt of the same material
Ditze, A.; Scharf, C.;
This study concerns the melting of ingots of different materials in melt of the same material. We investigated the pure materials ice, lead, tin, and zinc, the magnesium alloys AZ91 and AM50, and the aluminum alloy A226. We used melting pots made from steel (for Pb, Sn, Zn, AZ91, AM50) and clay graphite (for A226) with a volume of 16 L, inserted into a resistance furnace. Some experiments with AZ91 were also carried out in a 2500 kg industrial furnace. The ice ingots were melted in a 20 L beaker.
The temperature profile adjacent to the melting ingot was recorded over time. From this profile, the mean temperature of the melt adjacent to the ingots was calculated. Together with the geometrical and thermophysical properties of the investigated materials, the dimensionless Nusselt, Rayleigh, Prandtl, and Stefan numbers were calculated and interpreted as an empirical function, Nu = 0.114·(Ra·Pr)0.291·Ste0.754. This function describes the melting behavior of all of the materials considered. This partly agrees with results from the literature, but considerable deviations were also determined. Once the mean temperature is known, the time needed to melt the different materials in different geometrical shapes can be estimated along with the maximum melting rate. This simple model helps understand technical processes where melting of materials is relevant, for example when calculating energy consumption in the foundry industry.
Keywords: Melting Ice Metals Alloys Heat transfer Dimensionless numbers Natural convection Nusselt Rayleigh Prandtl Stefan

Publ.-Id: 24279 - Permalink


Numerical simulation of full scale Upper Plenum Test Facility experiments
Höhne, T.; Deendarlianto, A.;
Scaling of flow conditions are one of the still open topics for the use of Computational Fluid Dynamics (CFD) codes in nuclear reactor safety. For safety relevant flow phenomena of Konvoi type nuclear reactors it is recommended to use full scale tests for code validation. Experiments of the Upper Plenum Test Facility (UPTF) are predestined since they are 1:1 scaled tests. Therefore, three UPTF test series were selected and CFD post-test calculations were performed. The major focus was analysing the qualitative flow behaviour. In the case of the CFD calculation the stratification in the cold leg is accurately predicted by the code. The calculated lowest temperatures are in the range of the experiment. The flow behaviour in the downcomer is well predicted apart from some spurious circumferential oscillations. The two phase CFD calculation is in good agreement with the experimental data. It indicates that CFD is also a promising approach for analyzing multiphase problems in the nuclear reactor safety analysis. In addition, a full scale model with all details of the UPTF test facility was developed. The detailed numerical grid model can be used for further test analysis.
Keywords: CFD, horizontal flow, UPTF, PWR, AIAD, single phase flow, two-phase flow

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Publ.-Id: 24278 - Permalink


Stratified and Segregated Flow Modelling - AIAD 2016
Höhne, T.;
Today: Limits in simulating stratified & segregated two phase flow
Algebraic Interfacial Area Density Model (AIAD)
Free Surface Drag
Turbulence Damping
Sub-grid wave turbulence (SWT)
Verification and Validation is going on – more experimental data are required for the validation
Keywords: AIAD, Free Surface Drag, Sub-grid wave turbulence (SWT)
  • Contribution to proceedings
    14th Short Course “Multiphase Flow: Simulation,Experiment and Application”, 08.-10.11.2016, Dresden, Deutschland
  • Lecture (Conference)
    14th Short Course “Multiphase Flow: Simulation,Experiment and Application”, 08.-10.11.2016, Dresden, Deutschland

Publ.-Id: 24276 - Permalink


Comparison of Technologies for Nano Device Prototyping with a Special Focus on Ion Beams - A review
Bruchhaus, L.; Mazarov, P.; Bischoff, L.; Gierak, J.; Wieck, A. D.; Hövel, H.;
Nano device prototyping (NDP) is essential for realizing and assessing ideas as well as theories in form of nano devices, before they can be made available in or as commercial products. In this review, application results patterned similarly as in the semiconductor industry (for cell phone, computer processors or memory) will be presented. For NDP some requirements are different, thus different technologies are employed. Currently, in NDP, for many applications direct write Gaussian vector scan electron beam lithography (EBL) is used to define the required features in organic resist on this scale.
We will take a look at many application results carried out by EBL, self-organized 3D epitaxy, atomic probe microscopy (STM / AFM) and in more detail ion beam techniques. For ion beam techniques there is a special focus on those based upon liquid metal (alloy) ion sources (LM(A)IS), as recent developments have significantly increased their applicability for NDP.
Keywords: nanotechnology, nano device protoyping, nano patterning, nano fabrication, focused ion beam, electron beam lithography, self-organized 3D epitaxy, atomic, scanning probe nano patterning, magnetics, photonics, fluidics, implantation

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Publ.-Id: 24275 - Permalink


Prediction of Dysphagia and Xerostomia based on CT imaging features of HNSCC Patients
Pilz, K.; Leger, S.; Zwanenburg, A.; Richter, C.; Krause, M.; Baumann, M.; Löck, S.; Troost, E. G. C.;
Purpose/Objective: Radiochemotherapy (RCT) for patients with head and neck squamous cell carcinoma (HNSCC) frequently causes xerostomia and dysphagia, which may be alleviated by treatment adaption, e.g., modulation of dose distribution to the salivary glands. Current clinical models, which are based on dosimetric parameters, mostly achieve moderate prediction accuracy. Therefore, we aimed to improve the prediction of xerostomia and dysphagia by using additional imaging biomarkers based on computed tomography (CT) scans.

Material/Methods: In this study 46 patients with UICC stage III/IV advanced head and neck squamous cell carcinoma (HNSCC) were considered (NCT00180180, [1]). All patients received primary RCT and underwent a pre-treatment CT scan without intravenous contrast agent. Patient-reported xerostomia and dysphagia were evaluated at baseline, every week during RCT, four weeks after treatment and three monthly thereafter. 5040 imaging features were extracted from the parotid and submandibular glands. Feature reproducibility tests based on the RIDER re-test data set [2] were performed leading to 1513 imaging features in total. The most informative features were selected by a univariate logistic regression analysis. The developed radiomic signature was used to train and validate multivariate logistic regression and random forest models using repeated 5-fold cross validation. The predication accuracy was assessed by the area under the curve (AUC).

Results: The logistic regression and the random forest model achieved similar performance in predicting xerostomia (AUC=0.71). The developed signature consisted of one dosimetric parameter and one imaging feature. For the prediction of dysphagia both models achieved only a moderate prediction accuracy (AUC=0.55).

Conclusions: For prediction of xerostomia, a signature was developed and showed a good performance. For dysphagia only moderately performing models could be obtained in this cohort. Based on our results, subgroups of patients at a high risk of xerostomia may be identified and offered treatment adaption. However, further investigations are currently ongoing, i.e., externally validating the developed signature, which is an important step in developing clinically relevant prediction models.

References:
[1] D. Zips et al., “Exploratory prospective trial of hypoxia-specific PET imaging during radiochemotherapy in patients with locally advanced head-and-neck cancer.,” Radiother. Oncol., vol. 105, no. 1, pp. 21–8, Oct. 2012.
[2] B. Zhao et al., “Evaluating Variability in Tumor Measurements from Same-day Repeat CT Scans of Patients with Non–Small Cell Lung Cancer,” Radiology, vol. 252, no. 1, pp. 263–272, Jul. 2009.

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Publ.-Id: 24274 - Permalink


Raw material "criticality" - Sense or non-sense
Frenzel, M.; Kullik, J.; Reuter, M. A.; Gutzmer, J.;
The past decade has seen a resurgence of interest in the supply security of mineral raw materials. A key to the current debate is the concept of “criticality”. The present article provides a review of the criticality concept, as well as the methodologies used in its assessment, including a critical evaluation of their validity in view of classical risk theory. Furthermore, it discusses a number of risks present in global raw materials markets not captured by criticality assessments. Proposed measures for the alleviation of these risks are also presented.
We find that current assessments of raw material criticality are fundamentally flawed in several ways. This is mostly due to a lack of adherence to risk theory, and highly limits their applicability. Many of the raw materials generally identified as critical are probably not critical. Still, the flaws of current assessments do not mean that the general issue of raw material supply security can simply be ignored. Rather, it implies that new assessments are required. While the basic theoretical framework for such assessments is outlined in this review, detailed method development is beyond its scope, and will require a major collaborative effort between different disciplines along the value chain.
In the opinion of the authors, the greatest challenge in the resource sector for the longer term is to stop, or counteract the effects of, the escalation of unit energy costs of production. This issue is particularly pressing due to its close link to the renewable energy revolution, requiring more metal and mineral raw materials per unit energy produced.
Keywords: Supply security; Critical materials; Metals

Publ.-Id: 24273 - Permalink


A Multiple-Technique Round-Robin Test in Actinide Spectroscopy
Foerstendorf, H.ORC; Müller, K.; Tsushima, S.; Steudtner, R.; Kumke, M. U.; Lefèvre, G.; Rothe, J.; Mason, H.; Yang, P.
In the advent of the 2nd International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS 2014), held in November 2014 at HZDR, an inter-laboratory Round-Robin Test (RRT) was initiated. The main goal of the RRT is the comprehensive molecular analysis of an aqueous complexing system – U(VI)/acetate, which was selected to be independently investigated by different spectroscopic and quantum chemical methods applied by leading laboratories in actinide or geochemical research. Finally, more than 40 scientists hosted at twenty institutions in seven countries were attending this RRT, which was finally subdivided into five clusters. A representative speaker was nominated for each cluster who received the submitted raw data sets as well as the analyzed data (e.g. data transformations, background subtraction, smoothing, deconvolution…). A first reporting of the preliminary results followed by plenum discussions was given by the cluster speakers during special sessions at the ATAS workshop.
The outcome of this RRT can be considered on two levels: First, conformities as well as sources of discrepancies between the results of each cluster have to be evaluated. It was found that consistencies of the raw data by the experimental approaches are widely given. In particular, for complex set-ups such as accelerator based X-Ray absorption spectroscopy, the agreement of the raw data was surprisingly high, whereas data obtained from Luminescence spectroscopy turned out to be strongly related to the chosen acquisition parameters which were quite heterogeneously chosen by the participating experimentalists. More detailed results of the single clusters will be presented.
On the second level, the potentials and limitations of coupling different spectroscopic and, in particular, theoretical approaches for the comprehensive study of actinide molecule complexes are assessed. The additional benefit of the combined approach with respect to the exploration of the aqueous speciation of the U(VI)/acetate system will be elaborated.
  • Lecture (Conference)
    3rd International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS 2016), 07.-10.11.2016, Richland, U.S.A.

Publ.-Id: 24271 - Permalink


A Special Issue of the International Journal of Mineral Processing honoring Prof. Dr. sc. techn. Drs. h.c. Heinrich Schubert
Rudolph, M.ORC; Peuker, U. A.ORC
The year 2016 marks the 90th birthday of honorable Prof. Dr. sc. techn. Drs. h.c. Heinrich Schubert, emeritus Professor of the oldest mining academy in the world, the TU Bergakademie Freiberg. Even more, it is 25 years ago, in the year of his retirement, that he was hosting the XVII IMPC 1991 in Dresden, Germany and 10 years ago that he received the IMPC Lifetime Achievement Award at the XXIII IMPC 2006 in Istanbul, Turkey.

Born January 23rd 1926 in Pirna-Jessen close to the city of Dresden he enrolled at the TU Bergakademie Freiberg after lucky circumstances keeping him from the worst harm of the Second World War where he only had to fight the very last months. In 1951 and 1952 he graduated with “Diplomingenieur Dipl.-Ing.” degrees in mineral processing and mining engineering, respectively. He continued at the TU Bergakademie Freiberg and obtained his first PhD as Dr.-Ing. with distinction in 1956 on “flotability and structure relations in cationactive flotation”. In 1971 followed his second PhD as Dr. sc. techn. on “the role of association of non-polar groups in collector adsorption” after spending time in the non-ferrous metal industry of the German Democratic Republic from 1952 until 1959 and his appointment as an associate professor in mineral processing in 1960 at the TU Bergakademie Freiberg. From 1969 until 1991 he was full professor for Mechanical Process Engineering and Mineral Processing with approximately 60 doctorates and 550 graduate students under his supervision. He spent time as visiting professor 1981 in Queensland, Australia, 1982 in Iowa, USA and 1989 in Wuhan, China. He published more than 300 papers of which unfortunately not all of them are listed in electronic databases so far. His most lasting contributions, besides his papers, are the three volume “Aufbereitung fester Stoffe” which can said to be the most important mineral processing books in the German language and furthermore the two volume “Handbuch der Mechanischen Verfahrenstechnik”, a comprehensive textbook on the basics of Mechanical Process Technologies, which he edited and authored/co-authored. He has made many contributions in different areas of mineral processing, mechanical process engineering and particle technology with the aim to describe process unit operations with fundamental micro processes. As part of such approaches he became acknowledged for his work in the unit operations that are governed by multi-phase turbulent flows, like flotation. In recent years his flotation hydrodynamics results are being cited increasingly and it seems that him introducing the turbulent mechanisms in the field of flotation has shifted the flotation paradigm a bit. Based on his finding he often points out that the essential particle-bubble collection (collision and attachment) and thus flotation of fine particles is happening in the highly turbulent zone of a flotation cell, which he refers to as “rotor storm” and thus it is important to optimize the turbulent hydrodynamics.

In various contributions of this special issue one can find the latest research results in this field. Furthermore this special issue represents contributions besides the turbulent hydrodynamics aspects of flotation by well-respected international colleagues of Prof. Schubert, all of which told their own short stories with respect to Prof. Schubert after invitation. Unfortunately, there have been two invitations for this special issue to honorable professors, co-authors and colleagues of Prof. Schubert that sadly never meant to be. Very sadly, on August 21st 2015 Prof. Thomas Neeße at age 76 passed away and shortly after on November 24th 2015 Prof. Jürgen Tomas died at age 62.

Now with 90 years of age Prof. Schubert is still keeping active and supervising a PhD student Duong Huu Hoang meeting him for discussions together with the managing guest editor Martin Rudolph every two weeks at his emeritus office of his former institute, which is now led by his successor's successor and guest editor Prof. Urs A. Peuker. The first of publications in this special issue therefore is a collaborative work including those mentioned and showing the continuation in the fundamental mineral processing research in Freiberg, Germany. This would for sure not have been possible and still existing if it was not for Prof. Schubert's outstanding career (Fig. 1).

Managing guest editor Dr.-Ing. Martin Rudolph is a graduate of the TU Bergakademie Freiberg and now head of the processing department of the HIF, the Helmholtz Institute Freiberg for Resource Technology, established in 2011. His research is on heterocoagulation processes, like flotation and their fundamentals. The HIF would probably not have been founded in Freiberg by the federal government of Germany as part of the Helmholtz foundation, if it was not for Prof. Schubert's achievements in the past.

Guest editor Prof. Dr.-Ing. Urs Alexander Peuker, a graduate of the TH Karlsruhe, former assistant professor of the TU Clausthal and since 2008 full professor and director of the Institute of Mechanical Process Engineering and Mineral Processing of the TU Bergakademie Freiberg. Thus he is the successor of Prof. Klaus Husemann who led the institute from 1991 until 2008 as the successor of Prof. Heinrich Schubert. His main research interests are in the field of particle interactions, applying AFM-techniques as well as in mechanical separation processes, especially in filtration. In 2016 Prof. Peuker started the coordination of a DFG priority program focusing on the multidimensional separation of particle below 10 μm, which will hopefully give new insights and inspiration to the processing of ultra-fines in mineral processing.

We thank Dr. Bernd Kubier of TU Bergakademie Freiberg, former head assistant of Prof. Heinrich Schubert for valuable information on Prof. Schubert's career which unfortunately is exceeding the length of an editorial.

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  • Secondary publication expected

Publ.-Id: 24270 - Permalink


Influence of iron doping on the structural, chemical, and optoelectronic properties of sputtered zinc oxide thin films
Al-Kuhaili, M. F.; Durrani, S. M. A.; El-Said, A. S.; Heller, R.;
Iron (Fe)-doped zinc oxide (ZnO) thin films were deposited using two techniques: (i) radio-frequency (RF) sputtering of Fe-doped ZnO targets, and (ii) co-sputtering, where ZnO was RF-sputtered and iron was direct-current (DC)-sputtered. The as-deposited films were polycrystalline, with predominant growth along the (002) direction of hexagonal ZnO, and possessed a considerable concentration of oxygen vacancies. From an optoelectronic point of view, the films were highly transparent, with a band gap of 3.25 eV, and had electrical resistivity values in the range of 100–103 X cm. To improve the electrical conductivity of the films, they were annealed in a vacuum and in a hydrogen atmosphere. The annealing process did not affect the optical properties of the films. However, there were substantial structural and chemical changes in the films. Moreover, the electrical conductivity of the films was enhanced drastically upon annealing in hydrogen, where the electrical resistivity was reduced to 3.2 10 3 X cm.
Keywords: Doping, Fe, structure, optoelectronic properties, sputtering, zink oxid

Publ.-Id: 24269 - Permalink


Electron-beam pulse annealed Ti-implanted GaP
Werner, Z.; Barlak, M.; Ratajczak, R.; Konarski, P.; Markov, A. M.; Heller, R.;
Gallium phosphide heavily doped with substitutional titanium is a prospective material for intermediate band solar cells. To manufacture such a material, single crystals of GaP were implanted with 120keV Ti ions to doses between 5 1014cm 2 and 5 1015cm 2. They were next pulse annealed with 2 ls electron-beam pulses of electron energy of about 13 keV and pulse energy density between 1 and 2 Jcm 2. The samples were studied by channeled Rutherford Backscattering, particle induced X-ray emission, and SIMS. The results show full recovery of crystal structure damaged by implantation and good retention of the implanted titanium without, however, its significant substitu- tion at crystal sites.
Keywords: GaP, implantation, electron beam, annealing, Ti

Publ.-Id: 24268 - Permalink


Enhancement of the refractive index of sputtered zinc oxide thin films through doping with Fe2O3
Al-Kuhaili, M. F.; Durrani, S. M. A.; El-Said, A. S.; Heller, R.;
Certain optical applications, such as antireflective coatings on solar cells, require transparent films with high refractive indices (>2). Zinc oxide (ZnO) is a transparent semiconductor with exceptional optical properties. However, its refractive index in the transparent dispersionless region of the visible spectrum is lower than 2. In this study, we enhanced the refractive index of sputtered ZnO thin films through doping with iron oxide (Fe2O3), where ZnO targets were doped by 0.5e2.0 wt% of Fe2O3. The films were polycrystalline with smooth surfaces. Differential transmittance spectra were employed to derive the optical band gaps of the films, which showed a minor variation by ±0.03 eV due to doping. The refractive index was extracted from the transmittance spectra using a Cauchy equation and was further fitted by a single-oscillator model. The optimum refractive index was obtained for the films prepared from the target doped with 1.5 wt% of Fe2O3. Enhancement of the refractive index was accompanied by a reduction of optical absorption in the doped films.
Keywords: Zinc oxide, Iron oxide, Sputtering, Doping, Refractive index

Publ.-Id: 24267 - Permalink


ThermAc: A Joint Project on Aquatic Actinide Chemistry and Thermodynamics at Elevated Temperature Conditions
Bosbach, D.; Altmaier, M.; Gaona, X.; Endrizzi, F.; Brendler, V.; Steudtner, R.; Franzen, C.; Tsushima, S.; Panak, P. J.; Skerencak-Frech, A.; Hagemann, S.; Brandt, F.; Krüger, S.; Colàs, E.; Grivé, M.; Thoenen, T.; Kulik, D. A.;
The ThermAc project aims at extending the chemical understanding and available thermodynamic database for actinides, long-lived fission products and relevant matrix elements in aquatic systems at elevated temperatures. Such conditions are expected when storing highly active heat producing waste in a repository system over a significant period of time after starting repository operation. If early canister failure occurs, radionuclides therefore may contact aquatic systems at higher temperatures. Adequate scientific tools must be available to assess the related chemical effects and their impact upon safety. ThermAc approaches this challenge by evaluating the capabilities of a variety of estimation methods to obtain thermodynamic parameters (formation constants, enthalpic and entropic data) as f(T). This is done by both intercomparison between such methods and pointwise checks with experimental results. There, a clear focus is on long-lived actinides in oxidation states III, V and VI, with selected fission products and important redox controlling matrix elements like Fe also receiving attention. ThermAc addresses the temperature range from ~5°C up to ~90°C, focusing on systems at low or intermediate ionic strength. Only for selected cases with specific relevance or scientific interest, higher temperatures up to 200°C or salt brine solutions are investigated. Chemical analogs help to gain information on solid phase transformation processes. Ion-ion-interaction processes are treated with the SIT, in agreement with the NEA-TDB project. Quantum chemical calculations are used to support the interpretation of experimental findings, and establish a fundamental understanding of chemical effects on a molecular level.
  • Poster
    Goldschmidt2016, 26.06.-01.07.2016, Yokohama, Japan

Publ.-Id: 24266 - Permalink


ThermAc: A Joint Project on Aquatic Actinide Chemistry and Thermodynamics at Elevated Temperature Conditions
Panak, P. J.; Altmaier, M.; Brandt, F.; Brendler, V.; Chiorescu, I.; Colàs, E.; Curtius, H.; Endrizzi, F.; Franzen, C.; Gaona, X.; Grivé, M.; Hagemann, S.; Koke, C.; Kulik, D. A.; Krüger, S.; Lee, J.-Y.; Maiwald, M.; Skerencak-Frech, A.; Steudtner, R.; Thoenen, T.; Tsushima, S.;
The ThermAc project is extending the chemical understanding and available thermodynamic database for actinides, long-lived fission products and relevant matrix elements in aquatic systems at elevated temperatures. To this end, a systematic use of estimation methods, new experimental investigations and quantum-chemistry based information is used. ThermAc has started in March 2015 and is projected for three years, running until 28.02.2018. The project is funded by the German Federal Ministry for Education and Research (BMBF) and is coordinated by KIT-INE.
  • Poster
    9th international conference on nuclear and radiochemistry (NRC9), 29.08.-02.09.2016, Helsinki, Finnland

Publ.-Id: 24265 - Permalink


ThermAc - a collaborative project investigating aquatic chemistry and thermodynamics of actinides at elevated temperature conditions.
Altmaier, M.; Brandt, F.; Brendler, V.; Chiorescu, I.; Colàs, E.; Curtius, H.; Endrizzi, F.; Franzen, C.; Gaona, X.; Grivé, M.; Hagemann, S.; Koke, C.; Kulik, D. A.; Krüger, S.; Lee, J.-Y.; Maiwald, M.; Miron, G. D.; Panak, P. J.; Skerencak-Frech, A.; Steudtner, R.; Thoenen, T.; Tsushima, S.;
The ThermAc project is extending the chemical understanding and available thermodynamic database for actinides, long-lived fission products and relevant matrix elements in aquatic systems at elevated temperatures. To this end, a systematic use of estimation methods, new experimental investigations and quantum-chemistry based information is used. ThermAc has started in March 2015 and is projected for three years, running until 28.02.2018. The project is funded by the German Federal Ministry for Education and Research (BMBF) and is coordinated by KIT-INE.

The ThermAc project is developed with the aim of improving the scientific basis for assessing nuclear waste disposal scenarios at elevated temperature conditions. Adequate scientific tools must be available to assess the related chemical effects and their impact upon safety. A clear focus of ThermAc is on long-lived actinides in oxidation states III, V and VI, with selected fission products and important redox controlling matrix elements like Fe also receiving attention. Tetravalent actinides and detailed investigations of redox processes are excluded from the current ThermAc work programme. ThermAc mainly addresses the temperature range from ~5°C up to ~90°C, focusing on systems at low or intermediate ionic strength. Chemical analogs for the actinide elements will be used, especially in order to gain information on solid phase transformation processes. Ion-interactions are treated with the Specific Ion Interaction Theory (SIT), in agreement with the approach favored by the NEA-TDB project. Quantum chemical calculations are used to support the interpretation of experimental findings, and establish a fundamental understanding of chemical effects on a molecular level.

Within the scope of ThermAc, a significant impact can be realized within a strong collaborative and integrated concept with the following strategic components:
(1) Systematic use of estimation methods for thermodynamic data and model parameters.
(2) Comprehensive experimental validation of the estimations.
(3) Fundamental studies for improved process understanding of actinide chemistry at elevated T.
(4) Comprehensive critical evaluation of the work performed within (1-3).

A key result from the comparison of predictions based upon estimation methods with new experimental data derived within ThermAc will be the assessment of the use of estimations methods to set up a workable thermodynamic database for elevated temperatures with high applicability to nuclear waste disposal issues. In this context it will be clarified, to which extent systems will remain critical with regard to available thermodynamic data, and which relevant processes at elevated temperatures are still not sufficiently understood.
  • Lecture (Conference)
    Plutonium Futures, 18.-22.09.2016, Baden-Baden, Deutschland
  • Poster
    International Symposium on Solubility Phenomena and Related Equilibrium Processes (ISSP), 24.-29.07.2016, Genf, Schweiz

Publ.-Id: 24264 - Permalink


U(VI) – SO₄²¯ complexation at elevated temperature – a combination of spectroscopy and thermodynamic modeling.
Franzen, C.; Haubitz, T.; Drobot, B.; Firkala, T.; Brendler, V.; Steudtner, R.;
In order to evaluate the fate and transport of radionuclides in the environment, knowledge about complexation behaviour with inorganic ligands is mandatory. The complex stability constants (log10K) which are required for thermodynamic calculations are mostly determined at ambient conditions (293-303 K). However, high level radioactive waste is expected to considerably increase the temperature in the vicinity of waste disposal sites up to 373 K. The temperature dependence of the log10K value can be calculated if all necessary thermodynamic parameters (log10K(T0), ΔrSo(T0), ΔrHo (T0), and the temperature dependence of ΔrCpo) are known. However, reliable thermodynamic data for most actinide complexes with inorganic ligands, e.g. SO42− or CO32− are still lacking. Theoretical approximations may be helpful to estimate log10K values for higher temperatures, with the actual methods depending on the investigated temperature range and the chemical system.
In this study of the U(VI)−SO42− system, we compare two approximation methods (constant enthalpy of reaction and Ryzhenko-Bryzgalin model - RBM) for the calculation of log10K at different temperatures. Both models show an increase of log10K with increasing temperature for both the 1:1 and 1:2 complex. However, at the lowest and highest temperatures, the RBM gives slightly higher values than the constant enthalpy approach.
These predictions are compared to experimentally determined log10K values as f(T). They are based on various spectroscopic techniques (TRLFS, fluorimeter, UV-vis, conventional Raman and surface-enhanced Raman) and yielded with increasing sulfate-concentrations a stepwise complexation from the free UO22+, to the 1:1, 1:2 and 1:3 complex. This illustrated that a combination of different techniques is helpful for the distinct discrimination of the different complexes.
  • Lecture (Conference)
    Goldschmidt 2016, 26.06.-01.07.2016, Yokohama, Japan

Publ.-Id: 24263 - Permalink


Light control of Orbital Domains: case of the prototypical manganite La0.5Sr1.5MnO4
Miller, T.; Gensch, M.; Wall, S.;
Control of electronic and structural ordering in correlated materials on the ultrafast timescale with light is a new and emerging approach to disentangle the complex interplay of the charge, spin, orbital and structural degree of freedom. In this paper we present an overview of how orbital order and orbital domains can be controlled by near IR and THz radiation in the layered manganite La0.5Sr1.5MnO4. We show how near-IR pumping can efficiently and rapidly melt orbital ordering. However, the nanoscale domain structure recovers unchanged demonstrating the importance of structural defects for the orbital domain formation. On the contrary, we show that pulsed THz fields can be used to effectively orientate the domains. In this case the alignment depends on the in-plane electric field polarization and is induced by an energy penalty that arises from THz field induced hopping of the localized charges.
Keywords: THz control, High-field THz, TELBE, ultra-fast

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Publ.-Id: 24262 - Permalink


Direct experimental evidence for a multiparticle-hole ground state configuration of deformed 33-Mg
Datta, U.; Rahaman, A.; Aumann, T.; Beceiro-Novo, S.; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chakraborty, S.; Chartier, M.; Cortina-Gil, D.; de Angelis, G.; Diaz Fernandez, P.; Emling, H.; Ershova, O.; Fraile, L. M.; Geissel, H.; Gonzalez-Diaz, D.; Jonson, B.; Johansson, H.; Kalantar-Nayestanaki, N.; Kröll, T.; Krücken, R.; Kurcewicz, J.; Langer, C.; Le Bleis, T.; Leifels, Y.; Marganiec, J.; Münzenberg, G.; Najafi, M. A.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Plag, R.; Reifarth, R.; Ricciardi, V.; Rossi, D.; Scheit, H.; Scheidenberger, C.; Simon, H.; Taylor, J. T.; Togano, Y.; Typel, S.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Weigand, M.; Winfield, J. S.; Yakorev, D.; Zoric, M.;
The first direct experimental evidence of a multiparticle-hole ground state configuration of the neutron-rich Mg33 isotope has been obtained via intermediate energy (400 A MeV) Coulomb dissociation measurement. The major part ∼(70±13)% of the cross section is observed to populate the excited states of Mg32 after the Coulomb breakup of Mg33. The shapes of the differential Coulomb dissociation cross sections in coincidence with different core excited states favor that the valence neutron occupies both the s1/2 and p3/2 orbitals. These experimental findings suggest a significant reduction and merging of sd-pf shell gaps at N∼20 and 28. The ground state configuration of Mg33 is predominantly a combination of Mg32(3.0,3.5MeV;2-,1-)νs1/2, Mg32(2.5MeV;2+)νp3/2, and Mg32(0;0+)νp3/2. The experimentally obtained quantitative spectroscopic information for the valence neutron occupation of the s and p orbitals, coupled with different core states, is in agreement with Monte Carlo shell model (MCSM) calculation using 3 MeV as the shell gap at N=20.
Keywords: nuclear physics reaction neutron-rich shell model

Publ.-Id: 24261 - Permalink


The role of surface anisotropy for ion beam pattern formation
Engler, M.ORC; Škereň, T.; Facsko, S.
Ion beam irradiation can produce different patterns on semiconductor surface. While the surface is amorphized at low temperatures, the surface remains crystalline above the dynamic recrystallization temperature. Reverse epitaxy leads to pattern formation, which is driven by diffusion of vacancies and adatoms on the surface, above this temperaure.

In contrast to amorphous surfaces, diffusion on terraces, the energy for step formation, the height of the Ehrlich-Schwoebel barrier, and the attachment of adatoms and vacancies are anisotropic and depend on the step orientation. These anisotropies in diffusion lead to anisotropic patterns.

We studied the patterns formation by low energy ion irradiation of different surfaces with atomic force and scanning tunneling microscopy. The patterns are aligned to the surface crystal structure and reflect the surface symmetry. We present a model for reverse epitaxy based on atomic processes on the surface, which includes the surface anisotropies and ballistic atom redistribution by the ion beam. To test the model we studied the pattern formation on GaAs(0 0 1) and GaAs(0 0 -1). On both surfaces, a regular array of faceted nanoripples forms. The direction of the ripples is rotated by 90° between both surfaces, which can be explained with our model. The symmetry of the GaAs lattice leads to rotation of 90° of the Ga rows on GaAs(0 0 -1) compared to GaAs(0 0 1).
Keywords: ion irradiation, pattern formation, nano pattern
  • Lecture (Conference)
    20th International Conference on Ion Beam Modification of Materials (IBMM2016), 31.10.-04.11.2016, Wellington, New Zealand

Publ.-Id: 24259 - Permalink


Electron-density assessment using dual-energy CT: accuracy and robustness
Möhler, C.; Wohlfahrt, P.; Richter, C.; Greilich, S.;
Purpose/Objective:
Current treatment planning for essentially every external radiation therapy (photons, electrons, protons, heavier ions) is not able to account for patient-specific tissue variability or non-tissue materials (e.g. implants, contrast agent) which can lead to considerable differences in dose distributions (figure 1). This is due to the conversion of CT numbers to electron density or stopping power using a heuristic Hounsfield look-up table. In contrast, dual-energy CT (DECT) allows for a patient-specific determination of electron density – the only (most important) parameter influencing photon (ion) dose distributions. Among the many algorithms proposed for this purpose, a trend towards increased complexity is observed, which is not necessarily accompanied by increased accuracy and might at the same time militate against clinical implementation. Here, we therefore investigated the performance of a seemingly simple linear-superposition method (Saito, 2012, Hünemohr et al., 2014).

Material/methods:
Key feature of the studied approach is a parameterization of the electron density, given by 'alpha blending” of the two DECT images. The blending parameter can be obtained by empirical calibration using a set of bone tissue surrogates and a linear relationship between relative photon absorption cross sections of the higher and lower voltage spectrum. First, this linear relation was analyzed to quantify the purely methodological uncertainty (i.e. with ideal CT numbers as input), based on calculated spectral-weighted cross sections from the NIST XCOM database for tabulated reference tissues (Woodard and White, 1986). A clear separation from CT-related sources of uncertainty (e.g. noise, beam hardening) is hereby crucial for a conclusive assessment of accuracy. Secondly, we tested the proposed calibration method on published DECT measurements of typical tissue-surrogate phantoms and evaluated its uncertainty.

Results:
The methodological uncertainty of electron-density assessment for the alpha-blending method was found to be below 0.15% for arbitrary mixtures of human tissue. In the case of small abundance of high-Z elements, electron-density results are positively biased, e.g. 0.5% for thyroid containing 0.1% iodine (Z=53) by mass, which is due to the K edge of the photoelectric effect. The calibration parameters obtained from various published data sets, showed very little variation in spite of diverse experimental setups and CT protocols used. The calibration uncertainty was found to be negligible for soft tissue while it was dominated by beam hardening effects for bony tissue.

Conclusion:
The alpha-blending approach for electron-density determination shows universal applicability to any mixture of human tissue with a very small methodological uncertainty (< 0.15%); and a robust and bias-free calibration method, which is straightforward to implement. We conclude that further refinement of algorithms for DECT-based electron-density assessment is not advisable.
Keywords: Dual-energy CT proton therapy heavy ion therapy range uncertainty
  • Lecture (Conference)
    Annual Meeting of the European Society for Radiotherapy & Oncology (ESTRO), 05.-09.05.2017, Wien, Österreich
  • Open Access LogoAbstract in refereed journal
    Radiotherapy and Oncology 123(2017), S912
    DOI: 10.1016/S0167-8140(17)32205-3

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Publ.-Id: 24258 - Permalink


Hard X-ray Photon-in Photon-out Spectroscopy as a Probe of the Temperature-Induced Delocalization of Electrons in Nanoscale Semiconductors
Hirsch, O.; Kvashnina, K.; Willa, C.; Koziej, D.;
Hard X-ray photon-in photon-out spectroscopy has so far mainly been applied to investigate fundamental physical phenomena in superconductors and chemical reactivity of bioinorganic, photocatalytic, and catalytic materials. Here, we show, with the example of Pr6O11 nanoparticles, an n-type semiconductor, how high-energy resolution fluorescence detected (HERFD) X-ray absorption near edge structure (XANES) can be used to track the changes of partially filled f-bands. We observe a reversible variation of the spectral features related to the tetravalent Pr ions upon heating and cooling, whereas structural and chemical transformations can be excluded. We assign these changes to the occupancy of the O 2p−Pr 4f-band and show that they directly relate to changes in the electrical conductance. Our results demonstrate how HERFD-XANES can be used to particularly study in situ the electronic properties of f-electrons in a semiconductor and how this method can be further extended to other classes of semiconducting nanomaterials.

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Publ.-Id: 24257 - Permalink


Substrate-dependence of competitive nucleotide pyrophosphatase / phosphodiesterase1 (NPP1)
Lee, S.-Y.; Sarkar, S.; Bhattarai, S.; Namasivayam, V.; de Jonghe, S.; Stephan, H.ORC; Herdewijn, P.; El-Tayeb, A.; Müller, C. E.
Nucleotide pyrophosphatase / phosphodiesterase type 1 (NPP1) is a membrane glycoprotein involved in the hydrolysis of extracellular nucleotides. Its major substrate is ATP which is converted to AMP and diphosphate. NPP1 was proposed as a new therapeutic target in brain cancer and immuno-oncology. Several NPP1 inhibitors have been reported to date, most of which were evaluated versus the artificial substrate p-nitrophenyl 5’-thymidine monophosphate (p-Nph-5’-TMP). Recently, we observed large discrepancies in inhibitory potencies for a class of competitive NPP1 inhibitors when tested versus the artificial substrate p-Nph-5’-TMP as compared to the natural substrate ATP. Therefore, the goal of the present study was to investigate whether inhibitors of human NPP1 generally display substrate dependent inhibitory potency. Systematic evaluation of nucleotidic as well as non-nucleotidic NPP1 inhibitors revealed significant differences in determined Ki values for competitive, but not for non- and un-competitive inhibitors when tested versus the frequently used artificial substrate p-Nph-5’-TMP as compared to ATP. Allosteric modulation of NPP1 by p-Nph-5’- TMP may explain these discrepancies. Results obtained using the AMP derivative p41 nitrophenyl 5’-adenosine monophosphate (p-Nph-5’-AMP) as an alternative artificial substrate correlated much better with those employing the natural substrate ATP.
Keywords: Ectonucleotidase inhibitors, enzyme assay, p-nitrophenyl 5'-thymidine monophosphate, NPP1, NPP1 inhibitors, nucleotide pyrophosphatase 1

Publ.-Id: 24256 - Permalink


Activation studies at the HZDR medical cyclotron: Simulation and Experiment
Müller, S. E.;
First comparisons of simulation and experiments for activation studies.
  • Lecture (Conference)
    FLUKA collaboration meeting, 17.-18.10.2016, CERN (Geneva), Switzerland

Publ.-Id: 24255 - Permalink


Uranium(VI) reduction by isolated anaerobic microorganisms from the flooding water of the former uranium mine Königstein (Saxony/Germany)
Gerber, U.; Krawczyk-Bärsch, E.; Scheinost, A.; Arnold, T.;
The former uranium mine Königstein is currently in the process of remediation. The underground is flooded in a controlled way. Despite high uranium concentrations up to 13 mg/L and a low pH of 2.9, these waters contain a high microbial diversity [1]. Microorganisms are known to interact with metals and radionuclides in different ways [2]. For instance, anaerobic sulfate-reducing bacteria (SRB) reduce U(VI) to U(IV) and thus change the migration behavior from the more soluble U(VI) into the insoluble U(IV) [3]. By culture dependent methods it was possible to isolate anaerobic microorganisms from the flooding water. They were incubated with 10 mM glycerol using the flooding water as background solution. During an incubation time of six weeks the redox potential decreased from 660 mV to 300 mV. The cells were separated from the incubation medium by centrifugation and analyzed by U-LIII edge EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure) measurements. Iterative Target-Factor Analysis (ITFA) revealed that 100 % of U(VI) was reduced to U(IV). The results show that naturally occurring anaerobic microorganisms within the flooding water of the former uranium mine Königstein are able to reduce U(VI) to U(IV).

[1.] Zirnstein, I., Charakterisierung der mikrobiellen Biozönose im sauren Grubenwasser des ehemaligen Uranbergwerks Königstein, Institut für Ressourcenökologie, Dissertation, 2015, TU Dresden: Dresden.
[2.] Lloyd, J.R.M., L. E. , Interactions of microorganisms with radionuclides. Elsevier Science. 2002.
[3.] Lovley, D.R., et al., Enzymatic Iron and Uranium Reduction by Sulfate-Reducing Bacteria. Marine Geology, 1993. 113(1-2): p. 41-53.
Keywords: Uranium, reduction, bioremediation, sulfate-reducing bacteria (SRB)
  • Poster
    15th symposium on remediation, 13.-14.10.2016, Jena, Germany

Publ.-Id: 24254 - Permalink


Microbial Influence on Bentonite Transformation
Matschiavelli, N.; Steglich, J.; Kluge, S.; Arnold, T.; Cherkouk, A.;
Der Einfluss von Mikroorganismen auf das Barrierematerial Bentonit ist Gegenstand dieser Arbeit. Hierfür wird mittels Mikrokosmen die natürliche Umgebung in einem potentiellen Endlager simuliert. Um das Wachstum von bereits im Bentonit vorhandener Mikroorganismen zu stimulieren, werden die Mikrokosmen mit Substrat versetzt (Lactat, Azetat, Methanol) bzw. mit einem Huminanalogon (AQDS), welches als Elektronen-Shuttle fungieren soll. Für den Ansatz der Mikrokosmen wurde unbehandelter Bentonit B36 von der BGR bestellt und dieser mit steriler, anaerober synthetischer Opalinustonporenlösung versetzt. Die Proben und entsprechende Kontrollansätze wurden bei 30°C im Dunkeln inkubiert. Die Probenahme erfolgte an ausgewählten Zeitpunkten über einen Zeitraum von etwa 3 Monaten. Geochemische sowie molekularbiologische Analysen zeigen, dass ein mikrobieller Einfluss gegeben ist, welcher hauptsächlich in der Eisenreduktion erkennbar ist. Von dem für die Mikrokosmen verwendeten Bentonit B36, sowie aus den Mikrokosmenansätzen verschiedener Inkubationszeiten selbst konnte DNA isoliert und näher analysiert werden. Durch Verwendung von RISA (Ribosomal Intergenic Spacer Analysis) konnten Unterschiede in der mikrobiellen Gemeinschaft bereits durch elektrophoretische Auftrennung in einem Agarosegel nachverfolgt werden.
Keywords: Bentonit, Eisenreduktion, DNA-Extraktion, RISA
  • Lecture (others)
    UMB-Projekttreffen, 02.06.2016, Braunschweig, Deutschland

Publ.-Id: 24253 - Permalink


NTCP models for early toxicities in patients with prostate or brain tumours receiving proton therapy
Dutz, A.; Agolli, L.; Troost, E. G. C.; Krause, M.; Baumann, M.; Lühr, A.; Löck, S.;
Purpose: To identify patients who are likely to benefit most from proton therapy, based on the potential reduction in normal tissue complication probability (NTCP) compared to photon therapy. The NTCP models required for this comparison were developed using clinical data on early side effects for patients with brain or prostate cancer having received proton therapy.

Material and methods: Eighty patients with primary brain tumours and 30 patients with adenocarcinoma of the prostate who received proton therapy were included in this study. For the brain tumour patients, the radiation-induced early toxicities alopecia, erythema, pain and fatigue were considered, while for prostate cancer proctitis, diarrhoea, urinary frequency, urgency and incontinence, obstructive symptoms and radiation-induced cystitis were investigated. The occurrence of these side effects was correlated with different dose-volume parameters of associated organs at risk. NTCP models were created using logistic regression. A retrospective comparative treatment planning study was conducted to predict the potential reduction in NTCP of proton therapy compared to volumetric modulated arc therapy using the created models. For patients with brain tumours different subgroups were defined to identify patient groups which show a particularly high reduction in the considered toxicities.

Results: For patients with primary brain tumours significant correlations between the occurrence of alopecia grade 2 as well as erythema grade ≥ 2 and the dose-volume parameters D5% and V25Gy of the skin were found. Plan comparison showed an average reduction in NTCP for alopecia grade 2 of more than 5 % (see figure) and for erythema grade ≥ 2 of about 5 % using proton therapy. For patients with a brain tumour located in the skull base, with a clinical target volume less than 115 cm³ or with a prescribed dose less than 60 Gy, a potential reduction in NTCP for alopecia grade 2 of about 10 % could be achieved. For patients with prostate cancer significant correlations between obstructive symptoms grade ≥ 1 and the dose parameter D30% of the bladder as well as radiation-induced cystitis grade ≥ 1 and D20% of the bladder were found. Plan comparison showed an average reduction in NTCP for obstructive symptoms ≥ grade 1 of about 25 % and for radiation-induced cystitis about 15 % using proton therapy.

Conclusion: We found significant correlations between the occurence of early toxicities and dose-volume parameters of associated organs at risk for patients with primary brain tumours or prostate cancer receiving proton therapy. A reduction of NTCP could be predicted for proton therapy based on comparative treatment planning. After validation, these results may be used to identify patients who are likely to benefit most from proton therapy, as suggested by the model-based approach [1].

[1] Langendijk JA et al. (2013) Radiother Oncol 107, 267 - 273.
  • Poster
    ESTRO 2017, 05.-09.05.2017, Wien, Österreich
  • Open Access LogoAbstract in refereed journal
    Radiation Oncology 123(2017), S860
    DOI: 10.1016/S0167-8140(17)32030-3

Publ.-Id: 24252 - Permalink


MRI-based analysis of volumetric changes of healthy brain tissue in glioma patients after photon radio(chemo)therapy
Gommlich, A.; Wahl, H.; Raschke, F.; Baumann, M.; Krause, M.; Troost, E. G. C.;
Motivation and Objective
State-of-the-art Linac-based photon beam irradiation achieves highly conformal target volume coverage in glioma patients, but is also known to cause side-effects to surrounding tissues and organs. Apart from subjective measures (e.g., questionnaires, function tests) objective means to quantify tissue damage, e.g., anatomical or functional magnetic resonance imaging (MRI) are urgently needed to compare different treatment techniques and beam qualities (e.g., protons vs. photons) and to develop predictive measures for optimal sparing of normal brain tissue. As initial part of our program for dose-dependent spatial mapping of structural and functional radiation induced brain damage, we assessed here a retrospectively collected MRI-dataset in order to potentially detect volumetric changes of the healthy brain tissue (gray and white matter) in the non-affected hemisphere of glioma patients treated with photon irradiation.

Material and Methods
Structural MRI-scans (T1-weighted) from 18 glioma patients (grade II and III), who underwent high dose radio(chemo)therapy (54-60 Gy) with curative intent have been analyzed. MRIs were acquired before treatment and at several time intervals thereafter. Because of the individual characteristics of these data e.g., voxel size (0.5…6 mm³) and the field strength (1…3 T) a standardized image processing approach was developed. For bias field correction, registration with atlas data, resampling, and segmentation of different tissue types, image processing methods from the ANTs-, FSL- and SPM-toolbox were used, respectively. Based on these images the volumes of white matter and gray matter have been longitudinally analyzed.

Results
Figure 1 shows the changes of brain tissue volume depicted as box plots with the median values highlighted in red. While the entire brain volume on average remains constant over two years after therapy, in the same time period the volume of gray matter and white matter varies conversely in a wide range. Noteworthy, this work points out the difficulties of retrospectively analyzing clinically acquired data due to differences in acquisition parameters and in investigation intervals.

Outlook
The observed changes over time underpin the importance of exact follow-up protocols in quantitative evaluation of structural brain changes after radiotherapy. Together with the data on interpatient heterogeneity, our findings allowed to design a prospective study in a larger cohort of patients treated by photons vs. protons for assessing the dependence of MRI-detected volumetric changes with delivered dose.
Keywords: structural MRI; grade II/III glioma; healthy brain tissue; photon therapy; volume change; image processing;
  • Poster
    ESTRO 36 - European Society for Radiotherapy and Oncology, 05.-09.05.2017, Vienna, Austria

Publ.-Id: 24251 - Permalink


Monte Carlo Calculation Procedure and its Implementation for Radiation Load Estimation on Russian VVER Reactor Equipment
Baier, S.; Konheiser, J.; Boradkin, P.; Khrennikov, N.; Gazetdinov, A.;
A prediction of radiation load parameters (fluence, fluence rate, neutron energy spectrum) of reactor components, e.g. reactor pressure vessel (RPV), of Russian VVER reactors is regulated by the requirements of the Russian normative documents. One of the key measures is the validation of calculated procedures by ex-vessel neutron activation measurements at VVER nuclear power plants. The neutron dosimetry research for every reactor component includes validation calculations by appropriate codes.
The standard method was based on the three-dimensional (3D) synthesis method with input from results of calculations from the deterministic code DORT coupled with the BUGLE-96T library. It was identified in comparison between experiments and calculations that this method gives different results outside the active core. Hence, the usage of a 3D code is essential. For this reason, the Scientific and Engineering Centre for Nuclear and Radiation Safety (SEC NRS) wants to use the Monte-Carlo code TRAMO for own fluence calculations. Thus, the purpose of this work is the possible application of TRAMO for expert calculations of radiation load parameters of reactor components of all VVER reactor types, the verification of results by comparison with other codes (deterministic and Monte-Carlo) and the validation by neutron activation measured data. The paper presents possible options of the new version of TRAMO for neutrons fluence calculations suggested by SEC NRS.
Keywords: Monte Carlo code, TRAMO, reactor dosimetry, neutron fluence calcolation
  • Poster
    Sixteenth International Symposium on Reactor Dosimetry, 07.-12.05.2017, Santa Fe, USA
  • Contribution to proceedings
    Sixteenth International Symposium on Reactor Dosimetry (ISRD-16), 07.-12.05.2017, Santa Fe, USA
    Proceedings of the 16th International Symposium on Reactor Dosimetry, West Conshohocken: ASTM International, 978-0-8031-7661-4, 579-589
    DOI: 10.1520/STP160820170088

Publ.-Id: 24250 - Permalink


Dual-energy CT-based proton treatment planning to assess patient-specific range uncertainties
Wohlfahrt, P.; Möhler, C.; Enghardt, W.; Greilich, S.; Richter, C.;
Purpose/Objective:
To reduce range uncertainties in particle therapy arising from a generic heuristic conversion (HLUT) of CT numbers in stopping-power ratios (SPRs), an accurate patient-specific SPR prediction is desirable. Treatment planning based on dual-energy CT (DECT) can account for tissue diversity and potentially contribute to shrink clinical safety margins. Consequently, in this study dose distributions derived from both a clinical HLUT and a patient-specific DECT-based SPR prediction are compared and range deviations are quantified for two different treatment sites.

Material/methods:
Based on a database of more than 1000 clinical DECT scans acquired with a single-source DECT scanner (Siemens Somatom Definition AS), 10 prostate cancer and 52 head tumor patients were selected to assess intra- and interpatient tissue diversity and its impact on SPR prediction. To evaluate age- and sex- dependent variability, the head tumor cohort was divided in children, women and men. DECT scans were converted in 79 keV pseudo-monoenergetic CT scans (MonoCTs) and SPR datasets derived by voxelwise calculations of electron density and effective atomic number using syngo.via (Siemens Healthineers). In XiO (Elekta) clinical proton treatment plans were recalculated (a) on MonoCTs using the clinical HLUT and (b) on SPR datasets to quantify range-dependent dose differences.

Results:
The voxelwise correlation of SPR and CT number is similar for men and women, but differs considerably between adults and children in bony tissue, likely due to the amount of calcium embedded in bones, which increases with age. Based on voxelwise SPR comparisons, the clinical HLUT predicts on average (2.2 ± 0.6) % larger SPRs for head tumor patients and (1.7 ± 0.3) % larger SPRs for prostate cases. The impact of both approaches on dose distributions is shown in Fig. 1 and 2 for an exemplary head tumor and prostate cancer patient. In the head case, the HLUT predicts a 1.7 % shorter range (2.4 mm) resulting from a 0.7 mm range underestimation in water-filled ventricles (not precisely predicted by the HLUT) and different SPR predictions for brain. A range deviation of up to 3.0 % (7.1 mm) is obtained in the prostate case, which is mainly caused by different SPR predictions for bone marrow and muscle. These range differences in single beams are not compensated in the overall treatment plan.

Conclusion:
In contrast to a generic HLUT, a DECT-based SPR prediction can individually consider age- and sex- dependent tissue variability in proton treatment planning. This diversity information can also provide suggestions for subgroup-specific improvements of the heuristic CT calibration. The assessment of relative SPR and dose differences underlines the clinical potential of DECT, which now needs to be confirmed against a ground truth. Further investigations of patients’ DECT scans enable comprehensive SPR evaluations to quantify CT-related range uncertainties and to assess clinical safety margins.
Keywords: Dual-energy CT proton therapy proton range uncertainty
  • Lecture (Conference)
    Annual Meeting of the European Society for Radiotherapy & Oncology (ESTRO), 05.-09.05.2017, Wien, Österreich
  • Open Access LogoAbstract in refereed journal
    Radiotherapy and Oncology 123(2017), S73-S75
    DOI: 10.1016/S0167-8140(17)30593-5

Publ.-Id: 24249 - Permalink


Surface plasmon resonance coupling effect of micro-patterned gold film
in Chinese
Lu, N.-Y.; Yu, X.-J.; Wan, J.-W.; Weng, Y.-Y.; Guo, J.-H.; Liu, Y.;
Surface-enhanced Raman scattering has a high sensitivity in the detections of complex biological systems, and it has a lot of potential applications in food inspection, biological imaging and biosensors in biochemistry, etc. Here, we investigate the surface Raman enhancements on gold films of different morphologies and further simulate the enhancements by using the finite difference time domain.
To prepare the substrates with different morphologies, polymethyl methacrylate (PMMA) is spin coated 2000 rpm in one minute on a silicon wafer, followed by annealing at 180℃ for 5 min. Then, PMMA is etched by a 20 kV electron beam lithography. With the PMMA used as a soft imprint template, polydimethylsiloxane (PDMS) is dropped on the template then removed gently from the template after drying at 60℃ for 4 h. Finally, a gold thin film is prepared on the PDMS by magnetron sputtering with a current of 10 mA for 15 min. We design two kinds of morphologies:a four-way grid and a square morphology. The dimension of the four-way grids is 40 μm and the grid width is 4 μupm. The dimension of the square is also 4 μupm. The cystine and melamine solutions with concentrations of 50, 100, 200 and 400 ppm are deposited on the surfaces of the gold thin film, respectively. The Raman spectra of cystine and melamine solutions are measured on the substrates with four-way grids and dot arrays. The Raman spectra of cystine on two kinds of substrates show no obvious difference. Due to the relatively small enhancement of melamine, the Raman peaks of melamine solutions of concentrations 50 and 100 ppm on the substrate of square morphologies are not easy to detect. On the contrary, all of the Raman spectra of melamine on the substrate of four-way grid morphologies are clear. The result indicates that the substrate with four-way grids has better sensitivity and enhancement performance.
To verify the influence of the morphologies of the substrates on surface Raman enhancement and understand the mechanism of the enhancement, we simulate the scattering spectra and field distributions of different morphologies on gold thin films by using the finite difference time domain method. It is indicated that more complex the structure, the more obvious the enhanced Raman spectra will be. The calculations show that the enhancements of four-way grid morphologies are better than those of square morphologies. The predicted results of the surface enhanced Raman scattering are consistent with the measurements. These results will provide guidance and theoretical basis for further applications of surface enhanced.
Keywords: Surface enhanced Raman scattering, Soft template imprinting, Finite difference time domain, Surface micro-pattern

Publ.-Id: 24248 - Permalink


Robustness evaluation of single- and multifield optimized proton plans for unilateral head and neck targets
Cubillos-Mesías, M.; Troost, E. G. C.; Appold, S.; Krause, M.; Richter, C.; Stützer, K.;
Purpose:
To compare 4 different proton pencil beam scanning (PBS) treatment approaches for unilateral head and neck cancer (HNC) targets in terms of robustness, including anatomical changes during the treatment course.

Material and methods:
Eight patients with unilateral HNC treated with double scattered proton therapy were selected. Each patient dataset consists in a planning CT and several control CTs acquired by an in-room CT scanner during the treatment course. Four different proton PBS plans with simultaneous integrated boost and dose prescriptions of 50.3 Gy(RBE) to the low-risk CTV and 68 Gy(RBE) to the high-risk CTV in 34 fractions were calculated: conventional PTV-based single-field (SFO) and multifield optimization (MFO), and robustly optimized SFO and MFO plans on CTV level, considering ±3 mm and ±3.5% of setup and range uncertainty, respectively.
The treatment plans were recalculated on the registered control CTs and the cumulative doses calculated and compared with the nominal plan.
For robustness evaluation, perturbed doses using a probabilistic scenario-wise approach obtaining random setup shifts through Gaussian sampling, and range uncertainties of 0, +3,5% and -3,5% were calculated, using planning and control CTs, considering both anatomic changes and uncertainties. Cumulative doses from 30 different perturbed treatment courses were generated for each plan.

Results:
The target coverage for the four nominal plans was similar, fulfilling the clinical specification of D98≥95% of the prescribed dose (range 96.9-100.5% for low-risk CTV, 97.4-100.8% for high-risk CTV), being slightly lower on the robust optimized plans. The doses to the organs at risk were similar for all plans; however, for the ipsilateral parotid, higher median doses up to 5 Gy were found on the SFO approaches (Table 1), whereas the contralateral parotid is completely spared. The target coverage throughout the treatment course with slightly changing anatomy remains in general constant.
In terms of robustness evaluation, PTV-based MFO showed reduced robustness against both anatomical changes and uncertainties, i.e. wider DVH bands and a disagreement between planned and summed dose, whereas the robust MFO is less influenced. Both SFO approaches resulted in robust plans on the CTVs (Figure 1).

Conclusion:
The PTV-based MFO approach showed less robustness against uncertainties in setup and range, as well as for anatomical changes during the treatment course. Both SFO plans are robust in terms of CTV coverage; however, they present higher doses to the ipsilateral parotid gland. Robust MFO approach presents the lowest doses to the ipsilateral parotid and more robustness against uncertainties.
The dose to more organs at risk and the difference in normal tissue complication probabilities for the 4 planning approaches will be presented as well.
Keywords: Robust optimization, proton therapy
  • Lecture (Conference)
    Annual meeting of European Society of Radiotherapy and Oncology (ESTRO), 05.-09.05.2017, Vienna, Austria

Publ.-Id: 24247 - Permalink


Measurement of the stellar 58Ni(n, γ)59Ni cross section with AMS
Ludwig, P.; Rugel, G.; Dillmann, I.; Faestermann, T.; Fimiani, L.; Hain, K.; Korschinek, G.; Lachner, J.; Poutivtsev, M.; Knie, K.; Heil, M.; Käppeler, F.; Wallner, A.;
The 58Ni(n; γ)59Ni cross section was measured with a combination of the activation technique and accelerator mass spectrometry (AMS). The neutron activations were performed at the Karlsruhe 3.7 MV Van de Graaff accelerator using the quasi-stellar neutron spectrum at kT = 25 keV produced by the 7Li(p, n)7Be reaction. The subsequent AMS measurements were carried out at the 14 MV tandem accelerator of the Maier-Leibnitz-Laboratory in Garching using the Gas-filled Analyzing Magnet System (GAMS). Three individual samples were measured, yielding a Maxwellian-averaged cross section at kT = 30 keV of <σ>30keV= 30.4 (23)syst(9)stat mbarn. This value is slightly lower than two recently published measurements using the time-of-flight (TOF) method, but agrees within the uncertainties. Our new results also resolve the large discrepancy between older TOF measurements and our previous value.
Keywords: Neutron capture cross section, Accelerator Mass Spectrometry, s-process

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Publ.-Id: 24246 - Permalink


Characterizing geometrical accuracy in clinically optimized 7T and 3T MR images for high-precision radiation treatment of brain tumours
Peerlings, J.; Compter, I.; Janssen, F.; Wiggins, C.; Mottaghy, F.; Lambin, P.; Hoffmann, A.;
Purpose
In neuro-oncology, 3 Tesla (3T) MRI is the current clinical standard for tumor localization, radiotherapy volume delineation and stereotactic (radio)surgery. With superior SNR and image resolution, anatomical 7T MRI can visualize micro-vascularization in glioblastomas potentially allowing improved target volume delineation. However, concerns regarding geometrical distortion (GD) with increasing field strength (B0) are detrimental for applications of 7T MRI in image-guided interventions. For high-precision treatment strategies, the spatial integrity of anatomical images needs to be warranted within ±1 mm. The aim of the study was to evaluate B0- and sequence-related GD in clinically relevant 7T pulse sequences and compare it to equivalent 3T sequences, and CT images.

Material & Methods
To quantify B0- and sequence-related GD in T1-GRE, T1-TFE, T2-TSE, T2-TSE FLAIR on 7T pulse sequences, a dedicated anthropomorphic head-phantom (CIRS Model 603A) was used. The phantom is composed of bone- /soft-tissue equivalent materials and contains a rigid 3D grid (3 mm rods spaced 15 mm apart). System-based distortion correction methods were applied to restore the gradient uniformity for 3T and 7T. For all CT and MR images, 436 points of interests (POIs) were defined by manual reconstruction of the 3D grid points in the respective images. GD was assessed in 3 ways. Firstly, global GD was estimated by the mean absolute difference (MADglobal) between the measured and the true Euclidian distances of all unique combinations of POIs, independent of location within the phantom. Secondly, local GD was estimated by MADlocal between the measured and the true Euclidian distances of all POIs relative to the magnetic field isocenter. Thirdly, a distortion map was created by evaluating 3D displacement vectors for each individual grid point.

Results
MADglobal in 3T and 7T images ranged from 0.19−0.75 mm and 0.27−1.91 mm, respectively, and was more pronounced than in CT images. CT was not completely free of GD with MADglobal ranging from 0.14−0.64 mm. B0-related GD was larger in 7T than in 3T MRI with MADlocal ranging from 0.11-0.73 mm and 0.21-1.81 mm, respectively (p<0.05). MADlocal increased with increasing distance from the magnetic isocenter and largest GDs were noted at the level of the skull in T1-TFE (Fig. 1). MADlocal was <1 mm for all sequences up to 68.7 mm from the isocenter. Sequence-related GD at 7T was prominent in T1-TFE and significantly differed from other 7T sequences (p<0.001). Figure 2 indicates an anisotropic distribution of GD in T1-TFE with increasing GD along the frequency-encoding direction.

Conclusion
System-related GD was present in all 3T and 7T MR images but remained within the 2 mm tolerance limit. Near the magnetic isocenter, 7T anatomical images showed no difference in geometric reliability to 3T MR images. Careful selection of 7T pulse sequences and judicious use of GD correction methods can warrant the geometrical quality required for incorporation of 7T MR into image-guided interventions.
Keywords: ultra-high field MRI, radiotherapy, brain tumours, geometrical image distortion

Publ.-Id: 24245 - Permalink


The microbiology of subsurface, salt-based nuclear waste repositories: using microbial ecology, bioenergetics, and projected conditions to help predict microbial effects on repository performance
Swanson, J. S.; Cherkouk, A.; Arnold, T.; Meleshyn, A.; Reed, D. T.;
The evaluation of deep geological settings as sites for nuclear waste disposal is extensive and multidisciplinary, and among the many areas of study is the field of microbiology. The microbiology of granite, basalt, tuff, and clay formations in Europe and the US has been under investigation for decades, and much has been learned about the potential influence of microorganisms on repository performance and about deep subsurface microbiology in general. In spite of this, there is still uncertainty surrounding the effects of microorganisms on salt-based repository performance. One of the reasons for this is that negative findings (i.e., no growth) cannot be used as performance model input, so as a result, conditions are often manipulated to generate positive findings (i.e., growth). Given the unique microbiology of hypersaline environments, these negative results are both valid and meaningful and should be analyzed from the perspective of feasibility. The microbial communities present in hypersaline settings are limited in both structural and functional diversity. This is because, in order to survive at high salt concentrations, these organisms must osmotically balance their internal and external environments. This limits their ability to perform certain modes of metabolism, based on the energy required for survival and the energy derived from a given reaction. The field of repository microbiology has assumed that diverse organisms capable of diverse metabolic processes will be present and active in the repository setting; however, this is not likely to be the case at extremely high salt concentrations.
At the highest salt concentrations, extremely halophilic Archaea are dominant members of the microbial population because of their ability to balance osmotic pressure using a low-energy strategy. These organisms are almost all aerobic with limited anaerobic capability, thus their role in repository microbiology may be confined to early oxic periods. Still, they are able to survive tens of thousands of years encased in salt, such that they will be present throughout repository history. Some extremely halophilic Bacteria also exist in hypersaline environments. In general, these organisms will have a much more diverse metabolic repertoire, including aerobic and anaerobic capabilities. However, these capabilities narrow as salt concentration increases, due to the high-energy cost strategy utilized by bacteria to maintain osmotic balance. Bacteria present in repository waste or introduced during mining operations are not likely to be halophilic and may not survive long-term. However, the role of microorganisms within drums may be significant.
This report summarizes the potential role of microorganisms in salt-based nuclear waste repositories using available information on the microbial ecology of hypersaline environments, the bioenergetics of survival under high ionic strength conditions, and “repository microbiology” related studies. In areas where microbial activity is in question, there may be a need to shift the research focus toward feasibility studies rather than studies that generate actual input for performance assessments. In areas where activity is not necessary to affect performance (e.g., biocolloid transport), repository-relevant data should be generated. Both approaches will lend a realistic perspective to a safety case/performance scenario that will most likely underscore the conservative value of that case.
  • Other report
    Los Alamos National Laboratory: Los Alamos National Laboratory Report LA-UR-16-28895, 2016
  • Other report
    Nuclear Energy Agency: Nuclear Energy Agency (NEA) report, 2018

Publ.-Id: 24243 - Permalink


Predictive Value of Asphericity in Pretherapeutic [111In]DTPA-Octreotide SPECT/CT for Response to Peptide Receptor Radionuclide Therapy with [177Lu]DOTATATE
Wetz, C.; Apostolova, I.; Steffen, I. G.; Hofheinz, F.; Furth, C.; Kupitz, D.; Ruf, J.; Venerito, M.; Klose, S.; Amthauer, H.;
Purpose

The purpose of this study was to assess the value of the spatial heterogeneity of somatostatin receptor (SSR) volume, quantified as asphericity (ASP), and to predict response to peptide receptor radionuclide therapy (PRRT) in patients with metastatic gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN).

Procedures

From June 2011 to May 2013, patients suffering from GEP-NEN who underwent pretherapeutic [111In-DTPA0]octreotide scintigraphy (Octreoscan®) prior to [177Lu-DOTA0-Tyr3]octreotate ([177Lu]DOTATATE)-PRRT were enrolled in this retrospective evaluation. SSR expression in 20 NEN patients was qualitatively and quantitatively assessed using the Krenning score, the metastasis to liver uptake ratio (M/L ratio), and ASP at baseline. Response to PRRT was evaluated based on lesions, which were classified as responding lesions (RL) and non-responding lesions (NRL) after 4- and 12-month follow-ups. The values of the Krenning score, M/L ratio, and ASP for response prediction were compared by using the Mann-Whitney U test, Kruskal-Wallis test, and receiver operating characteristic (ROC) curves.

Results

Seventy-seven metastases (liver, n = 40; lymph node, n = 24; bone, n = 11; pancreas, n = 2) showed SSR expression. A higher ASP level was significantly associated with poorer response at both time points. ROC analyses revealed the highest area under the curve (AUC) for discrimination between RL and NRL for ASP after 4 months (AUC 0.97; p = 0.019) and after 12 months (AUC 0.96; p < 0.001), followed by the Krenning score (AUC 0.74; p = 0.082 and AUC 0.85; p < 0.001, respectively) and M/L ratio (AUC 0.77; p = 0.107 and AUC 0.82; p < 0.001). The optimal cutoff value for ASP was 5.12 % (sensitivity, 90 %; specificity, 93 %).

Conclusion

Asphericity of SSR-expressing lesions in pretherapeutic single-photon emission computed tomography with integrated computed tomography (SPECT/CT) is a promising parameter for predicting response to PRRT in gastroenteropancreatic neuroendocrine neoplasms.
Keywords: Neuroendocrine neoplasmPeptide receptor radionuclide therapy[111In-DTPA0]octreotide scintigraphyAsphericity

Publ.-Id: 24242 - Permalink


UV-vis-NIR spectroscopic Ellipsometry and Photospectrometry of thin films
Schumann, E.; Lungwitz, F.;
We present an introduction into the basics of light matter interaction, photospectroscopy and spectroscopic ellipsometry of thin films. Starting with the nature and description of polarized light, the interaction of light with matter in form of reflection, absorption and transmission and the physical effects leading to this behavior are shown. The optical constants, refractive index and extinction coefficient are derived and combined to a single complex parameter. This complex refractive index will be compared and connected to the dielectric function which describes the electric field inside a medium. It is shown that the dielectric function can be described by a sum of light driven oscillator motions of electric dipoles inside a medium. Fundamental different dielectric functions are related to optical and electrical behavior for dielectrics, semiconductors and metals.
To measure the behavior of light incident on a medium, photospectroscopy and spectroscopic ellipsometry is introduced. With photospectroscopy the intensity of reflected, transmitted and absorbed light can be measured. Here different measurement setup for specular and diffuse light is presented and major issues discussed. Complementary to photospectroscopy spectroscopic ellipsometry measures the change of the phase relation of s and p polarized light after the interaction with matter. This technique is very sensitive to various material properties like film thickness, roughness, interfaces, composition, crystallinity, stress and many more. It is shown how an ellipsometer retrieves data and how this data is used to model the dielectric function. Key aspects discussed are analysis procedures, the necessity of model building and fitting together with walk through steps and examples.
  • Invited lecture (Conferences)
    Advanced coating and characterization techniques, 19.-20.09.2016, Dresden, Deutschland

Publ.-Id: 24241 - Permalink


10Be in the Akademii Nauk ice core – first results for CE 1590-1950 and and implications for future chronology validation
von Albedyll, L.; Opel, T.; Fritzsche, D.; Merchel, S.; Laepple, T.; Rugel, G.;
Temporal variations of the radionuclide 10Be are broadly synchronous across the globe and thus provide a powerful tool to synchronize ice core chronologies from different locations. We compared the 10Be record of the Akademii Nauk (AN) ice core (Russian Arctic) for the time period CE 1590–1950 to the 10Be records of two well-dated Greenland ice cores (Dye3 and NGRIP). A high correlation (r=0.59) was found between the AN and Dye3 records whereas the correlation with NGRIP was distinctly lower (r=0.45). Sources of deviations may include local fluctuations in the deposition of 10Be due to changes in the precipitation patterns, and artefacts due to the core-sampling strategy. In general, the existing age model was validated, confirming the AN ice core to be a unique and well dated source of palaeoclimate parameters for the Russian Arctic. We further used numerical simulations to test the influence of the core-sampling strategy on the results and derived an optimised sampling strategy for the deeper parts of the ice core.
Keywords: accelerator mass spectrometry, ice core, climate

Publ.-Id: 24240 - Permalink


Science and Technology of CW Electron Source
Arnold, A.;
As part of the Basic Energy Sciences (DOE) workshop on the subject of "Future of Electron Sources" we share the many years of experience in building and operating a superconducting photo electron source (SRF gun). Based on this, we explain our current research projects to achieve the design performance of our existing 3.5 cell SRF gun by solving the most critical problems. Finally, the contribution will end with a detailed overview of long-term research projects to realize the ultimate performance of a new, not yet designed SRF gun.
Keywords: SRF gun, photo electron source, injector, ELBE, superconducting RF
  • Invited lecture (Conferences)
    Basic Energy Science Workshop on Future Electron Sources, 07.-09.09.2016, Menlo Park, CA 94025, USA

Publ.-Id: 24239 - Permalink


Mineralische Resourcen - Rohstoffe für Industrielle und Energetische Anwendungen
van den Boogaart, K. G.;
Die Versorgung mit Rohstoffen ist eine zentrale Voraussetzung für den Übergang zu erneuerbaren Energien. Jeder Rohstoff benötigt zu seiner Gestehung selbst Energie und Rohstoffe, so daß eine komplexe Rückwirkung entsteht, die sich aufgrund der Endlichkeit guter Resourcen in Abhängigkeit vom Bedarf ändert. Dadurch steigt der indirekte Rohstoffbedarf erheblich. Aufgrund der endlichen Anlagenlebensdauern und der aufgrund des zweiten Hauptsatzes der Theormodynamik niemals Exergie-verlustfreien Recyclingverfahren ist auch erneuerbare Energie systemisch gesehen niemals völlig erneuerbar. Einfache Rückkopplungsmechanismen erzeugen dabei keine Verlustminimalen Systeme und vereinfachte Betrachtungen, die diese Rückwirkung der Rohstoffversorgung ignorieren oder linearisieren, führen systematisch zu vereinfachenden Ergebnissen.
Keywords: Energiewende, Rohstoffversorgung, Systemische Betrachtung
  • Lecture (others)
    Arbeitskreis Energie (AKE) in der Deutschen Physikalischen Gesellschaft, 20.-21.10.2016, Bad Honef, Deutschland

Publ.-Id: 24238 - Permalink


A Compact Superconducting LINAC Module for CW Electron Acceleration
Arnold, A.; Büttig, H.; Freitag, M.; Justus, M.; Michel, P.; Staats, G.; Winter, A.;
ELBE, the superconducting Electron Linac with high Brilliance and low Emittance (ELBE) is providing an average beam current of 1 mA at a maximum beam energy up to 40 MeV for more than a decade to its users. The electrons are used to generate THz radiation, infrared light (Free Electron Lasers), X-rays (electron channeling) and MeV-bremsstrahlung as well as fast neutrons and positrons for semiconductor physics, nuclear astrophysics and radio biological investigations and many more. An integral part of the accelerator is the compact 20 MeV superconducting LINAC module for CW operation that has been designed and built at the Helmholtz-Zentrum Dresden-Rossendorf more than 15 years ago. Very recently, an upgraded version was taken into operation and thus we will report on design improvements to reduce heating, material selection and demagnetization to ensure magnetic hygiene as well as on RF conditioning of the CW couplers. Additionally, module parameters such as static heat load, tuner resolution, microphonics, pressure sensitivity, Lorentz force detuning and intrinsic quality factor vs. electric field will be discussed.
Keywords: ELBE SRF, Superconducting Linac, 1.3 GHz
  • Poster
    28th Linear Accelerator Conference, LINAC 16, 25.-30.09.2016, East Lansing, MI 48824, USA

Publ.-Id: 24237 - Permalink


Recent Beam Parameter Measurement of the 2nd 3.5 cell SRF Gun for ELBE
Arnold, A.; Freitag, M.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.; Kneisel, P.; Ciovati, G.; Turlington, L.;
In May 2014 the 1st superconducting photo injector (SRF gun) at HZDR was replaced by a new gun, featuring a new resonator and cryostat. The intention for this upgrade was to reach higher beam energy, higher bunch charge and lower emittance at the same time. With the improved parameters first user experiments of the superconducting CW accelerator ELBE are to be served, that benefit from an increased average beam current at a given repetition rate of some hundred kHz.
Although the cavity performance stays behind its specifications (Ecath~12 MV/m), beam commissioning is underway. In order to lower the risk of particle contamination and to get enough robustness against vacuum events in this early stage, we started with a laser cleaned magnesium cathode (QE~1e-3) instead of our standard Cs2Te cathode. In this contribution we will report on detailed parameter measurements of the electron beam that has a repetition rate of 100 kHz and a bunch charge up to 300 pC.
Keywords: SRF gun, photo electron source, injector, ELBE, superconducting RF
  • Poster
    28th Linear Accelerator Conference, LINAC 16, 25.-30.09.2016, East Lansing, MI 48824, USA

Publ.-Id: 24236 - Permalink


In-beam PET with Pulse Shape Discrimination at a Clinical Cyclotron Facility
Kormoll, T.; Enghardt, W.; Fiedler, F.; Iltzsche, M.; Pausch, G.; Tintori, C.; Helmbrecht, S.;
Positron emission tomography can yield in-vivo range information in hadron tumor therapy. Measurements are preferably done during the irradiation to minimize the loss of information due to physical decay and a metabolic transport of the nuclides. One challenge is the high number of background events due to prompt photons and neutron induced radiation. In this work, pulse shape discrimination has been applied to conventional Anger logic block detectors to enable an in-beam acquisition at a cyclotron generated beam. Images could be acquired with clinical dose rates in phantom experiments. This technique could pave the way towards more cost effective in-beam PET hardware.
Keywords: ion beam therapy, in-beam PET, proton therapy, in-vivo dosimetry, Positron Emission Tomography, cancer, oncology, radiooncology
  • Poster
    2016, IEEE NSS/MIC, 02.11.2016, Strasbourg, France

Publ.-Id: 24235 - Permalink


Positron Annihilation Lifetime Spectroscopy at a Superconducting Electron Accelerator
Wagner, A.ORC; Anwand, W.; Attallah, A. G.; Dornberg, G.; Elsayed, M.; Enke, D.; Hussein, A. E. M.; Krause-Rehberg, R.; Liedke, M. O.; Potzger, K.; Trinh, T. T.
The Helmholtz-Center at Dresden-Rossendorf operates several user beamlines for materials research employing positron annihilation. SPONSOR (Slow POsitroN System Of Rossendorf) uses moderated positrons from 22Na decay which are post-accelerated to energies from 27 eV to 37 keV which are guided magnetically towards the samples under study. The energy dependent range allows performing depth-dependent (coincidence) Doppler-broadening spectroscopy of thin films with thicknesses up to about 1 µm. SPONSOR has been extended by a new installation called AIDA (Apparatus for In-Situ Defect Analysis) which additionally allows temperature-dependent positron annihilation spectroscopy (PAS) from 50 to 1200 K, in-situ ion irradiation and sputtering with noble and reactive gases (up to 5keV ion energy), thin film deposition (Molecular Beam Epitaxy), and four-point probe resistometry. First experiments with this facility on open volume defects in Fe60Al40 alloys have been performed and the results will be presented. Two other user facilities dedicated to positron annihilation lifetime and Doppler-broadening studies in materials research are being operated at a superconducting electron linear accelerator. Hard X-rays from electron-bremsstrahlung generate 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 machines. Electron bunch lengths below 10 ps FWHM allows 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. Therefore, the source is especially suited for materials which are not qualified for vacuum conditions or because they are imposing hazardous conditions. MePS (The Monoenergetic Positron Source) is utilized to generate 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 porosimetric studies will be presented. [3].
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.

References
[1] W. Anwand, et al., Defect and Diffusion Forum Vl. 331 25 (2012).
[2] M. O. Liedke, et al., Journal of Applied Physics 117 163908 (2015).
[3] A. Uedono, et al., Applied Surface Science 368 272 (2016).
§Corresponding author, Email: A.Wagner@hzdr.de
Keywords: materials research positron annihilation SPONSOR depth-dependent (coincidence) Doppler-broadening spectroscopy thin films AIDA PAS Molecular Beam Epitaxy
  • Invited lecture (Conferences)
    14th International Workshop on Slow Positron Beam Techniques & Applications, 22.-27.05.2016, Matsue, Japan
  • Open Access LogoJournal of Physics: Conference Series 791(2017), 012004-1-012004-6
    DOI: 10.1088/1742-6596/791/1/012004

Publ.-Id: 24234 - Permalink


Is selective nodal irradiation in non-small cell lung cancer still safe when using IMRT? Results of a prospective cohort study.
Martinussen, H. M. A.; Reymen, B.; Wanders, R.; Troost, E. G. C.; Dingemans, A.-M. C.; Öllers, M.; Houben, R.; de Ruysscher, D.; Lambin, P.; van Baardwijk, A.;
Background and purpose: Isolated nodal failures (INF) are rare after 3D-conformal radiotherapy (3D-CRT) for stage III non-small cell lung cancer (NSCLC). Since incidental nodal irradiation doses are lower with Intensity Modulated Radiation Therapy (IMRT) than with 3D-CRT, INF may be higher after IMRT. We therefore investigated the incidence of INF after IMRT in stage III NSCLC patients.

Materials and Methods: Stage III NSCLC patients undergoing radical radiotherapy using IMRT in the period January 2010 till March 2012 were included. The primary endpoint was the rate of INF, secondary endpoints included patterns of failure, progression free survival (PFS), overall survival (OS) and toxicity.

Results: 183 stage III NSCLC patients were enrolled. With a median follow-up of 58.0 months 2.2 % of patients had an INF. The median PFS was 15.0 months, the median OS 19.5 months. Patterns of recurrence: 2.2 % INF, 11.5% local and 2.7% loco-regional recurrence, 26.8% distant metastases only, 18.0% a combination of local/loco-regional and distant metastases, and 38.3% patients without recurrence. One INF was out of field, in adjacent lymph nodes. Acute toxicity was limited.

Discussion: Selective nodal irradiation using IMRT in stage III NSCLC patients results in a low in-field incidence of INF (2.2%), similar to 3D-CRT, and may thus be considered safe.
Keywords: NSCLC, IMRT, selective nodal irradiation, isolated nodal failure.

Publ.-Id: 24233 - Permalink


Evaluation of two-group interfacial area transport equation model for vertical small diameter pipes against high-resolution experimental data
Dave, A.; Manera, A.; Beyer, M.; Lucas, D.; Bernard, M.;
Two-phase flow is ubiquitous in industrial, chemical and thermal plants alike. The current state-of-the-art system-code model for predicting fluid transport in two-phase flows is the two-fluid model. In the two-fluid transport model, the coupling of mass, momentum and energy transfer between phases is highly dependent on interfacial area transfer terms. Several research efforts in the past have been focused on the development of an interfacial area transport equation model (IATE) in order to eliminate the drawbacks of static regime flow maps currently used in best-estimate thermal-hydraulic system codes. The IATE attempts to model the dynamic evolution of the vapor/liquid interface by accounting for the different interaction mechanisms affecting gaseous phase transport.
The further development and validation of IATE models has been hindered by the lack of adequate experimental data in regions beyond the bubbly flow regime. At the Helmoltz-Zentrum Dresden-Rossendorf (HZDR) experiments
utilizing wire-mesh sensors have been performed over all flow regimes, establishing a database of high-resolution (in space and time) data. A 52.3 mm diameter pipe with a 16 by 16 wire-mesh sensor operating at 2.5 kHz is utilized in the air-water experimental database used in this work. There are a total of 37 tests (with varying superficial gas and liquid velocities, at approximately 0.25 MPa). Analysis of IATE performance in the bubbly flow and slug flow regimes is presented.
The performance of the Fu-Ishii two-group IATE model is evaluated. In all regions, the interfacial area concentration for small bubbles is predicted well. The model performs poorly in high void fraction regimes, in which large irregularly shaped bubbles are present. The interaction mechanisms that support and deter performance of the IATE model are highlighted. A sensitivity analysis of the coefficients indicates modification of the coefficient of group-2 wake entrainment may extend the validity of the Fu-Ishii model. An optimization study is presented to further explore improving IATE performance. It is concluded that the availability of accurate data at high void fractions from the HZDR facility provides a path to improve IATE performance.
Keywords: Interfacial area transport, Small-diameter pipes, Wire-mesh sensor, Genetic algotithm

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Publ.-Id: 24231 - Permalink


Carrier-induced ferromagnetism in the insulating Mn-doped III-V semiconductor InP
Bouzerar, R.; May, D.; Löw, U.; Machon, D.; Melinon, P.; Zhou, S.; Bouzerar, G.;
Although InP and GaAs have very similar band structure their magnetic properties appear to drastically differ. Critical temperatures in (In,Mn)P are much smaller than those of (Ga,Mn)As and scale linearly with Mn concentration. This is in contrast to the square-root behavior found in (Ga,Mn)As. Moreover the magnetization curve exhibits an unconventional shape in (In,Mn)P contrasting with the conventional one of well-annealed (Ga,Mn)As. By combining several theoretical approaches, the nature of ferromagnetism in Mn-doped InP is investigated. It appears that the magnetic properties are essentially controlled by the position of the Mn acceptor level. Our calculations are in excellent agreement with recent measurements for both critical temperatures and magnetizations. The results are only consistent with a Fermi level lying in an impurity band, ruling out the possibility to understand the physical properties of Mn-doped InP within the valence band scenario. The quantitative success found here reveals a predictive tool of choice that should open interesting pathways to address magnetic properties in other compounds.

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Publ.-Id: 24230 - Permalink


Electrochemical properties and optical transmission of high Li+ conducting LiSiPON electrolyte films
Su, Y.; Falgenhauer, J.; Leichtweiß, T.; Geiß, M.; Lupó, C.; Polity, A.; Zhou, S.; Obel, J.; Schlettwein, D.; Janek, J.; Meyer, B.;
Lithium silicon phosphorus oxynitride (LiSiPON) thin films with different compositions have been prepared by RF magnetron sputtering in N2 by using three targets xLi2SiO3 · (1 − x) Li3PO4 with x = 0.1, 0.3, and 0.5. Compared with LiPON, the electrical properties of LiSiPON have been improved by introducing silicon. LiSiPON films deposited from the target 0.5Li2SiO3 · 0.5Li3PO4 yield the highest ionic conductivity of up to 9.7 × 10−6 S cm−1 with an activation energy of only 0.41 eV. The main mechanism for increasing ionic conductivity is the enhancement of carrier mobility. By DC polarization measurements the electronic partial conductivity was found at least seven orders of magnitude smaller than the ionic conductivity. Linear voltammetry results showed that the LiSiPON films are electrochemically stable in contact with stainless steel in the voltage range of 0–6 V. The substitution of silicon for phosphorus in the film evidenced from X-ray photoelectron spectroscopy analysis indicated silicon in the film will create more abundant cross-linking structures Si–O–P and (P, Si)–N < (P, Si), hence created more Li+ conducting paths which favored the higher mobility of lithium ions and larger ionic conductivity. The optical bandgap was found to decrease with increasing silicon content. We demonstrate that the prepared LiSiPON films with their larger ionic conductivity and low electronic conductivity may serve as an alternative to LiPON for applications in high energy density and high voltage lithium batteries.
Keywords: electrochemical properties; inorganic solid electrolyte; lithium microbattery; LiSiPON

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Publ.-Id: 24229 - Permalink


Development of an 18F-labeled radiotracer for in vivo imaging of adenosine A2B receptors with positron emission tomography
Wenzel, B.; Lindemann, M.; Teodoro, R.; Hinz, S.; Müller, C.; Dukic-Stefanovic, S.; Schiller, E.; Juhl, C.; Brust, P.; Steinbach, J.;
Kein Abstract verfügbar.
  • Poster
    Neuroallianz Workshop 2016, 25.10.2016, Bonn, Deutschland

Publ.-Id: 24228 - Permalink


Development of a new F-18-labelled quinoline derivative as PET neuroimaging probe for PDE5
Wenzel, B.; Liu, J.; Teodoro, R.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Ludwig, F.-A.; Chezal, J. M.; Maisonial-Besset, A.; Brust, P.; Moreau, E.;
Aim:
Cyclic nucleotide phosphodiesterase 5 (PDE5) is an enzyme that regulates the intracellular levels of the second messenger cyclic guanosine monophosphate (cGMP). Within the CNS, PDE5 is highly expressed in the cerebellum and the hippocampus. There is currently a growing interest in using inhibitors of PDE5 such as Sildenafil (Viagra®) as possible drug for treatment of cognitive impairment in Alzheimer’s and Huntington’s Disease. Moreover, effects of PDE5 inhibitors on the growth of different tumour cells are reported. Therefore we aimed to develop a F-18-labelled radioligand for imaging of this enzyme particularly in brain.

Methods:
Based on a quinoline scaffold (1) a series of fluorinated derivatives was synthesized and their inhibitory activity for several PDEs was determined. F-18-labelling of the most promising candidate ICF24075* was performed by using a nosylate precursor. In vitro autoradiography of [18F]ICF24075 was performed on pig brain slices. In vivo metabolism was investigated in plasma and brain samples of mice at 30 min p.i. using micellar chromatography.
* 4-((3-chloro-4-methoxybenzyl)amino)-8-(3-(fluoro)azetidin-1-yl)-3-(hydroxymethyl)quinoline-6-carbonitrile

Results:
The inhibitory activity of ICF24075 toward PDE5 was determined with an IC50 value of 5.9 nM. F-18-labelling of the secondary carbon atom proceeded only with low labelling yields of around 7% resulting in RCY of 2%. In vitro binding studies demonstrated a specific blockade with sildenafil which was highest in the cerebellum. In vivo studies in mice revealed the formation of radiometabolites able to cross the blood-brain barrier.

Conclusions:
Due to the presence of radiometabolites in the brain, [18F]ICF24075 is not suitable for specific neuroimaging of PDE5. The unexpected fast metabolic degradation of the F-18-substituted azetidine ring is currently investigated by in vitro studies to confirm our assumption of N-dealkylation.
  • Lecture (Conference)
    DGN 2017 - Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin, 26.04.2017, Dresden, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 56(2017)2, A45

Publ.-Id: 24227 - Permalink


Loch an Loch und hält doch – Die Sprödbruchneigung genieteter Konstruktionen aus alten Baustählen
Sieber, L.; Stroetmann, R.; Viehrig, H.-W.; Houska, M.;
Zahlreiche erhaltene Stahlbauwerke des 19. und frühen 20. Jh. werden heute noch genutzt und haben somit ihre geplante Nutzungsdauer von 60 bis 80 Jahren deutlich überschritten. Aus wirtschaftlichen und oft auch denkmalpflegerischen Gründen besteht ein großes Inte-resse, die Nutzung dieser Bauwerke auch weiterhin sicherzustellen. Bedingt durch Schadensfälle infolge Sprödbruchversagen bei Altstahlkonstruktionen (z.B. an Stahlgeschossbauten und Stahlgittermasten) gewinnt neben der Tragsicherheit die Frage der Sprödbruchgefährdung alter Stahlkonstruktionen zunehmend an Bedeutung. Alte Stahlkonstruktionen bestehen überwiegend aus genieteten oder geschraubten Flachstählen, I-, L- und U-Profilen mit wiederkehrenden Konstruktionsprinzipien. Besonders sprödbruchgefährdet sind Bereiche in höher zugbeanspruchten Bauteilen aus stickstoffreichen Stählen, die durch gestanzte Löcher geschwächt sind.
Zur Beurteilung der Sprödbruchsicherheit stehen im Stahlbau verschiedene, unterschiedlich aufwendige und aussagefähige Methoden zur Verfügung, die in mehr oder weniger engem Zusammenhang mit dem eigentlichen Phänomen des Sprödbruchs stehen.
Keywords: basic oxygen steel, steel structure, rivet connection, fracture mechanics, Master Curve, integrity assessment
  • Lecture (Conference)
    7. Fachtagung Bemessung und Konstruktion, 07.03.2017, Halle/Saale, Deutschland

Publ.-Id: 24226 - Permalink


Untersuchung der Hydrodynamik von ovalen Biogasreaktoren mit instrumentierten Strömungsfolgern
Reinecke, S. F.; Jobst, K.; Hampel, U.;
Erstmals wurden instrumentierte strömungsfolgende Sensorpartikel mit magnetischer Positionsdetektion in einer Studie der Hydrodynamik von neuartigen, ovalen Biogasreaktoren im Labor- und Technikumsmaßstab eingesetzt. Die Sensorpartikel erfassen autonom die makroskopischen Strömungsvorgänge in den Reaktoren. Die gemessenen Daten der Sensorpartikel liefern vertikale Aufenthaltsprofile und Partikelumlaufzeitverteilungen. Anhand dieser Informationen werden die ovalen Reaktoren hinsichtlich der Durchmischung und der Suspensionseigenschaften bewertet und verglichen.
Keywords: Strömungsfolger, Sensorpartikel, Autonomer Sensor, Biogas, Hydrodynamik

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  • Secondary publication expected

Publ.-Id: 24225 - Permalink


Physical properties of the candidate quantum spin-ice system Pr2Hf2O7
Anand, V. K.; Opherden, L.; Xu, J.; Adroja, D. T.; Islam, A. T. M. N.; Herrmannsdörfer, T.; Hornung, J.; Schönemann, R.; Uhlarz, M.; Walker, H. C.; Casati, N; Lake, B;
Physical properties of a pyrohafnate compound Pr2Hf2O7 have been investigated by ac magnetic susceptibility χac(T ), dc magnetic susceptibility χ(T ), isothermal magnetization M(H), and heat-capacity Cp(T )measurements on polycrystalline as well as single-crystal samples combined with high-resolution synchrotron x-ray diffraction (XRD) for structural characterization and inelastic neutron scattering (INS) to determine the crystal-field energy-level scheme and wave functions. Synchrotron XRD data confirm the ordered cubic pyrochlore (Fd¯3m) structure without any noticeable site mixing or oxygen deficiency. No clear evidence of long-range magnetic ordering is observed down to 90 mK, however the χac(T ) evinces slow spin dynamics revealed by a frequency dependent broad peak associated with spin freezing. The INS data reveal the expected five well-defined magnetic excitations due to crystal-field splitting of the J = 4 ground-state multiplet of the Pr3+. The crystal-field parameters and ground-state wave function of Pr3+ have been determined. The Ising anisotropic nature of the magnetic ground state is inferred from the INS as well as χ(T) and M(H) data. Together these properties make Pr2Hf2O7 a candidate compound for quantum spin-ice behavior.

Publ.-Id: 24224 - Permalink


Photo-activated CO releasing molecules
Kubeil, M.; Stephan, H.; Graham, B.; Spiccia, L.;
Carbon monoxide has been demonstrated to exhibit several beneficial effects on biological targets (anti-inflammatory, anti-proliferative, anti-apoptotic, anti-oxidative and vasodilatory effects).1 The development of photo-activated CO releasing molecules (photoCORMs) has received considerable attention as a new prodrug approach.2 However, despite the number of photoCORMs reported in the literature, their mechanism of CO release has been little elucidated so far. Herein, we report the synthesis of ruthenium(II)-carbonyl complexes (Figure) functionalized with electron-donating and/or electron-withdrawing bipyridine ligands and investigate the mechanism of CO release (before and after light-activation) using a combination of UV-Vis and FTIR spectroscopy accompanied with a chemometric technique (Multivariate Curve Fitting Analysis).3 The photo-activated CO-release kinetics of the Ru(II)-photoCORMs, as well as the identity of the intermediates and photo-activated products, will be presented. These results have important implications in understanding their chemistry and guiding the design of new photoCORMs.


References
[1] R. Motterlini, L. E. Otterbein, Nat. Rev. Drug Discov. 2010. 9, 728-743
[2] U. Schatzschneider, British J. Pharmacol. 2014, 172, 1638-1650
[3] C. Bischof, T. Joshi, A. Dimri, L. Spiccia, U. Schatzschneider, Inorg. Chem. 2013, 52, 9297-9308
  • Lecture (Conference)
    8th Asian Biological Inorganic Chemistry Conference (AsBIC8), 04.-09.12.2016, Auckland, New Zealand

Publ.-Id: 24223 - Permalink


In-Situ Analysis and Experiment Regulation at HZDR
Frust, T.; Kelling, J.; Juckeland, G.;
A number of experiments at HZDR require in-situ evaluation of the experiment data of the results for automated responses by the experiment control systems. This talk presents two such examples and their current implementations.
  • Invited lecture (Conferences)
    PADC Annual Workshop 2016, 17.-18.10.2016, Jülich, Deutschland

Publ.-Id: 24222 - Permalink


PIConGPU: First Experiences on Minski
Widera, R.; Hübl, A.; Juckeland, G.;
PICOnGPU is a highly scalable GPU accelerated particle-in-cell code. This talk presents the first experiences on running this code on IBM Minski (Power8+ with NVIDIA P100 GPUs).
  • Invited lecture (Conferences)
    PADC Annual Workshop 2016, 17.-18.10.2016, Jülich, Deutschland

Publ.-Id: 24221 - Permalink


Luminescence spectra of uranium(VI) – why we observe a spectral shift in cryospectra
Geipel, G.; Stumpf, T.;
It is well known, that uranyl carbonates emits at room temperature only phosphorescence with very short lifetimes {Ca2UO2(CO3)3 ~ 50 ns}[1, 2]. The lifetime of UO2(CO3)34+ in aqueous solution at room temperature was determined to be 9.2 ± 0.05 ns. Freezing these solutions results normally in a strong increase of the luminescence lifetime as well as in a strong increase in the measured intensity. This effect is usually explained by the dynamic quench effect of the carbonate ion as well as the dynamic quench effect of the water molecules in the solvation shell. In addition all spectra of the uranyl carbonates show a hypsochromic shift.
The emission of the uranyl ion is assigned to a triplet state. It is also known that the non-complexed uranyl ion has two phosphorescence emitting levels (20500 and 21270 cm-1)[3,4]. The first one is assigned to the direct transition to the lowest vibronic level in the ground state, the second is assigned to the transition of a exited vibronic level to the ground state. The emission peaks at lower wavenumbers correspond to vibronic levels in the ground state and are usually assigned to the transition from the lowest triplet state[5].

We observe for the uranyltricarbonate at room temperature an emission at around 21420 cm-1 and at 20610 cm-1 which are the two emitting levels in this system. From the higher level also the vibronic levels in the ground state were populated. Under cryogenic conditions we observe that the emission from the higher level disappears. This induces a slight blue shift of the spectrum of about 65 cm-1.
Keywords: Uranium, luminescence, spectral shift, cryogenic
  • Poster
    ATAS Workshop, 07.-10.11.2016, Richland, USA

Publ.-Id: 24220 - Permalink


Neuroimaging of intracellular signalling: Development of an 18F-labelled quinoline derivative with high affinity for phosphodiesterase 5.
Wenzel, B.; Liu, J.; Teodoro, R.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Ludwig, F.-A.; Chezal, J. M.; Moreau, E.; Brust, P.; Maisonial-Besset, A.;
Objectives: The enzyme cyclic nucleotide phosphodiesterase 5 (PDE5) is involved in receptor-mediated signalling processes by regulation of the intracellular levels of the second messenger cGMP. PDE5 is peripherally located in heart, lungs and smooth muscle cells. Within the CNS it is highly expressed in the cerebellum and hippocampus. There is currently a growing interest in using inhibitors of PDE5 such as Sildenafil (Viagra®) as possible drugs in Alzheimer’s and Huntington’s Disease. Moreover, the effects of PDE5 inhibitors on the growth of different tumour cells are reported. Therefore we aimed to develop a 18F-labelled radioligand for imaging of this enzyme particularly in brain.

Methods: A quinoline scaffold (1) was used as basis for the synthesis of a small library of derivatives with fluoro-containing substituents in position 3, 4 and 8 of the quinoline core. The inhibitory activity of the compounds was determined for the human PDE5A1 and a panel of other PDEs by using an enzyme assay with sildenafil as reference. 18F-labelling of the best candidate ICF24075 was performed on an azetidine ring by using a nosylate precursor (Figure). In vitro autoradiography of [18F]ICF24075 was performed on pig brain slices. In vivo metabolism was investigated in plasma and brain samples of mice 30 min p.i. using micellar chromatography.


Figure: 18F-labelling of [18F]ICF24075

Results: The new ligand ICF24075 showed a good inhibitory activity for PDE5 (IC50 = 5.9 nM) and a high selectivity over other PDEs. 18F-labelling of the secondary carbon atom proceeded only with low labelling yields resulting in RCYs of 1.8 ± 0.3% (decay corr.) of the formulated product. In vitro binding studies demonstrated a specific blockade with sildenafil which was highest in the cerebellum. However, in vivo studies in mice revealed the formation of radiometabolites able to cross the blood-brain barrier.

Conclusions: Due to the presence of radiometabolites in the brain, [18F]ICF24075 is not suitable for specific neuroimaging of PDE5. In particular the unexpected fast metabolic degradation of the 18F-labelled azetidine ring is currently further investigated by in vitro studies to confirm our assumption of N-dealkylation.

Reference: (1) Bi, Y. et al; Bioorg. Med. Chem. Lett. 2004, 14, 1577-1580.
  • Poster
    ISRS 2017 - 22nd International Symposium on Radiopharmaceutical Sciences, 14.05.2017, Dresden, Deutschland
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 60(2017)S1, 534
    DOI: 10.1002/jlcr.3508

Publ.-Id: 24219 - Permalink


DFT study on the contribution of phonon and electron excitations to the free energy of embedded defect clusters
Posselt, M.; Devaraj, M.;
Modeling of nanostructure evolution in solids requires the knowledge of comprehensive data on the properties of point defects and defect clusters. Since most processes occur at elevated temperatures not only the energetics of the defects in the ground state but also their temperature-dependent free energy must be known. The determination of the contribution of phonon and electron excitations to the free binding energy of small embedded defect clusters is illustrated in the case of bcc-Fe. The fundamentals of the first-principles calculation method have been recently described [1]. First of all, the ground state properties of the clusters are determined under zero pressure (ZP) conditions. Second, the phonon contribution to the free energy is calculated within the harmonic approximation using the equilibrium atomic positions determined in the ground state. The application of a quasi-harmonic correction to the ZP-based data does not modify the results significantly. Therefore the obtained data are valid under zero-pressure conditions at higher temperatures than in the framework of the purely harmonic approach. These conditions are usually realized in experiments. Third, the contribution of electron excitations to the defect free energy is calculated. The electron excitations can lead to an additional deviation of the total free energy from the ground state value or can compensate the deviation caused by the phonon contribution. Depending on the examples considered the free binding energy of a defect cluster can differ significantly from the ground state value.
[1] D. Murali, M. Posselt, M. Schiwarth, Phys. Rev. B 92, 064103 (2015).
Keywords: DFT, defect clusters, free energy
  • Lecture (Conference)
    8th Int. Conf. on Multiscale Materials Modeling (MMM 2016), 09.-14.10.2016, Dijon, France

Publ.-Id: 24218 - Permalink


In-magnet measurement setup for proof-of-concept and commissioning of MR integrated proton therapy
Lühr, A.; Gantz, S.; Schellhammer, S.; Zarini, O.; Zeil, K.; Schramm, U.; Hoffmann, A.;
There is growing interest to explore the concept of magnetic resonance integrated proton therapy (MRiPT). However, no experimental proof-of-principle has been established so far. The aim of this work was to develop an in-magnet measurement setup that facilitates to investigate the dosimetric feasibility of MRiPT and to develop a commissioning procedure for future MRiPT devices.
Keywords: Proton therapy, MR integrated Radiotherapy, MR guidance, Commissioning, Magnetometry, Proton beam deflection, Pencil beam scanning
  • Contribution to proceedings
    ESTRO 36, 05.05.2017, Wien, Österreich
    Proceedings of ESTRO 36
  • Lecture (Conference)
    ESTRO 36, 05.05.2017, Wien, Österreich

Publ.-Id: 24217 - Permalink


Positron-Annihilation Lifetime Spectroscopy for Materials Science
Wagner, A.;
Early experiments on the interaction of positrons (the anti-particles of electrons) with materials revealed a significant sensitivity on the electronic structure. Especially, open-volume defects, such as vacancies, vacancy agglomerates, and dislocations cause attractive electric potentials due to the lack of the repulsive positive potential of the nuclei. With diffusion lengths in the order of 100 nm positrons probe large volumes before getting trapped at positively charged defects which in turn results in a sensitivity of defect concentrations of about 1 in 107 atoms (in metals) . While annihilation lifetimes increase with increasing defect sizes due to reduced local electron densities, one can also infer the momentum-distributions of the annihilation electrons which in turn tell about the chemical compositions in the vicinity of defects. Doppler-broadening spectroscopy and annihilation lifetime spectroscopy have therefore found widespread applications in defect studies in pure metals, alloys, and semiconductors. With increasing defect sizes the formation of the electron-positron bound state – called Positronium (Ps) – becomes possible. While the spin-parallel triplet state has a vacuum annihilation lifetime of 142 ns, this annihilation lifetime gets reduced when the Ps bounces off the walls of porous materials and flipping to the spin-singlet state with 125 ps. In contrast to standard intrusion techniques, porosimetry studies with positrons can be applied for closed porosity as well.
The Helmholtz-Center at Dresden-Rossendorf operates several user beamlines for materials research employing positron annihilation. SPONSOR (Slow POsitroN System Of Rossendorf) uses moderated positrons from 22Na decay which are post-accelerated to energies from 27 eV to 37 keV which are guided magnetically towards the samples under study [1]. The energy dependent range allows performing depth-dependent (coincidence) Doppler-broadening spectroscopy of thin films with thicknesses up to about 1 µm. SPONSOR has been extended by a new installation called AIDA (Apparatus for In-Situ Defect Analysis) which additionally allows temperature-dependent positron annihilation spectroscopy (PAS) from 50 to 1200 K, in-situ ion irradiation and sputtering with noble and reactive gases (up to 5keV ion energy), thin film deposition (Molecular Beam Epitaxy), and four-point probe resistometry. First experiments with this facility on open volume defects in Fe60Al40 alloys have been performed and the results will be presented [2]. Two other user facilities dedicated to positron annihilation lifetime and Doppler-broadening studies in materials research are being operated at a superconducting electron linear accelerator. Hard X-rays from electron-bremsstrahlung generate 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 allows 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 [3]. 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 [4] will be presented. MePS (the Monoenergetic Positron Source) utilizes positrons with fixed energies ranging from 500 eV to 16 keV[3]. 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 porosimetric studies in low-k dielectrics will be presented. [6].
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.

[1] W. Anwand, et al., Defect and Diffusion Forum Vl. 331 25 (2012).
[2] M. O. Liedke, et al., Journal of Applied Physics 117 163908 (2015).
[3] M. Butterling, et al., Nuclear Instruments and Methods in Physics Research B 269, 2623 (2011).
[4] M. Reiner, et al., Scientific Reports 6, 29109 (2016).
[5] M. Jungmann, et al., Journal of Physics: Conference Series 443, 012088 (2013)
[6] A. Uedono, et al., Applied Surface Science 368, 272 (2016).
Keywords: Positron annihilation EPOS MePS GiPS SPONSOR AIDA Memriox ELBE
  • Invited lecture (Conferences)
    2nd International Symposium for Innovative Measurement and Analysis for Structural Materials, Keynote Talk, 27.-29.09.2016, Tsukuba, Japan

Publ.-Id: 24215 - Permalink


Experimental setup to measure magnetic field effects of proton dose distributions: simulation study
Schellhammer, S.ORC; Oborn, B.; Lühr, A.; Gantz, S.; Wohlfahrt, P.; Bussmann, M.; Hoffmann, A.
Purpose/Objective:
As a first step towards proof-of-concept for MR-integrated proton therapy, the dose deposited by a slowing down proton pencil beam in tissue-equivalent material is assessed within a realistic magnet assembly. Furthermore, radiation-induced activation and demagnetization effects of the magnet are studied.

Material/Methods:
The dose distributions of proton pencil beams (energy range 70-180 MeV) passing through a transverse magnetic field of a permanent C-shaped NdFeB dipole magnet (maximum magnetic flux density Bmax = 0.95 T) while being stopped inside a tissue-equivalent slab phantom of PMMA were simulated (Figure 1). The beam was collimated to a diameter of 10 mm. A radiochromic EBT3 film dosimeter was placed centrally between the two phantom slabs parallel to the beam’s central axis. 3D magnetic field data was calculated using finite-element modelling (COMSOL Multiphysics) and experimentally validated using Hall-probe based magnetometry. A Monte Carlo model was designed using the simulation toolkit Geant4.10.2.p02 and validated by reference measurements of depth-dose distributions and beam profiles obtained with Giraffe and Lynx detectors (IBA Dosimetry), respectively. The beam trajectory and lateral deflection were extracted from the film’s planar dose distribution. Demagnetization was assessed by calculating the dose deposited in the magnet elements, and by relating this to radiation hardness data from literature. A worst-case estimate of the radioactivation of the magnet was obtained by taking into account the most common produced mother nuclides and their corresponding daughter nuclides.

Results:
The Monte Carlo model showed excellent agreement with the reference measurements (mean absolute range difference: 0.2 mm). The predicted planar dose distribution clearly showed the magnetic field induced beam deflection (Figure 2). The estimated in-plane deflection of the Bragg peak ranged from 0 cm for 70 MeV to 1 cm for 180 MeV in comparison to no magnetic field. No out-of-plane beam deflection was observed. Exposing the film to 2 Gy at the Bragg peak was estimated to cause a mean dose to the magnets of 20 μGy, which is expected to produce negligible magnetic flux loss. The initial activation was estimated to be below 25 kBq.

Conclusion:
A first experimental setup capable of measuring the trajectory of a proton pencil beam slowing down in a tissue-equivalent material within a realistic magnetic field has been designed and built. Monte Carlo simulations of the design show that magnetic field induced lateral beam deflections are measurable at the energies studied and radiation-induced magnet damage is expected to be manageable. These results have been validated by irradiation experiments, as reported by Lühr et al. in a separate abstract.
  • Lecture (Conference)
    ESTRO 2017, 05.-09.05.2017, Wien, Österreich

Publ.-Id: 24214 - Permalink


Sites of recurrent disease and prognostic factors in SCLC patients treated with radiochemotherapy
Bütof, R.; Gumina, C.; Valentini, C.; Sommerer, A.; Appold, S.; Zips, D.; Löck, S.; Baumann, M.; Troost, E.;
Purpose:
Concurrent radiochemotherapy (RCHT) is the standard treatment in locally advanced small cell lung cancer (SCLC) patients. Due to conflicting results on elective nodal irradiation (ENI) or selective node irradiation (SNI) there is no clear evidence on optimal target volumes. Therefore, the aims of this study were the evaluation of sites of recurrent disease in patients with limited stage SCLC undergoing radiochemotherapy to assess the feasibility and safety of SNI versus ENI and, moreover, the extraction of prognostic factors for loco-regional control, freedom from distant metastases and overall survival.
Material and methods:
A retrospective single-institution study was performed in 54 consecutive patients treated with RCHT. After state-of-the-art staging, all patients underwent three-dimensional conformal radiotherapy to a total dose of 45 Gy in twice-daily fractions of 1.5 Gy starting concurrently with the first or second chemotherapy cycle according to Turrisi et al. [1]. The gross tumour volume (GTV) consisted of the primary tumour and SNI visualized on CT and/or FDG-PET, or confirmed by cytology. The clinical target volume (CTV) was obtained by expanding the GTV, adjusting it for anatomical boundaries, and electively adding the supraclavicular lymph node stations. Thereafter, the CTV was expanded to a planning target volume based on institutional guidelines. Follow-up consisted of a 3-monthly chest x-ray or CT-scan. All sites of loco-regional recurrences were correlated to the initial tumour and dose delivered. The impact of potential prognostic variables on outcome was evaluated using the Cox-regression model.
Results:
After a median interval of 11.5 months, 17 patients (31%) relapsed locally or regionally: six within the initial primary tumour volume, five within the initially affected lymph nodes, three metachronously within primary tumour and initially affected lymph nodes, and three both inside and outside of the initial nodal disease. All sites of loco-regional recurrence had received 92%-106% of the prescribed dose. Thirty-seven patients (69%) developed distant metastases (37.8% liver, 35% brain). Among all investigated co-factors only total GTV revealed a significant correlation with patient outcome.
Conclusion:
In our study most recurrences occurred in the initial primary tumour or lymph node volume, or distantly. We did not register any case of isolated nodal failure, suggesting the use of selective nodal irradiation, possibly with the addition of supraclavicular irradiation in patients with affected lymph nodes in the upper mediastinum, instead of ENI.
Among all investigated patient- and tumour-related co-factors only total GTV revealed a significant correlation with patient outcome. Further prospective clinical trials are needed for final determination of optimal irradiation fields in SCLC patients.
Keywords: SCLC, locoregional control, distant metastases, overall survival, prognostic factors

Publ.-Id: 24213 - Permalink


Dirac loops in two-dimensional topological material T-graphene
Liu, Y.; Wang, G.; Huang, Q. S.; Guo, L. W.; Chen, X. L.; Zhou, S. Q.;
Graphene possesses a peculiar band structure and hence exhibits many fascinating properties from room temperature quantum Hall effect to massless Dirac fermions. With the understanding of graphene, topological materials with the properties similar to or even beyond graphene gradually rise and draw much attention, such as Silicene, Bi2Se3, WTe2 and most recently TaAs. Then a question arises: is it possible for another 2D carbon lattice to exhibit similar properties? If so, what are the determining factors? Here, we demonstrate that a novel two-dimensional carbon allotrope called T-graphene can possess Type-I Dirac points / loops based on the first-principles calculations [1]. T-graphene described by the plane group p4mm (See Fig. 1) can be energetically metastable and dynamically stable. The band structure of T-graphene in Fig. 1 shows the linear dispersion relation at the Fermi level. Two Dirac points are located at asymmetric positions Ξ(0.170, 0.170) between Γ and M and Λ(0, 0.249) between X and Γ, respectively. Furthermore, the linear dispersion relation near the Fermi surface exists in every direction and the cross points form a loop. Such Dirac fermions and a high υF are attributed to crossing π and π* bands and two sublattices. Under certain structure tailoring or straining, the linear dispersion relation is found to be retained. Two type of nanoribbons tailored from T graphene are predicted to have interesting magnetic properties. Besides, two possible routes to obtain T graphene are proposed: carbon deposition on certain metal substrates or electron beam irradiation on the tailored graphene growing on Ni (111). The results provide new insights to search and fabricate two-dimensional topological material.
Keywords: graphene, Dirac fermions, first-principles calculations, 2D materials
  • Poster
    33rd International Conference on the Physics of Semiconductors, 31.07.-05.08.2016, Beijing, China

Publ.-Id: 24212 - Permalink


Ferromagnetism in Silicon Single Crystals with Positively Charged Vacancy Clusters
Liu, Y.; Zhang, X.; Yuan, Q.; Han, J.; Zhou, S.; Song, B.;
Defect-induced ferromagnetism provides an alternative for organic and semiconductor spintronics. Here, we investigated the magnetism in Silicon after neutron irradiation and try to correlate the observed magnetism to particular defects in Si. Commercially available p-type Si single crystal wafer is cut into pieces for performing neutron irradiations. The magnetic impurities are ruled out as they can not be detected by secondary ion mass spectroscopy. With positron annihilation lifetime spectroscopy, the positron trapping center corresponding to lifetime 375 ps is assigned to a kind of stable vacancy clusters of hexagonal rings (V6) and its concentration is enhanced by increasing neutron doses. After irradiation, the samples still show strong diamagnetism. The weak ferromagnetic signal in Si after irradiation enhances and then weakens with increasing irradiation doses. The saturation magnetization at room temperature is almost the same as that at 5 K. The X-ray magnetic circular dichroism further provides the direct evidence that Silicon is the origin of this ferromagnetism. Using first-principles calculations, it is found that positively charged V6 brings the spin polarization and the defects have coupling with each other.
Keywords: defect-induced ferromagnetism; silicon; neutron irradiation; semiconductors
  • Lecture (Conference)
    APS March Meeting 2016, 14.-18.03.2016, Baltimore, United States of America

Publ.-Id: 24211 - Permalink


Esophageal wall dose-surface maps do not improve the predictive performance of a multivariable NTCP model for acute esophageal toxicity in advanced stage NSCLC patients treated with intensity-modulated (chemo-)radiotherapy
Dankers, F.; Wijsman, R.; Troost, E.; Monshouwer, R.; Bussink, J.; Hoffmann, A.;
In our previous work, a multivariable normal-tissue complication probability (NTCP) model for acute esophageal toxicity (AET) Grade ≥2 after highly conformal (chemo-)radiotherapy for non-small cell lung cancer (NSCLC) was developed using clinical parameters and mean esophageal dose (MED). Since the esophagus is a tubular organ, spatial information of the esophageal wall dose distribution may be important in predicting AET. We investigated whether the incorporation of esophageal wall dose-surface data with spatial information improves the predictive power of our NTCP model. For 149 NSCLC patients treated with highly conformal radiation therapy esophageal wall dose-surface histograms (DSHs) and polar dose-surface maps (DSMs) were generated. DSMs were used to generate new DSHs and dose-length-histograms (DLHs) that incorporate spatial information of the dose-surface distribution. Following our previous work, new multivariable NTCP models were developed using histogram derived parameters. Univariate logistic regression analysis showed that these histogram parameters correlated significantly with AET. However, incorporation of esophageal wall dose-surface data with spatial information did not improve the predictive performance of the established multivariable NTCP model based on conventional dose-volume data. For prediction of AET spatial information of the esophageal wall dose distribution is of no added value and it is sufficient to only consider MED as a predictive dosimetric parameter.
Keywords: Non-small cell lung cancer, esophagitis, NTCP, highly conformal radiation therapy, predictive models, dose maps

Publ.-Id: 24210 - Permalink


Targeting cancer with ultrasmall silicon nanoparticles
Licciardello, N.; Zarschler, K.; Singh, G.; Bergmann, R.; Faramus, A.; Ddungu, J. L. Z.; de Cola, L.; Stephan, H.;
Renal clearable ultrasmall nanoparticles (sub-10 nm size) have attracted increasing attention for medicinal applications [1, 2]. In this direction, ultrasmall silicon nanoparticles (Si-NPs) are gaining in importance, especially in the imaging of cancer cells [3]. Si-NPs display tuneable photoluminescence, high resistance against photo-bleaching, chemical stability after functionalization and biocompatibility. Covalent modification of the surface with red-emitting dyes for optical imaging, bifunctional chelator agents for radiometals enabling SPECT or PET, and simultaneously targeting vector molecules opens the avenue for the development of new targeted dual imaging agents. In vivo imaging with fast clearing agents possessing numerous surface groups is very attractive. However, defined surface functionalization, especially with suitable targeting molecules, is fairly challenging. Here we report on the surface functionalization of amine-terminated Si-NPs (< 5 nm) with a defined quantity of red-emitting dyes and vector molecules, in order to design targeting optical imaging agents. The modification of these Si-NPs with appropriate chelators for radiometals, such as 64Cu, allows for performing positron emission tomography.

Work financially supported by Helmholtz Virtual Institute “NanoTracking”, Agreement No. VH-VI-421

References
[1] B. H. Kim, M. J. Hackett, J. Park, T. Hyeon, Chemistry of Materials 2014, 26, 59-71.
[2] K. Zarschler, L. Rocks, N. Licciardello, L. Boselli, E. Polo, K. P. Garcia, L. De Cola, H. Stephan, K. A. Dawson, Nanomedicine: Nanotechnology, Biology and Medicine 2016, 12, 1663-1701.
[3] C. Tu, X. Ma, A. House, S. M. Kauzlarich, A. Y. Louie, ACS Medicinal Chemistry Letters 2011, 2, 285-288.
  • Lecture (Conference)
    8th International Conference on Nanomaterials - Research & Application (Nanocon 2016), 19.-21.10.2016, Brno, Czech Republic

Publ.-Id: 24209 - Permalink


Formation and properties of high-dose nitrogen implanted epitaxially grown Gd2O3 on silicon
Joseph, A.; Tetzlaff, D.; Schmidt, J.; Böttger, R.; Wietler, T. F.; Osten, H. J.;
The effects of nitrogen incorporation by high-dose ion implantation in epitaxial Gd2O3 films on Si(111) followed by annealing have been investigated. Nitrogen incorporation is believed to occur by filling the oxygen vacancies or by removing hydroxyl group ions in gadolinium oxide (Gd2O3). The nitrogen content in the oxide layer has been altered by changing the implantation dose. The impact of nitrogen incorporation on Gd-O bonding is studied using X-ray photoelectron spectroscopy. A shift in the Gd and O peak positions indicate the presence of nitrogen in the layer. Raman spectroscopy reveals heavy structural changes. The newly appearing structure is crystalline, but not in agreement with either the known bixbyite (Gd2O3) or rocksalt (GdN) structure. Electron microscopic investigations reveal the formation of cracks and small areas with lower densities or even voids. That structure exhibits similarities with transmission electron microscopy images of gadolinium nitride (GdN) layers. The electronic band gap of Gd2O3 estimated from O1s plasmon energy loss measurements was found to decrease significantly by the incorporation of nitrogen. Reduction in the valence band and conduction band offset is obtained as a function of implantation dose.
Keywords: Band gap, Crystal structure, Gadolinium, X-ray photoelectron spectroscopy, Transmission electron microscopy

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Publ.-Id: 24208 - Permalink


Human endothelial cell models in biomaterial research
Hauser, S.; Jung, F.; Pietzsch, J.ORC
Endothelial cell (EC) models have evolved as important tools in biomaterial research due to ubiquitously occurring interactions between implanted materials and the endothelium. However, screening the available literature has revealed a gap between material scientists and physiologists in terms of their understanding of these biomaterial–endothelium interactions and their relative importance. Consequently, EC models are often applied in nonphysiological experimental setups, or too extensive conclusions are drawn from their results. The question arises whether this might be one reason why, among the many potential biomaterials, only a few have found their way into the clinic. In this review, we provide an overview of established EC models and possible selection criteria to enable researchers to determine the most reliable and relevant EC model to use.
Keywords: endothelial cell heterogeneity; vascular grafts; stents; bone regeneration; soft tissue regeneration

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  • Secondary publication expected

Publ.-Id: 24207 - Permalink


Observation of 22Na+-Diffusion in Opalinus Clay using Positron Emission Tomography (GeoPET)
Kulenkampff, J.; Gründig, M.; Zakhnini, A.; Lippmann-Pipke, J.;
We applied positron emission tomography (PET) for investigating diffusion of Na-22 in Opalinus clay rock. This enables to derive diffusion parameters on the macroscopic scale of drill cores (diameter 100 mm), and thus to consider effects of anisotropy and heterogeneities. This method is complementary to laboratory measurements with common diffusion cells, which can hardly elucidate such macroscopical spatial effects.
Here, we present the measuring data as motion picture. The underlying PET-data are 20 scans over a period of 143 days after injection of synthetic Opalinus pore water, labelled with Na-22, into an axial blind hole.
Keywords: diffusion, clay rock, heterogeneity, anisotropy, positron emission tomography, PET

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Publ.-Id: 24206 - Permalink


Determining femtosecond plasma dynamics via radiation spectra A simulation approach with PIConGPU
Pausch, R.; Debus, A.; Huebl, A.; Steiniger, K.; Widera, R.; Schramm, U.; Bussmann, M.;
A vital step from simulating complex plasma dynamics and comparing it with experimental measurements or astrophysical observations is predicting observables as e.g. the emitted radiation. This poster focuses on how we compute spectrally and spatially resolved radiation based on Liénard Wiechert potentials in the 3D3V particle-in-cell code PIConGPU. Applications in laser plasma acceleration and astrophysics are given to demonstrate the wide applicability of our synthetic diagnostic method.
Keywords: PIConGPU, radiation, plasma, synthetic diagnostic
  • Poster
    11th Annual PhD Seminar 2016 (HZDR), 17.-19.10.2016, Oberwiesenthal, Deutschland

Publ.-Id: 24205 - Permalink


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