Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35836 Publications

Metal pad roll in cylinders: perturbation theory vs. DNS

Herreman, W.; Nore, C.; Guermond, J.-L.; Cappanera, L.; Weber, N.

Liquid metal batteries (LMBs) structurally have much in common with electrolysis cells that are used in the Al-industry and therefore it can be expected that they are prone to similar magneto-hydrodynamical instabilities. Metal pad rolling is one of many instabilities that is currently in the spotlight.

The physical origin of this metal pad roll instability in reduction cells is well described in a furnished literature that goes back to the 70’s. Most theoretical insights have however been found within the restrictive context of quite a number of supplementary assumptions (shallow layers, inviscid, magneto-static, negligible terms in Lorentz force). In lab-scale devices, fluid layers are however not necessarily shallow and the set-up is also small enough for viscous dissipation to become important. Finally, also the magnetic dissipation cannot be ignored given that stronger magnetic fields are necessary to trigger the instability. A critical
comparison between theory and experiments or direct numerical simulation (DNS) dedicated to lab-scale devices requires a more detailed stability model.

In this talk, I present a theoretical stability analysis dedicated to cylindrical reduction cells (2 layers). Using a perturbative approach we find explicit formula for the growth rate of the metal pad roll instability and without making the most common assumptions. We deal with fluid layers of arbitrary heights and incorporate both magnetic and viscous damping effects. We confront our theory to direct numerical simulations (DNS) that are done with two different multiphase MHD solvers (SFEMaNS and OpenFOAM). This comparison also allows us to measure what precision really is required to obtain converged three-dimensional numerical simulations.

  • Lecture (Conference)
    International workshop on liquid metal battery fluid dynamics, 16.-17.05.2017, Dresden, Deutschland

Publ.-Id: 25575

Writing magnonic waveguides in FeAl with an nano-sized ion beam

Osten, J.; Hula, T.; Wagner, K.; Xu, X.; Hlawacek, G.; Bali, R.; Potzger, K.; Lindner, J.; Fassbender, J.; Schultheiss, H.

Spin waves, the eigen-excitations of ferromagnets, are promising candidates for spin transport in lateral devices. Fe60Al40 films in the B2 phase are paramagnetic. Starting from a FeAl film in the paramagnetic phase the incident ions randomize the site occupancies and, thereby, transform it into the chemically disordered, ferromagnetic A2 phase.
The aim is to investigate spin wave propagation in this ferromagnetic material in free standing structures as well as in ferromagnetic structures embedded within a paramagnetic matrix. Using Helium-Ion microscopy we create spatially well defined ferromagnetic FeAl conduits for spin waves with resolution down to nm range. Two different ferromagnetic stripes were implanted in a microstructured paramagnetic FeAl. A freestanding 2 𝜇m width stripe. And a stripe of the same width which was embedded in a wider paramagnetic FeAl stripe. For the excitation of spin waves we processed a microwave antenna on top of these stripes. To detect spin waves we employed Brillouin light scattering microscopy. We show that the spin wave spectra are influenced by the surrounding paramagnetic material due to a different internal field distribution. The authors acknowledge financial support from the Deutsche Forschungsgemeinschaft within programme SCHU 2922/1-1.

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 19.-24.03.2017, Dresden, Deutschland

Publ.-Id: 25574

18F-Labeled indole-based analogs as highly selective radioligands for imaging sigma-2 receptors in the brain

Wang, L.; Ye, J.; He, Y.; Deuther-Conrad, W.; Zhang, J.; Zhang, X.; Cui, M.; Steinbach, J.; Huang, Y.; Brust, P.; Jia, H.

We have designed and synthesized a series of indole-based σ2 receptor ligands containing 5,6-dimethoxyisoindoline or 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline as pharmacophore. In vitro competition binding assays showed that all ten ligands possessed low nanomolar σ2 receptor affinity (Ki = 1.79–5.23 nM) and high subtype selectivity (Ki (σ2)/Ki (σ1) = 56–708). Moreover, they showed high selectivity for σ2 receptor over the vesicular acetylcholine transporter (>1000-fold). The corresponding radiotracers [18F]16 and [18F]21 were prepared by an efficient one-pot, two-step reaction sequence with a home-made automated synthesis module, with 10–15% radiochemical yield and radiochemical purity of >99%. Both radiotracers showed high brain uptake and σ2 receptor binding specificity in mice.

Keywords: sigma-2 receptors; 18F; indole-based analogs; brain

Publ.-Id: 25573

Ansys-cfx simulations – multiple size group (musig) model for bubble coalescence and break-up in multiphase flows

Liao, Y.

The main focus of the CFD department at HZDR is the qualification of CFD-codes for multiphase flows. This includes particularly model development as well as validation and testing based on high quality experimental data obtained at the TOPFLOW experimental test facility operated especially for this purpose in the research center. The models developed at HZDR are implemented into the commercial CFD-code CFX produced by the ANSYS Inc. Corporation.
The talk discusses the development of the MUSIG (Multiple-Size-Group) model for poly-disperse turbulent gas–liquid mixtures and its extension to phase change. It includes the development of a generalized model for bubble coalescence and breakup in turbulent bubbly flow, which takes into account all important mechnisms. The generalization makes it possible to use a unified set of models for different flow configurations and avoid arbitrary adjustment. The validation results for adiabatic air-water and evaporating/condesning steam-water flows are presented. In addition, the implementation of appropriate heterogeneous nucleation models for boiling flow is discussed.

Keywords: MUSIG; Poly-disperse bubbly flow; Coalescence and breakup; Nucleation; Phase change

  • Lecture (Conference)
    XXXVII Dynamics Days, Dynamics Days Europe International Conference, 05.-09.06.2017, Szeged, Hungary

Publ.-Id: 25572

Targets for high repetition rate laser facilities: needs, challenges and perspectives

Prencipe, I.; Fuchs, J.; Pascarelli, S.; Schumacher, D. W.; Stephens, R. B.; Alexander, N. B.; Briggs, R.; Büscher, M.; Cernaianu, M. O.; Choukourov, A.; de Marco, M.; Erbe, A.; Fassbender, J.; Fiquet, G.; Fitzsimmons, P.; Gheorghiu, C.; Hund, J.; Huang, L. G.; Harmand, M.; Hartley, N.; Irman, A.; Kluge, T.; Konopkova, Z.; Kraft, S.; Kraus, D.; Leca, V.; Margarone, D.; Metzkes, J.; Nagai, K.; Nazarov, W.; Lutoslawski, P.; Papp, D.; Passoni, M.; Pelka, A.; Perin, J. P.; Schulz, J.; Smid, M.; Spindloe, C.; Steinke, S.; Torchio, R.; Vass, C.; Wiste, T.; Zaffino, R.; Zeil, K.; Tschentscher, T.; Schramm, U.; Cowan, T. E.

A number of laser facilities coming on–line all over the world promise the capability of high–power laser experiments with shot repetition rates between 1 and 10 Hz. Target availability and technical issues related to the interaction environment could become a bottleneck for the exploitation of such facilities. In this paper, we report on target needs for three different classes of experiments: dynamic compression physics, electron transport and isochoric heating and laser–driven particle and radiation sources. We also review some of the most challenging issues in target fabrication and high repetition rate operation. Finally, we discuss current target supply strategies and future perspectives to establish a sustainable target provision infrastructure for advanced laser facilities.

Keywords: Target design and fabrication < High power laser related laser components; High energy density physics


Publ.-Id: 25571

Do we need improved (dual-energy) CT imaging?

Troost, E.

In the era of image-guided high-precision radiotherapy, all clinically used imaging modalities need to benefit the individual patient’s treatment outcome in order to be reimbursed. From a radiation oncologist’s point of view dual-energy CT (DECT) ought to (1) improve target volume delineation, (2) decrease proton range uncertainty and (3) guide patient stratification using advanced image analysis methods, i.e., Radiomics.

(1) With the acquisition of DECT scans more information on the tissue composition and its contrast can be gathered. This may potentially air delineation of the primary tumor and surrounding organs at risk. Possibly, even the inter-observer variability may be reduced. In order to assess whether this is a measurable effect, we are currently conducting a delineation study. However, can this potential benefit also be transferred into clinical routine?

(2) Using DECT, the prediction of electron density (for photon therapy) and stopping-power ratio (for proton therapy) can be improved. Consequently, DECT would increase overall accuracy due to a patient-specific calculation without neglecting the intra- and inter-patient tissue diversity and variability. In particle therapy, CT-related range uncertainties may be reduced and the full potential of the beam modality subsequently exploited. Do we, however, dare to directly apply this in our clinics?

(3) Apart from improved treatment planning and delivery, DECT may also further characterize the primary target volume and possibly metastatically affected lymph nodes to predict outcome and enable patient stratification. This approach has been shown beneficial on non-contrast enhanced CT scans in non-small cell lung and head and neck cancer patients. Thus far, there are no data on the value of DECT. Thus, we need to ask: Are our current imaging protocols good enough to be quantitative? Do we need standardized imaging protocols in our own institution and different institutions? What does it take to make clinical decisions based on Radiomics?

Keywords: Dual-energy CT; Radiomics; radiotherapy

  • Invited lecture (Conferences)
    Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreilaendertagung der MEDIZINISCHEN PHYSIK, 10.-13.09.2017, Dresden, Deutschland

Publ.-Id: 25570

Quantitative mineralogical analysis of European Kupferschiefer ore

Rahfeld, A.; Kleeber, R.; Möckel, R.; Gutzmer, J.

Kupferschiefer samples from five distinct deposits in Germany and Poland were studied with the aim to quantitatively determine their mineralogical composition using complementary approaches. Their inherently extremely fine-grained matrix, sheet silicate-dominated mineralogy, and highly variable copper sulphide content in the presence of organic components render quantitative mineralogical analysis difficult. In an attempt to develop a comprehensive yet feasible analytical routine for Kupferschiefer black shale and associated sandstone- and carbonate-hosted ores, analytical techniques were tested and adapted to suit this purpose. This study focuses on a combination of mineralogical approaches using quantitative X-ray diffraction (XRD) and image-based automatic mineral liberation analyses (MLA). Quantitative bulk-powder XRD was achieved by Rietveld refinement, based on phase identification and selection of suitable structural models. The identified minerals were verified with scanning electron microscopic measurements coupled with energy dispersive X-ray spectroscopy (EDX) and optical microscopy. Results of QXRD and MLA were compared to chemical assay data. It is concluded that MLA and QXRD deliver satisfactory results for this complex raw material, but only when used in combination). When used independently, XRD and MLA are susceptible to significant errors related especially to sample preparation, mineral misidentification or quantification. To assure a successful quantitative mineralogical description of complex raw materials or processing products it thus is strongly recommended to verify all mineralogical information by independent analytical techniques – and to validate quantitative mineralogical information with quantitative chemical data.

Keywords: Kupferschiefer; black shale; XRD; MLA; analysis; copper sulphides; Rietveld refinement


Publ.-Id: 25569

Impact of robust treatment planning on single- and multi-field optimized plans for proton beam therapy of unilateral head and neck target volumes

Cubillos-Mesías, M.; Baumann, M.; Troost, E. G. C.; Lohaus, F.; Löck, S.; Richter, C.; Stützer, K.

Background: Proton beam therapy is promising for the treatment of head and neck cancer (HNC), but it is sensitive to uncertainties in patient positioning and particle range. Studies have shown that the planning target volume (PTV) concept may not be sufficient to ensure robustness of the target coverage. A few planning studies have considered irradiation of unilateral HNC targets with protons, but they have only taken into account the dose on the nominal plan, without considering anatomy changes occurring during the treatment course.
Methods: Four pencil beam scanning (PBS) proton therapy plans were calculated for 8 HNC patients with unilateral target volumes: single-field (SFO) and multi-field optimized (MFO) plans, either using the PTV concept or clinical target volume (CTV)-based robust optimization. The dose was recalculated on computed tomography (CT) scans acquired during the treatment course. Doses to target volumes and organs at risk (OARs) were compared for the nominal plans, cumulative doses considering anatomical changes, and additional setup and range errors in each fraction. If required, the treatment plan was adapted, and the dose was compared with the non-adapted plan.
Results: All nominal plans fulfilled the clinical specifications for target coverage, but significantly higher doses on the ipsilateral parotid gland were found for both SFO approaches. MFO PTV-based plans had the lowest robustness against range and setup errors. During the treatment course, the influence of the anatomical variation on the dose has shown to be patient specific, mostly independent of the chosen planning approach. Nine plans in four patients required adaptation, which led to a significant improvement of the target coverage and a slight reduction in the OAR dose in comparison to the cumulative dose without adaptation.
Conclusions: The use of robust MFO optimization is recommended for ensuring plan robustness and reduced doses in the ipsilateral parotid gland. Anatomical changes occurring during the treatment course might degrade the target coverage and increase the dose in the OARs, independent of the chosen planning approach. For some patients, a plan adaptation may be required.

Keywords: proton therapy; single-field optimization; multi-field optimization; robust optimization; adaptive radiation therapy; head and neck cancer

Publ.-Id: 25568

Phage display – a new tool for the recovery of critical elements from primary and secondary sources

Lederer, F.; Matys, S.; Bachmann, S.; Curits, S.; Macgillivray, R. T. A.

The development of effective and ecofriendly processes for the recovery of critical elements poses a challenge for scientists all over the world. Beside the relevance for the environment new products and techniques have to be highly specific for target materials and be economically applicable. Critical elements such as rare earth elements are part of a multitude of modern electronic devices. However, their recycling rate is low partly due to the similar chemical and physical properties of the elements making their separation difficult.
To generate highly specific peptides that bind specifically to individual elements of interest, the phage surface display (PSD) technology was used. PSD technology was originally developed to identify peptides with high binding specificity for biological molecules such as viruses, antibodies or fusion proteins. Later the technology was successfully applied for inorganic targets as well.
In the current project four different fluorescent phosphor components were used to identify a small number of specific binding peptides via PSD. The newly identified peptides differ strongly in their amino acid composition and binding behavior. Binding properties can be improved by substitution of individual amino acids by more effective amino acids. The application of peptides in bioflotation processes is now being tested as an efficient separation process for rare earth minerals.
In summary, phage surface display is a promising tool for the development of highly specific binding peptides. The development of ecofriendly material specific collectors in bioflotation and separation processes has the potential to revolutionize traditional recycling techniques.

Keywords: bioflotation; phage surface display

  • Poster
    22.International Biohydrometallurgy Symposium, 24.-27.09.2017, Freiberg, Deutschland

Publ.-Id: 25567

Characterisation of porosity in zirconia-based nanopowders

Prochazka, I.; Cizek, J. A.; Melikhova, O.; Hruska, P.; Anwand, W.; Konstantinova, T. E.; Danilenko, I. A.

Porosity in several zirconia-based pressure compacted nanopowders was studied using the positron lifetime technique combined with the mass-density measurements. Two kinds of pores were identified: (i) the larger pores of. 10 to 19 nm diameter arising likely from a formation of secondary particle aggregates, and (ii) the smaller ones (. 1 nm) which are obviously of a more complex origin

Keywords: Nanopowders; Porosity; Positron lifetime; Zirconia

Publ.-Id: 25566

Early report on quality of life and dosimetric parameters related to adverse effects in prostate cancer patients following normo-fractionated proton therapy.

Agolli, L.; Dutz, A.; Löck, S.; Hölscher, T.; Simon, M.; Makocki, S.; Baumann, M.; Troost, E. G. C.; Krause, M.

Objectives: We report the quality of life (QoL) and the impact of dose-volume-parameters on the gastrointestinal (GI) and genitourinary (GU) toxicities in localized/locally advanced prostate cancer patients treated with definitive normo-fractionated (74-76Gy) proton therapy (PT).
Methods: Twenty-five patients treated in the context of an approved clinical study (Proto-R-Prostata) were selected. Three intraprostatic fiducial markers were placed for daily position verification. A water-filled endo-rectal balloon was placed prior to each fraction. Toxicity and QoL were collected prospectively. The first were graded according to CTCAE v4, the latter by EORTC C30 and PR25 QoL questionnaires. The organs at risk (OARs; rectal wall, whole rectum, whole bladder, bladder wall, anterior and posterior bladder wall) were re-contoured. The dose (Gy) to 5-95% of the volume of OARs (D5-D95%) was reported in 5 % increments, as the volume (cc) receiving an absolute dose of 5-75 Gy (V5-V75Gy). Correlations between dose-volume-parameters to the OARs and toxicities were modelled by logistic regression.
Results: Based on the EORTC-C30, physical functioning and social functioning had a slight worsening after PT, but they improved 3 months after PT, whereas the emotional functioning increased slightly during PT and significantly 3 month after PT (p=0.035). Role functioning showed a statistically significant decrease at the end of PT (p=0.017), but also a subsequent improvement. A correlation was found between GU toxicities during PT and the functional and symptom scale based on the EORTC-PR25 (pain, urinary symptoms and hormonal treatment related symptoms, respectively). Dose-volume parameters V5-V20Gy to the anterior bladder wall and V60–V70Gy to the posterior bladder wall were significantly related to cystitis. V5Gy, V15Gy to the posterior bladder wall and V15-V20Gy to the anterior bladder wall had significant impact on urinary incontinence and urinary frequency, respectively.
Conclusions: QoL during/after PT was reported to be good. The estimated dosimetric parameters can be useful to further plan optimization and to find adequate constraints to PT.

  • Poster
    Langendorff Symposium 2017, 14.-15.07.2017, Freiburg, Deutschland

Publ.-Id: 25565

Bio-collector based rare earth mineral flotation and recycling

Matys, S.; Lederer, F. L.; Bachmann, S.; Curtis, S.; Macgillivray, R. T. A.

Recycling of rare earth components from fluorescent phosphors of fluorescent light bulbs is focussed in the MinePep project. The current recycling rate of rare earths in spent electronic devices is less than 1%, partly due to the similar chemical and physical properties of the elements making their separation difficult. New recycling strategies needs to focus on effective and ecofriendly processes for the recovery of critical elements within such spent electronic devices. Beside the relevance for the environment, new products and techniques need to be highly-specific for target materials and be economically viable.
The identification of highly-specific bio-collector peptides for special fluorescent phosphors was successful by using phage surface display. This technique uses a phage library with a diversity of 109 different peptide expressing phage clones, where each clone expresses a different peptide sequence on one of the phage surface proteins. In affinity binding screens, the target was exposed to the phage library. Phage with a low target affinity were removed while strong binders were amplified and analyzed for their individual binding characteristics. Final goal of this approach is the application of the isolated peptides as bio-collectors in bio-flotation systems.
The fluorescent phosphors LaPO4:Ce,Tb and CeMgAl11O19:Tb were individually exposed to a phage library and highly-specific peptide expressing phage clones were identified and characterized. The amino acid compositions and the target material affinities differ significantly between the identified sequences. Phage specifically bound to the target were visualized by using phage-specific antibodies. A high number of specifically-bound phage was detected. The binding specificities of individual peptides were improved by substitution of individual amino acids within the peptide sequence.
In summary, phage surface display is a promising tool for the development of highly-specific binding peptides. The development of ecofriendly and specific collectors for use in bio-flotation and separation processes has the potential to revolutionize traditional recycling techniques.

Keywords: phage surface display; rare earth minerals; fluorescent lamp powder; flotation

  • Lecture (Conference)
    2nd. Green and Sustainable Chemistry Conference, 14.-17.05.2017, Berlin, Deutschland

Publ.-Id: 25563

Calorimetrically determined U(VI) toxicity in Brassica napus correlates with oxidoreductase activity and U(VI) speciation

Sachs, S.; Geipel, G.; Bok, F.; Oertel, J.; Fahmy, K.

Radioecological studies depend on the quantitative toxicity assessment of environmental radionuclides. In the low dose regime, the life span of affected organisms is barely shortened enabling the transfer of radionuclides through an almost intact food chain. Lethality-based toxicity estimates are not adequate in this regime because they require higher doses. In the case of radionuclides, increased dosage additionally alters radionuclide speciation, rendering the extrapolation to the low dose regime chemically inconsistent. Here, we demonstrate that microcalorimetry provides a sensitive real-time monitor of low dose toxicity of uranium (in the U(VI) oxidation state) in a plant cell model of Brassica napus. We introduce the calorimetric descriptor “metabolic capacity” and show that it correlates with enzymatically determined cell viability. It is independent of physiological models and robust against the naturally occurring fluctuations in the metabolic response to U(VI) of plant cell cultures. In combination with time-resolved laser-induced fluorescence spectroscopy and thermodynamic modeling, we show that the plant cell metabolism is affected predominantly by hydroxo-species of U(VI) with an IC50 threshold of 90 µM. The data emphasize the little exploited potential of microcalorimetry for the speciation-sensitive ecotoxicology of radionuclides.

Keywords: Uranium; plant cells; metabolism; isothermal microcalorimetry; speciation; TRLFS; thermodynamic modeling


Publ.-Id: 25562

Structure optimisation by thermal cycling for the hydrophobic-polar lattice model of protein folding

Günther, F.; Möbius, A.; Schreiber, M.

The function of a protein depends strongly on its spatial structure.
Therefore the transition from an unfolded stage to the functional fold is one of the most important problems in computational molecular biology. Since the corresponding free energy landscapes exhibit huge numbers of local minima, the search for the lowest-energy configurations is very demanding. Because of that, efficient heuristic algorithms are of high value. In the present work, we investigate whether and how the thermal cycling (TC) approach can be applied to the hydrophobic-polar (HP) lattice model of protein folding. Evaluating the efficiency of TC for a set of two-and three-dimensional examples, we compare the performance of this strategy with that of multi-start local search (MSLS) procedures and that of simulated annealing (SA). For this aim, we incorporated several simple but rather efficient modifications into the standard procedures: in particular, a strong improvement was achieved by also allowing energy conserving state modifications. Furthermore, the consideration of ensembles instead of single samples was found to greatly improve the efficiency of TC. In the framework of different benchmarks, for all considered HP sequences, we found TC to be far superior to SA, and to be faster than Wang-Landau sampling.

Publ.-Id: 25561

RNA-profiling of micromilieu parameters in different experimental hHNSCC models

Koi, L.; Wolf, A.; Linge, A.; Löck, S.; Baumann, M.; Krause, M.

Introduction: Previous in vivo studies demonstrated that hypoxia measured by pimonidazole staining is associated with local tumor control in human head and neck squamous cell carcinoma (hHNSCC). This project intends to identify and validate genes which are expressed differently in hypoxic and oxic cells and therefore may play an important role in radiation resistance. This might lead to the establishment of new targets and biomarkers for potential therapeutic. Materials and methods: Seven different hHNSCC in nude mice were studied. For gene expression analysis untreated tumors were excised and stained for pimonidazole hypoxic areas. Using laser-capture microdissection (LCM), material was collected separately from consecutive unstained slides. RNA was isolated and subjected to gene expression analysis using nanoString technologies. The applied gene panel included hypoxia classifier (Toustrup et al.) as well as genes that have been reported to be involved in radioresistance, such as genes which are encoding for putative cancer stem cell markers. Results: Several genes showed large differences in expression between hypoxic and well perfused areas. Differences were found in the expression level of hypoxia-associated genes within the hypoxic areas between the individual tumor models. In addition, the more radioresistant tumors do not necessarily coincide with the intensity of the expression of these genes. Besides the hypoxic gene signature, genes encoding for stem cell markers, are significantly different between these two micromilieu areas. Conclusion: LCM allows analysing RNA from different microenvironmental areas. We found significantly different expressions of genes which can play an important role with regard to radioresistance in tumors, and are involved in processes, such as DNA repair, proliferation and invasiveness. In this way, new targets and biomarkers could be established in order to obtain potential therapeutic approaches in combination with radiotherapy.

  • Lecture (Conference)
    15th Acta Oncologica Symposium Biology-Guided Adaptive Radiotherapy, 14.-16.06.2017, Aarhus, Dänemark

Publ.-Id: 25560

Fate of Plutonium Released from Nuclear Weapons Tests in Australia

Ikeda-Ohno, A.

In the 1950s and 1960s, a series of the British nuclear weapons tests were conducted at different sites in Australia, resulting in the significant dispersion of long-lived and highly radioactive nuclear debris. A reliable assessment of the environmental impact of these radioactive contaminants and their potential implication for human health requires an understanding of their physical/chemical characteristics. This study focuses particularly on the physical/chemical characterisation of the Pu contaminant, the most problematic radioactive contaminant remaining at the former testing sites, by synchrotron-based X-ray microscopy / spectroscopy. The chemical transformation of the Pu contaminant in the relevant environment over the last 50 years and the potential implication for radioecology will be discussed.

Keywords: Actinides; plutonium; nuclear weapons tests; radioactive contaminants; chemical analysis; synchrotron; radio ecology

  • Invited lecture (Conferences)
    Advanced Science Research Center Seminar, 18.07.2017, Tokai, Ibaraki, Japan

Publ.-Id: 25559

Evolution of antiferromagnetic domains in the all-in-all-out ordered pyrochlore Nd2Zr2O7

Opherden, L.; Hornung, J.; Herrmannsdörfer, T.; Xu, J.; Islam, A. T. M. N.; Lake, B.; Wosnitza, J.

We report the observation of magnetic domains in the exotic, antiferromagnetically ordered all-in-all-out state of Nd2Zr2O7, induced by spin canting. The all-in-all-out state can be realized by Ising-like spins on a pyrochlore lattice and is established in Nd2Zr2O7 below 0.31 K for external magnetic fields up to 0.14 T. Two different spin arrangements can fulfill this configuration which leads to the possibility of magnetic domains. The all-in-all-out domain structure can be controlled by an external magnetic field applied parallel to the [111] direction. This is a result of different spin canting mechanisms for the two all-in-all-out configurations for such a direction of the magnetic field. The change of the domain structure is observed through a hysteresis in the magnetic susceptibility. No hysteresis occurs, however, in the case the external magnetic field is applied along [100].


Publ.-Id: 25558

Materialwissenschaftliche Untersuchungen für den Orgelbau: Von Bleigieß-Rezepten des 17.Jh zu antikorrosiver Nanotechnologie

Skorupa, W.; Pelic, B.; Werner, H.; Eule, D.

Der Vortrag beschäftigt sich mit materialwissenschaftlichen Arbeiten, die in den letzten 10 Jahren stattfanden, um Probleme zu lösen, die sich aus verschiedenen Aspekten der Verwendung metallischer Werkstoffe im Orgelbau ergaben:
1. Die Zusammenarbeit begann mit der Erkundung alter Gießtechniken, wie sie im Zusammenhang mit einem Restaurierungsprojekt der Fa. Eule in Borgentreich/Ostwestfalen notwendig wurden, um Orgelpfeifen aus der Erbauungszeit der Orgel im 17.Jh und davor zu reparieren bzw. in vergleichbarer Weise nachzubauen. Dabei kam es darauf an, die Temperaturableitung am Gießtisch zu erhöhen, um dem Orgelmetall (Blei mit ca. 2% Zinn) eine feinkristalline Struktur und damit eine höhere Steifheit zu verleihen.
2. Eine weitere Arbeit bezog sich auf die Untersuchung von Korrosionsflecken auf den Prospektpfeifen von Silbermann-Orgeln im sächsischen Raum. Der Prospekt einer Orgel ist der Teil, der direkt dem Betrachter zugewandt ist, also die Pfeifen, die man vom Kirchenraum aus direkt sieht. Man sollte wissen, dass der größte Teil des Pfeifenmaterials hinter dem Prospekt verborgen ist. Dabei wurde eine weltweit relative selten verfügbare Technik eingesetzt, bei der ein hochenergetischer Ionenstrahl (Protonen mit 4 MeV) aus dem Vakuum herausgeführt und an der Oberfläche der Orgelpfeifen die Untersuchung mittel Rutherford-Rückstreuspektrometrie sowie protonen-induzierter Röntgen-und Gammastrahlungs-Spektroskopie ermöglicht.
3. Stark bleihaltiges Orgelmetall und Messing sind innerhalb von historischen, aber auch neuerbauten Orgeln korrosiver Belastung durch Essig-und Ameisensäure-Ausdünstungen aus den in den Orgeln notwendig vorhandenen Holzkonstruktionen ausgesetzt. Es wurde auf der Basis der Ionenimplantation und der Dünnschicht-Abscheidung eine Behandlungsmethode entwickelt, mit denen an der Metalloberfläche antikorrosive Schichten mit Dicken im Bereich kleiner 50 nm erzeugt werden können.

Keywords: Gießtechniken; Korrosion; Plasmaimmersions-Ionenimplantation; Orgelpfeife; Nanotechnologie; Blei-Zinn-Legierungen; Kupfer-Zink-Legierungen (Messing)

  • Lecture (others)
    Eingeladener Seminarvortrag, 26.04.2017, Steinfurt bei Münster, Deutschland

Publ.-Id: 25557

Zn-Vacancy Related Defects Identified in ZnO Films Grown by Pulsed Laser Deposition

Ling, F. C.-C.; Wang, Z.; Luo, C.; Anwand, W.; Wagner, A.

Undoped and Cu-doped ZnO grown on sapphire using pulsed laser deposition (PLD) were studied by positron annihilation spectroscopy (PAS), photoluminescence (PL), high-resolution transmission electron microscopy (HRTEM) and secondary ion mass spectroscopy (SIMS). In the undoped samples, two kinds of VZn-related defects, namely VZn1 and VZn2 are identified. VZn1 was identified in as-grown samples grown at relatively low substrate (~300°C). After annealing at 900°C, VZn-2, the green luminescence (GL) peaking at 2.47 eV and the near band edge (NBE) emission at
3.23 eV in the low temperature photoluminescence (LT-PL) were simultaneously introduced. Another kind of VZn-related defect is identified in the Cu-doped ZnO sample, and is tentatively assigned to the VZn decorated with the Cu.

Keywords: pulsed laser deposition PLD; positron annihilation spectroscopy PAS; photoluminescence PL; transmission electron microscopy TEM; secondary ion mass spectroscopy SIMS; ZnO

Publ.-Id: 25556

Fe+ Implantation Induced Damage in Oxide Dispersion Strengthened Steels Investigated by Doppler Broadening Spectroscopy

Anwand, W.; Leguey, T.; Scepanovic, M.; Jose Sanchez, F.; García-Cortés, I.; Wagner, A.

Open volume defects created by 1 MeV Fe+ implantation up to a damage of 15 displacements per atom into Fe14wt%Cr and into oxide dispersion strengthened (ODS) Fe14wt%Cr were investigated by positron annihilation spectroscopy, especially single Doppler broadening (DBS) and coincidence Doppler broadening spectroscopies (cDBS). The influence of W and Ti alloying elements on the evolution of defects during ion implantation were probed in addition. Whereas no effect of the W and Ti alloying constituents on the line-shape parameters S and W could be detected both before and after ion implantation, fine dispersed Y2O3 particles showed important changes in the structural properties compared to pure FeCr steel, which could be detected by DBS and cDBS. The distribution of the electron momenta in implanted ODS Fe14Cr, obtained with cDBS, shows that oxide particles form obstacles for expanded vacancy mobility and that the vacancies are localized around the oxide particles.

Keywords: defects implantation oxide dispersion strengthened (ODS) positron annihilation spectroscopy

Publ.-Id: 25555

E1 and M1 excitations in 54Fe and low-energy M1 strength in open-shell Fe isotopes

Schwengner, R.

Dipole excitations in the N = 28 nuclide 54Fe were studied in photon-scattering experiments using bremsstrahlung at the gELBE facility of Helmholtz-Zentrum Dresden-Rossendorf and using quasi-monoenergetic, polarized gamma beams at the HIgS facility of the Triangle Universities Nuclear Laboratory in Durham. We identified intense E1 as well as M1 transitions to spin-1 states up to about 10.6 MeV. In the second part, we present low-energy M1 strength functions of 60,64,68Fe determined on the basis of large-scale shell-model calculations with the goal to study their development from the bottom to the middle of the neutron shell. We find that the zero-energy spike develops toward the middle of the shell into a bimodal structure composed of a weaker zero-energy spike and a scissorslike resonance around 3 MeV, where the summed strengths of the two structures changes only slightly. The summed strength of the scissors region exceeds the total gammaabsorption strength from the ground state by a factor of about three, which explains the discrepancy between total strengths of the scissors resonance derived from (gamma,gamma') experiments and from experiments using light-ion induced reactions.

Keywords: Bremsstrahlung; polarized gamma beam; shell model; M1 gamma-strength function; scissors mode

  • Invited lecture (Conferences)
    6th Workshop on Nuclear Level Density and Gamma Strength, 08.-12.05.2017, Oslo, Norwegen

Publ.-Id: 25554

Simplified Expression and Production of Small Metal Binding Peptides

Braun, R.; Matys, S.; Schoenberger, N.; Lederer, F.; Pollmann, K.

Phage display for discovery of metal binding peptides is an innovative way to engineer metalsorptive biological structures with a broad spectrum of applications in geobiotechnology, for example in reusable filter modules in biosorption processes. Using state-of-the-art cloning techniques we developed an easy-to-use cloning and expression system, allowing the fast production of identified peptides.

Keywords: phage display; intein; protein engineering; Gibson Assembly; biomining; bioremediation; biosorption


Publ.-Id: 25553

Development of Cobalt- and Nickel-binding peptides for biosorption

Braun, R.; Lederer, F.; Matys, S.; Schoenberger, N.; Pollmann, K.

Usage of Phage Display for identification of peptide binding motifs has long been restricted to medical use. However, in the last years more and more publications focused on the interaction between peptides and inorganic material. Especially in Geobiotechnology the characterization of new metal-binding proteins as well as peptide motifs receives increasing attention, as they may be used in metal recovery, biosorption and bioremediation, as well. Here, we describe the application of artificial peptides for the recovery of metal ions form solutions, e.g. leachates. Limitations arise from complicated identification of metal-binding peptides, from high productions costs of chemical synthesized peptides and difficult heterologous expression of small peptides, as they are relatively fast proteolyzed. Therefore applications of such peptides require efficient and economic production systems.
In the present study we aimed for the development of an efficient expression system, expressing previously via Phage Display and Deep sequencing identified peptides as fusions proteins with integrated purification and cleavage tags. Characterization of the purified peptides was performed using quartz crystal microbalance with dissipation monitoring using special coatings for metal immobilization. Knowledge about peptide motifs and metal affinity is crucial for the intended usage of peptides in biosorption processes, e.g. immobilized on membranes. Furthermore, detailed information about peptide-metal interaction may lead to discovery of novel metal-incorporating and –binding enzymes.

Keywords: phage display; peptide; biosorption; metal-binding protein

  • Poster
    22. International Biohydrometallurgy Symposium, 24.-27.09.2017, Freiberg, Deutschland

Publ.-Id: 25552

Development of Cobalt- and Nickel-binding peptides for biosorption

Braun, R.

Usage of Phage Display for identification of peptide binding motifs has long been restricted to medical use. However, in the last years more and more publications focused on the interaction between peptides and inorganic material. Especially in Geobiotechnology the characterization of new metal-binding proteins as well as peptide motifs receives increasing attention, as they may be used in metal recovery, biosorption and bioremediation, as well. Here, we describe the application of artificial peptides for the recovery of metal ions form solutions, e.g. leachates. Limitations arise from complicated identification of metal-binding peptides, from high productions costs of chemical synthesized peptides and difficult heterologous expression of small peptides, as they are relatively fast proteolyzed. Therefore applications of such peptides require efficient and economic production systems. In the present study we aimed for the development of an efficient expression system, expressing previously via Phage Display and Deep sequencing identified peptides as fusions proteins with integrated purification and cleavage tags. Characterization of the purified peptides was performed using quartz crystal microbalance with dissipation monitoring using special coatings for metal immobilization. Knowledge about peptide motifs and metal affinity is crucial for the intended usage of peptides in biosorption processes, e.g. immobilized on membranes. Furthermore, detailed information about peptide-metal interaction may lead to discovery of novel metal-incorporating and –binding enzymes.

Keywords: phage display; peptide; biosorption

  • Lecture (others)
    Microbiology Meeting HZDR - TU Bergakademie Freiberg, 09.01.2017, Freiberg, Deutschland

Publ.-Id: 25551

Development of Cobalt- and Nickel binding peptides for biosorption

Braun, R.; Matys, S.; Pollmann, K.

Interactions between proteins and metals long been scientifically described but still remain hardly understood. They may be used for industrial purposes. In Geobiotechnology metal binding motifs of proteins and peptides are a promising tool in bioremediation as well as in biosorption processes for the recovery of metals. In this work peptide motifs, which have previously been identified using Phage Display, are characterized for their ability to specifically bind cobalt and nickel ions and for their applicability in industrial biosorption processes. Biosorption may be a future alternative to conventional metal sorption processes, as it is less energy-consuming, environmental-friendly and highly selective.

Keywords: biosorption; peptide; metal recovery; phage display

  • Poster
    HZDR PhD seminar, 17.-19.10.2016, Oberwiesenthal, Deutschland

Publ.-Id: 25550

Glacier melt buffers river runoff in the Pamir Mountains

Pohl, E.; Gloaguen, R.; Andermann, C.; Knoche, M.

Newly developed approaches based on satellite altimetry and gravity measurements provide promising results on glacier dynamics in the Pamir-Himalaya but cannot resolve short-term natural variability at regional and finer scale. We contribute to the ongoing debate by upscaling a hydrological model that we calibrated for the central Pamir. The model resolves the spatiotemporal variability in runoff over the entire catchment domain with high efficiency. We provide relevant information about individual components of the hydrological cycle and quantify short-term hydrological variability. For validation, we compare the modeled total water storages (TWS) with GRACE (Gravity Recovery and Climate Experiment) data with a very good agreement where GRACE uncertainties are low. The approach exemplifies the potential of GRACE for validating even regional scale hydrological applications in remote and hard to access mountain regions. We use modeled time series of individual hydrological components to characterize the effect of climate variability on the hydrological cycle. We demonstrate that glaciers play a twofold role by providing roughly 35% of the annual runoff of the Panj River basin and by effectively buffering runoff both during very wet and very dry years. The modeled glacier mass balance (GMB) of -0.52 m w.e. / yr (2002–2013) for the entire catchment suggests significant reduction of most Pamiri glaciers by the end of this century. The loss of glaciers and their buffer functionality in wet and dry years could not only result in reduced water availability and increase the regional instability, but also increase flood and drought hazards.

Keywords: Upscaling; hydrological model; Pamir; multisource validation data; glaciers; buffer; extreme meteorological events; sustainable river runoff; climate; hydrological cycle

Publ.-Id: 25549

Dual-energy CT for photon therapy – benefits and limitations

Möhler, C.; Wohlfahrt, P.; Richter, C.; Greilich, S.

In current treatment planning for both photon and particle therapy, a heuristic Hounsfield look-up table (HLUT) is used for the conversion of CT numbers to electron density or particle stopping-power ratios, respectively. However, this conversion is ambiguous and cannot account for patient-specific tissue variability or non-tissue materials (e.g., implants, contrast agent). This can lead to substantial difference in dose distributions. In contrast, dual-energy computed tomography (DECT) allows for direct patient- and tissue- specific determination of radiological quantities. Therefore, DECT is currently being investigated by many groups as an alternative imaging modality.
While the benefit of DECT is rather pertinent in particle therapy, where an accurate range prediction is crucial, we suggest that it might also improve conventional photon treatment planning, especially in the presence of non-tissue materials such as implants. In this context, DECT-based material characterization can help to identify implants of unkown composition. Moreover, their electron density can automatically be correctly assigned, as the DECT algorithm does not require tissue equivalency. This might provide more accurate dose distributions in cases, where the beam traverses a non-tissue material that would deviate considerably from the HLUT.
Furthermore, the acquisition of a DECT scan of patients with administered contrast agent enables the calculation of an image, where the influence of the contrast agent can effectively be removed. This would render the additional native CT scan obsolete, reducing overall CT dose to the patient. Finally, DECT also allows for a certain tuning of contrast by an overlay of the two images, which might be exploited for diagnostic or delineation purposes.

  • Lecture (Conference)
    Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreiländertagung der MEDIZINISCHEN PHYSIK, 10.-13.09.2017, Dresden, Germany

Publ.-Id: 25548

Dual-energy CT for particle therapy – benefits and limitations

Wohlfahrt, P.; Möhler, C.; Greilich, S.; Richter, C.

Due to the physical advantages of particles in energy deposition compared to photons, a high-conformal tumor coverage can be reached while sparing healthy tissue more effectively. However, particle treatment planning is currently associated with large uncertainties related to a CT-based stopping-power and eventually particle range prediction. To fully exploit the physical benefit of particles, this substantial part of the overall range uncertainty of approximately 3.5% of total range should be reduced.
Dual-energy CT (DECT) imaging is a promising technique to increase the accuracy of CT-based range predictions as already shown by many research groups. The effective benefit of DECT for particle treatment planning of cancer patients is currently proven using a comprehensive validation scheme to quantify the potential reduction of range uncertainties in daily clinical practise. In the framework of a joint project between DKFZ and OncoRay, extensive investigations on different levels (inhomogenous phantoms, biological tissue, clinical patient scans) have been performed. Here, a considerably improved accuracy of DECT compared to the current state-of-the-art, single-energy CT (SECT), could be shown in an anthropomorphic ground-truth phantom and biological tissues. Moreover, relative comparisons of predicted particle ranges in more than 100 proton treatment fields of patients reveal median range deviations of 1.5 – 2.0 % of total range between DECT and SECT. Based on these results, the clinical use of DECT-based range prediction would clearly improve the accuracy and robustness of particle treatment planning and is thus highly recommended to be the new standard imaging modality for treatment planning in particle therapy.

  • Lecture (Conference)
    Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreiländertagung der MEDIZINISCHEN PHYSIK, 10.-13.09.2017, Dresden, Germany

Publ.-Id: 25547

Comparative analysis of uranium bioassociation with halophilic bacteria and archaea

Bader, M.; Müller, K.; Foerstendorf, H.; Schmidt, M.; Simmons, K.; Swanson, J. S.; Reed, D. T.; Stumpf, T.; Cherkouk, A.

Rock salt represents a potential host rock formation for the final disposal of radioactive waste. The interactions between indigenous microorganisms and radionuclides, e.g. uranium, need to be investigated to better predict the influence of microorganisms on the safety assessment of the repository. Hence, the association process of uranium with two microorganisms isolated from rock salt was comparatively studied. Brachybacterium sp. G1, which was isolated from the German salt dome Gorleben, and Halobacterium noricense DSM15987T were selected as examples of a moderately halophilic bacterium and an extremely halophilic archaeon, respectively. The microorganisms exhibited completely different association behaviors with uranium. While a pure biosorption process took place with Brachybacterium sp. G1 cells, a multistage association process occurred with the archaeon. In addition to batch experiments, in situ attenuated total reflection Fourier-transform infrared spectroscopy was applied to characterize the U(VI) interaction process. Biosorption was identified as the dominating process for Brachybacterium sp. G1 with this method. Carboxylic functionalities are the dominant interacting groups for the bacterium, whereas phosphoryl groups are also involved in U(VI) association by the archaeon H. noricense.

Keywords: nuclear waste repository; microorganisms from rock salt; Brachybacterium; Halobacterium; in situ ATR FT-IR spectroscopy

Publ.-Id: 25546

Recent Progress using the Staudinger Ligation for Radiolabeling Applications

Mamat, C.; Gott, M.; Steinbach, J.

The increasing application of positron emission tomography (PET) and single photon emission computer tomography (SPECT) in radiopharmacy and nuclear medicine has stimulated the development of a multitude of novel and versatile bioorthogonal conjugation techniques. Currently, there is particular interest in radiolabeling biologically active, high molecular weight compounds like peptides, proteins or antibodies, but also for the labeling of small organic compounds. An enormous challenge in radiolabeling these biologically active molecules is that the introduction of radiohalogens like fluorine-18 as well as various radiometals proceeds under harsh conditions, which could destroy the biomolecule.
The Staudinger Ligation is one of the most powerful bioorthogonal conjugation techniques. The reaction proceeds over wide temperature and pH ranges; an amide (peptide) bond is formed as the ligation unit, which minimizes distortion of the structure; no isomers are obtained; and the reaction proceeds without any metal catalyst. Due to this adaptability, this robust ligation type is a perfect candidate with a high potential for various applications in the field of radiopharmacy for the labeling of biomolecules under mild conditions.
This review summarizes recent research concerning the implementation of the Staudinger Ligation for radiolabeling applications.

Keywords: fluorine-18; Staudinger Ligation; click chemistry; bioorthogonal

  • Open Access Logo Journal of Labelled Compounds and Radiopharmaceuticals 61(2018), 165-178
    DOI: 10.1002/jlcr.3562


Publ.-Id: 25545

Development of metal ion binding peptides using phage surface display technology

Schönberger, N.; Matys, S.; Flemming, K.; Lehmann, F.; Lederer, F.; Pollmann, K.

Phage surface display technology is a useful tool for the identification of biosorptive peptides. In this work it is used for the identification of cobalt, nickel and gallium binding peptides. We present methods for the enrichment of metal ion binding bacteriophage clones from a commercial phage display library. Metal ion selective peptides are suitable to separate as well as concentrate cobalt and nickel from copper black shale leaching products (EcoMetals project) and gallium from industrial waste waters (EcoGaIn project). In contrast to common capture methods of specific binding phage for solid materials the ionic species have to be immobilized prior to the bio-panning procedure. This was realized by chemical complexation of the metal ions using commercial complexing agents on porous matrices. Moreover, an option to harvest non elutable strong binding phage is proposed.

Keywords: Phage Surface Display; biopanning; immobilized metal ions; nickel; gallium; cobalt; metal binding peptides

  • Contribution to proceedings
    22. International Biohydrometallurgy Symposium, 24.-27.09.2017, Freiberg, Deutschland
    22. International Biohydrometallurgy Symposium 2017

Publ.-Id: 25544

SIMS on smallest scale

Klingner, N.; Heller, R.; Hlawacek, G.; Facsko, S.

Ongoing miniaturization in semiconductor industry, nanotechnology and life science demands further improvements for high-resolution imaging, fabrication and analysis of the produced nanostructures. Continuously shrinking object dimensions lead to an enhanced demand on spatial resolution and surface sensitivity of modern analysis techniques. Secondary Ion Mass Spectrometry (SIMS), as one of the most powerful technique for surface analysis, performed on nanometer scale may comply with this challenge. The mass of sputtered ions directly serves elemental and molecular information and even allows measuring isotope concentrations.

During last decades, primary ion species used in SIMS have optimized in terms of best ionization probabilities and small molecule fragmentation. Thereby, highest mass-resolution has been one of the biggest design goals in the development of new SIMS spectrometers. In contrast to former developments, our approach aims for ultimate lateral resolution.

Typically the lateral resolution is limited by the probe size of the primary ion beam. Minimal probe sizes can be achieved using Gas Field Ionization Sources (GFIS) in a Helium Ion Microscope (HIM). Due to the high brightness of up to 5•109 A•cm-2•sr-1 and the sharp primary ion energy of 30000 ± 1 eV spot sizes below 1 nm can be achieved. In recent years Helium Ion Microscopy has been developed as a valuable tool for nanofabrication and high-resolution imaging. However, in terms of analytical capabilities it is still lacking behind electron microscopes. Recently, we implemented Time of Flight (TOF) spectrometry to the HIM and thus enabled the measurement of the energy of backscattered particles and simultaneously the mass of sputtered ions [1, 2]. SIMS has also been achieved by adding a sophisticated magnetic sector field analyzer to the HIM [3]. In this way SIMS could be performed with unprecedented spot sizes.

Using a sufficient small ion probe size in the HIM the achievable lateral resolution for bulk samples is mainly determined by the size of the collision cascade and the sputtering process by impinging primary ions and backscattered particles. Different binary collision codes were utilized to simulate the ion-solid interaction for various beam and sample parameters. Here we discuss the origin of sputtered particles with respect to the primary ion impact. We will show simulation results for pristine samples as well as in dependence of increasing ion beam fluence. The size of the collision cascade influences the intermixing behavior and therefore the achievable depth resolution [3]. Low primary ion energies would be favorable but widen the spot size in the microscope.

Another constrain for the limited minimal resolution is the finite amount of available sample material, which is analyzed. Therefore it is crucial to collect as much information on the sample composition as possible prior the destruction or intermixing of the sample layers. Collection efficiency of the ion extraction optics should be close to one. Ultimately, the detection limit for an element is determined by the ratio of charged emitted particles during sputtering. This so-called useful yield (UY) was studied for Helium and Neon and could be enhanced by Oxygen gas flooding on the sample surface [4]. The detection limit was calculated for various minimal feature sizes for a 10nm thick layer (Fig 1). Unfortunately the charge state of sputtered particles is strongly influenced by the surface chemistry, which makes quantification hard and standards necessary.

Fig 1: Detection Limit for SIMS as a function of the minimum feature size and a layer thickness of 10 nm for various usefull yields (UY).

The available space in the HIM is strongly limited by the arrangement of multiple devices around the focal point making it necessary to extract the secondary ions and guide them to the mass spectrometer. We will discuss benefits and drawbacks of several approaches.

As a common feature for all kind of mass spectrometers, the ions have to be extracted in a narrow beam and accelerated to a sharp ion energy. Simultaneously, the applied extraction fields near the sample surface or extensions should not distort the primary beam focus and influence the optical performance of the microscope.

The TOF spectrometer presented here is minimal invasive to the microscope and therefore the high-resolution capabilities of the device are not derogated when the TOF setup is not in use. The system can be retrofitted and flange-mounted on one of the free ports the HIM offers.

The TOF measurements are triggered by blanking the primary ion beam into an existing Faraday cup and release the beam for short time windows to ensure minimal applied fluence. Using a custom made blanking electronic we could achieve pulse lengths down to 17 ns. The sputtered secondary ions are accelerated by applying a bias voltage up to +/-500 V towards the extraction system on ground potential. We used ion optics simulations and a genetic algorithm to tune the ion optics inside the spectrometer for high mass resolution and high extraction efficiency. A trajectory simulation for the secondary ions flight paths within the ion extraction system is shown in Fig. 2.

Fig 2: Simulated trajectories of 1000 ions through the ion extraction optics. For best extraction efficiency the sample (on the left side) must be oriented towards the extraction system. The optics was designed to use a maximum extraction potential of +/-500V to ensure use of standard sample holder.

The secondary ion mass spectrometry technique can be used in the microscope to measure mass spectra of selected regions of interest, to create depth profiles on small spots or to map the lateral distribution of selected element masses. The measurements are recorded in list mode and allow post evaluation. Preliminary TOF-SIMS spectra obtained from different samples are presented in Fig 3.

Fig 3: Secondary ion mass spectra using preliminary extraction system for different samples. (a) Reference sample containing carbon, silicon, nickel and gold (b) aluminum foil (c) organic glue.

TOF-SIMS in the HIM is perfectly capable of delivering an excellent elemental contrast for imaging purposes. However the lateral resolution could not reach the intrinsic imaging capabilities by just measuring the secondary electron yield. In order to combine the elemental information with the high resolution imaging correlative microscopy represents the best way. However, quantification of elements in mixed layers cannot be done from pure SIMS measurements without comparison to standards. This drawback of SIMS is partly compensated by additional measurement of TOF backscattering spectra.

In the present contribution we intent to present the technical realization of our TOF-SIMS approach and show first results, drawbacks and derived conclusions for the practical use of this promising technique. We will further stress out the benefits of correlative measurements in different modes (SIMS, backscattered particles, secondary electrons), giving a maximum of information on the subject of interest.

[1] N. Klingner, R. Heller, G. Hlawacek, J. von Borany, J.A. Notte, J. Huang, S. Facsko. Ultramicroscopy 162 (2016), 91-97
[2] R. Heller, N. Klingner, G. Hlawacek. Helium Ion Microscopy, Chapter 12, Springer (2016)
[3] T. Wirtz, D. Dowsett, P. Philipp. Helium Ion Microscopy, Chapter 13. Springer (2016)
[4] T. Wirtz, N. Vanhove, L. Pillatsch, D. Dowsett, S. Sijbrandij, J.A. Notte. Applied Physics Letters 101 (2012)

  • Invited lecture (Conferences)
    23-rd International Conference of Ion-Surface Interactions 2017, 21.-25.08.2017, Moscow, Russia

Publ.-Id: 25543

Influence of Electric Fields on the Electron Transport in Donor–Acceptor Polymers

Förster, A.; Günther, F.; Gemming, S.; Seifert, G.

The influence of an electric field on different properties of the donor–acceptor polymer diketo-pyrrolo-pyrrole bithiophene thienothiophene (DPPT-TT) that are essential for the charge transport process is studied. The main focus is on whether the transport in DPPT-TT-based organic transistors can be tuned by electric fields in the gate direction. The considered electric fields are in the range 108–1010 V m–1. We show that strong electric fields (∼109 V m–1) which are parallel to the polymer backbone can influence the reorganization energy in a Markus-type approach. Weaker electric fields parallel to the polymer backbone result in minimal changes to the reorganization energy. The coupling element of DPPT-TT shows a pronounced affinity to be influenced by electric fields in the charge transport direction independent of the field strength.

Keywords: organic electronics; Marcus model; transfer matrix elements; conductivity; mobility; field effect


Publ.-Id: 25540

Evaluation of stopping-power prediction by dual- and single-energy computed tomography in an anthropomorphic ground-truth phantom

Wohlfahrt, P.; Möhler, C.; Richter, C.; Greilich, S.

Purpose: To determine the accuracy of particle range prediction for proton and heavier ion radiotherapy based on dual-energy computed tomography (DECT) in a realistic inhomogeneous geometry and to compare it to the state-of-the-art clinical approach.

Methods and Materials: A 3D ground-truth map of stopping-power ratios (SPRs) was created for an anthropomorphic head phantom by assigning measured SPR values to segmented structures in a high-resolution CT scan. This reference map was validated independently comparing proton transmission measurements to Monte Carlo transport simulations.
Two DECT-based methods for direct SPR prediction via the Bethe formula (DirectSPR) and two established approaches based on Hounsfield look-up tables (HLUTs) were chosen for evaluation. SPR predictions from the four investigated methods were compared to the reference, employing material-specific voxel statistics and 2D gamma analysis. Furthermore, range deviations were analyzed in an exemplary proton treatment plan.

Results: The established reference SPR map was successfully validated for the discrimination of SPR and range differences well below 0.3% and 1 mm respectively, even in complex inhomogeneous settings. For the phantom materials of larger volume (mainly brain, soft tissue), the investigated methods were overall able to predict SPR within 1% median deviation. The DirectSPR methods generally performed better than the HLUT approaches. For smaller phantom parts (such as cortical bone, air cavities), all methods were affected by image smoothing, leading to considerable SPR under- or overestimation. This effect was superimposed on the general SPR prediction accuracy in the exemplary treatment plan.

Conclusions: DirectSPR predictions proved to be more robust with high accuracy in particular for larger volumes. In contrast, HLUT approaches exhibited a fortuitous component. The evaluation of accuracy in a realistic phantom with validated ground-truth SPR represents a crucial step towards possible clinical application of DECT-based SPR prediction methods.

Publ.-Id: 25539

Ultrabroadband single-cycle terahertz pulses with peak fields of 300 kV cm-1 from a metallic spintronic emitter

Seifert, T.; Jaiswal, S.; Sajadi, M.; Jakob, G.; Winnerl, S.; Wolf, M.; Kläui, M.; Kampfrath, T.

To explore the capabilities of metallic spintronic thin-film stacks as a source of intense and broadband terahertz electromagnetic fields, we excite a W/CoFeB/Pt trilayer on a large-area glass substrate (diameter of 7.5 cm) by a femtosecond laser pulse (energy 5.5 mJ, duration 40 fs, wavelength 800 nm). After focusing, the emitted terahertz pulse is measured to have a duration of 300 fs, a peak field of 300 kV cm-1 and an energy of 5 nJ. In particular, the waveform exhibits a gapless spectrum extending from 1 to 10 THz (at 10% of amplitude maximum).


Publ.-Id: 25538

99mTechnetium-based Small Molecule Radiopharmaceuticals and Radiotracers Targeting Inflammation and Infection

Kniess, T.; Laube, M.; Wüst, F.; Pietzsch, J.

In nuclear medicine the detection of inflamed and infected lesions is of growing interest and extensive efforts have been made to develop radiopharmaceuticals specific for inflammation or rather for discrimination of sterile inflammation from infection. 99mTc is the worldwide most-used radioisotope for SPECT investigations; the scope of this review article is to give an overview on the development of 99mTc-labeled small molecule radiotracers targeting inflammatory and infected lesions, from their radiopharmacological evaluation up to examples of clinical application. A systematic overview of 99mTc-citrate, 99mTc-antibiotics and antifungal agents as well as 99mTc-labeled antimicrobial peptides is provided. Additionally, the class of 99mTc-labeled cyclooxygenase-2 inhibitors is discussed, since cyclooxygenases are known to play a key role in inflammatory but also in malignant neoplastic diseases.


Publ.-Id: 25537

Bunch arrival-time monitor for synchronization of high power lasers and electron LINACs

Krämer, J. M.; Kuntzsch, M.; Couperus, J. P.; Zarini, O.; Köhler, A.; Lehnert, U.; Michel, P.; Irman, A.; Schramm, U.

The ELBE center of high power radiation sources at Helmholtz-Zentrum Dresden-Rossendorf combines a superconducting CW linear accelerator with Terawatt- and Petawatt-class laser sources. Key applications like the Thomson scattering x-ray source PHOENIX or external injection of electron bunches into a laser wakefield accelerator rely on precise timing and synchronization between the different radiation pulses.
An online single shot monitoring system has been set up measuring the timing between the high-power Ti:Sa laser DRACO and electron bunches generated by the conventional SRF accelerator. It uses a broadband RF pickup to acquire a probe of the particle bunch’s electric field and modulates a fraction of the high power laser pulse in a fast electro-optical modulator. The amplitude modulation gives a direct measure for the timing between both beams. Using this setup a resolution of <200 fs RMS has been demonstrated. The contribution will show the prototype, first measurement results and will discuss future modification in order to improve the resolution of the system.

  • Poster
    IPAC17 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Kopenhagen, Dänemark

Publ.-Id: 25536

Redshift and harmonic radiation of nonlinear Laser-Thomson scattering

Krämer, J. M.; Irman, A.; Jochmann, A.; Pausch, R.; Debus, A.; Couperus, J. P.; Köhler, A.; Zarini, O.; Kuntzsch, M.; Budde, M.; Lehnert, U.; Wagner, A.; Bussmann, M.; Cowan, T.; Schramm, U.

Thomson scattering of intense laser pulses from relativistic electrons not only allows for the generation of bright x-ray pulses but also serves as a laboratory for strong field physics and nonlinear interactions. We present high resolution angle and energy resolved characterization of laser-Thomson scattered X-rays generated by colliding picosecond electron bunches from the superconducting ELBE linear accelerator with counter-propagating laser pulses from the 150 TW DRACO Ti:Sapphire laser system.
The measurements quantify the influence of the two major interaction parameters, namely laser intensity and electron beam emittance, on the spectral bandwidth of the scattered photons. We also record and spectrally resolve the increasing redshift of the fundamental of the radiation, the rise of harmonics as well as the gain in total photon flux for increasing laser strength.
Numerical simulations of both studies performed with the classical radiation solver CLARA show good agreement, benchmarking this code with the experiments.

  • Poster
    IPAC17 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Kopenhagen, Dänemark

Publ.-Id: 25535

Redshift and harmonic radiation of nonlinear Laser-Thomson scattered X-rays

Krämer, J. M.; Irman, A.; Jochmann, A.; Pausch, R.; Debus, A.; Couperus, J. P.; Köhler, A.; Zarini, O.; Kuntzsch, M.; Budde, M.; Lehnert, U.; Wagner, A.; Bussmann, M.; Cowan, T.; Schramm, U.

Thomson scattering of intense laser pulses from relativistic electrons not only allows for the generation of bright x-ray pulses but also serves as a laboratory for strong field physics and nonlinear interactions. We present high resolution angle and energy resolved characterization of laser-Thomson scattered X-rays generated by colliding picosecond electron bunches from the superconducting ELBE linear accelerator with counter-propagating laser pulses from the 150 TW DRACO Ti:Sapphire laser system.
The measurements quantify the influence of the two major interaction parameters, namely laser intensity and electron beam emittance, on the spectral bandwidth of the scattered photons. The experimental range of normalized laser intensities (a0 from 0.15 to 1.7) covers the transition region from the linear to the nonlinear regime of the Thomson scattering interaction. In this parameter scan, we record and spectrally resolve the increasing redshift and broadening of the fundamental of the radiation, the rise of hamonics as well as the gain in total photon flux.
In the second study, we vary the interaction geometry, which allows for selecting only parts of the electron bunch to interact with the laser. By this means, we control the ensemble of interaction angles which is measured by the effective emittance of the electron beam. The bandwidth of the Thomson spectrum increases with the effective emittance, which can be used as a tuning knob for shaping the Thomson spectrum.
Numerical simulations of both studies performed with the classical radiation solver CLARA show good agreement, benchmarking this code with the experiments.

  • Lecture (Conference)
    SPIE Optics + Optoelectronics, 24.-27.04.2017, Prag, Tschechien

Publ.-Id: 25534

High-speed asynchronous optical sampling based on GHz Yb:KYW oscillators

Li, C.; Krauß, N.; Schäfer, G.; Ebner, L.; Kliebisch, O.; Schmidt, J.; Winnerl, S.; Hettich, M.; Dekorsy, T.

A low-cost scheme of high-speed asynchronous optical sampling based on Yb:KYW oscillators is reported. Two GHz diode-pumped oscillators with a slight pulse repetition rate offset serve as pump and probe source, respectively. The temporal resolution of this system is limited to 500 fs mainly by the pulse duration of the oscillators and also by relative timing jitter between the oscillators. A near-shot-noise noise floor around 10−6 (ΔR/R) is obtained within a data acquisition time of a few seconds. The performance of the system is demonstrated by measurements of coherent acoustic phonons in a semiconductor sample that resembles a semiconductor saturable absorber mirror or an optically pumped semiconductor chip.

Publ.-Id: 25533

Thermal Rayleigh-Marangoni convection in a liquid-metal-battery model

Köllner, T.; Boeck, T.; Schumacher, J.

The operation of a liquid metal battery (LMB) produces Ohmic losses in the electrolyte layer that separates both electrodes. As a consequence, temperature gradients will be established making the system prone to thermal convection since density and interfacial tension depend on the local temperature. The knowledge of convective transport mechanisms in LMBs is necessary for their design, e.g. preventing short-circuits and controlling the temperature.
Our numerical investigations follow recent studies of Shen and Zikanov that considered a three-layer model consisting of a liquid metal alloy cathode, a molten salt separation layer, and a liquid metal anode at the top. Both electrodes are held at a fixed ambient temperature. The model of Shen and Zikanov based on the Navier-Stokes-Boussinesq and heat transport equations, is extended by including interfacial tension gradients (the Marangoni effect) and completely accounting for all differences in the transport properties between phases.
We analyzed the linear stability of pure thermal conduction and performed three-dimensional direct-numerical simulations by a pseudospectral method, where we probed different: electrolyte layer heights, overall heights, and current densities.
Four instability mechanisms are identified, which are partly coupled to each other: buoyant convection in the upper electrode, buoyant convection in the molten salt layer, and Marangoni convection at both interfaces between molten salt and electrode.
The linear stability analysis confirms that the additional Marangoni effect increases the growth rates of the linearly unstable modes, i.e., Marangoni and Rayleigh-B\'{e}nard instability act together in the molten salt layer.
The critical Grashof and Marangoni numbers (based on the bottom electrode properties) decrease with increasing middle layer thickness. The calculated thresholds for the onset of convection are found to appear at practical current densities of laboratory-sized LMBs. The global turbulent heat transfer follows scaling predictions for internally heated buoyant convection. In summary, our studies show that incorporating Marangoni effects generates smaller flow structures, alters the velocity magnitudes, and enhances the turbulent heat transfer across the triple-layer configuration.

  • Lecture (Conference)
    International workshop on liquid metal battery fluid dynamics, 16.-17.05.2017, Dresden, Deutschland

Publ.-Id: 25532

Transparent Conductive Oxides as Selective Transmitters for solar thermal applications

Lungwitz, F.; Schumann, E.; Janke, D.; Escobar-Galindo, R.; Gemming, S.; Krause, M.

In solar-thermal power plants the receiver tubes are one of the key components for increasing the efficiency of concentrated solar power (CSP) technology. Absorber materials of those tubes have to exhibit high-temperature and air stability, high optical absorption in the solar region and low thermal emittance. Temperatures of up to 400 °C and up to 550 °C are reached in currently operated parabolic trough and central receiver plants, respectively. The CSP efficiency could be increased by 15 to 20% applying operation temperatures of around 800 °C. In state of the art central tower plants black paints are used as absorber material. Due to limited stability they have to be periodically replaced. Furthermore the high emissivity of those paints leads to high radiative energy losses. Most of the R&D approaches for high-temperature solar receiver materials are focused on complex multilayer coatings.
Here, an alternative concept for high-temperature stable solar-selective coatings is presented. It consists of a transparent conductive oxide (TCO) deposited as solar-selective transmitter on a black body absorber. The latter is responsible for high absorption in the solar spectral range (300 nm – 2000 nm), the former ensures low emissivity in the infrared range (> 2000 nm) and oxidation resistance. The concept is easily implementable and combines significant improvements of CSP technology performance and cost competiveness.
This study is focused on the solar-selective transmitter component of the concept. For this purpose, SnO2:Ta thin films are reactively magnetron co-sputtered from tantalum doped and undoped tin targets at high temperatures on fused quartz, silicon and carbon substrates. Their optical properties are tailored to meet the specific requirements of a solar-selective transmitter coating. The correlation between structural, optical, and electrical properties is analyzed by Raman spectroscopy, spectroscopic ellipsometry (SE) and Rutherford backscattering spectrometry (RBS). All the techniques are applied in situ at high- temperatures in a cluster tool. In order to simulate real operating conditions, cyclic heating tests and heating in reactive atmospheres are conducted. Additionally, X-ray Diffraction (XRD), UV-VIS spectrometry, and Hall Effect measurements are performed. It is shown that structural parameters like e.g. grain sizes and dopant concentration result in different electrical properties and as a result determine the optical behavior like spectral selectivity of the TCO.
Financial support by the EU, grant No. 645725, project FRIENDS2, and the HGF via the W3 program (S.G.) is gratefully acknowledged.

Keywords: TCO; solar-thermal electricity (STE); concentrated solar power (CSP); solar selectivity

  • Lecture (Conference)
    MRS Spring Meetings & Exhibit 2017, 17.-21.04.2017, Phoenix, Arizona, USA

Publ.-Id: 25531

In situ RBS, Raman, and ellipsometry study of nickel-catalyzed amorphous carbon graphitization

Janke, D.; Hulman, M.; Wenisch, R.; Lungwitz, F.; Gemming, S.; Rafaja, D.; Krause, M.

Metal-induced crystallization with and without layer exchange (MIC w/o LE) is a method to decrease the crystallization temperature of amorphous group 14 elements (G14E) by up to several hundred degrees. In situ experiments are expected to provide new insights into thin film evolution and elementary process steps of MIC w/o LE and to improve existing models of this type of phase transformation. While MIC w/o LE has been widely studied for Si and Ge in contact with catalytic metals, there exist only a few studies for the crystallization of amorphous carbon. Therefore, in this contribution in situ Rutherford backscattering spectrometry (RBS), Raman spectroscopy and spectroscopic ellipsometry studies were performed during annealing of amorphous carbon/nickel (a-C/Ni) layer stacks at temperatures up to 750°C.
Due to its small lattice mismatch with the basal plane of graphite and high diffusivity of C atoms, Ni is a suitable catalyst for the growth of graphene and crystalline graphitic nanostructures. During the annealing of an a-C/Ni layer stack covalent bonds between the carbon atoms at the catalyst interface are weakened. Liberated carbon atoms can move along the interface and diffuse along the grain boundaries into the Ni layer towards the catalyst surface, where nucleation and grain growth of graphitic crystallites occur. Our in situ studies showed a change in the stacking sequence between C and Ni layers under defined experimental conditions. According to in situ Raman measurements, this mechanism occurs independent of the stacking sequence, while the velocity of the LE differs significantly. As observed in time and temperature resolved Raman spectra, the position of the G peak and the I(D)/I(G) ratio changed according to the Three-Stage-Model by Ferrari and Robertson, confirming the transformation of amorphous carbon to nc-graphite. With the in situ RBS measurements more insight into LE was given. Here peak positions of C and Ni were shifted, indicating a change of the energy of the scattered ions for both layers respectively and proving the combination of the observed graphitization process with LE during annealing. The thickness of the synthesized crystalline graphitic layer is controlled by the finite carbon source – the deposited a-C film, which is a decisive advantage of this process compared to CVD. It is demonstrated that the structure and the crystallite size of the metallic catalyst layer has a strong influence on the crystallite size and the quality of the graphitic film.
LE is potentially interesting for industrial applications, as it allows the formation of polycrystalline thin films of G14E at much lower temperatures - than during thermal annealing without the metallic catalyst. Depending on the initial stacking sequence, the crystalline graphitic film can be deposited on a suitable device-ready substrate or transferred to another substrate after the dissolution of the transition metal catalyst.

Keywords: In situ RBS; In situ Raman; Amorphous carbon; Metal-induced crystallization

  • Poster
    2017 Materials Research Society Spring Meeting, 17.-21.04.2017, Phoenix, United States of America

Publ.-Id: 25530

Test-retest variability of lesion SUV and lesion SUR in 18F-FDG PET: an analysis of data from two prospective multicenter trials

Hofheinz, F.; Apostolova, I.; Oehme, L.; Kotzerke, J.; van den Hoff, J.

Quantitative assessment of radiation- and chemotherapy response with 18F-FDG (fluorodeoxyglucose) whole body PET has attracted increasing interest in recent years. In most published work the standardized uptake value (SUV) is utilized for this purpose. In the context of therapy response assessment the reliability of lesion SUVs, notably their test-retest stability, thus becomes of crucial importance. However, in a recent study substantial test-retest variability (TRV) of SUVs was demonstrated. The purpose of the present study was to investigate if the tumor-to-blood standard uptake ratio (SUR) can improve test-retest variability of tracer uptake. Methods: 73 patients with advanced non small cell ling cancer (NSCLC) from the prospective multicenter trials ACRIN 6678 (N = 34) and Merck MK-0646-008 (N = 39) were included in this study. All patients underwent two 18F-FDG PET/CT investigations at two different days (time difference: (3.6 +/- 2.1) days (range: 1-7)) prior to therapy. For each patient up to seven tumor lesions were evaluated. For each lesion maximum and peak SUV was determined. Blood SUV was determined as mean value of a three-dimensional aorta ROI that was delineated in the attenuation CT and transferred to the PET image. SUR values were computed as ratio of tumor SUV and blood SUV and were uptake time corrected to 75 min p.i.. TRV was quantified as TRV = 1.96 x RMS, where RMS is the root mean square deviation of the fractional paired differences of SUV and SUR, respectively. The combined effect of blood normalization and uptake time correction was inspected by considering the ratio RTRV = TRVSUR /TRVSUV reflecting the reduction in test-retest variability of SUR relative to SUV. RTRV was correlated with the group averaged value dCFmean of the quantity dCF = |CF - 1|, where CF is the numerical factor that converts individual ratios of paired SUV values into corresponding SUR ratios. This correlation analysis was performed by successively increasing a threshold value dCFmin and computing dCFmean and RTRV for the remaining sub-group of patients/lesions with CF >= CFmin. Results: The group-averaged test-retest variability of SUV and SUR was TRVSUV=32.1 and TRVSUR=29.0, respectively, which corresponds to a reduction of variability of SUR by a factor RTRV = 0.9 in comparison to SUV. This rather marginal improvement can be understood as of consequence of the untypically low intra-subject variability of blood SUV and uptake time and accordingly small dCF values in the investigated prospective study groups. In fact, sub-group analysis with increasing thresholds dCFmin revealed a very pronounced negative correlation (Spearman's rho = -0.99, P<0.001) between RTRV and dCFmean where RTRV ~ 0.4 in the dCFmin = 20% sub-group, corresponding to a more than twofold reduction of TRVSUR compared to TRVSUV. Conclusion: Variability of blood SUV and uptake time have been identified as causal factors contributing to the test-retest variability of lesion SUV. Therefore, test-retest variability of lesion uptake measurements can be reduced when replacing SUV by SUR as the uptake measure. The improvement becomes substantial for the level of variability of blood SUV and uptake time typically observed in the clinical context.

Keywords: Oncology: Lung PET FDG PET SUR SUV test-retest

Publ.-Id: 25529

In situ RBS, Raman, and ellipsometry studies of layered material systems at high temperatures in a ClusterTool

Wenisch, R.; Janke, D.; Heras, I.; Lungwitz, F.; Guillén, E.; Heller, R.; Gemming, S.; Escobar Galindo, R.; Krause, M.

The detailed knowledge of composition and microstructure is essential for the understanding of processes and properties of new materials for applications at high temperatures. To ensure materials functionality under in operando conditions, new concepts for analysis and process monitoring are necessary. In this contribution, selected PVD deposited thin film material systems were studied in situ at temperatures up to 830°C by Rutherford backscattering spectrometry (RBS), Raman spectroscopy, and spectroscopic ellipsometry (SE) within a cluster tool.
Metal-induced crystallization with and without layer exchange (MIC w/o LE) is an emerging technique for processing of amorphous group IV elements below their isothermal crystallization temperatures. In this study, a bilayer system of 60 nm amorphous Si covered by 30 nm Ag (a-Si/Ag) was annealed at temperatures of 380 to 700°C by the combination of the above mentioned in situ techniques. The process comprised a relatively long-term incubation period followed by a fast MIC w/o LE step. More than 90% of the initial a-Si could be crystallized on top of the Ag-layer for optimized process conditions with temperatures of about 550°C. The as-formed Si consisted of up to 95% crystalline Si.
As an example for high-temperature solar selective coatings for thermo-solar applications, AlTiN and AlTiN1-xOx (x = 0 - 0.2) thin films were investigated in order to understand the influence of the oxygen/nitrogen ratio on the optical properties and failure mechanisms at high temperatures. The elemental depth profiles and the phase structure of both coatings do not change during annealing in high vacuum at temperatures up to of 750°C, as revealed by unchanged RBS and Raman spectra, respectively. SE and RBS results showed the influence of the initial oxygen content on high temperature stability of AlTiN and AlTiN1-xOx thin films. The low emittance of AlTiN1-xOx, allowed performing in situ RBS analysis at temperatures up to 830°C for the first time.

Keywords: cluster tool; in situ analysis; RBS; Raman; ellipsometry

  • Lecture (Conference)
    2017 Materials Research Society Spring Meeting, 17.-21.04.2017, Phoenix, United States of America

Publ.-Id: 25528

FDG PET/MR in initial staging of sarcoma: Initial experience and comparison with conventional imaging

Platzek, I.; Beuthien-Baumann, B.; Schramm, G.; Maus, J.; Laniado, M.; Kotzerke, J.; van den Hoff, J.; Schuler, M.

Objective: To assess the feasibility of positron emission tomography/magnetic resonance imaging (PET/MR) with 18F-fluordeoxyglucose (FDG) for initial staging of sarcoma.
Materials and methods: Twenty-nine patients with sarcoma were included in this study. Weighted kappa (κ) was used to assess the agreement between PET/MR and conventional imaging (CT and MR). The accuracy of PET/MR and conventional imaging for distant metastases was compared using receiver operating characteristic (ROC) analysis.
Results: T and M stage were identical for PET/MR and conventional modalities in all patients (κ = 1). N stage was identical for 28/29 patients (κ = 0.65).
Conclusions: FDG PET/MR shows excellent agreement with the currently preferred imaging methods (CT and MR) in initial staging of sarcoma.

Keywords: Sarcoma; PET/MR; Staging


Publ.-Id: 25527

Positron emission tomography 2013 in Germany: Results of the query and current status

Kotzerke, J.; Oehme, L.; Grosse, J.; Hellwig, D.; Bartenstein, P.; Baum, R. P.; Buck, A. K.; Burchert, W.; Dietlein, M.; Drzezga, A.; Haberkorn, U.; Herrmann, K.; Kluge, R.; Krause, B. J.; Müller, H.-W.; Kuwert, T.; Nitzsche, E.; Reuland, P.; Scheidhauer, K.; Schwaiger, M.; Stabell, U.; van den Hoff, J.; Weber, W.

Aim: Five years after the first survey the positron emission tomography (PET) council of the German Society of Nuclear Medicine (DGN) repeated a survey to re-evaluate the status of PET diagnostics in Germany based on the data of the year 2013. Methods: A web-based questionnaire was used for gathering information retrospectively. Details regarding the physicians involved in PET operations, PET systems, and radiopharmaceuticals were also part of the survey as well as indications and number of studies. Furthermore, the role of PET and PET/CT within the diagnostic process was evaluated. In addition, official statistical hospital reports were analysed. Results: Responses from 52 sites were analysed. They reported a total of 38,350 PET studies in 2013. In the majority of cases PET was used in oncologic indications (87%). Further main applications were: neurology 6%, cardiology 1%, and inflammation 5%. University or other hospitals performed 85% of the studies. The portion of in-patients was 26%. Hybrid systems (56 PET/CT, 5 PET/MRT, and 2 stand-alone PET) were most frequently used for imaging. The radiotracers were labelled with F-18 in 90% of the studies, whereas Ga-68 was used in 9% and C-11 in 1%. Lung tumours were the most investigated tumour entity (40%), followed by malignant lymphoma (8%), tumours of the gastrointestinal tract (5%), and NET (5%). 20% of the 333 physicians hold a PET certificate awarded by the DGN. More than 50% of the facilities were certified according ISO9001, KTQ or QEP standard. The findings of nearly 60% of the oncological studies were discussed interdisciplinary in a tumour board. In federal statistical reports a 56% increase of in-patient PET operations during 5 years was found. Conclusion: In Germany, a moderate increase (9% per year) of PET studies is observed, but compared with other industrialised countries PET is still less established.

Keywords: Numerical data; Positron emission tomography; Utilization review; Utilization statistics

Publ.-Id: 25526

Self-assembly of magnetic nanoclusters in diamond-like carbon by diffusion processes enhanced by collision cascades

Gupta, P.; Williams, G. V. M.; Hübner, R.; Vajandar, S.; Osipowicz, T.; Heinig, K.-H.; Becker, H.-W.; Markwitz, A.

Mono-energetic cobalt implantation into hydrogenated diamond-like carbon at room temperature results in a bimodal distribution of implanted atoms without any thermal treatment. The ~100 nm thin films were synthesised by mass selective ion beam deposition. The films were implanted with cobalt at an energy of 30 keV and an ion current density of ~5 µA cm-2. Simulations suggest the implantation profile to be single Gaussian with a projected range of ~37 nm. High resolution Rutherford backscattering measurements reveal that a bimodal distribution evolves from a single near-Gaussian distribution as the fluence increases from 1.2 to 7x1016cm-2. Cross-sectional transmission electron microscopy further reveals that the implanted atoms cluster into nanoparticles. At high implantation doses, the nanoparticles assemble primarily in two bands: one near the surface with nanoparticle diameters of up to 5 nm and the other beyond the projected range with ~2 nm nanoparticles. The bimodal distribution along with the nanoparticle formation is explained with diffusion enhanced by energy deposited during collision cascades, relaxation of thermal spikes, and defects formed during ion implantation. This unique distribution of magnetic nanoparticles with the bimodal size and range is of significant interest to magnetic semiconductor and sensor applications.

Publ.-Id: 25525

Positron emission tomography 2008 in Germany: Results of the query and current status

Kotzerke, J.; Oehme, L.; Lindner, O.; Hellwig, D.; Bartenstein, P.; Baum, R. P.; Burchert, W.; Dietlein, M.; Haberkorn, U.; Kluge, R.; Knapp, W. H.; Kuwert, T.; Nitzsche, E.; Reske, S. N.; Reuland, P.; Schicha, H.; Schober, O.; Schwaiger, M.; van den Hoff, J.

Aim: The working group on positron emission tomography (PET) of the DGN (German Society of Nuclear Medicine) initiated this first survey to collect and analyse information on the practise of PET in Germany in the year 2008. Methods: A questionnaire was sent to PET performing facilities (medical practices, hospitals, university hospitals and others) for retrospective data acquisition. Details regarding the equipment and examination procedures were examined as well as indications and number of studies. In add ition, the role of PET within the diagnostic process was evaluated. Results: Responses from 65 sites were analysed, Their technical equipment consisted of 77 PET scanners (40 of them were combined PET/CT devices). About 63500 PET studies had been performed with 86% in the field of oncology, 8% in neurology and 3% in cardiology. The radiotracers were labelled with 18F in 91 % of the studies, whereas 68Ga was used in 4% and 11C in 3%. The analyses revealed lung tumours as the most investigated tumour entity, followed by malignant lymphoma, tumours of the g astro-intestinal tract and prostate cancer (about 14000, 6000, 5000 and 2000). Corresponding to the new scanners and software procedures, the number of studies with attenuation correction by CT was high (68%) and nearly all studies were reconstructed iteratively (99%). The PET images were analysed quantitatively in the majority of cases (91%). The clinical reports, which included image documentation for the greater part, were posted regularly within 3 days. However, in 70% of the sites electronic transfer possibilities were used additionally to speed up the diagnostic process. The high standard of quality was demonstrated by the fact, that 40 facilities were engaged in a tumour board. Further on, one third of the physicians had gained a PET certification awarded by the DGN. Conclusion: Relative to the high general standard of diagnostic instrumentation in Germany, PET is less established, in particular when compared with other industrialised countries such as USA and Switzerland.

Keywords: Numerical data; Positron emission tomography; Utilization review; Utilization statistics

Publ.-Id: 25524

FDG-PET/CT in oncology: German Guideline

Krause, B. J.; Beyer, T.; Bockisch, A.; Delbeke, D.; Kotzerke, J.; Minkov, V.; Reiser, M.; Willich, N.; Bartenstein, P.; Baum, R. P.; Burchert, W.; Haberkorn, U.; Kluge, R.; Knapp, W. H.; Kotzerke, J.; Kuwert, T.; Nitzsche, E.; Reske, S. N.; Reuland, P.; Schicha, H.; Schober, O.; Schwaiger, M.; Stabell, U.; van den Hoff, J.

FDG-PET/CT examinations combine metabolic and morphologic imaging within an integrated procedure. Over the past decade PET/CT imaging has gained wide clinical acceptance in the field of oncology. This FDG-PET/CT guideline focuses on indications, data acquisition and processing as well as documentation of FDG-PET/CT examinations in oncologic patients within a clinical and social context specific to Germany. Background information and definitions are followed by examples of clinical and research applications of FDG-PET/CT. Furthermore, protocols for CT scanning (low dose and contrast-enhanced CT) and PET emission imaging are discussed. Documentation and reporting of examinations are specified. Image interpretation criteria and sources of errors are discussed. Quality control for FDG and PET/CT-systems, qualification requirements of personnel as well as legal aspects are presented.

Keywords: Guideline; FDG; PET/CT; oncology

Publ.-Id: 25523

Assessment of thermal phenomena in Li-Bi liquid metal batteries through analytical and numerical models

Personnettaz, P.; Köllner, T.; Nimtz, M.; Weber, N.; Weier, T.

Liquid metal batteries (LMBs), built as stable density stratification of two liquid metals separated by a molten salt, are a promising electrical energy storage technology. While their operation has been proved for small prototypes, large industrial cells are not yet available. Up-scaling requires the full knowledge of the different phenomena occurring in LMBs. In this work we focus our attention on thermal phenomena, these are one of the main cause of flow inside the cell.

The system is first studied with a 0D electrochemical approach, focusing the attention on reversible and irreversible phenomena. A simple voltage model for the Li||Bi cell and the formulation of heat generation terms are proposed. From multi-physics considerations the geometrical and operating parameters are fully estimated.

Then thermal phenomena proper of LMBs are analyzed in the framework of continuum mechanics. 1D pure heat conduction models are built in order to assess the effect of different heat generation terms. Radiative heat transfer in the molten salt layer is also estimated.
Finally the VOF multiphase solver multiphaseInterFOAM is improved in order to study thermal convection in multi-layer systems. The comparison of results of our solver to the ones of a pseudo-spectral code and the first results of thermal convection in LMBs are also presented.

  • Lecture (Conference)
    International workshop on liquid metal battery fluid dynamics, 16.-17.05.2017, Dresden, Deutschland

Publ.-Id: 25522

Interstellar 60Fe detected on Earth - but where is the r-process nuclide 244Pu?

Wallner, A.; Kinoshita, N.; Feige, J.; Froehlich, M.; Hotchkis, M.; Paul, M.; Fifield, L. K.; Golser, R.; Honda, M.; Kivel, N.; Linnemann, U.; Matsuzaki, H.; Merchel, S.; Pavetich, S.; Rugel, G.; Schumann, D.; Tims, S. G.; Steier, P.; Winkler, S. R.; Yamagata, T.

The Interstellar Medium (ISM) is continuously fed with new nucleosynthetic products. The solar system moves through the ISM and collects dust particles. Therefore, direct detection of freshly produced radionuclides on Earth, before decaying, provides insight into recent and nearby nucleosynthesis [1,2]. Indeed, a pioneering work at Munich [3], using AMS for ocean crust-samples, showed an enhanced 60Fe signal of extraterrestrial origin.

Within an international collaboration we have continued to search for ISM radionuclides trapped in deep oceanarchives. We have analyzed sediments, crusts and nodules for extraterrestrial 60Fe (t1/2=2.6 Myr), 26Al (0.7 Myr) and 244Pu (81 Myr) [4-7] complemented by independent work at Munich [8-10]. We demonstrated that multiple events happened in our galactic neighbourhood and left their fingerprint on Earth. A global 60Fe influx is evidence for exposure to recent (<10 Myr) supernova explosions.

The site where the heaviest elements are made in nature is, however, still unknown. The low concentrations measured for 244Pu suggest an unexpectedly low abundance of interstellar 244Pu [5]. It signals a rarity of actinide r-process nucleosynthesis, which is incompatible with the rate and expected yield of supernovae as the predominant actinide-producing sites.

We will present new results for 60Fe measured at the ANU and 244Pu at ANSTO with unprecedented sensitivity.
These data provide new insights into their concomitant influx and their ISM concentrations over a time period of the last 11 Myr.

[1] Korschinek et al., Radiocarbon38 68, ‘96 [2] Ellis et al., ApJ.470 1227, ‘96 [3] Knie et al., PRL83, 18 (‘99) & PRL93 171103, ‘04 [4] Wallner et al., Nature Comm.6 5956, ‘15 [5] Feige et al., EPJ63 3003, ‘13 [6] Wallner et al., Nature532 69, ‘16 [7] Paul et al. ApJL558 L133, ‘01 [8] C. Wallner et al. NAstrRev48, 145150, ‘04 [9] Fimiani et al., PRL16 151104, ‘16 [10] Ludwig et al., PNAS113 9232, ‘16

Keywords: AMS; supernova; interstellar medium

  • Invited lecture (Conferences)
    14th International Conference on Accelerator Mass Spectrometry (AMS-14), 14.-18.08.2017, Ottawa, Canada

Publ.-Id: 25521

Attempts to understand potential deficiencies in chemical procedures for AMS: Hydroxides and silver chloride

Merchel, S.; Gurlit, S.; Opel, T.; Rugel, G.; Scharf, A.; Wetterich, S.

Since 2009, the DREAMS (DREsden Accelerator Mass Spectrometry) facility offers users to do their own sample preparation for AMS-targets. Several projects aimed at analysing 10Be, 26Al, and 36Cl as BeO, Al2O3, and AgCl, respectively. In cooperation with other AMS-facilities, also actinides (in Fe2O3) and 60Fe from Fe2O3 are measured. Thus, one of the essential steps for many projects is a hydroxide or silver chloride precipitation. For the determination of in-situ or atmospheric 26Al in marine and terrestrial sediments, we had sometimes unaccountable low chemical yields, which seemed to be due to redissolving aluminium hydroxide in the last washings. Hence, we investigated these potential losses by inductively coupled plasma mass spectrometry (ICP-MS) as a function of alteration (waiting) times. Indeed, up to 31% of the precipitated Al could be redissolved by immediate triple washings. After 2 h of waiting, this could be reduced to 11%. Further waiting (over-night) resulted in losses of 6% of Al (and equally Be) only. We also tested the behaviour of Fe(III), U(VI) (also as analogue for ~Pu(VI) and Np(VI)), and Er(III) (as analogue for Am(III), Cm(III), Pu(III)) when iron hydroxides are washed. Even including the supernatant, total losses of three times washing of over-night altered hydroxides are as low as 2.6-3.5%. Thus, repeated washing cycles are very advisable to reduce ions such as NH4 + and Cl- before drying and ignition. As we were facing problems with 10Be contamination in “dirty” ground ice [1], we measured 36Cl and natCl by isotope dilution in permafrost ice wedge samples as heavy as 1.6 kg. The chemical yield of AgCl was only 20-35% and is a function of total natCl. Thus, we explored preconcentration steps such as ion exchange (DOWEX 1x8, 5 ml), which look promising. Ackn.: Thanks to P. Steier, F. Quinto and S. Weiss. Ref.: [1] Merchel et al., AMS-13.

Keywords: AMS; in-situ; actinides

  • Poster
    14th International Conference on Accelerator Mass Spectrometry (AMS-14), 14.-18.08.2017, Ottawa, Canada

Publ.-Id: 25520

Mining with Microbes

Barthen, R.; Karimzadeh, L.; Kulenkampff, J.; Gründig, M.; Lehmann, F.; Mansel, A.; Lippmann-Pipke, J.

Microorganisms are ubiquitous and play a pivotal role in the environment. They have significant impact on nutrient cycles (e.g. carbon, nitrogen, sulfur, phosphor, iron) as well as mineral solubilization and precipitation. This talk gives an overview on metal-microbe interactions which are used for industrial applications such as bioleaching, but also highlights detrimental effects such as microbial induced corrosion (MIC), biogenic sulfuric acid corrosion of concrete, acid mine drainage (AMD) and the concomitant release of toxic heavy metals into the environment. Also, some methodology to study such systems, e.g. radiotracers, positron emission tomography (PET), chromatographic methods and mass spectrometry, are presented.

Keywords: Bioleaching; Microbial Induced Corrosion; Microorganisms; Radiotracer; Positron Emission Tomography (PET)

  • Invited lecture (Conferences)
    Guest lecture at the lecture series "Radioecology", 01.06.2017, Dresden, Germany

Publ.-Id: 25519

Attempts to understand potential deficiencies in chemical procedures for AMS: Dissolving quartz

Merchel, S.; Bookhagen, B.; Gärtner, A.; Gurlit, S.

Since 2009, the DREAMS (DREsden Accelerator Mass Spectrometry) facility offers users to do their own sample preparation for AMS targets. Several projects aimed at analysing quartz for in-situ-produced 10Be and 26Al. The goal is to dissolve quartz only, minimising other troublesome elements such as Al, Be, and Ti from other coexisting mineral phases. Obviously, low stable Al guarantees higher 26Al/27Al, thus, better 26Al-statistics, however, it also helps, with low Ti, to have fewer problems in chemistry, thus, also better 10Be-statistics. For correct calculation of ages and erosion rates, it is also advisable to have “pure quartz”, i.e. similar target elements as the calibration site used for production rates and no natural 9Be. One of the earliest established quartz cleaning methods has been routinely used at DREAMS: H2SiF6/HCl on a shaker table at room temperature [1]. In batches of seven samples we find up to 1.8% residue of the original “quartz” mass with a mean maximum value of 0.6% for the latest 17 batches from six different projects. Scanning Electron Microscopy with Energy Dispersive X-Ray Analysis (SEM-EDX) identified the most prominent minerals to be zircon Zr[SiO4], white sillimanite Al2[O|SiO4], transparent to blue kyanite Al2[O|SiO4], black chromite Fe2+Cr2O4, and orange rutile TiO2. For comparison, we have treated 3.5 g of these residues by microwave (MW) digestion resulting in dissolving 31% of the original residue. SEM-EDX analyses of the MW-residue showed mainly pristine kyanite and heavily-attacked sillimanite only. Inductively coupled plasma mass spectrometry of the MW-solution validated the dissolution of Al, Ti, Cr, Fe, and Zr. For a typical 50 g “quartz sample” the microwave method would add more than 3 mg of Ti, over 7 mg of Al and, and worst of all about 25 μg of Be to the sample. Ref.: [1] Brown et al., GCA 55 (1991) 2269.

Keywords: AMS; quartz; in-situ; erosion

  • Poster
    14th International Conference on Accelerator Mass Spectrometry (AMS-14), 14.-18.08.2017, Ottawa, Canada

Publ.-Id: 25518

Active tumor pretargeting with peptide nucleic acid bioconjugates as complementary system

Leonidova, A.; Foerster, C.; Zarschler, K.; Schubert, M.; Pietzsch, H.-J.; Steinbach, J.; Bergmann, R.; Stephan, H.; Gasser, G.

Highly tumor-affine compounds with purposeful pharmacological profile are absolutely necessary for early diagnosis of tumor malignancies and their personalized treatment. In this regard, monoclonal antibodies (mAbs) are particularly valuable as these molecules bind to tumor-associated epitopes with high specificity and affinity. The conventional concept of directly radiolabeled tumor-specific mAbs for radioimmunodetection (RID) and -therapy (RIT) has certainly several drawbacks, most prominently the prolonged radiation exposure of healthy tissues and organs. Tumor pretargeting, however, allows the rational use of long-circulating high-affinity mAbs for non-invasive cancer RID and RIT. The work presented here describes successful tumor pretargeting utilizing an EGFR-specific mAb and peptide nucleic acid (PNA) derivatives as the complementary system for specific radionuclide delivery to pretargeted tumor tissues.

After chemical synthesis, purification and detailed characterization of the individual components including antibody-PNA conjugates and different PNA oligomers, biodistribution studies were carried out using healthy Wistar rats. Finally, the pretargeting approach was evaluated in murine A431 tumor xenografts by single photon emission computed tomography.

After optimizing the pharmacokinetic properties of PNA oligomers and investigating their hybridization properties, a versatile conjugation protocol based on coupling a cysteine-functionalized PNA oligomer to a maleimido-functionalized mAb was elaborated. The in vivo studies demonstrated a rapid and efficient accumulation of activity at the tumor site with a tumor-to-muscle ratio of > 8 and clearly distinguishable tumor visualization.

This successful tumor pretargeting study has demonstrated the high potential of this concept by applying radiolabeled complementary PNA strands as an alternative in vivo recognition and radionuclide delivery system. The next step involves the translation of these results to the application of therapeutic relevant radionuclides.

  • Lecture (Conference)
    22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), 14.-19.05.2017, Dresden, Deutschland

Publ.-Id: 25517

Normal state above the upper critical field in Fe1+yTe1−x(Se,S)x

Wang, A.; Kampert, E.; Saadaoui, H.; Luetkens, H.; Hu, R.; Morenzoni, E.; Wosnitza, J.; Petrovic, C.

We have investigated the magnetotransport above the upper critical field (Hc2) in Fe1.14Te0.7Se0.3, Fe1.02Te0.61Se0.39, Fe1.05Te0.89Se0.11, and Fe1.06Te0.86S0.14. The μSR measurements confirm electronic phase separation in Fe1.06Te0.86S0.14, similar to Fe1+yTe1−xSex. Superconductivity is suppressed in high magnetic fields above 60 T, allowing us to gain insight into the normal-state properties below the zero-field superconducting transition temperature (Tc). We show that the resistivity of Fe1.14Te0.7Se0.3 and Fe1.02Te0.61Se0.39 above Hc2 is metallic as T → 0, just like the normal-state resistivity above Tc. On the other hand, the normal-state resistivity in Fe1.05Te0.89Se0.11 and Fe1.06Te0.86S0.14 is nonmetallic down to lowest temperatures, reflecting the superconductor-insulator transition due to electronic phase separation.

Publ.-Id: 25516

A new approach for the detection of 10Be with AMS based on a silicon nitride foil stack

Steier, P.; Schmidt, E.; Buchriegler, J.; Feige, J.; Lachner, J.; Martschini, M.; Merchel, S.; Michlmayr, L.; Priller, A.; Rugel, G.; Wallner, A.; Wild, E. M.; Golser, R.

An improved AMS method has been developed at VERA for detecting the long-lived radioisotope 10Be and for separating it from its isobar 10B. Recently installed and projected AMS facilities mainly apply a degrader foil followed by an electrostatic or magnetic separator to remove 10B from the ion beam. This provides the highest suppression of 10B, but suffers from significant transmission losses of 10Be ions.
The new method achieves comparable 10B suppression with a passive absorber, consisting of a stack of Silicon nitride foils. Compared to a gas absorber, the smaller energy straggling in foils allows separation at lower energies. For a tandem accelerator operated at 3 MV, the charge state 2+ instead of 3+ can be used, with a stripping yield as high as 55%. This way, a high overall efficiency is gained. The setup is simple to operate, and provides good precision. We compare this new approach with other methods used at VERA and at other facilities. The foil stack setup was fully characterized with artificial samples from chemically and isotopically well-defined reagents, and is now routinely applied to real samples in various research projects. The new method is straightforward to be implemented, and was already adopted at another facility at higher terminal voltage [1], the use at a tandem with lower terminal voltage is explored in [2].
[1] S. Winkler et al., this conference.
[2] G. Scognamiglio et al., this conference.

Keywords: AMS; accelerator masss spectrometry

  • Lecture (Conference)
    14th International Conference on Accelerator Mass Spectrometry (AMS-14), 14.-18.08.2017, Ottawa, Canada

Publ.-Id: 25515

Elucidating the lack of magnetic order in the heavy-fermion CeCu2Mg

Michor, H.; Sereni, J. G.; Giovannini, M.; Kampert, E.; Salamakha, L.; Hilscher, G.; Bauer, E.

Magnetic, transport, and thermal properties of CeCu2Mg are investigated to elucidate the lack of magnetic order in this heavy-fermion compound with a specific heat value, Cmag/T |T→0 ≈ 1.2 J/mol K2 and robust effective magnetic moments (μeff ≈ 2.46μB). The lack of magnetic order is attributed to magnetic frustration favored by the hexagonal configuration of the Ce sublattice. In fact, the effect of magnetic field on Cmag/T and residual resistivity ρ0 does not correspond to that of a Fermi liquid (FL) because a broad anomaly appears at Tmax ≈ 1.2 K in Cmag(T )/T , without changing its position up to μ0H = 7.5 T. However, the flattening of Cmag/T |T→0 and its magnetic susceptibility χT→0, together with the T2 dependence of ρ(T ), reveal a FL behavior for T _ 2 K which is also supported by Wilson and Kadowaki-Woods ratios. The unusual coexistence of FL and frustration phenomena can be understood by placing paramagnetic CeCu2Mg in an intermediate section of a frustration-Kondo model. The entropy, Smag, reaches 0.87 R ln 6 at T _ 100 K, with a tendency to approach the expected value Smag = R ln 6 of the J = 5/2 ground state of Ce3+.

Publ.-Id: 25514

Sheep models for cerebrovascular pathology

Nitzsche, B.; Ferrara, F.; Boltze, J.; Hainsworth, A.; Bridges, L.; Deuther-Conrad, W.; Dreyer, A.; Gräßer, F.; Großmann, U.; Lobsien, D.; Patt, M.; Härtig, W.; Sabri, O.; Barthel, H.

Worldwide, 5.5 M people die from stroke each year. Currently, stroke is still the third cause of death in industrialized countries and the leading cause of permanent disability in adulthood. About 78% of the incident stroke patients suffer from cerebral ischemia by occlusion of a cerebral vessel, while hemorrhage accounts for ~17% of all strokes [1]. Both conditions are medical emergencies with limited time for treatment. Recanalization by rtPA or thrombectomy are the only available therapeutic options, both being additionally hampered by a number of exclusion criteria. Despite thorough research, mostly in rodent models, no alternative treatment option has so far been successfully translated into clinical routine. Consequently, international academic and industrial expert consortia (STAIR, STEPS, [2]) suggest preclinical research strategies including validation of novel treatment strategies in gyrencephalic animal models. As a result, we subjected adult Merino sheep to (1) stereotaxic application of autologous blood as a model for intracerebral hemorrhage (ICH) [3], or to (2) territorial infarction by surgical occlusion of the middle cerebral artery (MCAO) [4]. We show the characteristics of perilesional deficits after ICH and the evaluation of a novel nicotinic acetylcholine receptor (nAChR) tracer for the identification of inflammation after MCAO by positron-emission-tomography (PET). All experimental procedures were approved by the local authority (animal licenses TVV33/12 and TVV56/15).
The ICH model led to ipsilateral GM and WM ablation and lateralization. The ipsilateral lateral ventricle was compressed and the contralateral ventricle dilated . Voxel-based-morphometry supports the compression of the ipsilateral ventricle, while the ventricle of the olfactory bulb was dilated bilaterally. Diffusion-weighed-imaging (DWI) revealed free diffused water of the hematoma, which was surrounded by reduced diffusion. The diffusion/perfusion mismatch was
calculated with 0.56 (Figure 1). Histological examination of the perilesional zone revealed hypoxic-ischemic neurons and WM vacuolation including axonal degenerations. The plasma protein fibrinogen was detected around small arteries distant from the cavity.
The MCAO model includes the transcranial surgical occlusion of all 3 branches of the MCAO, subsequently was confirmed by MR angiography. Acute ischemic alteration at day 1 were detected by [15O]H2O brain perfusion PET, MR perfusion and DWI, while structural MRI revealed the infarction at d7 and d14.. The infarctions were delineated at day 7 and 14 by FLAIR sequence. However, prominent edema complicated segmentation procedures. PET/MRI showed decreased nAChR tracer signal in the ischemia-related brain regions on day1 and day7, but a significant signal increase in the peri-infarct region on day14. These PET findings were confirmed by ex vivo autoradiography. Preliminary histopathological evaluation attributed the PET signal increase to glial activation and macrophage infiltration.
Peri-hematomal characteristics of the ICH altered brain tissue are comparable to the findings reported in human beings and other animal models. We show preliminary evidence for a protocol to visualize post-stroke neuroinflammation by PET/MRI. These results supports a potential role for our ovine models in translational stroke research.
Fig1: Intracerebral hemorrhage (ICH) in sheep: PWI (perfusion) and DWI (diffusion) were aligned to T2w turbo-spin-echography, resliced and smoothed . Crosshairs located at [-17, 0, 8].
Reference List
(1) Heuschmann, P. U., Busse, O., Wagner, M., Endres, M., Villringer, A., Röther, J., Kolominsky-Rabas, P. L., and Berger, K. Frequency and Care of Stroke in Germany. Akt Neurol. 2010. 37(7), 333-40.
(2) STAIR-group. Recommendations for standards regarding preclinical neuroprotective and restorative drug development. Stroke. 1999. 30(12):2752-58.
(3) Nitzsche, B., Lobsien, D., Geiger, K., Barthel, H., Zeisig, V., Boltze, J., and Dreyer, A. Large Mammals - translational stroke models in sheep. Amos, K. (Ed.). 9th International congress on vascular dementia. Ljubljana. 2015. Medimont. 2016.
(4) Nitzsche, B., Barthel, H., Lobsien, D., Boltze, J., Zeisig, V., and Dreyer, A. Focal cerebral ischemia by permanent middle cerebral artery occlusion in sheep - surgical technique, clinical imaging and histopathological results. In: Janowski, M., (Ed.) Experimental Neurosurgery in Animal Models .1 ed. Humana Press; 2016.

  • Lecture (Conference)
    New animal models to understand the brain, 15.05.2017, Nouzilly, Frankreich

Publ.-Id: 25513

Transition in a weakly turbulent Rayleigh-Bénard convection exposed to a horizontal megnetic field

Vogt, T.; Yanagisawa, T.; Ishimi, W.; Tasaka, Y.; Eckert, S.

MHD Rayleigh-Bénard convection was studied experimentally using the eutectic metal alloy GaInSn inside a box having a square horizontal cross section and an aspect ratio of length/height = 5/1. Systematic flow measurements were performed by means of ultrasound Doppler velocimetry that can capture time variations of instantaneous velocity profiles. Applying a horizontal magnetic field organizes the convective motion into a flow pattern of quasi-two dimensional rolls arranged parallel to the magnetic field [1], [2]. If the Rayleigh number (Ra) is increased over a certain threshold Ra/Q, whereby Q is the Chandrasekhar number, the convection flow undergoes a transition to turbulence. Besides the primary convection rolls the flow measurements reveal regular flow oscillations arising from 2D and 3D deformations of the rolls, Ekman-pumping induced flow as well as smaller side vortices that develop around the convection rolls. The aim of this paper is to give a detailed description of the flow field, which is often considered as quasi 2D. In this paper we demonstrate the importance to take 3D flow effects into account in order to explain the observed flow features. The experiments are accompanied by direct numerical simulations. The comparison between the DNS and the flow measurements shows a very good agreement.

  • Contribution to proceedings
    16TH European Turbulence Conference, 21.-24.08.2017, Stockholm, Sweden
  • Lecture (Conference)
    16TH European Turbulence Conference, 21.-24.08.2017, Stockholm, Sweden

Publ.-Id: 25512

Nanoelectronics Research in Dresden

Helm, M.

Dresden has been a center of microelectronics already since the 1960s, and this has continued and even been intensified after the German reunification. Fabs by Siemens, later Infineon and Qimonda, and also by AMD, later Globalfoundries were established. While those were mostly production sites, a concerted effort in fundamental research was started in the framework of the German Excellence Initiative. TU Dresden has established the “Exzellenzcluster” called “Center for Advancing Electronics Dresden (cfaed)”. In the first part of my talk I will introduce the concept of this cluster and give an overview about its activities. In the second part I will present some research going on in my institute at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), in particular related to the integration of III-V semiconductor nanostructures into silicon. If time permits, I may also say a few words about our research in terahertz spectroscopy utilizing the unique free-electron laser at HZDR.

Keywords: nanoelectronics; ion beam synthesis

  • Lecture (others)
    Kolloquium der Fakultät für Elektrotechnik und Informationstechnik, 05.05.2017, Wien, Austria

Publ.-Id: 25511

Precession driven flow at large nutation angles

Vogt, T.; Gundrum, T.; Giesecke, A.; Stefani, F.

Dynamos are very important, thats why we performed measurements that are motivated by a dynamo experiment currently under development at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in which the possibility of generating a magnetohydrodynamic dynamo will be investigated in a precessing cylinder filled with liquid sodium. The fluid dynamics of the precession driven dynamo experiment is investigated in a downscaled water experiment. Here, we focus on the emergence of non-axisymmetric time-dependent flow structures in terms of inertial waves which, in cylindrical geometry, form so-called Kelvin modes. Flow measurements based on Ultrasound Doppler Velocimetry (UDV) were conducted in order to identify the dominant wave modes. The azimuthal wavenumber is analyzed by four UDV transducers mounted at different azimuthal positions near the cylinder sidewall with a distance of 90° between neighbouring transducers. A radial array of six UDV transducers is utilized to resolve the radial flow structure. The aim of the work is to understand the flow structure and wave dynamics dependence on the precession ratio and to investigate their Reynolds number scalings. Besides, the results at moderate Reynolds numbers were compared to Direct Numerical Simulations and were found to be in very good agreement (see contribution from Andre Giesecke).

  • Contribution to proceedings
    2nd Conference on Natural Dynamos, 25.06.-01.07.2017, Valtice, Czech Republic
  • Poster
    2nd Conference on Natural Dynamos, 25.06.-01.07.2017, Valtice, Czech Republic

Publ.-Id: 25510

Hyperspectral and LiDAR Fusion Using Extinction Profiles and Total Variation Component Analysis

Rasti, B.; Ghamis, I. P.; Gloaguen, R.

The classification accuracy of remote sensing data can be increased by integrating ancillary data provided by multisource acquisition of the same scene. We propose to merge the spectral and spatial content of hyperspectral images (HSIs) with elevation information from light detection and ranging (LiDAR) measurements. In this paper, we propose to fuse the data sets using orthogonal total variation component analysis (OTVCA). Extinction profiles are used to automatically extract spatial and elevation information from HSI and rasterized LiDAR features. The extracted spatial and elevation information is then fused with spectral information using the OTVCA-based feature fusion method to produce the final classification map. The extracted features have high dimension, and therefore OTVCA estimates the fused features in a lower dimensional space. OTVCA also promotes piece-wise smoothness while maintaining the spatial structures. Both attributes are important to provide homogeneous regions in the final classification maps. We benchmark the proposed approach (OTVCA-fusion) with an urban data set captured over an urban area in Houston/USA and a rural region acquired in Trento/Italy. In the experiments, OTVCA-fusion is evaluated using random forest and support vector machine classifiers. Our experiments demonstrate the ability of OTVCA-fusion to produce accurate classification maps while using fewer features compared with other approaches investigated in this paper.

Keywords: Extinction profiles (EPs); feature fusion; orthogonal total variation component analysis (OTVCA); random forest (RF); support vector machines (SVMs)


Publ.-Id: 25509

Integration of spectral, spatial and morphometric data into lithological mapping: A comparison of different Machine Learning Algorithms in the Kurdistan Region, NE Iraq

Othman, A. A.; Gloaguen, R.

Lithological mapping in mountainous regions is often impeded by limited accessibility due to relief. This study aims to evaluate (1) the performance of different supervised classification approaches using remote sensing data and (2) the use of additional information such as geomorphology. We exemplify the methodology in the Bardi-Zard area in NE Iraq, a part of the Zagros Fold – Thrust Belt, known for its chromite deposits. We highlighted the improvement of remote sensing geological classification by integrating geomorphic features and spatial information in the classification scheme. We performed a Maximum Likelihood (ML) classification method besides two Machine Learning Algorithms (MLA): Support Vector Machine (SVM) and Random Forest (RF) to allow the joint use of geomorphic features, Band Ratio (BR), Principal Component Analysis (PCA), spatial information (spatial coordinates) and multispectral data of the Advanced Space-borne Thermal Emission and Reflection radiometer (ASTER) satellite. The RF algorithm showed reliable results and discriminated serpentinite, talus and terrace deposits, red argillites with conglomerates and limestone, limy conglomerates and limestone conglomerates, tuffites interbedded with basic lavas, limestone and Metamorphosed limestone and reddish green shales. The best overall accuracy (∼80%) was achieved by Random Forest (RF) algorithms in the majority of the sixteen tested combination datasets.

Keywords: Zagros; Classification; Random forest; SVM; remote sensing; Iraq


Publ.-Id: 25508

Mass Transfer and Liquid Mixing in a Bubble Column with Vertical Tube Bundles

Macisaac, A.

Bubble column reactors (BCRs) are multiphase contactors, used throughout the chemical process industry for reactions, such as, hydrogenation, oxidation and Fischer-Tropsch syntheses. The work in this report was done as part of a project at HZDR to investigate and further develop understanding of the impact of vertical tube bundle internals (for heat exchange), on the liquid mixing (LM) and mass transfer (MT) in bubble columns. Focus was placed on experimental and theoretical analysis of the liquid axial dispersion coefficient, Dz, and volumetric gas-liquid mass transfer coefficient, kla. A 10 cm diameter bubble column (DN100) was used with various typical tube bundle configurations (triangular and square pitch) and tube sizes (8 and 13 mm). As it is typical for industrial applications, one configuration was equipped with a U tube end and all internal configurations used constant coverage area of ~25 % (typical for the Fischer-Tropsch synthesis). All results were compared with the empty column to account for the influence of internals. A salt tracer pulse was used to introduce a change in liquid conductivity for LM experiments and a step change of oxygen concentration introduced to determine the MT coefficient. The axial dispersion and volumetric MT coefficient were estimated using the axial dispersion model (ADM) for LM and MT, respectively. Furthermore, radial effects were evaluated using the 2D ADM.
Key liquid mixing findings:

  • Internals caused turbulence dampening and decreased dispersion in slug flow
  • Mixing times increased with addition of internals
  • The U tube end mitigated this in the bubble flow regime
  • Radial effects were shown to factor in with internals at gas velocities > 10 cm s-1
  • Validated 1D ADM for Dz estimation for the empty column from 2-20 cm s-1
  • Strong recirculation was induced by the U tube end in the bubble flow regime
Key mass transfer findings:
  • All internals configurations slightly increased mass transfer time
  • kla data estimated using the ADM were consistent with literature
  • CSTR model was found not to be applicable for the investigated columns
Square pitch 8 mm tubes with the U tube end was shown to be the optimum configuration.
  • Master thesis
    University of Edinbourgh, 2017
    Mentor: Felix Möller
    65 Seiten

Publ.-Id: 25507

Hydrodynamic modeling of bubble column reactors with vertical heat exchanging internals

Dehmelt, T.

Bubble column reactors are frequently used apparatures regarding multiphase flows and chemical reactions such as the Fischer-Tropsch synthesis and the Methanol synthesis etc. Since most of these reactions are of exothermic nature, the emerging reaction heat has to be suficiently removed from the reactor. Therefore, longitudinal flow heat exchanger tube bundles are immersed into the column, which have the advantage of immediate heat removal at the source and they offer a large amount of specific surface area for good heat removal properties. On the downside, those internals cover a large portion of the reactor’s cross-sectional area, which leads to a strong influence on the hydrodynamics in bubble columns.
The main aim of this thesis was to develop and validate a hydrodynamic model for bubble column reactors with vertical heat exchanging internals. To fulfill this task, an existing phenomenological cell model by Schilling (2014) has been improved and further developed. The model combines several modeling ideas, such as the vertical compartment approach by Shimizu et al. (2000), the horizontal compartment model to capture up- and downflow regions by Gupta et al. (2001) and a two-bubble class model to account for polydispersity (large and small gas bubbles). Furthermore, sub-models for the prediction of flow Patterns (Vitankar and Joshi, 2002) as well as for breakup and coalescence (Liao, 2013) have been implemented. To incorporate the influence of heat exchanger internals, the developed model is based on the idea of multiple up- and downflow regions, as it has been proven by local radial holdup profiles for bubble columns with internals. These holdup profiles show strong fluctuations and follow a polynomial behavior. Therefore, the reactor is compartmentalized even further in horizontal direction according to the number of gas hold-up peaks detected from previous experimentally obtained results by ultrafast X-ray computer tomography.
The model was evaluated for superficial gas velocities ranging from 2 cm s-1 to 12 cm s-1 to cover homogeneous as well as heterogeneous flow regimes. Five internal configurations, namely, two different tube bundle patterns (triangular and square pitch) and two different tube sizes (8 and 13mm) as well as the empty bubble column reactor as counterpart were examined. Furthermore, the influence of a bended bottom structure (cf. u-tube heat exchanger) has been investigated with the developed model. The obtained parameters have been compared to experimental data provided by Seiler (2016) and empirical correlations from the literature (Shah et al. (1982), Akita and Yoshida (1973)). The results for the overall gas hold-up and the bubble size distribution are generally in good agreement with the experimental data and represent a significant improvement to the original phenomelogical cell model. On the other hand, the model predicts an increasing Sauter mean diameter, which is contrary to experimental findings for empty bubble column reactors. Those results also influence the specific gas-liquid interfacial area and the volumetric mass transfer coefficient significantly. Furthermore, the model is not able to represent the characteristics of the different internal configurations.
Finally, a sensitivity analysis after Plackett and Burman (1946) was carried out to determine the model’s stability and robustness against parameter changes.

  • Study thesis
    TU Dresden, 2017
    Mentor: Felix Möller, Uwe Hampel
    97 Seiten

Publ.-Id: 25506

Active versus passive targeting of renally excretable nanoparticles using multimodal diagnostic tumor imaging

Pant, K.; Zarschler, K.; Neuber, C.; Pufe, J.; Pietzsch, J.; Steinbach, J.; Haag, R.; Stephan, H.

Integration of multiple imaging modalities onto a single scaffold obviates the need to administer several compounds with different pharmacokinetics, increases the sensitivity of the detection and gives a deeper insight into the pathophysiological processes. This requires a scaffold with multiple attachment sites, a high tumor binding affinity, and a rapid renal elimination profile. In this regard, dendritic polyglycerols (dPGs) are well-defined, globular, highly biocompatible macromolecules with a nano-size (2-20 nm), narrow size distribution (PDI <1.26) and numerous surface functionalities, which make them amenable to a wide range of chemical modifications [1]. Previous studies done on 3H and 64Cu radiolabeled dPGs show their great potential as platforms for diagnostic applications [2]. Here, the development of dPGs as dual-modal agents for epidermal growth factor receptor (EGFR) specific tumor imaging is described.

A one-pot strategy was employed for simultaneous attachment of fluorescent labels for optical imaging (cy3/cy7) and macrocyclic chelators based on a 1,4,7-triazacyclononane system for 64Cu (PET tracer) to thiol anchoring groups of the dPGs. A small camelid single-domain antibody (sdAb) representing a potential recognition agent for EGFR as targeting vector was attached (1). In parallel, a probe with similar surface characteristics but an EGFR unspecific sdAb (control) was synthesized (2). The conjugates were purified using affinity chromatography, which selectively separates the antibody-conjugated multimodal conjugates. In vitro and in vivo studies were conducted to assess its diagnostic potential.

64Cu labeling was achieved under ambient temperature and physiological pH. Binding studies on A431 and FaDu cells using 64Cu and dye-labeled 1 and 2 showed a high specificity, colocalization and a receptor-mediated cellular uptake of 1. Intravenous injection of the 1 and 2 on mouse xenografted models studies using PET and optical imaging revealed an overwhelming tumor accumulation of the EGFR-specific 1 in comparison to the EGFR-unspecific 2 and a minimum off-target accumulation of both conjugates.

These results show the great potential of dendritic polyglycerols as multimodal platforms for various biomedical applications.

Keywords: nanoparticles; renal clearance; Tumor Imaging

  • Lecture (Conference)
    22nd International society of radiopharmaceutical sciences, 14.-19.05.2017, Dresden, Germany

Publ.-Id: 25505

Genesis of the Carbonate-Hosted Tres Marias Zn-Pb-(Ge) Deposit, Mexico: Constraints from Rb-Sr Sphalerite Geochronology and Pb Isotopes

Ostendorf, J.; Henjes-Kunst, F.; Schneider, J.; Melcher, F.; Gutzmer, J.

The Tres Marias Zn-Pb-(Ge) deposit in Chihuahua, northern Mexico, is hosted by mid-Cretaceous carbonate rocks. Sulfide ore occurs in a carbonate solution collapse breccia and has been partially altered to zinc silicates and oxides. We have used Rb-Sr sphalerite geochronology and Pb isotope systematics to constrain the age and genesis of the sulfide mineralization. An Rb-Sr sphalerite age of 28.8 ± 1.7 Ma was obtained from a quantitative, two-component paleomixing model. This age coincides with widespread volcanism in the region and is associated with a marked change from a compressional to an extensional tectonic regime. Furthermore, the Pb isotope compositions of galena, sphalerite, and late-stage hydrothermal calcite of the Tres Marias deposit overlap with values for coeval magmatic-hydrothermal, high-temperature Zn-Pb deposits of northern Chihuahua. We conclude that the formation of the Tres Marias deposit is related to magmatism and the onset of Basin and Range extensional tectonics, even though no direct spatial link between magmatic rocks and the mineralization is apparent.

Publ.-Id: 25504

Effect of Ge content on the formation of Ge nanoclusters in magnetron-sputtered GeZrOx-based structures

Khomenkova, L.; Lehninger, D.; Kondatenko, O.; Ponomaryov, S.; Gudymenko, O.; Tsybrii, Z.; Yukhymchuk, V.; Kladko, V.; von Borany, J.; Heitmann, J.

Ge-rich ZrO2 films, fabricated by confocal RF magnetron sputtering of pure Ge and ZrO2 targets in Ar plasma, were studied by multi-angle laser ellipsometry, Raman scattering, Auger electron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction for varied deposition conditions and annealing treatments. It was found that as-deposited films are homogeneous for all Ge contents, thermal treatment stimulated a phase separation and a formation of crystalline Ge and ZrO2. The “start point” of this process is in the range of 640–700 °C depending on the Ge content. The higher the Ge content, the lower is the temperature necessary for phase separation, nucleation of Ge nanoclusters, and crystallization. Along with this, the crystallization temperature of the tetragonal ZrO2 exceeds that of the Ge phase, which results in the formation of Ge crystallites in an amorphous ZrO2 matrix. The mechanism of phase separation is discussed in detail.

Keywords: Germanium; Zirconium oxide; Nanoclusters; Phase separation; Magnetron sputtering; Thin films; X-ray diffraction; Ellipsometry; Raman scattering; Fourier Transform infrared spectroscopy; Auger electron spectroscopy

Publ.-Id: 25503

High dynamic, high resolution and wide range single shot temporal pulse contrast measurement

Oksenhendler, T.; Bizouard, P.; Albert, O.; Bock, S.; Schramm, U.

A novel apparatus for the single-shot measurement of the temporal pulse contrast of modern ultra-short pulse lasers is presented, based on a simple yet conceptual refinement of the self-referenced spectral interferometry (SRSI) approach. The introduction of the spatial equivalent of a temporal delay by tilted beams analyzed with a high quality imaging spectrometer, enables unprecedented performance in dynamic, temporal range and resolution simultaneously. Demonstrated consistently in simulation and experiment at the front-end of the PW laser Draco, the full range of the ps temporal contrast defining the quality of relativistic laser-solid interaction could be measured with almost 80 dB dynamic range, 18ps temporal window, and 18fs temporal resolution. Additionally, spatio-temporal coupling as in the case of a pulse front tilt can be quantitatively explored.

Publ.-Id: 25502

The story of laser proton acceleration

Schramm, U.

Laser proton acceleration history at HZDR in light of medical applications

Keywords: PW laser; Whelmi

  • Invited lecture (Conferences)
    Inauguration of the Weizmann Helmholtz Institute for Laser Matter Interaction WHELMI, 25.-27.04.2017, Rehovot / Tel Aviv, Israel

Publ.-Id: 25501

Laser plasma accelerator research at the Dresden Petawatt systems

Schramm, U.

Progress report on PW commissioning and diagnostics

Keywords: PW laser

  • Invited lecture (Conferences)
    SPIE Optics and Optoelectronics, 24.-27.04.2017, Prag, Tschechien

Publ.-Id: 25500

Rotating thermal convection in liquid gallium: multi-modal flow, absent steady columns

Aurnou, J.; Bertin, V.; Grannan, A.; Horn, S.; Vogt, T.

Earth's magnetic field is generated by convective motions in its liquid metal core. In this fluid, the heat diffuses significantly more than momentum and thus, the ratio of these two diffusivities, the Prandtl number Pr, is well below unity. The thermally-driven convective flow dynamics of liquid metals are very different from Pr ~ 1 fluids, like water and those used in current dynamo simulations. In order to characterize rapidly rotating thermal convection in low Pr number fluids, we have performed laboratory experiments in an aspect ratio H/D = 1.94 cylinder using liquid gallium (Pr ~0.025) as the working fluid. The Ekman number, E, which characterizes the effect of rotation, varies from E = 5x10^-5 to 5x10^-6 and the Rayleigh number, Ra, which characterizes the buoyancy forcing, varies from Ra ~ 2x10^5 to 1.5x10^7. Using measurements of heat transfer effciency, characterized by the Nusselt number Nu, and point-wise temperature measurements within the fluid, we characterize the different styles of low Pr rotating convective flow.
The convection threshold is first overcome in the form of container scale inertial oscillatory modes. At stronger forcing, sidewall-attached modes are identifed for the first time in liquid metal laboratory experiments. These wall modes coexist with the bulk oscillatory modes. At Ra well below the values where steady rotating columnar convection occurs, the bulk flow becomes turbulent. Our results imply that rotating convective flows in liquid metals do not develop in the form of quasi-steady columns, as in Pr ~ 1 fluids, but in the form of oscillatory convective motions. Therefore, the flows that drive thermally-driven dynamo action in low Pr geophysical and astrophysical fluids can differ substantively than those occuring in current-day Pr ~ 1 numerical models. Since oscillatory convection is significantly easier to excite than steady convection, it may be that thermally-driven oscillatory motions will generate dynamo action in planetary settings, well before steady convective flows are even actuated. Furthermore, our experimental results show that relatively low wavenumber, wall-attached modes can be dynamically important in rapidly rotating convection in liquid metals.

Keywords: Rayleigh-Benard convection; geodynamo; rotating flows


Publ.-Id: 25499

First results with the novel Petawatt laser acceleration facility in Dresden

Schramm, U.; Bussmann, M.; Irman, A.; Siebold, M.; Zeil, K.; Albach, D.; Bernert, C.; Bock, S.; Brack, F.; Branco, J.; Couperus, J. P.; Cowan, T.; Debus, A.; Eisenmann, C.; Garten, M.; Gebhardt, R.; Grams, S.; Helbig, U.; Huebl, A.; Kluge, T.; Köhler, A.; Krämer, J.; Kraft, S.; Kroll, F.; Kuntzsch, M.; Lehnert, U.; Loeser, M.; Metzkes, J.; Michel, P.; Obst, L.; Pausch, R.; Rehwald, M.; Sauerbrey, R.; Schlenvoigt, H.-P.; Steiniger, K.; Zarini, O.

We report on first commissioning results of the DRACO Petawatt ultra-short pulse laser system implemented at the ELBE center for high power radiation sources of Helmholtz-Zentrum Dresden-Rossendorf. Key parameters of the laser system essential for efficient and reproducible performance of plasma accelerators are presented and discussed with the demonstration of 40MeV proton acceleration under TNSA conditions as well as peaked electron spectra with unprecedented bunch charge in the 0.5 nC range.

Keywords: PW laser; laser plasma acceleration; beam loading

  • Open Access Logo Journal of Physics: Conference Series 874(2017)1, 012028
    DOI: 10.1088/1742-6596/874/1/012028
  • Invited lecture (Conferences)
    17th International Particle Accelerator Conference IPAC17 (see Jacow), 15.-19.05.2017, Copenhagen, Denmark

Publ.-Id: 25498

Application of ATHLET-CD code for simulation of SBLOCA 50 cm² severe accident scenario for a generic German PWR

Jobst, M.; Wilhelm, P.; Kliem, S.

In the framework of the joint research project WASA-BOSS (Weiterentwicklung und Anwendung von Severe Accident Codes – Bewertung und Optimierung von Störfallmaßnahmen) of the Federal Ministry of Education and Research, an ATHLET-CD model for a generic German PWR of type KONVOI was developed. The model is applied to analyze the nuclear power plant response in case of a hypothetical SBLOCA severe accident scenario. The SBLOCA 50 cm² leak is modelled in cold leg No 2 (loop with pressurizer) close to the reactor pressure vessel. The scenario is initiated at nominal power conditions with additional assumptions for multiple systems failures, leading to a core degradation scenario. The model covers the in-vessel phase of the accident including core degradation, cladding oxidation, core quenching, hydrogen production, fission products release, material relocation, and RPV failure. The progress of the accident and timing of the main events is presented. Despite continuous improvement of the severe accidents codes, the model parameters for late accident phenomena are still subject to significant uncertainties. A parameter study investigates the influence of one of those uncertain parameters in ATHLET-CD, the onset of core melt relocation to the RPV lower head, to the late in-vessel phase of accident progression. In the ATHLET-CD model, the relocation to the lower head is initiated by a user defined criterion based on the amount of molten mass. The variation of this parameter within the range of 20 % – 60 % of total core mass leads to a time-shift of the lower head pool-formation of 45 min and a time-shift of all subsequent processes till RPV failure. This analysis contributes to the application and assessment of the ATHLET-CD code for simulation of severe accident scenarios.

Keywords: Severe accident analysis; SBLOCA; PWR; accident management measures

  • Contribution to proceedings
    8th European Review Meeting on Severe Accident Research - ERMSAR 2017 Conference, 16.-18.05.2017, Warszawa, Polska
    Proceedings of the ERMSAR 2017 Conference
  • Poster
    8th European Review Meeting on Severe Accident Research - ERMSAR 2017 Conference, 16.-18.05.2017, Warszawa, Polska

Publ.-Id: 25497

Residual currents generated from vacuum by an electric field pulse in 2+1 dimensional QED models

Smolyansky, S. A.; Churochkin, D. V.; Dmitriev, V. V.; Panferov, A. D.; Kämpfer, B.

Abstract. In the framework of strong field QED, the generation of a residual alternating polarization current is demonstrated, which remains after switching off an external field pulse. This effect is stipulated by inertial properties of the physical vacuum. In the standard vacuum D = 2+1 QED, this current is rapidly damped fast but can be available, apparently, for observation in the graphene, where the Fermi velocity vF << c plays an analogous role as the light velocity.

Publ.-Id: 25496

Steady state detection for fluid dynamic instabilities

Weber, N.; Boesler, M.

Fluid instabilities are characterised by a critical parameter for their onset, an exponential growth phase and a saturated state. The latter may be a steady, periodic or highly fluctuating flow. Investigating a certain instability, large parameter spaces have to be explored by hundreds of simulations, e.g. for finding the mean velocity of the saturated flow. Such parameter studies can crucially be simplified, if the user does not have to specify the simulation time. For this purpose, we present a steady state detection system for OpenFOAM. It terminates simulations automatically if the steady state is reached.

  • Lecture (Conference)
    OpenFOAM Workshop, 24.-27.07.2017, Exeter, United Kingdom

Publ.-Id: 25495

Multiphase simulation of thermal convection in liquid metal batteries

Weber, N.; Köllner, T.; Personnettaz, P.; Weier, T.

Liquid metal batteries, built as a stable density stratification of two liquid metals separated by a liquid salt , promise to be a cheap means for stationary energy storage. The latter is highly needed for stabilizing highly fluctuating renewable energies in the electric grid. The high resistance of the electrolyte will lead to internal heating and thermal convection in the cell. This flow may be beneficial when enhancing mass transfer, but it must not be strong enough to wipe away the electrolyte layer. We present here a new multiphase solver for thermal convection and some results of such flow in liquid metal batteries.

  • Lecture (Conference)
    OpenFOAM Workshop, 24.-27.07.2017, Exeter, United Kingdom

Publ.-Id: 25494

Prompt Gamma Imaging in Hadron Therapy

Fiedler, F.

not yet available

Keywords: Hadron Therapy; Prompt Gamma Imaging; Compton camera

  • Invited lecture (Conferences)
    Jagiellonian Symposium of Fundamental and Applied Subatomic Physics, 04.-9.6.2017, Krakow, Poland

Publ.-Id: 25493

Proton radiography for inline treatment planning and positioning verification of small animals

Müller, J.; Neubert, C.; von Neubeck, C.; Baumann, M.; Krause, M.; Enghardt, W.; Bütof, R.; Dietrich, A.; Lühr, A.

As proton therapy becomes increasingly well established, there is a need for high-quality clinically relevant in vivo data to gain better insight into the radiobiological effects of proton irradiation on both healthy and tumor tissue. This requires the development of easily applicable setups that allow for efficient, fractionated, image-guided proton irradiation of small animals, the most widely used pre-clinical model.
Here, a method is proposed to perform dual-energy proton radiography for inline positioning verification and treatment planning. Dual-energy proton radiography exploits the differential enhancement of object features in two successively measured two-dimensional (2D) dose distributions at two different proton energies. The two raw images show structures that are dominated by energy absorption (absorption mode) or scattering (scattering mode) of protons in the object, respectively. Data post-processing allowed for the separation of both signal contributions in the respective images. The images were evaluated regarding recognizable object details and feasibility of rigid registration to acquired planar X-ray scans.
Robust, automated rigid registration of proton radiography and planar X-ray images in scattering mode could be reliably achieved with the animal’s bedding unit used as registration landmark. Distinguishable external and internal features of the imaged mouse included the outer body contour, the skull with substructures, the lung, abdominal structures, and the hind legs. Image analysis based on the combined information of both imaging modes allowed image enhancement and calculation of 2D water-equivalent path length (WEPL) maps of the object along the beam direction.
Fractionated irradiation of exposed target volumes (e.g. subcutaneous tumor model or brain) can be realized with the suggested method being used for daily positioning and treatment planning. Robust registration of X-ray and proton radiography images allows for the irradiation of tumor entities that require conventional computed tomography (CT)-based planning, such as orthotopic lung or brain tumors, similar to conventional patient treatment.

Keywords: proton; dual-energy, radiography; preclinical; imaging; positioning


Publ.-Id: 25492

Quantitative visualization of heterogeneous transport processes at the host rock - cement interface

Kulenkampff, J.; Gründig, M.; Gruhne, S.; Lippman-Pipke, J.; Jantschik, K.; Moog, H.

We present a method for quantitative visualization and parametrization of heterogeneous transport processes at the host-rock – cement interface. As measuring method for spatiotemporal observation of the concentration of a radiotracer (22Na), we apply high-resolution positron emission tomography (PET). For illustration, the study here was conducted on a generic laboratory sample with drill core dimensions of a halite – salt cement contact. By sequential PET-imaging over a period of 70 days, we could delineate the initial patchy tracer distribution and the diffusional propagation of the tracer concentration into the cement. After 10 days, we observed significant propagation of the tracer into the cement. From the propagation pattern, we derived a first approximation of the penetration depth.

  • Open Access Logo Contribution to proceedings
    2nd Annual Workshop of the Cebama project, 16.-19.05.2017, Espoo, Finland
    Proceedings of the 2nd Annual Workshop of the Cebama project, Karlsruhe: KIT, 978-3-7315-0825-0, 119-124
    DOI: 10.5445/KSP/1000084618
  • Poster
    2nd Annual Workshop of the Cebama project, 16.-19.05.2017, Espoo, Finland

Publ.-Id: 25491

Range verification in proton therapy by prompt gamma-ray timing (PGT): Steps towards clinical implementation

Werner, T.; Berthold, J.; Enghardt, W.; Hueso González, F.; Kögler, T.; Petzoldt, J.; Richter, C.; Rinscheid, A.; Römer, K.; Ruhnau, K.; Smeets, J.; Stein, J.; Straessner, A.; Wolf, A.; Pausch, G.

In-situ range verification of ion beams during dose delivery is a key for further improving the precision and reducing side effects of radiotherapy with particle beams. The detection and analysis of prompt gamma rays with respect to their emission points, emission time, and emission energy can provide corresponding means. Prompt gamma-ray imaging (PGI) has already been used for range verification in patient treatments with proton beams. The prompt gamma-ray timing (PGT) technique promises range verification at lower hardware expense with simpler detection systems superseding heavy collimators. After proving the principle, this technique is now being translated to the treatment room. The paper presents latest experimental results obtained with clinically applicable PGT hardware in irradiations of plexiglass targets in pencil beam scanning (PBS) mode with proton beams at clinical dose rates. The data were acquired with multiple PGT detection units while the distal layer of an artificial 1 Gy dose cube treatment plan was repeatedly delivered to a solid PMMA target that sometimes comprised a cylindrical air cavity of 5, 10, or 20 mm depth. The corresponding local range shifts were clearly detected and visualized by analyzing position or variance of the prompt gamma-ray timing peaks in PGT spectra assigned to the individual PBS spots. In this context, a major challenge concerning all prompt-gamma based techniques is examined and discussed: collecting the event statistics that is needed for range verification of single pencil beam spots at an accuracy level of a few millimeters.

Keywords: Particle therapy; proton therapy; treatment verification; range verification; prompt gamma rays; prompt gamma imaging; prompt gamma timing; gamma spectroscopy; throughput

  • Lecture (Conference)
    2017 Nuclear Science Symposium and Medical Imaging Conference, 21.-28.10.2017, Atlanta, GA, USA
  • Contribution to proceedings
    Nuclear Science Symposium and Medical Imaging Conference, 21.-28.10.2017, Atlanta, GA, USA
    2017 IEEE NSS/MIC Conference Record: IEEE, 978-1-5386-2282-7
    DOI: 10.1109/NSSMIC.2017.8532807

Publ.-Id: 25490

Sn deportment within the diverse lithological units of the Hämmerlein skarn (Erzgebirge, Germany): implications for minerals processing

Kern, M.; Kästner, J.; Möckel, R.; Gutzmer, J.

The Hämmerlein skarn in the Erzgebirge, Germany, is assessed according to its beneficiation potential. A modified approach for automated mineralogy is used to evaluate the economic potential of the compositionally complex Sn ore. The lithological units show significant differences in modal mineralogy and Sn deportment. Petrographic observations and data from automated mineralogy suggest a close spatial relationship between chlorite and cassiterite, possibly pointing towards a cogenetic relationship. The association of these two minerals may be advantageous for beneficiation. Chlorite can easily be detected by a near-infrared detector used in commercially available sorting equipment. Chlorite- and cassiterite-rich rock fragments may thus be identified and separated for further processing by conventional milling, gravity separation and flotation.

  • Contribution to proceedings
    14th SGA Biennial Meeting, 20.-23.08.2017, Quebec, Kanada

Publ.-Id: 25489

Calculating the deportment of a fine-grained and compositionally complex Sn skarn with a modified approach for automated mineralogy

Kern, M.; Möckel, R.; Krause, J.; Teichmann, J.; Gutzmer, J.

A method was developed to determine the modal mineralogy and Sn deportment of a fine-grained skarn ore. Mineral Liberation Analysis and electron probe microanalysis were applied to crushed and uncrushed samples for mineralogical characterization. A comprehensive list of mineral references consisting of energy-dispersive X-ray spectra and information about elemental concentration and density was created. This conventional approach did not achieve reliable results in the characterization of some of the analyzed ore types. Small grain sizes and the variety of Sn-bearing minerals required adding mineral references with manually mixed EDX-spectra, calculated elemental concentrations and densities. Comparison of MLA data using this modified approach with bulk geochemistry and X-ray powder diffraction illustrates very good agreement for all ore-types characterized. The illustrated approach may well be considered for other mineralogically complex ores containing a multitude of ore minerals and complex deportment of metals.

Keywords: Deportment; tin skarn; Hämmerlein deposit; automated mineralogy; method development

Publ.-Id: 25488

Rare metal deportment of complex ores with a modified approach for automated mineralogy

Kern, M.; Möckel, R.; Krause, J.; Teichmann, J.; Gutzmer, J.

A method was developed to determine the modal mineralogy and Sn deportment of a fine-grained skarn ore. Mineral Liberation Analysis and electron probe microanalysis was applied to crushed and uncrushed samples for mineralogical characterization. A comprehensive list of mineral references consisting of energy dispersive X-ray spectra and information about elemental concentration and density was created. This conventional approach did not achieve reliable results in the characterization of some of the analyzed ore types. Small grain sizes and the variety of Sn-bearing minerals required adding mineral references with manually mixed EDX-spectra, calculated elemental concentrations and densities. The consequences of classifying a data set with a conventional vs a modified mineral reference list are explained in Figure 1. Comparison of MLA data using this modified approach with bulk chemistry and X-ray powder diffraction illustrates very good agreement for all ore-types characterized. The illustrated approach may well be considered for other mineralogically complex ores containing a multitude of ore minerals and complex deportment of rare metals.

  • Contribution to proceedings
    GOOD Meeting 2017, 20.-22.03.2017, Hannover, Deutschland
  • Lecture (Conference)
    GOOD Meeting 2017, 20.-22.03.2017, Hannover, Deutschland

Publ.-Id: 25487

Calculating the deportment of a fine-grained and compositionally complex Sn skarn with a modified approach for automated mineralogy

Kern, M.; Möckel, R.; Krause, J.; Teichmann, J.; Gutzmer, J.

A method was developed to determine the modal mineralogy and Sn deportment of a fine-grained skarn ore. Mineral Liberation Analysis and electron probe microanalysis was applied to crushed and uncrushed samples for mineralogical characterization. A comprehensive list of mineral references consisting of energy dispersive X-ray spectra and information about elemental concentration and density was created. This conventional approach did not achieve reliable results in the characterization of some of the analyzed ore types. Small grain sizes and the variety of Sn-bearing minerals required adding mineral references with manually mixed EDX-spectra, calculated elemental concentrations and densities. Comparison of MLA data using this modified approach with bulk chemistry and X-ray powder diffraction illustrates very good agreement for all ore-types characterized. The illustrated approach may well be considered for other mineralogically complex ores containing a multitude of ore minerals and complex deportment of metals.

Keywords: Deportment; tin skarn; Hämmerlein deposit; automated mineralogy; method development

  • Lecture (Conference)
    Process Mineralogy 2017, 20.-23.03.2017, Kapstadt, Südafrika
  • Contribution to proceedings
    Process Mineralogy 2017, 20.-22.03.2017, Kapstadt, Südafrika

Publ.-Id: 25486

Calculating the deportment of a fine-grained and complex Sn Skarn

Kern, M.; Gutzmer, J.

A method was developed to determine the modal mineralogy and Sn deportment of a fine-grained skarn ore. Mineral Liberation Analysis and electron probe microanalysis was applied to crushed and uncrushed samples for mineralogical characterization. A comprehensive list of mineral references consisting of energy dispersive X-ray spectra and information about elemental concentration and density was created. This conventional approach did not achieve reliable results in the characterization of some of the analyzed ore types. Small grain sizes and the variety of Sn-bearing minerals required adding mineral references with manually mixed EDX-spectra, calculated elemental concentrations and densities. The consequences of classifying a data set with a conventional vs a modified mineral reference list are explained in Figure 1. Comparison of MLA data using this modified approach with bulk chemistry and X-ray powder diffraction illustrates very good agreement for all ore-types characterized. The illustrated approach may well be considered for other mineralogically complex ores containing a multitude of ore minerals and complex deportment of rare metals.

  • Invited lecture (Conferences)
    ResErVar Netzwerktreffen Freiberg, 17.-20.10.2016, Freiberg, Deutschland

Publ.-Id: 25485

Der Hämmerlein Skarn im Erzgebirge: Lithologien und Sn-Deportment einer polymetallischen Sn-In-Zn Komplexerzlagerstätte

Kern, M.; Kästner, J.; Gutzmer, J.

The Hämmerlein orebody is part of the world class Tellerhäuser deposit in the Erzgebirge, Germany, and represents a compositionally complex polymetallic Sn-In-Zn skarn. Current resources amount to 100000t Sn at a cut-off grade of 0.2 wt.%. In addition, 2100 t of In and 270000t of Zn have been estimated. In the late 1970s, 50000t of ore from the Hämmerlein orebody were mined and processed experimentally in a pilot plant, but grade and recovery remained below expectations. Cited reasons for poor recovery include the complex mineralogy and variability in grain sizes of ore minerals [1].
A consortium of German research institutions currently conducts new beneficiation experiments on the Hämmerlein orebody. Determination of the Sn deportment and the characterization of the different lithological (skarn) units are the first steps in this process. For this purpose, three transects in the central part of the Hämmerlein orebody were mapped and a suite of hand specimen collected to represent all relevant lithotypes within the studied part of the orebody. Thin sections were prepared and analyzed using the Mineral Liberation Analyzer (MLA) to obtain quantitative data about mineralogy, mineral grain sizes, intergrowths, and associations. The remaining material of the hand specimen was crushed to 99% <250µm. This granular material was split to produce grain mounts for further mineralogical studies and in order to prepare sample powders for geochemical analysis.
The Hämmerlein skarn orebody can be subdivided into the following three macroscopically distinct lithotypes: 1. magnetite-dominated (40 – 80 wt.% magnetite), 2. sulphide-dominated (> 20 wt.% sphalerite) and 3. silicate-dominated (> 60 wt.% silicates). In the silicate-dominated unit a gradual transition of different silicate minerals enables further discrimination of a chlorite-rich, an amphibole-chlorite-rich, an epidote-pyroxene-rich and a garnet-rich subunit. The hanging and footwall are best described as mica schist and gneiss, respectively.
The primary host mineral for Sn is cassiterite (SnO2) with grain sizes between 1µm and 1mm. Some of the cassiterite has fibrous crystal habit. Significant amounts (ca. 1.4 wt.%) of coarse-grained (50µm to 1mm) cassiterite is present in the chlorite subunit. The amphibole-chlorite subunit contains an average of 0.3 wt.% cassiterite. Samples from other parts of the Hämmerlein orebody indicate significant amounts of cassiterite in the magnetite- and the sulphide-dominated lithotypes as well.
Malayaite (CaSnSiO5) is the second most abundant Sn mineral. It appears in fine-grained aggregates in the amphibole-chlorite subunit and in the magnetite-dominated ore type reaching concentrations of ca. 0.1 wt.%. Notable Sn concentrations were detected by EDX in some examples of titanite, epidote and iron oxides. However, the total amount of Sn in these minerals accounts for less than 10% of the total Sn content of the deposit.
Our preliminary results illustrate that the Sn mineralisation of the Hämmerlein skarn is indeed very complex. Cassiterite dominates, but other minerals (most notably malayaite) do contribute significantly to the deportment. Further studies will aim to quantify the variability of deportment and other resource characteristics, in order to guide mineral processing test work.

  • Invited lecture (Conferences)
    ResErVar Netzwerktreffen Clausthal, 24.-29.05.2016, Clausthal, Deutschland

Publ.-Id: 25484

Geochemical dispersal of thallium and accompanying metals in sediment profiles from a smelter-impacted area in South China

Liu, J.; Wang, J.; Xiao, T.; Bao, Z.; Lippold, H.; Luo, X.; Yin, M.; Ren, J.; Chen, Y.; Linghu, W.

Thallium is a trace metal with a toxicity greater than that of Pb, Cd and Hg. This study complements the authors’ previous research, with main focus on contamination by Tl and accompanying metals (Pb, Zn, Cd, and Cu) in sediments from an area historically affected by Pb-Zn smelting in Shaoguan city (northern Guangdong Province, South China). In order to provide complex data on the geochemistry of anthropogenic Tl in sediments, total contents and geochemical fractionation of Tl and the other metals were comparatively studied for two different sediment profiles, core A from the Pb-Zn smelter outlet (a major Tl pollution point-source) and core B from the inlet of the North River (natural water courses near the smelter). Surprisingly high enrichment of Tl was observed across both depth profiles, with varying distribution patterns versus depth. Further comparison of Tl contents and its geochemical fractions in the upper, middle and bottom horizons of core A and core B, in combination with mineralogical phases of the sediments, clearly demonstrated both lateral and vertical mobility of Tl, due to complex processes such as mechanical disturbance/mixing, long-term alteration/dissolution of smelter-derived particles, and vertical migration of Tl through colloidal (or microparticle) transport with alumino-phyllosilicates and Fe/Mn (hydr)oxides. Relatively high abundance of Tl in the labile fractions of all selected sediments from both locations highlights a potentially significant environmental risk to the local ecological system in the near future.

Keywords: Thallium; Sediment; Dispersal; Geochemical fractionation

Publ.-Id: 25483

Tuning and optimization for a variety of many-core architectures without changing a single line of implementation code using the Alpaka library

Matthes, A.; Widera, R.; Zenker, E.; Worpitz, B.; Huebl, A.; Bussmann, M.

We present an analysis on optimizing performance of a single C++11 source code using the Alpaka hardware abstraction library.
While in previous work Alpaka showed close-to-zero overhead compared to native implementations and similar relative numerical performance on a variety of many-core platforms, in this work we focus on performance optimization of the general matrix multiplication (GEMM) algorithm using a simple tiling strategy by tuning tile size and number of tiles computed in parallel. In addition we analyze the optimization potential available with vendor-specific compilers when confronted with the heavily templated abstractions of Alpaka.
We specifically tested the code for bleeding edge architectures such as Nvidia‘s Tesla P100, Intel‘s Knights Landing (KNL) and Haswell architecture as well as IBM‘s Power8 system. On some of these we have been able to reach almost 50% of the peak floating point operation performance using the aforementioned means. When adding compiler-specific #pragmas we were able to reach 5 TFLOPs/s on a P100 and over 1 TFLOPs/s on a KNL system.

Keywords: Heterogeneous computing; HPC; C++; CUDA; OpenMP; Platform portability; Performance portability; Parameter tuning

  • Contribution to proceedings
    2nd International Workshop on Performance Portable Programming Models for Accelerators (P^3MA), 22.06.2017, Frankfurt am Main, Deutschland
    ISC High Performance 2017: High Performance Computing, Vol 10524, 496-514
    DOI: 10.1007/978-3-319-67630-2_36
  • Lecture (Conference)
    2nd International Workshop on Performance Portable Programming Models for Accelerators (P^3MA), 22.06.2017, Frankfurt am Main, Deutschland

Publ.-Id: 25482

Das Kompetenzzentrum Ost für Kerntechnik

Kliem, S.; Hampel, U.; Hurtado, A.; Kästner, W.; Kratzsch, A.; Schlösser, D.; 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 (others)
    3. Projektstatusgespräch zur BMBF-geförderten Nuklearen Sicherheitsforschung, 27.-28.04.2017, Dresden, Deutschland

Publ.-Id: 25481

From Permeation to Cluster Arrays: Graphene on Ir(111) Exposed to Carbon Vapor

Herbig, C.; Knispel, T.; Simon, S.; SchröDer, U. A.; MartíNez-Galera, A. J.; Arman, M. A.; Teichert, C.; Knudsen, J.; Krasheninnikov, A. V.; Michely, T.

Our scanning tunneling microscopy and X-ray photoelectron spectroscopy experiments along with first-principles calculations uncover the rich phenomenology and enable a coherent understanding of carbon vapor interaction with graphene on Ir(111). At high temperatures, carbon vapor not only permeates to the metal surface but also densifies the graphene cover. Thereby, in addition to underlayer graphene growth, upon cool down also severe wrinkling of the densified graphene cover is observed. In contrast, at low temperatures the adsorbed carbon largely remains on top and self-organizes into a regular array of fullerene-like, thermally highly stable clusters that are covalently bonded to the underlying graphene sheet. Thus, a new type of predominantly sp2-hybridized nanostructured and ultrathin carbon material emerges, which may be useful to encage or stably bind metal in finely dispersed form.

Keywords: graphene; CVD growth; first-principles calcualtions


Publ.-Id: 25480

Suppressing correlations in massively parallel simulations of lattice models

Kelling, J.; Ódor, G.; Gemming, S.

For lattice Monte Carlo simulations parallelization is crucial to make studies of large systems and long Simulation time feasible, while sequential simulations remain the gold-standard for correlation-free dynamics. Here, various domain decomposition schemes are compared, concluding with one which delivers virtually correlation-free simulations on GPUs.
Extensive simulations of the octahedron model for 2 + 1 dimensional Kardar–Parisi–Zhang surface growth, which is very sensitive to correlation in the site-selection dynamics, were performed to show self-consistency of the parallel runs and agreement with the sequential algorithm. We present a GPU implementation providing a speedup of about 30× over a parallel CPU implementation on a single socket and at least 180× with respect to the sequential reference.

Keywords: Lattice Monte Carlo; Kardar-Parisi-Zhang; GPU; autocorrelation


Publ.-Id: 25479

Dual-energy CT for range prediction in particle therapy: What can we gain?

Richter, C.; Wohlfahrt, P.; Möhler, C.; Greilich, S.

Überblicksvortrag über DECT

  • Invited lecture (Conferences)
    BiGART2017 - 15th Acta Oncologica conference, 13.-16.06.2017, Aarhus, Danmark

Publ.-Id: 25478

Real-space bonding analysis of tetravalent actinide complexes with N-donor ligands

Kloditz, R.; Radoske, T.; Schöne, S.; Patzschke, M.; Stumpf, T.

The electronical properties of f-elements, especially of the actinides, are a very puzzling topic to investigate. The frontier orbitals (5f, 6d, 7s) all lying in a similar energy regime along with open shells and relativistic effects contribute to a very complex situation, where single-reference methods like DFT and Hartree-Fock are not suitable any more1. In recent years, the investigation of actinides in combination with organic ligands revealed a very rich chemistry with many forms of coordination and chemical bonding. Besides that, many visually appealing and intuitive tools have been developed, with which the chemical bond can be analysed. These tools for bond analysis include natural-bonding orbitals (NBO) and the methods of real-space bonding analysis, e.g. quantum theory of atoms in molecules (QTAIM), bond path analysis, the electron localisability indicator (ELI-D) and non-covalent interaction plots (NCI). The aim of this study is therefore to apply these bond analysis tools to a range of tetravalent actinide complexes with N-donor ligands, like Schiff bases and amidinates (Figure 1), to elucidate their complicated electronic properties. The influence of spin-orbit coupling on the chemical bonding in terms of ELI-D2 as well as thermodynamic computations on the stability of the complexes will be presented. In addition, various spectra, such as NMR and IR, acquired from the calculations will be compared with the experimental results to understand the chemical properties of the actinides and predict yet unknown complexes.

Keywords: Actinides; quantum chemistry; bonding analysis

  • Lecture (Conference)
    Actinides 2017, 09.-14.07.2017, Sendai, Japan

Publ.-Id: 25477

The influence of water chemistry on the efficiency of froth flotation: a simulation-based approach

Michaux, B.; Rudolph, M.; Reuter, M. A.

As the mining industry is facing an increasing number of issues related to its fresh water consumption, the role of water chemistry on the efficiency of froth flotation has recently become a particularly hot topic. In order to tackle the uncertainty of the flotation response when the water quality is changing, flotation tests are generally being carried in different water qualities to determine the shift of the grade – recovery curve.
Despite providing valuable information on the flotation response, the currently used approach does not deliver the required data for the simulation of a flotation circuit. Consequently, a novel approach needs to be implemented and provide a framework for such simulation and predictive modeling.
In this paper, the limitations of the currently used approach to predict the influence of water chemistry on froth flotation are highlighted. A simulation-based approach is presented as an alternative, along with the advantages and potentially considerable outcomes of this methodology for the sustainable use of fresh water in the mineral processing industry.

Keywords: Water chemistry; flotation; simulation

  • Poster
    International Symposium on Mining and Environment (ISME), 27.-29.09.2017, Bodrum, Turkey

Publ.-Id: 25476

Magnetic sensing platform technologies for biomedical applications

Lin, G.; Makarov, D.; Schmidt, O. G.

Detection and quantification of a variety of micro-and nanoscale entities, e.g. molecules, cells, and particles are crucial components of modern biomedical research, in which biosensing platform technologies are playing a vital role. Confronted with the drastic global demographic changes, future biomedical research entails continuous development of new-generation biosensing platforms targeting even lower costs, more compactness, higher throughput, sensitivity and selectivity. Among a wide choice of fundamental biosensing principles, magnetic sensing technologies enabled by magnetic field sensors and magnetic particles offer attractive advantages. The key features of a magnetic sensing format include the use of commercially-available magnetic field sensing elements, e.g. magnetoresistive sensors which bear huge potential for compact integration, a magnetic field sensing mechanism which is free from interference by complex biomedical samples, and an additional degree of freedom for the on-chip handling of biochemical species rendered by magnetic labels. In this review, we highlight the historical basis, routes, recent advances and applications of magnetic biosensing platform technologies based on magnetoresistive sensors.

Keywords: magnetic flow cytometry; magnetic field sensors; droplet fluidics

Publ.-Id: 25475

Profiling of RT-PICLS Code

Kelling, J.; Juckeland, G.

It was observed, that the RT-PICLS code ran by FWKT on the hypnos cluster was producing an unusual amount of system load, according to Ganglia metrics. Since this may point to an IO-problem in the code, this code was analyzed more closely.

Keywords: particle-in-cell; profiling

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  • Other report
    Dresden: Qucosa, 2017


Publ.-Id: 25474

MUSE plans for medical applications

Lutz, B.; Römer, K.; Weinberger, D.; Bemmerer, D.; Fiedler, F.

Silicon Photo-Multiplier (SiPM) have attractive features that enable new approaches in detector design. Especially the compact size, the insensitivity to magnetic fields, and the very competitive price, make them a prime candidate for use in detectors for particle therapy. To validate their usability in the secondary radiation field of particle therapy facilities, it is necessary to study their sensitivity to neutron fields of the characteristic spectrum. The talk gives an overview of the plans for such irradiation tests at the OncoRay facility.

Keywords: SiPM; neutron irradiation; MUSE

  • Lecture (Conference)
    MUSE General Meeting, 10.-12.05.2017, Frascati, Italia

Publ.-Id: 25473

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