Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34118 Publications

The controversial role of phospholipase C epsilon (PLCε) in cancer development and progression

Tyutyunnykova, A.; Telegeev, G.; Dubrovska, A.

The phospholipase C (PLC) enzymes are important regulators of membrane phospholipid metabolism. PLC proteins can be activated by the receptor tyrosine kinases (RTK) or G-protein coupled receptors (GPCR) in response to the different extracellular stimuli including hormones and growth factors. Activated PLC enzymes hydrolyze phosphoinositides to produce Ca2+ and diacylglycerol which are important mediators of the intracellular signaling transduction. PLC family includes 13 isozymes belonging to 6 subfamilies according to their domain structures and functions. Although importance of PLC enzymes for key cellular functions is well established, the PLC proteins belonging to the ε, ζ and η subfamilies were identified and characterized only during the last decade. As a largest known PLC protein, PLCε is involved in a variety of signaling pathways and controls different cellular properties. Nevertheless, its role in carcinogenesis remains elusive.
The aim of this review is to provide a comprehensive and up-to-date overview of the experimental and clinical data about the role of PLCε in the development and progression of the different types of human and experimental tumors.

Keywords: Phospholipase Cε; cancer development; intracellular signaling; oncogene; tumor suppressor

Permalink: https://www.hzdr.de/publications/Publ-24350
Publ.-Id: 24350


Cancer stem cells: the root of tumor recurrence and metastases

Peitzsch, C.; Tyutyunnykova, A.; Pantel, K.; Dubrovska, A.

Despite the progress in the prevention, diagnostics and treatment, cancer remains a major cause of morbidity and mortality around the world. According to the world health organization (WHO), more than 14 million newly diagnosed cases and more than 8 million deaths were reported in 2012, and increase in new cases of cancer by 70% and cancer related deaths by 45% is expected over the next 2 decades. Metastatic tumors are the cause of more than 90% of cancer related deaths due to the fact that current therapies frequently fail to provide durable curative response if tumor is spread. In this review, we summarize the main common hallmarks and evolving concept of cancer stem cells and metastasis initiating cells, their dynamic interaction with microenvironmental factors, discuss perspectives of using cancer stem cells and circulating tumor cells as prognostic and predictive tumor biomarkers as well as possible strategies for their targeting in the clinical setting.

Keywords: Cancer stem cells; Circulating tumor cells; Epithelial-mesenchymal transition; Metastatic niche; Metastasis-initiating cells; Liquid biopsy; Biomarkers

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Permalink: https://www.hzdr.de/publications/Publ-24349
Publ.-Id: 24349


Microbial Transformations of Selenite by Methane-Oxidizing Bacteria

Eswayah, A.; Hondow, N.; Scheinost, A. C.; Smith, T.; Gardiner, P.

Methane oxidizing bacteria are well known for their role in the global methane cycle and their potential for microbial transformation of wide range of hydrocarbon and chlorinated hydrocarbon pollution. In recent years it has also emerged that methane-oxidizing bacteria interact with inorganic pollutants in the environment, including heavy metals. Here we report what we believe to be the first study of the interaction of methane-oxidizing bacteria with selenite. Results indicate that the commonly used laboratory model strains of methane oxidizing bacteria, Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b are both able to reduce the toxic selenite (SeO32-) form to nanoparticulate elemental selenium (Se0). Subsequently, volatile selenium-containing species were detected from the Mc. capulatus and Ms. trichosporium cultures, concomitant with the loss of red colour due to Se0 from both cultures. This suggests that both strains may have an additional activity that can either transform Se0 or selenite into volatile methylated forms of selenium. Collectively these results are promising for the use of methane-oxidising bacteria for bioremediation or suggest possible uses in the production of selenium nanoparticles for biotechnology.

Keywords: selenium; Methylosinus trichosporium; Methylococcus capsulatus; EXAFS; XANES

Permalink: https://www.hzdr.de/publications/Publ-24348
Publ.-Id: 24348


Superiority in robustness of multi-field optimization over single-field optimization for pencil-beam proton therapy for oropharynx carcinoma: an enhanced robustness analysis

Stützer, K.; Lin, A.; Kirk, M.; Lin, L.

Purpose: To compare the difference in robustness of single-field (SFO) and robust multi-field optimized (rMFO) proton plans for oropharynx carcinoma patients by improved robustness analysis.
Methods: rMFO proton plans were generated for 11 oropharynx patients treated with SFO intensity modulated proton therapy (IMPT) with simultaneous integrated boost prescription. Doses from both planning approaches are compared for the initial plans and the worst cases from 20 optimization scenarios of setup errors (SE) and range uncertainties (RU). Expected average dose distributions per RU are obtained by adding the contributions from the respective scenarios with a weight according to their expected SE probability, and thus allowing quantification of the RU-related spread of dose parameters. Boundary dose distributions created from 56 combined SE and RU scenarios and considering the vanishing influence of SE after 30 fractions are used to approximate realistic worst case values for the total treatment course. Error bar distributions are derived from these boundary doses and error bar metrics are reported for the clinical target volumes (CTV) and organs at risk (OAR).
Results: rMFO-plans show improved CTV coverage and homogeneity while simultaneously reducing the average mean dose to the constrictor muscles, larynx and ipsilateral middle ear by 5.6Gy(RBE), 2.0Gy(RBE) and 3.9Gy(RBE), respectively. This is also observed by the different robustness evaluation methods, where additionally the average maximum brainstem and mean ipsilateral parotid dose significantly lower. For rMFO-plans, the RU-related spread in OAR dose parameters is smaller and many error bar metrics are found to be superior. SFO-plans show lower global maximum dose for single-scenario worst cases and slightly lower mean oral cavity dose throughout.
Conclusion: The benefit of better CTV coverage and OAR dose sparing by rMFO compared to SFO proton plans is preserved under considerations of SE and RU.

Keywords: Proton therapy; Robustness; Oropharynx

Permalink: https://www.hzdr.de/publications/Publ-24347
Publ.-Id: 24347


Polarization- and Wavelength-Dependent Surface-Enhanced Raman Spectroscopy Using Optically Anisotropic Rippled Substrates for Sensing

Gkogkou, D.; Schreiber, B.; Shaykhutdinov, T.; Ly, H.; Kuhlmann, U.; Gernert, U.; Facsko, S.; Hildebrandt, P.; Esser, N.; Hinrichs, K.; Weidinger, I.; Oates, T.

Anisotropic Ag nanoparticle arrays were created by metal evaporation on rippled silicon templates for sensing of molecules with surface-enhanced Raman spectroscopy. Our results show that these substrates can be used for analysis of complex molecular mixtures and discrimination of solvent molecules. These properties are due to their polarization and wavelength dependency that provide enhancement in a wide spectral range. The dielectric function parallel and perpendicular to the long axis of the nanostructures was determined via ellipsometry yielding two different plasmonic resonances. Polarized surface-enhanced raman scattering (SERS) was subsequently measured as a function of the polarization angle θ for a 4-mercaptobenzonitrile self-assembled monolayer covalently attached to the Ag surface. For 514 nm excitation a cos2 θ-dependence and for 647 nm excitation a sin2 θ-dependency were found, with the maxima expressing the resonances perpendicular and parallel to the ripples, respectively. Those results open the path for using such a substrate as a chemical sensor providing strong enhancement in a broad range of laser wavelengths on only one sensing surface and increasing the specificity by matching resonant Raman conditions.

Keywords: chemical sensors; anisotropic sensor substrates; polarized SERS; silver nanoparticle arrays; 4-mercaptobenzonitrile; enhancement substrate

Permalink: https://www.hzdr.de/publications/Publ-24346
Publ.-Id: 24346


Combination of 90Y-labelled-Cetuximab with fractionated radiotherapy: report on therapy scheduling and curative potential

Dietrich, A.; Andreeff, M.; Koi, L.; Schubert, M.; Sihver, W.; Faulhaber, D.; Pietzsch, H.-J.; Steinbach, J.; Kotzerke, J.; Baumann, M.; Krause, M.

External beam irradiation (EBRT) can precisely target solid tumors but is limited by the surrounding normal tissue. Radioimmunotherapy mediates additional internal irradiation with the potential to strike also (micro-)metastases. The combination of internal and external radiotherapy (CIERT) is a promising treatment strategy as it potentially combines advantages of both modalities without increasing toxicity. We previously showed that CIERT using 90Y-labelled-Cetuximab ([90Y]Y-Cet) massively increased tumor control probability (TCP) of FaDu xenografts compared to single dose EBRT alone. In the presented project, we investigated CIERT using clinical relevant fractionated EBRT with 30 fractions (fx) over 6 weeks. To model [90Y]Y-Cet uptake and study the best application timing, FaDu-bearing mice were injected with near-infrared-labeled-Cetuximab (NIR-Cet) at different time points during fxEBRT with differing doses. NIR-Cet uptake was longitudinally followed by in vivo optical imaging. From the results we concluded, that low to moderate doses of fxEBRT can enhance Cetuximab uptake. Based on the data, we injected [90Y]Y-Cet after 10 fx of EBRT in ongoing TCP-experiments for testing curative potential of CIERT. First analysis after 90 d observation period show that CIERT massively increase TCP compared to fxEBRT alone or in combination with unlabeled Cetuximab. Even in the group with the lowest external dose (1 Gy/fx, total dose = 30 Gy) plus [90Y]Y-Cet all tumors were permanently controlled. In contrast, the total fxEBRT dose to cure 50% of the tumors without [90Y]Y-Cet injection was 62.8 Gy [57.5, 69.5]. Our results indicate that the combination of radiolabeled therapeutics with fractionated external radiotherapy in a clinical relevant setting has a remarkably potential to improve treatment outcome. An efficient uptake of the drug is a prerequisite for the success of CIERT and may be improved by application of some EBRT dose prior to injection. This scheduling would enable patient stratification via a corresponding PET-tracer during ongoing therapy.

Keywords: internal and external radiotherapy (CIERT); HNSCC xenograft

  • Open Access Logo Contribution to proceedings
    22nd International Symposium on Radiopharmaceutical Sciences, 14.-19.05.2017, Dresden, Deutschland
    Journal of Labelled Compounds and Radiopharmaceuticals

Permalink: https://www.hzdr.de/publications/Publ-24345
Publ.-Id: 24345


Magnetism of Rare Earth Tetraborides

Mat'As, S.; Siemensmeyer, K.; Wheeler, E.; Wulf, E.; Beyer, R.; Herrmannsdörfer, T.; Ignatchik, O.; Uhlarz, M.; Flachbart, K.; Gabani, S.; Priputen, P.; Efdokimova, A.; Shitsevalova, N.

The rare earth tetraborides REB4 with RE = Ho, Er, Tm, crystallize in a tetragonal lattice where the positions of the RE ions can be mapped to a Shastry-Sutherland lattice. We have investigated the magnetic properties by means of magnetisation and specific heat experiments in a magnetic field. All compounds are anisotropic, with RE = Er, Tm they are strong Ising magnets, for RE = Ho we find xy anisotropy. In magnetic field we find complex behaviour with a number of different phases as a function of applied field, field direction and temperature. Remarkable is the observation of fractional magnetisation plateaux for magnetic field || (001) in HoB4 and TmB4.

Permalink: https://www.hzdr.de/publications/Publ-24344
Publ.-Id: 24344


Bimetallic MOFs (H3O)x[Cu(MF6)(pyrazine)2] (4-x)H2O (M = V4+, x = 0; M = Ga3+, x = 1): co-existence of ordered and disordered quantum spins in the V4+ system

Manson, J. L.; Schlueter, J. A.; Garrett, K. E.; Goddard, P. A.; Lancaster, T.; Möller, J. S.; Blundell, S. J.; Steele, A. J.; Franke, I.; Pratt, F. L.; Singleton, J.; Bendix, J.; Lapidus, S. H.; Uhlarz, M.; Ayala-Valenzuela, O.; Mcdonald, R. D.; Gurak, M.; Baines, C.

The title compounds are bimetallic MOFs containing [Cu(pyz)2]2+ square lattices linked by MF6n- octahedra. In each, only the Cu2+ spins exhibit long-range magnetic order below 3.5 K (M = V4+) and 2.6 K (M = Ga3+). The V4+ spins remain disordered down to 0.5 K.

Permalink: https://www.hzdr.de/publications/Publ-24343
Publ.-Id: 24343


PENELOPE – a high energy 150 fs diode-pumped laser system

Albach, D.; Loeser, M.; Röser, F.; Siebold, M.; Schramm, U.

The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is currently constructing a fully diode-pumped Petawatt laser ‒ PEnELOPE (Petawatt, Energy-Efficient Laser for Optical Plasma Experiments). A five stage amplifier system relying on Yb:CaF2 as gain medium designed for pulse energies of 150 J and a pulse duration of 150 fs operating at a repetition rate of 1 Hz...

  • Invited lecture (Conferences)
    7th International Conference on Ultrahigh Intensity Lasers (ICUIL), 11.-16.09.2016, Montebello, Canada

Permalink: https://www.hzdr.de/publications/Publ-24342
Publ.-Id: 24342


Magnetotransport and de Haas–van Alphen measurements in the type-II Weyl semimetal TaIrTe4

Khim, S.; Koepernik, K.; Efremov, D. V.; Klotz, J.; Förster, T.; Wosnitza, J.; Sturza, M. I.; Wurmehl, S.; Hess, C.; van den Brink, J.; Büchner, B.

The layered ternary compound TaIrTe4 has been predicted to be a type-II Weyl semimetal with only four Weyl points just above the Fermi energy. Performing magnetotransport measurements on this material we find that the resistivity does not saturate for fields up to 70 T and follows a ρ ∼ B1.5 dependence. Angular-dependent de Haas–van Alphen measurements reveal four distinct frequencies. Analyzing these magnetic quantum oscillations by use of density functional theory calculations we establish that in TaIrTe4 the Weyl points are located merely ∼40–50 meV above the chemical potential.

Permalink: https://www.hzdr.de/publications/Publ-24341
Publ.-Id: 24341


Identification of mineral-binding peptides that discriminate between chalcopyrite and enargite.

Curtis, S.; Lederer, F. L.; Dunbar, S. W.; Macgillivray, R. T. A.

Innovative approaches to the separation of minerals and subsequent extraction of metals are imperative owing to the increasing mineralogical complexity of ore deposits that are difficult or even impossible to separate into slurries or solutions containing only the minerals or metals of interest. Low recovery of metal is typical for these complex deposits leading to significant losses to tailings. In addition, the minerals often contain impurities, some toxic, which are difficult and costly to control or manage during the processing of a concentrate or other mineral product. One example of this complex situation is the significant economic and environmental costs associated with diluting and processing copper concentrates containing arsenic (in the form of the mineral enargite, Cu3AsS4) in the production of pure copper. To overcome these separation problems, we have utilized phage display to identify peptides that demonstrate selective recognition of enargite and the arsenic-free copper sulfide, chalcopyrite. Screening of two random peptide phage display libraries resulted in the identification of an enargite-selective peptide with the sequence MHKPTVHIKGPT and a chalcopyrite-selective peptide with the sequence RKKKCKGNCCYTPQ. Mineral-binding selectivity was demonstrated by binding studies, zeta potential determination and immunochemistry. Peptides that have the ability to discriminate between enargite and chalcopyrite provide a greener option for the separation of arsenic containing contaminants from copper concentrates. This represents the first step towards a major advance in the replacement or reduction of toxic collectors as well as reducing the level of arsenic-bearing minerals in the early stages of mineral processing.

Keywords: Phage display; mineral binding peptides; enargite; chalcopyrite

Permalink: https://www.hzdr.de/publications/Publ-24340
Publ.-Id: 24340


Neue Wege zum Recycling von Seltenen Erden

Lederer, F. L.; Curtis, S.; Dunbar, S. W.; Macgillivray, R. T. A.

Geeignete Methoden zur wirtschaftlichen Aufbereitung der Seltenen Erden im Leuchtpulver von Kompaktleuchtstofflampen (KLL) sind aufgrund fehlender Spezifität Mangelware. Phage Surface Display spielte bisher vor allem in der Medizin eine wichtige Rolle. Forscher der Universität von British Columbia in Kanada setzen es allerdings schon seit einigen Jahren erfolgreich ein, um Antikörper gegen anorganisches Material zu identifizieren. In der kanadischen Forschergruppe erlernte Methoden verhalfen zur Identifizierung von Peptiden mit einer hohen Spezifität für LaPO4:Ce,Tb, dem grünen Leuchtstoff der KLL. Gefundene Bakteriophagen mit Peptiden, die höchste Spezifität für ein Zielmaterial zeigen, sollen in Flotationsexperimenten auf ihre Bindungseigenschaften bei der Separation von Zielmaterial aus einem Materialgemisch untersucht werden. Bakteriophagen oder die Peptide selbst sollen zukünftig dabei helfen, Seltene Erden aus Elektroschrott gewinnbringend zu trennen.

This project has received funding by a Marie Curie International Outgoing Fellowship from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 623744.

Keywords: Seltene Erden; Kompaktleuchtstofflampen; Phage Surface Display

  • Lecture (Conference)
    ProcessNet-Jahrestagung und 32. DECHEMA-Jahrestagung der Biotechnologen 2016, 12.-15.09.2016, Aachen, Deutschland
  • Abstract in refereed journal
    Chemie Ingenieur Technik 88(2016)9, 1347-1347
    DOI: 10.1002/cite.201650149

Permalink: https://www.hzdr.de/publications/Publ-24339
Publ.-Id: 24339


Enhancement of carrier mobility in thin Ge layer by Sn co-doping

Prucnal, S.; Liu, F.; Berencén, Y.; Vines, L.; Bischoff, L.; Grenzer, J.; Andric, S.; Tiagulskyi, S.; Pyszniak, K.; Turek, M.; Drozdziel, A.; Helm, M.; Zhou, S.; Skorupa, W.

We present the development, optimization and fabrication of high carrier mobility materials based on GeOI wafers co-doped with Sn and P. The Ge thin films were fabricated using plasmaenhanced chemical vapour deposition followed by ion implantation and explosive solid phase epitaxy, which is induced by millisecond flash lamp annealing. The influence of the recrystallization mechanism and co-doping of Sn on the carrier distribution and carrier mobility both in n-type and p-type GeOI wafers is discussed in detail. This finding significantly contributes to the state-of-the-art of high carrier mobility-GeOI wafers since the results are comparable with GeOI commercial wafers fabricated by epitaxial layer transfer or SmartCut technology.

Keywords: GeOI; flash lamp annealing; ion implantation; explosive recrystallization

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Permalink: https://www.hzdr.de/publications/Publ-24338
Publ.-Id: 24338


Case report of the first lung cancer patient treated with passive scatter proton therapy at the University Proton Therapy Dresden

Stützer, K.; Jakobi, A.; Thiele, J.; Wohlfahrt, P.; Troost, E.; Richter, C.

Purpose: We present the data of the first lung cancer patient treated at the University Proton Therapy Dresden with double scattering with respect to dosimetric stability throughout the treatment course.
Material and Methods: In August 2016, the first lung cancer patient was enrolled in the proton therapy arm of the clinical trial PRONTOX (NCT02731001). The patient with a stage III disease underwent multiple CT imaging: a pre-treatment 4DCT which was used for treatment planning and sequential 4DCT imaging in treatment position once a week (5 in total) for evaluation of motion and anatomical changes. The tumour GTV was contoured on all 4DCT phases and its centre of mass was used for motion assessment. A double scattering proton treatment plan with 3 beams was generated on the average CT using the iCTV (iGTV+involved lymph node stations+8mm) as target. The iGTV was overwritten with an average density. Margins and smearing were applied following Moyers et al. 2001. A robustness assessment was undertaken before treatment by evaluating the dose on all 4DCT phases, and recalculating the doses with uncertainties of ±3.5% HU and 8 set-up shifts of x,y,z=±3 mm. A re-evaluation of the dose distribution was performed weekly on the sequential average CT. For this purpose, the delineated contours were transformed with deformable image registration to match the new CT data.
Results: Pre-treatment motion of the GTV was below 1.5 mm in all directions and did not change during treatment. The pre-treatment robustness evaluation showed median changes below 5% for all evaluated OAR parameters, not exceeding the dose constraints, and a median dose coverage drop of iCTV from V95=99.8 % to V95=97.7%, which was deemed acceptable. OAR parameters evaluated on the sequential CT scans increased throughout the treatment by maximum 8% in the worst case, but not exceeding any constraints, while iCTV coverage was only slightly decreased (worst case drop of 0.1% in V95). An anatomical and dosimetric comparison of the planning CT and the sequential CT which had the worst iCTV coverage is shown in Figure 1.
Conclusion: The first lung cancer patient double scattering proton treatment at the University Proton Therapy Dresden was safely implemented. Within the framework of the trial, follow-up data regarding side effects and outcome will be collected and analysed. The collected data will also be used for evaluations of interplay and motion mitigation for pencil beam scanning treatment, including daily recorded breathing patterns and irradiation log files to enable the implementation of this technique in future.

  • Poster
    4D Workshop 2016, 08.-09.12.2016, Groningen, Netherlands

Permalink: https://www.hzdr.de/publications/Publ-24337
Publ.-Id: 24337


PEnELOPE - a high energy 150 fs hybrid thin disk and gas-cooled multi-slab laser system

Siebold, M.; Albach, D.; Loeser, M.; Schramm, U.

The Helmholtz-Centre Dresden-Rossendorf (HZDR) is currently launching the fully diode-pumped Petawatt laser PEnELOPE (Petawatt, Energy-Efficient Laser for Optical Plasma Experiments). A five stage amplifier system using Yb:CaF2 as gain medium...

  • Lecture (Conference)
    Stuttgarter Lasertage, 31.05.-01.06.2016, Stuttgart, Germany

Permalink: https://www.hzdr.de/publications/Publ-24336
Publ.-Id: 24336


Enhanced Laser Proton Acceleration with Ultra-High Laser Contrast

Obst, L.; Poole, P.; Metzkes, J.; Zeil, K.; Cochran, G.; Kluge, T.; Schlenvoigt, H.-P.; Kraft, S.; Brack, F.; Kroll, F.; Prencipe, I.; Rehwald, M.; Schumacher, D.; Schramm, U.; Cowan, T.

We present results of our experimental campaign on laser proton acceleration, in which liquid crystal film targets of tunable thickness were irradiated with plasma mirror cleaned laser pulses. The data show a significant increase in proton cut-off energy up to 25 MeV for a target thickness of 10 nm as compared to the few- micron scale reference for this target configuration yielding roughly 12 MeV.

Keywords: Laser; Plasma; Particle Acceleration

  • Lecture (others)
    HZDR PhD Seminar, 17.10.2016, Oberwiesenthal, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24335
Publ.-Id: 24335


High-repetition-rate laser-proton acceleration from a condensed hydrogen jet

Obst, L.; Rehwald, M.; Göde, S.; Sommer, P.; Brack, F.; Schramm, U.; Gauthier, M.; Macdonald, M.; Roedel, C.; Glenzer, S.; Zeil, K.; Metzkes, J.; Schumaker, W.; Schlenvoigt, H.-P.

Applications of laser-accelerated protons demand a stable source of energetic particles at high repetition rates. We present the results of our experimental campaign in cooperation with MEC/SLAC at the 10Hz Ti:Sa laser Draco of Helmholtz-Zentrum Dresden-Rossendorf (HZDR), employing a pure condensed hydrogen jet as a renewable target. Draco delivers pulses of 30fs and 5J at 800nm, focused to a 3µm spot by an F/2.5 off-axis parabolic mirror. The jet's nominal electron density is approximately 30 times the critical density and its thickness is 2µm, 5µm or 10µm, depending on the applied aperture on the source. Ion diagnostics reveal mono-species proton acceleration in a solid angle of at least +/-45 ° with respect to the incoming laser beam, with maximum energies of around 5 MeV. The expanding jet could be monitored on-shot with a temporally synchronized probe beam perpendicular to the pump laser axis. Recorded probe images resemble those of z-pinch experiments with metal wires and indicate an m=0 instability in the plasma.

Keywords: Laser; Plasma; Targets; Particle Acceleration

  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft Frühjahrstagung 2016, 17.03.2016, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24334
Publ.-Id: 24334


Ultra-fast Thermal Processing for thin metallic films

Rebohle, L.; Schumann, T.; Prucnal, S.; Skorupa, W.

Thermal processing in the ms range comprises modern, non-equilibrium annealing techniques which allow various material modifications at the surface without affecting the bulk. Flash lamp annealing (FLA) is one of the most diverse methods of short time annealing with applications ranging from the classical field of semiconductor doping to the treatment of polymers and flexible substrates. The presentation focuses on several FLA aspects which are important for thin film applications, especially for thin metallic films.

Keywords: flash lamp annealing; thin film applications

  • Lecture (others)
    FLA Seminar, CERN, 19.10.2016, Genf, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-24333
Publ.-Id: 24333


Structural clarification of a tert-butyl-calix[4]arene-based 8-hydroxyquinoline complex with uranium(VI) in non-aqueous solution

Bauer, A.; März, J.; Barthen, R.; Jäschke, A.; Glasneck, F.; Schmeide, K.; Brendler, V.; Kersting, B.; Stumpf, T.

The actinides uranium and thorium are considered disturbing constituents in rare earth production. Thus they have to be removed, e.g. by extraction.[1] Due to their modifiable selectivity and solubility calix[n]arenes are interesting compounds for the extraction of uranium(VI).[2]
A new chalice-like tert-butyl-calix[4]arene-based 8-hydroxyquinoline ligand consisting of four phenolic units was synthesized. Tert-butyl substituents provide a hydrophobic character. Functionalizing of the phenolic hydroxyl groups by 8-hydroxyquinoline ensures the affinity to uranyl ions.[2]
For better process understanding we examined the mechanisms of uranyl complexation by the calix[4]arene derivative. The structure of the tert-butyl-calix[4]arene-based 8-hydroxyquinoline uranyl complex was unveiled by spectroscopy and microcalorimetry.
The complexation studies were performed in acetonitrile. Luminescence spectroscopic studies indicated the interaction of uranyl ions with the ligand. UV visible investigations evidenced the presence of a 1:1 and a 1:2 ligand uranyl complex with stability constants of log ß1:1 = 5.94 ± 0.016 and log ß1:2 = 6.33 ± 0.013.
Microcalorimetry provided the thermodynamic characterization of the complexation.
Single crystal X-ray analysis of the 1:1 complex revealed the coordination of the uranyl ion via a N2O2 donor set (Fig. 1). The charge is compensated by an additional coordinated nitrate ion. Due to the chelation reddish uranyl calix[4]arene complexes were formed as indicated by the absorption band at 525 nm. An increase of the peak up to the addition of two equivalents of uranyl ions suggested a complexation of both uranyl ions through chelation in acetonitrile.
The application of electrospray ionization time-of-flight mass spectrometry affirmed the coordination of two hexavalent uranyl nitrate ions in acetonitrile.
In addition, to improve the understanding of the ligand complexation properties the interaction with thorium is studied.

[1] Z. W. Zhu, Y. Pranolo, C.Y. Cheng, Miner Eng 2015, 77, 185-196.
[2] A. Jäschke, M. Kischel, A. Mansel, B. Kersting, 2016, in prep.

Keywords: SE-FLECX; rare earth production; calix[4]arene; uranium; complexation studies

  • Poster
    ANAKON 2017, 03.-06.04.2017, Tübingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24332
Publ.-Id: 24332


Structural investigations of (La,Pu)PO4 monazite solid solutions: XRD and XAFS study

Arinicheva, Y.; Popa, K.; Scheinost, A. C.; Rossberg, A.; Dieste-Blanco, O.; Raison, P.; Cambriani, A.; Neumeier, S.; Somers, J.; Bosbach, D.

A fundamental understanding of actinide incorporation processes in envisioned nuclear waste forms, such as monazite ceramics, is required for a reliable prediction of the long-term stability of such ceramic materials for safe nuclear disposal. The present study provides structural insights into the formation of monazite solid solutions by incorporation of PuIII and verifies previous results on surrogate materials, where Eu and Gd served as inactive analogues for trivalent actinides.
A solid state method was used to synthesize La1-xPuxPO4 (x = 0.01, 0.05, 0.10, 0.15, 0.5) solid solutions with monazite structure. XRD measurements of the compounds with x = 0.50 revealed the formation of two phases: (La,Pu)PO4-monazite and a cubic phase (PuO2). Pure-phase La1-xPuxPO4-monazite solid solutions were obtained for materials with x = 0.00-0.15 and confirmed by a linear dependence of the lattice parameters on composition according to Vegard’s law. X-ray absorption spectroscopy (XAS) analysis at the Pu-LIII and La-LIII edges verified the +III valence state of plutonium in the monazite solid solutions. The local environment of Pu is similar as in PuPO4-like along the solid solution series, except for the longest fitted cation-cation distance, which may be an indication of cluster formation consisting of a few Pu-atoms in the La-Pu-monazite lattice.

Keywords: Plutonium; monazite; waste form; solid state synthesis; solid solutions; XRD; EXAFS

Permalink: https://www.hzdr.de/publications/Publ-24331
Publ.-Id: 24331


Highly doped zinc oxide films produced by advanced thermal processing in the millisecond range

Rebohle, L.; Braun, M.; Prucnal, S.; Skorupa, W.; Guziewicz, E.; Snigurenko, D.

Zinc oxide (ZnO) is an attractive candidate to replace indium tin oxide in microelectronic and photovoltaic applications. Furthermore, ZnO nanostructures hold great promise for sensor applications. Whereas n-type doping can be easily achieved, p-type doping is a more challenging issue as most defects like Zn interstitials act as n-type dopants.
In this work 100 nm thick ZnO layers were grown by atomic layer deposition on a thermal SiO2 layer on top of a Si wafer. Subsequently, the layers were implanted by phosphorus or antimony, followed by flash lamp annealing (FLA). The ZnO layers were investigated by means of Raman, photoluminescence, sheet resistance and Hall measurements. Depending on the FLA conditions, the doping type shifts from n-type dominated by defects to p-type caused by the implanted group V elements.

Keywords: flash lamp annealing; ion implantation; zinc oxide

  • Lecture (Conference)
    Material Science and Engineering, 27.-29.09.2016, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24330
Publ.-Id: 24330


A Bayesian Approach for Measurements of Stray Neutrons at Proton Therapy Facilities: Quantifying Neutron Dose Uncertainty

Dommert, M.; Lutz, B.; Reginatto, M.; Zbořil, M.

The use of proton beams in radiation therapy allows for the deposition of high doses at the tumor position while minimizing the dose to the surrounding healthy tissue. However, in addition to proton radiation, the patient is also exposed to secondary radiation, which produces an unwanted out-of-field dose. As neutron radiation can provide the largest contribution to this out-of-field dose for proton therapy, it is important to characterize the stray neutron field in the therapy room.
As part of a collaboration with HZDR, PTB has carried out measurements with the Bonner sphere spectrometer NEMUS at the OncoRay Proton Therapy Facility in Dresden. The analysis of Bonner sphere measurements is typically done using unfolding codes. However, it is very difficult to implement reliable uncertainty propagation in standard unfolding codes. An alternative approach, which does provide reliable estimates of uncertainties of neutron spectra which lead to rigorous estimates of uncertainties of the dose, is to analyze the Bonner sphere data using Bayesian parameter estimation [1][2]. In this work, we extend previous approaches and apply this method to secondary neutrons from radiation therapy proton beams. This requires introducing a parameterized model which can describe the main features of the neutron spectra. We choose the parameterization based on information that is available from measurements and detailed Monte Carlo simulations.
To demonstrate the validity of this approach, we consider the results of an experiment carried out at the experimental hall of the OncoRay facility. Measurements were done with the following experimental set-up: a brass target was placed in the proton beam and the proton beam was pulsed with 10 Hz to mimic the operation of a range modulator wheel. Bonner spheres were placed at different angles with respect to the incoming proton beam. We selected a set of 7 polyethylene spheres and 3 extended spheres with lead or copper inserts. The results of the analysis are the spectra of secondary neutrons with their corresponding doses with uncertainties. The approach that we describe here provides a basic method to assess neutron spectra and their uncertainties and will be extended in future applications to include additional parameters; e.g., those describing the settings of the proton beam.
References:
[1] M. Reginatto, Radiat. Prot. Dosim 120, 64-69 (2006).
[2] M. Reginatto, Rad. Meas. 44, 692-699 (2009).

Keywords: unfolding; Bayesian parameter estimation; neutron dose; proton therapy

  • Poster
    Neutron and Ion Dosimetry Symposium, 14.-19.05.2017, Kraków, Polska

Permalink: https://www.hzdr.de/publications/Publ-24329
Publ.-Id: 24329


Flow Structures Analysis Downstream Gas Spargers of Different Orifice Pattern in Bubble Columns

Möller, F.; Bieberle, A.; Barthel, F.; Schubert, M.; Hampel, U.; Weber, M.; Weber, M.

Bubble column reactors are widely employed for gas-liquid reactions due to their superior mass and heat transfer accompanied by being geometrically simple and free from any moving part. However, the gas sparger is a crucial device, which directly determines the process performance. The bubbles released from the orifices of the gas sparger start rising up and buoyancy and drag forces etc., in turn, depending on bubble size, control the traveling velocity of the bubbles, and eventually the overall hydrodynamic behavior, such as mixing and gas holdup. Hence, to get an insight into the impact of orifice patterns and holes’ diameter of a gas sparger on the axially evolving gas-liquid dispersion, an ultrafast X-ray tomography study is performed in a 2 m height bubble column of 100 mm diameter. Two different perforated plate-type spargers are used, namely a single orifice sparger with a 2.9 mm center hole and a plate with 13 orifices arranged in a triangular pitch with a hole diameter of 0.8 mm, respectively. The experiments were performed in a non-coalescing system for superficial gas velocities up to 2.5 cm/s. From the X-ray measurements, the evolving gas structures, the bubble size distributions as well as the cross-sectional gas holdup distributions are extracted along the column height and the benefit of a fine initial distribution is evaluated.

  • Lecture (Conference)
    International Conference on Multiphase Flow, 22.-27.05.2016, Firenze, Italy
  • Contribution to proceedings
    International Conference on Multiphase Flows, 22.-27.05.2016, Firenze, Italy

Permalink: https://www.hzdr.de/publications/Publ-24328
Publ.-Id: 24328


Liquid Circulation and Swarm Dynamics in Bubble Columns with Internals

Möller, F.; Hampel, U.; Schubert, M.

Bubble column reactors are apparatuses of choice for many gas-liquid and gas-liquid-solid reactions due to their superior mixing, heat and mass transfer behavior as well as their simple design without any moving part. In particular, they are often used for exothermic reaction processes such as methanol synthesis, Fischer-Tropsch synthesis etc. Hence, the heat has to be removed out of the system in order to guarantee safe operation at optimal reaction conditions. For this purpose a variety of heat exchangers e.g. internal heat exchanging tube bundles, which can also be used to generate steam, are applied. However, the effects of heat exchanger installation in bubble columns on the gas-liquid flow are still fragmentary.
This contribution focusses on the effect of internals on liquid circulation and swarm dynamics. Internal longitudinal flow heat exchanging bundles with various tube pattern configurations (triangular, and square pitch) and tube diameters between 8 and 13 mm while covering a cross sectional area of ~25% are subject to hydrodynamic and mixing studies in a column of 100 mm diameter.
Wire-mesh sensors with measurement points suitably distributed in the cross-section between the internals’ tubes were installed at different axial positions to study liquid mixing and dispersion in the bubble column as well as lateral fluid exchange between sub-channels. Tracer studies were performed and suitable transfer functions were applied for the determination of the liquid dispersion coefficient. It was found that bubble columns with tube bundle internals show similar behavior as airlift reactors. In addition, ultrafast X-ray tomography is applied to study the effect of the internal configurations on the axial bubble size distribution and gas fraction evolution as well as on the prevailing flow regimes.

  • Poster
    Jahrestreffen Bingen 2016 - Fachgruppen Agglomerations- und Schüttguttechnik, Mehrphasenströmungen und Computational Fluid Dynamics (AGG, MPH, CFD), 29.02.-02.03.2016, Bingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24327
Publ.-Id: 24327


Electrical conduction and negative magnetoresistance in tellurium-hyperdoped silicon

Wang, M.; Liu, F.; Yuan, Y.; Prucnal, S.; Berencen, Y.; Rebohle, L.; Skorupa, W.; Helm, M.; Zhou, S.

Hyperdoping silicon with chalcogen atoms is a topic of increasing interest due to the strong sub-band gap absorption, which can be exploited to develop infrared photodectectors and intermediate band solar cells [1-3]. In our work, tellurium-hyperdoped Si layers have been fabricated by ion implantation followed by either millisecond flash lamp annealing (FLA) or nanosecond pulsed-laser melting (PLM). The electrical conduction and magnetoresistance of Te-hyperdoped Si are investigated at magnetic fields up to 5 T and temperatures ranging from 2 K to 300 K. With increasing Te concentration, an insulator-to-metal transition is observed although Te introduces a deep donor level (around 300–400 meV) below the Si conduction band. Moreover, the temperature-dependent conductivity measured at zero magnetic field shows that the charge transport is associated with variable-range hopping (VRH) at low temperatures, which scales as δ(T)=δ0 exp[-(T0/T)s] (S=1/4 or 1/2). In addition negative magnetoresistance is observed at low magnetic field, turning positive at B around 0.9 T.

Keywords: hyperdoped silicon; Tellurium; hopping conductivity; negative magnetoresistance

  • Poster
    33rd International Conference on the Physics of Semiconductors, 31.07.-05.08.2016, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-24326
Publ.-Id: 24326


An optimized small animal tumour model for experimentation with low energy protons

Beyreuther, E.; Brüchner, K.; Krause, M.; Schmidt, M.; Szabo, R.; Pawelke, J.

Background: The long-term aim of developing laser based particle acceleration towards clinical application requires not only substantial technological progress, but also the radiobiological characterization of the resulting ultra-short and ultra-intensive particle beam pulses. Subsequent to comprehensive cell studies a mouse ear tumour model was established allowing for the penetration of low energy protons (~20 MeV) currently available at laser driven accelerators. The model was successfully applied for a first tumour growth delay study with laser driven electrons, whereby the need of improvements crop out .
Methods: To optimise the mouse ear tumour model with respect to a stable, high take rate and a lower number of secondary tumours MatrigelTM was introduced for tumour cell injection. Different concentrations of two human tumour cell lines (FaDu, LN229) and Matrigel were evaluated for stable tumour growth and fulfilling the allocation criteria for irradiation experiments. The originally applied cell injection with PBS was performed for comparison and to assess the long-term stability of the model. Finally, the optimum suspension of cells and Matrigel was applied to determine applicable dose ranges for tumour growth delay studies by 200 kV X-ray irradiation.
Results: Both human tumour models showed a high take rate and exponential tumour growth starting at a volume of ~10 mm3. As disclosed by immunofluorescence analysis these small tumours already interact with the surrounding tissue and activate endothelial cells to form vessels. The formation of delimited, solid tumours at irradiation size was shown by standard H&E staining and a realistic dose range for inducing tumour growth delay, but not tumour control, was obtained for both tumour entities.
Conclusion: The already established mouse ear tumour model was successfully upgraded now providing stable tumour growth with high take rate for two tumour entities (HNSCC, glioblastoma) that are of interest for future irradiation experiments at experimental accelerators.

Keywords: mouse tumour model; low energy protons; laser particle acceleration; low penetrating radiation; proton therapy

Permalink: https://www.hzdr.de/publications/Publ-24324
Publ.-Id: 24324


Helium-ion microscopy, helium-ion irradiation and nanoindentation of Eurofer 97 and ODS Eurofer

Bergner, F.; Hlawacek, G.; Heintze, C.

Understanding of unsolved details of helium embrittlement requires experimental evidence for dedicated sets of materials and over a wide range of irradiation conditions. The study is focussed on the comparison of the reduced-activation ferritic-martensitic 9%Cr steel with its oxide dispersion strengthened (ODS) counterpart with respect to irradiation-induced hardening. Imaging and He-ion irradiation in the He-ion microscope at 30 ºC in a wide range of appm He (from 0.9 x 1E2 to 1.8 x 1E6) and displacements per atom (from 3 x 1E-3 to 65) were combined with post-irradiation nanoindentation in order to detect blistering and irradiation-induced hardness changes. The applicability of this combination of techniques is demonstrated and pros and cons are discussed. We have found that the irradiation-induced hardness increase is higher and the onset of significant hardening tends to occur at lower fluence for Eurofer 97 than for ODS Eurofer, indicating that the presence of oxide nanoparticles is efficient to reduce the detrimental effect of He under the applied irradiation conditions.

Keywords: Ferritic-martensitic chromium steel; Oxide dispersion strengthened steel; He-ion microscopy; Ion irradiation; Nanoindentation

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Permalink: https://www.hzdr.de/publications/Publ-24323
Publ.-Id: 24323


Mechanical properties and plasticity size effect of Fe-6%Cr irradiated by Fe ions and by neutrons

Hardie, C. D.; Odette, G. R.; Wu, Y.; Akhmadaliev, S.; Roberts, S. G.

The mechanical behaviour of Fe6%Cr in the un-irradiated, self-ion irradiated and neutron irradiated conditions was measured and compared. Irradiations were performed to the same dose and at the same temperature but to very different damage rates for both methods. The materials were tested using nanoindentation and micromechanical testing, and compared with microstructural observations from Transmission Electron Microscopy (TEM) and Atom Probe Tomography (APT) reported elsewhere. Irradiated and un-irradiated micro-cantilevers with a wide range of dimensions were used to study the interrelationships between irradiation hardening and size effects in small-scale plasticity. TEM and APT results identified that the dislocation loop densities were ~2.9 E22 m-3 for the neutron irradiated material and only 1.4E22 m-3 for the ion irradiated material. Cr segregation to loops was only found for the neutron-irradiated material. The nanoindentation hardness increase due to neutron irradiation was 3 GPa and that due to ion irradiation 1 GPa. The differences between the effects of the two irradiation types are discussed, taking into account inconsistencies in damage calculations, and the differences in PKA spectra, dose rate and transmutation products for the two irradiation types.

Permalink: https://www.hzdr.de/publications/Publ-24322
Publ.-Id: 24322


Ion-beam induced atomic mixing in isotopically controlled silicon multilayers

Radek, M.; Bracht, H.; Liedke, B.; Böttger, R.; Posselt, M.

Implantation of germanium (Ge), gallium (Ga), and arsenic (As) into crystalline and preamorphized isotopically controlled silicon (Si) multilayer structures at temperatures between 153 K and 973K was performed to study the mechanisms mediating ion-beam induced atomic mixing. Secondary-ion-mass-spectrometry (SIMS) was applied to determine concentration-depth profiles of the stable isotopes before and after ion implantation. The intermixing is analytically described by a depth-dependent displacement function. The maximum displacement is found to depend not only on temperature and microstructure but also on the doping type of the implanted ion. Molecular dynamics calculations evaluate the contribution of cascade mixing, i.e., thermal-spike mixing, to the overall observed atomic mixing. Calculated and experimental results on the temperature dependence of ion-beam mixing in the amorphous and crystalline structures provide strong evidence for ion-beam induced enhanced crystallization (IBIEC) and enhanced self-diffusion (IBIESD), respectively. Whereas the former process is confirmed by channeling Rutherford backscattering analyses of the amorphous layer thickness remaining after implantation, the latter process is consistently attributed to the formation of highly mobile Si di-interstitials formed under irradiation and in the course of damage annealing. The observed ion-beam mixing in Si is compared to recent results on ion-beam mixing of Ge isotope multilayers that, in contrast to Si, are fully described by thermal-spike mixing only.

Keywords: ion beam mixing; silicon isotope multilayers

Permalink: https://www.hzdr.de/publications/Publ-24321
Publ.-Id: 24321


Selektive Phasengeschwindigkeitsmessung in Blasenströmungen durch den kombinierten Einsatz einer Heißfilmsonde und der ultraschnellen Röntgentomographie

Kipping, R.; Kryk, H.; Hampel, U.

Blasensäulenreaktoren bieten aufgrund ihrer einfachen Bauweise und ihres ausgezeichneten Wärme- und Stofftransportverhaltens einen häufig genutzten Reaktortyp in der chemischen Industrie. Besonders die Beschreibung der Hydrodynamik und der Geschwindigkeitsprofile der unterschiedlichen Phasen, sowie deren radiale Verteilung haben einen erheblichen Einfluss auf den Stofftransport und chemische Reaktion. In diesem Beitrag sollen die Ergebnisse der Untersuchung zur Flüssigphasengeschwindigkeit in Blasenströmungen vorgestellt werden. Die Anwendbarkeit von Heißfilmsonden ist bei Vorliegen einer Mehrphasenströmung stark begrenzt. In Blasensäulen beinhaltet das gemessene Geschwindigkeitssignal Anteile der Gas- und Flüssigphase. Zur Untersuchung der Umströmung von Blasen und zur Bestimmung von Turbulenzparametern ist es notwendig diese Anteile voneinander zu trennen. Ausschließlich bei geringen Gasgehalten bietet der charakteristische Signalverlauf bei der Interaktion von Blase und Sonde eine Möglichkeit dazu. In dieser Arbeit kann mit Hilfe der Zwei-Ebenen Tomographie, die genaue Position der Heißfilmsonde und die vorliegende Phase an dieser Stelle in der Blasensäule bestimmt werden. Weiterhin können neben der Flüssigphasengeschwindigkeit auch Parameter der Hydrodynamik der Gasphase, wie Blasenform, Blasengröße bestimmt werden und in Abhängigkeit zur Flüssigphasengeschwindigkeit gestellt werden.

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Agglomerations-und Schüttguttechnik, Computational Fluid Dynamics und Mehrphasenströmungen, 29.02.-02.03.2016, Bingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24320
Publ.-Id: 24320


Experimental investigation of mass transfer of CO2 bubbles with ultrafast electron beam X-rax tomography

Kipping, R.; Kryk, H.; Hampel, U.

Bubble columns are a favored reactor type for the operation of gas-liquid reactions (e.g. oxidation and hydrogenation processes) in chemical industries. The improved design and operation of bubble column reactors requires a detailed understanding of the flow phenomena as well as mass transfer processes within these reactors. This study presents the experimental investigation the gas liquid mass transfer in a bubble column on the basis of the chemical absorption of CO2. This contribution presents ultrafast X-ray CT measurements within a bubble column. The mass transfer has been determined by the analysis of the decrease of gas the gas phase, especially the shrinkage of the CO2 bubbles.

Keywords: reactive two-phase flow; ultrafast X-ray tomography; chemical absorption; mass transfer

  • Lecture (Conference)
    FERMaT-SPP1740-Symposium, 06.-08.06.2016, Toulouse, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-24319
Publ.-Id: 24319


How gangue particle size can affect the recovery of ultrafine and fine particles during froth flotation

Leistner, T.; Peuker, U. A.; Rudolph, M.

In general, the poor flotation behavior of ultrafine (< 10 µm) particles is mainly associated with a low particle/bubble collision efficiency within the flotation process due to an unfavorable particle/bubble size ratio. In those considerations the size of the gangue particle system does not play a significant role. This study investigates the effect of gangue particle size on the recovery of ultrafine and fine (10…50 µm) particles. Artificial, binary model particle system, using magnetite as the target and quartz as the gangue mineral, are used for the investigation in order to considerably eliminate reported problems associated with ultrafine gangue particles. Results indicate that ultrafine magnetite can be recovered like fine magnetite when the gangue particles are fine as well. In contrast, fine magnetite recovery drops significantly when ultrafine quartz is used as the gangue mineral system.

Keywords: Flotation; ultrafines; gangue; hydrodynamics

Permalink: https://www.hzdr.de/publications/Publ-24318
Publ.-Id: 24318


Characterization of a chemical reaction in a bubble column using Wire-Mesh Sensor and ultrafast X-ray CT

Kipping, R.; Kryk, H.; Schleicher, E.; Hampel, U.

Design and operation of bubble columns are of main importance, since they strongly influence yield and selectivity of chemical reactions. In order to improve the process efficiency, a fundamental understanding of flow phenomena in bubble columns is necessary. A lot of research has been carried out for the investigation of hydrodynamics of bubble columns. Nonetheless, hydrodynamics is changing in the presence of a chemical reaction (e.g. shrinkage of bubbles due to mass-transfer processes). Hence, there is a strong interaction of hydrodynamics, mass-transfer and chemical reaction within bubble columns, which has been investigated in the past, amongst others, using the reaction of sodium hydroxide and carbon dioxide. However, most works are restricted to low gas holdups or provide only single point information due to the use of local probes (e.g. pH measurement). This contribution comprises the experimental investigation of the reaction of sodium hydroxide and carbon dioxide, applying Wire-Mesh Sensors for determining the locally occurring reaction steps at different operating conditions (e.g. gas flow rate of carbon dioxide, initial concentrations of sodium hydroxide). In turn, experimental results are compared with concentration profiles derived from known reaction kinetics. The application of Wire-Mesh Sensors for this purpose allows the visualization of the concentration distribution within the cross-section of the bubble column. Additionally, ultrafast X-ray computer tomography is used simultaneously to study the change of hydrodynamics during the reaction.

Keywords: Wire-Mesh Sensor; ultrafast X-ray tomography; two-phase flow; chemical reaction

  • Lecture (Conference)
    WCIPT8 - 8th World Congress on Insutrial Process Tomography, 26.-29.09.2016, Iguassu Falls, Brasilien
  • Contribution to proceedings
    WCIPT8 - 8th World Congress on Insutrial Process Tomography, 26.-29.09.2016, Iguassu Falls, Brasilien

Permalink: https://www.hzdr.de/publications/Publ-24317
Publ.-Id: 24317


Different oxidation states of Tc in solid state compounds and surface complexes – an XAS study

Schmeide, K.; Scheinost, A.

Results of XAS measurements of Tc siderite sorption samples as well as of solid state model compounds containing Tc in different oxidation states were presented.

Keywords: technetium; siderite; reduction; coordination; structure

  • Invited lecture (Conferences)
    8th International Workshop on “Coordination Chemistry of Metals with Medical Relevance and Supramolecular Building Blocks“, 26.-27.05.2016, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24316
Publ.-Id: 24316


Targetting microglia activation in schizophrenia by minocycline treatment

Mattei, D.; Ivanov, A.; Ferrai, G.; Jordan, P.; Guneykaya, D.; Schaafsma, W.; Przanowski, P.; Deuther-Conrad, W.; Brust, P.; Hesse, S.; Eggen, B.; Bodekke, E.; Kaminska, B.; Pombo, A.; Kettenmann, H.; Wolf, S. A.

The importance of the brain's phagocyte – the microglia – came recently into focus as a novel therapeutic target in psychiatric disorders. Dysregulations of microglia have been reported in post mortem tissue and also in vivo by increased radio ligand binding to the (phagocyte-specific) TSPO receptor in brains of schizophrenic patients. The tetracycline minocycline that partially acts on microglia has been shown to improve mainly negative symptoms in a few clinical studies. We here use an animal model of maternal immune activation to test its validity for clinical translation and investigate the pathways that are targeted by minocycline specific in microglia. Pregnant dams were injected intraperitoneally with the viral mimic PolyI:C or saline at gestational day 15 and the offspring was tested for behavioral deficits at postnatal day 60. Indeed, the offspring showed behavioral correlates of schizophrenia like decreased pre-pulse inhibition, sociability and cognitive performance along with an increased binding potential to the TSPO shown by autoradiography using [18F]GE-180 on hippocampal slices. This was accompanied by a profoundly altered transcriptome signature in hippocampal microglia and decreased phagocytic activity. Thereafter, mice were treated for five weeks with minocycline (3 mg/kg/day). This treatment normalized the behavioral deficits, TSPO binding and phagocytic activity and restored the transcriptome signature towards control levels. Our findings indicate that minocycline is a potent drug to affect specific microglial functions and thereby attenuate symptoms of schizophrenia in an animal model.

Keywords: Neuroimmunology; Schizophrenia: basic; Glia

  • Lecture (Conference)
    29th ECNP Congress, 17.-20.09.2016, Vienna, Österreich
  • European Neuropsychopharmacology 26(2016), 134

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Permalink: https://www.hzdr.de/publications/Publ-24315
Publ.-Id: 24315


Reactive absorption of CO2 in NaOH: Detailed study of enhancement factor models

Krauss, M.; Rzehak, R.

In a pioneering study, Darmana et al. [Chemical Engineering Science 62 (2007), 2556 - 2575], considered the reactive absorption of CO2 in aqueous NaOH in a bubble column. Although quite good agreement was obtained between an Euler-Lagrange simulation and measured pH-values at a single point, a number of aspects of the model deserve further discussion. This will be provided in the present work by using a simplified treatment that applies at the measurement location. Particularly relevant is the enhancement factor, which describes the effect of the chemical reaction on the mass transfer. An investigation of alternative expressions for this quantity is given, based on which an improved match with the data can be obtained. Furthermore, the complete network of possible reactions in this system has to be considered.

Keywords: mass transfer; chemical reaction; chemisorption; enhancement factor; dispersed gas liquid multiphase flow; modeling and simulation

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Permalink: https://www.hzdr.de/publications/Publ-24314
Publ.-Id: 24314


Euler-Euler Simulation und Modellvalidierung für Blasenströmungen

Guo, J.

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

Keywords: Blasenströmung; Euler-Euler zwei-Fluid-Modell; CFD-Simulation

  • Diploma thesis
    TU Dresden, 2016
    Mentor: Dr. Roland Rzehak (HZDR), Prof. Rüdiger Lange (TU-Dresden)
    57 Seiten

Permalink: https://www.hzdr.de/publications/Publ-24313
Publ.-Id: 24313


Analysis of SAM Coatings for Dropwise Condensation in Passive Safety Systems

Unger, S.; Sarker, D.; Harm, U.; Hampel, U.

Passive safety systems of spent fuel pools are one key technology for further improvement of the reliability of nuclear power plants. These systems transfer high amount of heat, while using air as a heat sink. For that reason the overall temperature differences are small. Since the heat transfer is based on natural convection and gravitational force, the heat transfer resistance of the heat exchangers are high compare to active systems. A Self-Assembled Monolayer (SAM) coating can address both challenges by enable a high compact condensation heat exchanger and by reducing the heat transfer resistance during condensation. Therefore different coating chemicals and surface roughness were analysed, to create the most beneficial heat transfer surface.

Keywords: Passive safety; dropwise condensation; condensation; heat transfer

  • Lecture (Conference)
    47th Annual Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Deutschland
  • Contribution to proceedings
    47th Annual Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Deutschland
    Proceedings of the 47th Annual Meeting on Nuclear Technology

Permalink: https://www.hzdr.de/publications/Publ-24312
Publ.-Id: 24312


Surprising effects of electron-electron scattering in graphene

Helm, M.; König-Otto, J.; Mittendorff, M.; Pashkin, A.; Schneider, H.; Wendler, F.; Winzer, T.; Malic, E.; Knorr, A.; Winnerl, S.

Two surprising effects related to electron-electron scattering in graphene are demonstrated: One is a long-lived anisotropic carrier distribution after THz excitation, and the other one is an unexpected sign reversal of the pump-probe signal in a magnetic field. The latter reflects an Auger scattering so strong that it overcomes the effect of optical pumping.

Keywords: graphene; pump-probe; terahertz; free-electron laser

  • Invited lecture (Conferences)
    5th Russia-Japan-USA-Europe Symposium on Fundamental & Applied Problems of Terahertz Devices & Technologies (RJUSE TeraTech-2016), 31.10.-04.11.2016, Sendai, Japan

Permalink: https://www.hzdr.de/publications/Publ-24311
Publ.-Id: 24311


Glacial chronology and production rate cross-calibration of five cosmogenic nuclide and mineral systems from the southern Central Andean Plateau

Luna, L. V.; Bookhagen, B.; Niedermann, S.; Rugel, G.; Scharf, A.; Merchel, S.

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

Keywords: cosmogenic nuclides; production rate; cross-calibration; South American Monsoon; Quaternary climate change; moraine

Permalink: https://www.hzdr.de/publications/Publ-24310
Publ.-Id: 24310


10Be surface exposure dating of the last deglaciation in the Aare Valley, Switzerland

Wüthrich, L.; Garcia Morabito, E.; Zech, J.; Trauerstein, M.; Veit, H.; Gnägi, C.; Merchel, S.; Scharf, A.; Rugel, G.; Christl, M.; Zech, R.

The combined Rhone and Aare Glaciers presumably reached their last glacial maximum (LGM) extent on the Swiss Plateau prior to 24 ka. Two well-preserved, less extensive moraine stades, the Gurten and Bern Stade, document the last deglaciation of the Aare Valley, yet age constraints are very scarce. In order to establish a more robust chronology for the glacial/deglacial history of the Aare Valley, we applied 10Be surface exposure dating on eleven boulders from the Gurten and Bern Stade. Several exposure ages are of Holocene age and likely document post-depositional processes, including boulder toppling and quarrying. The remaining exposure ages, however yield oldest ages of 20.7 ± 2.2 ka for the Gurten Stade and 19.0 ± 2.0 ka for the Bern Stade. Our results are in good agreement with published chronologies from other sites in the Alps.

Keywords: Pleistocene; Cosmogenic nuclides; Exposure Dating; Alpine foreland; accelerator mass spectrometry

Permalink: https://www.hzdr.de/publications/Publ-24309
Publ.-Id: 24309


Simulation of Liquid Metal Batteries by Continuum Mechanics

Weber, N.; Beckstein, P.; Galindo, V.; Landgraf, S.; Stefani, F.; Weier, T.

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

We will present numerical simulations of the fluid flow in LMBs and estimate their relevance for real cells. The numerical solvers combining heat transfer, fluid- and electrodynamics with the volume of fluid method are implemented in the open source library OpenFOAM. Reviewed phenomena include thermal convection, electro-vortex flow, the Tayler-instability as well as metal pad rolling, which is well known from aluminium reduction cells.

Keywords: OpenFOAM; liquid metal battery

  • Lecture (Conference)
    Helmholtz-Workshop "Multiscale Modeling of Energy Storage Materials", 10.-11.11.2016, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24308
Publ.-Id: 24308


Particles as concentrated sources related to uptake and radiological dose in mammals

Johansen, M. P.; Caffrey, E.; Child, D. P.; Collins, R.; Hotchkis, M. A. C.; Howell, N. A.; Payne, T. E.; Mokhber-Shahin, L.; Ikeda-Ohno, A.

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

Keywords: Plutonium; actinides; particulates; update; nuclear tests; dose; mammals; radio ecology

  • Lecture (Conference)
    2nd International Conference on Radioecological concentration processes (50 years later), 09.11.2016, Seville, Spain

Permalink: https://www.hzdr.de/publications/Publ-24307
Publ.-Id: 24307


The cosmic-ray exposure history of the Twannberg iron meteorite (IIG)

Smith, T.; Hofmann, B. A.; Leya, I.; Merchel, S.; Pavetich, S.; Rugel, G.; Scharf, A.

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

Keywords: AMS; cosmic rays; accelerator mass spectrometry; exposure age; terrestrial age; meteorite

Permalink: https://www.hzdr.de/publications/Publ-24306
Publ.-Id: 24306


Scaling EUV and X-ray Thomson Sources to Optical Free-Electron Laser Operation with Traveling-Wave Thomson-Scattering

Steiniger, K.; Albach, D.; Debus, A.; Loeser, M.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.

Traveling-Wave Thomson-Scattering (TWTS) allows for the realization of ultra-compact, inherently synchronized and highly brilliant light sources by providing optical undulators with hundreds to thousands of undulator periods from high-power, pulse-front tilted lasers pulses.

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

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

The talk will show that TWTS OFELs emitting ultraviolet radiation are realizable today with existing technology for electron accelerators and laser systems. Especially the ultra-low emittance of laser wakefield accelerated electron beams can be exploited to compensate for their one percent level energy spreads. We discuss an experimental setup to generate the tilted TWTS laser pulses. The method presented provides dispersion compensation, required due to angular dispersion, and is especially relevant when building compact, high-yield hard X-ray TWTS sources in large interaction angle setups.

Keywords: Traveling-Wave; Thomson scattering; FEL; X-ray; Laser dispersion compensation

  • Lecture (others)
    Invited Seminar talk at Helmholtz Institut Jena, 30.09.2016, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24305
Publ.-Id: 24305


Scaling EUV and X-ray Thomson Sources to Optical Free-Electron Laser Operation with Traveling-Wave Thomson-Scattering

Steiniger, K.; Albach, D.; Debus, A.; Loeser, M.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.

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

Keywords: Traveling-Wave; Thomson scattering; FEL; X-ray; Laser dispersion compensation

  • Poster
    The 15th International Conference on X-Ray Lasers, 22.-27.05.2016, Nara, Japan

Permalink: https://www.hzdr.de/publications/Publ-24304
Publ.-Id: 24304


Inclusive Λ production in proton-proton collisions at 3.5 GeV

Adamczewski-Musch, J.; Agakishiev, G.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Kuc, H.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Maurus, S.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataroe, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.

The inclusive production of {\Lambda} hyperons in proton-proton collisions at s√ = 3.18 GeV was measured with HADES at the GSI Helmholtzzentrum f\"ur Schwerionenforschung in Darmstadt. The experimental data are compared to a data-based model for individual exclusive {\Lambda} production channels in the same reaction. The contributions of intermediate resonances such as {\Sigma}(1385), {\Delta}++ or N* are considered in detail. In particular, the result of a partial wave analysis is accounted for the abundant pK+{\Lambda} final state. Model and data show a reasonable agreement at mid rapidities, while a difference is found for larger rapidities. A total {\Lambda} production cross section in p+p collisions at s√ = 3.18 GeV of {\sigma}(pp → {\Lambda} + X) = 207.3 ± 1.3 +6.0 -7.3 (stat.) ± 8.4 (syst.) +0.4 -0.5 (model) {\mu}b is found.

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Permalink: https://www.hzdr.de/publications/Publ-24303
Publ.-Id: 24303


MMM2016: Magnetic functionalities for flexible interactive electronics

Makarov, D.

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

  • Invited lecture (Conferences)
    61st Annual Conference on Magnetism and Magnetic Materials, 31.10.-04.11.2016, New Orleans, USA

Permalink: https://www.hzdr.de/publications/Publ-24302
Publ.-Id: 24302


Forschung und Lehre innerhalb des Kompetenzzentrums Ost für Kerntechnik auf den Gebieten Endlagerung, Reaktorsicherheit und Strahlenschutz

Kliem, S.; Hampel, U.; Hurtado, A.; Kästner, W.; Kratzsch, A.; Sahre, P.; Jansen, S.

Das Kompetenzzentrum Ost für Kerntechnik ist ein regionaler Zusammenschluss der kerntechnischen Einrichtungen mit dem Ziel, die kerntechnische, strahlentechnische und radiochemische Ausbildung an den sächsischen Ausbildungseinrichtungen wie bspw. der TU Dresden und der Hochschule Zittau/Görlitz zu erhalten und möglichst weiter zu entwickeln. Damit einhergehend werden für Lehre und Forschung Versuchseinrichtungen und andere Forschungsinfrastrukturen der Partner gemeinsam genutzt.
Das Kompetenzzentrum Ost für Kerntechnik hat sich die Sicherung des akademisch gebildeten Fachkräftenachwuchses in Universitäten, Hochschulen, Instituten, bei Kernkraftwerksbetreibern und -herstellern sowie in Behörden und Gutachtern zum obersten Ziel gemacht. Dazu werden die einschlägigen Anstrengungen der Mitgliedsorganisationen durch die Vertreter der einzelnen Unternehmen des Kompetenzzentrums koordiniert, um für effizienten Wissenstransfer und Kompetenzerhalt Sorge zu tragen.
Durch den politischen Beschluss bezüglich des Umbaus des Energieversorgungssystems in Deutschland und den damit verbundenen Entscheidungen zur Beendigung der Stromerzeugung aus Kernenergie bis Ende 2022 hat auch für die Mitglieder des Kompetenzzentrums Ost eine Zäsur im Bereich Lehre und Forschung zur Folge. Neben einer deutlichen Reduzierung der Forschungsförderung seitens der Industrie schlägt sich das auch in sinkenden Studenten- und Doktorandenzahlen nieder.
Im Vortrag werden die aktuellen Lehr- und Forschungsaktivitäten der Mitglieder des Kompetenzzentrums Ost mit besonderem Augenmerk auf die gemeinsam bearbeiteten Projekte vorgestellt und Perspektiven zukünftigen Wirkens aufgezeigt.

  • Lecture (Conference)
    48. Kraftwerkstechnisches Kolloquium, 18.-19.10.2016, Dresden, Deutschland
  • Contribution to proceedings
    48. Kraftwerkstechnisches Kolloquium, 18.-19.10.2016, Dresden, Deutschland
    Kraftwerkstechnik 2016, Freiberg: SAXONIA, 9783934409699, 725-733

Permalink: https://www.hzdr.de/publications/Publ-24301
Publ.-Id: 24301


The X2 Benchmark for VVER-1000 reactor calculations - overview and current status

Lötsch, T.; Kliem, S.; Bilodid, E.; Khalimonchuk, V.; Kuchin, A.; Ovdiienko, Y.; Ieremenko, M.; Blank, R.; Schultz, G.

The paper gives an overview about the tasks defined in the framework of the X2 benchmark, firstly proposed at the 19th symposium of the AER in 2009. The X2 benchmark was proposed for further validation and verification of the reactor physics code systems for VVER-1000 reactors with TVSA fuel assemblies. The X2 benchmark comprises all stages of reactor core calculations starting with the fuel assembly data preparation. Therefore X2 benchmark specifies the FA and core characteristics as well as the core loading patterns of four consecutive cycles for a Ukraine VVER-1000 reactor core. A set of operational data for comparisons with steady state reactor core calculations and transient neutron kinetics calculations were provided. The benchmark is useful for validating and verifying the whole system of codes and data libraries for reactor physics calculations including fuel assembly modelling, fuel assembly data preparation and reactor core modelling. Reviewed results of the tasks 1 and 2 for X2 benchmark steady state calculations were presented at the AER symposia. In the framework of several projects supported by the German BMU5) the 3D neutron kinetic code DYN3D and the coupling of DYN3d with thermo-hydraulics system codes were validated and verified on the basis of the data provided in the framework of the X2 benchmark. In preparing results for the X2 benchmark several organisations have been participated: IBBS, HZDR, SSTC, TÜV SÜD. On that basis TÜV SÜD has been provided the analysis and formulation of the specific X2 benchmark tasks. As continuation of the work on the X2 benchmark the tasks were extended with task 3 including data of the 3D calculations results and pin-by-pin distributions for selected fuel assemblies as well as task 4 providing data for 3D neutron kinetic calculations of reactor transients. The paper presents the current state of the X2 benchmark and discusses new results as continuation of the work started with the X2 benchmark proposal in 2009.

  • Contribution to proceedings
    26th Symposium of AER on VVER Reactor Physics and Reactor Safety, 10.-14.10.2016, Helsinki, Finland
    Proceedings of the 26th Symposium of AER on VVER Reactor Physics and Reactor Safety, Budapest: MTA EK

Permalink: https://www.hzdr.de/publications/Publ-24300
Publ.-Id: 24300


AER Working Group D on VVER Safety Analysis – Report of the 2016 Meeting

Kliem, S.

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

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

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

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

A list of the participants and a list of the handouts distributed at the meeting are attached to the report. The corresponding PDF-files of the handouts can be obtained from the chairman.

  • Contribution to proceedings
    26th Symposium of AER on VVER Reactor Physics and Reactor Safety, 10.-14.10.2016, Helsinki, Finland
    Proceedings of the 26th Symposium of AER on VVER Reactor Physics and Reactor Safety, Budapest: MTA EK
  • Lecture (Conference)
    26th Symposium of AER on VVER Reactor Physics and Reactor Safety, 10.-14.10.2016, Helsinki, Finland

Permalink: https://www.hzdr.de/publications/Publ-24299
Publ.-Id: 24299


Self-organized Ge & Si nanostructures by heavy-ion irradiation

Böttger, R.; Heinig, K.-H.; Bischoff, L.; Huebner, R.

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

Keywords: Silicon; Germanium; nanostructures; self-organization; ion irradiation

  • Invited lecture (Conferences)
    24th International Conference on the Application of Accelerators in Research and Industry, 30.10.-04.11.2016, Texas, USA

Permalink: https://www.hzdr.de/publications/Publ-24298
Publ.-Id: 24298


Fluid dynamics of bubbly flows

Ziegenhein, T.

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

Keywords: Bubbly flows; Fluid Dynamics; CFD; PTV; PIV; Lift-force; Bubble column

  • Doctoral thesis
    TU Berlin, 2016
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-074 2016
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-24297
Publ.-Id: 24297


Fundamentals of Ion-Solid Interaction - A Compact Introduction

Möller, W.

Keywords: Ion-Solid Interaction; Computer Simulation; Ion Stopping and Ranges; Ion Damage; Sputtering; Ion Mixing

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-073 2017
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-24296
Publ.-Id: 24296


Image-guided high precision proton irradiation of pancreatic adenocarcinoma using a gold fiducial marker

Stefanowicz, S.; Thiele, J.; Hoffmann, A.; Troost, E.

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

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

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

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

References
[1] Wysocka, B. et al.: Interfraction and Respiratory Organ Motion During Conformal Radiotherapy in Gastric Cancer, Int. J. Radiation Oncology Biol. Phys., 2010, 77 (1), pp. 53 – 59.

  • Lecture (Conference)
    4D Workshop 2016, 08.-09.12.2016, Groningen, Niederlande

Permalink: https://www.hzdr.de/publications/Publ-24295
Publ.-Id: 24295


Effect of baffles on bubble rising behavior

Sommer, A.-E.

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

Keywords: Activated sludge process; baffles; oxygen mass transfer; residence time

  • Diploma thesis
    TU Dresden, 2016
    Mentor: Herrmann-Heber, Robert; Reinecke, Sebastian
    94 Seiten

Permalink: https://www.hzdr.de/publications/Publ-24292
Publ.-Id: 24292


Enhanced proton acceleration in an applied longitudinal magnetic field

Arefiev, A.; Toncian, T.; Fiskal, G.

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

Keywords: proton acceleration; magnetic field; laser

Permalink: https://www.hzdr.de/publications/Publ-24291
Publ.-Id: 24291


Entwicklung und Umsetzung eines echtzeitfähigen Datenverarbeitungs- und Rekonstruktionsalgorithmus für die ultraschnelle Elektronenstrahl-Röntgen-CT

Frust, T.

This thesis demonstrates the development and the implementation of a real-time capable data processing and reconstruction algorithm for the ulftrafast X-ray scanner ROssendorf Fast Electron beam X-ray tomograph (ROFEX). This measuring system is built for non-invasive imaging of multiphase fluids. Thus, it requires a high scan rate of more than 1 kHz. This is achieved by an arrangement without mechanically rotating parts providing scan rates of up to 8 kHz. Current data processing is not suited to reconstruct a data stream of around 1,3 GB/s. Hence, visual inspection or active process feedback control is not possible yet. This work presents the design and implementation of real-time capable data processing providing a better usability and new fields of application for ROFEX. Therefore, the adjustment of data transfer from the measuring system to the reconstruction workstation as well as the implementation of a new software is essential. The application is implemented using a generic software pipeline consisting of distinct processing units exploiting data parallelism of NVIDIA GPUs with CUDA. Measurements on a NVIDIA GeForce GTX 1080 and NVIDIA Tesla K20c yield a reconstruction rate of more than 1 kHz, which is well-suited for an online application of ROFEX. Furthermore, a test system is introduced simulating an online capable detector. It shows the online visualization of reconstructed images as a first new application.

Keywords: cuda; parallel data processing; in-situ; ROFEX

  • Diploma thesis
    TU Dresden, 2016
    Mentor: Prof. Uwe Hampel
    81 Seiten
  • Lecture (others)
    Verteidigung der Diplomarbeit, 03.11.2016, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24290
Publ.-Id: 24290


Advanced Gamma and X-ray Computed Tomography for Multiphase Flow Analysis

Bieberle, A.

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

Keywords: computed tomography; multi-phase flow; CFD

  • Contribution to proceedings
    International Workshop on Process and Biomedical Tomography, 07.-09.11.2016, Warschau, Polen
  • Invited lecture (Conferences)
    International Workshop on Process and Biomedical Tomography, 07.-09.11.2016, Warschau, Polen

Permalink: https://www.hzdr.de/publications/Publ-24289
Publ.-Id: 24289


Simulation of a Main Steamline Break scenario using the 3D neutron kinetic core model Dyn3D coupled with the CFD software Trio U

Grahn, A.; Gommlich, A.; Kliem, S.

In the framework of the European project Nuresafe, the reactor dynamics code Dyn3D, developed at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), was coupled with the Computational Fluid Dynamics (CFD) solver Trio U, developed at CEA France, in order to replace Dyn3D’s one-dimensional hydraulic part with a full three-dimensional description of the coolant flow in the reactor core at higher spatial resolution. The present document gives an introduction into the coupling method and shows results of its application to the simulation of an Main Steamline Break (MSLB) accident of a Pressurised Water Reactor (PWR).

Keywords: reactor safety; code coupling; thermal hydraulics; computational fluid dynamics; reactor dynamics

  • Lecture (Conference)
    International Conference on Mathematics & Computational Methods Applied to Nuclear Science & Engineering (M&C 2017), 16.-20.04.2017, Jeju, Korea
  • Contribution to proceedings
    International Conference on Mathematics & Computational Methods Applied to Nuclear Science & Engineering (M&C 2017), 16.-20.04.2017, Jeju, Korea

Permalink: https://www.hzdr.de/publications/Publ-24287
Publ.-Id: 24287


Hindrance in MWCNT nanofluid flow through porous media observed by PET

Schymura, S.; Kulenkampff, J.; Franke, K.; Lippmann-Pipke, J.

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

Keywords: Kohlenstoffnanoröhrchen; carbon nanotubes; Positronenemissionstomografie; Positron Emission Tomography; Transport Experiment; transport experiment

  • Lecture (Conference)
    Interpore - First German National Chapter Meeting, 05.-06.12.2016, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24286
Publ.-Id: 24286


Environmental transformation of CeO2 Nanoparticles - Elucidating the role of dissolution by smart radiolabeling

Schymura, S.; Fricke, T.; Hildebrand, H.; Franke, K.

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

Keywords: Radiomarkierung, radiolabeling; Nanopartikel, nanoparticle; Cerdioxid, cerium dioxide; Planzenaufnahme, plan tuptake

  • Lecture (Conference)
    Nanosafe 2016, 07.-10.11.2016, Grenoble, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-24285
Publ.-Id: 24285


Measuring at relevant concentrations - radiolabeling as a versatile tool in nanosafety research

Schymura, S.; Hildebrand, H.; Fricke, T.; Bellido, E.; Ojea-Jimenez, I.; Cydzik, I.; Kozempel, J.; Dalmiglio, M.; Bulgheroni, A.; Freyer, A.; Cotogno, G.; Simonelli, F.; Mansel, A.; Kulenkampff, J.; Holzwarth, U.; Gibson, N.; Franke, K.

The employment of radiotracers is a versatile tool for the detection of nano-particulate materials in complex systems such as environmental samples or organisms. With the increasing usage of nanoparticles in applications outside of research laboratories, a careful risk assessment of their release into the environment becomes mandatory. However, the monitoring of nanoparticles in such complex natural systems as soil, natural waters, plants, sewage sludge, etc. is nearly impossible using conventional methods, especially at environmentally relevant concentrations. This obstacle can be overcome by radiolabeling, which may be of crucial value in enabling such research.
We have developed various methods of introducing radiotracers into some of the most common nanoparticles, such as Ag, carbon, SiO2, CeO2 and TiO2 nanoparticles. The labeling techniques are the synthesis of the nanoparticles using radioactive starting materials, the binding of the radiotracer to the nanoparticles, the activation of the nanoparticles using proton irradiation, the recoil labeling utilizing the recoil of a nuclear reaction to implant a radiotracer into the nanoparticle, and the in-diffusion of radiotracers into the nanoparticles at elevated temperatures. Using these methods we have produced [105/110mAg]Ag, [124/125/131I]CNTs, [48V]TiO2, [139Ce]CeO2, [7Be]MWCNT, [7Be]SiO2, [44/45Ti]TiO2, etc.. The methods are adaptable for a wide range of other nanoparticles. The so-labelled nanoparticles can be detected at minimal concentrations well in the ng/L range even with a background of the same element and without complicated sample preparations necessary.
Using our methods one can radiolabel commercial nanoparticle samples for sensitive detection in environmentally relevant trace concentrations. The labeled particles have been successfully used in release studies, environmental mobility studies, fate studies in waste water treatment and plant uptake studies.

Keywords: Radiomarkierung; radiolabeling; Nanopartikel; nanoparticles; cyclotron; Zyklotron

  • Poster
    Nanosafe 2016, 07.-10.11.2016, Grenoble, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-24284
Publ.-Id: 24284


Shielding and activation studies for the MYRRHA research reactor

Müller, S. E.; Ferrari, A.; Konheiser, J.

The planned MYRRHA research reactor in Mol (Belgium) aims to demonstrate efficient transmutation of high level waste and associated Accelerator-Driven Systems (ADS) technology. The system is based on a lead-bismuth eutectic (LBE) cooled reactor, working both in critical and in sub-critical operation modes. The neutrons needed to sustain fission in the sub-critical mode are produced via spallation processes by a 600 MeV, 4 mA proton beam, which is provided by a linear accelerator and hits a LBE spallation target located inside the reactor core. In order to assess the main shielding problems, a method based on the combined use of the two Monte Carlo codes MCNPX and FLUKA has been developed, with the goal to perform detailed analyses of both the radiation fields due to the system in operation, and the coupled residual radiation due to the activated materials. As a result, neutron and photon fluences as well as prompt and residual ambient dose equivalent rates have been evaluated. In addition, an activation database for many of the structural materials has been built.

  • Lecture (Conference)
    16th International Symposium on Reactor Dosimetry, 07.-12.05.2017, Santa Fe, New Mexico, USA
  • Contribution to proceedings
    16th International Symposium on Reactor Dosimetry, 08.-12.05.2017, Santa Fe, New Mexico, USA
    Proceedings of the 16th International Symposium on Reactor Dosimetry, West Conshohocken, PA (USA): ASTM International, West Conshohocken, PA,, 978-0-8031-7661-4, 15-22
    DOI: 10.1520/STP160820170088

Permalink: https://www.hzdr.de/publications/Publ-24283
Publ.-Id: 24283


Free-surface dynamics in Induction Processing Applications

Beckstein, P.; Galindo, V.; Gerbeth, G.

Induction processing technology is widely applied in metallurgical and crystal growth industry where conducting or semi-conducting material is involved. In many applications, alternating magnetic fields which are used to generate heat and force occur together with a free-surface flow. The numerical analysis of such three-dimensional, multi-physical phenomena on industrial scale is still a big challenge.
We present an overview of a novel multi-mesh model to address these kind of coupled problems by means of computational simulations. It is based on the Finite Volume Method (FVM) of the software foam-extend (http://www.foam-extend.org) - an extended version of OpenFOAM (Weller et al, 1998). Our development is motivated by the desire to investigate the so called Ribbon Growth on Substrate
(RGS) process. RGS is a crystallisation technique that allows the production of silicon wafers and advanced metal-silicide alloys (Schönecker et al, 2004) with high volume manufacturing and outstanding material yield.

Keywords: Numerical simulation; coupled multi-physics; free-surface flow; eddy-currents; Ribbon Growth on Substrate process

  • Book chapter
    J. Miguel Nóbrega and Hrvoje Jasak: OpenFOAM® - Selected papers of the 11th Workshop, Cham (ZG) Switzerland: Springer International Publishing AG, 2019, 978-3-319-60845-7, 197-210
    DOI: 10.1007/978-3-319-60846-4
  • Lecture (Conference)
    11th OpenFOAM® Workshop, 26.-30.06.2016, Guimarães, Portugal

Permalink: https://www.hzdr.de/publications/Publ-24282
Publ.-Id: 24282


Biotransformation and detoxification of selenite by microbial biogenesis of selenium-sulfur nanoparticles

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

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

Keywords: selenium; Azospirillum brasilense; nanoparticle; reduction; selenite

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Permalink: https://www.hzdr.de/publications/Publ-24281
Publ.-Id: 24281


Free-surface dynamics in the Ribbon Growth on Substrate (RGS) Process

Beckstein, P.; Galindo, V.; Gerbeth, G.

With the Ribbon Growth on Substrate (RGS) technology, a new crystallization technique is available that allows controlled high crystallization rate production of silicon wafers and advanced metal-silicide alloys. Compared to other casting methods, such as e.g. directional solidification, the RGS process allows better crystallization control, high volume manufacturing and high material yield due to its continuous, substrate-driven design. Insights from modelling the characteristic melt flow in the casting frame are very desirable. To address this demand, we are developing a new numerical tool based on OpenFOAM which can be utilized to simulate the free-surface dynamics of the melt flow under the influence of alternating electromagnetic fields. The underlying multi-physical model involves three-dimensional hydrodynamic and magnetodynamic effects and their interaction.

Keywords: Ribbon Growth on Substrate; numerical simulation; coupled multi-physics; free-surface flow; eddy-currents

  • Open Access Logo International Journal of Applied Electromagnetics and Mechanics 53(2017)51, 543-551
    DOI: 10.3233/JAE-162237
  • Poster
    International Conference on Heating by Electromagnetic Sources, 25.-27.05.2016, Padua, Italy
  • Contribution to proceedings
    International Conference on Heating by Electromagnetic Sources, 24.-27.05.2016, Padua, Italy
    Proceedings of the International Conference on Heating by Electromagnetic Sources, Padova: SGEditoriali Padova, 127-134

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-24280
Publ.-Id: 24280


Experimental measurements in melting ingots in the melt of the same material

Ditze, A.; Scharf, C.

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

Keywords: Melting; Ice; Metals; Alloys; Heat transfer; Dimensionless numbers; Natural convection; Nusselt; Rayleigh; Prandtl; Stefan

Permalink: https://www.hzdr.de/publications/Publ-24279
Publ.-Id: 24279


Numerical simulation of full scale Upper Plenum Test Facility experiments

Höhne, T.; Deendarlianto, A.

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

Keywords: CFD; horizontal flow; UPTF; PWR; AIAD; single phase flow; two-phase flow

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Permalink: https://www.hzdr.de/publications/Publ-24278
Publ.-Id: 24278


Stratified and Segregated Flow Modelling - AIAD 2016

Höhne, T.

Today: Limits in simulating stratified & segregated two phase flow
Algebraic Interfacial Area Density Model (AIAD)
Free Surface Drag
Turbulence Damping
Sub-grid wave turbulence (SWT)
Verification and Validation is going on – more experimental data are required for the validation

Keywords: AIAD; Free Surface Drag; Sub-grid wave turbulence (SWT)

  • Contribution to proceedings
    14th Short Course “Multiphase Flow: Simulation,Experiment and Application”, 08.-10.11.2016, Dresden, Deutschland
  • Lecture (Conference)
    14th Short Course “Multiphase Flow: Simulation,Experiment and Application”, 08.-10.11.2016, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24276
Publ.-Id: 24276


Comparison of Technologies for Nano Device Prototyping with a Special Focus on Ion Beams - A review

Bruchhaus, L.; Mazarov, P.; Bischoff, L.; Gierak, J.; Wieck, A. D.; Hövel, H.

Nano device prototyping (NDP) is essential for realizing and assessing ideas as well as theories in form of nano devices, before they can be made available in or as commercial products. In this review, application results patterned similarly as in the semiconductor industry (for cell phone, computer processors or memory) will be presented. For NDP some requirements are different, thus different technologies are employed. Currently, in NDP, for many applications direct write Gaussian vector scan electron beam lithography (EBL) is used to define the required features in organic resist on this scale.
We will take a look at many application results carried out by EBL, self-organized 3D epitaxy, atomic probe microscopy (STM / AFM) and in more detail ion beam techniques. For ion beam techniques there is a special focus on those based upon liquid metal (alloy) ion sources (LM(A)IS), as recent developments have significantly increased their applicability for NDP.

Keywords: nanotechnology; nano device protoyping; nano patterning; nano fabrication; focused ion beam; electron beam lithography; self-organized 3D epitaxy; atomic; scanning probe nano patterning; magnetics; photonics; fluidics; implantation

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Permalink: https://www.hzdr.de/publications/Publ-24275
Publ.-Id: 24275


Prediction of Dysphagia and Xerostomia based on CT imaging features of HNSCC Patients

Pilz, K.; Leger, S.; Zwanenburg, A.; Richter, C.; Krause, M.; Baumann, M.; Löck, S.; Troost, E. G. C.

Purpose/Objective: Radiochemotherapy (RCT) for patients with head and neck squamous cell carcinoma (HNSCC) frequently causes xerostomia and dysphagia, which may be alleviated by treatment adaption, e.g., modulation of dose distribution to the salivary glands. Current clinical models, which are based on dosimetric parameters, mostly achieve moderate prediction accuracy. Therefore, we aimed to improve the prediction of xerostomia and dysphagia by using additional imaging biomarkers based on computed tomography (CT) scans.

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

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-24274
Publ.-Id: 24274


Raw material "criticality" - Sense or non-sense

Frenzel, M.; Kullik, J.; Reuter, M. A.; Gutzmer, J.

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

Keywords: Supply security; Critical materials; Metals

Permalink: https://www.hzdr.de/publications/Publ-24273
Publ.-Id: 24273


A Multiple-Technique Round-Robin Test in Actinide Spectroscopy

Foerstendorf, H.; Müller, K.; Tsushima, S.; Steudtner, R.; Kumke, M. U.; Lefèvre, G.; Rothe, J.; Mason, H.; Yang, P.

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

  • Lecture (Conference)
    3rd International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS 2016), 07.-10.11.2016, Richland, U.S.A.

Permalink: https://www.hzdr.de/publications/Publ-24271
Publ.-Id: 24271


A Special Issue of the International Journal of Mineral Processing honoring Prof. Dr. sc. techn. Drs. h.c. Heinrich Schubert

Rudolph, M.; Peuker, U. A.

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

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

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

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

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

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

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

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-24270
Publ.-Id: 24270


Influence of iron doping on the structural, chemical, and optoelectronic properties of sputtered zinc oxide thin films

Al-Kuhaili, M. F.; Durrani, S. M. A.; El-Said, A. S.; Heller, R.

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

Keywords: Doping; Fe; structure; optoelectronic properties; sputtering; zink oxid

Permalink: https://www.hzdr.de/publications/Publ-24269
Publ.-Id: 24269


Electron-beam pulse annealed Ti-implanted GaP

Werner, Z.; Barlak, M.; Ratajczak, R.; Konarski, P.; Markov, A. M.; Heller, R.

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

Keywords: GaP; implantation; electron beam; annealing; Ti

Permalink: https://www.hzdr.de/publications/Publ-24268
Publ.-Id: 24268


Enhancement of the refractive index of sputtered zinc oxide thin films through doping with Fe2O3

Al-Kuhaili, M. F.; Durrani, S. M. A.; El-Said, A. S.; Heller, R.

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

Keywords: Zinc oxide; Iron oxide; Sputtering; Doping; Refractive index

Permalink: https://www.hzdr.de/publications/Publ-24267
Publ.-Id: 24267


ThermAc: A Joint Project on Aquatic Actinide Chemistry and Thermodynamics at Elevated Temperature Conditions

Bosbach, D.; Altmaier, M.; Gaona, X.; Endrizzi, F.; Brendler, V.; Steudtner, R.; Franzen, C.; Tsushima, S.; Panak, P. J.; Skerencak-Frech, A.; Hagemann, S.; Brandt, F.; Krüger, S.; Colàs, E.; Grivé, M.; Thoenen, T.; Kulik, D. A.

The ThermAc project aims at extending the chemical understanding and available thermodynamic database for actinides, long-lived fission products and relevant matrix elements in aquatic systems at elevated temperatures. Such conditions are expected when storing highly active heat producing waste in a repository system over a significant period of time after starting repository operation. If early canister failure occurs, radionuclides therefore may contact aquatic systems at higher temperatures. Adequate scientific tools must be available to assess the related chemical effects and their impact upon safety. ThermAc approaches this challenge by evaluating the capabilities of a variety of estimation methods to obtain thermodynamic parameters (formation constants, enthalpic and entropic data) as f(T). This is done by both intercomparison between such methods and pointwise checks with experimental results. There, a clear focus is on long-lived actinides in oxidation states III, V and VI, with selected fission products and important redox controlling matrix elements like Fe also receiving attention. ThermAc addresses the temperature range from ~5°C up to ~90°C, focusing on systems at low or intermediate ionic strength. Only for selected cases with specific relevance or scientific interest, higher temperatures up to 200°C or salt brine solutions are investigated. Chemical analogs help to gain information on solid phase transformation processes. Ion-ion-interaction processes are treated with the SIT, in agreement with the NEA-TDB project. Quantum chemical calculations are used to support the interpretation of experimental findings, and establish a fundamental understanding of chemical effects on a molecular level.

  • Poster
    Goldschmidt2016, 26.06.-01.07.2016, Yokohama, Japan

Permalink: https://www.hzdr.de/publications/Publ-24266
Publ.-Id: 24266


ThermAc: A Joint Project on Aquatic Actinide Chemistry and Thermodynamics at Elevated Temperature Conditions

Panak, P. J.; Altmaier, M.; Brandt, F.; Brendler, V.; Chiorescu, I.; Colàs, E.; Curtius, H.; Endrizzi, F.; Franzen, C.; Gaona, X.; Grivé, M.; Hagemann, S.; Koke, C.; Kulik, D. A.; Krüger, S.; Lee, J.-Y.; Maiwald, M.; Skerencak-Frech, A.; Steudtner, R.; Thoenen, T.; Tsushima, S.

The ThermAc project is extending the chemical understanding and available thermodynamic database for actinides, long-lived fission products and relevant matrix elements in aquatic systems at elevated temperatures. To this end, a systematic use of estimation methods, new experimental investigations and quantum-chemistry based information is used. ThermAc has started in March 2015 and is projected for three years, running until 28.02.2018. The project is funded by the German Federal Ministry for Education and Research (BMBF) and is coordinated by KIT-INE.

  • Poster
    9th international conference on nuclear and radiochemistry (NRC9), 29.08.-02.09.2016, Helsinki, Finnland

Permalink: https://www.hzdr.de/publications/Publ-24265
Publ.-Id: 24265


ThermAc - a collaborative project investigating aquatic chemistry and thermodynamics of actinides at elevated temperature conditions.

Altmaier, M.; Brandt, F.; Brendler, V.; Chiorescu, I.; Colàs, E.; Curtius, H.; Endrizzi, F.; Franzen, C.; Gaona, X.; Grivé, M.; Hagemann, S.; Koke, C.; Kulik, D. A.; Krüger, S.; Lee, J.-Y.; Maiwald, M.; Miron, G. D.; Panak, P. J.; Skerencak-Frech, A.; Steudtner, R.; Thoenen, T.; Tsushima, S.

The ThermAc project is extending the chemical understanding and available thermodynamic database for actinides, long-lived fission products and relevant matrix elements in aquatic systems at elevated temperatures. To this end, a systematic use of estimation methods, new experimental investigations and quantum-chemistry based information is used. ThermAc has started in March 2015 and is projected for three years, running until 28.02.2018. The project is funded by the German Federal Ministry for Education and Research (BMBF) and is coordinated by KIT-INE.

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

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

A key result from the comparison of predictions based upon estimation methods with new experimental data derived within ThermAc will be the assessment of the use of estimations methods to set up a workable thermodynamic database for elevated temperatures with high applicability to nuclear waste disposal issues. In this context it will be clarified, to which extent systems will remain critical with regard to available thermodynamic data, and which relevant processes at elevated temperatures are still not sufficiently understood.

  • Lecture (Conference)
    Plutonium Futures, 18.-22.09.2016, Baden-Baden, Deutschland
  • Poster
    International Symposium on Solubility Phenomena and Related Equilibrium Processes (ISSP), 24.-29.07.2016, Genf, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-24264
Publ.-Id: 24264


U(VI) – SO₄²¯ complexation at elevated temperature – a combination of spectroscopy and thermodynamic modeling.

Franzen, C.; Haubitz, T.; Drobot, B.; Firkala, T.; Brendler, V.; Steudtner, R.

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

  • Lecture (Conference)
    Goldschmidt 2016, 26.06.-01.07.2016, Yokohama, Japan

Permalink: https://www.hzdr.de/publications/Publ-24263
Publ.-Id: 24263


Light control of Orbital Domains: case of the prototypical manganite La0.5Sr1.5MnO4

Miller, T.; Gensch, M.; Wall, S.

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

Keywords: THz control; High-field THz; TELBE; ultra-fast

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Permalink: https://www.hzdr.de/publications/Publ-24262
Publ.-Id: 24262


Direct experimental evidence for a multiparticle-hole ground state configuration of deformed 33-Mg

Datta, U.; Rahaman, A.; Aumann, T.; Beceiro-Novo, S.; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chakraborty, S.; Chartier, M.; Cortina-Gil, D.; de Angelis, G.; Diaz Fernandez, P.; Emling, H.; Ershova, O.; Fraile, L. M.; Geissel, H.; Gonzalez-Diaz, D.; Jonson, B.; Johansson, H.; Kalantar-Nayestanaki, N.; Kröll, T.; Krücken, R.; Kurcewicz, J.; Langer, C.; Le Bleis, T.; Leifels, Y.; Marganiec, J.; Münzenberg, G.; Najafi, M. A.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Plag, R.; Reifarth, R.; Ricciardi, V.; Rossi, D.; Scheit, H.; Scheidenberger, C.; Simon, H.; Taylor, J. T.; Togano, Y.; Typel, S.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Weigand, M.; Winfield, J. S.; Yakorev, D.; Zoric, M.

The first direct experimental evidence of a multiparticle-hole ground state configuration of the neutron-rich Mg33 isotope has been obtained via intermediate energy (400 A MeV) Coulomb dissociation measurement. The major part ∼(70±13)% of the cross section is observed to populate the excited states of Mg32 after the Coulomb breakup of Mg33. The shapes of the differential Coulomb dissociation cross sections in coincidence with different core excited states favor that the valence neutron occupies both the s1/2 and p3/2 orbitals. These experimental findings suggest a significant reduction and merging of sd-pf shell gaps at N∼20 and 28. The ground state configuration of Mg33 is predominantly a combination of Mg32(3.0,3.5MeV;2-,1-)νs1/2, Mg32(2.5MeV;2+)νp3/2, and Mg32(0;0+)νp3/2. The experimentally obtained quantitative spectroscopic information for the valence neutron occupation of the s and p orbitals, coupled with different core states, is in agreement with Monte Carlo shell model (MCSM) calculation using 3 MeV as the shell gap at N=20.

Keywords: nuclear physics reaction neutron-rich shell model

Permalink: https://www.hzdr.de/publications/Publ-24261
Publ.-Id: 24261


The role of surface anisotropy for ion beam pattern formation

Engler, M.; Škereň, T.; Facsko, S.

Ion beam irradiation can produce different patterns on semiconductor surface. While the surface is amorphized at low temperatures, the surface remains crystalline above the dynamic recrystallization temperature. Reverse epitaxy leads to pattern formation, which is driven by diffusion of vacancies and adatoms on the surface, above this temperaure.

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

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

Keywords: ion irradiation; pattern formation; nano pattern

  • Lecture (Conference)
    20th International Conference on Ion Beam Modification of Materials (IBMM2016), 31.10.-04.11.2016, Wellington, New Zealand

Permalink: https://www.hzdr.de/publications/Publ-24259
Publ.-Id: 24259


Electron-density assessment using dual-energy CT: accuracy and robustness

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

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

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

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

Conclusion:
The alpha-blending approach for electron-density determination shows universal applicability to any mixture of human tissue with a very small methodological uncertainty (< 0.15%); and a robust and bias-free calibration method, which is straightforward to implement. We conclude that further refinement of algorithms for DECT-based electron-density assessment is not advisable.

Keywords: Dual-energy CT; proton therapy; heavy ion therapy; range uncertainty

  • Lecture (Conference)
    Annual Meeting of the European Society for Radiotherapy & Oncology (ESTRO), 05.-09.05.2017, Wien, Österreich
  • Open Access Logo Abstract in refereed journal
    Radiotherapy and Oncology 123(2017), S912
    DOI: 10.1016/S0167-8140(17)32205-3

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Permalink: https://www.hzdr.de/publications/Publ-24258
Publ.-Id: 24258


Hard X-ray Photon-in Photon-out Spectroscopy as a Probe of the Temperature-Induced Delocalization of Electrons in Nanoscale Semiconductors

Hirsch, O.; Kvashnina, K.; Willa, C.; Koziej, D.

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

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Permalink: https://www.hzdr.de/publications/Publ-24257
Publ.-Id: 24257


Substrate-dependence of competitive nucleotide pyrophosphatase / phosphodiesterase1 (NPP1)

Lee, S.-Y.; Sarkar, S.; Bhattarai, S.; Namasivayam, V.; de Jonghe, S.; Stephan, H.; Herdewijn, P.; El-Tayeb, A.; Müller, C. E.

Nucleotide pyrophosphatase / phosphodiesterase type 1 (NPP1) is a membrane glycoprotein involved in the hydrolysis of extracellular nucleotides. Its major substrate is ATP which is converted to AMP and diphosphate. NPP1 was proposed as a new therapeutic target in brain cancer and immuno-oncology. Several NPP1 inhibitors have been reported to date, most of which were evaluated versus the artificial substrate p-nitrophenyl 5’-thymidine monophosphate (p-Nph-5’-TMP). Recently, we observed large discrepancies in inhibitory potencies for a class of competitive NPP1 inhibitors when tested versus the artificial substrate p-Nph-5’-TMP as compared to the natural substrate ATP. Therefore, the goal of the present study was to investigate whether inhibitors of human NPP1 generally display substrate dependent inhibitory potency. Systematic evaluation of nucleotidic as well as non-nucleotidic NPP1 inhibitors revealed significant differences in determined Ki values for competitive, but not for non- and un-competitive inhibitors when tested versus the frequently used artificial substrate p-Nph-5’-TMP as compared to ATP. Allosteric modulation of NPP1 by p-Nph-5’- TMP may explain these discrepancies. Results obtained using the AMP derivative p41 nitrophenyl 5’-adenosine monophosphate (p-Nph-5’-AMP) as an alternative artificial substrate correlated much better with those employing the natural substrate ATP.

Keywords: Ectonucleotidase inhibitors; enzyme assay; p-nitrophenyl 5'-thymidine monophosphate; NPP1; NPP1 inhibitors; nucleotide pyrophosphatase 1

Permalink: https://www.hzdr.de/publications/Publ-24256
Publ.-Id: 24256


Activation studies at the HZDR medical cyclotron: Simulation and Experiment

Müller, S. E.

First comparisons of simulation and experiments for activation studies.

  • Lecture (Conference)
    FLUKA collaboration meeting, 17.-18.10.2016, CERN (Geneva), Switzerland

Permalink: https://www.hzdr.de/publications/Publ-24255
Publ.-Id: 24255


Uranium(VI) reduction by isolated anaerobic microorganisms from the flooding water of the former uranium mine Königstein (Saxony/Germany)

Gerber, U.; Krawczyk-Bärsch, E.; Scheinost, A.; Arnold, T.

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

[1.] Zirnstein, I., Charakterisierung der mikrobiellen Biozönose im sauren Grubenwasser des ehemaligen Uranbergwerks Königstein, Institut für Ressourcenökologie, Dissertation, 2015, TU Dresden: Dresden.
[2.] Lloyd, J.R.M., L. E. , Interactions of microorganisms with radionuclides. Elsevier Science. 2002.
[3.] Lovley, D.R., et al., Enzymatic Iron and Uranium Reduction by Sulfate-Reducing Bacteria. Marine Geology, 1993. 113(1-2): p. 41-53.

Keywords: Uranium; reduction; bioremediation; sulfate-reducing bacteria (SRB)

  • Poster
    15th symposium on remediation, 13.-14.10.2016, Jena, Germany

Permalink: https://www.hzdr.de/publications/Publ-24254
Publ.-Id: 24254


Microbial Influence on Bentonite Transformation

Matschiavelli, N.; Steglich, J.; Kluge, S.; Arnold, T.; Cherkouk, A.

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

Keywords: Bentonit; Eisenreduktion; DNA-Extraktion; RISA

  • Lecture (others)
    UMB-Projekttreffen, 02.06.2016, Braunschweig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24253
Publ.-Id: 24253


NTCP models for early toxicities in patients with prostate or brain tumours receiving proton therapy

Dutz, A.; Agolli, L.; Troost, E. G. C.; Krause, M.; Baumann, M.; Lühr, A.; Löck, S.

Purpose: To identify patients who are likely to benefit most from proton therapy, based on the potential reduction in normal tissue complication probability (NTCP) compared to photon therapy. The NTCP models required for this comparison were developed using clinical data on early side effects for patients with brain or prostate cancer having received proton therapy.

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

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

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

[1] Langendijk JA et al. (2013) Radiother Oncol 107, 267 - 273.

  • Poster
    ESTRO 2017, 05.-09.05.2017, Wien, Österreich
  • Open Access Logo Abstract in refereed journal
    Radiation Oncology 123(2017), S860
    DOI: 10.1016/S0167-8140(17)32030-3

Permalink: https://www.hzdr.de/publications/Publ-24252
Publ.-Id: 24252


MRI-based analysis of volumetric changes of healthy brain tissue in glioma patients after photon radio(chemo)therapy

Gommlich, A.; Wahl, H.; Raschke, F.; Baumann, M.; Krause, M.; Troost, E. G. C.

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

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

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

Outlook
The observed changes over time underpin the importance of exact follow-up protocols in quantitative evaluation of structural brain changes after radiotherapy. Together with the data on interpatient heterogeneity, our findings allowed to design a prospective study in a larger cohort of patients treated by photons vs. protons for assessing the dependence of MRI-detected volumetric changes with delivered dose.

Keywords: structural MRI; grade II/III glioma; healthy brain tissue; photon therapy; volume change; image processing

  • Poster
    ESTRO 36 - European Society for Radiotherapy and Oncology, 05.-09.05.2017, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-24251
Publ.-Id: 24251


Monte Carlo Calculation Procedure and its Implementation for Radiation Load Estimation on Russian VVER Reactor Equipment

Baier, S.; Konheiser, J.; Boradkin, P.; Khrennikov, N.; Gazetdinov, A.

A prediction of radiation load parameters (fluence, fluence rate, neutron energy spectrum) of reactor components, e.g. reactor pressure vessel (RPV), of Russian VVER reactors is regulated by the requirements of the Russian normative documents. One of the key measures is the validation of calculated procedures by ex-vessel neutron activation measurements at VVER nuclear power plants. The neutron dosimetry research for every reactor component includes validation calculations by appropriate codes.
The standard method was based on the three-dimensional (3D) synthesis method with input from results of calculations from the deterministic code DORT coupled with the BUGLE-96T library. It was identified in comparison between experiments and calculations that this method gives different results outside the active core. Hence, the usage of a 3D code is essential. For this reason, the Scientific and Engineering Centre for Nuclear and Radiation Safety (SEC NRS) wants to use the Monte-Carlo code TRAMO for own fluence calculations. Thus, the purpose of this work is the possible application of TRAMO for expert calculations of radiation load parameters of reactor components of all VVER reactor types, the verification of results by comparison with other codes (deterministic and Monte-Carlo) and the validation by neutron activation measured data. The paper presents possible options of the new version of TRAMO for neutrons fluence calculations suggested by SEC NRS.

Keywords: Monte Carlo code; TRAMO; reactor dosimetry; neutron fluence calcolation

  • Poster
    Sixteenth International Symposium on Reactor Dosimetry, 07.-12.05.2017, Santa Fe, USA
  • Contribution to proceedings
    Sixteenth International Symposium on Reactor Dosimetry (ISRD-16), 07.-12.05.2017, Santa Fe, USA
    Proceedings of the 16th International Symposium on Reactor Dosimetry, West Conshohocken: ASTM International, 978-0-8031-7661-4, 579-589
    DOI: 10.1520/STP160820170088

Permalink: https://www.hzdr.de/publications/Publ-24250
Publ.-Id: 24250


Dual-energy CT-based proton treatment planning to assess patient-specific range uncertainties

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

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

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

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

Conclusion:
In contrast to a generic HLUT, a DECT-based SPR prediction can individually consider age- and sex- dependent tissue variability in proton treatment planning. This diversity information can also provide suggestions for subgroup-specific improvements of the heuristic CT calibration. The assessment of relative SPR and dose differences underlines the clinical potential of DECT, which now needs to be confirmed against a ground truth. Further investigations of patients’ DECT scans enable comprehensive SPR evaluations to quantify CT-related range uncertainties and to assess clinical safety margins.

Keywords: Dual-energy CT; proton therapy; proton range uncertainty

  • Lecture (Conference)
    Annual Meeting of the European Society for Radiotherapy & Oncology (ESTRO), 05.-09.05.2017, Wien, Österreich
  • Open Access Logo Abstract in refereed journal
    Radiotherapy and Oncology 123(2017), S73-S75
    DOI: 10.1016/S0167-8140(17)30593-5

Permalink: https://www.hzdr.de/publications/Publ-24249
Publ.-Id: 24249


Surface plasmon resonance coupling effect of micro-patterned gold film

in Chinese

Lu, N.-Y.; Yu, X.-J.; Wan, J.-W.; Weng, Y.-Y.; Guo, J.-H.; Liu, Y.

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

Keywords: Surface enhanced Raman scattering; Soft template imprinting; Finite difference time domain; Surface micro-pattern

Permalink: https://www.hzdr.de/publications/Publ-24248
Publ.-Id: 24248


Robustness evaluation of single- and multifield optimized proton plans for unilateral head and neck targets

Cubillos-Mesías, M.; Troost, E. G. C.; Appold, S.; Krause, M.; Richter, C.; Stützer, K.

Purpose:
To compare 4 different proton pencil beam scanning (PBS) treatment approaches for unilateral head and neck cancer (HNC) targets in terms of robustness, including anatomical changes during the treatment course.

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

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

Conclusion:
The PTV-based MFO approach showed less robustness against uncertainties in setup and range, as well as for anatomical changes during the treatment course. Both SFO plans are robust in terms of CTV coverage; however, they present higher doses to the ipsilateral parotid gland. Robust MFO approach presents the lowest doses to the ipsilateral parotid and more robustness against uncertainties.
The dose to more organs at risk and the difference in normal tissue complication probabilities for the 4 planning approaches will be presented as well.

Keywords: Robust optimization; proton therapy

  • Lecture (Conference)
    Annual meeting of European Society of Radiotherapy and Oncology (ESTRO), 05.-09.05.2017, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-24247
Publ.-Id: 24247


Measurement of the stellar 58Ni(n, γ)59Ni cross section with AMS

Ludwig, P.; Rugel, G.; Dillmann, I.; Faestermann, T.; Fimiani, L.; Hain, K.; Korschinek, G.; Lachner, J.; Poutivtsev, M.; Knie, K.; Heil, M.; Käppeler, F.; Wallner, A.

The 58Ni(n; γ)59Ni cross section was measured with a combination of the activation technique and accelerator mass spectrometry (AMS). The neutron activations were performed at the Karlsruhe 3.7 MV Van de Graaff accelerator using the quasi-stellar neutron spectrum at kT = 25 keV produced by the 7Li(p, n)7Be reaction. The subsequent AMS measurements were carried out at the 14 MV tandem accelerator of the Maier-Leibnitz-Laboratory in Garching using the Gas-filled Analyzing Magnet System (GAMS). Three individual samples were measured, yielding a Maxwellian-averaged cross section at kT = 30 keV of <σ>30keV= 30.4 (23)syst(9)stat mbarn. This value is slightly lower than two recently published measurements using the time-of-flight (TOF) method, but agrees within the uncertainties. Our new results also resolve the large discrepancy between older TOF measurements and our previous value.

Keywords: Neutron capture cross section; Accelerator Mass Spectrometry; s-process

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-24246
Publ.-Id: 24246


Characterizing geometrical accuracy in clinically optimized 7T and 3T MR images for high-precision radiation treatment of brain tumours

Peerlings, J.; Compter, I.; Janssen, F.; Wiggins, C.; Mottaghy, F.; Lambin, P.; Hoffmann, A.

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

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

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

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

Keywords: ultra-high field MRI; radiotherapy; brain tumours; geometrical image distortion

Permalink: https://www.hzdr.de/publications/Publ-24245
Publ.-Id: 24245


The microbiology of subsurface, salt-based nuclear waste repositories: using microbial ecology, bioenergetics, and projected conditions to help predict microbial effects on repository performance

Swanson, J. S.; Cherkouk, A.; Arnold, T.; Meleshyn, A.; Reed, D. T.

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

  • Other report
    Los Alamos National Laboratory: Los Alamos National Laboratory Report LA-UR-16-28895, 2016
  • Other report
    Nuclear Energy Agency: Nuclear Energy Agency (NEA) report, 2018

Permalink: https://www.hzdr.de/publications/Publ-24243
Publ.-Id: 24243


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