Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32337 Publications
Bestimmung der Gas-Flüssigkeits-Grenzfläche in Anstaupackungen mittels ultraschneller Röntgentomographie
Sohr, J.; Bieberle, M.; Schubert, M.; Flechsig, S.; Kenig, E. Y.; Hampel, U.;
Durch die alternierend angeordneten Packungslagen mit unterschiedlichen geometrischen Oberflächen bilden sich in Anstaupackungen abhängig von den Betriebsbedingungen Filmströmung und Sprudelschicht gleichzeitig aus. Der intensive Kontakt zwischen der Gas- und Flüssigkeitsphase in den sprudelnden Bereichen der Anstaupackung führt zu einer Trenneffizienzsteigerung von bis zu 30 % im Vergleich zu konventionell gepackten Kolonnen [1]. Zur Abschätzung der Beiträge der jeweiligen Bereiche mit unterschiedlichen Strömungsregimen zur Gesamttrennleistung ist die Kenntnis der Gas-Flüssigkeits-Grenzfläche erforderlich. Die Grenzfläche kann mittels ultraschneller Röntgentomographie bestimmt werden, welche die dynamischen Strömungsstrukturen mit einer Bildrate von 1000 Bildern pro Sekunde erfasst. Mithilfe eines modifizierten Level-set-Algorithmus wird die Phasengrenze zwischen Gas einerseits und Flüssigkeit sowie Metallpackung andererseits in den Querschnittsbildern detektiert (Abb.1).
In diesem Beitrag werden sowohl die Methodik zur Bestimmung der Phasengrenzfläche als auch Ergebnisse für unterschiedliche Gas- und Flüssigkeitsbelastungen bei verschiedenen Packungskombinationen präsentiert.
Wir danken der DFG für die finanzielle Unterstützung des Kooperationsprojekts "Experimentelle und theoretische Untersuchung der Fluiddynamik und des Stofftrennverhaltens von Anstaupackungen" (KE 837/26-1, HA 3088/10-1).
[1] M. Jödecke, T. Friese, G. Schuch, B. Kaibel, H. Jansen, Institution of Chemical Engineers Symposium Series, Institution of Chemical Engineers, 2006, Vol.152, pp. 786–789.
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Membrantechnik, 27.-29.03.2019, Potsdam, Deutschland

Publ.-Id: 29129 - Permalink


Partieller Einsatz von teilweise gefluteten Packungen
Flechsig, S.; Utchenko, Y.; Sohr, J.; Schubert, M.; Hampel, U.; Kenig, E. Y.;
Ein Weg zur Reduzierung des hohen Energiebedarfs thermischer Trennverfahren ist die Prozessintegration. Ein Beispiel dafür ist die Integration verschiedener Strömungsformen in einem Trennapparat durch den Einsatz von Anstaupackungen, wodurch eine Erhöhung der Trennleistung im Vergleich zu Strukturpackungen erzielt wird. Anstaupackungen bestehen aus zwei alternierend angeordneten Lagen von industriell verfügbaren Standardpackungen mit unterschiedlichen spezifischen Oberflächen. Die untere Anstaulage weist eine geringere Lastgrenze als die darüber angeordnete Abscheidelage auf, wodurch im Betrieb zwischen den Flutpunkten
beider Lagen ein heterogenes Strömungsmuster entsteht. Dabei bildet sich in der gezielt gefluteten Anstaulage eine bis in die Abscheidelage hineinreichende Sprudelschicht, die durch eine intensive Phasenvermischung und große
Phasengrenzflächen geprägt ist.
Um die Leistungscharakteristik von Anstaupackungen mit der von anderen Einbauten vergleichen zu können, wurde in einer vorherigen Arbeit [1] ein rate-based-Modell entwickelt, welches die Auswirkungen der belastungsabhängig auftretenden Regime in Anstaupackungen berücksichtigt. Basierend auf experimentellen Daten zur CO2-Absorption mit wässrigen Aminlösungen im Technikumsmaßstab sowie tomographischen Untersuchungen wurden Abhängigkeiten der modellspezifischen Parameter identifiziert und anschließend regimespezifisch ins Modell implementiert. Mittels Prozesssimulationen der CO2-Absorption aus Abgasen gasbefeuerter Kraftwerke im industriellen Maßstab werden im Rahmen dieser Arbeit Anstaupackungen und Strukturpackungen hinsichtlich der benötigten Kolonnenabmessungen und des zu überwindenden Druckverlustes verglichen. Um eine abschließende Bewertung durchzuführen, wurden mithilfe von Aspen Process Economic AnalyzerTM die Anlagen- und Betriebskosten für die CO2-Abscheidung bestimmt. Zusätzlich wurde zur Ermittlung eines optimalen Designs der Einfluss der wesentlichen Geometrieparameter von Anstaupackungen auf die Kosten untersucht.
[1] S. Flechsig, J. Sohr, M. Schubert, U. Hampel, E.Y. Kenig, Chem. Eng. Trans., 2018, 69, 169-174, DOI: 10.3303/CET1869029.
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Membrantechnik, 27.-29.03.2019, Potsdam, Deutschland

Publ.-Id: 29128 - Permalink


Mass transfer and electrolyte flow during electrodeposition on a conically shaped electrode under the influence of a magnetic field
Huang, M.; Marinaro, G.; Yang, X.; Fritzsche, B.; Lei, Z.; Uhlemann, M.; Eckert, K.; Mutschke, G.;
The electrodeposition of copper on a conically shaped diamagnetic electrode was studied under the influence of a vertical magnetic field. Numerical simulations combined with measurements of the velocity and the concentration field were conducted to provide understanding of the influence of the Lorentz force on the deposition process. The secondary flow caused by the magnetic field is directed downward along the cone surface and thus supporting conical growth. Since the cathode is placed at the bottom of the electrochemical cell, natural convection is counteracting the influence of the Lorentz force. However, the different time scales of both forces involved allow to utilize the beneficial influence of the Lorentz force, e.g. in pulsed deposition regimes.
Keywords: copper electrodeposition, magnetic field, surface-structured electrode, Mach-Zehnder interferometry, shadowgraphy, numerical simulation

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  • Secondary publication expected from 01.06.2020

Publ.-Id: 29127 - Permalink


Multidimensional fluid mixing study during an asymmetric injection of cold water in the primary side of a generic PWR KONVOI with ATHLET 3.1A
Diaz Pescador, E.; Schäfer, F.; Kliem, S.;
The presented paper gathers the insights obtained during the study of the multidimensional fluid mixing in the reactor pressure vessel (RPV) during an asymmetric injection of cold or overcooled water in the primary side of a generic German PWR KONVOI reactor by means of the thermal-hydraulic system code ATHLET 3.1A. With this aim, the paper provides first an overview on the selection procedure of the accident scenarios to be studied together with the plant model development, with special emphasis on the pseudo multidimensional RPV configuration. Later on the fluid mixing study in the RPV is performed during an overcooling transient by means of two different developed vessel configurations and the obtained results are assessed against experimental data from analogous tests carried out at the ROCOM test facility, showing good agreement to each other.
  • Contribution to proceedings
    50th Annual Meeting on Nuclear Technology (AMNT) 2019, 07.05.2019, Berlin, Germany
  • Lecture (Conference)
    50th Annual meeting on Nuclear Technology (AMNT) 2019, 07.-08.05.2019, Berlin, Germany

Publ.-Id: 29125 - Permalink


Late life brain perfusion after prenatal famine exposure
de Rooij, S. R.; Mutsaerts, H. M.; Petr, J.; Asllani, I.; Caan, M. W.; Groot, P.; Nederveen, A.; Schwab, M.; Roseboom, T. J.;
Early nutritional deprivation may cause irreversible damage to the brain and seems to affect cognitive function in older age. We investigated whether prenatal undernutrition was associated with brain perfusion differences in older age. We acquired Arterial spin labelling scans in 118 Dutch famine birth cohort members. Cerebral blood flow (CBF) was compared between exposed and unexposed groups in grey and white matter, perfusion territories, neurodegeneration-related regions anterior and posterior cingulate cortex and precuneus. Furthermore, we compared the GM/WM-ratio and the spatial coefficient of variation (CoV) as a proxy of overall cerebrovascular health. The WM ASL signal and the GM/WM-ratio were significantly lower and higher respectively among exposed participants. Exposed men had lower CBF in anterior and posterior cingulate cortices and higher spatial CoV. The latter seemed largely mediated by higher 2h-glucose levels at age 50. Our findings suggest that overall brain perfusion was worse in exposed participants, especially men exposed to undernutrition in early gestation. These results provide further evidence for life-long effects of undernutrition during early brain development.
Keywords: brain perfusion; prenatal famine; fetal programming

Publ.-Id: 29117 - Permalink


Simulating air-breathing fuel cells using openFuelCell
Weber, N.; Chaparro, A. M.; Ferreira-Aparicio, P.; Zhang, S.; Reimer, U.; Beale, S.;
The talk will be dedicated to modelling polymer electrolyte fuel cells. In the first part, the theory of the fuel cell model is presented. Details on its implementation in the open source library openFuelCell will be given. Secondly, numerical results on modelling an air-breathing fuel cell operated at CIEMAT will be shown and discussed.
  • Lecture (Conference)
    OpenFOAM Workshop, 23.07.2019, Duisburg, Germany

Publ.-Id: 29113 - Permalink


Modelling electric potential distributions in batteries and fuel cells: an overview
Weber, N.; Personnettaz, P.; Weier, T.; Sadoway, D.;
The talk will give an overview on simulating electric potential and current distributions in the frame of the finite volume method. Special attention will be paid to modelling internal discontinuities of the electric potential, as they appear at the electrode-electrolyte interface in fuel cells, electrolysers and batteries. The theoretical background will be explained and illustrated with simple examples.
  • Lecture (Conference)
    OpenFOAM Workshop, 23.07.2019, Duisburg, Deutschland

Publ.-Id: 29112 - Permalink


Interaction of uranium with halophilic microorganisms
Bader, M.; Hilpmann, S.; Swanson, J. S.; Steudtner, R.; Drobot, B.; Schmidt, M.; Rossberg, A.; Ikeda-Ohno, A.; Stumpf, T.; Cherkouk, A.;
Rock salts are considered as potential host rocks for the long-term storage of highly radioactive waste in a deep geological repository. In addition to bacteria and fungi, extremely halophilic archaea, e.g. Halobacterium species, are predominantly present in this habitat. For long-term risk assessment it is of high interest to study how these microorganisms can potentially interact with radionuclides if the radionuclides are released from the waste repository. Given this fact, the interactions of extremely halophilic archaea from the genus Halobacterium and the moderately halophilic bacterium Brachybacterium sp. G1 with uranium, one of the major radionuclides of concern in the geological repository of radioactive wastes, were investigated in detail in batch experiments. The archaea and the bacterium showed different association mechanisms with uranium. Brachybacterium sp. G1 cells sorbed uranium within a short time, whereas a much longer and a multi-stage bioassociation process, dependent on the uranium concentration, occurred with the archaea. Furthermore, a multi-spectroscopic (time-resolved laser-induced fluorescence spectroscopy and X-ray absorption spectroscopy) and -microscopic (scanning electron microscopy coupled with energy-dispersive X-ray analysis for elemental mapping) approach was used to elucidate the U(VI) bioassociation behavior. By using these spectroscopic and microscopic tools, the formation of a U(VI) phosphate mineral, such as meta-autunite, by the Halobacterium species was demonstrated. These findings offer new insights into the microbe-actinide interactions at highly saline conditions relevant to the disposal of nuclear waste.
  • Lecture (Conference)
    Halophiles 2019, 24.-28.06.2019, Cluj-Napoca, Romania

Publ.-Id: 29110 - Permalink


Prediction of Bubble Departure in Forced Convection Boiling with a Mechanistic Model that Considers Dynamic Contact Angle and Base Expansion
Setoodeh, H.; Ding, W.; Lucas, D.; Hampel, U.;
A mechanistic model for bubble dynamics in flow boiling that is based on a force balance approach for a growing bubble is introduced. It considers evaporation of the microlayer underneath the bubble, thermal diffusion and condensation around the bubble cap as well as dynamic inclination and contact angles between the bubble and the heating wall. It requires no recalibration of parameters to predict the bubble growth. Validation against different experimental flow boiling data was carried out with no case-dependent recalibration and yielded good agreement. The simulations confirmed the dependency of bubble departure and lift-off diameters on different parameters, such as heat flux, liquid properties, subcooling temperature, system pressure, inclination angle of channel, channel geometry and mass flow rate.
Keywords: flow boiling; bubble growth; bubble departure; force balance

Publ.-Id: 29109 - Permalink


Revealing the Formation Dynamics of the Electric Double Layer by means of in-situ Rutherford Backscattering Spectrometry
Baghban Khojasteh Mohammadi, N.; Apelt, S.; Bergmann, U.; Facsko, S.; Heller, R.;
We report on a new versatile experimental setup for in-situ Rutherford backscattering spectrometry at solid- liquid interfaces that enables investigations of electric double layers directly, in-situ and in a quantitative manner. A liquid cell equipped with a three electrode arrangement is mounted in front of the beam line and a thin Si3N4 window down to a thickness of 150 nm separates the vacuum of the detector chamber from the electrolyte in the cell. Since the contribution of the window to the measured spectra is minimized, a large variety of elements at the solid-liquid interface with sensitivities far below one mono layer can be monitored. The attachment of Ba onto the Si3N4 surface as a function of contact time and pH value of the electrolyte solution was chosen as example system. From our measurement we can not only read the evolution of the double layer but also derive limits for the point of zero charge for the Si3N4 surface. Our findings of 5.7 ≤ pH_PZC ≤ 6.2 are in good accordance with values found in the literature obtained by other techniques. Despite the measurements shown in this work, the presented setup allows for a large variety of in-situ investigations at solid-liquid interfaces such as tracing electro-chemical reactions, monitoring segregation, adsorption and dissolution and corrosion processes.
Keywords: Electric Double Layer, in-situ RBS, solid-liquid interface

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Publ.-Id: 29106 - Permalink


Indium thiospinel In1-xxIn2S4 – structural characterization and thermoelectric properties
Wyżga, P.; Veremchuk, I.; Himcinshi, C.; Burkhardt, U.; Carrillo-Cabrera, W.; Bobnar, M.; Hennig, C.; Leithe-Jasper, A.; Kortus, J.; Gumeniuk, R.;
A detailed study of polycrystalline indium-based In1-xxIn2S4 (x = 0.16, 0.22, 0.28, 0.33) thiospinel is presented. The comprehensive description of synthesis conditions, phase composition and thermoelectric properties is performed applying various diffraction, microscopic and spectroscopic methods. Single-phase α- and β-In1-xxIn2S4 were found in the samples with 0.16  x  0.22 and x = 0.33 (In2S3), respectively, while In0.720.28In2S4 is proven to contain both α- and β-polymorphic modifications. Consequently, thermoelectric characterization of well-defined α-and β-In1-xxIn2S4 is conducted for the first time. α-In1-xxIn2S4 (x = 0.16, 0.22 and 0.28) revealed n-type semiconducting behavior, large Seebeck coefficient (< - 200 μV∙K-1) and moderate charge carrier mobility on the level of ~ 20 cm2V-1s-1 at room temperature (RT). The evident decrease of charge carrier concentration (increase of electrical resistivity) and thermal conductivity (even below 0.6 W∙m-1K-1 at 760 K) for larger In-content is observed. Although β-In0.670.33In2S4 (β-In2S3) is a distinct polymorphic modification, it followed the above-mentioned trend in thermal conductivity and displayed significantly higher charge carrier mobility (~ 104 cm2V-1s-1 at RT). These findings indicate that structural disorder in α-modification affects both electronic and thermal properties in this thiospinel. The reduction of thermal conductivity counterbalances lowered power factor and thus, thermoelectric figure of merit ZTmax = 0.2 at 760 K is nearly the same for both α- and β-In1-xxIn2S4.
Keywords: In2S3, thermoelectric properties, thiospinel, Raman spectroscopy, transmission electron microscopy

Publ.-Id: 29105 - Permalink


Structural stability and thermoelectric performance of high quality synthetic and natural pyrites (FeS2)
Zuñiga-Puelles, E.; Cardoso-Gil, R.; Bobnar, M.; Veremchuk, I.; Himcinschi, C.; Hennig, C.; Kortus, J.; Heide, G.; Gumeniuk, R.;
Synthetic bulk and natural pyrite from the hydrothermal mine in Schönbrunn (Saxony, Germany) are confirmed to be stoichiometric compounds with the composition FeS2 and to be stable up to ~600 K by combined chemical, spectroscopic and X-ray diffraction analyses. Natural pyrite with negligibly small amount (< 0.6 wt.%) of well-defined transition metal carbonates impurities revealed characteristics of a nondegenerate semiconductor and is considered as a model system for investigation of thermoelectric performance. In the temperature range 50-600 K both natural and synthetic high quality bulk FeS2 samples show electrical resistivity varying within (220)-(5×10-3) Ω m and Seebeck coefficients of (4)-(-450) μV K-1. The thermal conductivity is large (~40 W m-1 K-1 at 300 K) and exclusively due to phononic contribution. It reveals a well pronounced maximum centered at ~75 K for natural pyrite (grain size ≤ 5 mm), which becomes almost completely suppressed in the sintered bulk samples due to increase of the point defects concentration and additional scattering on the grain boundaries (grain size ≤ 100 μm). The thermoelectric efficiency of a pure pyrite with ZT ~ 10-6 at 600 K is indeed by a factor of ~1000 worse than those reported earlier for some minerals and synthetic samples.
Keywords: crystal structure, thermoelectric, natural mineral, pyrite

Publ.-Id: 29104 - Permalink


Reduced diffusion in normal appearing white matter of glioma patients following radio(chemo)therapy
Raschke, F.; Wesemann, T.; Wahl, H.; Appold, S.; Krause, M.; Linn, J.; Troost, E. G. C.;
Background and purpose:
Standard treatment of high grade gliomas includes gross tumour resection followed by radio(chemo)therapy. Radiotherapy inevitably leads to irradiation of normal brain tissue. The goal of this prospective, longitudinal study was to use MRI to quantify normal appearing white and grey matter changes following radiation treatment as a function of dose and time after radiotherapy.
Materials and methods:
Pre-radiotherapy MRI (proton or photon therapy) and follow-up MRIs collected in 3 monthly intervals thereafter were analysed for 22 glioma patients and included diffusion tensor imaging, quantitative T1, T2* and proton density mapping. Abnormal tissue was excluded from analysis. MR signal changes were quantified within different dose bin regions for grey and white matter and subsequently for whole brain white matter.
Results:
We found significant reductions of mean diffusivity, radial diffusivity, axial diffusivity and T2* in normal appearing white matter regions receiving a radiation dose as low as 10-20 Gy within the observational period of up to 18 months. The magnitude of these changes increased with the received radiation dose and progressed with time after radiotherapy. Whole brain white matter also showed a significant reduction in radial diffusivity as a function of radiation dose and time after radiotherapy. No significant changes were observed in grey matter.
Conclusion:
Diffusion tensor imaging and T2* imaging revealed normal appearing white matter changes following radiation treatment. The changes were dose dependant and progressed over time. Further work is needed to understand the underlying tissue changes and to correlate the observed diffusion changes with late brain malfunctions.
Keywords: White Matter; Grey Matter; Diffusion Tensor Imaging; Radiotherapy; quantitative MRI; Proton Therapy; Photon Therapy; glioma; normal tissue

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  • Secondary publication expected from 29.06.2020

Publ.-Id: 29101 - Permalink


Calcium binding to a disordered domain of a type III-secreted protein from a coral pathogen promotes secondary structure formation and catalytic activity
Hoyer, E.; Knöppel, J.; Liebmann, M.; Steppert, M.; Raiwa, M.; Herczynski, O.; Hanspach, E.; Zehner, S.; Göttfert, M.; Tsushima, S.; Fahmy, K.; Oertel, J.;
Strains of the Gram-negative bacterium Vibrio coralliilyticus cause the bleaching of corals due to decomposition of symbiotic microalgae. The V. coralliilyticus strain ATCC BAA-450 (Vc450) encodes a type III secretion system (T3SS). The gene cluster also encodes a protein (locus tag VIC_001052) with sequence homology to the T3SS-secreted nodulation proteins NopE1 and NopE2 of Bradyrhizobium japonicum (USDA110). VIC_001052 has been shown to undergo auto-cleavage in the presence of Ca2+ similar to the NopE proteins. We have studied the hitherto unknown secondary structure, Ca2+-binding affinity and stoichiometry of the “metal ion-inducible autocleavage” (MIIA) domain of VIC_001052 which does not possess a classical Ca2+-binding motif. CD and fluorescence spectroscopy revealed that the MIIA domain is intrinsically largely disordered. Binding of Ca2+ and other di- and trivalent cations induced secondary structure and hydrophobic packing after partial neutralization of the highly negatively charged MIIA domain. Mass spectrometry and isothermal titration calorimetry showed two Ca2+-binding sites which promote structure formation with a total binding enthalpy of -110 kJ mol-1 at a low micromolar Kd. Putative binding motifs were identified by sequence similarity to EF-hand domains and their structure analyzed by molecular dynamics calculations. The stoichiometric Ca2+-dependent induction of structure correlated with catalytic activity and may provide a “host-sensing” mechanism that is shared among pathogens that use a T3SS for efficient secretion of disordered proteins.
Keywords: metal protein interactions, protein folding, rhizobium, intrinsically disordered protein

Publ.-Id: 29100 - Permalink


Frontiers of applications of Petawatt lasers, Plasma accelerator development in Dresden
Schramm, U.ORC
Discussion on progress of PW laser applications and advanced accelerators of protons and electrons
Keywords: Petawatt laser, laser particle acceleration, LWFA, secondary sources
  • Invited lecture (Conferences)
    SPIE Optics + Optoelectronics, 02.-04.04.2019, Prag, Czech Republic
  • Invited lecture (Conferences)
    JuSPARC Kick-off Workshop, 27.-29.03.2019, Vaals, Niederlande

Publ.-Id: 29099 - Permalink


Laser plasma proton accelerators for therapy ?
Schramm, U.ORC
Workshop discussion on advanced accelerators for therapy.
Keywords: particle cancer therapy, laser acceleration
  • Invited lecture (Conferences)
    2nd ARIES Annual Meeting, 10.-11.04.2019, Budapest, Ungarn

Publ.-Id: 29098 - Permalink


Phonon Magnetochiral Effect
Nomura, T.; Zhang, X.-X.; Zherlitsyn, S.; Wosnitza, J.; Tokura, Y.; Nagaosa, N.; Seki, S.;
The magnetochiral effect (MCE) of phonons, a nonreciprocal acoustic propagation arising due to symmetry principles, is demonstrated in the chiral-lattice ferrimagnet Cu2OSeO3. Our high-resolution ultrasound experiments reveal that the sound velocity differs for parallel and antiparallel propagation with respect to the external magnetic field. The sign of the nonreciprocity depends on the chirality of the crystal in accordance with the selection rule of the MCE. The nonreciprocity is enhanced below the magnetic ordering temperature and at higher ultrasound frequencies, which is quantitatively explained by a proposed magnon-phonon hybridization mechanism.

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Publ.-Id: 29097 - Permalink


Quantification of the metabolic uptake rate in whole body F-18 FDG PET: a comparison between dynamic and static imaging
van den Hoff, J.; Hofheinz, F.; Weise, R.; Maus, J.; Preuß, R.; Burchert, W.;
Ziel/Aim:
Dynamic whole body (DWB) FDG PET has become available with the recent introduction of the "flow motion" package by Siemens which offers fully automated generation of parametric images of the metabolic uptake rate K[m]. While this approach is superior to SUV-based quantification, it requires substantially more scan time and reduces patient throughput. On the other hand, the tumor to blood standard uptake ratio (SUR) has outperformed SUV in several clinical studies, which is attributed to a very high correlation between SUR and K[m]. However, direct evidence for this correlation is scarce. Our study compares K[sur], the SUR-derived "static" estimate of K[m], with the Patlak-derived K[m].

Methodik/Methods:
Altogether, 12 oncological patients are enclosed and scheduled for DWB PET. Parametric images of K[m] and K[sur] are computed using the vendor provided Patlak procedure and in-house software, respectively. Evaluation of the voxel intensity correlation between both parametric images as well as ROI-based analysis is performed.

Ergebnisse/Results:
So far, 4 patients have been evaluated. K[m] and K[sur] are highly correlated (R^2=0.97) in areas with nonnegligible irreversible uptake (so far we investigated the range K[m]=[0.01,0.07]). K[m] and K[sur] images have very similar image contrast between such areas. Minor contrast differences exist in healthy soft tissue and regions where the Patlak approach is invalid (notably the liver). The relative scale factor between both parametric images is 0.86.

Schlussfolgerungen/Conclusions:
Our results suggest that SUR and K[sur] are proportional surrogates of true K[m]. The unquestionable potential of DWB PET might thus be more relevant for applications beyond oncological FDG PET. To test this conjecture, comprehensive studies in homogeneous patient groups are required in order to compare the prognostic value of K[m] and SUR/K[sur] in the context of survival analysis
  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Publ.-Id: 29096 - Permalink


Quantifizierung von pulmonalen 18F-FDG-PET/CT-Untersuchungen: Vergleich von Standard Uptake Ratio (SUR) und Patlak (Ki)
Braune, A.; Bluth, T.; Kiss, T.; Hofheinz, F.; Gama De Abreu, M.; Kotzerke, J.;
Ziel/Aim:
Dynamische PET/CT Scans gefolgt von Patlak Modellierung der 18F-FDG-Aufnahmerate (Ki) ist eine etablierte Methode zur Quantifizierung der Lungenentzündung im tierexp. Modell des akuten Lungenversagens (ARDS), erfordert aber zeitintensive Aufnahmen und erlaubt nur ein begrenztes cranio-caudales FoV. Dyn. PET/CT Scans von Patienten mit Lebermetastasen zeigten gute Korrelationen zwischen Ki und Standard Uptake Ratio (SUR = ROI-SUV / Blut-SUV) [1]. Wir analysierten in einem tierexp. ARDS-Modell, ob stat. PET/CT Messungen und SUR-Analysen alternativ zu dyn. PET/CT und Ki für die Quantifizierung der pulmonalen Inflammation genutzt werden können.

Methodik/Methods:
In 14 Schweinen erfolgten nach Induktion eines schweren ARDS sowie nach 24h Beatmung dyn. 18F-FDG-PET/CT Scans und Patlak Ki-Analysen. Anschließende stat. PET/CT Scans (77-81min p.i.) wurden für die Bestimmung von mittleren, zeitkorrigierten SUR-Werte genutzt. SUR- und Ki-Werte wurden für 5 ventro-dorsale ROIs mittels linearer Regression verglichen (Variationskoeffizient, r2). Anhand von Blutproben wurde die Variabilität der arteriellen Inputfunktion (AIF) zwischen Tieren und Messzeitpunkten verglichen.

Ergebnisse/Results:
SUR- und Ki-Werte korrelierten vor und nach 24h Beatmung (r2=0.84 bzw. 0.97). Der zeitliche Verlauf der AIF war zwischen Tieren und Aufnahmezeitpunkten vergleichbar und konnte mittels einer inversen Potenzfunktion beschrieben werden (r2 = 0.99). Die Patlak-Zeit war Zeit-, aber nicht AIF-abhängig, und wies eine geringe Variabilität auf (t=70min: 153.6 ± 13.3min).

Schlussfolgerungen/Conclusions:
Für die Quantifizierung der pulmonalen Inflammation in exp. Studien der Anästhesie können stat. PET/CT Scans und SUR-Analysen alternativ zu dyn. 18F-FDG-PET/CT und Patlak genutzt werden. Dies ermöglicht eine schnellere Datenakquisition, die Erfassung der gesamten Lunge und eine Reduktion der erforderlichen Blutproben. Grundlage der guten Ki-SUR Korrelation bildete die geringe Variabilität des AIF.
  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Publ.-Id: 29095 - Permalink


Validation of an independent prognostic value of the asphericity of FDG uptake in non-small cell cancer patients undergoing treatment in curative intent
Rogasch, J.; Chibolela, C.; Frost, N.; Wedel, F.; Hofheinz, F.; Rückert, J.; Neudecker, J.; Böhmer, D.; von Laffert, M.; Amthauer, H.; Furth, C.;
Ziel/Aim:
In patients with non-small cell lung cancer (NSCLC) undergoing treatment with curative intent, the asphericity (ASP) of the primary tumor’s metabolic tumor volume (MTV) has been demonstrated as a prognostic factor. This study aimed at validation in an independent cohort with sufficient sample size.

Methodik/Methods:
Retrospective study in 313 NSCLC patients (203 men; median age, 67 [41-87] a) undergoing FDG-PET/CT with the same scanner prior to treatment in curative intent (always including resection of the primary tumor). 137 patients had UICC stage I, 79 patients stage II and 97 patients stage III disease (adenocarcinoma [ADC], 153; squamous cell carcinoma [SCC], 143, other, 17). Delineation of primary tumor MTV with semiautomated background-adapted threshold relative to its SUVmax. Univariable Cox regression for progression-free (PFS) and overall survival (OS) for PET parameters (MTV, ASP, SUVmax, SUVmean), clinical (UICC stage I vs. II vs. III), histological (SCC vs. ADC) and treatment variables (Rx/1 vs. R0 resection, chemotherapy yes/no, radiotherapy yes/no). Multivariable Cox of parameters significant in univariate Cox.

Ergebnisse/Results:
Events (progression, relapse, death) occurred in 169/313 patients, 139 patients died (median follow-up in survivors, 37 months). In multivariable Cox for OS, ASP >33.3% (hazard ratio [HR], 1.53 [95%-confidence interval, 1.02-2.3]), Rx/1 vs. R0 resection (HR, 2.47 [1.5-4.2]) and SCC vs. ADC (HR, 1.53 [1.1-2.2]) were significant. Log-rank test for ASP was significant at any cut-off from 18% upwards. Among separate UICC stages, ASP was only prognostic for OS in stage II (optimal, >19.5%; median OS, 33 vs. 59 months; p<0.01). In multivariable Cox for PFS, ASP >21.2% (HR, 1.75 [1.2-2.5]) and Rx/1 vs. R0 (HR, 2.48 [1.5-4.1]) were significant. Log-rank test for ASP was significant at any cut-off from 10-60%.

Schlussfolgerungen/Conclusions:
ASP was validated as an independent predictor of PFS and OS in NSCLC patients with curative treatment intent. Subdividing UICC stages, ASP remained prognostic in stage II.
  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Publ.-Id: 29094 - Permalink


Interobserver variability of image–derived arterial blood SUV in FDG–PET
Hofheinz, F.; Maus, J.; Zschaeck, S.; Rogasch, J.; Schramm, G.; Oehme, L.; Apostolova, I.; Kotzerke, J.; van den Hoff, J.;
Ziel/Aim:
The standardized uptake value (SUV) is essentially the only means for quantitative evaluation of static FDG PET. However, the SUV approach has well-known shortcomings which adversely affect the reliability of the SUV as a surrogate of the metabolic rate of glucose consumption. The standard uptake ratio (SUR), i.e. the uptake time corrected ratio of tumor SUV to image-derived arterial blood SUV, has been shown to overcome most of these shortcomings and to increase the prognostic value in comparison to SUV. However, it is unclear, to what extent the SUR approach is vulnerable to observer variability of the required blood SUV (BSUV) determination. The goal of the present work was the investigation of the interobserver variability of image-derived BSUV.

Methodik/Methods:
FDG PET/CT scans from 83 patients were included. BSUV was determined by 8 individuals, each applying a dedicated delineation tool for the BSUV determination in the aorta. Altogether 5 different delineation tools were used. With each used tool, delineation was performed for the whole patient group, resulting in 12 distinct observations per patient. Interobserver variability of BSUV determination was assessed using the fractional deviations of the individual observers from the observer-average for the considered patient.

Ergebnisse/Results:
Interobserver variability in the pooled data amounts to SD=2.8% and is much smaller than the intersubject variability of BSUV (SD=16%). Averaged over the whole patient group, deviations of individual observers from the observer average are very small and fall in the range [-0.96,1.05]%. However, interobserver variability partly differs distinctly for different patients (range: [0.7,7.4]%).

Schlussfolgerungen/Conclusions:
The present investigation proofs unambiguously that the image-based manual determination of BSUV in the aorta provides sufficient accuracy and reproducibility for the purposes of the SUR approach. This finding is in line with the already demonstrated superiority of SUR in comparison to SUV in first clinical studies.
  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Publ.-Id: 29093 - Permalink


Die Asphärizität neuroendokriner Tumore in der prätherapeutischen Somatostatinrezeptor-Bildgebung: Ein innovativer Prädiktor für das progressionsfreie Überleben unter Everolimus?
Wetz, C.; Genseke, P.; Pape, U.; Jann, H.; Furth, C.; Kreißl, M.; Hofheinz, F.; Venrito, M.; Stüven, A.; Amthauer, H.;
Ziel/Aim:
Bei Patienten mit pulmonalen oder gastrointestinalen neuroendokrinen Tumoren (NET) kann der teils nebenwirkungsreiche mTOR-Inhibitor Everolimus das progressionsfreie Überleben (PFS) verlängern. Ziel dieser Studie war die Evaluation der läsionalen Asphärizität (ASP) in der prätherapeutischen Somatostatinrezeptor (SSR)-Bildgebung hinsichtlich einer weiteren Spezifizierung von Patientensubgruppen die von der Therapie im Besonderen profitieren.

Methodik/Methods:
Retrospektive, bizentrische Analyse von 30 Patienten (m=17; w=13; medianes Alter, 59 [38-75] Jahre) mit einer prätherapeutischen [111In-DTPA0]octreotid Szintigraphie. Die funktionellen Volumina von bis zu 3 führenden Läsionen je Patient (n=74) wurden mittels halbautomatischer, hintergrundadaptierter Segmentierung erhoben (ROVER, Version 2.1.20) und jeweils die sphärische Heterogenität des SSR-Besatzes - die ASP - berechnet. Für die maximal gemessene ASP je Patient erfolgten Kaplan-Meier-Analysen inklusive log-rank-Tests sowie eine univariate Cox Regression bzgl. des PFS.

Ergebnisse/Results:
Alle 30 Patienten waren unter Everolimus progredient oder entwickelten ein Rezidiv. In der univariaten Analyse erwies sich die ASP [Median, 12,7%; Spannweite, 1,1–43,5] als Prädiktor des PFS (p=0,033; Hazard Ratio [HR], 2,391 je eine Einheit). Patienten mit einer hohen ASP (>14%) zeigten ein medianes PFS von 6,7 Monaten (95%-Konfidenzintervall [CI], 2,1-11,4 Monate) gegenüber 14,4 Monaten (95%-CI, 12,5-16,3 Monate; p=0,028) für eine ASP ≤14%.

Schlussfolgerungen/Conclusions:
Mittels ASP kann im untersuchten Patientenkollektiv eine Prädiktion des PFS erreicht werden. In Bezug auf eine Nutzen-/Risiko-Abwägung zur Indikationsstellung der Everolimusgabe erscheint der Einsatz der prätherapeutischen ASP bzgl. einer optimalen Patientenauswahl bedeutsam; Patienten mit einer ASP >14% hatten ein signifikant kürzeres PFS.
  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Publ.-Id: 29092 - Permalink


Application of Fourier Analysis of Cerebral Glucose Metabolism in Color Induced Long-term Potentiation: A Novel Functional PET Spectroscopy (fPETS) Study in Mice
Njemanze, P. C.; Kranz, M.; Brust, P.;
Fourier time series analysis could be used to segregate changes in the ventral and dorsal streams of the visual system in male and female mice. Color memory processes of long-term potentiation and long-term depression could be identified through spectral analysis. We used small animal positron emission tomography and magnetic resonance imaging (PET/MRI) to measure the accumulation of [18F]fluorodeoxyglucose ([18F]FDG) in the mouse brain during light stimulation with blue and yellow filters compared to darkness condition. The mean standardized uptake values (SUV) of [18F]FDG for each stimulus condition was analyzed using standard Fourier analysis software to derive spectral density estimates for each condition. Spectral peaks were identified as originating from the subcortical region (S-peak) by subcortical long-term potentiation (SLTP) or depression (SLTD), and originating from the cortical region (C-peak) by cortical long-term potentiation (CLTP) or depression (CLTD). Luminance opponency occurred at S-peak by SLTP in the dorsal stream in the left visual cortex in male mice. On the other hand, chromatic opponency occurred by wavelength-differencing at C-peak by CLTP in the cortico-subcortical pathways in the ventral stream of the left visual cortex in male mice. In contrast in female mice, during luminance processing, there was resonance phenomenon at C-peak in the ventral stream in the right visual cortex. Chromatic opponency occurred at S-peak by SLTP in the dorsal stream in the right visual cortex in female mice. Application of Fourier analysis improved spatial and temporal resolutions of conventional fPET/MRI methods. Computation of colour processing as a conscious experience has wide range applications in neuroscience and artificial intelligence.
Keywords: Chromatic Opponency, Brain, Light Stimulation, Sex, Asymmetry, Spectroscopy, Memory
  • Open Access LogoBook chapter
    Dr. Goran S. Nikolić, Dr. Dragana Marković-Nikolić: Application of Fourier Analysis of Cerebral Glucose Metabolism in Color Induced Long-term Potentiation: A Novel Functional PET Spectroscopy (fPETS) Study in Mice / Fourier Transforms - Century of Digitalization and Increasing Expectations, London: IntechOpen, 2019, 1-23-1
    DOI: 10.5772/intechopen.85641

Publ.-Id: 29091 - Permalink


Nanomagnetism of Magnetoelectric Granular Thin-Film Antiferromagnets
Appel, P.; Shields, B. J.; Kosub, T.; Hedrich, N.; Hübner, R.; Fassbender, J.; Makarov, D.; Maletinsky, P.;
Antiferromagnets have recently emerged as attractive platforms for spintronics applications, offering fundamentally new functionalities compared with their ferromagnetic counterparts. Whereas nanoscale thin-film materials are key to the development of future antiferromagnetic spintronic technologies, existing experimental tools tend to suffer from low resolution or expensive and complex equipment requirements. We offer a simple, high-resolution alternative by addressing the ubiquitous surface magnetization of magnetoelectric antiferromagnets in a granular thin-film sample on the nanoscale using single-spin magnetometry in combination with spin-sensitive transport experiments. Specifically, we quantitatively image the evolution of individual nanoscale antiferromagnetic domains in 200 nm thin films of Cr2O3 in real space and across the paramagnet-to-antiferromagnet phase transition, finding an average domain size of 230 nm, several times larger than the average grain size in the film. These experiments allow us to discern key properties of the Cr2O3 thin film, including the boundary magnetic moment density, the variation of critical temperature throughout the film, the mechanism of domain formation, and the strength of exchange coupling between individual grains comprising the film. Our work offers novel insights into the magnetic ordering mechanism of Cr2O3 and firmly establishes single-spin magnetometry as a versatile and widely applicable tool for addressing antiferromagnetic thin films on the nanoscale.

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Publ.-Id: 29090 - Permalink


Magnetic interactions and spin dynamics in the bond-disordered pyrochlore fluoride NaCaCo2F7
Zeisner, J.; Bräuninger, S. A.; Opherden, L.; Sarkar, R.; Gorbunov, D. I.; Krizan, J. W.; Herrmannsdörfer, T.; Cava, R. J.; Wosnitza, J.; Büchner, B.; Klauss, H. H.; Kataev, V.;
We report high-frequency/high-field electron spin resonance (ESR) and high-field magnetization studies on single crystals of the bond-disordered pyrochlore NaCaCo2F7. Frequency- and temperature-dependent ESR investigations above the freezing temperature Tf ∼ 2.4 K reveal the coexistence of two distinct magnetic phases. A cooperative paramagnetic phase, evidenced by a gapless excitation mode, is found along with a spin-glass phase developing below 20 K which is associated with a gapped low-energy excitation. Effective g factors close to 2 are obtained for both modes, in line with pulsed high-field magnetization measurements which show an unsaturated isotropic behavior up to 58 T at 2 K. In order to describe the field-dependent magnetization in high magnetic fields, we propose an empirical model accounting for highly anisotropic ionic g tensors expected for this material and taking into account the strongly competing interactions between the spins which lead to a frustrated ground state. As a detailed quantitative relation between effective g factors as determined from ESR and the local g tensors obtained by neutron scattering [Ross et al., Phys. Rev. B 93, 014433 (2016)] is still sought after, our work motivates further theoretical investigations of the low-energy excitations in bond-disordered pyrochlores.

Publ.-Id: 29085 - Permalink


Reference Database for Photon Strength Functions
Goriely, S.; Dimitriou, P.; Wiedeking, M.; Belgya, T.; Firestone, R.; Kopecky, J.; Krticka, M.; Plujko, V.; Schwengner, R.ORC; Siem, S.; Utsunomiya, H.; Hilaire, S.; Peru, S.; Cho, Y. S.; Filipescu, S. M.; Iwamoto, N.; Kawano, T.; Oblozinsky, P.; Tao, X.; Varlamov, V.; Xu, R.
Photon strength functions describing the average response of the nucleus to an electromagnetic probe are key input information in the theoretical modelling of nuclear reactions and consequently they are highly relevant to a wide range of fields in basic sciences and applications such as nuclear structure, nuclear astrophysics, medical isotope production, fission and fusion reactor technologies, activation analyses and safeguards. They are also sources of information for widely used databases such as the IAEA Reference Input Parameter Library, the evaluated data files, such as ENSDF, EGAF, and the astrophysical reaction databases (e.g. BRUSLIB, STARLIB, REACLIB). In the past two decades, there has been considerable growth in the amount of reaction gamma-ray data measured to determine photon strength functions. Quite often the different experimental techniques lead to discrepant results and users are faced with the dilemma of deciding which (if any) amongst the divergent data they should adopt.
Keywords: Photon strength functions, gamma-ray strength, data base

Publ.-Id: 29084 - Permalink


Microscopic Nature of the First-Order Field-Induced Phase Transition in the Strongly Anisotropic Ferrimagnet HoFe5Al7
Gorbunov, D. I.; Strohm, C.; Henriques, M. S.; van der Linden, P.; Pedersen, B.; Mushnikov, N. V.; Rosenfeld, E. V.; Petricek, V.; Mathon, O.; Wosnitza, J.;
We report on x-ray magnetic circular dichroism experiments in pulsed fields up to 30 T to follow the rotations of individual magnetic moments through the field-induced phase transition in the ferrimagnet HoFe5Al7. Near the ground state, we observe simultaneous stepwise rotations of the Ho and Fe moments and explain them using a two-sublattice model for an anisotropic ferrimagnet with weak intersublattice exchange interactions. Near the compensation point, we find two phase transitions. The additional magnetization jump reflects the fact that the Ho moment is no longer rigid as the applied field acts against the intersublattice exchange field.

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Publ.-Id: 29081 - Permalink


Inductive Heating Using a High-Magnetic-Field Pulse to Initiate Chemical Reactions to Generate Composite Materials
Zimmerer, C.; Salazar Mejia, C.; Utech, T.; Arnhold, K.; Janke, A.; Wosnitza, J.;
Induction heating is efficient, precise, cost-effective, and clean. The heating process is coupled to an electrically conducting material, usually a metal. As most polymers are dielectric and non-conducting, induction heating is not applicable. In order to transfer energy from an electromagnetic field into polymer induction structures, conducting materials or materials that absorb the radiation are required. This report gives a brief overview of induction heating processes used in polymer technology. In contrast to metals, most polymer materials are not affected by electromagnetic fields. However, an unwanted temperature rise of the polymer can occur when a radio frequency field is applied. The now available high-field magnetic sources provide a new platform for induction heating at very low frequencies, avoiding unwanted thermal effects within the material. Using polycarbonate and octadecylamine as an example, it is demonstrated that induction heating performed by a magnetic-field pulse with a maximum flux density of 59 T can be used to initiate chemical reactions. A 50 nm thick Ag loop, with a mean diameter of 7 mm, placed in the polymer-polymer interface acts as susceptor and a resistive heating element. The formation of urethane as a linker compound was examined by infrared spectroscopic imaging and differential scanning calorimetry.

Publ.-Id: 29080 - Permalink


Selective CO2 Electroreduction to Ethylene and Multicarbon Alcohols via Electrolyte-Driven Nanostructuring
Gao, D.; Sinev, I.; Scholten, F.; Arán-Ais, R. M.; Divins, N. J.; Kvashnina, K.; Timoshenko, J.; Roldan Cuenya, B.;
The production of multicarbon products (C2+) from CO2 electroreduction reaction (CO2RR) is highly desirable for storing renewable energy and reducing carbon emission. Here we report the electrochemical synthesis of CO2RR catalysts that are highly selective for C2+ products via electrolyte-driven nanostructuring. Nanostructured Cu catalysts synthesized in the presence of specific anions can selectively convert CO2 to ethylene and multicarbon alcohols in aqueous 0.1 M KHCO3 solution, with the iodine-modified catalyst displaying the highest Faradaic efficiency of ~80% and partial current density of ~34 mA cm−2 for C2+ products at −0.9 V vs RHE. Operando X-ray absorption spectroscopy and quasi in situ X-ray photoelectron spectroscopy measurements revealed that the high C2+ selectivity of these nanostructured Cu catalysts can be mainly attributed to their nanoporous structure, presence of subsurface oxygen and Cu+ species, and the adsorbed halides. This work provides new insight into the parameters that should be tuned in order to rationally design C2+-selective CO2RR catalysts.

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  • Secondary publication expected from 02.09.2020

Publ.-Id: 29074 - Permalink


Predicting late magnetic resonance image changes in glioma patients after proton therapy
Eulitz, J.; Troost, E. G. C.; Raschk, F.; Schulz, E.; Lutz, B.; Dutz, A.; Löck, S.; Wohlfahrt, P.; Enghardt, W.; Karpowitz, C.; Krause, M.; Lühr, A.;
Introduction:

Proton radiation therapy is an effective treatment for glioma patients. To exploit its full potential, a better description of regional differences in radiation response within the brain is required. In this study, we present a model for predicting magnetic resonance (MR) image changes in glioma patients that considers the variability in proton relative biological effectiveness (RBE) as well as the regional susceptibility of brain tissue to radiation damage.

Material and methods:

Six glioma patients treated with adjuvant proton radio(chemo)therapy showed contrast enhancement on follow-up T1-weighted MR imaging corresponding to treatment-related changes. Physical dose and linear energy transfer (LET) were obtained from high-precision Monte-Carlo simulations. The periventricular region (PVR) was contoured as a 4 mm expansion around the ventricles. Correlations between the image changes and dose, LET, and the PVR were evaluated voxel-wise in univariable and multivariable logistic regression analyses. Model performance was assessed by the area under the curve (AUC) using leave-one-out cross validation. The tolerance dose TD50, at which 50% of the tissue voxels show toxicity was interpolated from the model and used for RBE estimation.

Results:

The spatial distribution of MR image changes in the brain was highly non-uniform and correlated poorly with the considered predictors in univariable analysis. Multivariable modelling with either only dose and LET or PVR as third predictor revealed AUC values of 0.89 and 0.92, respectively. TD50 decreased with increasing LET and the modelled RBE was found to vary between 0.9 and 2.3. No relevant difference in model performance was found for track- or dose-averaged LET.

Conclusion:

The strong correlation of MR image changes with dose, LET, and the PVR demonstrates the relevance of non-uniform dose response models. A larger patient cohort including patients without image changes will be used to validate the clinically observed indication of a variable proton RBE.
Keywords: Proton Therapy, Glioma, Variable RBE, MR image changes

Publ.-Id: 29073 - Permalink


Performance Analysis for Large Scale GPU Applications and DL Frameworks
Juckeland, G.ORC; Henschel, R.ORC
Get your hands on the latest versions of Score-P and Vampir to profile the execution behavior of your large-scale GPU-Accelerated applications. See how these HPC community tools pick up as other tools (such as NVVP) drop off when your application spans multiple compute nodes. Regardless of whether your application uses CUDA, OpenACC, OpenMP or OpenCL for acceleration, or whether it is written in C, C++, Fortran or Python, you will receive a high-resolution timeline view of all program activity alongside the standard profiles to identify hot spots and avenues for optimization. The novel Python support now also enables performance studies for optimizing the inner workings of deep learning frameworks.
  • Lecture (Conference)
    GPU Technology Conference 2019, 17.-21.03.2019, San Jose, CA, USA

Publ.-Id: 29070 - Permalink


Inter-observer variability in target delineation increases during adaptive treatment of head-and-neck and lung cancer
Apolle, R.; Appold, S.; Bijl, H. P.; Blanchard, P.; Bussink, J.; Faivre-Finn, C.; Khalifa, J.; Laprie, A.; Lievens, Y.; Madani, I.; Ruffier, A.; de Ruysscher, D.; van Elmpt, W.; Troost, E. G. C.;
Introduction
Inter-observer variability (IOV) in target volume delineation is a well-documented source of geometric uncertainty in radiotherapy. Such variability has not yet been explored in the context of adaptive re-delineation based on imaging data acquired during treatment. We compared IOV in the pre- and mid-treatment setting using expert primary gross tumour volume (GTV) and clinical target volume (CTV) delineations in locoregionally advanced head-and-neck squamous cell carcinoma (HNSCC) and (non-)small cell lung cancer [(N)SCLC].

Materials and Methods
Five and six observers participated in the HNSCC and (N)SCLC arm, respectively, and provided delineations for five cases each. Imaging data consisted of CT studies partly complemented by FDG-PET and was provided in two separate phases for pre- and mid-treatment. Global delineation compatibility was assessed with a volume overlap metric (the Generalised Conformity Index), while local extremes of IOV were identified through the standard deviation of surface distances from observer delineations to a median consensus delineation. Details of delineation procedures, in particular GTV to CTV expansion and adaptation strategies, were collected through a questionnaire.

Results
Volume overlap analysis revealed a worsening of IOV in all but one case per disease site, which failed to reach significance in this small sample (p-value range 0.063- 0.125). Changes in agreement were propagated from GTV to CTV delineations, but correlation could not be formally demonstrated. Surface distance based analysis identified longitudinal target extent as a pervasive source of disagreement for HNSCC. High variability in (N)SCLC was often associated with tumours abutting consolidated lung tissue or potentially invading the mediastinum. Adaptation practices were variable between observers with fewer than half stating that they consistently adapted pre-treatment delineations during treatment.

Conclusion
IOV in target volume delineation increases during treatment, where a disparity in institutional adaptation practices adds to the conventional causes of IOV. Consensus guidelines are urgently needed.
Keywords: Target volume delineation; Inter-observer variability; Adaptive radiotherapy; Head-and-neck squamous cell carcinoma; (Non-)small cell lung cancer

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Publ.-Id: 29068 - Permalink


Liquid Metal Model Experiments for Continuous Casting of Steel Under the Influence of Magnetic Fields
Schurmann, D.ORC; Glavinić, I.ORC; Timmel, K.ORC; Willers, B.ORC; Eckert, S.ORC
Magnetic fields are widely applied in the continuous casting process to modify the flow pattern in the mold and thereby improve the quality of the semi-finished product. While the use of Electromagnetic Brakes (EMBr) is common in slab casting, Electromagnetic Stirring (EMS) is mainly applied in bloom and billet casting and recently also in slab casting. Due to the harsh conditions in the real casting process, model experiments in cold liquid metals enable accurate measurements of velocity fields, surface oscillations, gas bubble characteristics, etc. These models improve understanding the effects of electromagnetic actuators and provide data to validate numerical models.

We present experimental results obtained in a model of a continuous caster, the Mini-LIMMCAST facility, where the velocity field is measured by Ultrasound Doppler Velocimetry (UDV). Results of experiments conducted with EMS in a round bloom geometry as well as experiments with EMBr in slab geometries are presented.
Keywords: Model Experiments, Ultrasound Doppler Velocimetry, Continuous Casting, Electromagnetic Brake, Electromagnetic Stirring
  • Contribution to proceedings
    8th International Conference on Modeling and Simulation of Metallurgical Processes in Steelmaking (STEELSIM2019), 13.-15.08.2019, Toronto, Ontario, Canada, 620-627
    DOI: 10.33313/503/065
  • Lecture (Conference)
    8th International Conference on Modeling and Simulation of Metallurgical Processes in Steelmaking (STEELSIM2019), 13.-15.08.2019, Toronto, Ontario, Kanada

Publ.-Id: 29064 - Permalink


A spectroscopic investigation of Eu3+ incorporation in LnPO4 (Ln = Tb, Gd1–xLux, x = 0.3, 0.5, 0.7, 1) ceramics
Huittinen, N.; Lösch, H.; Hirsch, A.; Holthausen, J.; Peters, L.; Xiao, B.; Neumeier, S.; Schmidt, M.;
Introduction
In recent years, rare-earth orthophosphates LnPO4 have attracted attention as potential hosts for the immobilization of specific radioactive waste streams.
Objectives
In the present work, the incorporation of Eu3+ in LnPO4 host materials predominantly having the xenotime structure has been investigated on the molecular level. As host cations we used Tb and Lu as well as a solid solution series of Gd1–xLuxPO4 (x = 0.3, 0.5, 0.7). The site selective laser luminescence spectroscopy (TRLFS) technique was applied to study the distribution of Eu3+ in the synthetic xenotime phases, while PXRD and Raman spectroscopy were used for bulk structural investigations direct after synthesis and after one year of storage at ambient conditions.
Results
The PXRD patterns of the solid solution series show the formation of a single xenotime phase up to a substitution of x = 0.5 both before and after aging. The TRLFS emission spectra also show that Eu3+ is substituted for the host cation site in the xenotime hosts. After one year, the emission spectra show a broad dominant signal between the transitions regions of the 7F1‒ and 7F2‒bands, and the luminescence signal no longer corresponds to Eu3+‒incorporation in a xenotime environment, only. These changes indicate a time-dependent change in the local structure of the europium dopant. Based on these observations we suggest an exclusion of Eu3+ from the crystal structure and subsequent migration of the cation to the grain boundaries during aging. The migration of Eu3+ in void spaces through the crystal structure could be responsible for the additional signals in the emission spectra, while the narrow void space forces an overlap between Eu3+ and oxygen atomic orbitals, resulting in the broad signal between the 7F1‒ and 7F2‒bands.
Conclusions
The segregation of Eu3+ to grain boundaries after a relatively short aging in the xenotime materials, indicates that xenotime ceramics will not serve as a suitable waste form for trivalent actinides from high–level nuclear waste.
  • Lecture (Conference)
    27th Annual Meeting of the German Crystallographic Society (DGK), 25.-28.03.2019, Leipzig, Germany

Publ.-Id: 29063 - Permalink


First-in-man validation of CT-based stopping-power prediction using prompt-gamma-based range verification
Berthold, J.; Khamfongkhruea, C.; Petzoldt, J.; Thiele, J.; Hölscher, T.; Wohlfahrt, P.; Pausch, G.; Janssens, G.; Smeets, J.; Richter, C.;
Introduction
Currently, the uncertainty in CT-based range prediction is substantially impairing the accuracy of particle therapy. Improvements like a determination of stopping-power ratio (SPR) from dual-energy CT (DECT) have been proposed. However, a validation of range prediction in patients has not been achieved by any means. Here, we present the first verification of proton range prediction in patients, using Prompt-Gamma-Imaging (PGI).

Materials & Methods
A PGI-slit-camera system was modified to enhance its positioning accuracy using a floor-based docking station. Its accuracy and positioning reproducibility were determined with x-ray and PGI measurements. The PGI system was clinically applied to monitor absolute proton ranges for a 1.5Gy field during eight fractions of hypo-fractionated treatment of two prostate-cancer patients using pencil beam scanning (Fig.1). For all monitored fractions, in-room control-CT scans were acquired in treatment position enabling PGI-based spot-by-spot range analysis for the actual patient anatomy. The PG measurements were compared to simulations of the expected PGI signal using either a standard CT-number-to-SPR conversion (HLUT) or a HLUT optimized with patient-specific DECT-derived SPR information (DECT-HLUT), respectively.

Results
The accuracy and precision for global range verification (averaging over multiple spots) was determined to be 0.6mm and 1.3mm (both 2σ-level), respectively. The precision is limited by remaining uncertainties in image registration and positioning reproducibility (1mm,2σ). To verify range prediction in patients, the histogram of range shifts was analyzed concerning its Gaussian mean (Fig. 2) as surrogate for the accuracy of the respective range prediction method, independent from random uncertainty contributions (e.g. positioning, statistical uncertainty in shift determination). The mean deviation for the DECT-HLUT and standard HLUT were -0.6mm and 1.3mm, respectively.

Conclusion
The accuracy of PGI-based range verification was improved to enable the verification of CT-based stopping-power prediction in patients for the first time. First data evaluation suggests a slight superiority of DECT-based range prediction.
  • Lecture (Conference)
    50. Jahrestagung DGMP, 18.-21.09.2019, Stuttgart, Deutschland

Publ.-Id: 29060 - Permalink


Combined measurement of velocity and temperature in liquid metal convection
Zürner, T.; Schindler, F.; Vogt, T.; Eckert, S.; Schumacher, J.;
Combined measurements of velocity components and temperature in a turbulent Rayleigh-Benard convection flow at a low Prandtl number and for large Rayleigh numbers are conducted in a series of experiments with durations of more than a thousand free fall time units. Multiple crossing ultrasound beam lines and an array of thermocouples at mid-height allow for a detailed analysis and characterization of the complex three-dimensional dynamics of the single large-scale circulation (LSC) roll in the cylindrical convection cell of unit aspect ratio which is filled with the liquid metal alloy GaInSn. We extract the superposition of short-term oscillations of the LSC with different orientation angles close to the top/bottom plates and the related sloshing motion in the mid-plane with the slow azimuthal drift of the mean roll orientation as a whole that proceeds on a hundred times slower time scale, and measure the internal temporal correlations of this complex large-scale flow. The coherent LSC drives a vigorous turbulence in the whole cell that is quantified by direct Reynolds number measurements at different locations in the cell. The velocity increment statistics in the bulk of the cell displays characteristic properties of intermittent small-scale fluid turbulence. We also show that the impact of the symmetry-breaking large-scale flow persists to small-scale velocity fluctuations thus preventing the establishment of isotropic turbulence in the cell center. Reynolds number amplitudes depend sensitively on beam line position in the cell such that different definitions have to be compared. The global momentum and heat transfer scalings with Rayleigh number are found to agree with those of direct numerical simulations and other laboratory experiments.

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  • Secondary publication expected from 15.02.2020

Publ.-Id: 29059 - Permalink


Microorganisms present in bentonites from a deep underground experiment
Lopez-Fernandez, M.; Drozdowski, J.; Kluge, S.; Cherkouk, A.;
The deep geological repository is one of the internationally accepted options to dispose highly radioactive waste. For this, a multi-barrier system where the radioactive waste will be encapsulated in a technical barrier (metal containers) surrounded by a geotechnical barrier (e.g. compacted bentonite) deep underground in a stable geological formation (host rock) can be used. Bentonites might be used as sealing and backfilling material due to their good properties such as high swelling capacity and low hydraulic conductivity. However, indigenous microorganisms and those introduce during the repository construction and operation can affect these properties.
Bentonite core samples were collected from the Full-scale Engineered Barrier Experiment (FEBEX) in the frame of the FEBEX-Dismantling Project [1] at the Grimsel Test Site (Switzerland) to study their microbial diversity. For that, total DNA was extracted directly from the cores. In addition, sulfate- and iron-reducing microorganisms were enriched from the bentonite samples using specific media. From those enrichments total DNA was extracted and sulfate- and iron-reducing microorganisms were isolated. The microbial communities of the cores, the enrichments, as well as the isolates were analyzed by 16S rRNA gene sequencing. The results showed that the FEBEX bentonite microbial population was directly affected by the continuous high temperature. The dominant phylum in both enrichments was Firmicutes. Desulfosporosinus, Clostridium and Bacillus spp. were identified from the medium for sulfate-reducers, while Desulfitobacterium and Bacillus spp. were detected in the iron-reducing enrichment. Pure cultures were isolated from both enrichments, identifying spore-forming bacteria.
This study revealed that microorganisms were detected on the FEBEX bentonite after almost twenty years of continuous heating. Sulfate- and iron-reducing microbes were enriched by using favorable conditions in specific media. Therefore, it is important to characterize the microbial population of the bentonite used as geotechnical barrier, because microbes might compromise the safety of the deep geological repository of highly radioactive waste.

[1] http://www.grimsel.com/gts-phase-vi/febex-dp/febex-dp-introduction
  • Lecture (Conference)
    Goldschmidt 2019, 18.-23.08.2019, Barcelona, Spain

Publ.-Id: 29058 - Permalink


Effect of Anions on the Changes in the Structure and Adsorption Mechanism of Zirconium Species at the Muscovite (001) – Water Interface
Yuan, K.; Bracco, J. N.; Schmidt, M.ORC; Soderholm, L.; Fenter, P.; Lee, S. S.
Multivalent cations primarily exist as polynuclear hydroxo and oxyhydroxo clusters and/or nanoparticles (NPs) in aqueous environments, where their interactions with mineral surfaces can be influenced by complexing anions. Here, we investigated the effect of background electrolyte anions (specifically ClO4-, Cl-, SO42-, and HPO42-) on the distribution of tetravalent Zr adsorbed on the negatively charged basal surface of muscovite mica. The experiments were conducted at constant pH (= 3), total Zr(IV) concentration (= 0.1 mM), and ionic strength (= 0.1 M). The Zr coverages measured by X-ray fluorescence (XRF) in ClO4- and Cl- systems were 1.3 and 2.1 Zr/AUC (where AUC = 46.72 Å2 is the area of the unit cell of the mica (001) surface), respectively, and mostly remained unchanged during the reaction time from 6 to 50 h. In these conditions, Zr adsorption occurred both as small NPs (with an average height of ~4 nm observed by ex situ atomic force microscopy, AFM) and in a ~2 nm-thick molecular layer (observed by in situ resonant anomalous X-ray reflectivity, RAXR). In comparison, higher Zr coverages that increased with reaction time (i.e., from ~4 to ~7 Zr/AUC from 6 to 50 h reactions) were observed in the SO42- system. Ex situ AFM revealed that the Zr uptake in this system occurred predominantly as NPs that were ca. 5 to 15 nm tall and 20 to 40 nm wide, but no evidence of the interfacial molecular-layer formation was observed by RAXR. In the HPO42– solution, all measurements unequivocally showed no significant Zr sorption, in stark contrast to the observations in the other solutions. Details of the Zr surface coverage and sorption modes are consistent with the known clustering of tetravalent Zr in solutions in the presence of these anions. These results demonstrate the significant impact of anions on the adsorption affinity and mechanism of Zr on the negatively charged mica surface.
Keywords: CTF/RAXR, Sorption, Zirconium, Nanoparticles, XRF, AFM

Publ.-Id: 29056 - Permalink


Towards the electronic structure of actinide oxides nanoparticles
Kvashnina, K.;
Understanding the mechanisms of different chemical reactions with actinides at the atomic level is a key step towards safe disposal of nuclear wastes and towards the identification of physical-chemical processes of radionuclides in the environment. This contribution will provide an overview of the recently performed studies on Uranium, Thorium, Plutonium and Cerium oxide nanoparticles at the Rossendorf Beamline (ROBL)[1] of the European Synchrotron (ESRF) in Grenoble (France). This innovative, recently upgraded, world-wide unique experimental station, funded and operated by HZDR in Dresden (Germany) was used to study actinide systems by several experimental methods, mainely by X-ray absorption spectroscopy in high energy resolution fluorescence detection (HERFD) mode and resonant inelastic X-ray scattering (RIXS) at the An/Ln L3 and An M4,5 edge [2–5]. The experimental results have been analysed using a number of theoretical methods based on density functional theory and atomic multiplet theory. This research has received funding from European Research Council (ERC) under grant agreement 759696
  • Lecture (Conference)
    Goldschmidt2019, 18.-23.08.2019, Barcelona, Spain

Publ.-Id: 29055 - Permalink


Reduction of NpO2+ and TcO4- at the FeII-montmorillonite-water interface
Marques Fernandes, M.; Scheinost, A. C.; Baeyens, B.;
The fate of the long-lived, redox-sensitive radionuclides neptunium (237Np) and technetium (99Tc) in deep geological radioactive waste repositories is a major environmental issue. Both elements are highly soluble in their oxidized redox state, and are not (TcO4-) or only weakly sorbed (NpO2+) by negatively charged clay minerals. In the presence of adsorbed and/or structural FeII, however, clay minerals have been shown to reduce (co-)adsorbed contaminants such as U and Se [1, 2], thereby increasing the solid-water distribution coefficient (retention) by several orders of magnitude. In order to investigate if, to which extent, and under which conditions NpV and TcVII are reduced to their tetravalent oxidation states, we conducted Np and Tc batch adsorption experiments with iron-free montmorillonite and with DCB-reduced Wyoming (2.9 wt. % Fe) montmorillonite under different experimental conditions (i.e. anoxic, electrochemical reduction, in the absence and presence of dissolved FeII). The final oxidation state and the type of surface complex formed was elucidated by X-ray absorption spectroscopy at Np-L3, Tc-K and Fe-K edges. We show that both adsorbed and structural FeII are able to reduce NpV and TcVII to NpIV and TcIV, respectively, but the extent strongly depends on the available amount of FeII and on the experimental conditions. The reduced Np strongly complexes towards co-adsorbed Fe and no NpO2 formation is observed. In the case of Tc, mainly TcO2-like nanoparticles form. Surface complexation via Fe is only observed at low Tc surface loadings.
Keywords: Technetium, Neptunium, ROBL, EXAFS, redox, clay, iron
  • Invited lecture (Conferences)
    Goldschmidt Conference, 18.08.2019, Barcelona, Spain

Publ.-Id: 29054 - Permalink


REMOO-2019 Blind Test Calculation Workshop (BTW)
Höhne, T.;
A blind test benchmark of transient 2-phase flow simulation codes will be organized.
The purpose is to give participants an opportunity to test their code capability to predict onset of dryout, post-dryout heat transfer phenomena as well as subsequent rewetting in a boiling water rod bundle geometry under realistic operational conditions. Experimental data that will be used in the blind test have been obtained in a 4 by 4 rod bundle and include pressure drops along the bundle divided into six sub-sections, rod clad temperatures at fourteen elevations and coolant temperatures at six elevations.
For analyzed experimental case, steady-state initial and boundary conditions as well as transient forcing functions have been recorded together with above-mentioned parameters.
Keywords: CFD, Subchannel codes, dryout, post dryout, rod bundle
  • Lecture (Conference)
    The 9th International Conference & Workshop REMOO–2019, 16.-18.04.2019, Hong Kong, China

Publ.-Id: 29053 - Permalink


Adsorption of UVI and EuIII on illite: The important role of accessory minerals
Marques Fernandes, M.; Scheinost, A. C.; Huittinen, N.; Baeyens, B.;
Adsorption models able to predict the fate of (radio-)contaminants at water-mineral interfaces are important tools to assess the risk related to their migration in natural environments. In general, adsorption in a multimineralic environment is assumed to be governed by the major reactive mineral constituents. A common procedure to predict the adsorption by a soil/rock entity is to combine in an additive way the adsorption models for each single mineral composing the mineral assemblage, i.e. based on the relative reactive amounts of each mineral.
Ideally, robust and reliable adsorption models should be developed for each environmentally relevant mineral based on experimental data obtained under a wide range of conditions to guarantee their predictive capability. For this it is of utmost importance to study the retention of contaminants on well-characterized minerals, under well-defined and controlled conditions.
Diocthahedral alumina-silicates such as illite and montmorillonite are common mineralogical components of soils and sedimentary rocks which control the migration of (radio-)contaminants in natural systems through their exceptional bulk physical and chemical properties.
In the present study we will illustrate how the adsorption properties of a presumably pure clay mineral, illite du Puy (IdP), can be strongly altered by an accessory mineral (< 0.5 wt.%). The adsorption of UVI as well EuIII on purified IdP (<0.5 µm) under certain conditions (i.e., pH, concentration, presence/absence of dissolved carbonate) showed an unexpected enhancement of the retention of UVI and trivalent actinides and lanthanides (Cm/Am/Eu). The application of extended X-ray absorption fine structure spectroscopy and time resolved laser fluorescence spectroscopy on IdP samples loaded with UVI and EuIII, respectively, clearly suggest complexation by phosphate groups not expected in IdP. For U, the formed surface complex could be identified as an autunite-like phase. In the case of Eu, the formation of a ternary apatite-like Eu-Ca-PO4 solid phase was observed. Furthermore, leached phosphate from the clay mineral resulted in the precipitation of non-sorbed EuIII as rhabdophane (EuPO4×nH2O). The accessory mineral phase itself responsible for this anomalous behaviour is difficult to identify with common analytical methods such as TEM or XRD due to e.g. the low concentration and/or amorphous nature of the accessory phase or the low electron density of its constituent elements. Repeated acid-pre-treatment of IdP released P and Ca, pointing towards an apatite-like accessory phase as source of phosphate for the formation of the UVI and EuIII solid phases. In the pre-treated solid phosphate complexation was greatly reduced. In the case of UVI, an inner-sphere surface complex on IdP edge sites could be identified in the XAFS investigations. Our results demonstrate that adsorption models calibrated over a wide range of experimental conditions, complemented by a molecular-level control and a true mechanistic understanding, is of paramount importance for reliable modelling of adsorption processes at the solid-liquid interface.
Keywords: uranium, autunite, apatite, XAFS, illite, sorption
  • Invited lecture (Conferences)
    Migration 2019, 15.-20.09.2019, Kyoto, Japan

Publ.-Id: 29052 - Permalink


A 224Ra-labeled polyoxopalladate as putative radiopharmaceutical
Gott, M.; Yang, P.; Kortz, U.; Stephan, H.; Pietzsch, H.-J.; Mamat, C.ORC
Despite its attractive properties, internal targeted alpha therapies using 223/224Ra are limited to bone-seeking applications. As there is no suitable chelator available, the search for new carriers to stably bind Ra2+ and to connect it to biological target molecules is necessary. Polyoxopalladates represent a class of compounds where Ra2+ can be easily introduced into the Pd-POM core during a facile one-pot preparation. Due to the formation of a protein corona the connection to other targeting (bio)macromolecules is possible.
Keywords: Radium, Barium, POM, alpha-therapy

Downloads:

  • Secondary publication expected from 04.06.2020

Publ.-Id: 29051 - Permalink


Improved electrode design for interdigitated large-area photoconductive terahertz emitters
Singh, A.; Welsch, M.; Winnerl, S.; Helm, M.; Schneider, H.;
We study here the effect of the electrode parameters on the terahertz emission efficiency of large-area emitters based on interdigitated electrodes. Electrode parameters are optimized to get maximum terahertz emission by optimizing the balance condition among the emission efficiency of individual electrode pairs, number of emitters per unit area, and fraction of semiconductor exposed for optical pumping. A maximum enhancement by about 50 % in the peak to peak electric field is observed as compared to the previous state of the art design.
Keywords: Terahertz emitters, photoconductive switch, interdigitated electrode

Publ.-Id: 29048 - Permalink


Implementation of HZDR baseline model for poly-dispersed bubbly flow in OpenFOAM
Liao, Y.;
The predictability of TFM-CFD is largely restricted by the reliability of closures that should reconstruct the information about the phenomena and processes occuring at the interface. The development of physically based models is severely obstructed by insufficient knowledge on the physics and numerous misleading work based on case-by-case tuning. A strategy towards general closures is necessary. A few years ago HZDR proposed a baseline model for TFM-CFD simulation of poly-dispersed bubbly flow with a fixed set of closures. It aims to identify the missing physics in the existing models and improve them step by step. In this work the baseline model is implemented and tested in the open source CFD code OpenFOAM for a large number of bubbly flow cases including vertical pipe flow and bubble column.
  • Lecture (Conference)
    CFD-Verbund, 11.-12.03.2019, Garching bei München, Deutschland

Publ.-Id: 29047 - Permalink


Application of computational fluid dynamics codes for nuclear power plant design
Krause, M.; Smith, B.; Höhne, T.; In, W. K.;
Computational Fluid Dynamics (CFD) codes have reached a level of maturity, at least for single-phase applications, to be utilized in the design process of Nuclear Power Plant (NPP) components, such that advanced NPPs over the past years have increasingly utilized CFD codes in their design. A recently completed Cooperative Research Project (CRP) addressed the application of CFD codes to the process of optimizing the design of components in Pressurized Water-cooled Reactors (PWRs). Following several initiatives within the IAEA where CFD codes have been applied to situations of interest in nuclear reactor technology, this CRP aimed to contribute to a consistent application of CFD codes by establishing a common platform to assess their capabilities and level of qualification.

Eleven participant organizations from nine Member States performed simulations against four “CFD-grade” experiments performed to investigate key phenomena for CFD simulations. Two are based on test data from the ROCOM (ROssendorf COolant Mixing) facility at HZDR in Germany, and another two are based on rod-bundle experiments in the OFEL (Omni Flow Experimental Loop) facility at KAERI in Korea.

This paper outlines the objectives of the CRP, provides a description of the test facilities and experiments, and discusses selected results obtained for the four above benchmark exercises.
Keywords: Computational Fluid Dynamics, Reactor Design, CFD Benchmark
  • Lecture (Conference)
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA
  • Contribution to proceedings
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA

Publ.-Id: 29046 - Permalink


Perfluorinated Calixarene Shuttles for Radium and Barium
Reissig, F.; Bauer, D.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.ORC
Alpha therapy is continually discussed in radiopharmaceutical research. [223Ra]RaCl2 is the only EMA- and FDA-approved alpha-emitting radiopharmaceutical so far. Since the use of 223Ra is only based on its calcimimetic behavior. It is directly bond to bone structures in the body. To enhance the therapeutic potential of radium isotopes, it is necessary to develop novel carrier systems for radium ions as a base of biological targeting units. By the combination of 223Ra or 224Ra, which both have suitable physical half-lives for therapeutic applications, and 131Ba which has a similar half-life but diagnostic radiation properties, a theragnostic idea can also be followed. Our project aims at the synthesis of calixarene-based ligands for the stable complexation of barium and radium ions. Recent studies in our group have already shown the high potential of such ligands.
Keywords: Radium-223, Barium-131, Calixarene
  • Poster
    23rd International Symposium on Radiopharmaceutical Sciences (ISRS 2019), 26.-31.05.2019, Peking, China
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 62(2019), S261

Publ.-Id: 29045 - Permalink


A multi-scale approach simulating generic pool boiling
Höhne, T.ORC; Lucas, D.
The paper presents an application of the GENTOP model for phase transfer and discusses the sub-models used. Boiling of a heated surface under atmospheric conditions is simulated by the multi-field CFD approach. Sub-cooled water in a generic pool is heated up first in the near wall region leading to the generation of small bubbles. Further away from the bottom wall larger bubbles are generated by coalescence and evaporation. The CFD simulation bases on the recently developed GEneralized TwO Phase flow (GENTOP) concept. It is a multi-field model using the Euler-Euler approach and it allows the consideration of different local flow morphologies including transitions between them. Small steam bubbles are handled as dispersed phases while the interface of large gas structures is statistically resolved. The GENTOP sub-models need a constant improvement and separate, intensive validation effort using CFD grade experiments. Recently, a bubble dynamics model inside the heat partitioning approach has been developed and will be applied in GENTOP in future.
Keywords: multi-phase, boiling, GENTOP, multi-scale, CFD
  • Lecture (Conference)
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA
  • Contribution to proceedings
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA

Publ.-Id: 29043 - Permalink


Multiphase CFD Modelling: State-of-the-art applications in Energy related Industrial Applications
Höhne, T.ORC
Two-phase flows occur in many industrial processes. Reliable predictions on flow characteristics are necessary for the design, process optimization and safety analysis of related apparatuses and processes. Experimental investigations are expensive and in most cases not transferable to modified geometries or different scales and flow conditions. For this reason there is a clear requirement for numerical tools. Due to the 3D nature of flows and the importance of turbulence in most cases this means a strong need for reliable 3D CFD-tools rather than 1D system codes or simplified correlations. The general aim is to provide simulation tools for the design, optimization and safety analyses of medium and large scale applications in which multiphase flows are involved. Such tools can contribute to improve the efficient use of energy and resources (e.g. in chemical engineering and oil industries) and to guarantee the safe operation (especially nuclear safety) – provided that they are predictive. Since large scale applications are considered such as chemical reactors or components of the cooling system of a nuclear power plant the Euler-Euler two- or multi fluid model is the base for the development. Presently the predictive capabilities for basic hydrodynamics are restricted due to limitations of the closure models. For this reason one focus of our multiphase flow research is the improvement of the closures first for adiabatic flow modelling but also phase transfer, chemical reactions etc. have to be considered. A second focus is to establish modelling frameworks as iMUSIG, AIAD and GENTOP to allow a proper consideration of the local physical phenomena. These activities will help to improve the CFD code capabilities in energy related industrial applications.
Keywords: CFD, Multiphase, Fluid Dynamics, HZDR, AIAD, GENTOP
  • Invited lecture (Conferences)
    The 9th International Conference & Workshop REMOO–2019, 16.-18.04.2019, Hong Kong, China
  • Contribution to proceedings
    The 9th International Conference & Workshop REMOO–2019, 16.-18.04.2019, Hong Kong, China

Publ.-Id: 29041 - Permalink


Radium-doped BaSO4 Nanoparticles for Future Targeted Alpha Therapy
Reissig, F.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.ORC
Targeted alpha therapy (TAT) is continually focused and discussed in radiopharmaceutical research [1]. By the combination of an alpha emitting radionuclide with a biological targeting unit, tumor cells can be affected very efficiently by inducing a high number of double strand breaks to the DNA. 223Ra and 224Ra are two alpha-emitting radionuclides with suitable half-lives for TAT. 223Ra in form of [223Ra]RaCl2 (Xofigo®) is the only EMA- and FDA-approved alpha-emitting radiopharmaceutical as well as the prime example for the working principle of TAT. Based on its calcimimetic behavior, radium is built into the bone structure. To exploit the therapeutic potential of alpha emitters like 223Ra and 224Ra, novel targeting strategies and carrier systems have to be developed. Therefore, it is worth to examine alternative carriers like nanoparticles, using the principle of co-precipitation of Ra/BaSO4. By the combination of a therapeutic alpha-emitting radionuclide like 223Ra on the one hand and the diagnostically applicable barium radioisotope 131Ba on the other hand with nearly identical physical half-lives it is also possible pursue theragnostic approaches. Thus, our research aims at developing a simple method for the synthesis of small radiolabeled Ra/BaSO4 nanoparticles and testing further surface functionalization regarding the ability of constructing biological targeting moieties.
Keywords: Radium-224, Barium-131, Nanoparticle
  • Poster
    23rd International Symposium on Radiopharmaceutical Sciences (ISRS 2019), 26.-31.05.2019, Peking, China
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 62(2019), S265

Publ.-Id: 29040 - Permalink


Calixarene-based ligands for Radium and Barium
Bauer, D.; Reissig, F.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.ORC
Due to their high biological effectiveness and suitable half-lives, there is increased interest in using the radionuclides radium-223 and radium-224 for radiopharmaceutical applications. Xofigo ([223Ra]radium chloride) is a bone-seeking, alpha-emitting radiopharmaceutical with EMA and FDA approval. It is used to treat bone metastasis of castrate-resistant prostate cancer. To expand the possible applications for these promising radionuclides, it is necessary to stably bind the radionuclide within a chelator. Therefore, calixarene-based ligands have been synthesized, which show encouraging affinities to radium ions. In our recent studies, we have already presented the high potential of these ligands. Since radium and barium have similar chemistry, and therefore comparable affinities to our ligands, it is possible to create a matched pair for theragnostic approaches. The radionuclide barium-131 has a suitable physical half-life for therapeutic applications and the potential of being a SPECT nuclide.
Keywords: Radium-224, Barium-131, Calixarene
  • Poster
    11th International Symposium on Targeted-Alpha-Therapy, 01.-06.04.2019, Ottawa, Kanada
  • Open Access LogoAbstract in refereed journal
    Journal of Medical Imaging and Radiation Sciences 50(2019)1, S39
    DOI: 10.1016/j.jmir.2019.03.118

Publ.-Id: 29039 - Permalink


Interobserver variability of image-derived arterial blood SUV in whole-body FDG PET
Hofheinz, F.; Maus, J.; Zschaeck, S.; Rogasch, J.; Schramm, G.; Oehme, L.; Apostolova, I.; Kotzerke, J.; van den Hoff, J.;
Background: Today, the standardized uptake value (SUV) is essentially the only means for quantitative evaluation of static [18 F-]fluorodeoxyglucose (FDG) positron emission tomography (PET) investigations. However, the SUV approach has several well-known shortcomings which adversely affect the reliability of the SUV as a surrogate of the metabolic rate of glucose consumption. The standard uptake ratio (SUR), i.e., the uptake time-corrected ratio of tumor SUV to image-derived arterial blood SUV, has been shown in the first clinical studies to overcome most of these shortcomings, to decrease test-retest variability, and to increase the prognostic value in comparison to SUV. However, it is unclear, to what extent the SUR approach is vulnerable to observer variability of the additionally required blood SUV (BSUV) determination. The goal of the present work was the investigation of the interobserver variability of image-derived BSUV.

Methods: FDG PET/CT scans from 83 patients (72 male, 11 female) with non-small cell lung cancer (N = 46) or head and neck cancer (N = 37) were included. BSUV was determined by 8 individuals, each applying a dedicated delineation tool for the BSUV determination in the aorta. Two of the observers applied two further tools. Altogether, five different delineation tools were used. With each used tool, delineation was performed for the whole patient group, resulting in 12 distinct observations per patient. Intersubject variability of BSUV determination was assessed using the fractional deviations for the individual patients from the patient group average and was quantified as standard deviation (SDis ), 95% confidence interval, and range. Interobserver variability of BSUV determination was assessed using the fractional deviations of the individual observers from the observer-average for the considered patient and quantified as standard deviations (SDp , SDd ) or root mean square (RMS), 95% confidence interval, and range in each patient, each observer, and the pooled data respectively.

Results: Interobserver variability in the pooled data amounts to RMS = 2.8% and is much smaller than the intersubject variability of BSUV (SDis = 16%). Averaged over the whole patient group, deviations of individual observers from the observer average are very small and fall in the range [− 0.96, 1.05]%. However, interobserver variability partly differs distinctly for different patients, covering a range of [0.7, 7.4]% in the investigated patient group.

Conclusion: The present investigation demonstrates that the image-based manual determination of BSUV in the aorta is sufficiently reproducible across different observers and delineation tools which is a prerequisite for accurate SUR determination. This finding is in line with the already demonstrated superior prognostic value of SUR in comparison to SUV in the first clinical studies.
Keywords: PET, FDG, Quantification, SUV, SUR, Blood SUV

Publ.-Id: 29038 - Permalink


Flexible IGZO TFTs and their Suitability for Space Applications
Costa, J. C.; Pouryazdan, A.; Panidi, J.; Spina, F.; Anthopoulos, T.; Liedke, M. O.; Schneider, C.; Wagner, A.; Münzenrieder, N.;
In this paper, Low Earth Orbit radiation, temperature and magnetic field conditions are mimicked to investigate the suitability of flexible Indium Gallium Zinc Oxide transistors for lightweight space wearables. Such wearable devices could be incorporated into spacesuits as unobtrusive radiation detectors or physiological monitors. Due to the harsh environment to which these space wearables would be exposed, they have to be able to withstand high radiation doses, low temperatures and magnetic fields. For this reason, the impacts of high energetic electron irradiation with fluences up to 1E12 e−/cm2, low operating temperatures down to 78K and magnetic fields up to 11mT are investigated. This simulates 278 h in Low Earth Orbit. The threshold voltage and mobility of transistors that were exposed to e- irradiation are found to shift by +(0.09 +- 0.05)V and (0.6 +- 0.5) cm 2 V−1 s−1. Subsequent low temperature exposure resulted in additional shifts of +0.38V and -5.95 cm2 V−1 s−1 for the same parameters. These values are larger than the ones obtained from non irradiated reference samples. In addition, the performance of the devices was observed not to be significantly affected by the magnetic fields. Finally, a Cascode amplifier presenting a voltage gain of 10.3 dB and a cutoff frequency of 1.2 kHz is demonstrated after the sample had been irradiate, cooled down and exposed to the magnetic fields. If these notions are considered during the systems’ design, these devices can be used to unobtrusively integrate sensor systems into space suits.
Keywords: Flexible electronics, Space applications, Amorphousnoxides; Wearables, Thin film transistors

Publ.-Id: 29037 - Permalink


Fifteen Years of Radionuclide Research at the KIT Synchrotron Source in the Context of the Nuclear Waste Disposal Safety Case
Rothe, J.; Altmaier, M.; Dagan, R.; Dardenne, K.; Fellhauer, D.; Gaona, X.; González-Robles Corrales, E.; Herm, M.; Kvashnina, K.; Metz, V.; Pidchenko, I.; Schild, D.; Vitova, T.; Geckeis, H.;
For more than 120 years, systematic studies of X-ray interaction with matter have been the basis for our understanding of materials—both of natural or man-made origin—and their structure-function relationships. Beginning with simple radiographic imaging at the end of the 19th century, X-ray based analytical tools such as X-ray diffraction, X-ray fluorescence and photoemission or X-ray absorption techniques are indispensable in almost any field of chemical and material sciences—including basic and applied actinide and radionuclide studies. The advent of dedicated synchrotron radiation (SR) sources in the second half of the last century has revolutionized the analytical power of X-ray probes, while—with increasing number of SR facilities—beamline instrumentation followed a trend towards increasing specialization and adaption to a major research topic. The INE-Beamline and ACT station at the KIT synchrotron source belong to the exclusive club of a few synchrotron beamline facilities—mostly located in Europe—dedicated to the investigation of highly radioactive materials. Since commissioning of the INE-Beamline in 2005, capabilities for synchrotron-based radionuclide and actinide sciences at KIT have been continuously expanded, driven by in-house research programs and external user needs.

Publ.-Id: 29035 - Permalink


Metallgewinnung durch Mikrobiologie – Biologisch assistierte Prozesse in der Rohstofftechnologie
Lederer, F.ORC
Der Rohstoffsektor ist geprägt von enormem Materialbedarf für die Entwicklung und Produktion neuer High-Tech Produkte. Neben der Optimierung von Bergbauprozessen zur Gewinnung von primären Rohstoffen fokussiert das Helmholtz-Institut Freiberg für Ressourcentechnologie die Vision der Kreislaufwirtschaft. Diese setzte neben dem Schwerpunkt Nachhaltigkeit im Hinblick auf Produktdesign, Produktion, Verteilung, Konsum, Verwendung, Reparatur und Sammlung vor allem auf das Recycling von Wertstoffen.
Mikrobiologisch assistierte Recyclingprozesse zur Rückgewinnung von Wertstoffen aus Elektronikschrott und Bergbauresthalden sowie innovative und umweltfreundliche Lösungen für die Ressourcensicherung standen im Fokus der 29. Jenaer Industriegespräche der DPG.
Themenschwerpunkte des Vortrages waren Interaktionen von Mikroorganismen mit Metallen, das biotechnologische Potential neuer Ressourcentechnologien, Grenzen überwindende Bioflotation, die Metallgewinnung mittels Siderophoren, Evolution im Reagenzglas sowie Biokollektoren für das Recycling von Wertstoffen aus Elektroschrott.
  • Invited lecture (Conferences)
    29. Jenaer Industriegespräche der DPG, 20.03.2019, Jena, Deutschland

Publ.-Id: 29034 - Permalink


Consolidative thoracic radiotherapy in stage IV small cell lung cancer: Selection of patients amongst European IASLC and ESTRO experts
Putora, P. M.; Glatzer, M.; de Ruysscher, D.; Faivre-Finn, C.; Belderbos, J.; Besse, B.; Blackhall, F.; Califano, R.; Cappuzzo, F.; de Marinis, F.; Dziadiuszko, R.; Felip, E.; Früh, M.; Garrido, P.; Le Pechoux, C.; Mcdonald, F.; Nestle, U.; Novello, S.; Brien, M. O.; Paz Ares, L.; Peeters, S.; Pöttgen, S.; Ramella, S.; Reck, M.; Troost, E. G. C.; van Houtte, P.; Westeel, V.; Widder, J.; Mornex, F.; Slotman, B. J.;
Background: The role of consolidative thoracic radiotherapy (TRT) in stage IV small cell lung cancer (SCLC) is not uniformly accepted. Methods: We obtained a list of 13 European medical oncologists from the International Association for the Study of Lung Cancer (IASLC) and 13 European radiation oncologists from the European Society for Therapeutic Radiation Oncology (ESTRO). The strategies in decision making for TRT in stage IV SCLC were collected. Decision trees were created representing these strategies. Frequencies of recommending TRT were analysed for various parameter combinations based on the objective consensus methodology. Results: The factors associated with the recommendation for TRT included fitness of the patient, limited extrathoracic tumour burden, initial bulky thoracic disease and response to chemotherapy. The highest consensus for TRT was in fit patients with limited extrathoracic tumour burden and initial bulky disease with either a complete extrathoracic response or partial thoracic response (92% recommend TRT). For these patients the recommendations were the same for medical and radiation oncologists. In the setting of partial response (intra- and extra-thoracically) without initial bulky thoracic disease radiation oncologists were more likely to recommend TRT than medical oncologists. For unfit patients or for patients with poor overall response to chemotherapy, the majority did not recommend TRT. Conclusion: European radiation and medical oncologists specializing in lung cancer recommend TRT in selected patients with stage IV SCLC and restrict its use primarily to fit patients who responded to chemotherapy with limited extrathoracic tumour burden.
Keywords: ESTRO, Expert opinion, IASLC, Small cell lung cancer, Stage IV, Thoracic radiotherapy

Publ.-Id: 29033 - Permalink


Repeat FMISO-PET imaging weakly correlates with hypoxia-associated gene expressions for locally advanced HNSCC treated by primary radiochemotherapy
Löck, S.; Linge, A.; Seidlitz, A.; Bandurska-Luque, A.; Nowak, A.; Gudziol, V.; Buchholz, F.; Aust, D. E.; Baretton, G. B.; Zöphel, K.; Steinbach, J.; Kotzerke, J.; Overgaard, J.; Zips, D.; Krause, M.; Baumann, M.; Troost, E. G. C.;
Background: Hypoxia is an important factor of tumour resistance to radiotherapy, chemotherapy and potentially immunotherapy. It can be measured e.g. by positron emission tomography (PET) imaging or hypoxia-associated gene expressions from tumour biopsies. Here we correlate [ 18 F]fluoromisonidazole (FMISO)-PET/CT imaging with hypoxia-associated gene expressions on a cohort of 50 head and neck squamous cell carcinoma (HNSCC) patients and compare their prognostic value for response to radiochemotherapy (RCTx). Methods: FMISO-PET/CT images of 50 HNSCC patients were acquired at four time-points before and during RCTx. For 42 of these patients, hypoxia-associated gene expressions were evaluated by nanoString technology based on a biopsy obtained before any treatment. The FMISO-PET parameters tumour-to-background ratio and hypoxic volume were correlated to the expressions of 58 hypoxia-associated genes using the Spearman correlation coefficient ρ. Three hypoxia-associated gene signatures were compared regarding their correlation with the FMISO-PET parameters using their median expression. In addition, the correlation with tumour volume was analysed. The impact of both hypoxia measurement methods on loco-regional tumour control (LRC) and overall survival (OS) was assessed by Cox regression. Results: The median expression of hypoxia-associated genes was weakly correlated to hypoxia measured by FMISO-PET imaging (ρ ≤ 0.43), with higher correlations to imaging after weeks 1 and 2 of treatment (p < 0.001). Moderate correlations were obtained between FMISO-PET imaging and tumour volume (ρ ≤ 0.69). Prognostic models for LRC and OS based on the FMISO-PET parameters could not be improved by including hypoxia classifiers. Conclusion: We observed low correlations between hypoxia FMISO-PET parameters and expressions of hypoxia-associated genes. Since FMISO-PET showed a superior patient stratification, it may be the preferred biomarker over hypoxia-associated genes for stratifying patients with locally advanced HNSCC treated by primary RCTx.
Keywords: FMISO-PET, Gene signature, Hypoxia, Locally advanced HNSCC, Radiochemotherapy

Publ.-Id: 29032 - Permalink


Combining magnetic forces for contactless manipulation of fluids in microelectrode-microfluidic systems
Hähnel, V.; Khan, F. Z.; Mutschke, G.; Cierpka, C.; Uhlemann, M.; Fritsch, I.;
A novel method to drive and manipulate fluid in a contactless way in a microelectrode-microfluidic system is demonstrated by combining the Lorentz and magnetic field gradient forces. The method is based on the redox-reaction [Fe(CN)6]3−/[Fe(CN)6]4− performed in a magnetic field oriented perpendicular to the ionic current that crosses the gap between two arrays of oppositely polarized microelectrodes, generating a magnetohydrodynamic flow. Additionally, a movable magnetized CoFe micro-strip is placed at different positions beneath the gap. In this region, the magnetic flux density is changed locally and a strong magnetic field gradient is formed. The redox-reaction changes the magnetic susceptibility of the electrolyte near the electrodes, and the resulting magnetic field gradient exerts a force on the fluid, which leads to a deflection of the Lorentz force-driven main flow.
Particle Image Velocity measurements and numerical simulations demonstrate that by combining the two magnetic forces, the flow is not only redirected, but also a local change of concentration of paramagnetic species is realized.
Keywords: microfluidics, electrochemistry, redox-reaction, magnetic field, Lorentz force, magnetic gradient force, flow control
  • Open Access LogoScientific Reports 9(2019), 5103
    DOI: 10.1038/s41598-019-41284-0
  • Lecture (Conference)
    11th International PAMIR International Conference - Fundamental and Applied MHD, 01.-05.07.2019, Reims, Frankreich

Publ.-Id: 29031 - Permalink


Avoided energy cost of producing minerals: The case of iron ore
Reuter, M. A.; Palacios, J.-L.; Fernandes, I.; Abadias, A.; Valero, A.; Valero, A.;
There is growing concern about the decline of the ore grade in mines and the increased energy usage for processing and refining metals. In the limit, where no concentrated deposits exist, minerals must be obtained from bare rock. A method for quantitatively assessing the “free bonus” granted by nature in providing concentrated minerals in mines and thus assessing the quality of the different resources is estimating how much energy is needed to concentrate the minerals, as they are already in mines, from bare rock. This bonus granted by nature reduces the costs of human mining and metallurgical processes, as well as the mining effort required of future generations. In this study, the concentration of high-iron-content minerals in common rocks was investigated via a computational model developed using the HSC software. As expected, the range of results for the specific energy for the concentration of iron from common rocks was considerably higher than the energy required by modern processes. This reveals the need to value current iron deposits and the challenge of developing sustainable methods of metal production to satisfy the needs of the present and future generations.
Keywords: Energy consumption, Exergy replacement cost, Iron, Metallurgy, Mining, Thanatia

Publ.-Id: 29030 - Permalink


Doping of silicon nanowires by ion implantation and flash lamp annealing
Berencen, Y.; Prucnal, S.; Wang, M.; Rebohle, L.; Helm, M.; Zhou, S.; Skorupa, W.;
In this work, we report on non-equilibrium processing for controlled doping of Si/SiO2 core/shell nanowires with shallow- and deep-level dopants below and above their equilibrium solid solubility. In detail, the shallow-level dopants B and P as well as the deep-level dopant Se was implanted, followed by millisecond flash lamp annealing. In case of amorphization upon high-fluence implantation, recrystallization takes place via a bottom-up template-assisted solid phase epitaxy. Non-equilibrium Se concentrations lead to the formation of an intermediate band in Si which in turn causes a room-temperature sub-band gap photoresponse of the nanowire when configured as a photoconductor device [1]. Alternatively, the formation of a cross-sectional p-n junction is demonstrated by co-implanting P and B in individual nanowires at different depth along the NW core.
[1] Y. Berencén, et al. Adv. Mater. Interfaces 2018, 1800101
Keywords: doping, nanowires, semiconductor, silicon, ion implantation, flash lamp annealing
  • Lecture (Conference)
    44. Treffen der Nutzergruppe Heißprozesse und RTP, 03.04.2019, Erlangen, Deutschland

Publ.-Id: 29028 - Permalink


Ultrasonic flow measurements in liquid metal flows with partial solidification
Franke, S.; Räbiger, D.; Eckert, S.;
The monitoring of the flow rate is an inherent part of process control in all technical large-scale plants to guarantee process stability and safety. It is particularly important for nuclear applications. In the case of a liquid metal coolant in addition, the control of the aggregate state is important.
The use of ultrasound techniques opens an attractive opportunity to measure both the fluid velocity by evaluating the Doppler phase shift and the phase boundary by the detection of the reflection signal from the interface. In addition, the measuring principle enables a noninvasive implementation of the measuring technique. A test facility is necessary to qualify the measuring technique for real applications.
In this study a new LBE experimental facility has been designed and constructed. The setup enables to control the temperature and the fluid flow in the liquid. Further a partial solidification can be induced. The liquid metal vessel is equipped with ten ports for ultrasonic probes. These ports allow for testing the ultrasound measuring principle for different conditions. It was demonstrated that the ultrasonic sensors can be operated up to 200°C at the piezo element. First measuring results demonstrate the potential of ultrasound measuring techniques for monitoring liquid metal applications.
  • Lecture (Conference)
    SESAME International Workshop, 19.-21.03.2019, Petten, Netherlands

Publ.-Id: 29026 - Permalink


Probing charged lepton flavor violation with the Mu2e experiment
Mueller, S. E.ORC; Ferrari, A.ORC
The Mu2e experiment, currently under construction at the Fermi National Accelerator Laboratory near Chicago, will search for the neutrinoless conversion of muons to electrons in the field of an aluminum nucleus. In the Standard Model, this process, which violates charged lepton flavor, is highly suppressed and therefore undetectable. However, scenarios for physics beyond the Standard Model predict small but observable rates. The Mu2e experiment aims at a sensitivity four orders of magnitude better than existing experiments. This is achieved by a rigorous control of all backgrounds that could mimic the monoenergetic conversion electron.

At HZDR, we use the ELBE radiation facility to study radiation hardness and performance of components for the Mu2e calorimeter and contribute with Monte Carlo simulations to the understanding of the optimal configuration for the detector that will monitor the rate of stopped muons in the aluminum target. Additional simulations are performed for both the pion production target and the muon stopping target.

In the presentation, the design and status of the Mu2e experiment will be presented, and results from the ELBE beamtimes and the simulation studies will be given.
Keywords: Mu2e, CLFV, ELBE
  • Lecture (Conference)
    Spring Meeting DPG, 22.03.2019, Muenchen, Deutschland

Publ.-Id: 29025 - Permalink


Composition and Structure of Surface Oxides on Press-Hardened Hot-Dip Galvanized Steel
Gaderbauer, W.; Arndt, M.; Steck, T.; Klingner, N.; Faderl, J.; Groiß, H.;
Zink-coated press hardened steel (PHS) is due to its extremely high tensile strength and its excellent corrosive protection indispensable for structural elements in modern automotive applications. Different studies clarify the resulting microstructure of the Zn-coating after press hardening [1] of such steel parts. Also, the uppermost surface oxide layer, which can be influenced by steel matrix alloy elements, has a significant impact on the processing properties like coating or welding.
In this study, we investigated these surface oxide layers for alloy compositions of four different PHS systems with scanning and conventional transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and helium ion microscopy (HIM). The complex and porous oxide-layers were stabilized by epoxy before the preparation of cross-sections and TEM-lamellae by focused ion beam milling.
The main oxides on top of the original thin Al2O3 layer, originating from the primary galvanizing process, could be determined with energy dispersive X-ray spectroscopy (EDX), selected area diffraction and AES as Zn-oxides and (Mn,Zn)Mn2O4 spinel (Fig. 1a). Also noticeable was a varying, nanometre thick Cr enrichment at this Al2O3 layer (Fig. 1b), which depends strongly on the steel alloy. Further experiments with secondary mass spectrometry (ToF-SIMS) attached to a HIM [2] allowed reliable distinguishing between ZnO and Zn(OH)2 (Fig. 2c), which are both present in our oxide layers.
Thus, we could show an influence of different steel alloy elements on the final oxide structure after press hardening. The formation of spinel is triggered by Mn, which is transported with the Zn above the Al2O3 layer, which itself is a trap for Cr, leading to a coverage of it with Cr-oxides.

Figure 1. a) AES Mapping. b) STEM-EDX Mapping c) ToF-SIMS Mapping

References:
[1] H. Järvinen et al, Surface and Coatings Technology 352 (2018), 378-391.
[2] N. Klingner et al, Ultramicroscopy 198 (2019), 10-17.

The financial support by the Austrian Federal Ministry for Digital and Economic Affairs and the National Foundation for Research, Technology and Development in the frame of the CDL for nanoscale phase transformations is gratefully acknowledged.
  • Lecture (Conference)
    9th Austrian Society for Electron Microscopy workshop, 25.-26.04.2019, Graz, Österreich

Publ.-Id: 29024 - Permalink


Critical heat flux as a mass flux dependent phenomenon: Theoretical analysis, experimental confirmation and further CFD application
Ding, W.; Geißler, T.; Krepper, E.; Hampel, U.;
In this work, we report on a theoretical analysis and experimental investigations on critical heat flux (CHF) in subcooled flow boiling firstly. Commonly, CHF is considered as a local phenomenon. A validated CHF- concept recently developed in our group indicated that CHF may be initiated in two different ways, that is, locally and globally. We designed and conducted an experiment to verify this hypothesis. The experimental results agree well with the expectations from our CHF- modelling and confirm the two mechanisms. Following that, we continued to clarify the role of different parameters, such as channel orientation, channel length and hydraulic diameter. The new concept of CHF is useful to explain and predict CHF at conditions of low pressure and low fluid velocity. Further we applied this concept into an Euler-Euler computational multiphase fluid dynamics (CMFD) approach with wall boiling model which successfully predict the critical volume fraction under different conditions. The simulation results also had a good agreement with the corresponding experimental results.
Keywords: Critical heat flux, Boiling, CMFD
  • Invited lecture (Conferences)
    9th China-Korea Workshop on Nuclear Reactor Thermal-Hydraulics (WORTH-9), 15.-18.05.2019, Chongqing, China

Publ.-Id: 29017 - Permalink


Pulse-front tilt in laser-plasma accelerators with short focal lengths
Steiniger, K.ORC; Albach, D.ORC; Bussmann, M.ORC; Debus, A.ORC; Kluge, T.ORC; Loeser, M.ORC; Pausch, R.ORC; Siebold, M.; Zeil, K.; Schramm, U.ORC
Laser ion accelerators utilize high-power laser pulses in tight-focusing geometries to provide pulsed, high-intensity ion beams. Efficient capturing, transport and application of these beams is an ongoing effort which depends on precise knowledge of the accelerated ion distribution's properties and how to control these. For example, it is known that the propagation direction of the accelerated ions can be controlled by tilting the driving laser pulse-front. Since laser pulse-front tilts can be present accidentally, for example by a small misalignment of the compressor gratings in a chirped-pulse amplification system, knowledge of the scaling of the pulse-front tilt at a target position is desired. The talk gives relations for pulse-front orientation dependent on setup parameters and identifies regimes were pulse-front tilt has a sizable impact.
Keywords: Pulse-front tilt, high-power laser
  • Lecture (Conference)
    DPG-Frühjahrstagung, 17.-22.03.2019, München, Deutschland

Publ.-Id: 29015 - Permalink


Flüssigmetallbatterien als Großspeicher - Technologie, Scale-Up und Optionen zur Sektorkopplung
Nimtz, M.;
Es werden die grundsätzlichen Eigenschaften von Flüssigmetallbatterien beschrieben sowie Methoden und Ergebnisse zum Scale-Up vorgestellt. Des weiteren werden Funktionsweise und Anwendung der LMB-System-Calculator Software erläutert sowie Anwendungsoptionen für Flüssigmetallbbatterien, insbesondere bei der Sektorkoppelung vorgestellt.

Basic properties of Liquid Metal Batteries are described and methods and results for scale-up calculations are presented.
Also, functioning and usage of the LMB-System-Calculator software are discussed and options for the operation of Liquid Metal Batteries, especially for the sector-coupling are presented.
Keywords: LMB, Flüssigmetallbatterien, Scale-Up, Speicher, Sektorkoppelung, LMB, liquid metal battery, scale-up, storage, sectro-coupling
  • Lecture (others)
    Energie System 2050 Forschungsthema 1, 1. Workshop 2019, 19.-20.03.2019, Karlsruhe, Deutschland

Publ.-Id: 29014 - Permalink


Chemistry and accelerator mass spectrometry – A life happily ever after?
Merchel, S.ORC
Accelerator mass spectrometry (AMS) is the most sensitive analytical method to measure long-lived radionuclides. The detection limits are generally several orders of magnitude better, i.e. as low as 10-16 (radionuclide/stable nuclide), than any other mass spectrometry or decay counting method. AMS needs smaller sample sizes and measurements are finished within a few minutes to hours.

However, it is often forgotten that research projects applying AMS start with taking appropriate samples, followed by labour- and cost-intensive sample preparation. The goal can easily be described as “making the big samples (up to several kg’s) to fit in an AMS target holder (< 10 mg)”. This includes getting rid of the matrix and the troublesome isobars. By technical improvements of AMS leading to lower detection limits or better mass-and-element discrimination, sample masses can be reduced to gram-quantities instead of kg’s allowing easier, faster, and cheaper chemistry. Recent AMS developments also address very efficiently isobar elimination.

Nevertheless, some samples can contain different sources of the radionuclide-of-interest such as ¹⁰Be produced in the Earth’s atmosphere polluting the ¹⁰Be of interest produced in-situ in quartz. Hence, in this case chemistry is inevitable for cleaning the samples from the contamination. Another “mission” of chemistry might be the reduction of corresponding stable nuclides, e.g. 35,37Cl, ²⁷Al, natFe by preceding cleaning or by gentle leaching to enhance the radionuclide/stable nuclide ratio or to minimize interfering nuclear reactions such as thermal-neutron capture on ³⁵Cl. When applying isotope-dilution AMS to simultaneously determine the natCl content of a sample, which is an absolute requirement for surface exposure dating of Ca- or K-rich minerals, chemical sample preparation is also mandatory.

As the majority of research projects involving AMS is of true interdisciplinary character, knowledge of sample preparation is usually passed-on to (young) non-chemists. These are trained learning-by-doing to perform the chemical preparation of their own samples. Therefore, the development of “routine” AMS sample preparation needs to have a strong focus on safety and easy-to-be-trained aspects with the least opportunity for failure.

In conclusion, although new AMS technical developments for isobar suppression like the laser-negative ion interaction system at VERA promise to reduce elaborate chemistry in some cases, we should keep in mind that chemical knowledge will always be needed for a lot of interdisciplinary research projects.
Keywords: AMS
  • Lecture (others)
    VERA-Seminar, Institut für Isotopenphysik, Universität Wien, 28.03.2019, Wien, Österreich

Publ.-Id: 29013 - Permalink


Li-containing liquid metal alloy ion sources for focused-ion beam instrumentation
Mazarov, P.; Nadzeyka, A.; Richter, T.; Yu, Y.; Sanabia, J. E.; Bischoff, L.; Hlawacek, G.; Pilz, W.; Klingner, N.;
Focused Ion Beams (FIB) gain an increasing interest in the field of nanotechnology particular for prototyping of microelectronic devices, patterning of 2D materials, high resolution imaging or high resolution ion lithography1. Concerning ion beam resolution and minimization of unwanted damage, light ions like He or Li are preferred candidates. Liquid metal alloy ion sources (LMAIS) with a life time of more than 1000 µAh on the basis of Ga35Bi60Li5 and Sn95Li5 alloys were developed, characterized and finally applied in a commercial mass-separated VELION FIB-SEM system (Raith GmbH). The resolution for imaging and also for the formation of nanostructures using a thin gold film was determined.
In the case of Li ions from the mass separated FIB a lateral resolution of 5.6 nm could be obtained in first experiments2 and the sputter yield was determined to 0.4 for 35 keV Li ions on Au. For reference, the helium ion microscope (HIM) has a lateral resolution of about 0.5 nm and 1.8 nm, for He and Ne respectively, He has a sputter yield of 0.13. For sub-10 nm focused ion beam nanofabrication and microscopy, the GaBiLi-FIB or the SnLi-FIB could therefore be considered alternatives to the HIM with the benefit of providing additional ion species in a mass separated FIB without changing the ion source.

1 L. Bischoff et al. Appl. Phys. Rev. 3, 021 101 (2016).
2 W. Pilz et al. J. Vac. Sci. Technol. B A-18-399 (submitted, 2018).
3 G. Hlawacek et al. J. Vac. Sci. Technol. B 32, 020 801 (2014).
  • Lecture (Conference)
    The 63rd International Conference On ELECTRON, ION, AND PHOTON BEAM TECHNOLOGY AND NANOFABRICATION, 28.-31.05.2019, Minneapolis, United States of America

Publ.-Id: 29012 - Permalink


SiCxNy:Fe films as a tunable ferromagnetic material with tailored conductivity
Pushkarev, R.; Fainer, N.; Kirienko, V.; Matsynin, A.; Nadolinnyy, V.; Merenkov, I.; Trubina, S.; Ehrenburg, S.; Kvashnina, K.;
Amorphous ferromagnetic materials with the variable composition are promising candidates for application in rapidlygrowing technological fields, such as spintronics. However, the significant downside of current state-of-art materials is a conductivity mismatch between injector and semiconductor which often is associated with the unavailability to control and precisely tailor magnetic properties and conductivity. We report on the synthesis of soft-magnetic SiCxNy:Fe films with the saturation magnetization of 20 e.m.u./cm3 and conductivity similar to the one of Si, which is crucial for possible applications.
XRD with synchrotron radiation and EXAFS revealed the complex composite structure of the films: crystals of Fe3Si, Fe5Si3, SiC and graphite are embedded into the amorphous matrix of SiCxNy. The variation of deposition conditions allowed us to separately control the magnetic properties through the iron concentration and the conductivity of the material through the amorphous SiCxNy matrix composition. The reported results revealed a significant potential of SiCxNy:Fe films as a prospective object for analysis of spin-polarized transport in amorphous semiconductors and for application in field of spintronics.

Downloads:

  • Secondary publication expected from 13.03.2020

Publ.-Id: 29011 - Permalink


Bridging the Green Gap: Metal–Organic Framework Heteromultilayers Assembled from Porphyrinic Linkers Identified by Using Computational Screening
Haldar, R.; Batra, K.; Marschner, S. M.; Kuc, A. B.; Zahn, S.; Fischer, R. A.; Bräse, S.; Heine, T.; Wöll, C.;
In organic photovoltaics, porphyrins (PPs) are among the most promising compounds owing to their large absorption cross section, wide spectral range, and stability. Nevertheless, a precise adjustment of absorption band positions to reach a full coverage of the so-called green gap has not been achieved yet. We demonstrate that a tuning of the PP Q- and the Soret bands can be done using a computational approach where substitution patterns are optimized in silico. The Most promising candidate structures were then synthesized. The experimental UV/Vis data for the solvated compounds were in excellent agreement with the theoretical predictions. By attaching further functionalities, which allow using the PP chromophores as linkers for the assembly of metal-organic frameworks (MOFs), we were additionally able to exploit packing effects resulting in pronounced red shifts, which allowed to further optimizing the photophysical properties of PP assemblies. Finally, we use a layer-by-layer method to assemble the PP linkers into surface-mounted MOFs (SURMOFs), thus obtaining high optical quality, homogeneous and crystalline multilayer films. Experimental results are in full accord with the calculations, demonstrating a huge potential of computational screening methods in the tailoring of MOF and SURMOF photophysical properties.

Downloads:

  • Secondary publication expected from 10.04.2020

Publ.-Id: 29010 - Permalink


Synthesis and Functionalization of Radium-doped Barium Sulfate Nanoparticles
Reissig, F.; Bauer, D.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.ORC
The radionuclides radium-223 and radium-224 are two alpha-emitting radionuclides with suitable properties for the TAT. To this date, radium-223 in form of [223Ra]radium chloride (Xofigo) is the only EMA and FDA approved alpha-emitting radiopharmaceutical. Due to its calcimimetic behavior, the radium ion is a bone-seeking therapeutic. To extend the radiopharmaceutical potential of both radionuclides, novel carrier systems have to be developed. Therefore, it is appropriate to investigate different kinds of nanoparticles for their ability to transport radium. Especially, a barium sulfate matrix seems to be sufficient since the principle of co-precipitating the sulfates of radium and barium allows an easy and fast synthesis of radium-doped nanoparticles. Beyond the incorporation of alpha-emitting radionuclides like radium-223 and radium-224, the homologue radionuclide barium-131 can be incorporated as well. Barium 131 decays by electron capture and provides suitable properties for diagnostic applications in nuclear medicine. Radium-223/-224 and barium-131 form a matched pair for new theragnostic approaches. In our research group, we are developing simple methods for the synthesis of small radiolabeled radium/barium sulfate nanoparticles. Furthermore, we are investigating suitable surface functionalizations to attach biological targeting moieties.
Keywords: Bariumsulfat, Radium-224, Nanopartikel
  • Poster
    11th International Symposium on Targeted-Alpha-Therapy, 01.-06.04.2019, Ottawa, Kanada
  • Open Access LogoAbstract in refereed journal
    Journal of Medical Imaging and Radiation Sciences 50(2019)1, S38-S38
    DOI: 10.1016/j.jmir.2019.03.117

Publ.-Id: 29009 - Permalink


Synthese neuartiger Calix[4]arenkäfige für die stabile Bindung von Ba2+ und Ra2+
Mamat, C.ORC; Reissig, F.; Steinbach, J.; Pietzsch, H.-J.
Therapieansätze in der Nuklearmedizin mit Radium-223 beschränken sich zurzeit auf die Behandlung von Knochenmetastasen. Ziel ist es, das Anwendungsfeld für Radium-223 zu erweitern. Dafür werden Liganden entwickelt, die Radium-223 stabil binden und gleichzeitig eine spezifische Erkennungssequenz für diverse Krebsentitäten besitzen. Calixkronen mit funktionalisierten Seitenketten sind dafür vielversprechend.

Calix[4]krone-6-derivate mit Trifluormethylsulfonyl- [1] und 4-Nitrophenylsulfonyl-Seitenketten wurden synthetisiert und mittels NMR und UV/Vis auf ihre Komplexierungseigenschaften für Ba2+ untersucht. Anschließend wurden mittels eines Extraktionsassays Komplexierungen durchgeführt und die resultierenden Komplexe auf ihre Stabilität in Gegenwart anderer Ionen wie Ca2+ untersucht. Die Extraktionsversuche wurden im Chloroform/Wasser-Zweiphasensystem durchgeführt. Dabei wurde eine wässrige Metallsalzlösung ([133Ba]Ba2+ c.a. bzw. [224Ra]Ra2+ n.c.a.) definierter Konzentration vorgelegt und mit einer definierten Stoffmenge des jeweiligen Liganden in Chloroform für 1 h bei RT extrahiert.
Die beiden Calixarenderivate wurden in einer vierstufigen Synthese hergestellt. Anschließende Komplexierungsversuche mit Ba(ClO4)2 verliefen erfolgreich und die Komplexe wurden mittels NMR-Spektroskopie nachgewiesen. Für beide Liganden wurden Stabilitätskonstanten von 5,3-6,3 (Ba2+) bzw. 5,8 (Ra2+) berechnet. Die Radiumkomplexe beider Liganden waren gegenüber Ca2+-Ionen stabil (Release <5%), der Bariumkomplex des Nitrophenylsulfonylliganden war ebenfalls stabil (Release <5%), der des Trifluormethylsulfonylliganden zeigte 30% Release.
Die Wahl der sterisch anspruchsvollen und elektronenziehenden Sulfonylgruppen hatte positive Auswirkungen sowohl auf das Komplexierungsverhalten mit Ba2+ und Ra2+ als auch auf die Stabilität der resultierenden Komplexe in Gegenwart von zweiwertigen Fremdionen.
Keywords: Barium-133, Radium-224, Calixaren
  • Lecture (Conference)
    57. Jahrestagung der DGN 2019, 03.-06.04.2019, Bremen, Deutschland

Publ.-Id: 29008 - Permalink


Synthesis and Biological Investigation of A Novel Fluorine-18 Labeled Benzoimidazotriazine: A Potential Radioligand for In Vivo Phosphodiesterase 2A (PDE2A) PET imaging
Ritawidya, R.; Teodoro, R.; Wenzel, B.; Kranz, M.; Toussaint, M.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Scheunemann, M.; Brust, P.;
Objectives: Cyclic nucleotide phosphodiesterase 2A (PDE2A), an enzyme which hydrolyzes the second messengers cAMP and cGMP, is highly enriched in distinct areas of the brain. Accordingly, PDE2A is involved in important signaling pathways related to normal brain function but also to
neurodegeneration and neuro-oncology [1]. To enable the visualization of this protein in the brainwith PET, we developed a novel fluorine-18 radioligand for PDE2A.
Methods: Based on the benzoimidazotriazine (BIT) tricyclic scaffold, several fluorine-containing derivatives were synthesized via a multi-step synthesis route, and their inhibitory profiles were assessed by PDE isoenzyme-specific activity assays. The most potent and selective PDE2A ligand
BIT1 was radiolabeled via nucleophilic aromatic substitution of the corresponding 2-nitro pyridine precursor by [18F]fluoride in DMSO with thermal heating (Figure 1). [18F]BIT1 was isolated using semi-preparative HPLC (Reprosil-Pur C18-AQ column, 250 x 10 mm, 46% ACN/aqu. 20 mM
NH4OAc, flow 5.5 mL/min) followed by final purification with solid-phase extraction and formulation in isotonic saline containing 10% ethanol. Preliminary in vitro autoradiography and in vivo PET studies (60 min dynamic PET imaging, nanoScan® PET/MRI, MEDISO, Budapest, Hungary) of [18F]BIT1 were performed using pig brain slices and female CD-1 mice, respectively. The in vivo metabolism of [18F]BIT1 was investigated by radio-HPLC analysis of mouse plasma and brain samples at 30 min p.i.
Results: From the series of BIT derivatives, BIT1 was selected as candidate for PET imaging of PDE2A based on the most suitable inhibitory potential and profile (IC50 PDE2A3 = 3.3 nM;16-fold selectivity over PDE10A). [18F]BIT1 was successfully synthesized with a radiochemical yield of 54 ± 2% (n = 3, EOB), molar activities of 155 – 175 GBq/μmol (EOS) and radiochemical purities of ≥99%. [18F]BIT1 was stable in saline, pig plasma, and n-octanol up to 60 min at 37 °C. The distribution pattern of [ 18F]BIT1 in pig brain cryosections corresponds to the spatial distribution of PDE2A with accumulation in the striatal regions caudate nucleus and nucleus accumbens. Additionally, the displacement of [18F]BIT1 with BIT1 as well as TA1 (a potent PDE2A ligand) indicated saturability and selectivity of these binding sites. Uptake of [18F]BIT1 in the brain was shown by subsequent imaging studies in mice (SUVwhole brain = 0.7 at 5 min p.i.); however, more detailed analyses revealed nonspecific distribution of the tracer in the brain (78% parent compound at 30 min p.i.).
Conclusions: The potent and selective PDE2A inhibitor [18F]BIT1 binds in vitro in brain regions known to express PDE2A. Further structural modifications will be performed to develop radiotracers with improved brain uptake and target-selective accumulation in vivo.
Acknowledgement
1. Deutsche Forschungsgemeinschaft (German Research Foundation, SCHE 1825/3-1).
2. Scholarship Program for Research and Innovation in Science and Technology Project
(RISET-PRO)-Indonesia Ministry of Research, Technology and Higher Education (World
Bank Loan No: 8245-ID)

References
[1] S. Schröder, B. Wenzel, W. Deuther-Conrad, M. Scheunemann, P. Brust, Novel Radioligands
for Cyclic Nucleotide Phosphodiesterase Imaging with Positron Emission Tomography: An Update
on Developments Since 2012, Molecules 21 (2016) 650–685.
Keywords: Phosphodiesterases, positron emission tomography, molecular imaging, benzoimidazotriazines
  • Poster
    International Symposium in Radiopharmaceutical Sciences, 26.-31.05.2019, Beijing, China

Publ.-Id: 29007 - Permalink


The effect of tumor volume changes on the boost-volume coverage in glioblastoma patients
Hessen, E.; Nijkamp, J.; Troost, E.; Makocki, S.; de Jong, M.; Dewit, L. H. G.; Jasperse, B.; van der Heide, U.; Borst, G.;
Purpose/Objective: Radiotherapy is one of the main treatment modalities in the multimodal therapy of glioblastoma patients. The ongoing NRG-BN001 trial (NCT02179086) is evaluating whether boosting a sub-volume with photons or protons improves overall survival as compared to standard-dose photon irradiation. We hypothesize that anatomical changes during irradiation may affect the dose coverage and that these changes may have a greater impact on proton treatment plans compared to photon treatment plans.
Material & Methods: For 24 glioblastoma patients, the MRI was repeated half way during radiation treatment. Three patients had a gross total resection (GTR), four patients underwent a biopsy and 17 patients had a subtotal resection (STR). These patients were treated according to the EORTC-ACROP guideline. A simulated photon and proton treatment plan (intensity modulated proton therapy; IMPT) according to the NRG-BN001 trial were made retrospectively. In this trial, patients in the experimental arm receive a dose of 46Gy/30fr on the T2w/FLAIR abnormalities and 75Gy/30fr on the planning target boost volume (PTV-7500). The PTV-7500 was defined as the resection cavity and/or contrast enhancing lesion on the T1w post gadolinium sequence of the MRI plus a margin of 5 mm (CTV) plus a 4 mm expansion in all dimensions. The trial constraints states that at least 95% of the PTV-7500 should receive 75Gy. To analyze the effect of anatomical changes during treatment on the dose coverage, we evaluated the planned dose distribution (based on the planning MRI) on the delineated PTV-7500 of the repeated MRI.
Results: The median time interval between the two MRIs was 25.5 days (range 15 – 36 days). Between the two scans, the PTV-7500 volume changed with a median of -0.1cc. However, we observed a wide range of -52.8 to +52.2cc. For the photon treatment plans we observed that 83% (n=20) of the patients showed a decline in PTV-7500 coverage (corresponding with a median decline of 6.5% and 8.3cc). The quartile of patients (n=6) with the largest PTV-7500 increase showed a 10% reduction in dose coverage (corresponding with a median volume of 33.2cc). There was no significant difference in coverage changes of the boost volume between the GTR, biopsy only and STR patients (p=0.632). The evaluation of the IMPT plans is ongoing and will be presented during the conference.
Conclusion: During fractionated radiation treatment for glioblastoma patients we observed large target volumetric changes in the boost volume half way during treatment. These target volume changes may lead to substantial declines in dose coverage when patients are treated according to dose-escalation protocol boosting specific sub-volumes. Thus, an important subset of glioblastoma patients may benefit from an MRI guided dose escalation strategy.
  • Open Access LogoAbstract in refereed journal
    International Journal of Radiation Oncology Biology Physics 105(2019)1, E99-E100
    DOI: 10.1016/j.ijrobp.2019.06.2290

Publ.-Id: 29006 - Permalink


Solving the Kuramoto Oscillator Model on Random Graphs
Kelling, J.ORC; Ódor, G.ORC; Gemming, G.
The problem of synchronization is recently attracting much attention because it relates to current topics in science. The dynamics of electrical grids can be affected by de-synchronizations between supplier and consumer nodes. In brains, synchronization of neuronal activity plays an important role in most functions. The Kuramoto model describes systems of coupled oscillators which, which exhibit non-trivial behavior on complex graphs, making it a suitable tool to study the synchronization dynamics of brains an other systems.

Numerical solution of Kuramoto type ordinary differential equations for long times and large systems requires strong computation power, due to the inherent chaoticity of this nonlinear system.

This poster presents a GPU implementation of a solver achieving large speedups over CPU on sparse random graphs. The key to performance here, is the presented memory layout which supplements the SIMT usage of our design.

# extended abstract
The problem of synchronization is recently attracting much attention because it relates to current topics in science. The dynamics of electrical grids can be affected by de-synchronizations between supplier and consumer nodes. In brains, synchronization of neuronal activity plays an important role in most functions.

Using the Kuramoto model[1], we are studying a range of problems, from basinc questions about synnchronisation transitions on disordered lattices and random graphs to problems mentioned in the short abstract. The model shows komplex behavior on human connectome graph, which allow the study of synchronization in the human brain[2]. An extension of the model allows modeling power grid networks[3,4].

Very intensive Simulations are required to obtain precise result especiall near criticality, which these systems show at synchronization transitons. To enable the study of these systems at sufficent precision, we implemented a GPU code, which we are presenting in this poster. To this end we used boost::odeint to get the standart numerical integartion out of the way an focus on the most performance critical aspect: the evaluation of the model itself. The key to our implementation is the choice of SIMT vectorization and a suitable memory layout, which are presented in the poster. The aspects also remain the same, when we add the extension to the second-order Kuramoto Model[2], which is required to model powergrids.

[1] Kuramoto, Y. In Araki, H. (ed.) Mathematical Problems in Theoretical Physics, vol. 39 of Lecture Notes in Physics, Berlin, 420
[2] Villegas, P., Moretti, P. & Muñoz, M. A. Scientific Reports 4, 5990 (2014).
[3] Filatrella, G., Nielsen, A. H. & Pedersen, N. F. Eur. Phys. J. B 61, 485–491 (2008)
[4] Ódor, G. & Hartmann, B. Phys. Rev. E 98, 022305 (2018).
Keywords: GPGPU, random graph, Kuramoto model

Publ.-Id: 29004 - Permalink


Fragment molecular orbital (FMO) method for studying actinide/lanthanide interaction with DNA/protein
Tsushima, S.; Mochizuki, Y.; Fahmy, K.;
Due to its potential health and environmental impacts, actinide binding to biomolecules has been a subject of intensive investigations. A large number of experimental works have been carried out but our understanding remains mostly in a macroscopic scale. Modeling actinide interaction with large biomolecules using ab initio quantum chemical calculations may drastically expand our molecular level knowledge but is challenged by a demand for huge computational resources.
Our strategy to overcome this difficulty is to apply fragment molecular orbital (FMO) method. In FMO, the molecular system of interest is partitioned into small fragments. Each fragment and fragment pair is subject to self-consistent field calculations under environmental electrostatic potentials and the electronic structure of the whole system is reconstituted [1]. This procedure drastically reduces computational cost of Hartree Fock calculations from N3 to N2 (or less) and is readily parallelizable. FMO has been extended to MP2 and to DFT to include electron correlation and was successfully applied to the systems such as hydrated DNA [2].
Currently we are upgrading the FMO program Abinit-MP [3] to implement 5f elements into the program. We first choose uranyl-bound DNA for a case study. Calculations are performed as follows. UO22+-bound d(CGCGAATTCGCG)2 (Dickerson-Drew dodecamer) with 20 Na+ ions and SPC/E water shell with 10 Å thickness is first thermally equilibrated and subsequently submitted to MD simulation at 300 K for 100 ns interval using AMBER 14 program. Force field parameters for UO22+ and coordinating water are those developed by Pomogaev et al. [4]. At each 1 ns time step of MD simulation, the structure is extracted and submitted to FMO single point energy calculation at the MP2 level. In FMO, nucleic unit is appropriately divided into sugar, base, and phosphate fragments. Inter-fragment interaction energy analysis is performed to explore the binding affinity of uranyl to DNA and its influence on base pairing.
[1] K.Kitaura et al. (1999) Chem. Phys. Lett. 313, 701–706.
[2] K.Fukuzawa et al. (2015) Comput.Theor.Chem. 1054, 29–37.
[3] S.Tanaka et al. (2014) Phys. Chem. Chem. Phys. 16, 10310–10344.
[4] V.Pomogaev et al. (2013) Phys. Chem. Chem. Phys. 15, 15954–15963.
  • Poster
    Joint 12th EBSA and 10th ICBP-IUPAP Biophysics Congress, 20.-24.07.2019, Madrid, Spain

Publ.-Id: 29002 - Permalink


Observations of Coherent Optical Transition Radiation Interference Fringes Generated by Laser Plasma Accelerator Electron Beamlets
Lumpkin, A.; Laberge, M.; Rule, D.; Zgadzaj, R.; Hannasch, A.; Downer, M.; Zarini, O.; Bowers, B.; Irman, A.; Couperus, J.ORC; Debus, A.; Kohler, A.; Schramm, U.
We report initial observations of coherent optical transition radiation interferometry (COTRI) patterns generated by microbunched electrons from laser-driven plasma accelerators (LPAs). These are revealed in the angular distribution patterns obtained by a CCD camera with the optics focused at infinity, or the far-field, viewing a Wartski two-foil interferometer. The beam divergences deduced by comparison to results from an analytical model are sub-mrad, and they are smaller than the ensemble vertical beam divergences measured at the downstream screen of the electron spectrometer. The transverse sizes of the beamlet images were obtained with focus at the object, or near field, and were in the few-micron regime as reported by LaBerge et al. [8]. The enhancements in intensity are significant relative to incoherent optical transition radiation (OTR) enabling multiple cameras to view each shot. We present two-foil interferometry effects coherently enhanced in both the 100-TW LPA at 215 MeV energy at Helmholtz-Zentrum Dresden-Rossendorf and the PW LPA at 1.0-GeV energy at the University of Texas-Austin. A transverse emittance estimate is reported for a microbunched beamlet example generated within the plasma bubble.
Keywords: LPA, microbunching, COTR, beam size, divergence
  • Contribution to proceedings
    18th Advanced Accelerator Concepts Workshop (AAC 2018), 12.-17.08.2018, Breckenridge, CO, USA
    2018 IEEE Advanced Accelerator Concepts Workshop (AAC): IEEE, 978-1-5386-7721-6
    DOI: 10.1109/AAC.2018.8659381

Publ.-Id: 29001 - Permalink


Photocatalytic Oxygenation of Cyclohexene Initiated by Excitation of [UO2(OPCyPh2)4]2+ under Visible Light
Mashita, T.; Tsushima, S.ORC; Takao, K.ORC
Oxygenation reaction of cyclohexene was studied under presence of a 4-fold UO22+ complex with cyclohexyldiphenylphosphine oxide, [UO2(OPCyPh2)4]2+, and blue light irradiation at 436 nm in acetonitrile. As a result, 1,6-hexanedial, cyclohexene oxide, 2-cyclohexen-1-one, and 2-cyclohexen-1-ol were photocatalytically generated as oxygenated products with TOF = 6.7 h−1. In contrast, dimerization of cyclohexene was observed under Ar atmosphere. This implies that a hydrogen atom at the allyl position is abstracted by photoexcited *[UO2(OPCyPh2)4]2+ to give a cyclohexene radical and a U(V) intermediate [UVO2(OPCyPh3)4]+, being well supported by DFT calculation. Under O2 atmosphere, the former reacts with dissolved O2 to give 2-cyclohexen-1-one and 2-cyclohexen-1-ol. Dissolved O2 would be activated by the U(V) intermediate to afford O22− in the end, which drives oxygenation of C=C bond of unreacted cyclohexene.

Publ.-Id: 28999 - Permalink


Time efficient scatter correction for time-of-flight PET: the immediate scatter approximation
Nikulin, P.ORC; Maus, J.ORC; Hofheinz, F.ORC; Lougovski, A.; van den Hoff, J.ORC
Utilization of Time-Of-Flight (TOF) information allows to improve image quality and convergence rate in iterative PET image reconstruction. In order to obtain quantitatively correct images accurate scatter correction (SC) is required that accounts for the non-uniform distribution of scatter events over the TOF bins. However, existing simplified TOF-SC algorithms frequently exhibit limited accuracy while the currently accepted gold standard — the TOF extension of the single scatter simulation approach (TOF-SSS) — is computationally demanding and can substantially slow down the reconstruction. In this paper we propose and evaluate a new accelerated TOF-SC algorithm in order to improve this situation. The key idea of the algorithm is the use of an immediate scatter approximation (ISA) for scatter time distribution calculation which speeds up estimation of the required TOF scatter by a factor of up to five in comparison to TOF-SSS. The proposed approach was evaluated in dedicated phantom measurements providing challenging high activity contrast conditions as well as in representative clinical patient data sets. Our results show that ISA is a viable alternative to TOF-SSS. The reconstructed images are in excellent quantitative agreement with those obtained with TOF-SSS while overall reconstruction time can be reduced by a factor of two in whole-body studies, even when using a listmode reconstruction not optimized for speed.
Keywords: PET, Scatter Correction, Immediate Scatter Approximation, Image Reconstruction, TOF, SSS, TOF-SSS, TOF-SC, ISA

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Publ.-Id: 28997 - Permalink


Influence of the bubble size distribution on the bubble column flow regime
Lucas, D.; Ziegenhein, T.;
The role of the bubble size dependent lateral lift force on the flow regime is experimentally investigated in a tall bubble column. In the experiments, only the initial bubble size distribution was modified by using a gas sparger with different injection needles and varying the flow through specific injection needles. The gas flow rate was kept unchanged in all experiments. Depending on the bubble size distribution homogeneous, transitional or heterogeneous flow regimes were observed. The flow regime is in good agreement with the predictions from the stability criterion obtained by a previously done linear stability analysis for poly-dispersed flow. It was found that as a rule of thumb the following criterion can be used.
If most of the gas volume is transported by bubbles smaller than the critical diameter at which the lift force changes its sign, the flow is stabilized leading to a homogeneous flow regime. If most of the gas volume is transported by bubbles larger than that diameter the flow is de-stabilized leading a heterogeneous flow regime. If the fraction of gas transported by small and large bubbles is about the same, the initial conditions remain dominant throughout the column height.
Keywords: bubble size, lift force, stability, bubble column, flow regime, regime transition

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  • Secondary publication expected from 12.08.2020

Publ.-Id: 28995 - Permalink


Quantum Critical Dynamics of a Heisenberg-Ising Chain in a Longitudinal Field: Many-Body Strings versus Fractional Excitations
Wang, Z.; Schmidt, M.; Loidl, A.; Wu, J.; Zou, H.; Yang, W.; Dong, C.; Kohama, Y.; Kindo, K.; Gorbunov, D. I.; Niesen, S.; Breunig, O.; Engelmayer, J.; Lorenz, T.;
We report a high-resolution terahertz spectroscopic study of quantum spin dynamics in the antiferromagnetic Heisenberg-Ising spin-chain compound BaCo2V2O8 as a function of temperature and longitudinal magnetic field. Confined spinon excitations are observed in an antiferromagnetic phase below TN ≃ 5.5 K. In a field-induced gapless phase above Bc = 3.8 T, we identify many-body string excitations as well as low-energy fractional psinon/antipsinon excitations by comparing to Bethe-Ansatz calculations. In the vicinity of Bc, the high-energy string excitations are found to be dynamically dominant over the fractional excitations.

Publ.-Id: 28993 - Permalink


Protecting Pulsed High-Power Lasers with Real-Time Object Detection
Kelling, J.; Gebhardt, R.; Helbig, U.; Bock, S.; Schramm, U.; Juckeland, G.;
In Petawatt laser systems, firing at 10Hz, suddenly appearing scatterers can damage components. Damage(-spreading) can be avoided by suspending operation immediately on occurrence of such an event. This poster presents our approach for the automatic detection of critical failure states in real-time, employing state-of-the-art object localization on intensity profiles of the laser beam.

Learn, how we fitted the You Look Only Once (YOLO) approach, which is suited to low-latency object detection, to our problem and how we adapted the required multi-step training protocol to the available experimental data.
In this application accuracy trumps high recall, as false positives would severely impede productivity or even render our system useless. This had us refrain from general anomaly detection and thus we also present different ways in which we tune the object-detection for minimal false-positive rates.

# extended abstract
High-power lasers are operated at our research center for investigations of exotic states of matter and medical applications, among others. This project to improve the automatic shutdown/interlock system of two lasers (one in operation, one currently under construction) has the goal of reducing the probability of, potentially expensive, damage-spreading scenarios, while at the same time avoiding false alarms. In order to achieve high precision, we train for high recall only for known indicators, instead of using anomaly detection.

After we presented a proof-of-concept for this type of failure-state-detection at GTC 2018, where the main challenge was in dealing with a far too small dataset, we are now working on a pure deep-learning approach driven by systematic experimental data. In the new design, intended for production use, the classification takes place on differences between a running average of non-signaling images and the current shot. This is required, because no images can be obtained which can be classified as "good" without context. In order to achieve fast object-detection, to highlight potential problems for the operator, the you look only once (YOLO) approach[1], which we modify by removing the final layers for bounding-box prediction and train the network to directly produce an expressive feature map (lazy YOLO).

From this talk, the audience can learn how we adapted the well-known YOLO approach to our real-world application, from the employed network to the multi-step training protocol. Another topic is the design for short response times, to which end we employ Caffe, OpenCV on GPU and use C++ as main programming language instead of python.

[1] Redmon, J., Farhadi, A.: YOLO9000: Better, Faster, Stronger, ArXiv e-prints, 2016
Keywords: Image Classification, Caffe, automatic Laser-safety shutdown, Object Detection

Publ.-Id: 28992 - Permalink


Dimeric Uranium(VI)–Citrate Complexes: Structures and Dynamics
Kretzschmar, J.ORC; Tsushima, S.; Jäckel, E.; Meyer, R.; Steudtner, R.; Müller, K.; Schmeide, K.; Brendler, V.; Stumpf, T.
The aqueous chemistry of the uranium(VI)–citrate system is challenging, as evidenced by still controversial discussions on complex stoichiometries and structures [1–4]. For a sound understanding of the chemical behavior in general and the environmental fate in particular, knowledge of both aqueous speciation and molecular structures in solution is crucial. Here, complexes formed by the uranyl ion, U(VI), and citrate (Cit) were examined in the pH range 2–8 by combining one- and two-dimensional NMR with UV-Vis, ATR FT-IR, and EXAFS spectroscopies as well as DFT-based quantum chemical calculations.
Upon complexation, a chiral center is induced in Cit’s central carbon, resulting in the formation of two diastereomeric pairs of enantiomers, whereupon the dimeric complexes exhibit syn and anti configured isomers. In fact, the combination of 17O NMR (note: at natural abundance) and DFT calculations allowed an unambiguous decision on complex geometry and overall configurations. It is evidenced for the first time that the syn isomer is favored in aqueous solution in contrast to the preferably crystallizing anti isomer. Both isomers coexist and interconvert among one another, with a rate estimated to be in the order of 10² s¹ at 25 °C in acidic media, and a corresponding activation energy of approximately 60 kJ mol¹.
Upon increasing pH, the ternary dimeric U(VI)–Cit mono- and bis-hydroxo (2:2:1 and 2:2:2) complexes form as evidenced by both UV-Vis and ATR FT-IR spectroscopy. The latter methods provided stability constants (log β): 19.5 (2:2:0), 14.0 (2:2:1), and 6.5 (2:2:2). Accordingly, the process can be referred to as U(VI) hydrolysis within the U(VI)–Cit complex as the two coordinating water molecules in the respective fifth coordination site each abstract H+. Thus, any U(VI)-coordinating water in ever so stable complexes is susceptible to hydrolysis even in strong acidic media as consequence of the interplay between metal ion Lewis acidity and solution pH.
Virtually all single-crystal X-ray structures containing the dimeric U(VI)–Cit complex in any manner, reveal anti configuration, e.g. [4]. The predominance of the syn isomer in solution was hitherto unnoticed, demonstrating that, particularly upon different physico-chemical properties of the isomers, the (crystalline) solid phase does not necessarily reflect speciation and structures found in (aqueous) solution, underlining the importance of rigorous solution studies.

References:
[1] I. Feldman et al., J. Am. Chem. Soc., 1954, 76, 4726.
[2] M. T. Nunes and V. M. S. Gil, Inorg. Chim. Acta, 1987, 129, 283.
[3] S. P. Pasilis and J. E. Pemberton, Inorg. Chem., 2003, 42, 6793.
[4] M. Basile et al., Chem. Commun. 2015, 51, 5306.
Keywords: uranium, uranyl, U(VI), citric acid, molecular structure, NMR, ATR FT-IR, UV-Vis, spectroscopy, ternary complex, uranium hydrolysis, stability constant, isomerization
  • Lecture (Conference)
    Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland

Publ.-Id: 28991 - Permalink


Simultaneous 8.2 keV phase-contrastimaging and 24.6 keV X-ray diffraction fromshock-compressed matter at the LCLS
Seiboth, F.; Fletcher, L. B.; Mcgonegle, D.; Anzellini, S.; Dresselhaus-Cooper, L. E.; Frost, M.; Galtier, E.; Goede, S.; Harmand, M.; Lee, H. J.; Levitan, A. L.; Miyanishi, K.; Nagler, B.; Nam, I.; Ozaki, N.; Rödel, M.; Schropp, A.; Spindloe, C.; Sun, P.; Wark, J. S.; Hastings, J.; Glenzer, S. H.; Mcbride, E. E.;
In this work, we demonstrate simultaneous phase-contrast imaging (PCI) and X-ray diffractionfrom shock compressed matter at the Matter in Extreme Conditions endstation, at the LinacCoherent Light Source (LCLS). We utilize the chromaticity from compound refractive X-ray lensesto focus the 24.6 keV 3rd order undulator harmonic of the LCLS to a spot size of 5lm on target toperform X-ray diffraction. Simultaneous PCI from the 8.2 keV fundamental X-ray beam is used tovisualize and measure the transient properties of the shock wave over a 500lm field of view.Furthermore, we demonstrate the ability to extend the reciprocal space measurements by 5 Angstroem, rel-ative to the fundamental X-ray energy, by utilizing X-ray diffraction from the 3rd harmonic of theLCLS.
Keywords: Phase Contrast Imaging, PCI, Matter in Extreme Conditions, MEC, LCLS, shock compression, x-ray diffraction, XFEL, germanium, shock, release

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Publ.-Id: 28990 - Permalink


A Polka-Dot Pattern Emerges in Superfluid Helium
Wosnitza, J.;
A surprising two-dimensional pattern appears in superfluid helium-3 when the liquid is confined to a micrometer-thick cell and exposed to a magnetic field.

Publ.-Id: 28989 - Permalink


Low anisotropic upper critical fields in SmO1−xFxFeAs thin films with a layered hybrid structure
Haindl, S.; Kampert, E.; Sasase, M.; Hiramatsu, H.; Hosono, H.;
We report on the upper critical fields in SmO1−xFxFeAs thin films prepared by pulsed laser deposition. With an F-content gradient along their thickness, the films could be described approximately as layered two-phase hybrid structures comprised of one superconducting layer and one antiferromagnetic layer. An analytical characterization of different thin film samples by Auger electron spectroscopy and energy-dispersive x-ray spectroscopy in scanning transmission electron microscopy is provided and structural defects, such as antiphase boundaries, were confirmed for films grown at lower deposition temperatures. Electrical transport measurements in pulsed magnetic fields yielded upper critical fields higher than 80 T with an anisotropy γHc2 ≤ 2.25.

Publ.-Id: 28988 - Permalink


Microscopic and spectroscopic investigations of the interactions of a Halobacterium-isolate with uranium
Hilpmann, S.; Bader, M.; Bachran, M.; Steudtner, R.; Schmidt, M.; Stumpf, T.; Cherkouk, A.;
Rock salt formations are potential host rocks for the long-term storage of high-level radioactive waste in a deep geological repository, besides clay and crystalline rock. There are multiple studies about the geological, geochemical and geophysical properties of these host rocks. However, there exists still a lack of knowledge about indigenous microorganisms and their influence on the chemical speciation. For a long-term risk assessment, it is of high interest to study how these microorganisms interact with radionuclides. Therefore, the interactions of an extremely halophilic archaeon, Halobacterium sp. GP5 1-1 with uranium, one of the major radionuclides of concern, were investigated in detail. This extremely halophilic archaeon was isolated from a German rock salt sample. Different microscopic and spectroscopic methods were combined to decipher the occurring processes on a molecular level.
To investigate the interaction kinetics of uranium(VI) onto the cells of Halobacterium sp. GP5 1-1, time-dependent association experiments with two different uranium(VI) concentrations were performed. At both concentrations the amount of bioassociated uranium(VI) increased with the incubation time. It was determined that the association process at the higher concentration (30 µM) was much slower than the kinetic at the lower uranium(VI) concentration (10 µM).
Various microscopic and spectroscopic methods were used to understand the interaction mechanisms on a molecular level. Overall, the association process is not exclusively a biosorption, which is a passive process and in general completed after a short time of incubation (0 – 2 h) [1]. The microscopic images of the live/dead staining show the formation of cell agglomerates after a certain exposition time at both concentrations. During the process, organic matter is excreted from the cells. Therefore, more functional groups are available for further uranium(VI) binding.
Electron microscopic images of the cells allowed drawing conclusions about different microbe-radionuclide interactions at different uranium(VI) concentrations. A biomineralization takes place at lower concentrations (10 µM) and uranium(VI) is bound to biofilm-like structures at higher concentrations (60 µM).
Using time-resolved laser-induced luminescence spectroscopy, different aqueous species could be extracted from the supernatant. These species differ slightly in dependence on the uranium(VI) concentration. In both cases, a uranyl-carbonate-complex is formed during the association process due to microbial released CO2. Additionally the formation of a phosphate species in the cell pellets at low uranium(VI) concentrations was observed in a uranium(VI) concentration-dependent experiment (10-60 µM). In contrast, at higher uranium(VI) concentrations a carboxylic species was formed. This is in agreement with the already mentioned excretion of organic matter from the cells during the uranium(VI) incubation.
These findings offer new insights into the microbe-actinide interactions at highly saline conditions relevant to high-level radioactive waste disposal in rock salt.[1]


[1] J. R. Lloyd, L. E. Macaskie (2002) in “Interactions of Microorganisms with Radionuclides” (Eds.: M.J. Keith-Roach, F. R. Livens), Elsevier, pp. 313-381
  • Lecture (Conference)
    Migration 2019, 15.-20.09.2019, Kyoto, Japan

Publ.-Id: 28987 - Permalink


Complex formation between UO22+ and α-isosaccharinic acid: insights on a molecular level
Brinkmann, H.ORC; Patzschke, M.ORC; Kaden, P.ORC; Raiwa, M.; Rossberg, A.; Kloditz, R.; Heim, K.; Moll, H.; Stumpf, T.
Cellulosic materials present as tissue, paper, wood, or filter materials in low and intermediate level waste will degrade under alkaline conditions if water ingresses in a cementitious backfilled repository. The main degradation product is isosaccharinic acid. Complex formation with isosaccharinic acid may adversely affect the retention of radionuclides by sorption or formation of solid phases. Hence, this compound is of particular concern in the context of nuclear waste disposal. Structural information of complexes are limited to spherical metal centers and little is known about the interaction of uranyl (UVIO22+) with isosaccharinic acid. Therefore, the interaction of UO22+ with α-isosaccharinate (ISA) was studied under acidic conditions focusing particularly on the structural characterization of the formed complexes. Attenuated total reflection Fourier-transform infrared (ATR-FTIR), nuclear magnetic resonance (NMR), UV-Vis, extended X-ray absorption fine structure (EXAFS) spectroscopy and electrospray-ionization mass spectrometry (ESI-MS) were combined with theoretical calculations to obtain a process understanding on the molecular level. The dominant binding motifs in the formed complexes are 5- and 6-membered rings involving the carboxylic group as well as the α- or β-hydroxy group of ISA. Two concentration dependent complex formation mechanisms were identified involving either mono- ([UO2(ISA)(H2O)3]+) or binuclear ([(UO2)2(ISA)(H2O)6]3+) species. Furthermore, this study unveils the interaction of UO22+ with the protonated α-isosaccharinic acid (HISA) promoting its transformation to the corresponding α-isosaccharinate-1,4-lactone (ISL) and inhibiting the formation of polynuclear UO22+-ISA species. Future studies on related systems will benefit from the comprehensive knowledge concerning the behavior of ISA as complexing agent gained in the present study.
Keywords: Uranium, Isosaccharinic acid, Complexation, Lactonization, Spectroscopy

Publ.-Id: 28986 - Permalink


From Exploration towards Predictive Geometallurgy - The Role of SEM-based Automated Mineralogy and Statistical Assessment
Birtel, S.; Bachmann, K.; Büttner, P.; Tolosana Degado, R.; van den Boogaart, K. G.; Gutzmer, J.;
Geometallurgical models are constructed to quantitatively predict how ores will behave during extraction and beneficiation. Depending on data availability, complexity of data and operational stage different classes of geometallurgical models can be distinguished: 1) resource potential, 2) recoverable resources, 3) first order predictive models, 4) predictive models, and 5) real-time mining models. Here, two case studies are presented where modal mineralogy and microstructural data obtained from SEM-based image analysis are combined with complementary analytical data and statistically assessed in order to predict raw material behaviour during mineral processing. For both case studies, the necessary steps to develop existing models into truly predictive geometallurgical models are outlined. The first case study concerns the recovery of Sn from a historic flotation tailings storage facility. The second case study centres on the recovery of PGE as by-products from a chromite ore deposit as a first order predictive geometallurgical model.
Keywords: SEM based automated mineraloy, statistcal assement, case studies, process optimization
  • Contribution to proceedings
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.-30.08.2019, Glasgow, UK
    Proceedings to 15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 1474-1477
  • Lecture (Conference)
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.-30.08.2019, Glasgow, UK

Publ.-Id: 28985 - Permalink


Photogeneration of Manganese(III) from Luminescent Manganese(II) Complexes with Thiacalixarene Ligands: Synthesis, Structures and Photophysical Properties
O'Toole, N.; Lecourt, C.; Suffren, Y.; Hauser, A.; Khrouz, L.; Jeanneau, E.; Brioude, A.; Luneau, D.; Desroches, C.;
The photophysical properties of the compound [(ThiaSO₂)(MnII)₂(DMF)₄(H₂O)₂] (2), ThiaSO₂ = p-tert-butylsulfonylcalix[4]arene, are presented and compared to the ones of [(ThiaSO₂)₂(MnII)₄F]K (1). The orange luminescence of 2 is attributed, as for 1, to the MnII centred ⁴T₁→⁶A₁ transition and shows, for this type of complex, the weak influence of the Mn²⁺ coordination and ThiaSO₂ conformation on this luminescence, the temperature and pressure dependence and quenching bymolecular dioxygen of which are reported for 2. The latter is attributed to energy transfer from the ⁴T₁ state exciting dioxygen to its ⁱΣ⁺ᵍ state and is responsible for the photosynthesis of the [(ThiaSO₂)(MnIII)(DMF)₂]Na (3) complex in DMF solution from 1 or 2. This reaction was studied by UV/Visible and EPR spectroscopy. The molecular structure and EPR spectroscopy of 3 are also presented.
Keywords: Thiacalixarene, Luminescence, Photooxidation, Manganese

Publ.-Id: 28984 - Permalink


Strong and Selective Ni(II) Extractants Based on Synergistic Mixtures of Sulfonic Acids and Bidentate N-Heterocycles
Roebuck, J. W.; Bailey, P. J.; Doidge, E. D.; Fischmann, A. J.; Healy, M. R.; Nichol, G. S.; O'Toole, N.; Pelser, M.; Sassi, T.; Sole, K. C.; Tasker, P. A.;
Bidentate 5,5ʹ-alkyl-3,3ʹ-bi-1H-pyrazole and 2-(5-alkyl-1H-pyrazol-3-yl)pyridine ligands, L⁵ and L⁶ , have been shown to be stronger synergists for the solvent extraction of Ni(II) from sulfate solutions by dinonylnaphthalene sulfonic acid (DNNSAH) than the structurally related tridentate ligand 2,6-bis-[5-n-nonylpyrazol-3-yl]pyridine, L¹ , previously reported by Zhou and Pesic. The bidentate ligands are highly selective, providing the option of sequential recovery of Ni(II) and Co(II) and rejection of other metals commonly found in the liquors resulting from the acidic sulfate leaching of laterite ores. They were the strongest synergists identified in a screening carried out on 18 types of bidentate and tridentate N-heterocyclic ligands, including the recently reported 2-(2ʹ-pyridyl)imidazoles, L⁹⁻¹¹ . X-ray crystal structures of Ni(II) complexes of model ligands for L⁵ and L⁶ , having t-butyl rather than long-chain alkyl groups and with 2-naphthalene sulfonate rather than DNNSA⁻ as counteranions, show that the [Ni(L)₃ ]²⁺ complexes form strong H-bonds from the pyrazolyl NH groups to the oxygen atoms of the sulfonate groups, an arrangement that will stabilize [Ni(L)₃ ·(DNNSA)₂ ] assemblies and shield their polar functionalities from diluent molecules of the water-immiscible phase. UV–visible spectra and mass spectrometry provide evidence for the strong synergists displacing all water molecules from the inner coordination sphere of the Ni(II) ions.
Keywords: Ni recovery, laterite processing, synergistic solvent extraction, outer-sphere bonding, supramolecular chemistry

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  • Secondary publication expected from 02.11.2019

Publ.-Id: 28983 - Permalink


Transmission Helium Ion Microscopy using sub-50 keV He+: Images and scattered intensity patterns from crystalline materials
Mousley, M.; Eswara, S.; de Castro, O.; Bouton, O.; Klingner, N.ORC; Koch, C. T.; Hlawacek, G.; Wirtz, T.
A dedicated Transmission Helium Ion Microscope (THIM) for sub-50 keV helium was developed to investigate ion scattering processes and contrast mechanisms to develop new imaging and analysis modalities. Unlike a commercial Helium Ion Microscope (HIM), the in-house built instrument allows full flexibility in experimental configuration. Here, we report transmission imaging and scattering patterns obtained from powder and bulk crystalline samples using a stationary broad-beam as well as convergent-beam illumination conditions in THIM. The scattered He+ ions formed unexpected spot patterns in the far-field for MgO, BN and NaCl powder samples, but not for Si bulk sample. The mechanistic origins of the spot patterns in these samples were investigated. Surface diffraction of ions was excluded as a possible cause because the recorded scattering angles do not correspond to the predicted Bragg angles. Complementary Secondary Electron (SE) imaging in a HIM revealed that these samples charge significantly under He+ ion irradiation. It is suggested that the spot patterns obtained in THIM experiments are artefacts related to sample charging. The results presented here indicate that factors other than channelling, blocking and surface diffraction of ions have an impact on the final scattered intensity distribution in the far-field. Hence, the different processes contributing to the final scattered intensities should be understood in more detail to decouple and study the relevant ion beam scattering phenomena.
Keywords: Helium Ion Microscopy; ion scattering; Transmission Ion Microscopy

Publ.-Id: 28982 - Permalink


Efficient calculation methods for the diffusion coefficient of interstitial solutes in dilute alloys
Wang, X.; Faßbender, J.; Posselt, M.;
In the example of oxygen diffusion in dilute ferritic iron alloys it is shown that the calculation of the diffusion coefficient can be separated into a contribution related to the migration in the interaction region between oxygen and the substitutional solute and a part related to diffusion in pure bcc Fe. The corresponding diffusion times are determined by analytical expressions using Density-Functional-Theory (DFT) data for the respective binding energies. The diffusion coefficient in the interaction region must be determined by atomistic kinetic Monte Carlo (AKMC) simulations with DFT values for the migration barriers as inputs data. However, in contrast to previous calculations, AKMC simulation must be performed only for one concentration of the substitutional solute, and the obtained results can be employed to obtain data for other concentrations in a very efficient manner. This leads to a tremendous decrease of computational efforts. Under certain conditions it is even possible to use only analytical expression where merely DFT data for the binding energies are needed. The limits of applicability of the presented calculation procedures are discussed in detail. The methods presented in this work can be generalized to interstitial diffusion in other host materials with small concentrations of substitutional solutes.
Keywords: Diffusion coefficient; Interstitial solute; dilute alloy; Efficient calculation; First-principle calculations; Atomistic kinetic Monte Carlo simulations

Publ.-Id: 28979 - Permalink


Defects and mechanical properties in weakly damaged Si ion implanted GaAs
Creutzburg, S.; Schmidt, E.; Kutza, P.; Loetzsch, R.; Uschmann, I.; Undisz, A.; Rettenmayr, M.; Gala, F.; Zollo, G.; Boulle, A.; Debelle, A.; Wendler, E.;
Damage formation is investigated in GaAs implanted with 1 MeV Si ions to ion fluences from 3 × 10¹² to 5 × 10¹⁵ cm⁻² at room temperature. Under the conditions applied, amorphization of the implanted layers does not occur. The weakly damaged layers are studied by applying different experimental techniques including Rutherford backscattering spectrometry in channeling configuration, x-ray diffraction, in situ curvature measurement, optical subgap spectroscopy, and transmission electron microscopy. The results are evaluated and quantitatively connected with each other. Damage formation is described as a function of the ion fluence using a common defect evolution model. Point defects and defect clusters have to be taken into account in the ion fluence range of main interest up to 2 × 10¹⁵ cm⁻². Point defects contribute by a factor of about 8 more to both perpendicular strain and in-plane stress than defect clusters. When the concentration of point defects or the induced strain reaches a critical value, defect clusters form, which ensures that no further increase of perpendicular strain occurs. This reveals a clear driving force for cluster formation. The microstructure of the defect clusters cannot be determined from the results. As₃Ga₂ interstitial clusters are supposed. A remarkable decrease of the shear modulus of the implanted layers below the value of pristine GaAs by ≈ −35% is observed. Surprisingly, the change of shear modulus already sets in at a very low damage level of a few percent

Publ.-Id: 28978 - Permalink


Performance enhancement and characterization of liquid displacement battery having faradaic membrane
Mushtaq, K.; Zhao, J.; Weber, N.; Sadoway, D.;
Übersicht über die Forschungsarbeiten zu "Liquid Displacement Batteries" am MIT, USA.
  • Poster
    14th Workshop on Reactive Metal Processing, 15.03.2019, Boston, USA

Publ.-Id: 28977 - Permalink


Compliance-current-modulated resistive switching with multi-level resistance states in single-crystalline LiNbO3 thin film
Pan, X.; Shuai, Y.; Wu, C.; Luo, W.; Sun, X.; Zeng, H.; Guo, H.; Yuan, Y.; Zhou, S.; Böttger, R.; Cheng, H.; Zhang, J.; Zhang, W.; Schmidt, H.;
Resistive switching behavior of a ca. 600 nm thick single-crystalline LiNbO3 (LNO) film has been investigated after vacuum-annealing. Oxygen vacancies (OVs) were generated in the LNO thin film during the annealing process. After electro-forming, filamentary resistive switching has been observed, and the performance of switching can be tuned by the compliance current level. Multi-level resistance states including four different low resistance states, were realized by setting different compliance currents, revealing that both concentration of OVs within the conductive filament and the geometry of the conductive filament influence the switching behavior. The conduction mechanisms of the charge transport during switching is discussed based on the current-voltage curves.

Publ.-Id: 28976 - Permalink


Proton irradiation induced defects in β-Ga2O3: A combined EPR and theory study
Bardeleben, H.; Zhou, S.; Gerstmann, U.; Skachkov, D.; Lambrecht, W.; Ho, Q.; Deák, P.;
Proton irradiation of both n-type and semi-insulating bulk samples of β-Ga2O3 leads to the formation of two paramagnetic defects with spin S = 1/2 and monoclinic point symmetry. Their high introduction rates indicate them to be primary irradiation induced defects. The first electron spin resonance (EPR1) has a g-tensor with principal values of gb = 2.0313, gc = 2.0079, and ga* = 2.0025 and quasi-isotropic superhyperfine interaction of 13G with two equivalent Ga neighbors. Under low temperature photoexcitation, this defect is quenched and replaced by a different metastable spin S = 1/2 center of comparable intensity. This second defect (EPR2) has similar principal g-values of gb = 2.0064, gc = 2.0464, and ga* = 2.0024 and shows equally superhyperfine interaction with two equivalent Ga atoms. This EPR2 defect is stable up to T = 100 K, whereas for T > 100 K the initial defect is recovered. Density functional theory calculations of the spin Hamiltonian parameters of various intrinsic defects are carried out using the gauge including projector augmented wave method in order to determine the microscopic structure of these defects. The intuitive models of undistorted gallium monovacancies or self-trapped hole centers are not compatible with neither of these two defects.

Publ.-Id: 28975 - Permalink


Double-peak specific heat and spin freezing in the spin-2 triangular lattice antiferromagnet FeAl2Se4
Li, K.; Jin, S.; Guo, J.; Xu, Y.; Su, Y.; Feng, E.; Liu, Y.; Zhou, S.; Ying, T.; Li, S.; Wang, Z.; Chen, G.; Chen, X.;
We report the properties of a triangular lattice iron-chalcogenide antiferromagnet FeAl2Se4.The spin susceptibility reveals a significant antiferromagnetic interaction with a Curie-Weiss temperature Θ_CW≃−200K and a spin-2 local moment. Despite a large spin and a large ∣Θ_CW∣, the low-temperature behaviors are incompatible with conventional classical magnets. No long-range order is detected down to 0.4 K. Similar to the well-known spin-1 magnet NiGa2S4, the specific heat of FeAl2Se4 exhibits a double-peak structure and a T2 power law at low temperatures, which are attributed to the underlying quadrupolar spin correlations and the Halperin-Saslow modes, respectively. The spin freezing occurs at ∼14 K, below which the relaxation dynamics is probed by the ac susceptibility. Our results are consistent with the early theory for the spin-1 system with Heisenberg and biquadratic spin interactions. We argue that the early proposal of the quadrupolar correlation and gauge glass dynamics may be well extended to FeAl2Se4. Our results provide useful insights about the magnetic properties of frustrated quantum magnets with high spins.

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Publ.-Id: 28974 - Permalink


Oxyhydride Nature of Rare-Earth-Based Photochromic Thin Films
Cornelius, S.; Colombi, G.; Nafezarefi, F.; Schreuders, H.; Heller, R.; Munnik, F.; Dam, B.;
Thin films of rare-earth (RE)−oxygen−hydrogen compounds prepared by reactive magnetron sputtering show a unique color-neutral photochromic effect at ambient conditions. While their optical properties have been studied extensively, the understanding of the relationship between photochromism, chemical composition, and structure is limited. Here we establish a ternary RE−O−H composition-phase diagram based on chemical composition analysis by a combination of Rutherford backscattering and elastic recoil detection. The photochromic films are identified as oxyhydrides with a wide composition range described by the formula REOxH3−2x where 0.5 ≤ x ≤ 1.5. We propose an anion-disordered structure model based on the face-centered cubic unit cell where the O2− and H− anions occupy tetrahedral and octahedral interstices. The optical band gap varies continuously with the anion ratio, demonstrating the potential of band gap tuning for reversible optical switching applications.

Publ.-Id: 28973 - Permalink


Extension of the nodal code DYN3D to SFR applications
Nikitin, E.;
DYN3D is a well-established Light Water Reactor (LWR) simulation tool and is being extended for safety analyses of Sodium cooled Fast Reactors (SFRs) at the Helmholtz-Zentrum Dresden-Rossendorf. This thesis focuses on the first stage of the development process, that is, the extension and application of DYN3D for steady-state and transient SFR calculations on reactor core level. In contrast to LWRs, the SFR behavior is especially sensitive to thermal expansions of the reactor components. Therefore, a new thermal-mechanical module accounting for thermal expansions is implemented into DYN3D. At first step, this module is capable of treating two important thermal expansion effects occurring within the core, namely axial expansion of fuel rods and radial expansion of diagrid. In order to perform nodal calculations with DYN3D, pre-generated homogenized few-group cross sections (XS) are necessarily needed. Therefore, prior to the development of thermal expansion models, a general methodology for XS generation is established for SFR nodal calculations based on the use of the Monte Carlo code Serpent. The new methodological developments presented in this thesis are verified against the Monte Carlo solutions of Serpent. Two SFR cores are used for testing: the large oxide core of the OECD/NEA benchmark and a smaller core from the Phenix end-of-life tests. Finally, the extended DYN3D is validated against selected IAEA benchmark tests on the Phenix end-of-life experiments that contain both steady-state and transient calculations. The contribution to the SFR-related developments at the HZDR, as presented in this thesis, makes it possible of performing steady-state and transient calculations for SFRs on reactor core level by using DYN3D. With this study, the basis of the next stage of DYN3D developments is established, that is, the up-scale of SFR analysis to system level can continue by coupling with a sodium capable thermal-hydraulic system code.
Keywords: SFR ; thermal expansion ; group constant generation ; nodal methods ; spatial kinetics ; Monte Carlo ; Serpent ; DYN3D

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Publ.-Id: 28972 - Permalink


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